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Sample records for active fault scarps

  1. 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.

  2. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  4. Characterization of active fault scarps from medium to high resolution DEM: case studies from Central and Southern Apennines (Italy)

    NASA Astrophysics Data System (ADS)

    Brunori, C.; Cinti, F. R.; Ventura, G.

    2013-12-01

    We identify geo-morphometric features of active fault scarps in Italy through a semiautomatic processing using GIS. Medium to high resolution DEM was used to characterize the geometry, structural, and erosive elements of two seismogenic normal faults in Central and Southern Apennines. The Pettino fault in L'Aquila area was detected using a 1 m pixel DEM derived from airborne LiDAR survey (Friuli Venezia Giulia Civil Protection). For the Castrovillari fault in northern Calabria region was used a 4 m pixel DEM (Regional Cartography Office of Regione Calabria). Scarp segments are region of planar discontinuities identified by selected values of DEM-derived Terrain Ruggedness Index (TRI) and Vector Ruggedness Measure (VRM). These planar discontinuities corresponds to landscape features such as, river terraces, roads scarps, and other natural or human features. The discrimination between these features have been accomplished overlaying extracted features on aerial photograph, geological and geomorphologic maps and in situ survey. After that, we perform the quantitative and statistical analysis of these areas identified as "fault scarps". The identification of elements relative to the scarps (e.g. base, crest, slope) is then obtained to derive the estimate of parameters describing the fault: altitude, height of the scarp, length, slope and aspect, Terrain Ruggedness Index (TRI) and Vector Ruggedness Measure (VRM). The spatial distribution of the extracted values was obtained through their statistical analysis. We analyze scarp parameters variations along the whole scarp extent, such as strike value from aspect variations, slope and profile curvature differences as indicators of tectonic and/or erosion activity. The combined analysis of the DEM-derived parameters allows us to (a) define aspects of three-dimensional scarp geometry, (b) decipher its geomorphological significance, and (c) estimate the long-term slip rate.

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

    NASA Astrophysics Data System (ADS)

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

    2006-12-01

    During the spring and summer of 2006 University of Kansas geophysics students and faculty acquired shallow, high resolution seismic reflection data over actively deforming alluvial fans developing across the Emmigrant Peak (in Fish Lake Valley) and Queen Valley Faults in western Nevada. These normal faults represent a portion of the transition from the right-lateral deformation associated with the Walker Lane/Eastern California Shear Zone to the normal and left-lateral faulting of the Mina Deflection. Data were gathered over areas of recent high resolution geological mapping and limited trenching by KU students. An extensive GPR data grid was also acquired. The GPR results are reported in Christie, et al., 2006. The seismic data gathered in the spring included both walkaway tests and a short CMP test line. These data indicated that a very near-surface P-wave to S-wave conversion was taking place and that very high quality S-wave reflections were probably dominating shot records to over one second in time. CMP lines acquired during the summer utilized a 144 channel networked Geode system, single 28 hz geophones, and a 30.06 downhole rifle source. Receiver spacing was 0.5 m, source spacing 1.0m and CMP bin spacings were 0.25m for all lines. Surveying was performed using an RTK system which was also used to develop a concurrent high resolution DEM. A dip line of over 400m and a strike line over 100m in length were shot across the active fan scarp in Fish Lake Valley. Data processing is still underway. However, preliminary interpretation of common-offset gathers and brute stacks indicates very complex faulting and detailed stratigraphic information to depths of over 125m. Depth of information was actually limited by the 1024ms recording time. Several west-dipping normal faults downstep towards the basin. East-dipping antithetic normal faulting is extensive. Several distinctive stratigraphic packages are bound by the faults and apparent unconformitites. A CMP dip line

  6. LiDAR Analysis of Hector Mine Fault Scarp Degradation

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Hudnut, K. W.; Glennie, C. L.; Sousa, F.; Stock, J. M.; Akciz, S. O.

    2014-12-01

    The Mw 7.1 right-lateral strike-slip Hector Mine earthquake occurred on 10/16/1999 and generated an approximately 48 km long surface rupture. The Lavic Lake fault and the central section of the Bullion fault and several lesser faults ruptured, characterized by maximum strike slip of 5.25 ±0.85 m [Treiman, 2002]. As a very remote and un-populated area of the Mojave Desert, southern California, the study area is highly favorable for fault degradation studies with essentially no influence from vegetation or human activity. Airborne LiDAR (light detection and ranging) data and terrestrial laser scanning (TLS) are used to evaluate the form and rate of degradation of scarps along the Hector Mine fault rupture, California, USA. Airborne LiDAR data were acquired in 2000 and 2012 and these data were differenced using a newly developed algorithm for point cloud matching, which is improved over prior methods by accounting for scan geometry error sources. Using the bi-temporal data (scrutinizing profiles from 2000 & 2012), parameters for a fault scarp diffusion model are estimated and then a simulation result is generated to predict the evolved landform shape at the time of the 2014 TLS data set. Results are checked against TLS 2014 data collected at five key sites within the maximum slip field study area. In the past, scarp degradation has been mostly investigated using traditional survey methods (e.g., measuring elevations of points in a line perpendicular to the scarp) that require time-consuming field work and tend to introduce bias and variance due to data limitations. Airborne, mobile and terrestrial LiDAR data offer great potential to precisely document and rigorously determine morphologic degradation of fault scarps [Hilley et al., 2010]. In the present study, a unique set of data have been acquired at three points in time across several classic types of fault scarps and offset fault zone features. This allows progress in assessing the fitting of functions and

  7. 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.

  8. 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.

  9. 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

  10. Fault Scarp Offsets and Fault Population Analysis on Dione

    NASA Astrophysics Data System (ADS)

    Tarlow, S.; Collins, G. C.

    2010-12-01

    Cassini images of Dione show several fault zones cutting through the moon’s icy surface. We have measured the displacement and length of 271 faults, and estimated the strain occurring in 6 different fault zones. These measurements allow us to quantify the total amount of surface strain on Dione as well as constrain what processes might have caused these faults to form. Though we do not have detailed topography across fault scarps on Dione, we can use their projected size on the camera plane to estimate their heights, assuming a reasonable surface slope. Starting with high resolution images of Dione obtained by the Cassini ISS, we marked points at the top to the bottom of each fault scarp to measure the fault’s projected displacement and its orientation along strike. Line and sample information for the measurements were then processed through ISIS to derive latitude/longitude information and pixel dimensions. We then calculate the three dimensional orientation of a vector running from the bottom to the top of the fault scarp, assuming a 45 degree angle with respect to the surface, and project this vector onto the spacecraft camera plane. This projected vector gives us a correction factor to estimate the actual vertical displacement of the fault scarp. This process was repeated many times for each fault, to show variations of displacement along the length of the fault. To compare each fault to its neighbors and see how strain was accommodated across a population of faults, we divided the faults into fault zones, and created new coordinate systems oriented along the central axis of each fault zone. We could then quantify the amount of fault overlap and add the displacement of overlapping faults to estimate the amount of strain accommodated in each zone. Faults in the southern portion of Padua have a strain of 0.031(+/-) 0.0097, central Padua exhibits a strain of .032(+/-) 0.012, and faults in northern Padua have a strain of 0.025(+/-) 0.0080. The western faults of

  11. Faceted spurs at normal fault scarps: Insights from numerical modeling

    NASA Astrophysics Data System (ADS)

    Petit, C.; Gunnell, Y.; Gonga-Saholiariliva, N.; Meyer, B.; SéGuinot, J.

    2009-05-01

    We present a combined surface processes and tectonic model which allows us to determine the climatic and tectonic parameters that control the development of faceted spurs at normal fault scarps. Sensitivity tests to climatic parameter values are performed. For a given precipitation rate, when hillslope diffusion is high and channel bedrock is highly resistant to erosion, the scarp is smooth and undissected. When, instead, the bedrock is easily eroded and diffusion is limited, numerous channels develop and the scarp becomes deeply incised. Between these two end-member states, diffusion and incision compete to produce a range of scarp morphologies, including faceted spurs. The sensitivity tests allow us to determine a dimensionless ratio of erosion, f, for which faceted spurs can develop. This study evidences a strong dependence of facet slope angle on throw rate for throw rates between 0.4 and 0.7 mm/a. Facet height is also shown to be a linear function of fault throw rate. Model performance is tested on the Wasatch Fault, Utah, using topographic, geologic, and seismologic data. A Monte Carlo inversion on the topography of a portion of the Weber segment shows that the 5 Ma long development of this scarp has been dominated by a low effective precipitation rate (˜1.1 m/a) and a moderate diffusion coefficient (0.13 m2/a). Results demonstrate the ability of our model to estimate normal fault throw rates from the height of triangular facets and to retrieve the average long-term diffusion and incision parameters that prevailed during scarp evolution using an accurate 2-D misfit criterion.

  12. 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., Jr.

    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.

  13. Small Fault Scarps on Mercury Detected in Low-Altitude MESSENGER Images

    NASA Astrophysics Data System (ADS)

    Watters, T. R.; Solomon, S. C.; Daud, K. E.; Banks, M. E.; Selvans, M. M.; Robinson, M. S.; Murchie, S. L.; Chabot, N. L.; Denevi, B. W.; Ernst, C. M.; Chapman, C. R.; Fassett, C.; Klimczak, C.; Byrne, P. K.; Blewett, D. T.

    2014-12-01

    Lowering MESSENGER's periapsis altitude has provided the opportunity to image the surface of Mercury at higher resolution than was possible during the earlier orbital phase of the mission. In images obtained at spatial scales as good as ~3 m/pixel, small thrust-fault scarps have been detected. The small scarps found thus far are less than 10 km in length and have only tens of meters of relief, much smaller than the large lobate scarps that are the dominant contractional tectonic landform on Mercury and have been attributed to cooling and contraction of the planetary interior. The small scarps on Mercury are nonetheless comparable in scale to similar small scarps documented on the Moon. High-resolution MESSENGER images also reveal that the small scarps crosscut small impact craters (<100 m in diameter). Transected small craters <100 m in diameter on the Moon are Copernican (<~800 My) in age, broadly equivalent to the Kuiperian period on Mercury. Their low relief, lack of superposed small craters, and pristine appearance support the inference that these scarps are geologically young, because small landforms on Mercury will not survive for billions of years under steady meteoroid bombardment. Lunar lobate scarps comparable in scale could be less than 50 My old on the basis of estimated rates of infilling of small, shallow graben in the back-scarp terrain. The impact flux on Mercury is estimated to be a factor of ~3 greater than on the Moon, so the rate of degradation of small landforms on Mercury is expected to be comparably greater. In addition to the detection of small, young scarps, MESSENGER is acquiring images of large lobate scarps from low altitudes. Disturbed and crosscut small impact craters (<100 m in diameter) have been found in high-resolution images on the northwest segment of Carnegie Rupes, indicating recent activity on thrust-fault segments associated with older, prominent scarps. The young, small fault scarps and small-diameter craters crosscut by

  14. Geophysical investigation of landslides and fault scarps in the Hockai Fault Zone, Belgium

    NASA Astrophysics Data System (ADS)

    Mreyen, Anne-Sophie; Havenith, Hans-Balder; Fernandez-Steeger, Tomas

    2016-04-01

    During several years, a series of geophysical surveys have been carried out in East Belgium to study the seismically active Hockai Fault Zone (HFZ). The most prominent earthquake that occurred in that fault zone is the 1692 Verviers Earthquake with a magnitude of M6-6.5; it is also the largest historical seismic event in NW Europe. The geomorphic impact of the fault zone is expressed by several landslides, NW-SE orientated scarps and paleo-valleys generated by river diversions. The NW part of the HFZ (near Battice, Belgium) is also known as the Graben de la Minerie; here, geophysical measurements confirmed the presence of a series of fault scarps and helped imaging the general basin structure related to vertical offsets of coal seams that had been found during former mining works. In the southern part of the HFZ, the ENE-SWS orientated Paleo-Warche-Valley (that was formed before upstream capturing of the Warche River) crosses the fault zone over a distance of 5 km. The shallow subsurface of this area was further investigated by geophysics to identify fault structures. The work presented here is focused on the SE prolongation of the HFZ (region of Malmedy, Belgium). Two new clear morphological markers unknown before were detected through analysis of a LiDAR-DEM recently published by the Walloon Region. The following geological-geomorphic survey confirmed the presence of a NNW-SSE oriented, 100 m long and 20 m high, scarp and an associated landslide (about 8 ha) with minimum age of 300 years. The landslide was formed in the Poudingue de Malmedy, a local Permian conglomerate lying on top of a quartz-phyllite bedrock. Different geophysical methods were applied to investigate the subsurface: microseismic measurements (H/V method), seismic refraction tomography (combined with surface wave analysis) and electrical resistivity tomography. To establish the structural relationship between the fault scarp and the landslide and to estimate the offset of the Poudingue de

  15. Seismic Hazard Analysis in EL Paso/juarez Area from Study of Young Fault Scarps

    NASA Astrophysics Data System (ADS)

    ashenfelter, K. R.

    2012-12-01

    The El Paso-Juarez metropolitan area contains a known record of active faulting, but also has one of the most poorly known paleoseismic records. The scarcity of data means that nearly 2 million people are exposed to a seismic hazard with little known on the actual risk. Active faults are known along the eastern side of the Franklin Mountains as well as young ruptures within the Hueco Bolson in East El Paso, yet the only fault with paleoseismic studies is the East Franklin's fault. Recent population increases in the El Paso region have led to a construction boom in east El Paso, and many of these construction sites cross known Quaternary fault ruptures. This research project contains two potential components: 1) An exploratory component: students can use existing fault maps and high resolution aerial photography to seek out sites where active construction sites might be unearthing exposures of young fault ruptures. The study is exploratory, and involves carefully mapping using field GIS systems to document areas for potential study, map possible faults, etc. 2) An active fault study in an urbanized environment: The east Franklins fault is a known active fault. The scarp is exposed near trans-mountain road, and along some side streets in NE El Paso. Potential studies include careful mapping of fault scarp topographic profiles, and mapping surface traces.

  16. 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.

  17. Mapping of normal fault scarps in airborne laser swath mapping data using wavelet analysis

    NASA Astrophysics Data System (ADS)

    Sare, R.; Hilley, G. E.

    2015-12-01

    Wavelet analysis of Digital Elevation Models (DEMs) successfully identifies degraded fault scarps where earthquakes produce topographic steps and provides an estimate of their morphologic age. However, these methods may fail to detect relatively young, sloping scarps created by more gently-dipping normal faults, misidentifying them as mature, highly-degraded vertical scarps if they are detected at all. We present new wavelet templates incorporating initial scarp slope and above- and below-scarp surface angles to better describe the curvature of observed fault scarps. These templates are based on an analytic solution for scarp curvature, allowing for more accurate estimation of the relative age of the scarp. Synthetic tests show that scarp-like landforms that went largely undetected by a vertical-scarp template are more clearly detected using profile geometries that reflect subtle changes in curvature due to scarp and far-field slope angles. Analysis of DEMs from sites in Surprise Valley in the northwestern Basin and Range and near Jenny Lake on the Teton rangefront illustrates the effects of along-strike variability in scarp morphology on best-fit template parameters. Where normal fault scarps have high slopes, they are identified by filters designed to detect topographic step functions. Scarps with finite initial slopes, as well as those that cut surfaces with different angles above and below the scarp, can be resolved with higher signal-to-noise ratios using more sophisticated template functions. Adaptive use of different wavelet templates could reduce the number of false negatives in wavelet analysis of data from complex faulting regimes, improving the robustness of these methods and enabling automated fault mapping of large areas.

  18. Degradation of the Hebgen Lake fault scarps of 1959.

    USGS Publications Warehouse

    Wallace, R.W.

    1980-01-01

    Scarps changed noticeably in 19yr although they still appeared remarkably fresh in 1978. They have degraded much more rapidly than have those produced in 1915 and 1954 in Nevada, but a quasi-stable slope of more than 40o characterizes the Hebgen Lake scarps as compared to an upper limit of 37o on the Nevada scarps. -Author

  19. Holocene Fault Scarps and Shallow Magnetic Anomalies Along the Southern Whidbey Island Fault Zone Near Woodinville, Washington

    NASA Astrophysics Data System (ADS)

    Sherrod, B.; Blakely, R. J.; Weaver, C.; Kelsey, H. M.; Barnett, E.; Wells, R.

    2005-12-01

    The southern Whidbey Island fault zone (SWIFZ), mapped previously using borehole data, potential-field anomalies, and marine seismic-reflection surveys, consists of four sub-parallel, northwest-trending fault strands, extending ~100 km from near Vancouver Island to the Washington mainland. The SWIFZ has been hypothesized to extend southeastward beneath the mainland, making landfall between the cities of Seattle and Everett. Linear, low-amplitude aeromagnetic anomalies in this mainland region are on strike with the mapped portion of the SWIFZ and may indicate that the fault continues southeast. The Cottage Lake aeromagnetic lineament, is most prominent, extends at least 16 km and is approximately on strike with the SWIFZ on Whidbey Island. Glacial deposits are slightly magnetic in this region, as indicated by magnetic susceptibility measurements and a ground-magnetic survey, and, in places, the Cottage Lake aeromagnetic lineament is associated with topographic lineaments. Spectral analysis and modeling experiments indicate that the source of the Cottage Lake aeromagnetic lineament extends to depths greater than 2 km and probably into Eocene sedimentary strata. Coastal marsh stratigraphy, lidar mapping, and fault scarp excavations help define recent activity along the SWIFZ. Abrupt uplift at a coastal marsh on south-central Whidbey Island suggests that the SWIFZ experienced a MW 6.5 - 7.0 earthquake between 3200 and 2800 years B.P. Subtle scarps on Pleistocene surfaces are delineated by high-resolution lidar topography at a number of locations in the mainland region, often closely associated with aeromagnetic lineaments. In the field, scarps exhibit northeast-side-up vertical relief of 1 to 5 m. Four excavations across two lidar scarps show evidence for multiple folding and faulting events since deglaciation, most likely above buried reverse/oblique faults. One trench exposed a normal fault, although it was not possible to determine whether glacial or tectonism

  20. 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.

  1. Role of Erosion on Closely-Spaced Fault Scarps: High-resolution Laser Scanning Data and Scarp Diffusion Modelling of the Rex Hills Flower Structure, Nevada

    NASA Astrophysics Data System (ADS)

    Baran, R.; Guest, B.; Friedrich, A. M.

    2007-12-01

    Flower structures are often associated with strike-slip faults. Their subsurface geometry is well known but additional information about their geometry and kinematics is also contained in their surface expression, especially in surfaces exhibiting closely-spaced fault scarps. However, detailed surface descriptions of flower structures are rare. Here, we present for the first time topographic profiles extracted from high-resolution digital elevation model (DEM) data using a ground-based laser scanner (Riegl company) to examine the surface expression of a flower structure in great detail. Our study site, the Rex Hills flower structure (40 m high, ~1 km long), is located on the transpressional left-bend between the Pahrump and Amargosa segments of the dextral Stateline fault system (Guest et al., 2007, GSAB). The southern Rex Hills slope exhibits three reverse fault- scarp generations related to three reverse fault branches, respectively. The basal scarp is the youngest and most continuous one. It exhibits five fault segments with an approximately constant displacement along the scarp. The upper two fault-scarp generations are less continuous, and older. The topography of the southern Rex Hills slope also is characterized by alternating valleys and ridges (each ~100 m long) extending perpendicular to the main ridge crest. Our analysis shows that fault scarp morphology varies laterally along this slope. Scarps exposed on ridge crests are typically more numerous (up to 4-5 scarps) and smaller (on average 5 m high), whereas adjacent valleys often exhibit single large (>10 m high) scarps. The larger valley-scarps did not result from the offset across a single fault branch, but resulted from merging of the three scarps mentioned above by enhanced scarp degradation. The preservation potential of small, individual scarps is therefore better on ridge crests relative to adjacent valleys. Assuming a known age of 2 kyrs (Menges et al., 2003, AGU), we examined the spatial

  2. 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

  3. Terrestrial Laser Scanner analysis of diffusion degradation models in morphological dating of fault scarp surfaces

    NASA Astrophysics Data System (ADS)

    Shilpakar, P.; Oldow, J. S.

    2015-12-01

    Morphological dating of fault scarps has the potential to provide a fast and cost-effective means of determining the spatial and temporal pattern of paleo-seismic events over broad regions. Scarp-morphology dating algorithms are based on diffusion degradation relations but have not been adequately calibrated for sensitivity or repeatability. Using Terrestrial Laser Scanner (TLS) images to characterize geomorphic surfaces at centimeter scale, we characterize fault scarps of known and differing ages ( 20 to 13,500 years) to evaluate the applicability of morphology-degradation models in estimating ages of fault scarps. We acquired TLS images of five Quaternary fault scarp surfaces formed in unconsolidated sediments in different parts of the western Basin and Range in western Nevada and southeastern California. Diffusion models assess the initial and final configuration of a scarp to yield the product of a diffusivity constant (K) and the scarp age (T). With known T we can solve for K and vice versa. Our sensitivity analysis of the diffusion models demonstrate that small variations in the measurable parameters such as maximum slope angle (θ), far field slope angle (α), and surface offset (d) can produce large variations in the calculated age of scarp formation. Even a 0.5° uncertainty in the value of θ or α will cause 10 to 20 percent variability in K, and a 25 cm uncertainty in d will make a 20 percent difference in calculated K. This uncertainty in K value will yield ± 3000 year variation in the estimated scarp age. Using 10 cm resolution digital elevation models of fault scarps acquired with TLS, we best fit profiles and digitally measure the geometric parameters. The ages of the scarps are known via historical records or through age brackets establish in trenching studies. Using the known ages and the modeled morphology, we compute K for the various scarps formed in similarly material and environments. Estimates of K range from 1.57 m2/kyr to 13.74 m2/kyr and

  4. 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.

  5. 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.

  6. Disentangling Fault Scarp Geometry and Slip-Distribution in 3D

    NASA Astrophysics Data System (ADS)

    Mackenzie, D.; Walker, R. T.

    2015-12-01

    We present a new and inherently 3D approach to the analysis of fault scarp geometry using high resolution topography. Recent advance in topographic measurement techniques (LiDAR and Structure from Motion) has allowed the extensive measurement of single earthquake scarps and multiple event cumulative scarps to draw conclusions about along-strike slip variation and characteristic slip. Present analysis of the resulting point clouds and digital elevation models is generally achieved by taking vertical or map view profiles of geomorphic markers across the scarp. Profiles are done at numerous locations along strike carefully chosen to avoid regions degraded by erosion/deposition. The resulting slip distributions are almost always extremely variable and "noisy", both for strike-slip and dip-slip faulting scarps and it is often unclear whether this reflects slip variation, noise/erosion, site effects or geometric variation. When observing palaeo-earthquake and even modern event scarps, the full geometry, such as the degree of oblique slip or the fault dip, is often poorly constrained. We first present the results of synthetic tests to demonstrate the introduction of significant apparent noise by simply varying terrain, fault and measurement geometry (slope angle, slope azimuth, fault dip and slip obliquity). Considering fully 3-dimensional marker surfaces (e.g. Planar or conical) we use the variation in apparent offset with terrain and measurement geometry, to constrain the slip geometry in 3D. Combining measurements windowed along strike, we show that determining the slip vector is reduced to a simple linear problem. We conclude that for scarps in regions of significant topography or with oblique slip, our method will give enhanced slip resolution while standard methods will give poor slip resolution. We test our method using a Structure from Motion pointcloud and digital elevation model covering a ~25 km stretch of a thrust fault scarp in the Kazakh Tien Shan.

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

    NASA Astrophysics Data System (ADS)

    Maccaferri, Francesco; Acocella, Valerio; Rivalta, Eleonora

    2016-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

  9. Fault dislocation modeled structure of lobate scarps from Lunar Reconnaissance Orbiter Camera digital terrain models

    NASA Astrophysics Data System (ADS)

    Williams, N. R.; Watters, T. R.; Pritchard, M. E.; Banks, M. E.; Bell, J. F.

    2013-02-01

    Before the launch of the Lunar Reconnaissance Orbiter, known characteristics of lobate scarps on the Moon were limited to studies of only a few dozen scarps revealed in Apollo-era photographs within ~20° of the equator. The Lunar Reconnaissance Orbiter Camera now provides meter-scale images of more than 100 lobate scarps, as well as stereo-derived topography of about a dozen scarps. High-resolution digital terrain models (DTMs) provide unprecedented insight into scarp morphology and dimensions. Here, we analyze images and DTMs of the Slipher, Racah X-1, Mandel'shtam-1, Feoktistov, Simpelius-1, and Oppenheimer F lobate scarps. Parameters in fault dislocation models are iteratively varied to provide best fits to DTM topographic profiles to test previous interpretations that the observed landforms are the result of shallow, low-angle thrust faults. Results suggest that these faults occur from the surface down to depths of hundreds of meters, have dip angles of 35-40°, and have typical maximum slips of tens of meters. These lunar scarp models are comparable to modeled geometries of lobate scarps on Mercury, Mars, and asteroid 433 Eros, but are shallower and ~10° steeper than geometries determined in studies with limited Apollo-era data. Frictional and rock mass strength criteria constrain the state of global differential stress between 3.5 and 18.6 MPa at the modeled maximum depths of faulting. Our results are consistent with thermal history models that predict relatively small compressional stresses that likely arise from cooling of a magma ocean.

  10. Investigating multiple fault rupture at the Salar del Carmen segment of the Atacama Fault System (northern Chile): Fault scarp morphology and knickpoint analysis

    NASA Astrophysics Data System (ADS)

    Ewiak, Oktawian; Victor, Pia; Oncken, Onno

    2015-02-01

    This study presents a new geomorphological approach to investigate the past activity and potential seismic hazard of upper crustal faults at the Salar del Carmen segment of the Atacama Fault System in the northern Chile forearc. Our contribution is based on the analysis of a large set of topographic profiles and allows extrapolating fault analysis from a few selected locations to distances of kilometers along strike of the fault. We detected subtle changes in the fault scarp geometry which may represent the number of paleoearthquakes experienced by the structure and extracted the cumulative and last incremental displacement along strike of the investigated scarps. We also tested the potential of knickpoints in channels crossing the fault scarps as markers for repeated fault rupture and proxies for seismic displacement. The number of paleoearthquakes derived from our analysis is 2-3, well in agreement with recent paleoseismological investigations, which suggest 2-3 earthquakes (Mw = 6.5-6.7) at the studied segments. Knickpoints record the number of events for about 55% of the analyzed profile pairs. Only few knickpoints represent the full seismic displacement, while most retain only a fraction of the displacement. The along-strike displacement distributions suggest fault growth from the center toward the tips and linkage of individual ruptures. Our approach also improves the estimation of paleomagnitudes in case of multiple fault rupture by allowing to quantify the last increment of displacement separately. Paleomagnitudes calculated from total segment length and the last increment of displacement (Mw = 6.5-7.1) are in agreement with paleoseismological results.

  11. 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

  12. 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.

  13. Extension across Tempe Terra, Mars, from measurements of fault scarp widths and deformed craters

    USGS Publications Warehouse

    Golombek, M.P.; Tanaka, K.L.; Franklin, B.J.

    1996-01-01

    Two independent methods, with no common assumptions, have been used to estimate the extension across the heavily deformed Tempe Terra province of the Tharsis region of Mars. One method uses measurements of normal fault scarp width with average scarp slope data for simple grabens and rifts on Mars to estimate the fault throw, which, combined with sparse fault dip data, can be used to estimate extension. Formal uncertainties in this method are only slightly greater than those in other methods, given that the total uncertainty is dominated by the likely uncertainty in the fault dip (assumed to be 60????15??). Measurement of normal fault scarp widths along two N25??-50??W directed traverses across Tempe Terra both yield about 22??16 km of extension (or ???2% strain across the northern traverse and nearly 3% across the southern one). About three quarters of the extension has occurred during the two main phases of Tharsis-related deformation from Middle/Late Noachian to Early Hesperian and from Late Hesperian to Early Amazonian, with more extension closer to the center of Tharsis during the first phase. Extension across the region was also determined by measuring the elongation and elongation direction of all ancient Noachian impact craters without ejecta blankets, which predate most of the deformation. Results have been corrected for initial non circularity of craters, established from similar measurements of young (post deformation) impact craters, yielding a statistically significant mean strain of 1.96??0.35% in a N38????10??W direction across Tempe Terra (extension of ???20??4, comparable in magnitude and direction to the average result from the scarp measurement method). Both methods indicate an average extension for single normal fault scarps (and shortening across wrinkle ridges for the crater method) of ???100 m. The agreement between the results of the two independent methods in overall extension and average single normal fault extension argues that the average

  14. 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.

  15. 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

  16. Inventory of post-glacial fault scarps in Sweden derived from a high-resolution digital elevation model

    NASA Astrophysics Data System (ADS)

    Smith, Colby A.; Mikko, Henrik; Lund, Björn; Munier, Raymond

    2015-04-01

    Post-glacial faults are well documented in northern Fennoscandia. They are pre-existing bedrock structures that were reactivated through a combination of isostatic and tectonic stresses following the retreat of the last Fennoscandian Ice Sheet. The locations and geometries of such features are important for evaluating seismic hazard. The current project utilizes LiDAR-derived imagery, which covers 80% of Sweden, to map linear scarps that cross cut glacial deposits or landforms. Through detailed manual interpretation of high-resolution imagery, previously unknown post-glacial fault scarps have been identified in central Sweden. Additionally, previously mapped scarps in northern Sweden have been refined or rejected. Despite full LiDAR coverage of southern Sweden, no post-glacial fault scarps were identified. The current dataset is available from the Geological Survey of Sweden, and will be kept up to date as new LiDAR coverage becomes available.

  17. 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

  18. 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.

  19. 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

  20. 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

  1. 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.

  2. 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.

  3. Deciphering cumulative fault slip vectors from fold scarps: Relationships between long-term and coseismic deformations in central Western Taiwan

    NASA Astrophysics Data System (ADS)

    Le Béon, Maryline; Suppe, John; Jaiswal, Manoj K.; Chen, Yue-Gau; Ustaszewski, Michaela E.

    2014-07-01

    We document the 30 ka cumulative slip history and long-term slip vector azimuth on the northern Chelungpu fault based on a series of fault-bend folded alluvial terraces and draw quantitative relationships between geological structure, deformation observed from the geomorphology, and coseismic displacements during the 1999 Mw = 7.6 Chi-Chi earthquake. In our study area, three main terrace levels show progressive folding by kink band migration in relation to the underlying fault geometry, forming a main N-S fold scarp up to ~193 m high and secondary E-W scarps. Detailed analysis using 5 m resolution digital elevation model allows us to characterize the scarp morphology and quantify the deformation parameters, namely, terrace heights, fold scarp relief, and fold limb width and slope angle. The 3-D deformation of the highest terrace, dated by optically stimulated luminescence at 30.2 ± 4.0 ka, enables to simultaneously determine amplitude and azimuth of the long-term slip vector based on scarp relief. The long-term slip vector, oriented N338° ± 6°, is found to parallel the Chi-Chi coseismic displacements in this area. Cumulative slip and dating results yield a constant slip rate of 17.7 ± 2.2 mm/a in the direction N338° ± 6°. Late Quaternary shortening rates observed at four sites vary along strike in a similar way to Chi-Chi coseismic displacements. Together with the collinearity of long-term and coseismic slip vectors at our study site, this suggests that Chi-Chi earthquake is a characteristic earthquake for the Chelungpu thrust with recurrence interval ~470 years. We also discuss implications for the regional and long-term distribution of shortening in the central Western Foothills.

  4. 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, II; 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.

  5. 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

  6. Late Holocene episodic displacement on fault scarps related to interstratal dissolution of evaporites (Teruel Neogene Graben, NE Spain)

    NASA Astrophysics Data System (ADS)

    Gutiérrez, F.; Carbonel, D.; Guerrero, J.; McCalpin, J. P.; Linares, R.; Roqué, C.; Zarroca, M.

    2012-01-01

    The Mio-Pliocene formations of the Turolian type section (Teruel Graben, Spain) have sagged due to dissolution of the underlying Triassic evaporites generating a 1.7 km long monocline and accompanying synform with 130 m of structural relief. The crest of the monocline is affected by a graben that counterbalances the shortening caused by passive bending in the adjacent syncline. This graben is controlled by a master synthetic fault and a swarm of antithetic and synthetic faults with a conspicuous geomorphic expression. After acquiring Ground Penetrating Radar (GPR) profiles, three trenches were excavated in depressions associated with uphill-facing fault scarps. To our knowledge, these are the first trenches excavated across faults caused by deep-seated dissolution of evaporites. The geometrical relationships observed in two trenches indicate late Holocene episodic displacement (as many as 3 events). Some of the parameters estimated for the investigated faults are clearly different from those expectable for tectonic faults in this intraplate area. They include high apparent vertical slip rates (0.6-1 mm/yr), low average recurrence of faulting events (1.2-2 ka) and very high displacement per event values (>65 cm) for surface ruptures less then 200 m long. Our findings suggest that considering evaporite collapse faults as creeping structures is not a reliable criterion to differentiate between tectonic faults (seismogenic) and dissolution-induced gravitational faults (nonseismogenic).

  7. 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.

  8. 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

  9. Discovery Scarp

    NASA Technical Reports Server (NTRS)

    1974-01-01

    One of the most prominent lobate scarps (Discovery Scarp), photographed by Mariner 10 during it's first encounter with Mercury, is located at the center of this image (extending from the top to near bottom). This scarp is about 350 kilometers long and transects two craters 35 and 55 kilometers in diameter. The maximum height of the scarp south of the 55-kilometer crater is about 3 kilometers. Notice the shallow older crater (near the center of the image) perched on the crest of the scarp. (FDS 17389 and 27399)

    The Mariner 10 mission, managed by the Jet Propulsion Laboratory for NASA's Office of Space Science, explored Venus in February 1974 on the way to three encounters with Mercury-in March and September 1974 and in March 1975. The spacecraft took more than 7,000 photos of Mercury, Venus, the Earth and the Moon.

    Image Credit: NASA/JPL/Northwestern University

  10. 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

  11. 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.

  12. 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.

  13. Toward determining the uncertainties associated with the seismic histories retrieved from in situ 36Cl cosmogenic nuclide fault scarp dating: model reappraisal.

    NASA Astrophysics Data System (ADS)

    Tesson, Jim; Benedetti, Lucilla

    2016-04-01

    How the past seismic activity of faults has varied over the last 20 ky is a crucial information for seismic hazard assessment and for the understanding of fault-interaction processes. Chlorine 36 in situ produced cosmogenic nuclide is increasingly used to retrieve past earthquakes histories on seismically exhumed limestone normal fault-scarps. Schlagenhauf et al. in 2010 developed a modeling code with a forward approach enabling the test of scenarii generated with a priori constraints (number of events, age and slip of events and pre-exposure time). The main shortcomings of this forward approach were the limited number of testable scenarii and the difficulty to derive the associated uncertainties. We present here a reappraisal methodology with an inverse approach using an optimization algorithm. This modelling approach enables 1-exploring the parameter space (age and slip of events), 2-finding the best scenario without a priori constraints and 3-precisely quantifying the associated uncertainties by determining the range of plausible models. Through a series of synthetic tests, we observed that the algorithm revealed a great capacity to constrain event slips and ages in a short computational time (several hours) with an accuracy that can reach 0.1 ky and 0.5 m for the age and slip of exhumation event, respectively. We also explore the influence of the pre-exposure history (amount of 36Cl accumulated when the sampled fault-plane was still buried under the colluvial wedge) and show that it has an important impact on the generated scenarii. This new modeling also allows now to accurately determining this parameter. Finally, the results show that any given [36Cl] profile results in a unique exhumation solution. We then apply this new model to the Magnola fault (Italy) dataset (Schlgenhauf et al. 2011). In agreement the previously published results, our model also results in 3 intense periods of seismic activity. However, the contribution of the pre-exposure history is

  14. 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

  15. 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

  16. Active fault traces along Bhuj Fault and Katrol Hill Fault, and trenching survey at Wandhay, Kachchh, Gujarat, India

    NASA Astrophysics Data System (ADS)

    Morino, Michio; Malik, Javed N.; Mishra, Prashant; Bhuiyan, Chandrashekhar; Kaneko, Fumio

    2008-06-01

    Several new active fault traces were identified along Katrol Hill Fault (KHF). A new fault (named as Bhuj Fault, BF) that extends into the Bhuj Plain was also identified. These fault traces were identified based on satellite photo interpretation and field survey. Trenches were excavated to identify the paleoseismic events, pattern of faulting and the nature of deformation. New active fault traces were recognized about 1km north of the topographic boundary between the Katrol Hill and the plain area. The fault exposure along the left bank of Khari River with 10m wide shear zone in the Mesozoic rocks and showing displacement of the overlying Quaternary deposits is indicative of continued tectonic activity along the ancient fault. The E-W trending active fault traces along the KHF in the western part changes to NE-SW or ENE-WSW near Wandhay village. Trenching survey across a low scarp near Wandhay village reveals three major fault strands F1, F2, and F3. These fault strands displaced the older terrace deposits comprising Sand, Silt and Gravel units along with overlying younger deposits from units 1 to 5 made of gravel, sand and silt. Stratigraphic relationship indicates at least three large magnitude earthquakes along KHF during Late Holocene or recent historic past.

  17. Callisto Scarp Mosaic

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This mosaic of two images shows an area within the Valhalla region on Jupiter's moon, Callisto. North is to the top of the mosaic and the Sun illuminates the surface from the left. The smallest details that can be discerned in this picture are knobs and small impact craters about 155 meters (170 yards) across. The resolution is 46 meters (50 yards) per picture element, and the mosaic covers an area approximately 33 kilometers (20 miles) across. A prominent fault scarp crosses the mosaic. This scarp is one of many structural features that form the Valhalla multi-ring structure, which has a diameter of 4,000 kilometers (2,485 miles). Scientists believe Valhalla is the result of a large impact early in the history of Callisto. Several smaller ridges are found parallel to the prominent scarp. Numerous impact craters ranging in size from 155 meters (170 yards) to 2.5 kilometers (1.5 miles) are seen in the mosaic. The images which form this mosaic were obtained by the solid state imaging system aboard NASA's Galileo spacecraft on Nov. 4, 1996 (Universal Time).

    The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.

    This image and other images and data received from Galileo are posted on the World Wide Web Galileo mission home page at http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at http://www.jpl.nasa.gov/galileo/sepo.

  18. 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

  19. 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.

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

    NASA Astrophysics Data System (ADS)

    Armijo, Rolando; Thiele, Ricardo

    1990-04-01

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

  1. Identification of active faults in enlarged stereo models of Skylab S-190B photographs

    NASA Technical Reports Server (NTRS)

    Merifield, P. M.

    1983-01-01

    Most of the physiographic indicators of recent movement known to be present along the Indio Hills segment of the San Andreas fault zone can be identified on enlarged Skylab S-190B stereo photographs. These include offset streams, beheaded streams, offset fans, shutter ridges, linear valleys, scarps and vegetation anomalies. Where physiographic indicators of recent movement are present, the S-190B system affords the necessary resolution and stereoscopy for distinguishing activate from inactive faults.

  2. Structural control of scarps in the Rembrandt region of Mercury

    NASA Astrophysics Data System (ADS)

    Ruiz, Javier; López, Valle; Dohm, James M.; Fernández, Carlos

    2012-06-01

    Lobate scarps, thought to be the surface expression of large thrust faults, are the most spectacular contractional tectonic features visible on Mercury. Most lobate scarps follow a general and relatively simple pattern, with a roughly arcuate or linear form in plan view, and an asymmetric cross section characterized by a steeply rising scarp face and a gently declining back scarp. In this work, we study two peculiar and complex scarps in the Rembrandt region of Mercury through MESSENGER imagery. On the one hand, the formation of these scarps resulted in the deformation of features such as impact craters, fractures, extensional faults, and volcanic plains, while on the other hand, the deformed features partly influenced the formation of the scarps. Evidence for structural control on the formation of the scarps includes their orientation, segmentation, bifurcation, change in structural trend and dip orientation, and transition into high-relief ridges or wrinkle ridge morphologies in some cases. Thus, these two lobate scarps provide examples of complex geological relations among other features, expanding the recognized richness of mercurian geology. Also, the southern scarp records a complex history of contraction, suggesting that the development of some mercurian lobate scarps may be more complex than usually thought.

  3. 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.

  4. 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

  5. Active flexural-slip faulting: A study from the Pamir-Tian Shan convergent zone, NW China

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    The flexural-slip fault (FSF), a type of secondary fault generated by bed-parallel slip, occurs commonly and plays an important role in accommodating fold growth. Although the kinematics and mechanics of FSFs are well studied, relatively few field observations or geometric models explore its geomorphic expression. In the Pamir-Tian Shan convergent zone, NW China, suites of well-preserved FSF scarps displace fluvial terraces in the Mingyaole and Wulagen folds. Integrating interpretations of Google Earth images, detailed geologic and geomorphic mapping, and differential GPS measurements of terrace surfaces, we summarize geomorphic features that typify these faults and create kinematic models of active flexural-slip faulting. Our study indicates the following: (i) FSF scarps commonly occur near synclinal hinges, irrespective of whether (a) the dip direction of beds on either side of the hinge is unidirectional or in opposite directions, (b) the hinge is migrating or fixed, or (c) the hinge shape is narrow and angular or wide and curved. (ii) Active FSFs are likely to produce higher scarps on steeper beds, whereas lower or no topographic scarps typify gentler beds. (iii) Tilt angles of the terrace surface displaced above FSFs progressively decrease farther away from the hinge, with abrupt changes in slope coinciding with FSF scarps; the changes in tilt angle and scarp height have a predictable geometric relationship. (iv) Active FSFs can accommodate a significant fraction of total slip and play a significant role in folding deformation. (v) Active FSFs may be used to assess seismic hazards associated with active folds and associated blind thrusts.

  6. Finding Active Faults in a Glaciated and Forested Landscape: the Southern Whidbey Island Fault, Washington

    NASA Astrophysics Data System (ADS)

    Blakely, R. J.; Sherrod, B. L.; Wells, R. E.; Weaver, C. S.

    2004-12-01

    The Puget Lowland, Washington, lies within the Cascadia forearc and is underlain by at least six seismically active and regionally significant crustal faults that together accommodate several mm/yr of net north-south shortening. The surface expression of pre-15-ka slip on Puget Lowland faults has been largely scoured away or covered by glacial deposits, and younger fault geomorphology is often concealed by vegetation and urban development. High-resolution aeromagnetic and lidar surveys, followed by geologic site investigations, have identified and confirmed late Holocene deformation on each of these mostly concealed but potentially hazardous faults. Most geomorphic features identified in lidar data are closely associated with linear magnetic anomalies that reflect the underlying basement structure of the fault and help map its full extent. The southern Whidbey Island fault (SWIF) is a case in point. The northwest-striking SWIF was mapped previously using borehole data and potential-field anomalies on Whidbey Island and marine seismic-reflection surveys beneath surrounding waterways. Gravity inversions and aeromagnetic mapping suggest that the SWIF extends at least 50 km southeast, from Vancouver Island to the Washington mainland, and transitions along its length from northeast-side-down beneath Puget Sound to northeast-side-up on the mainland. Abrupt subsidence at a coastal marsh on south-central Whidbey Island suggests that the SWIF experienced a MW 6.5 to 7.0 earthquake about 3 ka. Southeast of Whidbey Island, a hypothesized southeastward projection of the SWIF makes landfall between the cities of Seattle and Everett. Linear, northwest-striking magnetic anomalies in this mainland region do coincide with this hypothesized projection, are low in amplitude, and are best illuminated in residual magnetic fields. The most prominent of the residual magnetic anomalies extends at least 16 km, lies approximately on strike with the SWIF on Whidbey Island, and passes within

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  8. Using 10Be cosmogenic surface exposure dating to determine the evolution of the Purgatorio active fault in the Andean forearc, southern Peru

    NASA Astrophysics Data System (ADS)

    Carlos, Benavente; Swann, Zerathe; Laurence, Audin; Fabrizio, Delgado; Marianne, Saillard; Sarah, Hall R.; Aster Team

    2015-04-01

    Active transpressive deformation has been occurring along the Andean hyperarid forearc for the last 3 Myrs but many of these faults are still not described even if able to produce large damaging earthquakes. Active faulting along the northern part of the Arica Bend can be recognized due to the presence of well-preserved and sharp fault scarps indicating recent surface slip. During the Mio-Pliocene, deposition within the forearc continental basins resulted in the formation of vast fan deposits and conglomerates of the Moquegua Formation, which can be considered as bedrock in this exposure study (~45-4 Ma; Tosdal et al., 1984; Sebrier et al., 1988a; Roperch et al., 2006). The typical vertical Purgatorio fault scarps offset both the Moquegua bedrock and several younger geomorphic features associated with <300kyrs climatic and 400 years old volcanic extreme events. This study focus on quantifying slip rate variations in time along a 5-meters high vertical fault scarp to understand how the fault is evolving. These results are achieved via surface exposure dating of the sampled seismically broken cobbolds of the Moquegua formation outcroping vertically along the fault scarp. These samples are well-suited to the application of in situ produced cosmogenic radionuclides for surface exposure dating, as the hyperarid region has extremely low erosion rates. We sampled the scarp away from any significant drainage so as to avoid possibly disturbed areas. The sampling did involve extracting quarzite conglomeratic material along the bedrock scarp and on the upper surrounding crests. The aim has been to measure Berylium-20 TCN (Terrestrial in situ Cosmogenic Nuclides) concentrations to determine exposure age as a function of height on the scarp. This has been successfully employed on one scarp in Italy based on Chlorine-36 TCN (Palumbo et al., 2004). However, slow faults behaviour remains unclear and more contributions are needed. Quaternary activity of the Purgatorio fault system

  9. 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

  10. 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

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

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

    NASA Astrophysics Data System (ADS)

    Nakata, T.; Kumamoto, T.

    2004-12-01

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

  13. Geophysical prospecting of a slow active fault in the Lower Rhine Embayment, NW Germany

    NASA Astrophysics Data System (ADS)

    Streich, R.; Strecker, M.; Lück, E.; Scherbaum, F.; Schäbitz, F.; Spangenberg, U.

    2003-04-01

    The Lower Rhine embayment, Germany, is currently one of the most active sectors of the Cenozoic rift system of western and central Europe. Historical records denote at least 21 earthquakes with epicentral intensities >=7, and instrumental records show a concentration of seismicity at the major bounding Peel Boundary, Erft, Feldbiss and Rurrand faults. Many fault segments were active in the recent past and formed numerous morphologic scarps. However, fault scarps are poorly preserved since low displacement rates are opposed to interference of fluvioglacial with tectonic processes, a dense vegetation cover, high precipitation rates, and human landscape modification. This makes it difficult to determine the exact location, size and geometry of active fault segments in this region and hampers estimation of long-term displacement rates and fault activity. To overcome these difficulties, we applied a combination of morphologic, geophysical, and geological methods. We carried out detailed studies at the Hemmerich site located in the Erft fault system, SE Lower Rhine embayment (6.918oE, 50.758oN). The site is characterized by a topographic scarp, 4 m high and several km long. We placed special emphasis on testing the applicability of fast and simple geophysical prospecting techniques to fault assessment, and on evaluating the scarp as a potential site to excavate the suspected fault. The geophysical methods applied comprise resistivity and chargeability tomography, ground penetrating radar, and shallow seismic reflection, all carried out along profiles perpendicular to the topographic scarp. In addition, electromagnetic and magnetic maps were acquired. Beside geophysical prospecting, we conducted microtopographic levelling and coring. We detected a major break in a shallow radar reflector, and a steep seismic velocity contrast discernible both by seismic refraction tomography and dispersion analysis. These features are in good spatial correlation with each other and with

  14. Fault kinematics and active tectonics at the southeastern boundary of the eastern Alborz (Abr and Khij fault zones): Geodynamic implications for NNE Iran

    NASA Astrophysics Data System (ADS)

    Javidfakhr, Bita; Bellier, Olivier; Shabanian, Esmaeil; Siame, Lionel; Léanni, Laëtitia; Bourlès, Didier; Ahmadian, Seiran

    2011-10-01

    The Alborz is a region of active deformation within the Arabia-Eurasia collision zone. The Abr and the Khij Faults are two NE-trending left-lateral strike-slip faults in the eastern Alborz that correspond to the Shahrud fault system extended through an area of about 95 km × 55 km. Tectonic landforms typically associated with active strike-slip faults, such as deflected stream channels, offset ridges and fault scarps are documented along the mentioned faults. Detailed analyses of satellite images and digital topographic data accompanied by field surveys allowed us to measure horizontal offsets of about 420 ± 50 m and 400 ± 50 m for the Abr and Khij Faults, respectively. A total of 8 quartz-rich samples were sampled and dated from two different fan surfaces using in situ-produced 10Be cosmogenic dating method. Minimum exposure ages for the abandonment of the alluvial fan surfaces of 115 ± 14 kyr along the Abr Fault and of 230 ± 16 kyr along the Khij Fault imply that both faults are active with slip rates of about 3-4 mm yr -1 and 1-3 mm yr -1, respectively. The results of our study provide the first direct quantitative geological estimates of slip rate along these two active faults and place a new constraint on slip distribution between the faults in the eastern Alborz. Fault kinematic studies (from fault slip data) indicate a N35°E-trending maximum stress axis comprising a dominant strike-slip regime in agreement with the geomorphological analyses. The left-lateral strike-slip faulting along the Abr and Khij Faults and their associated fault zones in the eastern Alborz can be due to the westward component of motion of the South Caspian Basin with respect to Eurasia and Central Iran.

  15. Fitting degradation of shoreline scarps by a nonlinear diffusion model

    USGS Publications Warehouse

    Andrews, D.J.; Buckna, R.C.

    1987-01-01

    The diffusion model of degradation of topographic features is a promising means by which vertical offsets on Holocene faults might be dated. In order to calibrate the method, we have examined present-day profiles of wave-cut shoreline scarps of late Pleistocene lakes Bonneville and Lahontan. A table is included that allows easy application of the model to scarps with simple initial shape. -from Authors

  16. Fault scarp identification in side-scan sonar and bathymetry images from the Mid-Atlantic Ridge using wavelet-based digital filters

    NASA Astrophysics Data System (ADS)

    Little, Sarah A.; Smith, Deborah K.

    1996-12-01

    Digital filters designed using wavelet theory are applied to high resolution deep-towed side-scan sonar data from the median valley walls, crestal mountains, and flanks of the Mid-Atlantic Ridge at 29°10' N. With proper tuning, the digital filters are able to identify the location, orientation, length, and width of highly reflective linear features in sonar images. These features are presumed to represent the acoustic backscatter from axis-facing normal faults. The fault locations obtained from the digital filters are well correlated with visual geologic interpretation of the images. The side-scan sonar images are also compared with swath bathymetry from the same area. The digitally filtered bathymetry images contain nine of the eleven faults identified by eye in the detailed geologic interpretation of the side-scan data. Faults with widths (measured perpendicular to their strike) of less than about 150 m are missed in the bathymetry analysis due to the coarser resolution of these data. This digital image processing technique demonstrates the potential of wavelet-based analysis to reduce subjectivity and labor involved in mapping and analyzing topographic features in side-scan sonar and bathymetric image data.

  17. 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.

  18. Connecting the Yakima fold and thrust belt to active faults in the Puget Lowland, Washington

    NASA Astrophysics Data System (ADS)

    Blakely, Richard J.; Sherrod, Brian L.; Weaver, Craig S.; Wells, Ray E.; Rohay, Alan C.; Barnett, Elizabeth A.; Knepprath, Nichole E.

    2011-07-01

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

    NASA Astrophysics Data System (ADS)

    Salvi, Stefano

    1994-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  1. South Polar Scarps

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-438, 31 July 2003

    The terrain of the south polar residual ice cap, made up mostly of frozen carbon dioxide, has come to be known by many as 'swiss cheese terrain,' because many areas of the cap resemble slices of swiss cheese. However, not all of the south polar cap looks like a tasty lunch food. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a series of curving scarps formed by erosion and sublimation of carbon dioxide from the south polar cap. This area is located near 86.3oS, 51.2oW. The image is illuminated by sunlight from the upper left; the area is about 1.5 km (0.9 mi) wide.

  2. 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

  3. Derivation of Absolute Model Ages for Lunar Lobate Scarps

    NASA Astrophysics Data System (ADS)

    van der Bogert, C. H.; Hiesinger, H.; Banks, M. E.; Watters, T. R.; Robinson, M. S.

    2012-03-01

    Crater size-frequency distribution measurements indicate that the Mandel'shtam and Lee-Lincoln scarps were active as recently as ~91 Ma and ~75 Ma, respectively. These results confirm that lobate scarps are some of the youngest features on the Moon.

  4. Intracontinental active normal faulting and paleoseismicity in the eastern Weihe Graben, central China

    NASA Astrophysics Data System (ADS)

    Rao, G.; Lin, A.; Yan, B.; Jia, D.; Wu, X.

    2012-12-01

    During the past decades, tectonic deformation and seismogenic behavior of active strike-slip and thrust faults have been well investigated, due to the high-frequent occurrence of large-magnitude strike-slip and thrust-type earthquakes. In contrast, normal-faulting earthquakes of M≥7 scarcely occurred, and the rupture process and deformation features of seismogenic normal-faults are still not clear. The intracontinental graben systems around the stable Ordos Block, central China, experienced extension over the past ~50 Ma, which are ideal places to study the extensional tectonic deformation. As well, these regions with high historical seismicity including 3 large earthquakes of M≥8, provide a good chance to learn the rupture mechanism of large intracontinental normal-faulting earthquakes. Based on the 3D analysis of high-resolution remote-sensing images (0.5-m WorldView and 1-m IKONOS images) and field investigations, active normal faults are mainly distributed along the margin zones of the uplifted mountainous blocks (e.g., Weinan Loess Tableland and Huashan Mountains), characterized by the distributed fault scarps. Striations and scratch steps observed on the main fault planes, reveal a normal slip-sense of active faults in study area. In combination with the 14C age dating, the vertical offset amount of ~30 m during the past 14,050-16,270 years was observed, yielding an average vertical displacement-rate of ~1.8-2.1 mm/a, which is consistent with previous estimation in the Weihe Graben. According to the field observations of fault outcrops and the exposed trench walls, the offset strata, scarp-derived colluvial deposits and in-filled fissures generally can be observed, indicating the occurrence of paleoearthquakes. Together with the 14C ages, the late Pleistocene-Holocene activity of normal faults was demonstrated. Especially, it is concluded that at least 3 strong earthquakes associated with surface-faulting in the past 2600 years, including the most recent

  5. 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

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  7. Morphometric and geometric characterization of normal faults on Mars

    NASA Astrophysics Data System (ADS)

    Vaz, David A.; Spagnuolo, Mauro G.; Silvestro, Simone

    2014-09-01

    Using three different approaches (fault plane fitting, 3D crater rim palinspatic restorations and fault scarps morphometric analysis) we investigate the geometry and degradation history of Martian normal faults in two distinct areas. The three independent methods produce similar results, indicating that the average dip angle of the normal faults on these two locations is probably below the value that is usually assumed for Mars (∼60°). Our best estimate for this average dip angle is 46.8±9.8°, which is a value comparable with the mean dip angle inferred on Earth for seismically active normal faults. This lower average dip angle implies that all the rift strain estimates performed until now might be underestimated. From the comparative analysis of the two faulted regions (Phlegethon Catena and Claritas Fossae), we show that local and regional dip variabilities may exist on Mars. This reinforces the idea that the amount of extension associated with Martian rifts must be reconsidered. We also demonstrate the advantages of performing a comparative morphometric analysis of fault scarps. This approach enables the reconstruction of the faults scarps degradation history and can be used to evaluate how environmental conditions changed through time. After modeling the degradation of the fault scarps at the two sites we conclude that the observed morphometric variations are mainly due to the different faulting ages in an environment characterized by low scarp degradation rates (4×10-3 m/kyr) over the last 3 Ga.

  8. Finding concealed active faults: Extending the southern Whidbey Island fault across the Puget Lowland, Washington

    NASA Astrophysics Data System (ADS)

    Sherrod, Brian L.; Blakely, Richard J.; Weaver, Craig S.; Kelsey, Harvey M.; Barnett, Elizabeth; Liberty, Lee; Meagher, Karen L.; Pape, Kristin

    2008-05-01

    The southern Whidbey Island fault zone (SWIF), as previously mapped using borehole data, potential field anomalies, and marine seismic reflection surveys, consists of three subparallel, northwest trending strands extending ˜100 km from near Vancouver Island to the northern Puget Lowland. East of Puget Sound, the SWIF makes landfall between the cities of Seattle and Everett but is concealed beneath a thick mantle of young glacial deposits and vegetation. A ˜20-km-wide, northwest trending swath of subparallel, low-amplitude aeromagnetic anomalies crosses this region of the Puget Lowland and is on strike with the SWIF. The most prominent aeromagnetic anomaly, the Cottage Lake lineament, extends at least 18 km and lies approximately on strike with the SWIF on Whidbey Island. Subtle scarps and topographic lineaments on Pleistocene surfaces, visible on high-resolution lidar topography at a number of locations along the SWIF, lie on or near these magnetic anomalies. In the field, scarps exhibit northeast-side-up and vertical relief of 1 to 5 m. Excavations across several lidar scarps lying on or near magnetic anomalies show evidence for multiple folding and faulting events since deglaciation, most likely above buried reverse/oblique faults. Excavations in areas away from magnetic anomalies do not show evidence of tectonic deformation. In total, paleoseismological evidence suggests that the SWIF produced at least four earthquakes since deglaciation about 16,400 years ago, the most recent less than 2700 years ago.

  9. 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

  10. Near-Surface Seismic Reflection and GPR Imaging of the Active Emigrant Peak Fault, Fish Lake Valley, NV

    NASA Astrophysics Data System (ADS)

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

    2007-12-01

    Multifaceted near-surface geophysical studies of active faulting in the Eastern California Shear Zone are being conducted at the University of Kansas. During the summer of 2006 shallow seismic reflection and GPR data sets were acquired across the active Emigrant Peak fault on the east side of Fish Lake Valley, Nevada. This fault is a normal fault that aids in the transfer of regional right-lateral deformation associated with the Death Valley/Fish Lake Valley fault zone. Locally a 20 m high scarp marks the trace of the main fault across a large, active alluvial fan. The GPR experiment produced a pseudo-3D image approximately 500m by 115m in size with a bin size of 1m by 5m. Depth penetration was dependent on antenna frequency, but reached approximately 25m in the dry alluvial fan sediments. Two 2-D seismic lines were acquired with a depth penetration of approximately 200m using a 30.06 caliber rifle source. The main line was over 400m in length and the cross line over 150m in length. CMP bins were 0.25m in size. Both data types were processed to migrated images and imported into an industry-standard reflection interpretation package. Analysis of the GPR volume allowed the interpretation of numerous normal faults parallel to the main Emigrant fault both near the main scarp and as 'off-fault' deformation. Some are down-to-the-basin 'growth faults' and some are antithetic in nature. Faults were only mapped if they were continuous across many x-lines. The migrated seismic images contain numerous reflections, grouped in packages of short reflectors of different amplitudes and dip orientations. The GPR fault planes were transferred onto the seismic data and correlated with obvious breaks in dip and amplitude between the reflection packages. After basic interpretation of the faults the stratigraphic changes across the fault planes were analyzed on the seismic data to estimate offsets at different depths for each fault. Currently, we are working to estimate a quantitative

  11. 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.

  12. 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

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

    SciTech Connect

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

    1993-04-01

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

  14. 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

  15. High-Resolution Seismic Reflection Studies of Active Faults: a Case Study from Washington State

    NASA Astrophysics Data System (ADS)

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

    2007-12-01

    In the past five years, new high-resolution seismic surveys have filled in gaps in our understanding of active structures beneath the Puget Lowland region of Washington State. The extensive forests have made recognition of active faults difficult, but new Light Distance and Ranging (LIDAR) detailed topographic data have made a major breakthrough in mapping active faults. Extensive regional and high-resolution marine seismic surveys have been fundamental to understanding the tectonic framework of the area. These marine profiles, however, lack coverage beneath water bodies that large ships cannot navigate and beneath city streets underlain by late Pleistocene glacial deposits that are missing from the waterways. Recent land surveys and profiles in restricted waterways can therefore bridge the gap between paleoseismic and marine geophysical studies, and test elements of models proposed by regional-scale geophysical studies. We have also been venturing into more congested areas to seismically image faults in key urban locations. Results from recent surveys have: 1) documented new faults that had long been suspected in the Olympia area; 2) clarified the relationship between the LIDAR scarps and observed structures across the Tacoma fault zone; 3) provided a window into structures beneath the north and eastern portions of the western Tacoma fault zone; 4) documented deformation along the Seattle fault near a paleoseismic trench; 5) mapped the eastern part the Seattle fault zone beyond its previously mapped limits; and 6) documented multiple fault strands in the Seattle fault zone in the cities of Bellevue and Seattle. The results better constrain interpretations of paleoseismic data collected on these faults, and provide targets for future paleoseismic studies.

  16. The Lawanopo Fault, central Sulawesi, East Indonesia

    NASA Astrophysics Data System (ADS)

    Natawidjaja, Danny Hilman; Daryono, Mudrik R.

    2015-04-01

    The dominant tectonic-force factor in the Sulawesi Island is the westward Bangga-Sula microplate tectonic intrusion, driven by the 12 mm/year westward motion of the Pacific Plate relative to Eurasia. This tectonic intrusion are accommodated by a series of major left-lateral strike-slip fault zones including Sorong Fault, Sula-Sorong Fault, Matano Fault, Palukoro Fault, and Lawanopo Fault zones. The Lawanopo fault has been considered as an active left-lateral strike-slip fault. The natural exposures of the Lawanopo Fault are clear, marked by the breaks and liniemants of topography along the fault line, and also it serves as a tectonic boundary between the different rock assemblages. Inpections of IFSAR 5m-grid DEM and field checks show that the fault traces are visible by lineaments of topographical slope breaks, linear ridges and stream valleys, ridge neckings, and they are also associated with hydrothermal deposits and hot springs. These are characteristics of young fault, so their morphological expressions can be seen still. However, fault scarps and other morpho-tectonic features appear to have been diffused by erosions and young sediment depositions. No fresh fault scarps, stream deflections or offsets, or any influences of fault movements on recent landscapes are observed associated with fault traces. Hence, the faults do not show any evidence of recent activity. This is consistent with lack of seismicity on the fault.

  17. 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).

  18. Fault Mechanics and Active Strain Along the Garlock Fault in SE California

    NASA Astrophysics Data System (ADS)

    Rittase, W.; Walker, D.; Taylor, M.; Kirby, E.

    2008-12-01

    We report here results from new geologic mapping along a 38 km segment of the Garlock Fault (GF) between US 395 and the Slate Range, and an 8 km segment at the northern terminus of the Blackwater- Calico fault (BCF) in the Lava Mountains. This study area lies within the ENE-striking central segment of the sinistral GF. NNW-striking faults of the dextral Eastern California shear zone approach the GF, but do not offset it: exact mechanisms of strain transfer across the GF from the Mojave Desert to the Basin and Range is enigmatic. Field mapping reveals that the GF is complex with numerous sub-parallel strands both north and south of the mapped fault. Holocene slip on the GF is dominantly sinistral, but a major zone to the north adjacent to the bedrock of the southern Slate Range is dip-slip. The mapped portion of the northern BCF is expressed as a bedrock scarp and does not cut Holocene sediments. Significant N-S shortening is superimposed along the GF adjacent to the southern Slate Range, in the Christmas Canyon area, and the Lava Mountains. Pliocene- Pleistocene sediments are uplifted and deformed into E-W open to chevron folds in the Christmas Canyon and Slate Range areas. Cretaceous quartz-monzonite and overlying Miocene strata are deformed by similar structures in the northern Lava Mountains. In general, areas of topographic uplifts are disjointed and spatially restrictive in comparison to the more continuous GF and the BCF. These observations suggest several possibilities for the region. (1) Active slip on the GF and the Eastern California shear zone are driven by a single, Mojave-wide stress field with sigma-1 oriented roughly N-S. (2) The GF may be a weak zone in the lithosphere and crust with sigma-1 oriented nearly perpendicular to strike as evidenced by ENE- to East-trending fold hinges in Pliocene-Pleistocene sediments. (3) The continuous trace of the GF rupture through the 38-km-long study area suggests that it, at least locally, poses a mechanical

  19. Morphological Analysis of Lunar Lobate Scarps Using LROC NAC and LOLA Data

    NASA Astrophysics Data System (ADS)

    Banks, M. E.; Watters, T. R.; Robinson, M. S.; Tornabene, L. L.; Tran, T.; Ojha, L.

    2011-10-01

    Lobate scarps on the Moon are relatively smallscale tectonic landforms observed in mare basalts and more commonly, highland material [1-4]. These scarps are the surface expression of thrust faults, and are the most common tectonic landform on the lunar farside [1-4]. Prior to Lunar Reconnaissance Orbiter (LRO) observations, lobate scarps were largely detected only in equatorial regions because of limited Apollo Panoramic Camera and high resolution Lunar Orbiter coverage with optimum lighting geometry [1-3]. Previous measurements of the relief of lobate scarps were made for 9 low-latitude scarps (<±20°), and range from ~6 to 80 m (mean relief of ~32 m) [1]. However, the relief of these scarps was primarily determined from shadow measurements with limited accuracy from Apollo-era photography. We present the results of a detailed characterization of the relief and morphology of a larger sampling of the population of lobate scarps. Outstanding questions include what is the range of maximum relief of the lobate scarps? Is their size and structural relief consistent with estimates of the global contractional strain? What is the range of horizontal shortening expressed by lunar scarps and how does this range compare with that found for planetary lobate scarps? Lunar Reconnaissance Orbiter Camera (LROC) images and Lunar Orbiter Laser Altimeter (LOLA) ranging enable detection and detailed morphological analysis of lobate scarps at all latitudes. To date, previously undetected scarps have been identified in LROC imagery in 75 different locations, over 20 of which occur at latitudes greater than ±60° [5-6]. LROC stereo-derived digital terrain models (DTMs) and LOLA data are used to measure the relief and characterize the morphology of 26 previously known (n = 8) and newly detected (n = 18) lobate scarps. Lunar examples are compared to lobate scarps on Mars, Mercury, and 433 Eros (Hinks Dorsum).

  20. 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.

  1. Active thrust faulting offshore Boumerdes, Algeria, and its relations to the 2003 Mw 6.9 earthquake

    NASA Astrophysics Data System (ADS)

    Déverchère, J.; Yelles, K.; Domzig, A.; Mercier de Lépinay, B.; Bouillin, J.-P.; Gaullier, V.; Bracène, R.; Calais, E.; Savoye, B.; Kherroubi, A.; Le Roy, P.; Pauc, H.; Dan, G.

    2005-02-01

    We investigate the active seismogenic fault system in the area of the 2003 Mw 6.9 Boumerdes earthquake, Algeria, from a high-resolution swath bathymetry and seismic survey. A series of 5 main fault-propagation folds ~20-35 km long leave prominent cumulative escarpments on the steep slope and in the deep basin. Fault activity creates Plio-Quaternary growth strata within uplifted areas such as a rollover basin on the slope and piggyback basins in the deep ocean. Most thrusts turn to fault-propagation folds at the sub-surface and depict ramp-flat trajectories. We find that the two main slip patches of the 2003 Mw 6.9 Boumerdes earthquake are spatially correlated to two segmented cumulative scarps recognized on the slope and at the foot of the margin. The overall geometry indicates the predominance of back thrusts implying underthrusting of the Neogene oceanic crust.

  2. 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

  3. 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

  4. Late quaternary active characteristics and slip-rate of Pingding-Huama Fault, the eastern segment of Guanggaishan-Dieshan Fault zone ( West Qinlin Mountain )

    NASA Astrophysics Data System (ADS)

    Jingxing, Y.; Wenjun, Z.; Daoyang, Y.; Jianzhang, P.; Xingwang, L.; Baiyun, L.

    2012-12-01

    Stretching along the west QinlinShan in the north Tibet, the Guanggaishan-Dieshanfaultis composed of three sub-parallel faults among which the major one is a fault named Pingding-Huama fault. The Pingding-Huama fault can be further defined as a combination of a western segment and an eastern segment separated by Minjiang river at Dangchang. Along the western segment of the Pingding-Huama fault, significant linear characteristics, scars, and fault scarps cutting several alluvial fans can be easily distinguished, indicating that the western segment is active since the late Quatenary and the elapsed time of the last event should be less than 1ka B.P.. We estimated the slip rates of the western segment through geomorphology analysis and dating the age of the top surface of terraces and the deformed strata (OSL, 14C). The results show that its reverse slip rate ranges from 0.69±0.16 to 1.15±0.28mm/a and the sinistral slip rate is 0.51±0.13mm/a. In contrast to the simple structure of the western segment, the eastern segment consists of several sub-parallel faults as well as oblique intersected faults. On all faults of the eastern segment, no sign of recent movement was discovered. Along these faults, the tectonic topography features a sequence of linear valleys in the west and dominant folds in the east. Only striations in bedrock and geomorphology show that the eastern segment was reversely slipping on the whole with sinistral component. In summary, at present the Pingding-Huama fault is active along its western segment while shows very weak deformation along the eastern segment.

  5. Morphometric analysis of small-scale lobate scarps on the Moon using data from the Lunar Reconnaissance Orbiter

    NASA Astrophysics Data System (ADS)

    Banks, M. E.; Watters, T. R.; Robinson, M. S.; Tornabene, L. L.; Tran, T.; Ojha, L.; Williams, N. R.

    2012-03-01

    Prior to Lunar Reconnaissance Orbiter (LRO), the morphology and dimensions of only a limited number of lobate scarps, all located near the equator (within 21°), had been characterized. Topography derived from LRO Camera stereo images and Lunar Orbiter Laser Altimeter (LOLA) ranging is used to measure the relief and analyze the morphology of previously known and newly detected low and high latitude lobate scarps. The asymmetric profiles and maximum slopes on scarp faces (˜5° to 29°) of lunar lobate scarps are similar to those of lobate scarps observed on Mars and Mercury. Scarp lengths range from ˜0.6 to 21.6 km (mean = ˜6.0 km, median = ˜4.4 km, n = 79), and measured relief ranges from ˜5 to 150 m (mean = ˜35 m, median = ˜20 m, n = 26). Assuming a range of 20° to 40° for the fault plane dip, estimated lower limits for the horizontal shortening (S) expressed by the lobate scarp thrust faults range from ˜10 to 410 m. The range in S estimated for the lunar scarps is roughly an order of magnitude lower than estimates of S for lobate scarp thrust faults on Mars and Mercury. The relatively small range of S estimated for the growing number of well-characterized lunar scarps is consistent with a small amount of global contraction.

  6. Active tectonics evidences and seismicity registry of Servitá Fault, Colombia

    NASA Astrophysics Data System (ADS)

    Chicangana, G.; Vargas-Jimenez, C. A.; Pedraza, P.; Kammer, A.; Ochoa Gutierrez, L. H.

    2013-05-01

    The Servita fault is a thrust whose scarp is located 5km west of Villavicencio in the center of Colombia. Here with neotectonic evidences and the seismicity record obtained by the Colombian National Seismological Network for the 1993-2012 period confirms the potential occurrence of earthquakes in this region related to this fault because is the biggest thrust of the region.

  7. 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

  8. Identification of an active fault in the Japanese Alps from DEM-based hill shading

    NASA Astrophysics Data System (ADS)

    Oguchi, Takashi; Aoki, Tatsuto; Matsuta, Nobuhisa

    2003-08-01

    Shaded-relief images created from digital elevation models (DEMs) are helpful in identifying faults in rugged mountains. Unlike airphoto interpretation, the method enhances lineaments by simulating topographic illumination under varied light directions. Interpretation of shaded-relief images of the Japanese Alps led to the discovery of a lineament unrelated to bedrock structure. Field surveys and analysis of large-scale maps and airphotos reveal the lineament to be a fault with high rates of vertical and lateral slip. The new fault is the southernmost segment of a known adjacent fault, and the rate and direction of its slip provide fresh insight into the late Quaternary history of the fault system. Because previous research mistook the fault scarp for a fluvial terrace scarp, discovery of the fault also changed the correlation of river terraces in the Northern Japanese Alps. The new corrections affect Pleistocene glacial chronology in the upstream area.

  9. Geomorphological markers of faulting and neotectonic activity along the western Andean margin, northern Chile

    NASA Astrophysics Data System (ADS)

    Audin, Laurence; Herail, Gérard; Riquelme, Rodrigo; Darrozes, José; Martinod, Joseph; Font, Eric

    2003-12-01

    In the Atacama Desert, northern Chile, some ephemeral channels are developed in the Plio-Quaternary alluvial sequence that caps the Neogene Atacama Gravels Formation. Geomorphological studies and high-resolution digital elevation data (GPS) along a structural transect in the Central Depression are used to document modern growth history of subtle folding and faulting in the fore-arc region. Outcrop data of the most recent deposits are combined with observations of warped and faulted late Quaternary pediments, alluvial fans and terrace surfaces to propose unsuspected neotectonic processes on the western flank of the Domeyko Cordillera. Neotectonic process recognition is here based largely upon the interpretation of alluvial landforms, drainage organisation and evolution as the intermittent river network shows systematic patterns of course deflections, successive incisions or deposition processes as it encounters the fault scarps or folds in the superficial deposits. This area presents both N-S-trending active vertical faults in the topographically higher pampas, and N-S-trending active folding in the lower pampas. These faults seem to accommodate E-W extension and compression that could be related to uplift of the western Andean margin within a compressive context. Uplift may have taken place unevenly over the past few million years after the deposition of the superficial alluvial surfaces that cap the Neogene Atacama Gravels. Copyright

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

    USGS Publications Warehouse

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

    1997-01-01

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

  11. Is the Lishan fault of Taiwan active?

    NASA Astrophysics Data System (ADS)

    Kuo-Chen, Hao; Wu, Francis; Chang, Wu-Lung; Chang, Chih-Yu; Cheng, Ching-Yu; Hirata, Naoshi

    2015-10-01

    The Lishan fault has been characterized alternately as a major discontinuity in stratigraphy, structures and metamorphism, a ductile shear zone, a tectonic suture or non-existent. In addition to being a geological boundary, it also marks transitions in subsurface structures. Thus, the seismicity to the west of the fault permeates through the upper and mid-crust while beneath the Central Range it is noticeably less and largely concentrated in the upper 12 km. A prominent west-dipping conductive zone extends upward to meet the Lishan fault. Also, the eastward increase of crust thickness from ~ 30 km in the Taiwan Strait quickens under the Lishan fault to form a root of over 50 km under the Central Range. In the past, the small magnitude seismicity along the Lishan fault has been noticed but is too diffuse for definitive association with the fault. Recent processing of aftershock records of the 1999 Mw 7.6 Chi-Chi earthquake using Central Weather Bureau data and, especially, data from three post-Chi-Chi deployments of seismic stations across central Taiwan yielded hypocenters that appear to link directly to the Lishan structure. The presence of a near 4-km-long vertical seismic zone directly under the surface trace of the Lishan fault indicates that it is an active structure from the surface down to about 35 km, and the variety of focal mechanisms indicates that the fault motion can be complex and depth-dependent.

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

    SciTech Connect

    Cronin, V.S. . Geosciences Dept.)

    1992-01-01

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

  13. 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

  14. Spatial Patterns of Geomorphic Surface Features and Fault Morphology Based on Diffusion Equation Modeling of the Kumroch Fault Kamchatka Peninsula, Russia

    NASA Astrophysics Data System (ADS)

    Heinlein, S. N.

    2013-12-01

    Remote sensing data sets are widely used for evaluation of surface manifestations of active tectonics. This study utilizes ASTER GDEM and Landsat ETM+ data sets with Google Earth images draped over terrain models. This study evaluates 1) the surrounding surface geomorphology of the study area with these data sets and 2) the morphology of the Kumroch Fault using diffusion modeling to estimate constant diffusivity (κ) and estimate slip rates by means of real ground data measured across fault scarps by Kozhurin et al. (2006). Models of the evolution of fault scarp morphology provide time elapsed since slip initiated on a faults surface and may therefore provide more accurate estimates of slip rate than the rate calculated by dividing scarp offset by the age of the ruptured surface. Profile modeling of scarps collected by Kozhurin et al. (2006) formed by several events distributed through time and were evaluated using a constant slip rate (CSR) solution which yields a value A/κ (1/2 slip rate/diffusivity). Time elapsed since slip initiated on the fault is determined by establishing a value for κ and measuring total scarp offset. CSR nonlinear modeling estimated of κ range from 8m2/ka - 14m2/ka on the Kumroch Fault which indicates a slip rates of 0.6 mm/yr - 1.0 mm/yr since 3.4 ka -3.7 ka. This method provides a quick and inexpensive way to gather data for a regional tectonic study and establish estimated rates of tectonic activity. Analyses of the remote sensing data are providing new insight into the role of active tectonics within the region. Results from fault scarp diffusion models of Mattson and Bruhn (2001) and DuRoss and Bruhn (2004) and Kozhurin et al. (2006), Kozhurin (2007), Kozhurin et al. (2008) and Pinegina et al. 2012 trench profiles of the KF as calibrated age fault scarp diffusion rates were estimated. (-) mean that no data could be determined.

  15. 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.

  16. Fault activation due to glacially induced stresses

    NASA Astrophysics Data System (ADS)

    Steffen, R.; Lund, B.; Wu, P. P.

    2013-12-01

    Melting glaciers worldwide have an effect on sea level, but also on the stability of pre-existing faults. The load due to continental ice sheets or glaciers depresses the surface below, leading to changes in the lithospheric stresses. The accumulation of ice mass increases the vertical stress, and the horizontal stresses increase due to the accompanying flexure of the lithosphere. During deglaciation, ice-mass loss causes a simultaneous decrease in vertical stress; however, horizontal stresses decrease only slowly due to the slow readjusting of the Earth. After the end of deglaciation, only the induced horizontal stresses remain as the process of glacial isostatic adjustment (GIA) proceeds visco-elastically. The modelling of this process and the estimation of fault slip is enabled by a new GIA-fault model. However, this finite-element model is only available in two dimensions, and the extension to three dimensions is a necessary step further to allow the comparison of obtained fault slips to observations of glacially induced faults in Europe and North America. The model has several input parameters, which affect the activation time of faults and their resulting slip (e.g. ice history, rheology of the Earth, frictional properties, pore-fluid pressure). We will present the results of the new 3D model and show the sensitivity of faults with respect to modelling parameters. Furthermore, a comparison to observations will be presented.

  17. Fault activation due to glacially induced stresses

    NASA Astrophysics Data System (ADS)

    Steffen, Rebekka; Lund, Björn

    2014-05-01

    Melting glaciers worldwide have an effect on sea level, but also on the stability of pre-existing faults. The load due to continental ice sheets or glaciers depresses the surface below, leading to changes in the lithospheric stresses. The accumulation of ice mass increases the vertical stress, and the horizontal stresses increase due to the accompanying flexure of the lithosphere. During deglaciation, ice-mass loss causes a simultaneous decrease in vertical stress; however, horizontal stresses decrease only slowly due to the slow readjusting of the Earth. After the end of deglaciation, only the induced horizontal stresses remain as the process of glacial isostatic adjustment (GIA) proceeds visco-elastically. The modelling of this process and the estimation of fault slip is enabled by a new GIA-fault model. However, this finite-element model is only available in two dimensions, and the extension to three dimensions is a necessary step further to allow the comparison of obtained fault slips to observations of glacially induced faults in Europe and North America. The model has several input parameters, which affect the activation time of faults and their resulting slip (e.g. ice history, rheology of the Earth, frictional properties, pore-fluid pressure). We will present the results of the new 3D model and show the sensitivity of faults with respect to modelling parameters. Furthermore, a comparison to observations will be presented.

  18. 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

  19. 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

  20. 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.

  1. 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

  2. Lobate Scarp Modeling with Lunar Reconnaissance Orbiter Camera Digital Terrain Models

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    Lobate scarps are a type of contractional tectonic landform expressed on the Moon's surface in both highlands and maria. Typically only tens of meters in relief, these linear or curvilinear topographic rises are interpreted to be low-angle thrust fault scarps resulting from global radial contraction. Radial contraction of the Moon can be inferred from shortening across the population of lobate scarps and is estimated at ~100 m. However, the geometry and depth of the underlying faults and mechanical properties of the near-surface lunar crustal materials are not well constrained. The Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Cameras (NACs) acquire 0.5 to 2.0 m/pixel panchromatic images and digital terrain models (DTMs) with spatial resolutions of 2 m are derived from NAC stereo pairs. Topographic data are being used to constrain models of the lobate scarp thrust faults. DTMs are analyzed for relief and morphology of the Slipher (48.3°N, 160.6°E), Racah X-1 (10°S, 178°E), and Simpelius-1 (73.5°S, 13°E) scarps. Profiles are extracted, detrended, and compared along strike. LROC Wide Angle Camera (WAC) 100 m/pixel image mosaics and topography provide regional contexts. Using elastic dislocation modeling, the fault dip angles, depths, slip, and taper are each varied until the predicted surface displacement best fits the DTM profiles for each lobate scarp. Preliminary best-fit dip angles vary from 30-40°, maximum fault depths extend to several hundred meters, and the amount of slip varies from 10 to 30 meters for the three scarps. The modeled maximum depths suggest that the thrust faults are not deeply rooted.

  3. 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

  4. 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).

  5. 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

  6. Active and inactive faults in southern California viewed from Skylab

    NASA Technical Reports Server (NTRS)

    Merifield, P. M.; Lamar, D. L.

    1975-01-01

    The application is discussed of Skylab imagery along with larger scale photography and field investigations in preparing fault maps of California for use in land use planning. The images were used to assist in distinguishing active from inactive faults (by recognizing indications of recent displacement), determining the length of potentially active faults, identifying previously unmapped faults, and gaining additional information on regional tectonic history.

  7. 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.

  8. Complex history of the Rembrandt basin and scarp system, Mercury

    NASA Astrophysics Data System (ADS)

    Ferrari, S.; Massironi, M.; Klimczak, C.; Byrne, P. K.; Cremonese, G.; Solomon, S. C.

    2012-09-01

    During its second and third flybys, the MESSENGER spacecraft [1] imaged the wellpreserved Rembrandt basin in Mercury's southern hemisphere. With a diameter of 715 km, Rembrandt is the second largest impact structure recognized on Mercury after the 1550-km-diameter Caloris basin. Rembrandt is also one of the youngest major basins [2] and formed near the end of the Late Heavy Bombardment (~3.8 Ga). Much of the basin interior has been resurfaced by smooth, high-reflectance units interpreted to be of volcanic origin [3]. These units host sets of contractional and extensional landforms generally oriented in directions radial or concentric to the basin, similar to those observed within the Caloris basin [4-6]; these structures are probably products of multiple episodes of deformation [2,7,8]. Of particular note in the Rembrandt area is a 1,000-km-long reverse fault system [9] that cuts the basin at its western rim and bends eastward toward the north, tapering into the impact material. On the basis of its shape, the structure has previously been characterized as a lobate scarp. Its formation and localization have been attributed to the global contraction of Mercury [2]. From MESSENGER flyby and orbital images, we have identified previously unrecognized kinematic indicators of strike-slip motion along the Rembrandt scarp, together with evidence of interaction between the scarp orientation and the concentric basin-related structural pattern described above. Here we show through cross-cutting relationships and scarp morphology that the development of the Rembrandt scarp was strongly influenced by tectonics related to basin formation and evolution.

  9. Laser Altimetry by MESSENGER over Lobate Scarps Reveals the Lithospheric Structure of Mercury

    NASA Astrophysics Data System (ADS)

    Ritzer, J. A.; Johnson, C. L.; Hauck, S. A.; Watters, T. R.; Barnouin, O. S.; Neumann, G. A.; Mazarico, E.; Phillips, R. J.; Solomon, S. C.; Zuber, M. T.

    2011-12-01

    Images from the Mariner 10 flybys of Mercury demonstrated the widespread occurrence of lobate scarps over the ~45% of the surface imaged by that spacecraft. Lobate scarps are linear to arcuate structures that are tens to hundreds of kilometers long, have topographic relief of hundreds of meters to kilometers, and are interpreted as the surface expression of major thrust faults. Flybys of Mercury by the MESSENGER spacecraft confirmed that lobate scarps are the dominant tectonic feature over nearly the entire planet. Ranging to the surface by the Mercury Laser Altimeter (MLA) since MESSENGER's orbit insertion on March 18, 2011, has yielded hundreds of topographic profiles, largely over Mercury's northern hemisphere. We utilize MLA measurements of lobate scarp topography to constrain fault models and mechanical properties of Mercury's lithosphere. Mean along-track resolution of the MLA data is approximately 300 m, but cross-track spacing varies with latitude, so we currently confine our analyses to individual profiles. Overlaying MLA profiles on images taken by the Mercury Dual Imaging System (MDIS) allows the relief and morphology of lobate surface scarps in Mercury's northern hemisphere to be characterized. Many of these features display the expected signature for lithospheric flexure in response to bending moments applied at underlying thrust faults. We model these faults and their accompanying flexure by means of a mechanical model of the lithosphere that includes an elastic plate overlying an inviscid substrate to accommodate buoyancy forces. Model parameters that are varied are the geometry of the fault and the thickness of the effective elastic lithosphere. Long-wavelength pre-scarp topography is estimated by first de-trending the profiles. We estimate the thickness of the mechanical lithosphere via the relationship between bending moment and plate curvature given a yield strength envelope for Mercury's lithosphere. Comparison of model profiles to the MLA

  10. Late Quaternary Activity on the Cerro Goden Fault, Puerto Rico and Limitations of High-resolution Seismic Reflection/refraction Data for Trench-scale Investigations

    NASA Astrophysics Data System (ADS)

    Zachariasen, J.; Prentice, C. S.; Schweig, E.; Abreu, R.; Rymer, M. J.; Catchings, R. D.

    2005-12-01

    The Cerro Goden Fault runs along the base of the La Cadena de San Francisco range north of Añasco in western Puerto Rico, and joins with the Great Southern Puerto Rico Fault zone. This fault zone disrupts Eocene and older rocks but its Quaternary history is unclear. It bounds the northern Añasco Valley, which is seismically active. Offshore investigations suggest the fault cuts the sea floor (Grindlay et al., 2005) and an onshore reconnaissance study by Mann et al. (2005) found geomorphic evidence of Quaternary displacement. We gathered high-resolution seismic reflection/refraction data along two lines that crossed the projection of the fault in the Añasco Valley to help identify possible fault strands in the near subsurface. The seismic data were gathered using a shoot-through acquisition method with a BETSY-Seisgun shooting source consisting of 8-gauge, 400 grain shotgun blanks set in holes drilled about 30 cm below the ground surface. Both lines had shot and geophone spacings of 5 m. Common Depth Point (CDP) spacings for both lines were 2.5 m in the shallow section of the profiles. We used the results from the seismic lines to site six trenches where the data revealed discontinuities, possibly attributable to faulting, within the upper 2-3 meters. Our trenches ranged in depth from 2 - 5 meters, but in none of the trenches did we find evidence of surface faulting. A mountain-front-facing subsurface scarp, which may have been produced by older Quaternary faulting, appeared in several trenches. Holocene fluvial sediments have been deposited against this scarp and have buried it, but are unfaulted. Our results suggest either that the Cerro Goden Fault has not been active since the deposition of the Holocene fluvial sediments or that the high-resolution seismic data were not adequate to define the location of fault traces to the precision necessary for trench investigations. Both the seismic data and the buried scarps suggest there may be faults at depth, but

  11. Normal faults geometry and morphometry on Mars

    NASA Astrophysics Data System (ADS)

    Vaz, D. A.; Spagnuolo, M. G.; Silvestro, S.

    2014-04-01

    In this report, we show how normal faults scarps geometry and degradation history can be accessed using high resolution imagery and topography. We show how the initial geometry of the faults can be inferred from faulted craters and we demonstrate how a comparative morphometric analysis of faults scarps can be used to study erosion rates through time on Mars.

  12. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2006-12-01

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

  14. Tectonic and gravity-induced deformation along the active Talas-Fergana Fault, Tien Shan, Kyrgyzstan

    NASA Astrophysics Data System (ADS)

    Tibaldi, A.; Corazzato, C.; Rust, D.; Bonali, F. L.; Pasquarè Mariotto, F. A.; Korzhenkov, A. M.; Oppizzi, P.; Bonzanigo, L.

    2015-08-01

    This paper shows, by field palaeoseismological data, the Holocene activity of the central segment of the intracontinental Talas-Fergana Fault (TFF), and the relevance of possible future seismic shaking on slope stability around a large water reservoir. The fault, striking NW-SE, is marked by a continuous series of scarps, deflected streams and water divides, and prehistoric earthquakes that offset substrate and Holocene deposits. Fault movements are characterised by right-lateral strike-slip kinematics with a subordinate component of uplift of the NE block. Structural, geological and geomorphological field data indicate that shallow and deep landslides are aligned along the TFF, and some of them are active. Where the TFF runs close to the reservoir, the fault trace is obscured by a series of landslides, affecting rock and soil materials and ranging in size from small slope instabilities to deep-seated gravity-induced slope deformations (DGSDs). The largest of these, which does not show clear evidence of present-day activity, involves a volume of about 1 km3 and is associated with smaller but active landslides in its lower part, with volumes in the order of 2.5 × 104 m3 to 1 × 106 m3. Based on the spatial and temporal relations between landslides and faults, we argue that at least some of these slope failures may have a coseismic character. Stability analyses by means of limit equilibrium methods (LEMs), and stress-strain analysis by finite difference numerical modelling (FDM), were carried out to evaluate different hazard scenarios linked to these slope instabilities. The results indicate concern for the different threats posed, ranging from the possible disruption of the M-41 highway, the main transportation route in central Asia, to the possible collapse of huge rock masses into the reservoir, possibly generating a tsunami.

  15. Detecting young, slow-slipping active faults by geologic and multidisciplinary high-resolution geophysical investigations: A case study from the Apennine seismic belt, Italy

    NASA Astrophysics Data System (ADS)

    Improta, L.; Ferranti, L.; de Martini, P. M.; Piscitelli, S.; Bruno, P. P.; Burrato, P.; Civico, R.; Giocoli, A.; Iorio, M.; D'Addezio, G.; Maschio, L.

    2010-11-01

    The Southern Apennines range of Italy presents significant challenges for active fault detection due to the complex structural setting inherited from previous contractional tectonics, coupled to very recent (Middle Pleistocene) onset and slow slip rates of active normal faults. As shown by the Irpinia Fault, source of a M6.9 earthquake in 1980, major faults might have small cumulative deformation and subtle geomorphic expression. A multidisciplinary study including morphological-tectonic, paleoseismological, and geophysical investigations has been carried out across the extensional Monte Aquila Fault, a poorly known structure that, similarly to the Irpinia Fault, runs across a ridge and is weakly expressed at the surface by small scarps/warps. The joint application of shallow reflection profiling, seismic and electrical resistivity tomography, and physical logging of cored sediments has proved crucial for proper fault detection because performance of each technique was markedly different and very dependent on local geologic conditions. Geophysical data clearly (1) image a fault zone beneath suspected warps, (2) constrain the cumulative vertical slip to only 25-30 m, (3) delineate colluvial packages suggesting coseismic surface faulting episodes. Paleoseismological investigations document at least three deformation events during the very Late Pleistocene (<20 ka) and Holocene. The clue to surface-rupturing episodes, together with the fault dimension inferred by geological mapping and microseismicity distribution, suggest a seismogenic potential of M6.3. Our study provides the second documentation of a major active fault in southern Italy that, as the Irpinia Fault, does not bound a large intermontane basin, but it is nested within the mountain range, weakly modifying the landscape. This demonstrates that standard geomorphological approaches are insufficient to define a proper framework of active faults in this region. More in general, our applications have wide

  16. Lateral migration of fault activity in Weihe basin

    NASA Astrophysics Data System (ADS)

    Feng, Xi-Jie; Dai, Wang-Qiang

    2004-03-01

    Lateral migration of fault activity in Weihe basin is a popular phenomenon and its characteristics are also typical. Taking the activity migrations of Wangshun Mountain piedmont fault toward Lishan piedmont fault and Weinan platform front fault, Dabaopi-Niujiaojian fault toward Shenyusi-Xiaojiazhai fault, among a serial of NE-trending faults from Baoji city to Jingyang County as examples, their migration time and process are analyzed and discussed in the present paper. It is useful for further understanding the structure development and physiognomy evolution history of Weihe basin.

  17. 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.

  18. A 'Propagating' Active Across-Arc Normal Fault Shows Rupture Process of the Basement: the Case of the Southwestern Ryukyu Arc

    NASA Astrophysics Data System (ADS)

    Matsumoto, T.; Shinjo, R.; Nakamura, M.; Kubo, A.; Doi, A.; Tamanaha, S.

    2011-12-01

    Ryukyu Arc is located on the southwestern extension of Japanese Island-arc towards the east of Taiwan Island along the margin of the Asian continent off China. The island-arc forms an arcuate trench-arc-backarc system. A NW-ward subduction of the Philippine Sea Plate (PSP)at a rate of 6-8 cm/y relative to the Eurasian Plate (EP) causes frequent earthquakes. The PSP is subducting almost normally in the north-central area and more obliquely around the southwestern area. Behind the arc-trench system, the Okinawa Trough (OT) was formed by back-arc rifting, where active hydrothermal vent systems have been discovered. Several across-arc submarine faults are located in the central and southern Ryukyu Arc. The East Ishigaki Fault (EIF) is one of the across-arc normal faults located in the southwestern Ryukyu Arc, ranging by 44km and extending from SE to NW. This fault was surveyed by SEABAT8160 multibeam echo sounder and by ROV Hyper-Dolphin in 2005 and 2008. The result shows that the main fault consists of five fault segments. A branched segment from the main fault was also observed. The southernmost segment is most mature (oldest but still active) and the northernmost one is most nascent. This suggests the north-westward propagation of the fault rupture corresponding to the rifting of the southwestern OT and the southward retreat of the arc-trench system. Considering that the fault is segmented and in some part branched, propagation might take place episodically rather than continuously from SE to NW. The ROV survey also revealed the rupture process of the limestone basement along this fault from the nascent stage to the mature stage. Most of the rock samples collected from the basement outcrop were limestone blocks (or calcareous sedimentary rocks). Limestone basement was observed to the west on the hanging wall far away from the main fault scarp. Then fine-grained sand with ripple marks was observed towards the main scarp. Limestone basement was observed on the main

  19. 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.

  20. Paleoseismicity and neotectonics of the Cordillera Blanca fault zone, Northern Peruvian Andes.

    USGS Publications Warehouse

    Schwartz, D.P.

    1988-01-01

    The Cordillera Blanca fault zone is a major W dipping normal fault that bounds the W side of a 120- 170-km wide zone of active extension along the crest of the N Peruvian Andes. The fault is approximately 210 km long and exhibits continuous geomorphic evidence of repeated late Pleistocene and Holocene displacements but has not been the source of historical or teleseismically recorded earthquakes. Trenching and mapping of fault scarps provide new information on earthquake recurrence, slip rate, timing of the most recent events and Andean neotectonics. At Quebrada Queroccocha, 55 km from valley fill lacustrine and fluvial deposits are displaced 7.5-8 m. Scarp profiles, tectonic terraces, and trench exposures indicate 5 to 7 scarp-forming earthquakes of 2-3 m per event during the past 11 000-14 000 yrs at this location.-from Author

  1. 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.

    2015-12-01

    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.

  2. 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.

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

    NASA Astrophysics Data System (ADS)

    Awata, Y.; Yoshioka, T.

    2005-12-01

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

  4. 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

  5. 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

  6. MPF model ages of the Rembrandt basin and scarp system, Mercury.

    NASA Astrophysics Data System (ADS)

    Ferrari, Sabrina; Massironi, Matteo; Marchi, Simone; Byrne, Paul K.; Klimczak, Christian; Cremonese, Gabriele

    2013-04-01

    The 715-km-diameter Rembrandt basin is the largest well-preserved impact feature of the southern hemisphere of Mercury [1] (Fig. 1), and was imaged for the first time during the second flyby of the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission [2]. Much of the basin interior is covered by smooth, high-reflectance plains interpreted to be of volcanic origin [1-3] that host sets of contractional and extensional tectonic structures. Notably, Rembrandt basin and its smooth plains are cross-cut by a 1,000-km-long reverse fault system [1-5] that trends ~E-W, bending toward the north within the basin. The individual faults of this system accommodated crustal shortening that resulted from global contraction as Mercury's interior cooled [1]. The current shape of the reverse fault system may have been influenced by the formation of the Rembrandt basin [5]. The emplacement of the interior smooth plains predates both the basin-related tectonism and the final development of the giant scarp, which is suggestive of either short-lived volcanic activity immediately after basin formation or a later volcanic phase set against prolonged tectonic activity. In order to quantify the duration of volcanic and tectonic activity in and around Rembrandt basin, we determined the crater count-derived ages of the involved terrains by means of the Model Production Function (MPF) chronology of Mercury [6-8], which is rely on the knowledge of the impactors flux on the planet. Crater chronology allowed us to constrain the Rembrandt basin formation to the early Calorian period and a widespread resurfacing up to 3.5 Ga ago. The volcanic activity affected both the basin and its surroundings, but ended prior to some basin-related and regional faulting. Hence, if the giant scarp begun to develop even before the basin formation (as suggested by its length-displacement profile across the basin itself, [5]) the regional tectonic activity along this structure might have

  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. Formation of cataclasites in shallow-subsurface settings - meteoric diagenetic processes control fault rock formation at seismogenic faults in the Abruzzi Apennines, Italy

    NASA Astrophysics Data System (ADS)

    Ortner, Hugo; Pomella, Hannah; Sanders, Diethard

    2014-05-01

    To understand the interaction of surface and tectonic processes during the formation of fault rocks, we studied two faults located in the Abruzzi Appenines NE of L'Aquila, that have been active in historical time. The south-dipping Assergi fault is at least 17 km long, with an offset of 2.5 km in its central part. Over most of its extent, the fault is evident by a scarp. Present day morphology is related to selective erosion, as the fault scarp is covered in some areas by lithified talus deposits. The talus is, however, in many places involved in the faulting. The Campo Imperatore fault is about 30 km long, with an offset of 2 km. The fault is located a few km north of the Assergi fault and has approximately the same orientation. It seems to be complimentary to the Assergi fault: where the offset across the Assergi fault diminishes, throw of the Campo Imperatore fault increases. The fault scarp of the Campo Imperatore fault is partly covered by active alluvial fans, but older lithified fans are offset by related antithetic faults. Both faults have several meters of fault rocks; The fault rocks of the Campo Imperatore fault are kakirites. Cataclasites of the Assergi fault vary in thickness between 15 and 3 meters, which is related to the presence of Riedel shears that offset the boundary between the host rock and the fault rock. Within the cataclasites diffuse Riedel planes crosscut the fault rocks and offset diffuse or sharp planes parallel to the main fault that can be closely spaced. Diffuse zones parallel to the main fault show karstic vugs produced by meteoric dissolution. The vugs may be lined or filled by calcite cement, and/or with internal sediments (e. g., lime mud, vadose silt, dissolution clasts of cataclasite). Meteoric dissolution guided by the main faults also resulted in large karstic pores filled with collapse breccias and flowstones; clasts of flowstones and flowstone-cemented breccias, in turn, locally became reworked into cataclasites. Presence

  9. Late Quaternary Activity and Seismogenic Potential of the Gonave microplate: South Coast Fault Zone of Southern Jamaica

    NASA Astrophysics Data System (ADS)

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

    2008-12-01

    The South Coast fault zone (SCFZ) strikes east-west and forms a scarp as high as 600 m along the southern coast of Jamaica. It has been postulated that this fault acts as a left-lateral, strike-slip 'bypass' fault that truncates the large, right-stepping restraining bend formed between the Plantain Garden fault zone of southeastern Jamaica and the Duanvale-Walton fault zone of northwestern Jamaica. GPS measurements near the SCFZ show anomalously rotated vectors consistent with active left-lateral shear. Anomalous topography along the trace of the SCFZ includes two, doubly plunging anticlines: Kemp's Hill (119 m), an isolated high in the otherwise flat Vere Plain, and Round Hill (333 m), a larger high directly adjacent to the coast. Field work identified the most active trace of the SCFZ in a notch along the north flank of Round Hill; this trace can be extrapolated to the west along the coast and east that locally defines a low scarp in alluvium. Channel profiles constructed for six rivers and streams crossing the projected trace of the SCFZ show convex-upward morphologies, consistent with dominance of tectonic uplift over river downcutting. To better define the subsurface location of the SCFZ beneath the Vere Plain, a gravity survey network consisting of 327 stations and covering an areas of 500 km2 was performed using a Lacoste and Romberg G-meter. Differential GPS allowed centimeter-level elevation control for each station. Gravity corrections (elevation, latitude, instrument drift, and earth tides) were made using QC Tool software, and topographic and terrane corrections were made using both local topographic measurements and high-resolution SRTM data. An ~20 mgal negative gravity anomaly on the otherwise flat gravity field of the Vere Plain corresponds with the projected trace of the SCFZ across the Vere Plain and the locations of one river offset. We interpret that the SCFZ has down-to-the-south throw, which has led to thickening of Quaternary sediments south

  10. Is There any Relationship Between Active Tabriz Fault Zone and Bozkush Fault Zones, NW Iran?

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    Tectonic plate motions and consequent earthquakes can be actively observed along the northwestern Iran. The Tabriz fault zone (TFZ), also called the North Tabriz fault, active right-lateral strike-slip fault zone with slip rates estimated as ~8 mm/yr, has been vigorously deforming much of northwestern Iran for over the past several million years. Historical earthquakes on the TFZ consist of large magnitude, complimentary rupture length and changed the landscape of regions surrounding the fault zone. The TFZ in the city of Bostanabad is more segmented with several strands and joined by a series of WNW-ESE trending faults, called the Bozkush fault zones. The Bozkush fault zones (BFZ's) (south and north), bounding arch-shaped Bozkush mountains, generates not only hundreds of small earthquakes each year but also has provided significant earthquakes that have been historically documented. The rock units deformed within the BFZ's include Eocene-Oligocene volcanic rocks with intercalation limestone, Oligo-Miocene clastic rocks with intercalation gypsiferous marl and Plio-Quaternary volcano-sedimentary rocks, travertine and alluvium. The North and South Bozkush fault zones are characterized by development of structures typically associated with transpression. These include right-lateral strike-slip faults, thrust faults and foldings. Our field studies indicate that these zones include step to sub-vertical fault surfaces trending NW and NE with slickenlines. Slickensides preserve brittle kinematic indicators (e.g., Riedel shear patterns, slickenside marks) suggesting both dextral displacements and top-to-the-NE/NW and-SE/SW sense of shearing. Besides, mesoscopic and microscopic ductile kinematic indicators (e.g., asymmetric porphyroclasts, C/S fabrics) within Miocene gypsum marl show dextral displacements. Fault rocks along most of these faults consist of incohesive fault breccia and gauge. Adjacent to the fault contact evidence of bedding in Oligo-Miocene and Plio

  11. 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

  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. 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.

  14. Eastern Olympus Mons Basal Scarp and Aureole lobe: Recent Structural Evidence for Formation and Development

    NASA Astrophysics Data System (ADS)

    Weller, M. B.; McGovern, P. J.; Fournier, T.; Morgan, J. K.; Katz, O.

    2012-12-01

    The origin of the Olympus Mons (OM) basal scarp and the adjacent enigmatic aureole lobe deposits have long been controversial, with many hypotheses having been postulated for their linked formation, ranging from sub-glacial eruptions (e.g. Helgason, 1999), to numerous landslide and flank collapse models (e.g. Borgia, 1990; Lopes et al., 1980). While a landslide origin is compelling upon the examination of the OM basal scarp morphology, much of the controversy remains, and the subsurface structure of OM is not well understood. With the release of high resolution Digital Terrain Models (DTMs) of Mars from High Resolution Stereo Camera (HRSC) data, we examine a unique portion of the edifice, the Eastern OM Basal Scarp (EOMBS). The EOMBS exhibits two parallel bounding structures: a nearly 100 km-long up-slope extensional normal fault system, with associated offsets on the order of 10-100m, bordered by radial tear faults; and a 160-200 km-long down-slope contractional wrinkle ridge network of varying vergence, inferred to define the boundaries of a "pop-up" structure, associated offsets are on the order of 100m, and were last inferred to be active in recent geologic time at < 45 Ma (Basilevsky et al., 2006). The wrinkle ridge network extends an additional 60-100 km south of the identified normal fault system. We suggest that these fault systems, within the region of the radial tear faults, may be linked by failure surfaces, that their displacements accommodate downslope movement of the flank, and may be direct evidence linking the "East" aureole lobe to the EOMBS. Calculations based on limit equilibrium principles, and matched to the observed faulting locations and slope geometries, suggests a mechanically weak, pore-fluid saturated detachment layer (e.g. similar to phyllosilicates), at a depth of 0 to -3km below the reference datum, underlies eastern OM, consistent with models of OM as a spreading volcanic edifice (Borgia, 1990; McGovern and Morgan, 2009). Our

  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. 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.

  17. Ages estimated from a diffusion equation model for scarp degradation

    USGS Publications Warehouse

    Colman, Steven M.; Watson, K.E.N.

    1983-01-01

    The diffusion equation derived from the continuity equation for hillslopes is applied to scarp erosion in unconsolidated materials. Solutions to this equation allow direct calculation of the product of the rate coefficient and the age of the scarp from measurements of scarp morphology. Where the rate coefficient can be estimated or can be derived from scarps of known age, this method allows direct calculation of unknown ages of scarps.

  18. 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.

  19. 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)

  20. 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

  1. An underwater landslide or slump on an active submarine fault - a possible source of a devastating tsunami?

    NASA Astrophysics Data System (ADS)

    Matsumoto, T.

    2007-12-01

    A Mw 7.7 earthquake and subsequent large-scale tsunami occurred on 17th July 2006 off the southern coast of Java Island, Indonesia. A maximum of 7.7 m inundation height was recorded in Pangandaran on the southern coast of Java, according to the field survey just after the tsunami (Tsuji et al., 2006). However, since there are few residents who noticed the earthquake tremors, the earthquake may possibility be so-called "tsunami earthquake". The aftershocks from July to September occurred on the fore-arc area and their CMT solution suggests the predominant north-south tensile stress. R/V MIRAI passed the aftershock area in 2004 and 2005 with continuous multibeam bathymetric survey. The processed topographic map shows a lot of amphitheatres with the scale of 8-20 km along the fault scarps. Convexity landforms are located below the footwall of the amphitheatres, apparently the relics of an underwater landslide, and their relative elevation exceeds 1000 m in maximum. This area is characterised by the southeastern extension of Mentawai Fault and its associated minor faults ranging from the Sumatra fore-arc area. The observed amphitheatres and relics of underwater landslides are located along the active faults. Considering that the tsunami wave height distribution is concentrated on a specific narrow area compared with the scale of the mainshock, the mainshock possibly triggered underwater landslides on these amphitheatres and the slides generated a large-scale tsunami. The Ryukyu district was attacked by a M7-class earthquake followed by a devastating tsunami in 1771. 'The East Ishigaki Fault,' one of the across-arc active normal faults in this area was studied precisely by multibeam echo sounding. The study revealed a slump on the segmented active fault. The slump itself may generate a tsunami with the wave height of several meters and might cause the 1771 tsunami together with the faulting itself. Some recent geohazards also show that a landslide or a slump is

  2. 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.

  3. 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.

  4. Fault mirrors in seismically active fault zones: A fossil of small earthquakes at shallow depths

    NASA Astrophysics Data System (ADS)

    Kuo, Li-Wei; Song, Sheng-Rong; Suppe, John; Yeh, En-Chao

    2016-03-01

    Fault mirrors (FMs) are naturally polished and glossy fault slip surfaces that can record seismic deformation at shallow depths. They are important for investigating the processes controlling dynamic fault slip. We characterize FMs in borehole samples from the hanging wall damage zone of the active Hsiaotungshi reverse fault, Taiwan. Here we report the first documented occurrence of the combination of silica gel and melt patches coating FMs, with the silica gel resembling those observed on experimentally formed FMs that were cataclastically generated. In addition, the melt patches, which are unambiguous indicators of coseismic slip, suggest that the natural FMs were produced at seismic rates, presumably resulting from flash heating at asperities on the slip surfaces. Since flash heating is efficient at small slip, we propose that these natural FMs represent fossils of small earthquakes, formed in either coseismic faulting and folding or aftershock deformation in the active Taiwan fold-and-thrust belt.

  5. 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

  6. 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

  7. Characterizing subaqueous co-seismic scarps using coeval specific sedimentary events; a case study in Lesser Antilles

    NASA Astrophysics Data System (ADS)

    Beck, C.; Reyss, J.; Feuillet, N.; Leclerc, F.; Moreno, E.

    2012-12-01

    Improvements of active fault surveying have shown that creep, or alternating creep and co-seismic displacements, are not rare. Nevertheless, either on land (trenching), or in subaqueous setting (seismic imaging and coring), active fault offsets, investigated for paleoseismic purpose, are sometimes assumed as co-seismic without direct evidences. At the opposite, within adequate sedimentary archives, some gravity reworking events may be attributed to earthquake triggering, but often do not permit to locate the responsible fault and the co-seismic rupture. In the here-discussed example, both types of observations could be associated: faulting offsets and specific sedimentary events "sealing" them. Several very high resolution (VHR) seismic profiles obtained during The GWADASEIS cruise (Lesser Antilles volcanic arc, February-March 2009) evidenced frequent "ponding" of reworked sediments in the deepest areas. These bodies are acoustically transparent (few ms t.w.t. thick) and often deposited on the hanging walls of dominantly normal faults, at the base of scarps, as previously observed along the North Anatolian Fault (Beck et al., 2007, doi:10.1016/j.sedgeo.2005.12.031). Their thicknesses appear sufficient to compensate (i.e. bury) successive offsets, resulting in a flat and horizontal sea floor through time. Offshore Montserrat and Nevis islands, piston coring (4 to 7 m long) was dedicated to characterize the most recent of these particular layers. An up to 2m-thick "homogenite" appears capping the RedOx water/sediment interface. 210Pb and 137Cs activities lack in the homogenite, while a normal unsupported 210Pb decrease profile and a 137Cs peak, corresponding to the Atmospheric Nuclear Experiments (1962), are present below (Beck et al. 2012, doi:10.5194/nhess-12-1-2012). This sedimentary event and the coeval scarp are post-1970 AD, and attributed either to the March 16th 1985 earthquake or to the October 8th 1974 one (respectively Mw6.3 and Mw7.4). Based on the

  8. Characterization of recent Lake Tahoe fault activity: Combining Sub-Meter Resolution Seismic Imagery with AMS C-14 Dated Submerged Paleo-Surfaces.

    NASA Astrophysics Data System (ADS)

    Dingler, J. A.; Kent, G. M.; Babcock, J. A.; Driscoll, N. W.; Harding, A. J.; Gayes, P. T.; Karlin, B.; Morgan, C. W.; Heyvaert, A.; Richards, B. C.

    2002-12-01

    Deformational strain within the Lake Tahoe Basin was mapped during previous campaigns using a combination of high resolution seismic CHIRP, multi-beam swath bathymetry, and airborne laser altimetry. These previous campaigns identified submerged paleo-shorelines of Pleistocene to early Holocene age, which act as a tectonic strain marker due to fault related disruptions of this once flat surface, as well as significantly offset fault scarps. Building upon this previous work, specific sites were selected for additional investigation with seismic CHIRP and AMS C-14 dated vibra and piston cores. The combination of these three techniques is ideally suited for quantifying recent fault activity through the correlation of paleo-surfaces and accurate age determinations. Initial analysis of seismic CHIRP and piston coring conducted in Emerald Bay shows a complex normal fault system with a sedimentation rate much higher than other parts of the lake. Seismic CHIRP conducted near Zephyr Cove was able to image multiple paleo-shorelines. Vibra coring of these same surfaces recovered sands of the same consistency as beach sand. Additional piston cores were collected at various lake locations below 400 m depth, including two cores taken across the Stateline Fault. Core analysis and AMS C-14 dating combined with site-specific seismic CHIRP, and previous mapping, will improve chronological control on the fault activity within the Lake Tahoe Basin.

  9. 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.

  10. 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.

  11. Recurrent late Quaternary surface faulting along the southern Mohawk Valley fault zone, NE California

    SciTech Connect

    Sawyer, T.L.; Hemphill-Haley, M.A. ); Page, W.D. )

    1993-04-01

    The Mohawk Valley fault zone comprises NW- to NNW-striking, normal and strike-slip( ) faults that form the western edge of the Plumas province, a diffuse transitional zone between the Basin and Range and the northern Sierra Nevada. The authors detailed evaluation of the southern part of the fault zone reveals evidence for recurrent late Pleistocene to possibly Holocene, moderate to large surface-faulting events. The southern Mohawk fault zone is a complex, 6-km-wide zone of faults and related features that extends from near the crest of the Sierra Nevada to the middle of southern Sierra Valley. The fault zone has two distinct and generally parallel subzones, 3 km apart, that are delineated by markedly different geomorphic characteristics and apparently different styles of faulting. Paleoseismic activity of the western subzone was evaluated in two trenches: one across a fault antithetic to the main range-bounding fault, and the other across a splay fault delineated by a 3.7-m-high scarp in alluvium. Stratigraphic relations, soil development, and radiocarbon dates indicate that at least four mid- to late-Pleistocene surface-faulting events, having single-event displacements in excess of 1.6 to 2.6 m, occurred along the splay fault prior to 12 ka. The antithetic fault has evidence of three late Pleistocene events that may correspond to event documented on the splay fault, and a Holocene event that is inferred from youthful scarplets and small closed depressions.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  13. 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.

  14. The Quaternary Deformational History of the East Potrillo Fault, Dona Ana County, New Mexico

    NASA Astrophysics Data System (ADS)

    Cervera, S. N.; Hurtado, J. M.; Clague, J. W.; Andronicos, C. L.

    2006-12-01

    The East Potrillo Mountains are located immediately north of the U.S.-Mexico border in southwestern Dona Ana County, New Mexico. Along the east flank of the East Potrillo Mountains are north-striking piedmont scarps that indicate continuous, late Quaternary movement on the high-angle normal faults of the East Potrillo Fault system. This East Potrillo fault may pose a major seismic hazard to the 2.2 million people that live in the El Paso, Texas border region. We investigate the Quaternary deformational history in this area using GPS, field and remote sensing observations, traditional survey techniques, and new advances in desert varnish geochronology. We focus on estimating the average slip rate on the East Potrillo fault and the earthquake recurrence interval. The amount of Quaternary deformation is constrained by measuring displacements of geomorphic surfaces, including alluvial fans and fluvial deposits. A total of thirteen profiles perpendicular to the scarp have been surveyed to reproduce the fault scarp geometry. From these profiles, we estimate fault scarp age by using three types of slope degradation modeling: calibrated scarp-height-slope-angle relationships, a diffusion model, and a general morphologic dating method for transport-limited hillslopes. A total of 18 varnished rock samples were also collected from displaced alluvial fan surfaces and from cut terraces associated with slip events on the East Potrillo fault. These samples were analyzed using x-ray fluorescence (XRF) to obtain concentrations of Mn and Fe present in the varnish. The accumulation of Fe and Mn reflects the amount of time that varnish has accumulated on a clast, and, thus, provides a constraint on the age of the surface from which the clast was obtained. The morphologic dating results will be compared with the desert varnish results to better understand landform evolution, fault mechanics, and determine the slip history in the study area. These measurements are vital for constraining

  15. Active and inactive faults in southern California viewed from Skylab

    NASA Technical Reports Server (NTRS)

    Merifield, P. M.; Lamar, D. L.

    1977-01-01

    A number of prominent linears in basement terrane of the Peninsular Ranges appeared on Skylab images. In most cases, they were represented by straight or gently curved valleys; however, detailed field investigations have shown that several of these linears mark previously unmapped faults which form two distinct fault sets; one set trends northeast, the other west-northwest. No indications of recent movement were present on these faults which were truncated by seismically active, northwest trending fault zones such as the Elsinore and San Jacinto. Right-lateral separation is demonstrable on the northeast trending set.

  16. 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.

  17. 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

  18. 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.

  19. 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

  20. Slip distributions on active normal faults measured from LiDAR and field mapping of geomorphic offsets: an example from L'Aquila, Italy, and implications for modelling seismic moment release

    NASA Astrophysics Data System (ADS)

    Wilkinson, Maxwell; Roberts, Gerald P.; McCaffrey, Ken; Cowie, Patience A.; Faure Walker, Joanna P.; Papanikolaou, Ioannis; Phillips, Richard J.; Michetti, Alessandro Maria; Vittori, Eutizio; Gregory, Laura; Wedmore, Luke; Watson, Zoë K.

    2015-05-01

    Surface slip distributions for an active normal fault in central Italy have been measured using terrestrial laser scanning (TLS), in order to assess the impact of changes in fault orientation and kinematics when modelling subsurface slip distributions that control seismic moment release. The southeastern segment of the surface trace of the Campo Felice active normal fault near the city of L'Aquila was mapped and surveyed using techniques from structural geology and using TLS to define the vertical and horizontal offsets of geomorphic slopes since the last glacial maximum (15 ± 3 ka). The fault geometry and kinematics measured from 43 sites and throw/heave measurements from geomorphic offsets seen on 250 scarp profiles were analysed using a modification of the Kostrov equations to calculate the magnitudes and directions of horizontal principal strain-rates. The map trace of the studied fault is linear, except where a prominent bend has formed to link across a former left-stepping relay-zone. The dip of the fault and slip direction are constant across the bend. Throw-rates since 15 ± 3 ka decrease linearly from the fault centre to the tip, except in the location of the prominent bend where higher throw rates are recorded. Vertical coseismic offsets for two palaeo earthquake ruptures seen as fresh strips of rock at the base of the bedrock scarp also increase within the prominent bend. The principal strain-rate, calculated by combining strike, dip, slip-direction and post 15 ± 3 ka throw rate, decreases linearly from the fault centre towards the tip; the strain-rate does not increase across the prominent fault bend. The above shows that changes in fault strike, whilst having no effect on the principal horizontal strain-rate, can produce local maxima in throw-rates during single earthquakes that persist over the timescale of multiple earthquakes (15 ± 3 ka). Detailed geomorphological and structural characterisation of active faults is therefore a critical

  1. Spatial distribution of microfractures in damage zone along active faults

    NASA Astrophysics Data System (ADS)

    Mizoguchi, K.; Ueta, K.

    2011-12-01

    For basement faults without overlying quaternary sediments, there are few methods to determine whether the fault is active or not. Recently, we focus on microfracture characteristics of damage zone along active faults as used for the assessment of seismic activity of basement faults. In this study, we examined a newly-found active fault (Sasaki et al., 2011) located to the east of the epicentral area of 1943 Tottori earthquake, southwest Japan. The fault zone consists of the 75 cm thick fault core of the purple-colored clayey fault gouge and the fault breccia with cataclastic foliation, and the surrounding damage zone developed in Cretaceous Kyushozan granite. A subsidiary fault accompanying a fault core of white clayey fault gouge that ranges from 3 to 5 mm thickness is located at about 110 m from the main fault. We collected ten orientated samples 9 m to 180 m from the main fault. The samples were coated with epoxy and then thin sections were cut perpendicular to the fault plane and parallel to a horizontal plane because the slip direction is unknown. Microfracture density data were collected from 40 quartz grains per thin section (per sample). A thin section is marked with a square grid at 3 mm intervals and we picked one grain up in each square of the grid marked on the thin section to reduce operator sampling bias resulting from the selection of quartz grains. Quartz is suitable to estimate the damage that the rock sample has sustained because quartz without cleavage acts as an isotropic medium for fracturing and it is physically and chemically resistant to weathering than other minerals constituting the granite. We counted the number of microfractures that intersected a line which was drawn from the edge of each quartz grain, through the center point, to the other edge of the grain. The linear microfracture density for each sample is calculated to be the total number of microfractures intersecting the lines divided by the total counting line length. Under the

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    The Piano di Pezza fault is the north-westernmost segment of the >20 km long Ovindoli-Pezza active normal fault-system (central Italy). Although existing paleoseismic data document high vertical Holocene slip rates (~1 mm/yr) and a remarkable seismogenic potential of this fault, its subsurface setting and Pleistocene cumulative displacement are still poorly known. We investigated for the first time by means of high-resolution seismic and electrical resistivity tomography coupled with time domain electromagnetic (TDEM) measurements the shallow subsurface of a key section of the Piano di Pezza fault. Our surveys cross a ~5 m-high fault scarp that was generated by repeated surface-rupturing earthquakes displacing some Late Holocene alluvial fans. We provide 2-D Vp and resistivity images which clearly show significant details of the fault structure and the geometry of the shallow basin infill material down to 50 m depth. We can estimate the dip (~50°) and the Holocene vertical displacement of the master fault (~10 m). We also recognize in the hangingwall some low-velocity/low-resistivity regions that we relate to packages of colluvial wedges derived from scarp degradation, which may represent the record of several paleo-earthquakes older than the Late Holocene events previously recognized by paleoseismic trenching. Conversely, due to the limited investigation depth of seismic and electrical tomography, the estimation of the cumulative amount of Pleistocene throw is hampered. Therefore, to increase the depth of investigation, we performed 7 TDEM measurements along the electrical profile using a 50 m loop size both in central and offset configuration. The recovered 1-D resistivity models show a good match with 2-D resistivity images in the near surface. Moreover, TDEM inversion results indicate that in the hangingwall, ~200 m away from the surface fault trace, the carbonate pre-Quaternary basement may be found at ~90-100 m depth. The combined approach of electrical and

  3. Dynamic rupture activation of backthrust fault branching

    NASA Astrophysics Data System (ADS)

    Xu, Shiqing; Fukuyama, Eiichi; Ben-Zion, Yehuda; Ampuero, Jean-Paul

    2015-03-01

    We perform dynamic rupture simulations to investigate the possible reactivation of backthrust branches triggered by ruptures along a main thrust fault. Simulations with slip-weakening fault friction and uniform initial stress show that fast propagation speed or long propagation distance of the main rupture promotes reactivation of backthrust over a range of branch angles. The latter condition may occur separately from the former if rupture speed is limited by an increasing slip-weakening distance towards the junction direction. The results suggest a trade-off between the amplitude and duration of the dynamic stress near the main rupture front for backthrust reactivation. Termination of the main rupture by a barrier can provide enhanced loading amplitude and duration along a backthrust rooted near the barrier, facilitating its reactivation especially with a high frictional resistance. The free surface and depth-dependent initial stress can have several additional effects. The sign of the triggered motion along the backthrust can be reversed from thrust to normal if a deeply nucleated main rupture breaks the free surface, while it is preserved as thrust if the main rupture is terminated by a barrier at depth. The numerical results are discussed in relation to several recent megathrust earthquakes in Sumatra, Chile, and Japan, and related topics such as branch feedbacks to the main fault. The dynamic view on backthrust fault branching provided by the study fills a gap not covered by quasi-static models or observations. A specific examined case of antithetic fault branching may be useful for indicating a barrier-like behavior along the main fault.

  4. Evidence against Late Quaternary activity along the Northern Karakoram Fault

    NASA Astrophysics Data System (ADS)

    Robinson, A. C.; Owen, L. A.; Hedrick, K.; Blisniuk, K.; Sharp, W. D.; Chen, J.; Schoenbohm, L. M.; Imrecke, D. B.; Yuan, Z.; Li, W.

    2012-12-01

    Although the entire 1000 km long Karakoram fault has long been interpreted to be active, recent work based primarily on interpretation of satellite imagery suggests that the northern end of the fault, where it enters the Pamir mountains, is inactive. We present field observations and geochronologic data from the southern end of the Tashkurgan valley, in the Pamir, on the Karakoram fault where it splits into two identifiable strands; an eastern strand which is the main trace of the Karakoram fault, and a western strand called the Achiehkopai fault. These results support the interpretation that the northern Karakoram fault is currently inactive, and has been for at least 200 ka: 1) Near the village of Dabudaer in the southern Tashkurgan valley the main trace of the Karakoram fault is orthogonally cut by a narrow incised valley with no observed lateral offset across the fault. Within this valley, a strath terrace ~50 m above the active drainage which overlies the main trace of the Karakoram fault which is capped by a carbonate cemented conglomerate. U-series analyses of carbonate cement from a correlative deposit located several km away yields a minimum depositional age of 76±12 ka. This age is coeval with the local Tashkurgan glacial stage we dated using Be-10 surface exposure dating (66±10 ka; Owen et al., 2012, Quaternary Science Reviews) suggesting both the conglomerate and strath terrace formed during this glacial stage. 2) ~25 km south of Dabudar, the main trace of the Karakoram projects beneath Tashkurgan glacial stage moraine and fluvial-glacial deposits which similarly show no evidence of disturbance by strike-slip deformation. Both of the above results demonstrate the main trace of the Karakoram fault has been inactive since at least ~70 ka. 3) Both the Karakoram and Achiehkopai faults are overlain by older Dabudaer glacial stage moraine deposits which are interpreted to be at least as old as the penultimate glacial, but may be >200 ka based on our Be-10

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

    PubMed

    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

  6. 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

  7. 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

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

    NASA Astrophysics Data System (ADS)

    Meghraoui, Mustapha

    2014-05-01

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

  9. 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

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

    NASA Astrophysics Data System (ADS)

    Rizza, M.

    2011-12-01

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

  11. 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.

  12. New GPS Network on the Active Fault System in Taiwan

    NASA Astrophysics Data System (ADS)

    Hou, C.; Chen, Y.; Hu, J.; Lin, C.; Chen, C.; Wang, J.; Chung, L.; Chung, W.; Hsieh, C.; Chen, Y.

    2004-12-01

    According to the historical records, disastrous earthquakes occurred in Taiwan were caused by reactivations of active faults. In last century, there were five with the surface rupture: 1906 Meishan Eq. (the Meishan F.), 1935 Hsihchu Eq. (the Shihtan and the Tuntzuchiao F.), 1946 Hsinhua Eq. (Hsinhua F.), 1951 Hualien-Taitung Eq. (Longitudinal Valley F.), and 1999 Chi-Chi Eq. (the Chelungpu F.). In order to identify earthquake associated surface rupture and further to mitigate potential hazards, the investigation and monitoring on the active fault system are of great urgency. Central Geological Survey (CGS) of Taiwan is currently executing a 5-year (2002-2006) project, integrating geological and geodetic data to better characterize short-term and long-term spatial and temporal variations in deformation across major already-known active faults of Taiwan. For the former, we use field survey, drilling, geophysical exploration, and trenching to recognize the long-term slip rate and recurrence interval of each fault. For the latter, we deploy near-fault campaign-style GPS and leveling monitoring networks. Here we further combine the result of other GPS networks including continuous-mode. This project is actually concentrated on fault-specific investigation.. Until Dec. 2004, we have set up 756 GPS stations and 27 precise leveling lines including 1024 leveling benchmarks. For the purpose of understanding temporal variability and receive continuous record, the CGS began to deploy 6~10 new GPS stations of continuous mode since 2004. Upon the completion of the geodetic project, we are supposed to provide information on short-term slip rates of major active faults. By integrating other geological datasets we will also evaluate the short-term and long-term behavior of the active faults, and further offer insight into spatial and temporal variability in deformation processes.

  13. 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

  14. Slip distributions on active normal faults measured from Terrestrial Laser Scan (TLS) data and field mapping of geomorphic offsets: An example from L'Aquila, Italy, and implications for modeling seismic moment release

    NASA Astrophysics Data System (ADS)

    Wilkinson, M. W.; Roberts, G.; McCaffrey, K. J.; Cowie, P. A.; Faure Walker, J.; Papanikolaou, I.; Phillips, R. J.; Michetti, A.; Vittori, E.

    2012-12-01

    Surface slip distributions for an active normal fault in Italy have been measured using terrestrial laser scanning (TLS), concentrating on offsets developed since 15 ±3 ka and for 2 palaeoearthquake ruptures, in order to assess the impact of spatial changes in fault orientation and kinematics on sub-surface slip distributions that control seismic moment release. The southeastern half of the surface trace of the Campo Felice active normal fault near the city of L'Aquila, central Italy, was scanned with TLS to define the vertical and horizontal offsets of geomorphic slopes that formed during the last glacial maximum (15 ±3 ka) from the center of the fault to its southeastern tip. Field measurements were made to define the strike and dip of the fault plane and plunge and plunge direction of the slip vector from striations on slickensides. Throw measurements from 250 TLS-derived scarp profiles were analyzed using the crossint cross section interpretation program developed by the authors specifically for this study. Field data of fault kinematics from 43 sites were combined with the TLS-derived throw measurements using a modification of the Kostrov equations to calculate the magnitude and directions of the horizontal principle strain-rates. The studied 5 km long portion of the fault has an overall strike of 140°, but has a prominent bend where the strike is 100-140°, where the fault has linked across a former left-stepping relay-zone which had an along strike length of ~600 m and across strike width of ~300 m. Throw-rates defined by TLS-derived profiles across a 15 ±3 ka bedrock fault scarp decrease linearly from 0.95 ±0.025 mm/yr at the fault center through 0.5 ±0.025 mm/yr to zero at the fault tip, except in the position of the prominent bend where throws rates increase by 0.15 ±0.025 mm/yr over a distance of ~1 km. The vertical co-seismic offsets averaged between two palaeoearthquake ruptures that manifest themselves as fresh stripes of rock at the base of

  15. Erosion influences the seismicity of active thrust faults.

    PubMed

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

    2014-01-01

    Assessing seismic hazards remains one of the most challenging scientific issues in Earth sciences. Deep tectonic processes are classically considered as the only persistent mechanism driving the stress loading of active faults over a seismic cycle. Here we show via a mechanical model that erosion also significantly influences the stress loading of thrust faults at the timescale of a seismic cycle. Indeed, erosion rates of about ~0.1-20 mm yr(-1), as documented in Taiwan and in other active compressional orogens, can raise the Coulomb stress by ~0.1-10 bar on the nearby thrust faults over the inter-seismic phase. Mass transfers induced by surface processes in general, during continuous or short-lived and intense events, represent a prominent mechanism for inter-seismic stress loading of faults near the surface. Such stresses are probably sufficient to trigger shallow seismicity or promote the rupture of deep continental earthquakes up to the surface. PMID:25412707

  16. Kanda fault: A major seismogenic element west of the Rukwa Rift (Tanzania, East Africa)

    NASA Astrophysics Data System (ADS)

    Vittori, Eutizio; Delvaux, Damien; Kervyn, François

    1997-09-01

    The NW-SE trending Rukwa Rift, part of the East African Rift System, links the approximately N-S oriented Tanganyika and Nyassa (Malawi) depressions. The rift has a complex half-graben structure, generally interpreted as the result of normal and strike-slip faulting. Morphological and structural data (e.g. fault scarps, faceted spurs, tilting of Quaternary continental deposits, volcanism, seismicity) indicate Late Quaternary activity within the rift. In 1910 an earthquake of M = 7.4 (historically the largest felt in Africa) struck the Rukwa region. The epicentre was located near the Kanda fault, which affects the Ufipa plateau, separating the Rukwa depression from the south-Tanganyika basin. The geomorphic expression of the Kanda fault is a prominent fresh-looking scarp more than 180 km long, from Tunduma to north of Sumbawanga, that strikes roughly NW-SE, and dips constantly northeast. No evidence for horizontal slip was observed. Generally, the active faulting affects a very narrow zone, and is only locally distributed over several subparallel scarps. The height of the scarp progressively decreases towards the northwest, from about 40-50 m to a few metres north of Sumbawanga. Faulted lacustrine deposits exposed in a road cut near Kaengesa were dated as 8340 ± 700 and 13 600 ± 1240 radiocarbon years. These low-energy deposits now hang more than 15 m above the present-day valley floor, suggesting rapid uplift during the Holocene. Due to its high rate of activity in very recent times, the Kanda Fault could have produced the 1910 earthquake. Detailed paleoseismological studies are used to characterize its recent history. In addition, the seismic hazard posed by this fault, which crosses the fast growing town of Sumbawanga, must be seriously considered in urban planning.

  17. Quaternary estimates of average slip-rates for active faults in the Mongolian Altay Mountains: the advantages and assumptions of multiple dating techniques

    NASA Astrophysics Data System (ADS)

    Gregory, L. C.; Walker, R. T.; Thomas, A. L.; Amgaa, T.; Bayasgalan, G.; Amgalan, B.; West, A.

    2010-12-01

    Active faults in the Altay Mountains, western Mongolia, produce surface expressions that are generally well-preserved due to the arid central-Asian climate. Motion along the right-lateral strike-slip and oblique-reverse faults has displaced major river systems by kilometres over millions of years and there are clear scarps and linear features in the landscape along the surface traces of active fault strands. With combined remote sensing and field work, we have identified sites with surface features that have been displaced by tens of metres as a result of cumulative motion along faults. In an effort to accurately quantify an average slip-rate for the faults, we used multiple dating techniques to provide an age constraint for the displaced landscapes. At one site on the Olgiy fault, we applied 10Be terrestrial cosmogenic nuclides (TCN) and uranium-series geochronology on boulder tops and in-situ formed carbonate rinds, respectively. Based on a displacement of approximately 17m, and geochronology results that range from 20-60ky, we resolve a slip-rate of less than 1 mm/yr. We have also applied optically stimulated luminescence (OSL), 10Be TCN, and U-series methods on the Ar Hotol fault. Each of these dating techniques provides unique constraints on the relationship between the ‘age’ of a displaced surface and the actual amount of displacement, and each has inherent assumptions. We will consider the advantages and assumptions made in utilising these techniques in western Mongolia- e.g. U-series dating of carbonate rinds can provide a minimum age for alluvial fan deposition, and inheritance must be considered when using TCN techniques on boulder tops. This will be put into the context of estimating accurate and geologically relevant slip-rates, and improving our understanding of the active deformation of the Mongolian Altay.

  18. Activity of faults observed in caves of the Eastern Alps

    NASA Astrophysics Data System (ADS)

    Baroň, Ivo; Plan, Lukas; Grasemann, Bernhard; Mitrovič, Ivanka; Stemberk, Josef

    2015-04-01

    Major recent tectonic process in the Eastern Alps involves the Neogene and Quaternary lateral extrusion of parts of the Eastern Alps towards the Pannonian Basin coeval with north-south shortening of the collision realm between the Adriatic Plate and the Bohemian Massif (European Plate). Within the framework of the FWF project "Speleotect" (2013-2017), we observe recent activity of the major fault systems of the Eastern Alps, such as the (1) Salzach-Ennstal-Mariazell-Puchberg (SEMP), (2) Mur-Mürz, (3) Periadriatic, (4) Lavanttal, and (5) Vienna Basin marginal Faults. Totally seven high-accuracy 3D crack-gauges TM71 with automated reading devices were installed in five selected karst caves with faults younger than the particular caves and correlated to one of these fault zones. The recorded micro-displacement events have been compared to known regional fault kinematics and to regional seismic activity (seismic data provided by the ZAMG). Already within the first year of observation, several micro displacement events were registered; these events sometimes revealed the same mechanisms as the geologically documented kinematics of the particular active faults, but in some cases performed completely opposite kinematics. These micro displacement events occurred in seismically rather quiet periods, however, usually about 1 - 10 days prior to local seismic events of different magnitudes (varying between ML 0.1 and 3.3). Further, in some caves gravitational mass movements were recorded that accompanied the tectonic moments.

  19. Tectonic Geomorphology in the Laboratory: Evolution of landscape along an active thrust, normal and strike-slip fault

    NASA Astrophysics Data System (ADS)

    Graveleau, Fabien; Strak, Vincent; Dominguez, Stéphane; Malavieille, Jacques; Chatton, Marina; Manighetti, Isabelle; Petit, Carole

    2015-04-01

    Tectonically controlled landforms develop morphologic features that provide useful markers to investigate crustal deformation and relief growth dynamics. We present here results of morphotectonic experiments obtained with an innovative approach combining tectonic and surface processes (erosion, transport and sedimentation), coupled with accurate model monitoring techniques. This approach allows for a qualitative and quantitative analysis of landscape evolution in response to active deformation in the three end-member geological settings: compression, extension and strike-slip. Experimental results outline first that experimental morphologies evolve significantly at a short timescale. Numerous morphologic markers form continuously, but their lifetime is generally short because erosion and sedimentation processes tend to destroy or bury them. For the compressional setting, the formation of terraces above an active thrust appears mainly controlled by narrowing and incision of the main channel through the uplifting hanging-wall and by avulsion of deposits on fan-like bodies. Terrace formation is irregular even under steady tectonic rates and erosional conditions. Terrace deformation analysis allows retrieving the growth history of the structure and the fault slip rate evolution. For the extensional setting, the dynamics of hanging-wall sedimentary filling appears to control the position of the base level, which in turn controls footwall erosion. Two phases of relief evolution can be evidenced: the first is a phase of relief growth and the second is a phase of upstream propagation of topographic equilibrium that is reached first in the sedimentary basin. During the phase of relief growth, the formation of triangular facets occurs by degradation of the fault scarp and their geometry (height) becomes stationary during the phase of upstream propagation of the topographic equilibrium. For the strike-slip setting, the complex morphology of the wrench zone, composed of

  20. Curved Lobate Scarp on Crater Floor

    NASA Technical Reports Server (NTRS)

    1974-01-01

    A broadly curved lobate scarp (running from left to right in the large crater to the right of center in this image) is restricted to the floor of a crater 85 kilometers in diameter. The rim of this crater and the rims of those north of it have been disrupted by the process which caused the hilly and lineated terrain. This process has not affected the smooth plains on their floors, indicating that the floor materials post date the formation of the craters. In this case, the scarp on the crater floor may be a flow front formed during emplacement of the floor material.

    This image (FDS 27379) was acquired during the spacecraft's first encounter with Mercury.

    The Mariner 10 mission, managed by the Jet Propulsion Laboratory for NASA's Office of Space Science, explored Venus in February 1974 on the way to three encounters with Mercury-in March and September 1974 and in March 1975. The spacecraft took more than 7,000 photos of Mercury, Venus, the Earth and the Moon.

    Image Credit: NASA/JPL/Northwestern University

  1. 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

  2. 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

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

    NASA Astrophysics Data System (ADS)

    Yoshioka, T.; Miyamoto, F.

    2011-12-01

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

  4. Study on the Late Quaternary Activity of Niyang River Fault

    NASA Astrophysics Data System (ADS)

    Fangtou, T.

    2015-12-01

    Niyang River fault with north-west trending is located on the west side of the Eastern Himalayan Syntaxis. It dislocated the eastern segment of Brahmaputra fault zone. We study the late Quaternary activity of the Niyang River fault by the high-resolution image data in combination with detailed field investigation, GPS observation, trenching and radiocarbon dating of charcoal samples. The GPS observation data shows that the movement characteristics of Niyang River fault is dextral strike-slip with extrusion at present, its strike-slip rate is 3~4mm/a and its extrusion rate is 2~3mm/a. The trench at Bayi town revealed that the first terraces of Niyang River was dislocated 50cm by the fault and it is dated to be 1220±40cal.a BP.. We found that third Lake terraces of the Linzhi ancient lakes was dislocated about 1.5m at Mirui town and it is dated to be 18060±60cal.a BP.. By the fault influence, there are different elevations at the same level terraces of Niyang river and the Linzhi ancient lakes both sides of Niyang river near Bayi town. The altitude of the second terraces of Niyang River is about 20 meters at eastern side higher than western side and it is dated to be between 8860±40cal.a BP. and 9870±50cal.a BP., the altitude of the third lake terraces of the Linzhi ancient lakes is about 60 meters at eastern side higher than western side. So, the average vertical slip rate of Niyang River fault was about 2mm/a since Holocene and its average vertical slip rate was about 3mm/a since late period of the late Pleistocene. This is consistent with GPS observation data. All these data suggest that Niyang River fault is active since Holocene. So further detailed research will be necessary to determine the range of the latest activity of this fault, movement characteristics and velocity and recurrence intervals of major earthquakes. These data will be a great significance for earthquake zonation and assessment of seismic risk in this region. Keywords:Niyang River fault

  5. 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

  6. Scarp degraded by linear diffusion: inverse solution for age.

    USGS Publications Warehouse

    Andrews, D.J.; Hanks, T.C.

    1985-01-01

    Under the assumption that landforms unaffected by drainage channels are degraded according to the linear diffusion equation, a procedure is developed to invert a scarp profile to find its 'diffusion age'. The inverse procedure applied to synthetic data yields the following rules of thumb. Evidence of initial scarp shape has been lost when apparent age reaches twice its initial value. A scarp that appears to have been formed by one event may have been formed by two with an interval between them as large as apparent age. The simplicity of scarp profile measurement and this inversion makes profile analysis attractive. -from Authors

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

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

  8. 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.

  9. Hinge-migrated fold-scarp model based on an analysis of bed geometry: A study from the Mingyaole anticline, southern foreland of Chinese Tian Shan

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

    Fold scarps, a type of geomorphic scarp formed by folding mechanisms of hinge migration or limb rotation, serve to delineate both fault-bend characteristics and folding histories, which can, in turn, illuminate tectonic processes and seismic hazards associated with thrust systems. Because the subsurface geometry of folds is commonly difficult to determine, existing fold-scarp models, which rely on both the fold type and its causative fault geometries, remain uncertain with respect to the kinematic evolution of a given fold. In this paper, we develop a model to illustrate that, irrespective of specific fold type and subsurface geometries, fold-scarp growth in the mechanism of hinge migration can be successfully reconstructed based on analyses of bed geometry. This model reveals that the underlying bed dips and the ratio of hinge migration distance/hinge width control the fold-scarp shape and slope. During initial growth (ratio < 1), the scarp slope increases gradually with migration of the hinge. When the hinge totally exits from its original position (ratio > 1), the slope reaches a maximum, which solely depends on underlying bed dips. The scarp height, however, is independent of the hinge width and can be used to quantify folding magnitude. Application of our model to fold scarps in the Mingyaole anticline in the southern foreland of Chinese Tian Shan indicates that the modeled fold-scarp geometry can roughly match with field observations. The Mingyaole shortening rate is estimated to be ≥5.0 mm/a since ~15 ka, such that this single fold has accommodated about half of the regional convergence during the Holocene.

  10. 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.

  11. 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.

  12. High Frequency Monitoring of the Aigion Fault Activity

    NASA Astrophysics Data System (ADS)

    Cornet, Francois; Bourouis, Seid

    2013-04-01

    In 2007, a high frequency monitoring system was deployed in the 1000 m deep AIG10 well that intersects the Aigion fault at a depth of 760 m. This active 15 km long fault is located on the south shore of the Corinth rift, some 40 km east from Patras, in western central Greece. The borehole intersects quaternary sediments down to 495 m, then cretaceous and tertiary heavily tectonized deposits from the Pindos nappe. Below the fault encountered at 760 m, the borehole remains within karstic limestone of the Gavrovo Tripolitza nappe. The monitoring system involved two geophones located some 15 m above the fault, and two hydrophones located respectively at depths equal to 500 m and 250 m. The frequency domain for the data acquisition system ranged from a few Hz to 2500 Hz. The seismic velocity structure close to the borehole was determined through both sonic logs and vertical seismic profiles. This monitoring system has been active during slightly over six months and has recorded signals from microseismic events that occurred in the rift, the location of which was determined thanks to the local 11 stations, three components, short period (2 Hz), monitoring system. In addition, the borehole monitoring system has recorded more than 1000 events not identified with the regional network. Events were precisely correlated with pressure variations associated with two human interventions. These extremely low magnitude events occurred at distances that reached at least up to 1500 m from the well. They were associated, some ten days later, with some local rift activity. A tentative model is proposed that associates local short slip instabilities in the upper part of the fault close to the well, with a longer duration pore pressure diffusion process. Results demonstrate that the Aigion fault is continuously creeping down to a depth at least equal to 5 km but probably deeper.

  13. Quaternary faults near the proposed Eagle Flat low-level radioactive waste repository, Trans-Pecos Texas

    SciTech Connect

    Collins, E.W.; Raney, J.A. . Bureau of Economic Geology)

    1992-01-01

    The Eagle Flat basin, an intermontane basin in Trans-Pecos Texas, is being considered as a possible site for the Texas repository of low-level radioactive wastes. Intermontane basins and associated normal faults formed in response to Basin and Range tectonism that began about 24 Ma ago. The most active late Tertiary and Quaternary faults occur within the Hueco Bolson (HB) and the Salt Basin/Salt Flat/Lobo Valley, west and east, respectively, of the proposed repository. Several faults of the southeast HB which are within 50 km of the site, displace middle Pleistocene deposits 10 to 24 m. The most recent surface rupture in the southeast HB probably occurred on the Amargosa fault during the Holocene. Upper Pleistocene deposits are offset 2.5 to 4.5 m, and middle Pleistocene deposits are displaced 24 m. Fault scarps within 50 km east of the proposed repository are associated with faults bounding the Salt Basin/Salt Flat/Lobo Valley. In the southern Salt Basin and northern Salt Flat, faults offset probable upper Pleistocene to Holocene deposits as much as 1.5 m. A scarp in Red Light Bolson, 13.5 km south of the site, is the closest Quaternary fault scarp to the proposed site. Only 7 km long, this scarp is part of a mostly covered, probably multisegmented, 40-km-long fault that bounds the northeastern margin of Red Light Bolson. Offsets associated with single-rupture events range from 0.6 to 3 m, and average recurrence intervals between surface ruptures since middle Pleistocene are about 10,000 to 100,000 yr. The largest historical earthquake of the region, the 1931 Valentine earthquake, which had a magnitude of 6.4 and no reported surface rupture, occurred about 95 km southeast of the proposed repository.

  14. 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

  15. 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.

  16. Fault Activity, Seismicity and GPS Deformation of the Seismic Gap along the Red River Fault Zone (RRFZ) in Yunnan, China

    NASA Astrophysics Data System (ADS)

    Xue-Ze, Wen; Shengli, Ma; Fang, Du; Feng, Long

    2016-04-01

    Along the middle segment of the NW-trending and dextral-slip Red River fault zone (RRFZ), also the Honghe fault zone, Yunnan, China, there has been little of modern seismicity since the 1970's. Some Chinese researchers believed that this fault segment is inactive in the late Quaternary. However, more and more evidence shows that the middle segment of RRFZ is geologically-active in the late Quaternary, even is a Holocene-active one with evidence of paleo-earthquakes occurring. Our study suggests that along the fault segment there has been no any major earthquake occurring for over 500 years at least, and a large-scale seismic gap, the Honghe seismic gap, have formed there. On the modern seismicity, the middle segment of RRFZ has presented as a fault portion without or with very few small earthquakes occurring since the 1980's, but surrounded by several areas with low b-values, suggesting relatively high stress having built-up there. Also, GPS deformation analysis suggests that this fault segment has tightly locked already. Such tight locking would be associated with the fault geometry: A large-scale restraining bend of about 30°over a distance of ~100 km exists along the main fault trace along RRFZ between Yuanjiang and Yuanyang. However, how such a restraining bend makes the middle segment of RRFZ have tightly locked? How much strain has built up there? Moreover, how about the long-term seismic potential of major earthquake on the middle segment of RRFZ, and on some secondary active faults of the two sides of the segment, especially on the parallel faults Chuxiong, Qujiang and Shiping. All these are issues we want to study further. Keywords: Red River Fault Zone, Seismic Gap, Fault Activity, Seismicity, GPS Deformation

  17. Testing Damage Scenarios. From Historical Earthquakes To Silent Active Faults

    NASA Astrophysics Data System (ADS)

    Galli, P.; Orsini, G.; Bosi, V.; di Pasquale, G.; Galadini, F.

    Italy is rich with historical scenarios of disruption and death that arrived up to us through the insight descriptions of hundreds of manuscripts, reports, treatises, letters and epigraphs. All these historical data constitute today one of the most powerful data-base of earthquake-induced effects. Moreover, it is now possible to relate many of these earthquakes to geological structures, the seismogenetic behavior of which has been investigated by means of paleoseismological studies. On the basis of these information and of those gathered through the national census (performed on popu- lation and dwellings by ISTAT, Italian Institute of Statistics in 1991) we developed a methodology (FaCES, Fault-Controlled Earthquake Scenario) which reproduce the damage scenario caused by the rupture of a defined fault, providing an estimate of the losses in terms of damages to building and consequences to population. The reliabil- ity of scenarios has been tested by comparing the historical damage distribution of an earthquake with that obtained applying FaCES to the responsible fault. Finally, we hypothesize the scenario related to three historically-silent faults of central Apennines (Mt. Vettore, Mt. Gorzano and Gran Sasso faults), the Holocene activity of which has been recently ascertained though paleoseimological analyses.

  18. 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.

  19. Surface breakthrough of a basement fault by repeated seismic slip episodes: The Ostler Fault, South Island, New Zealand

    NASA Astrophysics Data System (ADS)

    Ghisetti, Francesca C.; Gorman, Andrew R.; Sibson, Richard H.

    2007-12-01

    The Ostler Fault is one of the major active reverse faults in the piedmont of the Southern Alps, SE of the Alpine Fault. We present a new geological and morphotectonic map of the southern Ostler Fault, integrated with two seismic reflection profiles across the active central segments of the fault. Segmented, subparallel scarps define a N-S belt (˜40 km long and 2-3 km wide) of pure reverse faults, which upthrow and back-tilt a panel of Plio-Pleistocene terrestrial units (2.4-1.0 Ma) plus the overlying glacial outwash (<200 ka). Uplift gradients, the chronology of newly faulted markers, and tectonically controlled diversion of paleodrainages, all indicate progressive S to N breakthrough of the surface trace of the Ostler Fault in the last 2.4 Ma. The new seismic data define a main fault segment dipping 50°-60°W to depths of ˜1.5 km, with a vertical throw of 800 m, and a shortening of ˜30%. The fault geometry and kinematics and the subsurface data favor the interpretation that the Ostler Fault propagated updip across the Plio-Quaternary terrestrial sequence as the emerging, high-angle splay of an inherited Late Cretaceous-Paleocene normal fault, that underwent repeated cycles of compressional reactivation in the last 2.4 Ma.

  20. Investigation of fault interaction and growth in Mygdonia basin (Greece) fault system

    NASA Astrophysics Data System (ADS)

    Gkarlaouni, Charikleia; Kilias, Adamantios; Papadimitriou, Eleftheria; Lasocki, Stanislaw; Karakostas, Vasileios

    2013-04-01

    Nowadays there is a scientific debate upon the strong correlation that exists between the earthquake clusters and the active seismogenic fault systems since they both constitute populations that participate in processes that include different states of initiation, interaction and coalescence. Since faults grow by the increase in their displacement and their length, the degree of fault interaction between two neighbour segments is expressed by scaling laws describing the fault dimensions, such as the displacement and the length. The distribution of the displacement along the fault trace, follows a bell-shaped pattern according to Dugdale model and is often a key to quantify the degree of interaction between two different fault segments since it gives an insight to the stage of growth and linkage between faults. In our case the fault attributes of Mygdonia basin that is located in the northern part of the Greek mainland are investigated under the prism of the scaling properties of its major active faults. Important seismogenic fault segments such as Lagina - Agios Vasilios, Gerakarou - Stivos and Sohos fault that define the boundaries of the basin and have generated important earthquakes in the past are investigated. Displacement - length profiles were constrained for the major fault segments, using digital elevation models (DEMs) since intense tectonics is etched upon the topography of the area such as to provide valuable seismotectonic information. In our case scarp heights are used for the approximation of fault displacement. Structural information, concerning displacement measurements on active fault scarps, and slip lineaments onto fault expressions are collected in-situ from field surveys. The information based on the field observations, justify the results coming out from the D.E.M. analysis. The final results are compared to conclusions derived from the investigation of different fault systems and the influence on the hazard assessment is discussed. This work

  1. 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

  2. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

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

  4. Recent Earthquake Breaks At The Sea of Marmara Pull-apart (North Anatolian Fault)

    NASA Astrophysics Data System (ADS)

    Ucarkus, G.; Armijo, R.; Cakir, Z.; Schmidt, S.; Meyer, B.

    2008-12-01

    The North Anatolian Fault (NAF) makes a major transtensional step-over in the west which forms the lithospheric scale Sea of Marmara pull-apart, between the strike-slip Ganos and Izmit faults. Smaller strike- slip segments and pull-apart basins alternate within the main step-over, combining strike-slip and normal faulting. During the MARMARASCARPS cruise clear morphologic evidence of recent faulting activity was found along several segments of the NAF in the Sea of Marmara. Sets of well-preserved earthquake scarps extend offshore from the Ganos and Izmit faults on land. Our observations from visual exploration and ultra- high resolution bathymetry data (microbathymetry) suggest that those scarps correspond to the submarine ruptures of the purely strike-slip 1999 Izmit (Mw 7.4) and the 1912 Ganos (Ms 7.4) earthquakes. One break extends offshore eastward of the Ganos fault and cuts continuously the Tekirdag basin and Western High up to the Central basin over 60 km. Scarps, here, are very well preserved and show fine-scale morphology typical of strike-slip faulting. The age of the last earthquake break is difficult to assess directly with dating approaches. However, recent sedimentation rates can provide information on the age of the sediment covering the scarps. With that purpose, ROV (remote operated vehicle) sampled interface cores (up to 35 cm) into the disturbed sediment in the immediate vicinity of those scarps. Our first geochronological analysis with 210Pb seems to confirm the connection of fresh fault scarps to the 1912 Ganos earthquake rupture. Sedimentation rates determined from 210Pb profiles (excluding disturbed layers) on cores show a narrow range between 0.1-0.2 cm/yr. Another very fresh break is seen where the Izmit fault enters westward into the Cinarcik Basin. It crosses the bottom of a submarine canyon at 180 m depth, 10 km west of the Hersek peninsula. Microbathymetry suggests the 1999 fault scarp is there 0.5 m high. The flat floor of the canyon

  5. Oblique strike-slip faulting of the Cascadia submarine forearc: The Daisy Bank fault zone off central Oregon

    NASA Astrophysics Data System (ADS)

    Goldfinger, Chris; Kulm, LaVerne D.; Yeats, Robert S.; Hummon, Cheryl; Huftile, Gary J.; Niem, Alan R.; McNeill, Lisa C.

    The Cascadia submarine forearc off Oregon and Washington is deformed by numerous active WNW-trending, left-lateral strike-slip faults. The kinematics of this set of sub-parallel left-lateral faults suggests clockwise block rotation of the forearc driven by oblique subduction. One major left-lateral strike-slip fault, the 94 km-long Daisy Bank fault, located off central Oregon, was studied in detail using high-resolution AMS 150 kHz and SeaMARC-lA sidescan sonar, swath bathymetry, multichannel seismic reflection profiles and a submersible. The Daisy Bank fault zone cuts the sediments and basaltic basement of the subducting Juan de Fuca plate, and the overriding North American plate, extending from the abyssal plain to the upper slope-outer shelf region. The Daisy Bank fault, a near-vertical left-lateral fault striking 292°, is a wide structural zone with multiple scarps observed in high-resolution sidescan images. From a submersible, we observe that these scarps offset late Pleistocene gray clay and overlying olive green Holocene mud, dating fault activity as post-12 ka on the upper slope. Vertical separation along individual fault scarps ranges from a few centimeters to 130 meters. Using a retrodeformation technique with multichannel reflection records, we calculate a net slip of 2.2±0.5 km. Fault movement commenced at about 380±50 ka near the western fault tip, based upon an analysis of growth strata and correlation with deep-sea drill hole biostratigraphy. We calculate a slip rate of 5.7±2.0 mm/yr. for the Daisy Bank fault at its western end on the Juan de Fuca plate. The motion of the set of oblique faults, including the Daisy Bank fault, may accommodate a significant portion of the oblique component of plate motion along the central Cascadia margin. We propose a block rotation model by which the seawardmost part of the forearc rotates clockwise and translates northward.

  6. Frictional properties of the active San Andreas Fault at SAFOD: Implications for fault strength and slip behavior

    NASA Astrophysics Data System (ADS)

    Carpenter, B. M.; Saffer, D. M.; Marone, C.

    2015-07-01

    We present results from a comprehensive laboratory study of the frictional strength and constitutive properties for all three active strands of the San Andreas Fault penetrated in the San Andreas Observatory at Depth (SAFOD). The SAFOD borehole penetrated the Southwest Deforming Zone (SDZ), the Central Deforming Zone (CDZ), both of which are actively creeping, and the Northeast Boundary Fault (NBF). Our results include measurements of the frictional properties of cuttings and core samples recovered at depths of ~2.7 km. We find that materials from the two actively creeping faults exhibit low frictional strengths (μ = ~0.1), velocity-strengthening friction behavior, and near-zero or negative rates of frictional healing. Our experimental data set shows that the center of the CDZ is the weakest section of the San Andreas Fault, with μ = ~0.10. Fault weakness is highly localized and likely caused by abundant magnesium-rich clays. In contrast, serpentine from within the SDZ, and wall rock of both the SDZ and CDZ, exhibits velocity-weakening friction behavior and positive healing rates, consistent with nearby repeating microearthquakes. Finally, we document higher friction coefficients (μ > 0.4) and complex rate-dependent behavior for samples recovered across the NBF. In total, our data provide an integrated view of fault behavior for the three active fault strands encountered at SAFOD and offer a consistent explanation for observations of creep and microearthquakes along weak fault zones within a strong crust.

  7. Erosion influence the seismicity of active thrust faults

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  8. Erosion influence the seismicity of active thrust faults

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  9. Topographic Studies of Lobate Scarps Near the Martian Crustal Dichotomy Using MOLA Data

    NASA Astrophysics Data System (ADS)

    Watters, T. R.; Robinson, M. S.

    1999-03-01

    MOLA data is being used to study martian lobate scarps in the Amenthes region, near the crustal dichotomy. The dimensions and morphology of a lobate scarp crossed by a MOLA profile agree well with other scarps studied using photoclinometric data.

  10. DTM analysis and displacement estimates of a major mercurian lobate scarp.

    NASA Astrophysics Data System (ADS)

    Ferrari, S.; Massironi, M.; Pozzobon, R.; Castelluccio, A.; Di Achille, G.; Cremonese, G.

    2012-04-01

    During its second and third flybys, the MErcury Surface Space ENvironment GEochemistry and Ranging (MESSENGER) mission imaged a new large and well-preserved basin called Rembrandt Basin (Watters et al., 2009, Science) in Mercury's southern hemisphere. This basin is a 715-km-diameter impact feature which displays a distinct hummocky rim broken up by the presence of several large impact craters. Its interior is partially filled by volcanic materials, that extend up to the southern, eastern and part of the western rims, and is crossed by the 1000-km long homonymous lobate scarp. In attempt to reveal the basin-scarp complex evolution, we used MESSENGER Mercury Dual Imaging System (MDIS) mosaics to map the basin geological domains - inferring where possible their stratigraphic relationships, and fix the tectonic patterns. In contrast to other well-seen basins, Rembrandt displays evidence of global-scale in addition to basin-localized deformation that in some cases may be controlled by rheological layering within the crust. Extensional features are essentially radial and confined to the inner part, displaying one or more uplifts episodes that follow the impact. The widespread wrinkle ridges form a polygonal pattern of radial and concentric features on the whole floor, probably due to one or more near-surface compressional stages. On the other hand, Rembrandt scarp seems to be clearly unrelated to the basin formation stage and rather belonging to a global process like cooling contraction and/or tidal despinning of the planet. The main compressional phase responsible of the overall scarp build-up was followed by minor compressional structures detected within younger craters in turn cutting the main scarp. This suggests a prolonged slowing down phase of a global tectonic process. The whole feature displays an unusual transpressional nature for a common lobate scarp. Then we performed a structural and kinematic analysis subdividing the main feature into three branches: the

  11. 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.

  12. The paleoseismology of the San Andreas fault at Pitman Canyon, San Bernadino, California

    SciTech Connect

    Seitz, G.; Weldon, R.J. . Dept. of Geological Sciences)

    1993-04-01

    The San Andreas fault at Pitman Canyon creates a well-defined downhill-facing scarp in young alluvium deposited mainly as debris flows. Groundwater rising on the uphill side of the scarp produces marshes that accumulate peat deposits. Trench exposures and C-14 dates confirm that this depositional environment, resulting in a datable section of inter-layered debris flows and peats, has existed for at least 1,400 years. The scarp extends across the entire canyon floor with the exception of a central shutterridge, offset along the fault, and the active channel. At the shutterridge this datable section overlies the fault and is involved in the faulting. A debris flow levee is offset approximately 4 meters and is inferred to be caused by the 1812 earthquake. To the northwest similar 4 meter offsets exist in Purdue and Lone Pine Canyons (Weldon and Sieh, 1985). An older debris flow lobe which postdates 1659 AD, the earliest possible age of a directly underlying C-14 dated peat is offset 7--8 meter indicating a similar size event post 1659 AD. Up to three additional events prior to 1280 AD were recognized in trench exposures based upon the upward termination of fault breaks, facies mismatches, and folding. Further study of offset buried debris flows and channels should allow determination of displacement per event. This preliminary record suggests extending the 1812 rupture into the San Bernadino region and is compatible with extending an approximately 1700 AD event from Indio to Wrightwood.

  13. 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.

  14. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  16. Imaging the San Andreas Fault between Parkfield and the Salton Sea Using Wavelet Analysis of Airborne Laser Swath Mapping Data

    NASA Astrophysics Data System (ADS)

    Cheung, K.; Hilley, G. E.; Moon, S.; Saltzman, J.; Sanquini, A.

    2011-12-01

    The distribution of fault related landforms may be used to divulge the spatial and temporal evolution of fault ruptures within a fault zone. In this study, wavelet analysis was performed on high-resolution Airborne Laser Swath Mapping (ALSM) topographic data to image the morphologic structure of the San Andreas Fault Zone (SAFZ) between Parkfield, CA and the US-Mexico border. ASLM data were collected by the National Center for Airborne Laser Mapping as part of the B4 project and were processed these data to produce a 2-m-resolution Digital Elevation Model (DEM). The DEM tiles were imported to ArcMap, which was used to mosaic, rotate, and crop them. Matlab was used to perform a progressive filling of NODATA values within each of the tiles using an iterative nearest-neighbor averaging scheme on these data. Next, scarp-like features roughly paralleling the average trend of the SAFZ were identified using a previously developed wavelet analysis method. This method convolves the second derivative of an elongated template of a scarp-like topography with the directional curvature of the ALSM DEM that is represented by each of the tiles. In this way, the analysis recovers, in a least-squares best-fitting sense, the amplitude of a particular scarp geometry and orientation. The Signal-to-Noise Ratio (SNR) is then computed at each point in the ALSM DEM for a given template scarp geometry and orientation-- this process is repeated for all scarp geometries and orientations to determine those that have the highest SNR. Such scarp forms are automatically identified as the best-fitting scarp geometry, amplitude, and orientation at each point in the DEM. The geometry gives a quantitative measure of the "roundness" of the profile of the scarp form, and supposing that sharper scarps have been created more recently than those whose forms have been rounded by prolonged erosion, a relative chronology of activity of various fault strands within the fault zone can be reconstructed. With

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

    USGS Publications Warehouse

    Knott, J.R.; Tinsley, J. C., III; 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.

  18. Are the Benches at Mormon Point, Death Valley, California, USA, Scarps or Strandlines?

    NASA Astrophysics Data System (ADS)

    Knott, Jeffrey R.; Tinsley, John C.; Wells, Stephen G.

    2002-11-01

    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.

  19. 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

  20. Geometric relations of dip slip to a faulted ground surface: new nomograms for estimating components of fault displacement

    NASA Astrophysics Data System (ADS)

    Caskey, S. J.

    1995-08-01

    The throw, heave, and dip-slip components of displacement on a fault scarp can be estimated from two easily collected field measurements when fault dip is known or assumed: the vertical separation and slope angle of the original ground surface displaced across the fault. Nomograms allow graphical determination of slip components for cases where fault dip is in the same or in an opposite direction as the slope of the ground surface. The technique has several advantages over a previous method that requires three field measurements; those of scarp height, scarp slope angle, and the slope of the original ground surface. The geometric relations of a fault scarp illustrate that although differences between throw and vertical separation of the ground surface are small in the cases of steep fault dips or flat ground surfaces, these differences can be greater than commonly assumed.

  1. 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

  2. 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

  3. Linking Slope Sedimentation, Gradient, Morphology, and Active Faulting: An Integrated Example from the Palos Verdes Slope, Southern California Borderland

    NASA Astrophysics Data System (ADS)

    Maier, K. L.; Brothers, D. S.; Paull, C. K.; McGann, M.; Caress, D. W.; Conrad, J. E.

    2015-12-01

    Seafloor gradient variations associated with restraining and releasing bends along the active (1.6-1.9 mm/yr) right-lateral Palos Verdes Fault appear to control Holocene sediment thickness, depositional environment, and morphodynamic processes along a section of the continental slope offshore Los Angeles, California. Autonomous underwater mapping vehicle (AUV), remotely operated vehicle (ROV), and shipboard methods were used to acquire a dense grid of high-resolution chirp profiles (150 m line spacing; 11 cm vertical resolution), multibeam bathymetry (2 m grid), and targeted sediment core samples (<2 m length). Detailed interpretation of Holocene deposits in the chirp profiles combined with radiocarbon dating and laser particle-size analyses allow correlation of Holocene sediment thickness and seafloor gradient with sediment gravity flow deposits. Holocene down-slope flows appear to have been generated by mass wasting processes, primarily on the upper slope (~100-200 m water depth) where shipboard multibeam bathymetry reveals submarine landslide headwall scarps in a region that has been isolated from terrigenous sediment sources throughout the Holocene. Submarine landslides appear to have transformed into sandy and organic-rich turbidity currents that created up-slope migrating sediment waves, a low relief (<5 m) fault-bounded channel, and a series of depocenters. A down-slope gradient profile and a Holocene isopach down-slope profile show that the primary depocenter occurs within a small pull-apart basin associated with a decrease in seafloor gradient of ~1.5°. Holocene sediment-flow deposits vary in number, thickness, and character with subtle changes in seabed gradient (<0.5°) and depositional environment. These results help quantify morphodynamic sensitivity to seafloor gradients and have implications for down-slope flow dynamics, deep-water depositional architecture, Holocene sediment, nutrient, and contaminant transport, and turbidite paleoseismology along

  4. 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.

  5. Olympus Mons Aureole and Basal Scarp: Rationale for In-situ Exploration

    NASA Astrophysics Data System (ADS)

    McGovern, P. J.

    1996-09-01

    Structural models of Olympus Mons, the largest volcano on Mars, suggest a strong rationale for robotic exploration. A scarp up to 10 km high defines the base of the edifice, which is surrounded by an aureole of disrupted terrain extending for hundreds of kilometers. One explanation for aureole and scarp formation involves repeated catastrophic flank failure along a detachment between the volcano and the underlying terrain. In this view, the aureole material consists of a series of highly fragmented landslides; the basal scarp is then the coalesced headwalls of these landslides. Material from depths up to 10 kilometers is thus potentially exposed at the current surface. On Earth, detachment structures (e.g., at Hawaii) are likely maintained by elevated pore fluid (water) pressure. A similar fluid-enhanced system may enable basal slip and edifice failure at Olympus Mons. Analysis of samples from deep within the earlier edifice (exposed in the aureole or basal scarp) would yield insight into volcanic processes, crustal formation, and planetary differentiation. The discovery of possible remnants of Martian life in meteorite Allan Hills 84001 provides an added impetus to seek deep samples. The deep flanks of Olympus Mons are shielded from exposure to ultraviolet radiation, extreme cold, and other surface conditions harmful to life. The volcano, and more generally the Tharsis region, have likely been a source of thermal energy for a large fraction of the planet's history. Given the argument for subsurface water, the flanks of Olympus Mons constitute a site favorable to the long-term maintenance of life on Mars, perhaps as hyperthermophile organisms analogous to those discovered in terrestrial hydrothermal vents. Fossil remnants of such activity may be exposed to examination in the aureole or basal scarp. Data from the upcoming Mars Global Surveyor mission will help to evaluate the landslide hypothesis and possibly to locate candidate sites around Olympus Mons for a

  6. 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.

  7. Stratigraphic Relationships Between Lobate Scarps and Young Impact Craters on Mercury: I mplications for the Duration of Lobate Scarp Formation

    NASA Astrophysics Data System (ADS)

    Banks, M. E.; Watters, T. R.; Strom, R. G.; Solomon, S. C.; Braden, S. E.; Chapman, C. R.; Xiao, Z.; Barlow, N. G.

    2012-03-01

    New results from MESSENGER MDIS images suggest that lobate scarp formation and development on Mercury occurred more recently than the formation of some Class 1 craters (Mansurian in age or younger) and may have continued into the Kuiperian system.

  8. 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.

  9. Growth and interaction of active faults within a nascent shear zone, central Mojave Desert, California

    NASA Astrophysics Data System (ADS)

    Oskin, M.; Strane, M.

    2006-12-01

    Compilation of new slip-distribution and slip-rate data from the Mojave Desert portion of the Eastern California shear zone (ECSZ) lends insight into the role of fault growth and interaction of conjugate fault systems in accommodating shear. Dextral faults of the Mojave Desert ECSZ approach but do not appear to cut the bounding ENE-striking sinistral Pinto Mountain and Garlock faults. Differing styles of accommodation of these bounding faults occur at opposite ends of the 140 km-long NW-striking Hidalgo-Calico-Blackwater dextral fault system. Total slip and slip rate of the Blackwater fault gradually diminish northward. The fault terminates as a single strand with a zero-slip fault tip before intersecting the Garlock fault. In contrast, the Calico and Hidalgo faults spread displacement southward onto multiple fault strands spaced several kilometers apart. Active folding further distributes displacement onto the adjacent Bullion and Mesquite Lake faults. These mechanisms appear to maintain a uniform gradient of displacement approaching the Pinto Mountain fault. The highest displacement (9.8 ± 0.2 km) and slip rate (1.8 ± 0.3 mm/yr) occur in the central part of the Hidalgo-Calico-Blackwater fault system where strain is concentrated onto a single fault strand. A significant drop in total displacement and slip rate occurs along the northern Calico fault. Strain appears to be transferred here onto ENE-striking sinistral faults that separate domains of clockwise rotation in the central Mojave Desert. The kinematically incompatible intersection of sinistral and dextral faults is accommodated, at least in part, by active folding and uplift of the Calico Mountains and Mud Hills. Total slip and slip rate are not correlative for dextral faults of the Mojave ECSZ, indicating ongoing evolution of the fault network. For example, the Lenwood fault is a highly segmented, immature dextral fault with only 1.0 ± 0.1 km of total displacement yet its slip rate (1.5 ± 0.4 mm/yr) is

  10. Fault kinematics and tectonic stress in the seismically active Manyara Dodoma Rift segment in Central Tanzania Implications for the East African Rift

    NASA Astrophysics Data System (ADS)

    Macheyeki, Athanas S.; Delvaux, Damien; De Batist, Marc; Mruma, Abdulkarim

    2008-07-01

    The Eastern Branch of the East African Rift System is well known in Ethiopia (Main Ethiopian Rift) and Kenya (Kenya or Gregory Rift) and is usually considered to fade away southwards in the North Tanzanian Divergence, where it splits into the Eyasi, Manyara and Pangani segments. Further towards the south, rift structures are more weakly expressed and this area has not attracted much attention since the mapping and exploratory works of the 1950s. In November 4, 2002, an earthquake of magnitude Mb = 5.5 struck Dodoma, the capital city of Tanzania. Analysis of modern digital relief, seismological and geological data reveals that ongoing tectonic deformation is presently affecting a broad N-S trending belt, extending southward from the North Tanzanian Divergence to the region of Dodoma, forming the proposed "Manyara-Dodoma Rift segment". North of Arusha-Ngorongoro line, the rift is confined to a narrow belt (Natron graben in Tanzania) and south of it, it broadens into a wide deformation zone which includes both the Eyasi and Manyara grabens. The two-stage rifting model proposed for Kenya and North Tanzania also applies to the Manyara-Dodoma Rift segment. In a first stage, large, well-expressed topographic and volcanogenic structures were initiated in the Natron, Eyasi and Manyara grabens during the Late Miocene to Pliocene. From the Middle Pleistocene onwards, deformations related to the second rifting stage propagated southwards to the Dodoma region. These young structures have still limited morphological expressions compared to the structures formed during the first stage. However, they appear to be tectonically active as shown by the high concentration of moderate earthquakes into earthquake swarms, the distribution of He-bearing thermal springs, the morphological freshness of the fault scarps, and the presence of open surface fractures. Fault kinematic and paleostress analysis of geological fault data in basement rocks along the active fault lines show that recent

  11. Effect of height and orientation ( microclimate) on geomorphic degradation rates and processes, late-glacial terrace scarps in central Idaho

    USGS Publications Warehouse

    Pierce, K.L.; Colman, Steven M.

    1986-01-01

    Examines the effects of scarp size (height) and orientation (microclimate) by keeping constant variables such as age, lithology, and regional climate. For scarps 2m high, the degradation rate on S-facing scarps is 2 times that on N-facing scarps; for 10-m scarps, it is 5 times. Scarp morphology may be used to estimate age. -from Authors

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

    SciTech Connect

    Borgia, A. ); Burr, J. ); Montero, W.; Morales, L.D. ); Alvarado, G.E. )

    1990-08-30

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

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. Continuous monitoring of an active fault in a plate suture zone: a creepmeter study of the Chihshang Fault, eastern Taiwan

    NASA Astrophysics Data System (ADS)

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

    2001-04-01

    Data from continuously monitored creepmeters across the active Chihshang Fault in eastern Taiwan are presented. The Chihshang Fault is an active segment of the Longitudinal Valley Fault, the main suture between the converging Philippine and Eurasian plates in Taiwan. Since the 1951 earthquake (Mw=7.0), no earthquake larger than magnitude 6.0 occurred in the Chihshang area. At least during the last 20 years, the Chihshang Fault underwent a steady creep movement, resulting in numerous fractures at the surface. Five creepmeters were installed in 1998 at two sites, Tapo and Chinyuan, within the Chihshang active fault zone. One-year results (from August 1998 to July 1999) show a horizontal shortening of 19.4±0.3 mm and 17.3±0.7 mm, at Tapo and Chinyuan, respectively. These annual shortening rates are in a good agreement with other estimates of strain rate independently obtained from geodetic measurements and geological site investigation. The creepmeter measurements were made on a daily basis, providing accurate information on the previously unknown evolution of creep during the year. The records of fault creep at the Tapo site thus revealed close seasonal correlation with average rainfall: the period of high creep rate coincides with the wet season, whereas that of low creep rate coincides with the dry season. Also, in comparison with the Tapo site, the creep behaviour as a function of time is complex at the Chinyuan site. Possible factors of irregularity are under investigation (thermal effect acting on the concrete basement of the creepmeters, earth tide effect, water table variations in a nearby rice field, and rainfall). The comparison between GPS measurements across the Longitudinal Valley (31 mm/year of horizontal displacement) and the creepmeter measurement across the Chihshang Fault zone (17-19 mm/year of horizontal displacement) suggests that there exists other shortening deformation across the active fault zone in addition to those we have measured from the

  18. Revealing the deeper structure of the end-glacial Pärvie fault system in northern Sweden by seismic reflection profiling

    NASA Astrophysics Data System (ADS)

    Ahmadi, O.; Juhlin, C.; Ask, M.; Lund, B.

    2015-02-01

    Fault scarps that extend up to 155 km and have offsets of tens of meters at the surface are present in the northern parts of Finland, Norway and Sweden. These fault scarps are inferred to have formed during earthquakes with magnitudes up to 8 at the time of the last deglaciation. The Pärvie fault system represents the largest earthquake so far documented in northern Scandinavia, both in terms of its length and its calculated magnitude. It is also the longest known glacially induced fault in the world. Present-day microearthquakes occur along the length of the fault scarp on the eastern side of the scarp, in general agreement with an east dipping main fault. In the central section of the fault, where there is a number of subsidiary faults east of the main fault, it has been unclear how the earthquakes relate to the faults mapped at the surface. A seismic profile across the Pärvie Fault system acquired in 2007, with a mechanical hammer as a source, showed a good correlation between the surface mapped faults and moderate to steeply dipping reflectors. The most pronounced reflector could be mapped to about 3 km depth. In an attempt to map the fault system to deeper levels, a new 22 km long 2-D seismic profile which followed the 2007 line was acquired in June 2014. For deeper penetration an explosive source with a maximum charge size of 8.34 kg in 20 m deep shot holes was used. Reflectors can now be traced to deeper levels with the main 65° east dipping fault interpreted as a weakly reflective structure. As in the previous profile, there is a pronounced strongly reflective 60° west dipping structure present to the east of the main fault that can now be mapped to about 8 km depth. Extrapolations of the main and subsidiary faults converge at a depth of about 11.5 km where current earthquake activity is concentrated, suggesting their intersection has created favorable conditions for seismic stress release. Based on the present and previous seismic reflection data

  19. 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.

  20. 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

  1. Height of faceted spurs, a proxy for determining long-term throw rates on normal faults: Evidence from the North Baikal Rift System, Siberia

    NASA Astrophysics Data System (ADS)

    Petit, Carole; Meyer, Bertrand; Gunnell, Yanni; Jolivet, Marc; San'kov, Vladimir; Strak, Vincent; Gonga-Saholiariliva, Nahossio

    2010-05-01

    We present new results on the long-term throw rates of active normal faults in the North Baikal Rift (NBR), eastern Siberia, based on a statistical analysis of triangular faceted scarps. Faceted spurs or triangular facets are morphologic features frequently observed along normal fault scarps, and result from the progressive denudation and incision of the footwall during fault activity. Fault-bounded ridges in the NBR display such typical morphologies with several contiguous facets separated by fault-perpendicular catchments. Over a range of 20 fault segments analyzed, triangular facet heights vary from ~200 to >900 m. As fault scarps have been developing under similar long-term climatic conditions, we infer that the scatter in mean facet height arises from long-term differences in fault throw rate. We compare the morphology of NBR facets with results obtained in a previously published numerical model of facet growth, which predicts that the mean height of triangular facets is proportional to the fault throw rate. Using facet height as an input, model results provide estimates of the long-term fault throw rates in the NBR. These vary between 0.2 and 1.2 mm/yr. The throw rates are then compared with the cumulated throw, which has been constrained by geophysical and stratigraphic data in the basins. This provides an estimate of the age of fault and basin initiation. We show that the modern stage of basin development started circa 3 Myr ago, except for the North Baikal basin (~ 8 Ma). Our results also suggest that a proportion of the observed throw is inherited from an earlier tectonic stage.

  2. 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

  3. 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).

  4. Offshore active faults of the Mikata fault zone in Fukui, Japan, revealed by high-resolution seismic profiles

    NASA Astrophysics Data System (ADS)

    Inoue, T.; Sugiyama, Y.; Sakamoto, I.; Takino, Y.; Murakami, F.; Hosoya, T.; Usami, T.

    2014-12-01

    The Mikata fault zone are located in coastal and shallow sea area off Fukui Prefecture, West Japan. National Institute of Advanced Industrial Science and Technology (AIST) and Tokai University conducted, as part of MEXT 2013 nearshore active fault survey project, a high-resolution multi-channel seismic survey using Boomer and a 12-channel streamer cable, acoustic profiling survey using parametric sub-bottom profiler and shallow-sea offshore drilling, in order to clarify distribution and activity of the Mikata fault zone. The seismic reflection surveys identified four reflection surfaces as vertical displacement markers in the post-glacial deposits at a depth ranging from ca. 4.5m to ca. 17m below the sea bottom on the downthrown side. We estimated the age of each marker reflection surface by using the C14 age and others from 4m-long core obtained on the downthrown side of fault and the sea level change in the latest Pleistocene and early Holocene around Japan. The results of these surveys have revealed that the fault system was reactivated three times since the latest Pleistocene. The vertical slip rate and average recurrence interval of the fault system are estimated at ca. 0.8-1.0 m/ky and 2,000-3,800 years, respectively.

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

    USGS Publications Warehouse

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

    2015-01-01

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

  6. 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.

  7. Paleoseismic and Geomorphic Evidence for Quaternary Fault Slip on the Central Range Fault, South American-Caribbean Plate Boundary, Trinidad

    NASA Astrophysics Data System (ADS)

    Prentice, C. S.; Weber, J.; Crosby, C. J.

    2001-12-01

    The island of Trinidad is located along the transform plate boundary between the South American and Caribbean plates. GPS measurements show that relative motion along this boundary is nearly E-W right-lateral shear (Weber et al., 2001). Analysis and comparison of historic triangulation and GPS data suggest that a significant fraction (14+/-3 mm/yr) of the total plate-boundary motion (about 20 mm/yr) is being accommodated across the Central Range Fault in central Trinidad. Our new paleoseismic studies demonstrate that Quaternary surface rupture has occurred on this previously unrecognized, historically aseismic, active fault. Geomorphic evidence of Quaternary faulting along the Central Range Fault includes linear drainages, aligned topographic saddles and troughs, offset ridges, right-laterally deflected streams, and linear scarps. We mapped these features using 1:20,000 scale aerial photographs and field reconnaissance along a 25-km-long section between Pointe-a-Pierre on the west coast and Navet Dam. Geomorphic features near Manzanilla Bay on the east coast suggest that the Central Range Fault continues across the island as a Quaternary feature for another 25 km to the northeast. Marine geophysical surveys suggest this fault continues offshore to the west (Warm Springs fault), and steps to the north across the Gulf of Paria pull-apart basin to the El Pilar Fault. The extent of the fault offshore to the east is unknown. We exposed a 6-m-wide shear zone within Pliocene(?) material in a trench cut into a fluvial terrace, south of Samlalsingh Road near Bonne Aventure. The overlying Quaternary fluvial gravel is faulted and folded across the shear zone, and Quaternary fluvial deposits are faulted against the shear zone on the north side. A second excavation across a prominent scarp near Tabaquite, 12 km northeast of Samlalsingh Road, exposed a colluvial wedge and overlying unfaulted sediments. We interpret the colluvial wedge to represent deposits shed off the scarp in

  8. Fault detection and isolation for an active wheelset control system

    NASA Astrophysics Data System (ADS)

    Mirzapour, Mohammad; Mei, T. X.; Xuesong, Jin

    2014-05-01

    Active control for railway wheelsets in the primary suspension has been shown to offer a number of performance gains, and especially it can be used to stabilise the wheelsets without compromising the vehicle's performance on curves. However, the use of actuators, sensors and data processors to replace the traditional passive suspension raises the issue of system safety in the event of a failure of the active control, which could result in the loss of stability (i.e. wheelset hunting), and in more severe cases, derailment. This paper studies the key issue of condition monitoring for an actively controlled railway system, with a focus on actuator failures to detect and isolate failure modes in such a system. It seeks to establish the necessary basis for fault detection to ensure system reliability in the event of malfunction in one of the two actuators. Computer simulations are used to demonstrate the effectiveness of the method.

  9. 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.

  10. 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

  11. 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.

  12. 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

  13. A complementary study of the Surprise Valley fault using a high-resolution shallow seismic reflection profile

    NASA Astrophysics Data System (ADS)

    Kell-Hills, A.; Thompson, M.; Dhar, M.; Louie, J.; Egger, A.; van Buer, N.; Vow, B.; Pullammanappallil, S.

    2008-12-01

    Despite a lack of large historical earthquakes, the Surprise Valley fault system in northeastern California is presumed to be seismically active based on the presence of numerous Holocene fault scarps and a fault- controlled geothermal system. The Surprise Valley fault is believed to be similar to historically active basin and range faults such as the Dixie Valley fault in central Nevada. A 5-m-deep paleoseismic trench across the main fault revealed a steeply-dipping (~68 degrees) normal fault, while a vibrator reflection profile located a few kilometers north of the trench imaged a much more shallowly dipping normal fault (~25-30 degrees) at 0.5-1.0 km depth. It is unclear from these data if the steeply dipping fault exposed in the trench soles into the more shallowly dipping fault at depth, or if the currently active fault cuts the fault imaged in the reflection profile. In June of 2008, we conducted a 200-m-long high-resolution shallow reflection profile across the fault at the location of the paleoseismic trench in order to further constrain the geometry of the currently active range-front fault. The survey was conducted with a 48-channel seismograph, a 16-lb sledge, and 48 groups of six 100-Hz phones each, spaced at 2-m intervals. Optimization of P-wave arrival times for a tomographic image of the upper 50 meters shows velocities ranging from 1000 to 2500 m/s. Preliminary reflection processing, together with the optimized velocity section, suggests that the fault dips at an angle of 60 degrees in the upper 40 meters, and may suggest an antithetic fault in the hanging wall. The unprocessed data display strong reflections at depths to 200 meters. A detailed understanding of the dip angle of the Surprise Valley fault will impact the ongoing geothermal development and the assessment of seismic hazard in the area, both of which will vary based on the angle of the active fault system.

  14. 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.

  15. 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

  16. Neotectonic faulting in northern Norway; the Stuoragurra and Nordmannvikdalen postglacial faults

    NASA Astrophysics Data System (ADS)

    Dehls, John F.; Olesen, Odleiv; Olsen, Lars; Harald Blikra, Lars

    2000-10-01

    radar (GPR) profiles show two prominent bedrock reflectors, dipping approximately 40° to the NE. An upward extrapolation of the northernmost reflector through the overburden coincides with the position of the surface scarp. The bedrock is well exposed along a streamed parallel to the GPR profiles. Bedding and foliation cannot be responsible for the reflectors visible in the GPR profiles. Gravitational forces have been ruled out as the origin of the fault. Although both faults probably formed shortly after Weichselian deglaciation, there is evidence that isostatic uplift was not the only force acting. Quaternary tilting of Fennoscandia due to ridge push, or mantle convection, may also play a role in neotectonic activity in Norway.

  17. 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.

  18. Revealing the deeper structure of the end-glacial Pärvie fault system in northern Sweden by seismic reflection profiling

    NASA Astrophysics Data System (ADS)

    Ahmadi, O.; Juhlin, C.; Ask, M.; Lund, B.

    2015-06-01

    A new seismic reflection survey for imaging deeper levels of the end-glacial Pärvie fault system in northern Sweden was acquired in June 2014. The Pärvie fault system hosts the largest fault scarp so far documented in northern Scandinavia, both in terms of its length and calculated magnitude of the earthquake that generated it. Present-day microearthquakes occur along the length of the fault scarp on the eastern side of the scarp, in general agreement with an east-dipping main fault. In the central section of the fault system, where there is a number of subsidiary faults east of the main Pärvie scarp, it has been unclear how the earthquakes relate to the structures mapped at the surface. A seismic profile across the Pärvie fault system acquired in 2007, with a mechanical hammer as a source, showed a good correlation between the surface mapped faults and moderate to steeply dipping reflections. The most pronounced reflectors could be mapped to about 3 km depth. In the new seismic survey, for deeper penetration an explosive source with a maximum charge size of 8.34 kg in 20 m deep shot holes was used. Reflectors can now be traced to deeper levels with the main 65° east-dipping fault interpreted as a weakly reflective structure. As in the previous profile, there is a strongly reflective 60° west-dipping structure present to the east of the main fault that can now be mapped to about 8 km depth. Extrapolations of the main and subsidiary faults converge at a depth of about 11.5 km, where current earthquake activity is concentrated, suggesting their intersection has created favorable conditions for seismic stress release. Based on the present and previous seismic reflection data, we propose potential locations for future boreholes for scientific drilling into the fault system. These boreholes will provide a better understanding of the reflective nature of the fault structures and stress fields along the faults at depth.

  19. 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

  20. Strike-slip fault geometry in Turkey and its influence on earthquake activity

    NASA Technical Reports Server (NTRS)

    Barka, A. A.; Kadinsky-Cade, K.

    1988-01-01

    The geometry of Turkish strike-slip faults is reviewed, showing that fault geometry plays an important role in controlling the location of large earthquake rupture segments along the fault zones. It is found that large earthquake ruptures generally do not propagate past individual stepovers that are wider than 5 km or bends that have angles greater than about 30 degrees. It is suggested that certain geometric patterns are responsible for strain accumulation along portions of the fault zone. It is shown that fault geometry plays a role in the characteristics of earthquake behavior and that aftershocks and swarm activity are often associated with releasing areas.

  1. Geomorphic mapping of the southern Maacama fault based on LiDAR data

    NASA Astrophysics Data System (ADS)

    Hoeft, J. S.; Sowers, J. M.; Kelsey, H. M.; Prentice, C. S.; Frankel, K. L.

    2008-12-01

    The Maacama fault is an active strike slip fault, and a potentially significant seismic source, within the San Andreas transform system. The fault is located east of and parallel to the San Andreas fault in Sonoma and Mendocino counties, California and is divided into a northern and southern section based on a NW to NNW change in strike. The southern segment comprises 54 km of the fault's 144 km total length and is primarily located in an upland area traversing mountainous terrain. Strain is thought to transfer northward from the East Bay fault zone along the Rodgers Creek fault and, through a right step, to the Maacama fault. LiDAR data collected in a 1-km-wide swath along the southern Maacama fault, as part of the GeoEarthscope project, were used to produce a bare-earth digital elevation model, from which hillshade, topographic contour, slope, and curvature maps with 0.5- to 1-m-resolution were derived. Mapping was primarily conducted digitally in a GIS environment, and interpretation of LiDAR data was supplemented with aerial photograph interpretation and field inspection. Primary, Holocene-age fault-related geomorphic features, consisting of scarps and dextrally offset drainages, define the southern Maacama. These features are sparsely distributed and comprise less than 20% of the fault length. The fault scarps define a sequence of left-stepping, en echelon fault segments with an average segment length of 230 m. By contrast, the northern Maacama fault is better defined geomorphically. The poor expression of the southern Maacama is likely due to the presence of active hillslope processes and low levels of seismicity. Seismicity along the southern segment is lower than that of the northern segment. The Coast Range uplands, primarily composed of Franciscan Complex, is characterized by numerous landslides and experiences annual precipitation of 75 to 180 cm. There is approximately 30 km of overlap between the northern end of the Rodgers Creek fault and the southern

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

  3. 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.

  4. 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.

  5. Great Scarps Above Sea Coasts in Global Morphotectonics

    NASA Astrophysics Data System (ADS)

    Ufimtsev, G. F.

    High and extensive tectonic scarps play an important part in global morphotectonics, and are one of the basic tectonic landforms of the southern continental and subcontinental margins and transition zones between the continent and the ocean in the east of Asia. These are proper rear boundaries of continental margins, the geodynamics of which are characterized by rifting on shelves, continental slopes, and marginal oceanic depressions. Great scarps are initiated at the thinning and breaking of the continental lithosphere and have a long phase in the ensuing development, with a successive self parallel retreat—a process that may be defined as tectonic planation, with the occurrence of a basal surface for shelf sediments. Great scarps are seen located above the passive continental margins and in the rear boundaries of the belt of transition from the continent to the ocean, in the western Pacific. Great scarps are uncommon in intracontinental regions and tend to have additional morphotectonic features at the land elevation and land subsidence boundaries.

  6. Fault Population Analyses in the Eastern California Shear Zone: Insights into the Development of Young, Actively Evolving Plate Boundary Structures

    NASA Astrophysics Data System (ADS)

    Zhou, X.; Dawers, N. H.; Amer, R. M.

    2014-12-01

    Relationships between cumulative fault displacement, slip rate and length, along with fault population statistics are analyzed for faults located within the Eastern California Shear Zone (ECSZ), focusing on areas north of the Garlock fault. Here many faults are geologically young and in an early stage of evolution, while many older and larger faults are also still active. We analyze scaling relationships for both strike-slip and normal faults in order to determine whether the two fault populations share the same properties or not. Cumulative displacement, slip rate and length data are collected from published maps and literature sources. The dataset spans fault lengths from tens of meters to hundreds of kilometers. Results of fault scaling analyses indicate that displacement has a linear relationship with fault length for normal faults in this area over the entire length span, whereas strike-slip faults do not have a clear displacement-length scaling relation. For a given length, the subset of strike-slip faults typically exhibits a much larger displacement than that for the normal faults. The slip rate versus length trends are similar but are considerably more scattered. In addition, we define a subpopulation of normal faults that are kinematically related to the right-lateral strike-slip faults; these have a maximum length set by the spacing between the right-lateral faults. Fault size-frequency distributions also indicate differences between the normal and strike-slip fault populations. Overall, the normal faults have higher ratios of cumulative number to fault length than the strike-slip population does, which we relate to different patterns of localization of faulting. We interpret these trends as reflecting different tectonic histories, with the majority of normal faults being intraplate faults associated with Basin and Range extension and the strike-slip faults being kinematically connected with plate boundary.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  8. Contribution of high resolution PLEIADES imagery to active faults analysis. Case study of the Longriba Fault System, eastern Tibet.

    NASA Astrophysics Data System (ADS)

    Ansberque, Claire; Bellier, Olivier; Godard, Vincent; Lasserre, Cécile; Wang, Mingming; Xu, Xiwei; Tan, Xibin

    2015-04-01

    High resolution imagery has largely developed during those two last decades allowing the possibility to observe and quantify geological and geomorphological features ranging from meter to few centimeters. Active tectonic and geomorphological studies have greatly benefited from the systematic use of such data. For that reason, we tested the contribution of PLEAIDES images to the analysis of an active strike-slip fault system in eastern Tibet. We used 50 cm resolution panchromatic PLEIADES images in order to map active fault segmentation, localize offsets of geomorphic markers and quantify vertical and horizontal displacements. We propose a preliminary study using PLEIADES images along the Longriba Fault System (LFS). The LFS, located at the eastern Tibetan Plateau margin, is constituted of two NW-SE dextral strike-slip and parallel fault zones: Longriqu and Maoergai, 80 and 120 km-long, respectively. It accommodates ~4 mm/yr dextral slip and very few vertical motion. We used stereo-pairs to build relative Digital Elevation Models (DEMs) (without ground control points) with a horizontal resolution ranging from 2 to 5 m, in order to understand the geometry of the system. We measured fault segments with lengths ranging from a hundred meters to several kilometers which are relatively close from each others, and several offsets of geomorphic markers (alluvial fans, ridges, rivers) ranging from a few meters to ~40 m. According to the segmentation deduced from those results we suggest that the fault has a high seismic potential (>Mw7.0) and that probably many surface rupturing earthquakes occurred along the LFS over the Holocene.

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

    NASA Astrophysics Data System (ADS)

    Besstrashnov, Vladimir; Strom, Alexander

    2010-05-01

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

  10. Relationship between normal faulting and volcanic activity in the Taranaki backarc basin, New Zealand

    NASA Astrophysics Data System (ADS)

    Giba, M.; Walsh, J. J.; Nicol, A.

    2009-04-01

    Volcanoes and normal faults are, by definition, both present within volcanic rifts. Despite this association the causal relationships between volcanism and normal faulting can be unclear and are poorly understood. One of the principal challenges for investigations of the links between faulting and volcanic activity, is the definition of the detailed temporal relationships between these two processes. The northern Taranaki Basin, which benefits from excellent seismic (2D and 3D) and drillhole coverage, provides the basis for a detailed study of volcanism and faulting over the last ca 15 Myr. Most of the basin is characterised by sedimentation rates which exceed fault displacement rates, a condition which permits displacement backstripping of these syn-sedimentary growth faults. The timing of a suite of mostly andesitic submarine volcanoes has been constrained by interdigitation of the volcanic cones with basinal sedimentary rocks. Eleven dated horizons within the ca 15 Myr and younger stratigraphy together with mapping provide a means of examining the temporal and spatial links between fault and volcanic activity within the basin. The northern Taranaki Basin has a multiphase deformation history, with extension during the Late Cretaceous to Mid Eocene (ca 80-45 Ma), followed by contraction in the Late Eocene to Early Miocene (ca 40-18 Ma) and then by Mid Miocene to recent back arc extension (ca 15-0 Ma). The youngest phase of extensional faulting initiated in the north and west of the basin and migrated to the southeast where present activity is focused. Volcanic activity also commenced in the north during the Mid Miocene and migrated towards the south and east. Volcanism and backarc extension are driven by subduction of the Pacific plate along the Hikurangi margin. The southward and eastward migration of both faulting and volcanic activity is attributed to the steepening and rotation of the subducting slab beneath the Taranaki Basin. Despite the common origin of

  11. 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.

  12. Geological and tectonic implications obtained from first seismic activity investigation around Lembang fault

    NASA Astrophysics Data System (ADS)

    Afnimar; Yulianto, Eko; Rasmid

    2015-12-01

    The Lembang fault located at northern part of populated Bandung basin is the most conspicuous fault that potentially capable in generating earthquakes. The first seismic investigation around Lembang fault has been done by deploying a seismic network from May 2010 till December 2011 to estimate the seismic activities around that fault. Nine events were recorded and distributed around the fault. Seven events were likely to be generated by the Lembang fault and two events were not. The events related to the Lembang fault strongly suggest that this fault has left-lateral kinematic. It shows vector movement of Australian plate toward NNE might have been responsible for the Lembang fault kinematic following its initial vertical gravitational movement. The 1-D velocity model obtained from inversion indicates the stratigraphy configuration around the fault composed at least three layers of low Vp/Vs at the top, high Vp/Vs at the middle layer and moderate Vp/Vs at the bottom. In comparison with general geology of the area, top, mid and bottom layers may consecutively represent Quaternary volcanic layer, pre-Quaternary water-filled sedimentary layer and pre-Quaternary basement. Two eastern events related to minor faults and were caused by a gravitational collapse.

  13. Gravity data of the Norcia and Castelluccio basins (central Italy): insight for active faulting of the area

    NASA Astrophysics Data System (ADS)

    Ruano, P.; Rustichelli, A.; Galindo-Zaldívar, J.; Piccardi, L.; Ruiz-Constán, A.; Tondi, E.; López-Garrido, A. C.; Sanz de Galdeano, C.

    2009-04-01

    , indicating an increase of crustal thickness towards the Apennine edge, in agreement with the regional Bouguer map available from whole Italy. Negative residual anomalies up to -4 mGal are located in Norcia and Castelluccio depressions. Norcia has a roughly triangular depocenter located to the northwestern part, where probably are situated the most intense tectonic activity. It is surrounded by sharps west and northeastern scarps, corresponding to faults, the second clearly formed on recent sediments. Surprisingly, the southern half of the Norcia Basin, in spite of its flat character, seems to have a very thin practically absent sedimentary infill. It may represent an old flat surface of erosion, perhaps downthrown during fault activity. Catelluccio basin has a slightly asymmetrical sinsedimentary infill, controlled by faults located to the northwestern and northeastern borders.

  14. 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

  15. 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

  16. 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

  17. 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

  18. The Search for Lunar Lobate Scarps Using Images from the Lunar Reconnaissance Orbiter Camera

    NASA Astrophysics Data System (ADS)

    Banks, M. E.; Watters, T. R.; Robinson, M. S.; Bell, J. F.; Pritchard, M. E.; Williams, N. R.; Daud, K.; Lroc Team

    2011-03-01

    A search for previously undetected lobate scarps was conducted using images from the Lunar Reconnaissance Orbiter Camera. To date, previously undetected lobate scarps have been identified in LROC images and mosaics in 73 different locations.

  19. 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

  20. Deep Springs fault, Inyo County, California: An example of the use of relative-dating techniques

    SciTech Connect

    Bryant, W.A.

    1989-11-01

    This article summarizes faulting in the Deep Springs Valley area, which was studied as part of a systematic evaluation of potentially active faults throughout California by the Division of Mines and Geology. Evaluation of surface fault-rupture hazard is authorized by the Alquist-Priolo Special Studies Zones Act of 1972. This act requires the State Geologist to delineate regulatory zones for faults that are well defined and show that displacement occurred during the last 11,000 years. Fault evaluations for the Division of Mines and Geology Fault Evaluation and Zoning Project are conducted at a detailed reconnaissance level. Evaluations are mainly based on aerial photographic interpretation in which ephemeral fault-produced landforms are identified and mapped. Young alluvial deposits and geomorphic surfaces are identified as either offset or not offset by faults. Field mapping is conducted to verify fault-related geomorphic features and to estimate ages of faulted and unfaulted deposits. The section on scarp degradation and relative dating techniques provides a brief survey of methods used in studies of the Basin and Range province. In these investigations geomorphic evidence is applied to determine the recency of faulting.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  2. Observability of Rembrandt scarp with Mercury Radio Science Experiment

    NASA Astrophysics Data System (ADS)

    Junior Mariani, Mirco; Marabucci, Manuela; Di Achille, Gaetano

    2015-04-01

    The radio science experiment of the ESA mission BepiColombo (MORE, Mercury Orbiter Radio science Experiment) is devoted to the estimation of Mercury's gravity field with unprecedented accuracy, by means of highly stable, multi-frequency radio links in X and Ka band, provided by the Ka band transponder (KaT) on-board the Mercury Planetary Orbiter (MPO). The estimation of gravity field coefficients and planetary tidal deformation with radio science experiment will provide fundamental constraints for modelling planet interior, but additional analysis can be carried out in order to verify whether radio science can give a significant contribution in the study of other physical phenomena, like for example crustal thickening due to tectonic phenomena. This paper reports on the observability of Mercury scarps and crustal thickening with the Mercury Orbiter Radio science experiment, exploiting the extremely precise radio observables (range rate accuracies of 3 micron/s at 1000 s integration time at nearly all elongation angles, and range observables accuracies of 20 cm two-way). One of the largest surface structures of Mercury's surface is the Rembrandt scarp, which can be modeled with a length of 1000 km, an average width of 300 km and a height of 5 km, assuming a flat-ramp-flat tectonic geometry for its enucleation. In general, a surface structure can be observed with radio science if the variation in velocity due to the change in the gravitational potential is larger than the accuracy of the signal at an integration time equal to the interaction time between the spacecraft and the structure, e.g. about 100s for the Rembrandt scarp. Based on our simualtions, the gravity anomalies associated to the Rembrandt scarp can potentially produce effects on the spacecraft orbit that are significantly higher than the expected noise. Therefore, there is an excellent chance that the density contrast generated by the crustal thickness along the Rembrandt scarp will be measurable to a

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

    SciTech Connect

    Rindell, A.K. )

    1993-04-01

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

  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. 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

  6. 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

  7. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

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

  9. Mapping Active Fault Zones in Southern California Using Master Multispectral Imagery Data

    NASA Astrophysics Data System (ADS)

    Harvey, J. C.; Peltzer, G. F.; Hook, S. J.; Alley, R.; Myers, J.; Coffland, B.; Dominguez, R.; Fitzgerald, M.

    2004-12-01

    Recent studies of active fault zones using the GPS and InSAR techniques have revealed slip rates that often differ from the slip rates determined from geological observations. This discrepancy is principally due to the different time windows over which surface movements are integrated in both approaches. If surface velocities near faults vary over cycles of several hundreds of years, it becomes important to document the slip history along faults over various time scales as it has been recorded in the Quaternary deposits along the fault. To this endeavor, we have acquired sets of images of the major active faults in Southern California using the MODIS/ASTER airborne simulator (MASTER) instrument. The lines are flown at low altitude above the ground to provide 4 to 5 m spatial resolution in the 50 spectral bands (0.5 to 13 microns) of the instrument. A preliminary set of data was acquired in the summer 2003 over the Garlock and the Blackwater faults in the Mojave. A more extensive campaign carried out in September 2004 covered more than 1000 km of fault lines from the central section of the San Andreas fault to the Salton Sea area. The data are being processed to extract reflectance and emissivity information. Preliminary analysis of the 2003 data confirmed the strong potential of the MASTER thermal bands to identify changes in surface emissivity due to subtle variations of the mineral composition of the deposits. Additional information on the near surface structure of the fault zones can be obtained by combining day and night surface temperature maps, as buried sections of faults are revealed by thermal capacity contrasts between the two sides of a given fault. The paper will present the data set acquired during the 2003 and 2004 campaigns and the status of the raw data processing into geo-referenced emissivity and reflectivity maps of the fault zones.

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

    NASA Astrophysics Data System (ADS)

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

    2007-07-01

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

  11. 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

  12. 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

  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. Structure and paleoearthquake records of active submarine faults, Cook Strait, New Zealand: Implications for fault interactions, stress loading, and seismic hazard

    NASA Astrophysics Data System (ADS)

    Pondard, Nicolas; Barnes, Philip M.

    2010-12-01

    A new interpretation of active faulting in central Cook Strait, New Zealand, reveals tectonic structures associated with the spatial transition from subduction to continental transform faulting. Marine seismic reflection profiles and multibeam bathymetric data indicate that there are no throughgoing crustal faults connecting the North Island Dextral Fault Belt and the Marlborough Fault System in South Island. The major faults terminate offshore, associated with 5-20 km wide step-overs and a change in regional fault strike. This structure implies that propagation of strike-slip earthquake ruptures across the strait is not probable. Faulted sedimentary sequences in the Wairau Basin (Marlborough shelf), correlated to glacioeustatic sea level cycles, provide a stratigraphic framework for fault analysis. A high-resolution study of the postglacial (<20 ka) vertical displacement history of the Cloudy and Vernon faults reveals up to six and five paleoearthquakes since 18 ka, respectively. These long-timescale records indicate variable recurrence intervals and possibly variable stress drop, thus conforming to the variable slip model of earthquake behavior. Integration of these data with other submarine and terrestrial paleoearthquake records indicates the presence of clustered earthquake sequences involving multiple faults. Different sequences do not always involve the same faults. It appears that earthquake clustering is driven by fault interactions that lead to specific loading conditions favoring the triggering of earthquakes on major faults in relatively short time intervals. Present-day regional Coulomb stress distribution has been calculated in two scenarios considered to represent minimum and maximum loading conditions. The models, incorporating secular tectonic loading and stress changes associated with major crustal earthquakes, indicate high stress loading in a large part of central Cook Strait. These conditions may favor the triggering of future damaging

  15. Active displacements recorded along major fault systems in caves (Eastern Alps, Austria)

    NASA Astrophysics Data System (ADS)

    Mitrovic, Ivanka; Plan, Lukas; Baron, Ivo; Grasemann, Bernhard

    2014-05-01

    Seismic data and GPS observations suggest that several major tectonic fault systems in the Eastern Alps are still active. However, direct geological evidences for recent movements along individual fault systems are rather scarce and limited to local observations in the Vienna Basin. Recently, tectonically damaged speleothems have been described from a cave close to the Salzach Ennstal Mariazeller Puchberger (SEMP) strike-slip fault, which accommodated the lateral extrusion of the Eastern Alps towards the Pannonian Basin. The project SPELEOTECT investigates the Quaternary tectonic activity and recent dynamics of micro-displacements along major fault systems of the Eastern Alps recorded in caves. The work focuses on cave passages, which have been displaced by active faulting and on speleothems, which have been damaged by fault movements. In order to bracket the tectonic events, flowstones, which have grown before and after the tectonic event are dated using the U-series disequilibrium method. For the reconstruction of the local stress field during (re)activation of the faults, the paleostress and the active stress field will be calculated from the fault-slip data of the recent micro-dislocations monitored with high-accuracy 3D crack-gauges. Cataclasites and fault gouges from sheared flowstones are investigated with high-resolution electron beam analytical techniques in order to characterize the microstructures caused by various deformation mechanisms within principal slip surfaces. Cathodoluminescense images are combined with electron backscattered diffraction maps in order to discriminating between fault displacements caused by seismic slip or aseismic creep. The major aim of SPELEOTECT is the record of a solid and broad data base of the paleoseismic record of the Eastern Alps for regional earthquake hazard assessment.

  16. Fault and graben growth along active magmatic divergent plate boundaries in Iceland and Ethiopia

    NASA Astrophysics Data System (ADS)

    Trippanera, D.; Acocella, V.; Ruch, J.; Abebe, B.

    2015-11-01

    Recent studies highlight the importance of annual-scale dike-induced rifting episodes in developing normal faults and graben along the active axis of magmatic divergent plate boundaries (MDPB). However, the longer-term (102-105 years) role of diking on the cumulative surface deformation and evolution of MDPB is not yet well understood. To better understand the longer-term normal faults and graben along the axis of MDPB, we analyze fissure swarms in Iceland and Ethiopia. We first focus on the simplest case of immature fissure swarms, with single dike-fed eruptive fissures; these consist of a <1 km wide graben bordered by normal faults with displacement up to a few meters, consistent with theoretical models and geodetic data. A similar structural pattern is found, with asymmetric and multiple graben, within wider mature fissure swarms, formed by several dike-fed eruptive fissures. We then consider the lateral termination of normal faults along these grabens to detect their upward or downward propagation. Most faults terminate as open fractures on flat surface, suggesting downward fault propagation; this is consistent with recent experiments showing dike-induced normal faults propagating downward from the surface. However, some normal faults also terminate as open fractures on monoclines, which resemble fault propagation folds; this suggests upward propagation of reactivated buried faults, promoted by diking. These results suggest that fault growth and graben development, as well as the longer-term evolution of the axis of MDPB, may be explained only through dike emplacement and that any amagmatic faulting is not necessary.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

    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.

  2. Active fault tolerant control of a flexible beam

    NASA Astrophysics Data System (ADS)

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

    2007-04-01

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

  3. 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

  4. 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

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

    NASA Astrophysics Data System (ADS)

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

    2006-12-01

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

  6. 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. PMID:22658334

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

  8. Insights into the internal structure and formation of striated fault surfaces of oceanic detachments from in situ observations (13°20'N and 13°30'N, Mid-Atlantic Ridge)

    NASA Astrophysics Data System (ADS)

    Escartin, J.; Bonnemains, D.; Mevel, C.; Cannat, M.; Petersen, S.; Augustin, N.; Bezos, A.; Chavagnac, V.; Choi, Y.; Godard, M.; Haaga, K.; Hamelin, C.; Ildefonse, B.; Jamieson, J. W.; John, B. E.; Leleu, T.; MacLeod, C. J.; Massot-Campos, M.; Nomikou, P.; Olive, J. A. L.; Paquet, M.; Rommevaux, C.; Rothenbeck, M.; Steinführer, A.; Tominaga, M.; Triebe, L.; Andreani, M.; Garcia, R.; Campos, R.

    2014-12-01

    Oceanic detachment faults (ODs) are known to play a significant role in oceanic crustal accretion along slow-spreading ridges, and many display a poorly understood corrugated fault surface. The ODEMAR cruise (Nov-Dec'14) studied the 13°20'N and 13°30'N ODs along the Mid-Atlantic Ridge via extensive microbathymetric surveys with AUV ABYSS (GEOMAR), combined with geological observations and sampling using ROV VICTOR (IFREMER). The 13°20'N OD is largely intact, with an undisrupted corrugated surface. An abrupt, continuous moat where the OD emerges from the seafloor sloping at ~12-18° continuously sheds rubble onto the OD fault plane, blanketing it. An apron surrounds the detachment dipping ~10-14° towards volcanic rift valley floor thus forming a thin wedge above the active OD fault, which uplifts hangingwall material. In contrast, the 13°30'N OD is cut by recent high-angle faults, and is likely inactive. The OD fault is well exposed along these recent high angle fault scarps, and along mass wasting scarps. The OD fault displays individual microbathymetric lineations throughout the >150 m of fault zone thickness, that are traced up to ~2 km in the spreading direction. Flanks of individual lineations display fault planes extending ~20-100 m laterally with well-developed, extension-parallel striae. At 13°20'N. These fault surfaces are primarily basalt fault breccias and minor serpentinite. At 13°30'N the scarps cutting the detachment system reveal highly heterogeneous deformation, with phacoidal blocks of undeformed peridotite, gabbro, and basalt enclosed in anastomosing shear zones. Basalt often shows greenschist grade alteration, and is only present in the upper 50 m of the OD fault zone. In detail, OD faults are characterized by anastomosing zones of localized, strongly anisotropic deformation at different scales (m to km), bounding bodies of largely undeformed rock (basalt, gabbro, peridotite) elongated in the extension direction. Hangingwall material

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

    NASA Astrophysics Data System (ADS)

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

    2011-01-01

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

  10. Geomorphological observations of active faults in the epicentral region of the Huaxian large earthquake in 1556 in Shaanxi Province, China

    NASA Astrophysics Data System (ADS)

    Hou, Jian-Jun; Han, Mu-Kang; Chai, Bao-Long; Han, Heng-Yue

    1998-05-01

    The Huaxian magnitude 8 great earthquake of January 23, 1556, is the largest one recorded in the Weihe basin, Shaanxi Province, China and caused 830,000 people either injury or death. The epicenter is located in the southeastern part of the Weihe basin, around Huaxian City. Earthquakes are closely related to active faults and active faults are well developed in the epicentral area of the Huaxian large earthquake. Thus we will discuss the activity of the major faults in the epicentral area by geomorphological observations. There are three major fault sets in the study area: striking approximately east-west, northeast and northwest. These are inhomogeneous in spatial distribution, rates and manners of faulting, as shown by geomorphological observations such as faulted fluvial terraces and alluvial fans. The ages of the second and first terraces are around 20,000 and 5,000 years B.P. by thermoluminescent dating, Carbon-14 dating and archeology. The terraces were faulted by the North Huashan fault (F 1), the main boundary fault of Weihe basin and the Piedmont fault (F 2) after the second and the first terraces formed. The distribution of the displacement shows that the intersections of the North Huashan fault and the Chishui fault (F 4) striking northwest, and the western margin fault (F 5) of Tongguan loess tableland, have the largest in offsets in the area. Perhaps the Huanxian great earthquake in 1556 A.D. had a close relation to the North Huashan fault. The Weihe fault (F 3) striking east-west is also an active fault by analysis of the flood plain structure. Thus we should pay attention to the activities of the faults to take precautions against another possible large earthquake in this region.

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

    NASA Astrophysics Data System (ADS)

    Natawidjaja, D. H.

    2012-12-01

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

  12. 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.

  13. Zipper Faults

    NASA Astrophysics Data System (ADS)

    Platt, J. P.; Passchier, C. W.

    2015-12-01

    Intersecting simultaneously active pairs of faults with different orientations and opposing slip sense ("conjugate faults") present geometrical and kinematic problems. Such faults rarely offset each other, even when they have displacements of many km. A simple solution to the problem is that the two faults merge, either zippering up or unzippering, depending on the relationship between the angle of intersection and the slip senses. A widely recognized example of this is the so-called blind front developed in some thrust belts, where a backthrust branches off a decollement surface at depth. The decollement progressively unzippers, so that its hanging wall becomes the hanging wall of the backthrust, and its footwall becomes the footwall of the active decollement. The opposite situation commonly arises in core complexes, where conjugate low-angle normal faults merge to form a single detachment; in this case the two faults zipper up. Analogous situations may arise for conjugate pairs of strike-slip faults. We present kinematic and geometrical analyses of the Garlock and San Andreas faults in California, the Najd fault system in Saudi Arabia, the North and East Anatolian faults, the Karakoram and Altyn Tagh faults in Tibet, and the Tonale and Guidicarie faults in the southern Alps, all of which appear to have undergone zippering over distances of several tens to hundreds of km. The zippering process may produce complex and significant patterns of strain and rotation in the surrounding rocks, particularly if the angle between the zippered faults is large. A zippering fault may be inactive during active movement on the intersecting faults, or it may have a slip rate that differs from either fault. Intersecting conjugate ductile shear zones behave in the same way on outcrop and micro-scales.

  14. Kinematic analysis of lobate scarps cross-cutting Mercurian craters

    NASA Astrophysics Data System (ADS)

    Galluzzi, V.; Di Achille, G.; Ferranti, L.; Popa, C.; Palumbo, P.

    2013-09-01

    Craters work as a good marker on planetary surfaces, both for kinematics and strain analysis. Some authors measured their elongation and elongation direction to estimate the strain of intensely faulted areas of Mars and Ganymede [2], [5], [9]. In other cases the craters' deformation was used to infer the nature of the crosscutting faults [8], [10], [12]. However, the latter studies did not make any assumption on the slip's geometry (i. e. the fault's true dip and the slip's vector), which is fundamental to estimate kinematic parameters, based on the analysis of craters cross-cut by faults. By using faulted craters of Mercury, we propose a new method to obtain quantitative kinematic parameters for the crosscutting faults. This method can be used as a univocal criterion for all types of faults, independently from their nature and hosting rocks' rheology, leading to assess their true slip direction, horizontal and vertical components of their displacement and thus the slip's plunge, fault's true dip and displacement along the fault's plane. Moreover, the latter parameters can be used to estimate fault's rake and then to study the overall kinematics of the analyzed faults with a quantitative and comprehensive approach. We analyzed 14 craters of Mercury found throughout the 30% of the Mercury's surface covered by the Digital Elevation Model (DEM) from [6].

  15. Late Quaternary slip rates and paleoearthquakes along the Yabrai range-front fault in the southern Gobi-Alashan block

    NASA Astrophysics Data System (ADS)

    Yu, Jingxing; Zheng, Wenjun; Lei, Qiyun; Shao, Yanxiu; Ge, Weipeng

    2014-05-01

    Study on the active faults of the southern Gobi-Alashan block is significant to understand the tectonic deformation processes associated with the Tibetan Plateau and Ordos block. With this knowledge in mind, the present study aims to answer what the major process is governing the tectonic deformation and the structural relationships between Gobi-Alashan and adjacent regions. Since this area was featured by late Quaternary active tectonics, the activities and paleoearthquakes around the block need be studied and reconciled. So, we will focus on one of those active structures, the ranger-front fault along Yabrai Shan, to address some basic problems. Three aspects are analyzed, i.e., geomorphology, kinematic characteristics and paleoearthquakes of the range-front fault along the Yabrai Shan. By combining previous studies and Differential GPS measurements, implications of the fault for the regional tectonics has been discussed. The main conclusions are summarized as follows: This fault consists of three segments. The most active segment is in the southwest. The southwest segment is about 35 km long. Its scarp, about 1-2 m high, might be the result of the most recent event (MRE) and stretches NE60° almost the full segment. Existence of free surface indicates that the elapsed time of the last event must be not long. The middle segment is about 31 km in length. Just a single fault plane was identified along the main bounds of the Yabrai Shan, but the fault consists of several splays in the north. In contrast to the simple geometric structure of the middle segment, the northeast segment comprises several faults. Scarps of the most recent earthquake event are clear but tend not to be continued. Field investigation reveals about 0.5-1.5 m up to 2 m height. This work determined slip rates by combining fault-scarp measurements and cosmogenic exposure age dating. Study on slip rates shows that the Holocene dip-slip rate of the Yabrai fault is 0.11±0.03 mm/a. Scarp vertical

  16. Active fault creep variations at Chihshang, Taiwan, revealed by creep meter monitoring, 1998-2001

    NASA Astrophysics Data System (ADS)

    Lee, Jian-Cheng; Angelier, Jacques; Chu, Hao-Tsu; Hu, Jyr-Ching; Jeng, Fu-Shu; Rau, Ruey-Juin

    2003-11-01

    The daily creep meter data recorded at Chihshang in 1998-2001 are presented. The Chihshang creep meter experiment was set up across the Chihshang thrust fault, the most active segment of the Longitudinal Valley Fault, which is the present-day plate suture between the Eurasian and the Philippine Sea plates in eastern Taiwan. Near-continuous data recording at two sites revealed different surface fault motions yet similar annual shortening rates: 16.2 mm at the Tapo site (comprising two connected creep meters) and 15.0 mm at the Chinyuan site (three creep meters straddling parallel fault branches). Four of the five creep meters showed a seasonal variation, with the fault moving steadily during the rainy season from April to October, and remaining quiescent during the rest of the year. The only exception was recorded by the creep meter located on a mélange-composed hillslope, where local gravitational landsliding played an additional role other than tectonic faulting. Through comparison with daily precipitation data, we inferred that moderate rainfall suffices to trigger or facilitate slippage on the surface fault, during the transition period of the dry/wet season. During the observation period from 1998 to 2001, the subsurface seismicity exhibited clusters of microearthquakes on the Chihshang Fault at depths of 10-25 km. Recurrent earthquakes occurred regardless of whether the season was wet or dry, indicating that the stress relaxation associated with seismicity in the seismogenic zone did not transfer immediately up to the surface. The accumulated strain on the Chihshang Fault at shallow surface levels was released through creep during the wet season. In addition to these short-term seasonal variations, an apparent decrease in the annual slipping rate on the Chihshang Fault during the last few years deserves further investigation in order to mitigate against seismic hazard.

  17. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

  19. Triggered tremors beneath the seismogenic zone of an active fault zone, Kyushu, Japan

    NASA Astrophysics Data System (ADS)

    Miyazaki, Masahiro; Matsumoto, Satoshi; Shimizu, Hiroshi

    2015-11-01

    Non-volcanic tremors were induced by the surface waves of the 2012 Sumatra earthquake around the Hinagu fault zone in Kyushu, Japan. We inferred from dense seismic observation data that the hypocenters of these tremors were located beneath the seismogenic zone of the Hinagu fault. Focal mechanisms of the tremors were estimated using S-wave polarization angles. The estimated focal mechanisms show similarities to those of shallow earthquakes in this region. In addition, one of the nodal planes of the focal mechanisms is almost parallel to the strike direction of the Hinagu fault. These observations suggest that the tremors were triggered at the deeper extension of the active fault zone under stress conditions similar to those in the shallower seismogenic region. A low-velocity anomaly beneath the hypocentral area of the tremors might be related to the tremor activity.

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

    USGS Publications Warehouse

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

    2000-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  2. Late Quaternary evolution of the La Cantera Fault System (Central Precordillera, Argentina): A morphotectonic and paleoseismic analysis

    NASA Astrophysics Data System (ADS)

    Perucca, Laura; Rothis, Martín; Bezerra, Francisco Hilario; Vargas, Nicolás; Lima, Jean

    2015-10-01

    The La Cantera Fault System (LCFS) is the most active Quaternary structure in the Central Precordillera of San Juan, in central-western Argentina; the system extends for 47 km along the intermountain valley that separates the Sierra de La Cantera and La Invernada, north of the San Juan River. The average fault trend is 20°; it dips at angles varying between 15° and 30° W in the northern section, to approximately 40° W in the central section, and up to 60° W in the southern section. The fault affects Holocene to recent alluvium deposits in the western piedmont of the Sierra de La Cantera and is defined by a series of landforms found in compressive tectonic environments, including simple and compound counterslope fault scarps, staircased alluvial terraces, sag ponds, flexural scarps, aligned springs, broom-shaped drainage patterns, river diversions, beheaded channels, changes in incision depths, sinuosity and a river gradient along channels. Trench investigations indicated that at least three events occurred in the past 1.1-10.1 ky. The topographic profiles of the selected channels and interfluves cutting across the northern and central trace of the fault were analyzed using a Stonex Vector GPS differential system to establish the relationship between the topography and slope of the rivers. This morphometric analysis of scarps indicates that active tectonics have played an essential role in controlling the drainage pattern in the piedmont, leading the rivers to adjust to these slope variations. Based on the analyzed geomorphologic, stratigraphic and structural characteristics, the LCFS is considered to be a relevant seismogenic source in the intraplate portion of southern South America, with a recurrence interval of at least 2000 ± 500 years for moderate magnitude earthquakes during the last 11,000 years.

  3. Evidence of recent thrust faulting on the Moon revealed by the Lunar Reconnaissance Orbiter Camera.

    PubMed

    Watters, Thomas R; Robinson, Mark S; Beyer, Ross A; Banks, Maria E; Bell, James F; Pritchard, Matthew E; Hiesinger, Harald; van der Bogert, Carolyn H; Thomas, Peter C; Turtle, Elizabeth P; Williams, Nathan R

    2010-08-20

    Lunar Reconnaissance Orbiter Camera images reveal previously undetected lobate thrust-fault scarps and associated meter-scale secondary tectonic landforms that include narrow extensional troughs or graben, splay faults, and multiple low-relief terraces. Lobate scarps are among the youngest landforms on the Moon, based on their generally crisp appearance, lack of superposed large-diameter impact craters, and the existence of crosscut small-diameter impact craters. Identification of previously known scarps was limited to high-resolution Apollo Panoramic Camera images confined to the equatorial zone. Fourteen lobate scarps were identified, seven of which are at latitudes greater than +/-60 degrees, indicating that the thrust faults are globally distributed. This detection, coupled with the very young apparent age of the faults, suggests global late-stage contraction of the Moon. PMID:20724632

  4. 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

    2016-01-01

    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

  5. Investigating the deformation of upper crustal faults at the N-Chilean convergent plate boundary at different scales using high-resolution topography datasets and creepmeter measurements

    NASA Astrophysics Data System (ADS)

    Ewiak, O.; Victor, P.; Ziegenhagen, T.; Oncken, O.

    2012-04-01

    The Chilean convergent plate boundary is one of the tectonically most active regions on earth and prone to large megathrust earthquakes as e. g. the 2010 Mw 8.8 Maule earthquake which ruptured a mature seismic gap in south-central Chile. In northern Chile historical data suggests the existence of a seismic gap between Arica and Mejillones Peninsula (MP), which has not ruptured since 1877. Further south, the 1995 Mw 8.0 Antofagasta earthquake ruptured the subduction interface between MP and Taltal. In this study we investigate the deformation at four active upper plate faults (dip-slip and strike-slip) located above the coupling zone of the subduction interface. The target faults (Mejillones Fault - MF, Salar del Carmen Fault - SCF, Cerro Fortuna Fault - CFF, Chomache Fault - CF) are situated in forearc segments, which are in different stages of the megathrust seismic cycle. The main question of this study is how strain is accumulated in the overriding plate, what is the response of the target faults to the megathrust seismic cycle and what are the mechanisms / processes involved. The hyper arid conditions of the Atacama desert and the extremely low erosion rates enable us to investigate geomorphic markers, e .g. fault scarps and knickpoints, which serve as a record for upper crustal deformation and fault activity about ten thousands years into the past. Fault scarp data has been acquired with Differential-GPS by measuring high-resolution topographic profiles perpendicular to the fault scarps and along incised gullies. The topographic data show clear variations between the target faults which possibly result from their position within the forearc. The surveyed faults, e. g. the SCF, exhibit clear along strike variations in the morphology of surface ruptures attributed to seismic events and can be subdivided into individual segments. The data allows us to distinguish single, composite and multiple fault scarps and thus to detect differences in fault growth initiated

  6. 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

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

    NASA Astrophysics Data System (ADS)

    Okumura, K.

    2011-12-01

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

  8. 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.

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

    DOE PAGESBeta

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

    2015-03-01

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

  10. 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.

  11. 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.

  12. 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.

  13. Tectonic control on the drainage system in a piedmont region in tectonically active eastern Himalayas

    NASA Astrophysics Data System (ADS)

    Goswami, Chandreyee; Mukhopadhyay, Dhruba; Poddar, Bikash Chandra

    2012-03-01

    The impact of neotectonic activity on drainage system has been studied in a large alluvial fan in the eastern Himalayan piedmont area between the Mal River and the Murti River. Two distinct E-Wlineaments passing through this area had been identified by Nakata (1972, 1989) as active faults. The northern lineament manifested as Matiali scarp and the southern one manifested as Chalsa scarp represent the ramp anticlines over two blind faults, probably the Main Boundary Thrust (MBT) and the Himalayan Frontal Thrust (HFT), respectively. The fan surface is folded into two antiforms with a synform in between. These folds are interpreted as fault propagation folds over the two north dipping blind thrusts. Two lineaments trending NNE-SSW and nearly N-S, respectively, are identified, and parts of present day courses of the Murti and Neora Rivers follow them. These lineaments are named as Murti and Neora lineaments and are interpreted to represent a conjugate set of normal faults. The rivers have changed their courses by the influence of these normal faults along the Murti and Neora lineaments and their profiles show knick points where they cross E-W thrusts. The overall drainage pattern is changed from radial pattern in north of the Matiali scarp to a subparallel one in south due to these conjugate normal faults. The interfluve area between these two rivers is uplifted as a result of vertical movements on the above mentioned faults. Four major terraces and some minor terraces are present along the major river valleys and these are formed due to episodic upliftment of the ground and subsequent down-cutting of the rivers. The uppermost terrace shows a northerly slope north of the Chalsa scarp as a result of folding mentioned above. But rivers on this terrace form incised channels keeping their flow southerly suggesting that they are antecedent to the folding and their downcutting kept pace with the tectonism.

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  15. Mesoscopic structure of the Punchbowl Fault, Southern California and the geologic and geophysical structure of active strike-slip faults

    NASA Astrophysics Data System (ADS)

    Schulz, Steven E.; Evans, James P.

    2000-07-01

    We examine the distribution, density, and orientation of outcrop-scale structures related to the Punchbowl Fault, an exhumed ancient trace of the San Andreas Fault, southern California, in order to determine the structure of the fault zone. The Punchbowl Fault has 44 km of right-lateral slip, and cuts the Cretaceous Pelona Schist in the study area. The mesoscopic structures examined include fractures, small faults, and veins; they were inventoried using scan lines at closely spaced stations along three strike-perpendicular traverses 200-250 m long across the fault. The fault zone thickness is a function of the type of structure measured. Slip along narrow (<2 m wide) ultracataclasite cores of the faults results in foliation reorientation over a distance of 50 m from the cores: fracture and fault densities appear to increase 50-80 m from the fault cores, and vein densities are highly variable across the fault zone. Fractures and faults in the damaged zone have a variety of orientations, but most are at high angles to the main fault zone. When coupled with previous geochemical and microstructural data, these data show that large-displacement faults of the San Andreas system, are up to 200-250 m thick, and enclose zones of mineralogic and geochemical alteration that are 20-30 m thick. Extreme slip localization occurs over zones 1-5 m thick. When reconciled with geophysical imaging, our data suggest that trapped headwaves travel in the damaged zone, and that some aftershock events produce slip on faults and fractures, which often have orientations very different from the principal slip surfaces.

  16. Seismic sequence near Zakynthos Island, Greece, April 2006: Identification of the activated fault plane

    NASA Astrophysics Data System (ADS)

    Serpetsidaki, A.; Sokos, E.; Tselentis, G.-A.; Zahradnik, J.

    2010-01-01

    The April 2006 earthquake sequence near Zakynthos (Western Greece) is analysed to identify the fault plane(-s). The sequence (33 events) was relocated to assess physical insight into the hypocenter uncertainty. Moment tensor solution of three major events was performed, simultaneously with the determination of the centroid position. Joint analysis of the hypocenter position, centroid position and nodal planes indicated sub-horizontal fault planes. Moment tensor solutions of 15 smaller events were performed under assumption that the source positions are those of the hypocenters (without seeking centroids). Their focal mechanisms are highly similar and agree with the analysis of the three major events. The preferable seismotectonic interpretation is that the whole sequence activated a single sub-horizontal fault zone at a depth of about 13 km, corresponding to the interplate subduction boundary. Considering that the Ionian Sea is a high-seismicity area, the identification of the seismic fault is significant for the seismic hazard investigation of the region.

  17. 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.

  18. Lobate Scarps within the Hummocky Plains East of Caloris Basin

    NASA Technical Reports Server (NTRS)

    1974-01-01

    Plains material east of the Caloris basin is shown this image (FDS 191) acquired during the spacecraft's first encounter with Mercury. Several west-facing lobate scarps occur in the hummocky plains interpreted as Caloris ejecta and may be short flow fronts of partially melted ejecta which flowed back toward the basin after deposition.

    The Mariner 10 mission, managed by the Jet Propulsion Laboratory for NASA's Office of Space Science, explored Venus in February 1974 on the way to three encounters with Mercury-in March and September 1974 and in March 1975. The spacecraft took more than 7,000 photos of Mercury, Venus, the Earth and the Moon.

    Image Credit: NASA/JPL/Northwestern University

  19. 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

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  1. A compilation of major active faults for parts of Montana and Idaho

    SciTech Connect

    Haller, K.M.; Dart, R.L. ); Stickney, M.C. )

    1993-04-01

    The area covered by Montana and Idaho was used as a prototypical test for developing and applying criteria with which to select and present data on Quaternary faults for the US contribution to the World Map of Active Faults (International Lithosphere Program Project II-2, see Machette and others, this session). The prototype is successful in part because the test area contains a large number of Quaternary faults of differing age and the present level of scientific knowledge of these faults is quite variable. As such, active faults in Montana and Idaho provide an excellent representative population from which to formulate database criteria. The compilation consists of a digital map and supporting relational database. Fault traces were compiled on 1:250,000-scale topographic maps and digitized using Geographic Information System software to permit output at State-map scales of 1:500,000 or 1:750,000. The timing of the most recent event and slip rates of the faults are shown by different line colors and thicknesses, according to the convention established for the US and World Map. Five age categories defined by color include historic, Holocene and latest Pleistocene (< [approximately]15 ka), late Quaternary (< [approximately]130 ka), late and middle Quaternary (< [approximately]750 ka), and undifferentiated Quaternary (< 1.6 Ma). Three slip-rate categories defined by line thickness include high (> 5 mm/yr), moderate (1--5 mm/yr), and low slip rates (< 1 mm/yr). The accompanying database provides supporting evidence for age of faulting and slip rates shown on the map as well as details of segmentation, location of exploratory trenches, recurrence intervals, and references to published studies.

  2. 3-D GPR data analysis for high-resolution imaging of shallow subsurface faults: the Mt Vettore case study (Central Apennines, Italy)

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  4. 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.

  5. Distribution and structure of active strike-slip faults in the Enshu forearc basin of the eastern Nankai subduction zone

    NASA Astrophysics Data System (ADS)

    Ojima, T.; Ashi, J.; Nakamura, Y.

    2010-12-01

    Accretionary prisms and forearc basins are developed in the Nankai Trough, SW Japan. Many active faults are recognized and classified into five fault systems in the eastern Nankai Trough. The Enshu Faults System, the most landward one, runs over 200 km along the northern edge of the Tokai, Enshu and Kumano forearc basins. Swath bathymetry and side-scan sonar surveys indicate a general fault trend of ENE-WSW and dextral displacement of submarine canyons across the landward-most fault. Seismic reflection profiles partly exhibit landward dipping fault planes and flower structures suggesting that the Enshu fault system is affected by oblique subduction of the Philippines Sea Plate. Structural investigation of this area is important for earthquake disaster mitigation as well as understanding of oblique subduction tectonics. However, activity of faults has not been clarified. Japan Oil, Gas and Metal National Corporation (JOGMEC) conducted dense seismic reflection survey at the Tokai-Kumano area in 2001. Seismic reflection profiles clearly show depositional sequences and deformation structures such as faults and folds. This study examined deformation styles and fault activities based on detailed interpretation of seismic reflection profiles. Sediment thickness mapped from seismic profiles clearly changes with age. Sediment thickness is almost homogeneous from the acoustic basement (probably Paleogene Shimanto Complex) to a Pliocene horizon in the survey area. In contrast, thickness between a Pliocene horizon and present seafloor shows large variations from east to west. It is suggested that sedimentary environments change drastically at this period. There are also small-scale variations in sediment thickness for all horizons. Some distinct changes are distributed along linear boundaries. It seems that they correspond to the faults recognized as lineaments on the sidescan sonar images. We estimated activities of faulting based on such sediment thickness changes and their

  6. The Bear River Fault Zone, Wyoming and Utah: Complex Ruptures on a Young Normal Fault

    NASA Astrophysics Data System (ADS)

    Schwartz, D. P.; Hecker, S.; Haproff, P.; Beukelman, G.; Erickson, B.

    2012-12-01

    The Bear River fault zone (BRFZ), a set of normal fault scarps located in the Rocky Mountains at the eastern margin of Basin and Range extension, is a rare example of a nascent surface-rupturing fault. Paleoseismic investigations (West, 1994; this study) indicate that the entire neotectonic history of the BRFZ may consist of two large surface-faulting events in the late Holocene. We have estimated a maximum per-event vertical displacement of 6-6.5 m at the south end of the fault where it abuts the north flank of the east-west-trending Uinta Mountains. However, large hanging-wall depressions resulting from back rotation, which front scarps that locally exceed 15 m in height, are prevalent along the main trace, obscuring the net displacement and its along-strike distribution. The modest length (~35 km) of the BRFZ indicates ruptures with a large displacement-to-length ratio, which implies earthquakes with a high static stress drop. The BRFZ is one of several immature (low cumulative displacement) normal faults in the Rocky Mountain region that appear to produce high-stress drop earthquakes. West (1992) interpreted the BRFZ as an extensionally reactivated ramp of the late Cretaceous-early Tertiary Hogsback thrust. LiDAR data on the southern section of the fault and Google Earth imagery show that these young ruptures are more extensive than currently mapped, with newly identified large (>10m) antithetic scarps and footwall graben. The scarps of the BRFZ extend across a 2.5-5.0 km-wide zone, making this the widest and most complex Holocene surface rupture in the Intermountain West. The broad distribution of Late Holocene scarps is consistent with reactivation of shallow bedrock structures but the overall geometry of the BRFZ at depth and its extent into the seismogenic zone are uncertain.

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

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

    NASA Technical Reports Server (NTRS)

    Meakin, Peter; Weitl, Raquel

    2013-01-01

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

  9. Assessment of the geodynamical setting around the main active faults at Aswan area, Egypt

    NASA Astrophysics Data System (ADS)

    Ali, Radwan; Hosny, Ahmed; Kotb, Ahmed; Khalil, Ahmed; Azza, Abed; Rayan, Ali

    2013-04-01

    The proper evaluation of crustal deformations in the Aswan region especially around the main active faults is crucial due to the existence of one major artificial structure: the Aswan High Dam. This construction created one of the major artificial lakes: Lake Nasser. The Aswan area is considered as an active seismic area in Egypt since many recent and historical felted earthquakes occurred such as the impressive earthquake occurred on November 14, 1981 at Kalabsha fault with a local magnitude ML=5.7. Lately, on 26 December 2011, a moderate earthquake with a local magnitude Ml=4.1 occurred at Kalabsha area too. The main target of this study is to evaluate the active geological structures that can potentially affect the Aswan High Dam and that are being monitored in detail. For implementing this objective, two different geophysical tools (magnetic, seismic) in addition to the Global Positioning System (GPS) have been utilized. Detailed land magnetic survey was carried out for the total component of geomagnetic field using two proton magnetometers. The obtained magnetic results reveal that there are three major faults parallel {F1 (Kalabsha), F2 (Seiyal) and F3} affecting the area. The most dominant magnetic trend strikes those faults in the WNW-ESE direction. The seismicity and fault plain solutions of the 26 December 2011 earthquake and its two aftershocks have been investigated. The source mechanisms of those events delineate two nodal plains. The trending ENE-WSW to E-W is consistent with the direction of Kalabsha fault and its extension towards east for the events located over it. The trending NNW-SSE to N-S is consistent with the N-S fault trending. The movement along the ENE-WSW plain is right lateral, but it is left lateral along the NNW-SSE plain. Based on the estimated relative motions using GPS, dextral strike-slip motion at the Kalabsha and Seiyal fault systems is clearly identified by changing in the velocity gradient between south and north stations

  10. 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.

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

    NASA Astrophysics Data System (ADS)

    Morrow, C.; Lockner, D. A.; Hickman, S.

    2015-12-01

    The San Andreas Fault Observatory at Depth (SAFOD) scientific drill hole 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 Ω-m) and permeability (10-21 to 10-22 m2) in the actively deforming zones were 1 to 2 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.

  12. Quantifying Coseismic Normal Fault Rupture at the Seafloor: The 2004 Les Saintes Earthquake (Mw 6.3) Along the Roseau Fault (French Antilles)

    NASA Astrophysics Data System (ADS)

    Escartin, J.; Leclerc, F.; Cannat, M.; Petersen, S.; Augustin, N.; Bezos, A.; Bonnemains, D.; Chavagnac, V.; Choi, Y.; Godard, M.; Haaga, K.; Hamelin, C.; Ildefonse, B.; Jamieson, J. W.; John, B. E.; Leleu, T.; Massot-Campos, M.; Mevel, C.; Nomikou, P.; Olive, J. A. L.; Paquet, M.; Rommevaux, C.; Rothenbeck, M.; Steinführer, A.; Tominaga, M.; Triebe, L.; Garcia, R.; Gracias, N.; Feuillet, N.; Deplus, C.

    2014-12-01

    Direct observations of coseismic fault displacement and rupture-related features are essential to understand seismic cycles, to quantify seismic hazard, and to constrain rupture dynamics. They are also needed to trace the paleoseismic history of active faults. Such observations in submarine environments are practically absent, but critical to assess associated tsunami hazard. The ODEMAR cruise studied a ~10 km section of the Roseau Fault (RF) off Les Saintes Islands (Guadeloupe, French Lesser Antilles), a normal fault that generated a Mw 6.3 earthquake in 2004 that triggered a tsunami (<3.5 m of run-up). Microbathymetric data and video observations conducted with the autonomous underwater vehicle ABYSS (GEOMAR) and the remotely operated vehicle VICTOR (IFREMER) allow us to document recent fault-related deformation features. First, the RF hangingwall shows an indurated and ubiquitous rippled sediment layer, locally covered by recent, unconsolidated sediments reworked by currents. Seafloor photomosaics show the indurated layer disrupted by extensional cracks (up to few m long, several 10s of cm wide, ~30 cm deep) along >1 km and by the RF scarp base, that are certainly very young as they are not covered by unconsolidated sediments. Second, video imagery reveals well-preserved, subvertical and polished fault planes exposed at the RF scarp base. Videomosacing and video derived 3D terrain models of a fault outcrop (~12 m long, ~5 m high) reveal on the fault plane a thin, continuous line of unconsolidated sediment sub-parallel to and 10s' of cm above the fault/sediment contact. The line represents the paleo-fault/sediment contact prior to a very recent displacement event, as strong currents in the area would otherwise have washed out the sediment. The fault surface above this line is rougher than that below it. Based on the apparent young age of these features, and given the recurrence time of seismic events along the RF (hundreds to a few thousands of years for Mw 6

  13. 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.

  14. 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.

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

    PubMed Central

    Halicioglu, Kerem; Ozener, Haluk

    2008-01-01

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

  16. 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.

  17. 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.

  18. 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

  19. High resolution seismic imaging of an active normal fault in the Agri Valley, Southern Apennines, Italy

    NASA Astrophysics Data System (ADS)

    Improta, L.; Bruno, P.; di Fiore, V.; Mariani, S.

    2004-12-01

    The Agri Valley is an intermontane basin located in the Southern Apennine seismic belt (Italy) whose formation in tied to large NW-trending trastensional and extensional faults active since Early Pleistocene. Recent faulting activity in the area is documented by faulted paleosoils and suggested by a M7 earthquake that struck the basin in 1857. On the contrary, present-day background seismicity in the area is extremely low. Despite intense geomorphic investigations, the identification of the source responsible for this historical event and of further large seismogenic faults in the area is still a matter of debate. A new NW trending normal faulting system has been recently recognized based on subtle geomorphic expressions on the ridge bounding the basin westward. Recent faulting activity along this structure is locally documented by a trench. Aimed at yielding new information about the shallow structure of the fault, we conducted a high resolution seismic experiment in a small lacustrine basin, located 4 km south of the trench, in which the presence of the fault is inferred by a linear surface warping but trench excavation is impractical. Both multi-fold wide-angle data and multichannel near vertical reflection data have been collected along a 220-m-long profile in order to obtain an accurate model of the basin combining seismic velocity and reflectivity images. About 3600 first arrival traveltimes picked on 36 wide-angle record sections have been inverted by a non-linear tomographic technique that is specially designed to image complex structures. The tomographic inversion provides a high-resolution velocity model of the basin down to 60 m depth. The model is strongly heterogeneous and displays sharp lateral velocity variations. Seismic reflection processing has been applied to both data sets. Data have been edited for trace quality and first (refracted and direct) arrivals have been muted. A following FK dip filtering on the shot gathers reduced the energy

  20. Reexamination of Faulting in the Tahoe Basin Using Airborne LiDAR Data and Seismic CHIRP Imagery

    NASA Astrophysics Data System (ADS)

    Schmauder, G. C.; Kent, G.; Smith, K. D.; Driscoll, N. W.; Maloney, J. M.

    2011-12-01

    Faulting across the Tahoe basin has been mapped using a combination of multibeam sonar, airborne Light Detection and Ranging (LiDAR), and high-resolution seismic CHIRP imagery. In August 2010, the Tahoe Regional Planning Agency (TRPA) collected 941 square kilometers of airborne LiDAR data in the Tahoe basin using a Leica ALS50 Phase II Laser system mounted on a Cessna Caravan 208B aircraft; our group was involved with data specification, selection of contractor and data QC. These data have a resolution of 11.82 points per square meter and a vertical accuracy of 3.5 centimeters. The high data resolution has allowed us to map with ease the many fault scarps associated with the three major active fault zones in the Tahoe basin, which include the West Tahoe-Dollar Point fault zone, the Stateline fault, and the Incline Village fault. By using the airborne LiDAR data, we were able to identify previously unmapped fault segments throughout the Tahoe basin. Future application of terrestrial LiDAR using an I-Site 4400 laser scanner at selected sites will provide better control and resolution of the fault scarp characteristics. This will allow us to not only ground truth the airborne LiDAR, but also look for subtle features that may be indicative of dextral motion on faults otherwise displaying predominantly normal displacement. Finally, to refine fault locations beneath Lake Tahoe, Fallen Leaf Lake and Cascade Lake, we collected additional CHIRP imagery using an Edgetech Subscan system, in some cases to groundtruth the new LiDAR fault data (i.e., Cascade Lake). By combining these images with the LiDAR, multibeam data and new multispectral imagery, we were able to link previously unknown segments of the faults and identify continuity in the individual fault systems. From our results, we have developed a much-improved model of the fault systems within the Lake Tahoe basin. Our model provides us with a better understanding of the tectonic environment of the basin and may help

  1. 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.

  2. 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.

  3. Geodetic evidence for continuing tectonic activity of the Carboneras fault (SE Spain)

    NASA Astrophysics Data System (ADS)

    Echeverria, Anna; Khazaradze, Giorgi; Asensio, Eva; Masana, Eulalia

    2015-11-01

    The Carboneras fault zone (CFZ) is a prominent onshore-offshore strike-slip fault that forms part of the Eastern Betic Shear Zone (EBSZ), located in SE Spain. In this work, we show for the first time, the continuing tectonic activity of the CFZ and quantify its geodetic slip-rates using continuous and campaign GPS observations conducted during the last decade. We find that the left-lateral motion dominates the kinematics of the CFZ, with a strike-slip rate of 1.3 ± 0.2 mm/yr along the N48° direction. The shortening component is significantly lower and poorly constrained. Recent onshore and offshore paleoseismic and geomorphic results across the CFZ suggest a minimum Late Pleistocene to present-day strike-slip rate of 1.1 mm/yr. Considering the similarity of the geologic and geodetic slip rates measured at different points along the fault, the northern segment of the CFZ must have been slipping approximately at a constant rate during the Quaternary. Regarding the eastern Alpujarras fault zone corridor (AFZ), located to the north of the CFZ, our GPS measurements corroborate that this zone is active and exhibits a right-lateral motion. These opposite type strike-slip motion across the AFZ and CFZ is a result of a push-type force due to Nubia and Eurasia plate convergence, which, in turn, causes the westward escape of the block bounded by these two fault zones.

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

    NASA Astrophysics Data System (ADS)

    Vitali, Luigino; Mattiozzi, Pierpaolo

    2008-07-01

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

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

    NASA Astrophysics Data System (ADS)

    Mattiozzi, Pierpaolo; Strom, Alexander

    2008-07-01

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

  6. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  8. Geometry of Thrust Faults Beneath Amenthes Rupes, Mars

    NASA Technical Reports Server (NTRS)

    Vidal, A.; Mueller, K. M.; Golombek, M. P.

    2005-01-01

    Amenthes Rupes is a 380 km-long lobate fault scarp located in the eastern hemisphere of Mars near the dichotomy boundary. The scarp is marked by about 1 km of vertical separation across a northeast dipping thrust fault (top to the SW) and offsets heavily-cratered terrain of Late Noachian age, the visible portion of which was in place by 3.92 Ga and the buried portion in place between 4.08 and 4.27 Ga. The timing of scarp formation is difficult to closely constrain. Previous geologic mapping shows that near the northern end of Amenthes Rupes, Hesperian age basalts terminate at the scarp, suggesting that fault slip predated the emplacement of these flows at 3.69 to 3.9 Ga. Maxwell and McGill also suggest the faulting ceased before the final emplacement of the Late Hesperian lavas on Isidis Planitia. The trend of the faults at Amenthes, like many thrust faults at the dichotomy boundary, parallels the boundary itself. Schultz and Watters used a dislocation modeling program to match surface topography and vertical offset of the scarp at Amenthes Rupes, varying the dip and depth of faulting, assuming a slip of 1.5 km on the fault. They modeled faulting below Amenthes Rupes as having a dip of between 25 and 30 degrees and a depth of 25 to 35 km, based on the best match to topography. Assuming a 25 degree dip and surface measurements of vertical offset of between 0.3 and 1.2 km, Watters later estimated the maximum displacement on the Amenthes Rupes fault to be 2.90 km. However, these studies did not determine the geometry of the thrust using quantitative constraints that included shortening estimates. Amenthes Rupes deforms large preexisting impact craters. We use these craters to constrain shortening across the scarp and combine this with vertical separation to infer fault geometry. Fault dip was also estimated using measurements of scarp morphology. Measurements were based on 460 m (1/128 per pixel) digital elevation data from the Mars Orbiter Laser Altimeter (MOLA), an

  9. Using fluvial channel morphology to obtain the neotectonic characteristics of the Liuchia fault, an important active structure in southwestern Taiwan

    NASA Astrophysics Data System (ADS)

    Shyu, J. H.; Du, K.

    2013-12-01

    The Liuchia fault in southwestern Taiwan has been considered as one of the major active faults in the active Taiwan orogen. It is identified by its clear geomorphic features, and forms a major geologic boundary of Taiwan's Western Foothills. No unanimous historical evidence for seismic activity of the Liuchia fault exists, thus the fault poses large earthquake hazard potentials for the populous southwestern Taiwan. Here we attempted to analyze the characteristics of the fault from fluvial channel morphology of the Kueichung River that flows across the fault. We also calculated actual river incision rates from the age of river terraces along the river to obtain the rock uplift rates of the hanging-wall block of the fault. We have obtained a detailed river long profile of the Kueichung River from surveys using RTK-GPS, and a channel width profile from actual field measurements using a Laser Rangefinder. The fluvial channel morphology of the Kueichung River appears to have been affected by active folding in the hanging-wall block of the Liuchia fault. Such active deformation pattern is also evident from river incision rate patterns. Combining these different datasets, we constructed a realistic model of the subsurface geometry of the Liuchia fault in southwestern Taiwan, and calculated the long-term slip rates of this important active structure in southwestern Taiwan.

  10. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    Over the last 20-25 years, geodetic measurements across the Gulf of Corinth have recorded high extension rates varying from 1.1 cm/a in the east to a maximum of 1.6 cm/a in the west. Geodetic studies also show that current deformation is confined between two relatively rigid blocks defined as Central Greece (to the north) and the Peloponnesus to the south. Active north dipping faults