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Sample records for large seismic fault

  1. Deeper penetration of large earthquakes on seismically quiescent faults.

    Science.gov (United States)

    Jiang, Junle; Lapusta, Nadia

    2016-06-10

    Why many major strike-slip faults known to have had large earthquakes are silent in the interseismic period is a long-standing enigma. One would expect small earthquakes to occur at least at the bottom of the seismogenic zone, where deeper aseismic deformation concentrates loading. We suggest that the absence of such concentrated microseismicity indicates deep rupture past the seismogenic zone in previous large earthquakes. We support this conclusion with numerical simulations of fault behavior and observations of recent major events. Our modeling implies that the 1857 Fort Tejon earthquake on the San Andreas Fault in Southern California penetrated below the seismogenic zone by at least 3 to 5 kilometers. Our findings suggest that such deeper ruptures may occur on other major fault segments, potentially increasing the associated seismic hazard. Copyright © 2016, American Association for the Advancement of Science.

  2. Estimation of recurrence interval of large earthquakes on the central Longmen Shan fault zone based on seismic moment accumulation/release model.

    Science.gov (United States)

    Ren, Junjie; Zhang, Shimin

    2013-01-01

    Recurrence interval of large earthquake on an active fault zone is an important parameter in assessing seismic hazard. The 2008 Wenchuan earthquake (Mw 7.9) occurred on the central Longmen Shan fault zone and ruptured the Yingxiu-Beichuan fault (YBF) and the Guanxian-Jiangyou fault (GJF). However, there is a considerable discrepancy among recurrence intervals of large earthquake in preseismic and postseismic estimates based on slip rate and paleoseismologic results. Post-seismic trenches showed that the central Longmen Shan fault zone probably undertakes an event similar to the 2008 quake, suggesting a characteristic earthquake model. In this paper, we use the published seismogenic model of the 2008 earthquake based on Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (InSAR) data and construct a characteristic seismic moment accumulation/release model to estimate recurrence interval of large earthquakes on the central Longmen Shan fault zone. Our results show that the seismogenic zone accommodates a moment rate of (2.7 ± 0.3) × 10¹⁷ N m/yr, and a recurrence interval of 3900 ± 400 yrs is necessary for accumulation of strain energy equivalent to the 2008 earthquake. This study provides a preferred interval estimation of large earthquakes for seismic hazard analysis in the Longmen Shan region.

  3. Estimation of Recurrence Interval of Large Earthquakes on the Central Longmen Shan Fault Zone Based on Seismic Moment Accumulation/Release Model

    Directory of Open Access Journals (Sweden)

    Junjie Ren

    2013-01-01

    Full Text Available Recurrence interval of large earthquake on an active fault zone is an important parameter in assessing seismic hazard. The 2008 Wenchuan earthquake (Mw 7.9 occurred on the central Longmen Shan fault zone and ruptured the Yingxiu-Beichuan fault (YBF and the Guanxian-Jiangyou fault (GJF. However, there is a considerable discrepancy among recurrence intervals of large earthquake in preseismic and postseismic estimates based on slip rate and paleoseismologic results. Post-seismic trenches showed that the central Longmen Shan fault zone probably undertakes an event similar to the 2008 quake, suggesting a characteristic earthquake model. In this paper, we use the published seismogenic model of the 2008 earthquake based on Global Positioning System (GPS and Interferometric Synthetic Aperture Radar (InSAR data and construct a characteristic seismic moment accumulation/release model to estimate recurrence interval of large earthquakes on the central Longmen Shan fault zone. Our results show that the seismogenic zone accommodates a moment rate of (2.7 ± 0.3 × 1017 N m/yr, and a recurrence interval of 3900 ± 400 yrs is necessary for accumulation of strain energy equivalent to the 2008 earthquake. This study provides a preferred interval estimation of large earthquakes for seismic hazard analysis in the Longmen Shan region.

  4. Study on seismic hazard assessment of large active fault systems. Evolution of fault systems and associated geomorphic structures: fault model test and field survey

    International Nuclear Information System (INIS)

    Ueta, Keichi; Inoue, Daiei; Miyakoshi, Katsuyoshi; Miyagawa, Kimio; Miura, Daisuke

    2003-01-01

    Sandbox experiments and field surveys were performed to investigate fault system evolution and fault-related deformation of ground surface, the Quaternary deposits and rocks. The summary of the results is shown below. 1) In the case of strike-slip faulting, the basic fault sequence runs from early en echelon faults and pressure ridges through linear trough. The fault systems associated with the 2000 western Tottori earthquake are shown as en echelon pattern that characterize the early stage of wrench tectonics, therefore no thoroughgoing surface faulting was found above the rupture as defined by the main shock and aftershocks. 2) Low-angle and high-angle reverse faults commonly migrate basinward with time, respectively. With increasing normal fault displacement in bedrock, normal fault develops within range after reverse fault has formed along range front. 3) Horizontal distance of surface rupture from the bedrock fault normalized by the height of the Quaternary deposits agrees well with those of model tests. 4) Upward-widening damage zone, where secondary fractures develop, forms in the handing wall side of high-angle reverse fault at the Kamioka mine. (author)

  5. Large earthquakes and creeping faults

    Science.gov (United States)

    Harris, Ruth A.

    2017-01-01

    Faults are ubiquitous throughout the Earth's crust. The majority are silent for decades to centuries, until they suddenly rupture and produce earthquakes. With a focus on shallow continental active-tectonic regions, this paper reviews a subset of faults that have a different behavior. These unusual faults slowly creep for long periods of time and produce many small earthquakes. The presence of fault creep and the related microseismicity helps illuminate faults that might not otherwise be located in fine detail, but there is also the question of how creeping faults contribute to seismic hazard. It appears that well-recorded creeping fault earthquakes of up to magnitude 6.6 that have occurred in shallow continental regions produce similar fault-surface rupture areas and similar peak ground shaking as their locked fault counterparts of the same earthquake magnitude. The behavior of much larger earthquakes on shallow creeping continental faults is less well known, because there is a dearth of comprehensive observations. Computational simulations provide an opportunity to fill the gaps in our understanding, particularly of the dynamic processes that occur during large earthquake rupture and arrest.

  6. Synthetic seismicity for the San Andreas fault

    Directory of Open Access Journals (Sweden)

    S. N. Ward

    1994-06-01

    Full Text Available Because historical catalogs generally span only a few repetition intervals of major earthquakes, they do not provide much constraint on how regularly earthquakes recur. In order to obtain better recurrence statistics and long-term probability estimates for events M ? 6 on the San Andreas fault, we apply a seismicity model to this fault. The model is based on the concept of fault segmentation and the physics of static dislocations which allow for stress transfer between segments. Constraints are provided by geological and seismological observations of segment lengths, characteristic magnitudes and long-term slip rates. Segment parameters slightly modified from the Working Group on California Earthquake Probabilities allow us to reproduce observed seismicity over four orders of magnitude. The model yields quite irregular earthquake recurrence patterns. Only the largest events (M ? 7.5 are quasi-periodic; small events cluster. Both the average recurrence time and the aperiodicity are also a function of position along the fault. The model results are consistent with paleoseismic data for the San Andreas fault as well as a global set of historical and paleoseismic recurrence data. Thus irregular earthquake recurrence resulting from segment interaction is consistent with a large range of observations.

  7. Seismic fault analysis of Chicoutimi region

    International Nuclear Information System (INIS)

    Woussen, G.; Ngandee, S.

    1996-01-01

    On November 25, 1988, an earthquake measuring 6.5 on the Richter Scale occurred at a depth of 29 km in Precambrian bedrock in the Saguenay Region (Quebec). Given that the seismic event was located near a major zone of normal faults, it is important to determine if the earthquake could be associated with this large structure or with faults associated with this structure. This is discussed through a compilation and interpretation of structural discontinuities on key outcrops in the vicinity of the epicenter. The report is broken in four parts. The first part gives a brief overview of the geology in order to provide a geologic context for the structural measurements. The second comprises an analysis of fractures in each of the three lithotectonic units defined in the first part. The third part discusses the data and the fourth provides a conclusion. 30 refs., 53 figs

  8. Identifying Conventionally Sub-Seismic Faults in Polygonal Fault Systems

    Science.gov (United States)

    Fry, C.; Dix, J.

    2017-12-01

    Polygonal Fault Systems (PFS) are prevalent in hydrocarbon basins globally and represent potential fluid pathways. However the characterization of these pathways is subject to the limitations of conventional 3D seismic imaging; only capable of resolving features on a decametre scale horizontally and metres scale vertically. While outcrop and core examples can identify smaller features, they are limited by the extent of the exposures. The disparity between these scales can allow for smaller faults to be lost in a resolution gap which could mean potential pathways are left unseen. Here the focus is upon PFS from within the London Clay, a common bedrock that is tunnelled into and bears construction foundations for much of London. It is a continuation of the Ieper Clay where PFS were first identified and is found to approach the seafloor within the Outer Thames Estuary. This allows for the direct analysis of PFS surface expressions, via the use of high resolution 1m bathymetric imaging in combination with high resolution seismic imaging. Through use of these datasets surface expressions of over 1500 faults within the London Clay have been identified, with the smallest fault measuring 12m and the largest at 612m in length. The displacements over these faults established from both bathymetric and seismic imaging ranges from 30cm to a couple of metres, scales that would typically be sub-seismic for conventional basin seismic imaging. The orientations and dimensions of the faults within this network have been directly compared to 3D seismic data of the Ieper Clay from the offshore Dutch sector where it exists approximately 1km below the seafloor. These have typical PFS attributes with lengths of hundreds of metres to kilometres and throws of tens of metres, a magnitude larger than those identified in the Outer Thames Estuary. The similar orientations and polygonal patterns within both locations indicates that the smaller faults exist within typical PFS structure but are

  9. Automated Fault Interpretation and Extraction using Improved Supplementary Seismic Datasets

    Science.gov (United States)

    Bollmann, T. A.; Shank, R.

    2017-12-01

    During the interpretation of seismic volumes, it is necessary to interpret faults along with horizons of interest. With the improvement of technology, the interpretation of faults can be expedited with the aid of different algorithms that create supplementary seismic attributes, such as semblance and coherency. These products highlight discontinuities, but still need a large amount of human interaction to interpret faults and are plagued by noise and stratigraphic discontinuities. Hale (2013) presents a method to improve on these datasets by creating what is referred to as a Fault Likelihood volume. In general, these volumes contain less noise and do not emphasize stratigraphic features. Instead, planar features within a specified strike and dip range are highlighted. Once a satisfactory Fault Likelihood Volume is created, extraction of fault surfaces is much easier. The extracted fault surfaces are then exported to interpretation software for QC. Numerous software packages have implemented this methodology with varying results. After investigating these platforms, we developed a preferred Automated Fault Interpretation workflow.

  10. Integrated seismic interpretation of the Carlsberg Fault zone, Copenhagen, Denmark

    DEFF Research Database (Denmark)

    Nielsen, Lars; Thybo, Hans; Jørgensen, Mette Iwanouw

    2005-01-01

    the fault zone. The fault zone is a shadow zone to shots detonated outside the fault zone. Finite-difference wavefield modelling supports the interpretations of the fan recordings. Our fan recording approach facilitates cost-efficient mapping of fault zones in densely urbanized areas where seismic normal......We locate the concealed Carlsberg Fault zone along a 12-km-long trace in the Copenhagen city centre by seismic refraction, reflection and fan profiling. The Carlsberg Fault is located in a NNW-SSE striking fault system in the border zone between the Danish Basin and the Baltic Shield. Recent...... earthquakes indicate that this area is tectonically active. A seismic refraction study across the Carlsberg Fault shows that the fault zone is a low-velocity zone and marks a change in seismic velocity structure. A normal incidence reflection seismic section shows a coincident flower-like structure. We have...

  11. Seismic Hazard Analysis on a Complex, Interconnected Fault Network

    Science.gov (United States)

    Page, M. T.; Field, E. H.; Milner, K. R.

    2017-12-01

    In California, seismic hazard models have evolved from simple, segmented prescriptive models to much more complex representations of multi-fault and multi-segment earthquakes on an interconnected fault network. During the development of the 3rd Uniform California Earthquake Rupture Forecast (UCERF3), the prevalence of multi-fault ruptures in the modeling was controversial. Yet recent earthquakes, for example, the Kaikora earthquake - as well as new research on the potential of multi-fault ruptures (e.g., Nissen et al., 2016; Sahakian et al. 2017) - have validated this approach. For large crustal earthquakes, multi-fault ruptures may be the norm rather than the exception. As datasets improve and we can view the rupture process at a finer scale, the interconnected, fractal nature of faults is revealed even by individual earthquakes. What is the proper way to model earthquakes on a fractal fault network? We show multiple lines of evidence that connectivity even in modern models such as UCERF3 may be underestimated, although clustering in UCERF3 mitigates some modeling simplifications. We need a methodology that can be applied equally well where the fault network is well-mapped and where it is not - an extendable methodology that allows us to "fill in" gaps in the fault network and in our knowledge.

  12. Estimating Fault Friction From Seismic Signals in the Laboratory

    Science.gov (United States)

    Rouet-Leduc, Bertrand; Hulbert, Claudia; Bolton, David C.; Ren, Christopher X.; Riviere, Jacques; Marone, Chris; Guyer, Robert A.; Johnson, Paul A.

    2018-02-01

    Nearly all aspects of earthquake rupture are controlled by the friction along the fault that progressively increases with tectonic forcing but in general cannot be directly measured. We show that fault friction can be determined at any time, from the continuous seismic signal. In a classic laboratory experiment of repeating earthquakes, we find that the seismic signal follows a specific pattern with respect to fault friction, allowing us to determine the fault's position within its failure cycle. Using machine learning, we show that instantaneous statistical characteristics of the seismic signal are a fingerprint of the fault zone shear stress and frictional state. Further analysis of this fingerprint leads to a simple equation of state quantitatively relating the seismic signal power and the friction on the fault. These results show that fault zone frictional characteristics and the state of stress in the surroundings of the fault can be inferred from seismic waves, at least in the laboratory.

  13. Source characterization and dynamic fault modeling of induced seismicity

    Science.gov (United States)

    Lui, S. K. Y.; Young, R. P.

    2017-12-01

    In recent years there are increasing concerns worldwide that industrial activities in the sub-surface can cause or trigger damaging earthquakes. In order to effectively mitigate the damaging effects of induced seismicity, the key is to better understand the source physics of induced earthquakes, which still remain elusive at present. Furthermore, an improved understanding of induced earthquake physics is pivotal to assess large-magnitude earthquake triggering. A better quantification of the possible causes of induced earthquakes can be achieved through numerical simulations. The fault model used in this study is governed by the empirically-derived rate-and-state friction laws, featuring a velocity-weakening (VW) patch embedded into a large velocity-strengthening (VS) region. Outside of that, the fault is slipping at the background loading rate. The model is fully dynamic, with all wave effects resolved, and is able to resolve spontaneous long-term slip history on a fault segment at all stages of seismic cycles. An earlier study using this model has established that aseismic slip plays a major role in the triggering of small repeating earthquakes. This study presents a series of cases with earthquakes occurring on faults with different fault frictional properties and fluid-induced stress perturbations. The effects to both the overall seismicity rate and fault slip behavior are investigated, and the causal relationship between the pre-slip pattern prior to the event and the induced source characteristics is discussed. Based on simulation results, the subsequent step is to select specific cases for laboratory experiments which allow well controlled variables and fault parameters. Ultimately, the aim is to provide better constraints on important parameters for induced earthquakes based on numerical modeling and laboratory data, and hence to contribute to a physics-based induced earthquake hazard assessment.

  14. Off-fault seismicity suggests creep below 10 km on the northern San Jacinto Fault

    Science.gov (United States)

    Cooke, M. L.; Beyer, J. L.

    2017-12-01

    Within the San Bernardino basin, CA, south of the juncture of the San Jacinto (SJF) and San Andreas faults (SAF), focal mechanisms show normal slip events that are inconsistent with the interseismic strike-slip loading of the region. High-quality (nodal plane uncertainty faults [Anderson et al., 2004]. However, the loading of these normal slip events remains enigmatic because the region is expected to have dextral loading between large earthquake events. These enigmatic normal slip events may be loaded by deep (> 10 km depth) spatially creep along the northern SJF. Steady state models show that over many earthquake cycles, the dextral slip rate on the northern SJF increases southward, placing the San Bernardino basin in extension. In the absence of recent large seismic events that could produce off-fault normal focal mechanisms in the San Bernardino basin, non-uniform deep aseismic slip on the SJF could account for this seismicity. We develop interseismic models that incorporate spatially non-uniform creep below 10 km on the SJF based on steady-state slip distribution. These model results match the pattern of deep normal slip events within the San Bernardino basin. Such deep creep on the SJF may not be detectable from the geodetic signal due to the close proximity of the SAF, whose lack of seismicity suggests that it is locked to 20 km. Interseismic models with 15 km locking depth on both faults are indistinguishable from models with 10 km locking depth on the SJF and 20 km locking depth on the SAF. This analysis suggests that the microseismicity in our multi-decadal catalog may record both the interseismic dextral loading of the region as well as off-fault deformation associated with deep aseismic creep on the northern SJF. If the enigmatic normal slip events of the San Bernardino basin are included in stress inversions from the seismic catalog used to assess seismic hazard, the results may provide inaccurate information about fault loading in this region.

  15. Multi-Fault Rupture Scenarios in the Brawley Seismic Zone

    Science.gov (United States)

    Kyriakopoulos, C.; Oglesby, D. D.; Rockwell, T. K.; Meltzner, A. J.; Barall, M.

    2017-12-01

    Dynamic rupture complexity is strongly affected by both the geometric configuration of a network of faults and pre-stress conditions. Between those two, the geometric configuration is more likely to be anticipated prior to an event. An important factor in the unpredictability of the final rupture pattern of a group of faults is the time-dependent interaction between them. Dynamic rupture models provide a means to investigate this otherwise inscrutable processes. The Brawley Seismic Zone in Southern California is an area in which this approach might be important for inferring potential earthquake sizes and rupture patterns. Dynamic modeling can illuminate how the main faults in this area, the Southern San Andreas (SSAF) and Imperial faults, might interact with the intersecting cross faults, and how the cross faults may modulate rupture on the main faults. We perform 3D finite element modeling of potential earthquakes in this zone assuming an extended array of faults (Figure). Our results include a wide range of ruptures and fault behaviors depending on assumptions about nucleation location, geometric setup, pre-stress conditions, and locking depth. For example, in the majority of our models the cross faults do not strongly participate in the rupture process, giving the impression that they are not typically an aid or an obstacle to the rupture propagation. However, in some cases, particularly when rupture proceeds slowly on the main faults, the cross faults indeed can participate with significant slip, and can even cause rupture termination on one of the main faults. Furthermore, in a complex network of faults we should not preclude the possibility of a large event nucleating on a smaller fault (e.g. a cross fault) and eventually promoting rupture on the main structure. Recent examples include the 2010 Mw 7.1 Darfield (New Zealand) and Mw 7.2 El Mayor-Cucapah (Mexico) earthquakes, where rupture started on a smaller adjacent segment and later cascaded into a larger

  16. Stress sensitivity of fault seismicity: A comparison between limited-offset oblique and major strike-slip faults

    Science.gov (United States)

    Parsons, T.; Stein, R.S.; Simpson, R.W.; Reasenberg, P.A.

    1999-01-01

    We present a new three-dimensional inventory of the southern San Francisco Bay area faults and use it to calculate stress applied principally by the 1989 M = 7.1 Loma Prieta earthquake and to compare fault seismicity rates before and after 1989. The major high-angle right-lateral faults exhibit a different response to the stress change than do minor oblique (right-lateral/thrust) faults. Seismicity on oblique-slip faults in the southern Santa Clara Valley thrust belt increased where the faults were unclamped. The strong dependence of seismicity change on normal stress change implies a high coefficient of static friction. In contrast, we observe that faults with significant offset (>50-100 km) behave differently; microseismicity on the Hayward fault diminished where right-lateral shear stress was reduced and where it was unclamped by the Loma Prieta earthquake. We observe a similar response on the San Andreas fault zone in southern California after the Landers earthquake sequence. Additionally, the offshore San Gregorio fault shows a seismicity rate increase where right-lateral/oblique shear stress was increased by the Loma Prieta earthquake despite also being clamped by it. These responses are consistent with either a low coefficient of static friction or high pore fluid pressures within the fault zones. We can explain the different behavior of the two styles of faults if those with large cumulative offset become impermeable through gouge buildup; coseismically pressurized pore fluids could be trapped and negate imposed normal stress changes, whereas in more limited offset faults, fluids could rapidly escape. The difference in behavior between minor and major faults may explain why frictional failure criteria that apply intermediate coefficients of static friction can be effective in describing the broad distributions of aftershocks that follow large earthquakes, since many of these events occur both inside and outside major fault zones.

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

    Science.gov (United States)

    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.

  18. Seismic Slip on an Oblique Detachment Fault at Low Angles

    Science.gov (United States)

    Janecke, S. U.; Steely, A. N.; Evans, J. P.

    2008-12-01

    Pseudotachylytes are one of the few accepted indicators of seismic slip along ancient faults. Low-angle normal faults have produced few large earthquakes in historic times and low-angle normal faults (detachment faults) are typically severely misoriented relative to a vertical maximum compressive stress. As a result many geoscientists question whether low-angle normal faults produce earthquakes at low angles. Relationships in southern California show that a major low-angle normal-oblique fault slipped at low angles and produced large earthquakes. The exhumed Late Cenozoic West Salton detachment fault preserves spectacular fault- related pseudotachylytes along its fault plane and injected into its hanging wall and footwall. Composite pseudotachylyte zones are up to 1.25 m thick and persists over lateral distances of at least 10's of meters. Pseudotachylyte is common in most thin sections of damaged fault rocks with more than 20% (by volume) of cataclasite. We recognized the presence of original melt using numerous criteria: abundant spherulites in thin sections, injection structures at both the thin-section and outcrop scale, black aphanitic textures, quenched vein margins, variations in microcrystallite textures and/or size with respect to the vein margin, and glassy textures in hand sample. Multiple earthquakes are inferred to produce the layered "stratigraphy" in some exposures of pseudotachylytes. We infer that the West Salton detachment fault formed and slipped at low angles because it nearly perfectly reactivates a Cretaceous ductile thrust system at the half km scale and dips between 10 and 45 degrees. The about 30 degree NNE dip of the detachment fault on the north side of Yaqui Ridge is likely steeper than its dip during detachment slip because there is local steepening on the flanks of the Yaqui Ridge antiform in a contractional stepover of a crosscutting Quaternary San Felipe dextral fault zone. These relationships indicate a low dip on the detachment

  19. Erosion influences the seismicity of active thrust faults.

    Science.gov (United States)

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

    2014-11-21

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

  20. Laboratory scale micro-seismic monitoring of rock faulting and injection-induced fault reactivation

    Science.gov (United States)

    Sarout, J.; Dautriat, J.; Esteban, L.; Lumley, D. E.; King, A.

    2017-12-01

    The South West Hub CCS project in Western Australia aims to evaluate the feasibility and impact of geosequestration of CO2 in the Lesueur sandstone formation. Part of this evaluation focuses on the feasibility and design of a robust passive seismic monitoring array. Micro-seismicity monitoring can be used to image the injected CO2plume, or any geomechanical fracture/fault activity; and thus serve as an early warning system by measuring low-level (unfelt) seismicity that may precede potentially larger (felt) earthquakes. This paper describes laboratory deformation experiments replicating typical field scenarios of fluid injection in faulted reservoirs. Two pairs of cylindrical core specimens were recovered from the Harvey-1 well at depths of 1924 m and 2508 m. In each specimen a fault is first generated at the in situ stress, pore pressure and temperature by increasing the vertical stress beyond the peak in a triaxial stress vessel at CSIRO's Geomechanics & Geophysics Lab. The faulted specimen is then stabilized by decreasing the vertical stress. The freshly formed fault is subsequently reactivated by brine injection and increase of the pore pressure until slip occurs again. This second slip event is then controlled in displacement and allowed to develop for a few millimeters. The micro-seismic (MS) response of the rock during the initial fracturing and subsequent reactivation is monitored using an array of 16 ultrasonic sensors attached to the specimen's surface. The recorded MS events are relocated in space and time, and correlate well with the 3D X-ray CT images of the specimen obtained post-mortem. The time evolution of the structural changes induced within the triaxial stress vessel is therefore reliably inferred. The recorded MS activity shows that, as expected, the increase of the vertical stress beyond the peak led to an inclined shear fault. The injection of fluid and the resulting increase in pore pressure led first to a reactivation of the pre

  1. Seismicity and Tectonics of the West Kaibab Fault Zone, AZ

    Science.gov (United States)

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

    2014-12-01

    The West Kaibab Fault Zone (WKFZ) is the westernmost bounding structure of the Kaibab Plateau of northern Arizona. The WKFZ is a branching complex of high angle, normal faults downthrown to the west. There are three main faults within the WKFZ, the Big Springs fault with a maximum of 165 m offset, the Muav fault with 350 m of displacement, and the North Road fault having a maximum throw of approximately 90 m. Mapping of geologically recent surface deposits at or crossing the fault contacts indicates that the faults are likely Quaternary with the most recent offsets occurring one of the most seismically active areas in Arizona and lies within the Northern Arizona Seismic Belt (NASB), which stretches across northern Arizona trending NW-SE. The data set for this study includes 156 well documented events with the largest being a M5.75 in 1959 and including a swarm of seven earthquakes in 2012. The seismic data set (1934-2014) reveals that seismic activity clusters in two regions within the study area, the Fredonia cluster located in the NW corner of the study area and the Kaibab cluster located in the south central portion of the study area. The fault plane solutions to date indicate NE-SW to EW extension is occurring in the study area. Source relationships between earthquakes and faults within the WKFZ have not previously been studied in detail. The goal of this study is to use the seismic data set, the available data on faults, and the regional physiography to search for source relationships for the seismicity. Analysis includes source parameters of the earthquake data (location, depth, and fault plane solutions), and comparison of this output to the known faults and areal physiographic framework to indicate any active faults of the WKFZ, or suggested active unmapped faults. This research contributes to a better understanding of the present nature of the WKFZ and the NASB as well.

  2. Simulating spontaneous aseismic and seismic slip events on evolving faults

    Science.gov (United States)

    Herrendörfer, Robert; van Dinther, Ylona; Pranger, Casper; Gerya, Taras

    2017-04-01

    Plate motion along tectonic boundaries is accommodated by different slip modes: steady creep, seismic slip and slow slip transients. Due to mainly indirect observations and difficulties to scale results from laboratory experiments to nature, it remains enigmatic which fault conditions favour certain slip modes. Therefore, we are developing a numerical modelling approach that is capable of simulating different slip modes together with the long-term fault evolution in a large-scale tectonic setting. We extend the 2D, continuum mechanics-based, visco-elasto-plastic thermo-mechanical model that was designed to simulate slip transients in large-scale geodynamic simulations (van Dinther et al., JGR, 2013). We improve the numerical approach to accurately treat the non-linear problem of plasticity (see also EGU 2017 abstract by Pranger et al.). To resolve a wide slip rate spectrum on evolving faults, we develop an invariant reformulation of the conventional rate-and-state dependent friction (RSF) and adapt the time step (Lapusta et al., JGR, 2000). A crucial part of this development is a conceptual ductile fault zone model that relates slip rates along discrete planes to the effective macroscopic plastic strain rates in the continuum. We test our implementation first in a simple 2D setup with a single fault zone that has a predefined initial thickness. Results show that deformation localizes in case of steady creep and for very slow slip transients to a bell-shaped strain rate profile across the fault zone, which suggests that a length scale across the fault zone may exist. This continuum length scale would overcome the common mesh-dependency in plasticity simulations and question the conventional treatment of aseismic slip on infinitely thin fault zones. We test the introduction of a diffusion term (similar to the damage description in Lyakhovsky et al., JMPS, 2011) into the state evolution equation and its effect on (de-)localization during faster slip events. We compare

  3. Time-predictable model application in probabilistic seismic hazard analysis of faults in Taiwan

    Directory of Open Access Journals (Sweden)

    Yu-Wen Chang

    2017-01-01

    Full Text Available Given the probability distribution function relating to the recurrence interval and the occurrence time of the previous occurrence of a fault, a time-dependent model of a particular fault for seismic hazard assessment was developed that takes into account the active fault rupture cyclic characteristics during a particular lifetime up to the present time. The Gutenberg and Richter (1944 exponential frequency-magnitude relation uses to describe the earthquake recurrence rate for a regional source. It is a reference for developing a composite procedure modelled the occurrence rate for the large earthquake of a fault when the activity information is shortage. The time-dependent model was used to describe the fault characteristic behavior. The seismic hazards contribution from all sources, including both time-dependent and time-independent models, were then added together to obtain the annual total lifetime hazard curves. The effects of time-dependent and time-independent models of fault [e.g., Brownian passage time (BPT and Poisson, respectively] in hazard calculations are also discussed. The proposed fault model result shows that the seismic demands of near fault areas are lower than the current hazard estimation where the time-dependent model was used on those faults, particularly, the elapsed time since the last event of the faults (such as the Chelungpu fault are short.

  4. Inferring Fault Frictional and Reservoir Hydraulic Properties From Injection-Induced Seismicity

    Science.gov (United States)

    Jagalur-Mohan, Jayanth; Jha, Birendra; Wang, Zheng; Juanes, Ruben; Marzouk, Youssef

    2018-02-01

    Characterizing the rheological properties of faults and the evolution of fault friction during seismic slip are fundamental problems in geology and seismology. Recent increases in the frequency of induced earthquakes have intensified the need for robust methods to estimate fault properties. Here we present a novel approach for estimation of aquifer and fault properties, which combines coupled multiphysics simulation of injection-induced seismicity with adaptive surrogate-based Bayesian inversion. In a synthetic 2-D model, we use aquifer pressure, ground displacements, and fault slip measurements during fluid injection to estimate the dynamic fault friction, the critical slip distance, and the aquifer permeability. Our forward model allows us to observe nonmonotonic evolutions of shear traction and slip on the fault resulting from the interplay of several physical mechanisms, including injection-induced aquifer expansion, stress transfer along the fault, and slip-induced stress relaxation. This interplay provides the basis for a successful joint inversion of induced seismicity, yielding well-informed Bayesian posterior distributions of dynamic friction and critical slip. We uncover an inverse relationship between dynamic friction and critical slip distance, which is in agreement with the small dynamic friction and large critical slip reported during seismicity on mature faults.

  5. A seismic fault recognition method based on ant colony optimization

    Science.gov (United States)

    Chen, Lei; Xiao, Chuangbai; Li, Xueliang; Wang, Zhenli; Huo, Shoudong

    2018-05-01

    Fault recognition is an important section in seismic interpretation and there are many methods for this technology, but no one can recognize fault exactly enough. For this problem, we proposed a new fault recognition method based on ant colony optimization which can locate fault precisely and extract fault from the seismic section. Firstly, seismic horizons are extracted by the connected component labeling algorithm; secondly, the fault location are decided according to the horizontal endpoints of each horizon; thirdly, the whole seismic section is divided into several rectangular blocks and the top and bottom endpoints of each rectangular block are considered as the nest and food respectively for the ant colony optimization algorithm. Besides that, the positive section is taken as an actual three dimensional terrain by using the seismic amplitude as a height. After that, the optimal route from nest to food calculated by the ant colony in each block is judged as a fault. Finally, extensive comparative tests were performed on the real seismic data. Availability and advancement of the proposed method were validated by the experimental results.

  6. Effects of fault heterogeneity on seismic energy and spectrum

    Science.gov (United States)

    Dragoni, Michele; Santini, Stefano

    2017-12-01

    We study the effects of friction heterogeneity on the dynamics of a seismogenic fault. To this aim, we consider a fault model containing two asperities with different static frictions and a rate-dependent dynamic friction. We consider the seismic events produced by the consecutive failure of the two asperities and study their properties as functions of the ratio between static frictions. In particular, we calculate the moment rate, the stress evolution during fault slip, the average stress drop, the partitioning of energy release, the seismic energy, the far-field waveforms and the spectrum of seismic waves. These quantities depend to various extent on the friction distribution on the fault. In particular, the stress distribution on the fault is always strongly heterogeneous at the beginning of the seismic event. Seismic energy and frictional heat decrease with increasing friction heterogeneity, while seismic efficiency is constant. We obtain an equation relating seismic efficiency to the parameters of the friction law, showing that the efficiency is maximum for smaller values of dynamic friction. The seismic spectrum depends on the friction distribution as to the positions and the values of the minima. However, under the model assumption that the slip durations are the same for both asperities, the corner frequency is independent of the friction distribution, but it depends on the friction law and on the coupling between asperities. The model provides a relation between the total radiated energy and the seismic moment that is consistent with the empirical relation between the two quantities. The fault model with one asperity is also considered as a particular case. The model is applied to the 1965 Rat Islands (Alaska) earthquake and shows the role of fault heterogeneity in controlling the spatial distribution of stress drop as well as the time dependence and the final amount of radiated energy.

  7. Maturity of nearby faults influences seismic hazard from hydraulic fracturing

    Science.gov (United States)

    Kozłowska, Maria; Brudzinski, Michael R.; Friberg, Paul; Skoumal, Robert J.; Baxter, Nicholas D.; Currie, Brian S.

    2018-02-01

    Understanding the causes of human-induced earthquakes is paramount to reducing societal risk. We investigated five cases of seismicity associated with hydraulic fracturing (HF) in Ohio since 2013 that, because of their isolation from other injection activities, provide an ideal setting for studying the relations between high-pressure injection and earthquakes. Our analysis revealed two distinct groups: (i) deeper earthquakes in the Precambrian basement, with larger magnitudes (M > 2), b-values 1.5, and few post–shut-in earthquakes. Based on geologic history, laboratory experiments, and fault modeling, we interpret the deep seismicity as slip on more mature faults in older crystalline rocks and the shallow seismicity as slip on immature faults in younger sedimentary rocks. This suggests that HF inducing deeper seismicity may pose higher seismic hazards. Wells inducing deeper seismicity produced more water than wells with shallow seismicity, indicating more extensive hydrologic connections outside the target formation, consistent with pore pressure diffusion influencing seismicity. However, for both groups, the 2 to 3 h between onset of HF and seismicity is too short for typical fluid pressure diffusion rates across distances of ˜1 km and argues for poroelastic stress transfer also having a primary influence on seismicity.

  8. Maturity of nearby faults influences seismic hazard from hydraulic fracturing.

    Science.gov (United States)

    Kozłowska, Maria; Brudzinski, Michael R; Friberg, Paul; Skoumal, Robert J; Baxter, Nicholas D; Currie, Brian S

    2018-02-20

    Understanding the causes of human-induced earthquakes is paramount to reducing societal risk. We investigated five cases of seismicity associated with hydraulic fracturing (HF) in Ohio since 2013 that, because of their isolation from other injection activities, provide an ideal setting for studying the relations between high-pressure injection and earthquakes. Our analysis revealed two distinct groups: ( i ) deeper earthquakes in the Precambrian basement, with larger magnitudes (M > 2), b-values 1.5, and few post-shut-in earthquakes. Based on geologic history, laboratory experiments, and fault modeling, we interpret the deep seismicity as slip on more mature faults in older crystalline rocks and the shallow seismicity as slip on immature faults in younger sedimentary rocks. This suggests that HF inducing deeper seismicity may pose higher seismic hazards. Wells inducing deeper seismicity produced more water than wells with shallow seismicity, indicating more extensive hydrologic connections outside the target formation, consistent with pore pressure diffusion influencing seismicity. However, for both groups, the 2 to 3 h between onset of HF and seismicity is too short for typical fluid pressure diffusion rates across distances of ∼1 km and argues for poroelastic stress transfer also having a primary influence on seismicity.

  9. Effect of fault roughness on aftershock distribution and post co-seismic strain accumulation.

    Science.gov (United States)

    Aslam, K.; Daub, E. G.

    2017-12-01

    We perform physics-based simulations of earthquake rupture propagation on geometrically complex strike-slip faults. We consider many different realization of the fault roughness and obtain heterogeneous stress fields by performing dynamic rupture simulation of large earthquakes. We calculate the Coulomb failure function (CFF) for all these realizations so that we can quantify zones of stress increase/shadows surrounding the main fault and compare our results to seismic catalogs. To do this comparison, we use relocated earthquake catalogs from Northern and Southern California. We specify the range of fault roughness parameters based on past observational studies. The Hurst exponent (H) varies in range from 0.5 to 1 and RMS height to wavelength ratio ( RMS deviation of a fault profile from planarity) has values between 10-2 to 10-3. For any realization of fault roughness, the Probability density function (PDF) values relative to the mean CFF change show a wider spread near the fault and this spread squeezes into a narrow band as we move away from fault. For lower value of RMS ratio ( 10-3), we see bigger zones of stress change near the hypocenter and for higher value of RMS ratio ( 10-2), we see alternate zones of stress increase/decrease surrounding the fault to have comparable lengths. We also couple short-term dynamic rupture simulation with long-term tectonic modelling. We do this by giving the stress output from one of the dynamic rupture simulation (of a single realization of fault roughness) to long term tectonic model (LTM) as initial condition and then run LTM over duration of seismic cycle. This short term and long term coupling enables us to understand how heterogeneous stresses due to fault geometry influence the dynamics of strain accumulation in the post-seismic and inter-seismic phase of seismic cycle.

  10. Characterization and application of microearthquake clusters to problems of scaling, fault zone dynamics, and seismic monitoring at Parkfield, California

    Energy Technology Data Exchange (ETDEWEB)

    Nadeau, Robert Michael [Univ. of California, Berkeley, CA (United States)

    1995-10-01

    This document contains information about the characterization and application of microearthquake clusters and fault zone dynamics. Topics discussed include: Seismological studies; fault-zone dynamics; periodic recurrence; scaling of microearthquakes to large earthquakes; implications of fault mechanics and seismic hazards; and wave propagation and temporal changes.

  11. A look inside the San Andreas Fault at Parkfield through vertical seismic profiling.

    Science.gov (United States)

    Chavarria, J Andres; Malin, Peter; Catchings, Rufus D; Shalev, Eylon

    2003-12-05

    The San Andreas Fault Observatory at Depth pilot hole is located on the southwestern side of the Parkfield San Andreas fault. This observatory includes a vertical seismic profiling (VSP) array. VSP seismograms from nearby microearthquakes contain signals between the P and S waves. These signals may be P and S waves scattered by the local geologic structure. The collected scattering points form planar surfaces that we interpret as the San Andreas fault and four other secondary faults. The scattering process includes conversions between P and S waves, the strengths of which suggest large contrasts in material properties, possibly indicating the presence of cracks or fluids.

  12. Vaporization of fault water during seismic slip

    Science.gov (United States)

    Chen, Jianye; Niemeijer, André R.; Fokker, Peter A.

    2017-06-01

    Laboratory and numerical studies, as well as field observations, indicate that phase transitions of pore water might be an important process in large earthquakes. We present a model of the thermo-hydro-chemo-mechanical processes, including a two-phase mixture model to incorporate the phase transitions of pore water, occurring during fast slip (i.e., a natural earthquake) in order to investigate the effects of vaporization on the coseismic slip. Using parameters from typical natural faults, our modeling shows that vaporization can indeed occur at the shallow depths of an earthquake, irrespective of the wide variability of the parameters involved (sliding velocity, friction coefficient, gouge permeability and porosity, and shear-induced dilatancy). Due to the fast kinetics, water vaporization can cause a rapid slip weakening even when the hydrological conditions of the fault zone are not favorable for thermal pressurization, e.g., when permeability is high. At the same time, the latent heat associated with the phase transition causes the temperature rise in the slip zone to be buffered. Our parametric analyses reveal that the amount of frictional work is the principal factor controlling the onset and activity of vaporization and that it can easily be achieved in earthquakes. Our study shows that coseismic pore fluid vaporization might have played important roles at shallow depths of large earthquakes by enhancing slip weakening and buffering the temperature rise. The combined effects may provide an alternative explanation for the fact that low-temperature anomalies were measured in the slip zones at shallow depths of large earthquakes.

  13. Simulation of Co-Seismic Off-Fault Stress Effects: Influence of Fault Roughness and Pore Pressure Coupling

    Science.gov (United States)

    Fälth, B.; Lund, B.; Hökmark, H.

    2017-12-01

    Aiming at improved safety assessment of geological nuclear waste repositories, we use dynamic 3D earthquake simulations to estimate the potential for co-seismic off-fault distributed fracture slip. Our model comprises a 12.5 x 8.5 km strike-slip fault embedded in a full space continuum where we apply a homogeneous initial stress field. In the reference case (Case 1) the fault is planar and oriented optimally for slip, given the assumed stress field. To examine the potential impact of fault roughness, we also study cases where the fault surface has undulations with self-similar fractal properties. In both the planar and the undulated cases the fault has homogeneous frictional properties. In a set of ten rough fault models (Case 2), the fault friction is equal to that of Case 1, meaning that these models generate lower seismic moments than Case 1. In another set of ten rough fault models (Case 3), the fault dynamic friction is adjusted such that seismic moments on par with that of Case 1 are generated. For the propagation of the earthquake rupture we adopt the linear slip-weakening law and obtain Mw 6.4 in Case 1 and Case 3, and Mw 6.3 in Case 2 (35 % lower moment than Case 1). During rupture we monitor the off-fault stress evolution along the fault plane at 250 m distance and calculate the corresponding evolution of the Coulomb Failure Stress (CFS) on optimally oriented hypothetical fracture planes. For the stress-pore pressure coupling, we assume Skempton's coefficient B = 0.5 as a base case value, but also examine the sensitivity to variations of B. We observe the following: (I) The CFS values, and thus the potential for fracture slip, tend to increase with the distance from the hypocenter. This is in accordance with results by other authors. (II) The highest CFS values are generated by quasi-static stress concentrations around fault edges and around large scale fault bends, where we obtain values of the order of 10 MPa. (III) Locally, fault roughness may have a

  14. Magnetic enhancement and softening of fault gouges during seismic slip: Laboratory observation and implications

    Science.gov (United States)

    Yang, T.; Chen, J.; Dekkers, M. J.

    2017-12-01

    Anomalous rock magnetic properties have been reported in slip zones of many previous earthquakes (e.g., the 1995 Kobe earthquake, Japan; the 1999 Chi-Chi earthquake, Taiwan, and the 2008 Wenchuan earthquake, China). However, it is unclear whether short-duration frictional heating can actually induce such rock magnetic anomalies in fault zones; identification of this process in natural fault zones is not that straightforward. A promising approach to solve this problem is to conduct high-velocity friction (HVF) experiments that reproduce seismic fault movements and frictional heating in a simulated fault zone. Afterwards natural fault zones can be analyzed with renewed insight. Our HVF experiments on fault gouges that are simulating large amounts of earthquake slip, show significant magnetic enhancement and softening of sheared gouges. Mineral magnetic measurements reveal that magnetite was formed due to thermal decomposition of smectite during the HVF experiment on the paramagnetic fault gouge. Also, goethite was transformed to intermediate magnetite during the HVF experiment on the goethite-bearing fault gouge. Magnetic susceptibility, saturation remanence and saturation magnetization of sheared samples are linearly increasing with and strongly depend on the temperature rise induced by frictional heating; in contrast, coecivities are decreasing with increasing temperature. Thus, frictional heating can induce thermal decomposition/transformation during short-duration, high-velocity seismic slip, leading to magnetic enhancement and softening of a slip zone. Mineral magnetic methods are suited for diagnosing earthquake slip and estimating the temperature rise of co-seismic frictional heating.

  15. Qademah Fault Seismic Data Set - Northern Part

    KAUST Repository

    Hanafy, Sherif M.

    2015-01-01

    Objective: Is the Qademah fault that was detected in 2010 the main fault? We collected a long 2D profile, 526 m, where the fault that was detected in 2010 is at around 300 m. Layout: We collected 264 CSGs, each has 264 receivers. The shot and receiver interval is 2 m. We also collected an extra 48 CSGs with offset = 528 to 622 m with shot interval = 2 m. The receivers are the same as the main survey.

  16. Rupture Dynamics and Seismic Radiation on Rough Faults for Simulation-Based PSHA

    Science.gov (United States)

    Mai, P. M.; Galis, M.; Thingbaijam, K. K. S.; Vyas, J. C.; Dunham, E. M.

    2017-12-01

    Simulation-based ground-motion predictions may augment PSHA studies in data-poor regions or provide additional shaking estimations, incl. seismic waveforms, for critical facilities. Validation and calibration of such simulation approaches, based on observations and GMPE's, is important for engineering applications, while seismologists push to include the precise physics of the earthquake rupture process and seismic wave propagation in 3D heterogeneous Earth. Geological faults comprise both large-scale segmentation and small-scale roughness that determine the dynamics of the earthquake rupture process and its radiated seismic wavefield. We investigate how different parameterizations of fractal fault roughness affect the rupture evolution and resulting near-fault ground motions. Rupture incoherence induced by fault roughness generates realistic ω-2 decay for high-frequency displacement amplitude spectra. Waveform characteristics and GMPE-based comparisons corroborate that these rough-fault rupture simulations generate realistic synthetic seismogram for subsequent engineering application. Since dynamic rupture simulations are computationally expensive, we develop kinematic approximations that emulate the observed dynamics. Simplifying the rough-fault geometry, we find that perturbations in local moment tensor orientation are important, while perturbations in local source location are not. Thus, a planar fault can be assumed if the local strike, dip, and rake are maintained. The dynamic rake angle variations are anti-correlated with local dip angles. Based on a dynamically consistent Yoffe source-time function, we show that the seismic wavefield of the approximated kinematic rupture well reproduces the seismic radiation of the full dynamic source process. Our findings provide an innovative pseudo-dynamic source characterization that captures fault roughness effects on rupture dynamics. Including the correlations between kinematic source parameters, we present a new

  17. Seismic Evidence for Conjugate Slip and Block Rotation Within the San Andreas Fault System, Southern California

    Science.gov (United States)

    Nicholson, Craig; Seeber, Leonardo; Williams, Patrick; Sykes, Lynn R.

    1986-08-01

    The pattern of seismicity in southern California indicates that much of the activity is presently occurring on secondary structures, several of which are oriented nearly orthogonal to the strikes of the major through-going faults. Slip along these secondary transverse features is predominantly left-lateral and is consistent with the reactivation of conjugate faults by the current regional stress field. Near the intersection of the San Jacinto and San Andreas faults, however, these active left-lateral faults appear to define a set of small crustal blocks, which in conjunction with both normal and reverse faulting earthquakes, suggests contemporary clockwise rotation as a result of regional right-lateral shear. Other left-lateral faults representing additional rotating block systems are identified in adjacent areas from geologic and seismologic data. Many of these structures predate the modern San Andreas system and may control the pattern of strain accumulation in southern California. Geodetic and paleomagnetic evidence confirm that block rotation by strike-slip faulting is nearly ubiquitous, particularly in areas where shear is distributed, and that it accommodates both short-term elastic and long-term nonelastic strain. A rotating block model accounts for a number of structural styles characteristic of strike-slip deformation in California, including: variable slip rates and alternating transtensional and transpressional features observed along strike of major wrench faults; domains of evenly-spaced antithetic faults that terminate against major fault boundaries; continued development of bends in faults with large lateral displacements; anomalous focal mechanisms; and differential uplift in areas otherwise expected to experience extension and subsidence. Since block rotation requires a detachment surface at depth to permit rotational movement, low-angle structures like detachments, of either local or regional extent, may be involved in the contemporary strike

  18. From Geodetic Imaging of Seismic and Aseismic Fault Slip to Dynamic Modeling of the Seismic Cycle

    Science.gov (United States)

    Avouac, Jean-Philippe

    2015-05-01

    Understanding the partitioning of seismic and aseismic fault slip is central to seismotectonics as it ultimately determines the seismic potential of faults. Thanks to advances in tectonic geodesy, it is now possible to develop kinematic models of the spatiotemporal evolution of slip over the seismic cycle and to determine the budget of seismic and aseismic slip. Studies of subduction zones and continental faults have shown that aseismic creep is common and sometimes prevalent within the seismogenic depth range. Interseismic coupling is generally observed to be spatially heterogeneous, defining locked patches of stress accumulation, to be released in future earthquakes or aseismic transients, surrounded by creeping areas. Clay-rich tectonites, high temperature, and elevated pore-fluid pressure seem to be key factors promoting aseismic creep. The generally logarithmic time evolution of afterslip is a distinctive feature of creeping faults that suggests a logarithmic dependency of fault friction on slip rate, as observed in laboratory friction experiments. Most faults can be considered to be paved with interlaced patches where the friction law is either rate-strengthening, inhibiting seismic rupture propagation, or rate-weakening, allowing for earthquake nucleation. The rate-weakening patches act as asperities on which stress builds up in the interseismic period; they might rupture collectively in a variety of ways. The pattern of interseismic coupling can help constrain the return period of the maximum- magnitude earthquake based on the requirement that seismic and aseismic slip sum to match long-term slip. Dynamic models of the seismic cycle based on this conceptual model can be tuned to reproduce geodetic and seismological observations. The promise and pitfalls of using such models to assess seismic hazard are discussed.

  19. Assessment of faulting and seismic hazards at Yucca Mountain

    International Nuclear Information System (INIS)

    King, J.L.; Frazier, G.A.; Grant, T.A.

    1989-01-01

    Yucca Mountain is being evaluated for the nation's first high-level nuclear-waste repository. Local faults appear to be capable of moderate earthquakes at recurrence intervals of tens of thousands of years. The major issues identified for the preclosure phase (<100 yrs) are the location and seismic design of surface facilities for handling incoming waste. It is planned to address surface fault rupture by locating facilities where no discernible recent (<100,000 yrs) faulting has occurred and to base the ground motion design on hypothetical earthquakes, postulated on nearby faults, that represent 10,000 yrs of average cumulative displacement. The major tectonic issues identified for the postclosure phase (10,000 yrs) are volcanism (not addressed here) and potential changes to the hydrologic system resulting from a local faulting event which could trigger potential thermal, mechanical, and chemical interactions with the ground water. Extensive studies are planned for resolving these issues. 33 refs., 3 figs

  20. Hysteresis behavior of seismic isolators in earthquakes near a fault ...

    African Journals Online (AJOL)

    Seismic performance and appropriate design of structures located near the faults has always been a major concern of design engineers. Because during an earthquake; the effects of plasticity will make differences in characteristics of near field records. These pulsed movements at the beginning of records will increase the ...

  1. Relationships among seismic velocity, metamorphism, and seismic and aseismic fault slip in the Salton Sea Geothermal Field region

    Science.gov (United States)

    McGuire, Jeffrey J.; Lohman, Rowena B.; Catchings, Rufus D.; Rymer, Michael J.; Goldman, Mark R.

    2015-01-01

    The Salton Sea Geothermal Field is one of the most geothermally and seismically active areas in California and presents an opportunity to study the effect of high-temperature metamorphism on the properties of seismogenic faults. The area includes numerous active tectonic faults that have recently been imaged with active source seismic reflection and refraction. We utilize the active source surveys, along with the abundant microseismicity data from a dense borehole seismic network, to image the 3-D variations in seismic velocity in the upper 5 km of the crust. There are strong velocity variations, up to ~30%, that correlate spatially with the distribution of shallow heat flow patterns. The combination of hydrothermal circulation and high-temperature contact metamorphism has significantly altered the shallow sandstone sedimentary layers within the geothermal field to denser, more feldspathic, rock with higher P wave velocity, as is seen in the numerous exploration wells within the field. This alteration appears to have a first-order effect on the frictional stability of shallow faults. In 2005, a large earthquake swarm and deformation event occurred. Analysis of interferometric synthetic aperture radar data and earthquake relocations indicates that the shallow aseismic fault creep that occurred in 2005 was localized on the Kalin fault system that lies just outside the region of high-temperature metamorphism. In contrast, the earthquake swarm, which includes all of the M > 4 earthquakes to have occurred within the Salton Sea Geothermal Field in the last 15 years, ruptured the Main Central Fault (MCF) system that is localized in the heart of the geothermal anomaly. The background microseismicity induced by the geothermal operations is also concentrated in the high-temperature regions in the vicinity of operational wells. However, while this microseismicity occurs over a few kilometer scale region, much of it is clustered in earthquake swarms that last from

  2. Criteria for Seismic Splay Fault Activation During Subduction Earthquakes

    Science.gov (United States)

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

    2008-12-01

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

  3. FiSH: put fault data in a seismic hazard basket

    Science.gov (United States)

    Pace, Bruno; Visini, Francesco; Peruzza, Laura

    2016-04-01

    The practice of using fault sources in seismic hazard studies is growing in popularity, including in regions with moderate seismic activity, such as the European countries. In these areas, fault identification may be affected by similarly large uncertainties in the historical and instrumental seismic histories of more active areas that have not been inhabited for long periods of time. Certain studies have effectively applied a time-dependent perspective to combine historical and instrumental seismic data with geological and paleoseismological information, partially compensating for a lack of information. We present a package of Matlab® tools (called FiSH), in publication on Seismological Research Letters, designed to help seismic hazard modellers analyse fault data. These tools enable the derivation of expected earthquake rates given common fault data, and allow you to test the consistency between the magnitude frequency distributions assigned to a fault and some available observations. The basic assumption of FiSH is that the geometric and kinematic features of a fault are the expression of its seismogenic potential. Three tools have been designed to integrate the variable levels of information available: (a) the first tool allows users to convert fault geometry and slip rates into a global budget of the seismic moment released in a given time frame, taking uncertainties into account; (b) the second tool computes the recurrence parameters and associated uncertainties from historical and/or paleoseismological data; 
(c) the third tool outputs time-independent or time-dependent earthquake rates for different magnitude frequency distribution models. We present moreover a test case to illustrate the capabilities of FiSH, on the Paganica normal fault in Central Italy that ruptured during the L'Aquila 2009 earthquake sequence (mainshock Mw 6.3). FiSH is available at http://fish-code.com, and the source codes are open. We encourage users to handle the scripts

  4. Intraplate seismicity along the Gedi Fault in Kachchh rift basin of western India

    Science.gov (United States)

    Joshi, Vishwa; Rastogi, B. K.; Kumar, Santosh

    2017-11-01

    The Kachchh rift basin is located on the western continental margin of India and has a history of experiencing large to moderate intraplate earthquakes with M ≥ 5. During the past two centuries, two large earthquakes of Mw 7.8 (1819) and Mw 7.7 (2001) have occurred in the Kachchh region, the latter with an epicenter near Bhuj. The aftershock activity of the 2001 Bhuj earthquake is still ongoing with migration of seismicity. Initially, epicenters migrated towards the east and northeast within the Kachchh region but, since 2007, it has also migrated to the south. The triggered faults are mostly within 100 km and some up to 200 km distance from the epicentral area of the mainshock. Most of these faults are trending in E-W direction, and some are transverse. It was noticed that some faults generate earthquakes down to the Moho depth whereas some faults show earthquake activity within the upper crustal volume. The Gedi Fault, situated about 50 km northeast of the 2001 mainshock epicenter, triggered the largest earthquake of Mw 5.6 in 2006. We have carried out detailed seismological studies to evaluate the seismic potential of the Gedi Fault. We have relocated 331 earthquakes by HypoDD to improve upon location errors. Further, the relocated events are used to estimate the b value, p value, and fractal correlation dimension Dc of the fault zone. The present study indicates that all the events along the Gedi Fault are shallow in nature, with focal depths less than 20 km. The estimated b value shows that the Gedi aftershock sequence could be classified as Mogi's type 2 sequence, and the p value suggests a relatively slow decay of aftershocks. The fault plane solutions of some selected events of Mw > 3.5 are examined, and activeness of the Gedi Fault is assessed from the results of active fault studies as well as GPS and InSAR results. All these results are critically examined to evaluate the material properties and seismic potential of the Gedi Fault that may be useful

  5. Why the 2002 Denali fault rupture propagated onto the Totschunda fault: implications for fault branching and seismic hazards

    Science.gov (United States)

    Schwartz, David P.; Haeussler, Peter J.; Seitz, Gordon G.; Dawson, Timothy E.

    2012-01-01

    The propagation of the rupture of the Mw7.9 Denali fault earthquake from the central Denali fault onto the Totschunda fault has provided a basis for dynamic models of fault branching in which the angle of the regional or local prestress relative to the orientation of the main fault and branch plays a principal role in determining which fault branch is taken. GeoEarthScope LiDAR and paleoseismic data allow us to map the structure of the Denali-Totschunda fault intersection and evaluate controls of fault branching from a geological perspective. LiDAR data reveal the Denali-Totschunda fault intersection is structurally simple with the two faults directly connected. At the branch point, 227.2 km east of the 2002 epicenter, the 2002 rupture diverges southeast to become the Totschunda fault. We use paleoseismic data to propose that differences in the accumulated strain on each fault segment, which express differences in the elapsed time since the most recent event, was one important control of the branching direction. We suggest that data on event history, slip rate, paleo offsets, fault geometry and structure, and connectivity, especially on high slip rate-short recurrence interval faults, can be used to assess the likelihood of branching and its direction. Analysis of the Denali-Totschunda fault intersection has implications for evaluating the potential for a rupture to propagate across other types of fault intersections and for characterizing sources of future large earthquakes.

  6. Methodology for the Seismic risk assessment in segments of fault

    International Nuclear Information System (INIS)

    1997-02-01

    The present study establishes the most adequate methods of Seismic Hazard Assessment for the Iberian Peninsula, in particular for low seismicity areas, through a review of methods used in other countries and its application to a certain area in Spain. In this area the geological context and recent activity of a specific tectonic structure is studied in detail, in order to asses its slip rate, and therefore, its capability of generating earthquakes. In the first stage of this project a review of Seismic Hazard Assessment methods used outside Spain was carried out, as well as, a study of several spanish cases. This stage also comprises a review of the spanish seismic record and a study of the general peninsular neotectonic context, this latter to select a particular fault for the next stage. (Author) 117 refs

  7. Seismicity rate surge on faults after shut-in: poroelastic response to fluid injection

    Science.gov (United States)

    Chang, K. W.; Yoon, H.; Martinez, M. J.

    2017-12-01

    Subsurface energy activities such as geological CO2 storage and wastewater injection require injecting large amounts of fluid into the subsurface, which will alter the states of pore pressure and stress in the storage formation. One of the main issues for injection-induced seismicity is the post shut-in increases in the seismicity rate, often observed in the fluid-injection operation sites. The rate surge can be driven by the following mechanisms: (1) pore-pressure propagation into distant faults after shut-in and (2) poroelastic stressing caused by well operations, depending on fault geometry, hydraulic and mechanical properties of the formation, and injection history. We simulate the aerial view of the target reservoir intersected by strike-slip faults, in which injection-induced pressure buildup encounters the faults directly. We examine the poroelastic response of the faults to fluid injection and perform a series of sensitivity tests considering: (1) permeability of the fault zone, (2) locations and the number of faults with respect to the injection point, and (3) well operations with varying the injection rate. Our analysis of the Coulomb stress change suggests that the sealing fault confines pressure diffusion which stabilizes or weakens the nearby conductive fault depending on the injection location. We perform the sensitivity test by changing injection scenarios (time-dependent rates), while keeping the total amount of injected fluids. Sensitivity analysis shows that gradual reduction of the injection rate minimizes the Coulomb stress change and the least seismicity rates are predicted. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525.

  8. Fault detection by surface seismic scanning tunneling macroscope: Field test

    KAUST Repository

    Hanafy, Sherif M.

    2014-08-05

    The seismic scanning tunneling macroscope (SSTM) is proposed for detecting the presence of near-surface impedance anomalies and faults. Results with synthetic data are consistent with theory in that scatterers closer to the surface provide brighter SSTM profiles than those that are deeper. The SSTM profiles show superresolution detection if the scatterers are in the near-field region of the recording line. The field data tests near Gulf of Aqaba, Haql, KSA clearly show the presence of the observable fault scarp, and identify the subsurface presence of the hidden faults indicated in the tomograms. Superresolution detection of the fault is achieved, even when the 35 Hz data are lowpass filtered to the 5-10 Hz band.

  9. Fault detection by surface seismic scanning tunneling macroscope: Field test

    KAUST Repository

    Hanafy, Sherif M.; Schuster, Gerard T.

    2014-01-01

    The seismic scanning tunneling macroscope (SSTM) is proposed for detecting the presence of near-surface impedance anomalies and faults. Results with synthetic data are consistent with theory in that scatterers closer to the surface provide brighter SSTM profiles than those that are deeper. The SSTM profiles show superresolution detection if the scatterers are in the near-field region of the recording line. The field data tests near Gulf of Aqaba, Haql, KSA clearly show the presence of the observable fault scarp, and identify the subsurface presence of the hidden faults indicated in the tomograms. Superresolution detection of the fault is achieved, even when the 35 Hz data are lowpass filtered to the 5-10 Hz band.

  10. Seismic and geodetic signatures of fault slip at the Slumgullion Landslide Natural Laboratory

    Science.gov (United States)

    Gomberg, J.; Schulz, W.; Bodin, P.; Kean, J.

    2011-01-01

    We tested the hypothesis that the Slumgullion landslide is a useful natural laboratory for observing fault slip, specifically that slip along its basal surface and side-bounding strike-slip faults occurs with comparable richness of aseismic and seismic modes as along crustal- and plate-scale boundaries. Our study provides new constraints on models governing landslide motion. We monitored landslide deformation with temporary deployments of a 29-element prism array surveyed by a robotic theodolite and an 88-station seismic network that complemented permanent extensometers and environmental instrumentation. Aseismic deformation observations show that large blocks of the landslide move steadily at approximately centimeters per day, possibly punctuated by variations of a few millimeters, while localized transient slip episodes of blocks less than a few tens of meters across occur frequently. We recorded a rich variety of seismic signals, nearly all of which originated outside the monitoring network boundaries or from the side-bounding strike-slip faults. The landslide basal surface beneath our seismic network likely slipped almost completely aseismically. Our results provide independent corroboration of previous inferences that dilatant strengthening along sections of the side-bounding strike-slip faults controls the overall landslide motion, acting as seismically radiating brakes that limit acceleration of the aseismically slipping basal surface. Dilatant strengthening has also been invoked in recent models of transient slip and tremor sources along crustal- and plate-scale faults suggesting that the landslide may indeed be a useful natural laboratory for testing predictions of specific mechanisms that control fault slip at all scales.

  11. Reflection seismic studies over the end-glacial Burträsk fault, Skellefteå, Sweden

    Directory of Open Access Journals (Sweden)

    C. Juhlin

    2011-01-01

    Full Text Available Reflection seismic data were acquired along a ca. 22 km long profile over the end-glacial Burträsk fault with a nominal receiver and source spacing of 20 m. A steeply dipping reflection can be correlated to the Burträsk fault, indicating that the fault dips at about 55° to the southeast near the surface. The reflection from the fault is rather poorly imaged, probably due to a lateral offset in the fault of about 1 km at this location and the crookedness of the seismic profile in the vicinity of the fault. A more pronounced steeply dipping reflection is observed about 4 km southeast of the Burträsk fault. Based on its correlation with a topographic low at the surface this reflection is interpreted to originate from a fracture zone. There are no signs of large displacements along this zone as the glacial ice receded, but earthquakes could be associated with it today. Other reflections on the processed seismic section may originate from changes in lithological variations in the supra-crustal rocks or from intrusions of more mafic rock. Constraints on the fault geometry provided by the reflection seismic data will help determine what stresses were required to activate the fault when the major rupture along it occurred ca. 9500 years ago.

  12. Automatic reconstruction of fault networks from seismicity catalogs including location uncertainty

    International Nuclear Information System (INIS)

    Wang, Y.

    2013-01-01

    Within the framework of plate tectonics, the deformation that arises from the relative movement of two plates occurs across discontinuities in the earth's crust, known as fault zones. Active fault zones are the causal locations of most earthquakes, which suddenly release tectonic stresses within a very short time. In return, fault zones slowly grow by accumulating slip due to such earthquakes by cumulated damage at their tips, and by branching or linking between pre-existing faults of various sizes. Over the last decades, a large amount of knowledge has been acquired concerning the overall phenomenology and mechanics of individual faults and earthquakes: A deep physical and mechanical understanding of the links and interactions between and among them is still missing, however. One of the main issues lies in our failure to always succeed in assigning an earthquake to its causative fault. Using approaches based in pattern-recognition theory, more insight into the relationship between earthquakes and fault structure can be gained by developing an automatic fault network reconstruction approach using high resolution earthquake data sets at largely different scales and by considering individual event uncertainties. This thesis introduces the Anisotropic Clustering of Location Uncertainty Distributions (ACLUD) method to reconstruct active fault networks on the basis of both earthquake locations and their estimated individual uncertainties. This method consists in fitting a given set of hypocenters with an increasing amount of finite planes until the residuals of the fit compare with location uncertainties. After a massive search through the large solution space of possible reconstructed fault networks, six different validation procedures are applied in order to select the corresponding best fault network. Two of the validation steps (cross-validation and Bayesian Information Criterion (BIC)) process the fit residuals, while the four others look for solutions that

  13. One-dimensional modeling of thermal energy produced in a seismic fault

    Science.gov (United States)

    Konga, Guy Pascal; Koumetio, Fidèle; Yemele, David; Olivier Djiogang, Francis

    2017-12-01

    Generally, one observes an anomaly of temperature before a big earthquake. In this paper, we established the expression of thermal energy produced by friction forces between the walls of a seismic fault while considering the dynamic of a one-dimensional spring-block model. It is noted that, before the rupture of a seismic fault, displacements are caused by microseisms. The curves of variation of this thermal energy with time show that, for oscillatory and aperiodic displacement, the thermal energy is accumulated in the same way. The study reveals that thermal energy as well as temperature increases abruptly after a certain amount of time. We suggest that the corresponding time is the start of the anomaly of temperature observed which can be considered as precursory effect of a big seism. We suggest that the thermal energy can heat gases and dilate rocks until they crack. The warm gases can then pass through the cracks towards the surface. The cracks created by thermal energy can also contribute to the rupture of the seismic fault. We also suggest that the theoretical model of thermal energy, produced in seismic fault, associated with a large quantity of experimental data may help in the prediction of earthquakes.

  14. Enriquillo–Plantain Garden fault zone in Jamaica: paleoseismology and seismic hazard

    Science.gov (United States)

    Koehler, R.D.; Mann, P.; Prentice, Carol S.; Brown, L.; Benford, B.; Grandison-Wiggins, M.

    2013-01-01

    The countries of Jamaica, Haiti, and the Dominican Republic all straddle the Enriquillo–Plantain Garden fault zone ( EPGFZ), a major left-lateral, strike-slip fault system bounding the Caribbean and North American plates. Past large earthquakes that destroyed the capital cities of Kingston, Jamaica (1692, 1907), and Port-au-Prince, Haiti (1751, 1770), as well as the 2010 Haiti earthquake that killed more than 50,000 people, have heightened awareness of seismic hazards in the northern Caribbean. We present here new geomorphic and paleoseismic information bearing on the location and relative activity of the EPGFZ, which marks the plate boundary in Jamaica. Documentation of a river bank exposure and several trenches indicate that this fault is active and has the potential to cause major destructive earthquakes in Jamaica. The results suggest that the fault has not ruptured the surface in at least 500 yr and possibly as long as 28 ka. The long period of quiescence and subdued geomorphic expression of the EPGFZ indicates that it may only accommodate part of the ∼7–9 mm=yr plate deformation rate measured geodetically and that slip may be partitioned on other undocumented faults. Large uncertainties related to the neotectonic framework of Jamaica remain and more detailed fault characterization studies are necessary to accurately assess seismic hazards.

  15. Seismic analysis of large pools

    Energy Technology Data Exchange (ETDEWEB)

    Dong, R.G.; Tokarz, F.J.

    1976-11-17

    Large pools for storing spent, nuclear fuel elements are being proposed to augment present storage capacity. To preserve the ability to isolate portions of these pools, a modularization requirement appears desirable. The purpose of this project was to investigate the effects of modularization on earthquake resistance and to assess the adequacy of current design methods for seismic loads. After determining probable representative pool geometries, three rectangular pool configurations, all 240 x 16 ft and 40 ft deep, were examined. One was unmodularized; two were modularized into 80 x 40 ft cells in one case and 80 x 80 ft cells in the other. Both embedded and above-ground installations for a hard site and embedded installations for an intermediate hard site were studied. It was found that modularization was unfavorable in terms of reducing the total structural load attributable to dynamic effects, principally because one or more cells could be left unfilled. The walls of unfilled cells would be subjected to significantly higher loads than the walls of a filled, unmodularized pool. Generally, embedded installations were preferable to above-ground installations, and the hard site was superior to the intermediate hard site. It was determined that Housner's theory was adequate for calculating hydrodynamic effects on spent fuel storage pools. Current design methods for seismic loads were found to be satisfactory when results from these methods were compared with those from LUSH analyses. As a design method for dynamic soil pressure, we found the Mononobe-Okabe theory, coupled with correction factors as suggested by Seed, to be acceptable. The factors we recommend for spent fuel storage pools are tabulated.

  16. Seismic analysis of large pools

    International Nuclear Information System (INIS)

    Dong, R.G.; Tokarz, F.J.

    1976-01-01

    Large pools for storing spent, nuclear fuel elements are being proposed to augment present storage capacity. To preserve the ability to isolate portions of these pools, a modularization requirement appears desirable. The purpose of this project was to investigate the effects of modularization on earthquake resistance and to assess the adequacy of current design methods for seismic loads. After determining probable representative pool geometries, three rectangular pool configurations, all 240 x 16 ft and 40 ft deep, were examined. One was unmodularized; two were modularized into 80 x 40 ft cells in one case and 80 x 80 ft cells in the other. Both embedded and above-ground installations for a hard site and embedded installations for an intermediate hard site were studied. It was found that modularization was unfavorable in terms of reducing the total structural load attributable to dynamic effects, principally because one or more cells could be left unfilled. The walls of unfilled cells would be subjected to significantly higher loads than the walls of a filled, unmodularized pool. Generally, embedded installations were preferable to above-ground installations, and the hard site was superior to the intermediate hard site. It was determined that Housner's theory was adequate for calculating hydrodynamic effects on spent fuel storage pools. Current design methods for seismic loads were found to be satisfactory when results from these methods were compared with those from LUSH analyses. As a design method for dynamic soil pressure, we found the Mononobe-Okabe theory, coupled with correction factors as suggested by Seed, to be acceptable. The factors we recommend for spent fuel storage pools are tabulated

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

    Science.gov (United States)

    Seelig, William George

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

  18. Seismicity Pattern and Fault Structure in the Central Himalaya Seismic Gap Using Precise Earthquake Hypocenters and their Source Parameters

    Science.gov (United States)

    Mendoza, M.; Ghosh, A.; Rai, S. S.

    2017-12-01

    The devastation brought on by the Mw 7.8 Gorkha earthquake in Nepal on 25 April 2015, reconditioned people to the high earthquake risk along the Himalayan arc. It is therefore imperative to learn from the Gorkha earthquake, and gain a better understanding of the state of stress in this fault regime, in order to identify areas that could produce the next devastating earthquake. Here, we focus on what is known as the "central Himalaya seismic gap". It is located in Uttarakhand, India, west of Nepal, where a large (> Mw 7.0) earthquake has not occurred for over the past 200 years [Rajendran, C.P., & Rajendran, K., 2005]. This 500 - 800 km long along-strike seismic gap has been poorly studied, mainly due to the lack of modern and dense instrumentation. It is especially concerning since it surrounds densely populated cities, such as New Delhi. In this study, we analyze a rich seismic dataset from a dense network consisting of 50 broadband stations, that operated between 2005 and 2012. We use the STA/LTA filter technique to detect earthquake phases, and the latest tools contributed to the Antelope software environment, to develop a large and robust earthquake catalog containing thousands of precise hypocentral locations, magnitudes, and focal mechanisms. By refining those locations in HypoDD [Waldhauser & Ellsworth, 2000] to form a tighter cluster of events using relative relocation, we can potentially illustrate fault structures in this region with high resolution. Additionally, using ZMAP [Weimer, S., 2001], we perform a variety of statistical analyses to understand the variability and nature of seismicity occurring in the region. Generating a large and consistent earthquake catalog not only brings to light the physical processes controlling the earthquake cycle in an Himalayan seismogenic zone, it also illustrates how stresses are building up along the décollment and the faults that stem from it. With this new catalog, we aim to reveal fault structure, study

  19. Time-Independent Annual Seismic Rates, Based on Faults and Smoothed Seismicity, Computed for Seismic Hazard Assessment in Italy

    Science.gov (United States)

    Murru, M.; Falcone, G.; Taroni, M.; Console, R.

    2017-12-01

    In 2015 the Italian Department of Civil Protection, started a project for upgrading the official Italian seismic hazard map (MPS04) inviting the Italian scientific community to participate in a joint effort for its realization. We participated providing spatially variable time-independent (Poisson) long-term annual occurrence rates of seismic events on the entire Italian territory, considering cells of 0.1°x0.1° from M4.5 up to M8.1 for magnitude bin of 0.1 units. Our final model was composed by two different models, merged in one ensemble model, each one with the same weight: the first one was realized by a smoothed seismicity approach, the second one using the seismogenic faults. The spatial smoothed seismicity was obtained using the smoothing method introduced by Frankel (1995) applied to the historical and instrumental seismicity. In this approach we adopted a tapered Gutenberg-Richter relation with a b-value fixed to 1 and a corner magnitude estimated with the bigger events in the catalogs. For each seismogenic fault provided by the Database of the Individual Seismogenic Sources (DISS), we computed the annual rate (for each cells of 0.1°x0.1°) for magnitude bin of 0.1 units, assuming that the seismic moments of the earthquakes generated by each fault are distributed according to the same tapered Gutenberg-Richter relation of the smoothed seismicity model. The annual rate for the final model was determined in the following way: if the cell falls within one of the seismic sources, we merge the respective value of rate determined by the seismic moments of the earthquakes generated by each fault and the value of the smoothed seismicity model with the same weight; if instead the cells fall outside of any seismic source we considered the rate obtained from the spatial smoothed seismicity. Here we present the final results of our study to be used for the new Italian seismic hazard map.

  20. Seismic tomography investigation of the Down Ampney fault research site

    International Nuclear Information System (INIS)

    Jackson, P.D.; Greenwood, P.G.; Raines, M.G.; Rainsbury, M.P.

    1991-01-01

    High resolution tomographic cross-hole seismic surveys have been designed and undertaken for fault characterisation in mudrocks at a higher resolution than is currently used in site investigations. Compressional waves were generated at a frequency of 1.04 kHz and a wavelength of 1.6 m in the formation, and were used to tomographically image a normally faulted clay sequence (Oxford Clay and Kellaways Beds) overlying limestone. The fault plane and lithologies are clearly visible in the tomograms, a 10% difference in velocity between the Oxford Clay and Kellaways Beds, being particularly prominent. A zone of 5% lower ''tomographic - velocity'' was observed to correspond with the fault zone within the Oxford Clay (as predicted from the geological logging of the core) which indicates substantial alteration that could be fluid affected. Geological constraints were found to be a crucial imput to the tomographic inversion, and examples show erroneous results that can arise. Seismic attenuation was very low (reflection observed from 80 m depth) and larger ranges could have been used to investigate larger scale geological structures. (author)

  1. Automatic picking of direct P, S seismic phases and fault zone head waves

    Science.gov (United States)

    Ross, Z. E.; Ben-Zion, Y.

    2014-10-01

    We develop a set of algorithms for automatic detection and picking of direct P and S waves, as well as fault zone head waves (FZHW), generated by earthquakes on faults that separate different lithologies and recorded by local seismic networks. The S-wave picks are performed using polarization analysis and related filters to remove P-wave energy from the seismograms, and utilize STA/LTA and kurtosis detectors in tandem to lock on the phase arrival. The early portions of P waveforms are processed with STA/LTA, kurtosis and skewness detectors for possible first-arriving FZHW. Identification and picking of direct P and FZHW is performed by a multistage algorithm that accounts for basic characteristics (motion polarities, time difference, sharpness and amplitudes) of the two phases. The algorithm is shown to perform well on synthetic seismograms produced by a model with a velocity contrast across the fault, and observed data generated by earthquakes along the Parkfield section of the San Andreas fault and the Hayward fault. The developed techniques can be used for systematic processing of large seismic waveform data sets recorded near major faults.

  2. Implications from palaeoseismological investigations at the Markgrafneusiedl Fault (Vienna Basin, Austria for seismic hazard assessment

    Directory of Open Access Journals (Sweden)

    E. Hintersberger

    2018-02-01

    slip rates of 0.02–0.05 mm a−1 derived from the trenches compare well to geomorphically derived slip rates of 0.02–0.09 mm a−1. Magnitude estimates from fault dimensions suggest that the largest earthquakes observed in the trenches activated the entire fault surface of the MF including the basal detachment that links the normal fault with the VBTF. The most important implications of these palaeoseismological results for seismic hazard assessment are as follows. (1 The MF is an active seismic source, capable of rupturing the surface despite the lack of historical earthquakes. (2 The MF is kinematically and geologically equivalent to a number of other splay faults of the VBTF. It is reasonable to assume that these faults are potential sources of large earthquakes as well. The frequency of strong earthquakes near Vienna is therefore expected to be significantly higher than the earthquake frequency reconstructed for the MF alone. (3 Although rare events, the potential for earthquake magnitudes equal or greater than M = 7.0 in the Vienna Basin should be considered in seismic hazard studies.

  3. Implications from palaeoseismological investigations at the Markgrafneusiedl Fault (Vienna Basin, Austria) for seismic hazard assessment

    Science.gov (United States)

    Hintersberger, Esther; Decker, Kurt; Lomax, Johanna; Lüthgens, Christopher

    2018-02-01

    trenches compare well to geomorphically derived slip rates of 0.02-0.09 mm a-1. Magnitude estimates from fault dimensions suggest that the largest earthquakes observed in the trenches activated the entire fault surface of the MF including the basal detachment that links the normal fault with the VBTF. The most important implications of these palaeoseismological results for seismic hazard assessment are as follows. (1) The MF is an active seismic source, capable of rupturing the surface despite the lack of historical earthquakes. (2) The MF is kinematically and geologically equivalent to a number of other splay faults of the VBTF. It is reasonable to assume that these faults are potential sources of large earthquakes as well. The frequency of strong earthquakes near Vienna is therefore expected to be significantly higher than the earthquake frequency reconstructed for the MF alone. (3) Although rare events, the potential for earthquake magnitudes equal or greater than M = 7.0 in the Vienna Basin should be considered in seismic hazard studies.

  4. A way to synchronize models with seismic faults for earthquake forecasting

    DEFF Research Database (Denmark)

    González, Á.; Gómez, J.B.; Vázquez-Prada, M.

    2006-01-01

    Numerical models are starting to be used for determining the future behaviour of seismic faults and fault networks. Their final goal would be to forecast future large earthquakes. In order to use them for this task, it is necessary to synchronize each model with the current status of the actual....... Earthquakes, though, provide indirect but measurable clues of the stress and strain status in the lithosphere, which should be helpful for the synchronization of the models. The rupture area is one of the measurable parameters of earthquakes. Here we explore how it can be used to at least synchronize fault...... models between themselves and forecast synthetic earthquakes. Our purpose here is to forecast synthetic earthquakes in a simple but stochastic (random) fault model. By imposing the rupture area of the synthetic earthquakes of this model on other models, the latter become partially synchronized...

  5. Seismic variability of subduction thrust faults: Insights from laboratory models

    Science.gov (United States)

    Corbi, F.; Funiciello, F.; Faccenna, C.; Ranalli, G.; Heuret, A.

    2011-06-01

    Laboratory models are realized to investigate the role of interface roughness, driving rate, and pressure on friction dynamics. The setup consists of a gelatin block driven at constant velocity over sand paper. The interface roughness is quantified in terms of amplitude and wavelength of protrusions, jointly expressed by a reference roughness parameter obtained by their product. Frictional behavior shows a systematic dependence on system parameters. Both stick slip and stable sliding occur, depending on driving rate and interface roughness. Stress drop and frequency of slip episodes vary directly and inversely, respectively, with the reference roughness parameter, reflecting the fundamental role for the amplitude of protrusions. An increase in pressure tends to favor stick slip. Static friction is a steeply decreasing function of the reference roughness parameter. The velocity strengthening/weakening parameter in the state- and rate-dependent dynamic friction law becomes negative for specific values of the reference roughness parameter which are intermediate with respect to the explored range. Despite the simplifications of the adopted setup, which does not address the problem of off-fault fracturing, a comparison of the experimental results with the depth distribution of seismic energy release along subduction thrust faults leads to the hypothesis that their behavior is primarily controlled by the depth- and time-dependent distribution of protrusions. A rough subduction fault at shallow depths, unable to produce significant seismicity because of low lithostatic pressure, evolves into a moderately rough, velocity-weakening fault at intermediate depths. The magnitude of events in this range is calibrated by the interplay between surface roughness and subduction rate. At larger depths, the roughness further decreases and stable sliding becomes gradually more predominant. Thus, although interplate seismicity is ultimately controlled by tectonic parameters (velocity of

  6. 3D Modelling of Seismically Active Parts of Underground Faults via Seismic Data Mining

    Science.gov (United States)

    Frantzeskakis, Theofanis; Konstantaras, Anthony

    2015-04-01

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

  7. Seismic Velocity Structure across the Hayward Fault Zone Near San Leandro, California

    Science.gov (United States)

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

    2017-12-01

    In Fall 2016 we conducted the East Bay Seismic Investigation, a NEHRP-funded collaboration between California State University, East Bay and the United State Geological Survey. The study produced a large volume of seismic data, allowing us to examine the subsurface across the East Bay plain and hills using a variety of geophysical methods. We know of no other survey performed in the past that has imaged this area, at this scale, and with this degree of resolution. Initial models show that seismic velocities of the Hayward Fault Zone (HFZ), the East Bay plain, and the East Bay hills are illuminated to depths of 5-6 km. We used explosive sources at 1-km intervals along a 15-km-long, NE-striking ( 055°), seismic line centered on the HFZ. Vertical- and horizontal-component sensors were spaced at 100 m intervals along the entire profile, with vertical-component sensors at 20 m intervals across mapped or suspected faults. Preliminary seismic refraction tomography across the HFZ, sensu lato, (includes sub-parallel, connected, and related faults), shows that the San Leandro Block (SLB) is a low-velocity feature in the upper 1-3 km, with nearly the same Vp as the adjacent Great Valley sediments to the east, and low Vs values. In our initial analysis we can trace the SLB and its bounding faults (Hayward, Chabot) nearly vertically, to at least 2-4 km depth. Similarly, preliminary migrated reflection images suggest that many if not all of the peripheral reverse, strike-slip and oblique-slip faults of the wider HFZ dip toward the SLB, into a curtain of relocated epicenters that define the HFZ at depth, indicative of a `flower-structure'. Preliminary Vs tomography identifies another apparently weak zone at depth, located about 1.5 km east of the San Leandro shoreline, that may represent the northward continuation of the Silver Creek Fault. Centered 4 km from the Bay, there is a distinctive, 2 km-wide, uplifted, horst-like, high-velocity structure (both Vp & Vs) that bounds the

  8. Seismic anisotropy in the vicinity of the Alpine fault, New Zealand, estimated by seismic interferometry

    Science.gov (United States)

    Takagi, R.; Okada, T.; Yoshida, K.; Townend, J.; Boese, C. M.; Baratin, L. M.; Chamberlain, C. J.; Savage, M. K.

    2016-12-01

    We estimate shear wave velocity anisotropy in shallow crust near the Alpine fault using seismic interferometry of borehole vertical arrays. We utilized four borehole observations: two sensors are deployed in two boreholes of the Deep Fault Drilling Project in the hanging wall side, and the other two sites are located in the footwall side. Surface sensors deployed just above each borehole are used to make vertical arrays. Crosscorrelating rotated horizontal seismograms observed by the borehole and surface sensors, we extracted polarized shear waves propagating from the bottom to the surface of each borehole. The extracted shear waves show polarization angle dependence of travel time, indicating shear wave anisotropy between the two sensors. In the hanging wall side, the estimated fast shear wave directions are parallel to the Alpine fault. Strong anisotropy of 20% is observed at the site within 100 m from the Alpine fault. The hanging wall consists of mylonite and schist characterized by fault parallel foliation. In addition, an acoustic borehole imaging reveals fractures parallel to the Alpine fault. The fault parallel anisotropy suggest structural anisotropy is predominant in the hanging wall, demonstrating consistency of geological and seismological observations. In the footwall side, on the other hand, the angle between the fast direction and the strike of the Alpine fault is 33-40 degrees. Since the footwall is composed of granitoid that may not have planar structure, stress induced anisotropy is possibly predominant. The direction of maximum horizontal stress (SHmax) estimated by focal mechanisms of regional earthquakes is 55 degrees of the Alpine fault. Possible interpretation of the difference between the fast direction and SHmax direction is depth rotation of stress field near the Alpine fault. Similar depth rotation of stress field is also observed in the SAFOD borehole at the San Andreas fault.

  9. Transpressive mantle uplift at large offset oceanic transform faults

    Science.gov (United States)

    Maia, M.; Briais, A.; Brunelli, D.; Ligi, M.; Sichel, S. E.; Campos, T.

    2017-12-01

    Large-offset transform faults deform due to changes in plate motions and local processes. At the St. Paul transform, in the Equatorial Atlantic, a large body of ultramafic rocks composed of variably serpentinized and mylonitized peridotites is presently being tectonically uplifted. We recently discovered that the origin of the regional mantle uplift is linked to long-standing compressive stresses along the transform fault (1). A positive flower structure, mainly made of mylonitized mantle rocks, can be recognized on the 200 km large push-up ridge. Compressive earthquakes mechanisms reveal seismically active thrust faults on the southern flank of the ridge . The regional transpressive stress field affects a large portion of the ridge segment south of the transform, as revealed by the presence of faults and dykes striking obliquely to the direction of the central ridge axis. A smaller thrust, affecting recent sediments, was mapped south of this segment, suggesting a regional active compressive stress field. The transpressive stress field is interpreted to derive from the propagation of the Mid-Atlantic Ridge (MAR) segment into the transform domain as a response to the enhanced melt supply at the ridge axis. The propagation forced the migration and segmentation of the transform fault southward and the formation of restraining step-overs. The process started after a counterclockwise change in plate motion at 11 Ma initially resulting in extensive stress of the transform domain. A flexural transverse ridge formed in response. Shortly after plate reorganization, the MAR segment started to propagate southwards due to the interaction of the ridge and the Sierra Leone thermal anomaly. 1- Maia et al., 2016. Extreme mantle uplift and exhumation along a transpressive transform fault Nat. Geo. doi:10.1038/ngeo2759

  10. Hypothesis for the mechanics and seismic behaviour of low-angle normal faults: the example of the Altotiberina fault Northern Apennines

    Directory of Open Access Journals (Sweden)

    C. Collettini

    2002-06-01

    Full Text Available Widespread mapping of low-angle normal faults in areas of former continental extension continues to prompt debate as to whether such structures may be seismically active at very low dips (? <30 °in the upper continental crust.The Northern Apennines provide an example where an active low-angle normal fault (Altotiberina fault, ATFcan be studied.A set of commercial seismic reflection profiles plus deep boreholes have been used to constrain the geometry of the fault at depth.These data have been integrated with a microseismic survey showing that part of the microseismicity (M <3.0is consistent with the geometry of the ATF as imaged by depth converted seismic reflection profiles.Frictional fault mechanics under Byerlee ?s friction coefficient and vertical ? 1 (constrained from the inversion of the focal mechanismsdefines the peculiar condition for reactivation of the ATF:small values of differential stress,? 1 ?? 3 <28 MPa,relatively high value of tensile strength of the fault surrounding rocks (T ~10 MPaand tensile fluid overpressure P f >? 3 (i.e.? v >0.93.The short-lived attainment of P f >? 3 along small fault portions,in an area characterised by large amounts of CO2,account for the microseismic activity located along the ATF,which occurs on rupture surfaces in the range of 10 ??10 ? 3 km 2..

  11. Do scaly clays control seismicity on faulted shale rocks?

    Science.gov (United States)

    Orellana, Luis Felipe; Scuderi, Marco M.; Collettini, Cristiano; Violay, Marie

    2018-04-01

    One of the major challenges regarding the disposal of radioactive waste in geological formations is to ensure isolation of radioactive contamination from the environment and the population. Shales are suitable candidates as geological barriers. However, the presence of tectonic faults within clay formations put the long-term safety of geological repositories into question. In this study, we carry out frictional experiments on intact samples of Opalinus Clay, i.e. the host rock for nuclear waste storage in Switzerland. We report experimental evidence suggesting that scaly clays form at low normal stress (≤20 MPa), at sub-seismic velocities (≤300 μm/s) and is related to pre-existing bedding planes with an ongoing process where frictional sliding is the controlling deformation mechanism. We have found that scaly clays show a velocity-weakening and -strengthening behaviour, low frictional strength, and poor re-strengthening over time, conditions required to allow the potential nucleation and propagation of earthquakes within the scaly clays portion of the formation. The strong similarities between the microstructures of natural and experimental scaly clays suggest important implications for the slip behaviour of shallow faults in shales. If natural and anthropogenic perturbations modify the stress conditions of the fault zone, earthquakes might have the potential to nucleate within zones of scaly clays controlling the seismicity of the clay-rich tectonic system, thus, potentially compromising the long-term safeness of geological repositories situated in shales.

  12. Seismic Imaging of the West Napa Fault in Napa, California

    Science.gov (United States)

    Goldman, M.; Catchings, R.; Chan, J. H.; Sickler, R. R.; Nevitt, J. M.; Criley, C.

    2017-12-01

    In October 2016, we acquired high-resolution P- and S-wave seismic data along a 120-m-long, SW-NE-trending profile in Napa, California. Our seismic survey was designed to image a strand of the West Napa Fault Zone (WNFZ), which ruptured during the 24 August 2014 Mw 6.0 South Napa Earthquake. We separately acquired P- and S-wave data at every station using multiple hammer hits, which were edited and stacked into individual shot gathers in the lab. Each shot was co-located with and recorded by 118 P-wave (40-Hz) geophones, spaced at 1 m, and by 180 S-wave (4.5-Hz) geophones, spaced at 1 m. We developed both P- and S-wave tomographic velocity models, as well as Poisson's ratio and a Vp/Vs ratio models. We observed a well-defined zone of elevated Vp/Vs ratios below about 10 m depth, centered beneath the observed surface rupture. P-wave reflection images show that the fault forms a flower-structure in the upper few tens of meters. This method has been shown to delineate fault structures even in areas of rough terrain.

  13. Evidence for chaotic fault interactions in the seismicity of the San Andreas fault and Nankai trough

    Science.gov (United States)

    Huang, Jie; Turcotte, D. L.

    1990-01-01

    The dynamical behavior introduced by fault interactions is examined here using a simple spring-loaded, slider-block model with velocity-weakening friction. The model consists of two slider blocks coupled to each other and to a constant-velocity driver by elastic springs. For an asymmetric system in which the frictional forces on the two blocks are not equal, the solutions exhibit chaotic behavior. The system's behavior over a range of parameter values seems to be generally analogous to that of weakly coupled segments of an active fault. Similarities between the model simulations and observed patterns of seismicity on the south central San Andreas fault in California and in the Nankai trough along the coast of southwestern Japan.

  14. Postglacial seismic activity along the Isovaara-Riikonkumpu fault complex

    Science.gov (United States)

    Ojala, Antti E. K.; Mattila, Jussi; Ruskeeniemi, Timo; Palmu, Jukka-Pekka; Lindberg, Antero; Hänninen, Pekka; Sutinen, Raimo

    2017-10-01

    Analysis of airborne LiDAR-based digital elevation models (DEMs), trenching of Quaternary deposits, and diamond drilling through faulted bedrock was conducted to characterize the geological structure and full slip profiles of the Isovaara-Riikonkumpu postglacial fault (PGF) complex in northern Finland. The PGF systems are recognized from LiDAR DEMs as a complex of surface ruptures striking SW-NE, cutting through late-Weichselian till, and associated with several postglacial landslides within 10 km. Evidence from the terrain rupture characteristics, the deformed and folded structure of late-Weichselian till, and the 14C age of 11,300 cal BP from buried organic matter underneath the Sotka landslide indicates a postglacial origin of the Riikonkumpu fault (PGF). The fracture frequency and lithology of drill cores and fault geometry in the trench log indicate that the Riikonkumpu PGF dips to WNW with a dip angle of 40-45° at the Riikonkumpu site and close to 60° at the Riikonvaara site. A fault length of 19 km and the mean and maximum cumulative vertical displacement of 1.3 m and 4.1 m, respectively, of the Riikonkumpu PGF system indicate that the fault potentially hosted an earthquake with a moment magnitude MW ≈ 6.7-7.3 assuming that slip was accumulated in one seismic event. Our interpretation further suggests that the Riikonkumpu PGF system is linked to the Isovaara PGF system and that, together, they form a larger Isovaara-Riikonkumpu fault complex. Relationships between the 38-km-long rupture of the Isovaara-Riikonkumpu complex and the fault offset parameters, with cumulative displacement of 1.5 and 8.3 m, respectively, indicate that the earthquake(s) contributing to the PGF complex potentially had a moment magnitude of MW ≈ 6.9-7.5. In order to adequately sample the uncertainty space, the moment magnitude was also estimated for each major segment within the Isovaara-Riikonkumpu PGF complex. These estimates vary roughly between MW ≈ 5-8 for the individual

  15. Use of controlled dynamic impacts on hierarchically structured seismically hazardous faults for seismically safe relaxation of shear stresses

    Science.gov (United States)

    Ruzhich, Valery V.; Psakhie, Sergey G.; Levina, Elena A.; Shilko, Evgeny V.; Grigoriev, Alexandr S.

    2017-12-01

    In the paper we briefly outline the experience in forecasting catastrophic earthquakes and the general problems in ensuring seismic safety. The purpose of our long-term research is the development and improvement of the methods of man-caused impacts on large-scale fault segments to safely reduce the negative effect of seismodynamic failure. Various laboratory and large-scale field experiments were carried out in the segments of tectonic faults in Baikal rift zone and in main cracks in block-structured ice cove of Lake Baikal using the developed measuring systems and special software for identification and treatment of deformation response of faulty segments to man-caused impacts. The results of the study let us to ground the necessity of development of servo-controlled technologies, which are able to provide changing the shear resistance and deformation regime of fault zone segments by applying vibrational and pulse triggering impacts. We suppose that the use of triggering impacts in highly stressed segments of active faults will promote transferring the geodynamic state of these segments from a metastable to a more stable and safe state.

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

    Science.gov (United States)

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

    2016-04-01

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

  17. DIAGNOSTICS OF META-INSTABLE STATE OF SEISMICALLY ACTIVE FAULT

    Directory of Open Access Journals (Sweden)

    S. A. Bornyakov

    2017-01-01

    Full Text Available Based on the results of a laboratory simulation of the seismic fault reactivation by “stick-slip” process, it was shown that the system of two blocks just before an impulse offset goes through the meta-instable dynamic state, with early and late stages of meta-instability [Ma et al., 2012]. In the first stage the offset begins in slow stationary mode with slow stresses relaxation on contact between blocks. In the second stage of the “accelerated synergies” strain rate increases and, subsequently, the deformation process through a process of self-organization came to dynamic impulse offset. The experimental results were used for interpretation of the results of spectral analysis of the deformation monitoring data. The data were held within the southern part ofLakeBaikal, where Kultuk earthquake (27.08.2008, Ms=6.1. took place. Its epicenter was located in the South end zone of the main Sayan fault. Monitoring of deformations of rocks was carried out from April to November2008 in tunnel, located at30 km from the epicenter of the earthquake. The time series data was divided into month periods and then the periods were processed by the method of spectral analysis. The results showed that before the earthquake has ordered view spectrogram, whereas in other time intervals, both before and after the earthquake such orderliness in spectrograms is missing. An ordered view spectrograms for deformation monitoring data can be interpreted as a consequence of the self-organiza­tion of deformation process in the transition of seismically active fault into meta-unstable before the Kultuk earthquake.

  18. Improving fault image by determination of optimum seismic survey parameters using ray-based modeling

    Science.gov (United States)

    Saffarzadeh, Sadegh; Javaherian, Abdolrahim; Hasani, Hossein; Talebi, Mohammad Ali

    2018-06-01

    In complex structures such as faults, salt domes and reefs, specifying the survey parameters is more challenging and critical owing to the complicated wave field behavior involved in such structures. In the petroleum industry, detecting faults has become crucial for reservoir potential where faults can act as traps for hydrocarbon. In this regard, seismic survey modeling is employed to construct a model close to the real structure, and obtain very realistic synthetic seismic data. Seismic modeling software, the velocity model and parameters pre-determined by conventional methods enable a seismic survey designer to run a shot-by-shot virtual survey operation. A reliable velocity model of structures can be constructed by integrating the 2D seismic data, geological reports and the well information. The effects of various survey designs can be investigated by the analysis of illumination maps and flower plots. Also, seismic processing of the synthetic data output can describe the target image using different survey parameters. Therefore, seismic modeling is one of the most economical ways to establish and test the optimum acquisition parameters to obtain the best image when dealing with complex geological structures. The primary objective of this study is to design a proper 3D seismic survey orientation to achieve fault zone structures through ray-tracing seismic modeling. The results prove that a seismic survey designer can enhance the image of fault planes in a seismic section by utilizing the proposed modeling and processing approach.

  19. Seismic and aseismic fault slip in response to fluid injection observed during field experiments at meter scale

    Science.gov (United States)

    Cappa, F.; Guglielmi, Y.; De Barros, L.; Wynants-Morel, N.; Duboeuf, L.

    2017-12-01

    During fluid injection, the observations of an enlarging cloud of seismicity are generally explained by a direct response to the pore pressure diffusion in a permeable fractured rock. However, fluid injection can also induce large aseismic deformations which provide an alternative mechanism for triggering and driving seismicity. Despite the importance of these two mechanisms during fluid injection, there are few studies on the effects of fluid pressure on the partitioning between seismic and aseismic motions under controlled field experiments. Here, we describe in-situ meter-scale experiments measuring synchronously the fluid pressure, the fault motions and the seismicity directly in a fault zone stimulated by controlled fluid injection at 280 m depth in carbonate rocks. The experiments were conducted in a gallery of an underground laboratory in south of France (LSBB, http://lsbb.eu). Thanks to the proximal monitoring at high-frequency, our data show that the fluid overpressure mainly induces a dilatant aseismic slip (several tens of microns up to a millimeter) at the injection. A sparse seismicity (-4 laws, we simulated an experiment and investigated the relative contribution of the fluid pressure diffusion and stress transfer on the seismic and aseismic fault behavior. The model reproduces the hydromechanical data measured at injection, and show that the aseismic slip induced by fluid injection propagates outside the pressurized zone where accumulated shear stress develops, and potentially triggers seismicity. Our models also show that the permeability enhancement and friction evolution are essential to explain the fault slip behavior. Our experimental results are consistent with large-scale observations of fault motions at geothermal sites (Wei et al., 2015; Cornet, 2016), and suggest that controlled field experiments at meter-scale are important for better assessing the role of fluid pressure in natural and human-induced earthquakes.

  20. Geomechanical Modeling of Fault Responses and the Potential for Notable Seismic Events during Underground CO2 Injection

    Science.gov (United States)

    Rutqvist, J.; Cappa, F.; Mazzoldi, A.; Rinaldi, A.

    2012-12-01

    The importance of geomechanics associated with large-scale geologic carbon storage (GCS) operations is now widely recognized. There are concerns related to the potential for triggering notable (felt) seismic events and how such events could impact the long-term integrity of a CO2 repository (as well as how it could impact the public perception of GCS). In this context, we review a number of modeling studies and field observations related to the potential for injection-induced fault reactivations and seismic events. We present recent model simulations of CO2 injection and fault reactivation, including both aseismic and seismic fault responses. The model simulations were conducted using a slip weakening fault model enabling sudden (seismic) fault rupture, and some of the numerical analyses were extended to fully dynamic modeling of seismic source, wave propagation, and ground motion. The model simulations illustrated what it will take to create a magnitude 3 or 4 earthquake that would not result in any significant damage at the groundsurface, but could raise concerns in the local community and could also affect the deep containment of the stored CO2. The analyses show that the local in situ stress field, fault orientation, fault strength, and injection induced overpressure are critical factors in determining the likelihood and magnitude of such an event. We like to clarify though that in our modeling we had to apply very high injection pressure to be able to intentionally induce any fault reactivation. Consequently, our model simulations represent extreme cases, which in a real GCS operation could be avoided by estimating maximum sustainable injection pressure and carefully controlling the injection pressure. In fact, no notable seismic event has been reported from any of the current CO2 storage projects, although some unfelt microseismic activities have been detected by geophones. On the other hand, potential future commercial GCS operations from large power plants

  1. Southern San Andreas Fault seismicity is consistent with the Gutenberg-Richter magnitude-frequency distribution

    Science.gov (United States)

    Page, Morgan T.; Felzer, Karen

    2015-01-01

    The magnitudes of any collection of earthquakes nucleating in a region are generally observed to follow the Gutenberg-Richter (G-R) distribution. On some major faults, however, paleoseismic rates are higher than a G-R extrapolation from the modern rate of small earthquakes would predict. This, along with other observations, led to formulation of the characteristic earthquake hypothesis, which holds that the rate of small to moderate earthquakes is permanently low on large faults relative to the large-earthquake rate (Wesnousky et al., 1983; Schwartz and Coppersmith, 1984). We examine the rate difference between recent small to moderate earthquakes on the southern San Andreas fault (SSAF) and the paleoseismic record, hypothesizing that the discrepancy can be explained as a rate change in time rather than a deviation from G-R statistics. We find that with reasonable assumptions, the rate changes necessary to bring the small and large earthquake rates into alignment agree with the size of rate changes seen in epidemic-type aftershock sequence (ETAS) modeling, where aftershock triggering of large earthquakes drives strong fluctuations in the seismicity rates for earthquakes of all magnitudes. The necessary rate changes are also comparable to rate changes observed for other faults worldwide. These results are consistent with paleoseismic observations of temporally clustered bursts of large earthquakes on the SSAF and the absence of M greater than or equal to 7 earthquakes on the SSAF since 1857.

  2. Active fault and other geological studies for seismic assessment: present state and problems

    International Nuclear Information System (INIS)

    Kakimi, Toshihiro

    1997-01-01

    Evaluation system of earthquakes from an active fault is, in Japan, based on the characteristic earthquake model of a wide sense that postulates essentially the same (nearly the maximum) magnitude and recurrence interval during the recent geological times. Earthquake magnitude M is estimated by empirical relations among M, surface rupture length L, and surface fault displacement D per event of the earthquake faults on land in Japan. Recurrence interval R of faulting/earthquake is calculated from D and the long-term slip rate S of a fault as R=D/S. Grouping or segmentation of complicatedly distributed faults is an important, but difficult problem in order to distinguish a seismogenic fault unit corresponding to an individual characteristic earthquake. If the time t of the latest event is obtained, the 'cautiousness' of a fault can be judged from R-t or t/R. According to this idea, several faults whose t/R exceed 0.5 have been designated as the 'precaution faults' having higher probability of earthquake occurrence than the others. A part of above evaluation has been introduced at first into the seismic-safety examination system of NPPs in 1978. According to the progress of research on active faults, the weight of interest in respect to the seismic hazard assessment shifted gradually from the historic data to the fault data. Most of recent seismic hazard maps have been prepared in consideration with active faults on land in Japan. Since the occurrence of the 1995 Hyogoken-Nanbu earthquake, social attention has been concentrated upon the seismic hazard due to active faults, because this event was generated from a well-known active fault zone that had been warned as a 'precaution fault'. In this paper, a few recent topics on other geological and geotechnical researches aiming at improving the seismic safety of NPPs in Japan were also introduced. (J.P.N.)

  3. Active fault and other geological studies for seismic assessment: present state and problems

    Energy Technology Data Exchange (ETDEWEB)

    Kakimi, Toshihiro [Nuclear Power Engineering Corp., Tokyo (Japan)

    1997-03-01

    Evaluation system of earthquakes from an active fault is, in Japan, based on the characteristic earthquake model of a wide sense that postulates essentially the same (nearly the maximum) magnitude and recurrence interval during the recent geological times. Earthquake magnitude M is estimated by empirical relations among M, surface rupture length L, and surface fault displacement D per event of the earthquake faults on land in Japan. Recurrence interval R of faulting/earthquake is calculated from D and the long-term slip rate S of a fault as R=D/S. Grouping or segmentation of complicatedly distributed faults is an important, but difficult problem in order to distinguish a seismogenic fault unit corresponding to an individual characteristic earthquake. If the time t of the latest event is obtained, the `cautiousness` of a fault can be judged from R-t or t/R. According to this idea, several faults whose t/R exceed 0.5 have been designated as the `precaution faults` having higher probability of earthquake occurrence than the others. A part of above evaluation has been introduced at first into the seismic-safety examination system of NPPs in 1978. According to the progress of research on active faults, the weight of interest in respect to the seismic hazard assessment shifted gradually from the historic data to the fault data. Most of recent seismic hazard maps have been prepared in consideration with active faults on land in Japan. Since the occurrence of the 1995 Hyogoken-Nanbu earthquake, social attention has been concentrated upon the seismic hazard due to active faults, because this event was generated from a well-known active fault zone that had been warned as a `precaution fault`. In this paper, a few recent topics on other geological and geotechnical researches aiming at improving the seismic safety of NPPs in Japan were also introduced. (J.P.N.)

  4. Transposing an active fault database into a seismic hazard fault model for nuclear facilities. Pt. 1. Building a database of potentially active faults (BDFA) for metropolitan France

    Energy Technology Data Exchange (ETDEWEB)

    Jomard, Herve; Cushing, Edward Marc; Baize, Stephane; Chartier, Thomas [IRSN - Institute of Radiological Protection and Nuclear Safety, Fontenay-aux-Roses (France); Palumbo, Luigi; David, Claire [Neodyme, Joue les Tours (France)

    2017-07-01

    The French Institute for Radiation Protection and Nuclear Safety (IRSN), with the support of the Ministry of Environment, compiled a database (BDFA) to define and characterize known potentially active faults of metropolitan France. The general structure of BDFA is presented in this paper. BDFA reports to date 136 faults and represents a first step toward the implementation of seismic source models that would be used for both deterministic and probabilistic seismic hazard calculations. A robustness index was introduced, highlighting that less than 15% of the database is controlled by reasonably complete data sets. An example of transposing BDFA into a fault source model for PSHA (probabilistic seismic hazard analysis) calculation is presented for the Upper Rhine Graben (eastern France) and exploited in the companion paper (Chartier et al., 2017, hereafter Part 2) in order to illustrate ongoing challenges for probabilistic fault-based seismic hazard calculations.

  5. Seismic cycle and seismic risk of an active faults network: the Corinth rift case (Greece)

    International Nuclear Information System (INIS)

    Boiselet, Aurelien

    2014-01-01

    The Corinth rift (Greece) is one of the regions with the highest strain rates (16 mm/y extension rate) in the Euro-Mediterranean area and as such it has long been identified as a site of major importance for earthquake studies in Europe (20 years of research by the Corinth Rift Laboratory and 4 years of in-depth studies by the ANR-SISCOR project). This enhanced knowledge, acquired in particular, in the western part of the Gulf of Corinth (CRL region), an area about 50 by 40 km 2 , between the city of Patras to the west and the city of Aigion to the east, provides an excellent opportunity to compare fault-based (FB) and classical seismo-tectonic (ST) approaches currently used in seismic hazard assessment studies. An homogeneous earthquake catalogue was thus constructed for the purpose of this study along with a comprehensive database of all relevant geological, geodetic and geophysical information available in the literature and recently collected within the ANR-SISCOR project. The homogenized Mw earthquake catalogue is composed of data from the National Observatory of Athens and from the university of Thessaloniki as well as data acquired through historical and instrumental work performed within the ANR-SISCOR group for the CRL region. A frequency magnitude analysis confirms that seismicity rates are governed by Gutenberg-Richter (GR) statistic for 1.2 =6 earthquakes were computed for the region of study. Time dependent models (Brownian Passage time and Weibull probability distributions) were also explored. The probability (normalized by area) of a M≥6.0 earthquake is found to be greater in the CRL region compared to the eastern part of the Corinth rift. Probability estimates corresponding to the 16. and 84. percentile are also provided, as a means of representing the range of uncertainties in the results. Probability estimates based on the ST-approach are then compared to those based on the FB approach approach. In general ST tends to overestimate probabilities

  6. "Handling" seismic hazard: 3D printing of California Faults

    Science.gov (United States)

    Kyriakopoulos, C.; Potter, M.; Richards-Dinger, K. B.

    2017-12-01

    As earth scientists, we face the challenge of how to explain and represent our work and achievements to the general public. Nowadays, this problem is partially alleviated by the use of modern visualization tools such as advanced scientific software (Paraview.org), high resolution monitors, elaborate video simulations, and even 3D Virtual Reality goggles. However, the ability to manipulate and examine a physical object in 3D is still an important tool to connect better with the public. For that reason, we are presenting a scaled 3D printed version of the complex network of earthquake faults active in California based on that used by the Uniform California Earthquake Rupture Forecast 3 (UCERF3) (Field et al., 2013). We start from the fault geometry in the UCERF3.1 deformation model files. These files contain information such as the coordinates of the surface traces of the faults, dip angle, and depth extent. The fault specified in the above files are triangulated at 1km resolution and exported as a facet (.fac) file. The facet file is later imported into the Trelis 15.1 mesh generator (csimsoft.com). We use Trelis to perform the following three operations: First, we scale down the model so that 100 mm corresponds to 100km. Second, we "thicken" the walls of the faults; wall thickness of at least 1mm is necessary in 3D printing. We thicken fault geometry by 1mm on each side of the faults for a total of 2mm thickness. Third, we break down the model into parts that will fit the printing bed size ( 25 x 20mm). Finally, each part is exported in stereolithography format (.stl). For our project, we are using the 3D printing facility within the Creat'R Lab in the UC Riverside Orbach Science Library. The 3D printer is a MakerBot Replicator Desktop, 5th Generation. The resolution of print is 0.2mm (Standard quality). The printing material is the MakerBot PLA Filament, 1.75 mm diameter, large Spool, green. The most complex part of the display model requires approximately 17

  7. Time-lapse imaging of fault properties at seismogenic depth using repeating earthquakes, active sources and seismic ambient noise

    Science.gov (United States)

    Cheng, Xin

    2009-12-01

    The time-varying stress field of fault systems at seismogenic depths plays the mort important role in controlling the sequencing and nucleation of seismic events. Using seismic observations from repeating earthquakes, controlled active sources and seismic ambient noise, five studies at four different fault systems across North America, Central Japan, North and mid-West China are presented to describe our efforts to measure such time dependent structural properties. Repeating and similar earthquakes are hunted and analyzed to study the post-seismic fault relaxation at the aftershock zone of the 1984 M 6.8 western Nagano and the 1976 M 7.8 Tangshan earthquakes. The lack of observed repeating earthquakes at western Nagano is attributed to the absence of a well developed weak fault zone, suggesting that the fault damage zone has been almost completely healed. In contrast, the high percentage of similar and repeating events found at Tangshan suggest the existence of mature fault zones characterized by stable creep under steady tectonic loading. At the Parkfield region of the San Andreas Fault, repeating earthquake clusters and chemical explosions are used to construct a scatterer migration image based on the observation of systematic temporal variations in the seismic waveforms across the occurrence time of the 2004 M 6 Parkfield earthquake. Coseismic fluid charge or discharge in fractures caused by the Parkfield earthquake is used to explain the observed seismic scattering properties change at depth. In the same region, a controlled source cross-well experiment conducted at SAFOD pilot and main holes documents two large excursions in the travel time required for a shear wave to travel through the rock along a fixed pathway shortly before two rupture events, suggesting that they may be related to pre-rupture stress induced changes in crack properties. At central China, a tomographic inversion based on the theory of seismic ambient noise and coda wave interferometry

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

    Science.gov (United States)

    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

  9. Study of fault configuration related mysteries through multi seismic attribute analysis technique in Zamzama gas field area, southern Indus Basin, Pakistan

    Directory of Open Access Journals (Sweden)

    Shabeer Ahmed Abbasi

    2016-03-01

    Full Text Available Seismic attribute analysis approach has been applied for the interpretation and identification of fault geometry of Zamzama Gas Field. Zamzama gas field area, which lies in the vicinity of Kirthar fold and thrust belt, Southern Indus Basin of Pakistan. The Zamzama fault and its related structure have been predicted by applying the Average Energy Attribute, Instantaneous Frequency Attribute, relative Acoustic Impedance Attribute and Chaotic Reflection Attribute on the seismic line GHPK98A.34. The results have been confirmed by applying the spectral decomposition attribute on the same seismic line that reveal the geometric configuration of Zamzama structure. The fault is reverse and started from 0 s and ended at the depth of 2.5 s on the vertical seismic section. Hanging wall moves up along the fault plane under the action of eastward oriented stress, which formed a large north–south oriented and eastward verging thrusted anticline.

  10. Automatic reconstruction of fault networks from seismicity catalogs including location uncertainty

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Y.

    2013-07-01

    Within the framework of plate tectonics, the deformation that arises from the relative movement of two plates occurs across discontinuities in the earth's crust, known as fault zones. Active fault zones are the causal locations of most earthquakes, which suddenly release tectonic stresses within a very short time. In return, fault zones slowly grow by accumulating slip due to such earthquakes by cumulated damage at their tips, and by branching or linking between pre-existing faults of various sizes. Over the last decades, a large amount of knowledge has been acquired concerning the overall phenomenology and mechanics of individual faults and earthquakes: A deep physical and mechanical understanding of the links and interactions between and among them is still missing, however. One of the main issues lies in our failure to always succeed in assigning an earthquake to its causative fault. Using approaches based in pattern-recognition theory, more insight into the relationship between earthquakes and fault structure can be gained by developing an automatic fault network reconstruction approach using high resolution earthquake data sets at largely different scales and by considering individual event uncertainties. This thesis introduces the Anisotropic Clustering of Location Uncertainty Distributions (ACLUD) method to reconstruct active fault networks on the basis of both earthquake locations and their estimated individual uncertainties. This method consists in fitting a given set of hypocenters with an increasing amount of finite planes until the residuals of the fit compare with location uncertainties. After a massive search through the large solution space of possible reconstructed fault networks, six different validation procedures are applied in order to select the corresponding best fault network. Two of the validation steps (cross-validation and Bayesian Information Criterion (BIC)) process the fit residuals, while the four others look for solutions that

  11. Probabilistic seismic hazard assessment for the two layer fault system of Antalya (SW Turkey) area

    Science.gov (United States)

    Dipova, Nihat; Cangir, Bülent

    2017-09-01

    Southwest Turkey, along Mediterranean coast, is prone to large earthquakes resulting from subduction of the African plate under the Eurasian plate and shallow crustal faults. Maximum observed magnitude of subduction earthquakes is Mw = 6.5 whereas that of crustal earthquakes is Mw = 6.6. Crustal earthquakes are sourced from faults which are related with Isparta Angle and Cyprus Arc tectonic structures. The primary goal of this study is to assess seismic hazard for Antalya area (SW Turkey) using a probabilistic approach. A new earthquake catalog for Antalya area, with unified moment magnitude scale, was prepared in the scope of the study. Seismicity of the area has been evaluated by the Gutenberg-Richter recurrence relationship. For hazard computation, CRISIS2007 software was used following the standard Cornell-McGuire methodology. Attenuation model developed by Youngs et al. Seismol Res Lett 68(1):58-73, (1997) was used for deep subduction earthquakes and Chiou and Youngs Earthq Spectra 24(1):173-215, (2008) model was used for shallow crustal earthquakes. A seismic hazard map was developed for peak ground acceleration and for rock ground with a hazard level of a 10% probability of exceedance in 50 years. Results of the study show that peak ground acceleration values on bedrock change between 0.215 and 0.23 g in the center of Antalya.

  12. Large scale phononic metamaterials for seismic isolation

    International Nuclear Information System (INIS)

    Aravantinos-Zafiris, N.; Sigalas, M. M.

    2015-01-01

    In this work, we numerically examine structures that could be characterized as large scale phononic metamaterials. These novel structures could have band gaps in the frequency spectrum of seismic waves when their dimensions are chosen appropriately, thus raising the belief that they could be serious candidates for seismic isolation structures. Different and easy to fabricate structures were examined made from construction materials such as concrete and steel. The well-known finite difference time domain method is used in our calculations in order to calculate the band structures of the proposed metamaterials

  13. Fault Mechanics and Post-seismic Deformation at Bam, SE Iran

    Science.gov (United States)

    Wimpenny, S. E.; Copley, A.

    2017-12-01

    The extent to which aseismic deformation relaxes co-seismic stress changes on a fault zone is fundamental to assessing the future seismic hazard following any earthquake, and in understanding the mechanical behaviour of faults. We used models of stress-driven afterslip and visco-elastic relaxation, in conjunction with a dense time series of post-seismic InSAR measurements, to show that there has been minimal release of co-seismic stress changes through post-seismic deformation following the 2003 Mw 6.6 Bam earthquake. Our modelling indicates that the faults at Bam may remain predominantly locked, and that the co- plus inter-seismically accumulated elastic strain stored down-dip of the 2003 rupture patch may be released in a future Mw 6 earthquake. Modelling also suggests parts of the fault that experienced post-seismic creep between 2003-2009 overlapped with areas that also slipped co-seismically. Our observations and models also provide an opportunity to probe how aseismic fault slip leads to the growth of topography at Bam. We find that, for our modelled afterslip distribution to be consistent with forming the sharp step in the local topography at Bam over repeated earthquake cycles, and also to be consistent with the geodetic observations, requires either (1) far-field tectonic loading equivalent to a 2-10 MPa deviatoric stress acting across the fault system, which suggests it supports stresses 60-100 times less than classical views of static fault strength, or (2) that the fault surface has some form of mechanical anisotropy, potentially related to corrugations on the fault plane, that controls the sense of slip.

  14. Purires and Picagres faults and its relationship with the 1990 Puriscal seismic sequence

    International Nuclear Information System (INIS)

    Montero, Walter; Rojas, Wilfredo

    2014-01-01

    The system of active faults in the region between the southern flank of the Montes del Aguacate and the northwest flank of the Talamanca mountain range was re-evaluated and defined in relation to the seismic activity that occurred between the end of March 1990 and the beginning of 1991. Aerial photographs of different scales of the Instituto Geografico Nacional de Costa Rica, aerial photographs of scale 1: 40000 of the TERRA project, of the Centro Nacional Geoambiental and infrared photos of scale 1: 40000 of the Mission CARTA 2003, of the Programa Nacional de Investigaciones Aerotransportadas y Sensores Remotos (PRIAS) were reviewed. Morphotectonic, structural and geological information related to the various faults was obtained with field work. A set of faults within the study area were determined with the neotectonic investigation. Several of these faults continue outside the zone both to the northwest within the Montes del Aguacate, and to the southeast to the NW foothills of the Cordillera de Talamanca. The superficial focus seismicity (<20 km), which occurred in the Puriscal area during 1990, was revised from previous studies, whose base information comes from the Red Sismologica Nacional (RSN, UCR-ICE). The relationship between the superficial seismic sequence and the defined faults was determined, allowing to conclude that the main seismic sources that originated the seismicity were the Purires and Picagres faults. A minor seismicity was related to the faults Jaris, Bajos de Jorco, Zapote and Junquillo [es

  15. Interseismic Coupling and Seismic Potential along the Indo-Burmese Arc and the Sagaing fault

    Science.gov (United States)

    Earnest, A.

    2017-12-01

    The Indo-burmese arc is formed by the oblique subduction of the Indian plate under the Eurasia. This region is a transition zone between the main Himalayan collision belt and the Andaman subduction zone. This obliquity causes strain partitioning which causes separation of a sliver plate, the Burma Plate. Considering the geomorphic, tectonic and geophysical signatures, IBR comprises all the structural features of an active subduction zone, whereas the present day tectonics of this region is perplexing. Ni et al. [1989] and Rao and Kalpana [2005] suggested that the subduction might have stopped in recent times or continues relatively in an aseismic fashion. This is implied by the NNE compressional stress orientations, instead of its downdip direction. The focal mechanism stress inversions show distinct stress fields above and below the 90 km depth. It is widely believed that the partitioning of Indian-Eurasia plate motion along the Indo-buremse arc and the Sagaing fault region the reason for earthquake occurrence in this region. The relative motion of 36mm/yr, between India and Eurasia, is partitioned across the Sagaing fault through a dextral movement of ˜20mm/yr and remaining velocity is accommodated at the Churachandapur-Mao fault (CMF) through dextral motion. The CMF and its surroundings are considered as seismically a low hazard region, an observation made from the absence of significant earthquakes and lack of field evidences. This made Kundu and Gahalaut [2013] to propose that the motion across the CMF happens in an aseismic manner. Recently, based on GPS studies Steckler et al. [2016] suggested that the region is still actively subducting and the presence of a locked megathrust plate boundary depicts the region as highly vulnerable for large magnitude seismic activities. Our study, based on various geodetic solutions and earthquake slip vectors, focus on interseisimic block models for the Indo-burmese arc and Sagaing fault region so as to model the crustal

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

    Science.gov (United States)

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

  17. Micromechanics and statistics of slipping events in a granular seismic fault model

    Energy Technology Data Exchange (ETDEWEB)

    Arcangelis, L de [Department of Information Engineering and CNISM, Second University of Naples, Aversa (Italy); Ciamarra, M Pica [CNR-SPIN, Dipartimento di Scienze Fisiche, Universita di Napoli Federico II (Italy); Lippiello, E; Godano, C, E-mail: dearcangelis@na.infn.it [Department of Environmental Sciences and CNISM, Second University of Naples, Caserta (Italy)

    2011-09-15

    The stick-slip is investigated in a seismic fault model made of a confined granular system under shear stress via three dimensional Molecular Dynamics simulations. We study the statistics of slipping events and, in particular, the dependence of the distribution on model parameters. The distribution consistently exhibits two regimes: an initial power law and a bump at large slips. The initial power law decay is in agreement with the the Gutenberg-Richter law characterizing real seismic occurrence. The exponent of the initial regime is quite independent of model parameters and its value is in agreement with experimental results. Conversely, the position of the bump is solely controlled by the ratio of the drive elastic constant and the system size. Large slips also become less probable in absence of fault gouge and tend to disappear for stiff drives. A two-time force-force correlation function, and a susceptibility related to the system response to pressure changes, characterize the micromechanics of slipping events. The correlation function unveils the micromechanical changes occurring both during microslips and slips. The mechanical susceptibility encodes the magnitude of the incoming microslip. Numerical results for the cellular-automaton version of the spring block model confirm the parameter dependence observed for size distribution in the granular model.

  18. Active intra-basin faulting in the Northern Basin of Lake Malawi from seismic reflection data

    Science.gov (United States)

    Shillington, D. J.; Chindandali, P. R. N.; Scholz, C. A.; Ebinger, C. J.; Onyango, E. A.; Peterson, K.; Gaherty, J. B.; Nyblade, A.; Accardo, N. J.; McCartney, T.; Oliva, S. J.; Kamihanda, G.; Ferdinand, R.; Salima, J.; Mruma, A. H.

    2016-12-01

    Many questions remain about the development and evolution of fault systems in weakly extended rifts, including the relative roles of border faults and intra-basin faults, and segmentation at various scales. The northern Lake Malawi (Nyasa) rift in the East African Rift System is an early stage rift exhibiting pronounced tectonic segmentation, which is defined by 100-km-long border faults. The basins also contain a series of intrabasinal faults and associated synrift sediments. The occurrence of the 2009 Karonga Earthquake Sequence on one of these intrabasinal faults indicates that some of them are active. Here we present new multichannel seismic reflection data from the Northern Basin of the Malawi Rift collected in 2015 as a part of the SEGMeNT (Study of Extension and maGmatism in Malawi aNd Tanzania) project. This rift basin is bound on its east side by the west-dipping Livingstone border fault. Over 650 km of seismic reflection profiles were acquired in the Northern Basin using a 500 to 1540 cu in air gun array and a 1200- to 1500-m seismic streamer. Dip lines image a series of north-south oriented west-dipping intra-basin faults and basement reflections up to 5 s twtt near the border fault. Cumulative offsets on intra-basin faults decrease to the west. The largest intra-basin fault has a vertical displacement of >2 s two-way travel time, indicating that it has accommodated significant total extension. Some of these intra-basin faults offset the lake bottom and the youngest sediments by up to 50 s twtt ( 37 m), demonstrating they are still active. The two largest intra-basin faults exhibit the largest offsets of young sediments and also correspond to the area of highest seismicity based on analysis of seismic data from the 89-station SEGMeNT onshore/offshore network (see Peterson et al, this session). Fault patterns in MCS profiles vary along the basin, suggesting a smaller scale of segmentation of faults within the basin; these variations in fault patterns

  19. Effects of Strike-Slip Fault Segmentation on Earthquake Energy and Seismic Hazard

    Science.gov (United States)

    Madden, E. H.; Cooke, M. L.; Savage, H. M.; McBeck, J.

    2014-12-01

    Many major strike-slip faults are segmented along strike, including those along plate boundaries in California and Turkey. Failure of distinct fault segments at depth may be the source of multiple pulses of seismic radiation observed for single earthquakes. However, how and when segmentation affects fault behavior and energy release is the basis of many outstanding questions related to the physics of faulting and seismic hazard. These include the probability for a single earthquake to rupture multiple fault segments and the effects of segmentation on earthquake magnitude, radiated seismic energy, and ground motions. Using numerical models, we quantify components of the earthquake energy budget, including the tectonic work acting externally on the system, the energy of internal rock strain, the energy required to overcome fault strength and initiate slip, the energy required to overcome frictional resistance during slip, and the radiated seismic energy. We compare the energy budgets of systems of two en echelon fault segments with various spacing that include both releasing and restraining steps. First, we allow the fault segments to fail simultaneously and capture the effects of segmentation geometry on the earthquake energy budget and on the efficiency with which applied displacement is accommodated. Assuming that higher efficiency correlates with higher probability for a single, larger earthquake, this approach has utility for assessing the seismic hazard of segmented faults. Second, we nucleate slip along a weak portion of one fault segment and let the quasi-static rupture propagate across the system. Allowing fractures to form near faults in these models shows that damage develops within releasing steps and promotes slip along the second fault, while damage develops outside of restraining steps and can prohibit slip along the second fault. Work is consumed in both the propagation of and frictional slip along these new fractures, impacting the energy available

  20. Seismic fragility analysis of a CANDU containment structure for near-fault ground motions

    International Nuclear Information System (INIS)

    Choi, In Kil; Choun, Young Sun; Seo, Jeong Moon; Ahn, Seong Moon

    2005-01-01

    The R. G. 1.60 spectrum used for the seismic design of Korean nuclear power plants provides a generally conservative design basis due to its broadband nature. A survey on some of the Quaternary fault segments near Korean nuclear power plants is ongoing. It is likely that these faults will be identified as active ones. If the faults are confirmed as active ones, it will be necessary to reevaluate the seismic safety of the nuclear power plants located near these faults. The probability based scenario earthquakes were identified as near-field earthquakes. In general, the near-fault ground motion records exhibit a distinctive long period pulse like time history with very high peak velocities. These features are induced by the slip of the earthquake fault. Near-fault ground motions, which have caused much of the damage in recent major earthquakes, can be characterized by a pulse-like motion that exposes the structure to a high input energy at the beginning of the motion. It is necessary to estimate the near-fault ground motion effects on the nuclear power plant structures and components located near the faults. In this study, the seismic fragility analysis of a CANDU containment structure was performed based on the results of nonlinear dynamic time-history analyses

  1. Probabilistic Seismic Hazard Analysis of Victoria, British Columbia, Canada: Considering an Active Leech River Fault

    Science.gov (United States)

    Kukovica, J.; Molnar, S.; Ghofrani, H.

    2017-12-01

    The Leech River fault is situated on Vancouver Island near the city of Victoria, British Columbia, Canada. The 60km transpressional reverse fault zone runs east to west along the southern tip of Vancouver Island, dividing the lithologic units of Jurassic-Cretaceous Leech River Complex schists to the north and Eocene Metchosin Formation basalts to the south. This fault system poses a considerable hazard due to its proximity to Victoria and 3 major hydroelectric dams. The Canadian seismic hazard model for the 2015 National Building Code of Canada (NBCC) considered the fault system to be inactive. However, recent paleoseismic evidence suggests there to be at least 2 surface-rupturing events to have exceeded a moment magnitude (M) of 6.5 within the last 15,000 years (Morell et al. 2017). We perform a Probabilistic Seismic Hazard Analysis (PSHA) for the city of Victoria with consideration of the Leech River fault as an active source. A PSHA for Victoria which replicates the 2015 NBCC estimates is accomplished to calibrate our PSHA procedure. The same seismic source zones, magnitude recurrence parameters, and Ground Motion Prediction Equations (GMPEs) are used. We replicate the uniform hazard spectrum for a probability of exceedance of 2% in 50 years for a 500 km radial area around Victoria. An active Leech River fault zone is then added; known length and dip. We are determining magnitude recurrence parameters based on a Gutenberg-Richter relationship for the Leech River fault from various catalogues of the recorded seismicity (M 2-3) within the fault's vicinity and the proposed paleoseismic events. We seek to understand whether inclusion of an active Leech River fault source will significantly increase the probabilistic seismic hazard for Victoria. Morell et al. 2017. Quaternary rupture of a crustal fault beneath Victoria, British Columbia, Canada. GSA Today, 27, doi: 10.1130/GSATG291A.1

  2. Ultra-thin clay layers facilitate seismic slip in carbonate faults.

    Science.gov (United States)

    Smeraglia, Luca; Billi, Andrea; Carminati, Eugenio; Cavallo, Andrea; Di Toro, Giulio; Spagnuolo, Elena; Zorzi, Federico

    2017-04-06

    Many earthquakes propagate up to the Earth's surface producing surface ruptures. Seismic slip propagation is facilitated by along-fault low dynamic frictional resistance, which is controlled by a number of physico-chemical lubrication mechanisms. In particular, rotary shear experiments conducted at seismic slip rates (1 ms -1 ) show that phyllosilicates can facilitate co-seismic slip along faults during earthquakes. This evidence is crucial for hazard assessment along oceanic subduction zones, where pelagic clays participate in seismic slip propagation. Conversely, the reason why, in continental domains, co-seismic slip along faults can propagate up to the Earth's surface is still poorly understood. We document the occurrence of micrometer-thick phyllosilicate-bearing layers along a carbonate-hosted seismogenic extensional fault in the central Apennines, Italy. Using friction experiments, we demonstrate that, at seismic slip rates (1 ms -1 ), similar calcite gouges with pre-existing phyllosilicate-bearing (clay content ≤3 wt.%) micro-layers weaken faster than calcite gouges or mixed calcite-phyllosilicate gouges. We thus propose that, within calcite gouge, ultra-low clay content (≤3 wt.%) localized along micrometer-thick layers can facilitate seismic slip propagation during earthquakes in continental domains, possibly enhancing surface displacement.

  3. Implications of Seismically Active Fault Structures in Ankay and Alaotra Regions of Northern and Central Madagascar

    Science.gov (United States)

    Malloy, S.; Stamps, D. S.

    2017-12-01

    The purpose of the study is to gain a better understanding of the seismically active fault structures in central and northern Madagascar. We study the Ankay and Lake Alaotra regions of Madagascar, which are segmented by multiple faults that strike N-S. In general, normal seismic events occur on faults bounding the Alaotra-Ankay rift basin where Quaternary alluvium is present. Due to this pattern and moderate amounts of low magnitude seismic activity along these faults, it is hypothesized the region currently undergoes E-W extension. In this work we test how variations in fault strength and net slip changes influence expected crustal movement in the region. Using the Coulomb stress failure point as a test of strength we are able to model the Alaotra-Ankay region using MATLAB Coulomb 3.3.01. This program allows us to define realistic Poisson's ratio and Young's modulus of mapped rock compositions in the region, i.e. paragneiss and orthogneiss, create 3D fault geometries, and calculate static stress changes with coinciding surface displacements. We impose slip along multiple faults and calculate seismic moment that we balance by the 3 observed earthquake magnitudes available in the USGS CMT database. Our calculations of surface displacements indicate 1-3 millimeters could be observed across the Alaotra-Ankay rift. These values are within the observable range of precision GNSS observations, therefore our results will guide future research into the area and direct potential GNSS station installation.

  4. Multicomponent seismic loss estimation on the North Anatolian Fault Zone (Turkey)

    Science.gov (United States)

    karimzadeh Naghshineh, S.; Askan, A.; Erberik, M. A.; Yakut, A.

    2015-12-01

    Seismic loss estimation is essential to incorporate seismic risk of structures into an efficient decision-making framework. Evaluation of seismic damage of structures requires a multidisciplinary approach including earthquake source characterization, seismological prediction of earthquake-induced ground motions, prediction of structural responses exposed to ground shaking, and finally estimation of induced damage to structures. As the study region, Erzincan, a city on the eastern part of Turkey is selected which is located in the conjunction of three active strike-slip faults as North Anatolian Fault, North East Anatolian Fault and Ovacik fault. Erzincan city center is in a pull-apart basin underlain by soft sediments that has experienced devastating earthquakes such as the 27 December 1939 (Ms=8.0) and the 13 March 1992 (Mw=6.6) events, resulting in extensive amount of physical as well as economical losses. These losses are attributed to not only the high seismicity of the area but also as a result of the seismic vulnerability of the constructed environment. This study focuses on the seismic damage estimation of Erzincan using both regional seismicity and local building information. For this purpose, first, ground motion records are selected from a set of scenario events simulated with the stochastic finite fault methodology using regional seismicity parameters. Then, existing building stock are classified into specified groups represented with equivalent single-degree-of-freedom systems. Through these models, the inelastic dynamic structural responses are investigated with non-linear time history analysis. To assess the potential seismic damage in the study area, fragility curves for the classified structural types are derived. Finally, the estimated damage is compared with the observed damage during the 1992 Erzincan earthquake. The results are observed to have a reasonable match indicating the efficiency of the ground motion simulations and building analyses.

  5. Acoustic and seismic imaging of the Adra Fault (NE Alboran Sea: in search of the source of the 1910 Adra earthquake

    Directory of Open Access Journals (Sweden)

    E. Gràcia

    2012-11-01

    Full Text Available Recently acquired swath-bathymetry data and high-resolution seismic reflection profiles offshore Adra (Almería, Spain reveal the surficial expression of a NW–SE trending 20 km-long fault, which we termed the Adra Fault. Seismic imaging across the structure depicts a sub-vertical fault reaching the seafloor surface and slightly dipping to the NE showing an along-axis structural variability. Our new data suggest normal displacement of the uppermost units with probably a lateral component. Radiocarbon dating of a gravity core located in the area indicates that seafloor sediments are of Holocene age, suggesting present-day tectonic activity. The NE Alboran Sea area is characterized by significant low-magnitude earthquakes and by historical records of moderate magnitude, such as the Mw = 6.1 1910 Adra Earthquake. The location, dimension and kinematics of the Adra Fault agree with the fault solution and magnitude of the 1910 Adra Earthquake, whose moment tensor analysis indicates normal-dextral motion. The fault seismic parameters indicate that the Adra Fault is a potential source of large magnitude (Mw ≤ 6.5 earthquakes, which represents an unreported seismic hazard for the neighbouring coastal areas.

  6. Steep-dip seismic imaging of the shallow San Andreas fault near Parkfield.

    Science.gov (United States)

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

    2001-11-16

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

  7. The Rock Record of Seismic Nucleation: examples from pseudotachylites beneath the Whipple Detachment Fault, eastern California

    Science.gov (United States)

    Ortega-Arroyo, D.; Behr, W. M.; Gentry, E.

    2017-12-01

    The mechanisms that lead to nucleation and dynamic weakening in the middle crust are not well understood. Proposed mechanisms include flash heating of asperities, thermal pressurization of pore fluids, dynamic instabilities, and fracture interactions. We investigate this issue in the rock record using exhumed mid-crustal rocks exposed beneath the Whipple Detachment fault (WDF) in eastern CA. Analysis of pseudotachylites (PS) beneath the WDF, representing paleo-earthquakes, reveal two types: Type 1 PS exhibit little to no precursory cataclasis and are concentrated along shear bands at the margins of feldspar-rich lenses embedded in more quartz-rich domains. These appear synkinematic with S-C fabrics in the surrounding mylonites and they exhibit finely dynamically recrystallized grains in quartz at their margins, suggesting coeval ductile deformation. By contrast, Type 2 PS occur along the principal slip surface of a brittle shear zone and show evidence for precursory cataclasis, brecciation, and fracturing. Some cataclasites inject into the host rock, forming eddies along the boundary with the PS. Slip appears to localize progressively into a 2 cm thick fault core, with PS concentrated primarily in the interior- the presence of solidified melt and fluidized cataclasite as clasts within the fault core suggests multiple slip events are preserved. We interpret the two types of pseudotachylites to represent different conditions and mechanisms of earthquake nucleation near the brittle-ductile transition (BDT). Type 1 PS are interpreted to represent nucleation in deeper sections of the BDT by failure along mineralogically-controlled stress concentrations hosted within an otherwise viscously deforming mylonite. Our data suggest that these do not develop into large-magnitude EQ's because seismic slip is dampened into the surrounding quartz-rich viscous matrix; instead they may represent deep microseismicity and/or seismic tremor. By contrast, Type 2 PS are interpreted to

  8. Groundwater penetrating radar and high resolution seismic for locating shallow faults in unconsolidated sediments

    International Nuclear Information System (INIS)

    Wyatt, D.E.

    1993-01-01

    Faults in shallow, unconsolidated sediments, particularly in coastal plain settings, are very difficult to discern during subsurface exploration yet have critical impact to groundwater flow, contaminant transport and geotechnical evaluations. This paper presents a case study using cross-over geophysical technologies in an area where shallow faulting is probable and known contamination exists. A comparison is made between Wenner and dipole-dipole resistivity data, ground penetrating radar, and high resolution seismic data. Data from these methods were verified with a cone penetrometer investigation for subsurface lithology and compared to existing monitoring well data. Interpretations from these techniques are compared with actual and theoretical shallow faulting found in the literature. The results of this study suggests that (1) the CPT study, combined with the monitoring well data may suggest that discontinuities in correlatable zones may indicate that faulting is present (2) the addition of the Wenner and dipole-dipole data may further suggest that offset zones exist in the shallow subsurface but not allow specific fault planes or fault stranding to be mapped (3) the high resolution seismic data will image faults to within a few feet of the surface but does not have the resolution to identify the faulting on the scale of our models, however it will suggest locations for upward continuation of faulted zones (4) offset 100 MHz and 200 MHz CMP GPR will image zones and features that may be fault planes and strands similar to our models (5) 300 MHz GPR will image higher resolution features that may suggest the presence of deeper faults and strands, and (6) the combination of all of the tools in this study, particularly the GPR and seismic may allow for the mapping of small scale, shallow faulting in unconsolidated sediments

  9. The hydraulic structure of the Gole Larghe Fault Zone (Italian Southern Alps) through the seismic cycle

    Science.gov (United States)

    Bistacchi, A.; Mittempergher, S.; Di Toro, G.; Smith, S. A. F.; Garofalo, P. S.

    2017-12-01

    The 600 m-thick, strike slip Gole Larghe Fault Zone (GLFZ) experienced several hundred seismic slip events at c. 8 km depth, well-documented by numerous pseudotachylytes, was then exhumed and is now exposed in beautiful and very continuous outcrops. The fault zone was also characterized by hydrous fluid flow during the seismic cycle, demonstrated by alteration halos and precipitation of hydrothermal minerals in veins and cataclasites. We have characterized the GLFZ with > 2 km of scanlines and semi-automatic mapping of faults and fractures on several photogrammetric 3D Digital Outcrop Models (3D DOMs). This allowed us obtaining 3D Discrete Fracture Network (DFN) models, based on robust probability density functions for parameters of fault and fracture sets, and simulating the fault zone hydraulic properties. In addition, the correlation between evidences of fluid flow and the fault/fracture network parameters have been studied with a geostatistical approach, allowing generating more realistic time-varying permeability models of the fault zone. Based on this dataset, we have developed a FEM hydraulic model of the GLFZ for a period of some tens of years, covering one seismic event and a postseismic period. The higher permeability is attained in the syn- to early post-seismic period, when fractures are (re)opened by off-fault deformation, then permeability decreases in the postseismic due to fracture sealing. The flow model yields a flow pattern consistent with the observed alteration/mineralization pattern and a marked channelling of fluid flow in the inner part of the fault zone, due to permeability anisotropy related to the spatial arrangement of different fracture sets. Amongst possible seismological applications of our study, we will discuss the possibility to evaluate the coseismic fracture intensity due to off-fault damage, and the heterogeneity and evolution of mechanical parameters due to fluid-rock interaction.

  10. Microtremor survey to investigate seismic vulnerability around the Seulimum Fault, Aceh Besar-Indonesia

    Science.gov (United States)

    Simanjuntak, Andrean V. H.; Muksin, Umar; Rahmayani, Febrina

    2018-05-01

    The Seulimeum Fault has generated inland earthquake with magnitude larger than M 6.5 that destroyed houses in the Lamteuba and Krueng Raya Villages. Earthquakes along the Seulimeum Fault are mostly right lateral strike-slip characterizing the Fault. The understanding of the seismic vulnerability around the highly populated Banda Aceh City and the villages in Aceh Besar is therefore very important since the city, and the villages are very close to the Seulimeum Fault. A microtremor survey has been conducted to investigate seismic vulnerability in the area closed to the Seulimeum Fault. The waveforms of the microtremor have been recorded in Lamteuba and Kreung Raya villages, Aceh Besar at 20 sites for 7 days from August 14, 2017 with the interval of measurement of 1 km. The waveforms recorded for 30 minutes at each site by using one Taurus Seismometer in miniseed format. The data has been analyzing by using Geopsy to obtain the Horizontal-Vertical Spectral Ratio for each site. The seismic vulnerability is considered to be high if the value of the Horizontal-Vertical Spectral Ratio is high. The HVSR values are then interpolated to obtain the seismic vulnerability map. The preliminary result shows high seismic vulnerability in the area around the first site.

  11. Spatial clustering and repeating of seismic events observed along the 1976 Tangshan fault, north China

    Science.gov (United States)

    Li, Le; Chen, Qi-Fu; Cheng, Xin; Niu, Fenglin

    2007-12-01

    Spatial and temporal features of the seismicity occurring along the Tangshan fault in 2001-2006 were investigated with data recorded by the Beijing metropolitan digital Seismic Network. The relocated seismicity with the double difference method clearly exhibits a dextral bend in the middle of the fault. More than 85% of the earthquakes were found in the two clusters forming the northern segment where relatively small coseismic slips were observed during the 1976 M7.8 earthquake. The b values calculated from the seismicity occurring in the northern and southern segment are 1.03 +/- 0.02 and 0.85 +/- 0.03, respectively. The distinct seismicity and b values are probably the collective effect of the fault geometry and the regional stress field that has an ENE-WSW oriented compression. Using cross-correlation and fine relocation analyses, we also identified a total of 21 doublets and 25 multiplets that make up >50% of the total seismicity. Most of the sequences are aperiodic with recurrence intervals varying from a few minutes to hundreds of days. Based on a quasi-periodic sequence, we obtained a fault slip rate of <=2.6 mm/yr at ~15 km, which is consistent with surface GPS measurements.

  12. Discriminating between natural versus induced seismicity from long-term deformation history of intraplate faults.

    Science.gov (United States)

    Magnani, Maria Beatrice; Blanpied, Michael L; DeShon, Heather R; Hornbach, Matthew J

    2017-11-01

    To assess whether recent seismicity is induced by human activity or is of natural origin, we analyze fault displacements on high-resolution seismic reflection profiles for two regions in the central United States (CUS): the Fort Worth Basin (FWB) of Texas and the northern Mississippi embayment (NME). Since 2009, earthquake activity in the CUS has increased markedly, and numerous publications suggest that this increase is primarily due to induced earthquakes caused by deep-well injection of wastewater, both flowback water from hydrofracturing operations and produced water accompanying hydrocarbon production. Alternatively, some argue that these earthquakes are natural and that the seismicity increase is a normal variation that occurs over millions of years. Our analysis shows that within the NME, faults deform both Quaternary alluvium and underlying sediments dating from Paleozoic through Tertiary, with displacement increasing with geologic unit age, documenting a long history of natural activity. In the FWB, a region of ongoing wastewater injection, basement faults show deformation of the Proterozoic and Paleozoic units, but little or no deformation of younger strata. Specifically, vertical displacements in the post-Pennsylvanian formations, if any, are below the resolution (~15 m) of the seismic data, far less than expected had these faults accumulated deformation over millions of years. Our results support the assertion that recent FWB earthquakes are of induced origin; this conclusion is entirely independent of analyses correlating seismicity and wastewater injection practices. To our knowledge, this is the first study to discriminate natural and induced seismicity using classical structural geology analysis techniques.

  13. Seismicity within the Irpinia Fault System As Monitored By Isnet (Irpinia Seismic Network) and Its Possible Relation with Fluid Storage

    Science.gov (United States)

    Festa, G.; Zollo, A.; Amoroso, O.; Ascione, A.; Colombelli, S.; Elia, L.; Emolo, A.; Martino, C.; Mazzoli, S.; Orefice, A.; Russo, G.

    2014-12-01

    ISNet (http://isnet.fisica.unina.it) is deployed in Southern Apennines along the active fault system responsible for the 1980, M 6.9 Irpinia earthquake. ISNet consists of 32 seismic stations equipped with both strong motion and velocimetric instruments (either broadband or short-period), with the aim of capture a broad set of seismic signals, from ambient noise to strong motion. Real time and near real time procedures run at ISNet with the goal of monitoring the seismicity, check possible space-time anomalies, detect seismic sequences and launch an earthquake early warning in the case of potential significant ground shaking in the area. To understand the role of fluids on the seismicity of the area, we investigated velocity and attenuation models. The former is built from accurate cross-correlation picking and S wave detection based onto polarization analysis. Joint inversion of both P and S arrival times is then based on a linearized multi-scale tomographic approach. Attenuation is instead obtained from inversion of displacement spectra, deconvolving for the source effect. High VP/VS and QS/QP >1 were found within a ~15 km wide rock volume where intense microseismicity is located. This indicates that concentration of seismicity is possibly controlled by high pore fluid pressure. This earthquake reservoir may come from a positive feedback between the seismic pumping that controls the fluid transmission through the fractured damage zone and the low permeability of cross fault barrier, increasing the fluid pore pressure within the fault bounded block. In this picture, sequences mostly occur at the base of this fluid rich layer. They show an anomalous pattern in the earthquake occurrence per magnitude classes; main events evolve with a complex source kinematics, as obtained from backprojection of apparent source time functions, indicating possible directivity effects. In this area sequences might be the key for understanding the transition between the deep

  14. Fault-Magma Interactions during Early Continental Rifting: Seismicity of the Magadi-Natron-Manyara basins, Africa

    Science.gov (United States)

    Weinstein, A.; Oliva, S. J.; Ebinger, C.; Aman, M.; Lambert, C.; Roecker, S. W.; Tiberi, C.; Muirhead, J.

    2017-12-01

    Although magmatism may occur during the earliest stages of continental rifting, its role in strain accommodation remains weakly constrained by largely 2D studies. We analyze seismicity data from a 13-month, 39-station broadband seismic array to determine the role of magma intrusion on state-of-stress and strain localization, and their along-strike variations. Precise earthquake locations using cluster analyses and a new 3D velocity model reveal lower crustal earthquakes along projections of steep border faults that degas CO2. Seismicity forms several disks interpreted as sills at 6-10 km below a monogenetic cone field. The sills overlie a lower crustal magma chamber that may feed eruptions at Oldoinyo Lengai volcano. After determining a new ML scaling relation, we determine a b-value of 0.87 ± 0.03. Focal mechanisms for 66 earthquakes, and a longer time period of relocated earthquakes from global arrays reveal an along-axis stress rotation of 50 o ( N150 oE) in the magmatically active zone. Using Kostrov summation of local and teleseismic mechanisms, we find opening directions of N122ºE and N92ºE north and south of the magmatically active zone. The stress rotation facilitates strain transfer from border fault systems, the locus of early stage deformation, to the zone of magma intrusion in the central rift. Our seismic, structural, and geochemistry results indicate that frequent lower crustal earthquakes are promoted by elevated pore pressures from volatile degassing along border faults, and hydraulic fracture around the margins of magma bodies. Earthquakes are largely driven by stress state around inflating magma bodies, and more dike intrusions with surface faulting, eruptions, and earthquakes are expected.

  15. Structural analysis of S-wave seismics around an urban sinkhole: evidence of enhanced dissolution in a strike-slip fault zone

    Directory of Open Access Journals (Sweden)

    S. H. Wadas

    2017-12-01

    Full Text Available In November 2010, a large sinkhole opened up in the urban area of Schmalkalden, Germany. To determine the key factors which benefited the development of this collapse structure and therefore the dissolution, we carried out several shear-wave reflection-seismic profiles around the sinkhole. In the seismic sections we see evidence of the Mesozoic tectonic movement in the form of a NW–SE striking, dextral strike-slip fault, known as the Heßleser Fault, which faulted and fractured the subsurface below the town. The strike-slip faulting created a zone of small blocks ( < 100 m in size, around which steep-dipping normal faults, reverse faults and a dense fracture network serve as fluid pathways for the artesian-confined groundwater. The faults also acted as barriers for horizontal groundwater flow perpendicular to the fault planes. Instead groundwater flows along the faults which serve as conduits and forms cavities in the Permian deposits below ca. 60 m depth. Mass movements and the resulting cavities lead to the formation of sinkholes and dissolution-induced depressions. Since the processes are still ongoing, the occurrence of a new sinkhole cannot be ruled out. This case study demonstrates how S-wave seismics can characterize a sinkhole and, together with geological information, can be used to study the processes that result in sinkhole formation, such as a near-surface fault zone located in soluble rocks. The more complex the fault geometry and interaction between faults, the more prone an area is to sinkhole occurrence.

  16. Hydrothermal fault zone mapping using seismic and electrical measurements

    Science.gov (United States)

    Onacha, Stephen Alumasa

    This dissertation presents a new method of using earthquakes and resistivity data to characterize permeable hydrothermal reservoirs. The method is applied to field examples from Casa Diablo in the Long Valley Caldera, California; Mt. Longonot, Kenya; and Krafla, Iceland. The new method has significant practical value in the exploration and production of geothermal energy. The method uses P- and S-wave velocity, S-wave polarization and splitting magnitude, resistivity and magnetotelluric (MT) strike directions to determine fracture-porosity and orientation. The conceptual model used to characterize the buried, fluid-circulating fault zones in hydrothermal systems is based on geological and fracture models. The method has been tested with field earthquake and resistivity data; core samples; temperature measurements; and, for the case of Krafla, with a drilled well. The use of resistivity and microearthquake measurements is based on theoretical formulation of shared porosity, anisotropy and polarization. The relation of resistivity and a double porosity-operator is solved using a basis function. The porosity-operator is used to generate a correlation function between P-wave velocity and resistivity. This correlation is then used to generate P-wave velocity from 2-D resistivity models. The resistivity models are generated from magnetotelluric (MT) by using the Non-Linear Conjugate Gradient (NLCG) inversion method. The seismic and electrical measurements used come from portable, multi station microearthquake (MEQ) monitoring networks and multi-profile, MT and transient electromagnetic (TEM) observation campaigns. The main conclusions in this dissertation are listed below: (1) Strong evidence exists for correlation between MT strike direction and anisotropy and MEQ S-wave splitting at sites close to fluid-filled fracture zones. (2) A porosity operator generated from a double porosity model has been used to generate valid P-wave velocity models from resistivity data. This

  17. Automated fault extraction and classification using 3-D seismic data for the Ekofisk field development

    Energy Technology Data Exchange (ETDEWEB)

    Signer, C.; Nickel, M.; Randen, T.; Saeter, T.; Soenneland, H.H.

    1998-12-31

    Mapping of fractures is important for the prediction of fluid flow in many reservoir types. The fluid flow depends mainly on the efficiency of the reservoir seals. Improved spatial mapping of the open and closed fracture systems will allow a better prediction of the fluid flow pattern. The primary objectives of this paper is to present fracture characterization at the reservoir scale combined with seismic facies mapping. The complexity of the giant Ekofisk field on the Norwegian continental shelf provides an ideal framework for testing the validity and the applicability of an automated seismic fault and fracture detection and mapping tool. The mapping of the faults can be based on seismic attribute grids, which means that attribute-responses related to faults are extracted along key horizons which were interpreted in the reservoir interval. 3 refs., 3 figs.

  18. Kinematics and Seismotectonics of the Montello Thrust Fault (Southeastern Alps, Italy) Revealed by Local GPS and Seismic Networks

    Science.gov (United States)

    Serpelloni, E.; Anderlini, L.; Cavaliere, A.; Danesi, S.; Pondrelli, S.; Salimbeni, S.; Danecek, P.; Massa, M.; Lovati, S.

    2014-12-01

    The southern Alps fold-and-thrust belt (FTB) in northern Italy is a tectonically active area accommodating large part of the ~N-S Adria-Eurasia plate convergence, that in the southeastern Alps ranges from 1.5 to 2.5 mm/yr, as constrained by a geodetically defined rotation pole. Because of the high seismic hazard of northeastern Italy, the area is well monitored at a regional scale by seismic and GPS networks. However, more localized seismotectonic and kinematic features, at the scale of the fault segments, are not yet resolved, limiting our knowledge about the seismic potential of the different fault segments belonging to the southeastern Alps FTB. Here we present the results obtained from the analysis of data collected during local seismic and geodetic experiments conducted installing denser geophysical networks across the Montello-Bassano-Belluno system, a segment of the FTB that is presently characterized by a lower sismicity rate with respect to the surrounding domains. The Montello anticline, which is the southernmost tectonic features of the southeastern Alps FTB (located ~15 km south of the mountain front), is a nice example of growing anticline associated with a blind thrust fault. However, how the Adria-Alps convergence is partitioned across the FTB and the seismic potential of the Montello thrust (the area has been struck by a Mw~6.5 in 1695 but the causative fault is still largely debated) remained still unresolved. The new, denser, GPS data show that this area is undergoing among the highest geodetic deformation rates of the entire south Alpine chain, with a steep velocity gradient across the Montello anticline. The earthquakes recorded during the experiment, precisely relocated with double difference methods, and the new earthquake focal mechanisms well correlate with available information about sub-surface geological structures and highlight the seismotectonic activity of the Montello thrust fault. We model the GPS velocities using elastic

  19. How Might Draining Lake Campotosto Affect Stress and Seismicity on the Monte Gorzano Normal Fault, Central Italy?

    Science.gov (United States)

    Verdecchia, A.; Deng, K.; Harrington, R. M.; Liu, Y.

    2017-12-01

    It is broadly accepted that large variations of water level in reservoirs may affect the stress state on nearby faults. While most studies consider the relationship between lake impoundment and the occurrence of large earthquakes or seismicity rate increases in the surrounding region, very few examples focus on the effects of lake drainage. The second largest reservoir in Europe, Lake Campotosto, is located on the hanging wall of the Monte Gorzano fault, an active normal fault responsible for at least two M ≥ 6 earthquakes in historical times. The northern part of this fault ruptured during the August 24, 2016, Mw 6.0 Amatrice earthquake, increasing the probability for a future large event on the southern section where an aftershock sequence is still ongoing. The proximity of the Campotosto reservoir to the active fault aroused general concern with respect to the stability of the three dams bounding the reservoir if the southern part of the Monte Gorzano fault produces a moderate earthquake. Local officials have proposed draining the reservoir as hazard mitigation strategy to avoid possible future catastrophes. In efforts to assess how draining the reservoir might affect earthquake nucleation on the fault, we use a finite-element poroelastic model to calculate the evolution of stress and pore pressure in terms of Coulomb stress changes that would be induced on the Monte Gorzano fault by emptying the Lake Campotosto reservoir. Preliminary results show that an instantaneous drainage of the lake will produce positive Coulomb stress changes, mostly on the shallower part of the fault (0 to 2 km), while a stress drop of the order of 0.2 bar is expected on the Monte Gorzano fault between 0 and 8 km depth. Earthquake hypocenters on the southern portion of the fault currently nucleate between 5 and 13 km depth, with activity distributed nearby the reservoir. Upcoming work will model the effects of varying fault geometry and elastic parameters, including geological

  20. Complex researches on substantiation of construction and seismic stability of large dams in seismic region

    International Nuclear Information System (INIS)

    Negmatullaev, S.Kh.; Yasunov, P.A.

    2001-01-01

    This article is devoted to complex researches on substantiation of construction and seismic stability of large dams (Nurec hydroelectric power station) in seismic region. Geological, seismological, model, and engineering investigations are discussed in this work. At construction of Nurec hydroelectric power station the rich experience is accumulated. This experience can be used in analogous seismically active regions at construction similar hydroelectric power stations.

  1. Multi-scale investigation into the mechanisms of fault mirror formation in seismically active carbonate rocks

    Science.gov (United States)

    Ohl, Markus; Chatzaras, Vasileios; Niemeijer, Andre; King, Helen; Drury, Martyn; Plümper, Oliver

    2017-04-01

    Mirror surfaces along principal slip zones in carbonate rocks have recently received considerable attention as they are thought to form during fault slip at seismic velocities and thus may be a marker for paleo-seismicity (Siman-Tov et al., 2013). Therefore, these structures represent an opportunity to improve our understanding of earthquake mechanics in carbonate faults. Recent investigations reported the formation of fault mirrors in natural rocks as well as in laboratory experiments and connected their occurrence to the development of nano-sized granular material (Spagnuolo et al., 2015). However, the underlying formation and deformation mechanisms of these fault mirrors are still poorly constrained and warrant further research. In order to understand the influence and significance of these fault products on the overall fault behavior, we analysed the micro-, and nanostructural inventory of natural fault samples containing mirror slip surfaces. Here we present first results on the possible formation mechanisms of fault mirrors and associated deformation mechanisms operating in the carbonate fault gouge from two seismically active fault zones in central Greece. Our study specifically focuses on mirror slip surfaces obtained from the Arkitsa fault in the Gulf of Evia and the Schinos fault in the Gulf of Corinth. The Schinos fault was reactivated by a magnitude 6.7 earthquake in 1981 while the Arkitsa fault is thought to have been reactivated by a magnitude 6.9 earthquake in 1894. Our investigations encompass a combination of state-of-the-art analytical techniques including X-ray computed tomography, focused ion beam scanning electron microscopy (FIB-SEM), transmission electron microscopy (TEM) and Raman spectroscopy. Using this multiscale analytical approach, we report decarbonation-reaction structures, considerable calcite twinning and grain welding immediately below the mirror slip surface. Grains or areas indicating decarbonation reactions show a foam

  2. Large-scale hydraulic structure of a seismogenic fault at 10 km depth (Gole Larghe Fault Zone, Italian Southern Alps)

    Science.gov (United States)

    Bistacchi, Andrea; Di Toro, Giulio; Smith, Steve; Mittempergher, Silvia; Garofalo, Paolo

    2014-05-01

    The definition of hydraulic properties of fault zones is a major issue in structural geology, seismology, and in several applications (hydrocarbons, hydrogeology, CO2 sequestration, etc.). The permeability of fault rocks can be measured in laboratory experiments, but its upscaling to large-scale structures is not straightforward. For instance, typical permeability of fine-grained fault rock samples is in the 10-18-10-20 m2 range, but, according to seismological estimates, the large-scale permeability of active fault zones can be as high as 10-10 m2. Solving this issue is difficult because in-situ measurements of large-scale permeability have been carried out just at relatively shallow depths - mainly in oil wells and exceptionally in active tectonic settings (e.g. SAFOD at 3 km), whilst deeper experiments have been performed only in the stable continental crust (e.g. KTB at 9 km). In this study, we apply discrete fracture-network (DFN) modelling techniques developed for shallow aquifers (mainly in nuclear waste storage projects like Yucca Mountain) and in the oil industry, in order to model the hydraulic structure of the Gole Larghe Fault Zone (GLFZ, Italian Southern Alps). This fault, now exposed in world-class glacier-polished outcrops, has been exhumed from ca. 8 km, where it was characterized by a well-documented seismic activity, but also by hydrous fluid flow evidenced by alteration halos and precipitation of hydrothermal minerals in veins and along cataclasites. The GLFZ does not show a classical seal structure that in other fault zones corresponds to a core zone characterized by fine-grained fault rocks. However, permeability is heterogeneous and the permeability tensor is strongly anisotropic due to fracture preferential orientation. We will show with numerical experiments that this hydraulic structure results in a channelized fluid flow (which is consistent with the observed hydrothermal alteration pattern). This results in a counterintuitive situation

  3. Fault specific GIS based seismic hazard maps for the Attica region, Greece

    Science.gov (United States)

    Deligiannakis, G.; Papanikolaou, I. D.; Roberts, G.

    2018-04-01

    Traditional seismic hazard assessment methods are based on the historical seismic records for the calculation of an annual probability of exceedance for a particular ground motion level. A new fault-specific seismic hazard assessment method is presented, in order to address problems related to the incompleteness and the inhomogeneity of the historical records and to obtain higher spatial resolution of hazard. This method is applied to the region of Attica, which is the most densely populated area in Greece, as nearly half of the country's population lives in Athens and its surrounding suburbs, in the Greater Athens area. The methodology is based on a database of 24 active faults that could cause damage to Attica in case of seismic rupture. This database provides information about the faults slip rates, lengths and expected magnitudes. The final output of the method is four fault-specific seismic hazard maps, showing the recurrence of expected intensities for each locality. These maps offer a high spatial resolution, as they consider the surface geology. Despite the fact that almost half of the Attica region lies on the lowest seismic risk zone according to the official seismic hazard zonation of Greece, different localities have repeatedly experienced strong ground motions during the last 15 kyrs. Moreover, the maximum recurrence for each intensity occurs in different localities across Attica. Highest recurrence for intensity VII (151-156 times over 15 kyrs, or up to a 96 year return period) is observed in the central part of the Athens basin. The maximum intensity VIII recurrence (115 times over 15 kyrs, or up to a 130 year return period) is observed in the western part of Attica, while the maximum intensity IX (73-77/15 kyrs, or a 195 year return period) and X (25-29/15 kyrs, or a 517 year return period) recurrences are observed near the South Alkyonides fault system, which dominates the strong ground motions hazard in the western part of the Attica mainland.

  4. New Geologic Data on the Seismic Risks of the Most Dangerous Fault on Shore in Central Japan, the Itoigawa-Shizuoka Tectonic Line Active Fault System

    Science.gov (United States)

    Okumura, K.; Kondo, H.; Toda, S.; Takada, K.; Kinoshita, H.

    2006-12-01

    Ten years have past since the first official assessment of the long-term seismic risks of the Itoigawa-Shizuoka tectonic line active fault system (ISTL) in 1996. The disaster caused by the1995 Kobe (Hyogo-ken-Nanbu) earthquake urged the Japanese government to initiated a national project to assess the long-term seismic risks of on-shore active faults using geologic information. ISTL was the first target of the 98 significant faults and the probability of a M7 to M8 event turned out to be the highest among them. After the 10 years of continued efforts to understand the ISTL, now it is getting ready to revise the assessment. Fault mapping and segmentation: The most active segment of the Gofukuji fault (~1 cm/yr left-lateral strike slip, R=500~800 yrs.) had been maped only for less than 10 km. Adjacent segments were much less active. This large slip on such a short segment was contradictory. However, detailed topographic study including Lidar survey revealed the length of the Gofukuji fault to be 25 km or more. High slip rate with frequent earthquakes may be restricted to the Gofukuji fault while the 1996 assessment modeled frequent >100 km rupture scenario. The geometry of the fault is controversial especially on the left-lateral strike-slip section of the ISTL. There are two models of high-angle Middel ISTL and low-angle Middle ISTL with slip partitioning. However, all geomorphic and shallow geologic data supports high-angle almost pure strike slip on the faults in the Middle ISTL. CRIEPI's 3- dimensional trenching in several sites as well as the previous results clearly demonstrated repeated pure strike-slip offset during past a few events. In Middle ISTL, there is no evidence of recent activity of pre-existing low-angle thrust faults that are inferred to be active from shallow seismic survey. Separation of high (~3000 m) mountain ranges and low (lack of reliable time constraints on past earthquakes. In order to solve this problem, we have carried out intensive

  5. Seismic Margin Assessment for Research Reactor using Fragility based Fault Tree Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Kwag, Shinyoung; Oh, Jinho; Lee, Jong-Min; Ryu, Jeong-Soo [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2016-10-15

    The research reactor has been often subjected to external hazards during the design lifetime. Especially, a seismic event can be one of significant threats to the failure of structure system of the research reactor. This failure is possibly extended to the direct core damage of the reactor. For this purpose, the fault tree for structural system failure leading to the core damage under an earthquake accident is developed. The failure probabilities of basic events are evaluated as fragility curves of log-normal distributions. Finally, the plant-level seismic margin is investigated by the fault tree analysis combining with fragility data and the critical path is identified. The plant-level probabilistic seismic margin assessment using the fragility based fault tree analysis was performed for quantifying the safety of research reactor to a seismic hazard. For this, the fault tree for structural system failure leading to the core damage of the reactor under a seismic accident was developed. The failure probabilities of basic events were evaluated as fragility curves of log-normal distributions.

  6. Seismic trapped modes in the oroville and san andreas fault zones.

    Science.gov (United States)

    Li, Y G; Leary, P; Aki, K; Malin, P

    1990-08-17

    Three-component borehole seismic profiling of the recently active Oroville, California, normal fault and microearthquake event recording with a near-fault three-component borehole seismometer on the San Andreas fault at Parkfield, California, have shown numerous instances of pronounced dispersive wave trains following the shear wave arrivals. These wave trains are interpreted as fault zone-trapped seismic modes. Parkfield earthquakes exciting trapped modes have been located as deep as 10 kilometers, as shallow as 4 kilometers, and extend 12 kilometers along the fault on either side of the recording station. Selected Oroville and Parkfield wave forms are modeled as the fundamental and first higher trapped SH modes of a narrow low-velocity layer at the fault. Modeling results suggest that the Oroville fault zone is 18 meters wide at depth and has a shear wave velocity of 1 kilometer per second, whereas at Parkfield, the fault gouge is 100 to 150 meters wide and has a shear wave velocity of 1.1 to 1.8 kilometers per second. These low-velocity layers are probably the rupture planes on which earthquakes occur.

  7. Estimation of Seismic Ground Motions and Attendant Potential Human Fatalities from Scenario Earthquakes on the Chishan Fault in Southern Taiwan

    Directory of Open Access Journals (Sweden)

    Kun-Sung Liu

    2017-01-01

    Full Text Available The purpose of this study is to estimate maximum ground motions in southern Taiwan as well as to assess potential human fatalities from scenario earthquakes on the Chishan active faults in this area. The resultant Shake Map patterns of maximum ground motion in a case of Mw 7.2 show the areas of PGA above 400 gals are located in the northeastern, central and northern parts of southwestern Kaohsiung as well as the southern part of central Tainan, as shown in the regions inside the yellow lines in the corresponding figure. Comparing cities with similar distances located in Tainan, Kaohsiung, and Pingtung to the Chishan fault, the cities in Tainan area have relatively greater PGA and PGV, due to large site response factors in Tainan area. Furthermore, seismic hazards in terms of PGA and PGV in the vicinity of the Chishan fault are not completely dominated by the Chishan fault. The main reason is that some areas located in the vicinity of the Chishan fault are marked with low site response amplification values from 0.55 - 1.1 and 0.67 - 1.22 for PGA and PGV, respectively. Finally, from estimation of potential human fatalities from scenario earthquakes on the Chishan active fault, it is noted that potential fatalities increase rapidly in people above age 45. Total fatalities reach a high peak in age groups of 55 - 64. Another to pay special attention is Kaohsiung City has more than 540 thousand households whose residences over 50 years old. In light of the results of this study, I urge both the municipal and central governments to take effective seismic hazard mitigation measures in the highly urbanized areas with a large number of old buildings in southern Taiwan.

  8. Structural analysis of S-wave seismics around an urban sinkhole: evidence of enhanced dissolution in a strike-slip fault zone

    Science.gov (United States)

    Wadas, Sonja H.; Tanner, David C.; Polom, Ulrich; Krawczyk, Charlotte M.

    2017-12-01

    In November 2010, a large sinkhole opened up in the urban area of Schmalkalden, Germany. To determine the key factors which benefited the development of this collapse structure and therefore the dissolution, we carried out several shear-wave reflection-seismic profiles around the sinkhole. In the seismic sections we see evidence of the Mesozoic tectonic movement in the form of a NW-SE striking, dextral strike-slip fault, known as the Heßleser Fault, which faulted and fractured the subsurface below the town. The strike-slip faulting created a zone of small blocks ( sinkholes and dissolution-induced depressions. Since the processes are still ongoing, the occurrence of a new sinkhole cannot be ruled out. This case study demonstrates how S-wave seismics can characterize a sinkhole and, together with geological information, can be used to study the processes that result in sinkhole formation, such as a near-surface fault zone located in soluble rocks. The more complex the fault geometry and interaction between faults, the more prone an area is to sinkhole occurrence.

  9. Dealing with completeness, structural hierarchy, and seismic coupling issues: three major challenges for #Fault2SHA

    Science.gov (United States)

    Valensise, Gianluca; Barba, Salvatore; Basili, Roberto; Bonini, Lorenzo; Burrato, Pierfrancesco; Carafa, Michele; Kastelic, Vanja; Fracassi, Umberto; Maesano, Francesco Emanuele; Tarabusi, Gabriele; Tiberti, Mara Monica; Vannoli, Paola

    2016-04-01

    The vast majority of active faulting studies are performed at the scale of individual, presumably seismogenic faults or fault strands. Most SHA approaches and models, however, require homogeneus information on potential earthquake sources over the entire tectonic domain encompassing the site(s) of interest. Although it is out of question that accurate SHA must rely on robust investigations of individual potential earthquake sources, it is only by gathering this information in regionally extensive databases that one can address some of the most outstanding issues in the use of #Fault2SHA. We will briefly recall three issues that are particularly relevant in the investigation of seismogenic faulting in southern Europe. A fundamental challenge is the completeness of the geologic record of active faulting. In most tectonic environments many potential seismogenic faults are blind or hidden, or deform the lower crust without leaving a discernible signal at the surface, or occur offshore, or slip so slowly that nontectonic erosional-depositional processes easily outpace their surface effects. Investigating only well-expressed faults is scientifically rewarding but also potentially misleading as it draws attention on the least insidious faults, leading to a potential underestimation of the regional earthquake potential. A further issue concerns the hierarchy of fault systems. Most active faults do not comprise seismogenic sources per se but are part of larger systems, and slip only in conjunction with the master fault of each system. In the most insidious cases, only secondary faults are expressed at the surface while the master fault lies hidden beneath them. This may result in an overestimation of the true number of seismogenic sources that occur in each region and in a biased identification of the characteristics of the main player in each system. Recent investigations of geologic and geodetic vs earthquake release budgets have shown that the "seismic coupling", which

  10. Study of the evolution of the seismic cycle of stress and strain associated to the El Salvador Fault Zone

    OpenAIRE

    Staller Vázquez, Alejandra

    2011-01-01

    • Central America: – Regional studies in Central America (Seismic Hazard). – El Salvador Fault Zone (ESFZ). – Aguacaliente‐Navarro Fault Zone (ANFZ), Central Valley of Costa Rica. – Haiti (seismic hazard) • Spain: – Regional‐Nacional studies of seismic hazards (applications to building codes, eurocode, emergency plans, etc.) – Betic range zone, south of Spain. – Ibero‐Maghrebi region (collision zone)

  11. Test on large-scale seismic isolation elements, 2

    International Nuclear Information System (INIS)

    Mazda, T.; Moteki, M.; Ishida, K.; Shiojiri, H.; Fujita, T.

    1991-01-01

    Seismic isolation test program of Central Research Inst. of Electric Power Industry (CRIEPI) to apply seismic isolation to Fast Breeder Reactor (FBR) plant was started in 1987. In this test program, demonstration test of seismic isolation elements was considered as one of the most important research items. Facilities for testing seismic isolation elements were built in Abiko Research Laboratory of CRIEPI. Various tests of large-scale seismic isolation elements were conducted up to this day. Many important test data to develop design technical guidelines was obtained. (author)

  12. Does seismic activity control carbon exchanges between transform-faults in old ocean crust and the deep sea? A hypothesis examined by the EU COST network FLOWS

    Science.gov (United States)

    Lever, M. A.

    2014-12-01

    The European Cooperation in Science and Technology (COST)-Action FLOWS (http://www.cost.eu/domains_actions/essem/Actions/ES1301) was initiated on the 25th of October 2013. It is a consortium formed by members of currently 14 COST countries and external partners striving to better understand the interplay between earthquakes and fluid flow at transform-faults in old oceanic crust. The recent occurrence of large earthquakes and discovery of deep fluid seepage calls for a revision of the postulated hydrogeological inactivity and low seismic activity of old oceanic transform-type plate boundaries, and indicates that earthquakes and fluid flow are intrinsically associated. This Action merges the expertise of a large number of research groups and supports the development of multidisciplinary knowledge on how seep fluid (bio)chemistry relates to seismicity. It aims to identify (bio)geochemical proxies for the detection of precursory seismic signals and to develop innovative physico-chemical sensors for deep-ocean seismogenic faults. National efforts are coordinated through Working Groups (WGs) focused on 1) geophysical and (bio)geochemical data acquisition; 2) modelling of structure and seismicity of faults; 3) engineering of deep-ocean physico-chemical seismic sensors; and 4) integration and dissemination. This poster will illustrate the overarching goals of the FLOWS Group, with special focus to research goals concerning the role of seismic activity in controlling the release of carbon from the old ocean crust into the deep ocean.

  13. Syntectonic Mississippi River Channel Response: Integrating River Morphology and Seismic Imaging to Detect Active Faults

    Science.gov (United States)

    Magnani, M. B.

    2017-12-01

    Alluvial rivers, even great rivers such as the Mississippi, respond to hydrologic and geologic controls. Temporal variations of valley gradient can significantly alter channel morphology, as the river responds syntectonically to attain equilibrium. The river will alter its sinuosity, in an attempt to maintain a constant gradient on a surface that changes slope through time. Therefore, changes of river pattern can be the first clue that active tectonics is affecting an area of pattern change. Here I present geomorphological and seismic imaging evidence of a previously unknown fault crossing the Mississippi river south of the New Madrid seismic zone, between Caruthersville, Missouri and Osceola, Arkansas, and show that both datasets support Holocene fault movement, with the latest slip occurring in the last 200 years. High resolution marine seismic reflection data acquired along the Mississippi river imaged a NW-SE striking north-dipping fault displacing the base of the Quaternary alluvium by 15 m with reverse sense of movement. The fault consistently deforms the Tertiary, Cretaceous and Paleozoic formations. Historical river channel planforms dating back to 1765 reveal that the section of the river channel across the fault has been characterized by high sinuosity and steep projected-channel slope compared to adjacent river reaches. In particular, the reach across the fault experienced a cutoff in 1821, resulting in a temporary lowering of sinuosity followed by an increase between the survey of 1880 and 1915. Under the assumption that the change in sinuosity reflects river response to a valley slope change to maintain constant gradient, I use sinuosity through time to calculate the change in valley slope since 1880 and therefore to estimate the vertical displacement of the imaged fault in the past 200 years. Based on calculations so performed, the vertical offset of the fault is estimated to be 0.4 m, accrued since at least 1880. If the base of the river alluvium

  14. Fault-magma interactions during early continental rifting: Seismicity of the Magadi-Natron-Manyara basins, Africa

    Science.gov (United States)

    Weinstein, A.; Oliva, S. J.; Ebinger, C. J.; Roecker, S.; Tiberi, C.; Aman, M.; Lambert, C.; Witkin, E.; Albaric, J.; Gautier, S.; Peyrat, S.; Muirhead, J. D.; Muzuka, A. N. N.; Mulibo, G.; Kianji, G.; Ferdinand-Wambura, R.; Msabi, M.; Rodzianko, A.; Hadfield, R.; Illsley-Kemp, F.; Fischer, T. P.

    2017-10-01

    Although magmatism may occur during the earliest stages of continental rifting, its role in strain accommodation remains weakly constrained by largely 2-D studies. We analyze seismicity data from a 13 month, 39-station broadband seismic array to determine the role of magma intrusion on state-of-stress and strain localization, and their along-strike variations. Precise earthquake locations using cluster analyses and a new 3-D velocity model reveal lower crustal earthquakes beneath the central basins and along projections of steep border faults that degas CO2. Seismicity forms several disks interpreted as sills at 6-10 km below a monogenetic cone field. The sills overlie a lower crustal magma chamber that may feed eruptions at Oldoinyo Lengai volcano. After determining a new ML scaling relation, we determine a b-value of 0.87 ± 0.03. Focal mechanisms for 65 earthquakes, and 13 from a catalogue prior to our array reveal an along-axis stress rotation of ˜60° in the magmatically active zone. New and prior mechanisms show predominantly normal slip along steep nodal planes, with extension directions ˜N90°E north and south of an active volcanic chain consistent with geodetic data, and ˜N150°E in the volcanic chain. The stress rotation facilitates strain transfer from border fault systems, the locus of early-stage deformation, to the zone of magma intrusion in the central rift. Our seismic, structural, and geochemistry results indicate that frequent lower crustal earthquakes are promoted by elevated pore pressures from volatile degassing along border faults, and hydraulic fracture around the margins of magma bodies. Results indicate that earthquakes are largely driven by stress state around inflating magma bodies.

  15. Seismic evidence of conjugate normal faulting: The 1994 Devil Canyon earthquake sequence near Challis, Idaho

    International Nuclear Information System (INIS)

    Jackson, S.M.

    1994-08-01

    In this study, the term ''conjugate'' refers to faults that occur in two intersecting sets and coordinated kinematically, with each set being distinctive in both orientation and sense of shear (Davis, 1984). Contemporaneous activity along the conjugate faults is defined as occurring within the time frame of the mainshock-aftershock sequence (three weeks for this sequence and generally less than one month in other observed cases). Detailed recordings of microearthquakes from a dense array of temporary analog seismic stations are analyzed. The focal mechanisms and hypocenter spatial and temporal characteristics are combined with geological information to assess the style, geometry, timing, kinematics, and mechanics of conjugate normal faulting. The characteristics of conjugate normal faulting observed in the Devil Canyon sequence are compared to other conjugate normal faulting sequences, and strike-slip and thrust conjugate sequences worldwide

  16. Quaternary layer anomalies around the Carlsberg Fault zone mapped with high-resolution shear-wave seismics south of Copenhagen

    DEFF Research Database (Denmark)

    Kammann, Janina; Hübscher, Christian; Nielsen, Lars

    Fault zone. The portable compact vibrator source ElViS III S8 was used to acquire a 1150 m long seismic section on the island Amager, south of Copenhagen. The shallow subsurface in the investigation area is dominated by Quaternary glacial till deposits in the upper 5-11 m and Danian limestone below....... In the shear-wave profile, we imaged the 30 m of the upward continuation of the Carlsberg Fault zone. In our area of investigation, the fault zone appears to comprise normal block faults and one reverse block fault showing the complexity of the fault zone. The observed faults appear to affect both the Danian...

  17. Seismic safety in conducting large-scale blasts

    Science.gov (United States)

    Mashukov, I. V.; Chaplygin, V. V.; Domanov, V. P.; Semin, A. A.; Klimkin, M. A.

    2017-09-01

    In mining enterprises to prepare hard rocks for excavation a drilling and blasting method is used. With the approach of mining operations to settlements the negative effect of large-scale blasts increases. To assess the level of seismic impact of large-scale blasts the scientific staff of Siberian State Industrial University carried out expertise for coal mines and iron ore enterprises. Determination of the magnitude of surface seismic vibrations caused by mass explosions was performed using seismic receivers, an analog-digital converter with recording on a laptop. The registration results of surface seismic vibrations during production of more than 280 large-scale blasts at 17 mining enterprises in 22 settlements are presented. The maximum velocity values of the Earth’s surface vibrations are determined. The safety evaluation of seismic effect was carried out according to the permissible value of vibration velocity. For cases with exceedance of permissible values recommendations were developed to reduce the level of seismic impact.

  18. Three-dimensional cellular automata as a model of a seismic fault

    International Nuclear Information System (INIS)

    Gálvez, G; Muñoz, A

    2017-01-01

    The Earth's crust is broken into a series of plates, whose borders are the seismic fault lines and it is where most of the earthquakes occur. This plating system can in principle be described by a set of nonlinear coupled equations describing the motion of the plates, its stresses, strains and other characteristics. Such a system of equations is very difficult to solve, and nonlinear parts leads to a chaotic behavior, which is not predictable. In 1989, Bak and Tang presented an earthquake model based on the sand pile cellular automata. The model though simple, provides similar results to those observed in actual earthquakes. In this work the cellular automata in three dimensions is proposed as a best model to approximate a seismic fault. It is noted that the three-dimensional model reproduces similar properties to those observed in real seismicity, especially, the Gutenberg-Richter law. (paper)

  19. Imaging the Chicxulub central crater zone from large scale seismic acoustic wave propagation and gravity modeling

    Science.gov (United States)

    Fucugauchi, J. U.; Ortiz-Aleman, C.; Martin, R.

    2017-12-01

    Large complex craters are characterized by central uplifts that represent large-scale differential movement of deep basement from the transient cavity. Here we investigate the central sector of the large multiring Chicxulub crater, which has been surveyed by an array of marine, aerial and land-borne geophysical methods. Despite high contrasts in physical properties,contrasting results for the central uplift have been obtained, with seismic reflection surveys showing lack of resolution in the central zone. We develop an integrated seismic and gravity model for the main structural elements, imaging the central basement uplift and melt and breccia units. The 3-D velocity model built from interpolation of seismic data is validated using perfectly matched layer seismic acoustic wave propagation modeling, optimized at grazing incidence using shift in the frequency domain. Modeling shows significant lack of illumination in the central sector, masking presence of the central uplift. Seismic energy remains trapped in an upper low velocity zone corresponding to the sedimentary infill, melt/breccias and surrounding faulted blocks. After conversion of seismic velocities into a volume of density values, we use massive parallel forward gravity modeling to constrain the size and shape of the central uplift that lies at 4.5 km depth, providing a high-resolution image of crater structure.The Bouguer anomaly and gravity response of modeled units show asymmetries, corresponding to the crater structure and distribution of post-impact carbonates, breccias, melt and target sediments

  20. Fault zone identification in the eastern part of the Persian Gulf based on combined seismic attributes

    Science.gov (United States)

    Mirkamali, M. S.; Keshavarz FK, N.; Bakhtiari, M. R.

    2013-02-01

    Faults, as main pathways for fluids, play a critical role in creating regions of high porosity and permeability, in cutting cap rock and in the migration of hydrocarbons into the reservoir. Therefore, accurate identification of fault zones is very important in maximizing production from petroleum traps. Image processing and modern visualization techniques are provided for better mapping of objects of interest. In this study, the application of fault mapping in the identification of fault zones within the Mishan and Aghajari formations above the Guri base unconformity surface in the eastern part of Persian Gulf is investigated. Seismic single- and multi-trace attribute analyses are employed separately to determine faults in a vertical section, but different kinds of geological objects cannot be identified using individual attributes only. A mapping model is utilized to improve the identification of the faults, giving more accurate results. This method is based on combinations of all individual relevant attributes using a neural network system to create combined attributes, which gives an optimal view of the object of interest. Firstly, a set of relevant attributes were separately calculated on the vertical section. Then, at interpreted positions, some example training locations were manually selected in each fault and non-fault class by an interpreter. A neural network was trained on combinations of the attributes extracted at the example training locations to generate an optimized fault cube. Finally, the results of the fault and nonfault probability cube were estimated, which the neural network applied to the entire data set. The fault probability cube was obtained with higher mapping accuracy and greater contrast, and with fewer disturbances in comparison with individual attributes. The computed results of this study can support better understanding of the data, providing fault zone mapping with reliable results.

  1. Fault zone identification in the eastern part of the Persian Gulf based on combined seismic attributes

    International Nuclear Information System (INIS)

    Mirkamali, M S; Keshavarz FK, N; Bakhtiari, M R

    2013-01-01

    Faults, as main pathways for fluids, play a critical role in creating regions of high porosity and permeability, in cutting cap rock and in the migration of hydrocarbons into the reservoir. Therefore, accurate identification of fault zones is very important in maximizing production from petroleum traps. Image processing and modern visualization techniques are provided for better mapping of objects of interest. In this study, the application of fault mapping in the identification of fault zones within the Mishan and Aghajari formations above the Guri base unconformity surface in the eastern part of Persian Gulf is investigated. Seismic single- and multi-trace attribute analyses are employed separately to determine faults in a vertical section, but different kinds of geological objects cannot be identified using individual attributes only. A mapping model is utilized to improve the identification of the faults, giving more accurate results. This method is based on combinations of all individual relevant attributes using a neural network system to create combined attributes, which gives an optimal view of the object of interest. Firstly, a set of relevant attributes were separately calculated on the vertical section. Then, at interpreted positions, some example training locations were manually selected in each fault and non-fault class by an interpreter. A neural network was trained on combinations of the attributes extracted at the example training locations to generate an optimized fault cube. Finally, the results of the fault and nonfault probability cube were estimated, which the neural network applied to the entire data set. The fault probability cube was obtained with higher mapping accuracy and greater contrast, and with fewer disturbances in comparison with individual attributes. The computed results of this study can support better understanding of the data, providing fault zone mapping with reliable results. (paper)

  2. Relating seismicity to the velocity structure of the San Andreas Fault near Parkfield, CA

    Science.gov (United States)

    Lippoldt, Rachel; Porritt, Robert W.; Sammis, Charles G.

    2017-06-01

    The central section of the San Andreas Fault (SAF) displays a range of seismic phenomena including normal earthquakes, low-frequency earthquakes (LFE), repeating microearthquakes (REQ) and aseismic creep. Although many lines of evidence suggest that LFEs are tied to the presence of fluids, their geological setting is still poorly understood. Here, we map the seismic velocity structures associated with LFEs beneath the central SAF using surface wave tomography from ambient seismic noise to provide constraints on the physical conditions that control LFE occurrence. Fault perpendicular sections show that the SAF, as revealed by lateral contrasts in relative velocities, is contiguous to depths of 50 km and appears to be relatively localized at depths between about 15 and 30 km. This is consistent with the hypothesis that LFEs are shear-slip events on a deep extension of the SAF. We find that along strike variations in seismic behaviour correspond to changes in the seismic structure, which support proposed connections between fluids and seismicity. LFEs and REQs occur within low-velocity structures, suggesting that the presence of fluids, weaker minerals, or hydrous phase minerals may play an important role in the generation of slow-slip phenomena.

  3. Seismic Evidence of A Widely Distributed West Napa Fault Zone, Hendry Winery, Napa, California

    Science.gov (United States)

    Goldman, M.; Catchings, R.; Chan, J. H.; Criley, C.

    2015-12-01

    Following the 24 August 2014 Mw 6.0 South Napa earthquake, surface rupture was mapped along the West Napa Fault Zone (WNFZ) for a distance of ~ 14 km and locally within zones up to ~ 2 km wide. Near the northern end of the surface rupture, however, several strands coalesced to form a narrow, ~100-m-wide zone of surface rupture. To determine the location, width, and shallow (upper few hundred meters) geometry of the fault zone, we acquired an active-source seismic survey across the northern surface rupture in February 2015. We acquired both P- and S-wave data, from which we developed reflection images and tomographic images of Vp, Vs, Vp/Vs, and Poisson's ratio of the upper 100 m. We also used small explosive charges within surface ruptures located ~600 m north of our seismic array to record fault-zone guided waves. Our data indicate that at the latitude of the Hendry Winery, the WNFZ is characterized by at least five fault traces that are spaced 60 to 200 m apart. Zones of low-Vs, low-Vp/Vs, and disrupted reflectors highlight the fault traces on the tomography and reflection images. On peak-ground-velocity (PGV) plots, the most pronounced high-amplitude guided-wave seismic energy coincides precisely with the mapped surface ruptures, and the guided waves also show discrete high PGV zones associated with unmapped fault traces east of the surface ruptures. Although the surface ruptures of the WNFZ were observed only over a 100-m-wide zone at the Hendry Winery, our data indicate that the fault zone is at least 400 m wide, which is probably a minimum width given the 400-m length of our seismic profile. Slip on the WNFZ is generally considered to be low relative to most other Bay Area faults, but we suggest that the West Napa Fault is a zone of widely distributed shear, and to fully account for the total slip on the WNFZ, slip on all traces of this wide fault zone must be considered.

  4. Mud volcano monitoring and seismic events along the North Anatolian Fault (Sea of Marmara)

    Science.gov (United States)

    Javad Fallahi, Mohammad; Lupi, Matteo; Mazzini, Adriano; Polonia, Alina; D'Alessandro, Antonino; D'Anna, Giuseppe; Gasperini, Luca

    2017-04-01

    The Sea of Marmara, a pull-apart basin formed along the northern strand of the North Anatolian Fault (NAF) system, is considered a seismic gap, that will be filled in the next decades by a large magnitude (M>7) earthquake, close to the Istanbul Metropolitan area (12 million inhabitants). For this reason, several marine geological and geophysical studies have been carried out in this region, starting from the destructive 1999 Mw 7.4 Izmit earthquake, to gather information relative to seismogenic potential of major fault strands. Together with these studies, in the frame of EC projects (i.e., MarmESONET and Marsite, among others), an intensive program of long-term monitoring of seismogenic faults was carried out using seafloor observatories deployed during several expeditions led by Italian, French and Turkish groups. These expeditions included MARM2013, on board of the R/V Urania, of the Italian CNR, when four ocean bottom seismometers (OBS) were deployed in the central part of the Sea of Marmara, at depths between 550 and 1000 m. One of the main aims of the experiment was to assess the long-term seismic activity along an active segment of the NAF, which connects the central and the western basins (depocenters), where the principal deformation zone appears relatively narrow and almost purely strike-slip. The present study shows the results of processing and analysis of continuous data records from these OBS stations during 50 days. We were able to detect seismic signal produced by an active mud volcano located close to the NAF trace, from about 3 to 6 km of distance from the OBS stations. Additionally, we captured the May 24, 2014, Mw 6.9 strike-slip earthquake occurred in the northern Aegean Sea between Greece and Turkey, which caused serious damage on the Turkish island of Imbros and the cities of Edirne and Çanakkale, as well as on the Greek island of Lemnos. The earthquake nucleated on the westward continuation of the NAF system in the NE Aegean Sea, and was

  5. Detection of frictional heat in seismic faults by coal reflectance

    Science.gov (United States)

    Kitamura, M.; Mukoyoshi, H.; Fulton, P. M.; Hirose, T.

    2012-12-01

    Quantitative assessment of heat generation along a fault during coseismic faulting is of primary importance in understanding the dynamics of earthquakes. Evidence of substantial frictional heating along a fault is also a reliable indicator determining whether a fault has slipped at high velocity in the past, which is crucial for assessing earthquake and tsunami hazard. The reflectance measurement of vitrinite (one of the primary components of coals) has been considered a possible geothermometer of fault zones, especially in accretionary wedges where vitrinite fragments are common [e.g., Sakaguchi et al., 2011]. Under normal burial conditions, vitrinite reflectance (Ro) increases by irreversible maturation reaction as temperature is elevated and thus sensitively records the maximum temperature to which the vitrinite is subjected. However, the commonly used kinetic models of vitrinite maturation [e.g., Sweeney and Burnham, 1990] may not yield accurate estimates of the peak temperature in a fault zone resulting from fast frictional heating rates [Fulton and Harris, 2012]. Whether or not coal can mature in typical earthquake rise time (e.g., ~10 seconds) remains uncertain. Here we present the results of friction experiments aimed at revealing coal maturation by frictional heat generated at slip velocities representative of natural earthquakes of up to 1.3 m/s. All friction experiments were conducted on a mixture of 90 wt% quartz powder and 10 wt% coal grains for simulated fault gouge at three different velocities of 0.0013 m/s, 0.65 m/s and 1.3 m/s, a constant normal stress of 1.0 MPa and ~15 m displacement under anoxic, dry nitrogen atmosphere at room temperature. We also measured temperature in the gouge zone during faulting by thermocouples. The initial coal fragments consist of vitrinite, inertinite and liptinite. Although liptinite was easy to identify microscopically, it was difficult to discriminate between vitrinite and inertinite grains as their grain size

  6. Characterization of Aftershock Sequences from Large Strike-Slip Earthquakes Along Geometrically Complex Faults

    Science.gov (United States)

    Sexton, E.; Thomas, A.; Delbridge, B. G.

    2017-12-01

    Large earthquakes often exhibit complex slip distributions and occur along non-planar fault geometries, resulting in variable stress changes throughout the region of the fault hosting aftershocks. To better discern the role of geometric discontinuities on aftershock sequences, we compare areas of enhanced and reduced Coulomb failure stress and mean stress for systematic differences in the time dependence and productivity of these aftershock sequences. In strike-slip faults, releasing structures, including stepovers and bends, experience an increase in both Coulomb failure stress and mean stress during an earthquake, promoting fluid diffusion into the region and further failure. Conversely, Coulomb failure stress and mean stress decrease in restraining bends and stepovers in strike-slip faults, and fluids diffuse away from these areas, discouraging failure. We examine spatial differences in seismicity patterns along structurally complex strike-slip faults which have hosted large earthquakes, such as the 1992 Mw 7.3 Landers, the 2010 Mw 7.2 El-Mayor Cucapah, the 2014 Mw 6.0 South Napa, and the 2016 Mw 7.0 Kumamoto events. We characterize the behavior of these aftershock sequences with the Epidemic Type Aftershock-Sequence Model (ETAS). In this statistical model, the total occurrence rate of aftershocks induced by an earthquake is λ(t) = λ_0 + \\sum_{i:t_i

  7. Nonlinear seismic analysis of a large sodium pump

    International Nuclear Information System (INIS)

    Huang, S.N.

    1985-01-01

    The bearings and seismic bumpers used in a large sodium pump of a typical breeder reactor plant may need to be characterized by nonlinear springs and gaps. Then, nonlinear seismic analysis utilizing the time-history method is an effective way to predict the pump behaviors during seismic events - especially at those bearing and seismic bumper areas. In this study, synthesized time histories were developed based on specified seismic response spectra. A nonlinear seismic analysis was then conducted and results were compared with those obtained by linear seismic analysis using the response spectrum method. In contrast to some previous nonlinear analysis trends, the bearing impact forces predicted by nonlinear analysis were higher than those obtained by the response spectrum method. This might be due to the larger gaps and stiffer bearing supports used in this specific pump. However, at locations distant from the impact source, the nonlinear seismic analysis has predicted slightly less responses than those obtained by linear seismic analysis. The seismically induced bearing impact forces were used to study the friction induced thermal stresses on the hydrostatic bearing and to predict the coastdown time of the pump. Results and discussions are presented

  8. Nonlinear seismic analysis of a large sodium pump

    International Nuclear Information System (INIS)

    Huang, S.N.

    1985-01-01

    The bearings and seismic bumpers used in a large sodium pump of a typical breeder reactor plant may need to be characterized by nonlinear springs and gaps. Then, nonlinear seismic analysis utilizing the time-history method is an effective way to predict the pump behaviors during seismic events, especially at those bearing and seismic bumper areas. In this study, synthesized time histories were developed based on specified seismic response spectra. A nonlinear seismic analysis was then conducted and results were compared with those obtained by linear seismic analysis using the response spectrum method. In contrast to some previous nonlinear analysis trends, the bearing impact forces predicted by nonlinear analysis were higher than those obtained by the response spectrum method. This might be due to the larger gaps and stiffer bearing supports used in this specific pump. However, at locations distant from the impact source, the nonlinear seismic analysis has predicted slightly less responses than those obtained by linear seismic analysis. The seismically induced bearing impact forces were used to study the friction induced thermal stresses on the hydrostatic bearing and to predict the coastdown time of the pump. Results and discussions are presented

  9. Faults survey by 3D reflection seismics; Sanjigen hanshaho jishin tansa ni yoru danso chosa

    Energy Technology Data Exchange (ETDEWEB)

    Tsuchiya, T; Ejiri, T; Yamada, N; Narita, N; Aso, H; Takano, H; Matsumura, M [Dia Consultants Company, Tokyo (Japan)

    1996-10-01

    This paper describes fault survey by 3D seismic reflection exploration. Survey has been conducted mainly at flat land area without pavement not in urban area in Japan. Subsurface structure is complicated with intersecting multiple faults. In this area, a lot of geological investigations have been done prior to the seismic reflection exploration. Fairly certain images of faults have been obtained. However, there were still unknown structures. Survey was conducted at an area of 170m{times}280m in the CDP range. Measurements were carried out by using 100 g of dynamite per seismic generation point combined with 40 Hz velocity geophones. Fixed distribution consisting of lattice points of 12{times}12 was adopted as an observation method. In and around the lattice, a great number of explosions were carried out. The CDP stacking method and the method of migration after stacking were used for the data processing. The 3D structures of six horizons and five faults could be interpreted. Interpreted horizons were well agreed with the logging results. 3 figs.

  10. Constructing constitutive relationships for seismic and aseismic fault slip

    Science.gov (United States)

    Beeler, N.M.

    2009-01-01

    For the purpose of modeling natural fault slip, a useful result from an experimental fault mechanics study would be a physically-based constitutive relation that well characterizes all the relevant observations. This report describes an approach for constructing such equations. Where possible the construction intends to identify or, at least, attribute physical processes and contact scale physics to the observations such that the resulting relations can be extrapolated in conditions and scale between the laboratory and the Earth. The approach is developed as an alternative but is based on Ruina (1983) and is illustrated initially by constructing a couple of relations from that study. In addition, two example constitutive relationships are constructed; these describe laboratory observations not well-modeled by Ruina's equations: the unexpected shear-induced weakening of silica-rich rocks at high slip speed (Goldsby and Tullis, 2002) and fault strength in the brittle ductile transition zone (Shimamoto, 1986). The examples, provided as illustration, may also be useful for quantitative modeling.

  11. Mineralogical compositions of fault rocks from surface ruptures of Wenchuan earthquake and implication of mineral transformation during the seismic cycle along Yingxiu-Beichuan fault, Sichuan Province, China

    Science.gov (United States)

    Dang, Jiaxiang; Zhou, Yongsheng; He, Changrong; Ma, Shengli

    2018-06-01

    There are two co-seismic bedrock surface ruptures from the Mw 7.9 Wenchuan earthquake in the northern and central parts of the Beichuan-Yingxiu fault, Sichuan Province, southwest China. In this study, we report on the macrostructure of the fault rocks and results from X-ray powder diffraction analysis of minerals from rocks in the fault zone. The most recent fault gouge (the gouge produced by the most recent co-seismic fault movement) in all the studied outcrops is dark or grayish-black, totally unconsolidated and ultrafine-grained. Older fault gouges in the same outcrops are grayish or yellowish and weakly consolidated. X-ray powder diffraction analysis results show that mineral assemblages in both the old fault gouge and the new fault gouge are more complicated than the mineral assemblages in the bedrock as the fault gouge is rich in clay minerals. The fault gouge inherited its major rock-forming minerals from the parent rocks, but the clay minerals in the fault gouge were generated in the fault zone and are therefore authigenic and synkinematic. In profiles across the fault, clay mineral abundances increase as one traverses from the bedrock to the breccia to the old gouge and from the old gouge to the new gouge. Quartz and illite are found in all collected gouge samples. The dominant clay minerals in the new fault gouge are illite and smectite along the northern part of the surface rupture and illite/smectite mixed-layer clay in the middle part of the rupture. Illite/smectite mixed-layer clay found in the middle part of the rupture indicates that fault slip was accompanied by K-rich fluid circulation. The existence of siderite, anhydrite, and barite in the northern part of the rupture suggests that fault slip at this locality was accompanied by acidic fluids containing ions of Fe, Ca, and Ba.

  12. Repetition of large stress drop earthquakes on Wairarapa fault, New Zealand, revealed by LiDAR data

    Science.gov (United States)

    Delor, E.; Manighetti, I.; Garambois, S.; Beaupretre, S.; Vitard, C.

    2013-12-01

    We have acquired high-resolution LiDAR topographic data over most of the onland trace of the 120 km-long Wairarapa strike-slip fault, New Zealand. The Wairarapa fault broke in a large earthquake in 1855, and this historical earthquake is suggested to have produced up to 18 m of lateral slip at the ground surface. This would make this earthquake a remarkable event having produced a stress drop much higher than commonly observed on other earthquakes worldwide. The LiDAR data allowed us examining the ground surface morphology along the fault at statistical analysis of the cumulative offsets per segment reveals that the alluvial morphology has well recorded, at every step along the fault, no more than a few (3-6), well distinct cumulative slips, all lower than 80 m. Plotted along the entire fault, the statistically defined cumulative slip values document four, fairly continuous slip profiles that we attribute to the four most recent large earthquakes on the Wairarapa fault. The four slip profiles have a roughly triangular and asymmetric envelope shape that is similar to the coseismic slip distributions described for most large earthquakes worldwide. The four slip profiles have their maximum slip at the same place, in the northeastern third of the fault trace. The maximum slips vary from one event to another in the range 7-15 m; the most recent 1855 earthquake produced a maximum coseismic slip of 15 × 2 m at the ground surface. Our results thus confirm that the Wairarapa fault breaks in remarkably large stress drop earthquakes. Those repeating large earthquakes share both similar (rupture length, slip-length distribution, location of maximum slip) and distinct (maximum slip amplitudes) characteristics. Furthermore, the seismic behavior of the Wairarapa fault is markedly different from that of nearby large strike-slip faults (Wellington, Hope). The reasons for those differences in rupture behavior might reside in the intrinsic properties of the broken faults, especially

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

    Science.gov (United States)

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

    2017-12-01

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

  14. Were Holocene large slumps in Lake Geneva off the city of Lausanne caused by fault activity?

    Science.gov (United States)

    Correia Demand, Jehanne; Marillier, François; Kremer, Katrina; Girardclos, Stéphanie

    2014-05-01

    Lake Geneva is set in an area where glacier advances and retreats have carved Tertiary Molasse rocks in front of the Alpine units. Glacial and lacustrine sediments have accumulated in the lake on top of the Molasse. Within Holocene sedimentary layers, seismic studies in the central part of Lake Geneva ("Grand-Lac") have shown the presence of several mass transport deposits (MTD). A large one, MTD A, is observed off the city of Lausanne. The depth of the associated failure scars (100 m water depth), its volume (~ 0.13 km3), and the occurrence of other smaller MTDs that were possibly co-deposited with MTD A point to the occurrence of a major slide event in the lake, most likely associated with an earthquake. Based on 14C dating, the sediment age model for MTD A gives an age interval of 1865-1608 BC (Kremer et al. 2014). To resolve the details of the MTDs off Lausanne, and to better understand its geological context different seismic systems were used. These were a 3.5 KHz pinger with a theoretical vertical resolution of 0.15 m and a multichannel system with water-gun or air-gun seismic sources with vertical resolution of 0.6 m and 1.1 m, respectively. After a first pass processing, the multi-channel data were reprocessed in order to take into account the shape of the streamer in the water and to enhance the results of migration. In addition to typical seismic images of MTDs observed in other alpine lakes such as chaotic or transparent seismic character between well-organized reflections, two intriguing positive water-bottom topographic features associated with apparent sub-vertical offsets are revealed by the seismic data. They are located in the near vicinity of the depot centers of the MTDs and conspicuously located near faults in the Tertiary Molasse. These are thrust faults that are offset by small strike-slip faults, and we suggest that the positive topographic features are linked to a compressive component within the sediments due to displacements along these

  15. Seismic hazard of the Enriquillog-Plantain Garden fault in Haiti inferred from palaeoseismology

    Science.gov (United States)

    Prentice, C.S.; Mann, P.; Crone, A.J.; Gold, R.D.; Hudnut, K.W.; Briggs, R.W.; Koehler, R.D.; Jean, P.

    2010-01-01

    The Enriquillog-Plantain Garden fault zone is recognized as one of the primary plate-bounding fault systems in Haiti. The strike-slip fault runs adjacent to the city of Port-au-Prince and was initially thought to be the source of the 12 January 2010, M w 7.0 earthquake. Haiti experienced significant earthquakes in 1751 and 1770 (refsA, 3, 4, 5), but the role of the Enriquillog-Plantain Garden fault zone in these earthquakes is poorly known. We use satellite imagery, aerial photography, light detection and ranging (LIDAR) and field investigations to document Quaternary activity on the Enriquillog-Plantain Garden fault. We report late Quaternary, left-lateral offsets of up to 160m, and a set of small offsets ranging from 1.3 to 3.3m that we associate with one of the eighteenth century earthquakes. The size of the small offsets implies that the historical earthquake was larger than M w 7.0, but probably smaller than M w 7.6. We found no significant surface rupture associated with the 2010 earthquake. The lack of surface rupture, coupled with other seismologic, geologic and geodetic observations, suggests that little, if any, accumulated strain was released on the Enriquillog-Plantain Garden fault in the 2010 earthquake. These results confirm that the Enriquillog-Plantain Garden fault remains a significant seismic hazard. ?? 2010 Macmillan Publishers Limited. All rights reserved.

  16. Seismic soil-structure interaction of foundations with large piles

    International Nuclear Information System (INIS)

    Zeevaert, L.

    1996-01-01

    In seismic regions with soft soil deposits subjected to ground surface subsidence, there is the necessity to support the weight of constructions on large diameter piles or piers hearing on deep firm strata. To justify the action of these elements working under flexo compression and shear, it is necessary to perform calculations of soil pile interaction from a practical engineering point of view and estimate the order of magnitude of the forces and displacements to which these elements will be subjected during the seismic action assigned to the foundation. In this paper we defined a pier as a large diameter pile constructed on site. Furthermore, in the seismic analysis it is necessary to evaluate the seismic pore water pressure to learn on the effective seismic soil stresses close to the ground surface. (author)

  17. Fault Specific Seismic Hazard Maps as Input to Loss Reserves Calculation for Attica Buildings

    Science.gov (United States)

    Deligiannakis, Georgios; Papanikolaou, Ioannis; Zimbidis, Alexandros; Roberts, Gerald

    2014-05-01

    Greece is prone to various natural disasters, such as wildfires, floods, landslides and earthquakes, due to the special environmental and geological conditions dominating in tectonic plate boundaries. Seismic is the predominant risk, in terms of damages and casualties in the Greek territory. The historical record of earthquakes in Greece has been published from various researchers, providing useful data in seismic hazard assessment of Greece. However, the completeness of the historical record in Greece, despite being one of the longest worldwide, reaches only 500 years for M ≥ 7.3 and less than 200 years for M ≥ 6.5. Considering that active faults in the area have recurrence intervals of a few hundred to several thousands of years, it is clear that many active faults have not been activated during the completeness period covered by the historical records. New Seismic Hazard Assessment methodologies tend to follow fault specific approaches where seismic sources are geologically constrained active faults, in order to address problems related to the historical records incompleteness, obtain higher spatial resolution and calculate realistic source locality distances, since seismic sources are very accurately located. Fault specific approaches provide quantitative assessments as they measure fault slip rates from geological data, providing a more reliable estimate of seismic hazard. We used a fault specific seismic hazard assessment approach for the region of Attica. The method of seismic hazard mapping from geological fault throw-rate data combined three major factors: Empirical data which combine fault rupture lengths, earthquake magnitudes and coseismic slip relationships. The radiuses of VI, VII, VIII and IX isoseismals on the Modified Mercalli (MM) intensity scale. Attenuation - amplification functions for seismic shaking on bedrock compared to basin filling sediments. We explicitly modeled 22 active faults that could affect the region of Attica, including

  18. Analysis of large fault trees based on functional decomposition

    International Nuclear Information System (INIS)

    Contini, Sergio; Matuzas, Vaidas

    2011-01-01

    With the advent of the Binary Decision Diagrams (BDD) approach in fault tree analysis, a significant enhancement has been achieved with respect to previous approaches, both in terms of efficiency and accuracy of the overall outcome of the analysis. However, the exponential increase of the number of nodes with the complexity of the fault tree may prevent the construction of the BDD. In these cases, the only way to complete the analysis is to reduce the complexity of the BDD by applying the truncation technique, which nevertheless implies the problem of estimating the truncation error or upper and lower bounds of the top-event unavailability. This paper describes a new method to analyze large coherent fault trees which can be advantageously applied when the working memory is not sufficient to construct the BDD. It is based on the decomposition of the fault tree into simpler disjoint fault trees containing a lower number of variables. The analysis of each simple fault tree is performed by using all the computational resources. The results from the analysis of all simpler fault trees are re-combined to obtain the results for the original fault tree. Two decomposition methods are herewith described: the first aims at determining the minimal cut sets (MCS) and the upper and lower bounds of the top-event unavailability; the second can be applied to determine the exact value of the top-event unavailability. Potentialities, limitations and possible variations of these methods will be discussed with reference to the results of their application to some complex fault trees.

  19. Analysis of large fault trees based on functional decomposition

    Energy Technology Data Exchange (ETDEWEB)

    Contini, Sergio, E-mail: sergio.contini@jrc.i [European Commission, Joint Research Centre, Institute for the Protection and Security of the Citizen, 21020 Ispra (Italy); Matuzas, Vaidas [European Commission, Joint Research Centre, Institute for the Protection and Security of the Citizen, 21020 Ispra (Italy)

    2011-03-15

    With the advent of the Binary Decision Diagrams (BDD) approach in fault tree analysis, a significant enhancement has been achieved with respect to previous approaches, both in terms of efficiency and accuracy of the overall outcome of the analysis. However, the exponential increase of the number of nodes with the complexity of the fault tree may prevent the construction of the BDD. In these cases, the only way to complete the analysis is to reduce the complexity of the BDD by applying the truncation technique, which nevertheless implies the problem of estimating the truncation error or upper and lower bounds of the top-event unavailability. This paper describes a new method to analyze large coherent fault trees which can be advantageously applied when the working memory is not sufficient to construct the BDD. It is based on the decomposition of the fault tree into simpler disjoint fault trees containing a lower number of variables. The analysis of each simple fault tree is performed by using all the computational resources. The results from the analysis of all simpler fault trees are re-combined to obtain the results for the original fault tree. Two decomposition methods are herewith described: the first aims at determining the minimal cut sets (MCS) and the upper and lower bounds of the top-event unavailability; the second can be applied to determine the exact value of the top-event unavailability. Potentialities, limitations and possible variations of these methods will be discussed with reference to the results of their application to some complex fault trees.

  20. A practical method for accurate quantification of large fault trees

    International Nuclear Information System (INIS)

    Choi, Jong Soo; Cho, Nam Zin

    2007-01-01

    This paper describes a practical method to accurately quantify top event probability and importance measures from incomplete minimal cut sets (MCS) of a large fault tree. The MCS-based fault tree method is extensively used in probabilistic safety assessments. Several sources of uncertainties exist in MCS-based fault tree analysis. The paper is focused on quantification of the following two sources of uncertainties: (1) the truncation neglecting low-probability cut sets and (2) the approximation in quantifying MCSs. The method proposed in this paper is based on a Monte Carlo simulation technique to estimate probability of the discarded MCSs and the sum of disjoint products (SDP) approach complemented by the correction factor approach (CFA). The method provides capability to accurately quantify the two uncertainties and estimate the top event probability and importance measures of large coherent fault trees. The proposed fault tree quantification method has been implemented in the CUTREE code package and is tested on the two example fault trees

  1. Application of Post-stack migration to seismic data associated with fault structures

    OpenAIRE

    Koduru Anitha; Mohanty P. R

    2015-01-01

    In hydrocarbon exploration, wave-equation migration techniques play an important role in imaging the complex geological structures. Usually, post-stack migration scheme is applied to the seismic data to improve the resolution with restoration of dipping reflectors to their true position. As a result, the migrated time sections are interpretable in terms of subsurface features. As a numerical study, three fault models are considered for the present study. First of all, ...

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

    Science.gov (United States)

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

    2017-12-01

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

  3. Staff technical position on investigations to identify fault displacement hazards and seismic hazards at a geologic repository

    International Nuclear Information System (INIS)

    McConnell, K.I.; Blackford, M.E.; Ibrahim, A.K.

    1992-07-01

    The purpose of this Staff Technical Position (STP) is to provide guidance to the US Department of Energy (DOE) on acceptable geologic repository investigations that can be used to identify fault displacement hazards and seismic hazards. ne staff considers that the approach this STP takes to investigations of fault displacement and seismic phenomena is appropriate for the collection of sufficient data for input to analyses of fault displacement hazards and seismic hazards, both for the preclosure and postclosure performance periods. However, detailed analyses of fault displacement and seismic data, such as those required for comprehensive assessments of repository performance, may identify the need for additional investigations. Section 2.0 of this STP describes the 10 CFR Part 60 requirements that form the basis for investigations to describe fault displacement hazards and seismic hazards at a geologic repository. Technical position statements and corresponding discussions are presented in Sections 3.0 and 4.0, respectively. Technical position topics in this STP are categorized thusly: (1) investigation considerations, (2) investigations for fault-displacement hazards, and (3) investigations for seismic hazards

  4. Structure of the Koyna-Warna Seismic Zone, Maharashtra, India: A possible model for large induced earthquakes elsewhere

    Science.gov (United States)

    Catchings, Rufus D.; Dixit, M.M.; Goldman, Mark R.; Kumar, S.

    2015-01-01

    The Koyna-Warna area of India is one of the best worldwide examples of reservoir-induced seismicity, with the distinction of having generated the largest known induced earthquake (M6.3 on 10 December 1967) and persistent moderate-magnitude (>M5) events for nearly 50 years. Yet, the fault structure and tectonic setting that has accommodated the induced seismicity is poorly known, in part because the seismic events occur beneath a thick sequence of basalt layers. On the basis of the alignment of earthquake epicenters over an ~50 year period, lateral variations in focal mechanisms, upper-crustal tomographic velocity images, geophysical data (aeromagnetic, gravity, and magnetotelluric), geomorphic data, and correlation with similar structures elsewhere, we suggest that the Koyna-Warna area lies within a right step between northwest trending, right-lateral faults. The sub-basalt basement may form a local structural depression (pull-apart basin) caused by extension within the step-over zone between the right-lateral faults. Our postulated model accounts for the observed pattern of normal faulting in a region that is dominated by north-south directed compression. The right-lateral faults extend well beyond the immediate Koyna-Warna area, possibly suggesting a more extensive zone of seismic hazards for the central India area. Induced seismic events have been observed many places worldwide, but relatively large-magnitude induced events are less common because critically stressed, preexisting structures are a necessary component. We suggest that releasing bends and fault step-overs like those we postulate for the Koyna-Warna area may serve as an ideal tectonic environment for generating moderate- to large- magnitude induced (reservoir, injection, etc.) earthquakes.

  5. Geomechanical effects on CO2 leakage through fault zones during large-scale underground injection

    Energy Technology Data Exchange (ETDEWEB)

    Rinaldi, Antonio P. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Rutqvist, Jonny [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Cappa, Frédéric [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of Nice Sophia-Antipolis, Nice (France). Cote d' Azur Observatory. GeoAzur

    2013-12-01

    The importance of geomechanics—including the potential for faults to reactivate during large-scale geologic carbon sequestration operations—has recently become more widely recognized. However, notwithstanding the potential for triggering notable (felt) seismic events, the potential for buoyancy-driven CO2 to reach potable groundwater and the ground surface is actually more important from public safety and storage-efficiency perspectives. In this context, this paper extends the previous studies on the geomechanical modeling of fault responses during underground carbon dioxide injection, focusing on the short-term integrity of the sealing caprock, and hence on the potential for leakage of either brine or CO2 to reach the shallow groundwater aquifers during active injection. We consider stress/strain-dependent permeability and study the leakage through the fault zone as its permeability changes during a reactivation, also causing seismicity. We analyze several scenarios related to the volume of CO2 injected (and hence as a function of the overpressure), involving both minor and major faults, and analyze the profile risks of leakage for different stress/strain-permeability coupling functions. We conclude that whereas it is very difficult to predict how much fault permeability could change upon reactivation, this process can have a significant impact on the leakage rate. Moreover, our analysis shows that induced seismicity associated with fault reactivation may not necessarily open up a new flow path for leakage. Results show a poor correlation between magnitude and amount of fluid leakage, meaning that a single event is generally not enough to substantially change the permeability along the entire fault length. Finally, and consequently, even if some changes in permeability occur, this does not mean that the CO2 will migrate up along the entire fault, breaking through the caprock to enter the overlying aquifer.

  6. GPS and seismic constraints on the M = 7.3 2009 Swan Islands earthquake: implications for stress changes along the Motagua fault and other nearby faults

    Science.gov (United States)

    Graham, Shannon E.; DeMets, Charles; DeShon, Heather R.; Rogers, Robert; Maradiaga, Manuel Rodriguez; Strauch, Wilfried; Wiese, Klaus; Hernandez, Douglas

    2012-09-01

    We use measurements at 35 GPS stations in northern Central America and 25 seismometers at teleseismic distances to estimate the distribution of slip, source time function and Coulomb stress changes of the Mw = 7.3 2009 May 28, Swan Islands fault earthquake. This event, the largest in the region for several decades, ruptured the offshore continuation of the seismically hazardous Motagua fault of Guatemala, the site of the destructive Ms = 7.5 earthquake in 1976. Measured GPS offsets range from 308 millimetres at a campaign site in northern Honduras to 6 millimetres at five continuous sites in El Salvador. Separate inversions of geodetic and seismic data both indicate that up to ˜1 m of coseismic slip occurred along a ˜250-km-long rupture zone between the island of Roatan and the eastern limit of the 1976 M = 7.5 Motagua fault earthquake in Guatemala. Evidence for slip ˜250 km west of the epicentre is corroborated independently by aftershocks recorded by a local seismic network and by the high concentration of damage to structures in areas of northern Honduras adjacent to the western limit of the rupture zone. Coulomb stresses determined from the coseismic slip distribution resolve a maximum of 1 bar of stress transferred to the seismically hazardous Motagua fault and further indicate unclamping of normal faults along the northern shore of Honduras, where two M > 5 normal-faulting earthquakes and numerous small earthquakes were triggered by the main shock.

  7. Quasi-periodic recurrence of large earthquakes on the southern San Andreas fault

    Science.gov (United States)

    Scharer, Katherine M.; Biasi, Glenn P.; Weldon, Ray J.; Fumal, Tom E.

    2010-01-01

    It has been 153 yr since the last large earthquake on the southern San Andreas fault (California, United States), but the average interseismic interval is only ~100 yr. If the recurrence of large earthquakes is periodic, rather than random or clustered, the length of this period is notable and would generally increase the risk estimated in probabilistic seismic hazard analyses. Unfortunately, robust characterization of a distribution describing earthquake recurrence on a single fault is limited by the brevity of most earthquake records. Here we use statistical tests on a 3000 yr combined record of 29 ground-rupturing earthquakes from Wrightwood, California. We show that earthquake recurrence there is more regular than expected from a Poisson distribution and is not clustered, leading us to conclude that recurrence is quasi-periodic. The observation of unimodal time dependence is persistent across an observationally based sensitivity analysis that critically examines alternative interpretations of the geologic record. The results support formal forecast efforts that use renewal models to estimate probabilities of future earthquakes on the southern San Andreas fault. Only four intervals (15%) from the record are longer than the present open interval, highlighting the current hazard posed by this fault.

  8. Seismic properties of lawsonite eclogites from the southern Motagua fault zone, Guatemala

    Science.gov (United States)

    Kim, Daeyeong; Wallis, Simon; Endo, Shunsuke; Ree, Jin-Han

    2016-05-01

    We present new data on the crystal preferred orientation (CPO) and seismic properties of omphacite and lawsonite in extremely fresh eclogite from the southern Motagua fault zone, Guatemala, to discuss the seismic anisotropy of subducting oceanic crust. The CPO of omphacite is characterized by (010)[001], and it shows P-wave seismic anisotropies (AVP) of 1.4%-3.2% and S-wave seismic anisotropies (AVS) of 1.4%-2.7%. Lawsonite exhibits (001) planes parallel to the foliation and [010] axes parallel to the lineation, and seismic anisotropies of 1.7%-6.6% AVP and 3.4%-14.7% AVS. The seismic anisotropy of a rock mass consisting solely of omphacite and lawsonite is 1.2%-4.1% AVP and 1.8%-6.8% AVS. For events that propagate more or less parallel to the maximum extension direction, X, the fast S-wave velocity (VS) polarization is parallel to the Z in the Y-Z section (rotated from the X-Z section), causing trench-normal seismic anisotropy for orthogonal subduction. Based on the high modal abundance and strong fabric of lawsonite, the AVS of eclogites is estimated as ~ 11.7% in the case that lawsonite makes up ~ 75% of the rock mass. On this basis, we suggest that lawsonite in both blueschist and eclogite may play important roles in the formation of complex pattern of seismic anisotropy observed in NE Japan: weak trench-parallel anisotropy in the forearc basin domains and trench-normal anisotropy in the backarc region.

  9. Analysis of large concrete storage tank under seismic response

    Energy Technology Data Exchange (ETDEWEB)

    Le, Jingyuan; Cui, Hongcheng; He, Qiang; Ju, Jinsan [China Agricultural University, Beijing (China); You, Xiaochuan [Tsinghua University, Beijing (China)

    2015-01-15

    This study adopted the finite element software ABAQUS to trace the dynamic response history of large reinforced concrete storage tank during different seismic excitations. The dynamic characteristics and failure modes of the tank's structure were investigated by considering the rebar's effect. Calculation results show that the large concrete storage tank remains in safe working conditions under a seismic acceleration of 55 cm/s{sup 2}. The joint of the concrete wall and dome begins to crack when seismic acceleration reaches 250 cm/s{sup 2}. As the earthquake continues, cracks spread until the top of the wall completely fails and stops working. The maximum displacement of the concrete tank and seismic acceleration are in proportion. Peak displacement and stress of the tank always appear behind the maximum acceleration.

  10. An integrated geodetic and seismic study of the Cusco Fault system in the Cusco Region-Southern Peru

    Science.gov (United States)

    Norabuena, E. O.; Tavera, H. J.

    2017-12-01

    The Cusco Fault system is composed by six main faults (Zurite, Tamboray, Qoricocha, Tambomachay, Pachatusan, and Urcos) extending in a NW-SE direction over the Cusco Region in southeastern Peru. From these, the Tambomachay is a normal fault of 20 km length, strikes N120°E and bounds a basin filled with quaternary lacustrine and fluvial deposits. Given its 5 km distance to Cusco, an historical and Inca's archeological landmark, it represents a great seismic hazard for its more than 350,000 inhabitants. The Tambomachay fault as well as the other secondary faults have been a source of significant seismic activity since historical times being the more damaging ones the Cusco earthquakes of 1650, 1950 and more recently April 1986 (M 5.8). Previous geological studies indicate that at the beginning of the Quaternary the fault showed a transcurrent mechanism leading to the formation of the Cusco basin. However, nowadays its mechanism is normal fault and scarps up to 22m can be observed. We report the current dynamics of the Tambomachay fault and secondary faults based on seismic activity imaged by a network of 29 broadband stations deployed in the Cusco Region as well as the deformation field inferred from GPS survey measurements carried out between 2014 and 2016.

  11. GPS measurements of crustal deformation across the southern Arava Valley section of the Dead Sea Fault and implications to regional seismic hazard assessment

    Science.gov (United States)

    Hamiel, Yariv; Masson, Frederic; Piatibratova, Oksana; Mizrahi, Yaakov

    2018-01-01

    Detailed analysis of crustal deformation along the southern Arava Valley section of the Dead Sea Fault is presented. Using dense GPS measurements we obtain the velocities of new near- and far-field campaign stations across the fault. We find that this section is locked with a locking depth of 19.9 ± 7.7 km and a slip rate of 5.0 ± 0.8 mm/yr. The geodetically determined locking depth is found to be highly consistent with the thickness of the seismogenic zone in this region. Analysis of instrumental seismic record suggests that only 1% of the total seismic moment accumulated since the last large event occurred about 800 years ago, was released by small to moderate earthquakes. Historical and paleo-seismic catalogs of this region together with instrumental seismic data and calculations of Coulomb stress changes induced by the 1995 Mw 7.2 Nuweiba earthquake suggest that the southern Arava Valley section of the Dead Sea Fault is in the late stage of the current interseismic period.

  12. Shallow Faulting in Morelia, Mexico, Based on Seismic Tomography and Geodetically Detected Land Subsidence

    Science.gov (United States)

    Cabral-Cano, E.; Arciniega-Ceballos, A.; Vergara-Huerta, F.; Chaussard, E.; Wdowinski, S.; DeMets, C.; Salazar-Tlaczani, L.

    2013-12-01

    Subsidence has been a common occurrence in several cities in central Mexico for the past three decades. This process causes substantial damage to the urban infrastructure and housing in several cities and it is a major factor to be considered when planning urban development, land-use zoning and hazard mitigation strategies. Since the early 1980's the city of Morelia in Central Mexico has experienced subsidence associated with groundwater extraction in excess of natural recharge from rainfall. Previous works have focused on the detection and temporal evolution of the subsidence spatial distribution. The most recent InSAR analysis confirms the permanence of previously detected rapidly subsiding areas such as the Rio Grande Meander area and also defines 2 subsidence patches previously undetected in the newly developed suburban sectors west of Morelia at the Fraccionamiento Del Bosque along, south of Hwy. 15 and another patch located north of Morelia along Gabino Castañeda del Rio Ave. Because subsidence-induced, shallow faulting develops at high horizontal strain localization, newly developed a subsidence areas are particularly prone to faulting and fissuring. Shallow faulting increases groundwater vulnerability because it disrupts discharge hydraulic infrastructure and creates a direct path for transport of surface pollutants into the underlying aquifer. Other sectors in Morelia that have been experiencing subsidence for longer time have already developed well defined faults such as La Colina, Central Camionera, Torremolinos and La Paloma faults. Local construction codes in the vicinity of these faults define a very narrow swath along which housing construction is not allowed. In order to better characterize these fault systems and provide better criteria for future municipal construction codes we have surveyed the La Colina and Torremolinos fault systems in the western sector of Morelia using seismic tomographic techniques. Our results indicate that La Colina Fault

  13. Reconciling experimental and static-dynamic numerical estimations of seismic anisotropy in Alpine Fault mylonites

    Science.gov (United States)

    Adam, L.; Frehner, M.; Sauer, K. M.; Toy, V.; Guerin-Marthe, S.; Boulton, C. J.

    2017-12-01

    Reconciling experimental and static-dynamic numerical estimations of seismic anisotropy in Alpine Fault mylonitesLudmila Adam1, Marcel Frehner2, Katrina Sauer3, Virginia Toy3, Simon Guerin-Marthe4, Carolyn Boulton5(1) University of Auckland, New Zealand, (2) ETH Zurich, Switzerland, (3) University of Otago, New Zealand (4) Durham University, Earth Sciences, United Kingdom (5) Victoria University of Wellington, New Zealand Quartzo-feldspathic mylonites and schists are the main contributors to seismic wave anisotropy in the vicinity of the Alpine Fault (New Zealand). We must determine how the physical properties of rocks like these influence elastic wave anisotropy if we want to unravel both the reasons for heterogeneous seismic wave propagation, and interpret deformation processes in fault zones. To study such controls on velocity anisotropy we can: 1) experimentally measure elastic wave anisotropy on cores at in-situ conditions or 2) estimate wave velocities by static (effective medium averaging) or dynamic (finite element) modelling based on EBSD data or photomicrographs. Here we compare all three approaches in study of schist and mylonite samples from the Alpine Fault. Volumetric proportions of intrinsically anisotropic micas in cleavage domains and comparatively isotropic quartz+feldspar in microlithons commonly vary significantly within one sample. Our analysis examines the effects of these phases and their arrangement, and further addresses how heterogeneity influences elastic wave anisotropy. We compare P-wave seismic anisotropy estimates based on millimetres-scale ultrasonic waves under in situ conditions, with simulations that account for micrometre-scale variations in elastic properties of constitutent minerals with the MTEX toolbox and finite-element wave propagation on EBSD images. We observe that the sorts of variations in the distribution of micas and quartz+feldspar within any one of our real core samples can change the elastic wave anisotropy by 10

  14. RMT focal plane sensitivity to seismic network geometry and faulting style

    Science.gov (United States)

    Johnson, Kendra L.; Hayes, Gavin; Herrmann, Robert B.; Benz, Harley M.; McNamara, Daniel E.; Bergman, Eric A.

    2016-01-01

    Modern tectonic studies often use regional moment tensors (RMTs) to interpret the seismotectonic framework of an earthquake or earthquake sequence; however, despite extensive use, little existing work addresses RMT parameter uncertainty. Here, we quantify how network geometry and faulting style affect RMT sensitivity. We examine how data-model fits change with fault plane geometry (strike and dip) for varying station configurations. We calculate the relative data fit for incrementally varying geometries about a best-fitting solution, applying our workflow to real and synthetic seismograms for both real and hypothetical station distributions and earthquakes. Initially, we conduct purely observational tests, computing RMTs from synthetic seismograms for hypothetical earthquakes and a series of well-behaved network geometries. We then incorporate real data and station distributions from the International Maule Aftershock Deployment (IMAD), which recorded aftershocks of the 2010 MW 8.8 Maule earthquake, and a set of regional stations capturing the ongoing earthquake sequence in Oklahoma and southern Kansas. We consider RMTs computed under three scenarios: (1) real seismic records selected for high data quality; (2) synthetic seismic records with noise computed for the observed source-station pairings and (3) synthetic seismic records with noise computed for all possible station-source pairings. To assess RMT sensitivity for each test, we observe the ‘fit falloff’, which portrays how relative fit changes when strike or dip varies incrementally; we then derive the ranges of acceptable strikes and dips by identifying the span of solutions with relative fits larger than 90 per cent of the best fit. For the azimuthally incomplete IMAD network, Scenario 3 best constrains fault geometry, with average ranges of 45° and 31° for strike and dip, respectively. In Oklahoma, Scenario 3 best constrains fault dip with an average range of 46°; however, strike is best constrained

  15. Non double couple seismic sources, faults interaction and hypothesis of self-organized criticality

    Directory of Open Access Journals (Sweden)

    S. Yunga

    2005-01-01

    Full Text Available Non double couple (NDC sources are considered in framework of the hypothesis that the process of seismic rupture can be viewed as a result of complicated fault geometry and its segmentation. Analytical approach is found to reveal reliability of NDC measure taking into consideration the values of seismic moment tensor errors. The study focuses on the comparison of the deformation modes of the NDC sources with the stress states in its vicinity. The deformation modes of faulting and fracturing at a small scale in NDC earthquake focus and at regional scale in geological unit were investigated using at the last case summation of seismic moment tensors. These local and regional deformation modes in some of geodynamic regimes confirm the self-similarity assumption. For the whole data set scaling relations seem to be more complicated. This feature implies that besides stresses second order factors, as the hydrothermal or magmatic pore fluids in rock, influence source characteristics and bring new complications in scaling relations.

  16. Triggered Seismicity in Utah from the November 3, 2002, Denali Fault Earthquake

    Science.gov (United States)

    Pankow, K. L.; Nava, S. J.; Pechmann, J. C.; Arabasz, W. J.

    2002-12-01

    Coincident with the arrival of the surface waves from the November 3, 2002, Mw 7.9 Denali Fault, Alaska earthquake (DFE), the University of Utah Seismograph Stations (UUSS) regional seismic network detected a marked increase in seismicity along the Intermountain Seismic Belt (ISB) in central and north-central Utah. The number of earthquakes per day in Utah located automatically by the UUSS's Earthworm system in the week following the DFE was approximately double the long-term average during the preceding nine months. From these preliminary data, the increased seismicity appears to be characterized by small magnitude events (M = 3.2) and concentrated in five distinct spatial clusters within the ISB between 38.75°and 42.0° N. The first of these earthquakes was an M 2.2 event located ~20 km east of Salt Lake City, Utah, which occurred during the arrival of the Love waves from the DFE. The increase in Utah earthquake activity at the time of the arrival of the surface waves from the DFE suggests that these surface waves triggered earthquakes in Utah at distances of more than 3,000 km from the source. We estimated the peak dynamic shear stress caused by these surface waves from measurements of their peak vector velocities at 43 recording sites: 37 strong-motion stations of the Advanced National Seismic System and six broadband stations. (The records from six other broadband instruments in the region of interest were clipped.) The estimated peak stresses ranged from 1.2 bars to 3.5 bars with a mean of 2.3 bars, and generally occurred during the arrival of Love waves of ~15 sec period. These peak dynamic shear stress estimates are comparable to those obtained from recordings of the 1992 Mw 7.3 Landers, California, earthquake in regions where the Landers earthquake triggered increased seismicity. We plan to present more complete analyses of UUSS seismic network data, further testing our hypothesis that the DFE remotely triggered seismicity in Utah. This hypothesis is

  17. Permeability and seismic velocity and their anisotropy across the Alpine Fault, New Zealand: An insight from laboratory measurements on core from the Deep Fault Drilling Project phase 1 (DFDP-1)

    Science.gov (United States)

    Allen, M. J.; Tatham, D.; Faulkner, D. R.; Mariani, E.; Boulton, C.

    2017-08-01

    The Alpine Fault, a transpressional plate boundary between the Australian and Pacific plates, is known to rupture quasiperiodically with large magnitude earthquakes (Mw 8). The hydraulic and elastic properties of fault zones are thought to vary over the seismic cycle, influencing the nature and style of earthquake rupture and associated processes. We present a suite of laboratory permeability and P (Vp) and S (Vs) wave velocity measurements performed on fault lithologies recovered during the first phase of the Deep Fault Drilling Project (DFDP-1), which sampled principal slip zone (PSZ) gouges, cataclasites, and fractured ultramylonites, with all recovered lithologies overprinted by abundant secondary mineralization, recording enhanced fluid-rock interaction. Core material was tested in three orthogonal directions, orientated relative to the down-core axis and, when present, foliation. Measurements were conducted with pore pressure (H2O) held at 5 MPa over an effective pressure (Peff) range of 5-105 MPa. Permeabilities and seismic velocities decrease with proximity to the PSZ with permeabilities ranging from 10-17 to 10-21 m2 and Vp and Vs ranging from 4400 to 5900 m/s in the ultramylonites/cataclasites and 3900 to 4200 m/s at the PSZ. In comparison with intact country rock protoliths, the highly variable cataclastic structures and secondary phyllosilicates and carbonates have resulted in an overall reduction in permeability and seismic wave velocity, as well as a reduction in anisotropy within the fault core. These results concur with other similar studies on other mature, tectonic faults in their interseismic period.

  18. Coseismic and postseismic deformation associated with the 2016 Mw 7.8 Kaikoura earthquake, New Zealand: fault movement investigation and seismic hazard analysis

    Science.gov (United States)

    Jiang, Zhongshan; Huang, Dingfa; Yuan, Linguo; Hassan, Abubakr; Zhang, Lupeng; Yang, Zhongrong

    2018-04-01

    The 2016 moment magnitude (Mw) 7.8 Kaikoura earthquake demonstrated that multiple fault segments can undergo rupture during a single seismic event. Here, we employ Global Positioning System (GPS) observations and geodetic modeling methods to create detailed images of coseismic slip and postseismic afterslip associated with the Kaikoura earthquake. Our optimal geodetic coseismic model suggests that rupture not only occurred on shallow crustal faults but also to some extent at the Hikurangi subduction interface. The GPS-inverted moment release during the earthquake is equivalent to a Mw 7.9 event. The near-field postseismic deformation is mainly derived from right-lateral strike-slip motions on shallow crustal faults. The afterslip did not only significantly extend northeastward on the Needles fault but also appeared at the plate interface, slowly releasing energy over the past 6 months, equivalent to a Mw 7.3 earthquake. Coulomb stress changes induced by coseismic deformation exhibit complex patterns and diversity at different depths, undoubtedly reflecting multi-fault rupture complexity associated with the earthquake. The Coulomb stress can reach several MPa during coseismic deformation, which can explain the trigger mechanisms of afterslip in two high-slip regions and the majority of aftershocks. Based on the deformation characteristics of the Kaikoura earthquake, interseismic plate coverage, and historical earthquakes, we conclude that Wellington is under higher seismic threat after the earthquake and great attention should be paid to potential large earthquake disasters in the near future.[Figure not available: see fulltext.

  19. Structure of Suasselkä Postglacial Fault in northern Finland obtained by analysis of ambient seismic noise

    Science.gov (United States)

    Afonin, Nikita; Kozlovskaya, Elena

    2016-04-01

    Understanding inner structure of seismogenic faults and their ability to reactivate is particularly important in investigating the continental intraplate seismicity regime. In our study we address this problem using analysis of ambient seismic noise recorded by the temporary DAFNE array in northern Fennoscandian Shield. The main purpose of the DAFNE/FINLAND passive seismic array experiment was to characterize the present-day seismicity of the Suasselkä post-glacial fault (SPGF) that was proposed as one potential target for the DAFNE (Drilling Active Faults in Northern Europe) project. The DAFNE/FINLAND array comprised the area of about 20 to 100 km and consisted of 8 short-period and 4 broad-band 3-component autonomous seismic stations installed in the close vicinity of the fault area. The array recorded continuous seismic data during September, 2011-May, 2013. Recordings of the array have being analyzed in order to identify and locate natural earthquakes from the fault area and to discriminate them from the blasts in the Kittilä Gold Mine. As a result, we found several dozens of natural seismic events originating from the fault area, which proves that the fault is still seismically active. In order to study the inner structure of the SPGF we use cross-correlation of ambient seismic noise recorded by the array. Analysis of azimuthal distribution of noise sources demonstrated that that during the time interval under consideration the distribution of noise sources is close to the uniform one. The continuous data were processed in several steps including single station data analysis, instrument response removal and time-domain stacking. The data were used to estimate empirical Green's functions between pairs of stations in the frequency band of 0.1-1 Hz and to calculate correspondent surface wave dispersion curves. After that S-wave velocity models were obtained as a result of dispersion curves inversion using Geopsy software. The results suggest that the area of

  20. Seismic Imaging of the Source Physics Experiment Site with the Large-N Seismic Array

    Science.gov (United States)

    Chen, T.; Snelson, C. M.; Mellors, R. J.

    2017-12-01

    The Source Physics Experiment (SPE) consists of a series of chemical explosions at the Nevada National Security Site. The goal of SPE is to understand seismic wave generation and propagation from these explosions. To achieve this goal, we need an accurate geophysical model of the SPE site. A Large-N seismic array that was deployed at the SPE site during one of the chemical explosions (SPE-5) helps us construct high-resolution local geophysical model. The Large-N seismic array consists of 996 geophones, and covers an area of approximately 2 × 2.5 km. The array is located in the northern end of the Yucca Flat basin, at a transition from Climax Stock (granite) to Yucca Flat (alluvium). In addition to the SPE-5 explosion, the Large-N array also recorded 53 weight drops. Using the Large-N seismic array recordings, we perform body wave and surface wave velocity analysis, and obtain 3D seismic imaging of the SPE site for the top crust of approximately 1 km. The imaging results show clear variation of geophysical parameter with local geological structures, including heterogeneous weathering layer and various rock types. The results of this work are being incorporated in the larger 3D modeling effort of the SPE program to validate the predictive models developed for the site.

  1. Pre-, Co-, and Post-Seismic Fault Slip in the Northern Chile Seismic Gap Associated with the April 1, 2014 (Mw 8.2) Pisagua Earthquake.

    Science.gov (United States)

    Simons, M.; Duputel, Z.; Fielding, E. J.; Galetzka, J.; Genrich, J. F.; Jiang, J.; Jolivet, R.; Kanamori, H.; Moore, A. W.; Ortega Culaciati, F. H.; Owen, S. E.; Riel, B. V.; Rivera, L. A.; Carrizo, D.; Cotte, N.; Jara, J.; Klotz, J.; Norabuena, E. O.; Ortega, I.; Socquet, A.; Samsonov, S. V.; Valderas Bermejo, M.

    2014-12-01

    The April 1, 2014 (Mw 8.2) Pisagua Earthquake occurred in Northern Chile, within a long recognized seismic gap in the Central Andean region that last experienced major megathrust events in 1868 and 1877. We built a continuous GPS network starting in 2005, with the ultimate goal of understanding the kinematics and dynamics of this portion of the subduction zone. Using observations from this network, as well as others in the region, combined with InSAR, seismic and tsunami observations, we obtain estimates of inter-seismic, co-seismic and initial post-seismic fault slip using an internally consistent Bayesian unregularized approach. We evaluate the extent of spatial overlap between regions of fault slip during this different time periods. Of particular interest to this event is the extent and nature of any geodetic evidence for transient slow fault slip preceding the Pisagua Earthquake mainshock. To this end, we compare daily and high rate GPS solutions, the former of which shows long period transient motion started about 15 days before the mainshock and with maximum registered amplitude of 14.2 +/- 2 [mm] at site PSGA. Contrary to published findings, we find that pre-seismic deformation seen by the GPS network can be explained as coseismic motion associated with the multiple foreshocks.

  2. Crustal structure at the western end of the North Anatolian Fault Zone from deep seismic sounding

    Directory of Open Access Journals (Sweden)

    B. Baier

    2001-06-01

    Full Text Available The first deep seismic sounding experiment in Northwestern Anatolia was carried out in October 1991 as part of the "German - Turkish Project on Earthquake Prediction Research" in the Mudurnu area of the North Anatolian Fault Zone. The experiment was a joint enterprise by the Institute of Meteorology and Geophysics of Frankfurt University, the Earthquake Research Institute (ERI in Ankara, and the Turkish Oil Company (TPAO. Two orthogonal profiles, each 120 km in length with a crossing point near Akyazi, were covered in succession by 30 short period tape recording seismograph stations with 2 km station spacing. 12 shots, with charge sizes between 100 and 250 kg, were fired and 342 seismograms out of 360 were used for evaluation. By coincidence an M b = 4.5 earthquake located below Imroz Island was also recorded and provided additional information on Moho and the sub-Moho velocity. A ray tracing method orginally developed by Weber (1986 was used for travel time inversion. From a compilation of all data two generalized crustal models were derived, one with velocity gradients within the layers and one with constant layer velocities. The latter consists of a sediment cover of about 2 km with V p » 3.6 km/s, an upper crystalline crust down to 13 km with V p » 5.9 km/s, a middle crust down to 25 km depth with V p » 6.5 km/s, a lower crust down to 39 km Moho depth with V p » 7.0 km/s and V p » 8.05 km/s below the Moho. The structure of the individual profiles differs slightly. The thickest sediment cover is reached in the Izmit-Sapanca-trough and in the Akyazi basin. Of particular interest is a step of about 4 km in the lower crust near Lake Sapanca and probably an even larger one in the Moho (derived from the Imroz earthquake data. After the catastrophic earthquake of Izmit on 17 August 1999 this significant heterogeneity in crustal structure appears in a new light with regard to the possible cause of the Izmit earthquake. Heterogeneities in

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

    Science.gov (United States)

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

    2016-10-01

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

  4. San Onofre/Zion auxiliary feedwater system seismic fault tree modeling

    International Nuclear Information System (INIS)

    Najafi, B.; Eide, S.

    1982-02-01

    As part of the study for the seismic evaluation of the San Onofre Unit 1 Auxiliary Feedwater System (AFWS), a fault tree model was developed capable of handling the effect of structural failure of the plant (in the event of an earthquake) on the availability of the AFWS. A compatible fault tree model was developed for the Zion Unit 1 AFWS in order to compare the results of the two systems. It was concluded that if a single failure of the San Onofre Unit 1 AFWS is to be prevented, some weight existing, locally operated locked open manual valves have to be used for isolation of a rupture in specific parts of the AFWS pipings

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

    Science.gov (United States)

    Weiwei, W.; Yaling, W.

    2017-12-01

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

  6. The large 1956 earthquake in the South Aegean: Macroseismic field configuration, faulting, and neotectonics of Amorgos Island

    Science.gov (United States)

    Papadopoulos, Gerassimos A.; Pavlides, Spyros B.

    1992-10-01

    New field observations of the seismic intensity distribution of the large (M s = 7.4) South Aegean (Amorgos) earthquake of 9 July 1956 are presented. Interpretations based on local ground conditions, structural properties of buildings and peculiarities of the rupture process lead to a re-evaluation of the macroseismic field configuration. This, together with the aftershock epicentral distribution, quite well defines the earthquake rupture zone, which trends NE-SW and coincides with the Amorgos Astypalea trough. The lateral extent of the rupture zone, however, is about 40% smaller than that predicted for Aegean earthquakes of M s = 7.4. This discrepancy could be attributed to sea-bottom topography changes, which seem to control the rupture terminations, and to relatively high stressdrop with respect to other Aegean earthquakes. Fault plane solutions obtained by several authors indicate either mainly normal faulting with a significant right-lateral strike-slip component or predominantly strike-slip motion. The neotectonism of Amorgos Island, based on new field observations, aerial photograph analysis and fault mechanisms, is consistent with the dip-slip interpretation. The neotectonic master fault of Amorgos and the 1956 seismic faulting appear to belong to the same tectonic phase (NE-SW strike and a southeasterly dip). However, the significant right-lateral strike-slip component supports the idea that the Amorgos region deviates from the simple description for pure extension in back-arc conditions.

  7. Seismic slip recorded in tourmaline fault mirrors from Elba Island (Italy)

    Science.gov (United States)

    Viti, C.; Brogi, A.; Liotta, D.; Mugnaioli, E.; Spiess, R.; Dini, A.; Zucchi, M.; Vannuccini, G.

    2016-05-01

    This paper reports the first example of fault mirrors developed in an unusual protolith, consisting of tourmaline crystals with interstitial goethite. The deformation mechanisms active in the fault zone have been investigated from the outcrop to the nanoscale, aiming to identify possible traces of frictional heating at seismic slip rate, as observed for other fault mirrors in different protoliths. The investigation revealed the superposition of two main deformational stages. The first was dominated by brittle processes and produced a cataclastic/ultracataclastic principal slip zone, a few mm thick; the second was associated with seismic slip and produced a sharp discontinuity (the principal slip surface) within the cataclastic/ultracataclastic zone. The mirror-like coating, a few microns thick, occurs on the principal slip surface, and is characterized by 1) absence of interstitial goethite; 2) occurrence of truncated tourmaline crystals; 3) highly variable grain size, from 200 μm to 200 nm; 4) tourmaline close packing with interlobate grain boundaries, and 5) tourmaline random crystallographic orientation. Micro and nanostructural investigations indicate the occurrence of thermally-activated processes, involving both interstitial goethite and tourmaline. In particular, close to the principal slip surface, goethite is completely decomposed, and produced an amorphous porous material, with local topotactic recrystallization of hematite. Tourmaline clasts are typically characterized by strongly lobate boundaries, indicative of reaction and partial decomposition at grain boundaries. TEM observations revealed the occurrence of tourmaline nanograins, a few tens of nm in size, characterized by rounded shape and fading amorphous boundaries, that cannot be obtained by brittle processes. Lastly, the peculiar interlobate microstructure of the mirror surface is interpreted as the result of grain boundary recrystallization processes taking place by deformation at high

  8. Spontaneous non-volcanic tremor detected in the Anza Seismic Gap of San Jacinto Fault

    Science.gov (United States)

    Hutchison, A. A.; Ghosh, A.

    2017-12-01

    Non-volcanic tremor (NVT), a type of slow earthquake, is becoming more frequently detected along plate boundaries, particularly in subduction zones, and is also observed along the San Andreas Fault [e.g. Nadeau & Dolenc, 2005]. NVT is typically associated with transient deformation (i.e. slow slip) in the transition zone [e.g. Ide et al., 2007], and at times it is observed with deep creep along faults [e.g. Beroza & Ide, 2011]. Using several independent location and detection methods including multi-beam backprojection [Ghosh et al., 2009a; 2012], envelope cross correlation [Wech & Creager, 2008], spectral analyses and visual inspection of existing network stations and high-density mini seismic array data, we detect multiple discrete spontaneous tremor events in the Anza Gap of the San Jacinto Fault (SJF) in June, 2011. The events occur on the SJF where the Hot Springs Fault terminates, on the northwestern boundary of the Anza Gap, below the inferred seismogenic zone characterized by velocity weakening frictional behavior [e.g. Lindsay et al., 2014]. The location methods provide consistent locations for each event in our catalog. Low slowness values help rule-out surface noise that may result in false detections. Analyses of frequency spectra show these time windows are depleted in high frequency energy in the displacement amplitude spectrum compared to small local regular (fast) earthquakes. This spectral pattern is characteristic of tremor [Shelly et al., 2007]. We interpret this tremor to be a seismic manifestation of slow-slip events below the seismogenic zone. Recently, an independent geodetic study suggests that the 2010 El Mayor-Cucupah earthquake triggered a slow-slip event in the Anza Gap [Inbal et al., 2017]. In addition, multiple studies infer deep creep in the SJF [e.g. Meng & Peng et al., 2016; Jiang & Fialko, 2016] indicating that this fault is capable of producing slow slip events. Transient tectonic behavior like tremor and slow slip may be playing

  9. A fast BDD algorithm for large coherent fault trees analysis

    International Nuclear Information System (INIS)

    Jung, Woo Sik; Han, Sang Hoon; Ha, Jaejoo

    2004-01-01

    Although a binary decision diagram (BDD) algorithm has been tried to solve large fault trees until quite recently, they are not efficiently solved in a short time since the size of a BDD structure exponentially increases according to the number of variables. Furthermore, the truncation of If-Then-Else (ITE) connectives by the probability or size limit and the subsuming to delete subsets could not be directly applied to the intermediate BDD structure under construction. This is the motivation for this work. This paper presents an efficient BDD algorithm for large coherent systems (coherent BDD algorithm) by which the truncation and subsuming could be performed in the progress of the construction of the BDD structure. A set of new formulae developed in this study for AND or OR operation between two ITE connectives of a coherent system makes it possible to delete subsets and truncate ITE connectives with a probability or size limit in the intermediate BDD structure under construction. By means of the truncation and subsuming in every step of the calculation, large fault trees for coherent systems (coherent fault trees) are efficiently solved in a short time using less memory. Furthermore, the coherent BDD algorithm from the aspect of the size of a BDD structure is much less sensitive to variable ordering than the conventional BDD algorithm

  10. Seismic Supercycles of Normal Faults in Central Italy over Various Time Scales Revealed by 36Cl Cosmogenic Dating

    Science.gov (United States)

    Benedetti, L. C.; Tesson, J.; Perouse, E.; Puliti, I.; Fleury, J.; Rizza, M.; Billant, J.; Pace, B.

    2017-12-01

    The use of 36Cl cosmogenic nuclide as a paleoseismological tool for normal faults in the Mediterranean has revolutionized our understanding of their seismic cycle (Gran Mitchell et al. 2001, Benedetti et al. 2002). Here we synthetized results obtained on 13 faults in Central Italy. Those records cover a period of 8 to 45 ka. The mean recurrence time of retrieved seismic events is 5.5 ±6 ka, with a mean slip per event of 2.5 ± 1.8 m and a mean slip-rate from 0.1 to 2.4 mm/yr. Most retrieved events correspond to single events according to scaling relationships. This is also supported by the 2 m-high co-seismic slip observed on the Mt Vettore fault after the October 30, 2016 M6.5 earthquake in Central Italy (EMERGEO working group). Our results suggest that all faults have experienced one or several periods of slip acceleration with bursts of seismic activity, associated with very high slip-rate of 1.7-9 mm/yr, corresponding to 2-20 times their long-term slip-rate. The duration of those bursts is variable from a fault to another (from recurrence time. This might suggest that the seismic activity of those faults could be controlled by their intrinsic properties (e.g. long-term slip-rate, fault-length, state of structural maturity). Our results also show events clustering with several faults rupturing in less than 500 yrs on adjacent or distant faults within the studied area. The Norcia-Amatrice seismic sequence, ≈ 50 km north of our study area, also evidenced this clustering behaviour, with over the last 20 yrs several successive events of Mw 5 to 6.5 (from north to south: Colfiorito 1997 Mw6.0, Norcia 2016 Mw6.5, L'Aquila 2009 Mw6.3), rupturing various fault systems, over a total length of ≈100 km. This sequence will allow to better understand earthquake kinematics and spatiotemporal slip distribution during those seismic bursts.

  11. Seismic attribute detection of faults and fluid pathways within an active strike-slip shear zone: New insights from high-resolution 3D P-Cable™ seismic data along the Hosgri Fault, offshore California

    Science.gov (United States)

    Kluesner, Jared W.; Brothers, Daniel

    2016-01-01

    Poststack data conditioning and neural-network seismic attribute workflows are used to detect and visualize faulting and fluid migration pathways within a 13.7 km2 13.7 km2 3D P-Cable™ seismic volume located along the Hosgri Fault Zone offshore central California. The high-resolution 3D volume used in this study was collected in 2012 as part of Pacific Gas and Electric’s Central California Seismic Imaging Project. Three-dimensional seismic reflection data were acquired using a triple-plate boomer source (1.75 kJ) and a short-offset, 14-streamer, P-Cable system. The high-resolution seismic data were processed into a prestack time-migrated 3D volume and publically released in 2014. Postprocessing, we employed dip-steering (dip and azimuth) and structural filtering to enhance laterally continuous events and remove random noise and acquisition artifacts. In addition, the structural filtering was used to enhance laterally continuous edges, such as faults. Following data conditioning, neural-network based meta-attribute workflows were used to detect and visualize faults and probable fluid-migration pathways within the 3D seismic volume. The workflow used in this study clearly illustrates the utility of advanced attribute analysis applied to high-resolution 3D P-Cable data. For example, results from the fault attribute workflow reveal a network of splayed and convergent fault strands within an approximately 1.3 km wide shear zone that is characterized by distinctive sections of transpressional and transtensional dominance. Neural-network chimney attribute calculations indicate that fluids are concentrated along discrete faults in the transtensional zones, but appear to be more broadly distributed amongst fault bounded anticlines and structurally controlled traps in the transpressional zones. These results provide high-resolution, 3D constraints on the relationships between strike-slip fault mechanics, substrate deformation, and fluid migration along an active

  12. Fault Lines: Seismicity and the Fracturing of Energy Narratives in Oklahoma

    Science.gov (United States)

    Grubert, E.; Drummond, V. A.; Brandt, A. R.

    2016-12-01

    Fault Lines: Seismicity and the Fracturing of Energy Narratives in Oklahoma Virginia Drummond1, Emily Grubert21Stanford University, Stanford Earth Summer Undergraduate Research Program2Stanford University, Emmett Interdisciplinary Program in Environment and ResourcesOklahoma is an oil state where residents have historically been supportive of the oil and gas industry. However, a dramatic increase in seismic activity between 2009 and 2015 widely attributed to wastewater injection associated with oil production is a new and highly salient consequence of oil development, affecting local communities' relationship to the environment and to the oil industry. Understanding how seismicity plays into Oklahoma's evolving dialogue about energy is integral to understanding both the current realities and the future of energy communities in Oklahoma.This research engages Oklahoma residents through open-ended interviews and mixed quantitative-qualitative survey research to characterize how energy narratives shape identity in response to conflict between environmental outcomes and economic interest. We perform approximately 20 interviews with residents of Oklahoma, with particular attention to recruiting residents from a wide range of age groups and who work either within or outside the oil and gas industry. General population surveys supplementing detailed interviews with information about community characteristics, social and environmental priorities, and experience with hazards are delivered to residents selected at random from zip codes known to have experienced significant seismicity. We identify narratives used by residents in response to tension between economic and environmental concerns, noting Oklahoma as an interesting case study for how a relatively pro-industry community reacts to and reframes its relationship with energy development, given conflict. In particular, seismicity has fractured the dominant narrative of oil development as positive into new narratives

  13. Geological Identification of Seismic Source at Opak Fault Based on Stratigraphic Sections of the Southern Mountains

    Directory of Open Access Journals (Sweden)

    Hita Pandita

    2016-08-01

    Full Text Available Earthquake is one of the unpredicted natural disasters on our earth. Despite of the absence of high-accuracy method to precisely predict the occurrence of earthquake, numerous studies have been carried out by seismologists to find it. One of the efforts to address the vulnerability of a region to earthquakes is by recognizing the type of rock as the source of the earthquake. Opak Fault is an active fault which was thought to be the source of earthquakes in Yogyakarta and adjacent areas. This study aimed to determine the seismic source types of rocks in Yogyakarta and adjacent areas. The methods were by measuring stratigraphic sections and the layer thickness in the western part of Southern Mountains. Field study was done in 6 (six research sites. Results of stratigraphic measurement indicated the sedimentary rocks in the Southern Mountains was 3.823 km in thick, while the bedrock was more than 1.042 km in thick. Based on the result, the rock types as the seismic source were thought to originate from the continental crust rocks formed of granite and metamorphic complex.

  14. Temporal b-Value Variations through out a Seismic Faulting Process: The 2008 Taoyuan Earthquake in Taiwan

    Directory of Open Access Journals (Sweden)

    Cheng-Horng Lin

    2010-01-01

    Full Text Available Temporal b-value variations have been completely obtained for the seismic faulting process of the 4 March 2008 Taoyuan earthquake (ML = 5.2, southern Taiwan. In addition to triggering several hundred after shocks, the mainshock was preceded by two groups of foreshocks (64 events that clustered along the narrow major fault zone. A high b-value of ~1.25, estimated from the foreshock series, representing fault growth, was significantly larger than the b-values of 0.80 and 0.81, obtained respectively from after shocks and back ground seismicity. Also there were some pre-shocks (i.e., micro-earth quakes that occurred one month before the earthquake sequence, with an extremely high b-value of ~2.1. This number might successfully indicate pre-nucleation seismic features in the vicinity of the fault zone. These seismic characteristics are fundamentally very similar to general features such as fracture nucleation and growth observed in rock samples under controlled stress in laboratory experiments, and thus ought to be considered to improve our understanding of crustal fault growth.

  15. Structure, Kinematics and Origin of Radial Faults: 3D Seismic Observations from the Santos Basin, offshore Brazil

    Science.gov (United States)

    Coleman, Alexander; Jackson, Christopher A.-L.

    2017-04-01

    Salt stock growth is typically accompanied by the development of geometrically and kinematically complex fault networks in the surrounding country rock. The most common networks comprise radial faults; these are characterised by low displacement (stock into flanking strata. Radial faults are commonly observed in an arched, unpierced roof developed above a rising salt stock; in these cases, the faults are typically well-imaged seismically and likely form due to outer-arc extension during overburden stretching. Radial faults are also found at deeper structural levels, in strata flanking the diapir stem; in these cases, they are typically less well-imaged, thus their structure, kinematics and origin are less well understood. Furthermore, understanding the growth of radial faults may provide insights into hydrocarbon reservoir compartmentalisation and the evolution of neighbouring salt stocks. Here, we use high-quality 3D seismic reflection data from the Santos Basin, offshore Brazil to determine the structure and kinematics, and infer the likely origin of exceptionally well-imaged radial faults overlying and flanking a mature salt stock. Furthermore, we compare the geometric (e.g. throw, geometry, spacing, distribution etc.) and kinematic (e.g. timing of formation and duration of activity) characteristics of radial faults at both structural levels, allowing us to infer their temporal relationship and likely origins. We show that radial faults regardless of their structural level typically have aspect ratios of c. 1.8 - 2, are laterally-restricted in the vicinity of the salt, and have lengths of indices of c. 1, with low throw gradients of 0.05 - 0.1 at the upper tip indicate that radial faults were likely blind. Throws range from 5 - 80 ms, with throw-maxima within 1 - 2 radii of the salt diapir. However, we note that the position of the throw maxima is not at the same level for all radial faults. We propose that radial faults nucleate and initially grow as blind

  16. Fluid activity within the North Anatolian Fault Zone according to 3D marine seismic data on the Sea of Marmara Western High

    Science.gov (United States)

    Grall, C.; Henry, P.; Thomas, Y.; Marsset, B.; Westbrook, G.; Saritas, H.; Géli, L.; Ruffine, L.; Dupré, S.; Scalabrin, C.; Augustin, J. M.; Cifçi, G.; Zitter, T.

    2012-04-01

    Along the northern branch of the North Anatolian Fault Zone (NAFZ) within the Sea of Marmara, numerous gas seeps occur. A large part of the gas origin is biogenic but on the Western High, gas bubbles and gas hydrate with a thermogenic signature have been sampled. The expulsion of deep fluids opened new perspective about the permeability, the mechanical properties and the monitoring of the NAFZ. Consequently, the Western High was selected for the deployment of a 3D seismic acquisition layout during the MARMESONET cruise (2009). Thirty-three km2 of high resolution seismic data (with a frequency content of 50-180 Hz) have been collected within the shear band of the fault. The SIMRAD EM-302 was also operated to detect acoustic anomalies related to the presence of gas bubbles in the water column. Within the upper sedimentary cover (seismic penetration ranges from 100 to 500 m bsf), high seismic amplitude variations of the reflectors allow to identify gas traps and gas pathways. Local high amplitude of negative polarity, such as flat spots and bright spots, are observed. Amplitude anomalies are located above and within anticlines and along normal faults. They often correlate with seafloor manifestations of fluid outflow and gas plumes in the water column. This suggests that gas migrates from depth towards the seafloor along normal faults and permeable strata, and part of it is trapped in anticlines. North of the NAF, seabed mounds, corresponding to active hydrocarbon gas seeps, are aligned along a NE-SW direction. They are linked in depth to buried mud volcanoes with an episodic activity. The last mud eruption activity apparently just before or during the Red-H1 horizon deposition which is a prominent reflector of high amplitude and negative polarity occurring all over the Sea of Marmara. It has been interpreted as a stratigraphic horizon, corresponding to slow sedimentation and high sea-level interglacial period.

  17. Imaging near-subsurface subrosion structures and faults using SH-wave reflection seismics

    Science.gov (United States)

    Wadas, Sonja; Polom, Ulrich; Buness, Hermann; Krawczyk, Charlotte

    2016-04-01

    Subrosion is a term for underground leaching of soluble rocks and is a global phenomenon. It involves dissolution of evaporites due to the presence of unsaturated water, fractures and faults. Fractures and faults are pathways for water to circulate and to generate subsurface cavities. Depending on the leached material and the parameters of the generation process, especially the dissolution rate, different kinds of subrosion structures evolve in the subsurface. The two end members are collapse and depression structures. Subrosion is a natural process, but it can be enhanced by anthropogenic factors like manipulation of the aquifer system and groundwater flow and by e.g. extraction of saline water. The formation of sinkholes and depressions are a dangerous geohazard, especially if they occur in urban areas, which often leads to building and infrastructural damage and life-threatening situations. For this reason investigations of the processes that induce subrosion and a detailed analysis of the resulting structures are of importance. To develop a comprehensive model of near-subsurface subrosion structures, reflection seismics is one of the methods used by the Leibniz Institute for Applied Geophysics. The study area is located in the city of Bad Frankenhausen in northern Thuringia, Germany. Most of the geological underground of Thuringia is characterized by Permian deposits. Bad Frankenhausen is situated directly south of the Kyffhäuser mountain range at the Kyffhäuser Southern Margin Fault. This major fault is one of the main pathways for the circulating ground- and meteoric waters that leach the Permian deposits, especially the Leine-, Staßfurt- and Werra Formations. 2014 and 2015 eight shear wave reflection seismic profiles were carried out in the urban area of Bad Frankenhausen and three profiles in the countrified surroundings. Altogether ca. 3.6 km were surveyed using a landstreamer as receiver and an electro-dynamic vibrator as source. The surveys were

  18. A Thermo-Hydro-Mechanical coupled Numerical modeling of Injection-induced seismicity on a pre-existing fault

    Science.gov (United States)

    Kim, Jongchan; Archer, Rosalind

    2017-04-01

    In terms of energy development (oil, gas and geothermal field) and environmental improvement (carbon dioxide sequestration), fluid injection into subsurface has been dramatically increased. As a side effect of these operations, a number of injection-induced seismic activities have also significantly risen. It is known that the main causes of induced seismicity are changes in local shear and normal stresses and pore pressure as well. This mechanism leads to increase in the probability of earthquake occurrence on permeable pre-existing fault zones predominantly. In this 2D fully coupled THM geothermal reservoir numerical simulation of injection-induced seismicity, we investigate the thermal, hydraulic and mechanical behavior of the fracture zone, considering a variety of 1) fault permeability, 2) injection rate and 3) injection temperature to identify major contributing parameters to induced seismic activity. We also calculate spatiotemporal variation of the Coulomb stress which is a combination of shear stress, normal stress and pore pressure and lastly forecast the seismicity rate on the fault zone by computing the seismic prediction model of Dieterich (1994).

  19. Permeability and seismic velocity anisotropy across a ductile-brittle fault zone in crystalline rock

    Science.gov (United States)

    Wenning, Quinn C.; Madonna, Claudio; de Haller, Antoine; Burg, Jean-Pierre

    2018-05-01

    This study characterizes the elastic and fluid flow properties systematically across a ductile-brittle fault zone in crystalline rock at the Grimsel Test Site underground research laboratory. Anisotropic seismic velocities and permeability measured every 0.1 m in the 0.7 m across the transition zone from the host Grimsel granodiorite to the mylonitic core show that foliation-parallel P- and S-wave velocities systematically increase from the host rock towards the mylonitic core, while permeability is reduced nearest to the mylonitic core. The results suggest that although brittle deformation has persisted in the recent evolution, antecedent ductile fabric continues to control the matrix elastic and fluid flow properties outside the mylonitic core. The juxtaposition of the ductile strain zone next to the brittle zone, which is bounded inside the two mylonitic cores, causes a significant elastic, mechanical, and fluid flow heterogeneity, which has important implications for crustal deformation and fluid flow and for the exploitation and use of geothermal energy and geologic waste storage. The results illustrate how physical characteristics of faults in crystalline rocks change in fault zones during the ductile to brittle transitions.

  20. Microstructures Indicate Large Influence of Temperature and Fluid Pressure on the Reactivation of the Alpine Fault, New Zealand

    Science.gov (United States)

    Schuck, B.; Janssen, C.; Schleicher, A.; Toy, V.; Dresen, G.

    2017-12-01

    The transpressional Alpine Fault within New Zealand's South Island is the major structure that accommodates relative motion between the Pacific and the Australian Plates. It has been intensively studied, because it is late in its 291-year seismic cycle (Cochran et al., 2017; doi: 10.1016/j.epsl.2017.02.026), is likely to generate large (i.e. MW > 8) earthquakes, thus presents the biggest seismic hazard in the region. However, because it is severely misoriented in the present-day stress field for reactivation (Boese et al., 2013; doi: 10.1016/j.epsl.2013.06.030), supra-lithostatic fluid-pressures are required for rupture nucleation. We have analyzed microstructures (SEM and TEM), geochemistry (ICP-OES) and mineralogy (XRD) of outcrop samples of the fault core to investigate the influence of fluids on the geomechanical behavior of the fault. Fluid-related alteration is pervasive within 20 m of the principal slip zone (PSZ) (Sutherland et al., 2012; doi: 10.1130/G33614.1), which is an incohesive, cemented and repeatedly reworked fault gouge mostly consisting of a fine-grained matrix composed of comminuted detrital quartz and feldspar as well as authigenic chlorite and calcite. Authigenic phases seal the PSZ for interseismic cross-fault fluid flow and enable fluid pressure to build-up. Notable, smectite, previously considered to significantly influence propagation of Alpine Fault ruptures, is not present in these samples. Undeformed, euhedral chlorite grains suggest that the processes leading to fault sealing are not only active at greater depths but also close to the surface. The absence of smectite and the presence of undeformed chlorite at very shallow depths can be attributed to the fault's high geothermal gradient of > 120 °C km-1 (Sutherland et al., 2012; doi:10.1038/nature22355), which gives temperature conditions unfavorable for smectite to be stable and fostering chlorite growth. A pervasive network of anastomosing calcite veins in the fault core, depicting

  1. Modelling Active Faults in Probabilistic Seismic Hazard Analysis (PSHA) with OpenQuake: Definition, Design and Experience

    Science.gov (United States)

    Weatherill, Graeme; Garcia, Julio; Poggi, Valerio; Chen, Yen-Shin; Pagani, Marco

    2016-04-01

    The Global Earthquake Model (GEM) has, since its inception in 2009, made many contributions to the practice of seismic hazard modeling in different regions of the globe. The OpenQuake-engine (hereafter referred to simply as OpenQuake), GEM's open-source software for calculation of earthquake hazard and risk, has found application in many countries, spanning a diversity of tectonic environments. GEM itself has produced a database of national and regional seismic hazard models, harmonizing into OpenQuake's own definition the varied seismogenic sources found therein. The characterization of active faults in probabilistic seismic hazard analysis (PSHA) is at the centre of this process, motivating many of the developments in OpenQuake and presenting hazard modellers with the challenge of reconciling seismological, geological and geodetic information for the different regions of the world. Faced with these challenges, and from the experience gained in the process of harmonizing existing models of seismic hazard, four critical issues are addressed. The challenge GEM has faced in the development of software is how to define a representation of an active fault (both in terms of geometry and earthquake behaviour) that is sufficiently flexible to adapt to different tectonic conditions and levels of data completeness. By exploring the different fault typologies supported by OpenQuake we illustrate how seismic hazard calculations can, and do, take into account complexities such as geometrical irregularity of faults in the prediction of ground motion, highlighting some of the potential pitfalls and inconsistencies that can arise. This exploration leads to the second main challenge in active fault modeling, what elements of the fault source model impact most upon the hazard at a site, and when does this matter? Through a series of sensitivity studies we show how different configurations of fault geometry, and the corresponding characterisation of near-fault phenomena (including

  2. Seismic hazard in Hawaii: High rate of large earthquakes and probabilistics ground-motion maps

    Science.gov (United States)

    Klein, F.W.; Frankel, A.D.; Mueller, C.S.; Wesson, R.L.; Okubo, P.G.

    2001-01-01

    The seismic hazard and earthquake occurrence rates in Hawaii are locally as high as that near the most hazardous faults elsewhere in the United States. We have generated maps of peak ground acceleration (PGA) and spectral acceleration (SA) (at 0.2, 0.3 and 1.0 sec, 5% critical damping) at 2% and 10% exceedance probabilities in 50 years. The highest hazard is on the south side of Hawaii Island, as indicated by the MI 7.0, MS 7.2, and MI 7.9 earthquakes, which occurred there since 1868. Probabilistic values of horizontal PGA (2% in 50 years) on Hawaii's south coast exceed 1.75g. Because some large earthquake aftershock zones and the geometry of flank blocks slipping on subhorizontal decollement faults are known, we use a combination of spatially uniform sources in active flank blocks and smoothed seismicity in other areas to model seismicity. Rates of earthquakes are derived from magnitude distributions of the modem (1959-1997) catalog of the Hawaiian Volcano Observatory's seismic network supplemented by the historic (1868-1959) catalog. Modern magnitudes are ML measured on a Wood-Anderson seismograph or MS. Historic magnitudes may add ML measured on a Milne-Shaw or Bosch-Omori seismograph or MI derived from calibrated areas of MM intensities. Active flank areas, which by far account for the highest hazard, are characterized by distributions with b slopes of about 1.0 below M 5.0 and about 0.6 above M 5.0. The kinked distribution means that large earthquake rates would be grossly under-estimated by extrapolating small earthquake rates, and that longer catalogs are essential for estimating or verifying the rates of large earthquakes. Flank earthquakes thus follow a semicharacteristic model, which is a combination of background seismicity and an excess number of large earthquakes. Flank earthquakes are geometrically confined to rupture zones on the volcano flanks by barriers such as rift zones and the seaward edge of the volcano, which may be expressed by a magnitude

  3. Seismic Moment and Recurrence using Luminescence Dating Techniques: Characterizing brittle fault zone materials suitable for luminescence dating

    Science.gov (United States)

    Tsakalos, E.; Lin, A.; Bassiakos, Y.; Kazantzaki, M.; Filippaki, E.

    2017-12-01

    During a seismic-geodynamic process, frictional heating and pressure are generated on sediments fragments resulting in deformation and alteration of minerals contained in them. The luminescence signal enclosed in minerals crystal lattice can be affected and even zeroed during such an event. This has been breakthrough in geochronological studies as it could be utilized as a chronometer for the previous seismic activity of a tectonically active area. Although the employment of luminescence dating has in some cases been successfully described, a comprehensive study outlining and defining protocols for routine luminescence dating applied to neotectonic studies has not been forthcoming. This study is the experimental investigation, recording and parameterization of the effects of tectonic phenomena on minerals luminescence signal and the development of detailed protocols for the standardization of the luminescence methodology for directly dating deformed geological formations, so that the long-term temporal behaviour of seismically active faults could be reasonably understood and modeled. This will be achieved by: a) identifying and proposing brittle fault zone materials suitable for luminescence dating using petrological, mineralogical and chemical analyses and b) investigating the "zeroing" potential of the luminescence signal of minerals contained in fault zone materials by employing experimental simulations of tectonic processes in the laboratory, combined with luminescence measurements on samples collected from real fault zones. For this to be achieved, a number of samples collected from four faults of four different geographical regions will be used. This preliminary-first step of the study presents the microstructural, and mineralogical analyses for the characterization of brittle fault zone materials that contain suitable minerals for luminescence dating (e.g., quartz and feldspar). The results showed that the collected samples are seismically deformed fault

  4. Seismic Search Engine: A distributed database for mining large scale seismic data

    Science.gov (United States)

    Liu, Y.; Vaidya, S.; Kuzma, H. A.

    2009-12-01

    The International Monitoring System (IMS) of the CTBTO collects terabytes worth of seismic measurements from many receiver stations situated around the earth with the goal of detecting underground nuclear testing events and distinguishing them from other benign, but more common events such as earthquakes and mine blasts. The International Data Center (IDC) processes and analyzes these measurements, as they are collected by the IMS, to summarize event detections in daily bulletins. Thereafter, the data measurements are archived into a large format database. Our proposed Seismic Search Engine (SSE) will facilitate a framework for data exploration of the seismic database as well as the development of seismic data mining algorithms. Analogous to GenBank, the annotated genetic sequence database maintained by NIH, through SSE, we intend to provide public access to seismic data and a set of processing and analysis tools, along with community-generated annotations and statistical models to help interpret the data. SSE will implement queries as user-defined functions composed from standard tools and models. Each query is compiled and executed over the database internally before reporting results back to the user. Since queries are expressed with standard tools and models, users can easily reproduce published results within this framework for peer-review and making metric comparisons. As an illustration, an example query is “what are the best receiver stations in East Asia for detecting events in the Middle East?” Evaluating this query involves listing all receiver stations in East Asia, characterizing known seismic events in that region, and constructing a profile for each receiver station to determine how effective its measurements are at predicting each event. The results of this query can be used to help prioritize how data is collected, identify defective instruments, and guide future sensor placements.

  5. Fractal properties and simulation of micro-seismicity for seismic hazard analysis: a comparison of North Anatolian and San Andreas Fault Zones

    Directory of Open Access Journals (Sweden)

    Naside Ozer

    2012-02-01

    Full Text Available We analyzed statistical properties of earthquakes in western Anatolia as well as the North Anatolian Fault Zone (NAFZ in terms of spatio-temporal variations of fractal dimensions, p- and b-values. During statistically homogeneous periods characterized by closer fractal dimension values, we propose that occurrence of relatively larger shocks (M >= 5.0 is unlikely. Decreases in seismic activity in such intervals result in spatial b-value distributions that are primarily stable. Fractal dimensions decrease with time in proportion to increasing seismicity. Conversely, no spatiotemporal patterns were observed for p-value changes. In order to evaluate failure probabilities and simulate earthquake occurrence in the western NAFZ, we applied a modified version of the renormalization group method. Assuming an increase in small earthquakes is indicative of larger shocks, we apply the mentioned model to micro-seismic (M<= 3.0 activity, and test our results using San Andreas Fault Zone (SAFZ data. We propose that fractal dimension is a direct indicator of material heterogeneity and strength. Results from a model suggest simulated and observed earthquake occurrences are coherent, and may be used for seismic hazard estimation on creeping strike-slip fault zones.

  6. Coseismic and Early Post-Seismic Slip Distributions of the 2012 Emilia (Northern Italy) Seismic Sequence: New Insights in the Faults Activation and Resulting Stress Changes on Adjacent Faults

    Science.gov (United States)

    Cheloni, D.; Giuliani, R.; D'Agostino, N.; Mattone, M.; Bonano, M.; Fornaro, G.; Lanari, R.; Reale, D.

    2015-12-01

    The 2012 Emilia sequence (main shocks Mw 6.1 May 20 and Mw 5.9 May 29) ruptured two thrust segments of a ~E-W trending fault system of the buried Ferrara Arc, along a portion of the compressional system of the Apennines that had remained silent during past centuries. Here we use the rupture geometry constrained by the aftershocks and new geodetic data (levelling, InSAR and GPS measurements) to estimate an improved coseismic slip distribution of the two main events. In addition, we use post-seismic displacements, described and analyzed here for the first time, to infer a brand new post-seismic slip distribution of the May 29 event in terms of afterslip on the same coseismic plane. In particular, in this study we use a catalog of precisely relocated aftershocks to explore the different proposed geometries of the proposed thrust segments that have been published so far and estimate the coseismic and post-seismic slip distributions of the ruptured planes responsible for the two main seismic events from a joint inversion of the geodetic data.Joint inversion results revealed that the two earthquakes ruptured two distinct planar thrust faults, characterized by single main coseismic patches located around the centre of the rupture planes, in agreement with the seismological and geological information pointing out the Ferrara and the Mirandola thrust faults, as the causative structures of the May 20 and May 29 main shocks respectively.The preferred post-seismic slip distribution related to the 29 May event, yielded to a main patch of afterslip (equivalent to a Mw 5.6 event) located westward and up-dip of the main coseismic patch, suggesting that afterslip was triggered at the edges of the coseismic asperity. We then use these co- and post-seismic slip distribution models to calculate the stress changes on adjacent fault.

  7. Hydraulic Fracture Induced Seismicity During A Multi-Stage Pad Completion in Western Canada: Evidence of Activation of Multiple, Parallel Faults

    Science.gov (United States)

    Maxwell, S.; Garrett, D.; Huang, J.; Usher, P.; Mamer, P.

    2017-12-01

    Following reports of injection induced seismicity in the Western Canadian Sedimentary Basin, regulators have imposed seismic monitoring and traffic light protocols for fracturing operations in specific areas. Here we describe a case study in one of these reservoirs, the Montney Shale in NE British Columbia, where induced seismicity was monitored with a local array during multi-stage hydraulic fracture stimulations on several wells from a single drilling pad. Seismicity primarily occurred during the injection time periods, and correlated with periods of high injection rates and wellhead pressures above fracturing pressures. Sequential hydraulic fracture stages were found to progressively activate several parallel, critically-stressed faults, as illuminated by multiple linear hypocenter patterns in the range between Mw 1 and 3. Moment tensor inversion of larger events indicated a double-couple mechanism consistent with the regional strike-slip stress state and the hypocenter lineations. The critically-stressed faults obliquely cross the well paths which were purposely drilled parallel to the minimum principal stress direction. Seismicity on specific faults started and stopped when fracture initiation points of individual injection stages were proximal to the intersection of the fault and well. The distance ranges when the seismicity occurs is consistent with expected hydraulic fracture dimensions, suggesting that the induced fault slip only occurs when a hydraulic fracture grows directly into the fault and the faults are temporarily exposed to significantly elevated fracture pressures during the injection. Some faults crossed multiple wells and the seismicity was found to restart during injection of proximal stages on adjacent wells, progressively expanding the seismogenic zone of the fault. Progressive fault slip is therefore inferred from the seismicity migrating further along the faults during successive injection stages. An accelerometer was also deployed close

  8. Impact of a Large San Andreas Fault Earthquake on Tall Buildings in Southern California

    Science.gov (United States)

    Krishnan, S.; Ji, C.; Komatitsch, D.; Tromp, J.

    2004-12-01

    In 1857, an earthquake of magnitude 7.9 occurred on the San Andreas fault, starting at Parkfield and rupturing in a southeasterly direction for more than 300~km. Such a unilateral rupture produces significant directivity toward the San Fernando and Los Angeles basins. The strong shaking in the basins due to this earthquake would have had a significant long-period content (2--8~s). If such motions were to happen today, they could have a serious impact on tall buildings in Southern California. In order to study the effects of large San Andreas fault earthquakes on tall buildings in Southern California, we use the finite source of the magnitude 7.9 2001 Denali fault earthquake in Alaska and map it onto the San Andreas fault with the rupture originating at Parkfield and proceeding southward over a distance of 290~km. Using the SPECFEM3D spectral element seismic wave propagation code, we simulate a Denali-like earthquake on the San Andreas fault and compute ground motions at sites located on a grid with a 2.5--5.0~km spacing in the greater Southern California region. We subsequently analyze 3D structural models of an existing tall steel building designed in 1984 as well as one designed according to the current building code (Uniform Building Code, 1997) subjected to the computed ground motion. We use a sophisticated nonlinear building analysis program, FRAME3D, that has the ability to simulate damage in buildings due to three-component ground motion. We summarize the performance of these structural models on contour maps of carefully selected structural performance indices. This study could benefit the city in laying out emergency response strategies in the event of an earthquake on the San Andreas fault, in undertaking appropriate retrofit measures for tall buildings, and in formulating zoning regulations for new construction. In addition, the study would provide risk data associated with existing and new construction to insurance companies, real estate developers, and

  9. Irregularities in Early Seismic Rupture Propagation for Large Events in a Crustal Earthquake Model

    Science.gov (United States)

    Lapusta, N.; Rice, J. R.; Rice, J. R.

    2001-12-01

    behavior at depth. Small events appear in our model at that transition as we decrease the characteristic slip distance for evolution of frictional strength (but not if that distance is unrealistically large). Such clustering of small events at transitions from seismogenic to creeping behavior seems to occur on real faults as well, as we show in examples. To compute moment acceleration that can be compared with data, we translate the results of our 2-D fault model to a 3-D model with essentially radial symmetry on the fault plane. We will discuss limitations of that interpretation; in particular, it may overestimate the effect of partial arrest of rupture in creeping regions. Our present work cannot resolve whether there are any differences in the early phases of seismic moment release, i.e. in the seismic nucleation phase, that would make the beginning of larger events look different from smaller ones that are about to arrest. We have shown that the aseismic nucleation phase and the earliest phases of dynamic breakout are virtually identical for small and large events in our simulations. If early moment release is mostly affected by stress heterogeneities left by previous small events and by creep processes, as our present study suggests, then any such differences would have to be related to as yet unidentified properties of the pre-stress field that might determine the ultimate event size. See http://esag.harvard.edu/lapusta/Lapusta_Rice_Jun01.pdf, Lapusta and Rice, submitted to JGR, 2001.

  10. Fault analysis in the very shallow seismic reflection method; Gokusenso jishin hanshaho ni okeru danso kaiseki. 1

    Energy Technology Data Exchange (ETDEWEB)

    Nagumo, S; Muraoka, S; Kaida, Y; Takahashi, T [OYO Corp., Tokyo (Japan)

    1996-10-01

    To effectively use the very shallow seismic reflection for active fault survey, a method has been investigated by which fault structures can be appropriately reconstructed from the fault information detected in the original records. The first step of reconstructing the fault system from the travel time reflection curve was to grasp an outline of fault structure from the patterns of travel time curve observed in the original record. For the very shallow seismic reflection method, especially, the low velocity layers in a shallow part succeeding from the ground surface made the issue complicated. Then, the travel time reflection curves were calculated in the case of existing several horizontal reflection surfaces in the surface layer. The constant values, mean velocities to the depth at individual reflection surfaces were used for the approximation of velocities. The outline of fault structure was grasped from the observation of original record. Then, the structure was reconstructed from the travel time curves. When the mean velocity in the medium was known, reconstruction of the feature of reflection surfaces from the travel time curves could be determined by simple mapping. When the mean velocity was unknown, it was calculated using the reciprocal travel time from the common reflection surface for individual reflection surfaces. 7 figs.

  11. Application of Post-stack migration to seismic data associated with fault structures

    Science.gov (United States)

    Koduru, Anitha; Mohanty, P. R.

    2015-06-01

    In hydrocarbon exploration, wave-equation migration techniques play an important role in imaging the complex geological structures. Usually, post-stack migration scheme is applied to the seismic data to improve the resolution with restoration of dipping reflectors to their true position. As a result, the migrated time sections are interpretable in terms of subsurface features. As a numerical study, three fault models are considered for the present study. First of all, synthetic time sections are generated corresponding to three models. Later, post stack migration schemes such as Gazdag(PS), Phase-shift with turning rays and reverse time migration (T-K) domain techniques are applied in order to judge the imaging accuracy, preservation of true amplitude and computational speed. All the three post stack time migrated sections delineate the structure with their throw.However, the reverse time migrations (T-K) clearly delineate the reflectors in restoring the throw properly with minimum computational time. In order to test the validity the numerical results, similar exercise has been undertaken using field seismic data of KG basin, India. The results indicates that the field migrated sections are imaged. But, the reverse time migration (T-K ) provides the best subsurface image with restoration of reflectors and collapse of diffracted events with least computational time. Gazdag (PS) and Phase-Shift with turning migrated section shows the reduction of amplitude whereas, the reverse time migration preserved the amplitude fully.

  12. Seismic Experiment at North Arizona To Locate Washington Fault - 3D Field Test

    KAUST Repository

    Hanafy, Sherif M

    2008-10-01

    No. of receivers in the inline direction: 80, Number of lines: 6, Receiver Interval: 1 m near the fault, 2 m away from the fault (Receivers 1 to 12 at 2 m intervals, receivers 12 to 51 at 1 m intervals, and receivers 51 to 80 at 2 m intervals), No. of shots in the inline direction: 40, Shot interval: 2 and 4 m (every other receiver location). Data Recording The data are recorded using two Bison equipment, each is 120 channels. We shot at all 240 shot locations and simultaneously recorded seismic traces at receivers 1 to 240 (using both Bisons), then we shot again at all 240 shot locations and we recorded at receivers 241 to 480. The data is rearranged to match the receiver order shown in Figure 3 where receiver 1 is at left-lower corner, receivers increase to 80 at right lower corner, then receiver 81 is back to left side at Y = 1.5 m, etc.

  13. Numerical seismic modelling of fault-fold structures in a mountainous setting

    Energy Technology Data Exchange (ETDEWEB)

    Kirtland Grech, M.G.; Lawton, D.C.; Spratt, D.A. (Calgary Univ., AB (Canada))

    1999-01-01

    Experiments were conducted to determine the performance of different prestack migration algorithms in complex structural areas, particularly in the presence of rugged topography and thrust faults that result in severe lateral and vertical velocity changes, using a series of numerical seismic models. The numerical model used was based on a cross section through the Rocky Mountains Front Ranges of Western Canada and is 33 km wide and 11 km deep. The best migrated section was obtained with FD shot migration in depth and from topography, using the known velocity model. This result was superior to Kirchhoff depth migration from topography and from a flat datum. As the velocities departed from their true value, the deeper events were most affected, because of the accumulation of velocity errors with depth. The small-scale features of Target A, in the shallower part of the section, could still be interpreted even when the velocities were inaccurate. In the presence of velocity errors, the different structures could still be interpreted, but were at the wrong depth and had the wrong structural shape and size. Layers that were of the order of 1 km in width and 500 km in thickness, such as Layer 4, were the most poorly imaged and focussed, both with time migration and with depth migration. Fault planes were not imaged in the absence of a velocity contrast across them, making some FW cutoffs difficult to interpret. 2 refs.

  14. Numerical seismic modelling of fault-fold structures in a mountainous setting

    Energy Technology Data Exchange (ETDEWEB)

    Kirtland Grech, M.G.; Lawton, D.C.; Spratt, D.A. [Calgary Univ., AB (Canada)

    1999-11-01

    Experiments were conducted to determine the performance of different prestack migration algorithms in complex structural areas, particularly in the presence of rugged topography and thrust faults that result in severe lateral and vertical velocity changes, using a series of numerical seismic models. The numerical model used was based on a cross section through the Rocky Mountains Front Ranges of Western Canada and is 33 km wide and 11 km deep. The best migrated section was obtained with FD shot migration in depth and from topography, using the known velocity model. This result was superior to Kirchhoff depth migration from topography and from a flat datum. As the velocities departed from their true value, the deeper events were most affected, because of the accumulation of velocity errors with depth. The small-scale features of Target A, in the shallower part of the section, could still be interpreted even when the velocities were inaccurate. In the presence of velocity errors, the different structures could still be interpreted, but were at the wrong depth and had the wrong structural shape and size. Layers that were of the order of 1 km in width and 500 km in thickness, such as Layer 4, were the most poorly imaged and focussed, both with time migration and with depth migration. Fault planes were not imaged in the absence of a velocity contrast across them, making some FW cutoffs difficult to interpret. 2 refs.

  15. New Constraints on Late Pleistocene - Holocene Slip Rates and Seismic Behavior Along the Panamint Valley Fault Zone, Eastern California

    Science.gov (United States)

    Hoffman, W.; Kirby, E.; McDonald, E.; Walker, J.; Gosse, J.

    2008-12-01

    Space-time patterns of seismic strain release along active fault systems can provide insight into the geodynamics of deforming lithosphere. Along the eastern California shear zone, fault systems south of the Garlock fault appear to have experienced an ongoing pulse of seismic activity over the past ca. 1 kyr (Rockwell et al., 2000). Recently, this cluster of seismicity has been implicated as both cause and consequence of the oft-cited discrepancy between geodetic velocities and geologic slip rates in this region (Dolan et al., 2007; Oskin et al., 2008). Whether other faults within the shear zone exhibit similar behavior remains uncertain. Here we report the preliminary results of new investigations of slip rates and seismic history along the Panamint Valley fault zone (PVFZ). The PVFZ is characterized by dextral, oblique-normal displacement along a moderately to shallowly-dipping range front fault. Previous workers (Zhang et al., 1990) identified a relatively recent surface rupture confined to a ~25 km segment of the southern fault zone and associated with dextral displacements of ~3 m. Our mapping reveals that youthful scarps ranging from 2-4 m in height are distributed along the central portion of the fault zone for at least 50 km. North of Ballarat, a releasing jog in the fault zone forms a 2-3 km long embayment. Displacement of debris-flow levees and channels along NE-striking faults that confirm that displacement is nearly dip-slip, consistent with an overall transport direction toward ~340°, and affording an opportunity to constrain fault displacement directly from the vertical offset of alluvial surfaces of varying age. At the mouth of Happy Canyon, the frontal fault strand displaces a fresh debris-flow by ~3-4 m; soil development atop the debris-flow surface is incipient to negligible. Radiocarbon ages from logs embedded in the flow matrix constrain the timing of the most recent event to younger than ~ 600 cal yr BP. Older alluvial surfaces, such as that

  16. Transposing an active fault database into a fault-based seismic hazard assessment for nuclear facilities - Part 2: Impact of fault parameter uncertainties on a site-specific PSHA exercise in the Upper Rhine Graben, eastern France

    Science.gov (United States)

    Chartier, Thomas; Scotti, Oona; Clément, Christophe; Jomard, Hervé; Baize, Stéphane

    2017-09-01

    We perform a fault-based probabilistic seismic hazard assessment (PSHA) exercise in the Upper Rhine Graben to quantify the relative influence of fault parameters on the hazard at the Fessenheim nuclear power plant site. Specifically, we show that the potentially active faults described in the companion paper (Jomard et al., 2017, hereafter Part 1) are the dominant factor in hazard estimates at the low annual probability of exceedance relevant for the safety assessment of nuclear installations. Geological information documenting the activity of the faults in this region, however, remains sparse, controversial and affected by a high degree of uncertainty. A logic tree approach is thus implemented to explore the epistemic uncertainty and quantify its impact on the seismic hazard estimates. Disaggregation of the peak ground acceleration (PGA) hazard at a 10 000-year return period shows that the Rhine River fault is the main seismic source controlling the hazard level at the site. Sensitivity tests show that the uncertainty on the slip rate of the Rhine River fault is the dominant factor controlling the variability of the seismic hazard level, greater than the epistemic uncertainty due to ground motion prediction equations (GMPEs). Uncertainty on slip rate estimates from 0.04 to 0.1 mm yr-1 results in a 40 to 50 % increase in hazard levels at the 10 000-year target return period. Reducing epistemic uncertainty in future fault-based PSHA studies at this site will thus require (1) performing in-depth field studies to better characterize the seismic potential of the Rhine River fault; (2) complementing GMPEs with more physics-based modelling approaches to better account for the near-field effects of ground motion and (3) improving the modelling of the background seismicity. Indeed, in this exercise, we assume that background earthquakes can only host M 6. 0 earthquakes have been recently identified at depth within the Upper Rhine Graben (see Part 1) but are not accounted

  17. Early estimation of epicenter seismic intensities according to co-seismic deformation

    OpenAIRE

    Weidong, Li; Chaojun, Zhang; Dahui, Li; Jiayong, He; Huizhong, Chen; Lomnitz, Cinna

    2010-01-01

    The absolute fault displacement in co-seismic deformation is derived assuming that location, depth, faulting mechanism and magnitude of the earthquake are known. The 2008 Wenchuan earthquake (M8.0) is used as an example to determine the distribution of seismic intensities using absolute displacement and a crustal model. We fnd that an early prediction of the distribution of seismic intensities after a large earthquake may be performed from the estimated absolute co-seismic displacements using...

  18. Evidence for a twelfth large earthquake on the southern hayward fault in the past 1900 years

    Science.gov (United States)

    Lienkaemper, J.J.; Williams, P.L.; Guilderson, T.P.

    2010-01-01

    We present age and stratigraphic evidence for an additional paleoearthquake at the Tyson Lagoon site. The acquisition of 19 additional radiocarbon dates and the inclusion of this additional event has resolved a large age discrepancy in our earlier earthquake chronology. The age of event E10 was previously poorly constrained, thus increasing the uncertainty in the mean recurrence interval (RI), a critical factor in seismic hazard evaluation. Reinspection of many trench logs revealed substantial evidence suggesting that an additional earthquake occurred between E10 and E9 within unit u45. Strata in older u45 are faulted in the main fault zone and overlain by scarp colluviums in two locations.We conclude that an additional surfacerupturing event (E9.5) occurred between E9 and E10. Since 91 A.D. (??40 yr, 1??), 11 paleoearthquakes preceded the M 6:8 earthquake in 1868, yielding a mean RI of 161 ?? 65 yr (1??, standard deviation of recurrence intervals). However, the standard error of the mean (SEM) is well determined at ??10 yr. Since ~1300 A.D., the mean rate has increased slightly, but is indistinguishable from the overall rate within the uncertainties. Recurrence for the 12-event sequence seems fairly regular: the coefficient of variation is 0.40, and it yields a 30-yr earthquake probability of 29%. The apparent regularity in timing implied by this earthquake chronology lends support for the use of time-dependent renewal models rather than assuming a random process to forecast earthquakes, at least for the southern Hayward fault.

  19. Seismic investigation on the Littoral Faults Zone in the northern continental margin of South China Sea

    Science.gov (United States)

    Sun, J.; Xu, H.; Xia, S.; Cao, J.; Wan, K.

    2017-12-01

    The continental margin of the northern South China Sea (SCS) had experienced continuous evolution from an active continental margin in the late Mesozoic to a passive continental margin in the Cenozoic. The 1200km-long Littoral Faults Zone (LFZ) off the mainland South China was suggested to represent one of the sub-plate boundaries and play a key role during the evolution. Besides, four devastating earthquakes with magnitude over 7 and another 11 destructive events with M>6 were documented to have occurred along the LFZ. However, its approximity to the shoreline, the shallow water depth, and the heavy fishing activities make it hard to conduct a marine seismic investigation. As a result, understandings about the LFZ before 2000 were relatively poor and mostly descriptive. After two experiments of joint onshore-offshore wide-angle seismic surveys in the 1st decade of this century, several cruses aiming to unveil the deep structure of the LFZ were performed in the past few years, with five joint onshore-offshore wide-angle seismic survey profiles completed. Each of these profiles is perpendicular to the shoreline, with four to five seismometers of campaign mode deployed on the landside and over ten Ocean Bottom Seismometers (OBSs) spacing at 20km deployed on the seaside. Meanwhile, multi-channel seismic (MCS) data along these profiles were obtained simultaneously. Based on these data, velocity models from both forward modeling and inversion were obtained. According to these models, the LFZ was imaged to be a low-velocity fractured zone dipping to the SSE-SE at a high-angle and cutting through the thinned continental crust at some locations. Width of the fractured zone varies from 6km to more than 10km from site to site. With these results, it is suggested that the LFZ accommodates the stresses from both the east side, where the Eurasia/Philippine Sea plate converging and mountain building is ongoing, and the west side, where a strike-slip between the Indochina

  20. Proterozoic structure, cambrian rifting, and younger faulting as revealed by a regional seismic reflection network in the Southern Illinois Basin

    Science.gov (United States)

    Potter, C.J.; Drahovzal, James A.; Sargent, M.L.; McBride, J.H.

    1997-01-01

    Four high-quality seismic reflection profiles through the southern Illinois Basin, totaling 245 km in length, provide an excellent regional subsurface stratigraphic and structural framework for evaluation of seismic risk, hydrocarbon occurrence, and other regional geologic studies. These data provide extensive subsurface information on the geometry of the intersection of the Cambrian Reelfoot and Rough Creek rifts, on extensive Proterozoic reflection sequences, and on structures (including the Fluorspar Area Fault Complex and Hicks Dome) that underlie a transitional area between the well-defined New Madrid seismic zone (to the southwest) and a more diffuse area of seismicity in the southern Illinois Basin. Our principal interpretations from these data are listed here in order of geologic age, from oldest to youngest: 1. Prominent Proterozoic layering, possibly equivalent to Proterozoic (???1 Ga) Middle Run Formation clastic strata and underlying (1.3-1.5 Ga) volcanic rocks of the East Continent rift basin, has been strongly deformed, probably as part of the Grenville foreland fold and thrust belt. 2. A well-defined angular unconformity is seen in many places between Proterozoic and Cambrian strata; a post-Grenville Proterozoic sequence is also apparent locally, directly beneath the base of the Cambrian. 3. We infer a major reversal in Cambrian rift polarity (accommodation zone) in the Rough Creek Graben in western Kentucky. 4. Seismic facies analysis suggests the presence of basin-floor fan complexes at and near the base of the Cambrian interval and within parts of a Proterozoic post-Grenville sequence in several parts of the Rough Creek Graben. 5. There is an abrupt pinchout of the Mount Simon Sandstone against crystalline basement beneath the Dale Dome (near the Texaco no. 1 Cuppy well, Hamilton County) in southeastern Illinois, and a more gradual Mount Simon pinchout to the southeast. 6. Where crossed by the seismic reflection line in southeast Illinois, some

  1. Geothermal and seismic evidence for a southeastern continuation of the three pagodas fault zone into the Gulf of Thailand

    Directory of Open Access Journals (Sweden)

    Prinya Putthapiban

    2012-09-01

    Full Text Available Aerial photographic maps and landsat image interpretations suggest the major fault segments of the Three PagodaFault (TPF Zone and Sri Swat Fault (SSF Zone are oriented parallel or sub-parallel in the same NW-SE directions. The KwaeNoi River is running along the TPF in the south whereas the Kwae Yai River is running along the SSF in the north. Thesoutheastern continuation of both faults is obscured by thick Cenozoic sediments. Hence, surface lineaments cannot betraced with confidence. However, based on some interpretations of the airborne magnetic survey data, the trace of such faultsare designated to run through the western part of Bangkok and the northern end of the Gulf of Thailand. Paleo-earthquakesand the presence of hot springs along the fault zones indicate that they are tectonically active. The changes of both physicaland chemical properties of the water from Hin Dart Hot Spring and those of the surface water from a shallow well at Ban KhaoLao during the Great Sumatra–Andaman Earthquake on 26th of December 2004 clearly indicated that the southeastern continuation of the TPF is at least as far south as Pak Tho District, Ratburi. Our new evidence of the alignment of the high heatflow in the upper part of the Gulf of Thailand verified that the TPF also extend into the Gulf via Samut Songkhram Province.Studies of the seismic data from two survey lines along the Western part of the upper Gulf of Thailand acquired by BritoilPlc. in 1986, namely Line A which is approximately 60 km long, starting from Bang Khen passing through Bang Khae andending in Samut Songkhram and Line B is approximately 30 km long starting from Samut Sakon ending in Samut Song Khramsuggest that all the faults or fractures along these seismic profiles are covered by sediments of approximately 230 m thickwhich explain that the fault underneath these seismic lines is quite old and may not be active. The absent of sign or trace ofthe TPF Path to the west suggested that there

  2. Parabolic distribution of circumeastern Snake River Plain seismicity and latest Quaternary faulting: Migratory pattern and association with the Yellowstone hotspot

    Science.gov (United States)

    Anders, Mark H.; Geissman, John Wm.; Piety, Lucille A.; Sullivan, J. Timothy

    1989-02-01

    The Intermountain and Idaho seismic belts within Idaho, Wyoming, and Montana form an unusual parabolic pattern about the axis of the aseismic eastern Snake River Plain (SRP). This pattern is also reflected in the distribution of latest Quaternary normal faults. Several late Cenozoic normal faults that trend perpendicular to the axis of the eastern SRP extend from the aseismic region to the region of latest Quaternary faulting and seismicity. A study of the late Miocene to Holocene displacement history of one of these, the Grand Valley fault system in southeastern Idaho and western Wyoming, indicates that a locus of high displacement rates has migrated away from the eastern SRP to its present location in southern Star Valley in western Wyoming. In Swan Valley the studied area closest to the eastern SRP, isotopic ages, and paleomagnetic data for over 300 samples from 47 sites on well-exposed late Cenozoic volcanic rocks (the tuff of Spring Creek, the tuff of Heise, the Huckleberry Ridge tuff, the Pine Creek Basalt, and an older tuff thought to be the tuff of Cosgrove Road) are used to demonstrate differences in the displacement rate on the Grand Valley fault over the last ˜10 m.y. Tectonic tilts for these volcanic rocks are estimated by comparing the results of paleomagnetic analyses in Swan Valley to similar analyses of samples from undeformed volcanic rocks outside of Swan Valley. Basin geometry and tilt axes are established using seismic reflection profiles and field mapping. Combining these data with the tilt data makes it possible to calculate displacement rates during discrete temporal intervals. An average displacement rate of ˜1.8 mm/yr is calculated for the Grand Valley fault in Swan Valley between 4.4 and 2.0 Ma. In the subsequent 2.0-m.y. interval the rate dropped 2 orders of magnitude to ˜0.014 mm/yr; during the preceding 5.5-m.y. interval the displacement rate is ˜0.15 mm/yr, or about 1 order of magnitude less than the rate between 4.4 and 2.0 Ma

  3. Fault Ride Through Capability Enhancement of a Large-Scale PMSG Wind System with Bridge Type Fault Current Limiters

    Directory of Open Access Journals (Sweden)

    ALAM, M. S.

    2018-02-01

    Full Text Available In this paper, bridge type fault current limiter (BFCL is proposed as a potential solution to the fault problems of permanent magnet synchronous generator (PMSG based large-scale wind energy system. As PMSG wind system is more vulnerable to disturbances, it is essential to guarantee the stability during severe disturbances by enhancing the fault ride through capability. BFCL controller has been designed to insert resistance and inductance during the inception of system disturbances in order to limit fault current. Constant capacitor voltage has been maintained by the grid voltage source converter (GVSC controller while current extraction or injection has been achieved by machine VSC (MVSC controller. Symmetrical and unsymmetrical faults have been applied in the system to show the effectiveness of the proposed BFCL solution. PMSG wind system, BFCL and their controllers have been implemented by real time hardware in loop (RTHIL setup with real time digital simulator (RTDS and dSPACE. Another significant feature of this work is that the performance of the proposed BFCL is compared with that of series dynamic braking resistor (SDBR. Comparative RTHIL implementation results show that the proposed BFCL is very efficient in improving system fault ride through capability by limiting the fault current and outperforms SDBR.

  4. Large-displacement, hydrothermal frictional properties of DFDP-1 fault rocks, Alpine Fault, New Zealand: Implications for deep rupture propagation.

    Science.gov (United States)

    Niemeijer, A R; Boulton, C; Toy, V G; Townend, J; Sutherland, R

    2016-02-01

    The Alpine Fault, New Zealand, is a major plate-bounding fault that accommodates 65-75% of the total relative motion between the Australian and Pacific plates. Here we present data on the hydrothermal frictional properties of Alpine Fault rocks that surround the principal slip zones (PSZ) of the Alpine Fault and those comprising the PSZ itself. The samples were retrieved from relatively shallow depths during phase 1 of the Deep Fault Drilling Project (DFDP-1) at Gaunt Creek. Simulated fault gouges were sheared at temperatures of 25, 150, 300, 450, and 600°C in order to determine the friction coefficient as well as the velocity dependence of friction. Friction remains more or less constant with changes in temperature, but a transition from velocity-strengthening behavior to velocity-weakening behavior occurs at a temperature of T  = 150°C. The transition depends on the absolute value of sliding velocity as well as temperature, with the velocity-weakening region restricted to higher velocity for higher temperatures. Friction was substantially lower for low-velocity shearing ( V  Fault rocks at higher temperatures may pose a barrier for rupture propagation to deeper levels, limiting the possible depth extent of large earthquakes. Our results highlight the importance of strain rate in controlling frictional behavior under conditions spanning the classical brittle-plastic transition for quartzofeldspathic compositions.

  5. Implications for stress changes along the Motagua fault and other nearby faults using GPS and seismic constraints on the M=7.3 2009 Swan Islands earthquake

    Science.gov (United States)

    Graham, S. E.; Rodriguez, M.; Rogers, R. D.; Strauch, W.; Hernandez, D.; Demets, C.

    2010-12-01

    The May 28, 2009 M=7.3 Swan Islands earthquake off the north coast of Honduras caused significant damage in the northern part of the country, including seven deaths. This event, the largest in the region for several decades, ruptured the offshore continuation of the Motagua-Polochic fault system, whose 1976 earthquake (located several hundred kilometers to the southwest of the 2009 epicenter) caused more than 23,000 deaths in Central America and left homeless 20% of Guatemala’s population. We use elastic half-space modeling of coseismic offsets measured at 39 GPS stations in Honduras, El Salvador, and Guatemala to better understand the slip source of the recent Swan Islands earthquake. Measured offsets range from .32 meters at a campaign site near the Motagua fault in northern Honduras to 4 millimeters at five continuous sites in El Salvador. Coulomb stress calculations based on the estimated distribution of coseismic slip will be presented and compared to earthquake focal mechanisms and aftershock locations determined from a portable seismic network that was installed in northern Honduras after the main shock. Implications of the Swan Islands rupture for the seismically hazardous Motagua-Polochic fault system will be described.

  6. User's manual of a computer code for seismic hazard evaluation for assessing the threat to a facility by fault model. SHEAT-FM

    International Nuclear Information System (INIS)

    Sugino, Hideharu; Onizawa, Kunio; Suzuki, Masahide

    2005-09-01

    To establish the reliability evaluation method for aged structural component, we developed a probabilistic seismic hazard evaluation code SHEAT-FM (Seismic Hazard Evaluation for Assessing the Threat to a facility site - Fault Model) using a seismic motion prediction method based on fault model. In order to improve the seismic hazard evaluation, this code takes the latest knowledge in the field of earthquake engineering into account. For example, the code involves a group delay time of observed records and an update process model of active fault. This report describes the user's guide of SHEAT-FM, including the outline of the seismic hazard evaluation, specification of input data, sample problem for a model site, system information and execution method. (author)

  7. Investigating effects of near fault rupture directivity on seismic hazard assessment of the site of Tehran Research Reactor (TRR)

    Energy Technology Data Exchange (ETDEWEB)

    Sepanloo, Kamran; Saberi, Reza [Nuclear Science and Technology Research Institute, Tehran (Iran, Islamic Republic of); Alinejad, Majid [Atomic Energy Organization of Iran, Tehran (Iran, Islamic Republic of); Bazarchi, Ehsan [Tabriz Univ. (Iran, Islamic Republic of)

    2017-10-15

    It is estimated that the occurrence of a major-earthquake in Tehran, Iran, which is not far-fetched, would face the country with a huge amount of collapsed structures, economical losses and fatalities. The issue becomes more important while the site of interest is attributed to the nuclear facilities and any under-estimation in predicting the design ground motion may cause a real disaster. In this study, using calculations coded in MATLAB, PSHA was conducted for the site of TRR. It was concluded that most of the hazard for considered site in a 10000-year period comes from distances lower than 20 km and considering rupture directivity effects of the North Tehran fault, as the nearest seismicity source to considered site, using narrowband method affected the response spectrum significantly. Therefore, it is necessary to incorporate the near fault rupture directivity effects into the higher levels of seismic hazard assessment attributed to important sites.

  8. Investigating effects of near fault rupture directivity on seismic hazard assessment of the site of Tehran Research Reactor (TRR)

    International Nuclear Information System (INIS)

    Sepanloo, Kamran; Saberi, Reza; Alinejad, Majid; Bazarchi, Ehsan

    2017-01-01

    It is estimated that the occurrence of a major-earthquake in Tehran, Iran, which is not far-fetched, would face the country with a huge amount of collapsed structures, economical losses and fatalities. The issue becomes more important while the site of interest is attributed to the nuclear facilities and any under-estimation in predicting the design ground motion may cause a real disaster. In this study, using calculations coded in MATLAB, PSHA was conducted for the site of TRR. It was concluded that most of the hazard for considered site in a 10000-year period comes from distances lower than 20 km and considering rupture directivity effects of the North Tehran fault, as the nearest seismicity source to considered site, using narrowband method affected the response spectrum significantly. Therefore, it is necessary to incorporate the near fault rupture directivity effects into the higher levels of seismic hazard assessment attributed to important sites.

  9. Interpretation of interseismic deformations and the seismic cycle associated with large subduction earthquakes

    Science.gov (United States)

    Trubienko, Olga; Fleitout, Luce; Garaud, Jean-Didier; Vigny, Christophe

    2013-03-01

    The deformations of the overriding and subducting plates during the seismic cycle associated with large subduction earthquakes are modelled using 2D and 3D finite element techniques. A particular emphasis is put on the interseismic velocities and on the impact of the rheology of the asthenosphere. The distance over which the seismic cycle perturbs significantly the velocities depends upon the ratio of the viscosity in the asthenosphere to the period of the seismic cycle and can reach several thousand km for rheological parameters deduced from the first years of deformation after the Aceh earthquake. For a same early postseismic velocity, a Burger rheology of the asthenosphere implies a smaller duration of the postseismic phase and thus smaller interseismic velocities than a Maxwell rheology. A low viscosity wedge (LVW) modifies very significantly the predicted horizontal and vertical motions in the near and middle fields. In particular, with a LVW, the peak in vertical velocity at the end of the cycle is predicted to be no longer above the deep end of the locked section of the fault but further away, above the continentward limit of the LVW. The lateral viscosity variations linked to the presence at depth of the subducting slab affect substantially the results. The north-south interseismic compression predicted by this preliminary 2D model over more than 1500 km within the Sunda block is in good agreement with the pre-2004 velocities with respect to South-China inferred from GPS observations in Thailand, Malaysia and Indonesia. In Japan, before the Tohoku earthquake, the eastern part of northern Honshu was subsiding while the western part was uplifting. This transition from subsidence to uplift so far away from the trench is well fitted by the predictions from our models involving a LVW. Most of the results obtained here in a 2D geometry are shown to provide a good estimate of the displacements for fault segments of finite lateral extent, with a 3D spherical

  10. Late Quaternary paleoseismicity and seismic potential of the Yilan-Yitong Fault Zone in NE China

    Science.gov (United States)

    Yu, Zhongyuan; Yin, Na; Shu, Peng; Li, Jincheng; Wei, Qinghai; Min, Wei; Zhang, Peizhen

    2018-01-01

    The Yilan-Yitong Fault Zone (YYFZ), which is composed of two nearly parallel branches with a spacing of 5-30 km and a length of ∼1100 km, is considered to be the key branch of the Tancheng-Lujiang Fault Zone (TLFZ) in NE China. It was traditionally believed that the YYFZ experienced weak activity or was inactive during the Late Quaternary, without the capability to generate strong earthquakes (M ≥ 7), based on the absence of typical outcrops and large historical or instrumental earthquakes (M > 6). However, our paleoseismic study shows that the YYFZ is the primary seismotectonic structure (M ≥ 7) that poses significant earthquake threats to NE China. The synthesis of data collected from geologic investigations, geomorphic mapping, trench logging and the dating of samples indicates that the YYFZ is an active structure that has undergone segmented strong tectonic deformation since the Late Quaternary with a characteristic assemblage of landforms, including linear scarps and troughs, offset or deflected streams, linear sag ponds, small horsts and grabens. The latest ruptures of the YYFZ migrated from previous boundary faults into the basin interior, forming a left-stepping en echelon pattern in plain view, and the kinematics of these events in the Late Quaternary were dominated by reverse dextral slipping. Multi-segment cluster faulting might have occurred during three cluster periods, i.e., ∼34750-35812 a BP, ∼21700-22640 a BP, and ∼4000 a BP-present, which implies that the recurrence interval of large earthquakes along the YYFZ may be as long as tens of thousands of years.

  11. Seismic and source characteristics of large chemical explosions. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Adushkin, V.V.; Kostuchenko, V.N.; Pernik, L.M.; Sultanov, D.D.; Zcikanovsky, V.I.

    1995-01-01

    From the very beginning of its arrangement in 1947, the Institute for Dynamics of the Geospheres RAS (former Special Sector of the Institute for physics of the Earth, RAS) was providing scientific observations of effects of nuclear explosions, as well as large-scale detonations of HE, on environment. This report presents principal results of instrumental observations obtained from various large-scale chemical explosions conducted in the Former-Soviet Union in the period of time from 1957 to 1989. Considering principal aim of the work, tamped and equivalent chemical explosions have been selected with total weights from several hundreds to several thousands ton. In particular, the selected explosions were aimed to study scaling law from excavation explosions, seismic effect of tamped explosions, and for dam construction for hydropower stations and soil melioration. Instrumental data on surface explosions of total weight in the same range aimed to test military technics and special objects are not included.

  12. Imaging Stress Transients and Fault Zone Processes with Crosswell Continuous Active-Source Seismic Monitoring at the San Andreas Fault Observatory at Depth

    Science.gov (United States)

    Niu, F.; Taira, T.; Daley, T. M.; Marchesini, P.; Robertson, M.; Wood, T.

    2017-12-01

    Recent field and laboratory experiments identify seismic velocity changes preceding microearthquakes and rock failure (Niu et al., 2008, Nature; Scuderi et al., 2016, NatureGeo), which indicates that a continuous monitoring of seismic velocity might provide a mean of understanding of the earthquake nucleation process. Crosswell Continuous Active-Source Seismic Monitoring (CASSM) using borehole sources and sensors has proven to be an effective tool for measurements of seismic velocity and its temporal variation at seismogenic depth (Silver, et al, 2007, BSSA; Daley, et al, 2007, Geophysics). To expand current efforts on the CASSM development, in June 2017 we have begun to conduct a year-long CASSM field experiment at the San Andreas Fault Observatory at Depth (SAFOD) in which the preceding field experiment detected the two sudden velocity reductions approximately 10 and 2 hours before microearthquakes (Niu et al., 2008, Nature). We installed a piezoelectric source and a three-component accelerometer at the SAFOD pilot and main holes ( 1 km depth) respectively. A seismic pulse was fired from the piezoelectric source four times per second. Each waveform was recorded 150-ms-long data with a sampling rate of 48 kHz. During this one-year experiment, we expect to have 10-15 microearthquakes (magnitude 1-3) occurring near the SAFOD site, and the data collected from the new experiment would allow us to further explore a relation between velocity changes and the Parkfield seismicity. Additionally, the year-long data provide a unique opportunity to study long-term velocity changes that might be related to seasonal stress variations at Parkfield (Johnson et al., 2017, Science). We will report on initial results of the SAFOD CASSM experiment and operational experiences of the CASSM development.

  13. Large-coil-test-facility fault-tree analysis

    International Nuclear Information System (INIS)

    1982-01-01

    An operating-safety study is being conducted for the Large Coil Test Facility (LCTF). The purpose of this study is to provide the facility operators and users with added insight into potential problem areas that could affect the safety of personnel or the availability of equipment. This is a preliminary report, on Phase I of that study. A central feature of the study is the incorporation of engineering judgements (by LCTF personnel) into an outside, overall view of the facility. The LCTF was analyzed in terms of 32 subsystems, each of which are subject to failure from any of 15 generic failure initiators. The study identified approximately 40 primary areas of concern which were subjected to a computer analysis as an aid in understanding the complex subsystem interactions that can occur within the facility. The study did not analyze in detail the internal structure of the subsystems at the individual component level. A companion study using traditional fault tree techniques did analyze approximately 20% of the LCTF at the component level. A comparison between these two analysis techniques is included in Section 7

  14. Large-Scale Seismic Test Program at Hualien, Taiwan

    International Nuclear Information System (INIS)

    Tang, H.T.; Graves, H.L.; Yeh, Y.S.

    1991-01-01

    The Large-Scale Seismic Test (LSST) Program at Hualien, Taiwan, is a follow-on to the soil-structure interaction (SSI) experiments at Lotung, Taiwan. The planned SSI studies will be performed at a stiff soil site in Hualien, Taiwan, that historically has had slightly more destructive earthquakes in the past than Lotung. The objectives of the LSST project is as follows: To obtain earthquake-induced SSI data at a stiff soil site having similar prototypical nuclear power plant soil conditions. To confirm the findings and methodologies validated against the Lotung soft soil SSI data for prototypical plant condition applications. To further validate the technical basis of realistic SSI analysis approaches. To further support the resolution of USI A-40 Seismic Design Criteria issue. These objectives will be accomplished through an integrated and carefully planned experimental program consisting of: soil characterization, test model design and field construction, instrumentation layout and deployment, in-situ geophysical information collection, forced vibration test, and synthesis of results and findings. The LSST is a joint effort among many interested parties. EPRI and Taipower are the organizers of the program and have the lead in planning and managing the program

  15. Using bathymetry and reflective seismic profiles to tests a suspected link between melt flux and cumulative fault heave at mid-ocean ridges

    Science.gov (United States)

    Haughton, G.; Murton, B. J.; Le Bas, T.; Henstock, T.

    2017-12-01

    The interplay between magma supply and spreading rate is believed to play a major role in determining large scale seafloor morphology. Here we use bathymetry to test this relationship in areas with similar spreading rates and differing magma supplies. By using open source bathymetry data we have developed a repeatable, automated method for categorising seafloor cumulative fault heave and then attempt to identify the controlling variables. We measure the total apparent fault heave along axis and off-axis at 29°N and 60°N on the Mid-Atlantic Ridge then compare this to proxies for deformation and magma supply. Two approaches are adopted for identifying faults: one using bathymetry and the other spreading-parallel seismic reflection data. The first re-examines the orthogonally spreading Broken Spur segment (26°N) spreading at 23 mm yr-1 (full rate). The other examines the Reykjanes Ridge (60°N) spreading obliquely at 21 mm yr-1 (full rate), which may be influenced by the Icelandic hotspot. Each have contrasting residual depth and structure, with the former being typical of slow spreading ridges, with marked axial valleys, whereas the latter is more typical of fast spreading ridge morphology, with smooth axial rise. We find that high total heave (indicating high tectonic spreading) on the Broken Spur segment does not correlate with high mantle Bouguer anomalies (indicating thin crust and low melt flux). From this we hypothesise that total heave on the large scale at the Broken Spur segment is not controlled by crustal thickness or melt supply. At the Raykjanes Ridge, V-shaped ridges have thicker crust (measured seismically) which converge south of Iceland. These are thought to reflect transient (every 4-6 Myrs) pulses of hot mantle radiating away from the Iceland plume. We find ridge-symmetrical variation in fault heave but with a lower frequency (6-8 Myrs) and longer wavelength (3-7 Myrs) than the V-shaped ridges. Our analysis shows that plume pulses do not

  16. Modeling of time-lapse multi-scale seismic monitoring of CO2 injected into a fault zone to enhance the characterization of permeability in enhanced geothermal systems

    Science.gov (United States)

    Zhang, R.; Borgia, A.; Daley, T. M.; Oldenburg, C. M.; Jung, Y.; Lee, K. J.; Doughty, C.; Altundas, B.; Chugunov, N.; Ramakrishnan, T. S.

    2017-12-01

    Subsurface permeable faults and fracture networks play a critical role for enhanced geothermal systems (EGS) by providing conduits for fluid flow. Characterization of the permeable flow paths before and after stimulation is necessary to evaluate and optimize energy extraction. To provide insight into the feasibility of using CO2 as a contrast agent to enhance fault characterization by seismic methods, we model seismic monitoring of supercritical CO2 (scCO2) injected into a fault. During the CO2 injection, the original brine is replaced by scCO2, which leads to variations in geophysical properties of the formation. To explore the technical feasibility of the approach, we present modeling results for different time-lapse seismic methods including surface seismic, vertical seismic profiling (VSP), and a cross-well survey. We simulate the injection and production of CO2 into a normal fault in a system based on the Brady's geothermal field and model pressure and saturation variations in the fault zone using TOUGH2-ECO2N. The simulation results provide changing fluid properties during the injection, such as saturation and salinity changes, which allow us to estimate corresponding changes in seismic properties of the fault and the formation. We model the response of the system to active seismic monitoring in time-lapse mode using an anisotropic finite difference method with modifications for fracture compliance. Results to date show that even narrow fault and fracture zones filled with CO2 can be better detected using the VSP and cross-well survey geometry, while it would be difficult to image the CO2 plume by using surface seismic methods.

  17. Seismicity preliminary results in a geothermal and volcano activity area: study case Liquiñe-Ofqui fault system in Southern Andes, Chile

    Science.gov (United States)

    Estay, N. P.; Yáñez Morroni, G.; Crempien, J. G. F.; Roquer, T.

    2017-12-01

    Fluid transport through the crust takes place in domains with high permeability. For this reason, fault damage zones are a main feature where fluids may circulate unimpeded, since they have much larger permeability than normal country rocks. With the location of earthquakes, it is possible to infer fault geometry and stress field of the crust, therefore we can determine potential places where fluid circualtion is taking place. With that purpose, we installed a seismic network in an active volcanic-geothermal system, the Liquiñe-Ofqui Fault System (LOFS), located in Puyuhuapi, Southern Andes (44°-45°S). This allowed to link epicentral seismicity, focal mechanisms and surface expression of fluid circulation (hot-springs and volcanos). The LOFS is composed by two NS-striking dextral master faults, and several secondary NE-striking dextral and normal faults. Surface manifestation of fluid circulation in Puyuhuapi area are: 1) six hot-springs, most of them spatially associated with different mapped faults; 2) seven minor eruptive centers aligned over a 10-km-along one of the master NS-striking fault, and; 3) the Melimouyu strato-volcano without any spatial relationship with mapped faults. The network consists of 6 short period seismometers (S31f-2.0a sensor of IESE, with natural frequency of 2Hz), that were installed between July 2016 and August 2017; also 4 permanent broad-band seismometers (Guralp 6TD/ CD 24 sensor) which belong to the Volcano Observatory of Southern Andes (OVDAS). Preliminary results show a correlation between seismicity and surface manifestation of fluid circulation. Seismicity has a heterogeneous distribution: most of the earthquake are concentrated is the master NS-striking fault with fluid circulation manifestations; however along the segments without surface manifestation of fluids do not have seismicity. These results suggest that fluid circulation mostly occur in areas with high seismicity, and thus, the increment in fluid pressure enhances

  18. Creep avalanches on San Andreas Fault and their underlying mechanism from 19 years of InSAR and seismicity

    Science.gov (United States)

    Khoshmanesh, M.; Shirzaei, M.

    2017-12-01

    Recent seismic and geodetic observations indicate that interseismic creep rate varies in both time and space. The spatial extent of creep determines the earthquake potential, while its temporal evolution, known as slow slip events (SSE), may trigger earthquakes. Although the conditions promoting fault creep are well-established, the mechanism for initiating self-sustaining and sometimes cyclic creep events is enigmatic. Here we investigate a time series of 19 years of surface deformation measured by radar interferometry between 1992 and 2011 along the Central San Andreas Fault (CSAF) to constrain the temporal evolution of creep. We show that the creep rate along the CSAF has a sporadic behavior, quantified with a Gumbel-like probability distribution characterized by longer tail toward the extreme positive rates, which is signature of burst-like creep dynamics. Defining creep avalanches as clusters of isolated creep with rates exceeding the shearing rate of tectonic plates, we investigate the statistical properties of their size and length. We show that, similar to the frequency-magnitude distribution of seismic events, the distribution of potency estimated for creep avalanches along the CSAF follows a power law, dictated by the distribution of their along-strike lengths. We further show that an ensemble of concurrent creep avalanches which aseismically rupture isolated fault compartments form the semi-periodic SSEs observed along the CSAF. Using a rate and state friction model, we show that normal stress is temporally variable on the fault, and support this using seismic observations. We propose that, through a self-sustaining fault-valve behavior, compaction induced elevation of pore pressure within hydraulically isolated fault compartments, and subsequent frictional dilation is the cause for the observed episodic SSEs. We further suggest that the 2004 Parkfield Mw6 earthquake may have been triggered by the SSE on adjacent creeping segment, which increased Coulomb

  19. Thermo-Hydro-Micro-Mechanical 3D Modeling of a Fault Gouge During Co-seismic Slip

    Science.gov (United States)

    Papachristos, E.; Stefanou, I.; Sulem, J.; Donze, F. V.

    2017-12-01

    A coupled Thermo-Hydro-Micro-Mechanical (THMM) model based on the Discrete Elements method (DEM) is presented for studying the evolving fault gouge properties during pre- and co-seismic slip. Modeling the behavior of the fault gouge at the microscale is expected to improve our understanding on the various mechanisms that lead to slip weakening and finally control the transition from aseismic to seismic slip.The gouge is considered as a granular material of spherical particles [1]. Upon loading, the interactions between particles follow a frictional behavior and explicit dynamics. Using regular triangulation, a pore network is defined by the physical pore space between the particles. The network is saturated by a compressible fluid, and flow takes place following Stoke's equations. Particles' movement leads to pore deformation and thus to local pore pressure increase. Forces exerted from the fluid onto the particles are calculated using mid-step velocities. The fluid forces are then added to the contact forces resulting from the mechanical interactions before the next step.The same semi-implicit, two way iterative coupling is used for the heat-exchange through conduction.Simple tests have been performed to verify the model against analytical solutions and experimental results. Furthermore, the model was used to study the effect of temperature on the evolution of effective stress in the system and to highlight the role of thermal pressurization during seismic slip [2, 3].The analyses are expected to give grounds for enhancing the current state-of-the-art constitutive models regarding fault friction and shed light on the evolution of fault zone propertiesduring seismic slip.[1] Omid Dorostkar, Robert A Guyer, Paul A Johnson, Chris Marone, and Jan Carmeliet. On the role of fluids in stick-slip dynamics of saturated granular fault gouge using a coupled computational fluid dynamics-discrete element approach. Journal of Geophysical Research: Solid Earth, 122

  20. The Strain Energy, Seismic Moment and Magnitudes of Large Earthquakes

    Science.gov (United States)

    Purcaru, G.

    2004-12-01

    The strain energy Est, as potential energy, released by an earthquake and the seismic moment Mo are two fundamental physical earthquake parameters. The earthquake rupture process ``represents'' the release of the accumulated Est. The moment Mo, first obtained in 1966 by Aki, revolutioned the quantification of earthquake size and led to the elimination of the limitations of the conventional magnitudes (originally ML, Richter, 1930) mb, Ms, m, MGR. Both Mo and Est, not in a 1-to-1 correspondence, are uniform measures of the size, although Est is presently less accurate than Mo. Est is partitioned in seismic- (Es), fracture- (Eg) and frictional-energy Ef, and Ef is lost as frictional heat energy. The available Est = Es + Eg (Aki and Richards (1980), Kostrov and Das, (1988) for fundamentals on Mo and Est). Related to Mo, Est and Es, several modern magnitudes were defined under various assumptions: the moment magnitude Mw (Kanamori, 1977), strain energy magnitude ME (Purcaru and Berckhemer, 1978), tsunami magnitude Mt (Abe, 1979), mantle magnitude Mm (Okal and Talandier, 1987), seismic energy magnitude Me (Choy and Boatright, 1995, Yanovskaya et al, 1996), body-wave magnitude Mpw (Tsuboi et al, 1998). The available Est = (1/2μ )Δ σ Mo, Δ σ ~=~average stress drop, and ME is % \\[M_E = 2/3(\\log M_o + \\log(\\Delta\\sigma/\\mu)-12.1) ,\\] % and log Est = 11.8 + 1.5 ME. The estimation of Est was modified to include Mo, Δ and μ of predominant high slip zones (asperities) to account for multiple events (Purcaru, 1997): % \\[E_{st} = \\frac{1}{2} \\sum_i {\\frac{1}{\\mu_i} M_{o,i} \\Delta\\sigma_i} , \\sum_i M_{o,i} = M_o \\] % We derived the energy balance of Est, Es and Eg as: % \\[ E_{st}/M_o = (1+e(g,s)) E_s/M_o , e(g,s) = E_g/E_s \\] % We analyzed a set of about 90 large earthquakes and found that, depending on the goal these magnitudes quantify differently the rupture process, thus providing complementary means of earthquake characterization. Results for some

  1. Shallow seismic structure of Kunlun fault zone in northern Tibetan Plateau, China: Implications for the 2001 M s8.1 Kunlun earthquake

    Science.gov (United States)

    Wang, Chun-Yong; Mooney, W.D.; Ding, Z.; Yang, J.; Yao, Z.; Lou, H.

    2009-01-01

    The shallow seismic velocity structure of the Kunlun fault zone (KLFZ) was jointly deduced from seismic refraction profiling and the records of trapped waves that were excited by five explosions. The data were collected after the 2001 Kunlun M s8.1 earthquake in the northern Tibetan Plateau. Seismic phases for the in-line record sections (26 records up to a distance of 15 km) along the fault zone were analysed, and 1-D P- and S-wave velocity models of shallow crust within the fault zone were determined by using the seismic refraction method. Sixteen seismic stations were deployed along the off-line profile perpendicular to the fault zone. Fault-zone trapped waves appear clearly on the record sections, which were simulated with a 3-D finite difference algorithm. Quantitative analysis of the correlation coefficients of the synthetic and observed trapped waveforms indicates that the Kunlun fault-zone width is 300 m, and S-wave quality factor Q within the fault zone is 15. Significantly, S-wave velocities within the fault zone are reduced by 30-45 per cent from surrounding rocks to a depth of at least 1-2 km, while P-wave velocities are reduced by 7-20 per cent. A fault-zone with such P- and S-low velocities is an indication of high fluid pressure because Vs is affected more than Vp. The low-velocity and low-Q zone in the KLFZ model is the effect of multiple ruptures along the fault trace of the 2001 M s8.1 Kunlun earthquake. ?? 2009 The Authors Journal compilation ?? 2009 RAS.

  2. Efficient reduction and modularization for large fault trees stored by pages

    International Nuclear Information System (INIS)

    Chen, Shanqi; Wang, Jin; Wang, Jiaqun; Wang, Fang; Hu, Liqin

    2016-01-01

    Highlights: • New fault tree pre-processing methods used in RiskA are presented. • Including the fault tree paging storage, simplification and modularization. • For getting MCS for fault trees containing more than 10,000 gates and events. • Reduce computer resources needs (RAM) and improve computation speed. - Abstract: Fault Tree Analysis (FTA), an indispensable tool used in Probabilistic Risk Assessment (PRA), has been used throughout the commercial nuclear power industry for safety and reliability analyses. However, large fault tree analysis, such as those used in nuclear power plant requires significant computer resources, which makes the analysis of PRA model inefficient and time consuming. This paper describes a fault tree pre-processing method used in the reliability and probabilistic safety assessment program RiskA that is capable of generating minimal cutsets for fault trees containing more than 10,000 gates and basic events. The novel feature of this method is not only that Boolean reduction rules are used but also that a new objective of simplification is proposed. Moreover, since the method aims to find more fault tree modules by the linear-time algorithm, it can optimize fault tree modularization, which further reduces the computational time of large fault tree analysis.

  3. Large magnitude earthquakes on the Awatere Fault, Marlborough

    International Nuclear Information System (INIS)

    Mason, D.P.M.; Little, T.A.; Van Dissen, R.J.

    2006-01-01

    The Awatere Fault is a principal active strike-slip fault within the Marlborough fault system, and last ruptured in October 1848, in the M w ∼7.5 Marlborough earthquake. The coseismic slip distribution and maximum traceable length of this rupture are calculated from the magnitude and distribution of small, metre-scale geomorphic displacements attributable to this earthquake. These data suggest this event ruptured ∼110 km of the fault, with mean horizontal surface displacement of 5.3 ± 1.6m. Based on these parameters, the moment magnitude of this earthquake would be M w ∼7.4-7.7. Paeloseismic trenching investigations along the eastern section reveal evidence for at least eight, and possibly ten, surface-rupturing paleoearthquakes in the last 8600 years, including the 1848 rupture. The coseismic slip distribution and rupture length of the 1848 earthquake, in combination with the paleoearthquake age data, suggest the eastern section of the Awatere Fault ruptures in M w ∼7.5 earthquakes, with over 5 m of surface displacement, every 860-1080 years. (author). 21 refs., 10 figs., 7 tabs

  4. Reducing Information Overload in Large Seismic Data Sets

    Energy Technology Data Exchange (ETDEWEB)

    HAMPTON,JEFFERY W.; YOUNG,CHRISTOPHER J.; MERCHANT,BION J.; CARR,DORTHE B.; AGUILAR-CHANG,JULIO

    2000-08-02

    Event catalogs for seismic data can become very large. Furthermore, as researchers collect multiple catalogs and reconcile them into a single catalog that is stored in a relational database, the reconciled set becomes even larger. The sheer number of these events makes searching for relevant events to compare with events of interest problematic. Information overload in this form can lead to the data sets being under-utilized and/or used incorrectly or inconsistently. Thus, efforts have been initiated to research techniques and strategies for helping researchers to make better use of large data sets. In this paper, the authors present their efforts to do so in two ways: (1) the Event Search Engine, which is a waveform correlation tool and (2) some content analysis tools, which area combination of custom-built and commercial off-the-shelf tools for accessing, managing, and querying seismic data stored in a relational database. The current Event Search Engine is based on a hierarchical clustering tool known as the dendrogram tool, which is written as a MatSeis graphical user interface. The dendrogram tool allows the user to build dendrogram diagrams for a set of waveforms by controlling phase windowing, down-sampling, filtering, enveloping, and the clustering method (e.g. single linkage, complete linkage, flexible method). It also allows the clustering to be based on two or more stations simultaneously, which is important to bridge gaps in the sparsely recorded event sets anticipated in such a large reconciled event set. Current efforts are focusing on tools to help the researcher winnow the clusters defined using the dendrogram tool down to the minimum optimal identification set. This will become critical as the number of reference events in the reconciled event set continually grows. The dendrogram tool is part of the MatSeis analysis package, which is available on the Nuclear Explosion Monitoring Research and Engineering Program Web Site. As part of the research

  5. SEISMIC PICTURE OF A FAULT ZONE. WHAT CAN BE GAINED FROM THE ANALYSIS OF FINE PATTERNS OF SPATIAL DISTRIBUTION OF WEAK EARTHQUAKE CENTERS?

    Directory of Open Access Journals (Sweden)

    Gevorg G. Kocharyan

    2010-01-01

    Full Text Available Association of earthquake hypocenters with fault zones appears more pronounced in cases with more accurately determined positions of the earthquakes. For complex, branched structures of major fault zones, it is assumed that some of the earthquakes occur at feathering fractures of smaller scale.It is thus possible to develop a «seismological» criterion for definition of a zone of dynamic influence of faults, i.e. the zone containing the majority of earthquakes associated with the fault zone under consideration.In this publication, seismogenic structures of several fault zones located in the San-Andreas fault system are reviewed. Based on the data from a very dense network of digital seismic stations installed in this region and with application of modern data processing methods, differential coordinates of microearthquakes can be determined with errors of about first dozens of meters.It is thus possible to precisely detect boundaries of the areas wherein active deformation processes occur and to reveal spatial patterns of seismic event localization.In our analyses, data from the most comprehensive seismic catalog were used. The catalogue includes information on events which occurred and were registered in North California in the period between January 1984 and May 2003. In this publication, the seismic data processing results and regularities revealed during the analyses are compared with the data obtained from studies of fault structures, modeling and numerical simulation results. Results of quantitative research of regularities of localization of seismic sources inside fault zones are presented.It is demonstrated by 3D models that seismic events are localized in the vicinity of an almost plain surface with a nearly constant angle of dip, the majority of events being concentrated at that conventional surface.Detection of typical scopes of seismicity localization may prove critical for solution of problems of technogenic impact on fault zones

  6. Quantitative Mapping of Precursory Seismic Quiescence Before Large Aftershocks

    Science.gov (United States)

    Neukomm, S.; Wiemer, S.; Giardini, D.

    2002-12-01

    A relative decrease of aftershock activity before the occurrence of large aftershocks to M6+ mainshocks is one of only few earthquake precursors accepted for the IASPEI preliminary list of significant earthquake precursors. If one considers earthquake rate to be dependent on stressing rate, aftershocks sequences offer in fact an ideal environment to detect precursory quiescence before large earthquakes: The numerous aftershocks allow a much higher spatial and temporal resolution of transients in seismicity than possible with the average background rate of micro-earthquakes. Past studies of precursory quiescence before larger aftershocks, however, have largely been based on bulk value. The aim of this study is to map the temporal and spatial variability of activity rate within several rich aftershock sequences, and, possibly, exploit the results for improving real time probabilistic aftershock hazard assessment. We introduce a new algorithm based on fitting the modified Omori law to the aftershock sequences. At arbitrarily chosen grid points, the Omori parameters of the sub-samples containing all aftershock within 5 or 10 km of the node are estimated at time t. We calculate the number of aftershocks N +/- dN in the time interval t + dt using the relevant four Omori parameters (p, c and k) parameters and their corresponding standard deviations estimated using a bootstrap analysis. The difference between the forecasted and the observed number of aftershocks, normalized by the standard deviation of the forecast, is our estimator of rate change. The algorithm is tested on synthetic aftershock sequences containing artificial quiescences in order to calibrate the free parameters for optimal detection of precursory quiescence. We then perform our spatial and temporal mapping for several prominent Californian and Japanese aftershock sequences (Landers, Hector Mine, Northridge, Loma Prieta, Kobe, Western Tottori and Hokkaido). Preliminary results suggest that we cannot

  7. Detecting Significant Stress Drop Variations in Large Micro-Earthquake Datasets: A Comparison Between a Convergent Step-Over in the San Andreas Fault and the Ventura Thrust Fault System, Southern California

    Science.gov (United States)

    Goebel, T. H. W.; Hauksson, E.; Plesch, A.; Shaw, J. H.

    2017-06-01

    A key parameter in engineering seismology and earthquake physics is seismic stress drop, which describes the relative amount of high-frequency energy radiation at the source. To identify regions with potentially significant stress drop variations, we perform a comparative analysis of source parameters in the greater San Gorgonio Pass (SGP) and Ventura basin (VB) in southern California. The identification of physical stress drop variations is complicated by large data scatter as a result of attenuation, limited recording bandwidth and imprecise modeling assumptions. In light of the inherently high uncertainties in single stress drop measurements, we follow the strategy of stacking large numbers of source spectra thereby enhancing the resolution of our method. We analyze more than 6000 high-quality waveforms between 2000 and 2014, and compute seismic moments, corner frequencies and stress drops. Significant variations in stress drop estimates exist within the SGP area. Moreover, the SGP also exhibits systematically higher stress drops than VB and shows more scatter. We demonstrate that the higher scatter in SGP is not a generic artifact of our method but an expression of differences in underlying source processes. Our results suggest that higher differential stresses, which can be deduced from larger focal depth and more thrust faulting, may only be of secondary importance for stress drop variations. Instead, the general degree of stress field heterogeneity and strain localization may influence stress drops more strongly, so that more localized faulting and homogeneous stress fields favor lower stress drops. In addition, higher loading rates, for example, across the VB potentially result in stress drop reduction whereas slow loading rates on local fault segments within the SGP region result in anomalously high stress drop estimates. Our results show that crustal and fault properties systematically influence earthquake stress drops of small and large events and should

  8. Analog Fault Diagnosis of Large-Scale Electronic Circuits.

    Science.gov (United States)

    1983-08-01

    operational amplifiers and electrolytic capacitors. Remarks. 1. For fault diagnosis problems, the nominal characteristics are usually given and the...fractional repre- m. sentation in (G,H,I,J) of the element peG ; then Z. is h,.,--p(l+cp)’---n,(yd,+xln,)-’y,. (3.13) well defined in H if and only if d...B3S3 A6-0 then C1 is faulty. The fifth row of Table lb reads that if AB2*0, £ 3350 , and AB-A34=0 then * where S is the complex frequency, and a fault

  9. Response of Seismically Isolated Steel Frame Buildings with Sustainable Lead-Rubber Bearing (LRB Isolator Devices Subjected to Near-Fault (NF Ground Motions

    Directory of Open Access Journals (Sweden)

    Jong Wan Hu

    2014-12-01

    Full Text Available Base isolation has been used as one of the most wildly accepted seismic protection systems that should substantially dissociate a superstructure from its substructure resting on a shaking ground, thereby sustainably preserving entire structures against earthquake forces as well as inside non-structural integrities. Base isolation devices can operate very effectively against near-fault (NF ground motions with large velocity pulses and permanent ground displacements. In this study, comparative advantages for using lead-rubber bearing (LRB isolation systems are mainly investigated by performing nonlinear dynamic time-history analyses with NF ground motions. The seismic responses with respects to base shears and inter-story drifts are compared according to the installation of LRB isolation systems in the frame building. The main function of the base LRB isolator is to extend the period of structural vibration by increasing lateral flexibility in the frame structure, and thus ground accelerations transferred into the superstructure can dramatically decrease. Therefore, these base isolation systems are able to achieve notable mitigation in the base shear. In addition, they make a significant contribution to reducing inter-story drifts distributed over the upper floors. Finally, the fact that seismic performance can be improved by installing isolation devices in the frame structure is emphasized herein through the results of nonlinear dynamic analyses.

  10. Satellite Geodetic Constraints On Earthquake Processes: Implications of the 1999 Turkish Earthquakes for Fault Mechanics and Seismic Hazards on the San Andreas Fault

    Science.gov (United States)

    Reilinger, Robert

    2005-01-01

    Our principal activities during the initial phase of this project include: 1) Continued monitoring of postseismic deformation for the 1999 Izmit and Duzce, Turkey earthquakes from repeated GPS survey measurements and expansion of the Marmara Continuous GPS Network (MAGNET), 2) Establishing three North Anatolian fault crossing profiles (10 sitedprofile) at locations that experienced major surface-fault earthquakes at different times in the past to examine strain accumulation as a function of time in the earthquake cycle (2004), 3) Repeat observations of selected sites in the fault-crossing profiles (2005), 4) Repeat surveys of the Marmara GPS network to continue to monitor postseismic deformation, 5) Refining block models for the Marmara Sea seismic gap area to better understand earthquake hazards in the Greater Istanbul area, 6) Continuing development of models for afterslip and distributed viscoelastic deformation for the earthquake cycle. We are keeping close contact with MIT colleagues (Brad Hager, and Eric Hetland) who are developing models for S. California and for the earthquake cycle in general (Hetland, 2006). In addition, our Turkish partners at the Marmara Research Center have undertaken repeat, micro-gravity measurements at the MAGNET sites and have provided us estimates of gravity change during the period 2003 - 2005.

  11. Fault Detection for Large-Scale Railway Maintenance Equipment Base on Wireless Sensor Networks

    Directory of Open Access Journals (Sweden)

    Junfu Yu

    2014-04-01

    Full Text Available Focusing on the fault detection application for large-scale railway maintenance equipment with the specialties of low-cost, energy efficiency, collecting data of the function units. This paper proposed energy efficiency, convenient installation fault detection application using Sigsbee wireless sensor networks, which Sigsbee is the most widely used protocol based on IEEE 802.15.4. This paper proposed a systematic application from hardware design using STM32F103 chips as processer, to software system. Fault detection application is the basic part of the fault diagnose system, wireless sensor nodes of the fault detection application with different kinds of sensors for verities function units communication by Sigsbee to collecting and sending basic working status data to the home gateway, then data will be sent to the fault diagnose system.

  12. Rapid Transient Fault Insertion in Large Digital Systems

    NARCIS (Netherlands)

    Rohani, A.; Kerkhoff, Hans G.

    This paper presents a technique for rapidtransientfault injection, regarding the CPU time, to perform simulation-based fault-injection in complex System-on-Chip Systems (SoCs). The proposed approach can be applied to complex circuits, as it is not required to modify the top-level modules of a

  13. The Greenville Fault: preliminary estimates of its long-term creep rate and seismic potential

    Science.gov (United States)

    Lienkaemper, James J.; Barry, Robert G.; Smith, Forrest E.; Mello, Joseph D.; McFarland, Forrest S.

    2013-01-01

    Once assumed locked, we show that the northern third of the Greenville fault (GF) creeps at 2 mm/yr, based on 47 yr of trilateration net data. This northern GF creep rate equals its 11-ka slip rate, suggesting a low strain accumulation rate. In 1980, the GF, easternmost strand of the San Andreas fault system east of San Francisco Bay, produced a Mw5.8 earthquake with a 6-km surface rupture and dextral slip growing to ≥2 cm on cracks over a few weeks. Trilateration shows a 10-cm post-1980 transient slip ending in 1984. Analysis of 2000-2012 crustal velocities on continuous global positioning system stations, allows creep rates of ~2 mm/yr on the northern GF, 0-1 mm/yr on the central GF, and ~0 mm/yr on its southern third. Modeled depth ranges of creep along the GF allow 5-25% aseismic release. Greater locking in the southern two thirds of the GF is consistent with paleoseismic evidence there for large late Holocene ruptures. Because the GF lacks large (>1 km) discontinuities likely to arrest higher (~1 m) slip ruptures, we expect full-length (54-km) ruptures to occur that include the northern creeping zone. We estimate sufficient strain accumulation on the entire GF to produce Mw6.9 earthquakes with a mean recurrence of ~575 yr. While the creeping 16-km northern part has the potential to produce a Mw6.2 event in 240 yr, it may rupture in both moderate (1980) and large events. These two-dimensional-model estimates of creep rate along the southern GF need verification with small aperture surveys.

  14. Radon emanation on San Andreas Fault

    International Nuclear Information System (INIS)

    King, C.-Y.

    1978-01-01

    It is stated that subsurface radon emanation monitored in shallow dry holes along an active segment of the San Andreas fault in central California shows spatially coherent large temporal variations that seem to be correlated with local seismicity. (author)

  15. Structure of the Suasselkä postglacial fault in northern Finland obtained by analysis of local events and ambient seismic noise

    Science.gov (United States)

    Afonin, Nikita; Kozlovskaya, Elena; Kukkonen, Ilmo; Dafne/Finland Working Group

    2017-04-01

    Understanding the inner structure of seismogenic faults and their ability to reactivate is particularly important in investigating the continental intraplate seismicity regime. In our study we address this problem using analysis of local seismic events and ambient seismic noise recorded by the temporary DAFNE array in the northern Fennoscandian Shield. The main purpose of the DAFNE/FINLAND passive seismic array experiment was to characterize the present-day seismicity of the Suasselkä postglacial fault (SPGF), which was proposed as one potential target for the DAFNE (Drilling Active Faults in Northern Europe) project. The DAFNE/FINLAND array comprised an area of about 20 to 100 km and consisted of eight short-period and four broadband three-component autonomous seismic stations installed in the close vicinity of the fault area. The array recorded continuous seismic data during September 2011-May 2013. Recordings of the array have being analysed in order to identify and locate natural earthquakes from the fault area and to discriminate them from the blasts in the Kittilä gold mine. As a result, we found a number of natural seismic events originating from the fault area, which proves that the fault is still seismically active. In order to study the inner structure of the SPGF we use cross-correlation of ambient seismic noise recorded by the array. Analysis of azimuthal distribution of noise sources demonstrated that during the time interval under consideration the distribution of noise sources is close to the uniform one. The continuous data were processed in several steps including single-station data analysis, instrument response removal and time-domain stacking. The data were used to estimate empirical Green's functions between pairs of stations in the frequency band of 0.1-1 Hz and to calculate corresponding surface wave dispersion curves. The S-wave velocity models were obtained as a result of dispersion curve inversion. The results suggest that the area of

  16. Fault structure analysis by means of large deformation simulator; Daihenkei simulator ni yoru danso kozo kaiseki

    Energy Technology Data Exchange (ETDEWEB)

    Murakami, Y.; Shi, B. [Geological Survey of Japan, Tsukuba (Japan); Matsushima, J. [The University of Tokyo, Tokyo (Japan). Faculty of Engineering

    1997-05-27

    Large deformation of the crust is generated by relatively large displacement of the mediums on both sides along a fault. In the conventional finite element method, faults are dealt with by special elements which are called joint elements, but joint elements, elements microscopic in width, generate numerical instability if large shear displacement is given. Therefore, by introducing the master slave (MO) method used for contact analysis in the metal processing field, developed was a large deformation simulator for analyzing diastrophism including large displacement along the fault. Analysis examples were shown in case the upper basement and lower basement were relatively dislocated with the fault as a boundary. The bottom surface and right end boundary of the lower basement are fixed boundaries. The left end boundary of the lower basement is fixed, and to the left end boundary of the upper basement, the horizontal speed, 3{times}10{sup -7}m/s, was given. In accordance with the horizontal movement of the upper basement, the boundary surface largely deformed. Stress is almost at right angles at the boundary surface. As to the analysis of faults by the MO method, it has been used for a single simple fault, but should be spread to lots of faults in the future. 13 refs., 2 figs.

  17. Long-Term Fault Memory: A New Time-Dependent Recurrence Model for Large Earthquake Clusters on Plate Boundaries

    Science.gov (United States)

    Salditch, L.; Brooks, E. M.; Stein, S.; Spencer, B. D.; Campbell, M. R.

    2017-12-01

    A challenge for earthquake hazard assessment is that geologic records often show large earthquakes occurring in temporal clusters separated by periods of quiescence. For example, in Cascadia, a paleoseismic record going back 10,000 years shows four to five clusters separated by approximately 1,000 year gaps. If we are still in the cluster that began 1700 years ago, a large earthquake is likely to happen soon. If the cluster has ended, a great earthquake is less likely. For a Gaussian distribution of recurrence times, the probability of an earthquake in the next 50 years is six times larger if we are still in the most recent cluster. Earthquake hazard assessments typically employ one of two recurrence models, neither of which directly incorporate clustering. In one, earthquake probability is time-independent and modeled as Poissonian, so an earthquake is equally likely at any time. The fault has no "memory" because when a prior earthquake occurred has no bearing on when the next will occur. The other common model is a time-dependent earthquake cycle in which the probability of an earthquake increases with time until one happens, after which the probability resets to zero. Because the probability is reset after each earthquake, the fault "remembers" only the last earthquake. This approach can be used with any assumed probability density function for recurrence times. We propose an alternative, Long-Term Fault Memory (LTFM), a modified earthquake cycle model where the probability of an earthquake increases with time until one happens, after which it decreases, but not necessarily to zero. Hence the probability of the next earthquake depends on the fault's history over multiple cycles, giving "long-term memory". Physically, this reflects an earthquake releasing only part of the elastic strain stored on the fault. We use the LTFM to simulate earthquake clustering along the San Andreas Fault and Cascadia. In some portions of the simulated earthquake history, events would

  18. Large-scale seismic signal analysis with Hadoop

    Science.gov (United States)

    Addair, T. G.; Dodge, D. A.; Walter, W. R.; Ruppert, S. D.

    2014-05-01

    In seismology, waveform cross correlation has been used for years to produce high-precision hypocenter locations and for sensitive detectors. Because correlated seismograms generally are found only at small hypocenter separation distances, correlation detectors have historically been reserved for spotlight purposes. However, many regions have been found to produce large numbers of correlated seismograms, and there is growing interest in building next-generation pipelines that employ correlation as a core part of their operation. In an effort to better understand the distribution and behavior of correlated seismic events, we have cross correlated a global dataset consisting of over 300 million seismograms. This was done using a conventional distributed cluster, and required 42 days. In anticipation of processing much larger datasets, we have re-architected the system to run as a series of MapReduce jobs on a Hadoop cluster. In doing so we achieved a factor of 19 performance increase on a test dataset. We found that fundamental algorithmic transformations were required to achieve the maximum performance increase. Whereas in the original IO-bound implementation, we went to great lengths to minimize IO, in the Hadoop implementation where IO is cheap, we were able to greatly increase the parallelism of our algorithms by performing a tiered series of very fine-grained (highly parallelizable) transformations on the data. Each of these MapReduce jobs required reading and writing large amounts of data. But, because IO is very fast, and because the fine-grained computations could be handled extremely quickly by the mappers, the net was a large performance gain.

  19. Seismic images of an extensional basin, generated at the hangingwall of a low-angle normal fault: The case of the Sansepolcro basin (Central Italy)

    Science.gov (United States)

    Barchi, Massimiliano R.; Ciaccio, Maria Grazia

    2009-12-01

    The study of syntectonic basins, generated at the hangingwall of regional low-angle detachments, can help to gain a better knowledge of these important and mechanically controversial extensional structures, constraining their kinematics and timing of activity. Seismic reflection images constrain the geometry and internal structure of the Sansepolcro Basin (the northernmost portion of the High Tiber Valley). This basin was generated at the hangingwall of the Altotiberina Fault (AtF), an E-dipping low-angle normal fault, active at least since Late Pliocene, affecting the upper crust of this portion of the Northern Apennines. The dataset analysed consists of 5 seismic reflection lines acquired in the 80s' by ENI-Agip for oil exploration and a portion of the NVR deep CROP03 profile. The interpretation of the seismic profiles provides a 3-D reconstruction of the basin's shape and of the sedimentary succession infilling the basin. This consisting of up to 1200 m of fluvial and lacustrine sediments: this succession is much thicker and possibly older than previously hypothesised. The seismic data also image the geometry at depth of the faults driving the basin onset and evolution. The western flank is bordered by a set of E-dipping normal faults, producing the uplifting and tilting of Early to Middle Pleistocene succession along the Anghiari ridge. Along the eastern flank, the sediments are markedly dragged along the SW-dipping Sansepolcro fault. Both NE- and SW-dipping faults splay out from the NE-dipping, low-angle Altotiberina fault. Both AtF and its high-angle splays are still active, as suggested by combined geological and geomorphological evidences: the historical seismicity of the area can be reasonably associated to these faults, however the available data do not constrain an unambiguous association between the single structural elements and the major earthquakes.

  20. Plate boundary deformation of the Pacific plate. Two case studies. (1) Crustal structure of the northwestern Vizcaino block and Gorda escarpment, offshore northern California, and implications for postsubduction deformation of a paleoaccretionary margin. (2) A focused look at the Alpine fault, New Zealand: Seismicity, focal mechanisms and stress observations

    Science.gov (United States)

    Leitner, Beate

    Two examples of Pacific rim plate boundary deformation are presented. In the first part of the thesis crustal models are derived for the northwestern part of the Vizcaino block in California using marine seismic and gravity data collected by the Mendocino Triple Junction Seismic Experiment. A northwest-southeast trending kink in the Moho is imaged and interpreted to have formed under compression by reactivation of preexisting thrust faults in the paleoaccretionary prism at the seaward margin of the Vizcaino block. The study suggests that the deformation resulted from mainly north-south compression between the Pacific-Juan de Fuca plates across the Mendocino transform fault and predates late Pliocene Pacific-North America plate convergence. In the second part, 195 earthquakes recorded during the duration of the Southern Alps Passive Seismic Experiment (SAPSE) are analysed. Precise earthquake locations and focal mechanisms provide unprecedented detail of the seismotectonics in the central South Island. The short term (6 month) SAPSE seismicity is compared with long term (8 years) seismicity recorded by the New Zealand National Seismic network and the Lake Pukaki network. The seismicity rate of the Alpine fault is low, but comparable to locked sections of the San Andreas fault, with large earthquakes expected. Changes of the depth of the seismogenic zone, generally uniform at about 10--12 km, occur only localised over distances smaller than 30 km, suggesting that thermal perturbations must be of similar scale. This implies that the thermal effects of the uplift of the Southern Alps do not change the seismogenic depth significantly and are not in accordance with most of the present thermal models. Both the Hope and Porters Pass fault zones are seismically active and deformation is accommodated near the fault zones and in the adjacent crust. North of Mt Cook, a triangular shaped region along the Alpine fault is characterised by absence of earthquakes. We interpret this

  1. Large-Scale Seismic Test Program at Hualien, Taiwan

    International Nuclear Information System (INIS)

    Tang, H.T.; Graves, H.L.; Chen, P.C.

    1992-01-01

    The Large-Scale Seismic Test (LSST) Program at Hualien, Taiwan, is a follow-on to the soil-structure interaction (SSI) experiments at Lotung, Taiwan. The planned SSI studies will be performed at a stiff soil site in Hualien, Taiwan, that historically has had slightly more destructive earthquakes in the past than Lotung. The LSST is a joint effort among many interested parties. Electric Power Research Institute (EPRI) and Taipower are the organizers of the program and have the lead in planning and managing the program. Other organizations participating in the LSST program are US Nuclear Regulatory Commission, the Central Research Institute of Electric Power Industry, the Tokyo Electric Power Company, the Commissariat A L'Energie Atomique, Electricite de France and Framatome. The LSST was initiated in January 1990, and is envisioned to be five years in duration. Based on the assumption of stiff soil and confirmed by soil boring and geophysical results the test model was designed to provide data needed for SSI studies covering: free-field input, nonlinear soil response, non-rigid body SSI, torsional response, kinematic interaction, spatial incoherency and other effects. Taipower had the lead in design of the test model and received significant input from other LSST members. Questions raised by LSST members were on embedment effects, model stiffness, base shear, and openings for equipment. This paper describes progress in site preparation, design and construction of the model and development of an instrumentation plan

  2. Test on large-scale seismic isolation elements

    International Nuclear Information System (INIS)

    Mazda, T.; Shiojiri, H.; Oka, Y.; Fujita, T.; Seki, M.

    1989-01-01

    Demonstration test of seismic isolation elements is considered as one of the most important items in the application of seismic isolation system to fast breeder reactor (FBR) plant. Facilities for testing seismic isolation elements have been built. This paper reports on tests for fullscale laminated rubber bearing and reduced scale models are conducted. From the result of the tests, the laminated rubber bearings turn out to satisfy the specification. Their basic characteristics are confirmed from the tests with fullscale and reduced scale models. The ultimate capacity of the bearings under the condition of ordinary temperature are evaluated

  3. Holocene Activity of the Enriquillo-Plantain Garden Fault in Lake Enriquillo Derived from Seismic Stratigraphy

    Science.gov (United States)

    Rios, J. K.; McHugh, C. M.; Hornbach, M. J.; Mann, P.; Wright, V. D.; Gurung, D.

    2013-12-01

    The Enriquillo-Plantain-Garden fault zone (EPGF) crosses Lake Enriquillo (LE) in the Dominican Republic and extends E-W across the southern peninsula of Haiti, south of the Baie de Port au Prince (BPP). Seismic stratigraphic studies of CHIRP high-resolution subbottom profiles calibrated to ages obtained from sediment cores and previous coral reef studies provide a Holocene record of relative sea level rise into the BPB and LE and a time frame for understanding tectonics of the EPGF. The BPP is 20 km wide, 20 km long, 150 m deep, and surrounded by coral reefs at water depths of 30 m. Three seismic units were identified: Unit 1: stepped terraces 5-10 m high. Laminated strata onlaps the terraces. This unit possibly represents Marine Isotope Stages 6 and 5, but has not been dated. Unit 2: laminated strata, thicker than 10 m and dated near its top at 22 ka BP. The microfossil assemblages reveal that during the latest Pleistocene sea level lowstand the BPP had a restricted connection with the global ocean. Few well-preserved marine microfossils are present and mostly are reworked. Geochemical analyses reveal that the laminated sediments were deposited during wet periods (>Si, Al wt %, Cu ppm) and dry periods (>Ca wt %). Unit 3: acoustically transparent, ~10 m thick, dated near its base and top at 14 ka BP and 2 ka BP, respectively. This unit represents the Holocene initiation of sea level rise and high stand containing well-preserved marine fossils. At ~9.5 ka BP planktonic foraminifers become abundant implying deepening of marine waters. Lake Enriquillo is 127 km east of the BPP. It is 15 km wide, 40 km long and 45 m deep. CHIRP subbottom profiles penetrated ~30 m below the lake floor. Four main acoustic units were identified: Unit 1: deformed basement with steeply dipping and folded beds. Based on land studies this unit is likely Plio-Pleistocene in age. Unit 2: laminated strata. Ages from coral reefs and deformed strata on land indicate this unit is likely pre-20 ka

  4. Seismic analysis of a large LMFBR with fluid-structure interactions

    International Nuclear Information System (INIS)

    Ma, D.C.

    1985-01-01

    The seismic analysis of a large LMFBR with many internal components and structures is presented. Both vertical and horizontal seismic excitations are considered. The important hydrodynamic phenomena such as fluid-structure interaction, sloshing, fluid coupling and fluid inertia effects are included in the analysis. The results of this study are discussed in detail. Information which is useful to the design of future reactions under seismic conditions is also given. 4 refs., 12 figs

  5. Preliminary Interpretations of Multi-Channel Seismic Reflection and Magnetic Data on North Anatolian Fault (NAF) in the Eastern Marmara Region, Turkey

    Science.gov (United States)

    Gözde Okut Toksoy, Nigar; Kurt, Hülya; İşseven, Turgay

    2017-04-01

    The North Anatolian Fault (NAF) is 1600 km long, right lateral strike-slip fault nearly E-W elongated between Karlıova in the east and Saros Gulf in the west. NAF splays into two major strands near the west of Bolu city as Northern and Southern strands. Northern strand passes Sapanca Lake and extends towards west and reaches Marmara Sea through the Gulf of Izmit. The area has high seismicity; 1999 Kocaeli (Mw=7.4) and 1999 Düzce (Mw=7.2) earthquakes caused approximately 150 km long surface rupture between the Gulf of Izmit and Bolu. The rupture has four distinct fault segments as Gölcük, Sapanca, Sakarya, and Karadere from west to east. In this study multi-channel seismic and magnetic data are collected for the first time on the Sapanca Segment to investigate the surficial and deeper geometry of the NAF. Previously, the NAF in the eastern Marmara region is investigated using by paleo-seismological data from trenches on the surface rupture of fault or the geomorphological data (Lettis et al., 2000; Dikbaş and Akyüz, 2010) which have shallower depth targets. Crustal structure and seismic velocities for Central Anatolia and eastern Marmara regions are obtained from deeper targeted refraction data (Gürbüz et al., 1992). However, their velocity models do not have the spatial resolution to determine details of the fault zone structure. Multi-channel seismic and magnetic data in this study were acquired on two N-S directed profiles crossing NAF perpendicularly near Kartepe on the western part of the Sapanca Lake in October 2016. The receiver interval is 5 m, shot interval is 5-10 m, and the total length of the profiles are approximately 1400 m. Buffalo Gun is used as a seismic source for deeper penetration. Conventional seismic reflection processing steps are applied to the data. These are geometry definition, editing, filtering, static correction, velocity analysis and deconvolution, stacking and migration. Echos seismic software package in Geophysical Department

  6. Research on bearing fault diagnosis of large machinery based on mathematical morphology

    Science.gov (United States)

    Wang, Yu

    2018-04-01

    To study the automatic diagnosis of large machinery fault based on support vector machine, combining the four common faults of the large machinery, the support vector machine is used to classify and identify the fault. The extracted feature vectors are entered. The feature vector is trained and identified by multi - classification method. The optimal parameters of the support vector machine are searched by trial and error method and cross validation method. Then, the support vector machine is compared with BP neural network. The results show that the support vector machines are short in time and high in classification accuracy. It is more suitable for the research of fault diagnosis in large machinery. Therefore, it can be concluded that the training speed of support vector machines (SVM) is fast and the performance is good.

  7. Fault-related-folding structures and reflection seismic sections. Study by seismic modeling and balanced cross section; Danso ga kaizaisuru shukyoku kozo no keitai to jishin tansa danmen. 2. Seismic modeling oyobi balanced cross section ni yoru study

    Energy Technology Data Exchange (ETDEWEB)

    Tamagawa, T; Matsuoka, T [Japan Petroleum Exploration Corp., Tokyo (Japan); Tsukui, R [Japan National Oil Corp., Tokyo (Japan). Technology Research Center

    1997-05-27

    It occasionally happens that there exists a part where reflection near the thrust is not clearly observed in a thrust zone seismic survey cross section. For the effective interpretation of such an occurrence, the use of geological structures as well as the reflected pattern is effective. When the velocity structures for a fold structure having a listric fault caused anticline (unidirectionally inclined with a backlimb, without a forelimb) and for a fault propagation fold are involved, a wrong interpretation may be made since they look alike in reflection wave pattern despite their difference in geological structure. In the concept of balanced cross section, a check is performed, when the stratum after deformation is recovered to the time of deposition, as to whether the geologic stratum area is conserved without excess or shortage. An excess or shortage occurs if there is an error in the model, and this shows that the fault surface or fold structure is not correctly reflected. Positive application of geological knowledge is required in the processing and interpreting of data from a seismic survey. 6 refs., 6 figs.

  8. the Preliminary Research Based on Seismic Signals Generated by Hutubi Transmitting Seismic Station with One Large-volume Airgun Array

    Science.gov (United States)

    Wang, Q.; Su, J.; Wei, Y.; Zhang, W.; Wang, H.; Wang, B.; Ji, Z.

    2017-12-01

    For studying the subsurface structure and its subtle changes, we built the Hutubi transmitting seismic station with one large-volume airgun array at one artificial water pool in the northern segment of Tianshan mountain, where earthquakes occurred frequently. The airgun array consists of six airguns with every airgun capacity of 2000in3, and the artificial water pool with the top diameter of 100m, bottom diameter of 20m and the depth of 18m.We started the regular excitation experiment with the large-volume airgun source every week since June, 2013. Using seismic signals geneated by the Hutubi airgun source, we made the preliminary research on the airgun source, waveform characteristics and the subsurface velocity changes in the northern Tiansh mountain. The results are as follows: The seismic signal exited by the airgun source is characteristic of low-frequency ,and the dominant frequency is in the range of 2 6Hz. The Hutubi transmitting seismic station can continuously generate long-distance detectable and highly repeatable signals, and the correlation coefficient of sigals is greater than 0.95; and the longest propagation distance arrives to 380km, in addition, the 5000-shot stacked sigal using the phase weighted stack technique can be identified in the station, which is about 1300km from the Hutubi transmitting seismic station. Hutubi large-volume airgun source is fitted to detect and monitor the regional-scale subsurface stress state. Applying correlation test method, we measured weak subsurface velocity changes in the northern Tianshan mountain, and found that the several stations, which are within 150km from the the Hutubi transmitting seismic station, appeared 0.1 0.2% relative velocity changes before the Hutubi MS6.2 earthquake on Dec.8, 2016.

  9. Evidence of Enhanced Subrosion in a Fault Zone and Characterization of Hazard Zones with Elastic Parameters derived from SH-wave reflection Seismics and VSP

    Science.gov (United States)

    Wadas, S. H.; Tanner, D. C.; Tschache, S.; Polom, U.; Krawczyk, C. M.

    2017-12-01

    Subrosion, the dissolution of soluble rocks, e.g., sulfate, salt, or carbonate, requires unsaturated water and fluid pathways that enable the water to flow through the subsurface and generate cavities. Over time, different structures can occur that depend on, e.g., rock solubility, flow rate, and overburden type. The two main structures are sinkholes and depressions. To analyze the link between faults, groundwater flow, and soluble rocks, and to determine parameters that are useful to characterize hazard zones, several shear-wave (SH) reflection seismic profiles were surveyed in Thuringia in Germany, where Permian sulfate rocks and salt subcrop close to the surface. From the analysis of the seismic sections we conclude that areas affected by tectonic deformation phases are prone to enhanced subrosion. The deformation of fault blocks leads to the generation of a damage zone with a dense fracture network. This increases the rock permeability and thus serves as a fluid pathway for, e.g., artesian-confined groundwater. The more complex the fault geometry and the more interaction between faults, the more fractures are generated, e.g., in a strike slip-fault zone. The faults also act as barriers for horizontal groundwater flow perpendicular to the fault surfaces and as conduits for groundwater flow along the fault strike. In addition, seismic velocity anomalies and attenuation of seismic waves are observed. Low velocities high attenuation may indicate areas affected by subrosion. Other parameters that characterize the underground stability are the shear modulus and the Vp/Vs ratio. The data revealed zones of low shear modulus high Vp/Vs ratio >2.5, which probably indicate unstable areas due to subrosion. Structural analysis of S-wave seismics is a valuable tool to detect near-surface faults in order to determine whether or not an area is prone to subrosion. The recognition of even small fault blocks can help to better understand the hydrodynamic groundwater conditions

  10. Adaptive Fuzzy Output-Constrained Fault-Tolerant Control of Nonlinear Stochastic Large-Scale Systems With Actuator Faults.

    Science.gov (United States)

    Li, Yongming; Ma, Zhiyao; Tong, Shaocheng

    2017-09-01

    The problem of adaptive fuzzy output-constrained tracking fault-tolerant control (FTC) is investigated for the large-scale stochastic nonlinear systems of pure-feedback form. The nonlinear systems considered in this paper possess the unstructured uncertainties, unknown interconnected terms and unknown nonaffine nonlinear faults. The fuzzy logic systems are employed to identify the unknown lumped nonlinear functions so that the problems of structured uncertainties can be solved. An adaptive fuzzy state observer is designed to solve the nonmeasurable state problem. By combining the barrier Lyapunov function theory, adaptive decentralized and stochastic control principles, a novel fuzzy adaptive output-constrained FTC approach is constructed. All the signals in the closed-loop system are proved to be bounded in probability and the system outputs are constrained in a given compact set. Finally, the applicability of the proposed controller is well carried out by a simulation example.

  11. Active crustal deformation of the El Salvador Fault Zone (ESFZ) using GPS data: Implications in seismic hazard assessment

    Science.gov (United States)

    Staller, Alejandra; Benito, Belen; Jesús Martínez-Díaz, José; Hernández, Douglas; Hernández-Rey, Román; Alonso-Henar, Jorge

    2014-05-01

    El Salvador, Central America, is part of the Chortis block in the northwestern boundary of the Caribbean plate. This block is interacting with a diffuse triple junction point with the Cocos and North American plates. Among the structures that cut the Miocene to Pleistocene volcanic deposits stands out the El Salvador Fault Zone (ESFZ): It is oriented in N90º-100ºE direction, and it is composed of several structural segments that deform Quaternary deposits with right-lateral and oblique slip motions. The ESFZ is seismically active and capable of producing earthquakes such as the February 13, 2001 with Mw 6.6 (Martínez-Díaz et al., 2004), that seriously affected the population, leaving many casualties. This structure plays an important role in the tectonics of the Chortis block, since its motion is directly related to the drift of the Caribbean plate to the east and not with the partitioning of the deformation of the Cocos subduction (here not coupled) (Álvarez-Gómez et al., 2008). Together with the volcanic arc of El Salvador, this zone constitutes a weakness area that allows the motion of forearc block toward the NW. The geometry and the degree of activity of the ESFZ are not studied enough. However their knowledge is essential to understand the seismic hazard associated to this important seismogenic structure. For this reason, since 2007 a GPS dense network was established along the ESFZ (ZFESNet) in order to obtain GPS velocity measurements which are later used to explain the nature of strain accumulation on major faults along the ESFZ. The current work aims at understanding active crustal deformation of the ESFZ through kinematic model. The results provide significant information to be included in a new estimation of seismic hazard taking into account the major structures in ESFZ.

  12. Seismic evidence for arc segmentation, active magmatic intrusions and syn-rift fault system in the northern Ryukyu volcanic arc

    Science.gov (United States)

    Arai, Ryuta; Kodaira, Shuichi; Takahashi, Tsutomu; Miura, Seiichi; Kaneda, Yoshiyuki

    2018-04-01

    Tectonic and volcanic structures of the northern Ryukyu arc are investigated on the basis of multichannel seismic (MCS) reflection data. The study area forms an active volcanic front in parallel to the non-volcanic island chain in the eastern margin of the Eurasian plate and has been undergoing regional extension on its back-arc side. We carried out a MCS reflection experiment along two across-arc lines, and one of the profiles was laid out across the Tokara Channel, a linear bathymetric depression which demarcates the northern and central Ryukyu arcs. The reflection image reveals that beneath this topographic valley there exists a 3-km-deep sedimentary basin atop the arc crust, suggesting that the arc segment boundary was formed by rapid and focused subsidence of the arc crust driven by the arc-parallel extension. Around the volcanic front, magmatic conduits represented by tubular transparent bodies in the reflection images are well developed within the shallow sediments and some of them are accompanied by small fragments of dipping seismic reflectors indicating intruded sills at their bottoms. The spatial distribution of the conduits may suggest that the arc volcanism has multiple active outlets on the seafloor which bifurcate at crustal depths and/or that the location of the volcanic front has been migrating trenchward over time. Further distant from the volcanic front toward the back-arc (> 30 km away), these volcanic features vanish, and alternatively wide rift basins become predominant where rapid transitions from normal-fault-dominant regions to strike-slip-fault-dominant regions occur. This spatial variation in faulting patterns indicates complex stress regimes associated with arc/back-arc rifting in the northern Okinawa Trough.[Figure not available: see fulltext.

  13. Cyclic loading of simulated fault gouge to large strains

    Science.gov (United States)

    Jones, Lucile M.

    1980-04-01

    As part of a study of the mechanics of simulated fault gouge, deformation of Kayenta Sandstone (24% initial porosity) was observed in triaxial stress tests through several stress cycles. Between 50- and 300-MPa effective pressure the specimens deformed stably without stress drops and with deformation occurring throughout the sample. At 400-MPa effective pressure the specimens underwent strain softening with the deformation occurring along one plane. However, the difference in behavior seems to be due to the density variation at different pressures rather than to the difference in pressure. After peak stress was reached in each cycle, the samples dilated such that the volumetric strain and the linear strain maintained a constant ratio (approximately 0.1) at all pressures. The behavior was independent of the number of stress cycles to linear strains up to 90% and was in general agreement with laws of soil behavior derived from experiments conducted at low pressure (below 5 MPa).

  14. Basic data features and results from a spatially dense seismic array on the San Jacinto fault zone

    Science.gov (United States)

    Ben-Zion, Yehuda; Vernon, Frank L.; Ozakin, Yaman; Zigone, Dimitri; Ross, Zachary E.; Meng, Haoran; White, Malcolm; Reyes, Juan; Hollis, Dan; Barklage, Mitchell

    2015-07-01

    We discuss several outstanding aspects of seismograms recorded during >4 weeks by a spatially dense Nodal array, straddling the damage zone of the San Jacinto fault in southern California, and some example results. The waveforms contain numerous spikes and bursts of high-frequency waves (up to the recorded 200 Hz) produced in part by minute failure events in the shallow crust. The high spatial density of the array facilitates the detection of 120 small local earthquakes in a single day, most of which not detected by the surrounding ANZA and regional southern California networks. Beamforming results identify likely ongoing cultural noise sources dominant in the frequency range 1-10 Hz and likely ongoing earthquake sources dominant in the frequency range 20-40 Hz. Matched-field processing and back-projection of seismograms provide alternate event location. The median noise levels during the experiment at different stations, waves generated by Betsy gunshots, and wavefields from nearby earthquakes point consistently to several structural units across the fault. Seismic trapping structure and local sedimentary basin produce localized motion amplification and stronger attenuation than adjacent regions. Cross correlations of high-frequency noise recorded at closely spaced stations provide a structural image of the subsurface material across the fault zone. The high spatial density and broad frequency range of the data can be used for additional high resolution studies of structure and source properties in the shallow crust.

  15. Modeling earthquake magnitudes from injection-induced seismicity on rough faults

    Science.gov (United States)

    Maurer, J.; Dunham, E. M.; Segall, P.

    2017-12-01

    It is an open question whether perturbations to the in-situ stress field due to fluid injection affect the magnitudes of induced earthquakes. It has been suggested that characteristics such as the total injected fluid volume control the size of induced events (e.g., Baisch et al., 2010; Shapiro et al., 2011). On the other hand, Van der Elst et al. (2016) argue that the size distribution of induced earthquakes follows Gutenberg-Richter, the same as tectonic events. Numerical simulations support the idea that ruptures nucleating inside regions with high shear-to-effective normal stress ratio may not propagate into regions with lower stress (Dieterich et al., 2015; Schmitt et al., 2015), however, these calculations are done on geometrically smooth faults. Fang & Dunham (2013) show that rupture length on geometrically rough faults is variable, but strongly dependent on background shear/effective normal stress. In this study, we use a 2-D elasto-dynamic rupture simulator that includes rough fault geometry and off-fault plasticity (Dunham et al., 2011) to simulate earthquake ruptures under realistic conditions. We consider aggregate results for faults with and without stress perturbations due to fluid injection. We model a uniform far-field background stress (with local perturbations around the fault due to geometry), superimpose a poroelastic stress field in the medium due to injection, and compute the effective stress on the fault as inputs to the rupture simulator. Preliminary results indicate that even minor stress perturbations on the fault due to injection can have a significant impact on the resulting distribution of rupture lengths, but individual results are highly dependent on the details of the local stress perturbations on the fault due to geometric roughness.

  16. Interseismic Coupling on the Quito Fault System in Ecuador Using New GPS and InSAR Data and Its Implication on Seismic Hazard Assessment.

    Science.gov (United States)

    Mariniere, J.; Champenois, J.; Nocquet, J. M.; Beauval, C. M.; Audin, L.; Baize, S.; Alvarado, A. P.; Yepes, H. A.; Jomard, H.

    2017-12-01

    Quito, the capital of Ecuador hosting two million inhabitants lies on an active reverse fault system within the Andes. Regular moderate size earthquakes (M 5) occur on these faults, widely felt within the city and its surrounding. Despite a relatively small magnitude of Mw 5.1, the 2014 August 12 earthquake triggered landslides that killed 4 people, cut off one of the main highways for several weeks and caused the temporary shutdown of the airport. Quantifying the seismic potential of the Quito fault system is therefore crucial for a better preparation and mitigation to seismic risk. Previous work using a limited GPS data set found that the Quito fault accommodates 4 mm/yr of EW shortening (Alvarado et al., 2014) at shallow locking depths (3-7 km). We combine GPS and new InSAR data to extend the previous analysis and better quantify the spatial distribution of locking of the Quito fault. GPS dataset includes new continuous sites operating since 2013. 18 ERS SAR scenes, spanning the 1993-2000 time period and covering an area of 85 km by 30 km, were processed using a Permanent Scatter strategy. We perform a joint inversion of both data set (GPS and InSAR) to infer a new and better-constrained kinematic model of the fault to determine both the slip rate and the locking distribution at depth. We find a highly variable level of locking which changes along strike. At some segments, sharp displacement gradients observed both for GPS and InSAR suggest that the fault is creeping up to the surface, while shallow locking is found for other segments. Previous Probabilistic Seismic Hazard Assessment studies have shown that the Quito fault fully controls the hazard in Quito city (Beauval et al. 2014). The results will be used to improve the forecast of earthquakes on the Quito fault system for PSHA studies.

  17. Physically based probabilistic seismic hazard analysis using broadband ground motion simulation: a case study for the Prince Islands Fault, Marmara Sea

    Science.gov (United States)

    Mert, Aydin; Fahjan, Yasin M.; Hutchings, Lawrence J.; Pınar, Ali

    2016-08-01

    The main motivation for this study was the impending occurrence of a catastrophic earthquake along the Prince Island Fault (PIF) in the Marmara Sea and the disaster risk around the Marmara region, especially in Istanbul. This study provides the results of a physically based probabilistic seismic hazard analysis (PSHA) methodology, using broadband strong ground motion simulations, for sites within the Marmara region, Turkey, that may be vulnerable to possible large earthquakes throughout the PIF segments in the Marmara Sea. The methodology is called physically based because it depends on the physical processes of earthquake rupture and wave propagation to simulate earthquake ground motion time histories. We included the effects of all considerable-magnitude earthquakes. To generate the high-frequency (0.5-20 Hz) part of the broadband earthquake simulation, real, small-magnitude earthquakes recorded by a local seismic array were used as empirical Green's functions. For the frequencies below 0.5 Hz, the simulations were obtained by using synthetic Green's functions, which are synthetic seismograms calculated by an explicit 2D /3D elastic finite difference wave propagation routine. By using a range of rupture scenarios for all considerable-magnitude earthquakes throughout the PIF segments, we produced a hazard calculation for frequencies of 0.1-20 Hz. The physically based PSHA used here followed the same procedure as conventional PSHA, except that conventional PSHA utilizes point sources or a series of point sources to represent earthquakes, and this approach utilizes the full rupture of earthquakes along faults. Furthermore, conventional PSHA predicts ground motion parameters by using empirical attenuation relationships, whereas this approach calculates synthetic seismograms for all magnitudes of earthquakes to obtain ground motion parameters. PSHA results were produced for 2, 10, and 50 % hazards for all sites studied in the Marmara region.

  18. Physically-Based Probabilistic Seismic Hazard Analysis Using Broad-Band Ground Motion Simulation: a Case Study for Prince Islands Fault, Marmara Sea

    Science.gov (United States)

    Mert, A.

    2016-12-01

    The main motivation of this study is the impending occurrence of a catastrophic earthquake along the Prince Island Fault (PIF) in Marmara Sea and the disaster risk around Marmara region, especially in İstanbul. This study provides the results of a physically-based Probabilistic Seismic Hazard Analysis (PSHA) methodology, using broad-band strong ground motion simulations, for sites within the Marmara region, Turkey, due to possible large earthquakes throughout the PIF segments in the Marmara Sea. The methodology is called physically-based because it depends on the physical processes of earthquake rupture and wave propagation to simulate earthquake ground motion time histories. We include the effects of all considerable magnitude earthquakes. To generate the high frequency (0.5-20 Hz) part of the broadband earthquake simulation, the real small magnitude earthquakes recorded by local seismic array are used as an Empirical Green's Functions (EGF). For the frequencies below 0.5 Hz the simulations are obtained using by Synthetic Green's Functions (SGF) which are synthetic seismograms calculated by an explicit 2D/3D elastic finite difference wave propagation routine. Using by a range of rupture scenarios for all considerable magnitude earthquakes throughout the PIF segments we provide a hazard calculation for frequencies 0.1-20 Hz. Physically based PSHA used here follows the same procedure of conventional PSHA except that conventional PSHA utilizes point sources or a series of point sources to represent earthquakes and this approach utilizes full rupture of earthquakes along faults. Further, conventional PSHA predicts ground-motion parameters using by empirical attenuation relationships, whereas this approach calculates synthetic seismograms for all magnitude earthquakes to obtain ground-motion parameters. PSHA results are produced for 2%, 10% and 50% hazards for all studied sites in Marmara Region.

  19. Seismic evaluation of large flat-bottomed tanks

    International Nuclear Information System (INIS)

    Kennedy, R.P.; Kassawara, R.P.

    1990-01-01

    This paper presents a procedure for conservatively evaluating the seismic capacity of flat-bottom fluid storage tanks. The authors know of no case of tank failures at capacity levels less than those predicted by this procedure. Thus, the predicted capacity represents a High Confidence Low Probability of Failure (HCLPF) capacity consistent with earthquake experience. (orig.)

  20. Numerical modeling of the deformations associated with large subduction earthquakes through the seismic cycle

    Science.gov (United States)

    Fleitout, L.; Trubienko, O.; Garaud, J.; Vigny, C.; Cailletaud, G.; Simons, W. J.; Satirapod, C.; Shestakov, N.

    2012-12-01

    A 3D finite element code (Zebulon-Zset) is used to model deformations through the seismic cycle in the areas surrounding the last three large subduction earthquakes: Sumatra, Japan and Chile. The mesh featuring a broad spherical shell portion with a viscoelastic asthenosphere is refined close to the subduction zones. The model is constrained by 6 years of postseismic data in Sumatra area and over a year of data for Japan and Chile plus preseismic data in the three areas. The coseismic displacements on the subduction plane are inverted from the coseismic displacements using the finite element program and provide the initial stresses. The predicted horizontal postseismic displacements depend upon the thicknesses of the elastic plate and of the low viscosity asthenosphere. Non-dimensionalized by the coseismic displacements, they present an almost uniform value between 500km and 1500km from the trench for elastic plates 80km thick. The time evolution of the velocities is function of the creep law (Maxwell, Burger or power-law creep). Moreover, the forward models predict a sizable far-field subsidence, also with a spatial distribution which varies with the geometry of the asthenosphere and lithosphere. Slip on the subduction interface does not induce such a subsidence. The observed horizontal velocities, divided by the coseismic displacement, present a similar pattern as function of time and distance from trench for the three areas, indicative of similar lithospheric and asthenospheric thicknesses and asthenospheric viscosity. This pattern cannot be fitted with power-law creep in the asthenosphere but indicates a lithosphere 60 to 90km thick and an asthenosphere of thickness of the order of 100km with a burger rheology represented by a Kelvin-Voigt element with a viscosity of 3.1018Pas and μKelvin=μelastic/3. A second Kelvin-Voigt element with very limited amplitude may explain some characteristics of the short time-scale signal. The postseismic subsidence is

  1. Incipient multiple fault diagnosis in real time with applications to large-scale systems

    International Nuclear Information System (INIS)

    Chung, H.Y.; Bien, Z.; Park, J.H.; Seon, P.H.

    1994-01-01

    By using a modified signed directed graph (SDG) together with the distributed artificial neutral networks and a knowledge-based system, a method of incipient multi-fault diagnosis is presented for large-scale physical systems with complex pipes and instrumentations such as valves, actuators, sensors, and controllers. The proposed method is designed so as to (1) make a real-time incipient fault diagnosis possible for large-scale systems, (2) perform the fault diagnosis not only in the steady-state case but also in the transient case as well by using a concept of fault propagation time, which is newly adopted in the SDG model, (3) provide with highly reliable diagnosis results and explanation capability of faults diagnosed as in an expert system, and (4) diagnose the pipe damage such as leaking, break, or throttling. This method is applied for diagnosis of a pressurizer in the Kori Nuclear Power Plant (NPP) unit 2 in Korea under a transient condition, and its result is reported to show satisfactory performance of the method for the incipient multi-fault diagnosis of such a large-scale system in a real-time manner

  2. Seismicity and tectonics of Bangladesh

    International Nuclear Information System (INIS)

    Hossain, K.M.

    1989-05-01

    Northern and eastern Bangladesh and surrounding areas belong to a seismically active zone and are associated with the subduction of the Indian plate. The seismicity and tectonics have been studied in detail and the observations have been correlated to understand the earthquake phenomenon in the region. The morphotectonic behaviour of northern Bangladesh shows that it is deeply related to the movement of the Dauki fault system and relative upliftment of the Shillong plateau. Contemporary seismicity in the Dauki fault system is relatively quiet comparing to that in the Naga-Disang-Haflong thrust belt giving rise to the probability of sudden release of energy being accumulated in the vicinity of the Dauki fault system. This observation corresponds with the predicted average return period of a large earthquake (1897 type) and the possibility of M > 8 earthquake in the vicinity of the Dauki fault within this century should not be ruled out. The seismicity in the folded belt in the east follows the general trend of Arakan-Yoma anticlinorium and represents shallow and low-angled thrust movements in conformity with the field observation. Seismotectonic behaviour in the deep basin part of Bangladesh demonstrates that an intraplate movement in the basement rock has been taking place along the deep-seated faults causing relative upliftment and subsidence in the basin. Bangladesh has been divided into three seismic zones on the basis of morphotectonic and seismic behaviour. Zone-I has been identified as the zone of high seismic risk. (author). 43 refs, 5 figs, 3 tabs

  3. Deformation around basin scale normal faults

    International Nuclear Information System (INIS)

    Spahic, D.

    2010-01-01

    Faults in the earth crust occur within large range of scales from microscale over mesoscopic to large basin scale faults. Frequently deformation associated with faulting is not only limited to the fault plane alone, but rather forms a combination with continuous near field deformation in the wall rock, a phenomenon that is generally called fault drag. The correct interpretation and recognition of fault drag is fundamental for the reconstruction of the fault history and determination of fault kinematics, as well as prediction in areas of limited exposure or beyond comprehensive seismic resolution. Based on fault analyses derived from 3D visualization of natural examples of fault drag, the importance of fault geometry for the deformation of marker horizons around faults is investigated. The complex 3D structural models presented here are based on a combination of geophysical datasets and geological fieldwork. On an outcrop scale example of fault drag in the hanging wall of a normal fault, located at St. Margarethen, Burgenland, Austria, data from Ground Penetrating Radar (GPR) measurements, detailed mapping and terrestrial laser scanning were used to construct a high-resolution structural model of the fault plane, the deformed marker horizons and associated secondary faults. In order to obtain geometrical information about the largely unexposed master fault surface, a standard listric balancing dip domain technique was employed. The results indicate that for this normal fault a listric shape can be excluded, as the constructed fault has a geologically meaningless shape cutting upsection into the sedimentary strata. This kinematic modeling result is additionally supported by the observation of deformed horizons in the footwall of the structure. Alternatively, a planar fault model with reverse drag of markers in the hanging wall and footwall is proposed. Deformation around basin scale normal faults. A second part of this thesis investigates a large scale normal fault

  4. Induced Seismicity

    Science.gov (United States)

    Keranen, Katie M.; Weingarten, Matthew

    2018-05-01

    The ability of fluid-generated subsurface stress changes to trigger earthquakes has long been recognized. However, the dramatic rise in the rate of human-induced earthquakes in the past decade has created abundant opportunities to study induced earthquakes and triggering processes. This review briefly summarizes early studies but focuses on results from induced earthquakes during the past 10 years related to fluid injection in petroleum fields. Study of these earthquakes has resulted in insights into physical processes and has identified knowledge gaps and future research directions. Induced earthquakes are challenging to identify using seismological methods, and faults and reefs strongly modulate spatial and temporal patterns of induced seismicity. However, the similarity of induced and natural seismicity provides an effective tool for studying earthquake processes. With continuing development of energy resources, increased interest in carbon sequestration, and construction of large dams, induced seismicity will continue to pose a hazard in coming years.

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

    Science.gov (United States)

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

    1983-01-01

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

  6. Risks posed by large seismic events in the gold mining districts of South Africa

    CSIR Research Space (South Africa)

    Durrheim, RJ

    2011-01-01

    Full Text Available buildings are considered vulnerable to damage by large seismic events, posing safety and financial risks. It is recommended that an earthquake engineer inspect the building stock and review the content and enforcement of building codes. Appropriate training...

  7. Seismic Activity Related to the 2002-2003 Mt. Etna Volcano Eruption (Italy): Fault Plane Solutions and Stress Tensor Computation

    Science.gov (United States)

    Barberi, G.; Cammarata, L.; Cocina, O.; Maiolino, V.; Musumeci, C.; Privitera, E.

    2003-04-01

    Late on the night of October 26, 2002, a bi-lateral eruption started on both the eastern and the southeastern flanks of Mt. Etna. The opening of the eruptive fracture system on the NE sector and the reactivation of the 2001 fracture system, on the S sector, were accompanied by a strong seismic swarm recorded between October 26 and 28 and by sharp increase of volcanic tremor amplitude. After this initial phase, on October 29 another seismogenetic zone became active in the SE sector of the volcano. At present (January 2003) the eruption is still in evolution. During the whole period a total of 862 earthquakes (Md≫1) was recorded by the local permanent seismic network run by INGV - Sezione di Catania. The maximum magnitude observed was Md=4.4. We focus our attention on 55 earthquakes with magnitude Md≫ 3.0. The dataset consists of accurate digital pickings of P- and S-phases including first-motion polarities. Firstly earthquakes were located using a 1D velocity model (Hirn et alii, 1991), then events were relocated by using two different 3D velocity models (Aloisi et alii, 2002; Patane et alii, 2002). Results indicate that most of earthquakes are located to the east of the Summit Craters and to northeast of them. Fault plane solutions (FPS) obtained show prevalent strike-slip rupture mechanisms. The suitable FPSs were considered for the application of Gephart and Forsyth`s algorithm in order to evaluate seismic stress field characteristics. Taking into account the preliminary results we propose a kinematic model of the eastern flank eastward movement in response of the intrusion processes in the central part of the volcano. References Aloisi M., Cocina O., Neri G., Orecchio B., Privitera E. (2002). Seismic tomography of the crust underneath the Etna volcano, Sicily. Physics of the Earth and Planetary Interiors 4154, pp. 1-17 Hirn A., Nercessian A., Sapin M., Ferrucci F., Wittlinger G. (1991). Seismic heterogeneity of Mt. Etna: structure and activity. Geophys. J

  8. Progress in Root Cause and Fault Propagation Analysis of Large-Scale Industrial Processes

    Directory of Open Access Journals (Sweden)

    Fan Yang

    2012-01-01

    Full Text Available In large-scale industrial processes, a fault can easily propagate between process units due to the interconnections of material and information flows. Thus the problem of fault detection and isolation for these processes is more concerned about the root cause and fault propagation before applying quantitative methods in local models. Process topology and causality, as the key features of the process description, need to be captured from process knowledge and process data. The modelling methods from these two aspects are overviewed in this paper. From process knowledge, structural equation modelling, various causal graphs, rule-based models, and ontological models are summarized. From process data, cross-correlation analysis, Granger causality and its extensions, frequency domain methods, information-theoretical methods, and Bayesian nets are introduced. Based on these models, inference methods are discussed to find root causes and fault propagation paths under abnormal situations. Some future work is proposed in the end.

  9. Irregular recurrence of large earthquakes along the san andreas fault: evidence from trees.

    Science.gov (United States)

    Jacoby, G C; Sheppard, P R; Sieh, K E

    1988-07-08

    Old trees growing along the San Andreas fault near Wrightwood, California, record in their annual ring-width patterns the effects of a major earthquake in the fall or winter of 1812 to 1813. Paleoseismic data and historical information indicate that this event was the "San Juan Capistrano" earthquake of 8 December 1812, with a magnitude of 7.5. The discovery that at least 12 kilometers of the Mojave segment of the San Andreas fault ruptured in 1812, only 44 years before the great January 1857 rupture, demonstrates that intervals between large earthquakes on this part of the fault are highly variable. This variability increases the uncertainty of forecasting destructive earthquakes on the basis of past behavior and accentuates the need for a more fundamental knowledge of San Andreas fault dynamics.

  10. Seismic potential of weak, near-surface faults revealed at plate tectonic slip rates.

    Science.gov (United States)

    Ikari, Matt J; Kopf, Achim J

    2017-11-01

    The near-surface areas of major faults commonly contain weak, phyllosilicate minerals, which, based on laboratory friction measurements, are assumed to creep stably. However, it is now known that shallow faults can experience tens of meters of earthquake slip and also host slow and transient slip events. Laboratory experiments are generally performed at least two orders of magnitude faster than plate tectonic speeds, which are the natural driving conditions for major faults; the absence of experimental data for natural driving rates represents a critical knowledge gap. We use laboratory friction experiments on natural fault zone samples at driving rates of centimeters per year to demonstrate that there is abundant evidence of unstable slip behavior that was not previously predicted. Specifically, weak clay-rich fault samples generate slow slip events (SSEs) and have frictional properties favorable for earthquake rupture. Our work explains growing field observations of shallow SSE and surface-breaking earthquake slip, and predicts that such phenomena should be more widely expected.

  11. Joint inversion of gravity and seismic data along a profile across the seismogenic fault of 2010 Yushu Ms7.1 earthquake

    Directory of Open Access Journals (Sweden)

    Yang Guangliang

    2011-11-01

    Full Text Available Yushu Ms7.1 earthquake occurred on the Ganzi-Yushu fault zone, across which we carried out a joint relative-gravity and seismic-reflection survey, and then performed a gravity inversion constrained by the seismic-reflection result. Based on the data of complete Bouguer gravity anomaly and seismic reflection, we obtained a layered interface structure in deep crust down to Moho. Our study showed that the inversion could reveal the interfaces of strata along the survey profile and the directions of regional faults in two-dimension. From the characteristics of the observed topography of the Moho basement, we tentatively confirmed that the uplift of eastern edge of Qinghai-Tibet plateau was caused by the subduction of the Indian plate.

  12. Crustal seismicity and active fault system in the SE of Romania

    International Nuclear Information System (INIS)

    Raileanu, V; Bala, A.; Radulian, M.; Popescu, E.; Mateciuc, D.; Popa, M.; Dinu, C.; Diaconescu, V.

    2007-01-01

    Romania is known as a country with a high seismicity located in the Vrancea region where 2-3 strong intermediate depth earthquakes/century generate great damages and casualties. A moderate crustal seismicity is also observed in other zones of the country, with events having a moderate magnitude but sometimes with important economic and social effects on the locale scale. The crustal seismogenic zones are located in front of the Eastern Carpathian Bend, South Carpathians, Dobrogea, Banat, Crisana and Maramures regions. The SE part of Romania comprises some of the most active crustal seismic sources that generated earthquakes up to Mw=6.5 concentrated in more zones, namely: Vrancea crustal domain, E Vrancea zone that is overlapped on the Focsani basin, Barlad and Predobrogean depressions along with the North Dobrogea Orogen, Intramoesian and Shabla (Bulgaria) zones and Fagaras-Campulung-Sinaia zone. (authors)

  13. The 2012 Emilia seismic sequence (Northern Italy): Imaging the thrust fault system by accurate aftershock location

    Science.gov (United States)

    Govoni, Aladino; Marchetti, Alessandro; De Gori, Pasquale; Di Bona, Massimo; Lucente, Francesco Pio; Improta, Luigi; Chiarabba, Claudio; Nardi, Anna; Margheriti, Lucia; Agostinetti, Nicola Piana; Di Giovambattista, Rita; Latorre, Diana; Anselmi, Mario; Ciaccio, Maria Grazia; Moretti, Milena; Castellano, Corrado; Piccinini, Davide

    2014-05-01

    Starting from late May 2012, the Emilia region (Northern Italy) was severely shaken by an intense seismic sequence, originated from a ML 5.9 earthquake on May 20th, at a hypocentral depth of 6.3 km, with thrust-type focal mechanism. In the following days, the seismic rate remained high, counting 50 ML ≥ 2.0 earthquakes a day, on average. Seismicity spreads along a 30 km east-west elongated area, in the Po river alluvial plain, in the nearby of the cities Ferrara and Modena. Nine days after the first shock, another destructive thrust-type earthquake (ML 5.8) hit the area to the west, causing further damage and fatalities. Aftershocks following this second destructive event extended along the same east-westerly trend for further 20 km to the west, thus illuminating an area of about 50 km in length, on the whole. After the first shock struck, on May 20th, a dense network of temporary seismic stations, in addition to the permanent ones, was deployed in the meizoseismal area, leading to a sensible improvement of the earthquake monitoring capability there. A combined dataset, including three-component seismic waveforms recorded by both permanent and temporary stations, has been analyzed in order to obtain an appropriate 1-D velocity model for earthquake location in the study area. Here we describe the main seismological characteristics of this seismic sequence and, relying on refined earthquakes location, we make inferences on the geometry of the thrust system responsible for the two strongest shocks.

  14. Airborne LiDAR analysis and geochronology of faulted glacial moraines in the Tahoe-Sierra frontal fault zone reveal substantial seismic hazards in the Lake Tahoe region, California-Nevada USA

    Science.gov (United States)

    Howle, James F.; Bawden, Gerald W.; Schweickert, Richard A.; Finkel, Robert C.; Hunter, Lewis E.; Rose, Ronn S.; von Twistern, Brent

    2012-01-01

    We integrated high-resolution bare-earth airborne light detection and ranging (LiDAR) imagery with field observations and modern geochronology to characterize the Tahoe-Sierra frontal fault zone, which forms the neotectonic boundary between the Sierra Nevada and the Basin and Range Province west of Lake Tahoe. The LiDAR imagery clearly delineates active normal faults that have displaced late Pleistocene glacial moraines and Holocene alluvium along 30 km of linear, right-stepping range front of the Tahoe-Sierra frontal fault zone. Herein, we illustrate and describe the tectonic geomorphology of faulted lateral moraines. We have developed new, three-dimensional modeling techniques that utilize the high-resolution LiDAR data to determine tectonic displacements of moraine crests and alluvium. The statistically robust displacement models combined with new ages of the displaced Tioga (20.8 ± 1.4 ka) and Tahoe (69.2 ± 4.8 ka; 73.2 ± 8.7 ka) moraines are used to estimate the minimum vertical separation rate at 17 sites along the Tahoe-Sierra frontal fault zone. Near the northern end of the study area, the minimum vertical separation rate is 1.5 ± 0.4 mm/yr, which represents a two- to threefold increase in estimates of seismic moment for the Lake Tahoe basin. From this study, we conclude that potential earthquake moment magnitudes (Mw) range from 6.3 ± 0.25 to 6.9 ± 0.25. A close spatial association of landslides and active faults suggests that landslides have been seismically triggered. Our study underscores that the Tahoe-Sierra frontal fault zone poses substantial seismic and landslide hazards.

  15. Prestate of Stress and Fault Behavior During the 2016 Kumamoto Earthquake (M7.3)

    Science.gov (United States)

    Matsumoto, Satoshi; Yamashita, Yusuke; Nakamoto, Manami; Miyazaki, Masahiro; Sakai, Shinichi; Iio, Yoshihisa; Shimizu, Hiroshi; Goto, Kazuhiko; Okada, Tomomi; Ohzono, Mako; Terakawa, Toshiko; Kosuga, Masahiro; Yoshimi, Masayuki; Asano, Youichi

    2018-01-01

    Fault behavior during an earthquake is controlled by the state of stress on the fault. Complex coseismic fault slip on large earthquake faults has recently been observed by dense seismic networks, which complicates strong motion evaluations for potential faults. Here we show the three-dimensional prestress field related to the 2016 Kumamoto earthquake. The estimated stress field reveals a spatially variable state of stress that forced the fault to slip in a direction predicted by the "Wallace and Bott Hypothesis." The stress field also exposes the pre-condition of pore fluid pressure on the fault. Large coseismic slip occurred in the low-pressure part of the fault. However, areas with highly pressured fluid also showed large displacement, indicating that the seismic moment of the earthquake was magnified by fluid pressure. These prerupture data could contribute to improved seismic hazard evaluations.

  16. Intra-arc Seismicity: Geometry and Kinematic Constraints of Active Faulting along Northern Liquiñe-Ofqui and Andean Transverse Fault Systems [38º and 40ºS, Southern Andes

    Science.gov (United States)

    Sielfeld, G.; Lange, D.; Cembrano, J. M.

    2017-12-01

    Intra-arc crustal seismicity documents the schizosphere tectonic state along active magmatic arcs. At oblique-convergent margins, a significant portion of bulk transpressional deformation is accommodated in intra-arc regions, as a consequence of stress and strain partitioning. Simultaneously, crustal fluid migration mechanisms may be controlled by the geometry and kinematics of crustal high strain domains. In such domains shallow earthquakes have been associated with either margin-parallel strike-slip faults or to volcano-tectonic activity. However, very little is known on the nature and kinematics of Southern Andes intra-arc crustal seismicity and its relation with crustal faults. Here we present results of a passive seismicity study based on 16 months of data collected from 33 seismometers deployed along the intra-arc region of Southern Andes between 38˚S and 40˚S. This region is characterized by a long-lived interplay among margin-parallel strike-slip faults (Liquiñe-Ofqui Fault System, LOFS), second order Andean-transverse-faults (ATF), volcanism and hydrothermal activity. Seismic signals recorded by our network document small magnitude (0.2P and 2,796 S phase arrival times have been located with NonLinLoc. First arrival polarities and amplitude ratios of well-constrained events, were used for focal mechanism inversion. Local seismicity occurs at shallow levels down to depth of ca. 16 km, associated either with stratovolcanoes or to master, N10˚E, and subsidiary, NE to ENE, striking branches of the LOFS. Strike-slip focal mechanisms are consistent with the long-term kinematics documented by field structural-geology studies. Unexpected, well-defined NW-SE elongated clusters are also reported. In particular, a 72-hour-long, N60˚W-oriented seismicity swarm took place at Caburgua Lake area, describing a ca. 36x12x1km3 faulting crustal volume. Results imply a unique snapshot on shallow crustal tectonics, contributing to the understanding of faulting processes

  17. Application of Anisotropy of Magnetic Susceptibility to large-scale fault kinematics: an evaluation

    Science.gov (United States)

    Casas, Antonio M.; Roman-Berdiel, Teresa; Marcén, Marcos; Oliva-Urcia, Belen; Soto, Ruth; Garcia-Lasanta, Cristina; Calvin, Pablo; Pocovi, Andres; Gil-Imaz, Andres; Pueyo-Anchuela, Oscar; Izquierdo-Llavall, Esther; Vernet, Eva; Santolaria, Pablo; Osacar, Cinta; Santanach, Pere; Corrado, Sveva; Invernizzi, Chiara; Aldega, Luca; Caricchi, Chiara; Villalain, Juan Jose

    2017-04-01

    Major discontinuities in the Earth's crust are expressed by faults that often cut across its whole thickness favoring, for example, the emplacement of magmas of mantelic origin. These long-lived faults are common in intra-plate environments and show multi-episodic activity that spans for hundred of million years and constitute first-order controls on plate evolution, favoring basin formation and inversion, rotations and the accommodation of deformation in large segments of plates. Since the post-Paleozoic evolution of these large-scale faults has taken place (and can only be observed) at shallow crustal levels, the accurate determination of fault kinematics is hampered by scarcely developed fault rocks, lack of classical structural indicators and the brittle deformation accompanying fault zones. These drawbacks are also found when thick clayey or evaporite levels, with or without diapiric movements, are the main detachment levels that facilitate large displacements in the upper crust. Anisotropy of Magnetic Susceptibility (AMS) provides a useful tool for the analysis of fault zones lacking fully developed kinematic indicators. However, its meaning in terms of deformational fabrics must be carefully checked by means of outcrop and thin section analysis in order to establish the relationship between the orientation of magnetic ellipsoid axes and the transport directions, as well as the representativity of scalar parameters regarding deformation mechanisms. Timing of faulting, P-T conditions and magnetic mineralogy are also major constraints for the interpretation of magnetic fabrics and therefore, separating ferro- and para-magnetic fabric components may be necessary in complex cases. AMS results indicate that the magnetic lineation can be parallel (when projected onto the shear plane) or perpendicular (i.e. parallel to the intersection lineation) to the transport direction depending mainly on the degree of shear deformation. Changes between the two end-members can

  18. co-seismic grace gravity based 11-layered 3-d thrust fault model for ...

    Indian Academy of Sciences (India)

    30

    It honours co-seismic deformation of ocean surface, ocean ... has caused great damage (Sumatra earthquake 2004 Wikipedia) when the Indian Plate ..... Gokula, A P, Sastry R G (2015a) Gravitational attraction of a vertical pyramid model of flat ... Journal. 14, 1-21. Lay T, Kanamori H, Ammon CJ, Nettles M, Ward SN, Aster ...

  19. Fault analysis in the very shallow seismic reflection method. Part 3. Migration; Gokusenso hanshaho ni okeru danso kaiseki. 3. Migration

    Energy Technology Data Exchange (ETDEWEB)

    Nagumo, S; Muraoka, S; Takahashi, T [OYO Corp., Tokyo (Japan)

    1997-10-22

    Concerning the analysis of data obtained by the seismic reflection method, migration in the very shallow layer is discussed. When the dip angle of the reflection plane involved is disclosed by DMO conversion, the amount of migration (travelling sideways) can be calculated by use of simple geometrical formulas though on the presumption that the sector velocity is constant. Categorized into this technique are such methods as DMO conversion migration, direct dip migration, F-K method, and finite difference method. This means that waveforms are not damaged by migration processing although elongation occurs due to time base conversion. When it is taken into account that waveform distortion is generally grave in the migration related methods widely in use, this feature has to be said valuable in holding information on faults. This is especially advantageous in the very shallow layer because the amount of migration is proportionally larger when the level is deeper and, in addition, migration processing is useful when it is necessary to know more accurately the character of the fault plane. 8 figs.

  20. Spatiotemporal seismic velocity change in the Earth's subsurface associated with large earthquake: contribution of strong ground motion and crustal deformation

    Science.gov (United States)

    Sawazaki, K.

    2016-12-01

    It is well known that seismic velocity of the subsurface medium changes after a large earthquake. The cause of the velocity change is roughly attributed to strong ground motion (dynamic strain change), crustal deformation (static strain change), and fracturing around the fault zone. Several studies have revealed that the velocity reduction down to several percent concentrates at the depths shallower than several hundred meters. The amount of velocity reduction correlates well with the intensity of strong ground motion, which indicates that the strong motion is the primary cause of the velocity reduction. Although some studies have proposed contributions of coseismic static strain change and fracturing around fault zone to the velocity change, separation of their contributions from the site-related velocity change is usually difficult. Velocity recovery after a large earthquake is also widely observed. The recovery process is generally proportional to logarithm of the lapse time, which is similar to the behavior of "slow dynamics" recognized in laboratory experiments. The time scale of the recovery is usually months to years in field observations, while it is several hours in laboratory experiments. Although the factor that controls the recovery speed is not well understood, cumulative strain change due to post-seismic deformation, migration of underground water, mechanical and chemical reactions on the crack surface could be the candidate. In this study, I summarize several observations that revealed spatiotemporal distribution of seismic velocity change due to large earthquakes; especially I focus on the case of the M9.0 2011 Tohoku earthquake. Combining seismograms of Hi-net (high-sensitivity) and KiK-net (strong motion), geodetic records of GEONET and the seafloor GPS/Acoustic ranging, I investigate contribution of the strong ground motion and crustal deformation to the velocity change associated with the Tohoku earthquake, and propose a gross view of

  1. Application of GPR for delineating the neotectonic setting and shallow subsurface nature of the seismically active Gedi fault, Kachchh, western India

    International Nuclear Information System (INIS)

    Maurya, D M; Chouksey, V; Joshi, Parul N; Chamyal, L S

    2013-01-01

    The present field and GPR based investigations were carried out along the E–W trending Gedi Fault to precisely constrain the field location and shallow subsurface nature of the fault. The field investigations revealed the presence of thin Quaternary sedimentary cover, especially in the central and western part. Field examination of the scanty exposures showed that the fault trace marks the lithotectonic contact between Mesozoic rocks in the north and the Tertiary (Miocene) sediments to the south. Five sites were selected after field studies for GPR investigations of the Gedi Fault. The well-compacted Mesozoic rocks showed high amplitude returns while the softer and finer grained Tertiary sediments yielded low amplitude returns. The Quaternary sediments are reflected as consistent with wavy reflections in the upper parts of the profiles. The GPR data indicate that the Gedi Fault is a steep north dipping reverse fault which becomes vertical at depth. Since the fault does not displace the Quaternary deposits, we infer that the Gedi Fault has been characterized by low to moderate seismic activity under a compressive stress regime during the late Quaternary period. (paper)

  2. Historical evidence of faulting in Eastern Anatolia and Northern Syria

    Directory of Open Access Journals (Sweden)

    C. P. Melville

    1995-06-01

    Full Text Available Historical data show that like the North Anatolian fault zone, which was delineated by a series of earthquakes during this century from east to west, so was the conjugate Eastern Anatolian fault zone delineated from the northeast to the southwest by a succession of large earthquakes in earlier times, with a major event at its junction with the Dead Sea fault system. This event was associated with surface faulting and occurred in a region seismically quiescent for nearly two centuries.

  3. New paleoseismic data across the Mt. Marine Fault between the 2016 Amatrice and 2009 L’Aquila seismic sequences (central Apennines

    Directory of Open Access Journals (Sweden)

    Marco Moro

    2016-11-01

    Full Text Available Paleoseismological investigations have been carried out along the Mt. Marine normal fault, a probable source of the February 2, 1703 (Me=6.7 earthquake. The fault affects the area between the 2016 Amatrice and 2009 L’Aquila seismic sequences. Paleoseismological analysis provides data which corroborate previous studies, highlighting the occurrence of 5 events of surface faulting after the 6th–5th millenium B.C., the most recent of which is probably the 2 February 1703 earthquake. A minimum displacement per event of about 0.35 m has been measured. The occurrence of a minimum four faulting events within the last 7,000 years suggests a maximum 1,700 years recurrence interval.

  4. Paleoearthquakes and long-term seismic regime in the Longmenshan fault zone, Southwest China

    Science.gov (United States)

    Liu, J.; Rodina, S. N.; Rogozhin, E. A.

    2017-11-01

    The collected paleoseismological data about the ancient earthquakes are analyzed for the zone of the Wenchuan earthquake. Four earthquakes with magnitude M = 8.0 occurred over a period of 10000 years and two earthquakes with magnitude 7.5 occurred over 1200 years. The obtained data allowed us to reconstruct the long-term seismic regime within the studied territory by constructing the frequency-magnitude relationship based on the instrumental, historical, and paleoseismological data.

  5. On the response of large dams to incoherent seismic excitation

    International Nuclear Information System (INIS)

    Ramadan, O.; Novak, M.

    1993-01-01

    An intensive parametric study was conducted to investigate the response of concrete gravity dams to horizontal, spatially variable seismic ground motions. Both segmented dams consisting of separate blocks, or monoliths, and continuous monolithic dams are considered. The study includes the effects of various parameters on system natural frequencies, vibration modes, modal displacement ratios, as well as dam displacements and internal stresses due to spatially variable ground motions. The dam analytical model, and dam response to incoherent ground motions are described. The results show that the dam vibrates almost as a rigid body under the fully correlated waves, but bends and twists significantly under the spatially correlated motions. Dam-foundation interaction magnifies the low frequency components of the dam response, more so for a full reservoir, but decreases the high frequency components. For long dams, the effects of spatially incoherent ground motions are qualitatively different and can be much greater than those due to surface travelling waves. 3 refs., 3 figs

  6. Imaging of Subsurface Faults using Refraction Migration with Fault Flooding

    KAUST Repository

    Metwally, Ahmed Mohsen Hassan

    2017-05-31

    We propose a novel method for imaging shallow faults by migration of transmitted refraction arrivals. The assumption is that there is a significant velocity contrast across the fault boundary that is underlain by a refracting interface. This procedure, denoted as refraction migration with fault flooding, largely overcomes the difficulty in imaging shallow faults with seismic surveys. Numerical results successfully validate this method on three synthetic examples and two field-data sets. The first field-data set is next to the Gulf of Aqaba and the second example is from a seismic profile recorded in Arizona. The faults detected by refraction migration in the Gulf of Aqaba data were in agreement with those indicated in a P-velocity tomogram. However, a new fault is detected at the end of the migration image that is not clearly seen in the traveltime tomogram. This result is similar to that for the Arizona data where the refraction image showed faults consistent with those seen in the P-velocity tomogram, except it also detected an antithetic fault at the end of the line. This fault cannot be clearly seen in the traveltime tomogram due to the limited ray coverage.

  7. Imaging of Subsurface Faults using Refraction Migration with Fault Flooding

    KAUST Repository

    Metwally, Ahmed Mohsen Hassan; Hanafy, Sherif; Guo, Bowen; Kosmicki, Maximillian Sunflower

    2017-01-01

    We propose a novel method for imaging shallow faults by migration of transmitted refraction arrivals. The assumption is that there is a significant velocity contrast across the fault boundary that is underlain by a refracting interface. This procedure, denoted as refraction migration with fault flooding, largely overcomes the difficulty in imaging shallow faults with seismic surveys. Numerical results successfully validate this method on three synthetic examples and two field-data sets. The first field-data set is next to the Gulf of Aqaba and the second example is from a seismic profile recorded in Arizona. The faults detected by refraction migration in the Gulf of Aqaba data were in agreement with those indicated in a P-velocity tomogram. However, a new fault is detected at the end of the migration image that is not clearly seen in the traveltime tomogram. This result is similar to that for the Arizona data where the refraction image showed faults consistent with those seen in the P-velocity tomogram, except it also detected an antithetic fault at the end of the line. This fault cannot be clearly seen in the traveltime tomogram due to the limited ray coverage.

  8. Implementing a C++ Version of the Joint Seismic-Geodetic Algorithm for Finite-Fault Detection and Slip Inversion for Earthquake Early Warning

    Science.gov (United States)

    Smith, D. E.; Felizardo, C.; Minson, S. E.; Boese, M.; Langbein, J. O.; Guillemot, C.; Murray, J. R.

    2015-12-01

    The earthquake early warning (EEW) systems in California and elsewhere can greatly benefit from algorithms that generate estimates of finite-fault parameters. These estimates could significantly improve real-time shaking calculations and yield important information for immediate disaster response. Minson et al. (2015) determined that combining FinDer's seismic-based algorithm (Böse et al., 2012) with BEFORES' geodetic-based algorithm (Minson et al., 2014) yields a more robust and informative joint solution than using either algorithm alone. FinDer examines the distribution of peak ground accelerations from seismic stations and determines the best finite-fault extent and strike from template matching. BEFORES employs a Bayesian framework to search for the best slip inversion over all possible fault geometries in terms of strike and dip. Using FinDer and BEFORES together generates estimates of finite-fault extent, strike, dip, preferred slip, and magnitude. To yield the quickest, most flexible, and open-source version of the joint algorithm, we translated BEFORES and FinDer from Matlab into C++. We are now developing a C++ Application Protocol Interface for these two algorithms to be connected to the seismic and geodetic data flowing from the EEW system. The interface that is being developed will also enable communication between the two algorithms to generate the joint solution of finite-fault parameters. Once this interface is developed and implemented, the next step will be to run test seismic and geodetic data through the system via the Earthworm module, Tank Player. This will allow us to examine algorithm performance on simulated data and past real events.

  9. Fault Transient Analysis and Protection Performance Evaluation within a Large-scale PV Power Plant

    Directory of Open Access Journals (Sweden)

    Wen Jinghua

    2016-01-01

    Full Text Available In this paper, a short-circuit test within a large-scale PV power plant with a total capacity of 850MWp is discussed. The fault currents supplied by the PV generation units are presented and analysed. According to the fault behaviour, the existing protection coordination principles with the plant are considered and their performances are evaluated. Moreover, these protections are examined in simulation platform under different operating situations. A simple measure with communication system is proposed to deal with the foreseeable problem about the current protection scheme in the PV power plant.

  10. Cenozoic pulsed compression of Da'an-Dedu Fault Zone in Songliao Basin (NE China) and its implications for earthquake potential: Evidence from seismic data

    Science.gov (United States)

    Yu, Zhongyuan; Zhang, Peizhen; Min, Wei; Wei, Qinghai; Zhao, Bin

    2018-01-01

    The Da'an-Dedu Fault Zone (DDFZ) is a major tectonic feature cutting through the Songliao Basin from south to north in NE China. Pulsed compression deformation of DDFZ during the Cenozoic implies a complex geodynamic process, and the latest stage of which occurred in the Quaternary directly influences the present seismicity of the interior basin. Although most of the evidence for Quaternary deformation about the Songliao Basin in the past decades was concentrated in marginal faults, all five earthquake swarms with magnitudes over 5.0 along the buried DDFZ with no surface expression during the past 30 years suggest it is a main seismogenic structure with seismic potential, which should deserve more attention of geologists. However, limited by the coverage of the Quaternary sedimentary and absence of strong historic and instrumental earthquakes records (M > 7), the geometric pattern, Quaternary activity and seismic potential of the DDFZ remain poorly understood. Thus, unlike previous geophysical studies focused on crust/mantle velocity structure across the fault and the aim of exploring possible mineral resources in the basin, in this study we have integrated a variety of the latest seismic data and drilling holes from petroleum explorations and shallow-depth seismic reflection profiles, to recognize the Cenozoic pulsed compression deformation of the DDFZ, and to discuss its implication for earthquake potential. The results show that at least four stages of compression deformation have occurred along the DDFZ in the Cenozoic: 65 Ma, 23 Ma, 5.3 Ma, and 1.8 Ma, respectively, although the geodynamic process behind which still in dispute. The results also imply that the tectonic style of the DDFZ fits well with the occurrence of modern seismic swarms. Moderate earthquake potential (M ≤ 7.0) is suggested along the DDFZ.

  11. Research on Fault Prediction of Distribution Network Based on Large Data

    Directory of Open Access Journals (Sweden)

    Jinglong Zhou

    2017-01-01

    Full Text Available With the continuous development of information technology and the improvement of distribution automation level. Especially, the amount of on-line monitoring and statistical data is increasing, and large data is used data distribution system, describes the technology to collect, data analysis and data processing of the data distribution system. The artificial neural network mining algorithm and the large data are researched in the fault diagnosis and prediction of the distribution network.

  12. Categorization of PWR accident sequences and guidelines for fault trees: seismic initiators

    International Nuclear Information System (INIS)

    Kimura, C.Y.

    1984-09-01

    This study developed a set of dominant accident sequences that could be applied generically to domestic commercial PWRs as a standardized basis for a probabilistic seismic risk assessment. This was accomplished by ranking the Zion 1 accident sequences. The pertinent PWR safety systems were compared on a plant-by-plant basis to determine the applicability of the dominant accident sequences of Zion 1 to other PWR plants. The functional event trees were developed to describe the system functions that must work or not work in order for a certain accident sequence to happen, one for pipe breaks and one for transients

  13. Paleoseismic observations along the Langshan range-front fault, Hetao Basin, China: Tectonic and seismic implications

    Science.gov (United States)

    Dong, Shaopeng; Zhang, Peizhen; Zheng, Wenjun; Yu, Zhongyuan; Lei, Qiyun; Yang, Huili; Liu, Jinfeng; Gong, Huilin

    2018-04-01

    The Langshan range-front fault (LRF) is an active Holocene normal fault that borders Langshan Mountain and the Hetao Basin, northwest of the Ordos Plateau, China. In this study, paleoseismic trenching was undertaken at three sites (North-South): Dongshen village (TC1), Qingshan (TC2), and Wulanhashao (TC3). The paleoevents ED1, ED2, ED3 from TC1 were constrained to 6.0 ± 1.3, 9.6 ± 2.0, and 19.7 ± 4.2 ka, respectively. The single paleoevent (EQ1) from TC2 was constrained to about 6.7 ± 0.1 ka, and the paleoevents EW1, EW2, and EW3 from TC3 were constrained to 2.3 ± 0.4, 6.0 ± 1.0, and before 7.0 ka, respectively. With reference to previous research, the Holocene earthquake sequence of the LRF can be established as 2.30-2.43 (E1), 3.06-4.41 (E2), 6.71-6.80 (E3), 7.60-9.81 (E4), and 19.70 ± 4.20 (E5) ka BP. Events E1, E3, and E4 might have been caused by events with magnitudes of Mw 7.6-7.8 that ruptured the entire LRF. Event E2 might have been smaller magnitude, about M7.0, and ruptured only a portion of the fault. The vertical slip rate of the LRF at the Qingshan site is inferred as 0.9 or 1.4-1.6 mm/year in the last 6.8 ka. The slip rate at Wulanhashao is considered to have been close to, but not recurrence interval of 2500 years.

  14. Status and needs for seismic instrumentation of structures along the Hayward fault

    Science.gov (United States)

    Kalkan, Erol; Çelebi, Mehmet

    2008-01-01

    The inventory of structures in heavily urbanized communities within the greater San Francisco (SF) Bay area that will experience strong ground motions from the rupture of the Hayward Fault includes a variety of types of recent and older structures built with a variety of materials and to different code standards. Those who remember the effects of the 1989 Loma Prieta earthquake on structures in the San Francisco Bay area also remember the collapse of one upper-deck segment of the Bay Bridge that halted transportation for approximately five weeks. In order to understand how these structures respond to earthquake motions and to improve building practices to resist these strong motions it is imperative that owners of these structures as well as governmental organizations acquire shaking response data from instrumented (or yet to be instrumented structures) during the forecast events. Within California, such data are acquired mainly by California Geological Survey and the United States Geological Survey. A small number of private owners contribute to this effort. The inventory of existing instrumented structures is much less than 0.1% of the total, and thus statistically it is not sufficient. For example, some of the existing important regular or lifeline structures are not instrumented(e.g. Bart Trans-Bay Tunnel, many segments of the Bart elevated structures in the proximity of the Hayward Fault, the yet to be completed eastern part of San Francisco Bay Bridge, Hetch-Hetchy pipeline system crossing the Hayward Fault)even though attempts and proposals have been developed to do so in the past. This paper presents a critical assessment of the status quo and the future needs for instrumentation of structures in the greater SF Bay area that includes the Hayward Fault. There are many new attempts and successes in instrumentation of structures in this region. Two successful examples are provided here, but more needs to be done. The paper does not present new research results

  15. Analysis of nonvolcanic tremor on the San Andreas fault near Parkfield, CA using U. S. Geological Survey Parkfield Seismic Array

    Science.gov (United States)

    Fletcher, Jon B.; Baker, Lawrence M.

    2010-10-01

    Reports by Nadeau and Dolenc (2005) that tremor had been detected near Cholame Valley spawned an effort to use UPSAR (U. S. Geological Survey Parkfield Seismic Array) to study characteristics of tremor. UPSAR was modified to record three channels of velocity at 40-50 sps continuously in January 2005 and ran for about 1 month, during which time we recorded numerous episodes of tremor. One tremor, on 21 January at 0728, was recorded with particularly high signal levels as well as another episode 3 days later. Both events were very emergent, had a frequency content between 2 and 8 Hz, and had numerous high-amplitude, short-duration arrivals within the tremor signal. Here using the first episode as an example, we discuss an analysis procedure, which yields azimuth and apparent velocity of the tremor at UPSAR. We then provide locations for both tremor episodes. The emphasis here is how the tremor episode evolves. Twelve stations were operating at the time of recording. Slowness of arrivals was determined using cross correlation of pairs of stations; the same method used in analyzing the main shock data from 28 September 2004. A feature of this analysis is that 20 s of the time series were used at a time to calculate correlation; the longer windows resulted in more consistent estimates of slowness, but lower peak correlations. These values of correlation (peaks of about 0.25), however, are similar to that obtained for the S wave of a microearthquake. Observed peaks in slowness were traced back to source locations assumed to lie on the San Andreas fault. Our inferred locations for the two tremor events cluster near the locations of previously observed tremor, south of the Cholame Valley. Tremor source depths are in the 14-24 km range, which is below the seismogenic brittle zone, but above the Moho. Estimates of error do not preclude locations below the Moho, however. The tremor signal is very emergent but contains packets that are several times larger than the background

  16. A model of characteristic earthquakes and its implications for regional seismicity

    DEFF Research Database (Denmark)

    López-Ruiz, R.; Vázquez-Prada, M.; Pacheco, A.F.

    2004-01-01

    Regional seismicity (i.e. that averaged over large enough areas over long enough periods of time) has a size-frequency relationship, the Gutenberg-Richter law, which differs from that found for some seismic faults, the Characteristic Earthquake relationship. But all seismicity comes in the end from...... active faults, so the question arises of how one seismicity pattern could emerge from the other. The recently introduced Minimalist Model of Vázquez-Prada et al. of characteristic earthquakes provides a simple representation of the seismicity originating from a single fault. Here, we show...... that a Characteristic Earthquake relationship together with a fractal distribution of fault lengths can accurately describe the total seismicity produced in a region. The resulting earthquake catalogue accounts for the addition of both all the characteristic and all the non-characteristic events triggered in the faults...

  17. Large-scale seismic test for soil-structure interaction research in Hualien, Taiwan

    International Nuclear Information System (INIS)

    Ueshima, T.; Kokusho, T.; Okamoto, T.

    1995-01-01

    It is important to evaluate dynamic soil-structure interaction more accurately in the aseismic design of important facilities such as nuclear power plants. A large-scale model structure with about 1/4th of commercial nuclear power plants was constructed on the gravelly layers in seismically active Hualien, Taiwan. This international joint project is called 'the Hualien LSST Project', where 'LSST' is short for Large-Scale Seismic Test. In this paper, research tasks and responsibilities, the process of the construction work and research tasks along the time-line, main results obtained up to now, and so on in this Project are described. (J.P.N.)

  18. Late Pleistocene and Holocene paleoseismology of an intraplate seismic zone in a large alluvial valley, the New Madrid seismic zone, Central USA

    Science.gov (United States)

    Guccione, Margaret J.

    2005-10-01

    The New Madrid seismic zone (NMSZ) is an intraplate right-lateral strike-slip and thrust fault system contained mostly within the Mississippi Alluvial Valley. The most recent earthquake sequence in the zone occurred in 1811 1812 and had estimated moment magnitudes of 7 8 (e.g., [Johnston, A.C., 1996. Seismic moment assessment of stable continental earthquakes, Part 3: 1811 1812 New Madrid, 1886 Charleston, and 1755 Lisbon. Geophysical Journal International 126, 314 344; Johnston, A.C., Schweig III, E.S, 1996. The enigma of the New Madrid earthquakes of 1811 1812. Annual Reviews of Earth and Planetary Sciences 24, 339 384; Hough, S.E., Armbruster, J.G., Seeber, L., Hough, J.F., 2000. On the modified Mercalli intensities and magnitudes of the New Madrid earthquakes. Journal of Geophysical Research 105 (B10), 23,839 23,864; Tuttle, M.P., 2001. The use of liquefaction features in paleoseismology: Lessons learned in the New Madrid seismic zone, central United States. Journal of Seismology 5, 361 380]). Four earlier prehistoric earthquakes or earthquake sequences have been dated A.D. 1450 ± 150, 900 ± 100, 300 ± 200, and 2350 B.C. ± 200 years using paleoliquefaction features, particularly those associated with native American artifacts, and in some cases surface deformation ([Craven, J. A. 1995. Paleoseismology study in the New Madrid seismic zone using geological and archeological features to constrain ages of liquefaction deposits. M.S thesis, University of Memphis, Memphis, TN, U.S.A.; Tuttle, M.P., Lafferty III, R.H., Guccione, M.J., Schweig III, E.S., Lopinot, N., Cande, R., Dyer-Williams, K., Haynes, M., 1996. Use of archaeology to date liquefaction features and seismic events in the New Madrid seismic zone, central United States. Geoarchaeology 11, 451 480; Guccione, M.J., Mueller, K., Champion, J., Shepherd, S., Odhiambo, B., 2002b. Stream response to repeated co-seismic folding, Tiptonville dome, western Tennessee. Geomorphology 43(2002), 313 349; Tuttle, M

  19. Crustal Seismicity and Geomorphic Observations of the Chiripa-Haciendas Fault System: The Guanacaste Volcanic Arc Sliver of Western Costa Rica

    Science.gov (United States)

    Lewis, J. C.; Montero Pohly, W. K.; Araya, M. C.

    2017-12-01

    It has recently been shown that contemporary northwest motion of the Nicoya Peninsula of Costa Rica reflects a tectonic sliver that includes much of the upper-plate arc, referred to as the Guanacaste Volcanic Arc Sliver (GVAS). Here we characterize historical seismicity and geomorphic expressions of faults that define the northeastern margin of the GVAS. Several crustal earthquakes and their aftershocks provide constraints on the geometry and/or kinematics of the fault system. These include the Armenia earthquake of July 12, 2011, the Bijagua earthquake of January 27, 2002, the Tilarán earthquake of April 13, 1973 and two much older events. We summarize these earthquakes in the context of recent fault mapping and focal mechanism solutions, and suggest that most of the deformation can be explained by slip on steeply dipping NW-striking fault planes accommodating dextral slip. Streams that cross the major fault traces we have mapped also show deflections consistent with dextral slip. These include map-view apparent offsets of 6.5 km for the Haciendas River, 1.0 km for the Orosi River and 0.6 km for the Pizote River. Although preservation is poor, we document stream terrace risers that reveal truncations and/or offsets consistent with dextral slip. Additional constraints on the fault system are apparent as it is traced into Lake Nicaragua. Previous workers have shown that earthquake clusters accommodate a combination of dextral slip on NW-strike faults and sinistral slip NE-strike faults, the latter described as part of a system of bookshelf fault blocks. Whether the northeastern margin of the GVAS under Lake Nicaragua is a single fault strand or an array of bookshelf blocks remains an open question. An equally important gap in our understanding is the kinematic link of the fault system to the east where the GVAS originates. Our results set the stage for expanded studies that will be essential to understanding the relative contributions of Cocos Ridge collision and

  20. Fault zone architecture of the San Jacinto fault zone in Horse Canyon, southern California: A model for focused post-seismic fluid flow and heat transfer in the shallow crust

    Science.gov (United States)

    Morton, Nissa; Girty, Gary H.; Rockwell, Thomas K.

    2012-05-01

    We report results of a new study of the architecture of the San Jacinto fault zone in Horse Canyon, California, where stream incision has exposed a nearly continuous outcrop of the fault zone at ~ 0.4 km depth. The fault zone at this location consists of a fault core, transition zone, damage zone, and tonalitic wall rocks. We collected and analyzed samples for their bulk and grain density, geochemical data, clay mineralogy, and textural and modal mineralogy. Progressive deformation within the fault zone is characterized by mode I cracking, subsequent shearing of already fractured rock, and cataclastic flow. Grain comminution advances towards the strongly indurated cataclasite fault core. Damage progression towards the core is accompanied by a decrease in bulk and grain density, and an increase in porosity and dilational volumetric strain. Palygorskite and mixed-layer illite/smectite clay minerals are present in the damage and transition zones and are the result of hydrolysis reactions. The estimated percentage of illite in illite/smectite increases towards the fault core where the illite/smectite to illite conversion is complete, suggesting elevated temperatures that may have reached 150 °C. Chemical alteration and elemental mass changes are observed throughout the fault zone and are most pronounced in the fault core. We conclude that the observed chemical and mineralogical changes can only be produced by the interaction of fractured wall rocks and chemically active fluids that are mobilized through the fault zone by thermo-pressurization during and after seismic events. Based on the high element mobility and absence of illite/smectite in the fault core, we expect that the greatest water/rock ratios occur within the fault core. These results indicate that hot pore fluids circulate upwards through the fractured fault core and into the surrounding damage zone. Though difficult to constrain, we speculate that the site studied during this investigation may represent

  1. Seismically-triggered soft-sediment deformation structures close to a major strike-slip fault system in the Eastern Alps (Hirlatz cave, Austria)

    Science.gov (United States)

    Salomon, Martina Lan; Grasemann, Bernhard; Plan, Lukas; Gier, Susanne; Schöpfer, Martin P. J.

    2018-05-01

    We investigate episodic soft-sediment deformation structures cross-cut by normal faults preserved in unlithified finely laminated calcite rich sediments in the Hirlatz cave in the Northern Calcareous Alps (Austria). These sediments comprise varve-like alternations of brighter carbonate/quartz rich layers, and darker clay mineral rich layers. The deformed sediments contain abundant millimeter to centimeter-scale soft-sediment structures (load casts, ball-and-pillow structures), sheet slumps (thrust faults and folds), erosive channels filled with slides and chaotic slumps. After deposition and soft-sediment deformation normal faults developed within the entire sedimentary succession, an event that probably correlates with an offset of c. 10 cm of the passage wall above the outcrop. Our major conclusions are: (i) The sediments have a glacial origin and were deposited in the Hirlatz cave under phreatic fluvio-lacustrine conditions. The deposition and the soft-sediment deformation occurred most likely during the last glaciation (i.e. around 25 ka ago); (ii) The liquefaction and formation of the soft-sediment structures in water-saturated stratified layers was triggered by episodic seismic events; (iii) The internally deformed sediments were later displaced by normal faults; (iv) A possible source for the seismic events is the active sinistral Salzach-Ennstal-Mariazeller-Puchberger (SEMP) strike-slip fault which is located about 10 km south of the outcrop and plays a major role in accommodating the extrusion of the Eastern Alps towards the Pannonian Basin. To our knowledge, the described structures are the first report of liquefaction and seismically induced soft-sediment deformations in Quaternary sediments in the Eastern Alps.

  2. Distribution of ground rigidity and ground model for seismic response analysis in Hualian project of large scale seismic test

    International Nuclear Information System (INIS)

    Kokusho, T.; Nishi, K.; Okamoto, T.; Tanaka, Y.; Ueshima, T.; Kudo, K.; Kataoka, T.; Ikemi, M.; Kawai, T.; Sawada, Y.; Suzuki, K.; Yajima, K.; Higashi, S.

    1997-01-01

    An international joint research program called HLSST is proceeding. HLSST is large-scale seismic test (LSST) to investigate soil-structure interaction (SSI) during large earthquake in the field in Hualien, a high seismic region in Taiwan. A 1/4-scale model building was constructed on the gravelly soil in this site, and the backfill material of crushed stone was placed around the model plant after excavation for the construction. Also the model building and the foundation ground were extensively instrumental to monitor structure and ground response. To accurately evaluate SSI during earthquakes, geotechnical investigation and forced vibration test were performed during construction process namely before/after base excavation, after structure construction and after backfilling. And the distribution of the mechanical properties of the gravelly soil and the backfill are measured after the completion of the construction by penetration test and PS-logging etc. This paper describes the distribution and the change of the shear wave velocity (V s ) measured by the field test. Discussion is made on the effect of overburden pressure during the construction process on V s in the neighbouring soil and, further on the numerical soil model for SSI analysis. (orig.)

  3. Supra-salt normal fault growth during the rise and fall of a diapir: Perspectives from 3D seismic reflection data, Norwegian North Sea

    Science.gov (United States)

    Tvedt, Anette B. M.; Rotevatn, Atle; Jackson, Christopher A.-L.

    2016-10-01

    Normal faulting and the deep subsurface flow of salt are key processes controlling the structural development of many salt-bearing sedimentary basins. However, our detailed understanding of the spatial and temporal relationship between normal faulting and salt movement is poor due to a lack of natural examples constraining their geometric and kinematic relationship in three-dimensions. To improve our understanding of these processes, we here use 3D seismic reflection and borehole data from the Egersund Basin, offshore Norway, to determine the structure and growth of a normal fault array formed during the birth, growth and decay of an array of salt structures. We show that the fault array and salt structures developed in response to: (i) Late Triassic-to-Middle Jurassic extension, which involved thick-skinned, sub-salt and thin-skinned supra-salt faulting with the latter driving reactive diapirism; (ii) Early Cretaceous extensional collapse of the walls; and (iii) Jurassic-to-Neogene, active and passive diapirism, which was at least partly coeval with and occurred along-strike from areas of reactive diapirism and wall collapse. Our study supports physical model predictions, showcasing a three-dimensional example of how protracted, multiphase salt diapirism can influence the structure and growth of normal fault arrays.

  4. Reassessment of seismic hazards at the Los Alamos National Laboratory

    International Nuclear Information System (INIS)

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

    1991-01-01

    A comprehensive seismic hazards evaluation program has been initiated at the Los Alamos National Laboratory (LANL) to update the current seismic design criteria. In part, this program has been motivated by recent studies which suggest that faults of the nearby Pajarito fault system may be capable of generating a large magnitude earthquake (M > 7). The specific objectives of this program are to: (1) characterize the tectonic setting of the LANL area; (2) characterize the nature, amount, and timing of late Quaternary fault displacements; (3) reevaluate the recorded seismicity in the LANL region to allow for the evaluation of seismogenic faults and the tectonic state of stress; (4) characterize the subsurface geologic conditions beneath the LANL required for the estimation of strong ground motions and site response; (5) estimate potential strong ground shaking both deterministically and probabilistically; and (6) develop the appropriate seismic design criteria. The approach and initial results of this seismic hazards program are described in this paper

  5. Fault healing promotes high-frequency earthquakes in laboratory experiments and on natural faults

    Science.gov (United States)

    McLaskey, Gregory C.; Thomas, Amanda M.; Glaser, Steven D.; Nadeau, Robert M.

    2012-01-01

    Faults strengthen or heal with time in stationary contact and this healing may be an essential ingredient for the generation of earthquakes. In the laboratory, healing is thought to be the result of thermally activated mechanisms that weld together micrometre-sized asperity contacts on the fault surface, but the relationship between laboratory measures of fault healing and the seismically observable properties of earthquakes is at present not well defined. Here we report on laboratory experiments and seismological observations that show how the spectral properties of earthquakes vary as a function of fault healing time. In the laboratory, we find that increased healing causes a disproportionately large amount of high-frequency seismic radiation to be produced during fault rupture. We observe a similar connection between earthquake spectra and recurrence time for repeating earthquake sequences on natural faults. Healing rates depend on pressure, temperature and mineralogy, so the connection between seismicity and healing may help to explain recent observations of large megathrust earthquakes which indicate that energetic, high-frequency seismic radiation originates from locations that are distinct from the geodetically inferred locations of large-amplitude fault slip

  6. Seismic evidence for overpressured subducted oceanic crust and megathrust fault sealing.

    Science.gov (United States)

    Audet, Pascal; Bostock, Michael G; Christensen, Nikolas I; Peacock, Simon M

    2009-01-01

    Water and hydrous minerals play a key part in geodynamic processes at subduction zones by weakening the plate boundary, aiding slip and permitting subduction-and indeed plate tectonics-to occur. The seismological signature of water within the forearc mantle wedge is evident in anomalies with low seismic shear velocity marking serpentinization. However, seismological observations bearing on the presence of water within the subducting plate itself are less well documented. Here we use converted teleseismic waves to obtain observations of anomalously high Poisson's ratios within the subducted oceanic crust from the Cascadia continental margin to its intersection with forearc mantle. On the basis of pressure, temperature and compositional considerations, the elevated Poisson's ratios indicate that water is pervasively present in fluid form at pore pressures near lithostatic values. Combined with observations of a strong negative velocity contrast at the top of the oceanic crust, our results imply that the megathrust is a low-permeability boundary. The transition from a low- to high-permeability plate interface downdip into the mantle wedge is explained by hydrofracturing of the seal by volume changes across the interface caused by the onset of crustal eclogitization and mantle serpentinization. These results may have important implications for our understanding of seismogenesis, subduction zone structure and the mechanism of episodic tremor and slip.

  7. Seismic Response Analysis of Concrete Lining Structure in Large Underground Powerhouse

    Directory of Open Access Journals (Sweden)

    Xiaowei Wang

    2017-01-01

    Full Text Available Based on the dynamic damage constitutive model of concrete material and seismic rock-lining structure interaction analysis method, the seismic response of lining structure in large underground powerhouse is studied in this paper. In order to describe strain rate dependence and fatigue damage of concrete material under cyclic loading, a dynamic constitutive model for concrete lining considering tension and shear anisotropic damage is presented, and the evolution equations of damage variables are derived. The proposed model is of simple form and can be programmed into finite element procedure easily. In order to describe seismic interaction characteristics of the surrounding rock and lining, an explicit dynamic contact analysis method considering bond and damage characteristics of contact face between the surrounding rock and lining is proposed, and this method can integrate directly without iteration. The proposed method is applied to seismic stability calculation of Yingxiuwan Underground Powerhouse, results reveal that the amplitude and duration of input seismic wave determine the damage degree of lining structure, the damage zone of lining structure is mainly distributed in its arch, and the contact face damage has great influence on the stability of the lining structure.

  8. Seismic hazard and risk assessment for large Romanian dams situated in the Moldavian Platform

    Science.gov (United States)

    Moldovan, Iren-Adelina; Popescu, Emilia; Otilia Placinta, Anica; Petruta Constantin, Angela; Toma Danila, Dragos; Borleanu, Felix; Emilian Toader, Victorin; Moldoveanu, Traian

    2016-04-01

    Besides periodical technical inspections, the monitoring and the surveillance of dams' related structures and infrastructures, there are some more seismic specific requirements towards dams' safety. The most important one is the seismic risk assessment that can be accomplished by rating the dams into seismic risk classes using the theory of Bureau and Ballentine (2002), and Bureau (2003), taking into account the maximum expected peak ground motions at the dams site - values obtained using probabilistic hazard assessment approaches (Moldovan et al., 2008), the structures vulnerability and the downstream risk characteristics (human, economical, historic and cultural heritage, etc) in the areas that might be flooded in the case of a dam failure. Probabilistic seismic hazard (PSH), vulnerability and risk studies for dams situated in the Moldavian Platform, starting from Izvorul Muntelui Dam, down on Bistrita and following on Siret River and theirs affluent will be realized. The most vulnerable dams will be studied in detail and flooding maps will be drawn to find the most exposed downstream localities both for risk assessment studies and warnings. GIS maps that clearly indicate areas that are potentially flooded are enough for these studies, thus giving information on the number of inhabitants and goods that may be destroyed. Geospatial servers included topography is sufficient to achieve them, all other further studies are not necessary for downstream risk assessment. The results will consist of local and regional seismic information, dams specific characteristics and locations, seismic hazard maps and risk classes, for all dams sites (for more than 30 dams), inundation maps (for the most vulnerable dams from the region) and possible affected localities. The studies realized in this paper have as final goal to provide the local emergency services with warnings of a potential dam failure and ensuing flood as a result of an large earthquake occurrence, allowing further

  9. Using SETS to find minimal cut sets in large fault trees

    International Nuclear Information System (INIS)

    Worrell, R.B.; Stack, D.W.

    1978-01-01

    An efficient algebraic algorithm for finding the minimal cut sets for a large fault tree was defined and a new procedure which implements the algorithm was added to the Set Equation Transformation System (SETS). The algorithm includes the identification and separate processing of independent subtrees, the coalescing of consecutive gates of the same kind, the creation of additional independent subtrees, and the derivation of the fault tree stem equation in stages. The computer time required to determine the minimal cut sets using these techniques is shown to be substantially less than the computer time required to determine the minimal cut sets when these techniques are not employed. It is shown for a given example that the execution time required to determine the minimal cut sets can be reduced from 7,686 seconds to 7 seconds when all of these techniques are employed

  10. Remotely Triggered Earthquakes Recorded by EarthScope's Transportable Array and Regional Seismic Networks: A Case Study Of Four Large Earthquakes

    Science.gov (United States)

    Velasco, A. A.; Cerda, I.; Linville, L.; Kilb, D. L.; Pankow, K. L.

    2013-05-01

    Changes in field stress required to trigger earthquakes have been classified in two basic ways: static and dynamic triggering. Static triggering occurs when an earthquake that releases accumulated strain along a fault stress loads a nearby fault. Dynamic triggering occurs when an earthquake is induced by the passing of seismic waves from a large mainshock located at least two or more fault lengths from the epicenter of the main shock. We investigate details of dynamic triggering using data collected from EarthScope's USArray and regional seismic networks located in the United States. Triggered events are identified using an optimized automated detector based on the ratio of short term to long term average (Antelope software). Following the automated processing, the flagged waveforms are individually analyzed, in both the time and frequency domains, to determine if the increased detection rates correspond to local earthquakes (i.e., potentially remotely triggered aftershocks). Here, we show results using this automated schema applied to data from four large, but characteristically different, earthquakes -- Chile (Mw 8.8 2010), Tokoku-Oki (Mw 9.0 2011), Baja California (Mw 7.2 2010) and Wells Nevada (Mw 6.0 2008). For each of our four mainshocks, the number of detections within the 10 hour time windows span a large range (1 to over 200) and statistically >20% of the waveforms show evidence of anomalous signals following the mainshock. The results will help provide for a better understanding of the physical mechanisms involved in dynamic earthquake triggering and will help identify zones in the continental U.S. that may be more susceptible to dynamic earthquake triggering.

  11. Seismic reflection survey of the Uemachi fault in Osaka Prefecture; Osaka Uemachi danso no hanshaho danseiha tansa

    Energy Technology Data Exchange (ETDEWEB)

    Sugiyama, Y [Geological Survey of Japan, Tsukuba (Japan); Yoshizawa, M; Hirooka, S [Nikko Exploration and Development Co. Ltd., Tokyo (Japan); Yokota, H; Ito, S [Hanshin Consultant Co., Osaka (Japan); Hayashi, K; Aizawa, H

    1997-05-27

    Reflection survey is conducted using three traverse lines in Sakai City for confirming the presence of a southward stretch of the Uemachi fault underground along the western periphery of the Uemachi terrace, Osaka, and for elucidating its connection to the Sakamoto fault distributed near Izumi. Another reflection survey is conducted in the bed of Kanzaki river, Osaka, for the confirmation of its connection to the Nembutsuji-zan fault in Senri hillock. It is estimated on the basis of boring data that there exists another flexural structure approximately 3km south of the flexural structure whose presence is confirmed by the Sakai second traverse line. Accordingly, possibilities are high that the southward stretch of the Uemachi fault connects to the Sakamoto fault. The confirmation by the Kanzaki river traverse line of the flexural structure again confirms the continuity between the Uemachi fault and Nembutsuji-zan fault. The above-said findings enable an inference that the three faults of Nembutsuji-zan, Uemachi, and Sakamoto constitute a chain of active faults. Furthermore, there exists an active fault to the south of the Sakamoto fault, which zigzags to the south on the right-hand side as far as the south of the Kumeda pond. Accordingly, the Uemachi fault system as a whole spans approximately 43km from the northern end of the Nembutsuji-zan fault as far as the south of the Kumeda pond. 5 refs., 6 figs.

  12. Efficient preparation of large-block-code ancilla states for fault-tolerant quantum computation

    Science.gov (United States)

    Zheng, Yi-Cong; Lai, Ching-Yi; Brun, Todd A.

    2018-03-01

    Fault-tolerant quantum computation (FTQC) schemes that use multiqubit large block codes can potentially reduce the resource overhead to a great extent. A major obstacle is the requirement for a large number of clean ancilla states of different types without correlated errors inside each block. These ancilla states are usually logical stabilizer states of the data-code blocks, which are generally difficult to prepare if the code size is large. Previously, we have proposed an ancilla distillation protocol for Calderbank-Shor-Steane (CSS) codes by classical error-correcting codes. It was assumed that the quantum gates in the distillation circuit were perfect; however, in reality, noisy quantum gates may introduce correlated errors that are not treatable by the protocol. In this paper, we show that additional postselection by another classical error-detecting code can be applied to remove almost all correlated errors. Consequently, the revised protocol is fully fault tolerant and capable of preparing a large set of stabilizer states sufficient for FTQC using large block codes. At the same time, the yield rate can be boosted from O (t-2) to O (1 ) in practice for an [[n ,k ,d =2 t +1

  13. Large seismic source imaging from old analogue seismograms

    Science.gov (United States)

    Caldeira, Bento; Buforn, Elisa; Borges, José; Bezzeghoud, Mourad

    2017-04-01

    In this work we present a procedure to recover the ground motions by a proper digital structure, from old seismograms in analogue physical support (paper or microfilm) to study the source rupture process, by application of modern finite source inversion tools. Despite the quality that the analog data and the digitizing technologies available may have, recover the ground motions with the accurate metrics from old seismograms, is often an intricate procedure. Frequently the general parameters of the analogue instruments response that allow recover the shape of the ground motions (free periods and damping) are known, but the magnification that allow recover the metric of these motions is dubious. It is in these situations that the procedure applies. The procedure is based on assign of the moment magnitude value to the integral of the apparent Source Time Function (STF), estimated by deconvolution of a synthetic elementary seismogram from the related observed seismogram, corrected with an instrument response affected by improper magnification. Two delicate issues in the process are 1) the calculus of the synthetic elementary seismograms that must consider later phases if applied to large earthquakes (the portions of signal should be 3 or 4 times larger than the rupture time) and 2) the deconvolution to calculate the apparent STF. In present version of the procedure was used the Direct Solution Method to compute the elementary seismograms and the deconvolution was processed in time domain by an iterative algorithm that allow constrains the STF to stay positive and time limited. The method was examined using synthetic data to test the accuracy and robustness. Finally, a set of 17 real old analog seismograms from the Santa Maria (Azores) 1939 earthquake (Mw=7.1) was used in order to recover the waveforms in the required digital structure, from which by inversion allows compute the finite source rupture model (slip distribution). Acknowledgements: This work is co

  14. Seismic Monitoring Prior to and During DFDP-2 Drilling, Alpine Fault, New Zealand: Matched-Filter Detection Testing and the Real-Time Monitoring System

    Science.gov (United States)

    Boese, C. M.; Chamberlain, C. J.; Townend, J.

    2015-12-01

    In preparation for the second stage of the Deep Fault Drilling Project (DFDP) and as part of related research projects, borehole and surface seismic stations were installed near the intended DFDP-2 drill-site in the Whataroa Valley from late 2008. The final four borehole stations were installed within 1.2 km of the drill-site in early 2013 to provide near-field observations of any seismicity that occurred during drilling and thus provide input into operational decision-making processes if required. The basis for making operational decisions in response to any detected seismicity had been established as part of a safety review conducted in early 2014 and was implemented using a "traffic light" system, a communications plan, and other operational documents. Continuous real-time earthquake monitoring took place throughout the drilling period, between September and late December 2014, and involved a team of up to 15 seismologists working in shifts near the drill-site and overseas. Prior to drilling, records from 55 local earthquakes and 14 quarry blasts were used as master templates in a matched-filter detection algorithm to test the capabilities of the seismic network for detecting seismicity near the drill site. The newly detected microseismicity was clustered near the DFDP-1 drill site at Gaunt Creek, 7.4 km southwest of DFDP-2. Relocations of these detected events provide more information about the fault geometry in this area. Although no detectable seismicity occurred within 5 km of the drill site during the drilling period, the region is capable of generating earthquakes that would have required an operational response had they occurred while drilling was underway (including a M2.9 event northwest of Gaunt Creek on 15 August 2014). The largest event to occur while drilling was underway was of M4.5 and occurred approximately 40 km east of the DFDP-2 drill site. In this presentation, we summarize the setup and operations of the seismic network and discuss key

  15. Temporal variations of the fractal properties of seismicity in the western part of the north Anatolian fault zone: possible artifacts due to improvements in station coverage

    Directory of Open Access Journals (Sweden)

    A. O. Öncel

    1995-01-01

    Full Text Available Seismically-active fault zones are complex natural systems exhibiting scale-invariant or fractal correlation between earthquakes in space and time, and a power-law scaling of fault length or earthquake source dimension consistent with the exponent b of the Gutenberg-Richter frequency-magnitude relation. The fractal dimension of seismicity is a measure of the degree of both the heterogeneity of the process (whether fixed or self-generated and the clustering of seismic activity. Temporal variations of the b-value and the two-point fractal (correlation dimension Dc have been related to the preparation process for natural earthquakes and rock fracture in the laboratory These statistical scaling properties of seismicity may therefore have the potential at least to be sensitive short- term predictors of major earthquakes. The North Anatolian Fault Zone (NAFZ is a seismicallyactive dextral strike slip fault zone which forms the northern boundary of the westward moving Anatolian plate. It is splayed into three branches at about 31oE and continues westward toward the northern Aegean sea. In this study, we investigate the temporal variation of Dc and the Gutenberg-Richter b-value for seismicity in the western part of the NAFZ (including the northern Aegean sea for earthquakes of Ms > 4.5 occurring in the period between 1900 and 1992. b ranges from 0.6-1.6 and Dc from 0.6 to 1.4. The b-value is found to be weakly negatively correlated with Dc (r=-0.56. However the (log of event rate N is positively correlated with b, with a similar degree of statistical significance (r=0.42, and negatively correlated with Dc (r=-0.48. Since N increases dramatically with improved station coverage since 1970, the observed negative correlation between b and Dc is therefore more likely to be due to this effect than any underlying physical process in this case. We present this as an example of how man-made artefacts of recording can have similar statistical effects to

  16. Evidence of a Large Triggered Event in the Nepal Himalaya Following the Gorkha Earthquake: Implications Toward Enhanced Seismic Hazard

    Science.gov (United States)

    Mandal, Prantik

    2018-03-01

    A DC (double couple) constrained multiple point-source moment-tensor inversion is performed on the band-passed (0.008-0.10 Hz) displacement data of the 25 April (M w 7.8) 2015 Nepal mainshock, from 17 broadband stations in India. Our results reveal that the 25 April event (strike = 324°, dip = 14°, rake = 88°) ruptured the north-dipping main Himalayan thrust (MHT) at 16 km depth. We modeled the Coulomb failure stress changes (ΔCFS) produced by the slip on the fault plane of the 25 April Nepal mainshock. A strong correlation with occurrences of aftershocks and regions of increased positive ΔCFS is obtained below the aftershock zone of the 2015 Nepal mainshock. We notice that predicted ΔCFS at 16 km depth show a positive Coulomb stress of 0.06 MPa at the location of the 12 May 2015 event. These small modeled stress changes can lead to trigger events if the crust is already near to failure, but these small stresses can also advance the occurrence of future earthquakes. The main finding of our ΔCFS modeling implies that the 25 April event increased the Coulomb stress changes by 0.06 MPa at 16 km depth below the site of the 12 May event, and thus, this event can be termed as triggered. We propose that the seismic hazard in the Himalaya is not only caused by the mainshock slip on the MHT; rather, the occurrence of large triggered event on the MHT can also enhance our understanding of the seismic hazard in the Nepal Himalaya.

  17. Seismically-induced soft-sediment deformation structures associated with the Magallanes-Fagnano Fault System (Isla Grande de Tierra del Fuego, Argentina)

    Science.gov (United States)

    Onorato, M. Romina; Perucca, Laura; Coronato, Andrea; Rabassa, Jorge; López, Ramiro

    2016-10-01

    In this paper, evidence of paleoearthquake-induced soft-sediment deformation structures associated with the Magallanes-Fagnano Fault System in the Isla Grande de Tierra del Fuego, southern Argentina, has been identified. Well-preserved soft-sediment deformation structures were found in a Holocene sequence of the Udaeta pond. These structures were analyzed in terms of their geometrical characteristics, deformation mechanism, driving force system and possible trigger agent. They were also grouped in different morphological types: sand dykes, convolute lamination, load structures and faulted soft-sediment deformation features. Udaeta, a small pond in Argentina Tierra del Fuego, is considered a Quaternary pull-apart basin related to the Magallanes-Fagnano Fault System. The recognition of these seismically-induced features is an essential tool for paleoseismic studies. Since the three main urban centers in the Tierra del Fuego province of Argentina (Ushuaia, Río Grande and Tolhuin) have undergone an explosive growth in recent years, the results of this study will hopefully contribute to future analyses of the seismic risk of the region.

  18. A high-speed transmission method for large-scale marine seismic prospecting systems

    International Nuclear Information System (INIS)

    KeZhu, Song; Ping, Cao; JunFeng, Yang; FuMing, Ruan

    2012-01-01

    A marine seismic prospecting system is a kind of data acquisition and transmission system with large-scale coverage and synchronous multi-node acquisition. In this kind of system, data transmission is a fundamental and difficult technique. In this paper, a high-speed data-transmission method is proposed, its implications and limitations are discussed, and conclusions are drawn. The method we propose has obvious advantages over traditional techniques with respect to long-distance operation, high speed, and real-time transmission. A marine seismic system with four streamers, each 6000 m long and capable of supporting up to 1920 channels, was designed and built based on this method. The effective transmission baud rate of this system was found to reach up to 240 Mbps, while the minimum sampling interval time was as short as 0.25 ms. This system was found to achieve a good synchronization: 83 ns. Laboratory and in situ experiments showed that this marine-prospecting system could work correctly and robustly, which verifies the feasibility and validity of the method proposed in this paper. In addition to the marine seismic applications, this method can also be used in land seismic applications and certain other transmission applications such as environmental or engineering monitoring systems. (paper)

  19. A high-speed transmission method for large-scale marine seismic prospecting systems

    Science.gov (United States)

    KeZhu, Song; Ping, Cao; JunFeng, Yang; FuMing, Ruan

    2012-12-01

    A marine seismic prospecting system is a kind of data acquisition and transmission system with large-scale coverage and synchronous multi-node acquisition. In this kind of system, data transmission is a fundamental and difficult technique. In this paper, a high-speed data-transmission method is proposed, its implications and limitations are discussed, and conclusions are drawn. The method we propose has obvious advantages over traditional techniques with respect to long-distance operation, high speed, and real-time transmission. A marine seismic system with four streamers, each 6000 m long and capable of supporting up to 1920 channels, was designed and built based on this method. The effective transmission baud rate of this system was found to reach up to 240 Mbps, while the minimum sampling interval time was as short as 0.25 ms. This system was found to achieve a good synchronization: 83 ns. Laboratory and in situ experiments showed that this marine-prospecting system could work correctly and robustly, which verifies the feasibility and validity of the method proposed in this paper. In addition to the marine seismic applications, this method can also be used in land seismic applications and certain other transmission applications such as environmental or engineering monitoring systems.

  20. Consideration on the applicability of the design seismic coefficient of a large cutting slope under the strong earthquake

    International Nuclear Information System (INIS)

    Ito, Hiroshi; Sawada, Yoshihiro; Satou, Kiyotaka

    1989-01-01

    In this study, the characteristic of equivalent seismic coefficient and the applicability of the design seismic coefficient of a large cutting rock slope around Nuclear Power Plant were examined by analytical parameter survey. As the results, the equivalent seismic coefficient by dynamic analysis become great with increase of transverse elastic wave velocity and the case of long period motion. That is, as the wave length of rock mass become longer, the equivalent seismic coefficient become great parabolically. Moreover, there is a inverse proportion relation between the ratio (dynamic safety factor/static safety factor) and wave length. In addition, the graph to forecast the dynamic sliding safety factor under the input seismic motion of the max. Acceleration 500 gal from the result of static simple method was proposed and the applicable range of design seismic coefficient of rock slope was indicated. (author)

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

    Science.gov (United States)

    LBNL, in consultation with the EPA, expanded upon a previous study by injecting directly into a 3D representation of a hypothetical fault zone located in the geologic units between the shale-gas reservoir and the drinking water aquifer.

  2. Large-band seismic characterization of the INFN Gran Sasso National Laboratory

    Science.gov (United States)

    Acernese, F.; Canonico, R.; De Rosa, R.; Giordano, G.; Romano, R.; Barone, F.

    2013-04-01

    In this paper we present the scientific data recorded by tunable mechanical monolithic horizontal seismometers located in the Gran Sasso National Laboratory of the INFN, within thermally insulating enclosures onto concrete slabs connected to the bedrock. The main goals of this long-term large-band measurements are for the seismic characterization of the site in the frequency band 10-6÷10Hz and the acquisition of all the relevant information for the optimization of the sensors.

  3. Automated classification of seismic sources in a large database: a comparison of Random Forests and Deep Neural Networks.

    Science.gov (United States)

    Hibert, Clement; Stumpf, André; Provost, Floriane; Malet, Jean-Philippe

    2017-04-01

    In the past decades, the increasing quality of seismic sensors and capability to transfer remotely large quantity of data led to a fast densification of local, regional and global seismic networks for near real-time monitoring of crustal and surface processes. This technological advance permits the use of seismology to document geological and natural/anthropogenic processes (volcanoes, ice-calving, landslides, snow and rock avalanches, geothermal fields), but also led to an ever-growing quantity of seismic data. This wealth of seismic data makes the construction of complete seismicity catalogs, which include earthquakes but also other sources of seismic waves, more challenging and very time-consuming as this critical pre-processing stage is classically done by human operators and because hundreds of thousands of seismic signals have to be processed. To overcome this issue, the development of automatic methods for the processing of continuous seismic data appears to be a necessity. The classification algorithm should satisfy the need of a method that is robust, precise and versatile enough to be deployed to monitor the seismicity in very different contexts. In this study, we evaluate the ability of machine learning algorithms for the analysis of seismic sources at the Piton de la Fournaise volcano being Random Forest and Deep Neural Network classifiers. We gather a catalog of more than 20,000 events, belonging to 8 classes of seismic sources. We define 60 attributes, based on the waveform, the frequency content and the polarization of the seismic waves, to parameterize the seismic signals recorded. We show that both algorithms provide similar positive classification rates, with values exceeding 90% of the events. When trained with a sufficient number of events, the rate of positive identification can reach 99%. These very high rates of positive identification open the perspective of an operational implementation of these algorithms for near-real time monitoring of

  4. A Method to Quantify Plant Availability and Initiating Event Frequency Using a Large Event Tree, Small Fault Tree Model

    International Nuclear Information System (INIS)

    Kee, Ernest J.; Sun, Alice; Rodgers, Shawn; Popova, ElmiraV; Nelson, Paul; Moiseytseva, Vera; Wang, Eric

    2006-01-01

    South Texas Project uses a large fault tree to produce scenarios (minimal cut sets) used in quantification of plant availability and event frequency predictions. On the other hand, the South Texas Project probabilistic risk assessment model uses a large event tree, small fault tree for quantifying core damage and radioactive release frequency predictions. The South Texas Project is converting its availability and event frequency model to use a large event tree, small fault in an effort to streamline application support and to provide additional detail in results. The availability and event frequency model as well as the applications it supports (maintenance and operational risk management, system engineering health assessment, preventive maintenance optimization, and RIAM) are briefly described. A methodology to perform availability modeling in a large event tree, small fault tree framework is described in detail. How the methodology can be used to support South Texas Project maintenance and operations risk management is described in detail. Differences with other fault tree methods and other recently proposed methods are discussed in detail. While the methods described are novel to the South Texas Project Risk Management program and to large event tree, small fault tree models, concepts in the area of application support and availability modeling have wider applicability to the industry. (authors)

  5. Korea-Japan Joint Research on Development of Seismic Capacity Evaluation and Enhancement Technology Considering Near-Fault Effect (Final Report)

    Energy Technology Data Exchange (ETDEWEB)

    Choun, Young Sun; Choi, In Kil; Kim, Min Kyu [KAERI, Daejeon (Korea, Republic of); Ohtori, Yasuki; Shiba, Yoshiaki; Nakajima, Masato [Central Research Institute of Electric Power Industry, Tokyo (Japan)

    2006-12-15

    We compiled the results of the source analysis obtained under the collaboration research. Recent construction scheme for source modeling adopted in Japan is described, and strong-motion prediction is performed assuming the scenario earthquakes occurring in the Ulsan fault system, Korea. Finally Qs values beneath the Korean inland crust are estimated using strong-motion records in Korea from the 2005 Off West Fukuoka earthquake (M7.0). Probabilistic seismic hazard for four NPP sites in Korea are evaluated, in which the site specific attenuation equations with Index SA developed for NPP sites are adopted. Furthermore, the uniform hazard spectra for the four NPP sites in Korea are obtained by conducting the PSHA by using the attenuation equations with the index of response spectra and seismic source model cases with maximum weights. The supporting tools for seismic response analysis, the evaluation tool for evaluating annual probability of failure, and system analysis program were developed for the collaboration. The tools were verified with theoretical results, the results written in the reference document of EQESRA, and so forth. The system analysis program was applied for the investigation of the effect of improving the seismic capacity of equipment. We evaluated the annual probability of failure of isolated and non-isolated EDG at Younggwang NPP site as the results of the collaboration. The input ground motion for generating the seismic fragility curve was determined based on the seismic hazard analysis. It was found that the annual probability of failure of isolated EDG is lower than that of non-isolated EDG.

  6. The Seismic Response of High-Speed Railway Bridges Subjected to Near-Fault Forward Directivity Ground Motions Using a Vehicle-Track-Bridge Element

    Directory of Open Access Journals (Sweden)

    Chen Ling-kun

    2014-01-01

    Full Text Available Based on the Next Generation Attenuation (NGA project ground motion library, the finite element model of the high-speed railway vehicle-bridge system is established. The model was specifically developed for such system that is subjected to near-fault ground motions. In addition, it accounted for the influence of the rail irregularities. The vehicle-track-bridge (VTB element is presented to simulate the interaction between train and bridge, in which a train can be modeled as a series of sprung masses concentrated at the axle positions. For the short period railway bridge, the results from the case study demonstrate that directivity pulse effect tends to increase the seismic responses of the bridge compared with far-fault ground motions or nonpulse-like motions and the directivity pulse effect and high values of the vertical acceleration component can notably influence the hysteretic behaviour of piers.

  7. Subsurface geometry of the San Andreas fault in southern California: Results from the Salton Seismic Imaging Project (SSIP) and strong ground motion expectations

    Science.gov (United States)

    Fuis, Gary S.; Bauer, Klaus; Goldman, Mark R.; Ryberg, Trond; Langenheim, Victoria; Scheirer, Daniel S.; Rymer, Michael J.; Stock, Joann M.; Hole, John A.; Catchings, Rufus D.; Graves, Robert; Aagaard, Brad T.

    2017-01-01

    The San Andreas fault (SAF) is one of the most studied strike‐slip faults in the world; yet its subsurface geometry is still uncertain in most locations. The Salton Seismic Imaging Project (SSIP) was undertaken to image the structure surrounding the SAF and also its subsurface geometry. We present SSIP studies at two locations in the Coachella Valley of the northern Salton trough. On our line 4, a fault‐crossing profile just north of the Salton Sea, sedimentary basin depth reaches 4 km southwest of the SAF. On our line 6, a fault‐crossing profile at the north end of the Coachella Valley, sedimentary basin depth is ∼2–3  km">∼2–3  km and centered on the central, most active trace of the SAF. Subsurface geometry of the SAF and nearby faults along these two lines is determined using a new method of seismic‐reflection imaging, combined with potential‐field studies and earthquakes. Below a 6–9 km depth range, the SAF dips ∼50°–60°">∼50°–60° NE, and above this depth range it dips more steeply. Nearby faults are also imaged in the upper 10 km, many of which dip steeply and project to mapped surface fault traces. These secondary faults may join the SAF at depths below about 10 km to form a flower‐like structure. In Appendix D, we show that rupture on a northeast‐dipping SAF, using a single plane that approximates the two dips seen in our study, produces shaking that differs from shaking calculated for the Great California ShakeOut, for which the southern SAF was modeled as vertical in most places: shorter‐period (TTfault.

  8. The 2014, MW6.9 North Aegean earthquake: seismic and geodetic evidence for coseismic slip on persistent asperities

    Science.gov (United States)

    Konca, Ali Ozgun; Cetin, Seda; Karabulut, Hayrullah; Reilinger, Robert; Dogan, Ugur; Ergintav, Semih; Cakir, Ziyadin; Tari, Ergin

    2018-05-01

    We report that asperities with the highest coseismic slip in the 2014 MW6.9 North Aegean earthquake persisted through the interseismic, coseismic and immediate post-seismic periods. We use GPS and seismic data to obtain the source model of the 2014 earthquake, which is located on the western extension of the North Anatolian Fault (NAF). The earthquake ruptured a bilateral, 90 km strike-slip fault with three slip patches: one asperity located west of the hypocentre and two to the east with a rupture duration of 40 s. Relocated pre-earthquake seismicity and aftershocks show that zones with significant coseismic slip were relatively quiet during both the 7 yr of interseismic and the 3-month aftershock periods, while the surrounding regions generated significant seismicity during both the interseismic and post-seismic periods. We interpret the unusually long fault length and source duration, and distribution of pre- and post-main-shock seismicity as evidence for a rupture of asperities that persisted through strain accumulation and coseismic strain release in a partially coupled fault zone. We further suggest that the association of seismicity with fault creep may characterize the adjacent Izmit, Marmara Sea and Saros segments of the NAF. Similar behaviour has been reported for sections of the San Andreas Fault, and some large subduction zones, suggesting that the association of seismicity with creeping fault segments and rapid relocking of asperities may characterize many large earthquake faults.

  9. Calibration of the seismic velocity structure and understanding of the fault formation in the environs of the Orkney M5.5 earthquake, South Africa

    Science.gov (United States)

    Ogasawara, H.; Manzi, M. S.; Durrheim, R. J.; Ogasawara, H.

    2017-12-01

    In August 2014, the largest seismic event (M5.5) to occur in a South African gold mining district took place near Orkney. The M5.5 event and aftershocks were recorded by strainmeters installed at 3 km depth hundreds of meters above the M5.5 fault, 46 in-mine 4.5Hz triaxial geophone stations at depths of 2-3 km within a hypocentral radius of 2-3 km, and 17 surface strong motion stations (South African Seismograph Network; SANSN) within an epicentral radius of 25 km. Aftershocks were distributed on a nearly vertical plane striking NNW-SSE. The upper edge of this fault was hundreds of meters below the deepest level of the mine. ICDP approved a project "Drilling into seismogenic zones of M2.0-5.5 earthquakes in South African gold mines" to elucidate the details of the events (DSeis; Yabe et al. invited talk in S020 in this AGU). On 1 August 2017 drilling was within a few hundreds of meters of intersecting the M5.5 fault zone. To locate the drilling target accurately it is very important to determine the velocity structure between the seismic events and sensors. We do this by using the interval velocities used to migrate 3D-reflection seismic data that was previously acquired by a mining company to image the gold-bearing reef and any fault structures close to the mining horizon. Less attention was given to the velocities below the mining horizon, as accurate imaging of the geological structure was not as important and very little drilling information was available. We used the known depths of prominent reflectors above the mining horizon to derive the interval velocities needed to convert two-way-travel-time to depth. We constrain the velocity below the mining horizon by comparing the DSeis drilling results with the 3D seismic cube. The geometric data is crucial for the kinematic modeling that Ogasawara et al. (S018 in this AGU) advocates. The efforts will result in a better understanding of the main rupture and aftershocks.

  10. The multi-parameter borehole system and high resolution seismic studies in the western part of the main Marmara Fault in the frame of MARSITE Project.

    Science.gov (United States)

    Ozel, Oguz; Guralp, Cansun; Tunc, Suleyman; Yalcinkaya, Esref

    2016-04-01

    The main objective of this study is to install a multi-parameter borehole system and surface array as close to the main Marmara Fault (MMF) in the western Marmara Sea as possible, and measure continuously the evolution of the state of the fault zone surrounding the MMF and to detect any anomaly or change, which may occur before earthquakes by making use of the data from the arrays already running in the eastern part of the Marmara Sea. The multi-parameter borehole system is composed of very wide dynamic range and stable borehole (VBB) broad band seismic sensor, and incorporate strain meter, tilt meter, and temperature and local hydrostatic pressure measuring devices. The borehole seismic station uses the latest update technologies and design ideas to record "Earth tides" signals to the smallest magnitude -3 events. Additionally, a surface microearthquake observation array, consisting of 8-10 seismometers around the borehole is established to obtain continuous high resolution locations of micro-seismicity and to better understand the existing seismically active structures and their roles in local tectonic settings.Bringing face to face the seismograms of microearthquakes recorded by borehole and surface instruments portrays quite different contents. The shorter recording duration and nearly flat frequency spectrum up to the Nyquist frequencies of borehole records are faced with longer recording duration and rapid decay of spectral amplitudes at higher frequencies of a surface seismogram. The main causative of the observed differences are near surface geology effects that mask most of the source related information the seismograms include, and that give rise to scattering, generating longer duration seismograms. In view of these circumstances, studies on microearthquakes employing surface seismograms may bring on misleading results. Particularly, the works on earthquake physics and nucleation process of earthquakes requires elaborate analysis of tiny events. It is

  11. Imaging inhomogeneous seismic velocity structure in and around the fault plane of the 2008 Iwate-Miyagi, Japan, Nairiku Earthquake (M7.2) - spatial variation in depth of seismic-aseismic transition and possible high-T/overpressurized fluid distribution

    Science.gov (United States)

    Okada, T.; Umino, N.; Hasegawa, A.; 2008 Iwate-Miyagi Nairiku Earthquake, G. O.

    2008-12-01

    A large shallow earthquake (named the 2008 Iwate-Miyagi Nairiku Earthquake) with a JMA magnitude of 7.2 occurred in the central part of NE Japan on June 14, 2008. Focal area of the present earthquake is located in the Tohoku backbone range strain concentration zone (Miura et al., 2004) along the volcanic front. Just after the occurrence of this earthquake, Japanese universities (Hokkaido, Hirosaki, Tohoku, Tokyo, Nagoya, Kyoto, Kochi, Kyusyu, Kagoshima) and NIED deployed a dense aftershock observation network in and around the focal area. Total number of temporal stations is 128. Using data from this dense aftershock observation and other temporary and routinely operated stations, we estimate hypocenter distribution and seismic velocity structure of the crust in and around the focal area of the present earthquake. We determined three-dimensional seismic velocity structure and relocated hypocenters simultaneously using the double- difference tomography method (Zhang and Thurber, 2003). Spatial extent of the aftershock area is about 45 km (NNE-SSW) by 15 km (WNW-ESE). Most of aftershocks are aligned in westward dipping. Shallower extensions of aftershock alignments seem to be located nearly at the coseismic surface deformations, which are along a geological fault, and the surface trace of the active fault (Detana fault). Note that some aftershocks seem to occur off the fault plane of the mainshock. The focal area of the present earthquake is located at a high Vs area. In the lower crust, we found some distinct low-Vs areas. These low velocity zones are located just beneath the strain concentration zones / seismic belts along the backbone range and in the northern Miyagi region. Focal area of the present earthquake is also located just above the low velocity zone in the lower crust. Beneath active volcanoes, these low velocity zones become more distinct and shallower, and aftershocks tend to occur shallower and not occur within such low-velocity zones. These low

  12. A KPI-based process monitoring and fault detection framework for large-scale processes.

    Science.gov (United States)

    Zhang, Kai; Shardt, Yuri A W; Chen, Zhiwen; Yang, Xu; Ding, Steven X; Peng, Kaixiang

    2017-05-01

    Large-scale processes, consisting of multiple interconnected subprocesses, are commonly encountered in industrial systems, whose performance needs to be determined. A common approach to this problem is to use a key performance indicator (KPI)-based approach. However, the different KPI-based approaches are not developed with a coherent and consistent framework. Thus, this paper proposes a framework for KPI-based process monitoring and fault detection (PM-FD) for large-scale industrial processes, which considers the static and dynamic relationships between process and KPI variables. For the static case, a least squares-based approach is developed that provides an explicit link with least-squares regression, which gives better performance than partial least squares. For the dynamic case, using the kernel representation of each subprocess, an instrument variable is used to reduce the dynamic case to the static case. This framework is applied to the TE benchmark process and the hot strip mill rolling process. The results show that the proposed method can detect faults better than previous methods. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

  13. Pen Branch fault: Confirmatory drilling results

    International Nuclear Information System (INIS)

    Stieve, A.; Coruh, C.; Costain, J.K.

    1994-01-01

    The Confirmatory Drilling Project is the final investigation under the Pen Branch Fault Program initiated to determine the capability of the Pen Branch fault (PBF) to release seismic energy. This investigation focused on a small zone over the fault where previously collected seismic reflection data had indicated the fault deforms the subsurface at 150 msec (with reference to an 80 m reference datum). Eighteen drill holes, 2 to basement and the others to 300 ft, were arranged in a scatter pattern over the fault. To adequately define configuration of the layers deformed by the fault boreholes were spaced over a zone of 800 ft, north to south. The closely spaced data were to confirm or refute the existence of flat lying reflectors observed in seismic reflection data and to enable the authors to identify and correlate lithologic layers with seismic reflection data. Results suggest that deformation by the fault in sediments 300 ft deep ad shallower is subtle. Corroboration of the geologic interpretation with the seismic reflection profile is ongoing but preliminary results indicate that specific reflectors can be assigned to lithologic layers. A large amplitude package of reflections below a flat lying continuous reflection at 40 msec can be correlated with a lithology that corresponds to carbonate sediments in geologic cross-section. Further, data also show that a geologic layer as shallow as 30 ft can be traced on these seismic data over the same subsurface distance where geologic cross-section shows corresponding continuity. The subsurface structure is thus corroborated by both methods at this study site

  14. Fault lubrication during earthquakes.

    Science.gov (United States)

    Di Toro, G; Han, R; Hirose, T; De Paola, N; Nielsen, S; Mizoguchi, K; Ferri, F; Cocco, M; Shimamoto, T

    2011-03-24

    The determination of rock friction at seismic slip rates (about 1 m s(-1)) is of paramount importance in earthquake mechanics, as fault friction controls the stress drop, the mechanical work and the frictional heat generated during slip. Given the difficulty in determining friction by seismological methods, elucidating constraints are derived from experimental studies. Here we review a large set of published and unpublished experiments (∼300) performed in rotary shear apparatus at slip rates of 0.1-2.6 m s(-1). The experiments indicate a significant decrease in friction (of up to one order of magnitude), which we term fault lubrication, both for cohesive (silicate-built, quartz-built and carbonate-built) rocks and non-cohesive rocks (clay-rich, anhydrite, gypsum and dolomite gouges) typical of crustal seismogenic sources. The available mechanical work and the associated temperature rise in the slipping zone trigger a number of physicochemical processes (gelification, decarbonation and dehydration reactions, melting and so on) whose products are responsible for fault lubrication. The similarity between (1) experimental and natural fault products and (2) mechanical work measures resulting from these laboratory experiments and seismological estimates suggests that it is reasonable to extrapolate experimental data to conditions typical of earthquake nucleation depths (7-15 km). It seems that faults are lubricated during earthquakes, irrespective of the fault rock composition and of the specific weakening mechanism involved.

  15. System seismic analysis of an innovative primary system for a large pool type LMFBR plant

    International Nuclear Information System (INIS)

    Pan, Y.C.; Wu, T.S.; Cha, B.K.; Burelbach, J.; Seidensticker, R.

    1984-01-01

    The system seismic analysis of an innovative primary system for a large pool type liquid metal fast breeder reactor (LMFBR) plant is presented. In this primary system, the reactor core is supported in a way which differs significantly from that used in previous designs. The analytical model developed for this study is a three-dimensional finite element model including one-half of the primary system cut along the plane of symmetry. The model includes the deck and deck mounted components,the reactor vessel, the core support structure, the core barrel, the radial neutron shield, the redan, and the conical support skirt. The sodium contained in the primary system is treated as a lumped mass appropriately distributed among various components. The significant seismic behavior as well as the advantages of this primary system design are discussed in detail

  16. Some considerations on the seismic stability of large slopes surrounding the nuclear power plant

    International Nuclear Information System (INIS)

    Ito, Hiroshi; Watanabe, Hiroyuki

    1982-01-01

    As a series of the research on the seismic stabilities of a large scale slope surrounding the Nuclear Power Plant, the numerical simulation and analytical stability calculation are conducted in order to clarify the applicability of static stability evaluation method (conventional circular arc slip method, static non-linear F.E. analysis) and dynamic one (2-dimensional dynamic F.E. analysis). The discussions on these slope stability methods are done and the followings are clarified, i) The results of numerical simulation by dynamic F.E. analysis concerning the response property and the failure mode are qualitatively corresponded with the behaviour of dynamic failure test. ii) From the results of static and dynamic stability analysis, it is concluded that the conventional circular arc slip method gives the severest evaluation for slope stability. iii) It is proposed that the seismic coefficient for static slope stability analysis should be used the value of the equivalent instant acceleration. (author)

  17. Some considerations on the seismic stability of large slopes surrounding the nuclear power plant

    International Nuclear Information System (INIS)

    Ito, Hiroshi; Watanabe, Hiroyuki; Imaide, Hiroshi

    1982-01-01

    As a part of the researches with regard to the seismic stability of large scale slope, the authors have carried out the model test, in which the static failure has been generated by inclining the slope model. In this report, the results of static inclination tests of slope model are described and discussions are done from viewpoints of, 1. the mechanical behaviours and failure state of slope during the inclination test, 2. comparison between the results obtained by the static failure test (that is, inclination test) and those of another report with regard to the dynamic failure test which had been performed using the shaking table, and the relationship between an equivalent seismic coefficient obtained by static failure test and acceleration by dynamic failure test, 3. relationship between the failure state of inclination test and the factor of convensional circular arc slip method. (author)

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

    Science.gov (United States)

    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.

  19. Carbon monoxide degassing from seismic fault zones in the Basin and Range province, west of Beijing, China

    Science.gov (United States)

    Sun, Yutao; Zhou, Xiaocheng; Zheng, Guodong; Li, Jing; Shi, Hongyu; Guo, Zhengfu; Du, Jianguo

    2017-11-01

    Degassing of carbon monoxide (CO), which plays a significant role in the contribution of deep carbon to the atmosphere, commonly occurs within active fault zones. CO degassing from soil to the atmosphere in the Basin and Range province, west of Beijing (BRPB), China, was investigated by in-situ field measurements in the active fault zones. The measured concentrations of CO in soil gas in the BRPB ranged from 0.29 × 10-6 to 1.1 × 10-6 with a mean value of 0.6 × 10-6, which is approximately twice as large as that in the atmosphere. Net fluxes of CO degassing ranged from -48.6 mg m-2 d-1 to 12.03 mg m-2 d-1. The diffusion of CO from soil to the atmosphere in the BRPB was estimated to be at least 7.6 × 103 ton/a, which is comparable to the corresponding result of about 1.2 × 104 ton/a for CO2. CO concentrations were spatially heterogeneous with clearly higher concentrations along the NE-SW trending in the BRPB. These elevated values of CO concentrations were also coincident with the region with low-velocity and high conductivity in deep mantle, and high Poisson's ratio in the crust, thereby suggesting that CO degassing from the soil might be linked to upwelling of the asthenospheric mantle. Other sources of CO in the soil gas are suggested to be dominated by chemical reactions between deep fluids and carbonate minerals (e.g., dolomite, limestone, and siderite) in country rocks. Biogenic processes may also contribute to the CO in soil gas. The spatial distribution patterns of CO concentrations are coincident with the stress field, suggesting that the concentrations of CO could be a potential indicator for crustal stress field and, hence is potential useful for earthquake monitoring in the BRPB.

  20. Why is North China seismically active while South China largely aseismic?

    Science.gov (United States)

    Yang, Y.; Liu, M.

    2002-12-01

    The North China block (also known as the Sino-Korean craton) is a region of strong intraplate seismicity and active crustal deformation. Many large earthquakes, including the most devastating earthquake in modern history at Tangshan in 1976 (M=7.5), occurred in this heavily populated region. The South China block (i.e., the Yangtz craton), in contrast, is largely aseismic, although its basement rocks are younger and much of the region is closer to the present plate boundaries than the North China block. We have investigated the contrasting active tectonics between the North and South China blocks using a three-dimensional finite element model. The model approximates the geometry of the two blocks and the surrounding tectonic units. The first-order variations of lithospheric rheology, both laterally and vertically, of these blocks are considered. The kinematic boundary conditions based on the GPS data are applied to the model, and the distribution of gravitational buoyancy force within the Asian continent is calculated using digital topography. Our results suggest that the particular boundary conditions surrounding the North and South China blocks may provide the basic explanation for the contrasting seismicity between these two regions. Aligned with the axis of compression from the indenting Indian plate and supported by the stable eastern Siberia, the North China block is predicted to experience strong deviatoric stresses. A weaker crust, as indicated by the widespread Late Cenozoic volcanism and rifts and high heat flow today, further explain the abundance of seismicity in the North China block. The South China block, on the other hand, sits in the "pressure shadow" of the Indo-Asian collision with little tectonic stresses transmitted from the collision zone. The east-southeastward extrusion of the Asian continent following the Indo-Asian collision allowed the South China block to move as a coherent block as shown by the GPS data, resulting in little internal

  1. Remote triggering of fault-strength changes on the San Andreas fault at Parkfield.

    Science.gov (United States)

    Taira, Taka'aki; Silver, Paul G; Niu, Fenglin; Nadeau, Robert M

    2009-10-01

    Fault strength is a fundamental property of seismogenic zones, and its temporal changes can increase or decrease the likelihood of failure and the ultimate triggering of seismic events. Although changes in fault strength have been suggested to explain various phenomena, such as the remote triggering of seismicity, there has been no means of actually monitoring this important property in situ. Here we argue that approximately 20 years of observation (1987-2008) of the Parkfield area at the San Andreas fault have revealed a means of monitoring fault strength. We have identified two occasions where long-term changes in fault strength have been most probably induced remotely by large seismic events, namely the 2004 magnitude (M) 9.1 Sumatra-Andaman earthquake and the earlier 1992 M = 7.3 Landers earthquake. In both cases, the change possessed two manifestations: temporal variations in the properties of seismic scatterers-probably reflecting the stress-induced migration of fluids-and systematic temporal variations in the characteristics of repeating-earthquake sequences that are most consistent with changes in fault strength. In the case of the 1992 Landers earthquake, a period of reduced strength probably triggered the 1993 Parkfield aseismic transient as well as the accompanying cluster of four M > 4 earthquakes at Parkfield. The fault-strength changes produced by the distant 2004 Sumatra-Andaman earthquake are especially important, as they suggest that the very largest earthquakes may have a global influence on the strength of the Earth's fault systems. As such a perturbation would bring many fault zones closer to failure, it should lead to temporal clustering of global seismicity. This hypothesis seems to be supported by the unusually high number of M >or= 8 earthquakes occurring in the few years following the 2004 Sumatra-Andaman earthquake.

  2. Earthquakes in Action: Incorporating Multimedia, Internet Resources, Large-scale Seismic Data, and 3-D Visualizations into Innovative Activities and Research Projects for Today's High School Students

    Science.gov (United States)

    Smith-Konter, B.; Jacobs, A.; Lawrence, K.; Kilb, D.

    2006-12-01

    The most effective means of communicating science to today's "high-tech" students is through the use of visually attractive and animated lessons, hands-on activities, and interactive Internet-based exercises. To address these needs, we have developed Earthquakes in Action, a summer high school enrichment course offered through the California State Summer School for Mathematics and Science (COSMOS) Program at the University of California, San Diego. The summer course consists of classroom lectures, lab experiments, and a final research project designed to foster geophysical innovations, technological inquiries, and effective scientific communication (http://topex.ucsd.edu/cosmos/earthquakes). Course content includes lessons on plate tectonics, seismic wave behavior, seismometer construction, fault characteristics, California seismicity, global seismic hazards, earthquake stress triggering, tsunami generation, and geodetic measurements of the Earth's crust. Students are introduced to these topics through lectures-made-fun using a range of multimedia, including computer animations, videos, and interactive 3-D visualizations. These lessons are further enforced through both hands-on lab experiments and computer-based exercises. Lab experiments included building hand-held seismometers, simulating the frictional behavior of faults using bricks and sandpaper, simulating tsunami generation in a mini-wave pool, and using the Internet to collect global earthquake data on a daily basis and map earthquake locations using a large classroom map. Students also use Internet resources like Google Earth and UNAVCO/EarthScope's Jules Verne Voyager Jr. interactive mapping tool to study Earth Science on a global scale. All computer-based exercises and experiments developed for Earthquakes in Action have been distributed to teachers participating in the 2006 Earthquake Education Workshop, hosted by the Visualization Center at Scripps Institution of Oceanography (http

  3. Structure and tectonics of the Main Himalayan Thrust and associated faults from recent earthquake and seismic imaging studies using the NAMASTE array

    Science.gov (United States)

    Karplus, M. S.; Pant, M.; Velasco, A. A.; Nabelek, J.; Kuna, V. M.; Sapkota, S. N.; Ghosh, A.; Mendoza, M.; Adhikari, L. B.; Klemperer, S. L.

    2017-12-01

    The India-Eurasia collision zone presents a significant earthquake hazard, as demonstrated by the recent, devastating April 25, 2015 M=7.8 Gorkha earthquake and the following May 12, 2015 M=7.3 earthquake. Important questions remain, including distinguishing possible geometries of the Main Himalayan Thrust (MHT), the role of other regional faults, the crustal composition and role of fluids in faulting, and the details of the rupture process, including structural causes and locations of rupture segmentation both along-strike and down-dip. These recent earthquakes and their aftershocks provide a unique opportunity to learn more about this collision zone. In June 2015, funded by NSF, we deployed the Nepal Array Measuring Aftershock Seismicity Trailing Earthquake (NAMASTE) array of 46 seismic stations distributed across eastern and central Nepal, spanning the region with most of the aftershocks. This array remained in place for 11 months from June 2015 to May 2016. We combine new results from this aftershock network in Nepal with previous geophysical and geological studies across the Himalaya to derive a new understanding of the tectonics of the Himalaya and southern Tibet in Nepal and surrounding countries. We focus on structure and composition of the Main Himalayan Thrust and compare this continent-continent subduction megathrust with megathrusts in other subduction zones.

  4. The typical seismic behavior in the vicinity of a large earthquake

    Science.gov (United States)

    Rodkin, M. V.; Tikhonov, I. N.

    2016-10-01

    The Global Centroid Moment Tensor catalog (GCMT) was used to construct the spatio-temporal generalized vicinity of a large earthquake (GVLE) and to investigate the behavior of seismicity in GVLE. The vicinity is made of earthquakes falling into the zone of influence of a large number (100, 300, or 1000) of largest earthquakes. The GVLE construction aims at enlarging the available statistics, diminishing a strong random component, and revealing typical features of pre- and post-shock seismic activity in more detail. As a result of the GVLE construction, the character of fore- and aftershock cascades was examined in more detail than was possible without of the use of the GVLE approach. As well, several anomalies in the behavior exhibited by a variety of earthquake parameters were identified. The amplitudes of all these anomalies increase with the approaching time of the generalized large earthquake (GLE) as the logarithm of the time interval from the GLE occurrence. Most of the discussed anomalies agree with common features well expected in the evolution of instability. In addition to these common type precursors, one earthquake-specific precursor was found. The decrease in mean earthquake depth presumably occurring in a smaller GVLE probably provides evidence of a deep fluid being involved in the process. The typical features in the evolution of shear instability as revealed in GVLE agree with results obtained in laboratory studies of acoustic emission (AE). The majority of the anomalies in earthquake parameters appear to have a secondary character, largely connected with an increase in mean magnitude and decreasing fraction of moderate size events (mw5.0-6.0) in the immediate GLE vicinity. This deficit of moderate size events could hardly be caused entirely by their incomplete reporting and can presumably reflect some features in the evolution of seismic instability.

  5. Thick deltaic sedimentation and detachment faulting delay the onset of continental rupture in the Northern Gulf of California: Analysis of seismic reflection profiles

    Science.gov (United States)

    Martin, A.; González-Escobar, M.; Fletcher, J. M.; Pacheco, M.; Oskin, M. E.; Dorsey, R. J.

    2013-12-01

    The transition from distributed continental extension to the rupture of continental lithosphere is imaged in the northern Gulf of California across the obliquely conjugate Tiburón-Upper Delfín basin segment. Structural mapping on a 5-20 km grid of seismic reflection lines of Petroleos Mexicanos (PEMEX) demonstrates that ~1000% extension is accommodated on a series of NNE-striking listric-normal faults that merge at depth into a detachment fault. The detachment juxtaposes a late-Neogene marine sequence over thinned continental crust and contains an intrabasinal divide due to footwall uplift. Two northwest striking, dextral-oblique faults bound both ends of the detachment and shear the continental crust parallel to the tectonic transport. A regional unconformity in the upper 0.5 seconds (TWTT) and crest erosion of rollover anticlines above the detachment indicates inversion and footwall uplift during the lithospheric rupture in the Upper Delfin and Lower Delfin basins. The maximum length of new crust in both Delfin basins is less than 40 km based on the lack of an acoustic basement and the absence of a lower sedimentary sequence beneath a wedge shaped upper sequence that reaches >5 km in thickness. A fundamental difference exists between the Tiburón-Delfin segment and the Guaymas segment to the south in terms of presence of low angle normal faults and amount of new oceanic lithosphere, which we attribute to thermal insulation, diffuse upper-plate extension, and slip on low angle normal faults engendered by a thick sedimentary lid.

  6. Postseismic relaxation along the San Andreas fault at Parkfield from continuous seismological observations.

    Science.gov (United States)

    Brenguier, F; Campillo, M; Hadziioannou, C; Shapiro, N M; Nadeau, R M; Larose, E

    2008-09-12

    Seismic velocity changes and nonvolcanic tremor activity in the Parkfield area in California reveal that large earthquakes induce long-term perturbations of crustal properties in the San Andreas fault zone. The 2003 San Simeon and 2004 Parkfield earthquakes both reduced seismic velocities that were measured from correlations of the ambient seismic noise and induced an increased nonvolcanic tremor activity along the San Andreas fault. After the Parkfield earthquake, velocity reduction and nonvolcanic tremor activity remained elevated for more than 3 years and decayed over time, similarly to afterslip derived from GPS (Global Positioning System) measurements. These observations suggest that the seismic velocity changes are related to co-seismic damage in the shallow layers and to deep co-seismic stress change and postseismic stress relaxation within the San Andreas fault zone.

  7. Promoting access to and use of seismic data in a large scientific community

    Directory of Open Access Journals (Sweden)

    Michel Eric

    2017-01-01

    Full Text Available The growing amount of seismic data available from space missions (SOHO, CoRoT, Kepler, SDO,… but also from ground-based facilities (GONG, BiSON, ground-based large programmes…, stellar modelling and numerical simulations, creates new scientific perspectives such as characterizing stellar populations in our Galaxy or planetary systems by providing model-independent global properties of stars such as mass, radius, and surface gravity within several percent accuracy, as well as constraints on the age. These applications address a broad scientific community beyond the solar and stellar one and require combining indices elaborated with data from different databases (e.g. seismic archives and ground-based spectroscopic surveys. It is thus a basic requirement to develop a simple and effcient access to these various data resources and dedicated tools. In the framework of the European project SpaceInn (FP7, several data sources have been developed or upgraded. The Seismic Plus Portal has been developed, where synthetic descriptions of the most relevant existing data sources can be found, as well as tools allowing to localize existing data for given objects or period and helping the data query. This project has been developed within the Virtual Observatory (VO framework. In this paper, we give a review of the various facilities and tools developed within this programme. The SpaceInn project (Exploitation of Space Data for Innovative Helio- and Asteroseismology has been initiated by the European Helio- and Asteroseismology Network (HELAS.

  8. Establishment of borehole observation system and high resolution seismic studies in the western part of the main Marmara Fault in the frame of MARSite Project

    Science.gov (United States)

    Ozel, A.; Yalcinkaya, E.; Guralp, C. M.; Tunc, S.; Meral Ozel, N.

    2013-12-01

    The main objective of this study is to install a multi-parameter borehole system and surface array as close to the main Marmara Fault (MMF) in the western Marmara Sea as possible, and measure continuously the evolution of the state of the fault zone surrounding the MMF and to detect any anomaly or change which may occur before earthquakes by making use of the data from the arrays already running in the eastern part of the Marmara Sea. The multi-parameter borehole system will be composed of very wide dynamic range and stable borehole (VBB) broad band seismic sensor, and incorporate 3-D strain meter, tilt meter, and temperature and local hydrostatic pressure measuring devices. The borehole seismic station will use the latest update technologies and design ideas to record 'Earth tides' signals to the smallest magnitude -3 events. Bringing face to face the seismograms of microearthquakes recorded by borehole and surface instruments portrays quite different contents. The shorter recording duration and nearly flat frequency spectrum up to the Nyquist frequencies of borehole records are faced with longer recording duration and rapid decay of spectral amplitudes at higher frequencies of a surface seismogram. The main causative of the observed differences are near surface geology effects that mask most of the source related information the seismograms include, and that give rise to scattering, generating longer duration seismograms. In view of these circumstances, studies on microearthquakes employing surface seismograms may bring on misleading results. Particularly, the works on earthquake physics and nucleation process of earthquakes requires elaborate analysis of tiny events. It is obvious from the studies on the nucleation process of the 1999 earthquake that tens of minutes before the major rupture initiate noteworthy microearthquake activity happened. The starting point of the 1999 rupture was a site of swarm activity noticed a few decades prior the main shock

  9. Cost reduction for large turbine generator Pedestal in high seismic zone

    International Nuclear Information System (INIS)

    Sawhney, P.S.; Irani, P.; Pusheck, B.N.

    1985-01-01

    Turbine Generator Pedestals have generally been designed using reinforced concrete. For present day large turbine generators (1100 MWe class and above) with tall (about 80 feet) pedestals, the amount of reinforcing steel becomes quite large, especially for plants in high seismic zones. With the prime objective of cost reduction, an approach using steel/concrete composite design has been studied for a large BWR Turbine Generator pedestal with 0.3g peak ground acceleration. Large prefabricated steel modules were adopted for composite design and simplified construction. Design was based on the ACI and AISC codes. Costs and schedules were developed and compared with those for a conventionally designed reinforced concrete pedestal. Composite design was found to give considerable cost and schedule advantage over the conventional reinforced concrete design

  10. Diagnosis of Short-Circuit Fault in Large-Scale Permanent-Magnet Wind Power Generator Based on CMAC

    Directory of Open Access Journals (Sweden)

    Chin-Tsung Hsieh

    2013-01-01

    Full Text Available This study proposes a method based on the cerebellar model arithmetic controller (CMAC for fault diagnosis of large-scale permanent-magnet wind power generators and compares the results with Error Back Propagation (EBP. The diagnosis is based on the short-circuit faults in permanent-magnet wind power generators, magnetic field change, and temperature change. Since CMAC is characterized by inductive ability, associative ability, quick response, and similar input signals exciting similar memories, it has an excellent effect as an intelligent fault diagnosis implement. The experimental results suggest that faults can be diagnosed effectively after only training CMAC 10 times. In comparison to training 151 times for EBP, CMAC is better than EBP in terms of training speed.

  11. Implementation and testing of a fault detection software tool for improving control system performance in a large commercial building

    Energy Technology Data Exchange (ETDEWEB)

    Salsbury, T.I.; Diamond, R.C.

    2000-05-01

    This paper describes a model-based, feedforward control scheme that can detect faults in the controlled process and improve control performance over traditional PID control. The tool uses static simulation models of the system under control to generate feed-forward control action, which acts as a reference of correct operation. Faults that occur in the system cause discrepancies between the feedforward models and the controlled process. The scheme facilitates detection of faults by monitoring the level of these discrepancies. We present results from the first phase of tests on a dual-duct air-handling unit installed in a large office building in San Francisco. We demonstrate the ability of the tool to detect a number of preexisting faults in the system and discuss practical issues related to implementation.

  12. The seismic cycles of large Romanian earthquake: The physical foundation, and the next large earthquake in Vrancea

    International Nuclear Information System (INIS)

    Purcaru, G.

    2002-01-01

    The occurrence patterns of large/great earthquakes at subduction zone interface and in-slab are complex in the space-time dynamics, and make even long-term forecasts very difficult. For some favourable cases where a predictive (empirical) law was found successful predictions were possible (eg. Aleutians, Kuriles, etc). For the large Romanian events (M > 6.7), occurring in the Vrancea seismic slab below 60 km, Purcaru (1974) first found the law of the occurrence time and magnitude: the law of 'quasicycles' and 'supercycles', for large and largest events (M > 7.25), respectively. The quantitative model of Purcaru with these seismic cycles has three time-bands (periods of large earthquakes)/century, discovered using the earthquake history (1100-1973) (however incomplete) of large Vrancea earthquakes for which M was initially estimated (Purcaru, 1974, 1979). Our long-term prediction model is essentially quasideterministic, it predicts uniquely the time and magnitude; since is not strict deterministic the forecasting is interval valued. It predicted the next large earthquake in 1980 in the 3rd time-band (1970-1990), and which occurred in 1977 (M7.1, M w 7.5). The prediction was successful, in long-term sense. We discuss the unpredicted events in 1986 and 1990. Since the laws are phenomenological, we give their physical foundation based on the large scale of rupture zone (RZ) and subscale of the rupture process (RP). First results show that: (1) the 1940 event (h=122 km) ruptured the lower part of the oceanic slab entirely along strike, and down dip, and similarly for 1977 but its upper part, (2) the RZ of 1977 and 1990 events overlap and the first asperity of 1977 event was rebroken in 1990. This shows the size of the events strongly depends on RZ, asperity size/strength and, thus on the failure stress level (FSL), but not on depth, (3) when FSL of high strength (HS) larger zones is critical largest events (eg. 1802, 1940) occur, thus explaining the supercyles (the 1940

  13. The risks to miners, mines, and the public posed by large seismic events in the gold mining districts of South Africa

    CSIR Research Space (South Africa)

    Durrheim, RJ

    2006-10-01

    Full Text Available are incorporating the risks of seismicity in their disaster management plans, and Johannesburg is urged to do likewise. Some buildings are considered vulnerable to damage by large seismic events, posing safety and financial risks....

  14. Active crustal deformation of the El Salvador Fault Zone by integrating geodetic, seismological and geological data: application in seismic hazard assessment

    Science.gov (United States)

    Staller, A.; Benito, B.; Martínez-Díaz, J.; Hernández, D.; Hernández-Rey, R.

    2013-05-01

    El Salvador, Central America, is part of the Chortis block in the northwestern boundary of the Caribbean plate. This block is interacting with a diffuse triple junction point with the Cocos and North American plates. Among the structures that cut the Miocene to Pleistocene volcanic deposits stands out the El Salvador Fault Zone (ESFZ): It is oriented in N90-100E direction, and it is composed of several structural segments that deform Quaternary deposits with right-lateral and oblique slip motions. The ESFZ is seismically active and capable of producing earthquakes such as the February 13, 2001 with Mw 6.6 (Martínez-Díaz et al., 2004), that seriously affected the population, leaving many casualties. This structure plays an important role in the tectonics of the Chortis block, since its motion is directly related to the drift of the Caribbean plate to the east and not with the partitioning of the deformation of the Cocos subduction (here not coupled) (Álvarez-Gómez et al., 2008). Together with the volcanic arc of El Salvador, this zone constitutes a weakness area that allows the motion of forearc block toward the NW. The geometry and the degree of activity of the ESFZ are not studied enough. However their knowledge is essential to understand the seismic hazard associated to this important seismogenic structure. For this reason, since 2007 a GPS dense network was established along the ESFZ (ZFESNet) in order to obtain GPS velocity measurements which are later used to explain the nature of strain accumulation on major faults along the ESFZ. The current work aims at understanding active crustal deformation of the ESFZ through kinematic model. The results provide significant information to be included in a new estimation of seismic hazard taking into account the major structures in ESFZ.

  15. Subsurface imaging in a sector of Cerro Prieto transform fault near to pull-apart basin, Mexicali Valley, Baja California, Mexico, based on crooked lines 2D seismic reflection.

    Science.gov (United States)

    Mares-Agüero, M. A.; González-Escobar, M.; Arregui, S.

    2016-12-01

    In the transition zone between San Andres continental transformation system and the coupled transform faults system and rifting of Gulf of California is located the Cerro Prieto pull-apart basin delimitated by Imperial fault (northeast) and Cerro Prieto fault (CPF) (southwest), this last, is the limit west of Cerro Prieto geothermic field (CPGF). Crooked lines 2D seismic reflection, covering a portion near the intersection of CPF and CPGF are processed and interpreted. The seismic data were obtained in the early 80's by Petróleos Mexicanos (PEMEX). By decades, technical and investigation works in Cerro Prieto geothermic field and its vicinity had mapped faults at several depths but do not stablish a clear limit where this faults and CPF interact due the complex hydrothermal effects imaging the subsurface. The profiles showing the presence of a zone of uplift effect due to CPF. Considering the proximity of the profiles to CPF, it is surprising almost total absence of faults. A strong reflector around 2 km of depth, it is present in all profiles. This seismic reflector is considered a layer of shale, result of the correlation with a well located in the same region.

  16. Adaptive Neural Networks Decentralized FTC Design for Nonstrict-Feedback Nonlinear Interconnected Large-Scale Systems Against Actuator Faults.

    Science.gov (United States)

    Li, Yongming; Tong, Shaocheng

    The problem of active fault-tolerant control (FTC) is investigated for the large-scale nonlinear systems in nonstrict-feedback form. The nonstrict-feedback nonlinear systems considered in this paper consist of unstructured uncertainties, unmeasured states, unknown interconnected terms, and actuator faults (e.g., bias fault and gain fault). A state observer is designed to solve the unmeasurable state problem. Neural networks (NNs) are used to identify the unknown lumped nonlinear functions so that the problems of unstructured uncertainties and unknown interconnected terms can be solved. By combining the adaptive backstepping design principle with the combination Nussbaum gain function property, a novel NN adaptive output-feedback FTC approach is developed. The proposed FTC controller can guarantee that all signals in all subsystems are bounded, and the tracking errors for each subsystem converge to a small neighborhood of zero. Finally, numerical results of practical examples are presented to further demonstrate the effectiveness of the proposed control strategy.The problem of active fault-tolerant control (FTC) is investigated for the large-scale nonlinear systems in nonstrict-feedback form. The nonstrict-feedback nonlinear systems considered in this paper consist of unstructured uncertainties, unmeasured states, unknown interconnected terms, and actuator faults (e.g., bias fault and gain fault). A state observer is designed to solve the unmeasurable state problem. Neural networks (NNs) are used to identify the unknown lumped nonlinear functions so that the problems of unstructured uncertainties and unknown interconnected terms can be solved. By combining the adaptive backstepping design principle with the combination Nussbaum gain function property, a novel NN adaptive output-feedback FTC approach is developed. The proposed FTC controller can guarantee that all signals in all subsystems are bounded, and the tracking errors for each subsystem converge to a small

  17. Microfluidic very large-scale integration for biochips: Technology, testing and fault-tolerant design

    DEFF Research Database (Denmark)

    Araci, Ismail Emre; Pop, Paul; Chakrabarty, Krishnendu

    2015-01-01

    of this paper is on continuous-flow biochips, where the basic building block is a microvalve. By combining these microvalves, more complex units such as mixers, switches, multiplexers can be built, hence the name of the technology, “microfluidic Very Large-Scale Integration” (mVLSI). A roadblock......Microfluidic biochips are replacing the conventional biochemical analyzers by integrating all the necessary functions for biochemical analysis using microfluidics. Biochips are used in many application areas, such as, in vitro diagnostics, drug discovery, biotech and ecology. The focus...... presents the state-of-the-art in the mVLSI platforms and emerging research challenges in the area of continuous-flow microfluidics, focusing on testing techniques and fault-tolerant design....

  18. Site-to-Source Finite Fault Distance Probability Distribution in Probabilistic Seismic Hazard and the Relationship Between Minimum Distances

    Science.gov (United States)

    Ortega, R.; Gutierrez, E.; Carciumaru, D. D.; Huesca-Perez, E.

    2017-12-01

    We present a method to compute the conditional and no-conditional probability density function (PDF) of the finite fault distance distribution (FFDD). Two cases are described: lines and areas. The case of lines has a simple analytical solution while, in the case of areas, the geometrical probability of a fault based on the strike, dip, and fault segment vertices is obtained using the projection of spheres in a piecewise rectangular surface. The cumulative distribution is computed by measuring the projection of a sphere of radius r in an effective area using an algorithm that estimates the area of a circle within a rectangle. In addition, we introduce the finite fault distance metrics. This distance is the distance where the maximum stress release occurs within the fault plane and generates a peak ground motion. Later, we can apply the appropriate ground motion prediction equations (GMPE) for PSHA. The conditional probability of distance given magnitude is also presented using different scaling laws. A simple model of constant distribution of the centroid at the geometrical mean is discussed, in this model hazard is reduced at the edges because the effective size is reduced. Nowadays there is a trend of using extended source distances in PSHA, however it is not possible to separate the fault geometry from the GMPE. With this new approach, it is possible to add fault rupture models separating geometrical and propagation effects.

  19. Constraints on Shallow Crustal Structure across the San Andreas Fault Zone, Coachella Valley, Southern California: Results from the Salton Seismic Imaging Project (SSIP)

    Science.gov (United States)

    Hernandez, A.; Persaud, P.; Bauer, K.; Stock, J. M.; Fuis, G. S.; Hole, J. A.; Goldman, M.

    2015-12-01

    The strong influence of basin structure and crustal heterogeneities on seismic wave propagation suggests that these factors should be included in calculations of strong ground shaking. Knowledge of the shallow subsurface is thus essential for an accurate seismic hazard estimate for the densely populated Coachella Valley, the region north of the potential M7.8 rupture near the Salton Sea. Using SSIP data, we analyzed first arrivals from nine 65-911 kg explosive shots recorded along a profile in the Coachella Valley in order to evaluate the interpretation of our 2D tomographic results and give added details on the structural complexity of the shallow crust. The line extends 37 km from the Peninsular Ranges to the Little San Bernardino Mountains crossing the major strands of the San Andreas Fault Zone. We fit traveltime curves to our picks with forward modeling ray tracing, and determined 1D P-wave velocity models for traveltime arrivals east and west of each shot, and a 2D model for the line. We also inferred the geometry of near-vertical faults from the pre-stack line migration method of Bauer et al. (2013). In general, the 1D models east of individual shots have deeper basement contacts and lower apparent velocities, ~5 km/s at 4 km depth, whereas the models west of individual shots have shallower basement and velocities up to 6 km/s at 2 km depth. Mismatches in basement depths (assuming 5-6 km/s) between individual 1D models indicate a shallowly dipping basement, deepening eastward towards the Banning Fault and shoaling abruptly farther east. An east-dipping structure in the 2D model also gives a better fit than horizontal layers. Based on high velocity zones derived from traveltimes at 9-20 km from the western end of the line, we included an offset from ~2 km to 4 km depth near the middle of the line, which significantly improved the 2D model fit. If fault-related, this offset could represent the Garnet Hill Fault if it continues southward in the subsurface.

  20. Seismic imaging beneath an InSAR anomaly in eastern Washington State: Shallow faulting associated with an earthquake swarm in a low-hazard area

    Science.gov (United States)

    Stephenson, William J.; Odum, Jackson K.; Wicks, Chuck; Pratt, Thomas L.; Blakely, Richard J.

    2016-01-01

    In 2001, a rare swarm of small, shallow earthquakes beneath the city of Spokane, Washington, caused ground shaking as well as audible booms over a five‐month period. Subsequent Interferometric Synthetic Aperture Radar (InSAR) data analysis revealed an area of surface uplift in the vicinity of the earthquake swarm. To investigate the potential faults that may have caused both the earthquakes and the topographic uplift, we collected ∼3  km of high‐resolution seismic‐reflection profiles to image the upper‐source region of the swarm. The two profiles reveal a complex deformational pattern within Quaternary alluvial, fluvial, and flood deposits, underlain by Tertiary basalts and basin sediments. At least 100 m of arching on a basalt surface in the upper 500 m is interpreted from both the seismic profiles and magnetic modeling. Two west‐dipping faults deform Quaternary sediments and project to the surface near the location of the Spokane fault defined from modeling of the InSAR data.

  1. Stress Models of the Annual Hydrospheric, Atmospheric, Thermal, and Tidal Loading Cycles on California Faults: Perturbation of Background Stress and Changes in Seismicity

    Science.gov (United States)

    Johnson, Christopher W.; Fu, Yuning; Bürgmann, Roland

    2017-12-01

    Stresses in the lithosphere arise from multiple natural loading sources that include both surface and body forces. The largest surface loads include near-surface water storage, snow and ice, atmosphere pressure, ocean loading, and temperature changes. The solid Earth also deforms from celestial body interactions and variations in Earth's rotation. We model the seasonal stress changes in California from 2006 through 2014 for seven different loading sources with annual periods to produce an aggregate stressing history for faults in the study area. Our modeling shows that the annual water loading, atmosphere, temperature, and Earth pole tides are the largest loading sources and should each be evaluated to fully describe seasonal stress changes. In California we find that the hydrological loads are the largest source of seasonal stresses. We explore the seasonal stresses with respect to the background principal stress orientation constrained with regional focal mechanisms and analyze the modulation of seismicity. Our results do not suggest a resolvable seasonal variation for the ambient stress orientation in the shallow crust. When projecting the seasonal stresses into the background stress orientation we find that the timing of microseismicity modestly increases from an 8 kPa seasonal mean-normal-stress perturbation. The results suggest that faults in California are optimally oriented with the background stress field and respond to subsurface pressure changes, possibly due to processes we have not considered in this study. At any time a population of faults are near failure as evident from earthquakes triggered by these slight seasonal stress perturbations.

  2. Subsurface geometry of the San Andreas fault in southern California: Results from the Salton Seismic Imaging Project (SSIP) and strong ground motion expectations

    Science.gov (United States)

    Fuis, Gary S.; Bauer, Klaus; Goldman, Mark R.; Ryberg, Trond; Langenheim, Victoria; Scheirer, Daniel S.; Rymer, Michael J.; Stock, Joann M.; Hole, John A.; Catchings, Rufus D.; Graves, Robert; Aagaard, Brad T.

    2017-01-01

    The San Andreas fault (SAF) is one of the most studied strike‐slip faults in the world; yet its subsurface geometry is still uncertain in most locations. The Salton Seismic Imaging Project (SSIP) was undertaken to image the structure surrounding the SAF and also its subsurface geometry. We present SSIP studies at two locations in the Coachella Valley of the northern Salton trough. On our line 4, a fault‐crossing profile just north of the Salton Sea, sedimentary basin depth reaches 4 km southwest of the SAF. On our line 6, a fault‐crossing profile at the north end of the Coachella Valley, sedimentary basin depth is ∼2–3  km">∼2–3  km and centered on the central, most active trace of the SAF. Subsurface geometry of the SAF and nearby faults along these two lines is determined using a new method of seismic‐reflection imaging, combined with potential‐field studies and earthquakes. Below a 6–9 km depth range, the SAF dips ∼50°–60°">∼50°–60° NE, and above this depth range it dips more steeply. Nearby faults are also imaged in the upper 10 km, many of which dip steeply and project to mapped surface fault traces. These secondary faults may join the SAF at depths below about 10 km to form a flower‐like structure. In Appendix D, we show that rupture on a northeast‐dipping SAF, using a single plane that approximates the two dips seen in our study, produces shaking that differs from shaking calculated for the Great California ShakeOut, for which the southern SAF was modeled as vertical in most places: shorter‐period (TT<1  s) shaking is increased locally by up to a factor of 2 on the hanging wall and is decreased locally by up to a factor of 2 on the footwall, compared to shaking calculated for a vertical fault.

  3. Seismic proving tests on the reliability for large components and equipment of nuclear power plants

    International Nuclear Information System (INIS)

    Ohno, Tokue; Tanaka, Nagatoshi

    1988-01-01

    Since Japan has destructive earthquakes frequently, the structural reliability for large components and equipment of nuclear power plants are rigorously required. They are designed using sophisticated seismic analyses and have not yet encountered a destructive earthquake. When nuclear power plants are planned, it is very important that the general public understand the structural reliability during and after an earthquake. Seismic Proving Tests have been planned by Ministry of International Trade and Industry (Miti) to comply with public requirement in Japan. A large-scale high-performance vibration table was constructed at Tasted Engineering Laboratory of Nuclear Power Engineering Test Center (NU PEC), in order to prove the structural reliability by vibrating the test model (of full scale or close to the actual size) in the condition of a destructive earthquake. As for the test models, the following four items were selected out of large components and equipment important to the safety: Reactor Containment Vessel; Primary Coolant Loop or Primary Loop Recirculation System; Reactor Pressure Vessel; and Reactor Core Internals. Here is described a brief of the vibration table, the test method and the results of the tests on PWR Reactor Containment Vessel and BWR Primary Loop Recirculation System (author)

  4. Identifying Faults Associated with the 2001 Avoca Induced(?) Seismicity Sequence of Western New York State Using Potential Field Wavelets.

    Science.gov (United States)

    Horowitz, F. G.; Ebinger, C.; Jordan, T. E.

    2017-12-01

    Results from recent DOE and USGS sponsored projects in the (intraplate) northeastern portions of the US and southeastern portions of Canada have identified locations of steeply dipping structures - many previously unknown - from a Poisson wavelet multiscale edge ('worm') analysis of gravity and magnetic fields. The Avoca sequence of induced(?) seismicity in western New York state occurred during January and February of 2001. The Avoca earthquake sequence is associated with industrial hydraulic fracturing activity "related to a proposed natural gas storage facility near Avoca to be constructed by solution mining" (Kim, 2001). The main Avoca event was a felt Mb = 3.2 earthquake on Feb. 3, 2001 recorded by the Lamont Cooperative Seismic Network. Earlier, smaller events were located by the Canadian Geological Survey's seismic network north of the Canadian border - implying that the event locations might be biased because they occurred off the southern edge of the array. Some of these events were also felt locally, according to local newspaper reports. By plotting the location of the seismic events and that of the injection well - reported via it's API number - we find a strong correlation with structures detected via our potential field worms. The injection occurred near a NE-SW striking structure that was not activated. All but one of the earthquakes occurred about 5 km north of the injection well on or nearby to an E-W striking structure that appears to intersect the NE-SW structure. The final, small (MN=2.2) earthquake was located on a different complex structure about 10 km north of the other events. We suggest that potential field methods such as ours might be appropriate to locating structures of concern for induced seismic activity in association with industrial activity. Reference: Kim, W.-Y. (2001). The Lamont cooperative seismic network and the national seismic system: Earthquake hazard studies in the northeastern United States. Tech. Rep. 98-01, Lamont

  5. Korea-Japan Joint Research on Development of Seismic Capacity Evaluation and Enhancement Technology Considering Near-Fault Effect

    Energy Technology Data Exchange (ETDEWEB)

    Choun, Young Sun; Choi, In Kil; Kim, Min Kyu [KAERI, Daejon (Korea, Republic of); Ohtori, Yasuki; Shiba, Yoshiaki; Nakajima, Masato [Central Research Institute of Electric Power Industry, Tokyo (Japan)

    2005-12-15

    Several recent improved methods for the EGFM are introduced in order to avoid artificial holes seen in the synthetic acceleration spectrum. Furthermore evaluation of input ground motions at Wolsung NPP are performed by varying the source parameters that may control the high-frequency wave radiation and the deviation of the synthetic motions are revealed. The PSHA case studies for four NPP sites (Wolsung, Kori, Uljin, Younggwang) are performed. In the analysis, site-specific attenuation equations developed for Korean NPP sites are employed, and the seismic hazards for the target sites are evaluated in the case where the four kind of seismic source models are considered. Moreover, the PSHA for Wolsung and Younggwang are conducted by using the site-specific attenuation equation with the index of response spectra and the uniform hazard spectra are evaluated for the two sites. The supporting tool for seismic response analysis and the evaluation tool for evaluating annual probability of failure were integrated in the frame of the seismic risk assessment system. Then, the tools were applied to the seismic risk assessment of the conventional EDG and isolated EDG. General information such as earthquake parameters and regional distribution of seismic intensity is summarized on the 2005 West Off Fukuoka earthquake. Then, the observed strong motion records in Japan and Korea sites are compiled, and regional distribution of peak accelerations are represented. Moreover, the peak accelerations of the records are compared with the values estimated from the existing attenuation equations.

  6. Use of Fault Displacement Vector to Identify Future Zones of Seismicity: An Example from the Earthquakes of Nepal Himalayas.

    Science.gov (United States)

    Naim, F.; Mukherjee, M. K.

    2017-12-01

    Earthquakes occur due to fault slip in the subsurface. They can occur either as interplate or intraplate earthquakes. The region of study is the Nepal Himalayas that defines the boundary of Indian-Eurasian plate and houses the focus of the most devastating earthquakes. The aim of the study was to analyze all the earthquakes that occurred in the Nepal Himalayas upto May 12, 2015 earthquake in order to mark the regions still under stress and vulnerable for future earthquakes. Three different fault systems in the Nepal Himalayas define the tectonic set up of the area. They are: (1) Main Frontal Thrust(MFT), (2) Main Central Thrust(MCT) and (3) Main Boundary Thrust(MBT) that extend from NW to SE. Most of the earthquakes were observed to occur between the MBT and MCT. Since the thrust faults are dipping towards NE, the focus of most of the earthquakes lies on the MBT. The methodology includes estimating the dip of the fault by considering the depths of different earthquake events and their corresponding distance from the MBT. In order to carry out stress analysis on the fault, the beach ball diagrams associated with the different earthquakes were plotted on a map. Earthquakes in the NW and central region of the fault zone were associated with reverse fault slip while that on the South-Eastern part were associated with a strike slip component. The direction of net slip on the fault associated with the different earthquakes was known and from this a 3D slip diagram of the fault was constructed. The regions vulnerable for future earthquakes in the Nepal Himalaya were demarcated on the 3D slip diagram of the fault. Such zones were marked owing to the fact that the slips due to earthquakes cause the adjoining areas to come under immense stress and this stress is directly proportional to the amount of slip occuring on the fault. These vulnerable zones were in turn projected on the map to show their position and are predicted to contain the epicenter of the future earthquakes.

  7. From tomographic images to fault heterogeneities

    Directory of Open Access Journals (Sweden)

    A. Amato

    1994-06-01

    Full Text Available Local Earthquake Tomography (LET is a useful tool for imaging lateral heterogeneities in the upper crust. The pattern of P- and S-wave velocity anomalies, in relation to the seismicity distribution along active fault zones. can shed light on the existence of discrete seismogenic patches. Recent tomographic studies in well monitored seismic areas have shown that the regions with large seismic moment release generally correspond to high velocity zones (HVZ's. In this paper, we discuss the relationship between the seismogenic behavior of faults and the velocity structure of fault zones as inferred from seismic tomography. First, we review some recent tomographic studies in active strike-slip faults. We show examples from different segments of the San Andreas fault system (Parkfield, Loma Prieta, where detailed studies have been carried out in recent years. We also show two applications of LET to thrust faults (Coalinga, Friuli. Then, we focus on the Irpinia normal fault zone (South-Central Italy, where a Ms = 6.9 earthquake occurred in 1980 and many thousands of attershock travel time data are available. We find that earthquake hypocenters concentrate in HVZ's, whereas low velocity zones (LVZ’ s appear to be relatively aseismic. The main HVZ's along which the mainshock rupture bas propagated may correspond to velocity weakening fault regions, whereas the LVZ's are probably related to weak materials undergoing stable slip (velocity strengthening. A correlation exists between this HVZ and the area with larger coseismic slip along the fault, according to both surface evidence (a fault scarp as high as 1 m and strong ground motion waveform modeling. Smaller wave-length, low-velocity anomalies detected along the fault may be the expression of velocity strengthening sections, where aseismic slip occurs. According to our results, the rupture at the nucleation depth (~ 10-12 km is continuous for the whole fault lenoth (~ 30 km, whereas at shallow depth

  8. Geological analysis of paleozoic large-scale faulting in the south-central Pyrenees

    OpenAIRE

    Speksnijder, A.

    1986-01-01

    Detailed structural and sedimentological analysis reveals the existence of an east-west directed fundamental fault zone in the south-central Pyrenees, which has been intermittently active from (at least) the Devonian on. Emphasis is laid on the stUdy of fault-bounded post-Variscan (StephanoPermian) sedimentary basins, and the influence of Late Paleozoic faulting on the underlying Variscan basement. The present structure of the basement is rather complex as it results from multiple Variscan an...

  9. Numerical simulation of seismic wave propagation from land-excited large volume air-gun source

    Science.gov (United States)

    Cao, W.; Zhang, W.

    2017-12-01

    The land-excited large volume air-gun source can be used to study regional underground structures and to detect temporal velocity changes. The air-gun source is characterized by rich low frequency energy (from bubble oscillation, 2-8Hz) and high repeatability. It can be excited in rivers, reservoirs or man-made pool. Numerical simulation of the seismic wave propagation from the air-gun source helps to understand the energy partitioning and characteristics of the waveform records at stations. However, the effective energy recorded at a distance station is from the process of bubble oscillation, which can not be approximated by a single point source. We propose a method to simulate the seismic wave propagation from the land-excited large volume air-gun source by finite difference method. The process can be divided into three parts: bubble oscillation and source coupling, solid-fluid coupling and the propagation in the solid medium. For the first part, the wavelet of the bubble oscillation can be simulated by bubble model. We use wave injection method combining the bubble wavelet with elastic wave equation to achieve the source coupling. Then, the solid-fluid boundary condition is implemented along the water bottom. And the last part is the seismic wave propagation in the solid medium, which can be readily implemented by the finite difference method. Our method can get accuracy waveform of land-excited large volume air-gun source. Based on the above forward modeling technology, we analysis the effect of the excited P wave and the energy of converted S wave due to different water shapes. We study two land-excited large volume air-gun fields, one is Binchuan in Yunnan, and the other is Hutubi in Xinjiang. The station in Binchuan, Yunnan is located in a large irregular reservoir, the waveform records have a clear S wave. Nevertheless, the station in Hutubi, Xinjiang is located in a small man-made pool, the waveform records have very weak S wave. Better understanding of

  10. Southeastward increase of the late Quaternary slip-rate of the Xianshuihe fault, eastern Tibet. Geodynamic and seismic hazard implications

    Science.gov (United States)

    Bai, Mingkun; Chevalier, Marie-Luce; Pan, Jiawei; Replumaz, Anne; Leloup, Philippe Hervé; Métois, Marianne; Li, Haibing

    2018-03-01

    The left-lateral strike-slip Xianshuihe fault system located in the eastern Tibetan Plateau is considered as one of the most tectonically active intra-continental fault system in China, along which more than 20 M > 6.5 and more than 10 M > 7 earthquakes occurred since 1700. Therefore, studying its activity, especially its slip rate at different time scales, is essential to evaluate the regional earthquake hazard. Here, we focus on the central segment of the Xianshuihe fault system, where the Xianshuihe fault near Kangding city splays into three branches: the Selaha, Yalahe and Zheduotang faults. In this paper we use precise dating together with precise field measurements of offsets to re-estimate the slip rate of the fault that was suggested without precise age constraints. We studied three sites where the active Selaha fault cuts and left-laterally offsets moraine crests and levees. We measured horizontal offsets of 96 ± 20 m at Tagong levees (TG), 240 ± 15 m at Selaha moraine (SLH) and 80 ± 5 m at Yangjiagou moraine (YJG). Using 10Be cosmogenic dating, we determined abandonment ages at Tagong, Selaha and Yangjiagou of 12.5 (+ 2.5 / - 2.2) ka, 22 ± 2 ka, and 18 ± 2 ka, respectively. By matching the emplacement age of the moraines or levees with their offsets, we obtain late Quaternary horizontal average slip-rates of 7.6 (+ 2.3 / - 1.9) mm/yr at TG and 10.7 (+ 1.3 / - 1.1) mm/yr at SLH, i.e., 5.7-12 mm/yr or between 9.6 and 9.9 mm/yr assuming that the slip rate should be constant between the nearby TG and SLH sites. At YJG, we obtain a lower slip rate of 4.4 ± 0.5 mm/yr, most likely because the parallel Zheduotang fault shares the slip rate at this longitude, therefore suggesting a ∼5 mm/yr slip rate along the Zheduotang fault. The ∼10 mm/yr late Quaternary rate along the Xianshuihe fault is higher than that along the Ganzi fault to the NW (6-8 mm/yr). This appears to be linked to the existence of the Longriba fault system that separates the Longmenshan

  11. Near surface structure of the North Anatolian Fault Zone near 30°E from Rayleigh and Love wave tomography using ambient seismic noise.

    Science.gov (United States)

    Taylor, G.; Rost, S.; Houseman, G. A.; Hillers, G.

    2017-12-01

    By utilising short period surface waves present in the noise field, we can construct images of shallow structure in the Earth's upper crust: a depth-range that is usually poorly resolved in earthquake tomography. Here, we use data from a dense seismic array (Dense Array for Northern Anatolia - DANA) deployed across the North Anatolian Fault Zone (NAFZ) in the source region of the 1999 magnitude 7.6 Izmit earthquake in western Turkey. The NAFZ is a major strike-slip system that extends 1200 km across northern Turkey and continues to pose a high level of seismic hazard, in particular to the mega-city of Istanbul. We obtain maps of group velocity variation using surface wave tomography applied to short period (1- 6 s) Rayleigh and Love waves to construct high-resolution images of SV and SH-wave velocity in the upper 5 km of a 70 km x 35 km region centred on the eastern end of the fault segment that ruptured in the 1999 Izmit earthquake. The average Rayleigh wave group velocities in the region vary between 1.8 km/s at 1.5 s period, to 2.2 km/s at 6 s period. The NAFZ bifurcates into northern and southern strands in this region; both are active but only the northern strand ruptured in the 1999 event. The signatures of both the northern and southern branches of the NAFZ are clearly associated with strong gradients in seismic velocity that also denote the boundaries of major tectonic units. This observation implies that the fault zone exploits the pre-existing structure of the Intra-Pontide suture zone. To the north of the NAFZ, we observe low S-wave velocities ( 2.0 km/s) associated with the unconsolidated sediments of the Adapazari basin, and blocks of weathered terrigenous clastic sediments. To the south of the northern branch of the NAFZ in the Armutlu block, we detect higher velocities ( 2.9 km/s) associated with a shallow crystalline basement, in particular a block of metamorphosed schists and marbles that bound the northern branch of the NAFZ.

  12. Model checking methodology for large systems, faults and asynchronous behaviour. SARANA 2011 work report

    International Nuclear Information System (INIS)

    Lahtinen, J.; Launiainen, T.; Heljanko, K.; Ropponen, J.

    2012-01-01

    Digital instrumentation and control (I and C) systems are challenging to verify. They enable complicated control functions, and the state spaces of the models easily become too large for comprehensive verification through traditional methods. Model checking is a formal method that can be used for system verification. A number of efficient model checking systems are available that provide analysis tools to determine automatically whether a given state machine model satisfies the desired safety properties. This report reviews the work performed in the Safety Evaluation and Reliability Analysis of Nuclear Automation (SARANA) project in 2011 regarding model checking. We have developed new, more exact modelling methods that are able to capture the behaviour of a system more realistically. In particular, we have developed more detailed fault models depicting the hardware configuration of a system, and methodology to model function-block-based systems asynchronously. In order to improve the usability of our model checking methods, we have developed an algorithm for model checking large modular systems. The algorithm can be used to verify properties of a model that could otherwise not be verified in a straightforward manner. (orig.)

  13. Model checking methodology for large systems, faults and asynchronous behaviour. SARANA 2011 work report

    Energy Technology Data Exchange (ETDEWEB)

    Lahtinen, J. [VTT Technical Research Centre of Finland, Espoo (Finland); Launiainen, T.; Heljanko, K.; Ropponen, J. [Aalto Univ., Espoo (Finland). Dept. of Information and Computer Science

    2012-07-01

    Digital instrumentation and control (I and C) systems are challenging to verify. They enable complicated control functions, and the state spaces of the models easily become too large for comprehensive verification through traditional methods. Model checking is a formal method that can be used for system verification. A number of efficient model checking systems are available that provide analysis tools to determine automatically whether a given state machine model satisfies the desired safety properties. This report reviews the work performed in the Safety Evaluation and Reliability Analysis of Nuclear Automation (SARANA) project in 2011 regarding model checking. We have developed new, more exact modelling methods that are able to capture the behaviour of a system more realistically. In particular, we have developed more detailed fault models depicting the hardware configuration of a system, and methodology to model function-block-based systems asynchronously. In order to improve the usability of our model checking methods, we have developed an algorithm for model checking large modular systems. The algorithm can be used to verify properties of a model that could otherwise not be verified in a straightforward manner. (orig.)

  14. Geological analysis of paleozoic large-scale faulting in the south-central Pyrenees

    NARCIS (Netherlands)

    Speksnijder, A.

    1986-01-01

    Detailed structural and sedimentological analysis reveals the existence of an east-west directed fundamental fault zone in the south-central Pyrenees, which has been intermittently active from (at least) the Devonian on. Emphasis is laid on the stUdy of fault-bounded post-Variscan

  15. Geological analysis of paleozoic large-scale faulting in the south-central Pyrenees

    NARCIS (Netherlands)

    Speksnijder, A.

    1986-01-01

    Detailed structural and sedimentological analysis reveals the existence of an east-west directed fundamental fault zone in the south-central Pyrenees, which has been intermittently active from (at least) the Devonian on. Emphasis is laid on the stUdy of fault-bounded post-Variscan (StephanoPermian)

  16. Back analysis of fault-slip in burst prone environment

    Science.gov (United States)

    Sainoki, Atsushi; Mitri, Hani S.

    2016-11-01

    In deep underground mines, stress re-distribution induced by mining activities could cause fault-slip. Seismic waves arising from fault-slip occasionally induce rock ejection when hitting the boundary of mine openings, and as a result, severe damage could be inflicted. In general, it is difficult to estimate fault-slip-induced ground motion in the vicinity of mine openings because of the complexity of the dynamic response of faults and the presence of geological structures. In this paper, a case study is conducted for a Canadian underground mine, herein called "Mine-A", which is known for its seismic activities. Using a microseismic database collected from the mine, a back analysis of fault-slip is carried out with mine-wide 3-dimensional numerical modeling. A back analysis is conducted to estimate the physical and mechanical properties of the causative fracture or shear zones. One large seismic event has been selected for the back analysis to detect a fault-slip related seismic event. In the back analysis, the shear zone properties are estimated with respect to moment magnitude of the seismic event and peak particle velocity (PPV) recorded by a strong ground motion sensor. The estimated properties are then validated through comparison with peak ground acceleration recorded by accelerometers. Lastly, ground motion in active mining areas is estimated by conducting dynamic analysis with the estimated values. The present study implies that it would be possible to estimate the magnitude of seismic events that might occur in the near future by applying the estimated properties to the numerical model. Although the case study is conducted for a specific mine, the developed methodology can be equally applied to other mines suffering from fault-slip related seismic events.

  17. The 2014 update to the National Seismic Hazard Model in California

    Science.gov (United States)

    Powers, Peter; Field, Edward H.

    2015-01-01

    The 2014 update to the U. S. Geological Survey National Seismic Hazard Model in California introduces a new earthquake rate model and new ground motion models (GMMs) that give rise to numerous changes to seismic hazard throughout the state. The updated earthquake rate model is the third version of the Uniform California Earthquake Rupture Forecast (UCERF3), wherein the rates of all ruptures are determined via a self-consistent inverse methodology. This approach accommodates multifault ruptures and reduces the overprediction of moderate earthquake rates exhibited by the previous model (UCERF2). UCERF3 introduces new faults, changes to slip or moment rates on existing faults, and adaptively smoothed gridded seismicity source models, all of which contribute to significant changes in hazard. New GMMs increase ground motion near large strike-slip faults and reduce hazard over dip-slip faults. The addition of very large strike-slip ruptures and decreased reverse fault rupture rates in UCERF3 further enhances these effects.

  18. Fault injection as a test method for an FPGA in charge of data readout for a large tracking detector

    CERN Document Server

    Roed, K; Richter, M; Fehlker, D; Helstrup, H; Alme, J; Ullaland, K

    2011-01-01

    This paper describes how fault injection has been implemented as a test method for an FPGA in an existing hardware configuration setup. As this FPGA is in charge of data readout for a large tracking detector, the reliability of this FPGA is of high importance. Due to the complexity of the readout electronics, irradiation testing is technically difficult at this stage of the system commissioning. The work presented in this paper is therefore motivated by introducing fault injection as an alternative method to characterize failures caused by SEUs. It is a method to study the effect that a configuration upset may have on the operation of the FPGA. The target platform consists of two independent modules for data acquisition and detector control functionality. Fault injection to test the response of the data acquisition module is made possible by implementing the solution as part of the detector control functionality. Correct implementation is validated by a simple shift register design. Our results demonstrate th...

  19. Spatial and Temporal Variations in Earthquake Stress Drop on Gofar Transform Fault, East Pacific Rise: Implications for Fault Strength

    Science.gov (United States)

    Moyer, P. A.; Boettcher, M. S.; McGuire, J. J.; Collins, J. A.

    2017-12-01

    During the last five seismic cycles on Gofar transform fault on the East Pacific Rise, the largest earthquakes (6.0 ≤ Mw ≤ 6.2) have repeatedly ruptured the same fault segment (rupture asperity), while intervening fault segments host swarms of microearthquakes. Previous studies on Gofar have shown that these segments of low (≤10%) seismic coupling contain diffuse zones of seismicity and P-wave velocity reduction compared with the rupture asperity; suggesting heterogeneous fault properties control earthquake behavior. We investigate the role systematic differences in material properties have on earthquake rupture along Gofar using waveforms from ocean bottom seismometers that recorded the end of the 2008 Mw 6.0 seismic cycle.We determine stress drop for 117 earthquakes (2.4 ≤ Mw ≤ 4.2) that occurred in and between rupture asperities from corner frequency derived using an empirical Green's function spectral ratio method and seismic moment obtained by fitting the omega-square source model to the low frequency amplitude of earthquake spectra. We find stress drops from 0.03 to 2.7 MPa with significant spatial variation, including 2 times higher average stress drop in the rupture asperity compared to fault segments with low seismic coupling. We interpret an inverse correlation between stress drop and P-wave velocity reduction as the effect of damage on earthquake rupture. Earthquakes with higher stress drops occur in more intact crust of the rupture asperity, while earthquakes with lower stress drops occur in regions of low seismic coupling and reflect lower strength, highly fractured fault zone material. We also observe a temporal control on stress drop consistent with log-time healing following the Mw 6.0 mainshock, suggesting a decrease in stress drop as a result of fault zone damage caused by the large earthquake.

  20. Seismic characterization of hydrates in faulted, fine-grained sediments of Krishna-Godavari Basin: Full waveform inversion

    Digital Repository Service at National Institute of Oceanography (India)

    Jaiswal, P.; Dewangan, P.; Ramprasad, T.; Zelt, C.A.

    (P)) and attenuation (Q sub(P) sup(-1)) character of the gas hydrate stability zone (GHSZ). In this paper, we apply frequency domain full-waveform inversion (FWI) to surface-towed 2D multichannel seismic data from the Krishna-Godavari (KG) Basin, India, to image...

  1. Seismic characterization of hydrates in faulted, fine-grained sediments of Krishna-Godavari basin: Full waveform inversion.

    Digital Repository Service at National Institute of Oceanography (India)

    Jaiswal, P.; Dewangan, P.; Ramprasad, T.; Zelt, C.A.

    (QP−1) character of the gas hydrate stability zone (GHSZ). In this paper, we apply frequency domain full-waveform inversion (FWI) to surface-towed 2D multichannel seismic data from the Krishna-Godavari (KG) Basin, India, to image the fine-scale (100...

  2. Mapping offshore portions of the Khlong Marui and Ranong faults in Thailand: Implications for seismic hazards in the Thai peninsula

    Science.gov (United States)

    Ramirez, H.; Furlong, K.; Pananont, P.; Krastel, S.; Nhongkai, S. N.

    2017-12-01

    Thailand experiences Mw 10.1016/S0191- 8141(01)00080-3 Watkinson, I., Elders, C., & Hall, R. (2008). The kinematic history of the Khlong Marui and Ranong Faults, southern Thailand. Journal of Structural Geology, 30, 1554-1571. http://doi.org/10.1016/j.jsg.2008.09.001

  3. Latest Pleistocene to Holocene thrust faulting paleoearthquakes at Monte Netto (Brescia, Italy): lessons learned from the Middle Ages seismic events in the Po Plain

    Science.gov (United States)

    Michetti, Alessandro Maria; Berlusconi, Andrea; Livio, Franz; Sileo, Giancanio; Zerboni, Andrea; Serva, Leonello; Vittori, Eutizio; Rodnight, Helena; Spötl, Christoph

    2010-05-01

    The seismicity of the Po Plain in Northern Italy is characterized by two strong Middle Ages earthquakes, the 1117, I° X MCS Verona, and the December 25, 1222, I° IX-X Brescia, events. Historical reports from these events describe relevant coseismic environmental effects, such as drainage changes, ground rupture and landslides. Due to the difficult interpretation of intensity data from such old seismic events, considerable uncertainty exists about their source parameters, and therefore about their causative tectonic structures. In a recent review, Stucchi et al. (2008) concluded that 'the historical data do not significantly help to constrain the assessment of the seismogenic potential of the area, which remains one of the most unknown, although potentially dangerous, seismic areas of the Italian region'. This issue needs therefore to be addressed by using the archaeological and geological evidence of past earthquakes, that is, archeoseismology and paleoseismology. Earthquake damage to archaeological sites in the study area has been the subject of several recent papers. Here we focus on new paleoseismological evidence, and in particular on the first observation of Holocene paleoseismic surface faulting in the Po Plain identified at the Monte Netto site, located ca. 10 km S of Brescia, in the area where the highest damage from the Christmas 1222 earthquake have been recorded. Monte Netto is a small hill, ca. 30 m higher than the surrounding piedmont plain, which represent the top of a growing fault-related fold belonging to the Quaternary frontal sector of the Southern Alps; the causative deep structure is a N-verging back thrust, well imaged in the industrial seismic reflection profiles kindly made available by ENI E&P. New trenching investigations have been conducted at the Cava Danesi of Monte Netto in October 2009, focused on the 1:10 scale analysis of the upper part of the 7 m high mid-Pleistocene to Holocene stratigraphic section exposed along the quarry

  4. Seismic loads in modularized and unmodularized large pools located on hard or intermediate hard sites

    Energy Technology Data Exchange (ETDEWEB)

    Dong, R G [California Univ., Livermore (USA). Lawrence Livermore Lab.

    1977-12-01

    To augment the present capacity of pools for storing spent nuclear fuel elements, pools larger than those in current use are being planned. These pools may or may not be modularized into cells. Because of the large size of the pools, seismic loads are of significant interest. In particular, the effects of modularization and site hardness are of concern. The study presented in this paper reveals that modularization is generally unfavourable, because it creates the option of leaving one or more cells empty which in turn results in higher structural loads. The wall which separates a filled cell from an empty cell, or the wall which bears against earth on one side and faces an empty cell on the other, becomes very highly stressed. For the particular pool geometries examined, a hard site is generally preferred over an intermediate hard site in terms of structural loads.

  5. Seismic evaluation of a large nuclear pump bearing using non-linear dynamic analysis

    International Nuclear Information System (INIS)

    Huber, K.A.; Hugins, M.S.

    1983-01-01

    Hydrostatic bearings of a large vertical pump using sodium as the lubricant were critically examined to determine their ability to withstand seismic loads. Initial linear dynamics analyses predicted journal displacements to exceed bearing clearance by a ratio of 3:1. Equivalent time-history excitations were then developed from the response spectra to determine the number, magnitude, and duration of the bearing impact loads. Predicted loads were further reduced by 50% by modeling non-linear bearing characteristics normally present but not generally included in conventional linear analyses. Results are presented of the comprehensive design evaluation performed, based on these non-linear predictions, that assess stress, wear, and fatigue to demonstrate hydrostatic bearing integrity

  6. The Research of Tectonic Framework and the Fault Activity in Large Detachment Basin System on Northern Margin of South China Sea

    Science.gov (United States)

    Pan, L., Sr.; Ren, J.

    2017-12-01

    The South China Sea (SCS) is one of the largest marginal sea on southeast Asia continental margin, developed Paleogene extension-rifting continental margin system which is rare in the world and preserving many deformed characterizes of this kind system. With the investigation of the SCS, guiding by the development of tectonics and geo-physics, especially the development of tectonics and the high quality seismic data based on the development of geo-physics, people gradually accept that the northern margin of the SCS has some detachment basin characterizes. After researching the northern margin of the SCS, we come up with lithosphere profiles across the shelf, slope and deep sea basin in the northeast of the SCS to confirm the tectonic style of ocean-continental transition and the property of the detachment fault. Furthermore, we describe the outline of large detachment basins at northern SCS. Based on the large number of high-quality 2D and 3D deep seismic profile(TWT,10s), drilling and logging data, combined with domestic and international relevant researches, using basin dynamics and tectono-stratigraphy theory, techniques and methods of geology and geophysics, qualitative and quantitative, we describe the formation of the detachment basin and calculate the fault activity rate, stretching factor and settlement. According to the research, we propose that there is a giant and complete detachment basin system in the northern SCS and suggest three conclusions. First of all, the detachment basin system can be divided into three domains: proximal domain covering the Yangjiang Sag, Shenhu uplift and part of Shunde Sag, necking zone covering part of the Shunde Sag and Heshan Sag, distal domain covering most part of Heshan Sag. Second, the difference of the stretching factor is observed along the three domains of the detachment basin system. The factor of the proximal domain is the minimum among them. On the other side, the distal domain is the maximum among them. This

  7. HOT Faults", Fault Organization, and the Occurrence of the Largest Earthquakes

    Science.gov (United States)

    Carlson, J. M.; Hillers, G.; Archuleta, R. J.

    2006-12-01

    We apply the concept of "Highly Optimized Tolerance" (HOT) for the investigation of spatio-temporal seismicity evolution, in particular mechanisms associated with largest earthquakes. HOT provides a framework for investigating both qualitative and quantitative features of complex feedback systems that are far from equilibrium and punctuated by rare, catastrophic events. In HOT, robustness trade-offs lead to complexity and power laws in systems that are coupled to evolving environments. HOT was originally inspired by biology and engineering, where systems are internally very highly structured, through biological evolution or deliberate design, and perform in an optimum manner despite fluctuations in their surroundings. Though faults and fault systems are not designed in ways comparable to biological and engineered structures, feedback processes are responsible in a conceptually comparable way for the development, evolution and maintenance of younger fault structures and primary slip surfaces of mature faults, respectively. Hence, in geophysical applications the "optimization" approach is perhaps more aptly replaced by "organization", reflecting the distinction between HOT and random, disorganized configurations, and highlighting the importance of structured interdependencies that evolve via feedback among and between different spatial and temporal scales. Expressed in the terminology of the HOT concept, mature faults represent a configuration optimally organized for the release of strain energy; whereas immature, more heterogeneous fault networks represent intermittent, suboptimal systems that are regularized towards structural simplicity and the ability to generate large earthquakes more easily. We discuss fault structure and associated seismic response pattern within the HOT concept, and outline fundamental differences between this novel interpretation to more orthodox viewpoints like the criticality concept. The discussion is flanked by numerical simulations of a

  8. The effect of lateral variations of friction on crustal faulting

    Directory of Open Access Journals (Sweden)

    M. Cocco

    1994-06-01

    Full Text Available We propose that lateral variations in fault friction control the heterogeneity of slip observed in large earthquakes, We model these variations using a rate and state-dependent friction law, where we differentiate velocity-weakening into strong and weak-seismic fields, and velocity-strengthening into compliant and viscous fields. The strong-seismic field comprises the seismic slip concentrations, or asperities. The two «intermediate» frictional fields, weak-seismic and compliant, modulate both the tectonic loading and the dynamic rupture process. During the interseismic period, the compliant and viscous regions slip aseismically while the strong-seismic regions remain locked, evolving into stress concentrations that fail only in main shocks. The weak-seismic regions contain most of the interseismic activity and aftershocks, but also «creep seismically», that is, most of the weak-seismic area slips aseismically, actuating the seismicity on the remaining area. This «mixed» frictional behavior can be obtained from a sufficiently heterogenous distribution for the critical slip distance. The interseismic slip provides an inherent rupture resistance: dynamic rupture fronts decelerate as they penetrate into these unloaded compliant or creeping weak-seismic areas, diffusing into broad areas of accelerated afterslip. Aftershocks occur in both the weak-seismic and compliant areas around the fault, but most of the stress is diffused through aseismic slip. Rapid afterslip on these peripheral areas can also produce aftershocks within the main shock rupture area, by reloading weak fault areas that slipped in the main shock and then healed. We test this frictional model by comparing the interevent seismicity and aftershocks to the coseismic slip distribution for the 1966 Parkfield, 1979 Coyote Lake, and 1984 Morgan Hill earthquakes.

  9. The incorporation of fault zone head wave and direct wave secondary arrival times and arrival polarizations into seismic tomography: Application to the Parkfield, California area

    Science.gov (United States)

    Bennington, N. L.; Thurber, C. H.; Peng, Z.; Zhao, P.

    2012-12-01

    We present a 3D P-wave velocity (Vp) model of the Parkfield region that utilizes existing P-wave arrival time data, including fault zone head waves (FZHW), plus new data from direct wave secondary arrivals (DWSA). The first-arrival and DWSA travel times are obtained as the global and local minimum travel time paths, respectively. The inclusion of DWSA results in as much as a 10% increase in the across-fault velocity contrast for the Vp model at Parkfield relative to Thurber et al. (2006). Viewed along strike, three pronounced velocity contrast regions are observed: a pair of strong positive velocity contrasts (SW fast), one NW of the 1966 Parkfield hypocenter and the other SE of the 2004 Parkfield hypocenter, and a strong negative velocity contrast (NE fast) between the two hypocenters. The negative velocity contrast partially to entirely encompasses peak coseismic slip estimated in several slip models for the 2004 earthquake, suggesting that the negative velocity contrast played a part in defining the rupture patch of the 2004 Parkfield earthquake. We expand on this work by modifying our seismic tomography algorithm to incorporate arrival polarizations (azimuths). Synthetic tests will be presented to demonstrate the improvements in velocity structure when arrival polarizations are incorporated. These tests will compare the synthetic model recovered when FZHW/DWSA arrivals as well as existing P-wave arrival time data are inverted to that recovered with the same dataset with the inclusion of arrival polarizations. We plan to extend this work to carry out a full scale seismic tomography/relocation inversion at Parkfield, CA utilizing arrival polarizations from all first-P arrivals, and FZHW/DWSA arrivals as well as existing P-wave arrival time data. This effort requires the determination of polarization data for all P-waves and FZHW's at Parkfield. To this end, we use changes in the arrival azimuth from fault normal to source-receiver direction to identify FZHW and

  10. Fault Rupture Model of the 2016 Gyeongju, South Korea, Earthquake and Its Implication for the Underground Fault System

    Science.gov (United States)

    Uchide, Takahiko; Song, Seok Goo

    2018-03-01

    The 2016 Gyeongju earthquake (ML 5.8) was the largest instrumentally recorded inland event in South Korea. It occurred in the southeast of the Korean Peninsula and was preceded by a large ML 5.1 foreshock. The aftershock seismicity data indicate that these earthquakes occurred on two closely collocated parallel faults that are oblique to the surface trace of the Yangsan fault. We investigate the rupture properties of these earthquakes using finite-fault slip inversion analyses. The obtained models indicate that the ruptures propagated NNE-ward and SSW-ward for the main shock and the large foreshock, respectively. This indicates that these earthquakes occurred on right-step faults and were initiated around a fault jog. The stress drops were up to 62 and 43 MPa for the main shock and the largest foreshock, respectively. These high stress drops imply high strength excess, which may be overcome by the stress concentration around the fault jog.

  11. A methodology for fault diagnosis in large chemical processes and an application to a multistage flash desalination process: Part I

    International Nuclear Information System (INIS)

    Tarifa, Enrique E.; Scenna, Nicolas J.

    1998-01-01

    This work presents a new strategy for fault diagnosis in large chemical processes (E.E. Tarifa, Fault diagnosis in complex chemistries plants: plants of large dimensions and batch processes. Ph.D. thesis, Universidad Nacional del Litoral, Santa Fe, 1995). A special decomposition of the plant is made in sectors. Afterwards each sector is studied independently. These steps are carried out in the off-line mode. They produced vital information for the diagnosis system. This system works in the on-line mode and is based on a two-tier strategy. When a fault is produced, the upper level identifies the faulty sector. Then, the lower level carries out an in-depth study that focuses only on the critical sectors to identify the fault. The loss of information produced by the process partition may cause spurious diagnosis. This problem is overcome at the second level using qualitative simulation and fuzzy logic. In the second part of this work, the new methodology is tested to evaluate its performance in practical cases. A multiple stage flash desalination system (MSF) is chosen because it is a complex system, with many recycles and variables to be supervised. The steps for the knowledge base generation and all the blocks included in the diagnosis system are analyzed. Evaluation of the diagnosis performance is carried out using a rigorous dynamic simulator

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

    Science.gov (United States)

    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

  13. Seismic characterization of hydrates in faulted, fine-grained sediments of Krishna-Godavari basin: Unified imaging

    Digital Repository Service at National Institute of Oceanography (India)

    Jaiswal, P.; Dewangan, P.; Ramprasad, T.; Zelt, C.A.

    (Clennell et al., 1999). However, in basins affected by structural deformation, local fluid and heat flow, and spatially variable sedimentation, e.g., Gulf of Mexico (Ding et al., 2008) and Krishna-Godavari (Dewangan et al., 2011), the BSR profile may..., northern Gulf of Mexico: Part I. A seismic approach based on geologic model, inversion, and rock physics principles. Marine and Petroleum Geology 25, 830-844. Daigle, H., Dugan, B., 2011. Capillary controls on methane hydrate distribution and fracturing...

  14. Oceanographer transform fault structure compared to that of surrounding oceanic crust: Results from seismic refraction data analysis

    Science.gov (United States)

    Ambos, E. L.; Hussong, D. M.

    1986-02-01

    A high quality seismic refraction data set was collected near the intersection of the tranform portion of the Oceanographer Fracture Zone (OFZ) with the adjacent northern limb of the Mid-Atlantic Ridge spreading center (MAR). One seismic line was shot down the axis of the transform valley. Another was shot parallel to the spreading center, crossing from normal oceanic crust into the transform valley, and out again. This latter line was recorded by four Ocean Bottom Seismometers (OBSs) spaced along its length, providing complete reversed coverage over the crucial transform valley zone. Findings indicate that whereas the crust of the transform valley is only slightly thinner (4.5 km) compared to normal oceanic crust (5-8 km), the structure is different. Velocities in the range of 6.9 to 7.7. km/sec, which are characteristics of seismic layer 3B, are absent, although a substantial thickness (approximately 3 km) of 6.1-6.8 km/sec material does appear to be present. The upper crust, some 2 km in thickness, is characterized by a high velocity gradient (1.5 sec -1) in which veloxity increases from 2.7 km/sec at the seafloor to 5.8 km/sec at the base of the section. A centrally-located deep of the transform valley has thinner crust (1-2 km), whereas the crust gradually thickens past the transform valley-spreading center intersection. Analysis of the seismic line crossing sub-perpendicular to the transform valley demonstrates abrupt thinning of the upper crustal section, and thickening of the lower crust outside of the trasform valley. In addition, high-velocity material seems to occur under the valley flanks, particularly the southern flanking ridge. This ridge, which is on the side of the transform opposite to the intersection of spreading ridge and transform, may be an expression of uplifted, partially serpentinized upper mantle rocks.

  15. Seismicity, groundwater level variations and Earth tides in the Hronov-Poříčí Fault Zone, Czech Republic

    Czech Academy of Sciences Publication Activity Database

    Kolínský, Petr; Valenta, Jan; Gaždová, Renata

    2012-01-01

    Roč. 9, č. 2 (2012), s. 191-209 ISSN 1214-9705 R&D Projects: GA ČR GA205/09/1244 Institutional research plan: CEZ:AV0Z30460519 Keywords : Eastern Bohemian Massif * groundwater level * seismic ity Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 0.530, year: 2011 http://www.irsm.cas.cz/materialy/acta_content/2012_02/9_Kolinsky.pdf

  16. Seismic sequences in the Sombrero Seismic Zone

    Science.gov (United States)

    Pulliam, J.; Huerfano, V. A.; ten Brink, U.; von Hillebrandt, C.

    2007-05-01

    The northeastern Caribbean, in the vicinity of Puerto Rico and the Virgin Islands, has a long and well-documented history of devastating earthquakes and tsunamis, including major events in 1670, 1787, 1867, 1916, 1918, and 1943. Recently, seismicity has been concentrated to the north and west of the British Virgin Islands, in the region referred to as the Sombrero Seismic Zone by the Puerto Rico Seismic Network (PRSN). In the combined seismicity catalog maintained by the PRSN, several hundred small to moderate magnitude events can be found in this region prior to 2006. However, beginning in 2006 and continuing to the present, the rate of seismicity in the Sombrero suddenly increased, and a new locus of activity developed to the east of the previous location. Accurate estimates of seismic hazard, and the tsunamigenic potential of seismic events, depend on an accurate and comprehensive understanding of how strain is being accommodated in this corner region. Are faults locked and accumulating strain for release in a major event? Or is strain being released via slip over a diffuse system of faults? A careful analysis of seismicity patterns in the Sombrero region has the potential to both identify faults and modes of failure, provided the aggregation scheme is tuned to properly identify related events. To this end, we experimented with a scheme to identify seismic sequences based on physical and temporal proximity, under the assumptions that (a) events occur on related fault systems as stress is refocused by immediately previous events and (b) such 'stress waves' die out with time, so that two events that occur on the same system within a relatively short time window can be said to have a similar 'trigger' in ways that two nearby events that occurred years apart cannot. Patterns that emerge from the identification, temporal sequence, and refined locations of such sequences of events carry information about stress accommodation that is obscured by large clouds of

  17. Incorporating fault zone head wave and direct wave secondary arrival times into seismic tomography: Application at Parkfield, California

    Science.gov (United States)

    Bennington, Ninfa L.; Thurber, Clifford; Peng, Zhigang; Zhang, Haijiang;