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Sample records for active faulting induced

  1. On the possible fault activation induced by UGS in depleted reservoirs

    NASA Astrophysics Data System (ADS)

    Feronato, Massimiliano; Gambolati, Giuseppe; Janna, Carlo; Teatini, Pietro; Tosattto, Omar

    2014-05-01

    Underground gas storage (UGS) represents an increasingly used approach to cope with the growing energy demand and occurs in many countries worldwide. Gas is injected in previously depleted deep reservoirs during summer when consumption is limited and removed in cold season mainly for heating. As a major consequence the pore pressure p within a UGS reservoir fluctuates yearly between a maximum close to the value pi prior to the field development and a minimum usually larger than the lowest pressure experienced by the reservoir at the end of its production life. The high frequency pressure fluctuations generally confine the pressure change volume to the reservoir volume without significantly involving the aquifers hydraulically connected to the hydrocarbon field (lateral and/or bottom waterdrive). The risk of UGS-induced seismicity is therefore restricted to those cases where existing faults cross or bound the reservoir. The possible risk of anthropogenic seismicity due to UGS operations is preliminary investigated by an advanced Finite Element (FE) - Interface Element (IE) 3-D elasto-plastic geomechanical model in a representative 1500 m deep reservoir bounded by a regional sealing fault and compartimentalized by an internal non-sealing thrust. Gas storage/production is ongoing with p ranging between pi in October/November and 60%pi in April/May. The yearly pressure fluctuation is assumed to be on the order of 50 bar. The overall geomechanical response of the porous medium has been calibrated by reproducing the vertical and horizontal cyclic displacements measured above the reservoir by advanced persistent scatterer interferometry. The FE-IE model shows that the stress variations remain basically confined within the gas field and negligibly propagate within the caprock and the waterdrive. Based on the Mohr-Coulomb failure criterion, IEs allow for the prediction of the fault activated area A, located at the reservoir depth as expected, and slip displacement d. A

  2. Modeling of fluid injection and withdrawal induced fault activation using discrete element based hydro-mechanical and dynamic coupled simulator

    NASA Astrophysics Data System (ADS)

    Yoon, Jeoung Seok; Zang, Arno; Zimmermann, Günter; Stephansson, Ove

    2016-04-01

    Operation of fluid injection into and withdrawal from the subsurface for various purposes has been known to induce earthquakes. Such operations include hydraulic fracturing for shale gas extraction, hydraulic stimulation for Enhanced Geothermal System development and waste water disposal. Among these, several damaging earthquakes have been reported in the USA in particular in the areas of high-rate massive amount of wastewater injection [1] mostly with natural fault systems. Oil and gas production have been known to induce earthquake where pore fluid pressure decreases in some cases by several tens of Mega Pascal. One recent seismic event occurred in November 2013 near Azle, Texas where a series of earthquakes began along a mapped ancient fault system [2]. It was studied that a combination of brine production and waste water injection near the fault generated subsurface pressures sufficient to induced earthquakes on near-critically stressed faults. This numerical study aims at investigating the occurrence mechanisms of such earthquakes induced by fluid injection [3] and withdrawal by using hydro-geomechanical coupled dynamic simulator (Itasca's Particle Flow Code 2D). Generic models are setup to investigate the sensitivity of several parameters which include fault orientation, frictional properties, distance from the injection well to the fault, amount of fluid withdrawal around the injection well, to the response of the fault systems and the activation magnitude. Fault slip movement over time in relation to the diffusion of pore pressure is analyzed in detail. Moreover, correlations between the spatial distribution of pore pressure change and the locations of induced seismic events and fault slip rate are investigated. References [1] Keranen KM, Weingarten M, Albers GA, Bekins BA, Ge S, 2014. Sharp increase in central Oklahoma seismicity since 2008 induced by massive wastewater injection, Science 345, 448, DOI: 10.1126/science.1255802. [2] Hornbach MJ, DeShon HR

  3. A test of the longevity of impact-induced faults as preferred sites for later tectonic activity

    NASA Technical Reports Server (NTRS)

    Solomon, Sean C.; Duxbury, Elizabeth D.

    1987-01-01

    The hypothesis that impact-induced faults have been preferred sites for later deformation in response to lithospheric stresses has been suggested for several planets and satellites. This hypothesis is investigated on earth by examining whether terrestrial impact structures show higher rates of nearby earthquake activity than do surrounding intraplate regions. For 28 of 30 probable impact structures having an original crater 20 km or more in diameter, the rates of nearby seismicity have been no higher than the regional background rates. For two large probable impact structures, Vredefort and Charlevoix, with higher than normal rates of nearby seismicity, factors other than slip on impact-induced faults appear to control the occurrence of earthquakes. It is concluded that impact-induced faults, at least on earth, do not persist as lithospheric 'weak zones' for periods in excess of several million years after the impact event.

  4. Active faulting induced by the slip partitioning in the Lesser Antilles arc

    NASA Astrophysics Data System (ADS)

    Leclerc, Frédérique; Feuillet, Nathalie

    2010-05-01

    AGUADOMAR marine cruise data acquired 11 years ago allowed us to identified and map two main sets of active faults within the Lesser Antilles arc (Feuillet et al., 2002; 2004). The faults belonging to the first set, such as Morne-Piton in Guadeloupe, bound up to 100km-long and 50km-wide arc-perpendicular graben or half graben that disrupt the fore-arc reef platforms. The faults of the second set form right-stepping en echelon arrays, accommodating left-lateral slip along the inner, volcanic islands. The two fault systems form a sinistral horsetail east of the tip of the left-lateral Puerto Rico fault zone that takes up the trench-parallel component of convergence between the North-American and Caribbean plates west of the Anegada passage. In other words, they together accommodate large-scale slip partitioning along the northeastern arc, consistent with recent GPS measurements (Lopez et al., 2006). These intraplate faults are responsible for a part of the shallow seismicity in the arc and have produce damaging historical earthquakes. Two magnitude 6.3 events occurred in the last 25 years along the inner en echelon faults, the last one on November 21 2004 in Les Saintes in the Guadeloupe archipelago. To better constrain the seismic hazard related to the inner arc faults and image the ruptures and effects on the seafloor of Les Saintes 2004 earthquake, we acquired new marine data between 23 February and 25 March 2009 aboard the French R/V le Suroît during the GWADASEIS cruise. We present here the data (high-resolution 72 channel and very high-resolution chirp 3.5 khz seismic reflection profiles, EM300 multibeam bathymetry, Küllenberg coring and SAR imagery) and the first results. We identified, mapped and characterized in detail several normal to oblique fault systems between Martinique and Saba. They offset the seafloor by several hundred meters and crosscut all active volcanoes, among them Nevis Peak, Soufriere Hills, Soufriere de Guadeloupe and Montagne Pel

  5. Central Asia Active Fault Database

    NASA Astrophysics Data System (ADS)

    Mohadjer, Solmaz; Ehlers, Todd A.; Kakar, Najibullah

    2014-05-01

    The ongoing collision of the Indian subcontinent with Asia controls active tectonics and seismicity in Central Asia. This motion is accommodated by faults that have historically caused devastating earthquakes and continue to pose serious threats to the population at risk. Despite international and regional efforts to assess seismic hazards in Central Asia, little attention has been given to development of a comprehensive database for active faults in the region. To address this issue and to better understand the distribution and level of seismic hazard in Central Asia, we are developing a publically available database for active faults of Central Asia (including but not limited to Afghanistan, Tajikistan, Kyrgyzstan, northern Pakistan and western China) using ArcGIS. The database is designed to allow users to store, map and query important fault parameters such as fault location, displacement history, rate of movement, and other data relevant to seismic hazard studies including fault trench locations, geochronology constraints, and seismic studies. Data sources integrated into the database include previously published maps and scientific investigations as well as strain rate measurements and historic and recent seismicity. In addition, high resolution Quickbird, Spot, and Aster imagery are used for selected features to locate and measure offset of landforms associated with Quaternary faulting. These features are individually digitized and linked to attribute tables that provide a description for each feature. Preliminary observations include inconsistent and sometimes inaccurate information for faults documented in different studies. For example, the Darvaz-Karakul fault which roughly defines the western margin of the Pamir, has been mapped with differences in location of up to 12 kilometers. The sense of motion for this fault ranges from unknown to thrust and strike-slip in three different studies despite documented left-lateral displacements of Holocene and late

  6. Packaged Fault Model for Geometric Segmentation of Active Faults Into Earthquake Source Faults

    NASA Astrophysics Data System (ADS)

    Nakata, T.; Kumamoto, T.

    2004-12-01

    In Japan, the empirical formula proposed by Matsuda (1975) mainly based on the length of the historical surface fault ruptures and magnitude, is generally applied to estimate the size of future earthquakes from the extent of existing active faults for seismic hazard assessment. Therefore validity of the active fault length and defining individual segment boundaries where propagating ruptures terminate are essential and crucial to the reliability for the accurate assessments. It is, however, not likely for us to clearly identify the behavioral earthquake segments from observation of surface faulting during the historical period, because most of the active faults have longer recurrence intervals than 1000 years in Japan. Besides uncertainties of the datasets obtained mainly from fault trenching studies are quite large for fault grouping/segmentation. This is why new methods or criteria should be applied for active fault grouping/segmentation, and one of the candidates may be geometric criterion of active faults. Matsuda (1990) used _gfive kilometer_h as a critical distance for grouping and separation of neighboring active faults. On the other hand, Nakata and Goto (1998) proposed the geometric criteria such as (1) branching features of active fault traces and (2) characteristic pattern of vertical-slip distribution along the fault traces as tools to predict rupture length of future earthquakes. The branching during the fault rupture propagation is regarded as an effective energy dissipation process and could result in final rupture termination. With respect to the characteristic pattern of vertical-slip distribution, especially with strike-slip components, the up-thrown sides along the faults are, in general, located on the fault blocks in the direction of relative strike-slip. Applying these new geometric criteria to the high-resolution active fault distribution maps, the fault grouping/segmentation could be more practically conducted. We tested this model

  7. Principal fault zone width and permeability of the active Neodani fault, Nobi fault system, Southwest Japan

    NASA Astrophysics Data System (ADS)

    Tsutsumi, A.; Nishino, S.; Mizoguchi, K.; Hirose, T.; Uehara, S.; Sato, K.; Tanikawa, W.; Shimamoto, T.

    2004-02-01

    The internal structure and permeability of the Neodani fault, which was last activated at the time of the 1891 Nobi earthquake (M8.0), were examined through field survey and experiments. A new exposure of the fault at a road construction site reveals a highly localized feature of the past fault deformation within a narrow fault core zone. The fault of the area consists of three zone units towards the fault core: (a) protolith rocks; (b) 15 to 30 m of fault breccia, and (c) 200 mm green to black fault gouge. Within the fault breccia zone, cataclastic foliation oblique to the fault has developed in a fine-grained 2-m-wide zone adjacent to the fault. Foliation is defined by subparallel alignment of intact lozenge shaped clasts, or by elongated aggregates of fine-grained chert fragments. The mean angle of 20°, between the foliation and the fault plane suggests that the foliated breccia accommodated a shear strain of γ<5 assuming simple shear for the rotation of the cataclastic foliation. Previous trench surveys have revealed that the fault has undergone at least 70 m of fault displacement within the last 20,000 years in this locality. The observed fault geometry suggests that past fault displacements have been localized into the 200-mm-wide gouge zone. Gas permeability analysis of the gouges gives low values of the order of 10 -20 m 2. Water permeability as low as 10 -20 m 2 is therefore expected for the fault gouge zone, which is two orders of magnitude lower than the critical permeability suggested for a fault to cause thermal pressurization during a fault slip.

  8. The property of fault zone and fault activity of Shionohira Fault, Fukushima, Japan

    NASA Astrophysics Data System (ADS)

    Seshimo, K.; Aoki, K.; Tanaka, Y.; Niwa, M.; Kametaka, M.; Sakai, T.; Tanaka, Y.

    2015-12-01

    The April 11, 2011 Fukushima-ken Hamadori Earthquake (hereafter the 4.11 earthquake) formed co-seismic surface ruptures trending in the NNW-SSE direction in Iwaki City, Fukushima Prefecture, which were newly named as the Shionohira Fault by Ishiyama et al. (2011). This earthquake was characterized by a westward dipping normal slip faulting, with a maximum displacement of about 2 m (e.g., Kurosawa et al., 2012). To the south of the area, the same trending lineaments were recognized to exist even though no surface ruptures occurred by the earthquake. In an attempt to elucidate the differences of active and non-active segments of the fault, this report discusses the results of observation of fault outcrops along the Shionohira Fault as well as the Coulomb stress calculations. Only a few outcrops have basement rocks of both the hanging-wall and foot-wall of the fault plane. Three of these outcrops (Kyodo-gawa, Shionohira and Betto) were selected for investigation. In addition, a fault outcrop (Nameishi-minami) located about 300 m south of the southern tip of the surface ruptures was investigated. The authors carried out observations of outcrops, polished slabs and thin sections, and performed X-ray diffraction (XRD) to fault materials. As a result, the fault zones originating from schists were investigated at Kyodo-gawa and Betto. A thick fault gouge was cut by a fault plane of the 4.11 earthquake in each outcrop. The fault materials originating from schists were fault bounded with (possibly Neogene) weakly deformed sandstone at Shionohira. A thin fault gouge was found along the fault plane of 4.11 earthquake. A small-scale fault zone with thin fault gouge was observed in Nameishi-minami. According to XRD analysis, smectite was detected in the gouges from Kyodo-gawa, Shionohira and Betto, while not in the gouge from Nameishi-minami.

  9. Loading of the San Andreas fault by flood-induced rupture of faults beneath the Salton Sea

    USGS Publications Warehouse

    Brothers, Daniel; Kilb, Debi; Luttrell, Karen; Driscoll, Neal W.; Kent, Graham

    2011-01-01

    The southern San Andreas fault has not experienced a large earthquake for approximately 300 years, yet the previous five earthquakes occurred at ~180-year intervals. Large strike-slip faults are often segmented by lateral stepover zones. Movement on smaller faults within a stepover zone could perturb the main fault segments and potentially trigger a large earthquake. The southern San Andreas fault terminates in an extensional stepover zone beneath the Salton Sea—a lake that has experienced periodic flooding and desiccation since the late Holocene. Here we reconstruct the magnitude and timing of fault activity beneath the Salton Sea over several earthquake cycles. We observe coincident timing between flooding events, stepover fault displacement and ruptures on the San Andreas fault. Using Coulomb stress models, we show that the combined effect of lake loading, stepover fault movement and increased pore pressure could increase stress on the southern San Andreas fault to levels sufficient to induce failure. We conclude that rupture of the stepover faults, caused by periodic flooding of the palaeo-Salton Sea and by tectonic forcing, had the potential to trigger earthquake rupture on the southern San Andreas fault. Extensional stepover zones are highly susceptible to rapid stress loading and thus the Salton Sea may be a nucleation point for large ruptures on the southern San Andreas fault.

  10. Erosion influences the seismicity of active thrust faults.

    PubMed

    Steer, Philippe; Simoes, Martine; Cattin, Rodolphe; Shyu, J Bruce H

    2014-11-21

    Assessing seismic hazards remains one of the most challenging scientific issues in Earth sciences. Deep tectonic processes are classically considered as the only persistent mechanism driving the stress loading of active faults over a seismic cycle. Here we show via a mechanical model that erosion also significantly influences the stress loading of thrust faults at the timescale of a seismic cycle. Indeed, erosion rates of about ~0.1-20 mm yr(-1), as documented in Taiwan and in other active compressional orogens, can raise the Coulomb stress by ~0.1-10 bar on the nearby thrust faults over the inter-seismic phase. Mass transfers induced by surface processes in general, during continuous or short-lived and intense events, represent a prominent mechanism for inter-seismic stress loading of faults near the surface. Such stresses are probably sufficient to trigger shallow seismicity or promote the rupture of deep continental earthquakes up to the surface.

  11. Active, capable, and potentially active faults - a paleoseismic perspective

    USGS Publications Warehouse

    Machette, M.N.

    2000-01-01

    Maps of faults (geologically defined source zones) may portray seismic hazards in a wide range of completeness depending on which types of faults are shown. Three fault terms - active, capable, and potential - are used in a variety of ways for different reasons or applications. Nevertheless, to be useful for seismic-hazards analysis, fault maps should encompass a time interval that includes several earthquake cycles. For example, if the common recurrence in an area is 20,000-50,000 years, then maps should include faults that are 50,000-100,000 years old (two to five typical earthquake cycles), thus allowing for temporal variability in slip rate and recurrence intervals. Conversely, in more active areas such as plate boundaries, maps showing faults that are <10,000 years old should include those with at least 2 to as many as 20 paleoearthquakes. For the International Lithosphere Programs' Task Group II-2 Project on Major Active Faults of the World our maps and database will show five age categories and four slip rate categories that allow one to select differing time spans and activity rates for seismic-hazard analysis depending on tectonic regime. The maps are accompanied by a database that describes evidence for Quaternary faulting, geomorphic expression, and paleoseismic parameters (slip rate, recurrence interval and time of most recent surface faulting). These maps and databases provide an inventory of faults that would be defined as active, capable, and potentially active for seismic-hazard assessments.

  12. InSAR measurements around active faults: creeping Philippine Fault and un-creeping Alpine Fault

    NASA Astrophysics Data System (ADS)

    Fukushima, Y.

    2013-12-01

    Recently, interferometric synthetic aperture radar (InSAR) time-series analyses have been frequently applied to measure the time-series of small and quasi-steady displacements in wide areas. Large efforts in the methodological developments have been made to pursue higher temporal and spatial resolutions by using frequently acquired SAR images and detecting more pixels that exhibit phase stability. While such a high resolution is indispensable for tracking displacements of man-made and other small-scale structures, it is not necessarily needed and can be unnecessarily computer-intensive for measuring the crustal deformation associated with active faults and volcanic activities. I apply a simple and efficient method to measure the deformation around the Alpine Fault in the South Island of New Zealand, and the Philippine Fault in the Leyte Island. I use a small-baseline subset (SBAS) analysis approach (Berardino, et al., 2002). Generally, the more we average the pixel values, the more coherent the signals are. Considering that, for the deformation around active faults, the spatial resolution can be as coarse as a few hundred meters, we can severely 'multi-look' the interferograms. The two applied cases in this study benefited from this approach; I could obtain the mean velocity maps on practically the entire area without discarding decorrelated areas. The signals could have been only partially obtained by standard persistent scatterer or single-look small-baseline approaches that are much more computer-intensive. In order to further increase the signal detection capability, it is sometimes effective to introduce a processing algorithm adapted to the signal of interest. In an InSAR time-series processing, one usually needs to set the reference point because interferograms are all relative measurements. It is difficult, however, to fix the reference point when one aims to measure long-wavelength deformation signals that span the whole analysis area. This problem can be

  13. Deformation Monitoring of AN Active Fault

    NASA Astrophysics Data System (ADS)

    Ostapchuk, A.

    2015-12-01

    The discovery of low frequency earthquakes, slow slip events and other deformation phenomena, new for geophysics, change our understanding of how the energy accumulated in the Earth's crust do release. The new geophysical data make one revise the underlying mechanism of geomechanical processes taking place in fault zones. Conditions for generating different slip modes are still unclear. The most vital question is whether a certain slip mode is intrinsic for a fault or may be controlled by external factors. This work presents the results of two and a half year deformation monitoring of a discontinuity in the zone of the Main Sayanskiy Fault. Main Sayanskiy Fault is right-lateral strike-slip fault. Observations were performed in the tunnel of Talaya seismic station (TLY), Irkutsk region, Russia. Measurements were carried out 70 m away from the entrance of the tunnel, the thickness of overlying rock was about 30 m. Inductive sensors of displacement were mounted at the both sides of a discontinuity, which recorded three components of relative fault side displacement with the accuracy of 0.2 mcm. Temperature variation inside the tunnel didn't exceed 0.5oC during the all period of observations. Important information about deformation properties of an active fault was obtained. A pronounced seasonality of deformation characteristics of discontinuity is observed in the investigated segment of rock. A great number of slow slip events with durations from several hours to several weeks were registered. Besides that alterations of fault deformation characteristics before the megathrust earthquake M9.0 Tohoku Oki 11 March 2011 and reaction to the event itself were detected. The work was supported by the Russian Science Foundation (grant no. 14-17-00719).

  14. Active faults in the Kashmir Valley

    NASA Astrophysics Data System (ADS)

    Shah, A.

    2012-04-01

    The risk of earthquake is ever increasing in mountains along with rapid growth of population and urbanization. Over half a million people died in the last decade due to earthquakes. The devastations of Sumatra and Thai coasts in 2004, of Kashmir and New Orleans in 2005, of SW Java in 2006, of Sumatra again in 2007, W Sichuan and Myanmar in 2008, of Haiti in 2010, Japan, New Zealand and Turkey in 2011, brought enormous damage. The primary step in this regard could be to establish an earthquake risk model. The Kashmir valley is a NW-SE trending oval-shaped inter-mountain basin. A number of low magnitude earthquakes have recently been reported from the border and few inside the Kashmir valley. A number of active reverse faults were identified in this valley using remote sensing images and active geomorphic features. NE dipping reverse faults uplifted the young alluvial fan at the SW side. An active tectonic environment has been created by these reverse faults; sediment filled streams at NE, and uplifted quaternary deposits at SW. These resulted in an overall tilting of the entire Kashmir valley towards NE. Dating of displaced deposits is required to estimate the total convergence along these faults. Broadly, these faults are because of the convergence of Indian plate beneath the Eurasian plate.

  15. Injection-induced seismicity on basement faults including poroelastic stressing

    NASA Astrophysics Data System (ADS)

    Chang, K. W.; Segall, P.

    2016-04-01

    Most significant induced earthquakes occur on faults within the basement beneath sedimentary cover. In this two-dimensional plane strain numerical study, we examine the full poroelastic response of basement faults to fluid injection into overlying strata, considering both (1) the permeability of the fault zone and (2) the hydraulic connectivity of the faults to the target horizon. Given hydraulic and mechanical properties, we compute the spatiotemporal change in Coulomb stress, which we separate into (1) the change in poroelastic stresses Δτs+fΔσn, where Δτs and Δσn are changes in shear and normal stress (Δτs>0 and Δσn>0 both favor slip), and (2) the change in pore pressure fΔp. Pore pressure diffusion into hydraulically connected, permeable faults dominates their mechanical stability. For hydraulically isolated or low-permeability faults, however, poroelastic stresses transmitted to deeper basement levels can trigger slip, even without elevated pore pressure. The seismicity rate on basement fault zones is predicted using the model of Dieterich (1994). High seismicity rates can occur on permeable, hydraulically connected faults due to direct pore pressure diffusion. Lower rates are predicted on isolated steeply dipping normal faults, caused solely by poroelastic stressing. In contrast, seismicity on similarly oriented reverse faults is inhibited.

  16. Fault Segmentation and its Implication to the Evaluation of Future Earthquakes from Active Faults in Japan

    NASA Astrophysics Data System (ADS)

    Awata, Y.; Yoshioka, T.

    2005-12-01

    Segmentation of active faults is essential for the evaluation both of past and future faulting using geologic data from paleoseismological sites. A behavioral segment is defined as the smallest segment of fault having a characteristic history of faulting. More over, we have to estimate the earthquake segments that can be consist of multiple faulting along a system of behavioral segments. Active fault strands in Japan are segmented into behavioral segments based on fault discontinuity of 2-3 km and larger (Active Fault Res. Group, GSJ, 2000), large bend of fault strand and paleoseismicity. 431 behavioral segments, >= 10 km in length and >= 0.1 m/ky in long-term slip-rate, are identified from a database of active faults in Japan, that is constructed at AFRC, GSJ/AIST. The length of the segments is averaged 21 km and approximately 70 km in maximum. Only 8 segments are exceed 45 km in length. These lengths are very similar to those of historical surface ruptures not only in Japan since 1891 Nobi earthquake, but also in other regions having different tectonic setting. According to the scaling law between fault length and amount of displacement of behavioral segment, a maximum length of ca. 70 km can estimate a slip of ca. 14 m. This amount of slip is as large as world largest slip occurred during the 1931 Fuyun earthquake of M 8, 1999 Chichi earthquake of M 7.4 and the 2001 Central Kunlun earthquake of M 7.9 in East Asia. Recent geological and seismological studies on large earthquakes have revealed that multiple-rupturing is very common during large earthquakes. Therefore, evaluation of simultaneous faulting along a system of active faults is indispensable for the estimation of earthquake size. A Matsuda's (1990) idea of "seismogenic faults", that is divided or grouped based on the geometric discontinuity of 5 km, may useful for the best estimation of earthquake segment. The Japanese behavioral segments are grouped into "seismogenic faults", each consists of about 2

  17. 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

  18. Delineation of Urban Active Faults Using Multi-scale Gravity Analysis in Shenzhen, South China

    NASA Astrophysics Data System (ADS)

    Xu, C.; Liu, X.

    2015-12-01

    In fact, many cities in the world are established on the active faults. As the rapid urban development, thousands of large facilities, such as ultrahigh buildings, supersized bridges, railway, and so on, are built near or on the faults, which may change the balance of faults and induce urban earthquake. Therefore, it is significant to delineate effectively the faults for urban planning construction and social sustainable development. Due to dense buildings in urban area, the ordinary approaches to identify active faults, like geological survey, artificial seismic exploration and electromagnetic exploration, are not convenient to be carried out. Gravity, reflecting the mass distribution of the Earth's interior, provides a more efficient and convenient method to delineate urban faults. The present study is an attempt to propose a novel gravity method, multi-scale gravity analysis, for identifying urban active faults and determining their stability. Firstly, the gravity anomalies are decomposed by wavelet multi-scale analysis. Secondly, based on the decomposed gravity anomalies, the crust is layered and the multilayer horizontal tectonic stress is inverted. Lastly, the decomposed anomalies and the inverted horizontal tectonic stress are used to infer the distribution and stability of main active faults. For validating our method, a case study on active faults in Shenzhen City is processed. The results show that the distribution of decomposed gravity anomalies and multilayer horizontal tectonic stress are controlled significantly by the strike of the main faults and can be used to infer depths of the faults. The main faults in Shenzhen may range from 4km to 20km in the depth. Each layer of the crust is nearly equipressure since the horizontal tectonic stress has small amplitude. It indicates that the main faults in Shenzhen are relatively stable and have no serious impact on planning and construction of the city.

  19. Effects induced by an earthquake on its fault plane:a boundary element study

    NASA Astrophysics Data System (ADS)

    Bonafede, Maurizio; Neri, Andrea

    2000-04-01

    Mechanical effects left by a model earthquake on its fault plane, in the post-seismic phase, are investigated employing the `displacement discontinuity method'. Simple crack models, characterized by the release of a constant, unidirectional shear traction are investigated first. Both slip components-parallel and normal to the traction direction-are found to be non-vanishing and to depend on fault depth, dip, aspect ratio and fault plane geometry. The rake of the slip vector is similarly found to depend on depth and dip. The fault plane is found to suffer some small rotation and bending, which may be responsible for the indentation of a transform tectonic margin, particularly if cumulative effects are considered. Very significant normal stress components are left over the shallow portion of the fault surface after an earthquake: these are tensile for thrust faults, compressive for normal faults and are typically comparable in size to the stress drop. These normal stresses can easily be computed for more realistic seismic source models, in which a variable slip is assigned; normal stresses are induced in these cases too, and positive shear stresses may even be induced on the fault plane in regions of high slip gradient. Several observations can be explained from the present model: low-dip thrust faults and high-dip normal faults are found to be facilitated, according to the Coulomb failure criterion, in repetitive earthquake cycles; the shape of dip-slip faults near the surface is predicted to be upward-concave; and the shallower aftershock activity generally found in the hanging block of a thrust event can be explained by `unclamping' mechanisms.

  20. Active Fault Characterization in the Urban Area of Vienna

    NASA Astrophysics Data System (ADS)

    Decker, Kurt; Grupe, Sabine; Hintersberger, Esther

    2016-04-01

    The identification of active faults that lie beneath a city is of key importance for seismic hazard assessment. Fault mapping and characterization in built-up areas with strong anthropogenic overprint is, however, a challenging task. Our study of Quaternary faults in the city of Vienna starts from the re-assessment of a borehole database of the municipality containing several tens of thousands of shallow boreholes. Data provide tight constraints on the geometry of Quaternary deposits and highlight several locations with fault-delimited Middle to Late Pleistocene terrace sediments of the Danube River. Additional information is obtained from geological descriptions of historical outcrops which partly date back to about 1900. The latter were found to be particularly valuable by providing unprejudiced descriptions of Quaternary faults, sometimes with stunning detail. The along-strike continuations of some of the identified faults are further imaged by industrial 2D/3D seismic acquired outside the city limits. The interpretation and the assessment of faults identified within the city benefit from a very well constrained tectonic model of the active Vienna Basin fault system which derived from data obtained outside the city limits. This data suggests that the urban faults are part of a system of normal faults compensating fault-normal extension at a releasing bend of the sinistral Vienna Basin Transfer Fault. Slip rates estimated for the faults in the city are in the range of several hundredths of millimetres per year and match the slip rates of normal faults that were trenched outside the city. The lengths/areas of individual faults estimated from maps and seismic reach up to almost 700 km² suggesting that all of the identified faults are capable of producing earthquakes with magnitudes M>6, some with magnitudes up to M~6.7.

  1. 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.

  2. Illuminating Northern California’s Active Faults

    USGS Publications Warehouse

    Prentice, Carol S.; Crosby, Christopher J.; Whitehill, Caroline S.; Arrowsmith, J. Ramon; Furlong, Kevin P.; Philips, David A.

    2009-01-01

    Newly acquired light detection and ranging (lidar) topographic data provide a powerful community resource for the study of landforms associated with the plate boundary faults of northern California (Figure 1). In the spring of 2007, GeoEarthScope, a component of the EarthScope Facility construction project funded by the U.S. National Science Foundation, acquired approximately 2000 square kilometers of airborne lidar topographic data along major active fault zones of northern California. These data are now freely available in point cloud (x, y, z coordinate data for every laser return), digital elevation model (DEM), and KMZ (zipped Keyhole Markup Language, for use in Google EarthTM and other similar software) formats through the GEON OpenTopography Portal (http://www.OpenTopography.org/data). Importantly, vegetation can be digitally removed from lidar data, producing high-resolution images (0.5- or 1.0-meter DEMs) of the ground surface beneath forested regions that reveal landforms typically obscured by vegetation canopy (Figure 2)

  3. 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

  4. Modeling of fault reactivation and induced seismicity during hydraulic fracturing of shale-gas reservoirs

    SciTech Connect

    Rutqvist, Jonny; Rinaldi, Antonio P.; Cappa, Frédéric; Moridis, George J.

    2013-07-01

    We have conducted numerical simulation studies to assess the potential for injection-induced fault reactivation and notable seismic events associated with shale-gas hydraulic fracturing operations. The modeling is generally tuned towards conditions usually encountered in the Marcellus shale play in the Northeastern US at an approximate depth of 1500 m (~;;4,500 feet). Our modeling simulations indicate that when faults are present, micro-seismic events are possible, the magnitude of which is somewhat larger than the one associated with micro-seismic events originating from regular hydraulic fracturing because of the larger surface area that is available for rupture. The results of our simulations indicated fault rupture lengths of about 10 to 20 m, which, in rare cases can extend to over 100 m, depending on the fault permeability, the in situ stress field, and the fault strength properties. In addition to a single event rupture length of 10 to 20 m, repeated events and aseismic slip amounted to a total rupture length of 50 m, along with a shear offset displacement of less than 0.01 m. This indicates that the possibility of hydraulically induced fractures at great depth (thousands of meters) causing activation of faults and creation of a new flow path that can reach shallow groundwater resources (or even the surface) is remote. The expected low permeability of faults in producible shale is clearly a limiting factor for the possible rupture length and seismic magnitude. In fact, for a fault that is initially nearly-impermeable, the only possibility of larger fault slip event would be opening by hydraulic fracturing; this would allow pressure to penetrate the matrix along the fault and to reduce the frictional strength over a sufficiently large fault surface patch. However, our simulation results show that if the fault is initially impermeable, hydraulic fracturing along the fault results in numerous small micro-seismic events along with the propagation, effectively

  5. Active faults of the Baikal depression

    USGS Publications Warehouse

    Levi, K.G.; Miroshnichenko, A.I.; San'kov, V. A.; Babushkin, S.M.; Larkin, G.V.; Badardinov, A.A.; Wong, H.K.; Colman, S.; Delvaux, D.

    1997-01-01

    The Baikal depression occupies a central position in the system of the basins of the Baikal Rift Zone and corresponds to the nucleus from which the continental lithosphere began to open. For different reasons, the internal structure of the Lake Baikal basin remained unknown for a long time. In this article, we present for the first time a synthesis of the data concerning the structure of the sedimentary section beneath Lake Baikal, which were obtained by complex seismic and structural investigations, conducted mainly from 1989 to 1992. We make a brief description of the most interesting seismic profiles which provide a rough idea of a sedimentary unit structure, present a detailed structural interpretation and show the relationship between active faults in the lake, heat flow anomalies and recent hydrothermalism.

  6. Active oblique ramp faulting in the Southern Tunisian Atlas

    NASA Astrophysics Data System (ADS)

    Saïd, Aymen; Chardon, Dominique; Baby, Patrice; Ouali, Jamel

    2011-03-01

    The Gafsa fault is the longest and most active structure of the fold-and-thrust belt achieving southeastward propagation of the Atlas belt of Eastern North Africa onto the Saharan platform. The Gafsa fault is a 75-km long dextral-oblique basement fault ramp that poses a sizable challenge in earthquake hazard assessment because the post-Paleozoic sedimentary cover is decoupled from its basement above the basement fault. In this study, we combine seismic lines interpretation, tectonic geomorphology and paleoseismological investigations to assess the level of seismic hazard of this fault and evaluate its role in the geodynamic framework of the Central Mediterranean. We show that despite a moderate instrumental and historical seismicity, the fault has produced M ≥ 6 earthquakes with a return period of ca. 500-5000 years during the Late Quaternary. The latest large event having produced a surface rupture on the fault occurred around 8000 yr BP, suggesting an M ≥ 6 earthquake is overdue on the fault. The fault has a minimum reverse component of slip rate of 0.21-0.34 mm/yr over the past 50 Ka. The occurrence of M ≥ 7 paleoearthquakes on the fault may be suspected but not established. Such very strong earthquakes would require transient coseismic linkage of the buried basement fault with the overlying listric fault ramping off the décollement layer. The level of seismic hazard may be underestimated on the Gafsa fault. Indeed, given the geometry of the basement-cover fault system, a number of earthquakes generated in the basement would have led to coseismic surface folding instead of to surface rupture. The Gafsa fault is a major structure accommodating eastward extrusion / spreading of the Atlas belt onto the Saharan and Pelagian plateforms above the retreating Ionian lithospheric slab.

  7. Significance of active growth faulting on marsh accretion processes in the lower Pearl River, Louisiana

    NASA Astrophysics Data System (ADS)

    Yeager, Kevin M.; Brunner, Charlotte A.; Kulp, Mark A.; Fischer, Dane; Feagin, Rusty A.; Schindler, Kimberly J.; Prouhet, Jeremiah; Bera, Gopal

    2012-06-01

    Neotectonic processes influence marsh accretion in the lower Pearl River valley. Active growth faults are suggested by groupings of ponded river channel sections, transverse and linear river channel sections, and down- and across-valley contrasts in channel sinuosity. Seismic profiles identified several likely, fault-induced structural anomalies, two of which parallel the axes of surface distributary networks. Lithostratigraphy and biostratigraphy of six cores from across a suspected fault in the West Middle River, combined with 14C-based age control, yielded evidence of vertical offsets, indicating that this river section is on the plane of a growth fault. These data were used to estimate fault slip rates over two time intervals, 1.2 mm/y over the last 1300 yr, and 0.2 mm yr- 1 over the last 3700 yr, and delineated a sinusoidal pattern of deformation moving distally from the fault, which we interpret as resulting from fault-propagation folding. Higher rates of sediment accumulation (of the order of cm yr- 1 from 210Pbxs and 137Cs activity data) on the down-thrown side are consistent with sedimentary response to increased accommodation space, and mass-based sediment accumulation rates (g cm- 2 yr- 1) exhibit a pattern inverse of that shown by fault-driven sinusoidal deformation. We contend that near-surface growth faults are critically important to driving accretion rates and marsh response to sea-level rise.

  8. Upper Pleistocene - Holocene activity of the Carrascoy Fault (Murcia, SE Spain): preliminary results from paleoseismological research.

    NASA Astrophysics Data System (ADS)

    Martin-Banda, Raquel; Garcia-Mayordomo, Julian; Insua-Arevalo, Juan M.; Salazar, Angel; Rodriguez-Escudero, Emilio; Alvarez-Gomez, Jose A.; Martinez-Diaz, Jose J.; Herrero, Maria J.; Medialdea, Alicia

    2014-05-01

    The Carrascoy Fault is located in the Internal Zones of the Betic Cordillera (Southern Spain). In particular, the Carrascoy Fault is one of the major faults forming the Eastern Betic Shear Zone, the main structure accommodating the convergence between Nubian and Eurasian plates in the westernmost Mediterranean. So far, the Carrascoy Fault has been defined as a left-lateral strike-slip fault. It extends for at least 31 km in a NE-SW trend from the village of Zeneta (Murcia) at its northeastern tip, to the Cañaricos village, controlling the northern edge of the Carrascoy Range and its linkage to the Guadalentin Depression towards the southwest. This is an area of moderate seismic activity, but densely populated, the capital of the region, Murcia, being settled very close to the fault. Hence, the knowledge of the structure and kinematics of the Carrascoy Fault is essential for assessing reliably the seismic hazard of the region. We present a detailed-scale geological and geomorphological map along the fault zone created from a LIDAR DEM combined with fieldwork, and geological and geophysical information. Furthermore, a number of trenches have been dug across the fault at different locations providing insights in the fault most recent activity as well as paleoseismic data. Preliminary results suggest that the Cararscoy Fault has recently changed its kinematic showing a near pure reverse motion. According to this, the fault can be divided into two distinct segments, the eastern one: Zeneta - Fuensanta, and the western one: Fuensanta - Cañaricos, each one having its own characteristic style and geodynamics. Some new active strands of the fault locate at the foot of the very first relief towards the North of the older strand, forming the current southern border of the Guadalentin Depression. These new faults show an increasingly reverse component westwards, so that the Fuensanta - Cañaricos segment is constituted by thrusts, which are blind at its western end

  9. Faulting processes in active faults - Evidences from TCDP and SAFOD drill core samples

    SciTech Connect

    Janssen, C.; Wirth, R.; Wenk, H. -R.; Morales, L.; Naumann, R.; Kienast, M.; Song, S. -R.; Dresen, G.

    2014-08-20

    The microstructures, mineralogy and chemistry of representative samples collected from the cores of the San Andreas Fault drill hole (SAFOD) and the Taiwan Chelungpu-Fault Drilling project (TCDP) have been studied using optical microscopy, TEM, SEM, XRD and XRF analyses. SAFOD samples provide a transect across undeformed host rock, the fault damage zone and currently active deforming zones of the San Andreas Fault. TCDP samples are retrieved from the principal slip zone (PSZ) and from the surrounding damage zone of the Chelungpu Fault. Substantial differences exist in the clay mineralogy of SAFOD and TCDP fault gouge samples. Amorphous material has been observed in SAFOD as well as TCDP samples. In line with previous publications, we propose that melt, observed in TCDP black gouge samples, was produced by seismic slip (melt origin) whereas amorphous material in SAFOD samples was formed by comminution of grains (crush origin) rather than by melting. Dauphiné twins in quartz grains of SAFOD and TCDP samples may indicate high seismic stress. The differences in the crystallographic preferred orientation of calcite between SAFOD and TCDP samples are significant. Microstructures resulting from dissolution–precipitation processes were observed in both faults but are more frequently found in SAFOD samples than in TCDP fault rocks. As already described for many other fault zones clay-gouge fabrics are quite weak in SAFOD and TCDP samples. Clay-clast aggregates (CCAs), proposed to indicate frictional heating and thermal pressurization, occur in material taken from the PSZ of the Chelungpu Fault, as well as within and outside of the SAFOD deforming zones, indicating that these microstructures were formed over a wide range of slip rates.

  10. 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.

  11. 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

  12. Paper 58714 - Exploring activated faults hydromechanical processes from semi-controled field injection experiments

    NASA Astrophysics Data System (ADS)

    Guglielmi, Y.; Cappa, F.; Nussbaum, C.

    2015-12-01

    The appreciation of the sensitivity of fractures and fault zones to fluid-induced-deformations in the subsurface is a key question in predicting the reservoir/caprock system integrity around fluid manipulations with applications to reservoir leakage and induced seismicity. It is also a question of interest in understanding earthquakes source, and recently the hydraulic behavior of clay faults under a potential reactivation around nuclear underground depository sites. Fault and fractures dynamics studies face two key problems (1) the up-scaling of laboratory determined properties and constitutive laws to the reservoir scale which is not straightforward when considering faults and fractures heterogeneities, (2) the difficulties to control both the induced seismicity and the stimulated zone geometry when a fault is reactivated. Using instruments dedicated to measuring coupled pore pressures and deformations downhole, we conducted field academic experiments to characterize fractures and fault zones hydromechanical properties as a function of their multi-scale architecture, and to monitor their dynamic behavior during the earthquake nucleation process. We show experiments on reservoir or cover rocks analogues in underground research laboratories where experimental conditions can be optimized. Key result of these experiments is to highlight how important the aseismic fault activation is compared to the induced seismicity. We show that about 80% of the fault kinematic moment is aseismic and discuss the complex associated fault friction coefficient variations. We identify that the slip stability and the slip velocity are mainly controlled by the rate of the permeability/porosity increase, and discuss the conditions for slip nucleation leading to seismic instability.

  13. 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

  14. An induced seismicity experiment across a creeping segment of the Philippine Fault

    NASA Astrophysics Data System (ADS)

    Prioul, R.; Cornet, F. H.; Dorbath, C.; Dorbath, L.; Ogena, M.; Ramos, E.

    2000-06-01

    The location of seismicity induced by forced fluid flow provides information about domains of pore pressure variation, while changes in fluid content are identified through changes in seismic velocity. These effects have been investigated in the geothermal field of Tongonan, which lies on a creeping portion of the Philippine Fault on Ley te Island. Locally, the left-lateral strike-slip Philippine Fault branches out into three subparallel segments (Eastern, Central and Western Fault Lines). In June-July 1997, a water stimulation was undertaken in a well that intersects the Central Fault Line 1980 m below ground surface; 36,000 m3 were injected between the casing shoe at 1308 m and the well bottom at 2177 m. The seismicity was monitored with a surface station network of 18 stations. More than 400 events, induced by the injection experiment as well as by routine injections associated with the geothermal field exploitation, were recorded in the vicinity of the well. They have been located through a simultaneous three-dimensional (3-D) velocity-hypocenter inversion procedure. None of the microearthquakes are located along the Central Fault Line, they all occurred below the casing shoe to the east of the fault line, i.e., within the geothermal reservoir and mostly below the bottom of the well. Results from the injection experiment and the 18 months of seismic monitoring along the Central and West Fault Lines suggest an aseismic behavior of this major continental fault at this location. The 3-D velocity model, determined from the travel time inversion for seismic events observed during injections, is compared to that obtained from seismic monitoring conducted prior to any injection activities. An increase of P wave velocity is observed during the water injection. This velocity increase is localized within the seismicity cloud and is interpreted as an increase in liquid content within the initial liquid-vapor multiphase part of the reservoir.

  15. Research of Earthquake Potential from Active Fault Observation in Taiwan

    NASA Astrophysics Data System (ADS)

    Chien-Liang, C.; Hu, J. C.; Liu, C. C.; En, C. K.; Cheng, T. C. T.

    2015-12-01

    We utilize GAMIT/GLOBK software to estimate the precise coordinates for continuous GPS (CGPS) data of Central Geological Survey (CGS, MOEA) in Taiwan. To promote the software estimation efficiency, 250 stations are divided by 8 subnets which have been considered by station numbers, network geometry and fault distributions. Each of subnets include around 50 CGPS and 10 international GNSS service (IGS) stations. After long period of data collection and estimation, a time series variation can be build up to study the effect of earthquakes and estimate the velocity of stations. After comparing the coordinates from campaign-mode GPS sites and precise leveling benchmarks with the time series from continuous GPS stations, the velocity field is consistent with previous measurement which show the reliability of observation. We evaluate the slip rate and slip deficit rate of active faults in Taiwan by 3D block model DEFNODE. First, to get the surface fault traces and the subsurface fault geometry parameters, and then establish the block boundary model of study area. By employing the DEFNODE technique, we invert the GPS velocities for the best-fit block rotate rates, long term slip rates and slip deficit rates. Finally, the probability analysis of active faults is to establish the flow chart of 33 active faults in Taiwan. In the past two years, 16 active faults in central and northern Taiwan have been assessed to get the recurrence interval and the probabilities for the characteristic earthquake occurred in 30, 50 and 100 years.

  16. GPR measurements to assess the Emeelt active fault's characteristics in a highly smooth topographic context, Mongolia

    NASA Astrophysics Data System (ADS)

    Dujardin, Jean-Rémi; Bano, Maksim; Schlupp, Antoine; Ferry, Matthieu; Munkhuu, Ulziibat; Tsend-Ayush, Nyambayar; Enkhee, Bayarsaikhan

    2014-07-01

    To estimate the seismic hazard, the geometry (dip, length and orientation) and the dynamics (type of displacements and amplitude) of the faults in the area of interest need to be understood. In this paper, in addition to geomorphologic observations, we present the results of two ground penetrating radar (GPR) campaigns conducted in 2010 and 2011 along the Emeelt fault in the vicinity of Ulaanbaatar, capital of Mongolia, located in an intracontinental region with low deformation rate that induces long recurrence time between large earthquakes. As the geomorphology induced by the fault activity has been highly smoothed by erosion processes since the last event, the fault location and geometry is difficult to determine precisely. However, by using GPR first, a non-destructive and fast investigation, the fault and the sedimentary deposits near the surface can be characterized and the results can be used for the choice of trench location. GPR was performed with a 50 MHz antenna over 2-D lines and with a 500 MHz antenna for pseudo-3-D surveys. The 500 MHz GPR profiles show a good consistency with the trench observations, dug next to the pseudo-3-D surveys. The 3-D 500 MHz GPR imaging of a palaeochannel crossed by the fault allowed us to estimate its lateral displacement to be about 2 m. This is consistent with a right lateral strike-slip displacement induced by an earthquake around magnitude 7 or several around magnitude 6. The 2-D 50 MHz profiles, recorded perpendicular to the fault, show a strong reflection dipping to the NE, which corresponds to the fault plane. Those profiles provided complementary information on the fault such as its location at shallow depth, its dip angle (from 23° to 35°) and define its lateral extension.

  17. Geodynamics of the Dead Sea Fault: Do active faulting and past earthquakes determine the seismic gaps?

    NASA Astrophysics Data System (ADS)

    Meghraoui, Mustapha

    2014-05-01

    The ~1000-km-long North-South trending Dead Sea transform fault (DSF) presents structural discontinuities and includes segments that experienced large earthquakes (Mw>7) in historical times. The Wadi Araba and Jordan Valley, the Lebanese restraining bend, the Missyaf and Ghab fault segments in Syria and the Ziyaret Fault segment in Turkey display geometrical complexities made of step overs, restraining and releasing bends that may constitute major obstacles to earthquake rupture propagation. Using active tectonics, GPS measurements and paleoseismology we investigate the kinematics and long-term/short term slip rates along the DSF. Tectonic geomorphology with paleoseismic trenching and archeoseismic investigations indicate repeated faulting events and left-lateral slip rate ranging from 4 mm/yr in the southern fault section to 6 mm/yr in the northern fault section. Except for the northernmost DSF section, these estimates of fault slip rate are consistent with GPS measurements that show 4 to 5 mm/yr deformation rate across the plate boundary. However, recent GPS results showing ~2.5 mm/yr velocity rate of the northern DSF appears to be quite different than the ~6 mm/yr paleoseismic slip rate. The kinematic modeling that combines GPS and seismotectonic results implies a complex geodynamic pattern where the DSF transforms the Cyprus arc subduction zone into transpressive tectonics on the East Anatolian fault. The timing of past earthquake ruptures shows the occurrence of seismic sequences and a southward migration of large earthquakes, with the existence of major seismic gaps along strike. In this paper, we discuss the role of the DSF in the regional geodynamics and its implication on the identification of seismic gaps.

  18. Challenges and perspectives in the geological study of active faults.

    NASA Astrophysics Data System (ADS)

    Rizza, M.

    2011-12-01

    Identification of active faults is important for understanding regional seismicity and seismic hazard. A large part of the world's population lives in areas where destructive earthquakes or tsunamis were recorded in the past. Most of the difficulties in estimating seismic hazard and anticipating earthquakes are due to a lack of knowledge about the location of active faults and their seismic history. Even where active faults are known the characteristics of past earthquakes and the seismic cycle are uncertain and subject to discussion. Investigations carried out on active faults during the past decade, however, have provided new high-quality data and powerful tools to better understand crustal deformation and the recurrence of earthquakes. In morphotectonic studies, the ever-improving resolution of satellites images allows geologists to identify with more certainty the traces of active faults and even earthquake surface ruptures of the past. The advantage of satellite imagery for identifying neotectonic features is it gives access to large areas, sometimes difficult to reach in the field and provides synoptic views. Using the potential of high-resolution imagery and digital elevation models, geologists can produce detailed 3D reconstructions of fault morphology and geometry, including the kinematics of repeated slip. The development of new dating techniques, coupled with paleoseismology and quantitative geomorphology, now allows bracketing the occurrence of paleoearthquakes back to several thousand years, as well as analyzing long time sequences of events. Despite such wealth of new data, however, the work remaining to do is huge. Earthquake forecast (location, timing, magnitude) remains an unsolved problem for the earthquake community at large (seismologists, geodesists, paleoseismologists and modelers). The most important challenges in the next decade will be to increase the efficiency of neotectonic studies to create more complete active fault databases and

  19. Max Magnitude of Induced Seismic Events Within CCS Projects, Related to the Permeability of Faults

    NASA Astrophysics Data System (ADS)

    Mazzoldi, A.; Rinaldi, A. P.; Rutqvist, J.

    2011-12-01

    The evaluation of the potential for induced seismicity and its effects on the surface is critical for public acceptance of geologic carbon sequestration. According to the Coulomb criterion, τ = C + μ (σn - p), seismic events can be induced by reactivation of existing faults due to enhancement in pore pressure (p) when the left-hand term (shear stress) of the equation is equal to or greater than the right-hand side (shear strength). However, large uncertainties exist in the values of in situ stress (σn) and fault properties; plus, faults may be below the detection limit and not identified prior to the start of a CO2 injection. In this study we discuss methods for bounding the earthquake magnitudes that could be induced during CO2 injection, focusing the attention on buried, undetectable faults (D < 10 m). We evaluate the maximum magnitude of a seismic event potentially due to a fault with these characteristics, theoretically, using empirical magnitude-versus-size formulas and allowing the whole fault plane to slip, and with the aid of a coupled multiphase fluid flow and geo-mechanical numerical model, for investigating the degree of conservatisms in the empirical approach. Faults can also act as preferential leaking paths, for brine and CO2, in a CCS reservoir. Permeability of fault planes during and after slip is a parameter that needs to be estimated in order to run computer-based simulations on the hydro-mechanical response of geological features to a pressure buildup due to a fluid injection. This parameter is variable and it can range between values orders of magnitude higher than the seal rocks, and comparable with this last. Both cases are present in nature: if on the one hand fluid flow through fractures and fault planes is the main path for water in intrusive rocks, on the other hand, over-pressurized porous reservoirs are easily found in sedimentary basins, bounded by growth-faults (Ref, ref). These last are known to be mechanically active, presenting

  20. 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; Moridis, George J.

    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

  1. Modeling of fault activation and seismicity by injection directly into a fault zone associated with hydraulic fracturing of shale-gas reservoirs

    SciTech Connect

    Rutqvist, Jonny; Rinaldi, Antonio P.; Cappa, Frédéric; Moridis, George J.

    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 seismic 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.

  2. Evolution of fault activity reflecting the crustal deformation: Insights from crustal stress and fault orientations in the northeast-southwest Japan

    NASA Astrophysics Data System (ADS)

    Miyakawa, A.; Otsubo, M.

    2015-12-01

    We evaluated fault activity in northeast- southwest Japan based on the regional stress and the fault orientation field for both active faults and inactive faults (here, an inactive fault is a fault which activity has not been identified in Quaternary). The regional stress field was calculated using the stress inversion method [Hardebeck and Michael, 2006] applied to earthquake focal mechanisms in the northeast-southwest Japan. The locations and orientations (i.e., strike and dip, assuming a planar fault geometry) of active faults in the study area were obtained from the Active Fault Database of Japan and inactive faults from a database compiled by Kosaka et al. [2011]. We employed slip tendency analysis [Morris et al., 1996] to evaluate the likelihood of fault slip. The values of the slip tendency is generally higher along active faults than along inactive faults. The difference between the slip tendencies of active and inactive faults reflects the difference in their activities. Furthermore the high slip tendency observed for some inactive faults suggests their high activity. These high slip tendencies imply that they have potential to be active. We propose the temporal evolution from inactive to active faulting during long-term crustal deformation to explain the potential for fault activity along inactive faults. When a region undergoes the transition from inactive to active faulting, potential active faults are observed as inactive faults with a high Part of this findig have been submitted to Tectonics (AGU Journal) (2015-07-27). We will presentate some new findings.slip tendency. The average slip tendency of inactive faults gradually increases from northeast to southwest Japan, because a relatively large number of inactive faults in southwest Japan have a high slip tendency. The representative deformation zones in Japan shows a relationship with the observed spatial variations in the evolution from inactive to active faulting. This study was supported by MEXT

  3. Active fault database of Japan: Its construction and search system

    NASA Astrophysics Data System (ADS)

    Yoshioka, T.; Miyamoto, F.

    2011-12-01

    The Active fault database of Japan was constructed by the Active Fault and Earthquake Research Center, GSJ/AIST and opened to the public on the Internet from 2005 to make a probabilistic evaluation of the future faulting event and earthquake occurrence on major active faults in Japan. The database consists of three sub-database, 1) sub-database on individual site, which includes long-term slip data and paleoseismicity data with error range and reliability, 2) sub-database on details of paleoseismicity, which includes the excavated geological units and faulting event horizons with age-control, 3) sub-database on characteristics of behavioral segments, which includes the fault-length, long-term slip-rate, recurrence intervals, most-recent-event, slip per event and best-estimate of cascade earthquake. Major seismogenic faults, those are approximately the best-estimate segments of cascade earthquake, each has a length of 20 km or longer and slip-rate of 0.1m/ky or larger and is composed from about two behavioral segments in average, are included in the database. This database contains information of active faults in Japan, sorted by the concept of "behavioral segments" (McCalpin, 1996). Each fault is subdivided into 550 behavioral segments based on surface trace geometry and rupture history revealed by paleoseismic studies. Behavioral segments can be searched on the Google Maps. You can select one behavioral segment directly or search segments in a rectangle area on the map. The result of search is shown on a fixed map or the Google Maps with information of geologic and paleoseismic parameters including slip rate, slip per event, recurrence interval, and calculated rupture probability in the future. Behavioral segments can be searched also by name or combination of fault parameters. All those data are compiled from journal articles, theses, and other documents. We are currently developing a revised edition, which is based on an improved database system. More than ten

  4. 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.

  5. Evaluation of feasibility of mapping seismically active faults in Alaska

    NASA Technical Reports Server (NTRS)

    Gedney, L. D.; Vanwormer, J. D. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. The sharp bend in the Alaska Range near 65 deg N, 150 deg W in now thought to enclose a corner of the northwesterly migrating north Pacific lithospheric plate. Subduction of the plate beneath the continent is believed, on the basis of hypocentral distribution, to occur along Cook Inlet and the eastern flanks of the Aleutian and Alaska Ranges as far northward as Mt. McKinley. The nature of tectonic deformation here, particularly in the area of the bend in the Alaska Range, is understandably complex. The Denali fault is thought to be a transform character in the vicinity of Mt. McKinley (i.e., it is thought to be the surface along which the oceanic plate separates from the continental plate). On the ERTS-1 imagery, however, it appears that there are a number of sub-parallel faults which branch off of the Denali fault in a southwesterly direction. Slippage along these would tend to squeeze material around the inside of the band rather than the plate being directly underthrust. All of these sub-parallel faults are seismically active. The right-lateral fault-plane solution obtained for this event is consistent with the concept of slippage around the bend on a set of sub-parallel faults in the manner postulated. The best images to show these features are 1066-20444 and 1266-20572.

  6. Fault geometries in basement-induced wrench faulting under different initial stress states

    NASA Astrophysics Data System (ADS)

    Naylor, M. A.; Mandl, G.; Supesteijn, C. H. K.

    Scaled sandbox experiments were used to generate models for relative ages, dip, strike and three-dimensional shape of faults in basement-controlled wrench faulting. The basic fault sequence runs from early en échelon Riedel shears and splay faults through 'lower-angle' shears to P shears. The Riedel shears are concave upwards and define a tulip structure in cross-section. In three dimensions, each Riedel shear has a helicoidal form. The sequence of faults and three-dimensional geometry are rationalized in terms of the prevailing stress field and Coulomb-Mohr theory of shear failure. The stress state in the sedimentary overburden before wrenching begins has a substantial influence on the fault geometries and on the final complexity of the fault zone. With the maximum compressive stress (∂ 1) initially parallel to the basement fault (transtension), Riedel shears are only slightly en échelon, sub-parallel to the basement fault, steeply dipping with a reduced helicoidal aspect. Conversely, with ∂ 1 initially perpendicular to the basement fault (transpression), Riedel shears are strongly oblique to the basement fault strike, have lower dips and an exaggerated helicoidal form; the final fault zone is both wide and complex. We find good agreement between the models and both mechanical theory and natural examples of wrench faulting.

  7. Active tectonics west of New Zealand's Alpine Fault: South Westland Fault Zone activity shows Australian Plate instability

    NASA Astrophysics Data System (ADS)

    De Pascale, Gregory P.; Chandler-Yates, Nicholas; Dela Pena, Federico; Wilson, Pam; May, Elijah; Twiss, Amber; Cheng, Che

    2016-04-01

    The 300 km long South Westland Fault Zone (SWFZ) is within the footwall of the Central Alpine Fault (<20 km away) and has 3500 m of dip-slip displacement, but it has been unknown if the fault is active. Here the first evidence for SWFZ thrust faulting in the "stable" Australian Plate is shown with cumulative dip-slip displacements up to 5.9 m (with 3 m throw) on Pleistocene and Holocene sediments and gentle hanging wall anticlinal folding. Cone penetration test (CPT) stratigraphy shows repeated sequences within the fault scarp (consistent with thrusting). Optically stimulated luminescence (OSL) dating constrains the most recent rupture post-12.1 ± 1.7 ka with evidence for three to four events during earthquakes of at least Mw 6.8. This study shows significant deformation is accommodated on poorly characterized Australian Plate structures northwest of the Alpine Fault and demonstrates that major active and seismogenic structures remain uncharacterized in densely forested regions on Earth.

  8. Neogene exhumation in the eastern Alaska Range and its relationship to splay fault activity in the Denali fault system

    NASA Astrophysics Data System (ADS)

    Waldien, T.; Roeske, S.; Benowitz, J.; Allen, W. K.; Ridgway, K.

    2015-12-01

    Dextral oblique convergence in the Denali fault system results from subduction zone strain in the Alaska syntaxis that is partitioned into the upper plate. This convergence is accommodated by dextral-reverse oblique slip on segments of the main strand of the Denali fault in the center of the Alaska Range and by splay faults north and south of the Denali fault at the margins of the Alaska Range. Low-temp. thermochronometry applied to basement rocks bounded by faults within the Denali fault system aids stratigraphic data to determine the timing and locations of exhumation in the Alaska Range, which augment regional seismicity studies aimed at resolving modern fault activity in the Denali fault system. The McCallum Creek and Broxson Gulch faults are north-dipping faults that splay southward from the Denali fault near the Delta River and mark the southern margin of the eastern Alaska Range. Apatite fission track thermochronometry on rocks north of the McCallum Creek fault shows rapid cooling in the hanging wall coeval with basin development in the footwall initiating at the Miocene-Pliocene boundary. Apatite fission track and apatite (U-Th)/He ages from plutonic rocks in the hanging wall of the Broxson Gulch fault, west of the McCallum Creek fault, show final cooling in the Miocene, slightly younger than hanging wall cooling associated with the Susitna Glacier thrust further to the west. Neogene low-temp. cooling ages in the hanging walls of the Susitna Glacier thrust, Broxson Gulch, and McCallum Creek faults suggest that these structures have been accommodating convergence in the Denali fault system throughout the Neogene. More recent cooling in the hanging wall of the McCallum Creek compared to the Susitna Glacier thrust suggests that this fault-related exhumation has migrated eastward throughout the Neogene. Convergence on these splay faults south of the Denali fault results in internal contraction of the crust south of the Denali fault, implying that the Southern

  9. Contradicting Estimates of Location, Geometry, and Rupture History of Highly Active Faults in Central Japan

    NASA Astrophysics Data System (ADS)

    Okumura, K.

    2011-12-01

    Accurate location and geometry of seismic sources are critical to estimate strong ground motion. Complete and precise rupture history is also critical to estimate the probability of the future events. In order to better forecast future earthquakes and to reduce seismic hazards, we should consider over all options and choose the most likely parameter. Multiple options for logic trees are acceptable only after thorough examination of contradicting estimates and should not be a result from easy compromise or epoche. In the process of preparation and revisions of Japanese probabilistic and deterministic earthquake hazard maps by Headquarters for Earthquake Research Promotion since 1996, many decisions were made to select plausible parameters, but many contradicting estimates have been left without thorough examinations. There are several highly-active faults in central Japan such as Itoigawa-Shizuoka Tectonic Line active fault system (ISTL), West Nagano Basin fault system (WNBF), Inadani fault system (INFS), and Atera fault system (ATFS). The highest slip rate and the shortest recurrence interval are respectively ~1 cm/yr and 500 to 800 years, and estimated maximum magnitude is 7.5 to 8.5. Those faults are very hazardous because almost entire population and industries are located above the fault within tectonic depressions. As to the fault location, most uncertainties arises from interpretation of geomorphic features. Geomorphological interpretation without geological and structural insight often leads to wrong mapping. Though non-existent longer fault may be a safer estimate, incorrectness harm reliability of the forecast. Also this does not greatly affect strong motion estimates, but misleading to surface displacement issues. Fault geometry, on the other hand, is very important to estimate intensity distribution. For the middle portion of the ISTL, fast-moving left-lateral strike-slip up to 1 cm/yr is obvious. Recent seismicity possibly induced by 2011 Tohoku

  10. Active faulting on the Wallula fault within the Olympic-Wallowa Lineament (OWL), eastern Washington State

    NASA Astrophysics Data System (ADS)

    Sherrod, B. L.; Lasher, J. P.; Barnett, E. A.

    2013-12-01

    Several studies over the last 40 years focused on a segment of the Wallula fault exposed in a quarry at Finley, Washington. The Wallula fault is important because it is part of the Olympic-Wallowa lineament (OWL), a ~500-km-long topographic and structural lineament extending from Vancouver Island, British Columbia to Walla Walla, Washington that accommodates Basin and Range extension. The origin and nature of the OWL is of interest because it contains potentially active faults that are within 50 km of high-level nuclear waste facilities at the Hanford Site. Mapping in the 1970's and 1980's suggested the Wallula fault did not offset Holocene and late Pleistocene deposits and is therefore inactive. New exposures of the Finley quarry wall studied here suggest otherwise. We map three main packages of rocks and sediments in a ~10 m high quarry exposure. The oldest rocks are very fine grained basalts of the Columbia River Basalt Group (~13.5 Ma). The next youngest deposits include a thin layer of vesicular basalt, white volcaniclastic deposits, colluvium containing clasts of vesicular basalt, and indurated paleosols. A distinct angular unconformity separates these vesicular basalt-bearing units from overlying late Pleistocene flood deposits, two colluvium layers containing angular clasts of basalt, and Holocene tephra-bearing loess. A tephra within the loess likely correlates to nearby outcrops of Mazama ash. We recognize three styles of faults: 1) a near vertical master reverse or oblique fault juxtaposing very fine grained basalt against late Tertiary-Holocene deposits, and marked by a thick (~40 cm) vertical seam of carbonate cemented breccia; 2) subvertical faults that flatten upwards and displace late Tertiary(?) to Quaternary(?) soils, colluvium, and volcaniclastic deposits; and 3) flexural slip faults along bedding planes in folded deposits in the footwall. We infer at least two Holocene earthquakes from the quarry exposure. The first Holocene earthquake deformed

  11. Effects of Mining-Induced Stress Perturbations on Pre-Existing Faults Near a Deep South African Gold Mine

    NASA Astrophysics Data System (ADS)

    Lucier, A. M.; Heesakkers, V.; Zoback, M. D.; Reches, Z.

    2007-12-01

    excavation. We analyze active faults observed in borehole image log data and mapped in the TauTona access tunnels. In the borehole image logs, we find evidence of recent slip on faults that have become critically stressed due to the mining-induced stress perturbation. In our investigation of the Pretorius Fault Zone (PFZ), an ancient (Pre-Cambrian) fault system, we find that stress perturbations due to recent mining advances may be responsible for reactivating segments of the PFZ that were observed to slip during a M2.2 event recorded in December 2004.

  12. Numerical simulation of coastal flooding after potential reactivation of an active normal fault in northern Taiwan

    NASA Astrophysics Data System (ADS)

    Chan, Yu-Chang; Kuo, Chih-Yu; Chang, Kuo-Jen; Chen, Rou-Fei; Hsieh, Yu-Chung

    2016-04-01

    Rapid coastal flooding from seawards may be resulted from storm surge, tsunamis, and sudden land subsidence due to fault activities. Many observations and numerical modeling of flooding have been made for cases resulted from storm surge and tsunami events; however, coastal flooding caused by a potential normal faulting event nearby coastal areas is rarely reported. In addition to the earthquake hazards from fault rupturing and ground shaking, the accompanied hazards of earthquake-induced flooding is also important to be investigated. The Jinshan area in northern Taiwan was reported to have been flooded by a tsunami event in the year of 1867 possibly resulted from the reactivation of the Shanchiao normal fault offshore. Historical records have shown that the Shanchiao Fault that extends from Shulin along the western edge of the Taipei Basin to the town of Jinshan may have also ruptured in the year of 1694. The rupturing event has created a depression on the western side of the Taipei Basin that was later filled by sea water called the Taipei Lake. The geological conditions in northern Taiwan provide an opportunity for numerically simulating the dynamic processes of sea water flooding nearby the coastal area immediately after an earthquake-induced normal faulting event. In this study, we focused on the potential active normal faulting that may occur and result in an expected catastrophic flooding in lowland area of Jinshan in northern Taiwan. We applied the continuum shallow water equation to evaluate the unknown inundation processes including location, extent, velocity and water depths after the flooding initiated and the final state of the flooding event. The modeling results were well compared with borehole observations of the extent of previous flooding events possibly due to tsunami events. In addition, the modeling results may provide a future basis for safety evaluation of the two nuclear power plants nearby the region.

  13. Active faulting and devastating earthquakes in continental China

    NASA Astrophysics Data System (ADS)

    Zhang, P.

    2003-04-01

    The primary pattern of active tectonics in continental China is characterized by relative movements and interactions of tectonic blocks bounded by major active faults. Earthquakes are results of abrupt releases of accumulated strain energy that excesses the threshold of strength of brittle part of the earth’s crust. Boundaries of tectonic blocks are the locations of most discontinuous deformation and highest gradient of stress accumulation, thus are the most likely places for strain energy accumulation and releases, and in turn, devastating earthquakes. Almost all earthquakes of magnitude larger than 8 and 80~90% of earthquakes of magnitude over 7 occur along boundaries of active tectonic blocks. This fact indicates that differential movements and interactions of active tectonic blocks are the primary mechanism for the occurrences of devastating earthquakes. Northeastern margin of Tibetan Plateau consists of two active fault zones, the Haiyuan and the Xiangshan fault zones. Each of the zones can be further divided into several segments. Historical earthquakes during the past 800 years ruptured all of them except one segment, the so-called Tianzhu seismic gap. We have conducted paleoseismological studies on each of the segments of the fault zones. Preliminary results reveal temporal clustering features of long-term paleoearthquake activity along these two fault zones. The 1920 Haiyuan earthquake of magnitude 8.5, for example, ruptured three segments of the fault zone. We dug 19 trenches along different segments of the surface ruptures. There were 3 events along the eastern segment during the past 14000 years, 7 events along the middle segment during the past 9000 years, and 6 events along the western segment during the past 10000 years. These events clearly depict two temporal clusters. The first cluster occurs from 4600 to 6400 years, and the second occurs from 1000 to 2800 years, approximately. Each cluster lasts about 2000 years. Time period between these two

  14. Active faulting and natural hazards in Armenia, eastern Turkey and northwestern Iran

    NASA Astrophysics Data System (ADS)

    Karakhanian, Arkady S.; Trifonov, Vladimir G.; Philip, Herve; Avagyan, Ara; Hessami, Khaled; Jamali, Farshad; Salih Bayraktutan, M.; Bagdassarian, H.; Arakelian, S.; Davtian, V.; Adilkhanyan, A.

    2004-03-01

    Active fault zones of Armenia, SE Turkey and NW Iran present a diverse set of interrelated natural hazards. Three regional case studies in this cross-border zone are examined to show how earthquakes interact with other hazards to increase the risk of natural disaster. In northern Armenia, a combination of several natural and man-made phenomena (earthquakes, landslides and unstable dams with toxic wastes) along the Pambak-Sevan-Sunik fault (PSSF) zone lowers from 0.4 to 0.2-0.3 g the maximum permissible level (MPL) of seismic hazard that may induce disastrous destruction and loss of life in the adjacent Vanadzor depression. In the Ararat depression, a large active fault-bounded pull-apart basin at the junction of borders of Armenia, Turkey, Iran and Azerbaijan, an earthquake in 1840 was accompanied by an eruption of Ararat Volcano, lahars, landslides, floods, soil subsidence and liquefaction. The case study demonstrates that natural hazards that are secondary with respect to earthquakes may considerably increase the damage and the casualties and increase the risk associated with the seismic impact. The North Tabriz-Gailatu fault system poses a high seismic hazard to the border areas of NW Iran, eastern Turkey, Nakhichevan (Azerbaijan) and southern Armenia. Right-lateral strike-slip motions along the North Tabriz fault have given rise to strong earthquakes, which threaten the city of Tabriz with its population of 1.2 million. The examples illustrate how the concentration of natural hazards in active fault zones increases the risk associated with strong earthquakes in Armenia, eastern Turkey and NW Iran. This generally occurs across the junctions of international borders. Hence, the transboundary character of active faults requires transboundary cooperation in the study and mitigation of the natural risk.

  15. Identification of recently active faults and folds in Java, Indonesia

    NASA Astrophysics Data System (ADS)

    Marliyani, G. I.; Arrowsmith, R.; Helmi, H.

    2013-12-01

    We analyze the spatial pattern of active deformation in Java, Indonesia with the aim of characterizing the deformation of the upper plate of the subduction zone in this region. The lack of detailed neotectonic studies in Java is mostly because of its relatively low rate of deformation in spite of significant historical seismic activity. In addition, the abundance of young volcanic materials as well as the region's high precipitation rate and vegetation cover obscure structural relationships and prevent reliable estimates of offset along active faults as well as exhumed intra-arc faults. Detailed maps of active faults derived from satellite and field-based neotectonic mapping, paleoseismic data, as well as new data on the fault kinematics and estimates of orientation of principal stresses from volcano morphology characterize recently active faults and folds. The structures in West Java are dominated by strike-slip faulting, while Central and northern part of East Java are dominated by folds and thrusting with minor normal faulting. The structures vary in length from hundreds meters to tens of kilometers and mainly trend N75°E, N8°E with some minor N45°W. Our preliminary mapping indicates that there are no large scale continuous structures in Java, and that instead deformation is distributed over wide areas along small structures. We established several paleoseismic sites along some of the identified structures. We excavated two shallow trenches along the Pasuruan fault, a normal fault striking NW-SE that forms a straight 13 km scarp cutting Pleistocene deltaic deposits of the north shore of East Java. The trenches exposed faulted and folded fluvial, alluvial and colluvial strata that record at least four ground-rupturing earthquakes since the Pleistocene. The Pasuruan site proves its potential to provide a paleoseismic record rarely found in Java. Abundant Quaternary volcanoes are emplaced throughout Java; most of the volcanoes show elongation in N100°E and N20

  16. A preliminary study on surface ground deformation near shallow foundation induced by strike-slip faulting

    NASA Astrophysics Data System (ADS)

    Wong, Pei-Syuan; Lin, Ming-Lang

    2016-04-01

    According to investigation of recent earthquakes, ground deformation and surface rupture are used to map the influenced range of the active fault. The zones of horizontal and vertical surface displacements and different features of surface rupture are investigated in the field, for example, the Greendale Fault 2010, MW 7.1 Canterbury earthquake. The buildings near the fault rotated and displaced vertically and horizontally due to the ground deformation. Besides, the propagation of fault trace detoured them because of the higher rigidity. Consequently, it's necessary to explore the ground deformation and mechanism of the foundation induced by strike-slip faulting for the safety issue. Based on previous study from scaled analogue model of strike-slip faulting, the ground deformation is controlled by material properties, depth of soil, and boundary condition. On the condition controlled, the model shows the features of ground deformation in the field. This study presents results from shear box experiment on small-scale soft clay models subjected to strike-slip faulting and placed shallow foundations on it in a 1-g environment. The quantifiable data including sequence of surface rupture, topography and the position of foundation are recorded with increasing faulting. From the result of the experiment, first en echelon R shears appeared. The R shears rotated to a more parallel angle to the trace and cracks pulled apart along them with increasing displacements. Then the P shears crossed the basement fault in the opposite direction appears and linked R shears. Lastly the central shear was Y shears. On the other hand, the development of wider zones of rupture, higher rising surface and larger the crack area on surface developed, with deeper depth of soil. With the depth of 1 cm and half-box displacement 1.2 cm, en echelon R shears appeared and the surface above the fault trace elevated to 1.15 mm (Dv), causing a 1.16 cm-wide zone of ground-surface rupture and deformation

  17. Discriminating Between Induced vs. Tectonic Seismicity From Long-Term History of Fault Behavior in Intraplate Regions

    NASA Astrophysics Data System (ADS)

    Magnani, M. B.; Hornbach, M. J.; DeShon, H. R.; Hayward, C.; Blanpied, M. L.

    2015-12-01

    Since 2009 there has been an increase in rate of seismicity in the Central US (CUS), a major fraction of which has been associated with shale gas production and related wastewater injection. Within this context it is important to discriminate between seismic activity that is anthropogenically induced from that arising from natural tectonic deformation. This discrimination is particularly challenging because tectonic strain rates and natural seismicity rates are low in this intraplate region, such that tectonically active faults may display periods of quiescence that are long (100's to 1000's of years) relative to the short (10's of years) instrumental record. In addition, causative faults are unknown with a poor surface expression, both types of seismicity occur on or reactivate ancient faults in the Precambrian basement, and the instrumental seismic record is sparse. While seismicity provides information about the short-term history of deformation on the involved faults, the long-term is missing. Seismic reflection data offer a means by which to interrogate the long-term history of these faults, which can be discriminatory. In this paper we present examples from two regions of the CUS. The first region shows examples of tectonically active faults within the northern Mississippi Embayment south of the New Madrid Seismic Zone, which were imaged by a high-resolution seismic reflection survey along the Mississippi River. The faults deform Quaternary alluvium and underlying sediments dating from Tertiary through Paleozoic, with increasing amount of deformation with formation age, suggesting a long history of activity. The second region shows examples from the North Texas basin, a region of ongoing shale gas exploitation. Here, industry seismic reflection data image basement faults showing deformation of the Precambrian and Paleozoic sequences, and little to no deformation of younger formations. Specifically, vertical offsets, if any, in the post

  18. Northwestern Australian Collision in the Timor Sea: Constraints From Flexurally-Induced Normal Faulting.

    NASA Astrophysics Data System (ADS)

    Londono, J.; Lorenzo, J.; O'Brien, G.

    2001-12-01

    rather than an increase in fault slip within the Pliocene section. Flexure-induced normal faults affecting present day sea floor are distributed in an area within 50 to 150 km of the tectonic wedge front (Banda Arc). Pliocene faults were located at least 100 km further away from the active tectonic wedge (i.e. >250 km). This difference in the spatial distribution of faults indicates a change in the rheologic regime of the lithosphere over time. Heterogeneous elastic thickness of the lithosphere in the area is causing a concentration of stresses on the modern narrow zone of high deformation. Also the fall in the rate of convergence (from 70 km/m.y. during Pliocene to about imperceptible today) reduces the amount of transferable stress into the continental plate

  19. Evaluation of feasibility of mapping seismically active faults in Alaska

    NASA Technical Reports Server (NTRS)

    Gedney, L. D. (Principal Investigator); Vanwormer, J. D.

    1973-01-01

    The author has identified the following significant results. ERTS-1 imagery is proving to be exceptionally useful in delineating structural features in Alaska which have never been recognized on the ground. Previously unmapped features such as seismically active faults and major structural lineaments are especially evident. Among the more significant results of this investigation is the discovery of an active strand of the Denali fault. The new fault has a history of scattered activity and was the scene of a magnitude 4.8 earthquake on October 1, 1972. Of greater significance is the disclosure of a large scale conjugate fracture system north of the Alaska Range. This fracture system appears to result from compressive stress radiating outward from around Mt. McKinley. One member of the system was the scene of a magnitude 6.5 earthquake in 1968. The potential value of ERTS-1 imagery to land use planning is reflected in the fact that this earthquake occurred within 10 km of the site which was proposed for the Rampart Dam, and the fault on which it occurred passes very near the proposed site for the bridge and oil pipeline crossing of the Yukon River.

  20. Numerical model of the glacially-induced intraplate earthquakes and faults formation

    NASA Astrophysics Data System (ADS)

    Petrunin, Alexey; Schmeling, Harro

    2016-04-01

    According to the plate tectonics, main earthquakes are caused by moving lithospheric plates and are located mainly at plate boundaries. However, some of significant seismic events may be located far away from these active areas. The nature of the intraplate earthquakes remains unclear. It is assumed, that the triggering of seismicity in the eastern Canada and northern Europe might be a result of the glacier retreat during a glacial-interglacial cycle (GIC). Previous numerical models show that the impact of the glacial loading and following isostatic adjustment is able to trigger seismicity in pre-existing faults, especially during deglaciation stage. However this models do not explain strong glaciation-induced historical earthquakes (M5-M7). Moreover, numerous studies report connection of the location and age of major faults in the regions undergone by glaciation during last glacial maximum with the glacier dynamics. This probably imply that the GIC might be a reason for the fault system formation. Our numerical model provides analysis of the strain-stress evolution during the GIC using the finite volume approach realised in the numerical code Lapex 2.5D which is able to operate with large strains and visco-elasto-plastic rheology. To simulate self-organizing faults, the damage rheology model is implemented within the code that makes possible not only visualize faulting but also estimate energy release during the seismic cycle. The modeling domain includes two-layered crust, lithospheric mantle and the asthenosphere that makes possible simulating elasto-plastic response of the lithosphere to the glaciation-induced loading (unloading) and viscous isostatic adjustment. We have considered three scenarios for the model: horizontal extension, compression and fixed boundary conditions. Modeling results generally confirm suppressing seismic activity during glaciation phases whereas retreat of a glacier triggers earthquakes for several thousand years. Tip of the glacier

  1. Analysis of microseismic activity detected by the WIZARD array, Alpine Fault, New Zealand

    NASA Astrophysics Data System (ADS)

    Feenstra, J. P.; Roecker, S. W.; Thurber, C. H.; Lord, N.; O'Brien, G.; Pesicek, J. D.; Townend, J.; Bannister, S. C.

    2012-12-01

    A primary goal for the UW-Madison-RPI WIZARD array is the characterization of background seismicity around the Deep Fault Drilling Project (DFDP) site on the Alpine Fault, South Island, New Zealand. The WIZARD array consists of 20 stations, half broadband, deployed for a planned 2-year period around the Whataroa Valley DFDP-2 drill site. Two neighboring arrays, SAMBA (Victoria University of Wellington) to the southwest and ALFA'12 (GNS Science) to the northeast, along with several GeoNet permanent stations, provide broad coverage of the region. The earthquakes that are detected will (1) help to define the geometry of the Alpine Fault and other active faults at depth, (2) provide data for seismic imaging, focal mechanisms, and shear-wave splitting analysis, and (3) enable the assessment of possible changes in seismic activity induced by future fault zone drilling. We are currently analyzing data from the first 2 months of the deployment. Dozens of nearby earthquakes (S-P time of up to a few seconds) have been detected, far more than are in the New Zealand GeoNET catalog. This is expected because the magnitude completion level of the GeoNet seismometer network is around 2.5 in the Whataroa region, due to a relatively sparse station coverage. In this presentation, we report on earthquake location results for 8 months of WIZARD data, along with focal mechanisms for selected larger events.

  2. Crossing Active Faults on the Sakhalin II Onshore Pipeline Route: Analysis Methodology and Basic Design

    SciTech Connect

    Vitali, Luigino; Mattiozzi, Pierpaolo

    2008-07-08

    Twin oil (20 and 24 inch) and gas (20 and 48 inch) pipeline systems stretching 800 km are being constructed to connect offshore hydrocarbon deposits from the Sakhalin II concession in the North to an LNG plant and oil export terminal in the South of Sakhalin island. The onshore pipeline route follows a regional fault zone and crosses individual active faults at 19 locations. Sakhalin Energy, Design and Construction companies took significant care to ensure the integrity of the pipelines, should large seismic induced ground movements occur during the Operational life of the facilities. Complex investigations including the identification of the active faults, their precise location, their particular displacement values and assessment of the fault kinematics were carried out to provide input data for unique design solutions. Lateral and reverse offset displacements of 5.5 and 4.5 m respectively were determined as the single-event values for the design level earthquake (DLE)--the 1000-year return period event. Within the constraints of a pipeline route largely fixed, the underground pipeline fault crossing design was developed to define the optimum routing which would minimize stresses and strain using linepipe materials which had been ordered prior to the completion of detailed design, and to specify requirements for pipe trenching shape, materials, drainage system, etc. This Paper describes the steps followed to formulate the concept of the special trenches and the analytical characteristics of the Model.

  3. Crossing Active Faults on the Sakhalin II Onshore Pipeline Route: Pipeline Design and Risk Analysis

    SciTech Connect

    Mattiozzi, Pierpaolo; Strom, Alexander

    2008-07-08

    Twin oil (20 and 24 inch) and gas (20 and 48 inch) pipeline systems stretching 800 km are being constructed to connect offshore hydrocarbon deposits from the Sakhalin II concession in the North to an LNG plant and oil export terminal in the South of Sakhalin island. The onshore pipeline route follows a regional fault zone and crosses individual active faults at 19 locations. Sakhalin Energy, Design and Construction companies took significant care to ensure the integrity of the pipelines, should large seismic induced ground movements occur during the Operational life of the facilities. Complex investigations including the identification of the active faults, their precise location, their particular displacement values and assessment of the fault kinematics were carried out to provide input data for unique design solutions. Lateral and reverse offset displacements of 5.5 and 4.5 m respectively were determined as the single-event values for the design level earthquake (DLE) - the 1000-year return period event. Within the constraints of a pipeline route largely fixed, the underground pipeline fault crossing design was developed to define the optimum routing which would minimize stresses and strain using linepipe materials which had been ordered prior to the completion of detailed design, and to specify requirements for pipe trenching shape, materials, drainage system, etc. Detailed Design was performed with due regard to actual topography and to avoid the possibility of the trenches freezing in winter, the implementation of specific drainage solutions and thermal protection measures.

  4. Crossing Active Faults on the Sakhalin II Onshore Pipeline Route: Analysis Methodology and Basic Design

    NASA Astrophysics Data System (ADS)

    Vitali, Luigino; Mattiozzi, Pierpaolo

    2008-07-01

    Twin oil (20 & 24 inch) and gas (20 & 48 inch) pipeline systems stretching 800 km are being constructed to connect offshore hydrocarbon deposits from the Sakhalin II concession in the North to an LNG plant and oil export terminal in the South of Sakhalin island. The onshore pipeline route follows a regional fault zone and crosses individual active faults at 19 locations. Sakhalin Energy, Design and Construction companies took significant care to ensure the integrity of the pipelines, should large seismic induced ground movements occur during the Operational life of the facilities. Complex investigations including the identification of the active faults, their precise location, their particular displacement values and assessment of the fault kinematics were carried out to provide input data for unique design solutions. Lateral and reverse offset displacements of 5.5 and 4.5 m respectively were determined as the single-event values for the design level earthquake (DLE)—the 1000-year return period event. Within the constraints of a pipeline route largely fixed, the underground pipeline fault crossing design was developed to define the optimum routing which would minimize stresses and strain using linepipe materials which had been ordered prior to the completion of detailed design, and to specify requirements for pipe trenching shape, materials, drainage system, etc. This Paper describes the steps followed to formulate the concept of the special trenches and the analytical characteristics of the Model.

  5. Crossing Active Faults on the Sakhalin II Onshore Pipeline Route: Pipeline Design and Risk Analysis

    NASA Astrophysics Data System (ADS)

    Mattiozzi, Pierpaolo; Strom, Alexander

    2008-07-01

    Twin oil (20 & 24 inch) and gas (20 & 48 inch) pipeline systems stretching 800 km are being constructed to connect offshore hydrocarbon deposits from the Sakhalin II concession in the North to an LNG plant and oil export terminal in the South of Sakhalin island. The onshore pipeline route follows a regional fault zone and crosses individual active faults at 19 locations. Sakhalin Energy, Design and Construction companies took significant care to ensure the integrity of the pipelines, should large seismic induced ground movements occur during the Operational life of the facilities. Complex investigations including the identification of the active faults, their precise location, their particular displacement values and assessment of the fault kinematics were carried out to provide input data for unique design solutions. Lateral and reverse offset displacements of 5.5 and 4.5 m respectively were determined as the single-event values for the design level earthquake (DLE)—the 1000-year return period event. Within the constraints of a pipeline route largely fixed, the underground pipeline fault crossing design was developed to define the optimum routing which would minimize stresses and strain using linepipe materials which had been ordered prior to the completion of detailed design, and to specify requirements for pipe trenching shape, materials, drainage system, etc. Detailed Design was performed with due regard to actual topography and to avoid the possibility of the trenches freezing in winter, the implementation of specific drainage solutions and thermal protection measures.

  6. Exhumation history of an active fault to constrain a fault-based seismic hazard scenario: the Pizzalto fault (central Apennines, Italy) example.

    NASA Astrophysics Data System (ADS)

    Tesson, Jim; Pace, Bruno; Benedetti, Lucilla; Visini, Francesco; Delli Rocioli, Mattia; Didier, Bourles; Karim, keddadouche; Gorges, Aumaitre

    2016-04-01

    A prerequisite to constrain fault-based and time-dependent earthquake rupture forecast models is to acquire data on the past large earthquake frequency on an individual seismogenic source and to compare all the recorded occurrences in the active fault-system. We investigated the Holocene seismic history of the Pizzalto normal fault, a 13 km long fault segment belonging to the Pizzalto-Rotella-Aremogna fault system in the Apennines (Italy). We collected 44 samples on the Holocene exhumed Pizzalto fault plane and analyzed their 36Cl and rare earth elements content. Conjointly used, the 36Cl and REE concentrations show that at least 6 events have exhumed 4.4 m of the fault scarp between 3 and 1 ka BP, the slip per event ranging from 0.3 to 1.2 m. No major events have been detected over the last 1 ka. The Rotella-Aremogna-Pizzalto fault system has a clustered earthquake behaviour with a mean recurrence time of 1.2 ka and a low to moderate probability (ranging from 4% to 26%) of earthquake occurrence over the next 50 years. We observed similarities between seismic histories of several faults belonging to two adjacent fault systems. This could again attest that non-random processes occurring in the release of the strain accumulated on faults, commonly referred to as fault interactions and leading to apparent synchronization. If these processes were determined as being the main parameter controlling the occurrence of earthquakes, it would be crucial to take them into account in seismic hazard models.

  7. Review of active faults in the Borborema Province, Intraplate South America — Integration of seismological and paleoseismological data

    NASA Astrophysics Data System (ADS)

    Bezerra, Francisco H. R.; do Nascimento, Aderson F.; Ferreira, Joaquim M.; Nogueira, Francisco C.; Fuck, Reinhardt A.; Neves, Benjamim B. Brito; Sousa, Maria O. L.

    2011-10-01

    In this paper, we provide a review of the properties and behavior of active faults in the Borborema Province, northeastern Brazil, using instrumental, historical and paleoseismological records. The Borborema Province is one of the most seismically active parts of the South American stable continental region (the South American Platform). The Province encompasses an area ~ 900 km long and ~ 600 km wide. It is composed of a branching system of Neoproterozoic orogens, encompassing Archean and Proterozoic inliers deformed during the Brasiliano orogeny at ~ 750-500 Ma. Active faults reactivate shear zones or regional foliation and quartz veins or cut across the preexisting fabric. Active faults are usually strike-slip and generate events ≤ 5.2 m b, which we interpret as the lower limit for maximum possible earthquakes. Seismicity is concentrated in the upper crust down to a depth of 12 km. Earthquake sequences illuminated naturally occurring faults up to 40 km long and segments in the order of 0.5-2.6 km in faults related to induced seismicity. Earthquakes have a recurrence interval of ~ 15 years for M s = 4. Paleoseismological data indicate that although earthquakes associated with surface ruptures have not occurred in the last 200 years, they struck the region in the last ~ 100 ka. Paleoearthquakes have a recurrence interval of ~ 15.8 ka for magnitudes of ~ 5.5 M w in individual faults. Moreover, earthquake-induced soft-sediment deformation caused by events of at least 5.5-6.0 M s have occurred at least six times in the last 400-10 ka in one alluvial valley. Seismically defined faults are concentrated along the continental margin at the border of sedimentary basins as far as 250-300 km inland in areas of extended crust; faults in the paleoseismic record are also found in rift basins along this margin. Both records also reveal that active faults tend to be hydraulically conductive.

  8. Palaeoseismology of the L'Aquila faults (central Italy, 2009, Mw 6.3 earthquake): implications for active fault linkage

    NASA Astrophysics Data System (ADS)

    Galli, Paolo A. C.; Giaccio, Biagio; Messina, Paolo; Peronace, Edoardo; Zuppi, Giovanni Maria

    2011-12-01

    Urgent urban-planning problems related to the 2009 April, Mw 6.3, L'Aquila earthquake prompted immediate excavation of palaeoseismological trenches across the active faults bordering the Aterno river valley; namely, the Mt. Marine, Mt. Pettino and Paganica faults. Cross-cutting correlations amongst existing and new trenches that were strengthened by radiocarbon ages and archaeological constraints show unambiguously that these three investigated structures have been active since the Last Glacial Maximum period, as seen by the metric offset that affected the whole slope/alluvial sedimentary succession up to the historical deposits. Moreover, in agreement with both 18th century accounts and previous palaeoseismological data, we can affirm now that these faults were responsible for the catastrophic 1703 February 2, earthquake (Mw 6.7). The data indicate that the Paganica-San Demetrio fault system has ruptured in the past both together with the conterminous Mt. Pettino-Mt. Marine fault system, along more than 30 km and causing an Mw 6.7 earthquake, and on its own, along ca. 19 km, as in the recent 2009 event and in the similar 1461 AD event. This behaviour of the L'Aquila faults has important implications in terms of seismic hazard assessment, while it also casts new light on the ongoing fault linkage processes amongst these L'Aquila faults.

  9. Evidence of sub Kilometer-scale Variability in Stress Directions near Active Faults: An Example from the Newport-Inglewood Fault, Southern California

    NASA Astrophysics Data System (ADS)

    Persaud, P.; Stock, J. M.; Smith, D.

    2015-12-01

    The active Newport-Inglewood Fault (NIF) zone is a series of right-lateral, left-stepping en echelon segments and associated anticlines that produced the 1933 Long Beach Mw 6.4 earthquake. Seismic hazard estimates, dynamic earthquake rupture models, and earthquake simulations for Southern California rely on information on the stress field obtained from the Community Stress Model (CSM), though the latter still lacks observational constraints. This study provides much needed observational constraints on in-situ stress, which are useful for validating the CSM. Our results highlight the possibility of variations in stress directions near active faults at length-scales less than 1 km. We determined the orientation of stress-induced compressive failures or borehole breakouts, which are reliable indicators of the orientation of the maximum horizontal stress (SH) in over 40 wellbores in the Los Angeles basin near the NIF. The compressional jogs along the fault have long been drilled for oil in this major metropolitan area, and so provide the dataset of oriented caliper logs. This allowed us to investigate the variation of SH direction in three oil fields. In the Inglewood oil field, a dense dataset of 24 wells in ~2 km2, SH varies from N9°E to N32°E over a depth range of 1-3 km and within 400 m of the fault in the western fault block, with more variability occurring in wells father away. At depths below 2 km, SH takes on a more northerly orientation. In contrast, SH is oriented E-W in the eastern fault block, based on constraints from two wells. In the Wilmington oil field located between the Thums-Huntington Beach Fault and the NIF, data from 11 deviated wells yields a pattern of elongation directions, which differs from the more complex pattern obtained for the Huntington Beach wells located ~12 km to the southeast. The short-length-scale variations in SH direction are attributed to the proximity to faults or fault segmentation, and indicate the likely complexity that

  10. The ground deformation field induced by a listric thrust fault with an overburden soil layer

    NASA Astrophysics Data System (ADS)

    Zeng, Shaogang; Cai, Yong'en

    2013-12-01

    The surface deformation field induced by a listric thrust fault with a thick, overburden soil layer is studied in this paper by the finite element method (FEM). The results show: (a) The maximum slip induced by the buried fault is not located at upper tip of the fault, but below it. (b) The vertical displacement changes remarkably near the fault, forming a fault scarp. With the increase of the soil layer thickness, the height of the scarp is decreased for the same earthquake magnitude. (c) The strong strain zone on the surface is localized near the projection of the fault tip on the ground surface. The horizontal strains in the zone are in tension above the hanging wall and in compression above the foot wall, and the vertical strains in the zone are vice versa, which is favorable for tensileshear, compression-shear fissures above hanging wall and foot wall, respectively.

  11. Lateral propagation of active normal faults throughout pre-existing fault zones: an example from the Southern Apennines, Italy

    NASA Astrophysics Data System (ADS)

    Agosta, Fabrizio; Prosser, Giacomo; Ivo Giano, Salvatore

    2013-04-01

    The main active structures in the Southern Apennines are represented by a set of NW-trending normal faults, which are mainly located in the axial sector of the chain. Evidences arising from neotectonics and seismology show activity of a composite seismic source, the Irpinia - Agri Valley, located across the Campania-Basilicata border. This seismic source is made up of two right-stepping, individual seismic sources forming a relay ramp. Each individual seismic source consists of a series of nearly parallel normal fault segments. The relay ramp area, located around the Vietri di Potenza town, is bounded by two seismic segments, the San Gregorio Magno Fault, to the NW, and the Pergola-Melandro Fault, to the SE. The possible interaction between the two right-stepping fault segments has not been proven yet, since the fault system of the area has never been analyzed in detail. This work is aimed at assessing the geometry of such fault system, inferring the relative age of the different fault sets by studying the crosscutting relationships, characterizing the micromechanics of fault rocks associated to the various fault sets, and understanding the modalities of lateral propagation of the two bounding fault segments. Crosscutting relationships are recognized by combining classical geological mapping with morphotectonic methods. This latter approach, which include the analysis of aerial photographs and field inspection of quaternary slope deposits, is used to identify the most recent structures among those cropping out in the field area. In the relay ramp area, normal faults crosscut different tectonic units of the Apennine chain piled up, essentially, during the Middle to Late Miocene. The topmost unit (only few tens of meter-thick) consists of a mélange containing blocks of different lithologies in a clayish matrix. The intermediate thrust sheet consists of 1-1.5 km-thick platform carbonates of late Triassic-Jurassic age, with dolomites at the base and limestones at the

  12. Induced seismicity and CO2 leakage through fault zones during large-scale underground injection in a multilayered sedimentary system

    NASA Astrophysics Data System (ADS)

    Rinaldi, A.; Rutqvist, J.; Jeanne, P.; Cappa, F.

    2013-12-01

    The importance of geomechanics including the potential for reactivating faults associated with large-scale geologic carbon sequestration operations has recently become more widely recognized. However, not withstanding the potential for triggering notable (felt) seismic events, the potential for buoyancy-driven CO2 to reach potable groundwater and the ground surface is more important from safety and storage-efficiency perspectives. In this context, this work extends previous studies on the geomechanical modeling of fault responses during underground carbon dioxide injection, focusing on short-term integrity of the sealing caprock, and hence of potential leakage of either brine or CO2 to shallow groundwater aquifers during active injection. We account for a stress/strain-dependent permeability and study the leakage through a fault zone as its permeability changes during a reactivation, also causing seismicity. We analyze several scenarios related to the injected amount of CO2 (and hence as a function of the overpressure) both involving minor and major faults, and analyze the profile risks of leakage for different stress/strain permeability coupling functions, as well as increasing the complexity of the fault zone in terms of hydromechanical heterogeneities. We conclude that whereas it is very difficult to predict how much fault permeability could change upon reactivation, this process can have a significant impact on the leakage rate. The presence of hydromechanical heterogeneity influences the pressure diffusion, as well as the effective normal and shear stress evolution. Hydromechanical heterogeneities (i) strengthen the fault zone resulting in earthquake of small magnitude, and (ii) prevent a good fluid migration upward along the fault. We also study the effects of the caprock and aquifer thickness on the resulting induced seismicity and CO2 leakage, both in heterogeneous and homogeneous fault zone. Results show that a thin caprock or aquifer allows smaller events

  13. Active fault segments as potential earthquake sources: Inferences from integrated geophysical mapping of the Magadi fault system, southern Kenya Rift

    NASA Astrophysics Data System (ADS)

    Kuria, Z. N.; Woldai, T.; van der Meer, F. D.; Barongo, J. O.

    2010-06-01

    Southern Kenya Rift has been known as a region of high geodynamic activity expressed by recent volcanism, geothermal activity and high rate of seismicity. The active faults that host these activities have not been investigated to determine their subsurface geometry, faulting intensity and constituents (fluids, sediments) for proper characterization of tectonic rift extension. Two different models of extension direction (E-W to ESE-WNW and NW-SE) have been proposed. However, they were based on limited field data and lacked subsurface investigations. In this research, we delineated active fault zones from ASTER image draped on ASTER DEM, together with relocated earthquakes. Subsequently, we combined field geologic mapping, electrical resistivity, ground magnetic traverses and aeromagnetic data to investigate the subsurface character of the active faults. Our results from structural studies identified four fault sets of different age and deformational styles, namely: normal N-S; dextral NW-SE; strike slip ENE-WSW; and sinistral NE-SW. The previous studies did not recognize the existence of the sinistral oblique slip NE-SW trending faults which were created under an E-W extension to counterbalance the NW-SE faults. The E-W extension has also been confirmed from focal mechanism solutions of the swarm earthquakes, which are located where all the four fault sets intersect. Our findings therefore, bridge the existing gap in opinion on neo-tectonic extension of the rift suggested by the earlier authors. Our results from resistivity survey show that the southern faults are in filled with fluid (0.05 and 0.2 Ωm), whereas fault zones to the north contain high resistivity (55-75 Ωm) material. The ground magnetic survey results have revealed faulting activity within active fault zones that do not contain fluids. In addition, the 2D inversion of the four aero-magnetic profiles (209 km long) revealed: major vertical to sub vertical faults (dipping 75-85° east or west); an

  14. 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.

  15. Determining the Through-Going Active Fault Geometry of the Western North Anatolian Fault Through Stress Modeling

    NASA Astrophysics Data System (ADS)

    Karimi, B.; McQuarrie, N.

    2015-12-01

    The North Anatolian Fault (NAF) is a seismically active 1200 km long dextral strike-slip fault part of an east-west trending dextral shear zone (NAF system) between the Anatolian and Eurasian plates. This shear zone widens to the west, complicating potential earthquake rupture paths and highlighting the importance of understanding the geometry of active fault systems. West of the town of Bolu - the NAF bifurcates into the northern and southern strands, which converge and are linked through the Mudurnu Valley, then diverge to border the Marmara Sea. The westward continuation of these two fault traces is marked by further complexities in potential active fault geometry, particularly in the Marmara Sea (northern strand), and the Biga Peninsula (southern strand). We evaluate potential active fault geometries for both strands by comparing stress models of various fault geometries in these regions to a record of focal mechanisms and inferred paleostress from a lineament analysis. For the Marmara region, two of the three possible geometries matched the maximum horizontal stress (σH) orientations determined from a record of focal mechanisms; however, only one represented the northern and southern sidewalls associated with the principal zone of deformation of the developing Marmara basin. This suggests that it is the most likely representation of the active through-going fault geometry in the region. In the Biga Peninsula region, the active geometry of the southern strand has the southern component approaching and intersecting the northern component through a linking feature in a narrow topographic valley. This geometry was selected over two others as it overlaps the σH orientation determined from focal mechanism data and a lineament analysis. Additionally, this geometry does not develop a prominent mis-oriented NE-SW stress feature observed in the model results of the other two geometries, otherwise absent in the focal mechanism data or inferred from a lineament analysis.

  16. Tectonic activity and structural features of active intracontinental normal faults in the Weihe Graben, central China

    NASA Astrophysics Data System (ADS)

    Rao, Gang; Lin, Aiming; Yan, Bing; Jia, Dong; Wu, Xiaojun

    2014-12-01

    This study examines the tectonic activity and structural features of active normal faults in the Weihe Graben, central China. The Weihe Graben is an area with a high level of historic seismicity, and it is one of the intracontinental systems that developed since Tertiary in the extensional environment around the Ordos Block. Analysis of high-resolution remote-sensing imagery data, field observations, and radiocarbon dating results reveal the following: i) active normal faults are mainly developed within a zone < 500 m wide along the southern border of the eastern part of the Weihe Graben; ii) the active faults that have been identified are characterized by stepwise fault scarps dipping into the graben at angles of 40°-71°; iii) there are numerous discontinuous individual fault traces, ranging in length from a few tens of meters to 450 m (generally < 200 m); iv) fault zone structures, topographic features, and fault striations on the main fault planes indicate almost pure normal-slip; and v) late Pleistocene-Holocene terrace risers, loess, and alluvial deposits have been vertically offset by up to ~ 80 m, with a non-uniform dip-slip rate (throw-rates) ranging from ~ 2.1 to 5.7 mm/yr, mostly 2-3 mm/yr. Our results reveal that active normal faults have been developing in the Weihe Graben under an ongoing extensional environment, probably associated with the pre-existing graben and spreading of the continental crust, and this is in contrast with the Ordos Block and neighboring orogenic regions. These results provide new insights into the nature of extensional tectonic deformation in intracontinental graben systems.

  17. An Ontology for Identifying Cyber Intrusion Induced Faults in Process Control Systems

    NASA Astrophysics Data System (ADS)

    Hieb, Jeffrey; Graham, James; Guan, Jian

    This paper presents an ontological framework that permits formal representations of process control systems, including elements of the process being controlled and the control system itself. A fault diagnosis algorithm based on the ontological model is also presented. The algorithm can identify traditional process elements as well as control system elements (e.g., IP network and SCADA protocol) as fault sources. When these elements are identified as a likely fault source, the possibility exists that the process fault is induced by a cyber intrusion. A laboratory-scale distillation column is used to illustrate the model and the algorithm. Coupled with a well-defined statistical process model, this fault diagnosis approach provides cyber security enhanced fault diagnosis information to plant operators and can help identify that a cyber attack is underway before a major process failure is experienced.

  18. Safety enhancement of oil trunk pipeline crossing active faults on Sakhalin Island

    NASA Astrophysics Data System (ADS)

    Tishkina, E.; Antropova, N.; Korotchenko, T.

    2015-11-01

    The article explores the issues concerning safety enhancement of pipeline active fault crossing on Sakhalin Island. Based on the complexity and analysis results, all the faults crossed by pipeline system are classified into five categories - from very simple faults to extremely complex ones. The pipeline fault crossing design is developed in accordance with the fault category. To enhance pipeline safety at fault crossing, a set of methods should be applied: use of pipes of different safety classes and special trench design in accordance with soil permeability characteristics.

  19. Late Quaternary reef growth history of Les Saintes submarine plateau: a key to constrain active faulting kinematics in Guadeloupe (FWI)

    NASA Astrophysics Data System (ADS)

    Leclerc, F.; Feuillet, N.; Deplus, C.; Cabioch, G.; Tapponnier, P.; LeBrun, J.; Bazin, S.; Beauducel, F.; Boudon, G.; Le Friant, A.; De Min, L.; Melezan, D.

    2012-12-01

    The damaging November 21 2004 earthquake (Mw 6.3) occurred on a large normal fault system offshore Les Saintes archipelago in Guadeloupe. To better constrain the seismic hazard related to this fault system, new data were acquired in 2009 and 2010 during the GWADASEIS and BATHYSAINTES cruises. Digital Elevation Models (DEM), with a horizontal resolution of 2.5 m, were calculated with the bathymetric data acquired at shallow depth on Les Saintes insular shelf. Together with seismic reflection profiles, this data makes it possible to identify and map the fault system and to understand its kinematics with respect to the plateau formation. The 15km wide, -45m deep drowned plateau of Les Saintes is composed of four coral terraces, down to 110 m bsl, piled-up on the Upper Pliocene to Quaternary Les Saintes volcanic centres. The shallowest terrace corresponds to a drowned Holocene reef system. Reef typical features, as double barriers, pinnacles, spurs and grooves, are well identified in the bathymetry. Seismic reflection profiles indicate that the Holocene terrace overlays Pleistocene ones. Geophysical data and reef growth modeling tend to show that the reef plateau has formed under subsidence conditions (~0.35 mm/yr) since Ionian ages, recording the main sea level highstands, before being drowned during the last sea level rise, around 11ka BP. The four terraces are crosscut by several NW-SE striking normal faults, which have scarps up to 8m. They offset them, the older, the more, inducing syntectonic sedimentation. The fault system extends from the northern plateau's edge to Les Saintes channel, toward Dominica, constituting the eastern side of Les Saintes graben. In the channel, the Roseau Fault, responsible for the 2004 earthquake, bounds the graben western side. The new data confirms its extent to the north, as the fault offsets the plateau's western cliff by several tens of meter, counter-slope like, dipping under Les Saintes islands and inducing a high seismic

  20. Active Fault Tolerant Control for Ultrasonic Piezoelectric Motor

    NASA Astrophysics Data System (ADS)

    Boukhnifer, Moussa

    2012-07-01

    Ultrasonic piezoelectric motor technology is an important system component in integrated mechatronics devices working on extreme operating conditions. Due to these constraints, robustness and performance of the control interfaces should be taken into account in the motor design. In this paper, we apply a new architecture for a fault tolerant control using Youla parameterization for an ultrasonic piezoelectric motor. The distinguished feature of proposed controller architecture is that it shows structurally how the controller design for performance and robustness may be done separately which has the potential to overcome the conflict between performance and robustness in the traditional feedback framework. A fault tolerant control architecture includes two parts: one part for performance and the other part for robustness. The controller design works in such a way that the feedback control system will be solely controlled by the proportional plus double-integral PI2 performance controller for a nominal model without disturbances and H∞ robustification controller will only be activated in the presence of the uncertainties or an external disturbances. The simulation results demonstrate the effectiveness of the proposed fault tolerant control architecture.

  1. Searching for Seismically Active Faults in the Gulf of Cadiz

    NASA Astrophysics Data System (ADS)

    Custodio, S.; Antunes, V.; Arroucau, P.

    2015-12-01

    The repeated occurrence of large magnitude earthquakes in southwest Iberia in historical and instrumental times suggests the presence of active fault segments in the region. However, due to an apparently diffuse seismicity pattern defining a broad region of distributed deformation west of Gibraltar Strait, the question of the location, dimension and geometry of such structures is still open to debate. We recently developed a new algorithm for earthquake location in 3D complex media with laterally varying interface depths, which allowed us to relocate 2363 events having occurred from 2007 to 2013, using P- and S-wave catalog arrival times obtained from the Portuguese Meteorological Institute (IPMA, Instituto Portugues do Mar e da Atmosfera), for a study area lying between 8.5˚W and 5˚W in longitude and 36˚ and 37.5˚ in latitude. The most remarkable change in the seismicity pattern after relocation is an apparent concentration of events, in the North of the Gulf of Cadiz, along a low angle northward-dipping plane rooted at the base of the crust, which could indicate the presence of a major fault. If confirmed, this would be the first structure clearly illuminated by seismicity in a region that has unleashed large magnitude earthquakes. Here, we present results from the joint analysis of focal mechanism solutions and waveform similarity between neighboring events from waveform cross-correlation in order to assess whether those earthquakes occur on the same fault plane.

  2. Seismicity on Basement Faults Induced by Simultaneous Fluid Injection-Extraction

    NASA Astrophysics Data System (ADS)

    Chang, Kyung Won; Segall, Paul

    2016-08-01

    Large-scale carbon dioxide (CO2) injection into geological formations increases pore pressure, potentially inducing seismicity on critically stressed faults by reducing the effective normal stress. In addition, poroelastic expansion of the reservoir alters stresses, both within and around the formation, which may trigger earthquakes without direct pore-pressure diffusion. One possible solution to mitigate injection-induced earthquakes is to simultaneously extract pre-existing pore fluids from the target reservoir. To examine the feasibility of the injection-extraction strategy, we compute the spatiotemporal change in Coulomb stress on basement normal faults, including: (1) the change in poroelastic stresses Δ τ _s+fΔ σ _n, where Δ τ _s and Δ σ _n are changes in shear and normal stress. respectively, and (2) the change in pore-pressure fΔ p. Using the model of (J. Geophys. Res. Solid Earth 99(B2):2601-2618, 1994), we estimate the seismicity rate on basement fault zones. Fluid extraction reduces direct pore-pressure diffusion into conductive faults, generally reducing the risk of induced seismicity. Limited diffusion into/from sealing faults results in negligible pore pressure changes within them. However, fluid extraction can cause enhanced seismicity rates on deep normal faults near the injector as well as shallow normal faults near the producer by poroelastic stressing. Changes in seismicity rate driven by poroelastic response to fluid injection-extraction depends on fault geometry, well operations, and the background stressing rate.

  3. Modeling of fault reactivation and induced seismicity during hydraulic fracturing of shale-gas reservoirs

    EPA Science Inventory

    We have conducted numerical simulation studies to assess the potential for injection-induced fault reactivation and notable seismic events associated with shale-gas hydraulic fracturing operations. The modeling is generally tuned toward conditions usually encountered in the Marce...

  4. Controls of the Xiannvshan Fault on landslides and Reservoir induced earthquakes located at head area of the Three Gorges Reservoir

    NASA Astrophysics Data System (ADS)

    Shimei, Wang; Yeming, Zhang

    2015-04-01

    Landslides and reservoir induced earthquakes are two main types of geological disasters, which have serious influence on the Three Gorges Project. The Xiannvshan Fault is ten kilometers away from the Three Gorges Dam, and it has important control on landslides and earthquakes located at head area of the Three Gorges Reservoir. Data collected show that: (1) the fault stretch runs in northwest-west orientation with a total length of more than 80 kilometers, it north endpoint extends to the Yangtze River and Jiuwanxi Fault is one of its branches. The Xiannvshan Fault has a high level of activity with the average annual decline of 0.076mm in the west wall and the dextral sliding of 0.116mm. (2) Controls on landslides resulted from the Xiannvshan Fault lie in two aspects. One is a large of landslide accumulation bodies resulted from two collapse events, which are corresponded to the two intense faulting. The other is that the Xintan landslide occurred in 1982, which is resulted from the stress accumulation of the fault. (3) The Xiannvshan Fault is active. Three big earthquakes had been induced by the fault from 1959 to the time of impounding, of which one occurred at its southern endpoint, Panjiawan of Yidu, and was magnitude 5, one occurred at its northern section, Zhou Ping, and was magnitude 3.3, and another occurred at Huilongguan of Zigui with a magnitude 5.1. Earthquakes have been happening more frequently after the impoundment of the Three Gorges Reservoir or on the high water level than before. More than 40 earthquakes with magnitudes bigger than 3.3 were recorded after the impoundment, of which 4 ranged from 4.1 to 5.1 and occurred when the high water level was decreasing. Otherwise, most earthquakes centered on the northern endpoint of the fault, which indicates a characteristics of tectonic reservoir earthquake. This study, for the three gorges reservoir area landslide and seismic reservoir prediction is of great significance.

  5. Aftershocks illuninate the 2011 Mineral, Virginia, earthquake causative fault zone and nearby active faults

    USGS Publications Warehouse

    Horton, Jr., J. Wright; Shah, Anjana K.; McNamara, Daniel E.; Snyder, Stephen L.; Carter, Aina M

    2015-01-01

    Deployment of temporary seismic stations after the 2011 Mineral, Virginia (USA), earthquake produced a well-recorded aftershock sequence. The majority of aftershocks are in a tabular cluster that delineates the previously unknown Quail fault zone. Quail fault zone aftershocks range from ~3 to 8 km in depth and are in a 1-km-thick zone striking ~036° and dipping ~50°SE, consistent with a 028°, 50°SE main-shock nodal plane having mostly reverse slip. This cluster extends ~10 km along strike. The Quail fault zone projects to the surface in gneiss of the Ordovician Chopawamsic Formation just southeast of the Ordovician–Silurian Ellisville Granodiorite pluton tail. The following three clusters of shallow (<3 km) aftershocks illuminate other faults. (1) An elongate cluster of early aftershocks, ~10 km east of the Quail fault zone, extends 8 km from Fredericks Hall, strikes ~035°–039°, and appears to be roughly vertical. The Fredericks Hall fault may be a strand or splay of the older Lakeside fault zone, which to the south spans a width of several kilometers. (2) A cluster of later aftershocks ~3 km northeast of Cuckoo delineates a fault near the eastern contact of the Ordovician Quantico Formation. (3) An elongate cluster of late aftershocks ~1 km northwest of the Quail fault zone aftershock cluster delineates the northwest fault (described herein), which is temporally distinct, dips more steeply, and has a more northeastward strike. Some aftershock-illuminated faults coincide with preexisting units or structures evident from radiometric anomalies, suggesting tectonic inheritance or reactivation.

  6. 3D Fault modeling of the active Chittagong-Myanmar fold belt, Bangladesh

    NASA Astrophysics Data System (ADS)

    Peterson, D. E.; Hubbard, J.; Akhter, S. H.; Shamim, N.

    2013-12-01

    region. These models will further our understanding of fault geometry and history of the CMFB, allowing us to investigate the region's potential for geologic hazards. At least twenty-five percent of the country of Bangladesh sits on top of this actively deforming region, which is home to more than 28 million people. The CMFB also extends offshore, meaning that a major thrusting event could induce a regional tsunami with little warning. Understanding the geometry of the region's underlying detachment as well as the location and ages of specific thrust faults is critical to assessing seismic hazards for this heavily populated area.

  7. Dynamic Modelling of Fault Slip Induced by Stress Waves due to Stope Production Blasts

    NASA Astrophysics Data System (ADS)

    Sainoki, Atsushi; Mitri, Hani S.

    2016-01-01

    Seismic events can take place due to the interaction of stress waves induced by stope production blasts with faults located in close proximity to stopes. The occurrence of such seismic events needs to be controlled to ensure the safety of the mine operators and the underground mine workings. This paper presents the results of a dynamic numerical modelling study of fault slip induced by stress waves resulting from stope production blasts. First, the calibration of a numerical model having a single blast hole is performed using a charge weight scaling law to determine blast pressure and damping coefficient of the rockmass. Subsequently, a numerical model of a typical Canadian metal mine encompassing a fault parallel to a tabular ore deposit is constructed, and the simulation of stope extraction sequence is carried out with static analyses until the fault exhibits slip burst conditions. At that point, the dynamic analysis begins by applying the calibrated blast pressure to the stope wall in the form of velocities generated by the blast holes. It is shown from the results obtained from the dynamic analysis that the stress waves reflected on the fault create a drop of normal stresses acting on the fault, which produces a reduction in shear stresses while resulting in fault slip. The influence of blast sequences on the behaviour of the fault is also examined assuming several types of blast sequences. Comparison of the blast sequence simulation results indicates that performing simultaneous blasts symmetrically induces the same level of seismic events as separate blasts, although seismic energy is more rapidly released when blasts are performed symmetrically. On the other hand when nine blast holes are blasted simultaneously, a large seismic event is induced, compared to the other two blasts. It is concluded that the separate blasts might be employed under the adopted geological conditions. The developed methodology and procedure to arrive at an ideal blast sequence can

  8. 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.

  9. A study to constrain the geometry of an active fault in southern Italy through borehole breakouts and downhole logs

    NASA Astrophysics Data System (ADS)

    Pierdominici, Simona; Mariucci, Maria Teresa; Montone, Paola

    2011-10-01

    Identification of an active fault and the local versus regional present-day stress field in the Irpinia region (southern Apennines) have been performed along a 5900 m deep well (San Gregorio Magno 1) by a detailed breakout and geophysical log analysis. The selected area is characterized by diffuse low magnitude seismicity, although in historical times moderate to large earthquakes have repeatedly struck it. On 23rd November 1980 a strong earthquake ( M = 6.9) nucleated on a 38-km long normal fault, named Irpinia fault, producing the first unequivocal historical surface faulting ever documented in Italy. The analysis of stress-induced wellbore breakouts shows a direction of minimum horizontal stress N18°±24°, fairly consistent with the regional stress trend (N44°±20°). The small discrepancy between our result and the regional stress orientation might be related to the influence of local stress sources such as variations of the Irpinia fault plane orientation and the presence of differently oriented active shear zones. This paper shows for the first time a detailed analysis on the present-day stress along a well to identify the Irpinia fault at depth and constrain its geometry.

  10. Tsunamigenic potential of Mediterranean fault systems and active subduction zones

    NASA Astrophysics Data System (ADS)

    Petricca, Patrizio; Babeyko, Andrey

    2016-04-01

    Since the North East Atlantic and Mediterranean Tsunami Warning System (NEAMTWS) is under development by the European scientific community, it becomes necessary to define guidelines for the characterization of the numerous parameters must be taken into account in a fair assessment of the risk. Definition of possible tectonic sources and evaluation of their potential is one of the principal issues. In this study we systematically evaluate tsunamigenic potential of up-to-now known real fault systems and active subduction interfaces in the NEAMTWS region. The task is accomplished by means of numerical modeling of tsunami generation and propagation. We have simulated all possible uniform-slip ruptures populating fault and subduction interfaces with magnitudes ranging from 6.5 up to expected Mmax. A total of 15810 individual ruptures were processed. For each rupture, a tsunami propagation scenario was computed in linear shallow-water approximation on 1-arc minute bathymetric grid (Gebco_08) implying normal reflection boundary conditions. Maximum wave heights at coastal positions (totally - 23236 points of interest) were recorded for four hours of simulation and then classified according to currently adopted warning level thresholds. The resulting dataset allowed us to classify the sources in terms of their tsunamigenic potential as well as to estimate their minimum tsunamigenic magnitude. Our analysis shows that almost every source in the Mediterranean Sea is capable to produce local tsunami at the advisory level (i.e., wave height > 20 cm) starting from magnitude values of Mw=6.6. In respect to the watch level (wave height > 50 cm), the picture is less homogeneous: crustal sources in south-west Mediterranean as well as East-Hellenic arc need larger magnitudes (around Mw=7.0) to trigger watch levels even at the nearby coasts. In the context of the regional warning (i.e., source-to-coast distance > 100 km) faults also behave more heterogeneously in respect to the minimum

  11. Magnetic fabrics induced by dynamic faulting reveal damage zone sizes in soft rocks, Dead Sea basin

    NASA Astrophysics Data System (ADS)

    Levi, T.; Weinberger, R.; Marco, S.

    2014-11-01

    The anisotropy of magnetic susceptibility (AMS) of soft rocks was measured in order to distinguish between the effect of remote and local strain fields, determine the size of the related inelastic damage zone and resolve the fault-plane solutions of past earthquakes. The AMS fabrics were explored next to late Pleistocene syndepositional normal faults (total displacement up to ˜3.5 m) that cross soft lacustrine rocks within the seismically active Dead Sea basin. `Deposition fabrics' prevail meters away from the fault planes and are characterized by scattered maximum and intermediate principal AMS axes. `Deformation fabrics' are detected up to tens of centimetres from the fault planes and are characterized by well-grouped AMS axes, in which one of the principal axes is parallel to the strike of the nearby fault. Variations in the AMS fabrics and magnetic lineations define the size of the inelastic damage zone around the faults. The results demonstrate that the deformation-driven magnetic fabrics and the associated inelastic damage zones are compatible with coseismic dynamic faulting and the effects of the local strain field during earthquakes. Most of the AMS fabrics show a conspicuous similarity to that of the fault-plane solutions, i.e., the principal AMS axes and instantaneous strain ellipsoids are coaxial. These results suggest a novel application of the AMS method for defining the shape and size of the damage zones surrounding dynamic faults and determining the full tensor of the local strain field.

  12. Structural and Lithologic Characteristics of the Wenchuan Earthquake Fault Zone and its Relationship with Seismic Activity

    NASA Astrophysics Data System (ADS)

    Wang, H.; Li, H.; Pei, J.; Li, T.; Huang, Y.; Zhao, Z.

    2010-12-01

    the older earthquake, but rather along the edge of the gouge. According to the gouge statistics of the whole fault zone, seismic events have the obvious tendency towards the foot wall, and the thickness of gouge is proportional to the activity of the fault, indicating that the width of fault zone is directly related to the number and evolution history of earthquakes . Repeated earthquakes maybe the main cause for the formation of the Longmenshan Moutains

  13. Structural Evidence for Fault Reactivation: the Active Priene-Sazli Fault Zone, Söke-Milet Basin, Western Anatolia

    NASA Astrophysics Data System (ADS)

    Sümer, Ö.; Inci, U.; Sözbilir, H.; Uzel, B.

    2009-04-01

    Western Anatolia is located at tha eastern part of the Aegean region that forms one of the most seismically active and rapidly extending regions in the world. One of the most prominent structural component of the Western Anatolia is E-W trending grabens. One of them is the Büyük Menderes Graben (BMG) showing a major change in strike ranging from E-W to NE-SW in its western end. This NE-SW oriented part of the graben is known as the Söke-Milet basin (SMB). The depression is 35 km long and 16 km wide. NW border of the basin is characterized by a morphotectonic structure namely Priene-Sazlı fault zone (PSFZ). The 16 July 1955 Söke-Balat earthquake (M=6.8) was atributed to this fault (Eyidogan and Jackson, 1985; Sengör, 1987; Altunel, 1998). However, field based kinematic studies on the PSFZ are lacking except for Gürer et. al. (2001). In this paper, we studied several reactivated fault segments of the PSFZ that are repeatedly formed under changing stress fields in order to evaluate the kinematic and stress history of the region by using structural relationships between striations and fault-plane related structures. The PSFZ consists of 5 fault segments which are en échelon arranged on the basis of mapping geological structures. The northern segments that strikes NE in the north and bends into an approximately E-W direction around Doganbey to the SW. Each segment is identified as steep opographic scarps ranging in height from a few meters to several hundred meters. Fault segments become to linkage and show breaching of the relay ramps between them. We interpret that such fault patterns have been formed in a region where extension has reactivated on pre-existing structures in an oblique sense. Evidence for this is the presence of three sets of striations each with different orientations on the same slip surface of the studied fault segments. Here, two differently oriented strike-slip slickenlines are postdated by dip-slip striations. Based on our structural

  14. Using optical dating to assess the recent activity of active faults in Hsinchu Area, northwestern Taiwan

    NASA Astrophysics Data System (ADS)

    Watanuki, T.; Chen, Y.

    2003-12-01

    The aim of this study is to evaluate the recent activity of active fault systems mapped in Hsinchu area, northwestern Taiwan. Since it is the largest site of industrial park and highly populated, it is essential to assess potential of earthquake hazards. As a result of previous work, two active fault systems (Hsinchu and Hsincheng) were identified as active. However, they have not been included in dangerous active faults on published map because Holocene offset has not been confirmed yet. Relationship between five river terraces and faults were discussed by mapping on geomorphic features; both of these thrust faults contain active anticlines in their hanging walls based on folded terraces that are composed of young alluvial deposits. Neither long-term nor short-term slip rate has been reported due to lack of age control on development timing of the terraces mentioned above. We collected samples from these terraces and open-pit trench on the highest terrace, where intercalated sandy layers are found within cobbles. As literatures optically stimulated luminescence (OSL) dating method can directly measure the burial ages of sedimentary deposits that underwent a short period of sunlight bleaching. Therefore, OSL dating is applied via single aliquot regeneration method on sand size quartz extract from our study terraces. OSL ages about 46ka and 68-75ka are obtained from 4 fluvial deposits at trenching site. We tentatively suggest that the terrace was abandoned by the main channel after 68ka and then upper strata were subsequently deposited by local small creeks. The vertical displacements cross these Hsinchu and Hsincheng active faults are ca. 90m and 70m, respectively since 68ka. Consequently, the derived long-term rates of vertical slip are 1.3 and 1.0 m/ka respectively for both of them. The details of the other age results and discussion on recent structural behavior will be presented.

  15. Induced seismicity and CO2 leakage through fault zones during large-scale underground injection in a multilayered sedimentary system

    NASA Astrophysics Data System (ADS)

    Pio Rinaldi, Antonio; Rutqvist, Jonny; Jeanne, Pierre; Cappa, Frederic; Guglielmi, Yves

    2014-05-01

    Overpressure caused by the direct injection of CO2 into a deep sedimentary system may produce changes in the state of stress, as well as, have an impact on the sealing capabilities of the targeted system. The importance of geomechanics including the potential for reactivating faults associated with large-scale geologic carbon sequestration operations has recently become more widely recognized. However, not withstanding the potential for triggering notable (felt) seismic events, the potential for buoyancy-driven CO2 to reach potable groundwater and the ground surface is more important from safety and storage-efficiency perspectives. In this context, this work extends previous studies on the geomechanical modeling of fault responses during underground carbon dioxide injection, focusing on both short- and long-term integrity of the sealing caprock, and hence of potential leakage of either brine or CO2 to shallow groundwater aquifers during active injection. The first part of this work aims to study the fault responses during underground carbon dioxide injection, focusing on the short-term (5 years) integrity of the CO2 repository, and hence on the potential leakage of CO2 to shallow groundwater aquifers. Increased pore pressure can alter the stress distribution on a fault/fracture zone, which may produce changes in the permeability related to the elastic and/or plastic strain (or stress) during single (or multiple) shear ruptures. We account for stress/strain-dependent permeability and study the leakage through the fault zone as its permeability changes along with strain and stress variations. We analyze several scenarios related to the injected amount of CO2 (and hence related to potential overpressure) involving both involving minor and major faults, and analyze the profile risks of leakage for different stress/strain permeability coupling functions, as well as increasing the complexity of the system in terms of hydromechanical heterogeneities. We conclude that

  16. Thrust-faulting earthquake induced many normal-faulting aftershocks, in northeastern Chiba Prefecture, Japan

    NASA Astrophysics Data System (ADS)

    Sakai, S.; Kato, A.; Hirata, N.; Nakagawa, S.; Kasahara, K.; Sato, H.; Kurashimo, E.; Nanjo, K.; Panayotopoulos, Y.; Obara, K.; Aketagawa, T.; Kimura, H.

    2010-12-01

    A thrust faulting type earthquake of a local body wave magnitude (MJMA) of 4.9 occurred near the upper interface of the subducting Philippine Sea Plate (PHS) in northeastern Chiba Prefecture on July 22, 2010. We have been developing a dense seismic net work call the MeSO-net in the Tokyo Metropolitan area. So far, 249 stations are available for the study of a large felt earthquakes and small event as low as M=1.5. We also deployed a temporary seismic array 24 of which were used for the analysis of the aftershocks. We locate the July 22 earthquake(MJMA=4.9) and its 19 aftershocks (M>1.5) by the double difference location algorithm. We also determine focal mechanisms for the main- and after-shocks. The locations of the main shock and three aftershocks are closely distributed near the upper interface of PHS, which is consistent with the idea that the event occurred on the plate interface. However, most aftershocks whose focal mechanism is normal-fault type with a T-axis directing NE-SW are located off the upper interface indicating that intra-slab events are also generated by the event. Acknowledgement: The present study is supported by Special Project for Earthquake Disaster Mitigation in Tokyo Metropolitan Area from the Ministry of Education, Culture, Sports, Science, and Technology of Japan.

  17. Relative tectonic activity assessment along the East Anatolian strike-slip fault, Eastern Turkey

    NASA Astrophysics Data System (ADS)

    Khalifa, Abdelrahman

    2016-04-01

    The East Anatolian transform fault is a morphologically distinct and seismically active left-lateral strike-slip fault that extends for ~ 500 km from Karlıova to the Maraş defining the boundary between the Anatolian Block and Syrian Foreland. Deformed landforms along the East Anatolian fault provide important insights into the nature of landscape development within an intra-continental strike-slip fault system. Geomorphic analysis of the East Anatolian fault using geomorphic indices including mountain front sinuosity, stream length-gradient index, drainage density, hypsometric integral, and the valley-width to valley height ratio helped differentiate the faulting into segments of differing degrees of the tectonic and geomorphic activity. Watershed maps for the East Anatolian fault showing the relative relief, incision, and maturity of basins along the fault zone help define segments of the higher seismic risk and help evaluate the regional seismic hazard. The results of the geomorphic indices show a high degree of activity, reveal each segment along the fault is active and represent a higher seismic hazard along the entire fault.

  18. 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.

  19. Late Quaternary tectonic activity and paleoseismicity of the Eastern Messinia Fault Zone, SW Peloponessus (Messinia, Greece).

    NASA Astrophysics Data System (ADS)

    Valkaniotis, Sotirios; Betzelou, Konstantina; Zygouri, Vassiliki; Koukouvelas, Ioannis; Ganas, Athanassios

    2015-04-01

    The southwestern part of Peloponnesus, Messinia and Laconia, is an area of significant tectonic activity situated near the Hellenic trench. Most of the deformation in this area is accommodated by the Eastern Messinia Fault Zone, bordering the western part of Taygetos Mt range and the west coast of Mani peninsula. The Eastern Messinia Fault Zone (EMFZ) is a complex system of primarily normal faults dipping westwards with a strike of NNW-SSE to N-S direction attaining a total length of more than 100 km from the northern Messinia plain in the north to the southern part of Mani peninsula in the south. The continuity of the EMFZ is disrupted by overlapping faults and relay ramp structures. The central part of the EMFZ, from the town of Oichalia to the city of Kalamata, was investigated by detailed field mapping of fault structures and post-alpine sediment formations together with re-evaluation of historical and modern seismicity. Several fault segments with lengths of 6 to 10 km were mapped, defined and evaluated according to their state of activity and age. Analysis of fault striation measurements along fault planes of the fault zone shows a present regime of WSW-ENE extension, in accordance with focal mechanisms from modern seismicity. Known faults like the Katsareika and Verga faults near the city of Kalamata are interpreted as older-generation faults that are re-activated (e.g. the 1986 Ms 6.0 Kalamata earthquake on Verga Fault) as part of a system of distributed deformation. New fault segments, some of them previously unmapped like the Asprohoma fault to the west of Kalamata, and offshore faults like Kitries and Kourtissa, are being assigned to the EMFZ. Moreover, a paleoseismological trench was excavated in the northern part of Pidima fault segment, one of the most prominent active segments of the central part of the EMFZ, in order to examine the paleoearthquake record of the fault system. A significant number of historical and instrumental earthquakes in the area

  20. Active faults crossing trunk pipeline routes: some important steps to avoid the disaster

    NASA Astrophysics Data System (ADS)

    Besstrashnov, Vladimir; Strom, Alexander

    2010-05-01

    Trunk pipelines that pass through tectonically active areas connecting oil and gas reservoirs with terminals and refineries cross active faults that can produce large earthquakes. Besides strong motion affecting vast areas, these earthquakes are often associated with surface faulting that provides additional hazard to pipelines. To avoid significant economic losses and environmental pollution, pipelines should be designed to sustain both effects (shaking and direct rupturing) without pipe damage and spill. Special studies aimed to provide necessary input data for the designers should be performed in the course of engineering survey. However, our experience on conducting and review of such studies for several oil and gas trunk pipelines in Russia show urgent need of more strict definition of basic conceptions and approaches used for identification and localization of these potentially hazardous tectonic features. Identification of active faults (fault zones) considered as causative faults - sources of strong motion caused by seismic waves that affect dozens kilometers of pipeline route can be done by use of both direct and indirect evidence of Late Pleistocene - Holocene activity of faults and fault zones. Since strong motion parameters can be considered as constant within the near-field zone, which width in case of large earthquake is up to dozens kilometers, accuracy of active fault location is not so critical and ±1-2 km precision provided by use of indirect evidence is acceptable. In contrast, if one have to identify and characterize zones of potential surface rupturing that require special design of the endangered pipeline section, only direct evidence of such activity can provide reliable input data for crossing design with relevant accuracy of fault location, amount and direction of displacement. Only traces of surface faults displacing Late Pleistocene - Holocene sediments and/or geomorphic features are considered as direct evidence of fault activity. Just

  1. Evolution and dynamics of active faults in southeastern Egyptian Western Desert

    NASA Astrophysics Data System (ADS)

    Abdeen, Mamdouh

    2016-07-01

    Remote sensing data processing and analysis together with interpretation of earthquake data that are followed by extensive field studies on some of the prevailing NS and EW striking faults indicate that these faults have an intimate relationship and were formed synchronously as a conjugate Riedel shears. Parallel to the NS and the EW faults open fractures filled with blown sand dominate the area of study. The Quaternary terraces adjacent to these faults are offset by the faults. Kinematic indicators on the NS striking faults indicate major sinistral (left-lateral) strike slip and minor dip-slip (normal) movement. On the other hand, kinematic indicators on the EW striking faults indicate major dextral (right-lateral) strike slip and minor dip-slip (normal) movement. Paleo-stress analysis of the fault striae measured on the NS and EW faults indicate that these faults were formed under NNE-SSW oriented extension. Instrumental earthquake data analysis shows a comparable extension direction to that derived from field measurements of slickenlineation. These observations indicate that the NS- and EW-striking faults are contemporaneous and are related to the Red Sea rifting that is currently active.

  2. Geomechanical Reservoir Characterization for Prediction of the Likelihood of Faulting Induced by CO2 Sequestration

    NASA Astrophysics Data System (ADS)

    Chiaramonte, L.; Zoback, M.; Friedmann, J.; Stamp, V.

    2006-12-01

    Geologic sequestration of CO2 has been proposed as a key technology for reducing greenhouse gas in the atmosphere. However, leakage of CO2 from any potential reservoir could seriously compromise the goal of long-term storage. Therefore understanding the likelihood of leakage is a key step toward the feasibility of this technology. Because it has long been known that fluid injection can lead to fault reactivation, assessing the potential of induced fault slip and leakage of CO2 from any potential storage reservoir is critical prior to injection of large quantities of CO2. We have developed a geomechanical model in advance of a proposed injection experiment at Teapot Dome, WY in order to study in detail the processes of a CO2 leak through predicted faults. Teapot Dome is an elongated asymmetrical, basement-cored anticline with a north-northeast axis. It is part of the Salt Creek structural trend, located in the southwestern edge of the Powder River Basin. The anticline is compartmentalized in a series of oblique-slip faults, generally oriented NE-SW, although varying in geometry, displacement, and complexity. In particular, the fault network referred to as S2 shows a greater complexity and a range of geometries and azimuths that enhances its potential for leakage. Furthermore its surface expression show alkali springs and hydrocarbon samples within the fault veins and gouge. The S2 fault intersects the oil-bearing 2nd Wall Creek around 650m, which is close in terms of temperature and pressure to conditions of supercritical CO2 phase injection and oil miscibility. We developed a preliminary geomechanical model of the deeper Tensleep Fm. previously, utilizing observations of wellbore breakouts, drilling induced fractures, leak-off or mini-frac tests and other available geophysical data. We used this information to evaluate the potential for injection to induce slip on the S1 fault, approximately 2 km south of the present study area. These results are compared and

  3. The containment set approach to digital system tolerance of lightning-induced transient faults

    NASA Technical Reports Server (NTRS)

    Masson, G. M.; Glaser, R. E.

    1982-01-01

    A fault model and a system model are necessary to assess the tolerance or resilience of a digital system to lightning-induced transients. It is noted that these models are usually developed separately. A new approach is outlined here for this assessment problem which combines the fault and system models into an overall model. With this approach, referred to as the containment set approach, an assessment of the effects of lightning-induced transients can be made in terms of a state transition matrix. This matrix can be generated by means of fault injection experiments. In addition, certain nonredundancy-oriented design alternatives to the achievement of lightning-induced transient tolerance in digital systems are indicated by the containment set approach.

  4. High-resolution imagery of active faulting offshore Al Hoceima, Northern Morocco

    NASA Astrophysics Data System (ADS)

    d'Acremont, E.; Gutscher, M.-A.; Rabaute, A.; Mercier de Lépinay, B.; Lafosse, M.; Poort, J.; Ammar, A.; Tahayt, A.; Le Roy, P.; Smit, J.; Do Couto, D.; Cancouët, R.; Prunier, C.; Ercilla, G.; Gorini, C.

    2014-09-01

    Two recent destructive earthquakes in 1994 and 2004 near Al Hoceima highlight that the northern Moroccan margin is one of the most seismically active regions of the Western Mediterranean area. Despite onshore geodetic, seismological and tectonic field studies, the onshore-offshore location and extent of the main active faults remain poorly constrained. Offshore Al Hoceima, high-resolution seismic reflection and swath-bathymetry have been recently acquired during the Marlboro-2 cruise. These data at shallow water depth, close to the coast, allow us to describe the location, continuity and geometry of three active faults bounding the offshore Nekor basin. The well-expressed normal-left-lateral onshore Trougout fault can be followed offshore during several kilometers with a N171°E ± 3° trend. Westward, the Bousekkour-Aghbal normal-left-lateral onshore fault is expressed offshore with a N020°E ± 4° trending fault. The N030°E ± 2° Bokkoya fault corresponds to the western boundary of the Plio-Quaternary offshore Nekor basin in the Al Hoceima bay and seems to define an en échelon tectonic pattern with the Bousekkour-Aghbal fault. We propose that these three faults are part of the complex transtensional system between the Nekor fault and the Al-Idrissi fault zone. Our characterization of the offshore expression of active faulting in the Al Hoceima region is consistent with the geometry and nature of the active fault planes deduced from onshore geomorphological and morphotectonic analyses, as well as seismological, geodetic and geodynamic data.

  5. 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.

  6. Active tectonics of the Ganzi-Yushu fault in the southeastern Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Shi, Feng; He, Honglin; Densmore, Alexander L.; Li, An; Yang, Xiaoping; Xu, Xiwei

    2016-04-01

    The ongoing convergence between India and Eurasia apparently is accommodated not merely by crustal shortening in Tibet, instead also by motions along strike slip faults which are usually boundaries between tectonic blocks, especially in the Tibetan Plateau. Quantification of this strike slip faulting is fundamental for understanding the collision between India and Eurasia. Here, we use a variety of geomorphic observations to place constraints on the late Quaternary kinematics and slip rates of the Ganzi-Yushu fault, one of the significant strike-slip faults in eastern Tibet. The Ganzi-Yushu fault is an active, dominantly left-lateral strike-slip structure that can be traced continuously for up to 500 km along the northern boundary of the clockwise-rotating southeastern block of the Tibetan Plateau. We analyse geomorphic evidence for deformation, and calculate the late Quaternary slip rates at four sites along the eastern portion of the fault trace. The latest Quaternary apparent throw rates are variable along strike but are typically ~ 1 mm/a. Rates of strike-slip displacement are likely to be an order of magnitude higher, 8-11 mm/a. Trenching at two locations suggests that the active fault behaviour is dominated by strike-slip faulting and reveals several earthquake events with refined information of timing. The 2010 Mw 6.9 Yushu earthquake, which occurred on the northwestern segment of the Ganzi-Yushu fault zone, provides additional evidence for fault activity. These observations agree with GPS-derived estimates, and show that late Quaternary slip rates on the Ganzi-Yushu fault are comparable to those on other major active strike-slip faults in the eastern Tibetan Plateau.

  7. Faults and associated landslides on the Torrey Pines mesa, an expression of the active Rose Canyon fault zone, La Jolla, California

    SciTech Connect

    Rindell, A.K. )

    1993-04-01

    The Rose Canyon fault zone (RCFZ), San Diego's active NW striking right-lateral wrench, bends to the left at La Jolla, creating a poorly understood zone of transpression. North of La Jolla, continuing investigations along seacliffs and road-cuts have exposed a number of en echelon, NE striking antithetic faults previously interpreted as either E-W striking faults, landslides, and/or Eocene soft-sediment deformations. However, thrust faulting and left-lateral movement, in addition to antithetic strikes, indicates that at least one of these, the Marine Fisheries fault, is associated with the RCFZ. A graben formed by a left-step along this fault has led to land subsidence and engineering problems for the National Marine Fisheries building. In addition, progressive seacliff retreat here and at other locations is partly controlled by fault associated fractures. A cliff-face exposure of the Salk fault reveals diverging fault splays flattening to the near horizontal with movement occurring along bedding planes within the sedimentary section, creating the appearance of landsliding. Classic flower structures have also been found up to 5 km inland, along NE strikes to the shoreline exposures of the Salk and Scripps faults. Faults traces are generally obscured by urbanization and numerous ancient and/or presently active coherent landslides. Although these faults are classified as only potentially active, timing and risk of seismic movement are not well constrained. In addition, record rainfalls in San Diego County have dramatically increased landsliding potential. A well exposed dike, dated at 11 Ma (older than the Pliocene age of the RCFZ), is exposed from the seacliffs offshore towards the RCFZ. It has a significant magnetic anomaly ranging up to 450 gammas and appears to be offset by the Marine Fisheries and Scripps faults. Measuring offsets of this and other reported and suspected offshore dikes may better define total offset from both the RCFZ and antithetic faulting.

  8. Multiplane-induced widening of stacking faults in fcc metals

    NASA Astrophysics Data System (ADS)

    Shehadeh, Mutasem A.; Lu, G.; Chen, Z.; Kioussis, N.; Ghoniem, N. M.

    2007-10-01

    Using an ab initio-based parametric dislocation dynamics approach we show that Shockley partials on successive glide planes greatly assist the widening of stacking faults (SFs) in Al and Ag. This effect is amplified when all trailing partials are pinned. Subsequent placement of Shockley partials on adjacent planes enhances further the widening of the SF width. In sharp contrast, dislocations with zero net Burgers vector across three successive planes form very compact cores in both Al and Ag, in agreement with recent experiments.

  9. Stacking fault induced tunnel barrier in platelet graphite nanofiber

    SciTech Connect

    Lan, Yann-Wen E-mail: ywlan@phys.sinica.edu.tw; Chang, Yuan-Chih; Chang, Chia-Seng; Chen, Chii-Dong E-mail: ywlan@phys.sinica.edu.tw; Chang, Wen-Hao; Li, Yuan-Yao

    2014-09-08

    A correlation study using image inspection and electrical characterization of platelet graphite nanofiber devices is conducted. Close transmission electron microscopy and diffraction pattern inspection reveal layers with inflection angles appearing in otherwise perfectly stacked graphene platelets, separating nanofibers into two domains. Electrical measurement gives a stability diagram consisting of alternating small-large Coulomb blockade diamonds, suggesting that there are two charging islands coupled together through a tunnel junction. Based on these two findings, we propose that a stacking fault can behave as a tunnel barrier for conducting electrons and is responsible for the observed double-island single electron transistor characteristics.

  10. Fault structure, stress, or pressure control of the seismicity in shale? Insights from a controlled experiment of fluid-induced fault reactivation

    NASA Astrophysics Data System (ADS)

    De Barros, Louis; Daniel, Guillaume; Guglielmi, Yves; Rivet, Diane; Caron, Hervé; Payre, Xavier; Bergery, Guillaume; Henry, Pierre; Castilla, Raymi; Dick, Pierre; Barbieri, Ernesto; Gourlay, Maxime

    2016-06-01

    Clay formations are present in reservoirs and earthquake faults, but questions remain on their mechanical behavior, as they can vary from ductile (aseismic) to brittle (seismic). An experiment, at a scale of 10 m, aims to reactivate a natural fault by fluid pressure in shale materials. The injection area was surrounded by a dense monitoring network comprising pressure, deformation, and seismicity sensors, in a well-characterized geological setting. Thirty-two microseismic events were recorded during several injection phases in five different locations within the fault zone. Their computed magnitude ranged between -4.3 and -3.7. Their spatiotemporal distribution, compared with the measured displacement at the injection points, shows that most of the deformation induced by the injection is aseismic. Whether the seismicity is controlled by the fault architecture, mineralogy of fracture filling, fluid, and/or stress state is then discussed. The fault damage zone architecture and mineralogy are of crucial importance, as seismic slip mainly localizes on the sealed-with-calcite fractures which predominate in the fault damage zone. As no seismicity is observed in the close vicinity of the injection areas, the presence of fluid seems to prevent seismic slips. The fault core acts as an impermeable hydraulic barrier that favors fluid confinement and pressurization. Therefore, the seismic behavior seems to be strongly sensitive to the structural heterogeneity (including permeability) of the fault zone, which leads to a heterogeneous stress response to the pressurized volume.

  11. 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.

  12. Palaeoseismological evidence for Holocene activity on the Manisa Fault Zone,Western Anatolia

    NASA Astrophysics Data System (ADS)

    Özkaymak, Ç.; Sözbilir, H.; Uzel, B.; Akyüz, H. S.

    2009-04-01

    Manisa Fault Zone (MFZ) is an active structural discontinuity that is geomorphologically expressed as a trace of north-facing Quaternary fault scarps bounding the southern margin of the Manisa basin which is subsidiary to the Gediz Graben. We note that the present-day fault trace is over 50 km long from Manisa city in the northwest to the Turgutlu town in the southeast. The MFZ consists of two major sections: (i) eastern section that strikes NW-SE direction in the south and bends into an approximately E-W direction around Manisa to the northwest, (ii) an approximately 10-km-long western section that strikes approximately WNW-ESE direction from Manisa city in the east to the Akgedik town in the west. In this study, we present the geologic, geomorphologic, and palaeoseismologic observations indicating Holocene activity on the western section of the fault zone. We identify that the MFZ, at its western end, consists of three fault segments which are en échelon arranged in left step; the fault segments show evidence for linkage and breaching at the relay ramps. One of them is named as the Manastir Fault. In front of this fault, two Holocene colluvial fans older of which is uncorformity bounded are cut and displaced by the syntethic faults. Palaeoseismologic data show that the syntethic fault segments correspond to the surface ruptures of the historical earthquakes. As a result of detailed stratigraphic, sedimentologic and structural observations on the trench walls, some evidences for at least two earthquakes are recorded which are supported by radio-carbon dating. Besides this, an archaic aqueduct that were used to transport water from Emlakdere town, located on the hanging wall of the Manastir Fault, to the basin is cut and displaced by the syntethic fault egments. It is known that this archaic architecture were in use after 11. century by the Ottomans. On the basis of the mentioned data, fault segments which are belong to the western part of the Manisa Fault Zone

  13. Paleoseismology of latest Pleistocene and Holocene fault activity in central Oregon

    SciTech Connect

    Pezzopane, S.K.; Weldon, R.J. II . Dept. of Geological Sciences)

    1993-04-01

    Latest Pleistocene and Holocene fault activity in Oregon concentrates along four zones that splay northward from seismically active faults along the Central Nevada and Eastern California seismic zones. The Central Oregon fault zone is one of these zones, which splays northward from dextral faults of the Walker Lane, stretching across the flanks of several ranges in south-central Oregon along a N20[degree]W trend, and ultimately merges with the Cascade volcanic arc near Newberry volcano. Aerial-photo interpretations and field investigations reveal fault scarps with, on average about 4 m, but in places as much as [approximately]10 m of vertical expression across latest Pleistocene pluvial lake deposits and geomorphic surfaces. Trenches across three different faults in the Central Oregon zone reveal evidence for multiple episodes of faulting in the form of fault-related colluvial deposits and deformed horizons which have been cut by younger fault movements. Trench exposures reveal faults with relatively steep dips and anastomosing traces, which are interpreted locally as evidence for a small oblique-slip component. Vertical offsets measured in the trenches are [approximately]2 m or more for each event. Radiocarbon analyses and preliminary tephra correlations indicate that the exposed deposits are [approximately]30,000 yr in age and younger, and record the decline of latest Pleistocene pluvial lakes. Commonly, reworked or deformed lacustrine deposits and interlayered and faulted colluvial deposits mark the second and third events back, which probably occurred in the Latest Pleistocene, at a time during low to moderate lake levels. If offsets of the past 18,000 yr are representative of the long-term average, then faults along this zone have slip rates of from 0.2 mm/yr to 0.6 mm/yr and recurrence intervals that range from [approximately]4,000 yr to 11,000 yr.

  14. Architectural evolution of the Nojima fault and identification of the activated slip layer by Kobe earthquake

    NASA Astrophysics Data System (ADS)

    Tanaka, Hidemi; Omura, Kentaro; Matsuda, Tatsuo; Ikeda, Ryuji; Kobayashi, Kenta; Murakami, Masaki; Shimada, Koji

    2007-07-01

    Evolutionary history of Nojima Fault zone is clarified by comprehensive examinations of petrological, geophysical, and geochemical characterizations on a fault zone in deep-drilled core penetrating the Nojima Fault. On the basis of the results, we reconstruct a whole depth profile of the architecture of the Nojima Fault and identify the primal slip layer activated by 1995 Kobe earthquake. The deepest part (8- to 12-km depth) of the fault zone is composed of thin slip layers of pseudotachylite (5 to 10 mm thick each, 10 cm in total). Middle depth (4- to 8-km depth) of the fault zone is composed of fault core (6 to 10 m thick), surrounded by thick (100 m thick) damage zone, characterized by zeolite precipitation. The shallow part of the fault zone (1- to 4-km depth) is composed of distributed narrow shear zones, which are characterized by combination of thin (0.5 cm thick each, 10 cm in total) ultracataclasite layers at the core of shear zones, surrounded by thicker (1 to 3 m thick) damage zones associated with carbonate precipitation. An extremely thin ultracataclasite layer (7 mm thick), activated by the 1995 Kobe earthquake, is clearly identified from numerous past slip layers, overprinting one of the shear zones, as evidenced by conspicuous geological and geophysical anomalies. The Nojima Fault zone was 10 to 100 times thicker at middle depth than that of shallower and deeper depths. The thickening would be explained as a combination of physical and chemical effects as follows. (1) Thickening of "fault core" at middle depth would be attributed to normal stress dependence on thickness of the shear zone and (2) an extreme thickening of "damage zone" in middle depth of the crust would result from the weakening of the fault zone due to super hydrostatic fluid pressure at middle depths. The high fluid pressure would result from faster sealing with low-temperature carbonate at the shallower fault zone.

  15. Magnetic fabrics induced by dynamic faulting reveal damage zone sizes in soft rocks, Dead Sea basin

    NASA Astrophysics Data System (ADS)

    Levi, Tsafrir; Weinberger, Rami; Marco, Shmulik

    2015-04-01

    Distinguishing between the effect of remote versus local strain fields, determining the size of the related inelastic damage zone, and resolving the fault-plane solutions of past earthquakes are of fundamental importance to neotectonic reconstructions and paleoseismic studies. In order to shad lights on these issues, we measured the anisotropy of magnetic susceptibility (AMS) of soft rocks within a seismically active region. The AMS fabrics were explored next to late Pleistocene syndepositional normal faults (total displacement up to ~3.5 m) that cross soft lacustrine rocks in the Dead Sea basin. 'Deposition fabrics' prevail meters away from the fault planes and are characterized by scattered maximum and intermediate principal AMS axes. 'Deformation fabrics' are detected up to tens of centimeters from the fault planes and are characterized by well-grouped AMS axes, in which one of the principal axes is parallel to the strike of the nearby fault. Variations in the AMS fabrics and magnetic lineations define the size of the inelastic damage zone around the faults. The results demonstrate that the deformation-driven magnetic fabrics and the associated inelastic deformation zones are compatible with coseismic dynamic faulting and the effects of the local strain field during earthquakes. Most of the AMS fabrics show a conspicuous similarity to that of the fault-plane solutions, i.e. the principal AMS axes and instantaneous strain ellipsoids are coaxial. These results suggest a novel application of the AMS method for defining the shape and size of the damage zones surrounding the paleo- dynamic faults and determining the principal axes of the local strain field.

  16. Determination of paleoseismic activity over a large time-scale: Fault scarp dating with 36Cl

    NASA Astrophysics Data System (ADS)

    Mozafari Amiri, Nasim; Tikhomirov, Dmitry; Sümer, Ökmen; Özkaymak, Çaǧlar; Uzel, Bora; Ivy-Ochs, Susan; Vockenhuber, Christof; Sözbilir, Hasan; Akçar, Naki

    2016-04-01

    Bedrock fault scarps are the most direct evidence of past earthquakes to reconstruct seismic activity in a large time-scale using cosmogenic 36Cl dating if built in carbonates. For this method, a surface along the fault scarp with a minimum amount of erosion is required to be chosen as an ideal target point. The section of the fault selected for sampling should cover at least two meters of the fault surface from the lower part of the scarp, where intersects with colluvium wedge. Ideally, sampling should be performed on a continuous strip along the direction of the fault slip direction. First, samples of 10 cm high and 15 cm wide are marked on the fault surface. Then, they are collected using cutters, hammer and chisel in a thickness of 3 cm. The main geometrical factors of scarp dip, scarp height, top surface dip and colluvium dip are also measured. Topographic shielding in the sampling spot is important to be estimated as well. Moreover, density of the fault scarp and colluvium are calculated. The physical and chemical preparations are carried in laboratory for AMS and chemical analysis of the samples. A Matlab® code is used for modelling of seismically active periods based on increasing production rate of 36Cl following each rupture, when a buried section of a fault is exposed. Therefore, by measuring the amount of cosmogenic 36Cl versus height, the timing of major ruptures and their offsets are determined. In our study, Manastır, Mugırtepe and Rahmiye faults in Gediz graben, Priene-Sazlı, Kalafat and Yavansu faults in Büyük Menderes graben and Ören fault in Gökava half-graben have been examined in the seismically active region of Western Turkey. Our results reconstruct at least five periods of high seismic activity during the Holocene time, three of which reveal seismic ruptures beyond the historical pre-existing data.

  17. Active fault, fault growth and segment linkage along the Janauri anticline (frontal foreland fold), NW Himalaya, India

    NASA Astrophysics Data System (ADS)

    Malik, Javed N.; Shah, Afroz A.; Sahoo, Ajit K.; Puhan, B.; Banerjee, Chiranjib; Shinde, Dattatraya P.; Juyal, Navin; Singhvi, Ashok K.; Rath, Shishir K.

    2010-03-01

    The 100 km long frontal foreland fold — the Janauri anticline in NW Himalayan foothills represents a single segment formed due to inter-linking of the southern (JS1) and the northern (JS2) Janauri segments. This anticline is a product of the fault related fold growth that facilitated lateral propagation by acquiring more length and linkage of smaller segments giving rise to a single large segment. The linked portion marked by flat-uplifted surface in the central portion represents the paleo-water gap of the Sutlej River. This area is comparatively more active in terms of tectonic activity, well justified by the occurrence of fault scarps along the forelimb and backlimb of the anticline. Occurrence of active fault scarps on either side of the anticline suggests that the slip accommodated in the frontal part is partitioned between the main frontal thrust i.e. the Himalayan Frontal Thrust (HFT) and associated back-thrust. The uplift in the piedmont zone along southern portion of Janauri anticline marked by dissected younger hill range suggests fore-landward propagation of tectonic activity along newly developed Frontal Piedmont Thrust (FPT), an imbricated emergent thrust branching out from the HFT system. We suggests that this happened because the southern segment JS1 does not linked-up with the northwestern end of Chandigarh anticline segment (CS). In the northwestern end of the Janauri anticline, due to no structural asperity the tectonic activity on HFT was taken-up by two (HF1 — in the frontal part and HF2 — towards the hinterland side) newly developed parallel active faults ( Hajipur Fault) branched from the main JS2 segment. The lateral propagation and movements along HF1 and HF2 resulted in uplift of the floodplain as well as responsible for the northward shift of the Beas River. GPR and trench investigations suggest that earthquakes during the recent past were accompanied with surface rupture. OSL (optical stimulated luminescence) dates from the trench

  18. A 665 year record of Coulomb stress changes on active faults in the central Apennines, Italy.

    NASA Astrophysics Data System (ADS)

    Wedmore, L. N. J.; Faure Walker, J.; Roberts, G.; McCaffrey, K. J. W.; Sammonds, P. R.

    2014-12-01

    Active extension in the central Apennines is accommodated on numerous 20-30km long normal faults. Over multiple earthquake cycles fault slip is controlled by viscous flow in narrow shear zones, which are below the brittle seismogenic crust and are driven by upwelling mantle beneath the central Apennines. However, on short timescales, there is evidence for clustering along strike on the north eastern set of faults in the region, with the south western faults comparatively quiet during the period of reliable historical earthquake records (since 1349 AD). In contrast, 15±3ka strain rates show no evidence of skewness towards the north eastern faults. This suggests that on short timescales, elastic loading and fault interaction may be controlling the location of earthquakes and the seismic hazard, as opposed to the view that fault activity has permanently migrated from the south west flank of the central Apennines to the north east flank. We used Coulomb stress modelling to test whether the sequence of historical earthquakes can be explained by stress triggering and elastic loading. Palaeoseismic and historical records were used to reconstruct the co-seismic static Coulomb stress changes for 27 earthquakes in central Italy from 1349-2009. 15±3ka throws measured across faults in the area were used as an analogue for the slip distributions, with the slip direction constrained by field measurements of frictional wear striae on exposed bedrock fault scarps. Interseismic loading was modelled using a shear zone rheology below the seismogenic zone of each fault; slip rates measured at the surface were used to control the rate of loading. The sensitivity of the model was explored by iterating varying slip distributions, fault kinematics and earthquake locations. We show that for sequences of clustered earthquakes that occurred on timescales of days to weeks, co-seismic static Coulomb stress transfer can explain the pattern of faulting with stress changes of 0.001-0.1 MPa

  19. Geomorphic features of active faults around the Kathmandu Valley, Nepal, and no evidence of surface rupture associated with the 2015 Gorkha earthquake along the faults

    NASA Astrophysics Data System (ADS)

    Kumahara, Yasuhiro; Chamlagain, Deepak; Upreti, Bishal Nath

    2016-04-01

    The M7.8 April 25, 2015, Gorkha earthquake in Nepal was produced by a slip on the low-angle Main Himalayan Thrust, a décollement below the Himalaya that emerges at the surface in the south as the Himalayan Frontal Thrust (HFT). The analysis of the SAR interferograms led to the interpretations that the event was a blind thrust and did not produce surface ruptures associated with the seismogenic fault. We conducted a quick field survey along four active faults near the epicentral area around the Kathmandu Valley (the Jhiku Khola fault, Chitlang fault, Kulekhani fault, Malagiri fault and Kolphu Khola fault) from July 18-22, 2015. Those faults are located in the Lesser Himalaya on the hanging side of the HFT. Based on our field survey carried out in the area where most typical tectonic landforms are developed, we confirmed with local inhabitants the lack of any new surface ruptures along these faults. Our observations along the Jhiku Khola fault showed that the fault had some definite activities during the Holocene times. Though in the past it was recognized as a low-activity thrust fault, our present survey has revealed that it has been active with a predominantly right-lateral strike-slip with thrust component. A stream dissecting a talus surface shows approximately 7-m right-lateral offset, and a charcoal sample collected from the upper part of the talus deposit yielded an age of 870 ± 30 y.B.P, implying that the talus surface formed close to 870 y.B.P. Accordingly, a single or multiple events of the fault must have occurred during the last 900 years, and the slip rate we estimate roughly is around 8 mm/year. The fault may play a role to recent right-lateral strike-slip tectonic zone across the Himalayan range. Since none of the above faults showed any relationship corresponding to the April 25 Gorkha earthquake, it is possibility that a potential risk of occurrence of large earthquakes does exist close to the Kathmandu Valley due to movements of these active

  20. Active fault tolerant control of a flexible beam

    NASA Astrophysics Data System (ADS)

    Bai, Yuanqiang; Grigoriadis, Karolos M.; Song, Gangbing

    2007-04-01

    This paper presents the development and application of an H∞ fault detection and isolation (FDI) filter and fault tolerant controller (FTC) for smart structures. A linear matrix inequality (LMI) formulation is obtained to design the full order robust H∞ filter to estimate the faulty input signals. A fault tolerant H∞ controller is designed for the combined system of plant and filter which minimizes the control objective selected in the presence of disturbances and faults. A cantilevered flexible beam bonded with piezoceramic smart materials, in particular the PZT (Lead Zirconate Titanate), in the form of a patch is used in the validation of the FDI filter and FTC controller design. These PZT patches are surface-bonded on the beam and perform as actuators and sensors. A real-time data acquisition and control system is used to record the experimental data and to implement the designed FDI filter and FTC. To assist the control system design, system identification is conducted for the first mode of the smart structural system. The state space model from system identification is used for the H∞ FDI filter design. The controller was designed based on minimization of the control effort and displacement of the beam. The residuals obtained from the filter through experiments clearly identify the fault signals. The experimental results of the proposed FTC controller show its e effectiveness for the vibration suppression of the beam for the faulty system when the piezoceramic actuator has a partial failure.

  1. Active fault systems and tectono-topographic configuration of the central Trans-Mexican Volcanic Belt

    NASA Astrophysics Data System (ADS)

    Szynkaruk, Ewa; Graduño-Monroy, Víctor Hugo; Bocco, Gerardo

    2004-07-01

    The central Trans-Mexican Volcanic Belt (TMVB) reflects the interplay between three regional fault systems: the NNW-SSE to NW-SE striking Taxco-Querétaro fault system, the NE-SW striking system, and the E-W striking Morelia-Acambay fault system. The latter is the youngest and consists of fault scarps up to 500 m high, whose formation caused structural and morphological reorganization of the region. In this paper, we investigate possible activity of the three systems within the central TMVB, and assess the role that they play in controlling the tectono-topographic configuration of the area. Our study is based on DEM-derived morphometric maps, longitudinal river profiles, geomorphologic mapping, and structural field data concerning recent faulting. We find that all three regional fault systems are active within the central TMVB, possibly with different displacement rates and/or type of motion; and that NNW-SSE and NE-SW striking faults control the major tectono-topographic elements that build up the region, which are being re-shaped by E-W striking faults. We also find that tectonic information can be deciphered from the topography of the youthful volcanic arc in question, regardless its complexity.

  2. Active low-angle (?) normal faulting along the North Lunggar rift, western Tibet

    NASA Astrophysics Data System (ADS)

    Logan, M. A.; Taylor, M. H.; Styron, R. H.; Gosse, J. C.; Ding, L.; Yang, G.

    2012-12-01

    Here we present surface exposure ages of faulted fluvial terraces using cosmogenic nuclides from the North Lunggar rift. The Lunggar rift is one of seven major north-striking rift basins accommodating east-west directed extension on the Tibetan Plateau. The Lunggar rift in west-central Tibet is divided into two distinct north and south segments based on fault geometry. The North Lunggar range is bounded on its east side by a <40 degree dipping, ~N-striking normal fault. This normal fault is considered inactive as the main detachment is unconformably overlain by unfaulted moraines and alluvial fans. Farther into the hanging wall basin, approximately 6 km eastward, several fault scarps parallel the Lunggar detachment. Locally, active faulting is distributed in the hanging wall with as many as seven normal fault scarps accommodating active east-west directed extension. Recent activity of these smaller faults is apparent from cross-cut fluvial terraces that have been uplifted by as much as 75 m. The geomorphology and fault geometry of the North Lunggar rift are consistent with high-angle normal faults that sole into a single master detachment fault at depth. A high-resolution digital elevation model constructed from real-time kinematic-GPS data has made details of the geomorphology clear and allowed for precise measurements of geomorphic offsets across the fault scarps. We estimate the surface abandonment ages using the depth profiling approach with cosmogenic nuclides. Three cosmogenic depth profiles are being analyzed in this study with each depth profile consisting of five samples at varying depths in order to account for inheritance. Site 1 is the southernmost and is on the highest uplifted fluvial terrace and is being prepared for 10Be analysis. Site 2 comprises two depth profiles on the highest and intermediate uplifted terraces, respectively. Samples at site 2 have low quartz yields and are being prepared for 36Cl analysis. Combining the fault offsets and

  3. Evidence for active creep on the Alto Tiberina low angle normal fault inferred using GPS geodesy

    NASA Astrophysics Data System (ADS)

    Rick, Bennett; Jackson, Lily; Mencin, David; Casale, Gabriele

    2014-05-01

    range ~43.2ºN and 43.5ºN. We also test the regional extent of the fault by extending the fault model to the north and south of the well-imaged portion of the fault, assuming a 20º dip. We estimated fault coupling along-strike and down-dip to assess spatial variations in creep on the model fault. Our modeling suggests that the portion of the model fault in the latitude band ~43.1ºN to ~43.7ºN, encompassing the geophysically imaged ATF fault, creeps at nearly the full fault slip rate of ~2 mm/yr below a depths of 3-5 km. Our model corroborates previous inferences, suggesting active creep at shallow depth on the well-imaged portion of the ATF. However, outside of this range of latitudes, where the existence of a regional low angle normal fault is speculative, the model fault appears to be coupled to greater depths (7-8 km or deeper). Interestingly, the apparent locked zones to the north and south of the creeping zone correlate with the locations of instrumentally recorded large magnitude hanging wall earthquakes. In contrast, there have been no instrumentally recorded large magnitude earthquakes in the hanging wall overlying the creeping portion of the fault.

  4. Results From NICLAKES Survey of Active Faulting Beneath Lake Nicaragua, Central American Volcanic Arc

    NASA Astrophysics Data System (ADS)

    Funk, J.; Mann, P.; McIntosh, K.; Wulf, S.; Dull, R.; Perez, P.; Strauch, W.

    2006-12-01

    In May of 2006 we used a chartered ferry boat to collect 520 km of seismic data, 886 km of 3.5 kHz subbottom profiler data, and 35 cores from Lake Nicaragua. The lake covers an area of 7700 km2 within the active Central American volcanic arc, forms the largest lake in Central America, ranks as the twentieth largest freshwater lake in the world, and has never been previously surveyed or cored in a systematic manner. Two large stratovolcanoes occupy the central part of the lake: Concepcion is presently active, Maderas was last active less than 2000 years ago. Four zones of active faulting and doming of the lake floor were mapped with seismic and 3.5 kHz subbottom profiling. Two of the zones consist of 3-5-km-wide, 20-30-km-long asymmetric rift structures that trend towards the inactive cone of Maderas Volcano in a radial manner. The northeastern rift forms a 20-27-m deep depression on the lake bottom that is controlled by a north-dipping normal fault. The southwestern rift forms a 25-35-m deep depression controlled by a northeast-dipping normal fault. Both depressions contain mound-like features inferred to be hydrothermal deposits. Two zones of active faulting are associated with the active Concepcion stratovolcano. A 600-m-wide and 6-km-long fault bounded horst block extends westward beneath the lake from a promontory on the west side of the volcano. Like the two radial rift features of Maderas, the horst points roughly towards the active caldera of Concepcion. A second north-south zone of active faulting, which also forms a high, extends off the north coast of Concepcion and corresponds to a localized zone of folding and faulting mapped by previous workers and inferred by them to have formed by gravitational spreading of the flank of the volcano. The close spatial relation of these faults to the two volcanic cones in the lake suggests that the mechanism for faulting is a result of either crustal movements related to magma intrusion or gravitational sliding and is

  5. Mapping Active Faults and Tectonic Geomorphology offshore central California

    NASA Astrophysics Data System (ADS)

    Johnson, S. Y.; Watt, J. T.; Hart, P. E.; Sliter, R. W.; Wong, F. L.

    2009-12-01

    In June 2008, and July 2009, the USGS conducted two high-resolution, marine, seismic-reflection surveys across the continental shelf and upper slope between Piedras Blancas and Point Sal, central California, in order to better characterize regional earthquake sources. More than 1,300 km of single-channel seismic data were acquired aboard the USGS R/V Parke Snavely using a 500-joule mini-sparker source fired at a 0.5-second shot interval and recorded with a 15-meter streamer. Most tracklines were run perpendicular to the coast at 800-meter spacing, extending from the nearshore (~ 10-15 m water depth) to as far as 20 km offshore. Sub-bottom imaging varies with substrate, ranging from outstanding (100 to 150 m of penetration) in inferred Quaternary shallow marine, shelf and upper slope deposits to poor (0 to 10 m) in the Mesozoic basement rocks. Marine magnetic data were collected simultaneously on this survey, and both data sets are being integrated with new aeromagnetic data, publicly available industry seismic-reflection data, onshore geology, seismicity, and high-resolution bathymetry. Goals of the study are to map geology, structure, and sediment distribution; to document fault location, length, segmentation, shallow geometry and structure; and to identify possible sampling targets for constraining fault slip rates, earthquake recurrence, and tsunami hazard potential. The structure and tectonic geomorphology of the >100-km-long, right-lateral, Hosgri fault zone and its connections to the Los Osos, Pecho, Oceano and other northwest-trending inboard faults are the focus of this ongoing work. The Hosgri fault forms the eastern margin of the offshore Santa Maria basin and coincides in places with the outer edge of the narrow (5- to 15-km-wide), structurally complex continental shelf. The Hosgri is imaged as a relatively continuous, vertical fault zone that extends upward to the seafloor; varies significantly and rapidly along strike; and incorporates numerous

  6. Distribution of fault activity in the early stages of continental breakup: an analysis of faults and volcanic products of the Natron Basin, East African Rift, Tanzania

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    Recent magmatic-tectonic crises in Ethiopia (e.g. 2005 Dabbahu rifting episode, Afar) have informed our understanding of the spatial and temporal distribution of strain in magmatic rifts transitioning to sea-floor spreading. However, the evolving contributions of magmatic and tectonic processes during the initial stages of rifting, is a subject of ongoing debate. The <5 Ma northern Tanzania and southern Kenya sectors of the East Africa Rift provide ideal locations to address this problem. We present preliminary findings from an investigation of fault structures utilizing aerial photography and satellite imagery of the ~35 km wide Natron rift-basin in northern Tanzania. Broad-scale structural mapping will be supplemented by field observations and 40Ar-39Ar dating of lava flows cut by faults to address three major aspects of magma-assisted rifting: (1) the relative timing of activity between the border fault and smaller faults distributed across the width of the rift; (2) time-averaged slip rates along rift-zone faults; and (3) the spatial distribution of faults and volcanic products, and their relative contributions to strain accommodation. Preliminary field observations suggest that the ~500 m high border fault system along the western edge of the Natron basin is either inactive or has experienced a reduced slip rate and higher recurrence interval between surface-breaking events, as evidence by a lack of recent surface-rupture along the main fault escarpments. An exception is an isolated, ~2 km-long segment of the Natron border fault, which is located in close proximity (< 5km) to the active Oldoinyo Lengai volcano. Here, ~10 m of seemingly recent throw is observed in volcaniclastic deposits. The proximity of the fault segment to Oldoinyo Lengai volcano and the localized distribution of fault-slip are consistent with magma-assisted faulting. Faults observed within the Natron basin and on the flanks of Gelai volcano, located on the eastern side of the rift, have

  7. Earthquake mechanism studies by active-fault drilling: Chi-Chi Taiwan to Wenchuan earthquakes

    NASA Astrophysics Data System (ADS)

    Togo, T.; Shimamoto, T.; Ma, S.; Noda, H.; Hirose, T.; Tanikawa, W.

    2010-12-01

    Why drill into active faults? How can such big projects be justified to society? We believe that a very important task for such projects is to understand earthquake mechanisms, i.e., to reproduce big earthquakes just occurred based on measured fault-zone properties. Post-earthquake fault-zone drilling provides rare opportunities for seeing and analyzing fault zones with minimum changes as “RAPID” group summarized its merits. Shallow and deep drilling into Chelungpu fault, that caused the 1999 Chi-Chi Taiwan earthquake, has demonstrated that reproducing an earthquake based on measured properties is becoming possible (Tanikawa and Shimamoto, 2009, JGR; Noda and Lapusta, 2009, JpGU). Another important outcome from Chelungpu drilling is finding of numerous changes in a fault zone during seismic fault motion (e.g., decomposition due to frictional heating), as highlighted by “black gouge” (many papers). Those changes can be reproduced now by high-velocity friction experiments. No so long ago, a renown geologist expressed his feeling that faults will not preserve a record of seismic slip, except for pseudotachylite (Cowan, 1999, JSG). In other words, seismic slip is of such a short duration that important changes, other than shearing deformation, will not occur in fault zones. Nojima and Chelungpu drilling has shown that this is not the case. On the other hand, seismic fault motion has been reproduced in laboratory for the last twenty years, demonstrating dramatic weakening of many natural fault gouges. We report here a set of data using fault gouge from Hongkou outcrop of Longmenshan fault system, very close to the first drilling site, under a constant slip rate and variable slip histories. Slip and velocity weakening behavior depends on slip history and can be described by an empirical equation. Importance of such experiments can be justified only by confirmation that the same processes indeed occur in natural fault zones. Integrated field and laboratory studies

  8. Fluid involvement in the active Helike normal Fault, Gulf of Corinth, Greece

    NASA Astrophysics Data System (ADS)

    Koukouvelas, Ioannis K.; Papoulis, Dimitris

    2009-03-01

    Rock fabric and mineralogical composition from the fault core and the unaffected protolith have been used to define the role of the segmented Helike Fault to fluid flow. Sixty samples were investigated by XRD, SEM observation and SEM-EDS microanalyses. Detrital smectite, calcite, and quartz represent the mineral assemblage at the crest of the footwall block in Foniskaria sampling site. In this site smectite is enriched at the rims of the fault core. All other sampling sites located at the base of the fault scarp are characterized by detrital and newly formed minerals. Detrital minerals include plagioclase, quartz, calcite and illite in Nikolaiika sampling site, and smectite, illite, kaolinite, quartz, calcite in Selinous sampling site. In the latter sampling site erionite and cerussite are newly formed minerals with erionite considered as the hydrothermal alteration product of fluids at 80-100 °C. At the eastern fault segment illite, quartz and calcite (T13 site) corresponds to detrital minerals. Mineralogy in the fault core reflects its high permeability to down-flowing meteoric water and weak hydrothermal alteration. The rock fabric suggests mineral alignment parallel to the fault plane. Mineralogy indicates that the Aigion, Helike and Pyrgaki Faults in the Gulf of Corinth host hydrothermal activity at shallow levels.

  9. Paleoseismic investigations along a key active fault within the Gulf of Corinth, Greece

    NASA Astrophysics Data System (ADS)

    Koukouvelas, I. K.; Kokkalas, S.; Xypolias, P.

    2008-07-01

    The study of paleoseismological and archaeological excavations provide clues for the evolution of Helike Fault, located along the westernmost end of the Gulf of Corinth, that displays high activity and exerts control on the landscape. In this study we present evidence from paleoseismic trenches which revealed well defined fault strands and clear colluvial stratigraphy. We focus on the two main segments of the Helike Fault and their implications on strong earthquake activity. The Helike Fault is a major tectonic structure that influenced the evolution of ancient settlements on the Helike Delta, from the Early Bronze Age through the Byzantine period, till present times. The eastern fault segment appears to control the southern Gulf morphology, while the western segment is controlling the large Aigion basin. Interbedded organic-rich soils and gravels dominate in all trenches. Fault strands that control successive scarp-derived colluvial deposits were identified within the trenches and indicate the continuous seismic activity along the fault trace. Co-seismic offsets, open cracks filled with debris and liquefaction related deformation was also recognized. At least seven seismic events were identified inside the excavated trenches, during the last 10 ka. The estimated vertical throw along the fault segments, observed within the trenches, is on the order of 1 meter per event. Based on dating of colluvial wedges we estimated the Holocene slip rate on the Helike Fault, which shows an increase from ~0.3 mm/yr to 2 mm/yr in the last 2 ka. We consider the derived slip rates to be minimum values due to the implication of erosional effects and sediment accumulation from the upthrown block. The Helike fault appears to play a crucial role both in subsidence of the Helike delta plain and in shifting Kerynites river course that runs between the two Helike fault segments. The Helike Fault activity and the clustering of surface rupturing events on the Helike fault seems to fit well

  10. Active normal faulting along the Mt. Morrone south-western slopes (central Apennines, Italy)

    NASA Astrophysics Data System (ADS)

    Gori, Stefano; Giaccio, Biagio; Galadini, Fabrizio; Falcucci, Emanuela; Messina, Paolo; Sposato, Andrea; Dramis, Francesco

    2011-01-01

    In the present work we analyse one of the active normal faults affecting the central Apennines, i.e. the Mt. Morrone normal fault system. This tectonic structure, which comprises two parallel, NW-SE trending fault segments, is considered as potentially responsible for earthquakes of magnitude ≥ 6.5 and its last activation probably occurred during the second century AD. Structural observations performed along the fault planes have allowed to define the mainly normal kinematics of the tectonic structure, fitting an approximately N 20° trending extensional deformation. Geological and geomorphological investigations performed along the whole Mt. Morrone south-western slopes permitted us to identify the displacement of alluvial fans, attributed to Middle and Late Pleistocene by means of tephro-stratigraphic analyses and geomorphological correlations with dated lacustrine sequences, along the western fault branch. This allowed to evaluate in 0.4 ± 0.07 mm/year the slip rate of this segment. On the other hand, the lack of synchronous landforms and/or deposits that can be correlated across the eastern fault segment prevented the definition of the slip rate related to this fault branch. Nevertheless, basing on a critical review of the available literature dealing with normal fault systems evolution, we hypothesised a total slip rate of the fault system in the range of 0.4 ± 0.07 to 0.8 ± 0.09 mm/year. Moreover, basing on the length at surface of the Mt. Morrone fault system (i.e. 22-23 km) we estimated the maximum expected magnitude of an earthquake that might originate along this tectonic structure in the order of 6.6-6.7.

  11. Geomorphic Indicators and Tectonic Implications of the Active Chaochou Fault, Southern Taiwan

    NASA Astrophysics Data System (ADS)

    Hung, J.; Liao, H.

    2003-12-01

    The Chaochou Fault, lying on the easternmost edge of the Pingtung plain, is the major geologic boundary between the Slate Belt to the east and the Western Foothills to the west. According to previous studies, the Chaochou fault is a high-angle reverse fault dipping 75-80 degrees to the east. Along strike, several transverse rivers cut across the fault and form alluvial fans in the foothills, which provide unique morphotectonic features to study the activity of the Chaochou Fault. Digitized data from topographic maps of 1/5,000 to 1/25,000 scales and digital elevation data of 40m resolution were input into GIS software and analyzed to quantitatively evaluate geomorphic indicators such as hypsometric integral, stream length-gradient index and drainage basin asymmetry etc. Anomalies of these indices are further checked in the field on bedrocks, man-made structures and fold and faults, to clarify spatial variations of indicators. These, coupled with GPS data, field survey in the slate belt and uplifted terraces and subsurface seismic profiles, can further constrain spatial and temporal kinematics of the Chaochou fault and the relationship between topographic evolution and subsurface structures. Our preliminary results show that river landforms are highly related to the Chaochou Fault. Drainages were tilted to the west in response to uplifting in the east of the Chaochou Fault. Geomorphic indices indicate that the uplift rate is higher in the north and decreases progressively toward the south. The peak tectonic activity occurs in the area between the Chaochou and the Chishan Fault.

  12. Experimental elaboration of faulting induced by fluid-releasing mineral reactions in subduction zones

    NASA Astrophysics Data System (ADS)

    Green, H.; Zhang, J.; Jung, H.; Dobrzinetskaya, L.

    2003-04-01

    Dehydration embrittlement has been cited repeatedly as a potential mechanism for triggering earthquakes at depths where unassisted brittle failure is impossible due to the normal-stress-dependence of friction. We are investigating two different aspects of this problem in the laboratory: (i) dehydration of antigorite under stress where the ΔV of reaction varies from strongly positive to distinctly negative; (ii) deformation of eclogite in which the nominally anhydrous minerals contain small amounts of dissolved H_2O that can lead to faulting induced by very small amounts of melting stimulated by exsolution of H_2O. (i) Antigorite has the largest stability field of the serpentines and is often cited as potentially being the source of most or all mantle earthquakes to a depth of over 200 km. However, like other low-pressure hydrous phases, the net volume change accompanying antigorite dehydration varies from strongly positive at low P to negative at P > ˜2-2.5 GPa. Fracture mechanics theory predicts that dehydration should not induce shear failure if ΔV<0. To test the effect of ΔV on faulting, we have deformed an extensively-serpentinized peridotite at P = 1-6 GPa. We conducted constant strain rate experiments in a Griggs-type apparatus at P = 1.0 - 3.4 GPa and rapid-pumping experiments in a Walker-type multianvil apparatus, culminating in pressures as high as 6 GPa. Independent of the sign of ΔV, specimens subjected to stress during dehydration yielded extremely thin zones of reaction products with shear offset across them. Some were clearly faults whereas others could be precursors to faulting. Fluid released at grain boundaries between antigorite and relict olivine locally produced Mode I cracks &fluid inclusions. (ii) Deformation of "wet" eclogite at 3 GPa and temperatures between the wet and dry solidi induced exsolution of H_2O and formation of very small amounts (<1%) of melt, leading to faulting. At lower temperature the rock was extremely strong but

  13. Assessing fault activity in intracontinental settings: paleoseismology and geomorphology in SE Kazakhstan

    NASA Astrophysics Data System (ADS)

    Grützner, Christoph; Carson, Emily; Mackenzie, David; Elliott, Austin; Campbell, Grace; Walker, Richard; Abdrakhmatov, Kanatbek

    2016-04-01

    Earthquake recurrence intervals of active faults often exceed the time span covered by instrumental, historical, and archaeological earthquake records in continental interiors. The identification of active faults then often relies on finding the geomorphological expression of surface faulting preserved in the landscape. In rather arid areas, single earthquake scarps can be preserved for thousands of years, but erosional and depositional processes will eventually obliterate features such as fault scarps and offset geological markers. Active faults with very long intervals between surface ruptures might therefore remain undetected, which constitutes a major problem for tectonic studies and seismic hazard assessment. Here we present data from the 50 km-long 'Charyn Canyon' thrust fault in the northern Tien Shan (SE Kazakhstan). Remote sensing, Structure-from-Motion (SfM), differential GPS, field mapping, and paleoseismic trenching were used to reveal the earthquake history of this fault. Radiocarbon dating, infra-red stimulated luminescence (IRSL), and scarp diffusion modelling were used for bracketing the occurrence of paleo-earthquakes. In the paleoseismological trenches we identified two surface rupturing events within the last ~37 ka BP. The most recent earthquake took place between 3.5 - 7.3 ka BP, the penultimate event occurred between ~17-37 ka BP. We estimate magnitudes of ~MW6.5-7.3. Only the younger event has a morphological expression as a 25 km-long fault scarp of ~2 m height. This implicates that a major landscape reset occurred between these two earthquakes, most likely related to the significant climatic change that marked the end of the last glacial maximum. Similar observations from other paleoseismic investigation sites in this area support this interpretation. Our study shows that faults in the northern Tien Shan tend to break in strong earthquakes with very long recurrence intervals. As a consequence, morphological evidence for the most recent

  14. Research program on Indonesian active faults to support the national earthquake hazard assesments

    NASA Astrophysics Data System (ADS)

    Natawidjaja, D. H.

    2012-12-01

    In mid 2010 an Indonesian team of earthquake scientists published the new Indonesian probabilistic seismic hazard analysis (PSHA) map. The new PSHA map replaced the previous version that is published in 2002. One of the major challenges in developing the new map is that data for many active fault zones in Indonesia is sparse and mapped only at regional scale, thus the input fault parameters for the PSHA introduce unavoidably large uncertainties. Despite the fact that most Indonesian islands are torn by active faults, only Sumatra has been mapped and studied in sufficient details. In other areas, such as Java and Bali, the most populated regions as well as in the east Indonesian region, where tectonic plate configurations are far more complex and relative plate motions are generally higher, many major active faults and plate boundaries are not well mapped and studied. In early 2011, we have initiated a research program to study major active faults in Indonesia together with starting a new graduate study program, GREAT (Graduate Research for Earthquake and Active Tectonics), hosted by ITB (Institute of Technology bandung) and LIPI (Indonesian Institute of Sciences) in partnership with the Australia-Indonesia Facility for Disaster Reduction (AIFDR). The program include acquisition of high-resolution topography and images required for detailed fault mapping, measuring geological slip rates and locating good sites for paleoseismological studies. It is also coupled by seismological study and GPS surveys to measure geodetic slip rates. To study submarine active faults, we collect and incorporate bathymetry and marine geophysical data. The research will be carried out, in part, through masters and Ph.D student theses. in the first four year of program we select several sites for active fault studies, particulary the ones that pose greater risks to society.

  15. Continuity, segmentation and faulting type of active fault zones of the 2016 Kumamoto earthquake inferred from analyses of a gravity gradient tensor

    NASA Astrophysics Data System (ADS)

    Matsumoto, Nayuta; Yoshihiro, Hiramatsu; Sawada, Akihiro

    2016-10-01

    We analyze Bouguer anomalies in/around the focal region of the 2016 Kumamoto earthquake to examine features, such as continuity, segmentation and faulting type, of the active fault zones related to the earthquake. Several derivatives and structural parameters calculated from a gravity gradient tensor are applied to highlight the features. First horizontal and vertical derivatives, as well as a normalized total horizontal derivative, characterize well the continuous subsurface fault structure along the Futagawa fault zone. On the other hand, the Hinagu fault zone is not clearly detected by these derivatives, especially in the case of the Takano-Shirahata segment, suggesting a difference of cumulative vertical displacement between the two fault zones. The normalized total horizontal derivative and the dimensionality index indicate a discontinuity of the subsurface structure of the Hinagu fault zone, that is, a segment boundary between the Takano-Shirahata and the Hinagu segments. The aftershock distribution does not extend beyond this segment boundary. In other words, this segment boundary controls the southern end of the rupture area of the foreshock. We also recognize normal fault structures dipping to the northwest in some areas of the fault zones from estimations of dip angles.[Figure not available: see fulltext.

  16. Model-based fault detection and isolation for intermittently active faults with application to motion-based thruster fault detection and isolation for spacecraft

    NASA Technical Reports Server (NTRS)

    Wilson, Edward (Inventor)

    2008-01-01

    The present invention is a method for detecting and isolating fault modes in a system having a model describing its behavior and regularly sampled measurements. The models are used to calculate past and present deviations from measurements that would result with no faults present, as well as with one or more potential fault modes present. Algorithms that calculate and store these deviations, along with memory of when said faults, if present, would have an effect on the said actual measurements, are used to detect when a fault is present. Related algorithms are used to exonerate false fault modes and finally to isolate the true fault mode. This invention is presented with application to detection and isolation of thruster faults for a thruster-controlled spacecraft. As a supporting aspect of the invention, a novel, effective, and efficient filtering method for estimating the derivative of a noisy signal is presented.

  17. Modeling of coulpled deformation and permeability evolution during fault reactivation induced by deep underground injection of CO2

    SciTech Connect

    Cappa, F.; Rutqvist, J.

    2010-06-01

    The interaction between mechanical deformation and fluid flow in fault zones gives rise to a host of coupled hydromechanical processes fundamental to fault instability, induced seismicity, and associated fluid migration. In this paper, we discuss these coupled processes in general and describe three modeling approaches that have been considered to analyze fluid flow and stress coupling in fault-instability processes. First, fault hydromechanical models were tested to investigate fault behavior using different mechanical modeling approaches, including slip interface and finite-thickness elements with isotropic or anisotropic elasto-plastic constitutive models. The results of this investigation showed that fault hydromechanical behavior can be appropriately represented with the least complex alternative, using a finite-thickness element and isotropic plasticity. We utilized this pragmatic approach coupled with a strain-permeability model to study hydromechanical effects on fault instability during deep underground injection of CO{sub 2}. We demonstrated how such a modeling approach can be applied to determine the likelihood of fault reactivation and to estimate the associated loss of CO{sub 2} from the injection zone. It is shown that shear-enhanced permeability initiated where the fault intersects the injection zone plays an important role in propagating fault instability and permeability enhancement through the overlying caprock.

  18. The Eastern Lower Tagus Valley Fault Zone in central Portugal: Active faulting in a low-deformation region within a major river environment

    NASA Astrophysics Data System (ADS)

    Canora, Carolina; Vilanova, Susana P.; Besana-Ostman, Glenda M.; Carvalho, João; Heleno, Sandra; Fonseca, Joao

    2015-10-01

    Active faulting in the Lower Tagus Valley, Central Portugal, poses a significant seismic hazard that is not well understood. Although the area has been affected by damaging earthquakes during historical times, only recently has definitive evidence of Quaternary surface faulting been found along the western side of the Tagus River. The location, geometry and kinematics of active faults along the eastern side of the Tagus valley have not been previously studied. We present the first results of mapping and paleoseismic analysis of the eastern strand of the Lower Tagus Valley Fault Zone (LTVFZ). Geomorphological, paleoseismological, and seismic reflection studies indicate that the Eastern LTVFZ is a left-lateral strike-slip fault. The detailed mapping of geomorphic features and studies in two paleoseismic trenches show that surface fault rupture has occurred at least six times during the past 10 ka. The river offsets indicate a minimum slip rate on the order of 0.14-0.24 mm/yr for the fault zone. Fault trace mapping, geomorphic analysis, and paleoseismic studies suggest a maximum magnitude for the Eastern LTVFZ of Mw ~ 7.3 with a recurrence interval for surface ruptures ~ 1.7 ka. At least two events occurred after 1175 ± 95 cal yr BP. Single-event displacements are unlikely to be resolved in the paleoseismic trenches, thus our observations most probably represent the minimum number of events identified in the trenches.

  19. How the differential load induced by normal fault scarps controls the distribution of monogenic volcanism

    NASA Astrophysics Data System (ADS)

    Maccaferri, F.; Acocella, V.; Rivalta, E.

    2015-09-01

    Understanding shallow magma transfer and the related vent distribution is crucial for volcanic hazard. Here we investigate how the stress induced by topographic scarps linked to normal faults affects the distribution of monogenic volcanoes at divergent plate boundaries. Our numerical models of dyke propagation below a fault scarp show that the dykes tend to propagate toward and erupt on the footwall side. This effect, increasing with the scarp height, is stronger for dykes propagating underneath the hanging wall side and decreases with the distance from the scarp. A comparison to the East African Rift System, Afar and Iceland shows that (1) the inner rift structure, which shapes the topography, controls shallow dyke propagation; (2) differential loading due to mass redistribution affects magma propagation over a broad scale range (100-105 m). Our results find application to any volcanic field with tectonics- or erosion-induced topographic variations and should be considered in any volcanic hazard assessment.

  20. 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.

  1. 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.

  2. Analysis of Landsat TM data for active tectonics: the case of the Big Chino Fault, Arizona

    NASA Astrophysics Data System (ADS)

    Salvi, Stefano

    1994-12-01

    The Big Chino Valley is a 50 km-long tectonic depression of the Basin and Range province of the South- western United States. It is bordered on the NE side by an important normal fault, the Big Chino Fault. The activity of the latter has been hypothesised on the basis of the presence of a 20 m-high fault scarp and on local geomorphological studies. Moreover, a magnitude 4.9 earthquake occurred in southern Arizona in 1976 has been attributed to this fault. The climate in the Big Chino Valley is semi-arid with average rainfall of about 400 mm per year; a very sparse vegetation cover is present, yielding a good possibility for the geo-lithologic application of remote sensing data. The analysis of the TM spectral bands shows, in the short wave infrared, a clear variation in the reflected radiance across the fault scarp. Also the available radar (SLAR) images show a marked difference in response between the two sides of the fault. An explanation of this phenomena has been found in the interaction between the geomorphic evolution, the pedological composition, and the periodic occurrence of coseismic deformation along the fault. Other effects of the latter process have been investigated on colour D- stretched images whose interpretation allowed to detect two paleoseismic events of the Big Chino Fault. This work demonstrates that important information on the seismological parameters of active faults in arid and semiarid climates can be extracted from the analysis of satellite spectral data in the visible and near -infrared.

  3. UAV's for active tectonics : case example from the Longitudinal Valley and the Chishan Faults (Southern Taiwan)

    NASA Astrophysics Data System (ADS)

    Deffontaines, Benoit; Chang, Kuo-Jen; Chan, Yu-Chang; Chen, Rou-Fei; Hsieh, Yu-Chung

    2015-04-01

    Taiwan is a case example to study active tectonics due to the active NW-SE collision of the Philippine and Eurasian Sea Plates as the whole convergence reaches 10cm/y. In order to decipher the structural active tectonics geometry, we used herein UAV's to get high resolution Digital Terrain Model (DTM) in local active tectonics key areas. Classical photo-interpretation where then developped in order to structurally interprete these data, confirmed by field studies. Two location had first been choosen in order to highlight the contribution of such high resolution DTM in SW Taiwan on the Longitudinal Valley Fault (SE Taiwan) on its southern branch from Pinting to Luyeh terraces (Pinanshan) where UAV's lead to better interprete the location of the outcropping active deformations. Combined with available GPS data and PALSAR interferometry (Deffontaines et Champenois et al., submitted) it is then possible to reconstruct the way of the present deformation in this local area. In the Pinting terraces, If the western branch of the fault correspond to an outcroping thrust fault, the eastern branch act as a a growing active anticline that may be characterized and quantified independantly. The interpretation of the UAV's high resolution DTM data on the Chishan Fault (SW Taiwan) reveals also the geometry of the outcropping active faults complex structural behaviour. If the Chishan Fault act as a thrusting in its northern tip (close to Chishan city), it acts as a right lateral strike-slip fault north of Chaoshan (Kaohsiung city) as described by Deffontaines et al. 2014. Therefore UAV's are a so useful tool to get very high resolution topographic data in Taiwan that are of great help to get the geometry of the active neotectonic structures in Taiwan.

  4. Synthetic modeling of a fluid injection-induced fault rupture with slip-rate dependent friction coefficient

    NASA Astrophysics Data System (ADS)

    Urpi, Luca; Rinaldi, Antonio Pio; Rutqvist, Jonny; Cappa, Frédéric; Spiers, Christopher J.

    2016-04-01

    Poro-elastic stress and effective stress reduction associated with deep underground fluid injection can potentially trigger shear rupture along pre-existing faults. We modeled an idealized CO2 injection scenario, to assess the effects on faults of the first phase of a generic CO2 aquifer storage operation. We used coupled multiphase fluid flow and geomechanical numerical modeling to evaluate the stress and pressure perturbations induced by fluid injection and the response of a nearby normal fault. Slip-rate dependent friction and inertial effects have been aken into account during rupture. Contact elements have been used to take into account the frictional behavior of the rupture plane. We investigated different scenarios of injection rate to induce rupture on the fault, employing various fault rheologies. Published laboratory data on CO2-saturated intact and crushed rock samples, representative of a potential target aquifer, sealing formation and fault gouge, have been used to define a scenario where different fault rheologies apply at different depths. Nucleation of fault rupture takes place at the bottom of the reservoir, in agreement with analytical poro-elastic stress calculations, considering injection-induced reservoir inflation and the tectonic scenario. For the stress state here considered, the first triggered rupture always produces the largest rupture length and slip magnitude, correlated with the fault rheology. Velocity weakening produces larger ruptures and generates larger magnitude seismic events. Heterogeneous faults have been considered including velocity-weakening or velocity strengthening sections inside and below the aquifer, while upper sections being velocity-neutral. Nucleation of rupture in a velocity strengthening section results in a limited rupture extension, both in terms of maximum slip and rupture length. For a heterogeneous fault with nucleation in a velocity-weakening section, the rupture may propagate into the overlying velocity

  5. Active Crustal Faults in the Forearc Region, Guerrero Sector of the Mexican Subduction Zone

    NASA Astrophysics Data System (ADS)

    Gaidzik, Krzysztof; Ramírez-Herrera, Maria Teresa; Kostoglodov, Vladimir

    2016-10-01

    This work explores the characteristics and the seismogenic potential of crustal faults on the overriding plate in an area of high seismic hazard associated with the occurrence of subduction earthquakes and shallow earthquakes of the overriding plate. We present the results of geomorphic, structural, and fault kinematic analyses conducted on the convergent margin between the Cocos plate and the forearc region of the overriding North American plate, within the Guerrero sector of the Mexican subduction zone. We aim to determine the active tectonic processes in the forearc region of the subduction zone, using the river network pattern, topography, and structural data. We suggest that in the studied forearc region, both strike-slip and normal crustal faults sub-parallel to the subduction zone show evidence of activity. The left-lateral offsets of the main stream courses of the largest river basins, GPS measurements, and obliquity of plate convergence along the Cocos subduction zone in the Guerrero sector suggest the activity of sub-latitudinal left-lateral strike-slip faults. Notably, the regional left-lateral strike-slip fault that offsets the Papagayo River near the town of La Venta named "La Venta Fault" shows evidence of recent activity, corroborated also by GPS measurements (4-5 mm/year of sinistral motion). Assuming that during a probable earthquake the whole mapped length of this fault would rupture, it would produce an event of maximum moment magnitude Mw = 7.7. Even though only a few focal mechanism solutions indicate a stress regime relevant for reactivation of these strike-slip structures, we hypothesize that these faults are active and suggest two probable explanations: (1) these faults are characterized by long recurrence period, i.e., beyond the instrumental record, or (2) they experience slow slip events and/or associated fault creep. The analysis of focal mechanism solutions of small magnitude earthquakes in the upper plate, for the period between 1995

  6. Geometry, kinematics and slip rate along the Mosha active fault, Central Alborz, Iran

    NASA Astrophysics Data System (ADS)

    Ritz, J.-F.; Pics Geological Team

    2003-04-01

    The Mosha fault is one of the major active fault in Central Alborz as shown by its strong historical seismicity and its clear morphological signature. Situated at the vicinity of Tehran city, this ~150 km long ~N100°E trending fault represents an important potential seismic source that threatens the Iranian metropolis. In the framework of an Iranian-French joint research program (PICS) devoted to seismic hazard assessment in the Tehran region, we undertook a morphotectonic (determination of the cumulative displacements and the ages of offset morphologic markers) and paleoseismic (determination of the ages and magnitudes of ancient events) study along the Mosha fault. Our objectives are the estimation of the long-term slip rate (Upper Pleistocene-Holocene) and the mean recurrence interval of earthquakes along the different segments of the fault. Our investigations within the Tar Lake valley, along the eastern part of the fault potentially the site of the 1665 (VII, 6.5) historical earthquake - allows us to calculate a preliminary 2 ± 0.1 mm/yr minimum left lateral slip rate. If we assume a characteristic coseismic average displacement comprised between 0.35 m (Mw 6.5) and 1.2 m (Mw 7.1) calculated from Wells &Coppersmith’s functions (1994) and taking the moment magnitudes attributed to the 1665 and 1830 earthquakes (e.g. Berberian &Yeats, 2001) the mean maximum recurrence intervals along this segment of the Mosha fault are comprised between 160 and 620 yrs.

  7. Eocene activity on the Western Sierra Fault System and its role incising Kings Canyon, California

    NASA Astrophysics Data System (ADS)

    Sousa, Francis J.; Farley, Kenneth A.; Saleeby, Jason; Clark, Marin

    2016-04-01

    Combining new and published apatite (U-Th)/He and apatite 4He/3He data from along the Kings River canyon, California we rediscover a west-down normal fault on the western slope of the southern Sierra Nevada, one of a series of scarps initially described by Hake (1928) which we call the Western Sierra Fault System. Integrating field observations with apatite (U-Th)/He data, we infer a single fault trace 30 km long, and constrain the vertical offset across this fault to be roughly a kilometer. Thermal modeling of apatite 4He/3He data documents a pulse of footwall cooling near the fault and upstream in the footwall at circa 45-40 Ma, which we infer to be the timing of a kilometer-scale incision pulse resulting from the fault activity. In the context of published data from the subsurface of the Sacramento and San Joaquin Valleys, our data from the Western Sierra Fault System suggests an Eocene tectonic regime dominated by low-to-moderate magnitude extension, surface uplift, and internal structural deformation of the southern Sierra Nevada and proximal Great Valley forearc.

  8. 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

  9. Stress changes induced at neighbouring faults by the June 2000 earthquakes, South Iceland Seismic Zone

    NASA Astrophysics Data System (ADS)

    Plateaux, Romain; Angelier, Jacques; Bergerat, Françoise; Cappa, Frédéric; Stefansson, Ragnar

    2010-05-01

    The Icelandic rift system belongs to the Mid-Atlantic Ridge and is connected to the offshore Reykjanes and Kolbeinsey ridges by two active transform zones. Plate separation occurs at a rate of nearly 2 cm/yr along the N105°E direction. With respect to the Icelandic Hotspot, westward plate velocities in Iceland are 1.8-2.2 cm/yr for North America and 0-0.4 cm/yr for Eurasia, resulting in a westward displacement of the Icelandic Rift relative to the hotspot. Rift jumps occur when the plate boundary has migrated to a critical point to the west, and a new rift develops above the hotspot apex while the old rift is dying out. The two active transform zones, the Tjörnes Fracture Zone (TFZ) and the South Iceland Seismic Zone (SISZ), resulted from such eastward rift jumps. Our study focuses on the SISZ which is an onland, E-W trending transform zone where N-S trending right-lateral strike-slip faults accommodate left-lateral transform motion as revealed by historical seismicity. During the most recent seismic crisis, in June 2000, two major earthquakes of magnitude (Mw) 6.4 occurred along N-S right-lateral faults in the central segment of the SISZ. The high sensitivity SIL (South Iceland Lowlands) seismic network run by the Icelandic Meteorological Office (IMO) provided a complete record of earthquakes down to magnitude Mw = -1. Here, we present an analysis of this earthquakes sequence in term of stress regimes in order to examine the response of two faults that did not experience significant motion during the earthquakes, and hence to determine how far such fault zones provide information about stress changes in space and time when large earthquakes occur at distance of some tens of kilometres. The faults considered are the Skard and Leirubakki faults, along which large earthquakes and significant displacement occurred in the past Using seismological data recorded from 1991 to 2007, we carried out stress inversion of focal mechanisms of 1,340 earthquakes that affected

  10. Active faults, stress field and plate motion along the Indo-Eurasian plate boundary

    NASA Astrophysics Data System (ADS)

    Nakata, Takashi; Otsuki, Kenshiro; Khan, S. H.

    1990-09-01

    The active faults of the Himalayas and neighboring areas are direct indicators of Recent and sub-Recent crustal movements due to continental collision between the Indian and Eurasian plates. The direction of the maximum horizontal shortening or horizontal compressive stress axes deduced from the strike and type of active faulting reveals a characteristic regional stress field along the colliding boundary. The trajectories of the stress axes along the transcurrent faults and the Eastern Himalayan Front, are approximately N-S, parallel to the relative motion of the two plates. However, along the southern margin of the Eurasian plate, they are NE-SW in the Western Himalayan Front and NW-SE to E-W in the Kirthar-Sulaiman Front, which is not consistent with the direction of relative plate motion. A simple model is proposed in order to explain the regional stress pattern. In this model, the tectonic sliver between the transcurrent faults and the plate margin, is dragged northward by the oblique convergence of the Indian plate. Thus, the direction of relative motion between the tectonic sliver and the Indian plate changes regionally, causing local compressive stress fields. Judging from the long-term slip rates along the active faults, the relative motion between the Indian and Eurasian plates absorbed in the colliding zone is about one fourth of its total amount; the rest may be consumed along the extensive strike-slip faults in Tibet and China.

  11. Delineation of Active Basement Faults in the Eastern Tennessee and Charlevoix Intraplate Seismic Zones

    NASA Astrophysics Data System (ADS)

    Powell, C. A.; Langston, C. A.; Cooley, M.

    2013-12-01

    Recognition of distinct, seismogenic basement faults within the eastern Tennessee seismic zone (ETSZ) and the Charlevoix seismic zone (CSZ) is now possible using local earthquake tomography and datasets containing a sufficiently large number of earthquakes. Unlike the New Madrid seismic zone where seismicity clearly defines active fault segments, earthquake activity in the ETSZ and CSZ appears diffuse. New arrival time inversions for hypocenter relocations and 3-D velocity variations using datasets in excess of 1000 earthquakes suggest the presence of distinct basement faults in both seismic zones. In the ETSZ, relocated hypocenters align in near-vertical segments trending NE-SW, parallel to the long dimension of the seismic zone. Earthquakes in the most seismogenic portion of the ETSZ delineate another set of near-vertical faults trending roughly E-ESE. These apparent trends and steep dips are compatible with ETSZ focal mechanism solutions. The solutions are remarkably consistent and indicate strike-slip motion along the entire length of the seismic zone. Relocated hypocenter clusters in the CSZ define planes that trend and dip in directions that are compatible with known Iapitan rift faults. Seismicity defining the planes becomes disrupted where the rift faults encounter a major zone of deformation produced by a Devonian meteor impact. We will perform a joint statistical analysis of hypocenter alignments and focal mechanism nodal plane orientations in the ETSZ and the CSZ to determine the spatial orientations of dominant seismogenic basement faults. Quantifying the locations and dimensions of active basement faults will be important for seismic hazard assessment and for models addressing the driving mechanisms for these intraplate zones.

  12. Subsidence Induced Faulting Hazard risk maps in Mexico City and Morelia, central Mexico

    NASA Astrophysics Data System (ADS)

    Cabral-Cano, E.; Solano-Rojas, D.; Hernández-Espriu, J.; Cigna, F.; Wdowinski, S.; Osmanoglu, B.; Falorni, G.; Bohane, A.; Colombo, D.

    2012-12-01

    Subsidence and surface faulting have affected urban areas in Central Mexico for decades and the process has intensified as a consequence of urban sprawl and economic growth. This process causes substantial damages to the urban infrastructure and housing structures and in several cities it is becoming a major factor to be considered when planning urban development, land use zoning and hazard mitigation strategies in the next decades. Subsidence is usually associated with aggressive groundwater extraction rates and a general decrease of aquifer static level that promotes soil consolidation, deformation and ultimately, surface faulting. However, local stratigraphic and structural conditions also play an important role in the development and extension of faults. Despite its potential for damaging housing, and other urban infrastructure, the economic impact of this phenomena is poorly known, in part because detailed, city-wide subsidence induced faulting risk maps have not been published before. Nevertheless, modern remote sensing techniques are most suitable for this task. We present the results of a risk analysis for subsidence induced surface faulting in two cities in central Mexico: Morelia and Mexico City. Our analysis in Mexico City and Morelia is based on a risk matrix using the horizontal subsidence gradient from a Persistent Scatterer InSAR (Morelia) and SqueeSAR (Mexico City) analysis and 2010 census population distribution data from Mexico's National Institute of Statistics and Geography. Defining subsidence induced surface faulting vulnerability within these urbanized areas is best determined using both magnitude and horizontal subsidence gradient. Our Morelia analysis (597,000 inhabitants with localized subsidence rates up to 80 mm/yr) shows that 7% of the urbanized area is under a high to very high risk level, and 14% of its population (11.7% and 2.3% respectively) lives within these areas. In the case of the Mexico City (15'490,000 inhabitants for the

  13. Lake Clark fault, assessment of tectonic activity based on reconnaissance mapping of glacial deposits, northwestern Cook Inlet Alaska

    NASA Astrophysics Data System (ADS)

    Reger, R. D.; Koehler, R. D.

    2009-12-01

    The Lake Clark fault extends ~247 km from the vicinity of Lake Clark in the Alaska-Aleutian Range batholith northeastward to the Castle Mountain fault along the northern margin of Cook Inlet. Documented Tertiary deformation along the fault includes dextral offsets (5-26 km) and north-side-up reverse displacements (500-1,000 m). The fault is along strike with the Holocene-active Castle Mountain fault and adjacent to the active northern Cook Inlet fold belt. As part of the STATEMAP program, the State of Alaska has begun a 2-year geologic mapping project in the vicinity of the Lake Clark fault, including assessment of Quaternary fault activity and its role in accommodating deformation in the Aleutian forearc. Here we present preliminary Quaternary mapping and tectonic geomorphic observations aimed at assessing the fault activity. Between the Beluga and Chakachatna rivers, large lateral moraines of the late Wisconsinan Naptowne glaciation cross the fault and are not displaced. In the vicinity of Lone Ridge, the fault is expressed as a ~25-m southeast-facing scarp in bedrock associated with springs and vertically offset Stage 4 or 6 moraines. In the Chuitna River drainage basin beyond the Naptowne ice limit, the fault extends across a fairly flat plateau with drumlins and ice-stagnation deposits related to Stage 4 or 6 glaciation. There the fault is expressed by subtle vegetation and tonal lineaments on air photos; however, scarps and lateral offsets were not observed. Stream profiles perpendicular to the fault along the Chuitna River and Chuitna Creek have convex profiles that could be related to tectonic folding. Our observations indicate that this part of the Lake Clark fault may be Quaternary active, but has been relatively quiescent in the late Pleistocene. Thus, blind thrust faults associated with the northern Cook Inlet fold belt may accommodate the majority of the tectonic deformation in this part of the Aleutian forearc. This information is applicable to

  14. 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

  15. Active faults and seismogenic models for the Urumqi city, Xinjiang Autonomous Region, China

    NASA Astrophysics Data System (ADS)

    Li, Yingzhen; Yu, Yang; Shen, Jun; Shao, Bo; Qi, Gao; Deng, Mei

    2016-06-01

    We have studied the characteristics of the active faults and seismicity in the vicinity of Urumqi city, the capital of Xinjiang Autonomous Region, China, and have proposed a seismogenic model for the assessment of earthquake hazard in this area. Our work is based on an integrated analysis of data from investigations of active faults at the surface, deep seismic reflection soundings, seismic profiles from petroleum exploration, observations of temporal seismic stations, and the precise location of small earthquakes. We have made a comparative study of typical seismogenic structures in the frontal area of the North Tianshan Mountains, where Urumqi city is situated, and have revealed the primary features of the thrust-fold-nappe structure there. We suggest that Urumqi city is comprised two zones of seismotectonics which are interpreted as thrust-nappe structures. The first is the thrust nappe of the North Tianshan Mountains in the west, consisting of the lower (root) thrust fault, middle detachment, and upper fold-uplift at the front. Faults active in the Pleistocene are present in the lower and upper parts of this structure, and the detachment in the middle spreads toward the north. In the future, M7 earthquakes may occur at the root thrust fault, while the seismic risk of frontal fold-uplift at the front will not exceed M6.5. The second structure is the western flank of the arc-like Bogda nappe in the east, which is also comprised a root thrust fault, middle detachment, and upper fold-uplift at the front, of which the nappe stretches toward the north; several active faults are also developed in it. The fault active in the Holocene is called the South Fukang fault. It is not in the urban area of Urumqi city. The other three faults are located in the urban area and were active in the late Pleistocene. In these cases, this section of the nappe structure near the city has an earthquake risk of M6.5-7. An earthquake M S6.6, 60 km east to Urumqi city occurred along the

  16. Rare normal faulting earthquake induced by subduction megaquake: example from 2011 Tohoku-oki earthquake

    NASA Astrophysics Data System (ADS)

    Ishiyama, T.; Sugito, N.; Echigo, T.; Sato, H.; Suzuki, T.

    2012-04-01

    , twice as large as coseismic vertical component of slip, indicative of penultimate seismic event prior to the 2011 earthquake. Abrupt thickening of overlying Unit I may also suggest preexisting topographic relief prior to its deposition. Radiocarbon dating of charred materials included in event horizons and tephrostratigraphy at two sites indicate that penultimate event prior to the 2011 event might occurred at about 40 ka. This normal fault earthquake is in contrast to compressional or neutral stress regimes in Tohoku region before the 2011 megaquake and rarity of the normal faulting earthquake inferred from these paleoseismic studies may reflect its mechanical relation to the gigantic megathrust earthquakes, such as unusual, enhanced extensional stress on the hangingwall block induced by mainshock and/or postseismic creep after the M~9 earthquake.

  17. Holocene activity of the Rose Canyon fault zone in San Diego, California

    NASA Astrophysics Data System (ADS)

    Lindvall, Scott C.; Rockwell, Thomas K.

    1995-12-01

    The Rose Canyon fault zone in San Diego, California, has many well-expressed geomorphic characteristics of an active strike-slip fault, including scarps, offset and deflected drainages and channel walls, pressure ridges, a closed depression, and vegetation lineaments. Geomorphic expression of the fault zone from Mount Soledad south to Mission Bay indicates that the Mount Soledad strand is the most active. A network of trenches excavated across the Mount Soledad strand in Rose Creek demonstrate a minimum of 8.7 m of dextral slip in a distinctive early to middle Holocene gravel-filled channel that crosses the fault zone. The gravel-filled channel was preserved within and east of the fault but was removed west of the fault zone by erosion or possibly grading during development. Consequently, the actual displacement of the channel could be greater than 8.7 m. Radiocarbon dates on detrital charcoal recovered from the sediments beneath the channel yield a maximum calibrated age of about 8.1±0.2 kyr. The minimum amount of slip along with the maximum age yield a minimum slip rate of 1.07±0.03 mm/yr on this strand of the Rose Canyon fault zone for much of Holocene time. Other strands of the Rose Canyon fault zone, which are east and west of our site, may also have Holocene activity. Based on an analysis of the geomorphology of fault traces within the Rose Canyon fault zone, along with the results of our trenching study, we estimate the maximum likely slip rate at about 2 mm/yr and a best estimate of about 1.5 mm/yr. Stratigraphie evidence of at least three events is present during the past 8.1 kyr. The most recent surface rupture displaces the modern A horizon (topsoil), suggesting that this event probably occurred within the past 500 years. Stratigraphie and structural relationships also indicate the occurrence of a scarp-forming event at about 8.1 kyr, prior to deposition of the gravel-filled channel that was used as a piercing line. A third event is indicated by the

  18. Active faulting in northern Chile: ramp stacking and lateral decoupling along a subduction plate boundary?

    NASA Astrophysics Data System (ADS)

    Armijo, Rolando; Thiele, Ricardo

    1990-04-01

    Two large features parallel to the coastline of northern Chile have long been suspected to be the sites of young or active deformation: (1) The 700-km long Coastal Scarp, with average height (above sea level) of about 1000 m; (2) The Atacama Fault zone, that stretches linearly for about 1100 km at an average distance of 30-50 km from the coastline. New field observations combined with extensive analysis of aerial photographs demonstrate that both the Coastal Scarp and the Atacama Fault are zones of Quaternary and current fault activity. Little-degraded surface breaks observed in the field indicate that these fault zones have recently generated large earthquakes ( M = 7-8). Normal fault offsets observed in marine terraces in the Coastal Scarp (at Mejillones Peninsula) require tectonic extension roughly orthogonal to the compressional plate boundary. Strike-slip offsets of drainage observed along the Salar del Carmen and Cerro Moreno faults (Atacama Fault system) imply left-lateral displacements nearly parallel to the plate boundary. The left-lateral movement observed along the Atacama Fault zone may be a local consequence of E-W extension along the Coastal Scarp. But if also found everywhere along strike, left-lateral decoupling along the Atacama Fault zone would be in contradiction with the right lateral component of Nazca-South America motion predicted by models of present plate kinematics. Clockwise rotation with left-lateral slicing of the Andean orogen south of the Arica bend is one way to resolve this contradiction. The Coastal Scarp and the Atacama Fault zone are the most prominent features with clear traces of activity within the leading edge of continental South America. The great length and parallelism of these features with the subduction zone suggest that they may interact with the subduction interface at depth. We interpret the Coastal Scarp to be a west-dipping normal fault or flexure and propose that it is located over an east-dipping ramp stack at

  19. 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.

  20. Unravelling the competing influence of regional uplift and active normal faulting in SW Calabria, Italy

    NASA Astrophysics Data System (ADS)

    Whittaker, Alex; Roda Boluda, Duna; Boulton, Sarah; Erhardt, Sebastian

    2015-04-01

    The Neogene geological and geomorphological evolution of Southern Italy is complex and is fundamentally controlled by the subduction of the Ionian slab along the Apennine belt from the Calabrian Arc, and back-arc extension driven by trench rollback. In the area of Calabria and the Straits of Messina the presence of (i) uplifted, deformed and dissected basin sediments and marine terraces, ranging in age from the early to mid-Pleistocene and (ii) seismicity associated with NE-SW normal faults that have well-developed footwall topography and triangular facets have led workers to suggest that both significant regional uplift and extensional faulting in SW Calabria have played a role in generating relief in the area since the mid Pleistocene. However, there is considerable uncertainty in the rates of total surface uplift relative to sea level in both time and space, and the relative partitioning of this uplift between a mantle-driven regional signal, potentially related to a slab tear, and the active extensional structures. Additionally, despite the widespread recognition of normal faults in Calabria to which historical earthquakes are often linked, there is much less agreement on (i) which ones are active and for what length of time; (ii) how the faults interact; and (iii) what their throw and throw rates are. In particular, the ability to resolve both regional uplift and normal faulting in SW Calabria is essential in order to fully understand the tectonic history of the region, while an understanding of location and slip rate of active faults, in an area where the population numbers more than two million people, is essential to assess regional seismic hazards. Here we address these important questions using a combination of tectonic geomorphology and structural geology. We critically examine existing constraints on the rates and distribution of active normal faulting and regional uplift in the area, and we derive new constraints on the along-strike variation in throw

  1. Exhumed analogues of seismically active carbonate-bearing thrusts: fault architecture and deformation mechanisms

    NASA Astrophysics Data System (ADS)

    Tesei, T.; Collettini, C.; Viti, C.; Barchi, M. R.

    2012-12-01

    In May 2012 a M = 5.9 earthquake followed by a long aftershock sequence struck the Northern Italy. The sequence occurred at 4-10 km depth within the active front of Northern Apennines Prism and the major events nucleate within, or propagate through, a thick sequence of carbonates. In an inner sector of the Northern Apennines, ancient carbonate-bearing thrusts exposed at the surface, represent exhumed analogues of structures generating seismicity in the active front. Here we document fault architecture and deformation mechanisms of three regional carbonate bearing thrusts with displacement of several kilometers and exhumation in the range of 1-4 km. Fault zone structure and deformation mechanisms are controlled by the lithology of the faulted rocks. In layered limestones and marly-limestones the fault zone is up to 200 m thick and is characterized by intense pressure solution. In massive limestones the deformation generally occurs along thin and sharp slip planes that are in contact with fault portions affected by either cataclasis or pressure solution. SEM and TEM observations show that pressure solution surfaces, made of smectite lamellae, with time tend to form an interconnected network affected by frictional sliding. Sharp slipping planes along massive limestones show localization along Y shear planes that separate an extremely comminuted cataclasites from an almost undeformed protolith. The comparison of the three shear zones depicts a fault zone structure extremely heterogeneous as the result of protolith lithology, geometrical complexities and the presence of inherited structures. We observe the competition between brittle (cataclasis, distributed frictional sliding along phyllosilicates and extremely localized slip within carbonates) and pressure solution processes, that suggest a multi-mode of slip behaviour. Extreme localization along carbonate-bearing Y shear planes is our favorite fault zone feature representing past seismic ruptures along the studied

  2. Cathodoluminescence and electron beam induced current investigations of stacking faults mechanically introduced in 4H-SiC in the brittle domain

    NASA Astrophysics Data System (ADS)

    Yakimov, E. B.; Regula, G.; Pichaud, B.

    2013-08-01

    The electrical and optical properties of stacking faults (SFs), introduced in 4H-SiC by plastic deformation in the brittle domain of temperature (823 K and 973 K), were studied by cathodoluminescence and electron beam induced current (EBIC) methods. As expected from previous studies, at 973 K, all the SFs generated were found to be double stacking faults (DSFs) and at 823 K, the latter also constituted the major part of the defects. Rather surprisingly, in addition to DSFs, single stacking faults (SSFs) were revealed but only very near the defect nucleation area. Moreover, an inversion of DSF EBIC contrast was obtained which designates these defects as relevant candidates for electron guides to enhance detector performances. Eventually, no dark contrast corresponding to the casual recombination activity of the partial dislocations dragging the DSFs was observed.

  3. Slip Rates of Main Active Fault Zones Through Turkey Inferred From GPS Observations

    NASA Astrophysics Data System (ADS)

    Ozener, H.; Aktug, B.; Dogru, A.; Tasci, L.; Acar, M.; Emre, O.; Yilmaz, O.; Turgut, B.; Halicioglu, K.; Sabuncu, A.; Bal, O.; Eraslan, A.

    2015-12-01

    Active Fault Map of Turkey was revised and published by General Directorate of Mineral Research and Exploration in 2012. This map reveals that there are about 500 faults can generate earthquakes.In order to understand the earthquake potential of these faults, it is needed to determine the slip rates. Although many regional and local studies were performed in the past, the slip rates of the active faults in Turkey have not been determined. In this study, the block modelling, which is the most common method to produce slip rates, will be done. GPS velocities required for block modeling is being compiled from the published studies and the raw data provided then velocity field is combined. To form a homogeneous velocity field, different stochastic models will be used and the optimal velocity field will be achieved. In literature, GPS site velocities, which are computed for different purposes and published, are combined globally and this combined velocity field are used in the analysis of strain accumulation. It is also aimed to develop optimal stochastic models to combine the velocity data. Real time, survey mode and published GPS observations is being combined in this study. We also perform new GPS observations. Furthermore, micro blocks and main fault zones from Active Fault Map Turkey will be determined and homogeneous velocity field will be used to infer slip rates of these active faults. Here, we present the result of first year of the study. This study is being supported by THE SCIENTIFIC AND TECHNOLOGICAL RESEARCH COUNCIL OF TURKEY (TUBITAK)-CAYDAG with grant no. 113Y430.

  4. Field evidence of subsidence and faulting induced by hydrocarbon production in coastal southeast Texas

    USGS Publications Warehouse

    Morton, Robert A.; Purcell, Noreen A.; Peterson, Russell L.

    2001-01-01

    Three large, mature hydrocarbon fields in coastal southeast Texas were examined to evaluate competing hypotheses of wetland losses and to characterize subaerial and submerged surfaces near reactivated faults and zones of subsidence. Detailed topographic and bathymetric profiles and shallow cores at the Port Neches, Clam Lake, and Caplen Fields provide a basis for distinguishing between (1) extensive land-surface subsidence without significant subaqueous erosion, and (2) localized minor subsidence near faults accompanied by extensive subaqueous erosion. Subaqueous erosion results from submergence of wetlands, current and wave excavation of surface sediments and organic detritus, and exportation of the eroded sediments through adjacent water bodies with swift currents such as navigation channels. Responses to induced subsidence and fault reactivation are different at each field site. Detailed stratigraphic correlations of sediment cores show that at Port Neches, subsidence of 35 to 90 cm and minor marsh erosion (20 to 35 cm) created more than 15 million m3 of accommodation space in a nearly circular pattern over the field. At Caplen the marsh surface subsided only about 4 cm, but the surface eroded 30 to 40 cm vertically, creating about 3.5 million m3 of accommodation space. The breakup of wetlands and their conversion to open water appears to be in an initial stage at the Clam Lake Field where marsh plants are being submerged along a fault. The different surficial responses and wetland losses at each field are related to the primary type of hydrocarbon produced and the rates of production. Although the absolute magnitude of induced subsidence may be less than 1 m, even a minor reduction in land elevation is sufficient to cause major wetland losses.

  5. Multilayer stress from gravity and its tectonic implications in urban active fault zone: A case study in Shenzhen, South China

    NASA Astrophysics Data System (ADS)

    Xu, Chuang; Wang, Hai-hong; Luo, Zhi-cai; Ning, Jin-sheng; Liu, Hua-liang

    2015-03-01

    It is significant to identify urban active faults for human life and social sustainable development. The ordinary methods to detect active faults, such as geological survey, artificial seismic exploration, and electromagnetic exploration, are not convenient to be carried out in urban area with dense buildings. It is also difficult to supply information about vertical extension of the deeper faults by these methods. Gravity, reflecting the mass distribution of the Earth's interior, provides an alternative way to detect faults, which is more efficient and convenient for urban active fault detection than the aforementioned techniques. Based on the multi-scale decomposition of gravity anomalies, a novel method to invert multilayer horizontal tectonic stresses is proposed. The inverted multilayer stress fields are further used to infer the distribution and stability of the main faults. In order to validate our method, the multilayer stress fields in the Shenzhen fault zone are calculated as a case study. The calculated stress fields show that their distribution is controlled significantly by the strike of the main faults and can be used to derive depths of the faults. The main faults in Shenzhen may range from 4 km to 20 km in the depth. Each layer of the crust is nearly equipressure since the horizontal tectonic stress has small amplitude. It indicates that the main faults in Shenzhen are relatively stable and have no serious impact on planning and construction of the city.

  6. Interactions between active faulting, volcanism, and sedimentary processes at an island arc: Insights from Les Saintes channel, Lesser Antilles arc

    NASA Astrophysics Data System (ADS)

    Leclerc, F.; Feuillet, N.; Deplus, C.

    2016-07-01

    New high-resolution marine geophysical data allow to characterize a large normal fault system in the Lesser Antilles arc, and to investigate the interactions between active faulting, volcanism, sedimentary, and mass-wasting processes. Les Saintes fault system is composed of several normal faults that form a 30 km wide half-graben accommodating NE-SW extension. It is bounded by the Roseau fault, responsible for the destructive Mw 6.3 21 November 2004 earthquake. The Roseau fault has been identified from the island of Basse-Terre to Dominica. It is thus 40 km long, and it could generate Mw 7 earthquakes in the future. Several submarine volcanoes are also recognized. We show that the fault system initiated after the main volcanic construction and subsequently controls the emission of volcanic products. The system propagates southward through damage zones. At the tip of the damage zones, several volcanic cones were recently emplaced probably due to fissures opening in an area of stress increase. A two-way interaction is observed between active faulting and sedimentary processes. The faults control the development of the main turbiditic system made of kilometer-wide canyons, as well as the location of sediment ponding. In turn, erosion and sedimentation prevent scarp growth at the seafloor. Faulting also enhances mass-wasting processes. Since its initiation, the fault system has consequently modified the morphologic evolution of the arc through perturbation of the sedimentary processes and localization of the more recent volcanic activity.

  7. Seismic Risk Assessment of Active Faults in Japan in Terms of Population Exposure to Seismic Intensity

    NASA Astrophysics Data System (ADS)

    Nojima, Nobuoto; Fujiwara, Hiroyuki; Morikawa, Nobuyuki; Ishikawa, Yutaka; Okumura, Toshihiko; Miyakoshi, Junichi

    This study evaluates and compares seismic risks associated with inland crustal earthquakes in Japan on the basis of published data available on the Japan Seismic Hazard Information Station (J-SHIS). First, taking account of prediction uncertainty of the attenuation law of seismic intensity, the evaluation method for population exposure (PEX) to seismic intensity is presented. The method is applied to 333 seismic events potentially caused by main active faults (154 cases) and other active faults (179 cases). The relationship between population exposure and the probability of occurrence of seismic events ("P-PEX relation") and the resultant seismic risk curves are obtained. Generalized risk index which incorporates the effects of focusing on urgency (probability) or significance (PEX) is defined, producing various risk rankings of active faults.

  8. Soil Moisture Active Passive Mission: Fault Management Design Analyses

    NASA Technical Reports Server (NTRS)

    Meakin, Peter; Weitl, Raquel

    2013-01-01

    As a general trend, the complexities of modern spacecraft are increasing to include more ambitious mission goals with tighter timing requirements and on-board autonomy. As a byproduct, the protective features that monitor the performance of these systems have also increased in scope and complexity. Given cost and schedule pressures, there is an increasing emphasis on understanding the behavior of the system at design time. Formal test-driven verification and validation (V&V) is rarely able to test the significant combinatorics of states, and often finds problems late in the development cycle forcing design changes that can be costly. This paper describes the approach the SMAP Fault Protection team has taken to address some of the above-mentioned issues.

  9. Faults paragenesis and paleostress state in the zone of actively propagating continental strike-slip on the example of North Khangai fault (Northern Mongolia)

    NASA Astrophysics Data System (ADS)

    Sankov, Vladimir; Parfeevets, Anna

    2014-05-01

    Sublatitudinal North Khangai fault extends from Ubsunuur basin to the eastern part of the Selenga corridor trough 800 km. It is the northern boundary of the massive Mongolian block and limits of the Baikal rift system structures propagation in the south (Logatchev, 2003). Late Cenozoic and present-day fault activity are expressed in the left-lateral displacements of a different order of river valleys and high seismicity. We have carried out studies of the kinematics of active faults and palaeostresses reconstruction in the zone of the dynamic influence of North Khangai fault, the width of which varies along the strike and can exceeds 100 km. The result shows that the fault zone has a longitudinal and a transverse zoning. Longitudinal zonation presented gradual change from west to east regions of compression and transpression regimes (Khan-Khukhey ridge) to strike-slip regime (Bolnay ridge) and strike-slip and transtensive regimes (west of Selenga corridor). Strike-slip zones are represented by linearly concentrated rupture deformations. In contrast, near the termination of the fault the cluster fault deformation formed. Here, from north to south, there are radical changes in the palaeostress state. In the north-western sector (east of Selenga corridor) strike-slip faults, strike-slip faults with normal components and normal faults are dominated. For this sector the stress tensors of extensive, transtension and strike-slip regimes are typical. South-western sector is separated from the north-eastern one by massive Buren Nuruu ridge within which the active faults are not identified. In the south-western sector between the Orkhon and Tola rivers the cluster of NW thrusts and N-S strike-slip faults with reverse component are discovered. The faults are perfectly expressed by NW and N-S scarps in the relief. The most structures dip to the east and north-east. Holocene fault activity is demonstrated by the hanging river valleys and horizontal displacements with amplitudes

  10. Laboratory simulations of fluid-induced seismicity in shallow volcanic faults

    NASA Astrophysics Data System (ADS)

    Fazio, M.; Benson, P. M.; Vinciguerra, S.

    2014-12-01

    Seismicity is a key tool used for monitoring fracturing and faulting in around volcanoes, with a particular emphasis placed on the frequency (Long period or Low Frequency, LF events) thought to be due to fluid movement, as compared to Volcano-Tectonic activity driven by pure fracture. To better understand these fundamental processes this research presents new rock deformation experiments designed to simulate shallow volcano-tectonic pressure/temperature conditions, linking pore fluid flow to the induced seismicity. A particular emphasis is placed on the conditions of pressure and temperature required to stimulate LF activity. Our setup imposes a rapid pore pressure release or "venting" via a small pre-drilled axial conduit to stimulate rapid fluid movement through an established fracture damage zone via a two stage process. Firstly experiments are conducted to generate a through-going shear fracture, with pore fluid connectivity to this fracture enhanced via the axial conduit. The shear failure is imaged via AE location with ~mm scale accuracy. The second stage vents pore fluid pressure via an electrical solenoid valve. We find that this second stage is accompanied by a swarm of LF activity akin to Long Period (LP) activity on active volcanoes. We find that a significant change in the dominant frequency of LF events is recorded as pore fluid pressure decrease through, and beyond, the water boiling point and the transition between LF and VLF occurred at the pressure at which the superheated water turn to vapour. In addition, we observe a significant dependence of the recorded LF upon the fluid flow rate. Finally, we present new data using low frequency (200 kHz) AE sensors, in conjunction with our standard 1 MHz-central-frequency sensors, which permit us to better constraint LF and VLF events with lower attenuation, and hence an improved characterization of these LF seismic signals. Data are used to forecast the final time of failure via the fracture forecast

  11. Laboratory simulations of fluid-induced seismicity in shallow volcanic faults

    NASA Astrophysics Data System (ADS)

    Fazio, Marco; Benson, Philip; Vinciguerra, Sergio; Meredith, Philip

    2015-04-01

    Seismicity is a key tool used for monitoring fracturing and faulting in around volcanoes, with a particular emphasis placed on the frequency (Long period or Low Frequency, LF events) thought to be due to fluid movement, as compared to Volcano-Tectonic activity driven by pure fracture. To better understand these fundamental processes this research presents new rock deformation experiments designed to simulate shallow volcano-tectonic pressure/temperature conditions, linking pore fluid flow to the induced seismicity. A particular emphasis is placed on the conditions of pressure and temperature required to stimulate LF activity. Our setup imposes a rapid pore pressure release or "venting" via a small pre-drilled axial conduit to stimulate rapid fluid movement through an established fracture damage zone via a two stage process. Firstly experiments are conducted to generate a through-going shear fracture, with pore fluid connectivity to this fracture enhanced via the axial conduit. The shear failure is imaged via AE location with ~mm scale accuracy. The second stage vents pore fluid pressure via an electrical solenoid valve. We find that this second stage is accompanied by a swarm of LF activity akin to Long Period (LP) activity on active volcanoes. We find that a significant change in the dominant frequency of LF events is recorded as pore fluid pressure decrease through, and beyond, the water boiling point and the transition between LF and VLF occurred at the pressure at which the superheated water turn to vapour. In addition, we observe a significant dependence of the recorded LF upon the fluid flow rate. Finally, we present new data using low frequency (200 kHz) AE sensors, in conjunction with our standard 1 MHz-central-frequency sensors, which permit us to better constraint LF and VLF events with lower attenuation, and hence an improved characterization of these LF seismic signals. Data are used to forecast the final time of failure via the fracture forecast

  12. New Constraints on the Geometry and Kinematics of Active Faults in the Hinterland of the Northwest Himalaya

    NASA Astrophysics Data System (ADS)

    Morell, K. D.; Sandiford, M.; Rajendran, C. C. P.; Fink, D.; Kohn, B. P.

    2014-12-01

    The geometry and kinematics of the active, and potentially seismogenic, fault structures within the hinterland of the Himalaya have proven challenging to constrain in the past, primarily because active faults in this region tend to be buried beneath the subsurface and active seismicity often does not align with surficially mapped fault traces. Here we present a series of complementary datasets, including results from low temperature thermochronology, basin-wide erosion rates from 10Be concentrations, and topographic and longitudinal profile analyses, that place constraints on the spatial distribution of fault-related rock uplift and erosion across a ~400-km long region of the lower and high Himalaya of northwest India. Results from our analyses reveal that hillslope morphology and channel steepness are relatively invariant parallel to strike but vary significantly across strike, with the most prominent and abrupt variations occurring at the physiographic transition between the lower and high Himalaya (PT2), near the axial trace of the ramp-flat transition in the Main Himalayan Thrust (MHT). The cross-strike changes in geomorphology observed across the PT2 correlate with an order of magnitude northward increase in basin-wide erosion rates (~0.06-0.8 mm/a) and a corresponding decrease in apatite (~5-2 Ma) and zircon (U-Th)/He (~10-2 Ma) cooling ages. Combined with published geophysical and seismicity data, we interpret these results to reflect spatial variations in rock uplift and exhumation induced by a segment of the MHT ramp-flat system that is at least ~400 km long and ~125 km wide. The relatively young (U-Th)/He ages (<10 Ma) greater than 20 km south of the MHT ramp-flat transition preliminarily suggest that the kinematics of this system are best explained by a model which incorporates an accreting duplex on the MHT ramp but additional forthcoming analyses, including thermal modeling, will confirm if this hypothesis is robust.

  13. Active faulting and neotectonics in the Baelo Claudia area, Campo de Gibraltar (southern Spain)

    NASA Astrophysics Data System (ADS)

    Grützner, Christoph; Reicherter, Klaus; Hübscher, Christian; Silva, Pablo G.

    2012-07-01

    The Strait of Gibraltar area is part of the western Eurasian-African convergence zone characterized by a complex pattern of deformation, including thrusting and folding and active normal faulting. Generally, the area is of low-seismicity; only some minor earthquakes have been recorded in the last hundred years. Archaeoseismological data evidences earthquake destruction occurring twice during Roman times. A better neotectonic framework and knowledge on the paleostress evolution of the Strait of Gibraltar area is necessary to find the local sources for those events and to establish an understanding of the recent deformation. Paleoseismic evidence for one moderate earthquake event around 6000-5000 BP along the normal Carrizales Fault is described in this paper. Off-shore high-resolution seismic investigations, structural and paleostress data, high-resolution GPR and geoelectrical resistivity measurements, outcrop investigations and trenching studies are discussed. The data reveal that active faulting takes place along N-S trending normal faults. Hence, N-S directed normal faults in the area are claimed as local candidates for moderate earthquake activity. Return periods of moderate earthquakes in the order of at least 2000-2500 years in the study area may have to be taken into account. Structural data, such a paleostress data and joints are presented and a deformation history for the Strait of Gibraltar area in southern Spain is developed in this study.

  14. Assessment of Morphotectonic Influences on Hydrological Environment in Vicinity of an Active Fault

    NASA Astrophysics Data System (ADS)

    Singh, A.; Mukherjee, S.

    2011-12-01

    Studying effects of faulted zones in shaping the hydrological environment of any landscape in a long run is difficult, though these can play a crucial role in regulating the flow and accumulation of water. While aquifer recharge is directly influenced by the structural changes associated with tectonic activity, surface flow may also be influenced depending upon the topography. While planning for water resource management, groundwater remediation or hydrological restoration it is imperative to understand and suitably include these influences to derive maximum benefit. This study aimed at characterization of surface as well as subsurface hydrological conditions in a hard-rock terrain, morphed under the influence of neotectonic activity, associated with tensional type of faulting. The area selected lies approximately between 28.20 - 28.60 N and 77.00 - 77.40 E, in vicinity of an active fault, with quartzitic rocks showing signs of multiple folding. Associated tear faults in adjoining areas have also been observed. To initially identify sites suitable for geophysical surveys, a spatial analysis involving seismic data and 3D visualization was done to identify the lineaments. The information thus obtained was correlated with geological information derived from hyperspectral satellite imagery. Geochemical analysis was also performed to verify the same. Influence of faulting activity on regulating water flow on surface as well as groundwater was studied. For surface water bodies hydrological analysis on elevation data (DEM) was performed whereas for subsurface recharge, margins of geological units were targeted. This was confirmed by actual field geophysical (resistivity) surveys at suitable strategic locations. The relative influences of structural lineaments on regulating subsurface water storage were also determined. The resulting database in GIS platform can also be used for flow modeling and aquifer potential / vulnerability studies. Also, the role of faulting

  15. Geodetic Network Design and Optimization on the Active Tuzla Fault (Izmir, Turkey) for Disaster Management

    PubMed Central

    Halicioglu, Kerem; Ozener, Haluk

    2008-01-01

    Both seismological and geodynamic research emphasize that the Aegean Region, which comprises the Hellenic Arc, the Greek mainland and Western Turkey is the most seismically active region in Western Eurasia. The convergence of the Eurasian and African lithospheric plates forces a westward motion on the Anatolian plate relative to the Eurasian one. Western Anatolia is a valuable laboratory for Earth Science research because of its complex geological structure. Izmir is a large city in Turkey with a population of about 2.5 million that is at great risk from big earthquakes. Unfortunately, previous geodynamics studies performed in this region are insufficient or cover large areas instead of specific faults. The Tuzla Fault, which is aligned trending NE–SW between the town of Menderes and Cape Doganbey, is an important fault in terms of seismic activity and its proximity to the city of Izmir. This study aims to perform a large scale investigation focusing on the Tuzla Fault and its vicinity for better understanding of the region's tectonics. In order to investigate the crustal deformation along the Tuzla Fault and Izmir Bay, a geodetic network has been designed and optimizations were performed. This paper suggests a schedule for a crustal deformation monitoring study which includes research on the tectonics of the region, network design and optimization strategies, theory and practice of processing. The study is also open for extension in terms of monitoring different types of fault characteristics. A one-dimensional fault model with two parameters – standard strike-slip model of dislocation theory in an elastic half-space – is formulated in order to determine which sites are suitable for the campaign based geodetic GPS measurements. Geodetic results can be used as a background data for disaster management systems.

  16. 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

  17. 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.

  18. Distribution of active faulting along orogenic wedges: Minimum-work models and natural analogue

    NASA Astrophysics Data System (ADS)

    Yagupsky, Daniel L.; Brooks, Benjamin A.; Whipple, Kelin X.; Duncan, Christopher C.; Bevis, Michael

    2014-09-01

    Numerical 2-D models based on the principle of minimum work were used to examine the space-time distribution of active faulting during the evolution of orogenic wedges. A series of models focused on thin-skinned thrusting illustrates the effects of arid conditions (no erosion), unsteady state conditions (accretionary influx greater than erosional efflux) and steady state conditions (accretionary influx balances erosional efflux), on the distribution of fault activity. For arid settings, a general forward accretion sequence prevails, although a significant amount of internal deformation is registered: the resulting fault pattern is a rather uniform spread along the profile. Under fixed erosional efficiency settings, the frontal advance of the wedge-front is inhibited, reaching a steady state after a given forward propagation. Then, the applied shortening is consumed by surface ruptures over a narrow frontal zone. Under a temporal increase in erosional efficiency (i.e., transient non-steady state mass balance conditions), a narrowing of the synthetic wedge results; a rather diffuse fault activity distribution is observed during the deformation front retreat. Once steady balanced conditions are reached, a single long-lived deformation front prevails. Fault activity distribution produced during the deformation front retreat of the latter scenario, compares well with the structural evolution and hinterlandward deformation migration identified in southern Bolivian Subandes (SSA) from late Miocene to present. This analogy supports the notion that the SSA is not in steady state, but is rather responding to an erosional efficiency increase since late Miocene. The results shed light on the impact of different mass balance conditions on the vastly different kinematics found in mountain ranges, suggesting that those affected by growing erosion under a transient unbalanced mass flux condition tend to distribute deformation along both frontal and internal faults, while others

  19. The Trans-Atlantic Geotraverse hydrothermal field: A hydrothermal system on an active detachment fault

    NASA Astrophysics Data System (ADS)

    Humphris, Susan E.; Tivey, Margaret K.; Tivey, Maurice A.

    2015-11-01

    Over the last ten years, geophysical studies have revealed that the Trans-Atlantic Geotraverse (TAG) hydrothermal field (26°08‧N on the Mid-Atlantic Ridge) is located on the hanging wall of an active detachment fault. This is particularly important in light of the recognition that detachment faulting accounts for crustal accretion/extension along a significant portion of the Mid-Atlantic Ridge, and that the majority of confirmed vent sites on this slow-spreading ridge are hosted on detachment faults. The TAG hydrothermal field is one of the largest sites of high-temperature hydrothermal activity and mineralization found to date on the seafloor, and is comprised of active and relict deposits in different stages of evolution. The episodic nature of hydrothermal activity over the last 140 ka provides strong evidence that the complex shape and geological structure of the active detachment fault system exerts first order, but poorly understood, influences on the hydrothermal circulation patterns, fluid chemistry, and mineral deposition. While hydrothermal circulation extracts heat from a deep source region, the location of the source region at TAG is unknown. Hydrothermal upflow is likely focused along the relatively permeable detachment fault interface at depth, and then the high temperature fluids leave the low-angle portion of the detachment fault and rise vertically through the highly fissured hanging wall to the seafloor. The presence of abundant anhydrite in the cone on the summit of the TAG active mound and in veins in the crust beneath provides evidence for a fluid circulation system that entrains significant amounts of seawater into the shallow parts of the mound and stockwork. Given the importance of detachment faulting for crustal extension at slow spreading ridges, the fundamental question that still needs to be addressed is: How do detachment fault systems, and the structure at depth associated with these systems (e.g., presence of plutons and/or high

  20. Active Faults of the Northwest Himalaya: Pattern, Rate, and Timing of Surface Rupturing Earthquakes

    NASA Astrophysics Data System (ADS)

    Yule, J.; Madden, C.; Gavillot, Y.; Hebeler, A.; Meigs, A.; Hussein, A.; Malik, M.; Bhat, M.; Kausar, A.; Ramzan, S.; Sayab, M.; Yeats, R. S.

    2012-12-01

    The 2005 Kashmir earthquake (Mw 7.6) is the only Himalayan earthquake to rupture the surface since the 15th to 16th century A.D. when >Mw 8.5 earthquakes ruptured the Himalayan Frontal thrust (HFT) in the central Himalaya. Megathrust-type earthquakes like these seem to relieve a majority of the accumulated interseismic strain and concentrate permanent strain across a narrow width at the deformation front (faults within the orogen appear to accommodate little strain). The 2005 within-plate rupture in Kashmir may be a clue that a different seismotectonic model applies to the northwest Himalaya where active deformation occurs on faults distributed more than 120 km across the orogen. An asymmetric anticline marks the deformation front in Kashmir where the HFT is inferred to be blind, though ~20 m-high escarpments suggest that unrecognized thrust fault(s) may reach the surface locally. Folded river terraces and dip data also suggest that this frontal fold contains a SW-dipping back thrust. In Pakistan the Salt Range thrust system (SRT) defines the thrust front. New mapping and preliminary OSL dates from deformed Holocene sediments exposed along the westernmost SRT reveal that the fault slips at 1-7 mm/yr and last ruptured within the last several thousand years. Within the orogenic wedge to the north of the deformation front, active shortening occurs along a system of surface-rupturing reverse faults, extending from the Balakot-Bagh fault (source of the 2005 Kashmir earthquake) to the Reasi fault (RF) in Indian Kashmir to the southeast. One strand of the RF displaces a 350 m-high, 80 ± 6 ka (preliminary OSL age) fluvial terrace, yielding a minimum shortening rate of 3-5 mm/yr. Trenches excavated across the RF nearby reveal a distinct angular unconformity that likely formed during a surface rupture ~4500 yrs BP. Farther north, three northeast-dipping reverse faults cut Quaternary terraces on the southwest side of the Kashmir Valley. Trenches expose evidence for at least

  1. Distribution of deformation on an active normal fault network, NW Corinth Rift

    NASA Astrophysics Data System (ADS)

    Ford, Mary; Meyer, Nicolas; Boiselet, Aurélien; Lambotte, Sophie; Scotti, Oona; Lyon-Caen, Hélène; Briole, Pierre; Caumon, Guillaume; Bernard, Pascal

    2013-04-01

    Over the last 20-25 years, geodetic measurements across the Gulf of Corinth have recorded high extension rates varying from 1.1 cm/a in the east to a maximum of 1.6 cm/a in the west. Geodetic studies also show that current deformation is confined between two relatively rigid blocks defined as Central Greece (to the north) and the Peloponnesus to the south. Active north dipping faults (<1 Ma) define the south coast of the subsiding Gulf, while high seismicity (major earthquakes and micro-seismicity) is concentrated at depth below and to the north of the westernmost Gulf. How is this intense deformation distributed in the upper crust? Our objectives here are (1) to propose two models for the distribution of deformation in the upper crust in the westernmost rift since 1 Ma, and (2) to place the tectonic behaviour of the western Gulf in the context of longer term rift evolution. Over 20 major active normal faults have been identified in the CRL area based specific characteristics (capable of generating earthquakes M> 5.5, active in the last 1 M yrs, slip rate >0.5 mm/a). Because of the uncertainty related to fault geometry at depth two models for 3D fault network geometry in the western rift down to 10 km were constructed using all available geophysical and geological data. The first model assumes planar fault geometries while the second uses listric geometries for major faults. A model for the distribution of geodetically-defined extension on faults is constructed along five NNE-SSW cross sections using a variety of data and timescales. We assume that the role of smaller faults in accommodating deformation is negligible so that extension is fully accommodated on the identified major faults. Uncertainties and implications are discussed. These models provide estimates of slip rate for each fault that can be used in seismic hazard models. A compilation of onshore and offshore data shows that the western Gulf is the youngest part of the Corinth rift having initiated

  2. The Active Mai'iu Low Angle Normal Fault, Woodlark Rift: Spatial and Temporal Slip Distributions, and Rider Block Abandonment Chronology.

    NASA Astrophysics Data System (ADS)

    Webber, S. M.; Little, T.; Norton, K. P.; Mizera, M.; Oesterle, J.; Ellis, S. M.

    2015-12-01

    Low-angle normal faults (LANFs) have induced debate due to their apparent non-Andersonian behavior and lack of significant seismicity associated with slip. Dipping ~21°, the Mai'iu Fault, Woodlark Rift is an active, rapidly slipping LANF located at the transition between continental extension and seafloor spreading. Based on campaign GPS data [Wallace et al., 2014] the Mai'iu Fault is thought to slip at 7-9 mm/yr, accommodating a large fraction of total basinal extension, although it is uncertain whether slip is seismic or aseismic. Surface geomorphology indicates that the fault scarp is not significantly eroded despite high rainfall and ~3000 m relief. We have obtained 15 rock samples (~5 m spacing) from the lowermost Mai'iu Fault scarp in order to determine Holocene slip rate and style over the last ~10 kyr using cosmogenic 10Be in quartz. This slip direction-parallel profile in exposed bedrock is supported by a suite of soil samples for 10Be analysis, which extend our temporal coverage. We model exposure age data in terms of slip rate and style by identification of discontinuities within the profile. Of particular interest is whether slip is seismic or aseismic. In addition we analyze the structure of conglomeratic strata and abandoned, back-rotated rider blocks in the Mai'iu Fault hanging wall, which record Quaternary splay faulting and tilting in response to sustained LANF slip. 20 quartz pebble samples were obtained from hanging wall conglomerates for the purpose of calculating cosmogenic burial (26Al/10Be) ages. These constrain the chronology of Quaternary hanging wall deformation. High-angle (~50°) faulting competes with LANF slip at <2 km depths, with high-angle faults cutting the main LANF and exposing footwall metabasalt up to 2 km north of the Mai'iu Fault. Past splay faulting is recorded in the progressive back-tilting and folding of the Gwoira rider block in a ~2 km deep depression in the corrugated Mai'iu fault plane. Our results provide new

  3. Faults Activities And Crustal Deformation near Hualien City, eastern Taiwan Analysed By Persistent Scatterer InSAR

    NASA Astrophysics Data System (ADS)

    Lu, C.; Lin, M.; Yen, J.; Chang, C.

    2008-12-01

    Hualien is located in eastern part of Taiwan, and is the collision boundary in the northern of Huatung Longitudinal Valley between the Philippine Sea tectonic plate and Eurasian tectonic plate(Biq, 1981; Barrier and Angelier, 1986). There are several active faults, such as Milun fault, Beipu fault and Minyi fault, pass through the Hualien city, and create many crustal deformation. According to previous researches (Hsu, 1956; Lin, 1962; Yu, 1997) we know Milun fault is a thrust and left lateral fault, and the fault plane incline to east. Minyi fault also is a left lateral and a slight reverse fault, but it's fault plane incline to west. (Chang, 1994; Yu, 1997) We applied the Persistent Scatterer Interferometric Synthetic Aperture Radar (PSInSAR, Hooper, 2007) to observe temporally-variable processes of Hualien city between 2004 to 2008. At the same time, precise leveling and GPS data were taken for the auxiliary data to verify the deformation rate and pattern in this area. In the Hualien city area, our observation showed that the active faults separate this area into several distinct blocks. Most of the blocks moved slowly, but the hanging wall of the Milun fault decreases 5- 8mm in line of sight (LOS) direction between 15 May 2004 to 24 Feb 2007, then increases 3-6mm in LOS between 1 Dec 2007 to 5 Jan 2008. The deformation reversed its direction in 2007. The western surface of Hualien City displays continuous deformation about 1.5-2mm/yr , which spread along the Beipu fault. Our preliminary investigation indicated that between late 2004 and middle 2005 there had been an abrupt increase in seismicity, which coincided with PSInSAR observation of a large displacement. The distribution of shallow source earthquakes correlate with the area with large deformation. Our following works include continuing observation of the Hualien City, and decipher the relationship between earthquakes and surface deformation, and model the fault action in Hualien City with time series.

  4. Hidden faults in the Gobi Desert (Inner Mongolia, China) - evidence for fault activity in a previously tectonically stable zone

    NASA Astrophysics Data System (ADS)

    Rudersdorf, Andreas; Haedke, Hanna; Reicherter, Klaus

    2013-04-01

    The Gaxun Nur Basin (GNB, also Ejina Basin, Hei River Basin, Ruoshui Basin) north of the Tibetan Plateau and the Hexi Corridor is an endorheic basin bounded by the Bei Shan ranges in the west, the Gobi Altai mountains in the north and the Badain Jaran sand desert in the east. The basin is fed from the south by the braided drainage system of the Hei He (Hei River) and its tributaries, which originate in the Qilian Shan; terminal lakes like the dried Gaxun Nur and Sogo Nur are and have been temporal. The sedimentary succession of up to 300 m comprises intercalations of not only alluvial deposits but also lake sediments and playa evaporites. The basin has been regarded as tectonically inactive by earlier authors; however, the dating of sediments from an earlier drill core in the basin center provided some implications for tectonic activity. Subsequent remote sensing efforts revealed large lineaments throughout the basin which are now considered as possible fault line fingerprints. We investigated well preserved Yardangs (clay terraces) in the northeastern part of the GNB, in the vicinity of the Juyanze (paleo) lake, and found evidence for Holocene active tectonics (seismites). We present a lithological analysis of the relevant sequences and conclusions on the recent tectonic activity within the study area.

  5. Active Tectonics along the Carboneras Fault (SE Iberian Margin): Onshore-Offshore Paleoseismological Approach

    NASA Astrophysics Data System (ADS)

    Moreno, X.; Masana, E.; Gràcia, E.; Pallàs, R.; Santanach, P.; Dañobeitia, J. J.; Party, I.

    2006-12-01

    The southern margin of the Iberian Peninsula hosts the convergent boundary between the European and African Plates. At the eastern Betic Cordillera, the Neogene and Quaternary shortening has mainly been absorbed by left-lateral strike-slip faults, which in the Iberian Peninsula is represented by the Eastern Betics Shear Zone (EBSZ). One of the longest structures in the EBSZ is the Carboneras Fault, with almost 50 km onshore and more than 100 km offshore. The low record seismicity along its trace, suggest either non seismic behaviour or long recurrence intervals (104 years). The aim of this work is an integrated onshore-offshore neotectonic and paleoseismological study of the Carboneras Fault Zone to characterize its seismic potential. The onshore study was made through regional geological and geomorphological analysis, geophysical prospecting, microtopography, trenching, and dating (14 C, U/Th, TL). Onshore macro and microstructures as beheaded and offset alluvial fans and S-C microstructures in the fault zone reveals a Quaternary left-lateral strike-slip motion combined with a vertical component along the fault. Trenching reveals this fault is seismogenic, with at least four late Quaternary events. The oldest occurred between 54.9 and 32.2 ka BP, the second one between 40.9 and 27.1 ka BP, and the two most recent events occurred between 30.8 and 0.875 ka BP. The thickness of the colluvial wedges suggest a Mw=7 for the first and Mw=6.6 for the second event. The mean recurrence rate is 14 ka, and the minimum elapsed time is 875 years. The offshore portion, studied by high-resolution marine geophysical methods, shows very similar strike-slip structures. The marine paleoseismic data will be integrated with the onland results in order to accurately determine the recent activity and seismic parameters of the entire Carboneras Fault.

  6. Estimating the detectability of faults in 3D-seismic data - A valuable input to Induced Seismic Hazard Assessment (ISHA)

    NASA Astrophysics Data System (ADS)

    Goertz, A.; Kraft, T.; Wiemer, S.; Spada, M.

    2012-12-01

    In the past several years, some geotechnical operations that inject fluid into the deep subsurface, such as oil and gas development, waste disposal, and geothermal energy development, have been found or suspected to cause small to moderate sized earthquakes. In several cases the largest events occurred on previously unmapped faults, within or in close vicinity to the operated reservoirs. The obvious conclusion drawn from this finding, also expressed in most recently published best practice guidelines and recommendations, is to avoid injecting into faults. Yet, how certain can we be that all faults relevant to induced seismic hazard have been identified, even around well studied sites? Here we present a probabilistic approach to assess the capability of detecting faults by means of 3D seismic imaging. First, we populate a model reservoir with seed faults of random orientation and slip direction. Drawing random samples from a Gutenberg-Richter distribution, each seed fault is assigned a magnitude and corresponding size using standard scaling relations based on a circular rupture model. We then compute the minimum resolution of a 3D seismic survey for given acquisition parameters and frequency bandwidth. Assuming a random distribution of medium properties and distribution of image frequencies, we obtain a probability that a fault of a given size is detected, or respectively overlooked, by the 3D seismic. Weighting the initial Gutenberg-Richter fault size distribution with the probability of imaging a fault, we obtain a modified fault size distribution in the imaged volume from which we can constrain the maximum magnitude to be considered in the seismic hazard assessment of the operation. We can further quantify the value of information associated with the seismic image by comparing the expected insured value loss between the image-weighted and the unweighted hazard estimates.

  7. Duration of activity on lobate-scarp thrust faults on Mercury

    NASA Astrophysics Data System (ADS)

    Banks, Maria E.; Xiao, Zhiyong; Watters, Thomas R.; Strom, Robert G.; Braden, Sarah E.; Chapman, Clark R.; Solomon, Sean C.; Klimczak, Christian; Byrne, Paul K.

    2015-11-01

    Lobate scarps, landforms interpreted as the surface manifestation of thrust faults, are widely distributed across Mercury and preserve a record of its history of crustal deformation. Their formation is primarily attributed to the accommodation of horizontal shortening of Mercury's lithosphere in response to cooling and contraction of the planet's interior. Analyses of images acquired by the Mariner 10 and MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft during flybys of Mercury showed that thrust faults were active at least as far back in time as near the end of emplacement of the largest expanses of smooth plains. However, the full temporal extent of thrust fault activity on Mercury, particularly the duration of this activity following smooth plains emplacement, remained poorly constrained. Orbital images from the MESSENGER spacecraft reveal previously unrecognized stratigraphic relations between lobate scarps and impact craters of differing ages and degradation states. Analysis of these stratigraphic relations indicates that contraction has been a widespread and long-lived process on the surface of Mercury. Thrust fault activity had initiated by a time near the end of the late heavy bombardment of the inner solar system and continued through much or all of Mercury's subsequent history. Such deformation likely resulted from the continuing secular cooling of Mercury's interior.

  8. Velocity-dependent frictional behavior and slip magnitude of a fault affected by fluid injection activities

    NASA Astrophysics Data System (ADS)

    Urpi, L.; Rinaldi, A. P.; Spiers, C. J.

    2014-12-01

    Fluid injection is performed or planned for various activities, such as CO2 sequestration, gas storage, waste water disposal, and engineered geothermal system. Static stress and pressure perturbation due to the fluid injection may cause different scale earthquake phenomena, from instrumental recorded micro-seismicity to triggering of human-felt events. With this study we present a sensitivity analysis of the slip magnitude for the fluid injection in a reservoir-like structure. The reservoir, confined within impervious rock units, is composed by a porous rock mass laterally bounded by a fault. The fault is hydraulically connected to the fluid hosting unit. The numerical analysis is based on fully explicit sequential coupling between a multiphase fluid flow and a hydromechanical finite element calculation code. When the system conditions approaches failure, the simulation is performed in a fully dynamic mode. The coupling allows simulating change in permeability due to stress/strain change, as well as the slip on the fault due to overpressure and associated stress changes. Interface elements have been used to include the constitutive law characterizing the frictional behaviour of the fault. The change in friction with different slip velocities has been derived from laboratory results. Velocity- and strain-dependent frictional behavior of different patches of the fault influence the system evolution, resulting in larger or smaller slip length for the same injected volume.

  9. Active tectonic extension across the Alto Tiberina normal fault system from GPS data modeling and InSAR velocity maps: new perspectives within TABOO Near Fault Observatory

    NASA Astrophysics Data System (ADS)

    Vadacca, Luigi; Anderlini, Letizia; Casarotti, Emanuele; Serpelloni, Enrico; Chiaraluce, Lauro; Polcari, Marco; Albano, Matteo; Stramondo, Salvatore

    2014-05-01

    The Alto Tiberina fault (ATF) is a low-angle (east-dipping at 15°) normal fault (LANF) 70 km long placed in the Umbria-Marche Apennines (central Italy), characterized by SW-NE oriented extension occurring at rates of 2-3 mm/yr. These rates were measured by continuous GPS stations belonging to several networks, which are denser in the study area thanks to additional sites recently installed in the framework of the INGV national RING network and of the ATF observatory. In this area historical and instrumental earthquakes mainly occur on west-dipping high-angle normal faults. Within this context the ATF has accumulated 2 km of displacement over the past 2 Ma, but at the same time the deformation processes active along this misoriented fault, as well as its mechanical behavior, are still unknown. We tackle this issue by solving for interseismic deformation models obtained by two different methods. At first, through the 2D and 3D finite element modeling, we define the effects of locking depth, synthetic and antithetic fault activity and lithology on the velocity gradient measured along the ATF system. Subsequently through a block modeling approach, we model the GPS velocities by considering the major fault systems as bounds of rotating blocks, while estimating the corresponding geodetic fault slip-rates and maps of heterogeneous fault coupling. Thanks to the latest imaging of the ATF deep structure obtained from seismic profiles, we improve the proposed models by modeling the fault as a complex rough surface to understand where the stress accumulations are located and the interseismic coupling changes. The preliminary results obtained show firstly that the observed extension is mainly accommodated by interseismic deformation on both the ATF and antithetic faults, highlighting the important role of this LANF inside an active tectonic contest. Secondarily, using the ATF surface "topography", we find an interesting correlation between microseismicty and creeping portions

  10. Earthquake Model of the Middle East (EMME) Project: Active Fault Database for the Middle East Region

    NASA Astrophysics Data System (ADS)

    Gülen, L.; Wp2 Team

    2010-12-01

    The Earthquake Model of the Middle East (EMME) Project is a regional project of the umbrella GEM (Global Earthquake Model) project (http://www.emme-gem.org/). EMME project region includes Turkey, Georgia, Armenia, Azerbaijan, Syria, Lebanon, Jordan, Iran, Pakistan, and Afghanistan. Both EMME and SHARE projects overlap and Turkey becomes a bridge connecting the two projects. The Middle East region is tectonically and seismically very active part of the Alpine-Himalayan orogenic belt. Many major earthquakes have occurred in this region over the years causing casualties in the millions. The EMME project will use PSHA approach and the existing source models will be revised or modified by the incorporation of newly acquired data. More importantly the most distinguishing aspect of the EMME project from the previous ones will be its dynamic character. This very important characteristic is accomplished by the design of a flexible and scalable database that will permit continuous update, refinement, and analysis. A digital active fault map of the Middle East region is under construction in ArcGIS format. We are developing a database of fault parameters for active faults that are capable of generating earthquakes above a threshold magnitude of Mw≥5.5. Similar to the WGCEP-2007 and UCERF-2 projects, the EMME project database includes information on the geometry and rates of movement of faults in a “Fault Section Database”. The “Fault Section” concept has a physical significance, in that if one or more fault parameters change, a new fault section is defined along a fault zone. So far over 3,000 Fault Sections have been defined and parameterized for the Middle East region. A separate “Paleo-Sites Database” includes information on the timing and amounts of fault displacement for major fault zones. A digital reference library that includes the pdf files of the relevant papers, reports is also being prepared. Another task of the WP-2 of the EMME project is to prepare

  11. Robust fault-tolerant H∞ control of active suspension systems with finite-frequency constraint

    NASA Astrophysics Data System (ADS)

    Wang, Rongrong; Jing, Hui; Karimi, Hamid Reza; Chen, Nan

    2015-10-01

    In this paper, the robust fault-tolerant (FT) H∞ control problem of active suspension systems with finite-frequency constraint is investigated. A full-car model is employed in the controller design such that the heave, pitch and roll motions can be simultaneously controlled. Both the actuator faults and external disturbances are considered in the controller synthesis. As the human body is more sensitive to the vertical vibration in 4-8 Hz, robust H∞ control with this finite-frequency constraint is designed. Other performances such as suspension deflection and actuator saturation are also considered. As some of the states such as the sprung mass pitch and roll angles are hard to measure, a robust H∞ dynamic output-feedback controller with fault tolerant ability is proposed. Simulation results show the performance of the proposed controller.

  12. Assessing low-activity faults for the seismic safety of dams

    SciTech Connect

    Page, W.D.; Savage, W.U.; McLaren, M.K.

    1995-12-31

    Dams have been a familiar construct in the northern Sierra Nevada range in California (north of the San Joaquin River) since the forty-niners and farmers diverted water to their gold mines and farms in the mid 19th century. Today, more than 370 dams dot the region from the Central Valley to the eastern escarpment. Fifty-five more dam streams on the eastern slope. The dams are of all types: 240 earth fill; 56 concrete gravity; 45 rock and earth fills; 35 rock fill; 14 concrete arch; 9 hydraulic fill; and 29 various other types. We use the northern Sierra Nevada to illustrate the assessment of low-activity faults for the seismic safety of dams. The approach, techniques, and methods of evaluation are applicable to other regions characterized by low seismicity and low-activity faults having long recurrence intervals. Even though several moderate earthquakes had shaken the Sierra Nevada since 1849 (for example, the 1875 magnitude 5.8 Honey Lake and the 1909 magnitudes 5 and 5.5 Downieville earthquakes), seismic analyses for dams in the area generally were not performed prior to the middle of this century. Following the 1971 magnitude 6.7 San Fernando earthquake, when the hydraulic-fill Lower Van Norman Dam in southern California narrowly escaped catastrophic failure, the California Division of Safety of Dams and the Federal Energy Regulatory Commission required seismic safety to be addressed with increasing rigor. In 1975, the magnitude 5.7 Oroville earthquake on the Cleveland Hill fault near Oroville Dam in the Sierra Nevada foothills, showed convincingly that earthquakes and surface faulting could occur within the range. Following this event, faults along the ancient Foothills fault system have been extensively investigated at dam sites.

  13. On the seismic activity of the Malibu Coast Fault Zone, and other ethical problems in engineering geoscience

    SciTech Connect

    Cronin, V.S. . Geosciences Dept.)

    1992-01-01

    The Malibu Coast Fault Zone (MCFZ) merges eastward with the active Santa Monica, Hollywood, Raymond Hill, Sierra Madre, and Cucamonga Faults of the central Transverse Ranges. West of Point Dume, the MCFZ extends offshore to join the active Santa Cruz Island Fault. Active microearthquake seismicity along the MCFZ trend indicates that it is seismogenic. Focal mechanism solutions for several of these earthquakes indicate thrusting along faults with the same orientation as the MCFZ. The geomorphology of the MCFZ is consistent with the interpretation that the MCFZ is active. Scarps in unconsolidated sands along the continental shelf just south of Malibu indicate recent offset. In the Santa Monica Mountains, late Tertiary and Quaternary marine sedimentary strata are exposed on the hanging-wall side of the MCFZ, indicating active uplift of the Santa Monica Mountains. Given the other indicators of fault activity, the trench studies that must still be undertaken across the MCFZ are more likely to establish the chronology of recent displacement along the MCFZ than to indicate that the fault is not active. It has been suggested that the MCFZ has not yet been formally recognized as an active, seismogenic fault zone because of the expected loss of property value should the MCFZ be designated an active fault. Geoscientists fear being held liable for loss of property value, even though their assessment of fault activity may be scientifically valid. What are the ethical responsibilities of geoscientists involved in seismic risk assessment along the MCFZ Are political or financial considerations valid criteria to use in assessing the activity of a fault These are not abstract questions of geoethics, because the lives and properties of countless people are potentially at risk.

  14. How the differential load induced by normal fault scarps controls the distribution of monogenic volcanism

    NASA Astrophysics Data System (ADS)

    Maccaferri, Francesco; Acocella, Valerio; Rivalta, Eleonora

    2016-04-01

    Understanding shallow magma transfer and the related vent distribution is crucial for volcanic hazard. In the present study we investigate the link between the stress induced by topographic scarps and the distribution of monogenic volcanoes at divergent plate boundaries. With a numerical model of dyke propagation we show that vertical dykes beneath a normal fault scarp tend to deflect towards the footwall side of the scarp. This effect increases with the scarp height, is stronger for dykes propagating underneath the hanging wall side, and decreases with the distance from the scarp. A comparison to the East African Rift System, Afar and Iceland shows that: 1) the inner rift structure, which shapes the topography, controls shallow dyke propagation; 2) differential loading due to mass redistribution affects magma propagation over a broad scale range (100 - 105 m). Our results find application to any volcanic field with tectonics- or erosion-induced topographic variations.

  15. InSAR Evidence for the Spokane Fault, an Active Shallow Thrust Fault Beneath the City of Spokane Washington, USA

    NASA Astrophysics Data System (ADS)

    Wicks, C.; Weaver, C. S.; Bodin, P.; Sherrod, B. L.

    2012-12-01

    In 2001 a nearly five month long sequence of shallow, mostly small magnitude earthquakes occurred beneath Spokane, a city with a population of about 200,000, in the state of Washington. The Spokane area, an area of low background seismicity, is on the northeastern edge of the Columbia Basin, a physiographic province largely covered with Miocene flood basalts of the Columbia River Basalt Group. The earthquake sequence appears to have begun with an isolated magnitude 2 earthquake on May 24, 2001, but began in earnest with a magnitude 3.9 earthquake on June 25, 2001 and ended on November 23, 2001, with a total of 105 earthquakes recorded up to a magnitude 4. During most of the sequence, the earthquakes were not well located because seismic instrumentation was sparse. Despite poor-quality locations, the earthquake hypocenters were likely very shallow, because residents in small areas of Spokane reported feeling many of the earthquakes in the sequence and hearing explosion-like noises associated with some of the earthquakes. Using interferometric synthetic aperture radar (InSAR) data from the European Space Agency ERS2 and ENVISAT satellites and the Canadian Space Agency RADARSAT-1 satellite we are able to show that slip on a shallow previously unknown thrust fault, that we name the Spokane Fault, is the source of the earthquake sequence. The fault strikes northeast, dips ~30 degrees to the northwest, and the maximum slip was ~45 mm. The part of the Spokane Fault that slipped during the 2001 earthquake sequence underlies the north part of the city, and slip on the fault was concentrated between ~0.3 and 2 km depth. Projecting the buried fault plane to the surface gives a possible surface trace for the Spokane Fault; it strikes northeast from the city center into north Spokane. An accurate assessment of the hazard potential of the Spokane Fault requires additional studies to delineate the fault and map the subsurface geology.

  16. Post failure localization instabilities in chemically active creeping faults: Steady-state bifurcation and transient analysis

    NASA Astrophysics Data System (ADS)

    Alevizos, S.; Poulet, T.; Veveakis, M.

    2014-12-01

    In this study we emphasize in the post failure evolution of a creeping fault, and provide temporal and spatial modes of evolution. In particular we study the behavior of a fluid-saturated fault under shear, based on the assumption that the fabric presents rate- and temperature dependent response to shear loading. A creeping fault of this type can, under certain conditions, produce excess heat due to shear heating, reaching temperatures which are high enough for triggering endothermic chemical reactions. We focus on the decomposition reactions and incorporate excess pore pressure generation and variations of the porosity due to the chemical effects (a process called chemical pressurization). After deriving the corresponding system of equations in the region of the ultra-cataclastic core, we study the influence of the model parameters, namely the frictional, hydraulic and chemical properties of the material, along with the boundary conditions of the problem, on the behavior of the fault and through a non-linear bifurcation analysis we provide regimes of stable-frictional sliding and pressurization. Furthermore, the system is integrated in time to extract its temporal behavior, providing regimes of stable creep, non-periodic and periodic seismic slip events due to chemical pressurization, depending on their frictional properties. It is shown that this chemically induced seismic slip is an ultra-localized event in the post failure regime. It takes place in an extremely narrow band, 2 orders of magnitude narrower than the initial one, verifying the field observations.

  17. Late Pleistocene to Historical Activity of the Hovd Fault (Mongolian Altay) from Tectonic Geomorphology and Paleoseismology

    NASA Astrophysics Data System (ADS)

    Ferry, M. A.; Battogtokh, D.; Ritz, J. F.; Kurtz, R.; Braucher, R.; Klinger, Y.; Ulzibat, M.; Chimed, O.; Demberel, S.

    2015-12-01

    Active tectonics of western Mongolia is dominated by large strike-slip fault systems that produced great historical earthquakes: the Bulnay fault (Mw 8.1 and 8.4 in 1905), the Fu-Yun fault (Mw 8.0 in 1931) and the Bogd fault (Mw 8.1 in 1957). Central to these faults is the Altay Range that accommodates ~4 mm/yr of right-lateral motion. An earthquake of similar magnitude occurred in 1761 and has been attributed to the Hovd fault were seemingly fresh surface rupture was reported in 1985. Here, we study the Ar-Hötöl section of the Hovd fault where surface rupture was described over a length of ~200 km. Detailed mapping of stream gullies from high-resolution Pleiades satellite images show a consistent pattern of right-lateral offsets from a few meters to ~500 m. At Climbing Rock, we surveyed a gully offset by 75 ± 5 m. The associated surface was sampled for 10Be profile which yields an exposure age of 154 ± 20 ka. The resulting minimal right-lateral slip rate ranges 0.4-0.6 mm/yr. However, drainage reconstruction suggests this surface may have recorded as much as 400 ± 20 m of cumulative offset. This implies the Hovd fault may accommodate as much as 2.6 ± 0.4 mm/yr, which would make it the main active fault of the Altay. At a smaller scale, TLS topography documents offsets in the order of 2.5-5 m that likely correspond to the most recent surface-rupturing event with Mw ~8. A value of 2.8-3.0 m is reconstructed from a Uiger grave dated AD 750-840. At Marmot Creek and Small Creek, short drainages flow across the fault and form ponds against the main scarp. Two paleoseimic trenches reveal similar stratigraphy with numerous peat layers that developed over alluvial sands. The fault exhibits near vertical strands affecting pre-ponding units as well as a well-developed peat unit radiocarbon-dated AD 1465-1635. This unit likely corresponds to the ground surface at the time of the last rupture. It is overlain with a sandy pond unit on top of which a second continuous peat

  18. Fault Activity Investigations in the Lower Tagus Valley (Portugal) With Seismic and Geoelectric Methods

    NASA Astrophysics Data System (ADS)

    Carvalho, J. G.; Gonçalves, R.; Torres, L. M.; Cabral, J.; Mendes-Victor, L. A.

    2004-05-01

    The Lower Tagus River Valley is located in Central Portugal, and includes a large portion of the densely populated area of Lisbon. It is sited in the Lower Tagus Cenozoic Basin, a tectonic depression where up to 2,000 m of Cenozoic sediments are preserved, which was developed in the Neogene as a compressive foredeep basin related to tectonic inversion of former Mesozoic extensional structures. It is only a few hundred kilometers distant from the Eurasia-Africa plate boundary, and is characterized by a moderate seismicity presenting a diffuse pattern, with historical earthquakes having caused serious damage, loss of lives and economical problems. It has therefore been the target of several seismic hazard studies in which extensive geological and geophysical research was carried out on several geological structures. This work focuses on the application of seismic and geoelectric methods to investigate an important NW-SE trending normal fault detected on deep oil-industry seismic reflection profiles in the Tagus Cenozoic Basin. In these seismic sections this fault clearly offsets horizons that are ascribed to the Upper Miocene. However, due to the poor near surface resolution of the seismic data and the fact that the fault is hidden under the recent alluvial cover of the Tagus River, it was not clear whether it displaced the upper sediments of Holocene age. In order to constrain the fault geometry and kinematics and to evaluate its recent tectonic activity, a few high-resolution seismic reflection profiles were acquired and refraction interpretation of the reflection data was performed. Some vertical electrical soundings were also carried out. A complex fault system was detected, apparently with normal and reverse faulting. The collected data strongly supports the possibility that one of the detected faults affects the uppermost Neogene sediments and very probably the Holocene alluvial sediments of the Tagus River. The evidence of recent activity on this fault, its

  19. Correlation Between Radon Outgassing and Seismic Activity Along the Hayward Fault Near Berkeley, California

    NASA Astrophysics Data System (ADS)

    Holtmann-Rice, D.; Cuff, K.

    2003-12-01

    Results from previous studies indicate that radon concentration values are significantly higher over selected sections of the Hayward fault than adjacent areas. This phenomenon is believed to be attributed to the presence of abundant fractures in rock associated with the fault, which act as pathways for radon as it migrates from depth towards the earth?s surface. In an attempt to determine whether or not a relationship exists between seismicity along the fault, the production of microfractures, and emanation of radon, a radon outgassing monitoring study was conducted along an active section of the Hayward fault in Berkeley, California. The study was carried out by using an alphaMETER 611, which is a device capable of accurately measuring radon concentrations every 15 minutes. The alphaMETER was placed at the bottom of a sealed one meter deep well, in close proximity to a section of the Hayward fault located along the northwestern face of the Berkeley Hills. Once per week for several months data collected by the alphaMETER was downloaded into a laptop computer. Data from the alphaMETER was then compared with seismic data recorded by local seismometers to see if any correlation existed. A general correlation between variation in radon concentration and the occurrence of small earthquakes was found. Significant peaks in radon concentration were observed within an approximately one week period before the occurrence of small earthquakes. Concentration values then decreased dramatically just prior to and during periods when the earthquakes occurred. Such correlation is very similar to that recently observed in association with a magnitude five earthquake along the Anatolian Fault, reported by geoscientists working in Turkey using similar instrumentation (Inan, 2003, personal communication). The most plausible explanation for the observed correlation is as follows: 1) prior to a given earthquake, stress build up within a particular fault region leads to the formation of

  20. 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.

  1. 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

  2. Results from NICLAKES Survey of Active Faulting Beneath Lake Managua,Central American Volcanic arc

    NASA Astrophysics Data System (ADS)

    McIntosh, K.; Funk, J.; Mann, P.; Perez, P.; Strauch, W.

    2006-12-01

    Lake Managua covers an area of 1,035 km2 of the Central American volcanic arc and is enclosed by three major stratovolcanoes: Momotombo to the northwest was last active in AD 1905, Apoyeque in the center on the Chiltepe Peninsula was last active ca. 4600 years BP, and Masaya to the southeast was last active in AD 2003. A much smaller volcano in the lake (Momotombito) is thought to have been active <4500 yrs B.P. In May of 2006, we used a chartered barge to collect 330 km of 3.5 kHz profiler data along with coincident 274 km of sidescan sonar and 27 km of seismic reflection data. These data identify three zones of faulting on the lake floor: 1) A zone of north-northeast-striking faults in the shallow (2.5-7.5 m deep) eastern part of the lake that extends from the capital city of Managua, which was severely damaged by shallow, left-lateral strike-slip displacements on two of these faults in 1931 (M 5.6) and 1972 (M 6.2): these faults exhibit a horst and graben character and include possible offsets on drowned river valleys 2) a semicircular rift zone that is 1 km wide and can be traced over a distance of 30 km in the central part of the lake; the rift structure defines the deepest parts of the lake ranging from 12 to 18 m deep and is concentric about the Apoyeque stratocone/Chiltepe Peninsula; and 3) a zone of fault scarps defining the northwestern lake shore that may correlate to the northwestern extension of the Mateare fault zone, a major scarp-forming fault that separates the Managua lowlands from the highlands south and west of the city. Following previous workers, we interpret the northeast- trending group of faults in the eastern part of the lake as part of a 15-km-long discontinuity where the trend of the volcanic arc is offset in a right-lateral sense. The semi-circular pattern of the rift zone that is centered on Chiltepe Peninsula appears to have formed as a distal effect of either magma intrusion or withdrawal from beneath this volcanic complex. The

  3. 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.

  4. 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.

  5. Evolution of elastic wave speed during shear-induced damage and healing within laboratory fault zones

    NASA Astrophysics Data System (ADS)

    Kaproth, Bryan M.; Marone, Chris

    2014-06-01

    Earthquake faults fail and restrengthen repeatedly during the seismic cycle. Faults restrengthen via a set of processes known collectively as fault healing, which is well documented in the laboratory but less well understood in tectonic fault zones. Recent observations of fault zone wave speed following earthquakes suggest opportunities to connect laboratory and field observations of fault healing. However, existing laboratory data lack detail necessary to identify specific processes linking elastic wave speed to fault damage and healing. Here we document changes in elastic properties during laboratory seismic cycles, simulated via periods of nonshear and quasistatic fault slip. Experiments were conducted on brine-saturated halite under conditions favoring pressure solution, analogous to healing processes within and at the base of the seismogenic zone. We find that elastic wave speed (V) and amplitude (A) correlate with porosity. For each percent of porosity lost during compaction, VP increases by ~3%, VS by ~2%, AP by ~10%, and AS by ~7%. Moreover, V and A decrease with granular dilation during fault slip. With increasing shear strain, fabric formation dominates the ultrasonic signals. We find that fault strength depends on fault porosity, making VP and VS potential proxies for fault strength evolution. Our data show that a 1% change in VP or VS results in a friction increase of 0.01 or 0.02, respectively. Within natural fault zones, advances in monitoring elastic wave speed may provide critical information on the evolution of fault strength and seismic hazard throughout the seismic cycle.

  6. 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

  7. Geomorphic evidence of active faults growth in the Norcia seismic area (central Apennines, Italy)

    NASA Astrophysics Data System (ADS)

    Materazzi, Marco; Aringoli, Domenico; Farabollini, Piero; Giacopetti, Marco; Pambianchi, Gilberto; Tondi, Emanuele; Troiani, Francesco

    2016-04-01

    Fault-growth by segment linkage is one of the fundamental processes controlling the evolution, in both time and the space, of fault systems. In fact, step-like trajectories shown by length-displacement diagrams for individual fault arrays suggest that the development of evolved structures result by the linkage of single fault segments. The type of interaction between faults and the rate at which faults reactivate not only control the long term tectonic evolution of an area, but also influence the seismic hazard, as earthquake recurrence intervals tend to decrease as fault slip rate increase. The use of Geomorphological investigations represents an important tool to constrain the latest history of active faults. In this case, attention has to be given to recognize morphostructural, historical, environmental features at the surface, since they record the long-term seismic behavior due to the fault growth processes (Tondi and Cello, 2003). The aim of this work is to investigate the long term morphotectonic evolution of a well know seismic area in the central Apennines: the Norcia intramontane basin (Aringoli et al., 2005). The activity of the Norcia seismic area is characterized by moderate events and by strong earthquakes with maximum intensities of X-XI degrees MCS and equivalent magnitudes around 6.5±7.0 (CPTI, 2004). Based on the morphostructural features as well as on the historical seismicity of the area, we may divide the Norcia seismic area into three minor basins roughly NW-SE oriented: the Preci sub-basin in the north; the S. Scolastica and the Castel S. Maria sub-basins in the south. The wider basin (S. Scolastica) is separated from the other two by ridges transversally oriented with respect the basins themselves; they are the geomorphological response to the tectonic deformation which characterizes the whole area. Other geomorphological evidences of tectonic activity are represented by deformation of old summit erosional surfaces, hydrographic network

  8. Along strike variation in fault creep on the active Alto Tiberina low angle normal fault inferred from GPS geodesy

    NASA Astrophysics Data System (ADS)

    Bennett, R. A.; Jackson, L. J.; Mencin, D.; Casale, G.

    2013-12-01

    The Alto Tiberina fault (ATF) in central Italy is a low angle normal fault (LANF) dipping ~20° to the east-northeast. The fault is inferred from surface geology, deep boreholes, seismic reflection lines, abundant microseismicity, and crustal motion data. Balanced cross sections show that the fault plays a major role in accommodating regional extension in central Italy, having accommodated up to 10 km of extension over the past 3 Ma. However, no large earthquakes have been attributed to the ATF. Instead, large earthquakes in the area occur on high angle west dipping normal faults that cut the ATF hanging wall. Several lines of evidence, including fine grained foliations composed of velocity strengthening phyllosilicate minerals in exhumed fault rocks, high fault fluid over-pressures observed in footwall boreholes (~85% lithostatic pressure at 3.7-4.8 km depth), persistent microseismicity coincident with the ATF fault plane, and pattern of geodetically observed crustal motions suggest that the ATF accommodates slip primarily by aseismic creep up to shallow (~4 km) depth in the crust. Previous studies using a simple fault model consisting of an edge dislocation buried in and elastic halfspace supported the shallow creeping hypothesis. But newer realizations of the crustal motion field, imaged with more precision and higher spatial resolution than previously reported, are not adequately explained by this 1-D creeping-fault model. Moreover, significant variations in the occurrence of large hanging wall earthquakes are observed along the strike of the ATF and may be indicative of along-strike variation in ATF fault mechanics. To test whether the along-strike variation in earthquake occurrence is accompanied by similar variation in the rate of fault creep on the ATF, we analyzed crustal motion data derived from more than a decade of continuous GPS measurements in central Italy. We used the TDEFNODE software to parameterize the ATF using the available high

  9. The Evolution of Deformation-Induced Grain-Boundary Porosity and Dynamic Permeability in Crustal Fault Zones: Insights From the Alpine Fault, New Zealand

    NASA Astrophysics Data System (ADS)

    Sauer, K. M.; Toy, V.

    2015-12-01

    Fluids and minor phases have an important influence on the bulk rheology of a deforming rock mass, but they are not uniformly distributed at any scale within fault zones. Additionally, exhumed ductile shear zones show little interconnected porosity or static permeability, requiring a dynamic process at depth to allow fluids to access the deforming rock mass. It was recently recognized that reactive fluids interact with high-strain sites to generate cavities on quartz grain boundaries, increasing the grain-scale porosity and dynamic permeability of the rock and allowing for additional fluids to infiltrate the shear zone along interlinking cavities, stimulating further reaction and cavitation. Grain-boundary cavities and fine-grained secondary phases impede grain-boundary mobility and cause a transition in deformation mechanisms from grain-size insensitive dislocation creep to grain-size sensitive creep, which is recognized as a weakening mechanism that promotes strain localisation. At present, it is unclear how the distribution of grain-boundary pores within fault rocks reflects the bulk mineralogy and phase arrangement, which is a function of shear strain. We have used micro-computed x-ray tomography (μ-CT), SEM imaging, and EDS analyses to examine how the distribution of grain-boundary pores varies in relation to the arrangement of secondary phases in exhumed protomylonites, mylonites, and ultramylonites within the actively-deforming Alpine Fault zone, and in samples acquired from the Deep Fault Drilling Project (DFDP). Additionally, EBSD is coupled with µ-CT and EDS analyses to characterise the evolution of microstructures in three dimensions across a finite strain gradient. Here we examine the relationship and competition between grain-boundary cavitation and microstructural processes during deformation in a high-strain shear zone, and discuss the implications of these grain-scale deformation processes on strain localisation and continental fault zone dynamics.

  10. Characterization of the Monument Hill fault system and implications for the active tectonics of the Red Rock Valley, Southwestern Montana

    NASA Astrophysics Data System (ADS)

    Regalla, Christine A.; Anastasio, David J.; Pazzaglia, Frank J.

    2007-08-01

    New geologic mapping, morphologic fault scarp modeling, and geomorphic metrics in the Red Rock Valley, southwestern Montana, help characterize the Quaternary history of the virtually unstudied Monument Hill fault and tectonics of the youthful and seismically active Red Rock graben. Two generations of Pleistocene surface ruptures are preserved along the Monument Hill fault. Similarity in rupture ages along multiple strands, determined from offset alluvial surfaces and morphologic modeling, suggest earthquake clusters at 22-32 ka and possibly >160 ka. Quaternary activity along the Monument Hill fault is also reflected in elongate drainage basins and channel profiles with anomalously steep reaches coincident with mapped faults. An anticlinal accommodation zone at Kidd accommodates a change in fault polarity between the en echelon Monument Hill and Red Rock faults and a northward decrease in extension within the Red Rock graben. The unique rupture histories of the Monument Hill and Red Rock faults, however, suggest the systems are not seismogenically linked and that the accommodation zone serves as a rupture barrier. The geometry, interconnectivity, and kinematics of faults in the Red Rock Valley may represent a snapshot of the early stages of extension applicable to the evolution of other Northern Basin and Range grabens.

  11. Stacking fault energy decrease in austenitic stainless steels induced by hydrogen pairs formation

    SciTech Connect

    Hermida, J.D.; Roviglione, A.

    1998-09-15

    The decrease of the Stacking Fault Energy (SFE), induced by hydrogen in austenitic stainless steels, was always invoked to explain the formation of {epsilon}-martensite at room temperature during cathodic charging of hydrogen. Pontini and Hermida measured by XRD a reduction of 37 pct of the SPE of an AISI 304 steel at room temperature, in the presence of only 274 ppm of hydrogen. However, the nature of this phenomenon is still unknown. Recently, Obiol et a., using the Atoms Superposition and Electron Delocalization-Molecular Obital (ASED-MO) method, calculated the binding energy for H-H pair formation in the faulted zone of an FCC iron matrix. It was shown that, the H-H pair formation is more likely to occur along directions connecting octahedral interstices of the HCP stacking sequence and that are normal to the {l_brace}111{r_brace} planes. The binding energy found was {minus}5.75 eV, being this value significantly larger than the corresponding one for vacuum: {minus}4.75 eV. In this work, an explanation of the SFE decrease is developed on the basis of this previous result.

  12. Strength recovery and vein growth during self-sealing of experimentally-induced faults in Westerly granite

    NASA Astrophysics Data System (ADS)

    Meredith, P. G.

    2013-12-01

    Numerous studies have shown that crustal deformation in the presence of a chemically-active pore fluid is commonly accompanied by self-sealing processes that can occur relatively rapidly compared with geological timescales. This is consistent with earthquake models involving transient fluid flow on faults during seismic slip, followed by self-sealing which may occur through the physico-chemical process of the crack-seal mechanism. In this mechanism, brittle deformation of water-saturated rock produces new fracture surfaces that are out of chemical equilibrium with the pore fluid, leading to mineral dissolution, mass transport and precipitation in a cycle of coupled deformation and fluid flow. Here, we present direct experimental evidence for the rapid development of dilatant crack-seal quartz veins during sequential stressing of pre-faulted rock samples. Right-cylindrical, pre-faulted samples of Westerly granite were held at a constant temperature of 400°C and an effective confining pressure in the range 100 to 160 MPa in a triaxial deformation apparatus. An differential axial stress was then applied cyclically to the samples at a strain rate of 10-5 s-1 to induce frictional sliding under either saturated (λ = 0.4) or dry (λ = 0) conditions using distilled water as the pore fluid. The samples were broken a number of times (5 to 7 depending on the test) over periods of up to several months, and left to cook between loading cycles at constant temperature and hydrostatic pressure for hold times varying between 1 hour and 78 days. On re-loading, all the saturated samples exhibited substantial strength recovery for hold times greater than about 100 hours, while dry samples showed no increase in strength for any hold time up to the maximum of 34 days. The reason for the strength recovery becomes clear from post-test microstructural analysis of the deformed samples. All of the saturated samples showed evidence of the development of quartz veins in the fault zones

  13. Upper plate deformation and seismic barrier in front of Nazca subduction zone: The Chololo Fault System and active tectonics along the Coastal Cordillera, southern Peru

    NASA Astrophysics Data System (ADS)

    Audin, Laurence; Lacan, Pierre; Tavera, Hernando; Bondoux, Francis

    2008-11-01

    The South America plate boundary is one of the most active subduction zone. The recent Mw = 8.4 Arequipa 2001 earthquake ruptured the subduction plane toward the south over 400 km and stopped abruptly on the Ilo Peninsula. In this exact region, the subduction seismic crisis induced the reactivation of continental fault systems in the coastal area. We studied the main reactivated fault system that trends perpendicular to the trench by detailed mapping of fault related-geomorphic features. Also, at a longer time scale, a recurrent Quaternary transtensive tectonic activity of the CFS is expressed by offset river gullies and alluvial fans. The presence of such extensional fault systems trending orthogonal to the trench along the Coastal Cordillera in southern Peru is interpreted to reflect a strong coupling between the two plates. In this particular case, stress transfer to the upper plate, at least along the coastal fringe, appears to have induced crustal seismic events that were initiated mainly during and after the 2001 earthquake. The seafloor roughness of the subducting plate is usually thought to be a cause of segmentation along subduction zones. However, after comparing and discussing the role of inherited structures within the upper plate to the subduction zone segmentation in southern Peru, we suggest that the continental structure itself may exert some feedback control on the segmentation of the subduction zone and thus participate to define the rupture pattern of major subduction earthquakes along the southern Peru continental margin.

  14. Redefining Medlicott-Wadia's main boundary fault from Jhelum to Yamuna: An active fault strand of the main boundary thrust in northwest Himalaya

    NASA Astrophysics Data System (ADS)

    Thakur, V. C.; Jayangondaperumal, R.; Malik, M. A.

    2010-06-01

    The MBT demarcates a tectonic boundary between the Tertiary Sub Himalaya and the pre-Tertiary Lesser Himalaya. South of the MBT, another tectonically important fault extends from Muzaffarabad and Riasi in Jammu-Kashmir to Bilaspur and Nahan in Himachal. Medlicott and Wadia had designated this fault the Main Boundary Fault (MBF) in Simla Hills and Jammu region respectively. In between these two areas, later workers gave local-area names to the MBF as the Riasi Thrust in Jammu, Palampur Thrust in Kangra, Bilaspur Thrust in Simla Hills and Nahan Thrust in Sirmur. We have reviewed and established the tectonostratigraphic framework and physical continuity of the lower Tertiary belt and the MBF. The lower Tertiary belt, lying south of the MBT, has characteristic tectonostratigraphic setting with discontinuous bodies of stromatolite-bearing Proterozoic limestone overlain with depositional contact by the Paleocene-lower part Middle Eocene marine Subathu/Patala formation which in turn overlain by the Upper Oligocene-Lower Miocene non-marine Dharamsala/Murree Formation. To avoid confusion with the MBT, we designate collectively the MBF and related faults as the Medlicott-Wadia Thrust (MWT). The MWT extends east of Hazara-Kashmir syntaxis to river Yamuna, covering a distance of ˜ 700 km. Further east of Yamuna, the lower Tertiary belt pinches out and the MWT merges with the sensuo-stricto MBT. The Proterozoic limestone represents the basement over which the lower Tertiary sediments were deposited. The limestone basement with its cover was detached by the MWT, exhuming to the surface and thrusting over largely the Siwalik group. The reactivated Balakot-Bagh Fault, causative fault for the 2005 Kashmir earthquake, extends southeast with right-step to the Riasi Thrust. The Riasi Thrust shows evidence of reactivation and active tectonic activity in Jammu region. It extends further east to the Palampur Thrust in Kangra reentrant, which lies within the 1905 Kangra earthquake

  15. Late Cenozoic and active transpression along the Dead Sea fault in northwestern Syria

    NASA Astrophysics Data System (ADS)

    Gomez, F.; Radwan, Y.; Al-Najjar, H.; Layyous, I.; Darkal, A.; Darawcheh, R.; Sbeinati, R.; Meghraoui, M.; Al-Ghazzi, R.; Barazangi, M.

    2004-12-01

    The left-lateral Dead Sea fault (DSF) constitutes the boundary between the Arabian and African plates as they converge with Eurasia. In northwestern Syria, the DSF emerges from the 200-km-long "Lebanese" restraining bend with a single fault trace that bifurcates at the Ghab Valley. Despite locally transtensional features like the Ghab Valley, neotectonic activity along the northern DSF in northwestern Syria demonstrates that oblique plate motions result in an overall transpressive tectonic regime. Constraints on recent tectonism are provided by neotectonic mapping, trenching of Holocene sediments, and analyses of a 20-meter pixel digital elevation model constructed using InSAR. Evidence of Neogene and Quaternary displacement on the northern DSF includes truncation and offset of a large, early Pliocene volcano. Preliminary estimates of the left-lateral slip rate south of the Ghab Valley are 4 - 7 mm / yr. In the Ghab Valley, hanging valleys, beheaded drainages, and displaced late Quaternary lava flows demonstrate that plate motion is distributed among several active fault branches. Furthermore, warping and tilting of a late Miocene - early Pliocene paleo-surface, as well as morphometric analyses, suggest that tectonic uplift of the Syrian Coastal Range has been coincident with recent left-lateral faulting on the adjacent DSF. Uplift is asymmetrically distributed in that it is almost exclusively located in the western block of the DSF. The region of uplift is greatest adjacent to the Ghab Valley. This may reflect a contribution from isostatic uplift as a result of the local transtension. We suggest that a convergent component of plate motion is responsible for uplift of the entire Syrian Coastal Range. Our hypothesis is consistent with regional plate tectonic models that predict 10° - 25° obliquity between the Arabian-African plate motion and the strike of the northern Dead Sea fault.

  16. Human-induced uplift of the Sierra Nevada Mountains and seismicity modulation on the San Andreas Fault

    NASA Astrophysics Data System (ADS)

    Amos, Colin; Audet, Pascal; Hammond, William C.; Burgmann, Roland; Johanson, Ingrid A.; Blewitt, Geoffrey

    2014-05-01

    We investigate the cause of geodetically observed mountain uplift in the Sierra Nevada, western US. In the process, we reveal a possible human-induced mechanism that may be driving Sierra Nevada uplift, and may also be pushing the San Andreas Fault closer to failure. An initial study of the Sierra Nevada [Hammond et al., Geology, 40, 2012] exploited the complementary strengths of point positions from GPS and blanket coverage measurements from InSAR, to show that contemporary vertical motion of the Sierra Nevada is between 1 - 2 mm/yr relative to the comparatively stable Great Basin to the east. One possible interpretation of this is that the most modern episode of tectonic uplift is still active in the Sierra Nevada. However, we now discover that GPS stations surrounding the southern San Joaquin Valley in California show a pattern of uplift concentrated not only in the Sierra Nevada to the east, but more broadly along the basin margins, including the adjacent central Coast Range to the west. Peak vertical velocities reach values up to 1 - 3 mm/yr. This suggests the San Joaquin Valley plays a key role in the uplift of the Sierra Nevada to the east, with possible implications for the San Andreas Fault to the west. Anthropogenic groundwater depletion in the southern San Joaquin Valley has been massive and sustained, therefore hydrological loading variation might explain contemporary uplift. To test this, we apply a simple elastic model that uses a line load centered along the valley axis, a range of elastic parameters, and published estimates of the integrated rate of mass loss due to groundwater removal over the last decade. Predicted uplift centered along the valley axis matches well with patterns of GPS motion, with the upward vertical rates decaying away from the valley margins. Observed seasonal variability in the vertical GPS positions lends support for this model, showing peak uplift for stations surrounding the valley during the dry summer and fall months. On

  17. Active faulting and tectonics of the Ningxia-Hui Autonomous Region, China

    NASA Astrophysics Data System (ADS)

    Qidong, Deng; Sung, Fengmin; Zhu, Shilong; Li, Mengluan; Wang, Tielin; Zhang, Weiqi; Burchfiel, B. C.; Molnar, Peter; Zhang, Peizhen

    1984-06-01

    Strike-slip, thrust, and normal faulting all seem to play an active role in the tectonics of Ningxia. In the southernmost part of the region a major left-lateral strike-slip fault enters the region from the neighboring Gansu province to the west and trends about S65°E. This fault is very clear on Landsat imagery and on aerial photos, and the portion in eastern Gansu and Ningxia broke in the Haiyuan earthquake of December 16, 1920. Displacements of 5-10 m caused by that earthquake are clear in numerous localities and accord with a revised value of the seismic moment of 1.2×1021N m. The eastern end of the Haiyuan fault terminates in a narrow south trending fold and thrust zone. Several other similar, north to northwest trending fold and thrust belts are present in the area about 50-200 km northeast of the Haiyuan fault and divide it into small, apparently relatively undeformed blocks 10-40 km in dimensions. The geometry of the structures in the fold and thrust zones and the apparently shallow depths at the time of deformation suggest that current deformation is similar to that that occurred in the fold and thrust belt of the Idaho-Wyoming Rocky Mountains. North of this area, both the Helan Shan (a horst) and the Yinchuan graben are bounded by clear, active northerly trending normal faults, in some cases with right-lateral strike-slip components. The overall deformation, hence, seems to include dominant components of east-west left-lateral strike-slip movement, northeast-southwest crustal shortening, and northwest-southeast extension. We interpret the extension as a response to a northeast directed force applied to the Ordos block and both this northeast directed force and the left-lateral slip on the Haiyuan fault to the eastward displacement of material on the northeast edge of the Tibetan plateau with respect to Eurasia north of it.

  18. COMPLEX RESISTIVITY OF FAULT GOUGE AND ITS SIGNIFICANCE FOR EARTHQUAKE LIGHTS AND INDUCED POLARIZATION.

    USGS Publications Warehouse

    Lockner, David A.; Byerlee, James D.

    1985-01-01

    The authors measured complex resistivity of 2 water-saturated San Andreas fault gouges from 10** minus **3 to 10**6 Hz and confining pressures of 0. 2 to 200 MPa. Consistent with earlier observations of clays and common rocks, large low-frequency permittivities were observed in all cases. Comparisons were made to induced polarization (IP) measurements by inversion of the data into the time domain, where it was found that principal features of the IP response curves were due to these large low-frequency permittivities. The results also suggest that following large earthquakes, significant electrical charge could remain for many seconds and could result in a variety of reported electromagnetic effects. Refs.

  19. Paleoseismic activity at the southern termination of Alhama de Murcia fault (Southeastern Betics, Spain): geomporphic and trenching evidence along a slow moving fault

    NASA Astrophysics Data System (ADS)

    Ortuño, M. C.; Masana, E.; Buylaert, J. P.; Canora, C.; Cunha, P.; García-Meléndez, E.; Martínez-Díaz, J.; Murrey, A.; Sohbati, R.; Štěpančíková, P.

    2009-12-01

    The Alhama de Murcia fault (FAM) is part of the Eastern Betics Shear Zone (EBSZ), one of the most seismically active regions of the Iberian Peninsula. The fault, of NE-SW strike, is prominent along an almost 100 km trace and constitutes the geomorphologic southeastern boundary between a train of ranges situated in the NW block (Eg. Las Estancias and La Tercia ranges) and the Plioquaternary basins in the SE block (Eg. Huercal-Overa and Guadalentin-Segura basins). Its activity as a senestral strike-slip fault with local reverse component has been well documented in its central and north-eastern segments in previous works. In this study, we have focused on its south-western termination, that has a special interest for the risk assessment since no historical damaging earthquake has been associated to it. At this part, the FAM has generated a splay-like structure composed of three main branches referred as septentrional, medium and meridional tips. Owing to a more E-W orientation of this fault arrangement compared to the northernmost segment, the faults are expected to have a greater reverse component. This assumption is corroborated by the geomorphological and geological survey, which has shown that the area is compartmentalized in tectonic highs that result from the folding and faulting of Plioquaternary units. The paleosismological survey and OSL dating of sediments in 5 trenches along the medium and meridional fault branches have permitted to better understand the most recent tectonic activity of the area: Alluvial fans draining from Las Estancias range have been blocked, strongly folded and faulted repeatedly in a complex manner during the Middle-Late Pliestocene. The occurrence of, at least, two paleoearthquakes during the last 150 ka has been recognized in each of the trenches, and a third event, in one of them. The structures observed suggest that the strike-slip component decreases gradually towards the western end, while the vertical component increases. A ~ 0

  20. Episodic nature of earthquake activity in stable continental regions revealed by palaeoseismicity studies of Australian and North American Quaternary faults

    USGS Publications Warehouse

    Crone, A.J.; Machette, M.N.; Bowman, J.R.

    1997-01-01

    Palaeoseismic investigations of recent faulting in stable continental regions of Australia, North America and India show that these faults typically have a long-term behaviour characterised by episodes of activity separated by quiescent intervals of at least 10 000 and commonly 100 000 years or more. Long recurrence intervals such as these are well documented by detailed studies of the faults that ruptured during the 1986 Marryat Creek, South Australia and 1988 Tennant Creek, Northern Territory earthquakes. Thus, neotectonic features associated with stable continental region faults such as scarps and grabens commonly have subtle geomorphic expression and may be poorly preserved. Many potentially hazardous faults in stable continental regions are aseismic, which is one reason why the inventory of these faults is incomplete. Although they may be currently aseismic, faults in stable continental regions that are favourably oriented for movement in the current stress field could produce damaging earthquakes, often in unexpected places. Comprehensive palaeoseismic investigations of modern and prehistoric faulting events in stable continental regions are needed to understand the long-term behaviour of these faults, and thereby, improve seismic-hazard assessments.

  1. Tectonics and Quaternary sequence development of basins along the active Vienna Basin strike-slip fault

    NASA Astrophysics Data System (ADS)

    Salcher, B.; Lomax, J.; Meurers, B.; Smit, J.; Preusser, F.; Decker, K.

    2012-04-01

    The Vienna Basin strike-slip fault is a continent scale active fault extending over a distance of some 300 km from the Eastern Alps through the Vienna Basin into the Western Carpathians. Sinistral movement causes the formation of several tight Pleistocene strike-slip basins within the older Miocene Vienna Basin. These sub-basins not only have a high relevance for groundwater exploitation but their fault activities depict serious seismic hazards. Basins are filled with fluvial sediments from the Danube and, closer to the Alpine front, with thick alluvial fan deposits. However, knowledge on the stratigraphy and tectonics is sparse and rather limited to the Miocene part of the Vienna Basin as it hosts giant hydrocarbon fields. This study tackles two major questions: (i) What is the effect of Quaternary climatic oscillations and subsidence on the sequence development of the alluvial fans and (ii) what is the deformation style of these basins? To answer (i) we present a series of new OSL ages and biotic data from both, surface and cores, to better constrain the timing of fan activity, fan abandonment but also to constrain the onset of Pleistocene basin formation. For (ii) we utilize information from unparalleled geophysical and geological data. Specifically we utilize industrial Bouguer gravity's derivatives to highlight shallow structures and to compensate for the lag of fault trace information. The integration of geological and geophysical data highlights textbook-like models of strike-slip basins, with typical features like Riedel shears with intervening relay ramps, en-echelon sidewall faults and a cross-basin fault zone delimiting opposite depocenters. The infill reflects a distinct cyclicity with thick sequences of coarse sediments deposited during colder periods and thin sequences of paleosol and flood sediments deposited during warmer periods. Ages indicate main activity around the short peak glacial periods and basin formation starting c. 300 ka ago. The

  2. Active faults on the eastern flank of Etna volcano (Italy) monitored through soil radon measurements

    NASA Astrophysics Data System (ADS)

    Neri, M.; Giammanco, S.; Ferrera, E.; Patanè, G.; Zanon, V.

    2012-04-01

    This study concerns measurements of radon and thoron emissions from soil carried out in 2004 on the unstable eastern flank of Mt. Etna, in a zone characterized by the presence of numerous seismogenic and aseismic faults. The statistical treatment of the geochemical data allowed recognizing anomaly thresholds for both parameters and producing distribution maps that highlighted a significant spatial correlation between soil gas anomalies and tectonic lineaments. In particular, the highest anomalies were found at the intersection between WNW-ESE and NW-SE -running faults. The seismic activity occurring in and around the study area during 2004 was analyzed, producing maps of hypocentral depth and released seismic energy. These maps revealed a progressive deepening of hypocenters from NW to SE, with the exception of a narrow zone in the central part of the area, with a roughly WNW-ESE direction. Also, the highest values of seismic energy were released during events in the southern and northwestern sectors of the area. Both radon and thoron anomalies were located in areas affected by relatively deep (5-10 km depth) seismic activity, while less evident correlation was found between soil gas anomalies and the released seismic energy. This study confirms that mapping the distribution of radon and thoron in soil gas can reveal hidden faults buried by recent soil cover or faults that are not clearly visible at the surface. The correlation between soil gas data and earthquake depth and intensity can give some hints on the source of gas and/or on fault dynamics. Lastly, an important spin-off of this study is the recognition of some areas where radon activity was so high (>50000 Bq/m3) that it may represent a potential hazard to the local population. In fact, radon is the leading cause of lung cancer after cigarette smoke for long exposures and, due to its molecular weight, it accumulates in underground rooms or in low ground, particularly where air circulation is low or absent

  3. 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.

  4. Effects of fluid-rock interactions on faulting within active fault zones - evidence from fault rock samples retrieved from international drilling projects

    NASA Astrophysics Data System (ADS)

    Janssen, C.; Wirth, R.; Kienast, M.; Yabe, Y.; Sulem, J.; Dresen, G. H.

    2015-12-01

    Chemical and mechanical effects of fluids influence the fault mechanical behavior. We analyzed fresh fault rocks from several scientific drilling projects to study the effects of fluids on fault strength. For example, in drill core samples on a rupture plane of an Mw 2.2 earthquake in a deep gold mine in South Africa the main shock occurred on a preexisting plane of weakness that was formed by fluid-rock interaction (magnesiohornblende was intensively altered to chlinochlore). The plane acted as conduit for hydrothermal fluids at some time in the past. The chemical influence of fluids on mineralogical alteration and geomechanical processes in fault core samples from SAFOD (San Andreas Fault Observatory at Depth) is visible in pronounced dissolution-precipitation processes (stylolites, solution seams) as well as in the formation of new phases. Detrital quartz and feldspar grains are partially dissolved and replaced by authigenic illite-smectite (I-S) mixed-layer clay minerals. Transmission Electron Microscopy (TEM) imaging of these grains reveals that the alteration processes and healing were initiated within pores and small intra-grain fissures. Newly formed phyllosilicates growing into open pore spaces likely reduced the fluid permeability. The mechanical influence of fluids is indicated by TEM observations, which document open pores that formed in-situ in the gouge material during or after deformation. Pores were possibly filled with formation water and/or hydrothermal fluids suggesting elevated fluid pressure preventing pore collapse. Fluid-driven healing of fractures in samples from SAFOD and the DGLab Gulf of Corinth project is visible in cementation. Cathodoluminescence microscopy (CL) reveals different generations of calcite veins. Differences in CL-colors suggest repeated infiltration of fluids with different chemical composition from varying sources (formation and meteoric water).

  5. 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.

  6. Review of magnetic field monitoring near active faults and volcanic calderas in California: 1974-1995

    USGS Publications Warehouse

    Mueller, R.J.; Johnston, M.J.S.

    1998-01-01

    Differential magnetic fields have been monitored along the San Andreas fault and the Long Valley caldera since 1974. At each monitoring location, proton precession magnetometers sample total magnetic field intensity at a resolution of 0.1 nT or 0.25 nT. Every 10 min, data samples are transmitted via satellite telemetry to Menlo Park, CA for processing and analysis. The number of active magnetometer sites has varied during the past 21 years from 6 to 25, with 12 sites currently operational. We use this network to identify magnetic field changes generated by earthquake and volcanic processes. During the two decades of monitoring, five moderate earthquakes (M5.9 to M7.3) have occurred within 20 km of magnetometer sites located along the San Andreas fault and only one preseismic signal of 1.5 nT has been observed. During moderate earthquakes, coseismic magnetic signals, with amplitudes from 0.7 nT to 1.3 nT, have been identified for 3 of the 5 events. These observations are generally consistent with those calculated from simple seismomagnetic models of these earthquakes and near-fault coseismic magnetic field disturbances rarely exceed one nanotesla. These data are consistent with the concept of low shear stress and relatively uniform displacement of the San Andreas fault system as expected due to high pore fluid pressure on the fault. A systematic decrease of 0.8-1 nT/year in magnetic field has occurred in the Long Valley caldera since 1989. These magnetic field data are similar in form to observed geodetically measured displacements from inflation of the resurgent dome. A simple volcanomagnetic model involving pressure increase of 50 MPa/a at a depth of 7 km under the resurgent dome can replicate these magnetic field observations. This model is derived from the intrusion model that best fits the surface deformation data. ?? 1998 Elsevier Science B.V.

  7. The interaction between active normal faulting and large scale gravitational mass movements revealed by paleoseismological techniques: A case study from central Italy

    NASA Astrophysics Data System (ADS)

    Moro, M.; Saroli, M.; Gori, S.; Falcucci, E.; Galadini, F.; Messina, P.

    2012-05-01

    Paleoseismological techniques have been applied to characterize the kinematic behaviour of large-scale gravitational phenomena located in proximity of the seismogenic fault responsible for the Mw 7.0, 1915 Avezzano earthquake and to identify evidence of a possible coseismic reactivation. The above mentioned techniques were applied to the surface expression of the main sliding planes of the Mt. Serrone gravitational deformation, located in the southeastern border of the Fucino basin (central Italy). The approach allows us to detect instantaneous events of deformation along the uphill-facing scarp. These events are testified by the presence of faulted deposits and colluvial wedges. The identified and chronologically-constrained episodes of rapid displacement can be probably correlated with seismic events determined by the activation of the Fucino seismogenic fault, affecting the toe of the gravitationally unstable rock mass. Indeed this fault can produce strong, short-term dynamic stresses able to trigger the release of local gravitational stress accumulated by Mt. Serrone's large-scale gravitational phenomena. The applied methodology could allow us to better understand the geometric and kinematic relationships between active tectonic structures and large-scale gravitational phenomena. It would be more important in seismically active regions, since deep-seated gravitational slope deformations can evolve into a catastrophic collapse and can strongly increase the level of earthquake-induced hazards.

  8. 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.

  9. Induced activation in accelerator components

    NASA Astrophysics Data System (ADS)

    Bungau, Cristian; Bungau, Adriana; Cywinski, Robert; Barlow, Roger; Edgecock, Thomas Robert; Carlsson, Patrick; Danared, Hâkan; Mezei, Ferenc; Holm, Anne Ivalu Sander; Møller, Søren Pape; Thomsen, Heine Dølrath

    2014-08-01

    The residual activity induced in particle accelerators is a serious issue from the point of view of radiation safety as the long-lived radionuclides produced by fast or moderated neutrons and impact protons cause problems of radiation exposure for staff involved in the maintenance work and when decommissioning the facility. This paper presents activation studies of the magnets and collimators in the High Energy Beam Transport line of the European Spallation Source due to the backscattered neutrons from the target and also due to the direct proton interactions and their secondaries. An estimate of the radionuclide inventory and induced activation are predicted using the GEANT4 code.

  10. Late Quaternary Activity and Seismogenic Potential of the Gonave Microplate: Plantain Garden Strike-Slip Fault Zone of Eastern Jamaica

    NASA Astrophysics Data System (ADS)

    Mann, P.; Prentice, C.; King, W.; Demets, C.; Wiggins-Grandison, M.; Benford, B.

    2008-12-01

    At the longitude of Jamaica, Caribbean (Carib)-North America (Noam) plate motion of 19 ± 2 mm/a is carried by two parallel, left-lateral strike-slip faults, the Oriente fault zone, immediately south of Cuba, and the Enriquillo-Plantain Garden fault zone (EPGFZ), which lies 100-150 km further south. It has been postulated that the lithosphere between these faults constitutes an independent Gonave microplate that has formed in response to the ongoing collision between the leading edge of Carib in Hispaniola and the Bahama carbonate platform. GPS measurements in Jamaica and Hispanola is supportive of the microplate hypothesis and indicates that roughly half of Carib-Noam plate motion (8-14 mm/a) is carried by the EPGFZ of southern Hispaniola and eastern Jamaica. This study applies geomorphic and paleoseismic methods as a direct test of the activity and amount of microplate motion carried on the Plantain Garden fault segment of eastern Hispaniola and how this motion is distributed across a large restraining bend that has formed the island of Jamaica since the late Miocene. The EPFZ curves gently to the northeast and forming a steep mountain front to the Blue Mountains restraining bend with elevations up to 2200 m. Geomorphic fault-related features along the mountain front fault zone include left-laterally deflected rivers and streams, but no small scale features indicative of Holocene activity. River and stream deflections range from 0.1 to 0.5 km. We identified and trenched the most active trace of the mountain front fault at the Morant River where the fault is characterized by a 1.5-m-wide sub-vertical fault zone juxtaposing sheared alluvium and fault Cretaceous basement rocks This section is overlain by a 6-m-thick fluvial terrace. Trenching in the unfaulted terrace immediately overlying the fault trace revealed radiocarbon and OSL ages ranging from 20 to 21 ka that are consistent with a prominent unfaulted alluvial fan along the projection of this fault 1.5 km to

  11. Viscous roots of active seismogenic faults revealed by geologic slip rate variations

    NASA Astrophysics Data System (ADS)

    Cowie, P. A.; Scholz, C. H.; Roberts, G.; Faure Walker, J.; Steer, P.

    2013-12-01

    Viscous flow at depth contributes to elastic strain accumulation along seismogenic faults during both post-seismic and inter-seismic phases of the earthquake cycle. Evaluating the importance of this contribution is hampered by uncertainties regarding (i) the extent to which viscous deformation occurs in shear zones or by distributed flow within the crust and/or upper mantle, and (ii) the value of the exponent, n, in the flow law that relates strain rate to applied stress. Geodetic data, rock deformation experiments, and field observations of exhumed (inactive) faults provide strong evidence for non-linear viscous flow but may not fully capture the long term, in situ behaviour of active fault zones. Here we demonstrate that strain rates derived from Holocene offsets on seismogenic normal faults in the actively uplifting and extending central and southern Italian Apennines may be used to address this issue. The measured strain rates, averaged over a time scale of 104 years, exhibit a well-defined power-law dependence on topographic elevation with a power-law exponent ≈ 3.0 (2.7 - 3.4 at 95% CI; 2.3 - 4.0 at 99% CI). Contemporary seismicity indicates that the upper crust in this area is at the threshold for frictional failure within an extensional stress field and therefore differential stress is directly proportional to elevation. Our data thus imply a relationship between strain rate and stress that is consistent with non-linear viscous flow, with n ≈ 3, but because the measurements are derived from slip along major crustal faults they do not represent deformation of a continuum. We know that, down-dip of the seismogenic part of active faults, cataclasis, hydrous alteration, and shear heating all contribute to grain size reduction and material weakening. These processes initiate localisation at the frictional-viscous transition and the development of mylonitic shear zones within the viscous regime. Furthermore, in quartzo-feldspathic crust, mylonites form a

  12. Active faulting in the Inner California Borderlands: new constraints from high-resolution multichannel seismic and multibeam bathymetric data.

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    Geodetic data indicate that faults offshore of Southern California accommodate 6-8 mm/yr of dextral Pacific-North American relative plate motion. In the Inner California Borderlands (ICB), modern strike-slip deformation is overprinted on topography formed during plate boundary reorganization 30-15 Ma. Despite its proximity to urban Southern California, the hazard posed by active faults in the ICB remains poorly understood. We acquired a 4000-line-km regional grid of high-resolution, 2D multichannel seismic (MCS) reflection data and multibeam bathymetry to examine the fault architecture and tectonic evolution of the ICB. We interpret the MCS data using a sequence stratigraphic approach to establish a chronostratigraphy and identify discrete episodes of deformation. We present our results in a regional fault model that distinguishes active deformation from older structures. Significant differences exist between our model of ICB deformation and existing models. Mounting evidence suggests a westward temporal migration of slip between faults in the ICB. In the eastern ICB, slip on the Newport-Inglewood/Rose Canyon fault and the neighboring Coronado Bank fault (CBF) diminishes to the north and appears to decrease over time. Undeformed Late Pliocene sediments overlie the northern extent of the CBF and the breakaway zone of the purported Oceanside Blind Thrust. Therefore, CBF slip rate estimates based on linkage with the Palos Verdes fault to the north are unwarranted. Deformation along the San Mateo, San Onofre, and Carlsbad trends is best explained as localized deformation resulting from geometrical complexities in a dextral strike-slip fault system. In the western ICB, the San Diego Trough fault (SDTF) offsets young sediments between the US/Mexico border and the eastern margin of Avalon Knoll, where the fault is spatially coincident with the San Pedro Basin fault (SPBF). Farther west, the San Clemente fault (SCF) has a strong linear bathymetric expression. The length

  13. Interseismic deformations along Ecuador active fault systems: Contribution of space-borne SAR Interferometry

    NASA Astrophysics Data System (ADS)

    Champenois, J.; Audin, L.; Baize, S.; Nocquet, J.; Alvarado, A.

    2013-05-01

    Located in the Northern Andes along the active subduction zone of the Nazca plate beneath the South American continent, Ecuador is highly exposed to seismic hazard. Up to now, numerous multidisciplinary studies for the last ten years focused on the seismicity related to the subduction, whereas few investigations concentrated on the crustal seismicity in the upper plate (through few strong events like the 1797 Riobamba earthquake, ML 8.3, 12.000 deaths). The faults that are responsible of these earthquakes are poorly known in term of slip rate and in some cases are even not identified yet. To address this issue and compare the interseismic data to the geomorphological long term signature of active faulting we propose to use multi-temporal Synthetic Aperture Radar Interferometry (InSAR) methods.Using these cost-effective techniques, we are able to investigate surface interseismic deformation with an unprecedented spatial density of measurements (highly superior to Global Positioning System network density). This study presents preliminary results of tectonic surface deformation using ERS (1993-2000) and Envisat (2002-2010) SAR data in the Inter Andean Valley and along the eastern border of the North Andean Block, where is accommodated the relative displacement between the North Andean Block and South America plate (~ 8 mm/yr). We generated average velocity maps and consistent time-series of displacements with values measured along the line of sight of the radar. Resulting maps of ground displacements are calibrated by GPS data in order to provide a homogeneous database. These preliminary results show large scale deformation localized on some major fault systems in the Inter Andean Valley (from Quito to north of Cuenca) and allow an updating of the active faults map. Moreover, these InSAR results permit detecting and quantifying ground deformation due to volcanic unrest.

  14. Geomorphic signal of active faulting at the northern edge of Lut Block: Insights on the kinematic scenario of Central Iran

    NASA Astrophysics Data System (ADS)

    Calzolari, Gabriele; Della Seta, Marta; Rossetti, Federico; Nozaem, Reza; Vignaroli, Gianluca; Cosentino, Domenico; Faccenna, Claudio

    2016-01-01

    Recent works documented Neogene to Quaternary dextral strike-slip tectonics along the Kuh-e-Sarhangi and Kuh-e-Faghan intraplate strike-slip faults at the northern edge of the Lut Block of Central Iran, previously thought to be dominated by sinistral strike-slip deformation. This work focuses on the evidence of Quaternary activity of one of these fault systems, in order to provide new spatiotemporal constraints on their role in the active regional kinematic scenario. Through geomorphological and structural investigation, integrated with optically stimulated luminescence dating of three generations of alluvial fans and fluvial terraces (at ~53, ~25, and ~6 ka), this study documents (i) the topographic inheritance of the long-term (Myr) punctuated history of fault nucleation, propagation, and exhumation along the northern edge of Lut Block; (ii) the tectonic control on drainage network evolution, pediment formation, fluvial terraces, and alluvial fan architecture; (iii) the minimum Holocene age of Quaternary dextral strike-slip faulting; and (iv) the evidence of Late Quaternary fault-related uplift localized along the different fault strands. The documented spatial and temporal constraints on the active dextral strike-slip tectonics at the northern edge of Lut Block provide new insights on the kinematic model for active faulting in Central Iran, which has been reinterpreted in an escape tectonic scenario.

  15. Active Faults and Seismic Sources of the Middle East Region: Earthquake Model of the Middle East (EMME) Project

    NASA Astrophysics Data System (ADS)

    Gulen, L.; EMME WP2 Team*

    2011-12-01

    The Earthquake Model of the Middle East (EMME) Project is a regional project of the GEM (Global Earthquake Model) project (http://www.emme-gem.org/). The EMME project covers Turkey, Georgia, Armenia, Azerbaijan, Syria, Lebanon, Jordan, Iran, Pakistan, and Afghanistan. Both EMME and SHARE projects overlap and Turkey becomes a bridge connecting the two projects. The Middle East region is tectonically and seismically very active part of the Alpine-Himalayan orogenic belt. Many major earthquakes have occurred in this region over the years causing casualties in the millions. The EMME project consists of three main modules: hazard, risk, and socio-economic modules. The EMME project uses PSHA approach for earthquake hazard and the existing source models have been revised or modified by the incorporation of newly acquired data. The most distinguishing aspect of the EMME project from the previous ones is its dynamic character. This very important characteristic is accomplished by the design of a flexible and scalable database that permits continuous update, refinement, and analysis. An up-to-date earthquake catalog of the Middle East region has been prepared and declustered by the WP1 team. EMME WP2 team has prepared a digital active fault map of the Middle East region in ArcGIS format. We have constructed a database of fault parameters for active faults that are capable of generating earthquakes above a threshold magnitude of Mw≥5.5. The EMME project database includes information on the geometry and rates of movement of faults in a "Fault Section Database", which contains 36 entries for each fault section. The "Fault Section" concept has a physical significance, in that if one or more fault parameters change, a new fault section is defined along a fault zone. So far 6,991 Fault Sections have been defined and 83,402 km of faults are fully parameterized in the Middle East region. A separate "Paleo-Sites Database" includes information on the timing and amounts of fault

  16. Interaction between the North-West Sahara Aquifer and the seismically active intraplate Hun Graben Fault system, Libya

    NASA Astrophysics Data System (ADS)

    Hamling, I. J.; Aoudia, A.

    2011-12-01

    the 1935 remain an enigma. However, displacement rates of ~10 mm/yr are observed along a ~35-40 km section of the western bounding fault. The pattern of deformation does not appear to be a result of tectonic activity but instead appears to be a result of water extraction in the region. The observed subsidence pattern correlates well with the location of well sites in the region, which, over the past few decades, have been extracting water. The lack of a tectonic signal may imply that the deformation rates are lower than those resolvable by InSAR. However, due to the proximity of the aquifer to the fault system, we propose that previous and future earthquakes may be related to the stresses induced by fluid flow at the edge of the aquifer.

  17. Dynamic modeling of injection-induced fault reactivation and ground motion and impact on surface structures and human perception

    SciTech Connect

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

    2014-12-31

    We summarize recent modeling studies of injection-induced fault reactivation, seismicity, and its potential impact on surface structures and nuisance to the local human population. We used coupled multiphase fluid flow and geomechanical numerical modeling, dynamic wave propagation modeling, seismology theories, and empirical vibration criteria from mining and construction industries. We first simulated injection-induced fault reactivation, including dynamic fault slip, seismic source, wave propagation, and ground vibrations. From co-seismic average shear displacement and rupture area, we determined the moment magnitude to about Mw = 3 for an injection-induced fault reactivation at a depth of about 1000 m. We then analyzed the ground vibration results in terms of peak ground acceleration (PGA), peak ground velocity (PGV), and frequency content, with comparison to the U.S. Bureau of Mines’ vibration criteria for cosmetic damage to buildings, as well as human-perception vibration limits. For the considered synthetic Mw = 3 event, our analysis showed that the short duration, high frequency ground motion may not cause any significant damage to surface structures, and would not cause, in this particular case, upward CO2 leakage, but would certainly be felt by the local population.

  18. Dynamic modeling of injection-induced fault reactivation and ground motion and impact on surface structures and human perception

    DOE PAGES

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

    2014-12-31

    We summarize recent modeling studies of injection-induced fault reactivation, seismicity, and its potential impact on surface structures and nuisance to the local human population. We used coupled multiphase fluid flow and geomechanical numerical modeling, dynamic wave propagation modeling, seismology theories, and empirical vibration criteria from mining and construction industries. We first simulated injection-induced fault reactivation, including dynamic fault slip, seismic source, wave propagation, and ground vibrations. From co-seismic average shear displacement and rupture area, we determined the moment magnitude to about Mw = 3 for an injection-induced fault reactivation at a depth of about 1000 m. We then analyzed themore » ground vibration results in terms of peak ground acceleration (PGA), peak ground velocity (PGV), and frequency content, with comparison to the U.S. Bureau of Mines’ vibration criteria for cosmetic damage to buildings, as well as human-perception vibration limits. For the considered synthetic Mw = 3 event, our analysis showed that the short duration, high frequency ground motion may not cause any significant damage to surface structures, and would not cause, in this particular case, upward CO2 leakage, but would certainly be felt by the local population.« less

  19. Recent tectonic activity on Mercury revealed by small thrust fault scarps

    NASA Astrophysics Data System (ADS)

    Watters, Thomas R.; Daud, Katie; Banks, Maria E.; Selvans, Michelle M.; Chapman, Clark R.; Ernst, Carolyn M.

    2016-10-01

    Large tectonic landforms on the surface of Mercury, consistent with significant contraction of the planet, were revealed by the flybys of Mariner 10 in the mid-1970s. The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission confirmed that the planet's past 4 billion years of tectonic history have been dominated by contraction expressed by lobate fault scarps that are hundreds of kilometres long. Here we report the discovery of small thrust fault scarps in images from the low-altitude campaign at the end of the MESSENGER mission that are orders of magnitude smaller than the large-scale lobate scarps. These small scarps have tens of metres of relief, are only kilometres in length and are comparable in scale to small young scarps on the Moon. Their small-scale, pristine appearance, crosscutting of impact craters and association with small graben all indicate an age of less than 50 Myr. We propose that these scarps are the smallest members of a continuum in scale of thrust fault scarps on Mercury. The young age of the small scarps, along with evidence for recent activity on large-scale scarps, suggests that Mercury is tectonically active today and implies a prolonged slow cooling of the planet's interior.

  20. Prospecting with ground radar in an active creep-fault zone

    NASA Astrophysics Data System (ADS)

    Ibanez Garduno, Dolores; Lorenzo Cimadevila, Henrique; Alvarez Bejar, Roman; Garduno Monroy, Victor H.

    2000-04-01

    In different places of Morelia, Michoacan, Mexico, there are evidences of four active geologic creep-faults system in. These events have damages (cracking and landslides) in the civil building (Garduno M., et. al, 1998; Garduno M., et. al, 1999; Lermo S., et. al., 1999). In order to find these structures in the first 10 m of depth, region where we have the influence in civil building, we carried out a geophysical study with georadar technique. We made 15 sounding in the fault zone to join the results to preliminar geologic studies in order to improve the security rules in the high risk places. In this work we show the results of three sounds with georadar, as well as the final Bidimensional Model effected with the technique of tracing of ray.

  1. Subsidence Induced Faulting Hazard Zonation Using Persistent Scatterer Interferometry and Horizontal Gradient Mapping in Mexican Urban Areas

    NASA Astrophysics Data System (ADS)

    Cabral-Cano, E.; Cigna, F.; Osmanoglu, B.; Dixon, T.; Wdowinski, S.

    2011-12-01

    Subsidence and faulting have affected Mexico city for more than a century and the process is becoming widespread throughout larger urban areas in central Mexico. This process causes substantial damages to the urban infrastructure and housing structures and will certainly become a major factor to be considered when planning urban development, land use zoning and hazard mitigation strategies in the next decades. Subsidence is usually associated with aggressive groundwater extraction rates and a general decrease of aquifer static level that promotes soil consolidation, deformation and ultimately, surface faulting. However, local stratigraphic and structural conditions also play an important role in the development and extension of faults. In all studied cases stratigraphy of the uppermost sediment strata and the structure of the underlying volcanic rocks impose a much different subsidence pattern which is most suitable for imaging through satellite geodetic techniques. We present examples from several cities in central Mexico: a) Mexico-Chalco. Very high rates of subsidence, up to 370 mm/yr are observed within this lacustrine environment surrounded by Pliocene-Quaternary volcanic structures. b) Aguascalientes where rates up to 90 mm/yr in the past decade are observed, is controlled by a stair stepped N-S trending graben that induces nucleation of faults along the edges of contrasting sediment package thicknesses. c) Morelia presents subsidence rates as high as 80 mm/yr. Differential deformation is observed across major basin-bounding E-W trending faults and with higher subsidence rates on their hanging walls, where the thickest sequences of compressible Quaternary sediments crop out. Our subsidence and faulting study in urban areas of central Mexico is based on a horizontal gradient analysis using displacement maps from Persistent Scatterer InSAR that allows definition of areas with high vulnerability to surface faulting. Correlation of the surface subsidence pattern

  2. FTAPE: A fault injection tool to measure fault tolerance

    NASA Technical Reports Server (NTRS)

    Tsai, Timothy K.; Iyer, Ravishankar K.

    1994-01-01

    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.

  3. 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.

  4. FTAPE: A fault injection tool to measure fault tolerance

    NASA Astrophysics Data System (ADS)

    Tsai, Timothy K.; Iyer, Ravishankar K.

    1994-07-01

    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.

  5. Planning a Preliminary program for Earthquake Loss Estimation and Emergency Operation by Three-dimensional Structural Model of Active Faults

    NASA Astrophysics Data System (ADS)

    Ke, M. C.

    2015-12-01

    Large scale earthquakes often cause serious economic losses and a lot of deaths. Because the seismic magnitude, the occurring time and the occurring location of earthquakes are still unable to predict now. The pre-disaster risk modeling and post-disaster operation are really important works of reducing earthquake damages. In order to understanding disaster risk of earthquakes, people usually use the technology of Earthquake simulation to build the earthquake scenarios. Therefore, Point source, fault line source and fault plane source are the models which often are used as a seismic source of scenarios. The assessment results made from different models used on risk assessment and emergency operation of earthquakes are well, but the accuracy of the assessment results could still be upgrade. This program invites experts and scholars from Taiwan University, National Central University, and National Cheng Kung University, and tries using historical records of earthquakes, geological data and geophysical data to build underground three-dimensional structure planes of active faults. It is a purpose to replace projection fault planes by underground fault planes as similar true. The analysis accuracy of earthquake prevention efforts can be upgraded by this database. Then these three-dimensional data will be applied to different stages of disaster prevention. For pre-disaster, results of earthquake risk analysis obtained by the three-dimensional data of the fault plane are closer to real damage. For disaster, three-dimensional data of the fault plane can be help to speculate that aftershocks distributed and serious damage area. The program has been used 14 geological profiles to build the three dimensional data of Hsinchu fault and HisnCheng faults in 2015. Other active faults will be completed in 2018 and be actually applied on earthquake disaster prevention.

  6. Active Strike-Slip Faulting in the Inner Continental Borderland, Southern California: Results From New High-Resolution Seismic Reflection Data

    NASA Astrophysics Data System (ADS)

    Conrad, J. E.; Ryan, H. F.; Sliter, R. W.

    2008-12-01

    The inner Continental Borderland offshore of southern California accommodates about 7 mm/yr of slip between the North American and Pacific plates. Nearly half of this total has previously been thought to be taken up on the Palos Verdes (PV) and Coronado Bank (CB) fault zones, which have been modeled as a single, continuous fault zone in recent seismic hazard assessments for southern California. Although these faults lie roughly on strike with each other, a connection between these faults has not been clearly demonstrated. Newly acquired high-resolution seismic reflection data indicate that the PV fault terminates southwest of Lasuen Knoll in a horsetail splay that becomes progressively buried to the south. The lack of a connection between the PV and CB fault zones implies that a significant amount of slip must be taken up elsewhere in the inner Continental Borderland. Two other significant offshore faults, the San Diego Trough (SDT) and San Pedro Basin (SPB) fault zones, lie about 10-15 km southwest of and sub parallel to the trace of the PV and CB faults. The SDT fault zone extends from south of the Mexican border near Punta Santo Tomas for about 150 km northward to near Crespi Knoll. The SPB fault zone extends northward from off Santa Catalina Island to near Point Dume. The new seismic reflection data reveal a previously unmapped but apparently active fault zone along strike and in the area between the known strands of the SDT and the SPB fault zones. This newly recognized fault links the SDT and SPB faults, forming a continuous, active fault zone that extends about 250 km along the inner Continental Borderland. Although there are no slip rate data available for this fault zone, its overall length, continuity, and active character suggest that a significant portion of the plate motion that occurs offshore is accommodated along the SDT-SPB fault zone, which may pose a more significant seismic hazard than previously recognized.

  7. Active fault systems of the Kivu rift and Virunga volcanic province, and implications for geohazards

    NASA Astrophysics Data System (ADS)

    Zal, H. J.; Ebinger, C. J.; Wood, D. J.; Scholz, C. A.; d'Oreye, N.; Carn, S. A.; Rutagarama, U.

    2013-12-01

    H Zal, C Ebinger, D. Wood, C. Scholz, N. d'Oreye, S. Carn, U. Rutagarama The weakly magmatic Western rift system, East Africa, is marked by fault-bounded basins filled by freshwater lakes that record tectonic and climatic signals. One of the smallest of the African Great Lakes, Lake Kivu, represents a unique geohazard owing to the warm, saline bottom waters that are saturated in methane, as well as two of the most active volcanoes in Africa that effectively dam the northern end of the lake. Yet, the dynamics of the basin system and the role of magmatism were only loosely constrained prior to new field and laboratory studies in Rwanda. In this work, we curated, merged, and analyzed historical and digital data sets, including spectral analyses of merged Shuttle Radar Topography Mission topography and high resolution CHIRP bathymetry calibrated by previously mapped fault locations along the margins and beneath the lake. We quantitatively compare these fault maps with the time-space distribution of earthquakes located using data from a temporary array along the northern sector of Lake Kivu, as well as space-based geodetic data. During 2012, seismicity rates were highest beneath Nyiragongo volcano, where a range of low frequency (1-3 s peak frequency) to tectonic earthquakes were located. Swarms of low-frequency earthquakes correspond to periods of elevated gas emissions, as detected by Ozone Monitoring Instrument (OMI). Earthquake swarms also occur beneath Karisimbi and Nyamuragira volcanoes. A migrating swarm of earthquakes in May 2012 suggests a sill intrusion at the DR Congo-Rwanda border. We delineate two fault sets: SW-NE, and sub-N-S. Excluding the volcano-tectonic earthquakes, most of the earthquakes are located along subsurface projections of steep border faults, and intrabasinal faults calibrated by seismic reflection data. Small magnitude earthquakes also occur beneath the uplifted rift flanks. Time-space variations in seismicity patterns provide a baseline

  8. Ground Motion Simulation for a Large Active Fault System using Empirical Green's Function Method and the Strong Motion Prediction Recipe - a Case Study of the Noubi Fault Zone -

    NASA Astrophysics Data System (ADS)

    Kuriyama, M.; Kumamoto, T.; Fujita, M.

    2005-12-01

    propagation. Moreover, it was clarified that the horizontal velocities by assuming the cascade model was underestimated more than one standard deviation of empirical relation by Si and Midorikawa (1999). The scaling and cascade models showed an approximately 6.4-fold difference for the case, in which the rupture started along the southeastern edge of the Umehara Fault at observation point GIF020. This difference is significantly large in comparison with the effect of different rupture starting points, and shows that it is important to base scenario earthquake assumptions on active fault datasets before establishing the source characterization model. The distribution map of seismic intensity for the 1891 Noubi Earthquake also suggests that the synthetic waveforms in the southeastern Noubi Fault zone may be underestimated. Our results indicate that outer fault parameters (e.g., earthquake moment) related to the construction of scenario earthquakes influence strong motion prediction, rather than inner fault parameters such as the rupture starting point. Based on these methods, we will predict strong motion for approximately 140 to 150 km of the Itoigawa-Shizuoka Tectonic Line.

  9. Levelling profiles and a GPS network to monitor the active folding and faulting deformation in the Campo de Dalias (Betic Cordillera, southeastern Spain).

    PubMed

    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

  10. 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

  11. An developing ICDP drilling project on intraplate seismicity: Drilling Active Faults in Northern Europe (DAFNE)

    NASA Astrophysics Data System (ADS)

    Ask, M. V.; Kukkonen, I. T.; Olesen, O.; Steffen, H.; Schmitt, D.

    2011-12-01

    The combined effects of reduced ice load and glacially affected rock stresses are believed to have generated dramatic postglacial fault (PGF) structures in northern Europe, reflecting a special type of intraplate seismicity. A total of 14 PGFs have been identified up to date, with fault scarps up to 160 km in length and 30 m in height. They are usually SE dipping, SW-NE oriented thrusts that represent reactivated, pre-existing crustal discontinuities. Local and national seismic networks reveal that, at least some of the faults are still very active, with several hundreds of microseismic events each year. It is evident that if they were formed in single events, they would imply massive intraplate earthquakes (up to M 7-8). Hence, PGFs may generate larger intraplate earthquakes than generally assumed. Similar structures in North America have not been reported yet. Currently, an International Continental Drilling Program (ICDP) project on Drilling Active Faults in Northern Europe (DAFNE) is under development. The aim of the project is to investigate tectonic and structural characteristics of PGFs in northern Fennoscandia, including their hydrogeology and associated deep biosphere. 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 PGFs would provide significant scientific results through generating new data and models, namely: 1. Understanding PGF genesis and controls of their locations; 2. Deep structure and depth extent of PGFs; 3. Textural, mineralogical and physical alteration of rocks in the PGFs; 4. State of stress and estimates of paleostress of PGFs; 5. Hydrogeology, hydrochemistry and hydraulic properties of PGFs; 6. Dating of tectonic reactivation

  12. Earthquake cycle associated with active strike slip faults in central Panamá

    NASA Astrophysics Data System (ADS)

    Rick, Bennett; Spinler, Joshua C.; Compton, Kathleen; Rockwell, Thomas K.; Gath, Eldon

    2013-04-01

    The rigidity of the Panamá Isthmus is currently under debate, with important implications for seismic hazards to the Panamá Canal and Panamá City. Whereas Panamá has traditionally been described as a non-deforming microplate caught between a number of larger tectonic plates, new paleoseismic data collected at a limited number of trench sites in association with the ongoing expansion of the Panamá Canal may challenge the validity of the rigid microplate hypothesis. Crustal velocities from a new, ~100 km aperture, 5-station continuous GPS network constructed across the Rio Gatún, Limón, and Pedro Miguel fault zones confirm that these fault zones are active, forming a system of faults that traverse central Panamá in close proximity to the Panamá Canal and Panamá City. However, the slip rates inferred from these new geodetic data are lower than the geologic rates when using an elastic halfspace model. Differences among previous geodetic investigations, which concluded that Panamá is rigid, and the geological slip rate estimates are explained by earthquake cycle effects associated with long recurrence intervals relative to lower crust and upper mantle Maxwell relaxation times. Late in the earthquake cycle the geodetic strain field is broadly distributed, giving the false appearance of low seismic hazards.

  13. Cooperation-Induced Topological Complexity: A Promising Road to Fault Tolerance and Hebbian Learning

    PubMed Central

    Turalska, Malgorzata; Geneston, Elvis; West, Bruce J.; Allegrini, Paolo; Grigolini, Paolo

    2011-01-01

    According to an increasing number of researchers intelligence emerges from criticality as a consequence of locality breakdown and long-range correlation, well known properties of phase transition processes. We study a model of interacting units, as an idealization of real cooperative systems such as the brain or a flock of birds, for the purpose of discussing the emergence of long-range correlation from the coupling of any unit with its nearest neighbors. We focus on the critical condition that has been recently shown to maximize information transport and we study the topological structure of the network of dynamically linked nodes. Although the topology of this network depends on the arbitrary choice of correlation threshold, namely the correlation intensity selected to establish a link between two nodes; the numerical calculations of this paper afford some important indications on the dynamically induced topology. The first important property is the emergence of a perception length as large as the flock size, thanks to some nodes with a large number of links, thus playing the leadership role. All the units are equivalent and leadership moves in time from one to another set of nodes, thereby insuring fault tolerance. Then we focus on the correlation threshold generating a scale-free topology with power index ν ≈ 1 and we find that if this topological structure is selected to establish consensus through the linked nodes, the control parameter necessary to generate criticality is close to the critical value corresponding to the all-to-all coupling condition. We find that criticality in this case generates also a third state, corresponding to a total lack of consensus. However, we make a numerical analysis of the dynamically induced network, and we find that it consists of two almost independent structures, each of which is equivalent to a network in the all-to-all coupling condition. This observation confirms that cooperation makes the system evolve toward

  14. Active Tectonics of the Lower Tagus Valley Fault(Portugal) and Implications for Seismic Hazard Assessment

    NASA Astrophysics Data System (ADS)

    Vilanova, S. P.; Meghraoui, M.; Bosi, V.; Fonseca, J. F.

    2001-12-01

    The Lower Tagus Valley (LTV) has been the locus of M6 to M7 onshore historical earthquakes in the vicinity of Lisbon, the best studied being those of 1531 and 1909 (Moreira, 1984). The distribution of damage in these events shows an elongated shape along the river valley, leading several authors to infer the existence of an active fault following the valley (Choffat and Bensaude, 1912; Fonseca, 1989; Cabral, 1995). However, no direct evidence of such structure - other than the occurrence of large earthquakes - was put forward until now. To address this problem we developed a series of geomorphic, geophysical and paleoseismological investigations along the LTV which indicated displacement of drainage system, uplifted alluvial terrace, and the presence of a scarp for a minimum length of 20 km. Upon trenching, we identified NNE-SSW trending thrust planes affecting Pliocene and Holocene formations, and measured a minimum displacement of 3m over the last 4000 years. The age of thrusting was constrained by radiocarbon dating and corroborated by archaeological findings. The most recent faulting event can likely be correlated with the M7 1531 earthquake. The thrust geometry shows a significant left-lateral component, as it is pointed out by the imbricate pattern of fault planes and kinematic indicators (striations), which suggest a N-S direction of maximum compression. A gravitational origin for the deformation exposed in the trenches is discussed and discarded. On a larger scale, fault segments inland may be a continuation of the offshore source of the 1755 Lisbon Earthquake (Vilanova et al., this conference). We present new calculations of seismic hazard for Western Iberia, and discuss the impact of the new seismotectonic data for the Lower Tagus Valley.

  15. Deep reaching versus vertically restricted Quaternary normal faults: Implications on seismic potential assessment in tectonically active regions: Lessons from the middle Aterno valley fault system, central Italy

    NASA Astrophysics Data System (ADS)

    Falcucci, E.; Gori, S.; Moro, M.; Fubelli, G.; Saroli, M.; Chiarabba, C.; Galadini, F.

    2015-05-01

    We investigate the Middle Aterno Valley fault system (MAVF), a poorly investigated seismic gap in the central Apennines, adjacent to the 2009 L'Aquila earthquake epicentral area. Geological and paleoseismological analyses revealed that the MAVF evolved through hanging wall splay nucleation, its main segment moving at 0.23-0.34 mm/year since the Middle Pleistocene; the penultimate activation event occurred between 5388-5310 B.C. and 1934-1744 B.C., the last event after 2036-1768 B.C. and just before 1st-2nd century AD. These data define hard linkage (sensu Walsh and Watterson, 1991; Peacock et al., 2000; Walsh et al., 2003, and references therein) with the contiguous Subequana Valley fault segment, able to rupture in large magnitude earthquakes (up to 6.8), that did not rupture since about two millennia. By the joint analysis of geological observations and seismological data acquired during to the 2009 seismic sequence, we derive a picture of the complex structural framework of the area comprised between the MAVF, the Paganica fault (the 2009 earthquake causative fault) and the Gran Sasso Range. This sector is affected by a dense array of few-km long, closely and regularly spaced Quaternary normal fault strands, that are considered as branches of the MAVF northern segment. Our analysis reveals that these structures are downdip confined by a decollement represented by to the presently inactive thrust sheet above the Gran Sasso front limiting their seismogenic potential. Our study highlights the advantage of combining Quaternary geological field analysis with high resolution seismological data to fully unravel the structural setting of regions where subsequent tectonic phases took place and where structural interference plays a key role in influencing the seismotectonic context; this has also inevitably implications for accurately assessing seismic hazard of such structurally complex regions.

  16. Active normal faulting during the 1997 seismic sequence in Colfiorito, Umbria: Did slip propagate to the surface?

    NASA Astrophysics Data System (ADS)

    Mildon, Zoë K.; Roberts, Gerald P.; Faure Walker, Joanna P.; Wedmore, Luke N. J.; McCaffrey, Ken J. W.

    2016-10-01

    In order to determine whether slip during an earthquake on the 26th September 1997 propagated to the surface, structural data have been collected along a bedrock fault scarp in Umbria, Italy. These collected data are used to investigate the relationship between the throw associated with a debated surface rupture (observed as a pale unweathered stripe at the base of the bedrock fault scarp) and the strike, dip and slip-vector. Previous studies have suggested that the surface rupture was produced either by primary surface slip or secondary compaction of hangingwall sediments. Some authors favour the latter because sparse surface fault dip measurements do not match nodal plane dips at depth. It is demonstrated herein that the strike, dip and height of the surface rupture, represented by a pale unweathered stripe at the base of the bedrock scarp, shows a systematic relationship with respect to the geometry and kinematics of faulting in the bedrock. The strike and dip co-vary and the throw is greatest where the strike is oblique to the slip-vector azimuth where the highest dip values are recorded. This implies that the throw values vary to accommodate spatial variation in the strike and dip of the fault across fault plane corrugations, a feature that is predicted by theory describing conservation of strain along faults, but not by compaction. Furthermore, published earthquake locations and reported fault dips are consistent with the analysed surface scarps when natural variation for surface dips and uncertainty for nodal plane dips at depth are taken into account. This implies that the fresh stripe is indeed a primary coseismic surface rupture whose slip is connected to the seismogenic fault at depth. We discuss how this knowledge of the locations and geometry of the active faults can be used as an input for seismic hazard assessment.

  17. Effects of fluids on faulting within active fault zones - evidence from drill core samples recovered during the San Andreas Fault Observatory at Depth (SAFOD) drilling project

    NASA Astrophysics Data System (ADS)

    Janssen, C.; Wirth, R.; Kienast, M.; Morales, L. G.; Rybacki, E.; Wenk, H.; Dresen, G. H.

    2011-12-01

    Low temperature microstructures observed in samples from SAFOD drill cores indicate fluid-related deformation and chemical reactions occurring simultaneously and interacting with each other. Transmission Electron Microscopy (TEM) observations, document open pores that formed in-situ during or after deformation. In TEM images, many pores with high aspect ratio appear to be unconnected. They were possibly filled with formation water and/or hydrothermal fluids suggesting that elevated pore fluid pressure exist in the fault gouge, preventing pore collapse. The chemical influence of fluids on mineralogical alteration and geomechanical processes in fault rocks is visible in pronounced dissolution-precipitation processes (stylolites, solution seams) as well as in the formation of new phases. Detrital quartz and feldspar grains are partially dissolved and replaced by authigenic illite-smectite (I-S) mixed-layer clay minerals. TEM imaging of these grains reveals that the alteration processes initiated within pores and small intra-grain fissures. In few samples syntectonic fluid-assisted overgrowth of chlorite-rich films on slickensides partly replaced sedimentary quartz grains. Quartz and feldspar grains are partially dissolved with sutured boundaries. Newly-formed phyllosilicates are illite-smectite phases, Mg-rich smectites and chlorite minerals. They are very fine-grained (down to 20 nm) and nucleate at grain surfaces (interfaces), which in many cases are pore or fracture walls. These relatively straight or curved crystals grow into open pore spaces and fractures. They are arranged in a card-house fabric with open pore spaces between the flakes. Locally, clay flakes are bent, folded or show sigmoidal shapes indicating that they were involved in faulting. The clay particles do not show a preferred shape orientation. The predominantly random orientation distribution of the clay minerals was confirmed by x-ray synchrotron texture analysis. Pole figures show very weak

  18. Active faults in the deformation zone off Noto Peninsula, Japan, revealed by high- resolution seismic profiles

    NASA Astrophysics Data System (ADS)

    Inoue, T.; Okamura, Y.; Murakami, F.; Kimura, H.; Ikehara, K.

    2008-12-01

    Recently, a lot of earthquakes occur in Japan. The deformation zone which many faults and folds have concentrated exists on the Japan Sea side of Japan. The 2007 Noto Hanto Earthquake (MJMA 6.9) and 2007 Chuetsu-oki Earthquake (MJMA 6.8) were caused by activity of parts of faults in this deformation zone. The Noto Hanto Earthquake occurred on 25 March, 2007 under the northwestern coast of Noto Peninsula, Ishikawa Prefecture, Japan. This earthquake is located in Quaternary deformation zone that is continued from northern margin of Noto Peninsula to southeast direction (Okamura, 2007a). National Institute of Advanced Industrial Science and Technology (AIST) carried out high-resolution seismic survey using Boomer and 12 channels short streamer cable in the northern part off Noto Peninsula, in order to clarify distribution and activities of active faults in the deformation zone. A twelve channels short streamer cable with 2.5 meter channel spacing developed by AIST and private corporation is designed to get high resolution seismic profiles in shallow sea area. The multi-channel system is possible to equip on a small fishing boat, because the data acquisition system is based on PC and the length of the cable is short and easy to handle. Moreover, because the channel spacing is short, this cable is very effective for a high- resolution seismic profiling survey in the shallow sea, and seismic data obtained by multi-channel cable can be improved by velocity analysis and CDP stack. In the northern part off Noto Peninsula, seismic profiles depicting geologic structure up to 100 meters deep under sea floor were obtained. The most remarkable reflection surface recognized in the seismic profiles is erosion surface at the Last Glacial Maximum (LGM). In the western part, sediments about 30 meters (40 msec) thick cover the erosional surface that is distributed under the shelf shallower than 100m in depth and the sediments thin toward offshore and east. Flexures like deformation in

  19. Drastic change in the rheology of serpentine-bearing faults induced by dehydration

    NASA Astrophysics Data System (ADS)

    Takahashi, M.; Uehara, S.; Mizoguchi, K.; Masuda, K.

    2010-12-01

    likely that dehydration, though limited in scale, caused drastic changes in the physical properties of the majority serpentine gouge. SEM observations demonstrated that submicron-sized forsterite particles, which had been generated in large numbers, were found only along shear-localized zones, e.g. Riedel-shear and/or comminuted zones. Our observations have thus revealed that serpentine in shear-localized zones reacted preferentially, implying a possibility of shear-induced dehydration. Owing to the drained condition, the embrittlement at the temperature inducing dehydration could not have been caused by an increase in the pore pressure. This suggests that faults that bear hydrous minerals like serpentine can become brittle, once dehydration begins to take place, even if the P-T and/or the poroelastic conditions do not allow the pore pressure to increase.

  20. Impact of the Yakutat indentor corner on present-day tectonics and fault activity in SE Alaska - SW Yukon

    NASA Astrophysics Data System (ADS)

    Mazzotti, S.; Marechal, A.; Ritz, J. F.; Ferry, M. A.

    2015-12-01

    We present an active tectonic model of the SE Alaska - SW Yukon region based principally on the integration of recent GPS velocity data and new fault-slip rates derived from geomorphology. In this region, the Yakutat collision results in complex tectonics with patterns of strain localization and strain partitioning that strongly vary across the various mountain ranges and active faults. We propose that deformation and fault activity in the St. Elias and Chugach Mountains are primarily controlled by the eastern syntaxis of the Yakutat collision, which produces a semi-radial tectonic pattern: Velocities, principal horizontal shortening rates, and maximum horizontal stress orientations rotate by 60 - 80 ° around the syntaxis, from roughly parallel to the relative Pacific - North America motion at the front of the collision to roughly orthogonal southeast of the syntaxis. The interaction between this strain pattern and major inherited tectonic structures inland of the collision zone (i.e., Denali and Duke River Faults) results in various reactivation modes of these structures. Specifically, the Denali Fault shows a very pronounced lateral variations of activity from ~12 mm/a of dextral slip rate in its central section to ~1 mm/a of mostly shortening slip rate along its southern section. This marked change of activity is associated with a possible relay system where the Duke River and Totschunda Faults accommodate a major part (8 - 12 mm/a) of the inland strain transfer directly in front of the syntaxis. This new tectonic model retains some questions, in particular regarding the mechanisms of deformation and strain transfer (1) from the syntaxis to the Duke River - Totschunda system and (2) at the junction between Totschunda and Denali Faults. Numerical models of present-day deformation may help address these issues and provide information about relative strength of the various crustal and inherited fault elements of this system.

  1. The effects of lateral property variations on fault-zone reactivation by fluid pressurization: Application to CO2 pressurization effects within major and undetected fault zones

    NASA Astrophysics Data System (ADS)

    Jeanne, Pierre; Guglielmi, Yves; Cappa, Frédéric; Rinaldi, Antonio P.; Rutqvist, Jonny

    2014-05-01

    In this study, we performed in situ multidisciplinary analyses of two different fault zones in carbonate formations. One is a seismically active fault zone several kilometers long (the Roccasseira Fault Zone); the other is a small fault zone a few hundred meters long (the GAS Fault Zone). The smaller, "immature" fault zone displays a discontinuous damage zone, because tectonic deformations have been accommodated differently according to the initial properties of the host rock. The larger, "mature" fault zone displays a continuous damage zone caused by the presence of secondary fault cores embedded in a heavily fractured area inside the damage zone. These markedly different fault-zone architectures were reflected in two hydraulic and geomechanical fault models, both generated from a coupled fluid-flow and geomechanical simulator, to examine the impact of hydromechanical property distribution on fault stability when the faults are reactivated by CO2 injection. In the smaller fault zone, marked differences in hydromechanical properties (Young's modulus and permeability) favor fluid accumulation, inducing high pressurization in parts of the damage zone, potentially resulting in small seismic events. On the other hand in the mature fault zone, fluid flows more easily and thus fluid-induced earthquakes may not readily occur, because the fault-zone pressurization is much lower, insufficient for triggering a seismic event.

  2. How Faults Shape the Earth.

    ERIC Educational Resources Information Center

    Bykerk-Kauffman, Ann

    1992-01-01

    Presents fault activity with an emphasis on earthquakes and changes in continent shapes. Identifies three types of fault movement: normal, reverse, and strike faults. Discusses the seismic gap theory, plate tectonics, and the principle of superposition. Vignettes portray fault movement, and the locations of the San Andreas fault and epicenters of…

  3. Mapping of active faults based on the analysis of high-resolution seismic reflection profiles in offshore Montenegro

    NASA Astrophysics Data System (ADS)

    Vucic, Ljiljana; Glavatovic, Branislav

    2014-05-01

    High-resolution seismic-reflection data analysis is considered as important tool for mapping of active tectonic faults, since seismic exploration methods on varied scales can image subsurface structures of different depth ranges. Mapping of active faults for the offshore area of Montenegro is performed in Petrel software, using reflection database consist of 2D profiles in length of about 3.500 kilometers and 311 square kilometers of 3D seismics, acquired from 1979 to 2003. Montenegro offshore area is influenced by recent tectonic activity with numerous faults, folded faults and over trusts. Based on reflection profiles analysis, the trust fault system offshore Montenegro is reveled, parallel to the coast and extending up to 15 kilometers from the offshore line. Then, the system of normal top carbonate fault planes is mapped and characterized on the southern Adriatic, with NE trending. The tectonic interpretation of the seismic reflection profiles in Montenegro point toward the existence of principally reverse tectonic forms in the carbonate sediments, covered by young Quaternary sandy sediments of thickness 1-3 kilometers. Also, reflective seismic data indicate the active uplifting of evaporite dome on about 10 kilometers of coastline.

  4. A new insight into the nature of seasonal variations in coordinate time series of GPS sites located near active faults

    NASA Astrophysics Data System (ADS)

    Trofimenko, Sergey V.; Bykov, Victor G.; Shestakov, Nikolay V.; Grib, Nikolay N.; Takahashi, Hiroaki

    2016-09-01

    This study provides new insights into the nature of seasonal variations in coordinate time series of GPS sites located near active faults and methods of their modeling. Monthly averaged coordinate time series were analyzed for several pairs of collocated GPS sites situated near the active fault intersection area, in close proximity to the central part of the northern boundary of the Amurian plate and the vicinity of the San Andreas Fault zone. It is concluded that the observed seasonal variations are best described by a breather function which is one of the solutions of the well-known sine-Gordon equation. The obtained results suggest that, in this case, the source of seasonal variations may be caused by the appearance of solitary strain waves in the fault intersection system, which may be qualitatively treated as standing waves of compression-extension of the geological medium. Based on statistical testing, the limits of applicability of the suggested model have been established.

  5. Searching for Active Faults in the Western Eurasia-Nubia plate boundary

    NASA Astrophysics Data System (ADS)

    Antunes, Veronica; Custodio, Susana; Arroucau, Pierre; Carrilho, Fernando

    2016-04-01

    The repeated occurrence of large magnitude earthquakes in southwest Iberia in historical and instrumental times suggests the presence of active faults in the region. However, the region undergoes slow deformation, which results in low rates of seismic activity, and the location, dimension and geometry of active structures remains unsettled. We recently developed a new algorithm for earthquake location in 3D complex media with laterally varying interface depths, which allowed us to relocate 2363 events that occurred from 2007 to 2013. The method takes as inputs P- and S-wave catalog arrival times obtained from the Portuguese Meteorological Institute (IPMA, Instituto Portugues do Mar e da Atmosfera), for a study area defined by 8.5°W < lon < 5°W and 36° < lat < 37.5°. After relocation, we obtain a lineation of events in the Guadalquivir bank region, in the northern Gulf of Cadiz. The lineation defines a low-angle northward-dipping plane rooted at the base of the crust, which could indicate the presence of a major fault. We provide seismological evidence for the existence of this seemingly active structure based on earthquake relocations, focal mechanisms and waveform similarity between neighboring events.

  6. Fault activation after vigorous eruption: the December 8, 2015 seismic swarm at Mt. Etna

    NASA Astrophysics Data System (ADS)

    Alparone, Salvatore; Bonforte, Alessandro; Guglielmino, Francesco; Maiolino, Vincenza; Puglisi, Giuseppe; Ursino, Andrea

    2016-04-01

    From December 2, 2015, volcanic activity suddenly occurred on Mt. Etna with very violent fire fountaining at central crater, known also as "Voragine". This activity continued with other intense episodes at the same crater during the three following days and involving also, in turn, all the other three summit craters. This sudden eruption produced a rapid deflation of the volcano and was followed, from December 8, by a seismic swarm, with almost eighty earthquakes during this day, located on the uppermost segment of the Pernicana-Provenzana fault system (PFS). This seismicity was characterized by shallow foci (from few hundred meters until 1.5 km below the sea level) and mainshock with 3.6 magnitude. In order to investigate and measure the dynamics controlling and accompanying the PFS activation, a dataset composed of C-Band Sentinel-1A data has been used for SAR Interferometry (InSAR) analysis. Some interferograms have been generated from ascending and descending orbits in order to analyze both short- and long-term deformation. The availability of GPS data allowed comparing and integrating them with InSAR for ground truth and modeling aims. The surface kinematics and modeling obtained by DInSAR and GPS data and integration have been compared to the distribution of the seismicity and related focal mechanisms in order to define the fault geometry and motion. Moreover, essential constraints have been achieved about the PFS dynamic and its relationship with the intense volcanic activity occurred.

  7. Catalysis and activation of magic states in fault-tolerant architectures

    SciTech Connect

    Campbell, Earl T.

    2011-03-15

    In many architectures for fault-tolerant quantum computing universality is achieved by a combination of Clifford group unitary operators and preparation of suitable nonstabilizer states, the so-called magic states. Universality is possible even for some fairly noisy nonstabilizer states, as distillation can convert many noisy copies into fewer purer magic states. Here we propose protocols that exploit multiple species of magic states in surprising ways. These protocols provide examples of previously unobserved phenomena that are analogous to catalysis and activation well known in entanglement theory.

  8. Active tendon control of reinforced concrete frame structures subjected to near-fault effects

    NASA Astrophysics Data System (ADS)

    Nigdeli, Sinan Melih; Boduroǧlu, M. Hasan

    2013-10-01

    A reinforced concrete (RC) frame structure was controlled with active tendons under the excitation of near-fault ground motions. Proportional Integral Derivative (PID) type controllers were used and the controller was tuned by using a numerical algorithm. In order to prevent brittle fracture of the structure, the aim of the control is to reduce maximum base shear force. The RC structure was investigated for different characteristic strengths of concrete and the approach is applicable for the structure with 14 MPa concrete strength or higher.

  9. Fluid injection induced seismicity reveals a NE dipping fault in the southeastern sector of the High Agri Valley (southern Italy)

    NASA Astrophysics Data System (ADS)

    Stabile, T. A.; Giocoli, A.; Perrone, A.; Piscitelli, S.; Lapenna, V.

    2014-08-01

    On 2 June 2006 the wastewater produced during the oil and gas field exploitation in High Agri Valley (southern Italy) started to be managed by disposal through pumping the fluids back into the subsurface at the Costa Molina 2 (CM2) injection well, located in the southeastern sector of the valley. The onset of microearthquakes (Ml ≤ 2) after 4 days at about 1.3 km SW of CM2 well suggests fluid injection induced seismicity by the diffusion of pore pressure. Moreover, the space-time evolution of 196 high-resolution relocated events reveals a previously unmapped NE dipping fault. We investigate the physical processes related to the fluid injection induced seismicity and delineate the previously unmapped fault by jointly analyzing seismicity data, geological observations, fluid injection data, the stratigraphic log of the CM2 well, and the electrical resistivity tomography survey carried out in the study area.

  10. 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.

  11. Observations of Seafloor Deformation and Methane Venting within an Active Fault Zone Offshore Southern California

    NASA Astrophysics Data System (ADS)

    Anderson, K.; Lundsten, E. M.; Paull, C. K.; Caress, D. W.; Thomas, H. J.; Brewer, P. G.; Vrijenhoek, R.; Lundsten, L.

    2013-12-01

    Detailed mapping surveys of the floor and flanks of the Santa Monica Basin, San Pedro Basin, and San Diego Trough were conducted during the past seven years using an Autonomous Underwater Vehicle (AUV) built and operated by MBARI specifically for seafloor mapping. The AUV collected data provide up to 1 m resolution multibeam bathymetric grids with a vertical precision of 0.15 m. Along with high-resolution multibeam, the AUV also collects chirp seismic reflection profiles. Structures within the uppermost 10-20 m of the seafloor, which in the surveys presented here is composed of recent sediment drape, can typically be resolved in the sub-bottom reflectors. Remotely operated vehicle (ROV) dives allowed for ground-truth observations and sampling within the surveyed areas. The objectives of these dives included finding evidence of recent seafloor deformation and locating areas where chemosynthetic biological communities are supported by fluid venting. Distinctive seafloor features within an active fault zone are revealed in unprecedented detail in the AUV generated maps and seismic reflection profiles. Evidence for recent fault displacements include linear scarps which can be as small as 20 cm high but traceable for several km, right lateral offsets within submarine channels and topographic ridges, and abrupt discontinuities in sub-bottom reflectors, which in places appear to displace seafloor sediments. Several topographic highs that occur within the fault zone appear to be anticlines related to step-overs in these faults. These topographic highs are, in places, topped with circular mounds that are up to 15 m high and have ~30° sloping sides. The crests of the topographic highs and the mounds both have distinctive rough morphologies produced by broken pavements of irregular blocks of methane-derived authigenic carbonates, and by topographic depressions, commonly more than 2 m deep. These areas of distinctive rough topography are commonly associated with living

  12. Geology of the area of induced seismic activity at Monticello Reservoir, South Carolina

    SciTech Connect

    Secor, D.T. Jr.; Smith, W.A.; Snoke, A.W.; Peck, L.S.; Pitcher, D.M.; Prowell, D.C.; Simpson, D.H.

    1982-08-10

    This study provides geological background information necessary for an evaluation of the earthquake hazard in an area of induced seismic activity at Monticello Reservoir, South Carolina. This region contains a thick stratified sequence of Proterozoic Z and Cambrian metasedimentary and metavolcanic rocks. In the early to middle Paleozoic, this sequence was recrystallized and deformed under metamorphic conditions that ranged from greenschist to amphibolite facies and experienced at least two episodes of folding. The region has been intruded by late kinematic to postkinematic granitoid plutons of Silurian and Carboniferous ages and by numerous northwest trending diabase diks of Late Traissic and Early Jurassic age. The region south of Monticello Reservoir in the Carolina slate belt experienced two episodes of faulting in the late Paleozoic and/or early to middle Mesozoic. The older group of faults trends approximately east, has only small displacements, and is characterized by extensive silicifiction of the fault zones. The younger group of faults trends approximately north has experienced dip slip displacements up to 1700 m and is characterized by carbonate mineralization in the fault zones. Both sets of faults are cut by an undeformed diabase dike of Late Triassic or Early Jurassic age. The induced seismic activity around Monticello Reservoir is occurring in a heterogeneous quartz monzonite pluton of Carboniferous age. The pluton contains large enclaves of country rock and is cut by numerous, diversely oriented small faults and joint. These local inhomogeneities in the pluton together with an irregular stress field are interpreted to control the diffuse seismic activity around the reservoir. In view of the apparent absence of lengthy faults it is unlikely that a large-magnitude earthquake will occur in response to the stress and pore pressure changes related to the impoundment of Monticello Reservoir.

  13. Geomorphic analysis of the Sierra Cabrera, an active pop-up in the constrictional domain of conjugate strike-slip faults: The Palomares and Polopos fault zones (eastern Betics, SE Spain)

    NASA Astrophysics Data System (ADS)

    Giaconia, Flavio; Booth-Rea, G.; Martínez-Martínez, J. M.; Azañón, J. M.; Pérez-Peña, J. V.

    2012-12-01

    The NNE-SSW sinistral Palomares and the conjugate dextral WNW-ESE striking Polopos fault zones terminate in the Sierra Cabrera antiform. In order to test the Quaternary activity and topographic relief control in the termination of these fault zones, here we present new qualitative and quantitative geomorphic analyses supported by a new structural map of the region. The main mountain fronts of the Cabrera antiform are formed by the North and South Cabrera reverse faults that merge laterally into the Palomares and Polopos faults, respectively. These faults produce knickpoints, stream deflections, complex basin hypsometric curves, high SLk anomalies and highly eroded basins in their proximity. Furthermore, the drainage network shows an S-shaped pattern reflecting progressive anticlockwise rotation related to the sinistral Palomares fault zone. The estimated uplift rates determined by the integration between mountain front sinuosity index and valley floor width to height ratio are larger than those obtained for strike-slip faults in the eastern Betics. These larger uplift rates with our geomorphic and structural dataset indicate that the topographic relief of the Sierra Cabrera antiform is controlled by reverse faults that form a pop-up structure in the constrictional domain between the larger Palomares-Polopos conjugate strike-slip faults. Existing GPS geodetic data suggest that the North and South Cabrera reverse faults probably accommodate a large part of Africa-Iberia convergence in the region.

  14. 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. PMID:16871215

  15. 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.

  16. 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.

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

    PubMed

    Berberich, Gabriele; Schreiber, Ulrich

    2013-01-01

    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.

  18. Mineral Reactions in Active Fault Strands of the SAFOD Borehole: Results from Mineralogical and U/Th Studies

    NASA Astrophysics Data System (ADS)

    Schleicher, A. M.; Ali, S.; Stute, M.; Torgersen, T.; van der Pluijm, B. A.; Warr, L. N.

    2009-12-01

    Mix-layered clay minerals are common in fault rocks, and their mineralization is strongly influenced by the surrounding environment. Based on detailed mineralogical and geochemical study of mudrock samples from the San Andreas Fault Observatory at Depth (SAFOD), phase 3, we present new TEM-XRD and U/Th results from bore hole depths of 3186.7 m to 3198.9 m, and 3294.9 m to 3313.5 m measured depth. These areas contain two actively creeping sections of the fault zone: Fault strand 10480 (~3194 m) and Fault strand 10830 (~3301 m). XRD analysis of the clay minerals in both fault strands show illite and illite-smectite (I-S) and chlorite dominating from 3186.7 m to 3196.3 m, and 3294.9 m to 3297 m measured depth. Samples containing increased chlorite-smectite (C-S) and corrensite (50:50 C-S) are mostly restricted to a well-defined interval in the center of the two fault strands between 3196.3 m to 3198.1 m, and 3297.5 to ~3305 m. Relatively high U/Th values in both creeping sections of the fault zone indicate that the presence of corrensite and chlorite is associated with reducing conditions during mineral formation, compared to more oxygenated adjacent rocks along the drill cores. TEM also shows serpentine minerals (chrysotile) especially in the fault centers at 3196.8 m and at 3297.5 m depth. These initially tubular phases are slightly flattened and oval in section with distinct strain features that reflect pre-faulting crystallization and subsequent ductile deformation within the fault zone. The C-S phases surrounding the chyrostile show no distinct deformation or subsequent alteration features. Chemical analyses show chlorite and C-S with a high Mg content, which indicates that their crystallization may have involved the destabilization of serpentine, providing Fe and Mg, whereas leaching of mica, feldspar and quartz from the wall-rock, is the probable source of Si and Al. This temporal sequence of reaction weakening suggests distinct changes in the fluid chemistry

  19. Active faulting in the frontal Rif Cordillera (Fes region, Morocco): Constraints from GPS data

    NASA Astrophysics Data System (ADS)

    Chalouan, Ahmed; Gil, Antonio J.; Galindo-Zaldívar, Jesús; Ahmamou, M.'Fedal; Ruano, Patricia; de Lacy, Maria Clara; Ruiz-Armenteros, Antonio Miguel; Benmakhlouf, Mohamed; Riguzzi, Federica

    2014-07-01

    The southern Rif cordillera front, between Fes and Meknes, is formed by the Prerif Ridges, which constitute a thrust and fold belt, in contact with the Saïss foreland basin. Geological evidence and regional GPS network data support recent and active tectonics of this Alpine cordillera, with a top-to-the-S-SW motion with respect to stable Africa. A local non-permanent GPS network was installed in 2007 around Fes to constrain the present-day activity of the mountain front. Six GPS sites are located in the Prerif mountain front (jbel Thratt and jbel Zalarh), the Saïss basin and the foreland constituted by the tabular Middle Atlas. Measurements of the GPS network in 2007, 2009 and 2012, over a five year span, seem to indicate that this region is tectonically active and is subjected to significant horizontal motions: (i) a regional displacement toward the SW with respect to stable Africa, showing an average rate of 2 mm/yr; (ii) a southwestward convergent motion between the jbel Thratt with respect to the Saïss basin and the eastern Zalarh ridge, with an average rate of about 4 mm/yr; and (iii) moderate NNE-SSW divergent dextral motion between the Saïss basin and the northern front of the tabular Middle Atlas with an average rate of about 1-2 mm/yr. The regional southwestward motion is related to the activity of the NE-SW sinistral North Middle Atlas-Kert fault zone, which follows the Moroccan Hot Line. Convergence between the Prerif ridges, located at the southern edge of the Rif, and the Saïss basin is accommodated by ENE-WSW striking northward dipping reverse sinistral faults and south vergent folds. In addition, increasing deformation toward the western ridges is in agreement with the stepped mountain front and the development of the arched structures of the Prerif ridges. Normal faults located south of the Saïss basin are responsible for local extension. Whereas the most active deformation occurs in the southern front of the jbel Thratt near Fes, the Sa

  20. Intelligent fault management for the Space Station active thermal control system

    NASA Technical Reports Server (NTRS)

    Hill, Tim; Faltisco, Robert M.

    1992-01-01

    The Thermal Advanced Automation Project (TAAP) approach and architecture is described for automating the Space Station Freedom (SSF) Active Thermal Control System (ATCS). The baseline functionally and advanced automation techniques for Fault Detection, Isolation, and Recovery (FDIR) will be compared and contrasted. Advanced automation techniques such as rule-based systems and model-based reasoning should be utilized to efficiently control, monitor, and diagnose this extremely complex physical system. TAAP is developing advanced FDIR software for use on the SSF thermal control system. The goal of TAAP is to join Knowledge-Based System (KBS) technology, using a combination of rules and model-based reasoning, with conventional monitoring and control software in order to maximize autonomy of the ATCS. TAAP's predecessor was NASA's Thermal Expert System (TEXSYS) project which was the first large real-time expert system to use both extensive rules and model-based reasoning to control and perform FDIR on a large, complex physical system. TEXSYS showed that a method is needed for safely and inexpensively testing all possible faults of the ATCS, particularly those potentially damaging to the hardware, in order to develop a fully capable FDIR system. TAAP therefore includes the development of a high-fidelity simulation of the thermal control system. The simulation provides realistic, dynamic ATCS behavior and fault insertion capability for software testing without hardware related risks or expense. In addition, thermal engineers will gain greater confidence in the KBS FDIR software than was possible prior to this kind of simulation testing. The TAAP KBS will initially be a ground-based extension of the baseline ATCS monitoring and control software and could be migrated on-board as additional computation resources are made available.

  1. Geomorphic analysis of the Sierra Cabrera, an active pop-up in the constriction domain of conjugate strike-slip faults: the Palomares and Polopos fault zones (eastern Betics, SE Spain)

    NASA Astrophysics Data System (ADS)

    Giaconia, F.; Booth-Rea, G.; Martínez-Martínez, J. M.; Pérez-Peña, V.; Azañón, J. M.

    2012-04-01

    Segments of the Quaternary sinistral Carboneras and Palomares fault zones, striking NE-SW and NNE-SSW, respectively, terminate in the Sierra Cabrera antiform together with the conjugate dextral WNW-ESE striking Polopos fault zone. In the constriction domain between these fault zones a pop-up structure occurs formed by the North and the South Cabrera reverse faults that bound the northern and the southern hillslopes, respectively. In order to test the Quaternary activity and relief control of these fault zones, here we present new qualitative and quantitative geomorphic analyses for the Sierra Cabrera using the following indices: mountain-front sinuosity, valley floor width-to-height ratio, drainage basin asymmetry factor, basin hypsometric curve and integral, and the SLk index. These analyses were performed with the aid of several maps such as the SLk and the minimum bulk erosion map. Qualitative observations carried out on the drainage network highlight the existence of a Late Miocene fold-related drainage network and a following late Miocene to Plio-Quaternary fault-related one. Integrating the mountain-front sinuosity and the valley floor width-to-height ratio for each mountain front we estimated the uplift rates associated to each of them. Fault-related mountain-fronts with a N50-60°E strike have reverse kinematics and uplift rates larger than 0.5 m ky-1 (e.g. North and South Cabrera reverse faults), whereas those with N20-30°E and N90-100°E strikes show oblique strike-slip kinematics and show lower uplift rates, between 0.05 and 0.5 m ky-1 (e.g. the Palomares and the Polopos fault segments). Furthermore, these faults produce knickpoints, complex basin hypsometric curves, high SLk anomalies and highly eroded basins above the fault traces. The estimated uplift rates are larger than those obtained from other authors for strike-slip faults in the eastern Betics that range between 0.1 and 0.05 m ky-1 (e.g. Palomares and southern Carboneras strike-slip fault

  2. Comparison between different methodologies for detecting radon in soil along an active fault: the case of the Pernicana fault system, Mt. Etna (Italy).

    PubMed

    Giammanco, S; Immè, G; Mangano, G; Morelli, D; Neri, M

    2009-01-01

    Three different methodologies were used to measure Radon ((222)Rn) in soil, based on both passive and active detection system. The first technique consisted of solid-state nuclear track detectors (SSNTD), CR-39 type, and allowed integrated measurements. The second one consisted of a portable device for short time measurements. The last consisted of a continuous measurement device for extended monitoring, placed in selected sites. Soil (222)Rn activity was measured together with soil Thoron ((220)Rn) and soil carbon dioxide (CO(2)) efflux, and it was compared with the content of radionuclides in the rocks. Two different soil-gas horizontal transects were investigated across the Pernicana fault system (NE flank of Mount Etna), from November 2006 to April 2007. The results obtained with the three methodologies are in a general agreement with each other and reflect the tectonic settings of the investigated study area. The lowest (222)Rn values were recorded just on the fault plane, and relatively higher values were recorded a few tens of meters from the fault axis on both of its sides. This pattern could be explained as a dilution effect resulting from high rates of soil CO(2) efflux. Time variations of (222)Rn activity were mostly linked to atmospheric influences, whereas no significant correlation with the volcanic activity was observed. In order to further investigate regional radon distributions, spot measurements were made to identify sites having high Rn emissions that could subsequently be monitored for temporal radon variations. SSNTD measurements allow for extended-duration monitoring of a relatively large number of sites, although with some loss of temporal resolution due to their long integration time. Continuous monitoring probes are optimal for detailed time monitoring, but because of their expense, they can best be used to complement the information acquired with SSNTD in a network of monitored sites.

  3. Coseismic uplift and fault model of marine active faults in 1729 AD revealed by fossilized intertidal sessile organisms along the northern coast of the Noto Peninsula, central Japan

    NASA Astrophysics Data System (ADS)

    Hamada, M.; Hiramatsu, Y.; Oda, M.; Yamaguchi, H.

    2015-12-01

    The Noto Peninsula is located in the backarc region of southwest Japan and is characterized by geomorphologic features formed by active tectonics and glacial eustasy through the Quaternary. Pleistocene marine terraces along the northern coast of the Noto Peninsula indicate uplift in the coastal area through the late Quaternary (Ota and Hirakawa, 1979). Recently, an active fault zone on the seafloor off the coast was found and was divided into four segments, Monzen-oki, Saruyama-oki, Wajima-oki, and Suzu-oki, from west to east (Inoue and Okamura, 2010). We investigated vertical displacement along the coast using intertidal sessile organisms at nine sites on the rocky coast. We measured the height of fossilized Pomatoleios kraussii by GPS surveying together with a sea-level change curve, and dated them using the AMS 14C method. The vertical displacements and dates at the sites implied that coastal uplift occurred along 20 km of coastline, corresponding to the Wajima-oki segment zone, and most likely between 1600 and 1800 AD. This is coincident with seismic damage in this area in 1729 AD recorded in historical documents. We constructed a fault model with three rectangular faults in a homogeneous elastic half-space and estimated the optimal net slip and rake by a non-linear inversion method (Matsu'ura and Hasegawa, 1987). The best fit to the estimated vertical displacements is provided by a net slip of 1.8 m with a rake of 90° for the western fault plane and a net slip of 0.6 m with a rake of 90° for the center and the eastern fault planes. The moment magnitude (Mw) calculated from these parameters with a rigidity of 30 GPa is 6.6. We compared the elevation distribution of the former shorelines based on coastal terraces and the 1729 earthquake uplifts. Assuming that the coastal uplift is caused by the cumulative crustal deformation produced by the same size event as the 1729 earthquake, the average recurrence interval of the events is estimated to be 1700 years.

  4. A Role of Low-angle Thrust Fault for the Occurrence of rain-induced Rockslides in an Accretionary Complex

    NASA Astrophysics Data System (ADS)

    Arai, N.; Chigira, M.

    2015-12-01

    Recently, extreme weather related to global warming occurs frequently all over the world; there have been many record-setting rainfall events. Accordingly, potential of rain-induced rockslides increases. Examples of recent rain-induced rock avalanches with tens or more than a hundred of fatalities are a rockslide in Shiaolin village, Taiwan by 2009 Typhoon Morakot, and rockslides induced by 2011 typhoon Talas in Japan. However, the method to predict potential sites of rockslides is not established. Geological causes of rockslides are site specific and they must be clarified for each case. 2011 Typhoon Talas induced more than 50 rockslides in the outer belt of the Southwest Japan, where is underlain by Cretaceous - lower Miocene accretionary complexes. We performed thorough geological mapping in the Akatani area, where two huge rockslides occurred with volumes of 2 million and 8 million m3 respectively. As a result, we found that these two rockslides had their sliding surfaces along a low-angle-thrust with a dip of 29°~40° extending more than 5 km, which fault we name Kawarabi-thrust. This thrust has a fracture zone of 6.0 m in the maximum width, composed of clayey fault breccia with a few layers of black gouges. These fault materials are very weak and impermeable, so the fracture zone is expected to prevent the groundwater filtration and build up the pore pressure. This thrust had been exposed along the riversides at the foot of the two rockslides, which suggests that the slopes on the thrust had been destabilized by the undercutting of long-term river incision. The destabilization induced gravitational slope deformation with small scarps before the catastrophic failure. Our finding suggests that locating a large-scale low-angle-thrust is essentially important to predict potential sites of catastrophic rockslides as well as interpreting the internal structure of gravitationally deformed slopes.

  5. Roughness of Frictional Sliding Surfaces in Actively Creeping Gouge of the San Andreas Fault

    NASA Astrophysics Data System (ADS)

    Hadizadeh, J.; Candela, T.; Renard, F.

    2012-12-01

    We studied microstructure and morphology of sliding surfaces in SAFOD gouge from 3197.2m MD within the actively creeping interval SDZ. The gouge is composed of Mg-rich-smectite clays interspersed with rounded lithic fragments and serpentinite porphyroclasts. At core scale, the gouge has a granular texture with anastomosing slickenside surfaces. Microscopically, the gouge shows lozenge-shaped fabric defined by microlithons separated along highly striated surfaces. We describe as first order (S1) the surfaces that crosscut the gouge fabric, and as the second order (S2) the surfaces bounding the microlithons. Some S1 surfaces were lined with 1-5 micron thick film of ultracataclasite isochemical with the underlying gouge. We ask whether the roughness properties of the gouge sliding surfaces are comparable to outcrop-scale fault surfaces studied by others, and how these properties might relate to mechanism of the deformation. Digital elevation model (DEM) of several typical S1 and S2 surface samples were produced using high resolution white light interferometry microscope. Scanning noise and sampling artifacts were removed from the raw DEMs. Profiles parallel and perpendicular to sliding were derived from the clean DEMs and the surface roughness, represented by Hurst exponent H, was estimated for all samples from the slope of the profile Fourier Power Spectrum each for parallel (HL) and perpendicular (HA) to sliding. Results: 1. the roughness spectra were characterized by two rather than one scaling regime with a crossover length-scale range of 5-25 micron. 2. both S1 and S2 surfaces were anisotropic (HL-HA)<0 above the crossover, and roughly isotropic below the crossover length scale. HL=0.6+/-0.1 and HA=0.8+/-0.1 for the anisotropic regime and HL=HA=0.3+/-0.1 for the isotropic regime. 3. S2 surfaces are smoother compared to S1 surfaces. The Hurst exponent values for the gouge surfaces in the anisotropic regime are similar to those found for a number of outcrop

  6. Tectonic Geomorphology of an Active Low-Angle Normal Fault, Sierra El Mayor, Northern Baja California

    NASA Astrophysics Data System (ADS)

    Fletcher, J. M.; Spelz, R.

    2007-05-01

    Low angle normal faults (LANF) are ubiquitously distributed throughout the northern Gulf of California. They commonly bound uplifted mountain ranges and are found in numerous seismic sections in the Altar Desert and Wagner Basin (A. Martin, unpublished data). The Canada David detachment (CDD) is a spectacular example of an active LANF that controls the western mountain front of Sierra El Mayor over a strike length of 60 Km. Like most LANFs, the CDD contains two prominent antiform-synform megamullion pairs that strongly control the tectonic geomorphology of the uplifted footwall block and alluvial terraces along the range flank. Quantitative morphometric analysis along the mountain front shows that drainage basins in antiformal domains have systematically higher outlet elevations, higher gradients, greater relief, and much greater hypsometric integrals. Additionally river valleys are narrower and dominated by bedrock channels that extend nearly to the outlet, which is consistent with the fact that mountain front sinuosity is almost an order of magnitude less in the antiformal domains. A sequence of as many as 8 different regional strath terraces are preserved along the range flank and reconnaissance dating of the deposits by cosmogenic isotopes suggests that they formed during the major interglacial-to-glacial climatic transitions. Strath terraces are generally much older, and relative heights between terraces is significantly lower in synformal domains. All of these geomorphologic characteristics suggest that the synformal domains have experienced much lower rates of uplift and erosion of the footwall and likewise lower rates of sedimentation in the adjacent hanging wall basin. The lack of slip gradients on the master fault between synformal and antiformal domains suggests that the megamullions formed instead by regional buckling perpendicular to the extension direction. A Quaternary scarp array extends along the entire length of the mountain front and also shows

  7. Self healing of open circuit faults: With active re-configurability and mimicry of synaptic plasticity

    NASA Astrophysics Data System (ADS)

    Yaswant, Vaddi; Kumar, Amit; Sambandan, Sanjiv

    2016-07-01

    We discuss the self-repair of open faults in circuits using electrically conductive particles dispersed in an insulating fluid. The repair is triggered by the electric field developed across the open circuit in a current carrying interconnect and results in the formation of a bridge of particles across the gap. We illustrate and model the dynamics of the resistance of the self-healed route, Rb, in low field conditions. Furthermore, active control of Rb and active re-wiring are also demonstrated. Considering Rb to be akin to weights between nodes, the formation and re-wiring of routes and the control of Rb mimic synaptic plasticity in biological systems and open interesting possibilities for computing.

  8. 3D Modelling of Seismically Active Parts of Underground Faults via Seismic Data Mining

    NASA Astrophysics Data System (ADS)

    Frantzeskakis, Theofanis; Konstantaras, Anthony

    2015-04-01

    During the last few years rapid steps have been taken towards drilling for oil in the western Mediterranean sea. Since most of the countries in the region benefit mainly from tourism and considering that the Mediterranean is a closed sea only replenishing its water once every ninety years careful measures are being taken to ensure safe drilling. In that concept this research work attempts to derive a three dimensional model of the seismically active parts of the underlying underground faults in areas of petroleum interest. For that purpose seismic spatio-temporal clustering has been applied to seismic data to identify potential distinct seismic regions in the area of interest. Results have been coalesced with two dimensional maps of underground faults from past surveys and seismic epicentres, having followed careful reallocation processing, have been used to provide information regarding the vertical extent of multiple underground faults in the region of interest. The end product is a three dimensional map of the possible underground location and extent of the seismically active parts of underground faults. Indexing terms: underground faults modelling, seismic data mining, 3D visualisation, active seismic source mapping, seismic hazard evaluation, dangerous phenomena modelling Acknowledgment This research work is supported by the ESPA Operational Programme, Education and Life Long Learning, Students Practical Placement Initiative. References [1] Alves, T.M., Kokinou, E. and Zodiatis, G.: 'A three-step model to assess shoreline and offshore susceptibility to oil spills: The South Aegean (Crete) as an analogue for confined marine basins', Marine Pollution Bulletin, In Press, 2014 [2] Ciappa, A., Costabile, S.: 'Oil spill hazard assessment using a reverse trajectory method for the Egadi marine protected area (Central Mediterranean Sea)', Marine Pollution Bulletin, vol. 84 (1-2), pp. 44-55, 2014 [3] Ganas, A., Karastathis, V., Moshou, A., Valkaniotis, S., Mouzakiotis

  9. Left-lateral active deformation along the Mosha-North Tehran fault system (Iran): Morphotectonics and paleoseismological investigations

    NASA Astrophysics Data System (ADS)

    Solaymani Azad, Shahryar; Ritz, Jean-François; Abbassi, Mohammad Reza

    2011-01-01

    The Mosha and North Tehran faults correspond to the nearest seismic sources for the northern part of the Tehran megacity. The present-day structural relationships and the kinematics of these two faults, especially at their junction in Lavasanat region, is still a matter of debate. In this paper, we present the results of a morphotectonic analysis (aerial photos and field investigations) within the central part of the Mosha and eastern part of the North Tehran faults between the Mosha valley and Tehran City. Our investigations show that, generally, the traces of activity do not follow the older traces corresponding to previous long-term dip-slip thrusting movements. The recent faulting mainly occurs on new traces trending E-W to ENE-WSW affecting Quaternary features (streams, ridges, risers, and young glacial markers) and cutting straight through the topography. Often defining en-echelon patterns (right- and left-stepping), these new traces correspond to steep faults with either north- or south-dipping directions, along which clear evidences for left-lateral strike-slip motion are found. At their junction zone, the two sinistral faults display a left-stepping en-echelon pattern defining a positive flower structure system clearly visible near Ira village. Further west, the left-lateral strike-slip motion is transferred along the ENE-WSW trending Niavaran fault and other faults. The cumulative offsets associated with this left-lateral deformation is small compared with the topography associated with the previous Late Tertiary thrusting motion, showing that it corresponds to a recent change of kinematics.

  10. 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

  11. Slip sense inversion on active strike-slip faults in southwest Japan and its implications for Cenozoic tectonic evolution

    NASA Astrophysics Data System (ADS)

    Maruyama, Tadashi; Lin, Aiming

    2004-05-01

    Analyses of deflected river channels, offset of basement rocks, and fault rock structures reveal that slip sense inversion occurred on major active strike-slip faults in southwest Japan such as the Yamasaki and Mitoke fault zones and the Median Tectonic Line (MTL). Along the Yamasaki and Mitoke fault zones, small-size rivers cutting shallowly mountain slopes and Quaternary terraces have been deflected sinistrally, whereas large-size rivers which deeply incised into the Mio-Pliocene elevated peneplains show no systematically sinistral offset or complicated hairpin-shaped deflection. When the sinistral offsets accumulated on the small-size rivers are restored, the large-size rivers show residual dextral deflections. This dextral offset sense is consistent with that recorded in the pre-Cenozoic basement rocks. S-C fabrics of fault gouge and breccia zone developed in the active fault zones show sinistral shear sense compatible with earthquake focal mechanisms, whereas those of the foliated cataclasite indicate a dextral shear sense. These observations show that the sinistral strike-slip shear fabrics were overprinted on dextral ones which formed during a previous deformation phase. Similar topographic and geologic features are observed along the MTL in the central-eastern part of the Kii Peninsula. Based on these geomorphological and geological data, we infer that the slip sense inversion occurred in the period between the late Tertiary and mid-Quaternary period. This strike-slip inversion might result from the plate rearrangement consequent to the mid-Miocene Japan Sea opening event. This multidisciplinary study gives insight into how active strike-slip fault might evolves with time.

  12. Unstable fault slip induced by lawsonite dehydration in blueschist: Implication for the seismicity in the subducting oceanic crusts

    NASA Astrophysics Data System (ADS)

    Okazaki, K.; Hirth, G.

    2015-12-01

    Intermediate-depth earthquakes in cold subduction zones are observed within the subducting oceanic crust, as well as the subducting mantle In contrast, intermediate-depth earthquakes in hot subduction zones predominantly occur just below the Moho. These observations have stimulated interest in potential relationships between blueschist-facies metamorphism and seismicity, particularly through the dehydration reactions involving lawsonite. The rheology of these high-pressure and low-temperature metamorphic minerals is largely unknown. We conducted experiments on lawsonite accompanied by monitoring of acoustic emission (AE) in a Griggs-type deformation apparatus. Deformation was started at the confining pressure of 1.0 GPa, the temperature of 300 ˚C, and constant displacement rates of 0.16 to 0.016 μm/s, that correspond to equivalent strain rates (ɛ) of 9 × 10-5 to 9 × 10-6 1/s. In these experiments, temperature was increased at the temperature ramp rate of 0.5 to 0.05˚C/s above the thermal stability of lawsonite (600˚C) while the sample was deforming to test whether the dehydration reaction induces unstable fault slip. In contrast to similar tests on antigorite, unstable fault slip (i.e., stick-slip) occurred during dehydration reactions in the lawsonite gouge layer, and AE signals were continuously observed. Microstructural observations indicate that strain is highly localized along the fault (R1 and B shear), and the fault surface shows mirror-like slickensides. The unloading slope (i.e., rate of stress drop as a function of slip) during the unstable slip follows the stiffness of the apparatus at all experimental conditions regardless of the strain rate and temperature ramping rate. A thermal-mechanical scaling factor in the experiments covers the range estimated for natural subduction zones, indicating the potential for unstable frictional sliding within natural lawsonite layers to induce seismicity in cold subduction zones.

  13. Neotectonic to Active Tectonic Situation along Ulsan-Yeonil Faults, SE. Korea

    NASA Astrophysics Data System (ADS)

    Choi, S.; Chwae, U.

    2006-05-01

    Characteristics of middle to late Pleistocene faults occurred along NNW Ulsan-Yeonil faults, SE. Korea, have been controverted during last decade due to very short and frequent distribution. Those faults, having NS strike and dip to the east, generally show the top-up-to-the-west movement sense. ESR ages came out 300ka in average and OSL data range 90-50ka. Therefore the faults movement could be considered to two times within 500ka, which indicates capable fault. Earthquake around the region ranges middle to weak. Historic earthquake record described damages of wooden house and some roof tiles, which is not considered as strong as mm6.5-7.0. However tectonic background has been remained yet. In this study, the aim is to figure out geometric relationship between NNW Ulsan fault and Yeonil fault and addresses how the above capable faults have left step pattern of NS strike and left lateral movement sense. As early stage around 23Ma, the eastern block of Yeonil fault had begun to rotate to clockwise due to right lateral movement of two master faults, which are interpreted to Yansan fault and possibly Tsushima tectonic line. Yeonil block, which was in between two master faults, had been undergone the effect of clockwise rotation until around 15ma. The western margin of Yeonil block, which strikes NNW and parallel to sub-parallel to Ulsan fault, had jigsaw-type left lateral movement sense because of the clockwise fan-shape rotation. Among those jigsaw-type fault segments, NS fault segments have been given the westward tectonic pressure since 5Ma. Therefore, small NS-faults have had the top-up-to-the-west movement sense up to present time since after Pliocene and those jigsaw-type fault length yielded to short due to several intermittent shearing along NNW Ulsan fault. As an early product, two Miocene basins developed along Ulsan fault, which strike is not shown because of flat plain.

  14. 15 years of zooming in and zooming out: Developing a new single scale national active fault database of New Zealand

    NASA Astrophysics Data System (ADS)

    Ries, William; Langridge, Robert; Villamor, Pilar; Litchfield, Nicola; Van Dissen, Russ; Townsend, Dougal; Lee, Julie; Heron, David; Lukovic, Biljana

    2014-05-01

    In New Zealand, we are currently reconciling multiple digital coverages of mapped active faults into a national coverage at a single scale (1:250,000). This seems at first glance to be a relatively simple task. However, methods used to capture data, the scale of capture, and the initial purpose of the fault mapping, has produced datasets that have very different characteristics. The New Zealand digital active fault database (AFDB) was initially developed as a way of managing active fault locations and fault-related features within a computer-based spatial framework. The data contained within the AFDB comes from a wide range of studies, from plate tectonic (1:500,000) to cadastral (1:2,000) scale. The database was designed to allow capture of field observations and remotely sourced data without a loss in data resolution. This approach has worked well as a method for compiling a centralised database for fault information but not for providing a complete national coverage at a single scale. During the last 15 years other complementary projects have used and also contributed data to the AFDB, most notably the QMAP project (a national series of geological maps completed over 19 years that include coverage of active and inactive faults at 1:250,000). AFDB linework and attributes was incorporated into this series but simplification of linework and attributes has occurred to maintain map clarity at 1:250,000 scale. Also, during this period on-going mapping of active faults has improved upon these data. Other projects of note that have used data from the AFDB include the National Seismic Hazard Model of New Zealand and the Global Earthquake Model (GEM). The main goal of the current project has been to provide the best digital spatial representation of a fault trace at 1:250,000 scale and combine this with the most up to date attributes. In some areas this has required a simplification of very fine detailed data and in some cases new mapping to provide a complete coverage

  15. Seismicity, fault plane solutions, depth of faulting, and active tectonics of the Andes of Peru, Ecuador, and southern Colombia

    NASA Technical Reports Server (NTRS)

    Suarez, G.; Molnar, P.; Burchfiel, B. C.

    1983-01-01

    The long-period P waveforms observed for 17 earthquakes in the Peruvian Andes during 1963-1976 are compared with synthetic waveforms to obtain fault-plane solutions and focal depths. The morphological units of the Peruvian Andes are characterized: coastal plains, Cordillera Occidental, altiplano and central high plateau, Cordillera Oriental, and sub-Andes. The data base and analysis methodology are discussed, and the results are presented in tables, diagrams, graphs, maps, and photographs illustrating typical formations. Most of the earthquakes are shown to occur in the transition zone from the sub-Andes to the Cordillera Oriental under formations of about 1 km elevation at focal depths of 10-38 km. It is suggested that the sub-Andean earthquakes reflect hinterland deformation of a detached fold and thrust belt, perhaps like that which occurred in parts of the Canadian Rockies. From the total crustal shortening evident in Andean morphology and the shortening rate of the recent earthquakes it is estimated that the topography and crustal root of the Andes have been formed during the last 90-135 Myr.

  16. Reconstruction of fault zone evolution from 40Ar/39Ar white mica, zircon and apatite fission track, and apatite U/Th-He thermochronology: 65 million years of fault activity along the Lavanttal Fault Zone (Eastern Alps)?

    NASA Astrophysics Data System (ADS)

    Kurz, Walter; Woelfler, Andreas; Rabitsch, Robert; Genser, Johann

    2010-05-01

    , and 43.6 ± 2.1 and 34.3 ± 1.8 Ma along the western margin. Single grain ages are variable within fault core rocks and range from 76.5±12.3 to 3.6±1.3 Ma. These samples do not pass the chi-square test and can be decomposed into two age clusters. The dominant age components yield a weighted mean of 56.1±4.3 Ma and 8.6±2.6 Ma. Samples from the fault cores show significantly reduced mean track lengths (MTL). There is a clear relationship between single grain ages, MTL and Dpar values. Therefore the smallest Dpar values are associated with the youngest single grain ages and the shortest MTĹs. Referring to the (U-Th)/He analysis a trend of decreasing ages from the host rock toward the damage zones and fault cores can be observed. The weighted mean age from the host rock is 11.8±3.2, from the damage zones 7.4±1.5 and 6.2±1.3 Ma and 4.7±0.5, 5.7±1.3 and 4.8±2.0 Ma from the fault cores. Thse thermochronoloical ages document that the exhumation and cooling of the Koralm massif was mainly completed at the end of the Cretaceous. Argon release spectra from muscovites in cataclastic shear zones show in parts highly reduced incremental ages. Rejuvenation of zircon fission track ages along the LFZ indicates a first phase of fault activity around 65 Ma and is most probably related to the subsidence evolution of the Central Alpine Gosau basins. Recognition of this displacement event is hampered by the fact that the spatial distribution of Late Cretaceous structural elements coincide frequently with Miocene extrusion-related structures. Fault zones within the Eastern Alps commonly regarded to have formed during the lateral extrusion event in Miocene times may therefore represent reactivated structures that formed during a Late Cretaceous event of orogen extension. Continuous displacement along the LFZ until Pliocene times is indicated by single grain apatite and U/Th-He ages.

  17. 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

  18. The 2013 earthquake swarm in Helike, Greece: seismic activity at the root of old normal faults

    NASA Astrophysics Data System (ADS)

    Kapetanidis, V.; Deschamps, A.; Papadimitriou, P.; Matrullo, E.; Karakonstantis, A.; Bozionelos, G.; Kaviris, G.; Serpetsidaki, A.; Lyon-Caen, H.; Voulgaris, N.; Bernard, P.; Sokos, E.; Makropoulos, K.

    2015-09-01

    The Corinth Rift in Central Greece has been studied extensively during the past decades, as it is one of the most seismically active regions in Europe. It is characterized by normal faulting and extension rates between 6 and 15 mm yr-1 in an approximately N10E° direction. On 2013 May 21, an earthquake swarm was initiated with a series of small events 4 km southeast of Aigion city. In the next days, the seismic activity became more intense, with outbursts of several stronger events of magnitude between 3.3 and 3.7. The seismicity migrated towards the east during June, followed by a sudden activation of the western part of the swarm on July 15th. More than 1500 events have been detected and manually analysed during the period between 2013 May 21 and August 31, using over 15 local stations in epicentral distances up to 30 km and a local velocity model determined by an error minimization method. Waveform similarity-based analysis was performed, revealing several distinct multiplets within the earthquake swarm. High-resolution relocation was applied using the double-difference algorithm HypoDD, incorporating both catalogue and cross-correlation differential traveltime data, which managed to separate the initial seismic cloud into several smaller, densely concentrated spatial clusters of strongly correlated events. Focal mechanism solutions for over 170 events were determined using P-wave first motion polarities, while regional waveform modelling was applied for the calculation of moment tensors for the 18 largest events of the sequence. Selected events belonging to common spatial groups were considered for the calculation of composite mechanisms to characterize different parts of the swarm. The solutions are mainly in agreement with the regional NNE-SSW extension, representing typical normal faulting on 30-50° north-dipping planes, while a few exhibit slip in an NNE-SSW direction, on a roughly subhorizontal plane. Moment magnitudes were calculated by spectral analysis

  19. Transition from collision to subduction in Western Greece: the Katouna-Stamna active fault system and regional kinematics

    NASA Astrophysics Data System (ADS)

    Pérouse, E.; Sébrier, M.; Braucher, R.; Chamot-Rooke, N.; Bourlès, D.; Briole, P.; Sorel, D.; Dimitrov, D.; Arsenikos, S.

    2016-06-01

    Transition from subduction to collision occurs in Western Greece and is accommodated along the downgoing plate by the Kefalonia right-lateral fault that transfers the Hellenic subduction front to the Apulian collision front. Here we present an active tectonic study of Aitolo-Akarnania (Western Greece) that highlights how such a transition is accommodated in the overriding plate. Based on new multi-scale geomorphic and tectonic observations, we performed an accurate active fault trace mapping in the region, and provide evidence for active normal and left-lateral faulting along the Katouna-Stamna Fault (KSF), a 65-km-long NNW-striking fault system connecting the Amvrakikos Gulf to the Patras Gulf. We further show that the Cenozoic Hellenide thrusts located west of the KSF are no longer active, either in field observation or in GPS data, leading us to propose that the KSF forms the northeastern boundary of a rigid Ionian Islands-Akarnania Block (IAB). Cosmic ray exposure measurements of 10Be and 36Cl were performed on a Quaternary alluvial fan offset along the KSF (~50 m left-lateral offset). A maximum abandonment age of ~12-14 ka for the alluvial fan surface can be determined, giving an estimated KSF minimum geological left-lateral slip rate of ~4 mm year-1, in agreement with high GPS slip rates (~10 mm year-1). Despite this high slip rate, the KSF is characterized by subdued morphological evidence of tectonic activity, a gypsum-breccia bedrock and a low level of seismicity, suggesting a dominantly creeping behavior for this fault. Finally, we discuss how the IAB appears to have been progressively individualized during the Pleistocene (younger than ~1.5 Ma).

  20. Normal faulting along the western side of the Matese Mountains: Implications for active tectonics in the Central Apennines (Italy)

    NASA Astrophysics Data System (ADS)

    Boncio, Paolo; Dichiarante, Anna Maria; Auciello, Eugenio; Saroli, Michele; Stoppa, Francesco

    2016-01-01

    We provide new field data from geologic mapping and bedrock structural geology along the western side of the Matese Mts in central Italy, a region of high seismicity, strain rates among the highest of the entire Apennines (4-5 mm/yr GPS-determined extension), and poorly constrained active faults. The existing knowledge on the Aquae Iuliae normal fault (AIF) was implemented with geometric and kinematic data that better constrain its total length (16.5 km), the minimum long-term throw rate (0.3-0.4 mm/yr, post-late glacial maximum, LGM), and the segmentation. For the first time, we provide evidence of post-350 ka and possibly late Quaternary activity of the Ailano - Piedimonte Matese normal fault (APMF). The APMF is 18 km long. It is composed of a main 11 km-long segment striking NW-SE and progressively bending to the E-W in its southern part, and a 7 km-long segment striking E-W to ENE-WSW with very poor evidence of recent activity. The available data suggest a possible post-LGM throw rate of the main segment of ≳0.15 mm/yr. There is no evidence of active linkage in the step-over zone between the AIF and APMF (Prata Sannita step-over). An original tectonic model is proposed by comparing structural and geodetic data. The AIF and APMF belong to two major, nearly parallel fault systems. One system runs at the core of the Matese Mts and is formed by the AIF and the faults of the Gallo-Letino-Matese Lake system. The other system runs along the western side of the Matese Mts and is formed by the APMF, linked to the SE with the Piedimonte Matese - Gioia Sannitica fault. The finite extension of the APMF might be transferred to the NW towards the San Pietro Infine fault. The nearly 2-3 mm/yr GPS-determined extension rate is probably partitioned between the two systems, with a ratio that is difficult to establish due to poor GPS coverage. The proposed model, though incomplete (several faults/transfer zones need further investigations), aids in the seismotectonic

  1. Constraining deformation history and recent activity along the Tuz Gölü fault zone, Central Anatolia, Turkey

    NASA Astrophysics Data System (ADS)

    Krystopowicz, N. J.; Schoenbohm, L. M.; Cosca, M. A.

    2013-12-01

    The 200 km long, dextral, transtensive Tuz Gölü fault zone is a prominent northwest-striking feature in Central Anatolia. It is one of the most significant structures in Central Anatolia in that it lies within the transition zone between the Western Anatolian Extensional Province and the Eastern Anatolian Contractional Province; its study therefore offers valuable insight into how Central Anatolia is affected by lateral extrusion related to collision in the east, and gravitational pull forces associated with subduction in the west. Proposals for the initiation of the Tuz Gölü fault zone range from Cretaceous to Neogene times, and the amount of recent activity along this fault system remains poorly constrained. Furthermore, potential basinward migration of deformation into the Tuz Gölü basin poses the question as to whether or not this fault system is active in the Holocene. Previous work suggests that migration of deformation towards the basin interior may be related to lithospheric-scale processes such as plateau development, microplate extrusion, or the onset of crustal thinning associated with slab-tear propagation in subducting African lithosphere. In this study, we use a combination of paleostress and morpho-tectonic analysis to further delineate the segmentation and present activity of the Tuz Gölü fault zone. Paleostress analysis offers insight into the deformation history of the region as well as the modern-day stress regime. We conducted a morphometric analysis of over 300 drainage basins along the range-front, which reveal variations that characterize the unique development of numerous fault strands in the region. Statistical analysis of hypsometric curves, systematic variation in basin morphology and orientation, as well as changes in mountain-front sinuosity reveal fault segmentation. Additionally, field mapping and Ar-Ar dating of offset lava flows from the Hasan Dag Volcano quantitatively constrain slip-rates in the southeastern portion of the

  2. Seismic Versus Aseismic Slip and Maximum Induced Earthquake Magnitude in Models of Faults Stimulated by Fluid Injection

    NASA Astrophysics Data System (ADS)

    Ampuero, J. P.; Cappa, F.; Galis, M.; Mai, P. M.

    2015-12-01

    The assessment of earthquake hazard induced by fluid injection or withdrawal could be advanced by understanding what controls the maximum magnitude of induced seismicity (Mmax) and the conditions leading to aseismic instead of seismic slip. This is particularly critical for the viability of renewable energy extraction through engineered geothermal systems, which aim at enhancing permeability through controlled fault slip. Existing empirical relations and models for Mmax lack a link between rupture size and the characteristics of the triggering stress perturbation based on earthquake physics. We aim at filling this gap by extending results on the nucleation and arrest of dynamic rupture. We previously derived theoretical relations based on fracture mechanics between properties of overstressed nucleation regions (size, shape and overstress level), the ability of dynamic ruptures to either stop spontaneously or run away, and the final size of stopping ruptures. We verified these relations by comparison to 3D dynamic rupture simulations under slip-weakening friction and to laboratory experiments of frictional sliding nucleated by localized stresses. Here, we extend these results to the induced seismicity context by considering the effect of pressure perturbations resulting from fluid injection, evaluated by hydromechanical modeling. We address the following question: given the amplitude and spatial extent of a fluid pressure perturbation, background stress and fracture energy on a fault, does a nucleated rupture stop spontaneously at some distance from the pressure perturbation region or does it grow away until it reaches the limits of the fault? We present fracture mechanics predictions of the rupture arrest length in this context, and compare them to results of 3D dynamic rupture simulations. We also conduct a systematic study of the effect of localized fluid pressure perturbations on faults governed by rate-and-state friction. We investigate whether injection

  3. Stress-strain sensor for monitoring seismic precursors and fault activities in the sand

    NASA Astrophysics Data System (ADS)

    Du, Qiujiao; Sun, Wei; Zeng, Zuoxun

    2016-04-01

    In this paper, a sensor to monitor stress-strain signals in a granular medium is used to detect seismic precursory information. Compared with the widely used sensors of borehole stress in the rock, the sensor has more convenient operation, higher output sensitivity, compactness and farther propagation effect. The stress and strain changes before Pu'er Ms6.4 earthquake in China are recorded by Beijing and Xinmin stations, and its corresponding fault activities are analyzed. Study indicates anomalous amplitude of strain signal reaches 10 times higher than that of ordinary background, and compressive oscillation and extensional oscillation occurred constantly before the earthquake. The method and results presented in the paper provide a new way for investigating seismic precursors for shallow-source earthquakes.

  4. Active interrogation of helicopter main rotor faults using trailing edge flap actuation

    NASA Astrophysics Data System (ADS)

    Stevens, Patricia Lynn

    Over the past decade, the helicopter community has become increasingly interested in health monitoring. The rotor system, however, is not sufficiently covered in the current Health and Usage Monitoring Systems (HUMS). This dissertation describes the development and evaluation of a new approach for detecting helicopter rotor faults in which active trailing edge flaps are used to interrogate the system. This work is based on the presumption that trailing edge flaps would be installed for the primary purpose of vibration and/or noise control; health monitoring is a secondary use. Using this approach, the blade is excited by an interrogation signal, which is a low amplitude oscillation at a few discrete frequencies. The blade response is measured and the health of the system is determined using a frequency domain damage identification algorithm. Damage detection and location are achieved via the residual force vector. The residual force vector, coupled with an understanding of the system physics, also provides nature characterization. Quantification of damage extent is achieved via a frequency domain adaptation of the Asymmetric Minimum Rank Perturbation Theory. The active interrogation system is evaluated using an aeroelastic finite element model of the rotor system in hover, including an advanced unsteady aerodynamic model to predict the trailing edge flap loads. Realistic damage models, including distributed bending stiffness damage, torsional stiffness damage, control system stiffness damage, cracks and ballistic damage, are seeded in the rotor system model. Results demonstrate detection, location and quantification of extent of all of the faults tested. The effects of noise and modeling errors are discussed and mitigation techniques are developed. Additionally, a measurability study is included. Benefits of this work include both improved health monitoring for rotorcraft as well as insights into the application of structural damage detection algorithms to a

  5. Preliminary results on the tectonic activity of the Ovacık Fault (Malatya-Ovacık Fault Zone, Turkey): Implications of the morphometric analyses

    NASA Astrophysics Data System (ADS)

    Yazıcı, Müge; Zabci, Cengiz; Sançar, Taylan; Sunal, Gürsel; Natalin, Boris A.

    2016-04-01

    The Anatolian 'plate' is being extruded westward relative to the Eurasia along two major tectonic structures, the North Anatolian and the East Anatolian shear zones, respectively making its northern and eastern boundaries. Although the main deformation is localized along these two structures, there is remarkable intra-plate deformation within Anatolia, especially which are characterized by NE-striking sinistral and NW-striking dextral strike-slip faults (Şengör et al. 1985). The Malatya-Ovacık Fault Zone (MOFZ) and its northeastern member, the Ovacık Fault (OF), is a one of the NE-striking sinistral strike slip faults in the central 'ova' neotectonic province of Anatolia, located close to its eastern boundary. Although this fault zone is claimed to be an inactive structure in some studies, the recent GPS measurements (Aktuǧ et al., 2013) and microseismic activity (AFAD, 2013) strongly suggest the opposite. In order to understand rates and patterns of vertical ground motions along the OF, we studied the certain morphometric analyses such as hypsometric curves and integrals, longitudinal channel profiles, and asymmetry of drainage basins. The Karasu (Euphrates) and Munzur rivers form the main drainage systems of the study area. We extracted all drainage network from SRTM-based Digital Elevation Model with 30 m ground pixel resolution and totally identified 40 sub-drainage basins, which are inhomogeneously distributed to the north and to the south of the OF. Most of these basins show strong asymmetry, which are mainly tilted to SW. The asymmetry relatively decreases from NE to SW in general. The only exception is at the margins of the Ovacık Basin (OB), where almost the highest asymmetry values were calculated. On the other hand, the characteristics of hypsometric curves and the calculated hypsometric integrals do not show the similar systematic spatial pattern. The hypsometric curves with convex-shaped geometry, naturally indicating relatively young morphology

  6. Preliminary results on the tectonic activity of the Ovacık Fault (Malatya-Ovacık Fault Zone, Turkey): Implications of the morphometric analyses

    NASA Astrophysics Data System (ADS)

    Yazıcı, Müge; Zabci, Cengiz; Sançar, Taylan; Sunal, Gürsel; Natalin, Boris A.

    2016-04-01

    The Anatolian 'plate' is being extruded westward relative to the Eurasia along two major tectonic structures, the North Anatolian and the East Anatolian shear zones, respectively making its northern and eastern boundaries. Although the main deformation is localized along these two structures, there is remarkable intra-plate deformation within Anatolia, especially which are characterized by NE-striking sinistral and NW-striking dextral strike-slip faults (Şengör et al. 1985). The Malatya-Ovacık Fault Zone (MOFZ) and its northeastern member, the Ovacık Fault (OF), is a one of the NE-striking sinistral strike slip faults in the central 'ova' neotectonic province of Anatolia, located close to its eastern boundary. Although this fault zone is claimed to be an inactive structure in some studies, the recent GPS measurements (Aktuǧ et al., 2013) and microseismic activity (AFAD, 2013) strongly suggest the opposite. In order to understand rates and patterns of vertical ground motions along the OF, we studied the certain morphometric analyses such as hypsometric curves and integrals, longitudinal channel profiles, and asymmetry of drainage basins. The Karasu (Euphrates) and Munzur rivers form the main drainage systems of the study area. We extracted all drainage network from SRTM-based Digital Elevation Model with 30 m ground pixel resolution and totally identified 40 sub-drainage basins, which are inhomogeneously distributed to the north and to the south of the OF. Most of these basins show strong asymmetry, which are mainly tilted to SW. The asymmetry relatively decreases from NE to SW in general. The only exception is at the margins of the Ovacık Basin (OB), where almost the highest asymmetry values were calculated. On the other hand, the characteristics of hypsometric curves and the calculated hypsometric integrals do not show the similar systematic spatial pattern. The hypsometric curves with convex-shaped geometry, naturally indicating relatively young morphology

  7. Characterization of Appalachian faults

    SciTech Connect

    Hatcher, R.D. Jr.; Odom, A.L.; Engelder, T.; Dunn, D.E.; Wise, D.U.; Geiser, P.A.; Schamel, S.; Kish, S.A.

    1988-02-01

    This study presents a classification/characterization of Appalachian faults. Characterization factors include timing of movement relative to folding, metamorphism, and plutonism; tectonic position in the orogen; relations to existing anisotropies in the rock masses; involvement of particular rock units and their ages, as well as the standard Andersonian distinctions. Categories include faults with demonstrable Cenozoic activity, wildflysch-associated thrusts, foreland bedding-plane thrusts, premetamorphic to synmetamorphic thrusts in medium- to high-grade terranes, postmetamorphic thrusts in medium- to high-grade terranes, thrusts rooted in Precambrian basement, reverse faults, strike-slip faults, normal (block) faults, compound faults, structural lineaments, faults associated with local centers of disturbance, and geomorphic (nontectonic) faults.

  8. Inferences on active faults at the Southern Alps-Liguria basin junction from accurate analysis of low energy seismicity

    NASA Astrophysics Data System (ADS)

    Turino, Chiara; Scafidi, Davide; Eva, Elena; Solarino, Stefano

    2009-10-01

    Seismotectonic studies concern themselves with understanding the distribution of earthquakes in space, time, size and style. Therefore, the better these parameters are known, the most correct the association of any seismic event with the faulting structure that caused it will result. The use of accurate location methods is especially required when dealing with very complex areas, where several faulting systems or relatively small seismogenic structures exist. In fact, even though routinely determined epicentres are capable of revealing the rough picture of the seismicity, they are not suitable for studies of the fine structure of the causative fault, as their location uncertainties are often larger than the source dimension itself. In this work the probabilistic approach of the "Non Linear Localization" has been used to compute precise locations for earthquakes occurred in the last twenty years nearby the Saorge-Taggia line, a complex fault system situated in Western Liguria, close to the border between Italy and France. Together with the Breil-Sospel-Monaco and the Peille-Laghet faults, this line is responsible for the seismic activity of the area. The seismotectonic study is completed through a local tomographic study and the analysis of the focal mechanisms computed for an enlarged area. The results show that the seismicity associated with this fault system is confined within the first 10 km depth. Many clusters of seismic events are identified along the Saorge-Taggia line. The existence of a not previously mapped branch perpendicular to the Saorge-Taggia line is also recognized. Although its position may suggest it to be the continuation of the Breil-Sospel-Monaco fault system towards NE, our finding would rather suggest no association with the fault. The overall results confirm the complexity of the area; in particular the hypothesis that the Saorge-Taggia system may represent the eastward limit of a subalpine crustal block comprised within the Nice Arc, the

  9. The southern Whidbey Island fault: An active structure in the Puget Lowland, Washington

    USGS Publications Warehouse

    Johnson, S.Y.; Potter, C.J.; Armentrout, J.M.; Miller, J.J.; Finn, C.; Weaver, C.S.

    1996-01-01

    Information from seismic-reflection profiles, outcrops, boreholes, and potential field surveys is used to interpret the structure and history of the southern Whidbey Island fault in the Puget Lowland of western Washington. This northwest-trending fault comprises a broad (as wide as 6-11 km), steep, northeast-dipping zone that includes several splays with inferred strike-slip, reverse, and thrust displacement. Transpressional deformation along the southern Whidbey Island fault is indicated by alongstrike variations in structural style and geometry, positive flower structure, local unconformities, out-of-plane displacements, and juxtaposition of correlative sedimentary units with different histories. The southern Whidbey Island fault represents a segment of a boundary between two major crustal blocks. The Cascade block to the northeast is floored by diverse assemblages of pre-Tertiary rocks; the Coast Range block to the southwest is floored by lower Eocene marine basaltic rocks of the Crescent Formation. The fault probably originated during the early Eocene as a dextral strike-slip fault along the eastern side of a continental-margin rift. Bending of the fault and transpressional deformation began during the late middle Eocene and continues to the present. Oblique convergence and clockwise rotation along the continental margin are the inferred driving forces for ongoing deformation. Evidence for Quaternary movement on the southern Whidbey Island fault includes (1) offset and disrupted upper Quaternary strata imaged on seismic-reflection profiles; (2) borehole data that suggests as much as 420 m of structural relief on the Tertiary-Quaternary boundary in the fault zone; (3) several meters of displacement along exposed faults in upper Quaternary sediments; (4) late Quaternary folds with limb dips of as much as ???9??; (5) large-scale liquefaction features in upper Quaternary sediments within the fault zone; and (6) minor historical seismicity. The southern Whidbey

  10. Integrated near surface geophysics across the active Mount Marzano Fault System (southern Italy): seismogenic hints

    NASA Astrophysics Data System (ADS)

    Galli, P. A. C.; Giocoli, A.; Peronace, E.; Piscitelli, S.; Quadrio, B.; Bellanova, J.

    2014-01-01

    Here, we describe an original geophysical multi-method approach applied to the Mount Marzano Fault System. This is one of the most hazardous seismogenic faults of the Apennines (Irpinia, southern Italy), and it was responsible for the 1980, Mw 6.9, earthquake, along with many others before. We carried out electrical resistivity tomography (ERT), ground penetrating radar (GPR) measurements, and horizontal-to-vertical spectral ratio (HVSR) microtremor analysis along several common transects designed across the potential and/or certain fault traces. The data obtained from these non-invasive, inexpensive, expeditious methods mutually integrate with and complement each other, providing a valuable subsurface image of the near surface fault architecture. ERT depicts the general shallow image of the fault zone and of the fault-controlled sedimentary basin, with the depth of the buried bedrock cross-correlated through ambient-noise HVSR results. GPR delineates the very shallow geometry of the fault and of the associated deformation. Coupled with previous paleoseismological studies, these data allow the evaluation of some fault parameters and the precise locating of the fault trace, to aid future paleoseismological investigations aimed at seismic risk reduction programs.

  11. Measuring fault tolerance with the FTAPE fault injection tool

    NASA Technical Reports Server (NTRS)

    Tsai, Timothy K.; Iyer, Ravishankar K.

    1995-01-01

    This paper describes FTAPE (Fault Tolerance And Performance Evaluator), a tool that can be used to compare fault-tolerant computers. The major parts of the tool include a system-wide fault-injector, a workload generator, and a workload activity measurement tool. The workload creates high stress conditions on the machine. Using stress-based injection, the fault injector is able to utilize knowledge of the workload activity to ensure a high level of fault propagation. The errors/fault ratio, performance degradation, and number of system crashes are presented as measures of fault tolerance.

  12. Measuring fault tolerance with the FTAPE fault injection tool

    NASA Astrophysics Data System (ADS)

    Tsai, Timothy K.; Iyer, Ravishankar K.

    1995-05-01

    This paper describes FTAPE (Fault Tolerance And Performance Evaluator), a tool that can be used to compare fault-tolerant computers. The major parts of the tool include a system-wide fault-injector, a workload generator, and a workload activity measurement tool. The workload creates high stress conditions on the machine. Using stress-based injection, the fault injector is able to utilize knowledge of the workload activity to ensure a high level of fault propagation. The errors/fault ratio, performance degradation, and number of system crashes are presented as measures of fault tolerance.

  13. Stress induced near fault-zone breakout rotation: Two case studies in TCDP and JFAST

    NASA Astrophysics Data System (ADS)

    Wu, H. Y.; Brodsky, E. E.; Moe, K.; Kinoshita, M.

    2014-12-01

    Within the past decade, two successful rapid-response drilling projects have measured breakouts within the nearfault of a recently ruptured fault. Breakout observation is the direct way to detect the far and near filed stress orientation in drilling. Here we compare those data. In 2006, ICDP performed an inland drilling project to penetrate Chelungpu fault plane in central of Taiwan, which had recently slipped in 1999 Mw 7.6 Chi-Chi earthquake. This drilling project succeeded in full coring and collecting comprehensive logging data in the borehole. The resistivity images run by Formation Micro Imager (FMI) indicated that a breakout rotation in the vicinity of the fault (1111mbf). Leak-off tests on site constrained the magnitude of minimum horizontal principal stress. Here we use these data to determine the stress variation in the fault plane in our breakout dislocation model. Based on the amount of breakout azimuth, rotation and fault geometry, the stress drop can be estimated in this model. In 2012, IODP initiated a rapid drilling project after the 2011 Mw9.0 Tohoku earthquake in Japan Trench. Due to the deep-water depth, only a real-time resistivity image recorded by Logging While Drilling (LWD) and few core samples are recovered by this expedition. However, the breakout azimuth occurred near the plate boundary (820mbsf) represents the stress disturbance after the dramatic slip comparing to TCDP case. In this research, we are attempting to discuss the possible effect factors and reconstruct the geo-mechanical models to interpret the breakout distribution observed from logging data and the stress state after these huge earthquakes.

  14. Establishment of Active Traces of Lower Tagus Valley Fault Zone through an Integrated Approach

    NASA Astrophysics Data System (ADS)

    Besana-Ostman, G. M.; Vilanova, S.; Flor, A.; Canora, C.; Heleno, S.; Domingues, A.; Narciso, J.; Pinheiro, P.; Pinto, L.; Fonseca, J. F.

    2013-05-01

    Despite the occurrence of at least two damaging earthquakes in historical times - the M~7 1531 and the M6 1909 earthquakes - the Lower Tagus Valley Fault Zone (LTVFZ) has only recently been mapped (Besana-Ostman et al., 2012). In addition, a new set of active traces has been identified to the east during recent analysis and field inspections. The major challenges to the identification of active traces within Lower Tagus Valley (LTV) are both the presence of the very dynamic Tagus River (LTR) and the extensive urban and agricultural modifications introduced in the landscape. The detailed reports on the geological effects of the 1909 earthquake, while documenting extensively the secondary, shaking-related effects, provide no indication of surface rupture. The active traces of the northeast-southwest trending left-lateral LTVFZ within the LTV were established through integrated approaches as follows: aerial photo analysis, drainage system and satellite images examination, geomorphic feature identification, field mapping, geomorphic index measurements and trenching. The mapped traces extend to about 80 kilometers long and transect Quaternary and Holocene deposits. The mapped length of the western splay is compatible with an M7.2 earthquake. On the other hand, the newly mapped eastern traces plot almost parallel with the western splay, which may extend southwards to a comparable length. Preliminary analysis of satellite data show some evidence of additional splays located further east and south relative to the LTV. The new active traces suggest that the LTVFZ is a left-stepping left-lateral fault system with a regional NNE-SSW trend. Moreover, its extent and kinematics suggest magnitudes higher than previously assessed for the region. The location of the active traces displays a better correlation with the damage distribution of the historical events. Given the significance and implications of these findings for earthquake hazards assessment in Portugal, further studies

  15. 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.

  16. Multi-phase inversion tectonics related to the Hendijan-Nowrooz-Khafji Fault activity, Zagros Mountains, SW Iran

    NASA Astrophysics Data System (ADS)

    Kazem Shiroodi, Sadjad; Ghafoori, Mohammad; Faghih, Ali; Ghanadian, Mostafa; Lashkaripour, Gholamreza; Hafezi Moghadas, Naser

    2015-11-01

    Distinctive characteristics of inverted structures make them important criteria for the identification of certain structural styles of folded belts. The interpretation of 3D seismic reflection and well data sheds new light on the structural evolution and age of inverted structures associated to the Hendijan-Nowrooz-Khafji Fault within the Persian Gulf Basin and northeastern margin of Afro-Arabian plate. Analysis of thickness variations of growth strata using "T-Z plot" (thickness versus throw plot) method revealed the kinematics of the fault. Obtained results show that the fault has experienced a multi-phase evolutionary history over six different extension and compression deformation events (i.e. positive and negative inversion) between 252.2 and 11.62 Ma. This cyclic activity of the growth fault was resulted from alteration of sedimentary processes during continuous fault slip. The structural development of the study area both during positive and negative inversion geometry styles was ultimately controlled by the relative motion between the Afro-Arabian and Central-Iranian plates.

  17. The role of mechanical heterogeneities in evaporite sequence during deformation initiated by basement fault activity

    NASA Astrophysics Data System (ADS)

    Adamuszek, Marta; Dabrowski, Marcin; Burliga, Stanisław

    2016-04-01

    Kłodawa Salt Structure (KSS) situated in the centre of the Polish Zechstein Basin started to rise above a basement fault in the Early Triassic. Geological studies of the KSS revealed significant differences in the deformation patterns between the PZ1-PZ2 (intensely deformed) and PZ3-PZ4 (less deformed) cycle evaporites. These two older and two younger cycle evaporite complexes are separated by the thick Main Anhydrite (A3) bed. We use numerical simulations to assess the impact of a thick anhydrite bed on intrasalt deformation. In our models, the overburden consists of clastic sediments. A normal fault located in the rigid basement beneath the salt is activated due to model extension. At the same time, the sedimentation process takes place. The evaporites consist of a salt bed intercalated with a thick anhydrite layer of varying position and geometry. To understand the role of anhydrite layer, we run comparative simulations, in which no anhydrite layer is present. In the study, we use our own numerical codes implemented in MATLAB combined with the MILAMIN and MUTILS numerical packages. Our investigations revealed a significant influence of the anhydrite on deformation style in the evaporate series. The supra-anhydrite domain is characterized by weaker deformation and lower rates of salt flow in comparison to the sub-anhydrite domain. The highest contrast in the rate of salt flow between the two domains is observed in the case of the anhydrite layer situated close to the bottom of the salt complex. The thick anhydrite layer additionally diminishes the deformation rate in the supra-anhydrite domain and can lead to detachment of the basement deformation from its overlay. Our numerical simulations showed that the presence of the A3 Main Anhydrite bed could be the dominant factor responsible for the decoupling of deformation in the KSS salt complex.

  18. Active source monitoring at the Wenchuan fault zone: coseismic velocity change associated with aftershock event and its implication

    NASA Astrophysics Data System (ADS)

    Yang, Wei; Ge, Hongkui; Wang, Baoshan; Hu, Jiupeng; Yuan, Songyong; Qiao, Sen

    2014-12-01

    With the improvement of seismic observation system, more and more observations indicate that earthquakes may cause seismic velocity change. However, the amplitude and spatial distribution of the velocity variation remains a controversial issue. Recent active source monitoring carried out adjacent to Wenchuan Fault Scientific Drilling (WFSD) revealed unambiguous coseismic velocity change associated with a local M s5.5 earthquake. Here, we carry out forward modeling using two-dimensional spectral element method to further investigate the amplitude and spatial distribution of observed velocity change. The model is well constrained by results from seismic reflection and WFSD coring. Our model strongly suggests that the observed coseismic velocity change is localized within the fault zone with width of ~120 m rather than dynamic strong ground shaking. And a velocity decrease of ~2.0 % within the fault zone is required to fit the observed travel time delay distribution, which coincides with rock mechanical experiment and theoretical modeling.

  19. Active tectonics along the Wadi Araba-Jordan Valley transform fault

    NASA Astrophysics Data System (ADS)

    Galli, Paolo

    1999-02-01

    A geological study has been carried out along the 200 km long Wadi Araba following the transform fault that separates the Arabian and Sinai-African Plates. Recent movements along this structure affect upper Pleistocene-Holocene deposits and archaeological sites. Kinematic indicators show sinistral strike-slip and oblique movements, in agreement with the relative motion between the two plates. Other evidence of recent horizontal displacement exists along the Jordan Valley Fault, both on the Dead Sea-Lake Tiberias segment and on the segment north of Lake Tiberias. A minimum horizontal slip rate of 1 cm yr-1 has been estimated for both the southern segment of the Wadi Araba Fault and for the southern Jordan River Fault. The two faults can be roughly subdivided into at least four segments: two in the Wadi Araba (80 km long each), one from the Dead Sea to Lake Tiberias (130 km), and one from Lake Tiberias to the Hula graben (>30 km). Faulting may also occur along shorter subsegments, as shown by bends in the Wadi Araba-Jordan River Fault and by the growth of local compression and extension features. Instrument-recorded seismicity appears to be mainly concentrated along some of these subsegments. A comparison between the observed seismic and field-determined slip rates across the fault indicates possible strain accumulation during the last 2000 years.

  20. Geomechanical Risk Assessment on Shear Activation of Faults in the CO2 Storage Test Site, Offshore Pohang, South Korea

    NASA Astrophysics Data System (ADS)

    Jo, Y.; Chang, C.; Shinn, Y. J.; Song, I.; Kwon, Y. K.

    2015-12-01

    A pilot CO2 sequestration test project is underway in offshore Pohang, South Korea. The target brine aquifer for CO2 storage is 100 m-thick sandstone/conglomerate formations at a depth range between 750 and 850 mbsf (meter below seafloor), which were verified by a 3D seismic survey and a cored borehole (980 m deep). We also found that a family of steep-dip, NE-striking faults cross the target aquifer. In order to analyze potential risk of shear activation along the faults, we characterize in situ stress state at the site. Borehole image logs, generated by an acoustic televiewer tool showed borehole breakouts along the whole logged section to ~705 mbsf, which consistently indicate an average maximum horizontal principal stress (SHmax) direction of N135°±15°E. A leak-off test conducted at the bottom of a casing shoe (700 mbsf) yielded the magnitude of the minimum horizontal principal stress (Shmin) of 12.1 MPa, which is lower than the vertical stress (Sv =14.8 MPa). For the given Shmin and Sv conditions, we used the logged breakout widths and laboratory determined rock compressive strength to constrain possible SHmax magnitudes that could create the observed breakouts. Our stress estimation indicates that the stress regime in the CO2 injection test site is in favor of strike-slip faulting (Shmin < Sv < SHmax). We utilized our estimated stress conditions to analyze slip tendency of the faults. All regional-scale faults turn out to have relatively low slip tendency under the given stress condition, suggesting a low risk of triggering shear activation of faults during CO2 injection.

  1. An integral-free expression for short-term changes in fault stability due to pore pressure induced when a point load is placed on the pervious boundary of a porous elastic half space containing a fault

    NASA Astrophysics Data System (ADS)

    Chander, Ramesh; Tomar, S. K.

    2014-10-01

    A concentrated load with step-function time behaviour is placed normal to the planar, pervious boundary of a porous elastic half space (PEHS) with compressible constituents. A planar fault exists in the PEHS in such a way that the poroelastic behaviour of the medium is unhindered. We derive an approximate but integral-free expression for CFSCPP, i.e., changes in fault stability due to changes in pore pressure, at a point not too far off the line along which the load acts. But, in the interest of simplicity, the main discussion is focussed on a consideration of CFSCPP at a point P located on the fault at depth z directly beneath the load. It is convenient to introduce dimensionless time t D directly proportional to real time t. The constant of proportionality is 4 c/ z 2, where c is hydraulic diffusivity. The derived approximate expression gives results with an accuracy of greater than 99% for limited values of t D after the load is imposed. We learn from the derived expression that, for a given z, fault stability undergoes an initial sudden decrease commensurate with the undrained pore pressure induced in the PEHS. This is followed by a more gradual decrease in fault stability with increasing t D until a minimum is reached. The real time t to minimum fault stability increases with z. The magnitude of CFSCPP decreases with z as z -2 for a given t D in the permissible range. The derived expression and the inferences based on it should be useful during earth science investigations of the possible hazards due to reactivation of a pre-existing shallow fault when a civil engineering project involving imposition of a heavy load on the earth's surface is to be executed nearby. They should be useful also for investigations if a shallow earthquake occurs near such a project soon after its execution.

  2. In situ stress heterogeneity induced by weak natural fractures and faults with high slip-tendency

    NASA Astrophysics Data System (ADS)

    Chang, Chandong

    2014-05-01

    In situ stress measurements typically conducted using several geotechnical methods (hydraulic fracturing and overcoring) often show quite scattered and inconsistent stress magnitudes. Would they be artifacts from test errors or genuine stress signals in the crust? I report two field examples of stress measurements, in which lateral stresses represented by maximum (SHmax) and minimum (Shmin) horizontal principal stresses scatter quite widely, to investigate the cause of the observed stress heterogeneity. Hydraulic fracturing stress measurements were conducted in vertical boreholes at two different locations in South Korea. The boreholes are 300 and 400 m deep, respectively, both penetrating granites. Several isolated intervals of intact rocks over depths in the boreholes were vertically fractured by injecting water. Magnitudes of Shmin were determined from shut-in pressures. Magnitudes of SHmax were estimated based on the Hubbert-Willis (1957) equation using reliably determined hydraulic fracturing tensile strengths. The stress states in both locations are in reverse faulting stress regimes, in which vertical stress (Sv) is the least principal stress. The magnitudes of SHmax are generally within or close to stress range limited by frictional coefficients of 0.6-1.0 of nearby faults. However, SHmax do not increase consistently with depth, but rather scatter quite significantly. Over only a few tens of meter depth interval, the SHmax magnitudes jump up and down by an order of ~10 MPa, often resulting in lower SHmax values at deeper depths. Near the depths of relatively low stress, natural fractures and faults with wide apertures (for instance, wider than ~10 mm, observed from borehole image logs) are abundant, and near those of relatively high stress, those wide discontinuities are scarce. Such wide discontinuities are inferred to be filled with weak gouges or rock fragments, and thus tend to have relatively low frictional coefficients. In particular, the wide

  3. Spatial and temporal variation of palaeoseismic activity at an intraplate, historically quiescent structure: The Concud fault (Iberian Chain, Spain)

    NASA Astrophysics Data System (ADS)

    Lafuente, Paloma; Arlegui, Luis E.; Liesa, Carlos L.; Pueyo, Óscar; Simón, José L.

    2014-09-01

    Several faults in the Teruel and Jiloca grabens (Iberian Chain, NE Spain), particularly the targeted Concud fault, show evidences of recent, continuous activity, despite their scarce instrumental and historic seismic record. Three trenches are studied in two locations (central and southeastern sectors of the Concud fault, respectively). After comparing with previous works, we reconstruct a palaeoseismic succession with nine events distributed along a maximum time lapse bracketed between 81.6 and 14.0 ka. This succession involves an average recurrence interval of 7.4 ± 2.8 ka, with individual interseismic periods between 4 and 11 ka. The calculated coseismic displacements range from 0.6 to 2.7 m, with an average value of 1.9 m that results in a slip rate of 0.26 mm/a. Due to the incomplete sedimentary record for Holocene times, we cannot affirm that the youngest event detected was actually the last one. We conjecture that some other events may have occurred during the period between 15.0 and 3.4 ka. Temporal and spatial variations have been detected in palaeoseismic activity, specifically in the distribution of coseismic displacements. First, a non-steady slip rate is evidenced during Plio-Pleistocene times: a long-term tendency towards increasing slip rate is modulated in detail by the occurrence of minor cycles, as the sequence of increasing/decreasing activity recorded within the studied time window suggests. Secondly, an asymmetric distribution of coseismic slip along the fault trace is observed, paralleling the distribution of total fault throw, which shows an absolute maximum close to the southeastern tip. A combination of factors is proposed to explain this: branching of the main fault; dominant, remote-stress-driven slip towards N 220° E on the NW-SE fault segment; guided movement on the passive, NNW-SSE segment giving rise to an oblique roll-over monocline; and decoupling of the hanging-wall block owing to the transverse Los Mansuetos-Valdecebro fault

  4. Detection and characterization of stacking faults by light beam induced current mapping and scanning infrared microscopy in silicon

    NASA Astrophysics Data System (ADS)

    Vève-Fossati, C.; Martinuzzi, S.

    1998-08-01

    Non destructive techniques like scanning infrared microscopy and light beam induced current mapping are used to reveal the presence of stacking faults in heat treated Czochralski grown silicon wafers. In oxidized or contaminated samples, scanning infrared microscopy reveals that stacking faults grow around oxygen precipitates. This could be due to an aggregation of silicon self-interstitials emitted by the growing precipitates in the (111) plane. Light beam induced current maps show that the dislocations which surround the stacking faults are the main source of recombination centers, especially when they are decorated by a fast diffuser like copper. Des techniques non destructives telles que la microscopie infrarouge à balayage et la cartographie de photocourant induit par un spot lumineux ont été utilisées pour révéler la présence de fautes d'empilement après traitements thermiques, dans des plaquettes de silicium préparées par tirage Czochralski. Dans des échantillons oxydés ou contaminés, la microscopie infrarouge à balayage révèle des fautes d'empilement qui se développent autour des précipités d'oxygène. Cela peut être dû à la formation d'un agglomérat d'auto-interstitiels de silicium émis par la croissance des précipités dans les plans (111). Les cartographies de photocourant montrent que les dislocations qui entourent les fautes d'empilement sont la principale source de centres de recombinaison, et cela tout particulièrement quand ces fautes sont décorées par un diffuseur rapide tel que le cuivre.

  5. Early Proterozoic activity on Archean faults in the western Superior province - evidence from pseudotachylite

    USGS Publications Warehouse

    Peterman, Z.E.; Day, W.

    1989-01-01

    Major transcurrent faults in the Superior province developed in the Late Archean at the close of the Kenoran orogeny. Reactivation of some of these faults late in the Early Proterozoic is indicated by Rb-Sr analyses of pseudotachylite from the Rainy Lake-Seine River and Quetico faults in the Rainy Lake region of Minnesota and Ontario. Fault veins of pseudotachylite and immediately adjacent country rock at two localities yielded subparallel isochrons that are pooled for an age of 1947??23 Ma. K-Ar and Rb-Sr biotite ages register earlier regional cooling of the terrane at about 2500 Ma with no evidence of younger thermal overprinting at temperatures exceeding 300??C. Accordingly, the 1947??23 Ma age is interpreted as dating the formation of the pseudotachylite. Reactivation of existing faults at this time was caused by stresses transmitted from margins of the Superior province where compressional tectonic events were occurring. -Authors

  6. Detection of active faults using EMR-Technique and Cerescope at Landau area in central Upper Rhine Graben, SW Germany

    NASA Astrophysics Data System (ADS)

    Hagag, Wael; Obermeyer, Hennes

    2016-01-01

    Two conjugate sets of active faults oriented NNE-SSW and NNW-SSE have been detected at Landau area in SW Germany. These faults follow the old trends of the rift-related structures predominating in the Upper Rhine Graben (URG), which originated during Late Eocene-Miocene time. Linear and horizontal measurements were performed by using the Cerescope device and interpreted, applying the Electromagnetic Radiation (EMR) Technique. Linear EMR-profiles were helpful for mapping active faults, while the main horizontal stress (σH, N to NNE) was easily identified with EMR-horizontal measurements. Reactivation of rift-related structures of the Upper Rhine Graben at Landau area produces a new system of active shallow fractures following old trends, and has been detected through the present study by Cerescope applying the EMR-Technique. The present results imply that the Enhanced Geothermal System (EGS) to the south of Landau has a great impact on reactivation of the pre-existing rift-related faults by mechanical hydro-fracturing occurring within the reservoir rocks underneath the area.

  7. High-resolution relocation of aftershocks of the Mw 7.1 Darfield, New Zealand, earthquake and implications for fault activity

    NASA Astrophysics Data System (ADS)

    Syracuse, E. M.; Thurber, C. H.; Rawles, C. J.; Savage, M. K.; Bannister, S.

    2013-08-01

    Low-slip-rate regions often represent under-recognized hazards, and understanding the progression of seismicity when faults in such areas rupture will help us to better understand earthquake rupture patterns. The 3 September 2010 (UTC) Mw 7.1 Darfield earthquake revealed a formerly unrecognized set of faults in the Canterbury region of New Zealand, an area that had previously been mapped as one of the lower-hazard areas in the country. In this study, we analyze the first four months of its aftershock sequence to identify active faults and temporal changes in seismicity along them. We jointly invert for three-dimensional P wave and S wave velocities and hypocentral locations, using data for 2840 aftershocks recorded at 36 temporary and permanent seismic stations within 70 km of the main shock epicenter. These relocations delineate eight individual faults active prior to the 22 February 2011 Mw 6.3 Christchurch earthquake, the largest aftershock of the Darfield earthquake. Two of these faults are in the Christchurch region, one of which corresponds to geodetically determined rupture planes of the Christchurch earthquake. Using focal mechanisms calculated from first-motion polarities, we find mainly strike-slip faulting events, with some reverse and normal faulting events as well. We compare the orientations of these faults to the prevailing regional stress directions to identify which faults may have been active prior to the Darfield earthquake and which may be newly developed.

  8. 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

  9. A Signal of Ice Loading in Late Pleistocene Activity of the Sudetic Marginal Fault (Central Europe)

    NASA Astrophysics Data System (ADS)

    Hartvich, F.; Stepancikova, P.; Rockwell, T. K.; Nývlt, D.; Stemberk, J.; Rood, D. H.; Hók, J.; Ortuňo, M.; Myers, M.; Luttrell, K. M.; Wechsler, N.

    2014-12-01

    We combine paleoseismic trench and cosmogenic dating results to study the late Pleistocene-Holocene history of morphologically pronounced NW-SE trending Sudetic Marginal Fault (SMF) situated at the northeastern limit of the Bohemian Massif in central Europe. Eighteen trenches were excavated at the Bila Voda site to study 3D distribution of a beheaded alluvial fan on the NE block of the fault and to find the offset "feeder channel" that sourced the deposits. We interpret a small drainage of about 40-60 m to the SE of the fan apex as the feeder channel. A 2.5 m depth profile was collected for cosmogenic exposure dating from a well-preserved part of the fan. Using a simple model that accounts for pre-depositional exposure (inheritance) and assuming no surface erosion, 10Be concentrations are well-fit with an apparent exposure age of ~12 ka. However, this is a minimum limiting age if the surface was eroded by gelifluction in the late Pleistocene. Assuming a ~25 ka OSL age for the base of the fan apex it gives a left-lateral slip rate of ~2 mm/yr. As the Holocene deposits do not show significant displacement, most of the recorded slip took place during Late Pleistocene with corresponding slip rate of 2.8 to 3.5 mm/yr. Bila Voda site lies ~150 km south from the Late Pleistocene Weichselian maximum (~20 ka) ice-sheet front. Thus, we hypothesize that the slip rate acceleration was due to ice-loading and subsequent unloading during deglaciation. To test this, we calculated the stress induced in the lithosphere from ablation of the Weichselian ice sheet modeled as a flexing elastic plate. Preliminary modeling results indicate that complete deglaciation alters the stress field such that it would inhibit left lateral failure on the SMF, consistent with observations suggesting no slip occurred during the Holocene. Although the SMF is ~150 km from the Weichselian ice sheet front, it is well within the flexural rebound area of the ice sheet, causing normal stress on the SMF to

  10. Time constraints on faults activity in the Eastern California Shear Zone from U-Pb (SHRIMP-RG) dating of syntectonic opal

    NASA Astrophysics Data System (ADS)

    Nuriel, P.; Maher, K.; Miller, D. M.

    2013-12-01

    Absolute time constraints for fault activity are of fundamental importance in active fault systems. Such constraints are necessary for estimation of long-term slip-rates and earthquake recurrence intervals required for seismic-hazard assessments. Notwithstanding, paleoseismological records are often limited to the past 1 Ma, and important information such as fault initiation and early stage displacement are seldom determined. Here we present a novel methodological approach for direct dating of brittle deformation events over a geological time scale. We use in situ U-Pb SHRIMP-RG (Sensitive High Resolution Ion Microprobe - Reverse Geometry) analyses of opal precipitates in order to constrain the relative and absolute timing of brittle deformation events. The Mojave Desert fault segments within the Eastern California Shear Zone (ECSZ) are ideal faults to investigate the long-term history because of the need for improved constraints on the timing of fault initiation and the observed discrepancy between long-term and short-term estimates for strain accumulation rates in this area. We analyzed fault-related opal samples from ten different fault exposures within the Camp Rock, Cave Mountain, and the Cady fault systems. Millimeter size fragments of fault-related opal, occurring as fault coating, filling or fault-breccia cement, were imaged using cathodoluminescence and backscattering electron microscopy in order to identify distinct phases of opal associated with specific syntectonic microstructures. Sub-samples within each phase are then targeted with multiple SHRIMP-RG analyses (<50 μm in diameter) to allow the construction of 238U/208Pb-206Pb/208Pb and/or Tera-Wasserburg U-Pb isochrons. Of the 50 distinct phases that were identified, 20 were successfully dated and U-Pb age results range from 8.4 to 0.58 Ma. The timing of fault initiation along the Cave Mountain Fault system was previously estimated to be between 15 Ma and 5 Ma. Our results suggest that initial

  11. An automatic continuous monitoring station for groundwater geochemistry at an active fault zone in SW Taiwan

    NASA Astrophysics Data System (ADS)

    Lai, Chun-Wei; Yang, Tsanyao F.; Fu, Ching-Chou; Hilton, David R.; Liu, Tsung-Kwei; Walia, Vivek; Lai, Tzu-Hua

    2015-04-01

    Previous studies have revealed that gas compositions of fluid samples collected from southwestern Taiwan where many hot springs and mud volcanoes are distributed along tectonic sutures show significant variation prior to and after some disaster seismic events. Such variations, including radon activity, CH4/CO2, CO2/3He and 3He/4He ratios of gas compositions, are considered to be precursors of earthquakes in this area. To validate the relationship between fluid compositions and local earthquakes, a continuous monitoring station has been established at Yun-Shui, which is an artesian well located at an active fault zone in SW Taiwan. It is equipped with a radon detector and a quadrupole mass spectrometer (QMS) for in-situ measurement of the dissolved gas composition. Data is telemetered to Taipei so we are able to monitor variations of gas composition in real time. Furthermore, we also installed a syringe pump apparatus for the retrieval and temporal analysis of helium (SPARTAH) at this station. From the SPARTAH samples, we can obtain detailed time series records of H-O isotopic compositions, DIC concentration and δ13C isotopic ratios, and anion concentration of the water samples at this station. After continuous monitoring for about one year, some anomalies occurred prior to some local earthquakes. It demonstrates that this automated system is feasible for long-term continuous seismo-geochemical research in this area. Keywords: monitoring; geochemistry; isotope; dissolved gases; pre-seismic signal.

  12. Multiscale seismic imaging of active fault zones for hazard assessment: A case study of the Santa Monica fault zone, Los Angeles, California

    USGS Publications Warehouse

    Pratt, T.L.; Dolan, J.F.; Odum, J.K.; Stephenson, W.J.; Williams, R.A.; Templeton, M.E.

    1998-01-01

    High-resolution seismic reflection profiles at two different scales were acquired across the transpressional Santa Monica Fault of north Los Angeles as part of an integrated hazard assessment of the fault. The seismic data confirm the location of the fault and related shallow faulting seen in a trench to deeper structures known from regional studies. The trench shows a series of near-vertical strike-slip faults beneath a topographic scarp inferred to be caused by thrusting on the Santa Monica fault. Analysis of the disruption of soil horizons in the trench indicates multiple earthquakes have occurred on these strike-slip faults within the past 50 000 years, with the latest being 1000 to 3000 years ago. A 3.8-km-long, high-resolution seismic reflection profile shows reflector truncations that constrain the shallow portion of the Santa Monica Fault (upper 300 m) to dip northward between 30?? and 55??, most likely 30?? to 35??, in contrast to the 60?? to 70?? dip interpreted for the deeper portion of the fault. Prominent, nearly continuous reflectors on the profile are interpreted to be the erosional unconformity between the 1.2 Ma and older Pico Formation and the base of alluvial fan deposits. The unconformity lies at depths of 30-60 m north of the fault and 110-130 m south of the fault, with about 100 m of vertical displacement (180 m of dip-slip motion on a 30??-35?? dipping fault) across the fault since deposition of the upper Pico Formation. The continuity of the unconformity on the seismic profile constrains the fault to lie in a relatively narrow (50 m) zone, and to project to the surface beneath Ohio Avenue immediately south of the trench. A very high-resolution seismic profile adjacent to the trench images reflectors in the 15 to 60 m depth range that are arched slightly by folding just north of the fault. A disrupted zone on the profile beneath the south end of the trench is interpreted as being caused by the deeper portions of the trenched strike

  13. Imaging active faults in a region of distributed deformation from joint focal mechanism and hypocenter clustering: Application to western Iberia

    NASA Astrophysics Data System (ADS)

    Custodio, S.; Lima, V.; Vales, D.; Carrilho, F.; Cesca, S.

    2015-12-01

    Mainland Portugal, on the SW edge of the European continent, is located directly north of the boundary between the Eurasian and Nubian plates. It lies in a region of slow lithospheric deformation, which has generated some of the largest earthquakes in Europe, both intraplate (mainland) and interplate (offshore). The seismicity of mainland Portugal and its adjacent offshore has been repeatedly classified as diffuse. We analyse the instrumental earthquake catalog for western Iberia, enriched with data from recent dense broadband deployments. We show that although the plate boundary south of Portugal is diffuse, in that deformation is accommodated along several distributed faults rather than along one long linear plate boundary, the seismicity itself is not diffuse. Rather, when located using high quality data, earthquakes collapse into well-defined clusters and lineations. We then present a new joint focal mechanism and hypocenter cluster algorithm that is able to extract coherent information between hypocenter locations and focal mechanisms. We apply the method to the Azores-western Mediterranean region, with emphasis on western Iberia. In addition to identifying well-known seismo-tectonic features, the joint clustering algorithm identifies eight new clusters of earthquakes with a good match between the directions of epicentre lineations and focal mechanism fault planes. These clusters may signal single active faults or wider fault zones accommodating a consistent type of faulting. Mainland Portugal is dominated by strike-slip faulting, consistent with the NNE-SSW and WNW-ESE oriented lineations. The region offshore SW Iberia displays clusters that are either predominantly strike-slip or reverse, indicating slip partitioning. This work shows that the study of low-magnitude earthquakes using dense seismic deployments is a powerful tool to study lithospheric deformation in slowly deforming regions, where high-magnitude earthquakes occur with long recurrence intervals.

  14. Active faulting within a megacity: the geometry and slip rate of the Pardisan thrust in central Tehran, Iran

    NASA Astrophysics Data System (ADS)

    Talebian, M.; Copley, A. C.; Fattahi, M.; Ghoraishi, M.; Jackson, J. A.; Nazari, H.; Sloan, R. A.; Walker, R. T.

    2016-09-01

    Tehran, the capital city of Iran with a population of over 12 million, is one of the largest urban centres within the seismically active Alpine-Himalayan orogenic belt. Although several historic earthquakes have affected Tehran, their relation to individual faults is ambiguous for most. This ambiguity is partly due to a lack of knowledge about the locations, geometries, and seismic potential of structures that have been obscured by dramatic urban growth over the past three decades, and which have covered most of the young geomorphic markers and natural exposures. Here we use aerial photographs from 1956, combined with an ˜1 m DEM derived from stereo Pleiades satellite imagery, to investigate the geomorphology of a growing anticline above a thrust fault - the Pardisan thrust - within central Tehran. The topography across the ridge is consistent with a steep ramp extending from close to the surface to a depth of ˜2 km, where it presumably connects with a shallow-dipping detachment. No primary fault is visible at the surface, and it is possible that the faulting dissipates in the near surface as distributed shearing. We use optically-stimulated luminescence to date remnants of uplifted and warped alluvial deposits that are offset vertically across the Pardisan fault, providing minimum uplift and slip-rates of at least 1 mm/yr. Our study shows that the faults within the Tehran urban region have relatively rapid rates of slip, are important in the regional tectonics, and have a great impact on earthquake hazard assessment of the city and surrounding region.

  15. Transient Fluid Flow Along Basement Faults and Rupture Mechanics: Can We Expect Injection-Induced Earthquake Behavior to Correspond Directly With Injection Operations?

    NASA Astrophysics Data System (ADS)

    Norbeck, J. H.; Horne, R. N.

    2015-12-01

    We explored injection-induced earthquake behavior in geologic settings where basement faults are connected hydraulically to overlying saline aquifers targeted for wastewater disposal. Understanding how the interaction between natural geology and injection well operations affects the behavior of injection-induced earthquake sequences has important implications for characterizing seismic hazard risk. Numerical experiments were performed to investigate the extent to which seismicity is influenced by the migration of pressure perturbations along fault zones. Two distinct behaviors were observed: a) earthquake ruptures that were confined to the pressurized region of the fault and b) sustained earthquake ruptures that propagated far beyond the pressure front. These two faulting mechanisms have important implications for assessing the manner in which seismicity can be expected respond to injection well operations.Based upon observations from the numerical experiments, we developed a criterion that can be used to classify the expected faulting behavior near wastewater disposal sites. The faulting criterion depends on the state of stress, the initial fluid pressure, the orientation of the fault, and the dynamic friction coefficient of the fault. If the initial ratio of shear to effective normal stress resolved on the fault (the prestress ratio) is less than the fault's dynamic friction coefficient, then earthquake ruptures will tend to be limited by the distance of the pressure front. In this case, parameters that affect seismic hazard assessment, like the maximum earthquake magnitude or earthquake recurrence interval, could correlate with injection well operational parameters. For example, the maximum earthquake magnitude might be expected to grow over time in a systematic manner as larger patches of the fault are exposed to significant pressure changes. In contrast, if the prestress ratio is greater than dynamic friction, a stress drop can occur outside of the pressurized

  16. Block-like motion of Tibetan Plateau: Evidences from active faults , GPS velocities and recent earthquake slips

    NASA Astrophysics Data System (ADS)

    Xu, X.; Cheng, J.

    2012-12-01

    continuous models have been proposed to explain GPS observations in many active regions. Here we first describe a division of active blocks in the Tibetan plateau and its adjacent regions in detail from recently published and unpublished maps showing distribution of active faults, discuss basic features of boundary faults around the blocks, block-like motions and their interior deformation patterns in the Quaternary. Then we examine present-day vectors and mechanical parameters of the active blocks both from the GPS observations and recent earthquake slips. All these analyses demonstrate that the block-like motion prevail in the Tibetan Plateau.

  17. Surface evidence of active tectonics along the Pergola-Melandro fault: A critical issue for the seismogenic potential of the southern Apennines, Italy

    NASA Astrophysics Data System (ADS)

    Moro, Marco; Amicucci, Laura; Cinti, Francesca R.; Doumaz, Fawzi; Montone, Paola; Pierdominici, Simona; Saroli, Michele; Stramondo, Salvatore; Di Fiore, Boris

    2007-08-01

    The Pergola-Melandro basin (southern Apennines) is characterized by a below-average release of seismic energy within a wider earthquake-prone region. In fact, it is placed between the maximum intensity areas of two of the most destructive earthquakes reported in the Italian seismic catalogue: the M ≥ 7.0 Agri Valley earthquake in 1857 and the Ms = 6.9 Irpinia earthquake in 1980. In this work, we present geomorphologic analysis, electrical resistivity surveys and field data, including paleoseismologic evidence, that provided the first direct constraints on the presence of a ˜20 km long, seismogenic fault at the western border of the Pergola-Melandro basin. We also obtained geological information on the recent deformation history of the Pergola-Melandro fault that indicates the occurrence of at least four surface faulting earthquakes since Late Pleistocene age. The empirical relationships linking fault length and magnitude would assign to the Pergola-Melandro fault an event of M ≥ 6.5. These new data have important implication on the seismic hazard assessment of this sector of the Apennines, that also includes large cities such as Potenza, about 20 km far from the recognized Pergola-Melandro fault, and highlight the relevance of the geological approach in areas where the seismological records are poor. Finally, we discuss the Pergola-Melandro fault within the regional seismotectonic context. In particular, this fault belongs to the system of normal faults with an apenninic orientation, both NE and SW dipping, accommodating the NE-crustal extension taking place in the area. Nearby faults, similarly oriented but with opposite dip, may coexist whether linked by secondary faults that act as slip transfer structures. This complex system of active faults would be more realistic than a narrow band of faults running along the belt axis with an homogenous geometry, and moreover, it is more consistent with the high extension rate measured by historical earthquakes and

  18. Diking-induced moderate-magnitude earthquakes on a youthful rift border fault: The 2002 Nyiragongo-Kalehe sequence, D.R. Congo

    NASA Astrophysics Data System (ADS)

    Wauthier, C.; Smets, B.; Keir, D.

    2015-12-01

    On 24 October 2002, Mw 6.2 earthquake occurred in the central part of the Lake Kivu basin, Western Branch of the East African Rift. This is the largest event recorded in the Lake Kivu area since 1900. An integrated analysis of radar interferometry (InSAR), seismic and geological data, demonstrates that the earthquake occurred due to normal-slip motion on a major preexisting east-dipping rift border fault. A Coulomb stress analysis suggests that diking events, such as the January 2002 dike intrusion, could promote faulting on the western border faults of the rift in the central part of Lake Kivu. We thus interpret that dike-induced stress changes can cause moderate to large-magnitude earthquakes on major border faults during continental rifting. Continental extension processes appear complex in the Lake Kivu basin, requiring the use of a hybrid model of strain accommodation and partitioning in the East African Rift.

  19. Discovery of an Active Submarine Mud Volcano Along the Nootka Fault West of Vancouver Island

    NASA Astrophysics Data System (ADS)

    Riedel, M.; Riedel, M.; Kelly, D. S.; Delaney, J. R.; Spence, G. D.; Hyndman, R. D.; Hyndman, R. D.; Mayer, L.; Calder, B.; Lilley, M. D.; Olson, E. O.; Schrenk, M. O.; Coffin, R.

    2001-12-01

    Submarine mud volcanoes are a common feature in margin environments, but few of them have been documented in the Northeast Pacific. However, during a Hydrosweep bathymetric survey in July, 2001, and a follow-on sub-surface seismic survey in August two mud volcanoes were imaged along the Nootka Fault, 16-18 km west of Vancouver Island at a water depth of 2500 m. The southern volcano, called Maquinna, lies directly along the southern expression of the left lateral, strike slip Nootka Fault. It is 1.5 km across, has a breached caldera and two small summit craters, and it stands about 30 m above the seafloor. The base is bounded by a narrow moat, partially filled by Holocene sediments that are flat lying; older, underlying sediments show steep downwarping towards the sides of the volcano. Subsurface imaging shows a dramatic loss of reflectivity beneath the volcano mound, which may indicate significant mobilization of material. However, a very bright reflector is seen at about 400 m depth below the volcano. This reflector is too deep for stability of methane clathrate, and is interpreted as a zone of high fluid content. A CTD vertical cast above the summit of the volcano showed strong, co-registered thermal, particulate, and oxygen anomalies that extend 50 m up into the overlying water column. These data indicate that the volcano is actively venting warm hydrothermal fluids. The fluids are depleted in CO2, contain background concentrations of CH4, but show elevated H2 concentrations above ocean background water. Microscopic examination of the Nootka hydrothermal samples shows that they contain dense and morphologically diverse microbial communities in comparison to background seawater with cell densities of 106 cells/ml. Enrichment culturing indicates that these communities include both anaerobic and aerobic organisms, some of which are thermophilic with optimal growth temperatures in excess of 50 deg C. Some of these cultures can use methane oxidation as an energy

  20. Coseismic Faulting and Folding in an Active Thrust Sheet over Multiple Rupture Cycles Resolved by Integrating Surface and Subsurface Records of Earthquake Deformation

    NASA Astrophysics Data System (ADS)

    Stockmeyer, J. M.; Shaw, J. H.; Brown, N.; Rhodes, E. J.; Wang, M.; Lavin, L. C.; Guan, S.

    2015-12-01

    Many recent thrust fault earthquakes have involved coseismic surface faulting and folding, revealing the complex nature of surface deformation in active thrust sheets. In this study, we characterize deformation along the active Southern Junggar Thrust (SJT) in the Junggar basin, NW China - which sourced the 1906 M8 Manas earthquake - to gain insight into how fault slip at depth is partitioned between faulting and folding strains at Earth's surface by integrating deformed terrace records, subsurface geophysical data, and luminescence geochronology. Using a 1-m digital elevation model and field surveys, we have mapped the precise geometries of fluvial terraces across the entire Tugulu anticline, which lies in the hanging wall of the SJT. These profiles reveal progressive uplift of several terraces along prominent fault scarps where the SJT is surface-emergent. Similarly aged terraces are folded in the backlimb of the Tugulu fold, providing a sequential record of surface folding. These folded terraces are progressively rotated such that the oldest terraces are dipping much steeper than younger terraces within the same fold limb. Using 2- and 3-D seismic reflection data, we integrate subsurface deformation constraints with records of surface strain. Structural interpretations of these seismic data define the geometry of the SJT and reveal that folding is localized across synclinal bends along the SJT. We evaluate a range of distinct fault-related fold models (e.g. fault-bend folding, shear fault-bend folding) to assess which structural style best describes the geometries of the subsurface and surface fold patterns. By doing so, we have the opportunity to directly relate surface fault slip measures from terrace folding and uplift to total fault slip at depth. This integration of surface and subsurface deformation - combined with constraints on terrace ages from post-IR IRSL geochronology - allows us to characterize how fault slip and seismic moment are partitioned

  1. 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

    Ruleman, Cal; Grauch, V. J.

    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.

  2. Continental subduction induced tremor activity?

    NASA Astrophysics Data System (ADS)

    Tai, H. J.; Chen, K. H.; Ide, S.; Mouyen, M.; Byrne, T. B.

    2015-12-01

    Southern Central Range of Taiwan, a place where deep-seated tectonic tremors (a proxy of slow slip) and earthquake swarms are closely located in space and highly correlated in time, provides rare opportunity towards the understanding of physical mechanisms governing different style of slip. To identify tremor events, we used the identification scheme similar to Ide et al. (2015) but applied slightly different techniques: (1) Higher waveform cross-correlation coefficient (>0.6) (2) careful visual inspection for excluding local earthquakes and short-lasted event (duration < 60 s) (3) Signal to noise ratio higher than 1.2 and lower than 30 (4) No spatio-temporal clustering technique used. During the study period of 2007-2012, we identified 2320 tremor events with duration ranging from 60 s to 1550 s. They are located underneath southern Central Range, forming a NS-striking and SE-dipping pipe-like structure at a depth of 20-40 km. The up-dip extension of this tremor structure reaches an aseismic zone under the western flank of Central Range at shallow depths, where is an area characterized by high heat flow, low Vp and Vs anomaly. Such seismic gap was explained by the buoyancy induced crust detachment during continental subduction of Eurasian Plate. This detachment may open a new channel for hot and ductile material ascending to shallow depth, producing high temperatures along the way. This provides a common mechanism for down-dip tremor and up-dip shallow seismic gap along the same eastern dipping channel. In addition, the tremor events are found to be mostly occurred in high tides and exhibit higher correlation with tide data from west coast of Taiwan. This may again imply the association between tremor activity and subduction of Eurasian Plate.

  3. Active tectonic deformation along rejuvenated faults in tropical Borneo: Inferences obtained from tectono-geomorphic evaluation

    NASA Astrophysics Data System (ADS)

    Mathew, Manoj Joseph; Menier, David; Siddiqui, Numair; Kumar, Shashi Gaurav; Authemayou, Christine

    2016-08-01

    active folding of the Rajang Group fold-thrust belt to present and these events reactivated old major faults and minor related dislocations. From geomorphic analysis associated with sedimentary record, we posit that the terrain could have undergone high uplift rates since 5 Ma or multi-phased uplift with periodic intermittent pulses of high and low uplift rates.

  4. A Sensor Fault Detection Methodology applied to Piezoelectric Active Systems in Structural Health Monitoring Applications

    NASA Astrophysics Data System (ADS)

    Tibaduiza, D.; Anaya, M.; Forero, E.; Castro, R.; Pozo, F.

    2016-07-01

    Damage detection is the basis of the damage identification task in Structural Health Monitoring. A good damage detection process can ensure the adequate work of a SHM System because allows to know early information about the presence of a damage in a structure under evaluation. However this process is based on the premise that all sensors are well installed and they are working properly, however, it is not true all the time. Problems such as debonding, cuts and the use of the sensors under different environmental and operational conditions result in changes in the vibrational response and a bad functioning in the SHM system. As a contribution to evaluate the state of the sensors in a SHM system, this paper describes a methodology for sensor fault detection in a piezoelectric active system. The methodology involves the use of PCA for multivariate analysis and some damage indices as pattern recognition technique and is tested in a blade from a wind turbine where different scenarios are evaluated including sensor cuts and debonding.

  5. 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.

  6. Abnormal fault-recovery characteristics of the fault-tolerant multiprocessor uncovered using a new fault-injection methodology

    NASA Astrophysics Data System (ADS)

    Padilla, Peter A.

    1991-03-01

    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.

  7. Detailed velocity ratio mapping during the aftershock sequence as a tool to monitor the fluid activity within the fault plane

    NASA Astrophysics Data System (ADS)

    Bachura, Martin; Fischer, Tomáš

    2016-11-01

    The rheological properties of Earth materials are expressed by their seismic velocities and VP /VS ratio, which is easily obtained by the Wadati method. Its double-difference version based on cross-correlated waveforms enables focusing on very local structures and allows tracking, monitoring and analysing the fluid activity along faults. We applied the method to three 2014 mainshock-aftershock sequences in the West Bohemia/Vogtland (Czech Republic) earthquake swarm area and found pronounced VP /VS variations in time and space for different clusters of events located on a steeply dipping fault zone at depths ranging from 7 to 11 km. Each cluster reflects the spatial distribution of earthquakes along the fault plane but also the temporal evolution of the activity. Low values of VP /VS ratio down to 1.59 ± 0.02 were identified in the deeper part of the fault zone whereas higher values up to 1.73 ± 0.01 were estimated for clusters located on a shallower segment of the fault. Temporally the low VP /VS values are associated with the early aftershocks, while the higher VP /VS ratios are related only to later aftershocks. We interpret this behaviour as a result of saturation of the focal zone by compressible fluids: in the beginning the mainshock and early aftershocks driven by over-pressured fluids increased the porosity due to opening the fluid pathways. This process was associated with a decrease of the velocity ratio. In later stages the pressure and porosity decreased and the velocity ratio recovered to levels of 1.73, typical for a Poissonian medium and Earth's crust.

  8. LiDAR-Assisted identification of an active fault near Truckee, California

    USGS Publications Warehouse

    Hunter, L.E.; Howle, J.F.; Rose, R.S.; Bawden, G.W.

    2011-01-01

    We use high-resolution (1.5-2.4 points/m2) bare-earth airborne Light Detection and Ranging (LiDAR) imagery to identify, map, constrain, and visualize fault-related geomorphology in densely vegetated terrain surrounding Martis Creek Dam near Truckee, California. Bare-earth LiDAR imagery reveals a previously unrecognized and apparently youthful right-lateral strike-slip fault that exhibits laterally continuous tectonic geomorphic features over a 35-km-long zone. If these interpretations are correct, the fault, herein named the Polaris fault, may represent a significant seismic hazard to the greater Truckee-Lake Tahoe and Reno-Carson City regions. Three-dimensional modeling of an offset late Quaternary terrace riser indicates a minimum tectonic slip rate of 0.4 ?? 0.1 mm/yr.Mapped fault patterns are fairly typical of regional patterns elsewhere in the northern Walker Lane and are in strong coherence with moderate magnitude historical seismicity of the immediate area, as well as the current regional stress regime. Based on a range of surface-rupture lengths and depths to the base of the seismogenic zone, we estimate a maximum earthquake magnitude (M) for the Polaris fault to be between 6.4 and 6.9.

  9. Dynamic fracturing by successive coseismic loadings leads to pulverization in active fault zones

    NASA Astrophysics Data System (ADS)

    Aben, F. M.; Doan, M.-L.; Mitchell, T. M.; Toussaint, R.; Reuschlé, T.; Fondriest, M.; Gratier, J.-P.; Renard, F.

    2016-04-01

    Previous studies show that pulverized rocks observed along large faults can be created by single high-strain rate loadings in the laboratory, provided that the strain rate is higher than a certain pulverization threshold. Such loadings are analogous to large seismic events. In reality, pulverized rocks have been subject to numerous seismic events rather than one single event. Therefore, the effect of successive "milder" high-strain rate loadings on the pulverization threshold is investigated by applying loading conditions below the initial pulverization threshold. Single and successive loading experiments were performed on quartz-monzonite using a Split Hopkinson Pressure Bar apparatus. Damage-dependent petrophysical properties and elastic moduli were monitored by applying incremental strains. Furthermore, it is shown that the pulverization threshold can be reduced by successive "milder" dynamic loadings from strain rates of ~180 s-1 to ~90 s-1. To do so, it is imperative that the rock experiences dynamic fracturing during the successive loadings prior to pulverization. Combined with loading conditions during an earthquake rupture event, the following generalized fault damage zone structure perpendicular to the fault will develop: furthest from the fault plane, there is a stationary outer boundary that bounds a zone of dynamically fractured rocks. Closer to the fault, a pulverization boundary delimits a band of pulverized rock. Consecutive seismic events will cause progressive broadening of the band of pulverized rocks, eventually creating a wider damage zone observed in mature faults.

  10. Late Pleistocene-Holocene Faulting History Along the Northern El Carrizal Fault, Baja California Sur, Mexico: Earthquake Recurrence at a Persistently Active Rifted Margin

    NASA Astrophysics Data System (ADS)

    Maloney, S. J.; Umhoefer, P. J.; Arrowsmith, J. R.; Gutiérrez, G. M.; Santillanez, A. U.; Rittenour, T. R.

    2007-12-01

    The El Carrizal fault is a NW striking, east dipping normal fault located 25 km west of the city of La Paz, Baja California Sur, Mexico and is the westernmost bounding fault of the gulf-margin system at this latitude. The fault is ~70 km long onshore and ~50 km long offshore to the north in La Paz Bay. As many as three Quaternary geomorphic surfaces formed on the footwall and were identified on the basis of mapping and topographic profiling. In the north, the El Carrizal fault splays into multiple strands and exhibits a pattern of alternating N-S and NW-trending segments. Results from geologic mapping, paleoseismic investigations, and preliminary optically stimulated luminescence (OSL) geochronology provide some of the first numerical constraints on late Pleistocene-Holocene faulting along the El Carrizal fault. A 20 m long, 2-3 m deep trench (Trench 28) was excavated across the fault 23 km south of La Paz Bay. The trench was photographed, hand logged, and sampled for OSL dating. The trench revealed a succession of fluvial and channel deposits of sands, gravels, and cobbles. The main fault zone is manifested by a 0.5 m thick wedge-shaped deposit that consists of silty-sand and also contains rotated blocks of caliche- cemented gravels. Preliminary OSL ages from a silty-sand unit offset 2 m by the fault average latest Pleistocene. A trench 4 km south of Trench 28 (Cuadradito Trench) was also documented and sampled for OSL analysis. Preliminary OSL ages from a fluvial sand unit deposited against faulted bedrock range from mid to late Holocene. Sedimentary comparisons and surficial mapping suggest that the Holocene unit at Cuadradito Trench may be correlative to sediment that overlies faulted units from Trench 28. Such a correlation would constrain the timing of the 2 m offset at Trench 28 to be between latest Pleistocene and mid Holocene. A quarry 10 km north of Trench 28 exposes Quaternary sand and gravels buttressed against a 5-10 m wide bedrock shear zone. Here

  11. Study and comparison of the maximum stress directions and main fault orientations in some active zones in Iran

    NASA Astrophysics Data System (ADS)

    Forouhid, Khatereh; Faraji, Atefeh; Ghorashi, Manouchehr

    2010-05-01

    Study and comparison of the maximum stress directions and main fault orientations in some active zones in Iran Khatereh Forouhid, Manouchehr Ghorashi, Atefeh Faraji Institute of Geophysics, Tehran University, Tehran, Iran kforouhid@yahoo.com Farajiatefeh@yahoo.com The Iranian plateau is the widest active zone in Alpine-Himalayan collision system that is located between two stable platforms, the Arabia in southwest and Eurasia in northeast. The convergence of these two platforms towards each other is the main reason for seismicity and different styles of deformation observed in Iran. In this study, the Iranian plateau is divided into 7 regions based on their seismotectonic characteristics. These regions are; Zagros, Makran, East Iran, Alborz, Kopeh Dagh, Central Iran and Azarbayejan (northwest of Iran). In each region, focal mechanism solutions of early and modern instrumental earthquakes (the only source of information suitable to use for stress distribution study in Iran) with magnitudes more than 5.0 and their relations to active faults are considered. By studying each maximum stress direction based on a group of earthquake focal mechanisms and considering main fault orientations, each region is studied individually. According to these data, some of these regions are divided into smaller parts. These sub-divided parts have some characters that make them different from their neighbors in the same region. In this regard, Zagros is studied in detail based on seismotectonic characteristics and divided into three parts, with N-S maximum stress direction (compressional) in one part and two different kind of NE-SW direction in two other. We use this information to investigate the style and distribution of active faulting in the Zagros and the relationships of this activity with shortening of the Arabia-Eurasia collision. It is worth to mention that as the fault slip will almost occur in the direction of maximum resolved shear stress on the fault plane, probably strain

  12. Active faulting and deformation of the Coalinga anticline as interpreted from three-dimensional velocity structure and seismicity

    USGS Publications Warehouse

    Eberhart-Phillips, D.

    1989-01-01

    This work gives a clear picture of the geometry of aftershock seismicity in a large thrust earthquake. Interpretation of hypocenters and fault plane solutions, from the 1983 Coalinga, Coast Range California, earthquake sequence, in combination with the three-dimensional velocity structure shows that the active faulting beneath the fold primarily consists of a set of southwest dipping thrusts uplifting blocks of higher-velocity material. With the three-dimensional velocity model each individual hypocenter moved slightly (0-2km) in accord with the details of the surrounding velocity structure, so that secondary features in the seismicity pattern are more detailed than with a local one-dimensional model and station corrections. The overall character of the fault plane solutions was not altered by the three-dimensional model, but the more accurate ray paths did result in distinct changes. In particular, the mainshock has a fault plane dipping 30?? southwest instead of the 23?? obtained with the one-dimensional model. -from Author

  13. Late Quaternary Activity and Seismogenic Potential of the Gonave microplate: South Coast Fault Zone of Southern Jamaica

    NASA Astrophysics Data System (ADS)

    Benford, B.; Mann, P.; Prentice, C.; King, W.; Wiggins-Grandison, M.; Demets, C.; Tikoff, B.

    2008-12-01

    The South Coast fault zone (SCFZ) strikes east-west and forms a scarp as high as 600 m along the southern coast of Jamaica. It has been postulated that this fault acts as a left-lateral, strike-slip 'bypass' fault that truncates the large, right-stepping restraining bend formed between the Plantain Garden fault zone of southeastern Jamaica and the Duanvale-Walton fault zone of northwestern Jamaica. GPS measurements near the SCFZ show anomalously rotated vectors consistent with active left-lateral shear. Anomalous topography along the trace of the SCFZ includes two, doubly plunging anticlines: Kemp's Hill (119 m), an isolated high in the otherwise flat Vere Plain, and Round Hill (333 m), a larger high directly adjacent to the coast. Field work identified the most active trace of the SCFZ in a notch along the north flank of Round Hill; this trace can be extrapolated to the west along the coast and east that locally defines a low scarp in alluvium. Channel profiles constructed for six rivers and streams crossing the projected trace of the SCFZ show convex-upward morphologies, consistent with dominance of tectonic uplift over river downcutting. To better define the subsurface location of the SCFZ beneath the Vere Plain, a gravity survey network consisting of 327 stations and covering an areas of 500 km2 was performed using a Lacoste and Romberg G-meter. Differential GPS allowed centimeter-level elevation control for each station. Gravity corrections (elevation, latitude, instrument drift, and earth tides) were made using QC Tool software, and topographic and terrane corrections were made using both local topographic measurements and high-resolution SRTM data. An ~20 mgal negative gravity anomaly on the otherwise flat gravity field of the Vere Plain corresponds with the projected trace of the SCFZ across the Vere Plain and the locations of one river offset. We interpret that the SCFZ has down-to-the-south throw, which has led to thickening of Quaternary sediments south

  14. A record of long-time rift activity and earthquake-induced ground effects in Pleistocene deposits of southern Tenerife (Canary Islands, Spain)

    NASA Astrophysics Data System (ADS)

    Buchner, Elmar; Kröchert, Jörg

    2009-09-01

    Faults with a well-defined strike direction that precisely coincides with the southern rift fault system occur in the study area in southern Tenerife. This fault system was generated contemporaneously with a chain of cinder cones ~948 ka. Open fractures in ignimbrites (~668 ka) and fossil beach deposits (~42 ka) of the El Médano area suggest that the rift-associated fault system was seismically active in the aftermath of the initial volcanic activity (~948 ka) and is probably still active. A second fault system striking perpendicular to the rift-related faults probably originates from a Holocene paleoearthquake of moderate intensity. Earthquake-induced ground effects in fossil beach deposits within the study area are consistent with seismically induced ground effects of several recent and well-documented earthquakes, as well as gravitational sliding triggered by an intense earthquake in the Nicoya Peninsula of Costa Rica in 1990. Both, the rift-associated and the earthquake-induced fault system, initially produced open fractures that were occupied by plants and subsequently stabilized by cementation, forming conspicuous sediment structures in fossil beach deposits of the El Médano site in southern Tenerife.

  15. Viscosity determinations of some frictionally generated silicate melts: Implications for slip zone rheology during impact-induced faulting

    NASA Technical Reports Server (NTRS)

    Spray, John G.

    1992-01-01

    Analytical scanning electron microscopy, using combined energy dispersive and wavelength dispersive spectrometry, was used to determine the major-element compositions of some natural and artificial glasses and their crystalline equivalents derived by the frictional melting of acid to intermediate protoliths. The major-element compositions are used to calculate the viscosities of their melt precursors using the model of Shaw at temperatures of 800-1400 C, with Fe(2+)/Fe(tot) = 0.5 and for 1-3 wt percent H2O. These results are then modified to account for suspension effects in order to determine viscosities. The results have implications for the generation of pseudotachylitic breccias as seen in the basement lithologies of the Sudbury and Vredefort structures and possibly certain dimict lunar breccias. Many of these breccias show similarities with the more commonly developed pseudotachylite fault and injection veins seen in endogenic fault zones that typically occur in thicknesses of a few centimeters or less. The main difference is one of scale: Impact-induced pseudotachylite breccias can attain several meters in thickness. This would suggest that they were generated under exceptionally high slip rates and hence high strain rates and that the friction melts generated possessed extremely low viscosities.

  16. Faulting induced by precipitation of water at grain boundaries in hot subducting oceanic crust.

    PubMed

    Zhang, Junfeng; Green, Harry W; Bozhilov, Krassimir; Jin, Zhenmin

    2004-04-01

    Dehydration embrittlement has been proposed to explain both intermediate- and deep-focus earthquakes in subduction zones. Because such earthquakes primarily occur at shallow depths or within the core of the subducting plate, dehydration at relatively low temperatures has been emphasized. However, recent careful relocation of subduction-zone earthquakes shows that at depths of 100-250 km, earthquakes continue in the uppermost part of the slab (probably the former oceanic crust that has been converted to eclogite) where temperatures are higher. Here we show that at such pressures and temperatures, eclogite lacking hydrous phases but with significant hydroxyl incorporated as defects in pyroxene and garnet develops a faulting instability associated with precipitation of water at grain boundaries and the production of very small amounts of melt. This new faulting mechanism satisfactorily explains high-temperature earthquakes in subducting oceanic crust and could potentially be involved in much deeper earthquakes in connection with similar precipitation of water in the mantle transition zone (400-700 km depth). Of potential importance for all proposed high-pressure earthquake mechanisms is the very small amount of fluid required to trigger this instability.

  17. Active flexural-slip faulting: A study from the Pamir-Tian Shan convergent zone, NW China

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    The flexural-slip fault (FSF), a type of secondary fault generated by bed-parallel slip, occurs commonly and plays an important role in accommodating fold growth. Although the kinematics and mechanics of FSFs are well studied, relatively few field observations or geometric models explore its geomorphic expression. In the Pamir-Tian Shan convergent zone, NW China, suites of well-preserved FSF scarps displace fluvial terraces in the Mingyaole and Wulagen folds. Integrating interpretations of Google Earth images, detailed geologic and geomorphic mapping, and differential GPS measurements of terrace surfaces, we summarize geomorphic features that typify these faults and create kinematic models of active flexural-slip faulting. Our study indicates the following: (i) FSF scarps commonly occur near synclinal hinges, irrespective of whether (a) the dip direction of beds on either side of the hinge is unidirectional or in opposite directions, (b) the hinge is migrating or fixed, or (c) the hinge shape is narrow and angular or wide and curved. (ii) Active FSFs are likely to produce higher scarps on steeper beds, whereas lower or no topographic scarps typify gentler beds. (iii) Tilt angles of the terrace surface displaced above FSFs progressively decrease farther away from the hinge, with abrupt changes in slope coinciding with FSF scarps; the changes in tilt angle and scarp height have a predictable geometric relationship. (iv) Active FSFs can accommodate a significant fraction of total slip and play a significant role in folding deformation. (v) Active FSFs may be used to assess seismic hazards associated with active folds and associated blind thrusts.

  18. Active tectonics, paleoseismology and associated methodological challenges posed by the slow moving Alhama de Murcia fault (SE Iberia)

    NASA Astrophysics Data System (ADS)

    Ferrater, Marta; Ortuño, Maria; Masana, Eulàlia; Pallàs, Raimon; Perea, Hector; Baize, Stephane; García-Meléndez, Eduardo; Martínez-Díaz, José J.; Echeverria, Anna; Rockwell, Thomas; Sharp, Warren D.; Arrowsmith, Ramon; Medialdea, Alicia; Rhodes, Edward

    2016-04-01

    The Alhama de Murcia fault (AMF) is a 87 km-long left-lateral slow moving fault and is responsible for the 5.1 Mw 2011 Lorca earthquake. The characterization of the seismic potential of seismogenic strike-slip slow moving faults is necessary but raises huge methodological challenges, as most paleoseismological and active tectonic techniques have been designed on and for fast moving faults. The AMF is used here as a pilot study area to adapt the traditional geomorphological and trenching analyses, especially concerning the precise quantification of offset channels. We: 1) adapted methodologies to slow moving faults, 2) obtained, for the first time, the slip rate of the AMF, and 3) updated its recurrence period and maximum expected magnitude. Morphotectonic studies aim to use the measured tectonic offset of surface channels to calculate seismic parameters. However, these studies lack a standard criterion to score the analysed features. We improved this by differentiating between subjective and objective qualities, and determining up to three objective parameters (lithological changes, associated morphotectonics and shape, and three shape sub-parameters; all ranging from 0 to 1). By applying this methodology to the AMF, we identified and characterized 138 offset features that we mapped on a high-resolution (0.5 × 0.5 m pixel size) Digital Elevation Model (DEM) from a point cloud acquired in 2013 by airborne light detection and ranging (lidar). The identified offsets, together with the ongoing datings, are going to be used to calculate the lateral slip rate of the AMF. In three-dimensional trenches, we measured the offsets of a buried channel by projecting the far-field tendency of the channel onto the fault. This procedure is inspired by the widespread geomorphological procedure and aims to avoid the diffuse deformation in the fault zone associated with slow moving faults. The calculation of the 3D tendency of the channel and its projection onto the fault permitted

  19. Modeling fault diagnosis as the activation and use of a frame system. [for pilot problem-solving rating

    NASA Technical Reports Server (NTRS)

    Smith, Philip J.; Giffin, Walter C.; Rockwell, Thomas H.; Thomas, Mark

    1986-01-01

    Twenty pilots with instrument flight ratings were asked to perform a fault-diagnosis task for which they had relevant domain knowledge. The pilots were asked to think out loud as they requested and interpreted information. Performances were then modeled as the activation and use of a frame system. Cognitive biases, memory distortions and losses, and failures to correctly diagnose the problem were studied in the context of this frame system model.

  20. Geomorphic Assessment of Activity Levels of the Three Strands of North Anatolian Fault Zone in NW Turkey

    NASA Astrophysics Data System (ADS)

    Gürbüz, E.; Gurbuz, A.

    2014-12-01

    The North Anatolian Fault Zone is a narrow zone along a length of ~900 km and width of 10 km between the Karlıova to the east and Dokurcun Valley to the west. The fault zone splays into three strands around the Dokurcun Valley and forms a wide zone with a length of 400 km and width of 100 km. From the Dokurcun Valley, while the northern strand follows a route along the Lake Sapanca, Izmit Gulf, Marmara Sea and Saroz Gulf and connects to the North Aegean Trough, the middle strand tracks Lake Iznik, Gemlik and Bandırma Bays and southern coasts of the Marmara Sea. Although there is not a consensus on where it branches from the main strand, it is generally accepted that it trails a definite route along the Yenişehir, Bursa, Manyas-Karacabey and Yenice basins, and continues towards the Edremit Gulf in the west. Given the slip rates and seismic activities of the last century, the ranking between these three strands show a decrease from north to south. Among these three strands, the northern one offers significant differences with high values compared to the middle and southern strands. The aim of this study is to compare the differences represented by slip rate and seismicity data with morphometric features of the three strands of North Anatolian Fault Zone that controlled by their activities during the Quaternary period. We have calculated the morphometric values for each of the fault strands in the Marmara Region according to geomorphic indices. Our study presents the middle strand, which has represented the lower activity during the instrumental period, has an important sense of activity.

  1. Potential-induced degradation in solar cells: Electronic structure and diffusion mechanism of sodium in stacking faults of silicon

    SciTech Connect

    Ziebarth, Benedikt Gumbsch, Peter; Mrovec, Matous; Elsässer, Christian

    2014-09-07

    Sodium decorated stacking faults (SFs) were recently identified as the primary cause of potential-induced degradation in silicon (Si) solar-cells due to local electrical short-circuiting of the p-n junctions. In the present study, we investigate these defects by first principles calculations based on density functional theory in order to elucidate their structural, thermodynamic, and electronic properties. Our calculations show that the presence of sodium (Na) atoms leads to a substantial elongation of the Si-Si bonds across the SF, and the coverage and continuity of the Na layer strongly affect the diffusion behavior of Na within the SF. An analysis of the electronic structure reveals that the presence of Na in the SF gives rise to partially occupied defect levels within the Si band gap that participate in electrical conduction along the SF.

  2. Potential-induced degradation in solar cells: Electronic structure and diffusion mechanism of sodium in stacking faults of silicon

    NASA Astrophysics Data System (ADS)

    Ziebarth, Benedikt; Mrovec, Matous; Elsässer, Christian; Gumbsch, Peter

    2014-09-01

    Sodium decorated stacking faults (SFs) were recently identified as the primary cause of potential-induced degradation in silicon (Si) solar-cells due to local electrical short-circuiting of the p-n junctions. In the present study, we investigate these defects by first principles calculations based on density functional theory in order to elucidate their structural, thermodynamic, and electronic properties. Our calculations show that the presence of sodium (Na) atoms leads to a substantial elongation of the Si-Si bonds across the SF, and the coverage and continuity of the Na layer strongly affect the diffusion behavior of Na within the SF. An analysis of the electronic structure reveals that the presence of Na in the SF gives rise to partially occupied defect levels within the Si band gap that participate in electrical conduction along the SF.

  3. Late Quaternary Deformation along the North Wuitaishan Fault of the Shanxi Graben System: Active Intracontinental Rifting in North China

    NASA Astrophysics Data System (ADS)

    Corley, J.; Cochran, W. J.; Hinrichs, N.; Ding, R.; Zhang, S.; Gomez, F.

    2012-12-01

    The Shanxi rift system in north China is an intracontinental rift zone which has been active since the late Tertiary. and has produced many destructive earthquakes in recorded history. This area is of particular interest for earthquake research because of the high seismicity levels in an intraplate setting. The Shanxi rift system is composed of NNE-oriented en-echelon half-graben basins controlled by normal faults. This study focuses on the north Wutaishan fault, which bounds the Wutai Mountains and the Xingding basin, located in the northern part of the Shanxi rift system. Quaternary tectonism is investigated using remotely-sensed imagery for mapping of large tectonically-influenced landforms, field investigations for ground truth, and structural analyses. Initial neotectonic mapping utilized stereoscopic Corona satellite imagery to differentiate between fluvial and agricultural terraces; Cartosat-based DEMs were used to correct altitude measurements of terrace heights and to analyze streams and other landforms for morphometric analysis. Fluvial terraces are used to reconstruct paleo-stream profiles of the Yangyan River and nearby tributaries to determine mountain uplift rates inferred from fluvial incision, basin extension rates, and possible warping of the footwall basin block. Field work provided ground truth for fluvial terrace altitude, type of terrace, and thicknesses of alluvial and loess deposits. Another aspect of the study involves development of structural cross-section to relate fault slip to regional tectonic strain. Fault kinematic analysis of micro-fault features found in bedrock were used to assess the Quaternary stress field. Results of this study have implications in the understanding of earthquake recurrence intervals and basin evolution in the Shanxi rift system and more generally, can improve the understanding of spatial and temporal variations of seismic events in intraplate settings.

  4. Paleoseismologic and geomorphic constraints to the deformation style and activity of the Cittanova Fault (southern Calabria, Italy)

    NASA Astrophysics Data System (ADS)

    Peronace, Edoardo; Della Seta, Marta; Fredi, Paola; Galli, Paolo; Giaccio, Biagio; Messina, Paolo; Troiani, Francesco

    2016-04-01

    The western side of Southern Calabria is the epicentral region of the strongest earthquakes of Italy. These are mainly generated by extensional faults which are still poorly investigated and/or parameterized. In this study, we explore the potential of the combined analysis of geomorphic markers, stream network morphometry and paleosimological investigations, aimed at identifying and time-constraining the surface effects of the Calabrian seismogenic faults. In this perspective, we presents results from i) plano-altimetric analysis of geomorphic markers related to active tectonics (such as marine and fluvial terraces), ii) paleoseismological investigations, and iii) time-dependent river basin and long-profile metrics of the Cittanova Fault (CF). The CF, responsible for the catastrophic Mw 7.0 earthquake of 5 February 1783, is a N220° striking, 30 km-long normal fault that downthrows the crystalline-metamorphic basement of the Aspromonte massif (~1000 m asl) below the Gioia Tauro Plain, to elevations of ~500-800 m bsl. Radiocarbon dating allowed us to ascribe the depostion of a major terraced alluvial fan (Cittanova-Taurianova terrace, TAC) to the early Last Glacial Maximum (LGM) and to date the avulsion of the depositional top surface of TAC to 28 ka. As we have found remnants of the TAC also in the CF footwall offset by 12-17 m, we estimate a vertical slip rate of 0.6 ± 0.1 mm/yr for the past 28 ka. Paleoseismological data across the fault scarp evidenced at least three surface ruptures associated to ~Mw 7.0 paleoearthquakes prior to the 1783 event. The recurrence time (~3.2 kyr) is rather longer than other Apennine normal faults (0.3-2.4 kyr), whereas it is consistent with the low slip rate of CF for the late Upper Pleistocene (0.6 mm/yr). On a longer time scale, the spatial configuration of river basin morphometry evidenced the morphodynamic rensponse to the higher slip in the central sector of CF. Furthermore, long-profile metrics, and in particular the spatial

  5. Natural Radiation for Identification and Evaluation of Risk Zones for Affectation of Activated Faults in Aquifer Overexploited.

    NASA Astrophysics Data System (ADS)

    Ramos-Leal, J.; Lopez-Loera, H.; Carbajal-Perez, N.

    2007-05-01

    In basins as Mexico, Michoacán, Guanajuato, Queretaro, Aguascalientes and San Luis Potosi, the existence of faults and fractures have affected the urban infrastructure, lines of conduction of drinkable water, pipelines, etc., that when not being identified and considered, they don't reflect the real impact that these cause also to the aquifer system, modifying the permeability of the means and in occasions they work as preferential conduits that communicate hydraulically potentially to the aquifer with substances pollutants (metals, fertilizers, hydrocarbons, waste waters, etc.) located in the surface. In the Valley of San Luis Potosi, Villa of Reyes, Arista, Ahualulco and recently The Huizache-Matehuala is being strongly affected by faulting and supposedly due cracking to subsidence, however, the regional tectonic could also be the origin of this phenomenon. To know the origin of the faults and affectation to the vulnerability of the aquifer few works they have been carried out in the area. A preliminary analysis indicates that it is possible that a tectonic component is affecting the area and that the vulnerability of the aquifer in that area you this increasing. Before such a situation, it is necessary to carry out the isotopic study of the same one, for this way to know among other things, isotopic characterization, recharge places and addresses of flow of the groundwater; quality of waters and the behavior hydrochemistry with relationship to the faults. High radon values were measured in San Luis Potosi Valley, the natural source of radon could be the riolites and however, these are located to almost a once thousand meters deep for what the migration of the gas is not very probable. The anomalies radiometrics was not correlation with the faults in this case. In some areas like the Valley of Celaya, the origin of the structures and the tectonic activity in the area was confirmed, identifying the structural arrangement of the faulting, the space relationships

  6. Identifying active interplate and intraplate fault zones in the western Caribbean plate from seismic reflection data and the significance of the Pedro Bank fault zone in the tectonic history of the Nicaraguan Rise

    NASA Astrophysics Data System (ADS)

    Ott, B.; Mann, P.

    2015-12-01

    The offshore Nicaraguan Rise in the western Caribbean Sea is an approximately 500,000 km2 area of Precambrian to Late Cretaceous tectonic terranes that have been assembled during the Late Cretaceous formation of the Caribbean plate and include: 1) the Chortis block, a continental fragment; 2) the Great Arc of the Caribbean, a deformed Cretaceous arc, and 3) the Caribbean large igneous province formed in late Cretaceous time. Middle Eocene to Recent eastward motion of the Caribbean plate has been largely controlled by strike-slip faulting along the northern Caribbean plate boundary zone that bounds the northern margin of the Nicaraguan Rise. These faults reactivate older rift structures near the island of Jamaica and form the transtensional basins of the Honduran Borderlands near Honduras. Recent GPS studies suggest that small amount of intraplate motion within the current margin of error of GPS measurements (1-3 mm/yr) may occur within the center of the western Caribbean plate at the Pedro Bank fault zone and Hess Escarpment. This study uses a database of over 54,000 km of modern and vintage 2D seismic data, combined with earthquake data and results from previous GPS studies to define the active areas of inter- and intraplate fault zones in the western Caribbean. Intraplate deformation occurs along the 700-km-long Pedro Bank fault zone that traverses the center of the Nicaraguan Rise and reactivates the paleo suture zone between the Great Arc of the Caribbean and the Caribbean large igneous province. The Pedro Bank fault zone also drives active extension at the 200-km-long San Andres rift along the southwest margin of the Nicaraguan Rise. Influence of the Cocos Ridge indentor may be contributing to reactivation of faulting along the southwesternmost, active segment of the Hess Escarpment.

  7. Growth-induced Stacking Faults of ZnO Nanorods Probed by Spatial Resolved Cathodoluminescence

    NASA Astrophysics Data System (ADS)

    Xie, Yong; Jie, Wan-Qi; Wang, Tao; Wiedenmann, Michael; Neuschl, Benjamin; Madel, Manfred; Wang, Ya-Bin; Feneberg, Martin; Thonke, Klaus

    2012-07-01

    Low density ZnO nanorods are grown by modified chemical vapor deposition on silicon substrates using gold as a catalyst. We use high resolution photoluminescence spectroscopy to gain the optical properties of these nanorods in large scale. The as-grown samples show sharp near-band-gap luminescence with a full width at half maximum of bound exciton peaks at about 300 μeV, and the ratio of ultraviolet/yellow luminescence larger than 100. Highly spatial and spectral resolved scanning electron microscope-cathodoluminescence is performed to excite the ZnO nanorods in single rods or different positions of single rods with the vapour-solid growth mechanism. The bottom of the nanorod has a 3.31-eV luminescence, which indicates that basal plane stacking faults are related to the defects that are created at the first stage of growth due to the misfit between ZnO and Si.

  8. Active tectonics in southern Xinjiang, China: Analysis of terrace riser and normal fault scarp degradation along the Hotan-Qira fault system

    NASA Technical Reports Server (NTRS)

    Avouac, Jean-Philippe; Peltzer, Gilles

    1993-01-01

    The northern piedmont of the western Kunlun mountains (Xinjiang, China) is marked at its easternmost extremity, south of the Hotan-Qira oases, by a set of normal faults trending N50E for nearly 70 km. Conspicuous on Landsat and SPOT images, these faults follow the southeastern border of a deep flexural basin and may be related to the subsidence of the Tarim platform loaded by the western Kunlun northward overthrust. The Hotan-Qira normal fault system vertically offsets the piedmont slope by 70 m. Highest fault scarps reach 20 m and often display evidence for recent reactivations about 2 m high. Successive stream entrenchments in uplifted footwallls have formed inset terraces. We have leveled topographic profiles across fault scarps and transverse abandoned terrace risers. The state of degradation of each terrace edge has been characterized by a degradation coefficient tau, derived by comparison with analytical erosion models. Edges of highest abandoned terraces yield a degradation coefficient of 33 +/- 4 sq.m. Profiles of cumulative fault scarps have been analyzed in a similar way using synthetic profiles generated with a simple incremental fault scarp model.

  9. Active tectonics in southern Xinjiang, China: Analysis of terrace riser and normal fault scarp degradation along the Hotan-Qira fault system

    SciTech Connect

    Avouac, J.P.; Peltzer, G. |

    1993-12-01

    The northern piedmont of the western Kunlun mountains (Xinjiang, China) is marked at its easternmost extremity, south of the Hotan-Qira oases, by a set of normal faults trending N50E for nearly 70 km. Conspicuous on Landsat and SPOT images, these faults follow the southeastern border of a deep flexural basin and may be related to the subsidence of the Tarim platform loaded by the western Kunlun northward overthrust. The Hotan-Qira normal fault system vertically offsets the piedmont slope by 70 m. Highest fault scarps reach 20 m and often display evidence for recent reactivations about 2 m high. Successive stream entrenchments in uplifted footwallls have formed inset terraces. We have leveled topographic profiles across fault scarps and transverse abandoned terrace risers. The state of degradation of each terrace edge has been characterized by a degradation coefficient tau, derived by comparison with analytical erosion models. Edges of highest abandoned terraces yield a degradation coefficient of 33 +/- 4 sq.m. Profiles of cumulative fault scarps have been analyzed in a similar way using synthetic profiles generated with a simple incremental fault scarp model.

  10. Effects of fault propagation on superficial soils/gravel aquifer properties: The Chihshang Fault in Eastern Taiwan

    NASA Astrophysics Data System (ADS)

    Mu, C.; Lee, J.; guglielmi, Y.

    2013-12-01

    A mature bedrock fault zone generally consists of a fault core, a damage zone, and a surrounding host rock with different permeabilities, which mainly depend on the fracture density. However, near the surface, when an active thrust fault propagates from bedrocks into an unconsolidated surface cover, it results in a diffused fault zone, which may influence the hydraulic and mechanical properties around the fault zone. It is thus of great concern to understand to which extent surface soil/gravel hydraulic properties modifications by continuously active faulting can impact geotechnical projects in countries under active tectonic context, such as Taiwan, where active faults often are blinded beneath thick soil/gravel covers. By contrast, it is also interesting to decipher those fault-induced permeability modifications to estimate potential activity precursors to large earthquakes. Here, we combined a variety of measurements and analyses on the Chihshang fault, located at the plate suture between the Philippine Sea and Eurasian plates, which converge at a rapid rate of 8 cm/yr in Taiwan. At the Chinyuan site, the Chihshang fault is propagating from depth to emerge through thick alluvial deposits. We characterized the fault geometry and slip behavior at the shallow level by measuring and analyzing horizontal, vertical displacements, and groundwater table across the surface fault zone. The yielded fault dip of 45o in the shallow alluvium is consistent with the observations from surface ruptures and subsurface core logging. The 7-year-long groundwater table record shows that the piezometric level in the hanging wall is about 8 meter higher than that in the footwall in the summer; and about 10 meter higher in the winter. Repeated slug tests have been monthly conducted since 2007 to provide the average permeability within the fault zone and the presumably low-deformed zone outside of the diffused fault zone. Based on in-situ measurements at four wells across the fault zone

  11. Topography, river network and recent fault activity at the margins of the Central Main Ethiopian Rift (East Africa)

    NASA Astrophysics Data System (ADS)

    Molin, Paola; Corti, Giacomo; Sembroni, Andrea

    2016-04-01

    Along its length, the Main Ethiopian Rift (MER) in East Africa records a transition from early fault-dominated morphology in the South to axial magma assisted-rifting typical of continental break-up in the North. It is one of the few locations on Earth offering a complete picture of the evolution of continental rifting and thus provides a unique opportunity to directly analyze how the drainage network reorganize under extensional tectonic forcing. In this paper we present a new analysis of the river network and relative landforms - complemented with a summary of recent geological data - at both rift margins of the Central MER, a key sector of the rift capturing the phase of drainage reorganization between incipient and mature rifting. This analysis shows that hydrography is strongly influenced by recent tectonics. Rectangular drainage patterns, windgaps, and lacustrine/swampy areas formed by structural dams document that the rivers are in continuous competition with fault activity. The irregular longitudinal profiles (with knickpoints/knickzones in correspondence with faults) also suggest that rivers are in a transient state of disequilibrium related to recent tectonic activity at rift margins, in agreement with previous geological and seismological data. A more regional analysis extended to the adjoining Northern and Southern MER indicates that rifting evolves from initial stages characterized by margins poorly incised by rivers with gentle channel gradients (except in correspondence with faults), to mature phases in which rift margins are highly incised by a well organized fluvial network composed by concave and steep rivers. Our regional analysis also indicates a stronger and/or more recent tectonic activity at the rift margins proceeding to the south, in line with previous models of rift development.

  12. Topography, river network and recent fault activity at the margins of the Central Main Ethiopian Rift (East Africa)

    NASA Astrophysics Data System (ADS)

    Molin, Paola; Corti, Giacomo

    2015-11-01

    Along its length, the Main Ethiopian Rift (MER) in East Africa records a transition from early fault-dominated morphology in the South to axial magma assisted-rifting typical of continental break-up in the North. It is one of the few locations on Earth offering a complete picture of the evolution of continental rifting and thus provides a unique opportunity to directly analyze how the drainage network reorganizes under extensional tectonic forcing. In this paper we present a new analysis of the river network and relative landforms-complemented with a summary of recent geological data-at both rift margins of the Central MER, a key sector of the rift capturing the phase of drainage reorganization between incipient and mature rifting. This analysis shows that hydrography is strongly influenced by recent tectonics. Rectangular drainage patterns, windgaps, and lacustrine/swampy areas formed by structural dams document that the rivers are in continuous competition with fault activity. The irregular longitudinal profiles (with knickpoints/knickzones in correspondence with faults) also suggest that rivers are in a transient state of disequilibrium related to recent tectonic activity at rift margins, in agreement with previous geological and seismological data. A more regional analysis extended to the adjoining Northern and Southern MER indicates that rifting evolves from initial stages characterized by margins poorly incised by rivers with gentle channel gradients (except in correspondence with faults), to mature phases in which rift margins are highly incised by a well organized fluvial network composed by concave and steep rivers. Our regional analysis also indicates a stronger and/or more recent tectonic activity at the rift margins proceeding to the south, in line with previous models of rift development.

  13. Physical modeling of the formation and evolution of seismically active fault zones

    USGS Publications Warehouse

    Ponomarev, A.V.; Zavyalov, A.D.; Smirnov, V.B.; Lockner, D.A.

    1997-01-01

    Acoustic emission (AE) in rocks is studied as a model of natural seismicity. A special technique for rock loading has been used to help study the processes that control the development of AE during brittle deformation. This technique allows us to extend to hours fault growth which would normally occur very rapidly. In this way, the period of most intense interaction of acoustic events can be studied in detail. Characteristics of the acoustic regime (AR) include the Gutenberg-Richter b-value, spatial distribution of hypocenters with characteristic fractal (correlation) dimension d, Hurst exponent H, and crack concentration parameter Pc. The fractal structure of AR changes with the onset of the drop in differential stress during sample deformation. The change results from the active interaction of microcracks. This transition of the spatial distribution of AE hypocenters is accompanied by a corresponding change in the temporal correlation of events and in the distribution of event amplitudes as signified by a decrease of b-value. The characteristic structure that develops in the low-energy background AE is similar to the sequence of the strongest microfracture events. When the AR fractal structure develops, the variations of d and b are synchronous and d = 3b. This relation which occurs once the fractal structure is formed only holds for average values of d and b. Time variations of d and b are anticorrelated. The degree of temporal correlation of AR has time variations that are similar to d and b variations. The observed variations in laboratory AE experiments are compared with natural seismicity parameters. The close correspondence between laboratory-scale observations and naturally occurring seismicity suggests a possible new approach for understanding the evolution of complex seismicity patterns in nature. ?? 1997 Elsevier Science B.V. All rights reserved.

  14. Study of Active Faults in the Three Gorges Dam region by Detecting and Relocating Aftershocks

    NASA Astrophysics Data System (ADS)

    Huang, R.; Zhu, L.; Xu, Y.

    2014-12-01

    Seismicity in the Three Gorges Dam (TGD) region and its adjacent areas increased dramatically as the water- level of the TGD reservoir rises since its completion in 2003. Accordingly, many efforts have been put forward to quantify the seismicity and geological hazards in the region. However, the precise detective of earthquakes, especially for the minor ones, remains difficulty because of sparse distribution of permanent seismic stations. From December 2013 to June 2014, we deployed 30 three-component broadband seismic stations in the TGD region. During the deployment, we recorded two earthquakes of magnitudes lager than 5.0, one occurred on December 16th 2013 in Badong and another on March 30th 2014 in Zigui. We firstly used a sliding-window cross-correlation (SCC) detection technique to supplement the events catalog from the China Earthquake Networks Center. Over 500 new events with ML lager than 0.5 were detected. We then relocated 502 events out of the total 987 events using the double-difference (DD) relocation algorithm. We also determined moment tensors of some large earthquakes using gCAP. The results clearly show two active faults along Yangtze River with dips of 50 degrees and 90 degrees to a maximum depth of 10 km, respectively. And they also reveal that water might have permeated to a depth of 6 km corresponds to the interface of sediments and metamorphic basement beneath Zigui Basin. We thus preliminarily judge that the quakes are triggered by local stress adjustment resulting of fluctuation of Three Gorges reservoir's loading.

  15. Synthetic earthquake catalogs simulating seismic activity in the Corynth Gulf, Greece, fault system

    NASA Astrophysics Data System (ADS)

    Console, R.; Carluccio, R.; Papadimitriou, E. E.; Karakostas, V. G.

    2014-12-01

    The characteristic earthquake hypothesis is the basis of time-dependent modeling of earthquake recurrence on major faults, using the renewal process methodology. However, the characteristic earthquake hypothesis is not strongly supported by observational data. Few fault segments have long historical or paleoseismic records of individually dated ruptures, and when data and parameter uncertainties are allowed for, the form of the recurrence-distribution is difficult to establish. This is the case, for instance, of the Corinth gulf fault system, for which documents about strong earthquakes exist for at least two thousand years, but they can be considered complete for magnitudes > 6.0 only for the latest 300 years, during which only few characteristic earthquakes are reported for single fault segments. The use of a physics-based earthquake simulator has allowed the production of catalogs lasting 100,000 years and containing more than 500,000 events of magnitudes > 4.0. The main features of our simulation algorithm are (1) the imposition of an average slip rate released by earthquakes to every single segment recognized in the investigated fault system, (2) the interaction between earthquake sources, (3) a self-organized earthquake magnitude distribution, and (4) the effect of minor earthquakes in redistributing stress. The application of our simulation algorithm to the Corinth gulf fault system has shown realistic features in time, space and magnitude behavior of the seismicity. These features include long-term periodicity of strong earthquakes, short-term clustering of both strong and smaller events, and a realistic earthquake magnitude distribution departing from the Gutenberg-Richter distribution in the higher magnitude range.

  16. Fluvial Record of Active Deformation Along the Canyon River Fault in the Wynoochee River Valley, WA

    NASA Astrophysics Data System (ADS)

    Delano, J.; Amos, C. B.; Loveless, J. P.; Rittenour, T. M.

    2015-12-01

    Ongoing uplift of the Olympic Peninsula of Washington State represents unknown contributions from Cascadia subduction zone processes, including earthquakes, interseismic deformation, aseismic slow slip events, and north-south shortening of the North American plate focused on upper plate faults. The relationship between upper plate faults and Cascadia subduction is poorly understood, as is the seismic hazard posed by these structures to the greater Puget Sound region. The Wynoochee River is a south-flowing drainage in the southern Olympic Mountains bisected by a previously uncharacterized section of the Canyon River reverse fault. In this study we utilize high-resolution aerial lidar and optically stimulated luminescence (OSL) dating of offset fluvial terraces to determine the kinematics and slip rate of the Canyon River fault over the late Quaternary. In combination with surficial geologic mapping and differential GPS surveys of terrace straths observed in the field, we also determine incision rates along the Wynoochee River from OSL dates. Our mapping reveals eight generations of fluvial and glaciofluvial terraces, with twenty-one pending ages from OSL sampling of fluvial sands intercalated with outwash and river gravels. Additionally, we compare our slip rate results with a boundary element model, estimating the stress on the Canyon River fault over the recent decades, as constrained by GPS data from the Cascadia subduction zone. Preliminary results indicate that the Canyon River fault is a long-lived feature with south-side-up and left-lateral displacement. Taken together, our results enable comparison of deformation rates constrained by short-term, geodetic data with those acting over longer-term geologic time scales.

  17. Quaternary tectonic activity of the Carboneras Fault in the La Serrata range (SE Iberia): Geomorphological and chronological constraints

    NASA Astrophysics Data System (ADS)

    Moreno, Ximena; Masana, Eulàlia; Pallàs, Raimon; Gràcia, Eulàlia; Rodés, Ángel; Bordonau, Jaume

    2015-11-01

    The Eastern Betic Shear Zone (EBSZ) in Southern Iberia is known to accommodate part of the 4-5 mm/yr convergence between Africa and Iberia, but its seismic hazard is not sufficiently understood for an accurate risk assessment. One of the main structures of the EBSZ, the left-lateral 150 km-long Carboneras Fault, displays no clear instrumental and historical activity despite being morphologically expressive. Detailed geomorphological mapping, geochronological analysis, and structural observation on the La Serrata segment of the Carboneras Fault were designed to investigate its recent evolution. Quaternary sediments and geomorphic features were targeted and 42 new numerical ages were obtained based on 66 samples (thermoluminescence, U-series, 14C, 10Be). The chronological framework of La Serrata was constructed by combining these numerical ages with a conceptual model previously developed in the region, which assumes that alluvial fan aggradation was produced during cold and dry periods (glacials and stadials), whereas stability and phases of calcrete formation were favored during warm and wetter periods (interglacials and interstadials). The spatial distribution of dated alluvial fans suggests an early phase of uplift that probably occurred between 1 Ma and 56.6 ka in the northeastern portion of the study area, whereas in the southwest sector the main uplift phase occurred later than 110.3 ka. A decline in fault activity would have taken place after 30.8 ka. Vertically offset dated units indicate minimum dip-slip rates of 0.05 mm/yr and 0.18 mm/yr, averaged for the last 1 Ma and the last 110.3 ka, respectively. Deflected channels and associated dated units yield a minimum left-lateral strike-slip rate of 1.31 mm/yr, averaged for the last 110.3 ka. The most recent fault movement of the fault could be younger than AD 637. Our results suggest therefore that the Carboneras Fault is among the fastest in Iberia, and should be considered in future hazard analyses.

  18. Evolution of earthquake rupture potential along active faults, inferred from seismicity rates and size distributions

    NASA Astrophysics Data System (ADS)

    Tormann, Thessa; Wiemer, Stefan; Enescu, Bogdan; Woessner, Jochen

    2016-04-01

    One of the major unresolved questions in seismology is the evolution in time and space of the earthquake rupture potential and thus time-dependent hazard along active faults. What happens after a major event: is the potential for further large events reduced as predicted from elastic rebound, or increased as proposed by current-state short-term clustering models? How does the rupture potential distribute in space, i.e. does it reveal imprints of stress transfer? Based on the rich earthquake record from the Pacific Plate along the Japanese coastline we investigate what information on spatial distributions and temporal changes of a normalized rupture potential (NRP) for different magnitudes can be derived from time-varying, local statistical characteristics of well and frequently observed small-to-moderate seismicity. Seismicity records show strong spatio-temporal variability in both activity rates and size distribution. We analyze 18 years of seismicity, including the massive 2011 M9 Tohoku earthquake and its aftermath. We show that the size distribution of earthquakes has significantly changed before (increased fraction of larger magnitudes) and after that mainshock (increased fraction of smaller magnitudes), strongest in areas of highest coseismic slip. Remarkably, a rapid recovery of this effect is observed within only few years. We combine this significant temporal variability in earthquake size distributions with local activity rates and infer the evolution of NRP distributions. We study complex spatial patterns and how they evolve, and more detailed temporal characteristics in a simplified spatial selection, i.e. inside and outside the high slip zone of the M9 earthquake. We resolve an immediate and strong NRP increase for large events prior to the Tohoku event in the subsequent high slip patch and a very rapid decrease inside this high-stress-release area, coupled with a lasting increase of NRP in the immediate surroundings. Even in the center of the Tohoku

  19. Late Cenozoic deformation of the Da'an-Dedu Fault Zone and its implications for the earthquake activities in the Songliao basin, NE China

    NASA Astrophysics Data System (ADS)

    Zhongyuan, Yu; Peizhen, Zhang; Wei, Min; Qinghai, Wei; Limei, Wang; Bin, Zhao; Shuang, Liu; Jian, Kang

    2015-08-01

    The Da'an-Dedu Fault Zone is a major tectonic feature cutting through the Songliao Basin from south to north in NE China. Five earthquakes with magnitudes over 5 that occurred during the past 30 years suggest the fault zone is a seismogenic structure with future seismic potential. The structural pattern, tectonic history, Quaternary activity and seismic potential have previously been unknown due to the Quaternary sedimentary coverage and lack of large historic earthquakes (M > 7). In this paper, we use seismic reflection profiles and drilling from petroleum explorations and shallow-depth seismic reflections to study those problems. The total length of the Da'an-Dedu Fault Zone is more than 400 km; modern seismicity delineates it into 4 segments each with a length of 90-100 km. In cross-section view, the folds and associated faults form a complex structural belt with a width of more than 10 km. Shallow-level seismic reflection across the Da'an-Dedu Fault Zone reveals that the Late Quaternary sediments were folded and faulted, indicating its present tectonic activity. The Da'an-Dedu Fault Zone and Songliao Basin have been subjected to three stages of tectonic evolution: a rifting stage characterized by normal faulting and extension (∼145-112 Ma), a prolonged stage of thermal subsidence (∼112-65 Ma), and a tectonic reversal that has been taking place since ∼65 Ma. Our shallow-level reflection profiles show that the folding and reverse faulting have influenced the Late Quaternary sediments. The seismicity and moderate earthquakes suggest that the tectonic activity persists today. The deformation rate across the Da'an-Dedu Fault Zone, however, is measured to be very slow. In conjunction with the inference that most deformation in NE China may be taken up by the Yilan-Yitong Fault Zone bounding the Songliao Basin to the east, we suggest moderate earthquake potential and thus moderate seismic hazards along the Da'an-Dedu Fault Zone. The geological structures, which

  20. 3D seismic imaging of an active, normal fault zone in southern Apennines (Italy): Clues on fluid-driven microearthquake fracturing

    NASA Astrophysics Data System (ADS)

    Amoroso, O.; Zollo, A.; Virieux, J.

    2012-12-01

    Lagonegro units located in the axial sector is well reproduced by the low P-wave anomalies ranging between 4.0-4.5 km/s. Their eastward extension is just above the Apulian Platform in the depth range between 4.0 and 8.0 km . The seismicity spatial distribution delineates at SE the border of the Irpinia master fault, while at NE it shows a more diffused pattern due to the presence of a system of highly organized, sub-parallel normal faults as it has been inferred from the fault mechanisms and the coherent orientation of the tensional axes. The Vp/Vs ratio shows a large variability ranging from 1.7-1.8 at shallow depths and increasing up to 2-2.2 between 5 km and 12 km depths, where most of present microseismicity occurs. Such high values are a strong proxy for a fluid-saturated state of rock formations and of their inner pore pressure conditions. The evidence for a predominant microearthquake activity confined within the volume of highest Vp/Vs ratio indicates that pore pressure changes induced by fluid flow/diffusion in a highly fractured medium, may be the primary mechanism controlling and driving the background seismic activity along the Irpinia fault zone.

  1. Compilation of selected faults and lineaments that may be relevant to a study of seismic activity in southern Nevada and part of adjacent California

    SciTech Connect

    Bucknam, R.C.

    1983-02-01

    The enclosed preliminary map shows selected prominent faults and regional topographic lineaments that may be relevant to a study of known or potential seismic activity in the California-southern Nevada region surrounding the Nevada Test Site.

  2. Modeling crustal deformation near active faults and volcanic centers: a catalog of deformation models and modeling approaches

    USGS Publications Warehouse

    Battaglia, Maurizio; ,; Peter, F.; Murray, Jessica R.

    2013-01-01

    This manual provides the physical and mathematical concepts for selected models used to interpret deformation measurements near active faults and volcanic centers. The emphasis is on analytical models of deformation that can be compared with data from the Global Positioning System (GPS) receivers, Interferometric synthetic aperture radar (InSAR), leveling surveys, tiltmeters and strainmeters. Source models include pressurized spherical, ellipsoidal, and horizontal penny-shaped geometries in an elastic, homogeneous, flat half-space. Vertical dikes and faults are described following the mathematical notation for rectangular dislocations in an elastic, homogeneous, flat half-space. All the analytical expressions were verified against numerical models developed by use of COMSOL Multyphics, a Finite Element Analysis software (http://www.comsol.com). In this way, typographical errors present were identified and corrected. Matlab scripts are also provided to facilitate the application of these models.

  3. K-Ar age data of clay fault gouges from some major Neoalpine faults

    NASA Astrophysics Data System (ADS)

    Pleuger, J.; Zwingmann, H.; Mancktelow, N.; Manser, M.

    2012-04-01

    In the Central Alps, the Insubric Phase in the sense of Argand (1916, Eclogae geol. Helv. 14, 145-191) was related to underthrusting of South Alpine units below the Penninic nappes along the Periadriatic Fault. Several other large-scale faults were active during the same, though not always the entire, Oligocene to Miocene time span. These faults form an array interpreted as to result from the partitioning of strain induced by the crustal convergence between the European and Adriatic plates (e.g. Handy et al. 2005, Geol. Soc. Spec. Publ. 243, 249-276). With ongoing Alpine convergence and deformation during exhumation there is a general progression from ductile to brittle behaviour on the Periadriatic Fault and kinematically related faults further north (e.g. the Simplon Rhone Fault and a diffuse, discontinous zone of generally dextral strike-slip movement on the southern boundary of the Aar massif). K-Ar dating of fine grained illite from clay fault gouges provides a reliable method for establishing the approximate time of faulting. New results establish that brittle faulting on the northeastern segment of the Canavese Fault (i.e. the part of the Periadriatic Fault SW of Val d'Ossola) occurred around 20 Ma, with south-side-up kinematics. An age of ca. 17 Ma for the crosscutting Giudicarie Fault in the Eastern Alps is effectively identical with an already published pseudotachylyte age and places a lower limit on major and continuous strike slip movements the Periadriatic Fault. The age of brittle faulting further north, on the southern border of the Aar massif, is from 13.6±0.3 to 8.3±1.1 Ma, consistent with the younger cooling and exhumation in this area. The dominantly dextral brittle faulting becoming younger to the north reflects the continued indentation and anticlockwise rotation of Adria as Alpine units become exhumed and progressively welded to the southern block. In contrast to the eastern Alps, there is no field evidence for (westward) lateral extrusion

  4. Recognition of coseismic-related microstructures and behaviour of clay minerals within the core of active fault

    NASA Astrophysics Data System (ADS)

    Buatier, M.; Chauvet, A.; Ritz, J.; Jolivet, M.; Bayarjargal, B.; Vitalie, M.; Vassalo, R.

    2008-12-01

    Seismogenic faults are commonly characterized by a zonation with foliated gouge and breccias surrounded by damage zone. This zonation results from co-seismic or inter-seismic deformation and fluid-rock interactions. Based on field, textural, microtextural and clay mineralogical analysis, the core zone of an active fault located in the Bogd Mongolian massif has been studied. This fault is supposed to be an ancient major ductile shear zone re-activated during the Quaternary. Field studies reveal the complexity of the fault cores with the association between fragmented/ brecciated domains and at least two generations of gouge. The first gouge presents a foliated structure. The second one is characterized by an homogeneous black, thin, fine-grained, gouge. According to field constraints, the thin gouge level can correspond to the last seismic event. Catholuminescence and SEM investigations allow to characterize the texture of each gouge and surrounding rocks. Additional measurement of grain size distribution, grain circularity, grain shape and grain fabrics allow the clear distinction between the two different gouge textures: foliated and isotropic. In the foliated gouge, mineralogical study (SEM-BSE and DRX) displays evidence of fluid-rock interactions with alteration of micas to illite/smectite and formation of kaolinite. The presence of authigenic gypsum crystals and Fe-oxyhydroxyde suggests interseismic fluid circulation in this permeable structure. The last generation of gouge with isotropic texture is clay rich and is characterized by the presence of smectite (hydrated clay mineral). The data suggest polyphase deformation with ductile structures associated with brittle deformation implying communition process. The debate concerns the mode of formation of the gouge and the origin of clay minerals.

  5. Recent faulting and active shortening of the Middle Atlas Mountains, Morocco, within the diffuse African-Eurasian plate boundary

    NASA Astrophysics Data System (ADS)

    Rigby, M.; Gomez, F.; Zakir, A.; Hahou, Y.; Jabour, N.

    2007-12-01

    The NE-SW trending Middle Atlas Mountains are an active intracontinental mountain belt within the diffuse African - Eurasian plate boundary. The mountain belt is obliquely oriented to the NNW-SSE direction of Late Cenozoic plate convergence. Both shear and compressional features are exhibited with apparent slip partitioning: Folding and thrusting is concentrated in the Folded Middle Atlas, whereas strike-slip dominates in the Tabular Middle Atlas. In the central part of the Folded Middle Atlas, fault scarps of Quaternary alluvium, including a 4.5 meter (probably composite) scarp and a 1 meter (possibly single event) scarp, attest to recent faulting along the mountain front. Detailed topographic mapping of the scarps provides a basis for geomorphic analysis and degradation modeling. Furthermore, the reconstruction of longitudinal stream terrace profiles helps constrain a long term deformation history. Radiocarbon and pending cosmogenic dates provide age constraints on the faulted surfaces and the multiple stream terraces in the area. To place these active tectonic observations in a larger context, the fault and fold geometry has been assessed by completing a 10 km structural transect across the frontal thrust, providing basis for the construction of a balanced cross-section. By combining the structural geometry with the uplift rate, a minimum estimate of the rate of horizontal shortening in the Middle Atlas can be evaluated. Preliminary results suggest the Middle Atlas may accommodate 5 - 10 percent of the total 4.5 mm/yr convergence between the African and Eurasian plates. These results demonstrate that the Middle Atlas Mountains are a integral part of the diffuse plate boundary, as well as suggesting a modest level of earthquake hazard in the region.

  6. Cenozoic Tectonic Activity of the "Passive" North America Margin: Evidence for Cenozoic Activity on Mesozoic or Paleozoic Faults

    NASA Astrophysics Data System (ADS)

    Nedorub, O. I.; Knapp, C. C.

    2012-12-01

    The tectonic history of the Eastern North American Margin (ENAM) incorporates two cycles of continental assembly, multiple pulses of orogeny, rifting, and post-rift geodynamic evolution. This is reflected in the heterogeneous lithosphere of the ENAM which contains fault structures originated in Paleozoic to Mesozoic eras. The South Georgia Rift basin is probably the largest Mesozoic graben within its boundaries that is associated with the breakup of Pangea. It is composed of smaller sub-basins which appear to be bounded by high-angle normal faults, some of which may have been inverted in late Cretaceous and Cenozoic eras. Paleozoic structures may have been reactivated in Cenozoic time as well. The ENAM is characterized by N-NE maximum horizontal compressive stress direction. This maximum compressional stress field is sub-parallel to the strike of the Atlantic Coast province fault systems. Camden, Augusta, Allendale, and Pen Branch faults are four of the many such reactivated faults along the southern part of ENAM. These faults are now buried under the 0-400 m of loosely consolidated Cretaceous and Cenozoic age sediments and thus are either only partially mapped or currently not recognized. Some of the objectives of this study are to map the subsurface expression and geometry of these faults and to investigate the post Cretaceous deformation and possible causes of fault reactivation on a passive margin. This study employs an integrated geophysical approach to investigate the upper 200 m of identified locations of the above mentioned faults. 2-D high-resolution shallow seismic reflection and refraction methods, gravity surveys, GPR, 2-D electrical resistivity and well data are used for analyses and interpretation. Preliminary results suggest that Camden fault shows signs of Cenozoic reactivation through an approximately 30 m offset NW side up mainly along a steeply dipping fault zone in the basal contact of Coastal Plain sediments with the Carolina Piedmont. Drill

  7. Active tectonics of the Devils Mountain Fault and related structures, northern Puget Lowland and eastern Strait of Juan de Fuca region, Pacific Northwest

    USGS Publications Warehouse

    Johnson, Samuel Y.; Dadisman, Shawn V.; Mosher, David C.; Blakely, Richard J.; Childs, Jonathan R.

    2001-01-01

    Information from marine high-resolution and conventional seismic-reflection surveys, aeromagnetic mapping, coastal exposures of Pleistocene strata, and lithologic logs of water wells is used to assess the active tectonics of the northern Puget Lowland and eastern Strait of Juan de Fuca region of the Pacific Northwest. These data indicate that the Devils Mountain Fault and the newly recognized Strawberry Point and Utsalady Point faults are active structures and represent potential earthquake sources.

  8. Stresslets Induced by Active Swimmers

    NASA Astrophysics Data System (ADS)

    Lauga, Eric; Michelin, Sébastien

    2016-09-01

    Active particles disturb the fluid around them as force dipoles, or stresslets, which govern their collective dynamics. Unlike swimming speeds, the stresslets of active particles are rarely determined due to the lack of a suitable theoretical framework for arbitrary geometry. We propose a general method, based on the reciprocal theorem of Stokes flows, to compute stresslets as integrals of the velocities on the particle's surface, which we illustrate for spheroidal chemically active particles. Our method will allow tuning the stresslet of artificial swimmers and tailoring their collective motion in complex environments.

  9. Spatial distribution of soil radon as a tool to recognize active faulting on an active volcano: the example of Mt. Etna (Italy).

    PubMed

    Neri, Marco; Giammanco, Salvatore; Ferrera, Elisabetta; Patanè, Giuseppe; Zanon, Vittorio

    2011-09-01

    This study concerns measurements of radon and thoron emissions from soil carried out in 2004 on the eastern flank of Mt. Etna, in a zone characterized by the presence of numerous seismogenic and aseismic faults. The statistical treatment of the geochemical data allowed recognizing anomaly thresholds for both parameters and producing distribution maps that highlighted a significant spatial correlation between soil gas anomalies and tectonic lineaments. The seismic activity occurring in and around the study area during 2004 was analyzed, producing maps of hypocentral depth and released seismic energy. Both radon and thoron anomalies were located in areas affected by relatively deep (5-10 km depth) seismic activity, while less evident correlation was found between soil gas anomalies and the released seismic energy. This study confirms that mapping the distribution of radon and thoron in soil gas can reveal hidden faults buried by recent soil cover or faults that are not clearly visible at the surface. The correlation between soil gas data and earthquakes depth and intensity can give some hints on the source of gas and/or on fault dynamics. PMID:21704438

  10. Spatial distribution of soil radon as a tool to recognize active faulting on an active volcano: the example of Mt. Etna (Italy).

    PubMed

    Neri, Marco; Giammanco, Salvatore; Ferrera, Elisabetta; Patanè, Giuseppe; Zanon, Vittorio

    2011-09-01

    This study concerns measurements of radon and thoron emissions from soil carried out in 2004 on the eastern flank of Mt. Etna, in a zone characterized by the presence of numerous seismogenic and aseismic faults. The statistical treatment of the geochemical data allowed recognizing anomaly thresholds for both parameters and producing distribution maps that highlighted a significant spatial correlation between soil gas anomalies and tectonic lineaments. The seismic activity occurring in and around the study area during 2004 was analyzed, producing maps of hypocentral depth and released seismic energy. Both radon and thoron anomalies were located in areas affected by relatively deep (5-10 km depth) seismic activity, while less evident correlation was found between soil gas anomalies and the released seismic energy. This study confirms that mapping the distribution of radon and thoron in soil gas can reveal hidden faults buried by recent soil cover or faults that are not clearly visible at the surface. The correlation between soil gas data and earthquakes depth and intensity can give some hints on the source of gas and/or on fault dynamics.

  11. Complex Paleotopography and Faulting near the Elsinore Fault, Coyote Mountains, southern California

    NASA Astrophysics Data System (ADS)

    Brenneman, M. J.; Bykerk-Kauffman, A.

    2012-12-01

    The Coyote Mountains of southern California are bounded on the southwest by the Elsinore Fault, an active dextral fault within the San Andreas Fault zone. According to Axen and Fletcher (1998) and Dorsey and others (2011), rocks exposed in these mountains comprise a portion of the hanging wall of the east-vergent Salton Detachment Fault, which was active from the late Miocene-early Pliocene to Ca. 1.1-1.3 Ma. Detachment faulting was accompanied by subsidence, resulting in deposition of a thick sequence of marine and nonmarine sedimentary rocks. Regional detachment faulting and subsidence ceased with the inception of the Elsinore Fault, which has induced uplift of the Coyote Mountains. Detailed geologic mapping in the central Coyote Mountains supports the above interpretation and adds some intriguing details. New discoveries include a buttress unconformity at the base of the Miocene/Pliocene section that locally cuts across strata at an angle so high that it could be misinterpreted as a fault. We thus conclude that the syn-extension strata were deposited on a surface with very rugged topography. We also discovered that locally-derived nonmarine gravel deposits exposed near the crest of the range, previously interpreted as part of the Miocene Split Mountain Group by Winker and Kidwell (1996), unconformably overlie units of the marine Miocene/Pliocene Imperial Group and must therefore be Pliocene or younger. The presence of such young gravel deposits on the crest of the range provides evidence for its rapid uplift. Additional new discoveries flesh out details of the structural history of the range. We mapped just two normal faults, both of which were relatively minor, thus supporting Axen and Fletcher's assertion that the hanging wall block of the Salton Detachment Fault had not undergone significant internal deformation during extension. We found abundant complex synthetic and antithetic strike-slip faults throughout the area, some of which offset Quaternary alluvial

  12. Compression-induced stacking fault tetrahedra around He bubbles in Al

    SciTech Connect

    Shao, Jian-Li Wang, Pei; He, An-Min

    2014-10-28

    Classic molecular dynamics methods are used to simulate the uniform compression process of the fcc Al containing He bubbles. The formation of stacking fault tetrahedra (SFTs) during the collapse of He bubbles is found, and their dependence on the initial He bubble size (0.6–6 nm in diameter) is presented. Our simulations indicate only elastic deformation in the samples for the He bubble size not more than 2 nm. Instead, increasing the He bubble size, we detect several small SFTs forming on the surface of the He bubble (3 nm), as well as the two intercrossed SFTs around the He bubbles (4–6 nm). All these SFTs are observed to be stable under further compression, though there may appear some SF networks outside the SFTs (5–6 nm). Furthermore, the dynamic analysis on the SFTs shows that the yield pressure keeps a near-linear increase with the initial He bubble pressure, and the potential energy of Al atoms inside the SFTs is lower than outside because of their gliding inwards. In addition, the pressure increments of 2–6 nm He bubbles with strain are less than that of Al, which just provides the opportunity for the He bubble collapse and the SFTs formation. Note that the current work only focuses on the case that the number ratio between He atoms and Al vacancies is 1:1.

  13. Insights into Surface Manifestation of Aseismic vs. Coseismic Strike-Slip Faulting from UAV Imagery of Creep-Induced Surface Fracturing Along the Central San Andreas Fault

    NASA Astrophysics Data System (ADS)

    Bunds, M. P.; Toke, N. A.; Lawrence, A.; Arrowsmith, R.; Salisbury, J. B.

    2015-12-01

    Left-stepping en echelon fractures formed at the Dry Lake Valley paleoseismic site (DLV, 36.470N, 121.057W) on the central creeping segment of the San Andreas Fault (SAF) during the 2012-14 drought. The fractures were investigated using high resolution DEMs and orthophotos made by applying Structure from Motion processing to photos taken using a UAV and handheld cameras on 9/20/2014. At DLV the SAF is marked by a distinctive 2-7 m high west-facing scarp that extends northwestward from a dilational step-over. The orthophotos and DEMs were used to measure 110 fractures along a 37 m section of scarp and 15 additional fracture sets along a further 79 m of scarp. The fractures averaged 54 cm long by 1.8 cm wide with 22% overlap, and were mode 1 opening fractures that on average trended 184o, nearly perpendicular to the maximum extension direction for right-lateral slip along the 144o - trending SAF. The fractures occurred in ~5 m long sets that were themselves left-stepping, on average trended 159o, and were confined to a 3-4 m wide zone along the fault scarp. We interpret the fracture sets to be incipient Riedel shears with a component of extension across them based on the orientation of the sets relative to the SAF, the obliquity of the individual fractures to the trend of the sets, and the presence of topographic lows along them. We conservatively estimate 2.5 ± 1 cm of right-lateral creep on the SAF was recorded in the opening of the fractures, which probably began forming at most 21 months before the photographic survey based on precipitation records and prior site inspection. From these results and the 2.5-3.2 cm/yr creep rate for the SAF, we infer that at least ~30%, and probably 50-80% or more of creep occurs along the narrow 5-50 m wide primary geomorphic expression of the fault, and that the same amount of creep can be accommodated by brittle fracturing in a narrow 3-4 m wide zone along the fault scarp during drought periods. In comparison to seismically

  14. Insights into Surface Manifestation of Aseismic vs. Coseismic Strike-Slip Faulting from UAV Imagery of Creep-Induced Surface Fracturing Along the Central San Andreas Fault

    NASA Astrophysics Data System (ADS)

    Bunds, M. P.; Toke, N. A.; Lawrence, A.; Arrowsmith, R.; Salisbury, J. B.

    2014-12-01

    Left-stepping en echelon fractures formed at the Dry Lake Valley paleoseismic site (DLV, 36.470N, 121.057W) on the central creeping segment of the San Andreas Fault (SAF) during the 2012-14 drought. The fractures were investigated using high resolution DEMs and orthophotos made by applying Structure from Motion processing to photos taken using a UAV and handheld cameras on 9/20/2014. At DLV the SAF is marked by a distinctive 2-7 m high west-facing scarp that extends northwestward from a dilational step-over. The orthophotos and DEMs were used to measure 110 fractures along a 37 m section of scarp and 15 additional fracture sets along a further 79 m of scarp. The fractures averaged 54 cm long by 1.8 cm wide with 22% overlap, and were mode 1 opening fractures that on average trended 184o, nearly perpendicular to the maximum extension direction for right-lateral slip along the 144o - trending SAF. The fractures occurred in ~5 m long sets that were themselves left-stepping, on average trended 159o, and were confined to a 3-4 m wide zone along the fault scarp. We interpret the fracture sets to be incipient Riedel shears with a component of extension across them based on the orientation of the sets relative to the SAF, the obliquity of the individual fractures to the trend of the sets, and the presence of topographic lows along them. We conservatively estimate 2.5 ± 1 cm of right-lateral creep on the SAF was recorded in the opening of the fractures, which probably began forming at most 21 months before the photographic survey based on precipitation records and prior site inspection. From these results and the 2.5-3.2 cm/yr creep rate for the SAF, we infer that at least ~30%, and probably 50-80% or more of creep occurs along the narrow 5-50 m wide primary geomorphic expression of the fault, and that the same amount of creep can be accommodated by brittle fracturing in a narrow 3-4 m wide zone along the fault scarp during drought periods. In comparison to seismically

  15. Activation of Fault Structures South of the La Habra Earthquake Rupture As Evidenced By UAVSAR Imaging

    NASA Astrophysics Data System (ADS)

    Donnellan, A.; Parker, J. W.; Grant Ludwig, L.; Hauksson, E.

    2014-12-01

    The 28 March, 2014 M 5.2 La Habra earthquake occurred on a northeast striking, northwest dipping left-lateral oblique thrust fault at the northeastern margin of the LA Basin, where regional right-lateral shear is accommodated by major northwest trending faults of the Peninsular Ranges, and north-south shortening is accommodated by north-dipping thrust faults and east-west trending folds of the Transverse Ranges. The La Habra mainshock location and focal mechanism is northwest of but sub-parallel to the Puente Hills thrust fault. Relocated seismicity highlights a northeast-trending rupture plane consistent with the magnitude and focal mechanism of the event. NASA's UAVSAR L-Band radar instrument was flown for north and south looking lines before the earthquake on 22 January 2014. The north looking line was reflown three days after the earthquake on 31 March, 2014, and the south looking line was reflown a week later on 4 April 2014. The UAVSAR Repeat Pass Interferogram (RPI) products show deformation consistent with the location of the mainshock beneath the town of La Habra. The results also show considerable aseismic northward horizontal deformation with minor uplift in the West Coyote Hills, south of the relocated seismicity. Inversion of the combined interferograms is consistent with south dipping low-angle (7°) shallow slip that corresponds to bedding plane attitudes and a mapped unconformity. The entire West Coyote Hills show 37 mm of modeled northward slip with an additional 34 mm of modeled slip concentrated near the Coyote Hills Park northeast of the intersection of Rosecrans Avenue and North Gilbert Street. A narrow band of shortening was also observed with UAVSAR, and confirmed with on-the-ground field observations, at the Trojan Way Kink Band, nearly one fault dimension southwest of the main rupture.

  16. Estimate of the post-Last Glacial Maximum tectonic subsidence and attempt to elucidate the subsurface geometry of the active Shanchiao Fault in the Taipei metropolis, Taiwan

    NASA Astrophysics Data System (ADS)

    Chen, C.; Lee, J.; Chan, Y.; Lu, C.; Teng, L. S.

    2011-12-01

    The Taipei Metropolis, home to some 10 million people, is subject to seismic hazard originated from not only ground shaking in thick alluvial deposits due to distant faults or sources scattered throughout the Taiwan region, but also active faulting directly underneath. Northern Taiwan including the Taipei region is currently affected by post-orogenic (Plio-Pleistocene 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 the areal extent and magnitude of its recent activity. Based on the growth faulting analysis in the Wuku profile in the central portion of the fault, one key horizon - the top of the Jingmei Conglomerate which was an alluvial fan formed rapidly when a major drainage reorganization occurred during the Last Glacial Maximum - serves to be the marker of tectonic subsidence since its inception around 23 ka. A determination and compilation of the depths of the Jingmei Conglomerate top horizon from nearly 500 borehole records within the Taipei Basin demonstrates that the hanging-wall deforms in a roll-over fashion and the offset is largest in the Wuku-Luzhou area in the central portion of the fault and decreases toward the southern tip of the fault. A geologic profile across the fault zone in the Luzhou area reveals the similar main-branch fault half-negative flower structural pattern observed in the Wuku profile, a phenomenon we interpreted to be originated from the geometry of the basin basement and the strong rheological contrast between unconsolidated basin sediments and basement rocks. We also attempt to resolve the poorly-known subsurface geometry of the Shanchiao Fault by simple elastic dislocation models. The surface deformation recorded by the above compilation is representative of the latest Quaternary period as it spans probably more than 10 earthquake

  17. On the Origin and Distribution of Fracture Damage Surrounding Strike-Slip Fault Zones

    NASA Astrophysics Data System (ADS)

    Mitchell, T. M.; Faulkner, D. R.

    2006-12-01

    with distance. We believe we have successfully isolated fracture damage which is related to fault tip processes, and the damage zone width scales linearly with the active fault length (proportional to fault displacement), which is consistent with a post- yield fracture mechanics model. Macrofractures are a combination of shear and opening mode, but a significant proportion also occur at a high angle to the main fault trace, which may be related to dynamic loading or hydrofracturing with the greatest principal stress oriented at a high angle to the fault trace. It has been thought that the overall fault structure of large displacement zones is established early in a fault's history. We interpret the microfracture damage surrounding the faults studied accumulated as a result of the initial process zone migration; geometrical irregularities on the fault plane and dynamic loading have also contributed to off-fault damage, although this is less well understood. Early fault damage zone width scales with displacement, and core structure becomes more complex with increased displacement. By separating damage from fault tip processes from dynamic slip induced damage, we can make better estimates of fracture energies related to slip events, and also better understand how fault zone permeability evolves with time.

  18. Active fault detection and isolation of discrete-time linear time-varying systems: a set-membership approach

    NASA Astrophysics Data System (ADS)

    Mojtaba Tabatabaeipour, Seyed

    2015-08-01

    Active fault detection and isolation (AFDI) is used for detection and isolation of faults that are hidden in the normal operation because of a low excitation signal or due to the regulatory actions of the controller. In this paper, a new AFDI method based on set-membership approaches is proposed. In set-membership approaches, instead of a point-wise estimation of the states, a set-valued estimation of them is computed. If this set becomes empty the given model of the system is not consistent with the measurements. Therefore, the model is falsified. When more than one model of the system remains un-falsified, the AFDI method is used to generate an auxiliary signal that is injected into the system for detection and isolation of faults that remain otherwise hidden or non-isolated using passive FDI (PFDI) methods. Having the set-valued estimation of the states for each model, the proposed AFDI method finds an optimal input signal that guarantees FDI in a finite time horizon. The input signal is updated at each iteration in a decreasing receding horizon manner based on the set-valued estimation of the current states and un-falsified models at the current sample time. The problem is solved by a number of linear and quadratic programming problems, which result in a computationally efficient algorithm. The method is tested on a numerical example as well as on the pitch actuator of a benchmark wind turbine.

  19. Knickpoint series of gullies along the Luoyunshan Piedmont and its relation with fault activity since late Pleistocene

    NASA Astrophysics Data System (ADS)

    Sun, Changbin; Wan, Tianfeng; Xie, Xinsheng; Shen, Xiaoming; Liang, Kuan

    2016-09-01

    The authors surveyed the longitudinal profiles of 28 gullies across the Luoyunshan Piedmont fault (LPF) by differential GPS and dating of sediments well preserved in the typical terraces and obtained 6-level knickpoint series of the gullies along the Luoyunshan Piedmont. The authors compared it with previous studies on the paleo-earthquakes of the LPF revealed by trenches and found that the paleo-earthquake events from knickpoint and trench studies are in good agreement in terms of the time of occurrence and vertical displacement of the fault. It shows studying the paleo-earthquake events of the fault by knickpoint series is feasible. At last, the authors established a more complete paleo-earthquake sequence of the LPF supported by geomorphologic and sedimentary evidence, i.e., six paleo-earthquake events happened on the LPF from about 28,000 years ago; the LPF has the characteristic of quasi-periodic recurrence and the average recurrence interval is 4585 years. The vertical displacement of the paleo-earthquake events is 2.4-3.0 m; according to the empirical equations between co-seismic displacement and earthquake magnitude the magnitude of these events is Ms 7.0-7.5. This study aims to complement and improve the traditional trenching method, provide theoretical and methodological support for the research of active tectonics, and contribute important information for the seismic hazard assessment of the densely populated Linfen area.

  20. Active emergent thrust associated with a detachment fold: A case study of the eastern boundary fault of Takada plain, central Japan

    NASA Astrophysics Data System (ADS)

    Kato, N.; Ishiyama, T.; Sato, H.; Saito, H.; Kurashimo, E.; Abe, S.

    2012-04-01

    To estimate seismic hazards, understanding the relationship between active fault and seismic source fault is crucial. Along the Japan Sea coast of Northern Honshu, Japan, thick sediments, deposited in the Miocene rift-grabens, formed fold-and-thrust belt, due to the shortening deformation since the Pliocene time. Most of the thrusts are active and show clear geomorphological evidences. Some of the thrusts are secondary faults, produced by the folding of competent layers. To elucidate the relationship between an emergent thrust and deep-sited seismogenic source fault, we performed shallow high-resolution seismic reflection profiling across the eastern boundary fault of the Takada plain, central Japan. Based on the moropho-tectonic data, the vertical slip rate of the Eastern boundary fault of the Takada plain is 0.9 mm/y and has potential to produce M7.2 earthquake (AIST, 2006). For shallow structure, we obtained CMP-seismic reflection data from a 7-km-long seismic line, using 541 channels of off-line recorders. Seismic source was an Envirovibe (IVI). Receiver and shot intervals are 12.5 m and seismic signals were recorded by fixed channels. Shallow seismic data were acquired as a piggy-bag project of 70 km-long onshore-offshore deep seismic profiling. High-resolution seismic section portrays the emergent thrust, dipping to the east at about 30 degrees. The hanging wall consist Pliocene interbedded mudstone and sandstone and deeper extension of the thrust can be traced down to the Miocene mudstone of the Teradoamri Formation as a low-angle fault. In the Niigata basin, the lower part of the Teradomari Formation is known as over pressured mudstone and shallow detachments are commonly developed in this unit. Based on the deep seismic section, including velocity profile obtained by refraction tomography, deep sited fault does not connect to the shallow active fault directly.

  1. Solar system fault detection

    NASA Astrophysics Data System (ADS)

    Farrington, R. B.; Pruett, J. C., Jr.

    1984-05-01

    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 combing 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.

  2. 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.

  3. 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.

  4. Active Fault Deformation Along the South Boundary of the Western Transverse Ranges Province, Point Dume to the Northern Channel Islands, Southern California

    NASA Astrophysics Data System (ADS)

    Fisher, M. A.; Langenheim, V. E.; Sorlien, C. C.; Nicholson, C.; Sliter, R. W.

    2005-12-01

    The regional fault system forming the south boundary of the Western Transverse Ranges Province (WTRP) extends for about 200 km, from near the city of Los Angeles westward along the south flank of the Santa Monica Mountains and through the northern Channel Islands. Multichannel seismic-reflection data show that fault strands within the province-bounding system are active, and some have dip-slip displacements measured in kilometers. The left-oblique Dume fault is active and shows large displacement as far west as Sycamore knoll, but farther west, the fault tip and a superjacent fold are deeply buried. Thus during future earthquakes, the structural transition near the knoll could represent a boundary between earthquake-rupture segments. The east-west province-bounding fault system strikes at a high angle across and terminates the northwest-trending faults, basins and ridges of the California Continental Borderland. Borderland structures considered here form the western limit of intense middle Miocene oblique extension that accompanied rotation of the WTRP. The transition between extended and intact crust lies along the northwest-trending Santa Cruz-Catalina and Santa Rosa-Cortes Ridges. After the Miocene rotation,