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Sample records for active fault scarps

  1. 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.

  2. 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.

  3. Holocene fault scarps near Tacoma, Washington, USA

    USGS Publications Warehouse

    Sherrod, B.L.; Brocher, T.M.; Weaver, C.S.; Bucknam, R.C.; Blakely, R.J.; Kelsey, H.M.; Nelson, A.R.; Haugerud, R.

    2004-01-01

    Airborne laser mapping confirms that Holocene active faults traverse the Puget Sound metropolitan area, northwestern continental United States. The mapping, which detects forest-floor relief of as little as 15 cm, reveals scarps along geophysical lineaments that separate areas of Holocene uplift and subsidence. Along one such line of scarps, we found that a fault warped the ground surface between A.D. 770 and 1160. This reverse fault, which projects through Tacoma, Washington, bounds the southern and western sides of the Seattle uplift. The northern flank of the Seattle uplift is bounded by a reverse fault beneath Seattle that broke in A.D. 900-930. Observations of tectonic scarps along the Tacoma fault demonstrate that active faulting with associated surface rupture and ground motions pose a significant hazard in the Puget Sound region.

  4. Holocene fault scarps in the Western Alps

    NASA Astrophysics Data System (ADS)

    Hippolyte, J. C.

    2003-04-01

    In the Tarentaise Valley, Goguel (1969) had described recent fault scarps. The present work shows that they are normal faults indicating a SE-directed trend of extension in agreement with recent microseismicity data (Sue et al., 1999). It is proposed that they reflect the Quaternary normal reactivation of the "Front du Houiller" thrust fault. In the Belledonne external crystalline massif, Bordet (1970) had observed from helicopter three main fault scarps that he interpreted as active SE-dipping reverse faults. Partly owing to the difficulties of access this area was not visited until now. Field observations reveal that these faults dip in fact 61-68° to the NW, and are normal faults. The faults scarps are 1 to 13 meters high. These faults, together with at least 10 newly discovered conjugate SE-dipping normal fault scarps of 0.5 to 18 meters high, form an about 2 km wide fault zone along the "Synclinal Median" (S.M.) fault. They attest for the activity of this 70 km-long NNE-striking main fault running in the middle of the Belledonne Massif. Its activity is confirmed by major faceted spurs at the La Perche, the La Perrière and the Claran passes, and by ruptures cutting moraines. Other fault scarps are discovered in the whole Belledonne massif showing in particular that the Font-de-France fault, a 60 km-long SE-dipping fault, is also active. All the observed active faults are normal. Their offsets of mountains slopes, of screes and of rock glacier morphologies demonstrate their activity during the Holocene. They indicate a present SE-directed extension in agreement with recent GPS data (Calais et al., 2002). This mapping shows that the present extensional deformation of the Alps is not limited to the west by the "Frontal Pennine thrust" (Sue et al., 1999) but affects also the external Alps. Taking into account focal plane mechanisms, extension affects at least 70 % of the Western Alps. Some scarps have been sampled for Beryllium cosmogenic dating. However

  5. 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.

  6. 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.

  7. Late Quaternary Range-Front Fault Scarps in the Western Sierra El Mayor, Baja California, Mexico: A Geomorphologic Expression of Slip Across an Active Low-Angle Normal Fault

    NASA Astrophysics Data System (ADS)

    Spelz, R. M.; Fletcher, J.; Owen, L.

    2006-12-01

    The western margin of the Sierra El Mayor (SEM), in northeastern Baja California, is controlled by an active, top-to-the-west, low-angle normal fault named the Canada David detachment (CDD) that accommodates part of the extensional component of shearing between the Pacific and North American plates. The CDD has a length of 60 km and shows a curvilinear trace with two major antiformal and synformal megamullion pairs. Late Quaternary slip has produced a broad array of Quaternary scarps cutting alluvial fans along nearly the entire length of the CDD. Detailed mapping reveals eight regional strath terraces distinguished by surface weathering characteristics, soil profile development and relative elevation. Relative height between terraces increases in domains where the CDD and basin deposits are being uplifted due to either the basinward migration of faulting (e.g., rolling hinge) or flexural uplift in antiformal megamullion domains. Linear diffusion analysis of 46 synthetic fault scarps, with a calculated angle of repose Θo = 28.75°, reveal fault scarp domains exhibiting both multi-modal and unimodal distribution of diffusion ages (kt). Uni-modal domains are typically younger, but there is no systematic variation in scarp age with distance along the CDD. Scarps yielding negative kt ages (i.e. scarps steeper than Θo) are common in the north, near inferred locations of important historic seismic events. Microseismicity drops off significantly adjacent to these very young scarp arrays, which likely reflects a recent post-seismic stress drop. Domains of high seismic risk are identified by high microseismicity and lack of young scarps. Minimum estimates of the diffusivity constant (k) are calculated by coupling scarp diffusion ages and 10Be surface exposure ages of the faulted deposits. In the southernmost SEM a Q6 terrace with a minimum surface exposure age t = 233±6.6 ky (weighted mean of six rock samples) is cut by scarps with an average kt = 11.25±9.31 m2, which

  8. Rates of scarp retreat: A means of dating Neotectonic activity

    NASA Astrophysics Data System (ADS)

    Schmidt, Karl-Heinz

    Tectonically induced scraps have attracted much geomorphic and geologic interest in recent years. The distance of a cuesta scarp from a fault line or a domal structure is an age indicator of tectonic movements, if information on the rate of scarp retreat can be obtained. In Southern Morocco rates of retreat were determined by using the information given (1) by dated volcanic or sedimentary material in the foreland of scarps, (2) by gravels that were deposited on the cuesta backslope before the formation of the scarp, and (3) especially by talus relics or sequences of talus relics in the foreland of scarps. The methods were applied to a number of different cuesta scarps in Mio-Pliocene conglomerates, in Paleogene and Cretaceous limestones. The rates of retreat avarage 1,3 km/Mio. years for the thin conglomeratic caprocks, and 0,5 km/Mio. years for the more resistant and thicker limestone caprocks. Sequences of talus relics proved to be most valuable for determining rates of retreat, because the talus and pediment flatirons represent former scarp slope positions. As caprock lithology does not differ very much in the area under investigation the recession rates calculated so far yield a reliable basis for estimating the time of activation of scarps in geodynamically relevant positions. The transition from depositional environments to subaerial erosion in the Pre-Saharan depression happened much earlier between Goulmima and Errachidia (Middle Tertiary) than in the western part (Late Miocene to Early Pliocene).

  9. Holocene Scarp on the Sawtooth Normal Fault, Central Idaho

    NASA Astrophysics Data System (ADS)

    Thackray, G. D.; Rodgers, D. W.; Streutker, D. R.; Kemp, C. D.; Drabick, A. J.

    2006-12-01

    Analysis of LiDAR, air photo, and field data indicates the east-dipping, range-front normal fault of the Sawtooth Mountains has previously unrecognized Holocene offset. A fault scarp is most clearly represented in a bare- earth digital elevation model (DEM) derived from high-resolution LiDAR data. First and last pulse LiDAR data with an average post spacing of 0.5 m were used to compute both bare-earth elevation and local slope values. As the area is forested, vegetation removal was performed using an iterative interpolation method. Holocene fault offset likely extends along at least 23 km of the range front. In the vicinity of Redfish Lake, the scarp can be traced discontinuously for ca. 13 km (the length of LiDAR coverage) along the eastern range-front and cuts glacial, fluvial, and hillslope landforms of Late Pleistocene to Holocene age. Air photo analysis of the range-front north and south of the LiDAR coverage area yields strong evidence, such as topographic offsets, vegetation lineaments, and stream alignments, that late Pleistocene and Holocene faulting likely extends ca. 23 km along the range front, from Decker Creek to Stanley Lake. This zone of clearest postglacial offset corresponds with the highest range front topography in the Sawtooth Range. Weaker evidence suggests that postglacial faulting may extend as much as 10 km further NW of and 17 km further SE of that 23 km section. Scarp geometry and offset vary with location. The fault scarp generally strikes 025 deg. but changes to 040 deg. north of Goat Creek. A single, east-facing scarp is present in some places, such as at Bench Lakes, but more commonly en echelon scarps define a fault zone about 20 m wide. Scarp height, as measured from LiDAR data, ranges from 2.5 to 8 m (typically 3-5 m). Late Pleistocene glacial landforms are offset 4-8 m, while uncommon Holocene fluvial surfaces (e.g., at Fishhook Creek) are offset 2.5 to 3 m. These relationships potentially document two fault ruptures since

  10. Morphologic dating of fault scarps using airborne laser swath mapping (ALSM) data

    USGS Publications Warehouse

    Hilley, G.E.; Delong, S.; Prentice, C.; Blisniuk, K.; Arrowsmith, J.R.

    2010-01-01

    Models of fault scarp morphology have been previously used to infer the relative age of different fault scarps in a fault zone using labor-intensive ground surveying. We present a method for automatically extracting scarp morphologic ages within high-resolution digital topography. Scarp degradation is modeled as a diffusive mass transport process in the across-scarp direction. The second derivative of the modeled degraded fault scarp was normalized to yield the best-fitting (in a least-squared sense) scarp height at each point, and the signal-to-noise ratio identified those areas containing scarp-like topography. We applied this method to three areas along the San Andreas Fault and found correspondence between the mapped geometry of the fault and that extracted by our analysis. This suggests that the spatial distribution of scarp ages may be revealed by such an analysis, allowing the recent temporal development of a fault zone to be imaged along its length.

  11. Nucleation of Waterfalls at Fault Scarps Temporarily Shielded By Alluvial Fan Aggradation.

    NASA Astrophysics Data System (ADS)

    Malatesta, L. C.; Lamb, M. P.

    2014-12-01

    Waterfalls are important components of mountain river systems and they can serve as an agent to transfer tectonic, climatic, or authigenic signals upstream through a catchment. Retreating waterfalls lower the local base level of the adjacent hillslopes, and temporarily increase sediment delivery to the fluvial system. Their creation is often attributed to seismic ruptures, lithological boundaries, or the coalescence of multiple smaller steps. We explore here a mechanism for the nucleation of waterfalls that does not rely on sudden seismic slip but on the build-up of accumulated slip during periods of fault burial by fluvial aggradation. Alluvial fans are common features at the front of mountain ranges bound by normal or thrust faults. Climate change or internal forcing in the mountain catchment modifies the equilibrium slope of alluvial fans. When alluvial fans aggrade, they shield the active fault scarp from fluvial erosion allowing the scarp to grow undisturbed. The scarp may then be exposed when the channel incises into the fan exposing a new bedrock waterfall. We explore this mechanism analytically and using a numerical model for bedrock river incision and sediment deposition. We find that the creation of waterfalls by scarp burial is limited by three distinct timescales: 1) the critical timescale for the scarp to grow to the burial height, 2) the timescale of alluvial re-grading of the fan, and 3) the timescale of the external or internal forcing, such as climate change. The height of the waterfall is controlled by i) the difference in equilibrium alluvial-fan slopes, ii) the ratio of the respective fan and catchment sizes, iii) the catchment wide denudation rate, and iv) the fault slip rate. We test whether an individual waterfall could be produced by alluvial shielding of a scarp, and identify the tectonic, climatic, or authigenic nature of waterfalls using example field sites in the southwest United States.

  12. Characterizing the Iron Wash fault: A fault line scarp in Utah

    NASA Astrophysics Data System (ADS)

    Kozaci, O.; Ostenaa, D.; Goodman, J.; Zellman, M.; Hoeft, J.; Sowers, J. M.; Retson, T.

    2015-12-01

    The Iron Wash fault (IWF) is an approximately 30 mile-long, NW-SE trending structure, oriented perpendicular to the San Rafael Monocline near Green River in Utah. IWF exhibits well-expressed geomorphic features such as a linear escarpment with consistently north side down displacement. The fault coincides with an abrupt change in San Rafael Monocline dip angle along its eastern margin. The IWF is exposed in incised drainages where Jurassic Navajo sandstone (oldest) and Lower Carmel Formation (old), are juxtaposed against Jurassic Entrada sandstone (younger) and Quaternary alluvium (youngest). To assess the recency of activity of the IWF we performed detailed geomorphic mapping and a paleoseismic trenching investigation. A benched trench was excavated across a Quaternary fluvial terrace remnant across the mapped trace of the IWF. The uppermost gravel units and overlying colluvium are exposed in the trench across the projection of the fault. In addition, we mapped the basal contact of the Quaternary gravel deposit in relation to the adjacent fault exposures in detail to show the geometry of the basal contact near and across the fault. We find no evidence of vertical displacement of these Quaternary gravels. A preliminary U-series date of calcite cementing unfaulted fluvial gravels and OSL dating of a sand lens within the unfaulted fluvial gravels yielded approximately 304,000 years and 78,000 years, respectively. These preliminary results of independent dating methods constrains the timing of last activity of the IWF to greater than 78,000 years before present suggesting that IWF not an active structure. Its distinct geomorphic expression is most likely the result of differential erosion, forming a fault-line scarp.

  13. Micro-geomorphology Surveying and Analysis of Xiadian Fault Scarp, China

    NASA Astrophysics Data System (ADS)

    Ding, R.

    2014-12-01

    Historic records and field investigations reveal that the Mw 8.0 Sanhe-Pinggu (China) earthquake of 1679 produced a 10 to 18 km-long surface rupture zone, with dominantly dip-slip accompanied by a right-lateral component along the Xiadian fault, resulting in extensive damage throughout north China. The fault scarp that was coursed by the co-seismic ruptures from Dongliuhetun to Pangezhang is about 1 to 3 meters high, and the biggest vertical displacement locates in Pangezhuang, it is easily to be seen in the flat alluvial plain. But the 10 to 18 km-long surface rupture couldn't match the Mw 8.0 earthquake scale. After more than 300 years land leveling, the fault scarps in the meizoseismal zone which is farmland are retreat at different degree, some small scarps are becoming disappeared, so it is hard to identify by visual observation in the field investigations. The meizoseismal zone is located in the alluvial plain of the Chaobai river and Jiyun river, and the fault is perpendicular to the river. It is easy to distinguish fault scarps from erosion scarps. Land leveling just changes the slope of the fault scarp, but it can't eliminate the height difference between two side of the fault. So it is possible to recover the location and height of the fault scarp by using Digital Elevation Model (DEM) analysis and landform surveying which is constrained by 3D centimeter-precision RTK GPS surveying method in large scale crossing the fault zone. On the base of the high-precision DEM landform analysis, we carried out 15 GPS surveying lines which extends at least 10km for each crossing the meizoseismal zone. Our findings demonstrate that 1) we recover the complete rupture zone of the Sanhe-Pinggu earthquake in 1679, and survey the co-seismic displacement at 15 sites; 2) we conform that the Xiadian fault scarp is consist of three branches with left stepping. Height of the scarp is from 0.5 to 4.0 meters, and the total length of the scarp is at least 50km; 3) Combined with the

  14. Deriving Fault Slip Histories From Cosmogenic Exposure Ages Along Bedrock Fault Scarps Using Synthetic And Natural Data

    NASA Astrophysics Data System (ADS)

    Phillips, R. J.; Cowie, P. A.; Walker, M. J.; Roberts, G.; Dunai, T. J.; Zijerveld, L.; Wilkinson, M. W.; McCaffrey, K. J.; Bubeck, A. A.

    2010-12-01

    Cosmogenic surface exposure dating is a powerful tool for reconstructing long term slip rates on active faults and may provide evidence for temporal earthquake clustering (e.g. Benedetti et al., GRL, v.29, 2002). Extensional faults in limestone are particularly amenable to this type of study because they commonly produce a striated bedrock scarp, exhumed by faulting, that can be sampled to obtain the cosmogenic 36Cl concentration as a function of throw. The number of earthquakes, their timing and the magnitude of the associated slip strongly influence the shape of 36Cl profile. Existing methods for extracting paleo-earthquake records from such data use forward modelling and conclude that individual slip events ≥1m (≥ Magnitude 7.0) may be resolved although a cluster of smaller magnitude events produce a similar 36Cl variation. Due to uneven scarp preservation sample spacing in real data sets is variable (up to 10’s cm), further limiting our ability to extract tectonic information. Here we carry out a Monte Carlo inversion on synthetic 36Cl data sets to investigate the effect of sample spacing and analytical error on the interpretation of fault slip histories. We transform the 36Cl concentration versus height data into a linear form. For a given set of fault slip events, event timings are determined using least squares inversion of the linearised data. By searching all possible combinations of slip event size (ranging from the sampling interval to the total scarp height), and using a range of different statistical measures for the goodness of fit, we rank the best fit scenario(s). By applying this approach to synthetic 36Cl profiles, generated using a numerical fault growth model, we show how sample density and analytical error influence our interpretation of the true slip history (which for the synthetic data is known). We find that determining the timing of specific earthquakes requires (quasi-) uniform as well as dense sampling (5cm spacing), whereas long

  15. Fault Scarp Detection Beneath Dense Vegetation Cover: Airborne Lidar Mapping of the Seattle Fault Zone, Bainbridge Island, Washington State

    NASA Technical Reports Server (NTRS)

    Harding, David J.; Berghoff, Gregory S.

    2000-01-01

    The emergence of a commercial airborne laser mapping industry is paying major dividends in an assessment of earthquake hazards in the Puget Lowland of Washington State. Geophysical observations and historical seismicity indicate the presence of active upper-crustal faults in the Puget Lowland, placing the major population centers of Seattle and Tacoma at significant risk. However, until recently the surface trace of these faults had never been identified, neither on the ground nor from remote sensing, due to cover by the dense vegetation of the Pacific Northwest temperate rainforests and extremely thick Pleistocene glacial deposits. A pilot lidar mapping project of Bainbridge Island in the Puget Sound, contracted by the Kitsap Public Utility District (KPUD) and conducted by Airborne Laser Mapping in late 1996, spectacularly revealed geomorphic features associated with fault strands within the Seattle fault zone. The features include a previously unrecognized fault scarp, an uplifted marine wave-cut platform, and tilted sedimentary strata. The United States Geologic Survey (USGS) is now conducting trenching studies across the fault scarp to establish ages, displacements, and recurrence intervals of recent earthquakes on this active fault. The success of this pilot study has inspired the formation of a consortium of federal and local organizations to extend this work to a 2350 square kilometer (580,000 acre) region of the Puget Lowland, covering nearly the entire extent (approx. 85 km) of the Seattle fault. The consortium includes NASA, the USGS, and four local groups consisting of KPUD, Kitsap County, the City of Seattle, and the Puget Sound Regional Council (PSRC). The consortium has selected Terrapoint, a commercial lidar mapping vendor, to acquire the data.

  16. Logs and Scarp Data from a Paloseismic Investigation of the Surprise Valley Fault Zone, Modoc County, California

    USGS Publications Warehouse

    Personius, Stephen F.; Crone, Anthony J.; Machette, Michael N.; Lidke, David J.; Bradley, Lee-Ann; Mahan, Shannon

    2007-01-01

    This report contains field and laboratory data from a paleoseismic study of the Surprise Valley fault zone near Cedarville, California. The 85-km-long Surprise Valley fault zone forms the western active margin of the Basin and Range province in northeastern California. The down-to-the-east normal fault is marked by Holocene fault scarps along most of its length, from Fort Bidwell on the north to near the southern end of Surprise Valley. We studied the central section of the fault to determine ages of paleoearthquakes and to better constrain late Quaternary slip rates, which we hope to compare to deformation rates derived from a recently established geodetic network in the region (Hammond and Thatcher, 2005; 2007). We excavated a trench in June 2005 across a prominent fault scarp on pluvial Lake Surprise deltaic sediments near the mouth of Cooks Canyon, 4 km north of Cedarville. This site was chosen because of the presence of a well-preserved fault scarp and its development on lacustrine deposits thought to be suitable for luminescence dating. We also logged a natural exposure of the fault in similar deltaic sediments near the mouth of Steamboat Canyon, 11 km south of Cedarville, to better understand the along-strike extent of surface ruptures. The purpose of this report is to present photomosaics, trench, drill hole, and stream exposure logs; scarp profiles; and fault slip, tephrochronologic, radiocarbon, luminescence, and unit description data obtained during this investigation. We do not attempt to use the data presented herein to construct a paleoseismic history of this part of the Surprise Valley fault zone; that history will be the subject of a future report.

  17. Young thrust-fault scarps in the highlands - Evidence for an initially totally molten moon

    NASA Technical Reports Server (NTRS)

    Binder, A. B.; Gunga, H.-C.

    1985-01-01

    Attention is given to thermoelastic stress calculations implying that if only the outer few hundreds of km of a moon with a cool interior were initially molten, the lunar highlands should not have young compressional tectonic features. Extrapolations from Apollo panoramic images showing young thrust faults in the highlands suggest that about 2000 thrust fault scarps exist on the highlands, generally occurring in series or complexes of four or five scarps that are on average 5 km long. The ages of the scarps range from 60 + or - 30 to 680 + or - 250 my, with a possible factor bias of +2 to -4. The scarps are the youngest endogenic features on the moon, and indicate that the moon was initially molten.

  18. Surveying the Newly Digitized Apollo Metric Images for Highland Fault Scarps on the Moon

    NASA Astrophysics Data System (ADS)

    Williams, N. R.; Pritchard, M. E.; Bell, J. F.; Watters, T. R.; Robinson, M. S.; Lawrence, S.

    2009-12-01

    The presence and distribution of thrust faults on the Moon have major implications for lunar formation and thermal evolution. For example, thermal history models for the Moon imply that most of the lunar interior was initially hot. As the Moon cooled over time, some models predict global-scale thrust faults should form as stress builds from global thermal contraction. Large-scale thrust fault scarps with lengths of hundreds of kilometers and maximum relief of up to a kilometer or more, like those on Mercury, are not found on the Moon; however, relatively small-scale linear and curvilinear lobate scarps with maximum lengths typically around 10 km have been observed in the highlands [Binder and Gunga, Icarus, v63, 1985]. These small-scale scarps are interpreted to be thrust faults formed by contractional stresses with relatively small maximum (tens of meters) displacements on the faults. These narrow, low relief landforms could only be identified in the highest resolution Lunar Orbiter and Apollo Panoramic Camera images and under the most favorable lighting conditions. To date, the global distribution and other properties of lunar lobate faults are not well understood. The recent micron-resolution scanning and digitization of the Apollo Mapping Camera (Metric) photographic negatives [Lawrence et al., NLSI Conf. #1415, 2008; http://wms.lroc.asu.edu/apollo] provides a new dataset to search for potential scarps. We examined more than 100 digitized Metric Camera image scans, and from these identified 81 images with favorable lighting (incidence angles between about 55 and 80 deg.) to manually search for features that could be potential tectonic scarps. Previous surveys based on Panoramic Camera and Lunar Orbiter images found fewer than 100 lobate scarps in the highlands; in our Apollo Metric Camera image survey, we have found additional regions with one or more previously unidentified linear and curvilinear features on the lunar surface that may represent lobate thrust

  19. Are tectonic or erosive processes that happen in faults scarps of main faults of Villavicencio area, Colombia?

    NASA Astrophysics Data System (ADS)

    Leon, L. E.; Chicangana, G.; Acosta-Sabogal, I.; Pardo-Mayorga, J.; Ochoa Gutierrez, L.

    2013-12-01

    Villavicencio (500.000 inhabitants approx.) is the main economic center of Colombian Llanos and for last forty years had a near to 500% population growth. In its metropolitan area are several fault segments related to the Eastern Frontal Fault System how Bavaria, Coladepato, Mirador, Servita and Villavicencio. This fault system is the eastern cortical deformation front of Colombian Eastern Cordillera and defines the orogenic style that characterizes to the Llanos Foothills. According to some authors that they have verified with Apatite fission tracks data, this orogenic style was derivate of high exhumation crust rate that occur in this cordillera sector and that it exceeded to 3 km for last 2.5 million years. Also several authors have indicated for some of these fault segments neotectonics evidences based mainly in morphotectonic features. In this work we has realized an analysis that search define if it is possible find active tectonics evidences in these fault scarps, because in this region the erosive rate is high due to three main factors that contributes to its: High relief, high rainfall annual rate, and human activity. For these analysis we was used some tools how photogeologic data, field data, multi - temporal analysis of aerial and high spatial resolution imagery, and morphometric analysis.

  20. Paleoseismology of a possible fault scarp in Wenas Valley, central Washington

    USGS Publications Warehouse

    Sherrod, Brian L.; Barnett, Elizabeth A.; Knepprath, Nichole; Foit, Franklin F.

    2013-01-01

    In October 2009, two trenches excavated across an 11-kilometer-long scarp at Wenas Valley in central Washington exposed evidence for late Quaternary deformation. Lidar imagery of the Wenas Valley illuminated the west-northwest-trending, 2- to 8-meter-high scarp as it bisected alluvial fans developed at the mouths of canyons along the south side of Umtanum Ridge. The alignment of the scarp and aeromagnetic lineaments suggested that the scarp may be a product of and controlled by the same tectonic structure that produced the magnetic lineaments. Several large landslides mapped in the area demonstrated the potential for large mass-wasting events in the area. In order to test whether the scarp was the result of an earthquake-generated surface rupture or a landslide, trenches were excavated at Hessler Flats and McCabe Place. The profiles of bedrock and soil stratigraphy that underlie the scarp in each trench were photographed, mapped, and described, and a sequence of depositional and deformational events established for each trench. The McCabe Place trench exposed a sequence of volcaniclastic deposits overlain by soils and alluvial deposits separated by three unconformities. Six normal faults and two possible reverse faults deformed the exposed strata. Crosscutting relations indicated that up to five earthquakes occurred on a blind reverse fault, and a microprobe analysis of lapilli suggested that the earliest faulting occurred after 47,000 years before present. The Hessler Flat trench exposure revealed weathered bedrock that abuts loess and colluvium deposits and is overlain by soil, an upper sequence of loess, and colluvium. The latter two units bury a distinctive paloesol.

  1. Depth of faulting and ancient heat flows in the Kuiper region of Mercury from lobate scarp topography

    NASA Astrophysics Data System (ADS)

    Egea-González, Isabel; Ruiz, Javier; Fernández, Carlos; Williams, Jean-Pierre; Márquez, Álvaro; Lara, Luisa M.

    2012-01-01

    Mercurian lobate scarps are interpreted to be the surface expressions of thrust faults formed by planetary cooling and contraction, which deformed the crust down to the brittle-ductile transition (BDT) depth at the time of faulting. In this work we have used a forward modeling procedure in order to analyze the relation between scarp topography and fault geometries and depths associated with a group of prominent lobate scarps (Santa Maria Rupes and two unnamed scarps) located in the Kuiper region of Mercury for which Earth-based radar altimetry is available. Also a backthrust associated with one of the lobate scarps has been included in this study. We have obtained best fits for depths of faulting between 30 and 39 km; the results are consistent with the previous results for other lobate scarps on Mercury. The so-derived fault depths have been used to calculate surface heat flows for the time of faulting, taking into account crustal heat sources and a heterogeneous surface temperature due to the variable insolation pattern. Deduced surface heat flows are between 19 and 39 mW m-2 for the Kuiper region, and between 22 and 43 mW m-2 for Discovery Rupes. Both BDT depths and heat flows are consistent with the predictions of thermal history models for the range of time relevant for scarp formation.

  2. Searching palaeoearthquakes in fault bedrock scarps based on reflectivity, erosion features and surface ruptures with terrestrial laser scanning

    NASA Astrophysics Data System (ADS)

    Wiatr, Thomas; Reicherter, Klaus; Papanikolaou, Ioannis; Fernandez-Steeger, Tomas

    2010-05-01

    The terrestrial laser scanner (TLS) has been used for the investigation of escarpments (bedrock fault scarps) at different sites in Greece in order to identify the palaeo-slip events and rates. Our approach is based on differential weathering, karstification and bioerosion of the subsequentially exposed limestone free face from repeated earthquake surface faulting events. Data acquisition with the TLS method and the high-resolution spatial surface analysis can help to improve data quality and to provide a more accurate prediction for a plane analysis of the fault bedrock scarps. Scientific objectives are the analysis of rock surface roughness in different scales, orientations and methods, which may help us to determine the relative age of slip. Furthermore, the intensity of the backscattered reflection of the scarp surface can offer us the possibility to identify different weathering stages semi-automatically. The degradation and erosion features of the fault plane can help to reconstruct the plane geomorphology. We applied the LiDAR at limestone fault scarps with clear free faces that have experienced large surface faulting events in the past, such as the Kaparelli Fault or the Sparta Fault in mainland Greece. Some of these scarps have been dated with cosmogenic isotopes. The results of the cosmogenic nuclide dating on scarps give an absolute age of the individual palaeoseismological slip events. This ensures the cross validation of the TLS data. Additionally, geodetic measurements with compass and GPS were carried out to cross-validate the quality of the TLS point cloud data and to georeference.

  3. Numerical reconstruction of Late-Cenosoic evolution of normal-fault scarps in Baikal Rift Zone

    NASA Astrophysics Data System (ADS)

    Byzov, Leonid; San'kov, Vladimir

    2014-05-01

    Numerical landscape development modeling has recently become a popular tool in geo-logic and geomorphic investigations. We employed this technique to reconstruct Late-Cenosoic evolution of Baikal Rift Zone mountains. The objects of research were Barguzin Range and Svyatoy Nos Upland. These structures are formed under conditions of crustal extension and bounded by active normal faults. In our experiments we used instruments, engineered by Greg Tucker (University of Colo-rado) - CHILD (Channel-Hillslope Integrated Landscape Development) and 'Bedrock Fault Scarp'. First program allowed constructing the complex landscape model considering tectonic uplift, fluvial and hillslope processes; second program is used for more accurate simulating of triangular facet evolution. In general, our experiments consisted in testing of tectonic parameters, and climatic char-acteristic, erosion and diffusion properties, hydraulic geometry were practically constant except for some special runs. Numerous experiments, with various scenarios of development, showed that Barguzin range and Svyatoy Nos Upland has many common features. These structures characterized by internal differentiation, which appear in height and shape of slopes. At the same time, individual segments of these objects are very similar - this conclusion refers to most developing parts, with pronounced facets and V-shaped valleys. Accordingly modelling, these landscapes are in a steady state and are undergoing a uplift with rate 0,4 mm/yr since Early Pliocene (this solution accords with AFT-dating). Lower segments of Barguzin Range and Svyatoy Nos Upland also have some general fea-tures, but the reasons of such similarity probably are different. In particular, southern segment of Svyatoy Nos Upland, which characterized by relative high slope with very weak incision, may be formed as result very rapid fault movement or catastrophic landslide. On the other hand, a lower segment of Barguzin Range (Ulun segment, for example

  4. Large Earthquake Repeat on Normal Faults: Insights from dense in-situ 36Cl Exposure Dating of Limestone Fault Scarps, Central Apennines, Italy

    NASA Astrophysics Data System (ADS)

    Schlagenhauf, A.; Benedetti, L.; Manighetti, I.

    2007-12-01

    The only chance to learn how major earthquakes have repeated in the past on major active faults is to analyze their surface geological record, if any. We analyze such a record on 11 active normal faults to seek identifying, dating and measuring the large earthquake ruptures that have broken these faults in the last 10-20 kyrs, and determine how these major ruptures have followed in space and time on each fault and from one fault to another. As large earthquakes repeat on a normal fault, the fault plane is progressively exhumed and exposed at the free air, forming an escarpment at the surface. Provided that this escarpment is preserved from erosion, its surface holds the complete record of the successive ruptures (and possible aseismic slip) as they have broken the ground surface. We have started to analyze such a record on 11 neighboring, likely interacting active faults in the Fucino area, Central Italy, where seismic activity can be devastating (1915, M7 Avezzano earthquake, 30 000 casualties). Faults offset limestone rocks and form several hundred meters high cumulative escarpments, whose youngest parts (10-20 kyrs) are well preserved in the form of 10-20 m high, steep scarps running along the fault lengths (10-20 km). The Holocene seismic slip history of the faults can be recovered from base-to-top continuous in-situ 36Cl exposure dating of the limestone scarps (Benedetti et al. 2002, 2003; Palumbo et al. 2004). To reach that objective, we have sampled the faults in two different ways: two faults (Magnola and Roccapreturo) were sampled at several, regularly spaced sites along their length, so that to recover the earthquake slip variability in both space and time. Nine other faults (Fiamigniano, Campo-Felice, Velino, Tre- Monti, Trasacco, Parasano, San Sebastiano, Castel di Ieri, Roccacasale) were sampled at one single spot along their length, so that to examine the possible earthquake interactions within the entire fault system. Doing so, we have collected one

  5. Reconstruction of the Earthquake History of Limestone Fault Scarps in Knidos Fault Zone Using in-situ Chlorine-36 Exposure Dating and "R" Programming Language

    NASA Astrophysics Data System (ADS)

    Sahin, Sefa; Yildirim, Cengiz; Akif Sarikaya, Mehmet; Tuysuz, Okan; Genc, S. Can; Ersen Aksoy, Murat; Ertekin Doksanalti, Mustafa

    2016-04-01

    Cosmogenic surface exposure dating is based on the production of rare nuclides in exposed rocks, which interact with cosmic rays. Through modelling of measured 36Cl concentrations, we might obtain information of the history of the earthquake activity. Yet, there are several factors which may impact production of rare nuclides such as geometry of the fault, topography, geographic location of the study area, temporal variations of the Earth's magnetic field, self-cover and denudation rate on the scarp. Recently developed models provides a method to infer timing of earthquakes and slip rates on limited scales by taking into account these parameters. Our study area, the Knidos Fault Zone, is located on the Datça Peninsula in Southwestern Anatolia and contains several normal fault scarps formed within the limestone, which are appropriate to generate cosmogenic chlorine-36 (36Cl) dating models. Since it has a well-preserved scarp, we have focused on the Mezarlık Segment of the fault zone, which has an average length of 300 m and height 12-15 m. 128 continuous samples from top to bottom of the fault scarp were collected to carry out analysis of cosmic 36Cl isotopes concentrations. The main purpose of this study is to analyze factors affecting the production rates and amount of cosmogenic 36Cl nuclides concentration. Concentration of Cl36 isotopes are measured by AMS laboratories. Through the local production rates and concentration of the cosmic isotopes, we can calculate exposure ages of the samples. Recent research elucidated each step of the application of this method by the Matlab programming language (e.g. Schlagenhauf et al., 2010). It is vitally helpful to generate models of Quaternary activity of the normal faults. We, however, wanted to build a user-friendly program through an open source programing language "R" (GNU Project) that might be able to help those without knowledge of complex math programming, making calculations as easy and understandable as

  6. The Catfish Lake Scarp, Allyn, Washington preliminary field data and implications for earthquake hazards posed by the Tacoma Fault

    USGS Publications Warehouse

    Sherrod, Brian L.; Nelson, Alan R.; Kelsey, Harvey M.; Brocher, Thomas M.; Blakely, Richard J.; Weaver, Craig S.; Rountree, Nancy K.; Rhea, B. Susan; Jackson, Bernard S.

    2004-01-01

    The Tacoma fault bounds gravity and aeromagnetic anomalies for 50 km across central Puget lowland from Tacoma to western Kitsap County. Tomography implies at least 6 km of post-Eocene uplift to the north of the fault relative to basinal sedimentary rocks to the south. Coastlines north of the Tacoma fault rose about 1100 years ago during a large earthquake. Abrupt uplift up to several meters caused tidal flats at Lynch Cove, North Bay, and Burley Lagoon to turn into forested wetlands and freshwater marshes. South of the fault at Wollochet Bay, Douglas-fir forests sank into the intertidal zone and changed into saltmarsh. Liquefaction features found beneath the marsh at Burley Lagoon point to strong ground shaking at the time of uplift. Recent lidar maps of the area southwest of Allyn, Washington revealed a 4 km long scarp, or two closely spaced en-echelon scarps, which correspond closely to the Tacoma fault gravity and aeromagnetic anomalies. The scarp, named the Catfish Lake scarp, is north-side-up, trends east-west, and clearly displace striae left by a Vashon-age glacier. A trench across the scarp exposed evidence for postglacial folding and reverse slip. No organic material for radiocarbon dating was recovered from the trench. However, relationships in the trench suggest that the folding and faulting is postglacial in age.

  7. Updating the Displacement-Length Relationship of Thrust Faults Associated with Lobate Scarps on the Moon: Preliminary Results

    NASA Astrophysics Data System (ADS)

    Banks, M. E.; Watters, T. R.; Robinson, M. S.; Williams, N. R.

    2012-12-01

    Lobate scarps on the Moon are relatively small-scale tectonic landforms observed in mare basalts and more commonly, highland material. These thrust fault scarps are the most common tectonic landform on the lunar farside. Prior to Lunar Reconnaissance Orbiter Camera (LROC) observations, lobate scarps were only detected in equatorial regions because of limited Apollo Panoramic Camera and high resolution Lunar Orbiter coverage with optimum lighting geometry for identifying low-relief features. Thus, our previous understanding of lobate scarp morphometry was based on measurements of a limited number of low-latitude scarps. LROC images combined with Lunar Orbiter Laser Altimeter (LOLA) ranging enable detection and detailed morphometric analysis of lobate scarps at all latitudes; previously undetected scarps have been identified in more than 150 different locations, and are globally distributed. Measurements of the maximum relief, h, of lobate scarps provide a means to estimate the displacement-length (D-L) relation of the thrust faults. Measurements of h are used to estimate displacement, D, by assuming it is a function of the relief of the lobate scarp and the dip of the surface-breaking fault-plane (θ) such that D = h/sin θ (assuming h is a function of the total slip on the thrust fault). Maximum displacement on a fault scales with the planimetric length, L, of the fault. Populations of terrestrial faults formed in uniform rock types indicate a linear relationship such that D = γL, where γ is a constant determined by tectonic setting and rock type. If the D-L relationship of a fault population is known, the strain can be calculated using only fault lengths. In this ongoing study, LROC stereo-derived digital terrain models (DTMs) and where possible LOLA altimetry, are used to accurately determine the maximum relief of lobate scarps. So far we have measured the maximum relief for 11 scarp segments resulting in ranges of ~8 to 164 m for maximum relief, ~0.8 to 14 km

  8. Quantitative constraints on the formation of post-glacial normal-fault scarps in Greece determined by chlore 36 cosmogenic dating.

    NASA Astrophysics Data System (ADS)

    Benedetti, L.; King, G.; Finkel, R.; Papanastassiou, D.; Armijo, R.; Ryerson, F.; Farber, D.; Flerit, F.

    2003-04-01

    Recent activity of normal faults in Greece has produced steep limestone fault scarps at the base of the mountain fronts. For example, on the Sparta fault located in the Peloponnese, and responsible for the 464 B.C. M˜7 earthquake, a continuous fresh scarp cuts limestone bedrock and indurated conglomerates. The scarp is nearly continuous dipping at 65-68o with well-preserved slickensides. The maximum height of the scarp is 10-12 metres, progressively decreasing towards the ends. The few local variations are associated with active streams where hangingwall erosion causes the scarp to be locally higher. The regularity of the scarp is powerful evidence that the footwall and hangingwall surfaces were originally continuous and the scarp surface represents fault slip alone. It also suggests that there was no significant erosion or deposition on the hanging-wall (except near active gullies) since the scarp began to form. Such observations have led to the suggestion that numerous well-preserved limestone escarpments around the eastern Mediterranean, similar to those in Sparta, are post-glacial in age. Using 36Cl cosmogenic dating we tested the foregoing ideas. Limestones (largely calcite) contain an abundance of calcium, which is a major target element for cosmogenic 36Cl production. Samples were collected from the limestone scarp surface to recover the continuous exposure history of the scarp and also from the footwall and hanging wall surfaces as well as a depth profile in the hanging wall wedge. The concentration of 36Cl and of stable chlorine has been measured by accelerator mass spectrometry (AMS) at the LLNL-CAMS for each of the samples (about 150). The result confirm: 1- that the fault scarp was formed between about 2000 B.P. and 13 ka B.P. as the result of 5 earthquakes (including the known event in 464 B.C.) with similar slip amplitudes of about 2m and with time intervals ranging from 500yr to 4500yr (Benedetti et al., GRL, 2002), 2- that both hanging wall and

  9. Fault-scarp morphology and amount of surface offset on late-Quaternary surficial deposits, eastern escarpment of the central Sierra Nevada, CA

    SciTech Connect

    Berry, M.E. . Dept. of Geology)

    1992-01-01

    Faults scarps, formed on glacial deposits and an alluvial fan near the east-central Sierra Nevada mountain front by late-Quaternary movement on the Hilton Creek (HCF), Wheeler Crest (WCFZ) and Coyote Warp (CWFZ) fault zones, were profiled to determine the amount and to estimate the recency of fault offset. Areas studied include McGee (N--near Lake Crowley), Pine, Mount Tom, Basin Mountain, McGee (S--near Bishop), and Bishop Creek drainages. The profile data indicate that movement of the range-front faults (HCF and WCFZ), which is characterized by normal slip, has offset Tioga-age deposits 6.5-26 m. Offset of Tahoe-age moraines cannot be measured directly because the landforms are buried at the mountain-front by moraines from later glaciations. However, the amount of offset is estimated at 52--130 m, based on crest-height differences between Tahoe and Tioga moraines. The rates of slip are highest on the northern end of the HCF, at McGee (N) Creek; the higher slip rates in this latter area may be related to its close proximity to the Long Valley caldera, where tectonic processes are complex and considered closely related to ongoing magmatic activity. The preservation of bevels on the fault scarps in both HCF and WCFZ, combined with the amounts of surface offset on the late-Pleistocene moraines, and AMS C-14 dates for charcoal found in fault-scarp colluvium, indicate that large ground-rupturing events have occurred on these faults during the Holocene. In contrast to the mountain-front faults, faults in the CWFZ, on a broad warp that separates the WCFZ from range-front faults to the south of Bishop, do not cross Tioga moraines, implying that surface rupture has not occurred in the CWFZ for at least 15,000-25,000 years. The degraded morphology of the fault scarps on adjacent Tahoe and pre-Tahoe moraines, which have been offset between 10.5 and 30 m, attests to the lack of late-Pleistocene and Holocene fault activity in this latter area.

  10. Three-dimensional Geometry of Buried Fold Scarps Associated With Ancient Earthquakes on the Puente Hills Blind Thrust Fault

    NASA Astrophysics Data System (ADS)

    Leon, L. A.; Dolan, J. F.; Hoeft, J. S.; Shaw, J. H.; Hartleb, R. D.

    2003-12-01

    The Puente Hills thrust fault (PHT) is a large blind thrust fault that extends east-west beneath the heart of the metropolitan Los Angeles region (Shaw and Shearer, 1999; Shaw et al., 2003). Christofferson (2002; in prep.) and Dolan et al. (2003) identified four buried fold scarps associated with large (Mw greater than or equal to 7), ancient earthquakes on the PHT beneath the City of Bellflower, in northern Orange County. One of the major outstanding questions regarding this research concerns the subsurface, three-dimensional geometry of these buried scarps. Specifically, we want to determine the extent to which the subsurface geometry of these scarps is controlled by tectonic versus fluvial processes. In order to begin addressing these questions, we drilled a north-south transect of hollow-stem, continuously cored boreholes across the buried fold scarps. This new borehole transect, which comprises six, 20-m-deep boreholes, was drilled parallel to, and ˜ 100 m west of, the original Carfax Avenue transect of Christofferson (2002) and Dolan et al. (2003). The overall pattern of progressive southward thickening of sedimentary units observed in the Carfax borehole transect extends westward to the new transect. Moreover, several key sedimentary contacts that are traceable laterally between the two transects occur at approximately the same depths at all locations along both transects. This three-dimensional data set thus defines several buried fold scarps that extend east-west beneath the study site. These observations confirm that the buried scarps are primarily tectonic, rather than fluvial features.

  11. Field and Laboratory Data From an Earthquake History Study of Scarps in the Hanging Wall of the Tacoma Fault, Mason and Pierce Counties, Washington

    USGS Publications Warehouse

    Nelson, Alan R.; Personius, Stephen F.; Sherrod, Brian L.; Buck, Jason; Bradley, Lee-Ann; Henley, Gary; Liberty, Lee M.; Kelsey, Harvey M.; Witter, Robert C.; Koehler, R.D.; Schermer, Elizabeth R.; Nemser, Eliza S.; Cladouhos, Trenton T.

    2008-01-01

    As part of the effort to assess seismic hazard in the Puget Sound region, we map fault scarps on Airborne Laser Swath Mapping (ALSM, an application of LiDAR) imagery (with 2.5-m elevation contours on 1:4,000-scale maps) and show field and laboratory data from backhoe trenches across the scarps that are being used to develop a latest Pleistocene and Holocene history of large earthquakes on the Tacoma fault. We supplement previous Tacoma fault paleoseismic studies with data from five trenches on the hanging wall of the fault. In a new trench across the Catfish Lake scarp, broad folding of more tightly folded glacial sediment does not predate 4.3 ka because detrital charcoal of this age was found in stream-channel sand in the trench beneath the crest of the scarp. A post-4.3-ka age for scarp folding is consistent with previously identified uplift across the fault during AD 770-1160. In the trench across the younger of the two Stansberry Lake scarps, six maximum 14C ages on detrital charcoal in pre-faulting B and C soil horizons and three minimum ages on a tree root in post-faulting colluvium, limit a single oblique-slip (right-lateral) surface faulting event to AD 410-990. Stratigraphy and sedimentary structures in the trench across the older scarp at the same site show eroded glacial sediments, probably cut by a meltwater channel, with no evidence of post-glacial deformation. At the northeast end of the Sunset Beach scarps, charcoal ages in two trenches across graben-forming scarps give a close maximum age of 1.3 ka for graben formation. The ages that best limit the time of faulting and folding in each of the trenches are consistent with the time of the large regional earthquake in southern Puget Sound about AD 900-930.

  12. Deriving earthquake history of the Knidos Fault Zone, SW Turkey, using cosmogenic 36Cl surface exposure dating of the fault scarp.

    NASA Astrophysics Data System (ADS)

    Yildirim, Cengiz; Ersen Aksoy, Murat; Akif Sarikaya, Mehmet; Tuysuz, Okan; Genc, S. Can; Ertekin Doksanalti, Mustafa; Sahin, Sefa; Benedetti, Lucilla; Tesson, Jim; Aster Team

    2016-04-01

    Formation of bedrock fault scarps in extensional provinces is a result of large and successive earthquakes that ruptured the surface several times. Extraction of seismic history of such faults is critical to understand the recurrence intervals and the magnitude of paleo-earthquakes and to better constrain the regional seismic hazard. Knidos on the Datca Peninsula (SW Turkey) is one of the largest cities of the antique times and sits on a terraced hill slope formed by en-echelon W-SW oriented normal faults. The Datça Peninsula constitutes the southern boundary of the Gulf of Gökova, one of the largest grabens developed on the southernmost part of the Western Anatolian Extensional Province. Our investigation relies on cosmogenic 36Cl surface exposure dating of limestone faults scarps. This method is a powerful tool to reconstruct the seismic history of normal faults (e.g. Schlagenhauf et al 2010, Benedetti et al. 2013). We focus on one of the most prominent fault scarp (hereinafter Mezarlık Fault) of the Knidos fault zone cutting through the antique Knidos city. We collected 128 pieces of tablet size (10x20cm) 3-cm thick samples along the fault dip and opened 4 conventional paleoseismic trenches at the base of the fault scarp. Our 36Cl concentration profile indicates that 3 to 4 seismic events ruptured the Mezarlık Fault since Last Glacial Maximum (LGM). The results from the paleoseismic trenching are also compatible with 36Cl results, indicating 3 or 4 seismic events that disturbed the colluvium deposited at the base of the scarp. Here we will present implications for the seismic history and the derived slip-rate of the Mezarlık Fault based on those results. This project is supported by The Scientific and Technological Research Council of Turkey (TUBITAK, Grant number: 113Y436) and it was conducted with the Decision of the Council of Ministers with No. 2013/5387 on the date 30.09.2013 and was done with the permission of Knidos Presidency of excavation in

  13. Thermoluminescence dating of fault-scarp-derived colluvium: Deciphering the timing of paleoearthquakes on the Weber segment of the Wasatch fault zone, north central Utah

    SciTech Connect

    Forman, S.L. ); Nelson, A.R. ); McCalpin J.P. )

    1991-01-10

    The timing of middle to late Holocene faulting on the Weber segment of the Wasatch fault zone, Utah, is constrained by thermoluminescence (TL) and radiocarbon age estimates on fine-grained, fault-related colluvial sediments. The stratigraphy in two trenches excavated across fault scarps is characterized by a stack of three colluvial wedges, deposited in response to three separate faulting events, the oldest of which buried a soil developed on a middle Holocene debris flow. Thermoluminescence age estimates by the partial and total bleach methods and the regeneration method on fine-grained colluvium from the trenches agree within 1 sigma and are concordant with the radiocarbon chronology. A synthesis of the TL and {sup 14}C age estimates indicate that these three faulting events occurred sometime between 4,500 and 3,500, between 3,200 and 2,500, and between 1,400 and 1,000 years ago. Detailed investigation of a sequence of fine-grained, scarp-derived distal colluvium shows that much of the sediment was deposited during <600-year intervals immediately after faulting. The sedimentation rate of colluvium is inferred to increase shortly after faulting, and TL dating of these sediments provides additional information to constrain the timing of faulting events.

  14. Fault-scarp related features and cascade-rupturing model for the Wenchuan earthquake (Mw7.9), eastern Tibetan Plateau, China

    NASA Astrophysics Data System (ADS)

    Yu, G.; Xu, X.; Klinger, Y.; Diao, G.; Chen, G.; Feng, X.; Li, C.; Zhu, A.; Yuan, R.; Guo, T.; Sun, X.; Tan, X.; An, Y.

    2009-12-01

    The post-earthqauke field investigations reveal that the Mw 7.9 Wenchuan earthquake of 12th May 2008 ruptured three reverse faults, two NE-trending imbricated reverse faults and another NW-trending reverse fault, along the middle Longmenshan fold-and-thrust belt at the eastern margin of the Tibetan plateau. The fault-scarp related features can be categorized into eight characterized groups: simple thrust scarp, hanging-wall collapse scarp, simple pressure ridge, dextral pressure ridge, fault-related fold scarp, back-thrust pressure ridge, local normal fault scarp and crocodile-mouth-like scarp. The local normal scarp is first discovered in the reverse-faulting earthquake events as ever reported in the world. The combination of different fault-scarp features, along-strike variation of the co-seismic offsets and fault-trace discontinuity sizes demonstrates that the surface ruptures associated with Wenchuan earthquake are dominated by reverse sense with right-lateral components, but the relative ratio varies from site to site. Also, the surface ruptures can be divided, for the first order, into two segments, the Yingxiu and Beichuan segments, corresponding to Mw 7.8 and Mw 7.57 events, respectively. These two segments further can be divided, for the second order, into four sub-segments in total, which are equivalent to four sub-events of Mw 7.46, Mw 7.69, Mw 6.99 and Mw 7.52, respectively. The rupture segmentation, for different orders, shows a cascade-rupturing pattern and may help explain why the quake time of the Wenchuan earthquake was so long as up to 100 second. Aftershock focal mechanisms are also used to constrain the fault geometry for the sub-segments, indicating that the seismogenic faults are listric at depth and in general, the fault plane becomes steeper northward, which enables the fault to accommodate larger strike-slip motion. This earthquake also confirms that the crustal shortening across the Longmenshan fold-and-thrust belt should be responsible

  15. Review of the origin of the Braid Scarp near the Pebble prospect, southwestern Alaska

    USGS Publications Warehouse

    Haeussler, Peter J.; Waythomas, Christopher F.

    2011-01-01

    A linear geomorphic scarp, referred to as the 'Braid Scarp,' lies about 5 kilometers north of Iliamna Lake, Alaska, and has been identified as a possible seismically active fault. We examined the geomorphology of the area and an 8.5-meter-long excavation across the scarp. We conclude that the scarp was formed by incision of a glacial outwash braid plain into a slightly older outwash plain as ice stagnated in the region during deglaciation 11-15 thousand years ago. We found no evidence for active faulting along the scarp.

  16. Trench Logs and Scarp Data from an Investigation of the Steens Fault Zone, Bog Hot Valley and Pueblo Valley, Humboldt County, Nevada

    USGS Publications Warehouse

    Personius, Stephen F.; Crone, Anthony J.; Machette, Michael N.; Kyung, Jai Bok; Cisneros, Hector; Lidke, David J.; Mahan, Shannon

    2006-01-01

    Introduction: This report contains field and laboratory data from a study of the Steens fault zone near Denio, Nev. The 200-km-long Steens fault zone forms the longest, most topographically prominent fault-bounded escarpment in the Basin and Range of southern Oregon and northern Nevada. The down-to-the-east normal fault is marked by Holocene fault scarps along nearly half its length, including the southern one-third of the fault from the vicinity of Pueblo Mountain in southern Oregon to the southern margin of Bog Hot Valley (BHV) southwest of Denio, Nev. We studied this section of the fault to better constrain late Quaternary slip rates, which we hope to compare to deformation rates derived from a recently established geodetic network in the region (Hammond and Thatcher, 2005). We excavated a trench in May 2003 across one of a series of right-stepping fault scarps that extend south from the southern end of the Pueblo Mountains and traverse the floor of Bog Hot Valley, about 4 km south of Nevada State Highway 140. This site was chosen because of the presence of well-preserved fault scarps, their development on lacustrine deposits thought to be suitable for luminescence dating, and the proximity of two geodetic stations that straddle the fault zone. We excavated a second trench in the southern BHV, but the fault zone in this trench collapsed during excavation and thus no information about fault history was documented from this site. We also excavated a soil pit on a lacustrine barrier bar in the southern Pueblo Valley (PV) to better constrain the age of lacustrine deposits exposed in the trench. The purpose of this report is to present photomosaics and trench logs, scarp profiles and slip data, soils data, luminescence and radiocarbon ages, and unit descriptions obtained during this investigation. We do not attempt to use the data presented herein to construct a paleoseismic history of this part of the Steens fault zone; that history will be the subject of a future

  17. Generation of waterfalls at intermittently alluviated fault scarps releases tectonic forcing on a climatic beat.

    NASA Astrophysics Data System (ADS)

    Malatesta, Luca C.; Lamb, Michael P.

    2016-04-01

    Normal or reverse faults bonding mountain catchments typically mark the transition from the erosional to the depositional domain where bedrock channels flow into alluvial fans. We show here that interactions between the two fluvial domains can result in knickpoints that convolve tectonic and climatic signals. Changes in the ratio of sediment and water fluxes (Qs/Qw) modify the equilibrium geometry of the system and in particular of the reactive alluvial reaches so that a larger Qs/Qw forces steepening of the fan, backfilling of the bedrock reach and a heightened base level. Under these conditions, slip on the fault - covered and shielded by alluvium - can accumulate over several seismic cycles before being released at once by incision of the alluvial fan back to a shallow geometry. We demonstrate in this study that climate-driven aggradation and incision of alluvial fans in the Death Valley area can account for otherwise unexplained waterfalls at the base of catchments manyfold the height of coseismic throw. As a consequence, in this common configuration, tectonic slip can accumulate and be released at once on a tempo set by climatic fluctuations. Such that the faster denudation rate that might follow from increased precipitations is accompanied by an important retreating knickpoint. We propose that this mechanism can increase catchment reactivity and broaden the range of external forcings potentially recorded in the stratigraphy.

  18. Seasonally active frost-dust avalanches on a north polar scarp of Mars captured by HiRISE

    USGS Publications Warehouse

    Russell, P.; Thomas, N.; Byrne, S.; Herkenhoff, K.; Fishbaugh, K.; Bridges, N.; Okubo, C.; Milazzo, M.; Daubar, I.; Hansen, C.; McEwen, A.

    2008-01-01

    North-polar temporal monitoring by the High Resolution Imaging Science Experiment (HiRISE) orbiting Mars has discovered new, dramatic examples that Mars1 CO2-dominated seasonal volatile cycle is not limited to quiet deposition and sublimation of frost. In early northern martian spring, 2008, HiRISE captured several cases of CO2 frost and dust cascading down a steep, polar scarp in discrete clouds. Analysis of morphology and process reveals these events to be similar to terrestrial powder avalanches, sluffs, and falls of loose, dry snow. Potential material sources and initiating mechanisms are discussed in the context of the Martian polar spring environment and of additional, active, aeolian processes observed on the plateau above the scarp. The scarp events are identified as a trigger for mass wasting of bright, fractured layers within the basal unit, and may indirectly influence the retreat rate of steep polar scarps in competing ways. Copyright 2008 by the American Geophysical Union.

  19. Field and Laboratory Data From an Earthquake History Study of Scarps of the Lake Creek-Boundary Creek Fault Between the Elwha River and Siebert Creek, Clallam County, Washington

    USGS Publications Warehouse

    Nelson, Alan R.; Personius, Stephen F.; Buck, Jason; Bradley, Lee-Ann; Wells, Ray E.; Schermer, Elizabeth R.

    2007-01-01

    Fault scarps recently discovered on Airborne Laser Swath Mapping (ALSM; also known as LiDAR) imagery show Holocene movement on the Lake Creek-Boundary Creek fault on the north flank of the Olympic Mountains of northwestern Washington State. Such recent movement suggests the fault is a potential source of large earthquakes. As part of the effort to assess seismic hazard in the Puget Sound region, we map scarps on ALSM imagery and show primary field and laboratory data from backhoe trenches across scarps that are being used to develop a latest Pleistocene and Holocene history of large earthquakes on the fault. Although some scarp segments 0.5-2 km long along the fault are remarkably straight and distinct on shaded ASLM imagery, most scarps displace the ground surface <1 m, and, therefore, are difficult to locate in dense brush and forest. We are confident of a surface-faulting or folding origin and a latest Pleistocene to Holocene age only for scarps between Lake Aldwell and the easternmost fork of Siebert Creek, a distance of 22 km. Stratigraphy in five trenches at four sites help determine the history of surface-deforming earthquakes since glacier recession and alluvial deposition 11-17 ka. Although the trend and plunge of indicators of fault slip were measured only in the weathered basalt exposed in one trench, upward-splaying fault patterns and inconsistent displacement of successive beds along faults in three of the five trenches suggest significant lateral as well as vertical slip during the surface-faulting or folding earthquakes that produced the scarps. Radiocarbon ages on fragments of wood charcoal from two wedges of scarp-derived colluvium in a graben-fault trench suggest two surface-faulting earthquakes between 2,000 and 700 years ago. The three youngest of nine radiocarbon ages on charcoal fragments from probable scarp-derived colluvum in a fold-scarp trench 1.2 km to the west suggest a possible earlier surface-faulting earthquake less than 5,000 years

  20. A 1500 yr record of North Atlantic storm activity based on optically dated relict beach scarps

    NASA Astrophysics Data System (ADS)

    Buynevich, Ilya V.; Fitzgerald, Duncan M.; Goble, Ronald J.

    2007-06-01

    Understanding of long-term dynamics of intense coastal storms is important for determining the frequency and impact of these events on sandy coasts. We use optically stimulated luminescence (OSL) dates on relict scarps within a prograded barrier sequence to reconstruct the chronology of large-magnitude erosional events in the western Gulf of Maine. OSL dates obtained on quartz-rich sediments immediately overlying relict scarps indicate severe beach erosion and retreat due to erosional events ca. 1550, 390, 290, and 150 cal yr B.P. Our data provide new evidence of increased storm activity (most likely frequency and/or intensity of extratropical storms) during the past 500 yr, which was preceded by a relatively calm period lasting ˜1000 yr. The width of the coastal sequence preserved between successive paleoscarps shows strong correlation with the time interval elapsed between storms. Our findings indicate that diagnostic geophysical and sedimentological signatures of severe erosional events offer new opportunities for assessing the impact and timing of major storms along sandy coasts.

  1. Decadal changes in fault-scarp knickpoints by bedrock erosion following 1999 Chi-Chi Earthquake in Taiwan

    NASA Astrophysics Data System (ADS)

    Hayakawa, Yuichi S.; Matsuta, Nobuhisa; Maekado, Akira; Matsukura, Yukinori

    2010-05-01

    Surface ruptures along the Chelungpu thrust fault in west-central Taiwan caused formation of knickpoints (waterfalls) according with bedrock exposure in riverbeds when the 921 Chi-Chi Earthquake occurred on September 21, 1999. Since then the fault-scarp knickpoints have receded upstream at extremely rapid rates, causing bedrock incision for tens to hundreds of meters in length within a decade. The rapid erosion of the knickpoints provides us an opportunity to investigate actual changes of bedrock morphology of the rivers, and here we examine the changes in the knickpoint recession rates during the last decade from 1999 to 2009. Field measurements of the topography revealed that the mean rate of a knickpoint recession in the largest river (Ta-chia) was 3.3 m/y in the earlier 6 years (1999-2005) and 220 m/y in the last 4 years (2005-2009). This acceleration of the recession can be due to the increase in flood frequency and intensity, narrowing of the channel width, and/or anisotropy of rock strength (sandstones and mudstones) along the stream. The other knickpoints showed relatively similar recession rates throughout the decade on the order of 20-60 m/y. These rates are then compared to an empirical model of knickpoint recession, in which relevant physical parameters of erosive force of stream and bedrock resistance are involved as a dimensionless index. The actual recession rates of the knickpoints are considerably higher than those expected by the model, suggesting that abundant sediment particles supplied from upstream catchment enhance the knickpoint erosion. In fact, all the abundant gravels on the riverbed around the knickpoints that are supplied from further upstream areas with different lithology (mostly older sandstones) are quite harder than the bedrock therein. The model analysis for the two time periods for each knickpoint suggests that the changes in their recession rates can be commonly affected by severe flood occurrence in the study area. Also, some

  2. Spatio-temporal trends in normal-fault segmentation recorded by low-temperature thermochronology: Livingstone fault scarp, Malawi Rift, East African Rift System

    NASA Astrophysics Data System (ADS)

    Mortimer, Estelle; Kirstein, Linda A.; Stuart, Finlay M.; Strecker, Manfred R.

    2016-12-01

    The evolution of through-going normal-fault arrays from initial nucleation to growth and subsequent interaction and mechanical linkage is well documented in many extensional provinces. Over time, these processes lead to predictable spatial and temporal variations in the amount and rate of displacement accumulated along strike of individual fault segments, which should be manifested in the patterns of footwall exhumation. Here, we investigate the along-strike and vertical distribution of low-temperature apatite (U-Th)/He (AHe) cooling ages along the bounding fault system, the Livingstone fault, of the Karonga Basin of the northern Malawi Rift. The fault evolution and linkage from rift initiation to the present day has been previously constrained through investigations of the hanging wall basin fill. The new cooling ages from the footwall of the Livingstone fault can be related to the adjacent depocentre evolution and across a relay zone between two palaeo-fault segments. Our data are complimented by published apatite fission-track (AFT) data and reveal significant variation in rock cooling history along-strike: the centre of the footwall yields younger cooling ages than the former tips of earlier fault segments that are now linked. This suggests that low-temperature thermochronology can detect fault interactions along strike. That these former segment boundaries are preserved within exhumed footwall rocks is a function of the relatively recent linkage of the system. Our study highlights that changes in AHe (and potentially AFT) ages associated with the along-strike displacement profile can occur over relatively short horizontal distances (of a few kilometres). This is fundamentally important in the assessment of the vertical cooling history of footwalls in extensional systems: temporal differences in the rate of tectonically driven exhumation at a given location along fault strike may be of greater importance in controlling changes in rates of vertical exhumation

  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. Quantifying fault-zone activity in arid environments with high-resolution topography

    NASA Astrophysics Data System (ADS)

    Oskin, Michael E.; Le, Kimberly; Strane, Michael D.

    2007-11-01

    High-resolution airborne laser swath-mapping (ALSM) topography illuminates active faulting with unprecedented clarity. We contrast ALSM topography of two dextral faults in arid regions of California with slip rates that differ by an order of magnitude: The Lenwood fault, with rate of ~1 mm/yr, and the Clark fault, a strand of the San Jacinto fault with net slip rate >10 mm/yr. Visualization of ALSM data reveals abundant fault scarps and deflected channels that when reconstructed can yield powerful slip constraints. Though many of these features may also be detected in existing aerial photography, these data are limited by stereo depth resolution and fixed illumination angle.

  5. 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.

  6. Recent seismogenic fault activity in a Late Quaternary closed-lake graben basin (Albacete, SE Spain)

    NASA Astrophysics Data System (ADS)

    Rodríguez-Pascua, M. A.; Pérez-López, R.; Calvo, J. P.; García del Cura, M. A.

    2008-11-01

    The Cordovilla basin, located within the frontal thrust belt of the Betic Cordillera, SE Spain, is an elongated NW-SE graben showing discrete surface rupture generated by Holocene paleoearthquake activity. A main and an antithetic normal, NW-SE trending, active faults bound the basin. Paleoseismological evidence is reported on upslope-facing scarps of the antithetic fault, acting as dams to runoff, which contributed to temporary lacustrine conditions, as well as sediment uplift. The fluvial network in the area shows a poor drainage activity, whereas a present lake is dammed by the antithetic fault. The modern landscape is controlled by Holocene faulting, modifying the geological environment according to earthquake occurrence, from flat alluvial plains to lacustrine local basins. The application of the diffusion dating technique to unconsolidated sediments for the antithetic fault scarp indicates an age between 1 and 2 ka. Various geometric parameters have been obtained in order to reconstruct the paleoseismic history of the Cordovilla graben basin. The surface rupture and fault-offset values are associated with discrete active morpholineaments, parallel to the Pozohondo Fault. The Tobarra-Cordovilla segment (the structural boundary of the Cordovilla Basin) was generated by earthquakes with magnitudes (Mw) greater than 6.0, based on Wells and Coppersmith fault scarp relations.

  7. Erosional scarps on Io

    USGS Publications Warehouse

    McCauley, J.F.; Smith, B.A.; Soderblom, L.A.

    1979-01-01

    Irregular or fretted scarps on Io are similar to those found on Earth and Mars. A sapping mechanism involving liquid SO2 is proposed to explain these complexly eroded terrains on Io. ?? 1979 Nature Publishing Group.

  8. The Meers Fault: Tectonic activity in southwestern Oklahoma

    SciTech Connect

    Ramelli, A.R.; Slemmons, D.B.; Brocoum, S.J.

    1987-03-01

    The Meers Fault in Southwestern Oklahoma is capable of producing large, damaging earthquakes. By comparison to historical events, a minimum of M = 6-3/4 to 7-1/4 could be expected. The most recent surface rupturing event occurred in the late Holocene, and it appears that one or more pre-Holocene events preceded it. Surface rupture length is at least 37 km. Displacements comprising the present-day scarp have left-lateral and high-angle reverse components. Vertical separation of the ground surface reaches 5 m, while lateral separation exceeds the vertical by a ratio of about 3:1 to 5:1, reaching about 20 m. Individual events apparently had maximum displacements of several meters. The Meers Fault may be part of a larger active zone. Based on surface expressions, the Washita Valley, Oklahoma and Potter County, Texas Faults may also have ruptures during the late Quaternary, although not as recently as the Meers Fault. Low sun angle photography in Southwestern Oklahoma revealed no evidence of fault activity, other than that of the Meers Fault, although activity may be concealed by poor preservation or ductile surface deformation. This suggests that additional areas of activity may be sparse and rupture infrequently.

  9. 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

  10. Assessing the activity of faults in continental interiors: Palaeoseismic insights from SE Kazakhstan

    NASA Astrophysics Data System (ADS)

    Grützner, C.; Carson, E.; Walker, R. T.; Rhodes, E. J.; Mukambayev, A.; Mackenzie, D.; Elliott, J. R.; Campbell, G.; Abdrakhmatov, K.

    2017-02-01

    The presence of fault scarps is a first-order criterion for identifying active faults. Yet the preservation of these features depends on the recurrence interval between surface rupturing events, combined with the rates of erosional and depositional processes that act on the landscape. Within arid continental interiors single earthquake scarps can be preserved for thousands of years, and yet the interval between surface ruptures on faults in these regions may be much longer, such that the lack of evidence for surface faulting in the morphology may not preclude activity on those faults. In this study we investigate the 50 km-long 'Toraigyr' thrust fault in the northern Tien Shan. From palaeoseismological trenching we show that two surface rupturing earthquakes occurred in the last 39.9 ± 2.7 ka BP, but only the most recent event (3.15-3.6 ka BP) has a clear morphological expression. We conclude that a landscape reset took place in between the two events, likely as a consequence of the climatic change at the end of the last glacial maximum. These findings illustrate that in the Tien Shan evidence for the most recent active faulting can be easily obliterated by climatic processes due to the long earthquake recurrence intervals. Our results illustrate the problems related to the assessment of active tectonic deformation and seismic hazard assessments in continental interior settings.

  11. 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.

  12. 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

  13. 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

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

    It is important to evaluate the magnitude of earthquake caused by multiple active faults, taking into account the simultaneous effects. The simultaneity of adjacent active faults are often decided on the basis of geometric distances except for known these paleoseismic records. We have been studied the step area between the Nukumi fault and the Neodani fault, which appeared as consecutive ruptures in the 1891 Nobi earthquake, since 2009. The purpose of this study is to establish innovation in valuation technique of the simultaneity of adjacent active faults in addition to the paleoseismic record and the geometric distance. Geomorphological, geological and reconnaissance microearthquake surveys are concluded. The present work is intended to clarify the distribution of tectonic geomorphology along the Nukumi fault and the Neodani fault by high-resolution interpretations of airborne LiDAR DEM and aerial photograph, and the field survey of outcrops and location survey. The study area of this work is the southeastern Nukumi fault and the northwestern Neodani fault. We interpret DEM using shaded relief map and stereoscopic bird's-eye view made from 2m mesh DEM data which is obtained by airborne laser scanner of Kokusai Kogyo Co., Ltd. Aerial photographic survey is for confirmation of DEM interpretation using 1/16,000 scale photo. As a result of topographic survey, we found consecutive tectonic topography which is left lateral displacement of ridge and valley lines and reverse scarplets along the Nukumi fault and the Neodani fault . From Ogotani 2km southeastern of Nukumi pass which is located at the southeastern end of surface rupture along the Nukumi fault by previous study to Neooppa 9km southeastern of Nukumi pass, we can interpret left lateral topographies and small uphill-facing fault scarps on the terrace surface by detail DEM investigation. These topographies are unrecognized by aerial photographic survey because of heavy vegetation. We have found several new

  15. Naval Weapons Center Active Fault Map Series.

    DTIC Science & Technology

    1987-08-31

    SECURITY CLASSIFICATION OF ’MiS PACE NWC TP 6828 CONTENTS Introduction . . . . . . . . . . . . . . . . . ........... 2 Active Fault Definition ...established along the trace of the Little Take fault zone, within the City of Ridgecrest. ACTIVE FAULT DEFINITION Although it is a commonly used term...34active fault" lacks a pre- cise and universally accepted definition . Most workers, however, accept the following: "Active fault - a fault along

  16. Extracting tectonic information from cosmogenic exposure ages along bedrock scarps using synthetic and natural data

    NASA Astrophysics Data System (ADS)

    Cowie, Patience; Walker, Matthew; Roberts, Gerald; Phillips, Richard; Dunai, Tibor; Zijerveld, Leo; McCaffrey, Ken

    2010-05-01

    Cosmogenic surface exposure dating is a powerful tool for reconstructing long term slip histories on active faults and extracting earthquake recurrence intervals (e.g. Benedetti et al., GRL, v.29, 2002). Extensional faults are particularly amenable to this type of study because they commonly produce a striated bedrock scarp, exhumed by faulting, that can be directly dated. Bedrock scarps in limestone can be sampled to obtain the concentration of cosmogenic 36Cl, produced primarily through interactions of cosmic ray secondary neutrons and muons with Ca within the scarp limestone. To first order the production rate decreases exponentially with depth beneath the ground surface. Because each normal-faulting earthquake uplifts a new portion of the scarp above the surface, the 36Cl concentration along the scarp is the sum of that 36Cl produced below the surface prior to the earthquake and that accumulated above the surface after the earthquake. For a scarp being seismically exhumed, the characteristic profile is therefore a series of exponentials with discontinuities marking the timing of each earthquake. The number of events, their timing and the magnitude of the associated slip strongly influence the shape of 36Cl profile. Existing methods for extracting paleo-earthquakes from these data are based on a forward modelling approach and have shown that slip events ≥0.5m (≥ Magnitude 6.0) are well resolved by fully sampling the height of the exposed bedrock scarp. A forward model for 36Cl accumulation generates 36Cl concentration versus fault height for different potential fault slip histories, which is then compared with the measured 36Cl concentrations. The best fit scenario(s) are then ranked using the Aikake Information Criterion (AIC), which is sensitive to the goodness of fit as well as the number of parameters included in the model. A key feature of published results using this approach is that slip events of several meters have, in several cases, been inferred

  17. Scarp within Chasma Boreale

    NASA Technical Reports Server (NTRS)

    2006-01-01

    This HiRISE image is of the north polar layered deposits (PLD) and underlying units exposed along the margins of Chasma Boreale. Chasma Boreale is the largest trough in the north PLD, thought to have formed due to outflow of water from underneath the polar cap, or due to winds blowing off the polar cap, or a combination of both. At the top and left of the image, the bright area with uniform striping is the gently sloping surface of the PLD. In the middle of the image this surface drops off in a steeper scarp, or cliff. At the top of this cliff we see the bright PLD in a side view, or cross-section. From these two perspectives of the PLD it is evident that the PLD are a stack of roughly horizontal layers. The gently sloping top surface cuts through the vertical sequence of layers at a low angle, apparently stretching the layers out horizontally and thus revealing details of the brightness and texture of individual layers. The surface of the PLD on the scarp is also criss-crossed by fine scale fractures. The layers of the PLD are probably composed of differing proportions of ice and dust, believed to be related to the climate conditions at the time they were deposited. In this way, sequences of polar layers are records of past climates on Mars, as ice cores from terrestrial ice sheets hold evidence of past climates on Earth. Further down the scarp in the center of the image the bright layers give way suddenly to a much darker section where a few layers are visible intermittently amongst aprons of dark material. The darkest material, with a smooth surface suggestive of loose grains, is thought to be sandy because similar exposures elsewhere show it to be formed into dunes by the wind. An intermediate-toned material also appears to form aprons draped over layers in the scarp, but its surface contains lobate structures that appear hardened into place and its edges are more abrupt in places, suggesting it may contain some ice or other cementing agent that makes it

  18. 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.

  19. Beagle Rupes and Rembrandt scarp: a comparison on Mercury surface

    NASA Astrophysics Data System (ADS)

    Ferrari, S.; Massironi, M.; Rothery, D. A.; Cremonese, G.

    2011-10-01

    Areas of crustal convergence and shortening on Earth, Mars and Venus are often characterized by structural domains where thrust faults are associated with strike-slip systems [1]. In the case of Mercury most structures maintain a wide elongated frontal scarp and only few of them show kinematic indicators of lateral slip. The comparison between two Mercurian linked fault systems like Beagle Rupes [2] [3] and Rembrandt scarp [4] could aid understanding of whether diverse hermean strike-slip structures are influenced by geological context such as surface heterogeneity and crustal layering or have different deformational history.

  20. Active faulting in Raghunandan Anticline, NE Bengal Basin, implications for future earthquake hazards

    NASA Astrophysics Data System (ADS)

    Ahsan, A.; Kali, E.; Coudurier Curveur, A.; van der Woerd, J.; Tapponnier, P.; Alam, A. K.; Ildefonso, S.; Banerjee, P.; Dorbath, C.

    2015-12-01

    The Bengal basin is situated in a complex tectonic zone where the Indian-Eurasian Plates and Indian-Burmese Plates are colliding. This region is known for some of the largest intra-continental seismic events of the last 500 years, the 1548 Bengal earthquake of magnitude M>8?, the 1762 Arakan earthquake of magnitude M>8?, the 1897 Shillong earthquakes of magnitude Ms 8.7, the 1918 Srimangal earthquake of magnitude Ms 7.6 and the 1950 Assam earthquake of magnitude Mw 8.6. The source faults of these events and whether these large earthquakes occurred on faults that reached the surface or reminded blind remain controversial. The Bengal basin still needs to be better understood in terms of active faulting and seismicity. The Eastern boundary of Bengal basin is marked by numerous NS trending folds of the Indo-Burma Ranges. We focused on the Raghunandan Anticline, NE Bengal basin, a broad, asymmetric, growing ramp anticline, steep west-facing front and bounded westwards by a steep tectonic scarp truncating gently east dipping Quaternary sandstone beds. The scarp morphology is suggestive of a still preserved co-seismic free face above a colluvial wedge. We carried out more than 20 topographic profiles to document the precise height and shape of this 12-15 m high scarp (above alluvial surface) and to survey a set of uplifted alluvial terraces located along the Shahapur River behind the scarp. The analysis of the topographic profiles around the Shajibazar area reveals the presence of 5 alluvial terraces hanging 3 m to 19 m above Shahapur River bed. T1 and T2 terraces are the best-preserved terraces on both sides of the Shahapur River. C14 and Be 10 ages allow to date the lowest abandonned terrace and to estimate the uplift rate of this area.

  1. 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

  2. Deep pulverization along active faults ?

    NASA Astrophysics Data System (ADS)

    Doan, M.

    2013-12-01

    Pulverization is a intensive damage observed along some active faults. Rarely found in the field, it has been associated with dynamic damage produced by large earthquakes. Pulverization has been so far only described at the ground surface, consistent with the high frequency tensile loading expected for earthquake occurring along bimaterial faults. However, we discuss here a series of hints suggesting that pulverization is expected also several hundred of meters deep. In the deep well drilled within Nojima fault after the 1995 Kobe earthquake, thin sections reveal non localized damage, with microfractured pervading a sample, but with little shear disturbing the initial microstructure. In the SAFOD borehole drilled near Parkfield, Wiersberg and Erzinger (2008) made gas monitoring while drilling found large amount of H2 gas in the sandstone west to the fault. They attribute this high H2 concentration to mechanochemical origin, in accordance with some example of diffuse microfracturing found in thin sections from cores of SAFOD phase 3 and from geophysical data from logs. High strain rate experiments in both dry (Yuan et al, 2011) and wet samples (Forquin et al, 2010) show that even under confining pressures of several tens of megapascals, diffuse damage similar to pulverization is possible. This could explain the occurrence of pulverization at depth.

  3. 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.

  4. 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

  5. Erosion rates along fault scarps and rift-shoulder environments in central and northern Kenya: Insights from new 10Be-derived basin-wide erosion rates

    NASA Astrophysics Data System (ADS)

    Torres-Acosta, V.; Strecker, M. R.; Schildgen, T. F.; Wittmann, H.; Scherler, D.; Bookhagen, B.

    2011-12-01

    The Kenya Rift is typical example of an active continental rift zone and is a fundamental part of the East African Rift system. The rift valley plays a central role in archiving the relationships between sedimentation, erosion, and climate in the region. However, the links between surface processes (i.e., erosion, sedimentation) and tectonic setting are currently poorly understood. In this study we analyze to what degree tectono-geomorphic setting and/or climatic characteristics control erosion rates in the region. We extract morphometric characteristics of the rift flanks and the plateau surface from SRTM 90-m resolution digital elevation data. We rely on calibrated, satellite-derived Tropical Rainfall Measurement Mission (TRMM 2B31) rainfall to characterize the different climatic compartments throughout the study region. We calculate specific stream power amounts using integrated rainfall as discharge amounts. Next, we analyze the relation between cosmogenic radionuclide (CRN) basin-wide erosion rates and climatic and geomorphic parameters. We determined erosion rates from twenty-six river sand samples acquired from along the flanks of the Elgeyo Escarpment (northern section of western rift flank), the Nguruman Escarpment (southern section of western flank), the Tirr Tirr Plateau (north), the Kapute Plains, and the Suguta Valley. Catchment-wide erosion rates range from 0.001 to 0.1 mm/y across the different climatic compartments. Comparisons to catchment climate and topographic characteristics suggest that more than 60% of variation in erosion can be explain by specific stream power amounts using rainfall as discharge component. The catchment-averaged normalized channel steepness index, which doesn't take into account variations in precipitation, explains only 42% of the variation in erosion rates. These observations demonstrate that the strong spatial variations in erosion rates are largely controlled by both catchment morphology and climatic gradients. In

  6. Recent high-resolution seismic reflection studies of active faults in the Puget Lowland

    NASA Astrophysics Data System (ADS)

    Liberty, L. M.; Pratt, T. L.

    2005-12-01

    In the past four years, new high-resolution seismic surveys have filled in key gaps in our understanding of active structures beneath the Puget Lowland, western Washington State. Although extensive regional and high-resolution marine seismic surveys have been fundamental to understanding the tectonic framework of the area, these marine profiles lack coverage on land and in shallow or restricted waterways. The recent high-resolution seismic surveys have targeted key structures beneath water bodies that large ships cannot navigate, and beneath city streets underlain by late Pleistocene glacial deposits that are missing from the waterways. The surveys can therefore bridge the gap between paleoseismic and marine geophysical studies, and test key elements of models proposed by regional-scale geophysical studies. Results from these surveys have: 1) documented several meters of vertical displacement on at least two separate faults in the Olympia area; 2) clarified the relationship between the Catfish Lake scarp and the underlying kink band in the Tacoma fault zone; 3) provided a first look at the structures beneath the north portion of the western Tacoma fault zone, north of previous marine profiles; 4) documented that deformation along the Seattle fault extends well east of Lake Sammamish; 5) imaged the Seattle fault beneath the Vasa Park trench; and 6) documented multiple fault strands in and south of the Seattle fault zone south of Bellevue. The results better constrain interpretations of paleoseismic investigations of past earthquakes on these faults, and provide targets for future paleoseismic studies.

  7. 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.

  8. 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

  9. 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

  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. Naval weapons center active fault map series

    NASA Astrophysics Data System (ADS)

    Roquemore, G. R.; Zellmer, J. T.

    1987-08-01

    The NWC Active Fault Map Series shows the locations of active faults and features indicative of active faulting within much of Indian Wells Valley and portions of the Randsburg Wash/Mojave B test range areas of the Naval Weapons Center. Map annotations are used extensively to identify criteria employed in identifying the fault offsets, and to present other valuable data. All of the mapped faults show evidence of having moved during about the last 12,500 years or represent geologically young faults that occur within seismic gaps. Only faults that offset the surface or show other evidence of surface deformation were mapped. A portion of the City of Ridgecrest is recommended as being a Seismic Hazard Special Studies Zone in which detailed earthquake hazard studies should be required.

  12. 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

  13. Illuminating Northern California's Active Faults

    NASA Astrophysics Data System (ADS)

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

    2009-02-01

    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 Earth™ 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).

  14. 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.

  15. Approximate active fault detection and control

    NASA Astrophysics Data System (ADS)

    Škach, Jan; Punčochář, Ivo; Šimandl, Miroslav

    2014-12-01

    This paper deals with approximate active fault detection and control for nonlinear discrete-time stochastic systems over an infinite time horizon. Multiple model framework is used to represent fault-free and finitely many faulty models. An imperfect state information problem is reformulated using a hyper-state and dynamic programming is applied to solve the problem numerically. The proposed active fault detector and controller is illustrated in a numerical example of an air handling unit.

  16. Exploring the shallow structure of the San Ramón thrust fault in Santiago, Chile (∼33.5° S), using active seismic and electric methods

    NASA Astrophysics Data System (ADS)

    Díaz, D.; Maksymowicz, A.; Vargas, G.; Vera, E.; Contreras-Reyes, E.; Rebolledo, S.

    2014-01-01

    The crustal-scale west-vergent San Ramón thrust fault system at the foot of the main Andean Cordillera in central Chile is a geologically active structure with Quaternary manifestations of complex surface rupture along fault segments in the eastern border of Santiago city. From the comparison of geophysical and geological observations, we assessed the subsurface structure pattern affecting sedimentary cover and rock-substratum topography across fault scarps, which is critic for evaluating structural modeling and associated seismic hazard along this kind of faults. We performed seismic profiles with an average length of 250 m, using an array of twenty-four geophones (GEODE), and 25 shots per profile, supporting high-resolution seismic tomography for interpreting impedance changes associated to deformed sedimentary cover. The recorded traveltime refractions and reflections were jointly inverted by using a 2-D tomographic approach, which resulted in variations across the scarp axis in both velocities and reflections interpreted as the sedimentary cover-rock substratum topography. Seismic anisotropy observed from tomographic profiles is consistent with sediment deformation triggered by west-vergent thrust tectonics along the fault. Electrical soundings crossing two fault scarps supported subsurface resistivity tomographic profiles, which revealed systematic differences between lower resistivity values in the hanging wall with respect to the footwall of the geological structure, clearly limited by well-defined east-dipping resistivity boundaries. The latter can be interpreted in terms of structurally driven fluid content-change between the hanging wall and the footwall of a permeability boundary associated with the San Ramón fault. The overall results are consistent with a west-vergent thrust structure dipping ∼55° E at subsurface levels in piedmont sediments, with local complexities being probably associated to fault surface rupture propagation, fault-splay and

  17. Exploring the shallow structure of the San Ramón thrust fault in Santiago, Chile (~33.5° S), using active seismic and electric methods

    NASA Astrophysics Data System (ADS)

    Díaz, D.; Maksymowicz, A.; Vargas, G.; Vera, E.; Contreras-Reyes, E.; Rebolledo, S.

    2014-08-01

    The crustal-scale west-vergent San Ramón thrust fault system, which lies at the foot of the main Andean Cordillera in central Chile, is a geologically active structure with manifestations of late Quaternary complex surface rupture on fault segments along the eastern border of the city of Santiago. From the comparison of geophysical and geological observations, we assessed the subsurface structural pattern that affects the sedimentary cover and rock-substratum topography across fault scarps, which is critical for evaluating structural models and associated seismic hazard along the related faults. We performed seismic profiles with an average length of 250 m, using an array of 24 geophones (Geode), with 25 shots per profile, to produce high-resolution seismic tomography to aid in interpreting impedance changes associated with the deformed sedimentary cover. The recorded travel-time refractions and reflections were jointly inverted by using a 2-D tomographic approach, which resulted in variations across the scarp axis in both the velocities and the reflections that are interpreted as the sedimentary cover-rock substratum topography. Seismic anisotropy observed from tomographic profiles is consistent with sediment deformation triggered by west-vergent thrust tectonics along the fault. Electrical soundings crossing two fault scarps were used to construct subsurface resistivity tomographic profiles, which reveal systematic differences between lower resistivity values in the hanging wall with respect to the footwall of the geological structure, and clearly show well-defined east-dipping resistivity boundaries. These boundaries can be interpreted in terms of structurally driven fluid content change between the hanging wall and the footwall of the San Ramón fault. The overall results are consistent with a west-vergent thrust structure dipping ~55° E in the subsurface beneath the piedmont sediments, with local complexities likely associated with variations in fault

  18. Extensive Submarine Active Fault and the 2011 off the Pacific Coast of Tohoku Earthquake

    NASA Astrophysics Data System (ADS)

    Nakata, T.; Kumamoto, T.; Muroi, S.; Watanabe, M.

    2013-12-01

    Active faults observed on seafloor along Japan Trench are resultants of repeated large earthquakes. We discuss on the relation between large earthquakes and their source faults based on a detailed active fault map along Japan Trench. Judging from location and continuation of active faults in the earthquake source area, we consider that one of the extensive thrust faults which extends from off-Sanriku to off-Ibaraki for about 500km, is directly related to the source fault of the 2011 off the Pacific coast of Tohoku Earthquake. The 2011 off the Pacific Coast of Tohoku Earthquake (Mw9.0) generated large tsunami with massive pulsating pattern of waves (Maeda et al. 2011). A leading hypothesis believed among many seismologists that an earthquake source fault that generated the earthquake, caused the near-surface fault rupture along the axis of Japan Trench, and large displacement ~50m eastward and ~7 to ~10m upward was estimated from comparison of data obtained before and after the earthquake in 2004 and 2011 by multibeam bathymetric surveys across the trench (Fujiwara et al. 2011). Satake et al. (2011) explained the large tsunami height by simultaneous faulting on two different fault planes, one on subducting plate boundary and the other near the trench axis. Since most of the workers hypothesized without any doubt believed that the earthquake was caused by the fault ruptured up to the trench axis, existence of submarine active fault is rather overlooked so far. However, we consider the large displacement is due to landslide and do not find any extensive fault scarp on the trench axis. We simulated pattern of seafloor deformation associated with the earthquake using a simple dislocation model for a single fault plane with uniform slip that dips 14 degree in depth and 33.6 degree beneath the tectonic bulge related to the extensive active fault. A result shows that an area of large uplift agrees more or less with the location of tectonic bulge with width of about 20km

  19. Rare Earth Elements reveal past earthquakes on limestone normal faults

    NASA Astrophysics Data System (ADS)

    Manighetti, I.; Boucher, E.; Chauvel, C.; Schlagenhauf, A.; Benedetti, L.

    2009-12-01

    separating the major earthquake ruptures that produced the scarp exhumation (the identification was independently performed using cosmogenic 36Cl modeling). This finding confirms that the REE concentration peaks are excellent indicators of the position of paleo-ground levels and good markers for the large earthquake ruptures that created the exhumation. We thus conclude that simple REE chemical analyses of seismically exhumed fault scarp rocks may be used to identify past major earthquakes. They also allow the measurement of the vertical slip produced by the earthquakes along the fault. This simple novel approach is thus very promising to recover seismic histories on active faults.

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

    NASA Astrophysics Data System (ADS)

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

    2007-12-01

    As a result of continued distributed deformation in the Gulf Extensional Province along an oblique-divergent plate margin, active normal faulting is well manifest in southeastern Baja California. By characterizing normal-fault related deformation along the San Juan de los Planes fault zone (SJPFZ) southwest of La Paz, Baja California Sur we contribute to understanding the patterns and rates of faulting along the southwest gulf-margin fault system. The geometry, history, and rate of faulting provide constraints on the relative significance of gulf-margin deformation as compared to axial system deformation. The SJPFZ is a major north-trending structure in the southern Baja margin along which we focused our field efforts. These investigations included: a detailed strip map of the active fault zone, including delineation of active scarp traces and geomorphic surfaces on the hanging wall and footwall; fault scarp profiles; analysis of bedrock structures to better understand how the pattern and rate of strain varied during the development of this fault zone; and a gravity survey across the San Juan de los Planes basin to determine basin geometry and fault behavior. The map covers a N-S swath from the Gulf of California in the north to San Antonio in the south, an area ~45km long and ~1-4km wide. Bedrock along the SJPFZ varies from Cretaceous Las Cruces Granite in the north to Cretaceous Buena Mujer Tonalite in the south and is scarred by shear zones and brittle faults. The active scarp-forming fault juxtaposes bedrock in the footwall against Late Quaternary sandstone-conglomerate. This ~20m wide zone is highly fractured bedrock infused with carbonate. The northern ~12km of the SJPFZ, trending 200°, preserves discontinuous scarps 1-2km long and 1-3m high in Quaternary units. The scarps are separated by stretches of bedrock embayed by hundreds of meters-wide tongues of Quaternary sandstone-conglomerate, implying low Quaternary slip rate. Further south, ~2 km north of the

  1. Active faults in southeastern Harris County, Texas

    NASA Technical Reports Server (NTRS)

    Clanton, U. S.; Amsbury, D. L.

    1975-01-01

    Aerial color infrared photography was used to investigate active faults in a complex graben in southeastern Harris County, Tex. The graben extends east-west across an oil field and an interstate highway through Ellington Air Force Base (EAFB), into the Clear Lake oil field and on to LaPorte, Tex. It was shown that the fault pattern at EAFB indicates an appreciable horizontal component associated with the failure of buildings, streets, and runways. Another fault system appears to control the shoreline configuration of Clear Lake, with some of the faults associated with tectonic movements and the production of oil and gas, but many related to extensive ground water withdrawal.

  2. Identifying past earthquakes on an active normal fault (Magnola, Italy) from the chemical analysis of its exhumed carbonate fault plane

    NASA Astrophysics Data System (ADS)

    Carcaillet, Julien; Manighetti, Isabelle; Chauvel, Catherine; Schlagenhauf, Aloé; Nicole, Jean-Marc

    2008-07-01

    A normal fault scarp exhumed by repeated strong earthquakes is made of a series of rupture zones that were exposed, thus weathered, over significantly different time spans. We show that such differential weathering can be detected in the chemical content of the fault scarp rocks, and its signature used as a base to decipher the past earthquake history of the fault. We focus on the Magnola normal fault, Central Italy, whose Holocene seismic slip history has already been determined by Palumbo et al. (ESPL, 225, 163-176, 2004) from in situ36Cl cosmic ray exposure dating of the fault limestone scarp surface. Five major earthquakes were found to have occurred over the last 12 ka, with slips of 1.5-3 m and recurrence times of 0.7-3.1 ka. We analyze the major and trace element concentrations of 15 carbonate samples collected from base to top of the 10 m-high Magnola Holocene scarp, next to the previous sampling done by Palumbo et al. [Palumbo, L., Benedetti, L., Bourlès, D., Cinque, A., Finkel, R., 2004. Slip history of the Magnola fault (Apennines, Central Italy) from 36Cl surface exposure dating: evidence for strong earthquake over Holocene. Earth Planet. Sci. Lett. 225, 163-176.]. We find that most element concentrations decrease upscarp at a rate averaging 5%/m. This decrease is attributed to leaching and re-precipitation of purer calcite that increase with exposure time. Superimposed to the overall leaching, concentration peaks are found at the transition zones separating the earthquake ruptures. These concentration peaks likely result from enrichment of the scarp sections that remained stuck in the 30-50 cm-thick impurity-rich upper soil during the quiescence periods that separated the earthquakes. Because the rare earth elements (REE) are among those most significantly enriched at the earthquake transition zones, they are the best chemical markers of past large seismic events. We finally propose a first-order model that reproduces adequately the observations. Our

  3. Active faulting Vs other surface displacing complex geomorphic phenomena. Case studies from a tectonically active area, Abruzzi Region, central Apennines, Italy

    NASA Astrophysics Data System (ADS)

    Lo Sardo, Lorenzo; Gori, Stefano; Falcucci, Emanuela; Saroli, Michele; Moro, Marco; Galadini, Fabrizio; Lancia, Michele; Fubelli, Giandomenico; Pezzo, Giuseppe

    2016-04-01

    How can be univocally inferred the genesis of a linear surface scarp as the result of an active and capable fault (FAC) in tectonically active regions? Or, conversely, how it is possible to exclude that a scarp is the result of a capable fault activation? Trying to unravel this open questions, we show two ambiguous case studies about the problem of the identification of active and capable faults in a tectonically active area just based on the presence of supposed fault scarps at surface. The selected cases are located in the area comprised between the Middle Aterno Valley Fault (MAVF) and the Campo Imperatore Plain (Abruzzi Region, central Apennines), nearby the epicentral area of the April 6th, 2009 L'Aquila earthquake. In particular, the two case studies analysed are located in a region characterized by a widespread Quaternary faults and by several linear scarps: the case studies of (i) Prata D'Ansidonia area and (ii) Santo Stefano di Sessanio area. To assess the origin and the state of activity of the investigated geomorphic features, we applied a classical geological and geomorphological approach, based on the analysis of the available literature, the interpretation of the aerial photographs, field surveying and classical paleoseismological approach, the latter consisting in digging excavations across the analysed scarps. These analysis were then integrated by morphometrical analyses. As for case (i), we focused on determining the geomorphic "meaning" of linear scarps carved onto fluvial-deltaic conglomerates (dated to the Early Pleistocene; Bertini and Bosi, 1993), up to 3 meters high and up to 1,5 km long, that border a narrow, elongated and flat-bottom depressions, filled by colluvial deposits. These features groove the paleo-landsurface of Valle Daria (Bosi and Bertini, 1970), wide landsurface located between Barisciano and Prata D'Ansidonia. Entwining paleoseismological trenching with geophysical analyses (GPR, ERT and microgravimetrical prospections), it

  4. Evidence for propagating, active tensional faulting in Upper Kåfjord valley, Troms County, Norway

    NASA Astrophysics Data System (ADS)

    Redfield, T. F.; Osmundsen, P. T.; Henderson, I. H. C.; Hermanns, R. L.

    2010-05-01

    New concepts governing margin extension and post-rift passive margin evolution are appearing from onshore and offshore studies. In Norway topographic escarpments, creation, preservation and destruction of landforms, and drainage patterns are related to structural templates created during the Jurassic rift phase. Contradicting the notion that post-rift isostatic compensation, thermal subsidence, and topographic degradation mark a passive margin's final evolutionary phases, we present geological evidence for currently-active tensional deformation, accommodated by release faulting, in uppermost Kåfjordalen and Signaldalen. In Signaldalen, propagation of the deformation tip has introduced active normal faulting to Finland. Ground observations indicate a large normal fault defines the eastern border of the Lyngen 'Alps' peninsula. There, a series of exceptionally well-preserved triangular facets adorn a sharp, elevated escarpment. To the east a swarm of small NE-trending normal faults are exposed in roadside outcrops near the mouth of Kåfjord, dipping both to the NW and SE. Displacement across the fault swarm is asymmetric, the greatest component of motion being down-to-the-NW in the direction of the Lyngen Fault. Another set of NE trending, NW dipping faults crop out at Revsdalfjellet. We interpret these faults to reflect splays to the Lyngen Fault. The hanging wall of the Lyngen Fault is characterized by numerous clusters of fault-controlled rockslides. We interpret the valleys of Signaldalen, Skibotndalen, and Kåfjordalen, located in the hanging wall of the Lyngen Fault, to have formed at least partly under the influence of release faults that accommodated hanging wall flexure and failure. Other fault scarps, trending more NW-SE, crop out at two Kåfjord rockslide sites, Nomandalstinden and Litledalen. Mineralized surfaces exhibiting dip-slip slickenlines indicate most of these faults are true tectonic features, not simply gravitationally-driven 'sackung' planes

  5. Wrinkle ridge-upland scarp transitions: Implications for the mechanical properties of the deformed materials

    NASA Technical Reports Server (NTRS)

    Watters, Thomas R.; Tuttle, Michael J.; Simpson, Debra

    1991-01-01

    Wrinkle ridge-upland scarp transitions are structures that occur at the contact between smooth plains material and highlands or uplands materials on the Moon and Mars. In the smooth plains material the structures have a morphology typical of wrinkle ridges, interpreted to be the result of a combination of folding and thrust faulting. Where the structures extend into the uplands, a distinct change in the morphology occurs. The generally asymmetric cross sectional geometry characteristics of wrinkle ridges becomes that of a one-sided, often lobate scarp. The scarp is indistinguishable from other highland/upland scarps, interpreted to be the result of reverse or thrust faulting. Although these structures are rare, they provide important insight into the mechanical properties of deformed materials. These insights are discussed.

  6. 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

  7. High-resolution 3D seismic reflection imaging across active faults and its impact on seismic hazard estimation in the Tokyo metropolitan area

    NASA Astrophysics Data System (ADS)

    Ishiyama, Tatsuya; Sato, Hiroshi; Abe, Susumu; Kawasaki, Shinji; Kato, Naoko

    2016-10-01

    We collected and interpreted high-resolution 3D seismic reflection data across a hypothesized fault scarp, along the largest active fault that could generate hazardous earthquakes in the Tokyo metropolitan area. The processed and interpreted 3D seismic cube, linked with nearby borehole stratigraphy, suggests that a monocline that deforms lower Pleistocene units is unconformably overlain by middle Pleistocene conglomerates. Judging from structural patterns and vertical separation on the lower-middle Pleistocene units and the ground surface, the hypothesized scarp was interpreted as a terrace riser rather than as a manifestation of late Pleistocene structural growth resulting from repeated fault activity. Devastating earthquake scenarios had been predicted along the fault in question based on its proximity to the metropolitan area, however our new results lead to a significant decrease in estimated fault length and consequently in the estimated magnitude of future earthquakes associated with reactivation. This suggests a greatly reduced seismic hazard in the Tokyo metropolitan area from earthquakes generated by active intraplate crustal faults.

  8. Active faulting in the Walker Lane

    NASA Astrophysics Data System (ADS)

    Wesnousky, Steven G.

    2005-06-01

    Deformation across the San Andreas and Walker Lane fault systems accounts for most relative Pacific-North American transform plate motion. The Walker Lane is composed of discontinuous sets of right-slip faults that are located to the east and strike approximately parallel to the San Andreas fault system. Mapping of active faults in the central Walker Lane shows that right-lateral shear is locally accommodated by rotation of crustal blocks bounded by steep-dipping east striking left-slip faults. The left slip and clockwise rotation of crustal blocks bounded by the east striking faults has produced major basins in the area, including Rattlesnake and Garfield flats; Teels, Columbus and Rhodes salt marshes; and Queen Valley. The Benton Springs and Petrified Springs faults are the major northwest striking structures currently accommodating transform motion in the central Walker Lane. Right-lateral offsets of late Pleistocene surfaces along the two faults point to slip rates of at least 1 mm/yr. The northern limit of northwest trending strike-slip faults in the central Walker Lane is abrupt and reflects transfer of strike-slip to dip-slip deformation in the western Basin and Range and transformation of right slip into rotation of crustal blocks to the north. The transfer of strike slip in the central Walker Lane to dip slip in the western Basin and Range correlates to a northward broadening of the modern strain field suggested by geodesy and appears to be a long-lived feature of the deformation field. The complexity of faulting and apparent rotation of crustal blocks within the Walker Lane is consistent with the concept of a partially detached and elastic-brittle crust that is being transported on a continuously deforming layer below. The regional pattern of faulting within the Walker Lane is more complex than observed along the San Andreas fault system to the west. The difference is attributed to the relatively less cumulative slip that has occurred across the Walker

  9. Field experiments of beach scarp erosion during oblique wave, stormy conditions (Normandy, France)

    NASA Astrophysics Data System (ADS)

    Bonte, Yoann; Levoy, Franck

    2015-05-01

    A field-based experimental study of beach scarp morphodynamic evolution was conducted on the shoreface of a macrotidal sandy beach subject to storms combined with spring tide events (Luc-sur-Mer, France). Both video and in-situ measurements on an artificial berm are used to understand beach scarp evolution over one tide during stormy conditions. Image time stacks are used to analyze the swash action on the beach scarp and topographical data of the scarp are recorded with a terrestrial scanner laser to quantify the morphodynamic response of the beach scarp to wave action. This work provides a new and unique dataset about beach scarp changes and berm morphology in particular under rising tide and oblique wind-wave conditions. During one stormy event, the berm was completely destroyed. However, contrasting alongshore changes were measured during the erosive phase with different crest and foot scarp retreats and eroded volumes between the west and the east side of the berm. The beach in front of the scarp also shows a contrasting residual evolution, indicating an evident longshore sediment transport on the study area as a consequence of incident oblique wave conditions. A strong connection between beach evolution and beach scarp changes is clearly identified. The scarp erosion increases on the west side of the berm when the beach level is lowered and reduces when the beach surface rises on the east side. The beach slope and foreshore elevation as a result of a longshore sediment transport between east and west profiles, influence swash activity. Overall, water depth and swash activity became progressively different along the scarp during the experiment. Swash measurements indicate that the presence of the beach scarp strongly influences the swash motion. At high tide, the reflection of the uprush on the scarp front induces a collision between the reflected backwash and the following uprush dynamic. These collisions reduce and sometimes stop the motion of the following

  10. 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.

  11. 3D modelling of the active normal fault network in the Apulian Ridge (Eastern Mediterranean Sea): Integration of seismic and bathymetric data with implicit surface methods

    NASA Astrophysics Data System (ADS)

    Bistacchi, Andrea; Pellegrini, Caludio; Savini, Alessandra; Marchese, Fabio

    2016-04-01

    The Apulian ridge (North-eastern Ionian Sea, Mediterranean), interposed between the facing Apennines and Hellenides subduction zones (to the west and east respectively), is characterized by thick cretaceous carbonatic sequences and discontinuous tertiary deposits crosscut by a penetrative network of NNW-SSE normal faults. These are exposed onshore in Puglia, and are well represented offshore in a dataset composed of 2D seismics and wells collected by oil companies from the '60s to the '80s, more recent seismics collected during research projects in the '90s, recent very high resolution seismics (VHRS - Sparker and Chirp-sonar data), multibeam echosounder bathymetry, and sedimentological and geo-chronological analyses of sediment samples collected on the seabed. Faults are evident in 2D seismics at all scales, and their along-strike geometry and continuity can be characterized with multibeam bathymetric data, which show continuous fault scarps on the seabed (only partly reworked by currents and covered by landslides). Fault scarps also reveal the finite displacement accumulated in the Holocene-Pleistocene. We reconstructed a 3D model of the fault network and suitable geological boundaries (mainly unconformities due to the discontinuous distribution of quaternary and tertiary sediments) with implicit surface methods implemented in SKUA/GOCAD. This approach can be considered very effective and allowed reconstructing in details complex structures, like the frequent relay zones that are particularly well imaged by seafloor geomorphology. Mutual cross-cutting relationships have been recognized between fault scarps and submarine mass-wasting deposits (Holocene-Pleistocene), indicating that, at least in places, these features are coeval, hence the fault network should be considered active. At the regional scale, the 3D model allowed measuring the horizontal WSW-ENE stretching, which can be associated to the bending moment applied to the Apulian Plate by the combined effect

  12. Strain pattern represented by scarps formed during the earthquakes of October 2, 1915, Pleasant Valley, Nevada

    USGS Publications Warehouse

    Wallace, R.E.

    1979-01-01

    The pattern of scarps developed during the earthquakes of October 2, 1915, in Pleasant Valley, Nevada, may have formed as a result of a modern stress system acting on a set of fractures produced by an earlier stress system which was oriented differently. Four major scarps developed in a right-stepping, en-echelon pattern suggestive of left-lateral slip across the zone and an extension axis oriented approximately S85??W. The trend of the zone is N25??E. However, the orientation of simple dip-slip on most segments trending approximately N20-40?? E and a right-lateral component of displacement on several N- and NW-trending segments of the scarps indicate that the axis of regional extension was oriented between N50?? and 70?? W, normal to the zone. The cumulative length of the scarps is 60 km, average vertical displacement 2 m, and the maximum vertical displacement near the Pearce School site 5.8 m. Almost everywhere the 1915 scarps formed along an older scarp line, and in some places older scarps represent multiple previous events. The most recent displacement event prior to 1915 is interpreted to have occurred more than 6600 years ago, but possibly less than 20,000 years ago. Some faults expressed by older scarps that trend northwest were not reactivated in 1915, possibly because they are oriented at a low angle with respect to the axis of modern regional extension. The 1915 event occurred in an area of overlap of three regional fault trends oriented northwest, north, and northeast and referred to, respectively, as the Oregon-Nevada, Northwest Nevada, and Midas-Battle Moutain trends. Each of these trends may have developed at a different time; the Oregon-Nevada trend was possibly the earliest and developed in Late Miocene time (Stewart et al. 1975). Segments of the 1915 scarps are parallel to each of these trends, suggesting influence by older sets of fractures. ?? 1979.

  13. 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

  14. 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

  15. The Analysis of Scarp Populations to Constrain Slow--Spreading Ridge Kinematics

    NASA Astrophysics Data System (ADS)

    Thomas, M. F.; Irving, D. B.

    2006-12-01

    Quantitative studies of scarps and associated mass--wasting complexes show that the evolution of off--axis topography, in particular inner Corner High (ICHs) but also at other locations, are a function of measured seismicity and may correlate with the presence of serpentinized Peridotites. Deep-tow sidescan sonar data from the Fifteen-Twenty, Kane and Atlantis fracture zones (15--30 degrees N, Mid Atlantic Ridge) allow high-resolution morphotectonic models to be developed for ridge--transform intersections. These intersections are characterised by ridge-asymmetric extensional faulting which causes "megamullion" exhumation surfaces to reach high relief before distal normal faulting and crustal cooling lower the topography back to the abyssal plain. Scarp development occurs in two distinct locations: i) the walls of the axial valley, which correspond to fault scarps where constant slumping occurs. Here, frequency--magnitude analysis suggests seismicity is the main driving force. ii) Inward facets of ICHs possess long--lived (1--3 Ma) scarp slopes which fail along hydrothermally--altered normal fault zones. Several episodes of failure are inferred from geomorphic analysis of downslope deposits. Ridge kinematics are modelled using fabric studies from recovered core, interpolated magnetic isochrons and teleseismic data. We suggest that ICHs are stable and necessary features at transform- controlled slow- spreading segments and that the variation in scarp populations that give them such differing morphologies can be explained by a combination of seismicity and exposure to hydrothermal alteration during exhumation.

  16. 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).

  17. 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.

  18. Holocene faulting on the Mission fault, northwest Montana

    SciTech Connect

    Ostenaa, D.A.; Klinger, R.E.; Levish, D.R. )

    1993-04-01

    South of Flathead Lake, fault scarps on late Quaternary surfaces are nearly continuous for 45 km along the western flank of the Mission Range. On late Pleistocene alpine lateral moraines, scarp heights reach a maximum of 17 m. Scarp heights on post glacial Lake Missoula surfaces range from 2.6--7.2 m and maximum scarp angles range from 10[degree]--24[degree]. The stratigraphy exposed in seven trenches across the fault demonstrates that the post glacial Lake Missoula scarps resulted from at least two surface-faulting events. Larger scarp heights on late Pleistocene moraines suggests a possible third event. This yields an estimated recurrence of 4--8 kyr. Analyses of scarp profiles show that the age of the most surface faulting is middle Holocene, consistent with stratigraphic evidence found in the trenches. Rupture length and displacement imply earthquake magnitudes of 7 to 7.5. Previous studies have not identified geologic evidence of late Quaternary surface faulting in the Rocky Mountain Trench or on faults north of the Lewis and Clark line despite abundant historic seismicity in the Flathead Lake area. In addition to the Mission fault, reconnaissance studies have located late Quaternary fault scarps along portions of faults bordering Jocko and Thompson Valleys. These are the first documented late Pleistocene/Holocene faults north of the Lewis and Clark line in Montana and should greatly revise estimates of earthquake hazards in this region.

  19. A summary of the active fault investigation in the extension sea area of Kikugawa fault and the Nishiyama fault , N-S direction fault in south west Japan

    NASA Astrophysics Data System (ADS)

    Abe, S.

    2010-12-01

    In this study, we carried out two sets of active fault investigation by the request from Ministry of Education, Culture, Sports, Science and Technology in the sea area of the extension of Kikugawa fault and the Nishiyama fault. We want to clarify the five following matters about both active faults based on those results. (1)Fault continuity of the land and the sea. (2) The length of the active fault. (3) The division of the segment. (4) Activity characteristics. In this investigation, we carried out a digital single channel seismic reflection survey in the whole area of both active faults. In addition, a high-resolution multichannel seismic reflection survey was carried out to recognize the detailed structure of a shallow stratum. Furthermore, the sampling with the vibrocoring to get information of the sedimentation age was carried out. The reflection profile of both active faults was extremely clear. The characteristics of the lateral fault such as flower structure, the dispersion of the active fault were recognized. In addition, from analysis of the age of the stratum, it was recognized that the thickness of the sediment was extremely thin in Holocene epoch on the continental shelf in this sea area. It was confirmed that the Kikugawa fault extended to the offing than the existing results of research by a result of this investigation. In addition, the width of the active fault seems to become wide toward the offing while dispersing. At present, we think that we can divide Kikugawa fault into some segments based on the distribution form of the segment. About the Nishiyama fault, reflection profiles to show the existence of the active fault was acquired in the sea between Ooshima and Kyushu. From this result and topographical existing results of research in Ooshima, it is thought that Nishiyama fault and the Ooshima offing active fault are a series of structure. As for Ooshima offing active fault, the upheaval side changes, and a direction changes too. Therefore, we

  20. Late Quaternary faulting on the Manas and Hutubi reverse faults in the northern foreland basin of Tian Shan, China

    NASA Astrophysics Data System (ADS)

    Gong, Zhijun; Li, Sheng-Hua; Li, Bo

    2015-08-01

    The Tian Shan Range lies in the actively deforming part of the India-Asia collision zone. In the northern foreland basin of Tian Shan, the strata were intensively deformed by Cenozoic folding and faulting. Slip rate studies along these faults are important for understanding the dynamics of crustal deformation and evaluating the seismic hazards in the region. Two reverse faults (the Manas and Hutubi faults) in the northern foreland basin were investigated. Due to past faulting events along these faults, the terrace treads along the Manas River were ruptured, forming fault scarps several meters in height. Loess deposits were trapped and preserved at the surface ruptures along these scarps. The thickness of the trapped loess is dependent on the size of the ruptures. The minimum and maximum ages of these scarps are constrained by dating the loess preserved at the surface ruptures and the terrace treads, respectively, using the quartz optically stimulated luminescence (OSL) dating technique. Our dating results suggest that the loess trapped at the ruptures was deposited from the early to mid-Holocene at the Hutubi Fault, and from the mid- to late-Holocene at the Manas Fault. The vertical displacements of the faults were evaluated by measuring the topographic profiles across the investigated fault scarps using the differential global position system (DGPS). Our results suggest that, during the late Quaternary in the studied region, the vertical slip rates of the Manas Fault were between ˜ 0.74 mm /yr and ˜ 1.6 mm /yr, while the Hutubi Fault had a much lower vertical slip rate between ˜ 0.34 mm /yr and ˜ 0.40 mm /yr. The tectonic implications of our results are discussed.

  1. a case of casing deformation and fault slip for the active fault drilling

    NASA Astrophysics Data System (ADS)

    Ge, H.; Song, L.; Yuan, S.; Yang, W.

    2010-12-01

    Active fault is normally defined as a fault with displacement or seismic activity during the geologically recent period (in the last 10,000 years, USGS). Here, we refer the active fault to the fault that is under the post-seismic stress modification or recovery. Micro-seismic, fault slip would happen during the recovery of the active faults. It is possible that the drilling through this active fault, such as the Wenchuan Fault Scientific Drilling(WFSD), will be accompanied with some possible wellbore instability and casing deformation, which is noteworthy for the fault scientific drilling. This presentation gives a field case of the Wenchuan earthquake. The great Wenchuan earthquake happened on May 12, 2008. An oilfield is 400km apart from the epicenter and 260km from the main fault. Many wells were drilled or are under drilling. Some are drilled through the active fault and a few tectonic active phenomenons were observed. For instance, a drill pipe was cut off in the well which was just drilled through the fault. We concluded that this is due to the fault slip,if not, so thick wall pipe cannot be cut off. At the same time, a mass of well casings of the oilfield deformed during the great Wenchuan Earthquake. The analysis of the casing deformation characteristic, formation structure, seismicity, tectonic stress variation suggest that the casing deformation is closely related to the Wenchuan Earthquake. It is the tectonic stress variation that induces seismic activities, fault slip, salt/gypsum creep speedup, and deformation inconsistent between stratums. Additional earthquake dynamic loads were exerted on the casing and caused its deformation. Active fault scientific drilling has become an important tool to understand earthquake mechanism and physics. The casing deformation and wellbore instability is not only a consequence of the earthquake but also an indicator of stress modification and fault activity. It is noteworthy that tectonic stress variation and fault

  2. 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.

  3. Fault structure and deformation rates at the Lastros-Sfaka Graben, Crete

    NASA Astrophysics Data System (ADS)

    Mason, J.; Schneiderwind, S.; Pallikarakis, A.; Wiatr, T.; Mechernich, S.; Papanikolaou, I.; Reicherter, K.

    2016-06-01

    The Lastros and Sfaka faults have an antithetic relationship and form a ca. 2 km wide graben within the Ierapetra fault zone in eastern Crete. Both faults have impressive bedrock fault scarps many metres in height which form prominent features within the landscape. t-LiDAR investigations undertaken on the Lastros fault are used to accurately determine vertical displacements along a ca. 1.3 km long scanned segment. Analyses show that previous estimations of post glacial slip rate are too high because there are many areas along strike where the scarp is exhumed by natural erosion and/or anthropogenic activity. In areas not affected by erosion there is mean scarp height of 9.4 m. This leads to a slip rate of 0.69 ± 0.15 mm/a using 15 ± 3 ka for scarp exhumation. Using empirical calculations the expected earthquake magnitudes and displacement per event are discussed based on our observations. Trenching investigations on the Sfaka fault identify different generations of fissure fills. Retrodeformation analyses and 14C dating of the fill material indicate at least four events dating back to 16,055 ± 215 cal BP, with the last event having occurred soon after 6102 ± 113 cal BP. The Lastros fault is likely the controlling fault in the graben, and ruptures on the Lastros fault will sympathetically affect the Sfaka fault, which merges with the Lastros fault at a depth of 2.4 km. The extracted dates from the Sfaka fault fissure fills therefore either represent activity on the Lastros fault, assuming they formed coseismically, or accommodation events. Cross sections show that the finite throw is limited to around 300 m, and the derived slip rate for the Lastros fault therefore indicates that both faults are relatively young having initiated 435 ± 120 ka.

  4. Geophysical characterization of buried active faults: the Concud Fault (Iberian Chain, NE Spain)

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

    The Concud Fault is a 14-km-long active fault that extends close to Teruel, a city with about 35,000 inhabitants in the Iberian Range (NE Spain). It shows evidence of recurrent activity during Late Pleistocene time, posing a significant seismic hazard in an area of moderate-to-low tectonic rates. A geophysical survey was carried out along the mapped trace of the southern branch of the Concud Fault to evaluate the geophysical signature from the fault and the location of paleoseismic trenches. The survey identified a lineation of inverse magnetic dipoles at residual and vertical magnetic gradient, a local increase in apparent conductivity, and interruptions of the underground sediment structure along GPR profiles. The origin of these anomalies is due to lateral contrast between both fault blocks and the geophysical signature of Quaternary materials located above and directly south of the fault. The spatial distribution of anomalies was successfully used to locate suitable trench sites and to map non-exposed segments of the fault. The geophysical anomalies are related to the sedimentological characteristics and permeability differences of the deposits and to deformation related to fault activity. The results illustrate the usefulness of geophysics to detect and map non-exposed faults in areas of moderate-to-low tectonic activity where faults are often covered by recent pediments that obscure geological evidence of the most recent earthquakes. The results also highlight the importance of applying multiple geophysical techniques in defining the location of buried faults.

  5. Episodic activity of a dormant fault in tectonically stable Europe: The Rauw fault (NE Belgium)

    NASA Astrophysics Data System (ADS)

    Verbeeck, Koen; Wouters, Laurent; Vanneste, Kris; Camelbeeck, Thierry; Vandenberghe, Dimitri; Beerten, Koen; Rogiers, Bart; Schiltz, Marco; Burow, Christoph; Mees, Florias; De Grave, Johan; Vandenberghe, Noël

    2017-03-01

    Our knowledge about large earthquakes in stable continental regions comes from studies of faults that generated historical surface rupturing earthquakes or were identified by their recent imprint in the morphology. Here, we evaluate the co-seismic character and movement history of the Rauw fault in Belgium, which lacks geomorphological expression and historical/present seismicity. This 55-km-long normal fault, with known Neogene and possibly Early Pleistocene activity, is the largest offset fault west of the active Roer Valley Graben. Its trace was identified in the shallow subsurface based on high resolution geophysics. All the layers within the Late Pliocene Mol Formation (3.6 to 2.59 Ma) are displaced 7 m vertically, without growth faulting, but deeper deposits show increasing offset. A paleoseismic trench study revealed cryoturbated, but unfaulted, late glacial coversands overlying faulted layers of Mol Formation. In-between those deposits, the fault tip was eroded, along with evidence for individual displacement events. Fragmented clay gouge observed in a micromorphology sample of the main fault evidences co-seismic faulting, as opposed to fault creep. Based on optical and electron spin resonance dating and trench stratigraphy, the 7 m combined displacement is bracketed to have occurred between 2.59 Ma and 45 ka. The regional presence of the Sterksel Formation alluvial terrace deposits, limited to the hanging wall of the Rauw fault, indicates a deflection of the Meuse/Rhine confluence (1.0 to 0.5 Ma) by the fault's activity, suggesting that most of the offset occurred prior to/at this time interval. In the trench, Sterksel Formation is eroded but reworked gravel testifies for its former presence. Hence, the Rauw fault appears as typical of plate interior context, with an episodic seismic activity concentrated between 1.0 and 0.5 Ma or at least between 2.59 Ma to 45 ka, possibly related to activity variations in the adjacent, continuously active Roer Valley

  6. Sag-ponding and its Significance in determining Paleo-seismic events along the active strike- slip fault

    NASA Astrophysics Data System (ADS)

    Li, C.; Zhang, P.; Yuan, D.

    2007-12-01

    During the development of one active fault, we really want to know how it behaves and what it will do next. This mostly depends on the record and preservation of the information showing the action of the fault. Sparse young sediments or sediments with coarse grain along most of big strike-slip faults make it hard record and preserve the vestige of the paleo-seismic events. This extremely restricts the development of the Paleo-seismic research. Sag-ponding as well as the deposits in ponds, which are formed by the movement of the fault, can help settling the difficulty. Periodic sag-ponding is a feature to which should be paid more attention along the strike-slip fault, it can develop a pond to capture plenty fine sediments which well record the action of the faults. Sag-ponding can easily be found on the main active strike-slip faults in northern and eastern Tibet. By disclosing the sag-ponding depositions with 3-D excavations, sediment distribution and characters of relevant sag-ponds, and the relation between the sag-ponding and faulting were discussed. 1. Mechanism of the formation of the sag-pond When the valleys and ridges intersecting with the fault are displaced, the fault scarps will block the flow of the streams cut by the fault, or make the gullies develop ancon-like bend. This would form a space for water-storage, and thus a sag-pond comes into being. If the fault behaves like this many times, multi-sag-ponding will occur. 2. Rhythmic sag-ponding deposition features and stratigraphic sequence (1) Vertical characteristics. Observed from the stratigraphic profiles disclosed by the excavation, stratigraphic sequence shows good rhythms. There are several rhythms in each pond, and one rhythm is composed of the lower coarse layers and the upper fine layers. That is, the grains are coarser below and finer upward. (2) Transverse variation. In the direction parallel to the fault, the deposition center of each sag-pond appears regular movement, or migration

  7. 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

  8. 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

  9. 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

  10. Holocene and latest Pleistocene oblique dextral faulting on the southern Inyo Mountains fault, Owens Lake basin, California

    USGS Publications Warehouse

    Bacon, S.N.; Jayko, A.S.; McGeehin, J.P.

    2005-01-01

    The Inyo Mountains fault (IMF) is a more or less continuous range-front fault system, with discontinuous late Quaternary activity, at the western base of the Inyo Mountains in Owens Valley, California. The southern section of the IMF trends ???N20??-40?? W for at least 12 km at the base of and within the range front near Keeler in Owens Lake basin. The southern IMF cuts across a relict early Pliocene alluvial fan complex, which has formed shutter ridges and northeast-facing scarps, and which has dextrally offset, well-developed drainages indicating long-term activity. Numerous fault scarps along the mapped trace are northeast-facing, mountain-side down, and developed in both bedrock and younger alluvium, indicating latest Quaternary activity. Latest Quaternary multiple- and single-event scarps that cut alluvium range in height from 0.5 to 3.0 m. The penultimate event on the southern IMF is bracketed between 13,310 and 10,590 cal years B.P., based on radiocarbon dates from faulted alluvium and fissure-fill stratigraphy exposed in a natural wash cut. Evidence of the most recent event is found at many sites along the mapped fault, and, in particular, is seen in an ???0.5-m northeast-facing scarp and several right-stepping en echelon ???0.5-m-deep depressions that pond fine sediment on a younger than 13,310 cal years B.P. alluvial fan. A channel that crosses transverse to this scarp is dextrally offset 2.3 ?? 0.8 m, providing a poorly constrained oblique slip rate of 0.1-0. 3 m/ k.y. The identified tectonic geomorphology and sense of displacement demonstrate that the southern IMF accommodates predominately dextral slip and should be integrated into kinematic fault models of strain distribution in Owens Valley.

  11. Surface Morphology of Active Normal Faults in Hard Rock: Implications for the Mechanics of the Asal Rift, Djibouti

    NASA Astrophysics Data System (ADS)

    Pinzuti, P.; Mignan, A.; King, G. C.

    2009-12-01

    Mechanical stretching models have been previously proposed to explain the process of continental break-up through the example of the Asal Rift, Djibouti, one of the few places where the early stages of seafloor spreading can be observed. In these models, deformation is distributed starting at the base of a shallow seismogenic zone, in which sub-vertical normal faults are responsible for subsidence whereas cracks accommodate extension. Alternative models suggest that extension results from localized magma injection, with normal faults accommodating extension and subsidence above the maximum reach of the magma column. In these magmatic intrusion models, normal faults have dips of 45-55° and root into dikes. Using mechanical and kinematics concepts and vertical profiles of normal fault scarps from an Asal Rift campaign, where normal faults are sub-vertical on surface level, we discuss the creation and evolution of normal faults in massive fractured rocks (basalt). We suggest that the observed fault scarps correspond to sub-vertical en echelon structures and that at greater depth, these scarps combine and give birth to dipping normal faults. Finally, the geometry of faulting between the Fieale volcano and Lake Asal in the Asal Rift can be simply related to the depth of diking, which in turn can be related to magma supply. This new view supports the magmatic intrusion model of early stages of continental breaking.

  12. Landform development in a zone of active Gedi Fault, Eastern Kachchh rift basin, India

    NASA Astrophysics Data System (ADS)

    Kothyari, Girish Ch.; Rastogi, B. K.; Morthekai, P.; Dumka, Rakesh K.

    2016-02-01

    An earthquake of 2006 Mw 5.7 occurred along east-west trending Gedi Fault (GF) to the north of the Kachchh rift basin in western India which had the epicenter in the Wagad upland, which is approximately 60 km northeast of the 2001 Mw 7.7 earthquake site (or epicenter). Development of an active fault scarp, shifting of a river channel, offsetting of streams and uplift of the ground indicate that the terrain is undergoing active deformation. Based on detailed field investigations, three major faults that control uplifts have been identified in the GF zone. These uplifts were developed in a step-over zone of the GF, and formed due to compressive force generated by left-lateral motion within the segmented blocks. In the present research, a terrace sequence along the north flowing Karaswali river in a tectonically active GF zone has been investigated. Reconstructions based on geomorphology and terrace stratigraphy supported by optical chronology suggest that the fluvial aggradation in the Wagad area was initiated during the strengthening (at ~ 8 ka) and declining (~ 4 ka) of the Indian Summer Monsoon (ISM). The presence of younger valley fill sediments which are dated ~ 1 ka is ascribed to a short lived phase of renewed strengthening of ISM before present day aridity. Based on terrace morphology two major phases of enhanced uplift have been estimated. The older uplift event dated to 8 ka is represented by the Tertiary bedrock surfaces which accommodated the onset of valley-fill aggradation. The younger event of enhanced uplift dated to 4 ka was responsible for the incision of the older valley fill sediments and the Tertiary bedrock. These ages suggest that the average rate of uplift ranges from 0.3 to 1.1 mm/yr during the last 9 ka implying active nature of the area.

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

    USGS Publications Warehouse

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

    2010-01-01

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

  14. Evidence for Holocene palaeoseismicity along the Basel-Reinach active normal fault (Switzerland): a seismic source for the 1356 earthquake in the Upper Rhine graben

    NASA Astrophysics Data System (ADS)

    Ferry, Matthieu; Meghraoui, Mustapha; Delouis, Bertrand; Giardini, Domenico

    2005-02-01

    We conducted a palaeoseismic study with geomorphologic mapping, geophysical prospecting and trenching along an 8-km-long NNE-SSW trending fault scarp south of Basel. The city as well as 40 castles within a 20-km radius were destroyed or heavily damaged by the earthquake of 1356 October 18 (Io = IX-X), the largest historical seismic event in central Europe. Active river incisions as well as late Quaternary alluvial terraces are uplifted along the linear Basel-Reinach (BR) fault scarp. The active normal fault is comprised of at least two main branches reaching the surface as evident by resistivity profiles, reflection seismic data and direct observations in six trenches. In trenches, the normal fault rupture affects three colluvial wedge deposits up to the base of the modern soil. Radiocarbon as well as thermoluminescence (TL) age determinations from other trenches helped to reconstruct the Holocene event chronology. We identified three seismic events with an average coseismic movement of 0.5-0.8 m and a total vertical displacement of 1.8 m in the last 7800 yr and five events in the last 13 200 yr. The most recent event occurred in the interval AD 500-1450 (2σ) and may correspond to the 1356 earthquake. Furthermore, the morphology suggests both a southern and northern fault extensions that may reach 20 km across the Jura mountains and across the Rhine valley. Taking this fault length and a 10-km-thick seismogenic layer suggests a Mw 6.5 or greater event as a possible scenario for the seismic hazard assessment of the Basel region.

  15. Evidence for Holocene paleoseismicity along the Basel-Reinach Active Normal Fault (Switzerland): A Seismic Source for the 1356 Earthquake in the Upper Rhine Graben

    NASA Astrophysics Data System (ADS)

    Ferry, M.; Meghraoui, M.; Delouis, B.; Giardini, D.

    2003-04-01

    We conducted a paleoseismic study with geomorphologic mapping, geophysical prospecting and trenching along an 8-km-long NNE-SSW trending fault scarp south of Basel. The city as well as 40 castles within a 20-km radius were destroyed or heavily damaged by the earthquake of 18th October 1356 (Io = IX-X MKS), the largest historical seismic event in central Europe. Active river incisions as well as late Quaternary alluvial terraces are uplifted along the linear Basel-Reinach fault scarp. The active normal fault shows at least two main branches reaching the surface as attested by resistivity profiles, reflection seismic data, and direct observations in six trenches. In trenches, the normal fault rupture affects three colluvial wedge deposits up to the base of the present day soil. Radiocarbon as well as thermoluminescence age determinations from other trenches helped reconstruct the Holocene events chronology. We identified three seismic events with an average coseismic movement of 0.5 - 0.8 m and a total vertical displacement of 1.8 m in the last 7800 years and five events in the last 13200 years. The most recent event occurred in the interval 610 - 1475 A.D. (2sigma) and may likely correspond to the 1356 earthquake. Furthermore, the morphology suggests both a southern and northern fault extensions that may reach 20 km across the Jura Mountains and across the Rhine Valley. Taking this fault length and a 10 km-thick seismogenic layer suggests a M 6.5 or greater event as a possible scenario for the seismic hazard assessment of the Basel region.

  16. 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.

  17. Faulting arrested by control of ground-water withdrawal in Houston, Texas.

    USGS Publications Warehouse

    Holzer, T.; Gabrysch, R.K.; Verbeek, E.R.

    1983-01-01

    More than 86 historically active faults with an aggregate length of 150 miles have been identified within and adjacent to the Houston, Texas, metropolitan area. Although scarps of these faults grow gradually and without causing damaging earthquakes, historical fault offset has cost millions of dollars in damage to houses and other buildings, utilities, and highways that were built on or across the faults. The historical fault activity results from renewed movement along preexisting faults and appears to be caused principally by withdrawal of ground water for municipal, industrial, and agricultural uses in the Houston area. Approximately one-half of the area's water supply is obtained from local ground water. Monitoring by the US Geological Survey of heights of fault scarps indicates that many of the scarps have recently stopped increasing in height. The area where faulting has ceased coincides with the area where ground-water pumping was cut back in the mid-1970s to slow the damage caused by land subsidence along Galveston Bay and the Houston Ship Channel. Thus, it appears that efforts to halt land subsidence in the coastal area have provided the additional benefit of arresting damaging surface faulting. -from Authors

  18. 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)

  19. 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

  20. Extreme Hydrothermal Conditions Near an Active Geological Fault, DFDP-2B Borehole, Alpine Fault, New Zealand

    NASA Astrophysics Data System (ADS)

    Sutherland, R.; Townend, J.; Toy, V.; Allen, M.; Baratin, L. M.; Barth, N. C.; Beacroft, L.; Benson, A.; Boese, C. M.; Boles, A.; Boulton, C. J.; Capova, L.; Carpenter, B. M.; Celerier, B. P.; Chamberlain, C. J.; Conze, R.; Cooper, A.; Coussens, J.; Coutts, A.; Cox, S.; Craw, L.; Doan, M. L.; Eccles, J. D.; Faulkner, D.; Grieve, J.; Grochowski, J.; Gulley, A.; Henry, G.; Howarth, J. D.; Jacobs, K. M.; Jeppson, T.; Kato, N.; Keys, S.; Kirilova, M.; Kometani, Y.; Lukács, A.; Langridge, R.; Lin, W.; Little, T.; Mallyon, D.; Mariani, E.; Marx, R.; Massiot, C.; Mathewson, L.; Melosh, B.; Menzies, C. D.; Moore, J.; Morales, L. F. G.; Morgan, C.; Mori, H.; Niemeijer, A. R.; Nishikawa, O.; Nitsch, O.; Paris Cavailhes, J.; Pooley, B.; Prior, D. J.; Pyne, A.; Sauer, K. M.; Savage, M. K.; Schleicher, A.; Schmitt, D. R.; Shigematsu, N.; Taylor-Offord, S.; Tobin, H. J.; Upton, P.; Valdez, R. D.; Weaver, K.; Wiersberg, T.; Williams, J. N.; Yeo, S.; Zimmer, M.; Broderick, N.

    2015-12-01

    The DFDP-2B borehole sampled rocks above and within the upper part of the Alpine Fault, New Zealand, to a depth of 893 m in late 2014. The experiment was the first to drill a major geological fault zone that is active and late in its earthquake cycle. We determined ambient fluid pressures 8-10% above hydrostatic and a geothermal gradient of 130-150 °C/km in rocks above the fault. These unusual ambient conditions can be explained by a combination of: rock advection that transports heat from depth by uplift and oblique slip on the fault; and fluid advection through fractured rock, driven by topographic forcing, which concentrates heat and causes fluid over-pressure in the valley. Highly-anomalous ambient conditions can exist in the vicinity of active faults, and earthquake and mineralization processes occur within these zones.

  1. Fault displacement rates and recent activity on the Ierapetra Fault Zone, Crete, Greece

    NASA Astrophysics Data System (ADS)

    Veliz, V.

    2015-12-01

    Crete is an eastern Mediterranean island that includes the highest forearc topography of the Hellenic subduction margin, along which the African and Eurasian plates converge at rates of ~40 mm/yr. The island is currently experiencing regional uplift and is broken up by numerous active normal faults that contribute to the shaping of its topography. The largest of these onshore tectonic features is, the Ierapetra Fault Zone (IFZ), a normal fault that traverses the entire width of eastern Crete (>20 km) with a NNE strike and west diping. Here we use geomorphologic, structural and kinematic indicators to discuss fault segmentation along the IFZ and to provide quantitative constraints on the late Quaternary (~16.5 and 33 kyr) displacement rate on the fault, including evidence of Holocene earthquake activity on its central segment.

  2. Fault growth and propagation during incipient continental rifting: Insights from a combined aeromagnetic and Shuttle Radar Topography Mission digital elevation model investigation of the Okavango Rift Zone, northwest Botswana

    NASA Astrophysics Data System (ADS)

    Kinabo, B. D.; Hogan, J. P.; Atekwana, E. A.; Abdelsalam, M. G.; Modisi, M. P.

    2008-06-01

    Digital Elevation Models (DEM) extracted from the Shuttle Radar Topography Mission (SRTM) data and high-resolution aeromagnetic data are used to characterize the growth and propagation of faults associated with the early stages of continental extension in the Okavango Rift Zone (ORZ), northwest Botswana. Significant differences in the height of fault scarps and the throws across the faults in the basement indicate extended fault histories accompanied by sediment accumulation within the rift graben. Faults in the center of the rift either lack topographic expressions or are interpreted to have become inactive, or have large throws and small scarp heights indicating waning activity. Faults on the outer margins of the rift exhibit either (1) large throws or significant scarp heights and are considered older and active or (2) throws and scarp heights that are in closer agreement and are considered young and active. Fault linkages between major fault systems through a process of "fault piracy" have combined to establish an immature border fault for the ORZ. Thus, in addition to growing in length (by along-axis linkage of segments), the rift is also growing in width (by transferring motion to younger faults along the outer margins while abandoning older faults in the middle). Finally, utilization of preexisting zones of weakness allowed the development of very long faults (>100 km) at a very early stage of continental rifting, explaining the apparent paradox between the fault length versus throw for this young rift. This study clearly demonstrates that the integration of the SRTM DEM and aeromagnetic data provides a 3-D view of the faults and fault systems, providing new insight into fault growth and propagation during the nascent stages of continental rifting.

  3. 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.

  4. Hydrogen Gas Emissions from Active Faults and Identification of Flow Pathway in a Fault Zone

    NASA Astrophysics Data System (ADS)

    Ishimaru, T.; Niwa, M.; Kurosawa, H.; Shimada, K.

    2010-12-01

    It has been observed that hydrogen gas emissions from the subsurface along active faults exceed atmospheric concentrations (e.g. Sugisaki et. al., 1983). Experimental studies have shown that hydrogen gas is generated in a radical reaction of water with fractured silicate minerals due to rock fracturing caused by fault movement (e.g. Kita et al., 1982). Based on such research, we are studying an investigation method for an assessment of fault activity using hydrogen gas emissions from fracture zones. To start, we have devised portable equipment for rapid and simple in situ measurement of hydrogen gas emissions (Shimada et al., 2008). The key component of this equipment is a commercially available and compact hydrogen gas sensor with an integral data logger operable at atmospheric pressure. In the field, we have drilled shallow boreholes into incohesive fault rocks to depths ranging from 15 to 45 cm using a hand-operated drill with a 9mm drill-bit. Then, we have measured the hydrogen gas concentrations in emissions from active faults such as: the western part of the Atotsugawa fault zone, the Atera fault zone and the Neodani fault in central Japan; the Yamasaki fault zone in southwest Japan; and the Yamagata fault zone in northeast Japan. In addition, we have investigated the hydrogen gas concentrations in emissions from other major geological features such as tectonic lines: the Butsuzo Tectonic Line in the eastern Kii Peninsula and the Atokura Nappe in the Northeastern Kanto Mountains. As a result of the investigations, hydrogen gas concentration in emissions from the active faults was measured to be in the approximate range from 6,000 ppm to 26,000 ppm in two to three hours after drilling. A tendency for high concentrations of hydrogen gas in active faults was recognized, in contrast with low concentrations in emissions from tectonic lines that were observed to be in the range from 730 ppm to 2,000 ppm. It is inferred that the hydrogen gas migrates to ground

  5. Top of head scarp and internal scarps for landslide deposits in the Little North Santiam River Basin, Oregon

    USGS Publications Warehouse

    Sobieszczyk, Steven

    2010-01-01

    Data points represent head scarps, flank scarps, and minor internal scarps (linear) associated with landslide deposits in the Little North Santiam River Basin, Oregon. This work was completed as part of the Master's thesis "Turbidity Monitoring and LiDAR Imagery Indicate Landslides are Primary Source of Suspended-Sediment Load in the Little North Santiam River Basin, Oregon, Winter 2009-2010" by Steven Sobieszczyk, Portland State University and U.S. Geological Survey. Data layers in this geodatabase include: landslide deposit boundaries (Deposits); field-verfied location imagery (Photos); head scarp or scarp flanks (Scarp_Flanks); and secondary scarp features (Scarps).The geodatabase template was developed by the Oregon Department of Geology and Mineral Industries (Burns and Madin, 2009).

  6. Geomorphic features of surface ruptures associated with the 2016 Kumamoto earthquake in and around the downtown of Kumamoto City, and implications on triggered slip along active faults

    NASA Astrophysics Data System (ADS)

    Goto, Hideaki; Tsutsumi, Hiroyuki; Toda, Shinji; Kumahara, Yasuhiro

    2017-02-01

    The 30-km-long surface ruptures associated with the M w 7.0 ( M j 7.3) earthquake at 01:25 JST on April 16 in Kumamoto Prefecture appeared along the previously mapped 100-km-long active fault called the Futagawa-Hinagu fault zone (FHFZ). The surface ruptures appeared to have extended further west out of the main FHFZ into the Kumamoto Plain. Although InSAR analysis by Geospatial Information Authority of Japan (GSI) indicated coseismic surface deformation in and around the downtown of Kumamoto City, the surface ruptures have not been clearly mapped in the central part of the Kumamoto Plain, and whether there are other active faults other than the Futagawa fault in the Kumamoto Plain remained unclear. We produced topographical stereo images (anaglyph) from 5-m-mesh digital elevation model of GSI, which was generated from light detection and ranging data. We interpreted them and identified that several SW-sloping river terraces formed after the deposition of the pyroclastic flow deposits related to the latest large eruption of the Aso caldera (86.8-87.3 ka) are cut and deformed by several NW-trending flexure scarps down to the southwest. These 5.4-km-long scarps that cut across downtown Kumamoto were identified for the first time, and we name them as the Suizenji fault zone. Surface deformation such as continuous cracks, tilts, and monoclinal folding associated with the main shock of the 2016 Kumamoto earthquake was observed in the field along the fault zone. The amount of vertical deformation ( 0.1 m) along this fault associated with the 2016 Kumamoto earthquake was quite small compared to the empirically calculated coseismic slip (0.5 m) based on the fault length. We thus suggest that the slip on this fault zone was triggered by the Kumamoto earthquake, but the fault zone has potential to generate an earthquake with larger slip that poses a high seismic risk in downtown Kumamoto area.[Figure not available: see fulltext.

  7. Earthquake source parameters at the sumatran fault zone: Identification of the activated fault plane

    NASA Astrophysics Data System (ADS)

    Kasmolan, Madlazim; Santosa, Bagus Jaya; Lees, Jonathan M.; Utama, Widya

    2010-12-01

    Fifteen earthquakes (Mw 4.1-6.4) occurring at ten major segments of the Sumatran Fault Zone (SFZ) were analyzed to identify their respective fault planes. The events were relocated in order to assess hypocenter uncertainty. Earthquake source parameters were determined from three-component local waveforms recorded by IRIS-DMC and GEOFON broadband lA networks. Epicentral distances of all stations were less than 10°. Moment tensor solutions of the events were calculated, along with simultaneous determination of centroid position. Joint analysis of hypocenter position, centroid position, and nodal planes produced clear outlines of the Sumatran fault planes. The preferable seismotectonic interpretation is that the events activated the SFZ at a depth of approximately 14-210 km, corresponding to the interplate Sumatran fault boundary. The identification of this seismic fault zone is significant to the investigation of seismic hazards in the region.

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  9. Spacing and strength of active continental strike-slip faults

    NASA Astrophysics Data System (ADS)

    Zuza, Andrew V.; Yin, An; Lin, Jessica; Sun, Ming

    2017-01-01

    Parallel and evenly-spaced active strike-slip faults occur widely in nature across diverse tectonic settings. Despite their common existence, the fundamental question of what controls fault spacing remains unanswered. Here we present a mechanical model for the generation of parallel strike-slip faults that relates fault spacing to the following parameters: (1) brittle-crust thickness, (2) fault strength, (3) crustal strength, and (4) crustal stress state. Scaled analogue experiments using dry sand, dry crushed walnut shells, and viscous putty were employed to test the key assumptions of our quantitative model. The physical models demonstrate that fault spacing (S) is linearly proportional to brittle-layer thickness (h), both in experiments with only brittle materials and in two-layer trials involving dry sand overlying viscous putty. The S / h slope in the two-layer sand-putty experiments may be controlled by the (1) rheological/geometric properties of the viscous layer, (2) effects of distributed basal loading caused by the viscous shear of the putty layer, and/or (3) frictional interaction at the sand-putty interface (i.e., coupling between the viscous and brittle layers). We tentatively suggest that this third effect exerts the strongest control on fault spacing in the analogue experiments. By applying our quantitative model to crustal-scale strike-slip faults using fault spacing and the seismogenic-zone thickness obtained from high-resolution earthquake-location data, we estimate absolute fault friction of active strike-slip faults in Asia and along the San Andreas fault system in California. We show that the average friction coefficient of strike-slip faults in the India-Asia collisional orogen is lower than that of faults in the San Andreas fault system. Weaker faults explain why deformation penetrates >3500 km into Asia from the Himalaya and why the interior of Asia is prone to large (M > 7.0) devastating earthquakes along major intra-continental strike

  10. Preliminary observations on Quaternary reverse faulting along the southern front of the Northern Range of Trinidad

    SciTech Connect

    Beltran, C. , Caracus )

    1993-02-01

    Several geomorphological evidences of Quaternary reverse faulting are observed along the southern front of the Northern Range in Trinidad between Port-of-Spain and Matura Point. Such a mountain front is associated to a reverse fault system showing an imbricated pattern southward. In the north, the system is limited by a structural feature showing an important vertical component. Southward this system progressively changes to low angle faults. This geometry is corroborated by seismic profiling in the continent shelf. The active faulting evidences consist in lateral drainage offsets, fault trenches, sag-ponds, triangular facets, and saddles. Some quaternary terraces show fault scarps and tilting. We postulate that these reverse fault systems as Arima Fault instead of El Pilar fault as it is not actually connected to the San Sebestian-El Pilar right-lateral slip system, due to the southward prolongation of the southern limit of the Caribbean Plate through the fault system of Los Bajos-El Soldado.

  11. Segmentation and the coseismic behavior of Basin and Range normal faults: examples from east-central Idaho and southwestern Montana, U.S.A.

    USGS Publications Warehouse

    Crone, A.J.; Haller, K.M.

    1991-01-01

    The range-front normal faults of the Lost River and Lemhi Ranges, and the Beaverhead and Tendoy Mountains in east-central Idaho and southwestern Montana have well-preserved fault scarps on Quaternary deposits along much of their lengths. Fault-scarp morphology, the age of deposits displaced by the faults, and the morphology of the range fronts provide a basis for dividing the faults into segments that are typically 20-25 km long. The Lost River, Lemhi and Beaverhead fault zones are 141-151 km long, and each has six segments. The 60-km-long Red Rock fault (the range-front fault of the Tendoy Mountains) has two central segments that have been active in late Quaternary time; these two segments span the central 27 km of the fault. We recognize four characteristics that help to identify segment boundaries: (1) major en e??chelon offsets or pronounced gaps in the continuity of fault scarps; (2) distinct, persistent, along-strike changes in fault-scarp morphology that indicate different ages of faulting; (3) major salients in the range front; and (4) transverse bedrock ridges where the cumulative throw is low compared to other places along the fault zone. Only features whose size is measured on the scale of kilometers are regarded as significant enough to represent a segment boundary that could inhibit or halt a propagating rupture. The ability to identify segments of faults that are likely to behave as independent structural entities will improve seismic-hazard assessment. However, one should not assume that the barriers at segment boundaries will completely stop all propagating ruptures. The topographic expression of mountain ranges is evidence that, at times during their history, all barriers fail. Some barriers apparently create 'leaky' segment boundaries that impede propagating ruptures but do not completely prevent faulting on adjacent segments. ?? 1991.

  12. 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.

  13. 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

  14. Have graben wall scarps accumulated sand and dust on Mars?

    NASA Technical Reports Server (NTRS)

    Golombek, M. P.; Davis, P. A.

    1991-01-01

    Grabens are linear fault bounded troughs that are extremely abundant on Mars (about 7000 cover the Western Hemisphere). Analysis of lunar and Martian grabens as well as analogous structures on Earth indicates that grabens form under extension when the crust is pulled apart. On Mars, topographic maps are not of sufficient resolution to measure graben wall slopes. Seismic shaking on Mars might be capable of reducing 60 deg fault scarps to an angle of repose. Some other process must be responsible for further reducing graben wall slopes. If the deposition of sand and dust along graben walls is responsible for their extremely low slopes, then a variety of implications are possible. Sand and/or dust movement and deposition is ubiquitous in grabens over most of Mars, as similar looking grabens are found over the entire Western Hemisphere and this requires a plentiful supply of sand or dust. If the material that accumulates is of low density and cohesion, attempts to traverse graben walls might be difficult. Rimless shallow depressions could be more effective sinks for sand and dust on Mars than has been realized.

  15. 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

  16. Surface morphology of active normal faults in hard rock: Implications for the mechanics of the Asal Rift, Djibouti

    NASA Astrophysics Data System (ADS)

    Pinzuti, Paul; Mignan, Arnaud; King, Geoffrey C. P.

    2010-10-01

    Tectonic-stretching models have been previously proposed to explain the process of continental break-up through the example of the Asal Rift, Djibouti, one of the few places where the early stages of seafloor spreading can be observed. In these models, deformation is distributed starting at the base of a shallow seismogenic zone, in which sub-vertical normal faults are responsible for subsidence whereas cracks accommodate extension. Alternative models suggest that extension results from localised magma intrusion, with normal faults accommodating extension and subsidence only above the maximum reach of the magma column. In these magmatic rifting models, or so-called magmatic intrusion models, normal faults have dips of 45-55° and root into dikes. Vertical profiles of normal fault scarps from levelling campaign in the Asal Rift, where normal faults seem sub-vertical at surface level, have been analysed to discuss the creation and evolution of normal faults in massive fractured rocks (basalt lava flows), using mechanical and kinematics concepts. We show that the studied normal fault planes actually have an average dip ranging between 45° and 65° and are characterised by an irregular stepped form. We suggest that these normal fault scarps correspond to sub-vertical en echelon structures, and that, at greater depth, these scarps combine and give birth to dipping normal faults. The results of our analysis are compatible with the magmatic intrusion models instead of tectonic-stretching models. The geometry of faulting between the Fieale volcano and Lake Asal in the Asal Rift can be simply related to the depth of diking, which in turn can be related to magma supply. This new view supports the magmatic intrusion model of early stages of continental breaking.

  17. Fault-controlled geomorphology and paleoseismology of Fethiye fault and gulf

    NASA Astrophysics Data System (ADS)

    Chatzipetros, Alexandros; Pavlides, Spyros; Yaǧmurlu, Fuzuli; Özgür, Nevzat; Kamaci, Züheyr; Şentürk, Murat

    2010-05-01

    Fethiye gulf is located at the south-westernmost part of the large left-lateral Fethiye-Burdur fault zone. It is modified and controlled by sets of NE - SW trending normal and oblique left-lateral faults. The gulf forms coastlines that are often aligned nearly perpendicular to one another. Coastlines are mainly NE - SW trending and they are inundated by small bays, mainly in NNW-SSE direction. Those directions are comparable to the main mainland fault lines, as measured on outcrops in the area. The brittle features of the area overprint the pre-existing tectonic fabric of low-angle thrusts and pure strike-slip faults. Recent activity of the faults seems to be possible, since there is indication for hangingwall submergence at the "Cleopatra's bath" site, where an early-Byzantine building complex has been submerged by at least 2 m. The mainland active fault zone is located S-SE of Fethiye town and it forms an N-NW dipping fault scarp that is characterized by multiple en échelon segments. The quantitative tectonic geomorphology of this fault has been studied by using morphotectonic indices (scarp sinuosity, valley width/depth ratio, etc.), which show that the fault has a rather low level of activity. Nevertheless, the fault zone near Fethiye presents other morphotectonic features, such as riverbed catchment, slight left-lateral bend of streams at the foot of the scarp, etc. The fault zone seems to fan out towards the west and the deformation is less evident. Although the fault segments near Fethiye are classified as low-activity ones, they are associated with the large 1957 earthquake (Ms 7.1). This earthquake produced extensive damage and casualties. It was physically manifested by surface ruptures, rockfalls, etc. A palaeoseismological survey has been carried out in the area. Trenches in two different segments show that the 1957 surface rupture is traceable along the fault, while at least two previous events seem to have affected the area and produced surface

  18. 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.

  19. Timing of activity of two fault systems on Mercury

    NASA Astrophysics Data System (ADS)

    Galluzzi, V.; Guzzetta, L.; Giacomini, L.; Ferranti, L.; Massironi, M.; Palumbo, P.

    2015-10-01

    Here we discuss about two fault systems found in the Victoria and Shakespeare quadrangles of Mercury. The two fault sets intersect each other and show probable evidence for two stages of deformation. The most prominent system is N-S oriented and encompasses several tens to hundreds of kilometers long and easily recognizable fault segments. The other system strikes NE- SW and encompasses mostly degraded and short fault segments. The structural framework of the studied area and the morphological appearance of the faults suggest that the second system is older than the first one. We intend to apply the buffered crater counting technique on both systems to make a quantitative study of their timing of activity that could confirm the already clear morphological evidence.

  20. Anatomy of a microearthquake sequence on an active normal fault

    PubMed Central

    Stabile, T. A.; Satriano, C.; Orefice, A.; Festa, G.; Zollo, A.

    2012-01-01

    The analysis of similar earthquakes, such as events in a seismic sequence, is an effective tool with which to monitor and study source processes and to understand the mechanical and dynamic states of active fault systems. We are observing seismicity that is primarily concentrated in very limited regions along the 1980 Irpinia earthquake fault zone in Southern Italy, which is a complex system characterised by extensional stress regime. These zones of weakness produce repeated earthquakes and swarm-like microearthquake sequences, which are concentrated in a few specific zones of the fault system. In this study, we focused on a sequence that occurred along the main fault segment of the 1980 Irpinia earthquake to understand its characteristics and its relation to the loading-unloading mechanisms of the fault system. PMID:22606366

  1. Active faults and minor plates in NE Asia

    NASA Astrophysics Data System (ADS)

    Kozhurin, Andrey I.; Zelenin, Egor A.

    2014-05-01

    Stated nearly 40 yr ago the uncertainty with plate boundaries location in NE Asia (Chapman, Solomon, 1976) still remains unresolved. Based on the prepositions that a plate boundary must, first, reveal itself in linear sets of active structures, and, second, be continuous and closed, we have undertaken interpretation of medium-resolution KH-9 Hexagon satellite imageries, mostly in stereoscopic regime, for nearly the entire region of NE Asia. Main findings are as follows. There are two major active fault zones in the region north of the Bering Sea. One of them, the Khatyrka-Vyvenka zone, stretches NE to ENE skirting the Bering Sea from the Kamchatka isthmus to the Navarin Cape. Judging by the kinematics of the Olyutorsky 2006 earthquake fault, the fault zones move both right-laterally and reversely. The second active fault zone, the Lankovaya-Omolon zone, starts close to the NE margin of the Okhotsk Sea and extends NE up to nearly the margin of the Chukcha Sea. The fault zone is mostly right-lateral, with topographically expressed cumulative horizontal offsets amounting to 2.5-2.6 km. There may be a third NE-SW zone between the major two coinciding with the Penzhina Range as several active faults found in the southern termination of the Range indicate. The two active fault zones divide the NE Asia area into two large domains, which both could be parts of the Bering Sea plate internally broken and with uncertain western limit. Another variant implies the Khatyrka-Vyvenka zone as the Bering Sea plate northern limit, and the Lankovaya-Omolon zone as separating an additional minor plate from the North-American plate. The choice is actually not crucial, and more important is that both variants leave the question of where the Bering Sea plate boundary is in Alaska. The Lankovaya-Omolon zone stretches just across the proposed northern boundary of the Okhorsk Sea plate. NW of the zone, there is a prominent left-lateral Ulakhan fault, which is commonly interpreted to be a

  2. Paleoseismic investigations at the Cal thrust fault, Mendoza, Argentina

    NASA Astrophysics Data System (ADS)

    Salomon, Eric; Schmidt, Silke; Hetzel, Ralf; Mingorance, Francisco

    2010-05-01

    Along the active mountain front of the Andean Precordillera between 30°S and 34°S in western Argentina several earthquakes occurred in recent times, including a 7.0 Ms event in 1861 which destroyed the city of Mendoza and killed two thirds of its population. The 1861 event and two other earthquakes (Ms = 5.7 in 1929 and Ms = 5.6 in 1967) were generated on the Cal thrust fault, which extends over a distance of 31 km north-south and runs straight through the center of Mendoza. In the city, which has now more than 1 million inhabitants, the fault forms a 3-m-high fault scarp. Although the Cal thrust fault poses a serious seismic hazard, the paleoseismologic history of this fault and its long-term slip rate remains largely unknown (Mingorance, 2006). We present the first results of an ongoing paleoseismologic study of the Cal thrust at a site located 5 km north of Mendoza. Here, the fault offsets Late Holocene alluvial fan sediments by 2.5 m vertically and exhibits a well developed fault scarp. A 15-m-long and 2-3-m-deep trench across the scarp reveals three east-vergent folds that we interpret to have formed during three earthquakes. Successive retrodeformation of the two youngest folds suggests that the most recent event (presumably the 1861 earthquake) caused ~1.1 m of vertical offset and ~1.8 m of horizontal shortening. For the penultimate event we obtain a vertical offset of ~0.7 m and a horizontal shortening of ~1.9 m. A vertical displacement of ~0.7 m observed on a steeply west-dipping fault may be associated with an older event. The cumulative vertical offset of 2.5 m for the three inferred events is in excellent agreement with the height of the scarp. Based on the retrodeformation of the trench deposits the fault plane dips ~25° to the west. In the deepest part of the trench evidence for even older seismic events is preserved beneath an angular unconformity that was formed during a period of erosion and pre-dates the present-day scarp. Dating of samples to

  3. Evidence for Quaternary Slip on a Low Angle Normal Fault: Searles Valley, CA

    NASA Astrophysics Data System (ADS)

    Numelin, T.; Kirby, E.

    2004-12-01

    Low angle normal faults have been documented in extensional terranes worldwide, however conventional models of fault mechanics preclude slip on planes dipping less than 30 degrees. The global catalogue of earthquake focal mechanisms reveals very few occurrences of seismicity (active slip) on low angle structures, lending support to mechanical arguments against active slip on shallowly dipping planes. Recent field studies of low-angle normal faults in the Baja California and Death Valley regions of western North America, however, suggest that active slip on these structures may be more common than typically thought. Here we investigate the relationship between high angle alluvial scarps in Searles Valley and a low-angle detachment fault in order to determine if displacement on the detachment is active. The network of young and recent fault scarps along the eastern margin Searles Valley can be broadly separated into two primary segments with overlapping fault tips that form a range-scale relay zone in the vicinity of Sand Canyon. South of this relay, the active trace of the fault is marked by a series of graben developed within Late Pleistocene - Holocene alluvial fans. Within the bedrock of the Slate Range, and immediately along-strike of the graben system, is a west dipping, low-angle fault system (Sand Canyon `thrust' - Smith et al., 1968). This fault is continuous within the range for some 20 km and links with a west-dipping normal fault near Manly Pass, and is thus thought to have accommodated west directed normal-sense displacement during Plio-Quaternary time (Andrew and Walker, 2002). Mapping and structural observations at the intersection of the active fault system and the Sand Canyon fault reveals that high-angle scarps cutting Pleistocene alluvium root into a low-angle (10-15°), west-dipping gouge zone. Faults do not significantly displace the detachment surface, and thus, scarp-forming displacement must have been accommodated by slip on the detachment

  4. Active faulting in the Southwestern Venezuelan Andes and Colombia borderland

    SciTech Connect

    Singer, A.; Beltran, C.; Lugo, M. , Caracas )

    1993-02-01

    In the southern Andes, the Bocono fault shows a progressive disactivation of its right lateral movement, resulting from its attenuation against the transversal system of Bramon and its kinematic connection to the [open quotes]Pamplona indenter,[close quotes] considered as a part of the plate boundary between the Caribbean and South America. Near the Colombian frontier, the velocity of Bocono fault is probably less than 1 mm/yr. Such a decrease is explained because an increasing amount of the 1 cm/yr slip movement of the northern part of the fault is absorbed through a complex branching of the active trace, southwest Merida. Another significative amount of the rate movement of Bocono fault, considered as plate boundary, results absorbed by subparallel active faulting systems located to the east (Uribante and Caparo Systems) and to the west sides (San Simon-Seboruco, and San Pedro-Aguas Calientes-La Don Juana systems). The last system, extending beyond the frontier, shows a particular seimotectonic importance, as a probable source of the 1875 Cucata earthquake. In this way, the weight of the southwestern end of Bocono fault as a seismic source loses importance respect to the northern segment located between la Grita and Merida where the 1610 and 1894 earthquakes occurred, and also as compared to the faults that define the [open quotes]Pamplona indenter[close quotes] like probable source for several other destructive earthquakes.

  5. Spatial radon anomalies on active faults in California

    USGS Publications Warehouse

    King, C.-Y.; King, B.-S.; Evans, William C.; Zhang, W.

    1996-01-01

    Radon emanation has been observed to be anomalously high along active faults in many parts of the world. We tested this relationship by conducting and repeating soil air radon surveys with a portable radon meter across several faults in California. The results confirm the existence of fault-associated radon anomalies, which show characteristic features that may be related to fault structures but vary in time due to other environmental changes, such as rainfall. Across two creeping faults in San Juan Bautista and Hollister, the radon anomalies showed prominent double peaks straddling the fault gouge zone during dry summers, but the peak-to-background ratios diminished after significant rain fall during winter. Across a locked segment of the San Andreas fault near Olema, the anomaly has a single peak located several meters southwest of the slip zone associated with the 1906 San Francisco earthquake. Across two fault segments that ruptured during the magnitude 7.5 Landers earthquake in 1992, anomalously high radon concentration was found in the fractures three weeks after the earthquake. We attribute the fault-related anomalies to a slow vertical gas flow in or near the fault zones. Radon generated locally in subsurface soil has a concentration profile that increases three orders of magnitude from the surface to a depth or several meters; thus an upward flow that brings up deeper and radon-richer soil air to the detection level can cause a significantly higher concentration reading. This explanation is consistent with concentrations of carbon dioxide and oxygen, measured in soil-air samples collected during one of the surveys.

  6. Large-magnitude, late Holocene earthquakes on the Genoa fault, West-Central Nevada and Eastern California

    USGS Publications Warehouse

    Ramelli, A.R.; Bell, J.W.; DePolo, C.M.; Yount, J.C.

    1999-01-01

    The Genoa fault, a principal normal fault of the transition zone between the Basin and Range Province and the northern Sierra Nevada, displays a large and conspicuous prehistoric scarp. Three trenches excavated across this scarp exposed two large-displacement, late Holocene events. Two of the trenches contained multiple layers of stratified charcoal, yielding radiocarbon ages suggesting the most recent and penultimate events on the main part of the fault occurred 500-600 cal B.P., and 2000-2200 cal B.P., respectively. Normal-slip offsets of 3-5.5 m per event along much of the rupture length are comparable to the largest historical Basin and Range Province earthquakes, suggesting these paleoearthquakes were on the order of magnitude 7.2-7.5. The apparent late Holocene slip rate (2-3 mm/yr) is one of the highest in the Basin and Range Province. Based on structural and behavioral differences, the Genoa fault is here divided into four principal sections (the Sierra, Diamond Valley, Carson Valley, and Jacks Valley sections) and is distinguished from three northeast-striking faults in the Carson City area (the Kings Canyon, Carson City, and Indian Hill faults). The conspicuous scarp extends for nearly 25 km, the combined length of the Carson Valley and Jacks Valley sections. The Diamond Valley section lacks the conspicuous scarp, and older alluvial fans and bedrock outcrops on the downthrown side of the fault indicate a lower activity rate. Activity further decreases to the south along the Sierra section, which consists of numerous distributed faults. All three northeast-striking faults in the Carson City area ruptured within the past few thousand years, and one or more may have ruptured during recent events on the Genoa fault.

  7. Fault mirrors of seismically active faults: A fossil of small earthquakes at shallow depths

    NASA Astrophysics Data System (ADS)

    Kuo, L.; Song, S.; Suppe, J.

    2013-12-01

    Many faults are decorated with naturally polished and glossy surfaces named fault mirrors (FMs) formed during slips. The characterization of FMs is of paramount importance to investigate physico-chemical processes controlling dynamic fault mechanics during earthquakes. Here we present detailed microstructural and mineralogical observations of the FMs from borehole cores of seismically active faults. The borehole cores were recovered from 600 to 800 m depth located in the hanging wall of the Hsiaotungshi fault in Taiwan which ruptured during 1935 Mw7.1 Hsinchu-Taichung earthquake. Scanning electron microscope (SEM) images of FMs show that two distinct textural domains, fault gouge and coated materials (nanograins, melt patchs, and graphite), were cut by a well-defined boundary. Melt patches and graphite, determined by X-ray diffraction (XRD), Transmission electron microscope (TEM), and SEM-EDS analysis, were found to be distributed heterogeneously on the slip surfaces. On the basis of the current kinematic cross section of the Hsiaotungshi fault, all the FMs were exhumed less than 5 km, where ambient temperatures are less than 150°C. It seems that the amorphous materials on the FMs were generated by seismic slips. The sintering nanograins coating the slip surfaces was also suggested to be produced at high slip rates from both natural observation and recent rock deformation experiments. In addition, graphite could be produced by seismic slips and lubricate the fault based on the rock deformation experiments. Our observation suggests that the FMs were composed of several indicators of coseismic events (melt patches, sintering nanograins, and graphite) corresponding to small thermal perturbation generated by seismic slips. Although the contribution of these coseismic indicators on frictional behavior remains largely unknown, it suggests that multiple dynamic weakening mechanisms such as flash heating, powder lubrication and graphitization may be involved during

  8. Mineralogy and porosity transformation induced by normal fault activity, Pirgaki fault zone (Corinth rift, Greece).

    NASA Astrophysics Data System (ADS)

    Géraud, Y.; Diraison, M.

    2003-04-01

    The Pirgaki fault displays an average N095-100 strike direction and contributes to the south part of the Corinth graben. Several interconnected segments compose it and it forms a quite continuous fault scrap elevated up to 300 meters. The total length of outcropping fault zone is at least 30 km. The dip angle involves between 40° to 70° for the highest. The high angle part of the fault marks the contact between limestone and sediments of the rift series (Ghisetti et al. 2001). A large set of structural and sedimentological criteria are evidence of repeated activity of the Pirgaki fault during the whole Pliocene-Pleistocene period (Ghisetti et al., 2001). The studied part of the Pirgaki fault zone has low angle dip and affects limestones. These limestones, as well as in the hanging wall than in the footwall, are strongly affected by a previous neogene orogen with ductile (folds) and brittle (faults) structures. The sampling zone concerns the low dipping part of the fault. A set of 12 samples is analysed by Hg and water porosimetry, X-ray diffraction and SEM. Protolith is characterised by a very low porosity material, porous volume lower than 1% and threshold size lower 0.1µm. Clay fraction of the protolith material is formed by a set of interstratified illite-smectite and kaolinite minerals. The gouge zone is characterized by an important structural modification with formation of ductile strain part and a brittle strain part. Transformations of the clay content are important in this part of the fault zone. Interstratified phases disappear and are replaced by illite and chlorite phases. The highest illite content is measured for the brittle part of the gouge zone and the highest chlorite content is measured in the ductile part. These structural transformations are also associated with porosity modifications with an large increase of the porosity volume (10%) an of the threshold diameter (3µm) in the brittle part and a lower increase (porosity value, 2% and

  9. Preliminary Results on the Mechanics of the Active Mai'iu Low Angle Normal Fault (Dayman Dome), Woodlark Rift, SE Papua New Guinea

    NASA Astrophysics Data System (ADS)

    Little, T. A.; Boulton, C. J.; Mizera, M.; Webber, S. M.; Oesterle, J.; Ellis, S. M.; Norton, K. P.; Wallace, L. M.; Biemiller, J.

    2015-12-01

    Rapid slip on the Mai'iu low-angle normal fault (LANF) has exhumed a smooth, corrugated fault surface contiguous for >24 km up-dip, rising from near sea level to ~2900 m. The fault emerges from the ground dipping ~21° N and flattens over the crest of the dome to dip south. Geomorphic analysis reveals a progressive back-tilting of the surface during exhumation accompanied by cross-cutting antithetic-sense high-angle faults—features that we attribute to "rolling-hinge" deformation of a once more steeply-dipping fault. Near the scarp base, the footwall exposes mafic mylonites that deformed at ~400-450°C. The younger Mai'iu fault cross-cuts this ductile mylonite zone, with most brittle slip being localized into a ~20 cm-thick, gouge-filled core. Near the range front, active faults bite across both the hangingwall and footwall of the Mai'iu fault and record overprinting across a dying, shallow (<~1 km deep) part of the fault by more optimally oriented, steeper faults. Such depth-dependent locking up of the fault suggests it weakens primarily by friction reduction rather than cohesion loss. Outcrop-scale fractures in the exhumed footwall reflect formation in an Andersonian stress regime. Previous campaign GPS data suggest the fault slips at up to ~1 cm/yr. To improve resolution and test for aseismic creep, we installed 12 GPS sites across the fault trace in 2015. Quantitative XRD indicates the gouges were derived primarily from mafic footwall, containing up to 65% corrensite and saponite. Hydrothermal friction experiments on two gouges from a relict LANF strand were done at varying normal stresses (30-120 MPa), temperatures (50-200oC), and sliding velocities (0.3-100 μm/s). Results reveal very weak frictional strength (μ=0.13-0.15 and 0.20-0.28) and velocity-strengthening behavior conducive to fault creep. At the highest temperatures (T≥150oC) and lowest sliding velocities (<3 μm/s), a transition to velocity-weakening behavior indicates the potential for

  10. Surface faults in the gulf coastal plain between Victoria and Beaumont, Texas

    USGS Publications Warehouse

    Verbeek, E.R.

    1979-01-01

    Displacement of the land surface by faulting is widespread in the Houston-Galveston region, an area which has undergone moderate to severe land subsidence associated with fluid withdrawal (principally water, and to a lesser extent, oil and gas). A causative link between subsidence and fluid extraction has been convincingly reported in the published literature. However, the degree to which fluid withdrawal affects fault movement in the Texas Gulf Coast, and the mechanism(s) by which this occurs are as yet unclear. Faults that offset the ground surface are not confined to the large (>6000-km2) subsidence "bowl" centered on Houston, but rather are common and characteristic features of Gulf Coast geology. Current observations and conclusions concerning surface faults mapped in a 35,000-km2 area between Victoria and Beaumont, Texas (which area includes the Houston subsidence bowl) may be summarized as follows: 1. (1) Hundreds of faults cutting the Pleistocene and Holocene sediments exposed in the coastal plain have been mapped. Many faults lie well outside the Houston-Galveston region; of these, more than 10% are active, as shown by such features as displaced, fractured, and patched road surfaces, structural failure of buildings astride faults, and deformed railroad tracks. 2. (2) Complex patterns of surface faults are common above salt domes. Both radial patterns (for example, in High Island, Blue Ridge, Clam Lake, and Clinton domes) and crestal grabens (for example, in the South Houston and Friendswood-Webster domes) have been recognized. Elongate grabens connecting several known and suspected salt domes, such as the fault zone connecting Mykawa, Friendswood-Webster, and Clear Lake domes, suggest fault development above rising salt ridges. 3. (3) Surface faults associated with salt domes tend to be short (10 km), occur singly or in simple grabens, have gently sinuous traces, and tend to lie roughly parallel to the ENE-NE "coastwise" trend common to regional growth

  11. Paleoseismic Study of the Southern Part of the Chelungpu Fault

    NASA Astrophysics Data System (ADS)

    Chen, W.; Lee, K.; Lee, L.; Chen, Y.; Chang, H.; Ponti, D.; Prentice, C.

    2001-12-01

    The Chi-Chi earthquake ruptures frequently followed the preexisting Holocene terrace scarps that have already been recognized as a Holocene fault scarp. Uplifted Holocene terraces are important indicators of active tectonics, and its presence can be interpreted as a geomorphic expression of active faulting. Therefore, the Quaternary fold-and-thrust belts along the Chelungpu fault are one of the best areas for neotectonic studies. In this study, we are to discuss paleoseismicity of the Chelungpu fault with the help of careful observation based on the trenching study. These trenching sites are located on the southern part of the Chelungpu fault occurring vertical displacement ranging from 0.2 m to 3 m during the Chi-Chi earthquake. Through the paleoseismic investigation, the deformation pattern of surface rupture can be subdivided into fault and fold ruptures. Prehistoric ruptures for six trenching sites have been produced the vertical displacement ranging from 0.4 to 1.7 m. The evaluated data is approximately similar to the observations from the paleoseismic rupture and the Chi-Chi earthquake ruptures. In the Chushan, Wanfung, and Pineapple field sits, the paleoseismic analysis reveals clear evidence of recurrence timing of the Chelungpu fault occurring younger than 200 yr BP by 14C dating. Based on the historical earthquake record, 1792 A.D. and 1848 A.D. earthquakes were the two markedly damaging earthquakes striking central Taiwan. We suggest that one of the strong earthquakes may have caused the last paleoseismic event.

  12. Paleoseismology of a newly discovered scarp in the Yakima fold-and-thrust belt, Kittitas County, Washington

    USGS Publications Warehouse

    Barnett, Elizabeth A.; Sherrod, Brian L.; Norris, Robert; Gibbons, Douglas

    2013-01-01

    The Boylston Mountains anticlinal ridge is one of several that are cored by rocks of the Columbia River Basalt Group and, with the interceding synclinal valleys, constitute the Yakima fold-and-thrust belt of central Washington. Lidar data acquired from the U.S. Army's Yakima Training Center reveal a prominent, northwest-side-up, 65°- to 70°-trending, 3- to 4-meter-high scarp that cuts across the western end of the Boylston Mountains, perpendicular to the mapped anticline. The scarp continues to the northeast from the ridge on the southern side of Park Creek and across the low ridges for a total length of about 3 kilometers. A small stream deeply incises its flood plain where it projects across Johnson Canyon. The scarp is inferred to be late Quaternary in age based on its presence on the modern landscape and the incised flood-plain sediments in Johnson Canyon. Two trenches were excavated across this scarp. The most informative of the two, the Horned Lizard trench, exposed shallow, 15.5-Ma Grande Ronde Basalt, which is split by a deep, wide crack that is coincident with the base of the scarp and filled with wedges of silty gravels that are interpreted to represent at least two generations of fault colluvium that offset a buried soil.

  13. Principal faults in the Houston, Texas, metropolitan area

    USGS Publications Warehouse

    Shah, Sachin D.; Lanning-Rush, Jennifer

    2005-01-01

    Summary -- This report, prepared by the U.S. Geological Survey in cooperation with the Harris-Galveston Coastal Subsidence District, documents and refines the locations of principal faults mapped in the Houston, Texas, metropolitan area in previous studies. Numerous subsurface faults have been documented beneath the Houston metropolitan area at depths of 3,200 to 13,000 feet. Some of these subsurface faults have affected shallower sediments, offset the present land surface (which has resulted in substantial, costly damage), and produced recognizable fault scarps. Evidence from previous studies indicates that these faults are natural geologic features with histories of movement spanning tens of thousands to millions of years. Present-day scarps reflect only the most recent displacements of faults that were active long before the present land surface of the area was formed. The precision of previously mapped fault locations was enhanced by overlaying mapped faults on a digital elevation model (DEM) of Harris County derived using light detection and ranging (Lidar). Lidar is a high-precision, laser-based system that enables collection of high-resolution topographic data. Previously mapped faults were adjusted to coincide with surface features that clearly indicate faults, which were made visible by the high-resolution topography depicted on the Lidar-derived DEM. Results of a previous study, supported by this study, indicate that faults in the southeastern part of the metropolitan area primarily occur in well-defined groups of high fault density. Faults in northern and western parts of the metropolitan area tend to occur either individually or in pairs with little tendency to cluster in high-density groups.

  14. Is there really an active fault (Cibyra Fault?) cutting the Stadion of the ancient city of Cibyra? (Burdur-Fethiye Fault Zone, Turkey)

    NASA Astrophysics Data System (ADS)

    Elitez, İrem; Yaltırak, Cenk

    2013-04-01

    The Cibyra segment of the Burdur-Fethiye Fault Zone (BFFZ) is in a tectonically very active region of southwestern Anatolia. The presence of the Cibyra Fault was firstly suggested by Akyüz and Altunel (1997, 2001). Researchers identified traces of historical earthquakes in Cibyra by taking into account the collapsed seat rows on the east side of the stadion as reference. They claimed that the NNE-SSW left lateral fault Cibyra Fault (related to Burdur-Fethiye Fault Zone) continues through Pliocene sediments on both eastern and western sides of the stadion of Cibyra. The questionable left-lateral fault had been examined in detail by ourselves during our 60-days accommodation in the ancient city of Cibyra excavations for the Burdur-Fethiye Fault Zone Project in 2008, 2009 and 2012. A left-lateral offset on the Stadion was firstly mentioned in a study whose aim is to find the traces of Burdur-Fethiye Fault (Akyüz and Altunel, 2001) and many researchers accepted this fault by reference (for example Alçiçek et al. 2002, 2004, 2005, 2006 and Karabacak, 2011). However as a result of the field observations it is understood that there is no fault cutting the Stadion. By the reason of the fact that there are a lot of faults in the region, however the fault that devastated the ancient city is unknown. The deformation traces on the ruins of the ancient city display a seismic movement occured in the region. It is strongly possible that this movement is related to the NE-SW left lateral oblique normal fault named as Cibyra Fault at the northwestern side of the city. Especially the ravages in the eastern part of the city indicate that the deformations are related to ground properties. If the rotation and overturn movement are considered and if both movements are the product of the same earthquake, the real Cibyra Fault is compatible with normal fault with left lateral compenent. After the 2011 excavations and 2012 field studies, the eastern wall of the Stadion showed that

  15. 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

  16. Bedload flux in southern Brazilian basalt scarp

    NASA Astrophysics Data System (ADS)

    Merten, G. H.; Minella, J. P. G.

    2015-03-01

    Frequently, to assess the life expectancy of Brazilian reservoirs, bedload flux has been estimated by using formulas (e.g. the Einstein equations) or by assuming that bedload represents a fixed percentage of the suspended load. This study was carried out to characterize the bedload flux on the basalt scarps of southern Brazil. The bedload was measured over the course of 12 stormflows. The results demonstrated that the bedload flux-streamflow relationship was adequately described by a potential mathematical function. Bedload flux selectively transported particles smaller than D50 surface and subsurface bedstream sediments. When considering the bedload flux-streamflow relationship, the flux ranged from a minimum of 0.24 g m-1 s-1 for a streamflow of 0.53 m3 s-1 to a maximum of 44 g m-1 s-1 for a streamflow of 1.3 m3 s-1. The percentage of bedload/suspended load varied between <1% up to 60%, and this variation was strongly associated with peak flow.

  17. Fault tolerant photodiode and photogate active pixel sensors

    NASA Astrophysics Data System (ADS)

    Jung, Cory; Chapman, Glenn H.; La Haye, Michelle L.; Djaja, Sunjaya; Cheung, Desmond Y. H.; Lin, Henry; Loo, Edward; Audet, Yves R.

    2005-03-01

    As the pixel counts of digital imagers increase, the challenge of maintaining high yields and ensuring reliability over an imager"s lifetime increases. A fault tolerant active pixel sensor (APS) has been designed to meet this need by splitting an APS in half and operating both halves in parallel. The fault tolerant APS will perform normally in the no defect case and will produce approximately half the output for single defects. Thus, the entire signal can be recovered by multiplying the output by two. Since pixels containing multiple defects are rare, this design can correct for most defects allowing for higher production yields. Fault tolerant photodiode and photogate APS" were fabricated in 0.18-micron technology. Testing showed that the photodiode APS could correct for optically induced and electrically induced faults, within experimental error. The photogate APS was only tested for optically induced defects and also corrects for defects within experimental error. Further testing showed that the sensitivity of fault tolerant pixels was approximately 2-3 times more sensitive than the normal pixels. HSpice simulations of the fault tolerant APS circuit did not show increased sensitivity, however an equivalent normal APS circuit with twice width readout and row transistors was 1.90 times more sensitive than a normal pixel.

  18. Late Tertiary faulting along the coastal plain of Israel

    NASA Astrophysics Data System (ADS)

    Steinberg, J.; Gvirtzman, Z.; Gvirtzman, H.; Ben-Gai, Y.

    2008-08-01

    This study documents a 70-km long and 200-400 m high step at the base of the Pliocene section in the Israeli coastal plain. Depositional explanations for this lineament, such as a buried shelf edge or reef front, are very unlikely; whereas a fault scarp explanation is supported by seismic profiles and geological cross sections. The eastern elevated side of the fault was eroded before its burial, though a quantitive distinction between this erosion, earlier truncations, and original hiatuses, is not possible at this stage. Sediments covering the fault scarp constrain its age to Late Miocene and/or Early Pliocene. The presence of such a fault along the Israeli coastal plain may also shed light on numerous post-Mid-Cretaceous faults previously documented along the coastal plain, but never explained. In a wider perspective, the fault described here along with other documented processes indicate that in the Late Tertiary tectonism along the Levant continental margin resumed after a long passive history. This renewed activity is coeval with the Africa-Arabian breakup and the Red Sea- Suez rifting. In particular, the fault described here is coeval with plate reorganization and vertical motions along the Dead Sea transform and possibly along the Cypriot Arc during the Late Miocene-Early Pliocene.

  19. Fault activation by hydraulic fracturing in western Canada.

    PubMed

    Bao, Xuewei; Eaton, David W

    2016-12-16

    Hydraulic fracturing has been inferred to trigger the majority of injection-induced earthquakes in western Canada, in contrast to the Midwestern United States, where massive saltwater disposal is the dominant triggering mechanism. A template-based earthquake catalog from a seismically active Canadian shale play, combined with comprehensive injection data during a 4-month interval, shows that earthquakes are tightly clustered in space and time near hydraulic fracturing sites. The largest event [moment magnitude (MW) 3.9] occurred several weeks after injection along a fault that appears to extend from the injection zone into crystalline basement. Patterns of seismicity indicate that stress changes during operations can activate fault slip to an offset distance of >1 km, whereas pressurization by hydraulic fracturing into a fault yields episodic seismicity that can persist for months.

  20. Fault activation by hydraulic fracturing in western Canada

    NASA Astrophysics Data System (ADS)

    Bao, Xuewei; Eaton, David W.

    2016-12-01

    Hydraulic fracturing has been inferred to trigger the majority of injection-induced earthquakes in western Canada, in contrast to the Midwestern United States, where massive saltwater disposal is the dominant triggering mechanism. A template-based earthquake catalog from a seismically active Canadian shale play, combined with comprehensive injection data during a 4-month interval, shows that earthquakes are tightly clustered in space and time near hydraulic fracturing sites. The largest event [moment magnitude (MW) 3.9] occurred several weeks after injection along a fault that appears to extend from the injection zone into crystalline basement. Patterns of seismicity indicate that stress changes during operations can activate fault slip to an offset distance of >1 km, whereas pressurization by hydraulic fracturing into a fault yields episodic seismicity that can persist for months.

  1. Examples of Holocene and latest Pleistocene faulting in northern and eastern Nevada

    SciTech Connect

    Ramelli, A.R.; Depolo, C.M. )

    1993-04-01

    Although it is generally accepted that tectonic activity in the Basin and Range province (BRP) is highest along the region's eastern and western margins, significant Holocene and latest Pleistocene activity has occurred in the central BRP as well, including northern and eastern Nevada. Some such faults are depicted in the few existing active fault compilations, but detailed studies are generally lacking and the actual levels of activity are often misrepresented. Examples of Holocene or latest Pleistocene faulting in northern and eastern Nevada include the Black Rock, Tuscarora, Thousand Springs Valley, and Railroad Valley fault zones. The Black Rock ault zone has hosted two or more Holocene events, including an event within the past 1.1 ka and resulting in a prominent fault scarp about 2.2 m high crossing the playa floor of the Black Rock Desert. The Tuscarora fault zone cuts an alluvial/pediment surface in southwestern Independence Valley, north-central Nevada, forming a complex graben at least 15 km long and 3.5 km wide, and has probable late Holocene activity. Single- and multiple-event scarps along the Thousand Springs Valley fault zone in northeastern Nevada suggest a 2 m Holocene/latest Pleistocene event and a minimum 17 m displacement of an early- to mid-Quaternary surface. Fault scarp profiles from the Railroad Valley fault zone in east-central Nevada, which has an overall length of about 120 km suggest an early Holocene or latest Pleistocene event, single event displacements of 1.5 to 2.5 m, and a late Quaternary slip rate of 0.1 to 0.2 mm/yr.

  2. Sliding mode fault detection and fault-tolerant control of smart dampers in semi-active control of building structures

    NASA Astrophysics Data System (ADS)

    Yeganeh Fallah, Arash; Taghikhany, Touraj

    2015-12-01

    Recent decades have witnessed much interest in the application of active and semi-active control strategies for seismic protection of civil infrastructures. However, the reliability of these systems is still in doubt as there remains the possibility of malfunctioning of their critical components (i.e. actuators and sensors) during an earthquake. This paper focuses on the application of the sliding mode method due to the inherent robustness of its fault detection observer and fault-tolerant control. The robust sliding mode observer estimates the state of the system and reconstructs the actuators’ faults which are used for calculating a fault distribution matrix. Then the fault-tolerant sliding mode controller reconfigures itself by the fault distribution matrix and accommodates the fault effect on the system. Numerical simulation of a three-story structure with magneto-rheological dampers demonstrates the effectiveness of the proposed fault-tolerant control system. It was shown that the fault-tolerant control system maintains the performance of the structure at an acceptable level in the post-fault case.

  3. 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

  4. Structural Analysis of Active North Bozgush Fault Zone (NW Iran)

    NASA Astrophysics Data System (ADS)

    Saber, R.; Isik, V.; Caglayan, A.

    2013-12-01

    NW Iran is one of the seismically active regions between Zagros Thrust Belt at the south and Caucasus at the north. Not only large magnitude historical earthquakes (Ms>7), but also 1987 Bozgush, 1997 Ardebil (Mw 6.1) and 2012 Ahar-Varzagan (Mw 6.4) earthquakes reveal that the region is seismically active. The North Bozgush Fault Zone (NBFZ) in this region has tens of kilometers in length and hundreds of meters in width. The zone has produced some large and destructive earthquakes (1593 M:6.1 and 1883 M:6.2). The NBFZ affects the Cenozoic units and along this zone Eocene units thrusted over Miocene and/or Plio-Quaternary sedimentary units. Together with morphologic features (stream offsets and alluvial fan movements) affecting the young unites reveal that the zone is active. The zone is mainly characterized by strike-slip faults with reverse component and reverse faults. Reverse faults striking N55°-85°E and dip of 40°-50° to the SW while strike-slip faults show right lateral slip with N60°-85°W and N60°-80°E directions. Our structural data analysis in NBFZ indicates that the axis direction of σ2 principal stress is vertical and the stress ratio (R) is 0.12. These results suggest that the tectonic regime along the North Bozgush Fault Zone is transpressive. Obtained other principal stresses (σ1, σ3) results are compatible with stress directions and GPS velocity suggested for NW Iran.

  5. Potential for a large earthquake rupture of the San Ramón fault in Santiago, Chile

    NASA Astrophysics Data System (ADS)

    Vargas Easton, G.; Klinger, Y.; Rockwell, T. K.; Forman, S. L.; Rebolledo, S.; Lacassin, R.; Armijo, R.

    2013-12-01

    The San Ramón fault is an active west-vergent thrust fault system located along the eastern border of Santiago, capital of Chile, at the foot of the main Andes Cordillera. This is part of the continental-scale West Andean Thrust, at the western slope of the Andean orogen. The fault system is constituted by fault segments in the order of 10-15 km length, evidenced by conspicuous 3-over 100 m height fault scarps systematically located along the fault trace. This evidence Quaternary faulting activity, which together with the geometry, structure and geochronological data support slip rate estimations in the order of ~0.4 mm/year. To probe seismic potential for the west flank of the Andes in front of Santiago, we excavated and analyzed a trench across a prominent-young fault scarp. Together with geochronological data from Optically Stimulated Luminiscence complemented by radiocarbon ages, our paleoseismic results demonstrate recurrent late Quaternary faulting along this structure, with nearly 5 m of displacement in each event. With the last large earthquake nearly 8,000-9,000 years ago and two ruptures within the past 17,000-19,000 years ago, the San Ramon fault appears ripe for another large earthquake up to M7.5 in the near future, making Santiago another major world city at significant risk.

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

    NASA Astrophysics Data System (ADS)

    Besstrashnov, V. M.; Strom, A. L.

    2011-05-01

    Assessment of seismic strong motion hazard produced by earthquakes originating within causative fault zones allows rather low accuracy of localisation of these structures that can be provided by indirect evidence of fault activity. In contrast, the relevant accuracy of localisation and characterisation of active faults, capable of surface rupturing, can be achieved solely by the use of direct evidence of fault activity. This differentiation requires strict definition of what can be classified as "active fault" and the normalisation of methods used for identification and localisation of active faults crossing oil and natural gas trunk pipelines.

  7. Are the benches at Mormon Point, Death Valley, California, USA, scarps or strandlines?

    USGS Publications Warehouse

    Knott, J.R.; Tinsley, J. C.; Wells, S.G.

    2002-01-01

    The benches and risers at Mormon Point, Death Valley, USA, have long been interpreted as strandlines cut by still-stands of pluvial lakes correlative with oxygen isotope stage (OIS) 5e/6 (120,000-186,000 yr B.P.) and OIS-2 (10,000-35,000 yr B.P.). This study presents geologic mapping and geomorphic analyses (Gilbert's criteria, longitudinal profiles), which indicate that only the highest bench at Mormon Point (~90 m above mean sea level (msl)) is a lake strandline. The other prominent benches on the north-descending slope immediately below this strandline are interpreted as fault scarps offsetting a lacustrine abrasion platform. The faults offsetting the abrasion platform most likely join downward into and slip sympathetically with the Mormon Point turtleback fault, implying late Quaternary slip on this low-angle normal fault. Our geomorphic reinterpretation implies that the OIS-5e/6 lake receded rapidly enough not to cut strandlines and was ~90 m deep. Consistent with independent core studies of the salt pan, no evidence of OIS-2 lake strandlines was found at Mormon Point, which indicates that the maximum elevation of the OIS-2 lake surface was -30 m msl. Thus, as measured by pluvial lake depth, the OIS-2 effective precipitation was significantly less than during OIS-5e/6, a finding that is more consistent with other studies in the region. The changed geomorphic context indicates that previous surface exposure dates on fault scarps and benches at Mormon Point are uninterpretable with respect to lake history. ?? 2002 University of Washington.

  8. Inferring Earthquake Physics from Deep Drilling Projects of Active Faults

    NASA Astrophysics Data System (ADS)

    Di Toro, G.; Smith, S. A. F.; Kuo, L. W.; Mittempergher, S.; Remitti, F.; Spagnuolo, E.; Mitchell, T. M.; Gualtieri, A.; Hadizadeh, J.; Carpenter, B. M.

    2014-12-01

    Deep drilling projects of active faults offer the opportunity to correlate physical and chemical processes identified in core samples with experiments reproducing the seismic cycle in the laboratory and with high-resolution seismological and geophysical data. Here we discuss the constraints about earthquakes source processes at depth gained by fault cores retrieved from the deep drilling projects SAFOD (2.7 km depth, San Andreas Fault), J-FAST (0.9 km depth, following the Mw 9.0 Tohoku 2011 earthquake), TCDP (1.1 km depth, following the Mw 7.6 Chi-Chi 1999 earthquake) and WFSD (1.2 km depth, following the Mw 7.9 Wenchuan 2008 earthquake). Recovered samples were tested at room temperature with the rotary shear apparatus SHIVA installed in Rome (INGV, Italy). All the tested samples were made by clay-rich gouges (usually including smectite/illite), though their bulk mineralogy and modal composition were different (e.g., SAFOD samples included saponite, WFSD carbonaceous materials). The gouges were investigated before and after the experiments with scanning and transmission electron microscopy, X-Ray diffraction, micro-Raman spectroscopy, etc. A common behavior of all the tested gouges was that their friction coefficient was low (often less than 0.1) under room-humidity and wet conditions when sheared at slip rates of ca. 1 m/s (seismic deformation conditions). Moreover, when the natural fault rocks next to the principal slipping zones were sheared from sub-seismic (few micrometers/s) to seismic slip rates, the experimental products had similar microstructures to those found in the principal slipping zones of the drilled faults. This included the formation of mirror-like surfaces, graphite-rich materials, foliated gouges, nanograins, amorphous materials, etc. In most cases the mechanical data were consistent with several seismological (> 50 m of seismic slip for the fault zone drilled by J-FAST) and geophysical observations (absence of a thermal anomaly in the fault

  9. How quickly do earthquakes get locked in the landscape? One year of erosion on El Mayor-Cucapah rupture scarps imaged by repeat terrestrial lidar scans

    NASA Astrophysics Data System (ADS)

    Elliott, A. J.; Oskin, M. E.; Banesh, D.; Gold, P. O.; Hinojosa-Corona, A.; Styron, R. H.; Taylor, M. H.

    2012-12-01

    Differencing repeat terrestrial lidar scans of the 2010 M7.2 El Mayor-Cucapah (EMC) earthquake rupture reveals the rapid onset of surface processes that simultaneously degrade and preserve evidence of coseismic fault rupture in the landscape and paleoseismic record. We surveyed fresh fault rupture two weeks after the 4 April 2010 earthquake, then repeated these surveys one year later. We imaged fault rupture through four substrates varying in degree of consolidation and scarp facing-direction, recording modification due to a range of aeolian, fluvial, and hillslope processes. Using lidar-derived DEM rasters to calculate the topographic differences between years results in aliasing errors because GPS uncertainty between years (~1.5cm) exceeds lidar point-spacing (<1.0cm) shifting the raster sampling of the point cloud. Instead, we coregister each year's scans by iteratively minimizing the horizontal and vertical misfit between neighborhoods of points in each raw point cloud. With the misfit between datasets minimized, we compute the vertical difference between points in each scan within a specified neighborhood. Differencing results reveal two variables controlling the type and extent of erosion: cohesion of the substrate controls the degree to which hillslope processes affect the scarp, while scarp facing direction controls whether more effective fluvial erosion can act on the scarp. In poorly consolidated materials, large portions (>50% along strike distance) of the scarp crest are eroded up to 5cm by a combination of aeolian abrasion and diffusive hillslope processes, such as rainsplash and mass-wasting, while in firmer substrate (i.e., bedrock mantled by fault gouge) there is no detectable hillslope erosion. On the other hand, where small gullies cross downhill-facing scarps (<5% along strike distance), fluvial erosion has caused 5-50cm of headward scarp retreat in bedrock. Thus, although aeolian and hillslope processes operate over a greater along

  10. A neotectonic tour of the Death Valley fault zone, Inyo County

    SciTech Connect

    Wills, C.J.

    1989-09-01

    The Death Valley fault zone has recently been evaluated by the Division of Mines and Geology for zoning under the Alquist-Priolo Special Studies Zones Act of 1972. This act requires the State Geologist to zone for special studies those faults that are sufficiently active and well defined as to constitute a potential hazard to structures from surface faulting or fault creep. The Death Valley fault zone is part of a system of faults that extends over 180 miles (300 km) from Fish Lake Valley in Nevada to the Garlock fault. The northern part of this system, the Northern Death Valley-Furnace Creek fault zone, is an active right-lateral fault zone. The southern part of the system, the Death Valley fault zone, is a right-lateral oblique-slip fault between Furnace Creek and Shoreline Butte. From Shoreline Butte to the Garlock fault, it is a right-lateral strike-slip fault. Landforms along this fault indicate that it is the source of many earthquakes and that it has been active in Holocene time. The heights of the scarps and magnitude of the smallest right-lateral offsets (4 feet; 1.2 m) suggest that the most recent of these events was M 6.5 or larger. The freshness of the geomorphic features and the youth of the offset materials suggest that event occurred late in the Holocene, and that multiple Holocene earthquakes have occurred.

  11. Armenia-To Trans-Boundary Fault: AN Example of International Cooperation in the Caucasus

    NASA Astrophysics Data System (ADS)

    Karakhanyan, A.; Avagyan, A.; Avanesyan, M.; Elashvili, M.; Godoladze, T.; Javakishvili, Z.; Korzhenkov, A.; Philip, S.; Vergino, E. S.

    2012-12-01

    Studies of a trans-boundary active fault that cuts through the border of Armenia to Georgia in the area of the Javakheti volcanic highland have been conducted since 2007. The studies have been implemented based on the ISTC 1418 and NATO SfP 983284 Projects. The Javakheti Fault is oriented to the north-northwest and consists of individual segments displaying clear left-stepping trend. Fault mechanism is represented by right-lateral strike-slip with normal-fault component. The fault formed distinct scarps, deforming young volcanic and glacial sediments. The maximum-size displacements are recorded in the central part of the fault and range up to 150-200 m by normal fault and 700-900 m by right-lateral strike-slip fault. On both flanks, fault scarps have younger appearance, and displacement size there decreases to tens of meters. Fault length is 80 km, suggesting that maximum fault magnitude is estimated at 7.3 according to the Wells and Coppersmith (1994) relation. Many minor earthquakes and a few stronger events (1088, Mw=6.4, 1899 Mw=6.4, 1912, Mw=6.4 and 1925, Mw=5.6) are associated with the fault. In 2011/2012, we conducted paleoseismological and archeoseismological studies of the fault. By two paleoseismological trenches were excavated in the central part of the fault, and on its northern and southern flanks. The trenches enabled recording at least three strong ancient earthquakes. Presently, results of radiocarbon age estimations of those events are expected. The Javakheti Fault may pose considerable seismic hazard for trans-boundary areas of Armenia and Georgia as its northern flank is located at the distance of 15 km from the Baku-Ceyhan pipeline.

  12. 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

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

    USGS Publications Warehouse

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

    2003-01-01

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

  14. Kinematic indicators on active normal faults in Western Turkey

    NASA Astrophysics Data System (ADS)

    Hancock, P. L.; Barka, A. A.

    Quaternary normal fault zones in western Turkey comprise multiple slip planes and zone-parallel layers of fault breccia. They also contain several little-known kinematic indicators that are probably typical of many formed at shallow levels in extending terrains. The recent exhumation by contractors of about 2000 m 2 of slip planes in a SSE-dipping fault zone separating Quaternary colluvium from bedrock carbonates at Yavansu (7 km SE of Kuşadasi) permits an unusually complete inventory of the indicators to be compiled. The most spectacular indicators are metre-scale 69°W-pitching corrugations in slip planes and recemented breccia sheets underlying them. Corrugations, characterized by sinusoidal profiles normal to their long axes and, less commonly, culminations and depression along their axes possibly developed as a result of upwards-propagating slip planes seeking undemanding pathways through heterogeneous fault-precursor breccias that formed in advance of tip lines. Parallel to corrugation long axes are those of gutters, flat-floored, sleep-sided channels a few centimetres wide, probably related to the abrasion of subslip-plane breccia sheets. Centimetre-scale tool tracks scored in the uppermost subslip-plane breccia sheet by resistant colluvial clasts are irregular at their proximal ends but distally they swing into alignment with corrugation axes. Frictional-wear striae, centimetres long but only a few millimetres wide and pitching 78°W, are superimposed on the other slip-parallel lineations. Comb fractures nearly perpendicular to slip planes define an intersection lineation which is normal to corrugation axes. Fault-plane solutions of earthquakes on SSE-dipping active faults in the West Anatolian extensional province indicate that mainly normal, combined with minor dextral slip is the dominant mode, a conclusion in accord with the sense of slip inferred from the indicators exposed on the Yavansu slip planes.

  15. Measuring Active Faulting in Bolivia: the 1998 Aiquile Earthquake

    NASA Astrophysics Data System (ADS)

    Funning, G. J.; Barke, R.; Lamb, S. H.; Minaya, E.; Parsons, B. E.; Woodhouse, J. H.

    2003-12-01

    The Aiquile region of central Bolivia is situated in the core of the actively deforming Bolivian Orocline. Palaeomagnetic data show that differential rotations consistent with oblique convergence have continued over the past 10 Myr. Structural mapping of the sub-Andean fold-and-thrust belt to the east shows that the majority of this convergence has occurred there as shortening; however there exists a significant transverse component of motion which must be accommodated as strike-slip faulting elsewhere. Many topographic lineations assumed to be related to strike-slip faulting have been identified in the area around Aiquile, however none has been associated with large earthquakes or demonstrated to be active over the past million years. On 22nd May 1998, a Mw = 6.5 earthquake struck the region, the largest shallow earthquake to occur in Bolivia for 50 years, resulting in over 105 fatalities and rendering thousands homeless in the towns of Aiquile and Totora and their surrounding villages. Seismic observations of the event are inconclusive; the correct orientation and style of the faulting -- either right-lateral strike-slip on a N--S fault, or left-lateral on an E--W fault -- cannot be determined as large uncertainties in earthquake location mean we do not know a priori which of the two nodal planes in the focal mechanism is the fault plane, or upon which structure the earthquake occurred. We present here the first study of a Bolivian earthquake using InSAR. Despite the rugged nature of the terrain in the Aiquile region, with its sharp changes of relief ( ˜ 3000 m over 20 km) -- a consequence of its location between the high Altiplano to the west and the foreland basin to the east -- we demonstrate that by using freely-available SRTM digital elevation data we can correct for topographic artifacts and generate a clear deformation signal. Our preferred model is for slip on a N--S-striking fault, with a location which validates Modified Mercalli Intensity maps

  16. Post-glacial reactivation of the Bollnäs fault, central Sweden

    NASA Astrophysics Data System (ADS)

    Malehmir, A.; Andersson, M.; Mehta, S.; Brodic, B.; Munier, R.; Place, J.; Maries, G.; Smith, C.; Kamm, J.; Bastani, M.; Mikko, H.; Lund, B.

    2015-10-01

    Glacially induced intraplate faults are conspicuous in Fennoscandia where they reach trace lengths of up to 155 km with estimated magnitudes up to 8 for the associated earthquakes. While they are typically found in northern parts of Fennoscandia, there are a number of published accounts claiming their existence further south in Fennoscandia and even in northern central Europe. This study focuses on a prominent scarp discovered recently in LiDAR (light detection and ranging) imagery hypothesized to be from a post-glacial fault and located about 250 km north of Stockholm near the town of Bollnäs. The Bollnäs scarp strikes approximately north-south for about 12 km. The maximum vertical offset in the sediments across the scarp is 4-5 m with the western block being elevated relative to the eastern block. To investigate potential displacement in the bedrock and identify structures in it that are related to the scarp, we conducted a multidisciplinary geophysical investigation that included gravity and magnetic measurements, high-resolution seismics, radio-magnetotellurics (RMT), electrical resistivity tomography (ERT) and ground penetrating radar (GPR). Results of the investigations suggest a zone of low-velocity and high-conductivity in the bedrock associated also with a magnetic lineament that is offset horizontally about 50 m to the west of the scarp. The top of bedrock is found ~ 10 m below the surface on the eastern side of the scarp while about ~ 20 m below on its western side. This difference is due to the different thicknesses of the overlying sediments, accounting for the surface topography, while the bedrock surface is likely more or less at the same topographic level on both sides of the scarp. This makes an estimation of the bedrock displacement challenging if not impossible with our datasets. To explain this, we suggest that the Bollnäs scarp is likely associated with an earlier deformation zone, within a wide (> 150 m), highly fractured and water

  17. A “mesh” of crossing faults: Fault networks of southern California

    NASA Astrophysics Data System (ADS)

    Janecke, S. U.

    2009-12-01

    Detailed geologic mapping of active fault systems in the western Salton Trough and northern Peninsular Ranges of southern California make it possible to expand the inventory of mapped and known faults by compiling and updating existing geologic maps, and analyzing high resolution imagery, LIDAR, InSAR, relocated hypocenters and other geophysical datasets. A fault map is being compiled on Google Earth and will ultimately discriminate between a range of different fault expressions: from well-mapped faults to subtle lineaments and geomorphic anomalies. The fault map shows deformation patterns in both crystalline and basinal deposits and reveals a complex fault mesh with many curious and unexpected relationships. Key findings are: 1) Many fault systems have mutually interpenetrating geometries, are grossly coeval, and allow faults to cross one another. A typical relationship reveals a dextral fault zone that appears to be continuous at the regional scale. In detail, however, there are no continuous NW-striking dextral fault traces and instead the master dextral fault is offset in a left-lateral sense by numerous crossing faults. Left-lateral faults also show small offsets where they interact with right lateral faults. Both fault sets show evidence of Quaternary activity. Examples occur along the Clark, Coyote Creek, Earthquake Valley and Torres Martinez fault zones. 2) Fault zones cross in other ways. There are locations where active faults continue across or beneath significant structural barriers. Major fault zones like the Clark fault of the San Jacinto fault system appears to end at NE-striking sinistral fault zones (like the Extra and Pumpkin faults) that clearly cross from the SW to the NE side of the projection of the dextral traces. Despite these blocking structures, there is good evidence for continuation of the dextral faults on the opposite sides of the crossing fault array. In some instances there is clear evidence (in deep microseismic alignments of

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    In the early stages of continental rifting, East African Rift (EAR) basins are conventionally depicted as asymmetric basins bounded on one side by a ~100 km-long border fault. As rifting progresses, strain concentrates into the rift center, producing intra-rift faults. The timing and nature of the transition from border fault to intra-rift-dominated strain accommodation is unclear. Our study focuses on this transitional phase of continental rifting by exploring the spatial and temporal evolution of faulting in the Natron (border fault initiation at ~3 Ma) and Magadi (~7 Ma) basins of northern Tanzania and southern Kenya, respectively. We compare the morphologies and activity histories of faults in each basin using field observations and remote sensing in order to address the relative contributions of border faults and intra-rift faults to crustal strain accommodation as rifting progresses. The ~500 m-high border fault along the western margin of the Natron basin is steep compared to many border faults in the eastern branch of the EAR, indicating limited scarp degradation by mass wasting. Locally, the escarpment shows open fissures and young scarps 10s of meters high and a few kilometers long, implying ongoing border fault activity in this young rift. However, intra-rift faults within ~1 Ma lavas are greatly eroded and fresh scarps are typically absent, implying long recurrence intervals between slip events. Rift-normal topographic profiles across the Natron basin show the lowest elevations in the lake-filled basin adjacent to the border fault, where a number of hydrothermal springs along the border fault system expel water into the lake. In contrast to Natron, a ~1600 m high, densely vegetated, border fault escarpment along the western edge of the Magadi basin is highly degraded; we were unable to identify evidence of recent rupturing. Rift-normal elevation profiles indicate the focus of strain has migrated away from the border fault into the rift center, where

  19. Crestal graben associated with lobate scarps on Mercury

    NASA Astrophysics Data System (ADS)

    Vaughan, Rubio; Foing, Bernard; van Westrenen, Wim

    2014-05-01

    Mercury is host to various tectonic landforms which can be broadly divided into localized, basin-related features on the one hand, and regional or global features on the other. The globally distributed tectonic landforms are dominantly contractional in nature and consist of lobate scarps, wrinkle ridges and high-relief ridges [1]. Until now, extensional features have only been found within the Caloris basin, several smaller impact basins, such as Raditladi, Rachmaninoff & Rembrandt [2], and within volcanic deposits in the northern smooth plains [3,4]. New imagery obtained from the MESSENGER spacecraft, shows localized, along-strike troughs associated with several lobate scarps on Mercury. These troughs occur at or near the crest of the lobate scarps and are interpreted to be graben. While previously discovered graben on Mercury are thought to be related to thermal contraction of localized volcanic fill, these crestal graben are the first extensional tectonic features which have been discovered outside of such settings and have not been reported in literature previously. Of the 49 lobate scarps investigated in this study, 7 exhibit graben along their crest. The graben are usually only present along small sections of the scarp, but in some cases extend up to 180 km along the scarp crest. The persistent along-strike orientation of the graben with respect to the scarps, combined with several observed cross-cutting relations, suggests that the graben developed coeval with the formation of the lobate scarps. Numerical mechanical modeling using the Discrete Element Method (DEM) is currently being employed in order to better understand the mechanisms which control the formation of crestal graben associated with lobate scarps on Mercury. References: [1] Watters, Thomas R., and F. Nimmo. "The tectonics of Mercury." Planetary Tectonics 11 (2010): 15. [2] Blair, David M., et al. "The origin of graben and ridges in Rachmaninoff, Raditladi, and Mozart basins, Mercury." Journal

  20. Temporal and spatial patterns of late Pleistocene-Holocene faulting in Arizona

    SciTech Connect

    Menges, C.M. ); Pearthree, P.A. )

    1993-04-01

    Geomorphic and geologic analyses of Quaternary faults in Arizona and adjoining areas conducted in the past 15 years have revealed the general patterns of late Pleistocene and Holocene (< 150 ka) faulting. Nearly all of the late Quaternary faults in Arizona are located within a broad band stretching from northwest to southeast across the State. The greatest density of late Quaternary faults is found along the Basin and Range-Colorado Plateau transition in central and northwestern Arizona; a lesser concentration of these faults exists in the Mexican Highland portion of the Basin and Range in southeastern Arizona and southwestern New Mexico. Several active faults are located in southwestern Arizona, outside the main band of faulting. The band of late Quaternary faults in Arizona coincides with a zone of moderate historical seismicity. Studies of 15 individual fault zones provide more detailed information about the patterns of late Pleistocene and Holocene faulting in Arizona. These studies have involved geologic mapping, soils and stratigraphic analyses, morphologic fault scarp analyses, or trenching. The most active faults in Arizona, with recurrence intervals as short as 10,000--20,000 yrs, are found in the northwestern portion of the State. Faults in north-central and southwesternmost Arizona have somewhat longer recurrence intervals (ca. 20,000--50,000 yrs). Late Pleistocene and younger faulting (< 150 ka) has occurred in all areas where there is evidence of Quaternary faulting. Latest Pleistocene-Holocene faulting (< 20 ka) has occurred on 17--20 faults. These events are concentrated in several restricted belts in northwestern Arizona, central Arizona, and the border region between AZ, NM, and Sonora, Mex. Given the long recurrence intervals for individual faults in central and southeastern AZ, faulting in the past 20 k.y. may represent a burst of activity that is a low-strain analog of the historical burst of surface faulting in the central NV seismic belt.

  1. Ridges and scarps in the equatorial belt of Mars

    USGS Publications Warehouse

    Lucchitta, B.K.; Klockenbrink, J.L.

    1981-01-01

    The morphology and distribution of ridges and scarps on Mars in the ?? 30?? latitude belt were investigated. Two distinct types of ridges were recognized. The first is long and linear, resembling mare ridges on the Moon; it occurs mostly in plains areas. The other is composed of short, anastomosing segments and occurs mostly in ancient cratered terrain and intervening plateaus. Where ridges are eroded, landscape configurations suggest that they are located along regional structures. The age of ridges is uncertain, but some are as young as the latest documented volcanic activity on Mars. The origins of ridges are probably diverse-they may result from wrinkling due to compression or from buckling due to settling over subsurface structures. The similar morphologic expressions of ridge types of various origins may be related to a similar deformation mechanism caused by two main factors: (1) most ridges are developed in thick layers of competent material and (2) ridges formed under stresses near a free surface. ?? 1981 D. Reidel Publishing Co.

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

    NASA Astrophysics Data System (ADS)

    Pratt, Thomas L.; Shaw, John H.; Dolan, James F.; Christofferson, Shari A.; Williams, Robert A.; Odum, Jack K.; Plesch, Andreas

    2002-05-01

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

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

    USGS Publications Warehouse

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

    2002-01-01

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

  4. 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

  5. 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.

  6. 400My of Deformation Along Tibet Active Strike Slip Faults

    NASA Astrophysics Data System (ADS)

    Arnaud, N. O.

    2003-12-01

    While it is widely accepted that strike slip faults in Tibet accommodate a significant part of the tertiary convergence between India and Asia, the true Cenozoic magnitude of the offset is still largely debated. Direct dating of Cenozoic piercing points is the most powerful tool to assess the total offset, but their use is not always possible. Therefore one gets to use older markers although this leads to significant results ONLY at the supreme condition that pre-Cenozoic movement of those markers be accurately known. The Kunlun and Altyn Tagh faults for example form a prominent example of Tibetan presently active fault, but they also constitute geological frontiers between blocks of different geological histories accreted at various times since early Paleozoic. One may thus question how much of the visible offset is indeed Cenozoic. Although deformation facies agree with recent kinematics, multi-geochronological approach indicates a series of events from 280-230 Ma to 120+/-10 Ma. The former may be linked either with suturing of the Qiantang and Kunlun blocks farther to the south, or collision further to the north or east in the Qilian Shan and Bei Shan ranges, while the latter range appears to be growing in importance with ongoing work but is still largely unexplained. Oblique subductions of collision to the north of the Qilian Shan are adequate candidates. Argon loss suggests that deformation was associated to a 250-300° C thermal pulse that lasted 5 to 20 Ma after the onset of movement (Arnaud et al., 2003). Unroofing on all faults occurred much later, around 25 Ma ago when sudden cooling suggests a component of normal faulting (Mock et al., 1999). Strong inheritage was also found along the Ghoza active fault, in central western Tibet. Of course the fact that some of the deformation is much older than the Cretaceous and shares compatible deformation criteria with the present-day deformation leads to false appreciation of the pure Cenozoic offset, potentially

  7. Identifying paleoseismic information from limestone normal faults with a handheld XRF

    NASA Astrophysics Data System (ADS)

    Fritzon, Ruben; Stroeven, Arjen P.; Skelton, Alasdair; Goodfellow, Brad W.; Caffee, Marc W.

    2014-05-01

    Predicting earthquakes would help immensely in saving human lives and protecting economic interest but a reliable method has not yet been found. When making risk assessments scientists continue to rely on paleoseismic studies. Determining a fast and cheap proxy for paleoseismicity is therefore of much interest. Surface exposure dating is an emergent method for paleoseismic studies of active normal fault scarps in the Mediterranean region. This method gives crucial paleoearthquake information such as timing and vertical slip along the fault but the analysis of cosmogenic nuclides is costly and the sampling is both complicated and time consuming. In our study we employ an Olympus Innov-X DeltaTM handheld XRF to analyse the geochemistry of a scarp surface in order to determine the number and magnitude of slips along the fault. This method requires no drilling and it is possible to analyse the results at the fault scarp. Exposure dating is still required to yield the timeframe of the paleoearthquake record, but the number of sampling points may be significantly reduced since it would be possible to pin-point the sampling locations around suspected former soil horizons. We have analysed 200 sample points with the handheld XRF from a 6.8 m section of the limestone normal fault scarp surface close to Sparta, southern Greece. Our profile is taken next to the Benedetti et al.[Geophysical Research Letters, 29, 8 (2002)] sampling site. Our results show significant variations in Yttrium concentration along the profile with a strong peak just below the present soil cover at the base of the section and then repeated peaks up along the transect on the subaerially exposed scarp surface. These Yttrium concentrations at the surface are correlated with Yttrium concentrations in the rock determined from drill cores taken every 10 cm from the same profile. The preliminary dataset appears to indicate a good correlation between the Yttrium concentrations and the earthquake events

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

    NASA Technical Reports Server (NTRS)

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

    1976-01-01

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

  9. 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.

  10. 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.

  11. 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.

  12. A refinement of the chronology of rift-related faulting in the Broadly Rifted Zone, southern Ethiopia, through apatite fission-track analysis

    NASA Astrophysics Data System (ADS)

    Balestrieri, Maria Laura; Bonini, Marco; Corti, Giacomo; Sani, Federico; Philippon, Melody

    2016-03-01

    To reconstruct the timing of rift inception in the Broadly Rifted Zone in southern Ethiopia, we applied the fission-track method to basement rocks collected along the scarp of the main normal faults bounding (i) the Amaro Horst in the southern Main Ethiopian Rift and (ii) the Beto Basin in the Gofa Province. At the Amaro Horst, a vertical traverse along the major eastern scarp yielded pre-rift ages ranging between 121.4 ± 15.3 Ma and 69.5 ± 7.2 Ma, similarly to two other samples, one from the western scarp and one at the southern termination of the horst (103.4 ± 24.5 Ma and 65.5 ± 4.2 Ma, respectively). More interestingly, a second traverse at the Amaro northeastern terminus released rift-related ages spanning between 12.3 ± 2.7 and 6.8 ± 0.7 Ma. In the Beto Basin, the ages determined along the base of the main (northwestern) fault scarp vary between 22.8 ± 3.3 Ma and 7.0 ± 0.7 Ma. We ascertain through thermal modeling that rift-related exhumation along the northwestern fault scarp of the Beto Basin started at 12 ± 2 Ma while in the eastern margin of the Amaro Horst faulting took place later than 10 Ma, possibly at about 8 Ma. These results suggest a reconsideration of previous models on timing of rift activation in the different sectors of the Ethiopian Rift. Extensional basin formation initiated more or less contemporaneously in the Gofa Province (~ 12 Ma) and Northern Main Ethiopian Rift (~ 10-12 Ma) at the time of a major reorganization of the Nubia-Somalia plate boundary (i.e., 11 ± 2 Ma). Afterwards, rift-related faulting involved the Southern MER (Amaro Horst) at ~ 8 Ma, and only later rifting seemingly affected the Central MER (after ~ 7 Ma).

  13. First paleoseismological assessment of active deformation along the eastern front of the southern Alps (NE Italy, Friuli). Insights on the 1511 earthquake causative fault.

    NASA Astrophysics Data System (ADS)

    Falcucci, Emanuela; Eliana Poli, Maria; Galadini, Fabrizio; Paiero, Giovanni; Scardia, Giancarlo; Zanferrari, Adriano

    2014-05-01

    The study area belongs to the Julian Prealps that represent the easternmost portion of the Plio-Quaternary front of the eastern Southalpine Chain (ESC), a south-verging polyphase fold and thrust belt, in evolution from the Middle Miocene to the Present. Here, the WSW-ENE trending, SW- verging thrusts of the ESC join the NW-SE trending, right-lateral strike slip Idrija fault system, which develops along the Italian-Slovenian boundary. The area is characterized by medium/high seismicity testified by both large historical and instrumental earthquakes. The DBMI11 (Locati et al., 2011) records the 1348 Carinzia earthquake (Mw= 7.02), the 1511 Idrija earthquake (Mw=6.98), and the 1976 Friuli earthquakes on May (Mw=6.46) and September (Mw=5.98) We studied a segment of the Susans-Tricesimo thrust system, namely the Colle Villano (CV) thrust, identified by means of geological and geophysical investigations (Galadini et al., 2005). New geological and geomorphological analyses allowed identifying the surficial geomorphic evidence of recent blind thrusting along the structure, represented by gentle scarps and surface warping. In order to characterise the Late Pleistocene-Holocene activity of this blind thrust, paleoseismological investigations were performed along one of CV thrust-related fault scarps. We dug three trenches ~1 km to the north of the Magredis village. The analysis of the trench walls allowed identifying deformation events induced by the fault activity. Two subsequent episodes of deformation are distinguished by localised warping (few metres in wave length) of the sedimentary sequences exposed by the excavations and secondary extrados faulting. One event occurred between 544-646 AD (radiocarbon cal. age, 2σ) and 526-624 AD the other - probably the last one - occurred close to 1485-1604 AD. The last displacement event is consistent with the aforementioned 1511 earthquake both in terms of chronology of the deformation and location of the causative fault. This

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

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

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

  15. Post-glacial reactivation of the Bollnäs fault, central Sweden - a multidisciplinary geophysical investigation

    NASA Astrophysics Data System (ADS)

    Malehmir, Alireza; Andersson, Magnus; Mehta, Suman; Brodic, Bojan; Munier, Raymond; Place, Joachim; Maries, Georgiana; Smith, Colby; Kamm, Jochen; Bastani, Mehrdad; Mikko, Henrik; Lund, Björn

    2016-04-01

    Glacially induced intraplate faults are conspicuous in Fennoscandia where they reach trace lengths of up to 155 km with estimated magnitudes up to 8 for the associated earthquakes. While they are typically found in northern parts of Fennoscandia, there are a number of published accounts claiming their existence further south and even in northern central Europe. This study focuses on a prominent scarp discovered recently in lidar (light detection and ranging) imagery hypothesized to be from a post-glacial fault and located about 250 km north of Stockholm near the town of Bollnäs. The Bollnäs scarp strikes approximately north-south for about 12 km. The maximum vertical offset in the sediments across the scarp is 4-5 m with the western block being elevated relative to the eastern block. To investigate potential displacement in the bedrock and identify structures in it that are related to the scarp, we conducted a multidisciplinary geophysical investigation that included gravity and magnetic measurements, high-resolution seismics, radio-magnetotellurics (RMT), electrical resistivity tomography (ERT) and ground-penetrating radar (GPR). Results of the investigations suggest a zone of low-velocity and high-conductivity in the bedrock associated with a magnetic lineament that is offset horizontally about 50 m to the west of the scarp. The top of the bedrock is found ˜ 10 m below the surface on the eastern side of the scarp and about ˜ 20 m below on its western side. This difference is due to the different thicknesses of the overlying sediments accounting for the surface topography, while the bedrock surface is likely to be more or less at the same topographic level on both sides of the scarp; else the difference is not resolvable by the methods used. To explain the difference in the sediment covers, we suggest that the Bollnäs scarp is associated with an earlier deformation zone, within a wide (> 150 m), highly fractured, water-bearing zone that became active as a

  16. Aftershocks illuminate 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.

  17. Discrete element modeling of the faulting in the sedimentary cover above an active salt diapir

    NASA Astrophysics Data System (ADS)

    Yin, Hongwei; Zhang, Jie; Meng, Lingsen; Liu, Yuping; Xu, Shijing

    2009-09-01

    Geological mapping, seismic analyses, and analogue experiments show that active salt diapirism results in significant faulting in the overburden strata. Faults associated with active diapirism generally develop over the crest of the dome and form a radial pattern. In this study, we have created a 3-D discrete element model and used this model to investigate the fault system over active diapirs. The model reproduces some common features observed in physical experiments and natural examples. The discrete element results show that most faults initiate near the model surface and have displacement decreasing downward. In addition, model results indicate that the earliest fault, working as the master fault, has a strong influence on the subsequent fault pattern. The footwall of the master fault is mainly deformed by arc-parallel stretching and develops a subradial fault pattern, whereas the hanging wall is deformed by both arc-parallel stretching and gliding along the master fault and top of salt, and hence develops both parallel and oblique faults. Model results replicate the fault pattern and deformation mechanism of the Reitbrook dome, Germany.

  18. Lidar-Based Mapping of Late Quaternary Faulting Along the Grizzly Valley Fault, Walker Lane Seismic Belt, California

    NASA Astrophysics Data System (ADS)

    Hitchcock, C. S.; Hoirup, D. F.; Barry, G.; Pearce, J.; Glick, F.

    2012-12-01

    The Grizzly Valley fault (GVF) is located within the northern Walker Lane, a zone of right-lateral shear between the Sierra Nevada and the Basin and Range in Plumas County. The GVF extends southeasterly from near Mt. Ingalls along the eastern side of Lake Davis. It may partially connect with the Hot Creek fault within Sierra Valley and extend south to Loyalton with an overall approximate length of 50 km. Comparison of high-resolution topography developed from LiDAR data with published bedrock geologic mapping documents the presence of geomorphic features that provide information on fault activity of the GVF. Field mapping verified tectonically deformed and offset late Quaternary surfaces identified on bare-earth LiDAR imagery across the GVF within glacial deposits on the eastern margin of Lake Davis, and alluvial deposits in Sierra Valley. Along the GVF, conspicuous geomorphic and hydrologic features include scarps in alluvial surfaces, elongated depressions aligned with adjacent linear escarpments, truncated bedrock spurs, closed depressions, linear swales, right-lateral deflections of creeks and river courses, and shutter ridges, as well as springs and linear seeps consistent with right-lateral strike-slip faulting. The discontinuous nature of observed fault traces combined with the apparent down-to-the-west offset of alluvial surfaces at the southern and northern ends of the eastern margin of Lake Davis are consistent with a broad bend or step over in the fault. Scarp profiles of apparently faulted surfaces extracted from LiDAR data document vertical offsets of up to 14 m. Our study suggest that the GVF is an oblique, right-lateral fault that has been active in the late Quaternary. This study complements on-going investigations by DWR to assess the impact of seismic hazards on State Water Project infrastructure.

  19. Tectonic geomorphology and neotectonics of the Kyaukkyan Fault, Myanmar

    NASA Astrophysics Data System (ADS)

    Crosetto, Silvia; Watkinson, Ian; Gori, Stefano; Falcucci, Emanuela; Min, Soe

    2016-04-01

    The Kyaukkyan Fault is a dextral strike-slip fault, part of a complex zone of active dextral transpression that absorbs most of the northward motion of India relative to Sundaland. While much of the strike-slip displacement is localised in western Myanmar and along the prominent Sagaing Fault, significant dextral shear also occurs across the Kyaukkyan Fault, on the Shan Plateau in the east. The largest recorded earthquake in Myanmar occurred on the Kyaukkyan Fault in 1912, near Maymyo (Mw 7.7), but the fault has generated little significant seismicity since then. Despite its demonstrated seismic potential and remarkable topographic expression, the fault's neotectonic history remains poorly known. Interpretation of ≤30 m Landsat TM/ETM+ images, together with field investigations, reveals deformation features developed along the Kyaukkyan Fault system, mostly indicative of Quaternary dextral strike-slip faulting. Well-marked fault scarps and valleys locate the fault especially in its northernmost and southernmost part; geomorphic features related with Kyaukkyan Fault activity are sag ponds, shutter ridges, offset and beheaded streams, triangular facets and low-sinuosity mountain fronts. Geomorphic markers of young fault activity such as offset and deformed alluvial fans, wind-gaps were also identified during field observation. The fault's central section is characterised by a complex pull-apart system, whose normal border faults show signals of relatively slow neotectonic activity. In the central part of the basin, deformation of Quaternary sediments by a locally-buried cross-basin fault system includes dip-slip faulting, where subsidence adjacent to linear ridges is suggested by notably active mountain fronts, dextral strike-slip faulting and local transpression. Although no direct evidence of a 1912 surface rupture has been detected, the fresh geomorphic expression of the cross-basin fault system indicates that it is likely to have been the focus of that event

  20. 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.

  1. CRE dating on the scarps of large landslides affecting the Belledonne massif ( French Alps)

    NASA Astrophysics Data System (ADS)

    Lebrouc, V.; Baillet, L.; Schwartz, S.; Jongmans, D.; Gamond, J. F.; Bourles, D.; Le Roux, O.; Carcaillet, J.; Braucher, R.

    2012-04-01

    The southwestern edge of the Belledonne Massif (French Alps) consists of micaschists unconformably covered with Mesozoic sediments and Quaternary deposits. The morphology corresponds to a glacial plateau (Mont Sec plateau) bordered by steep slopes (around 40°), where moraines and peat bog subsist. The massif is incised by the East-West trending Romanche valley that was shaped by several cycles of quaternary glaciations and deglaciations. Slopes are affected by several active or past large scale rock mass instabilities. Cosmic Ray Exposure (CRE) dating was applied on the head scarps of three large landslides, one of which being the active Séchilienne landslide whose headscarp was already dated by Leroux et al. [2009]. Dating results suggest a concomitant initiation of these instabilities at about 7 ± 2 10Be ka, thousands years after the total downwastage of the valley. A different kinematic behaviour was however observed on two contiguous landslides for which continuous exposure profiles were obtained. On the Séchilienne landslide, 23 samples were collected from internal and lateral scarps, as well as on polished bedrock surfaces, with the aim of dating the internal kinematics of the landslide. Preliminary dating results obtained on polished surfaces and near the top of the scarps show unexpected low 10Be concentrations, suggesting the existence of thin moraine or peat bog deposits masking the bedrock, which have been subsequently eroded. The minimum thickness of these deposits was estimated assuming a constant denudation rate over time. Exposure date profiles show that the studied lateral and internal scarps were initiated at the same period as the Sechilienne headscarp. An increase in the exposure rate was also observed between 2 and 1 ka, in agreement with that evidenced along the headscarp. Forty other samples have been collected in the landslide to corroborate these results. Reference Le Roux, O., S. Schwartz , J.-F. Gamond, D. Jongmans, D. Bourles, R

  2. Active Faulting within the Atlantis Massif at 30°N Mid-Atlantic Ridge Located by an Ocean Bottom Seismograph Array

    NASA Astrophysics Data System (ADS)

    McGuire, J. J.; Smith, D. K.; Collins, J. A.

    2011-12-01

    The Atlantis Massif, located at the intersection of the Mid-Atlantic Ridge (MAR) spreading axis and the Atlantis transform fault at 30N, is an oceanic core complex. Slip along the detachment fault for the last 1.5-2 Ma has brought lower crust and mantle rocks to the seafloor and has led to one of the most striking topographic features on the MAR. Hydroacoustic data collected between 1999 and 2003 indicate seismicity at the top of the Atlantis Massif, mostly on the southeastern section; little seismic activity was hydroacoustically detected at the adjacent ridge axis. In 2005, five short-period ocean bottom seismometers (OBS) were deployed at the Atlantis Massif in a pilot experiment to determine if there was active faulting within the massif and if the seismicity rate within the massif was higher than that beneath the rift valley as suggested by the hydroacoustic data. The analysis of the first six months of OBS data indicates that the majority of seismicity is associated with normal faults beneath the spreading axis, and composed of a relatively constant background seismicity rate and two large aftershock sequences. The OBS array captured 5 teleseismic events with magnitudes between 4.0 and 4.5. The aftershock sequences, following two of the M 4 earthquakes are located in the axial valley close to the ridge-transform intersection. They make up more than half of the detected earthquakes. Omori's law of aftershock decay is clearly demonstrated by both aftershock sequences. In addition, the OBS data indicate active faulting within the Atlantis Massif. These events are located in the same region as the hydroacoustic seismicity suggesting that the hydroacoustically-derived locations could indeed represent earthquake epicenters. Analysis of a cluster of earthquakes on the 1500-m-high north-facing scarp of the South Ridge section of the massif indicates a normal fault with an orientation that is either ridge parallel or ridge perpendicular. Data analysis to date cannot

  3. Active strike-slip faulting history inferred from offsets of topographic features and basement rocks: a case study of the Arima Takatsuki Tectonic Line, southwest Japan

    NASA Astrophysics Data System (ADS)

    Maruyama, Tadashi; Lin, Aiming

    2002-01-01

    Geological, geomorphological and geophysical data have been used to determine the total displacement, slip rates and age of formation of the Arima-Takatsuki Tectonic Line (ATTL) in southwest Japan. The ATTL is an ENE-WSW-trending dextral strike-slip fault zone that extends for about 60 km from northwest of the Rokko Mountains to southwest of the Kyoto Basin. The ATTL marks a distinct topographic boundary between mountainous regions and basin regions. Tectonic landforms typically associated with active strike-slip faults, such as systematically-deflected stream channels, offset ridges and fault scarps, are recognized along the ATTL. The Quaternary drainage system shows progressive displacement along the fault traces: the greater the magnitude of stream channel, the larger the amount of offset. The maximum dextral deflection of stream channels is 600-700 m. The field data and detailed topographic analyses, however, show that pre-Neogene basement rocks on both sides of the ATTL are displaced by about 16-18 km dextrally and pre-Mio-Pliocene elevated peneplains are also offset 16-17 km in dextral along the ATTL. This suggests that the ATTL formed in the period between the development of the pre-Mio-Pliocene peneplains and deflection of the Quaternary stream channels. The geological, geomorphological and geophysical evidence presented in this study indicates that (1) the ATTL formed after the mid-Miocene, (2) the ATTL has moved as a dextral strike-slip fault with minor vertical component since its formation to late Holocene and (3) the ATTL is presently active with dextral slip rates of 1-3 mm/year and a vertical component of >0.3 mm/year. The formation of the ATTL was probably related to the opening of the Japan Sea, which is the dominant tectonic event around Japan since mid-Miocene. The case study of the ATTL provides insight into understanding the tectonic history and relationship between tectonic landforms and structures in active strike-slip faults.

  4. Late Pliocene To Pleistocene Tectonic Activity In SW Portugal: The S.Teotónio-Aljezur- Sinceira Fault System And Evidence For Coastal Uplift

    NASA Astrophysics Data System (ADS)

    Figueiredo, P.; Cabral, J.; Rockwell, T.

    2008-12-01

    Southwestern Portugal is located close to the Eurasia-Nubia plate boundary. East of the Gloria transform fault, this boundary becomes complex, particularly as it approaches the Gorringe Bank, the Horseshoe Plain, and the Gulf of Cadiz, where deformation related to the NW-SE convergence of Iberia and Nubia, at a rate of ~4-5 mm/ year, becomes distributed across a few hundred kilometer-wide zone. This area corresponds to the inferred seismogenic source zone for the 1755 earthquake and tsunami (estimated ≥ Mw 8), and also for the Mw 7.9 1969 event. During the past decade, several off-shore active folds and faults have been recognized in this region however, in spite of increased knowledge, none of the recognized active structures are clearly associated with the 1755 earthquake. Major likely sources are the Marquês de Pombal and Horseshoe faults. The Marquês de Pombal fault is a major NNE-SSW trending thrust located ~100 km SW of Cape S.Vicente that exhibits a ~1 km-high, 60 km-long scarp. Assuming rupture of this entire structure suggests earthquake magnitudes in the Mw 7.8 range. The Horseshoe fault, which is oriented NE- SW along a 175 km-long trend parallel to Säo Vicente canyon, a major morphological feature in the off- shore that has been interpreted as a possible extend for the Alentejo-Plasencia fault. Rupture of this entire fault could yield moment magnitude events up to Mw 8, assuming 10 m of average displacement. Neither of these potential sources can likely produce, by themselves, an earthquake that matches the upper estimates for the 1755 earthquake (Mw 8.7). Along the southwestern Portuguese coast, mainly at the western coastline, cliffs in Palaeozoic schist reach more than 100m in altitude, with evidence of uplift in the form of raised beach deposits, paleo-sea cliffs and multiple eolianite units. Several abrasion platforms with regional expression may have formed during multiple marine occupations. In contrast, the southern coast is underlain

  5. On-going post-glacial reverse faulting in Scandinavia, field evidence from Finnmark, northern Norway

    NASA Astrophysics Data System (ADS)

    Pascal, C.; Gabrielsen, R. H.; Cloetingh, S.

    2003-04-01

    Deglaciation in Scandinavia was followed by a dramatic seismic burst as evidenced by the numerous post-glacial fault scarps documented in Lapland. The post-glacial faults usually show reverse slip and trend NE-SW. This climax of earthquake activity is believed to have been triggered by the sudden removal of the glacial load and Scandinavia is considered tectonically quiet present-day. Roberts (1991, 2000) observed in Finnmark, northern Norway, various boreholes offset by reverse faults with few cm of displacement. It was unclear if these reverse faults represented active faulting or stress-relief features. Following Roberts, a field work campaign was conducted in July 2002. The purpose was to examine boreholes along road-sections and in quarries of Finnmark. About 20 drill-hole reverse offsets ranging from a few mm up to 14 cm were measured in western and central Finnmark. The azimuth of the associated slip vectors was found to be consistent towards the E-SE. In the Ifjord area, central Finnmark, some of the fault planes offsetting boreholes show continuous mud-smears of ~10 cm long. In the same area, additional observations include two reverse faults with 2 cm of offset each. The first one disrupts a wall road worked out in 1986. The second reverse fault disrupts a natural scarp presumably of glacial origin. In direct connection with these observations numerous rock blocks are seen to disrupt the ground surface. The most impressive ones are more than 1 m high. The blocks are bounded by pre-existing fractures and cleavage and appear to be displaced to the SE as well. These "standing-stones" are interpreted as small-scale tectonic push-ups. Field observations argue for active reverse faulting in Finnmark. The documented fault motions agree with a regional NW-SE compression induced by the North Atlantic ridge-push.

  6. 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

  7. Surface faults on Montague Island associated with the 1964 Alaska earthquake: Chapter G in The Alaska earthquake, March 27, 1964: regional effects

    USGS Publications Warehouse

    Plafter, George

    1967-01-01

    -half foot near the southern end of the scarp. Warping and extension cracking occurred in bedrock near the midpoint on the upthrown block within about 1,000 feet of the fault scarp. The reverse faults on Montague Island and their postulated submarine extensions lie within a tectonically important narrow zone of crustal attenuation and maximum uplift associated with the earthquake. However, there are no significant lithologic differences in the rock sequences across these faults to suggest that they form major tectonic boundaries. Their spatial distribution relative to the regional uplift associated with the earthquake, the earthquake focal region, and the epicenter of the main shock suggest that they are probably subsidiary features rather than the causative faults along which the earthquake originated. Approximately 70 percent of the new breakage along the Patton Bay and the Hanning Bay faults on Montague Island was along obvious preexisting active fault traces. The estimated ages of undisturbed trees on and near the fault trace indicate that no major disc placement had occurred on these faults for at least 150 to 300 years before the 1964 earthquake.

  8. Use of OSL dating to establish the stratigraphic framework of Quaternary eolian sediments, Anton scarp upper trench, Northeastern Colorado High Plains, USA

    USGS Publications Warehouse

    Mahan, S.A.; Noe, D.C.; McCalpin, J.P.

    2009-01-01

    This paper contains the results of the optically stimulated luminescence (OSL) dating used to establish stratigraphic ages and relationships of eolian sediments in a trench in northeastern Colorado, USA. This trench was located in the upper face of the Anton scarp, a major topographic lineament trending NW-SE for a distance of 135 km, in anticipation of intersecting near-surface faulting. The trench was 180 m long, 4.5-6.0 m deep, and exposed 22 m of stratigraphic section, most of which dipped gently west and was truncated by gulley channeling at the face of the scarp. No direct evidence of faulting was found in the upper trench. The stratigraphy from the trench was described, mapped and dated using OSL on quartz and potassium feldspar, and 14C obtained from woody material. OSL dating identified two upper loess units as Peoria Loess and Gilman Canyon Loess, deposited between 16 and 30 ka ago. The bottom layers of the trench were substantially older, giving OSL ages in excess of 100 ka. These older ages are interpreted as underestimates, owing to saturation of the fast component of OSL. Using OSL and 14C dating, we can constrain the erosion and down cutting of the scarp face as occurring between 16 and 5.7 ka. As the trenching investigation continues in other parts of the scarp face, the results of this preliminary study will be of importance in relating the ages of the strata that underlie different parts of the scarp, and in determining whether Quaternary faulting was a mechanism that contributed to the formation of this regional geomorphic feature.

  9. Estimation of active faulting in a slow deformation area: Culoz fault as a case study (Jura-Western Alps junction).

    NASA Astrophysics Data System (ADS)

    de La Taille, Camille; Jouanne, Francois; Crouzet, Christian; Jomard, Hervé; Beck, Christian; de Rycker, Koen; van Daele, Maarten; Lebourg, Thomas

    2014-05-01

    The north-western Alps foreland is considered as still experiencing distal effects of Alpine collision, resulting in both horizontal and vertical relative displacements. Based on seismological and geodetic surveys, detailed patterns of active faulting (including subsurface décollements, blind ramps and deeper crustal thrusts have been proposed (Thouvenot et al., 1998), underlining the importance of NW-SE left-lateral strike-slip offsets as along the Vuache and Culoz faults (cf. the 1996 Epagny event: M=5.4; Thouvenot et al., 1998 and the 1822 Culoz event I=VII-VIII; Vogt, 1979). In parallel to this tectonic evolution, the last glaciation-deglaciation cycles contributed to develop large and over-deepened lacustrine basins, such as Lake Le Bourget (Perrier, 1980). The fine grain, post LGM (ie post 18 ky), sedimentary infill gives a good opportunity to evidence late quaternary tectonic deformations. This study focuses on the Culoz fault, extending from the Jura to the West, to the Chautagne swamp and through the Lake Le Bourget to the East. Historical earthquakes are known nearby this fault as ie the 1822 Culoz event. The precise location and geometry of the main fault is illustrated but its Eastern termination still needs to be determined. High resolution seismic sections and side-scan sonar images performed in the 90's (Chapron et al., 1996) showed that the Col du Chat and Culoz faults have locally deformed the quaternary sedimentary infill of the lake. These studies, mainly devoted to paleo-climate analysis were not able to determine neither the geometry of the fault, or to quantify the observed deformations. A new campaign devoted to highlight the fault geometry and associated deformation, has been performed in October 2013. Very tight profiles were performed during this high resolution seismic survey using seistec boomer and sparker sources. In several places the rupture reaches the most recent seismic reflectors underlying that these faults were active during

  10. Geodetic evidence for aseismic reverse creep across the Teton fault, Teton Range, Wyoming

    SciTech Connect

    Sylvester, A.G. ); Byrd, J.O.D.; Smith R.B. )

    1991-06-01

    The valley block (hanging wall) of the central segment of the Teton fault rose 8 {plus minus} 0.7 mm during 1988 and 1989, relative to the mountain block west of the fault, a displacement opposite to that expected on a normal fault. The height change is based on first-order leveling data over a 21.2 km-long fault-crossing line of 42 permanent bench marks established and initially surveyed in 1988 and resurveyed in 1989. The rapid height change took place across a 1,200 m-wide zone coincident with the steep escarpment at the base of the range front including the surface trace of the east-dipping Teton fault, a major, active, range-front normal fault bounding the east side of the Teton Range at the northeastern edge of the Basin and Range province. The total stratigraphic offset across the fault, as much as 9 km, accumulated over the last 7 to 9 million years. Quaternary fault scarps, up to 52 m in height, cut Pinedale (about 14,000 yr) glacial and younger fluvial-alluvial deposits, indicating that the Teton fault has been the locus of several large, scarp-forming earthquakes in the past 14,000 years, and it exhibits up to 25 m of latest Quarternary displacement where crossed by the level line. Although the relative uplift of the hanging wall may be local and unique to the Teton fault, this unexpected observation of aseismic, reverse creep may have a variety of tectonic and non-tectonic causes, including hydrologic effects, aseismic fault creep or tilt, and pre-seismic dilation.

  11. Fault-bound valley associated with the Rembrandt basin on Mercury

    NASA Astrophysics Data System (ADS)

    Watters, Thomas R.; Montési, Laurent G. J.; Oberst, Jürgen; Preusker, Frank

    2016-11-01

    The Rembrandt basin is crosscut by the largest fault scarp on Mercury, Enterprise Rupes, and a second scarp complex, Belgica Rupes, extends to the basin's rim. Topographic data derived from MESSENGER orbital stereo images show that these tectonic landforms bound a broad, relatively flat-floored valley with a mean width of 400 km. Crosscutting relations suggest that the accumulation of structural relief likely postdates the formation and volcanic infilling of the Rembrandt basin. The valley floor, bound by fault scarps of opposite vergence, is significantly offset below the elevation of the back-scarp terrains. Along with an offset section of Rembrandt's rim, the elevation differences are evidence that the valley floor was lowered as a result of the formation of bounding fault scarps. The localization of the widely spaced thrust faults of Enterprise and Belgica Rupis and the offset of the valley floor may be the result of long-wavelength buckling of Mercury's lithosphere.

  12. Geomorphological Dating Using an Improved Scarp Degradation Model: Is This a Reliable Approach Compared With Common Absolute Dating Methods?

    NASA Astrophysics Data System (ADS)

    Oemisch, M.; Hergarten, S.; Neugebauer, H. J.

    2002-12-01

    Geomorphological dating of a certain landform or geomorphological structure is based on the evolution of the landscape itself. In this context it is difficult to use common absolute dating techniques such as luminescence and radiocarbon dating because they require datable material which is often not available. Additionally these methods do not always date the time since the formation of these structures. For these reasons the application of geomorphological dating seems one reliable possibility to date certain geomorphological features. The aim of our work is to relate present-day shapes of fault scarps and terrace risers to their ages. The time span since scarp formation ceased is reflected by the stage of degradation as well as the rounding of the profile edges due to erosive processes. It is assumed that the average rate of downslope soil movement depends on the local slope angle and can be described in terms of a diffusion equation. On the basis of these assumptions we present a model to simulate the temporal development of scarp degradation by erosion. A diffusivity reflecting the effects of soil erosion, surface runoff and detachability of particles as well as present-day shapes of scarps are included in the model. As observations of present-day scarps suggest a higher diffusivity at the toe than at the head of a slope, we suggest a linear approach with increasing diffusivities in downslope direction. First results show a better match between simulated and observed profiles of the Upper Rhine Graben in comparison to models using a constant diffusivity. To date the scarps the model has to be calibrated. For this purpose we estimate diffusivities by fitting modelled profiles to observed ones of known age. Field data have been collected in the area around Bonn, Germany and in the Alps, Switzerland. It is a matter of current research to assess the quality of this dating technique and to compare the results and the applicability with some of the absolute dating

  13. 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.

  14. 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.

  15. 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.

  16. Millennial strain partitioning and fault interaction revealed by 36Cl cosmogenic nuclide datasets from Abruzzo, Central Italy

    NASA Astrophysics Data System (ADS)

    Gregory, L. C.; Phillips, R. J.; Roberts, G.; Cowie, P. A.; Shanks, R. P.; McCaffrey, K. J. W.; Wedmore, L. N. J.; Zijerveld, L.

    2015-12-01

    In zones of distributed continental faulting, it is critical to understand how slip is partitioned onto brittle structures over both long-term millennial time scales and shorter-term individual earthquake cycles. The comparison of slip distributions on different timescales is challenging due to earthquake repeat-times being longer or similar to historical earthquake records, and a paucity of data on fault activity covering millennial to Quaternary scales in detail. Cosmogenic isotope analyses from bedrock fault scarps have the potential to bridge the gap, as these datasets track the exposure of fault planes due to earthquakes with better-than-millennial resolution. In this presentation, we will use an extensive 36Cl dataset to characterise late Holocene activity across a complicated network of normal faults in Abruzzo, Italy, comparing the most recent fault behaviour with the historical earthquake record in the region. Extensional faulting in Abruzzo has produced scarps of exposed bedrock limestone fault planes that have been preserved since the last glacial maximum (LGM). 36Cl accumulates in bedrock fault scarps as the plane is progressively exhumed by earthquakes and thus the concentration of 36Cl measured up the fault plane reflects the rate and patterns of slip. In this presentation, we will focus on the most recent record, revealed at the base of the fault. Utilising new Bayesian modelling techniques on new and previously collected data, we compare evidence for this most recent period of slip (over the last several thousands of years) across 5-6 fault zones located across strike from each other. Each sampling site is carefully characterised using LiDAR and GPR. We demonstrate that the rate of slip on individual fault strands varies significantly, between having periods of accelerated slip to relative quiescence. Where data is compared between across-strike fault zones and with the historical catalogue, it appears that slip is partitioned such that one fault

  17. Active fault and water loading are important factors in triggering earthquake activity around Aswan Lake

    NASA Astrophysics Data System (ADS)

    Kebeasy, R. M.; Gharib, A. A.

    Aswan Lake started impounding in 1964 and reached the highest water level so far in 1978 with a capacity of 133.8 km 3, thus forming the second largest man-made lake in the world. An earthquake of magnitude 5.3 (Ms) took place on 14 November 1981 along the most active part of the E-W Kalabsha fault beneath the Kalabsha bay (the largest bay of the lake). This earthquake was followed by a tremendous number of smaller events that continue till now. A radio-telemetry network of 13 seismic short period stations and a piezometer network of six wells were established around the northern part of the lake. Epicenters were found to cluster around active faults near the lake. The space-time distribution and the relation of the seismicity with the lake water level fluctuations were studied. Six years after flooding the eastern segment of the Kalabsha fault, strong seismicity began following the main shock of 14 November 1981. It occurred four days after the reservoir had reached its seasonal max level. The effect of the North African drought (1982 to present) is clearly seen in the reservoir water level. As it decreased and left the most active fault segments uncovered, the activity (Gebel Marawa area) decreased sharply. Also, the shallow activity was found to be more sensitive to rapid discharging than to the filling. This study indicates that geology, topography, lineations in seismicity, offsets in the faults, changes in fault trends and focal mechanisms are closely related. No relation was found between earthquake activity and both-ground water table fluctuations and water temperatures measured in wells located around the Kalabsha area.

  18. Modification of wave-cut and faulting-controlled landforms.

    USGS Publications Warehouse

    Hanks, T.C.; Bucknam, R.C.; Lajoie, K.R.; Wallace, R.E.

    1984-01-01

    From a casual observation that the form of degraded fault scarps resembles the error function, this investigation proceeds through an elementary diffusion equation representation of landform evolution to the application of the resulting equations to the modern topography of scarplike landforms. The value of K = 1 GKG (K = 'mass diffusivity'; 1 GKG = 1m2/ka) may be generally applicable as a good first approximation, to the modification of alluvial terranes within the semiarid regions of the western United States. The Lake Bonneville shoreline K is the basis for dating four sets of fault scarps in west-central Utah. The Drum Mountains fault scarps date at 3.6 to 5.7 ka BP. Fault scarps along the eastern base of the Fish Springs Range are very young, 3 ka BP. We estimate the age of fault scarps along the western flank of the Oquirrh Mountains to be 32 ka B.P. Fault scarps along the NE margin of the Sheeprock Mountains are even older, 53 ka BP. -from Authors

  19. 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.

  20. Morphostructural study of the Belledonne faults system (French Alps).

    NASA Astrophysics Data System (ADS)

    Billant, Jérémy; Bellier, Olivier; Hippolyte, Jean-Claude; Godard, Vincent; Manchuel, Kevin

    2016-04-01

    The NE trending Belledonne faults system, located in the Alps, is a potentially active faults system that extends from the Aiguilles Rouges and Mont Blanc massifs in the NE to the Vercors massif in the SW (subalpine massifs). It includes the Belledonne border fault (BBF), defined by an alignment of micro earthquakes (ML≤3.5) along the eastern part of the Grésivaudan valley (Thouvenot et al., 2003). Focal mechanisms and their respective depths tend to confirm a dextral strike-slip faulting at crustal scale. In the scope of the Sigma project (http://projet-sigma.com/index.html, EDF), this study aims at better constraining the geometry, kinematic and seismogenic potential of the constitutive faults of the Belledonne fault system, by using a multidisciplinary approach that includes tectonics, geomorphology and geophysics. Fault kinematic analysis along the BBF (Billant et al., 2015) and the Jasneuf fault allows the determination of a strike-slip tectonic regime characterised by an ENE trending σ1 stress axes, which is consistent with stress state deduced from the focal mechanisms. Although no morphological anomalies could be related to recent faulting along the BBF, new clues of potential Quaternary deformations were observed along the other faults of the system: -right lateral offset of morphologic markers (talwegs...) along the NE trending Arcalod fault located at the north-eastern terminations of the BBF; -left lateral offset of the valley formed by the Isère glacier along the NW trending Brion fault which is consistent with its left-lateral slip inferred from the focal mechanisms; -fault scarps and right lateral offsets of cliffs bordering a calcareous plateau and talwegs along the four fault segments of the NE trending Jasneuf fault located at the south-western termination of the BBF in the Vercors massif. Some offsets were measured using a new method that does not require the identification of piercing points and take advantage of the high resolution

  1. Morphotectonic, Quaternary and Structural Geology Analyses of the Shallow Geometry of the Mw 6.1, 2009 L'Aquila Earthquake Fault (central Italy): A Missed Opportunity for Surface Faulting Prevention.

    NASA Astrophysics Data System (ADS)

    Pucci, S.; Villani, F.; Civico, R.; Pantosti, D.; Smedile, A.; De Martini, P. M.; Di Naccio, D.; Gueli, A.

    2014-12-01

    The surface-rupturing 2009 L'Aquila earthquake evidenced the limited knowledge of active faults in the Middle Aterno Valley area. Gaps in detailed mapping of Quaternary deposits and tectonic landforms did not trigger researches on active faults, but after the tragic event. We present a morphotectonic study of geometry and evolution of the activated fault system (Paganica-San Demetrio, PSDFS). The LIDAR analysis and field survey yield to a new geological and structural map of the area with an unprecedented detail for the Quaternary deposits. It shows an alluvial depositional system prograding and migrating due to fault system evolution. The normal faults offset both the Quaternary deposits and the bedrock. The structural analysis allows us to recognize two fault systems: (A) NNE- and WNW-trending conjugate extensional system overprinting a strike-slip kinematics and (B) dip-slip NW-trending system. Crosscut relationship suggests that the activity of system B prevails, since Early Pleistocene, on system A, which earlier may have controlled a differently shaped basin. System B is the main responsible for the present-day compound outline of the Middle Aterno Valley, while system A major splays now act as segment boundaries. The long-term expression of B results in prominent fault scarps offsetting Quaternary deposits, dissecting erosional and depositional flat landforms. We retrieved detailed morphologic throws along fault scarps and we dated landforms by 14C, OSL (Optically Stimulated Luminescence), CRN (Cosmogenic Radionuclide) and tephra chronology. We show the persistent role of extensional faulting in dominating Quaternary landform evolution and we estimate slip-rate of the PSDFS at different time-scales. The results support repeated activity of PSDFS for ~20 km total length, thus implying M6.6 maximum expected earthquake. Such an approach should have been applied beforehand for the actual hazard estimation, to trigger, early enough, the adoption of precautionary

  2. Geomorphology of intraplate postglacial faults in Sweden

    NASA Astrophysics Data System (ADS)

    Ask, M. V. S.; Abdujabbar, M.; Lund, B.; Smith, C.; Mikko, H.; Munier, R.

    2015-12-01

    Melting of the Weichselian ice sheet at ≈10 000 BP is inferred to have induced large to great intraplate earthquakes in northern Fennoscandia. Over a dozen large so-called postglacial faults (PGF) have been found, mainly using aerial photogrammetry, trenching, and recognition of numerous paleolandslides in the vicinity of the faults (e.g. Lagerbäck & Sundh 2008). Recent LiDAR-based mapping led to the extension of known PGFs, the discovery of new segments of existing PGFs, and a number of new suspected PGFs (Smith et al. 2014; Mikko et al. 2015). The PGFs in Fennoscandia occur within 14-25°E and 61-69°N; the majority are within Swedish territory. PGFs generally are prominent features, up to 155 km in length and 30 m maximum surface offset. The most intense microseismic activity in Sweden occurs near PGFs. The seismogenic zone of the longest known PGF (Pärvie fault zone, PFZ) extends to ≈40 km depth. From fault geometry and earthquake scaling relations, the paleomagnitude of PFZ is estimated to 8.0±0.3 (Lindblom et al. 2015). The new high-resolution LiDAR-derived elevation model of Sweden offers an unprecedented opportunity to constrain the surface geometry of the PGFs. The objective is to reach more detailed knowledge of the surface offset across their scarps. This distribution provides a one-dimensional view of the slip distribution during the inferred paleorupture. The second objective is to analyze the pattern of vertical displacement of the hanging wall, to obtain a two-dimensional view of the displaced area that is linked to the fault geometry at depth. The anticipated results will further constrain the paleomagnitude of PGFs and will be incorporated into future modeling efforts to investigate the nature of PGFs. ReferencesLagerbäck & Sundh 2008. Early Holocene faulting and paleoseismicity in northern Sweden. http://resource.sgu.se/produkter/c/c836-rapport.pdf Smith et al. 2014. Surficial geology indicates early Holocene faulting and seismicity

  3. Paleoseismic study of the South Lajas fault: First documentation of an onshore Holocene fault in Puerto Rico

    USGS Publications Warehouse

    Prentice, C.S.; Mann, P.

    2005-01-01

    The island of Puerto Rico is located within the complex boundary between the North America and Caribbean plates. The relative motion along this boundary is dominantly left-lateral strike slip, but compression and extension are locally significant. Although tectonic models proposed for the region suggest the presence of onshore active faults in Puerto Rico, no faults with Holocene displacement have been documented on the island before this study. Current seismic hazard assessments primarily consider only the impact of distant, offshore seismic sources because onshore fault hazard is unknown. Our mapping and trenching studies demonstrate Holocene surface rupture on a previously undocumented fault in southwestern Puerto Rico. We excavated a trench across a scarp near the southern edge of the Lajas Valley that exposed a narrow fault zone disrupting alluvial deposits. Structural relations indicate valley-side-down fault slip, with a component of strike-slip motion. Radiocarbon analyses of organic material collected from the sediments suggest that the most recent surface rupture occurred during the past 5000 yr, but no minimum age has yet been established. This fault may be part of a larger fault zone that extends from the western end of the Lajas Valley toward Ponce, the second largest city in Puerto Rico. ?? 2005 Geological Society of America.

  4. Paleoseismology of the Hluboká Fault in the near-region of the NPP Temelin

    NASA Astrophysics Data System (ADS)

    Tschegg, Dana; Popotnig, Ankelika; Porpaczy, Clemens; Lomax, Johanna; Decker, Kurt

    2015-04-01

    Temelin is located in the Bohemian Massif, a Variscan basement unit characterized by very low historical/instrumental seismicity. Previous seismic hazard assessments for the site revealed very low hazard (PGA<0.1g) for a non-exceedance probability of 10-4 per year. The assessments are based on historical/instrumental earthquake data of the Bohemian Massif that cover the time period since about 1800 and 1903, respectively. In this study we assess the late Variscan Hluboká fault in the vicinity of the site, which was repeatedly re-activated in Mesozoic, Miocene and Pliocene times. The fault is part of the several tens of kilometres long NW-striking Jáchymov (Joachimsthal) Fault zone. It is located about 10 to 20 km south of the NPP. Geological, geophysical, and structural data characterize the fault as a dextral strike-slip fault system. Reflection seismic shows an up to a few hundred meters wide zone with steeply dipping faults that are supposed to merge into a common master fault at depth. The fault is characterized by fault bends defining a restraining and a releasing segment. The latter coincides with a pronounced morphological scarp. Recent uplift of the footwall of the fault at this releasing bend is indicated by previously published geodetic data (P. Vyskočil, 1973) and geomorphological data comparing the tectonic morphology of the fault scarp near Hluboká nad Vltavou with slopes, which are not fault controlled. All analysed geomorphological indices characterize the Hluboká scarp as a unique morphological feature, which results from Quaternary uplift of the footwall of the Hluboká Fault with respect to its hanging wall. The assessment of the youngest tectonic history of the fault further uses correlations of Quaternary terraces of the Vltava River across the fault. We established a new Late Pleistocene stratigraphy of fluvial terraces using field and borehole data combined with OSL/IRSL age dating. The results show terrace staircases in the hanging wall

  5. 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.

  6. San Jacinto Fault Zone guided waves: A discrimination for recently active fault strands near Anza, California

    NASA Astrophysics Data System (ADS)

    Li, Yong-Gang; Aki, Keiiti; Vernon, Frank L.

    1997-06-01

    We deployed three 350-m-long eight-element linear seismic arrays in the San Jacinto Fault Zone (SJFZ) near Anza, California, to record microearthquakes starting in August through December 1995. Two arrays were deployed 18 km northwest of Anza, across the Casa Loma fault (CLF) and the Hot Springs fault (HSF) strands of the SJFZ. The third array was deployed across the San Jacinto fault (SJF) in the Anza slip gap. We observed fault zone guided waves characterized by low-frequency, large amplitudes following S waves at the CLF array and the SJF array for earthquakes occurring within the fault zone. However, we did not observe guided waves at the HSF array for any events. The amplitude spectra of these guided waves showed peaks at 4 Hz at the CLF and 6 Hz at the SJF, which decreased sharply with the distance from the fault trace. In contrast, no spectral peaks at frequency lower than 6 Hz were registered at the HSF array. We used a finite difference method to simulate these guided modes as 5 waves trapped in a low-velocity waveguide sandwiched between high-velocity wall rocks. The guided mode data are adequately fit by a waveguide on the CLF with the average width of 120 m and S velocity of 2.5 km/s, about 25% reduced from the S velocity of the surrounding rock; this waveguide becomes 40 to 60 m wide with the 5 velocity of 2.8 km/s in the Anza slip gap. On the other hand, there is not a continuous waveguide on the HSF at depth. Locations of the events with guided modes suggest that the fault plane waveguide extends along the CLF between the towns of San Jacinto and Anza, dipping northeastward at 75°-80° to a depth of about 18 km; it becomes nearly vertical in the Anza gap. We speculate that the existence of a continuous low-velocity waveguide on the CLF can be caused by the rupture of the magnitude 6.9 earthquake on April 21, 1918, occurring near the towns of San Jacinto and Hemet. Further, the lack of a clear waveguide on the HSF suggests that it was not ruptured in

  7. 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.

  8. Slip rate depth distribution for active faults in Central Italy using numerical models

    NASA Astrophysics Data System (ADS)

    Finocchio, Debora; Barba, Salvatore; Basili, Roberto

    2016-09-01

    Slip rate is a critical parameter for describing geologic and earthquake rates of known active faults. Although faults are inherently three-dimensional surfaces, the paucity of data allows for estimating only the slip rate at the ground surface and often only few values for an entire fault. These values are frequently assumed as proxies or as some average of slip rate at depth. Evidence of geological offset and single earthquake displacement, as well as mechanical requirements, show that fault slip varies significantly with depth. Slip rate should thus vary in a presumably similar way, yet these variations are rarely considered. In this work, we tackle the determination of slip rate depth distributions by applying the finite element method on a 2D vertical section, with stratification and faults, across the central Apennines, Italy. In a first step, we perform a plane-stress analysis assuming visco-elasto-plastic rheology and then search throughout a large range of values to minimize the RMS deviation between the model and the interseismic GPS velocities. Using a parametric analysis, we assess the accuracy of the best model and the sensitivity of its parameters. In a second step, we unlock the faults and let the model simulate 10 kyr of deformation to estimate the fault long-term slip rates. The overall average slip rate at depth is approximately 1.1 mm/yr for normal faults and 0.2 mm/yr for thrust faults. A maximum value of about 2 mm/yr characterizes the Avezzano fault that caused the 1915, Mw 7.0 earthquake. The slip rate depth distribution varies significantly from fault to fault and even between neighbouring faults, with maxima and minima located at different depths. We found uniform distributions only occasionally. We suggest that these findings can strongly influence the forecasting of cumulative earthquake depth distributions based on long-term fault slip rates.

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

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

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

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

    PubMed Central

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

    2016-01-01

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

  11. Holocene activity and paleoseismicity of the Selaha Fault, southeastern segment of the strike-slip Xianshuihe Fault Zone, Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Yan, Bing; Lin, Aiming

    2017-01-01

    In this study we examine the Holocene activity, including slip rate and paleoseismicity, of the Selaha Fault, a branch of the left-lateral strike-slip Xianshuihe Fault Zone located along the southeastern segment of the Ganzhi-Yushu-Xianshuihe Fault System (GYXFS) of the Tibetan Plateau. Interpretation of high-resolution images and field investigations reveal that the Selaha Fault is characterized by left-lateral strike-slip faulting with an average horizontal slip-rate of 9.0 mm/year during the Holocene. Trench excavations and 14C dating results show that at least three morphogenic earthquakes occurred during the past millennium; the most recent event occurred in the past 450 years and corresponds to the 1786 M 7.75 earthquake. The penultimate seismic event (E2) occurred in the period between 560 and 820 year BP (i.e., 1166-1428 CE) and is probably associated with the 1327 M 7.5 earthquake. The antepenultimate event (E3) is inferred to have occurred in the period between 820 ± 30 and 950 ± 30 year BP. Our results confirm that the Selaha Fault, as a portion of the GYXFS, plays an important role as a tectonic boundary in releasing the strain energy accumulated during the northeastward motion of the Tibetan Plateau in response to the ongoing northward penetration of the Indian Plate into the Eurasian Plate. The strain energy is released in the form of repeated large earthquakes that are recorded by strike-slip displacements of stream channels and alluvial fans.

  12. Head scarp boundary for the landslides in the Little North Santiam River Basin, Oregon

    USGS Publications Warehouse

    Sobieszczyk, Steven

    2010-01-01

    Polygons represent head scarps and flank scarps associated with landslide deposits in the Little North Santiam River Basin, Oregon. This work was completed as part of the Master's thesis "Turbidity Monitoring and LiDAR Imagery Indicate Landslides are Primary Source of Suspended-Sediment Load in the Little North Santiam River Basin, Oregon, Winter 2009-2010" by Steven Sobieszczyk, Portland State University and U.S. Geological Survey. Data layers in this geodatabase include: landslide deposit boundaries (Deposits); field-verfied location imagery (Photos); head scarp or scarp flanks (Scarp_Flanks); and secondary scarp features (Scarps).The geodatabase template was developed by the Oregon Department of Geology and Mineral Industries (Burns and Madin, 2009).

  13. Active faults in Lebanon : kinematics and interseismic behavior measured from radar interferometry (InSAR)

    NASA Astrophysics Data System (ADS)

    Lasserre, C.; Pinel-Puysségur, B.; Vergnolle, M.; Klinger, Y.; Pathier, E.

    2012-12-01

    The Levant fault system, more than 1000 km-long, marks the limit between the Arabian and Sinaï tectonic plates, extending from the Aqaba gulf in the Red Sea to Turkey. Mostly left-lateral, it forms a transpression zone in Lebanon, associating strike-slip faults such as the Yammouneh fault and thrust faults such as the Mount Lebanon thrust. This fault system in Lebanon is at the origin of large historical earthquakes during the past two thousand years (551 AD on the thrust offshore and 1837 along the Roum fault inland, 1759 along the Rashaia and Sergaya faults). We aim at characterizing the present-day behavior of active faults in Lebanon, in particular the Yammouneh fault which did not break since 1202, to contribute to a better assessment of the seismic hazard in this region. Space geodesy techniques (GPS, InSAR) allow to quantify the present-day displacements across faults (a few mm/yr during the interseismic period), and to model stress loading and relaxation processes during the seismic cycle, at the fault scale and at the regional scale. GPS campaign measurements have been made along profiles perpendicular to the Yammouneh fault. In addition, an important archive of radar images covering Lebanon (acquired by the ERS and Envisat satellites, along descending and ascending orbits) is also available. We process ERS and Envisat radar data to obtain the average interseismic velocity field across faults over the past 15-20 years. Techniques of interferograms networks processing (MuLSAR), atmospheric phase delays correction from global atmospherical models, DEM correction and time series inversion (NSBAS) are used to overcome the main remaining limitations in the measurements accuracy (low coherence, strong atmospheric delays, long wavelength deformation signal). The final goal is to propose a modelling of the surface displacement field to quantify the present-day kinematics of active fauts in Lebanon, taking into account GPS data as well as tectonic and

  14. Active Faults, Modern Seismicity And Block Structure Of Eurasia

    NASA Astrophysics Data System (ADS)

    Gatinsky, Y.; Rundquist, D.

    2004-12-01

    The analysis of on active faults and seismicity shows that the only a northern part of Eurasia should be regarded as an indivisible lithosphere unit. We defined it as the North Eurasian plate (Gatinsky, Rundquist, 2004) unlike the Eurasian plate s.l., which can be used only for paleotectonic reconstructions. The North Eurasian plate is bordered by zones of seismic activity traced along the Gakkel ridge, the Chersky and Stanovoi ranges, the Baikal rift, Altai--Sayany region, northern Tien Shan, Pamir, Hindu Kush and Kopet Dagh, Great Caucasus, northern Anatolia, Rhodopes, Carpathians, eastern and central Alps. Relationships between this plate and Europe west of the Rhine grabens remain ambiguous. The satellite measurements for them seem to be similar (Nocquet, Calais, 2003), but structural and seismic evidences allow suggesting their incipient division. Wide zones between this plate and neighboring ones can be distinguished outside north Eurasia. These zones consist of numerous blocks of various sizes. Block boundaries are mainly characterized by the high seismicity and development of active wrench faults, thrusts or modern rifts. Some of such zones were named earlier as "diffuse plate boundaries" (Stein et al., 2002; Bird et al, 2003). We suggest to name them as "transit zones" because they are situated between large lithosphere plates and as if transfer the stress field of one of them to other. Blocks within the transit zones reveal local divergences in GPS vectors of their displacements in the ITRF system and especially with respect to fixed Eurasia. At the same time data of satellite measurements emphasize the unity of the North Eurasian plate, which moves eastward in absolute coordinates with some clockwise rotation. The stress distribution in inner parts of the continent is being affected by the interaction with different plates and blocks. It can be more effectively illustrated by a «triangle» of the maximal seismic activity of Eurasia in the central Asia

  15. Thermal Field Indicator for Identifying Active Faults and its Instability From Laboratory Experiments

    NASA Astrophysics Data System (ADS)

    Ma, J.; Liu, L.; Liu, P.; Ma, S.

    2007-12-01

    The relationship between the thermal filed and strain field during deformation of faults is the physical basis to clarify whether satellite infrared information and the ground temperature field can be used to study fault activity. This study attempts to discuss these problems by experiments in the laboratory. The two-direction servo-control system was used to load on the samples with compressional and extensional en echelon faults. An infrared thermal image system and a contact-type thermometer recorded synchronously variations of the bright temperature field of infrared radiation and temperature field during deformation of the rock specimens. A digital CCD camera and a soft ware based on the digital speckle correlation method (DSCM) was utilized to capture images and to analyze them, yielding processes of displacement and strain fields. The experimental result shows as follows: 1 The temperature is highest at the jog area of the compressional en echelon faults, whereas that is lowest at the extensional en echelon faults prior to failure of the jog area. The record by DSCM displays that the mean strain of the jog area is largest for the compressional en echelon faults, while that is smallest for the extensional en echelon faults. These mean that the temperature field has clear responses to the opposite stress states at the jog areas of two kinds of en echelon faults, providing an indicator for determining whether the fault segment has slid. 2 The en echelon faults experience two deformation stages from stress building up and fault propagating at the jog area to unstable sliding along the fault. Correspondingly the mechanism of heating-up is turned from strain heating into frictional heating. Three kinds of phenomena have been observed at the jog area and its vicinity during the stage of transformation. They are temperature drop, fast fluctuation of temperature, and pulses of temperature rising, respectively. Mechanism of these phenomena is discussed. 3 These

  16. Geomorphic evidence of active tectonics in the San Gorgonio Pass region of the San Andreas Fault system: an example of discovery-based research in undergraduate teaching

    NASA Astrophysics Data System (ADS)

    Reinen, L. A.; Yule, J. D.

    2014-12-01

    Student-conducted research in courses during the first two undergraduate years can increase learning and improve student self-confidence in scientific study, and is recommended for engaging and retaining students in STEM fields (PCAST, 2012). At Pomona College, incorporating student research throughout the geology curriculum tripled the number of students conducting research prior to their senior year that culminated in a professional conference presentation (Reinen et al., 2006). Here we present an example of discovery-based research in Neotectonics, a second-tier course predominantly enrolling first-and second-year students; describe the steps involved in the four week project; and discuss early outcomes of student confidence, engagement and retention. In the San Gorgonio Pass region (SGPR) in southern California, the San Andreas fault undergoes a transition from predominantly strike-slip to a complex system of faults with significant dip-slip, resulting in diffuse deformation and raising the question of whether a large earthquake on the San Andreas could propagate through the region (Yule, 2009). In spring 2014, seven students in the Neotectonics course conducted original research investigating quantifiable geomorphic evidence of tectonic activity in the SGPR. Students addressed questions of [1] unequal uplift in the San Bernardino Mountains, [2] fault activity indicated by stream knick points, [3] the role of fault style on mountain front sinuosity, and [4] characteristic earthquake slip determined via fault scarp degradation models. Students developed and revised individual projects, collaborated with each other on methods, and presented results in a public forum. A final class day was spent reviewing the projects and planning future research directions. Pre- and post-course surveys show increases in students' self-confidence in the design, implementation, and presentation of original scientific inquiries. 5 of 6 eligible students participated in research the

  17. 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

  18. Seismic slip history of the Pizzalto fault (Central Apennines, Italy) using in situ 36Cl cosmogenic dating

    NASA Astrophysics Data System (ADS)

    Delli Rocioli, Mattia; Pace, Bruno; Benedetti, Lucilla; Visini, Francesco; Guillou, Valery; Bourlès, Didier; Arnorld, Maurice; Aumaître, Georges; Keddadouche, Karim

    2013-04-01

    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. Here we present a paleoseismological study on the Pizzalto fault using the in situ produced cosmogenic nuclide 36Cl (Schlagenhauf et al., 2011). The Pizzalto fault, located in central Italy about 50 km southeast of the epicenter of L'Aquila 2009 earthquake, is about 12 km long, SW dipping and belongs to the 30 km long Rotella-Aremogna active normal fault system. Recent activity along the Pizzalto fault is suggested by the presence of a continuous and linear 2 to 5 m high limestone fault scarp that was sampled every 10 cm at a site located in its particularly well-preserved central portion. 49 samples have been chemically processed and measured, and their 36Cl and Cl concentrations have been determined using isotope dilution mass spectrometry at the French AMS national facility ASTER located at CEREGE. Modeling the in situ 36Cl concentration with the scarp height allow deciphering the age and slip of the last major earthquake events on the fault. To derive those earthquake parameters, we used the published Matlab code from Schlagenhauf et al. (2011) that we implemented with a Monte Carlo approach to explore a large number of earthquake recurrence scenarios varying both the number of events, their slip and their ages. The "a priori" constraints input in the Monte Carlo code were: 1-the number of events, which is given by the stacking of individual probability density functions (assumed to be Gaussian) of each sample concentration; and, 2-the cumulative slip that should be equal to the height of the fault scarp. The first results show that 36Cl concentrations are reproduced better considering five events occurring over the last 5 ka and a previous one at about 13 ka. This suggests that most earthquake events clustered during a period of intense seismic activity preceded by a longer

  19. Structural Analysis of the Pärvie Fault in Northern Scandinavia

    NASA Astrophysics Data System (ADS)

    Baeckstroem, A.; Rantakokko, N.; Ask, M. V.

    2011-12-01

    The Pärvie fault is the largest known postglacial fault in the world with a length of about 160 km. The structure has a dominating fault scarp as its western perimeter but in several locations it is rather a system of several faults. The current fault scarps, mainly caused by reverse faulting, are on average, 10-15 m in height and are thought to have been formed during one momentous event near the end of the latest glaciation (the Weichselian, 9,500-115,000 BP ) (Lagerbäck & Sundh, 2008). This information has been learnt from studying deformation features in sediments from the latest glaciation. However, the fault is believed to have been formed as early as the Precambrian, and it has been reactivated repeatedly throughout its history. The earlier history of this fault zone is still largely unknown. Here we present a pre-study to the scientific drilling project "Drilling Active Faults in Northern Europe", that was submitted to the International Continental Scientific Drilling Program (ICDP) in 2009 (Kukkonen et al. 2010) with an ICDP-sponsored workshop in 2010 (Kukkonen et al. 2011). During this workshop a major issue to be addressed before the start of drilling was to reveal whether the fault scarps were formed by one big earthquake or by several small ones (Kukkonen et al. 2011). Initial results from a structural analysis by Riad (1990) have produced information of the latest kinematic event where it is suggested that the latest event coincides with the recent stress field, causing a transpressional effect. The geometrical model suggested for an extensive area of several fault scarps along the structure is the compressive tulip structure. In the southern part, where the fault dips steeply E, the structure is parallel to the foliation of the country rock and earlier breccias, thus indicating a dependence of earlier structures. Modelling of the stress field during the latest glaciation show that a reverse background stress field together with excess pore pressure

  20. Newly identified active faults in the Pollino seismic gap, southern Italy, and their seismotectonic significance

    NASA Astrophysics Data System (ADS)

    Brozzetti, Francesco; Cirillo, Daniele; de Nardis, Rita; Cardinali, Mauro; Lavecchia, Giusy; Orecchio, Barbara; Presti, Debora; Totaro, Cristina

    2017-01-01

    The following is a geological study of a Quaternary and active normal fault-system, which crops out in the Pollino area, a seismogenic sector of the Southern Apennines, Italy. From 2010 to 2014, this area was affected by long lasting seismic activity characterized by three major events which occurred in May 2012 (Mw 4.3), in October 2012 (Mw 5.2) and in June 2014 (Mw 4.0). The integration of structural-geological data with morpho-structural and remote sensing analyses, led to define the geometry, the kinematics, the cross-cutting relationships and the slip rates of the inferred active fault segments within and near the epicentral area. We reconstructed an asymmetric extensional pattern characterized by low-angle, E and NNE-dipping faults, and by antithetic, high-angle, SW- to WSW-dipping faults. The geometry of the faults at depth was constrained using high-resolution hypocenter distributions. The overall system fits well with the deformation field obtained from focal mechanisms and geodetic data. Comparing the fault pattern with the time-space evolution of the Pollino seismic activity, we identified the seismogenic sources in two, near-parallel, WSW-dipping faults, whose seismogenic potential were assessed. The peculiar perpendicular-to-fault-strike evolution of the seismic activity, is discussed in the frame of the reconstructed seismotectonic model.

  1. 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.

  2. Shallow Lunar Seismic Activity and the Current Stress State of the Moon

    NASA Technical Reports Server (NTRS)

    Watters, T. R.; Weber, R. C.; Collins, G. C.; Johnson, C. L.

    2017-01-01

    A vast, global network of more than 3200 lobate thrust fault scarps has been revealed in high resolution Lunar Reconnaissance Orbiter Camera (LROC) images. The fault scarps very young, less than 50 Ma, based on their small scale and crisp appearance, crosscutting relations with small-diameter impact craters, and rates of infilling of associated small, shallow graben and may be actively forming today. The population of young thrust fault scarps provides a window into the recent stress state of the Moon and offers insight into the origin of global lunar stresses. The distribution of orientations of the fault scarps is non-random, inconsistent with isotropic stresses from late-stage global contraction as the sole source of stress Modeling shows that tidal stresses contribute significantly to the current stress state of the lunar crust. Tidal stresses (orbital recession and diurnal tides) superimposed on stresses from global contraction result in non-isotropic compressional stress and thrust faults consistent with lobate scarp orientations. Stresses due to orbital recession do not change with orbital position, thus it is with the addition of diurnal stresses that peak stresses are reached. At apogee, diurnal and recession stresses are most compressive near the tidal axis, while at perigee they are most compressive 90 degrees away from the tidal axis. Coseismic slip events on currently active thrust faults are expected to be triggered when peak stresses are reached. Analysis of the timing of the 28 the shallow moonquakes recorded by the Apollo seismic network shows that 19 indeed occur when the Moon is closer to apogee, while only 9 shallow events occur when the Moon is closer to perigee. Here we show the results of relocating the shallow moonquake using an algorithm designed for sparse networks to better constrain their epicentral locations in order to compare them with stress models. The model for the current stress state of the Moon is refined by investigating the

  3. Shallow Lunar Seismic Activity and the Current Stress State of the Moon

    NASA Technical Reports Server (NTRS)

    Watters, Thomas R.; Weber, Renee C.; Collins, Geoffrey C.; Johnson, Catherine L.

    2017-01-01

    A vast, global network of more than 3200 lobate thrust fault scarps has been revealed in high resolution Lunar Reconnaissance Orbiter Camera (LROC) images. The fault scarps are very young, less than 50 Ma, based on their small scale and crisp appearance, crosscutting relations with small-diameter impact craters, and rates of infilling of associated small, shallow graben and may be actively forming today. The population of young thrust fault scarps provides a window into the recent stress state of the Moon and offers insight into the origin of global lunar stresses. The distribution of orientations of the fault scarps is non-random, inconsistent with isotropic stresses from late-stage global contraction as the sole source of stress. Modeling shows that tidal stresses contribute significantly to the current stress state of the lunar crust. Tidal stresses (orbital recession and diurnal tides) superimposed on stresses from global contraction result in non-isotropic compressional stress and may produce thrust faults consistent with lobate scarp orientations. At any particular point on the lunar surface, peak compressive stress will be reached at a certain time in the diurnal cycle. Coseismic slip events on currently active thrust faults are expected to be triggered when peak stresses are reached. Analysis of the timing of the 28 the shallow moonquakes recorded by the Apollo seismic network shows that 19 indeed occur when the Moon is closer to apogee, while only 9 shallow events occur when the Moon is closer to perigee. Here we report efforts to refine the model for the current stress state of the Moon by investigating the contribution of polar wander. Progress on relocating the epicentral locations of the shallow moonquakes using an algorithm designed for sparse networks is also reported.

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

    PubMed

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

    2017-03-21

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

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

    NASA Astrophysics Data System (ADS)

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

    2017-03-01

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

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

    PubMed Central

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

    2017-01-01

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

  7. Active Fault Geometry and Crustal Deformation Along the San Andreas Fault System Through San Gorgonio Pass, California: The View in 3D From Seismicity

    NASA Astrophysics Data System (ADS)

    Nicholson, C.; Hauksson, E.; Plesch, A.

    2012-12-01

    Understanding the 3D geometry and deformation style of the San Andreas fault (SAF) is critical to accurate dynamic rupture and ground motion prediction models. We use 3D alignments of hypocenter and focal mechanism nodal planes within a relocated earthquake catalog (1981-2011) [Hauksson et al., 2012] to develop improved 3D fault models for active strands of the SAF and adjacent secondary structures. Through San Gorgonio Pass (SGP), earthquakes define a mechanically layered crust with predominantly high-angle strike-slip faults in the upper ~10 km, while at greater depth, intersecting sets of strike-slip, oblique slip and low-angle thrust faults define a wedge-shaped volume deformation of the lower crust. In some places, this interface between upper and lower crustal deformation may be an active detachment fault, and may have controlled the down-dip extent of recent fault rupture. Alignments of hypocenters and nodal planes define multiple principal slip surfaces through SGP, including a through-going steeply-dipping predominantly strike-slip Banning fault strand at depth that upward truncates a more moderately dipping (40°-50°) blind, oblique North Palm Springs fault. The North Palm Springs fault may be the active down-dip extension of the San Gorgonio Pass thrust offset at depth by the principal, through-going Banning strand. In the northern Coachella Valley, seismicity indicates that the Garnet Hill and Banning fault strands are most likely sub-parallel and steeply dipping (~70°NE) to depths of 8-10 km, where they intersect and merge with a stack of moderately dipping to low-angle oblique thrust faults. Gravity and water well data confirm that these faults are sub-parallel and near vertical in the upper 2-3 km. Although the dense wedge of deep seismicity below SGP and largely south of the SAF contains multiple secondary fault sets of different orientations, the predominant fault set appears to be a series of en echelon NW-striking oblique strike-slip faults

  8. The Servita Fault, Colombian Eastern Cordillera: Origin, Geotectonics, and Seismicity

    NASA Astrophysics Data System (ADS)

    Chicangana, G.; Kammer, A.; Vargas Jiménez, C. A.; Caneva, A.; Pedraza, P.; Salcedo, E.; Gomez, A.; Muñoz, F.

    2014-12-01

    The Servita fault is a thrust located in the center of Colombia and whose main scarp is at 5 km west of Villavicencio (500.000 inhabitants). According to geophysics data as gravity, magnetic, and seismic, this fault was confirmed how a large cortical structure in the Colombian Eastern Cordillera. The Servita fault possibly was originated like a suture that derived of a continental collision in Late Mesoproterozoic times when Rodinia was conform totally. The Servita Fault as normal fault in Mesozoic times contributed to the Colombian Cretaceous basin development. In Late Cretaceous because to collision of the Caribbean plate with the northwestern corner of South America a strong compressive stress was occur and kinematics changes were presented in the normal faults restrained to the basin like among others the Servita Fault, where these were converted in inverse faults. From early Pliocene until Present times the Servita Fault controlled the growth of the Cordillera and the Llanos foothills in this sector of Central Colombia. Result of this is the seismicity activity registered for this region from historical times (less of 500 years for Colombian case). Two earthquakes have transcended in this region in last three centuries: the first one occurred on October 18th, 1743 with a current probabilistic magnitude greater than 6.5 and the second one struck on May 24th, 2008 with a M = 5.9. In this work we show how this fault has develop from its origin, and how this can would produce a M > 6.5 earthquake very close to metropolitan area of Bogota D.C., and Villavicencio. This earthquake would destroy both urban areas resulting in high losses in lives and economic terms. The seismicity activity of the Servita Fault and its associated structures is registered by the National Seismological Network of Colombia and the Sabana de Bogotá Seismological Network.

  9. Tertiary sedimentation along the Lake Mead fault system, Virgin Mountains, Nevada-Arizona

    SciTech Connect

    Beard, L.S. ); Ward, S. . Dept. of Geology)

    1993-04-01

    Sedimentary rocks of the Thumb and Rainbow Gardens Members of the Tertiary Horse Spring Formation crop out within the Virgin and South Virgin Mountains in Nevada-Arizona. The Virgins are cut by a broad zone of northeast-striking left-lateral and north-striking normal faults collectively part of the Lake Mead oblique left-lateral fault system (LMFS). Horse Spring rocks are faulted and variably eastward tilted (10--50[degree]) within the LMFS and extend northward from the Gold Butte left-lateral fault across the Lime Ridge left-lateral fault to the south flank of the Virgin Mountains. The Rainbow Gardens Member (24--18 Ma) was deposited in a shallow basin; gradual facies changes show no influence of active faulting. In contrast, lateral and vertical facies in the Thumb (16--14) Ma change abruptly and are strongly influenced by oblique-slip faulting and uplift. An unconformity separates pedogenically altered limestone of the Rainbow Gardens from overlying well-bedded lacustrine limestones of the Thumb. Locally the unconformity is overlain by conglomerate and megabreccia deposits composed of underlying Rainbow Gardens carbonate clasts derived from energy fault scarps. Thumb carbonates above the unconformity grade laterally and vertically into thick deposits of lacustrine gypsum and fine-grained sandstone, which in turn intertongue laterally and vertically with marginal lake and alluvial fan facies. Abrupt influx of megabreccia and coarse conglomerate into Thumb lacustrine deposits northward from both the Gold Butte and Lime Ridge faults indicates continued faulting.

  10. Borehole and High-Resolution Seismic Reflection Evidence for Holocene Activity on the Compton Blind-Thrust Fault, Los Angeles Basin, California

    NASA Astrophysics Data System (ADS)

    Leon, L. A.; Dolan, J. F.; Shaw, J. H.; Pratt, T. L.

    2006-12-01

    abundant detrital charcoal, should yield 14C dates that will allow us to accurately date these uplift events. A stratigraphically abrupt downward transition from an upper section dominated by clays, silts, and sands into a gravel-dominated lower section occurs at ~25 m depth. If this transition is similar in age to well-dated sections elsewhere in the Los Angeles region (e.g. our Carfax site along the Puente Hills Thrust fault), then it marks the Pleistocene-Holocene change in climate and stream power at ~9.5 ¨C 10 ka. The total uplift across the Holocene/Pleistocene boundary is ~8 m, yielding a minimum uplift rate of ~0.8 mm/yr, which in turn suggests a slip rate on the blind thrust of 1.5 to 2 mm/yr. The depth of the shallowest buried fold scarp (1 m) attests to the recency of the youngest large-magnitude earthquake on the Compton blind-thrust fault. These observations clearly indicate that the Compton fault is active and capable of producing damaging, large-magnitude earthquakes directly beneath metropolitan Los Angeles.

  11. Trench logs from a strand of the Rock Valley Fault System, Nevada Test Site, Nye County, Nevada

    SciTech Connect

    Yount, J.C.; Shroba, R.R.; McMasters, C.R.; Huckins, H.E.; Rodriguez, E.A.

    1987-12-31

    The Rock Valley fault system trends northeasterly through the southeast corner of the Nevada Test Site. The system records left-lateral offset of Paleozoic and Tertiary rocks, although total offset amounts to only a few kilometers. Distinct scarps in alluvial deposits of Quaternary age and a concentration of seismicity, particularly at its north end, suggest that the Rock Valley fault system may be active. Two trenches were excavated by backhoe in 1978 across a 0.5-m-high scarp produced by a strand of the Rock Valley fault system. A detailed logging of the two Rock Valley fault trenches was undertaken during the spring of 1984. This report presents: (1) logs of both walls of the two trenches, (2) a general description of the lithologic units and the soils formed in these units that are exposed in and near the fault trenches, (3) observations of the clast fabric of unfaulted and faulted deposits exposed in the trench walls, and (4) a map of the surficial deposits in the vicinity of the trenches.

  12. The Palos Verdes Fault offshore southern California: late Pleistocene to present tectonic geomorphology, seascape evolution and slip rate estimate based on AUV and ROV surveys

    USGS Publications Warehouse

    Brothers, Daniel S.; Conrad, James E.; Maier, Katherine L.; Paull, Charles K.; McGann, Mary L.; Caress, David W.

    2015-01-01

    The Palos Verdes Fault (PVF) is one of few active faults in Southern California that crosses the shoreline and can be studied using both terrestrial and subaqueous methodologies. To characterize the near-seafloor fault morphology, tectonic influences on continental slope sedimentary processes and late Pleistocene to present slip rate, a grid of high-resolution multibeam bathymetric data, and chirp subbottom profiles were acquired with an autonomous underwater vehicle (AUV) along the main trace of PVF in water depths between 250 and 600 m. Radiocarbon dates were obtained from vibracores collected using a remotely operated vehicle (ROV) and ship-based gravity cores. The PVF is expressed as a well-defined seafloor lineation marked by subtle along-strike bends. Right-stepping transtensional bends exert first-order control on sediment flow dynamics and the spatial distribution of Holocene depocenters; deformed strata within a small pull-apart basin record punctuated growth faulting associated with at least three Holocene surface ruptures. An upper (shallower) landslide scarp, a buried sedimentary mound, and a deeper scarp have been right-laterally offset across the PVF by 55 ± 5, 52 ± 4 , and 39 ± 8 m, respectively. The ages of the upper scarp and buried mound are approximately 31 ka; the age of the deeper scarp is bracketed to 17–24 ka. These three piercing points bracket the late Pleistocene to present slip rate to 1.3–2.8 mm/yr and provide a best estimate of 1.6–1.9 mm/yr. The deformation observed along the PVF is characteristic of strike-slip faulting and accounts for 20–30% of the total right-lateral slip budget accommodated offshore Southern California.

  13. Recent Fault Activity in the 1886 Charleston, South Carolina Earthquake Epicentral Area and its Relation to Buried Structures

    NASA Astrophysics Data System (ADS)

    Pratt, T. L.; Shah, A. K.; Horton, J. W., Jr.; Chapman, M. C.; Beale, J.

    2014-12-01

    The 1886 Charleston, SC earthquake (M6.8-7.3) is the largest recorded earthquake to strike the U.S. east of the Appalachian Mountains. It occurred along the U.S. passive margin within an area of extensive Mesozoic rifting and beneath the ~800-m thick, subhorizontal Atlantic Coastal Plain (ACP) strata. The fault(s) that caused the 1886 earthquake remain the subject of debate. We examine reprocessed seismic reflection data in the epicentral area to discern faults cutting the Cretaceous and Cenozoic ACP strata, and relate them to deeper structures revealed by the seismic profiles and filtered aeromagnetic data. Faults are identified on the seismic profiles by sharp vertical displacements of strata, abrupt but small changes in dip, and folding of the ACP strata. Some of these faults dip steeply and locally displace deeper reflectors within the underlying South Georgia rift basin with minor displacement; in places they bound uplifted blocks of ACP strata. These observations and the lack of surface scarps during the 1886 earthquake suggest a component of strike-slip for the Cretaceous and Cenozoic displacements, whereas some modern focal mechanisms show thrust motion. A prominent magnetic anomaly high shows a NE-trending west edge in the epicentral area, and short-wavelength magnetic anomalies show disruptions aligned along NE trends. These latter disruptions appear to be related to the seismically imaged faults that offset ACP strata. One of the faults, previously interpreted by Chapman and Beale (2010), shows folding and perhaps faulting of ACP strata with ~50 m vertical displacement and is aligned along the NW edge of the magnetic high. The vertical uplift is nearly equal through the ACP section with little or no upward decrease across the fault, indicating the motion is primarily Cenozoic. The fault lies near Summerville about 35 km NW of Charleston, where 1886 ground deformation was focused. Another NE-trending fault, crossing beneath the Ashley River ~15 km NW of

  14. Identifying active faults in Switzerland using relocated earthquake catalogs and optimal anisotropic dynamic clustering

    NASA Astrophysics Data System (ADS)

    Wagner, M.; Wang, Y.; Husen, S.; Woessner, J.; Kissling, E. H.; Ouillon, G.; Giardini, D.; Sornette, D.

    2010-12-01

    Active fault zones are the causal locations of most earthquakes, which release tectonic stresses. Yet, identification and association of faults and earthquakes is not straightforward. On the one hand, many earthquakes occur on faults that are unknown. On the other hand, systematic biases and uncertainties in earthquake locations hamper the association of earthquakes and known faults. We tackle the problem of linking earthquakes to faults by relocating them in a non-linear probabilistic manner and by applying a three-dimensional optimal anisotropic dynamic clustering approach to the relocated events to map fault networks. Non-linear probabilistic earthquake location allows to compute probability density functions that provide the complete probabilistic solution to the earthquake hypocenter location problem, including improved information on location uncertainties. To improve absolute earthquake locations we use a newly developed combined controlled-source seismology and local earthquake tomography model, which allows the use of secondary phases, such as PmP. Dynamic clustering is a very general image processing technique that allows partitioning a set of data points. Our improved optimal anisotropic dynamic clustering technique accounts for uncertainties in earthquake locations by the use of probability density functions, as provided by non-linear probabilistic earthquake location. Hence, number and size of the reconstructed faults is controlled by earthquake location uncertainty. We apply our approach to seismicity in Switzerland to identify active faults in the region. Relocated earthquake catalogs and associated fault networks will be compared to already existing information on faults, such as geological and seismotectonic maps, to derive a more complete picture of active faulting in Switzerland.

  15. A reconnaissance technique for estimating the slip rates of normal-slip faults in the Great Basin, and application to faults in Nevada, United States of America

    NASA Astrophysics Data System (ADS)

    Depolo, Craig Michael

    The slip rates of 270 normal-slip faults in Nevada are estimated using a new procedure that uses geomorphic features. The slip rate estimation scheme is based on the existence and non-existence of alluvial fault scarps and fault facets, and the height of the maximum basal fault facet. Faults that lack alluvial fault scarps and fault facets are assigned a vertical slip rate of 0.001 m/kyr and a range of 0.0005 to 0.009 m/kyr. Fault with alluvial fault scarps that lack active fault facets are assigned a vertical slip rate of 0.01 m/kyr and a range of 0.003 to 0.07 m/kyr. Faults that have relict facets, that is facets left over from a prior, more active period of the fault, are included in the 0.01 m/kyr group. Faults with active facets have vertical slip rates of ≥0.1 m/kyr. Slip rates for these higher activity faults are estimated using the height of the largest basal fault facet and the relationship,$log\\ S = 0.00267 H - 0.963where S is vertical slip rate in m/kyr and H is maxiμm basal facet height in meters. One standard deviation in this relationship is equivalent to a multiplicative factor of 1.8 in vertical slip rate. In Nevada, the fastest normal-slip faults (geq0.5 m/kyr) are located along the province-boundary with the Sierra Nevada and in Western Nevada, in the Walker Lane belt. In regions that are relatively active within the Great Basin, faults have vertical slip rates of up to 0.5 m/kyr. Less active parts of Nevada are characterized by faults with vertical slip rates of 0.001 and 0.01 m/kyr. Strain rates calculated for subregions indicate the state is deforming at rates comparable to the overall strain rate of the Great Basin or less, and support the division of the state into different subprovinces. An east-west strain-rate transect was made at the Latitude of 40spcirc\\ 30spprimeN, from the Wasatch front in Utah to the western Nevada border. A cumulative horizontal slip vector of 3.9 mm/yr in a N79spcircW direction is estimated if the preferred

  16. Repeated surveys reveal nontectonic exposure of supposedly active normal faults in the central Apennines, Italy

    NASA Astrophysics Data System (ADS)

    Kastelic, Vanja; Burrato, Pierfrancesco; Carafa, Michele M. C.; Basili, Roberto

    2017-01-01

    We investigate the geomorphic processes that expose bedrock fault surfaces from under their slope-deposit cover in the central Apennines (Italy). These bedrock fault surfaces are generally located at various heights on mountain fronts above the local base level of glacio-fluvial valleys and intermountain fluvio-lacustrine basins and are laterally confined to the extent of related mountain fronts. The process that led to the exposure of fault surfaces has often been exclusively attributed to coseismic earthquake slip and used as proxy for tectonic slip rates and earthquake recurrence estimations. We present the results of monitoring the contact between the exposed fault surfaces and slope deposits at 23 measurement points on 12 different faults over 3.4 year long observation period. We detected either downward or upward movements of the slope deposit with respect to the fault surface between consecutive measurements. During the entire observation period all points, except one, registered a net downward movement in the 2.9-25.6 mm/yr range, resulting in the progressive exposure of the fault surface. During the monitoring period no major earthquakes occurred in the region, demonstrating that the measured exposure process is disconnected from seismic activity. Our results indicate that the fault surface exposure rates are rather due to gravitational and landsliding movements aided by weathering and slope degradation processes. The so far neglected slope degradation and other (sub)surface processes should thus be carefully taken into consideration before attempting to recover fault slip rates using surface gathered data.

  17. The Nature of Extension on the Western Edge of the Basin and Range: Evolution of the Surprise Valley Fault System

    NASA Astrophysics Data System (ADS)

    Surpless, B.; Egger, A. E.

    2006-12-01

    The Warner Range is a major west-tilted fault block in northeastern California bound on its eastern side by the Surprise Valley normal fault system, which has accommodated a minimum of 3 km of uplift. The fault system separates the northeastern Basin and Range Province on the east, which has undergone 10-15% extension since the Miocene, from the Modoc Plateau to the west, a relatively unextended region with a thick sequence of flat-lying Pliocene and younger volcanic rocks. Although no major earthquakes have occurred along the fault system in historic times, significant Quaternary fault scarps, ~3 Ma U-Th/He ages, and trenching suggest that the system is still active, and recently published GPS data suggest ongoing extension and right- lateral deformation across the region. Thus, the Surprise Valley fault system is ideally located to gain insight into extensional processes at the edge of the Basin and Range province and to reveal potential seismic hazard. Dip-slip displacement along the Surprise Valley fault system decreases toward the system's north and south terminations. The northern termination is complicated by the Fandango Valley, a northwest-trending, graben- like structure that cuts across the Warner Range at an oblique angle. South of the Fandango Valley, Eocene to Miocene volcanic and volcaniclastic rocks in the range dip ~25 degrees to the west, and the east- dipping Surprise Valley fault system bounds the east side of the range. North of the valley, Miocene age volcanic rocks in the range dip gently to the east, and the dominant normal fault system is west-dipping and bounds the west side of the range. These two significant normal fault systems overlap at the latitude of the Fandango Valley, suggesting that the structure is an antithetic accommodation zone, but the Valley's northwest-trending orientation is orthogonal to that expected for an accommodation zone controlled exclusively by the propagation of oppositely-dipping normal faults. It is possible

  18. 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

  19. Seismic hazard in low slip rate crustal faults, estimating the characteristic event and the most hazardous zone: study case San Ramón Fault, in southern Andes

    NASA Astrophysics Data System (ADS)

    Estay, Nicolás P.; Yáñez, Gonzalo; Carretier, Sebastien; Lira, Elias; Maringue, José

    2016-11-01

    Crustal faults located close to cities may induce catastrophic damages. When recurrence times are in the range of 1000-10 000 or higher, actions to mitigate the effects of the associated earthquake are hampered by the lack of a full seismic record, and in many cases, also of geological evidences. In order to characterize the fault behavior and its effects, we propose three different already-developed time-integration methodologies to define the most likely scenarios of rupture, and then to quantify the hazard with an empirical equation of peak ground acceleration (PGA). We consider the following methodologies: (1) stream gradient and (2) sinuosity indexes to estimate fault-related topographic effects, and (3) gravity profiles across the fault to identify the fault scarp in the basement. We chose the San Ramón Fault on which to apply these methodologies. It is a ˜ 30 km N-S trending fault with a low slip rate (0.1-0.5 mm yr-1) and an approximated recurrence of 9000 years. It is located in the foothills of the Andes near the large city of Santiago, the capital of Chile (> 6 000 000 inhabitants). Along the fault trace we define four segments, with a mean length of ˜ 10 km, which probably become active independently. We tested the present-day seismic activity by deploying a local seismological network for 1 year, finding five events that are spatially related to the fault. In addition, fault geometry along the most evident scarp was imaged in terms of its electrical resistivity response by a high resolution TEM (transient electromagnetic) profile. Seismic event distribution and TEM imaging allowed the constraint of the fault dip angle (˜ 65°) and its capacity to break into the surface. Using the empirical equation of Chiou and Youngs (2014) for crustal faults and considering the characteristic seismic event (thrust high-angle fault, ˜ 10 km, Mw = 6.2-6.7), we estimate the acceleration distribution in Santiago and the hazardous zones. City domains that are under

  20. Plio-Pleistocene synsedimentary fault compartments, foundation for the eastern Olduvai Basin paleoenvironmental mosaic, Tanzania.

    PubMed

    Stollhofen, Harald; Stanistreet, Ian G

    2012-08-01

    Normal faults displacing Upper Bed I and Lower Bed II strata of the Plio-Pleistocene Lake Olduvai were studied on the basis of facies and thickness changes as well as diversion of transport directions across them in order to establish criteria for their synsedimentary activity. Decompacted differential thicknesses across faults were then used to calculate average fault slip rates of 0.05-0.47 mm/yr for the Tuff IE/IF interval (Upper Bed I) and 0.01-0.13 mm/yr for the Tuff IF/IIA section (Lower Bed II). Considering fault recurrence intervals of ~1000 years, fault scarp heights potentially achieved average values of 0.05-0.47 m and a maximum value of 5.4 m during Upper Bed I, which dropped to average values of 0.01-0.13 m and a localized maximum of 0.72 m during Lower Bed II deposition. Synsedimentary faults were of importance to the form and paleoecology of landscapes utilized by early hominins, most traceably and provably Homo habilis as illustrated by the recurrent density and compositional pattern of Oldowan stone artifact assemblage variation across them. Two potential relationship factors are: (1) fault scarp topographies controlled sediment distribution, surface, and subsurface hydrology, and thus vegetation, so that a resulting mosaic of microenvironments and paleoecologies provided a variety of opportunities for omnivorous hominins; and (2) they ensured that the most voluminous and violent pyroclastic flows from the Mt. Olmoti volcano were dammed and conduited away from the Olduvai Basin depocenter, when otherwise a single or set of ignimbrite flows might have filled and devastated the topography that contained the central lake body. In addition, hydraulically active faults may have conduited groundwater, supporting freshwater springs and wetlands and favoring growth of trees.

  1. Lithospheric Control on Spatial Patterns of Active Faulting in the Southeastern Sierra Nevada, California

    NASA Astrophysics Data System (ADS)

    Amos, C. B.; Unruh, J. R.; Lutz, A.; Fisher, B.; Kelson, K. I.; Rood, D. H.; Jayko, A. S.

    2011-12-01

    Patterns of active faulting in the southeastern Sierra Nevada of California reflect both far-field plate motion as well as localized forces that drive seismogenic deformation. Oblique divergence between the Sierra and the western Cordillera results in an overall pattern of dextral shear and northwest-directed extension in the eastern California shear zone (ECSZ) and southern Walker Lane belt. Within the nominally rigid southern Sierra Nevada block, newly recognized active normal faulting, as well as seismicity, indicate primarily extensional deformation beneath the high topography of the southern range. Investigations of the northern Kern Canyon fault, the Little Lake fault, and the Sierra Nevada range-front faults in Rose Valley combine data from both aerial and ground-based laser scanning, paleoseismic trenching, geologic and geomorphic mapping, and surface exposure dating to define spatial and temporal patterns of fault slip. Taken together, these studies indicate that deformation kinematics along the southeastern Sierran escarpment undergo a pronounced shift at an approximate latitude of 36.5° N. To the north in Owens valley, range-front faults accommodate active extension and normal faulting, while the adjacent Owens Valley fault displays primarily dextral strike-slip motion. South of Lone Pine, however, a component of active normal faulting steps westward into the southern Sierra Nevada block to the Kern Canyon fault, while range-front faults in Rose Valley accommodate a significant component of oblique dextral extension. Focal mechanism inversion of earthquakes in the southern Sierra Nevada reveals a zone of horizontal extension and vertical crustal thinning coincident with this westward shift of normal faulting into the range. The zone of extension is directly east of the "Isabella Anomaly," a zone of anomalous high P-wave mantle velocities thought to reflect convectively downwelling or foundering lower Sierran lithosphere below the Central Valley. As such

  2. Paleoseismology study of Luyeh fault, the west branch of southern-most Longitudinal Valley fault

    NASA Astrophysics Data System (ADS)

    Chi, C.; Chen, W.

    2010-12-01

    The Longitudinal Valley fault (LVF) is the active suture between Eurasian plate and Philippine Sea plate. This study we focus on the southern-most segment of LVF, where it branches into two parallel imbricated faults, the Luyeh fault (LYF) in the west and Lichi fault (LCF) in the east. A trench for paleoseismologic research has been excavated across a 3 m high monoclino-scarp near the north end of the LYF. All the layers in the trench are folded and are west dipping with a tendency of steepening downward. Based on the onlapping structures, dip angle change, and fault cutting relation, we resolve 3 paleoearthquake events. The timing of these events which are in about 4300 yr BP (E3), 2200 yr BP (E2), and after 2200 yr BP (E1) are constrained by 14C dating of the sedimentary layers. The vertical uplift restored from the unconformities are 2.24-2.47 m (E3), 1.02-1.36 m (E2), and 2.92-3.07 m (E1) respectively. Long-term uplift rate is about 1.5 mm/yr and the slip rate is about 4.5 mm/yr calculated by fault dip angle 20°. Two boreholes in the south of the trench were drilled. The mud deposits dated as 13060-12840 cal yr BP in MB-01 core has sheared, these shear zone can be correlated to the surface lineament (F1) extend to the trench site. This suggests the fault has activated after 13000 yr BP. The shear zone in 186.0-187.0 m of MB-02 core can be extrapolated to the scarp in the surface. This branch (F2) should be less or no more active because it doesn’t have any imprint on the terrace surface in the north. The unusual thick mud deposit in MB-01 core is dated as 18510-17690 cal yr BP in 69.6 m depth. This means a sudden depositional environment change from fluvial to lacustrine environment before this age. We infer the F2 branch was active and uplifted the terrace at that time. Therefore it can serve as a barrier that dammed the downstream side of the stream and formed a lake. The recurrence time deduced from E3 and E2 is about 2100 yr. If this is almost the same

  3. The offshore Yangsan fault activity in the Quaternary, SE Korea: Analysis of high-resolution seismic profiles

    NASA Astrophysics Data System (ADS)

    Kim, Han-Joon; Moon, Seonghoon; Jou, Hyeong-Tae; Lee, Gwang Hoon; Yoo, Dong Geun; Lee, Sang Hoon; Kim, Kwang Hee

    2016-12-01

    The NNE-trending dextral Yangsan fault is a > 190-km-long structure in the Korean Peninsula traced to the southeastern coast. The scarcity of Quaternary deposits onland precludes any detailed investigation of the Quaternary activity and structure of the Yangsan fault using seismic reflection profiling. We acquired offshore high-resolution seismic profiles to investigate the extension of the Yangsan fault and constrain its Quaternary activity using stratigraphic markers. The seismic profiles reveal a NNE-trending fault system consisting of a main fault and an array of subsidiary faults that displaced Quaternary sequences. Stratigraphic analysis of seismic profiles indicates that the offshore faults were activated repeatedly in the Quaternary. The up-to-the-east sense of throw on the main fault and plan-view pattern of the fault system are explained by dextral strike-slip faulting. The main fault, when projected toward the Korean Peninsula along its strike, aligns well with the Yangsan fault. We suggest that the offshore fault system is a continuation of the Yangsan fault and has spatial correlation with weak but ongoing seismicity.

  4. Evidence of a Large-Magnitude Recent Prehistoric Earthquake on the Bear River Fault, Wyoming and Utah: Implications for Recurrence

    NASA Astrophysics Data System (ADS)

    Hecker, S.; Schwartz, D. P.

    2015-12-01

    Trenching across the antithetic strand of the Bear River normal fault in Utah has exposed evidence of a very young surface rupture. AMS radiocarbon analysis of three samples comprising pine-cone scales and needles from a 5-cm-thick faulted layer of organic detritus indicates the earthquake occurred post-320 CAL yr. BP (after A.D. 1630). The dated layer is buried beneath topsoil and a 15-cm-high scarp on the forest floor. Prior to this study, the entire surface-rupturing history of this nascent normal fault was thought to consist of two large events in the late Holocene (West, 1994; Schwartz et al., 2012). The discovery of a third, barely pre-historic, event led us to take a fresh look at geomorphically youthful depressions on the floodplain of the Bear River that we had interpreted as possible evidence of liquefaction. The appearance of these features is remarkably similar to sand-blow craters formed in the near-field of the M6.9 1983 Borah Peak earthquake. We have also identified steep scarps (<2 m high) and a still-forming coarse colluvial wedge near the north end of the fault in Wyoming, indicating that the most recent event ruptured most or all of the 40-km length of the fault. Since first rupturing to the surface about 4500 years ago, the Bear River fault has generated large-magnitude earthquakes at intervals of about 2000 years, more frequently than most active faults in the region. The sudden initiation of normal faulting in an area of no prior late Cenozoic extension provides a basis for seismic hazard estimates of the maximum-magnitude background earthquake (earthquake not associated with a known fault) for normal faults in the Intermountain West.

  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. Late quaternary faulting along the Death Valley-Furnace Creek fault system, California and Nevada

    SciTech Connect

    Brogan, G.E.; Kellogg, K.S.; Terhune, C.L.; Slemmons, D.B.

    1991-12-31

    The Death Valley-Furnace Creek fault system, in California and Nevada, has a variety of impressive late Quaternary neotectonic features that record a long history of recurrent earthquake-induced faulting. Although no neotectonic features of unequivocal historical age are known, paleoseismic features from multiple late Quaternary events of surface faulting are well developed throughout the length of the system. Comparison of scarp heights to amount of horizontal offset of stream channels and the relationships of both scarps and channels to the ages of different geomorphic surfaces demonstrate that Quaternary faulting along the northwest-trending Furnace Creek fault zone is predominantly right lateral, whereas that along the north-trending Death Valley fault zone is predominantly normal. These observations are compatible with tectonic models of Death Valley as a northwest- trending pull-apart basin.

  7. Late Pleistocene displacement and slip rate for the Breckenridge fault, Walker Basin, southern Sierra Nevada, California

    NASA Astrophysics Data System (ADS)

    Brossy, C. C.; Baldwin, J. N.; Kelson, K. I.; Rood, D. H.; Kozlowicz, B.; Simpson, D.; Ticci, M.; Amos, C. B.; Kozaci, O.; Lutz, A.

    2010-12-01

    The north-striking Breckenridge fault occurs along the 11-km-long western margin of Walker Basin, a west-tilted intermontane alluvial basin in the southern Sierra Nevada. This east-dipping normal fault has prominent geomorphic expression in the form of east-facing fault scarps on alluvial-fan deposits and distinct triangular facets of granitic bedrock along the range front. Steep, east-draining valleys are incised into bedrock west of the fault and are associated with inset or overlapping alluvial fan surfaces east of the fault. Detailed analysis of lidar-derived digital elevation models (DEMs) and field geomorphic mapping suggest that a 2-km-wide series of small right-stepovers separate the Breckenridge fault from the Holocene-active Kern Canyon fault to the north. Directly south of Walker Basin, prominent geomorphic expression of the Breckenridge fault dies out in an area of complex and distributed microseismicity, suggesting that the fault does not connect with the active White Wolf fault to the south. Herein, on the basis of geologic and geomorphic mapping, DEM interpretation, and cosmogenic radionuclide (CRN) dating, we report the first documented evidence for late Pleistocene normal faulting on the Breckenridge fault. At the Oak Tree site (38.431N, 118.545W), two alluvial-fan deposits (Qf1 and Qf3) exhibit east-down normal fault displacement. The active channel is entrenched about 8 and 14 m below these abandoned surfaces. Topographic profiles generated from DEMs along the extensive Qf1 and Qf3 surfaces show that fault scarp heights are progressively lower on younger surfaces. The oldest surface (Qf1) shows vertical separation of ~7 m, and the intermediate Qf3 surface exhibits ~4 m of vertical separation. The next youngest surface (Qf4) appears undeformed across the fault trace. Samples from granitic boulders exposed on the Qf1, Qf3, and Qf4 surfaces were collected for 10Be exposure dating. The CRN dates are consistent with stratigraphic position and yield

  8. Mass Movement on Vesta at Steep Scarps and Crater Rims

    NASA Technical Reports Server (NTRS)

    Krohn, K.; Jaumann, R.; Otto, K.; Hoogenboom, T.; Wagner, R.; Buczkowski, D. L.; Garry, B.; Williams, D. A.; Yingst, R. A.; Scully, J.; De Sanctis, M. C.; Kneissl, T.; Schmedemann, N.; Kersten, E.; Stephan, K.; Matz, K.-D.; Pieters, C. M.; Preusker, F.; Roatsch, T.; Schenk, P.; Russell, C. T.; Raymond, C. A.

    2014-01-01

    The Quadrangles Av-11 and Av-12 on Vesta are located at the northern rim of the giant Rheasilvia south polar impact basin. The primary geologic units in Av-11 and Av-12 include material from the Rheasilvia impact basin formation, smooth material and different types of impact crater structures (such as bimodal craters, dark and bright crater ray material and dark ejecta material). Av-11 and Av-12 exhibit almost the full range of mass wasting features observed on Vesta, such as slump blocks, spur-and-gully morphologies and landslides within craters. Processes of collapse, slope instability and seismically triggered events force material to slump down crater walls or scarps and produce landslides or rotational slump blocks. The spur-and-gully morphology that is known to form on Mars is also observed on Vesta; however, on Vesta this morphology formed under dry conditions.

  9. Nature of Active Traces of the Hayward Fault at the University of California, Berkeley

    NASA Astrophysics Data System (ADS)

    Wells, D. L.; Swan, F. H.; Thompson, S. C.; Baldwin, J. N.; Williams, P. L.; Rubin, R. S.; Lavine, A.; Hall, N. T.

    2007-12-01

    The location of the Hayward fault zone at the University of California Berkeley Campus is well defined by geomorphic features including offset stream channels, side-hill benches, and the break-in-slope at the base of the Berkeley Hills, as well as by fault-creep related deformation of curbs, buried culverts and utilities, and structures--most notably Memorial Stadium. Based on the mapped fault traces associated with these surficial features, more than 30 trenches have been excavated at various locations on the campus during the past twenty years to assess the exact location and width of the active fault zone near existing and planned structures. These trenches show that the active fault trace(s) range from well expressed to poorly expressed in various surficial materials as a function of (1) the local geometry of the fault, (2) the stability of the near-surface deposits (e.g., it is poorly expressed where it crosses active landslides), and (3) the age of the deposits (i.e., it is better expressed in older deposits). At locations near the Smyth-Fernwald Housing, Prospect Court, the Greek Theater, and Foothill Housing, trenches showed that the fault is characterized by multiple distinct traces that in many places bound alluvial/colluvial-filled depressions up to 6 meters wide, and are in-filled with Holocene deposits. Quaternary deposits and bedrock units are truncated, indicating that significant lateral and vertical displacement has occurred along these fault traces. The creeping trace of the fault generally coincides with these well expressed fault traces. Trenches also revealed that two sub-parallel active fault traces as much as 40 to 60 meters apart extend along the hillslope directly east of the Greek Theater and north and east of Bowles Hall. It remains uncertain as to how fault creep occurs along the two separate branches. Between Memorial Stadium and Bowles Hall, there is a small right bend or stepover in the fault. The location of the creeping trace is

  10. Deformed Neogene basins, active faulting and topography in Westland: Distributed crustal mobility west of the Alpine Fault transpressive plate boundary (South Island, New Zealand)

    NASA Astrophysics Data System (ADS)

    Ghisetti, Francesca; Sibson, Richard H.; Hamling, Ian

    2016-12-01

    Tectonic activity in the South Island of New Zealand is dominated by the Alpine Fault component of the Australia-Pacific plate boundary. West of the Alpine Fault deformation is recorded by Paleogene-Neogene basins coeval with the evolution of the right-lateral/transpressive plate margin. Initial tectonic setting was controlled by N-S normal faults developed during Late Cretaceous and Eocene-early Miocene rifting. Following inception of the Alpine Fault (c. 25 Ma) reverse reactivation of the normal faults controlled tectonic segmentation that became apparent in the cover sequences at c. 22 Ma. Based on restored transects tied to stratigraphic sections, seismic lines and wells, we reconstruct the vertical mobility of the Top Basement Unconformity west of Alpine Fault. From c. 37-35 Ma to 22 Ma subsidence was controlled by extensional faulting. After 22 Ma the region was affected by differential subsidence, resulting from eastward crustal flexure towards the Alpine Fault boundary and/or components of transtension. Transition from subsidence to uplift started at c. 17 Ma within a belt of basement pop-ups, separated by subsiding basins localised in the common footwall of oppositely-dipping reverse faults. From 17 to 7-3 Ma reverse fault reactivation and uplift migrated to the WSW. Persistent reverse reactivation of the inherited faults in the present stress field is reflected by the close match between tectonic block segmentation and topography filtered at a wavelength of 25 km, i.e. at a scale comparable to crustal thickness in the region. However, topography filtered at wavelength of 75 km shows marked contrasts between the elevated Tasman Ranges region relative to regions to the south. Variations in thickness and rigidity of the Australian lithosphere possibly control N-S longitudinal changes, consistent with our estimates of increase in linear shortening from the Tasman Ranges to the regions located west of the Alpine Fault bend.

  11. Actively evolving microplate formation by oblique collision and sideways motion along strike-slip faults: An example from the northeastern Caribbean plate margin

    NASA Astrophysics Data System (ADS)

    Mann, Paul; Taylor, F. W.; Edwards, R. Lawrence; Ku, Teh-Lung

    1995-06-01

    The pattern of folding, faulting, and late Quaternary coral-reef uplift rates in western and central Hispaniola (Haiti and Dominican Republic) suggest that the elongate Gonave microplate, a 190,000-km 2 area of the northeastern Caribbean plate, is in the process of shearing off the Caribbean plate and accreting to the North American plate. Late Cenozoic transpression between the southeastern Bahama Platform and the Caribbean plate in Hispaniola has inhibited the eastward motion of the northeastern corner of the plate. Transpression is manifested in western and central Hispaniola by the formation of regional scale folds that correspond to present-day, anticlinal topographic mountain chains continuous with offshore anticlinal ridges. Areas of most rapid Quaternary uplift determined from onland coral reefs 125 ka and younger, coincide with the axial traces of these folds. Offshore data suggest recent folding and faulting of the seafloor. Onshore reef data do not conclusively require late Quaternary folding, but demonstrate that tectonic uplift rates of the axial areas of the anticlines decrease from the Northwest Peninsula of Haiti (0.37 mm/yr) to to the central part of the coast of western Haiti (0.19 mm/yr) to the south-central part of western Haiti (0 mm/yr). Formation of the 1200-km-long Enriquillo-Plantain Garden-Walton fault zone as a 'bypass' strike-slip fault has isolated the southern edge of the Gonave microplate and is allowing continued, unimpeded eastward motion of a smaller Caribbean plate past the zone of late Neogene convergence and Quaternary uplift of coral reefs in Hispaniola. Offshore seismic reflection data from the Jamaica Passage, the marine strait separating Jamaica and Haiti, show that the Enriquillo-Plantain Garden fault zone forms a narrow but deep, active fault-bounded trough beneath the passage. The active fault is continuous with active faults mapped onshore in western Haiti and eastern Jamaica; the bathymetric deep is present because the

  12. Fault linkage: Three-dimensional mechanical interaction between echelon normal faults

    NASA Astrophysics Data System (ADS)

    Crider, Juliet G.; Pollard, David D.

    1998-10-01

    Field observations of two overlapping normal faults and associated deformation document features common to many normal-fault relay zones: a topographic ramp between the fault segments, tapering slip on the faults as they enter the overlap zone, and associated fracturing, especially at the top of the ramp. These observations motivate numerical modeling of the development of a relay zone. A three-dimensional boundary element method numerical model, using simple fault-plane geometries, material properties, and boundary conditions, reproduces the principal characteristics of the observed fault scarps. The model, with overlapping, semicircular fault segments under orthogonal extension, produces a region of high Coulomb shear stress in the relay zone that would favor fault linkage at the center to upper relay ramp. If the fault height is increased, the magnitude of the stresses in the relay zone increases, but the position of the anticipated linkage does not change. The amount of fault overlap changes the magnitude of the Coulomb stress in the relay zone: the greatest potential for fault linkage occurs with the closest underlapping fault tips. Ultimately, the mechanical interaction between segments of a developing normal-fault system promote the development of connected, zigzagging fault scarps.

  13. 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.

  14. Quaternary strike-slip crustal deformation around an active fault based on paleomagnetic analysis: a case study of the Enako fault in central Japan

    NASA Astrophysics Data System (ADS)

    Kimura, Haruo; Itoh, Yasuto; Tsutsumi, Hiroyuki

    2004-10-01

    To evaluate cumulative strike-slip deformation around an active fault, we carried out tectonic geomorphic investigations of the active right-lateral strike-slip Enako fault in central Japan and paleomagnetic investigations of the Kamitakara pyroclastic flow deposit (KPFD; 0.6 Ma welded tuff) distributed around the fault. Tectonic geomorphic study revealed that the strike-slip displacement on the fault is ca. 150 m during the past 600 ka. We carried out measurements of paleomagnetic directions and anisotropy of magnetic susceptibility (AMS) within the pyroclastic flow deposit. Stable primary magnetic directions at each sampling site are well clustered and the AMS fabric is very oblate. We then applied tilt correction of paleomagnetic directions at 15 sites using tilting data obtained by the AMS property and orientations of eutaxitic structures. Within a distance of about 500 m from the fault trace, differential clockwise rotations were detected; the rotation angle is larger for zones closer to the fault. Because of this relation and absence of block boundary faults, a continuous deformation model explains the crustal deformation in the study area. The calculated minimum value of strike-slip displacement associated with this deformation detected within the shear zone is 210 m. The sum of this and offset on the Enako fault is 360 m and the slip rate is estimated at 0.6 mm/year.

  15. 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.

  16. Timing of the faulting on the Wispy Terrain of Dione based on stratigraphic relationships with impact craters

    NASA Astrophysics Data System (ADS)

    Hirata, Naoyuki

    2016-11-01

    The trailing hemisphere of Dione is characterized by the Wispy Terrain, where it exhibits a hemispheric-scale network of extensional tectonic faults superposed on the moon's cratered surface. The faults likely reflect past endogenic activity and Dione's interior thermal history. Although fresh exposures of pristine scarps indicate that the timing of the faulting is relatively recent, the absolute age of the faulting remains uncertain. To estimate the timing of the faulting, we investigated stratigraphic relationships between impact craters and faults. Using high-resolution images obtained by the ISS camera onboard the Cassini spacecraft, we investigated craters with diameters exceeding or equal to 10 km that coincide spatially with the faults and classified the craters as crosscut craters or superposed craters. As a result, at least 82% of the craters were interpreted as clear examples of crosscut craters and 12% of the craters were interpreted to be candidates of superposed craters, although stratigraphic relationships are often ambiguous. The paucity of superposed craters and a predicted cratering rate indicate that the faulting of the Wispy Terrain is 0.30-0.79 Ga. If 12-18% of the craters are assumed to be superposed, the timing of the faulting could be in the range 0.30-0.79 Ga. However, it is possible that the faulting of the Wispy Terrain is still ongoing.

  17. GIS coverages of the Castle Mountain Fault, south central Alaska

    USGS Publications Warehouse

    Labay, Keith A.; Haeussler, Peter J.

    2001-01-01

    The Castle Mountain fault is one of several major east-northeast-striking faults in southern Alaska, and it is the only fault with had historic seismicity and Holocene surface faulting. This report is a digital compilation of three maps along the Castle Mountain fault in south central Alaska. This compilation consists only of GIS coverages of the location of the fault, line attributes indicating the certainty of the fault location, and information about scarp height, where measured. The files are presented in ARC/INFO export file format and include metadata.

  18. Airborne LiDAR detection of postglacial faults and Pulju moraine in Palojärvi, Finnish Lapland

    NASA Astrophysics Data System (ADS)

    Sutinen, Raimo; Hyvönen, Eija; Middleton, Maarit; Ruskeeniemi, Timo

    2014-04-01

    Postglacial faults (PGFs) are indicative of young tectonic activity providing crucial information for nuclear repository studies. Airborne LiDAR (Light Detection And Ranging) data revealed three previously unrecognized late- or postglacial faults in northernmost Finnish Lapland. Under the canopies of mountain birch (Betula pubescens ssp. czerepanovii) we also found clusters of the Pulju moraine, typically found on the ice-divide zone of the former Fennoscandian ice sheet (FIS), to be spatially associated with the fault-scarps. Tilt derivative (TDR) filtered LiDAR data revealed the previously unknown Palojärvi fault that, by the NE-SW orientation parallels with the well documented Lainio-Suijavaara PGF in northern Sweden. This suggests that PGFs are more extensive features than previously recognized. Two inclined diamond drill holes verified the fractured system of the Palojärvi fault and revealed clear signs of postglacial reactivation. Two other previously unrecognized PGFs, the W-E trending Paatsikkajoki fault and the SE-NW trending Kultima fault, differ from the Palojärvi faulting in orientation and possibly also with regard to age. The Pulju moraine, a morphological feature showing transitions from shallow (< 2-m-high) circular/arcuate ridges to sinusoidal/anastomosing esker networks was found to be concentrated within 6 km from the Kultima fault-scarp. We advocate that some of the past seismic events took place under the retreating wet-base ice sheet and the increased pore-water pressure triggered the sediment mass flows and formation of the Pulju moraine-esker landscape.

  19. 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

  20. 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

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

    DOE PAGES

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

    2015-03-01

    We conducted three-dimensional coupled fluid-flow and geomechanical modeling of fault activation and seismicity associated with hydraulic fracturing stimulation of a shale-gas reservoir. We simulated a case in which a horizontal injection well intersects a steeply dip- ping fault, with hydraulic fracturing channeled within the fault, during a 3-hour hydraulic fracturing stage. Consistent with field observations, the simulation results show that shale-gas hydraulic fracturing along faults does not likely induce seismic events that could be felt on the ground surface, but rather results in numerous small microseismic events, as well as aseismic deformations along with the fracture propagation. The calculated seismicmore » moment magnitudes ranged from about -2.0 to 0.5, except for one case assuming a very brittle fault with low residual shear strength, for which the magnitude was 2.3, an event that would likely go unnoticed or might be barely felt by humans at its epicenter. The calculated moment magnitudes showed a dependency on injection depth and fault dip. We attribute such dependency to variation in shear stress on the fault plane and associated variation in stress drop upon reactivation. Our simulations showed that at the end of the 3-hour injection, the rupture zone associated with tensile and shear failure extended to a maximum radius of about 200 m from the injection well. The results of this modeling study for steeply dipping faults at 1000 to 2500 m depth is in agreement with earlier studies and field observations showing that it is very unlikely that activation of a fault by shale-gas hydraulic fracturing at great depth (thousands of meters) could cause felt seismicity or create a new flow path (through fault rupture) that could reach shallow groundwater resources.« less

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. Fault Growth and Propagation and its Effect on Surficial Processes within the Incipient Okavango Rift Zone, Northwest Botswana, Africa (Invited)

    NASA Astrophysics Data System (ADS)

    Atekwana, E. A.

    2010-12-01

    The Okavango Rift Zone (ORZ) is suggested to be a zone of incipient continental rifting occuring at the distal end of the southwestern branch of the East African Rift System (EARS), therefore providing a unique opportunity to investigate neotectonic processes during the early stages of rifting. We used geophysical (aeromagnetic, magnetotelluric), Shuttle Radar Tomography Mission, Digital Elevation Model (SRTM-DEM), and sedimentological data to characterize the growth and propagation of faults associated with continental extension in the ORZ, and to elucidate the interplay between neotectonics and surficial processes. The results suggest that: (1) fault growth occurs by along axis linkage of fault segments, (2) an immature border fault is developing through the process of “Fault Piracy” by fault-linkages between major fault systems, (3) significant discrepancies exits between the height of fault scarps and the throws across the faults compared to their lengths in the basement, (4) utilization of preexisting zones of weakness allowed the development of very long faults (> 25-100 km) at a very early stage of continental rifting, explaining the apparent paradox between the fault length versus throw for this young rift, (5) active faults are characterized by conductive anomalies resulting from fluids, whereas, inactive faults show no conductivity anomaly; and 6) sedimentlogical data reveal a major perturbation in lake sedimentation between 41 ka and 27 ka. The sedimentation perturbation is attributed to faulting associated with the rifting and may have resulted in the alteration of hydrology forming the modern day Okavango delta. We infer that this time period may represent the age of the latest rift reactivation and fault growth and propagation within the ORZ.

  7. 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.

  8. Reconstructing the paleoseismic history of the Priene-Sazli Fault using 36Cl cosmogenic nuclide dating method, Western Anatolia, Turkey

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    The 300-km wide West Anatolian Extensional Province is one of the regions of intense seismic activity in the world within the Alpine-Himalayan belt. Deformation pattern in the area is controlled by three major E-W trending graben systems of Gediz, Küçük Menderes and Büyük Menderes which have been formed as a result of roughly N-S extensional tectonic regime since the early Miocene. These graben systems show evidences of surface faulting during the Pleistocene-Holocene and are geomorphologically characterized by well-exposed limestone normal fault scarps with a relief of tens of meters and well-preserved slickenlines. Since limestones are resistant to weathering, the limestone scarps can efficiently record several past earthquakes. Cosmogenic 36Cl is the only element to identify and date the rupture events. Each rupture causes exposure of previously buried section of the scarp to the surface. Accordingly, due to being well enough exposed to cosmic rays, accumulation of 36Cl accelerates during period of quiescence. Thus, distribution of measured 36Cl concentrations can be applied to investigate periods of seismic activity and inactivity and also to calculate the vertical displacement along the fault plane in association with each rupture. In this study, we focus on the Priene-Sazli Fault, located on the most western part of Büyük Menderes graben. Along the active fault zone, well exposed archaeological sites (e.g. Priene) have been discovered, where destructive historical earthquakes have left evidence of ancient damages in the historical period and during the 20th century. The Priene-Sazli Fault caused the July 16, 1955 Söke-Balat earthquake (M=6.8) with fault-plane solution indicating of normal southeast downthrow along with subsidiary dextral motion. We collected 117 samples from four continuous strips on the Priene-Sazli Fault to measure 36Cl concentrations. We used a new Matlab code to identify the significant ruptures and their timing. Our preliminary

  9. 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

  10. 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.

  11. A rod-type creepmeter for measurement of displacement in active fault zone

    NASA Astrophysics Data System (ADS)

    Lee, J.-C.; Jeng, F.-S.; Chu, H.-T.; Angelier, J.; Hu, J.-C.

    2000-05-01

    A creepmeter has been developed to monitor gradual displacements of near-surface movement in an active fault zone. This rod-type creepmeter is a robust, low-cost instrument that is simple to construct and install. This creepmeter consists of two 3-m invar rods attached to anchored steel piers at each end, straddling the surface traces of active fault. The invar rods are supported by a pair of U-shaped solid steel girders. A mechanical dial-gauge sensor in the middle of the creepmeter is adopted to record the displacement of fault creep, and has a precision of 0.01 mm. Because the creepmeter is installed on the surface, the temperature effect is important. To calibrate and correct for the temperature effect, we carried out hourly measurements over a period of 30 hours to calculate the thermal expansion coefficients for each creepmeter. Thermal corrections could thus be made when readings were taken. Five of these creepmeters have been installed in the Chihshang active fault zone of eastern Taiwan, in the present collision suture zone between the Philippine Sea plate and the Eurasian plate. Readings taken over one year have shown that this rod-type creepmeter is effective in providing a near-continuous record of active fault creep with a good precision.

  12. Coseismic growth of sedimentary basins along the Yammouneh strike-slip fault (Lebanon)

    NASA Astrophysics Data System (ADS)

    Nemer, Tony; Gomez, Francisco; Al Haddad, Sharbel; Tabet, Charles

    2008-12-01

    The left-lateral Yammouneh fault (YF) is the main active branch of the Dead Sea Transform Fault (DSTF) within the Lebanese restraining bend. Despite the overall transpressional setting, a series of sedimentary basins have developed along the trace of the YF. Consequently, palaeoseismic studies within these basins provide an opportunity to study the processes of coseismic growth of the basins, as well as elucidate earthquake behaviour of the fault, in general. Geodetic measurements of contemporary fault slip within the Lebanese restraining bend indicate that the YF accommodates most of the expected left-lateral strike-slip motion, despite the apparent lack of present-day seismicity. We studied the YF, using combined investigations of remote imagery, geomorphology and palaeoseismology. The active fault trace along a 51 km strip was delineated as relatively young surface ruptures and fault scarps that affect Holocene deposits with intermittent offset geomorphic markers. Seven closed basins that occur along-strike of the YF, were found to be related to faulting, with at least three of them displaying evident pull-apart settings. We concentrated our work on the rhombohedral Yammouneh basin, an actively evolving example of pull-apart basins, which is presently obliquely cut by the active fault, with an apparently young age of 1.4 +/- 0.3 Myr. 3-D correlation and analysis of palaeoseismic investigations exposed a composite shear zone with a total subsidence that exceeds 1.6 m over the past 4000-4400 yr. Stratigraphic and geochronological constraints suggest the occurrences of at least five large faulting events during that period. By correlating the stratigraphy and ages of this trench with a previously published study located nearby, a combined palaeoseismic history for the past five events is constructed. This suggests a mean recurrence period of 1020-1175 yr for large earthquakes along this section of the YF. Our results suggest a subsidence rate due to faulting of

  13. Detecting Blind Fault with Fractal and Roughness Factors from High Resolution LiDAR DEM at Taiwan

    NASA Astrophysics Data System (ADS)

    Cheng, Y. S.; Yu, T. T.

    2014-12-01

    There is no obvious fault scarp associated with blind fault. The traditional method of mapping this unrevealed geological structure is the cluster of seismicity. Neither the seismic event nor the completeness of cluster could be captured by network to chart the location of the entire possible active blind fault within short period of time. High resolution DEM gathered by LiDAR could denote actual terrain information despite the existence of plantation. 1-meter interval DEM of mountain region at Taiwan is utilized by fractal, entropy and roughness calculating with MATLAB code. By jointing these handing, the regions of non-sediment deposit are charted automatically. Possible blind fault associated with Chia-Sen earthquake at southern Taiwan is served as testing ground. GIS layer help in removing the difference from various geological formation, then multi-resolution fractal index is computed around the target region. The type of fault movement controls distribution of fractal index number. The scale of blind fault governs degree of change in fractal index. Landslide induced by rainfall and/or earthquake possesses larger degree of geomorphology alteration than blind fault; special treatment in removing these phenomena is required. Highly weathered condition at Taiwan should erase the possible trace remained upon DEM from the ruptured of blind fault while reoccurrence interval is higher than hundreds of years. This is one of the obstacle in finding possible blind fault at Taiwan.

  14. Late Quaternary slip rate and seismic hazards of the West Klamath Lake fault zone near Crater Lake, Oregon Cascades

    USGS Publications Warehouse

    Bacon, C.R.; Lanphere, M.A.; Champion, D.E.

    1999-01-01

    Crater Lake caldera is at the north end of the Klamath graben, where this N10??W-trending major Basin and Range structure impinges upon the north-south-trending High Cascades volcanic arc. East-facing normal faults, typically 10-15 km long, form the West Klamath Lake fault zone, which bounds the graben on its west side. The fault zone terminates on the south near the epicentral area of the September 1993 Klamath Falls earthquakes. It continues north past Crater Lake as the Annie Spring fault, which is within ~1 km of the west caldera rim, and Red Cone Spring fault. We have determined a long-term vertical slip rate of 0.3 mm/yr for these two faults using high-precision K-Ar and 40Ar/39Ar age measurements on offset lava flows ranging in age from ca. 35 to 300 ka. Holocene offset reported by Hawkins et al. and epicenters of eight MW 2 earthquakes in 1994 and 1995 indicate that the West Klamath Lake fautl zone is active. Empirical relations between earthquake magnitudes and scarp heights or fault lengths suggest that the fault zone is capable of producing earthquakes as large as MW 7 1/4 . Earthquakes on these or other faults of the zone could trigger landslides and rockfalls from the walls of the caldera, possibly resulting in large waves on Crater Lake.

  15. Evidence of Multiple Ground-rupturing Earthquakes in the Past 4000 Years along the Pasuruan Fault, East Java, Indonesia

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    Instrumental and historical records of earthquakes, supplemented by paleoeseismic constraints can help reveal the earthquake potential of an area. The Pasuruan fault is a high angle normal fault with prominent youthful scarps cutting young deltaic sediments in the north coast of East Java, Indonesia and may pose significant hazard to the densely populated region. This fault has not been considered a significant structure, and mapped as a lineament with no sense of motion. Information regarding past earthquakes along this fault is not available. The fault is well defined both in the imagery and in the field as a ~13km long, 2-50m-high scarp. Open and filled fractures and natural exposures of the south-dipping fault plane indicate normal sense of motion. We excavated two fault-perpendicular trenches across a relay ramp identified during our surface mapping. Evidence for past earthquakes (documented in both trenches) includes upward fault termination with associated fissure fills, colluvial wedges and scarp-derived debris, folding, and angular unconformities. The ages of the events are constrained by 23 radiocarbon dates on detrital charcoal. We calibrated the dates using IntCal13 and used Oxcal to build the age model of the events. Our preliminary age model indicates that since 2006±134 B.C., there has been at least five ground rupturing earthquakes along the fault. The oldest event identified in the trench however, is not well-dated. Our modeled 95th percentile ranges of the next four earlier earthquakes (and their mean) are A.D. 1762-1850 (1806), A.D. 1646-1770 (1708), A.D. 1078-1648 (1363), and A.D. 726-1092 (909), yielding a rough recurrence rate of 302±63 yrs. These new data imply that Pasuruan fault is more active than previously thought. Additional well-dated earthquakes are necessary to build a solid earthquake recurrence model. Rupture along the whole section implies a minimum earthquake magnitude of 6.3, considering 13km as the minimum surface rupture

  16. Evaluating knickpoint recession along an active fault for paleoseismological analysis: The Huoshan Piedmont, Eastern China

    NASA Astrophysics Data System (ADS)

    Wei, Zhanyu; Bi, Lisi; Xu, Yueren; He, Honglin

    2015-04-01

    Ground-rupturing earthquakes can generate tectonic knickpoints within upstream reaches of streams across active fault zones. These knickpoints are characteristic of upstream propagation of time-related process once generated by an earthquake, so analysis of knickpoint series in streams which cross fault zones can be used to infer paleoearthquake events. We studied the knickpoints along the Huoshan Piedmont Fault (HPF), which is an active normal fault in the Shanxi Faulted Basin zone, China, and demonstrate that analysis of knickpoints shows evidence for two paleoearthquakes in the HPF. First, we identified knickpoints in bedrock reaches upstream of the HPF using high-resolution DEMs derived from IRS-P5 stereo images and the stream-gradient method. After excluding non-faulting knickpoints, 47 knickpoints were identified in 23 bedrock reaches upstream from the HPF. Analysis of the most recent knickpoints caused by the 1303 CE Hongdong Earthquake allowed for local calibration of the retreat rates. Applying these retreat rates across the study area allows for the estimation of the age of other knickpoints, and constrains the age ranges of two knickpoint groups to be 2269-3336 a BP and 4504-5618 a BP. These ages constrain the ages of two paleoearthquake events at 2710 ± 102 and 4980 ± 646 a BP. The knickpoints along the HPF obey the parallel retreating model in which knickpoint morphology was roughly maintained during retreat, so the heights of knickpoints represent the coseismic vertical displacements generated by the earthquakes along the HPF. The vertical offsets for these three earthquake events are similar and are approximately 4 m, which indicates that the ruptures on the HPF obey a characteristic slip model with a similar slip distribution for several successive earthquakes. These results provide additional evidence of paleoearthquakes on the HPF and show that analysis of knickpoint recession along an active fault is a valuable tool for paleoseismology.

  17. Steady activity of microfractures on geological faults loaded by mining stress

    NASA Astrophysics Data System (ADS)

    Naoi, Makoto; Nakatani, Masao; Otsuki, Kenshiro; Yabe, Yasuo; Kgarume, Thabang; Murakami, Osamu; Masakale, Thabang; Ribeiro, Luiz; Ward, Anthony; Moriya, Hirokazu; Kawakata, Hironori; Durrheim, Raymond; Ogasawara, Hiroshi

    2015-05-01

    Acoustic Emissions (AE) down to MW -4 were recorded at a site 1 km beneath the surface in the Cooke 4 Mine, South Africa. Several planar AE clusters with lateral extent of 10-100 m were identified. Most of them were located several tens of meters away from the mining front, and exhibited steady activity during the analysis period of about two months. Some of the clusters coincided with mapped faults. The planar-cluster AEs were sharply aggregated within a thickness of several decimeters, likely delineating the fracture interface of the fault and its higher-order morphology such as branches, bends, and stepovers. The composite focal mechanism evaluated for each cluster was consistent with slip events on the fracture interface. These results imply that numerous shear microfractures occur steadily on a natural fault surface subjected to a mining-related stress increase. The planar clusters consist of very small AEs (99.7% were smaller than MW -2), exhibiting high b-values much exceeding unity. This contrasts with the more usual b-values of the stope-cluster AEs, which were aggregated within 20 m of the mining front and exhibited a more scattered distribution. The size distribution of microfractures on a fracture interface may directly reflect fine-scale irregularities of the interface. On the other hand, many other mapped faults near the planar AE clusters were not accompanied by AE activities, despite the fact that these quiet faults were subjected to a similar stress history. The presence or absence of AE activities on a fault may reflect different states of the fault, including stress and strength.

  18. Low resistivity and permeability in actively deforming shear zones on the San Andreas Fault at SAFOD

    USGS Publications Warehouse

    Morrow, Carolyn A.; Lockner, David A.; Hickman, Stephen H.

    2015-01-01

    The San Andreas Fault Observatory at Depth (SAFOD) scientific drillhole near Parkfield, California crosses the San Andreas Fault at a depth of 2.7 km. Downhole measurements and analysis of core retrieved from Phase 3 drilling reveal two narrow, actively deforming zones of smectite-clay gouge within a roughly 200 m-wide fault damage zone of sandstones, siltstones and mudstones. Here we report electrical resistivity and permeability measurements on core samples from all of these structural units at effective confining pressures up to 120 MPa. Electrical resistivity (~10 ohm-m) and permeability (10-21 to 10-22 m2) in the actively deforming zones were one to two orders of magnitude lower than the surrounding damage zone material, consistent with broader-scale observations from the downhole resistivity and seismic velocity logs. The higher porosity of the clay gouge, 2 to 8 times greater than that in the damage zone rocks, along with surface conduction were the principal factors contributing to the observed low resistivities. The high percentage of fine-grained clay in the deforming zones also greatly reduced permeability to values low enough to create a barrier to fluid flow across the fault. Together, resistivity and permeability data can be used to assess the hydrogeologic characteristics of the fault, key to understanding fault structure and strength. The low resistivities and strength measurements of the SAFOD core are consistent with observations of low resistivity clays that are often found in the principal slip zones of other active faults making resistivity logs a valuable tool for identifying these zones.

  19. Geometry and faults tectonic activity of the Okavango Rift Zone, Botswana: Evidence from magnetotelluric and electrical resistivity tomography imaging

    NASA Astrophysics Data System (ADS)

    Bufford, Kelsey Mosley; Atekwana, Estella A.; Abdelsalam, Mohamed G.; Shemang, Elijah; Atekwana, Eliot A.; Mickus, Kevin; Moidaki, Moikwathai; Modisi, Motsoptse P.; Molwalefhe, Loago

    2012-04-01

    We used Magnetotelluric (MT) and Electrical Resistivity Tomography (ERT) to investigate the geometry and nature of faults activity of the Okavango Rift Zone (ORZ) in Botswana, an incipient rift at the southern tip of the Southwestern Branch of the East African Rift System. The ORZ forms a subtle topographic depression filled with Quaternary lacustrine and fluvio-deltaic sediments and is bounded by NE-trending normal faults that are more prominent in the southeastern portion of the rift basin. An MT model from a regional (˜140 km) NW-SE trending MT transect shows that much of the rift basin is underlain by a broad asymmetrical low resistivity anomaly that slopes gently (˜1°) from NW to SE reaching a depth of ˜300 m. This anomaly suggests that faults in the southeastern part of the rift form a NW-dipping border fault zone and that the lacustrine and fluvio-deltaic sediments contain brackish to saline water filling the broad half-graben structure. Furthermore, MT and ERT models from detailed (4-13 km long) MT transects and resistivity profiles show that one border fault (Thamalakane) and two within-basin faults (Lecha and Tsau) in the southeastern part of the ORZ are characterized by a localized high conductivity anomaly while another border fault (Kunyere) lacks such an anomaly. These localized anomalies are attributed to channelized fresh surface water and saline groundwater percolating through these faults forming "fault zone conductors" and suggest actively displacing faults. The lack of a "fault zone conductor" in the Kunyere fault is interpreted as indicating diminishing displacement on this fault, and that strain was transferred to the Thamalakane fault further to the east. The fluids provide lubricant for the ORZ faults, hence preventing infrequent large magnitude earthquakes, but favoring frequent micro-seismicity.

  20. 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.

  1. Increased radon-222 in soil gas because of cumulative seismicity at active faults

    NASA Astrophysics Data System (ADS)

    Koike, Katsuaki; Yoshinaga, Tohru; Ueyama, Takayoshi; Asaue, Hisafumi

    2014-12-01

    This study demonstrates how the radon-222 (222Rn) concentration of soil gas at an active fault is sensitive to cumulative recent seismicity by examining seven active faults in western Japan. The 222Rn concentration was found to correlate well with the total earthquake energy within a 100-km radius of each fault. This phenomenon can probably be ascribed to the increase of pore pressure around the source depth of 222Rn in shallow soil caused by frequently induced strain. This increase in pore pressure can enhance the ascent velocity of 222Rn carrier gas as governed by Darcy's law. Anomalous 222Rn concentrations are likely to originate from high gas velocities, rather than increased accumulations of parent nuclides. The high velocities also can yield unusual young gas under the radioactive nonequilibrium condition of short elapsed time since 222Rn generation. The results suggest that ongoing seismicity in the vicinity of an active fault can cause accumulation of strain in shallow fault soils. Therefore, the 222Rn concentration is a possible gauge for the degree of strain accumulation.

  2. High Resolution Seismic Imaging of the Trench Canyon Fault Zone, Mono Lake, Northeastern California

    NASA Astrophysics Data System (ADS)

    Novick, M. W.; Jayko, A. S.; Roeske, S.; McClain, J. S.; Hart, P. E.; Boyle, M.

    2009-12-01

    High resolution seismic imaging of Mono Lake, located in northeastern California, has revealed an approximately northwest striking fault in the area to the west of aerially exposed Negit Volcano. This fault, henceforth referred to as the Trench Canyon Fault (TCF), has also been mapped onshore along a correlating strike as far north as Cedar Hill Volcano, located to the northeast of the lake on the California/Nevada border. Onshore, the TCF was mapped for approximately 10 kilometers using air photos, DEM images, and standard geologic pace and compass mapping techniques. The TCF post- dates the last glacial maximum, evidenced by the cutting of wave cut benches along Cedar Hill Volcano. Relict, non-historic shorelines, left by the steady evaporation of Mono Lake beginning approximately 13k, are also repeatedly cut by the fault. Additional evidence of fault presence includes sag ponds, pressure ridges, tectonically fractured rocks, and normal fault scarps found along strike. Offshore, DEM images show a northeast striking structure to the northwest of Negit Volcano, which is co-linear with the onshore TCF. High resolution seismic imaging of the structure, using an applied acoustic/SIG mini-sparker system, reveals steeply dipping Holocene sediments, as well as volcanic deposits from active vents which have erupted in the last 1000 years, offset by the fault. Detailed structural analysis of the previously unstudied Trench Canyon Fault (TFC) and faults in the Cedar Hill region of northern California, along with seismic studies of sediments beneath Mono Lake not only allow for a better comprehension of this minor fault system, but provide greater understanding of the larger and more complex Walker Lane Shear Zone. Fault analyses, combined and correlated with those from CHV, give a better understanding of how slip is transferred into the complicated Mina defection to the east, from the dextral and normal faults along the Sierra Nevada Range front.

  3. Cross-Cutting Faults

    NASA Technical Reports Server (NTRS)

    2005-01-01

    16 May 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows cross-cutting fault scarps among graben features in northern Tempe Terra. Graben form in regions where the crust of the planet has been extended; such features are common in the regions surrounding the vast 'Tharsis Bulge' on Mars.

    Location near: 43.7oN, 90.2oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Summer

  4. Characterising Active Fault Earthquake Sources Beneath the Coastal Environments of Christchurch and Wellington Cities, New Zealand, Using Seismic Reflection Profiles and Fault Displacement Analysis Techniques

    NASA Astrophysics Data System (ADS)

    Barnes, P.; Nodder, S.; Gorman, A. R.; Woelz, S.; Orpin, A. R.

    2014-12-01

    The coastal cities of Christchurch and Wellington, New Zealand, lie in different tectonic settings within the obliquely convergent Pacific-Australian plate boundary zone. Both cities have experienced damaging earthquakes in the last three years, which highlight the importance of locating and characterising hidden active faults close to urban areas. The devastating and geologically complex Canterbury earthquake sequence of 2010-2012 developed on the periphery of the plate boundary, and reactivated several previously unidentified strike-slip and reverse faults. Major aftershocks initially beneath land, generally migrated eastward over time, and finally advanced offshore into Pegasus Bay. A study of active submarine faulting beneath the bay highlights the role of inherited crustal structure and inversion tectonics. Marine seismic reflection data reveals that faults have very low slip rate and negligible post-glacial (<15 ka) deformation, which is consistent with inferred long recurrence intervals between large magnitude (Mw>6) earthquakes. Wellington City is surrounded by numerous high-slip rate strike-slip faults overlying the Hikurangi subduction zone. A dense network of secondary basement structures previously recognised throughout the region, mainly from tectonic geomorphology, have, until recently, been considered mostly inactive and excluded from seismic hazard models. We used high-resolution geophysical, bathymetric and sediment-core data to determine the structure, earthquake history and earthquake potential of a newly discovered active reverse fault beneath the inner reaches of Wellington Harbour. The fault has a slip rate of ~0.6 ± 0.3 mm/y, and a vertical displacement history indicating at least two large magnitude (Mw 6.3-7.1), surface-rupturing earthquakes in the last 10 ka. We infer that the fault extends southwards onshore beneath the city and potentially into Cook Strait, and represents a significant previously unrecognised seismic hazard.

  5. Neogene compressional deformation and possible thrust faulting in southwest Dominican Republic

    NASA Technical Reports Server (NTRS)

    Golombek, M. P.; Goreau, P.; Dixon, T. H.

    1985-01-01

    Analysis of regional and high resolution remote sensing data coupled with detailed field investigations indicates Neogene compressional deformation in the southwest Dominican Republic. Airborne synthetic aperture radar data and high resolution near infrared photography show folds in Tertiary sediments and possible thrust fault scarps implying NE to SW compression in the region. Large road cuts through the scarps allow study of otherwise poorly accessible, heavily vegetated karst terrain. Deformation increases toward scrap fronts where small bedding-plane thrust faults become more numerous. Analysis of mesoscopic faults with slickensides indicates compression oriented between N to S and E to W. The lowermost scarp has highly sheared fault breccia and undeformed frontal talus breccias implying it is the basal thrust into which the higher thrust faults sole. Thus, the scarps probably formed in a regional NE to SW compressional stress regime and are the toes of thrust sheets. Previous workers have suggested that these scarps are ancient shorelines. However, the gross morphology of the scarps differs substantially from well known erosional terraces on the north coast.

  6. 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. PMID:27873783

  7. 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.

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

    PubMed

    Halicioglu, Kerem; Ozener, Haluk

    2008-08-19

    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.

  9. Late Quaternary Deformation Along the Wairarapa Fault, North Island, New Zealand

    NASA Astrophysics Data System (ADS)

    Schermer, E. R.; Little, T. A.

    2006-12-01

    The Wairarapa fault, one of the largest active faults in the hanging wall of the Hikurangi subduction margin, New Zealand, averaged 16m dextral slip during the M >8.1 1855 earthquake. Previous workers inferred that uplift of 2.7m at the coast, observed by a surveyor in 1855, occurred on the southern continuation of the Wairarapa fault, the Wharekauhau (WH) thrust. New mapping, stratigraphic, and paloseismologic results from the WH thrust suggest the pattern of surface rupture in 1855 and earlier earthquakes was significantly different than previously inferred, requiring a more complex model for seismic hazard and tectonic evolution of the region. Detailed mapping indicates that the coastal segment of the WH thrust did not rupture the surface in 1855. The thrust, a major range-bounding fault, emplaces Mesozoic graywacke over ~80-100 ka last- interglacial marine, and lacustrine rocks, and in part coeval to younger alluvial gravels. Fault activity is indicated by facies and thickness changes. This older sequence is tilted and overlapped unconformably by a silt layer and much less deformed alluvial fan gravels that range in age from >22ka to <9 ka. These younger gravels were deposited in a valley incised across the fault scarp, in-filled this topography, and show no evidence of syn-depositional deformation. New 14C ages record a period of fault inactivity from 14 - 9 ka (calib yrs BP). The abandoned, overlapping fan surface is slightly deformed across the fault (15 m of folding- related throw). We infer that the thrust has propagated eastward in the subsurface, uplifting the abandoned WH fault, an inference that is supported by the pattern of Holocene incision. The only recent faulting consists of subvertical en echelon segments that have undergone minor dip-slip and dextral slip. A trench excavated across the fault scarp in late Holocene gravels suggests that the only fault along the trace of the WH thrust that broke within 3 m of the surface in 1855 was a minor

  10. Trench logs, terrestrial lidar system imagery, and radiocarbon data from the kilometer-62 site on the Greenville Fault, southeastern Alameda County, California, 2014

    USGS Publications Warehouse

    Lienkaemper, James J.; DeLong, Stephen B.; Avdievitch, Nikita N.; Pickering, Alexandra J; Guilderson, Thomas P.

    2015-01-01

    In 2014, we investigated an abrupt 8.5-meter (m), right-laterally deflected stream channel located near the Greenville Fault in southeastern Alameda County, California (-121.56224° E, 37.53430° N) that we discovered using 0.5-m resolution, 2011 aerial lidar imagery flown along the active fault trace. Prior to trenching we surveyed the site using a terrestrial lidar system (TLS) to document the exact geomorphic expression of this deflected stream channel before excavating a trench adjacent to it. We trenched perpendicular to the fault hoping to document the prehistoric history of earthquake ruptures along the fault. However, the alluvial stratigraphy that we document in these trench logs shows conclusively that this trench did not expose any active fault trace. Using other local geomorphic evidence for the fault location, a straight fault scarp immediately north of this stream projects slightly upslope of the west end of our trench and may be the actual location of the active fault trace. Five radiocarbon samples establish age control for the alluvial sequence documented in the trench, which may in the future be useful in constraining the long-term slip rate of the Greenville Fault. The deflection had been caused by an abrupt nontectonic termination of unit u30, a relatively thick (0.15–0.35 m) silt that is more erosion resistant than the adjacent cohesionless sand and gravel. 

  11. The Teton fault, Wyoming: Topographic signature, neotectonics, and mechanisms of deformation

    NASA Technical Reports Server (NTRS)

    Byrd, John O. D.; Smith, Robert B.; Geissman, John W.

    1994-01-01

    We integrated geophysical and geological methods to evalute the structural evolution of the active Teton normal fault, Wyoming, and its role in the development of the dramatic topography of Teton Range and Jackson Hole. Comparison of variations in surface offsets with the topographic expression of the Teton range crest and drainage divide, and the overall structure of the range, suggests that the effects ofpostglacial faulting cannot be discriminated from the influence of pre-extensional structures and differential; erosion on the footwall topography. In contrast, the effects of multiple scarp-forming normal faulting earthquakes are expressed by the anomalous drainage pattern and westward tilt of the hanging wall, Jackson Hole, toward the Teton fault. Kinematic boundary element fault models suggest that the westward tilt of the valley floor is the product of 110-125 m of displacement on a 45 deg-75 deg E dipping Teton fault in the past 25,000-75,000 years. Comparisons with historic normal faulting earthquake displacements imply that this range of displacement corresponds to 10-50, M greater than 7 scarp-forming earthquakes. A total throw of 2.5 to 3.5 km across the Teton fault is suggested by inverse ray-tracing and forward gravity models. These models also suggest that Laramide age structures have been offset across the Teton fault and obscure its geophysical signature but also continue to influence the structural and topographic expression of the footwall and hanging wall blocks. Paleomagnetic analyses of the approximately 2.0 Ma Huckelberry Ridge Tuff suggest that the overall westward tilt of the Teton Range is a result ofabout 10 deg of west side down tilt across the Teton fault since tuff emplacement. This suggests that much if not all of the throw across the Teton fault has accumulated in the past 2 m.y. Complex demagnetization and rock magnetic behavior and local emplacement of the Huckleberry Ridge Tuff on preexisting topogrpahy preclude determination of

  12. The Lower Tagus Valley (LTV) Fault System

    NASA Astrophysics Data System (ADS)

    Besana-Ostman, G. M.; Fereira, H.; Pinheiro, A.; Falcao Flor, A. P.; Nemser, E.; Villanova, S. P.; Fonseca, J. D.

    2010-05-01

    , aerial photographs, and river systems together with other remotely-sensed data. Active fault-related features that were identified include fault scarps, pressure ridges, pull-apart basin, saddles, and linear valleys. Limited ocular investigation has also been undertaken to verify modifications that post-date the aerial photos, quantify both elevation differences across the fault, and possibly evaluate the cumulative lateral displacements. Thus, the newly-identified traces of an active fault in the LTV corresponds with a left-lateral fault along the Lower Tagus floodplains striking parallel to the principal structural trend (NNE-SSW) in the region. This trace clearly indicates continued tectonic movement along the LTV fault during the Holocene. Taking into account the newly-mapped location and length of the active trace, trenching work is being planned to determine recurrence intervals along the LTV fault while further mapping of its possible extension and other related active structures are underway. Moreover, new estimates of slip rate along this structure will result from this study and can be used for an improved seismic hazard assessment for the region.

  13. 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.

  14. Middle to Late Pleistocene activity of the northern Matese fault system (southern Apennines, Italy)

    NASA Astrophysics Data System (ADS)

    Galli, Paolo; Giaccio, Biagio; Messina, Paolo; Peronace, Edoardo; Amato, Vincenzo; Naso, Giuseppe; Nomade, Sebastian; Pereira, Alison; Piscitelli, Sabatino; Bellanova, Jessica; Billi, Andrea; Blamart, Dominique; Galderisi, Antonio; Giocoli, Alessandro; Stabile, Tony; Thil, Francoise

    2017-03-01

    An integrated investigation including geological, geomorphological, geophysical and structural survey, tephra analyses, 14C and 40Ar/39Ar dating, as well as paleoseismic trenching along the N-Matese fault system is presented. The study allowed the characterization of the tectonic mobility of this structure as well as the associated Bojano basin sedimentary-tectonic evolution since the early Middle Pleistocene, providing also new clues concerning the fault historical activity and the associated Mw > 6.5 earthquakes. We have found lines of evidence for > 1 mm/yr slip rate along the presently buried Bojano fault during the mid Middle Pleistocene, and similar rates for the main fault segments paralleling the Matese flanks. The buried Bojano fault significantly slowed down during the last 300 kyr, ceasing its activity before the Holocene. In turn, the segments outcropping along the Matese flanks reactivated at the onset of Late Pleistocene, after a long period of quiescence (480-110 ka), with robust slip rates that would seem even accelerating in post LGM times. Paleoseismic data suggest the occurrence of four Mw > 6.6 earthquakes in the past 3 ka, three of which match the little known 280 BC event, and the devastating 1456 and 1805 earthquakes.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. GPS-derived slip rates of active faults in eastern Venezuela, along the southeastern Caribbean PBZ

    NASA Astrophysics Data System (ADS)

    Audemard, F. A.; Beck, C.; Jouanne, F.; Reinoza, C. E.; Fegag

    2013-05-01

    For over 20 years, GPS campaign measurements have been performed in eastern Venezuela, as well as in other areas of the country, by different scientific groups and in the frame of different either national or international efforts and/or projects, essentially aiming at the estimation of the rate of motion along the major Quaternary faults (i.e., Boconó, San Sebastián and El Pilar faults) composing the plate boundary zone (PBZ) between the Caribbean and South America, along onshore northern and western Venezuela. The slip rates and sense of slip of those major faults derived from the comparison of several GPS campaigns carried out through the years have confirmed the slip data (fault kinematics) previously derived from geologic data, through comprehensive neotectonic and paleoseismic studies mainly made by the FUNVISIS' Earth Sciences Dpt. staff. In a rough way, we could conclude that those faults are dextrally moving at a rate in the order of 10-12 mm/a. More recently, it has been shown that the El Pilar fault has a locking depth close to 10 km deep and that about half of the PBZ dextral motion is accommodated as creep, reducing the seismic hazard for northeastern Venezuela almost by half. On the contrary, in the near past, very little attention has been paid to the secondary active faulting in eastern Venezuela. In that sense, FUNVISIS, in collaboration with the Université de Savoie, started the monitoring of these secondary features by installing 36 brass benchmarks on bedrock in that region in 2003, which have been occupied 3 times, in late 2003 and 2005 and in early 2013. The comparison between the 2003 and 2005 occupations shows promising results, such as: a) The Charagato fault on Cubagua island is left-lateral with a slip rate of about 2 mm/a; b) slip vectors across the El Pilar fault tend to head to the ESE, suggesting that the tectonic regime is compressive transcurrent to transcurrent compressional (transpressional); c) The NW-SE-trending San Francisco

  1. Estimating Earthquake Magnitude from the Kentucky Bend Scarp in the New Madrid Seismic Zone Using Field Geomorphic Mapping and High-Resolution LiDAR Topography

    NASA Astrophysics Data System (ADS)

    Kelson, K. I.; Kirkendall, W. G.

    2014-12-01

    Recent suggestions that the 1811-1812 earthquakes in the New Madrid Seismic Zone (NMSZ) ranged from M6.8-7.0 versus M8.0 have implications for seismic hazard estimation in the central US. We more accurately identify the location of the NW-striking, NE-facing Kentucky Bend scarp along the northern Reelfoot fault, which is spatially associated with the Lake County uplift, contemporary seismicity, and changes in the Mississippi River from the February 1812 earthquake. We use 1m-resolution LiDAR hillshades and slope surfaces, aerial photography, soil surveys, and field geomorphic mapping to estimate the location, pattern, and amount of late Holocene coseismic surface deformation. We define eight late Holocene to historic fluvial deposits, and delineate younger alluvia that are progressively inset into older deposits on the upthrown, western side of the fault. Some younger, clayey deposits indicate past ponding against the scarp, perhaps following surface deformational events. The Reelfoot fault is represented by sinuous breaks-in-slope cutting across these fluvial deposits, locally coinciding with shallow faults identified via seismic reflection data (Woolery et al., 1999). The deformation pattern is consistent with NE-directed reverse faulting along single or multiple SW-dipping fault planes, and the complex pattern of fluvial deposition appears partially controlled by intermittent uplift. Six localities contain scarps across correlative deposits and allow evaluation of cumulative surface deformation from LiDAR-derived topographic profiles. Displacements range from 3.4±0.2 m, to 2.2±0.2 m, 1.4±0.3 m, and 0.6±0.1 m across four progressively younger surfaces. The spatial distribution of the profiles argues against the differences being a result of along-strike uplift variability. We attribute the lesser displacements of progressively younger deposits to recurrent surface deformation, but do not yet interpret these initial data with respect to possible earthquake

  2. 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.

  3. Identification of active faults in Abruzzo area (central Italy) through the analysis of geological, seismological and gravimetric data

    NASA Astrophysics Data System (ADS)

    Luiso, Paola; Paoletti, Valeria; Gaudiosi, Germana; Nappi, Rosa; Cella, Federico; Fedi, Maurizio

    2016-04-01

    Identification of active faults in abruzzo area (central italy) through the analysis of geological, seismological and gravimetric data The aim of this study is to identify and constrain the geometry of the seismogenic structures (active, outcropping and buried fault systems) of the Abruzzo area (central Italy), through an integrated analysis of geo-structural, seismic and gravimetric data. We generated three thematic: "faults", "earthquakes" and "gravimetric" data: i) The fault dataset consists of data extracted from the available structural and geological maps (ITHACA catalogue; the "Neotectonic Map of Italy" 1:500.000; several geological sheets 1:50.000 from ISPRA CARG project; the Geological Map 1:100.000 Sheet 1), and many geological studies. ii) The earthquakes datasets was created by merging the data from historical and instrumental Catalogues (CPTI04 and CPTI11; ISIDE - INGV). iii) The gravimetric datasets consists in the Multiscale Derivative Analysis (MDA) of the Bouguer anomaly map of the area, whose maxima show the presence of density lineaments. The merge of these datasets in GIS environment, highlighted four possible scenarios of correlation between faults, earthquakes and MDA maxima: 1) the existence of active faults, revealed by a strong correlation between epicentral location of seismic clusters, fault positions and MDA maxima; 2) the existence of buried active faults, highlighted by a good correlation between MDA maxima and epicentral positions, without correspondence with faults known from geological data; 3) the existence of inactive or silent faults, detected by the presence of faults reported in the geological datasets and literature which are associated with MDA maxima, without correlation of earthquakes; 4) the existence of faults not correlated with MDA maxima; this could be due to faults putting in contact two lithologies with a similar density. A comparison between seismic hypocentral locations and the fault geometry retrieved by DEXP

  4. The Nisi Fault as a key structure for understanding the active deformation of the NW Peloponnese, Greece

    NASA Astrophysics Data System (ADS)

    Zygouri, V.; Koukouvelas, I. K.; Kokkalas, S.; Xypolias, P.; Papadopoulos, G. A.

    2015-05-01

    The previously unknown Nisi Fault in NW Peloponnese was ruptured during the 2008 Movri Mountain earthquake attaining a maximum offset of 25 cm. The fault is interpreted as a branch of a flower structure above a blind strike-slip fault. We investigate the Nisi Fault seismotectonic evolution using morphotectonic analysis in order to determine whether the landscape is affected by tectonic forcing and paleoseismology to determine earthquake recurrence interval and fault slip rates. We applied several geomorphic indices, such as the asymmetry factor (AF), the stream length-gradient index (SL), the valley floor width to valley height ratio (Vf), the mountain-front sinuosity (Smf), the drainage basin shape (Bs) and the hypsometric curve (Hc), in four large drainage basins of the study area. The results show that fault-related vertical motions and the associated tilting influenced the drainage geometry and the landscape development. Values of stream-gradient indices (SL) are relatively high close to the fault trace. Mountain-front sinuosity (Smf) mean values along the fault zones range from 1.12 to 1.23. Valley floor width to valley height ratios (Vf) mean values along the studied fault range between 0.21 and 2.50. Drainage basin shape (BS) mean values along the fault range from 1.04 to 3.72. Lateral fault growth was likely achieved by propagation primarily towards north-northwestward. The paleoseismic history of the fault, investigated by a trench and 14C dating of seven samples, indicates two morphogenic earthquakes in the last 1 kyr. Therefore, we suggest that the Nisi Fault displays a slip rate on the order of 1 mm/yr and a recurrence interval ranging between 300 and 600 years. From a seismotectonic point of view, the fault is classified as high activity rate, with abundant but discontinuous geomorphic evidence of its activity. Other similar faults affecting the western Peloponnese can be envisaged with a similar procedure. Additionally, the seismic history and surface

  5. Active faulting in low- to moderate-seismicity regions: the SAFE project

    NASA Astrophysics Data System (ADS)

    Sebrier, M.; Safe Consortium

    2003-04-01

    SAFE (Slow Active Faults in Europe) is an EC-FP5 funded multidisciplinary effort which proposes an integrated European approach in identifying and characterizing active faults as input for evaluating seismic hazard in low- to moderate-seismicity regions. Seismically active western European regions are generally characterized by low hazard but high risk, due to the concentration of human and material properties with high vulnerability. Detecting, and then analysing, tectonic deformations that may lead to destructive earthquakes in such areas has to take into account three major limitations: - the typical climate of western Europe (heavy vegetation cover and/or erosion) ; - the subdued geomorphic signature of slowly deforming faults ; - the heavy modification of landscape by human activity. The main objective of SAFE, i.e., improving the assessment of seismic hazard through understanding of the mechanics and recurrence of active faults in slowly deforming regions, is achieved through four major steps : (1) extending geologic and geomorphic investigations of fault activity beyond the Holocene to take into account various time-windows; (2) developing an expert system that combines diverse lines of geologic, seismologic, geomorphic, and geophysical evidence to diagnose the existence and seismogenic potential of slow active faults; (3) delineating and characterising high seismic risk areas of western Europe, either from historical or geological/geomorphic evidence; (4) demonstrating and discussing the impact of the project results on risk assessment through a seismic scenario in the Basel-Mulhouse pilot area. To take properly into account known differences in source behavior, these goals are pursued both in extensional (Lower and Upper Rhine Graben, Catalan Coast) and compressional tectonic settings (southern Upper Rhine Graben, Po Plain, and Provence). Two arid compressional regions (SE Spain and Moroccan High Atlas) have also been selected to address the limitations

  6. Origin, Behavior and Texture of Clay Minerals in Mongolian Active Fault of Bogd and Comparison with SAFOD Fault Gouge

    NASA Astrophysics Data System (ADS)

    Wenk, H.; Buatier, M.; Chauvet, A.; Kanitpanyacharoen, W.

    2010-12-01

    Fault gouges are generally considered as the highly deformed zone corresponding to the localization of shear during seismic events. Clays are ubiquitous minerals in fault gouges but the origin is unclear. They can form as a result of break up of inherited phyllosilicates during faulting, or during co- or post- deformation events or even during interseismic creeping. In this study, we aim to characterize the origin and nature of the clay minerals, to observe the microtexture and preferred orientation of clay at various scales in order to understand the behavior of clay mineral in seismic faults. The investigation relied on x-ray powder patterns, SEM, TEM and high energy synchrotron x-ray diffraction. The major clay components are smectite, illite-smectite, illite-mica and kaolinite. Our observations suggest that the protolith and the fault rock of the Bogd and paleo-Bogd faults in Mongolia were highly altered by fluids. The fluid-rock interactions allows clay minerals to form and to precipitate kaolinite and smectite. Thus, newly formed clay minerals are heterogeneously distributed in the fault zone. The decrease of smectite component of the highly deformed samples suggests a dehydration process during deformation, leading to illite precipitation. From synchrotron diffraction images, volume fractions and preferred orientation were analyzed. Our analysis shows that texture strength of constituent clays is very weak ranging from 1.05 to 2.59 m.r.d., which is consistent with similar data from SAFOD fault gouge. The clays minerals of the Bogd fault favors the slip weakening behavior of the fault.

  7. 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

  8. 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

  9. Fault Branching

    NASA Astrophysics Data System (ADS)

    Dmowska, R.; Rice, J. R.; Poliakov, A. N.

    2001-12-01

    Theoretical stress analysis for a propagating shear rupture suggests that the propensity of the rupture path to branch is determined by rupture speed and by the preexisting stress state. See Poliakov, Dmowska and Rice (JGR, submitted April 2001, URL below). Deviatoric stresses near a mode II rupture tip are found to be much higher to both sides of the fault plane than directly ahead, when rupture speed becomes close to the Rayleigh speed. However, the actual pattern of predicted Coulomb failure on secondary faults is strongly dependent on the angle between the fault and the direction of maximum compression Smax in the pre-stress field. Steep Smax angles lead to more extensive failure on the extensional side, whereas shallow angles give comparable failure regions on both. Here we test such concepts against natural examples. For crustal thrust faults we may assume that Smax is horizontal. Thus nucleation on a steeply dipping plane, like the 53 ° dip for the 1971 San Fernando earthquake, is consistent with rupture path kinking to the extensional side, as inferred. Nucleation on a shallow dip, like for the 12 ° -18 ° of the 1985 Kettleman Hills event, should activate both sides, as seems consistent with aftershock patterns. Similarly, in a strike slip example, Smax is inferred to be at approximately 60 ° with the Johnson Valley fault where it branched to the extensional side onto the Landers-Kickapoo fault in the 1992 event, and this too is consistent. Further, geological examination of the activation of secondary fault features along the Johnson Valley fault and the Homestead Valley fault consistently shows that most activity occurs on the extensional side. Another strike-slip example is the Imperial Valley 1979 earthquake. The approximate Smax direction is north-south, at around 35 ° with the main fault, where it branched, on the extensional side, onto Brawley fault, again interpretable with the concepts developed.

  10. Logs and Geologic Data from a Paleoseismic Investigation of the Susitna Glacier fault, Central Alaska Range, Alaska

    USGS Publications Warehouse

    Personius, Stephen F.; Crone, Anthony J.; Burns, Patricia A.C.; Beget, James E.; Seitz, Gordon G.; Bemis, Sean P.

    2010-01-01

    This report contains field and laboratory data from a paleoseismic study of the Susitna Glacier fault, Alaska. The initial M 7.2 subevent of the November 3, 2002, M 7.9 Denali fault earthquake sequence produced a 48-km-long set of complex fault scarps, folds, and aligned landslides on the previously unknown, north-dipping Susitna Glacier thrust fault along the southern margin of the Alaska Range in central Alaska. Most of the 2002 folds and fault scarps are 1-3 m high, implying dip-slip thrust offsets (assuming a near-surface fault dip of approximately 20 degrees)of 3-5 m. Locally, some of the 2002 ruptures were superimposed on preexisting scarps that have as much as 5-10 m of vertical separation and are evidence of previous surface-rupturing earthquakes on the Susitna Glacier fault. In 2003-2005, we focused follow-up studies on several of the large scarps at the 'Wet fan' site in the central part of the 2002 rupture to determine the pre-2002 history of large surface-rupturing earthquakes on the fault. We chose this site for several reasons: (1) the presence of pre-2002 thrust- and normal-fault scarps on a gently sloping, post-glacial alluvial fan; (2) nearby natural exposures of underlying fan sediments revealed fine-grained fluvial silts with peat layers and volcanic ash beds useful for chronological control; and (3) a lack of permafrost to a depth of more than 1 m. Our studies included detailed mapping, fault-scarp profiling, and logging of three hand-excavated trenches. We were forced to restrict our excavations to 1- to 2-m-high splay faults and folds because the primary 2002 ruptures mostly were superimposed on such large scarps that it was impossible to hand dig through the hanging wall to expose the fault plane. Additional complications are the pervasive effects of cryogenic processes (mainly solifluction) that can mask or mimic tectonic deformation. The purpose of this report is to present photomosaics, trench logs, scarp profiles, and fault slip

  11. 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.

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

    USGS Publications Warehouse

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

    2013-01-01

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

  13. Holocene tectonics and fault reactivation in the foothills of the north Cascade Mountains, Washington

    USGS Publications Warehouse

    Sherrod, Brian L.; Barnett, Elizabeth; Schermer, Elizabeth; Kelsey, Harvey M.; Hughes, Jonathan; Foit, Franklin F.; Weaver, Craig S.; Haugerud, Ralph; Hyatt, Tim

    2013-01-01

    We use LiDAR imagery to identify two fault scarps on latest Pleistocene glacial outwash deposits along the North Fork Nooksack River in Whatcom County, Washington (United States). Mapping and paleoseismic investigation of these previously unknown scarps provide constraints on the earthquake history and seismic hazard in the northern Puget Lowland. The Kendall scarp lies along the mapped trace of the Boulder Creek fault, a south-dipping Tertiary normal fault, and the Canyon Creek scarp lies in close proximity to the south-dipping Canyon Creek fault and the south-dipping Glacier Extensional fault. Both scarps are south-side-up, opposite the sense of displacement observed on the nearby bedrock faults. Trenches excavated across these scarps exposed folded and faulted late Quaternary glacial outwash, locally dated between ca. 12 and 13 ka, and Holocene buried soils and scarp colluvium. Reverse and oblique faulting of the soils and colluvial deposits indicates at least two late Holocene earthquakes, while folding of the glacial outwash prior to formation of the post-glacial soil suggests an earlier Holocene earthquake. Abrupt changes in bed thickness across faults in the Canyon Creek excavation suggest a lateral component of slip. Sediments in a wetland adjacent to the Kendall scarp record three pond-forming episodes during the Holocene—we infer that surface ruptures on the Boulder Creek fault during past earthquakes temporarily blocked the stream channel and created an ephemeral lake. The Boulder Creek and Canyon Creek faults formed in the early to mid-Tertiary as normal faults and likely lay dormant until reactivated as reverse faults in a new stress regime. The most recent earthquakes—each likely Mw > 6.3 and dating to ca. 8050–7250 calendar years B.P. (cal yr B.P.), 3190–2980 cal. yr B.P., and 910–740 cal. yr B.P.—demonstrate that reverse faulting in the northern Puget Lowland poses a hazard to urban areas between Seattle (Washington) and Vancouver

  14. Threshold of Geomorphic Detectability Estimated from Geologic Observations of Active Slow-Slipping Strike-Slip Faults

    NASA Astrophysics Data System (ADS)

    Kaneda, H.

    2002-12-01

    Sources of catastrophic earthquakes include not only major active faults, but also slow-slipping ones. However, geomorphic characteristics and long-term seismic behavior of slow-slipping faults have not been well understood, although intensive paleoseismic studies were carried out after the unexpected 1992 Landers and 1999 Hector Mine earthquakes. Two Japanese surface faulting earthquakes on slow-slipping strike-slip faults (the 1927 Mw=7.0 Kita-Tango and 1943 Mw=7.0 Tottori earthquakes) provided good opportunity to examine these problems. Analysis of coseismic surface slip, cumulative geomorphic expressions, and paleoseismicity for these two events not only supports a characteristic-slip behavior for these faults, but also suggests a concept of threshold of geomorphic detectability for intramontane strike-slip faults, which must be exceeded in order that progressive coseismic surface offsets can be preserved against surface processes as detectable systematic deflections of channels and ridge crests. The determined threshold slip rates for these examples are in the range of 0.06-0.13 mm/yr, which can be a quantitative explanation for an extremely small number of mapped active faults with slip rates of less than 0.1 mm/yr in Japan islands. On the contrary, the threshold of geomorphic detectability is probably negligible in arid regions where denudation rate would be extremely low. To date, the issue of geomorphologically undetectable active faults has been that of blind thrust faults buried beneath thick sediments, but another type of blind active faults or fault segments can exist in humid and mountainous regions. In spite of their low slip rates and long recurrence intervals, their potential presence must be considered, especially in regions under the tectonically undeveloped regime, where regional strain is accommodated by many scattered slow-slipping faults.

  15. Late Pleistocene intraplate extension of the Central Anatolian Plateau, Turkey: Inferences from cosmogenic exposure dating of alluvial fan, landslide and moraine surfaces along the Ecemiş Fault Zone

    NASA Astrophysics Data System (ADS)

    Yildirim, Cengiz; Akif Sarikaya, Mehmet; Ciner, Attila

    2016-04-01

    Late Pleistocene activity of the Ecemiş Fault Zone is integrally tied to ongoing intraplate crustal deformation in the Central Anatolian Plateau. Here we document the vertical displacement, slip rate, extension rate, and geochronology of normal faults within a narrow strip along the main strand of the fault zone. The Kartal, Cevizlik and Lorut faults are normal faults that have evident surface expression within the strip. Terrestrial cosmogenic nuclide geochronology reveals that the Kartal Fault deformed a 104.2 ± 16.5 ka alluvial fan surface and the Cevizlik Fault deformed 21.9 ± 1.8 ka glacial moraine and talus fan surfaces. The Cevizlik Fault delimits mountain front of the Aladaglar and forms >1 km relief. Our topographic surveys indicate 13.1 ± 1.4 m surface breaking vertical displacements along Cevizlik Faults, respectively. Accordingly, we suggest a 0.60 ± 0.08 mm a-1 slip rate and 0.35 ± 0.05 mm a-1 extension rate for the last 21.9 ± 1.8 ka on the Cevizlik Fault. Taken together with other structural observations in the region, we believe that the Cevizlik, Kartal ve Lorut faults are an integral part of intraplate crustal deformation in Central Anatolia. They imply that intraplate structures such as the Ecemiş Fault Zone may change their mode through time; presently, the Ecemiş Fault Zone has been deformed predominantly by normal faults. The presence of steep preserved fault scarps along the Kartal, Cevizlik and Lorut faults point to surface breaking normal faulting away from the main strand and particularly signify that these structures need to be taken into account for regional seismic hazard assessments. This project is supported by The Scientific and Technological Research Council of Turkey (TUBITAK, Grant number: 112Y087).

  16. SAFE-Tools: a Web-based application for identifying active faults

    NASA Astrophysics Data System (ADS)

    Atakan, K.; Sebrier, M.; Camelbeeck, T.; Siame, L.; Valensise, G.; Winter, T.

    2003-04-01

    Recognition of active faults, particularly in low seismicity regions such as Western Europe, has been a subject puzzling seismologists for many years. These regions are generally characterized by low-hazard but high-risk, due to the concentration of human and material properties with high-vulnerability. Detecting tectonic deformations that may lead to destructive earthquakes in such areas requires innovative research strategies that suit climate, slowly deforming fault, and heavily human-modified areas. The variety and amount of information involved in the characterization of slowly deforming faults are in general disseminated in several institutions with no easy access to. This information should be gathered, parameterized and stored in a way that make them feasible to be used in seismic hazard studies. In this sense, within the framework of the European project SAFE (Slow Active Faults in Europe; EVG1-2000-22005) a Web-based application (SAFE-Tools) for diagnosing slow active faults is developed. The basic design of the SAFE-Tools (SAFE-T) is based on server-client architecture, with data communication and visualization occurring through the Internet. The system is developed using the Java programming language and operates through an Internet browser. SAFE-T handles both parametric and graphical (image) data with a display and manipulation capability of pre-prepared data sets from a relational database with an interactive processing capacity all conducted through applets. A distributed database structure is developed opening a possibility for a network of interconnected servers. Layers of graphical data (e.g. geological maps, DEM images etc.) and sets of parametric data (e.g. historical or instrumental earthquake catalogues) are entered to the system either through an interactive process using HTML-forms, or as a bulk entry. Data are stored as geographical co-ordinate points with different attributes in the relational database. For identification of active faults

  17. 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.

  18. 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

  19. Can pocket gopher burrowing explain the long-term evolution of uplifted marine terrace scarps?

    NASA Astrophysics Data System (ADS)

    Loso, M. G.; Anderson, R. S.; Doak, D. F.

    2009-12-01

    For over a century, geomorphologists have sought to understand and model the mechanisms that control long-term evolution of soil-mantled hillslopes. Early workers acknowledged the importance of biological processes like soil anchoring by plant roots and bioturbation by burrowing animals, but only recently have substantial efforts been made to incorporate these factors into quantitative models. Several of these recent efforts have focused on the effects of burrowing by pocket gophers (Thomomys bottae). Field studies have documented the impressive volumes of sediment moved by these common fossorial mammals, and hillslope evolution models that implicitly reflect gopher activity (for example in sediment transport equations that are nonlinear functions of slope and soil depth) are increasingly successful in reproducing the steady-state form of gophered landscapes. But are gopher burrows simply one among many effective slope transport processes, or in some landscapes might they be—as some have suggested—the primary agent of sediment transport? To answer this question, we use a combination of field measurements, published data, and numerical modeling to determine whether modern rates of gopher-induced sediment transport are sufficient, over the long-term, to explain the observed evolution of scarps that separate a flight of four tectonically uplifted marine terraces north of Santa Cruz, California. The terraces are well-dated and the initial forms of the scarps—all former sea cliffs—are well constrained. We use two numerical models: a small-scale mound model that calculates the slope-dependent transport of sediment by a single gopher burrow, and a large-scale hillslope model that relies on a given distribution of gopher mounds to simulate the long-term evolution of these scarps from rocky sea cliffs to gentle, soil-mantled hillslopes. Our mound model accounts for the orientation and dimensions of a subterranean foraging tunnel and its associated

  20. The three-dimensional pattern of crustal deformation associated with active normal fault systems observed using continuous GPS geodesy

    NASA Astrophysics Data System (ADS)

    Bennett, R. A.; Hreinsdottir, S.

    2009-12-01

    Geological examples of shallow dipping normal faults with large displacements are exposed at numerous locations throughout the world and it is widely recognized that extensional deformation at brittle crustal levels is most efficiently accomplished by slip across such structures. It has previously been shown that lower dip angles reduce the regional stresses required to drive large horizontal displacements. Nevertheless, the traditional theory of fault mechanics—based on Anderson’s classification of stress regimes, the Coulomb failure criterion, and Byerlee’s friction law—precludes such faults from slipping at low angle. Observational support for this traditional theory includes the absence of large unequivocally low-angle normal fault earthquakes in the global catalog; all well-determined normal fault earthquakes appear to have occurred on moderate to steeply dipping planes. However, precise measurements of 3D crustal motions based on continuous GPS in central Italy and Utah reveal deformation patterns across active normal fault systems that are inconsistent with active slip across steeply dipping planes. Instead, the combination of observed horizontal and vertical surface motions are consistent with slip across low angle surfaces independently imaged in the subsurface by seismic reflection and other geophysical data. For the Alto Tiberina fault in central Italy, active aseismic creep occurs at shallow crustal levels, most likely within the brittle-frictional regime at which Andersonian-Byerlee fault mechanics should be applicable. The actively creeping portion of the fault inferred using GPS geodesy correlates well with the observed pattern of micro-seismicity, which concentrates along the inferred subsurface fault plane. GPS measurements across the greater Wasatch fault zone in the vicinity of Salt Lake City, Utah, reveal crustal motions consistent with aseismic displacement across a shallow dipping fault or sub-horizontal shear zone at mid

  1. 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

  2. Active faults and induced seismicity in the Val d'Agri area (Southern Apennines, Italy)

    NASA Astrophysics Data System (ADS)

    Valoroso, L.; Improta, L.; Chiaraluce, L.; Di Stefano, R.; Ferranti, L.; Govoni, A.; Chiarabba, C.

    2009-07-01

    The NW-SE trending Val d'Agri extensional basin is one of the regions in Italy with the highest seismogenic potential. Field data do not univocally define which of the fault systems bordering the basin on the two opposite sides is accommodating the active deformation. In this study, we detect and locate, by using an automatic picking procedure, almost 2000 low-magnitude earthquakes (-0.2 < ML < 2.7) recorded by a dense network during a 13-months-long seismic experiment. Events are mostly located along the southwestern flank of the basin. To the south, intense swarm-type microseismicity defines a major cluster ~5km wide from 1 to 5km depth. To the west, a clear alignment of events, characterized by normal faulting kinematics, defines a NE-dipping normal fault between 1 and 6km depth. The upward continuation of this structure, ~5km long, matches a mapped active normal fault recognized by field and palaeoseismological surveys. A temporal correlation found between the intense swarm-type microseismicity and the water level changes in the nearby artificial Pertusillo lake suggests that this seismicity is reservoir-induced.

  3. 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

  4. Characterizing Recent Slip on the Kuikui Fault, a Link Between the Green Valley and Bartlett Springs Fault Zones, Wilson Valley, Northern California.

    NASA Astrophysics Data System (ADS)

    Lienkaemper, J. J.; DeLong, S. B.; McPherson, R. C.; Mielke, J.; Avdievitch, N.; Pickering, A.; Lloyd, C.

    2014-12-01

    The Green Valley and Bartlett Springs faults (GVF-BSF) together form the third largest branch of the dextral San Andreas transform fault system in northern California. Wilson Valley lies at the center of a tectonic pull-apart basin formed in the 2.5-km stepover between the Hunting Creek fault (northernmost section of the GVF) and the Highway-20 section of the BSF. A major regional drainage, Cache Creek flows through this depression and has been offset ~6 km right-laterally by the GVF-BSF during the Quaternary. We recently discovered the Kuikui fault, a dextral-oblique slip fault within the stepover, using high-resolution imagery from LiDAR acquired by USGS in 2011 along major northern California fault zones (ARRA11_USGS, DOI: 10.5069/G9H70CRD, http://dx.doi.org/10.5069/G9H70CRD). The Kuikui fault is ~2-3 km in length and forms steep, well-preserved scarps up to ~2.5 m high. It has only subtle expression of dextral slip, so its ratio of dip slip to strike slip is uncertain. Any evidence of large paleoearthquakes in the Wilson Valley stepover might indicate rupture of either the GVF or the BSF or both together, and timing information could be used to correlate events with other paleoseismic sites on the fault system. Additionally, fault creep has been documented on both the Highway 20 and Hunting Creek fault sections, so that any fault offset on the Kuikui fault might also include some aseismic slip. Because wilderness regulations required manual excavation, several participants from USGS, HSU, other colleagues and volunteers together dug an 8-m long by ≤1 m deep trench by hand to expose faulting in thin layers of alluvium deposited across the Kuikui fault. The youngest, and currently active soil layer is vertically offset by a minimum of 7 cm on a single fault strand. A much broader fault zone suggests larger movement has occurred. This exposure did not allow us to discriminate whether slip occurred as creep or by dynamic rupture. Future additional exposures may

  5. The susitna glacier thrust fault: Characteristics of surface ruptures on the fault that initiated the 2002 denali fault earthquake

    USGS Publications Warehouse

    Crone, A.J.; Personius, S.F.; Craw, P.A.; Haeussler, P.J.; Staft, L.A.

    2004-01-01

    The 3 November 2002 Mw 7.9 Denali fault earthquake sequence initiated on the newly discovered Susitna Glacier thrust fault and caused 48 km of surface rupture. Rupture of the Susitna Glacier fault generated scarps on ice of the Susitna and West Fork glaciers and on tundra and surficial deposits along the southern front of the central Alaska Range. Based on detailed mapping, 27 topographic profiles, and field observations, we document the characteristics and slip distribution of the 2002 ruptures and describe evidence of pre-2002 ruptures on the fault. The 2002 surface faulting produced structures that range from simple folds on a single trace to complex thrust-fault ruptures and pressure ridges on multiple, sinuous strands. The deformation zone is locally more than 1 km wide. We measured a maximum vertical displacement of 5.4 m on the south-directed main thrust. North-directed backthrusts have more than 4 m of surface offset. We measured a well-constrained near-surface fault dip of about 19?? at one site, which is considerably less than seismologically determined values of 35??-48??. Surface-rupture data yield an estimated magnitude of Mw 7.3 for the fault, which is similar to the seismological value of Mw 7.2. Comparison of field and seismological data suggest that the Susitna Glacier fault is part of a large positive flower structure associated with northwest-directed transpressive deformation on the Denali fault. Prehistoric scarps are evidence of previous rupture of the Sustina Glacier fault, but additional work is needed to determine if past failures of the Susitna Glacier fault have consistently induced rupture of the Denali fault.

  6. 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

  7. Dense seismic networks as a tool to characterize active faulting in regions of slow deformation

    NASA Astrophysics Data System (ADS)

    Custódio, Susana; Arroucau, Pierre; Carrilho, Fernando; Cesca, Simone; Dias, Nuno; Matos, Catarina; Vales, Dina

    2016-04-01

    The theory of plate tectonics states that the relative motion between lithospheric plates is accommodated at plate boundaries, where earthquakes occur on long faults. However, earthquakes with a wide range of magnitudes also occur both off plate boundaries, in intra-plate settings, and along discontinuous, diffuse plate boundaries. These settings are characterized by low rates of lithospheric deformation. A fundamental limitation in the study of slowly deforming regions is the lack of high-quality observations. In these regions, earthquake catalogs have traditionally displayed diffuse seismicity patterns. The location, geometry and activity rate of faults - all basic parameters for understanding fault dynamics - are usually poorly known. The dense seismic networks deployed in the last years around the world have opened new windows in observational seismology. Although high-magnitude earthquakes are rare in regions of slow deformation, low-magnitude earthquakes are well observable on the time-scale of these deployments. In this presentation, we will show how data from dense seismic deployments can be used to characterize faulting in regions of slow deformation. In particular, we will present the case study of western Iberia, a region undergoing low-rate deformation and which has generated some of the largest earthquakes in Europe, both intraplate (mainland) and interplate (offshore). The methods that we employ include automated earthquake detection methods to lower the completeness magnitude of catalogs, earthquake relocations, focal mechanisms patterns, waveform similarity and clustering analysis.

  8. 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

    The Chittagong-Myanmar fold belt (CMFB), located in eastern Bangladesh, eastern India and western Myanmar, accommodates east-west shortening at the India-Burma plate boundary. Oblique subduction of the Indian Plate beneath the Burma Plate since the Eocene has led to the development of a large accretionary prism complex, creating a series of north-south trending folds. A continuous sediment record from ~55 Ma to the present has been deposited in the Bengal Basin by the Ganges-Brahmaputra-Meghna rivers, providing an opportunity to learn about the history of tectonic deformation and activity in this fold-and-thrust belt. Surface mapping indicates that the fold-and-thrust belt is characterized by extensive N-S-trending anticlines and synclines in a belt ~150-200 km wide. Seismic reflection profiles from the Chittagong and Chittagong Hill Tracts, Bangladesh, indicate that the anticlines mapped at the surface narrow with depth and extend to ~3.0 seconds TWTT (two-way travel time), or ~6.0 km. The folds of Chittagong and Chittagong Hill Tracts are characterized by doubly plunging box-shaped en-echelon anticlines separated by wide synclines. The seismic data suggest that some of these anticlines are cored by thrust fault ramps that extend to a large-scale décollement that dips gently to the east. Other anticlines may be the result of detachment folding from the same décollement. The décollement likely deepens to the east and intersects with the northerly-trending, oblique-slip Kaladan fault. The CMFB region is bounded to the north by the north-dipping Dauki fault and the Shillong Plateau. The tectonic transition from a wide band of E-W shortening in the south to a narrow zone of N-S shortening along the Dauki fault is poorly understood. We integrate surface and subsurface datasets, including topography, geological maps, seismicity, and industry seismic reflection profiles, into a 3D modeling environment and construct initial 3D surfaces of the major faults in this

  9. Active Features of Guguan-Guizhen Fault at the Northeast Margin of Qinghai-Tibet Block since Late Quaternary

    NASA Astrophysics Data System (ADS)

    Shi, Yaqin; Feng, Xijie; Li, Gaoyang; Ma, Ji; Li, Miao; Zhang, Yi

    2015-04-01

    Guguan-Guizhen fault is located at the northeast margin of Qinghai-Tibet Block and northwest margin of Ordos Block; it is the boundary of the two blocks, and one of the multiple faults of northwest Haiyuan-Liupanshan-Baoji fault zone. Guguan-Guizhen fault starts from Putuo Village, Huating County, Gansu Province, and goes through Badu Town, Long County in Shaanxi Province ends in Guozhen Town in Baoji City, Shaanxi Province. The fault has a full length of about 130km with the strike of 310-330°, the dip of SW and the rake of 50-60°, which is a sinistral slip reverse fault in the north part, and a sinistral slip normal fault in the southeast part. Guguan-Guizhen fault has a clear liner structure in satellite images and significant landform elevation difference with a maximum difference of 80m, and is higher in the east lower in the west. The northwest side of Guguan-Guizhen fault is composed of purplish-red Lower Cretaceous sandstones and river terrace; the northeast side is composed of Ordovician Limestone. Shigou, Piliang, Songjiashan, Tianjiagou and Chenjiagou fault profiles are found to the south of Badu Village. After 14C and optically stimulated luminescence dating, the fault does not dislocate the stratum since late Pleistocene (90.5±4.4ka) in Shigou, Piliang and Songjiashan fault profiles, and does not dislocate the cobble layer of Holocene first terrace and recent sliderock (3180±30 BP). But the fault dislocated the stratum of middle Pleistocene in some of the fault profiles. All the evidences above indicate that the fault is active in middle Pleistocene, and being silence since late Pleistocene. It might be active in Holocene to the north of Badu Village due to collapses are found in a certain area. The cause of these collapses is Qinlong M6-7 earthquake in 600 A.D., and might be relevant with Guguan-Guizhen fault after analysis of the scale, feature and age determination of the collapse. If any seismic surface rupture and ancient earthquake traces

  10. Large mid-Holocene and late Pleistocene earthquakes on the Oquirrh fault zone, Utah

    USGS Publications Warehouse

    Olig, S.S.; Lund, W.R.; Black, B.D.

    1994-01-01

    The Oquirrh fault zone is a range-front normal fault that bounds the east side of Tooele Valley and it has long been recognized as a potential source for large earthquakes that pose a significant hazard to population centers along the Wasatch Front in central Utah. Scarps of the Oquirrh fault zone offset the Provo shoreline of Lake Bonneville and previous studies of scarp morphology suggested that the most recent surface-faulting earthquake occurred between 9000 and 13,500 years ago. Based on a potential rupture length of 12 to 21 km from previous mapping, moment magnitude (Mw) estimates for this event range from 6.3 to 6.6 In contrast, our results from detailed mapping and trench excavations at two sites indicate that the most-recent event actually occurred between 4300 and 6900 yr B.P. (4800 and 7900 cal B.P.) and net vertical displacements were 2.2 to 2.7 m, much larger than expected considering estimated rupture lengths for this event. Empirical relations between magnitude and displacement yield Mw 7.0 to 7.2. A few, short discontinuous fault scarps as far south as Stockton, Utah have been identified in a recent mapping investigation and our results suggest that they may be part of the Oquirrh fault zone, increasing the total fault length to 32 km. These results emphasize the importance of integrating stratigraphic and geomorphic information in fault investigations for earthquake hazard evaluations. At both the Big Canyon and Pole Canyon sites, trenches exposed faulted Lake Bonneville sediments and thick wedges of fault-scarp derived colluvium associated with the most-recent event. Bulk sediment samples from a faulted debris-flow deposit at the Big Canyon site yield radiocarbon ages of 7650 ?? 90 yr B.P. and 6840 ?? 100 yr B.P. (all lab errors are ??1??). A bulk sediment sample from unfaulted fluvial deposits that bury the fault scarp yield a radiocarbon age estimate of 4340 ?? 60 yr B.P. Stratigraphic evidence for a pre-Bonneville lake cycle penultimate

  11. Fault Diagnosis Based on Chemical Sensor Data with an Active Deep Neural Network.

    PubMed

    Jiang, Peng; Hu, Zhixin; Liu, Jun; Yu, Shanen; Wu, Feng

    2016-10-13

    Big sensor data provide significant potential for chemical fault diagnosis, which involves the baseline values of security, stability and reliability in chemical processes. A deep neural network (DNN) with novel active learning for inducing chemical fault diagnosis is presented in this study. It is a method using large amount of chemical sensor data, which is a combination of deep learning and active learning criterion to target the difficulty of consecutive fault diagnosis. DNN with deep architectures, instead of shallow ones, could be developed through deep learning to learn a suitable feature representation from raw sensor data in an unsupervised manner using stacked denoising auto-encoder (SDAE) and work through a layer-by-layer successive learning process. The features are added to the top Softmax regression layer to construct the discriminative fault characteristics for diagnosis in a supervised manner. Considering the expensive and time consuming labeling of sensor data in chemical applications, in contrast to the available methods, we employ a novel active learning criterion for the particularity of chemical processes, which is a combination of Best vs. Second Best criterion (BvSB) and a Lowest False Positive criterion (LFP), for further fine-tuning of diagnosis model in an active manner rather than passive manner. That is, we allow models to rank the most informative sensor data to be labeled for updating the DNN parameters during the interaction phase. The effectiveness of the proposed method is validated in two well-known industrial datasets. Results indicate that the proposed method can obtain superior diagnosis accuracy and provide significant performance improvement in accuracy and false positive rate with less labeled chemical sensor data by further active learning compared with existing methods.

  12. Fault Diagnosis Based on Chemical Sensor Data with an Active Deep Neural Network

    PubMed Central

    Jiang, Peng; Hu, Zhixin; Liu, Jun; Yu, Shanen; Wu, Feng

    2016-01-01

    Big sensor data provide significant potential for chemical fault diagnosis, which involves the baseline values of security, stability and reliability in chemical processes. A deep neural network (DNN) with novel active learning for inducing chemical fault diagnosis is presented in this study. It is a method using large amount of chemical sensor data, which is a combination of deep learning and active learning criterion to target the difficulty of consecutive fault diagnosis. DNN with deep architectures, instead of shallow ones, could be developed through deep learning to learn a suitable feature representation from raw sensor data in an unsupervised manner using stacked denoising auto-encoder (SDAE) and work through a layer-by-layer successive learning process. The features are added to the top Softmax regression layer to construct the discriminative fault characteristics for diagnosis in a supervised manner. Considering the expensive and time consuming labeling of sensor data in chemical applications, in contrast to the available methods, we employ a novel active learning criterion for the particularity of chemical processes, which is a combination of Best vs. Second Best criterion (BvSB) and a Lowest False Positive criterion (LFP), for further fine-tuning of diagnosis model in an active manner rather than passive manner. That is, we allow models to rank the most informative sensor data to be labeled for updating the DNN parameters during the interaction phase. The effectiveness of the proposed method is validated in two well-known industrial datasets. Results indicate that the proposed method can obtain superior diagnosis accuracy and provide significant performance improvement in accuracy and false positive rate with less labeled chemical sensor data by further active learning compared with existing methods. PMID:27754386

  13. Possible young faulting in the Piedmont of North-Central Colorado

    USGS Publications Warehouse

    Shawe, D.R.; Steven, T.A.; Knepper, D.H.

    2008-01-01

    We interpret several linear topographic scarps in both alluvium and bedrock in the piedmont of north-central Colorado between Denver and Wyoming to be fault scarps. The scarps, ranging from tens of feet to about 150 ft in height, bound trough-like (graben and half-graben) forms. These features coincide in part with the floodplains of the South Platte River and Lone Tree, St. Vrain, and Boulder Creeks. Details of their topographic forms as well as relations of the Holocene and Pleistocene gravels underlying the floodplains suggest to us that the forms resulted from Quaternary tectonism.

  14. 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.

  15. 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

  16. Origin of active blind-thrust faults in the southern Inner California Borderlands

    NASA Astrophysics Data System (ADS)

    Rivero-Ramirez, Carlos Alberto

    This dissertation describes the origins, three-dimensional geometry, slip history and present activity of a regional system of blind-thrust faults located in the Inner California Borderlands, and analyses the new earthquake scenarios they imply for the nearby coastal region of southern California. Chapter 1 is an overview of the main observations and inferences derived from geophysical data (seismic reflection profiles, well information, and seismicity) and coastal tectonics studies that are used to document the reactivation of two regional, low-angle Miocene detachments---the Oceanside and the Thirtymile faults. These active blind-thrusts comprise the Inner California Blind-Thrust System. The paper is co-authored by Prof. John H. Shaw (Harvard University) and Prof. Karl Muller (University of Colorado), and was published in the journal Geology. In this paper we associate the 1986 (ML 5.3) Oceanside earthquake and uplift of coastal marine terraces with activity on these blind-thrust faults, demonstrating their current activity and earthquake potential. We also describe the structural interactions of the blind-thrust system with regional strike-slip fault zones, and propose new earthquake hazards scenarios for the Inner California Borderlands based on these interactions. Chapter 2 presents a methodology used to generate regional 3D velocity models that allows converting seismic reflection data and derived geological surfaces into the depth domain. This chapter is co-authored with Dr. Peter Suss (University of Tubingen) and Prof. John H. Shaw (Harvard University), who developed aspects of the methodology used here in their velocity modeling of the Los Angeles basin. In our study, geologic constraints are employed to guide the interpolation of velocity structure in the Inner California Borderlands, yielding a comprehensive 3D velocity model that is consistent with the structural and stratigraphic architectures of the offshore basins. The need to properly scale time

  17. Paleoseismologic studies of the Pajarito fault system, western margin of the Rio Grande rift near Los Alamos, NM

    SciTech Connect

    Kelson, K.I. ); Hemphill-Haley, M.A.; Wong, I.G. ); Gardner, J.N.; Reneau, S.L. )

    1993-04-01

    As in much of the Basin and Range province, low levels of historical seismicity in the Rio Grande rift (RGR) are inconsistent with abundant geologic evidence for large-magnitude, late Pleistocene and Holocene earthquakes. Recent trenching and surficial mapping along the 40-km-long, north-trending Pajarito fault system (PFS) near Los Alamos provide evidence for multiple surface-rupture events during the late Pleistocene and Holocene. Near Los Alamos, the Pajarito fault (PAF) exhibits an east-facing scarp up to 120 m high that has had at least four surface-rupture events in the past few hundred thousand years. Four trenches across the base of the highest, easternmost fault scarp show that the most-recent rupture occurred prior to about 9 ka, and possible prior to deposition of the 100- to 150-ka El Cajete Pumice. The long-term (post-1.1 Ma) slip rate on the PAF is about 0.1 mm/yr. The down-to-the-west Rendija Canyon (RCF) and Guaje Mountain (GMF) faults both have had at least two surface ruptures since the middle Pleistocene, including most-recent events at about 7.4 ka along the RCF and about 4 to 6 ka along the GMF. Slickensides and other indirect evidence suggest right-oblique normal slip on the RCF and GMF. Long-term (post-1.1 Ma) slip rates on these two faults are approximately an order of magnitude less than that on the PAF. Based on the observed spatial and temporal variations in activity, the subparallel PAF, RCF, and GMF apparently act as independent seismic sources, although they are located only about 1 to 3 km apart. Nevertheless, the average recurrence interval for faults within the PFS is probably comparable to intervals of 10[sup 4] yr estimated along the eastern rift margin near Taos.

  18. 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.

  19. Progressive failure during the 1596 Keicho earthquakes on the Median Tectonic Line active fault zone, southwest Japan

    NASA Astrophysics Data System (ADS)

    Ikeda, M.; Toda, S.; Nishizaka, N.; Onishi, K.; Suzuki, S.

    2015-12-01

    Rupture patterns of a long fault system are controlled by spatial heterogeneity of fault strength and stress associated with geometrical characteristics and stress perturbation history. Mechanical process for sequential ruptures and multiple simultaneous ruptures, one of the characteristics of a long fault such as the North Anatolian fault, governs the size and frequency of large earthquakes. Here we introduce one of the cases in southwest Japan and explore what controls rupture initiation, sequential ruptures and fault branching on a long fault system. The Median Tectonic Line active fault zone (hereinafter MTL) is the longest and most active fault in Japan. Based on historical accounts, a series of M ≥ 7 earthquakes occurred on at least a 300-km-long portion of the MTL in 1596. On September 1, the first event occurred on the Kawakami fault segment, in Central Shikoku, and the subsequent events occurred further west. Then on September 5, another rupture initiated from the Central to East Shikoku and then propagated toward the Rokko-Awaji fault zone to Kobe, a northern branch of the MTL, instead of the eastern main extent of the MTL. Another rupture eventually extended to near Kyoto. To reproduce this progressive failure, we applied two numerical models: one is a coulomb stress transfer; the other is a slip-tendency analysis under the tectonic stress. We found that Coulomb stress imparted from historical ruptures have triggered the subsequent ruptures nearby. However, stress transfer does not explain beginning of the sequence and rupture directivities. Instead, calculated slip-tendency values show highly variable along the MTL: high and low seismic potential in West and East Shikoku. The initiation point of the 1596 progressive failure locates near the boundary in the slip-tendency values. Furthermore, the slip-tendency on the Rokko-Awaji fault zone is far higher than that of the MTL in Wakayama, which may explain the rupture directivity toward Kobe-Kyoto.

  20. 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.

  1. Determining K/Ar age of fault activity through analysis of clay mineralogy: A case study of "El Doctor Fault", México

    NASA Astrophysics Data System (ADS)

    Garduño, D. E.; Pi, T.; Sole, J.; Martini, M.; Alcala, J. R.

    2013-05-01

    The upper continental crust of Mexico is cut by several major faults, some of which were interpreted as terrane boundaries. Although the age of such faults is key to reconstructing the tectonic evolution of Mexico, geochronologic studies focused on the absolute dating of a fault are scattered. The Doctor fault zone is a decakilometric NNW-SSE structure that produced the overriding of the Lower Cretaceus El Doctor carbonate platform onto foreland calcareous turbidites of Upper Cretaceous Soyatal Formation. In the fault zone, turbidites of the Soyatal Formation display a pervasive foliation at the submillimeter-scale. In calcareous layers, this foliation is defined by seams of opaque minerals concentrated along stilolitic surfaces, whereas in lutitic layers it is defined by iso-oriented fine-grained illite. We collected 17 samples from a traverse across the Doctor fault zone, in order to (1) defining and quantifying fault-related changes in clay mineralogy, (2) studying fabrics in clay-rich fault rocks and protolith, and (3) dating the fault activity by illite K/Ar with laser. Texture was studied with petrographic microscope on polished thin sections. Three size fractions (from 2 μm to 0.05 μm) were extracted using centrifugation. Clay mineralogy was determined using XRD in clay oriented samples and the illite crystallinity (IC) has been determined by the Kübler method (Kisch, 1990). The amount of 2M1 illite was quantified using XRD patterns from a randomly oriented sample, achieved using WILDFIRE (Reynolds, 1994, Haines and Van der Pluijm, 2008) and RIETVELD methods and the timing of fault main activity is determined using K/Ar dating. The mineralogy of the samples consists of quartz, calcite, plagioclase, hematite and clays. The clay mineralogy contain illite (zone 1, zone 2 and zone 3), smectite (zone 2), chlorite (zone 3), kaolinite (zone 1 and zone3), and vermiculite (zone 3). The range of IC (0.24 to 0.4) is attributed to heterogeneous origins of illite

  2. 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).

  3. Determination of a Holocene Slip Rate on the Puente Hills Blind-Thrust Fault, Los Angeles Basin, California

    NASA Astrophysics Data System (ADS)

    Christofferson, S. A.; Dolan, J. F.; Shaw, J. H.; Pratt, T. L.

    2001-12-01

    Paleoseismologic observations of slip histories and slip rates of faults that break the surface are available at an ever-increasing rate, but the nature of blind-thrust faults has kept paleoearthquake information on these faults out of reach. The complex network of blind thrust faults beneath the Los Angeles metropolitan region includes the Puente Hills thrust fault (PHT), which extends southeastward for >35 km from beneath downtown Los Angeles into northern Orange County. This thrust is active, as demonstrated by the occurrence of the 1987 Mw 6.0 Whittier Narrows earthquake (Shaw and Shearer 1999). Despite our awareness of the hazard posed by this fault, we do not know its current slip rate or its earthquake history prior to the 1987 event. To determine these critical data, we have begun a two-phase project in which we will acquire high-resolution seismic reflection data and excavate paleoseismologic boreholes and trenches across the zone of active folding associated with major earthquakes on the PHT. We have acquired high-resolution seismic reflection profiles along two transects across the zone of active folding. In our eastern most profile, along Trojan Way in La Mirada, the seismic reflection data show that the locus of active folding extends to < 30 m below the surface as a discrete zone < 30-m-wide. Our first borehole at this site, excavated at the top of the prominent fold scarp, revealed a soil with a >1.5- 2-m-thick reddish-brown argillic horizon. This soil indicates that the geomorphic surface atop the scarp is late Pleistocene in age. The 9 m height of the scarp provides a minimum estimate of total structural relief since stabilization of the ground surface. These observations yield an approximate uplift rate on the order of a few tenths of a mm/yr. Assuming simple hangingwall block translation and given the 19° -22° N dip of the PHT beneath the site, we calculate a minimum average late Pleistocene-Recent dip-slip rate of \\sim 0.2 to 1.1 mm/yr. This

  4. 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

  5. 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

  6. Thrust faults and related structures in the crater floor of Mount St. Helens volcano, Washington

    USGS Publications Warehouse

    Chadwick, W.W.; Swanson, D.A.

    1989-01-01

    A lava dome was built in the crater of Mount St. Helens by intermittent intrusion and extrusion of dacite lava between 1980 and 1986. Spectacular ground deformation was associated with the dome-building events and included the development of a system of radial cracks and tangential thrust faults in the surrounding crater floor. These cracks and thrusts, best developed and studied in 1981-1982, formed first and, as some evolved into strike-slip tear faults, influenced the subsequent geometry of thrusting. Once faulting began, deformation was localized near the thrust scarps and their bounding tear faults. The magnitude of displacements systematically increased before extrusions, whereas the azimuth and inclination of displacements remained relatively constant. The thrust-fault scarps were bulbous in profile, lobate in plan, and steepened during continued fault movement. The hanging walls of each thrust were increasingly disrupted as cumulative fault slip increased. -from Authors

  7. Fault barriers favor activation of backthrusts near segment ends of megathrust ruptures

    NASA Astrophysics Data System (ADS)

    Xu, S.; Fukuyama, E.; Ben-Zion, Y.; Ampuero, J. P.

    2013-12-01

    Increasing evidence indicates that backthrusts may become active during or after megathrust ruptures in subduction zones, such as in Chile and Sumatra areas (Melnick et al., 2012; Singh et al., 2011). Previous studies on relevant mechanisms mainly focused on the interaction between forethrusts and the megathrust. Here we aim to investigate through dynamic rupture simulations how backthrusts may be activated by megathrust ruptures in subduction zone environment. Assuming a single backthrust branch, our preliminary results show that the activation of backthrust is difficult if the megathrust rupture can easily pass through the fault junction, owing to a quickly established stress shadow zone in the wake of the megathrust rupture front. In contrast, if the megathrust rupture is arrested or delayed around the junction, a resultant backward stress lobe of the type discussed by Xu and Ben-Zion (2013) can load the backthrust over a considerable amount of time and facilitates rupture activation along the backthrust. A number of candidates can serve to arrest or delay megathrust ruptures, such as the velocity-strengthening frictional behavior and off-fault weak materials in the shallow portion of subduction zones, fault bend or ramp, and subducted seamount. Moreover, these features are also found capable of generating backthrusts during the long-term quasi-static process, which provide pre-existing weakness to be reactivated by later dynamic ruptures. Our results agree, from a different point of view, with the study based on the critical taper theory (Cubas et al., 2013) that an increase of friction towards the trench favors the activation of backthrusts near the up-dip limit of megathrust ruptures. The results highlight the role of fault geometric or strength heterogeneities in controlling the strain partitioning on and off the main fault plane. Accordingly, activated backthrusts may be treated as markers that reflect the limits of seismogenic zones, and thus may be used

  8. 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.

  9. Recent Motion on the Kern Canyon Fault, Southern Sierra Nevada, California

    NASA Astrophysics Data System (ADS)

    Nadin, E. S.; Saleeby, J. B.

    2005-12-01

    Evidence suggests that the Kern Canyon Fault (KCF), the longest fault in the southern Sierra Nevada, is an active fault. Along the 140-km-long KCF, batholithic and metamorphic rocks were displaced up to 16~km in apparent dextral strike slip during at least three discrete phases of deformation throughout the past ~90~Myr. Early ductile shear is preserved along a 1.5-km-wide zone of S-C mylonites and phyllonites that constitutes the Proto-KCF; a later phase of brittle faulting led to through-going cataclasis along the 50-m-wide KCF; and finally, late-stage minor faulting resulted in thin, hematitic gouge zones. The KCF has been considered inactive since 3.5~Ma based on a dated basalt flow reported to cap the fault. However, we believe this basalt to be disturbed, and several pieces of evidence support the idea that the KCF has been reactivated in a normal sense during the Quaternary. Fresh, high-relief fault scarps at Engineer Point in Lake Isabella and near Brush Creek, suggest recent, west-side-up vertical offset. And seismicity in the area hints at local motion. The center of activity during the 1983--1984 Durrwood Meadows earthquake swarm, a series of more than 2,000 earthquakes, the largest of which was M = 4.5, was 10~km east of the KCF. The swarm spanned a discrete, 100~km-long north-south trajectory between latitudes 35° 20'N and 36° 30'N, and its focal mechanisms were consistent with pure normal faulting, but the KCF has been disqualified as too far west and too steep to accommodate the seismic activity. But it could be part of the fault system: Near latitude 36°N, we documented a well-preserved expression of the KCF, which places Cretaceous granitic rocks against a Quaternary glacial debris flow. This fault plane strikes N05°E and is consistent with west-side-up normal faulting, in agreement with the focal mechanism slip planes of the Durrwood Meadows swarm. It is possible that the recent swarm represents a budding strand of the KCF system, much like

  10. 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

  11. 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.

  12. 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.

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

    PubMed

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

    2005-04-21

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

  14. 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