Active faults and minor plates in NE Asia

NASA Astrophysics Data System (ADS)

Kozhurin, Andrey I.; Zelenin, Egor A.

2014-05-01

Stated nearly 40 yr ago the uncertainty with plate boundaries location in NE Asia (Chapman, Solomon, 1976) still remains unresolved. Based on the prepositions that a plate boundary must, first, reveal itself in linear sets of active structures, and, second, be continuous and closed, we have undertaken interpretation of medium-resolution KH-9 Hexagon satellite imageries, mostly in stereoscopic regime, for nearly the entire region of NE Asia. Main findings are as follows. There are two major active fault zones in the region north of the Bering Sea. One of them, the Khatyrka-Vyvenka zone, stretches NE to ENE skirting the Bering Sea from the Kamchatka isthmus to the Navarin Cape. Judging by the kinematics of the Olyutorsky 2006 earthquake fault, the fault zones move both right-laterally and reversely. The second active fault zone, the Lankovaya-Omolon zone, starts close to the NE margin of the Okhotsk Sea and extends NE up to nearly the margin of the Chukcha Sea. The fault zone is mostly right-lateral, with topographically expressed cumulative horizontal offsets amounting to 2.5-2.6 km. There may be a third NE-SW zone between the major two coinciding with the Penzhina Range as several active faults found in the southern termination of the Range indicate. The two active fault zones divide the NE Asia area into two large domains, which both could be parts of the Bering Sea plate internally broken and with uncertain western limit. Another variant implies the Khatyrka-Vyvenka zone as the Bering Sea plate northern limit, and the Lankovaya-Omolon zone as separating an additional minor plate from the North-American plate. The choice is actually not crucial, and more important is that both variants leave the question of where the Bering Sea plate boundary is in Alaska. The Lankovaya-Omolon zone stretches just across the proposed northern boundary of the Okhorsk Sea plate. NW of the zone, there is a prominent left-lateral Ulakhan fault, which is commonly interpreted to be a portion of the plate northern boundary. With this, we have discovered no active faults or fault zones of the Ulakhan fault strike, which could be the portion of the boundary between the Lankovaya-Omolon zone and either the western margin of the Komandor basin or the westernmost Aleutians. We conclude that there is a certain disagreement between active faulting pattern and plate models for NE Asia, relating to the extent of the plates and missing portions of the plate boundaries. The research was supported by grant # 110500136-a from the Russian Foundation for Basic Research.

How Do Normal Faults Grow?

NASA Astrophysics Data System (ADS)

Jackson, C. A. L.; Bell, R. E.; Rotevatn, A.; Tvedt, A. B. M.

2015-12-01

Normal faulting accommodates stretching of the Earth's crust and is one of the fundamental controls on landscape evolution and sediment dispersal in rift basins. Displacement-length scaling relationships compiled from global datasets suggest normal faults grow via a sympathetic increase in these two parameters (the 'isolated fault model'). This model has dominated the structural geology literature for >20 years and underpins the structural and tectono-stratigraphic models developed for active rifts. However, relatively recent analysis of high-quality 3D seismic reflection data suggests faults may grow by rapid establishment of their near-final length prior to significant displacement accumulation (the 'coherent fault model'). The isolated and coherent fault models make very different predictions regarding the tectono-stratigraphic evolution of rift basin, thus assessing their applicability is important. To-date, however, very few studies have explicitly set out to critically test the coherent fault model thus, it may be argued, it has yet to be widely accepted in the structural geology community. Displacement backstripping is a simple graphical technique typically used to determine how faults lengthen and accumulate displacement; this technique should therefore allow us to test the competing fault models. However, in this talk we use several subsurface case studies to show that the most commonly used backstripping methods (the 'original' and 'modified' methods) are, however, of limited value, because application of one over the other requires an a priori assumption of the model most applicable to any given fault; we argue this is illogical given that the style of growth is exactly what the analysis is attempting to determine. We then revisit our case studies and demonstrate that, in the case of seismic-scale growth faults, growth strata thickness patterns and relay zone kinematics, rather than displacement backstripping, should be assessed to directly constrain fault length and thus tip behaviour through time. We conclude that rapid length establishment prior to displacement accumulation may be more common than is typically assumed, thus challenging the well-established, widely cited and perhaps overused, isolated fault model.

Active Fault Topography and Fault Outcrops in the Central Part of the Nukumi fault, the 1891 Nobi Earthquake Fault System, Central Japan

NASA Astrophysics Data System (ADS)

Sasaki, T.; Ueta, K.; Inoue, D.; Aoyagi, Y.; Yanagida, M.; Ichikawa, K.; Goto, N.

2010-12-01

It is important to evaluate the magnitude of earthquake caused by multiple active faults, taking into account the simultaneous effects. The simultaneity of adjacent active faults are often decided on the basis of geometric distances except for known these paleoseismic records. We have been studied the step area between the Nukumi fault and the Neodani fault, which appeared as consecutive ruptures in the 1891 Nobi earthquake, since 2009. The purpose of this study is to establish innovation in valuation technique of the simultaneity of adjacent active faults in addition to the paleoseismic record and the geometric distance. Geomorphological, geological and reconnaissance microearthquake surveys are concluded. The present work is intended to clarify the distribution of tectonic geomorphology along the Nukumi fault and the Neodani fault by high-resolution interpretations of airborne LiDAR DEM and aerial photograph, and the field survey of outcrops and location survey. The study area of this work is the southeastern Nukumi fault and the northwestern Neodani fault. We interpret DEM using shaded relief map and stereoscopic bird's-eye view made from 2m mesh DEM data which is obtained by airborne laser scanner of Kokusai Kogyo Co., Ltd. Aerial photographic survey is for confirmation of DEM interpretation using 1/16,000 scale photo. As a result of topographic survey, we found consecutive tectonic topography which is left lateral displacement of ridge and valley lines and reverse scarplets along the Nukumi fault and the Neodani fault . From Ogotani 2km southeastern of Nukumi pass which is located at the southeastern end of surface rupture along the Nukumi fault by previous study to Neooppa 9km southeastern of Nukumi pass, we can interpret left lateral topographies and small uphill-facing fault scarps on the terrace surface by detail DEM investigation. These topographies are unrecognized by aerial photographic survey because of heavy vegetation. We have found several new outcrops in this area where the surface ruptures of the 1891 Nobi earthquake have not been known. These outcrops have active fault which cut the layer of terrace deposit and slope deposit to the bottom of present soil layer in common. At the locality of Ogotani outcrop, the humic layer which age is from14th century to 15th century by 14C age dating is deformed by the active fault. The vertical displacement of the humic layer is 0.8-0.9m and the terrace deposit layer below the humic layer is ca. 1.3m. For this reason and the existence of fain grain deposit including AT tephra (28ka) in the footwall of the fault, this fault movement occurred more than once since the last glacial age. We conclude that the surface rupture of Nukumi fault in the 1891 Nobi earthquake is continuous to 9km southeast of Nukumi pass. In other words, these findings indicate that there is 10km parallel overlap zone between the surface rupture of the southeastern end of Nukumi fault and the northwestern end of Neodani fault.

A pilot GIS database of active faults of Mt. Etna (Sicily): A tool for integrated hazard evaluation

NASA Astrophysics Data System (ADS)

Barreca, Giovanni; Bonforte, Alessandro; Neri, Marco

2013-02-01

A pilot GIS-based system has been implemented for the assessment and analysis of hazard related to active faults affecting the eastern and southern flanks of Mt. Etna. The system structure was developed in ArcGis® environment and consists of different thematic datasets that include spatially-referenced arc-features and associated database. Arc-type features, georeferenced into WGS84 Ellipsoid UTM zone 33 Projection, represent the five main fault systems that develop in the analysed region. The backbone of the GIS-based system is constituted by the large amount of information which was collected from the literature and then stored and properly geocoded in a digital database. This consists of thirty five alpha-numeric fields which include all fault parameters available from literature such us location, kinematics, landform, slip rate, etc. Although the system has been implemented according to the most common procedures used by GIS developer, the architecture and content of the database represent a pilot backbone for digital storing of fault parameters, providing a powerful tool in modelling hazard related to the active tectonics of Mt. Etna. The database collects, organises and shares all scientific currently available information about the active faults of the volcano. Furthermore, thanks to the strong effort spent on defining the fields of the database, the structure proposed in this paper is open to the collection of further data coming from future improvements in the knowledge of the fault systems. By layering additional user-specific geographic information and managing the proposed database (topological querying) a great diversity of hazard and vulnerability maps can be produced by the user. This is a proposal of a backbone for a comprehensive geographical database of fault systems, universally applicable to other sites.

Technology transfer by means of fault tree synthesis

NASA Astrophysics Data System (ADS)

Batzias, Dimitris F.

2012-12-01

Since Fault Tree Analysis (FTA) attempts to model and analyze failure processes of engineering, it forms a common technique for good industrial practice. On the contrary, fault tree synthesis (FTS) refers to the methodology of constructing complex trees either from dentritic modules built ad hoc or from fault tress already used and stored in a Knowledge Base. In both cases, technology transfer takes place in a quasi-inductive mode, from partial to holistic knowledge. In this work, an algorithmic procedure, including 9 activity steps and 3 decision nodes is developed for performing effectively this transfer when the fault under investigation occurs within one of the latter stages of an industrial procedure with several stages in series. The main parts of the algorithmic procedure are: (i) the construction of a local fault tree within the corresponding production stage, where the fault has been detected, (ii) the formation of an interface made of input faults that might occur upstream, (iii) the fuzzy (to count for uncertainty) multicriteria ranking of these faults according to their significance, and (iv) the synthesis of an extended fault tree based on the construction of part (i) and on the local fault tree of the first-ranked fault in part (iii). An implementation is presented, referring to 'uneven sealing of Al anodic film', thus proving the functionality of the developed methodology.

Reverse fault growth and fault interaction with frictional interfaces: insights from analogue models

NASA Astrophysics Data System (ADS)

Bonanno, Emanuele; Bonini, Lorenzo; Basili, Roberto; Toscani, Giovanni; Seno, Silvio

2017-04-01

The association of faulting and folding is a common feature in mountain chains, fold-and-thrust belts, and accretionary wedges. Kinematic models are developed and widely used to explain a range of relationships between faulting and folding. However, these models may result not to be completely appropriate to explain shortening in mechanically heterogeneous rock bodies. Weak layers, bedding surfaces, or pre-existing faults placed ahead of a propagating fault tip may influence the fault propagation rate itself and the associated fold shape. In this work, we employed clay analogue models to investigate how mechanical discontinuities affect the propagation rate and the associated fold shape during the growth of reverse master faults. The simulated master faults dip at 30° and 45°, recalling the range of the most frequent dip angles for active reverse faults that occurs in nature. The mechanical discontinuities are simulated by pre-cutting the clay pack. For both experimental setups (30° and 45° dipping faults) we analyzed three different configurations: 1) isotropic, i.e. without precuts; 2) with one precut in the middle of the clay pack; and 3) with two evenly-spaced precuts. To test the repeatability of the processes and to have a statistically valid dataset we replicate each configuration three times. The experiments were monitored by collecting successive snapshots with a high-resolution camera pointing at the side of the model. The pictures were then processed using the Digital Image Correlation method (D.I.C.), in order to extract the displacement and shear-rate fields. These two quantities effectively show both the on-fault and off-fault deformation, indicating the activity along the newly-formed faults and whether and at what stage the discontinuities (precuts) are reactivated. To study the fault propagation and fold shape variability we marked the position of the fault tips and the fold profiles for every successive step of deformation. Then we compared precut models with isotropic models to evaluate the trends of variability. Our results indicate that the discontinuities are reactivated especially when the tip of the newly-formed fault is either below or connected to them. During the stage of maximum activity along the precut, the faults slow down or even stop their propagation. The fault propagation systematically resumes when the angle between the fault and the precut is about 90° (critical angle); only during this stage the fault crosses the precut. The reactivation of the discontinuities induces an increase of the apical angle of the fault-related fold and produces wider limbs compared to the isotropic reference experiments.

How do normal faults grow?

NASA Astrophysics Data System (ADS)

Jackson, Christopher; Bell, Rebecca; Rotevatn, Atle; Tvedt, Anette

2016-04-01

Normal faulting accommodates stretching of the Earth's crust, and it is arguably the most fundamental tectonic process leading to continent rupture and oceanic crust emplacement. Furthermore, the incremental and finite geometries associated with normal faulting dictate landscape evolution, sediment dispersal and hydrocarbon systems development in rifts. Displacement-length scaling relationships compiled from global datasets suggest normal faults grow via a sympathetic increase in these two parameters (the 'isolated fault model'). This model has dominated the structural geology literature for >20 years and underpins the structural and tectono-stratigraphic models developed for active rifts. However, relatively recent analysis of high-quality 3D seismic reflection data suggests faults may grow by rapid establishment of their near-final length prior to significant displacement accumulation (the 'coherent fault model'). The isolated and coherent fault models make very different predictions regarding the tectono-stratigraphic evolution of rift basin, thus assessing their applicability is important. To-date, however, very few studies have explicitly set out to critically test the coherent fault model thus, it may be argued, it has yet to be widely accepted in the structural geology community. Displacement backstripping is a simple graphical technique typically used to determine how faults lengthen and accumulate displacement; this technique should therefore allow us to test the competing fault models. However, in this talk we use several subsurface case studies to show that the most commonly used backstripping methods (the 'original' and 'modified' methods) are, however, of limited value, because application of one over the other requires an a priori assumption of the model most applicable to any given fault; we argue this is illogical given that the style of growth is exactly what the analysis is attempting to determine. We then revisit our case studies and demonstrate that, in the case of seismic-scale growth faults, growth strata thickness patterns and relay zone kinematics, rather than displacement backstripping, should be assessed to directly constrain fault length and thus tip behaviour through time. We conclude that rapid length establishment prior to displacement accumulation may be more common than is typically assumed, thus challenging the well-established, widely cited and perhaps overused, isolated fault model.

Structural localization and origin of compartmentalized fluid flow, Comstock lode, Virginia City, Nevada

USGS Publications Warehouse

Berger, B.R.; Tingley, J.V.; Drew, L.J.

2003-01-01

Bonanza-grade orebodies in epithermal-style mineral deposits characteristically occur as discrete zones within spatially more extensive fault and/or fracture systems. Empirically, the segregation of such systems into compartments of higher and lower permeability appears to be a key process necessary for high-grade ore formation and, most commonly, it is such concentrations of metals that make an epithermal vein district world class. In the world-class silver- and gold-producing Comstock mining district, Nevada, several lines of evidence lead to the conclusion that the Comstock lode is localized in an extensional stepover between right-lateral fault zones. This evidence includes fault geometries, kinematic indicators of slip, the hydraulic connectivity of faults as demonstrated by veins and dikes along faults, and the opening of a normal-fault-bounded, asymmetric basin between two parallel and overlapping northwest-striking, lateral- to lateral-oblique-slip fault zones. During basin opening, thick, generally subeconomic, banded quartz-adularia veins were deposited in the normal fault zone, the Comstock fault, and along one of the bounding lateral fault zones, the Silver City fault. As deformation continued, the intrusion of dikes and small plugs into the hanging wall of the Comstock fault zone may have impeded the ability of the stepover to accommodate displacement on the bounding strike-slip faults through extension within the stepover. A transient period of transpressional deformation of the Comstock fault zone ensued, and the early-stage veins were deformed through boudinaging and hydraulic fragmentation, fault-motion inversion, and high- and low-angle axial rotations of segments of the fault planes and some fault-bounded wedges. This deformation led to the formation of spatially restricted compartments of high vertical permeability and hydraulic connectivity and low lateral hydraulic connectivity. Bonanza orebodies were formed in the compartmentalized zones of high permeability and hydraulic connectivity. As heat flow and related hydrothermal activitv waned along the Comstock fault zone, extension was reactivated in the stepover along the Occidental zone of normal faults east of the Comstock fault zone. Volcanic and related intrusive activity in this part of the stepover led to a new episode of hydrothermal activity and formation of the Occidental lodes.

3-D kinematics analysis of surface ruptures on an active creeping fault at Chihshang, Eastern Taiwan

NASA Astrophysics Data System (ADS)

Lee, J.; Angelier, J.; Chen, H.; Chu, H.; Hu, J.

2003-12-01

The Chihshang fault is one of the most active segments of the Longitudinal Valley Fault, the plate suture between the converging Philippine and Eurasian plates. A destructive earthquake of M 7.1 with substantial surface scarps resulted from rupturing of the Chihshang fault in 1951. From that on, no big earthquake greater than M 5.5 occurred in this area. Instead, the Chihshang fault reveals a creeping behavior at a rapid rate of about 20 mm/yr at least during the past 20 years. The surface breaks of the creeping Chihshang fault can be observed at the several places. A typical feature is reverse-fault-like fractures on the retaining wall. We deployed small geodetic networks across the fault zone at five sites. Each network comprises of 5 to 15 benchmarks. Trilateration measurements including angles and distances as well as leveling among the benchmarks have been carried out on an annual basis or twice a year since 1998. Compared to previous other measurements which have shown the first order creep rate for the entire fault zone, the present geodetic data provides the detailed information of the surface movements across the fault zone which usually composed of more than one fault strands and folds structures. According to our data from the local geodetic networks, we are able to reconstruct the 3-D kinematics of surface deformation across the Chihshang fault zone. Multiple fault strands are common along the Chihshang fault. Oblique shortening occurred at all sites and was characterized by a combination of thrusts, backthrust and surface warps. Strike-slip motion can also be distinguished on some fault strands. It is worth to note that the cultural feature, such as concrete basement of strong resistance, sometimes acted as deflection of surface ruptures. It should be taken into consideration for mitigation against seismic hazards.

Fracture structures of active Nojima fault, Japan, revealed by borehole televiewer imaging

NASA Astrophysics Data System (ADS)

Nishiwaki, T.; Lin, A.

2017-12-01

Most large intraplate earthquakes occur as slip on mature active faults, any investigation of the seismic faulting process and assessment of seismic hazards require an understanding of the nature of active fault damage zones as seismogenic source. In this study, we focus on the fracture structures of the Nojima Fault (NF) that triggered the 1995 Kobe Mw 7.2 earthquake using ultrasonic borehole televiewer (BHTV) images from a borehole wall. The borehole used in this study was drilled throughout the NF at 1000 m in depth by a science project of Drilling into Fault Damage Zone(DFDZ) in 2016 (Lin, 2016; Miyawaki et al., 2016). In the depth of <230 m of the borehole, the rocks are composed of weak consolidated sandstone and conglomerate of the Plio-Pleistocene Osaka-Group and mudstone and sandstone of the Miocene Kobe Group. The basement rock in the depth of >230 m consist of pre-Neogene granitic rock. Based on the observations of cores and analysis of the BHTV images, the main fault plane was identified at a depth of 529.3 m with a 15 cm thick fault gouge zone and a damage zone of 100 m wide developed in the both sides of the main fault plane. Analysis of the BHTV images shows that the fractures are concentrated in two groups: N45°E (Group-1), parallel to the general trend of the NF, and another strikes N70°E (Group-2), oblique to the fault with an angle of 20°. It is well known that Riedel shear structures are common within strike-slip fault zones. Previous studies show that the NF is a right-lateral strike-slip fault with a minor thrust component, and that the fault damage zone is characterized by Riedel shear structures dominated by Y shears (main faults), R shears and P foliations (Lin, 2001). We interpret that the fractures of Group (1) correspond to Y Riedel fault shears, and those of Group (2) are R shears. Such Riedel shear structures indicate that the NF is a right-lateral strike-slip fault which is activated under a regional stress field oriented to the direction close to east-west, coincident with that inferred from geophysical observations (Tsukahara et al., 2001), seismic inversion results (Katao, 1997) and geological structures (Lin, 2001).Katao et al., 1997. J. Phys. Earth, 45, 105.Lin, 2016. AGU, Fall Meeting.Lin, 2001. J. Struc. Geo., 23, 1167.Miyawaki and Uchida, 2016. AGU, Fall Meeting.Tsukahara et al., 2001. Isl. Arc, 10, 261.

Introduction to Special Section: Paleoseismology

NASA Astrophysics Data System (ADS)

Yeats, Robert S.; Prentice, Carol S.

1996-03-01

A proverb of Confucius states "Study the past if you would divine the future." If we could learn about the past history of earthquakes on a specific fault, then we could serve society well by better forecasting the future earthquake behavior of that fault. For most of the world, the period of historical records is short: about 200 years in California and less than that in New Zealand, Oregon, and other parts of the world. And even where the historical record is thousands of years long, such as in north central China or the eastern Mediterranean region, it is commonly difficult to correlate a major historical earthquake with a specific active fault. Even if this correlation could be made without ambiguity, the recurrence intervals for many faults are longer than even a historical record of several thousand years. For these reasons, the history of large earthquakes on faults must, for the most part, be learned from the geological record.

A broader classification of damage zones

NASA Astrophysics Data System (ADS)

Peacock, D. C. P.; Dimmen, V.; Rotevatn, A.; Sanderson, D. J.

2017-09-01

Damage zones have previously been classified in terms of their positions at fault tips, walls or areas of linkage, with the latter being described in terms of sub-parallel and synchronously active faults. We broaden the idea of linkage to include structures around the intersections of non-parallel and/or non-synchronous faults. These interaction damage zones can be divided into approaching damage zones, where the faults kinematically interact but are not physically connected, and intersection damage zones, where the faults either abut or cross-cut. The damage zone concept is applied to other settings in which strain or displacement variations are taken up by a range of structures, such as at fault bends. It is recommended that a prefix can be added to a wide range of damage zones, to describe the locations in which they formed, e.g., approaching, intersection and fault bend damage zone. Such interpretations are commonly based on limited knowledge of the 3D geometries of the structures, such as from exposure surfaces, and there may be spatial variations. For example, approaching faults and related damage seen in outcrop may be intersecting elsewhere on the fault planes. Dilation in intersection damage zones can represent narrow and localised channels for fluid flow, and such dilation can be influenced by post-faulting stress patterns.

Southern San Andreas Fault evaluation field activity: approaches to measuring small geomorphic offsets--challenges and recommendations for active fault studies

USGS Publications Warehouse

Scharer, Katherine M.; Salisbury, J. Barrett; Arrowsmith, J. Ramon; Rockwell, Thomas K.

2014-01-01

In southern California, where fast slip rates and sparse vegetation contribute to crisp expression of faults and microtopography, field and high‐resolution topographic data (<1  m/pixel) increasingly are used to investigate the mark left by large earthquakes on the landscape (e.g., Zielke et al., 2010; Zielke et al., 2012; Salisbury, Rockwell, et al., 2012, Madden et al., 2013). These studies measure offset streams or other geomorphic features along a stretch of a fault, analyze the offset values for concentrations or trends along strike, and infer that the common magnitudes reflect successive surface‐rupturing earthquakes along that fault section. Wallace (1968) introduced the use of such offsets, and the challenges in interpreting their “unique complex history” with offsets on the Carrizo section of the San Andreas fault; these were more fully mapped by Sieh (1978) and followed by similar field studies along other faults (e.g., Lindvall et al., 1989; McGill and Sieh, 1991). Results from such compilations spurred the development of classic fault behavior models, notably the characteristic earthquake and slip‐patch models, and thus constitute an important component of the long‐standing contrast between magnitude–frequency models (Schwartz and Coppersmith, 1984; Sieh, 1996; Hecker et al., 2013). The proliferation of offset datasets has led earthquake geologists to examine the methods and approaches for measuring these offsets, uncertainties associated with measurement of such features, and quality ranking schemes (Arrowsmith and Rockwell, 2012; Salisbury, Arrowsmith, et al., 2012; Gold et al., 2013; Madden et al., 2013). In light of this, the Southern San Andreas Fault Evaluation (SoSAFE) project at the Southern California Earthquake Center (SCEC) organized a combined field activity and workshop (the “Fieldshop”) to measure offsets, compare techniques, and explore differences in interpretation. A thorough analysis of the measurements from the field activity will be provided separately; this paper discusses the complications presented by such offset measurements using two channels from the San Andreas fault as illustrative cases. We conclude with best approaches for future data collection efforts based on input from the Fieldshop.

Probabilistic seismic hazard assessments of Sabah, east Malaysia: accounting for local earthquake activity near Ranau

NASA Astrophysics Data System (ADS)

Khalil, Amin E.; Abir, Ismail A.; Ginsos, Hanteh; Abdel Hafiez, Hesham E.; Khan, Sohail

2018-02-01

Sabah state in eastern Malaysia, unlike most of the other Malaysian states, is characterized by common seismological activity; generally an earthquake of moderate magnitude is experienced at an interval of roughly every 20 years, originating mainly from two major sources, either a local source (e.g. Ranau and Lahad Dato) or a regional source (e.g. Kalimantan and South Philippines subductions). The seismicity map of Sabah shows the presence of two zones of distinctive seismicity, these zones are near Ranau (near Kota Kinabalu) and Lahad Datu in the southeast of Sabah. The seismicity record of Ranau begins in 1991, according to the international seismicity bulletins (e.g. United States Geological Survey and the International Seismological Center), and this short record is not sufficient for seismic source characterization. Fortunately, active Quaternary fault systems are delineated in the area. Henceforth, the seismicity of the area is thus determined as line sources referring to these faults. Two main fault systems are believed to be the source of such activities; namely, the Mensaban fault zone and the Crocker fault zone in addition to some other faults in their vicinity. Seismic hazard assessments became a very important and needed study for the extensive developing projects in Sabah especially with the presence of earthquake activities. Probabilistic seismic hazard assessments are adopted for the present work since it can provide the probability of various ground motion levels during expected from future large earthquakes. The output results are presented in terms of spectral acceleration curves and uniform hazard curves for periods of 500, 1000 and 2500 years. Since this is the first time that a complete hazard study has been done for the area, the output will be a base and standard for any future strategic plans in the area.

Paleoseismicity of two historically quiescent faults in Australia: Implications for fault behavior in stable continental regions

USGS Publications Warehouse

Crone, A.J.; De Martini, P. M.; Machette, M.M.; Okumura, K.; Prescott, J.R.

2003-01-01

Paleoseismic studies of two historically aseismic Quaternary faults in Australia confirm that cratonic faults in stable continental regions (SCR) typically have a long-term behavior characterized by episodes of activity separated by quiescent intervals of at least 10,000 and commonly 100,000 years or more. Studies of the approximately 30-km-long Roopena fault in South Australia and the approximately 30-km-long Hyden fault in Western Australia document multiple Quaternary surface-faulting events that are unevenly spaced in time. The episodic clustering of events on cratonic SCR faults may be related to temporal fluctuations of fault-zone fluid pore pressures in a volume of strained crust. The long-term slip rate on cratonic SCR faults is extremely low, so the geomorphic expression of many cratonic SCR faults is subtle, and scarps may be difficult to detect because they are poorly preserved. Both the Roopena and Hyden faults are in areas of limited or no significant seismicity; these and other faults that we have studied indicate that many potentially hazardous SCR faults cannot be recognized solely on the basis of instrumental data or historical earthquakes. Although cratonic SCR faults may appear to be nonhazardous because they have been historically aseismic, those that are favorably oriented for movement in the current stress field can and have produced unexpected damaging earthquakes. Paleoseismic studies of modern and prehistoric SCR faulting events provide the basis for understanding of the long-term behavior of these faults and ultimately contribute to better seismic-hazard assessments.

Reexaming Owens Valley: Partitioning of Discrete and Distributed Transtension, Structural Controls on Magmatism, and Seismic Potential within an Active Rift Zone, Eastern California.

NASA Astrophysics Data System (ADS)

Levy, D. A.; Haproff, P. J.; Yin, A.

2016-12-01

Crustal-scale transtensional deformation is common in intracontinental extensional settings. However, along-strike variations in the geometry, kinematics, and linkages between rift-related faults, along with controls on local magmatic plumbing, remain inadequately examined. In this study, we conducted geologic mapping of active structures within central and northern Owens Valley of eastern California. C. Owens Valley features right-slip oblique deformation accommodated by three discrete north-south-trending faults: (1) the right-slip Owens Valley fault (OVF) and rift-bounding (2) Sierra Nevada Frontal fault (SNFF) and (3) the White-Inyo Mountains fault (WIMF). The OVF also serves as a lithospheric-scale, vertical conduit for asthenospheric-derived magma to migrate upwards and erupt at Big Pine Volcanic Field. Right-slip shear within C. Owens Valley is transferred to the SNFF of N. Owens Valley via the Poverty Hills restraining bend. In contrast to C. Owens Valley, the northern segment is dominated by distributed E-W to NE-SW-oriented extension, evidenced by normal fault scarps throughout Volcanic Tablelands and basin floor. Furthermore, the White Mountain fault which bounds N. Owens Valley to the east consists of a master west-dipping detachment fault that thinned the lithosphere, allowing for asthenospheric upwelling into the crust beneath the western rift shoulder. Subvertical, right-slip faults of the SNFF provide a conduit for magma to erupt on the surface throughout the Long Valley Caldera, Mono-Inyo Craters, and Mono Basin region. Our mapping demonstrates complex strain partitioning of discrete and distributed deformation within an alternating pure and simple shear, transtensional rift zone. Lastly, we present previously unknown relationships in Owens Valley between lithospheric-scale fault systems, seismic potential, and rift magmatism.

Evolution of Friction, Wear, and Seismic Radiation Along Experimental Bi-material Faults

NASA Astrophysics Data System (ADS)

Carpenter, B. M.; Zu, X.; Shadoan, T.; Self, A.; Reches, Z.

2017-12-01

Faults are commonly composed by rocks of different lithologies and mechanical properties that are positioned against one another by fault slip; such faults are referred to as bimaterial-faults (BF). We investigate the mechanical behavior, wear production, and seismic radiation of BF via laboratory experiments on a rotary shear apparatus. In the experiments, two rock blocks of dissimilar or similar lithology are sheared against each other. We used contrasting rock pairs of a stiff, igneous block (diorite, granite, or gabbro) against a more compliant, sedimentary block (sandstone, limestone, or dolomite). The cylindrical blocks have a ring-shaped contact, and are loaded under conditions of constant normal stress and shear velocity. Fault behavior was monitored with stress, velocity and dilation sensors. Acoustic activity is monitored with four 3D accelerometers mounted at 2 cm distance from the experimental fault. These sensors can measure accelerations up to 500 g, and their full waveform output is recorded at 1MHz for periods up to 14 sec. Our preliminary results indicate that the bi-material nature of the fault has a strong affect on slip initiation, wear evolution, and acoustic emission activity. In terms of wear, we observe enhanced wear in experiments with a sandstone block sheared against a gabbro or limestone block. Experiments with a limestone or sandstone block produced distinct slickenline striations. Further, significant differences appeared in the number and amplitude of acoustic events depending on the bi-material setting and slip-distance. A gabbro-gabbro fault showed a decrease in both amplitude and number of acoustic events with increasing slip. Conversely, a gabbro-limestone fault showed a decrease in the number of events, but an increase in average event amplitude. Ongoing work focuses on advanced characterization of mechanical, dynamic weakening, and acoustic, frequency content, parameters.

Geophysical methods for identification of active faults between the Sannio-Matese and Irpinia areas of the Southern Apennines.

NASA Astrophysics Data System (ADS)

Gaudiosi, Germana; Nappi, Rosa; Alessio, Giuliana; Cella, Federico; Fedi, Maurizio; Florio, Giovanni

2014-05-01

The Southern Apennines is one of the Italian most active areas from a geodynamic point of view since it is characterized by occurrence of intense and widely spread seismic activity. Most seismicity of the area is concentrated along the chain, affecting mainly the Irpinia and Sannio-Matese areas. The seismogenetic sources responsible for the destructive events of 1456, 1688, 1694, 1702, 1732, 1805, 1930, 1962 and 1980 (Io = X-XI MCS) occurred mostly on NW-SE faults, and the relative hypocenters are concentrated within the upper 20 km of the crust. Structural observations on the Pleistocene faults suggest normal to sinistral movements for the NW-SE trending faults and normal to dextral for the NE-SW trending structures. The available focal mechanisms of the largest events show normal solutions consistent with NE-SW extension of the chain. After the 1980 Irpinia large earthquake, the release of seismic energy in the Southern Apennines has been characterized by occurrence of moderate energy sequences of main shock-aftershocks type and swarm-type activity with low magnitude sequences. Low-magnitude (Md<5) historical and recent earthquakes, generally clustered in swarms, have commonly occurred along the NE-SW faults. This paper deals with integrated analysis of geological and geophysical data in GIS environment to identify surface, buried and hidden active faults and to characterize their geometry. In particular we have analyzed structural data, earthquake space distribution and gravimetric data. The main results of the combined analysis indicate good correlation between seismicity and Multiscale Derivative Analysis (MDA) lineaments from gravity data. Furthermore 2D seismic hypocentral locations together with high-resolution analysis of gravity anomalies have been correlated to estimate the fault systems parameters (strike, dip direction and dip angle) through the application of the DEXP method (Depth from Extreme Points).

Active out-of-sequence thrust faulting in the central Nepalese Himalaya.

PubMed

Wobus, Cameron; Heimsath, Arjun; Whipple, Kelin; Hodges, Kip

2005-04-21

Recent convergence between India and Eurasia is commonly assumed to be accommodated mainly along a single fault--the Main Himalayan Thrust (MHT)--which reaches the surface in the Siwalik Hills of southern Nepal. Although this model is consistent with geodetic, geomorphic and microseismic data, an alternative model incorporating slip on more northerly surface faults has been proposed to be consistent with these data as well. Here we present in situ cosmogenic 10Be data indicating a fourfold increase in millennial timescale erosion rates occurring over a distance of less than 2 km in central Nepal, delineating for the first time an active thrust fault nearly 100 km north of the surface expression of the MHT. These data challenge the view that rock uplift gradients in central Nepal reflect only passive transport over a ramp in the MHT. Instead, when combined with previously reported 40Ar-39Ar data, our results indicate persistent exhumation above deep-seated, surface-breaking structures at the foot of the high Himalaya. These results suggest that strong dynamic interactions between climate, erosion and tectonics have maintained a locus of active deformation well to the north of the Himalayan deformation front.

Tectonoestratigraphic and Thermal Models of the Tiburon and Wagner Basins, northern Gulf of California Rift System

NASA Astrophysics Data System (ADS)

Contreras, J.; Ramirez Zerpa, N. A.; Negrete-Aranda, R.

2014-12-01

The northern Gulf of California Rift System consist sofa series faults that accommodate both normal and strike-slip motion. The faults formed a series of half-greens filled with more than 7 km of siliciclastic suc­cessions. Here, we present tectonostratigraphic and heat flow models for the Tiburón basin, in the southern part of the system, and the Wag­ner basin in the north. The models are constrained by two-dimensional seis­mic lines and by two deep boreholes drilled by PEMEX­-PEP. Analysis of the seismic lines and models' results show that: (i) subsidence of the basins is controlled by high-angle normal faults and by flow of the lower crust, (ii) basins share a common history, and (iii) there are significant differences in the way brittle strain was partitioned in the basins, a feature frequently observed in rift basins. On one hand, the bounding faults of the Tiburón basin have a nested geometry and became active following a west-to-east sequence of activation. The Tiburon half-graben was formed by two pulses of fault activity. One took place during the protogulf extensional phase in the Miocene and the other during the opening of Gulf of California in the Pleistocene. On the other hand, the Wagner basin is the result of two fault generations. During the late-to middle Miocene, the west-dipping Cerro Prieto and San Felipe faults formed a domino array. Then, during the Pleistocene the Consag and Wagner faults dissected the hanging-wall of the Cerro Prieto fault forming the modern Wagner basin. Thermal modeling of the deep borehole temperatures suggests that the heat flow in these basins in the order of 110 mW/m2 which is in agreement with superficial heat flow measurements in the northern Gulf of California Rift System.

Composite transform-convergent plate boundaries: description and discussion

USGS Publications Warehouse

Ryan, H.F.; Coleman, P.J.

1992-01-01

The leading edge of the overriding plate at an obliquely convergent boundary is commonly sliced by a system of strike-slip faults. This fault system is often structurally complex, and may show correspondingly uneven strain effects, with great vertical and translational shifts of the component blocks of the fault system. The stress pattern and strain effects vary along the length of the system and change through time. These margins are considered to be composite transform-convergent (CTC) plate boundaries. Examples are given of structures formed along three CTC boundaries: the Aleutian Ridge, the Solomon Islands, and the Philippines. The dynamism of the fault system along a CTC boundary can enhance vertical tectonism and basin formation. This concept provides a framework for the evaluation of petroleum resources related to basin formation, and mineral exploration related to igneous activity associated with transtensional processes. ?? 1992.

The 2009 Samoa-Tonga great earthquake triggered doublet

USGS Publications Warehouse

Lay, T.; Ammon, C.J.; Kanamori, H.; Rivera, L.; Koper, K.D.; Hutko, Alexander R.

2010-01-01

Great earthquakes (having seismic magnitudes of at least 8) usually involve abrupt sliding of rock masses at a boundary between tectonic plates. Such interplate ruptures produce dynamic and static stress changes that can activate nearby intraplate aftershocks, as is commonly observed in the trench-slope region seaward of a great subduction zone thrust event1-4. The earthquake sequence addressed here involves a rare instance in which a great trench-slope intraplate earthquake triggered extensive interplate faulting, reversing the typical pattern and broadly expanding the seismic and tsunami hazard. On 29 September 2009, within two minutes of the initiation of a normal faulting event with moment magnitude 8.1 in the outer trench-slope at the northern end of the Tonga subduction zone, two major interplate underthrusting subevents (both with moment magnitude 7.8), with total moment equal to a second great earthquake of moment magnitude 8.0, ruptured the nearby subduction zone megathrust. The collective faulting produced tsunami waves with localized regions of about 12metres run-up that claimed 192 lives in Samoa, American Samoa and Tonga. Overlap of the seismic signals obscured the fact that distinct faults separated by more than 50km had ruptured with different geometries, with the triggered thrust faulting only being revealed by detailed seismic wave analyses. Extensive interplate and intraplate aftershock activity was activated over a large region of the northern Tonga subduction zone. ?? 2010 Macmillan Publishers Limited. All rights reserved.

The 2009 Samoa-Tonga great earthquake triggered doublet.

PubMed

Lay, Thorne; Ammon, Charles J; Kanamori, Hiroo; Rivera, Luis; Koper, Keith D; Hutko, Alexander R

2010-08-19

Great earthquakes (having seismic magnitudes of at least 8) usually involve abrupt sliding of rock masses at a boundary between tectonic plates. Such interplate ruptures produce dynamic and static stress changes that can activate nearby intraplate aftershocks, as is commonly observed in the trench-slope region seaward of a great subduction zone thrust event. The earthquake sequence addressed here involves a rare instance in which a great trench-slope intraplate earthquake triggered extensive interplate faulting, reversing the typical pattern and broadly expanding the seismic and tsunami hazard. On 29 September 2009, within two minutes of the initiation of a normal faulting event with moment magnitude 8.1 in the outer trench-slope at the northern end of the Tonga subduction zone, two major interplate underthrusting subevents (both with moment magnitude 7.8), with total moment equal to a second great earthquake of moment magnitude 8.0, ruptured the nearby subduction zone megathrust. The collective faulting produced tsunami waves with localized regions of about 12 metres run-up that claimed 192 lives in Samoa, American Samoa and Tonga. Overlap of the seismic signals obscured the fact that distinct faults separated by more than 50 km had ruptured with different geometries, with the triggered thrust faulting only being revealed by detailed seismic wave analyses. Extensive interplate and intraplate aftershock activity was activated over a large region of the northern Tonga subduction zone.

Interactive Retro-Deformation of Terrain for Reconstructing 3D Fault Displacements.

PubMed

Westerteiger, R; Compton, T; Bernadin, T; Cowgill, E; Gwinner, K; Hamann, B; Gerndt, A; Hagen, H

2012-12-01

Planetary topography is the result of complex interactions between geological processes, of which faulting is a prominent component. Surface-rupturing earthquakes cut and move landforms which develop across active faults, producing characteristic surface displacements across the fault. Geometric models of faults and their associated surface displacements are commonly applied to reconstruct these offsets to enable interpretation of the observed topography. However, current 2D techniques are limited in their capability to convey both the three-dimensional kinematics of faulting and the incremental sequence of events required by a given reconstruction. Here we present a real-time system for interactive retro-deformation of faulted topography to enable reconstruction of fault displacement within a high-resolution (sub 1m/pixel) 3D terrain visualization. We employ geometry shaders on the GPU to intersect the surface mesh with fault-segments interactively specified by the user and transform the resulting surface blocks in realtime according to a kinematic model of fault motion. Our method facilitates a human-in-the-loop approach to reconstruction of fault displacements by providing instant visual feedback while exploring the parameter space. Thus, scientists can evaluate the validity of traditional point-to-point reconstructions by visually examining a smooth interpolation of the displacement in 3D. We show the efficacy of our approach by using it to reconstruct segments of the San Andreas fault, California as well as a graben structure in the Noctis Labyrinthus region on Mars.

Active Flexural-Slip Faulting: Controls Exerted by Stratigraphy, Geometry, and Fold Kinematics

NASA Astrophysics Data System (ADS)

Li, Tao; Chen, Jie; Thompson Jobe, Jessica A.; Burbank, Douglas W.

2017-10-01

Flexural slip plays an important role in accommodating fold growth, and its topographic expression, flexural-slip fault (FSF) scarps, may be one of the most commonly occurring secondary structures in areas dominated by active thrusts and folds. Where FSF scarps are present and what factors control their occurrence, however, are typically poorly known. Through an investigation of clearly expressed FSF scarps, well-preserved fluvial terraces, and well-exposed bedrock at eight sites in the Pamir-Tian Shan convergent zone and Kuche fold belt, NW China, we summarize the most favorable conditions for active flexural-slip faulting. Our study yields six key results. First, flexural slip operates commonly in well-layered beds, although uncommonly can occur in massive, poorly layered beds as well. Second, in well-layered beds, the slip surface is commonly located either (a) close to the contact of competent and incompetent beds or (b) within thin incompetent beds. Third, FSF scarps are always found overlying steep beds with dips of 30-100°. Fourth, slip surfaces are typically spaced between 10 and 440 m but can reach up to 600 m. Fifth, FSF scarps at most sites can be observed far away from the hinge-migrated fold scarps, suggesting that compared to hinge migration, limb rotation is generally required to accumulate flexural slip and produce associated topographic scarps. Finally, a higher regional convergent rate seems to facilitate the creation of FSF scarps more often than lower rates, whereas well-preserved, old terraces capped by thin deposits are more likely to record FSF scarps than unevenly preserved, young terraces with thick sedimentary caps.

Characterising the range of seismogenic behaviour on detachment faults - the case of 13o20'N, Mid Atlantic Ridge.

NASA Astrophysics Data System (ADS)

Craig, T. J.; Parnell-Turner, R.

2017-12-01

Extension at slow- and intermediate-spreading mid-ocean ridges is commonly accommodated through slip on long-lived detachment faults. These curved, convex-upward faults consist of a steeply-dipping section thought to be rooted in the lower crust or upper mantle which rotates to progressively shallower dip-angles at shallower depths, resulting in a domed, sub-horizontal oceanic core complex at the seabed. Although it is accepted that detachment faults can accumulate kilometre-scale offsets over millions of years, the mechanism of slip, and their capacity to sustain the shear stresses necessary to produce large earthquakes, remains debated. In this presentation we will show a comprehensive seismological study of an active oceanic detachment fault system on the Mid-Atlantic Ridge near 13o20'N, combining the results from a local ocean-bottom seismograph deployment with waveform inversion of a series of larger, teleseismically-observed earthquakes. The coincidence of these two datasets provides a more complete characterisation of rupture on the fault, from its initial beginnings within the uppermost mantle to its exposure at the surface. Our results demonstrate that although slip on the steeply-dipping portion of detachment fault is accommodated by failure in numerous microearthquakes, the shallower-dipping section of the fault within the upper few kilometres is relatively strong, and is capable of producing large-magnitude earthquakes. Slip on the shallow portion of active detachment faults at relatively low angles may therefore account for many more large-magnitude earthquakes at mid-ocean ridges than previously thought, and suggests that the lithospheric strength at slow-spreading mid-ocean ridges may be concentrated at shallow depths.

Regional Characteristics of Stress State of Main Seismic Active Faults in Mid-Northern Part of Sichuan-Yunnan Block

NASA Astrophysics Data System (ADS)

Weiwei, W.; Yaling, W.

2017-12-01

We restore the seismic source spectrums of 1012 earthquakes(2.0 ≤ ML ≤ 5.0) in the mid-northern part of Sichuan-Yunnan seismic block(26 ° N-33 ° N, 99 ° E-104 ° E),then calculate the source parameters.Based on the regional seismic tectonic background, the distribution of active faults and seismicity, the study area is divided into four statistical units (Z1 Jinshajiang and Litang fault zone, Z2 Xianshuihe fault zone, Z3 Anninghe-Zemuhe fault zone, Z4 Lijiang-Xiaojinhe fault zone). Seismic source stress drop results show the following, (1)The stress at the end of the Jinshajiang fault is low, strong earthquake activity rare.Stress-strain loading deceases gradually from northwest to southeast along Litang fault, the northwest section which is relatively locked is more likely to accumulate strain than southeast section. (2)Stress drop of Z2 is divided by Kangding, the southern section is low and northern section is high. Southern section (Kangding-Shimian) is difficult to accumulate higher strain in the short term, but in northern section (Garzê-Kangding), moderate and strong earthquakes have not filled the gaps of seismic moment release, there is still a high stress accumulation in partial section. (3)High stress-drop events were concentrated on Z3, strain accumulation of this unit is strong, and stress level is the highest, earthquake risk is high. (4)On Z4, stress drop characteristics of different magnitude earthquakes are not the same, which is related to complex tectonic setting, the specific reasons still need to be discussed deeply.The study also show that, (1)Stress drops display a systematic change with different faults and locations, high stress-drop events occurs mostly on the fault intersection area. Faults without locking condition and mainly creep, are mainly characterized by low stress drop. (2)Contrasting to what is commonly thought that "strike-slip faults are not easy to accumulate stress ", Z2 and Z3 all exhibit high stress levels, which may be due to that the magnitude and intensity of medium-strong earthquakes are not enough to release the accumulated energy. On the other hand, when the tectonic unit blocking fault movement and its contribution to accumulation of stress play a key role, the earthquake of same magnitude will release higher stress drop.

Constraining fault activity by investigating tectonically-deformed Quaternary palaeoshorelines using a synchronous correlation method: the Capo D'Orlando Fault as a case study (NE Sicily, Italy)

NASA Astrophysics Data System (ADS)

Meschis, Marco; Roberts, Gerald P.; Robertson, Jennifer

2016-04-01

Long-term curstal extension rates, accommodated by active normal faults, can be constrained by investigating Late Quaternary vertical movements. Sequences of marine terraces tectonically deformed by active faults mark the interaction between tectonic activity, sea-level changes and active faulting throughout the Quaternary (e.g. Armijo et al., 1996, Giunta et al, 2011, Roberts et al., 2013). Crustal deformation can be calculated over multiple seismic cycles by mapping Quaternary tectonically-deformed palaeoshorelines, both in the hangingwall and footwall of active normal faults (Roberts et al., 2013). Here we use a synchronous correlation method between palaeoshorelines elevations and the ages of sea-level highstands (see Roberts et al., 2013 for further details) which takes advantage of the facts that (i) sea-level highstands are not evenly-spaced in time, yet must correlate with palaeoshorelines that are commonly not evenly-spaced in elevation, and (ii) that older terraces may be destroyed and/or overprinted by younger highstands, so that the next higher or lower paleoshoreline does not necessarily correlate with the next older or younger sea-level highstand. We investigated a flight of Late Quaternary marine terraces deformed by normal faulting as a result of the Capo D'Orlando Fault in NE Sicily (e.g. Giunta et al., 2011). This fault lies within the Calabrian Arc which has experienced damaging seismic events such as the 1908 Messina Straits earthquake ~ Mw 7. Our mapping and previous mapping (Giunta et al. (2011) demonstrate that the elevations of marine terraces inner edges change along the strike the NE - SW oriented normal fault. This confirms active deformation on the Capo D'Orlando Fault, strongly suggesting that it should be added into the Database of Individual Seismogenic Sources (DISS, Basili et al., 2008). Giunta et al. (2011) suggested that uplift rates and hence faults lip-rates vary through time for this examples. We update the ages assigned to each palaeoshoreline from the initial work by Giunta et al., (2011) using synchronous correlation. This alternative approach suggests that uplift rates were constant through the Late Quaternary, suggesting that the fault slip-rate governing seismic hazard has also been constant. Reference Armijo, R., Meyer, B. G. C. P., King, G. C. P., Rigo, A., & Papanastassiou, D. (1996). Quaternary evolution of the Corinth Rift and its implications for the Late Cenozoic evolution of the Aegean. Geophysical Journal International, 126(1): 11 - 53. Basili R., Valensise, G., Vannoli, P., Burrato, P., Fracassi, U., Mariano, S., Tiberti, M.M., Boschi. E. (2008). The Database of Individual Seismogenic Sources (DISS), version 3: summarizing 20 years of research on Italy's earthquake geology, Tectonophysics, doi:10.1016/j.tecto.2007.04.014. Giunta, G., Gueli, A.M., Monaco, C., Orioli, S., Ristuccia, G.M., Stella, G., Troja, S.O. (2011). Middle-Late Pleistocene marine terraces and fault activity in the Sant'Agata di Militello coastal area (north-eastern Sicily). Journal of Geodynamics. 55, 32 - 40. Roberts, G. P., Meschis, M., Houghton, S., Underwood, C., & Briant, R. M. (2013). The implications of revised Quaternary palaeoshoreline chronologies for the rates of active extension and uplift in the upper plate of subduction zones.Quaternary Science Reviews, 78: 169 - 187.

Hanging canyons of Haida Gwaii, British Columbia, Canada: Fault-control on submarine canyon geomorphology along active continental margins

NASA Astrophysics Data System (ADS)

Harris, Peter T.; Barrie, J. Vaughn; Conway, Kim W.; Greene, H. Gary

2014-06-01

Faulting commonly influences the geomorphology of submarine canyons that occur on active continental margins. Here, we examine the geomorphology of canyons located on the continental margin off Haida Gwaii, British Columbia, that are truncated on the mid-slope (1200-1400 m water depth) by the Queen Charlotte Fault Zone (QCFZ). The QCFZ is an oblique strike-slip fault zone that has rates of lateral motion of around 50-60 mm/yr and a small convergent component equal to about 3 mm/yr. Slow subduction along the Cascadia Subduction Zone has accreted a prism of marine sediment against the lower slope (1500-3500 m water depth), forming the Queen Charlotte Terrace, which blocks the mouths of submarine canyons formed on the upper slope (200-1400 m water depth). Consequently, canyons along this margin are short (4-8 km in length), closely spaced (around 800 m), and terminate uniformly along the 1400 m isobath, coinciding with the primary fault trend of the QCFZ. Vertical displacement along the fault has resulted in hanging canyons occurring locally. The Haida Gwaii canyons are compared and contrasted with the Sur Canyon system, located to the south of Monterey Bay, California, on a transform margin, which is not blocked by any accretionary prism, and where canyons thus extend to 4000 m depth, across the full breadth of the slope.

Finding Faults: Tohoku and other Active Megathrusts/Megasplays

NASA Astrophysics Data System (ADS)

Moore, J. C.; Conin, M.; Cook, B. J.; Kirkpatrick, J. D.; Remitti, F.; Chester, F.; Nakamura, Y.; Lin, W.; Saito, S.; Scientific Team, E.

2012-12-01

Current subduction-fault drilling procedure is to drill a logging hole, identify target faults, then core and instrument them. Seismic data may constrain faults but the additional resolution of borehole logs is necessary for efficient coring and instrumentation under difficult conditions and tight schedules. Thus, refining the methodology of identifying faults in logging data has become important, and thus comparison of log signatures of faults in different locations is worthwhile. At the C0019 (JFAST) drill site, the Tohoku megathrust was principally identified as a decollement where steep cylindrically-folded bedding abruptly flattens below the basal detachment. A similar structural contrast occurs across a megasplay fault in the NanTroSEIZE transect (Site C0004). At the Tohoku decollement, a high gamma-ray value from a pelagic clay layer, predicted as a likely decollement sediment type, strengthens the megathrust interpretation. The original identification of the pelagic clay as a decollement candidate was based on results of previous coring of an oceanic reference site. Negative density anomalies, often seen as low resistivity zones, identified a subsidiary fault in the deformed prism overlying the Tohoku megathrust. Elsewhere, at Barbados, Nankai (Moroto), and Costa Rica, negative density anomalies are associated with the decollement and other faults in hanging walls. Log-based density anomalies in fault zones provide a basis for recognizing in-situ fault zone dilation. At the Tohoku Site C0019, breakouts are present above but not below the megathrust. Changes in breakout orientation and width (stress magnitude) occur across megasplay faults at Sites C0004 and C0010 in the NantroSEIZE transect. Annular pressure anomalies are not apparent at the Tohoku megathrust, but are variably associated with faults and fracture zones drilled along the NanTroSEIZE transect. Overall, images of changes in structural features, negative density anomalies, and changes in breakout occurrence and orientation provide the most common log criteria for recognizing major thrust zones in ocean drilling holes at convergent margins. In the case of JFAST, identification of faults by logging was confirmed during subsequent coring activities, and logging data was critical for successful placement of the observatory down hole.

An update of Quaternary faults of central and eastern Oregon

USGS Publications Warehouse

Weldon, Ray J.; Fletcher, D.K.; Weldon, E.M.; Scharer, K.M.; McCrory, P.A.

2002-01-01

This is the online version of a CD-ROM publication. We have updated the eastern portion of our previous active fault map of Oregon (Pezzopane, Nakata, and Weldon, 1992) as a contribution to the larger USGS effort to produce digital maps of active faults in the Pacific Northwest region. The 1992 fault map has seen wide distribution and has been reproduced in essentially all subsequent compilations of active faults of Oregon. The new map provides a substantial update of known active or suspected active faults east of the Cascades. Improvements in the new map include (1) many newly recognized active faults, (2) a linked ArcInfo map and reference database, (3) more precise locations for previously recognized faults on shaded relief quadrangles generated from USGS 30-m digital elevations models (DEM), (4) more uniform coverage resulting in more consistent grouping of the ages of active faults, and (5) a new category of 'possibly' active faults that share characteristics with known active faults, but have not been studied adequately to assess their activity. The distribution of active faults has not changed substantially from the original Pezzopane, Nakata and Weldon map. Most faults occur in the south-central Basin and Range tectonic province that is located in the backarc portion of the Cascadia subduction margin. These faults occur in zones consisting of numerous short faults with similar rates, ages, and styles of movement. Many active faults strongly correlate with the most active volcanic centers of Oregon, including Newberry Craters and Crater Lake.

Origin and late quaternary tectonism of a western Canadian continental shelf trough

NASA Astrophysics Data System (ADS)

Moslow, Thomas F.; Luternauer, John L.; Rohr, Kristin

1991-08-01

Analyses of high resolution and multi-channel seismic profiles from the central continental shelf of western Canada ascribe a late Quaternary glacial origin to large-scale troughs. Along the margins of Moresby Trough, one of three large-scale cross-shelf bathymetric depressions in Queen Charlotte Sound, seismic profiles within Quaternary sediments show a divergence of reflectors, thickening and folding of seismic units, and concavity of reflectors suggestive of drag. Compactional subsidence, growth faulting, and compaction faulting are also observed. Fault traces commonly terminate below the seabed. Deformation of Quaternary sediments due to faulting is plastic in nature and maximum offset of reflectors is 2.5 m. The observed Quaternary deformation appears to be a product of rapid deposition, loading and subsidence of late Quaternary sediment, which is unrelated to seismic activity. In addition, Quaternary faulting was probably activated by post-glacial loading and isostatic rebound of consolidated Tertiary strata along the margins of continental shelf troughs. The presence of mass movement (slump or debris flow) deposits overlying lithified Tertiary strata along the flanks of Moresby Trough provides the only evidence of seismic activity in the study area. The lack of a mud drape over these deposits implies a late Holocene age for the timing of their emplacement. The Quaternary troughs are incised into Tertiary-aged sedimentary fill of the Queen Charlotte basin. Previous workers had interpreted seafloor escarpments paralleling the trough margins to indicate that the location of Moresby Trough was controlled by renewed or continued activity on Tertiary-aged faults. A multi-channel seismic line across Moresby Trough shows that such an escarpment on the seafloor does not correlate to faults either in the Tertiary basin fill or the underlying basement. Tertiary reflectors are continuous underneath Moresby Trough; the seafloor escarpment is an erosional feature and was not created by reactivation of Tertiary structures. Trough erosion and subsequent fill (up to 175 m thick) are entirely of Quaternary age.

The evolving contribution of border faults and intra-rift faults in early-stage East African rifts: insights from the Natron (Tanzania) and Magadi (Kenya) basins

NASA Astrophysics Data System (ADS)

Muirhead, J.; Kattenhorn, S. A.; Dindi, E.; Gama, R.

2013-12-01

In the early stages of continental rifting, East African Rift (EAR) basins are conventionally depicted as asymmetric basins bounded on one side by a ~100 km-long border fault. As rifting progresses, strain concentrates into the rift center, producing intra-rift faults. The timing and nature of the transition from border fault to intra-rift-dominated strain accommodation is unclear. Our study focuses on this transitional phase of continental rifting by exploring the spatial and temporal evolution of faulting in the Natron (border fault initiation at ~3 Ma) and Magadi (~7 Ma) basins of northern Tanzania and southern Kenya, respectively. We compare the morphologies and activity histories of faults in each basin using field observations and remote sensing in order to address the relative contributions of border faults and intra-rift faults to crustal strain accommodation as rifting progresses. The ~500 m-high border fault along the western margin of the Natron basin is steep compared to many border faults in the eastern branch of the EAR, indicating limited scarp degradation by mass wasting. Locally, the escarpment shows open fissures and young scarps 10s of meters high and a few kilometers long, implying ongoing border fault activity in this young rift. However, intra-rift faults within ~1 Ma lavas are greatly eroded and fresh scarps are typically absent, implying long recurrence intervals between slip events. Rift-normal topographic profiles across the Natron basin show the lowest elevations in the lake-filled basin adjacent to the border fault, where a number of hydrothermal springs along the border fault system expel water into the lake. In contrast to Natron, a ~1600 m high, densely vegetated, border fault escarpment along the western edge of the Magadi basin is highly degraded; we were unable to identify evidence of recent rupturing. Rift-normal elevation profiles indicate the focus of strain has migrated away from the border fault into the rift center, where faults pervasively dissect 1.2-0.8 Ma trachyte lavas. Unlike Natron, intra-rift faults in the Magadi basin exhibit primarily steep, little-degraded fault scarps, implying greater activity than Natron intra-rift faults. Numerous fault-associated springs feed water into perennial Lake Magadi, which has no surface drainage input, yet survives despite a high evaporation rate that has created economically viable evaporite deposits. Calcite vein-filled joints are common along fault zones around Lake Magadi, as well as several cm veins around columnar joints that imply isotropic expansion of the fracture network under high pressures of CO2-rich fluids. Our work indicates that the locus of strain in this portion of the EAR transfers from the border fault to the center of the rift basin some time between 3 and 7 million years after rift initiation. This transition likely reflects the evolving respective roles of crustal flexure and magma budget in focusing strain, as well as the hydrothermal fluid budget along evolving fault zones.

A review on data-driven fault severity assessment in rolling bearings

NASA Astrophysics Data System (ADS)

Cerrada, Mariela; Sánchez, René-Vinicio; Li, Chuan; Pacheco, Fannia; Cabrera, Diego; Valente de Oliveira, José; Vásquez, Rafael E.

2018-01-01

Health condition monitoring of rotating machinery is a crucial task to guarantee reliability in industrial processes. In particular, bearings are mechanical components used in most rotating devices and they represent the main source of faults in such equipments; reason for which research activities on detecting and diagnosing their faults have increased. Fault detection aims at identifying whether the device is or not in a fault condition, and diagnosis is commonly oriented towards identifying the fault mode of the device, after detection. An important step after fault detection and diagnosis is the analysis of the magnitude or the degradation level of the fault, because this represents a support to the decision-making process in condition based-maintenance. However, no extensive works are devoted to analyse this problem, or some works tackle it from the fault diagnosis point of view. In a rough manner, fault severity is associated with the magnitude of the fault. In bearings, fault severity can be related to the physical size of fault or a general degradation of the component. Due to literature regarding the severity assessment of bearing damages is limited, this paper aims at discussing the recent methods and techniques used to achieve the fault severity evaluation in the main components of the rolling bearings, such as inner race, outer race, and ball. The review is mainly focused on data-driven approaches such as signal processing for extracting the proper fault signatures associated with the damage degradation, and learning approaches that are used to identify degradation patterns with regards to health conditions. Finally, new challenges are highlighted in order to develop new contributions in this field.

The Active Fault Parameters for Time-Dependent Earthquake Hazard Assessment in Taiwan

NASA Astrophysics Data System (ADS)

Lee, Y.; Cheng, C.; Lin, P.; Shao, K.; Wu, Y.; Shih, C.

2011-12-01

Taiwan is located at the boundary between the Philippine Sea Plate and the Eurasian Plate, with a convergence rate of ~ 80 mm/yr in a ~N118E direction. The plate motion is so active that earthquake is very frequent. In the Taiwan area, disaster-inducing earthquakes often result from active faults. For this reason, it's an important subject to understand the activity and hazard of active faults. The active faults in Taiwan are mainly located in the Western Foothills and the Eastern longitudinal valley. Active fault distribution map published by the Central Geological Survey (CGS) in 2010 shows that there are 31 active faults in the island of Taiwan and some of which are related to earthquake. Many researchers have investigated these active faults and continuously update new data and results, but few people have integrated them for time-dependent earthquake hazard assessment. In this study, we want to gather previous researches and field work results and then integrate these data as an active fault parameters table for time-dependent earthquake hazard assessment. We are going to gather the seismic profiles or earthquake relocation of a fault and then combine the fault trace on land to establish the 3D fault geometry model in GIS system. We collect the researches of fault source scaling in Taiwan and estimate the maximum magnitude from fault length or fault area. We use the characteristic earthquake model to evaluate the active fault earthquake recurrence interval. In the other parameters, we will collect previous studies or historical references and complete our parameter table of active faults in Taiwan. The WG08 have done the time-dependent earthquake hazard assessment of active faults in California. They established the fault models, deformation models, earthquake rate models, and probability models and then compute the probability of faults in California. Following these steps, we have the preliminary evaluated probability of earthquake-related hazards in certain faults in Taiwan. By accomplishing active fault parameters table in Taiwan, we would apply it in time-dependent earthquake hazard assessment. The result can also give engineers a reference for design. Furthermore, it can be applied in the seismic hazard map to mitigate disasters.

A grid-doubling finite-element technique for calculating dynamic three-dimensional spontaneous rupture on an earthquake fault

USGS Publications Warehouse

Barall, Michael

2009-01-01

We present a new finite-element technique for calculating dynamic 3-D spontaneous rupture on an earthquake fault, which can reduce the required computational resources by a factor of six or more, without loss of accuracy. The grid-doubling technique employs small cells in a thin layer surrounding the fault. The remainder of the modelling volume is filled with larger cells, typically two or four times as large as the small cells. In the resulting non-conforming mesh, an interpolation method is used to join the thin layer of smaller cells to the volume of larger cells. Grid-doubling is effective because spontaneous rupture calculations typically require higher spatial resolution on and near the fault than elsewhere in the model volume. The technique can be applied to non-planar faults by morphing, or smoothly distorting, the entire mesh to produce the desired 3-D fault geometry. Using our FaultMod finite-element software, we have tested grid-doubling with both slip-weakening and rate-and-state friction laws, by running the SCEC/USGS 3-D dynamic rupture benchmark problems. We have also applied it to a model of the Hayward fault, Northern California, which uses realistic fault geometry and rock properties. FaultMod implements fault slip using common nodes, which represent motion common to both sides of the fault, and differential nodes, which represent motion of one side of the fault relative to the other side. We describe how to modify the traction-at-split-nodes method to work with common and differential nodes, using an implicit time stepping algorithm.

Common Faults and Their Prioritization in Small Commercial Buildings: February 2017 - December 2017

DOE Office of Scientific and Technical Information (OSTI.GOV)

Frank, Stephen M; Kim, Janghyun; Cai, Jie

To support an ongoing project at NREL titled 'An Open, Cloud-Based Platform for Whole-Building Fault Detection and Diagnostics' (work breakdown structure number 3.2.6.18 funded by the Department of Energy Building Technologies Office), this report documents faults that are commonly found in small commercial buildings (with a floor area of 10,000 ft2 or less) based on a literature review and discussions with building commissioning experts. It also provides a list of prioritized faults based on an estimation of the prevalence, energy impact, and financial impact of each fault.

Fault zone architecture of a major oblique-slip fault in the Rawil depression, Western Helvetic nappes, Switzerland

NASA Astrophysics Data System (ADS)

Gasser, D.; Mancktelow, N. S.

2009-04-01

The Helvetic nappes in the Swiss Alps form a classic fold-and-thrust belt related to overall NNW-directed transport. In western Switzerland, the plunge of nappe fold axes and the regional distribution of units define a broad depression, the Rawil depression, between the culminations of Aiguilles Rouge massif to the SW and Aar massif to the NE. A compilation of data from the literature establishes that, in addition to thrusts related to nappe stacking, the Rawil depression is cross-cut by four sets of brittle faults: (1) SW-NE striking normal faults that strike parallel to the regional fold axis trend, (2) NW-SE striking normal faults and joints that strike perpendicular to the regional fold axis trend, and (3) WNW-ESE striking normal plus dextral oblique-slip faults as well as (4) WSW-ENE striking normal plus dextral oblique-slip faults that both strike oblique to the regional fold axis trend. We studied in detail a beautifully exposed fault from set 3, the Rezli fault zone (RFZ) in the central Wildhorn nappe. The RFZ is a shallow to moderately-dipping (ca. 30-60˚) fault zone with an oblique-slip displacement vector, combining both dextral and normal components. It must have formed in approximately this orientation, because the local orientation of fold axes corresponds to the regional one, as does the generally vertical orientation of extensional joints and veins associated with the regional fault set 2. The fault zone crosscuts four different lithologies: limestone, intercalated marl and limestone, marl and sandstone, and it has a maximum horizontal dextral offset component of ~300 m and a maximum vertical normal offset component of ~200 m. Its internal architecture strongly depends on the lithology in which it developed. In the limestone, it consists of veins, stylolites, cataclasites and cemented gouge, in the intercalated marls and limestones of anastomosing shear zones, brittle fractures, veins and folds, in the marls of anastomosing shear zones, pressure solution seams and veins and in the sandstones of coarse breccia and veins. Later, straight, sharp fault planes cross-cut all these features. In all lithologies, common veins and calcite-cemented fault rocks indicate the strong involvement of fluids during faulting. Today, the southern Rawil depression and the Rhone Valley belong to one of the seismically most active regions in Switzerland. Seismogenic faults interpreted from earthquake focal mechanisms strike ENE-WSW to WNW-ESE, with dominant dextral strike-slip and minor normal components and epicentres at depths of < 15 km. All three Neogene fault sets (2-4) could have been active under the current stress field inferred from the current seismicity. This implies that the same mechanisms that formed these fault zones in the past may still persist at depth. The Rezli fault zone allows the detailed study of a fossil fault zone that can act as a model for processes still occurring at deeper levels in this seismically active region.

Fault-Related Sanctuaries

NASA Astrophysics Data System (ADS)

Piccardi, L.

2001-12-01

Beyond the study of historical surface faulting events, this work investigates the possibility, in specific cases, of identifying pre-historical events whose memory survives in myths and legends. The myths of many famous sacred places of the ancient world contain relevant telluric references: "sacred" earthquakes, openings to the Underworld and/or chthonic dragons. Given the strong correspondence with local geological evidence, these myths may be considered as describing natural phenomena. It has been possible in this way to shed light on the geologic origin of famous myths (Piccardi, 1999, 2000 and 2001). Interdisciplinary researches reveal that the origin of several ancient sanctuaries may be linked in particular to peculiar geological phenomena observed on local active faults (like ground shaking and coseismic surface ruptures, gas and flames emissions, strong underground rumours). In many of these sanctuaries the sacred area is laid directly above the active fault. In a few cases, faulting has affected also the archaeological relics, right through the main temple (e.g. Delphi, Cnidus, Hierapolis of Phrygia). As such, the arrangement of the cult site and content of relative myths suggest that specific points along the trace of active faults have been noticed in the past and worshiped as special `sacred' places, most likely interpreted as Hades' Doors. The mythological stratification of most of these sanctuaries dates back to prehistory, and points to a common derivation from the cult of the Mother Goddess (the Lady of the Doors), which was largely widespread since at least 25000 BC. The cult itself was later reconverted into various different divinities, while the `sacred doors' of the Great Goddess and/or the dragons (offspring of Mother Earth and generally regarded as Keepers of the Doors) persisted in more recent mythologies. Piccardi L., 1999: The "Footprints" of the Archangel: Evidence of Early-Medieval Surface Faulting at Monte Sant'Angelo (Gargano, Italy). European Union of Geophysics Congress, Strasbourg, March 1999. Piccardi L., 2000: Active faulting at Delphi (Greece): seismotectonic remarks and a hypothesis for the geological environment of a myth. Geology, 28, 651-654. Piccardi L., 2001: Seismotectonic Origin of the Monster of Loch Ness. Earth System Processes, Joint Meeting of G.S.A. and G.S.L., Edinburgh, June 2001.

Fault activation and induced seismicity in geological carbon storage – Lessons learned from recent modeling studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rutqvist, Jonny; Rinaldi, Antonio P.; Cappa, Frederic

In the light of current concerns related to induced seismicity associated with geological carbon sequestration (GCS), this paper summarizes lessons learned from recent modeling studies on fault activation, induced seismicity, and potential for leakage associated with deep underground carbon dioxide (CO 2) injection. Model simulations demonstrate that seismic events large enough to be felt by humans require brittle fault properties and continuous fault permeability allowing pressure to be distributed over a large fault patch to be ruptured at once. Heterogeneous fault properties, which are commonly encountered in faults intersecting multilayered shale/sandstone sequences, effectively reduce the likelihood of inducing felt seismicitymore » and also effectively impede upward CO 2 leakage. A number of simulations show that even a sizable seismic event that could be felt may not be capable of opening a new flow path across the entire thickness of an overlying caprock and it is very unlikely to cross a system of multiple overlying caprock units. Site-specific model simulations of the In Salah CO 2 storage demonstration site showed that deep fractured zone responses and associated microseismicity occurred in the brittle fractured sandstone reservoir, but at a very substantial reservoir overpressure close to the magnitude of the least principal stress. We conclude by emphasizing the importance of site investigation to characterize rock properties and if at all possible to avoid brittle rock such as proximity of crystalline basement or sites in hard and brittle sedimentary sequences that are more prone to injection-induced seismicity and permanent damage.« less

Fault activation and induced seismicity in geological carbon storage – Lessons learned from recent modeling studies

DOE PAGES

Rutqvist, Jonny; Rinaldi, Antonio P.; Cappa, Frederic; ...

2016-09-20

In the light of current concerns related to induced seismicity associated with geological carbon sequestration (GCS), this paper summarizes lessons learned from recent modeling studies on fault activation, induced seismicity, and potential for leakage associated with deep underground carbon dioxide (CO 2) injection. Model simulations demonstrate that seismic events large enough to be felt by humans require brittle fault properties and continuous fault permeability allowing pressure to be distributed over a large fault patch to be ruptured at once. Heterogeneous fault properties, which are commonly encountered in faults intersecting multilayered shale/sandstone sequences, effectively reduce the likelihood of inducing felt seismicitymore » and also effectively impede upward CO 2 leakage. A number of simulations show that even a sizable seismic event that could be felt may not be capable of opening a new flow path across the entire thickness of an overlying caprock and it is very unlikely to cross a system of multiple overlying caprock units. Site-specific model simulations of the In Salah CO 2 storage demonstration site showed that deep fractured zone responses and associated microseismicity occurred in the brittle fractured sandstone reservoir, but at a very substantial reservoir overpressure close to the magnitude of the least principal stress. We conclude by emphasizing the importance of site investigation to characterize rock properties and if at all possible to avoid brittle rock such as proximity of crystalline basement or sites in hard and brittle sedimentary sequences that are more prone to injection-induced seismicity and permanent damage.« less

Seismicity patterns of earthquake swarms in the West-Bohemia/Vogtland as a hint to their triggering mechanisms

NASA Astrophysics Data System (ADS)

Fischer, T.; Hainzl, S.; Horalek, J.; Michalek, J.

2009-04-01

The distribution of West-Bohemia/Vogtland seismicity is clustered both in time and space. The time occurrence is manifested in a variety of forms including both swarms with fast and with slow energy release that last from hours to months and also solitary events. The lateral distribution of seismicity is limited to a small number of focal zones, which have been periodically reactivated during the past 18 years of instrumental observations. We don't observe an apparent migration of seismic activity. Instead, the activity has been switching between the focal zones with its largest part residing in the area of Nový Kostel, which dominates with 85% of energy release. Analysis of the activity in the period 1991-2007 has revealed that the interevent times of the seismic activity measured between events in separated focal zones show increased occurrence for time intervals below 8 hours. This fast switching of activity among focal zones with mutual distances above 10 km shows that the seismicity is correlated in a broader area and points to a common triggering force acting in the whole region of West-Bohemia/Vogtland. This force could be stress changes due to earth tides, barometric pressure disturbances, or an abrupt change of the crustal fluid pore pressure. It would trigger the activity in the focal zones which are close to failure. Depending on the local stress and mechanical conditions in each zone, the activity could either cease or an earthquake swarm could be initiated. To disclose the forces governing the already running swarm activity we investigated the space-time relations between consecutive earthquakes of the 2000 swarm. The swarm lasted four months and consisted of more that 8000 M=3.3 strike-slip microearthquakes, which were located along a fault plane at depths 6.5-10.5 km and showed a common rake angle of 30°. We found that the relative positions of consecutive event pairs showed maximum occurrence in the slip-parallel directions. Comparison with the complete Coulomb stress change upon the fault plane due to a typical rupture showed that the observed elongation of the space-time distribution of the relative positions can be explained by a common effect of both static and dynamic stress changes, which act on different distance and timescale. The relatively small magnitudes of the Coulomb stress changes upon the fault plane in the order of 10 kPa, which are supposed to trigger the swarm events, support the idea that high pressurized crustal fluids increase the pore pressure and bring the fault close to its critical state. This is in accordance with the results of our model of the 2000 swarm which took into account both the fluid diffusion and stress triggering. The model consisted of a planar brittle patch placed in a 3-D elastic half-space divided into the number of cells with variable strength. The individual cells rupture when the Coulomb failure criterion including both shear stress and pore pressure is fulfilled. The initial tectonic loading of the patch is presumed subcritical until the pore pressure of diffused fluids brings it into a critical state. Then the earthquake activity is governed by the stress changes due to the co-seismic and post-seismic slip, so that mutual triggering between ruptured cells occurs. It turns out that once the pressurized crustal fluids bring a fault from a subcritical steady-state into a critical state, the self-organization prevails in governing the swarm activity. This is in accordance with the possible effect of a regionally scaled force bringing one or multiple focal zones to the critical state and trigger seismicity. The recent M=3.7 swarm from October 2008 occurred at the identical fault plane as the 2000 swarm and showed a similar areal extent of the ruptured area. The overall migration of activity with first events at the bottom of the activated fault patch and the last events in the northward tail at its top indicates similar triggering scenario. However, the step-wise monotonous event migration in the first swarm period differs significantly from the complex migration patterns of the 2000 swarm, A further analysis is needed to learn if such a pattern could be due to a fluid or magma propagation along the fault plane.

A Classification of Geometric Styles for Paleoseismic Trenches across Normal Faults in the North Island, New Zealand: An Interplay between Tectonic and Erosional/Depositional Processes

NASA Astrophysics Data System (ADS)

Villamor, P.; Berryman, K.; Langridge, R.; van Dissen, R.; Persaud, M.; Canora, C.; Nicol, A.; Alloway, B.; Litchfield, N.; Cochran, U.; Stirling, M.; Mouslopoulou, V.; Wilson, K.

2006-12-01

Over the last ~15 years we have excavated 73 trenches across active normal faults in the Taupo and Hauraki Rifts, North Island, New Zealand. The stratigraphy in these trenches is quite similar because of the predominance of volcanic and volcanic-derived deposits, sourced from the active Taupo Volcanic Zone. These deposits, whether alluvial (reworked, mainly volcanics) or volcanic (tephra), are all characterized by relative loose, to moderately loose, medium-size gravel and sands, and cohesive (sticky) clays. The homogeneity of the materials and of the sedimentation rates across these paleoseismic trenches has allowed us to assess the influence of different materials on the faulting style. The predominant types of material, their relative thickness, and their stratigraphic order (e.g. whether cohesive materials are overlying or underlying loose materials) in the trench strongly determine the deformation style when subjected to normal faulting. However, the final geometric relation between the sedimentary layers and the faults also depends on the sediment depositional environment (e.g., alluvial vs air fall deposition), the fault dip, and cumulative displacement (i.e., the size of the scarp). For example, the cumulative displacement of the fault conditions the amount of erosion/deposition at/derived from the scarp itself. When we combine observations from the tectonic deformation style and from geometries derived from erosional/depositional processes, we can define at least five "geometric styles" present in paleoseismic trenches in our study area: 1) folding, where the fault does not reach the upper layers, and relative displacement of the fault walls is achieved by folding (dragging of the layer); 2) folding-large cracks, where relative movement of the fault walls is achieved by folding and opening of large fissures; 3) faulting, the most common style where a layer is displaced along the fault plane; 4) faulting- erosion, similar to the previous style but with larger cumulative displacements which cause large amounts of erosion and/or deposition at the fault scarp; and 5) faulting-toppling, when due to gravitational forces the materials on the up-thrown side of the fault topple towards the downthrown side causing rotation of the fault plane itself, which induces a geometry of "false reverse fault". These observations can be used to analyze the criteria to identify individual earthquakes within each "geometric style". We present examples from New Zealand to describe the "geometric styles", their faulting criteria and the uncertainties associated with these criteria.

Formation and inversion of transtensional basins in the western part of the Lachlan Fold Belt, Australia, with emphasis on the Cobar Basin

NASA Astrophysics Data System (ADS)

Glen, R. A.

The Palaeozoic history of the western part of the Lachlan Fold Belt in New South Wales was dominated by strike-slip tectonics. In the latest Silurian to late Early Devonian, an area of crust >25,000 km 2 lying west of the Gilmore Suture underwent regional sinistral transtension, leading to the development of intracratonic successor basins, troughs and flanking shelves. The volcaniclastic deep-water Mount Hope Trough and Rast Trough, the siliciclastic Cobar Basin and the volcanic-rich Canbelego-Mineral Hill Belt of the Kopyje Shelf all were initiated around the Siluro-Devonian boundary. They all show clear evidence of having evolved by both active syn-rift processes and passive later post-rift (sag-phase) processes. Active syn-rift faulting is best documented for the Cobar Basin and Mount Hope Trough. In the former case, the synchronous activity on several fault sets suggests that the basin formed by sinistral transtension in response to a direction of maximum extension oriented NE-SW. Structures formed during inversion of the Cobar Basin and Canbelego-Mineral Hill Belt indicate closure under a dextral transpressive strain regime, with a far-field direction of maximum shortening oriented NE-SW. In the Cobar Basin, shortening was partitioned into two structural zones. A high-strain zone in the east was developed into a positive half-flower structure by re-activation of early faults and by formation of short-cut thrusts, some with strike-slip movement, above an inferred steep strike-slip fault. Intense subvertical cleavage, a steep extension lineation and variably plunging folds are also present. A lower-strain zone to the west developed by syn-depositional faults being activated as thrusts soling into a gently dipping detachment. A subvertical cleavage and steep extension lineation are locally present, and variably plunging folds are common. Whereas Siluro-Devonian basin-opening appeared to be synchronous in the western part of the fold belt, the different period of basin inversion in the Cobar region (late Early Devonian and Carboniferous) may reflect different movement histories on the master strike-slip faults in this part of the fold belt, the Gilmore Suture and Kiewa Fault.

Geomorphic indices indicated differential active tectonics of the Longmen Shan

NASA Astrophysics Data System (ADS)

Gao, M.; Xu, X.; Tan, X.

2012-12-01

The Longmen Shan thrust belt is located at the eastern margin of the Tibetan Plateau. It is a region of rapid active tectonics with high erosion rates and dense vegetation. The structure of the Longmen Shan region is dominated by northeast-trending thrusts and overturned folds that verge to the east and southeast (Burchfiel et al. 1995, Chen and Wilson 1996). The Longmen Shan thrust belt consists of three major faults from west to east: back-range fault, central fault, and frontal-range fault. The Mw 7.9 Wenchuan earthquake ruptured two large thrust faults along the Longmen Shan thrust belt (Xiwei et al., 2009). In this paper, we focus on investigating the spatial variance of tectonic activeness from the back-range fault to the frontal-range fault, particular emphasis on the differential recent tectonic activeness reflected by the hypsometry and the asymmetric factor of the drainage. Results from asymmetric factor indicate the back-rannge thrust fault on the south of the Maoxian caused drainage basins tilted on the hanging wall. For the north of the Maoxian, the strike-slip fault controlled the shapes of the drainage basins. Constantly river capture caused the expansion of the drainage basins which traversed by the fault. The drainages on the central fault and the frontal-range fault are also controlled by the fault slip. The drainage asymmetric factor suggested the central and southern segments of the Longmen Shan are more active than the northern segment, which is coherence with results of Huiping et al. (2010). The results from hypsometry show the back-range fault is the most active fault among the three major faults. Central fault is less active than the back-range fault but more active than the frontal-range fault. Beichuan is identified as the most active area along the central fault. Our geomorphic indices reflect an overall eastward decreasing of tectonic activeness of the Longmen Shan thrust belt.

The Role of Near-Fault Relief in Creating and Maintaining Strike-Slip Landscape Features

NASA Astrophysics Data System (ADS)

Harbert, S.; Duvall, A. R.; Tucker, G. E.

2016-12-01

Geomorphic landforms, such as shutter ridges, offset river terraces, and deflected stream channels, are often used to assess the activity and slip rates of strike-slip faults. However, in some systems, such as parts of the Marlborough Fault System (South Island, NZ), an active strike-slip fault does not leave a strong landscape signature. Here we explore the factors that dampen or enhance the landscape signature of strike-slip faulting using the Channel-Hillslope Integrated Landscape Development model (CHILD). We focus on variables affecting the length of channel offsets, which enhance the signature of strike-slip motion, and the frequency of stream captures, which eliminate offsets and reduce this signature. We model a strike-slip fault that passes through a mountain ridge, offsetting streams that drain across this fault. We use this setup to test the response of channel offset length and capture frequency to fault characteristics, such as slip rate and ratio of lateral to vertical motion, and to landscape characteristics, such as relief contrasts controlled by erodibility. Our experiments show that relief downhill of the fault, whether generated by differential uplift across the fault or by an erodibility contrast, has the strongest effect on offset length and capture frequency. This relief creates shutter ridges, which block and divert streams while being advected along a fault. Shutter ridges and the streams they divert have long been recognized as markers of strike-slip motion. Our results show specifically that the height of shutter ridges is most responsible for the degree to which they create long channel offsets by preventing stream captures. We compare these results to landscape metrics in the Marlborough Fault System, where shutter ridges are common and often lithologically controlled. We compare shutter ridge length and height to channel offset length in order to assess the influence of relief on offset channel features in a real landscape. Based on our model and field results, we conclude that vertical relief is important for generating and preserving offset features that are viewed as characteristic of a strike-slip fault. Therefore, the geomorphic expression of a fault may be dependent on characteristics of the surrounding landscape rather than primarily a function of the nature of slip on the fault.

Illite authigenesis during faulting and fluid flow - a microstructural study of fault rocks

NASA Astrophysics Data System (ADS)

Scheiber, Thomas; Viola, Giulio; van der Lelij, Roelant; Margreth, Annina

2017-04-01

Authigenic illite can form synkinematically during slip events along brittle faults. In addition it can also crystallize as a result of fluid flow and associated mineral alteration processes in hydrothermal environments. K-Ar dating of illite-bearing fault rocks has recently become a common tool to constrain the timing of fault activity. However, to fully interpret the derived age spectra in terms of deformation ages, a careful investigation of the fault deformation history and architecture at the outcrop-scale, ideally followed by a detailed mineralogical analysis of the illite-forming processes at the micro-scale, are indispensable. Here we integrate this methodological approach by presenting microstructural observations from the host rock immediately adjacent to dated fault gouges from two sites located in the Rolvsnes granodiorite (Bømlo, western Norway). This granodiorite experienced multiple episodes of brittle faulting and fluid-induced alteration, starting in the Mid Ordovician (Scheiber et al., 2016). Fault gouges are predominantly associated with normal faults accommodating mainly E-W extension. K-Ar dating of illites separated from representative fault gouges constrains deformation and alteration due to fluid ingress from the Permian to the Cretaceous, with a cluster of ages for the finest (<0.1 µm) fraction in the early to middle Jurassic. At site one, high-resolution thin section structural mapping reveals a complex deformation history characterized by several coexisting types of calcite veins and seven different generations of cataclasite, two of which contain a significant amount of authigenic and undoubtedly deformation-related illite. At site two, fluid ingress along and adjoining the fault core induced pervasive alteration of the host granodiorite. Quartz is crosscut by calcite veinlets whereas plagioclase, K-feldspar and biotite are almost completely replaced by the main alteration products kaolin, quartz and illite. Illite-bearing micro-domains were physically separated by means of microsawing and drilling devices. K-Ar and XRD data from these separates are compared with bulk K-Ar and XRD data from the adjacent fault gouges, which may help to further unravel complex histories archived in multiply activated brittle fault zones. Scheiber, T., Viola, G., Wilkinson, C.M., Ganerød, M., Skår, Ø., and D. Gasser (2016): Direct 40Ar/39Ar dating of Late-Ordovician and Silurian brittle faulting in the southwestern Norwegian Caledonides. Terra Nova 28, 374-382.

Combined structural analysis and dating of authigenic/synkinematic illite: A step towards unravelling brittle faulting processes in time and space

NASA Astrophysics Data System (ADS)

Viola, Giulio

2017-04-01

Faulting accommodates momentous deformation and its style reflects the complex interplay of often transient processes such as friction, fluid flow and rheological changes within generally dilatant systems. Brittle faults are thus unique archives of the stress state and the physical and chemical conditions at the time of both initial strain localization and subsequent slip(s) during structural reactivation. Opening those archives, however, may be challenging due to the commonly convoluted (if not even chaotic) nature of brittle fault architectures and fault rocks. This is because, once formed, faults are extremely sensitive to variations in stress field and environmental conditions and are prone to readily slip in a variety of conditions, also in regions affected by only weak, far-field stresses. The detailed, multi-scalar structural analysis of faults and of fault rocks has to be the starting point for any study aiming at reconstructing the complex framework of brittle deformation. However, considering that present-day exposures of faults only represent the end result of the faults' often protracted and heterogeneous histories, the obtained structural and mechanical results have to be integrated over the life span of the studied fault system. Dating of synkinematic illite/muscovite to constrain the time-integrated evolution of faults is therefore the natural addition to detailed structural studies. By means of selected examples it will be demonstrated how careful structural analysis integrated with illite characterization and K-Ar dating allows the high-resolution reconstruction of brittle deformation histories and, in turn, multiple constraints to be placed on strain localization, deformation mechanisms, fluid flow, mineral alteration and authigenesis within actively deforming brittle fault rocks. Complex and long brittle histories can thus be reconstructed and untangled in any tectonic setting.

The Hills are Alive: Dynamic Ridges and Valleys in a Strike-Slip Environment

NASA Astrophysics Data System (ADS)

Duvall, A. R.; Tucker, G. E.

2014-12-01

Strike-slip fault zones have long been known for characteristic landforms such as offset and deflected rivers, linear strike-parallel valleys, and shutter ridges. Despite their common presence, questions remain about the mechanics of how these landforms arise or how their form varies as a function of slip rate, geomorphic process, or material properties. We know even less about what happens far from the fault, in drainage basin headwaters, as a result of strike-slip motion. Here we explore the effects of horizontal fault slip rate, bedrock erodibility, and hillslope diffusivity on river catchments that drain across an active strike-slip fault using the CHILD landscape evolution model. Model calculations demonstrate that lateral fault motion induces a permanent state of landscape disequilibrium brought about by fault offset-generated river lengthening alternating with abrupt shortening due to stream capture. This cycle of shifting drainage patterns and base level change continues until fault motion ceases thus creating a perpetual state of transience unique to strike-slip systems. Our models also make the surprising prediction that, in some cases, hillslope ridges oriented perpendicular to the fault migrate laterally in conjunction with fault motion. Ridge migration happens when slip rate is slow enough and/or diffusion and river incision are fast enough that the hillslopes can respond to the disequilibrium brought about by strike-slip motion. In models with faster slip rates, stronger rocks or less-diffusive hillslopes, ridge mobility is limited or arrested despite the fact that the process of river lengthening and capture continues. Fast-slip cases also develop prominent steep fault-facing hillslope facets proximal to the fault valley and along-strike topographic profiles with reduced local relief between ridges and valleys. Our results demonstrate the dynamic nature of strike-slip landscapes that vary systematically with a ratio of bedrock erodibility (K) and hillslope diffusivity (D) to the rate of horizontal advection of topography (v). These results also reveal a potential set of recognizable geomorphic signatures within strike-slip systems that should be looked to as indicators of fault activity and/or material properties.

Recent tectonic stress field, active faults and geothermal fields (hot-water type) in China

NASA Astrophysics Data System (ADS)

Wan, Tianfeng

1984-10-01

It is quite probable that geothermal fields of the hot-water type in China do not develop in the absence of recently active faults. Such active faults are all controlled by tectonic stress fields. Using the data of earthquake fault-plane solutions, active faults, and surface thermal manifestations, a map showing the recent tectonic stress field, and the location of active faults and geothermal fields in China is presented. Data collected from 89 investigated prospects with geothermal manifestations indicate that the locations of geothermal fields are controlled by active faults and the recent tectonic stress field. About 68% of the prospects are controlled by tensional or tensional-shear faults. The angle between these faults and the direction of maximum compressive stress is less than 45°, and both tend to be parallel. About 15% of the prospects are controlled by conjugate faults. Another 14% are controlled by compressive-shear faults where the angle between these faults and the direction maximum compressive stress is greater than 45°.

Structural geology of the proposed site area for a high-level radioactive waste repository, Yucca Mountain, Nevada

USGS Publications Warehouse

Potter, C.J.; Day, W.C.; Sweetkind, D.S.; Dickerson, R.P.

2004-01-01

Geologic mapping and fracture studies have documented the fundamental patterns of joints and faults in the thick sequence of rhyolite tuffs at Yucca Mountain, Nevada, the proposed site of an underground repository for high-level radioactive waste. The largest structures are north-striking, block-bounding normal faults (with a subordinate left-lateral component) that divide the mountain into numerous 1-4-km-wide panels of gently east-dipping strata. Block-bounding faults, which underwent Quaternary movement as well as earlier Neogene movement, are linked by dominantly northwest-striking relay faults, especially in the more extended southern part of Yucca Mountain. Intrablock faults are commonly short and discontinuous, except those on the more intensely deformed margins of the blocks. Lithologic properties of the local tuff stratigraphy strongly control the mesoscale fracture network, and locally the fracture network has a strong influence on the nature of intrablock faulting. The least faulted part of Yucca Mountain is the north-central part, the site of the proposed repository. Although bounded by complex normal-fault systems, the 4-km-wide central block contains only sparse intrablock faults. Locally intense jointing appears to be strata-bound. The complexity of deformation and the magnitude of extension increase in all directions away from the proposed repository volume, especially in the southern part of the mountain where the intensity of deformation and the amount of vertical-axis rotation increase markedly. Block-bounding faults were active at Yucca Mountain during and after eruption of the 12.8-12.7 Ma Paintbrush Group, and significant motion on these faults postdated the 11.6 Ma Rainier Mesa Tuff. Diminished fault activity continued into Quaternary time. Roughly half of the stratal tilting in the site area occurred after 11.6 Ma, probably synchronous with the main pulse of vertical-axis rotation, which occurred between 11.6 and 11.45 Ma. Studies of sequential formation of tectonic joints, in the context of regional paleostress studies, indicate that north- and northwest-striking joint sets formed coevally with the main faulting episode during regional east-northeast-west-southwest extension and that a prominent northeast-striking joint set formed later, probably after 9 Ma. These structural analyses contribute to the understanding of several important issues at Yucca Mountain, including potential hydrologic pathways, seismic hazards, and fault-displacement hazards. ?? 2004 Geological Society of America.

Near Fault Observatories: multidisciplinary research infrastructures, high resolution data and scientific products available through dedicated services implemented within the EPOS-IP project

NASA Astrophysics Data System (ADS)

Festa, Gaetano; Chiaraluce, Lauro; Ergintav, Semih; Bernard, Pascal; Clinton, John; Marmureanu, Alexandru; Tataru, Dragos; Vogfjord, Kristin

2017-04-01

Near Fault Observatories (NFOs) are innovative research infrastructures based on dense, state of the art networks of multi-parametric sensors that continuously monitor the underlying Earth instability processes over a broad time interval. They aim at understanding the physical/chemical processes responsible for earthquakes and faulting and tracking their evolution over time by enabling advancements in ground shaking prediction. EPOS-IP is aimed at contributing in creating and harmonizing data and products distributors from seven NFOs, operating on different tectonic regimes and different areas of Europe. They include plate boundary systems at South Iceland Seismic Zone, the Marmara Sea and the Corinth rift. In mountain settings, NFOs monitor the Alto Tiberina and Irpinia faults in the Apennine mountain range, the Valais region in the Alps, and the Vrancea fault in the Carpathian Mountains. They monitor diverse faulting mechanisms (strike-slip, normal and thrust), high to low angle faults, shallow and deep faults, as well as regions with fast and slow strain rate accumulation. The focus of the observatories varies, ranging from small- to large-scale seismicity and includes the role of different parameters such as fluid playing in fault initiation, the internal structure of fault systems, site effects and derived processes such as earthquake generated landslides and tsunamis. In response to their specific objectives, the NFOs operate a diverse set of monitoring instrumentation using seismic, deformation, strain, geochemical and electromagnetic equipment. Since NFO methodological approach is based on extremely dense networks and less common instruments deserving multi-parameter data description, a main goal of this group is to build inclusive and harmonised services supporting the installation over the next decade of tens of near-fault observatories monitoring active faults in different tectonic environments in Europe. The NFO Thematic Core Service (TCS) relies on external platforms and services for accessing to standard data (e.g. seismic and geodetic) and on the direct access to the e-infrastructures of individual NFOs for distribution of non standard data (e.g. strain- and tilt-meters, geochemical data, electro- magneto-telluric data) and high-level data products. To define standards for formats and metadata, the TCS actively participates into the several harmonization groups across EPOS. Two main specific services are under implementation at the TCS level. FRIDGE (EU - NFO Specific Data and Products Gateway and Virtual Laboratory) is a NFO common gateway that enables the specific data and high-level data products availability also furnishing simple visualization tools. CREW (EU - Testing Centre for Early Warning and Source characterization) is a testing facility built on real-time and offline high-resolution data, whose focus is on operating and benchmarking various existing Earthquake Early Warning (EEW) methodologies. The backbone of the testing centre is the Irpinia NFO.

On the physics-based processes behind production-induced seismicity in natural gas fields

NASA Astrophysics Data System (ADS)

Zbinden, Dominik; Rinaldi, Antonio Pio; Urpi, Luca; Wiemer, Stefan

2017-05-01

Induced seismicity due to natural gas production is observed at different sites worldwide. Common understanding states that the pressure drop caused by gas production leads to compaction, which affects the stress field in the reservoir and the surrounding rock formations and hence reactivates preexisting faults and induces earthquakes. In this study, we show that the multiphase fluid flow involved in natural gas extraction activities should be included. We use a fully coupled fluid flow and geomechanics simulator, which accounts for stress-dependent permeability and linear poroelasticity, to better determine the conditions leading to fault reactivation. In our model setup, gas is produced from a porous reservoir, divided into two compartments that are offset by a normal fault. Results show that fluid flow plays a major role in pore pressure and stress evolution within the fault. Fault strength is significantly reduced due to fluid flow into the fault zone from the neighboring reservoir compartment and other formations. We also analyze scenarios for minimizing seismicity after a period of production, such as (i) well shut-in and (ii) gas reinjection. In the case of well shut-in, a highly stressed fault zone can still be reactivated several decades after production has ceased, although on average the shut-in results in a reduction in seismicity. In the case of gas reinjection, fault reactivation can be avoided if gas is injected directly into the compartment under depletion. However, gas reinjection into a neighboring compartment does not stop the fault from being reactivated.

Brittle fracture damage around the Alpine Fault, New Zealand

NASA Astrophysics Data System (ADS)

Williams, J. N.; Toy, V.; Smith, S. A. F.; Boulton, C. J.; Massiot, C.; Mcnamara, D. D.

2017-12-01

We use field and drill-core samples to characterize macro- to micro-scale brittle fracture networks within the hanging-wall of New Zealand's Alpine Fault, an active plate-boundary fault that is approaching the end of its seismic cycle. Fracture density in the hanging-wall is roughly constant for distances of up to 500 m from the principal slip zone gouges (PSZs). Fractures >160 m from the PSZs are typically open and parallel to the regional mylonitic foliation or host rock schistosity, and likely formed as unloading joints during rapid exhumation of the hanging-wall at shallow depths. Fractures within c. 160 m of the PSZs are broadly oriented shear-fractures filled with gouge or cataclasite, and are interpreted to constitute the hanging-wall damage zone of the Alpine Fault. This is comparable to the 60-200 m wide "geophysical damage zone" estimated from low seismic wave velocities surrounding the Alpine Fault. Veins are pervasive within the c. 20 m-thick hanging-wall cataclasites and are most commonly filled by calcite, chlorite, muscovite and K-feldspar. Notably, there is a set of intragranular clast-hosted veins, as well as a younger set of veins that cross-cut both clasts and cataclasite matrix. The intragranular veins formed prior to cataclasis or during synchronous cataclasis and calcite-silicate mineralisation. Broad estimates for the depth of vein formation indicate that the cataclasites formed a c. 20 m wide actively deforming zone at depths of c. 4-8 km. Conversely, the cross-cutting veins are interpreted to represent off-fault damage within relatively indurated cataclasites following slip localization onto the <10 cm wide smectite-bearing PSZ gouges at depths of <4 km. Our observations therefore highlight a strong depth-dependence of the width of the actively deforming zone within the brittle seismogenic crust around the Alpine Fault.

Seismic investigation of the Kunlun Fault: Analysis of the INDEPTH IV 2-D active-source seismic dataset

NASA Astrophysics Data System (ADS)

Seelig, William George

The Tibetan Plateau has experienced significant crustal thickening and deformation since the continental subduction and collision of the Asian and Indian plates in the Eocene. Deformation of the northern Tibetan Plateau is largely accommodated by strike-slip faulting. The Kunlun Fault is a 1000-km long strike-slip fault near the northern boundary of the Plateau that has experienced five magnitude 7.0 or greater earthquakes in the past 100 years and represents a major rheological boundary. Active-source, 2-D seismic reflection/refraction data, collected as part of project INDEPTH IV (International Deep Profiling of Tibet and the Himalaya, phase IV) in 2007, was used to examine the structure and the dip of the Kunlun fault. The INDEPTH IV data was acquired to better understand the tectonic evolution of the northeastern Tibetan Plateau, such as the far-field deformation associated with the continent-continent collision and the potential subduction of the Asian continent beneath northern Tibet. Seismic reflection common depth point (CDP) stacks were examined to look for reflectivity patterns that may be associated with faulting. A possible reflection from the buried North Kunlun Thrust (NKT) is identified at 18-21 km underneath the East Kunlun Mountains, with an estimated apparent dip of 15°S and thrusting to the north. Minimally-processed shot gathers were also inspected for reflections off near-vertical structures such as faults and information on first-order velocity structure. Shot offset and nearest receiver number to reflection was catalogued to increase confidence of picks. Reflections off the North Kunlun (NKF) and South Kunlun Faults (SKF) were identified and analyzed for apparent dip and subsurface geometry. Fault reflection analysis found that the North Kunlun Fault had an apparent dip of approximately 68ºS to an estimated depth of 5 km, while the South Kunlun Fault dipped at approximately 78ºN to an estimated 3.5 km depth. Constraints on apparent dip and geometry of the NKF/SKF and NKT provide information valuable for seismic hazard analysis.

Tectonic controls on rift basin morphology: Evolution of the northern Malawi (Nyasa) rift

NASA Technical Reports Server (NTRS)

Ebinger, C. J.; Deino, A. L.; Tesha, A. L.; Becker, T.; Ring, U.

1993-01-01

Radiometric (K-Ar and Ar-40/Ar-39) age determinations of volcanic and volcaniclastic rocks, combined with structural, gravity, and seismic reflection data, are used to constrain the age of sedimentary strata contained within the seismically and volcanically active northern Malawi (Nyasa) rift and to characterize changes in basin and flank morphologies with time. Faulting and volcanism within the Tukuyu-Karonga basin began at approximately 8.6 Ma, when sediments were deposited in abroad, initially asymmetric lake basin bounded on its northeastern side by a border fault system with minor topographic relief. Extensions, primarily by a slip along the border fault, and subsequent regional isostatic compensation led to the development of a 5-km-deep basin bounded by broad uplifted flanks. Along the low-relief basin margin opposite border fault, younger stratigraphic sequences commonly onlap older wedge-shaped sequences, although their internal geometry is often progradational. Intrabasinal faulting, flankuplift, and basaltic and felsic volcanism from centers at the northern end of the basin became more important at about 2.5 Ma when cross-rift transfer faults developed to link the Tukuyu-Karonga basin to the Rukwa basin. Local uplift and volcanic construction at the northern end of the basin led to a southeastward shift in the basin's depocenter. Sequence boundaries are commonly erosional along this low-relief (hanging wall) margin and conformable in the deep lake basin. The geometry of stratigraphic sequences and the distribution of the erosion indicate that horizontal and vertical crustal movements both across and along the length of the rift basin led to changes in levels of the lake, irrespective of paleoclimatic fluctuations.

Structural features of the Pernicana Fault (M. Etna, Sicily, Italy) inferred by high precise location of the microseismicity

NASA Astrophysics Data System (ADS)

Alparone, S.; Gambino, S.; Mostaccio, A.; Spampinato, S.; Tuvè, T.; Ursino, A.

2009-04-01

The north-eastern flank of Mt. Etna is crossed by an important and active tectonic structure, the Pernicana Fault having a mean strike WNW-ESE. It links westward to the active NE Rift and seems to have an important role in controlling instability processes affecting the eastern flank of the volcano. Recent studies suggest that Pernicana Fault is very active through sinistral, oblique-slip movements and is also characterised by frequent shallow seismicity (depth < 2 km bsl) on the uphill western segment and by remarkable creeping on the downhill eastern one. The Pernicana Fault earthquakes, which can reach magnitudes up to 4.2, sometimes with coseismic surface faulting, caused severe damages to tourist resorts and villages along or close this structure. In the last years, a strong increase of seismicity, also characterized by swarms, was recorded by INGV-CT permanent local seismic network close the Pernicana Fault. A three-step procedure was applied to calculate precise hypocentre locations. In a first step, we chose to apply cross-correlation analysis, in order to easily evaluate the similarity of waveforms useful to identify earthquakes families. In a second step, we calculate probabilistic earthquake locations using the software package NONLINLOC, which includes systematic, complete grid search and global, non-linear search methods. Subsequently, we perform relative relocation of correlated event pairs using the double-difference earthquake algorithm and the program HypoDD. The double-difference algorithm minimizes the residuals between observed and calculated travel time difference for pairs of earthquakes at common stations by iteratively adjusting the vector difference between the hypocenters. We show the recognized spatial seismic clusters identifying the most active and hazarding sectors of the structure, their geometry and depth. Finally, in order to clarify the geodynamic framework of the area, we associate these results with calculated focal mechanisms for the most energetic earthquakes.

Georgia-Armenia Transboarder seismicity studies

NASA Astrophysics Data System (ADS)

Godoladze, T.; Tvaradze, N.; Javakishvili, Z.; Elashvili, M.; Durgaryan, R.; Arakelyan, A.; Gevorgyan, M.

2012-12-01

In the presented study we performed Comprehensive seismic analyses for the Armenian-Georgian transboarder active seismic fault starting on Armenian territory, cutting the state boarder and having possibly northern termination on Adjara-Triealeti frontal structure in Georgia. In the scope of International projects: ISTC A-1418 "Open network of scientific Centers for mitigation risk of natural hazards in the Southern Caucasus and Central Asia" and NATO SfP- 983284 Project "Caucasus Seismic Emergency Response" in Akhalkalaki (Georgia) seismic center, Regional Summer school trainings and intensive filed investigations were conducted. Main goal was multidisciplinary study of the Javakheti fault structure and better understanding seismicity of the area. Young scientists from Turkey, Armenia, Azerbaijan and Georgia were participated in the deployment of temporal seismic network in order to monitor seisimity on the Javakheti highland and particularly delineate fault scarf and identify active seismic structures. In the scope of international collaboration the common seismic database has been created in the southern Caucasus and collected data from the field works is available now online. Javakheti highland, which is located in the central part of the Caucasus, belongs to the structure of the lesser Caucasus and represents a history of neotectonic volcanism existed in the area. Jasvakheti highland is seismicalu active region devastating from several severe earthquakes(1088, 1283, 1899…). Hypocenters located during analogue network were highly scattered and did not describe real pattern of seismicity of the highland. We relocated hypocenters of the region and improved local velocity model. The hypocenters derived from recently deployed local seismic network in the Javakheti highland, clearly identified seismically active structures. Fault plane solutions of analogue data of the Soviet times have been carefully analyzed and examined. Moment tensor inversion were preformed for the recent moderate size earthquakes and the results are in an agreement with paleo-trenching data showing normal fault mechanism on the south and strake slip on the northern edge of the fault. Local seismic tomography of Javakheti area has been performed in order to improve 3D structure of the region.

Alteration of fault rocks by CO2-bearing fluids with implications for sequestration

NASA Astrophysics Data System (ADS)

Luetkemeyer, P. B.; Kirschner, D. L.; Solum, J. G.; Naruk, S.

2011-12-01

Carbonates and sulfates commonly occur as primary (diagenetic) pore cements and secondary fluid-mobilized veins within fault zones. Stable isotope analyses of calcite, formation fluid, and fault zone fluids can help elucidate the carbon sources and the extent of fluid-rock interaction within a particular reservoir. Introduction of CO2 bearing fluids into a reservoir/fault system can profoundly affect the overall fluid chemistry of the reservoir/fault system and may lead to the enhancement or degradation of porosity within the fault zone. The extent of precipitation and/or dissolution of minerals within a fault zone can ultimately influence the sealing properties of a fault. The Colorado Plateau contains a number of large carbon dioxide reservoirs some of which leak and some of which do not. Several normal faults within the Paradox Basin (SE Utah) dissect the Green River anticline giving rise to a series of footwall reservoirs with fault-dependent columns. Numerous CO2-charged springs and geysers are associated with these faults. This study seeks to identify regional sources and subsurface migration of CO2 to these reservoirs and the effect(s) faults have on trap performance. Data provided in this study include mineralogical, elemental, and stable isotope data for fault rocks, host rocks, and carbonate veins that come from two localities along one fault that locally sealed CO2. This fault is just tens of meters away from another normal fault that has leaked CO2-charged waters to the land surface for thousands of years. These analyses have been used to determine the source of carbon isotopes from sedimentary derived carbon and deeply sourced CO2. XRF and XRD data taken from several transects across the normal faults are consistent with mechanical mixing and fluid-assisted mass transfer processes within the fault zone. δ13C range from -6% to +10% (PDB); δ18O values range from +15% to +24% (VSMOW). Geochemical modeling software is used to model the alteration productions of fault rocks from fluids of various chemistries coming from several different reservoirs within an active CO2-charged fault system. These results are compared to data obtained in the field.

Actively dewatering fluid-rich zones along the Costa Rica plate boundary fault

NASA Astrophysics Data System (ADS)

Bangs, N. L.; McIntosh, K. D.; Silver, E. A.; Kluesner, J. W.; Ranero, C. R.; von Huene, R.

2012-12-01

New 3D seismic reflection data reveal distinct evidence for active dewatering above a 12 km wide segment of the plate boundary fault within the Costa Rica subduction zone NW of the Osa Peninsula. In the spring of 2011 we acquired a 11 x 55 km 3D seismic reflection data set on the R/V Langseth using four 6,000 m streamers and two 3,300 in3 airgun arrays to examine the structure of the Costa Rica margin from the trench into the seismogenic zone. We can trace the plate-boundary interface from the trench across our entire survey to where the plate-boundary thrust lies > 10 km beneath the margin shelf. Approximately 20 km landward of the trench beneath the mid slope and at the updip edge of the seismogenic zone, a 12 km wide zone of the plate-boundary interface has a distinctly higher-amplitude seismic reflection than deeper or shallower segments of the fault. Directly above and potentially directly connected with this zone are high-amplitude, reversed-polarity fault-plane reflections that extend through the margin wedge and into overlying slope sediment cover. Within the slope cover, high-amplitude reversed-polarity reflections are common within the network of closely-spaced nearly vertical normal faults and several broadly spaced, more gently dipping thrust faults. These faults appear to be directing fluids vertically toward the seafloor, where numerous seafloor fluid flow indicators, such as pockmarks, mounds and ridges, and slope failure features, are distinct in multibeam and backscatter images. There are distinctly fewer seafloor and subsurface fluid flow indicators both updip and downdip of this zone. We believe these fluids come from a 12 km wide fluid-rich segment of the plate-boundary interface that is likely overpressured and has relatively low shear stress.

Novel Coupled Thermochronometric and Geochemical Investigation of Blind Geothermal Resources in Fault-Controlled Dilational Corners

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stockli, Daniel

Geothermal plays in extensional and transtensional tectonic environments have long been a major target in the exploration of geothermal resources and the Dixie Valley area has served as a classic natural laboratory for this type of geothermal plays. In recent years, the interactions between normal faults and strike-slip faults, acting either as strain relay zones have attracted significant interest in geothermal exploration as they commonly result in fault-controlled dilational corners with enhanced fracture permeability and thus have the potential to host blind geothermal prospects. Structural ambiguity, complications in fault linkage, etc. often make the selection for geothermal exploration drilling targetsmore » complicated and risky. Though simplistic, the three main ingredients of a viable utility-grade geothermal resource are heat, fluids, and permeability. Our new geological mapping and fault kinematic analysis derived a structural model suggest a two-stage structural evolution with (a) middle Miocene N -S trending normal faults (faults cutting across the modern range), - and tiling Olio-Miocene volcanic and sedimentary sequences (similar in style to East Range and S Stillwater Range). NE-trending range-front normal faulting initiated during the Pliocene and are both truncating N-S trending normal faults and reactivating some former normal faults in a right-lateral fashion. Thus the two main fundamental differences to previous structural models are (1) N-S trending faults are pre-existing middle Miocene normal faults and (2) these faults are reactivated in a right-later fashion (NOT left-lateral) and kinematically linked to the younger NE-trending range-bounding normal faults (Pliocene in age). More importantly, this study provides the first constraints on transient fluid flow through the novel application of apatite (U-Th)/He (AHe) and 4He/ 3He thermochronometry in the geothermally active Dixie Valley area in Nevada.« less

Multi-version software reliability through fault-avoidance and fault-tolerance

NASA Technical Reports Server (NTRS)

Vouk, Mladen A.; Mcallister, David F.

1989-01-01

A number of experimental and theoretical issues associated with the practical use of multi-version software to provide run-time tolerance to software faults were investigated. A specialized tool was developed and evaluated for measuring testing coverage for a variety of metrics. The tool was used to collect information on the relationships between software faults and coverage provided by the testing process as measured by different metrics (including data flow metrics). Considerable correlation was found between coverage provided by some higher metrics and the elimination of faults in the code. Back-to-back testing was continued as an efficient mechanism for removal of un-correlated faults, and common-cause faults of variable span. Software reliability estimation methods was also continued based on non-random sampling, and the relationship between software reliability and code coverage provided through testing. New fault tolerance models were formulated. Simulation studies of the Acceptance Voting and Multi-stage Voting algorithms were finished and it was found that these two schemes for software fault tolerance are superior in many respects to some commonly used schemes. Particularly encouraging are the safety properties of the Acceptance testing scheme.

Comparison of GPS and Quaternary slip rates: Insights from a new Quaternary fault database for Central Asia

NASA Astrophysics Data System (ADS)

Mohadjer, Solmaz; Ehlers, Todd; Bendick, Rebecca; Mutz, Sebastian

2016-04-01

Previous studies related to the kinematics of deformation within the India-Asia collision zone have relied on slip rate data for major active faults to test kinematic models that explain the deformation of the region. The slip rate data, however, are generally disputed for many of the first-order faults in the region (e.g., Altyn Tagh and Karakorum faults). Several studies have also challenged the common assumption that geodetic slip rates are representative of Quaternary slip rates. What has received little attention is the degree to which geodetic slip rates relate to Quaternary slip rates for active faults in the India-Asia collision zone. In this study, we utilize slip rate data from a new Quaternary fault database for Central Asia to determine the overall relationship between Quaternary and GPS-derived slip rates for 18 faults. The preliminary analysis investigating this relationship uses weighted least squares and a re-sampling analysis to test the sensitivity of this relationship to different data point attributes (e.g., faults associated with data points and dating methods used for estimating Quaternary slip rates). The resulting sample subsets of data points yield a maximum possible Pearson correlation coefficient of ~0.6, suggesting moderate correlation between Quaternary and GPS-derived slip rates for some faults (e.g., Kunlun and Longmen Shan faults). Faults with poorly correlated Quaternary and GPS-derived slip rates were identified and dating methods used for the Quaternary slip rates were examined. Results indicate that a poor correlation between Quaternary and GPS-derived slip rates exist for the Karakorum and Chaman faults. Large differences between Quaternary and GPS slip rates for these faults appear to be connected to qualitative dating of landforms used in the estimation of the Quaternary slip rates and errors in the geomorphic and structural reconstruction of offset landforms (e.g., offset terrace riser reconstructions for Altyn Tagh fault). Other factors such as a low density in the GPS network (e.g., GPS rate based on data from a single station for the Karakorum fault) appear to also contribute to the mismatch observed between the slip rates. Taken together, these results suggest that GPS-derived slip rates are often (but not always) representative of Quaternary slip rates and that the dating methods and sampling approaches used to identify transients in a fault slip rate history should be heavily scrutinized before interpreting the seismic hazards for a region.

Focused exhumation along megathrust splay faults in Prince William Sound, Alaska

USGS Publications Warehouse

Haeussler, Peter J.; Armstrong, Phillip A; Liberty, Lee M; Ferguson, Kelly M; Finn, Shaun P; Arkle, Jeannette C; Pratt, Thomas L.

2015-01-01

Megathrust splay faults are a common feature of accretionary prisms and can be important for generating tsunamis during some subduction zone earthquakes. Here we provide new evidence from Alaska that megathrust splay faults have been conduits for focused exhumation in the last 5 Ma. In most of central Prince William Sound, published and new low-temperature thermochronology data indicate little to no permanent rock uplift over tens of thousands of earthquake cycles. However, in southern Prince William Sound on Montague Island, apatite (U–Th)/He ages are as young as 1.1 Ma indicating focused and rapid rock uplift. Montague Island lies in the hanging wall of the Patton Bay megathrust splay fault system, which ruptured during the 1964 M9.2 earthquake and produced ∼9 m of vertical uplift. Recent geochronology and thermochronology studies show rapid exhumation within the last 5 Ma in a pattern similar to the coseismic uplift in the 1964 earthquake, demonstrating that splay fault slip is a long term (3–5 my) phenomena. The region of slower exhumation correlates with rocks that are older and metamorphosed and constitute a mechanically strong backstop. The region of rapid exhumation consists of much younger and weakly metamorphosed rocks, which we infer are mechanically weak. The region of rapid exhumation is separated from the region of slow exhumation by the newly identified Montague Strait Fault. New sparker high-resolution bathymetry, seismic reflection profiles, and a 2012 Mw4.8 earthquake show this feature as a 75-km-long high-angle active normal fault. There are numerous smaller active normal(?) faults in the region between the Montague Strait Fault and the splay faults. We interpret this hanging wall extension as developing between the rapidly uplifting sliver of younger and weaker rocks on Montague Island from the essentially fixed region to the north. Deep seismic reflection profiles show the splay faults root into the subduction megathrust where there is probable underplating. Thus the exhumation and extension in the hanging wall are likely driven by underplating along the megathrust décollement, thickening in the overriding plate and a change in rheology at the Montague Strait Fault to form a structural backstop. A comparison with other megathrust splay faults around the world shows they have significant variability in their characteristics, and the conditions for their formation are not particularly unique.

Geomorphic expression of strike-slip faults: field observations vs. analog experiments: preliminary results

NASA Astrophysics Data System (ADS)

Hsieh, S. Y.; Neubauer, F.; Genser, J.

2012-04-01

The aim of this project is to study the surface expression of strike-slip faults with main aim to find rules how these structures can be extrapolated to depth. In the first step, several basic properties of the fault architecture are in focus: (1) Is it possible to define the fault architecture by studying surface structures of the damage zone vs. the fault core, particularly the width of the damage zone? (2) Which second order structures define the damage zone of strike-slip faults, and how relate these to such reported in basement fault strike-slip analog experiments? (3) Beside classical fault bend structures, is there a systematic along-strike variation of the damage zone width and to which properties relates the variation of the damage zone width. We study the above mentioned properties on the dextral Altyn fault, which is one of the largest strike-slip on Earth with the advantage to have developed in a fully arid climate. The Altyn fault includes a ca. 250 to 600 m wide fault valley, usually with the trace of actual fault in its center. The fault valley is confined by basement highs, from which alluvial fans develop towards the center of the fault valley. The active fault trace is marked by small scale pressure ridges and offset of alluvial fans. The fault valley confining basement highs are several kilometer long and ca. 0.5 to 1 km wide and confined by rotated dextral anti-Riedel faults and internally structured by a regular fracture pattern. Dextral anti-Riedel faults are often cut by Riedel faults. Consequently, the Altyn fault comprises a several km wide damage zone. The fault core zone is a barrier to fluid flow, and the few springs of the region are located on the margin of the fault valley implying the fractured basement highs as the reservoir. Consequently, the southern Silk Road was using the Altyn fault valley. The preliminary data show that two or more orders of structures exist. Small-scale develop during a single earthquake. These finally accumulate to a several 100 m wide fault core, which is in part exposed at surface to arid climate and a km wide damage zone. The basic structures of analog experiments can be well transferred to nature, although along strike changes are common due to fault bending and fracture failure of country rocks.

Software for determining the true displacement of faults

NASA Astrophysics Data System (ADS)

Nieto-Fuentes, R.; Nieto-Samaniego, Á. F.; Xu, S.-S.; Alaniz-Álvarez, S. A.

2014-03-01

One of the most important parameters of faults is the true (or net) displacement, which is measured by restoring two originally adjacent points, called “piercing points”, to their original positions. This measurement is not typically applicable because it is rare to observe piercing points in natural outcrops. Much more common is the measurement of the apparent displacement of a marker. Methods to calculate the true displacement of faults using descriptive geometry, trigonometry or vector algebra are common in the literature, and most of them solve a specific situation from a large amount of possible combinations of the fault parameters. True displacements are not routinely calculated because it is a tedious and tiring task, despite their importance and the relatively simple methodology. We believe that the solution is to develop software capable of performing this work. In a previous publication, our research group proposed a method to calculate the true displacement of faults by solving most combinations of fault parameters using simple trigonometric equations. The purpose of this contribution is to present a computer program for calculating the true displacement of faults. The input data are the dip of the fault; the pitch angles of the markers, slickenlines and observation lines; and the marker separation. To prevent the common difficulties involved in switching between operative systems, the software is developed using the Java programing language. The computer program could be used as a tool in education and will also be useful for the calculation of the true fault displacement in geological and engineering works. The application resolves the cases with known direction of net slip, which commonly is assumed parallel to the slickenlines. This assumption is not always valid and must be used with caution, because the slickenlines are formed during a step of the incremental displacement on the fault surface, whereas the net slip is related to the finite slip.

Secondary Fracturing of Europa's Crust in Response to Combined Slip and Dilation Along Strike-Slip Faults

NASA Technical Reports Server (NTRS)

Kattenhorn, S. A.

2003-01-01

A commonly observed feature in faulted terrestrial rocks is the occurrence of secondary fractures alongside faults. Depending on exact morphology, such fractures have been termed tail cracks, wing cracks, kinks, or horsetail fractures, and typically form at the tip of a slipping fault or around small jogs or steps along a fault surface. The location and orientation of secondary fracturing with respect to the fault plane or the fault tip can be used to determine if fault motion is left-lateral or right-lateral.

Radon measurements in an area of tectonic zone: A case study in Central Slovakia.

PubMed

Mojzeš, Andrej; Marko, František; Porubčanová, Barbara; Bartošová, Andrea

2017-01-01

General overviews of the spatial distribution of radon and other natural radionuclides in the geological basement as commonly presented on regional or country maps tend to offer a low density of information, insufficient for gaining relevant knowledge of the environmental impact, especially in the areas of tectonic zones often assumed to be radon prone and therefore dangerous for the human population. An additional survey, employing radon measurements in soil and indoor air, was carried out seeking to provide a more detailed characterization of the expressive fault zone of the Malá Magura in the Horná Nitra region of Central Slovakia. Eventually, the results of soil 222 Rn volume activity measurements along two short profiles crossing the assumed fault line did not reveal any indication of active nature of local tectonics, but merely pointed to an existence of a zone of contact between different types of rocks. The results of indoor radon measurements in dwellings of two villages lying on the studied fault showed values that were lower than those commonly observed on the Slovak territory, ruling out any negative health impact on population. Nevertheless, in order to add new findings to an already well established study of geological structure of the region, the indoor radon data collected through a previous survey require a further analysis. Copyright © 2016 Elsevier Ltd. All rights reserved.

Examining Relay Ramp Evolution Through Paleo-shoreline Deformation Analysis, Warner Valley Fault, Oregon

NASA Astrophysics Data System (ADS)

Young, C. S.; Dawers, N. H.

2017-12-01

Fault growth is often accomplished by linking a series of en echelon faults through relay ramps. A relay ramp is the area between two overlapping fault segments that tilts and deforms as the faults accrue displacement. The structural evolution of breached normal fault relay ramps remains poorly understood because of the difficulty in defining how slip is partitioned between the most basinward fault (known as the outboard fault), the overlapping fault (inboard fault), and any ramp-breaching linking faults. Along the Warner Valley fault in south-central Oregon, two relay ramps displaying different fault linkage geometries are lined with a series of paleo-lacustrine shorelines that record a Pleistocene paleolake regression. The inner edges of these shorelines act as paleo-horizontal datums that have been deformed by fault activity, and are used to measure relative slip variations across the relay ramp bounding faults. By measuring the elevation changes using a 10m digital elevation model (DEM) of shoreline inner edges, we estimate the amount of slip partitioned between the inboard, outboard and ramp-breaching linking faults. In order to attribute shoreline deformation to fault activity we identify shoreline elevation anomalies, where deformation exceeds a ± 3.34 m window, which encompass our conservative estimates of natural variability in the shoreline geomorphology and the error associated with the data collection. Fault activity along the main length of the fault for each ramp-breaching style is concentrated near the intersection of the linking fault and the outboard portion of the main fault segment. However, fault activity along the outboard fault tip varies according to breaching style. At a footwall breach the entire outboard fault tip appears relatively inactive. At a mid-ramp breach the outboard fault tip remains relatively active because of the proximity of the linking fault to this fault tip.

Investigation of Aceh Segment and Seulimeum Fault by using seismological data; A preliminary result

NASA Astrophysics Data System (ADS)

Muksin, U.; Irwandi; Rusydy, I.; Muzli; Erbas, K.; Marwan; Asrillah; Muzakir; Ismail, N.

2018-04-01

The Seulimeum Fault has not generated large earthquake after last large earthquake with magnitude of M 7.3 occured in 1936. The Seulimeum Fault is accompanied by the Seulawah volcano that reported to be active in 1839, 1975 and 2010. The activity of the Seulimeum Fault could be related with the existence of the Seulawah volcano and the Seulawah volcano activity could also triggered by the Seulumeum Fault activity. The objective of the longterm research is to investigate the relation between the Seulimeum Fault and the Seulawah Volcano. The aim of this paper is to present the first result of the investigation of the Seulimeum Fault based on the seismicity and geomorphology. A seismic network consisting of 17 seismometers (Trilium Compact) and data logger (DSS Cube) were deployed in Aceh Besar. The seismic network was installed for 3 months to record earthquakes along the Seulimeum and the Aceh Faults. The Seulimeum Fault is considered to be active as several local earthquakes were recorded. The Seulimeum Fault is much more active in the region of the bifurcation of the The Aceh Segment and the Seulimeum Fault. The mechanisms of earthquakes along the Seulimeum Fault were mostly strike slip following similar to the Sumatran Fault characteristics.

Geologic map of the Paintbrush Canyon Area, Yucca Mountain, Nevada

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dickerson, R.P.; Drake, R.M. II

This geologic map is produced to support site characterization studies of Yucca Mountain, Nevada, site of a potential nuclear waste storage facility. The area encompassed by this map lies between Yucca Wash and Fortymile Canyon, northeast of Yucca Mountain. It is on the southern flank of the Timber Mountain caldera complex within the southwest Nevada volcanic field. Miocene tuffs and lavas of the Calico Hills Formation, the Paintbrush Group, and the Timber Mountain Group crop out in the area of this map. The source vents of the tuff cones and lava domes commonly are located beneath the thickest deposits ofmore » pyroclastic ejecta and lava flows. The rocks within the mapped area have been deformed by north- and northwest-striking, dominantly west-dipping normal faults and a few east-dipping normal faults. Faults commonly are characterized by well developed fault scarps, thick breccia zones, and hanging-wall grabens. Latest movement as preserved by slickensides on west-dipping fault scarps is oblique down towards the southwest. Two of these faults, the Paintbrush Canyon fault and the Bow Ridge fault, are major block-bounding faults here and to the south at Yucca Mountain. Offset of stratigraphic units across faults indicates that faulting occurred throughout the time these volcanic units were deposited.« less

Active faults in Africa: a review

NASA Astrophysics Data System (ADS)

Skobelev, S. F.; Hanon, M.; Klerkx, J.; Govorova, N. N.; Lukina, N. V.; Kazmin, V. G.

2004-03-01

The active fault database and Map of active faults in Africa, in scale of 1:5,000,000, were compiled according to the ILP Project II-2 "World Map of Major Active Faults". The data were collected in the Royal Museum of Central Africa, Tervuren, Belgium, and in the Geological Institute, Moscow, where the final edition was carried out. Active faults of Africa form three groups. The first group is represented by thrusts and reverse faults associated with compressed folds in the northwest Africa. They belong to the western part of the Alpine-Central Asian collision belt. The faults disturb only the Earth's crust and some of them do not penetrate deeper than the sedimentary cover. The second group comprises the faults of the Great African rift system. The faults form the known Western and Eastern branches, which are rifts with abnormal mantle below. The deep-seated mantle "hot" anomaly probably relates to the eastern volcanic branch. In the north, it joins with the Aden-Red Sea rift zone. Active faults in Egypt, Libya and Tunis may represent a link between the East African rift system and Pantellerian rift zone in the Mediterranean. The third group included rare faults in the west of Equatorial Africa. The data were scarce, so that most of the faults of this group were identified solely by interpretation of space imageries and seismicity. Some longer faults of the group may continue the transverse faults of the Atlantic and thus can penetrate into the mantle. This seems evident for the Cameron fault line.

Tectonic state: its significance and characterization in the assessment of seismic effects associated with reservoir impounding

USGS Publications Warehouse

Castle, R.O.; Clark, M.M.; Grantz, A.; Savage, J.C.

1980-01-01

Any analysis of seismicity associated with the filling of large reservoirs requires an evaluation of the natural tectonic state in order to determine whether impoundment is the basic source, a mechanically unrelated companion feature, or a triggering stimulus of the observed seismicity. Several arguments indicate that the associated seismicity is usually a triggered effect. Among the elements of tectonic state considered here (existing fractures, accumulated elastic strain, and deformational style), deformational style is especially critical in forecasting the occurrence of impoundment-induced seismicity. The observational evidence indicates that seismicity associated with impounding generally occurs in areas that combine steeply dipping faults, relatively high strain rates, and either extensional or horizontal-shear strain. Simple physical arguments suggest: (1) that increased fluid pressures resulting from increased reservoir head should enhance the likelihood of seismic activity, whatever the tectonic environment; (2) that stress changes resulting from surface loading may increase the likelihood of crustal failure in areas of normal and transcurrent faulting, whereas they generally inhibit failure in areas of thrust faulting. Comparisons with other earthquake-producing artificial and natural processes (underground explosions, fluid injection, underground mining, fluid extraction, volcanic emissions) indicate that reservoir loading may similarly modify the natural tectonic state. Subsurface loading resulting from fluid extraction may be a particularly close analogue of reservoir loading; "seismotectonic" events associated with fluid extraction have been recognized in both seismically active and otherwise aseismic regions. Because the historic record of seismicity and surface faulting commonly is short in comparison with recurrence intervals of earthquake and fault-slip events, tectonic state is most reliably appraised through combined studies of historic seismicity and faulting, instrumentally measured strain, and the geological record, especially that of the Quaternary. Experience in California and elsewhere demonstrates that the character and activity of recognized faults can be assessed by means of: instrumental earthquake investigations, repeated geodetic measurements, written history, archeological studies, fault topography, and local stratigraphic relations. Where faults are less easily distinguished, appraisals of tectonic state may be based on both the regional seismicity and the regional history of vertical movement as shown by: repeated levelling and sea-level measurements, written history, archeologic investigations, terrace and shoreline deformation, and denudation and sedimentation studies. ?? 1980.

Shallow Seismic Reflection Study of Recently Active Fault Scarps, Mina Deflection, Western Nevada

NASA Astrophysics Data System (ADS)

Black, R. A.; Christie, M.; Tsoflias, G. P.; Stockli, D. F.

2006-12-01

During the spring and summer of 2006 University of Kansas geophysics students and faculty acquired shallow, high resolution seismic reflection data over actively deforming alluvial fans developing across the Emmigrant Peak (in Fish Lake Valley) and Queen Valley Faults in western Nevada. These normal faults represent a portion of the transition from the right-lateral deformation associated with the Walker Lane/Eastern California Shear Zone to the normal and left-lateral faulting of the Mina Deflection. Data were gathered over areas of recent high resolution geological mapping and limited trenching by KU students. An extensive GPR data grid was also acquired. The GPR results are reported in Christie, et al., 2006. The seismic data gathered in the spring included both walkaway tests and a short CMP test line. These data indicated that a very near-surface P-wave to S-wave conversion was taking place and that very high quality S-wave reflections were probably dominating shot records to over one second in time. CMP lines acquired during the summer utilized a 144 channel networked Geode system, single 28 hz geophones, and a 30.06 downhole rifle source. Receiver spacing was 0.5 m, source spacing 1.0m and CMP bin spacings were 0.25m for all lines. Surveying was performed using an RTK system which was also used to develop a concurrent high resolution DEM. A dip line of over 400m and a strike line over 100m in length were shot across the active fan scarp in Fish Lake Valley. Data processing is still underway. However, preliminary interpretation of common-offset gathers and brute stacks indicates very complex faulting and detailed stratigraphic information to depths of over 125m. Depth of information was actually limited by the 1024ms recording time. Several west-dipping normal faults downstep towards the basin. East-dipping antithetic normal faulting is extensive. Several distinctive stratigraphic packages are bound by the faults and apparent unconformitites. A CMP dip line was also run across a large active scarp in Queen Valley near Boundary Peak. Due to slope steepness and extensive boulder armoring shot and receiver locations had to be skipped within several meters of the actual scarp location. Initial structural and stratigraphic interpretations are similar to those in the Fish Lake Valley location. Overall the data prove that the actively deforming fans can be imaged in detail sufficient to perform structural and possibly seismic stratigraphic analysis within the upper one hundred meters of the fans, if not deeper.

Fault structure and mechanics of the Hayward Fault, California from double-difference earthquake locations

USGS Publications Warehouse

Waldhauser, F.; Ellsworth, W.L.

2002-01-01

The relationship between small-magnitude seismicity and large-scale crustal faulting along the Hayward Fault, California, is investigated using a double-difference (DD) earthquake location algorithm. We used the DD method to determine high-resolution hypocenter locations of the seismicity that occurred between 1967 and 1998. The DD technique incorporates catalog travel time data and relative P and S wave arrival time measurements from waveform cross correlation to solve for the hypocentral separation between events. The relocated seismicity reveals a narrow, near-vertical fault zone at most locations. This zone follows the Hayward Fault along its northern half and then diverges from it to the east near San Leandro, forming the Mission trend. The relocated seismicity is consistent with the idea that slip from the Calaveras Fault is transferred over the Mission trend onto the northern Hayward Fault. The Mission trend is not clearly associated with any mapped active fault as it continues to the south and joins the Calaveras Fault at Calaveras Reservoir. In some locations, discrete structures adjacent to the main trace are seen, features that were previously hidden in the uncertainty of the network locations. The fine structure of the seismicity suggest that the fault surface on the northern Hayward Fault is curved or that the events occur on several substructures. Near San Leandro, where the more westerly striking trend of the Mission seismicity intersects with the surface trace of the (aseismic) southern Hayward Fault, the seismicity remains diffuse after relocation, with strong variation in focal mechanisms between adjacent events indicating a highly fractured zone of deformation. The seismicity is highly organized in space, especially on the northern Hayward Fault, where it forms horizontal, slip-parallel streaks of hypocenters of only a few tens of meters width, bounded by areas almost absent of seismic activity. During the interval from 1984 to 1998, when digital waveforms are available, we find that fewer than 6.5% of the earthquakes can be classified as repeating earthquakes, events that rupture the same fault patch more than one time. These most commonly are located in the shallow creeping part of the fault, or within the streaks at greater depth. The slow repeat rate of 2-3 times within the 15-year observation period for events with magnitudes around M = 1.5 is indicative of a low slip rate or a high stress drop. The absence of microearthquakes over large, contiguous areas of the northern Hayward Fault plane in the depth interval from ???5 to 10 km and the concentrations of seismicity at these depths suggest that the aseismic regions are either locked or retarded and are storing strain energy for release in future large-magnitude earthquakes.

Active Structures as Deduced from Geomorphic Features: A case in Hsinchu Area, northwestern Taiwan

NASA Astrophysics Data System (ADS)

Chen, Y.; Shyu, J.; Ota, Y.; Chen, W.; Hu, J.; Tsai, B.; Wang, Y.

2002-12-01

Hsinchu area is located in the northwestern Taiwan, the fold-and thrust belt created by arc-continent collision between Eurasian and Philippine. Since the collision event is still ongoing, the island is tectonically active and full of active faults. According to the historical records, some of the faults are seismically acting. In Hsinchuarea two active faults, the Hsinchu and Hsincheng, have been previously mapped. To evaluate the recent activities, we studied the related geomorphic features by using newly developed Digital Elevation Model (DEM), the aerial photos and field investigation. Geologically, both of the faults are coupled with a hanging wall anticline. The anticlines are recently active due to the deformation of the geomorphic surfaces. The Hsinchu fault system shows complicate corresponding scarps, distributed sub-parallel to the fault trace previously suggested by projection of subsurface geology. This is probably caused by its strike-slip component tearing the surrounding area along the main trace. The scarps associated with the Hsincheng fault system are rather simple and unique. It offsets a flight of terraces all the way down to recent flood plain, indicating its long lasting activity. One to two kilometers to east of main trace a back-thrust is found, showing coupled vertical surface offsets with the main fault. The striking discovery in this study is that the surface deformation is only distributed in the southern bank of Touchien river, also suddenly decreasing when crossing another tear fault system, which is originated from Hsincheng fault in the west and extending southeastward parallel to the Touchien river. The strike-slip fault system mentioned above not only bisects the Hsinchu fault, but also divides the Hsincheng fault into segments. The supporting evidence found in this study includes pressure ridges and depressions. As a whole, the study area is tectonically dominated by three active fault systems and two actively growing anticlines. The interactions between active structural systems formed the complicate geomorphic features presented in this paper.

A Negative Selection Immune System Inspired Methodology for Fault Diagnosis of Wind Turbines.

PubMed

Alizadeh, Esmaeil; Meskin, Nader; Khorasani, Khashayar

2017-11-01

High operational and maintenance costs represent as major economic constraints in the wind turbine (WT) industry. These concerns have made investigation into fault diagnosis of WT systems an extremely important and active area of research. In this paper, an immune system (IS) inspired methodology for performing fault detection and isolation (FDI) of a WT system is proposed and developed. The proposed scheme is based on a self nonself discrimination paradigm of a biological IS. Specifically, the negative selection mechanism [negative selection algorithm (NSA)] of the human body is utilized. In this paper, a hierarchical bank of NSAs are designed to detect and isolate both individual as well as simultaneously occurring faults common to the WTs. A smoothing moving window filter is then utilized to further improve the reliability and performance of the FDI scheme. Moreover, the performance of our proposed scheme is compared with another state-of-the-art data-driven technique, namely the support vector machines (SVMs) to demonstrate and illustrate the superiority and advantages of our proposed NSA-based FDI scheme. Finally, a nonparametric statistical comparison test is implemented to evaluate our proposed methodology with that of the SVM under various fault severities.

Characterization of the Hosgri Fault Zone and adjacent structures in the offshore Santa Maria Basin, south-central California: Chapter CC of Evolution of sedimentary basins/onshore oil and gas investigations - Santa Maria province

USGS Publications Warehouse

Willingham, C. Richard; Rietman, Jan D.; Heck, Ronald G.; Lettis, William R.

2013-01-01

The Hosgri Fault Zone trends subparallel to the south-central California coast for 110 km from north of Point Estero to south of Purisima Point and forms the eastern margin of the present offshore Santa Maria Basin. Knowledge of the attributes of the Hosgri Fault Zone is important for petroleum development, seismic engineering, and environmental planning in the region. Because it lies offshore along its entire reach, our characterizations of the Hosgri Fault Zone and adjacent structures are primarily based on the analysis of over 10,000 km of common-depth-point marine seismic reflection data collected from a 5,000-km2 area of the central and eastern parts of the offshore Santa Maria Basin. We describe and illustrate the along-strike and downdip geometry of the Hosgri Fault Zone over its entire length and provide examples of interpreted seismic reflection records and a map of the structural trends of the fault zone and adjacent structures in the eastern offshore Santa Maria Basin. The seismic data are integrated with offshore well and seafloor geologic data to describe the age and seismic appearance of offshore geologic units and marker horizons. We develop a basin-wide seismic velocity model for depth conversions and map three major unconformities along the eastern offshore Santa Maria Basin. Accompanying plates include maps that are also presented as figures in the report. Appendix A provides microfossil data from selected wells and appendix B includes uninterpreted copies of the annotated seismic record sections illustrated in the chapter. Features of the Hosgri Fault Zone documented in this investigation are suggestive of both lateral and reverse slip. Characteristics indicative of lateral slip include (1) the linear to curvilinear character of the mapped trace of the fault zone, (2) changes in structural trend along and across the fault zone that diminish in magnitude toward the ends of the fault zone, (3) localized compressional and extensional structures characteristic of constraining and releasing bends and stepovers, (4) changes in the sense and magnitude of vertical separation along strike within the fault zone, and (5) changes in downdip geometry between the major traces and segments of the fault zone. Characteristics indicative of reverse slip include (1) reverse fault geometries that occur across major strands of the fault zone and (2) fault-bend folds and localized thrust faults that occur along the northern and southern reaches of the fault. Analyses of high-resolution, subbottom profiler and side-scan sonar records indicate localized Holocene activity along most of the extent of the fault zone. Collectively, these features are the basis of our characterization of the Hosgri Fault Zone as an active, 110-km-long, convergent right-oblique slip (transpressional) fault with identified northern and southern terminations. This interpretation is consistent with recently published analyses of onshore geologic data, regional tectonic kinematic models, and instrumental seismicity.

Geometry and architecture of faults in a syn-rift normal fault array: The Nukhul half-graben, Suez rift, Egypt

NASA Astrophysics Data System (ADS)

Wilson, Paul; Gawthorpe, Rob L.; Hodgetts, David; Rarity, Franklin; Sharp, Ian R.

2009-08-01

The geometry and architecture of a well exposed syn-rift normal fault array in the Suez rift is examined. At pre-rift level, the Nukhul fault consists of a single zone of intense deformation up to 10 m wide, with a significant monocline in the hanging wall and much more limited folding in the footwall. At syn-rift level, the fault zone is characterised by a single discrete fault zone less than 2 m wide, with damage zone faults up to approximately 200 m into the hanging wall, and with no significant monocline developed. The evolution of the fault from a buried structure with associated fault-propagation folding, to a surface-breaking structure with associated surface faulting, has led to enhanced bedding-parallel slip at lower levels that is absent at higher levels. Strain is enhanced at breached relay ramps and bends inherited from pre-existing structures that were reactivated during rifting. Damage zone faults observed within the pre-rift show ramp-flat geometries associated with contrast in competency of the layers cut and commonly contain zones of scaly shale or clay smear. Damage zone faults within the syn-rift are commonly very straight, and may be discrete fault planes with no visible fault rock at the scale of observation, or contain relatively thin and simple zones of scaly shale or gouge. The geometric and architectural evolution of the fault array is interpreted to be the result of (i) the evolution from distributed trishear deformation during upward propagation of buried fault tips to surface faulting after faults breach the surface; (ii) differences in deformation response between lithified pre-rift units that display high competence contrasts during deformation, and unlithified syn-rift units that display low competence contrasts during deformation, and; (iii) the history of segmentation, growth and linkage of the faults that make up the fault array. This has important implications for fluid flow in fault zones.

Influence of crystallised igneous intrusions on fault nucleation and reactivation during continental extension

NASA Astrophysics Data System (ADS)

Magee, Craig; McDermott, Kenneth G.; Stevenson, Carl T. E.; Jackson, Christopher A.-L.

2014-05-01

Continental rifting is commonly accommodated by the nucleation of normal faults, slip on pre-existing fault surfaces and/or magmatic intrusion. Because crystallised igneous intrusions are pervasive in many rift basins and are commonly more competent (i.e. higher shear strengths and Young's moduli) than the host rock, it is theoretically plausible that they locally intersect and modify the mechanical properties of pre-existing normal faults. We illustrate the influence that crystallised igneous intrusions may have on fault reactivation using a conceptual model and observations from field and subsurface datasets. Our results show that igneous rocks may initially resist failure, and promote the preferential reactivation of favourably-oriented, pre-existing faults that are not spatially-associated with solidified intrusions. Fault segments situated along strike from laterally restricted fault-intrusion intersections may similarly be reactivated. This spatial and temporal control on strain distribution may generate: (1) supra-intrusion folds in the hanging wall; (2) new dip-slip faults adjacent to the igneous body; or (3) sub-vertical, oblique-slip faults oriented parallel to the extension direction. Importantly, stress accumulation within igneous intrusions may eventually initiate failure and further localise strain. The results of our study have important implications for the structural of sedimentary basins and the subsurface migration of hydrocarbons and mineral-bearing fluids.

Origin and structure of major orogen-scale exhumed strike-slip

NASA Astrophysics Data System (ADS)

Cao, Shuyun; Neubauer, Franz

2016-04-01

The formation of major exhumed strike-slip faults represents one of the most important dynamic processes affecting the evolution of the Earth's lithosphere and surface. Detailed models of the potential initiation and properties and architecture of orogen-scale exhumed strike-slip faults and how these relate to exhumation are rare. In this study, we deal with key properties controlling the development of major exhumed strike-slip fault systems, which are equivalent to the deep crustal sections of active across fault zones. We also propose two dominant processes for the initiation of orogen-scale exhumed strike-slip faults: (1) pluton-controlled and (2) metamorphic core complex-controlled strike-slip faults. In these tectonic settings, the initiation of faults occurs by rheological weakening along hot-to-cool contacts and guides the overall displacement and ultimate exhumation. These processes result in a specific thermal and structural architecture of such faults. These types of strike-slip dominated fault zones are often subparallel to mountain ranges and expose a wide variety of mylonitic, cataclastic and non-cohesive fault rocks, which were formed at different structural levels of the crust during various stages of faulting. The high variety of distinctive fault rocks is a potential evidence for recognition of these types of strike-slip faults. Exhumation of mylonitic rocks is, therefore, a common feature of such reverse oblique-slip strike-slip faults, implying major transtensive and/or transpressive processes accompanying pure strike-slip motion during exhumation. Some orogen-scale strike-slip faults nucleate and initiate along rheologically weak zones, e.g. at granite intrusions, zones of low-strength minerals, thermally weakened crust due to ascending fluids, and lateral borders of hot metamorphic core complexes. A further mechanism is the juxtaposition of mechanically strong mantle lithosphere to hot asthenosphere in continental transform faults (e.g., San Andreas Fault, Alpine Fault in New Zealand) and transtensional rift zones such as the East African rift. In many cases, subsequent shortening exhumes such faults from depth to the surface. A major aspect of many exhumed strike-slip faults is its lateral thermal gradient induced by the juxtaposition of hot and cool levels of the crust controlling relevant properties of such fault zones, e.g. the overall fault architecture (e.g., fault core, damage zone, shear lenses, fault rocks) and the thermal structure. These properties and the overall fault architecture include strength of fault rocks, permeability and porosity, the hydrological regime, as well as the nature and origin of circulating hydrothermal fluids.

Mountain front migration and drainage captures related to fault segment linkage and growth: The Polopos transpressive fault zone (southeastern Betics, SE Spain)

NASA Astrophysics Data System (ADS)

Giaconia, Flavio; Booth-Rea, Guillermo; Martínez-Martínez, José Miguel; Azañón, José Miguel; Pérez-Romero, Joaquín; Villegas, Irene

2013-01-01

The Polopos E-W- to ESE-WNW-oriented dextral-reverse fault zone is formed by the North Alhamilla reverse fault and the North and South Gafarillos dextral faults. It is a conjugate fault system of the sinistral NNE-SSW Palomares fault zone, active from the late most Tortonian (≈7 Ma) up to the late Pleistocene (≥70 ky) in the southeastern Betics. The helicoidal geometry of the fault zone permits to shift SE-directed movement along the South Cabrera reverse fault to NW-directed shortening along the North Alhamilla reverse fault via vertical Gafarillos fault segments, in between. Since the Messinian, fault activity migrated southwards forming the South Gafarillos fault and displacing the active fault-related mountain-front from the north to the south of Sierra de Polopos; whilst recent activity of the North Alhamilla reverse fault migrated westwards. The Polopos fault zone determined the differential uplift between the Sierra Alhamilla and the Tabernas-Sorbas basin promoting the middle Pleistocene capture that occurred in the southern margin of the Sorbas basin. Continued tectonic uplift of the Sierra Alhamilla-Polopos and Cabrera anticlinoria and local subsidence associated to the Palomares fault zone in the Vera basin promoted the headward erosion of the Aguas river drainage that captured the Sorbas basin during the late Pleistocene.

A study of Quaternary structures in the Qom region, West Central Iran

NASA Astrophysics Data System (ADS)

Babaahmadi, A.; Safaei, H.; Yassaghi, A.; Vafa, H.; Naeimi, A.; Madanipour, S.; Ahmadi, M.

2010-12-01

West Central Iran comprises numerous Quaternary faults. Having either strike-slip or thrust mechanisms, these faults are potentially active and therefore capable of creating destructive earthquakes. In this paper, we use satellite images as well as field trips to identify these active faults in the Qom region. The Qom and Indes faults are the main NW-trending faults along which a Quaternary restraining step-over zone has formed. Kamarkuh, Mohsen Abad, and Ferdows anticlines are potentially active structures that formed in this restraining step-over zone. There are some thrusts and anticlines, such as the Alborz anticline and Alborz fault, which are parallel to strike-slip faults such as the Qom fault, indicating deformation partitioning in the area. In addition to NW-trending structures, there is an important NE-trending fault known as the Qomrud fault that has deformed Quaternary deposits and affected Kushk-e-Nosrat fault, Alborz anticline, and Qomrud River. The results of this study imply that the major Quaternary faults of West Central Iran and their restraining step-over zones are potentially active.

General Monte Carlo reliability simulation code including common mode failures and HARP fault/error-handling

NASA Technical Reports Server (NTRS)

Platt, M. E.; Lewis, E. E.; Boehm, F.

1991-01-01

A Monte Carlo Fortran computer program was developed that uses two variance reduction techniques for computing system reliability applicable to solving very large highly reliable fault-tolerant systems. The program is consistent with the hybrid automated reliability predictor (HARP) code which employs behavioral decomposition and complex fault-error handling models. This new capability is called MC-HARP which efficiently solves reliability models with non-constant failures rates (Weibull). Common mode failure modeling is also a specialty.

Mapping fault-controlled volatile migration in equatorial layered deposits on Mars

NASA Astrophysics Data System (ADS)

Okubo, C. H.

2006-12-01

Research in terrestrial settings shows that clastic sedimentary deposits are productive host rocks for underground volatile reservoirs because of their high porosity and permeability. Within such reservoirs, faults play an important role in controlling pathways for volatile migration, because faults act as either barriers or conduits. Therefore faults are important volatile concentrators, which means that evidence of geochemical, hydrologic and biologic processes are commonly concentrated at these locations. Accordingly, faulted sedimentary deposits on Mars are plausible areas to search for evidence of past volatile activity and associated processes. Indeed, evidence for volatile migration through layered sedimentary deposits on Mars has been documented in detail by the Opportunity rover in Meridiani Planum. Thus evidence for past volatile- driven processes that could have occurred within the protective depths of these deposits may now exposed at the surface and more likely found around faults. Owing to the extensive distribution of layered deposits on Mars, a major challenge in looking for and investigating evidence of past volatile processes in these deposits is identifying and prioritizing study areas. Toward this end, this presentation details initial results of a multiyear project to develop quantitative maps of latent pathways for fault-controlled volatile migration through the layered sedimentary deposits on Mars. Available MOC and THEMIS imagery are used to map fault traces within equatorial layered deposits, with an emphasis on proposed regions for MSL landing sites. These fault maps define regions of interest for stereo imaging by HiRISE and identify areas to search for existing MOC stereo coverage. Stereo coverage of identified areas of interest allows for the construction of digital elevation models and ultimately extraction of fault plane and displacement vector orientations. These fault and displacement data will be fed through numerical modeling techniques that are developed for exploring terrestrial geologic reservoirs. This will yield maps of latent pathways for volatile migration through the faulted layered deposits and provide insight into the geologic history of volatiles on Mars.

The buried active faults in southeastern China as revealed by the relocated background seismicity and fault plane solutions

NASA Astrophysics Data System (ADS)

Zhu, A.; Wang, P.; Liu, F.

2017-12-01

The southeastern China in the mainland corresponds to the south China block, which is characterized by moderate historical seismicity and low stain rate. Most faults are buried under thick Quaternary deposits, so it is difficult to detect and locate them using the routine geological methods. Only a few have been identified to be active in late Quaternary, which leads to relatively high potentially seismic risk to this region due to the unexpected locations of the earthquakes. We performed both hypoDD and tomoDD for the background seismicity from 2000 to 2016 to investigate the buried faults. Some buried active faults are revealed by the relocated seismicity and the velocity structure, no geologically known faults corresponding to them and no surface active evidence ever observed. The geometries of the faults are obtained by analyzing the hypocentral distribution pattern and focal mechanism. The focal mechanism solutions indicate that all the revealed faults are dominated in strike-slip mechanisms, or with some thrust components. While the previous fault investigation and detection results show that most of the Quaternary faults in southeastern China are dominated by normal movement. It suggests that there may exist two fault systems in deep and shallow tectonic regimes. The revealed faults may construct the deep one that act as the seismogenic faults, and the normal faults at shallow cannot generate the destructive earthquakes. The variation in the Curie-point depths agrees well with the structure plane of the revealed active faults, suggesting that the faults may have changed the deep structure.

Precursory slow-slip loaded the 2009 L'Aquila earthquake sequence

NASA Astrophysics Data System (ADS)

Borghi, A.; Aoudia, A.; Javed, F.; Barzaghi, R.

2016-05-01

Slow-slip events (SSEs) are common at subduction zone faults where large mega earthquakes occur. We report here that one of the best-recorded moderate size continental earthquake, the 2009 April 6 moment magnitude (Mw) 6.3 L'Aquila (Italy) earthquake, was preceded by a 5.9 Mw SSE that originated from the decollement beneath the reactivated normal faulting system. The SSE is identified from a rigorous analysis of continuous GPS stations and occurred on the 12 February and lasted for almost two weeks. It coincided with a burst in the foreshock activity with small repeating earthquakes migrating towards the main-shock hypocentre as well as with a change in the elastic properties of rocks in the fault region. The SSE has caused substantial stress loading at seismogenic depths where the magnitude 4.0 foreshock and Mw 6.3 main shock nucleated. This stress loading is also spatially correlated with the lateral extent of the aftershock sequence.

Simultaneous Sensor and Process Fault Diagnostics for Propellant Feed System

NASA Technical Reports Server (NTRS)

Cao, J.; Kwan, C.; Figueroa, F.; Xu, R.

2006-01-01

The main objective of this research is to extract fault features from sensor faults and process faults by using advanced fault detection and isolation (FDI) algorithms. A tank system that has some common characteristics to a NASA testbed at Stennis Space Center was used to verify our proposed algorithms. First, a generic tank system was modeled. Second, a mathematical model suitable for FDI has been derived for the tank system. Third, a new and general FDI procedure has been designed to distinguish process faults and sensor faults. Extensive simulations clearly demonstrated the advantages of the new design.

A distributed fault-tolerant signal processor /FTSP/

NASA Astrophysics Data System (ADS)

Bonneau, R. J.; Evett, R. C.; Young, M. J.

1980-01-01

A digital fault-tolerant signal processor (FTSP), an example of a self-repairing programmable system is analyzed. The design configuration is discussed in terms of fault tolerance, system-level fault detection, isolation and common memory. Special attention is given to the FDIR (fault detection isolation and reconfiguration) logic, noting that the reconfiguration decisions are based on configuration, summary status, end-around tests, and north marker/synchro data. Several mechanisms of fault detection are described which initiate reconfiguration at different levels. It is concluded that the reliability of a signal processor can be significantly enhanced by the use of fault-tolerant techniques.

Fault zone structure and inferences on past activities of the active Shanchiao Fault in the Taipei metropolis, northern Taiwan

NASA Astrophysics Data System (ADS)

Chen, C.; Lee, J.; Chan, Y.; Lu, C.

2010-12-01

The Taipei Metropolis, home to around 10 million people, is subject to seismic hazard originated from not only distant faults or sources scattered throughout the Taiwan region, but also active fault lain directly underneath. Northern Taiwan including the Taipei region is currently affected by post-orogenic (Penglai arc-continent collision) processes related to backarc extension of the Ryukyu subduction system. The Shanchiao Fault, an active normal fault outcropping along the western boundary of the Taipei Basin and dipping to the east, is investigated here for its subsurface structure and activities. Boreholes records in the central portion of the fault were analyzed to document the stacking of post- Last Glacial Maximum growth sediments, and a tulip flower structure is illuminated with averaged vertical slip rate of about 3 mm/yr. Similar fault zone architecture and post-LGM tectonic subsidence rate is also found in the northern portion of the fault. A correlation between geomorphology and structural geology in the Shanchiao Fault zone demonstrates an array of subtle geomorphic scarps corresponds to the branch fault while the surface trace of the main fault seems to be completely erased by erosion and sedimentation. Such constraints and knowledge are crucial in earthquake hazard evaluation and mitigation in the Taipei Metropolis, and in understanding the kinematics of transtensional tectonics in northern Taiwan. Schematic 3D diagram of the fault zone in the central portion of the Shanchiao Fault, displaying regional subsurface geology and its relation to topographic features.

Tremor evidence for dynamically triggered creep events on the deep San Andreas Fault

NASA Astrophysics Data System (ADS)

Peng, Z.; Shelly, D. R.; Hill, D. P.; Aiken, C.

2010-12-01

Deep tectonic tremor has been observed along major subduction zones and the San Andreas fault (SAF) in central and southern California. It appears to reflect deep fault slip, and it is often seen to be triggered by small stresses, including passing seismic waves from large regional and teleseismic earthquakes. Here we examine tremor activity along the Parkfield-Cholame section of the SAF from mid-2001 to early 2010, scrutinizing its relationship with regional and teleseismic earthquakes. Based on similarities in the shape and timing of seismic waveforms, we conclude that triggered and ambient tremor share common sources and a common physical mechanism. Utilizing this similarity in waveforms, we detect tremor triggered by numerous large events, including previously unreported triggering from the recent 2009 Mw7.3 Honduras, 2009 Mw8.1 Samoa, and 2010 Mw8.8 Chile earthquakes at teleseismic distances, and the relatively small 2007 Mw5.4 Alum Rock and 2008 Mw5.4 Chino Hills earthquakes at regional distances. We also find multiple examples of systematic migration in triggered tremor, similar to ambient tremor migration episodes observed at other times. Because these episodes propagate much more slowly than the triggering waves, the migration likely reflects a small, triggered creep event. As with ambient tremor bursts, triggered tremor at times persists for multiple days, probably indicating a somewhat larger creep event. This activity provides a clear example of delayed dynamic triggering, with a mechanism perhaps also relevant for triggering of regular earthquakes.

Hydrotectonics; principles and relevance

USGS Publications Warehouse

Kopf, R.W.

1982-01-01

Hydrotectonics combines the principles of hydraulics and rock mechanics. The hypothesis assumes that: (1) no faults are truly planar, (2) opposing noncongruent wavy wallrock surfaces form chambers and bottlenecks along the fault, and (3) most thrusting occurs beneath the water table. These physical constraints permit the following dynamics. Shear displacement accompanying faulting must constantly change the volume of each chamber. Addition of ground water liquefies dry fault breccia to a heavy incompressible viscous muddy breccia I call fault slurry. When the volume of a chamber along a thrust fault decreases faster than its fault slurry can escape laterally, overpressurized slurry is hydraulically injected into the base of near-vertical fractures in the otherwise impervious overriding plate. Breccia pipes commonly form where such fissures intersect. Alternating decrease and increase in volume of the chamber subjects this injection slurry to reversible surges that not only raft and abrade huge clasts sporadically spalled from the walls of the conduit but also act as a forceful hydraulic ram which periodically widens the conduit and extends its top. If the pipe perforates a petroleum reservoir, leaking hydrocarbons float to its top. Sudden faulting may generate a powerful water hammer that can be amplified at some distal narrow ends of the anastomosing plumbing system, where the shock may produce shatter cones. If vented on the Earth's surface, the muddy breccia, now called extrusion slurry, forms a mud volcano. This hypothesis suggests that many highly disturbed features presently attributed to such catastrophic processes as subsurface explosions or meteorite impacts are due to the rheology of tectonic slurry in an intermittently reactivated pressure-relief tube rooted in a powerful reciprocating hydrotectonic pump activated by a long-lived deep-seated thrust fault.

INTEGRATION OF SHORT-TERM CO-SEISMIC DEFORMATION (InSAR) IN THE GEOMORPHIC DEVELOPMENT OF AN ACTIVELY UPLIFTING FOOTWALL, L’AQUILA EARTHQUAKE (06 APRIL, 2009), ITALY

NASA Astrophysics Data System (ADS)

Berti, C.; Pazzaglia, F. J.; Ramage, J. M.; Miccadei, E.; Piacentini, T.

2009-12-01

Central Italy is a well know region of frequent seismic activity focused along the topographic axis of the Apennines, with several, damaging > M. 5 events in the past decade. Conversely, the integrated effect of these earthquakes in shaping the long term development of the landscape is a poorly understood, but potentially powerful process in describing the region’s paleoseismicity and steadiness of hazardous earthquakes. The recent M. 6.3 L’Aquila earthquake of 06 April, 2009 ruptured a fault in a region of well-known geologic, geomorphic, and geodetic constraining data including hanging wall continental basin Quaternary deposits, footwall stream networks with distinct knickpoints, a dense GPS network, and InSAR interferometry. Collectively, the geodetic data describe the short-term, co- and immediately post-seismic behavior of the earthquake, whereas the geologic and geomorphic data record how discrete rupture events are encoded in the landscape and reflected in processes actively shaping the topography. Envisat and ALOS derived interferograms generated using ROI PAC show close spatial overlap of the InSAR-determined rupture and the Paganica fault, separating a deeply incised, uplifted carbonate footwall block and an actively subsiding Quaternary continental basin. Deposition in the continental basin has been unsteady and is commonly attributed to climate-modulated sediment flux from the uplifted footwall. We note however, that the longitudinal profiles of streams in the footwall are marked by distinct knickpoints that do not correspond to known or obvious lithologic or structural controls. Rather, the knickpoints are located a linear distance from the Paganica fault and at a topographic elevation consistent with detachment-limited stream-power erosional retreat processes instigated by instantaneous base level fall at the mountain front. Furthermore, the magnitude of river incision and elevation of the knickpoints scales with the co-seismic deformation pattern we measure through our InSAR approach. The time of the base level falls can be estimated assuming a model for knickpoint retreat rate and through correlation of knickpoints to lithostratigraphic packages of sediment in the continental basin. These results suggest that the Paganica fault has a characteristic rupture geometry, but an unsteady rupture behavior punctuated by periods of frequent activity interspersed with periods of quiescence that persist for several millennia. We conclude that the Paganica fault is currently in an active rupture phase. Regional geomorphic metrics suggest that as the Paganica fault passes through its current active phase, deformation should be transferred to the Campo Imperatore fault, which is currently in a relatively inactive, interseismic phase. Such a prediction is testable by geodetic techniques including InSAR to capture the slow, but cumulative interseismic component of active extension for this part of the Apennines.

Protecting Against Faults in JPL Spacecraft

NASA Technical Reports Server (NTRS)

Morgan, Paula

2007-01-01

A paper discusses techniques for protecting against faults in spacecraft designed and operated by NASA s Jet Propulsion Laboratory (JPL). The paper addresses, more specifically, fault-protection requirements and techniques common to most JPL spacecraft (in contradistinction to unique, mission specific techniques), standard practices in the implementation of these techniques, and fault-protection software architectures. Common requirements include those to protect onboard command, data-processing, and control computers; protect against loss of Earth/spacecraft radio communication; maintain safe temperatures; and recover from power overloads. The paper describes fault-protection techniques as part of a fault-management strategy that also includes functional redundancy, redundant hardware, and autonomous monitoring of (1) the operational and health statuses of spacecraft components, (2) temperatures inside and outside the spacecraft, and (3) allocation of power. The strategy also provides for preprogrammed automated responses to anomalous conditions. In addition, the software running in almost every JPL spacecraft incorporates a general-purpose "Safe Mode" response algorithm that configures the spacecraft in a lower-power state that is safe and predictable, thereby facilitating diagnosis of more complex faults by a team of human experts on Earth.

Evidence for faulting related to dissociation of gas hydrate and release of methane off the southeastern United States

USGS Publications Warehouse

Dillon, William P.; Danforth, W.W.; Hutchinson, D.R.; Drury, R.M.; Taylor, M.H.; Booth, J.S.

1998-01-01

This paper is part of the special publication Gas hydrates: relevance to world margin stability and climatic change (eds J.P. Henriet and J. Mienert). An irregular, faulted, collapse depression about 38 x 18 km in extent is located on the crest of the Blake Ridge offshore from the south- eastern United States. Faults disrupt the sea floor and terminate or sole out about 40-500 m below the sea floor at the base of the gas hydrate stable zone, which is identified from the location of the bottom simulating reflection (BSR). Normal faults are common but reverse faults and folds also are widespread. Folds commonly convert upward into faults. Sediment diapirs and deposits of sediments that were erupted onto the sea floor are also present. Sea-floor depressions at faults may represent locations of liquid/gas vents. The collapse was probably caused by overpressures and by the decoupling of the overlying sediments by gassy muds that existed just beneath the zone of gas hydrate stability.

Tectonic setting of the Taubaté Basin (Southeastern Brazil): Insights from regional seismic profiles and outcrop data

NASA Astrophysics Data System (ADS)

Cogné, Nathan; Cobbold, Peter R.; Riccomini, Claudio; Gallagher, Kerry

2013-03-01

In southeastern Brazil, a series of onshore Tertiary basins provides good evidence for post-rift tectonic activity. So as better to constrain their tectonic setting, we have revisited outcrops in the Taubaté and Resende basins and have reinterpreted 11 seismic profiles of the Taubaté Basin. Where Eocene to Oligocene strata crop out, syn-sedimentary faults are common and their senses of slip are mainly normal. In contrast, for two outcrops in particular, where syn-sedimentary faults have put Precambrian crystalline basement against Eocene strata, senses of slip are strongly left-lateral, as well as normal. Thus we distinguish between thin-skinned and thick-skinned faulting. Furthermore, at four outcrops, Precambrian basement has overthrust Tertiary or Quaternary strata. On the seismic profiles, basal strata onlap basement highs. Structures and stratigraphic relationships are not typical of a rift basin. Although normal faults are common, they tend to be steeply dipping, their stratigraphic offsets are small (tens of metres) and the faults do not bound large stratigraphic wedges or tilted blocks. At the edges of the basin, Eocene or Oligocene strata dip basinward, have been subject to exhumation, and in places form gentle anticlines, so that we infer post-Oligocene inversion. We conclude that, after an earlier phase of deformation, probably during the Late Cretaceous, the Taubaté Basin formed under left-lateral transtension during the Palaeogene, but was subject to right-lateral transpression during the Neogene. Thus the principal directions of stress varied in time. Because they did so consistently with those of the adjacent regions, as well as those of the Incaic and Quechua phases of Andean orogeny, we argue that the Tertiary basins of southeast Brazil have resulted from reactivation of Precambrian shear zones under plate-wide stress.

Coordinated Fault Tolerance for High-Performance Computing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dongarra, Jack; Bosilca, George; et al.

2013-04-08

Our work to meet our goal of end-to-end fault tolerance has focused on two areas: (1) improving fault tolerance in various software currently available and widely used throughout the HEC domain and (2) using fault information exchange and coordination to achieve holistic, systemwide fault tolerance and understanding how to design and implement interfaces for integrating fault tolerance features for multiple layers of the software stack—from the application, math libraries, and programming language runtime to other common system software such as jobs schedulers, resource managers, and monitoring tools.

Structural controls on the spatial distribution and geochemical composition of volcanism in a continental rift zone; an example from Owens Valley, eastern California

NASA Astrophysics Data System (ADS)

Haproff, P. J.; Yin, A.

2014-12-01

Bimodal volcanism is common in continental rift zones. Structural controls to the emplacement and compositions of magmas, however, are not well understood. To address this issue, we examine the location, age, and geochemistry of active volcanic centers, and geometry and kinematics of rift-related faults across the active transtensional Owens Valley rift zone. Building on existing studies, we postulate that the spatial distribution and geochemical composition of volcanism are controlled by motion along rift-bounding fault systems. Along-strike variation in fault geometry and characteristics of active volcanism allow us to divide Owens Valley into three segments: southern, northern, and central. The southern segment of Owens Valley is a simple shear, asymmetric rift bounded to the west by the east-dipping Sierra Nevada frontal fault (SNFF). Active vents of Coso volcanic field are distributed along the eastern rift shoulder and characterized by the eruption of bimodal lavas. The SNFF within this segment is low-angle and penetrates through the lithosphere and into the ductile asthenosphere, allowing for mantle-derived magma to migrate across the weakest part of the fault zone beneath the eastern rift shoulder. Magma thermally weakens wall rocks and eventually stalls in the crust where the melt develops a greater felsic component prior to eruption. The northern segment of Owens Valley displays similar structural geometry, as the west-dipping White Mountains fault (WMF) is listric at depth and offsets the crust and mantle lithosphere, allowing for vertical transport of magma and reservoir emplacement within the crust. Bimodal lavas periodically erupted in the Long Valley Caldera region along the western rift shoulder. The central segment of Owens Valley is a pure shear, symmetric graben generated by motion along the SNFF and WMF. The subvertical, right-slip Owens Valley fault (OVF) strikes along the axis of the valley and penetrates through the lithosphere into the asthenosphere. Volcanic centers of Big Pine volcanic field are located along the trace of the OVF and characterized by mafic eruptions. The OVF is interpreted to provide a subvertical conduit for asthenospheric magma to migrate across the LAB and Moho and erupt on the rift surface without significant contamination with felsic crust.

Structural Analysis of Mt. Epomeo Resurgent Block (ischia, Italy): Deformational Features, Uplifting Mechanism and Implications For Volcanic Hazard Assessment.

NASA Astrophysics Data System (ADS)

de Vita, S.; Marotta, E.; Orsi, G.

The studies carried out on the resurgent calderas of Campi Flegrei, Pantelleria and Is- chia, evidenced that the geometry of the resurgent blocks and the arial distribution of volcanic vents active after the caldera collapse, are not compatible with the commonly accepted resurgent dome model. For these areas a simple shearing block resurgence mechanism, that take in account all the geological and volcanological constraints, has been proposed. In order to define the structural setting of a resurgent block for which this mechanism has been proposed, a detailed structural study has been carried out on the island of Ischia, where the Mt. Epomeo was uplifted of about 900 m in the past 30 ka. The attitude of 1400 planar surfaces has been measured in 50 different sites around the resurgent block. These features have been distinguished in: a) faults; b) joints; c) fracture cleavages. It has been observed that the resurgent area is composed of differentially displaced blocks whose uplifting is maximum for the Mt. Epomeo and decreases southeastward. The resurgent area has a poligonal shape resulting from the reactivation of regional faults and by the activation of faults directly related to volcan- otectonism. Northeastward the limit of the resurgent area is not defined, as along the coastline are exposed beach deposits displaced at variable elevation by E-W and NW- SE trending faults. The western sector is bordered by inward dipping, high angle re- verse faults, whose directions vary from N40E to NS and N50W from the northwestern to the southwestern parts of the block, testifying a compressional stress regime active in this area. These features are cut by late outward dipping normal faults due to grav- itational readjustment of the slopes. The northeastern and the southwestern sides are bordered by vertical faults with right transtensive and left transpressive movements, respectively. The area located to the east of the most uplifted block is characterized by a tensile stress regime and has been deformed by N-S, N40-70E and N15W trending normal faults, which demonstrates that the maximum elongation direction is N50W. The results of this study, together with the volcanological data available for the past 3 ka of activity, suggest that the eastern part of the resurgent block is the area with the highest probability of vent opening in case of renewal of volcanism.

Dating Tectonic Activity on Mercury’s Large-Scale Lobate-Scarp Thrust Faults

NASA Astrophysics Data System (ADS)

Barlow, Nadine G.; E Banks, Maria

2017-10-01

Mercury’s widespread large-scale lobate-scarp thrust faults reveal that the planet’s tectonic history has been dominated by global contraction, primarily due to cooling of its interior. Constraining the timing and duration of this contraction provides key insight into Mercury’s thermal and geologic evolution. We combine two techniques to enhance the statistical validity of size-frequency distribution crater analyses and constrain timing of the 1) earliest and 2) most recent detectable activity on several of Mercury’s largest lobate-scarp thrust faults. We use the sizes of craters directly transected by or superposed on the edge of the scarp face to define a count area around the scarp, a method we call the Modified Buffered Crater Counting Technique (MBCCT). We developed the MBCCT to avoid the issue of a near-zero scarp width since feature widths are included in area calculations of the commonly used Buffered Crater Counting Technique (BCCT). Since only craters directly intersecting the scarp face edge conclusively show evidence of crosscutting relations, we increase the number of craters in our analysis (and reduce uncertainties) by using the morphologic degradation state (i.e. relative age) of these intersecting craters to classify other similarly degraded craters within the count area (i.e., those with the same relative age) as superposing or transected. The resulting crater counts are divided into two categories: transected craters constrain the earliest possible activity and superposed craters constrain the most recent detectable activity. Absolute ages are computed for each population using the Marchi et al. [2009] model production function. A test of the Blossom lobate scarp indicates the MBCCT gives statistically equivalent results to the BCCT. We find that all scarps in this study crosscut surfaces Tolstojan or older in age (>~3.7 Ga). The most recent detectable activity along lobate-scarp thrust faults ranges from Calorian to Kuiperian (~3.7 Ga to present). Our results complement previous relative-age studies with absolute ages and indicate global contraction continued over the last ~3-4 Gyr. At least some thrust fault activity occurred on Mercury in relatively recent times (<280 Ma).

Fault-based PSHA of an active tectonic region characterized by low deformation rates: the case of the Lower Rhine Graben

NASA Astrophysics Data System (ADS)

Vanneste, Kris; Vleminckx, Bart; Camelbeeck, Thierry

2016-04-01

The Lower Rhine Graben (LRG) is one of the few regions in intraplate NW Europe where seismic activity can be linked to active faults, yet probabilistic seismic hazard assessments of this region have hitherto been based on area-source models, in which the LRG is modeled as a single or a small number of seismotectonic zones with uniform seismicity. While fault-based PSHA has become common practice in more active regions of the world (e.g., California, Japan, New Zealand, Italy), knowledge of active faults has been lagging behind in other regions, due to incomplete tectonic inventory, low level of seismicity, lack of systematic fault parameterization, or a combination thereof. The past few years, efforts are increasingly being directed to the inclusion of fault sources in PSHA in these regions as well, in order to predict hazard on a more physically sound basis. In Europe, the EC project SHARE ("Seismic Hazard Harmonization in Europe", http://www.share-eu.org/) represented an important step forward in this regard. In the frame of this project, we previously compiled the first parameterized fault model for the LRG that can be applied in PSHA. We defined 15 fault sources based on major stepovers, bifurcations, gaps, and important changes in strike, dip direction or slip rate. Based on the available data, we were able to place reasonable bounds on the parameters required for time-independent PSHA: length, width, strike, dip, rake, slip rate, and maximum magnitude. With long-term slip rates remaining below 0.1 mm/yr, the LRG can be classified as a low-deformation-rate structure. Information on recurrence interval and elapsed time since the last major earthquake is lacking for most faults, impeding time-dependent PSHA. We consider different models to construct the magnitude-frequency distribution (MFD) of each fault: a slip-rate constrained form of the classical truncated Gutenberg-Richter MFD (Anderson & Luco, 1983) versus a characteristic MFD following Youngs & Coppersmith (1985). The summed Anderson & Luco fault MFDs show a remarkably good agreement with the MFD obtained from the historical and instrumental catalog for the entire LRG, whereas the summed Youngs & Coppersmith MFD clearly underpredicts low to moderate magnitudes, but yields higher occurrence rates for M > 6.3 than would be obtained by simple extrapolation of the catalog MFD. The moment rate implied by the Youngs & Coppersmith MFDs is about three times higher, but is still within the range allowed by current GPS uncertainties. Using the open-source hazard engine OpenQuake (http://openquake.org/), we compute hazard maps for return periods of 475, 2475, and 10,000 yr, and for spectral periods of 0 s (PGA) and 1 s. We explore the impact of various parameter choices, such as MFD model, GMPE distance metric, and inclusion of a background zone to account for lower magnitudes, and we also compare the results with hazard maps based on area-source models. References: Anderson, J. G., and J. E. Luco (1983), Consequences of slip rate constraints on earthquake occurrence relations, Bull. Seismol. Soc. Am., 73(2), 471-496. Youngs, R. R., and K. J. Coppersmith (1985), Implications of fault slip rates and earthquake recurrence models to probabilistic seismic hazard estimates, Bull. Seismol. Soc. Am., 75(4), 939-964.

The hazard education model in the high school science-club activities above active huge fault

NASA Astrophysics Data System (ADS)

Nakamura, R.

2017-12-01

Along the west coast of pacific ocean, includes Japan, there are huge numerous volcanoes and earthquakes. The biggest cause is their location on the border of plates. The pressure among the plates cause strains and cracks. By the island arc lines, strains make long and enormous faults. More than huge 150 faults are reported (the head quarters for earthquake research promotion, Japan, 2017). Below my working school, it is laying one of the biggest faults Nagamachi-Rifu line which is also laying under 1 million population city Sendai. Before 2011 Tohoku earthquake, one of the hugest earthquake was predicted because of the fault activities. Investigating the fault activity with our school student who live in the closest area is one of the most important hazard education. Therefore, now we are constructing the science club activity with make attention for (1) seeking fault line(s) with topographic land maps and on foot search (2) investigate boling core sample soils that was brought in our school founded. (1) Estimate of displacement of the faults on foot observation In order to seek the unknown fault line in Rifu area, at first it was needed to estimate on the maps(1:25,000 Scale Topographic Maps and Active Faults in Urban Area of Map(Sendai), Geographical Survey Institute of Japan). After that estimation, walked over the region with club students to observe slopes which was occurred by the faults activation and recorded on the maps. By observant slope gaps, there has a possibilities to have 3 or 4 fault lines that are located parallel to the known activate faults. (2) Investigate of the boling core samples above the fault. We investigated 6 columnar-shaped boling core samples which were excavated when the school has been built. The maximum depth of the samples are over 20m, some are new filled sands over original ash tephra and pumice from old volcanoes located west direction. In the club activities, we described column diagram of sediments and discussed the sediment circumstances by the sediments grain observation, however, it was impossible to describe the sediments origin of exact volcano(es).

Structural superposition in fault systems bounding Santa Clara Valley, California

USGS Publications Warehouse

Graymer, Russell W.; Stanley, Richard G.; Ponce, David A.; Jachens, Robert C.; Simpson, Robert W.; Wentworth, Carl M.

2015-01-01

Santa Clara Valley is bounded on the southwest and northeast by active strike-slip and reverse-oblique faults of the San Andreas fault system. On both sides of the valley, these faults are superposed on older normal and/or right-lateral normal oblique faults. The older faults comprised early components of the San Andreas fault system as it formed in the wake of the northward passage of the Mendocino Triple Junction. On the east side of the valley, the great majority of fault displacement was accommodated by the older faults, which were almost entirely abandoned when the presently active faults became active after ca. 2.5 Ma. On the west side of the valley, the older faults were abandoned earlier, before ca. 8 Ma and probably accumulated only a small amount, if any, of the total right-lateral offset accommodated by the fault zone as a whole. Apparent contradictions in observations of fault offset and the relation of the gravity field to the distribution of dense rocks at the surface are explained by recognition of superposed structures in the Santa Clara Valley region.

Quaternary Geology and Surface Faulting Hazard: Active and Capable Faults in Central Apennines, Italy

NASA Astrophysics Data System (ADS)

Falcucci, E.; Gori, S.

2015-12-01

The 2009 L'Aquila earthquake (Mw 6.1), in central Italy, raised the issue of surface faulting hazard in Italy, since large urban areas were affected by surface displacement along the causative structure, the Paganica fault. Since then, guidelines for microzonation were drew up that take into consideration the problem of surface faulting in Italy, and laying the bases for future regulations about related hazard, similarly to other countries (e.g. USA). More specific guidelines on the management of areas affected by active and capable faults (i.e. able to produce surface faulting) are going to be released by National Department of Civil Protection; these would define zonation of areas affected by active and capable faults, with prescriptions for land use planning. As such, the guidelines arise the problem of the time interval and general operational criteria to asses fault capability for the Italian territory. As for the chronology, the review of the international literature and regulatory allowed Galadini et al. (2012) to propose different time intervals depending on the ongoing tectonic regime - compressive or extensional - which encompass the Quaternary. As for the operational criteria, the detailed analysis of the large amount of works dealing with active faulting in Italy shows that investigations exclusively based on surface morphological features (e.g. fault planes exposition) or on indirect investigations (geophysical data), are not sufficient or even unreliable to define the presence of an active and capable fault; instead, more accurate geological information on the Quaternary space-time evolution of the areas affected by such tectonic structures is needed. A test area for which active and capable faults can be first mapped based on such a classical but still effective methodological approach can be the central Apennines. Reference Galadini F., Falcucci E., Galli P., Giaccio B., Gori S., Messina P., Moro M., Saroli M., Scardia G., Sposato A. (2012). Time intervals to assess active and capable faults for engineering practices in Italy. Eng. Geol., 139/140, 50-65.

Evolving transpressional strain fields along the San Andreas fault in southern California: implications for fault branching, fault dip segmentation and strain partitioning

NASA Astrophysics Data System (ADS)

Bergh, Steffen; Sylvester, Arthur; Damte, Alula; Indrevær, Kjetil

2014-05-01

The San Andreas fault in southern California records only few large-magnitude earthquakes in historic time, and the recent activity is confined primarily on irregular and discontinuous strike-slip and thrust fault strands at shallow depths of ~5-20 km. Despite this fact, slip along the San Andreas fault is calculated to c. 35 mm/yr based on c.160 km total right lateral displacement for the southern segment of the fault in the last c. 8 Ma. Field observations also reveal complex fault strands and multiple events of deformation. The presently diffuse high-magnitude crustal movements may be explained by the deformation being largely distributed along more gently dipping reverse faults in fold-thrust belts, in contrast to regions to the north where deformation is less partitioned and localized to narrow strike-slip fault zones. In the Mecca Hills of the Salton trough transpressional deformation of an uplifted segment of the San Andreas fault in the last ca. 4.0 My is expressed by very complex fault-oblique and fault-parallel (en echelon) folding, and zones of uplift (fold-thrust belts), basement-involved reverse and strike-slip faults and accompanying multiple and pervasive cataclasis and conjugate fracturing of Miocene to Pleistocene sedimentary strata. Our structural analysis of the Mecca Hills addresses the kinematic nature of the San Andreas fault and mechanisms of uplift and strain-stress distribution along bent fault strands. The San Andreas fault and subsidiary faults define a wide spectrum of kinematic styles, from steep localized strike-slip faults, to moderate dipping faults related to oblique en echelon folds, and gently dipping faults distributed in fold-thrust belt domains. Therefore, the San Andreas fault is not a through-going, steep strike-slip crustal structure, which is commonly the basis for crustal modeling and earthquake rupture models. The fault trace was steep initially, but was later multiphase deformed/modified by oblique en echelon folding, renewed strike-slip movements and contractile fold-thrust belt structures. Notably, the strike-slip movements on the San Andreas fault were transformed outward into the surrounding rocks as oblique-reverse faults to link up with the subsidiary Skeleton Canyon fault in the Mecca Hills. Instead of a classic flower structure model for this transpressional uplift, the San Andreas fault strands were segmented into domains that record; (i) early strike-slip motion, (ii) later oblique shortening with distributed deformation (en echelon fold domains), followed by (iii) localized fault-parallel deformation (strike-slip) and (iv) superposed out-of-sequence faulting and fault-normal, partitioned deformation (fold-thrust belt domains). These results contribute well to the question if spatial and temporal fold-fault branching and migration patterns evolving along non-vertical strike-slip fault segments can play a role in the localization of earthquakes along the San Andreas fault.

The Rome trough and evolution of the Iapetean margin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walker, D.; Hamilton-Smith, T.; Drahovzal, J.A.

1991-08-01

Recent structural mapping of the Rome trough suggests a complex structure very different from the symmetrical and laterally continuous graben commonly depicted. Early and Middle Cambrian extension in the Rome trough of eastern Kentucky and adjacent areas resulted in a series of alternately facing half-grabens with variable displacement. These half-grabens are bounded by southwest-northeast-trending normal faults (e.g., Kentucky River and Warfield faults), which are laterally continuous only on the order to tens of kilometers. The Rome trough is laterally segmented by north-south-trending faults (e.g., Lexington fault) commonly expressed as flexures in younger rocks (e.g., Burning Springs anticline and Floyd Countymore » channel). Many of these north-south-trending faults have significant left-lateral displacement, and probably represent reactivated thrust faults of the Grenville tectonic front. The Rome trough and the associated Mississippi Valley, Rough Creek, and Birmingham fault systems were initiated during an Early Cambrian shift in sea-floor spreading from the Blue Ridge-Pine Mountain rift to the Ouachita rift along the Alabama-Oklahoma transform fault. These fault systems have been proposed as having originated from extensional stress propagated northward from the Ouachita rift across the transform fault. In the alternate model proposed here, faulting was brittle, extensional failure resulting form subsidence and flexure of the continental margin to the east. Following initiation of sea-floor spreading at the Blue Ridge-Pine Mountain rift in the latest Proterozoic, margin subsidence in the presence of the Alabama-Oklahoma transform boundary and the inherited Grenville tectonic front resulted in this interior cratonic fault system.« less

Levelling Profiles and a GPS Network to Monitor the Active Folding and Faulting Deformation in the Campo de Dalias (Betic Cordillera, Southeastern Spain)

PubMed Central

Marín-Lechado, Carlos; Galindo-Zaldívar, Jesús; Gil, Antonio José; Borque, María Jesús; de Lacy, María Clara; Pedrera, Antonio; López-Garrido, Angel Carlos; Alfaro, Pedro; García-Tortosa, Francisco; Ramos, Maria Isabel; Rodríguez-Caderot, Gracia; Rodríguez-Fernández, José; Ruiz-Constán, Ana; de Galdeano-Equiza, Carlos Sanz

2010-01-01

The Campo de Dalias is an area with relevant seismicity associated to the active tectonic deformations of the southern boundary of the Betic Cordillera. A non-permanent GPS network was installed to monitor, for the first time, the fault- and fold-related activity. In addition, two high precision levelling profiles were measured twice over a one-year period across the Balanegra Fault, one of the most active faults recognized in the area. The absence of significant movement of the main fault surface suggests seismogenic behaviour. The possible recurrence interval may be between 100 and 300 y. The repetitive GPS and high precision levelling monitoring of the fault surface during a long time period may help us to determine future fault behaviour with regard to the existence (or not) of a creep component, the accumulation of elastic deformation before faulting, and implications of the fold-fault relationship. PMID:22319309

Faults in parts of north-central and western Houston metropolitan area, Texas

USGS Publications Warehouse

Verbeek, Earl R.; Ratzlaff, Karl W.; Clanton, Uel S.

1979-01-01

Hundreds of residential, commercial, and industrial structures in the Houston metropolitan area have sustained moderate to severe damage owing to their locations on or near active faults. Paved roads have been offset by faults at hundreds of locations, butted pipelines have been distorted by fault movements, and fault-induced gradient changes in drainage lines have raised concern among flood control engineers. Over 150 faults, many of them moving at rates of 0.5 to 2 cm/yr, have been mapped in the Houston area; the number of faults probably far exceeds this figure.This report includes a map of eight faults, in north-central and western Houston, at a scale useful for land-use planning. Seven of the faults, are known, to be active and have caused considerable damage to structures built on or near them. If the eighth fault is active, it may be of concern to new developments on the west side of Houston. A ninth feature shown on the map is regarded only as a possible fault, as an origin by faulting has not been firmly established.Seismic and drill-hold data for some 40 faults, studied in detail by various investigators have verified connections between scarps at the land surface and growth faults in the shallow subsurface. Some scarps, then, are known to be the surface manifestations of faults that have geologically long histories of movement. The degree to which natural geologic processes contribute to current fault movement, however, is unclear, for some of man’s activities may play a role in faulting as well.Evidence that current rates of fault movement far exceed average prehistoric rates and that most offset of the land surface in the Houston area has occurred only within the last 50 years indirectly suggest that fluid withdrawal may be accelerating or reinitiating movement on pre-existing faults. This conclusion, however, is based only on a coincidence in time between increased fault activity and increased rates of withdrawal of water, oil, and gas from subsurface sediments; no cause-and-effect relationship has been demonstrated. An alternative hypothesis is that natural fault movements are characterized by short—term episodicity and that Houston is experiencing the effects of a brief period of accelerated natural fault movement. Available data from monitored faults are insufficient to weigh the relative importance of natural vs. induced fault movements.

Size matters: The effects of displacement magnitude on the fluid flow properties of faults in poorly lithified sediments

NASA Astrophysics Data System (ADS)

Loveless, S. E.; Bense, V.; Turner, J.

2011-12-01

Many aquifers worldwide occur in poorly lithified sediments, often in regions that experience active tectonic deformation. Faulting of these sediments introduces heterogeneities that may affect aquifer porosity and permeability, and consequently subsurface fluid flow and groundwater storage. The specific hydrogeological effects of faults depend upon the fault architecture and deformation mechanisms. These are controlled by factors such as rheology, stratigraphy and burial depth. Here, we analyse fault permeability in poorly lithified sediments as a function of fault displacement. We have carried out detailed outcrop studies of minor normal faults at five study sites within the rapidly extending Corinth rift, Central Greece. Gravel conglomerates of giant Gilbert delta facies form productive but localised shallow aquifers within the region. Exposures reveal dense (average 20 faults per 100 m) networks of minor (0.1 to 50 m displacement) normal faults within the uplifted sequences, proximal to many of the crustal-scale normal faults. Analysis of 42 faults shows that fault zones are primarily composed of smeared beds that can either retain their definition or mix with surrounding sediment. Lenses or blocks of sediment are common in fault zones that cut beds with contrasting rheology, and a few faults have a clay core and/or damage zone. Fault thickness increases at a rate of about 0.4 m per 10 m increase in displacement. Comparison of sediment micro-structures from the field, hand samples and thin sections show grain-scale sediment mixing, fracturing of clasts, and in some cases cementation, within fault zones. In faults with displacements >12 m we also find a number of roughly parallel, highly indurated shear planes, up to 20 mm in thickness, composed of highly fragmented clasts and a fine grained matrix. Image analysis of thin sections from hand samples collected in the field was used to quantify the porosity of fault zones and adjacent undeformed sediment. These data show a reduction in average porosity from 21% (± 4) in undisturbed sediments to 14% (± 8) within fault zones. We find that fault zone porosity decreases by approximately 5% per 1 m displacement (up to 2 m displacement), as sediments undergo greater micro-scale deformation. Porosity within the shear planes of larger displacement faults (> 12 m) is significantly less than 5%. In summary, with an increase in fault displacement there is an increase in fault thickness and decrease in fault zone porosity, in addition to the occurrence of extremely low porosity shear planes. Consequently, the impact of faults in poorly lithified sediment on fluid flow is, to a large degree, dependent upon the magnitude of fault displacement.

Glacial loess or shoreface sands: a re-interpretation of the Upper Ordovician (Ashgillian) glacial Ammar Formation, Southern Jordan

NASA Astrophysics Data System (ADS)

Turner, B. R.; Makhlouf, I. M.; Armstrong, H. A.

2003-04-01

Upper Ordovician (Ashgillian) glacial deposits of the Ammar Formation, Southern Jordan, comprise locally deformed, structureless fine sandstone, incised by glacial channels filled by braided outwash plain sandstones and transgressive marine mudstones. The structureless sandstones, previously interpreted as a glacial rock flour or loessite derived from the underlying undisturbed sandstones, differ significantly from typical loessite and contain hitherto unrecognised sedimentary structures, including hummocky cross-stratification. The sandstones, which grade laterally and vertically into stratigraphically equivalent undeformed marginal marine sandstones, are interpreted as a deformed facies of the underlying sandstones, deposited in a similar high energy shoreface environment. Although deformation of the shoreface sandstones was post-depositional, the origin of the deformation, and its confinement to the Jebel Ammar area is unknown. Deformation due to the weight of the overlying ice is unlikely as the glaciofluvial channels are now thought to have been cut by tunnel valley activity not ice. A more likely mechanism is post-glacial crustal tectonics. Melting of ice caps is commonly associated with intraplate seismicity and the development of an extensional crustal stress regime around the perimeter of ice caps; the interior is largely aseismic because the weight of the ice supresses seismic activity and faulting. Since southern Jordan lay close to the ice cap in Saudi Arabia it may have been subjected to postglacial seismicity and crustal stress, which induced ground shaking, reduced overburden pressure, increased hydrostatic pressure and possibly reactivation of existing tectonic faults. This resulted in liquefaction and extensive deformation of the sediments, which show many characteristics of seismites, generated by earthquake shocks. Since the glaciation was a very short-lived event (0.2-1 Ma), deglaciation and associated tectonism triggering deformation, lasted not more than a few hundred thousand years. Deglaciation and crustal unloading commonly lead to seismically-induced reactivation of tectonic faults. This relationship provides a possible explanation for the localisation of the deformation to the Jebel Ammar area which lies on the footwall of the Hutayya graben. The fault may also have acted as a conduit for post-seismic fluid movement along the fault plane under high pressure, thereby enhancing permeability and promoting fluid migration.

Recent deformation along the offshore Malibu Coast, Dume, and related faults west of Point Dume, southern California

USGS Publications Warehouse

Fisher, M.A.; Langenheim, V.E.; Sorlien, C.C.; Dartnell, P.; Sliter, R.W.; Cochrane, G.R.; Wong, F.L.

2005-01-01

Offshore faults west of Point Dume, southern California, are part of an important regional fault system that extends for about 206 km, from near the city of Los Angeles westward along the south flank of the Santa Monica Mountains and through the northern Channel Islands. This boundary fault system separates the western Transverse Ranges, on the north, from the California Continental Borderland, on the south. Previous research showed that the fault system includes many active fault strands; consequently, the entire system is considered a serious potential earthquake hazard to nearby Los Angeles. We present an integrated analysis of multichannel seismic- and high-resolution seismic-reflection data and multibeam-bathymetric information to focus on the central part of the fault system that lies west of Point Dume. We show that some of the main offshore faults have cumulative displacements of 3-5 km, and many faults are currently active because they deform the seafloor or very shallow sediment layers. The main offshore fault is the Dume fault, a large north-dipping reverse fault. In the eastern part of the study area, this fault offsets the seafloor, showing Holocene displacement. Onshore, the Malibu Coast fault dips steeply north, is active, and shows left-oblique slip. The probable offshore extension of this fault is a large fault that dips steeply in its upper part but flattens at depth. High-resolution seismic data show that this fault deforms shallow sediment making up the Hueneme fan complex, indicating Holocene activity. A structure near Sycamore knoll strikes transversely to the main faults and could be important to the analysis of the regional earthquake hazard because the structure might form a boundary between earthquake-rupture segments.

Activation of preexisting transverse structures in an evolving magmatic rift in East Africa

NASA Astrophysics Data System (ADS)

Muirhead, J. D.; Kattenhorn, S. A.

2018-01-01

Inherited crustal weaknesses have long been recognized as important factors in strain localization and basin development in the East African Rift System (EARS). However, the timing and kinematics (e.g., sense of slip) of transverse (rift-oblique) faults that exploit these weaknesses are debated, and thus the roles of inherited weaknesses at different stages of rift basin evolution are often overlooked. The mechanics of transverse faulting were addressed through an analysis of the Kordjya fault of the Magadi basin (Kenya Rift). Fault kinematics were investigated from field and remote-sensing data collected on fault and joint systems. Our analysis indicates that the Kordjya fault consists of a complex system of predominantly NNE-striking, rift-parallel fault segments that collectively form a NNW-trending array of en echelon faults. The transverse Kordjya fault therefore reactivated existing rift-parallel faults in ∼1 Ma lavas as oblique-normal faults with a component of sinistral shear. In all, these fault motions accommodate dip-slip on an underlying transverse structure that exploits the Aswa basement shear zone. This study shows that transverse faults may be activated through a complex interplay among magma-assisted strain localization, preexisting structures, and local stress rotations. Rather than forming during rift initiation, transverse structures can develop after the establishment of pervasive rift-parallel fault systems, and may exhibit dip-slip kinematics when activated from local stress rotations. The Kordjya fault is shown here to form a kinematic linkage that transfers strain to a newly developing center of concentrated magmatism and normal faulting. It is concluded that recently activated transverse faults not only reveal the effects of inherited basement weaknesses on fault development, but also provide important clues regarding developing magmatic and tectonic systems as young continental rift basins evolve.

Structural character of the Ghost Dance fault, Yucca Mountain, Nevada

USGS Publications Warehouse

Spengler, R.W.; Braun, C.A.; Linden, R.M.; Martin, L.G.; Ross-Brown, D. M.; Blackburn, R.L.

1993-01-01

Detailed structural mapping of an area that straddles the southern part of the Ghost Dance Fault has revealed the presence of several additional subparallel to anastomosing faults. These faults, mapped at a scale of 1:240, are: 1) dominantly north trending, 2) present on both the upthrown and downthrown sides of the surface trace of the Ghost Dance fault, 3) near-vertical features that commonly offset strata down to the west by 3 to 6 m (10 to 20 ft), and 4) commonly spaced 15 to 46 m (50 to 150 ft) apart. The zone also exhibits a structural fabric, containing an abundance of northwest-trending fractures. The width of the zone appears to be at least 213 m (700 ft) near the southernmost boundary of the study area but remains unknown near the northern extent of the study area, where the width of the study area is only 183 m (600 ft).

Interactions between Polygonal Normal Faults and Larger Normal Faults, Offshore Nova Scotia, Canada

NASA Astrophysics Data System (ADS)

Pham, T. Q. H.; Withjack, M. O.; Hanafi, B. R.

2017-12-01

Polygonal faults, small normal faults with polygonal arrangements that form in fine-grained sedimentary rocks, can influence ground-water flow and hydrocarbon migration. Using well and 3D seismic-reflection data, we have examined the interactions between polygonal faults and larger normal faults on the passive margin of offshore Nova Scotia, Canada. The larger normal faults strike approximately E-W to NE-SW. Growth strata indicate that the larger normal faults were active in the Late Cretaceous (i.e., during the deposition of the Wyandot Formation) and during the Cenozoic. The polygonal faults were also active during the Cenozoic because they affect the top of the Wyandot Formation, a fine-grained carbonate sedimentary rock, and the overlying Cenozoic strata. Thus, the larger normal faults and the polygonal faults were both active during the Cenozoic. The polygonal faults far from the larger normal faults have a wide range of orientations. Near the larger normal faults, however, most polygonal faults have preferred orientations, either striking parallel or perpendicular to the larger normal faults. Some polygonal faults nucleated at the tip of a larger normal fault, propagated outward, and linked with a second larger normal fault. The strike of these polygonal faults changed as they propagated outward, ranging from parallel to the strike of the original larger normal fault to orthogonal to the strike of the second larger normal fault. These polygonal faults hard-linked the larger normal faults at and above the level of the Wyandot Formation but not below it. We argue that the larger normal faults created stress-enhancement and stress-reorientation zones for the polygonal faults. Numerous small, polygonal faults formed in the stress-enhancement zones near the tips of larger normal faults. Stress-reorientation zones surrounded the larger normal faults far from their tips. Fewer polygonal faults are present in these zones, and, more importantly, most polygonal faults in these zones were either parallel or perpendicular to the larger faults.

The mechanism of post-rift fault activities in Baiyun sag, Pearl River Mouth basin

NASA Astrophysics Data System (ADS)

Sun, Zhen; Xu, Ziying; Sun, Longtao; Pang, Xiong; Yan, Chengzhi; Li, Yuanping; Zhao, Zhongxian; Wang, Zhangwen; Zhang, Cuimei

2014-08-01

Post-rift fault activities were often observed in deepwater basins, which have great contributions to oil and gas migration and accumulation. The main causes for post-rift fault activities include tectonic events, mud or salt diapirs, and gravitational collapse. In the South China Sea continental margin, post-rift fault activities are widely distributed, especially in Baiyun sag, one of the largest deepwater sag with its main body located beneath present continental slope. During the post-rift stage, large population of faults kept active for a long time from 32 Ma (T70) till 5.5 Ma (T10). Seismic interpretation, fault analysis and analogue modeling experiments indicate that the post-rift fault activities in Baiyun sag between 32 Ma (T70) and 13.8 Ma (T30) was mainly controlled by gravity pointing to the Main Baiyun sag, which caused the faults extensive on the side facing Main Baiyun sag and the back side compressive. Around 32 Ma (T70), the breakup of the continental margin and the spreading of the South China Sea shed a combined effect of weak compression toward Baiyun sag. The gravity during post-rift stage might be caused by discrepant subsidence and sedimentation between strongly thinned sag center and wing areas. This is supported by positive relationship between sedimentation rate and fault growth index. After 13.8 Ma (T30), fault activity shows negative relationship with sedimentation rate. Compressive uplift and erosion in seismic profiles as well as negative tectonic subsiding rates suggest that the fault activity from 13.8 Ma (T30) to 5.5 Ma (T10) might be controlled by the subductive compression from the Philippine plate in the east.

Fault Activity in the Terrebonne Trough, Southeastern Louisiana: A Continuation of Salt-Withdrawal Fault Activity from the Miocene into the late Quaternary and Implication for Subsidence Hot-Spots

NASA Astrophysics Data System (ADS)

Akintomide, A. O.; Dawers, N. H.

2017-12-01

The observed displacement along faults in southeastern Louisiana has raised questions about the kinematic history of faults during the Quaternary. The Terrebonne Trough, a Miocene salt withdrawal basin, is bounded by the Golden Meadow fault zone on its northern boundary; north dipping, so-called counter-regional faults, together with a subsurface salt ridge, define its southern boundary. To date, there are relatively few published studies on fault architecture and kinematics in the onshore area of southeastern Louisiana. The only publically accessible studies, based on 2d seismic reflection profiles, interpreted faults as mainly striking east-west. Our interpretation of a 3-D seismic reflection volume, located in the northwestern Terrebonne Trough, as well as industry well log correlations define a more complex and highly-segmented fault architecture. The northwest striking Lake Boudreaux fault bounds a marsh on the upthrown block from Lake Boudreaux on the downthrown block. To the east, east-west striking faults are located at the Montegut marsh break and north of Isle de Jean Charles. Portions of the Lake Boudreaux and Isle de Jean Charles faults serve as the northern boundary of the Madison Bay subsidence hot-spot. All three major faults extend to the top of the 3d seismic volume, which is inferred to image latest Pleistocene stratigraphy. Well log correlation using 11+ shallow markers across these faults and kinematic techniques such as stratigraphic expansion indices indicate that all three faults were active in the middle(?) and late Pleistocene. Based on expansion indices, both the Montegut and Isle de Jean Charles faults were active simultaneously at various times, but with different slip rates. There are also time intervals when the Lake Boudreaux fault was slipping at a faster rate compared to the east-west striking faults. Smaller faults near the margins of the 3d volume appear to relate to nearby salt stocks, Bully Camp and Lake Barre. Our work to date suggests both salt and fault activity continued at least into the latest Pleistocene.

Shear concentration in a collision zone: kinematics of the Chihshang Fault as revealed by outcrop-scale quantification of active faulting, Longitudinal Valley, eastern Taiwan

NASA Astrophysics Data System (ADS)

Angelier, J.; Chu, H.-T.; Lee, J.-C.

1997-06-01

Repeated measurements of active deformation were carried out at three sites along the active Chihshang Fault, a segment of the Longitudinal Valley Fault zone of eastern Taiwan (the present-day plate boundary between the Philippine Sea Plate and Eurasia). Reliable annual records of displacement along an active fault, were obtained based on detailed surveys of faulted concrete structures. Along the active Chihshang Fault striking N18°E, we determined average motion vectors trending N37°W with an average shortening of 2.2 cm/yr. Thus, the transverse component of motion related to westward thrusting is 1.8 cm/yr, whereas the left-lateral strike-slip component of motion is 1.3 cm/yr. The fault dips 39-45° to the east, so that the vertical displacement is 1.5-3 cm/yr and the actual oblique offset of the fault increases at a rate of 2.7-3.7 cm/yr. This is in good agreement with the results of regional geodetic and tectonic analyses in Taiwan, and consistent with the N54°W trend of convergence between the northernmost Luzon Arc and South China revealed by GPS studies. Our study provides an example of extreme shear concentration in an oblique collision zone. At Chihshang, the whole horizontal shortening of the Longitudinal Valley Fault, 2.2 cm/yr on average, occurs across a single, narrow fault zone, so that the whole reverse slip (about 2.7-3.7 cm/yr depending on fault dip) was entirely recorded by walls 20-200 m long where faults are tightly localized. This active faulting accounts for more than one fourth (27%) of the total shortening between the Luzon Arc and South China recorded through GPS analyses. Further surveys should indicate whether the decreasing shortening velocity across the fault is significant (revealing increasing earthquake risk due to stress accumulation) or not (revealing continuing fault creep and 'weak' behaviour of the Chihshang Fault).

Structural controls of the Tuscarora geothermal field, Elko County, Nevada

NASA Astrophysics Data System (ADS)

Dering, G.; Faulds, J. E.

2012-12-01

Tuscarora is an amagmatic geothermal system located ~90 km northwest of Elko, Nevada, in the northern part of the Basin and Range province ~15 km southeast of the Snake River Plain. Detailed geologic mapping, structural analysis, and well data have been integrated to identify the structural controls of the Tuscarora geothermal system. The structural framework of the geothermal field is defined by NNW- to NNE-striking normal faults that are approximately orthogonal to the present extension direction. Boiling springs, fumaroles, and siliceous sinter emanate from a single NNE-striking, west-dipping normal fault. Normal faults west of these hydrothermal features mostly dip steeply east, whereas normal faults east of the springs primarily dip west. Thus, the springs, fumaroles, and sinter straddle a zone of interaction between fault sets that dip toward each other, classified as a strike-parallel anticlinal accommodation zone. Faults within the geothermal area are mostly discontinuous along strike with offsets of tens to hundreds of meters, whereas the adjacent range-bounding fault systems of the Bull Run and Independence Mountains accommodate several kilometers of displacement. The geothermal field lies within a broad step over between the southward terminating west-dipping Bull Run fault zone and the northward terminating west-dipping Independence Mountains fault zone. Neither of these major fault zones is known to host high temperature geothermal systems. The accommodation zone lies within the broad step over and contains both east-dipping antithetic and west-dipping synthetic faults. Accommodation zones are relatively common structural components of extended terranes that transfer strain between oppositely dipping fault sets via a network of subsidiary normal faults. This study has identified the hinge zone of an anticlinal accommodation zone as the site most conducive to fluid up-flow. The recognition of this specific portion of an accommodation zone as a favorable structural setting for geothermal activity may be a useful exploration tool for development of drilling targets in extensional terranes, as well as for developing geologic models of known geothermal fields. This type of information may ultimately help to reduce the risks of targeting successful geothermal wells in such settings.

Geologic map of the Vail West quadrangle, Eagle County, Colorado

USGS Publications Warehouse

Scott, Robert B.; Lidke, David J.; Grunwald, Daniel J.

2002-01-01

This new 1:24,000-scale geologic map of the Vail West 7.5' quadrangle, as part of the USGS Western Colorado I-70 Corridor Cooperative Geologic Mapping Project, provides new interpretations of the stratigraphy, structure, and geologic hazards in the area on the southwest flank of the Gore Range. Bedrock strata include Miocene tuffaceous sedimentary rocks, Mesozoic and upper Paleozoic sedimentary rocks, and undivided Early(?) Proterozoic metasedimentary and igneous rocks. Tuffaceous rocks are found in fault-tilted blocks. Only small outliers of the Dakota Sandstone, Morrison Formation, Entrada Sandstone, and Chinle Formation exist above the redbeds of the Permian-Pennsylvanian Maroon Formation and Pennsylvanian Minturn Formation, which were derived during erosion of the Ancestral Front Range east of the Gore fault zone. In the southwestern area of the map, the proximal Minturn facies change to distal Eagle Valley Formation and the Eagle Valley Evaporite basin facies. The Jacque Mountain Limestone Member, previously defined as the top of the Minturn Formation, cannot be traced to the facies change to the southwest. Abundant surficial deposits include Pinedale and Bull Lake Tills, periglacial deposits, earth-flow deposits, common diamicton deposits, common Quaternary landslide deposits, and an extensive, possibly late Pliocene landslide deposit. Landscaping has so extensively modified the land surface in the town of Vail that a modified land-surface unit was created to represent the surface unit. Laramide movement renewed activity along the Gore fault zone, producing a series of northwest-trending open anticlines and synclines in Paleozoic and Mesozoic strata, parallel to the trend of the fault zone. Tertiary down-to-the-northeast normal faults are evident and are parallel to similar faults in both the Gore Range and the Blue River valley to the northeast; presumably these are related to extensional deformation that occurred during formation of the northern end of the Rio Grande rift system in Colorado. In the southwestern part of the map area, a diapiric(?) exposure of the Eagle Valley Evaporite exists and chaotic faults and folds suggest extensive dissolution and collapse of overlying bedrock, indicating the presence of a geologic hazard. Quaternary landslides are common and indicate that landslide hazards are widespread in the area, particularly where old slide deposits are disturbed by construction. The late Pliocene(?) landslide that consists largely of a smectitic upper Morrison Formation matrix and boulders of Dakota Sandstone is readily reactivated. Debris flows are likely to invade low-standing areas within the towns of Vail and West Vail where tributaries of Gore Creek issue from the mountains on the north side of the valley.

Volcanic facies architecture of an intra-arc strike-slip basin, Santa Rita Mountains, Southern Arizona

NASA Astrophysics Data System (ADS)

Busby, Cathy J.; Bassett, Kari N.

2007-09-01

The three-dimensional arrangement of volcanic deposits in strike-slip basins is not only the product of volcanic processes, but also of tectonic processes. We use a strike-slip basin within the Jurassic arc of southern Arizona (Santa Rita Glance Conglomerate) to construct a facies model for a strike-slip basin dominated by volcanism. This model is applicable to releasing-bend strike-slip basins, bounded on one side by a curved and dipping strike-slip fault, and on the other by curved normal faults. Numerous, very deep unconformities are formed during localized uplift in the basin as it passes through smaller restraining bends along the strike-slip fault. In our facies model, the basin fill thins and volcanism decreases markedly away from the master strike-slip fault (“deep” end), where subsidence is greatest, toward the basin-bounding normal faults (“shallow” end). Talus cone-alluvial fan deposits are largely restricted to the master fault-proximal (deep) end of the basin. Volcanic centers are sited along the master fault and along splays of it within the master fault-proximal (deep) end of the basin. To a lesser degree, volcanic centers also form along the curved faults that form structural highs between sub-basins and those that bound the distal ends of the basin. Abundant volcanism along the master fault and its splays kept the deep (master fault-proximal) end of the basin overfilled, so that it could not provide accommodation for reworked tuffs and extrabasinally-sourced ignimbrites that dominate the shallow (underfilled) end of the basin. This pattern of basin fill contrasts markedly with that of nonvolcanic strike-slip basins on transform margins, where clastic sedimentation commonly cannot keep pace with subsidence in the master fault-proximal end. Volcanic and subvolcanic rocks in the strike-slip basin largely record polygenetic (explosive and effusive) small-volume eruptions from many vents in the complexly faulted basin, referred to here as multi-vent complexes. Multi-vent complexes like these reflect proximity to a continuously active fault zone, where numerous strands of the fault frequently plumb small batches of magma to the surface. Releasing-bend extension promotes small, multivent styles of volcanism in preference to caldera collapse, which is more likely to form at releasing step-overs along a strike-slip fault.

Managing Space System Faults: Coalescing NASA's Views

NASA Technical Reports Server (NTRS)

Muirhead, Brian; Fesq, Lorraine

2012-01-01

Managing faults and their resultant failures is a fundamental and critical part of developing and operating aerospace systems. Yet, recent studies have shown that the engineering "discipline" required to manage faults is not widely recognized nor evenly practiced within the NASA community. Attempts to simply name this discipline in recent years has been fraught with controversy among members of the Integrated Systems Health Management (ISHM), Fault Management (FM), Fault Protection (FP), Hazard Analysis (HA), and Aborts communities. Approaches to managing space system faults typically are unique to each organization, with little commonality in the architectures, processes and practices across the industry.

Initiation of a Low-Angle Normal Fault Active Across the Upper Brittle-Plastic Transition, Chemehuevi Mountains, CA

NASA Astrophysics Data System (ADS)

LaForge, J.; John, B. E.; Grimes, C. B.; Stunitz, H.; Heilbronner, R.

2016-12-01

The Chemehuevi detachment fault system, part of the regionally developed Colorado River extensional corridor, hosts exceptional exposures of a denuded fault system related to Miocene extension. Here, we characterize the early history of extension associated with a small slip (1-2 km) low-angle normal fault, the Mohave Wash fault (MWF), initially active across the brittle-plastic transition. Strain localized in three principal ways across the 23-km down-dip exposure (T <150° to >400°C): a brittle fault zone, localized, disseminated quartz mylonites, and syntectonic dikes hosting mylonitic fabrics. Brittle deformation in these crystalline rocks was concentrated into a 10-62-m thick brittle fault zone hosting localized, unmineralized to chlorite-epidote-quartz mineralized zones of cataclasite series fault rocks ≤3 m thick and rare pseudotachylite. Mylonitic deformation played an increased role in deformation down dip (NE), with mylonites increasing in quantity and average thickness. At shallow structural levels, footwall mylonites are absent; at 9-18 km down dip, cm-scale quartz mylonites are common; ≥18 km down dip, meter-scale syntectonic intermediate-felsic dikes are mylonitic, are attenuated into parallelism with the MWF, and host well-developed L-S fabric; 23 km down dip, the footwall hosts meter-thick zones of disseminated mylonitic quartz of varying intensities. These mylonites host microstructures that record progressively higher deformation temperature down dip, with dislocation-creep in quartz indicative of T of 280-400°C to ≥500°C, and diffusion creep with grain boundary sliding in dikes suggestive of even higher T deformation. Dike emplacement in the system is syntectonic with MWF slip; mafic-intermediate composition dikes intruded damage zone fractures and cataclasites, and were in turn fractured; Pb/U zircon ages of intermediate-felsic dikes range from ca. 1.5 ± 1 Ma to 3.8 ± 1 Ma after the onset of regional extension, but predate rapid slip. Cross cutting relations and absolute dating suggest the early history of the MWF evolved in two distinct phases: 1) seismogenic rupture with contemporaneous localized footwall mylonitization, followed by 2) additional cataclasis, episodic localized and magmatism, mylonitization and fluid-flow.

[X-ray diffraction and infrared spectrum analysis of fault gouge in Wenchuan seismic belt].

PubMed

Wang, Zheng-Yang; Cao, Jian-Jin; Luo, Song-Ying; Liao, Yi-Peng

2014-05-01

Wenchuan earthquake produced a series of co-seismic surface ruptures in Leigu and Zhaojiagou, and we collected samples of co-seismic fault gouge in the surface ruptures as well as the old gouge in the fault of Nanba. Testing The new and old fault gouge was tested with X-ray diffraction and infrared absorption spectra, and its characteristics such as mineral compositions, clay mineral contents and combinations were comprehensively analyzed. The results display obvious differences between the new and old fault gouge, showing that the old fault gouge is mainly composed of wall rock debris or milled powders, while the main components of new fault gouge are clay minerals. The assemblage of clay minerals composition shows that the environment of the fault activity was mainly warm and humid, and the clay minerals were mainly transformed by low temperature and low pressure dynamic metamorphism. And this also partly indicates that the latest way of the fault activity in this area may be a creeping. However the previous researches on the fault gouge of Wenchuan earthquake fault zone are mainly focused on its mechanical properties as well as its texture and structure, the research in this paper is to determine the physical and chemical environment of fault activity through the mineral compositions and clay mineral contents in the fault gouge characteristics, and this research has important scientific significance to the researches on the evolution of the fault environment and the activity mechanism of the earthquake.

Active Fault Near-Source Zones Within and Bordering the State of California for the 1997 Uniform Building Code

USGS Publications Warehouse

Petersen, M.D.; Toppozada, Tousson R.; Cao, T.; Cramer, C.H.; Reichle, M.S.; Bryant, W.A.

2000-01-01

The fault sources in the Project 97 probabilistic seismic hazard maps for the state of California were used to construct maps for defining near-source seismic coefficients, Na and Nv, incorporated in the 1997 Uniform Building Code (ICBO 1997). The near-source factors are based on the distance from a known active fault that is classified as either Type A or Type B. To determine the near-source factor, four pieces of geologic information are required: (1) recognizing a fault and determining whether or not the fault has been active during the Holocene, (2) identifying the location of the fault at or beneath the ground surface, (3) estimating the slip rate of the fault, and (4) estimating the maximum earthquake magnitude for each fault segment. This paper describes the information used to produce the fault classifications and distances.

Active fault databases: building a bridge between earthquake geologists and seismic hazard practitioners, the case of the QAFI v.3 database

NASA Astrophysics Data System (ADS)

García-Mayordomo, Julián; Martín-Banda, Raquel; Insua-Arévalo, Juan M.; Álvarez-Gómez, José A.; Martínez-Díaz, José J.; Cabral, João

2017-08-01

Active fault databases are a very powerful and useful tool in seismic hazard assessment, particularly when singular faults are considered seismogenic sources. Active fault databases are also a very relevant source of information for earth scientists, earthquake engineers and even teachers or journalists. Hence, active fault databases should be updated and thoroughly reviewed on a regular basis in order to keep a standard quality and uniformed criteria. Desirably, active fault databases should somehow indicate the quality of the geological data and, particularly, the reliability attributed to crucial fault-seismic parameters, such as maximum magnitude and recurrence interval. In this paper we explain how we tackled these issues during the process of updating and reviewing the Quaternary Active Fault Database of Iberia (QAFI) to its current version 3. We devote particular attention to describing the scheme devised for classifying the quality and representativeness of the geological evidence of Quaternary activity and the accuracy of the slip rate estimation in the database. Subsequently, we use this information as input for a straightforward rating of the level of reliability of maximum magnitude and recurrence interval fault seismic parameters. We conclude that QAFI v.3 is a much better database than version 2 either for proper use in seismic hazard applications or as an informative source for non-specialized users. However, we already envision new improvements for a future update.

Fault-related fold styles and progressions in fold-thrust belts: Insights from sandbox modeling

NASA Astrophysics Data System (ADS)

Yan, Dan-Ping; Xu, Yan-Bo; Dong, Zhou-Bin; Qiu, Liang; Zhang, Sen; Wells, Michael

2016-03-01

Fault-related folds of variable structural styles and assemblages commonly coexist in orogenic belts with competent-incompetent interlayered sequences. Despite their commonality, the kinematic evolution of these structural styles and assemblages are often loosely constrained because multiple solutions exist in their structural progression during tectonic restoration. We use a sandbox modeling instrument with a particle image velocimetry monitor to test four designed sandbox models with multilayer competent-incompetent materials. Test results reveal that decollement folds initiate along selected incompetent layers with decreasing velocity difference and constant vorticity difference between the hanging wall and footwall of the initial fault tips. The decollement folds are progressively converted to fault-propagation folds and fault-bend folds through development of fault ramps breaking across competent layers and are followed by propagation into fault flats within an upper incompetent layer. Thick-skinned thrust is produced by initiating a decollement fault within the metamorphic basement. Progressive thrusting and uplifting of the thick-skinned thrust trigger initiation of the uppermost incompetent decollement with formation of a decollement fold and subsequent converting to fault-propagation and fault-bend folds, which combine together to form imbricate thrust. Breakouts at the base of the early formed fault ramps along the lowest incompetent layers, which may correspond to basement-cover contacts, domes the upmost decollement and imbricate thrusts to form passive roof duplexes and constitute the thin-skinned thrust belt. Structural styles and assemblages in each of tectonic stages are similar to that in the representative orogenic belts in the South China, Southern Appalachians, and Alpine orogenic belts.

The complex architecture of the 2009 MW 6.1 L'Aquila normal fault system (Central Italy) as imaged by 64,000 high-resolution aftershock locations

NASA Astrophysics Data System (ADS)

Valoroso, L.; Chiaraluce, L.; Di Stefano, R.; Piccinini, D.; Schaff, D. P.; Waldhauser, F.

2011-12-01

On April 6th 2009, a MW 6.1 normal faulting earthquake struck the axial area of the Abruzzo region in Central Italy. We present high-precision hypocenter locations of an extraordinary dataset composed by 64,000 earthquakes recorded at a very dense seismic network of 60 stations operating for 9 months after the main event. Events span in magnitude (ML) between -0.9 to 5.9, reaching a completeness magnitude of 0.7. The dataset has been processed by integrating an accurate automatic picking procedure together with cross-correlation and double-difference relative location methods. The combined use of these procedures results in earthquake relative location uncertainties in the range of a few meters to tens of meters, comparable/lower than the spatial dimension of the earthquakes themselves). This data set allows us to image the complex inner geometry of individual faults from the kilometre to meter scale. The aftershock distribution illuminates the anatomy of the en-echelon fault system composed of two major faults. The mainshock breaks the entire upper crust from 10 km depth to the surface along a 14-km long normal fault. A second segment, located north of the normal fault and activated by two Mw>5 events, shows a striking listric geometry completely blind. We focus on the analysis of about 300 clusters of co-located events to characterize the mechanical behavior of the different portions of the fault system. The number of events in each cluster ranges from 4 to 24 events and they exhibit strongly correlated seismograms at common stations. They mostly occur where secondary structures join the main fault planes and along unfavorably oriented segments. Moreover, larger clusters nucleate on secondary faults located in the overlapping area between the two main segments, where the rate of earthquake production is very high with a long-lasting seismic decay.

3-D GPR data analysis for high-resolution imaging of shallow subsurface faults: the Mt Vettore case study (Central Apennines, Italy)

NASA Astrophysics Data System (ADS)

Ercoli, Maurizio; Pauselli, Cristina; Frigeri, Alessandro; Forte, Emanuele; Federico, Costanzo

2014-07-01

The activation of Late Quaternary faults in the Central Apennines (Italy) could generate earthquakes with magnitude of about 6.5, and the Monte Vettore fault system probably belongs to the same category of seismogenetic faults. Such structure has been defined `silent', because of its geological and geomorphological evidences of past activation, but the absence of historical records in the seismic catalogues to be associated with its activation. The `Piano di Castelluccio' intramountain basin, resulting from the Quaternary activity of normal faults, is characterized by a secondary fault strand highlighted by a NW-SE fault scarp: it has been already studied through palaeoseismological trenches, which highlighted evidences of Quaternary shallow faulting due to strong earthquakes, and through a 2-D ground penetrating radar (GPR) survey, showing the first geophysical signature of faulting for this site. Within the same place, a 3-D GPR volume over a 20 × 20 m area has been collected. The collection of radar echoes in three dimensions allows to map both the vertical and lateral continuity of shallow geometries of the fault zone (Fz), imaging features with high resolution, ranging from few metres to centimetres and therefore imaging also local variations at the microscale. Several geophysical markers of faulting, already highlighted on this site, have been taken as reference to plan the 3-D survey. In this paper, we provide the first 3-D subsurface imaging of an active shallow fault belonging to the Umbria-Marche Apennine highlighting the subsurface fault geometry and the stratigraphic sequence up to a depth of about 5 m. From our data, geophysical faulting signatures are clearly visible in three dimensions: diffraction hyperbolas, truncations of layers, local attenuated zones and varying dip of the layers have been detected within the Fz. The interpretation of the 3-D data set provided qualitative and quantitative geological information in addition to the fault location, like its geometry, boundaries and an estimation of the fault throw.

Earthquake Potential of the St. Louis District

DTIC Science & Technology

1981-02-01

The trends of the fault plane solutions strike northwest, northeast, and north-south indicating a complex generating mechanism . The focal depth for...thrust, strike-slip, oblique) is of prime importance in understanding seismic activity. Focal Mechanism Studies: A common method of obtaining regional... focal mechanisms , and to better understand magnitude-recurrence relations. Gravity and Magnetics: Gravity and magnetic contours may be used to

Preservation of amorphous ultrafine material: A proposed proxy for slip during recent earthquakes on active faults

NASA Astrophysics Data System (ADS)

Hirono, Tetsuro; Asayama, Satoru; Kaneki, Shunya; Ito, Akihiro

2016-11-01

The criteria for designating an “Active Fault” not only are important for understanding regional tectonics, but also are a paramount issue for assessing the earthquake risk of faults that are near important structures such as nuclear power plants. Here we propose a proxy, based on the preservation of amorphous ultrafine particles, to assess fault activity within the last millennium. X-ray diffraction data and electron microscope observations of samples from an active fault demonstrated the preservation of large amounts of amorphous ultrafine particles in two slip zones that last ruptured in 1596 and 1999, respectively. A chemical kinetic evaluation of the dissolution process indicated that such particles could survive for centuries, which is consistent with the observations. Thus, preservation of amorphous ultrafine particles in a fault may be valuable for assessing the fault’s latest activity, aiding efforts to evaluate faults that may damage critical facilities in tectonically active zones.

Is Slow Slip a Cause or a Result of Tremor?

NASA Astrophysics Data System (ADS)

Luo, Y.; Ampuero, J. P.

2017-12-01

While various modeling efforts have been conducted to reproduce subsets of observations of tremor and slow-slip events (SSE), a fundamental but yet unanswered question is whether slow slip is a cause or a result of tremor. Tremor is commonly regarded as driven by SSE. This view is mainly based on observations of SSE without detected tremors and on (frequency-limited) estimates of total tremor seismic moment being lower than 1% of their concomitant SSE moment. In previous studies we showed that models of heterogeneous faults, composed of seismic asperities embedded in an aseismic fault zone matrix, reproduce quantitatively the hierarchical patterns of tremor migration observed in Cascadia and Shikoku. To address the title question, we design two end-member models of a heterogeneous fault. In the SSE-driven-tremor model, slow slip events are spontaneously generated by the matrix (even in the absence of seismic asperities) and drive tremor. In the Tremor-driven-SSE model the matrix is stable (it slips steadily in the absence of asperities) and slow slip events result from the collective behavior of tremor asperities interacting via transient creep (local afterslip fronts). We study these two end-member models through 2D quasi-dynamic multi-cycle simulations of faults governed by rate-and-state friction with heterogeneous frictional properties and effective normal stress, using the earthquake simulation software QDYN (https://zenodo.org/record/322459). We find that both models reproduce first-order observations of SSE and tremor and have very low seismic to aseismic moment ratio. However, the Tremor-driven-SSE model assumes a simpler rheology than the SSE-driven-tremor model and matches key observations better and without fine tuning, including the ratio of propagation speeds of forward SSE and rapid tremor reversals and the decay of inter-event times of Low Frequency Earthquakes. These modeling results indicate that, in contrast to a common view, SSE could be a result of tremor activity. We also find that, despite important interactions between asperities, tremor activity rates are proportional to the underlying aseismic slip rate, supporting an approach to estimate SSE properties with high spatial-temporal resolutions via tremor activity.

Along-strike variations of geometry and kinematics on the border fault of Nanpu sag, Bohai Bay Basin

NASA Astrophysics Data System (ADS)

Zhang, C.; Ren, J.; Liu, X.; Sun, Z.; Su, M.

2010-12-01

Nanpu sag is located in the north-eastern portion of the Huanghua depression, covering an area of approximately 1900km2, and comprises one of the most important petroliferous basins of the Bohai Bay Basin. The Nanpu sag is bordered by two master faults with long-term activity: the Xi’nanzhuang (XNZ) and Bogezhuang (BGZ) fault. By analysis of horizontal slices, gravity anomaly map and seismic reflection sections, we found there is no cutting relationship, and thus considered the XNZ and BGZ fault as a same one. However it showed striking differences between the XNZ and BGZ segment in fault occurrence, fault throw and residual formation thickness and so on. The BGZ fault was NW trending fault with a steep inclination. Taken section across the northern region in Nanpu sag for example, its controlling depocenter is located in eastern subsag (Fig.1); the XNZ fault was a NE fault and displayed a Shovel-shaped to plate-like geometry, with its controlling depocenter located in western subsag. We qualitify the fault throw, showing that the XNZ fault strongly acted during the sedimentary period of Es3-Es2, while the BGZ fault presented weak activity, and especially during Es31 submember-Es2 member, the XNZ fault acted so strongly that the hanging wall of BGZ fault was tilt-lifted and suffered erosion (Fig.1), which created Es1 uncomformity; The BGZ fault acted strongly during the sedimentary period of Es1-Ed, which led the hanging wall of XNZ fault to be tilt-lifted. Controlled by such segmented activity of the whole border fault, which we suggested a "seesaw" model for its evolution, the northern part in the Nanpu sag experienced an alternative variation between a deposition center and an erosion region after tilt-lifting. Combination of the sediment stacking patterns, we further classified the history of "seesaw" activities into four stages: 1) Early double-break stage (Es35-Es31), both of the XNZ and BGZ fault acted; 2) Middle the XNZ segment throw and the BGZ tilting (Es2); 3) Late the XNZ segment tilting and BGZ throw (Es1-Ed3); 4) End weak double-break stage (Ed2-Present), the whole fault acted weakly and were superposed by neotectonic movement. Fig.1 Seesaw activity of the whole border fault

Gently dipping normal faults identified with Space Shuttle radar topography data in central Sulawesi, Indonesia, and some implications for fault mechanics

USGS Publications Warehouse

Spencer, J.E.

2011-01-01

Space-shuttle radar topography data from central Sulawesi, Indonesia, reveal two corrugated, domal landforms, covering hundreds to thousands of square kilometers, that are bounded to the north by an abrupt transition to typical hilly to mountainous topography. These domal landforms are readily interpreted as metamorphic core complexes, an interpretation consistent with a single previous field study, and the abrupt northward transition in topographic style is interpreted as marking the trace of two extensional detachment faults that are active or were recently active. Fault dip, as determined by the slope of exhumed fault footwalls, ranges from 4?? to 18??. Application of critical-taper theory to fault dip and hanging-wall surface slope, and to similar data from several other active or recently active core complexes, suggests a theoretical limit of three degrees for detachment-fault dip. This result appears to conflict with the dearth of seismological evidence for slip on faults dipping less than ~. 30??. The convex-upward form of the gently dipping fault footwalls, however, allows for greater fault dip at depths of earthquake initiation and dominant energy release. Thus, there may be no conflict between seismological and mapping studies for this class of faults. ?? 2011 Elsevier B.V.

Composition, Alteration, and Texture of Fault-Related Rocks from Safod Core and Surface Outcrop Analogs: Evidence for Deformation Processes and Fluid-Rock Interactions

NASA Astrophysics Data System (ADS)

Bradbury, Kelly K.; Davis, Colter R.; Shervais, John W.; Janecke, Susanne U.; Evans, James P.

2015-05-01

We examine the fine-scale variations in mineralogical composition, geochemical alteration, and texture of the fault-related rocks from the Phase 3 whole-rock core sampled between 3,187.4 and 3,301.4 m measured depth within the San Andreas Fault Observatory at Depth (SAFOD) borehole near Parkfield, California. This work provides insight into the physical and chemical properties, structural architecture, and fluid-rock interactions associated with the actively deforming traces of the San Andreas Fault zone at depth. Exhumed outcrops within the SAF system comprised of serpentinite-bearing protolith are examined for comparison at San Simeon, Goat Rock State Park, and Nelson Creek, California. In the Phase 3 SAFOD drillcore samples, the fault-related rocks consist of multiple juxtaposed lenses of sheared, foliated siltstone and shale with block-in-matrix fabric, black cataclasite to ultracataclasite, and sheared serpentinite-bearing, finely foliated fault gouge. Meters-wide zones of sheared rock and fault gouge correlate to the sites of active borehole casing deformation and are characterized by scaly clay fabric with multiple discrete slip surfaces or anastomosing shear zones that surround conglobulated or rounded clasts of compacted clay and/or serpentinite. The fine gouge matrix is composed of Mg-rich clays and serpentine minerals (saponite ± palygorskite, and lizardite ± chrysotile). Whole-rock geochemistry data show increases in Fe-, Mg-, Ni-, and Cr-oxides and hydroxides, Fe-sulfides, and C-rich material, with a total organic content of >1 % locally in the fault-related rocks. The faults sampled in the field are composed of meters-thick zones of cohesive to non-cohesive, serpentinite-bearing foliated clay gouge and black fine-grained fault rock derived from sheared Franciscan Formation or serpentinized Coast Range Ophiolite. X-ray diffraction of outcrop samples shows that the foliated clay gouge is composed primarily of saponite and serpentinite, with localized increases in Ni- and Cr-oxides and C-rich material over several meters. Mesoscopic and microscopic textures and deformation mechanisms interpreted from the outcrop sites are remarkably similar to those observed in the SAFOD core. Micro-scale to meso-scale fabrics observed in the SAFOD core exhibit textural characteristics that are common in deformed serpentinites and are often attributed to aseismic deformation with episodic seismic slip. The mineralogy and whole-rock geochemistry results indicate that the fault zone experienced transient fluid-rock interactions with fluids of varying chemical composition, including evidence for highly reducing, hydrocarbon-bearing fluids.

Earthquake disaster mitigation of Lembang Fault West Java with electromagnetic method

NASA Astrophysics Data System (ADS)

Widodo

2015-04-01

The Lembang fault is located around eight kilometers from Bandung City, West Java, Indonesia. The existence of this fault runs through densely populated settlement and tourism area. It is an active fault structure with increasing seismic activity where the 28 August 2011 earthquake occurred. The seismic response at the site is strongly influenced by local geological conditions. The ambient noise measurements from the western part of this fault give strong implication for a complex 3-D tectonic setting. Hence, near surface Electromagnetic (EM) measurements are carried out to understand the location of the local active fault of the research area. Hence, near surface EM measurements are carried out to understand the location of the local active fault and the top of the basement structure of the research area. The Transientelectromagnetic (TEM) measurements are carried out along three profiles, which include 35 TEM soundings. The results indicate that TEM data give detailed conductivity distribution of fault structure in the study area.

Earthquake disaster mitigation of Lembang Fault West Java with electromagnetic method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Widodo, E-mail: widodo@gf.itb.ac.id

The Lembang fault is located around eight kilometers from Bandung City, West Java, Indonesia. The existence of this fault runs through densely populated settlement and tourism area. It is an active fault structure with increasing seismic activity where the 28 August 2011 earthquake occurred. The seismic response at the site is strongly influenced by local geological conditions. The ambient noise measurements from the western part of this fault give strong implication for a complex 3-D tectonic setting. Hence, near surface Electromagnetic (EM) measurements are carried out to understand the location of the local active fault of the research area. Hence,more » near surface EM measurements are carried out to understand the location of the local active fault and the top of the basement structure of the research area. The Transientelectromagnetic (TEM) measurements are carried out along three profiles, which include 35 TEM soundings. The results indicate that TEM data give detailed conductivity distribution of fault structure in the study area.« less

States of stress and slip partitioning in a continental scale strike-slip duplex: Tectonic and magmatic implications by means of finite element modeling

NASA Astrophysics Data System (ADS)

Iturrieta, Pablo Cristián; Hurtado, Daniel E.; Cembrano, José; Stanton-Yonge, Ashley

2017-09-01

Orogenic belts at oblique convergent subduction margins accommodate deformation in several trench-parallel domains, one of which is the magmatic arc, commonly regarded as taking up the margin-parallel, strike-slip component. However, the stress state and kinematics of volcanic arcs is more complex than usually recognized, involving first- and second-order faults with distinctive slip senses and mutual interaction. These are usually organized into regional scale strike-slip duplexes, associated with both long-term and short-term heterogeneous deformation and magmatic activity. This is the case of the 1100 km-long Liquiñe-Ofqui Fault System in the Southern Andes, made up of two overlapping margin-parallel master faults joined by several NE-striking second-order faults. We present a finite element model addressing the nature and spatial distribution of stress across and along the volcanic arc in the Southern Andes to understand slip partitioning and the connection between tectonics and magmatism, particularly during the interseismic phase of the subduction earthquake cycle. We correlate the dynamics of the strike-slip duplex with geological, seismic and magma transport evidence documented by previous work, showing consistency between the model and the inferred fault system behavior. Our results show that maximum principal stress orientations are heterogeneously distributed within the continental margin, ranging from 15° to 25° counter-clockwise (with respect to the convergence vector) in the master faults and 10-19° clockwise in the forearc and backarc domains. We calculate the stress tensor ellipticity, indicating simple shearing in the eastern master fault and transpressional stress in the western master fault. Subsidiary faults undergo transtensional-to-extensional stress states. The eastern master fault displays slip rates of 5 to 10 mm/yr, whereas the western and subsidiary faults show slips rates of 1 to 5 mm/yr. Our results endorse that favorably oriented subsidiary faults serve as magma pathways, particularly where they are close to the intersection with a master fault. Also, the slip of a fault segment is enhanced when an adjacent fault kinematics is superimposed on the regional tectonic loading. Hence, finite element models help to understand coupled tectonics and volcanic processes, demonstrating that geological and geophysical observations can be accounted for by a small number of key first order boundary conditions.

Regional Survey of Structural Properties and Cementation Patterns of Fault Zones in the Northern Part of the Albuquerque Basin, New Mexico - Implications for Ground-Water Flow

USGS Publications Warehouse

Minor, Scott A.; Hudson, Mark R.

2006-01-01

Motivated by the need to document and evaluate the types and variability of fault zone properties that potentially affect aquifer systems in basins of the middle Rio Grande rift, we systematically characterized structural and cementation properties of exposed fault zones at 176 sites in the northern Albuquerque Basin. A statistical analysis of measurements and observations evaluated four aspects of the fault zones: (1) attitude and displacement, (2) cement, (3) lithology of the host rock or sediment, and (4) character and width of distinctive structural architectural components at the outcrop scale. Three structural architectural components of the fault zones were observed: (1) outer damage zones related to fault growth; these zones typically contain deformation bands, shear fractures, and open extensional fractures, which strike subparallel to the fault and may promote ground-water flow along the fault zone; (2) inner mixed zones composed of variably entrained, disrupted, and dismembered blocks of host sediment; and (3) central fault cores that accommodate most shear strain and in which persistent low- permeability clay-rich rocks likely impede the flow of water across the fault. The lithology of the host rock or sediment influences the structure of the fault zone and the width of its components. Different grain-size distributions and degrees of induration of the host materials produce differences in material strength that lead to variations in width, degree, and style of fracturing and other fault-related deformation. In addition, lithology of the host sediment appears to strongly control the distribution of cement in fault zones. Most faults strike north to north-northeast and dip 55? - 77? east or west, toward the basin center. Most faults exhibit normal slip, and many of these faults have been reactivated by normal-oblique and strike slip. Although measured fault displacements have a broad range, from 0.9 to 4,000 m, most are <100 m, and fault zones appear to have formed mainly at depths less than 1,000 m. Fault zone widths do not exceed 40 m (median width = 15.5 m). The mean width of fault cores (0.1 m) is nearly one order of magnitude less than that of mixed zones (0.75 m) and two orders of magnitude less than that of damage zones (9.7 m). Cements, a proxy for localized flow of ancient ground water, are common along fault zones in the basin. Silica cements are limited to faults that are near and strike north to northwest toward the Jemez volcanic field north of the basin, whereas carbonate fault cements are widely distributed. Coarse sediments (gravel and sand) host the greatest concentrations of cement within fault zones. Cements fill some extension fractures and, to a lesser degree, are concentrated along shear fractures and deformation bands within inner damage zones. Cements are commonly concentrated in mixed zones and inner damage zones on one side of a fault and thus are asymmetrically distributed within a fault zone, but cement does not consistently lie on the basinward side of faults. From observed spatial patterns of asymmetrically distributed fault zone cements, we infer that ancient ground-water flow was commonly localized along, and bounded by, faults in the basin. It is apparent from our study that the Albuquerque Basin contains a high concentration of faults. The geometry of, internal structure of, and cement and clay distribution in fault zones have created and will continue to create considerable heterogeneity of permeability within the basin aquifers. The characteristics and statistical range of fault zone features appear to be predictable and consistent throughout the basin; this predictability can be used in ground-water flow simulations that consider the influence of faults.

Induction motor inter turn fault detection using infrared thermographic analysis

NASA Astrophysics Data System (ADS)

Singh, Gurmeet; Anil Kumar, T. Ch.; Naikan, V. N. A.

2016-07-01

Induction motors are the most commonly used prime movers in industries. These are subjected to various environmental, thermal and load stresses that ultimately reduces the motor efficiency and later leads to failure. Inter turn fault is the second most commonly observed faults in the motors and is considered the most severe. It can lead to the failure of complete phase and can even cause accidents, if left undetected or untreated. This paper proposes an online and non invasive technique that uses infrared thermography, in order to detect the presence of inter turn fault in induction motor drive. Two methods have been proposed that detect the fault and estimate its severity. One method uses transient thermal monitoring during the start of motor and other applies pseudo coloring technique on infrared image of the motor, after it reaches a thermal steady state. The designed template for pseudo-coloring is in acquiescence with the InterNational Electrical Testing Association (NETA) thermographic standard. An index is proposed to assess the severity of the fault present in the motor.

Tectonic and Structural Controls of Geothermal Activity in the Great Basin Region, Western USA

NASA Astrophysics Data System (ADS)

Faulds, J. E.; Hinz, N.; Kreemer, C. W.

2012-12-01

We are conducting a thorough inventory of structural settings of geothermal systems (>400 total) in the extensional to transtensional Great Basin region of the western USA. Most of the geothermal systems in this region are not related to upper crustal magmatism and thus regional tectonic and local structural controls are the most critical factors controlling the locations of the geothermal activity. A system of NW-striking dextral faults known as the Walker Lane accommodates ~20% of the North American-Pacific plate motion in the western Great Basin and is intimately linked to N- to NNE-striking normal fault systems throughout the region. Overall, geothermal systems are concentrated in areas with the highest strain rates within or proximal to the eastern and western margins of the Great Basin, with the high temperature systems clustering in transtensional areas of highest strain rate in the northwestern Great Basin. Enhanced extension in the northwestern Great Basin probably results from the northwestward termination of the Walker Lane and the concomitant transfer of dextral shear into west-northwest directed extension, thus producing a broad transtensional region. The capacity of geothermal power plants also correlates with strain rates, with the largest (hundreds of megawatts) along the Walker Lane or San Andreas fault system, where strain rates range from 10-100 nanostrain/yr to 1,000 nanostrain/yr, respectively. Lesser systems (tens of megawatts) reside in the Basin and Range (outside the Walker Lane), where local strain rates are typically < 10 nanostrain/yr. Of the 250+ geothermal fields catalogued, step-overs or relay ramps in normal fault zones serve as the most favorable setting, hosting ~32% of the systems. Such areas have multiple, overlapping fault strands, increased fracture density, and thus enhanced permeability. Other common settings include a) intersections between normal faults and strike-slip or oblique-slip faults (27%), where multiple minor faults connect major structures and fluids can flow readily through highly fractured, dilational quadrants, and b) normal fault terminations or tip-lines (22%), where horse-tailing generates closely-spaced faults and increased permeability. Other settings include accommodation zones (i.e., belts of intermeshing, oppositely dipping normal faults; 8%), major range-front faults (5-6%), and pull-aparts in strike-slip faults (4%). In addition, Quaternary faults lie within or near most systems. The relative scarcity of geothermal systems along displacement-maxima of major normal faults may be due to reduced permeability in thick zones of clay gouge and periodic release of stress in major earthquakes. Step-overs, terminations, intersections, and accommodation zones correspond to long-term, critically stressed areas, where fluid pathways are more likely to remain open in networks of closely-spaced, breccia-dominated fractures. These findings may help guide future exploration efforts, especially for blind geothermal systems, which probably comprise the bulk of the geothermal resources in the Great Basin.

E-W strike slip shearing of Kinwat granitoid at South East Deccan Volcanic Province, Kinwat, Maharashtra, India

NASA Astrophysics Data System (ADS)

Kaplay, R. D.; Kumar, T. Vijay; Mukherjee, Soumyajit; Wesanekar, P. R.; Babar, Md; Chavan, Sumeet

2017-07-01

We study the margin of South East Deccan Volcanic Province around Kinwat lineament, Maharashtra, India, which is NW extension of the Kaddam Fault. Structural field studies document ˜ E-W strike-slip mostly brittle faults from the basement granite. We designate this as `Western boundary East Dharwar Craton Strike-slip Zone' (WBEDCSZ). At local level, the deformation regime from Kinwat, Kaddam Fault, micro-seismically active Nanded and seismically active Killari corroborate with the nearby lineaments. Morphometric analyses suggest that the region is moderately tectonically active. The region of intense strike-slip deformation lies between seismically active fault along Tapi in NW and Bhadrachalam in the SE part of the Kaddam Fault/lineament. The WBEDCSZ with the surface evidences of faulting, presence of a major lineaments and intersection of faults could be a zone of intraplate earthquake.

Imaging the complexity of an active normal fault system: The 1997 Colfiorito (central Italy) case study

USGS Publications Warehouse

Chiaraluce, L.; Ellsworth, W.L.; Chiarabba, C.; Cocco, M.

2003-01-01

Six moderate magnitude earthquakes (5 < Mw < 6) ruptured normal fault segments of the southern sector of the North Apennine belt (central Italy) in the 1997 Colfiorito earthquake sequence. We study the progressive activation of adjacent and nearby parallel faults of this complex normal fault system using ???1650 earthquake locations obtained by applying a double-difference location method, using travel time picks and waveform cross-correlation measurements. The lateral extent of the fault segments range from 5 to 10 km and make up a broad, ???45 km long, NW trending fault system. The geometry of each segment is quite simple and consists of planar faults gently dipping toward SW with an average dip of 40??-45??. The fault planes are not listric but maintain a constant dip through the entire seismogenic volume, down to 8 km depth. We observe the activation of faults on the hanging wall and the absence of seismicity in the footwall of the structure. The observed fault segmentation appears to be due to the lateral heterogeneity of the upper crust: preexisting thrusts inherited from Neogene's compressional tectonic intersect the active normal faults and control their maximum length. The stress tensor obtained by inverting the six main shock focal mechanisms of the sequence is in agreement with the tectonic stress active in the inner chain of the Apennine, revealing a clear NE trending extension direction. Aftershock focal mechanisms show a consistent extensional kinematics, 70% of which are mechanically consistent with the main shock stress field.

Fracture zone drilling through Atotsugawa fault in central Japan - geological and geophysical structure -

NASA Astrophysics Data System (ADS)

Omura, K.; Yamashita, F.; Yamada, R.; Matsuda, T.; Fukuyama, E.; Kubo, A.; Takai, K.; Ikeda, R.; Mizuochi, Y.

2004-12-01

Drilling is an effective method to investigate the structure and physical state in and around the active fault zone, such as, stress and strength distribution, geological structure and materials properties. In particular, the structure in the fault zone is important to understand where and how the stress accumulates during the earthquake cycle. In previous studies, we did integrate investigation on active faults in central Japan by drilling and geophysical prospecting. Those faults are estimated to be at different stage in the earthquake cycle, i.e., Nojima fault which appeared on the surface by the 1995 Great Kobe earthquake (M=7.2), the Neodani fault which appeared by the 1891 Nobi earth-quake (M=8.0), the Atera fault, of which some parts have seemed to be dislocated by the 1586 Tensyo earthquake (M=7.9), and Gofukuji Fault that is considered to have activated about 1200 years ago. Each faults showed characteristic features of fracture zone structure according to their geological and geophysical situations. In a present study, we did core recovery and down hole measurements at the Atotsugawa fault, central Japan, that is considered to have activated at 1858 Hida earthquake (M=7.0). The Atotsugawa fault is characterized by active seismicity along the fault. But, at the same time, the shallow region in the central segment of the fault seems to have low seismicity. The high seismicity segment and low seismicity segments may have different mechanical, physical and material properties. A 350m depth borehole was drilled vertically beside the surface trace of the fault in the low seismicity segment. Recovered cores were overall heavily fractured and altered rocks. In the cores, we observed many shear planes holding fault gouge. Logging data showed that the apparent resistance was about 100 - 600 ohm-m, density was about 2.0 - 2.5g/cm3, P wave velocity was approximately 3.0 - 4.0 km/sec, neutron porosity was 20 - 40 %. Results of physical logging show features of fault fracture zone that were the same as the fault fracture zones of other active faults that we have drilled previously. By the BHTV logging, we detected many fractures of which the strikes are not only parallel to the fault trace bur also oblique to the fault trace. The observations of cores and logging data indicate that the borehole passed in the fracture zone down to the bottom, and that the fracture zone has complicate internal structure including foliation not parallel to the fault trace. The core samples are significant for further investigation on material properties in the fracture zone. And we need data of geophysical prospecting to infer the deeper structure of the fracture zone.

An Intelligent Harmonic Synthesis Technique for Air-Gap Eccentricity Fault Diagnosis in Induction Motors

NASA Astrophysics Data System (ADS)

Li, De Z.; Wang, Wilson; Ismail, Fathy

2017-11-01

Induction motors (IMs) are commonly used in various industrial applications. To improve energy consumption efficiency, a reliable IM health condition monitoring system is very useful to detect IM fault at its earliest stage to prevent operation degradation, and malfunction of IMs. An intelligent harmonic synthesis technique is proposed in this work to conduct incipient air-gap eccentricity fault detection in IMs. The fault harmonic series are synthesized to enhance fault features. Fault related local spectra are processed to derive fault indicators for IM air-gap eccentricity diagnosis. The effectiveness of the proposed harmonic synthesis technique is examined experimentally by IMs with static air-gap eccentricity and dynamic air-gap eccentricity states under different load conditions. Test results show that the developed harmonic synthesis technique can extract fault features effectively for initial IM air-gap eccentricity fault detection.

Optimal Non-Invasive Fault Classification Model for Packaged Ceramic Tile Quality Monitoring Using MMW Imaging

NASA Astrophysics Data System (ADS)

Agarwal, Smriti; Singh, Dharmendra

2016-04-01

Millimeter wave (MMW) frequency has emerged as an efficient tool for different stand-off imaging applications. In this paper, we have dealt with a novel MMW imaging application, i.e., non-invasive packaged goods quality estimation for industrial quality monitoring applications. An active MMW imaging radar operating at 60 GHz has been ingeniously designed for concealed fault estimation. Ceramic tiles covered with commonly used packaging cardboard were used as concealed targets for undercover fault classification. A comparison of computer vision-based state-of-the-art feature extraction techniques, viz, discrete Fourier transform (DFT), wavelet transform (WT), principal component analysis (PCA), gray level co-occurrence texture (GLCM), and histogram of oriented gradient (HOG) has been done with respect to their efficient and differentiable feature vector generation capability for undercover target fault classification. An extensive number of experiments were performed with different ceramic tile fault configurations, viz., vertical crack, horizontal crack, random crack, diagonal crack along with the non-faulty tiles. Further, an independent algorithm validation was done demonstrating classification accuracy: 80, 86.67, 73.33, and 93.33 % for DFT, WT, PCA, GLCM, and HOG feature-based artificial neural network (ANN) classifier models, respectively. Classification results show good capability for HOG feature extraction technique towards non-destructive quality inspection with appreciably low false alarm as compared to other techniques. Thereby, a robust and optimal image feature-based neural network classification model has been proposed for non-invasive, automatic fault monitoring for a financially and commercially competent industrial growth.

Late Miocene-Early Pliocene reactivation of the Main Boundary Thrust: Evidence from the seismites in southeastern Kumaun Himalaya, India

NASA Astrophysics Data System (ADS)

Mishra, Anurag; Srivastava, Deepak C.; Shah, Jyoti

2013-05-01

Tectonic history of the Himalaya is punctuated by successive development of the faults that run along the boundaries between different lithotectonic terrains. The Main Boundary Fault, defining the southern limit of the Lesser Himalayan terrain, is tectonically most active. A review of published literature reveals that the nature and age of reactivation events on the Main Boundary Fault is one of the poorly understood aspects of the Himalayan orogen. By systematic outcrop mapping of the seismites, this study identifies a Late Miocene-Early Pliocene reactivation on the Main Boundary Thrust in southeast Kumaun Himalaya. Relatively friable and cohesionless Neogene sedimentary sequences host abundant soft-sediment deformation structures in the vicinity of the Main Boundary Thrust. Among a large variety of structures, deformed cross-beds, liquefaction pockets, slump folds, convolute laminations, sand dykes, mushroom structures, fluid escape structures, flame and load structures and synsedimentary faults are common. The morphological attributes, the structural association and the distribution pattern of the soft-sediment deformation structures with respect to the Main Boundary Fault strongly suggest their development by seismically triggered liquefaction and fluidization. Available magnetostratigraphic age data imply that the seismites were developed during a Late Miocene-Early Pliocene slip on the Main Boundary Thrust. The hypocenter of the main seismic event may lie on the Main Boundary Thrust or to the north of the study area on an unknown fault or the Basal Detachment Thrust.

Shallow very-low-frequency earthquakes accompany slow slip events in the Nankai subduction zone.

PubMed

Nakano, Masaru; Hori, Takane; Araki, Eiichiro; Kodaira, Shuichi; Ide, Satoshi

2018-03-14

Recent studies of slow earthquakes along plate boundaries have shown that tectonic tremor, low-frequency earthquakes, very-low-frequency events (VLFEs), and slow-slip events (SSEs) often accompany each other and appear to share common source faults. However, the source processes of slow events occurring in the shallow part of plate boundaries are not well known because seismic observations have been limited to land-based stations, which offer poor resolution beneath offshore plate boundaries. Here we use data obtained from seafloor observation networks in the Nankai trough, southwest of Japan, to investigate shallow VLFEs in detail. Coincident with the VLFE activity, signals indicative of shallow SSEs were detected by geodetic observations at seafloor borehole observatories in the same region. We find that the shallow VLFEs and SSEs share common source regions and almost identical time histories of moment release. We conclude that these slow events arise from the same fault slip and that VLFEs represent relatively high-frequency fluctuations of slip during SSEs.

Fluid-rock interaction during a large earthquake recorded in fault gouge: A case study of the Nojima fault, Japan

NASA Astrophysics Data System (ADS)

Bian, D.; Lin, A.

2016-12-01

Distinguishing the seismic ruptures during the earthquake from a lot of fractures in borehole core is very important to understand rupture processes and seismic efficiency. In particular, a great earthquake like the 1995 Mw 7.2 Kobe earthquake, but again, evidence has been limited to the grain size analysis and the color of fault gouge. In the past two decades, increasing geological evidence has emerged that seismic faults and shear zones within the middle to upper crust play a crucial role in controlling the architectures of crustal fluid migration. Rock-fluid interactions along seismogenic faults give us a chance to find the seismic ruptures from the same event. Recently, a new project of "Drilling into Fault Damage Zone" has being conducted by Kyoto University on the Nojima Fault again after 20 years of the 1995 Kobe earthquake for an integrated multidisciplinary study on the assessment of activity of active faults involving active tectonics, geochemistry and geochronology of active fault zones. In this work, we report on the signature of slip plane inside the Nojima Fault associated with individual earthquakes on the basis of trace element and isotope analyses. Trace element concentrations and 87Sr/86Sr ratios of fault gouge and host rocks were determined by an inductively coupled plasma mass spectrometer (ICP-MS) and thermal ionization mass spectrometry (TIMS). Samples were collected from two trenches and an outcrop of Nojima Fault which. Based on the geochemical result, we interpret these geochemical results in terms of fluid-rock interactions recorded in fault friction during earthquake. The trace-element enrichment pattern of the slip plane can be explained by fluid-rock interactions at high temperature. It also can help us find the main coseismic fault slipping plane inside the thick fault gouge zone.

Identifying buried segments of active faults in the northern Rio Grande Rift using aeromagnetic, LiDAR,and gravity data, south-central Colorado, USA

USGS Publications Warehouse

Grauch, V.J.S.; Ruleman, Chester A.

2013-01-01

Combined interpretation of aeromagnetic and LiDAR data builds on the strength of the aeromagnetic method to locate normal faults with significant offset under cover and the strength of LiDAR interpretation to identify the age and sense of motion of faults. Each data set helps resolve ambiguities in interpreting the other. In addition, gravity data can be used to infer the sense of motion for totally buried faults inferred solely from aeromagnetic data. Combined interpretation to identify active faults at the northern end of the San Luis Basin of the northern Rio Grande rift has confirmed general aspects of previous geologic mapping but has also provided significant improvements. The interpretation revises and extends mapped fault traces, confirms tectonic versus fluvial origins of steep stream banks, and gains additional information on the nature of active and potentially active partially and totally buried faults. Detailed morphology of surfaces mapped from the LiDAR data helps constrain ages of the faults that displace the deposits. The aeromagnetic data provide additional information about their extents in between discontinuous scarps and suggest that several totally buried, potentially active faults are present on both sides of the valley.

Millennial strain partitioning revealed by 36Cl cosmogenic data on active bedrock fault scarps from Abruzzo, Italy

NASA Astrophysics Data System (ADS)

Gregory, Laura; Roberts, Gerald; Cowie, Patience; Wedmore, Luke; McCaffrey, Ken; Shanks, Richard; Zijerveld, Leo; Phillips, Richard

2017-04-01

In zones of distributed continental faulting, it is critical to understand how slip is partitioned onto brittle structures over both long-term millennial time scales and shorter-term individual earthquake cycles. Measuring earthquake slip histories on different timescales is challenging due to earthquake repeat-times being longer or similar to historical earthquake records, and a paucity of data on fault activity covering millennial to Quaternary scales in detail. Cosmogenic isotope analyses from bedrock fault scarps have the potential to bridge the gap, as these datasets track the exposure of fault planes due to earthquakes with millennial resolution. In this presentation, we present new 36Cl data combined with historical earthquake records to document orogen-wide changes in the distribution of seismicity on millennial timescales in Abruzzo, central Italy. Seismic activity due to extensional faulting was concentrated on the northwest side of the mountain range during the historical period, or since approximately the 14th century. Seismicity is more limited on the southwest side of Abruzzo during historical times. This pattern has led some to suggest that faults on the southwest side of Abruzzo are not active, however clear fault scarps cutting Holocene-aged slopes are well preserved across the whole of the orogen. These scarps preserve an excellent record of Late Pleistocene to Holocene earthquake activity, which can be quantified using cosmogenic isotopes that track the exposure of the bedrock fault scarps. 36Cl accumulates in the fault scarps as the plane is progressively exhumed by earthquakes and the concentration of 36Cl measured up the fault plane reflects the rate and patterns of slip. We utilise Bayesian modelling techniques to estimate slip histories based on the cosmogenic data. Each sampling site is carefully characterised using LiDAR and GPR to ensure that fault plane exposure is due to slip during earthquakes and not sediment transport processes. In this presentation we will focus on new data from faults located across-strike in Abruzzo. Many faults in Abruzzo demonstrate slip rate variability on millennial timescales, with relatively fast slip interspersed between quiescent periods. We show that heightened activity is co-located and spatially migrates across Abruzzo over time. We highlight the importance of understanding this dynamic fault behaviour of migrating seismic activity, and in particular how our research is relevant to the 2016 Amatrice-Vettore seismic sequence in central Italy.

Computer simulation of earthquakes

NASA Technical Reports Server (NTRS)

Cohen, S. C.

1976-01-01

Two computer simulation models of earthquakes were studied for the dependence of the pattern of events on the model assumptions and input parameters. Both models represent the seismically active region by mechanical blocks which are connected to one another and to a driving plate. The blocks slide on a friction surface. In the first model elastic forces were employed and time independent friction to simulate main shock events. The size, length, and time and place of event occurrence were influenced strongly by the magnitude and degree of homogeniety in the elastic and friction parameters of the fault region. Periodically reoccurring similar events were frequently observed in simulations with near homogeneous parameters along the fault, whereas, seismic gaps were a common feature of simulations employing large variations in the fault parameters. The second model incorporated viscoelastic forces and time-dependent friction to account for aftershock sequences. The periods between aftershock events increased with time and the aftershock region was confined to that which moved in the main event.

Mobility and coalescence of stacking fault tetrahedra in Cu

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martínez, Enrique; Uberuaga, Blas P.

Stacking fault tetrahedra (SFTs) are ubiquitous defects in face-centered cubic metals. They are produced during cold work plastic deformation, quenching experiments or under irradiation. From a dislocation point of view, the SFTs are comprised of a set of stair-rod dislocations at the (110) edges of a tetrahedron bounding triangular stacking faults. These defects are extremely stable, increasing their energetic stability as they grow in size. At the sizes visible within transmission electron microscope they appear nearly immobile. Contrary to common belief, we show in this report, using a combination of molecular dynamics and temperature accelerated dynamics, how small SFTs canmore » diffuse by temporarily disrupting their structure through activated thermal events. More over, we demonstrate that the diffusivity of defective SFTs is several orders of magnitude higher than perfect SFTs, and can be even higher than isolated vacancies. Finally, we show how SFTs can coalesce, forming a larger defect in what is a new mechanism for the growth of these omnipresent defects.« less

Mobility and coalescence of stacking fault tetrahedra in Cu

DOE PAGES

Martínez, Enrique; Uberuaga, Blas P.

2015-03-13

Stacking fault tetrahedra (SFTs) are ubiquitous defects in face-centered cubic metals. They are produced during cold work plastic deformation, quenching experiments or under irradiation. From a dislocation point of view, the SFTs are comprised of a set of stair-rod dislocations at the (110) edges of a tetrahedron bounding triangular stacking faults. These defects are extremely stable, increasing their energetic stability as they grow in size. At the sizes visible within transmission electron microscope they appear nearly immobile. Contrary to common belief, we show in this report, using a combination of molecular dynamics and temperature accelerated dynamics, how small SFTs canmore » diffuse by temporarily disrupting their structure through activated thermal events. More over, we demonstrate that the diffusivity of defective SFTs is several orders of magnitude higher than perfect SFTs, and can be even higher than isolated vacancies. Finally, we show how SFTs can coalesce, forming a larger defect in what is a new mechanism for the growth of these omnipresent defects.« less

Mobility and coalescence of stacking fault tetrahedra in Cu

PubMed Central

Martínez, Enrique; Uberuaga, Blas P.

2015-01-01

Stacking fault tetrahedra (SFTs) are ubiquitous defects in face-centered cubic metals. They are produced during cold work plastic deformation, quenching experiments or under irradiation. From a dislocation point of view, the SFTs are comprised of a set of stair-rod dislocations at the (110) edges of a tetrahedron bounding triangular stacking faults. These defects are extremely stable, increasing their energetic stability as they grow in size. At the sizes visible within transmission electron microscope they appear nearly immobile. Contrary to common belief, we show in this report, using a combination of molecular dynamics and temperature accelerated dynamics, how small SFTs can diffuse by temporarily disrupting their structure through activated thermal events. More over, we demonstrate that the diffusivity of defective SFTs is several orders of magnitude higher than perfect SFTs, and can be even higher than isolated vacancies. Finally, we show how SFTs can coalesce, forming a larger defect in what is a new mechanism for the growth of these omnipresent defects. PMID:25765711

Stress changes from the 2008 Wenchuan earthquake and increased hazard in the Sichuan basin

USGS Publications Warehouse

Parsons, T.; Ji, C.; Kirby, E.

2008-01-01

On 12 May 2008, the devastating magnitude 7.9 (Wenchuan) earthquake struck the eastern edge of the Tibetan plateau, collapsing buildings and killing thousands in major cities aligned along the western Sichuan basin in China. After such a large-magnitude earthquake, rearrangement of stresses in the crust commonly leads to subsequent damaging earthquakes. The mainshock of the 12 May earthquake ruptured with as much as 9 m of slip along the boundary between the Longmen Shan and Sichuan basin, and demonstrated the complex strike-slip and thrust motion that characterizes the region. The Sichuan basin and surroundings are also crossed by other active strike-slip and thrust faults. Here we present calculations of the coseismic stress changes that resulted from the 12 May event using models of those faults, and show that many indicate significant stress increases. Rapid mapping of such stress changes can help to locate fault sections with relatively higher odds of producing large aftershocks. ??2008 Macmillan Publishers Limited. All rights reserved.

Neotectonic Reactivation of the Gobi Corridor Region, Central Asia

NASA Astrophysics Data System (ADS)

Cunningham, D.

2016-12-01

In this presentation, I review the neotectonic development of the Gobi Corridor region of Central Asia and explore crustal controls on the style and kinematics of mountain building north of Tibet. The Gobi Corridor includes the actively deforming Gobi Altai-Altai, eastern Tien Shan, Beishan and North Tibetan Foreland. Archean basement beneath Central Mongolia has acted as a rigid backstop focusing Late Miocene-Recent crustal reactivation in the Altai and Gobi Altai around the western, southwestern and southern margins of the Hangay Dome. The northern Gobi Altai is characterized by sinistral transpression and growth and coalescence of restraining bends and thrust blocks along the Ih Bogd deforming belt. The southern Gobi Altai is kinematically linked with the easternmost Tien Shan as a separate deforming belt nucleated along the Gobi-Tien Shan sinistral strike-slip fault system. The enigmatic Beishan plateau may be a peripheral bulge to northernmost Tibet and contains two structural culminations within it characterized by sinistral transpression along the Mazong Shan and Xingxingxia fault systems. The North Tibetan foreland contains the Sanweishan and Nanjieshan basement ridges also characterized by Quaternary uplift and oblique sinistral-thrust kinematics. The diffusely reactivated, crust of the Gobi Corridor is largely comprised of amalgamated Cambrian-Permian terranes that are non-cratonized. The region was mechanically weakened by widespread Cretaceous continental rifting and thermally weakened by Jurassic-Tertiary basaltic volcanism and can be regarded as the rheological `soft core' of Central Asia. The kinematics of Late Cenozoic reactivation throughout the region are fundamentally controlled by the angular relationship between SHmax and older basement strike trends. The diffuse array of faults active in the Quaternary and distribution of historical seismicity suggests that tectonic loading is shared by many potentially active faults, thus extrapolation of derived fault slip rates to derive seismic hazard assessments is not straightforward. Intracontinental, intraplate deformation in the Gobi Corridor region reminds us that reactivation of non-cratonized continental interior regions may be a common effect of distant continental collisions.

Identification of active fault using analysis of derivatives with vertical second based on gravity anomaly data (Case study: Seulimeum fault in Sumatera fault system)

NASA Astrophysics Data System (ADS)

Hududillah, Teuku Hafid; Simanjuntak, Andrean V. H.; Husni, Muhammad

2017-07-01

Gravity is a non-destructive geophysical technique that has numerous application in engineering and environmental field like locating a fault zone. The purpose of this study is to spot the Seulimeum fault system in Iejue, Aceh Besar (Indonesia) by using a gravity technique and correlate the result with geologic map and conjointly to grasp a trend pattern of fault system. An estimation of subsurface geological structure of Seulimeum fault has been done by using gravity field anomaly data. Gravity anomaly data which used in this study is from Topex that is processed up to Free Air Correction. The step in the Next data processing is applying Bouger correction and Terrin Correction to obtain complete Bouger anomaly that is topographically dependent. Subsurface modeling is done using the Gav2DC for windows software. The result showed a low residual gravity value at a north half compared to south a part of study space that indicated a pattern of fault zone. Gravity residual was successfully correlate with the geologic map that show the existence of the Seulimeum fault in this study space. The study of earthquake records can be used for differentiating the active and non active fault elements, this gives an indication that the delineated fault elements are active.

Power plant fault detection using artificial neural network

NASA Astrophysics Data System (ADS)

Thanakodi, Suresh; Nazar, Nazatul Shiema Moh; Joini, Nur Fazriana; Hidzir, Hidzrin Dayana Mohd; Awira, Mohammad Zulfikar Khairul

2018-02-01

The fault that commonly occurs in power plants is due to various factors that affect the system outage. There are many types of faults in power plants such as single line to ground fault, double line to ground fault, and line to line fault. The primary aim of this paper is to diagnose the fault in 14 buses power plants by using an Artificial Neural Network (ANN). The Multilayered Perceptron Network (MLP) that detection trained utilized the offline training methods such as Gradient Descent Backpropagation (GDBP), Levenberg-Marquardt (LM), and Bayesian Regularization (BR). The best method is used to build the Graphical User Interface (GUI). The modelling of 14 buses power plant, network training, and GUI used the MATLAB software.

Structural character of the Ghost Dance Fault, Yucca Mountain, Nevada

DOE Office of Scientific and Technical Information (OSTI.GOV)

Spengler, R.W.; Braun, C.A.; Linden, R.M.

1993-12-31

Detailed structural mapping of an area that straddles the southern part of the Ghost Dance Fault has revealed the presence of several additional subparallel to anastomosing faults. These faults, mapped at a scale of 1:240, are: (1) dominantly north-trending, (2) present on both the upthrown and downthrown sides of the surface trace of the Ghost Dance fault, (3) near-vertical features that commonly offset strata down to the west by 3 to 6 m (10 to 20 ft), and (4) commonly spaced 15 to 46 m (50 to 150 ft) apart. The zone also exhibits a structural fabric, containing an abundancemore » of northwest-trending fractures. The width of the zone appears to be at least 213 m (700 ft) near the southernmost boundary of the study area but remains unknown near the northern extent of the study area, where the width of the study area is only 183 m (600 ft).« less

Database and Map of Quaternary Faults and Folds in Peru and its Offshore Region

USGS Publications Warehouse

Machare, Jose; Fenton, Clark H.; Machette, Michael N.; Lavenu, Alain; Costa, Carlos; Dart, Richard L.

2003-01-01

This publication consists of a main map of Quaternary faults and fiolds of Peru, a table of Quaternary fault data, a region inset map showing relative plate motion, and a second inset map of an enlarged area of interest in southern Peru. These maps and data compilation show evidence for activity of Quaternary faults and folds in Peru and its offshore regions of the Pacific Ocean. The maps show the locations, ages, and activity rates of major earthquake-related features such as faults and fault-related folds. These data are accompanied by text databases that describe these features and document current information on their activity in the Quaternary.

Fracture properties from tight reservoir outcrop analogues with application to geothermal exploration

NASA Astrophysics Data System (ADS)

Philipp, Sonja L.; Reyer, Dorothea; Afsar, Filiz; Bauer, Johanna F.; Meier, Silke; Reinecker, John

2015-04-01

In geothermal reservoirs, similar to other tight reservoirs, fluid flow may be intensely affected by fracture systems, in particular those associated with fault zones. When active (slipping) the fault core, that is, the inner part of a fault zone, which commonly consists of breccia or gouge, can suddenly develop high permeability. Fault cores of inactive fault zones, however, may have low permeabilities and even act as flow barriers. In the outer part of a fault zone, the damage zone, permeability depends mainly on the fracture properties, that is, the geometry (orientation, aperture, density, connectivity, etc.) of the fault-associated fracture system. Mineral vein networks in damage zones of deeply eroded fault zones in palaeogeothermal fields demonstrate their permeability. In geothermal exploration, particularly for hydrothermal reservoirs, the orientation of fault zones in relation to the current stress field as well as their internal structure, in particular the properties of the associated fracture system, must be known as accurately as possible for wellpath planning and reservoir engineering. Here we present results of detailed field studies and numerical models of fault zones and associated fracture systems in palaeogeo¬thermal fields and host rocks for geothermal reservoirs from various stratigraphies, lithologies and tectonic settings: (1) 74 fault zones in three coastal sections of Upper Triassic and Lower Jurassic age (mudstones and limestone-marl alternations) in the Bristol Channel Basin, UK. (2) 58 fault zones in 22 outcrops from Upper Carboniferous to Upper Cretaceous in the Northwest German Basin (siliciclastic, carbonate and volcanic rocks); and (3) 16 fault zones in 9 outcrops in Lower Permian to Middle Triassic (mainly sandstone and limestone) in the Upper Rhine Graben shoulders. Whereas (1) represent palaeogeothermal fields with mineral veins, (2) and (3) are outcrop analogues of reservoir horizons from geothermal exploration. In the study areas of palaeo¬geothermal fields in the Bristol Channel (1), all mineral veins, most of which are extension fractures, are of calcite. They are clearly associated with the faults and indicate that geothermal water was transported along the then-active faults into the host rocks with evidence of injection as hydrofractures. Layers with contrasting mechanical properties (in particular, stiffnesses), however, acted as stress barriers and lead to fracture arrest. Along some faults, veins propagated through the barriers along faults to shallower levels. In the Northwest German Basin (2) there are pronounced differences between normal-fault zones in carbonate and clastic rocks. Only in carbonate rocks clear damage zones occur, characterized by increased fracture frequencies and high amounts of fractures with large apertures. On the Upper Rhine Graben shoulders (3) damage zones in Triassic Muschelkalk limestones are well developed; fault cores are narrow and comprise breccia, clay smear, host rock lenses and mineralization. A large fault zone in Triassic Bunter sandstone shows a clearly developed fault core with fault gouge, slip zones, deformation bands and host rock lenses, a transition zone with mostly disturbed layering and highest fracture frequency, and a damage zone. The latter damage zone is compared to the damage zone of a large Bunter sandstone fault zone currently explored for geothermal energy production. The numerical models focus on stress field development, fracture propagation and associated permeability changes. These studies contribute to the understanding of the hydromechanical behaviour of fault zones and related fluid transport in fractured reservoirs complementing predictions based on geophysical measurements. Eventually we aim at classifying and quantifying fracture system properties in fault zones to improve exploration and exploitation of geothermal reservoirs. Acknowledgements The authors appreciate the support of 'Niedersächsisches Ministerium für Wissen¬schaft und Kultur' and 'Baker Hughes' within the gebo research project (http://www.gebo-nds.de), the Bundesministerium für Umwelt, Naturschutz, Bau und Reaktorsicherheit (BMU; FKZ: 0325302, AuGE) and the Deutsche Forschungsgemeinschaft. GeoEnergy GmbH, Karlsruhe, is thanked for explorational data.

Active tectonic deformation of the western Indian plate boundary: A case study from the Chaman Fault System

NASA Astrophysics Data System (ADS)

Crupa, Wanda E.; Khan, Shuhab D.; Huang, Jingqiu; Khan, Abdul S.; Kasi, Aimal

2017-10-01

Collision of the Eurasian and Indian plates has resulted in two spatially offset subduction zones, the Makran subduction zone to the south and the Himalayan convergent margin to the north. These zones are linked by a system of left-lateral strike-slip faults known as the Chaman Fault System, ∼1200 km, which spans along western Pakistan. Although this is one of the greatest strike-slip faults, yet temporal and spatial variation in displacement has not been adequately defined along this fault system. This study conducted geomorphic and geodetic investigations along the Chaman Fault in a search for evidence of spatial variations in motion. Four study areas were selected over the span of the Chaman Fault: (1) Tarnak-Rud area over the Tarnak-Rud valley, (2) Spinatizha area over the Spinatizha Mountain Range, (3) Nushki area over the Nushki basin, and (4) Kharan area over the northern tip of the Central Makran Mountains. Remote sensing data allowed for in depth mapping of different components and faults within the Kohjak group. Wind and water gap pairs along with offset rivers were identified using high-resolution imagery and digital-elevation models to show displacement for the four study areas. The mountain-front-sinuosity ratio, valley height-to-width-ratio, and the stream-length-gradient index were calculated and used to determine the relative tectonic activity of each area. These geomorphic indices suggest that the Kharan area is the most active and the Tarnak-Rud area is the least active. GPS data were processed into a stable Indian plate reference frame and analyzed. Fault parallel velocity versus fault normal distance yielded a ∼8-10 mm/yr displacement rate along the Chaman Fault just north of the Spinatizha area. InSAR data were also integrated to assess displacement rates along the fault system. Geodetic data support that ultra-slow earthquakes similar to those that strike along other major strike-slip faults, such as the San Andreas Fault System, are possible along the northern segments of the Chaman Fault zone. Geomorphic data suggest that the Chaman Fault along southern part is not very active now but may have gone through high tectonic activity in the past.

Towards a Fault-based SHA in the Southern Upper Rhine Graben

NASA Astrophysics Data System (ADS)

Baize, Stéphane; Reicherter, Klaus; Thomas, Jessica; Chartier, Thomas; Cushing, Edward Marc

2016-04-01

A brief overview at a seismic map of the Upper Rhine Graben area (say between Strasbourg and Basel) reveals that the region is seismically active. The area has been hit recently by shallow and moderate quakes but, historically, strong quakes damaged and devastated populated zones. Several authors previously suggested, through preliminary geomorphological and geophysical studies, that active faults could be traced along the eastern margin of the graben. Thus, fault-based PSHA (probabilistic seismic hazard assessment) studies should be developed. Nevertheless, most of the input data in fault-based PSHA models are highly uncertain, based upon sparse or hypothetical data. Geophysical and geological data document the presence of post-Tertiary westward dipping faults in the area. However, our first investigations suggest that the available surface fault map do not provide a reliable document of Quaternary fault traces. Slip rate values that can be currently used in fault-PSHA models are based on regional stratigraphic data, but these include neither detailed datings nor clear base surface contours. Several hints on fault activity do exist and we have now relevant tools and techniques to figure out the activity of the faults of concern. Our preliminary analyses suggest that the LiDAR topography can adequately image the fault segments and, thanks to detailed geomorphological analysis, these data allow tracking cumulative fault offsets. Because the fault models can therefore be considered highly uncertain, our coming project for the next 3 years is to acquire and analyze these accurate topographical data, to trace the active faults and to determine slip rates through relevant features dating. Eventually, we plan to find a key site to perform a paleoseismological trench because this approach has been proved to be worth in the Graben, both to the North (Wörms and Strasbourg) and to the South (Basel). This would be done in order to definitely prove whether the faults ruptured the ground surface during the Quaternary, and in order to determine key fault parameters such as magnitude and age of large events.

Fault structure, properties and activity of the Makran Accretionary Prism and implications for seismogenic potential

NASA Astrophysics Data System (ADS)

Smith, G. L.; McNeill, L. C.; Henstock, T.; Bull, J. M.

2011-12-01

The Makran subduction zone is the widest accretionary prism in the world (~400km), generated by convergence between the Arabian and Eurasian tectonic plates. It represents a global end-member, with a 7km thick incoming sediment section. Accretionary prisms have traditionally been thought to be aseismic due to the presence of unconsolidated sediment and elevated basal pore pressures. The seismogenic potential of the Makran subduction zone is unclear, despite a Mw 8.1 earthquake in 1945 that may have been located on the plate boundary beneath the prism. In this study, a series of imbricate landward dipping (seaward verging) thrust faults have been interpreted across the submarine prism (outer 70 km) using over 6000km of industry multichannel seismic data and bathymetric data. A strong BSR (bottom simulating reflector) is present throughout the prism (excluding the far east). An unreflective décollement is interpreted from the geometry of the prism thrusts. Two major sedimentary units are identified in the input section, the lower of which contains the extension of the unreflective décollement surface. Between 60%-100% of the input section is currently being accreted. The geometry of piggy-back basin stratigraphy shows that the majority of thrusts, including those over 50km from the trench, are recently active. Landward thrusts show evidence for reactivation after periods of quiescence. Negative polarity fault plane reflectors are common in the frontal thrusts and in the eastern prism, where they may be related to increased fault activity and fluid expulsion, and are rarer in older landward thrusts. Significant NE-SW trending basement structures (The Murray Ridge and Little Murray Ridge) on the Arabian plate intersect the deformation front and affect sediment input to the subduction zone. Prism taper and structure are apparently primarily controlled by sediment supply and the secondary influence of subducting basement ridges. The thick, likely distal, sediment section in the west produces a prism with a simple imbricate structure. As basement depth is reduced over the Little Murray Ridge, the accretionary prism structure (fault spacing and deformation front position) changes. In the east, proximity to the Murray Ridge and triple junction is expressed through a reduction in prism width and reduced fault activity. The resulting prism structure and morphology can ultimately be used to assess likely sediment properties and hence seismic potential at the plate boundary.

Fault displacement hazard assessment for nuclear installations based on IAEA safety standards

NASA Astrophysics Data System (ADS)

Fukushima, Y.

2016-12-01

In the IAEA Safety NS-R-3, surface fault displacement hazard assessment (FDHA) is required for the siting of nuclear installations. If any capable faults exist in the candidate site, IAEA recommends the consideration of alternative sites. However, due to the progress in palaeoseismological investigations, capable faults may be found in existing site. In such a case, IAEA recommends to evaluate the safety using probabilistic FDHA (PFDHA), which is an empirical approach based on still quite limited database. Therefore a basic and crucial improvement is to increase the database. In 2015, IAEA produced a TecDoc-1767 on Palaeoseismology as a reference for the identification of capable faults. Another IAEA Safety Report 85 on ground motion simulation based on fault rupture modelling provides an annex introducing recent PFDHAs and fault displacement simulation methodologies. The IAEA expanded the project of FDHA for the probabilistic approach and the physics based fault rupture modelling. The first approach needs a refinement of the empirical methods by building a world wide database, and the second approach needs to shift from kinematic to the dynamic scheme. Both approaches can complement each other, since simulated displacement can fill the gap of a sparse database and geological observations can be useful to calibrate the simulations. The IAEA already supported a workshop in October 2015 to discuss the existing databases with the aim of creating a common worldwide database. A consensus of a unified database was reached. The next milestone is to fill the database with as many fault rupture data sets as possible. Another IAEA work group had a WS in November 2015 to discuss the state-of-the-art PFDHA as well as simulation methodologies. Two groups jointed a consultancy meeting in February 2016, shared information, identified issues, discussed goals and outputs, and scheduled future meetings. Now we may aim at coordinating activities for the whole FDHA tasks jointly.

Seismicity and Seismotectonic Properties of The Sultandağı Fault Zone (Afyonkarahisar-Konya): Western Anatolia,Turkey

NASA Astrophysics Data System (ADS)

Kalafat, D.; Gunes, Y.; Kekovali, K.; Kara, M.; Gorgun, E.

2017-12-01

n this study we investigated seismicity and source characteristics of the Sultandağı Fault Zone (SFZ). As known Western Anatolia is one of the most important seismically active region in Turkey. The relative movement of the African-Arabian plates, it causes the Anatolian Plate to movement to the west-Southwest direction 2.5 cm per year and this result provides N-S direction with extensional regime in the recent tectonic. In this study, especially with the assessment of seismic activity occurring in Afyon and around between 200-2002 years, we have been evaluated to date with seismic activity as well as fault mechanism solution. We analyzed recent seismicity and distribution of earthquakes in this region. In the last century, 3 important earthquakes occurred in the Sultandağı Fault zone (Afyon-Akşehir Graben), this result shown it was seismic active and broken fault segments caused stress balance in the region and it caused to occur with short intervals of earthquakes in 2000 and 2002, triggering each other. The scope of this tudy, we installed new BB stations in the region and we have been done of the fault plane solutions for important earthquakes. The focal mechanisms clearly exhibit the activation of a NE-SW trending normal faulting system along the SFZ region. The results of stress analysis showed that the effective current tectonic evolution of normal faulting in this region. This study is supported by Bogazici University Research Projects Commission under SRP/BAP project No. 12280. Key Words: Sultandağı fault zone, normal faulting, seismicity, fault mechanism

Fault propagation folds induced by gravitational failure and slumping of the Central Costa Rica volcanic range: Implications for large terrestrial and Martian volcanic edifices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Borgia, A.; Burr, J.; Montero, W.

1990-08-30

Long sublinear ridges and related scarps located at the base of large volcanic structures are frequently interpreted as normal faults associated with extensional regional stress. In contrast, the ridges bordering the Central Costa Rica volcanic range (CCRVR) are the topographic expression of hanging wall asymmetric angular anticlines overlying low-angle thrust faults at the base of the range. These faults formed by gravitational failure and slumping of the flanks of the range due to the weight of the volcanic edifices and were perhaps triggered by the intrusion of magma over the past 20,000 years. These anticlines are hypothesized to occur alongmore » the base of the volcano, where the thrust faults ramp up toward the sea bottom. Ridges and scarps between 2,000 and 5,000 m below sea level are interpreted as the topographic expression of these folds. The authors further suggest that the scarps of the CCRVR and valid scaled terrestrial analogs of the perimeter scarp of the Martian volcano Olympus Mons. They suggest that the crust below Olympus Mons has failed under the load of the volcano, triggering the radial slumping of the flanks of the volcano on basal thrusts. The thrusting would have, in turn, formed the anticlinal ridges and scarps that surround the edifice. The thrust faults may extend all the way to the base of the Martian crust (about 40 km), and they may have been active until almost the end of the volcanic activity. They suggest that gravitational failure and slumping of the flanks of volcanoes is a process common to most large volcanic edifices. In the CCRVR this slumping of the flanks is a slow intermittent process, but it could evolve to rapid massive avalanching leading to catastrophic eruptions. Thus monitoring of uplift and displacement of the folds related to the slump tectonics could become an additional effective method for mitigating volcanic hazards.« less

Integrating Near Fault Observatories (NFO) for EPOS Implementation Phase

NASA Astrophysics Data System (ADS)

Chiaraluce, Lauro

2015-04-01

Following the European Plate Observing System (EPOS) project vision aimed at creating a pan-European infrastructure for Earth sciences to support science for a more sustainable society, we are working on the integration of Near-Fault Observatories (NFOs). NFOs are state of the art research infrastructures consisting of advanced networks of multi-parametric sensors continuously monitoring the chemical and physical processes related to the common underlying earth instabilities governing active faults evolution and the genesis of earthquakes. Such a methodological approach, currently applicable only at the local scale (areas of tens to few hundreds of kilometres), is based on extremely dense networks and less common instruments deserving an extraordinary work on data quality control and multi-parameter data description. These networks in fact usually complement regional seismic and geodetic networks (typically with station spacing of 50-100km) with high-density distributions of seismic, geodetic, geochemical and geophysical sensors located typically within 10-20 km of active faults where large earthquakes are expected in the future. In the initial phase of EPOS-IP, seven NFO nodes will be linked: the Alto Tiberina and Irpinia Observatories in Italy, the Corinth Observatory in Greece, the South-Iceland Seismic Zone, the Valais Observatory in Switzerland, Marmara Sea GEO Supersite in Turkey (EU MARSite) and the Vrancea Observatory in Romania. Our work is aimed at establishing standards and integration within this first core group of NFOs while other NFOs are expected to be installed in the next years adopting the standards established and developed within the EPOS Thematic Core Services (TCS). The goal of our group is to build upon the initial development supported by these few key national observatories coordinated under previous EU projects (NERA and REAKT), inclusive and harmonised TCS supporting the installation over the next decade of tens of near-fault observatories monitoring active faults in different tectonic environments in Europe. We will assist these new NFOs in their design, installation and inclusion in EPOS. These infrastructures will substantially enable advancements in our fundamental understanding of earthquakes generation processes and associated ground shaking due to their high quality near source multidisciplinary data retrieval. While guaranteeing the continuous acquisition and storage of long time-series of such data, we will allow also an easy and direct data discovery and access to the whole community. This implies to strengthen the collaborations with other related EU and global initiatives devoted to the multidisciplinary monitoring and study of active fault zones (such as the GEO Geohazards Supersites initiative). Another key goal is the establishment of a legal governance for such a young community to ensure the long-term sustainability of the services and data access to databases to be used for scientific investigations and accessible via the Integrated Services that will be implemented within the EPOS IP project. The availability of real-time data retrieved by dense and multi-parametric networks located at close distance from the fault provides the unique opportunity of observing all phase of preparation, nucleation and propagation of the earthquake rupture. It is thus of crucial importance to develop methodologies that follow in real-time the evolution of the event. Hence the NFO is the unique and ideal infrastructure for hosting testing centers where a variety of scientific algorithms for real-time monitoring can be operated side-by-side and their performance independently evaluated. Besides the high interest for fundamental science, such developments have obvious societal impact, as they allow precise and timely release of alerts as the seismic event develops, and can attract new stakeholders such as industry partners who are interested in adopting and investing in early warning technologies and evolutionary ground shaking maps. Finally, we will describe how we intend to implement novel tools for visualization and analysis of multidisciplinary data and products to describe the anatomy of active faults and the physical processes governing earthquake generation and faulting. A sort of virtual laboratory aimed at promoting and disseminating Earth sciences at different levels.

Central Japan's Atera Active Fault's Wide-Fractured Zone: An Examination of the Structure and In-situ Crustal Stress

NASA Astrophysics Data System (ADS)

Ikeda, R.; Omura, K.; Matsuda, T.; Mizuochi, Y.; Uehara, D.; Chiba, A.; Kikuchi, A.; Yamamoto, T.

2001-12-01

In-situ downhole measurements and coring within and around an active fault zone are needed to better understand the structure and material properties of fault rocks as well as the physical state of active faults and intra-plate crust. Particularly, the relationship between the stress concentration state and the heterogeneous strength of an earthquake fault zone is important to estimate earthquake occurrence mechanisms which correspond to the prediction of an earthquake. It is necessary to compare some active faults in different conditions of the chrysalis stage and their relation to subsequent earthquake occurrence. To better understand such conditions, "Active Fault Zone Drilling Project" has been conducted in the central part of Japan by the National Research Institute for Earth Science and Disaster Prevention. The Nojima fault which appeared on the surface by the 1995 Great Kobe earthquake (M=7.2) and the Neodani fault created by the 1981 Nobi earthquake, the greatest inland earthquake M=8.0 in Japan, have been drilled through the fault fracture zones. During these past four years, a similar experiment and research at the Atera fault, of which some parts seem to have been dislocated by the 1586 Tensyo earthquake, has been undertaken. The features of the Atera fault are as follows: (1) total length is about 70 km, (2) general trend is NW45_Kwith a left-lateral strike slip, (3) slip rate is estimated as 3-5 m/1000 yrs. and the average recurrence time as 1700 yrs., (4) seismicity is very low at present, and (5) lithologies around the fault are basically granitic rocks and rhyolite. We have conducted integrated investigations by surface geophysical survey and drilling around the Atera fault. Six boreholes have been drilled from the depth of 400 m to 630 m. Four of these boreholes are located on a line crossing the fracture zone of the Atera fault. Resistivity and gravity structures inferred from surface geophysical surveys were compared with the physical properties determined from the borehole logging data and core samples. These results were also compared with in situ stress data by the hydraulic fracturing stress measurements in the boreholes. We obtained characteristic states on crustal stress and strength of the fault from these investigations. Our findings are as follows: (1) The fracture zone around the Atera fault shows a very wide and complex fracture structure, from approximately 1 km to 4 km wide. The average slip rate was estimated to be 5.3 m /1000 yrs. by the distribution of basalt in age of 1.5 Ma by radioactive dating. We inferred that the Atera fault has been repeatedly active in recent geologic time; however, it is in a very weak state at present. (2) The stress magnitude decreases in the area closer to the center of the fracture zone. Furthermore the orientation of the maximum horizontal compressive stress was almost in a North-South direction, just reverse of the fault moving direction. These are important results to evaluate fault activity. We argue that the stress state observed in these sites exists only when the faults are quite "weak," and thus does not reach to a critical level of fault activation in the present situation.

Subsurface signature of North Anatolian Fault Zone and its relation with old sutures: New insight from receiver function analysis.

NASA Astrophysics Data System (ADS)

Özacar, Arda A.; Abgarmi, Bizhan

2017-04-01

The North Anatolian Fault Zone (NAFZ) is an active continental transform plate boundary that accommodates the westward extrusion of the Anatolian plate. The central segment of NAFZ displays northward convex surface trace which coincides partly with the Paleo-Tethyan suture formed during the early Cenozoic. The depth extent and detailed structure of the actively deforming crust along the NAF is still under much debate and processes responsible from rapid uplift are enigmatic. In this study, over five thousand high quality P receiver functions are computed using teleseismic earthquakes recorded by permanent stations of national agencies and temporary North Anatolian Fault Passive Seismic experiment (2005-2008). In order to map the crustal thickness and Vp/Vs variations accurately, the study area is divided into grids with 20 km spacing and along each grid line Moho phase and its multiples are picked through constructed common conversion point (CCP) profiles. According to our results, nature of discontinuities and crustal thickness display sharp changes across the main strand of NAFZ supporting a lithospheric scale faulting that offsets Moho discontinuity. In the southern block, crust is relatively thin in the west ( 35 km) and becomes thicker gradually towards east ( 40 km). In contrast, the northern block displays a strong lateral change in crustal thickness reaching up to 10 km across a narrow roughly N-S oriented zone which is interpreted as the subsurface signature of the ambiguous boundary between Istanbul Block and Pontides located further west at the surface.

Preservation of amorphous ultrafine material: A proposed proxy for slip during recent earthquakes on active faults

PubMed Central

Hirono, Tetsuro; Asayama, Satoru; Kaneki, Shunya; Ito, Akihiro

2016-01-01

The criteria for designating an “Active Fault” not only are important for understanding regional tectonics, but also are a paramount issue for assessing the earthquake risk of faults that are near important structures such as nuclear power plants. Here we propose a proxy, based on the preservation of amorphous ultrafine particles, to assess fault activity within the last millennium. X-ray diffraction data and electron microscope observations of samples from an active fault demonstrated the preservation of large amounts of amorphous ultrafine particles in two slip zones that last ruptured in 1596 and 1999, respectively. A chemical kinetic evaluation of the dissolution process indicated that such particles could survive for centuries, which is consistent with the observations. Thus, preservation of amorphous ultrafine particles in a fault may be valuable for assessing the fault’s latest activity, aiding efforts to evaluate faults that may damage critical facilities in tectonically active zones. PMID:27827413

Preliminary atlas of active shallow tectonic deformation in the Puget Lowland, Washington

USGS Publications Warehouse

Barnett, Elizabeth A.; Haugerud, Ralph A.; Sherrod, Brian L.; Weaver, Craig S.; Pratt, Thomas L.; Blakely, Richard J.

2010-01-01

This atlas presents an up-to-date map compilation of the geological and geophysical observations that underpin interpretations of active, surface-deforming faults in the Puget Lowland, Washington. Shallow lowland faults are mapped where observations of deformation from paleoseismic, seismic-reflection, and potential-field investigations converge. Together, results from these studies strengthen the identification and characterization of regional faults and show that as many as a dozen shallow faults have been active during the Holocene. The suite of maps presented in our atlas identifies sites that have evidence of deformation attributed to these shallow faults. For example, the paleoseismic-investigations map shows where coseismic surface rupture and deformation produced geomorphic scarps and deformed shorelines. Other maps compile results of seismic-reflection and potential-field studies that demonstrate evidence of deformation along suspected fault structures in the subsurface. Summary maps show the fault traces derived from, and draped over, the datasets presented in the preceding maps. Overall, the atlas provides map users with a visual overview of the observations and interpretations that support the existence of active, shallow faults beneath the densely populated Puget Lowland.

On the physics-based processes behind production-induced seismicity in natural gas fields

NASA Astrophysics Data System (ADS)

Zbinden, Dominik; Rinaldi, Antonio Pio; Urpi, Luca; Wiemer, Stefan

2017-04-01

Induced seismicity due to natural gas production is observed at different sites around the world. Common understanding is that the pressure drop caused by gas production leads to compaction, which affects the stress field in the reservoir and the surrounding rock formations, hence reactivating pre-existing faults and inducing earthquakes. Previous studies have often assumed that pressure changes in the reservoir compartments and intersecting fault zones are equal, while neglecting multi-phase fluid flow. In this study, we show that disregarding fluid flow involved in natural gas extraction activities is often inappropriate. We use a fully coupled multiphase fluid flow and geomechanics simulator, which accounts for stress-dependent permeability and linear poroelasticity, to better determine the conditions leading to fault reactivation. In our model setup, gas is produced from a porous reservoir, cut in two compartments that are offset by a normal fault, and overlain by impermeable caprock. Results show that fluid flow plays a major role pertaining to pore pressure and stress evolution within the fault. Hydro-mechanical processes include rotation of the principal stresses due to reservoir compaction, as well as poroelastic effects caused by the pressure drop in the adjacent reservoir. Fault strength is significantly reduced due to fluid flow into the fault zone from the neighbouring reservoir compartment and other formations. We also analyze the case of production in both compartments, and results show that simultaneous production does not prevent the fault to be reactivated, but the magnitude of the induced event is smaller. Finally, we analyze scenarios for minimizing seismicity after a period of production, such as (i) well shut-in and (ii) gas re-injection. Results show that, in the case of well shut-in, a highly stressed fault zone can still be reactivated several decades after production stop, although in average the shut-in results in reduction of seismicity. In the case of gas re-injection, fault reactivation can be avoided if gas is injected directly into the compartment under depletion. However, accounting for continuous production at a given reservoir and gas re-injection at a neighbouring compartment does not stop the fault from being reactivated.

Structural Controls of Neal Hot Springs Geothermal Field, Malhuer County, Oregon

NASA Astrophysics Data System (ADS)

Edwards, J. H.; Faulds, J. E.

2012-12-01

Detailed mapping (1:24,000) of the Neal Hot Springs area (90 km2) in eastern Oregon is part of a larger study of geothermal systems in the Basin and Range, which focuses on the structural controls of geothermal activity. The study area lies within the intersection of two regional grabens, the middle-late Miocene, N-striking, Oregon-Idaho graben and younger late Miocene to Holocene, NW-striking, western Snake River Plain graben. The geothermal field is marked by Neal Hot Springs, which effuse from opaline sinter mounds just north of Bully Creek. Wells producing geothermal fluids, with temperatures at 138°C, intersect a major, W-dipping, NNW-striking, high-angle normal fault at depths of 850-915 m. Displacement along this structure dies southward, with likely horse-tailing, which commonly produces high fracture density and a zone of high permeability conducive for channeling hydrothermal fluids. Mapping reveals that the geothermal resource lies within a local, left step-over. 'Hard-linkage' between strands of the left-stepping normal fault, revealed through a study of well chips and well logs, occurs through two concealed structures. Both are W-striking faults, with one that runs parallel to Cottonwood Creek and one 0.5 km N of the creek. Injection wells intersect these two transverse structures within the step-over. Stepping and displacement continue to the NW of the known geothermal field, along W-dipping, N-striking faults that cut lower to middle Miocene Hog Creek Formation, consisting of silicic and mafic volcanic rocks. These N-striking faults were likely initiated during initial Oregon-Idaho graben subsidence (15.3-15.1 Ma), with continued development through late Miocene. Bully Creek Formation deposits, middle to upper Miocene lacustrine and pyroclastic rocks, concomitantly filled the sub half-grabens, and they dip gently to moderately eastward. Younger, western Snake River Plain deposits, upper Miocene to Pliocene fluvial, lacustrine, and pyroclastic rocks, show various dip directions and gentle tilting. Extensive alluvial fan cover hinders collection of fault kinematic data, which coupled with limited regional seismicity, precludes careful calculation of local stress field orientations. However, the proximity of Neal (4 km) to the active, N- to NW-striking, oblique-normal slip Cottonwood Mountain fault and active hot springs (~90°C), opaline sinter mounds, and geothermal fluid flow at Neal suggest that the geothermal field lies within a reactived (Quaternary), southward-terminating, left-stepping, fault zone, which probably accommodates oblique-slip with a dominant normal component. Sugarloaf Butte (completely silicified and replaced) lies within a left step of this fault zone, ~5 km of Neal Hot Springs and is possibly related to the evolution of the geothermal system. Epithermal deposits and argillic to propylitic alteration in other nearby areas (e.g., Hope Butte, ~3 Ma, 5 km N) indicate previous geothermal activity.

A remote sensing study of active folding and faulting in southern Kerman province, S.E. Iran

NASA Astrophysics Data System (ADS)

Walker, Richard Thomas

2006-04-01

Geomorphological observations reveal a major oblique fold-and-thrust belt in Kerman province, S.E. Iran. The active faults appear to link the Sabzevaran right-lateral strike-slip fault in southeast Iran to other strike-slip faults within the interior of the country and may provide the means of distributing right-lateral shear between the Zagros and Makran mountains over a wider region of central Iran. The Rafsanjan fault is manifest at the Earth's surface as right-lateral strike-slip fault scarps and folding in alluvial sediments. Height changes across the anticlines, and widespread incision of rivers, are likely to result from hanging-wall uplift above thrust faults at depth. Scarps in recent alluvium along the northern margins of the folds suggest that the thrusts reach the surface and are active at the present-day. The observations from Rafsanjan are used to identify similar late Quaternary faulting elsewhere in Kerman province near the towns of Mahan and Rayen. No instrumentally recorded destructive earthquakes have occurred in the study region and only one historical earthquake (Lalehzar, 1923) is recorded. In addition GPS studies show that present-day rates of deformation are low. However, fault structures in southern Kerman province do appear to be active in the late Quaternary and may be capable of producing destructive earthquakes in the future. This study shows how widely available remote sensing data can be used to provide information on the distribution of active faulting across large areas of deformation.

Recent advances in understanding the characteristics of seismogenic intraplate deformation in Australia, and the potential for using global analogues

NASA Astrophysics Data System (ADS)

Clark, Dan; McPherson, Andrew

2017-04-01

Continental intraplate Australia can be divided according to crustal type in terms of seismogenic potential and fault characteristics. Three 'superdomains' are recognized, representing cratonic, non-cratonic and extended crust. In the Australian context, cratonic crust is Archaean to Proterozoic in age and has not been significantly tectonically reactivated during the Phanerozoic Eon. Non-cratonic crust includes Phanerozoic accretionary terranes and older crust significantly deformed during Phanerozoic tectonic events. Extended crust includes any crustal type that has been significantly extended during the Mesozoic and Cenozoic, and often to a lesser degree in the Paleozoic. Aulacogens and passive margins fit into this category. Cratonic crust is characterized by the thickest lithosphere and has the lowest seismogenic potential, despite all eight documented historic surface ruptures in Australia having occurred within this category. Little strain accumulation is observed on individual faults and isolated single-rupture scarps are common. Where recurrence has been demonstrated, average slip rates of only a few metres per million years are indicated. In contrast, extended crust is associated with thinner lithosphere, better connection between faults, and strain localization on faults which can result in regional relief-building. The most active faults have accumulated several hundred metres of slip under the current crustal stress regime at rates of several tens of metres per million years. Non-cratonic crust is typically intermediate in lithospheric thickness and seismogenic character. The more active faults have accumulated tens to a couple of hundreds of metres of slip, at rates of a few to a few tens of metres per million years. Across all superdomains paleoseismological data suggest that the largest credible earthquakes are likely to exceed those experienced in historic times. In general, the concept of large earthquake recurrence might only be meaningful in relation to individual faults in non-cratonic and extended superdomains. However, large earthquake recurrence and slip are demonstrably not evenly distributed in time. Within the limitations of the sparse paleoseismological data, temporal clustering of large events appears to be a common (perhaps ubiquitous?) characteristic. Over the last few decades, permanent and campaign GPS studies have failed to detect a tectonic deformation signal from which a strain budget could be calculated. Recent studies have used these observations, amongst others, to propose an orders of magnitude difference in the timescales of strain accumulation and seismogenic strain release in intraplate environments - i.e. clusters of large events deplete long-lived pools of lithospheric strain. The recognition of a relationship between crustal type/lithospheric thickness and seismogenic potential in Australia provides a framework for assessing whether ergodic substitution (i.e. global analogue studies) might be warranted as a tool to better understand intraplate seismicity worldwide. Further research is required to assess how variation in crustal stress regime may influence faulting characteristics within different superdomains.

Response of deformation patterns to reorganizations of the southern San Andreas fault system since ca. 1.5 Ma

NASA Astrophysics Data System (ADS)

Cooke, M. L.; Fattaruso, L.; Dorsey, R. J.; Housen, B. A.

2015-12-01

Between ~1.5 and 1.1 Ma, the southern San Andreas fault system underwent a major reorganization that included initiation of the San Jacinto fault and termination of slip on the extensional West Salton detachment fault. The southern San Andreas fault itself has also evolved since this time, with several shifts in activity among fault strands within San Gorgonio Pass. We use three-dimensional mechanical Boundary Element Method models to investigate the impact of these changes to the fault network on deformation patterns. A series of snapshot models of the succession of active fault geometries explore the role of fault interaction and tectonic loading in abandonment of the West Salton detachment fault, initiation of the San Jacinto fault, and shifts in activity of the San Andreas fault. Interpreted changes to uplift patterns are well matched by model results. These results support the idea that growth of the San Jacinto fault led to increased uplift rates in the San Gabriel Mountains and decreased uplift rates in the San Bernardino Mountains. Comparison of model results for vertical axis rotation to data from paleomagnetic studies reveals a good match to local rotation patterns in the Mecca Hills and Borrego Badlands. We explore the mechanical efficiency at each step in the evolution, and find an overall trend toward increased efficiency through time. Strain energy density patterns are used to identify regions of off-fault deformation and potential incipient faulting. These patterns support the notion of north-to-south propagation of the San Jacinto fault during its initiation. The results of the present-day model are compared with microseismicity focal mechanisms to provide additional insight into the patterns of off-fault deformation within the southern San Andreas fault system.

GeoBioScience: Red Wood Ants as Bioindicators for Active Tectonic Fault Systems in the West Eifel (Germany)

PubMed Central

Berberich, Gabriele; Schreiber, Ulrich

2013-01-01

Simple Summary In a 1.140 km² study area of the volcanic West Eifel, approx. 3,000 Red Wood Ant (RWA; Formica rufa-group) mounds had been identified and correlated with tectonically active gas-permeable faults, mostly strike-slip faults. Linear alignment of RWA mounds and soil gas anomalies distinctly indicate the course of these faults, while clusters of mounds indicate crosscut zones of fault systems, which can be correlated with voids caused by crustal block rotation. This demonstrates that RWA are bioindicators for identifying active fault systems and useful where information on the active regime is incomplete or the resolution by technical means is insufficient. Abstract In a 1.140 km² study area of the volcanic West Eifel, a comprehensive investigation established the correlation between red wood ant mound (RWA; Formica rufa-group) sites and active tectonic faults. The current stress field with a NW-SE-trending main stress direction opens pathways for geogenic gases and potential magmas following the same orientation. At the same time, Variscan and Mesozoic fault zones are reactivated. The results showed linear alignments and clusters of approx. 3,000 RWA mounds. While linear mound distribution correlate with strike-slip fault systems documented by quartz and ore veins and fault planes with slickensides, the clusters represent crosscut zones of dominant fault systems. Latter can be correlated with voids caused by crustal block rotation. Gas analyses from soil air, mineral springs and mofettes (CO2, Helium, Radon and H2S) reveal limiting concentrations for the spatial distribution of mounds and colonization. Striking is further the almost complete absence of RWA mounds in the core area of the Quaternary volcanic field. A possible cause can be found in occasionally occurring H2S in the fault systems, which is toxic at miniscule concentrations to the ants. Viewed overall, there is a strong relationship between RWA mounds and active tectonics in the West Eifel. PMID:26487413

Structural control on the CO2 release west of Mt. Epomeo resurgent block (Ischia, Italy)

NASA Astrophysics Data System (ADS)

de Vita, S.; Marotta, E.; Ventura, G.; Chiodini, G.

2003-04-01

Volcanism at Ischia started more than 150 ka B.P. and continued until the last eruption occurred in 1302 A.D. Ischia is dominated by the caldera forming eruption of Mt. Epomeo Green Tuff (55 ka), which was followed by block resurgence inside the caldera from 33 ka B.P. Resurgence influenced the volcanic activity determining the conditions for magma ascent mainly along the eastern edge of the resurgent block. The resurgent area has a poligonal shape resulting from reactivation of regional faults and by activation of faults related to volcanotectonism. The western sector is bordered by inward dipping, high angle strike-slip/reverse faults testifying a compressional stress regime in this area. These features are cut by late outward dipping normal faults due to gravitational stress. The activity of the volcanic system is testified by seismicity and thermal manifestations. Fumarolic activity concentrates along the faults that borders westward the Mt. Epomeo resurgent block, where the Green Tuff overlies fractured lavas. The structural data show that, outside the most active degassing zone, fractures show a NNW-SSE strike and dip toward Mt. Epomeo. These fractures delimit the northern sector of Mt. Epomeo and show strike and dip consistent with the inward dipping reverse faults. Inside the degassing area fractures show a NW-SE strike and dip outward Mt. Epomeo. These gravity-related faults cut the lavas where the hydrothermal circulation is active. The dip direction of the NW-SE striking fractures within the degassing zone is not consistent with that of the strike-slip/reverse faults (i.e. towards NE) but agrees well with that of the gravity-induced faults (dip direction towards SW). Inside the degassing zone, NW-SE striking faults with lengths not exceeding the hydrothermalized extension occur. This arrangement indicate that the syn-resurgence faults act as permeability barriers, whereas the youngest faults act as the main fluid pathway.

Deep heterogeneous structure of active faults in the Kinki region, southwest Japan: Inversion analysis of coda envelopes

NASA Astrophysics Data System (ADS)

Nishigami, K.

2006-12-01

It is essential to estimate the deep structure of active faults related to the earthquake rupture process as well as the crustal structure related to the propagation of seismic waves, in order to improve the accuracy of estimating strong ground motion caused by future large inland earthquakes. In the Kinki region, southwest Japan, there are several active fault zones near large cities such as Osaka and Kyoto, and the evaluation of realistic strong ground motion is an important subject. We have been carrying out the Special Project for Earthquake Disaster Mitigation in Urban Areas, in the Kinki region for these purposes. In this presentation we will show the result of estimating the fault structure model of the Biwako-seigan, Hanaore, and Arima- Takatsuki fault zones. We estimated a 3-D distribution of relative scattering coefficients in the Kinki region, also in the vicinity of each active fault zone, by inversion of coda envelopes from local earthquakes. We analyzed 758 seismograms from 52 events which occurred in 2003, recorded at 50 stations of Kyoto Univ., Hi- net, and JMA. The preliminary result shows that active fault zones can be imaged as higher scattering than the surroundings. Based on previous studies of scattering properties in the crust, we consider that the relatively weaker scattering (namely more homogeneous) part on the fault plane may act as an asperity during future large earthquakes, and also that the part with relatively stronger scattering (namely more heterogeneous part) may become an initiation point of rupture. We are also studying the detailed distribution of microearthquakes, b-values, and velocity anomalies along these active fault zones. Combining these results, we will construct a possible fault model for each of the active fault zones. This study is sponsored by the Special Project for Earthquake Disaster Mitigation in Urban Areas from the Ministry of Education, Culture, Sports, Science and Technology of Japan.

Tectonics earthquake distribution pattern analysis based focal mechanisms (Case study Sulawesi Island, 1993–2012)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ismullah M, Muh. Fawzy, E-mail: mallaniung@gmail.com; Lantu,; Aswad, Sabrianto

Indonesia is the meeting zone between three world main plates: Eurasian Plate, Pacific Plate, and Indo – Australia Plate. Therefore, Indonesia has a high seismicity degree. Sulawesi is one of whose high seismicity level. The earthquake centre lies in fault zone so the earthquake data gives tectonic visualization in a certain place. This research purpose is to identify Sulawesi tectonic model by using earthquake data from 1993 to 2012. Data used in this research is the earthquake data which consist of: the origin time, the epicenter coordinate, the depth, the magnitude and the fault parameter (strike, dip and slip). Themore » result of research shows that there are a lot of active structures as a reason of the earthquake in Sulawesi. The active structures are Walannae Fault, Lawanopo Fault, Matano Fault, Palu – Koro Fault, Batui Fault and Moluccas Sea Double Subduction. The focal mechanism also shows that Walannae Fault, Batui Fault and Moluccas Sea Double Subduction are kind of reverse fault. While Lawanopo Fault, Matano Fault and Palu – Koro Fault are kind of strike slip fault.« less

Response of deformation patterns to reorganization of the southern San Andreas fault system since ca. 1.5 Ma

NASA Astrophysics Data System (ADS)

Fattaruso, Laura A.; Cooke, Michele L.; Dorsey, Rebecca J.; Housen, Bernard A.

2016-12-01

Between 1.5 and 1.1 Ma, the southern San Andreas fault system underwent a major reorganization that included initiation of the San Jacinto fault zone and termination of slip on the extensional West Salton detachment fault. The southern San Andreas fault itself has also evolved since this time, with several shifts in activity among fault strands within San Gorgonio Pass. We use three-dimensional mechanical Boundary Element Method models to investigate the impact of these changes to the fault network on deformation patterns. A series of snapshot models of the succession of active fault geometries explore the role of fault interaction and tectonic loading in abandonment of the West Salton detachment fault, initiation of the San Jacinto fault zone, and shifts in activity of the San Andreas fault. Interpreted changes to uplift patterns are well matched by model results. These results support the idea that initiation and growth of the San Jacinto fault zone led to increased uplift rates in the San Gabriel Mountains and decreased uplift rates in the San Bernardino Mountains. Comparison of model results for vertical-axis rotation to data from paleomagnetic studies reveals a good match to local rotation patterns in the Mecca Hills and Borrego Badlands. We explore the mechanical efficiency at each step in the modeled fault evolution, and find an overall trend toward increased efficiency through time. Strain energy density patterns are used to identify regions of incipient faulting, and support the notion of north-to-south propagation of the San Jacinto fault during its initiation.

Active faulting in apparently stable peninsular India: Rift inversion and a Holocene-age great earthquake on the Tapti Fault

NASA Astrophysics Data System (ADS)

Copley, Alex; Mitra, Supriyo; Sloan, R. Alastair; Gaonkar, Sharad; Reynolds, Kirsty

2014-08-01

We present observations of active faulting within peninsular India, far from the surrounding plate boundaries. Offset alluvial fan surfaces indicate one or more magnitude 7.6-8.4 thrust-faulting earthquakes on the Tapti Fault (Maharashtra, western India) during the Holocene. The high ratio of fault displacement to length on the alluvial fan offsets implies high stress-drop faulting, as has been observed elsewhere in the peninsula. The along-strike extent of the fan offsets is similar to the thickness of the seismogenic layer, suggesting a roughly equidimensional fault rupture. The subsiding footwall of the fault is likely to have been responsible for altering the continental-scale drainage pattern in central India and creating the large west flowing catchment of the Tapti river. A preexisting sedimentary basin in the uplifting hanging wall implies that the Tapti Fault was active as a normal fault during the Mesozoic and has been reactivated as a thrust, highlighting the role of preexisting structures in determining the rheology and deformation of the lithosphere. The slip sense of faults and earthquakes in India suggests that deformation south of the Ganges foreland basin is driven by the compressive force transmitted between India and the Tibetan Plateau. The along-strike continuation of faulting to the east of the Holocene ruptures we have studied represents a significant seismic hazard in central India.

The Generation of Oceanic Lithosphere in an Embryonic Oceanic Crust : the Example of the Chenaillet Ophiolite in the Western Alps

NASA Astrophysics Data System (ADS)

Masini, E.; Manatschal, G.; Muntener, O.

2007-12-01

The Chenaillet Ophiolite exposed in the Franco-Italian Alps represents a well-preserved ocean-floor sequence that was only weakly affected by later Alpine convergence. Based on the similarity between rock types and structures reported from ultraslow spreading ridges and those observed in the Chenaillet Ophiolite, it may represent a field analogue for slow to ultraslow spreading ridges such as the Gakkel Ridge or the Southwest Indian Ridge. Mapping of the Chenaillet Ophiolite enabled to identify an oceanic detachment fault that extends over a surface of about 16 km2 capping exhumed mantle and gabbros onto which clastic sediments have been deposited. The footwall of the detachment is formed by mafic and ultramafic rocks. The mantle rocks are strongly serpentinized lherzolites and subordinate harzburgites and dunites. Microstructures reminiscent of impregnation, and cpx major and trace element chemistry indicate that spinel peridotite is (locally) replaced by plagioclase-bearing assemblages. Pyroxene thermometry on primary minerals indicates high temperatures of equilibration ( max 1200°C) for the mantle rocks. Gabbros range from troctolite and olivine-gabbros to Fe-Ti gabbros and show clear evidence of syn-magmatic deformation, partially obliterated by retrograde amphibolite and low-grade metamorphic conditions. In sections perpendicular to the detachment within the footwall, syn-tectonic gabbros and serpentinized peridotites grade over some tens of meters into cataclasites that are capped by fault gouges. Petro-structural investigations of the fault rocks reveal a syn-tectonic retrograde metamorphic evolution. Clasts of dolerite within the fault zone suggest that detachment faulting was accompanied by magmatic activity. Hydrothermal alteration is indicated by strong mineralogical and chemical modifications. Gabbro and serpentinized peridotite, together with serpentinite cataclasites occur as clasts in tectono-sedimentary breccias overlying directly the detachment fault. Across the whole Chenaillet Ophiolite, volcanic rocks directly overlie either the detachment fault or the sediments. In several places, N-S trending high-angle normal faults have been mapped. These faults truncate and displace the detachment fault leading to small domino-like structures. The basins, limited by these high-angle faults, are some hundreds to a few kilometres wide and few tens to some hundreds of meters deep. Because these high- angle faults are sealed locally by basalts and obliterated by volcanic structures, we interpret them as oceanic structures being active during the emplacement of the basalts. The alignment of porphyritic basaltic dykes parallel to, and their increasing abundance towards the high-angle faults suggest that they may have served as feeder channels for the overlying volcanic rocks. The complex poly-phase tectonic and magmatic processes observed in the Chenaillet Ophiolite are reminiscent of those reported from slow to ultraslow spreading ridges. The key result from our study is that mantle exhumation along detachment faults is followed by syn-magmatic normal faulting resulting in the emplacement of laterally variable, up to 300 meters thick massive lavas and pillow basalts covering the exhumed detachment fault. This implies that off-axis processes are more important as previously assumed and that large-scale detachment faults may be buried under massive volcanic sequences suggesting that detachment faulting is presumably more common than suggested by dredging or morpho-structural investigations of ultra- to slow- spreading oceanic crust.

Moment tensor inversion of recent local moderate sized Van Earthquakes: seismicity and active tectonics of the Van region : Eastern Turkey

NASA Astrophysics Data System (ADS)

Kalafat, D.; Suvarikli, M.; Ogutcu, Z.; Kekovali, K.; Ocal, M. F.; Gunes, Y.; Pinar, A.

2013-12-01

The study area of the present research, the Van Region is located at the norththern end of the collision zone between the Anatolia and Arabian plates. Therefore, the southeast border of the Anatolian plate collides with the Arabian plate along the Bitlis Suture Zone. This zone is formed by collision of Arabian and in large scale Eurasian plates at mid-Miocen age. This type of thrust generation as a result of compressional regime extends east-west. The largest recorded earthquakes have all taken place along Southern Turkey (e.g. Lice, 1971; Varto, 1966; Caldiran, 1976). On the 23th of October 2011, an earthquake shook the Van Lake, Eastern Turkey, following a seismic sequence of more than three months in an unprecedented episode for this region characterized by null or low seismicity. The October 23, 2011 Van-Ercis Earthquake (Mw=7.1) was the most devastating resulting in loss of life and destruction. In order to study the aftershocks' activity of this main event, we installed and kept a seismic network of 10 broad-band (BB) stations in the area for an interval of nearly fifteen months. We characterized the seismogenic structure of the zone by calculating a minimum 1-D local velocity model and obtaining precise hypocentre locations. We also calculated fault plane solutions for more than 200 moderate sized earthquakes based on first motion polarities and commonly Moment Tensor Inversion Methods. The seismogenic zone would be localized at aproximately 10 km depth. Generally, the distribution of the important moderate earthquakes and the aftershock distribution shows that the E-W and NE-SW oriented fault segments cause the earthquake activities. Aftershock events are located along the eastern border of Lake Van and mainly between 5 and 10 km depth and disposed in two alignments: a ~E-W-trending alignment that matches with the trace of the Van Trust fault Zone and a NE-trending which could correspond to an structure not previously seen. Selected focal mechanisms show a strong trust faulting which coincides with the nature of the Van fault. We were currently analysing an archive of over 5000 local events recorded by the KOERI seismic network of over 20 broadband stations between 2010 and 2013 in the whole Van Region. The Van Earthquake initiated and caused an increase in seismic activity of the region. Van Earthquake and its important aftershocks fault mechanism solutions show that the region is under compression and reverse faulting is a result of this regime which is effective on the active compressional tectonics of the region. This study was supported by Bogazici University Research Projects Commission under SRP/BAP project No. 6040.

Evaluation of Earthquake-Induced Effects on Neighbouring Faults and Volcanoes: Application to the 2016 Pedernales Earthquake

NASA Astrophysics Data System (ADS)

Bejar, M.; Alvarez Gomez, J. A.; Staller, A.; Luna, M. P.; Perez Lopez, R.; Monserrat, O.; Chunga, K.; Herrera, G.; Jordá, L.; Lima, A.; Martínez-Díaz, J. J.

2017-12-01

It has long been recognized that earthquakes change the stress in the upper crust around the fault rupture and can influence the short-term behaviour of neighbouring faults and volcanoes. Rapid estimates of these stress changes can provide the authorities managing the post-disaster situation with a useful tool to identify and monitor potential threads and to update the estimates of seismic and volcanic hazard in a region. Space geodesy is now routinely used following an earthquake to image the displacement of the ground and estimate the rupture geometry and the distribution of slip. Using the obtained source model, it is possible to evaluate the remaining moment deficit and to infer the stress changes on nearby faults and volcanoes produced by the earthquake, which can be used to identify which faults and volcanoes are brought closer to failure or activation. Although these procedures are commonly used today, the transference of these results to the authorities managing the post-disaster situation is not straightforward and thus its usefulness is reduced in practice. Here we propose a methodology to evaluate the potential influence of an earthquake on nearby faults and volcanoes and create easy-to-understand maps for decision-making support after an earthquake. We apply this methodology to the Mw 7.8, 2016 Ecuador earthquake. Using Sentinel-1 SAR and continuous GPS data, we measure the coseismic ground deformation and estimate the distribution of slip. Then we use this model to evaluate the moment deficit on the subduction interface and changes of stress on the surrounding faults and volcanoes. The results are compared with the seismic and volcanic events that have occurred after the earthquake. We discuss potential and limits of the methodology and the lessons learnt from discussion with local authorities.

Upward extension of the Nankai accretionary prism megasplay fault into slope basin strata. Insights from drilling at IODP Expedition 338 Site C0022

NASA Astrophysics Data System (ADS)

Fabbri, O.; Oohashi, K.; Kanagawa, K.; Yamaguchi, A.

2013-12-01

Megasplay faults have been recognized on seismic reflection profiles across several convergent margins in the world. Understanding the behavior of these faults during large to very large inter-plate earthquakes is a major challenge in assessing strong-motion and tsunami hazards at or near subduction zones. One of the goals of the IODP NanTroSEIZE project is to drill across and to obtain data from the megasplay fault crossing the Nankai accretionary prism off Kii peninsula (Kumano transect), SW Japan. This fault is considered to have been activated during the 1944 Tonankai earthquake (Baba et al., 2006 ; Moore et al., 2007). Drilling and coring during IODP Expedition 316 (Expedition 316 Scientists, 2009) showed that the megasplay fault at 300 mbsf at Site C0004 consists in a 60 m thick package of fractured and brecciated rocks. Combined analysis of 3D reflection data in the vicinity of Site C0004 and core data from sites C0004 and C0008 (Strasser et al., 2009 ; Kimura et al., 2011) suggest that the lower boundary of the megasplay fault ceased activity at about 1.55 Ma while its upper boundary has remained active since about 1.95 Ma and probably 1.24 Ma. In order to determine whether the megasplay fault upper boundary crosscuts slope sediments or is sealed by them, drilling at IODP Site C0022 was carried out during Expedition 338. Two 420 m deep holes were drilled: C0022A (LWD) and C0022B (coring). At Hole C0022A, LWD resistivity images show that the 85-105.5 mbsf interval is fractured and extends above and below a ca. 1 m thick interval characterized by a low resistivity value at 100-101 mbsf. Structures observed in cores from Hole C0022B confirm LWD data. While gently dipping elsewhere, bedding in the 73-146 mbsf interval is steep, commonly exceeding 30°. This bedding dip increase may be a consequence of fault activity (folding ?). Though the low-resistivity interval at 100-101 mbsf could not be sampled at Hole C0022B (no recovery between 95.5 and 99.5 mbsf), cores immediately from above this interval show three ca. 2 cm thick zones of claystone characterized by a marked planar fabric bearing faint striations raking at about 90°. Preliminary biostratigraphic dating in Hole C0022B indicate age reversals at 80.5, 137.5 and 145.5 mbsf, suggesting reverse offset bringing older strata over younger strata. Drilling at IODP Site C0022 confirms that a branch of the megasplay fault previously cored at Expedition 316 Site C0004 extends upwards and southeastwards. The core zone of this branch lies at about 100 mbsf and is about 1 m thick. The presence of weakly foliated claystone suggests aseismic motion immediately above the core zone. The lack of samples from the core zone prevents to determine whether motion was aseismic or not.

Driving Processes of Earthquake Swarms: Evidence from High Resolution Seismicity

NASA Astrophysics Data System (ADS)

Ellsworth, W. L.; Shelly, D. R.; Hill, D. P.; Hardebeck, J.; Hsieh, P. A.

2017-12-01

Earthquake swarms are transient increases in seismicity deviating from a typical mainshock-aftershock pattern. Swarms are most prevalent in volcanic and hydrothermal areas, yet also occur in other environments, such as extensional fault stepovers. Swarms provide a valuable opportunity to investigate source zone physics, including the causes of their swarm-like behavior. To gain insight into this behavior, we have used waveform-based methods to greatly enhance standard seismic catalogs. Depending on the application, we detect and precisely relocate 2-10x as many events as included in the initial catalog. Recently, we have added characterization of focal mechanisms (applied to a 2014 swarm in Long Valley Caldera, California), addressing a common shortcoming in microseismicity analyses (Shelly et al., JGR, 2016). In analysis of multiple swarms (both within and outside volcanic areas), several features stand out, including: (1) dramatic expansion of the active source region with time, (2) tendency for events to occur on the immediate fringe of prior activity, (3) overall upward migration, and (4) complex faulting structure. Some swarms also show an apparent mismatch between seismicity orientations (as defined by patterns in hypocentral locations) and slip orientations (as inferred from focal mechanisms). These features are largely distinct from those observed in mainshock-aftershock sequences. In combination, these swarm behaviors point to an important role for fluid pressure diffusion. Swarms may in fact be generated by a cascade of fluid pressure diffusion and stress transfer: in cases where faults are critically stressed, an increase in fluid pressure will trigger faulting. Faulting will in turn dramatically increase permeability in the faulted area, allowing rapid equilibration of fluid pressure to the fringe of the rupture zone. This process may perpetuate until fluid pressure perturbations drop and/or stresses become further from failure, such that any perturbation (fluid + stress transfer) is insufficient to generate further faulting. Numerical modeling supports this hypothesis - for example, the main features of the 2014 Long Valley swarm can be reproduced by a relatively simple model incorporating both stress transfer and rupture-aided fluid pressure diffusion (Hsieh et al., AGU FM, 2016).

The study of active tectonic based on hyperspectral remote sensing

NASA Astrophysics Data System (ADS)

Cui, J.; Zhang, S.; Zhang, J.; Shen, X.; Ding, R.; Xu, S.

2017-12-01

As of the latest technical methods, hyperspectral remote sensing technology has been widely used in each brach of the geosciences. However, it is still a blank for using the hyperspectral remote sensing to study the active structrure. Hyperspectral remote sensing, with high spectral resolution, continuous spectrum, continuous spatial data, low cost, etc, has great potentialities in the areas of stratum division and fault identification. Blind fault identification in plains and invisible fault discrimination in loess strata are the two hot problems in the current active fault research. Thus, the study of active fault based on the hyperspectral technology has great theoretical significance and practical value. Magnetic susceptibility (MS) records could reflect the rhythm alteration of the formation. Previous study shown that MS has correlation with spectral feature. In this study, the Emaokou section, located to the northwest of the town of Huairen, in Shanxi Province, has been chosen for invisible fault study. We collected data from the Emaokou section, including spectral data, hyperspectral image, MS data. MS models based on spectral features were established and applied to the UHD185 image for MS mapping. The results shown that MS map corresponded well to the loess sequences. It can recognize the stratum which can not identity by naked eyes. Invisible fault has been found in this section, which is useful for paleoearthquake analysis. The faults act as the conduit for migration of terrestrial gases, the fault zones, especially the structurally weak zones such as inrtersections or bends of fault, may has different material composition. We take Xiadian fault for study. Several samples cross-fault were collected and these samples were measured by ASD Field Spec 3 spectrometer. Spectral classification method has been used for spectral analysis, we found that the spectrum of the fault zone have four special spectral region(550-580nm, 600-700nm, 700-800nm and 800-900nm), which different with the spectrum of the none-fault zone. It could help us welly located the fault zone. The located result correspond well to the physical prospecting method result. The above study shown that Hypersepctral remote sensing technology provide a new method for active study.

Map showing recently active breaks along the San Andreas Fault between Pt. Delgada and Bolinas Bay, California

USGS Publications Warehouse

Brown, Robert D.; Wolfe, Edward W.

1970-01-01

This strip map is one of a series of maps showing recently active fault breaks along the San Andreas and other active faults in California. It is designed to inform persons who are concerned with land use near the fault of the location of those fault breaks that have moved recently. The lines on the map are lines of rupture and creep that can be identified by field evidence and that clearly affect the present surface of the land. Map users should keep in mind that these lines are intended primarily as guides to help locate the fault; the mapped lines are not necessarily shown with the precision demanded by some engineering or land utilization needs.

Modeling, Detection, and Disambiguation of Sensor Faults for Aerospace Applications

NASA Technical Reports Server (NTRS)

Balaban, Edward; Saxena, Abhinav; Bansal, Prasun; Goebel, Kai F.; Curran, Simon

2009-01-01

Sensor faults continue to be a major hurdle for systems health management to reach its full potential. At the same time, few recorded instances of sensor faults exist. It is equally difficult to seed particular sensor faults. Therefore, research is underway to better understand the different fault modes seen in sensors and to model the faults. The fault models can then be used in simulated sensor fault scenarios to ensure that algorithms can distinguish between sensor faults and system faults. The paper illustrates the work with data collected from an electro-mechanical actuator in an aerospace setting, equipped with temperature, vibration, current, and position sensors. The most common sensor faults, such as bias, drift, scaling, and dropout were simulated and injected into the experimental data, with the goal of making these simulations as realistic as feasible. A neural network based classifier was then created and tested on both experimental data and the more challenging randomized data sequences. Additional studies were also conducted to determine sensitivity of detection and disambiguation efficacy to severity of fault conditions.

Geometry and active tectonics of the Los Osos-Hosgri Fault Intersection in Estero Bay, CA: Reconciling seismicity patterns with near-surface geology

NASA Astrophysics Data System (ADS)

Watt, J. T.; Hardebeck, J.; Johnson, S. Y.; Kluesner, J.

2016-12-01

Characterizing active structures within structurally complex fault intersections is essential for unraveling the deformational history and for assessing the importance of fault intersections in regional earthquake hazard assessments. We employ an integrative, multi-scale geophysical approach to describe the 3D geometry and active tectonics of the offshore Los Osos fault (LOF) in Estero Bay, California. The shallow structure of the LOF, as imaged with multibeam and high-resolution seismic-reflection data, reveals a complex west-diverging zone of active faulting that bends into and joins the Hosgri fault. The down-dip geometry of the LOF as revealed by gravity, magnetic, and industry multi-channel seismic data, is vertical to steeply-dipping and varies along strike. As the LOF extends offshore, it is characterized by SW-side-up motion on a series of W-NW trending, steeply SW-dipping reverse faults. The LOF bends to the north ( 23°) as it approaches the Hosgri fault and dips steeply to the NE along a magnetic basement block. Inversion of earthquake focal mechanisms within Estero Bay yields maximum compressive stress axes that are near-horizontal and trend approximately N15E. This trend is consistent with dextral strike-slip faulting along NW-SE trending structures such as the Hosgri fault and northern LOF, and oblique dip-slip motion along the W-NW trending section of the LOF. Notably, NW-SE trending structures illuminated by seismicity in Estero Bay coincide with, but also appear to cross-cut, LOF structures imaged in the near-surface. We suggest this apparent disconnect reflects ongoing fault reorganization at a dynamic and inherently unstable fault intersection, in which the seismicity reflects active deformation at depth that is not clearly expressed in the near-surface geology. Direct connectivity between the Hosgri and Los Osos faults suggests a combined earthquake rupture is possible; however, the geometrical complexity along the offshore LOF may limit the extent of rupture.

Characterization of Seismogenic Faults of Central Japan by Geophysical Survey and Drilling

NASA Astrophysics Data System (ADS)

Ikeda, R.; Omura, K.; Matsuda, T.

2004-12-01

Integrated investigations on seismogenic faults by geophysical survey and drilling are indispensable to better understand deep structure and physical properties of a fault fracture zone. In central Japan, three large active faults, Neodani, Atotsugawa and Atera faults, exist and are remarkable for research because of the potentiality of a scale of magnitude 7 to 8 class earthquake and the different characteristics of the seismogenic activities in these faults. Each individual fault shows its own characteristic features, which may reflect different stages in an earthquake cycle. High seismicity is concentrated with a clear lineation on and around the Atotsugawa fault, which is recognized as aftershocks from the latest event of the 1858 Hida earthquake (M=7.0). On the other hand, extremely low seismicity is found around the Atera fault, of which some parts seemed to be dislocated by the 1586 Tensyo earthquake (M=7.9). As an example of the results of study at the Atera fault, we obtained a wide variety of fault structures, composed materials, states of crustal stress and strengths of the fault from the geophysical survey (resistivity and gravity) and in-situ borehole experiments. Our findings are as follows: (1) The fracture zone around the Atera fault shows a very wide and complex fracture structure, from approximately 1 km to 4 km wide. (2) The average slip rate was estimated to be 5.3 m /1000 yr by the distribution of basalt in the age of 1.5 Ma as determined by radioactive dating. We inferred that the Atera fault has been repeatedly active in recent geologic time; however, it is in a very weak state at present. (3) Stress magnitude decreases in the area closer to the center of the fracture zone. These are important results to evaluate fault activity. Recent in-situ downhole measurements and coring through active faults have provided us with new insights into the physical properties of fault zones. In the vicinity of the epicenter of the 1995 Hyogo-ken Nanbu (Kobe) earthquake, we have conducted an integrated study by using 1,000 m to 1,800 m deep drilling wells. In particular, the Nojima-Hirabayashi borehole was drilled to a depth of 1,838 m and directly intersected the Nojima fault. Three possible fault strands were detected at depths of 1,140 m, 1,313 m and 1,800 m. Major results obtained from this study include the following: (1) Shear stress around the fault zone is very small, and the orientation of the maximum horizontal compression is perpendicular to the surface trace of faults. (2) From the results of a heat flow study, the lower cut-off depth of the aftershocks was estimated to be roughly 300 _E#8249;C. (3) Cores were classified into several types of fault rocks, and an asymmetric distribution pattern of these fault rocks in the fracture zones was identified. (4) Country rock is characterized by very low permeability and high strength. (5) Resistivity structure can be explained by a model of a fault extending to greater depths but with low resistivity. The integrated study by geophysical survey, drilling and core analyses, downhole measurements and long-term monitoring directly within these fault zones, provide us with characteristic features and dynamics of active faults.

Current state of active-fault monitoring in Taiwan

NASA Astrophysics Data System (ADS)

Hou, C.; Lin, C.; Chen, Y.; Liu, H.; Chen, C.; Lin, Y.; Chen, C.

2008-12-01

The earthquake is one of the major hazard sources in Taiwan where an arc-continent collision is on-going. For the purpose of seismic hazard mitigation, to understand current situation of each already-known active fault is urgently needed. After the 1999 Chi-chi earthquake shocked Taiwan, the Central Geological Survey (CGS) of Taiwan aggressively promoted the tasks on studying the activities of active faults. One of them is the deployment of miscellaneous monitoring networks to cover all the target areas, where the earthquake occurrence potentials on active faults are eager to be answered. Up to the end of 2007, CGS has already deployed over 1000 GPS campaign sites, 44 GPS stations in continuous mode, and 42 leveling transects across the major active faults with a total ground distance of 974 km. The campaign sites and leveling tasks have to be measured once a year. The resulted crustal deformation will be relied on to derive the fault slip model. The time series analysis on continuous mode of GPS can further help understand the details of the fault behavior. In addition, 12 down-hole strain meters, five stations for liquid flux and geochemical proxies, and two for water table monitoring have been also installed to seek possible anomalies related to the earthquake activities. It may help discover reliable earthquake precursors.

Anatomy of an Active Seismic Source: the Interplay between Present-Day Seismic Activity and Inherited Fault Zone Architecture (Central Apennines, Italy)

NASA Astrophysics Data System (ADS)

Fondriest, M.; Demurtas, M.; Bistacchi, A.; Fabrizio, B.; Storti, F.; Valoroso, L.; Di Toro, G.

2017-12-01

The mechanics and seismogenic behaviour of fault zones are strongly influenced by their internal structure, in terms of both fault geometry and fault rock constitutive properties. In recent years high-resolution seismological techniques yielded new constraints on the geometry and velocity structure of seismogenic faults down to 10s meters length scales. This reduced the gap between geophysical imaging of active seismic sources and field observations of exhumed fault zones. Nevertheless fundamental questions such as the origin of geometrical and kinematic complexities associated to seismic faulting remain open. We addressed these topics by characterizing the internal structure of the Vado di Corno Fault Zone, an active seismogenic normal fault cutting carbonates in the Central Apennines of Italy and comparing it with the present-day seismicity of the area. The fault footwall block, which was exhumed from < 2 km depth, was mapped with high detail (< 1 m spatial resolution) for 2 km of exposure along strike, combining field structural data and photogrammetric surveys in a three dimensional structural model. Three main structural units separated by principal fault strands were recognized: (i) cataclastic unit (20-100 m thick), (ii) damage zone (≤ 300 m thick), (iii) breccia unit ( 20 thick). The cataclastic unit lines the master fault and represents the core of the normal fault zone. In-situ shattering together with evidence of extreme (possibly coseismic) shear strain localization (e.g., mirror-like faults with truncated clasts, ultrafine-grained sheared veins) was recognized. The breccia unit is an inherited thrust zone affected by pervasive veining and secondary dolomitization. It strikes subparallel to the active normal fault and is characterized by a non-cylindrical geometry with 10-100 m long frontal and lateral ramps. The cataclastic unit cuts through thrust flats within the breccia unit, whereas normal to oblique inversion occur on frontal and lateral ramps. A comparable structural setting was imaged South-West of the study area, during the 2009 L'Aquila seismic sequence. Here at 2 km depth, the master normal fault cross-cuts a 10 km long flat structure and clear lateral ramps are illuminated, suggesting the superposition of normal seismic faulting on inherited compressional structures.

Neotectonics and geomorphic evolution of the northwestern arm of the Yellowstone Tectonic Parabola: Controls on intra-cratonic extensional regimes, southwest Montana

USGS Publications Warehouse

Ruleman, Chester A.; Larsen, Mort; Stickney, Michael C.

2014-01-01

The catastrophic Hebgen Lake earthquake of 18 August 1959 (MW 7.3) led many geoscientists to develop new methods to better understand active tectonics in extensional tectonic regimes that address seismic hazards. The Madison Range fault system and adjacent Hebgen Lake–Red Canyon fault system provide an intermountain active tectonic analog for regional analyses of extensional crustal deformation. The Madison Range fault system comprises fault zones (~100 km in length) that have multiple salients and embayments marked by preexisting structures exposed in the footwall. Quaternary tectonic activity rates differ along the length of the fault system, with less displacement to the north. Within the Hebgen Lake basin, the 1959 earthquake is the latest slip event in the Hebgen Lake–Red Canyon fault system and southern Madison Range fault system. Geomorphic and paleoseismic investigations indicate previous faulting events on both fault systems. Surficial geologic mapping and historic seismicity support a coseismic structural linkage between the Madison Range and Hebgen Lake–Red Canyon fault systems. On this trip, we will look at Quaternary surface ruptures that characterize prehistoric earthquake magnitudes. The one-day field trip begins and ends in Bozeman, and includes an overview of the active tectonics within the Madison Valley and Hebgen Lake basin, southwestern Montana. We will also review geologic evidence, which includes new geologic maps and geomorphic analyses that demonstrate preexisting structural controls on surface rupture patterns along the Madison Range and Hebgen Lake–Red Canyon fault systems.

Active tectonics of the Binalud Mountains, a key puzzle segment to describe Quaternary deformations at the northeastern boundary of the Arabia-Eurasia collision

NASA Astrophysics Data System (ADS)

Shabanian, Esmaeil; Bellier, Olivier; Siame, Lionel L.; Abbassi, Mohammad R.; Leanni, Laetitia; Braucher, Régis; Farbod, Yassaman; Bourlès, Didier L.

2010-05-01

In northeast Iran, the Binalud Mountains accommodate part of active convergence between the Arabian and Eurasian plates. This fault-bounded mountain range has been considered a key region to describe Quaternary deformations at the northeastern boundary of the Arabia-Eurasia collision. But, the lack of knowledge on active faulting hampered evaluating the geological reliability of tectonic models describing the kinematics of deformation in northeast Iran. Morphotectonic investigations along both sides of the Binalud Mountains allowed us to characterize the structural and active faulting patterns along the Neyshabur and Mashhad fault systems on the southwest and northeast sides of the mountain range, respectively. We applied combined approaches of morphotectonic analyses based on satellite imageries (SPOT5 and Landsat ETM+), STRM and site-scale digital topographic data, and field surveys complemented with in situ-produced 10Be exposure dating to determine the kinematics and rate of active faulting. Three regional episodes of alluvial surface abandonments were dated at 5.3±1.1 kyr (Q1), 94±5 kyr (Q3), and 200±14 kyr (S3). The geomorphic reconstruction of both vertical and right-lateral fault offsets postdating these surface abandonment episodes yielded Quaternary fault slip rates on both sides of the Binalud Mountains. On the Neyshabur Fault System, thanks to geomorphic reconstructions of cumulative offsets recorded by Q3 fan surfaces, slip rates of 2.7±0.8 mm/yr and 2.4±0.2 mm/yr are estimated for right-lateral and reverse components of active faulting, respectively. Those indicate a total slip rate of 3.6±1.2 mm/yr for the late Quaternary deformation on the southwest flank of the Binalud Mountains. Reconstructing the cumulative right-lateral offset recorded by S3 surfaces, a middle-late Quaternary slip rate of 1.6±0.1 mm/yr is determined for the Mashhad Fault System. Altogether, our geomorphic observations reveal that, on both sides of the Binalud Mountains, the relative motion between central Iran and Eurasia is partly taken-up by dextral-reverse oblique-slip faulting along the Neyshabur and Mashhad fault systems. This faulting mechanism implies a long-term rate of ~4 mm/yr for the range-parallel strike-slip faulting, and an uplift rate of ~2.4 mm/yr due to the range-normal shortening during late Quaternary. Our data provide the first geological constraints on the rate of active faulting on both sides of the Binalud Mountains, and allow us to examine the geological reliability of preexisting tectonic models proposed to describe the kinematics of active deformation at the northeastern boundary of the Arabia-Eurasia collision. Our results favor the northward translation of central Iran with respect to Eurasia through strike-slip faulting localized along distinct crustal scale fault systems rather than systematic block rotations around vertical axes.

Hydrogeochemistry Characteristics and Daily Variation of Geothermal Water in the Moxi Fault,Southwest of China

NASA Astrophysics Data System (ADS)

Qi, Jihong; Xu, Mo; An, Chenjiao; Zhang, Yunhui; Zhang, Qiang

2017-04-01

The Xianshuihe Fault with frequent earthquakes activities is the regional deep fault in China. The Moxi Fault is the southern part of the Xianshuihe Fault, where the strong activities of geothermal water could bring abundant information of deep crust. In this article, some typical geothermal springs were collected along the Moxi fault from Kangding to Shimian. Using the the Na-K-Mg equilibrium diagram, it explains the state of water-rock equilibrium, and estimates the reservoir temperature basing appropriate geothermometers. Basing on the relationship between the enthalpy and chlorine concentration of geothermal water, it analyze the mixing progress of thermal water with shallow groundwater. Moreover, the responses of variation of geothermal water to the solid tides are considered to study the hydrothermal activities of this fault. The Guanding in Kangding are considered as the center of the geothermal system, and the hydrothermal activities decrease southward extending. Geothermal water maybe is heated by the deep heat source of the Himalayan granites, while the springs in the south area perform the mixture with thermal water in the sub-reservoir of the Permian crystalline limestone. It improves the research of hydrothermal activities in the Moxi Fault, meanwhile using the variation of geothermal water maybe become a important method to study the environment of deep earth in the future.

The Devils Mountain Fault zone: An active Cascadia upper plate zone of deformation, Pacific Northwest of North America

NASA Astrophysics Data System (ADS)

Barrie, J. Vaughn; Greene, H. Gary

2018-02-01

The Devils Mountain Fault Zone (DMFZ) extends east to west from Washington State to just south of Victoria, British Columbia, in the northern Strait of Juan de Fuca of Canada and the USA. Recently collected geophysical data were used to map this fault zone in detail, which show the main fault trace, and associated primary and secondary (conjugate) strands, and extensive northeast-southwest oriented folding that occurs within a 6 km wide deformation zone. The fault zone has been active in the Holocene as seen in the offset and disrupted upper Quaternary strata, seafloor displacement, and deformation within sediment cores taken close to the seafloor expression of the faults. Data suggest that the present DMFZ and the re-activated Leech River Fault may be part of the same fault system. Based on the length and previously estimated slip rates of the fault zone in Washington State, the DMFZ appears to have the potential of producing a strong earthquake, perhaps as large as magnitude 7.5 or greater, within 2 km of the city of Victoria.

Modelling of hydrothermal fluid flow and structural architecture in an extensional basin, Ngakuru Graben, Taupo Rift, New Zealand

NASA Astrophysics Data System (ADS)

Kissling, W. M.; Villamor, P.; Ellis, S. M.; Rae, A.

2018-05-01

Present-day geothermal activity on the margins of the Ngakuru graben and evidence of fossil hydrothermal activity in the central graben suggest that a graben-wide system of permeable intersecting faults acts as the principal conduit for fluid flow to the surface. We have developed numerical models of fluid and heat flow in a regional-scale 2-D cross-section of the Ngakuru Graben. The models incorporate simplified representations of two 'end-member' fault architectures (one symmetric at depth, the other highly asymmetric) which are consistent with the surface locations and dips of the Ngakuru graben faults. The models are used to explore controls on buoyancy-driven convective fluid flow which could explain the differences between the past and present hydrothermal systems associated with these faults. The models show that the surface flows from the faults are strongly controlled by the fault permeability, the fault system architecture and the location of the heat source with respect to the faults in the graben. In particular, fault intersections at depth allow exchange of fluid between faults, and the location of the heat source on the footwall of normal faults can facilitate upflow along those faults. These controls give rise to two distinct fluid flow regimes in the fault network. The first, a regular flow regime, is characterised by a nearly unchanging pattern of fluid flow vectors within the fault network as the fault permeability evolves. In the second, complex flow regime, the surface flows depend strongly on fault permeability, and can fluctuate in an erratic manner. The direction of flow within faults can reverse in both regimes as fault permeability changes. Both flow regimes provide insights into the differences between the present-day and fossil geothermal systems in the Ngakuru graben. Hydrothermal upflow along the Paeroa fault seems to have occurred, possibly continuously, for tens of thousands of years, while upflow in other faults in the graben has switched on and off during the same period. An asymmetric graben architecture with the Paeroa being the major boundary fault will facilitate the predominant upflow along this fault. Upflow on the axial faults is more difficult to explain with this modelling. It occurs most easily with an asymmetric graben architecture and heat sources close to the graben axis (which could be associated with remnant heat from recent eruptions from Okataina Volcanic Centre). Temporal changes in upflow can also be associated with acceleration and deceleration of fault activity if this is considered a proxy for fault permeability. Other explanations for temporal variations in hydrothermal activity not explored here are different permeability on different faults, and different permeability along fault strike.

Fault tectonics and earthquake hazards in parts of southern California. [penninsular ranges, Garlock fault, Salton Trough area, and western Mojave Desert

NASA Technical Reports Server (NTRS)

Merifield, P. M. (Principal Investigator); Lamar, D. L.; Gazley, C., Jr.; Lamar, J. V.; Stratton, R. H.

1976-01-01

The author has identified the following significant results. Four previously unknown faults were discovered in basement terrane of the Peninsular Ranges. These have been named the San Ysidro Creek fault, Thing Valley fault, Canyon City fault, and Warren Canyon fault. In addition fault gouge and breccia were recognized along the San Diego River fault. Study of features on Skylab imagery and review of geologic and seismic data suggest that the risk of a damaging earthquake is greater along the northwestern portion of the Elsinore fault than along the southeastern portion. Physiographic indicators of active faulting along the Garlock fault identifiable in Skylab imagery include scarps, linear ridges, shutter ridges, faceted ridges, linear valleys, undrained depressions and offset drainage. The following previously unrecognized fault segments are postulated for the Salton Trough Area: (1) An extension of a previously known fault in the San Andreas fault set located southeast of the Salton Sea; (2) An extension of the active San Jacinto fault zone along a tonal change in cultivated fields across Mexicali Valley ( the tonal change may represent different soil conditions along opposite sides of a fault). For the Skylab and LANDSAT images studied, pseudocolor transformations offer no advantages over the original images in the recognition of faults in Skylab and LANDSAT images. Alluvial deposits of different ages, a marble unit and iron oxide gossans of the Mojave Mining District are more readily differentiated on images prepared from ratios of individual bands of the S-192 multispectral scanner data. The San Andreas fault was also made more distinct in the 8/2 and 9/2 band ratios by enhancement of vegetation differences on opposite sides of the fault. Preliminary analysis indicates a significant earth resources potential for the discrimination of soil and rock types, including mineral alteration zones. This application should be actively pursued.

Temporal evolution of fault systems in the Upper Jurassic of the Central German Molasse Basin: case study Unterhaching

NASA Astrophysics Data System (ADS)

Budach, Ingmar; Moeck, Inga; Lüschen, Ewald; Wolfgramm, Markus

2018-03-01

The structural evolution of faults in foreland basins is linked to a complex basin history ranging from extension to contraction and inversion tectonics. Faults in the Upper Jurassic of the German Molasse Basin, a Cenozoic Alpine foreland basin, play a significant role for geothermal exploration and are therefore imaged, interpreted and studied by 3D seismic reflection data. Beyond this applied aspect, the analysis of these seismic data help to better understand the temporal evolution of faults and respective stress fields. In 2009, a 27 km2 3D seismic reflection survey was conducted around the Unterhaching Gt 2 well, south of Munich. The main focus of this study is an in-depth analysis of a prominent v-shaped fault block structure located at the center of the 3D seismic survey. Two methods were used to study the periodic fault activity and its relative age of the detected faults: (1) horizon flattening and (2) analysis of incremental fault throws. Slip and dilation tendency analyses were conducted afterwards to determine the stresses resolved on the faults in the current stress field. Two possible kinematic models explain the structural evolution: One model assumes a left-lateral strike slip fault in a transpressional regime resulting in a positive flower structure. The other model incorporates crossing conjugate normal faults within a transtensional regime. The interpreted successive fault formation prefers the latter model. The episodic fault activity may enhance fault zone permeability hence reservoir productivity implying that the analysis of periodically active faults represents an important part in successfully targeting geothermal wells.

Shallow seismic imaging of folds above the Puente Hills blind-thrust fault, Los Angeles, California

USGS Publications Warehouse

Pratt, T.L.; Shaw, J.H.; Dolan, J.F.; Christofferson, S.A.; Williams, R.A.; Odum, J.K.; Plesch, A.

2002-01-01

High-resolution seismic reflection profiles image discrete folds in the shallow subsurface (<600 m) above two segments of the Puente Hills blind-thrust fault system, Los Angeles basin, California. The profiles demonstrate late Quaternary activity at the fault tip, precisely locate the axial surfaces of folds within the upper 100 m, and constrain the geometry and kinematics of recent folding. The Santa Fe Springs segment of the Puente Hills fault zone shows an upward-narrowing kink band with an active anticlinal axial surface, consistent with fault-bend folding above an active thrust ramp. The Coyote Hills segment shows an active synclinal axial surface that coincides with the base of a 9-m-high scarp, consistent with tip-line folding or the presence of a backthrust. The seismic profiles pinpoint targets for future geologic work to constrain slip rates and ages of past events on this important fault system.

Identification and interpretation of tectonic features from Skylab imagery. [California to Arizona

NASA Technical Reports Server (NTRS)

Abdel-Gawad, M. (Principal Investigator)

1974-01-01

The author has identified the following significant results. S190-B imagery confirmed previous conclusions from S190-A that the Garlock fault does not extend eastward beyond its known termination near the southern end of Death Valley. In the Avawatz Mountains, California, two faults related to the Garlock fault zone (Mule Spring fault and Leach Spring fault) show evidence of recent activity. There is evidence that faulting related to Death Valley fault zone extends southeastward across the Old Dad Mountains. There, the Old Dad fault shows evidence of recent activity. A significant fault lineament has been identified from McCullough Range, California southeastward to Eagle Tail Mountains in southwestern Arizona. The lineament appears to control tertiary and possible cretaceous intrusives. Considerable right lateral shear is suspected to have taken place along parts of this lineament.

Late Quaternary Faulting along the San Juan de los Planes Fault Zone, Baja California Sur, Mexico

NASA Astrophysics Data System (ADS)

Busch, M. M.; Coyan, J. A.; Arrowsmith, J.; Maloney, S. J.; Gutierrez, G.; Umhoefer, P. J.

2007-12-01

As a result of continued distributed deformation in the Gulf Extensional Province along an oblique-divergent plate margin, active normal faulting is well manifest in southeastern Baja California. By characterizing normal-fault related deformation along the San Juan de los Planes fault zone (SJPFZ) southwest of La Paz, Baja California Sur we contribute to understanding the patterns and rates of faulting along the southwest gulf-margin fault system. The geometry, history, and rate of faulting provide constraints on the relative significance of gulf-margin deformation as compared to axial system deformation. The SJPFZ is a major north-trending structure in the southern Baja margin along which we focused our field efforts. These investigations included: a detailed strip map of the active fault zone, including delineation of active scarp traces and geomorphic surfaces on the hanging wall and footwall; fault scarp profiles; analysis of bedrock structures to better understand how the pattern and rate of strain varied during the development of this fault zone; and a gravity survey across the San Juan de los Planes basin to determine basin geometry and fault behavior. The map covers a N-S swath from the Gulf of California in the north to San Antonio in the south, an area ~45km long and ~1-4km wide. Bedrock along the SJPFZ varies from Cretaceous Las Cruces Granite in the north to Cretaceous Buena Mujer Tonalite in the south and is scarred by shear zones and brittle faults. The active scarp-forming fault juxtaposes bedrock in the footwall against Late Quaternary sandstone-conglomerate. This ~20m wide zone is highly fractured bedrock infused with carbonate. The northern ~12km of the SJPFZ, trending 200°, preserves discontinuous scarps 1-2km long and 1-3m high in Quaternary units. The scarps are separated by stretches of bedrock embayed by hundreds of meters-wide tongues of Quaternary sandstone-conglomerate, implying low Quaternary slip rate. Further south, ~2 km north of the Los Planes highway, the fault steps to the right 2km with no overlap. The fault is inactive until ~3km south of the Los Planes highway where scarp heights in the Quaternary sediments rise to ~3-11m for ~11km with an average trend of 160°, implying increasing slip rate. The fault then steps left 2km with no overlap, trending 145°. Scarp heights range from 3-6m in the step. The southernmost 9km of the fault zone, trending 200°, is marked by discontinuous scarps and embayed bedrock, reflecting diminished fault activity. The footwall landscape in this area is characterized by a broad, gently-sloping, low-relief pediment surface with thin Quaternary cover, disrupted by inselberg-like hills. The young scarp-forming fault appears to have reactivated older faults to rupture this pediment, reflecting the episodic nature of slip along this fault zone. Preliminary OSL ages of the youngest faulted deposit imply a Late Pleistocene-Holocene slip rate of 0.1-1mm/yr. The SJPFZ is thus characterized by reactivation of pre-existing faults to rupture a pre-existing low relief erosional landscape. Whereas the entire region might have experienced the quiescent period that allowed for development of the low- relief, stable surface along the SJPFZ, we speculate that while the SJPFZ was dormant, other faults within the gulf-margin system were actively accommodating strain.

Recently active traces of the Bartlett Springs Fault, California: a digital database

USGS Publications Warehouse

Lienkaemper, James J.

2010-01-01

The purpose of this map is to show the location of and evidence for recent movement on active fault traces within the Bartlett Springs Fault Zone, California. The location and recency of the mapped traces is primarily based on geomorphic expression of the fault as interpreted from large-scale aerial photography. In a few places, evidence of fault creep and offset Holocene strata in trenches and natural exposures have confirmed the activity of some of these traces. This publication is formatted both as a digital database for use within a geographic information system (GIS) and for broader public access as map images that may be browsed on-line or download a summary map. The report text describes the types of scientific observations used to make the map, gives references pertaining to the fault and the evidence of faulting, and provides guidance for use of and limitations of the map.

Character and Implications of a Newly Identified Creeping Strand of the San Andreas fault NE of Salton Sea, Southern California

NASA Astrophysics Data System (ADS)

Janecke, S. U.; Markowski, D.

2015-12-01

The overdue earthquake on the Coachella section, San Andreas fault (SAF), the model ShakeOut earthquake, and the conflict between cross-fault models involving the Extra fault array and mapped shortening in the Durmid Hill area motivate new analyses at the southern SAF tip. Geologic mapping, LiDAR, seismic reflection, magnetic and gravity datasets, and aerial photography confirm the existence of the East Shoreline strand (ESS) of the SAF southwest of the main trace of the SAF. We mapped the 15 km long ESS, in a band northeast side of the Salton Sea. Other data suggest that the ESS continues N to the latitude of the Mecca Hills, and is >35 km long. The ESS cuts and folds upper Holocene beds and appears to creep, based on discovery of large NW-striking cracks in modern beach deposits. The two traces of the SAF are parallel and ~0.5 to ~2.5 km apart. Groups of east, SE, and ENE-striking strike-slip cross-faults connect the master dextral faults of the SAF. There are few sinistral-normal faults that could be part of the Extra fault array. The 1-km wide ESS contains short, discontinuous traces of NW-striking dextral-oblique faults. These en-echelon faults bound steeply dipping Pleistocene beds, cut out section, parallel tight NW-trending folds, and produced growth folds. Beds commonly dip toward the ESS on both sides, in accord with persistent NE-SW shortening across the ESS. The dispersed fault-fold structural style of the ESS is due to decollements in faulted mud-rich Pliocene to Holocene sediment and ramps and flats along the strike-slip faults. A sheared ladder-like geometric model of the two master dextral strands of the SAF and their intervening cross-faults, best explains the field relationships and geophysical datasets. Contraction across >40 km2 of the southernmost SAF zone in the Durmid Hills suggest that interaction of active structures in the SAF zone may inhibit the nucleation of large earthquakes in this region. The ESS may cross the northern Coachella Valley to join the blind Palm Spring dextral fault- a source of microearthquakes and differential subsidence. The ESS may also continue north parallel to the margin of the Salton Trough or have both a NW and NE branch. The risk of a future large earthquake directly beneath the greater Palm Springs metropolitan area may be larger if the first or last options are correct.

Developing seismogenic source models based on geologic fault data

USGS Publications Warehouse

Haller, Kathleen M.; Basili, Roberto

2011-01-01

Calculating seismic hazard usually requires input that includes seismicity associated with known faults, historical earthquake catalogs, geodesy, and models of ground shaking. This paper will address the input generally derived from geologic studies that augment the short historical catalog to predict ground shaking at time scales of tens, hundreds, or thousands of years (e.g., SSHAC 1997). A seismogenic source model, terminology we adopt here for a fault source model, includes explicit three-dimensional faults deemed capable of generating ground motions of engineering significance within a specified time frame of interest. In tectonically active regions of the world, such as near plate boundaries, multiple seismic cycles span a few hundred to a few thousand years. In contrast, in less active regions hundreds of kilometers from the nearest plate boundary, seismic cycles generally are thousands to tens of thousands of years long. Therefore, one should include sources having both longer recurrence intervals and possibly older times of most recent rupture in less active regions of the world rather than restricting the model to include only Holocene faults (i.e., those with evidence of large-magnitude earthquakes in the past 11,500 years) as is the practice in tectonically active regions with high deformation rates. During the past 15 years, our institutions independently developed databases to characterize seismogenic sources based on geologic data at a national scale. Our goal here is to compare the content of these two publicly available seismogenic source models compiled for the primary purpose of supporting seismic hazard calculations by the Istituto Nazionale di Geofisica e Vulcanologia (INGV) and the U.S. Geological Survey (USGS); hereinafter we refer to the two seismogenic source models as INGV and USGS, respectively. This comparison is timely because new initiatives are emerging to characterize seismogenic sources at the continental scale (e.g., SHARE in the Euro-Mediterranean, http://www.share-eu.org/; EMME in the Middle East, http://www.emme-gem.org/) and global scale (e.g., GEM, http://www.globalquakemodel.org/; Anonymous 2008). To some extent, each of these efforts is still trying to resolve the level of optimal detail required for this type of compilation. The comparison we provide defines a common standard for consideration by the international community for future regional and global seismogenic source models by identifying the necessary parameters that capture the essence of geological fault data in order to characterize seismogenic sources. In addition, we inform potential users of differences in our usage of common geological/seismological terms to avoid inappropriate use of the data in our models and provide guidance to convert the data from one model to the other (for detailed instructions, see the electronic supplement to this article). Applying our recommendations will permit probabilistic seismic hazard assessment codes to run seamlessly using either seismogenic source input. The USGS and INGV database schema compare well at a first-level inspection. Both databases contain a set of fields representing generalized fault three-dimensional geometry and additional fields that capture the essence of past earthquake occurrences. Nevertheless, there are important differences. When we further analyze supposedly comparable fields, many are defined differently. These differences would cause anomalous results in hazard prediction if one assumes the values are similarly defined. The data, however, can be made fully compatible using simple transformations.

Multifaulting in a tectonic syntaxis revealed by InSAR: The case of the Ziarat earthquake sequence (Pakistan)

NASA Astrophysics Data System (ADS)

Pinel-Puysségur, B.; Grandin, R.; Bollinger, L.; Baudry, C.

2014-07-01

On 28-29 October 2008, within 12 h, two similar Mw = 6.4 strike-slip earthquakes struck Baluchistan (Pakistan), as part of a complex seismic sequence. Interferometric Synthetic Aperture Radar (InSAR) data reveal that the peak of surface displacement is near the Ziarat anticline, a large active fold affected by Quaternary strike-slip faulting. All coseismic interferograms integrate the deformation due to both earthquakes. As their causative faults ruptured close to each other, the individual signals cannot be separated. According to their focal mechanisms, each earthquake may have activated a NE-SW sinistral or a NW-SE dextral fault segment, which leads to four possible scenarios of fault orientations. A nonlinear inversion of the InSAR data set allows rejecting two scenarios. The best slip distributions on the two fault segments for the two remaining scenarios are determined by linear inversion. Stress-change modeling favors a scenario involving two abutting conjugate strike-slip faults. Two other fault segments accommodated left-lateral strike slip during the seismic sequence. The activated fault system includes multiple fault segments with different orientations and little surface expression. This may highlight, at a smaller scale, the distributed, possibly transient character of deformation within a broader right-lateral shear zone. It suggests that the activated faults delineate a small tectonic block extruding and subtly rotating within the shear zone. It occurs in the vicinity of the local tectonic syntaxis where orogenic structures sharply turn around a vertical axis. These mechanisms could participate in the long-term migration of active tectonic structures within this kinematically unstable tectonic syntaxis.

Seismicity and Tectonics of the West Kaibab Fault Zone, AZ

NASA Astrophysics Data System (ADS)

Wilgus, J. T.; Brumbaugh, D. S.

2014-12-01

The West Kaibab Fault Zone (WKFZ) is the westernmost bounding structure of the Kaibab Plateau of northern Arizona. The WKFZ is a branching complex of high angle, normal faults downthrown to the west. There are three main faults within the WKFZ, the Big Springs fault with a maximum of 165 m offset, the Muav fault with 350 m of displacement, and the North Road fault having a maximum throw of approximately 90 m. Mapping of geologically recent surface deposits at or crossing the fault contacts indicates that the faults are likely Quaternary with the most recent offsets occurring <1.6 Ma. Slip rates are estimated to be less than 0.2 mm/yr. No historic fault slip has been documented. The WKFZ is one of the most seismically active areas in Arizona and lies within the Northern Arizona Seismic Belt (NASB), which stretches across northern Arizona trending NW-SE. The data set for this study includes 156 well documented events with the largest being a M5.75 in 1959 and including a swarm of seven earthquakes in 2012. The seismic data set (1934-2014) reveals that seismic activity clusters in two regions within the study area, the Fredonia cluster located in the NW corner of the study area and the Kaibab cluster located in the south central portion of the study area. The fault plane solutions to date indicate NE-SW to EW extension is occurring in the study area. Source relationships between earthquakes and faults within the WKFZ have not previously been studied in detail. The goal of this study is to use the seismic data set, the available data on faults, and the regional physiography to search for source relationships for the seismicity. Analysis includes source parameters of the earthquake data (location, depth, and fault plane solutions), and comparison of this output to the known faults and areal physiographic framework to indicate any active faults of the WKFZ, or suggested active unmapped faults. This research contributes to a better understanding of the present nature of the WKFZ and the NASB as well.

Subsurface Resistivity Structures in and Around Strike-Slip Faults - Electromagnetic Surveys and Drillings Across Active Faults in Central Japan -

NASA Astrophysics Data System (ADS)

Omura, K.; Ikeda, R.; Iio, Y.; Matsuda, T.

2005-12-01

Electrical resistivity is important property to investigate the structure of active faults. Pore fluid affect seriously the electrical properties of rocks, subsurface electrical resistivity can be an indicator of the existence of fluid and distribution of pores. Fracture zone of fault is expected to have low resistivity due to high porosity and small gain size. Especially, strike-slip type fault has nearly vertical fracture zone and the fracture zone would be detected by an electrical survey across the fault. We performed electromagnetic survey across the strike-slip active faults in central Japan. At the same faults, we also drilled borehole into the fault and did downhole logging in the borehole. We applied MT or CSAMT methods onto 5 faults: Nojima fault which appeared on the surface by the 1995 Great Kobe earthquake (M=7.2), western Nagano Ohtaki area(1984 Nagano-ken seibu earthquake (M=6.8), the fault did not appeared on the surface), Neodani fault which appeared by the 1891 Nobi earthquake (M=8.0), Atera fault which seemed to be dislocated by the 1586 Tensyo earthquake (M=7.9), Gofukuji fault that is considered to have activated about 1200 years ago. The sampling frequencies of electrical and magnetic field were 2 - 1024Hz (10 frequencies) for CSAMT survey and 0.00055 - 384Hz (40 frequencies) for MT survey. The electromagnetic data were processed by standard method and inverted to 2-D resistivity structure along transects of the faults. Results of the survey were compared with downhole electrical logging data and observational descriptions of drilled cores. Fault plane of each fault were recognized as low resistivity region or boundary between relatively low and high resistivity region, except for Gofukuji fault. As for Gofukuji fault, fault was located in relatively high resistivity region. During very long elapsed time from the last earthquake, the properties of fracture zone of Gofukuji fault might changed from low resistivity properties as observed for other faults. Downhole electrical logging data were consistent to values of resistivity estimated by electromagnetic survey for each fault. The existence of relatively low and high resistivity regions in 2-D structure from electromagnetic survey was observed again by downhole logging at the correspondent portion in the borehole. Cores recovered from depthes where the electrical logging showed low resistivity were hardly fractured and altered from host rock which showed high resistivity. Results of electromagnetic survey, downhole electrical logging and observation of drilled cores were consistent to each other. In present case, electromagnetic survey is useful to explore the properties of fault fracture zone. In the further investigations, it is important to explore relationships among features of resistivity structure and geological and geophysical situations of the faults.

Do mesoscale faults near the tip of an active strike-slip fault indicate regional or local stress?

NASA Astrophysics Data System (ADS)

Yamaji, Atsushi

2017-04-01

Fault-slip analysis is used in Japan after the Great Tohoku Earthquake (2011) to judge the stability of fractures in the foundations of nuclear power plants. In case a fault-slip datum from a fracture surface is explained by the present stress condition, the fracture is thought to have a risk to be activated as a fault. So, it is important to understand the relative significance of regional and local stresses. To answer the question whether mesoscale faults indicate regional or local stress, fault-slip data were collected from the walls of a trenching site of the Nojima Fault in central Japan—an active, dextral, strike-slip fault. The fault gave rise to the 1995 Kobe earthquake, which killed more than 6000 people. The trench was placed near the fault tip, which produced compressional and extensional local stress conditions on the sides of the fault near the tip. A segment of the fault, which ruptured the surface in 1995, bounded Cretaceous granite and latest Pliocene sediments in the trench. As a result, the stress inversion of the data from the mesoscale faults observed in the trench showed both the local stresses. The present WNW-ESE regional compression was found from the compressive side, but was not in the extensional side, probably because local extension surpassed the regional compression. Instead, the regional N-S compression of the Early Pleistocene was found from the extensional side. From this project, we got the lesson that fault-slip analysis reveals regional and local stresses, and that local stress sometimes masks regional one. This work was supported by a science project of "Drilling into Fault Damage Zone" (awarded to A. Lin) of the Secretariat of Nuclear Regulation Authority (Japan).

Study geomorphology, past and present, linear trench, tectonics relationship between Pyrenees and Alps

NASA Technical Reports Server (NTRS)

Guillemot, J. (Principal Investigator)

1974-01-01

The author has identified the following significant results. ERTS-1 images obviously show up some large linear features trending N 80 E or N 30 E common to both Alps and Pyrenees. One of them, the Ligurian Fault, had been previously forecast by Laubscher in an interpretation of the Alps by the plate tectonic theory, but it extends westward farthest from the Alps, cutting the Pyrenees axis. These lineaments have been interpreted as reflections of deep seated wrench faults in the surficial part of the sedimentary series. A large set of such lineaments is perceptible in western Europe, such as the Guadalquivir Fault in southern Spain, Ligurian Fault, Insubrian Fault, Northern-Jura Fault, Metz Fault. Perhaps these may be interpreted as transform faults of the mid-Atlantic ridge or of a paleo-rift seated in the Rhine-Rhone graben.

Mantle fault zone beneath Kilauea Volcano, Hawaii.

PubMed

Wolfe, Cecily J; Okubo, Paul G; Shearer, Peter M

2003-04-18

Relocations and focal mechanism analyses of deep earthquakes (>/=13 kilometers) at Kilauea volcano demonstrate that seismicity is focused on an active fault zone at 30-kilometer depth, with seaward slip on a low-angle plane, and other smaller, distinct fault zones. The earthquakes we have analyzed predominantly reflect tectonic faulting in the brittle lithosphere rather than magma movement associated with volcanic activity. The tectonic earthquakes may be induced on preexisting faults by stresses of magmatic origin, although background stresses from volcano loading and lithospheric flexure may also contribute.

Mantle fault zone beneath Kilauea Volcano, Hawaii

USGS Publications Warehouse

Wolfe, C.J.; Okubo, P.G.; Shearer, P.M.

2003-01-01

Relocations and focal mechanism analyses of deep earthquakes (???13 kilometers) at Kilauea volcano demonstrate that seismicity is focused on an active fault zone at 30-kilometer depth, with seaward slip on a low-angle plane, and other smaller, distinct fault zones. The earthquakes we have analyzed predominantly reflect tectonic faulting in the brittle lithosphere rather than magma movement associated with volcanic activity. The tectonic earthquakes may be induced on preexisting faults by stresses of magmatic origin, although background stresses from volcano loading and lithospheric flexure may also contribute.

Frictional and hydraulic behaviour of carbonate fault gouge during fault reactivation - An experimental study

NASA Astrophysics Data System (ADS)

Delle Piane, Claudio; Giwelli, Ausama; Clennell, M. Ben; Esteban, Lionel; Nogueira Kiewiet, Melissa Cristina D.; Kiewiet, Leigh; Kager, Shane; Raimon, John

2016-10-01

We present a novel experimental approach devised to test the hydro-mechanical behaviour of different structural elements of carbonate fault rocks during experimental re-activation. Experimentally faulted core plugs were subject to triaxial tests under water saturated conditions simulating depletion processes in reservoirs. Different fault zone structural elements were created by shearing initially intact travertine blocks (nominal size: 240 × 110 × 150 mm) to a maximum displacement of 20 and 120 mm under different normal stresses. Meso-and microstructural features of these sample and the thickness to displacement ratio characteristics of their deformation zones allowed to classify them as experimentally created damage zones (displacement of 20 mm) and fault cores (displacement of 120 mm). Following direct shear testing, cylindrical plugs with diameter of 38 mm were drilled across the slip surface to be re-activated in a conventional triaxial configuration monitoring the permeability and frictional behaviour of the samples as a function of applied stress. All re-activation experiments on faulted plugs showed consistent frictional response consisting of an initial fast hardening followed by apparent yield up to a friction coefficient of approximately 0.6 attained at around 2 mm of displacement. Permeability in the re-activation experiments shows exponential decay with increasing mean effective stress. The rate of permeability decline with mean effective stress is higher in the fault core plugs than in the simulated damage zone ones. It can be concluded that the presence of gouge in un-cemented carbonate faults results in their sealing character and that leakage cannot be achieved by renewed movement on the fault plane alone, at least not within the range of slip measureable with our apparatus (i.e. approximately 7 mm of cumulative displacement). Additionally, it is shown that under sub seismic slip rates re-activated carbonate faults remain strong and no frictional weakening was observed during re-activation.

Role of the offshore Pedro Banks left-lateral strike-slip fault zone in the plate tectonic evolution of the northern Caribbean

NASA Astrophysics Data System (ADS)

Ott, B.; Mann, P.; Saunders, M.

2013-12-01

Previous workers, mainly mapping onland active faults on Caribbean islands, defined the northern Caribbean plate boundary zone as a 200-km-wide bounded by two active and parallel strike-slip faults: the Oriente fault along the northern edge of the Cayman trough with a GPS rate of 14 mm/yr, and and the Enriquillo-Plaintain Garden fault zone (EPGFZ) with a rate of 5-7 mm/yr. In this study we use 5,000 km of industry and academic data from the Nicaraguan Rise south and southwest of the EPGFZ in the maritime areas of Jamaica, Honduras, and Colombia to define an offshore, 700-km-long, active, left-lateral strike-slip fault in what has previously been considered the stable interior of the Caribbean plate as determined from plate-wide GPS studies. The fault was named by previous workers as the Pedro Banks fault zone because a 100-km-long segment of the fault forms an escarpment along the Pedro carbonate bank of the Nicaraguan Rise. Two fault segments of the PBFZ are defined: the 400-km-long eastern segment that exhibits large negative flower structures 10-50 km in width, with faults segments rupturing the sea floor as defined by high resolution 2D seismic data, and a 300-km-long western segment that is defined by a narrow zone of anomalous seismicity first observed by previous workers. The western end of the PBFZ terminates on a Quaternary rift structure, the San Andres rift, associated with Plio-Pleistocene volcanism and thickening trends indicating initial rifting in the Late Miocene. The southern end of the San Andreas rift terminates on the western Hess fault which also exhibits active strands consistent with left-lateral, strike-slip faults. The total length of the PBFZ-San Andres rift-Southern Hess escarpment fault is 1,200 km and traverses the entire western end of the Caribbean plate. Our interpretation is similar to previous models that have proposed the "stable" western Caribbean plate is broken by this fault whose rate of displacement is less than the threshold recognizable from the current GPS network (~3 mm/yr). The Late Miocene age of the fault indicates it may have activated during the Late Miocene to recent Hispaniola-Bahamas oblique collision event.

Fault zone structure from topography: signatures of en echelon fault slip at Mustang Ridge on the San Andreas Fault, Monterey County, California

USGS Publications Warehouse

DeLong, Stephen B.; Hilley, George E.; Rymer, Michael J.; Prentice, Carol

2010-01-01

We used high-resolution topography to quantify the spatial distribution of scarps, linear valleys, topographic sinks, and oversteepened stream channels formed along an extensional step over on the San Andreas Fault (SAF) at Mustang Ridge, California. This location provides detail of both creeping fault landform development and complex fault zone kinematics. Here, the SAF creeps 10–14 mm/yr slower than at locations ∼20 km along the fault in either direction. This spatial change in creep rate is coincident with a series of en echelon oblique-normal faults that strike obliquely to the SAF and may accommodate the missing deformation. This study presents a suite of analyses that are helpful for proper mapping of faults in locations where high-resolution topographic data are available. Furthermore, our analyses indicate that two large subsidiary faults near the center of the step over zone appear to carry significant distributed deformation based on their large apparent vertical offsets, the presence of associated sag ponds and fluvial knickpoints, and the observation that they are rotating a segment of the main SAF. Several subsidiary faults in the southeastern portion of Mustang Ridge are likely less active; they have few associated sag ponds and have older scarp morphologic ages and subdued channel knickpoints. Several faults in the northwestern part of Mustang Ridge, though relatively small, are likely also actively accommodating active fault slip based on their young morphologic ages and the presence of associated sag ponds.

The relationship of near-surface active faulting to megathrust splay fault geometry in Prince William Sound, Alaska

NASA Astrophysics Data System (ADS)

Finn, S.; Liberty, L. M.; Haeussler, P. J.; Northrup, C.; Pratt, T. L.

2010-12-01

We interpret regionally extensive, active faults beneath Prince William Sound (PWS), Alaska, to be structurally linked to deeper megathrust splay faults, such as the one that ruptured in the 1964 M9.2 earthquake. Western PWS in particular is unique; the locations of active faulting offer insights into the transition at the southern terminus of the previously subducted Yakutat slab to Pacific plate subduction. Newly acquired high-resolution, marine seismic data show three seismic facies related to Holocene and older Quaternary to Tertiary strata. These sediments are cut by numerous high angle normal faults in the hanging wall of megathrust splay. Crustal-scale seismic reflection profiles show splay faults emerging from 20 km depth between the Yakutat block and North American crust and surfacing as the Hanning Bay and Patton Bay faults. A distinct boundary coinciding beneath the Hinchinbrook Entrance causes a systematic fault trend change from N30E in southwestern PWS to N70E in northeastern PWS. The fault trend change underneath Hinchinbrook Entrance may occur gradually or abruptly and there is evidence for similar deformation near the Montague Strait Entrance. Landward of surface expressions of the splay fault, we observe subsidence, faulting, and landslides that record deformation associated with the 1964 and older megathrust earthquakes. Surface exposures of Tertiary rocks throughout PWS along with new apatite-helium dates suggest long-term and regional uplift with localized, fault-controlled subsidence.

Widespread seismicity excitation throughout central Japan following the 2011 M=9.0 Tohoku earthquake and its interpretation by Coulomb stress transfer

USGS Publications Warehouse

Toda, S.; Stein, R.S.; Lin, J.

2011-01-01

We report on a broad and unprecedented increase in seismicity rate following the M=9.0 Tohoku mainshock for M ≥ 2 earthquakes over inland Japan, parts of the Japan Sea and Izu islands, at distances of up to 425 km from the locus of high (≥15 m) seismic slip on the megathrust. Such an increase was not seen for the 2004 M=9.1 Sumatra or 2010 M=8.8 Chile earthquakes, but they lacked the seismic networks necessary to detect such small events. Here we explore the possibility that the rate changes are the product of static Coulomb stress transfer to small faults. We use the nodal planes of M ≥ 3.5 earthquakes as proxies for such small active faults, and find that of fifteen regions averaging ~80 by 80 km in size, 11 show a positive association between calculated stress changes and the observed seismicity rate change, 3 show a negative correlation, and for one the changes are too small to assess. This work demonstrates that seismicity can turn on in the nominal stress shadow of a mainshock as long as small geometrically diverse active faults exist there, which is likely quite common.

Active faults system and related potential seismic events near Ulaanbaatar, capital of Mongolia.

NASA Astrophysics Data System (ADS)

Schlupp, Antoine; Ferry, Matthieu; Munkhuu, Ulziibat; Sodnomsambuu, Demberel; Al-Ashkar, Abeer

2013-04-01

The region of Ulaanbaatar lies several hundred kilometers from large known active faults that produced magnitude 6 to 8+ earthquakes during the last century. Beside the Hustai fault, which displays a clear morphological expression, no active fault was previously described less than 100 km from the city. In addition, no large historical (i.e. more recent than the 16th c.) earthquakes are known in this region. However, since 2005 a very dense seismic activity has developed over the Emeelt Township area, a mere 10 km from Ulaanbaatar. The activity is characterized by numerous low magnitude events (M<2.8), which are distributed linearly along several tens of kilometers where no active fault has been identified. This raises several questions: Is this seismicity associated to a -yet- unknown active fault? If so, are there other unknown active faults near Ulaanbaatar? Hence, we deployed a multi-disciplinary approach including morpho-tectonic, near-surface geophysical and paleoseismological investigations. We describe four large active faults west and south of Ulaanbaatar, three of them are newly discovered (Emeelt, Sharai, Avdar), one was previously known (Hustai) but without precise study on its seismic potential. The Emeelt seismicity can be mapped over 35 km along N150 and corresponds in the field to a smoothed, but clear, active fault morphology that can be mapped along a 10-km-long section. The fault dips at ~30° NE (GPR and surface morphology observations) and uplifts the eastern block. The age of the last surface rupture observed in trenches is about 10 ka (preliminary OSL dating). Considering a rupture length of 35 km, a full segment rupture would be comparable to the 1967 Mogod earthquake with a magnitude as large as Mw 7. It has to be considered today as a possible scenario for the seismic risk of Ulaanbaatar. The 90-km-long Hustai Range Fault System, oriented WSW-ENE and located about 10 km west of Ulaanbaatar, displays continuous microseismicity with five light to moderate (M 4 - 5.4) earthquakes over the last 40 years. The last surface-rupturing earthquake occurred about 1000 years ago (OSL dating). Alluvial fans affected by the fault suggest the rate of deformation (left lateral with normal component) along the main segment ranges from 0.3 to 0.4 mm/year for the last 120 000 years. Hence, the average recurrence interval for a full-segment M 7-7.5 is likely in the order of 10 ky. However, if the Hustai fault also releases strain during partial ruptures along its strongly segmented trace, a Mw 6.5 event may be expected anytime. However, only the main central fault segment has been investigated in terms of paleoseismicity. The Sharai and Avdar faults, oriented NNE-SSW, were mapped along ~50-km-long sections. Each of these faults was the site of earthquakes of magnitude 6 and more in the past as suggested by morphology and trench observations. Full-segment-ruptures could produce events as large as M 7.2. The precise relationship and interactions between these faults as well as associated earthquakes have to be clarified by collecting more data. They are the key of the seismic hazard and risk of Ulaanbaatar.

FTAPE: A fault injection tool to measure fault tolerance

NASA Technical Reports Server (NTRS)

Tsai, Timothy K.; Iyer, Ravishankar K.

1995-01-01

The paper introduces FTAPE (Fault Tolerance And Performance Evaluator), a tool that can be used to compare fault-tolerant computers. The tool combines system-wide fault injection with a controllable workload. A workload generator is used to create high stress conditions for the machine. Faults are injected based on this workload activity in order to ensure a high level of fault propagation. The errors/fault ratio and performance degradation are presented as measures of fault tolerance.

Geomorphic Proxies to Test Strain Accommodation in Southwestern Puerto Rico from Digital Elevation Models

NASA Astrophysics Data System (ADS)

Barrios Galindez, I. M.; Xue, L.; Laó-Dávila, D. A.

2017-12-01

The Puerto Rico and the Virgin Island microplate is located in at the northeastern corner of the Caribbean plate boundary with North America is placed within an oblique subduction zone in which strain patterns remain unresolved. Seismic hazard is a major concern in the region as seen from the seismic history of the Caribbean-North America plate boundary zone. Most of the tectonic models of the microplate show the accommodation of strain occurring offshore, despite evidence from seismic activity, trench studies, and geodetic studies suggesting the existence of strain accomodation in southwest Puerto Rico. These studies also suggest active faulting specially in the western part of the island, but limited work has been done regarding their mechanism. Therefore, this work aims to define and map these active faults in western Puerto Rico by integrating data from analysis of fluvial terrains, and detailed mapping using digital elevation model (DEM) extracted from Shuttle Radar Topography Mission (SRTM) and LIDAR data. The goal is to (1) identify structural features such as surface lineaments and fault scarps for the Cerro Goden fault, South Lajas fault, and other active faults in the western of Puerto Rico, (2) correlate these information with the distribution pattern and values of the geomorphic proxies, including Chi integral (χ), normalized steepness (ksn) and Asymmetric factor (AF). Our preliminary results from geomorphic proxies and Lidar data provide some insight of the displacement and stage of activities of these faults (e.g. Boqueron-Punta Malva Fault and Cerro Goden fault). Also, the anomaly of the geomorphic proxies generally correlate with the locations of the landslides in the southwestern Puerto Rico. The geomorphic model of this work include new information of active faulting fundamental to produce better seismic hazards maps. Additionally, active tectonics studies are vital to issue and adjust construction buildings codes and zonification codes.

Plate-rate laboratory friction experiments reveal potential slip instability on weak faults

NASA Astrophysics Data System (ADS)

Ikari, M.; Kopf, A.

2016-12-01

In earthquake science, it is commonly assumed that earthquakes nucleate on strong patches or "asperities", and data from laboratory friction experiments indicate a tendency for unstable slip (exhibited as velocity-weakening frictional behavior) in strong geologic materials. However, an overwhelming amount of these experiments were conducted at driving velocities ranging from 0.1 µm/s to over 1 m/s. Less data exists for shearing experiments driven at slow velocities on the order of cm/yr (nm/s), approximating plate tectonic rates which represent the natural driving condition on plate boundary faults. Recent laboratory work using samples recovered from the Tohoku region at the Japan Trench, within the high coseismic slip region of the 2011 M9 Tohoku earthquake, showed that the fault is extremely weak with a friction coefficient < 0.2. At sliding velocities of at least 0.1 µm/s mostly velocity-strengthening friction is observed, which is favorable for stable creep, consistent with earlier work. However, shearing at an imposed rate of 8.5 cm/yr produced both velocity-weakening friction and discrete slow slip events, which are likely instances of frictional instabilities or quasi-instabilities. Here, we expand on the Tohoku experiment by conducting cm/yr friction experiments on natural gouges obtained from a variety of other major fault zones obtained by scientific drilling; these include the San Andreas Fault, Costa Rica subduction zone, Nankai Trough (Japan), Barbados subduction zone, Alpine Fault (New Zealand), southern Cascadia, and Woodlark Basin (Papua New Guinea). We focus here on weak fault materials having a friction coefficient of < 0.5. At conventional laboratory driving rates of 0.1-30 µm/s, velocity strengthening is common. However, at cm/yr driving rates we commonly observe velocity-weakening friction and slow slip events, with most samples exhibit both behaviors. These results demonstrate when fault samples are sheared at plate tectonic rates in the laboratory, which best replicates natural forcing conditions, a tendency for unstable slip is revealed. Thus, weak faults should not be considered frictionally stable, but have the ability to participate in earthquake rupture or generate events themselves.

Uplifted Yellow river terraces across the Haiyuan fault, China and their implications to geometrical complexity of strike-slip fault system

NASA Astrophysics Data System (ADS)

Liu, J.; van der Woerd, J.; Li, Z.; Klinger, Y.; Matrau, R.; Shao, Y.; Zhang, J.; Wang, P.

2016-12-01

Geometrical complexities and discontinues, such as fault bends, splays and step-overs, are common along large strike-slip faults. Numerical and observational studies show that geometrical complexities above some threshold degree may inhibit thoroughgoing rupture, limiting rupture length and the size of the resulting earthquake. Studying the fine structure and long-term evolution of fault step-overs would help us better understand their effect on earthquake ruptures. In this study, we focus on a prominent geometrical "knot" on the left-lateral Haiyuan fault, where the fault curves with multi-strand splays bounding the Mijia Shan-Hasi Shan ranges. Incidentally, the Yellow river flows between the Mijia Shan and Hasi Shan and cuts a deep gorge when crossing the fault. On the western bank of the river, a series of at least twelve levels of fluvial strath terraces perch above river bed, and are capped with no more than 5 meters of alluvial deposits. We measured the terrace heights above river bed, using RTK and UAV surveys. We collected quartz-rich pebbles of yellow river gravel for cosmogenic radio nuclide (CRN), and silt layers within gravel and the overlying loess cap for optimally stimulated luminescence (OSL) dating to constrain the terrace formation ages. Quartz-rich pebbles were sampled both in hand-dug pit for depth-profile method and surface samples on terrace surfaces. The CRN age results were corrected in terms of inheritance and shielding by loess. The dates and heights of serial terraces yielded an average uplift rate of 2±0.34 mm/yr, which represents the late Quaternary uplifting rate of the Mijia Shan. The uplift of the Mijia Shan-Hasi Shan may result from the oblique shear of positive flower in the deep crust of the left-lateral Haiyuan fault. We further speculate that with progressively uplifted mountain ranges, the active fault trace shifts with time among the multi-strands of the fault system. In addition, the coincidence of prominent uplifted mountains at the position where the Yellow river cut across the left-lateral strike-slip fault suggests that Yellow river may play a role in enhancing the uplifting rate, though efficient mass unloading.

Integration of high-resolution seismic and aeromagnetic data for earthquake hazards evaluations: An example from the Willamette Valley, Oregon

USGS Publications Warehouse

Liberty, L.M.; Trehu, A.M.; Blakely, R.J.; Dougherty, M.E.

1999-01-01

Aeromagnetic and high-resolution seismic reflection data were integrated to place constraints on the history of seismic activity and to determine the continuity of the possibly active, yet largely concealed Mount Angel fault in the Willamette Valley, Oregon. Recent seismic activity possibly related to the 20-km-long fault includes a swarm of small earthquakes near Woodburn in 1990 and the magnitude 5.6 Scotts Mills earthquake in 1993. Newly acquired aeromagnetic data show several large northwest-trending anomalies, including one associated with the Mount Angel fault. The magnetic signature indicates that the fault may actually extend 70 km across the Willamette Valley to join the Newberg and Gales Creek faults in the Oregon Coast Range. We collected 24-fold high-resolution seismic reflection data along two transects near Woodburn, Oregon, to image the offset of the Miocene-age Columbia River Basalts (CRB) and overlying sediments at and northwest of the known mapped extent of the Mount Angel fault. The seismic data show a 100-200-m offset in the CRB reflector at depths from 300 to 700 m. Folded or offset sediments appear above the CRB with decreasing amplitude to depths as shallow as were imaged (approximately 40 m). Modeling experiments based on the magnetic data indicate, however, that the anomaly associated with the Mount Angel fault is not caused solely by an offset of the CRB and overlying sediments. Underlying magnetic sources, which we presume to be volcanic rocks of the Siletz terrane, must have vertical offsets of at least 500 m to fit the observed data. We conclude that the Mount Angel fault appears to have been active since Eocene age and that the Gales Creek, Newberg, and Mount Angel faults should be considered a single potentially active fault system. This fault, as well as other parallel northwest-trending faults in the Willamette Valley, should be considered as risks for future potentially damaging earthquakes.

Implications of river morphology response to Dien Bien Phu fault in NW Vietnam

NASA Astrophysics Data System (ADS)

Lai, K.; Chen, Y.; Lam, D.

2007-12-01

In northern Vietnam, most rivers are flowing southeastward sub- or parallel to the valley of Red River and characterized by long but narrow catchments. The Dien Bien Phu fault is associated with the most seismically active zone in Vietnam and situated in the potential eastern boundary of the rotating southeastern Tibetan block. It cuts the Da River, the largest tributary of Red River in northwest Vietnam and has distorted the drainage basin resulting in complex river patterns. To assess the river morphology response to active Dien Bien Phu fault, we use 1/50,000 topographic data and ASTER images to map the precise river courses and digital elevation model data of SRTM to retrieve and analyze the river profiles. From the mapping results, the N-S striking fault results in three conspicuous north-trending river valleys coincided with the different fault segments to facilitate the measurement and reconstruction of the offsets along the fault. Further combining the longitudinal profile analysis we obtain ca. 10 km offsets by deflected river as the largest left-lateral displacement recorded along the active fault. The restored results show the downstream paleochannel of the Da River had been abandoned and becomes two small tributaries in opposite flow directions at present due to differential crustal uplift. Also the present crisscross valley at the junction of the Da River and the fault is resulted from the capture by another river which has been also deflected by the neotectonics. Based on our observations on river response, the Dien Bien Phu fault is a sinistral dominant fault with an uplift occurring in its eastern block. Furthermore the active Dien Bien Phu fault does not cut through the Red River northward indicating the western block of the fault can not be regarded as a single rigid block. There should be possible to find NW-SE trending faults paralleling to Red River to accommodate the deformation of the western block of the fault.

Implications of river morphology response to Dien Bien Phu fault in NW Vietnam

NASA Astrophysics Data System (ADS)

Lai, K.; Chen, Y.; Lam, D.

2004-12-01

In northern Vietnam, most rivers are flowing southeastward sub- or parallel to the valley of Red River and characterized by long but narrow catchments. The Dien Bien Phu fault is associated with the most seismically active zone in Vietnam and situated in the potential eastern boundary of the rotating southeastern Tibetan block. It cuts the Da River, the largest tributary of Red River in northwest Vietnam and has distorted the drainage basin resulting in complex river patterns. To assess the river morphology response to active Dien Bien Phu fault, we use 1/50,000 topographic data and ASTER images to map the precise river courses and digital elevation model data of SRTM to retrieve and analyze the river profiles. From the mapping results, the N-S striking fault results in three conspicuous north-trending river valleys coincided with the different fault segments to facilitate the measurement and reconstruction of the offsets along the fault. Further combining the longitudinal profile analysis we obtain ca. 10 km offsets by deflected river as the largest left-lateral displacement recorded along the active fault. The restored results show the downstream paleochannel of the Da River had been abandoned and becomes two small tributaries in opposite flow directions at present due to differential crustal uplift. Also the present crisscross valley at the junction of the Da River and the fault is resulted from the capture by another river which has been also deflected by the neotectonics. Based on our observations on river response, the Dien Bien Phu fault is a sinistral dominant fault with an uplift occurring in its eastern block. Furthermore the active Dien Bien Phu fault does not cut through the Red River northward indicating the western block of the fault can not be regarded as a single rigid block. There should be possible to find NW-SE trending faults paralleling to Red River to accommodate the deformation of the western block of the fault.

A probabilistic assessment of waste water injection induced seismicity in central California

NASA Astrophysics Data System (ADS)

Goebel, T.; Hauksson, E.; Ampuero, J. P.; Aminzadeh, F.; Cappa, F.; Saleeby, J.

2014-12-01

The recent, large increase in seismic activity within the central and eastern U.S. may be connected to an increase in fluid injection activity since ~2001. Anomalous seismic sequences can easily be identified in regions with low background seismicity rates. Here, we analyze seismicity in plate boundary regions where tectonically-driven earthquake sequences are common, potentially masking injection-induced events. We show results from a comprehensive analysis of waste water disposal wells in Kern county, the largest oil-producing county in California. We focus on spatial-temporal correlations between seismic and injection activity and seismicity-density changes due to injection. We perform a probabilistic assessment of induced vs. tectonic earthquakes, which can be applied to different regions independent of background rates and may provide insights into the probability of inducing earthquakes as a function of injection parameters and local geological conditions. Our results show that most earthquakes are caused by tectonic forcing, however, waste water injection contributes to seismic activity in four different regions with several events above M4. The seismicity shows different migration characteristics relative to the injection sites, including linear and non-linear trends. The latter is indicative of diffusive processes which take advantage of reservoir properties and fault structures and can induce earthquakes at distances of up to 10 km. Our results suggest that injection-related triggering processes are complex, possibly involving creep, and delayed triggering. Pore-pressure diffusion may be more extensive in the presence of active faults and high-permeability damage zones thus altering the local seismic hazard in a non-linear fashion. As a consequence, generic "best-practices" for fluid injections like a maximum distance from the nearest active fault may not be sufficient to mitigate a potential seismic hazard increase.

A regional assessment of potential environmental hazards to and limitations on petroleum development of the Southeastern United States Atlantic continental shelf, slope, and rise, offshore North Carolina

USGS Publications Warehouse

Popenoe, Peter; Coward, E.L.; Cashman, K.V.

1982-01-01

More than 11,000 km of high-resolution seismic-reflection data, 325 km of mid-range sidescan-sonar data, and 500 km of long-range sidescan-sonar data were examined and used to construct an environmental geology map of the Continental Shelf, Slope, and Rise for the area of the U.S. Atlantic margin between lats. 32?N. and 37?N. Hardgrounds and two faults described in previous literature also are shown on the map. On the Continental Shelf, at least two faults, the Helena Banks fault and the White Oak lineament, appear to be tectonic in origin. However, a lack of historical seismicity associated with these faults indicates that they are probably not active at the present time. Hardgrounds are widely scattered but are most abundant in Onslow Bay. Although paleostream channels are common nearshore, they do not appear to be common on the central and outer shelf except off Albemarle Sound where extensive Pleistocene, Pliocene, and late Miocene channels extend across the shelf. Mobile bottom sediments are confined mainly to the shoals off Cape Romain, Cape Fear, Cape Lookout, and Cape Hatteras. Elsewhere the sand cover is thin, and older more indurated rocks are present in subcrop. No slope-instability features were noted on the Florida-Hatteras slope off North Carolina. The lack of features indicates that this slope is relatively stable. Evidence for scour by strong currents is ubiquitous on the northern Blake Plateau although deep-water reefs are sparse. The outer edge of the plateau is dominated by a major growth fault and numerous splay and antithetic faults. These faults are the product of salt tectonism in the Carolina trough and thus are not associated with seismicity. Displacements observed near the sea floor and breached diapirs offshore indicate that the main fault is still moving. Associated with the faults are collapse features that are interpreted to be caused by karst solution and cavernous porosity in Eocene and Oligocene limestones at depth. Major slumps have taken place in two large areas of the Continental Slope. Seismic-reflection profiles of the southern area, centered on the lower slope at 1at. 33?N., long. 76?W., show a 80-m-hlgh scarp in which bedding has been truncated. Rotational slump faults are present in this area on the middle and upper slope. Sidescan images show that large blocks have slid downslope from the scarp face, furrowing the bottom. High-resolution (3.5-kHz) records show that the rotational slump faults upslope are active. The association of these slumps and the scarps with salt diapirs suggests subsidence accompanying salt tectonism as the cause. Seismic-reflection records over the northern area, at about fat. 36?20'N., long. 74?40'W., show two steep scarps, each about 225 m high on the upper and middle-slope. These slump scars and an absence of Pleistocene sediments indicate that large blocks of the slope have been removed by slumping. The slope north of fat. 35?N. is highly dissected by canyons. Mid-range sidescan-sonar records suggest that the canyons are the product of mass wasting and have probably formed largely by slumping. Sediments in a wide zone on the upper rise are highly disturbed and faulted owing to salt tectonism. Twenty-six salt diapirs are mapped, as is a zone of disturbed bottom related to salt tectonism. An area of frozen bottom (clathrate) under which shallow free gas is trapped underlies the outer Blake Plateau, the slope, and the upper rise. Although the hazards of drilling into or through clathrates have not been tested, the release of gas from beneath this frozen layer may prove to be a primary hazard to exploration.

Quantitative Assessment of Potentially Active Faults in Oklahoma Utilizing Detailed Information on In Situ Stress Orientation and Relative Magnitude

NASA Astrophysics Data System (ADS)

Walsh, R.; Zoback, M. D.

2015-12-01

Over the past six years, the earthquake rate in the central and eastern U.S. has increased markedly, and is related to fluid injection. Nowhere has seismicity increased more than in Oklahoma, where large volumes of saline pore water are co-produced with oil and gas, then injected into deeper sedimentary formations. These deeper formations appear to be in hydraulic communication with potentially active faults in crystalline basement, where nearly all the earthquakes are occurring. Although the majority of the recent earthquakes have posed little danger to the public, the possibility of triggering damaging earthquakes on potentially active basement faults cannot be discounted. To understand probability of slip on a given fault, we invert for stresses from the hundreds of M4+ events in Oklahoma for which moment tensors have been made. We then resolve these stresses, while incorporating uncertainties, on the faults from the preliminary Oklahoma fault map. The result is a probabilistic understanding of which faults are most likely active and best avoided.

Network Connectivity for Permanent, Transient, Independent, and Correlated Faults

NASA Technical Reports Server (NTRS)

White, Allan L.; Sicher, Courtney; henry, Courtney

2012-01-01

This paper develops a method for the quantitative analysis of network connectivity in the presence of both permanent and transient faults. Even though transient noise is considered a common occurrence in networks, a survey of the literature reveals an emphasis on permanent faults. Transient faults introduce a time element into the analysis of network reliability. With permanent faults it is sufficient to consider the faults that have accumulated by the end of the operating period. With transient faults the arrival and recovery time must be included. The number and location of faults in the system is a dynamic variable. Transient faults also introduce system recovery into the analysis. The goal is the quantitative assessment of network connectivity in the presence of both permanent and transient faults. The approach is to construct a global model that includes all classes of faults: permanent, transient, independent, and correlated. A theorem is derived about this model that give distributions for (1) the number of fault occurrences, (2) the type of fault occurrence, (3) the time of the fault occurrences, and (4) the location of the fault occurrence. These results are applied to compare and contrast the connectivity of different network architectures in the presence of permanent, transient, independent, and correlated faults. The examples below use a Monte Carlo simulation, but the theorem mentioned above could be used to guide fault-injections in a laboratory.

Focal mechanisms and inter-event times of low-frequency earthquakes reveal quasi-continuous deformation and triggered slow slip on the deep Alpine Fault

NASA Astrophysics Data System (ADS)

Baratin, Laura-May; Chamberlain, Calum J.; Townend, John; Savage, Martha K.

2018-02-01

Characterising the seismicity associated with slow deformation in the vicinity of the Alpine Fault may provide constraints on the stresses acting on a major transpressive margin prior to an anticipated great (≥M8) earthquake. Here, we use recently detected tremor and low-frequency earthquakes (LFEs) to examine how slow tectonic deformation is loading the Alpine Fault late in its typical ∼300-yr seismic cycle. We analyse a continuous seismic dataset recorded between 2009 and 2016 using a network of 10-13 short-period seismometers, the Southern Alps Microearthquake Borehole Array. Fourteen primary LFE templates are used in an iterative matched-filter and stacking routine, allowing the detection of similar signals corresponding to LFE families sharing common locations. This yields an 8-yr catalogue containing 10,000 LFEs that are combined for each of the 14 LFE families using phase-weighted stacking to produce signals with the highest possible signal-to-noise ratios. We show that LFEs occur almost continuously during the 8-yr study period and highlight two types of LFE distributions: (1) discrete behaviour with an inter-event time exceeding 2 min; (2) burst-like behaviour with an inter-event time below 2 min. We interpret the discrete events as small-scale frequent deformation on the deep extent of the Alpine Fault and LFE bursts (corresponding in most cases to known episodes of tremor or large regional earthquakes) as brief periods of increased slip activity indicative of slow slip. We compute improved non-linear earthquake locations using a 3-D velocity model. LFEs occur below the seismogenic zone at depths of 17-42 km, on or near the hypothesised deep extent of the Alpine Fault. The first estimates of LFE focal mechanisms associated with continental faulting, in conjunction with recurrence intervals, are consistent with quasi-continuous shear faulting on the deep extent of the Alpine Fault.

Late Quaternary strike-slip along the Taohuala Shan-Ayouqi fault zone and its tectonic implications in the Hexi Corridor and the southern Gobi Alashan, China

NASA Astrophysics Data System (ADS)

Yu, Jing-xing; Zheng, Wen-jun; Zhang, Pei-zhen; Lei, Qi-yun; Wang, Xu-long; Wang, Wei-tao; Li, Xin-nan; Zhang, Ning

2017-11-01

The Hexi Corridor and the southern Gobi Alashan are composed of discontinuous a set of active faults with various strikes and slip motions that are located to the north of the northern Tibetan Plateau. Despite growing understanding of the geometry and kinematics of these active faults, the late Quaternary deformation pattern in the Hexi Corridor and the southern Gobi Alashan remains controversial. The active E-W trending Taohuala Shan-Ayouqi fault zone is located in the southern Gobi Alashan. Study of the geometry and nature of slip along this fault zone holds crucial value for better understanding the regional deformation pattern. Field investigations combined with high-resolution imagery show that the Taohuala Shan fault and the E-W trending faults within the Ayouqi fault zone (F2 and F5) are left-lateral strike-slip faults, whereas the NW or WNW-trending faults within the Ayouqi fault zone (F1 and F3) are reverse faults. We collected Optically Stimulated Luminescence (OSL) and cosmogenic exposure age dating samples from offset alluvial fan surfaces, and estimated a vertical slip rate of 0.1-0.3 mm/yr, and a strike-slip rate of 0.14-0.93 mm/yr for the Taohuala Shan fault. Strata revealed in a trench excavated across the major fault (F5) in the Ayouqi fault zone and OSL dating results indicate that the most recent earthquake occurred between ca. 11.05 ± 0.52 ka and ca. 4.06 ± 0.29 ka. The geometry and kinematics of the Taohuala Shan-Ayouqi fault zone enable us to build a deformation pattern for the entire Hexi Corridor and the southern Gobi Alashan, which suggest that this region experiences northeastward oblique extrusion of the northern Tibetan Plateau. These left-lateral strike-slip faults in the region are driven by oblique compression but not associated with the northeastward extension of the Altyn Tagh fault.

Active tectonics of the northern Mojave Desert: The 2017 Desert Symposium field trip road log

USGS Publications Warehouse

Miller, David; Reynolds, R.E.; Phelps, Geoffrey; Honke, Jeff; Cyr, Andrew J.; Buesch, David C.; Schmidt, Kevin M.; Losson, G.

2017-01-01

The 2017 Desert Symposium field trip will highlight recent work by the U.S. Geological Survey geologists and geophysicists, who have been mapping young sediment and geomorphology associated with active tectonic features in the least well-known part of the eastern California Shear Zone (ECSZ). This area, stretching from Barstow eastward in a giant arc to end near the Granite Mountains on the south and the Avawatz Mountains on the north (Fig. 1-1), encompasses the two major structural components of the ECSZ—east-striking sinistral faults and northwest-striking dextral faults—as well as reverseoblique and normal-oblique faults that are associated with topographic highs and sags, respectively. In addition, folds and stepovers (both restraining stepovers that form pop-up structures and releasing stepovers that create narrow basins) have been identified. The ECSZ is a segment in the ‘soft’ distributed deformation of the North American plate east of the San Andreas fault (Fig. 1-1), where it takes up approximately 20-25% of plate motion in a broad zone of right-lateral shear (Sauber et al., 1994) The ECSZ (sensu strictu) begins in the Joshua Tree area and passes north through the Mojave Desert, past the Owens Valley-to-Death Valley swath and northward, where it is termed the Walker Lane. It has been defined as the locus of active faulting (Dokka and Travis, 1990), but when the full history from about 10 Ma forward is considered, it lies in a broader zone of right shear that passes westward in the Mojave Desert to the San Andreas fault (Mojave strike-slip province of Miller and Yount, 2002) and passes eastward to the Nevada state line or beyond (Miller, this volume).We will visit several accessible highlights for newly studied faults, signs of young deformation, and packages of syntectonic sediments. These pieces of a complex active tectonic puzzle have yielded some answers to longstanding questions such as: How is fault slip transfer in this area accommodated between northwest-striking dextral faults and eaststriking sinistral faults?How is active deformation on the Ludlow fault transferred northward, presumably to connect to the southern Death Valley fault zone?When were faults in this area of the central Mojave Desert initiated?Are faults in this area more or less active than faults in the ECSZ to the west?What is the role of NNW-striking faults and when did they form?How has fault slip changed over time? Locations and fault names are provided in figure 1-2. Important turns and locations are identified with locations in the projection: UTM, zone 11; datum NAD 83: (578530 3917335).

Project DAFNE - Drilling Active Faults in Northern Europe

NASA Astrophysics Data System (ADS)

Kukkonen, I. T.; Ask, M. S. V.; Olesen, O.

2012-04-01

We are currently developing a new ICDP project 'Drillling Active Faults in Northern Europe' (DAFNE) which aims at investigating, via scientific drilling, the tectonic and structural characteristics of postglacial (PG) faults in northern Fennoscandia, including their hydrogeology and associated deep biosphere [1, 2]. During the last stages of the Weichselian glaciation (ca. 9,000 - 15,000 years B.P.), reduced ice load and glacially affected stress field resulted in active faulting in Fennoscandia with fault scarps up to 160 km long and 30 m high. These postglacial (PG) faults are usually SE dipping, SW-NE oriented thrusts, and represent reactivated, pre-existing crustal discontinuities. Postglacial faulting indicates that the glacio-isostatic compensation is not only a gradual viscoelastic phenomenon, but includes also unexpected violent earthquakes, suggestively larger than other known earthquakes in stable continental regions. The research is anticipated to advance science in neotectonics, hydrogeology and deep biosphere studies, and provide important information for nuclear waste and CO2 disposal, petroleum exploration on the Norwegian continental shelf and studies of mineral resources in PG fault areas. We expect that multidisciplinary research applying shallow and deep drilling of postglacial faults would provide significant scientific results through generating new data and models, namely: (1) Understanding PG fault genesis and controls of their locations; (2) Deep structure and depth extent of PG faults; (3) Textural, mineralogical and physical alteration of rocks in the PG faults; (4) State of stress and estimates of paleostress of PG faults; (5) Hydrogeology, hydrochemistry and hydraulic properties of PG faults; (6) Dating of tectonic reactivation(s) and temporal evolution of tectonic systems hosting PG faults; (7) Existence/non-existence of deep biosphere in PG faults; (8) Data useful for planning radioactive waste disposal in crystalline bedrock; (9) Data on rock stress changes in the periphery of the inland ice; (10) Stress pattern along the Norwegian continental margin in relation to the bending spreading ridge and Plio-Pleistocene erosion, uplift and sedimentation with implications for fluid migration and sealing properties of petroleum reservoirs. (11) Data useful in predicting future seismic activity in areas of current deglaciation due to ongoing climatic warming.

The Quaternary thrust system of the northern Alaska Range

USGS Publications Warehouse

Bemis, Sean P.; Carver, Gary A.; Koehler, Richard D.

2012-01-01

The framework of Quaternary faults in Alaska remains poorly constrained. Recent studies in the Alaska Range north of the Denali fault add significantly to the recognition of Quaternary deformation in this active orogen. Faults and folds active during the Quaternary occur over a length of ∼500 km along the northern flank of the Alaska Range, extending from Mount McKinley (Denali) eastward to the Tok River valley. These faults exist as a continuous system of active structures, but we divide the system into four regions based on east-west changes in structural style. At the western end, the Kantishna Hills have only two known faults but the highest rate of shallow crustal seismicity. The western northern foothills fold-thrust belt consists of a 50-km-wide zone of subparallel thrust and reverse faults. This broad zone of deformation narrows to the east in a transition zone where the range-bounding fault of the western northern foothills fold-thrust belt terminates and displacement occurs on thrust and/or reverse faults closer to the Denali fault. The eastern northern foothills fold-thrust belt is characterized by ∼40-km-long thrust fault segments separated across left-steps by NNE-trending left-lateral faults. Altogether, these faults accommodate much of the topographic growth of the northern flank of the Alaska Range.Recognition of this thrust fault system represents a significant concern in addition to the Denali fault for infrastructure adjacent to and transecting the Alaska Range. Although additional work is required to characterize these faults sufficiently for seismic hazard analysis, the regional extent and structural character should require the consideration of the northern Alaska Range thrust system in regional tectonic models.

Software For Fault-Tree Diagnosis Of A System

NASA Technical Reports Server (NTRS)

Iverson, Dave; Patterson-Hine, Ann; Liao, Jack

1993-01-01

Fault Tree Diagnosis System (FTDS) computer program is automated-diagnostic-system program identifying likely causes of specified failure on basis of information represented in system-reliability mathematical models known as fault trees. Is modified implementation of failure-cause-identification phase of Narayanan's and Viswanadham's methodology for acquisition of knowledge and reasoning in analyzing failures of systems. Knowledge base of if/then rules replaced with object-oriented fault-tree representation. Enhancement yields more-efficient identification of causes of failures and enables dynamic updating of knowledge base. Written in C language, C++, and Common LISP.

Testing the Extensional Detachment Paradigm: A Borehole Observatory in the Sevier Desert Basin, Utah

NASA Astrophysics Data System (ADS)

Christie-Blick, N.; Wernicke, B. P.

2007-12-01

The Sevier Desert basin, Utah represents a world-class target for scientific drilling and for the development of an in situ borehole observatory of active faulting, with potential for establishing that normal-sense slip can occur along a brittle low-angle fault and, by determining the conditions under which that may take place, for resolving the mechanical paradox associated with such structures. The Sevier Desert detachment was defined in the mid- 1970s on the basis seismic reflection data and commercial wells as the contact between Paleozoic carbonate rocks and Cenozoic basin fill over a depth range of ~0-4 km. Today, the interpreted fault is thought by most workers to root into the crust to the west, to have large estimated offset (< 47 km), to have been active over most of its history near its present 11° dip, and to be associated with contemporary surface extension (a 30- km-long zone of prominent Holocene fault scarps immediately west of Clear Lake). Although no seismicity has been documented on the detachment, its scale is consistent with earthquake magnitudes as large as M 7.0. A published alternative interpretation of the Paleozoic-Cenozoic contact as an unconformity rather than a fault has not been generally accepted. Deformation at detachment faults is commonly spatially restricted, and may have been missed in well cuttings. Exhumation of the detachment would have made it possible to remove critical footwall evidence prior to later sedimentary onlap, particularly at updip locations. The incomplete coverage and uneven quality of seismic reflection data on which the detachment interpretation depends, and an unresolved debate about stratigraphic ties to a critical well, leave room for discussion about interpretive details, including the possibility that deformation was distributed across several closely spaced faults. An apparent mismatch between stratigraphically based ages and fission-track evidence for the timing of footwall exhumation cannot be resolved with available well data. Drilling is now needed to make in situ measurements at depth, to obtain critical core of fault rocks at a down-dip site where offset should be large, and to establish more clearly the relationship between basin development and displacement along the interpreted fault. A workshop will take place from July 15-18, 2008, in Utah, under the auspices of the International Continental Scientific Drilling Program, to flesh out objectives, strategies and operational details, and to develop a consensus on the location of a drill site.

Geometry and kinematics of adhesive wear in brittle strike-slip fault zones

NASA Astrophysics Data System (ADS)

Swanson, Mark T.

2005-05-01

Detailed outcrop surface mapping in Late Paleozoic cataclastic strike-slip faults of coastal Maine shows that asymmetric sidewall ripouts, 0.1-200 m in length, are a significant component of many mapped faults and an important wall rock deformation mechanism during faulting. The geometry of these structures ranges from simple lenses to elongate slabs cut out of the sidewalls of strike-slip faults by a lateral jump of the active zone of slip during adhesion along a section of the main fault. The new irregular trace of the active fault after this jump creates an indenting asperity that is forced to plow through the adjoining wall rock during continued adhesion or be cut off by renewed motion along the main section of the fault. Ripout translation during adhesion sets up the structural asymmetry with trailing extensional and leading contractional ends to the ripout block. The inactive section of the main fault trace at the trailing end can develop a 'sag' or 'half-graben' type geometry due to block movement along the scallop-shaped connecting ramp to the flanking ripout fault. Leading contractional ramps can develop 'thrust' type imbrication and forces the 'humpback' geometry to the ripout slab due to distortion of the inactive main fault surface by ripout translation. Similar asymmetric ripout geometries are recognized in many other major crustal scale strike-slip fault zones worldwide. Ripout structures in the 5-500 km length range can be found on the Atacama fault system of northern Chile, the Qujiang and Xiaojiang fault zones in western China, the Yalakom-Hozameen fault zone in British Columbia and the San Andreas fault system in southern California. For active crustal-scale faults the surface expression of ripout translation includes a coupled system of extensional trailing ramps as normal oblique-slip faults with pull-apart basin sedimentation and contractional leading ramps as oblique thrust or high angle reverse faults with associated uplift and erosion. The sidewall ripout model, as a mechanism for adhesive wear during fault zone deformation, can be useful in studies of fault zone geometry, kinematics and evolution from outcrop- to crustal-scales.

Active transfer fault zone linking a segmented extensional system (Betics, southern Spain): Insight into heterogeneous extension driven by edge delamination

NASA Astrophysics Data System (ADS)

Martínez-Martínez, José Miguel; Booth-Rea, Guillermo; Azañón, José Miguel; Torcal, Federico

2006-08-01

Pliocene and Quaternary tectonic structures mainly consisting of segmented northwest-southeast normal faults, and associated seismicity in the central Betics do not agree with the transpressive tectonic nature of the Africa-Eurasia plate boundary in the Ibero-Maghrebian region. Active extensional deformation here is heterogeneous, individual segmented normal faults being linked by relay ramps and transfer faults, including oblique-slip and both dextral and sinistral strike-slip faults. Normal faults extend the hanging wall of an extensional detachment that is the active segment of a complex system of successive WSW-directed extensional detachments which have thinned the Betic upper crust since middle Miocene. Two areas, which are connected by an active 40-km long dextral strike-slip transfer fault zone, concentrate present-day extension. Both the seismicity distribution and focal mechanisms agree with the position and regime of the observed faults. The activity of the transfer zone during middle Miocene to present implies a mode of extension which must have remained substantially the same over the entire period. Thus, the mechanisms driving extension should still be operating. Both the westward migration of the extensional loci and the high asymmetry of the extensional systems can be related to edge delamination below the south Iberian margin coupled with roll-back under the Alborán Sea; involving the asymmetric westward inflow of asthenospheric material under the margins.

Criteria for Seismic Splay Fault Activation During Subduction Earthquakes

NASA Astrophysics Data System (ADS)

Dedontney, N.; Templeton, E.; Bhat, H.; Dmowska, R.; Rice, J. R.

2008-12-01

As sediment is added to the accretionary prism or removed from the forearc, the material overlying the plate interface must deform to maintain a wedge structure. One of the ways this internal deformation is achieved is by slip on splay faults branching from the main detachment, which are possibly activated as part of a major seismic event. As a rupture propagates updip along the plate interface, it will reach a series of junctions between the shallowly dipping detachment and more steeply dipping splay faults. The amount and distribution of slip on these splay faults and the detachment determines the seafloor deformation and the tsunami waveform. Numerical studies by Kame et al. [JGR, 2003] of fault branching during dynamic slip-weakening rupture in 2D plane strain showed that branch activation depends on the initial stress state, rupture velocity at the branching junction, and branch angle. They found that for a constant initial stress state, with the maximum principal stress at shallow angles to the main fault, branch activation is favored on the compressional side of the fault for a range of branch angles. By extending the part of their work on modeling the branching behavior in the context of subduction zones, where critical taper wedge concepts suggest the angle that the principal stress makes with the main fault is shallow, but not horizontal, we hope to better understand the conditions for splay fault activation and the criteria for significant moment release on the splay. Our aim is to determine the range of initial stresses and relative frictional strengths of the detachment and splay fault that would result in seismic splay fault activation. In aid of that, we conduct similar dynamic rupture analyses to those of Kame et al., but use explicit finite element methods, and take fuller account of overall structure of the zone (rather than focusing just on the branching junction). Critical taper theory requires that the basal fault be weaker than the overlying material, so we build on previous work by incorporating the effect of strength contrasts between the basal and splay faults. The relative weakness of the basal fault is often attributed to high pore pressures, which lowers the effective normal stress and brings the basal fault closer to failure. We vary the initial stress state, while maintaining a constant principal stress orientation, to see how the closeness to failure affects the branching behavior for a variety of branch step-up angles.

Faults on Skylab imagery of the Salton Trough area, Southern California

NASA Technical Reports Server (NTRS)

Merifield, P. M.; Lamar, D. L. (Principal Investigator)

1975-01-01

The author has identified the following significant results. Large segments of the major high angle faults in the Salton Trough area are readily identifiable in Skylab images. Along active faults, distinctive topographic features such as scarps and offset drainage, and vegetation differences due to ground water blockage in alluvium are visible. Other fault-controlled features along inactive as well as active faults visible in Skylab photography include straight mountain fronts, linear valleys, and lithologic differences producing contrasting tone, color or texture. A northwestern extension of a fault in the San Andreas set, is postulated by the regional alignment of possible fault-controlled features. The suspected fault is covered by Holocene deposits, principally windblown sand. A northwest trending tonal change in cultivated fields across Mexicali Valley is visible on Skylab photos. Surface evidence for faulting was not observed; however, the linear may be caused by differences in soil conditions along an extension of a segment of the San Jacinto fault zone. No evidence of faulting could be found along linears which appear as possible extensions of the Substation and Victory Pass faults, demonstrating that the interpretation of linears as faults in small scale photography must be corroborated by field investigations.

Orogen-scale uplift in the central Italian Apennines drives episodic behaviour of earthquake faults

PubMed Central

Cowie, P. A.; Phillips, R. J.; Roberts, G. P.; McCaffrey, K.; Zijerveld, L. J. J.; Gregory, L. C.; Faure Walker, J.; Wedmore, L. N. J.; Dunai, T. J.; Binnie, S. A.; Freeman, S. P. H. T.; Wilcken, K.; Shanks, R. P.; Huismans, R. S.; Papanikolaou, I.; Michetti, A. M.; Wilkinson, M.

2017-01-01

Many areas of the Earth’s crust deform by distributed extensional faulting and complex fault interactions are often observed. Geodetic data generally indicate a simpler picture of continuum deformation over decades but relating this behaviour to earthquake occurrence over centuries, given numerous potentially active faults, remains a global problem in hazard assessment. We address this challenge for an array of seismogenic faults in the central Italian Apennines, where crustal extension and devastating earthquakes occur in response to regional surface uplift. We constrain fault slip-rates since ~18 ka using variations in cosmogenic 36Cl measured on bedrock scarps, mapped using LiDAR and ground penetrating radar, and compare these rates to those inferred from geodesy. The 36Cl data reveal that individual faults typically accumulate meters of displacement relatively rapidly over several thousand years, separated by similar length time intervals when slip-rates are much lower, and activity shifts between faults across strike. Our rates agree with continuum deformation rates when averaged over long spatial or temporal scales (104 yr; 102 km) but over shorter timescales most of the deformation may be accommodated by <30% of the across-strike fault array. We attribute the shifts in activity to temporal variations in the mechanical work of faulting. PMID:28322311

Orogen-scale uplift in the central Italian Apennines drives episodic behaviour of earthquake faults.

PubMed

Cowie, P A; Phillips, R J; Roberts, G P; McCaffrey, K; Zijerveld, L J J; Gregory, L C; Faure Walker, J; Wedmore, L N J; Dunai, T J; Binnie, S A; Freeman, S P H T; Wilcken, K; Shanks, R P; Huismans, R S; Papanikolaou, I; Michetti, A M; Wilkinson, M

2017-03-21

Many areas of the Earth's crust deform by distributed extensional faulting and complex fault interactions are often observed. Geodetic data generally indicate a simpler picture of continuum deformation over decades but relating this behaviour to earthquake occurrence over centuries, given numerous potentially active faults, remains a global problem in hazard assessment. We address this challenge for an array of seismogenic faults in the central Italian Apennines, where crustal extension and devastating earthquakes occur in response to regional surface uplift. We constrain fault slip-rates since ~18 ka using variations in cosmogenic 36 Cl measured on bedrock scarps, mapped using LiDAR and ground penetrating radar, and compare these rates to those inferred from geodesy. The 36 Cl data reveal that individual faults typically accumulate meters of displacement relatively rapidly over several thousand years, separated by similar length time intervals when slip-rates are much lower, and activity shifts between faults across strike. Our rates agree with continuum deformation rates when averaged over long spatial or temporal scales (10 4  yr; 10 2  km) but over shorter timescales most of the deformation may be accommodated by <30% of the across-strike fault array. We attribute the shifts in activity to temporal variations in the mechanical work of faulting.

Assessing active faulting by hydrogeological modeling and superconducting gravimetry: A case study for Hsinchu Fault, Taiwan

NASA Astrophysics Data System (ADS)

Lien, Tzuyi; Cheng, Ching-Chung; Hwang, Cheinway; Crossley, David

2014-09-01

We develop a new hydrology and gravimetry-based method to assess whether or not a local fault may be active. We take advantage of an existing superconducting gravimeter (SG) station and a comprehensive groundwater network in Hsinchu to apply the method to the Hsinchu Fault (HF) across the Hsinchu Science Park, whose industrial output accounts for 10% of Taiwan's gross domestic product. The HF is suspected to pose seismic hazards to the park, but its existence and structure are not clear. The a priori geometry of the HF is translated into boundary conditions imposed in the hydrodynamic model. By varying the fault's location, depth, and including a secondary wrench fault, we construct five hydrodynamic models to estimate groundwater variations, which are evaluated by comparing groundwater levels and SG observations. The results reveal that the HF contains a low hydraulic conductivity core and significantly impacts groundwater flows in the aquifers. Imposing the fault boundary conditions leads to about 63-77% reduction in the differences between modeled and observed values (both water level and gravity). The test with fault depth shows that the HF's most recent slip occurred in the beginning of Holocene, supplying a necessary (but not sufficient) condition that the HF is currently active. A portable SG can act as a virtual borehole well for model assessment at critical locations of a suspected active fault.

Dating previously balanced rocks in seismically active parts of California and Nevada

USGS Publications Warehouse

Bell, J.W.; Brune, J.N.; Liu, T.; Zreda, M.; Yount, J.C.

1998-01-01

Precariously balanced boulders that could be knocked down by strong earthquake ground motion are found in some seismically active areas of southern California and Nevada. In this study we used two independent surface-exposure dating techniques - rock-varnish microlamination and cosmogenic 36Cl dating methodologies - to estimate minimum- and maximum-limiting ages, respectively, of the precarious boulders and by inference the elapsed time since the sites were shaken down. The results of the exposure dating indicate that all of the precarious rocks are >10.5 ka and that some may be significantly older. At Victorville and Jacumba, California, these results show that the precarious rocks have not been knocked down for at least 10.5 k.y., a conclusion in apparent conflict with some commonly used probabilistic seismic hazard maps. At Yucca Mountain, Nevada, the ages of the precarious rocks are >10.5 to >27.0 ka, providing an independent measure of the minimum time elapsed since faulting occurred on the Solitario Canyon fault.

Fault-related clay authigenesis along the Moab Fault: Implications for calculations of fault rock composition and mechanical and hydrologic fault zone properties

USGS Publications Warehouse

Solum, J.G.; Davatzes, N.C.; Lockner, D.A.

2010-01-01

The presence of clays in fault rocks influences both the mechanical and hydrologic properties of clay-bearing faults, and therefore it is critical to understand the origin of clays in fault rocks and their distributions is of great importance for defining fundamental properties of faults in the shallow crust. Field mapping shows that layers of clay gouge and shale smear are common along the Moab Fault, from exposures with throws ranging from 10 to ???1000 m. Elemental analyses of four locations along the Moab Fault show that fault rocks are enriched in clays at R191 and Bartlett Wash, but that this clay enrichment occurred at different times and was associated with different fluids. Fault rocks at Corral and Courthouse Canyons show little difference in elemental composition from adjacent protolith, suggesting that formation of fault rocks at those locations is governed by mechanical processes. Friction tests show that these authigenic clays result in fault zone weakening, and potentially influence the style of failure along the fault (seismogenic vs. aseismic) and potentially influence the amount of fluid loss associated with coseismic dilation. Scanning electron microscopy shows that authigenesis promotes that continuity of slip surfaces, thereby enhancing seal capacity. The occurrence of the authigenesis, and its influence on the sealing properties of faults, highlights the importance of determining the processes that control this phenomenon. ?? 2010 Elsevier Ltd.

A study of microseismicity in northern Baja California, Mexico

NASA Technical Reports Server (NTRS)

Johnson, T. L.; Koczynski, T.; Madrid, J.

1976-01-01

Five microearthquake instruments were operated for 2 months in 1974 in a small mobile array deployed at various sites near the Agua Blanca and San Miguel faults. An 80-km-long section of the San Miguel fault zone is presently active seismically, producing the vast majority of recorded earthquakes. Very low activity was recorded on the Agua Blanca fault. Events were also located near normal faults forming the eastern edge of the Sierra Juarez suggesting that these faults are active. Hypocenters on the San Miguel fault range in depth from 0 to 20 km although two-thirds are in the upper 10 km. A composite focal mechanism showing a mixture of right-lateral and dip slip, east side up, is similar to a solution obtained for the 1956 San Miguel earthquake which proved consistent with observed surface deformation.

The temporal and spatial distribution of upper crustal faulting and magmatism in the south Lake Turkana rift, East Africa

NASA Astrophysics Data System (ADS)

Muirhead, J.; Scholz, C. A.

2017-12-01

During continental breakup extension is accommodated in the upper crust largely through dike intrusion and normal faulting. The Eastern branch of the East African Rift arguably represents the premier example of active continental breakup in the presence magma. Constraining how faulting is distributed in both time and space in these regions is challenging, yet can elucidate how extensional strain localizes within basins as rifting progresses to sea-floor spreading. Studies of active rifts, such as the Turkana Rift, reveal important links between faulting and active magmatic processes. We utilized over 1100 km of high-resolution Compressed High Intensity Radar Pulse (CHIRP) 2D seismic reflection data, integrated with a suite of radiocarbon-dated sediment cores (3 in total), to constrain a 17,000 year history of fault activity in south Lake Turkana. Here, a set of N-S-striking intra-rift faults exhibit time-averaged slip-rates as high as 1.6 mm/yr, with the highest slip-rates occurring along faults within 3 km of the rift axis. Results show that strain has localized into a zone of intra-rift faults along the rift axis, forming an approximately 20 km-wide graben in central parts of the basin. Subsurface structural mapping and fault throw profile analyses reveal increasing basin subsidence and fault-related strain as this faulted graben approaches a volcanic island in the center of the basin (South Island). The long-axis of this island trends north-south, and it contains a number of elongate cones that support recent emplacement of N-S-striking dike intrusions, which parallel recently active intra-rift faults. Overall, these observations suggest strain localization into intra-rift faults in the rift center is likely a product of both volcanic loading and the mechanical and thermal effects of diking along the rift axis. These results support the establishment of magmatic segmentation in southern Lake Turkana, and highlight the importance of magmatism for focusing upper crustal strain as rifts evolve to sea-floor spreading.

Sandstone-filled normal faults: A case study from central California

NASA Astrophysics Data System (ADS)

Palladino, Giuseppe; Alsop, G. Ian; Grippa, Antonio; Zvirtes, Gustavo; Phillip, Ruy Paulo; Hurst, Andrew

2018-05-01

Despite the potential of sandstone-filled normal faults to significantly influence fluid transmissivity within reservoirs and the shallow crust, they have to date been largely overlooked. Fluidized sand, forcefully intruded along normal fault zones, markedly enhances the transmissivity of faults and, in general, the connectivity between otherwise unconnected reservoirs. Here, we provide a detailed outcrop description and interpretation of sandstone-filled normal faults from different stratigraphic units in central California. Such faults commonly show limited fault throw, cm to dm wide apertures, poorly-developed fault zones and full or partial sand infill. Based on these features and inferences regarding their origin, we propose a general classification that defines two main types of sandstone-filled normal faults. Type 1 form as a consequence of the hydraulic failure of the host strata above a poorly-consolidated sandstone following a significant, rapid increase of pore fluid over-pressure. Type 2 sandstone-filled normal faults form as a result of regional tectonic deformation. These structures may play a significant role in the connectivity of siliciclastic reservoirs, and may therefore be crucial not just for investigation of basin evolution but also in hydrocarbon exploration.

Subsurface geometry and evolution of the Seattle fault zone and the Seattle Basin, Washington

USGS Publications Warehouse

ten Brink, Uri S.; Molzer, P.C.; Fisher, M.A.; Blakely, R.J.; Bucknam, R.C.; Parsons, T.; Crosson, R.S.; Creager, K.C.

2002-01-01

The Seattle fault, a large, seismically active, east-west-striking fault zone under Seattle, is the best-studied fault within the tectonically active Puget Lowland in western Washington, yet its subsurface geometry and evolution are not well constrained. We combine several analysis and modeling approaches to study the fault geometry and evolution, including depth-converted, deep-seismic-reflection images, P-wave-velocity field, gravity data, elastic modeling of shoreline uplift from a late Holocene earthquake, and kinematic fault restoration. We propose that the Seattle thrust or reverse fault is accompanied by a shallow, antithetic reverse fault that emerges south of the main fault. The wedge enclosed by the two faults is subject to an enhanced uplift, as indicated by the boxcar shape of the shoreline uplift from the last major earthquake on the fault zone. The Seattle Basin is interpreted as a flexural basin at the footwall of the Seattle fault zone. Basin stratigraphy and the regional tectonic history lead us to suggest that the Seattle fault zone initiated as a reverse fault during the middle Miocene, concurrently with changes in the regional stress field, to absorb some of the north-south shortening of the Cascadia forearc. Kingston Arch, 30 km north of the Seattle fault zone, is interpreted as a more recent disruption arising within the basin, probably due to the development of a blind reverse fault.

Active tectonics and strain partitioning along dextral fault system in Central Iran: Analysis of geomorphological observations and geophysical data in the Kashan region

NASA Astrophysics Data System (ADS)

Jamali, Farshad; Hessami, Khaled; Ghorashi, Manoochehr

2011-03-01

This paper uses high-resolution images and field investigations, in conjunction with seismic reflection data, to constrain active structural deformation in the Kashan region of Central Iran. Offset stream beds and Qanats indicate right-lateral strike slip motion at a rate of about 2 mm/yr along the NW-SE trending Qom-Zefreh fault zone which has long been recognized as one of the major faults in Central Iran. However, the pattern of drainage systems across the active growing folds including deep incision of stream beds and deflected streams indicate uplift at depth on thrust faults dipping SW beneath the anticlines. Therefore, our studies in the Kashan region indicate that deformation occurs within Central Iran which is often considered to behave as a non-deforming block within the Arabia-Eurasia collision zone. The fact that the active Qom-Zefreh strike-slip fault runs parallel to the active folds, which overlie blind thrust faults, suggests that oblique motion of Arabia with respect to Eurasia is partitioned in this part of Central Iran.

Topographic expression of active faults in the foothills of the Northern Apennines

NASA Astrophysics Data System (ADS)

Picotti, Vincenzo; Ponza, Alessio; Pazzaglia, Frank J.

2009-09-01

Active faults that rupture the earth's surface leave an imprint on the topography that is recognized using a combination of geomorphic and geologic metrics including triangular facets, the shape of mountain fronts, the drainage network, and incised river valleys with inset terraces. We document the presence of a network of active, high-angle extensional faults, collectively embedded in the actively shortening mountain front of the Northern Apennines, that possess unique geomorphic expressions. We measure the strain rate for these structures and find that they have a constant throw-to-length ratio. We demonstrate the necessary and sufficient conditions for triangular facet development in the footwalls of these faults and argue that rock-type exerts the strongest control. The slip rates of these faults range from 0.1 to 0.3 mm/yr, which is similar to the average rate of river incision and mountain front unroofing determined by corollary studies. The faults are a near-surface manifestation of deeper crustal processes that are actively uplifting rocks and growing topography at a rate commensurate with surface processes that are eroding the mountain front to base level.

A shallow fault-zone structure illuminated by trapped waves in the Karadere-Duzce branch of the North Anatolian Fault, western Turkey

USGS Publications Warehouse

Ben-Zion, Y.; Peng, Z.; Okaya, D.; Seeber, L.; Armbruster, J.G.; Ozer, N.; Michael, A.J.; Baris, S.; Aktar, M.

2003-01-01

We discuss the subsurface structure of the Karadere-Duzce branch of the North Anatolian Fault based on analysis of a large seismic data set recorded by a local PASSCAL network in the 6 months following the Mw = 7.4 1999 Izmit earthquake. Seismograms observed at stations located in the immediate vicinity of the rupture zone show motion amplification and long-period oscillations in both P- and S-wave trains that do not exist in nearby off-fault stations. Examination of thousands of waveforms reveals that these characteristics are commonly generated by events that are well outside the fault zone. The anomalous features in fault-zone seismograms produced by events not necessarily in the fault may be referred to generally as fault-zone-related site effects. The oscillatory shear wave trains after the direct S arrival in these seismograms are analysed as trapped waves propagating in a low-velocity fault-zone layer. The time difference between the S arrival and trapped waves group does not grow systematically with increasing source-receiver separation along the fault. These observations imply that the trapping of seismic energy in the Karadere-Duzce rupture zone is generated by a shallow fault-zone layer. Traveltime analysis and synthetic waveform modelling indicate that the depth of the trapping structure is approximately 3-4 km. The synthetic waveform modelling indicates further that the shallow trapping structure has effective waveguide properties consisting of thickness of the order of 100 m, a velocity decrease relative to the surrounding rock of approximately 50 per cent and an S-wave quality factor of 10-15. The results are supported by large 2-D and 3-D parameter space studies and are compatible with recent analyses of trapped waves in a number of other faults and rupture zones. The inferred shallow trapping structure is likely to be a common structural element of fault zones and may correspond to the top part of a flower-type structure. The motion amplification associated with fault-zone-related site effects increases the seismic shaking hazard near fault-zone structures. The effect may be significant since the volume of sources capable of generating motion amplification in shallow trapping structures is large.

Right-lateral shear across Iran and kinematic change in the Arabia-Eurasia collision zone

NASA Astrophysics Data System (ADS)

Allen, M. B.; Kheirkhah, M.; Emami, M.

2009-04-01

New offset determinations for right-lateral strike-slip faults in Iran redefine the kinematics of the Arabia-Eurasia collision. A series of right-lateral strike-slip faults is present across Iran between 48° and 57° E. Fault strikes vary between NW-SE and NNW-SSE. Individual faults west of ~53° E were active in the late Tertiary, but have limited evidence of activity. Faults east of ~53° E are seismically active and/or have geomorphic evidence for Holocene slip. None of the faults affects the GPS-derived regional velocity field, indicating active slip rates are ≤2 mm/yr. We estimate overall slip on these faults from offset geological and geomorphic markers, based on observations from satellite imagery, digital topography, geology maps and our own fieldwork observations, and combine these results with published estimates for fault slip in the east of the study area. Total offset of the Takab, Soltanieh, Indes, Bid Hand, Qom, Kashan, Deh Shir, Anar, Daviran, Kuh Banan and Dehu faults is at least 270 km and possibly higher. Other faults (e.g. Rafsanjan) have unknown amounts of right-lateral slip. Collectively, these faults are inferred to have accommodated part of the Arabia-Eurasia convergence by two mechanisms: (1) anti-clockwise, vertical axis rotations; (2) strain partitioning with coeval NE-SW crustal thickening in the Turkish-Iranian plateau to produce ~350 km of north-south plate convergence. The strike-slip faulting across Iran requires along-strike lengthening of the deformation zone. This was possible until the Pliocene, when the Afghan crust collided with the western margin of the Indian plate, thereby sealing off a free face at the eastern side of the Arabia-Eurasia collision zone. Continuing Arabia-Eurasia plate convergence had to be accommodated in new ways and new areas, leading to the present pattern of faulting from eastern Iran to western Turkey.

Combined Application of Shallow Seismic Reflection and High-resolution Refraction Exploration Approach to Active Fault Survey, Central Orogenic Belt, China

NASA Astrophysics Data System (ADS)

Lin, S.; Luo, D.; Yanlin, F.; Li, Y.

2016-12-01

Shallow Seismic Reflection (SSR) is a major geophysical exploration method with its exploration depth range, high-resolution in urban active fault exploration. In this paper, we carried out (SSR) and High-resolution refraction (HRR) test in the Liangyun Basin to explore a buried fault. We used NZ distributed 64 channel seismic instrument, 60HZ high sensitivity detector, Geode multi-channel portable acquisition system and hammer source. We selected single side hammer hit multiple overlay, 48 channels received and 12 times of coverage. As there are some coincidence measuring lines of SSR and HRR, we chose multi chase and encounter observation system. Based on the satellite positioning, we arranged 11 survey lines in our study area with total length for 8132 meters. GEOGIGA seismic reflection data processing software was used to deal with the SSR data. After repeated tests from the aspects of single shot record compilation, interference wave pressing, static correction, velocity parameter extraction, dynamic correction, eventually got the shallow seismic reflection profile images. Meanwhile, we used Canadian technology company good refraction and tomographic imaging software to deal with HRR seismic data, which is based on nonlinear first arrival wave travel time tomography. Combined with drilling geological profiles, we explained 11 measured seismic profiles. Results show 18 obvious fault feature breakpoints, including 4 normal faults of south-west, 7 reverse faults of south-west, one normal fault of north-east and 6 reverse faults of north-east. Breakpoints buried depth is 15-18 meters, and the inferred fault distance is 3-12 meters. Comprehensive analysis shows that the fault property is reverse fault with northeast incline section, and fewer branch normal faults presenting southwest incline section. Since good corresponding relationship between the seismic interpretation results, drilling data and SEM results on the property, occurrence, broken length of the fault, we considered the Liangyun fault to be an active fault which has strong activity during the Neogene Pliocene and early Pleistocene, Middle Pleistocene period. The combined application of SSR and HRR can provide more parameters to explain the seismic results, and improve the accuracy of the interpretation.

Characterizing the structural maturity of fault zones using high-resolution earthquake locations.

NASA Astrophysics Data System (ADS)

Perrin, C.; Waldhauser, F.; Scholz, C. H.

2017-12-01

We use high-resolution earthquake locations to characterize the three-dimensional structure of active faults in California and how it evolves with fault structural maturity. We investigate the distribution of aftershocks of several recent large earthquakes that occurred on immature faults (i.e., slow moving and small cumulative displacement), such as the 1992 (Mw7.3) Landers and 1999 (Mw7.1) Hector Mine events, and earthquakes that occurred on mature faults, such as the 1984 (Mw6.2) Morgan Hill and 2004 (Mw6.0) Parkfield events. Unlike previous studies which typically estimated the width of fault zones from the distribution of earthquakes perpendicular to the surface fault trace, we resolve fault zone widths with respect to the 3D fault surface estimated from principal component analysis of local seismicity. We find that the zone of brittle deformation around the fault core is narrower along mature faults compared to immature faults. We observe a rapid fall off of the number of events at a distance range of 70 - 100 m from the main fault surface of mature faults (140-200 m fault zone width), and 200-300 m from the fault surface of immature faults (400-600 m fault zone width). These observations are in good agreement with fault zone widths estimated from guided waves trapped in low velocity damage zones. The total width of the active zone of deformation surrounding the main fault plane reach 1.2 km and 2-4 km for mature and immature faults, respectively. The wider zone of deformation presumably reflects the increased heterogeneity in the stress field along complex and discontinuous faults strands that make up immature faults. In contrast, narrower deformation zones tend to align with well-defined fault planes of mature faults where most of the deformation is concentrated. Our results are in line with previous studies suggesting that surface fault traces become smoother, and thus fault zones simpler, as cumulative fault slip increases.

Foreshocks, aftershocks, and earthquake probabilities: Accounting for the landers earthquake

USGS Publications Warehouse

Jones, Lucile M.

1994-01-01

The equation to determine the probability that an earthquake occurring near a major fault will be a foreshock to a mainshock on that fault is modified to include the case of aftershocks to a previous earthquake occurring near the fault. The addition of aftershocks to the background seismicity makes its less probable that an earthquake will be a foreshock, because nonforeshocks have become more common. As the aftershocks decay with time, the probability that an earthquake will be a foreshock increases. However, fault interactions between the first mainshock and the major fault can increase the long-term probability of a characteristic earthquake on that fault, which will, in turn, increase the probability that an event is a foreshock, compensating for the decrease caused by the aftershocks.

Investigation of late Pleistocene and Holocene activity in the San Gregorio fault zone on the continental slope north of Monterey Canyon, offshore central California

USGS Publications Warehouse

Maier, Katherine L.; Paull, Charles K.; Brothers, Daniel; Caress, David W.; McGann, Mary; Lundsten, Eve M.; Anderson, Krystle; Gwiazda, Roberto

2017-01-01

We provide an extensive high‐resolution geophysical, sediment core, and radiocarbon dataset to address late Pleistocene and Holocene fault activity of the San Gregorio fault zone (SGFZ), offshore central California. The SGFZ occurs primarily offshore in the San Andreas fault system and has been accommodating dextral strike‐slip motion between the Pacific and North American plates since the mid‐Miocene. Our study focuses on the SGFZ where it has been mapped through the continental slope north of Monterey Canyon. From 2009 to 2015, the Monterey Bay Aquarium Research Institute collected high‐resolution multibeam bathymetry and chirp sub‐bottom profiles using an autonomous underwater vehicle (AUV). Targeted samples were collected using a remotely operated vehicle (ROV) to provide radiocarbon age constraints. We integrate the high‐resolution geophysical data with radiocarbon dates to reveal Pleistocene seismic horizons vertically offset less than 5 m on nearly vertical faults. These faults are buried by continuous reflections deposited after ∼17.5  ka and likely following erosion during the last sea‐level lowstand ∼21  ka, bracketing the age of faulting to ∼32–21  ka. Clearly faulted horizons are only detected in a small area where mass wasting exhumed older strata to within ∼25  m of the seafloor. The lack of clearly faulted Holocene deposits and possible highly distributed faulting in the study area are consistent with previous interpretations that late Pleistocene and Holocene activity along the SGFZ may decrease to the south. This study illustrates the complexity of the SGFZ, offshore central California, and demonstrates the utility of very high‐resolution data from combined AUV (geophysical)–ROV (seabed sampling) surveys in offshore studies of fault activity.

Evidence for a complex archean deformational history; southwestern Michipicoten Greenstone Belt, Ontario

NASA Technical Reports Server (NTRS)

Mcgill, George E.; Shrady, Catherine H.

1986-01-01

The Michipicoten Greenstone Belt extends for about 150 km ENE from the northeastern angle of Lake Superior. In common with many other Archean greenstone belts, it is characterized by generally steep bedding dips and a distribution of major lithologic types suggesting a crudely synclinal structure for the belt as a whole. Detailed mapping and determination of structural sequence demonstrates that the structure is much more complex. The Archean history of the belt includes formation of at least three regionally significant cleavages, kilometer-scale overturning, extensive shearing, and diabase intrusion. Most well defined, mappable 'packages' of sedimentary rocks appear to be bounded by faults. These faults were active relatively early in the structural history of the belt, when extensive overturning also occurred. Steepening of dips, NW-SE shortening, development of steep NE cleavage, and pervasive shearing all postdate the early faulting and the regional overturning, obscuring much of the detail needed to define the geometry of the earlier structures. The results obtained so far suggest, however, that the Michipicoten Greenstone Belt underwent an early stage of thrusting and associated isoclinal folding, probably in a convergent tectonic environment.

Kinematic Evolution of the North-Tehran Fault (NTF), Alborz Mountains, Iran

NASA Astrophysics Data System (ADS)

Landgraf, A.; Ballato, P.; Strecker, M. R.; Shahpasandzadeh, M.; Friedrich, A.; Tabatabaei, S. H.

2007-12-01

The ENE-to NW-striking NTF is an active frontal thrust that delimits the Alborz Mountain range to the south with an up to 2000 m topographic break with respect to the adjacent Tehran plain. Eocene rocks of the Alborz range are thrusted over Neogene and Quaternary sediments of the alluvial Tehran embayment. The fault consists of right- stepping segments and merges to the east with the active Mosha-Fasham strike-slip fault (MFF). The complex tectonic history, involving changes in the direction of SHmax, has resulted in a composite tectonic landscape with inherited topographic and fault-kinematic fingerprints along the NTF. We therefore used a combination of fault-kinematic measurements and geomorphic observations to unravel the temporal tectonic evolution of this fault. Presently, the NTF is virtually inactive, although the tectonically overprinted landforms reflect tectonic activity on longer time scales during the Quaternary. Being located adjacent north of the Tehran megacity, there is thus considerable interest to decipher its youngest tectonic evolution and to better understand the relation with other fault systems. Our fault kinematic study has revealed an early dextral kinematic history for the NTF. Dextral strike-slip and oblique reverse faulting took place during NW-oriented shortening. The overall fault-geometry of the NTF suggests that it has evolved in relation to dextral transpression along the MFF. This early kinematic regime was superseded by NE-oriented shortening, associated with sinistral-oblique thrusting along the fault segments. Fault linkage between the semi-independent ENE-striking NTF-segments and NW-striking thrusts (Emamzadeh Davud Fault [EDF], Purkan Vardij Thrust [PVT], NTF-prolongation) point towards an evolution into a nascent transpressional duplex. In this scenario the NTF segments constitute lateral ramps and the NW-striking faults act as frontal ramps. Topographic residuals, as an expression of high-uplift zones, indicate that the central segment of the NTF, incorporating the EDF was most effective in accommodating oblique convergence during this time. However, subtle knickpoints in the longitudinal river profiles crossing the PVT may indicate a relatively recent transfer of deformation onto this block. The youngest manifestations of deformation along the NTF, however, are left-lateral and normal faulting. This youngest phase of activity is documented by numerous striated and rotated conglomeratic clasts, meter-scale fault gouge zones with shear-sense indicators of oblique normal faulting, and multiple colluvial wedges with drag phenomena. Rupture traces and filled extensional cracks reaching the surface also document the seismogenic nature of these features. Since recent left-lateral transtension is also known from neighboring faults, e.g., the eastern MFF, our observations suggest that this youngest phase of tectonic activity of the NTF is a regional phenomenon, rather than the result of locally-determined geometries.

The Gabbs Valley, Nevada, geothermal prospect: Exploring for a potential blind geothermal resource

NASA Astrophysics Data System (ADS)

Payne, J.; Bell, J. W.; Calvin, W. M.

2012-12-01

The Gabbs Valley prospect in west-central Nevada is a potential blind geothermal resource system. Possible structural controls on this system were investigated using high-resolution LiDAR, low sun-angle aerial (LSA) photography, exploratory fault trenching and a shallow temperature survey. Active Holocene faults have previously been identified at 37 geothermal systems with indication of temperatures greater than 100° C in the western Nevada region. Active fault controls in Gabbs Valley include both Holocene and historical structures. Two historical earthquakes occurring in 1932 and 1954 have overlapping surface rupture patterns in Gabbs Valley. Three active fault systems identified through LSA and LiDAR mapping have characteristics of Basin and Range normal faulting and Walker Lane oblique dextral faulting. The East Monte Cristo Mountains fault zone is an 8.5 km long continuous NNE striking, discrete fault with roughly 0.5 m right-normal historic motion and 3 m vertical Quaternary separation. The Phillips Wash fault zone is an 8.2 km long distributed fault system striking NE to N, with Quaternary fault scarps of 1-3 m vertical separation and a 500 m wide graben adjacent to the Cobble Cuesta anticline. This fault displays ponded drainages, an offset terrace riser and right stepping en echelon fault patterns suggestive of left lateral offset, and fault trenching exposed non-matching stratigraphy typical of a significant component of lateral offset. The unnamed faults of Gabbs Valley are a 10.6 km long system of normal faults striking NNE and Quaternary scarps are up to 4 m high. These normal faults largely do not have historic surface rupture, but a small segment of 1932 rupture has been identified. A shallow (2 m deep) temperature survey of 80 points covering roughly 65 square kilometers was completed. Data were collected over approximately 2 months, and continual base station temperature measurements were used to seasonally correct temperature measurements. A 2.5 km long temperature anomaly greater than 3° C above background temperatures forms west-northwest trending zone between terminations of the Phillips Wash fault zone and unnamed faults of Gabbs Valley to the south. Rupture segments of two young active faults bracket the temperature anomaly. The temperature anomaly may be due to several possible causes. 1. Increases in stress near the rupture segments or tip-lines of these faults, or where multiple fault splays exist, can increase fault permeability. The un-ruptured segments of these faults may be controlling the location of the Gabbs Valley thermal anomaly between ruptured segments of the 1932 Cedar Mountain and 1954 Fairview Peak earthquakes. 2. Numerous unnamed normal faults may interact and the hanging wall of these faults is hosting the thermal anomaly. The size and extent of the anomaly may be due to its proximity to a flat playa and not the direct location of the shallow heat anomaly. 3. The linear northwest nature of the thermal anomaly may reflect a hydrologic barrier in the subsurface controlling where heated fluids rise. A concealed NW- striking fault is possible, but has not been identified in previous studies or in the LiDAR or LSA fault mapping.

The West Beverly Hills Lineament and Beverly Hills High School: Ethical Issues in Geo-Hazard Communication

NASA Astrophysics Data System (ADS)

Gath, Eldon; Gonzalez, Tania; Roe, Joe; Buchiarelli, Philip; Kenny, Miles

2014-05-01

Results of geotechnical studies for the Westside Subway were disclosed in a public hearing on Oct. 19, 2011, showing new "active faults" of the Santa Monica fault and the West Beverly Hills Lineament (WBHL), identified as a northern extension of the Newport-Inglewood fault. Presentations made spoke of the danger posed by these faults, the possibility of killing people, and how it was good news that these faults had been discovered now instead of later. The presentations were live and are now memorialized as YouTube videos, (http://www.youtube.com/watch?v=Omx2BTIpzAk and others). No faults had been physically exposed or observed by the study; the faults were all interpreted from cone penetrometer probes, supplemented by core borings and geophysical transects. Several of the WBHL faults traversed buildings of the Beverly Hills High School (BHHS), triggering the school district to geologically map and characterize these faults for future planning efforts, and to quantify risk to the students in the 1920's high school building. 5 exploratory trenches were excavated within the high school property, 12 cone penetrometers were pushed, and 26-cored borings were drilled. Geologic logging of the trenches and borings and interpretation of the CPT data failed to confirm the presence of the mapped WBHL faults, instead showing an unfaulted, 3° NE dipping sequence of mid-Pleistocene alluvial fan deposits conformably overlying an ~1 Ma marine sand. Using 14C, OSL, and soil pedology for stratigraphic dating, the BHHS site was cleared from fault rupture hazards and the WBHL was shown to be an erosional margin of Benedict Canyon, partially buttressed by 40-200 ka alluvial deposits from Benedict Wash. The consequence of the Westside Subway's active fault maps has been the unexpected expenditure of millions of dollars for emergency fault investigations at BHHS and several other private properties within a densely developed urban highrise environment. None of these studies have found any active faults where they had been interpreted, mapped, and published by the subway's consultants. Litigation is underway by the affected parties to recoup their geological expenditures and recover costs for lost business revenues. Even had the active fault map been correct, its public release was poorly managed. That the released active fault map has now been found to be badly in error poses more significant ethical issues about hazard communication and likely legal consequences.

Shallow subsurface imaging of the Piano di Pezza active normal fault (central Italy) by high-resolution refraction and electrical resistivity tomography coupled with time-domain electromagnetic data

NASA Astrophysics Data System (ADS)

Villani, Fabio; Tulliani, Valerio; Sapia, Vincenzo; Fierro, Elisa; Civico, Riccardo; Pantosti, Daniela

2015-12-01

The Piano di Pezza fault is the central section of the 35 km long L'Aquila-Celano active normal fault-system in the central Apennines of Italy. Although palaeoseismic data document high Holocene vertical slip rates (˜1 mm yr-1) and a remarkable seismogenic potential of this fault, its subsurface setting and Pleistocene cumulative displacement are still poorly known. We investigated for the first time the shallow subsurface of a key section of the main Piano di Pezza fault splay by means of high-resolution seismic and electrical resistivity tomography coupled with time-domain electromagnetic soundings (TDEM). Our surveys cross a ˜5-m-high fault scarp that was generated by repeated surface-rupturing earthquakes displacing Holocene alluvial fans. We provide 2-D Vp and resistivity images, which show significant details of the fault structure and the geometry of the shallow basin infill material down to 50 m depth. Our data indicate that the upper fault termination has a sub-vertical attitude, in agreement with palaeoseismological trench evidence, whereas it dips ˜50° to the southwest in the deeper part. We recognize some low-velocity/low-resistivity regions in the fault hangingwall that we relate to packages of colluvial wedges derived from scarp degradation, which may represent the record of some Holocene palaeo-earthquakes. We estimate a ˜13-15 m throw of this fault splay since the end of the Last Glacial Maximum (˜18 ka), leading to a 0.7-0.8 mm yr-1 throw rate that is quite in accordance with previous palaeoseismic estimation of Holocene vertical slip rates. The 1-D resistivity models from TDEM soundings collected along the trace of the electrical profile significantly match with 2-D resistivity images. Moreover, they indicate that in the fault hangingwall, ˜200 m away from the surface fault trace, the pre-Quaternary carbonate basement is at ˜90-100 m depth. We therefore provide a minimal ˜150-160 m estimate of the cumulative throw of the Piano di Pezza fault system in the investigated section. We further hypothesize that the onset of the Piano di Pezza fault activity may date back to the Middle Pleistocene (˜0.5 Ma), so this is a quite young active normal fault if compared to other mature normal fault systems active since 2-3 Ma in this portion of the central Apennines.

Insurance Applications of Active Fault Maps Showing Epistemic Uncertainty

NASA Astrophysics Data System (ADS)

Woo, G.

2005-12-01

Insurance loss modeling for earthquakes utilizes available maps of active faulting produced by geoscientists. All such maps are subject to uncertainty, arising from lack of knowledge of fault geometry and rupture history. Field work to undertake geological fault investigations drains human and monetary resources, and this inevitably limits the resolution of fault parameters. Some areas are more accessible than others; some may be of greater social or economic importance than others; some areas may be investigated more rapidly or diligently than others; or funding restrictions may have curtailed the extent of the fault mapping program. In contrast with the aleatory uncertainty associated with the inherent variability in the dynamics of earthquake fault rupture, uncertainty associated with lack of knowledge of fault geometry and rupture history is epistemic. The extent of this epistemic uncertainty may vary substantially from one regional or national fault map to another. However aware the local cartographer may be, this uncertainty is generally not conveyed in detail to the international map user. For example, an area may be left blank for a variety of reasons, ranging from lack of sufficient investigation of a fault to lack of convincing evidence of activity. Epistemic uncertainty in fault parameters is of concern in any probabilistic assessment of seismic hazard, not least in insurance earthquake risk applications. A logic-tree framework is appropriate for incorporating epistemic uncertainty. Some insurance contracts cover specific high-value properties or transport infrastructure, and therefore are extremely sensitive to the geometry of active faulting. Alternative Risk Transfer (ART) to the capital markets may also be considered. In order for such insurance or ART contracts to be properly priced, uncertainty should be taken into account. Accordingly, an estimate is needed for the likelihood of surface rupture capable of causing severe damage. Especially where a high deductible is in force, this requires estimation of the epistemic uncertainty on fault geometry and activity. Transport infrastructure insurance is of practical interest in seismic countries. On the North Anatolian Fault in Turkey, there is uncertainty over an unbroken segment between the eastern end of the Dazce Fault and Bolu. This may have ruptured during the 1944 earthquake. Existing hazard maps may simply use a question mark to flag uncertainty. However, a far more informative type of hazard map might express spatial variations in the confidence level associated with a fault map. Through such visual guidance, an insurance risk analyst would be better placed to price earthquake cover, allowing for epistemic uncertainty.

Transfer fault earthquake in compressionally reactivated back-arc failed rift: 1948 Fukui earthquake (M7.1), Japan

NASA Astrophysics Data System (ADS)

Ishiyama, Tatsuya; Kato, Naoko; Sato, Hiroshi; Koshiya, Shin

2017-04-01

Back-arc rift structures in many subduction zones are recognized as mechanically and thermally weak zones that possibly play important roles in strain accommodation at later post-rift stages within the overriding plates. In case of Miocene back-arc failed rift structures in the Sea of Japan in the Eurasian-Pacific subduction system, the mechanical contrasts between the crustal thrust wedges of the pre-rift continental crust and high velocity lower crust have fundamentally controlled the styles of post-rift, Quaternary active deformation (Ishiyama et al. 2016). In this study, we show a possibility that strike-slip M>7 devastating earthquakes in this region have been gregion enerated by reactivation of transfer faults highly oblique to the rift axes. The 1948 Fukui earthquake (M7.1), onshore shallow seismic event with a strike-slip faulting mechanism (Kanamori, 1973), resulted in more than 3,500 causalities and destructive damages on the infrastructures. While geophysical analyses on geodetic measurements based on leveling and triangulation networks clearly show coseismic left-lateral fault slip on a NNW striking vertical fault plane beneath the Fukui plain (Sagiya, 1999), no evidence for coseismic surface rupture has been identified based on both post-earthquake intensive fieldwork and recent reexamination of stereopair interpretations using 1/3,000 aerial photographs taken in 1948 (Togo et al., 2000). To find recognizable fault-related structures that deform Neogene basin fill sediments, we collected new 9.6-km-long high-resolution seismic reflection data across the geodetically estimated fault plane and adjacent subparallel active strike slip faults, using 925 offline recorders and Envirovib truck as a seismic source. A depth-converted section to 1.5 km depth contains discontinuous seismic reflectors correlated to Miocene volcaniclastic deposits and depression of the overlying Plio-Pleistocene sediments above the geodetically determined fault plane. We interpreted these structural features as negative flower structures related to the strike-slip fault activated during the 1948 seismic event. Locations of these strike-slip faults are consistent with Miocene transfer faults that offset syn- and post-rift sediments and underlying crustal wedges, suggesting that reactivation of transfer faults resulted in active strike-slip faulting including the 1948 seismic event. These findings demonstrate that not only rift-related normal faults but also transfer faults have strong structural inheritances and played essential roles on their active reactivation and seismicity during the post-rift stress regime.

Structural and microstructural evolution of fault zones in Cretaceous poorly lithified sandstones of the Rio do Peixe basin, Paraiba, NE Brazil

NASA Astrophysics Data System (ADS)

Balsamo, Fabrizio; Nogueira, Francisco; Storti, Fabrizio; Bezerra, Francisco H. R.; De Carvalho, Bruno R.; André De Souza, Jorge

2017-04-01

In this contribution we describe the structural architecture and microstructural features of fault zones developed in Cretaceous, poorly lithified sandstones of the Rio do Peixe basin, NE Brazil. The Rio do Peixe basin is an E-W-trending, intracontinental half-graben basin developed along the Precambrian Patos shear zone where it is abutted by the Porto Alegre shear zone. The basin formed during rifting between South America and Africa plates and was reactivated and inverted in a strike-slip setting during the Cenozoic. Sediments filling the basin consist of an heterolithic sequence of alternating sandstones, conglomerates, siltstone and clay-rich layers. These lithologies are generally poorly lithified far from the major fault zones. Deformational structures in the basin mostly consist of deformation band-dominated fault zones. Extensional and strike-slip fault zones, clusters of deformation bands, and single deformation bands are commonly well developed in the proximity of the basin-boundary fault systems. All deformation structures are generally in positive relief with respect to the host rocks. Extensional fault zones locally have growth strata in their hangingwall blocks and have displacement generally <10 m. In map view, they are organized in anastomosed segments with high connectivity. They strike E-W to NE-SW, and typically consist of wide fault cores (< 1 m in width) surrounded by up to few-meter wide damage zones. Fault cores are characterized by distributed deformation without pervasive strain localization in narrow shear bands, in which bedding is transposed into foliation imparted by grain preferred orientation. Microstructural observations show negligible cataclasis and dominant non-destructive particulate flow, suggesting that extensional fault zones developed in soft-sediment conditions in a water-saturated environment. Strike-slip fault zones commonly overprint the extensional ones and have displacement values typically lower than about 2 m. They are arranged in conjugate system consisting of NNW-SSE- and WNW-ESE-trending fault zones with left-lateral and right-lateral kinematics, respectively. Compared to extensional fault zones, strike-slip fault zones have narrow fault cores (few cm thick) and up to 2-3 m-thick damage zones. Microstructural observations indicate that cataclasis with pervasive grain size reduction is the dominant deformation mechanisms within the fault core, thus suggesting that late-stage strike-slip faulting occurred when sandstones were partially lithified by diagenetic processes. Alternatively, the change in deformation mechanisms may indicate faulting at greater depth. Structural and microstructural data suggest that fault zones in the Rio do Peixe basin developed in a progression from "ductile" (sensu Rutter, 1986) to more "brittle" deformation during changes from extensional to strike-slip kinematic fields. Such rheological and stress configuration evolution is expected to impact the petrophysical and permeability structure of fault zones in the study area.

Optimal design and use of retry in fault tolerant real-time computer systems

NASA Technical Reports Server (NTRS)

Lee, Y. H.; Shin, K. G.

1983-01-01

A new method to determin an optimal retry policy and for use in retry of fault characterization is presented. An optimal retry policy for a given fault characteristic, which determines the maximum allowable retry durations to minimize the total task completion time was derived. The combined fault characterization and retry decision, in which the characteristics of fault are estimated simultaneously with the determination of the optimal retry policy were carried out. Two solution approaches were developed, one based on the point estimation and the other on the Bayes sequential decision. The maximum likelihood estimators are used for the first approach, and the backward induction for testing hypotheses in the second approach. Numerical examples in which all the durations associated with faults have monotone hazard functions, e.g., exponential, Weibull and gamma distributions are presented. These are standard distributions commonly used for modeling analysis and faults.

The emergence of asymmetric normal fault systems under symmetric boundary conditions

NASA Astrophysics Data System (ADS)

Schöpfer, Martin P. J.; Childs, Conrad; Manzocchi, Tom; Walsh, John J.; Nicol, Andrew; Grasemann, Bernhard

2017-11-01

Many normal fault systems and, on a smaller scale, fracture boudinage often exhibit asymmetry with one fault dip direction dominating. It is a common belief that the formation of domino and shear band boudinage with a monoclinic symmetry requires a component of layer parallel shearing. Moreover, domains of parallel faults are frequently used to infer the presence of a décollement. Using Distinct Element Method (DEM) modelling we show, that asymmetric fault systems can emerge under symmetric boundary conditions. A statistical analysis of DEM models suggests that the fault dip directions and system polarities can be explained using a random process if the strength contrast between the brittle layer and the surrounding material is high. The models indicate that domino and shear band boudinage are unreliable shear-sense indicators. Moreover, the presence of a décollement should not be inferred on the basis of a domain of parallel faults alone.

Strike-slip faulting in the Inner California Borderlands, offshore Southern California.

NASA Astrophysics Data System (ADS)

Bormann, J. M.; Kent, G. M.; Driscoll, N. W.; Harding, A. J.; Sahakian, V. J.; Holmes, J. J.; Klotsko, S.; Kell, A. M.; Wesnousky, S. G.

2015-12-01

In the Inner California Borderlands (ICB), offshore of Southern California, modern dextral strike-slip faulting overprints a prominent system of basins and ridges formed during plate boundary reorganization 30-15 Ma. Geodetic data indicate faults in the ICB accommodate 6-8 mm/yr of Pacific-North American plate boundary deformation; however, the hazard posed by the ICB faults is poorly understood due to unknown fault geometry and loosely constrained slip rates. We present observations from high-resolution and reprocessed legacy 2D multichannel seismic (MCS) reflection datasets and multibeam bathymetry to constrain the modern fault architecture and tectonic evolution of the ICB. We use a sequence stratigraphy approach to identify discrete episodes of deformation in the MCS data and present the results of our mapping in a regional fault model that distinguishes active faults from relict structures. Significant differences exist between our model of modern ICB deformation and existing models. From east to west, the major active faults are the Newport-Inglewood/Rose Canyon, Palos Verdes, San Diego Trough, and San Clemente fault zones. Localized deformation on the continental slope along the San Mateo, San Onofre, and Carlsbad trends results from geometrical complexities in the dextral fault system. Undeformed early to mid-Pleistocene age sediments onlap and overlie deformation associated with the northern Coronado Bank fault (CBF) and the breakaway zone of the purported Oceanside Blind Thrust. Therefore, we interpret the northern CBF to be inactive, and slip rate estimates based on linkage with the Holocene active Palos Verdes fault are unwarranted. In the western ICB, the San Diego Trough fault (SDTF) and San Clemente fault have robust linear geomorphic expression, which suggests that these faults may accommodate a significant portion of modern ICB slip in a westward temporal migration of slip. The SDTF offsets young sediments between the US/Mexico border and the eastern margin of Avalon Knoll, where the fault is spatially coincident and potentially linked with the San Pedro Basin fault (SPBF). Kinematic linkage between the SDTF and the SPBF increases the potential rupture length for earthquakes on either fault and may allow events nucleating on the SDTF to propagate much closer to the LA Basin.

Influence of the Saros Fault on the Periodicity of Earthquake Activity (Gelibolu Peninsula, NW Turkey)

NASA Astrophysics Data System (ADS)

İpek Gültekin, Derya; Karakoç, Okan; Şahin, Murat; Elitez, İrem; Yaltırak, Cenk

2017-04-01

Active faults are vital in terms of settlement and socio-economic aspects of a region. For this reason, it is important to determine the characteristics and impact areas of active faults correctly. The Marmara region is a tectonically active region located in the northwestern Anatolia. The northern part of the North Anatolian Fault, which was named the Saros Fault, passes through the westernmost part of this region. The Saros Fault is a 52 km-long and NE-SW-trending right-lateral strike-slip fault. In this study, the seismicity of the Gelibolu Peninsula has been examined in the light of historical records. When considering the historical records, 545, 986, 1354 and 1756 earthquakes led to damage on the settlements close to the Saros Fault. The dates of historical earthquakes were calculated by integration of previously published empirical formulas, year difference between events and velocity of GPS vectors. The acceleration map (PGA MAPS) of the region has been produced by taking into account these earthquake magnitudes, fault geometry and geology of the region, and consequently, it was seen that these maps overlap quite well with the damage records of historical earthquakes. Considering the periodicity of the Saros Fault, which majorly controls the seismicity in the region, it is aimed to find an answer to the question "how does a recent earthquake affect the region?" by the help of historical earthquake records and PGA modelling. In conclusion, our data showed that PGA values are dominant in the northern side of the Gelibolu Peninsula and this region may be affected by a magnitude 7.3 earthquake.

Common faults and their impacts for rooftop air conditioners

DOE Office of Scientific and Technical Information (OSTI.GOV)

Breuker, M.S.; Braun, J.E.

This paper identifies important faults and their performance impacts for rooftop air conditioners. The frequencies of occurrence and the relative costs of service for different faults were estimated through analysis of service records. Several of the important and difficult to diagnose refrigeration cycle faults were simulated in the laboratory. Also, the impacts on several performance indices were quantified through transient testing for a range of conditions and fault levels. The transient test results indicated that fault detection and diagnostics could be performed using methods that incorporate steady-state assumptions and models. Furthermore, the fault testing led to a set of genericmore » rules for the impacts of faults on measurements that could be used for fault diagnoses. The average impacts of the faults on cooling capacity and coefficient of performance (COP) were also evaluated. Based upon the results, all of the faults are significant at the levels introduced, and should be detected and diagnosed by an FDD system. The data set obtained during this work was very comprehensive, and was used to design and evaluate the performance of an FDD method that will be reported in a future paper.« less

Active tectonics of the Seattle fault and central Puget sound, Washington - Implications for earthquake hazards

USGS Publications Warehouse

Johnson, S.Y.; Dadisman, S.V.; Childs, J. R.; Stanley, W.D.

1999-01-01

We use an extensive network of marine high-resolution and conventional industry seismic-reflection data to constrain the location, shallow structure, and displacement rates of the Seattle fault zone and crosscutting high-angle faults in the Puget Lowland of western Washington. Analysis of seismic profiles extending 50 km across the Puget Lowland from Lake Washington to Hood Canal indicates that the west-trending Seattle fault comprises a broad (4-6 km) zone of three or more south-dipping reverse faults. Quaternary sediment has been folded and faulted along all faults in the zone but is clearly most pronounced along fault A, the northernmost fault, which forms the boundary between the Seattle uplift and Seattle basin. Analysis of growth strata deposited across fault A indicate minimum Quaternary slip rates of about 0.6 mm/yr. Slip rates across the entire zone are estimated to be 0.7-1.1 mm/yr. The Seattle fault is cut into two main segments by an active, north-trending, high-angle, strike-slip fault zone with cumulative dextral displacement of about 2.4 km. Faults in this zone truncate and warp reflections in Tertiary and Quaternary strata and locally coincide with bathymetric lineaments. Cumulative slip rates on these faults may exceed 0.2 mm/yr. Assuming no other crosscutting faults, this north-trending fault zone divides the Seattle fault into 30-40-km-long western and eastern segments. Although this geometry could limit the area ruptured in some Seattle fault earthquakes, a large event ca. A.D. 900 appears to have involved both segments. Regional seismic-hazard assessments must (1) incorporate new information on fault length, geometry, and displacement rates on the Seattle fault, and (2) consider the hazard presented by the previously unrecognized, north-trending fault zone.

Steep-dip seismic imaging of the shallow San Andreas Fault near Parkfield

USGS Publications Warehouse

Hole, J.A.; Catchings, R.D.; St. Clair, K.C.; Rymer, M.J.; Okaya, D.A.; Carney, B.J.

2001-01-01

Seismic reflection and refraction images illuminate the San Andreas Fault to a depth of 1 kilometer. The prestack depth-migrated reflection image contains near-vertical reflections aligned with the active fault trace. The fault is vertical in the upper 0.5 kilometer, then dips about 70° to the southwest to at least 1 kilometer subsurface. This dip reconciles the difference between the computed locations of earthquakes and the surface fault trace. The seismic velocity cross section shows strong lateral variations. Relatively low velocity (10 to 30%), high electrical conductivity, and low density indicate a 1-kilometer-wide vertical wedge of porous sediment or fractured rock immediately southwest of the active fault trace.

Map and database of Quaternary faults and folds in Colombia and its offshore regions

USGS Publications Warehouse

Paris, Gabriel; Machette, Michael N.; Dart, Richard L.; Haller, Kathleen M.

2000-01-01

As part of the International Lithosphere Program’s “World Map of Major Active Faults,” the U.S. Geological Survey (USGS) is assisting in the compilation of a series of digital maps of Quaternary faults and folds in Western Hemisphere countries. The maps show the locations, ages, and activity rates of major earthquake-related features such as faults and fault-related folds. They are accompanied by databases that describe these features and document current information on their activity in the Quaternary. Top date, the project has published fault and fold maps for Costa Rica (Montero and others, 1998), Panama (Cowan and others, 1998), Venezuela (Audemard and others, 2000), Bolovia/Chile (Lavenu, and others, 2000), and Argentina (Costa and others, 2000). The project is a key part of the Global Seismic Hazards Assessment Program (ILP Project II-0) for the International Decade for Natural Hazard Disaster Reduction.

Software fault-tolerance by design diversity DEDIX: A tool for experiments

NASA Technical Reports Server (NTRS)

Avizienis, A.; Gunningberg, P.; Kelly, J. P. J.; Lyu, R. T.; Strigini, L.; Traverse, P. J.; Tso, K. S.; Voges, U.

1986-01-01

The use of multiple versions of a computer program, independently designed from a common specification, to reduce the effects of an error is discussed. If these versions are designed by independent programming teams, it is expected that a fault in one version will not have the same behavior as any fault in the other versions. Since the errors in the output of the versions are different and uncorrelated, it is possible to run the versions concurrently, cross-check their results at prespecified points, and mask errors. A DEsign DIversity eXperiments (DEDIX) testbed was implemented to study the influence of common mode errors which can result in a failure of the entire system. The layered design of DEDIX and its decision algorithm are described.

Engine Data Interpretation System (EDIS), phase 2

NASA Technical Reports Server (NTRS)

Cost, Thomas L.; Hofmann, Martin O.

1991-01-01

A prototype of an expert system was developed which applies qualitative constraint-based reasoning to the task of post-test analysis of data resulting from a rocket engine firing. Data anomalies are detected and corresponding faults are diagnosed. Engine behavior is reconstructed using measured data and knowledge about engine behavior. Knowledge about common faults guides but does not restrict the search for the best explanation in terms of hypothesized faults. The system contains domain knowledge about the behavior of common rocket engine components and was configured for use with the Space Shuttle Main Engine (SSME). A graphical user interface allows an expert user to intimately interact with the system during diagnosis. The system was applied to data taken during actual SSME tests where data anomalies were observed.

What Can We Learn from a Simple Physics-Based Earthquake Simulator?

NASA Astrophysics Data System (ADS)

Artale Harris, Pietro; Marzocchi, Warner; Melini, Daniele

2018-03-01

Physics-based earthquake simulators are becoming a popular tool to investigate on the earthquake occurrence process. So far, the development of earthquake simulators is commonly led by the approach "the more physics, the better". However, this approach may hamper the comprehension of the outcomes of the simulator; in fact, within complex models, it may be difficult to understand which physical parameters are the most relevant to the features of the seismic catalog at which we are interested. For this reason, here, we take an opposite approach and analyze the behavior of a purposely simple earthquake simulator applied to a set of California faults. The idea is that a simple simulator may be more informative than a complex one for some specific scientific objectives, because it is more understandable. Our earthquake simulator has three main components: the first one is a realistic tectonic setting, i.e., a fault data set of California; the second is the application of quantitative laws for earthquake generation on each single fault, and the last is the fault interaction modeling through the Coulomb Failure Function. The analysis of this simple simulator shows that: (1) the short-term clustering can be reproduced by a set of faults with an almost periodic behavior, which interact according to a Coulomb failure function model; (2) a long-term behavior showing supercycles of the seismic activity exists only in a markedly deterministic framework, and quickly disappears introducing a small degree of stochasticity on the recurrence of earthquakes on a fault; (3) faults that are strongly coupled in terms of Coulomb failure function model are synchronized in time only in a marked deterministic framework, and as before, such a synchronization disappears introducing a small degree of stochasticity on the recurrence of earthquakes on a fault. Overall, the results show that even in a simple and perfectly known earthquake occurrence world, introducing a small degree of stochasticity may blur most of the deterministic time features, such as long-term trend and synchronization among nearby coupled faults.

Fault reactivation by fluid injection considering permeability evolution in fault-bordering damage zones

NASA Astrophysics Data System (ADS)

Yang, Z.; Yehya, A.; Rice, J. R.; Yin, J.

2017-12-01

Earthquakes can be induced by human activity involving fluid injection, e.g., as wastewater disposal from hydrocarbon production. The occurrence of such events is thought to be, mainly, due to the increase in pore pressure, which reduces the effective normal stress and hence the strength of a nearby fault. Change in subsurface stress around suitably oriented faults at near-critical stress states may also contribute. We focus on improving the modeling and prediction of the hydro-mechanical response due to fluid injection, considering the full poroelastic effects and not solely changes in pore pressure in a rigid host. Thus we address the changes in porosity and permeability of the medium due to the changes in the local volumetric strains. Our results also focus on including effects of the fault architecture (low permeability fault core and higher permeability bordering damage zones) on the pressure diffusion and the fault poroelastic response. Field studies of faults have provided a generally common description for the size of their bordering damage zones and how they evolve along their direction of propagation. Empirical laws, from a large number of such observations, describe their fracture density, width, permeability, etc. We use those laws and related data to construct our study cases. We show that the existence of high permeability damage zones facilitates pore-pressure diffusion and, in some cases, results in a sharp increase in pore-pressure at levels much deeper than the injection wells, because these regions act as conduits for fluid pressure changes. This eventually results in higher seismicity rates. By better understanding the mechanisms of nucleation of injection-induced seismicity, and better predicting the hydro-mechanical response of faults, we can assess methodologies and injection strategies to avoid risks of high magnitude seismic events. Microseismic events occurring after the start of injection are very important indications of when injection should be stopped and how to avoid major events. Our work contributes to the assessment or mitigation of seismic hazard and risk, and our long-term target question is: How to not make an earthquake?

Coulomb stress analysis of the 21 February 2008 Mw= 6.0 Wells, Nevada, earthquake

USGS Publications Warehouse

Sevilgen, Volkan

2011-01-01

Static Coulomb stress changes imparted by the February 21, 2008 Wells, Nevada earthquake are calculated, using an 8 x 6 km rectangular patch with a uniform slip as a source fault. Stress changes are resolved on nearby active faults using their rake, dip, and strike direction, assuming a fault friction of 0.4. The largest Coulomb stress increase (0.2 bars) imparted to surrounding major active faults from the Wells earthquake occurs on the Clover Hill fault, which may be the southern continuation of the ruptured fault. A 0.1 bar Coulomb stress increase is calculated on the western Snake Mountains fault. Coulomb stress decreases of 0.5 bars are calculated for the northern parts of the Independence and Ruby Mountains faults. The Coulomb stress change is calculated on relocated aftershocks assuming that they have the same strike, dip, and rake, as the source fault. Under this assumption, 75% of the aftershocks received a Coulomb stress increase.

Comparison of thermal modeling, microstructural analysis, and Ti-in-quartz thermobarometry to constrain the thermal history of a cooling pluton during deformation in the Mount Abbot Quadrangle, CA

NASA Astrophysics Data System (ADS)

Nevitt, Johanna M.; Warren, Jessica M.; Kidder, Steven; Pollard, David D.

2017-03-01

Granitic plutons commonly preserve evidence for jointing, faulting, and ductile fabric development during cooling. Constraining the spatial variation and temporal evolution of temperature during this deformation could facilitate an integrated analysis of heterogeneous deformation over multiple length-scales through time. Here, we constrain the evolving temperature of the Lake Edison granodiorite within the Mount Abbot Quadrangle (central Sierra Nevada, CA) during late Cretaceous deformation by combining microstructural analysis, titanium-in-quartz thermobarometry (TitaniQ), and thermal modeling. Microstructural and TitaniQ analyses were applied to 12 samples collected throughout the pluton, representative of either the penetrative "regional" fabric or the locally strong "fault-related" fabric. Overprinting textures and mineral assemblages indicate the temperature decreased from 400-500°C to <350°C during faulting. TitaniQ reveals consistently lower Ti concentrations for partially reset fault-related fabrics (average: 12 ± 4 ppm) than for regional fabrics (average: 31 ± 12 ppm), suggesting fault-related fabrics developed later, following a period of pluton cooling. Uncertainties, particularly in TiO2 activity, significantly limit further quantitative thermal estimates using TitaniQ. In addition, we present a 1-D heat conduction model that suggests average pluton temperature decreased from 585°C at 85 Ma to 332°C at 79 Ma, consistent with radiometric age data for the field. Integrated with the model results, microstructural temperature constraints suggest faulting initiated by ˜83 Ma, when the temperature was nearly uniform across the pluton. Thus, spatially heterogeneous deformation cannot be attributed to a persistent temperature gradient, but may be related to regional structures that develop in cooling plutons.

Kinematic vicissitudes and the spatial distribution of the alteration zone related to the Byobuyama fault, central Japan. (Implication; Influence of another faults.)

NASA Astrophysics Data System (ADS)

Katori, T.; Kobayashi, K.

2015-12-01

The central Japan is one of the most concentrated area of active faults (Quaternary fault). These are roughly classified into two orthogonally-oriented fault sets of NE-SW and NW-SE strikes. The study area is located in Gifu prefecture, central Japan. In there, the basement rocks are composed mainly of Triassic-Jurassic accretionary prism (Mino belt), Cretaceous Nohi Rhyolite and Cretaceous granitic rocks. Miocene Mizunami G. and Pliocene-Pleistocene Toki Sand and Gravel F. unconformably cover the basement rocks. The Byobuyama fault, 32 km in length, is NE-SW strike and displaces perpendicularly the Toki Sand and Gravel F. by 500 m. The northeastern terminal of the fault has contact with the southern terminal of the Atera fault of NW-SE strike and offset their displacements each other. It is clear that the activity of the Byobuyama fault plays a role of the development of the complicated fault geometry system in the central Japan. In this study, we performed a broad-based investigation along the Byobuyama fault and collected samples. Actually, we observed 400 faults and analyzed 200 fault rocks. Based on these results, we obtained the following new opinion. 1. The Byobuyama fault has experienced following activities that can be divided to 3 stages at least under different stress field. 1) Movement with the sinisterly sense (preserved in cataclasite zone). 2) Dextral movement (preserved in fault gouge zone). 3) Reverse fault movement (due to the aggressive rise of mountains). In addition, the change from Stage 2 to Stage 3 is a continuous. 2. There is a relationship between the distance from the trace of the Byobuyama fault and the combination of alteration minerals included in the fault rocks. 3. In the central part of the Byobuyama fault (CPBF), fault plane trend and combination of alteration minerals shows specific features. The continuous change is considered to mean the presence of factors that interfere with the dextral movement of the Byobuyama fault. What is considered as one of the factors is the effect of the fault zone adjacent, especially the Atera fault. CPBF is located just southeast extension of the Akou fault, NW-SE strike. We think that this extension reaches up to CPBF. Based on the above, we make a presentation about interaction of two faults from the point of view of kinematic vicissitudes and alteration process.

Detecting Taiwan's Shanchiao Active Fault Using AMT and Gravity Methods

NASA Astrophysics Data System (ADS)

Liu, H.-C.; Yang, C.-H.

2009-04-01

Taiwan's Shanchiao normal fault runs in a northeast-southwest direction and is located on the western edge of the Taipei Basin in northern Taiwan. The overburden of the fault is late Quaternary sediment with a thickness of approximately a few tenth of a meter to several hundred meters. No detailed studies of the western side of the Shanchiao fault are available. As Taiwan is located on the Neotectonic Belt in the western Pacific, detecting active faults near the Taipei metropolitan area will provide necessary information for further disaster prevention. It is the responsibility of geologists and geophysicists in Taiwan to perform this task. Examination of the resistivity and density contrasts of subsurface layers permits a mapping of the Shanchiao fault and the deformed Tertiary strata of the Taipei Basin. The audio-frequency magnetotelluric (AMT) method and gravity method were chosen for this study. Significant resistivity and gravity anomalies were observed in the suspected fault zone. The interpretation reveals a good correlation between the features of the Shanchiao fault and resistivity and density distribution at depth. In this observation, AMT and gravity methods provides a viable means for mapping the Shanchiao fault position and studying its features associated with the subsidence of the western side of the Taipei Basin. This study indicates the AMT and gravity methods' considerable potential for accurately mapping an active fault.

Active tectonics of the onshore Hengchun Fault using UAS DSM combined with ALOS PS-InSAR time series (Southern Taiwan)

NASA Astrophysics Data System (ADS)

Deffontaines, Benoit; Chang, Kuo-Jen; Champenois, Johann; Lin, Kuan-Chuan; Lee, Chyi-Tyi; Chen, Rou-Fei; Hu, Jyr-Ching; Magalhaes, Samuel

2018-03-01

Characterizing active faults and quantifying their activity are major concerns in Taiwan, especially following the major Chichi earthquake on 21 September 1999. Among the targets that still remain poorly understood in terms of active tectonics are the Hengchun and Kenting faults (Southern Taiwan). From a geodynamic point of view, the faults affect the outcropping top of the Manila accretionary prism of the Manila subduction zone that runs from Luzon (northern Philippines) to Taiwan. In order to better locate and quantify the location and quantify the activity of the Hengchun Fault, we start from existing geological maps, which we update thanks to the use of two products derived from unmanned aircraft system acquisitions: (1) a very high precision (< 50 cm) and resolution (< 10 cm) digital surface model (DSM) and (2) a georeferenced aerial photograph mosaic of the studied area. Moreover, the superimposition of the resulting structural sketch map with new Persistent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR) results obtained from PALSAR ALOS images, validated by Global Positioning System (GPS) and leveling data, allows the characterization and quantification of the surface displacements during the monitoring period (2007-2011). We confirm herein the geometry, characterization and quantification of the active Hengchun Fault deformation, which acts as an active left-lateral transpressive fault. As the Hengchun ridge was the location of one of the last major earthquakes in Taiwan (26 December 2006, depth: 44 km, ML = 7.0), Hengchun Peninsula active tectonics must be better constrained in order if possible to prevent major destructions in the near future.

Geomorphology and Kinematics of the Nobi-Ise Active Fault Zone, Central Japan: Implications for the kinematic growth of tectonic landforms within an active thrust belt

NASA Astrophysics Data System (ADS)

Ishiyama, T.; Mueller, K. J.; Togo, M.; Takemura, K.; Okada, A.

2002-12-01

We present structural models constrained by tectonic geomorphology, surface geologic mapping and high-resolution seismic reflection profiles to define the kinematic evolution and geometry of active fault-related folds along the Nobi-Ise active fault zone (NAFZ). The NAFZ is an active intraplate fault system in central Japan, and consists of a 110-km-long array of active, east-verging reverse faults. We focus on the northern half of the NAFZ, where we use the kinematic evolution of active fault-related folds to constrain rates of slip on underlying blind thrusts and the rate of contraction across the belt since early Quaternary time. Fluvial terraces folded across the east-dipping forelimb, and west-dipping backlimb of the frontal Kuwana anticline suggest that it grows above a stacked sequence of thin-skinned wedge thrusts. Numerous secondary, bedding-parallel thrusts also deform the terraces and are interpreted to form by flexural slip folding that acts to consume slip on the primary blind thrusts across synclinal axial surfaces. Late Holocene fold scarps formed in the floodplain of the Ibi River east of Kuwana anticline coincide with the projected surface trace of the east-vergent wedge thrust tip and indicate the structure has accommodated coseismic (?) kink-band migration of a fault-bend fold during a historic blind thrust earthquake in 1586. A topographic cross-section based on a detailed photogrammetric map suggests 111 m of uplift of ca. 50-80 ka fluvial terraces deposited across the forelimb. For a 35° thrust, this yields the minimum slip rate of 2.7-4.8 mm/yr on the deepest wedge thrust beneath Kuwana anticline. Kinematic analysis for the much larger thrust defined to the west (the Fumotomura fault) suggests that folding of fluvial terraces occurred by trishear fault-propagation folding above a more steeply-dipping (54°), basement-involved blind thrust that propagated upward from the base of the seismogenic crust (about 12 km). Pleistocene growth strata defined by tephra (ca. 1.6 Ma) suggest the Fumotomura fault slips at a rate of 0.7-0.9 mm/yr.

Improved alignment of the Hengchun Fault (southern Taiwan) based on fieldwork, structure-from-motion, shallow drilling, and levelling data

NASA Astrophysics Data System (ADS)

Giletycz, Slawomir Jack; Chang, Chung-Pai; Lin, Andrew Tien-Shun; Ching, Kuo-En; Shyu, J. Bruce H.

2017-11-01

The fault systems of Taiwan have been repeatedly studied over many decades. Still, new surveys consistently bring fresh insights into their mechanisms, activity and geological characteristics. The neotectonic map of Taiwan is under constant development. Although the most active areas manifest at the on-land boundary of the Philippine Sea Plate and Eurasia (a suture zone known as the Longitudinal Valley), and at the southwestern area of the Western Foothills, the fault systems affect the entire island. The Hengchun Peninsula represents the most recently emerged part of the Taiwan orogen. This narrow 20-25 km peninsula appears relatively aseismic. However, at the western flank the peninsula manifests tectonic activity along the Hengchun Fault. In this study, we surveyed the tectonic characteristics of the Hengchun Fault. Based on fieldwork, four years of monitoring fault displacement in conjunction with levelling data, core analysis, UAV surveys and mapping, we have re-evaluated the fault mechanisms as well as the geological formations of the hanging and footwall. We surveyed features that allowed us to modify the existing model of the fault in two ways: 1) correcting the location of the fault line in the southern area of the peninsula by moving it westwards about 800 m; 2) defining the lithostratigraphy of the hanging and footwall of the fault. A bathymetric map of the southern area of the Hengchun Peninsula obtained from the Atomic Energy Council that extends the fault trace offshore to the south distinctively matches our proposed fault line. These insights, coupled with crust-scale tomographic data from across the Manila accretionary system, form the basis of our opinion that the Hengchun Fault may play a major role in the tectonic evolution of the southern part of the Taiwan orogen.

Shallow Vs Structure Accross Hayward Fault Zone Inferred from Multichannel Analysis of Surface Waves (MASW)

NASA Astrophysics Data System (ADS)

Chan, J. H.; Richardson, I. S.; Strayer, L. M.; Catchings, R.; McEvilly, A.; Goldman, M.; Criley, C.; Sickler, R. R.

2017-12-01

The Hayward Fault Zone (HFZ) includes the Hayward fault (HF), as well as several named and unnamed subparallel, subsidiary faults to the east, among them the Quaternary-active Chabot Fault (CF), the Miller Creek Fault (MCF), and a heretofore unnamed fault, the Redwood Thrust Fault (RTF). With an ≥M6.0 recurrence interval of 130 y for the HF and the last major earthquake in 1868, the HFZ is a major seismic hazard in the San Francisco Bay Area, exacerbated by the many unknown and potentially active secondary faults of the HFZ. In 2016, researchers from California State University, East Bay, working in concert with the United States Geological Survey conducted the East Bay Seismic Investigation (EBSI). We deployed 296 RefTek RT125 (Texan) seismographs along a 15-km-long linear seismic profile across the HF, extending from the bay in San Leandro to the hills in Castro Valley. Two-channel seismographs were deployed at 100 m intervals to record P- and S-waves, and additional single-channel seismographs were deployed at 20 m intervals where the seismic line crossed mapped faults. The active-source survey consisted of 16 buried explosive shots located at approximately 1-km intervals along the seismic line. We used the Multichannel Analysis of Surfaces Waves (MASW) method to develop 2-D shear-wave velocity models across the CF, MCF, and RTF. Preliminary MASW analysis show areas of anomalously low S-wave velocities , indicating zones of reduced shear modulus, coincident with these three mapped faults; additional velocity anomalies coincide with unmapped faults within the HFZ. Such compliant zones likely correspond to heavily fractured rock surrounding the faults, where the shear modulus is expected to be low compared to the undeformed host rock.

The 2003 Bam (Iran) earthquake: Rupture of a blind strike-slip fault

NASA Technical Reports Server (NTRS)

Talebian, M.; Fielding, E. J.; Funning, G. J.; Ghorashi, M.; Jackson, J.; Nazari, H.; Parsons, B.; Priestley, K.; Rosen, P. A.; Walker, R.;

The northwest trending north Boquerón Bay-Punta Montalva Fault Zone; A through going active fault system in southwestern Puerto Rico

USGS Publications Warehouse

Roig‐Silva, Coral Marie; Asencio, Eugenio; Joyce, James

2013-01-01

The North Boquerón Bay–Punta Montalva fault zone has been mapped crossing the Lajas Valley in southwest Puerto Rico. Identification of the fault was based upon detailed analysis of geophysical data, satellite images, and field mapping. The fault zone consists of a series of Cretaceous bedrock faults that reactivated and deformed Miocene limestone and Quaternary alluvial fan sediments. The fault zone is seismically active (local magnitude greater than 5.0) with numerous locally felt earthquakes. Focal mechanism solutions suggest strain partitioning with predominantly east–west left-lateral displacements with small normal faults striking mostly toward the northeast. Northeast-trending fractures and normal faults can be found in intermittent streams that cut through the Quaternary alluvial fan deposits along the southern margin of the Lajas Valley, an east–west-trending 30-km-long fault-controlled depression. Areas of preferred erosion within the alluvial fan trend toward the west-northwest parallel to the onland projection of the North Boquerón Bay fault. The North Boquerón Bay fault aligns with the Punta Montalva fault southeast of the Lajas Valley. Both faults show strong southward tilting of Miocene strata. On the western end, the Northern Boquerón Bay fault is covered with flat-lying Holocene sediments, whereas at the southern end the Punta Montalva fault shows left-lateral displacement of stream drainage on the order of a few hundred meters.

Paleoseismic Investigation of the Ranong and Khlong Marui faults, Chumphon Province, Southern Thailand

NASA Astrophysics Data System (ADS)

Fenton, C. H.; Sutiwanich, C.

2005-12-01

The Ranong and Khlong Marui faults are northeast-southwest trending structures in the Isthmus of Kra, southern Thailand, that apparently link the extensional regimes of the Mergui Basin in the Andaman Sea and the Gulf of Thailand. These faults are depicted commonly as strike-slip faults, acting as conjugate structures to the dominant northwest-southeast trending strike-slip faults, in Southeast Asia. These faults are parallel to the predominant structural grain in the Carboniferous rocks of peninsular Thailand. In addition, they appear to be bounding structures for several Tertiary basins, including the onshore parts of the Surat Thani basin and the offshore Chumphon basin. Initial remote sensing studies showed that both faults have relatively subdued geomorphic expressions. Field reconnaissance investigations indicated a lack of youthful tectonic geomorphology along the Khlong Marui fault and ambiguous evidence for recent movement along the Ranong fault. Fault exposures along both fault trends and on minor parallel faults in the region indicated that, rather than predominantly strike-slip motion, these faults have experienced up-to-the-west reverse movement. Because of its more youthful geomorphic expression, several sites along the Ranong fault were chosen for paleoseismic trenching. Initial trench exposures indicate an absence of Holocene movement. Some exposures indicate the possibility of Late Tertiary-Early Holocene vertical movement. These investigations are currently ongoing and we hope to report our conclusions at the Fall Meeting.

A testing-coverage software reliability model considering fault removal efficiency and error generation.

PubMed

Li, Qiuying; Pham, Hoang

2017-01-01

In this paper, we propose a software reliability model that considers not only error generation but also fault removal efficiency combined with testing coverage information based on a nonhomogeneous Poisson process (NHPP). During the past four decades, many software reliability growth models (SRGMs) based on NHPP have been proposed to estimate the software reliability measures, most of which have the same following agreements: 1) it is a common phenomenon that during the testing phase, the fault detection rate always changes; 2) as a result of imperfect debugging, fault removal has been related to a fault re-introduction rate. But there are few SRGMs in the literature that differentiate between fault detection and fault removal, i.e. they seldom consider the imperfect fault removal efficiency. But in practical software developing process, fault removal efficiency cannot always be perfect, i.e. the failures detected might not be removed completely and the original faults might still exist and new faults might be introduced meanwhile, which is referred to as imperfect debugging phenomenon. In this study, a model aiming to incorporate fault introduction rate, fault removal efficiency and testing coverage into software reliability evaluation is developed, using testing coverage to express the fault detection rate and using fault removal efficiency to consider the fault repair. We compare the performance of the proposed model with several existing NHPP SRGMs using three sets of real failure data based on five criteria. The results exhibit that the model can give a better fitting and predictive performance.

Contribution of Transverse Structures, Magma, and Crustal Fluids to Continental Rift Evolution: The East African Rift in Southern Kenya

NASA Astrophysics Data System (ADS)

Kattenhorn, S. A.; Muirhead, J.; Dindi, E.; Fischer, T. P.; Lee, H.; Ebinger, C. J.

2013-12-01

The Magadi rift in southern Kenya formed at ~7 Ma within Proterozoic rocks of the Mozambique orogenic belt, parallel to its contact with the Archean Tanzania craton. The rift is bounded to the west by the ~1600-m-high Nguruman border fault. The rift center is intensely dissected by normal faults, most of which offset ~1.4-0.8 Ma lavas. Current E-W extensional velocities are ~2-4 mm/yr. Published crustal tomography models from the rift center show narrow high velocity zones in the upper crust, interpreted as cooled magma intrusions. Local, surface-wave, and SKS-splitting measurements show a rift-parallel anisotropy interpreted to be the result of aligned melt zones in the lithosphere. Our field observations suggest that recent fault activity is concentrated at the rift center, consistent with the location of the 1998 seismic swarm that was associated with an inferred diking event. Fault zones are pervasively mineralized by calcite, likely from CO2-rich fluids. A system of fault-fed springs provides the sole fluid input for Lake Magadi in the deepest part of the basin. Many of these springs emanate from the Kordjya fault, a 50-km-long, NW-SE striking, transverse structure connecting a portion of the border fault system (the NW-oriented Lengitoto fault) to the current locus of strain and magmatism at the rift center. Sampled springs are warm (44.4°C) and alkaline (pH=10). Dissolved gas data (mainly N2-Ar-He) suggests two-component mixing (mantle and air), possibly indicating that fluids are delivered into the fault zone from deep sources, consistent with a dominant role of magmatism to the focusing of strain at the rift center. The Kordjya fault has developed prominent fault scarps (~150 m high) despite being oblique to the dominant ~N-S fault fabric, and has utilized an en echelon alignment of N-S faults to accommodate its motion. These N-S faults show evidence of sinistral-oblique motion and imply a bookshelf style of faulting to accommodate dextral-oblique motion along the Kordjya fault. Fault relationships imply that the NW-SE transverse structures represent recent activity in the rift, and have locally tilted Late Pleistocene sediments. Given the abundance of N-S striking faults in the rift, the tendency for fault activity along transverse features suggests a change in the rifting driving forces that are likely the result of an interplay between strain localization at the rift center, inherited crustal fabric (NW structures in the Mozambique belt), a possible counterclockwise rotation of stress related to interacting rift segments in southern Kenya, and an active hydrothermal fluid regime that facilitates faulting. By connecting the Lengitoto fault to the rift center, the Kordjya fault has effectively caused the Magadi rift to bypass the Nguruman border fault, which has been rendered inactive and thus no longer a contributor to the rifting process.

Audio-frequency magnetotelluric imaging of the Hijima fault, Yamasaki fault system, southwest Japan

NASA Astrophysics Data System (ADS)

Yamaguchi, S.; Ogawa, Y.; Fuji-Ta, K.; Ujihara, N.; Inokuchi, H.; Oshiman, N.

2010-04-01

An audio-frequency magnetotelluric (AMT) survey was undertaken at ten sites along a transect across the Hijima fault, a major segment of the Yamasaki fault system, Japan. The data were subjected to dimensionality analysis, following which two-dimensional inversions for the TE and TM modes were carried out. This model is characterized by (1) a clear resistivity boundary that coincides with the downward projection of the surface trace of the Hijima fault, (2) a resistive zone (>500 Ω m) that corresponds to Mesozoic sediment, and (3) shallow and deep two highly conductive zones (30-40 Ω m) along the fault. The shallow conductive zone is a common feature of the Yamasaki fault system, whereas the deep conductor is a newly discovered feature at depths of 800-1,800 m to the southwest of the fault. The conductor is truncated by the Hijima fault to the northeast, and its upper boundary is the resistive zone. Both conductors are interpreted to represent a combination of clay minerals and a fluid network within a fault-related fracture zone. In terms of the development of the fluid networks, the fault core of the Hijima fault and the highly resistive zone may play important roles as barriers to fluid flow on the northeast and upper sides of the conductive zones, respectively.

Seismic hazards and land-use planning

USGS Publications Warehouse

Nichols, Donald R.; Buchanan-Banks, Jane M.

1974-01-01

Basic earth-science data are necessary for a realistic assessment of seismic hazards and as a basis for limiting corrective land-use controls only to those areas of greatest hazard. For example, the location, character, and amount of likely displacement and activity of surface faulting can be predicted if detailed geologic maps and seismic data are available and are augmented by field studies at critical localities. Because few structures can withstand displacement of their foundations, they should be located off active fault traces, the distance varying with the character of faulting, the certainty with which fault traces are known, and the importance of the structure. Recreational activities and other nonoccupancy land uses should be considered for fault zone areas where land is under pressure for development; elsewhere, such areas should remain as open space. Two methods of predicting ground shaking effects have applications to land-use decisions: (1) Relative earthquake effects can be related to firmness of the ground and can be used in a gross way to allocate population density in the absence of more sophisticated analyses; and (2) intensity maps, based on, (a) damage from former earthquakes, or (b) a qualitative analyses of geologic units added to a design earthquake, can be helpful both for general and specific plans. Theoretical models are used with caution to predict ground motion for critical structures to be located at specific sites with unique foundation conditions. Fully adequate methods of assessing possible shaking remain to be developed. Where land-use decisions do not reflect likely ground shaking effects, stringent building codes are needed, particularly for important structures. Ground failure (landsliding, ground cracking and lurching, differential settlement, sand boils, and subsidence) commonly results from liquefaction, loss of soil strength, or compaction. Areas suspected of being most likely to fail should not be developed unless detailed site studies can demonstrate the hazard does not exist or can be overcome. Various methods can be used to reduce the high, long-term public costs that follow development of unstable ground. However, areas subject to tectonic deformation generally cannot be predicted nor can effects of such deformation be minimized. Large water waves, such as produced by tsunamis, seiches, and dam failure or overtopping, can be anticipated in many places. Their effects can be lessened by land-use regulations similar to flood-plain zoning, restrictions on location of critical structures, and appropriate warning systems. Many local, state, and federal government agencies, universities, and private consultants may be able to assist planners by advising them of pertinent data and where those data can be obtained. Interpretation of the data for an evaluation of seismic risk commonly requires a team of planners, geologists, and soil and structural engineers.

Holocene faulting in the Bellingham forearc basin: upper-plate deformation at the northern end of the Cascadia subduction zone

USGS Publications Warehouse

Kelsey, Harvey M.; Sherrod, Brian L.; Blakely, Richard J.; Haugerud, Ralph A.

2013-01-01

The northern Cascadia forearc takes up most of the strain transmitted northward via the Oregon Coast block from the northward-migrating Sierra Nevada block. The north-south contractional strain in the forearc manifests in upper-plate faults active during the Holocene, the northern-most components of which are faults within the Bellingham Basin. The Bellingham Basin is the northern of four basins of the actively deforming northern Cascadia forearc. A set of Holocene faults, Drayton Harbor, Birch Bay, and Sandy Point faults, occur within the Bellingham Basin and can be traced from onshore to offshore using a combination of aeromagnetic lineaments, paleoseismic investigations and scarps identified using LiDAR imagery. With the recognition of such Holocene faults, the northernmost margin of the actively deforming Cascadia forearc extends 60 km north of the previously recognized limit of Holocene forearc deformation. Although to date no Holocene faults are recognized at the northern boundary of the Bellingham Basin, which is 15 km north of the international border, there is no compelling tectonic reason to expect that Holocene faults are limited to south of the international border.

A 13 km Long Paleoseismological Trench in Western Germany

NASA Astrophysics Data System (ADS)

Grützner, C. H.; Reicherter, K.; Winandy, J.

2012-04-01

The expansion of an open pit lignite mine in this area makes it necessary to translocate one of Germany's most frequented, E-W trending highways for a length of 13 km during the next months and years. By this occasion, one of the largest faults of the Lower Rhine Embayment (LRE), the Rurrand Fault, was already cut in 2010. We applied geological mapping and surface-near geophysical techniques for investigating this possible candidate for the 1756 Düren earthquake (M>6; and considered as the strongest historical earthquake in Germany), and found clear hints for recent active faulting. The LRE in western Germany is one of the seismically most active areas in Central Europe. Earthquakes stronger than M6 have been documented by paleoseismological and archeoseismological investigations and written sources. Instrumental seismicity reached ML5.9 (Mw5.4; April 13th, 1992) in this densely populated area with alone nearby Cologne having more than one million inhabitants. Active faults trend NW-SE in a horst-graben system, parallel to the rivers Rhine and Rur. Recent studies reported that active faults in the study area are characterized by recurrence periods in the order of tens of ka. Those faults in western Germany are often not visible in the field due to relatively high erosion rates and therefore, the seismic hazard might be underestimated. The ongoing highway construction works will cut more (active) faults. We expect at least eight already mapped faults to be cut by the earth works, some of which capable of causing damaging earthquakes judging from their mere length. The construction work is a unique opportunity for paleoseismological investigations at already known, but yet unstudied faults. We hope to gather additional data for an improvement of seismic hazard estimations in Western Germany.

Transform fault earthquakes in the North Atlantic: Source mechanisms and depth of faulting

NASA Technical Reports Server (NTRS)

Bergman, Eric A.; Solomon, Sean C.

1987-01-01

The centroid depths and source mechanisms of 12 large earthquakes on transform faults of the northern Mid-Atlantic Ridge were determined from an inversion of long-period body waveforms. The earthquakes occurred on the Gibbs, Oceanographer, Hayes, Kane, 15 deg 20 min, and Vema transforms. The depth extent of faulting during each earthquake was estimated from the centroid depth and the fault width. The source mechanisms for all events in this study display the strike slip motion expected for transform fault earthquakes; slip vector azimuths agree to 2 to 3 deg of the local strike of the zone of active faulting. The only anomalies in mechanism were for two earthquakes near the western end of the Vema transform which occurred on significantly nonvertical fault planes. Secondary faulting, occurring either precursory to or near the end of the main episode of strike-slip rupture, was observed for 5 of the 12 earthquakes. For three events the secondary faulting was characterized by reverse motion on fault planes striking oblique to the trend of the transform. In all three cases, the site of secondary reverse faulting is near a compression jog in the current trace of the active transform fault zone. No evidence was found to support the conclusions of Engeln, Wiens, and Stein that oceanic transform faults in general are either hotter than expected from current thermal models or weaker than normal oceanic lithosphere.

Structural characteristics of epicentral areas in Central Europe: study case Cheb Basin (Czech Republic)

NASA Astrophysics Data System (ADS)

Bankwitz, P.; Schneider, G.; Kämpf, H.; Bankwitz, E.

2003-03-01

The earthquake distribution pattern of Central Europe differs systematically from the neighbouring areas of NW and southern Europe regarding the fault plane kinematics. Within a belt between the French Massif Central and the northern part of the Bohemian Massif (1000 km) sinistral faulting along N-S zones dominates on the contrary to the Alps and their foreland with common bookshelf shears. One of the prominent N-S structures is the Regensburg-Leipzig-Rostock Zone (A) with several epicentral areas, where the main seismic center occurs in the northern Cheb Basin (NW Bohemia). The study demonstrates new structural results for the swarm-quake region in NW-Bohemia, especially for the Nový Kostel area in the Cheb Basin. There the N-S-trending newly found Počatky-Plesná zone (PPZ) is identical with the main earthquake line. The PPZ is connected with a mofette line between Hartušov and Bublák with evidence for CO 2 degassing from the subcrustal mantle. The morphologically more prominent Mariánské Lázně fault (MLF) intersects the PPZ obliquely under an acuate angle. In the past the MLF was supposed to be the tectonic structure connected with the epicentral area of Nový Kostel. But evidence from the relocated hypocentres along the PPZ (at 7-12 kms depth) indicate that the MLF is seismically non-active. Asymmetric drainage patterns of the Cheb Basin are caused by fault related movement along Palaeozoic basement faults which initiate a deformation of the cover (Upper Pliocene to Holocene basin filling). The PPZ forms an escarpment in Pliocene and Pleistocene soft rock and is supposingly acting as an earthquake zone since late Pleistocene time. The uppermost Pleistocene of 0.12-0.01 Ma deposited only in front of the fault scarp dates the fault activity. The crossing faults envelope crustal wedges under different local stress conditions. Their intersection line forms a zone beginning at the surface near Nový Kostel, dipping south with increasing depth, probably down to about 12 km. The intersection zone represents a crustal anomaly. There fault movements can be blocked up and peculiar stress condition influence the behaviour of the adjacent crust. An ENE-WNW striking dextral wrench fault was detected which is to expect as kinematic counterpart to the ca. N-S striking sinistral shear zones. Nearly E-W striking fracture segments were formerly only known as remote sensing lineaments or as joint density zones. The ENE shear zone is characterized by a set of compressional m-scale folds and dm-scale faults scattered within a 20 m wide wrench zone. It is built up of different sets of cleavage-like clay plate pattern of microscopical scale. The associated shear planes fit into a Riedel shear system. One characteristic feature are tiny channels of micrometer scale. They have originated after shear plane bending and are the sites of CO 2 mantle degassing.

Preliminary Studies of the Structural Characteristics of the Lubao Fault using 2D High Resolution Shallow Seismic Reflection Profile

NASA Astrophysics Data System (ADS)

Bonus, A. A. B.; Lagmay, A. M. A.; Rodolfo, K. S.

2016-12-01

The Lubao fault, located in the province of Pampanga, Philippines, is part of the Bataan Volcanic Arc Complex (BVAC). Active faults within and around the BVAC include the East Zambales and Iba faults; according to the official active faults map of the Philippine Institute of Volcanology and Seismology (PHIVOLCS) there are no other existing active faults in the area. The Lubao Fault distinctly separates wetlands to the northeast and dry alluvial plains to the northwest of Manila Bay. Long term subsidence and high sedimentation rates were observed in the fault and over the past 1.5 thousand years, the northeastern block has dropped 3.5 meters. Along the southwest flank of Mount Natib, tectonic structures were identified using surface mapping and remote sensing. The Persistent Scattering Interferometric Synthetic Aperture Radar (PSInSAR) data results of Eco et al. in 2015 shows uplifts and subsidence in the BVAC area delineating the Lubao Fault. A 480-meter seismic reflection line was laid down perpendicular to the fault with a recording system consisting of 48 channels of Geometrics geophones spaced 10 meters apart. Acquired data were processed using the standard seismic reflection processing sequence by Yilmaz 2001. This preliminary study produced a high resolution subsurface profile of the Lubao fault in the village of San Rafael, Lubao where it is well manifested. The velocity model integrated by stratigraphic data of drilled core shows subsurface lithology. The depth converted profile reveals clear structures and dipping segments which indicates a history of movement along the Lubao fault. Discontinuity of reflectors, either offsets or breaks, are considered structures along the subsurface of the study area. Additional structural mapping and seismic lines along the projected fault are planned in the future to further detail the characteristics of the Lubao Fault. The surface observations made by other researchers coupled with the subsurface seismic profile mapping of this study hopes to clearly delineate and characterize the Lubao Fault.

Probabilistic seismic hazard study based on active fault and finite element geodynamic models

NASA Astrophysics Data System (ADS)

Kastelic, Vanja; Carafa, Michele M. C.; Visini, Francesco

2016-04-01

We present a probabilistic seismic hazard analysis (PSHA) that is exclusively based on active faults and geodynamic finite element input models whereas seismic catalogues were used only in a posterior comparison. We applied the developed model in the External Dinarides, a slow deforming thrust-and-fold belt at the contact between Adria and Eurasia.. is the Our method consists of establishing s two earthquake rupture forecast models: (i) a geological active fault input (GEO) model and, (ii) a finite element (FEM) model. The GEO model is based on active fault database that provides information on fault location and its geometric and kinematic parameters together with estimations on its slip rate. By default in this model all deformation is set to be released along the active faults. The FEM model is based on a numerical geodynamic model developed for the region of study. In this model the deformation is, besides along the active faults, released also in the volumetric continuum elements. From both models we calculated their corresponding activity rates, its earthquake rates and their final expected peak ground accelerations. We investigated both the source model and the earthquake model uncertainties by varying the main active fault and earthquake rate calculation parameters through constructing corresponding branches of the seismic hazard logic tree. Hazard maps and UHS curves have been produced for horizontal ground motion on bedrock conditions VS 30 ≥ 800 m/s), thereby not considering local site amplification effects. The hazard was computed over a 0.2° spaced grid considering 648 branches of the logic tree and the mean value of 10% probability of exceedance in 50 years hazard level, while the 5th and 95th percentiles were also computed to investigate the model limits. We conducted a sensitivity analysis to control which of the input parameters influence the final hazard results in which measure. The results of such comparison evidence the deformation model and with their internal variability together with the choice of the ground motion prediction equations (GMPEs) are the most influencing parameter. Both of these parameters have significan affect on the hazard results. Thus having good knowledge of the existence of active faults and their geometric and activity characteristics is of key importance. We also show that PSHA models based exclusively on active faults and geodynamic inputs, which are thus not dependent on past earthquake occurrences, provide a valid method for seismic hazard calculation.

Heterogeneity in friction strength of an active fault by incorporation of fragments of the surrounding host rock

NASA Astrophysics Data System (ADS)

Kato, Naoki; Hirono, Tetsuro

2016-07-01

To understand the correlation between the mesoscale structure and the frictional strength of an active fault, we performed a field investigation of the Atera fault at Tase, central Japan, and made laboratory-based determinations of its mineral assemblages and friction coefficients. The fault zone contains a light gray fault gouge, a brown fault gouge, and a black fault breccia. Samples of the two gouges contained large amounts of clay minerals such as smectite and had low friction coefficients of approximately 0.2-0.4 under the condition of 0.01 m s-1 slip velocity and 0.5-2.5 MP confining pressure, whereas the breccia contained large amounts of angular quartz and feldspar and had a friction coefficient of 0.7 under the same condition. Because the fault breccia closely resembles the granitic rock of the hangingwall in composition, texture, and friction coefficient, we interpret the breccia as having originated from this protolith. If the mechanical incorporation of wall rocks of high friction coefficient into fault zones is widespread at the mesoscale, it causes the heterogeneity in friction strength of fault zones and might contribute to the evolution of fault-zone architectures.

Fault recovery characteristics of the fault tolerant multi-processor

NASA Technical Reports Server (NTRS)

Padilla, Peter A.

1990-01-01

The fault handling performance of the fault tolerant multiprocessor (FTMP) was investigated. Fault handling errors detected during fault injection experiments were characterized. In these fault injection experiments, the FTMP disabled a working unit instead of the faulted unit once every 500 faults, on the average. System design weaknesses allow active faults to exercise a part of the fault management software that handles byzantine or lying faults. It is pointed out that these weak areas in the FTMP's design increase the probability that, for any hardware fault, a good LRU (line replaceable unit) is mistakenly disabled by the fault management software. It is concluded that fault injection can help detect and analyze the behavior of a system in the ultra-reliable regime. Although fault injection testing cannot be exhaustive, it has been demonstrated that it provides a unique capability to unmask problems and to characterize the behavior of a fault-tolerant system.

Convergence between the Georgian Lesser and Greater Caucasus: Implications for seismic risk around Tbilisi

NASA Astrophysics Data System (ADS)

Sokhadze, Giorgi; Floyd, Michael; Godoladze, Tea; King, Robert; Cowgill, Eric; Javakhishvili, Zurab; Hahubia, Galaktion; Reilinger, Robert

2017-04-01

The Caucasus region, including the Lesser and Greater Caucasus Mountains and intervening Rioni, Kartli and Kura basins, defines the northern margin of the Arabia-Eurasia continental collision between the Black and Caspian Seas. Although geodetic, geologic and seismological data attest to active crustal shortening in the region, both the structures accommodating this deformation and the potential seismic hazards they pose remain unclear. Here we present and interpret newly determined site motions derived from GPS observations made at 21 campaign sites and 4 continuous GPS stations in the Republic of Georgia from 2008 through 2015. The sites are located along two, 160 km-long, range-perpendicular profiles crossing the Lesser-Greater Caucasus boundary zone. The Racha profile in the west spans the Rioni Basin and epicentral area of the 1991 Mw6.9 Racha earthquake. To the east, the Tbilisi profile crosses near the capital city of Tbilisi, with a population of 1.2 million. To estimate site velocities, we processed the GPS observations using the GAMIT/GLOBK software package, and then combined new and previously published velocities in a common Eurasian reference frame. Both profiles indicate 3 mm/yr of shortening between the Greater and Lesser Caucasus. On the Racha profile, the locus of shortening roughly coincides with the Main Caucasus Thrust Fault as defined by the location of the 1991 Racha earthquake. In contrast, on the Tbilisi profile shortening is concentrated 40-60 km further south, in the vicinity of the Lesser Caucasus Thrust Fault (locally, the Adjara-Trialeti Fault). Simple elastic models of planar faults in an elastic half-space indicate that convergence along the Racha profile is consistent with strain accumulation on a north-dipping thrust fault rooting beneath the Greater Caucasus, generally consistent with the coseismic fault parameters for the 1991 Racha earthquake. In contrast, principal convergence along the Tbilisi profile appears to be associated with a fault that roots near the northern boundary of the Lesser Caucasus. This change in the location of active convergence may be related to incipient collision between the Lesser and Greater Caucasus blocks that is occurring along this section of the boundary ( 44°E). Focused geodetic, seismic and neotectonic investigations are continuing to better characterize the underlying structures accommodating shortening, and associated seismic hazards around Tbilisi.

Fault-tolerant, high-level quantum circuits: form, compilation and description

NASA Astrophysics Data System (ADS)

Paler, Alexandru; Polian, Ilia; Nemoto, Kae; Devitt, Simon J.

2017-06-01

Fault-tolerant quantum error correction is a necessity for any quantum architecture destined to tackle interesting, large-scale problems. Its theoretical formalism has been well founded for nearly two decades. However, we still do not have an appropriate compiler to produce a fault-tolerant, error-corrected description from a higher-level quantum circuit for state-of the-art hardware models. There are many technical hurdles, including dynamic circuit constructions that occur when constructing fault-tolerant circuits with commonly used error correcting codes. We introduce a package that converts high-level quantum circuits consisting of commonly used gates into a form employing all decompositions and ancillary protocols needed for fault-tolerant error correction. We call this form the (I)initialisation, (C)NOT, (M)measurement form (ICM) and consists of an initialisation layer of qubits into one of four distinct states, a massive, deterministic array of CNOT operations and a series of time-ordered X- or Z-basis measurements. The form allows a more flexible approach towards circuit optimisation. At the same time, the package outputs a standard circuit or a canonical geometric description which is a necessity for operating current state-of-the-art hardware architectures using topological quantum codes.

Microstructural study of natural fractures in Cape Roberts Project 3 core, Western Ross Sea, Antarctica

USGS Publications Warehouse

Millan, C.; Wilson, T.; Paulsen, T.

2007-01-01

Microstructures in natural fractures in core recovered offshore from Cape Roberts, Ross Sea, Antarctica, provide new constraints on the relative timing of faulting and sedimentation in the Victoria Land Basin along the Transantarctic Mountain rift flank. This study characterizes the textures, fabrics and grain-scale structures from thin section analysis of samples of microfaults, veins, and clastic dikes. Microfaults are abundant and display two different types of textures, interpreted to record two different deformation modes: pre-lithification shearing and brittle faulting of cohesive sediment. Both clastic dikes and calcite veins commonly follow fault planes, indicating that injections of liquefied sediment and circulating fluids used pre-existing faults as conduits. The close association of clastic injections, diagenetic mineralization, and faulting indicates that faulting was synchronous with deposition in the rift basin

Paleo-earthquake Analysis from the Morphologic Features of Unconsolidated-sediment Fault Scarp: An Example from Dushanzi Thrust Fault in the Northern Tianshan, China

NASA Astrophysics Data System (ADS)

Wei, Z.; He, H.

2016-12-01

Fault scarp is important specific tectonic landform caused by surface-rupture earthquake. The morphology of the fault scarp in unconsolidated sediment could evolve in a predictable, time-dependent diffusion model. As a result, the investigation of fault-generated fault scarps is a prevalent technique used to study fault activity, geomorphic evolution, and the recurrence of faulting events. Addition to obtainment of cumulative displacement, gradient changes, i.e. slope breaks, in the morphology of fault scarps could indicate multiple rupture events along an active fault. In this study, we exacted a large set of densely spaced topographic profiles across fault scarp from LiDAR-derive DEM to detect subtle changes in the fault scarp geometry at the Dushanzi trust fault in the Northern Tianshan, China. Several slope breaks in topographic profiles can be identified, which may represent repeated rupture at the investigated fault. The number of paleo-earthquakes derived from our analysis is 4-3, well in agreement with the investigation results from the paleoseismological trenches. Statistical analysis results show that the scarp height of fault scarp with one slope break is 0.75±0.12 (mean value ±1 standard deviation) m representing the last incremental displacement during earthquakes; the height of fault scarp with two slope breaks is 1.86±0.32 m, and the height of fault scarp with three-four slope break is 6.45±1.44 m. Our approach enables us to obtain paleo-earthquake information from geomorphological analysis of fault scarps, and to assess the multiple rupture history of a complex fault system.

Active backstop faults in the Mentawai region of Sumatra, Indonesia, revealed by teleseismic broadband waveform modeling

NASA Astrophysics Data System (ADS)

Wang, Xin; Bradley, Kyle Edward; Wei, Shengji; Wu, Wenbo

2018-02-01

Two earthquake sequences that affected the Mentawai islands offshore of central Sumatra in 2005 (Mw 6.9) and 2009 (Mw 6.7) have been highlighted as evidence for active backthrusting of the Sumatran accretionary wedge. However, the geometry of the activated fault planes is not well resolved due to large uncertainties in the locations of the mainshocks and aftershocks. We refine the locations and focal mechanisms of medium size events (Mw > 4.5) of these two earthquake sequences through broadband waveform modeling. In addition to modeling the depth-phases for accurate centroid depths, we use teleseismic surface wave cross-correlation to precisely relocate the relative horizontal locations of the earthquakes. The refined catalog shows that the 2005 and 2009 "backthrust" sequences in Mentawai region actually occurred on steeply (∼60 degrees) landward-dipping faults (Masilo Fault Zone) that intersect the Sunda megathrust beneath the deepest part of the forearc basin, contradicting previous studies that inferred slip on a shallowly seaward-dipping backthrust. Static slip inversion on the newly-proposed fault fits the coseismic GPS offsets for the 2009 mainshock equally well as previous studies, but with a slip distribution more consistent with the mainshock centroid depth (∼20 km) constrained from teleseismic waveform inversion. Rupture of such steeply dipping reverse faults within the forearc crust is rare along the Sumatra-Java margin. We interpret these earthquakes as 'unsticking' of the Sumatran accretionary wedge along a backstop fault separating imbricated material from the stronger Sunda lithosphere. Alternatively, the reverse faults may have originated as pre-Miocene normal faults of the extended continental crust of the western Sunda margin. Our waveform modeling approach can be used to further refine global earthquake catalogs in order to clarify the geometries of active faults.

The aftershock signature of supershear earthquakes.

PubMed

Bouchon, Michel; Karabulut, Hayrullah

2008-06-06

Recent studies show that earthquake faults may rupture at speeds exceeding the shear wave velocity of rocks. This supershear rupture produces in the ground a seismic shock wave similar to the sonic boom produced by a supersonic airplane. This shock wave may increase the destruction caused by the earthquake. We report that supershear earthquakes are characterized by a specific pattern of aftershocks: The fault plane itself is remarkably quiet whereas aftershocks cluster off the fault, on secondary structures that are activated by the supershear rupture. The post-earthquake quiescence of the fault shows that friction is relatively uniform over supershear segments, whereas the activation of off-fault structures is explained by the shock wave radiation, which produces high stresses over a wide zone surrounding the fault.

Timing of activity of two fault systems on Mercury

NASA Astrophysics Data System (ADS)

Galluzzi, V.; Guzzetta, L.; Giacomini, L.; Ferranti, L.; Massironi, M.; Palumbo, P.

2015-10-01

Here we discuss about two fault systems found in the Victoria and Shakespeare quadrangles of Mercury. The two fault sets intersect each other and show probable evidence for two stages of deformation. The most prominent system is N-S oriented and encompasses several tens to hundreds of kilometers long and easily recognizable fault segments. The other system strikes NE- SW and encompasses mostly degraded and short fault segments. The structural framework of the studied area and the morphological appearance of the faults suggest that the second system is older than the first one. We intend to apply the buffered crater counting technique on both systems to make a quantitative study of their timing of activity that could confirm the already clear morphological evidence.

New constraints on the active tectonic deformation of the Aegean

USGS Publications Warehouse

Nyst, M.; Thatcher, W.

2004-01-01

Site velocities from six separate Global Positioning System (GPS) networks comprising 374 stations have been referred to a single common Eurasia-fixed reference frame to map the velocity distribution over the entire Aegean. We use the GPS velocity field to identify deforming regions, rigid elements, and potential microplate boundaries, and build upon previous work by others to initially specify rigid elements in central Greece, the South Aegean, Anatolia, and the Sea of Marmara. We apply an iterative approach, tentatively defining microplate boundaries, determining best fit rigid rotations, examining misfit patterns, and revising the boundaries to achieve a better match between model and data. Short-term seismic cycle effects are minor contaminants of the data that we remove when necessary to isolate the long-term kinematics. We find that present day Aegean deformation is due to the relative motions of four microplates and straining in several isolated zones internal to them. The RMS misfit of model to data is about 2-sigma, very good when compared to the typical match between coseismic fault models and GPS data. The simplicity of the microplate description of the deformation and its good fit to the GPS data are surprising and were not anticipated by previous work, which had suggested either many rigid elements or broad deforming zones that comprise much of the Aegean region. The isolated deforming zones are also unexpected and cannot be explained by the kinematics of the microplate motions. Strain rates within internally deforming zones are extensional and range from 30 to 50 nanostrain/year (nstrain/year, 10-9/year), 1 to 2 orders of magnitude lower than rates observed across the major microplate boundaries. Lower strain rates may exist elsewhere withi the microplates but are only resolved in Anatolia, where extension of 13 ?? 4 nstrain/ year is required by the data. Our results suggest that despite the detailed complexity of active continental deformation revealed by seismicity, active faulting, fault geomorphology, and earthquake fault plane solutions, continental tectonics, at least in the Aegean, is to first order very similar to global plate tectonics and obeys the same simple kinematic rules. Although the widespread distribution of Aegean seismicity and active faulting might suggest a rather spatially homogeneous seismic hazard, the focusing of deformation near microplate boundaries implies the highest hazard is comparably localized.

Faults Discovery By Using Mined Data

NASA Technical Reports Server (NTRS)

Lee, Charles

2005-01-01

Fault discovery in the complex systems consist of model based reasoning, fault tree analysis, rule based inference methods, and other approaches. Model based reasoning builds models for the systems either by mathematic formulations or by experiment model. Fault Tree Analysis shows the possible causes of a system malfunction by enumerating the suspect components and their respective failure modes that may have induced the problem. The rule based inference build the model based on the expert knowledge. Those models and methods have one thing in common; they have presumed some prior-conditions. Complex systems often use fault trees to analyze the faults. Fault diagnosis, when error occurs, is performed by engineers and analysts performing extensive examination of all data gathered during the mission. International Space Station (ISS) control center operates on the data feedback from the system and decisions are made based on threshold values by using fault trees. Since those decision-making tasks are safety critical and must be done promptly, the engineers who manually analyze the data are facing time challenge. To automate this process, this paper present an approach that uses decision trees to discover fault from data in real-time and capture the contents of fault trees as the initial state of the trees.

Map and database of Quaternary faults in Venezuela and its offshore regions

USGS Publications Warehouse

Audemard, F.A.; Machette, M.N.; Cox, J.W.; Dart, R.L.; Haller, K.M.

2000-01-01

As part of the International Lithosphere Program’s “World Map of Major Active Faults,” the U.S. Geological Survey is assisting in the compilation of a series of digital maps of Quaternary faults and folds in Western Hemisphere countries. The maps show the locations, ages, and activity rates of major earthquake-related features such as faults and fault-related folds. They are accompanied by databases that describe these features and document current information on their activity in the Quaternary. The project is a key part of the Global Seismic Hazards Assessment Program (ILP Project II-0) for the International Decade for Natural Hazard Disaster Reduction.The project is sponsored by the International Lithosphere Program and funded by the USGS’s National Earthquake Hazards Reduction Program. The primary elements of the project are general supervision and interpretation of geologic/tectonic information, data compilation and entry for fault catalog, database design and management, and digitization and manipulation of data in †ARCINFO. For the compilation of data, we engaged experts in Quaternary faulting, neotectonics, paleoseismology, and seismology.

Recently Active Traces of the Berryessa Fault, California: A Digital Database

USGS Publications Warehouse

Lienkaemper, James J.

2012-01-01

The purpose of this map is to show the location of and evidence for recent movement on active fault traces within the Berryessa section and parts of adjacent sections of the Green Valley Fault Zone, California. The location and recency of the mapped traces is primarily based on geomorphic expression of the fault as interpreted from large-scale 2010 aerial photography and from 2007 and 2011 0.5 and 1.0 meter bare-earth LiDAR imagery (that is, high-resolution topographic data). In a few places, evidence of fault creep and offset Holocene strata in trenches and natural exposures have confirmed the activity of some of these traces. This publication is formatted both as a digital database for use within a geographic information system (GIS) and for broader public access as map images that may be browsed on-line or download a summary map. The report text describes the types of scientific observations used to make the map, gives references pertaining to the fault and the evidence of faulting, and provides guidance for use of and limitations of the map.

Preliminary Monitoring of Soil gas Radon in Potentially Active Faults, San Sai District, Chiang Mai Province, Thailand

NASA Astrophysics Data System (ADS)

Pondthai, P.; Udphuay, S.

2013-05-01

The magnitude of 5.1 Mw earthquake occurred in San Sai District, Chiang Mai Province, Thailand in December 2006 was considered an uncommon event due to the fact that there was no statistical record of such significant earthquake in the area. Therefore the earthquake might have been associated with a potentially active fault zone within the area. The objective of this study is to measure soil gas radon across this unknown fault zone within the Chiang Mai Basin, northern Thailand. Two profiles traversing the expected fault zone of soil gas radon measurements have been monitored, using TASTRAK solid state track nuclear detectors (SSNTDs). Radon signals from three periods of measurement show a distinctive consistent spatial distribution pattern. Anomalous radon areas along the profiles are connected to fault locations previously interpreted from other geophysical survey results. The increased radon signal changes from the radon background level with the signal-to-background ratio above 3 are considered anomalous. Such pattern of radon anomaly supports the existence of the faults. The radon measurement, therefore is a powerful technique in mapping active fault zone.

Active faulting in the central Betic Cordillera (Spain): Palaeoseismological constraint of the surface-rupturing history of the Baza Fault (Central Betic Cordillera, Iberian Peninsula)

NASA Astrophysics Data System (ADS)

Castro, J.; Martin-Rojas, I.; Medina-Cascales, I.; García-Tortosa, F. J.; Alfaro, P.; Insua-Arévalo, J. M.

2018-06-01

This paper on the Baza Fault provides the first palaeoseismic data from trenches in the central sector of the Betic Cordillera (S Spain), one of the most tectonically active areas of the Iberian Peninsula. With the palaeoseismological data we constructed time-stratigraphic OxCal models that yield probability density functions (PDFs) of individual palaeoseismic event timing. We analysed PDF overlap to quantitatively correlate the walls and site events into a single earthquake chronology. We assembled a surface-rupturing history of the Baza Fault for the last ca. 45,000 years. We postulated six alternative surface rupturing histories including 8-9 fault-wide earthquakes. We calculated fault-wide earthquake recurrence intervals using Monte Carlo. This analysis yielded a 4750-5150 yr recurrence interval. Finally, compared our results with the results from empirical relationships. Our results will provide a basis for future analyses of more of other active normal faults in this region. Moreover, our results will be essential for improving earthquake-probability assessments in Spain, where palaeoseismic data are scarce.

Active faults newly identified in Pacific Northwest

NASA Astrophysics Data System (ADS)

Balcerak, Ernie

2012-05-01

The Bellingham Basin, which lies north of Seattle and south of Vancouver around the border between the United States and Canada in the northern part of the Cascadia subduction zone, is important for understanding the regional tectonic setting and current high rates of crustal deformation in the Pacific Northwest. Using a variety of new data, Kelsey et al. identified several active faults in the Bellingham Basin that had not been previously known. These faults lie more than 60 kilometers farther north of the previously recognized northern limit of active faulting in the area. The authors note that the newly recognized faults could produce earthquakes with magnitudes between 6 and 6.5 and thus should be considered in hazard assessments for the region. (Journal of Geophysical Reserch-Solid Earth, doi:10.1029/2011JB008816, 2012)

Mechanics of slip and fracture along small faults and simple strike-slip fault zones in granitic rock

NASA Astrophysics Data System (ADS)

Martel, Stephen J.; Pollard, David D.

1989-07-01

We exploit quasi-static fracture mechanics models for slip along pre-existing faults to account for the fracture structure observed along small exhumed faults and small segmented fault zones in the Mount Abbot quadrangle of California and to estimate stress drop and shear fracture energy from geological field measurements. Along small strike-slip faults, cracks that splay from the faults are common only near fault ends. In contrast, many cracks splay from the boundary faults at the edges of a simple fault zone. Except near segment ends, the cracks preferentially splay into a zone. We infer that shear displacement discontinuities (slip patches) along a small fault propagated to near the fault ends and caused fracturing there. Based on elastic stress analyses, we suggest that slip on one boundary fault triggered slip on the adjacent boundary fault, and that the subsequent interaction of the slip patches preferentially led to the generation of fractures that splayed into the zones away from segment ends and out of the zones near segment ends. We estimate the average stress drops for slip events along the fault zones as ˜1 MPa and the shear fracture energy release rate during slip as 5 × 102 - 2 × 104 J/m2. This estimate is similar to those obtained from shear fracture of laboratory samples, but orders of magnitude less than those for large fault zones. These results suggest that the shear fracture energy release rate increases as the structural complexity of fault zones increases.

Assessing the likelihood of volcanic eruption through analysis of volcanotectonic earthquake fault plane solutions

NASA Astrophysics Data System (ADS)

Roman, D. C.; Neuberg, J.; Luckett, R. R.

2006-08-01

Episodes of volcanic unrest do not always lead to an eruption. Many of the commonly monitored signals of volcanic unrest, including surface deformation and increased degassing, can reflect perturbations to a deeper magma storage system, and may persist for years without accompanying eruptive activity. Signals of volcanic unrest can also persist following the end of an eruption. Furthermore, the most reliable eruption precursor, the occurrence of low-frequency seismicity, appears to reflect very shallow processes and typically precedes eruptions by only hours to days. Thus, the identification of measurable and unambiguous indicators that are sensitive to changes in the mid-level conduit system during an intermediate stage of magma ascent is of critical importance to the field of volcano monitoring. Here, using data from the ongoing eruption of the Soufrière Hills Volcano, Montserrat, we show that ˜90° changes in the orientation of double-couple fault-plane solutions for high-frequency 'volcanotectonic' (VT) earthquakes reflect pressurization of the mid-level conduit system prior to eruption and may precede the onset of eruptive episodes by weeks to months. Our results demonstrate that, once the characteristic stress field response to magma ascent at a given volcano is established, a relatively simple analysis of VT fault-plane solutions may be used to make intermediate-term assessments of the likelihood of future eruptive activity.

Seismic Reflection Profiles Image the Rodgers Creek Fault and Cotati Basin Beneath Urban Santa Rosa, California

NASA Astrophysics Data System (ADS)

Williams, R. A.; Langenheim, V. E.; McLaughlin, R. J.; Stephenson, W. J.; Odum, J. K.

2008-12-01

The USGS in collaboration with the Network for Earthquake Engineering Simulation (NEES) group at the University of Texas, Austin, the Sonoma County Water Agency, the city of Santa Rosa, and with support from NSF, collected 13-km of high-resolution seismic-reflection data in two profiles on the Santa Rosa Plain. The purpose of this survey was to image basin structure and stratigraphy in this seismically-active area and to provide constraints for earthquake hazard assessment. We acquired the data using a 9,990 kg minivib I truck in P-wave mode, which swept from 15 to 120 Hz, along city streets and creek-side roads. The common- midpoint spacing of these data is 2.5 m while nominal fold is 36 traces. The Rodgers Creek fault, a northward extension of the Hayward fault which passes through the city of Santa Rosa, has not been imaged previously by seismic reflection data. The east-west trending Santa Rosa Creek profile images several faults including the steeply dipping Rodgers Creek fault as it passes near Doyle Elementary School. In this vicinity the fault zone appears to consist of at least two strands with a set of arched reflectors between them. West of the Rodgers Creek fault, and in general agreement with preexisting gravity data and geologic mapping, we interpret a sedimentary basin more than 1 km deep that underlies downtown Santa Rosa, which was heavily damaged in the 1906 earthquake. This basin shallows to the west as the profile crosses the southeastern side of Trenton Ridge, a concealed basement high. Reflectors within the basin show a thickening sequence of layered strata and apparent dips of about 10 degrees east in the 400 to 800 m depth range that decrease to about 1 degree at 50 m depth. These new data will help to constrain existing seismic velocity models for this area which currently show only flat-lying basin fill.

Kinematics of rotating panels of E-W faults in the San Andreas system: what can we tell from geodesy?

NASA Astrophysics Data System (ADS)

Platt, J. P.; Becker, T. W.

2013-09-01

Sets of E- to NE-trending sinistral and/or reverse faults occur within the San Andreas system, and are associated with palaeomagnetic evidence for clockwise vertical-axis rotations. These structures cut across the trend of active dextral faults, posing questions as to how displacement is transferred across them. Geodetic data show that they lie within an overall dextral shear field, but the data are commonly interpreted to indicate little or no slip, nor any significant rate of rotation. We model these structures as rotating by bookshelf slip in a dextral shear field, and show that a combination of sinistral slip and rotation can produce the observed velocity field. This allows prediction of rates of slip, rotation, fault-parallel extension and fault-normal shortening within the panel. We use this method to calculate the kinematics of the central segment of the Garlock Fault, which cuts across the eastern California shear zone at a high angle. We obtain a sinistral slip rate of 6.1 ± 1.1 mm yr-1, comparable to geological evidence, but higher than most previous geodetic estimates, and a rotation rate of 4.0 ± 0.7° Myr-1 clockwise. The western Transverse Ranges transect a similar shear zone in coastal and offshore California, but at an angle of only 40°. As a result, the faults, which were sinistral when they were at a higher angle to the shear zone, have been reactivated in a dextral sense at a low rate, and the rate of rotation of the panel has decreased from its long-term rate of ˜5° to 1.6° ± 0.2° Myr-1 clockwise. These results help to resolve some of the apparent discrepancies between geological and geodetic slip-rate estimates, and provide an enhanced understanding of the mechanics of intracontinental transform systems.

Late Quaternary paleoearthquakes along the northern segment of the Nantinghe fault on the southeastern margin of the Tibetan Plateau

NASA Astrophysics Data System (ADS)

Sun, Haoyue; He, Honglin; Wei, Zhanyu; Shi, Feng; Gao, Wei

2017-05-01

The strong earthquake behaviors of faults are significant for learning crustal deformation mechanisms and for assessing regional seismic risk. To date, faults that bound tectonic blocks have attracted considerable concern and many studies; however, scant attention has been paid to faults within blocks that can also host devastating earthquakes. The Nantinghe fault is a left-lateral strike-slip fault within the Southwestern Yunnan Block, and it slips at ∼4 mm/yr suggesting strong activity in the late Quaternary. Nevertheless, no earthquake greater than 6 has ever been recorded along it, except for the 1941 M ∼7 earthquake near the Myanmar-China border region. In contrast, many earthquakes have occurred in the near region, delineating a seismic gap near the Nantinghe fault. Although several studies have been conducted upon it, the activity of its northern segment is confusing, and whether this fault segment has loaded sufficient stress to fail remains debatable. Furthermore, previous work failed to conduct any paleoseismological studies bringing out great uncertainty in learning its activity and faulting behavior, as well as in assessing the regional seismic risk. To solve these problems, we mapped the fault traces utilizing high-resolution satellite images and aerial photographs, and conducted three paleoseismological trenches along the northern segment of the Nantinghe fault. The trench excavations revealed a ∼45,000-year incomplete paleoearthquake history and confirmed that this fault segment has been active since the late Pleistocene but was not ruptured during the 1941 earthquake. Additionally, at least five paleoearthquakes are identified with their respective age ranges of before 39,030 BCE; 38,500-37,220 BCE; 28,475-5445 BCE; 3535 BCE-800 CE; and 1320-1435 CE based on radiocarbon dating. Among the paleoearthquakes, the latest is suggested to have generated a surface rupture much longer than 14 km with a magnitude likely up to Ms 7.0. Furthermore, based on the elapsed time since the latest paleoearthquake and the sinistral slip rate along the fault, it is proposed that the northern segment of the Nantinghe fault has accumulated a seismic energy equivalent to Ms 7.0, and it is in a high seismic risk along this fault segment and in the neighboring area.

A data structure and algorithm for fault diagnosis

NASA Technical Reports Server (NTRS)

Bosworth, Edward L., Jr.

1987-01-01

Results of preliminary research on the design of a knowledge based fault diagnosis system for use with on-orbit spacecraft such as the Hubble Space Telescope are presented. A candidate data structure and associated search algorithm from which the knowledge based system can evolve is discussed. This algorithmic approach will then be examined in view of its inability to diagnose certain common faults. From that critique, a design for the corresponding knowledge based system will be given.

Active Tectonics of Himalayan Faults/Thrusts System in Northern India on the basis of recent & Paleo earthquake Studies

NASA Astrophysics Data System (ADS)

Kumar, S.; Biswal, S.; Parija, M. P.

2016-12-01

The Himalaya overrides the Indian plate along a decollement fault, referred as the Main Himalayan Thrust (MHT). The 2400 km long Himalayan mountain arc in the northern boundary of the Indian sub-continent is one of the most seismically active regions of the world. The Himalayan Frontal Thrust (HFT) is characterized by an abrupt physiographic and tectonic break between the Himalayan front and the Indo-Gangetic plain. The HFT represents the southern surface expression of the MHT on the Himalayan front. The tectonic zone between the Main Boundary Thrust (MBT) and the HFT encompasses the Himalayan Frontal Fault System (HFFS). The zone indicates late Quaternary-Holocene active deformation. Late Quaternary intramontane basin of Dehradun flanked to the south by the Mohand anticline lies between the MBT and the HFT in Garhwal Sub Himalaya. Slip rate 13-15 mm/yr has been estimated on the HFT based on uplifted strath terrace on the Himalyan front (Wesnousky et al. 2006). An out of sequence active fault, Bhauwala Thrust (BT), is observed between the HFT and the MBT. The Himalayan Frontal Fault System includes MBT, BT, HFT and PF active fault structures (Thakur, 2013). The HFFS structures were developed analogous to proto-thrusts in subduction zone, suggesting that the plate boundary is not a single structure, but series of structures across strike. Seismicity recorded by WIHG shows a concentrated belt of seismic events located in the Main Central Thrust Zone and the physiographic transition zone between the Higher and Lesser Himalaya. However, there is quiescence in the Himalayan frontal zone where surface rupture and active faults are reported. GPS measurements indicate the segment between the southern extent of microseismicity zone and the HFT is locked. The great earthquake originating in the locked segment rupture the plate boundary fault and propagate to the Himalaya front and are registered as surface rupture reactivating the fault in the HFFS.

Geology along the Fairweather-Queen Charlotte fault system off southeast Alaska and British Columbia from GLORIA images and seismic-reflection data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bruns, T.R.; Carlson, P.R.; Stevenson, A.J.

1990-06-01

GLORIA images collected in 1989 along southeast Alaska and British Columbia strikingly show the active trace of the Fairweather-Queen Charlotte transform fault system beneath the outer shelf and slope; seismic-reflection data are used to track the fault system across the continental shelf where GLORIA data are not available. From Cross Sound to Chatham Strait, the fault system is comprised of two sets of subparallel fault traces separated by 3 to 6 km. The fault system crosses the shelf from Icy Point to south of Yakobi Valley, then follows the shelf edge to Chatham Strait. Between Chatham Strait and Dixon Entrance,more » a single, sharply defined active fault trace underlies the upper and middle slope. This fault segment is bounded on the seaward side by a high, midslope ridge and by lower slope Quaternary( ) anticlines up to 35 km wide. Southeast of Dixon Entrance, the active fault trace trends back onto the outer shelf until midway along the Queen Charlotte Islands, then cuts back to and stays at midslope to the Tuzo Wilson Knolls south of the Queen Charlotte Islands. The fault steps westward at Tuzo Wilson Knolls, which are likely part of a spreading ridge segment. Major deep-sea fans along southeast Alaska show a southeastward age progression from older to younger and record both point source deposition at Chatham Strait and Dixon Entrance and subsequent (Quaternary ) offset along the fault system. Subsidence of ocean plate now adjacent to the Chatham Strait-Dixon Entrance fault segment initiated development of both Mukluk and Horizon Channels.« less

Multidisciplinary approach for fault detection: Integration of PS-InSAR, geomorphological, stratigraphic and structural data in the Venafro intermontane basin (Central-Southern Apennines, Italy)

NASA Astrophysics Data System (ADS)

Amato, Vincenzo; Aucelli, Pietro P. C.; Bellucci Sessa, Eliana; Cesarano, Massimo; Incontri, Pietro; Pappone, Gerardo; Valente, Ettore; Vilardo, Giuseppe

2017-04-01

A multidisciplinary methodology, integrating stratigraphic, geomorphological and structural data, combined with GIS-aided analysis and PS-InSAR interferometric data, was applied to characterize the relationships between ground deformations and the stratigraphic and the morphostructural setting of the Venafro intermontane basin. This basin is a morphostructural depression related to NW-SE and NE-SW oriented high angle normal faults bordering and crossing it. In particular, a well-known active fault crossing the plain is the Aquae Juliae Fault, whose recent activity is evidenced by archeoseismological data. The approach applied here reveals new evidence of possible faulting, acting during the Lower to Upper Pleistocene, which has driven the morphotectonic and the environmental evolution of the basin. In particular, the tectonic setting emerging from this study highlights the influence of the NW-SE oriented extensional phase during the late Lower Pleistocene - early Middle Pleistocene, in the generation of NE-SW trending, SE dipping, high-angle faults and NW-SE trending, high-angle transtensive faults. This phase has been followed by a NE-SW extensional one, responsible for the formation of NW-SE trending, both NW and SE dipping, high-angle normal faults, and the reactivation of the oldest NE-SW oriented structures. These NW-SE trending normal faults include the Aquae Juliae Fault and a new one, unknown until now, crossing the plain between the Venafro village and the Colle Cupone Mt. (hereinafter named the Venafro-Colle Cupone Fault, VCCF). This fault has controlled deposition of the youngest sedimentary units (late Middle Pleistocene to late Upper Pleistocene) suggesting its recent activity and it is well constrained by PS-InSAR data, as testified by the increase of the subsidence rate in the hanging wall block.

New Geologic Data on the Seismic Risks of the Most Dangerous Fault on Shore in Central Japan, the Itoigawa-Shizuoka Tectonic Line Active Fault System

NASA Astrophysics Data System (ADS)

Okumura, K.; Kondo, H.; Toda, S.; Takada, K.; Kinoshita, H.

2006-12-01

Ten years have past since the first official assessment of the long-term seismic risks of the Itoigawa-Shizuoka tectonic line active fault system (ISTL) in 1996. The disaster caused by the1995 Kobe (Hyogo-ken-Nanbu) earthquake urged the Japanese government to initiated a national project to assess the long-term seismic risks of on-shore active faults using geologic information. ISTL was the first target of the 98 significant faults and the probability of a M7 to M8 event turned out to be the highest among them. After the 10 years of continued efforts to understand the ISTL, now it is getting ready to revise the assessment. Fault mapping and segmentation: The most active segment of the Gofukuji fault (~1 cm/yr left-lateral strike slip, R=500~800 yrs.) had been maped only for less than 10 km. Adjacent segments were much less active. This large slip on such a short segment was contradictory. However, detailed topographic study including Lidar survey revealed the length of the Gofukuji fault to be 25 km or more. High slip rate with frequent earthquakes may be restricted to the Gofukuji fault while the 1996 assessment modeled frequent >100 km rupture scenario. The geometry of the fault is controversial especially on the left-lateral strike-slip section of the ISTL. There are two models of high-angle Middel ISTL and low-angle Middle ISTL with slip partitioning. However, all geomorphic and shallow geologic data supports high-angle almost pure strike slip on the faults in the Middle ISTL. CRIEPI's 3- dimensional trenching in several sites as well as the previous results clearly demonstrated repeated pure strike-slip offset during past a few events. In Middle ISTL, there is no evidence of recent activity of pre-existing low-angle thrust faults that are inferred to be active from shallow seismic survey. Separation of high (~3000 m) mountain ranges and low (<1000 m) basin floor requires significant dip-slip component, but basin-fill sediments and geology of the range do not need vertical separation along the Gofukuji fault. The key issue for the time-dependent assessment of the Northern ISTL (east dipping reverse faults) was the lack of reliable time constraints on past earthquakes. In order to solve this problem, we have carried out intensive geoslicer and boring survey of buried faults at Kisaki. Along a 35 m long transect, we collected total 150 m complete cores in 9 geoslicer and 5 all-core boring holes. This is one of the most intensive surveys of a buried fault scarp under the water table. About 20 m vertical offset of 6000-year-old buried A-horizon is now underlain by a series of flood deposits, point bars and over-bank sediments, that intercalates 2 or 3 faulting events. The precise timing and offset of each event recorded in the section will be the critical evidence to tell the synchroneity of earthquakes in the Northern ISTL and the Middle ISTL. The magnitude of the coming event on ISTL is the most important but uncertain parameter of the 1996 assessment. The structural and paleoseimological information will present better constraints on the earthquake.

Ground Deformation near active faults in the Kinki district, southwest Japan, detected by InSAR

NASA Astrophysics Data System (ADS)

Hashimoto, M.; Ozawa, T.

2016-12-01

The Kinki district, southwest Japan, consists of ranges and plains between which active faults reside. The Osaka plain is in the middle of this district and is surrounded by the Rokko, Arima-Takatsuki, Ikoma, Kongo and Median Tectonic Line fault zones in the clockwise order. These faults are considered to be capable to generate earthquakes of larger magnitude than 7. The 1995 Kobe earthquake is the most recent activity of the Rokko fault (NE-SW trending dextral fault). Therefore the monitoring of ground deformation with high spatial resolution is essential to evaluate seismic hazards in this area. We collected and analyzed available SAR images such as ERS-1/2, Envisat, JERS-1, TerraSAR-X, ALOS/PALSAR and ALOS-2/PALSAR-2 to reveal ground deformation during these 20 years. We made DInSAR and PSInSAR analyses of these images using ASTER-GDEM ver.2. We detected three spots of subsidence along the Arima-Takatsuki fault (ENE-WSW trending dextral fault, east neighbor of the Rokko fault) after the Kobe earthquake, which continued up to 2010. Two of them started right after the Kobe earthquake, while the easternmost one was observed after 2000. However, we did not find them in the interferograms of ALOS-2/PALSAR-2 acquired during 2014 - 2016. Marginal uplift was recognized along the eastern part of the Rokko fault. PS-InSAR results of ALOS/PALSAR also revealed slight uplift north of the Rokko Mountain that uplift by 20 cm coseismically. These observations suggest that the Rokko Mountain might have uplifted during the postseismic period. We found subsidence on the eastern frank of the Kongo Mountain, where the Kongo fault (N-S trending reverse fault) exits. In the southern neighbor of the Median Tectonic Line (ENE-WSW trending dextral fault), uplift of > 5 mm/yr was found by Envisat and ALOS/PALSAR images. This area is shifted westward by 4 mm/yr as well. Since this area is located east of a seismically active area in the northwestern Wakayama prefecture, this deformation may generate E-W compressive stress, which is dominant in focal mechanism of most earthquakes, in the epicentral area.

Intraplate seismicity along the Gedi Fault in Kachchh rift basin of western India

NASA Astrophysics Data System (ADS)

Joshi, Vishwa; Rastogi, B. K.; Kumar, Santosh

2017-11-01

The Kachchh rift basin is located on the western continental margin of India and has a history of experiencing large to moderate intraplate earthquakes with M ≥ 5. During the past two centuries, two large earthquakes of Mw 7.8 (1819) and Mw 7.7 (2001) have occurred in the Kachchh region, the latter with an epicenter near Bhuj. The aftershock activity of the 2001 Bhuj earthquake is still ongoing with migration of seismicity. Initially, epicenters migrated towards the east and northeast within the Kachchh region but, since 2007, it has also migrated to the south. The triggered faults are mostly within 100 km and some up to 200 km distance from the epicentral area of the mainshock. Most of these faults are trending in E-W direction, and some are transverse. It was noticed that some faults generate earthquakes down to the Moho depth whereas some faults show earthquake activity within the upper crustal volume. The Gedi Fault, situated about 50 km northeast of the 2001 mainshock epicenter, triggered the largest earthquake of Mw 5.6 in 2006. We have carried out detailed seismological studies to evaluate the seismic potential of the Gedi Fault. We have relocated 331 earthquakes by HypoDD to improve upon location errors. Further, the relocated events are used to estimate the b value, p value, and fractal correlation dimension Dc of the fault zone. The present study indicates that all the events along the Gedi Fault are shallow in nature, with focal depths less than 20 km. The estimated b value shows that the Gedi aftershock sequence could be classified as Mogi's type 2 sequence, and the p value suggests a relatively slow decay of aftershocks. The fault plane solutions of some selected events of Mw > 3.5 are examined, and activeness of the Gedi Fault is assessed from the results of active fault studies as well as GPS and InSAR results. All these results are critically examined to evaluate the material properties and seismic potential of the Gedi Fault that may be useful for seismic hazard assessment in the region.

Map and Database of Probable and Possible Quaternary Faults in Afghanistan

USGS Publications Warehouse

Ruleman, C.A.; Crone, A.J.; Machette, M.N.; Haller, K.M.; Rukstales, K.S.

2007-01-01

The U.S. Geological Survey (USGS) with support from the U.S. Agency for International Development (USAID) mission in Afghanistan, has prepared a digital map showing the distribution of probable and suspected Quaternary faults in Afghanistan. This map is a key component of a broader effort to assess and map the country's seismic hazards. Our analyses of remote-sensing imagery reveal a complex array of tectonic features that we interpret to be probable and possible active faults within the country and in the surrounding border region. In our compilation, we have mapped previously recognized active faults in greater detail, and have categorized individual features based on their geomorphic expression. We assigned mapped features to eight newly defined domains, each of which contains features that appear to have similar styles of deformation. The styles of deformation associated with each domain provide insight into the kinematics of the modern tectonism, and define a tectonic framework that helps constrain deformational models of the Alpine-Himalayan orogenic belt. The modern fault movements, deformation, and earthquakes in Afghanistan are driven by the collision between the northward-moving Indian subcontinent and Eurasia. The patterns of probable and possible Quaternary faults generally show that much of the modern tectonic activity is related to transfer of plate-boundary deformation across the country. The left-lateral, strike-slip Chaman fault in southeastern Afghanistan probably has the highest slip rate of any fault in the country; to the north, this slip is distributed onto several fault systems. At the southern margin of the Kabul block, the style of faulting changes from mainly strike-slip motion associated with the boundary between the Indian and Eurasian plates, to transpressional and transtensional faulting. North and northeast of the Kabul block, we recognized a complex pattern of potentially active strike-slip, thrust, and normal faults that form a conjugate shear system in a transpressional region of the Trans-Himalayan orogenic belt. The general patterns and orientations of faults and the styles of deformation that we interpret from the imagery are consistent with the styles of faulting determined from focal mechanisms of historical earthquakes. Northwest-trending strike-slip fault zones are cut and displaced by younger, southeast-verging thrust faults; these relations define the interaction between northwest-southeast-oriented contraction and northwest-directed extrusion in the western Himalaya, Pamir, and Hindu Kush regions. Transpression extends into north-central Afghanistan where north-verging contraction along the east-west-trending Alburz-Marmul fault system interacts with northwest-trending strike-slip faults. Pressure ridges related to thrust faulting and extensional basins bounded by normal faults are located at major stepovers in these northwest-trending strike-slip systems. In contrast, young faulting in central and western Afghanistan indicates that the deformation is dominated by extension where strike-slip fault zones transition into regions of normal faults. In addition to these initial observations, our digital map and database provide a foundation that can be expanded, complemented, and modified as future investigations provide more detailed information about the location, characteristics, and history of movement on Quaternary faults in Afghanistan.

Geomorphology, kinematic history, and earthquake behavior of the active Kuwana wedge thrust anticline, central Japan

NASA Astrophysics Data System (ADS)

Ishiyama, Tatsuya; Mueller, Karl; Togo, Masami; Okada, Atsumasa; Takemura, Keiji

2004-12-01

We combine surface mapping of fault and fold scarps that deform late Quaternary alluvial strata with interpretation of a high-resolution seismic reflection profile to develop a kinematic model and determine fault slip rates for an active blind wedge thrust system that underlies Kuwana anticline in central Japan. Surface fold scarps on Kuwana anticline are closely correlated with narrow fold limbs and angular hinges on the seismic profile that suggest at least ˜1.3 km of fault slip completely consumed by folding in the upper 4 km of the crust. The close coincidence and kinematic link between folded terraces and the underlying thrust geometry indicate that Kuwana anticline has accommodated slip at an average rate of 2.2 ± 0.5 mm/yr on a 27°, west dipping thrust fault since early-middle Pleistocene time. In contrast to classical fault bend folds the fault slip budget in the stacked wedge thrusts also indicates that (1) the fault tip propagated upward at a low rate relative to the accrual of fault slip and (2) fault slip is partly absorbed by numerous bedding plane flexural-slip faults above the tips of wedge thrusts. An historic earthquake that occurred on the Kuwana blind thrust system possibly in A.D. 1586 is shown to have produced coseismic surface deformation above the doubly vergent wedge tip. Structural analyses of Kuwana anticline coupled with tectonic geomorphology at 103-105 years timescales illustrate the significance of active folds as indicators of slip on underlying blind thrust faults and thus their otherwise inaccessible seismic hazards.

Alternative interpretation for the active zones of Cuba

NASA Astrophysics Data System (ADS)

Rodríguez, Mario Octavio Cotilla

2014-11-01

An alternative explanation to the seismoactivity of Cuban faults is presented. The model is a consequence of the interaction between Caribbean and North American plates. It is made with 12 geodynamic cells form by a set of 13 active faults and their 14 areas of intersection. These cells are recognized morpho-structural blocks. The area between Eastern Matanzas and Western Cauto-Nipe is excluded because of the low level of seismic information. Cuba has two types of seismogenetic structures: faults and intersection of faults.

Tectonic geomorphology and paleoseismology of strike-slip faults in Jamaica: Implications for distribution of strain and seismic hazard along the southern edge of the Gonave microplate

NASA Astrophysics Data System (ADS)

Koehler, R. D.; Mann, P.; Brown, L. A.

2009-12-01

The east-west, left lateral strike-slip fault system forming the southern edge of the Gonave microplate crosses the110-km-long and 70-km-wide island of Jamaica. GPS measurements in the northeastern Caribbean are supportive of the microplate interpretation and indicate that ~ half of the Caribbean-North America left-lateral plate motion (8-14 mm/yr) is carried by the Plantain Garden (PGFZ) and associated faults in Jamaica. We performed Neotectonic mapping of the Plantain Garden fault along the southern rangefront of the Blue Mountains and conducted a paleoseismic study of the fault at Morant River. Between Holland Bay and Morant River, the fault is characterized by a steep, faceted, linear mountain front, prominent linear valleys and depressions, shutter ridges, and springs. At the eastern end of the island, the PGFZ is characterized by a left-stepping fault geometry that includes a major, active hot spring. The river cut exposure at Morant River exposes a 1.5-m-wide, sub-vertical fault zone juxtaposing sheared alluvium and faulted Cretaceous basement rocks. This section is overlain by an, unfaulted 3-m-thick fluvial terrace inset into a late Pleistocene terrace that is culturally modified. Upward fault terminations indicate the occurrence of three paleoearthquakes that occurred prior to deposition of the flat lying inset terrace around 341-628 cal yr BP. At this time, our radiocarbon results suggest that we can rule out the PGFZ as the source of the 1907 Kingston earthquake 102 years ago, as well as, the 1692 event that destroyed Port Royal 317 years ago and produced a major landslide at Yallahs. Pending OSL ages will constrain the age of the penultimate and most recent ruptures. Gently to steeply dipping rocks as young as Pliocene exposed in roadcuts within the low coastal hills south of and parallel to the Plantain Garden fault may indicate active folding and blind thrust faulting. These structures are poorly characterized and may accommodate an unknown amount of oblique strain. Reconnaissance mapping was also performed along the South Coast fault in south-central Jamaica north of Portland Ridge, and along the Crawle River-Rio Minho fault near Frankfield in the Central Inlier. The absence of fault scarps or other tectonic geomorphic features across fluvial terraces of the Milk and Minho Rivers indicate that the South Coast fault has not been active in Holocene time. Left laterally offset streams, linear valleys, and saddles support active faulting along the east-west Crawle River-Rio Minho fault that is roughly collinear with the western extension of the Plantain Garden fault.

Palaeopermeability structure within fault-damage zones: A snap-shot from microfracture analyses in a strike-slip system

NASA Astrophysics Data System (ADS)

Gomila, Rodrigo; Arancibia, Gloria; Mitchell, Thomas M.; Cembrano, Jose M.; Faulkner, Daniel R.

2016-02-01

Understanding fault zone permeability and its spatial distribution allows the assessment of fluid-migration leading to precipitation of hydrothermal minerals. This work is aimed at unraveling the conditions and distribution of fluid transport properties in fault zones based on hydrothermally filled microfractures, which reflect the ''frozen-in'' instantaneous advective hydrothermal activity and record palaeopermeability conditions of the fault-fracture system. We studied the Jorgillo Fault, an exposed 20 km long, left-lateral strike-slip fault, which juxtaposes Jurassic gabbro against metadiorite belonging to the Atacama Fault System in northern Chile. Tracings of microfracture networks of 19 oriented thin sections from a 400 m long transect across the main fault trace was carried out to estimate the hydraulic properties of the low-strain fault damagezone, adjacent to the high-strain fault core, by assuming penny-shaped microfractures of constant radius and aperture within an anisotropic fracture system. Palaeopermeability values of 9.1*10-11 to 3.2*10-13 m2 in the gabbro and of 5.0*10-10 to 1.2*10-13 m2 in the metadiorite were determined, both decreasing perpendicularly away from the fault core. Fracture porosity values range from 40.00% to 0.28%. The Jorgillo Fault has acted as a left-lateral dilational fault-bend, generating large-scale dilation sites north of the JF during co-seismic activity.

Tectonic context of moderate to large historical earthquakes in the Lesser Antilles and mechanical coupling with volcanoes

NASA Astrophysics Data System (ADS)

Feuillet, Nathalie; Beauducel, FrançOis; Tapponnier, Paul

2011-10-01

The oblique convergence between North American and Caribbean plates is accommodated in a bookshelf faulting manner by active, oblique-normal faults in the northern part of the Lesser Antilles arc. In the last 20 years, two M > 6 earthquakes occurred along a large, arc parallel, en echelon fault system, the 16 March 1985 in Redonda and 21 November 2004 in Les Saintes. A better understanding of active faulting in this region permit us to review the location and magnitude of historical earthquakes by using a regional seismic attenuation law. Several others moderate earthquakes may have occurred along the en echelon fault system implying a strong seismic hazard along the arc. These faults control the effusion of volcanic products and some earthquakes seem to be correlated in time with volcanic unrest. Shallow earthquakes on intraplate faults induced normal stress and pressure changes around neighboring volcano and may have triggered volcanic activity. The Redonda earthquake could have initiated the 1995 eruption of Montserrat's Soufrière Hills by compressing its plumbing system. Conversely, pressure changes under the volcano increased Coulomb stress changes and brought some faults closer to failure, promoting seismicity. We also discuss the magnitude of the largest 11 January 1839 and 8 February 1843 megathrust interplate earthquakes. We calculate that they have increased the stress on some overriding intraplate faults and the extensional strain beneath several volcanoes. This may explain an increase of volcanic and seismic activity in the second half of the 19th century culminating with the devastating, 1902 Mount Pelée eruption.

Active transpressional tectonics in the Andean forearc of southern Peru quantified by 10Be surface exposure dating of an active fault scarp

NASA Astrophysics Data System (ADS)

Benavente, Carlos; Zerathe, Swann; Audin, Laurence; Hall, Sarah R.; Robert, Xavier; Delgado, Fabrizio; Carcaillet, Julien; Team, Aster

2017-09-01

Our understanding of the style and rate of Quaternary tectonic deformation in the forearc of the Central Andes is hampered by a lack of field observations and constraints on neotectonic structures. Here we present a detailed analysis of the Purgatorio fault, a recently recognized active fault located in the forearc of southern Peru. Based on field and remote sensing analysis (Pléiades DEM), we define the Purgatorio fault as a subvertical structure trending NW-SE to W-E along its 60 km length, connecting, on its eastern end, to the crustal Incapuquio Fault System. The Purgatorio fault accommodates right-lateral transpressional deformation, as shown by the numerous lateral and vertical plurimetric offsets recorded along strike. In particular, scarp with a 5 m cumulative throw is preserved and displays cobbles that are cut and covered by slickensides. Cosmogenic radionuclide exposure dating (10Be) of quartzite cobbles along the vertical fault scarp yields young exposure ages that can be bracketed between 0 to 6 ka, depending on the inheritance model that is applied. Our preferred scenario, which takes in account our geomorphic observations, implies at least two distinct rupture events, each associated with 3 and 2 m of vertical offset. These two events plausibly occurred during the last thousand years. Nevertheless, an interpretation invoking more tectonic events along the fault cannot be ruled out. This work affirms crustal deformation along active faults in the Andean forearc of southern Peru during the last thousand years.

Microstructures and composition of brittle faults in claystones: Constraints on the barrier behavior

NASA Astrophysics Data System (ADS)

Kneuker, Tilo; Hammer, Jörg; Jahn, Steffen; Zulauf, Gernold

2017-04-01

Investigations of fault rocks are crucial to evaluate the barrier properties of clay rich formations used for the storage of hydrocarbons, carbon dioxide gas or for the storage of heat generating radioactive waste. Claystones are considered as a geological barrier. However, their barrier capability can be reduced if the claystones are cut by brittle faults. Our study is focusing on the microfabrics and element mobility of artificially and naturally fractured claystones using a multi-method approach. Particular attention was paid to small scale lithological heterogeneities occurring in the clayey sequence. The microfabrics were investigated using SEM and optical microscopy. Geochemical and phase analyses were carried out using XRD, XRF and ICP-MS. In addition, organic (TOC) and inorganic carbon (TIC), total sulphur (TS) as well as the cation exchange capacity (CEC) were determined. Macroscopic observations of fault zones on outcrops and drill cores indicate closely spaced planar and undulating discontinuities, including slickenside striations. The investigated fault zones are often accompanied by calcite veins and calcite enriched zones. The fault core is formed by a mm to cm thick clayey, fine grained, cohesionless fault gouge including reworked calcite fragments. Duplex-like domains are separated by discrete microshears, along which the rocks disintegrate. Calcareous fossils, common in undeformed claystones, appear in these zones fragmented and rotated. In contrast to calcite, quartz is more resistant to solution-precipitation processes. Rarely intracrystalline fracturing was observed. The calcite mineralization in veins, and solution-precipitation processes of calcite, documented by stylolites, reflect enhanced palaeo-permeability and activity of Ca2+- and CO2-rich fluids inside some of the fault zones, mainly along fault parallel shear planes. Elevated Sr and Ba concentrations are bound to the tectonic, secondary calcite veins within and outside the investigated fault zone. The geochemical data presented in form of isocon diagrams suggest volume gain related to the opening of veins and pores, which are now filled with calcite. Our results do not provide evidence for presently open pores or fractures, which might be related to non-artificial tectonic deformation. However, (micro)fractures as well as mineralized veins represent inherited damage in the rock, and are prone to brittle reactivation during fluid pressure increase or during the excavation of underground galleries. A complex, polyphase deformation history including a possible reactivation of older structures is supported by our observations.

A review of recently active faults in Taiwan

USGS Publications Warehouse

Bonilla, Manuel G.

1975-01-01

Six faults associated with five large earthquakes produced surface displacements ranging from 1 to 3 m in the period 1906 through 1951. Four of the ruptures occurred in the western coastal plain and foothills, and two occurred in the Longitudinal Valley of eastern Taiwan. Maps are included showing the locations and dimensions of the displacements. The published geological literature probably would not lead one to infer the existence of a fault along most of the 1906 rupture, except for descriptions of the rupture itself. Over most of its length the 1935 rupture on the Chihhu fault is parallel to but more than 0.5 km from nearby faults shown on geologic maps published in 1969 and 1971; only about 1.5 km of its 15 km length coincides with a mapped fault. The coastal plain part of the Tuntzuchio fault which ruptured in 1935 is apparently not revealed by landforms, and only suggested by other data. Part of the 1946 Hsinhua faulting coincides with a fault identified in the subsurface by seismic work but surface indications of the fault are obscure. The 1951 Meilun faulting occurred along a conspicuous pre-1951 scarp and the 1951 Yuli faulting occurred near or in line with pre-1951 scarps. More than 40 faults which, according to the published literature, have had Pleistocene or later movement are shown on a small-scale map. Most of these faults are in the densely-populated western part of Taiwan. The map and text calls attention to faults that may be active and therefore may be significant in planning important structures. Equivocal evidence suggestive of fault creep was found on the Yuli fault and the Hsinhua fault. Fault creep was not found at several places examined along the 1906 fault trace. Tectonic uplift has occurred in Taiwan in the last 10,000 years and application of eustatic sea level curves to published radiocarbon dates shows that the minimum rate of uplift is considerably different in different parts of the island. Incomplete data indicate that the rate is high near Hualien, where an uplift of at least 0.6 m and probably more than 1 m occurred in the 1951 earthquake, and near and south of the 1946 faulting. Sudden uplifts can have serious consequences for installations near the shore. Investigation of this process, study of recently active faults, and continuing study of seismicity are necessary parts of a practical earthquake-hazard reduction program.

A microstructural study of fault rocks from the SAFOD: Implications for the deformation mechanisms and strength of the creeping segment of the San Andreas Fault

NASA Astrophysics Data System (ADS)

Hadizadeh, Jafar; Mittempergher, Silvia; Gratier, Jean-Pierre; Renard, Francois; Di Toro, Giulio; Richard, Julie; Babaie, Hassan A.

2012-09-01

The San Andreas Fault zone in central California accommodates tectonic strain by stable slip and microseismic activity. We study microstructural controls of strength and deformation in the fault using core samples provided by the San Andreas Fault Observatory at Depth (SAFOD) including gouge corresponding to presently active shearing intervals in the main borehole. The methods of study include high-resolution optical and electron microscopy, X-ray fluorescence mapping, X-ray powder diffraction, energy dispersive X-ray spectroscopy, white light interferometry, and image processing. The fault zone at the SAFOD site consists of a strongly deformed and foliated core zone that includes 2-3 m thick active shear zones, surrounded by less deformed rocks. Results suggest deformation and foliation of the core zone outside the active shear zones by alternating cataclasis and pressure solution mechanisms. The active shear zones, considered zones of large-scale shear localization, appear to be associated with an abundance of weak phases including smectite clays, serpentinite alteration products, and amorphous material. We suggest that deformation along the active shear zones is by a granular-type flow mechanism that involves frictional sliding of microlithons along phyllosilicate-rich Riedel shear surfaces as well as stress-driven diffusive mass transfer. The microstructural data may be interpreted to suggest that deformation in the active shear zones is strongly displacement-weakening. The fault creeps because the velocity strengthening weak gouge in the active shear zones is being sheared without strong restrengthening mechanisms such as cementation or fracture sealing. Possible mechanisms for the observed microseismicity in the creeping segment of the SAF include local high fluid pressure build-ups, hard asperity development by fracture-and-seal cycles, and stress build-up due to slip zone undulations.

Structural Analysis and Evolution of the Kashan (Qom-Zefreh) Fault, Central Iran

NASA Astrophysics Data System (ADS)

Safaei, H.; Taheri, A.; Vaziri-Moghaddam, H.

The main objectives of this research were to identify the geometry and structure of the Qom-Zefreh fault and to determine the extent of its effects on stratigraphy and facies changes. The identification of movement mechanism of major faults in basement, extent and time of their activities are important effects for evaluation of paleogeography of the Iran plateau. In the Orumieh-Dokhtar volcanic band, there are nearly parallel faults to the Zagros Zone. These faults were formed during closure of the Neothetys and collision of the Arabic plate with crust of Iran. The Qom-Zefreh fault is one of these faults, which is known as having four different trend faults. The result indicates that, this fault is not divided in four segments with different trends but the major trend is of Central section, which is the Kashan segment with AZ140 trend and other segments are just related faults. Thus the name of the Kashan fault is recommended for this fault. The mechanism of the Kashan fault is dextral transpression and other related faults in the region are in good correlation with fractures in a dextral transpression system. The stratigraphic studies conducted on the present formations show the effect of fault movements in Upper Cretaceous sedimentary basin. Lack of noticeable changes in Lower Cretaceous sediments and before that indicates that, the fault system activity has been started from the Upper Cretaceous. Thus, based upon these results, the effect of the Neothetys sea closure in this region could be considered at least from the Upper Cretaceous.

Trench logs, terrestrial lidar system imagery, and radiocarbon data from the kilometer-62 site on the Greenville Fault, southeastern Alameda County, California, 2014

USGS Publications Warehouse

Lienkaemper, James J.; DeLong, Stephen B.; Avdievitch, Nikita N.; Pickering, Alexandra J; Guilderson, Thomas P.

2015-01-01

In 2014, we investigated an abrupt 8.5-meter (m), right-laterally deflected stream channel located near the Greenville Fault in southeastern Alameda County, California (-121.56224° E, 37.53430° N) that we discovered using 0.5-m resolution, 2011 aerial lidar imagery flown along the active fault trace. Prior to trenching we surveyed the site using a terrestrial lidar system (TLS) to document the exact geomorphic expression of this deflected stream channel before excavating a trench adjacent to it. We trenched perpendicular to the fault hoping to document the prehistoric history of earthquake ruptures along the fault. However, the alluvial stratigraphy that we document in these trench logs shows conclusively that this trench did not expose any active fault trace. Using other local geomorphic evidence for the fault location, a straight fault scarp immediately north of this stream projects slightly upslope of the west end of our trench and may be the actual location of the active fault trace. Five radiocarbon samples establish age control for the alluvial sequence documented in the trench, which may in the future be useful in constraining the long-term slip rate of the Greenville Fault. The deflection had been caused by an abrupt nontectonic termination of unit u30, a relatively thick (0.15–0.35 m) silt that is more erosion resistant than the adjacent cohesionless sand and gravel. 

Ground-penetrating radar investigation of active faults along the Dead Sea Transform and implications for seismic hazards within the city of Aqaba, Jordan

NASA Astrophysics Data System (ADS)

Slater, Lee; Niemi, Tina M.

2003-06-01

Ground-penetrating radar (GPR) was used in an effort to locate a major active fault that traverses Aqaba City, Jordan. Measurements over an exposed (trenched) cross fault outside of the city identify a radar signature consisting of linear events and horizontal offset/flexured reflectors both showing a geometric correlation with two known faults at a control site. The asymmetric linear events are consistent with dipping planar reflectors matching the known direction of dip of the faults. However, other observations regarding this radar signature render the mechanism generating these events more complex and uncertain. GPR measurements in Aqaba City were limited to vacant lots. Seven GPR profiles were conducted approximately perpendicular to the assumed strike of the fault zone, based on regional geological evidence. A radar response very similar to that obtained over the cross fault was observed on five of the profiles in Aqaba City, although the response is weaker than that obtained at the control site. The positions of the identified responses form a near straight line with a strike of 45°. Although subsurface verification of the fault by trenching within the city is needed, the geophysical evidence for fault zone location is strong. The location of the interpreted fault zone relative to emergency services, military bases, commercial properties, and residential areas is defined to within a few meters. This study has significant implications for seismic hazard analysis in this tectonically active and heavily populated region.

Neotectonics of interior Alaska and the late Quaternary slip rate along the Denali fault system

USGS Publications Warehouse

Haeussler, Peter J.; Matmon, Ari; Schwartz, David P.; Seitz, Gordon G.

2017-01-01

The neotectonics of southern Alaska (USA) are characterized by a several hundred kilometers–wide zone of dextral transpressional that spans the Alaska Range. The Denali fault system is the largest active strike-slip fault system in interior Alaska, and it produced a Mw 7.9 earthquake in 2002. To evaluate the late Quaternary slip rate on the Denali fault system, we collected samples for cosmogenic surface exposure dating from surfaces offset by the fault system. This study includes data from 107 samples at 19 sites, including 7 sites we previously reported, as well as an estimated slip rate at another site. We utilize the interpreted surface ages to provide estimated slip rates. These new slip rate data confirm that the highest late Quaternary slip rate is ∼13 mm/yr on the central Denali fault near its intersection with the eastern Denali and the Totschunda faults, with decreasing slip rate both to the east and west. The slip rate decreases westward along the central and western parts of the Denali fault system to 5 mm/yr over a length of ∼575 km. An additional site on the eastern Denali fault near Kluane Lake, Yukon, implies a slip rate of ∼2 mm/yr, based on geological considerations. The Totschunda fault has a maximum slip rate of ∼9 mm/yr. The Denali fault system is transpressional and there are active thrust faults on both the north and south sides of it. We explore four geometric models for southern Alaska tectonics to explain the slip rates along the Denali fault system and the active fault geometries: rotation, indentation, extrusion, and a combination of the three. We conclude that all three end-member models have strengths and shortcomings, and a combination of rotation, indentation, and extrusion best explains the slip rate observations.

Evolution of triangular topographic facets along active normal faults

NASA Astrophysics Data System (ADS)

Balogun, A.; Dawers, N. H.; Gasparini, N. M.; Giachetta, E.

2011-12-01

Triangular shaped facets, which are generally formed by the erosion of fault - bounded mountain ranges, are arguably one of the most prominent geomorphic features on active normal fault scarps. Some previous studies of triangular facet development have suggested that facet size and slope exhibit a strong linear dependency on fault slip rate, thus linking their growth directly to the kinematics of fault initiation and linkage. Other studies, however, generally conclude that there is no variation in triangular facet geometry (height and slope) with fault slip rate. The landscape of the northeastern Basin and Range Province of the western United States provides an opportunity for addressing this problem. This is due to the presence of well developed triangular facets along active normal faults, as well as spatial variations in fault scale and slip rate. In addition, the Holocene climatic record for this region suggests a dominant tectonic regime, as the faulted landscape shows little evidence of precipitation gradients associated with tectonic uplift. Using GIS-based analyses of USGS 30 m digital elevation data (DEMs) for east - central Idaho and southwestern Montana, we analyze triangular facet geometries along fault systems of varying number of constituent segments. This approach allows us to link these geometries with established patterns of along - strike slip rate variation. For this study, we consider major watersheds to include only catchments with upstream and downstream boundaries extending from the drainage divide to the mapped fault trace, respectively. In order to maintain consistency in the selection criteria for the analyzed triangular facets, only facets bounded on opposite sides by major watersheds were considered. Our preliminary observations reflect a general along - strike increase in the surface area, average slope, and relief of triangular facets from the tips of the fault towards the center. We attribute anomalies in the along - strike geometric measurements of the triangular facets to represent possible locations of fault segment linkage associated with normal fault evolution.

How does the 2010 El Mayor - Cucapah Earthquake Rupture Connect to the Southern California Plate Boundary Fault System

NASA Astrophysics Data System (ADS)

Donnellan, A.; Ben-Zion, Y.; Arrowsmith, R.

2016-12-01

The Pacific - North American plate boundary in southern California is marked by several major strike slip faults. The 2010 M7.2 El Mayor - Cucapah earthquake ruptured 120 km of upper crust in Baja California to the US-Mexico border. The earthquake triggered slip along an extensive network of faults in the Salton Trough from the Mexican border to the southern end of the San Andreas fault. Earthquakes >M5 were triggered in the gap between the Laguna Salada and Elsinore faults at Ocotillo and on the Coyote Creek segment of the San Jacinto fault 20 km northwest of Borrego Springs. UAVSAR observations, collected since October of 2009, measure slip associated with the M5.7 Ocotillo aftershock with deformation continuing into 2014. The Elsinore fault has been remarkably quiet, however, with only M5.0 and M5.2 earthquakes occurring on the Coyote Mountains segment of the fault in 1940 and 1968 respectively. In contrast, the Imperial Valley has been quite active historically with numerous moderate events occurring since 1935. Moderate event activity is increasing along the San Jacinto fault zone (SJFZ), especially the trifurcation area, where 6 of 12 historic earthquakes in this 20 km long fault zone have occurred since 2000. However, no recent deformation has been detected using UAVSAR measurements in this area, including the recent M5.2 June 2016 Borrego earthquake. Does the El Mayor - Cucapah rupture connect to and transfer stress primarily to a single southern California fault or several? What is its role relative to the background plate motion? UAVSAR observations indicate that the southward extension of the Elsinore fault has recently experienced the most localized deformation. Seismicity suggests that the San Jacinto fault is more active than neighboring major faults, and geologic evidence suggests that the Southern San Andreas fault has been the major plate boundary fault in southern California. Topographic data with 3-4 cm resolution using structure from motion from a small UAV on the southern San Andreas fault and the San Jacinto fault south of Anza, decimeter level B4 lidar data, GPS, and UAVSAR observations flown as recently as June 2016 will serve as baseline data for future large earthquakes in the region. Models that combine the different data sets are required to better understand the interconnections of the faults.

Space-time evolution of a growth fold (Betic Cordillera, Spain). Evidences from 3D geometrical modelling

NASA Astrophysics Data System (ADS)

Martin-Rojas, Ivan; Alfaro, Pedro; Estévez, Antonio

2014-05-01

We present a study that encompasses several software tools (iGIS©, ArcGIS©, Autocad©, etc.) and data (geological mapping, high resolution digital topographic data, high resolution aerial photographs, etc.) to create a detailed 3D geometric model of an active fault propagation growth fold. This 3D model clearly shows structural features of the analysed fold, as well as growth relationships and sedimentary patterns. The results obtained permit us to discuss the kinematics and structural evolution of the fold and the fault in time and space. The study fault propagation fold is the Crevillente syncline. This fold represents the northern limit of the Bajo Segura Basin, an intermontane basin in the Eastern Betic Cordillera (SE Spain) developed from upper Miocene on. 3D features of the Crevillente syncline, including growth pattern, indicate that limb rotation and, consequently, fault activity was higher during Messinian than during Tortonian; consequently, fault activity was also higher. From Pliocene on our data point that limb rotation and fault activity steadies or probably decreases. This in time evolution of the Crevillente syncline is not the same all along the structure; actually the 3D geometric model indicates that observed lateral heterogeneity is related to along strike variation of fault displacement.

Active faulting at Delphi, Greece: Seismotectonic remarks and a hypothesis for the geologic environment of a myth

NASA Astrophysics Data System (ADS)

Piccardi, Luigi

2000-07-01

Historical data are fundamental to the understanding of the seismic history of an area. At the same time, knowledge of the active tectonic processes allows us to understand how earthquakes have been perceived by past cultures. Delphi is one of the principal archaeological sites of Greece, the main oracle of Apollo. It was by far the most venerated oracle of the Greek ancient world. According to tradition, the mantic proprieties of the oracle were obtained from an open chasm in the earth. Delphi is directly above one of the main antithetic active faults of the Gulf of Corinth Rift, which bounds Mount Parnassus to the south. The geometry of the fault and slip-parallel lineations on the main fault plane indicate normal movement, with minor right-lateral slip component. Combining tectonic data, archaeological evidence, historical sources, and a reexamination of myths, it appears that the Helice earthquake of 373 B.C. ruptured not only the master fault of the Gulf of Corinth Rift at Helice, but also the antithetic fault at Delphi, similarly to the Corinth earthquake of 1981. Moreover, the presence of an active fault directly below the temples of the oldest sanctuary suggests that the mythological oracular chasm might well have been an ancient tectonic surface rupture.

Subsurface structure identification of active fault based on magnetic anomaly data (Case study: Toru fault in Sumatera fault system)

NASA Astrophysics Data System (ADS)

Simanjuntak, Andrean V. H.; Husni, Muhammad; Syirojudin, Muhammad

2017-07-01

Toru segment, which is one of the active faults and located in the North of Sumatra, broke in 1984 ago on Pahae Jahe's earthquake with a magnitude 6.4 at the northern part of the fault which has a length of 23 km, and also broke again at the same place in 2008. The event of recurrence is very fast, which only 25 years old have repeatedly returned. However, in the elastic rebound theory, it probably happen with a fracture 50 cm and an average of the shear velocity 20 mm/year. The average focus of the earthquake sourced at a depth of 10 km and 23 km along its fracture zones, which can generate enough shaking 7 MMI and could breaking down buildings and create landslides on the cliff. Due to its seismic activity, this study was made to identify the effectiveness of this fault with geophysical methods. Geophysical methods such as gravity, geomagnetic and seismology are powerful tools for detecting subsurface structures of local, regional as well as of global scales. This study used to geophysical methods to discuss about total intensity of the geomagnetic anomaly data, resulted in the distribution of susceptibility values corresponding to the fault movement. The geomagnetic anomalies data was obtained from Geomag, such as total intensity measured by satellite. Data acquisition have been corrected for diurnal variations and reduced by IGRF. The study of earthquake records can be used for differentiating the active and non active fault elements. Modeling has been done using several methods, such as pseudo-gravity, reduce to pole, and upward or downward continuation, which is used to filter the geomagnetic anomaly data because the data has not fully representative of the fault structure. The results indicate that rock layers of 0 - 100 km depth encountered the process of intrusion and are dominated by sedimentary rocks that are paramagnetic, and that the ones of 100 - 150 km depth experienced the activity of subducting slab consisting of basalt and granite which are ferromagnetic and semi-ferromagnetic. This concluded that all the occurences correspond to the high seismicity and seismotectonic condition of Toru fault.

Dynamics and materials physics of fault rupture and glacial processes

NASA Astrophysics Data System (ADS)

Platt, John Daniel

This thesis focuses on two main topics, the physics governing how faults rapidly weaken during an earthquake and the thermal and mechanical structure of ice stream shear margins. The common theme linking these two projects is the desire to understand how the complicated interactions between stress and temperature control deformation and failure. All of the problems in this thesis are attacked using a combination of analytic and numerical methods, and the interplay between these two approaches provides a powerful way to understand the different physical balances that dominate in different regimes. We also use aspects of materials science to understand how the often complicated rheologies are controlled by underlying physical phenomena such as melting, phase transitions, diffusion, and dislocation motion. With regards to fault mechanics, we begin by showing how co-seismic weakening mechanisms driven by elevated pore fluid pressures lead to micron-scale strain localization during an earthquake. We solve for the localized zone thickness for a range of fault temperatures, test these predictions using numerical simulations, and show how the onset of localization accelerates fault weakening. Next we present the first solutions to account for thermal decomposition reactions during a dynamic rupture, showing that the activation of thermal decomposition may lead to a larger slip duration and total slip. Finally we present a new set of experiments studying flash heating of serpentinite, highlighting the dependence of friction on normal stress and the presence of gouge, and producing the first model to explain the hysteresis commonly observed in flash heating experiments. With regards to ice stream shear margins, we begin by extending the work of Perol and Rice [2011] to study the formation of temperate ice in shear margins, and quantify the total melt that may be generated within the shear margins. We conclude by investigating how the presence of such a channel alters the stress on and strength of the undeforming bed in the shear margin, showing that the transition from a deforming to an undeforming bed across a channel is stable when the water flux in the channel exceeds a critical value.

Evidences of a lithospheric fault zone in the Sicily Channel continental rift (southern Italy) from instrumental seismicity data

NASA Astrophysics Data System (ADS)

Calò, M.; Parisi, L.

2014-10-01

Sicily Channel is a portion of Mediterranean Sea, between Sicily (Southern Italy) and Tunisia, representing a part of the foreland Apennine-Maghrebian thrust belt. The seismicity of the region is commonly associated with the normal faulting related to the rifting process and volcanic activity of the region. However, certain seismic patterns suggest the existence of some mechanism coexisting with the rifting process. In this work, we present the results of a statistical analysis of the instrumental seismicity and a reliable relocalization of the events recorded in the last 30 yr in the Sicily Channel and western Sicily using the Double Difference method and 3-D Vp and Vs tomographic models. Our procedure allows us to discern the seismic regime of the Sicily sea from the Tyrrhenian one and to describe the main features of an active fault zone in the study area that could not be related to the rifting process. We report that most of the events are highly clustered in the region between 12.5°-13.5°E and 35.5°-37°N with hypocentral depth of 5-40 km, and reaching 70 km depth in the southernmost sector. The alignment of the seismic clusters, the distribution of volcanic and geothermal regions and the location of some large events occurred in the last century suggest the existence of a subvertical shear zone extending for least 250 km and oriented approximately NNE-SSW. The spatial distribution of the seismic moment suggests that this transfer fault zone is seismically discontinuous showing large seismic gaps in proximity of the Ferdinandea Island, and Graham and Nameless Bank.

Structural controls on a geothermal system in the Tarutung Basin, north central Sumatra

NASA Astrophysics Data System (ADS)

Nukman, Mochamad; Moeck, Inga

2013-09-01

The Sumatra Fault System provides a unique geologic setting to evaluate the influence of structural controls on geothermal activity. Whereas most of the geothermal systems in Indonesia are controlled by volcanic activity, geothermal systems at the Sumatra Fault System might be controlled by faults and fractures. Exploration strategies for these geothermal systems need to be verified because the typical pattern of heat source and alteration clays are missing so that conventional exploration with magnetotelluric surveys might not provide sufficient data to delineate favorable settings for drilling. We present field geological, structural and geomorphological evidence combined with mapping of geothermal manifestations to allow constraints between fault dynamics and geothermal activity in the Tarutung Basin in north central Sumatra. Our results indicate that the fault pattern in the Tarutung Basin is generated by a compressional stress direction acting at a high angle to the right-lateral Sumatra Fault System. NW-SE striking normal faults possibly related to negative flower structures and NNW-SSE to NNE-SSW oriented dilative Riedel shears are preferential fluid pathways whereas ENE-WSW striking faults act as barriers in this system. The dominant of geothermal manifestations at the eastern part of the basin indicates local extension due to clockwise block rotation in the Sumatra Fault System. Our results support the effort to integrate detailed field geological surveys to refined exploration strategies even in tropical areas where outcrops are limited.

Microstructural characterization of high-manganese austenitic steels with different stacking fault energies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sato, Shigeo, E-mail: s.sato@imr.tohoku.ac.jp; Kwon, Eui-Pyo; Imafuku, Muneyuki

Microstructures of tensile-deformed high-manganese austenitic steels exhibiting twinning-induced plasticity were analyzed by electron backscatter diffraction pattern observation and X-ray diffraction measurement to examine the influence of differences in their stacking fault energies on twinning activity during deformation. The steel specimen with the low stacking fault energy of 15 mJ/m{sup 2} had a microstructure with a high population of mechanical twins than the steel specimen with the high stacking fault energy (25 mJ/m{sup 2}). The <111> and <100> fibers developed along the tensile axis, and mechanical twinning occurred preferentially in the <111> fiber. The Schmid factors for slip and twinning deformationsmore » can explain the origin of higher twinning activity in the <111> fiber. However, the high stacking fault energy suppresses the twinning activity even in the <111> fiber. A line profile analysis based on the X-ray diffraction data revealed the relationship between the characteristics of the deformed microstructures and the stacking fault energies of the steel specimens. Although the variation in dislocation density with the tensile deformation is not affected by the stacking fault energies, the effect of the stacking fault energies on the crystallite size refinement becomes significant with a decrease in the stacking fault energies. Moreover, the stacking fault probability, which was estimated from a peak-shift analysis of the 111 and 200 diffractions, was high for the specimen with low stacking fault energy. Regardless of the difference in the stacking fault energies of the steel specimens, the refined crystallite size has a certain correlation with the stacking fault probability, indicating that whether the deformation-induced crystallite-size refinement occurs depends directly on the stacking fault probability rather than on the stacking fault energies in the present steel specimens. - Highlights: {yields} We studied effects of stacking fault energies on deformed microstructures of steels. {yields} Correlations between texture and occurrence of mechanical twinning are discussed. {yields} Evolutions of dislocations and crystallite are analyzed by line profile analysis.« less

A testing-coverage software reliability model considering fault removal efficiency and error generation

PubMed Central

Li, Qiuying; Pham, Hoang

2017-01-01

In this paper, we propose a software reliability model that considers not only error generation but also fault removal efficiency combined with testing coverage information based on a nonhomogeneous Poisson process (NHPP). During the past four decades, many software reliability growth models (SRGMs) based on NHPP have been proposed to estimate the software reliability measures, most of which have the same following agreements: 1) it is a common phenomenon that during the testing phase, the fault detection rate always changes; 2) as a result of imperfect debugging, fault removal has been related to a fault re-introduction rate. But there are few SRGMs in the literature that differentiate between fault detection and fault removal, i.e. they seldom consider the imperfect fault removal efficiency. But in practical software developing process, fault removal efficiency cannot always be perfect, i.e. the failures detected might not be removed completely and the original faults might still exist and new faults might be introduced meanwhile, which is referred to as imperfect debugging phenomenon. In this study, a model aiming to incorporate fault introduction rate, fault removal efficiency and testing coverage into software reliability evaluation is developed, using testing coverage to express the fault detection rate and using fault removal efficiency to consider the fault repair. We compare the performance of the proposed model with several existing NHPP SRGMs using three sets of real failure data based on five criteria. The results exhibit that the model can give a better fitting and predictive performance. PMID:28750091

Late Cenozoic strike-slip faulting in the NE Mojave Block: Deformation at the southwest boundary of the Walker Lane belt

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schermer, E.R.

1993-04-01

New structural and stratigraphy data from the NE Mojave Block (NEMB) establish the timing and style of Cenozoic deformation south of the Garlock fault and west of the Avawatz Mts. Unlike adjacent areas, most of the NEMB did not undergo early-mid Miocene extension. Major fault zones strike EW; offset markers and small-scale shear criteria indicate left-lateral strike slip with a small reverse component. Lateral offsets average ca. 1--6 km and vertical offset is locally >200m. Pre-Tertiary markers indicate minimum cumulative sinistral shear of ca. 15 km in the area between the Garlock and Coyote Lake faults. Tertiary strata are deformedmore » together with the older rocks. Along the Ft. Irwin fault, alluvial fan deposits interpreted to be <11Ma appear to be displaced as much as Mesozoic igneous rocks. EW sinistral faults S. of the Garlock fault cut unconsolidated Quaternary deposits; geomorphologic features and trench exposures along segments of the McLean Lake fault and the Tiefort Mt. fault suggest Late Quaternary activity. The EW faults do not cut modern drainages and are not seismically active. NW-striking faults are largely absent within the NEMB; the largest faults bound the domain of EW-striking faults. Offset of Cretaceous and Miocene rocks suggests the W boundary (Goldstone Lake fault) has <2km right separation. Along the E boundary (Soda-Avawatz fault zone), the presence of distinctive clasts in mid-late Miocene conglomerates west of the Avawatz Mts. supports the suggestion of Brady (1984) of ca. 20 km dextral displacement. Other NW-striking faults are cut by EW faults, have unknown or minor dextral displacement (Desert King Spring Fault, Garlic Spring fault) or are low- to moderate-angle left-oblique thrust faults (Red Pass Lake fault zone).« less

Probabilistic Seismic Hazard Analysis of Victoria, British Columbia, Canada: Considering an Active Leech River Fault

NASA Astrophysics Data System (ADS)

Kukovica, J.; Molnar, S.; Ghofrani, H.

2017-12-01

The Leech River fault is situated on Vancouver Island near the city of Victoria, British Columbia, Canada. The 60km transpressional reverse fault zone runs east to west along the southern tip of Vancouver Island, dividing the lithologic units of Jurassic-Cretaceous Leech River Complex schists to the north and Eocene Metchosin Formation basalts to the south. This fault system poses a considerable hazard due to its proximity to Victoria and 3 major hydroelectric dams. The Canadian seismic hazard model for the 2015 National Building Code of Canada (NBCC) considered the fault system to be inactive. However, recent paleoseismic evidence suggests there to be at least 2 surface-rupturing events to have exceeded a moment magnitude (M) of 6.5 within the last 15,000 years (Morell et al. 2017). We perform a Probabilistic Seismic Hazard Analysis (PSHA) for the city of Victoria with consideration of the Leech River fault as an active source. A PSHA for Victoria which replicates the 2015 NBCC estimates is accomplished to calibrate our PSHA procedure. The same seismic source zones, magnitude recurrence parameters, and Ground Motion Prediction Equations (GMPEs) are used. We replicate the uniform hazard spectrum for a probability of exceedance of 2% in 50 years for a 500 km radial area around Victoria. An active Leech River fault zone is then added; known length and dip. We are determining magnitude recurrence parameters based on a Gutenberg-Richter relationship for the Leech River fault from various catalogues of the recorded seismicity (M 2-3) within the fault's vicinity and the proposed paleoseismic events. We seek to understand whether inclusion of an active Leech River fault source will significantly increase the probabilistic seismic hazard for Victoria. Morell et al. 2017. Quaternary rupture of a crustal fault beneath Victoria, British Columbia, Canada. GSA Today, 27, doi: 10.1130/GSATG291A.1

Surface fault rupture during the Mw 7.8 Kaikoura earthquake, New Zealand, with specific comment on the Kekerengu Fault - one of the country's fastest slipping onland active faults

NASA Astrophysics Data System (ADS)

Van Dissen, Russ; Little, Tim

2017-04-01

The Mw 7.8 Kaikoura earthquake of 14 November, 2016 (NZDT) was a complex event. It involved ground-surface (or seafloor) fault rupture on at least a dozen onland or offshore faults, and subsurface rupture on a handful of additional faults. Most of the surface ruptures involved previously known (or suspected) active faults, as well as surface rupture on at least two hitherto unrecognised active faults. The southwest to northeast extent of surface fault rupture, as generalised by two straight-line segments, is approximately 180 km, though this is a minimum for the collective length of surface rupture due to multiple overlapping faults with various orientations. Surface rupture displacements on specific faults involved in the Kaikoura Earthquake span approximately two orders of magnitude. For example, maximum surface displacement on the Heaver's Creek Fault is cm- to dm-scale in size; whereas, maximum surface displacement on the nearby Kekerengu Fault is approximately 10-12 m (predominantly in a dextral sense). The Kekerengu Fault has a Late Pleistocene slip-rate rate of 20-26 mm/yr, and is possibly the second fastest slipping onland fault in New Zealand, behind the Alpine Fault. Located in the northeastern South Island of New Zealand, the Kekerengu Fault - along with the Hope Fault to the southwest and the Needles Fault offshore to the northeast - comprise the fastest slipping elements of the Pacific-Australian plate boundary in this part of the country. In January 2016 (about ten months prior to the Kaikoura earthquake) three paleo-earthquake investigation trenches were excavated across pronounced traces of the Kekerengu Fault at two locations. These were the first such trenches dug and evaluated across the fault. All three trenches displayed abundant evidence of past surface fault ruptures (three surface ruptures in the last approximately 1,200 years, four now including the 2016 rupture). An interesting aspect of the 2016 rupture is that two of the trenches received surface fault rupture, and are now dextrally offset by about 9 m, while the third trench did not have any 2016 surface rupture pass through it. In this instance, ground-surface rupture along this trace of the fault died out within tens of metres of the trench. Another salient aspect of the Kaikoura earthquake is that the determined (or estimated) recurrence intervals of the faults that ruptured the ground surface vary by an order of magnitude or more. This strongly implies that the ensemble of faults that ruptured with the Kekerengu Fault in the 2016 earthquake has not always been the same for past earthquakes. Possible reasons for this could include the state of stress at the time of a specific earthquake, the direction of rupture propagation, and whether or not rupture on one fault system cascades into rupture on another as is suspected to have happened in the Kaikoura earthquake.

Block rotations, fault domains and crustal deformation in the western US

NASA Technical Reports Server (NTRS)

Nur, Amos

1990-01-01

The aim of the project was to develop a 3D model of crustal deformation by distributed fault sets and to test the model results in the field. In the first part of the project, Nur's 2D model (1986) was generalized to 3D. In Nur's model the frictional strength of rocks and faults of a domain provides a tight constraint on the amount of rotation that a fault set can undergo during block rotation. Domains of fault sets are commonly found in regions where the deformation is distributed across a region. The interaction of each fault set causes the fault bounded blocks to rotate. The work that has been done towards quantifying the rotation of fault sets in a 3D stress field is briefly summarized. In the second part of the project, field studies were carried out in Israel, Nevada and China. These studies combined both paleomagnetic and structural information necessary to test the block rotation model results. In accordance with the model, field studies demonstrate that faults and attending fault bounded blocks slip and rotate away from the direction of maximum compression when deformation is distributed across fault sets. Slip and rotation of fault sets may continue as long as the earth's crustal strength is not exceeded. More optimally oriented faults must form, for subsequent deformation to occur. Eventually the block rotation mechanism may create a complex pattern of intersecting generations of faults.

Enigmatic rift-parallel, strike-slip faults around Eyjafjörður, Northern Iceland

NASA Astrophysics Data System (ADS)

Proett, J. A.; Karson, J. A.

2014-12-01

Strike-slip faults along mid-ocean ridge spreading centers are generally thought to be restricted to transform boundaries connecting rift segments. Faults that are parallel to spreading centers are generally assumed to be normal faults associated with tectonic extension. However, clear evidence of north-south (rift-parallel), strike-slip displacements occur widely around the southern portion of Eyjafjörður, northern Iceland about 50 km west of the Northern Rift Zone. The area is south of the southernmost strand (Dalvík Lineament) of the NW-SE-trending, dextral-slip, Tjӧrnes Fracture Zone (where N-S, sinistral, strike-slip "bookshelf" faulting occurs). Faults in the Eyjafjörður area cut 8.5-10 m.y. basaltic crust and are parallel to spreading-related dikes and are commonly concentrated along dike margins. Fault rocks range from fault breccia to gouge. Riedel shears and other kinematic indicators provide unambiguous evidence of shear sense. Most faults show evidence of sinistral, strike-slip movement but smaller proportions of normal and oblique-slip faults also are present. Cross cutting relations among the different types of faults are inconsistent and appear to be related to a single deformation event. Fault slip-line kinematic analysis yields solutions indicating sinistral-normal oblique-slip overall. These results may be interpreted in terms of either previously unrecognized transform-fault bookshelf faulting or slip accommodating block rotation associated with northward propagation of the Northern Rift Zone.

A study of the relationship between the performance and dependability of a fault-tolerant computer

NASA Technical Reports Server (NTRS)

Goswami, Kumar K.

1994-01-01

This thesis studies the relationship by creating a tool (FTAPE) that integrates a high stress workload generator with fault injection and by using the tool to evaluate system performance under error conditions. The workloads are comprised of processes which are formed from atomic components that represent CPU, memory, and I/O activity. The fault injector is software-implemented and is capable of injecting any memory addressable location, including special registers and caches. This tool has been used to study a Tandem Integrity S2 Computer. Workloads with varying numbers of processes and varying compositions of CPU, memory, and I/O activity are first characterized in terms of performance. Then faults are injected into these workloads. The results show that as the number of concurrent processes increases, the mean fault latency initially increases due to increased contention for the CPU. However, for even higher numbers of processes (less than 3 processes), the mean latency decreases because long latency faults are paged out before they can be activated.

Faulting arrested by control of ground-water withdrawal in Houston, Texas.

USGS Publications Warehouse

Holzer, T.; Gabrysch, R.K.; Verbeek, E.R.

1983-01-01

More than 86 historically active faults with an aggregate length of 150 miles have been identified within and adjacent to the Houston, Texas, metropolitan area. Although scarps of these faults grow gradually and without causing damaging earthquakes, historical fault offset has cost millions of dollars in damage to houses and other buildings, utilities, and highways that were built on or across the faults. The historical fault activity results from renewed movement along preexisting faults and appears to be caused principally by withdrawal of ground water for municipal, industrial, and agricultural uses in the Houston area. Approximately one-half of the area's water supply is obtained from local ground water. Monitoring by the US Geological Survey of heights of fault scarps indicates that many of the scarps have recently stopped increasing in height. The area where faulting has ceased coincides with the area where ground-water pumping was cut back in the mid-1970s to slow the damage caused by land subsidence along Galveston Bay and the Houston Ship Channel. Thus, it appears that efforts to halt land subsidence in the coastal area have provided the additional benefit of arresting damaging surface faulting. -from Authors

Active faulting, earthquakes, and restraining bend development near Kerman city in southeastern Iran

NASA Astrophysics Data System (ADS)

Walker, Richard Thomas; Talebian, Morteza; Saiffori, Sohei; Sloan, Robert Alastair; Rasheedi, Ali; MacBean, Natasha; Ghassemi, Abbas

2010-08-01

We provide descriptions of strike-slip and reverse faulting, active within the late Quaternary, in the vicinity of Kerman city in southeastern Iran. The faults accommodate north-south, right-lateral, shear between central Iran and the Dasht-e-Lut depression. The regions that we describe have been subject to numerous earthquakes in the historical and instrumental periods, and many of the faults that are documented in this paper constitute hazards for local populations, including the city of Kerman itself (population ˜200,000). Faults to the north and east of Kerman are associated with the transfer of slip from the Gowk to the Kuh Banan right-lateral faults across a 40 km-wide restraining bend. Faults south and west of the city are associated with oblique slip on the Mahan and Jorjafk systems. The patterns of faulting observed along the Mahan-Jorjafk system, the Gowk-Kuh Banan system, and also the Rafsanjan-Rayen system further to the south, appear to preserve different stages in the development of these oblique-slip fault systems. We suggest that the faulting evolves through time. Topography is initially generated on oblique slip faults (as is seen on the Jorjafk fault). The shortening component then migrates to reverse faults situated away from the high topography whereas strike-slip continues to be accommodated in the high, mountainous, regions (as is seen, for example, on the Rafsanjan fault). The reverse faults may then link together and eventually evolve into new, through-going, strike-slip faults in a process that appears to be occurring, at present, in the bend between the Gowk and Kuh Banan faults.

Imaging the concealed section of the Whakatane fault below Whakatane city, New Zealand, with a shear wave land streamer system

NASA Astrophysics Data System (ADS)

Polom, Ulrich; Mueller, Christof; Krawczyk, CharLotte M.

2016-04-01

The Mw 7.1 Darfield Earthquake in September 2010 ruptured the surface along the Greendale Fault that was not known prior to the earthquake. The subsequent Mw 6.3 Christchurch earthquake in February 2011 demonstrated that concealed active faults have a significant risk potential for urban infrastructure and human life in New Zealand if they are located beneath or close to such areas. Mapping exposures and analysis of active faults incorporated into the National Seismic Hazard Model (NSHM) suggests that several thousands of these active structures are yet to be identified and have the potential to generate moderate to large magnitude earthquakes (i.e. magnitudes >5). Geological mapping suggests that active faults pass beneath, or within many urban areas in New Zealand, including Auckland, Blenheim, Christchurch, Hastings/Napier, Nelson, Rotorua, Taupo, Wellington, and Whakatane. Since no established methodology for routinely locating and assessing the earthquake hazard posed by concealed active faults is available, the principal objective of the presented study was to evaluate the usefulness of high-resolution shear wave seismic reflection profiling using a land streamer to locate buried faults in urban areas of New Zealand. During the survey carried out in the city of Whakatane in February 2015, the method was first tested over a well known surface outcrop of the Edgecumbe Fault 30 km south-west of Whakatane city. This allowed further to investigate the principle shear wave propagation characteristics in the unknown sediments, consisting mainly of effusive rock material of the Taupo volcanic zone mixed with marine transgression units. Subsequently the survey was continued within Whakatane city using night operation time slots to reduce the urban noise. In total, 11 profiles of 5.7 km length in high data quality were acquired, which clearly show concealed rupture structures of obviously different age in the shallow sediments down to 100 m depth. Subject to depth verification by drillings normal fault displacements of up to 15 m are visible in depths of 20-40 m, deeper rupture structures show displacements of up to 20 m. Furthermore, indications of strike-slip fault activities are visible. The concealed rupture structures found are not aligned along former estimated fault lineaments or main surface structures like the Whakatane river bed. Correlations exist with small topographic variations detected by LIDAR imaging and surface signatures on a historic map of 1867.

Hybrid Model-Based and Data-Driven Fault Detection and Diagnostics for Commercial Buildings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Frank, Stephen; Heaney, Michael; Jin, Xin

Commercial buildings often experience faults that produce undesirable behavior in building systems. Building faults waste energy, decrease occupants' comfort, and increase operating costs. Automated fault detection and diagnosis (FDD) tools for buildings help building owners discover and identify the root causes of faults in building systems, equipment, and controls. Proper implementation of FDD has the potential to simultaneously improve comfort, reduce energy use, and narrow the gap between actual and optimal building performance. However, conventional rule-based FDD requires expensive instrumentation and valuable engineering labor, which limit deployment opportunities. This paper presents a hybrid, automated FDD approach that combines building energymore » models and statistical learning tools to detect and diagnose faults noninvasively, using minimal sensors, with little customization. We compare and contrast the performance of several hybrid FDD algorithms for a small security building. Our results indicate that the algorithms can detect and diagnose several common faults, but more work is required to reduce false positive rates and improve diagnosis accuracy.« less

Hybrid Model-Based and Data-Driven Fault Detection and Diagnostics for Commercial Buildings: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Frank, Stephen; Heaney, Michael; Jin, Xin

Commercial buildings often experience faults that produce undesirable behavior in building systems. Building faults waste energy, decrease occupants' comfort, and increase operating costs. Automated fault detection and diagnosis (FDD) tools for buildings help building owners discover and identify the root causes of faults in building systems, equipment, and controls. Proper implementation of FDD has the potential to simultaneously improve comfort, reduce energy use, and narrow the gap between actual and optimal building performance. However, conventional rule-based FDD requires expensive instrumentation and valuable engineering labor, which limit deployment opportunities. This paper presents a hybrid, automated FDD approach that combines building energymore » models and statistical learning tools to detect and diagnose faults noninvasively, using minimal sensors, with little customization. We compare and contrast the performance of several hybrid FDD algorithms for a small security building. Our results indicate that the algorithms can detect and diagnose several common faults, but more work is required to reduce false positive rates and improve diagnosis accuracy.« less

Potential for larger earthquakes in the East San Francisco Bay Area due to the direct connection between the Hayward and Calaveras Faults

NASA Astrophysics Data System (ADS)

Chaussard, E.; Bürgmann, R.; Fattahi, H.; Nadeau, R. M.; Taira, T.; Johnson, C. W.; Johanson, I.

2015-04-01

The Hayward and Calaveras Faults, two strike-slip faults of the San Andreas System located in the East San Francisco Bay Area, are commonly considered independent structures for seismic hazard assessment. We use Interferometric Synthetic Aperture RADAR to show that surface creep on the Hayward Fault continues 15 km farther south than previously known, revealing new potential for rupture and damage south of Fremont. The extended trace of the Hayward Fault, also illuminated by shallow repeating micro-earthquakes, documents a surface connection with the Calaveras Fault. At depths greater than 3-5 km, repeating micro-earthquakes located 10 km north of the surface connection highlight the 3-D wedge geometry of the junction. Our new model of the Hayward and Calaveras Faults argues that they should be treated as a single system with potential for earthquake ruptures generating events with magnitudes greater than 7, posing a higher seismic hazard to the East San Francisco Bay Area than previously considered.

Solar system fault detection

DOEpatents

Farrington, R.B.; Pruett, J.C. Jr.

1984-05-14

A fault detecting apparatus and method are provided for use with an active solar system. The apparatus provides an indication as to whether one or more predetermined faults have occurred in the solar system. The apparatus includes a plurality of sensors, each sensor being used in determining whether a predetermined condition is present. The outputs of the sensors are combined in a pre-established manner in accordance with the kind of predetermined faults to be detected. Indicators communicate with the outputs generated by combining the sensor outputs to give the user of the solar system and the apparatus an indication as to whether a predetermined fault has occurred. Upon detection and indication of any predetermined fault, the user can take appropriate corrective action so that the overall reliability and efficiency of the active solar system are increased.

Solar system fault detection

DOEpatents

Farrington, Robert B.; Pruett, Jr., James C.

1986-01-01

A fault detecting apparatus and method are provided for use with an active solar system. The apparatus provides an indication as to whether one or more predetermined faults have occurred in the solar system. The apparatus includes a plurality of sensors, each sensor being used in determining whether a predetermined condition is present. The outputs of the sensors are combined in a pre-established manner in accordance with the kind of predetermined faults to be detected. Indicators communicate with the outputs generated by combining the sensor outputs to give the user of the solar system and the apparatus an indication as to whether a predetermined fault has occurred. Upon detection and indication of any predetermined fault, the user can take appropriate corrective action so that the overall reliability and efficiency of the active solar system are increased.

A highly reliable, high performance open avionics architecture for real time Nap-of-the-Earth operations

NASA Technical Reports Server (NTRS)

Harper, Richard E.; Elks, Carl

1995-01-01

An Army Fault Tolerant Architecture (AFTA) has been developed to meet real-time fault tolerant processing requirements of future Army applications. AFTA is the enabling technology that will allow the Army to configure existing processors and other hardware to provide high throughput and ultrahigh reliability necessary for TF/TA/NOE flight control and other advanced Army applications. A comprehensive conceptual study of AFTA has been completed that addresses a wide range of issues including requirements, architecture, hardware, software, testability, producibility, analytical models, validation and verification, common mode faults, VHDL, and a fault tolerant data bus. A Brassboard AFTA for demonstration and validation has been fabricated, and two operating systems and a flight-critical Army application have been ported to it. Detailed performance measurements have been made of fault tolerance and operating system overheads while AFTA was executing the flight application in the presence of faults.

Interpretations on the Geologic Setting of Yogyakarta Earthquakes 2006 (Central Java, Indonesia) Based on Integration of Aftershock Monitoring and Existing Geologic, Geophysical and Remote Sensing Data

NASA Astrophysics Data System (ADS)

Setijadji, L. D.; Watanabe, K.; Fukuoka, K.; Ehara, S.; Setiadji, Y.; Rahardjo, W.; Susilo, A.; Barianto, D. H.; Harijoko, A.; Sudarno, I.; Pramumijoyo, S.; Hendrayana, H.; Akmalludin, A.; Nishijima, J.; Itaya, T.

2007-05-01

The unprecedented 26 May 2006 Yogyakarta earthquake (central Java, Indonesia) that took victims of 5,700 lives was generally accepted to have a depth of about 10 km and moment magnitude of 6.4. However, the definition of location of active fault is still under debate as the epicenter of mainshock was reported quite differently by several institutions. Many researchers believe that the Opak fault which is located at the eastern boundary of Yogyakarta low-land area (or Yogyakarta Basin) and the high-land region of Southern Mountains was the source of year 2006 earthquakes. However, our result of aftershocks observation suggests that the ruptured zone was not located along the Opak fault but from an unknown fault located about 10 km to the east from it and within the Southern Mountains domain. Unfortunately, surface geologic manifestations are scarce as this area is now largely covered by limestone. Therefore the suspected active fault system must be studied through interpretations of the subsurface geology and evaluation of the Cenozoic geo-history of the region utilizing existing geologic, geophysical and remote sensing data. This work suggests that the Yogyakarta Basin is a volcano-tectonic depression formed gradually since the early Tertiary period (Oligo-Miocene or older). Geological and geophysical evidence suggest that structural trends changed from the Oligocene NE-SW towards the Oligo-Miocene NNE-SSW and the Plio-Pleistocene NW-SE and E-W directions. The ruptured "X" fault during the Yogyakarta earthquakes 2006 is likely to be a NNE-SSW trending fault which is parallel to the Opak fault and both were firstly active in the Oligo-Miocene as sinistral strike-slip faults. However, while the Opak fault had changed into a normal faulting after the Pliocene, the evidence from Kali Ngalang and Kali Widoro suggests that the "X" fault system was still reactivated as a strike-slip one during the Plio-Pleistocene orogeny. As this new interpretation of active fault causes spatial discrepancy between locations of earthquakes epicenters and highly damaged regions, other geo-engineering factors must be considerably important in determining the final scale of seismic hazards. The most vulnerable areas for seismic hazards are those located nearest to the ruptured fault and are underlain by thick Quaternary unconsolidated deposits. In case of regions along the fault line, seismic hazards seem to reach more distance region, such as the case of Gantiwarno region, as the seismic waves can travel more easily along the fault line.

The Deformation of Overburden Soil and Interaction with Pile Foundations of Bridges Induced by Normal Faulting

NASA Astrophysics Data System (ADS)

Wu, Liang-Chun; Li, Chien-Hung; Chan, Pei-Chen; Lin, Ming-Lang

2017-04-01

According to the investigations of well-known disastrous earthquakes in recent years, ground deformation induced by faulting is one of the causes for engineering structure damages in addition to strong ground motion. Most of structures located on faulting zone has been destroyed by fault offset. Take the Norcia Earthquake in Italy (2016, Mw=6.2) as an example, the highway bridge in Arquata crossing the rupture area of the active normal fault suffered a quantity of displacement which causing abutment settlement, the piers of bridge fractured and so on. However, The Seismic Design Provisions and Commentary for Highway Bridges in Taiwan, the stating of it in the general rule of first chapter, the design in bridges crossing active fault: "This specification is not applicable of making design in bridges crossing or near active fault, that design ought to the other particular considerations ".This indicates that the safty of bridges crossing active fault are not only consider the seismic performance, the most ground deformation should be attended. In this research, to understand the failure mechanism and the deformation characteristics, we will organize the case which the bridges subjected faulting at home and abroad. The processes of research are through physical sandbox experiment and numerical simulation by discrete element models (PFC3-D). The normal fault case in Taiwan is Shanchiao Fault. As above, the research can explore the deformation in overburden soil and the influences in the foundations of bridges by normal faulting. While we can understand the behavior of foundations, we will make the bridge superstructures into two separations, simple beam and continuous beam and make a further research on the main control variables in bridges by faulting. Through the above mentioned, we can then give appropriate suggestions about planning considerations and design approaches. This research presents results from sandbox experiment and 3-D numerical analysis to simulate overburden soil and embedded pile foundations subjected to normal faulting. In order to validate this numerical model, it is compared to sandbox experiments. Since the 3-D numerical analysis corresponds to the sandbox expeiments, the response of pile foundations and ground deformation induced by normal faulting are discussed. To understand the 3-D behavior of ground deformation and pile foundations, the observation such as the triangular shear zone, the width of primary deformation zone and the inclination, displacements, of the pile foundations are discussed in experiments and simulations. Furthermore, to understand the safty of bridges crossing faulting zone. The different superstructures of bridges, simple beam and continuous beam will be discussed subsequently in simulations.

Abnormal fault-recovery characteristics of the fault-tolerant multiprocessor uncovered using a new fault-injection methodology

NASA Technical Reports Server (NTRS)

Padilla, Peter A.

1991-01-01

An investigation was made in AIRLAB of the fault handling performance of the Fault Tolerant MultiProcessor (FTMP). Fault handling errors detected during fault injection experiments were characterized. In these fault injection experiments, the FTMP disabled a working unit instead of the faulted unit once in every 500 faults, on the average. System design weaknesses allow active faults to exercise a part of the fault management software that handles Byzantine or lying faults. Byzantine faults behave such that the faulted unit points to a working unit as the source of errors. The design's problems involve: (1) the design and interface between the simplex error detection hardware and the error processing software, (2) the functional capabilities of the FTMP system bus, and (3) the communication requirements of a multiprocessor architecture. These weak areas in the FTMP's design increase the probability that, for any hardware fault, a good line replacement unit (LRU) is mistakenly disabled by the fault management software.

Structures associated with strike-slip faults that bound landslide elements

USGS Publications Warehouse

Fleming, R.W.; Johnson, A.M.

1989-01-01

Large landslides are bounded on their flanks and on elements within the landslides by structures analogous to strike-slip faults. We observed the formation of thwse strike-slip faults and associated structures at two large landslides in central Utah during 1983-1985. The strike-slip faults in landslides are nearly vertical but locally may dip a few degrees toward or away from the moving ground. Fault surfaces are slickensided, and striations are subparallel to the ground surface. Displacement along strike-slip faults commonly produces scarps; scarps occur where local relief of the failure surface or ground surface is displaced and becomes adjacent to higher or lower ground, or where the landslide is thickening or thinning as a result of internal deformation. Several types of structures are formed at the ground surface as a strike-slip fault, which is fully developed at some depth below the ground surface, propagates upward in response to displacement. The simplest structure is a tension crack oriented at 45?? clockwise or counterclockwise from the trend of an underlying right- or left-lateral strike-slip fault, respectively. The tension cracks are typically arranged en echelon with the row of cracks parallel to the trace of the underlying strike-slip fault. Another common structure that forms above a developing strike-slip fault is a fault segment. Fault segments are discontinuous strike-slip faults that contain the same sense of slip but are turned clockwise or counterclockwise from a few to perhaps 20?? from the underlying strike-slip fault. The fault segments are slickensided and striated a few centimeters below the ground surface; continued displacement of the landslide causes the fault segments to open and a short tension crack propagates out of one or both ends of the fault segments. These structures, open fault segments containing a short tension crack, are termed compound cracks; and the short tension crack that propagates from the tip of the fault segment is typically oriented 45?? to the trend of the underlying fault. Fault segments are also typically arranged en echelon above the upward-propagating strike-slip fault. Continued displacement of the landslide causes the ground to buckle between the tension crack portions of the compound cracks. Still more displacement produces a thrust fault on one or both limbs of the buckle fold. These compressional structures form at right angles to the short tension cracks at the tips of the fault segments. Thus, the compressional structures are bounded on their ends by one face of a tension crack and detached from underlying material by thrusting or buckling. The tension cracks, fault segments, compound cracks, folds, and thrusts are ephemeral; they are created and destroyed with continuing displacement of the landslide. Ultimately, the structures are replaced by a throughgoing strike-slip fault. At one landslide, we observed the creation and destruction of the ephemeral structures as the landslide enlarged. Displacement of a few centimeters to about a decimeter was sufficient to produce scattered tension cracks and fault segments. Sets of compound cracks with associated folds and thrusts were produced by displacements of up to 1 m, and 1 to 2 m of displacement was required to produce a throughgoing strike-slip fault. The type of first-formed structure above an upward-propagating strike-slip fault is apparently controlled by the rheology of the material. Brittle material such as dry topsoil or the compact surface of a gravel road produces echelon tension cracks and sets of tension cracks and compressional structures, wherein the cracks and compressional structures are normal to each other and 45?? to the strike-slip fault at depth. First-formed structures in more ductile material such as moist cohesive soil are fault segments. In very ductile material such as soft clay and very wet soil in swampy areas, the first-formed structure is a throughgoing strike-slip fault. There are othe

Experiments in fault tolerant software reliability

NASA Technical Reports Server (NTRS)

Mcallister, David F.; Vouk, Mladen A.

1989-01-01

Twenty functionally equivalent programs were built and tested in a multiversion software experiment. Following unit testing, all programs were subjected to an extensive system test. In the process sixty-one distinct faults were identified among the versions. Less than 12 percent of the faults exhibited varying degrees of positive correlation. The common-cause (or similar) faults spanned as many as 14 components. However, a majority of these faults were trivial, and easily detected by proper unit and/or system testing. Only two of the seven similar faults were difficult faults, and both were caused by specification ambiguities. One of these faults exhibited variable identical-and-wrong response span, i.e. response span which varied with the testing conditions and input data. Techniques that could have been used to avoid the faults are discussed. For example, it was determined that back-to-back testing of 2-tuples could have been used to eliminate about 90 percent of the faults. In addition, four of the seven similar faults could have been detected by using back-to-back testing of 5-tuples. It is believed that most, if not all, similar faults could have been avoided had the specifications been written using more formal notation, the unit testing phase was subject to more stringent standards and controls, and better tools for measuring the quality and adequacy of the test data (e.g. coverage) were used.

Fault diagnosis and fault-tolerant finite control set-model predictive control of a multiphase voltage-source inverter supplying BLDC motor.

PubMed

Salehifar, Mehdi; Moreno-Equilaz, Manuel

2016-01-01

Due to its fault tolerance, a multiphase brushless direct current (BLDC) motor can meet high reliability demand for application in electric vehicles. The voltage-source inverter (VSI) supplying the motor is subjected to open circuit faults. Therefore, it is necessary to design a fault-tolerant (FT) control algorithm with an embedded fault diagnosis (FD) block. In this paper, finite control set-model predictive control (FCS-MPC) is developed to implement the fault-tolerant control algorithm of a five-phase BLDC motor. The developed control method is fast, simple, and flexible. A FD method based on available information from the control block is proposed; this method is simple, robust to common transients in motor and able to localize multiple open circuit faults. The proposed FD and FT control algorithm are embedded in a five-phase BLDC motor drive. In order to validate the theory presented, simulation and experimental results are conducted on a five-phase two-level VSI supplying a five-phase BLDC motor. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.

Reconnaissance engineering geology of the Metlakatla area, Annette Island, Alaska, with emphasis on evaluation of earthquakes and other geologic hazards

USGS Publications Warehouse

Yehle, Lynn A.

1977-01-01

A program to study the engineering geology of most larger Alaska coastal communities and to evaluate their earthquake and other geologic hazards was started following the 1964 Alaska earthquake; this report about the Metlakatla area, Annette Island, is a product of that program. Field-study methods were of a reconnaissance nature, and thus the interpretations in the report are tentative. Landscape of the Metlakatla Peninsula, on which the city of Metlakatla is located, is characterized by a muskeg-covered terrane of very low relief. In contrast, most of the rest of Annette Island is composed of mountainous terrane with steep valleys and numerous lakes. During the Pleistocene Epoch the Metlakatla area was presumably covered by ice several times; glaciers smoothed the present Metlakatla Peninsula and deeply eroded valleys on the rest. of Annette Island. The last major deglaciation was completed probably before 10,000 years ago. Rebound of the earth's crust, believed to be related to glacial melting, has caused land emergence at Metlakatla of at least 50 ft (15 m) and probably more than 200 ft (61 m) relative to present sea level. Bedrock in the Metlakatla area is composed chiefly of hard metamorphic rocks: greenschist and greenstone with minor hornfels and schist. Strike and dip of beds are generally variable and minor offsets are common. Bedrock is of late Paleozoic to early Mesozoic age. Six types of surficial geologic materials of Quaternary age were recognized: firm diamicton, emerged shore, modern shore and delta, and alluvial deposits, very soft muskeg and other organic deposits, and firm to soft artificial fill. A combination map unit is composed of bedrock or diamicton. Geologic structure in southeastern Alaska is complex because, since at least early Paleozoic time, there have been several cycles of tectonic deformation that affected different parts of the region. Southeastern Alaska is transected by numerous faults and possible faults that attest to major movements of the earth's crust. The latest of the major tectonic events in the Metlakatla region occurred in middle Tertiary time; some minor fault activity probably continues today at depth. Along the outer coast of southeastern Alaska and British Columbia, major faulting activity occurs in the form of active, strike-slip movement along the Queen Charlotte fault about 100 mi (160 kin) west-southwest of Metlakatla. Some branching subsidiary faults also may be active, at least one of which may be the Sandspit fault. Many major and smaller earthquakes occur along the outer coast. These shocks are related to movements along the Queen Charlotte fault. A few small earthquakes occur in the region between the outer coast and the Coast Mountains, which includes Metlakatla. 0nly a few earthquakes have been reported as felt at Metlakatla; these shocks and others felt in the region are tabulated. Historically, the closest major earthquake was the magnitude 8.1 Queen Charlotte Islands earthquake of August 22, 1949, which occurred along the Queen Charlotte fault 125 mi (200 km) southwest of Metlakatla. No damage was reported at Metlakatla. The probability of destructive earthquakes affecting Metlakatla is unknown. A consideration of the tectonics and earthquake history of the region, however, suggests that sometime in the future an earthquake with a magnitude of about 8 will occur along that segment of the Queen Charlotte fault nearest to Metlakatla. Smaller earthquakes with magnitudes of 6 or more might occur elsewhere in the Metlakatla region or south-southeastward near Dixon Entrance or Hecate Strait. Several geologic effects that have characterized large earthquakes elsewh6re may be expected to accompany some of the possible major earthquakes that might affect the Metlakatla area in the future. Evaluation of effects indicates that fault displacement and tectonic uplift or subsidence are probably unlikely, and ground shaking in general probably would be strongest

Active Tectonics Around Pisagua, Northern Chile Gap: Seismological and Neotectonic Approaches

NASA Astrophysics Data System (ADS)

Comte, D.; Carrizo, D.; Peyrat, S.

2013-12-01

Northern Chile is a recognized mature seismic gap that is reaching the end of its megathrust cycle. Deformation associated with the convergence between the Nazca and the South American Plates is mainly absorbed along the interplate contact, but also partially accommodated along the upper plate. Even though distribution of the active deformation along this plate has been documented mainly in the backarc region, Late Cenozoic structures have been recognized along the forearc suggesting that some part of this deformation is also accommodated along the coastal region. Recent paleoseismological studies suggest that some of these structures are tectonically active and some could be potentially active, capable to generate shallow intraplate earthquakes (Mw˜7). However, seismological and geodetical evidences of the fault activation mechanisms are poorly documented, and the activation process remain not elucidate. Currently, Northern Chile seismic gap is monitored by regional seismic networks and partially studied by temporary local seismological experiments. Results of these studies suggest the presence of shallow seismicity along the forearc, but the relationships between upper plate faults and the seismicity has not been yet explored. We perform a detailed seismotectonic analysis of the subduction-forearc system in the central part of the Northern Chile seismic gap to establish relationships between the plate contact deformation and the upper plate faults. We present preliminary results of data recorded by a dense seismic network (three components continuous recording) deployed around Pisagua, between the coastline and the Central Depression, during several months. Pisagua region was chosen because the forearc faults exhibit an extraordinary well-preserved morphotectonic expression, and the upper part of the seismogenic interplate contact shows abundant continental intraplate seismicity that could be associated with the faults systems. The data recorded in this area allow us to better constrain the 3D geometry of faults related to plate contact using morphotectonis fault signature, well-located shallow seismicity and passive tomography. By this way, the architecture of the major forearc faults in the study area is determined for the first time using geological and geophysical approaches. Through this work, we contribute to better understand the physical relations between dynamics of the plate contact and the coastal fault activation.

Earthquake geology of Kashmir Basin and its implications for future large earthquakes

NASA Astrophysics Data System (ADS)

Shah, A. A.

2013-09-01

Two major traces of active thrust faults were identified in the Kashmir Basin (KB) using satellite images and by mapping active geomorphic features. The ~N130°E strike of the mapped thrust faults is consistent with the regional ~NE-SW convergence along the Indian-Eurasian collision zone. The ~NE dipping thrust faults have uplifted the young alluvial fan surfaces at the SW side of the KB. This created a major tectono-geomorphic boundary along the entire strike length of the KB that is characterised by (1) a low relief with sediment-filled sluggish streams to the SE and (2) an uplifted region, with actively flowing streams to the SW. The overall tectono-geomorphic expression suggests that recent activity along these faults has tilted the entire Kashmir valley towards NE. Further, the Mw 7.6 earthquake, which struck Northern Pakistan and Kashmir on 8 October 2005, also suggests a similar strike and NE dipping fault plane, which could indicate that the KB fault is continuous over a distance of ~210 km and connects on the west with the Balakot Bagh fault. However, the geomorphic and the structural evidences of such a structure are not very apparent on the north-west, which thus suggest that it is not a contiguous structure with the Balakot Bagh fault. Therefore, it is more likely that the KB fault is an independent thrust, a possible ramp on the Main Himalayan Thrust, which has uplifting the SW portion of the KB and drowning everything to the NE (e.g. Madden et al. 2011). Furthermore, it seems very likely that the KB fault could be a right stepping segment of the Balakot Bagh fault, similar to Riasi Thrust, as proposed by Thakur et al. (2010). The earthquake magnitude is measured by estimating the fault rupture parameters (e.g. Wells and Coppersmith in Bull Seismol Soc Am 84:974-1002, 1994). Therefore, the total strike length of the mapped KB fault is ~120 km and by assuming a dip of 29° (Avouac et al. in Earth Planet Sci Lett 249:514-528, 2006) and a down-dip limit of 20 km, a Mw of 7.6 is possible on this fault.

Ground-Penatrating Radar Investigations Across the Sawmill Branch Fault Near Charleston, South Carolina

NASA Astrophysics Data System (ADS)

Dura-Gomez, I.; Addison, A.; Knapp, C. C.; Talwani, P.; Chapman, A.

2005-12-01

During the 1886 Charleston earthquake, two parallel tabby walls of Fort Dorchester broke left-laterally, and a strike of ~N25°W was inferred for the causative Sawmill Branch fault. To better define this fault, which does not have any surface expression, we planned to cut trenches across it. However, as Fort Dorchester is a protected archeological site, we were required to locate the fault accurately away from the fort, before permission could be obtained to cut short trenches. The present GPR investigations were planned as a preliminary step to determine locations for trenching. A pulseEKKO 100 GPR was used to collect data along eight profiles (varying in length from 10 m to 30 m) that were run across the projected strike of the fault, and one 50 m long profile that was run parallel to it. The locations of the profiles were obtained using a total station. To capture the signature of the fault, sixteen common-offset (COS) lines were acquired by using different antennas (50, 100 and 200 MHz) and stacking 64 times to increase the signal-to-noise ratio. The location of trees and stumps were recorded. In addition, two common-midpoint (CMP) tests were carried out, and gave an average velocity of about 0.097 m/ns. Processing included the subtraction of the low frequency "wow" on the trace (dewow), automatic gain control (AGC) and the application of bandpass filters. The signals using the 50 MHz, 100 MHz and 200 MHz antennas were found to penetrate up to about 30 meters, 20 meters and 12 meters respectively. Vertically offset reflectors and disruptions of the electrical signal were used to infer the location of the fault(s). Comparisons of the locations of these disruptions on various lines were used to infer the presence of a N30°W fault zone We plan to confirm these locations by cutting shallow trenches.

Paleoseismological History of the Acambay Graben (Central Mexico)

NASA Astrophysics Data System (ADS)

Lacan, P.; Zúñiga, R.; Ortuño, M.; Persaud, M.; Aguirre-Diaz, G. J.; Langridge, R. M.; Villamor, P.; Perea, H.; Štěpančíková, P.; Carreon, D.; Cerca, M.; Suñe Puchol, I.; Corominas Calvet, O.; Audin, L.; Baize, S.; Lawton, T. F.; Rendón, A.

2013-12-01

The Acambay graben is part of the Trans-Mexican Volcanic Belt (TMVB) which strikes ESE-WNW across central Mexico, where the major part of the Mexican population is concentrated. The TMVB is an active, calc-alkaline volcanic arc that is related to the subduction of the Rivera and Cocos plates underneath the North American plate. The TMVB contains a series of intra-arc basins that form the Chapala-Tula fault zone (450 km long, 50 km wide). One of these extensive basins, the Acambay graben, is 80 km long and 15 to 30 km wide. It is limited north by the E-W striking Epitacio-Huerta (EHF) and Acambay-Tixmadejé normal faults and south by the Venta de Bravo (VBF) and the Pastores faults (PF) in the south. Other minor active faults are located within the basin, along the axis of the Graben. In the area, the instrumental seismicity is low to moderate, although one major historical earthquake (Ms = 6.9 Acambay event) occurred on November 19, 1912, causing widespread damage. In the last decade, our group has focused on the neotectonic and paleoseismological study of the major faults of the Acambay graben. More than 30 trenches have been dug at 15 sites in order to interpret the paleoseismological history of 7 major faults of the graben. In addition to paleoseismological trench studies, tectonic geomorphology, subsurface geophysics and micro topographic surveys have been used to assess the rupture history. All of the studied faults have to be considered as active faults, with a minimum of 2 to 5 paleoseismic events on each fault during the last 20 ka. Each fault rupture corresponds to a vertical displacement ranging from 1 to 150 centimetres. Considering the size of the observed displacements and the length of active segments, we demonstrate that large earthquakes with magnitude higher than 7 have occurred along some of these faults. Based on paleoseismological results, we calculate a major earthquake recurrence interval ranging from 2,000 to 5,000 years over a time span (~20 ka). These recurrence values overpass the Mexican historical seismicity catalogue that incorporates no more than the last 500 years. This suggests that most of the faults of the TMVB may be active despite the lack of known historical destructive events and could be able to produce earthquakes with serious consequences in the most populated area of Mexico.

Earthquake Hazard Assessment Based on Geological Data: An approach from Crystalline Terrain of Peninsular India

NASA Astrophysics Data System (ADS)

John, B.

2009-04-01

Earthquake Hazard Assessment Based on Geological Data: An approach from Crystalline Terrain of Peninsular India Biju John National Institute of Rock Mechanics b_johnp@yahoo.co.in Peninsular India was for long considered as seismically stable. But the recent earthquake sequence of Latur (1993), Jabalpur (1997), Bhuj (2001) suggests this region is among one of the active Stable Continental Regions (SCRs) of the world, where the recurrence intervals is of the order of tens of thousands of years. In such areas, earthquake may happen at unexpected locations, devoid of any previous seismicity or dramatic geomorphic features. Even moderate earthquakes will lead to heavy loss of life and property in the present scenario. So it is imperative to map suspected areas to identify active faults and evaluate its activities, which will be a vital input to seismic hazard assessment of SCR area. The region around Wadakkanchery, Kerala, South India has been experiencing micro seismic activities since 1989. Subsequent studies, by the author, identified a 30 km long WNW-ESE trending reverse fault, dipping south (45°), that influenced the drainage system of the area. The macroscopic and microscopic studies of the fault rocks from the exposures near Desamangalam show an episodic nature of faulting. Dislocations of pegmatitic veins across the fault indicate a cumulative dip displacement of 2.1m in the reverse direction. A minimum of four episodes of faulting were identified in this fault based on the cross cutting relations of different structural elements and from the mineralogic changes of different generations of gouge zones. This suggests that an average displacement of 52cm per event might have occurred for each event. A cyclic nature of faulting is identified in this fault zone in which the inter-seismic period is characterized by gouge induration and fracture sealing aided by the prevailing fluids. Available empirical relations connecting magnitude with displacement and rupture length show that each event might have produced an earthquake of magnitude ≥ 6.0, which could be a damaging one to an area like peninsular India. Electron Spin Resonance dating of fault gouge indicates a major event around 430ka. In the present stress regime this fault can be considered as seismically active, because the orientation of the fault is favorable for reactivation.

Low-Temperature Thermochronology for Unraveling Thermal Processes and Dating of Fault Zones

NASA Astrophysics Data System (ADS)

Tagami, T.

2016-12-01

Thermal signatures as well as timing of fault motions can be constrained by thermochronological analyses of fault-zone rocks (e.g., Tagami, 2012). Fault-zone materials suitable for such analyses are produced by tectocic and geochemical processes, such as (1) mechanical fragmentation of host rocks, grain-size reduction of fragments and recrystallization of grains to form mica and clay minerals, (2) secondary heating/melting of host rocks by frictional fault motions, and (3) mineral vein formation as a consequence of fluid advection associated with fault motions. The geothermal structure of fault zones are primarily controlled by the following three factors: (a) regional geothermal structure around the fault zone that reflect background thermo-tectonic history of studied province, (b) frictional heating of wall rocks by fault motions and resultant heat transfer into surrounding rocks, and (c) thermal influences by hot fluid advection in and around the fault zone. Thermochronological methods widely applied in fault zones are K-Ar (40Ar/39Ar), fission-track (FT), and U-Th methods. In addition, OSL, TL, ESR and (U-Th)/He methods are applied in some fault zones, in order to extract temporal imformation related to low temperature and/or very recent fault activities. Here I briefly review the thermal sensitivity of individual thermochronological systems, which basically controls the response of each method against faulting processes. Then, the thermal sensitivity of FTs is highlighted, with a particular focus on the thermal processes characteristic to fault zones, i.e., flash and hydrothermal heating. On these basis, representative examples as well as key issues, including sampling strategy, are presented to make thermochronologic analysis of fault-zone materials, such as fault gouges, pseudotachylytes and mylonites, along with geological, geomorphological and seismological implications. Finally, the thermochronologic analyses of the Nojima fault are overviewed, as an example of multidisciplinary investigations of an active seismogenic fault system. References: T. Tagami, 2012. Thermochronological investigation of fault zones. Tectonophys., 538-540, 67-85, doi:10.1016/j.tecto.2012.01.032.

Spatial Relationship Between Crustal Structure and Mantle Seismicity in the Vrancea Seismogenic Zone of Romania

NASA Astrophysics Data System (ADS)

Knapp, C. C.; Enciu, D. M.; Knapp, J. H.

2007-12-01

Active crustal deformation and subsidence in the Southeast Carpathian foreland has previously been attributed to active foundering of thickened continental lithosphere beneath the Carpathian bend region (Knapp et al, 2005). The present study involves integration of active and passive-source seismic data in order to place constraints on the duration, timing, and scale of crustal deformation in the Carpathian foreland, and in particular to assess the genetic relationship with the Vrancea intermediate-depth seismogenic zone (VSZ). Relocated crustal earthquakes and focal mechanisms were correlated with four deep industry seismic profiles, the reprocessed DACIA PLAN deep seismic profile, and the DRACULA (Deep Reflection Acquisition Constraining Unusual Lithospheric Activity) II and III profiles. Projection of foreland crustal hypocenters onto the deep seismic lines correlates well with previously identified crustal faults such as the Trotus and Sinaia, as well as the newly identified Ialomita Fault. Specifically, results of this study (1) image the full crustal and uppermost mantle structure of the Focsani Basin in the close proximity of the VSZ, (2) show evidence for a sub-horizontal, slightly east-dipping Moho in the vicinity of the VSZ and thinning of the crust towards the Carpathian orogen, (3) illustrate the conspicuous absence of west-dipping fabrics or structures in the crust and across the Moho, (4) present evidence that the Trotus Fault is a crustal-scale active fault with a dextral sense of motion, (5) suggest that the Paleozoic age Peceneaga-Camena and Capidava-Ovidiu Faults have not been active in post-Paleozoic time, and (6) show evidence for a new active crustal scale sinistral fault, named the Ialomita fault. Both the seismogenic Vrancea body and deformation in the Focsani Basin appear to be concentrically bound by the Trotus Fault in the north and east and the Sinaia-Ialomita Fault in the south, suggesting a coupled deformation between the VSZ and the foreland deformation, possibly accommodated on these two major fault systems. These results contradict both the "subduction-in-place" and "slab- break-off" hypotheses as feasible explanations for VSZ intermediate-depth seismicity, and lend additional support to a lithospheric delamination model to explain both the origin of the VSZ and the crustal architecture of the Southeast Carpathian foreland.

Post-caldera faulting of the Late Quaternary Menengai caldera, Central Kenya Rift (0.20°S, 36.07°E)

NASA Astrophysics Data System (ADS)

Riedl, Simon; Melnick, Daniel; Mibei, Geoffrey K.; Njue, Lucy; Strecker, Manfred R.

2015-04-01

A structural geological analysis of young caldera volcanoes is necessary to characterize their volcanic activity, assess their geothermal potential, and decipher the spatio-temporal relationships of faults on a larger tectonic scale. Menengai caldera is one of several major Quaternary trachytic caldera volcanoes that are aligned along the volcano-tectonic axis of the Kenya Rift, the archetypal active magmatic rift and nascent plate boundary between the Nubia and Somalia plates. The caldera covers an area of approximately 80 km² and is among the youngest and also largest calderas in the East African Rift, situated close to Nakuru - a densely populated urban area. There is an increasing interest in caldera volcanoes in the Kenya Rift, because these are sites of relatively young volcanic and tectonic activity, and they are considered important sites for geothermal exploration and future use for the generation of geothermal power. Previous studies of Menengai showed that the caldera collapsed in a multi-event, multiple-block style, possibly as early as 29 ka. In an attempt to characterize the youngest tectonic activity along the volcano-tectonic axis in the transition between the Central and Northern Kenya rifts we first used a high-resolution digital surface model, which we derived by structure-from-motion from an unmanned aerial vehicle campaign. This enabled us to identify previously unrecognized normal faults, associated dyke intrusions and volcanic eruptive centers, and transfer faults with strike-slip kinematics in the caldera interior and its vicinity. In a second step we verified these structures at outcrop scale, assessed their relationship with known stratigraphic horizons and dated units, and performed detailed fault measurements, which we subsequently used for fault-kinematic analysis. The most important structures that we mapped are a series of north-northeast striking normal faults, which cross-cut both the caldera walls and early Holocene lake shorelines outside the caldera. These faults have similar strikes as Pleistocene faults that define the left-stepping, north-northeast oriented segments of the volcano-tectonic axis of the inner trough of the Central Kenya Rift. In the center of the caldera, these faults are kinematically linked with oblique-slip and strike-slip transfer faults, similar to other sectors in the Central Kenya Rift. The structural setup of Menengai and the faults to the north and south of the eruptive center is thus compatible with tectono-magmatic activity in an oblique extensional tectonic regime, which reflects the tectonic and seismic activity along a nascent plate boundary.

Rates and patterns of surface deformation from laser scanning following the South Napa earthquake, California

USGS Publications Warehouse

DeLong, Stephen B.; Lienkaemper, James J.; Pickering, Alexandra J; Avdievitch, Nikita N.

2015-01-01

The A.D. 2014 M6.0 South Napa earthquake, despite its moderate magnitude, caused significant damage to the Napa Valley in northern California (USA). Surface rupture occurred along several mapped and unmapped faults. Field observations following the earthquake indicated that the magnitude of postseismic surface slip was likely to approach or exceed the maximum coseismic surface slip and as such presented ongoing hazard to infrastructure. Using a laser scanner, we monitored postseismic deformation in three dimensions through time along 0.5 km of the main surface rupture. A key component of this study is the demonstration of proper alignment of repeat surveys using point cloud–based methods that minimize error imposed by both local survey errors and global navigation satellite system georeferencing errors. Using solid modeling of natural and cultural features, we quantify dextral postseismic displacement at several hundred points near the main fault trace. We also quantify total dextral displacement of initially straight cultural features. Total dextral displacement from both coseismic displacement and the first 2.5 d of postseismic displacement ranges from 0.22 to 0.29 m. This range increased to 0.33–0.42 m at 59 d post-earthquake. Furthermore, we estimate up to 0.15 m of vertical deformation during the first 2.5 d post-earthquake, which then increased by ∼0.02 m at 59 d post-earthquake. This vertical deformation is not expressed as a distinct step or scarp at the fault trace but rather as a broad up-to-the-west zone of increasing elevation change spanning the fault trace over several tens of meters, challenging common notions about fault scarp development in strike-slip systems. Integrating these analyses provides three-dimensional mapping of surface deformation and identifies spatial variability in slip along the main fault trace that we attribute to distributed slip via subtle block rotation. These results indicate the benefits of laser scanner surveys along active faults and demonstrate that fine-scale variability in fault slip has been missed by traditional earthquake response methods.

Fault zone hydrogeology

NASA Astrophysics Data System (ADS)

Bense, V. F.; Gleeson, T.; Loveless, S. E.; Bour, O.; Scibek, J.

2013-12-01

Deformation along faults in the shallow crust (< 1 km) introduces permeability heterogeneity and anisotropy, which has an important impact on processes such as regional groundwater flow, hydrocarbon migration, and hydrothermal fluid circulation. Fault zones have the capacity to be hydraulic conduits connecting shallow and deep geological environments, but simultaneously the fault cores of many faults often form effective barriers to flow. The direct evaluation of the impact of faults to fluid flow patterns remains a challenge and requires a multidisciplinary research effort of structural geologists and hydrogeologists. However, we find that these disciplines often use different methods with little interaction between them. In this review, we document the current multi-disciplinary understanding of fault zone hydrogeology. We discuss surface- and subsurface observations from diverse rock types from unlithified and lithified clastic sediments through to carbonate, crystalline, and volcanic rocks. For each rock type, we evaluate geological deformation mechanisms, hydrogeologic observations and conceptual models of fault zone hydrogeology. Outcrop observations indicate that fault zones commonly have a permeability structure suggesting they should act as complex conduit-barrier systems in which along-fault flow is encouraged and across-fault flow is impeded. Hydrogeological observations of fault zones reported in the literature show a broad qualitative agreement with outcrop-based conceptual models of fault zone hydrogeology. Nevertheless, the specific impact of a particular fault permeability structure on fault zone hydrogeology can only be assessed when the hydrogeological context of the fault zone is considered and not from outcrop observations alone. To gain a more integrated, comprehensive understanding of fault zone hydrogeology, we foresee numerous synergistic opportunities and challenges for the discipline of structural geology and hydrogeology to co-evolve and address remaining challenges by co-locating study areas, sharing approaches and fusing data, developing conceptual models from hydrogeologic data, numerical modeling, and training interdisciplinary scientists.

Anatomy of a Plate Boundary at Shallow Crustal Levels: a Composite Section from the Alpine Fault, New Zealand

NASA Astrophysics Data System (ADS)

Barth, N. C.; Toy, V. G.; Boulton, C. J.; Carpenter, B. M.

2010-12-01

New Zealand's Alpine Fault is mostly a moderately SE-dipping dextral reverse plate boundary structure, but at its southern end, strike-slip-normal motion is indicated by offset of recent surfaces, juxtaposition of sediments, and both brittle and ductile shear sense indicators. At the location of uplift polarity reversal fault rocks exhumed from both the hangingwall Pacific and footwall Australian Plates are juxtaposed, offering a remarkably complete cross section of the plate boundary at shallow crustal levels. We describe Alpine Fault damage zone and fault core structures overprinted on Pacific and Australian plate mylonites of a variety of compositions, in a fault-strike perpendicular composite section spanning the reversal in dip-slip polarity. The damage zone is asymmetric; on the Australian Plate 160m of quartzose paragneiss-derived mylonites are overprinted by brittle faults and fractures that increase in density towards the principal slip surface (PSS). This damage zone fabric consists of 1-10m-spaced, moderately to steeply-dipping, 1-20cm-thick gouge-filled faults, overprinted on and sub-parallel to a mylonitic foliation sub-parallel to the PSS. On the Pacific Plate, only 40m of the 330m section of volcaniclastic-derived mylonites have brittle damage in the form of unhealed fractures and faults, as well as a pervasive greenschist facies hydrothermal alteration absent in the footwall. These damage-related structures comprise a network of small-offset faults and fractures with increasing density and intensity towards the PSS. The active Pacific Plate fault core is composed of ~1m of cataclasite grading into folded protocataclasite that is less folded and fractured with increasing distance from the PSS. The active Australian Plate fault core is <1.5m wide and consists of 3 distinct foliated clay gouges, as well as a 4cm thick brittle ultracataclasite immediately adjacent to the active PSS. The Australian Plate foliated clay gouge contains stringers of quartz that become less continuous and more sigmoidal toward the PSS, indicating a strain gradient across the gouge zone. Gouge textures are consistent with deformation by pressure solution. Intact wafers from one of the gouges, experimentally -sheared in a biaxial configuration under true-triaxial loading at σn’= 31MPa and Pf = 10MPa, yielded a friction coefficient, μss = 0.32 and displayed velocity strengthening behavior. No significant re-strengthening was observed during hold periods of slide-hold tests. Well-cemented glacial till (~8000 years old), which caps many outcrops, is a marker that shows that the damage zone is not active in the near-surface, but most of the fault core is. The active near-surface damage zone here is <40m wide and the active fault core is <2.5m wide. Both overprint a much wider, inactive damage zone. The combination of rheologically-weak Australian Plate fault rocks with surface rupture traces indicates distinctly different coseismic and interseismic behaviors along the southern strike-slip-normal segment of the Alpine Fault.

The Padul normal fault activity constrained by GPS data: Brittle extension orthogonal to folding in the central Betic Cordillera

NASA Astrophysics Data System (ADS)

Gil, Antonio J.; Galindo-Zaldívar, Jesús; Sanz de Galdeano, Carlos; Borque, Maria Jesús; Sánchez-Alzola, Alberto; Martinez-Martos, Manuel; Alfaro, Pedro

2017-08-01

The Padul Fault is located in the Central Betic Cordillera, formed in the framework of the NW-SE Eurasian-African plate convergence. In the Internal Zone, large E-W to NE-SW folds of western Sierra Nevada accommodated the greatest NW-SE shortening and uplift of the cordillera. However, GPS networks reveal a present-day dominant E-W to NE-SW extensional setting at surface. The Padul Fault is the most relevant and best exposed active normal fault that accommodates most of the NE-SW extension of the Central Betics. This WSW-wards dipping fault, formed by several segments of up to 7 km maximum length, favored the uplift of the Sierra Nevada footwall away from the Padul graben hanging wall. A non-permanent GPS network installed in 1999 constrains an average horizontal extensional rate of 0.5 mm/yr in N66°E direction. The fault length suggests that a (maximum) 6 magnitude earthquake may be expected, but the absence of instrumental or historical seismic events would indicate that fault activity occurs at least partially by creep. Striae on fault surfaces evidence normal-sinistral kinematics, suggesting that the Padul Fault may have been a main transfer fault of the westernmost end of the Sierra Nevada antiform. Nevertheless, GPS results evidence: (1) shortening in the Sierra Nevada antiform is in its latest stages, and (2) the present-day fault shows normal with minor oblique dextral displacements. The recent change in Padul fault kinematics will be related to the present-day dominance of the ENE-WSW regional extension versus NNW-SSE shortening that produced the uplift and northwestwards displacement of Sierra Nevada antiform. This region illustrates the importance of heterogeneous brittle extensional tectonics in the latest uplift stages of compressional orogens, as well as the interaction of folding during the development of faults at shallow crustal levels.

Distributed deformation and block rotation in 3D

NASA Technical Reports Server (NTRS)

Scotti, Oona; Nur, Amos; Estevez, Raul

1990-01-01

The authors address how block rotation and complex distributed deformation in the Earth's shallow crust may be explained within a stationary regional stress field. Distributed deformation is characterized by domains of sub-parallel fault-bounded blocks. In response to the contemporaneous activity of neighboring domains some domains rotate, as suggested by both structural and paleomagnetic evidence. Rotations within domains are achieved through the contemporaneous slip and rotation of the faults and of the blocks they bound. Thus, in regions of distributed deformation, faults must remain active in spite of their poor orientation in the stress field. The authors developed a model that tracks the orientation of blocks and their bounding faults during rotation in a 3D stress field. In the model, the effective stress magnitudes of the principal stresses (sigma sub 1, sigma sub 2, and sigma sub 3) are controlled by the orientation of fault sets in each domain. Therefore, adjacent fault sets with differing orientations may be active and may display differing faulting styles, and a given set of faults may change its style of motion as it rotates within a stationary stress regime. The style of faulting predicted by the model depends on a dimensionless parameter phi = (sigma sub 2 - sigma sub 3)/(sigma sub 1 - sigma sub 3). Thus, the authors present a model for complex distributed deformation and complex offset history requiring neither geographical nor temporal changes in the stress regime. They apply the model to the Western Transverse Range domain of southern California. There, it is mechanically feasible for blocks and faults to have experienced up to 75 degrees of clockwise rotation in a phi = 0.1 strike-slip stress regime. The results of the model suggest that this domain may first have accommodated deformation along preexisting NNE-SSW faults, reactivated as normal faults. After rotation, these same faults became strike-slip in nature.

Evolutionary Based Techniques for Fault Tolerant Field Programmable Gate Arrays

NASA Technical Reports Server (NTRS)

Larchev, Gregory V.; Lohn, Jason D.

2006-01-01

The use of SRAM-based Field Programmable Gate Arrays (FPGAs) is becoming more and more prevalent in space applications. Commercial-grade FPGAs are potentially susceptible to permanently debilitating Single-Event Latchups (SELs). Repair methods based on Evolutionary Algorithms may be applied to FPGA circuits to enable successful fault recovery. This paper presents the experimental results of applying such methods to repair four commonly used circuits (quadrature decoder, 3-by-3-bit multiplier, 3-by-3-bit adder, 440-7 decoder) into which a number of simulated faults have been introduced. The results suggest that evolutionary repair techniques can improve the process of fault recovery when used instead of or as a supplement to Triple Modular Redundancy (TMR), which is currently the predominant method for mitigating FPGA faults.

The implication of gouge mineralogy evolution on fault creep: an example from The North Anatolian Fault, Turkey

NASA Astrophysics Data System (ADS)

Kaduri, M.; Gratier, J. P.; Renard, F.; Cakir, Z.; Lasserre, C.

2015-12-01

Aseismic creep is found along several sections of major active faults at shallow depth, such as the North Anatolian Fault in Turkey, the San Andreas Fault in California (USA), the Longitudinal Valley Fault in Taiwan, the Haiyuan fault in China and the El Pilar Fault in Venezuela. Identifying the mechanisms controlling creep and their evolution with time and space represents a major challenge for predicting the mechanical evolution of active faults, the interplay between creep and earthquakes, and the link between short-term observations from geodesy and the geological setting. Hence, studying the evolution of initial rock into damaged rock, then into gouge, is one of the key question for understanding the origin of fault creep. In order to address this question we collected samples from a dozen well-preserved fault outcrops along creeping and locked sections of the North Anatolian Fault. We used various methods such as microscopic and geological observations, EPMA, XRD analysis, combined with image processing, to characterize their mineralogy and strain. We conclude that (1) there is a clear correlation between creep localization and gouge composition. The locked sections of the fault are mostly composed of massive limestone. The creeping sections comprises clay gouges with 40-80% low friction minerals such as smectite, saponite, kaolinite, that facilitates the creeping. (2) The fault gouge shows two main structures that evolve with displacement: anastomosing cleavage develop during the first stage of displacement; amplifying displacement leads to layering development oblique or sub-parallel to the fault. (3) We demonstrate that the fault gouge result from a progressive evolution of initial volcanic rocks including dissolution of soluble species that move at least partially toward the damage zones and alteration transformations by fluid flow that weaken the gouge and strengthen the damage zone.

Historical coseismic surface deformation of fluvial gravel deposits, Schafberg fault, Lower Rhine Graben, Germany

NASA Astrophysics Data System (ADS)

Kübler, Simon; Friedrich, Anke M.; Gold, Ryan D.; Strecker, Manfred R.

2018-03-01

Intraplate earthquakes pose a significant seismic hazard in densely populated rift systems like the Lower Rhine Graben in Central Europe. While the locations of most faults in this region are well known, constraints on their seismogenic potential and earthquake recurrence are limited. In particular, the Holocene deformation history of active faults remains enigmatic. In an exposure excavated across the Schafberg fault in the southwestern Lower Rhine Graben, south of Untermaubach, in the epicentral region of the 1756 Düren earthquake ( M L 6.2), we mapped a complex deformation zone in Holocene fluvial sediments. We document evidence for at least one paleoearthquake that resulted in vertical surface displacement of 1.2 ± 0.2 m. The most recent earthquake is constrained to have occurred after 815 AD, and we have modeled three possible earthquake scenarios constraining the timing of the latest event. Coseismic deformation is characterized by vertical offset of sedimentary contacts distributed over a 10-m-wide central damage zone. Faults were identified where they fracture and offset pebbles in the vertically displaced gravel layers and fracture orientation is consistent with the orientation of the Schafberg fault. This study provides the first constraint on the most recent surface-rupturing earthquake on the Schafberg fault. We cannot rule out that this fault acted as the source of the 1756 Düren earthquake. Our study emphasizes the importance of, and the need for, paleoseismic studies in this and other intracontinental regions, in particular on faults with subtle geomorphic expression that would not typically be recognized as being potentially seismically active. Our study documents textural features in unconsolidated sediment that formed in response to coseismic rupturing of the underlying bedrock fault. We suggest that these features, e.g., abundant oriented transgranular fractures in their context, should be added to the list of criteria used to identify a fault as potentially active. Such information would result in an increase of the number of potentially active faults that contribute to seismic hazards of intracontinental regions.

Active tectonics of the Imperial Valley, southern California: fault damage zones, complex basins and buried faults

NASA Astrophysics Data System (ADS)

Persaud, P.; Ma, Y.; Stock, J. M.; Hole, J. A.; Fuis, G. S.; Han, L.

2016-12-01

Ongoing oblique slip at the Pacific-North America plate boundary in the Salton Trough produced the Imperial Valley. Deformation in this seismically active area is distributed across a complex network of exposed and buried faults resulting in a largely unmapped seismic hazard beneath the growing population centers of El Centro, Calexico and Mexicali. To better understand the shallow crustal structure in this region and the connectivity of faults and seismicity lineaments, we used data primarily from the Salton Seismic Imaging Project (SSIP) to construct a P-wave velocity profile to 15 km depth, and a 3-D velocity model down to 8 km depth including the Brawley Geothermal area. We obtained detailed images of a complex wedge-shaped basin at the southern end of the San Andreas Fault system. Two deep subbasins (VP <5.65 km/s) are located in the western part of the larger Imperial Valley basin, where seismicity trends and active faults play a significant role in shaping the basin edge. Our 3-D VP model reveals previously unrecognized NE-striking cross faults that are interacting with the dominant NW-striking faults to control deformation. New findings in our profile include localized regions of low VP (thickening of a 5.65-5.85 km/s layer) near faults or seismicity lineaments interpreted as possibly faulting-related. Our 3-D model and basement map reveal velocity highs associated with the geothermal areas in the eastern valley. The improved seismic velocity model from this study, and the identification of important unmapped faults or buried interfaces will help refine the seismic hazard for parts of Imperial County, California.

Active faulting in low- to moderate-seismicity regions: the SAFE project

NASA Astrophysics Data System (ADS)

Sebrier, M.; Safe Consortium

2003-04-01

SAFE (Slow Active Faults in Europe) is an EC-FP5 funded multidisciplinary effort which proposes an integrated European approach in identifying and characterizing active faults as input for evaluating seismic hazard in low- to moderate-seismicity regions. Seismically active western European regions are generally characterized by low hazard but high risk, due to the concentration of human and material properties with high vulnerability. Detecting, and then analysing, tectonic deformations that may lead to destructive earthquakes in such areas has to take into account three major limitations: - the typical climate of western Europe (heavy vegetation cover and/or erosion) ; - the subdued geomorphic signature of slowly deforming faults ; - the heavy modification of landscape by human activity. The main objective of SAFE, i.e., improving the assessment of seismic hazard through understanding of the mechanics and recurrence of active faults in slowly deforming regions, is achieved through four major steps : (1) extending geologic and geomorphic investigations of fault activity beyond the Holocene to take into account various time-windows; (2) developing an expert system that combines diverse lines of geologic, seismologic, geomorphic, and geophysical evidence to diagnose the existence and seismogenic potential of slow active faults; (3) delineating and characterising high seismic risk areas of western Europe, either from historical or geological/geomorphic evidence; (4) demonstrating and discussing the impact of the project results on risk assessment through a seismic scenario in the Basel-Mulhouse pilot area. To take properly into account known differences in source behavior, these goals are pursued both in extensional (Lower and Upper Rhine Graben, Catalan Coast) and compressional tectonic settings (southern Upper Rhine Graben, Po Plain, and Provence). Two arid compressional regions (SE Spain and Moroccan High Atlas) have also been selected to address the limitations imposed by vegetation and human modified landscapes. The first results demonstrate that the strong added value provided by SAFE consists in its integrated multidisciplinary and multiscalar approach that allows robust diagnostic conclusions on fault activity and on the associated earthquake potential. This approach will be illustrated through selected methodological results.

Geometric and kinematic analysis of structural elements along north front of Bagharan Kuh Mountain, NE Iran

NASA Astrophysics Data System (ADS)

Samimi, S.; Gholami, E.

2017-03-01

At the end of the western part of Bagharan Kuh Mountain in the northeast of Iran, mountain growth has been stopped toward the west because of the stress having been consumed by the thrusting movements and region rising instead of shear movement. Chahkand fault zone is situated at the western part of this mountain; this fault zone includes several thrust sheets that caused upper cretaceous ophiolite rocks up to younger units, peridotite exposure and fault related fold developing in the surface. In transverse perpendicular to the mountain toward the north, reduction in the parameters like faults dip, amount of deformation, peridotite outcrops show faults growth sequence and thrust sheets growth from mountain to plain, thus structural vergence is toward the northeast in this fault zone. Deformation in the east part of the region caused fault propagation fold with axial trend of WNW-ESE that is compatible with trending of fault plane. In the middle part, two types of folds is observed; in the first type, folding occurred before faulting and folds was cut by back thrust activity; in the second type, faults activity caused fault related folds with N60-90W axial trend. In order to hanging wall strain balance, back thrusts have been developed in the middle and western part which caused popup and fault bend folds with N20-70E trend. Back thrusts activity formed footwall synclines, micro folds, foliations, and uplift in this part of the region. Kinematic analysis of faults show stress axis σ1 = N201.6, 7, σ2 = N292.6, 7.1, σ3 = N64.8, 79.5; stress axis obtained by fold analysis confirm that minimum stress (σ3) is close to vertical so it is compatible with fault analysis. Based on the results, deformation in this region is controlled by compressional stress regime. This stress state is consistent with the direction of convergence between the Arabian and Eurasian plates. Also study of transposition, folded veins, different movements on the fault planes and back thrusts confirm the progressive deformation is dominant in this region that it increases from the east to the west.

Consistent earthquake catalog derived from changing network configurations: Application to the Rawil Depression in the southwestern Helvetic Alps

NASA Astrophysics Data System (ADS)

Lee, Timothy; Diehl, Tobias; Kissling, Edi; Wiemer, Stefan

2017-04-01

Earthquake catalogs derived from several decades of observations are often biased by network geometries, location procedures, and data quality changing with time. To study the long-term spatio-temporal behavior of seismogenic fault zones at high-resolution, a consistent homogenization and improvement of earthquake catalogs is required. Assuming that data quality and network density generally improves with time, procedures are needed, which use the best available data to homogeneously solve the coupled hypocenter - velocity structure problem and can be as well applied to earlier network configurations in the same region. A common approach to uniformly relocate earthquake catalogs is the calculation of a so-called "minimum 1D" model, which is derived from the simultaneous inversion for hypocenters and 1D velocity structure, including station specific delay-time corrections. In this work, we will present strategies using the principles of the "minimum 1D" model to consistently relocate hypocenters recorded by the Swiss Seismological Service (SED) in the Swiss Alps over a period of 17 years in a region, which is characterized by significant changes in network configurations. The target region of this study is the Rawil depression, which is located between the Aar and Mont Blanc massifs in southwestern Switzerland. The Rhone-Simplon Fault is located to the south of the Rawil depression and is considered as a dextral strike-slip fault representing the dominant tectonic boundary between Helvetic nappes to the north and Penninic nappes to the south. Current strike-slip earthquakes, however, occur predominantly in a narrow, east-west striking cluster located in the Rawil depression north of the Rhone-Simplon Fault. Recent earthquake swarms near Sion and Sierre in 2011 and 2016, on the other hand, indicate seismically active dextral faults close to the Rhone valley. The region north and south of the Rhone-Simplon Fault is one of the most seismically active regions in Switzerland and therefore a prime target to study the mechanics of active fault zones in the Swiss Alps. In the presented study, existing travel-time data from the SED bulletin from the entire instrumental era (1984-today) are used to calculate a "minimum 1D" model for the region. The dataset is complemented by data of three broadband stations, recently installed to further densify the seismic network of the SED in the Rawil area. The new model is compared to previous local and regional 1D and 3D models. The derived model is used for systematic relocation of the seismicity in the Rawil region and will be used as reference model for high-resolution 3D models imaging the velocity structure of the Rawil fault zone in a next step. The presented procedure is of relevance for similar studies planned in other regions of the Alps, which have been densified by AlpArray stations.

Characteristics of the recent seismic activity on a near-shore fault south of Malta, Central Mediterranean

NASA Astrophysics Data System (ADS)

Bozionelos, George; Galea, Pauline; D'Amico, Sebastiano; Agius, Matthew

2017-04-01

The tectonic setting of the Maltese islands is mainly influenced by two dominant rift systems belonging to different ages and having different trends. The first and older rift created the horst and graben structure in northern Malta. The second rift generation, in the south, including the Maghlaq Fault, is associated with the Pantelleria Rift. The Maghlaq Fault is a spectacular NW - SE trending and left-stepping normal fault running along the southern coastline of the Maltese islands, cutting the Oligo-Miocene pre to syn-rift carbonates. Its surface expression is traceable along 4 km of the coastline, where vertical displacements of the island's Tertiary stratigraphic sequence are clearly visible and exceed 210m. These displacements have given rise to sheer, slickensided fault scarps, as well as isolating the small island of Filfla 4km offshore the southern coast. Identification and assessment of the seismic activity related with Maghlaq fault, for the recent years, is performed, re-evaluating and redetermining the hypocentral locations and the source parameters of both recent and older events. The earthquakes that have affected the Maltese islands in the historical past, have occurred mainly at the Sicily Channel, at eastern Sicily, even as far away as the Hellenic arc. Some of these earthquakes also have caused considerable damage to buildings. The Maghlaq fault is believed to be one of the master faults of the Sicily Channel Rift, being parallel to the Malta graben, which passes around 20km south of Malta and shows continuous seismic activity. Despite the relationship of this fault with the graben system, no seismic activity on the Maghlaq fault had been documented previous to 2015. On the July 30nth 2015, an earthquake was widely felt in the southern half of Malta and was approximately located just offshore the southern coast. Since then, a swarm of seismic events lasting several days, as well as other isolated events have occurred, indicating the fault to be seismically active. Investigation of the nature of the seismic events and other previous activity that may have been misclassified due to poor location capability, is performed. Such results are of utmost importance in order to reveal the implication of this newly-discovered activity on the seismic hazard to the Maltese islands and also to improve understanding of the local geodynamics, highlighting the mechanisms that contribute to both the crustal deformation and the tectonics of the upper crust. The investigation is carried out using the stations of the recently extended Malta Seismic Network and regional stations. The results are evaluated in the context of the role of the Maghlaq fault in the extensional tectonics associated with the Sicily Channel Rift and the African continental margin.

The continuation of the Kazerun fault system across the Sanandaj-Sirjan zone (Iran)

NASA Astrophysics Data System (ADS)

Safaei, Homayon

2009-08-01

The Kazerun (or Kazerun-Qatar) fault system is a north-trending dextral strike-slip fault zone in the Zagros mountain belt of Iran. It probably originated as a structure in the Panafrican basement. This fault system played an important role in the sedimentation and deformation of the Phanerozoic cover sequence and is still seismically active. No previous studies have reported the continuation of this important and ancient fault system northward across the Sanandaj-Sirjan zone. The Isfahan fault system is a north-trending dextral strike-slip fault across the Sanandaj-Sirjan zone that passes west of Isfahan city and is here recognized for the first time. This important fault system is about 220 km long and is seismically active in the basement as well as the sedimentary cover sequence. This fault system terminates to the south near the Main Zagros Thrust and to the north at the southern boundary of the Urumieh-Dokhtar zone. The Isfahan fault system is the boundary between the northern and southern parts of Sanandaj-Sirjan zone, which have fundamentally different stratigraphy, petrology, geomorphology, and geodynamic histories. Similarities in the orientations, kinematics, and geologic histories of the Isfahan and Kazerun faults and the way they affect the magnetic basement suggest that they are related. In fact, the Isfahan fault is a continuation of the Kazerun fault across the Sanandaj-Sirjan zone that has been offset by about 50 km of dextral strike-slip displacement along the Main Zagros Thrust.

Fault orientations in extensional and conjugate strike-slip environments and their implications

USGS Publications Warehouse

Thatcher, W.; Hill, D.P.

1991-01-01

Seismically active conjugate strike-slip faults in California and Japan typically have mutually orthogonal right- and left-lateral fault planes. Normal-fault dips at earthquake nucleation depths are concentrated between 40?? and 50??. The observed orientations and their strong clustering are surprising, because conventional faulting theory suggests fault initiation with conjugate 60?? and 120?? intersecting planes and 60?? normal-fault dip or fault reactivation with a broad range of permitted orientations. The observations place new constraints on the mechanics of fault initiation, rotation, and evolutionary development. We speculate that the data could be explained by fault rotation into the observed orientations and deactivation for greater rotation or by formation of localized shear zones beneath the brittle-ductile transition in Earth's crust. Initiation as weak frictional faults seems unlikely. -Authors

The characteristics of the western extension of the Karakax fault in NW Tibet and its tectonic implications

NASA Astrophysics Data System (ADS)

Ge, C.; Liu, D.; Li, H.; Zheng, Y.; Pan, J.

2017-12-01

The Karakax strike-slip fault, located in northwest Tibet, is a mature deformation belt with a long-time evolutionary history, which is also active at present and plays an important role in the tectonic deformation of the northwestern Tibetan Plateau. Nowadays, most geologists consider that the Karakax fault is generally east-west striking along the Karakax river valley, and northwest striking until to the Tashkorgan in the Mazar area. However, an ENE-WSW fault was identified at the Mazar area, which sited at the bend of the Karakax fault, we named this fault as the Matar fault. Via the detailed geological survey, the similar geometry and kinematic characteristics were identified between the Karakax and Matar faults: (1) The similar fault zone scale(Karakax:90 300m; Matar:100 220m); (2) The similar preferred orientation (nearly EW) of the stretching lineations and foliations; (3) All the fault planes of the both faults have a high dip angle and is nearly EW striking; (4) Lots of ductile deformations, such as σ-type quartz rotational mortar, S-C fabric, symmetric drag fold and so on, indicated that the Matar fault is a right-lateral strike-slip and thrust fault during the early ductile deformation stage; (5) the deluvium, sheared by Matar fault, indicated that the Matar fault has already transformed into a left-lateral strike-slip fault during the later brittle deformation stage. All the above showed that the Matar fault has a similar geometry and kinematic characteristics with the Karakax fault, and the former is the probable the western extension of the latter. Moreover, the form of the Karakax-Matar fault may had an impact to the geomorphology of the west Kunlun-Pamir area, such as the strike of the moutains and faults. considering the age of west Kunlun mountains uplifting and Karakax fault activating, we regard that the Matar fault (the westward extension of Karakax fault) may contributes much in forming the modern geomorphology features of the west Kunlun-Pamir area.

Fault distribution in the Precambrian basement of South Norway

NASA Astrophysics Data System (ADS)

Gabrielsen, Roy H.; Nystuen, Johan Petter; Olesen, Odleiv

2018-03-01

Mapping of the structural pattern by remote sensing methods (Landsat, SPOT, aerial photography, potential field data) and field study of selected structural elements shows that the cratonic basement of South Norway is strongly affected by a regular lineament pattern that encompasses fault swarms of different orientation, age, style, attitude and frequency. Albeit counting numerous fault and fracture populations, the faults are not evenly distributed and N-S to NNE-SSW/NNW-SSE and NE-SE/ENE-WSW-systems are spatially dominant. N-S to NNW-SSE structures can be traced underneath the Caledonian nappes to the Western Gneiss Region in western and central South Norway, emphasizing their ancient roots. Dyke swarms of different ages are found within most of these zones. Also, the Østfold, Oslo-Trondheim and the Mandal-Molde lineament zones coincide with trends of Sveconorwegian post-collision granites. We conclude that the N-S-trend includes the most ancient structural elements, and that the trend can be traced back to the Proterozoic (Svecofennian and Sveconorwegian) orogenic events. Some of the faults may have been active in Neoproterozoic times as marginal faults of rift basins at the western margin of Baltica. Remnants of such fault activity have survived in the cores of many of the faults belonging to this system. The ancient systems of lineaments were passively overridden by the Caledonian fold-and-thrust system and remained mostly, but note entirely inactive throughout the Sub-Cambrian peneplanation and the Caledonian orogenic collapse in the Silurian-Devonian. The system was reactivated in extension from Carboniferous times, particularly in the Permian with the formation of the Oslo Rift and parts of it remain active to the Present, albeit by decreasing extension and fault activity.

Late Pleistocene - Holocene ruptures of the Lima Reservoir fault, SW Montana

NASA Astrophysics Data System (ADS)

Anastasio, David J.; Majerowicz, Christina N.; Pazzaglia, Frank J.; Regalla, Christine A.

2010-12-01

Active tectonics within the northern Basin and Range province provide a natural laboratory for the study of normal fault growth, linkage, and interaction. Here, we present new geologic mapping and morphologic fault-scarp modeling within the Centennial Valley, Montana to characterize Pleistocene - Holocene ruptures of the young and active Lima Reservoir fault. Geologic relationships and rupture ages indicate Middle Pleistocene activity on the Henry Gulch (>50 ka and 23-10 ka), Trail Creek (>43 ka and ˜13 ka), and reservoir (˜23 ka) segments. Offset Quaternary deposits also record Holocene rupture of the reservoir segment (˜8 ka), but unfaulted modern streams show that no segments of the Lima Reservoir fault have experienced a large earthquake in at least several millennia. The clustered pattern of rupture ages on the Lima Reservoir fault segments suggests a seismogenic linkage though segment length and spacing make a physical connection at depth unlikely. Trail Creek and reservoir segment slip rates were non-steady and appear to be increasing. The fault helps accommodate differential horizontal surface velocity measured by GPS geodesy across the boundary between the northern Basin and Range province and the Snake River Plain.

The DSeis Project: Drilling into Seismogenic zones of M2.0 to M5.5 earthquakes in South African gold mines

NASA Astrophysics Data System (ADS)

Yabe, Y.; Ogasawara, H.; Ito, T.; van Aswegen, G.; Durrheim, R. J.; Cichowicz, A.; Onstott, T. C.; Kieft, T. L.; Boettcher, M. S.; Wiemer, S.; Ziegler, M.; Shapiro, S. A.; Gupta, H. K.; Dight, P.

2017-12-01

The DSeis project under ICDP consists of drilling in three mines; MK, TT and C4 mines. Common scientific targets among them are the stress state and the microstructure in the seismogenic zone. In addition to these targets, specific targets in individual mines are detailed below. A M5.5 earthquake occurred beneath the MK mine on 5 August 2014. The hypocenter of this event was 5km depth from the surface. In contrast to the normal faulting of induced earthquakes in mining horizons (<4km depth), the M5.5 event was a strike-slip one with an N-S striking, sub-vertical nodal plane along which aftershocks aligned. Aftershocks extend up to 3.5km depth. We established a drilling site at 2.8km depth in the mine, from where two boreholes 800m-long penetrate into the areas of high and low aftershock densities. Targets of these drilling are 1) to investigate a depth variation in the stress state from the normal faulting to the strike-slip one, 2) to know what controls the spatial variation in the aftershock activity, and 3) to explore a limit of deep life that might be trapped in Archean sediments. Our site in the TT mine is 50m under the hypocenter of a M3.2 earthquake which occurred on 28 January 2017 at 3.6km depth. Although aftershock activity recorded by the seismic network operated by the mine is low, the source fault looks to extend along or parallel to a pre-existing, N-S striking fault. Three boreholes go through the fault at the hypocenter and the northern and the southern margins of the fault to compare the stress states and the microfracture distributions. Further, monitoring of microseismicity down to M -4 and geochemistry is planned to evaluate how much is a ratio of microseismicity associated with creation of new fractures. In the C4 mine, there was the site of a previous project, in which the microseismicity monitoring and the stress measurement by the CCBO technique were carried out. A M2.8 earthquake occurred 1 year after the CCBO and its hypocenter was only 100m away from the CCBO site. Due to little mining activity in the source region, the stress state just after the M2.8 event should be preserved. We will measure the stress again. Damage zones that evolved quasi-statically were seen by the microseismicity monitoring. Drilling into these zones would provide a clue to see a difference between faults evolved dynamically and quasi-statically.

Determining the Positions of Seismically Active Faults in Platform Regions Based on the Integrated Profile Observations

NASA Astrophysics Data System (ADS)

Levshenko, V. T.; Grigoryan, A. G.

2018-03-01

By the examples of the Roslavl'skii, Grafskii, and Platava-Varvarinskii faults, the possibility is demonstrated of mapping the geological objects by the measurement algorithm that includes successively measuring the spectra of microseisms at the points of the measurement network by movable instruments and statistical accumulation of the ratios of the power spectra of the amplitudes. Based on this technique, the positions of these seismically active faults are determined by the integrated profile observations of the parameters of microseismic and radon fields. The refined positions of the faults can be used in estimating the seismic impacts on the critical objects in the vicinity of these faults.

Connecting the Yakima fold and thrust belt to active faults in the Puget Lowland, Washington

USGS Publications Warehouse

Blakely, R.J.; Sherrod, B.L.; Weaver, C.S.; Wells, R.E.; Rohay, A.C.; Barnett, E.A.; Knepprath, N.E.

2011-01-01

High-resolution aeromagnetic surveys of the Cascade Range and Yakima fold and thrust belt (YFTB), Washington, provide insights on tectonic connections between forearc and back-arc regions of the Cascadia convergent margin. Magnetic surveys were measured at a nominal altitude of 250 m above terrain and along flight lines spaced 400 m apart. Upper crustal rocks in this region have diverse magnetic properties, ranging from highly magnetic rocks of the Miocene Columbia River Basalt Group to weakly magnetic sedimentary rocks of various ages. These distinctive magnetic properties permit mapping of important faults and folds from exposures to covered areas. Magnetic lineaments correspond with mapped Quaternary faults and with scarps identified in lidar (light detection and ranging) topographic data and aerial photography. A two-dimensional model of the northwest striking Umtanum Ridge fault zone, based on magnetic and gravity data and constrained by geologic mapping and three deep wells, suggests that thrust faults extend through the Tertiary section and into underlying pre-Tertiary basement. Excavation of two trenches across a prominent scarp at the base of Umtanum Ridge uncovered evidence for bending moment faulting possibly caused by a blind thrust. Using aeromagnetic, gravity, and paleoseismic evidence, we postulate possible tectonic connections between the YFTB in eastern Washington and active faults of the Puget Lowland. We suggest that faults and folds of Umtanum Ridge extend northwestward through the Cascade Range and merge with the Southern Whidbey Island and Seattle faults near Snoqualmie Pass 35 km east of Seattle. Recent earthquakes (MW ≤ 5.3) suggest that this confluence of faults may be seismically active today.

Detailed seismicity analysis revealing the dynamics of the southern Dead Sea area

NASA Astrophysics Data System (ADS)

Braeuer, B.; Asch, G.; Hofstetter, R.; Haberland, Ch.; Jaser, D.; El-Kelani, R.; Weber, M.

2014-10-01

Within the framework of the international DESIRE (DEad Sea Integrated REsearch) project, a dense temporary local seismological network was operated in the southern Dead Sea area. During 18 recording months, 648 events were detected. Based on an already published tomography study clustering, focal mechanisms, statistics and the distribution of the microseismicity in relation to the velocity models from the tomography are analysed. The determined b value of 0.74 leads to a relatively high risk of large earthquakes compared to the moderate microseismic activity. The distribution of the seismicity indicates an asymmetric basin with a vertical strike-slip fault forming the eastern boundary of the basin, and an inclined western boundary, made up of strike-slip and normal faults. Furthermore, significant differences between the area north and south of the Bokek fault were observed. South of the Bokek fault, the western boundary is inactive while the entire seismicity occurs on the eastern boundary and below the basin-fill sediments. The largest events occurred here, and their focal mechanisms represent the northwards transform motion of the Arabian plate along the Dead Sea Transform. The vertical extension of the spatial and temporal cluster from February 2007 is interpreted as being related to the locking of the region around the Bokek fault. North of the Bokek fault similar seismic activity occurs on both boundaries most notably within the basin-fill sediments, displaying mainly small events with strike-slip mechanism and normal faulting in EW direction. Therefore, we suggest that the Bokek fault forms the border between the single transform fault and the pull-apart basin with two active border faults.

Structural inheritance versus magmatic weakening: What controls the style of deformation at rift segment boundaries in the Gulf of California, Mexico?

NASA Astrophysics Data System (ADS)

Seiler, Christian; Gleadow, Andrew; Kohn, Barry

2013-04-01

Rifts are commonly segmented into several hundred kilometre long zones of opposing upper-plate transport direction with boundaries defined by accommodation and transfer zones. A number of such rift segments have been recognized in the Gulf of California, a youthful oceanic basin that is currently undergoing the rift-drift transition. However, detailed field studies have so far failed to identify suitable structures that could accommodate the obvious deformation gradients between different rift segments, and the nature of strain transfer at segment boundaries remains enigmatic. The Bocana transfer zone (BTZ) in central Baja California is a linear, WNW striking structural discontinuity separating two rift segments with different magnitudes and styles of extensional deformation. North of the BTZ, the Libertad fault is part of the Main Gulf Escarpment, which represents the breakaway fault that separates the Gulf of California rift to the east from the relatively stable western portion of the Baja peninsula. The N-striking Libertad escarpment developed during the Late Miocene (~10-8Ma) and exhibits a topographic relief of ca. 1,000m along a strike-length of ca. 50km. Finite displacement decreases from ~1000m in the central fault segment to ~500m further south, where the fault bends SE and merges with the BTZ. In the hanging wall of the Libertad fault, a series of W-tilted horsts are bound along their eastern margins by two moderate-displacement E-dipping normal faults. South of the BTZ, extension was much less than further north, which explains the comparatively subdued relief and generally shallower tilt of pre-rift strata in this area. The BTZ itself is characterized by two en echelon WNW-ESE striking dextral-oblique transfer faults with a significant down-to-the-NNE extensional component. Strain is transferred from the Libertad breakaway fault onto the transfer faults over a distance of >20km through a network of interacting normal, oblique and strike-slip faults. The shape, location and orientation of the main faults were strongly influenced by pre-existing rheological heterogeneities. Major normal faults are parallel to either the Mesozoic metamorphic foliation or Cretaceous intrusive contacts, and developed where the foliation was at a high angle to the extension direction. In contrast, the oblique-slip faults of the BTZ formed parallel to the metamorphic foliation where formlines are at a small angle to the regional extension direction. Compared to the BTZ, deformation in other known accommodation zones of the Gulf of California rift occurred distributed across a much wider zone, and appropriate transfer faults are either lacking or minor. In these cases, however, the accommodation zones coincide with the locations of significant pre- and synrift volcanism, suggesting that thermal weakening associated with magmatic activity may have promoted the distribution of strain across a wider region instead of localising it into discrete transfer faults.

Controls on Patterns of Repeated Fault Rupture: Examples From the Denali and Bear River Faults

NASA Astrophysics Data System (ADS)

Schwartz, D. P.; Hecker, S.

2013-12-01

A requirement for estimating seismic hazards is assigning magnitudes to earthquake sources. This relies on anticipating rupture length and slip along faults. Fundamental questions include whether lengths of past surface ruptures can be reasonably determined from fault zone characteristics and whether the variability in length and slip during repeated faulting can be constrained. To address these issues, we look at rupture characteristics and their possible controls from examples in very different tectonic settings: the high slip rate (≥15 mm/yr) Denali fault system, Alaska, and the recently activated Bear River normal fault, Wyoming-Utah. The 2002 rupture of the central Denali fault (CDF) is associated with two noteworthy geometric features. First, rupture initiated where the Susitna Glacier thrust fault (SG) intersects the CDF at depth, near the apex of a structurally complex restraining bend along the Denali. Paleoseismic data show that for the past 700 years the timing of large surface ruptures on the Denali fault west of the 2002 rupture has been distinct from those along the CDF. For the past ~6ka the frequency of SG to Denali ruptures has been ~1:12, indicating that this complexity of the 2002 rupture has not been common. Second, rupture propagated off of one strike-slip fault (CDF) onto another (the Totschunda fault, TF), an occurrence that seldom has been observed. LiDAR mapping of the intersection shows direct connectivity of the two faults--the CDF simply branches into both the TF and the eastern Denali fault (EDF). Differences in the timing of earthquakes during the past 700-800 years at sites surrounding this intersection, and estimates of accumulated slip from slip rates, indicate that for the 2002 rupture sufficient strain had accumulated on the TF to favor its failure. In contrast, the penultimate CDF rupture, with the same slip distribution as in 2002, appears to have stopped at or near the branch point, implying that neither the TF nor the EDF was stressed sufficiently to fail at that time. The Bear River fault zone (BRFZ) is a young normal fault along the eastern margin of basin-range extension that appears to have reactivated a ramp in the Laramide-age Darby-Hogsback thrust. The entire Cenozoic history of the BRFZ may consist of only two surface-rupturing events in the late Holocene (one at ~5 ka and the most recent at ~2.5 ka). The 40-km-long fault comprises synthetic and antithetic scarps extending across a zone up to 5 km wide. Remote sensing, including airborne LiDAR, and field studies show that, despite the complexity, the pattern of faulting was similar (in location and amount) for each of the two events and, at the south end, was strongly influenced by the east-west-trending Uinta Arch. Pre-existing structure clearly has exerted a first-order control on moment release on this immature fault. As shown by these examples, data on timing of surface ruptures, coseismic slip, slip rate, and fault geometry can provide a basis to constrain lengths of past and future earthquake ruptures, including possible alternative rupture scenarios. The difficult question for hazard analysis is whether the available data capture the full range of behavior and with what relative frequency do the alternatives occur?

Fault weakening and earthquake instability by powder lubrication

USGS Publications Warehouse

Reches, Z.; Lockner, D.A.

2010-01-01

Earthquake instability has long been attributed to fault weakening during accelerated slip1, and a central question of earthquake physics is identifying the mechanisms that control this weakening2. Even with much experimental effort2-12, the weakening mechanisms have remained enigmatic. Here we present evidence for dynamic weakening of experimental faults that are sheared at velocities approaching earthquake slip rates. The experimental faults, which were made of room-dry, solid granite blocks, quickly wore to form a fine-grain rock powder known as gouge. At modest slip velocities of 10-60mms-1, this newly formed gouge organized itself into a thin deforming layer that reduced the fault's strength by a factor of 2-3. After slip, the gouge rapidly 'aged' and the fault regained its strength in a matter of hours to days. Therefore, only newly formed gouge can weaken the experimental faults. Dynamic gouge formation is expected to be a common and effective mechanism of earthquake instability in the brittle crust as (1) gouge always forms during fault slip5,10,12-20; (2) fault-gouge behaves similarly to industrial powder lubricants21; (3) dynamic gouge formation explains various significant earthquake properties; and (4) gouge lubricant can form for a wide range of fault configurations, compositions and temperatures15. ?? 2010 Macmillan Publishers Limited. All rights reserved.

Evidence for Phanerozoic reactivation of the Najd Fault System in AVHRR, TM, and SPOT images of central Arabia

NASA Technical Reports Server (NTRS)

Andre, Constance G.

1989-01-01

SPOT stereoscopic and TM multispectral images support evidence in AVHRR thermal-IR images of a major unmapped shear zone in Phanerozoic cover rocks southeast of the ancient Najd Fault System in the Arabian Shield. This shear zone and faults of the Najd share a common alignment, orientation, and sinistral sense of movement. These similarities suggest a 200-km extension of the Najd Fault System and reactivation since it formed in the late Precambrian. Topographic and lithologic features in the TM and SPOT data along one of three faults inferred from the AVHRR data indicate sinistral offsets up to 2.5 km, en echelon folds and secondary faults like those predicted by models of left-lateral strike-slip faulting. The age of the affected outcrops indicates reactivation of Najd faults in the Cretaceous, judging from TM and SPOT data or in the Tertiary, based on AVHRR data. The total length of the system visible at the surface measures 1300 km. If the Najd Fault System is extrapolated beneath sands of the Empty Quarter to faults of a similar trend in South Yemen, the shear zone would span the Arabian Plate. Furthermore, if extensions into the Arabian Sea bed and into Egypt proposed by others are considered, it would exceed 3000 km.

Active intra-basin faulting in the Northern Basin of Lake Malawi from seismic reflection data

NASA Astrophysics Data System (ADS)

Shillington, D. J.; Chindandali, P. R. N.; Scholz, C. A.; Ebinger, C. J.; Onyango, E. A.; Peterson, K.; Gaherty, J. B.; Nyblade, A.; Accardo, N. J.; McCartney, T.; Oliva, S. J.; Kamihanda, G.; Ferdinand, R.; Salima, J.; Mruma, A. H.

2016-12-01

Many questions remain about the development and evolution of fault systems in weakly extended rifts, including the relative roles of border faults and intra-basin faults, and segmentation at various scales. The northern Lake Malawi (Nyasa) rift in the East African Rift System is an early stage rift exhibiting pronounced tectonic segmentation, which is defined by 100-km-long border faults. The basins also contain a series of intrabasinal faults and associated synrift sediments. The occurrence of the 2009 Karonga Earthquake Sequence on one of these intrabasinal faults indicates that some of them are active. Here we present new multichannel seismic reflection data from the Northern Basin of the Malawi Rift collected in 2015 as a part of the SEGMeNT (Study of Extension and maGmatism in Malawi aNd Tanzania) project. This rift basin is bound on its east side by the west-dipping Livingstone border fault. Over 650 km of seismic reflection profiles were acquired in the Northern Basin using a 500 to 1540 cu in air gun array and a 1200- to 1500-m seismic streamer. Dip lines image a series of north-south oriented west-dipping intra-basin faults and basement reflections up to 5 s twtt near the border fault. Cumulative offsets on intra-basin faults decrease to the west. The largest intra-basin fault has a vertical displacement of >2 s two-way travel time, indicating that it has accommodated significant total extension. Some of these intra-basin faults offset the lake bottom and the youngest sediments by up to 50 s twtt ( 37 m), demonstrating they are still active. The two largest intra-basin faults exhibit the largest offsets of young sediments and also correspond to the area of highest seismicity based on analysis of seismic data from the 89-station SEGMeNT onshore/offshore network (see Peterson et al, this session). Fault patterns in MCS profiles vary along the basin, suggesting a smaller scale of segmentation of faults within the basin; these variations in fault patterns appear to correlate with variations in the distribution of aftershocks from the 2009 and 2014 Karonga earthquakes and in background seismicity beneath the lake, providing new constraints on length-displacement scaling for predictive models and earthquake hazards.

Splay fault slip in a subduction margin, a new model of evolution

NASA Astrophysics Data System (ADS)

Conin, Marianne; Henry, Pierre; Godard, Vincent; Bourlange, Sylvain

2012-08-01

In subduction zones, major thrusts called splay faults are thought to slip coseismically during large earthquakes affecting the main plate interface. We propose an analytical condition for the activation of a splay fault based on force balance calculations and suggest thrusting along the splay fault is generally conditioned by the growth of the accretionary wedge, or by the erosion of the hanging wall. In theory, normal slip on the splay fault may occur when the décollement has a very low friction coefficient seaward. Such a low friction also implies an unstable extensional state within the outer wedge. Finite element elasto-plastic calculations with a geometry based on the Nankai Kumano section were performed and confirm that this analytical condition is a valid approximation. Furthermore, localized extension at a shallow level in the splay hanging wall is observed in models for a wide range of friction coefficients (from ∼0 to the value of internal friction coefficient of the rock, here equals to 0.4). The timing of slip established for the splay fault branch drilled on Nankai Kumano transect suggests a phase of concurrent splay and accretionary wedge growth ≈2 Ma to ≈1.5 Ma, followed by a locking of the splay ≈1.3 Ma. Active extension is observed in the hanging wall. This evolution can be explained by the activation of a deeper and weaker décollement, followed by an interruption of accretion. Activation of a splay as a normal fault, as hypothesized in the case of the Tohoku 2011 earthquake, can be achieved only if the friction coefficient on the décollement drops to near zero. We conclude that the tectonic stress state largely determines long-term variations of tightly related splay fault and outer décollement activity and thus influences where and how coseismic rupture ends, but that occurrence of normal slip on a splay fault requires coseismic friction reduction.

Constraining the Distribution of Vertical Slip on the South Heli Shan Fault (Northeastern Tibet) From High-Resolution Topographic Data

NASA Astrophysics Data System (ADS)

Bi, Haiyun; Zheng, Wenjun; Ge, Weipeng; Zhang, Peizhen; Zeng, Jiangyuan; Yu, Jingxing

2018-03-01

Reconstruction of the along-fault slip distribution provides an insight into the long-term rupture patterns of a fault, thereby enabling more accurate assessment of its future behavior. The increasing wealth of high-resolution topographic data, such as Light Detection and Ranging and photogrammetric digital elevation models, allows us to better constrain the slip distribution, thus greatly improving our understanding of fault behavior. The South Heli Shan Fault is a major active fault on the northeastern margin of the Tibetan Plateau. In this study, we built a 2 m resolution digital elevation model of the South Heli Shan Fault based on high-resolution GeoEye-1 stereo satellite imagery and then measured 302 vertical displacements along the fault, which increased the measurement density of previous field surveys by a factor of nearly 5. The cumulative displacements show an asymmetric distribution along the fault, comprising three major segments. An increasing trend from west to east indicates that the fault has likely propagated westward over its lifetime. The topographic relief of Heli Shan shows an asymmetry similar to the measured cumulative slip distribution, suggesting that the uplift of Heli Shan may result mainly from the long-term activity of the South Heli Shan Fault. Furthermore, the cumulative displacements divide into discrete clusters along the fault, indicating that the fault has ruptured in several large earthquakes. By constraining the slip-length distribution of each rupture, we found that the events do not support a characteristic recurrence model for the fault.

A 667 year record of coseismic and interseismic Coulomb stress changes in central Italy reveals the role of fault interaction in controlling irregular earthquake recurrence intervals

NASA Astrophysics Data System (ADS)

Wedmore, L. N. J.; Faure Walker, J. P.; Roberts, G. P.; Sammonds, P. R.; McCaffrey, K. J. W.; Cowie, P. A.

2017-07-01

Current studies of fault interaction lack sufficiently long earthquake records and measurements of fault slip rates over multiple seismic cycles to fully investigate the effects of interseismic loading and coseismic stress changes on the surrounding fault network. We model elastic interactions between 97 faults from 30 earthquakes since 1349 A.D. in central Italy to investigate the relative importance of co-seismic stress changes versus interseismic stress accumulation for earthquake occurrence and fault interaction. This region has an exceptionally long, 667 year record of historical earthquakes and detailed constraints on the locations and slip rates of its active normal faults. Of 21 earthquakes since 1654, 20 events occurred on faults where combined coseismic and interseismic loading stresses were positive even though 20% of all faults are in "stress shadows" at any one time. Furthermore, the Coulomb stress on the faults that experience earthquakes is statistically different from a random sequence of earthquakes in the region. We show how coseismic Coulomb stress changes can alter earthquake interevent times by 103 years, and fault length controls the intensity of this effect. Static Coulomb stress changes cause greater interevent perturbations on shorter faults in areas characterized by lower strain (or slip) rates. The exceptional duration and number of earthquakes we model enable us to demonstrate the importance of combining long earthquake records with detailed knowledge of fault geometries, slip rates, and kinematics to understand the impact of stress changes in complex networks of active faults.

Ground Surface Deformation in Unconsolidated Sediments Caused by Bedrock Fault Movements: Dip-Slip and Strike-Slip Fault Model Test and Field Survey

NASA Astrophysics Data System (ADS)

Ueta, K.; Tani, K.

2001-12-01

Sandbox experiments were performed to investigate ground surface deformation in unconsolidated sediments caused by dip-slip and strike-slip motion on bedrock faults. A 332.5 cm long, 200 cm high, and 40 cm wide sandbox was used in a dip-slip fault model test. In the strike-slip fault test, a 600 cm long, 250 cm wide, and 60 cm high sandbox and a 170 cm long, 25 cm wide, 15 cm high sandbox were used. Computerized X-ray tomography applied to the sandbox experiments made it possible to analyze the kinematic evolution, as well as the three-dimensional geometry, of the faults. The fault type, fault dip, fault displacement, thickness and density of sandpack and grain size of the sand were varied for different experiments. Field survey of active faults in Japan and California were also made to investigate the deformation of unconsolidated sediments overlying bedrock faults. A comparison of the experimental results with natural cases of active faults reveals the following: (1) In the case of dip-slip faulting, the shear bands are not shown as one linear plane but as en echelon pattern. Thicker and finer unconsolidated sediments produce more shear bands and clearer en echelon shear band patterns. (2) In the case of left-lateral strike-slip faulting, the deformation of the sand pack with increasing basement displacement is observed as follows. a) In three dimensions, the right-stepping shears that have a "cirque" / "shell" / "ship body" shape develop on both sides of the basement fault. The shears on one side of the basement fault join those on the other side, resulting in helicoidal shaped shear surfaces. Shears reach the surface of the sand near or above the basement fault and en echelon Riedel shears are observed at the surface of the sand. b) Right-stepping pressure ridges develop within the zone defined by the Riedel shears. c) Lower-angle shears generally branch off from the first Riedel shears. d) Right-stepping helicoidal shaped lower-angle shears offset Riedel shears and pressure ridges, and left-stepping and right-stepping pressure ridges are observed. d) With displacement concentrated on the central throughgoing fault zone, a "Zone of shear band" (ZSB) developed directly above the basement fault. The geometry of the ZSB shows a strong resemblance to linear ridge and trough geomorphology associated with active strike-slip faulting. (3) In the case of normal faulting, the location of the surface fault rupture is just above the bedrock faults, which have no relationship with the fault dip. On the other hand, the location of the surface rupture of the reverse fault has closely relationship with the fault dip. In the case of strike-slip faulting, the width of the deformation zone in dense sand is wider than that in loose sand. (4) The horizontal distance of surface rupture from the bedrock fault normalized by the height of sand mass (W/H) does not depend on the height of sand mass and grain size of sand. The values of W/H from the test agree well with those of earthquake faults. (5) The normalized base displacement required to propagate the shear rupture zone to the ground surface (D/H), in the case of normal faulting, is lower than those for reverse faulting and strike-slip faulting.

Recent Motion on the Kern Canyon Fault, Southern Sierra Nevada, California

NASA Astrophysics Data System (ADS)

Nadin, E. S.; Saleeby, J. B.

2005-12-01

Evidence suggests that the Kern Canyon Fault (KCF), the longest fault in the southern Sierra Nevada, is an active fault. Along the 140-km-long KCF, batholithic and metamorphic rocks were displaced up to 16~km in apparent dextral strike slip during at least three discrete phases of deformation throughout the past ~90~Myr. Early ductile shear is preserved along a 1.5-km-wide zone of S-C mylonites and phyllonites that constitutes the Proto-KCF; a later phase of brittle faulting led to through-going cataclasis along the 50-m-wide KCF; and finally, late-stage minor faulting resulted in thin, hematitic gouge zones. The KCF has been considered inactive since 3.5~Ma based on a dated basalt flow reported to cap the fault. However, we believe this basalt to be disturbed, and several pieces of evidence support the idea that the KCF has been reactivated in a normal sense during the Quaternary. Fresh, high-relief fault scarps at Engineer Point in Lake Isabella and near Brush Creek, suggest recent, west-side-up vertical offset. And seismicity in the area hints at local motion. The center of activity during the 1983--1984 Durrwood Meadows earthquake swarm, a series of more than 2,000 earthquakes, the largest of which was M = 4.5, was 10~km east of the KCF. The swarm spanned a discrete, 100~km-long north-south trajectory between latitudes 35° 20'N and 36° 30'N, and its focal mechanisms were consistent with pure normal faulting, but the KCF has been disqualified as too far west and too steep to accommodate the seismic activity. But it could be part of the fault system: Near latitude 36°N, we documented a well-preserved expression of the KCF, which places Cretaceous granitic rocks against a Quaternary glacial debris flow. This fault plane strikes N05°E and is consistent with west-side-up normal faulting, in agreement with the focal mechanism slip planes of the Durrwood Meadows swarm. It is possible that the recent swarm represents a budding strand of the KCF system, much like the Punchbowl Fault took up lateral slip 5~km from the main San Andreas Fault plane. Although the offset is not appreciable, we propose that recent activity along the KCF has accommodated stresses imparted by either Basin and Range extension or by San Andreas and/or Garlock Fault motion.

Using 10Be erosion rates and fluvial channel morphology to constrain fault throw rates in the southwestern Sacramento River Valley, California, USA

NASA Astrophysics Data System (ADS)

Cyr, A. J.

2013-12-01

The Sacramento - San Joaquin River Delta, California, USA, is a critical region for California water resources, agriculture, and threatened or endangered species. This landscape is affected by an extensive set of levees that enclose artificial islands created for agricultural use. In addition to their importance for sustaining agriculture, this levee system also supports extensive transport and power transmission infrastructure and urban/suburban development. These levees are susceptible to damage from even moderate ground shaking by either a large earthquake on one of the high-activity faults in the nearby San Francisco Bay region, or even a moderate earthquake on one of the low-activity faults in the Delta region itself. However, despite this danger the earthquake hazards in this region are poorly constrained due to our lack of understanding of faults in and near the Delta region. As part of an effort to better constrain the seismic hazard associated with known, but poorly constrained, faults in the region, a geomorphic analysis of the Dunnigan Hills, northwest of Woodland, CA, is being combined with cosmogenic 10Be catchment-averaged erosion rates. The Dunnigan Hills are a low-relief (maximum elevation 87 m) landscape generated by fault-bend folding above the west-vergent Sweitzer reverse fault that soles into a blind east-vergent reverse fault. These faults have been imaged by seismic reflection data, and local microseismicity indicates that this system is actively propagating to the east. However, the throw rates on the faults in this system remain unconstrained, despite the potential for significant shaking such as that experienced in the nearby April, 1892 earthquake sequence between Winters and Vacaville, Ca, ~25 km to the south, which has been estimated at magnitude 6.0 or greater. Geomorphic and cosmogenic 10Be analyses from 12 catchments draining the eastern flank of the Dunnigan Hills will be used to infer vertical rock uplift rates to better constrain activity on the west-vergent Sweitzer fault and the east-vergent blind reverse fault. All of the sampled catchments are underlain exclusively by Tehama Sandstone. Moreover, there are no mapped surface traces of faults in the sampled catchments. This minimizes the possibility of changes in lithogic resistance to impact the erosion rates and channel analyses. These analyses, combined with fault geometries derived from published seismic reflection data and structural cross sections, allows us to constrain the throw rates on these faults and thus better evaluate the associated seismic hazard.

Widespread active detachment faulting and core complex formation near 13 degrees N on the Mid-Atlantic Ridge.

PubMed

Smith, Deborah K; Cann, Johnson R; Escartín, Javier

2006-07-27

Oceanic core complexes are massifs in which lower-crustal and upper-mantle rocks are exposed at the sea floor. They form at mid-ocean ridges through slip on detachment faults rooted below the spreading axis. To date, most studies of core complexes have been based on isolated inactive massifs that have spread away from ridge axes. Here we present a survey of the Mid-Atlantic Ridge near 13 degrees N containing a segment in which a number of linked detachment faults extend for 75 km along one flank of the spreading axis. The detachment faults are apparently all currently active and at various stages of development. A field of extinct core complexes extends away from the axis for at least 100 km. Our observations reveal the topographic characteristics of actively forming core complexes and their evolution from initiation within the axial valley floor to maturity and eventual inactivity. Within the surrounding region there is a strong correlation between detachment fault morphology at the ridge axis and high rates of hydroacoustically recorded earthquake seismicity. Preliminary examination of seismicity and seafloor morphology farther north along the Mid-Atlantic Ridge suggests that active detachment faulting is occurring in many segments and that detachment faulting is more important in the generation of ocean crust at this slow-spreading ridge than previously suspected.

Investigating the deformation of upper crustal faults at the N-Chilean convergent plate boundary at different scales using high-resolution topography datasets and creepmeter measurements

NASA Astrophysics Data System (ADS)

Ewiak, O.; Victor, P.; Ziegenhagen, T.; Oncken, O.

2012-04-01

The Chilean convergent plate boundary is one of the tectonically most active regions on earth and prone to large megathrust earthquakes as e. g. the 2010 Mw 8.8 Maule earthquake which ruptured a mature seismic gap in south-central Chile. In northern Chile historical data suggests the existence of a seismic gap between Arica and Mejillones Peninsula (MP), which has not ruptured since 1877. Further south, the 1995 Mw 8.0 Antofagasta earthquake ruptured the subduction interface between MP and Taltal. In this study we investigate the deformation at four active upper plate faults (dip-slip and strike-slip) located above the coupling zone of the subduction interface. The target faults (Mejillones Fault - MF, Salar del Carmen Fault - SCF, Cerro Fortuna Fault - CFF, Chomache Fault - CF) are situated in forearc segments, which are in different stages of the megathrust seismic cycle. The main question of this study is how strain is accumulated in the overriding plate, what is the response of the target faults to the megathrust seismic cycle and what are the mechanisms / processes involved. The hyper arid conditions of the Atacama desert and the extremely low erosion rates enable us to investigate geomorphic markers, e .g. fault scarps and knickpoints, which serve as a record for upper crustal deformation and fault activity about ten thousands years into the past. Fault scarp data has been acquired with Differential-GPS by measuring high-resolution topographic profiles perpendicular to the fault scarps and along incised gullies. The topographic data show clear variations between the target faults which possibly result from their position within the forearc. The surveyed faults, e. g. the SCF, exhibit clear along strike variations in the morphology of surface ruptures attributed to seismic events and can be subdivided into individual segments. The data allows us to distinguish single, composite and multiple fault scarps and thus to detect differences in fault growth initiated either by seismic rupture or fault creep. Additional information on the number of seismic events responsible for the cumulative displacement can be derived from the mapping of knickpoints. By reconstructing the stress field responsible for the formation of identified seismic surface ruptures we can determine stress conditions for failure of upper crustal faults. Comparing these paleo stress conditions with the recent forearc stresses (interseismic / coseismic) we can derive information about a possible activation of upper crustal faults during the megathrust seismic cycle. In addition to the morphotectonic surveys we explore the recent deformation of the target faults by analyzing time series of displacements recorded with micron precision by an array of creepmeters at the target faults for over three years. Total displacement is composed of steady state creep, creep events and sudden displacement events (SDEs) related to seismic rupture. The percentage of SDEs accounts for >50 % (SCF) to 90 % (CFF) of the cumulative displacement. This result very well reflects the field observation that a considerable amount of the total displacement has been accumulated during multiple seismic events.

Widespread uplift and 'trapdoor' faulting on Galápagos volcanoes observed with radar interferometry.

PubMed

Amelung, F; Jónsson, S; Zebker, H; Segall, P

2000-10-26

Volcanic uplift, caused by the accumulation of magma in subsurface reservoirs, is a common precursor to eruptions. But, for some volcanoes, uplift of metres or more has not yet led to an eruption. Here we present displacement maps of volcanoes in the Galápagos Islands, constructed using satellite radar interferometry, that might help explain this dichotomy. We show that all but one of the seven volcanoes on the islands of Isabela and Fernandina deformed during 1992-99. Cerro Azul and Fernandina erupted during the observation period and show evidence of inflation, co-eruptive deflation and shallow dyke intrusion. In contrast, the largest volcano, Sierra Negra, has not erupted, yet exhibits spatially and temporally variable deformation, with a maximum uplift of 2.7 m between 1992 and 1999, which can be modelled by a shallow inflating sill. Inflation during 1997-98, however, was accompanied by 'trapdoor' faulting on a steeply dipping fracture system within the caldera. Repeated trapdoor faulting over geological time has formed an arcuate intra-caldera ridge within Sierra Negra and may have acted to relax stresses above the magma chamber, inhibiting summit eruptions. Similar processes may help explain large uplift unaccompanied by eruptive activity at other volcanoes.

Stafford fault system: 120 million year fault movement history of northern Virginia

USGS Publications Warehouse

Powars, David S.; Catchings, Rufus D.; Horton, J. Wright; Schindler, J. Stephen; Pavich, Milan J.

2015-01-01

The Stafford fault system, located in the mid-Atlantic coastal plain of the eastern United States, provides the most complete record of fault movement during the past ~120 m.y. across the Virginia, Washington, District of Columbia (D.C.), and Maryland region, including displacement of Pleistocene terrace gravels. The Stafford fault system is close to and aligned with the Piedmont Spotsylvania and Long Branch fault zones. The dominant southwest-northeast trend of strong shaking from the 23 August 2011, moment magnitude Mw 5.8 Mineral, Virginia, earthquake is consistent with the connectivity of these faults, as seismic energy appears to have traveled along the documented and proposed extensions of the Stafford fault system into the Washington, D.C., area. Some other faults documented in the nearby coastal plain are clearly rooted in crystalline basement faults, especially along terrane boundaries. These coastal plain faults are commonly assumed to have undergone relatively uniform movement through time, with average slip rates from 0.3 to 1.5 m/m.y. However, there were higher rates during the Paleocene–early Eocene and the Pliocene (4.4–27.4 m/m.y), suggesting that slip occurred primarily during large earthquakes. Further investigation of the Stafford fault system is needed to understand potential earthquake hazards for the Virginia, Maryland, and Washington, D.C., area. The combined Stafford fault system and aligned Piedmont faults are ~180 km long, so if the combined fault system ruptured in a single event, it would result in a significantly larger magnitude earthquake than the Mineral earthquake. Many structures most strongly affected during the Mineral earthquake are along or near the Stafford fault system and its proposed northeastward extension.

Geothermal Target Areas in Colorado as Identified by Remote Sensing Techniques

DOE Data Explorer

Khalid Hussein

2012-02-01

This layer contains the areas identified as targets of potential geothermal activity. The Criteria used to identify the target areas include: hot/warm surface exposures modeled from ASTER/Landsat satellite imagery and geological characteristics, alteration mineral commonly associated with hot springs (clays, Si, and FeOx) modeled from ASTER and Landsat data, Colorado Geological Survey (CGS) known thermal hot springs/wells and heat-flow data points, Colorado deep-seated fault zones, weakened basement identified from isostatic gravity data, and Colorado sedimentary and topographic characteristics.

Modelling Active Faults in Probabilistic Seismic Hazard Analysis (PSHA) with OpenQuake: Definition, Design and Experience

NASA Astrophysics Data System (ADS)

Weatherill, Graeme; Garcia, Julio; Poggi, Valerio; Chen, Yen-Shin; Pagani, Marco

2016-04-01

The Global Earthquake Model (GEM) has, since its inception in 2009, made many contributions to the practice of seismic hazard modeling in different regions of the globe. The OpenQuake-engine (hereafter referred to simply as OpenQuake), GEM's open-source software for calculation of earthquake hazard and risk, has found application in many countries, spanning a diversity of tectonic environments. GEM itself has produced a database of national and regional seismic hazard models, harmonizing into OpenQuake's own definition the varied seismogenic sources found therein. The characterization of active faults in probabilistic seismic hazard analysis (PSHA) is at the centre of this process, motivating many of the developments in OpenQuake and presenting hazard modellers with the challenge of reconciling seismological, geological and geodetic information for the different regions of the world. Faced with these challenges, and from the experience gained in the process of harmonizing existing models of seismic hazard, four critical issues are addressed. The challenge GEM has faced in the development of software is how to define a representation of an active fault (both in terms of geometry and earthquake behaviour) that is sufficiently flexible to adapt to different tectonic conditions and levels of data completeness. By exploring the different fault typologies supported by OpenQuake we illustrate how seismic hazard calculations can, and do, take into account complexities such as geometrical irregularity of faults in the prediction of ground motion, highlighting some of the potential pitfalls and inconsistencies that can arise. This exploration leads to the second main challenge in active fault modeling, what elements of the fault source model impact most upon the hazard at a site, and when does this matter? Through a series of sensitivity studies we show how different configurations of fault geometry, and the corresponding characterisation of near-fault phenomena (including hanging wall and directivity effects) within modern ground motion prediction equations, can have an influence on the seismic hazard at a site. Yet we also illustrate the conditions under which these effects may be partially tempered when considering the full uncertainty in rupture behaviour within the fault system. The third challenge is the development of efficient means for representing both aleatory and epistemic uncertainties from active fault models in PSHA. In implementing state-of-the-art seismic hazard models into OpenQuake, such as those recently undertaken in California and Japan, new modeling techniques are needed that redefine how we treat interdependence of ruptures within the model (such as mutual exclusivity), and the propagation of uncertainties emerging from geology. Finally, we illustrate how OpenQuake, and GEM's additional toolkits for model preparation, can be applied to address long-standing issues in active fault modeling in PSHA. These include constraining the seismogenic coupling of a fault and the partitioning of seismic moment between the active fault surfaces and the surrounding seismogenic crust. We illustrate some of the possible roles that geodesy can play in the process, but highlight where this may introduce new uncertainties and potential biases into the seismic hazard process, and how these can be addressed.

Analysis of past recurrent methane seep activity using radiocarbon dating of Calyptogena spp. shells in the eastern Nankai subduction zone, Japan

NASA Astrophysics Data System (ADS)

Yagasaki, Kazuhiro; Ashi, Juichiro; Yokoyama, Yusuke; Miyairi, Yosuke; Kuramoto, Shin'ichi

2016-04-01

Fault activity around subduction zones have been widely studied and monitored through drilling of oceanic plates, studying piston cores, use of monitoring equipment or through visual analysis using submersible vehicles. Yet the understanding of how small scale faults near shallow regions of the seabed behave in relation to cold seep vent activity is still vague, especially determining when they were active in the past. In tectonically active margins such as the Nankai and Tokai regions off Japan, dense methane hydrate reservoirs have been identified. Cold seeps releasing methane rich hydrocarbon fluids are common here, supporting a wide variety of biological species that hold a symbiotic relationship with the chemosynthetic bacteria. In 1998 a large dead Calyptogena spp. bivalve colony (over 400m2 in size) was discovered off Tokai, Japan. It is unusual for a bivalve colony this size to mostly be dead, raising questions as to what caused their death. In this study we document the radiocarbon 14C age of these bivalve shells to attempt analysing the possible methane seep bahaviour in the past. The measured 14C age ranged in three age groups of 1396±36-1448±34, 1912±31-1938±35 and 5975±34. The 14C age of shells that were alive upon collection and the dissolved inorganic carbon (DIC) in seawater show little difference (˜100 14C age) indicating that shells are not heavily affected by the dead carbon effect from cold seeps that is of biogenic or thermogenic origin, which can make the age to become considerably older than the actual age. Thus the novel calibration model used was based on the seawater DIC collected above the Calyptogena spp. colony site (1133±31), which resulted in the dead shells to be clustered around 1900 Cal AD. This proves to be interesting as the predicted epicenter of the Ansei-Tokai earthquake (M 8.4) in 1854 is extremely close to the bibalve colony site. Using geological data obtained using visual analysis and sub-seafloor structural analysis that show multiple shallow faults and chaotic sediment structure below the colony site, the Calyptogena spp. shells have a strong connection to the coseismic faulting activity and could show potential for radiocarbon dating to be applied on marine samples providing the necessary calibration tools are available.

Upper mantle diapers, lower crustal magmatic underplating, and lithospheric dismemberment of the Great Basin and Colorado Plateau regions, Nevada and Utah; implications from deep MT resistivity surveying

NASA Astrophysics Data System (ADS)

Wannamaker, P. E.; Doerner, W. M.; Hasterok, D. P.

2005-12-01

In the rifted Basin and Range province of the southwestern U.S., a common faulting model for extensional basins based e.g. on reflection seismology data shows dominant displacement along master faults roughly coincident with the main topographic scarp. On the other hand, complementary data such as drilling, earthquake focal mechanisms, volcanic occurrences, and trace indicators such as helium isotopes suggest that there are alternative geometries of crustal scale faulting and material transport from the deep crust and upper mantle in this province. Recent magnetotelluric (MT) profiling results reveal families of structures commonly dominated by high-angle conductors interpreted to reflect crustal scale fault zones. Based mainly on cross cutting relationships, these faults appear to be late Cenozoic in age and are of low resistivity due to fluids or alteration (including possible graphitization). In the Ruby Mtns area of north-central Nevada, high angle faults along the margins of the core complex connect from near surface to a regional lower crustal conductor interpreted to contain high-temperature fluids and perhaps melts. Such faults may exemplify the high angle normal faults upon which the major earthquakes of the Great Basin appear to nucleate. A larger-scale transect centered on Dixie Valley shows major conductive crustal-scale structures connecting to conductive lower crust below Dixie Valley, the Black Rock desert in NW Nevada, and in east-central Nevada in the Monitor-Diamond Valley area. In the Great Basin-Colorado Plateau transition of Utah, the main structures revealed are a series of nested low-angle detachment structures underlying the incipient development of several rift grabens. All these major fault zones appear to overlie regions of particularly conductive lower crust interpreted to be caused by recent basaltic underplating. In the GB-CP transition, long period data show two, low-resistivity upper mantle diapirs underlying the concentrated conductive lower crust and nested faults, and these are advanced as melt source regions for the underplating. MT, with its wide frequency bandwidth, allows views of nearly a complete melting and emplacement process, from mantle source region, through lower crustal intrusion, to brittle regime deformational response.

A multidisciplinary approach to characterize the geometry of active faults: the example of Mt. Massico, Southern Italy

NASA Astrophysics Data System (ADS)

Luiso, P.; Paoletti, V.; Nappi, R.; La Manna, M.; Cella, F.; Gaudiosi, G.; Fedi, M.; Iorio, M.

2018-06-01

We present the results of a multidisciplinary and multiscale study at Mt. Massico, Southern Italy. Mt. Massico is a carbonate horst located along the Campanian-Latial margin of the Tyrrhenian basin, bordered by two main NE-SW systems of faults, and by NW-SE and N-S trending faults. Our analysis deals with the modelling of the main NE-SW faults. These faults were capable during Plio-Pleistocene and are still active today, even though with scarce and low-energy seismicity (Mw maximum = 4.8). We inferred the pattern of the fault planes through a combined interpretation of 2-D hypocentral sections, a multiscale analysis of gravity field and geochemical data. This allowed us to characterize the geometry of these faults and infer their large depth extent. This region shows very striking gravimetric signatures, well-known Quaternary faults, moderate seismicity and a localized geothermal fluid rise. Thus, this analysis represents a valid case study for testing the effectiveness of a multidisciplinary approach, and employing it in areas with buried and/or silent faults of potential high hazard, such as in the Apennine chain.

History of fault slip and interaction with deltaic depostion from the middle Miocene to the Present - Barataria Fault, coastal Louisiana

NASA Astrophysics Data System (ADS)

McLindon, C.

2017-12-01

The Barataria fault is a major component of the Terrebonne Trough, a structural system of faults and salt domes underlying coastal Louisiana. High-quality 3-D seismic reflection data, industry well logs, micro-paleontological data and published literature on regional depositional patterns are integrated to provide an evolutionary history of the Barataria fault. The fault is a segment within a series of south-dipping normal faults that define the northern boundary of the Terrebonne Trough. The fault segment tips at depth interact with the Lake Washington and Bay de Chene salt domes, which appear to have limited its along-strike length. This study shows that the Barataria fault has exhibited continuous but episodic slip since at least the middle Miocene and through the present. Periods of maximum rates of fault slip are related to periods of maximum rates of sediment accumulation associated with Miocene deltaic deposition. The expansion of interval thickness between biostratigraphic markers in the hanging wall section of the fault relative to the footwall section (expansion index) indicate that rates of subsidence on the footwall during active fault slip were substantially greater than on the footwall. Pliocene-Pleistocene stratigraphic intervals exhibiting lower expansion indexes indicate that the fault remained active, but with a pattern of slower slip rate in which stratigraphic thickening was more limited to the area immediately adjacent to the fault. The Barataria fault defines the modern-day width of Barataria Bay, and also has a surface expression in the coastal marsh indicating that recent episodic slip has been associated with patterns of Holocene deltaic deposition.

Quaternary Activity of the Erciyes Fault Southeast of the Kayseri Basin, Turkey

NASA Astrophysics Data System (ADS)

Okumura, K.; Hayakawa, Y. S.; Kontani, R.; Fikri, K.

2016-12-01

The Erciyes fault in SE of the Kayseri basin is one of the most active Quaternary faults in Central Anatolia. Emre et al. (2011) mapped about 100 km long faults including a section runs across the Erciyes volcano. A M 7+ earthquake from the fault would be a big threat for the 1.5 million people in Kayseri basin, but little has been know about its activity and earthquake potential. We studied Plio-Pleistocene volacanics, Quaternary sediments, and UAV-SfM topography in southeast of the Kayseri basin and recognized significant dip-slip separation as well as sinistral slip in Late Quaternary. The Incesu ignimbrite (IC) of 2.52±0.49 Ma (Aydar et al., 2012) is a very distinctive densely welded ignimbrite layer in and around Kayseri basin. The Plinian pumice fall deposits from the Erciyes in Late Pleistocene (Sen et al. 2003) at Gesi Bagpnar (GBP) is another key-bed. There are two strands and one group of faults. The NE strike frontal strand separates the basin floor and the upland in SW extending from Kayseri city to more than 50 km NE. The Gesi Guney strand runs parallel to the frontal strand at 3 to 4 km away from the basin floor for 20 km from Ali Dag. The NS trending fault group is observed both inside and outside of the basin under IC. These NS faults are swarm of normal Pliocene faults. The Gesi Guney strand offsets IC around 120 m vertically. There is no information to infer the initiation of its activity, but the normal offset of an alluvial fan and unconsolidated fresh talus deposits indicate Late Quaternary activities. Near the SW end of the frontal strand, IC is vertically offset around 40 m. 15 km NE from the SW end, sand and gravel layers that intercalates GBP (0.11-0.14 Ma) are tilted to NW for 30 to 40 m and truncated by a sub-vertical sinistral faults. Most of frontal strand deformation occurred in Late Pleistocene because the offset of IC and GBP are similar. Estimated slip-rate of 0.3 to 0.4 mm/yr is significant for Central Anatolia.

Can a Red Wood-Ant Nest Be Associated with Fault-Related CH4 Micro-Seepage? A Case Study from Continuous Short-Term In-Situ Sampling

PubMed Central

Grumpe, Arne; Becker, Adrian; Wöhler, Christian

2018-01-01

Simple Summary Methane (CH4) is common on Earth but its natural sources are not well-characterized. We investigated concentrations of CH4 and its stable carbon isotope (δ13C-CH4) within a red wood-ant (RWA; Formica polyctena) nest in the Neuwied Basin, a part of the East Eifel Volcanic Field (EEVF), and tested for associations between methane concentration and RWA activity patterns, earthquakes, and earth tides. Methane degassing was not synchronized with earth tides, nor was it influenced by a micro-earthquake or RWA activity. Elevated CH4 concentrations in nest gas appear to result from a combination of microbial activity and fault-related emissions. The latter could result from micro-seepage of methane derived from low-temperature gas-water-rock reactions that subsequently moves via fault networks through the RWA nest or from overlapping micro-seepage of magmatic CH4 from the Eifel plume. Given the abundance of RWA nests on the landscape, their role as sources of microbial CH4 and biological indicators for abiotically-derived CH4 should be included in estimations of methane emissions that are contributing to climatic change. Abstract We measured methane (CH4) and stable carbon isotope of methane (δ13C-CH4) concentrations in ambient air and within a red wood-ant (RWA; Formica polyctena) nest in the Neuwied Basin (Germany) using high-resolution in-situ sampling to detect microbial, thermogenic, and abiotic fault-related micro-seepage of CH4. Methane degassing from RWA nests was not synchronized with earth tides, nor was it influenced by micro-earthquake degassing or concomitantly measured RWA activity. Two δ13C-CH4 signatures were identified in nest gas: −69‰ and −37‰. The lower peak was attributed to microbial decomposition of organic matter within the RWA nest, in line with previous observations that RWA nests are hot-spots of microbial CH4. The higher peak has not been reported in previous studies. We attribute this peak to fault-related CH4 emissions moving via fault networks into the RWA nest, which could originate either from thermogenic or abiotic CH4 formation. Sources of these micro-seepages could be Devonian schists, iron-bearing “Klerf Schichten”, or overlapping micro-seepage of magmatic CH4 from the Eifel plume. Given the abundance of RWA nests on the landscape, their role as sources of microbial CH4 and biological indicators for abiotically-derived CH4 should be included in estimation of methane emissions that are contributing to climatic change. PMID:29597318

An integrated geodetic and seismic study of the Cusco Fault system in the Cusco Region-Southern Peru

NASA Astrophysics Data System (ADS)

Norabuena, E. O.; Tavera, H. J.

2017-12-01

The Cusco Fault system is composed by six main faults (Zurite, Tamboray, Qoricocha, Tambomachay, Pachatusan, and Urcos) extending in a NW-SE direction over the Cusco Region in southeastern Peru. From these, the Tambomachay is a normal fault of 20 km length, strikes N120°E and bounds a basin filled with quaternary lacustrine and fluvial deposits. Given its 5 km distance to Cusco, an historical and Inca's archeological landmark, it represents a great seismic hazard for its more than 350,000 inhabitants. The Tambomachay fault as well as the other secondary faults have been a source of significant seismic activity since historical times being the more damaging ones the Cusco earthquakes of 1650, 1950 and more recently April 1986 (M 5.8). Previous geological studies indicate that at the beginning of the Quaternary the fault showed a transcurrent mechanism leading to the formation of the Cusco basin. However, nowadays its mechanism is normal fault and scarps up to 22m can be observed. We report the current dynamics of the Tambomachay fault and secondary faults based on seismic activity imaged by a network of 29 broadband stations deployed in the Cusco Region as well as the deformation field inferred from GPS survey measurements carried out between 2014 and 2016.

Lembang fault plane identification using electrical resistivity method for disaster mitigation

NASA Astrophysics Data System (ADS)

Maulinadya, S.; Ramadhan, M. Lutfi; N. Wening, F.; Pinehas, D.; Widodo

2017-07-01

Lembang Fault is an active fault lies from West to East located 10 kilometers in north of Bandung. It is a normal fault that its foot wall raises 40-450 meters above the ground. Its location that is not so far from Bandung, which is densely populated and frequently visited by tourists, makes Lembang Fault a threat if it becomes suddenly active. Its movement can cause earthquakes that can result in fatalities. Therefore, act of mitigation is necessary, such as educating people about Lembang Fault and its potential to cause disaster. The objective of this study is to find Lembang Fault plane below the surface with geo electrical mapping method and vertical elect rical sounding method around Ciwarega and The Peak, Lembang (west side of Lembang Fault). Both of these methods are using electricity current to measure rock resistivity. Currents are injected to the ground and potential differences are measured. According to Ohm's Law, resistivity can be calculated so that resistivity distribution can be obtained. In this study, high resistivity contrast is obtained; it is about 1400-5000 Ohm.m. This resistivity contrast can be caused by lateral lithology difference resulted by fault existence. This proves that there is actually a fault in Lembang that potentially cause disasters like earthquakes.

Intra-caldera active fault: An example from the Mw 7.0 2016 Kumamoto, Japan, earthquake

NASA Astrophysics Data System (ADS)

Toda, S.; Murakami, T.; Takahashi, N.

2017-12-01

A NE-trending 30-km-long surface rupture with up to 2.4 m dextral slip emerged during the Mw=7.0 16 April 2016 Kumamoto earthquake along the previously mapped Futagawa and northern Hinagu fault systems. The 5-km-long portion of the northeast rupture end, which was previously unidentified, crossed somma and extended to the 20-km-diameter Aso Caldera, one of the major active volcanoes, central Kyushu. We here explore geologic exposures of interplays of active faulting and active volcanism, and then argue the Futagawa fault system has been influenced by the ring fault system associated with the caldera forming gigantic eruptions since 270 ka, last of which occurred 90 ka ejecting a huge amount of ignimbrite. To understand the interplays, together with the mapping of the 2016 rupture, we employed an UAV to capture numerous photos of the exposures along the canyon and developed 3D orthochromatic topographic model using PhotoScan. One-hundred-meter-deep Kurokawa River canyon by the Aso Caldera rim exposes two lava flow units of 50 ka vertically offset by 10 m by the Futatawa fault system. Reconstructions of the collapsed bridges across the Kurokawa River also reveal cross sections of a 30-meter-high tectonic bulge and 10-m-scale negative flower structure deformed by the frequent fault movements. We speculate two fault developing models across the Aso Caldera. One is that the NE edge of the Futagawa fault system was cut and reset by the caldera forming ring fault, which indicates the 3-km-long rupture extent within the Aso Caldera would be a product of the fault growth since the last Aso-4 eruption of 90 ka. It enables us to estimate the 33 mm/yr of the fault propagation speed. An alternative model is that subsurface rupture of the Kumamoto earthquake extended further to the NE rim, the other side of the caldera edge, which is partially supported by the geodetic and seismic inversions. With respect to the model, the clear surface rupture of the 2016 Kumamoto earthquake was invisible due to the lava and fallout layers younger than 4ka that probably experienced only one or two events and do not have the pre-existing weak and sharp fault plane yet.

High-resolution shallow reflection seismic image and surface evidence of the Upper Tiber Basin active faults (Northern Apennines, Italy)

USGS Publications Warehouse

Donne, D.D.; Plccardi, L.; Odum, J.K.; Stephenson, W.J.; Williams, R.A.

2007-01-01

Shallow seismic reflection prospecting has been carried out in order to investigate the faults that bound to the southwest and northeast the Quaternary Upper Tiber Basin (Northern Apennines, Italy). On the northeastern margin of the basin a ??? 1 km long reflection seismic profile images a fault segment and the associated up to 100 meters thick sediment wedge. Across the southwestern margin a 0.5 km-long seismic profile images a 50-55??-dipping extensional fault, that projects to the scarp at the base of the range-front, and against which a 100 m thick syn-tectonic sediment wedge has formed. The integration of surface and sub-surface data allows to estimate at least 190 meters of vertical displacement along the fault and a slip rate around 0.25 m/kyr. Southwestern fault might also be interpreted as the main splay structure of regional Alto Tiberina extensional fault. At last, the 1917 Monterchi earthquake (Imax=X, Boschi et alii, 2000) is correlable with an activation of the southwestern fault, and thus suggesting the seismogenic character of this latter.

Low resistivity and permeability in actively deforming shear zones on the San Andreas Fault at SAFOD

USGS Publications Warehouse

Morrow, Carolyn A.; Lockner, David A.; Hickman, Stephen H.

2015-01-01

The San Andreas Fault Observatory at Depth (SAFOD) scientific drillhole near Parkfield, California crosses the San Andreas Fault at a depth of 2.7 km. Downhole measurements and analysis of core retrieved from Phase 3 drilling reveal two narrow, actively deforming zones of smectite-clay gouge within a roughly 200 m-wide fault damage zone of sandstones, siltstones and mudstones. Here we report electrical resistivity and permeability measurements on core samples from all of these structural units at effective confining pressures up to 120 MPa. Electrical resistivity (~10 ohm-m) and permeability (10-21 to 10-22 m2) in the actively deforming zones were one to two orders of magnitude lower than the surrounding damage zone material, consistent with broader-scale observations from the downhole resistivity and seismic velocity logs. The higher porosity of the clay gouge, 2 to 8 times greater than that in the damage zone rocks, along with surface conduction were the principal factors contributing to the observed low resistivities. The high percentage of fine-grained clay in the deforming zones also greatly reduced permeability to values low enough to create a barrier to fluid flow across the fault. Together, resistivity and permeability data can be used to assess the hydrogeologic characteristics of the fault, key to understanding fault structure and strength. The low resistivities and strength measurements of the SAFOD core are consistent with observations of low resistivity clays that are often found in the principal slip zones of other active faults making resistivity logs a valuable tool for identifying these zones.

Structural Features of the Western Taiwan Foreland Basin in the Eastern Taiwan Strait since Late Miocene

NASA Astrophysics Data System (ADS)

WANG, J. H.; Liu, C. S.; Chang, J. H.; Yang, E. Y.

2017-12-01

The western Taiwan Foreland Basin lies on the eastern part of Taiwan Strait. The structures in this region are dominated by crustal stretch and a series of flexural normal faults have been developed since Late Miocene owing to the flexural of Eurasia Plate. Through deciphering multi-channel seismic data and drilling data, these flexural features are observed in the offshore Changhua coastal area. The flexure normal faults are important features to realize structural activity in the western Taiwan Foreland Basin. Yang et al. (2016) mention that the reactivated normal faults are found north of the Zhushuixi estuary. It should be a significant issue to decipher whether these faults are still active. In this study, we have analyzed all the available seismic reflections profiles in the central part of the Taiwan Strait, and have observed many pre-Pliocene normal faults that are mainly distributed in the middle of the Taiwan Strait to Changyun Rise, and we tentatively suggest that the formation of these faults may be associated with the formation of the foreland basal unconformity. Furthermore, we will map the distribution of these normal faults and examine whether the reactivated normal faults have extended to south of the Zhushuixi estuary. Finally, we discuss the relation between the reactivated normal faults in the Taiwan Strait and those faults onshore. Key words: Multichannel seismic reflection profile, Taiwan Strait, Foreland basin, normal fault.

Precursory, Nucleation and Propagation of Ruptures Along Heterogeneously Loaded, Circular Experimental Faults

NASA Astrophysics Data System (ADS)

Reches, Z.; Zu, X.; Jeffers, J.

2017-12-01

We explored the evolution of dynamic rupture along a circular experimental fault composed of clear acrylic blocks. The ring-shaped fault surface has inner and outer diameters of 7.72 and 10.16 cm, respectively. An array of ten rossette strain-gauges is attached to the outer rim of one block that provide the 2D strain tensor in a plane normal to the fault. The 30 components of the gauges are monitored at 10^6 samples/second. One 3D miniature accelerometer is attached to the fault block. The initial asperities of the fault surface generated a non-uniform strain (=stress) distribution that was recorded, and indicated local deviations of ±30% from the mean stress. The mean normal stress was up to 3.5 MPa, the remotely applied velocity was up to .002 m/s, and the slip velocities during rupture were not measured. The rupture characteristics, namely propagation velocity and rupture front strain-field, were determined from strain-gauge outputs. The analysis of tens of stick-slip events revealed the following preliminary results: (1) The ruptures consistently nucleated at sites of high local strains (=stresses) that were formed by the pre-shear, normal stress loading. (2) The pre-rupture nucleation process was recognized a by temporal (< 0.1 s), local (<20 mm) reduction of the shear strain. (3) Commonly, the initiation of nucleation was associated with micro acoustic emissions, whereas the initiation of rupture was associated with intense acoustic activity. (4) Nucleation could occur quasi-simultaneously at two, highly stressed sites. (5) From the nucleation site, the ruptures propagated in two directions along the ring-shaped fault, and the collision between the two fronts led to rupture `shut-off'. (5) The strain-field of rupture fronts was well-recognized for ruptures propagating faster than 50 m/s, and the fastest fronts propagated at 1000 m/s. (7) It appears that the rupture front strain-field close to the nucleation site differs from the front strain-field far from nucleation site. (8) Post-shear examination of the fault surfaces revealed evidence of brittle wear of the acrylic including gouge formation, ploughing, and powder smearing. (9) Work in progress includes attempts to achieve faster dynamic ruptures, and the utilization of the existing monitoring system to rupture granite faults.

Off-fault tip splay networks: a genetic and generic property of faults indicative of their long-term propagation, and a major component of off-fault damage

NASA Astrophysics Data System (ADS)

Perrin, C.; Manighetti, I.; Gaudemer, Y.

2015-12-01

Faults grow over the long-term by accumulating displacement and lengthening, i.e., propagating laterally. We use fault maps and fault propagation evidences available in literature to examine geometrical relations between parent faults and off-fault splays. The population includes 47 worldwide crustal faults with lengths from millimeters to thousands of kilometers and of different slip modes. We show that fault splays form adjacent to any propagating fault tip, whereas they are absent at non-propagating fault ends. Independent of parent fault length, slip mode, context, etc, tip splay networks have a similar fan shape widening in direction of long-term propagation, a similar relative length and width (~30 and ~10 % of parent fault length, respectively), and a similar range of mean angles to parent fault (10-20°). Tip splays more commonly develop on one side only of the parent fault. We infer that tip splay networks are a genetic and a generic property of faults indicative of their long-term propagation. We suggest that they represent the most recent damage off-the parent fault, formed during the most recent phase of fault lengthening. The scaling relation between parent fault length and width of tip splay network implies that damage zones enlarge as parent fault length increases. Elastic properties of host rocks might thus be modified at large distances away from a fault, up to 10% of its length. During an earthquake, a significant fraction of coseismic slip and stress is dissipated into the permanent damage zone that surrounds the causative fault. We infer that coseismic dissipation might occur away from a rupture zone as far as a distance of 10% of the length of its causative fault. Coseismic deformations and stress transfers might thus be significant in broad regions about principal rupture traces. This work has been published in Comptes Rendus Geoscience under doi:10.1016/j.crte.2015.05.002 (http://www.sciencedirect.com/science/article/pii/S1631071315000528).

Neogene-Recent Reactivation of Cretaceous-age Faults in Southern Vietnam, with Implications for the Himalayan-Tibetan Orogen

NASA Astrophysics Data System (ADS)

Burberry, C. M.; Elkins, L. J.; Hoang, N.; Anh, L. D.; Dinh, S. Q.

2017-12-01

The tectonic activity and ongoing diffuse volcanic activity of the Central Highlands of Vietnam have, to date, been challenging to explain using accepted plate tectonics principles. The various hypotheses invoked to explain the voluminous magmatism include extrusion related to the Himalayan-Tibetan orogen, extension related to the South China Sea, and plume activity beneath Hainan. We present a combined remote sensing and field study, focused on fault orientation and age relative to lava flows in order to discriminate between these models. Landsat ETM+ and SPOT data were processed to highlight variations in lithology and to remove vegetation, and lineaments were interpreted from these images. The lineament data were compared to existing geologic maps, and to regions of known flow age. Key locations were visited in the field, where fault orientations and relative age were recorded. At many locations, the slip direction could be measured using trend and plunge of mineral lineations. The remote data reveal a complex pattern of lineaments, with prominent N-S, NE-SW and NW-SE directions. Lineaments are observed to cut lava flows with ages of 2.2+/- 0.1 Ma and younger. In the field, NE-SW oriented faults were identified in Jurassic-Cretaceous sedimentary rocks with two phases of movement; a dip-slip phase and a younger, dominantly strike-slip phase. Strike-slip faults were identified in lava flows of approx. 3.2 Ma, also oriented NE-SW. These results indicate that there has been fault activity since the Pliocene, and that this fault activity includes reactivation of dip-slip faults as strike-slip. This is consistent with the movement vector of the southern Indochina Block SE with respect to the Sunda block, and with microplate rotation due to asthenospheric extrusion. These results therefore suggest that ongoing Himalayan-Tibetan collision is still being accommodated, in part, by active lithospheric extrusion of the Indo-China block.

Evidence of Quaternary and recent activity along the Kyaukkyan Fault, Myanmar

NASA Astrophysics Data System (ADS)

Crosetto, Silvia; Watkinson, Ian M.; Soe Min; Gori, Stefano; Falcucci, Emanuela; Nwai Le Ngal

2018-05-01

Cenozoic right-lateral shear between the eastern Indian margin and Eurasia is expressed by numerous N-S trending fault systems inboard of the Sunda trench, including the Sagaing Fault. The most easterly of these fault systems is the prominent ∼500 km long Kyaukkyan Fault, on the Shan Plateau. Myanmar's largest recorded earthquake, Mw 7.7 on 23rd May 1912, focused near Maymyo, has been attributed to the Kyaukkyan Fault, but the area has experienced little significant seismicity since then. Despite its demonstrated seismic potential and remarkable topographic expression, questions remain about the Kyaukkyan Fault's neotectonic history.

How Might Draining Lake Campotosto Affect Stress and Seismicity on the Monte Gorzano Normal Fault, Central Italy?

NASA Astrophysics Data System (ADS)

Verdecchia, A.; Deng, K.; Harrington, R. M.; Liu, Y.

2017-12-01

It is broadly accepted that large variations of water level in reservoirs may affect the stress state on nearby faults. While most studies consider the relationship between lake impoundment and the occurrence of large earthquakes or seismicity rate increases in the surrounding region, very few examples focus on the effects of lake drainage. The second largest reservoir in Europe, Lake Campotosto, is located on the hanging wall of the Monte Gorzano fault, an active normal fault responsible for at least two M ≥ 6 earthquakes in historical times. The northern part of this fault ruptured during the August 24, 2016, Mw 6.0 Amatrice earthquake, increasing the probability for a future large event on the southern section where an aftershock sequence is still ongoing. The proximity of the Campotosto reservoir to the active fault aroused general concern with respect to the stability of the three dams bounding the reservoir if the southern part of the Monte Gorzano fault produces a moderate earthquake. Local officials have proposed draining the reservoir as hazard mitigation strategy to avoid possible future catastrophes. In efforts to assess how draining the reservoir might affect earthquake nucleation on the fault, we use a finite-element poroelastic model to calculate the evolution of stress and pore pressure in terms of Coulomb stress changes that would be induced on the Monte Gorzano fault by emptying the Lake Campotosto reservoir. Preliminary results show that an instantaneous drainage of the lake will produce positive Coulomb stress changes, mostly on the shallower part of the fault (0 to 2 km), while a stress drop of the order of 0.2 bar is expected on the Monte Gorzano fault between 0 and 8 km depth. Earthquake hypocenters on the southern portion of the fault currently nucleate between 5 and 13 km depth, with activity distributed nearby the reservoir. Upcoming work will model the effects of varying fault geometry and elastic parameters, including geological layering. In addition, we will consider more realistic unloading strategies to test the time-dependent stress and pore pressure changes on the fault.

Deformation rates and localization of an active fault system in relation with rheological and frictional slip properties: The Corinth Rift case

NASA Astrophysics Data System (ADS)

El Arem, S.; Lyon-Caen, H.; Bernard, P.; Garaud, J. D.; Rolandone, F.; Briole, P.

2012-04-01

The Gulf of Corinth in Greece has attracted increasing attention because of its seismically active complex fault system and considerable seismic hazard. It is one of the most active extensional regions in the Mediterranean area. However, there are still open questions concerning the role and the geometry of the numerous active faults bordering the basin, as well as the mechanisms governing the seismicity. The Corinth Rift Laboratory (CRL http://crlab.eu) project is based on the cooperation of various European institutions that merge their efforts to study fault mechanics and related hazards in this natural laboratory with 10 destructive earthquakes per century (Magnitude > 6), among which 4 in the selected region of CRL. This active rift continues to open over 10-12 Km of width at a rate of 1:5 cm=yr. Most of the faults of the investigated area are in their latest part of cycle, so that the probability of at least one moderate to large earthquake (Magnitude = 6 to 6:7) is very high within a few decades. In the first part of this work, two-dimensional finite element models of a fault system is considered to estimate the effects of the crust rheological parameters on the stress distribution, the horizontal and vertical deformation in the vicinity of the faults, and the plastic deformation localization. We consider elasto-visco-plastic rheology with a power law viscosity for dislocation creep modelling and the Drucker-Prager yield criterion for plasticity. We investigate the rheological properties of the crust and examine their compatibility with both horizontal and vertical GPS observations recorded during campaigns conducted in the last twenty years. The second part is devoted to simulations involving rate and slip history friction laws for earthquake occurence prediction and seismogenic depth approximation. The case of a single fault is examined first, then two active faults are considered to highlight the effect of their interactions on the seismic cycle characteristics and improve our ability to predict earthquakes.

Characterizing the Alpine Fault Strike Slip System Using a Novel Method for Analyzing GPS Data

NASA Astrophysics Data System (ADS)

Haines, A. J.; Dimitrova, L. L.; Wallace, L. M.; Williams, C. A.

2013-12-01

Plate motion across the South Island is dominated by right-lateral strike-slip (38-39 mm/yr total in the direction parallel to the Alpine Fault), with a small convergent component (8-10 mm/yr). The Alpine Fault is the most active fault in the region taking up 27×5 mm/yr in right-lateral strike-slip and ~10 mm/yr in dip-slip. It fails in large >=7 Mw earthquakes with recurrence time of 200-400 years and last ruptured around 1717. A significant component of the plate motion budget must occur on faults other than the Alpine Fault, but this is not fully accounted for in catalogues of known active faults. In the central part of the South Island, low slip rate active faults are not well-expressed due to the rapid erosion of the Southern Alps and deposition of these sediments onto the Canterbury plains; the devastating 2010 Darfield earthquake sequence occurred on such previously unknown faults. We apply a novel inversion technique (Dimitrova et al. 2012, 2013) to dense campaign GPS velocities in the region to solve for the vertical derivatives of horizontal stress (VDoHS) rates which are a substantially higher resolution expression of subsurface sources of ongoing deformation than the GPS velocities or GPS derived strain rates. Integrating the VDoHS rates gives us strain rates. Relationships between the VDoHS and strain rates allow us to calculate the variation in fault slip rate and locking depth for the identified faults; e.g., we estimate along fault variations for locking depth and slip rate for the Alpine Fault in the South Island in good agreement with previous estimates, and provide first estimates for those properties on the smaller, previously-uncharacterized faults which account for as much as 50% of the plate motion depending on location. For the first time, we note that the area between the Alpine Fault and the Main Divide of the Southern Alps is undergoing extensional areal strain, potentially indicative of gravitational collapse of the Southern Alps. The Arthur's Pass section of the Alpine Fault exhibits no shear component in the spatial derivatives of the VDoHS rates, in marked contrast to the Alpine Fault segments just northeast and southwest, suggesting that post-seismic deformation related to the 1994 Arthur's Pass earthquake is masking the signal from the Alpine Fault beneath. We characterize in detail the transfer of slip further north into the Marlborough Fault System, where we find much of the slip on the Alpine Fault passes onto the Kelly and Hope Faults, in accord with previous geological studies.

Geology and structure of the North Boqueron Bay-Punta Montalva Fault System

NASA Astrophysics Data System (ADS)

Roig Silva, Coral Marie

The North Boqueron Bay-Punta Montalva Fault Zone is an active fault system that cuts across the Lajas Valley in southwestern Puerto Rico. The fault zone has been recognized and mapped based upon detailed analysis of geophysical data, satellite images and field mapping. The fault zone consists of a series of Cretaceous bedrock faults that reactivated and deformed Miocene limestone and Quaternary alluvial fan sediments. The fault zone is seismically active (ML < 5.0) with numerous locally felt earthquakes. Focal mechanism solutions and structural field data suggest strain partitioning with predominantly east-west left-lateral displacements with small normal faults oriented mostly toward the northeast. Evidence for recent displacement consists of fractures and small normal faults oriented mostly northeast found in intermittent streams that cut through the Quaternary alluvial fan deposits along the southern margin of the Lajas Valley, Areas of preferred erosion, within the alluvial fan, trend toward the west-northwest parallel to the on-land projection of the North Boqueron Bay Fault. Beyond the faulted alluvial fan and southeast of the Lajas Valley, the Northern Boqueron Bay Fault joins with the Punta Montalva Fault. The Punta Montalva Fault is defined by a strong topographic WNW lineament along which stream channels are displaced left laterally 200 meters and Miocene strata are steeply tilted to the south. Along the western end of the fault zone in northern Boqueron Bay, the older strata are only tilted 3° south and are covered by flat lying Holocene sediments. Focal mechanisms solutions along the western end suggest NW-SE shortening, which is inconsistent with left lateral strain partitioning along the fault zone. The limited deformation of older strata and inconsistent strain partitioning may be explained by a westerly propagation of the fault system from the southwest end. The limited geomorphic structural expression along the North Boqueron Bay Fault segment could also be because most of the displacement along the fault zone is older than the Holocene and that the rate of displacement is low, such that the development of fault escarpments and deformation all along the fault zone has yet to occur.

Seismicity and recent faulting in eastern California and western and central Nevada: A preliminary report

NASA Technical Reports Server (NTRS)

Abdel-Gawad, M. (Principal Investigator); Silverstein, J.; Tubbesing, L.

1973-01-01

The author has identified the following significant results. ERTS-1 imagery covering the eastern California-Nevada seismic belt were utilized to study the fault pattern in relation to the distribution of earthquake epicenters and Quaternary volcanic rocks. Many suspected faults not previously mapped were identified. These include several suspected shear zones in Nevada, faults showing evidence of recent breakage, and major lineaments. Highly seismic areas are generally characterized by Holocene faulting and Quaternary volcanic activity. However, several major fault segments showing evidence of recent breakage are associated with little or no seismicity. The tectonic pattern strongly suggests that the eastern California-Nevada seismic belt coincides with a major crustal rift associated with zones of lateral shear. New data on potentially active fault zones have direct practical applications in national and local earthquake hazard reduction programs. Positive contacts have been made with Kern and Ventura Counties to make results of this investigation available for application to their earthquake hazards definition projects.

Digital Database of Recently Active Traces of the Hayward Fault, California

USGS Publications Warehouse

Lienkaemper, James J.

2006-01-01

The purpose of this map is to show the location of and evidence for recent movement on active fault traces within the Hayward Fault Zone, California. The mapped traces represent the integration of the following three different types of data: (1) geomorphic expression, (2) creep (aseismic fault slip),and (3) trench exposures. This publication is a major revision of an earlier map (Lienkaemper, 1992), which both brings up to date the evidence for faulting and makes it available formatted both as a digital database for use within a geographic information system (GIS) and for broader public access interactively using widely available viewing software. The pamphlet describes in detail the types of scientific observations used to make the map, gives references pertaining to the fault and the evidence of faulting, and provides guidance for use of and limitations of the map. [Last revised Nov. 2008, a minor update for 2007 LiDAR and recent trench investigations; see version history below.

Proceedings of Workshop XVI; The dynamic characteristics of faulting inferred from recordings of strong ground motion

USGS Publications Warehouse

Boatwright, John; Jacobson, Muriel L.

1982-01-01

The strong ground motions radiated by earthquake faulting are controlled by the dynamic characteristics of the faulting process. Although this assertion seems self-evident, seismologists have only recently begun to derive and test quantitative relations between common measures of strong ground motion and the dynamic characteristics of faulting. Interest in this problem has increased dramatically in past several years, however, resulting in a number of important advances. The research presented in this workshop is a significant part of this scientific development. Watching this development occur through the work of many scientists is exciting; to be able to gather a number of these scientists together in one workshop is a remarkable opportunity.

Modeling of fault activation and seismicity by injection directly into a fault zone associated with hydraulic fracturing of shale-gas reservoirs

DOE PAGES

Rutqvist, Jonny; Rinaldi, Antonio P.; Cappa, Frédéric; ...

2015-03-01

We conducted three-dimensional coupled fluid-flow and geomechanical modeling of fault activation and seismicity associated with hydraulic fracturing stimulation of a shale-gas reservoir. We simulated a case in which a horizontal injection well intersects a steeply dip- ping fault, with hydraulic fracturing channeled within the fault, during a 3-hour hydraulic fracturing stage. Consistent with field observations, the simulation results show that shale-gas hydraulic fracturing along faults does not likely induce seismic events that could be felt on the ground surface, but rather results in numerous small microseismic events, as well as aseismic deformations along with the fracture propagation. The calculated seismicmore » moment magnitudes ranged from about -2.0 to 0.5, except for one case assuming a very brittle fault with low residual shear strength, for which the magnitude was 2.3, an event that would likely go unnoticed or might be barely felt by humans at its epicenter. The calculated moment magnitudes showed a dependency on injection depth and fault dip. We attribute such dependency to variation in shear stress on the fault plane and associated variation in stress drop upon reactivation. Our simulations showed that at the end of the 3-hour injection, the rupture zone associated with tensile and shear failure extended to a maximum radius of about 200 m from the injection well. The results of this modeling study for steeply dipping faults at 1000 to 2500 m depth is in agreement with earlier studies and field observations showing that it is very unlikely that activation of a fault by shale-gas hydraulic fracturing at great depth (thousands of meters) could cause felt seismicity or create a new flow path (through fault rupture) that could reach shallow groundwater resources.« less

Modeling of fault activation and seismicity by injection directly into a fault zone associated with hydraulic fracturing of shale-gas reservoirs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rutqvist, Jonny; Rinaldi, Antonio P.; Cappa, Frédéric

We conducted three-dimensional coupled fluid-flow and geomechanical modeling of fault activation and seismicity associated with hydraulic fracturing stimulation of a shale-gas reservoir. We simulated a case in which a horizontal injection well intersects a steeply dip- ping fault, with hydraulic fracturing channeled within the fault, during a 3-hour hydraulic fracturing stage. Consistent with field observations, the simulation results show that shale-gas hydraulic fracturing along faults does not likely induce seismic events that could be felt on the ground surface, but rather results in numerous small microseismic events, as well as aseismic deformations along with the fracture propagation. The calculated seismicmore » moment magnitudes ranged from about -2.0 to 0.5, except for one case assuming a very brittle fault with low residual shear strength, for which the magnitude was 2.3, an event that would likely go unnoticed or might be barely felt by humans at its epicenter. The calculated moment magnitudes showed a dependency on injection depth and fault dip. We attribute such dependency to variation in shear stress on the fault plane and associated variation in stress drop upon reactivation. Our simulations showed that at the end of the 3-hour injection, the rupture zone associated with tensile and shear failure extended to a maximum radius of about 200 m from the injection well. The results of this modeling study for steeply dipping faults at 1000 to 2500 m depth is in agreement with earlier studies and field observations showing that it is very unlikely that activation of a fault by shale-gas hydraulic fracturing at great depth (thousands of meters) could cause felt seismicity or create a new flow path (through fault rupture) that could reach shallow groundwater resources.« less

Progressive failure during the 1596 Keicho earthquakes on the Median Tectonic Line active fault zone, southwest Japan

NASA Astrophysics Data System (ADS)

Ikeda, M.; Toda, S.; Nishizaka, N.; Onishi, K.; Suzuki, S.

2015-12-01

Rupture patterns of a long fault system are controlled by spatial heterogeneity of fault strength and stress associated with geometrical characteristics and stress perturbation history. Mechanical process for sequential ruptures and multiple simultaneous ruptures, one of the characteristics of a long fault such as the North Anatolian fault, governs the size and frequency of large earthquakes. Here we introduce one of the cases in southwest Japan and explore what controls rupture initiation, sequential ruptures and fault branching on a long fault system. The Median Tectonic Line active fault zone　(hereinafter MTL) is the longest and most active fault in Japan. Based on historical accounts, a series of M ≥ 7 earthquakes occurred on at least a 300-km-long portion of the MTL in 1596. On September 1, the first event occurred on the Kawakami fault segment, in Central Shikoku, and the subsequent events occurred further west. Then on September 5, another rupture initiated from the Central to East Shikoku and then propagated toward the Rokko-Awaji fault zone to Kobe, a northern branch of the MTL, instead of the eastern main extent of the MTL. Another rupture eventually extended to near Kyoto. To reproduce this progressive failure, we applied two numerical models: one is a coulomb stress transfer; the other is a slip-tendency analysis under the tectonic stress. We found that Coulomb stress imparted from historical ruptures have triggered the subsequent ruptures nearby. However, stress transfer does not explain beginning of the sequence and rupture directivities. Instead, calculated slip-tendency values show highly variable along the MTL: high and low seismic potential in West and East Shikoku. The initiation point of the 1596 progressive failure locates near the boundary in the slip-tendency values. Furthermore, the slip-tendency on the Rokko-Awaji fault zone is far higher than that of the MTL in Wakayama, which may explain the rupture directivity toward Kobe-Kyoto.

Active fault mapping in Karonga-Malawi after the December 19, 2009 Ms 6.2 seismic event

NASA Astrophysics Data System (ADS)

Macheyeki, A. S.; Mdala, H.; Chapola, L. S.; Manhiça, V. J.; Chisambi, J.; Feitio, P.; Ayele, A.; Barongo, J.; Ferdinand, R. W.; Ogubazghi, G.; Goitom, B.; Hlatywayo, J. D.; Kianji, G. K.; Marobhe, I.; Mulowezi, A.; Mutamina, D.; Mwano, J. M.; Shumba, B.; Tumwikirize, I.

2015-02-01

The East African Rift System (EARS) has natural hazards - earthquakes, volcanic eruptions, and landslides along the faulted margins, and in response to ground shaking. Strong damaging earthquakes have been occurring in the region along the EARS throughout historical time, example being the 7.4 (Ms) of December 1910. The most recent damaging earthquake is the Karonga earthquake in Malawi, which occurred on 19th December, 2009 with a magnitude of 6.2 (Ms). The earthquake claimed four lives and destroyed over 5000 houses. In its effort to improve seismic hazard assessment in the region, Eastern and Southern Africa Seismological Working Group (ESARSWG) under the sponsorship of the International Program on Physical Sciences (IPPS) carried out a study on active fault mapping in the region. The fieldwork employed geological and geophysical techniques. The geophysical techniques employed are ground magnetic, seismic refraction and resistivity surveys but are reported elsewhere. This article gives findings from geological techniques. The geological techniques aimed primarily at mapping of active faults in the area in order to delineate presence or absence of fault segments. Results show that the Karonga fault (the Karonga fault here referred to as the fault that ruptured to the surface following the 6th-19th December 2009 earthquake events in the Karonga area) is about 9 km long and dominated by dip slip faulting with dextral and insignificant sinistral components and it is made up of 3-4 segments of length 2-3 km. The segments are characterized by both left and right steps. Although field mapping show only 9 km of surface rupture, maximum vertical offset of about 43 cm imply that the surface rupture was in little excess of 14 km that corresponds with Mw = 6.4. We recommend the use or integration of multidisciplinary techniques in order to better understand the fault history, mechanism and other behavior of the fault/s for better urban planning in the area.

Subsurface structures of the active reverse fault zones in Japan inferred from gravity anomalies.

NASA Astrophysics Data System (ADS)

Matsumoto, N.; Sawada, A.; Hiramatsu, Y.; Okada, S.; Tanaka, T.; Honda, R.

2016-12-01

The object of our study is to examine subsurface features such as continuity, segmentation and faulting type, of the active reverse fault zones. We use the gravity data published by the Gravity Research Group in Southwest Japan (2001), the Geographical Survey Institute (2006), Yamamoto et al. (2011), Honda et al. (2012), and the Geological Survey of Japan, AIST (2013) in this study. We obtained the Bouguer anomalies through terrain corrections with 10 m DEM (Sawada et al. 2015) under the assumed density of 2670 kg/m3, a band-pass filtering, and removal of linear trend. Several derivatives and structural parameters calculated from a gravity gradient tensor are applied to highlight the features, such as a first horizontal derivatives (HD), a first vertical derivatives (VD), a normalized total horizontal derivative (TDX), a dip angle (β), and a dimensionality index (Di). We analyzed 43 reverse fault zones in northeast Japan and the northern part of southwest Japan among major active fault zones selected by Headquarters for Earthquake Research Promotion. As the results, the subsurface structural boundaries clearly appear along the faults at 21 faults zones. The weak correlations appear at 13 fault zones, and no correlations are recognized at 9 fault zones. For example, in the Itoigawa-Shizuoka tectonic line, the subsurface structure boundary seems to extend further north than the surface trace. Also, a left stepping structure of the fault around Hakuba is more clearly observed with HD. The subsurface structures, which detected as the higher values of HD, are distributed on the east side of the surface rupture in the north segments and on the west side in the south segments, indicating a change of the dip direction, the east dipping to the west dipping, from north to south. In the Yokote basin fault zone, the subsurface structural boundary are clearly detected with HD, VD and TDX along the fault zone in the north segment, but less clearly in the south segment. Also, Di implies the existence of 3D-like structure with E-W trend around the segment boundary. The distribution of dip angle β along the fault zone implies a reverse faulting, corresponding to the faulting type of this fault zone reported by previous studies.

Active faulting on the Wallula fault zone within the Olympic-Wallowa lineament, Washington State, USA

USGS Publications Warehouse

Sherrod, Brian; Blakely, Richard J.; Lasher, John P.; Lamb, Andrew P.; Mahan, Shannon; Foit, Franklin F.; Barnett, Elizabeth

2016-01-01

The Wallula fault zone is an integral feature of the Olympic-Wallowa lineament, an ∼500-km-long topographic lineament oblique to the Cascadia plate boundary, extending from Vancouver Island, British Columbia, to Walla Walla, Washington. The structure and past earthquake activity of the Wallula fault zone are important because of nearby infrastructure, and also because the fault zone defines part of the Olympic-Wallowa lineament in south-central Washington and suggests that the Olympic-Wallowa lineament may have a structural origin. We used aeromagnetic and ground magnetic data to locate the trace of the Wallula fault zone in the subsurface and map a quarry exposure of the Wallula fault zone near Finley, Washington, to investigate past earthquakes along the fault. We mapped three main packages of rocks and unconsolidated sediments in an ∼10-m-high quarry exposure. Our mapping suggests at least three late Pleistocene earthquakes with surface rupture, and an episode of liquefaction in the Holocene along the Wallula fault zone. Faint striae on the master fault surface are subhorizontal and suggest reverse dextral oblique motion for these earthquakes, consistent with dextral offset on the Wallula fault zone inferred from offset aeromagnetic anomalies associated with ca. 8.5 Ma basalt dikes. Magnetic surveys show that the Wallula fault actually lies 350 m to the southwest of the trace shown on published maps, passes directly through deformed late Pleistocene or younger deposits exposed at Finley quarry, and extends uninterrupted over 120 km.

What does fault tolerant Deep Learning need from MPI?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amatya, Vinay C.; Vishnu, Abhinav; Siegel, Charles M.

Deep Learning (DL) algorithms have become the {\\em de facto} Machine Learning (ML) algorithm for large scale data analysis. DL algorithms are computationally expensive -- even distributed DL implementations which use MPI require days of training (model learning) time on commonly studied datasets. Long running DL applications become susceptible to faults -- requiring development of a fault tolerant system infrastructure, in addition to fault tolerant DL algorithms. This raises an important question: {\\em What is needed from MPI for designing fault tolerant DL implementations?} In this paper, we address this problem for permanent faults. We motivate the need for amore » fault tolerant MPI specification by an in-depth consideration of recent innovations in DL algorithms and their properties, which drive the need for specific fault tolerance features. We present an in-depth discussion on the suitability of different parallelism types (model, data and hybrid); a need (or lack thereof) for check-pointing of any critical data structures; and most importantly, consideration for several fault tolerance proposals (user-level fault mitigation (ULFM), Reinit) in MPI and their applicability to fault tolerant DL implementations. We leverage a distributed memory implementation of Caffe, currently available under the Machine Learning Toolkit for Extreme Scale (MaTEx). We implement our approaches by extending MaTEx-Caffe for using ULFM-based implementation. Our evaluation using the ImageNet dataset and AlexNet neural network topology demonstrates the effectiveness of the proposed fault tolerant DL implementation using OpenMPI based ULFM.« less

Comparative study of two active faults in different stages of the earthquake cycle in central Japan -The Atera fault (with 1586 Tensho earthquake) and the Nojima fault (with 1995 Kobe earthquake)-

NASA Astrophysics Data System (ADS)

Matsuda, T.; Omura, K.; Ikeda, R.

2003-12-01

National Research Institute for Earth Science and Disaster Prevention (NIED) has been conducting _gFault zone drilling_h. Fault zone drilling is especially important in understanding the structure, composition, and physical properties of an active fault. In the Chubu district of central Japan, large active faults such as the Atotsugawa (with 1858 Hietsu earthquake) and the Atera (with 1586 Tensho earthquake) faults exist. After the occurrence of the 1995 Kobe earthquake, it has been widely recognized that direct measurements in fault zones by drilling. This time, we describe about the Atera fault and the Nojima fault. Because, these two faults are similar in geological situation (mostly composed of granitic rocks), so it is easy to do comparative study of drilling investigation. The features of the Atera fault, which have been dislocated by the 1586 Tensho earthquake, are as follows. Total length is about 70 km. That general trend is NW45 degree with a left-lateral strike slip. Slip rate is estimated as 3-5 m / 1000 years. Seismicity is very low at present and lithologies around the fault are basically granitic rocks and rhyolite. Six boreholes have been drilled from the depth of 400 m to 630 m. Four of these boreholes (Hatajiri, Fukuoka, Ueno and Kawaue) are located on a line crossing in a direction perpendicular to the Atera fault. In the Kawaue well, mostly fractured and alternating granitic rock continued from the surface to the bottom at 630 m. X-ray fluorescence analysis (XRF) is conducted to estimate the amount of major chemical elements using the glass bead method for core samples. The amounts of H20+ are about from 0.5 to 2.5 weight percent. This fractured zone is also characterized by the logging data such as low resistivity, low P-wave velocity, low density and high neutron porosity. The 1995 Kobe (Hyogo-ken Nanbu) earthquake occurred along the NE-SW-trending Rokko-Awaji fault system, and the Nojima fault appeared on the surface on Awaji Island when this rupture occurred. It is more than 10 km long with 1-2 m offset along the Nojima fault. About one year after the earthquake, NIED drilled a borehole (the Hirabayashi NIED borehole) and penetrated the Nojima fault. The Hirabayashi NIED borehole was drilled to a depth of 1838 m and recovered the drill core. The main types of rock intersected by the borehole are granodiorite and cataclastic fault rocks. Three fracture zones were recognized in cores at approximate depth of 1140 m, 1300 m and 1800 m. There is remarkable foliated blue-gray gouge at a depth of 1140 m. We investigate chemical compositions by XRF analysis in the fracture zone. The amounts of H20+ are about from 1.0 to 15.0 weight percent. We investigate mineral assemblage in both drilling cores by X-ray powder diffraction analysis. From the results, we can_ft recognize so difference between the two faults. But the amount of H2O+ is very different. In the Hirabayashi NIED core at a depth of 1140 m, there is about ten times as much as the average of the Kawaue core. This is probably due to the greater degree of wall-rock fracturing in the fracture zone. We suggest that this characteristic is associated with the fault activity at the time of the 1995 Kobe earthquake and the nature of fluid-rock interactions in the fracture zone.

Testing fault growth models with low-temperature thermochronology in the northwest Basin and Range, USA

USGS Publications Warehouse

Curry, Magdalena A. E.; Barnes, Jason B.; Colgan, Joseph P.

2016-01-01

Common fault growth models diverge in predicting how faults accumulate displacement and lengthen through time. A paucity of field-based data documenting the lateral component of fault growth hinders our ability to test these models and fully understand how natural fault systems evolve. Here we outline a framework for using apatite (U-Th)/He thermochronology (AHe) to quantify the along-strike growth of faults. To test our framework, we first use a transect in the normal fault-bounded Jackson Mountains in the Nevada Basin and Range Province, then apply the new framework to the adjacent Pine Forest Range. We combine new and existing cross sections with 18 new and 16 existing AHe cooling ages to determine the spatiotemporal variability in footwall exhumation and evaluate models for fault growth. Three age-elevation transects in the Pine Forest Range show that rapid exhumation began along the range-front fault between approximately 15 and 11 Ma at rates of 0.2–0.4 km/Myr, ultimately exhuming approximately 1.5–5 km. The ages of rapid exhumation identified at each transect lie within data uncertainty, indicating concomitant onset of faulting along strike. We show that even in the case of growth by fault-segment linkage, the fault would achieve its modern length within 3–4 Myr of onset. Comparison with the Jackson Mountains highlights the inadequacies of spatially limited sampling. A constant fault-length growth model is the best explanation for our thermochronology results. We advocate that low-temperature thermochronology can be further utilized to better understand and quantify fault growth with broader implications for seismic hazard assessments and the coevolution of faulting and topography.

Paleoseismic and geomorphologic evidence of recent tectonic activity of the Pozohondo Fault (Betic Cordillera, SE Spain)

USGS Publications Warehouse

Rodríguez-Pascua, M.A.; Pérez-López, R.; Garduño-Monroy, V.H.; Giner-Robles, J.L.; Silva, P.G.; Perucha-Atienza, M.A.; Hernández-Madrigal, V.M.; Bischoff, J.

2012-01-01

Instrumental and historical seismicity in the Albacete province (External Prebetic Zone) has been scarcely recorded. However, major strike-slip faults showing NW-SE trending provide geomorphologic and paleoseismic evidence of recent tectonic activity (Late Pleistocene to Present). Moreover, these faults are consistently well oriented under the present stress tensor and therefore, they can trigger earthquakes of magnitude greater than M6, according to the lengths of surface ruptures and active segments recognized in fieldwork. Present landscape nearby the village of Hellin (SE of Albacete) is determined by the recent activity of the Pozohondo Fault (FPH), a NW-SE right-lateral fault with 90 km in length. In this study, we have calculated the Late Quaternary tectonic sliprate of the FPH from geomorphological, sedimentological, archaeoseimological, and paleoseismological approaches. All of these data suggest that the FPH runs with a minimum slip-rate of 0.1 mm/yr during the last 100 kyrs (Upper Pleistocene-Holocene). In addition, we have recognized the last two major paleoearthquakes associated to this fault. Magnitudes of these paleoearthquakes were gretarer than M6 and their recurrence intervals ranged from 6600 to 8600 yrs for the seismic cycle of FPH. The last earthquake was dated between the 1st and 6th centuries, though two earthquakes could be interpreted in this wide time interval, one at the FPH and other from a far field source. Results obtained here, suggest an increasing of the tectonic activity of the Pozohondo Fault during the last 10,000 yrs.

Two-Dimensional Boundary Element Method Application for Surface Deformation Modeling around Lembang and Cimandiri Fault, West Java

NASA Astrophysics Data System (ADS)

Mahya, M. J.; Sanny, T. A.

2017-04-01

Lembang and Cimandiri fault are active faults in West Java that thread people near the faults with earthquake and surface deformation risk. To determine the deformation, GPS measurements around Lembang and Cimandiri fault was conducted then the data was processed to get the horizontal velocity at each GPS stations by Graduate Research of Earthquake and Active Tectonics (GREAT) Department of Geodesy and Geomatics Engineering Study Program, ITB. The purpose of this study is to model the displacement distribution as deformation parameter in the area along Lembang and Cimandiri fault using 2-dimensional boundary element method (BEM) using the horizontal velocity that has been corrected by the effect of Sunda plate horizontal movement as the input. The assumptions that used at the modeling stage are the deformation occurs in homogeneous and isotropic medium, and the stresses that acted on faults are in elastostatic condition. The results of modeling show that Lembang fault had left-lateral slip component and divided into two segments. A lineament oriented in southwest-northeast direction is observed near Tangkuban Perahu Mountain separating the eastern and the western segments of Lembang fault. The displacement pattern of Cimandiri fault shows that Cimandiri fault is divided into the eastern segment with right-lateral slip component and the western segment with left-lateral slip component separated by a northwest-southeast oriented lineament at the western part of Gede Pangrango Mountain. The displacement value between Lembang and Cimandiri fault is nearly zero indicating that Lembang and Cimandiri fault are not connected each other and this area is relatively safe for infrastructure development.

Research on bearing fault diagnosis of large machinery based on mathematical morphology

NASA Astrophysics Data System (ADS)

Wang, Yu

2018-04-01

To study the automatic diagnosis of large machinery fault based on support vector machine, combining the four common faults of the large machinery, the support vector machine is used to classify and identify the fault. The extracted feature vectors are entered. The feature vector is trained and identified by multi - classification method. The optimal parameters of the support vector machine are searched by trial and error method and cross validation method. Then, the support vector machine is compared with BP neural network. The results show that the support vector machines are short in time and high in classification accuracy. It is more suitable for the research of fault diagnosis in large machinery. Therefore, it can be concluded that the training speed of support vector machines (SVM) is fast and the performance is good.

Lithospheric thickness variations across the North Anatolian Fault Zone

NASA Astrophysics Data System (ADS)

Thompson, D. A.; Rost, S.; Cornwell, D. G.; Houseman, G.; Turkelli, N.; Teoman, U.; Altuncu Poyraz, S.; Kahraman, M.; Gulen, L.; Utkucu, M.; Williams, J. R.

2017-12-01

The North Anatolian Fault Zone (NAFZ) is a major continental strike-slip fault zone, similar in size and scale to the San Andreas system, that extends 1200km across Turkey. These type of faults may broaden significantly with depth or penetrate as narrow features all the way to the lithosphere-asthenosphere boundary (LAB), potentially providing pathways for fluids and magma to shallower levels. The Dense Array for North Anatolia (DANA) was a 73 station broadband seismic network arranged in a rectangular grid (7km station spacing) deployed to image the deep structure of the fault zone. We present here new S-receiver function images that map out both the depth to the Moho and to negative velocity gradients commonly ascribed to the LAB, with preliminary results suggesting lithospheric thicknesses on the order of 80-100km for the region.

What major faults look like, and why this matters for lithospheric dynamics

NASA Astrophysics Data System (ADS)

Fagereng, Ake

2016-04-01

Earthquakes involve seconds to minutes of frictional sliding on a discontinuity, likely of sub-cm thickness, within a damage zone. Earthquakes are separated by an interseismic period of hundreds to thousands of years, during which a number of healing and weakening processes occur within the fault zone. The next earthquake occurs as shear stress exceeds frictional resistance, on the same or a different discontinuity as the previous event, embedded within the fault damage zone. After incremental damage and healing in multiple earthquake cycles, the fault zone rock assemblage evolves to a structure and composition distinctly different from the host rock(s). This presentation presents field geology evidence from a range of settings, to discuss the interplay between the earthquake cycle, long-term deformation, and lithospheric rheology. Classic fault zone models are based on continental transforms, which generally form discrete faults in the upper crust, and wide, anastomosing shear zones in the lower crust. In oceanic crust, transforms are considered frictionally weak, and appear to exploit dyke margins and joint surfaces, but also locally cross-cut these structures in anastomosing networks. In the oceanic lower crust and upper mantle, serpentinisation significantly alters fault structure. In old continental crust, previous deformation events leave a heterogeneous geology affecting active faulting. For example, the amagmatic, southern East African Rift has long been thought to exploit weak Proterozoic 'mobile belts'. However, detailed look at the Bilila-Mtakataka border fault in Malawi indicates that this fault locally exploits weak foliation in existing deformed zones, but also locally forms a new set of anastomosing fault surfaces cross-cutting existing weak foliation. In exhumed lower crust, the Antarctic Maud Belt provides an example of multiple phases of plastic deformation, where the second event is only visible in localised shear zones, likely inherited from the first event. The subduction thrust interface provides an example of fault evolution in underthrust sediments as they deform and dewater. At shallow levels, distributed shear leads to development of scaly cleavage, which in places provides weak, clay surfaces on which earthquakes can propagate to the sea floor. With further deformation, a melange is progressively developed, with increasingly dismembered, sheared lenses of higher viscosity sedimentary rock and slivers of oceanic crust, in a low viscosity, cleaved matrix. The range of examples presented here illustrate how long-term deformation results in weak structures that likely control future deformation. Yet, the rheology of these structures is modulated by strength fluctuations during the earthquake cycle, illustrated by common evidence of episodic fault healing. The take home message from these field studies of fault zones is therefore the heterogeneity of the Earth's crust, the importance of long-term weak zones as a first order control on crustal deformation, and short-term strength fluctuations within these zones as a consequence of, and reason for, the earthquake cycle.

Magma-tectonic Interaction at Laguna del Maule, Chile

NASA Astrophysics Data System (ADS)

Keranen, K. M.; Peterson, D. E.; Miller, C. A.; Garibaldi, N.; Tikoff, B.; Williams-Jones, G.

2016-12-01

The Laguna del Maule Volcanic Field (LdM), Chile, the largest concentration of rhyolite <20 kyr globally, exhibits crustal deformation at rates higher than any non-erupting volcano. The interaction of large magmatic systems with faulting is poorly understood, however, the Chaitén rhyolitic system demonstrated that faults can serve as magma pathways during an eruption. We present a complex fault system at LdM in close proximity to the magma reservoir. In March 2016, 18 CHIRP seismic reflection lines were acquired at LdM to identify faults and analyze potential spatial and temporal impacts of the fault system on volcanic activity. We mapped three key horizons on each line, bounding sediment packages between Holocene onset, 870 ybp, and the present date. Faults were mapped on each line and offset was calculated across key horizons. Our results indicate a system of normal-component faults in the northern lake sector, striking subparallel to the mapped Troncoso Fault SW of the lake. These faults correlate to prominent magnetic lineations mapped by boat magnetic data acquired February 2016 which are interpreted as dykes intruding along faults. We also imaged a vertical fault, interpreted as a strike-slip fault, and a series of normal faults in the SW lake sector near the center of magmatic inflation. Isochron and fault offset maps illuminate areas of growth strata and indicate migration and increase of fault activity from south to north through time. We identify a domal structure in the SW lake sector, coincident with an area of low magnetization, in the region of maximum deformation from InSAR results. The dome experienced 10 ms TWT ( 10 meters) of uplift throughout the past 16 kybp, which we interpret as magmatic inflation in a shallow magma reservoir. This inflation is isolated to a 1.5 km diameter region in the hanging wall of the primary normal fault system, indicating possible fault-facilitated inflation.

Assessment of the geodynamical setting around the main active faults at Aswan area, Egypt

NASA Astrophysics Data System (ADS)

Ali, Radwan; Hosny, Ahmed; Kotb, Ahmed; Khalil, Ahmed; Azza, Abed; Rayan, Ali

2013-04-01

The proper evaluation of crustal deformations in the Aswan region especially around the main active faults is crucial due to the existence of one major artificial structure: the Aswan High Dam. This construction created one of the major artificial lakes: Lake Nasser. The Aswan area is considered as an active seismic area in Egypt since many recent and historical felted earthquakes occurred such as the impressive earthquake occurred on November 14, 1981 at Kalabsha fault with a local magnitude ML=5.7. Lately, on 26 December 2011, a moderate earthquake with a local magnitude Ml=4.1 occurred at Kalabsha area too. The main target of this study is to evaluate the active geological structures that can potentially affect the Aswan High Dam and that are being monitored in detail. For implementing this objective, two different geophysical tools (magnetic, seismic) in addition to the Global Positioning System (GPS) have been utilized. Detailed land magnetic survey was carried out for the total component of geomagnetic field using two proton magnetometers. The obtained magnetic results reveal that there are three major faults parallel {F1 (Kalabsha), F2 (Seiyal) and F3} affecting the area. The most dominant magnetic trend strikes those faults in the WNW-ESE direction. The seismicity and fault plain solutions of the 26 December 2011 earthquake and its two aftershocks have been investigated. The source mechanisms of those events delineate two nodal plains. The trending ENE-WSW to E-W is consistent with the direction of Kalabsha fault and its extension towards east for the events located over it. The trending NNW-SSE to N-S is consistent with the N-S fault trending. The movement along the ENE-WSW plain is right lateral, but it is left lateral along the NNW-SSE plain. Based on the estimated relative motions using GPS, dextral strike-slip motion at the Kalabsha and Seiyal fault systems is clearly identified by changing in the velocity gradient between south and north stations. However, at the area between Kalabha and Seiyal faults, the movement has been changed in a different direction which is consistent with the other set of faults (N-S).

The 2016-2017 central Italy coseismic surface ruptures and their meaning with respect to foreseen active fault systems segmentation

NASA Astrophysics Data System (ADS)

De Martini, P. M.; Pucci, S.; Villani, F.; Civico, R.; Del Rio, L.; Cinti, F. R.; Pantosti, D.

2017-12-01

In 2016-2017 a series of moderate to large normal faulting earthquakes struck central Italy producing severe damage in many towns including Amatrice, Norcia and Visso and resulting in 299 casualties and >20,000 homeless. The complex seismic sequence depicts a multiple activation of the Mt. Vettore-Mt. Bove (VBFS) and the Laga Mts. fault systems, which were considered in literature as independent segments characterizing a recent seismic gap in the region comprised between two modern seismic sequences: the 1997-1998 Colfiorito and the 2009 L'Aquila. We mapped in detail the coseismic surface ruptures following three mainshocks (Mw 6.0 on 24th August, Mw 5.9 and Mw 6.5 on 26th and 30th October, 2016, respectively). Primary surface ruptures were observed and recorded for a total length of 5.2 km, ≅10 km and ≅25 km, respectively, along closely-spaced, parallel or subparallel, overlapping or step-like synthetic and antithetic fault splays of the activated fault systems, in some cases rupturing repeatedly the same location. Some coseismic ruptures were mapped also along the Norcia Fault System, paralleling the VBFS about 10 km westward. We recorded geometric and kinematic characteristics of the normal faulting ruptures with an unprecedented detail thanks to almost 11,000 oblique photographs taken from helicopter flights soon after the mainshocks, verified and integrated with field data (more than 7000 measurements). We analyze the along-strike coseismic slip and slip vectors distribution to be observed in the context of the geomorphic expression of the disrupted slopes and their depositional and erosive processes. Moreover, we constructed 1:10.000 scale geologic cross-sections based on updated maps, and we reconstructed the net offset distribution of the activated fault system to be compared with the morphologic throws and to test a cause-effect relationship between faulting and first-order landforms. We provide a reconstruction of the 2016 coseismic rupture pattern as representative of the VBFS behavior, a discussion on the fault system boundaries persistence, and on the significance of the repeated surface faulting at same location.

Active normal fault network of the Apulian Ridge (Eastern Mediterranean Sea) imaged by multibeam bathymetry and seismic data

NASA Astrophysics Data System (ADS)

Pellegrini, Claudio; Marchese, Fabio; Savini, Alessandra; Bistacchi, Andrea

2016-04-01

The Apulian ridge (North-eastern Ionian margin - Mediterranean Sea) is formed by thick cretaceous carbonatic sequences and discontinuous tertiary deposits crosscut by a NNW-SSE penetrative normal fault system and is part of the present foreland system of both the Apennine to the west and the Hellenic arc to the east. The geometry, age, architecture and kinematics of the fault network were investigated integrating data of heterogeneous sources, provided by previous studies: regional scale 2D seismics and three wells collected by oil companies from the '60s to the '80s, more recent seismics collected during research projects in the '90s, very high resolution seismic (VHRS - Sparker and Chirp-sonar data), multi-beam echosounder bathymetry and results from sedimentological and geo-chronological analysis of sediment samples collected on the seabed. Multibeam bathymetric data allowed in particular assessing the 3D continuity of structures imaged in 2D seismics, thanks to the occurrence of continuous fault scarps on the seabed (only partly reworked by currents and covered by landslides), revealing the vertical extent and finite displacement associated to fault scarps. A penetrative network of relatively small faults, always showing a high dip angle, composes the NNW-SSE normal fault system, resulting in frequent relay zones, which are particularly well imaged by seafloor geomorphology. In addition, numerous fault scarps appear to be roughly coeval with quaternary submarine mass-wasting deposits colonised by Cold-Water Corals (CWC). Coral colonies, yielding ages between 11 and 14 kA, develop immediately on top of late Pleistocene mass-wasting deposits. Mutual cross-cutting relationships have been recognized between fault scarps and landslides, indicating that, at least in places, these features may be coeval. We suppose that fault activity lasted at least as far as the Holocene-Pleistocene boundary and that the NNW-SSW normal fault network in the Apulian Plateau can be considered active (or at least active till the Holocene-Pleistocene boundary), and that the cumulative horizontal displacement is consistent with a relevant WSW-ENE stretching, that can be associated to the bending moment applied to the Apulian Plate by the combined effect of the Appennines and Hellenides subduction.

Rift flank segmentation, basin initiation and propagation: a neotectonic example from Lake Baikal

USGS Publications Warehouse

Agar, Susan M.; Klitgord, Kim D.

1995-01-01

New surficial data (field, Landsat TM and topography) define morpho-tectonic domains and rift flank segmentation in the Ol'khon region of the Central Baikal rift. Deformation, drainage and depositional patterns indicate a change in the locus of active extension that may relate to a recent (

Fault linkage and continental breakup

NASA Astrophysics Data System (ADS)

Cresswell, Derren; Lymer, Gaël; Reston, Tim; Stevenson, Carl; Bull, Jonathan; Sawyer, Dale; Morgan, Julia

2017-04-01

The magma-poor rifted margin off the west coast of Galicia (NW Spain) has provided some of the key observations in the development of models describing the final stages of rifting and continental breakup. In 2013, we collected a 68 x 20 km 3D seismic survey across the Galicia margin, NE Atlantic. Processing through to 3D Pre-stack Time Migration (12.5 m bin-size) and 3D depth conversion reveals the key structures, including an underlying detachment fault (the S detachment), and the intra-block and inter-block faults. These data reveal multiple phases of faulting, which overlap spatially and temporally, have thinned the crust to between zero and a few km thickness, producing 'basement windows' where crustal basement has been completely pulled apart and sediments lie directly on the mantle. Two approximately N-S trending fault systems are observed: 1) a margin proximal system of two linked faults that are the upward extension (breakaway faults) of the S; in the south they form one surface that splays northward to form two faults with an intervening fault block. These faults were thus demonstrably active at one time rather than sequentially. 2) An oceanward relay structure that shows clear along strike linkage. Faults within the relay trend NE-SW and heavily dissect the basement. The main block bounding faults can be traced from the S detachment through the basement into, and heavily deforming, the syn-rift sediments where they die out, suggesting that the faults propagated up from the S detachment surface. Analysis of the fault heaves and associated maps at different structural levels show complementary fault systems. The pattern of faulting suggests a variation in main tectonic transport direction moving oceanward. This might be interpreted as a temporal change during sequential faulting, however the transfer of extension between faults and the lateral variability of fault blocks suggests that many of the faults across the 3D volume were active at least in part simultaneously. Alternatively, extension may have varied in direction spatially if it were a rotation about a pole located to the north.

Dynamical Instability Produces Transform Faults at Mid-Ocean Ridges

NASA Astrophysics Data System (ADS)

Gerya, Taras

2010-08-01

Transform faults at mid-ocean ridges—one of the most striking, yet enigmatic features of terrestrial plate tectonics—are considered to be the inherited product of preexisting fault structures. Ridge offsets along these faults therefore should remain constant with time. Here, numerical models suggest that transform faults are actively developing and result from dynamical instability of constructive plate boundaries, irrespective of previous structure. Boundary instability from asymmetric plate growth can spontaneously start in alternate directions along successive ridge sections; the resultant curved ridges become transform faults within a few million years. Fracture-related rheological weakening stabilizes ridge-parallel detachment faults. Offsets along the transform faults change continuously with time by asymmetric plate growth and discontinuously by ridge jumps.

Fault creep rates of the Chaman fault (Afghanistan and Pakistan) inferred from InSAR

NASA Astrophysics Data System (ADS)

Barnhart, William D.

2017-01-01

The Chaman fault is the major strike-slip structural boundary between the India and Eurasia plates. Despite sinistral slip rates similar to the North America-Pacific plate boundary, no major (>M7) earthquakes have been documented along the Chaman fault, indicating that the fault either creeps aseismically or is at a late stage in its seismic cycle. Recent work with remotely sensed interferometric synthetic aperture radar (InSAR) time series documented a heterogeneous distribution of fault creep and interseismic coupling along the entire length of the Chaman fault, including an 125 km long creeping segment and an 95 km long locked segment within the region documented in this study. Here I present additional InSAR time series results from the Envisat and ALOS radar missions spanning the southern and central Chaman fault in an effort to constrain the locking depth, dip, and slip direction of the Chaman fault. I find that the fault deviates little from a vertical geometry and accommodates little to no fault-normal displacements. Peak-documented creep rates on the fault are 9-12 mm/yr, accounting for 25-33% of the total motion between India and Eurasia, and locking depths in creeping segments are commonly shallower than 500 m. The magnitude of the 1892 Chaman earthquake is well predicted by the total area of the 95 km long coupled segment. To a first order, the heterogeneous distribution of aseismic creep combined with consistently shallow locking depths suggests that the southern and central Chaman fault may only produce small to moderate earthquakes (

Frictional power dissipation on plate boundary faults: Implications for coseismic slip propagation at near-surface depths

NASA Astrophysics Data System (ADS)

Ikari, M.; Kopf, A.; Saffer, D. M.; Marone, C.; Carpenter, B. M.

2013-12-01

The general lack of earthquake slip at shallow (< ~4 km) depths on plate-boundary faults suggests that they creep stably, a behavior associated with laboratory observations that disaggregated fault gouges commonly strengthen with increasing sliding velocity (i.e. velocity-strengthening friction), which precludes strain energy release via stress drops. However, the 2011 Tohoku earthquake demonstrated that coseismic rupture and slip can sometimes propagate to the surface in subduction zones. Surface rupture is also known to occur on other plate boundary faults, such as the Alpine Fault in New Zealand. It is uncertain how the extent of coseismic slip propagation from depth is controlled by the frictional properties of the near-surface portion of major faults. In these situations, it is common for slip to localize within gouge having a significant component of clay minerals, which laboratory experiments have shown are generally weak and velocity strengthening. However, low overall fault strength should facilitate coseismic slip, while velocity-strengthening behavior would resist it. In order to investigate how frictional properties may control the extent of coseismic slip propagation at shallow depths, we compare frictional strength and velocity-dependence measurements using samples from three subduction zones known for hosting large magnitude earthquakes. We focus on samples recovered during scientific drilling projects from the Nankai Trough, Japan, the Japan Trench in the region of the Tohoku earthquake, and the Middle America Trench, offshore Costa Rica; however we also include comparisons with other major fault zones sampled by drilling. In order to incorporate the combined effects of overall frictional strength and friction velocity-dependence, we estimate shear strength as a function of slip velocity (at constant effective normal stress), and integrate this function to obtain the areal power density, or frictional power dissipation capability of the fault zone. We also explore the role of absolute shear stress level before arrival of a propagating rupture. Preliminary results show that weak, velocity-strengthening fault zones have a low net power density, but are unlikely to contribute to instability via dynamic stress drops unless they are initially very close to failure. By contrast, strong and velocity-weakening faults will tend to resist coseismic slip by consuming energy if stresses are initially low; however their velocity-weakening nature means that they can support a stress drop even if relatively far below their failure strength.

Slip triggered on southern California faults by the 1992 Joshua Tree, Landers, and big bear earthquakes

USGS Publications Warehouse

Bodin, Paul; Bilham, Roger; Behr, Jeff; Gomberg, Joan; Hudnut, Kenneth W.

1994-01-01

Five out of six functioning creepmeters on southern California faults recorded slip triggered at the time of some or all of the three largest events of the 1992 Landers earthquake sequence. Digital creep data indicate that dextral slip was triggered within 1 min of each mainshock and that maximum slip velocities occurred 2 to 3 min later. The duration of triggered slip events ranged from a few hours to several weeks. We note that triggered slip occurs commonly on faults that exhibit fault creep. To account for the observation that slip can be triggered repeatedly on a fault, we propose that the amplitude of triggered slip may be proportional to the depth of slip in the creep event and to the available near-surface tectonic strain that would otherwise eventually be released as fault creep. We advance the notion that seismic surface waves, perhaps amplified by sediments, generate transient local conditions that favor the release of tectonic strain to varying depths. Synthetic strain seismograms are presented that suggest increased pore pressure during periods of fault-normal contraction may be responsible for triggered slip, since maximum dextral shear strain transients correspond to times of maximum fault-normal contraction.

The correlation of 2D-resistivity and magnetic methods in fault verification at northern Sumatra, Indonesia

NASA Astrophysics Data System (ADS)

Kamaruddin, Nur Aminuda; Saad, Rosli; Nordiana, M. M.; Azwin, I. N.

2015-04-01

The Great Sumatra Fault system was split into two sub-parallel lines or segments at the Northern Sumatra. This event is one of the impacts of powerful earthquakes that hit Sumatra Island especially one that occurred in 2004. These two sub-parallel segments known as Aceh and Seulimeum fault. The study is focused on the Seulimeum fault and two geophysical methods chosen aimed to compare and verified the result obtained respectively. 2-D resistivity method is a common geophysical method used in determination of near surface structures such as faults, cavities, voids and sinkholes. Meanwhile, the magnetic method often chosen to delineate subsurface structures, determine depth of magnetic source bodies and possibly sediment thickness. Three survey lines of resistivity method and randomly magnetic stations were carried out covering Krueng district. The resistivity data processed using Res2Dinv and result presented using Surfer software. The fault identified by the contrast of low and high resistivity value. Meanwhile, the magnetic data were presented in magnetic residual contour map and the extended fault system is suspected represent by the contrast value of the magnetic anomalies. Within suspected fault zone, the results of resistivity are tally with magnetic result.

TWT transmitter fault prediction based on ANFIS

NASA Astrophysics Data System (ADS)

Li, Mengyan; Li, Junshan; Li, Shuangshuang; Wang, Wenqing; Li, Fen

2017-11-01

Fault prediction is an important component of health management, and plays an important role in the reliability guarantee of complex electronic equipments. Transmitter is a unit with high failure rate. The cathode performance of TWT is a common fault of transmitter. In this dissertation, a model based on a set of key parameters of TWT is proposed. By choosing proper parameters and applying adaptive neural network training model, this method, combined with analytic hierarchy process (AHP), has a certain reference value for the overall health judgment of TWT transmitters.

Passive fault current limiting device

DOEpatents

Evans, Daniel J.; Cha, Yung S.

1999-01-01

A passive current limiting device and isolator is particularly adapted for use at high power levels for limiting excessive currents in a circuit in a fault condition such as an electrical short. The current limiting device comprises a magnetic core wound with two magnetically opposed, parallel connected coils of copper, a high temperature superconductor or other electrically conducting material, and a fault element connected in series with one of the coils. Under normal operating conditions, the magnetic flux density produced by the two coils cancel each other. Under a fault condition, the fault element is triggered to cause an imbalance in the magnetic flux density between the two coils which results in an increase in the impedance in the coils. While the fault element may be a separate current limiter, switch, fuse, bimetal strip or the like, it preferably is a superconductor current limiter conducting one-half of the current load compared to the same limiter wired to carry the total current of the circuit. The major voltage during a fault condition is in the coils wound on the common core in a preferred embodiment.

Passive fault current limiting device

DOEpatents

Evans, D.J.; Cha, Y.S.

1999-04-06

A passive current limiting device and isolator is particularly adapted for use at high power levels for limiting excessive currents in a circuit in a fault condition such as an electrical short. The current limiting device comprises a magnetic core wound with two magnetically opposed, parallel connected coils of copper, a high temperature superconductor or other electrically conducting material, and a fault element connected in series with one of the coils. Under normal operating conditions, the magnetic flux density produced by the two coils cancel each other. Under a fault condition, the fault element is triggered to cause an imbalance in the magnetic flux density between the two coils which results in an increase in the impedance in the coils. While the fault element may be a separate current limiter, switch, fuse, bimetal strip or the like, it preferably is a superconductor current limiter conducting one-half of the current load compared to the same limiter wired to carry the total current of the circuit. The major voltage during a fault condition is in the coils wound on the common core in a preferred embodiment. 6 figs.

Convergence and objective functions of some fault/noise-injection-based online learning algorithms for RBF networks.

PubMed

Ho, Kevin I-J; Leung, Chi-Sing; Sum, John

2010-06-01

In the last two decades, many online fault/noise injection algorithms have been developed to attain a fault tolerant neural network. However, not much theoretical works related to their convergence and objective functions have been reported. This paper studies six common fault/noise-injection-based online learning algorithms for radial basis function (RBF) networks, namely 1) injecting additive input noise, 2) injecting additive/multiplicative weight noise, 3) injecting multiplicative node noise, 4) injecting multiweight fault (random disconnection of weights), 5) injecting multinode fault during training, and 6) weight decay with injecting multinode fault. Based on the Gladyshev theorem, we show that the convergence of these six online algorithms is almost sure. Moreover, their true objective functions being minimized are derived. For injecting additive input noise during training, the objective function is identical to that of the Tikhonov regularizer approach. For injecting additive/multiplicative weight noise during training, the objective function is the simple mean square training error. Thus, injecting additive/multiplicative weight noise during training cannot improve the fault tolerance of an RBF network. Similar to injective additive input noise, the objective functions of other fault/noise-injection-based online algorithms contain a mean square error term and a specialized regularization term.

GeoBioScience: Red Wood Ants as Bioindicators for Active Tectonic Fault Systems in the West Eifel (Germany).

PubMed

Berberich, Gabriele; Schreiber, Ulrich

2013-05-17

In a 1.140 km² study area of the volcanic West Eifel, a comprehensive investigation established the correlation between red wood ant mound (RWA; Formica rufa-group) sites and active tectonic faults. The current stress field with a NW-SE-trending main stress direction opens pathways for geogenic gases and potential magmas following the same orientation. At the same time, Variscan and Mesozoic fault zones are reactivated. The results showed linear alignments and clusters of approx. 3,000 RWA mounds. While linear mound distribution correlate with strike-slip fault systems documented by quartz and ore veins and fault planes with slickensides, the clusters represent crosscut zones of dominant fault systems. Latter can be correlated with voids caused by crustal block rotation. Gas analyses from soil air, mineral springs and mofettes (CO₂, Helium, Radon and H₂S) reveal limiting concentrations for the spatial distribution of mounds and colonization. Striking is further the almost complete absence of RWA mounds in the core area of the Quaternary volcanic field. A possible cause can be found in occasionally occurring H₂S in the fault systems, which is toxic at miniscule concentrations to the ants. Viewed overall, there is a strong relationship between RWA mounds and active tectonics in the West Eifel.

The geology and mineral deposits of part of the western half of the Hailey 1 degree x 2 degrees quadrangle, Idaho; with sections on the Neal mining district and the Dixie mining district

USGS Publications Warehouse

Bennett, Earl H.

2001-01-01

Rocks in the western half of the Hailey 1 ?? 2 ? quadrangle of south-central Idaho include various units of the Atlanta lobe of the Idaho batholith (biotite granodiorite to two-mica granite) of Cretaceous age and plutons and dikes of Tertiary (Eocene to Miocene) age that intrude the batholith. Eocene plutonic rocks consist of a bimodal suite of anorogenic granite and tonalite-granodiorite and hypabyssal rhyolite and rhyodacite dikes. Rocks of the Eocene Challis Volcanics are scarce in the map area but are widespread to the east. Rhyolite ash flows of the Miocene Idavada Volcanics and basalt of the Snake River Plain crop out in the southern part of the area. Lacustrine rocks of probable Eocene to Holocene age are present in the vicinity of Anderson Ranch Reservoir. Quaternary basalts and gravels are widespread on the South Fork of the Boise River, and alluvial deposits are common along active drainages. Metasedimentary rocks of unknown age crop out on House Mountain, Chimney Peak, and on the ridges east of Anderson Ranch Reservoir. Older structures in the Idaho batholith include a major fault beneath House Mountain that may be a decollement for one of the large thrust sheets in eastern Idaho or part of an extensional core complex. The southern part of the Atlanta lobe of the Idaho batholith is cut by northeast-striking faults (parallel with the Trans-Challis fault system) that are related to Eocene extension and by northwest-oriented faults that formed during basin and range extension in the Miocene. The basin and range faults have prominent scarps typical of basin and range topography. The combination of northeast and northwest faults has broken the batholith into a series of rhomboid blocks. Some of these northeast and northwest faults are older structures that were reactivated in the Eocene or Miocene, as indicated by Ar 40 /Ar 39 dates on mineralized rock contained in some of the structures. The Idaho batholith and associated rocks in the map area host several hundred mines and prospects in 18 mining districts. The deposits range in age from Cretaceous to Eocene, and many were developed for precious metals. Most of the deposits are in quartz veins in shear zones in granitic rocks of the batholith. Several districts were actively being explored for low-grade, bulk-minable, precious-metal deposits in the late 1980s and early 1990s.

Surface-wave potential for triggering tectonic (nonvolcanic) tremor

USGS Publications Warehouse

Hill, D.P.

2010-01-01

Source processes commonly posed to explain instances of remote dynamic triggering of tectonic (nonvolcanic) tremor by surface waves include frictional failure and various modes of fluid activation. The relative potential for Love- and Rayleigh-wave dynamic stresses to trigger tectonic tremor through failure on critically stressed thrust and vertical strike-slip faults under the Coulomb-Griffith failure criteria as a function of incidence angle is anticorrelated over the 15- to 30-km-depth range that hosts tectonic tremor. Love-wave potential is high for strike-parallel incidence on low-angle reverse faults and null for strike-normal incidence; the opposite holds for Rayleigh waves. Love-wave potential is high for both strike-parallel and strike-normal incidence on vertical, strike-slip faults and minimal for ~45?? incidence angles. The opposite holds for Rayleigh waves. This pattern is consistent with documented instances of tremor triggered by Love waves incident on the Cascadia mega-thrust and the San Andreas fault (SAF) in central California resulting from shear failure on weak faults (apparent friction, ????? 0.2). However, documented instances of tremor triggered by surface waves with strike-parallel incidence along the Nankai megathrust beneath Shikoku, Japan, is associated primarily with Rayleigh waves. This is consistent with the tremor bursts resulting from mixed-mode failure (crack opening and shear failure) facilitated by near-lithostatic ambient pore pressure, low differential stress, with a moderate friction coefficient (?? ~ 0.6) on the Nankai subduction interface. Rayleigh-wave dilatational stress is relatively weak at tectonic tremor source depths and seems unlikely to contribute significantly to the triggering process, except perhaps for an indirect role on the SAF in sustaining tremor into the Rayleigh-wave coda that was initially triggered by Love waves.

Surface-wave potential for triggering tectonic (nonvolcanic) tremor-corrected

USGS Publications Warehouse

Hill, David P.

2012-01-01

Source processes commonly posed to explain instances of remote dynamic triggering of tectonic (nonvolcanic) tremor by surface waves include frictional failure and various modes of fluid activation. The relative potential for Love- and Rayleigh-wave dynamic stresses to trigger tectonic tremor through failure on critically stressed thrust and vertical strike-slip faults under the Coulomb-Griffith failure criteria as a function of incidence angle are anticorrelated over the 15- to 30-km-depth range that hosts tectonic tremor. Love-wave potential is high for strike-parallel incidence on low-angle reverse faults and null for strike-normal incidence; the opposite holds for Rayleigh waves. Love-wave potential is high for both strike-parallel and strike-normal incidence on vertical, strike-slip faults and minimal for ~45° incidence angles. The opposite holds for Rayleigh waves. This pattern is consistent with documented instances of tremor triggered by Love waves incident on the Cascadia megathrust and the San Andreas fault (SAF) in central California resulting from shear failure on weak faults (apparent friction is μ* ≤ 0:2). Documented instances of tremor triggered by surface waves with strike-parallel incidence along the Nankai megathrust beneath Shikoku, Japan, however, are associated primarily with Rayleigh waves. This is consistent with the tremor bursts resulting from mixed-mode failure (crack opening and shear failure) facilitated by near-lithostatic ambient pore pressure, low differential stress, with a moderate friction coefficient (μ ~ 0:6) on the Nankai subduction interface. Rayleigh-wave dilatational stress is relatively weak at tectonic tremor source depths and seems unlikely to contribute significantly to the triggering process, except perhaps for an indirect role on the SAF in sustaining tremor into the Rayleigh-wave coda that was initially triggered by Love waves.

Fault Management Architectures and the Challenges of Providing Software Assurance

NASA Technical Reports Server (NTRS)

Savarino, Shirley; Fitz, Rhonda; Fesq, Lorraine; Whitman, Gerek

2015-01-01

Fault Management (FM) is focused on safety, the preservation of assets, and maintaining the desired functionality of the system. How FM is implemented varies among missions. Common to most missions is system complexity due to a need to establish a multi-dimensional structure across hardware, software and spacecraft operations. FM is necessary to identify and respond to system faults, mitigate technical risks and ensure operational continuity. Generally, FM architecture, implementation, and software assurance efforts increase with mission complexity. Because FM is a systems engineering discipline with a distributed implementation, providing efficient and effective verification and validation (V&V) is challenging. A breakout session at the 2012 NASA Independent Verification & Validation (IV&V) Annual Workshop titled "V&V of Fault Management: Challenges and Successes" exposed this issue in terms of V&V for a representative set of architectures. NASA's Software Assurance Research Program (SARP) has provided funds to NASA IV&V to extend the work performed at the Workshop session in partnership with NASA's Jet Propulsion Laboratory (JPL). NASA IV&V will extract FM architectures across the IV&V portfolio and evaluate the data set, assess visibility for validation and test, and define software assurance methods that could be applied to the various architectures and designs. This SARP initiative focuses efforts on FM architectures from critical and complex projects within NASA. The identification of particular FM architectures and associated V&V/IV&V techniques provides a data set that can enable improved assurance that a system will adequately detect and respond to adverse conditions. Ultimately, results from this activity will be incorporated into the NASA Fault Management Handbook providing dissemination across NASA, other agencies and the space community. This paper discusses the approach taken to perform the evaluations and preliminary findings from the research.

Subsurface structure of the East Bay Plain ground-water basin: San Francisco Bay to the Hayward fault, Alameda County, California

USGS Publications Warehouse

Catchings, R.D.; Borchers, J.W.; Goldman, M.R.; Gandhok, G.; Ponce, D.A.; Steedman, C.E.

2006-01-01

The area of California between the San Francisco Bay, San Pablo Bay, Santa Clara Valley, and the Diablo Ranges (East Bay Hills), commonly referred to as the 'East Bay', contains the East Bay Plain and Niles Cone ground-water basins. The area has a population of 1.46 million (2003 US Census), largely distributed among several cities, including Alameda, Berkeley, Fremont, Hayward, Newark, Oakland, San Leandro, San Lorenzo, and Union City. Major known tectonic structures in the East Bay area include the Hayward Fault and the Diablo Range to the east and a relatively deep sedimentary basin known as the San Leandro Basin beneath the eastern part of the bay. Known active faults, such as the Hayward, Calaveras, and San Andreas pose significant earthquake hazards to the region, and these and related faults also affect ground-water flow in the San Francisco Bay area. Because most of the valley comprising the San Francisco Bay area is covered by Holocene alluvium or water at the surface, our knowledge of the existence and locations of such faults, their potential hazards, and their effects on ground-water flow within the alluvial basins is incomplete. To better understand the subsurface stratigraphy and structures and their effects on ground-water and earthquake hazards, the U.S. Geological Survey (USGS), in cooperation with the East Bay Municipal Utility District (EBMUD), acquired a series of high-resolution seismic reflection and refraction profiles across the East Bay Plain near San Leandro in June 2002. In this report, we present results of the seismic imaging investigations, with emphasis on ground water.