Modeling fluid flow and heat transfer at Basin and Range faults: preliminary results for Leach hot springs, Nevada

USGS Publications Warehouse

López, Dina L.; Smith, Leslie; Storey, Michael L.; Nielson, Dennis L.

1994-01-01

The hydrothermal systems of the Basin and Range Province are often located at or near major range bounding normal faults. The flow of fluid and energy at these faults is affected by the advective transfer of heat and fluid from an to the adjacent mountain ranges and valleys, This paper addresses the effect of the exchange of fluid and energy between the country rock, the valley fill sediments, and the fault zone, on the fluid and heat flow regimes at the fault plane. For comparative purposes, the conditions simulated are patterned on Leach Hot Springs in southern Grass Valley, Nevada. Our simulations indicated that convection can exist at the fault plane even when the fault is exchanging significant heat and fluid with the surrounding country rock and valley fill sediments. The temperature at the base of the fault decreased with increasing permeability of the country rock. Higher groundwater discharge from the fault and lower temperatures at the base of the fault are favored by high country rock permabilities and fault transmissivities. Preliminary results suggest that basal temperatures and flow rates for Leach Hot Springs can not be simulated with a fault 3 km deep and an average regional heat flow of 150 mW/m2 because the basal temperature and mass discharge rates are too low. A fault permeable to greater depths or a higher regional heat flow may be indicated for these springs.

Paleoseismic study of the Cathedral Rapids fault in the northern Alaska Range near Tok, Alaska

NASA Astrophysics Data System (ADS)

Koehler, R. D.; Farrell, R.; Carver, G. A.

2010-12-01

The Cathedral Rapids fault extends ~40 km between the Tok and Robertson River valleys and is the easternmost fault in a series of active south-dipping imbricate thrust faults which bound the northern flank of the Alaska Range. Collectively, these faults accommodate a component of convergence transferred north of the Denali fault and related to the westward (counterclockwise) rotation of the Wrangell Block driven by relative Pacific/North American plate motion along the eastern Aleutian subduction zone and Fairweather fault system. To the west, the system has been defined as the Northern Foothills Fold and Thrust Belt (NFFTB), a 50-km-wide zone of east-west trending thrust faults that displace Quaternary deposits and have accommodated ~3 mm/yr of shortening since latest Pliocene time (Bemis, 2004). Over the last several years, the eastward extension of the NFFTB between Delta Junction and the Canadian border has been studied by the Alaska Division of Geological & Geophysical Surveys to better characterize faults that may affect engineering design of the proposed Alaska-Canada natural gas pipeline and other infrastructure. We summarize herein reconnaissance field observations along the western part of the Cathedral Rapids fault. The western part of the Cathedral Rapids fault extends 21 km from Sheep Creek to Moon Lake and is characterized by three roughly parallel sinuous traces that offset glacial deposits of the Illinoian to early Wisconsinan Delta glaciations and the late Wisconsinan Donnelly glaciation, as well as, Holocene alluvial deposits. The northern trace of the fault is characterized by an oversteepened, beveled, ~2.5-m-high scarp that obliquely cuts a Holocene alluvial fan and projects into the rangefront. Previous paleoseismic studies along the eastern part of the Cathedral Rapids fault and Dot “T” Johnson fault indicate multiple latest Pleistocene and Holocene earthquakes associated with anticlinal folding and thrust faulting (Carver et al., 2010

Geomorphic evidence for enhanced Pliocene-Quaternary faulting in the northwestern Basin and Range

USGS Publications Warehouse

Ellis, Magdalena A; Barnes Jason B,; Colgan, Joseph P.

2014-01-01

Mountains in the U.S. Basin and Range Province are similar in form, yet they have different histories of deformation and uplift. Unfortunately, chronicling fault slip with techniques like thermochronology and geodetics can still leave sizable, yet potentially important gaps at Pliocene–Quaternary (∼105–106 yr) time scales. Here, we combine existing geochronology with new geomorphic observations and approaches to investigate the Miocene to Quaternary slip history of active normal faults that are exhuming three footwall ranges in northwestern Nevada: the Pine Forest Range, the Jackson Mountains, and the Santa Rosa Range. We use the National Elevation Dataset (10 m) digital elevation model (DEM) to measure bedrock river profiles and hillslope gradients from these ranges. We observe a prominent suite of channel convexities (knickpoints) that segment the channels into upper reaches with low steepness (mean ksn = ∼182; θref = 0.51) and lower, fault-proximal reaches with high steepness (mean ksn = ∼361), with a concomitant increase in hillslope angles of ∼6°–9°. Geologic maps and field-based proxies for rock strength allow us to rule out static causes for the knickpoints and interpret them as transient features triggered by a drop in base level that created ∼20% of the existing relief (∼220 m of ∼1050 m total). We then constrain the timing of base-level change using paleochannel profile reconstructions, catchment-scale volumetric erosion fluxes, and a stream-power–based knickpoint celerity (migration) model. Low-temperature thermochronology data show that faulting began at ca. 11–12 Ma, yet our results estimate knickpoint initiation began in the last 5 Ma and possibly as recently as 0.1 Ma with reasonable migration rates of 0.5–2 mm/yr. We interpret the collective results to be evidence for enhanced Pliocene–Quaternary fault slip that may be related to tectonic reorganization in the American West, although we cannot rule out climate as a

Unusually low rates of slip on the Santa Rosa Range fault zone, northern Nevada

USGS Publications Warehouse

Personius, S.F.; Mahan, S.A.

2005-01-01

The Santa Rosa Range fault zone (SRRFZ) is one of the most topographically prominent normal fault systems in the northern Basin and Range province of the western United States. It has been assigned high rates of vertical slip by others and has been identified as a possible site of the future extension of the central Nevada seismic belt (CNSB). We use detailed trench mapping and luminescence dating to estimate displacements and timing of the last several large-magnitude paleoearthquakes on the southern part of the SRRFZ at a trench site near Orovada, Nevada. Coseismic vertical displacements ranged from 1 to 2.8 m for each of the last four events. Luminescence ages provide time limits for the last three events of 125-155 ka, 90-108 ka, and 11-16 ka. These data yield recurrence intervals of 17-65 k.y. and 74-97 k.y. and an elapsed time of 11-16 k.y. since the youngest event. Slip-rate determinations at the Orovada site are complicated by multiple fault strands, but rates calculated from a variety of data are surprisingly low (0.01-0.16 mm/yr), given the topographic prominence of the Santa Rosa Range. A lack of compelling patterns in a comparison of paleoseismic parameters indicate that the SRRFZ is no more likely a location for a large-magnitude earthquake than previously identified seismic gaps or along faults that lie directly north of the CNSB.

Fault geometry and cumulative offsets in the central Coast Ranges, California: Evidence for northward increasing slip along the San Gregorio-San Simeon-Hosgri fault

USGS Publications Warehouse

Langenheim, V.E.; Jachens, R.C.; Graymer, R.W.; Colgan, J.P.; Wentworth, C.M.; Stanley, R.G.

2012-01-01

Estimates of the dip, depth extent, and amount of cumulative displacement along the major faults in the central California Coast Ranges are controversial. We use detailed aeromagnetic data to estimate these parameters for the San Gregorio–San Simeon–Hosgri and other faults. The recently acquired aeromagnetic data provide an areally consistent data set that crosses the onshore-offshore transition without disruption, which is particularly important for the mostly offshore San Gregorio–San Simeon–Hosgri fault. Our modeling, constrained by exposed geology and in some cases, drill-hole and seismic-reflection data, indicates that the San Gregorio–San Simeon–Hosgri and Reliz-Rinconada faults dip steeply throughout the seismogenic crust. Deviations from steep dips may result from local fault interactions, transfer of slip between faults, or overprinting by transpression since the late Miocene. Given that such faults are consistent with predominantly strike-slip displacement, we correlate geophysical anomalies offset by these faults to estimate cumulative displacements. We find a northward increase in right-lateral displacement along the San Gregorio–San Simeon–Hosgri fault that is mimicked by Quaternary slip rates. Although overall slip rates have decreased over the lifetime of the fault, the pattern of slip has not changed. Northward increase in right-lateral displacement is balanced in part by slip added by faults, such as the Reliz-Rinconada, Oceanic–West Huasna, and (speculatively) Santa Ynez River faults to the east.

Crustal structure of the alaska range orogen and denali fault along the richardson highway

USGS Publications Warehouse

Fisher, M.A.; Pellerin, L.; Nokleberg, W.J.; Ratchkovski, N.A.; Glen, J.M.G.

2007-01-01

A suite of geophysical data obtained along the Richardson Highway crosses the eastern Alaska Range and Denali fault and reveals the crustal structure of the orogen. Strong seismic reflections from within the orogen north of the Denali fault dip as steeply as 25?? north and extend downward to depths between 20 and 25 km. These reflections reveal what is probably a shear zone that transects most of the crust and is part of a crustal-scale duplex structure that probably formed during the Late Cretaceous. These structures, however, appear to be relict because over the past 20 years, they have produced little or no seismicity despite the nearby Mw = 7.9 Denali fault earthquake that struck in 2002. The Denali fault is nonreflective, but we interpret modeled magnetotelluric (MT), gravity, and magnetic data to propose that the fault dips steeply to vertically. Modeling of MT data shows that aftershocks of the 2002 Denali fault earthquake occurred above a rock body that has low electrical resistivity (>10 ohm-m), which might signify the presence of fluids in the middle and lower crust. Copyright ?? 2007 The Geological Society of America.

Talc friction in the temperature range 25°–400 °C: relevance for fault-zone weakening

USGS Publications Warehouse

Moore, Diane E.; Lockner, David A.

2008-01-01

Talc has a temperature–pressure range of stability that extends from surficial to eclogite-facies conditions, making it of potential significance in a variety of faulting environments. Talc has been identified in exhumed subduction zone thrusts, in fault gouge collected from oceanic transform and detachment faults associated with rift systems, and recently in serpentinite from the central creeping section of the San Andreas fault. Typically, talc crystallized in the active fault zones as a result of the reaction of ultramafic rocks with silica-saturated hydrothermal fluids. This mode of formation of talc is a prime example of a fault-zone weakening process. Because of its velocity-strengthening behavior, talc may play a role in stabilizing slip at depth in subduction zones and in the creeping faults of central and northern California that are associated with ophiolitic rocks.

Rock Geochemistry and Mineralogy from Fault Zones and Polymetallic Fault Veins of the Central Front Range, Colorado

USGS Publications Warehouse

Caine, Jonathan S.; Bove, Dana J.

2010-01-01

During the 2004 to 2008 field seasons, approximately 200 hand samples of fault and polymetallic vein-related rocks were collected for geochemical and mineralogical analyses. The samples were collected by the U.S. Geological Survey as part of the Evolution of Brittle Structures Task under the Central Colorado Assessment Project (CCAP) of the Mineral Resources Program (http://minerals.cr.usgs.gov/projects/colorado_assessment/index.html). The purpose of this work has been to characterize the relation between epithermal, polymetallic mineral deposits, paleostress, and the geological structures that hosted fluid flow and localization of the deposits. The data in this report will be used to document and better understand the processes that control epithermal mineral-deposit formation by attempting to relate the geochemistry of the primary structures that hosted hydrothermal fluid flow to their heat and fluid sources. This includes processes from the scale of the structures themselves to the far field scale, inclusive of the intrusive bodies that have been thought to be the sources for the hydrothermal fluid flow. The data presented in this report are part of a larger assessment effort on public lands. The larger study area spans the region of the southern Rocky Mountains in Colorado from the Wyoming to New Mexico borders and from the eastern boundary of the Front Range to approximately the longitude of Vail and Leadville, Colorado. Although the study area has had an extensive history of geological mapping, the mapping has resulted in a number of hypotheses that are still in their infancy of being tested. For example, the proximity of polymetallic veins to intrusive bodies has been thought to reflect a genetic relation between the two features; however, this idea has not been well tested with geochemical indicators. Recent knowledge regarding the coupled nature of stress, strain, fluid flow, and geochemistry warrant new investigations and approaches to test a variety of

Late Pleistocene to Holocene paleoseismicity of the House Range fault from UAV photogrammetry and exposure-age dating

NASA Astrophysics Data System (ADS)

Niemi, N. A.; Stahl, T.; Andreini, J.; Wells, J.; Bunds, M. P.

2016-12-01

The western face of the House Range in Utah is one of the steepest normal fault-bounded blocks in the Basin and Range. In spite of this, clear evidence of recent faulting is limited to a single c. 10 km-long, 1-2 m high scarp at the surface. A drone-based photogrammetric DEM with <10 cm resolution reveals that the fault displaces transgressive Lake Bonneville (c. 20-18 ka) and Provo highstand shorelines (c. 17 cal. ka) by similar amounts, suggesting a single event displacement of c. 1.5 m. Elastic strain models that incorporate shoreline geometry are best-fit by a fault dip of 50-60° in the uppermost crust, whereas previous studies have noted that the fault becomes listric or is truncated by a low-angle fault at depth. Exposure-ages of surface clasts on undeformed alluvial fans suggest that regression from the Provo shoreline occurred rapidly and that the last surface-rupturing earthquake occurred during occupation of the Provo shoreline. This pattern is consistent with other areas in the Great Basin that observe enhanced seismic moment release and earthquake ruptures during late Pleistocene lake regression. We calculate a time-averaged slip rate of 0.1-0.2 mm/yr and minimum recurrence interval of 17 ka. This study highlights the utility of drone surveys and high-resolution geochronology in neotectonic studies and in defining paleoseismic fault parameters.

Study of Magnetic Fabrics across the Central Part of the Chimei Fault, the Coastal Range of Eastern Taiwan

NASA Astrophysics Data System (ADS)

Yeh, E. C.; Chu, Y. R.; Chou, Y. M.; Lee, T. Q.; Kuo, S. T.; Cai, Y. M.

2015-12-01

Taiwan is an ongoing collisional mountain belt located in the conjunction of two subduction-arc systems with opposite vergences between the Philippine Sea and Eurasian plates. The Coastal Range along the eastern Taiwan is the accreted Luzon arcs and surrounding basins onto the Eurasian crust. The Chimei fault, a typical lithology-contrast fault thrusting the Miocene volcanic Tuluanshan Formation over the Pleistocene sedimentary Paliwan Formation, is the only major reverse fault across the entire Coastal Range. To investigate the deformation pattern and strain history across the Chimei fault, we analyzed oriented samples of mudstone and volcanic rocks across the fault zone, fold zone, damage zone, and wall rocks along the Hsiukuluan River via anisotropy of magnetic susceptibility (AMS). AMS can be represented as a susceptibility ellipsoid with 3 principal directions and values (Kmax, Kint, Kmin) and therefore is well known as a tool of magnetic fabrics to study the deformation. Results of AMS across the central part of the Chimei fault show that the direction of Kmax changed from N-S orientation to sub-vertical and the orientation of Kmin switched from 270/70 to N-S orientation when samples were closed to the fault zone. At the same time, anisotropy was increasing and susceptibility ellipsoid changed from oblate to prolate in the fold zone back to oblate in the fault zone. Based on identification works of magnetic minerals, the major magnetic carrier is magnetite with pseudo-single domain. As a result, it strongly speculated when samples were approaching to the central part of Chimei fault, stress altered from sub-vertical sedimentary loading to horizontally N-S tectonic compression. Due to increasing deformation, oblate ellipsoids with strong anisotropy developed within the fault zone highlighted the strain history of the central part of the Chimei fault.

Geophysical characterization of Range-Front Faults, Snake Valley, Nevada

USGS Publications Warehouse

Asch, Theodore H.; Sweetkind, Donald S.

2010-01-01

In September 2009, the U.S. Geological Survey, in cooperation with the National Park Service, collected audiomagnetotelluric (AMT) data along two profiles on the eastern flank of the Snake Range near Great Basin National Park to refine understanding of the subsurface geology. Line 1 was collected along Baker Creek, was approximately 6.7-km long, and recorded subsurface geologic conditions to approximately 800-m deep. Line 2, collected farther to the southeast in the vicinity of Kious Spring, was 2.8-km long, and imaged to depths of approximately 600 m. The two AMT lines are similar in their electrical response and are interpreted to show generally similar subsurface geologic conditions. The geophysical response seen on both lines may be described by three general domains of electrical response: (1) a shallow (mostly less than 100-200-m deep) domain of highly variable resistivity, (2) a deep domain characterized by generally high resistivity that gradually declines eastward to lower resistivity with a steeply dipping grain or fabric, and (3) an eastern domain in which the resistivity character changes abruptly at all depths from that in the western domain. The shallow, highly variable domain is interpreted to be the result of a heterogeneous assemblage of Miocene conglomerate and incorporated megabreccia blocks overlying a shallowly eastward-dipping southern Snake Range detachment fault. The deep domain of generally higher resistivity is interpreted as Paleozoic sedimentary rocks (Pole Canyon limestone and Prospect Mountain Quartzite) and Mesozoic and Cenozoic plutonic rocks occurring beneath the detachment surface. The range of resistivity values within this deep domain may result from fracturing adjacent to the detachment, the presence of Paleozoic rock units of variable resistivities that do not crop out in the vicinity of the lines, or both. The eastern geophysical domain is interpreted to be a section of Miocene strata at depth, overlain by Quaternary alluvial

Geophysical investigation of the Denali fault and Alaska Range orogen within the aftershock zone of the October-November 2002, M = 7.9 Denali fault earthquake

USGS Publications Warehouse

Fisher, M.A.; Nokleberg, W.J.; Ratchkovski, N.A.; Pellerin, L.; Glen, J.M.; Brocher, T.M.; Booker, J.

2004-01-01

The aftershock zone of the 3 November 2002, M = 7.9 earthquake that ruptured along the right-slip Denali fault in south-central Alaska has been investigated by using gravity and magnetic, magnetotelluric, and deep-crustal, seismic reflection data as well as outcrop geology and earthquake seismology. Strong seismic reflections from within the Alaska Range orogen north of the Denali fault dip as steeply as 25°N and extend to depths as great as 20 km. These reflections outline a relict crustal architecture that in the past 20 yr has produced little seismicity. The Denali fault is nonreflective, probably because this fault dips steeply to vertical. The most intriguing finding from geophysical data is that earthquake aftershocks occurred above a rock body, with low electrical resistivity (>10 Ω·m), that is at depths below ∼10 km. Aftershocks of the Denali fault earthquake have mainly occurred shallower than 10 km. A high geothermal gradient may cause the shallow seismicity. Another possibility is that the low resistivity results from fluids, which could have played a role in locating the aftershock zone by reducing rock friction within the middle and lower crust.

Two-dimensional seismic image of the San Andreas Fault in the Northern Gabilan Range, central California: Evidence for fluids in the fault zone

USGS Publications Warehouse

Thurber, C.; Roecker, S.; Ellsworth, W.; Chen, Y.; Lutter, W.; Sessions, R.

1997-01-01

A joint inversion for two-dimensional P-wave velocity (Vp), P-to-S velocity ratio (Vp/Vs), and earthquake locations along the San Andreas fault (SAF) in central California reveals a complex relationship among seismicity, fault zone structure, and the surface fault trace. A zone of low Vp and high Vp/Vs lies beneath the SAF surface trace (SAFST), extending to a depth of about 6 km. Most of the seismic activity along the SAF occurs at depths of 3 to 7 km in a southwest-dipping zone that roughly intersects the SAFST, and lies near the southwest edge of the low Vp and high Vp/Vs zones. Tests indicate that models in which this seismic zone is significantly closer to vertical can be confidently rejected. A second high Vp/Vs zone extends to the northeast, apparently dipping beneath the Diablo Range. Another zone of seismicity underlies the northeast portion of this Vp/Vs high. The high Vp/Vs zones cut across areas of very different Vp values, indicating that the high Vp/Vs values are due to the presence of fluids, not just lithology. The close association between the zones of high Vp/Vs and seismicity suggests a direct involvement of fluids in the faulting process. Copyright 1997 by the American Geophysical Union.

Subsurface geometry of the San Andreas-Calaveras fault junction: influence of serpentinite and the Coast Range Ophiolite

USGS Publications Warehouse

Watt, Janet Tilden; Ponce, David A.; Graymer, Russell W.; Jachens, Robert C.; Simpson, Robert W.

2014-01-01

While an enormous amount of research has been focused on trying to understand the geologic history and neotectonics of the San Andreas-Calaveras fault (SAF-CF) junction, fundamental questions concerning fault geometry and mechanisms for slip transfer through the junction remain. We use potential-field, geologic, geodetic, and seismicity data to investigate the 3-D geologic framework of the SAF-CF junction and identify potential slip-transferring structures within the junction. Geophysical evidence suggests that the San Andreas and Calaveras fault zones dip away from each other within the northern portion of the junction, bounding a triangular-shaped wedge of crust in cross section. This wedge changes shape to the south as fault geometries change and fault activity shifts between fault strands, particularly along the Calaveras fault zone (CFZ). Potential-field modeling and relocated seismicity suggest that the Paicines and San Benito strands of the CFZ dip 65° to 70° NE and form the southwest boundary of a folded 1 to 3 km thick tabular body of Coast Range Ophiolite (CRO) within the Vallecitos syncline. We identify and characterize two steeply dipping, seismically active cross structures within the junction that are associated with serpentinite in the subsurface. The architecture of the SAF-CF junction presented in this study may help explain fault-normal motions currently observed in geodetic data and help constrain the seismic hazard. The abundance of serpentinite and related CRO in the subsurface is a significant discovery that not only helps constrain the geometry of structures but may also help explain fault behavior and the tectonic evolution of the SAF-CF junction.

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

USGS Publications Warehouse

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

2010-01-01

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

Syn-extensional lithogenetic sequences of the Soledad basin, central Transverse Ranges: Implications for detachment-fault models

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

Hendrix, E.D.

1993-04-01

The Soledad Basin (central Transverse Ranges, CA) contains the first recognized example of mid-Tertiary detachment-faulting west of the San Andreas fault. Displacements along the Pelona detachment fault and syn-extensional upper-plate sedimentation occurred between [approximately] 26--18 Ma, resulting in deposition of at least 4 separate lithogenetic sequences (LS) which record distinct phases of crustal response to extension. The 1st LS (lower Vasquez Fm.) predates syn-extensional volcanism and records initial basin subsidence along small, discontinuous faults. The 2nd LS (middle Vasquez Fm.) consists of both volcanic and sedimentary strata and signals simultaneous onset of magmatism and initial development of a well-defined networkmore » of high-angle, upper-plate normal faults, creating 2 separate sub-basins. Resulting alluvial fans were non-entrenched, implying that subsidence rates, and thus vertical displacement rates on high-angle faults, equaled or exceeded an estimated average sedimentation rate of 1.4 mm/yr. The 3rd LS (upper Vasquez Fm.) reflects transition to a single, well-integrated depositional basin characterized by streamflood sedimentation. This suggests an enlarged drainage basin and a decrease in subsidence rate relative to sedimentation rate, triggered possibly by uplift of the detachment lower-plate. The 4th LS (Tick Canyon Fm.) lies with angular unconformity above the 3rd LS and contains the 1st clasts eroded from the detachment lower plate. Detachment faulting in the Soledad basin appears to involve, in part, reactivation of structural zones of weakness along the Vincent thrust. Preliminary reconstructions of Soledad extension imply 25--30 km of displacement along the Pelona detachment fault system at an averaged slip rate of 3.6--4.3 mm/yr.« less

The Border Ranges fault system in Glacier Bay National Park, Alaska: Evidence for major early Cenozoic dextral strike-slip motion

USGS Publications Warehouse

Smart, K.J.; Pavlis, T.L.; Sisson, V.B.; Roeske, S.M.; Snee, L.W.

1996-01-01

The Border Ranges fault system of southern Alaska, the fundamental break between the arc basement and the forearc accretionary complex, is the boundary between the Peninsular-Alexander-Wrangellia terrane and the Chugach terrane. The fault system separates crystalline rocks of the Alexander terrane from metamorphic rocks of the Chugach terrane in Glacier Bay National Park. Mylonitic rocks in the zone record abundant evidence for dextral strike-slip motion along north-northwest-striking subvertical surfaces. Geochronologic data together with regional correlations of Chugach terrane rocks involved in the deformation constrain this movement between latest Cretaceous and Early Eocene (???50 Ma). These findings are in agreement with studies to the northwest and southeast along the Border Ranges fault system which show dextral strike-slip motion occurring between 58 and 50 Ma. Correlations between Glacier Bay plutons and rocks of similar ages elsewhere along the Border Ranges fault system suggest that as much as 700 km of dextral motion may have been accommodated by this structure. These observations are consistent with oblique convergence of the Kula plate during early Cenozoic and forearc slivering above an ancient subduction zone following late Mesozoic accretion of the Peninsular-Alexander-Wrangellia terrane to North America.

Highly focused asymmetric surface uplift and bedrock exhumation along the San Gregorio-Hosgri fault in the Santa Lucia range, central California

NASA Astrophysics Data System (ADS)

Steely, A.; Hourigan, J. K.; Mere, A.; Orme, D. A.; Ooms, J.; Gallagher, C.

2016-12-01

We use two new datasets to constrain the Late Cretaceous through modern history of vertical deformation in the Santa Lucia range of the central California coast to better understand the tectonic evolution of the plate boundary between the San Andreas fault and San Gregorio-Hosgri fault (SGHF). New data presented here include 46 apatite and 31 zircon (U-Th)/He ages and 1,200 elevation measurements of the first marine terrace (presumably the MIS 5a or 5e terrace) along 190 km of coastline. The San Gregorio-Hosgri fault (SGHF) initiated in the late Miocene and appears to have asymmetrically focused exhumation on its NE side. Apatite ages are 1.5-4 Ma directly NE of the fault in both crystalline and Franciscan bedrock, but 20-60 Ma older directly SW of the fault or >5 km NE of the fault; zircon ages reflect a similar pattern and are as young as 8 Ma directly NE of the fault. These data appear to show that bedrock exhumation has been highly focused in narrow fault slivers parallel and subparallel to the SGHF and has been sufficient to exhume apatite and zircon from below their partial retention zones. We suggest that this focusing may occur along pre-existing weak faults in crustal blocks with shallow (<10 km) underplated schist—a rheologic feature of the Salinian bedrock in the Santa Lucia range not found in the surrounding crustal blocks. Surveys of the lowest marine terrace south from Monterey and northwest from Santa Cruz show a similar asymmetric pattern of increasing elevation towards the SGHF. The terrace south of Monterey rises gently from 5 m to 20 m above MSL obliquely southward toward the fault. After crossing into one of the highly exhumed crustal blocks, the terrace rises sharply to over 84 m and then drops sharply after crossing the fault zone. Inferred uplift rates from the late Quaternary (0.7-1.1 mm/yr) are higher than those during the main late Miocene-Pliocene phase of activity on the SGHF ( 0.3 mm/yr). This is puzzling in light of the low rates of

White Sands Missile Range Main Cantonment and NASA Area Faults, New Mexico

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

Nash, Greg

This is a zipped ArcGIS shapefile containing faults mapped for the Tularosa Basin geothermal play fairway analysis project. The faults were interpolated from gravity and seismic (NASA area) data, and from geomorphic features on aerial photography. Field work was also done for validation of faults which had surface expressions.

Geophysical data reveal the crustal structure of the Alaska Range orogen within the aftershock zone of the Mw 7.9 Denali fault earthquake

USGS Publications Warehouse

Fisher, M.A.; Ratchkovski, N.A.; Nokleberg, W.J.; Pellerin, L.; Glen, J.M.G.

2004-01-01

Geophysical information, including deep-crustal seismic reflection, magnetotelluric (MT), gravity, and magnetic data, cross the aftershock zone of the 3 November 2002 Mw 7.9 Denali fault earthquake. These data and aftershock seismicity, jointly interpreted, reveal the crustal structure of the right-lateral-slip Denali fault and the eastern Alaska Range orogen, as well as the relationship between this structure and seismicity. North of the Denali fault, strong seismic reflections from within the Alaska Range orogen show features that dip as steeply as 25?? north and extend downward to depths between 20 and 25 km. These reflections reveal crustal structures, probably ductile shear zones, that most likely formed during the Late Cretaceous, but these structures appear to be inactive, having produced little seismicity during the past 20 years. Furthermore, seismic reflections mainly dip north, whereas alignments in aftershock hypocenters dip south. The Denali fault is nonreflective, but modeling of MT, gravity, and magnetic data suggests that the Denali fault dips steeply to vertically. However, in an alternative structural model, the Denali fault is defined by one of the reflection bands that dips to the north and flattens into the middle crust of the Alaska Range orogen. Modeling of MT data indicates a rock body, having low electrical resistivity (>10 ??-m), that lies mainly at depths greater than 10 km, directly beneath aftershocks of the Denali fault earthquake. The maximum depth of aftershocks along the Denali fault is 10 km. This shallow depth may arise from a higher-than-normal geothermal gradient. Alternatively, the low electrical resistivity of deep rocks along the Denali fault may be associated with fluids that have weakened the lower crust and helped determine the depth extent of the after-shock zone.

Basin geometry and cumulative offsets in the Eastern Transverse Ranges, southern California: Implications for transrotational deformation along the San Andreas fault system

USGS Publications Warehouse

Langenheim, V.E.; Powell, R.E.

2009-01-01

The Eastern Transverse Ranges, adjacent to and southeast of the big left bend of the San Andreas fault, southern California, form a crustal block that has rotated clockwise in response to dextral shear within the San Andreas system. Previous studies have indicated a discrepancy between the measured magnitudes of left slip on through-going east-striking fault zones of the Eastern Transverse Ranges and those predicted by simple geometric models using paleomagnetically determined clockwise rotations of basalts distributed along the faults. To assess the magnitude and source of this discrepancy, we apply new gravity and magnetic data in combination with geologic data to better constrain cumulative fault offsets and to define basin structure for the block between the Pinto Mountain and Chiriaco fault zones. Estimates of offset from using the length of pull-apart basins developed within left-stepping strands of the sinistral faults are consistent with those derived by matching offset magnetic anomalies and bedrock patterns, indicating a cumulative offset of at most ???40 km. The upper limit of displacements constrained by the geophysical and geologic data overlaps with the lower limit of those predicted at the 95% confidence level by models of conservative slip located on margins of rigid rotating blocks and the clockwise rotation of the paleomagnetic vectors. Any discrepancy is likely resolved by internal deformation within the blocks, such as intense deformation adjacent to the San Andreas fault (that can account for the absence of basins there as predicted by rigid-block models) and linkage via subsidiary faults between the main faults. ?? 2009 Geological Society of America.

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

NASA Astrophysics Data System (ADS)

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

2017-12-01

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

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

USGS Publications Warehouse

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

2004-01-01

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

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

USGS Publications Warehouse

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

2010-01-01

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

Cenozoic volcanic geology and probable age of inception of basin-range faulting in the southeasternmost Chocolate Mountains, California

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

Crowe, B.M.

1978-02-01

A complex sequence of Oligocene-age volcanic and volcaniclastic rocks form a major volcanic center in the Picacho area of the southeasternmost Chocolate Mountains, Imperial County, California. Basal-volcanic rocks consist of lava flows and flow breccia of trachybasalt, pyroxene rhyodacite, and pyroxene dacite (32 My old). These volcanic rocks locally overlie fanglomerate and rest unconformably on pre-Cenozoic basement rocks. South and southeast of a prominent arcuate fault zone in the central part of the area, the rhyolite ignimbrite (26 My old) forms a major ash-flow sheet. In the southwestern part of the Picacho area the rhyolite ignimbrite interfingers with and ismore » overlain by dacite flows and laharic breccia. The rhyolite ignimbrite and the dacite of Picacho Peak are overlapped by lava flows and breccia of pyroxene andesite (25 My old) that locally rest on pre-Cenozoic basement rocks. The volcanic rocks of the Picacho area form a slightly bimodal volcanic suite consisting chiefly of silicic volcanic rocks with subordinate andesite. Late Miocene augite-olivine basalt is most similar in major-element abundances to transitional alkali-olivine basalt of the Basin and Range province. Normal separation faults in the Picacho area trend northwest and north parallel to major linear mountain ranges in the region. The areal distribution of the 26-My-old rhyolite ignimbrite and the local presence of megabreccia and fanglomerate flanking probable paleohighs suggest that the ignimbrite was erupted over irregular topography controlled by northwest- and north-trending probable basin-range faults. These relations date the inception of faulting in southeasternmost California at pre-26 and probably pre-32 My ago. A transition of basaltic volcanism in the area is dated at 13 My ago. 9 figures, 2 tables.« less

Cenozoic structural inversion from transtension to transpression in Yingxiong Range, western Qaidam Basin: New insights into strike-slip superimposition controlled by Altyn Tagh and Eastern Kunlun Faults

NASA Astrophysics Data System (ADS)

Cheng, Xiang; Zhang, Daowei; Jolivet, Marc; Yu, Xiangjiang; Du, Wei; Liu, Runchao; Guo, Zhaojie

2018-01-01

A Cenozoic structural inversion event from transtension to transpression involving salt tectonics has been uncovered in the Yingxiong Range, the western Qaidam Basin. Seismic reflection data show that there are two common structural styles in the Yingxiong Range: (1) the positive flower structure; (2) the thrust-controlled fold at shallow depth and the positive inverted flower structure at deep levels, which are separated by a salt layer in the upper Xiaganchaigou Formation. The Yingxiong Range experienced a first stage of transtension in the Eocene, induced by the Altyn Tagh Fault, and a second stage of transpression from the early Miocene to present, jointly controlled by the Altyn Tagh and Eastern Kunlun Faults. The Eocene transtension produced numerous NW-striking right-stepping en-échelon transtensional normal faults or fractures in the Yingxiong Range. At the same time, evaporites and mudstone were deposited in the vicinity of these faults. In the early Miocene, the Eocene transtensional normal faults were reactivated in a reverse sense, and the thrust-controlled folds at shallow depth started to form simultaneously. With transpression enhanced in the late Cenozoic, positive flower structures directly formed in places without evaporites. The Cenozoic transtension to transpression inversion of the Yingxiong Range is the result of strike-slip superimposition controlled by the Altyn Tagh and Eastern Kunlun Faults in time and space.

Kinematics of wrench and divergent-wrench deformation along a central part of the Border Ranges Fault System, Northern Chugach Mountains, Alaska

NASA Astrophysics Data System (ADS)

Little, Timothy A.

1990-08-01

The Border Ranges fault system (BRFS) bounds the inboard edge of the subduction-accretion complex of southern Alaska. In Eocene time a central segment of this fault system was reactivated as a zone of dextral wrench- and oblique-slip faulting having a cumulative strike-slip offset of at least several tens of kilometers, but probably less than 100 km. Early wrench folds are upright, trend at less than 45° to the strike of adjacent faults and developed with fold axes oriented subparallel to the axis of maximum incremental stretch λ1. These en echelon folds rotated and tightened with progressive deformation and then were overprinted by younger wrench folds that trend at about 60° to adjacent throughgoing faults. The latter folds are interpreted as forming during a late increment of distributed wrench deformation within the BRFS that included a component of extension (divergence) orthogonal to the mean strike of the fault system. A sharp releasing bend in exposures of a strike-slip fault originally at >4 km depth today coincides with a narrow pull-apart graben bounded by oblique-normal faults that dip toward the basin. Widening of this pull-apart graben by brittle faulting and dike intrusion accommodated less than 2 km of strike-slip and was a late-stage phenomenon, possibly occurring at supracrustal levels. Prior to formation of this graben during a period of predominantly ductile deformation at deeper structural levels, wrench-folded rocks on one side of the nonplanar fault were translated around the releasing bend without significant faulting or loss of coherence. Kinematically, the earlier deformation was accomplished by fault-bend folding and rotation of a relatively deformable block as it passed through a system of upright megakinks. Such a ductile mechanism of fault block translation around a strike-slip bend may be typical of intermediate levels of the crust beneath pull-apart grabens and may be transitional downward into heterogeneous laminar flow occuring

Earthquake epicenters and fault intersections in central and southern California

NASA Technical Reports Server (NTRS)

Abdel-Gawad, M. (Principal Investigator); Silverstein, J.

1972-01-01

The author has identifed the following significant results. ERTS-1 imagery provided evidence for the existence of short transverse fault segments lodged between faults of the San Andreas system in the Coast Ranges, California. They indicate that an early episode of transverse shear has affected the Coast Ranges prior to the establishment of the present San Andreas fault. The fault has been offset by transverse faults of the Transverse Ranges. It appears feasible to identify from ERTS-1 imagery geomorphic criteria of recent fault movements. Plots of historic earthquakes in the Coast Ranges and western Transverse Ranges show clusters in areas where structures are complicated by interaction of tow active fault systems. A fault lineament apparently not previously mapped was identified in the Uinta Mountains, Utah. Part of the lineament show evidence of recent faulting which corresponds to a moderate earthquake cluster.

Meteoric water circulation and rolling-hinge detachment faulting: Example of the Northern Snake Range core complex, Nevada

NASA Astrophysics Data System (ADS)

Gébelin, Aude; Teyssier, Christian; Heizler, Matthew T.; Andreas, Mulch

2014-05-01

The Northern Snake Range metamorphic core complex developed as a consequence of Oligo-Miocene extension of the Basin and Range Province and is bounded by an arched detachment that separates the cold, brittle upper crust from the ductile middle crust. On the western and eastern limbs of the arch, the detachment footwall displays continuous sections of muscovite-bearing quartzite and schist from which we report new microfabrics, δD values, and 40Ar/39Ar ages. Results indicate that the two limbs record distinct stages of the metamorphic and kinematic Cenozoic events, including Eocene collapse of previously overthickned crust in the west, and one main Oligo-Miocene extensional event in the east. Quartzite from the western part of the range preserves Eocene fabrics (~49-45 Ma) that developed during coaxial deformation in the presence of metamorphic fluids. In contrast, those from the east reveal a large component of non coaxial strain, Oligo-Miocene ages (27-21 Ma) and contain recrystallized muscovite grains indicating that meteoric fluids sourced at high elevation (low-δD) infiltrated the brittle-ductile transition zone during deformation. Percolation of meteoric fluids down to the mylonitic detachment footwall was made possible by the development of an east-dipping rolling-hinge detachment system that controlled the timing and location of active faulting in the brittle upper crust and therefore the pathway of fluids from the surface to the brittle-ductile transition. Oligo-Miocene upper crustal extension was accommodated by a fan-shaped fault pattern that generated shear and tension fractures and channelized surface fluids, while top-to-the-east ductile shearing and advection of hot material in the lower plate allowed the system to be progressively exhumed. As extension proceeded, brittle normal faults active in the wedge of the hanging wall gradually rotated and translated above the detachment fault where, became inactive and precluded the circulation of fluids

Complex Paleotopography and Faulting near the Elsinore Fault, Coyote Mountains, southern California

NASA Astrophysics Data System (ADS)

Brenneman, M. J.; Bykerk-Kauffman, A.

2012-12-01

The Coyote Mountains of southern California are bounded on the southwest by the Elsinore Fault, an active dextral fault within the San Andreas Fault zone. According to Axen and Fletcher (1998) and Dorsey and others (2011), rocks exposed in these mountains comprise a portion of the hanging wall of the east-vergent Salton Detachment Fault, which was active from the late Miocene-early Pliocene to Ca. 1.1-1.3 Ma. Detachment faulting was accompanied by subsidence, resulting in deposition of a thick sequence of marine and nonmarine sedimentary rocks. Regional detachment faulting and subsidence ceased with the inception of the Elsinore Fault, which has induced uplift of the Coyote Mountains. Detailed geologic mapping in the central Coyote Mountains supports the above interpretation and adds some intriguing details. New discoveries include a buttress unconformity at the base of the Miocene/Pliocene section that locally cuts across strata at an angle so high that it could be misinterpreted as a fault. We thus conclude that the syn-extension strata were deposited on a surface with very rugged topography. We also discovered that locally-derived nonmarine gravel deposits exposed near the crest of the range, previously interpreted as part of the Miocene Split Mountain Group by Winker and Kidwell (1996), unconformably overlie units of the marine Miocene/Pliocene Imperial Group and must therefore be Pliocene or younger. The presence of such young gravel deposits on the crest of the range provides evidence for its rapid uplift. Additional new discoveries flesh out details of the structural history of the range. We mapped just two normal faults, both of which were relatively minor, thus supporting Axen and Fletcher's assertion that the hanging wall block of the Salton Detachment Fault had not undergone significant internal deformation during extension. We found abundant complex synthetic and antithetic strike-slip faults throughout the area, some of which offset Quaternary alluvial

Clustering of velocities in a GPS network spanning the Sierra Nevada Block, the Northern Walker Lane Belt, and the Central Nevada Seismic Belt, California-Nevada

NASA Astrophysics Data System (ADS)

Savage, J. C.; Simpson, R. W.

2013-09-01

The deformation across the Sierra Nevada Block, the Walker Lane Belt, and the Central Nevada Seismic Belt (CNSB) between 38.5°N and 40.5°N has been analyzed by clustering GPS velocities to identify coherent blocks. Cluster analysis determines the number of clusters required and assigns the GPS stations to the proper clusters. The clusters are shown on a fault map by symbols located at the positions of the GPS stations, each symbol representing the cluster to which the velocity of that GPS station belongs. Fault systems that separate the clusters are readily identified on such a map. Four significant clusters are identified. Those clusters are strips separated by (from west to east) the Mohawk Valley-Genoa fault system, the Pyramid Lake-Wassuk fault system, and the Central Nevada Seismic Belt. The strain rates within the westernmost three clusters approximate simple right-lateral shear (~13 nstrain/a) across vertical planes roughly parallel to the cluster boundaries. Clustering does not recognize the longitudinal segmentation of the Walker Lane Belt into domains dominated by either northwesterly trending, right-lateral faults or northeasterly trending, left-lateral faults.

Clustering of velocities in a GPS network spanning the Sierra Nevada Block, the northern Walker Lane Belt, and the Central Nevada Seismic Belt, California-Nevada

USGS Publications Warehouse

Savage, James C.; Simpson, Robert W.

2013-01-01

The deformation across the Sierra Nevada Block, the Walker Lane Belt, and the Central Nevada Seismic Belt (CNSB) between 38.5°N and 40.5°N has been analyzed by clustering GPS velocities to identify coherent blocks. Cluster analysis determines the number of clusters required and assigns the GPS stations to the proper clusters. The clusters are shown on a fault map by symbols located at the positions of the GPS stations, each symbol representing the cluster to which the velocity of that GPS station belongs. Fault systems that separate the clusters are readily identified on such a map. Four significant clusters are identified. Those clusters are strips separated by (from west to east) the Mohawk Valley-Genoa fault system, the Pyramid Lake-Wassuk fault system, and the Central Nevada Seismic Belt. The strain rates within the westernmost three clusters approximate simple right-lateral shear (~13 nstrain/a) across vertical planes roughly parallel to the cluster boundaries. Clustering does not recognize the longitudinal segmentation of the Walker Lane Belt into domains dominated by either northwesterly trending, right-lateral faults or northeasterly trending, left-lateral faults.

Geologic strip map along the Hines Creek Fault showing evidence for Cenozoic displacement in the western Mount Hayes and northeastern Healy quadrangles, eastern Alaska Range, Alaska

USGS Publications Warehouse

Nokleberg, Warren J.; Aleinikoff, John N.; Bundtzen, Thomas K.; Hanshaw, Maiana N.

2013-01-01

Geologic mapping of the Hines Creek Fault and the adjacent Trident Glacier and McGinnis Glacier Faults to the north in the eastern Alaska Range, Alaska, reveals that these faults were active during the Cenozoic. Previously, the Hines Creek Fault, which is considered to be part of the strike-slip Denali Fault system (Ridgway and others, 2002; Nokleberg and Richter, 2007), was interpreted to have been welded shut during the intrusion of the Upper Cretaceous Buchanan Creek pluton (Wahrhaftig and others, 1975; Gilbert, 1977; Sherwood and Craddock, 1979; Csejtey and others, 1992). Our geologic mapping along the west- to west-northwest-striking Hines Creek Fault in the northeastern Healy quadrangle and central to northwestern Mount Hayes quadrangle reveals that (1) the Buchanan Creek pluton is truncated by the Hines Creek Fault and (2) a tectonic collage of fault-bounded slices of various granitic plutons, metagabbro, metabasalt, and sedimentary rock of the Pingston terrane occurs south of the Hines Creek Fault.

Regional Tectonic Control of Tertiary Mineralization and Recent Faulting in the Southern Basin-Range Province, an Application of ERTS-1 Data

NASA Technical Reports Server (NTRS)

Bechtold, I. C.; Liggett, M. A.; Childs, J. F.

1973-01-01

Research based on ERTS-1 MSS imagery and field work in the southern Basin-Range Province of California, Nevada and Arizona has shown regional tectonic control of volcanism, plutonism, mineralization and faulting. This paper covers an area centered on the Colorado River between 34 15' N and 36 45' N. During the mid-Tertiary, the area was the site of plutonism and genetically related volcanism fed by fissure systems now exposed as dike swarms. Dikes, elongate plutons, and coeval normal faults trend generally northward and are believed to have resulted from east-west crustal extension. In the extensional province, gold silver mineralization is closely related to Tertiary igneous activity. Similarities in ore, structural setting, and rock types define a metallogenic district of high potential for exploration. The ERTS imagery also provides a basis for regional inventory of small faults which cut alluvium. This capability for efficient regional surveys of Recent faulting should be considered in land use planning, geologic hazards study, civil engineering and hydrology.

Influence of fault trend, fault bends, and fault convergence on shallow structure, geomorphology, and hazards, Hosgri strike-slip fault, offshore central California

NASA Astrophysics Data System (ADS)

Johnson, S. Y.; Watt, J. T.; Hartwell, S. R.

2012-12-01

dies out northward where we propose that its slip transfers to active structures in the Piedras Blancas fold belt. Given the continuity of the Hosgri Fault Zone through our study area, earthquake hazard assessments should incorporate a minimum rupture length of 110 km. Our data do not constrain lateral slip rates on the Hosgri, which probably vary along the fault (both to the north and south) as different structures converge and diverge but are likely in the geodetically estimated range of 2 to 4 mm/yr. More focused mapping of lowstand geomorphic features (e.g., channels, paleoshorelines) has the potential to provide better constraints. The post-Last-Glacial Maximum unconformity is an important surface for constraining vertical deformation, yielding local fault offset rates that may be as high as 1.4 mm/yr and off-fault deformation rates as high as 0.5 mm/yr. These vertical rates are short-term and not sustainable over longer geologic time, emphasizing the complex evolution and dynamics of strike-slip zones.

Frictional properties of low-angle normal fault gouges and implications for low-angle normal fault slip

NASA Astrophysics Data System (ADS)

Haines, Samuel; Marone, Chris; Saffer, Demian

2014-12-01

The mechanics of slip on low-angle normal faults (LANFs) remain an enduring problem in structural geology and fault mechanics. In most cases, new faults should form rather than having slip occur on LANFs, assuming values of fault friction consistent with Byerlee's Law. We present results of laboratory measurements on the frictional properties of natural clay-rich gouges from low-angle normal faults (LANF) in the American Cordillera, from the Whipple Mts. Detachment, the Panamint range-front detachment, and the Waterman Hills detachment. These clay-rich gouges are dominated by neoformed clay minerals and are an integral part of fault zones in many LANFs, yet their frictional properties under in situ conditions remain relatively unknown. We conducted measurements under saturated and controlled pore pressure conditions at effective normal stresses ranging from 20 to 60 MPa (corresponding to depths of 0.9-2.9 km), on both powdered and intact wafers of fault rock. For the Whipple Mountains detachment, friction coefficient (μ) varies depending on clast content, with values ranging from 0.40 to 0.58 for clast-rich material, and 0.29-0.30 for clay-rich gouge. Samples from the Panamint range-front detachment were clay-rich, and exhibit friction values of 0.28 to 0.38, significantly lower than reported from previous studies on fault gouges tested under room humidity (nominally dry) conditions, including samples from the same exposure. Samples from the Waterman Hills detachment are slightly stronger, with μ ranging from 0.38 to 0.43. The neoformed gouge materials from all three localities exhibits velocity-strengthening frictional behavior under almost all of the experimental conditions we explored, with values of the friction rate parameter (a - b) ranging from -0.001 to +0.025. Clast-rich samples exhibited frictional healing (strength increases with hold time), whereas clay-rich samples do not. Our results indicate that where clay-rich neoformed gouges are present along

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

NASA Astrophysics Data System (ADS)

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

2017-04-01

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

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

NASA Technical Reports Server (NTRS)

Borgia, Andrea; Burr, Jeremiah; Montero, Walter; Morales, Luis Diego; Alvarado, Guillermo E.

1990-01-01

Maps are presented that describe the compressional tectonic structures found at the base of the Central Costa Rica volcanic range (CCRVR), which comprise thrust faults and related fault propagation folds, only partly covered by syntectonic and posttectonic volcanoclastic deposits. Evidence is presented that these structures formed by gravitational failure and lumping of the flanks of the volcanic range. It is suggested that similar structures may be found at the toe of the southern flank of Kilauea volcano, Hawaii, and along the perimeter scarp of the Olympus Mons volcano on Mars.

Earth Observation

NASA Image and Video Library

2012-07-29

ISS032-E-010487 (29 July 2012) --- Walker Lake, Nevada is featured in this image photographed by an Expedition 32 crew member on the International Space Station. According to scientists, the Pleistocene landscape of western Nevada approximately 15,000 years ago was one of narrow mountain ranges and numerous interconnected lakes that together formed the extensive glacial Lake Lahontan. Scientists believe drying and warming of the regional climate since the last Ice Age led to the disappearance of the glaciers feeding meltwater to Lake Lahontan, and eventual disappearance of the lake itself. Today, few remnants of Lahontan remain; most of its arms have become dry enclosed basins known as playas. This photograph highlights Walker Lake, one of only two remnant lakes that contain water throughout the year (Pyramid Lake in Nevada is the other). The lake is located in an enclosed basin bounded by the Wassuk Range to the west and the Gillis Range to the east. It is fed by the Walker River flowing from the north. The current dimensions of the lake are approximately 21 kilometers north-south by 9 kilometers east-west. Shoreline deposits at higher elevations than the current lake level form concentric bands that are just visible in the image (bottom center) ? these record varying lake levels in the geologic past. The nearest town is Hawthorne, Nevada to the southeast. To the southwest the highest peak of the Wassuk Range, Mount Grant (elevation 3,496 meters above sea level), dominates the skyline. Green agricultural fields, primarily alfalfa, located to the west of the Wassuk Range (lower right) provide a striking contrast to the surrounding Great Basin desert. These fields are irrigated using water from the nearby East Fork of the Walker River (right, just visible alongside the fields).

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

NASA Astrophysics Data System (ADS)

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 <0.66 mm/year since 15 ka BP. We deem the LRF is an unsegmented active fault. Although the possibility of missing events in Late Pleistocene can not be dismissed, we argue the Holocene paleoearthquake history is complete, indicating an average recurrence interval of 2500 years.

Fault rocks as indicators of slip behavior

NASA Astrophysics Data System (ADS)

Hayman, N. W.

2017-12-01

Forty years ago, Sibson ("Fault rocks and fault mechanisms", J. Geol. Soc. Lon., 1977) explored plastic flow mechanisms in the upper and lower crust which he attributed to deformation rates faster than tectonic ones, but slower than earthquakes. We can now combine observations of natural fault rocks with insights from experiments to interpret a broad range of length and time scales of fault slip in more detail. Fault rocks are generally weak, with predominantly frictionally stable materials in some fault segments, and more unstable materials in others. Both upper and lower crustal faults contain veins and mineralogical signatures of transiently elevated fluid pressure, and some contain relicts of pseudotachylite and bear other thermal-mechanical signatures of seismic slip. Varying strain rates and episodic-tremor-and-slip (ETS) have been attributed to fault zones with varying widths filled with irregular foliations, veins, and dismembered blocks of varying sizes. Particle-size distributions and orientations in gouge appear to differ between locked and creeping faults. These and other geologic observations can be framed in terms of constitutive behaviors derived from experiments and modeling. The experimental correlation of velocity-dependence with microstructure and the behavior of natural fault-rocks under shear suggest that friction laws may be applied liberally to fault-zone interpretation. Force-chains imaged in stress-sensitive granular aggregates or in numerical simulations show that stick-slip behavior with stress drops far below that of earthquakes can occur during quasi-periodic creep, yet localize shear in larger, aperiodic events; perhaps the systematic relationship between sub-mm shear bands and surrounding gouge and/or cataclasites causes such slip partitioning in nature. Fracture, frictional sliding, and viscous creep can experimentally produce a range of slip behavior, including ETS-like events. Perhaps a similar mechanism occurs to cause ETS at the

Paleomagnetic, structural, and seismological evidence for oblique-slip deformation in fault-related folds in the Rocky Mountain Foreland, Colorado Plateau, and central Coast Ranges

NASA Astrophysics Data System (ADS)

Tetreault, Joya Liana

The two geologic questions I address in this research are: do fault-related folds accommodate oblique-slip shortening, and how is oblique-slip deformation absorbed within the folded strata? If the strata is deforming as a strike-slip shear zone, then we should be able to observe material rotations produced by strike-slip shear by measuring paleomagnetic vertical-axis rotations. I have approached these problems by applying paleomagnetic vertical-axis rotations, minor fault analyses, and focal mechanism strain inversions to identify evidence of strike-slip shear and to quantify oblique-slip deformation within fault-related folds in the Rocky Mountain Foreland, Colorado Plateau, and the central Coast Ranges. Clockwise paleomagnetic vertical-axis rotations and compressive paleostress rotations of 15-40º in the forelimb of the Grayback Monocline, northeastern Front Range Colorado, indicate that this Laramide fold is absorbing right-lateral shear from a N90E regional shortening direction. This work shows that paleomagnetic vertical-axis rotations in folded strata can be used to identify strike-slip motion on an underlying fault, and that oblique-slip deformation is localized in the forelimb of the fold. I applied the same paleomagnetic methods to identify oblique-slip on the underlying faults of the Nacimiento, East Kaibab, San Rafael, and Grand Hogback monoclines of the Colorado Plateau. The absence of paleomagnetic rotations and structural evidence for small displacements at the Nacimiento and East Kaibab monoclines indicate minor (<1km) right-lateral slip is being accommodated in these folds. Paleomagnetic vertical-axis rotations are found in the forelimbs of the San Rafael and Grand Hogback monoclines, yielding strike-slip displacements of ˜5km within these two folds. These results are consistent with a northeast Laramide compressive stress direction. In the Coalinga anticline, central Coast Ranges, California, clockwise paleomagnetic rotations and an 8º

Evolving geometrical heterogeneities of fault trace data

NASA Astrophysics Data System (ADS)

Wechsler, Neta; Ben-Zion, Yehuda; Christofferson, Shari

2010-08-01

We perform a systematic comparative analysis of geometrical fault zone heterogeneities using derived measures from digitized fault maps that are not very sensitive to mapping resolution. We employ the digital GIS map of California faults (version 2.0) and analyse the surface traces of active strike-slip fault zones with evidence of Quaternary and historic movements. Each fault zone is broken into segments that are defined as a continuous length of fault bounded by changes of angle larger than 1°. Measurements of the orientations and lengths of fault zone segments are used to calculate the mean direction and misalignment of each fault zone from the local plate motion direction, and to define several quantities that represent the fault zone disorder. These include circular standard deviation and circular standard error of segments, orientation of long and short segments with respect to the mean direction, and normal separation distances of fault segments. We examine the correlations between various calculated parameters of fault zone disorder and the following three potential controlling variables: cumulative slip, slip rate and fault zone misalignment from the plate motion direction. The analysis indicates that the circular standard deviation and circular standard error of segments decrease overall with increasing cumulative slip and increasing slip rate of the fault zones. The results imply that the circular standard deviation and error, quantifying the range or dispersion in the data, provide effective measures of the fault zone disorder, and that the cumulative slip and slip rate (or more generally slip rate normalized by healing rate) represent the fault zone maturity. The fault zone misalignment from plate motion direction does not seem to play a major role in controlling the fault trace heterogeneities. The frequency-size statistics of fault segment lengths can be fitted well by an exponential function over the entire range of observations.

Heterogeneity in the Fault Damage Zone: a Field Study on the Borrego Fault, B.C., Mexico

NASA Astrophysics Data System (ADS)

Ostermeijer, G.; Mitchell, T. M.; Dorsey, M. T.; Browning, J.; Rockwell, T. K.; Aben, F. M.; Fletcher, J. M.; Brantut, N.

2017-12-01

The nature and distribution of damage around faults, and its impacts on fault zone properties has been a hot topic of research over the past decade. Understanding the mechanisms that control the formation of off fault damage can shed light on the processes during the seismic cycle, and the nature of fault zone development. Recent published work has identified three broad zones of damage around most faults based on the type, intensity, and extent of fracturing; Tip, Wall, and Linking damage. Although these zones are able to adequately characterise the general distribution of damage, little has been done to identify the nature of damage heterogeneity within those zones, often simplifying the distribution to fit log-normal linear decay trends. Here, we attempt to characterise the distribution of fractures that make up the wall damage around seismogenic faults. To do so, we investigate an extensive two dimensional fracture network exposed on a river cut platform along the Borrego Fault, BC, Mexico, 5m wide, and extending 20m from the fault core into the damage zone. High resolution fracture mapping of the outcrop, covering scales ranging three orders of magnitude (cm to m), has allowed for detailed observations of the 2D damage distribution within the fault damage zone. Damage profiles were obtained along several 1D transects perpendicular to the fault and micro-damage was examined from thin-sections at various locations around the outcrop for comparison. Analysis of the resulting fracture network indicates heterogeneities in damage intensity at decimetre scales resulting from a patchy distribution of high and low intensity corridors and clusters. Such patchiness may contribute to inconsistencies in damage zone widths defined along 1D transects and the observed variability of fracture densities around decay trends. How this distribution develops with fault maturity and the scaling of heterogeneities above and below the observed range will likely play a key role in

Fluid involvement in normal faulting

NASA Astrophysics Data System (ADS)

Sibson, Richard H.

2000-04-01

Evidence of fluid interaction with normal faults comes from their varied role as flow barriers or conduits in hydrocarbon basins and as hosting structures for hydrothermal mineralisation, and from fault-rock assemblages in exhumed footwalls of steep active normal faults and metamorphic core complexes. These last suggest involvement of predominantly aqueous fluids over a broad depth range, with implications for fault shear resistance and the mechanics of normal fault reactivation. A general downwards progression in fault rock assemblages (high-level breccia-gouge (often clay-rich) → cataclasites → phyllonites → mylonite → mylonitic gneiss with the onset of greenschist phyllonites occurring near the base of the seismogenic crust) is inferred for normal fault zones developed in quartzo-feldspathic continental crust. Fluid inclusion studies in hydrothermal veining from some footwall assemblages suggest a transition from hydrostatic to suprahydrostatic fluid pressures over the depth range 3-5 km, with some evidence for near-lithostatic to hydrostatic pressure cycling towards the base of the seismogenic zone in the phyllonitic assemblages. Development of fault-fracture meshes through mixed-mode brittle failure in rock-masses with strong competence layering is promoted by low effective stress in the absence of thoroughgoing cohesionless faults that are favourably oriented for reactivation. Meshes may develop around normal faults in the near-surface under hydrostatic fluid pressures to depths determined by rock tensile strength, and at greater depths in overpressured portions of normal fault zones and at stress heterogeneities, especially dilational jogs. Overpressures localised within developing normal fault zones also determine the extent to which they may reutilise existing discontinuities (for example, low-angle thrust faults). Brittle failure mode plots demonstrate that reactivation of existing low-angle faults under vertical σ1 trajectories is only likely if

Reconnaissance study of late quaternary faulting along cerro GoDen fault zone, western Puerto Rico

USGS Publications Warehouse

Mann, P.; Prentice, C.S.; Hippolyte, J.-C.; Grindlay, N.R.; Abrams, L.J.; Lao-Davila, D.

2005-01-01

The Cerro GoDen fault zone is associated with a curvilinear, continuous, and prominent topographic lineament in western Puerto Rico. The fault varies in strike from northwest to west. In its westernmost section, the fault is ???500 m south of an abrupt, curvilinear mountain front separating the 270- to 361-m-high La CaDena De San Francisco range from the Rio A??asco alluvial valley. The Quaternary fault of the A??asco Valley is in alignment with the bedrock fault mapped by D. McIntyre (1971) in the Central La Plata quadrangle sheet east of A??asco Valley. Previous workers have postulated that the Cerro GoDen fault zone continues southeast from the A??asco Valley and merges with the Great Southern Puerto Rico fault zone of south-central Puerto Rico. West of the A??asco Valley, the fault continues offshore into the Mona Passage (Caribbean Sea) where it is characterized by offsets of seafloor sediments estimated to be of late Quaternary age. Using both 1:18,500 scale air photographs taken in 1936 and 1:40,000 scale photographs taken by the U.S. Department of Agriculture in 1986, we iDentified geomorphic features suggestive of Quaternary fault movement in the A??asco Valley, including aligned and Deflected drainages, apparently offset terrace risers, and mountain-facing scarps. Many of these features suggest right-lateral displacement. Mapping of Paleogene bedrock units in the uplifted La CaDena range adjacent to the Cerro GoDen fault zone reveals the main tectonic events that have culminated in late Quaternary normal-oblique displacement across the Cerro GoDen fault. Cretaceous to Eocene rocks of the La CaDena range exhibit large folds with wavelengths of several kms. The orientation of folds and analysis of fault striations within the folds indicate that the folds formed by northeast-southwest shorTening in present-day geographic coordinates. The age of Deformation is well constrained as late Eocene-early Oligocene by an angular unconformity separating folDed, Deep

The Quaternary thrust system of the northern Alaska Range

USGS Publications Warehouse

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

2012-01-01

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

Climate change: detecting climate's imprint on California forests

Treesearch

Anne M. Rosenthal; Constance I. Millar

2003-01-01

Hiking the nearly treeless slopes of western Nevada's Wassuk Range, researcher Connie Millar found dead limber pine throughout the watersheds. Where scanty forests were present, the dead wood occurred above treeline. Investigation of these wood remnants, sculpted by the elements over hundreds of years, revealed a cyclical pattern of limber pine colonization and...

Measuring Relative Motions Across a Fault Using Seafloor Transponders Installed at Close Range to each Other Based on Differential GPS/Acoustic Technique

NASA Astrophysics Data System (ADS)

Kido, M.; Ashi, J.; Tsuji, T.; Tomita, F.

2016-12-01

Seafloor geodesy based on acoustic ranging technique is getting popular means to reveal crustal deformation beneath the ocean. GPS/acoustic technique can be applied to monitoring regional deformation or absolute position, while direct-path acoustic ranging can be applied to detecting localized strain or relative motion in a short distance ( 1-10 km). However the latter observation sometimes fails to keep the clearance of an acoustic path between the seafloor transponders because of topographic obstacle or of downward bending nature of the path due to vertical gradient of sound speed in deep-ocean. Especially at steep fault scarp, it is almost impossible to keep direct path between the top and bottom of the fault scarp. Even in such a situation, acoustic path to the sea surface might be always clear. Then we propose a new approach to monitor the relative motion of across a fault scarp using "differential" GPS/acoustic measurement, which account only for traveltime differences among the transponders. The advantages of this method are that: (1) uncertainty in sound speed in shallow water is almost canceled; (2) possible GPS error is also canceled; (3) picking error in traveltime detection is almost canceled; (4) only a pair of transponders can fully describe relative 3-dimensional motion. On the other hand the disadvantages are that: (5) data is not continuous but only campaign; (6) most advantages are only effective only for very short baseline (< 100-300 m). Our target being applied this method is a steep fault scarp near the Japan trench, which is expected as a surface expression of back thrust, in where time scale of fault activity is still controversial especially after the Tohoku earthquake. We have carefully installed three transponders across this scarp using a NSS system, which can remotely navigate instrument near the seafloor from a mother vessel based on video camera image. Baseline lengths among the transponders are 200-300 m at 3500 m depth. Initial

How fault evolution changes strain partitioning and fault slip rates in Southern California: Results from geodynamic modeling

NASA Astrophysics Data System (ADS)

Ye, Jiyang; Liu, Mian

2017-08-01

In Southern California, the Pacific-North America relative plate motion is accommodated by the complex southern San Andreas Fault system that includes many young faults (<2 Ma). The initiation of these young faults and their impact on strain partitioning and fault slip rates are important for understanding the evolution of this plate boundary zone and assessing earthquake hazard in Southern California. Using a three-dimensional viscoelastoplastic finite element model, we have investigated how this plate boundary fault system has evolved to accommodate the relative plate motion in Southern California. Our results show that when the plate boundary faults are not optimally configured to accommodate the relative plate motion, strain is localized in places where new faults would initiate to improve the mechanical efficiency of the fault system. In particular, the Eastern California Shear Zone, the San Jacinto Fault, the Elsinore Fault, and the offshore dextral faults all developed in places of highly localized strain. These younger faults compensate for the reduced fault slip on the San Andreas Fault proper because of the Big Bend, a major restraining bend. The evolution of the fault system changes the apportionment of fault slip rates over time, which may explain some of the slip rate discrepancy between geological and geodetic measurements in Southern California. For the present fault configuration, our model predicts localized strain in western Transverse Ranges and along the dextral faults across the Mojave Desert, where numerous damaging earthquakes occurred in recent years.

Fault geometries illuminated from seismicity in central Taiwan: Implications for crustal scale structural boundaries in the northern Central Range

NASA Astrophysics Data System (ADS)

Gourley, Jonathan R.; Byrne, Timothy; Chan, Yu-Chang; Wu, Francis; Rau, Ruey-Juin

2007-12-01

Data sets of collapsed earthquake locations, earthquake focal mechanisms, GPS velocities and geologic data are integrated to constrain the geometry and kinematics of a crustal block within the accreted continental margin rocks of Taiwan's northeastern Central Range. This block is laterally extruding and exhuming towards the north-northeast. The block is bound on the west-southwest by the previously recognized Sanyi-Puli seismic zone and on the east by a vertical seismic structure that projects to the eastern mountain front of the Central Range. Focal mechanisms from the Broadband Array of Taiwan Seismicity (BATS) catalog consistently show west-side-up reverse displacements for this fault zone. A second vertical structure is recognized beneath the Slate Belt-Metamorphic Belt boundary as a post-Chi-Chi relaxation oblique normal fault. BATS focal mechanisms show east-side-up, normal displacements with a minor left-lateral component. The vertical and lateral extrusion of this crustal block may be driven by the current collision between the Philippine Sea Plate and the Puli basement high indenter on the Eurasian Plate and/or trench rollback along the Ryukyu subduction zone. In addition, the vertical extent of the two shear zones suggests that a basal décollement below the eastern Central Range is deeper than previously proposed and may extend below the brittle-ductile transition.

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

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

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

1990-08-30

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

Aftershocks illuminate the 2011 Mineral, Virginia, earthquake causative fault zone and nearby active faults

USGS Publications Warehouse

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

2015-01-01

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

Crustal strain accumulation on Southern Basin and Range Province faults modulated by distant plate boundary earthquakes? Evidence from geodesy, seismic imaging, and paleoseismology

NASA Astrophysics Data System (ADS)

Bennett, R. A.; Shirzaei, M.; Broermann, J.; Spinler, J. C.; Holland, A. A.; Pearthree, P.

2014-12-01

GPS in Arizona reveals a change in the pattern of crustal strain accumulation in 2010 and based on viscoelastic modeling appears to be associated with the distant M7.2 El Mayor-Cucapah (EMC) earthquake in Baja California, Mexico. GPS data collected between 1999 and 2009 near the Santa Rita normal fault in SE Arizona reveal a narrow zone of crustal deformation coincident with the fault trace, delineated by W-NW facing Pleistocene fault scarps of heights 1 to 7 m. The apparent deformation zone is also seen in a preliminary InSAR interferogram. Total motion across the zone inferred using an elastic block model constrained by the pre-2010 GPS measurements is ~1 mm/yr in a sense consistent with normal fault motion. However, continuous GPS measurements throughout Arizona reveal pronounced changes in crustal velocity following the EMC earthquake, such that the relative motion across the Santa Rita fault post-2010 is negligible. Paleoseismic evidence indicates that mapped Santa Rita fault scarps were formed by two or more large magnitude (M6.7 to M7.6) surface rupturing normal-faulting earthquakes 60 to 100 kyrs ago. Seismic refraction and reflection data constrained by deep (~800 m) well log data provide evidence of progressive, possibly intermittent, displacement on the fault through time. The rate of strain accumulation observed geodetically prior to 2010, if constant over the past 60 to 100 kyrs, would imply an untenable minimum slip rate deficit of 60 to 100 m since the most recent earthquake. One explanation for the available geodetic, seismic, and paleoseismic evidence is that strain accumulation is modulated by viscoelastic relaxation associated with frequent large magnitude earthquakes in the Salton Trough region, episodically inhibiting the accumulation of elastic strain required to generate large earthquakes on the Santa Rita and possibly other faults in the Southern Basin and Range. An important question is thus for how long the postseismic velocity changes

Paleoseismologic evidence for large-magnitude (Mw 7.5-8.0) earthquakes on the Ventura blind thrust fault: Implications for multifault ruptures in the Transverse Ranges of southern California

USGS Publications Warehouse

McAuliffe, Lee J.; Dolan, James F.; Rhodes, Edward J.; Hubbard, Judith; Shaw, John H.; Pratt, Thomas L.

2015-01-01

Detailed analysis of continuously cored boreholes and cone penetrometer tests (CPTs), high-resolution seismic-reflection data, and luminescence and 14C dates from Holocene strata folded above the tip of the Ventura blind thrust fault constrain the ages and displacements of the two (or more) most recent earthquakes. These two earthquakes, which are identified by a prominent surface fold scarp and a stratigraphic sequence that thickens across an older buried fold scarp, occurred before the 235-yr-long historic era and after 805 ± 75 yr ago (most recent folding event[s]) and between 4065 and 4665 yr ago (previous folding event[s]). Minimum uplift in these two scarp-forming events was ∼6 m for the most recent earthquake(s) and ∼5.2 m for the previous event(s). Large uplifts such as these typically occur in large-magnitude earthquakes in the range of Mw7.5–8.0. Any such events along the Ventura fault would likely involve rupture of other Transverse Ranges faults to the east and west and/or rupture downward onto the deep, low-angle décollements that underlie these faults. The proximity of this large reverse-fault system to major population centers, including the greater Los Angeles region, and the potential for tsunami generation during ruptures extending offshore along the western parts of the system highlight the importance of understanding the complex behavior of these faults for probabilistic seismic hazard assessment.

Investigation of the Hosgri Fault, offshore Southern California, Point Sal to Point Conception

USGS Publications Warehouse

Payne, C.M.; Swanson, O.E.; Schell, B.A.

1979-01-01

A high-resolution seismic reflection survey of the inner continental shelf between Point Sal and Point Conception has revealed faults that displace post-Wisconsin strata (less than 17,000-20,000 years). These faults are the Hosgri fault, the Offshore Lompoc fault, and smaller unnamed faults. Faults trending offshore from the adjacent shoreline such as the Pezzoni, Lions Head, Honda, and Pacifico faults, do not show post-Wisconsin activity. The Hosgri fault trends directly toward the coastline between Purisima Point and Point Arguello where it appears to merge with folds and smaller faults in the western Transverse Ranges. This trend of offshore structures toward the Point Arguello-Point Conception area is consistent with a hypothesis that the regional structural fabric of the southern California Coast Ranges and its adjacent offshore area merge with the Transverse Ranges.

Off-fault tip splay networks: a genetic and generic property of faults indicative of their long-term propagation, and a major component of off-fault damage

NASA Astrophysics Data System (ADS)

Perrin, C.; Manighetti, I.; Gaudemer, Y.

2015-12-01

Faults grow over the long-term by accumulating displacement and lengthening, i.e., propagating laterally. We use fault maps and fault propagation evidences available in literature to examine geometrical relations between parent faults and off-fault splays. The population includes 47 worldwide crustal faults with lengths from millimeters to thousands of kilometers and of different slip modes. We show that fault splays form adjacent to any propagating fault tip, whereas they are absent at non-propagating fault ends. Independent of parent fault length, slip mode, context, etc, tip splay networks have a similar fan shape widening in direction of long-term propagation, a similar relative length and width (~30 and ~10 % of parent fault length, respectively), and a similar range of mean angles to parent fault (10-20°). Tip splays more commonly develop on one side only of the parent fault. We infer that tip splay networks are a genetic and a generic property of faults indicative of their long-term propagation. We suggest that they represent the most recent damage off-the parent fault, formed during the most recent phase of fault lengthening. The scaling relation between parent fault length and width of tip splay network implies that damage zones enlarge as parent fault length increases. Elastic properties of host rocks might thus be modified at large distances away from a fault, up to 10% of its length. During an earthquake, a significant fraction of coseismic slip and stress is dissipated into the permanent damage zone that surrounds the causative fault. We infer that coseismic dissipation might occur away from a rupture zone as far as a distance of 10% of the length of its causative fault. Coseismic deformations and stress transfers might thus be significant in broad regions about principal rupture traces. This work has been published in Comptes Rendus Geoscience under doi:10.1016/j.crte.2015.05.002 (http://www.sciencedirect.com/science/article/pii/S1631071315000528).

The San Andreas Fault and a Strike-slip Fault on Europa

NASA Technical Reports Server (NTRS)

1998-01-01

materials, but may be filled in mostly by sedimentary and erosional material deposited from above. Comparisons between faults on Europa and Earth may generate ideas useful in the study of terrestrial faulting.

One theory is that fault motion on Europa is induced by the pull of variable daily tides generated by Jupiter's gravitational tug on Europa. The tidal tension opens the fault; subsequent tidal stress causes it to move lengthwise in one direction. Then the tidal forces close the fault up again. This prevents the area from moving back to its original position. If it moves forward with the next daily tidal cycle, the result is a steady accumulation of these lengthwise offset motions.

Unlike Europa, here on Earth, large strike-slip faults such as the San Andreas are set in motion not by tidal pull, but by plate tectonic forces from the planet's mantle.

North is to the top of the picture. The Earth picture (left) shows a LandSat Thematic Mapper image acquired in the infrared (1.55 to 1.75 micrometers) by LandSat5 on Friday, October 20th 1989 at 10:21 am. The original resolution was 28.5 meters per picture element.

The Europa picture (right)is centered at 66 degrees south latitude and 195 degrees west longitude. The highest resolution frames, obtained at 40 meters per picture element with a spacecraft range of less than 4200 kilometers (2600 miles), are set in the context of lower resolution regional frames obtained at 200 meters per picture element and a range of 22,000 kilometers (13,600 miles). The images were taken on September 26, 1998 by the Solid State Imaging (SSI) system on NASA's Galileo spacecraft.

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

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

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

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

Janssen, C.; Wirth, R.; Wenk, H. -R.

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

Monitoring of crustal movements in the San Andreas fault zone by a satellite-borne ranging system. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Kumar, M.

1976-01-01

The Close Grid Geodynamic Measurement System is conceived as an orbiting ranging device with a ground base grid of reflectors or transponders (spacing 1.0 to 30 km), which are projected to be of low cost (maintenance free and unattended), and which will permit the saturation of a local area to obtain data useful to monitor crustal movements in the San Andreas fault zone. The system includes a station network of 75 stations covering an area between 36 deg N and 38 deg N latitudes, and 237 deg E and 239 deg E longitudes, with roughly half of the stations on either side of the faults. In addition, the simulation of crustal movements through the introduction of changes in the relative positions between grid stations, weather effect for intervisibility between satellite and station and loss of observations thereof, and comparative evaluation of various observational scheme-patterns have been critically studied.

Quantifying Anderson's fault types

USGS Publications Warehouse

Simpson, R.W.

1997-01-01

Anderson [1905] explained three basic types of faulting (normal, strike-slip, and reverse) in terms of the shape of the causative stress tensor and its orientation relative to the Earth's surface. Quantitative parameters can be defined which contain information about both shape and orientation [Ce??le??rier, 1995], thereby offering a way to distinguish fault-type domains on plots of regional stress fields and to quantify, for example, the degree of normal-faulting tendencies within strike-slip domains. This paper offers a geometrically motivated generalization of Angelier's [1979, 1984, 1990] shape parameters ?? and ?? to new quantities named A?? and A??. In their simple forms, A?? varies from 0 to 1 for normal, 1 to 2 for strike-slip, and 2 to 3 for reverse faulting, and A?? ranges from 0?? to 60??, 60?? to 120??, and 120?? to 180??, respectively. After scaling, A?? and A?? agree to within 2% (or 1??), a difference of little practical significance, although A?? has smoother analytical properties. A formulation distinguishing horizontal axes as well as the vertical axis is also possible, yielding an A?? ranging from -3 to +3 and A?? from -180?? to +180??. The geometrically motivated derivation in three-dimensional stress space presented here may aid intuition and offers a natural link with traditional ways of plotting yield and failure criteria. Examples are given, based on models of Bird [1996] and Bird and Kong [1994], of the use of Anderson fault parameters A?? and A?? for visualizing tectonic regimes defined by regional stress fields. Copyright 1997 by the American Geophysical Union.

Carbon monoxide degassing from seismic fault zones in the Basin and Range province, west of Beijing, China

NASA Astrophysics Data System (ADS)

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.

The Point Sal–Point Piedras Blancas correlation and the problem of slip on the San Gregorio–Hosgri fault, central California Coast Ranges

USGS Publications Warehouse

Colgan, Joseph P.; Stanley, Richard G.

2016-01-01

Existing models for large-magnitude, right-lateral slip on the San Gregorio–Hosgri fault system imply much more deformation of the onshore block in the Santa Maria basin than is supported by geologic data. This problem is resolved by a model in which dextral slip on this fault system increases gradually from 0–10 km near Point Arguello to ∼150 km at Cape San Martin, but such a model requires abandoning the cross-fault tie between Point Sal and Point Piedras Blancas, which requires 90–100 km of right-lateral slip on the southern Hosgri fault. We collected stratigraphic and detrital zircon data from Miocene clastic rocks overlying Jurassic basement at both localities to determine if either section contained unique characteristics that could establish how far apart they were in the early Miocene. Our data indicate that these basins formed in the early Miocene during a period of widespread transtensional basin formation in the central Coast Ranges, and they filled with sediment derived from nearby pre-Cenozoic basement rocks. Although detrital zircon data do not indicate a unique source component in either section, they establish the maximum depositional age of the previously undated Point Piedras Blancas section to be 18 Ma. We also show that detrital zircon trace-element data can be used to discriminate between zircons of oceanic crust and arc affinity of the same age, a potentially useful tool in future studies of the California Coast Ranges. Overall, we find no characteristics in the stratigraphy and provenance of the Point Sal and Point Piedras Blancas sections that are sufficiently unique to prove whether they were far apart or close together in the early Miocene, making them of questionable utility as piercing points.

Late Holocene earthquakes on the Toe Jam Hill fault, Seattle fault zone, Bainbridge Island, Washington

USGS Publications Warehouse

Nelson, A.R.; Johnson, S.Y.; Kelsey, H.M.; Wells, R.E.; Sherrod, B.L.; Pezzopane, S.K.; Bradley, L.A.; Koehler, R. D.; Bucknam, R.C.

2003-01-01

Five trenches across a Holocene fault scarp yield the first radiocarbon-measured earthquake recurrence intervals for a crustal fault in western Washington. The scarp, the first to be revealed by laser imagery, marks the Toe Jam Hill fault, a north-dipping backthrust to the Seattle fault. Folded and faulted strata, liquefaction features, and forest soil A horizons buried by hanging-wall-collapse colluvium record three, or possibly four, earthquakes between 2500 and 1000 yr ago. The most recent earthquake is probably the 1050-1020 cal. (calibrated) yr B.P. (A.D. 900-930) earthquake that raised marine terraces and triggered a tsunami in Puget Sound. Vertical deformation estimated from stratigraphic and surface offsets at trench sites suggests late Holocene earthquake magnitudes near M7, corresponding to surface ruptures >36 km long. Deformation features recording poorly understood latest Pleistocene earthquakes suggest that they were smaller than late Holocene earthquakes. Postglacial earthquake recurrence intervals based on 97 radiocarbon ages, most on detrital charcoal, range from ???12,000 yr to as little as a century or less; corresponding fault-slip rates are 0.2 mm/yr for the past 16,000 yr and 2 mm/yr for the past 2500 yr. Because the Toe Jam Hill fault is a backthrust to the Seattle fault, it may not have ruptured during every earthquake on the Seattle fault. But the earthquake history of the Toe Jam Hill fault is at least a partial proxy for the history of the rest of the Seattle fault zone.

Homogeneity of small-scale earthquake faulting, stress, and fault strength

USGS Publications Warehouse

Hardebeck, J.L.

2006-01-01

Small-scale faulting at seismogenic depths in the crust appears to be more homogeneous than previously thought. I study three new high-quality focal-mechanism datasets of small (M < ??? 3) earthquakes in southern California, the east San Francisco Bay, and the aftershock sequence of the 1989 Loma Prieta earthquake. I quantify the degree of mechanism variability on a range of length scales by comparing the hypocentral disctance between every pair of events and the angular difference between their focal mechanisms. Closely spaced earthquakes (interhypocentral distance faults of many orientations may or may not be present, only similarly oriented fault planes produce earthquakes contemporaneously. On these short length scales, the crustal stress orientation and fault strength (coefficient of friction) are inferred to be homogeneous as well, to produce such similar earthquakes. Over larger length scales (???2-50 km), focal mechanisms become more diverse with increasing interhypocentral distance (differing on average by 40-70??). Mechanism variability on ???2- to 50 km length scales can be explained by ralatively small variations (???30%) in stress or fault strength. It is possible that most of this small apparent heterogeneity in stress of strength comes from measurement error in the focal mechanisms, as negligibble variation in stress or fault strength (<10%) is needed if each earthquake is assigned the optimally oriented focal mechanism within the 1-sigma confidence region. This local homogeneity in stress orientation and fault strength is encouraging, implying it may be possible to measure these parameters with enough precision to be useful in studying and modeling large earthquakes.

Map of normal faults and extensional folds in the Tendoy Mountains and Beaverhead Range, Southwest Montana and eastern Idaho

USGS Publications Warehouse

Janecke, S.U.; Blankenau, J.J.; VanDenburg, C.J.; VanGosen, B.S.

2001-01-01

Compilation of a 1:100,000-scale map of normal faults and extensional folds in southwest Montana and adjacent Idaho reveals a complex history of normal faulting that spanned at least the last 50 m.y. and involved six or more generations of normal faults. The map is based on both published and unpublished mapping and shows normal faults and extensional folds between the valley of the Red Rock River of southwest Montana and the Lemhi and Birch Creek valleys of eastern Idaho between latitudes 45°05' N. and 44°15' N. in the Tendoy and Beaverhead Mountains. Some of the unpublished mapping has been compiled in Lonn and others (2000). Many traces of the normal faults parallel the generally northwest to north-northwest structural grain of the preexisting Sevier fold and thrust belt and dip west-southwest, but northeastand east-striking normal faults are also prominent. Northeaststriking normal faults are subparallel to the traces of southeast-directed thrusts that shortened the foreland during the Laramide orogeny. It is unlikely that the northeast-striking normal faults reactivated fabrics in the underlying Precambrian basement, as has been documented elsewhere in southwestern Montana (Schmidt and others, 1984), because exposures of basement rocks in the map area exhibit north-northwest- to northwest-striking deformational fabrics (Lowell, 1965; M’Gonigle, 1993, 1994; M’Gonigle and Hait, 1997; M’Gonigle and others, 1991). The largest normal faults in the area are southwest-dipping normal faults that locally reactivate thrust faults (fig. 1). Normal faulting began before middle Eocene Challis volcanism and continues today. The extension direction flipped by about 90° four times.

Origin of narrow terranes and adjacent major terranes occurring along the denali fault in the eastern and central alaska range, alaska

USGS Publications Warehouse

Nokleberg, W.J.; Richter, D.H.

2007-01-01

Several narrow terranes occur along the Denali fault in the Eastern and Central Alaska Range in Southern Alaska. These terranes are the Aurora Peak, Cottonwood Creek, Maclaren, Pingston, and Windy terranes, and a terrane of ultramafic and associated rocks. Exterior to the narrow terranes to the south is the majorWrangellia island arc composite terrane, and to the north is the major Yukon Tanana metamorphosed continental margin terrane. Overlying mainly the northern margin of the Wrangellia composite terrane are the Kahiltna overlap assemblage to the west, and the Gravina- Nutzotin-Gambier volcanic-plutonic- sedimentary belt to the east and southeast. The various narrow terranes are interpreted as the result of translation of fragments of larger terranes during two major tectonic events: (1) Late Jurassic to mid-Cretaceous accretion of the Wrangellia island arc composite terrane (or superterrane composed of the Wrangellia, Peninsular, and Alexander terranes) and associated subduction zone complexes; and (2) starting in about the Late Cretaceous, dextral transport of the Wrangellia composite terrane along the Denali fault. These two major tectonic events caused: (1) entrapment of a lens of oceanic lithosphere along the suture belt between the Wrangellia composite terrane and the North American Craton Margin and outboard accreted terranes to form the ultramafic and mafic part of the terrane of ultramafic and associated rocks, (2) subsequent dextral translation along the Denali fault of the terrane of ultramafic and associated rocks, (3) dextral translation along the Denali fault of the Aurora Peak, Cottonwood Creek, and Maclaren and continental margin arc terranes from part of the Coast plutonic-metamorphic complex (Coast-North Cascade plutonic belt) in the southwest Yukon Territory or Southeastern Alaska, (4) dextral translation along the Denali fault of the Pingston passive continental margin from a locus along the North American Continental Margin, and (5

Identifying Conventionally Sub-Seismic Faults in Polygonal Fault Systems

NASA Astrophysics Data System (ADS)

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

Experimental Measurements of Permeability Evolution along Faults during Progressive Slip

NASA Astrophysics Data System (ADS)

Strutz, M.; Mitchell, T. M.; Renner, J.

2010-12-01

Little is currently known about the dynamic changes in fault-parallel permeability along rough faults during progressive slip. With increasing slip, asperities are worn to produce gouge which can dramatically reduce along fault permeability within the slip zone. However, faults can have a range of roughness which can affect both the porosity and both the amount and distribution of fault wear material produced in the slipping zone during the early stages of fault evolution. In this novel study we investigate experimentally the evolution of permeability along a fault plane in granite sawcut sliding blocks with a variety of intial roughnesses in a triaxial apparatus. Drillholes in the samples allow the permeability to be measured along the fault plane during loading and subsequent fault displacement. Use of the pore pressure oscillation technique (PPO) allows the continuous measurement of permeability without having to stop loading. To achieve a range of intial starting roughnesses, faults sawcut surfaces were prepared using a variety of corundum powders ranging from 10 µm to 220 µm, and for coarser roughness were air-blasted with glass beads up to 800µm in size. Fault roughness has been quantified with a laser profileometer. During sliding, we measure the acoustic emissions in order to detect grain cracking and asperity shearing which may relate to both the mechanical and permeability data. Permeability shows relative reductions of up to over 4 orders of magnitude during stable sliding as asperities are sheared to produce a fine fault gouge. This variation in permeability is greatest for the roughest faults, reducing as fault roughness decreases. The onset of permeability reduction is contemporaneous with a dramatic reduction in the amount of detected acoustic emissions, where a continuous layer of fault gouge has developed. The amount of fault gouge produced is related to the initial roughness, with the rough faults showing larger fault gouge layers at the end of

Surface faulting. A preliminary view

USGS Publications Warehouse

Sharp, R.V.

1989-01-01

This description of surface faulting near Spitak, Armenia, is based on a field inspection made December 22-26, 1988. The surface rupture west of Spitak, displacement of the ground surface, pre-earthquake surface expressions of the fault, and photolineaments in landsat images are described and surface faulting is compared to aftershocks. It is concluded that the 2 meters of maximum surface displacement fits well within the range of reliably measured maximum surface offsets for historic reverse and oblique-reverse faulting events throughout the world. By contrast, the presently known length of surface rupture near Spitak, between 8 and 13 km, is shorter than any other reverse or oblique-reverse event of magnitude greater than 6.0. This may be a reason to suppose that additional surface rupture might remain unmapped.

The fault-tree compiler

NASA Technical Reports Server (NTRS)

Martensen, Anna L.; Butler, Ricky W.

1987-01-01

The Fault Tree Compiler Program is a new reliability tool used to predict the top event probability for a fault tree. Five different gate types are allowed in the fault tree: AND, OR, EXCLUSIVE OR, INVERT, and M OF N gates. The high level input language is easy to understand and use when describing the system tree. In addition, the use of the hierarchical fault tree capability can simplify the tree description and decrease program execution time. The current solution technique provides an answer precise (within the limits of double precision floating point arithmetic) to the five digits in the answer. The user may vary one failure rate or failure probability over a range of values and plot the results for sensitivity analyses. The solution technique is implemented in FORTRAN; the remaining program code is implemented in Pascal. The program is written to run on a Digital Corporation VAX with the VMS operation system.

Structural setting and kinematics of Nubian fault system, SE Western Desert, Egypt: An example of multi-reactivated intraplate strike-slip faults

NASA Astrophysics Data System (ADS)

Sakran, Shawky; Said, Said Mohamed

2018-02-01

Detailed surface geological mapping and subsurface seismic interpretation have been integrated to unravel the structural style and kinematic history of the Nubian Fault System (NFS). The NFS consists of several E-W Principal Deformation Zones (PDZs) (e.g. Kalabsha fault). Each PDZ is defined by spectacular E-W, WNW and ENE dextral strike-slip faults, NNE sinistral strike-slip faults, NE to ENE folds, and NNW normal faults. Each fault zone has typical self-similar strike-slip architecture comprising multi-scale fault segments. Several multi-scale uplifts and basins were developed at the step-over zones between parallel strike-slip fault segments as a result of local extension or contraction. The NNE faults consist of right-stepping sinistral strike-slip fault segments (e.g. Sin El Kiddab fault). The NNE sinistral faults extend for long distances ranging from 30 to 100 kms and cut one or two E-W PDZs. Two nearly perpendicular strike-slip tectonic regimes are recognized in the NFS; an inactive E-W Late Cretaceous - Early Cenozoic dextral transpression and an active NNE sinistral shear.

Earthquake Clustering on Normal Faults: Insight from Rate-and-State Friction Models

NASA Astrophysics Data System (ADS)

Biemiller, J.; Lavier, L. L.; Wallace, L.

2016-12-01

Temporal variations in slip rate on normal faults have been recognized in Hawaii and the Basin and Range. The recurrence intervals of these slip transients range from 2 years on the flanks of Kilauea, Hawaii to 10 kyr timescale earthquake clustering on the Wasatch Fault in the eastern Basin and Range. In addition to these longer recurrence transients in the Basin and Range, recent GPS results there also suggest elevated deformation rate events with recurrence intervals of 2-4 years. These observations suggest that some active normal fault systems are dominated by slip behaviors that fall between the end-members of steady aseismic creep and periodic, purely elastic, seismic-cycle deformation. Recent studies propose that 200 year to 50 kyr timescale supercycles may control the magnitude, timing, and frequency of seismic-cycle earthquakes in subduction zones, where aseismic slip transients are known to play an important role in total deformation. Seismic cycle deformation of normal faults may be similarly influenced by its timing within long-period supercycles. We present numerical models (based on rate-and-state friction) of normal faults such as the Wasatch Fault showing that realistic rate-and-state parameter distributions along an extensional fault zone can give rise to earthquake clusters separated by 500 yr - 5 kyr periods of aseismic slip transients on some portions of the fault. The recurrence intervals of events within each earthquake cluster range from 200 to 400 years. Our results support the importance of stress and strain history as controls on a normal fault's present and future slip behavior and on the characteristics of its current seismic cycle. These models suggest that long- to medium-term fault slip history may influence the temporal distribution, recurrence interval, and earthquake magnitudes for a given normal fault segment.

Field-based perspective on fault rock evolution and microstructures in low-angle fault zones (W-Cyclades, Greece)

NASA Astrophysics Data System (ADS)

Grasemann, Bernhard

2010-05-01

The mechanics of sub-horizontal faults, typically active at the brittle/ductile transition zone, are still controversial because they do not conform to current fault-mechanical theory. In the Western Cyclades (Greece) conjugate high-angle brittle faults mechanically interact with sub-horizontal faults and therefore models based on fault and/or stress rotation can be rejected. A range of different deformation mechanisms and/or rock properties must have resulted in an reduction of the fault strength in both the ductily and cataclastically deformed fault rocks. Typically the low-angle faults have following characteristics: The footwall below the subhorizontal faults consists of coarse-grained impure marbles and greenschists, which record an increase in shear strain localizing in several meters to tens of meters thick ultra fine-grained marble mylonites. These ultamylonites are delimited along a knife-sharp slickenside plane juxtaposing tens of decimeter thick zones of polyphase ultracataclasites. The marbles accommodated high shear strain by ductile deformation mechanisms such as dislocation creep and/or grain size sensitive flow by recrystallization, which might have result in fault zone weakening. Typically the marbles are impure and record spatial arrangement of mica and quartz grains, which might have lead to structural softening by decoupling of the calcite matrix from the clasts. During brittle deformation the massif marble ultramylonites act as a strong plate and ultracataclastic deformation is localizing exactly along the border of this plate. Although some of the cataclastic deformation mechanisms lead to chaotic fabrics with evidence for frictional sliding and comminution, others favor the formation of foliated cataclasites and fault gouges with various intensities of phyllosilicate fabrics. Frequently, a repeated switch between grain fracturing processes and processes, which created a sc or scc'-type foliation can be observed. On Serifos the low-angle fault

High-resolution mapping of two large-scale transpressional fault zones in the California Continental Borderland: Santa Cruz-Catalina Ridge and Ferrelo faults

NASA Astrophysics Data System (ADS)

Legg, Mark R.; Kohler, Monica D.; Shintaku, Natsumi; Weeraratne, Dayanthie S.

2015-05-01

New mapping of two active transpressional fault zones in the California Continental Borderland, the Santa Cruz-Catalina Ridge fault and the Ferrelo fault, was carried out to characterize their geometries, using over 4500 line-km of new multibeam bathymetry data collected in 2010 combined with existing data. Faults identified from seafloor morphology were verified in the subsurface using existing seismic reflection data including single-channel and multichannel seismic profiles compiled over the past three decades. The two fault systems are parallel and are capable of large lateral offsets and reverse slip during earthquakes. The geometry of the fault systems shows evidence of multiple segments that could experience throughgoing rupture over distances exceeding 100 km. Published earthquake hypocenters from regional seismicity studies further define the lateral and depth extent of the historic fault ruptures. Historical and recent focal mechanisms obtained from first-motion and moment tensor studies confirm regional strain partitioning dominated by right slip on major throughgoing faults with reverse-oblique mechanisms on adjacent structures. Transpression on west and northwest trending structures persists as far as 270 km south of the Transverse Ranges; extension persists in the southern Borderland. A logjam model describes the tectonic evolution of crustal blocks bounded by strike-slip and reverse faults which are restrained from northwest displacement by the Transverse Ranges and the southern San Andreas fault big bend. Because of their potential for dip-slip rupture, the faults may also be capable of generating local tsunamis that would impact Southern California coastlines, including populated regions in the Channel Islands.

Seismic images and fault relations of the Santa Monica thrust fault, West Los Angeles, California

USGS Publications Warehouse

Catchings, R.D.; Gandhok, G.; Goldman, M.R.; Okaya, D.

2001-01-01

In May 1997, the US Geological Survey (USGS) and the University of Southern California (USC) acquired high-resolution seismic reflection and refraction images on the grounds of the Wadsworth Veterans Administration Hospital (WVAH) in the city of Los Angeles (Fig. 1a,b). The objective of the seismic survey was to better understand the near-surface geometry and faulting characteristics of the Santa Monica fault zone. In this report, we present seismic images, an interpretation of those images, and a comparison of our results with results from studies by Dolan and Pratt (1997), Pratt et al. (1998) and Gibbs et al. (2000). The Santa Monica fault is one of the several northeast-southwest-trending, north-dipping, reverse faults that extend through the Los Angeles metropolitan area (Fig. 1a). Through much of area, the Santa Monica fault trends subparallel to the Hollywood fault, but the two faults apparently join into a single fault zone to the southwest and to the northeast (Dolan et al., 1995). The Santa Monica and Hollywood faults may be part of a larger fault system that extends from the Pacific Ocean to the Transverse Ranges. Crook et al. (1983) refer to this fault system as the Malibu Coast-Santa Monica-Raymond-Cucamonga fault system. They suggest that these faults have not formed a contiguous zone since the Pleistocene and conclude that each of the faults should be treated as a separate fault with respect to seismic hazards. However, Dolan et al. (1995) suggest that the Hollywood and Santa Monica faults are capable of generating Mw 6.8 and Mw 7.0 earthquakes, respectively. Thus, regardless of whether the overall fault system is connected and capable of rupturing in one event, individually, each of the faults present a sizable earthquake hazard to the Los Angeles metropolitan area. If, however, these faults are connected, and they were to rupture along a continuous fault rupture, the resulting hazard would be even greater. Although the Santa Monica fault represents

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

USGS Publications Warehouse

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

2005-01-01

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

Relationship between displacement and gravity change of Uemachi faults and surrounding faults of Osaka basin, Southwest Japan

NASA Astrophysics Data System (ADS)

Inoue, N.; Kitada, N.; Kusumoto, S.; Itoh, Y.; Takemura, K.

2011-12-01

The Osaka basin surrounded by the Rokko and Ikoma Ranges is one of the typical Quaternary sedimentary basins in Japan. The Osaka basin has been filled by the Pleistocene Osaka group and the later sediments. Several large cities and metropolitan areas, such as Osaka and Kobe are located in the Osaka basin. The basin is surrounded by E-W trending strike slip faults and N-S trending reverse faults. The N-S trending 42-km-long Uemachi faults traverse in the central part of the Osaka city. The Uemachi faults have been investigated for countermeasures against earthquake disaster. It is important to reveal the detailed fault parameters, such as length, dip and recurrence interval, so on for strong ground motion simulation and disaster prevention. For strong ground motion simulation, the fault model of the Uemachi faults consist of the two parts, the north and south parts, because of the no basement displacement in the central part of the faults. The Ministry of Education, Culture, Sports, Science and Technology started the project to survey of the Uemachi faults. The Disaster Prevention Institute of Kyoto University is carried out various surveys from 2009 to 2012 for 3 years. The result of the last year revealed the higher fault activity of the branch fault than main faults in the central part (see poster of "Subsurface Flexure of Uemachi Fault, Japan" by Kitada et al., in this meeting). Kusumoto et al. (2001) reported that surrounding faults enable to form the similar basement relief without the Uemachi faults model based on a dislocation model. We performed various parameter studies for dislocation model and gravity changes based on simplified faults model, which were designed based on the distribution of the real faults. The model was consisted 7 faults including the Uemachi faults. The dislocation and gravity change were calculated based on the Okada et al. (1985) and Okubo et al. (1993) respectively. The results show the similar basement displacement pattern to the

Investigating Strain Transfer Along the Southern San Andreas Fault: A Geomorphic and Geodetic Study of Block Rotation in the Eastern Transverse Ranges, Joshua Tree National Park, CA

NASA Astrophysics Data System (ADS)

Guns, K. A.; Bennett, R. A.; Blisniuk, K.

2017-12-01

To better evaluate the distribution and transfer of strain and slip along the Southern San Andreas Fault (SSAF) zone in the northern Coachella valley in southern California, we integrate geological and geodetic observations to test whether strain is being transferred away from the SSAF system towards the Eastern California Shear Zone through microblock rotation of the Eastern Transverse Ranges (ETR). The faults of the ETR consist of five east-west trending left lateral strike slip faults that have measured cumulative offsets of up to 20 km and as low as 1 km. Present kinematic and block models present a variety of slip rate estimates, from as low as zero to as high as 7 mm/yr, suggesting a gap in our understanding of what role these faults play in the larger system. To determine whether present-day block rotation along these faults is contributing to strain transfer in the region, we are applying 10Be surface exposure dating methods to observed offset channel and alluvial fan deposits in order to estimate fault slip rates along two faults in the ETR. We present observations of offset geomorphic landforms using field mapping and LiDAR data at three sites along the Blue Cut Fault and one site along the Smoke Tree Wash Fault in Joshua Tree National Park which indicate recent Quaternary fault activity. Initial results of site mapping and clast count analyses reveal at least three stages of offset, including potential Holocene offsets, for one site along the Blue Cut Fault, while preliminary 10Be geochronology is in progress. This geologic slip rate data, combined with our new geodetic surface velocity field derived from updated campaign-based GPS measurements within Joshua Tree National Park will allow us to construct a suite of elastic fault block models to elucidate rates of strain transfer away from the SSAF and how that strain transfer may be affecting the length of the interseismic period along the SSAF.

Controls on Patterns of Repeated Fault Rupture: Examples From the Denali and Bear River Faults

NASA Astrophysics Data System (ADS)

Schwartz, D. P.; Hecker, S.

2013-12-01

was stressed sufficiently to fail at that time. The Bear River fault zone (BRFZ) is a young normal fault along the eastern margin of basin-range extension that appears to have reactivated a ramp in the Laramide-age Darby-Hogsback thrust. The entire Cenozoic history of the BRFZ may consist of only two surface-rupturing events in the late Holocene (one at ~5 ka and the most recent at ~2.5 ka). The 40-km-long fault comprises synthetic and antithetic scarps extending across a zone up to 5 km wide. Remote sensing, including airborne LiDAR, and field studies show that, despite the complexity, the pattern of faulting was similar (in location and amount) for each of the two events and, at the south end, was strongly influenced by the east-west-trending Uinta Arch. Pre-existing structure clearly has exerted a first-order control on moment release on this immature fault. As shown by these examples, data on timing of surface ruptures, coseismic slip, slip rate, and fault geometry can provide a basis to constrain lengths of past and future earthquake ruptures, including possible alternative rupture scenarios. The difficult question for hazard analysis is whether the available data capture the full range of behavior and with what relative frequency do the alternatives occur?

The mechanics of fault-bend folding and tear-fault systems in the Niger Delta

NASA Astrophysics Data System (ADS)

Benesh, Nathan Philip

This dissertation investigates the mechanics of fault-bend folding using the discrete element method (DEM) and explores the nature of tear-fault systems in the deep-water Niger Delta fold-and-thrust belt. In Chapter 1, we employ the DEM to investigate the development of growth structures in anticlinal fault-bend folds. This work was inspired by observations that growth strata in active folds show a pronounced upward decrease in bed dip, in contrast to traditional kinematic fault-bend fold models. Our analysis shows that the modeled folds grow largely by parallel folding as specified by the kinematic theory; however, the process of folding over a broad axial surface zone yields a component of fold growth by limb rotation that is consistent with the patterns observed in natural folds. This result has important implications for how growth structures can he used to constrain slip and paleo-earthquake ages on active blind-thrust faults. In Chapter 2, we expand our DEM study to investigate the development of a wider range of fault-bend folds. We examine the influence of mechanical stratigraphy and quantitatively compare our models with the relationships between fold and fault shape prescribed by the kinematic theory. While the synclinal fault-bend models closely match the kinematic theory, the modeled anticlinal fault-bend folds show robust behavior that is distinct from the kinematic theory. Specifically, we observe that modeled structures maintain a linear relationship between fold shape (gamma) and fault-horizon cutoff angle (theta), rather than expressing the non-linear relationship with two distinct modes of anticlinal folding that is prescribed by the kinematic theory. These observations lead to a revised quantitative relationship for fault-bend folds that can serve as a useful interpretation tool. Finally, in Chapter 3, we examine the 3D relationships of tear- and thrust-fault systems in the western, deep-water Niger Delta. Using 3D seismic reflection data and new

Gravity and Magnetic Anomaly Interpretations and 2.5D Cross-Section Models over the Border Ranges Fault System and Aleutian Subduction Zone, Alaska

NASA Astrophysics Data System (ADS)

Mankhemthong, N.; Doser, D. I.; Baker, M. R.; Kaip, G.; Jones, S.; Eslick, B. E.; Budhathoki, P.

2011-12-01

Quaternary glacial covers and lack of dense geophysical data on the Kenai Peninsula cause a location and geometry of the Border Ranges fault system (BRFS) within a recent forearc-accretionary boundary of Aleutian subduction zone in southern Alaska are unclear. Using new ~1,300 gravity collections within the Anchorage and Kenai Peninsula regions complied with prior 1997 gravity and aeromagnetic data help us better imaging these fault and the subduction structures. Cook Inlet forearc basin is corresponded by deep gravity anomaly lows; basin boundaries are characterized by a strong gravity gradient, where are considered to be traces of Border Ranges fault system on the east and Castle Mountain and Bruin Bay fault system on the west and northwest of the forearc basin respectively. Gravity anomaly highs over accreted rocks generally increase southeastward to the Aleutian trench, but show a gravity depression over the Kenai Mountains region. The lineament between gravity high and low in the same terrenes over the Kenai Peninsula is may be another evidence to determine the Southern Edge of the Yakutat Microplate (SEY) as inferred by Eberhart-Phillips et al. (2006). Our 2.5-D models illustrate the main fault of the BRFS dips steeply toward the west with a downslip displacement. Gravity and Magnetic anomaly highs, on the east of the BRFS, probably present a slice of the ultramafic complex emplaced by faults along the boundary of the forearc basin and accretionary wedge terranes. Another magnetic high beneath the basin in the southern forearc basin support a serpentiznied body inferred by Saltus et al. (2001), with a decreasing size toward the north. Regional density-gravity models show the Pacific subducting slab beneath the foreacre-arc teranes with a gentle and flatted dip where the subducting plate is located in north of SEY and dips more steeply where it is located on the south of SEY. The gravity depression over the accreted terrene can be explained by a density low

Interacting faults

NASA Astrophysics Data System (ADS)

Peacock, D. C. P.; Nixon, C. W.; Rotevatn, A.; Sanderson, D. J.; Zuluaga, L. F.

2017-04-01

The way that faults interact with each other controls fault geometries, displacements and strains. Faults rarely occur individually but as sets or networks, with the arrangement of these faults producing a variety of different fault interactions. Fault interactions are characterised in terms of the following: 1) Geometry - the spatial arrangement of the faults. Interacting faults may or may not be geometrically linked (i.e. physically connected), when fault planes share an intersection line. 2) Kinematics - the displacement distributions of the interacting faults and whether the displacement directions are parallel, perpendicular or oblique to the intersection line. Interacting faults may or may not be kinematically linked, where the displacements, stresses and strains of one fault influences those of the other. 3) Displacement and strain in the interaction zone - whether the faults have the same or opposite displacement directions, and if extension or contraction dominates in the acute bisector between the faults. 4) Chronology - the relative ages of the faults. This characterisation scheme is used to suggest a classification for interacting faults. Different types of interaction are illustrated using metre-scale faults from the Mesozoic rocks of Somerset and examples from the literature.

Quantifying Vertical Exhumation in Intracontinental Strike-Slip Faults: the Garlock fault zone, southern California

NASA Astrophysics Data System (ADS)

Chinn, L.; Blythe, A. E.; Fendick, A.

2012-12-01

using apatite fission-track thermochronometry. In model #1 slip on the Mule Spring fault may have propagated towards the range front, and may be responsible for the fault-propagation-folding currently observed along the northern branch of the Southern Death Valley fault zone. Model #2 may serve to determine where faulting has historically included a component of thrust faulting to the east of sample locations. Model #3 would further determine total offset along the Mule Spring fault from Miocene-present. Anticipated fission-track and U-Th/He data will help distinguish between these alternative models.

Late Quaternary slip rate determination by CRN dating on the Haiyuan fault, China, and implication for complex geometry fault systems

NASA Astrophysics Data System (ADS)

Matrau, Rémi; Klinger, Yann; Van der Woerd, Jérôme; Liu-Zeng, Jing; Li, Zhanfei; Xu, Xiwei

2017-04-01

Late Quaternary slip rate determination by CRN dating on the Haiyuan fault, China, and implication for complex geometry fault systems Matrau Rémi, Klinger Yann, Van der Woerd Jérôme, Liu-Zeng Jing, Li Zhanfei, Xu Xiwei The Haiyuan fault in Gansu Province, China, is a major left-lateral strike-slip fault forming the northeastern boundary of the Tibetan plateau and accommodating part of the deformation from the India-Asia collision. Geomorphic and geodetic studies of the Haiyuan fault show slip rates ranging from 4 mm/yr to 19 mm/yr from east to west along 500 km of the fault. Such discrepancy could be explained by the complex geometry of the fault system, leading to slip distribution on multiple branches. Combining displacement measurements of alluvial terraces from high-resolution Pléiades images and 10Be - 26Al cosmogenic radionuclides (CRN) dating, we bracket the late Quaternary slip rate along the Hasi Shan fault segment (37°00' N, 104°25' E). At our calibration site, terrace riser offsets for 5 terraces ranging from 6 m to 227 m and CRN ages ranging from 6.5±0.6 kyr to 41±4 kyr - yield geological left-lateral slip rates from 2.0 mm/yr to 4.4 mm/yr. We measured consistent terrace riser offset values along the entire 25 km-long segment, which suggests that some external forcing controls the regional river-terrace emplacement, regardless of each specific catchment. Hence, we extend our slip rate determination to the entire Hasi Shan fault segment to be 4.0±1.0 mm/yr since the last 40 kyr. This rate is consistent with other long-term rates of 4 mm/yr to 5 mm/yr east and west of Hasi Shan - as well as geodetic rates of 4 mm/yr to 6 mm/yr west of Hasi Shan. However, Holocene terraces and moraines offsets have suggested higher rates of 15 to 20 mm/yr further west. Such disparate rates may be explained by slip distribution on multiple branches. In particular, the Zhongwei fault splay in the central part of the Haiyuan fault, with a slip rate of 4-5 mm/yr could

Fault recovery characteristics of the fault tolerant multi-processor

NASA Technical Reports Server (NTRS)

Padilla, Peter A.

1990-01-01

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

Spatiotemporal analysis of Quaternary normal faults in the Northern Rocky Mountains, USA

NASA Astrophysics Data System (ADS)

Davarpanah, A.; Babaie, H. A.; Reed, P.

2010-12-01

The mid-Tertiary Basin-and-Range extensional tectonic event developed most of the normal faults that bound the ranges in the northern Rocky Mountains within Montana, Wyoming, and Idaho. The interaction of the thermally induced stress field of the Yellowstone hot spot with the existing Basin-and-Range fault blocks, during the last 15 my, has produced a new, spatially and temporally variable system of normal faults in these areas. The orientation and spatial distribution of the trace of these hot-spot induced normal faults, relative to earlier Basin-and-Range faults, have significant implications for the effect of the temporally varying and spatially propagating thermal dome on the growth of new hot spot related normal faults and reactivation of existing Basin-and-Range faults. Digitally enhanced LANDSAT 7 Enhanced Thematic Mapper Plus (ETM+) and Landsat 4 and 5 Thematic Mapper (TM) bands, with spatial resolution of 30 m, combined with analytical GIS and geological techniques helped in determining and analyzing the lineaments and traces of the Quaternary, thermally-induced normal faults in the study area. Applying the color composite (CC) image enhancement technique, the combination of bands 3, 2 and 1 of the ETM+ and TM images was chosen as the best statistical choice to create a color composite for lineament identification. The spatiotemporal analysis of the Quaternary normal faults produces significant information on the structural style, timing, spatial variation, spatial density, and frequency of the faults. The seismic Quaternary normal faults, in the whole study area, are divided, based on their age, into four specific sets, which from oldest to youngest include: Quaternary (>1.6 Ma), middle and late Quaternary (>750 ka), latest Quaternary (>15 ka), and the last 150 years. A density map for the Quaternary faults reveals that most active faults are near the current Yellowstone National Park area (YNP), where most seismically active faults, in the past 1.6 my

Methods to enhance seismic faults and construct fault surfaces

NASA Astrophysics Data System (ADS)

Wu, Xinming; Zhu, Zhihui

2017-10-01

Faults are often apparent as reflector discontinuities in a seismic volume. Numerous types of fault attributes have been proposed to highlight fault positions from a seismic volume by measuring reflection discontinuities. These attribute volumes, however, can be sensitive to noise and stratigraphic features that are also apparent as discontinuities in a seismic volume. We propose a matched filtering method to enhance a precomputed fault attribute volume, and simultaneously estimate fault strikes and dips. In this method, a set of efficient 2D exponential filters, oriented by all possible combinations of strike and dip angles, are applied to the input attribute volume to find the maximum filtering responses at all samples in the volume. These maximum filtering responses are recorded to obtain the enhanced fault attribute volume while the corresponding strike and dip angles, that yield the maximum filtering responses, are recoded to obtain volumes of fault strikes and dips. By doing this, we assume that a fault surface is locally planar, and a 2D smoothing filter will yield a maximum response if the smoothing plane coincides with a local fault plane. With the enhanced fault attribute volume and the estimated fault strike and dip volumes, we then compute oriented fault samples on the ridges of the enhanced fault attribute volume, and each sample is oriented by the estimated fault strike and dip. Fault surfaces can be constructed by directly linking the oriented fault samples with consistent fault strikes and dips. For complicated cases with missing fault samples and noisy samples, we further propose to use a perceptual grouping method to infer fault surfaces that reasonably fit the positions and orientations of the fault samples. We apply these methods to 3D synthetic and real examples and successfully extract multiple intersecting fault surfaces and complete fault surfaces without holes.

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

NASA Technical Reports Server (NTRS)

Padilla, Peter A.

1991-01-01

An investigation was made in AIRLAB of the fault handling performance of the Fault Tolerant MultiProcessor (FTMP). Fault handling errors detected during fault injection experiments were characterized. In these fault injection experiments, the FTMP disabled a working unit instead of the faulted unit once in every 500 faults, on the average. System design weaknesses allow active faults to exercise a part of the fault management software that handles Byzantine or lying faults. Byzantine faults behave such that the faulted unit points to a working unit as the source of errors. The design's problems involve: (1) the design and interface between the simplex error detection hardware and the error processing software, (2) the functional capabilities of the FTMP system bus, and (3) the communication requirements of a multiprocessor architecture. These weak areas in the FTMP's design increase the probability that, for any hardware fault, a good line replacement unit (LRU) is mistakenly disabled by the fault management software.

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

NASA Astrophysics Data System (ADS)

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

2016-10-01

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

Slip Potential of Faults in the Fort Worth Basin

NASA Astrophysics Data System (ADS)

Hennings, P.; Osmond, J.; Lund Snee, J. E.; Zoback, M. D.

2017-12-01

Similar to other areas of the southcentral United States, the Fort Worth Basin of NE Texas has experienced an increase in the rate of seismicity which has been attributed to injection of waste water in deep saline aquifers. To assess the hazard of induced seismicity in the basin we have integrated new data on location and character of previously known and unknown faults, stress state, and pore pressure to produce an assessment of fault slip potential which can be used to investigate prior and ongoing earthquake sequences and for development of mitigation strategies. We have assembled data on faults in the basin from published sources, 2D and 3D seismic data, and interpretations provided from petroleum operators to yield a 3D fault model with 292 faults ranging in strike-length from 116 to 0.4 km. The faults have mostly normal geometries, all cut the disposal intervals, and most are presumed to cut into the underlying crystalline and metamorphic basement. Analysis of outcrops along the SW flank of the basin assist with geometric characterization of the fault systems. The interpretation of stress state comes from integration of wellbore image and sonic data, reservoir stimulation data, and earthquake focal mechanisms. The orientation of SHmax is generally uniform across the basin but stress style changes from being more strike-slip in the NE part of the basin to normal faulting in the SW part. Estimates of pore pressure come from a basin-scale hydrogeologic model as history-matched to injection test data. With these deterministic inputs and appropriate ranges of uncertainty we assess the conditional probability that faults in our 3D model might slip via Mohr-Coulomb reactivation in response to increases in injected-related pore pressure. A key component of the analysis is constraining the uncertainties associated with each of the principal parameters. Many of the faults in the model are interpreted to be critically-stressed within reasonable ranges of uncertainty.

Porosity variations in and around normal fault zones: implications for fault seal and geomechanics

NASA Astrophysics Data System (ADS)

Healy, David; Neilson, Joyce; Farrell, Natalie; Timms, Nick; Wilson, Moyra

2015-04-01

Porosity forms the building blocks for permeability, exerts a significant influence on the acoustic response of rocks to elastic waves, and fundamentally influences rock strength. And yet, published studies of porosity around fault zones or in faulted rock are relatively rare, and are hugely dominated by those of fault zone permeability. We present new data from detailed studies of porosity variations around normal faults in sandstone and limestone. We have developed an integrated approach to porosity characterisation in faulted rock exploiting different techniques to understand variations in the data. From systematic samples taken across exposed normal faults in limestone (Malta) and sandstone (Scotland), we combine digital image analysis on thin sections (optical and electron microscopy), core plug analysis (He porosimetry) and mercury injection capillary pressures (MICP). Our sampling includes representative material from undeformed protoliths and fault rocks from the footwall and hanging wall. Fault-related porosity can produce anisotropic permeability with a 'fast' direction parallel to the slip vector in a sandstone-hosted normal fault. Undeformed sandstones in the same unit exhibit maximum permeability in a sub-horizontal direction parallel to lamination in dune-bedded sandstones. Fault-related deformation produces anisotropic pores and pore networks with long axes aligned sub-vertically and this controls the permeability anisotropy, even under confining pressures up to 100 MPa. Fault-related porosity also has interesting consequences for the elastic properties and velocity structure of normal fault zones. Relationships between texture, pore type and acoustic velocity have been well documented in undeformed limestone. We have extended this work to include the effects of faulting on carbonate textures, pore types and P- and S-wave velocities (Vp, Vs) using a suite of normal fault zones in Malta, with displacements ranging from 0.5 to 90 m. Our results show a

Editorial: Spatial arrangement of faults and opening-mode fractures

NASA Astrophysics Data System (ADS)

Laubach, Stephen E.; Lamarche, Juliette; Gauthier, Bertand D. M.; Dunne, William M.

2018-03-01

This issue of the Journal of Structural Geology titled Spatial arrangement of faults and opening-mode fractures explores a fundamental characteristic of fault and fracture arrays. The pattern of fault and opening-mode fracture positions in space defines structural heterogeneity and anisotropy in a rock volume, governs how faults and fractures affect fluid flow, and impacts our understanding of the initiation, propagation and interactions during the formation of fracture patterns. This special issue highlights recent progress with respect to characterizing and understanding the spatial arrangements of fault and fracture patterns, providing examples over a wide range of scales and structural settings.

Structural analysis using thrust-fault hanging-wall sequence diagrams: Ogden duplex, Wasatch Range, Utah

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

Schirmer, T.W.

1988-05-01

Detailed mapping and cross-section traverses provide the control for structural analysis and geometric modeling of the Ogden duplex, a complex thrust system exposed in the Wasatch Mountains, east of Ogden, Utah. The structures consist of east-dipping folded thrust faults, basement-cored horses, lateral ramps and folds, and tear faults. The sequence of thrusting determined by means of lateral overlap of horses, thrust-splay relationships, and a top-to-bottom piggyback development is Willard thrust, Ogden thrust, Weber thrust, and Taylor thrust. Major decollement zones occur in the Cambrian shales and limestones. The Tintic Quartzite is the marker for determining gross geometries of horses. Thismore » exposed duplex serves as a good model to illustrate the method of constructing a hanging-wall sequence diagram - a series of longitudinal cross sections that move forward in time and space, and show how a thrust system formed as it moved updip over various footwall ramps. A hanging wall sequence diagram also shows the complex lateral variations in a thrust system and helps to locate lateral ramps, lateral folds, tear faults, and other features not shown on dip-oriented cross sections. 8 figures.« less

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

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

Stockli, Daniel

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

Postobductional extension along and within the Frontal Range of the Eastern Oman Mountains

NASA Astrophysics Data System (ADS)

Mattern, Frank; Scharf, Andreas

2018-04-01

The Oman Mountains formed by late Cretaceous obduction of the Tethys-derived Semail Ophiolite. This study concerns the postobductional extension on the northern flank of the mountain belt. Nine sites at the northern margins of the Jabal Akhdar/Nakhl and Saih Hatat domes of the Eastern Oman ("Hajar") Mountains were investigated. The northern margins are marked by a system of major interconnected extensional faults, the "Frontal Range Fault". While the vertical displacements along the Saih Hatat and westerly located Jabal Nakhl domes measure 2.25-6.25 km, 0.5-4.5 km and 4-7 km, respectively, it amounts to 1-5 km along the Jabal Akhdar Dome. Extension had started during the late Cretaceous, towards the end of ophiolite emplacement. Two stages of extension can be ascertained (late Cretaceous to early Eocene and probably Oligocene) at the eastern part of the Frontal Range Fault System (Wadi Kabir and Fanja Graben faults of similar strike). Along the intervening and differently striking fault segments at Sad and Sunub the same two stages of deformation are deduced. The first stage is characterized again by extension. The second stage is marked by dextral motion, including local transtension. Probable Oligocene extension affected the Batinah Coast Fault while it also affected the Wadi Kabir Fault and the Fanja Graben. It is unclear whether the western portion of the Frontal Range Fault also went through two stages of deformation. Bedding-parallel ductile and brittle deformation is a common phenomenon. Hot springs and listwaenite are associated with dextral releasing bends within the fault system, as well as a basalt intrusion of probable Oligocene age. A structural transect through the Frontal Range along the superbly exposed Wadi Bani Kharous (Jabal Akhdar Dome) revealed that extension affected the Frontal Range at least 2.5 km south of the Frontal Range Fault. Also here, bedding-parallel shearing is important, but not exclusive. A late Cretaceous thrust was

Mountain building, strike-slip faulting, and landscape evolution in the Marlborough Fault System, NZ: Insights from new low-temperature thermochronology and modeling

NASA Astrophysics Data System (ADS)

Duvall, A. R.; Collett, C.; Flowers, R. M.; Tucker, G. E.; Upton, P.

2016-12-01

The 150 km wide Marlborough Fault System (MFS) and adjacent dextral-reverse Alpine Fault accommodate oblique convergence of the Australian and Pacific plates in a broad transform boundary that extends for much of the South Island New Zealand. Understanding the deformation history of the Marlborough region offers the opportunity to study topographic evolution in a strike-slip setting and a fuller picture of the evolving New Zealand plate boundary as the MFS lies at the transition from oceanic Pacific plate subduction to oblique continental collision. Here we present low-temperature thermochronology from the MFS to place new limits on the timing and style of mountain building. We sampled a range of elevations spanning 2 km within and adjacent to the Kaikoura Mountains, which stand high as topographic anomalies above active strike-slip faults. Young apatite (U-Th)/He ages ( 2-5 Ma) on both sides of range-bounding faults are consistent with regional distributed deformation since the Pliocene initiation of strike-slip faulting. However, large differences in both zircon helium and apatite fission track ages, from Paleogene/Neogene ages within hanging walls to unreset >100 Ma ages in footwalls, indicate an early phase of fault-related vertical exhumation. Thermal modeling using the QTQt program reveals two phases of exhumation within the Kaikoura Ranges: rapid cooling at 15-12 Ma localized to hanging wall rocks and regional rapid cooling reflected in all samples starting at 4-5 Ma. These results and landscape evolution models suggest that, despite the presence of active mountain front faults, much of the topographic relief in this region may predate the onset of strike-slip faulting and that portions of the Marlborough Faults are re-activated thrusts that coincide with the early development of the transpressive plate boundary. Regional exhumation after 5 Ma likely reflects increased proximity to the migrating Pacific plate subduction zone and the buoyant Chatham Rise.

Spatiotemporal patterns of fault slip rates across the Central Sierra Nevada frontal fault zone

NASA Astrophysics Data System (ADS)

Rood, Dylan H.; Burbank, Douglas W.; Finkel, Robert C.

2011-01-01

Patterns in fault slip rates through time and space are examined across the transition from the Sierra Nevada to the Eastern California Shear Zone-Walker Lane belt. At each of four sites along the eastern Sierra Nevada frontal fault zone between 38 and 39° N latitude, geomorphic markers, such as glacial moraines and outwash terraces, are displaced by a suite of range-front normal faults. Using geomorphic mapping, surveying, and 10Be surface exposure dating, mean fault slip rates are defined, and by utilizing markers of different ages (generally, ~ 20 ka and ~ 150 ka), rates through time and interactions among multiple faults are examined over 10 4-10 5 year timescales. At each site for which data are available for the last ~ 150 ky, mean slip rates across the Sierra Nevada frontal fault zone have probably not varied by more than a factor of two over time spans equal to half of the total time interval (~ 20 ky and ~ 150 ky timescales): 0.3 ± 0.1 mm year - 1 (mode and 95% CI) at both Buckeye Creek in the Bridgeport basin and Sonora Junction; and 0.4 + 0.3/-0.1 mm year - 1 along the West Fork of the Carson River at Woodfords. Data permit rates that are relatively constant over the time scales examined. In contrast, slip rates are highly variable in space over the last ~ 20 ky. Slip rates decrease by a factor of 3-5 northward over a distance of ~ 20 km between the northern Mono Basin (1.3 + 0.6/-0.3 mm year - 1 at Lundy Canyon site) to the Bridgeport Basin (0.3 ± 0.1 mm year - 1 ). The 3-fold decrease in the slip rate on the Sierra Nevada frontal fault zone northward from Mono Basin is indicative of a change in the character of faulting north of the Mina Deflection as extension is transferred eastward onto normal faults between the Sierra Nevada and Walker Lane belt. A compilation of regional deformation rates reveals that the spatial pattern of extension rates changes along strike of the Eastern California Shear Zone-Walker Lane belt. South of the Mina Deflection

Spatiotemporal Patterns of Fault Slip Rates Across the Central Sierra Nevada Frontal Fault Zone

NASA Astrophysics Data System (ADS)

Rood, D. H.; Burbank, D.; Finkel, R. C.

2010-12-01

We examine patterns in fault slip rates through time and space across the transition from the Sierra Nevada to the Eastern California Shear Zone-Walker Lane belt. At each of four sites along the eastern Sierra Nevada frontal fault zone between 38-39° N latitude, geomorphic markers, such as glacial moraines and outwash terraces, are displaced by a suite of range-front normal faults. Using geomorphic mapping, surveying, and Be-10 surface exposure dating, we define mean fault slip rates, and by utilizing markers of different ages (generally, ~20 ka and ~150 ka), we examine rates through time and interactions among multiple faults over 10-100 ky timescales. At each site for which data are available for the last ~150 ky, mean slip rates across the Sierra Nevada frontal fault zone have probably not varied by more than a factor of two over time spans equal to half of the total time interval (~20 ky and ~150 ky timescales): 0.3 ± 0.1 mm/yr (mode and 95% CI) at both Buckeye Creek in the Bridgeport basin and Sonora Junction; and 0.4 +0.3/-0.1 mm/yr along the West Fork of the Carson River at Woodfords. Our data permit that rates are relatively constant over the time scales examined. In contrast, slip rates are highly variable in space over the last ~20 ky. Slip rates decrease by a factor of 3-5 northward over a distance of ~20 km between the northern Mono Basin (1.3 +0.6/-0.3 mm/yr at Lundy Canyon site) and the Bridgeport Basin (0.3 ± 0.1 mm/yr). The 3-fold decrease in the slip rate on the Sierra Nevada frontal fault zone northward from Mono Basin reflects a change in the character of faulting north of the Mina Deflection as extension is transferred eastward onto normal faults between the Sierra Nevada and Walker Lane belt. A compilation of regional deformation rates reveal that the spatial pattern of extension rates changes along strike of the Eastern California Shear Zone-Walker Lane belt. South of the Mina Deflection, extension is accommodated within a diffuse zone of

A fault-based model for crustal deformation, fault slip-rates and off-fault strain rate in California

USGS Publications Warehouse

Zeng, Yuehua; Shen, Zheng-Kang

2016-01-01

We invert Global Positioning System (GPS) velocity data to estimate fault slip rates in California using a fault‐based crustal deformation model with geologic constraints. The model assumes buried elastic dislocations across the region using Uniform California Earthquake Rupture Forecast Version 3 (UCERF3) fault geometries. New GPS velocity and geologic slip‐rate data were compiled by the UCERF3 deformation working group. The result of least‐squares inversion shows that the San Andreas fault slips at 19–22  mm/yr along Santa Cruz to the North Coast, 25–28  mm/yr along the central California creeping segment to the Carrizo Plain, 20–22  mm/yr along the Mojave, and 20–24  mm/yr along the Coachella to the Imperial Valley. Modeled slip rates are 7–16  mm/yr lower than the preferred geologic rates from the central California creeping section to the San Bernardino North section. For the Bartlett Springs section, fault slip rates of 7–9  mm/yr fall within the geologic bounds but are twice the preferred geologic rates. For the central and eastern Garlock, inverted slip rates of 7.5 and 4.9  mm/yr, respectively, match closely with the geologic rates. For the western Garlock, however, our result suggests a low slip rate of 1.7  mm/yr. Along the eastern California shear zone and southern Walker Lane, our model shows a cumulative slip rate of 6.2–6.9  mm/yr across its east–west transects, which is ∼1  mm/yr increase of the geologic estimates. For the off‐coast faults of central California, from Hosgri to San Gregorio, fault slips are modeled at 1–5  mm/yr, similar to the lower geologic bounds. For the off‐fault deformation, the total moment rate amounts to 0.88×1019  N·m/yr, with fast straining regions found around the Mendocino triple junction, Transverse Ranges and Garlock fault zones, Landers and Brawley seismic zones, and farther south. The overall California moment rate is 2.76×1019�

Series and parallel arc-fault circuit interrupter tests.

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

Johnson, Jay Dean; Fresquez, Armando J.; Gudgel, Bob

2013-07-01

While the 2011 National Electrical Codeª (NEC) only requires series arc-fault protection, some arc-fault circuit interrupter (AFCI) manufacturers are designing products to detect and mitigate both series and parallel arc-faults. Sandia National Laboratories (SNL) has extensively investigated the electrical differences of series and parallel arc-faults and has offered possible classification and mitigation solutions. As part of this effort, Sandia National Laboratories has collaborated with MidNite Solar to create and test a 24-string combiner box with an AFCI which detects, differentiates, and de-energizes series and parallel arc-faults. In the case of the MidNite AFCI prototype, series arc-faults are mitigated by openingmore » the PV strings, whereas parallel arc-faults are mitigated by shorting the array. A range of different experimental series and parallel arc-fault tests with the MidNite combiner box were performed at the Distributed Energy Technologies Laboratory (DETL) at SNL in Albuquerque, NM. In all the tests, the prototype de-energized the arc-faults in the time period required by the arc-fault circuit interrupt testing standard, UL 1699B. The experimental tests confirm series and parallel arc-faults can be successfully mitigated with a combiner box-integrated solution.« less

FTAPE: A fault injection tool to measure fault tolerance

NASA Technical Reports Server (NTRS)

Tsai, Timothy K.; Iyer, Ravishankar K.

1995-01-01

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

Fault compaction and overpressured faults: results from a 3-D model of a ductile fault zone

NASA Astrophysics Data System (ADS)

Fitzenz, D. D.; Miller, S. A.

2003-10-01

A model of a ductile fault zone is incorporated into a forward 3-D earthquake model to better constrain fault-zone hydraulics. The conceptual framework of the model fault zone was chosen such that two distinct parts are recognized. The fault core, characterized by a relatively low permeability, is composed of a coseismic fault surface embedded in a visco-elastic volume that can creep and compact. The fault core is surrounded by, and mostly sealed from, a high permeability damaged zone. The model fault properties correspond explicitly to those of the coseismic fault core. Porosity and pore pressure evolve to account for the viscous compaction of the fault core, while stresses evolve in response to the applied tectonic loading and to shear creep of the fault itself. A small diffusive leakage is allowed in and out of the fault zone. Coseismically, porosity is created to account for frictional dilatancy. We show in the case of a 3-D fault model with no in-plane flow and constant fluid compressibility, pore pressures do not drop to hydrostatic levels after a seismic rupture, leading to an overpressured weak fault. Since pore pressure plays a key role in the fault behaviour, we investigate coseismic hydraulic property changes. In the full 3-D model, pore pressures vary instantaneously by the poroelastic effect during the propagation of the rupture. Once the stress state stabilizes, pore pressures are incrementally redistributed in the failed patch. We show that the significant effect of pressure-dependent fluid compressibility in the no in-plane flow case becomes a secondary effect when the other spatial dimensions are considered because in-plane flow with a near-lithostatically pressured neighbourhood equilibrates at a pressure much higher than hydrostatic levels, forming persistent high-pressure fluid compartments. If the observed faults are not all overpressured and weak, other mechanisms, not included in this model, must be at work in nature, which need to be

Evolution of triangular topographic facets along active normal faults

NASA Astrophysics Data System (ADS)

Balogun, A.; Dawers, N. H.; Gasparini, N. M.; Giachetta, E.

2011-12-01

Triangular shaped facets, which are generally formed by the erosion of fault - bounded mountain ranges, are arguably one of the most prominent geomorphic features on active normal fault scarps. Some previous studies of triangular facet development have suggested that facet size and slope exhibit a strong linear dependency on fault slip rate, thus linking their growth directly to the kinematics of fault initiation and linkage. Other studies, however, generally conclude that there is no variation in triangular facet geometry (height and slope) with fault slip rate. The landscape of the northeastern Basin and Range Province of the western United States provides an opportunity for addressing this problem. This is due to the presence of well developed triangular facets along active normal faults, as well as spatial variations in fault scale and slip rate. In addition, the Holocene climatic record for this region suggests a dominant tectonic regime, as the faulted landscape shows little evidence of precipitation gradients associated with tectonic uplift. Using GIS-based analyses of USGS 30 m digital elevation data (DEMs) for east - central Idaho and southwestern Montana, we analyze triangular facet geometries along fault systems of varying number of constituent segments. This approach allows us to link these geometries with established patterns of along - strike slip rate variation. For this study, we consider major watersheds to include only catchments with upstream and downstream boundaries extending from the drainage divide to the mapped fault trace, respectively. In order to maintain consistency in the selection criteria for the analyzed triangular facets, only facets bounded on opposite sides by major watersheds were considered. Our preliminary observations reflect a general along - strike increase in the surface area, average slope, and relief of triangular facets from the tips of the fault towards the center. We attribute anomalies in the along - strike geometric

Seismic measurements of the internal properties of fault zones

USGS Publications Warehouse

Mooney, W.D.; Ginzburg, A.

1986-01-01

The internal properties within and adjacent to fault zones are reviewed, principally on the basis of laboratory, borehole, and seismic refraction and reflection data. The deformation of rocks by faulting ranges from intragrain microcracking to severe alteration. Saturated microcracked and mildly fractured rocks do not exhibit a significant reduction in velocity, but, from borehole measurements, densely fractured rocks do show significantly reduced velocities, the amount of reduction generally proportional to the fracture density. Highly fractured rock and thick fault gouge along the creeping portion of the San Andreas fault are evidenced by a pronounced seismic low-velocity zone (LVZ), which is either very thin or absent along locked portions of the fault. Thus there is a correlation between fault slip behavior and seismic velocity structure within the fault zone; high pore pressure within the pronounced LVZ may be conductive to fault creep. Deep seismic reflection data indicate that crustal faults sometimes extend through the entire crust. Models of these data and geologic evidence are consistent with a composition of deep faults consisting of highly foliated, seismically anisotropic mylonites. ?? 1986 Birkha??user Verlag, Basel.

Flight elements: Fault detection and fault management

NASA Technical Reports Server (NTRS)

Lum, H.; Patterson-Hine, A.; Edge, J. T.; Lawler, D.

1990-01-01

Fault management for an intelligent computational system must be developed using a top down integrated engineering approach. An approach proposed includes integrating the overall environment involving sensors and their associated data; design knowledge capture; operations; fault detection, identification, and reconfiguration; testability; causal models including digraph matrix analysis; and overall performance impacts on the hardware and software architecture. Implementation of the concept to achieve a real time intelligent fault detection and management system will be accomplished via the implementation of several objectives, which are: Development of fault tolerant/FDIR requirement and specification from a systems level which will carry through from conceptual design through implementation and mission operations; Implementation of monitoring, diagnosis, and reconfiguration at all system levels providing fault isolation and system integration; Optimize system operations to manage degraded system performance through system integration; and Lower development and operations costs through the implementation of an intelligent real time fault detection and fault management system and an information management system.

Subsidence and Fault Displacement Along the Long Point Fault Derived from Continuous GPS Observations (2012-2017)

NASA Astrophysics Data System (ADS)

Tsibanos, V.; Wang, G.

2017-12-01

The Long Point Fault located in Houston Texas is a complex system of normal faults which causes significant damage to urban infrastructure on both private and public property. This case study focuses on the 20-km long fault using high accuracy continuously operating global positioning satellite (GPS) stations to delineate fault movement over five years (2012 - 2017). The Long Point Fault is the longest active fault in the greater Houston area that damages roads, buried pipes, concrete structures and buildings and creates a financial burden for the city of Houston and the residents who live in close vicinity to the fault trace. In order to monitor fault displacement along the surface 11 permanent and continuously operating GPS stations were installed 6 on the hanging wall and 5 on the footwall. This study is an overview of the GPS observations from 2013 to 2017. GPS positions were processed with both relative (double differencing) and absolute Precise Point Positioning (PPP) techniques. The PPP solutions that are referred to IGS08 reference frame were transformed to the Stable Houston Reference Frame (SHRF16). Our results show no considerable horizontal displacements across the fault, but do show uneven vertical displacement attributed to regional subsidence in the range of (5 - 10 mm/yr). This subsidence can be associated to compaction of silty clays in the Chicot and Evangeline aquifers whose water depths are approximately 50m and 80m below the land surface (bls). These levels are below the regional pre-consolidation head that is about 30 to 40m bls. Recent research indicates subsidence will continue to occur until the aquifer levels reach the pre-consolidation head. With further GPS observations both the Long Point Fault and regional land subsidence can be monitored providing important geological data to the Houston community.

Global strike-slip fault distribution on Enceladus reveals mostly left-lateral faults

NASA Astrophysics Data System (ADS)

Martin, E. S.; Kattenhorn, S. A.

2013-12-01

Within the outer solar system, normal faults are a dominant tectonic feature; however, strike-slip faults have played a role in modifying the surfaces of many icy bodies, including Europa, Ganymede, and Enceladus. Large-scale tectonic deformation in icy shells develops in response to stresses caused by a range of mechanisms including polar wander, despinning, volume changes, orbital recession/decay, diurnal tides, and nonsynchronous rotation (NSR). Icy shells often preserve this record of tectonic deformation as patterns of fractures that can be used to identify the source of stress responsible for creating the patterns. Previously published work on Jupiter's moon Europa found that right-lateral strike-slip faults predominantly formed in the southern hemisphere and left-lateral strike-slip faults in the northern hemisphere. This pattern suggested they were formed in the past by stresses induced by diurnal tidal forcing, and were then rotated into their current longitudinal positions by NSR. We mapped the distribution of strike-slip faults on Enceladus and used kinematic indicators, including tailcracks and en echelon fractures, to determine their sense of slip. Tailcracks are secondary fractures that form as a result of concentrations of stress at the tips of slipping faults with geometric patterns dictated by the slip sense. A total of 31 strike-slip faults were identified, nine of which were right-lateral faults, all distributed in a seemingly random pattern across Enceladus's surface, in contrast to Europa. Additionally, there is a dearth of strike-slip faults within the tectonized terrains centered at 90°W and within the polar regions north and south of 60°N and 60°S, respectively. The lack of strike-slip faults in the north polar region may be explained, in part, by limited data coverage. The south polar terrain (SPT), characterized by the prominent tiger stripes and south polar dichotomy, yielded no discrete strike-slip faults. This does not suggest that

Up-dip partitioning of displacement components on the oblique-slip Clarence Fault, New Zealand

NASA Astrophysics Data System (ADS)

Nicol, Andrew; Van Dissen, Russell

2002-09-01

Active strike-slip faults in New Zealand occur within an obliquely-convergent plate boundary zone. Although the traces of these faults commonly delineate the base of mountain ranges, they do not always accommodate significant shortening at the free surface. Along the active trace of Clarence Fault in northeastern South Island, New Zealand, displaced landforms and slickenside striations indicate predominantly horizontal displacements at the ground surface, and a right-lateral slip rate of ca. 3.5-5 mm/year during the Holocene. The Inland Kaikoura mountain range occupies the hanging wall of the fault and rises steeply from the active trace to altitudes of ca. 3 km. The geomorphology of the range indicates active uplift and mountain building, which is interpreted to result, in part, from a vertical component of fault slip at depth. These data are consistent with the fault accommodating oblique-slip at depth aligned parallel to the plate-motion vector and compatible with regional geodetic data and earthquake focal-mechanisms. Oblique-slip on the Clarence Fault at depth is partitioned at the free surface into: (1) right-lateral displacement on the fault, and (2) hanging wall uplift produced by distributed displacement on small-scale faults parallel to the main fault. Decoupling of slip components reflects an up-dip transfer of fault throw to an off-fault zone of distributed uplift. Such zones are common in the hanging walls of thrusts and reverse faults, and support the idea that the dip of the oblique-slip Clarence Fault steepens towards the free surface.

Evaluation of fault-normal/fault-parallel directions rotated ground motions for response history analysis of an instrumented six-story building

USGS Publications Warehouse

Kalkan, Erol; Kwong, Neal S.

2012-01-01

According to regulatory building codes in United States (for example, 2010 California Building Code), at least two horizontal ground-motion components are required for three-dimensional (3D) response history analysis (RHA) of buildings. For sites within 5 km of an active fault, these records should be rotated to fault-normal/fault-parallel (FN/FP) directions, and two RHA analyses should be performed separately (when FN and then FP are aligned with the transverse direction of the structural axes). It is assumed that this approach will lead to two sets of responses that envelope the range of possible responses over all nonredundant rotation angles. This assumption is examined here using a 3D computer model of a six-story reinforced-concrete instrumented building subjected to an ensemble of bidirectional near-fault ground motions. Peak responses of engineering demand parameters (EDPs) were obtained for rotation angles ranging from 0° through 180° for evaluating the FN/FP directions. It is demonstrated that rotating ground motions to FN/FP directions (1) does not always lead to the maximum responses over all angles, (2) does not always envelope the range of possible responses, and (3) does not provide maximum responses for all EDPs simultaneously even if it provides a maximum response for a specific EDP.

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

USGS Publications Warehouse

Spencer, J.E.

2011-01-01

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

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

NASA Astrophysics Data System (ADS)

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

2017-12-01

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

Diagnostics Tools Identify Faults Prior to Failure

NASA Technical Reports Server (NTRS)

2013-01-01

Through the SBIR program, Rochester, New York-based Impact Technologies LLC collaborated with Ames Research Center to commercialize the Center s Hybrid Diagnostic Engine, or HyDE, software. The fault detecting program is now incorporated into a software suite that identifies potential faults early in the design phase of systems ranging from printers to vehicles and robots, saving time and money.

Physical and Transport Property Variations Within Carbonate-Bearing Fault Zones: Insights From the Monte Maggio Fault (Central Italy)

NASA Astrophysics Data System (ADS)

Trippetta, F.; Carpenter, B. M.; Mollo, S.; Scuderi, M. M.; Scarlato, P.; Collettini, C.

2017-11-01

The physical characterization of carbonate-bearing normal faults is fundamental for resource development and seismic hazard. Here we report laboratory measurements of density, porosity, Vp, Vs, elastic moduli, and permeability for a range of effective confining pressures (0.1-100 MPa), conducted on samples representing different structural domains of a carbonate-bearing fault. We find a reduction in porosity from the fault breccia (11.7% total and 6.2% connected) to the main fault plane (9% total and 3.5% connected), with both domains showing higher porosity compared to the protolith (6.8% total and 1.1% connected). With increasing confining pressure, P wave velocity evolves from 4.5 to 5.9 km/s in the fault breccia, is constant at 5.9 km/s approaching the fault plane and is low (4.9 km/s) in clay-rich fault domains. We find that while the fault breccia shows pressure sensitive behavior (a reduction in permeability from 2 × 10-16 to 2 × 10-17 m2), the cemented cataclasite close to the fault plane is characterized by pressure-independent behavior (permeability 4 × 10-17 m2). Our results indicate that the deformation processes occurring within the different fault structural domains influence the physical and transport properties of the fault zone. In situ Vp profiles match well the laboratory measurements demonstrating that laboratory data are valuable for implications at larger scale. Combining the experimental values of elastic moduli and frictional properties it results that at shallow crustal levels, M ≤ 1 earthquakes are less favored, in agreement with earthquake-depth distribution during the L'Aquila 2009 seismic sequence that occurred on carbonates.

Contrasting fault fluids along high-angle faults: a case study from Southern Apennines (Italy)

NASA Astrophysics Data System (ADS)

Sinisi, Rosa; Petrullo, Angela Vita; Agosta, Fabrizio; Paternoster, Michele; Belviso, Claudia; Grassa, Fausto

2016-10-01

This work focuses on two fault-controlled deposits, the Atella and Rapolla travertines, which are associated with high-angle extensional faults of the Bradano Trough, southern Apennines (Italy). The Atella travertine is along a NW-SE striking, deep-seated extensional fault, already described in literature, which crosscuts both Apulian carbonates and the overlying foredeep basin infill. The Rapolla travertine is on top of a NE-SW striking, shallow-seated fault, here described for the first time, which is interpreted as a tear fault associated with a shallow thrust displacing only the foredeep basin infill. The results of structural, sedimentological, mineralogical, and C and O isotope analyses are here reported and discussed to assess the provenance of mineralizing fluids, and to evaluate the control exerted by the aforementioned extensional faults on deep, mantle-derived and shallow, meteoric fluids. Sedimentological analysis is consistent with five lithofacies in the studied travertines, which likely formed in a typical lacustrine depositional environment. Mineralogical analysis show that travertines mainly consist of calcite, and minor quartz, feldspar and clay minerals, indicative of a terrigenous supply during travertine precipitation. The isotope signature of the two studied travertines shows different provenance for the mineralizing fluids. At the Atella site, the δ13CPDB values range between + 5.2 and + 5.7‰ and the δ18OPDB values between - 9.0 and - 7.3‰, which are consistent with a mantle-derived CO2 component in the fluid. In contrast, at the Rapolla site the δ13CPDB values vary from - 2.7 to + 1.5‰ and the δ18OPDB values from - 6.8 to - 5.4‰, suggesting a mixed CO2 source with both biogenic-derived and mantle-derived fluids. The results of structural analyses conducted along the footwall damage zone of the fault exposed at the Rapolla site, show that the whole damage zone, in which fractures and joints likely channeled the mixed fluids, acted

Ground Motions Due to Earthquakes on Creeping Faults

NASA Astrophysics Data System (ADS)

Harris, R.; Abrahamson, N. A.

2014-12-01

We investigate the peak ground motions from the largest well-recorded earthquakes on creeping strike-slip faults in active-tectonic continental regions. Our goal is to evaluate if the strong ground motions from earthquakes on creeping faults are smaller than the strong ground motions from earthquakes on locked faults. Smaller ground motions might be expected from earthquakes on creeping faults if the fault sections that strongly radiate energy are surrounded by patches of fault that predominantly absorb energy. For our study we used the ground motion data available in the PEER NGA-West2 database, and the ground motion prediction equations that were developed from the PEER NGA-West2 dataset. We analyzed data for the eleven largest well-recorded creeping-fault earthquakes, that ranged in magnitude from M5.0-6.5. Our findings are that these earthquakes produced peak ground motions that are statistically indistinguishable from the peak ground motions produced by similar-magnitude earthquakes on locked faults. These findings may be implemented in earthquake hazard estimates for moderate-size earthquakes in creeping-fault regions. Further investigation is necessary to determine if this result will also apply to larger earthquakes on creeping faults. Please also see: Harris, R.A., and N.A. Abrahamson (2014), Strong ground motions generated by earthquakes on creeping faults, Geophysical Research Letters, vol. 41, doi:10.1002/2014GL060228.

Surface fault slip associated with the 2004 Parkfield, California, earthquake

USGS Publications Warehouse

Rymer, M.J.; Tinsley, J. C.; Treiman, J.A.; Arrowsmith, J.R.; Ciahan, K.B.; Rosinski, A.M.; Bryant, W.A.; Snyder, H.A.; Fuis, G.S.; Toke, N.A.; Bawden, G.W.

2006-01-01

Surface fracturing occurred along the San Andreas fault, the subparallel Southwest Fracture Zone, and six secondary faults in association with the 28 September 2004 (M 6.0) Parkfield earthquake. Fractures formed discontinuous breaks along a 32-km-long stretch of the San Andreas fault. Sense of slip was right lateral; only locally was there a minor (1-11 mm) vertical component of slip. Right-lateral slip in the first few weeks after the event, early in its afterslip period, ranged from 1 to 44 mm. Our observations in the weeks following the earthquake indicated that the highest slip values are in the Middle Mountain area, northwest of the mainshock epicenter (creepmeter measurements indicate a similar distribution of slip). Surface slip along the San Andreas fault developed soon after the mainshock; field checks in the area near Parkfield and about 5 km to the southeast indicated that surface slip developed more than 1 hr but generally less than 1 day after the event. Slip along the Southwest Fracture Zone developed coseismically and extended about 8 km. Sense of slip was right lateral; locally there was a minor to moderate (1-29 mm) vertical component of slip. Right-lateral slip ranged from 1 to 41 mm. Surface slip along secondary faults was right lateral; the right-lateral component of slip ranged from 3 to 5 mm. Surface slip in the 1966 and 2004 events occurred along both the San Andreas fault and the Southwest Fracture Zone. In 1966 the length of ground breakage along the San Andreas fault extended 5 km longer than that mapped in 2004. In contrast, the length of ground breakage along the Southwest Fracture Zone was the same in both events, yet the surface fractures were more continuous in 2004. Surface slip on secondary faults in 2004 indicated previously unmapped structural connections between the San Andreas fault and the Southwest Fracture Zone, further revealing aspects of the structural setting and fault interactions in the Parkfield area.

Near-fault peak ground velocity from earthquake and laboratory data

USGS Publications Warehouse

McGarr, A.; Fletcher, Joe B.

2007-01-01

We test the hypothesis that peak ground velocity (PGV) has an upper bound independent of earthquake magnitude and that this bound is controlled primarily by the strength of the seismogenic crust. The highest PGVs, ranging up to several meters per second, have been measured at sites within a few kilometers of the causative faults. Because the database for near-fault PGV is small, we use earthquake slip models, laboratory experiments, and evidence from a mining-induced earthquake to investigate the factors influencing near-fault PGV and the nature of its scaling. For each earthquake slip model we have calculated the peak slip rates for all subfaults and then chosen the maximum of these rates as an estimate of twice the largest near-fault PGV. Nine slip models for eight earthquakes, with magnitudes ranging from 6.5 to 7.6, yielded maximum peak slip rates ranging from 2.3 to 12 m/sec with a median of 5.9 m/sec. By making several adjustments, PGVs for small earthquakes can be simulated from peak slip rates measured during laboratory stick-slip experiments. First, we adjust the PGV for differences in the state of stress (i.e., the difference between the laboratory loading stresses and those appropriate for faults at seismogenic depths). To do this, we multiply both the slip and the peak slip rate by the ratio of the effective normal stresses acting on fault planes measured at 6.8 km depth at the KTB site, Germany (deepest available in situ stress measurements), to those acting on the laboratory faults. We also adjust the seismic moment by replacing the laboratory fault with a buried circular shear crack whose radius is chosen to match the experimental unloading stiffness. An additional, less important adjustment is needed for experiments run in triaxial loading conditions. With these adjustments, peak slip rates for 10 stick-slip events, with scaled moment magnitudes from -2.9 to 1.0, range from 3.3 to 10.3 m/sec, with a median of 5.4 m/sec. Both the earthquake and

The role of large strike-slip faults in a convergent continental setting - first results from the Dzhungarian Fault in Eastern Kazakhstan

NASA Astrophysics Data System (ADS)

Grützner, Christoph; Campbell, Grace; Elliott, Austin; Walker, Richard; Abdrakhmatov, Kanatbek

2016-04-01

The Tien Shan and the Dzhungarian Ala-tau mountain ranges in Eastern Kazakhstan and China take up a significant portion of the total convergence between India and Eurasia, despite the fact that they are more than 1000 km away from the actual plate boundary. Shortening is accommodated by large thrust faults that strike more or less perpendicular to the convergence vector, and by a set of conjugate strike-slip faults. Some of these strike-slip faults are major features of several hundred kilometres length and have produced great historical earthquakes. In most cases, little is known about their slip-rates and earthquake history, and thus, about their role in the regional tectonic setting. This study deals with the NW-SE trending Dzhungarian Fault, a more than 350 km-long, right-lateral strike slip feature. It borders the Dzhungarian Ala-tau range and forms one edge of the so-called Dzhungarian Gate. The fault curves from a ~305° strike at its NW tip in Kazakhstan to a ~328° strike in China. No historical ruptures are known from the Kazakh part of the fault. A possible rupture in 1944 in the Chinese part remains discussed. We used remote sensing, Structure-from-Motion (SfM), differential GPS, field mapping, and Quaternary dating of offset geological markers in order to map the fault-related morphology and to measure the slip rate of the fault at several locations along strike. We also aimed to find out the age of the last surface rupturing earthquake and to determine earthquake recurrence intervals and magnitudes. We were further interested in the relation between horizontal and vertical motion along the fault and possible fault segmentation. Here we present first results from our 2015 survey. High-resolution digital elevation models of offset river terraces allowed us to determine the slip vector of the most recent earthquake. Preliminary dating results from abandoned fluvial terraces allow us to speculate on a late Holocene surface rupturing event. Morphological

Seismic reflection study of the East Potrillo Fault, southwestern Dona Ana County, New Mexico

NASA Astrophysics Data System (ADS)

Carley, Shane Alan

The East Potrillo Mountains are located just north of the U.S.-Mexico border in southwestern Dona Ana County, New Mexico. Laramide and Rio Grande rift deformation has formed low-angle and high-angle Tertiary normal faults that are exposed in the area. Along the east flank of the range is the East Potrillo Fault identified on the surface as a north-striking scarp. Fault scarps associated with the East Potrillo Fault have been dated using slope degradation models and they range between 56 ka and 377 ka in age. Offset of geomorphic surfaces interpreted to be tectonic terraces records at least four earthquakes over that period of time, leading to an estimated recurrence interval of 33.5 kyr. Because of this paleoseismic history, the East Potrillo Fault potentially poses a significant seismic hazard to the over 2 million residents living in the border region. Our study presents two 2D seismic reflection profiles to give the first subsurface image of the East Potrillo Fault and potentially other subsidiary faults that have not broken the surface. Three faults are identified in the subsurface, two of which were previously unknown. The range bounding fault is identified 300 m west of observed fault scarps. The fault scarp is found to be formed from one of two secondary faults. It dips 75°s east and has a fault offset of 150 m. The other secondary fault is an antithetic fault dipping 75°s west and forms a graben within the EPF system. The vibroseis source data acquisition is found to be beneficial for characterizing unknown subsurface features.

Moderate rates of late Quaternary slip along the northwestern margin of the Basin and Range Province, Surprise Valley fault, northeastern California

USGS Publications Warehouse

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

2009-01-01

The 86-km-long Surprise Valley normal fault forms part of the active northwestern margin of the Basin and Range province in northeastern California. We use trench mapping and radiocarbon, luminescence, and tephra dating to estimate displacements and timing of the past five surface-rupturing earthquakes on the central part of the fault near Cedarville. A Bayesian OxCal analysis of timing constraints indicates earthquake times of 18.2 ± 2.6, 10.9 ± 3.2, 8.5 ± 0.5, 5.8 ± 1.5, and 1.2 ± 0.1 ka. These data yield recurrence intervals of 7.3 ± 4.1, 2.5 ± 3.2, 2.7 ± 1.6, and 4.5 ± 1.5 ka and an elapsed time of 1.2 ± 0.1 ka since the latest surface-rupturing earthquake. Our best estimate of latest Quaternary vertical slip rate is 0.6 ?? 0.1 mm/a. This late Quaternary rate is remarkably similar to long-term (8-14 Ma) minimum vertical slip rates (>0.4-0.5 ± 0.3 mm/a) calculated from recently acquired seismic reflection and chronologic and structural data in Surprise Valley and the adjacent Warner Mountains. However, our slip rate yields estimates of extension that are lower than recent campaign GPS determinations by factors of 1.5-4 unless the fault has an unusually shallow (30°-35°) dip as suggested by recently acquired seismic reflection data. Coseismic displacements of 2-4.5 ± 1 m documented in the trench and probable rupture lengths of 53-65 km indicate a history of latest Quaternary earthquakes of M 6.8-7.3 on the central part of the. Surprise Valley fault.

Thermal regime of the San Andreas fault near Parkfield, California

USGS Publications Warehouse

Sass, J.H.; Williams, C.F.; Lachenbruch, A.H.; Galanis, S.P.; Grubb, F.V.

1997-01-01

Knowledge of the temperature variation with depth near the San Andreas fault is vital to understanding the physical processes that occur within the fault zone during earthquakes and creep events. Parkfield is near the southern end of the Coast Ranges segment of the San Andreas fault. This segment has higher mean heat flow than the Cape Mendocino segment to the northwest or the Mojave segment to the southeast. Boreholes were drilled specifically for the U.S. Geological Survey's Parkfield earthquake prediction experiment or converted from other uses at 25 sites within a few kilometers of the fault near Parkfield. These holes, which range in depth from 150 to over 1500 m, were intended mainly for the deployment of volumetric strain meters, water-level recorders, and other downhole instruments. Temperature profiles were obtained from all the holes, and heat flow values were estimated from 17 of them. For a number of reasons, including a paucity of thermal conductivity data and rugged local topography, the accuracy of individual determinations was not sufficiently high to document local variations in heat flow. Values range from 54 to 92 mW m-2, with mean and 95% confidence limits of 74 ?? 4 mW m-2. This mean is slightly lower than the mean (83 ?? 3) of 39 previously published values from the central Coast Ranges, but it is consistent with the overall pattern of elevated heat flow in the Coast Ranges, and it is transitional to the mean of 68 ?? 2 mW m-2 that characterizes the Mojave segment of the San Andreas fault immediately to the south. The lack of a heat flow peak near the fault underscores the absence of a frictional thermal anomaly and provides additional support for a very small resolved shear stress parallel to the San Andreas fault and the nearly fault-normal maximum compressive stress observed in this region. Estimates of subsurface thermal conditions indicate that the seismic-aseismic transition for the Parkfield segment corresponds to temperatures in the

Stress before and after the 2002 Denali fault earthquake

USGS Publications Warehouse

Wesson, R.L.; Boyd, O.S.

2007-01-01

Spatially averaged, absolute deviatoric stress tensors along the faults ruptured during the 2002 Denali fault earthquake, both before and after the event, are derived, using a new method, from estimates of the orientations of the principal stresses and the stress change associated with the earthquake. Stresses are estimated in three regions along the Denali fault, one of which also includes the Susitna Glacier fault, and one region along the Totschunda fault. Estimates of the spatially averaged shear stress before the earthquake resolved onto the faults that ruptured during the event range from near 1 MPa to near 4 MPa. Shear stresses estimated along the faults in all these regions after the event are near zero (0 ?? 1 MPa). These results suggest that deviatoric stresses averaged over a few tens of km along strike are low, and that the stress drop during the earthquake was complete or nearly so.

Relationship of faults in basin sediments to the gravity and magnetic expression of their underlying fault systems

USGS Publications Warehouse

Baldyga, Christopher A.

2001-01-01

Gravity and magnetic surveys were performed along the western flanks of the Santa Rita Mountain range located in southeastern Arizona to develop an understanding of the relationship between surface fault scarps within the basin fill sediments and theirgeophysical response of the faults at depth within the bedrock. Data were acquired for three profiles, one of them along the northern terrace of Montosa Canyon, and the other two along the northern and southern terraces of Cottonwood Canyon. A total of 122 gravity stations were established as well as numerous magnetic data collected by a truckmounted cesium-vapor magnetometer. In addition, aeromagnetic data previously acquired were interpreted to obtain a geologically sound model, which produced a good fit to the data. Gravity anomalies associated with faults exhibiting surface rupture were more pronounced than the respective magnetic anomalies. More credence was given to the gravity data when determining fault structures and it was found in all three profiles that faults at depth projected through alluvium at a steeper dip than the bedrock fault indicating brittle behavior within the overlying sediments. The gravity data also detected a significant horst and graben structure within Cottonwood Canyon. The aeromagnetic data did not provide any insight into the response of the minor faults but rather served to verify the regional response of the whole profile.

Nickel-Hydrogen Battery Fault Clearing at Low State of Charge

NASA Technical Reports Server (NTRS)

Lurie, C.

1997-01-01

Fault clearing currents were achieved and maintained at discharge rates from C/2 to C/3 at high and low states of charge. The fault clearing plateau voltage is strong function of: discharge current, and voltage-prior-to-the-fault-clearing-event and a weak function of state of charge. Voltage performance, for the range of conditions reported, is summarized.

The basin and range viewed from Borah Peak, Idaho.

USGS Publications Warehouse

Stein, R.S.; Bucknam, R.C.

1985-01-01

Today, more than a hundred years later, Borah Peak has proved to be among those mountains still rising. During the 28 October 1983 M=7 Borah Peak, Idaho, earthquake, the Lost River Range that Borah Peak caps was lifted 20-30 cm relative to distant points, and was tilted downward away from the range-bounding Lost River fault. The downthrown side of the fault, which subsided as much as 120 cm, was also tilted down toward the fault. The similarity between the earthquake deformation and the cumulative deformation preserved by the dip of strata is striking; it tends to confirm Gilbert's notion that Basin-and-Range topography is built by repeated slip events on normal faults that bound the range. The U.S Geological Survey had just published a preliminary volume of 40 research papers on the Borah Peak earthquake, focusing on the surface faulting, seismology, geodesy, hydrology, and geology of the earthquake and tis setting (Stein and Bucknam 1985). Also included is a field guide to the spectacular earthquake landforms, such as sruface rupture, exploratory trench excavations, sand blows, and landslides. 

Breaks in Pavement and Pipes as Indicators of Range-Front Faulting Resulting from the 1989 Loma Prieta Earthquake near the Southwest Margin of the Santa Clara Valley, California

USGS Publications Warehouse

Schmidt, Kevin M.; Ellen, Stephen D.; Haugerud, Ralph A.; Peterson, David M.; Phelps, Geoffery A.

1995-01-01

Damage to pavement and near-surface utility pipes, caused by the October 17, 1989, Loma Prieta earthquake, provide indicators for ground deformation in a 663 km2 area near the southwest margin of the Santa Clara Valley, California. The spatial distribution of 1284 sites of such damage documents the extent and distribution of detectable ground deformation. Damage was concentrated in four zones, three of which are near previously mapped faults. The zone through Los Gatos showed the highest concentration of damage, as well as evidence for pre- and post-earthquake deformation. Damage along the foot of the Santa Cruz Mountains reflected shortening that is consistent with movement along reverse faults in the region and with the hypothesis that tectonic strain is distributed widely across numerous faults in the California Coast Ranges.

The 1868 Hayward fault, California, earthquake: Implications for earthquake scaling relations on partially creeping faults

USGS Publications Warehouse

Hough, Susan E.; Martin, Stacey

2015-01-01

The 21 October 1868 Hayward, California, earthquake is among the best-characterized historical earthquakes in California. In contrast to many other moderate-to-large historical events, the causative fault is clearly established. Published magnitude estimates have been fairly consistent, ranging from 6.8 to 7.2, with 95% confidence limits including values as low as 6.5. The magnitude is of particular importance for assessment of seismic hazard associated with the Hayward fault and, more generally, to develop appropriate magnitude–rupture length scaling relations for partially creeping faults. The recent reevaluation of archival accounts by Boatwright and Bundock (2008), together with the growing volume of well-calibrated intensity data from the U.S. Geological Survey “Did You Feel It?” (DYFI) system, provide an opportunity to revisit and refine the magnitude estimate. In this study, we estimate the magnitude using two different methods that use DYFI data as calibration. Both approaches yield preferred magnitude estimates of 6.3–6.6, assuming an average stress drop. A consideration of data limitations associated with settlement patterns increases the range to 6.3–6.7, with a preferred estimate of 6.5. Although magnitude estimates for historical earthquakes are inevitably uncertain, we conclude that, at a minimum, a lower-magnitude estimate represents a credible alternative interpretation of available data. We further discuss implications of our results for probabilistic seismic-hazard assessment from partially creeping faults.

Common faults and their impacts for rooftop air conditioners

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

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

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

Is there a "blind" strike-slip fault at the southern end of the San Jacinto Fault system?

NASA Astrophysics Data System (ADS)

Tymofyeyeva, E.; Fialko, Y. A.

2015-12-01

We have studied the interseismic deformation at the southern end of the San Jacinto fault system using Interferometric Synthetic Aperture Radar (InSAR) and Global Positioning System (GPS) data. To complement the continuous GPS measurements from the PBO network, we have conducted campaign-style GPS surveys of 19 benchmarks along Highway 78 in the years 2012, 2013, and 2014. We processed the campaign GPS data using GAMIT to obtain horizontal velocities. The data show high velocity gradients East of the surface trace of the Coyote Creek Fault. We also processed InSAR data from the ascending and descending tracks of the ENVISAT mission between the years 2003 and 2010. The InSAR data were corrected for atmospheric artifacts using an iterative common point stacking method. We combined average velocities from different look angles to isolate the fault-parallel velocity field, and used fault-parallel velocities to compute strain rate. We filtered the data over a range of wavelengths prior to numerical differentiation, to reduce the effects of noise and to investigate both shallow and deep sources of deformation. At spatial wavelengths less than 2km the strain rate data show prominent anomalies along the San Andreas and Superstition Hills faults, where shallow creep has been documented by previous studies. Similar anomalies are also observed along parts of the Coyote Creek Fault, San Felipe Fault, and an unmapped southern continuation of the Clark strand of the San Jacinto Fault. At wavelengths on the order of 20km, we observe elevated strain rates concentrated east of the Coyote Creek Fault. The long-wavelength strain anomaly east of the Coyote Creek Fault, and the localized shallow creep observed in the short-wavelength strain rate data over the same area suggest that there may be a "blind" segment of the Clark Fault that accommodates a significant portion of the deformation on the southern end of the San Jacinto Fault.

Fault zone architecture within Miocene-Pliocene syn-rift sediments, Northwestern Red Sea, Egypt

NASA Astrophysics Data System (ADS)

Zaky, Khairy S.

2017-04-01

The present study focusses on field description of small normal fault zones in Upper Miocene-Pliocene sedimentary rocks on the northwestern side of the Red Sea, Egypt. The trend of these fault zones is mainly NW-SE. Paleostress analysis of 17 fault planes and slickenlines indicate that the tension direction is NE-SW. The minimum ( σ3) and intermediate ( σ2) paleostress axes are generally sub-horizontal and the maximum paleostress axis ( σ1) is sub-vertical. The fault zones are composed of damage zones and fault core. The damage zone is characterized by subsidiary faults and fractures that are asymmetrically developed on the hanging wall and footwall of the main fault. The width of the damage zone varies for each fault depending on the lithology, amount of displacement and irregularity of the fault trace. The average ratio between the hanging wall and the footwall damage zones width is about 3:1. The fault core consists of fault gouge and breccia. It is generally concentrated in a narrow zone of ˜0.5 to ˜8 cm width. The overall pattern of the fault core indicates that the width increases with increasing displacement. The faults with displacement < 1 m have fault cores ranging from 0.5 to 4.0 cm, while the faults with displacements of > 2 m have fault cores ranging from 4.0 to 8.0 cm. The fault zones are associated with sliver fault blocks, clay smear, segmented faults and fault lenses' structural features. These features are mechanically related to the growth and linkage of the fault arrays. The structural features may represent a neotectonic and indicate that the architecture of the fault zones is developed as several tectonic phases.

Crustal Density Variation Along the San Andreas Fault Controls Its Secondary Faults Distribution and Dip Direction

NASA Astrophysics Data System (ADS)

Yang, H.; Moresi, L. N.

2017-12-01

The San Andreas fault forms a dominant component of the transform boundary between the Pacific and the North American plate. The density and strength of the complex accretionary margin is very heterogeneous. Based on the density structure of the lithosphere in the SW United States, we utilize the 3D finite element thermomechanical, viscoplastic model (Underworld2) to simulate deformation in the San Andreas Fault system. The purpose of the model is to examine the role of a big bend in the existing geometry. In particular, the big bend of the fault is an initial condition of in our model. We first test the strength of the fault by comparing the surface principle stresses from our numerical model with the in situ tectonic stress. The best fit model indicates the model with extremely weak fault (friction coefficient < 0.1) is requisite. To the first order, there is significant density difference between the Great Valley and the adjacent Mojave block. The Great Valley block is much colder and of larger density (>200 kg/m3) than surrounding blocks. In contrast, the Mojave block is detected to find that it has lost its mafic lower crust by other geophysical surveys. Our model indicates strong strain localization at the jointer boundary between two blocks, which is an analogue for the Garlock fault. High density lower crust material of the Great Valley tends to under-thrust beneath the Transverse Range near the big bend. This motion is likely to rotate the fault plane from the initial vertical direction to dip to the southwest. For the straight section, north to the big bend, the fault is nearly vertical. The geometry of the fault plane is consistent with field observations.

Deep permeability of the San Andreas Fault from San Andreas Fault Observatory at Depth (SAFOD) core samples

USGS Publications Warehouse

Morrow, Carolyn A.; Lockner, David A.; Moore, Diane E.; Hickman, Stephen H.

2014-01-01

The San Andreas Fault Observatory at Depth (SAFOD) scientific borehole near Parkfield, California crosses two actively creeping shear zones at a depth of 2.7 km. Core samples retrieved from these active strands consist of a foliated, Mg-clay-rich gouge containing porphyroclasts of serpentinite and sedimentary rock. The adjacent damage zone and country rocks are comprised of variably deformed, fine-grained sandstones, siltstones, and mudstones. We conducted laboratory tests to measure the permeability of representative samples from each structural unit at effective confining pressures, Pe up to the maximum estimated in situ Pe of 120 MPa. Permeability values of intact samples adjacent to the creeping strands ranged from 10−18 to 10−21 m2 at Pe = 10 MPa and decreased with applied confining pressure to 10−20–10−22 m2 at 120 MPa. Values for intact foliated gouge samples (10−21–6 × 10−23 m2 over the same pressure range) were distinctly lower than those for the surrounding rocks due to their fine-grained, clay-rich character. Permeability of both intact and crushed-and-sieved foliated gouge measured during shearing at Pe ≥ 70 MPa ranged from 2 to 4 × 10−22 m2 in the direction perpendicular to shearing and was largely insensitive to shear displacement out to a maximum displacement of 10 mm. The weak, actively-deforming foliated gouge zones have ultra-low permeability, making the active strands of the San Andreas Fault effective barriers to cross-fault fluid flow. The low matrix permeability of the San Andreas Fault creeping zones and adjacent rock combined with observations of abundant fractures in the core over a range of scales suggests that fluid flow outside of the actively-deforming gouge zones is probably fracture dominated.

Refining fault slip rates using multiple displaced terrace risers-An example from the Honey Lake fault, NE California, USA

NASA Astrophysics Data System (ADS)

Gold, Ryan D.; Briggs, Richard W.; Crone, Anthony J.; DuRoss, Christopher B.

2017-11-01

Faulted terrace risers are semi-planar features commonly used to constrain Quaternary slip rates along strike-slip faults. These landforms are difficult to date directly and therefore their ages are commonly bracketed by age estimates of the adjacent upper and lower terrace surfaces. However, substantial differences in the ages of the upper and lower terrace surfaces (a factor of 2.4 difference observed globally) produce large uncertainties in the slip-rate estimate. In this investigation, we explore how the full range of displacements and bounding ages from multiple faulted terrace risers can be combined to yield a more accurate fault slip rate. We use 0.25-m cell size digital terrain models derived from airborne lidar data to analyze three sites where terrace risers are offset right-laterally by the Honey Lake fault in NE California, USA. We use ages for locally extensive subhorizontal surfaces to bracket the time of riser formation: an upper surface is the bed of abandoned Lake Lahontan having an age of 15.8 ± 0.6 ka and a lower surface is a fluvial terrace abandoned at 4.7 ± 0.1 ka. We estimate lateral offsets of the risers ranging between 6.6 and 28.3 m (median values), a greater than fourfold difference in values. The amount of offset corresponds to the riser's position relative to modern stream meanders: the smallest offset is in a meander cutbank position, whereas the larger offsets are in straight channel or meander point-bar positions. Taken in isolation, the individual terrace-riser offsets yield slip rates ranging from 0.3 to 7.1 mm/a. However, when the offset values are collectively assessed in a probabilistic framework, we find that a uniform (linear) slip rate of 1.6 mm/a (1.4-1.9 mm/a at 95% confidence) can satisfy the data, within their respective uncertainties. This investigation demonstrates that integrating observations of multiple offset elements (crest, midpoint, and base) from numerous faulted and dated terrace risers at closely spaced

Refining fault slip rates using multiple displaced terrace risers—An example from the Honey Lake fault, NE California, USA

USGS Publications Warehouse

Gold, Ryan D.; Briggs, Richard; Crone, Anthony J.; Duross, Christopher

2017-01-01

Faulted terrace risers are semi-planar features commonly used to constrain Quaternary slip rates along strike-slip faults. These landforms are difficult to date directly and therefore their ages are commonly bracketed by age estimates of the adjacent upper and lower terrace surfaces. However, substantial differences in the ages of the upper and lower terrace surfaces (a factor of 2.4 difference observed globally) produce large uncertainties in the slip-rate estimate. In this investigation, we explore how the full range of displacements and bounding ages from multiple faulted terrace risers can be combined to yield a more accurate fault slip rate. We use 0.25-m cell size digital terrain models derived from airborne lidar data to analyze three sites where terrace risers are offset right-laterally by the Honey Lake fault in NE California, USA. We use ages for locally extensive subhorizontal surfaces to bracket the time of riser formation: an upper surface is the bed of abandoned Lake Lahontan having an age of 15.8 ± 0.6 ka and a lower surface is a fluvial terrace abandoned at 4.7 ± 0.1 ka. We estimate lateral offsets of the risers ranging between 6.6 and 28.3 m (median values), a greater than fourfold difference in values. The amount of offset corresponds to the riser's position relative to modern stream meanders: the smallest offset is in a meander cutbank position, whereas the larger offsets are in straight channel or meander point-bar positions. Taken in isolation, the individual terrace-riser offsets yield slip rates ranging from 0.3 to 7.1 mm/a. However, when the offset values are collectively assessed in a probabilistic framework, we find that a uniform (linear) slip rate of 1.6 mm/a (1.4–1.9 mm/a at 95% confidence) can satisfy the data, within their respective uncertainties. This investigation demonstrates that integrating observations of multiple offset elements (crest, midpoint, and base) from numerous faulted and dated terrace risers at closely spaced

Physical and Transport Properties of the carbonate-bearing faults: experimental insights from the Monte Maggio Fault zone (Central Italy)

NASA Astrophysics Data System (ADS)

Trippetta, Fabio; Scuderi, Marco Maria; Collettini, Cristiano

2015-04-01

Physical properties of fault zones vary with time and space and in particular, fluid flow and permeability variations are strictly related to fault zone processes. Here we investigate the physical properties of carbonate samples collected along the Monte Maggio normal Fault (MMF), a regional structure (length ~10 km and displacement ~500 m) located within the active system of the Apennines. In particular we have studied an exceptionally exposed outcrop of the fault within the Calcare Massiccio formation (massive limestone) that has been recently exposed by new roadworks. Large cores (100 mm in diameter and up to 20 cm long) drilled perpendicular to the fault plane have been used to: 1) characterize the damage zone adjacent to the fault plane and 2) to obtain smaller cores, 38 mm in diameter both parallel and perpendicular to the fault plane, for rock deformation experiments. At the mesoscale two types of cataclastic damage zones can be identified in the footwall block (i) a Cemented Cataclasite (CC) and (ii), a Fault Breccia (FB). Since in some portions of the fault the hangingwall (HW) is still preserved we also collected HW samples. After preliminary porosity measurements at ambient pressure, we performed laboratory measurements of Vp, Vs, and permeability at effective confining pressures up to 100 MPa in order to simulate crustal conditions. The protolith has a primary porosity of about 7 %, formed predominantly by isolated pores since the connected porosity is only 1%. FB samples are characterized by 10% and 5% of bulk and connected porosity respectively, whilst CC samples show lower bulk porosity (7%) and a connected porosity of 2%. From ambient pressure to 100 MPa, P-wave velocity is about 5,9-6,0 km/s for the protolith, ranges from 4,9 km/s to 5,9 km/s for FB samples, whereas it is constant at 5,9 km/s for CC samples and ranges from 5,4 to 5,7 for HW sample. Vs shows the same behaviour resulting in a constant Vp/Vs ratio from 0 to 100 MPa that ranges from 1

Spatial arrangement and size distribution of normal faults, Buckskin detachment upper plate, Western Arizona

NASA Astrophysics Data System (ADS)

Laubach, S. E.; Hundley, T. H.; Hooker, J. N.; Marrett, R. A.

2018-03-01

Fault arrays typically include a wide range of fault sizes and those faults may be randomly located, clustered together, or regularly or periodically located in a rock volume. Here, we investigate size distribution and spatial arrangement of normal faults using rigorous size-scaling methods and normalized correlation count (NCC). Outcrop data from Miocene sedimentary rocks in the immediate upper plate of the regional Buckskin detachment-low angle normal-fault, have differing patterns of spatial arrangement as a function of displacement (offset). Using lower size-thresholds of 1, 0.1, 0.01, and 0.001 m, displacements range over 5 orders of magnitude and have power-law frequency distributions spanning ∼ four orders of magnitude from less than 0.001 m to more than 100 m, with exponents of -0.6 and -0.9. The largest faults with >1 m displacement have a shallower size-distribution slope and regular spacing of about 20 m. In contrast, smaller faults have steep size-distribution slopes and irregular spacing, with NCC plateau patterns indicating imposed clustering. Cluster widths are 15 m for the 0.1-m threshold, 14 m for 0.01-m, and 1 m for 0.001-m displacement threshold faults. Results demonstrate normalized correlation count effectively characterizes the spatial arrangement patterns of these faults. Our example from a high-strain fault pattern above a detachment is compatible with size and spatial organization that was influenced primarily by boundary conditions such as fault shape, mechanical unit thickness and internal stratigraphy on a range of scales rather than purely by interaction among faults during their propagation.

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

USGS Publications Warehouse

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.

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

NASA Astrophysics Data System (ADS)

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

2016-12-01

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

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

NASA Astrophysics Data System (ADS)

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

2010-12-01

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

The Oakland Conglomerate: a Hayward Fault Teconite?

NASA Astrophysics Data System (ADS)

Strayer, L. M.; Allen, J. R.

2008-12-01

The Late Cretaceous Oakland Conglomerate (OC), a coarse-grained cobble and sandstone unit of the Great Valley Sequence is a tectonite. Faulted and shattered cobbles and well developed grain-on-grain contact features between clasts are ubiquitous and penetrative throughout conglomeratic lenses. The OC outcrops east of the Hayward fault (HF) and adjacent to the Chabot fault in the East Bay Hills. It overlies the Knoxville Formation and may have been buried beneath 4-6 km of younger units. The OC is a proximal submarine fan deposit with sediment sourced to the ancestral Klamath and Sierra Nevada. Clast types are dominated by volcanics, granitoids, as well as numerous quartzites, perhaps reflecting complex provenance:Klamath and pre-Sierran arc and pre-Cretaceous Basin and Range. And although there was a significant interval between the Late-K deposition of the OC and the inception of San Andreas faulting in the Bay Area, its 1-2 km proximity to the HF in the Oakland Metropolitan area strongly suggests that much of the brittle-plastic deformation within the OC may be due to earthquakes upon the nearby Hayward fault. Clasts with the OC are frequently shattered, fractured or faulted. Most have grain-on-grain contact features on their surfaces regardless of whether they are matrix or grain supported. Faulting in the cobbles ranges from outcrop scale, penetrative and often conjugate shear fracture sets that run through both cobbles and matrix (if present), to closely spaced en-echelon faults that clearly deform cobbles, and radially shattered specimens with nearly conical conjugate shear fractures that are clearly the result of point loading due to grain-on-grain contact. There are at least 3 types of contact structures, ranging from: 1) Type-H, bright circular halos with little or no surface dimpling, likely the result of intense microfracture at the contact; 2) Type-S, shattered, rounded 'firing-pin' structures that have pulverized, depressed contact that is the locus of

Crustal extension and transform faulting in the southern Basin Range Province. [California, Arizona, and Nevada

NASA Technical Reports Server (NTRS)

Liggett, M. A. (Principal Investigator); Childs, J. F.

1974-01-01

The author has identified the following significant results. Field reconnaissance and study of geologic literature guided by analysis of ERTS-1 MSS imagery have led to a hypothesis of tectonic control of Miocene volcanism, plutonism, and related mineralization in part of the Basin Range Province of southern Nevada and northwestern Arizona. The easterly trending right-lateral Las Vegas Shear Zone separates two volcanic provinces believed to represent areas of major east-west crustal extension. One volcanic province is aligned along the Colorado River south of the eastern termination of the Las Vegas Shear Zone; the second province is located north of the western termination of the shear zone in southern Nye County, Nevada. Geochronologic, geophysical, and structural evidence suggests that the Las Vegas Shear Zone may have formed in response to crustal extension in the two volcanic provinces in a manner similar to the formation of a ridge-ridge transform fault, as recognized in ocean floor tectonics.

Predeployment validation of fault-tolerant systems through software-implemented fault insertion

NASA Technical Reports Server (NTRS)

Czeck, Edward W.; Siewiorek, Daniel P.; Segall, Zary Z.

1989-01-01

Fault injection-based automated testing (FIAT) environment, which can be used to experimentally characterize and evaluate distributed realtime systems under fault-free and faulted conditions is described. A survey is presented of validation methodologies. The need for fault insertion based on validation methodologies is demonstrated. The origins and models of faults, and motivation for the FIAT concept are reviewed. FIAT employs a validation methodology which builds confidence in the system through first providing a baseline of fault-free performance data and then characterizing the behavior of the system with faults present. Fault insertion is accomplished through software and allows faults or the manifestation of faults to be inserted by either seeding faults into memory or triggering error detection mechanisms. FIAT is capable of emulating a variety of fault-tolerant strategies and architectures, can monitor system activity, and can automatically orchestrate experiments involving insertion of faults. There is a common system interface which allows ease of use to decrease experiment development and run time. Fault models chosen for experiments on FIAT have generated system responses which parallel those observed in real systems under faulty conditions. These capabilities are shown by two example experiments each using a different fault-tolerance strategy.

Climatic and Tectonic Controls on Topography in the Northern Basin and Range

NASA Astrophysics Data System (ADS)

Foster, D.; Brocklehurst, S. H.; Gawthorpe, R. L.

2006-12-01

This study takes advantage of the relatively simple tectonics of the normal fault-bounded Lost River and Lemhi Ranges and the Beaverhead Mountains, eastern Idaho, USA, to assess the roles of climate, erosion, and tectonics in topographic evolution through a combination of digital topographic analyses and field observations. These ranges transect the southern limit of Quaternary glaciation, and drainage basins record a range of glacial extents and histories, allowing for comparisons between climatic and tectonic controls. At a catchment scale, topography is controlled by both the degree of glaciation, and the response of the drainage system to range-front faulting. The range-bounding normal faults are segmented along-strike, and fault uplift rates vary systematically, being greatest at the fault centres. Here catchments predominantly drain normal to the range-front fault, although the trend of some catchments is influenced by pre-existing tectonic fabrics related to Cretaceous (northeast-southwest trending) and early Miocene (northwest-southeast trending) extension. For catchments that drain through fault segment boundaries, one of two general morphologies occurs. Either large drainage basins form, capturing drainage area from neighbouring basins, or, when fault segment boundaries are en echelon, a series of small drainage basins may form as catchments as the inboard- and outboard- footwalls interact and respond to fault linkage. Quaternary glaciation affected all but the southern portions of each of the ranges, most extensively at the north-eastern range flank. Increased extent of glaciation within a catchment results in wider valley floors, steeper valley walls, and greater relief at elevations close to the ELA. Cirque formation occurs preferentially on the north-eastern range flank, where glaciers are sheltered from both solar radiation and snow re-distribution by the prevailing winds. Snow accumulation is promoted in this setting by the increased influx of wind

Fault orientations in extensional and conjugate strike-slip environments and their implications

USGS Publications Warehouse

Thatcher, W.; Hill, D.P.

1991-01-01

Seismically active conjugate strike-slip faults in California and Japan typically have mutually orthogonal right- and left-lateral fault planes. Normal-fault dips at earthquake nucleation depths are concentrated between 40?? and 50??. The observed orientations and their strong clustering are surprising, because conventional faulting theory suggests fault initiation with conjugate 60?? and 120?? intersecting planes and 60?? normal-fault dip or fault reactivation with a broad range of permitted orientations. The observations place new constraints on the mechanics of fault initiation, rotation, and evolutionary development. We speculate that the data could be explained by fault rotation into the observed orientations and deactivation for greater rotation or by formation of localized shear zones beneath the brittle-ductile transition in Earth's crust. Initiation as weak frictional faults seems unlikely. -Authors

Development of Hydrologic Characterization Technology of Fault Zones (in Japanese; English)

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

Karasaki, Kenzi; Onishi, Tiemi; Wu, Yu-Shu

2008-03-31

Through an extensive literature survey we find that there is very limited amount of work on fault zone hydrology, particularly in the field using borehole testing. The common elements of a fault include a core, and damage zones. The core usually acts as a barrier to the flow across it, whereas the damage zone controls the flow either parallel to the strike or dip of a fault. In most of cases the damage zone isthe one that is controlling the flow in the fault zone and the surroundings. The permeability of damage zone is in the range of two tomore » three orders of magnitude higher than the protolith. The fault core can have permeability up to seven orders of magnitude lower than the damage zone. The fault types (normal, reverse, and strike-slip) by themselves do not appear to be a clear classifier of the hydrology of fault zones. However, there still remains a possibility that other additional geologic attributes and scaling relationships can be used to predict or bracket the range of hydrologic behavior of fault zones. AMT (Audio frequency Magneto Telluric) and seismic reflection techniques are often used to locate faults. Geochemical signatures and temperature distributions are often used to identify flow domains and/or directions. ALSM (Airborne Laser Swath Mapping) or LIDAR (Light Detection and Ranging) method may prove to be a powerful tool for identifying lineaments in place of the traditional photogrammetry. Nonetheless not much work has been done to characterize the hydrologic properties of faults by directly testing them using pump tests. There are some uncertainties involved in analyzing pressure transients of pump tests: both low permeability and high permeability faults exhibit similar pressure responses. A physically based conceptual and numerical model is presented for simulating fluid and heat flow and solute transport through fractured fault zones using a multiple-continuum medium approach. Data from the Horonobe URL site are analyzed to

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

NASA Astrophysics Data System (ADS)

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

2007-12-01

Los Planes highway, the fault steps to the right 2km with no overlap. The fault is inactive until ~3km south of the Los Planes highway where scarp heights in the Quaternary sediments rise to ~3-11m for ~11km with an average trend of 160°, implying increasing slip rate. The fault then steps left 2km with no overlap, trending 145°. Scarp heights range from 3-6m in the step. The southernmost 9km of the fault zone, trending 200°, is marked by discontinuous scarps and embayed bedrock, reflecting diminished fault activity. The footwall landscape in this area is characterized by a broad, gently-sloping, low-relief pediment surface with thin Quaternary cover, disrupted by inselberg-like hills. The young scarp-forming fault appears to have reactivated older faults to rupture this pediment, reflecting the episodic nature of slip along this fault zone. Preliminary OSL ages of the youngest faulted deposit imply a Late Pleistocene-Holocene slip rate of 0.1-1mm/yr. The SJPFZ is thus characterized by reactivation of pre-existing faults to rupture a pre-existing low relief erosional landscape. Whereas the entire region might have experienced the quiescent period that allowed for development of the low- relief, stable surface along the SJPFZ, we speculate that while the SJPFZ was dormant, other faults within the gulf-margin system were actively accommodating strain.

The history of late holocene surface-faulting earthquakes on the central segments of the Wasatch fault zone, Utah

USGS Publications Warehouse

Duross, Christopher; Personius, Stephen; Olig, Susan S; Crone, Anthony J.; Hylland, Michael D.; Lund, William R; Schwartz, David P.

2017-01-01

The Wasatch fault (WFZ)—Utah’s longest and most active normal fault—forms a prominent eastern boundary to the Basin and Range Province in northern Utah. To provide paleoseismic data for a Wasatch Front regional earthquake forecast, we synthesized paleoseismic data to define the timing and displacements of late Holocene surface-faulting earthquakes on the central five segments of the WFZ. Our analysis yields revised histories of large (M ~7) surface-faulting earthquakes on the segments, as well as estimates of earthquake recurrence and vertical slip rate. We constrain the timing of four to six earthquakes on each of the central segments, which together yields a history of at least 24 surface-faulting earthquakes since ~6 ka. Using earthquake data for each segment, inter-event recurrence intervals range from about 0.6 to 2.5 kyr, and have a mean of 1.2 kyr. Mean recurrence, based on closed seismic intervals, is ~1.1–1.3 kyr per segment, and when combined with mean vertical displacements per segment of 1.7–2.6 m, yield mean vertical slip rates of 1.3–2.0 mm/yr per segment. These data refine the late Holocene behavior of the central WFZ; however, a significant source of uncertainty is whether structural complexities that define the segments of the WFZ act as hard barriers to ruptures propagating along the fault. Thus, we evaluate fault rupture models including both single-segment and multi-segment ruptures, and define 3–17-km-wide spatial uncertainties in the segment boundaries. These alternative rupture models and segment-boundary zones honor the WFZ paleoseismic data, take into account the spatial and temporal limitations of paleoseismic data, and allow for complex ruptures such as partial-segment and spillover ruptures. Our data and analyses improve our understanding of the complexities in normal-faulting earthquake behavior and provide geological inputs for regional earthquake-probability and seismic hazard assessments.

Normal Faulting at the Western Margin of the Altiplano Plateau, Southern Peru

NASA Astrophysics Data System (ADS)

Schildgen, T. F.; Hodges, K. V.; Whipple, K. X.; Perignon, M.; Smith, T. M.

2004-12-01

Although the western margin of the Altiplano Plateau is commonly used to illustrate the marked differences in the evolution of a mountain range with strong latitudinal and longitudinal precipitation gradients, the nature of tectonism in this semi-arid region is poorly understood and much debated. The western margin of the Altiplano in southern Peru and northern Chile marks an abrupt transition from the forearc region of the Andes to the high topography of the Cordillera Occidental. This transition has been interpreted by most workers as a monocline, with modifications due to thrust faulting, normal faulting, and gravity slides. Based on recent fieldwork and satellite image analysis, we suggest that, at least in the semi-arid climate of southern Peru, this transition has been the locus of significant high-angle normal faulting related to the block uplift of the Cordillera Occidental. We have focused our initial work in the vicinity of 15\\deg S latitude, 71\\deg W longitude, where the range front crosses Colca Canyon, a major antecedent drainage northwest of Arequipa. In that area, Oligocene to Miocene sediments of the Moquegua Formation, which were eroded from uplifted terrain to the northeast, presently dip to the northeast at angles between 2 and 10º. Field observations of a normal fault contact between the Moquegua sedimentary rocks and Jurassic basement rocks, as well as 15-m resolution 3-D images generated from ASTER satellite imagery, show that the Moquegua units are down-dropped to the west across a steeply SW-dipping normal fault of regional significance. Morphology of the range front throughout southern Peru suggests that normal faulting along the range front has characterized the recent tectonic history of the region. We present geochronological data to constrain the timing of movement both directly from the fault zone as well as indirectly from canyon incision that likely responded to fault movement.

Criteria for Seismic Splay Fault Activation During Subduction Earthquakes

NASA Astrophysics Data System (ADS)

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

2008-12-01

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

Automated Fault Interpretation and Extraction using Improved Supplementary Seismic Datasets

NASA Astrophysics Data System (ADS)

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.

Fault weakening and earthquake instability by powder lubrication

USGS Publications Warehouse

Reches, Z.; Lockner, D.A.

2010-01-01

Earthquake instability has long been attributed to fault weakening during accelerated slip1, and a central question of earthquake physics is identifying the mechanisms that control this weakening2. Even with much experimental effort2-12, the weakening mechanisms have remained enigmatic. Here we present evidence for dynamic weakening of experimental faults that are sheared at velocities approaching earthquake slip rates. The experimental faults, which were made of room-dry, solid granite blocks, quickly wore to form a fine-grain rock powder known as gouge. At modest slip velocities of 10-60mms-1, this newly formed gouge organized itself into a thin deforming layer that reduced the fault's strength by a factor of 2-3. After slip, the gouge rapidly 'aged' and the fault regained its strength in a matter of hours to days. Therefore, only newly formed gouge can weaken the experimental faults. Dynamic gouge formation is expected to be a common and effective mechanism of earthquake instability in the brittle crust as (1) gouge always forms during fault slip5,10,12-20; (2) fault-gouge behaves similarly to industrial powder lubricants21; (3) dynamic gouge formation explains various significant earthquake properties; and (4) gouge lubricant can form for a wide range of fault configurations, compositions and temperatures15. ?? 2010 Macmillan Publishers Limited. All rights reserved.

Interseismic Strain Accumulation of the Gazikoy-Saros segment (Ganos fault) of the North Anatolian Fault Zone

NASA Astrophysics Data System (ADS)

Havazli, E.; Wdowinski, S.; Amelung, F.

2017-12-01

The North Anatolian Fault Zone (NAFZ) is one of the most active continental transform faults in the world. A westward migrating earthquake sequence has started in 1939 in Erzincan and the last two events of this sequence occurred in 1999 in Izmit and Duzce manifesting the importance of NAFZ on the seismic hazard potential of the region. NAFZ exhibits slip rates ranging from 14-30 mm/yr along its 1500 km length with a right lateral strike slip characteristic. In the East of the Marmara Sea, the NAFZ splits into two branches. The Gazikoy-Saros segment (Ganos Fault) is the westernmost and onshore segment of the northern branch. The ENE-WSW oriented Ganos Fault is seismically active. It produced a Ms 7.2 earthquake in 1912, which was followed by several large aftershocks, including Ms 6.3 and Ms 6.9 events. Since 1912, the Ganos Fault did not produce any significant earthquakes (> M 5), in contrast to its adjacent segments, which produced 20 M>5 earthquakes, including a M 6.7 event, offshore in Gulf of Saros. Interseismic strain accumulation along the Ganos Fault was assessed from sparse GPS measurements along a single transect located perpendicular to the fault zone, suggesting strain accumulation rate of 20-25 mm/yr. Insofar, InSAR studies, based on C-band data, didn't produce conclusive results due to low coherence over the fault zone area, which is highly vegetated. In this study, we present a detailed interseismic velocity map of the Ganos Fault zone derived from L-band InSAR observations. We use 21 ALOS PALSAR scenes acquired over a 5-year period, from 2007 to 2011. We processed the ALOS data using the PySAR software, which is the University of Miami version of the Small Baseline (SB) method. The L-band observations enabled us to overcome the coherence issue in the study area. Our initial results indicate a maximum velocity of 15 mm/yr across the fault zone. The high spatial resolution of the InSAR-based interseismic velocity map will enable us to better to

Fault finder

DOEpatents

Bunch, Richard H.

1986-01-01

A fault finder for locating faults along a high voltage electrical transmission line. Real time monitoring of background noise and improved filtering of input signals is used to identify the occurrence of a fault. A fault is detected at both a master and remote unit spaced along the line. A master clock synchronizes operation of a similar clock at the remote unit. Both units include modulator and demodulator circuits for transmission of clock signals and data. All data is received at the master unit for processing to determine an accurate fault distance calculation.

Pseudo-dynamic source characterization accounting for rough-fault effects

NASA Astrophysics Data System (ADS)

Galis, Martin; Thingbaijam, Kiran K. S.; Mai, P. Martin

2016-04-01

Broadband ground-motion simulations, ideally for frequencies up to ~10Hz or higher, are important for earthquake engineering; for example, seismic hazard analysis for critical facilities. An issue with such simulations is realistic generation of radiated wave-field in the desired frequency range. Numerical simulations of dynamic ruptures propagating on rough faults suggest that fault roughness is necessary for realistic high-frequency radiation. However, simulations of dynamic ruptures are too expensive for routine applications. Therefore, simplified synthetic kinematic models are often used. They are usually based on rigorous statistical analysis of rupture models inferred by inversions of seismic and/or geodetic data. However, due to limited resolution of the inversions, these models are valid only for low-frequency range. In addition to the slip, parameters such as rupture-onset time, rise time and source time functions are needed for complete spatiotemporal characterization of the earthquake rupture. But these parameters are poorly resolved in the source inversions. To obtain a physically consistent quantification of these parameters, we simulate and analyze spontaneous dynamic ruptures on rough faults. First, by analyzing the impact of fault roughness on the rupture and seismic radiation, we develop equivalent planar-fault kinematic analogues of the dynamic ruptures. Next, we investigate the spatial interdependencies between the source parameters to allow consistent modeling that emulates the observed behavior of dynamic ruptures capturing the rough-fault effects. Based on these analyses, we formulate a framework for pseudo-dynamic source model, physically consistent with the dynamic ruptures on rough faults.

The 2015 M w 6.0 Mt. Kinabalu earthquake: an infrequent fault rupture within the Crocker fault system of East Malaysia

NASA Astrophysics Data System (ADS)

Wang, Yu; Wei, Shengji; Wang, Xin; Lindsey, Eric O.; Tongkul, Felix; Tapponnier, Paul; Bradley, Kyle; Chan, Chung-Han; Hill, Emma M.; Sieh, Kerry

2017-12-01

The M w 6.0 Mt. Kinabalu earthquake of 2015 was a complete (and deadly) surprise, because it occurred well away from the nearest plate boundary in a region of very low historical seismicity. Our seismological, space geodetic, geomorphological, and field investigations show that the earthquake resulted from rupture of a northwest-dipping normal fault that did not reach the surface. Its unilateral rupture was almost directly beneath 4000-m-high Mt. Kinabalu and triggered widespread slope failures on steep mountainous slopes, which included rockfalls that killed 18 hikers. Our seismological and morphotectonic analyses suggest that the rupture occurred on a normal fault that splays upwards off of the previously identified normal Marakau fault. Our mapping of tectonic landforms reveals that these faults are part of a 200-km-long system of normal faults that traverse the eastern side of the Crocker Range, parallel to Sabah's northwestern coastline. Although the tectonic reason for this active normal fault system remains unclear, the lengths of the longest fault segments suggest that they are capable of generating magnitude 7 earthquakes. Such large earthquakes must occur very rarely, though, given the hitherto undetectable geodetic rates of active tectonic deformation across the region.

Mid-crustal detachment and ramp faulting in the Markham Valley, Papua New Guinea

NASA Astrophysics Data System (ADS)

Stevens, C.; McCaffrey, R.; Silver, E. A.; Sombo, Z.; English, P.; van der Kevie, J.

1998-09-01

Earthquakes and geodetic evidence reveal the presence of a low-angle, mid-crustal detachment fault beneath the Finisterre Range that connects to a steep ramp surfacing near the Ramu-Markham Valley of Papua New Guinea. Waveforms of three large (Mw 6.3 to 6.9) thrust earthquakes that occurred in October 1993 beneath the Finisterre Range 10 to 30 km north of the valley reveal 15° north-dipping thrusts at about 20 km depth. Global Positioning System measurements show up to 20 cm of coseismic slip occurred across the valley, requiring that the active fault extend to within a few hundred meters of the Earth's surface beneath the Markham Valley. Together, these data imply that a gently north-dipping thrust fault in the middle or lower crust beneath the Finisterre Range steepens and shallows southward, forming a ramp fault beneath the north side of the Markham Valley. Waveforms indicate that both the ramp and detachment fault were active during at least one of the earthquakes. While the seismic potential of mid-crustal detachments elsewhere is debated, in Papua New Guinea the detachment fault shows the capability of producing large earthquakes.

Modification of wave-cut and faulting-controlled landforms.

USGS Publications Warehouse

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

1984-01-01

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

Fault Mitigation Schemes for Future Spaceflight Multicore Processors

NASA Technical Reports Server (NTRS)

Alexander, James W.; Clement, Bradley J.; Gostelow, Kim P.; Lai, John Y.

2012-01-01

Future planetary exploration missions demand significant advances in on-board computing capabilities over current avionics architectures based on a single-core processing element. The state-of-the-art multi-core processor provides much promise in meeting such challenges while introducing new fault tolerance problems when applied to space missions. Software-based schemes are being presented in this paper that can achieve system-level fault mitigation beyond that provided by radiation-hard-by-design (RHBD). For mission and time critical applications such as the Terrain Relative Navigation (TRN) for planetary or small body navigation, and landing, a range of fault tolerance methods can be adapted by the application. The software methods being investigated include Error Correction Code (ECC) for data packet routing between cores, virtual network routing, Triple Modular Redundancy (TMR), and Algorithm-Based Fault Tolerance (ABFT). A robust fault tolerance framework that provides fail-operational behavior under hard real-time constraints and graceful degradation will be demonstrated using TRN executing on a commercial Tilera(R) processor with simulated fault injections.

The Sorong Fault Zone, Indonesia: Mapping a Fault Zone Offshore

NASA Astrophysics Data System (ADS)

Melia, S.; Hall, R.

2017-12-01

The Sorong Fault Zone is a left-lateral strike-slip fault zone in eastern Indonesia, extending westwards from the Bird's Head peninsula of West Papua towards Sulawesi. It is the result of interactions between the Pacific, Caroline, Philippine Sea, and Australian Plates and much of it is offshore. Previous research on the fault zone has been limited by the low resolution of available data offshore, leading to debates over the extent, location, and timing of movements, and the tectonic evolution of eastern Indonesia. Different studies have shown it north of the Sula Islands, truncated south of Halmahera, continuing to Sulawesi, or splaying into a horsetail fan of smaller faults. Recently acquired high resolution multibeam bathymetry of the seafloor (with a resolution of 15-25 meters), and 2D seismic lines, provide the opportunity to trace the fault offshore. The position of different strands can be identified. On land, SRTM topography shows that in the northern Bird's Head the fault zone is characterised by closely spaced E-W trending faults. NW of the Bird's Head offshore there is a fold and thrust belt which terminates some strands. To the west of the Bird's Head offshore the fault zone diverges into multiple strands trending ENE-WSW. Regions of Riedel shearing are evident west of the Bird's Head, indicating sinistral strike-slip motion. Further west, the ENE-WSW trending faults turn to an E-W trend and there are at least three fault zones situated immediately south of Halmahera, north of the Sula Islands, and between the islands of Sanana and Mangole where the fault system terminates in horsetail strands. South of the Sula islands some former normal faults at the continent-ocean boundary with the North Banda Sea are being reactivated as strike-slip faults. The fault zone does not currently reach Sulawesi. The new fault map differs from previous interpretations concerning the location, age and significance of different parts of the Sorong Fault Zone. Kinematic

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

USGS Publications Warehouse

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.

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

NASA Astrophysics Data System (ADS)

Swanson, Mark T.

2005-05-01

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

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

NASA Astrophysics Data System (ADS)

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

2012-12-01

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

Fault zone hydrogeology

NASA Astrophysics Data System (ADS)

Bense, V. F.; Gleeson, T.; Loveless, S. E.; Bour, O.; Scibek, J.

2013-12-01

Deformation along faults in the shallow crust (< 1 km) introduces permeability heterogeneity and anisotropy, which has an important impact on processes such as regional groundwater flow, hydrocarbon migration, and hydrothermal fluid circulation. Fault zones have the capacity to be hydraulic conduits connecting shallow and deep geological environments, but simultaneously the fault cores of many faults often form effective barriers to flow. The direct evaluation of the impact of faults to fluid flow patterns remains a challenge and requires a multidisciplinary research effort of structural geologists and hydrogeologists. However, we find that these disciplines often use different methods with little interaction between them. In this review, we document the current multi-disciplinary understanding of fault zone hydrogeology. We discuss surface- and subsurface observations from diverse rock types from unlithified and lithified clastic sediments through to carbonate, crystalline, and volcanic rocks. For each rock type, we evaluate geological deformation mechanisms, hydrogeologic observations and conceptual models of fault zone hydrogeology. Outcrop observations indicate that fault zones commonly have a permeability structure suggesting they should act as complex conduit-barrier systems in which along-fault flow is encouraged and across-fault flow is impeded. Hydrogeological observations of fault zones reported in the literature show a broad qualitative agreement with outcrop-based conceptual models of fault zone hydrogeology. Nevertheless, the specific impact of a particular fault permeability structure on fault zone hydrogeology can only be assessed when the hydrogeological context of the fault zone is considered and not from outcrop observations alone. To gain a more integrated, comprehensive understanding of fault zone hydrogeology, we foresee numerous synergistic opportunities and challenges for the discipline of structural geology and hydrogeology to co-evolve and

LiDAR-Assisted identification of an active fault near Truckee, California

USGS Publications Warehouse

Hunter, L.E.; Howle, J.F.; Rose, R.S.; Bawden, G.W.

2011-01-01

We use high-resolution (1.5-2.4 points/m2) bare-earth airborne Light Detection and Ranging (LiDAR) imagery to identify, map, constrain, and visualize fault-related geomorphology in densely vegetated terrain surrounding Martis Creek Dam near Truckee, California. Bare-earth LiDAR imagery reveals a previously unrecognized and apparently youthful right-lateral strike-slip fault that exhibits laterally continuous tectonic geomorphic features over a 35-km-long zone. If these interpretations are correct, the fault, herein named the Polaris fault, may represent a significant seismic hazard to the greater Truckee-Lake Tahoe and Reno-Carson City regions. Three-dimensional modeling of an offset late Quaternary terrace riser indicates a minimum tectonic slip rate of 0.4 ?? 0.1 mm/yr.Mapped fault patterns are fairly typical of regional patterns elsewhere in the northern Walker Lane and are in strong coherence with moderate magnitude historical seismicity of the immediate area, as well as the current regional stress regime. Based on a range of surface-rupture lengths and depths to the base of the seismogenic zone, we estimate a maximum earthquake magnitude (M) for the Polaris fault to be between 6.4 and 6.9.

Late Pleistocene - Holocene ruptures of the Lima Reservoir fault, SW Montana

NASA Astrophysics Data System (ADS)

Anastasio, David J.; Majerowicz, Christina N.; Pazzaglia, Frank J.; Regalla, Christine A.

2010-12-01

Active tectonics within the northern Basin and Range province provide a natural laboratory for the study of normal fault growth, linkage, and interaction. Here, we present new geologic mapping and morphologic fault-scarp modeling within the Centennial Valley, Montana to characterize Pleistocene - Holocene ruptures of the young and active Lima Reservoir fault. Geologic relationships and rupture ages indicate Middle Pleistocene activity on the Henry Gulch (>50 ka and 23-10 ka), Trail Creek (>43 ka and ˜13 ka), and reservoir (˜23 ka) segments. Offset Quaternary deposits also record Holocene rupture of the reservoir segment (˜8 ka), but unfaulted modern streams show that no segments of the Lima Reservoir fault have experienced a large earthquake in at least several millennia. The clustered pattern of rupture ages on the Lima Reservoir fault segments suggests a seismogenic linkage though segment length and spacing make a physical connection at depth unlikely. Trail Creek and reservoir segment slip rates were non-steady and appear to be increasing. The fault helps accommodate differential horizontal surface velocity measured by GPS geodesy across the boundary between the northern Basin and Range province and the Snake River Plain.

A review of recently active faults in Taiwan

USGS Publications Warehouse

Bonilla, Manuel G.

1975-01-01

Six faults associated with five large earthquakes produced surface displacements ranging from 1 to 3 m in the period 1906 through 1951. Four of the ruptures occurred in the western coastal plain and foothills, and two occurred in the Longitudinal Valley of eastern Taiwan. Maps are included showing the locations and dimensions of the displacements. The published geological literature probably would not lead one to infer the existence of a fault along most of the 1906 rupture, except for descriptions of the rupture itself. Over most of its length the 1935 rupture on the Chihhu fault is parallel to but more than 0.5 km from nearby faults shown on geologic maps published in 1969 and 1971; only about 1.5 km of its 15 km length coincides with a mapped fault. The coastal plain part of the Tuntzuchio fault which ruptured in 1935 is apparently not revealed by landforms, and only suggested by other data. Part of the 1946 Hsinhua faulting coincides with a fault identified in the subsurface by seismic work but surface indications of the fault are obscure. The 1951 Meilun faulting occurred along a conspicuous pre-1951 scarp and the 1951 Yuli faulting occurred near or in line with pre-1951 scarps. More than 40 faults which, according to the published literature, have had Pleistocene or later movement are shown on a small-scale map. Most of these faults are in the densely-populated western part of Taiwan. The map and text calls attention to faults that may be active and therefore may be significant in planning important structures. Equivocal evidence suggestive of fault creep was found on the Yuli fault and the Hsinhua fault. Fault creep was not found at several places examined along the 1906 fault trace. Tectonic uplift has occurred in Taiwan in the last 10,000 years and application of eustatic sea level curves to published radiocarbon dates shows that the minimum rate of uplift is considerably different in different parts of the island. Incomplete data indicate that the rate is

Fault diagnosis

NASA Technical Reports Server (NTRS)

Abbott, Kathy

1990-01-01

The objective of the research in this area of fault management is to develop and implement a decision aiding concept for diagnosing faults, especially faults which are difficult for pilots to identify, and to develop methods for presenting the diagnosis information to the flight crew in a timely and comprehensible manner. The requirements for the diagnosis concept were identified by interviewing pilots, analyzing actual incident and accident cases, and examining psychology literature on how humans perform diagnosis. The diagnosis decision aiding concept developed based on those requirements takes abnormal sensor readings as input, as identified by a fault monitor. Based on these abnormal sensor readings, the diagnosis concept identifies the cause or source of the fault and all components affected by the fault. This concept was implemented for diagnosis of aircraft propulsion and hydraulic subsystems in a computer program called Draphys (Diagnostic Reasoning About Physical Systems). Draphys is unique in two important ways. First, it uses models of both functional and physical relationships in the subsystems. Using both models enables the diagnostic reasoning to identify the fault propagation as the faulted system continues to operate, and to diagnose physical damage. Draphys also reasons about behavior of the faulted system over time, to eliminate possibilities as more information becomes available, and to update the system status as more components are affected by the fault. The crew interface research is examining display issues associated with presenting diagnosis information to the flight crew. One study examined issues for presenting system status information. One lesson learned from that study was that pilots found fault situations to be more complex if they involved multiple subsystems. Another was pilots could identify the faulted systems more quickly if the system status was presented in pictorial or text format. Another study is currently under way to

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

USGS Publications Warehouse

Blakely, R.J.; Sherrod, B.L.; Weaver, C.S.; Wells, R.E.; Rohay, A.C.; Barnett, E.A.; Knepprath, N.E.

2011-01-01

High-resolution aeromagnetic surveys of the Cascade Range and Yakima fold and thrust belt (YFTB), Washington, provide insights on tectonic connections between forearc and back-arc regions of the Cascadia convergent margin. Magnetic surveys were measured at a nominal altitude of 250 m above terrain and along flight lines spaced 400 m apart. Upper crustal rocks in this region have diverse magnetic properties, ranging from highly magnetic rocks of the Miocene Columbia River Basalt Group to weakly magnetic sedimentary rocks of various ages. These distinctive magnetic properties permit mapping of important faults and folds from exposures to covered areas. Magnetic lineaments correspond with mapped Quaternary faults and with scarps identified in lidar (light detection and ranging) topographic data and aerial photography. A two-dimensional model of the northwest striking Umtanum Ridge fault zone, based on magnetic and gravity data and constrained by geologic mapping and three deep wells, suggests that thrust faults extend through the Tertiary section and into underlying pre-Tertiary basement. Excavation of two trenches across a prominent scarp at the base of Umtanum Ridge uncovered evidence for bending moment faulting possibly caused by a blind thrust. Using aeromagnetic, gravity, and paleoseismic evidence, we postulate possible tectonic connections between the YFTB in eastern Washington and active faults of the Puget Lowland. We suggest that faults and folds of Umtanum Ridge extend northwestward through the Cascade Range and merge with the Southern Whidbey Island and Seattle faults near Snoqualmie Pass 35 km east of Seattle. Recent earthquakes (MW ≤ 5.3) suggest that this confluence of faults may be seismically active today.

Using Magnetics and Topography to Model Fault Splays of the Hilton Creek Fault System within the Long Valley Caldera

NASA Astrophysics Data System (ADS)

De Cristofaro, J. L.; Polet, J.

2017-12-01

The Hilton Creek Fault (HCF) is a range-bounding extensional fault that forms the eastern escarpment of California's Sierra Nevada mountain range, near the town of Mammoth Lakes. The fault is well mapped along its main trace to the south of the Long Valley Caldera (LVC), but the location and nature of its northern terminus is poorly constrained. The fault terminates as a series of left-stepping splays within the LVC, an area of active volcanism that most notably erupted 760 ka, and currently experiences continuous geothermal activity and sporadic earthquake swarms. The timing of the most recent motion on these fault splays is debated, as is the threat posed by this section of the Hilton Creek Fault. The Third Uniform California Earthquake Rupture Forecast (UCERF3) model depicts the HCF as a single strand projecting up to 12km into the LVC. However, Bailey (1989) and Hill and Montgomery-Brown (2015) have argued against this model, suggesting that extensional faulting within the Caldera has been accommodated by the ongoing volcanic uplift and thus the intracaldera section of the HCF has not experienced motion since 760ka.We intend to map the intracaldera fault splays and model their subsurface characteristics to better assess their rupture history and potential. This will be accomplished using high-resolution topography and subsurface geophysical methods, including ground-based magnetics. Preliminary work was performed using high-precision Nikon Nivo 5.C total stations to generate elevation profiles and a backpack mounted GEM GS-19 proton precession magnetometer. The initial results reveal a correlation between magnetic anomalies and topography. East-West topographic profiles show terrace-like steps, sub-meter in height, which correlate to changes in the magnetic data. Continued study of the magnetic data using Oasis Montaj 3D modeling software is planned. Additionally, we intend to prepare a high-resolution terrain model using structure-from-motion techniques

Active faults and minor plates in NE Asia

NASA Astrophysics Data System (ADS)

Kozhurin, Andrey I.; Zelenin, Egor A.

2014-05-01

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

Present-day crustal motion along the Longitudinal Valley Fault, eastern Taiwan

NASA Astrophysics Data System (ADS)

Yu, Shui-Beih; Kuo, Long-Chen

2001-04-01

The NNE-striking Longitudinal Valley Fault (LVF) in eastern Taiwan is an extremely active high-angle thrust fault. It bounds the Coastal Range and the Longitudinal Valley, which is considered a collision boundary between the Philippine Sea and the Eurasian plates. Repeated GPS data in the Longitudinal Valley area from 1992 to 1999 are utilized to study the spatial variation of crustal motion along the LVF. With respect to Penghu in the Chinese continental margin, velocities for stations on the western side of the LVF (Longitudinal Valley and eastern Central Range) are 18-35 mm/yr in directions 283-311°, whereas those on the eastern side of the LVF, the Coastal Range, are 28-68 mm/yr in directions 303-324°. A major discontinuity of about 30 mm/yr on the rate of crustal motion across the Longitudinal Valley is attributed to the aseismic slip along the LVF as revealed by trilateration data previously. To the south of Fengping, the block motions of the Coastal Range are 31-40 mm/yr in 317-330° relative to the Central Range, while the near-fault motions are 13-33 mm/yr in 309-336°. Various partitions on the left-lateral strike-slip and convergent components along the LVF are found. In the southern Longitudinal Valley crustal motion is mainly accommodated on the LVF and the Luyeh Fault. In contrast, those in the central and northern Longitudinal Valley are partly taken up on the faults to the east of the LVF or result in the elastic deformation of the Coastal Range. The crustal motion in the northern Longitudinal Valley area is likely to be distributed in the several NE-striking thrusts in a horsetail pattern and obliquely cut the northern Coastal Range, with a small portion of fault-slips along the LVF. Data from dense-deployed GPS networks across the LVF can be employed to give better estimates of near-fault motions and delineate the surface traces of the LVF. Repeated GPS and leveling data from two stations on both ends of the Yuli Bridge that are 575 m apart

The effects of transistor source-to-gate bridging faults in complex CMOS gates

NASA Astrophysics Data System (ADS)

Visweswaran, G. S.; Ali, Akhtar-Uz-Zaman M.; Lala, Parag K.; Hartmann, Carlos R. P.

1991-06-01

A study of the effect of gate-to-source bridging faults in the pull-up section of a complex CMOS gate is presented. The manifestation of these faults depends on the resistance value of the connection causing the bridging. It is shown that such faults manifest themselves either as stuck-at or stuck-open faults and can be detected by tests for stuck-at and stuck-open faults generated for the equivalent logic current. It is observed that for transistor channel lengths larger than 1 microns there exists a range of values of the bridging resistance for which the fault behaves as a pseudo-stuck-open fault.

A New Kinematic Model for Polymodal Faulting: Implications for Fault Connectivity

NASA Astrophysics Data System (ADS)

Healy, D.; Rizzo, R. E.

2015-12-01

Conjugate, or bimodal, fault patterns dominate the geological literature on shear failure. Based on Anderson's (1905) application of the Mohr-Coulomb failure criterion, these patterns have been interpreted from all tectonic regimes, including normal, strike-slip and thrust (reverse) faulting. However, a fundamental limitation of the Mohr-Coulomb failure criterion - and others that assume faults form parallel to the intermediate principal stress - is that only plane strain can result from slip on the conjugate faults. However, deformation in the Earth is widely accepted as being three-dimensional, with truly triaxial stresses and strains. Polymodal faulting, with three or more sets of faults forming and slipping simultaneously, can generate three-dimensional strains from truly triaxial stresses. Laboratory experiments and outcrop studies have verified the occurrence of the polymodal fault patterns in nature. The connectivity of polymodal fault networks differs significantly from conjugate fault networks, and this presents challenges to our understanding of faulting and an opportunity to improve our understanding of seismic hazards and fluid flow. Polymodal fault patterns will, in general, have more connected nodes in 2D (and more branch lines in 3D) than comparable conjugate (bimodal) patterns. The anisotropy of permeability is therefore expected to be very different in rocks with polymodal fault patterns in comparison to conjugate fault patterns, and this has implications for the development of hydrocarbon reservoirs, the genesis of ore deposits and the management of aquifers. In this contribution, I assess the published evidence and models for polymodal faulting before presenting a novel kinematic model for general triaxial strain in the brittle field.

Fault Tolerant Real-Time Systems

DTIC Science & Technology

1993-09-30

The ART (Advanced Real-Time Technology) Project of Carnegie Mellon University is engaged in wide ranging research on hard real - time systems . The...including hardware and software fault tolerance using temporal redundancy and analytic redundancy to permit the construction of real - time systems whose

An update of Quaternary faults of central and eastern Oregon

USGS Publications Warehouse

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

2002-01-01

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

Fault tree models for fault tolerant hypercube multiprocessors

NASA Technical Reports Server (NTRS)

Boyd, Mark A.; Tuazon, Jezus O.

1991-01-01

Three candidate fault tolerant hypercube architectures are modeled, their reliability analyses are compared, and the resulting implications of these methods of incorporating fault tolerance into hypercube multiprocessors are discussed. In the course of performing the reliability analyses, the use of HARP and fault trees in modeling sequence dependent system behaviors is demonstrated.

Fault Tree Analysis.

PubMed

McElroy, Lisa M; Khorzad, Rebeca; Rowe, Theresa A; Abecassis, Zachary A; Apley, Daniel W; Barnard, Cynthia; Holl, Jane L

The purpose of this study was to use fault tree analysis to evaluate the adequacy of quality reporting programs in identifying root causes of postoperative bloodstream infection (BSI). A systematic review of the literature was used to construct a fault tree to evaluate 3 postoperative BSI reporting programs: National Surgical Quality Improvement Program (NSQIP), Centers for Medicare and Medicaid Services (CMS), and The Joint Commission (JC). The literature review revealed 699 eligible publications, 90 of which were used to create the fault tree containing 105 faults. A total of 14 identified faults are currently mandated for reporting to NSQIP, 5 to CMS, and 3 to JC; 2 or more programs require 4 identified faults. The fault tree identifies numerous contributing faults to postoperative BSI and reveals substantial variation in the requirements and ability of national quality data reporting programs to capture these potential faults. Efforts to prevent postoperative BSI require more comprehensive data collection to identify the root causes and develop high-reliability improvement strategies.

Structure and seismic hazard of the Ventura Avenue anticline and Ventura fault, California: Prospect for large, multisegment ruptures in the Western Transverse Ranges

USGS Publications Warehouse

Hubbard, Judith; Shaw, John H.; Dolan, James F.; Pratt, Thomas L.; McAuliffe, Lee J.; Rockwell, Thomas K.

2014-01-01

The Ventura Avenue anticline is one of the fastest uplifting structures in southern California, rising at ∼5  mm/yr. We use well data and seismic reflection profiles to show that the anticline is underlain by the Ventura fault, which extends to seismogenic depth. Fault offset increases with depth, implying that the Ventura Avenue anticline is a fault‐propagation fold. A decrease in the uplift rate since ∼30±10  ka is consistent with the Ventura fault breaking through to the surface at that time and implies that the fault has a recent dip‐slip rate of ∼4.4–6.9  mm/yr.To the west, the Ventura fault and fold trend continues offshore as the Pitas Point fault and its associated hanging wall anticline. The Ventura–Pitas Point fault appears to flatten at about 7.5 km depth to a detachment, called the Sisar decollement, then step down on a blind thrust fault to the north. Other regional faults, including the San Cayetano and Red Mountain faults, link with this system at depth. We suggest that below 7.5 km, these faults may form a nearly continuous surface, posing the threat of large, multisegment earthquakes.Holocene marine terraces on the Ventura Avenue anticline suggest that it grows in discrete events with 5–10 m of uplift, with the latest event having occurred ∼800 years ago (Rockwell, 2011). Uplift this large would require large earthquakes (Mw 7.7–8.1) involving the entire Ventura/Pitas Point system and possibly more structures along strike, such as the San Cayetano fault. Because of the local geography and geology, such events would be associated with significant ground shaking amplification and regional tsunamis.

Digital release of the Alaska Quaternary fault and fold database

NASA Astrophysics Data System (ADS)

Koehler, R. D.; Farrell, R.; Burns, P.; Combellick, R. A.; Weakland, J. R.

2011-12-01

The Alaska Division of Geological & Geophysical Surveys (DGGS) has designed a Quaternary fault and fold database for Alaska in conformance with standards defined by the U.S. Geological Survey for the National Quaternary fault and fold database. Alaska is the most seismically active region of the United States, however little information exists on the location, style of deformation, and slip rates of Quaternary faults. Thus, to provide an accurate, user-friendly, reference-based fault inventory to the public, we are producing a digital GIS shapefile of Quaternary fault traces and compiling summary information on each fault. Here, we present relevant information pertaining to the digital GIS shape file and online access and availability of the Alaska database. This database will be useful for engineering geologic studies, geologic, geodetic, and seismic research, and policy planning. The data will also contribute to the fault source database being constructed by the Global Earthquake Model (GEM), Faulted Earth project, which is developing tools to better assess earthquake risk. We derived the initial list of Quaternary active structures from The Neotectonic Map of Alaska (Plafker et al., 1994) and supplemented it with more recent data where available. Due to the limited level of knowledge on Quaternary faults in Alaska, pre-Quaternary fault traces from the Plafker map are shown as a layer in our digital database so users may view a more accurate distribution of mapped faults and to suggest the possibility that some older traces may be active yet un-studied. The database will be updated as new information is developed. We selected each fault by reviewing the literature and georegistered the faults from 1:250,000-scale paper maps contained in 1970's vintage and earlier bedrock maps. However, paper map scales range from 1:20,000 to 1:500,000. Fault parameters in our GIS fault attribute tables include fault name, age, slip rate, slip sense, dip direction, fault line type

Fault-tolerant cooperative output regulation for multi-vehicle systems with sensor faults

NASA Astrophysics Data System (ADS)

Qin, Liguo; He, Xiao; Zhou, D. H.

2017-10-01

This paper presents a unified framework of fault diagnosis and fault-tolerant cooperative output regulation (FTCOR) for a linear discrete-time multi-vehicle system with sensor faults. The FTCOR control law is designed through three steps. A cooperative output regulation (COR) controller is designed based on the internal mode principle when there are no sensor faults. A sufficient condition on the existence of the COR controller is given based on the discrete-time algebraic Riccati equation (DARE). Then, a decentralised fault diagnosis scheme is designed to cope with sensor faults occurring in followers. A residual generator is developed to detect sensor faults of each follower, and a bank of fault-matching estimators are proposed to isolate and estimate sensor faults of each follower. Unlike the current distributed fault diagnosis for multi-vehicle systems, the presented decentralised fault diagnosis scheme in each vehicle reduces the communication and computation load by only using the information of the vehicle. By combing the sensor fault estimation and the COR control law, an FTCOR controller is proposed. Finally, the simulation results demonstrate the effectiveness of the FTCOR controller.

Preliminary paleoseismic observations along the western Denali fault, Alaska

NASA Astrophysics Data System (ADS)

Koehler, R. D.; Schwartz, D. P.; Rood, D. H.; Reger, R.; Wolken, G. J.

2013-12-01

The Denali fault in south-central Alaska, from Mt. McKinley to the Denali-Totschunda fault branch point, accommodates ~9-12 mm/yr of the right-lateral component of oblique convergence between the Pacific/Yakutat and North American plates. The eastern 226 km of this fault reach was part of the source of the 2002 M7.9 Denali fault earthquake. West of the 2002 rupture there is evidence of two large earthquakes on the Denali fault during the past ~550-700 years but the paleoearthquake chronology prior to this time is largely unknown. To better constrain fault rupture parameters for the western Denali fault and contribute to improved seismic hazard assessment, we performed helicopter and ground reconnaissance along the southern flank of the Alaska Range between the Nenana Glacier and Pyramid Peak, a distance of ~35 km, and conducted a site-specific paleoseismic study. We present a Quaternary geologic strip map along the western Denali fault and our preliminary paleoseismic results, which include a differential-GPS survey of a displaced debris flow fan, cosmogenic 10Be surface exposure ages for boulders on this fan, and an interpretation of a trench across the main trace of the fault at the same site. Between the Nenana Glacier and Pyramid Peak, the Denali fault is characterized by prominent tectonic geomorphic features that include linear side-hill troughs, mole tracks, anastamosing composite scarps, and open left-stepping fissures. Measurements of offset rills and gullies indicate that slip during the most recent earthquake was between ~3 and 5 meters, similar to the average displacement in the 2002 earthquake. At our trench site, ~ 25 km east of the Parks Highway, a steep debris fan is displaced along a series of well-defined left-stepping linear fault traces. Multi-event displacements of debris-flow and snow-avalanche channels incised into the fan range from 8 to 43 m, the latter of which serves as a minimum cumulative fan offset estimate. The trench, excavated into

Mountain Meadows Dacite: Oligocene intrusive complex that welds together the Los Angeles Basin, northwestern Peninsular Ranges, and central Transverse Ranges, California

USGS Publications Warehouse

McCulloh, Thane H.; Beyer, Larry A.; Morin, Ronald W.

2001-01-01

Dikes and irregular intrusive bodies of distinctive Oligocene biotite dacite and serially related hornblende latite and felsite occur widely in the central and eastern San Gabriel Mountains, southern California, and are related to the Telegraph Peak granodiorite pluton. Identical dacite is locally present beneath Middle Miocene Topanga Group Glendora Volcanics at the northeastern edge of the Los Angeles Basin, where it is termed Mountain Meadows Dacite. This study mapped the western and southwestern limits of the dacite distribution to understand the provenance of derived redeposited clasts, to perceive Neogene offsets on several large strike-slip faults, to test published palinspastic reconstructions, and to better understand the tectonic boundaries that separate contrasting pre-Tertiary rock terranes where the Peninsular Ranges meet the central and western Transverse Ranges and the Los Angeles Basin. Transported and redeposited clasts of dacite-latite occur in deformed lower Miocene and lower middle Miocene sandy conglomerates (nonmarine, nearshore, and infrequent upper bathyal) close to the northern and northeastern margins of the Los Angeles Basin for a distance of nearly 60 km. Tie-lines between distinctive source suites and clast occurrences indicate that large tracts of the ancestral San Gabriel Mountains were elevated along range-bounding faults as early as 16–15 Ma. The tie-lines prohibit very large strike-slip offsets on those faults. Transport of eroded dacite began south of the range as early as 18 Ma. Published and unpublished data about rocks adjacent to the active Santa Monica-Hollywood-Raymond oblique reverse left-lateral fault indicate that cumulative left slip totals 13–14 km and total offset postdates 7 Ma. This cumulative slip, with assembly of stratigraphic and paleogeographic data, invalidates prior estimates of 60 to 90 km of left slip on these faults beginning about 17–16 Ma. A new and different palinspastic reconstruction of a region

Earthquake stress drops and inferred fault strength on the Hayward Fault, east San Francisco Bay, California

USGS Publications Warehouse

Hardebeck, J.L.; Aron, A.

2009-01-01

We study variations in earthquake stress drop with respect to depth, faulting regime, creeping versus locked fault behavior, and wall-rock geology. We use the P-wave displacement spectra from borehole seismic recordings of M 1.0-4.2 earthquakes in the east San Francisco Bay to estimate stress drop using a stack-and-invert empirical Green's function method. The median stress drop is 8.7 MPa, and most stress drops are in the range between 0.4 and 130 MPa. An apparent correlation between stress drop and magnitude is entirely an artifact of the limited frequency band of 4-55 Hz. There is a trend of increasing stress drop with depth, with a median stress drop of ~5 MPa for 1-7 km depth, ~10 MPa for 7-13 km depth, and ~50 MPa deeper than 13 km. We use S=P amplitude ratios measured from the borehole records to better constrain the first-motion focal mechanisms. High stress drops are observed for a deep cluster of thrust-faulting earthquakes. The correlation of stress drops with depth and faulting regime implies that stress drop is related to the applied shear stress. We compare the spatial distribution of stress drops on the Hayward fault to a model of creeping versus locked behavior of the fault and find that high stress drops are concentrated around the major locked patch near Oakland. This also suggests a connection between stress drop and applied shear stress, as the locked patch may experience higher applied shear stress as a result of the difference in cumulative slip or the presence of higher-strength material. The stress drops do not directly correlate with the strength of the proposed wall-rock geology at depth, suggesting that the relationship between fault strength and the strength of the wall rock is complex.

Determining on-fault earthquake magnitude distributions from integer programming

NASA Astrophysics Data System (ADS)

Geist, Eric L.; Parsons, Tom

2018-02-01

Earthquake magnitude distributions among faults within a fault system are determined from regional seismicity and fault slip rates using binary integer programming. A synthetic earthquake catalog (i.e., list of randomly sampled magnitudes) that spans millennia is first formed, assuming that regional seismicity follows a Gutenberg-Richter relation. Each earthquake in the synthetic catalog can occur on any fault and at any location. The objective is to minimize misfits in the target slip rate for each fault, where slip for each earthquake is scaled from its magnitude. The decision vector consists of binary variables indicating which locations are optimal among all possibilities. Uncertainty estimates in fault slip rates provide explicit upper and lower bounding constraints to the problem. An implicit constraint is that an earthquake can only be located on a fault if it is long enough to contain that earthquake. A general mixed-integer programming solver, consisting of a number of different algorithms, is used to determine the optimal decision vector. A case study is presented for the State of California, where a 4 kyr synthetic earthquake catalog is created and faults with slip ≥3 mm/yr are considered, resulting in >106 variables. The optimal magnitude distributions for each of the faults in the system span a rich diversity of shapes, ranging from characteristic to power-law distributions.

Determining on-fault earthquake magnitude distributions from integer programming

USGS Publications Warehouse

Geist, Eric L.; Parsons, Thomas E.

2018-01-01

Earthquake magnitude distributions among faults within a fault system are determined from regional seismicity and fault slip rates using binary integer programming. A synthetic earthquake catalog (i.e., list of randomly sampled magnitudes) that spans millennia is first formed, assuming that regional seismicity follows a Gutenberg-Richter relation. Each earthquake in the synthetic catalog can occur on any fault and at any location. The objective is to minimize misfits in the target slip rate for each fault, where slip for each earthquake is scaled from its magnitude. The decision vector consists of binary variables indicating which locations are optimal among all possibilities. Uncertainty estimates in fault slip rates provide explicit upper and lower bounding constraints to the problem. An implicit constraint is that an earthquake can only be located on a fault if it is long enough to contain that earthquake. A general mixed-integer programming solver, consisting of a number of different algorithms, is used to determine the optimal decision vector. A case study is presented for the State of California, where a 4 kyr synthetic earthquake catalog is created and faults with slip ≥3 mm/yr are considered, resulting in >106  variables. The optimal magnitude distributions for each of the faults in the system span a rich diversity of shapes, ranging from characteristic to power-law distributions. 

Coseismic stresses indicated by pseudotachylytes in the Outer Hebrides Fault Zone, UK.

NASA Astrophysics Data System (ADS)

Campbell, Lucy; Lloyd, Geoffrey; Phillips, Richard; Holdsworth, Robert; Walcott, Rachel

2015-04-01

During the few seconds of earthquake slip, dynamic behaviour is predicted for stress, slip velocity, friction and temperature, amongst other properties. Fault-derived pseudotachylyte is a coseismic frictional melt and provides a unique snapshot of the rupture environment. Exhumation of ancient fault zones to seismogenic depths can reveal the structure and distribution of seismic slip as pseudotachylyte bearing fault planes. An example lies in NW Scotland along the Outer Hebrides Fault Zone (OHFZ) - this long-lived fault zone displays a suite of fault rocks developed under evolving kinematic regimes, including widespread pseudotachylyte veining which is distributed both on and away from the major faults. This study adds data derived from the OHFZ pseudotachylytes to published datasets from well-constrained fault zones, in order to explore the use of existing methodologies on more complex faults and to compare the calculated results. Temperature, stress and pressure are calculated from individual fault veins and added to existing datasets. The results pose questions on the physical meaning of the derived trends, the distribution of seismic energy release across scattered cm-scale faults and the range of earthquake magnitudes calculated from faults across any given fault zone.

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

USGS Publications Warehouse

Machette, M.N.

2000-01-01

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

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

NASA Astrophysics Data System (ADS)

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

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

States of paleostress north and south of the Periadriatic fault: Comparison of the Drau Range and the Friuli Southalpine wedge

PubMed Central

Bartel, Esther Maria; Neubauer, Franz; Genser, Johann; Heberer, Bianca

2014-01-01

This study focuses on the analysis of structures and kinematics of a N–S profile along the axis of maximum shortening of the European Eastern Alps. The area includes the southern Austroalpine unit in the north and the Southalpine unit, which is a part of the Adriatic indenter. The stratigraphically different units are separated by the Periadriatic fault, the major strike-slip fault within the Alps. In order to assess the kinematics of these units, mainly fault-slip data from north and south of the Periadriatic fault were analyzed. We distinguish a succession of five main kinematic groups in both units: (1) N–S compression; (2) NW–SE compression; (3) NE–SW compression, σ3 changes gradually from subvertical to subhorizontal; (4) N–S compression; and (5) NW–SE compression. Our study reveals that the deformation sequence on either sides of the PAF is similar. The mean orientations of the principal stress axes, however, show small, but consistent differences: The subhorizontal axes north of the Periadriatic fault plunge northward, in the south southward. A counterclockwise (CCW) rotation of the southern part in respect to the north is evident and in line with the well-known counterclockwise rotation of the Adriatic indenter as well as dextral displacement of the N-fanning stress-field along the Periadriatic fault. Opposing plunge directions are interpreted as a primary feature of the internal stress-field within an orogenic wedge further increased during ongoing compression. PMID:27064736

Neogene contraction between the San Andreas fault and the Santa Clara Valley, San Francisco Bay region, California

USGS Publications Warehouse

McLaughlin, R.J.; Langenheim, V.E.; Schmidt, K.M.; Jachens, R.C.; Stanley, R.G.; Jayko, A.S.; McDougall, K.A.; Tinsley, J.C.; Valin, Z.C.

1999-01-01

In the southern San Francisco Bay region of California, oblique dextral reverse faults that verge northeastward from the San Andreas fault experienced triggered slip during the 1989 M7.1 Loma Prieta earthquake. The role of these range-front thrusts in the evolution of the San Andreas fault system and the future seismic hazard that they may pose to the urban Santa Clara Valley are poorly understood. Based on recent geologic mapping and geophysical investigations, we propose that the range-front thrust system evolved in conjunction with development of the San Andreas fault system. In the early Miocene, the region was dominated by a system of northwestwardly propagating, basin-bounding, transtensional faults. Beginning as early as middle Miocene time, however, the transtensional faulting was superseded by transpressional NE-stepping thrust and reverse faults of the range-front thrust system. Age constraints on the thrust faults indicate that the locus of contraction has focused on the Monte Vista, Shannon, and Berrocal faults since about 4.8 Ma. Fault slip and fold reconstructions suggest that crustal shortening between the San Andreas fault and the Santa Clara Valley within this time frame is ~21%, amounting to as much as 3.2 km at a rate of 0.6 mm/yr. Rates probably have not remained constant; average rates appear to have been much lower in the past few 100 ka. The distribution of coseismic surface contraction during the Loma Prieta earthquake, active seismicity, late Pleistocene to Holocene fluvial terrace warping, and geodetic data further suggest that the active range-front thrust system includes blind thrusts. Critical unresolved issues include information on the near-surface locations of buried thrusts, the timing of recent thrust earthquake events, and their recurrence in relation to earthquakes on the San Andreas fault.

The role of rock anisotropy in developing non-Andersonian faults: staircase trajectories for strike-slip faults

NASA Astrophysics Data System (ADS)

Barchi, M. R.; Collettini, C.; Lena, G.

2012-04-01

order to reconstruct the σ1 direction, calcite veins syntectonic to strike-slip faulting, have been used to constrain the σ1-σ2 plane: fixing the σ2 direction at the conjugate fault intersection, the σ1 is oriented N15°, forming an angle of about 70° with the bedding direction. Once constrained the σ1 direction, we have calculated the θ angle that is comprised between 40° and 55°, resulting therefore larger than expected from Andersonian theory, i.e. 22°-32° for friction coefficient in the range of 0.5-1.0. Initiation/reactivation angles, θ, as a function of the different lithologies, are less than 35° for calcareous beds, 50°-70° for the marly and clayey layers, and around 60° for the black shales. Our studies, focused on strike-slip small displacement faults, show that: 1) irrespective of the σ1 orientation, ramp and flat form along competent and less competent material respectively and 2) the overall fault orientation/initiation is at high-angle to the σ1 direction. Our results suggest that rock anisotropy and layering are one of the possible causes for faulting at high angle to the σ1 direction, i.e. fault weakness. Further studies are required to up-scale the results of our outcrop-based study to crustal scale structures.

Late quaternary paleoseismology of the southern Steens fault zone, northern Nevada

USGS Publications Warehouse

Personius, S.F.; Crone, A.J.; Machette, M.N.; Mahan, S.A.; Kyung, J.B.; Cisneros, H.; Lidke, D.J.

2007-01-01

The 192-km-long Steens fault zone is the most prominent normal fault system in the northern Basin and Range province of western North America. We use trench mapping and radiometric dating to estimate displacements and timing of the last three surface-rupturing earthquakes (E1-E3) on the southern part of the fault south of Denio, Nevada. Coseismic displacements range from 1.1 to 2.2 ?? 0.5 m, and radiometric ages indicate earthquake times of 11.5 ?? 2.0 ka (E3), 6.1 ?? 0.5 ka (E2), and 4.6 ?? 1.0 ka (E1). These data yield recurrence intervals of 5.4 ?? 2.1 k.y. between E3 and E2, 1.5 ?? 1.1 k.y. between E2 and E1, and an elapsed time of 4.6 ?? 1.0 k.y. since E1. The recurrence data yield variable interval slip rates (between 0.2 ?? 0.22 and 1.5 ?? 2.3 mm/yr), but slip rates averaged over the past ???18 k.y. (0.24 ?? 0.06 mm/year) are similar to long-term (8.5-12.5 Ma) slip rates (0.2 ?? 0.1 mm /yr) measured a few kilometers to the north. We infer from the lack of significant topographic relief across the fault in Bog Hot Valley that the fault zone is propagating southward and may now be connected with a fault at the northwestern end of the Pine Forest Range. Displacements documented in the trench and a rupture length of 37 km indicate a history of three latest Quaternary earthquakes with magnitudes of M 6.6-7.1 on the southern part of the Steens fault zone.

On-board fault management for autonomous spacecraft

NASA Technical Reports Server (NTRS)

Fesq, Lorraine M.; Stephan, Amy; Doyle, Susan C.; Martin, Eric; Sellers, Suzanne

1991-01-01

The dynamic nature of the Cargo Transfer Vehicle's (CTV) mission and the high level of autonomy required mandate a complete fault management system capable of operating under uncertain conditions. Such a fault management system must take into account the current mission phase and the environment (including the target vehicle), as well as the CTV's state of health. This level of capability is beyond the scope of current on-board fault management systems. This presentation will discuss work in progress at TRW to apply artificial intelligence to the problem of on-board fault management. The goal of this work is to develop fault management systems. This presentation will discuss work in progress at TRW to apply artificial intelligence to the problem of on-board fault management. The goal of this work is to develop fault management systems that can meet the needs of spacecraft that have long-range autonomy requirements. We have implemented a model-based approach to fault detection and isolation that does not require explicit characterization of failures prior to launch. It is thus able to detect failures that were not considered in the failure and effects analysis. We have applied this technique to several different subsystems and tested our approach against both simulations and an electrical power system hardware testbed. We present findings from simulation and hardware tests which demonstrate the ability of our model-based system to detect and isolate failures, and describe our work in porting the Ada version of this system to a flight-qualified processor. We also discuss current research aimed at expanding our system to monitor the entire spacecraft.

Fault zone property near Xinfengjiang Reservoir using dense, across-fault seismic array

NASA Astrophysics Data System (ADS)

Lee, M. H. B.; Yang, H.; Sun, X.

2017-12-01

Properties of fault zones are important to the understanding of earthquake process. Around the fault zone is a damaged zone which is characterised by a lower seismic velocity. This is detectable as a low velocity zone and measure some physical property of the fault zone, which is otherwise difficult sample directly. A dense, across-fault array of short period seismometer is deployed on an inactive fault near Xinfengjiang Reservoir. Local events were manually picked. By computing the synthetic arrival time, we were able to constrain the parameters of the fault zone Preliminary result shows that the fault zone is around 350 m wide with a P and S velocity increase of around 10%. The fault is geologically inferred, and this result suggested that it may be a geological layer. The other possibility is that the higher velocity is caused by a combination of fault zone healing and fluid intrusion. Whilst the result was not able to tell us the nature of the fault, it demonstrated that this method is able to derive properties from a fault zone.

Dependence of frictional strength on compositional variations of Hayward fault rock gouges

USGS Publications Warehouse

Morrow, Carolyn A.; Moore, Diane E.; Lockner, David A.

2010-01-01

The northern termination of the locked portion of the Hayward Fault near Berkeley, California, is found to coincide with the transition from strong Franciscan metagraywacke to melange on the western side of the fault. Both of these units are juxtaposed with various serpentinite, gabbro and graywacke units to the east, suggesting that the gouges formed within the Hayward Fault zone may vary widely due to the mixing of adjacent rock units and that the mechanical behavior of the fault would be best modeled by determining the frictional properties of mixtures of the principal rock types. To this end, room temperature, water-saturated, triaxial shearing tests were conducted on binary and ternary mixtures of fine-grained gouges prepared from serpentinite and gabbro from the Coast Range Ophiolite, a Great Valley Sequence graywacke, and three different Franciscan Complex metasedimentary rocks. Friction coefficients ranged from 0.36 for the serpentinite to 0.84 for the gabbro, with four of the rock types having coefficients of friction ranging from 0.67-0.84. The friction coefficients of the mixtures can be predicted reliably by a simple weighted average of the end-member dry-weight percentages and strengths for all samples except those containing serpentinite. For the serpentinite mixtures, a linear trend between end-member values slightly overestimates the coefficients of friction in the midcomposition ranges. The range in strength for these rock admixtures suggests that both theoretical and numerical modeling of the fault should attempt to account for variations in rock and gouge properties.

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

NASA Astrophysics Data System (ADS)

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

2014-05-01

The San Andreas fault in southern California records only few large-magnitude earthquakes in historic time, and the recent activity is confined primarily on irregular and discontinuous strike-slip and thrust fault strands at shallow depths of ~5-20 km. Despite this fact, slip along the San Andreas fault is calculated to c. 35 mm/yr based on c.160 km total right lateral displacement for the southern segment of the fault in the last c. 8 Ma. Field observations also reveal complex fault strands and multiple events of deformation. The presently diffuse high-magnitude crustal movements may be explained by the deformation being largely distributed along more gently dipping reverse faults in fold-thrust belts, in contrast to regions to the north where deformation is less partitioned and localized to narrow strike-slip fault zones. In the Mecca Hills of the Salton trough transpressional deformation of an uplifted segment of the San Andreas fault in the last ca. 4.0 My is expressed by very complex fault-oblique and fault-parallel (en echelon) folding, and zones of uplift (fold-thrust belts), basement-involved reverse and strike-slip faults and accompanying multiple and pervasive cataclasis and conjugate fracturing of Miocene to Pleistocene sedimentary strata. Our structural analysis of the Mecca Hills addresses the kinematic nature of the San Andreas fault and mechanisms of uplift and strain-stress distribution along bent fault strands. The San Andreas fault and subsidiary faults define a wide spectrum of kinematic styles, from steep localized strike-slip faults, to moderate dipping faults related to oblique en echelon folds, and gently dipping faults distributed in fold-thrust belt domains. Therefore, the San Andreas fault is not a through-going, steep strike-slip crustal structure, which is commonly the basis for crustal modeling and earthquake rupture models. The fault trace was steep initially, but was later multiphase deformed/modified by oblique en echelon folding

Rule-based fault diagnosis of hall sensors and fault-tolerant control of PMSM

NASA Astrophysics Data System (ADS)

Song, Ziyou; Li, Jianqiu; Ouyang, Minggao; Gu, Jing; Feng, Xuning; Lu, Dongbin

2013-07-01

Hall sensor is widely used for estimating rotor phase of permanent magnet synchronous motor(PMSM). And rotor position is an essential parameter of PMSM control algorithm, hence it is very dangerous if Hall senor faults occur. But there is scarcely any research focusing on fault diagnosis and fault-tolerant control of Hall sensor used in PMSM. From this standpoint, the Hall sensor faults which may occur during the PMSM operating are theoretically analyzed. According to the analysis results, the fault diagnosis algorithm of Hall sensor, which is based on three rules, is proposed to classify the fault phenomena accurately. The rotor phase estimation algorithms, based on one or two Hall sensor(s), are initialized to engender the fault-tolerant control algorithm. The fault diagnosis algorithm can detect 60 Hall fault phenomena in total as well as all detections can be fulfilled in 1/138 rotor rotation period. The fault-tolerant control algorithm can achieve a smooth torque production which means the same control effect as normal control mode (with three Hall sensors). Finally, the PMSM bench test verifies the accuracy and rapidity of fault diagnosis and fault-tolerant control strategies. The fault diagnosis algorithm can detect all Hall sensor faults promptly and fault-tolerant control algorithm allows the PMSM to face failure conditions of one or two Hall sensor(s). In addition, the transitions between health-control and fault-tolerant control conditions are smooth without any additional noise and harshness. Proposed algorithms can deal with the Hall sensor faults of PMSM in real applications, and can be provided to realize the fault diagnosis and fault-tolerant control of PMSM.

Evolution of Microroughness with Increasing Slip Magnitude on Pseudotachylyte-Bearing Fault Surfaces

NASA Astrophysics Data System (ADS)

Bessey, S.; Resor, P. G.; Di Toro, G.

2013-12-01

High velocity rock friction experiments reproducing seismic slip deformation conditions have shown that there is an initial shear strengthening prior to a significant weakening with slip. This change in shear resistance is inferred to occur due to the development of melt patches, which initially strengthen the fault, and is associated with the evolution of microroughness of the melt-wall rock interface (Hirose and Shimamoto, 2003). Additional melting leads to a continuous layer of melt, allowing easier sliding and weakening. Once there is a balance between formation and extrusion of melt, a steady state shear resistance (and associated effective friction coefficient) is reached (Nielsen et al. 2008). In natural fault zones, the process of frictional melting, slip weakening, and steady state is both recorded and influenced by the microroughness of the fault surface. Our study explores natural faults over a range of slip magnitudes from mm to m of slip, the magnitudes over which this process is most likely to occur during earthquakes. The Gole Larghe fault zone (Italy) is an exhumed strike-slip fault zone in tonalite of the Adamello batholith. The fault zone is characterized by multiple fault strands containing pseudotachylyte or pseudotachylyte overprinting cataclasite. We have sampled several individual faults segments from within the fault zone, with slips ranging from 23 mm to 1.9 m. The smaller scale samples are from pseudotachylyte-only fault strands and therefore probably record single-slip events. The two largest slip faults have pseudotachylyte and cataclasite, indicating that they may have more complicated slip histories. Individual samples consist of cores (2-3.5 cm diameter, 2-6 cm length) drilled parallel to the fault surface and ~perpendicular to the slip. Samples were scanned with an Xradia MicroCT scanner to image the 3D geometry of the fault and wall rocks. Fault surfaces (contact between the pseudotachylyte-bearing slipping zone and the wall rock

Implications of Preliminary Gravity and Magnetic Surveys to the Understanding of the Bartlett Springs Fault Zone, Northern California Coast Ranges

NASA Astrophysics Data System (ADS)

Langenheim, V. E.; Jachens, R. C.; Morin, R. L.; McCabe, C. M.; Page, W. D.

2007-12-01

We use new gravity and magnetic data in the Lake Pillsbury region to help understand the geometry and character of the Bartlett Springs fault zone, one of the three main strands of the San Andreas system north of the San Francisco Bay area. We collected 153 new gravity stations in the Lake Pillsbury region that complement the sparse regional dataset and are used to estimate the thickness of Quaternary deposits in the inferred Gravelly Valley (Lake Pillsbury) pull-apart basin. We also collected 38 line-km of ground magnetic data on roads and 65 line-km by boat on the lake to supplement regional aeromagnetic surveys and to map concealed fault strands beneath the lake. The new gravity data show a significant northwest-striking gravity gradient at the base of which lies the Bartlett Springs fault zone. Superposed on this major east-facing gravity gradient is a 5 mGal low centered on Lake Pillsbury and Gravelly Valley. Inversion of the gravity field for basin thickness assuming a density contrast of 400 kg/m3 indicates the deepest part of the basin is about 400 m and located in the northern part of the valley, although the inversion lacks gravity stations within the lake. The basin is about 3 km wide and 5 km long and basin edges coincide with strands of the Bartlett Springs fault zone. Our gravity data suggest that Potter Valley, which lies between the Maacama and Bartlett Springs faults, is also as much as 400 m deep in the southern part of the valley, although additional data west of the valley would better isolate the gravity low. Geomorphologic characteristics of the valley suggest that this structure has been quiescent during the late Quaternary. Ground magnetic data are very noisy but the data in conjunction with 9.6 km-spaced NURE aeromagnetic lines suggest that regional analog aeromagnetic data flown in 1962 may suffer from location errors. The regional and NURE data show a northwest-striking magnetic high that extends across Lake Pillsbury. The northeast edge

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

NASA Astrophysics Data System (ADS)

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

2011-12-01

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

Fault segmentation: New concepts from the Wasatch Fault Zone, Utah, USA

USGS Publications Warehouse

Duross, Christopher; Personius, Stephen F.; Crone, Anthony J.; Olig, Susan S.; Hylland, Michael D.; Lund, William R.; Schwartz, David P.

2016-01-01

The question of whether structural segment boundaries along multisegment normal faults such as the Wasatch fault zone (WFZ) act as persistent barriers to rupture is critical to seismic hazard analyses. We synthesized late Holocene paleoseismic data from 20 trench sites along the central WFZ to evaluate earthquake rupture length and fault segmentation. For the youngest (<3 ka) and best-constrained earthquakes, differences in earthquake timing across prominent primary segment boundaries, especially for the most recent earthquakes on the north-central WFZ, are consistent with segment-controlled ruptures. However, broadly constrained earthquake times, dissimilar event times along the segments, the presence of smaller-scale (subsegment) boundaries, and areas of complex faulting permit partial-segment and multisegment (e.g., spillover) ruptures that are shorter (~20–40 km) or longer (~60–100 km) than the primary segment lengths (35–59 km). We report a segmented WFZ model that includes 24 earthquakes since ~7 ka and yields mean estimates of recurrence (1.1–1.3 kyr) and vertical slip rate (1.3–2.0 mm/yr) for the segments. However, additional rupture scenarios that include segment boundary spatial uncertainties, floating earthquakes, and multisegment ruptures are necessary to fully address epistemic uncertainties in rupture length. We compare the central WFZ to paleoseismic and historical surface ruptures in the Basin and Range Province and central Italian Apennines and conclude that displacement profiles have limited value for assessing the persistence of segment boundaries but can aid in interpreting prehistoric spillover ruptures. Our comparison also suggests that the probabilities of shorter and longer ruptures on the WFZ need to be investigated.

Low-angle normal faulting in the Basin and Range-Colorado Plateau transition zone during the January 3, 2011 Circleville, UT earthquake sequence

NASA Astrophysics Data System (ADS)

Gammans, Christine Naomi Louise

On January 3, 2011, an Mw 4.5 earthquake occurred in the Tushar Mountains near Circleville, Utah (38.248°N, -112.329°W, 7.75 km depth, and origin time of 12:06:36.58). The Tushar Mountains are located in the transition zone between the stable Colorado Plateau (CP) to the east and the deforming Basin and Range (BR) province to the west. In this area, seismicity associated with the Intermountain Seismic Belt is relatively common. The University of Utah Seismograph Stations (UUSS) detected and located 97 aftershocks in the 33 weeks following the mainshock. On January 6, UUSS installed a portable station in the source region. Using three aftershocks recorded by the portable station as master events, including the largest (Mw 3.8), we relocated the mainshock/aftershock sequence. These refined locations were used as initial locations for the HypoDD method of Waldhauser and Ellsworth [2001] to produce a second, improved set of relocations. In addition to P- and S-arrival time picks, we used the lag-times from waveform cross-correlations as input to HypoDD. We analyzed the fault geometry apparent in the final locations by comparing them to known moment-tensor focal planes and by applying principal component analysis to measure the degree of planarity and orientation of the sequence as a whole. Additionally, using cross-correlation analysis, we identified aftershocks best suited for an empirical Green's function analysis of the mainshock and a strike-slip aftershock that occurred on January 6. From the events chosen by cross-correlation, we were able to obtain source-time functions that were used to obtain fault dimensions, stress drops, and evidence for or against directivity. Lastly, we determined focal mechanisms for ten of the events using first-motion methods. The results of the combined analyses indicate that the mainshock occurred on a low-angle normal fault and that the entire sequence occurred on at least two different fault planes.

Multi-Fault Rupture Scenarios in the Brawley Seismic Zone

NASA Astrophysics Data System (ADS)

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

Geometrical and Structural Asperities on Fault Surfaces

NASA Astrophysics Data System (ADS)

Sagy, A.; Brodsky, E. E.; van der Elst, N.; Agosta, F.; di Toro, G.; Collettini, C.

2007-12-01

Earthquake dynamics are strongly affected by fault zone structure and geometry. Fault surface irregularities and the nearby structure control the rupture nucleation and propagation, the fault strength, the near-field stress orientations and the hydraulic properties. New field observations demonstrate the existence of asperities in faults as displayed by topographical bumps on the fault surface and hardening of the internal structure near them. Ground-based LIDAR measurements on more than 30 normal and strike slip faults in different lithologies demonstrate that faults are not planar surfaces and roughness is strongly dependent on fault displacement. In addition to the well-understood roughness exemplified by abrasive striations and fracture segmentation, we found semi-elliptical topographical bumps with wavelengths of a few meters. In many faults the bumps are not spread equally on the surface and zones can be bumpier than others. The bumps are most easily identified on faults with total displacement of dozens to hundreds of meters. Smaller scale roughness on these faults is smoothed by abrasive processes. A key site in southern Oregon shows that the topographic bumps are closely tied to the internal structure of the fault zone. At this location, we combine LiDAR data with detailed structural analysis of the fault zone embedded in volcanic rocks. Here the bumps correlate with an abrupt change in the width of the cohesive cataclasite layer that is exposed under a thin ultracataclasite zone. In most of the exposures the cohesive layer thickness is 10-20 cm. However, under protruding bumps the layer is always thickened and the width can locally exceed one meter. Field and microscopic analyses show that the layer contains grains with dimensions ranging from less than 10 μ up to a few centimeters. There is clear evidence of internal flow, rotation and fracturing of the grains in the layer. X-Ray diffraction measurements of samples from the layer show that the bulk

A model for the geomorphic development of normal-fault facets

NASA Astrophysics Data System (ADS)

Tucker, G. E.; Hobley, D. E. J.; McCoy, S. W.

2014-12-01

Triangular facets are among the most striking landforms associated with normal faulting. The genesis of facets is of great interest both for the information facets contain about tectonic motion, and because the progressive emergence of facets makes them potential recorders of both geomorphic and tectonic history. In this report, we present observations of triangular facets in the western United States and in the Italian Central Apennines. Facets in these regions typically form quasi-planar surfaces that are aligned in series along and above the trace of an active fault. Some facet surfaces consist mainly of exposed bedrock, with a thin and highly discontinuous cover of loose regolith. Other facets are mantled by a several-decimeter-thick regolith cover. Over the course of its morphologic development, a facet slope segment may evolve from a steep (~60 degree) bedrock fault scarp, well above the angle of repose for soil, to a gentler (~20-40 degree) slope that can potentially sustain a coherent regolith cover. This evolutionary trajectory across the angle of repose renders nonlinear diffusion theory inapplicable. To formulate an alternative process-based theory for facet evolution, we use a particle-based approach that acknowledges the possibility for both short- and long-range sediment-grain motions, depending on the topography. The processes of rock weathering, grain entrainment, and grain motion are represented as stochastic state-pair transitions with specified transition rates. The model predicts that facet behavior can range smoothly along the spectrum from a weathering-limited mode to a transport-limited mode, depending on the ratio of fault-slip rate to bare-bedrock regolith production rate. The model also implies that facets formed along a fault with pinned tips should show systematic variation in slope angle that correlates with along-fault position and slip rate. Preliminary observations from central Italy and the eastern Basin and Range are consistent

What can the dihedral angle of conjugate-faults tell us?

NASA Astrophysics Data System (ADS)

Ismat, Zeshan

2015-04-01

Deformation within the upper crust (elastico-frictional regime) is largely accommodated by fractures and conjugate faults. The Coulomb fracture criterion leads us to expect that the average dihedral angle of conjugate-fault sets is expected to be ∼60°. Experiments, however, reveal a significant amount of scatter from this 60° average. The confining pressure under which these rocks are deformed is a contributing factor to this scatter. The Canyon Range syncline, Sevier fold-thrust belt (USA) and the Jebel Bani, Anti-Atlas fold-belt (Morocco) both folded under different depths, within the elastico-frictional regime, by cataclastic flow. Conjugate-fault sets assisted deformation by cataclastic flow. The Canyon Range syncline and the Jebel Bani are used here as natural examples to test the relationship between the dihedral angle of conjugate-faults and confining pressure. Variations is confining pressure are modeled by the difference in depth of deformation and position within the folds. Results from this study show that the dihedral angle increases with an increase in depth and within the hinge regions of folds, where space problems commonly occur. Moreover, the shortening directions based on the acute bisectors of conjugate-faults may not be accurately determined if the dihedral angles are unusually large or small, leading to incorrect kinematic analyses.

Net dextral slip, Neogene San Gregorio–Hosgri fault zone, coastal California: Geologic evidence and tectonic implications

USGS Publications Warehouse

Dickinson, William R.; Ducea, M.; Rosenberg, Lewis I.; Greene, H. Gary; Graham, Stephan A.; Clark, Joseph C.; Weber, Gerald E.; Kidder, Steven; Ernst, W. Gary; Brabb, Earl E.

2005-01-01

Reinterpretation of onshore and offshore geologic mapping, examination of a key offshore well core, and revision of cross-fault ties indicate Neogene dextral strike slip of 156 ± 4 km along the San Gregorio–Hosgri fault zone, a major strand of the San Andreas transform system in coastal California. Delineating the full course of the fault, defining net slip across it, and showing its relationship to other major tectonic features of central California helps clarify the evolution of the San Andreas system.San Gregorio–Hosgri slip rates over time are not well constrained, but were greater than at present during early phases of strike slip following fault initiation in late Miocene time. Strike slip took place southward along the California coast from the western fl ank of the San Francisco Peninsula to the Hosgri fault in the offshore Santa Maria basin without significant reduction by transfer of strike slip into the central California Coast Ranges. Onshore coastal segments of the San Gregorio–Hosgri fault include the Seal Cove and San Gregorio faults on the San Francisco Peninsula, and the Sur and San Simeon fault zones along the flank of the Santa Lucia Range.Key cross-fault ties include porphyritic granodiorite and overlying Eocene strata exposed at Point Reyes and at Point Lobos, the Nacimiento fault contact between Salinian basement rocks and the Franciscan Complex offshore within the outer Santa Cruz basin and near Esalen on the flank of the Santa Lucia Range, Upper Cretaceous (Campanian) turbidites of the Pigeon Point Formation on the San Francisco Peninsula and the Atascadero Formation in the southern Santa Lucia Range, assemblages of Franciscan rocks exposed at Point Sur and at Point San Luis, and a lithic assemblage of Mesozoic rocks and their Tertiary cover exposed near Point San Simeon and at Point Sal, as restored for intrabasinal deformation within the onshore Santa Maria basin.Slivering of the Salinian block by San Gregorio–Hosgri displacements

Geophysical Characterization of the Hilton Creek Fault System

NASA Astrophysics Data System (ADS)

Lacy, A. K.; Macy, K. P.; De Cristofaro, J. L.; Polet, J.

2016-12-01

The Long Valley Caldera straddles the eastern edge of the Sierra Nevada Batholith and the western edge of the Basin and Range Province, and represents one of the largest caldera complexes on Earth. The caldera is intersected by numerous fault systems, including the Hartley Springs Fault System, the Round Valley Fault System, the Long Valley Ring Fault System, and the Hilton Creek Fault System, which is our main region of interest. The Hilton Creek Fault System appears as a single NW-striking fault, dipping to the NE, from Davis Lake in the south to the southern rim of the Long Valley Caldera. Inside the caldera, it splays into numerous parallel faults that extend toward the resurgent dome. Seismicity in the area increased significantly in May 1980, following a series of large earthquakes in the vicinity of the caldera and a subsequent large earthquake swarm which has been suggested to be the result of magma migration. A large portion of the earthquake swarms in the Long Valley Caldera occurs on or around the Hilton Creek Fault splays. We are conducting an interdisciplinary geophysical study of the Hilton Creek Fault System from just south of the onset of splay faulting, to its extension into the dome of the caldera. Our investigation includes ground-based magnetic field measurements, high-resolution total station elevation profiles, Structure-From-Motion derived topography and an analysis of earthquake focal mechanisms and statistics. Preliminary analysis of topographic profiles, of approximately 1 km in length, reveals the presence of at least three distinct fault splays within the caldera with vertical offsets of 0.5 to 1.0 meters. More detailed topographic mapping is expected to highlight smaller structures. We are also generating maps of the variation in b-value along different portions of the Hilton Creek system to determine whether we can detect any transition to more swarm-like behavior towards the North. We will show maps of magnetic anomalies, topography

Strain release along ocean transform faults

NASA Astrophysics Data System (ADS)

Stewart, L. M.

A global study of the nature of seismic rupture along oceanic transform faults (TFs) is presented, and many aspects of fault behavior and Mid-Ocean Ridge processes are discussed. A classification of TF earthquakes is developed based on their relative excitation of short period body waves to long period surface waves. Since the ways in which transform faults release their accumulated strain varies, for more than 50 earthquakes occurring on 30 TFs since 1963 form the database for a comparison of rupture processes. The variation of TF rupture processes is not related to spreading rate or TF offset. A study of seismicity of the Eltanin Fracture Zone system shows that unlike many TFs, the Eltanin FZ realizes more than 90% of its slip aseismically. This identifies a major portion of plate boundary whose motion persists undetected by seismic instruments. The global variations in rupture patterns are discussed in terms of current models of fault behavior. The versatility of the asperity model accommodates the entire range of observed patterns. Variations in physical properties within TF contact zones (asperities) are documented in the petrology and geochemistry of rocks from ophiolite sections and TFs.

Advanced Information Processing System - Fault detection and error handling

NASA Technical Reports Server (NTRS)

Lala, J. H.

1985-01-01

The Advanced Information Processing System (AIPS) is designed to provide a fault tolerant and damage tolerant data processing architecture for a broad range of aerospace vehicles, including tactical and transport aircraft, and manned and autonomous spacecraft. A proof-of-concept (POC) system is now in the detailed design and fabrication phase. This paper gives an overview of a preliminary fault detection and error handling philosophy in AIPS.

The Fault Block Model: A novel approach for faulted gas reservoirs

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

Ursin, J.R.; Moerkeseth, P.O.

1994-12-31

The Fault Block Model was designed for the development of gas production from Sleipner Vest. The reservoir consists of marginal marine sandstone of Hugine Formation. Modeling of highly faulted and compartmentalized reservoirs is severely impeded by the nature and extent of known and undetected faults and, in particular, their effectiveness as flow barrier. The model presented is efficient and superior to other models, for highly faulted reservoir, i.e. grid based simulators, because it minimizes the effect of major undetected faults and geological uncertainties. In this article the authors present the Fault Block Model as a new tool to better understandmore » the implications of geological uncertainty in faulted gas reservoirs with good productivity, with respect to uncertainty in well coverage and optimum gas recovery.« less

Fault detection and fault tolerance in robotics

NASA Technical Reports Server (NTRS)

Visinsky, Monica; Walker, Ian D.; Cavallaro, Joseph R.

1992-01-01

Robots are used in inaccessible or hazardous environments in order to alleviate some of the time, cost and risk involved in preparing men to endure these conditions. In order to perform their expected tasks, the robots are often quite complex, thus increasing their potential for failures. If men must be sent into these environments to repair each component failure in the robot, the advantages of using the robot are quickly lost. Fault tolerant robots are needed which can effectively cope with failures and continue their tasks until repairs can be realistically scheduled. Before fault tolerant capabilities can be created, methods of detecting and pinpointing failures must be perfected. This paper develops a basic fault tree analysis of a robot in order to obtain a better understanding of where failures can occur and how they contribute to other failures in the robot. The resulting failure flow chart can also be used to analyze the resiliency of the robot in the presence of specific faults. By simulating robot failures and fault detection schemes, the problems involved in detecting failures for robots are explored in more depth.

Rupture of the Pitáycachi Fault in the 1887 Mw 7.5 Sonora, Mexico earthquake (southern Basin-and-Range Province): Rupture kinematics and epicenter inferred from rupture branching patterns

NASA Astrophysics Data System (ADS)

Suter, Max

2015-01-01

During the 3 May 1887 Mw 7.5 Sonora earthquake (surface rupture end-to-end length: 101.8 km), an array of three north-south striking Basin-and-Range Province faults (from north to south Pitáycachi, Teras, and Otates) slipped sequentially along the western margin of the Sierra Madre Occidental Plateau. This detailed field survey of the 1887 earthquake rupture zone along the Pitáycachi fault includes mapping the rupture scarp and measurements of surface deformation. The surface rupture has an endpoint-to-endpoint length of ≥41.0 km, dips 70°W, and is characterized by normal left-lateral extension. The maximum surface offset is 487 cm and the mean offset 260 cm. The rupture trace shows a complex pattern of second-order segmentation. However, this segmentation is not expressed in the 1887 along-rupture surface offset profile, which indicates that the secondary segments are linked at depth into a single coherent fault surface. The Pitáycachi surface rupture shows a well-developed bipolar branching pattern suggesting that the rupture originated in its central part, where the polarity of the rupture bifurcations changes. Most likely the rupture first propagated bilaterally along the Pitáycachi fault. The southern rupture front likely jumped across a step over to the Teras fault and from there across a major relay zone to the Otates fault. Branching probably resulted from the lateral propagation of the rupture after breaching the seismogenic part of the crust, given that the much shorter ruptures of the Otates and Teras segments did not develop branches.

Fault2SHA- A European Working group to link faults and Probabilistic Seismic Hazard Assessment communities in Europe

NASA Astrophysics Data System (ADS)

Scotti, Oona; Peruzza, Laura

2016-04-01

The key questions we ask are: What is the best strategy to fill in the gap in knowledge and know-how in Europe when considering faults in seismic hazard assessments? Are field geologists providing the relevant information for seismic hazard assessment? Are seismic hazard analysts interpreting field data appropriately? Is the full range of uncertainties associated with the characterization of faults correctly understood and propagated in the computations? How can fault-modellers contribute to a better representation of the long-term behaviour of fault-networks in seismic hazard studies? Providing answers to these questions is fundamental, in order to reduce the consequences of future earthquakes and improve the reliability of seismic hazard assessments. An informal working group was thus created at a meeting in Paris in November 2014, partly financed by the Institute of Radioprotection and Nuclear Safety, with the aim to motivate exchanges between field geologists, fault modellers and seismic hazard practitioners. A variety of approaches were presented at the meeting and a clear gap emerged between some field geologists, that are not necessarily familiar with probabilistic seismic hazard assessment methods and needs and practitioners that do not necessarily propagate the "full" uncertainty associated with the characterization of faults. The group thus decided to meet again a year later in Chieti (Italy), to share concepts and ideas through a specific exercise on a test case study. Some solutions emerged but many problems of seismic source characterizations with people working in the field as well as with people tackling models of interacting faults remained. Now, in Wien, we want to open the group and launch a call for the European community at large to contribute to the discussion. The 2016 EGU session Fault2SHA is motivated by such an urgency to increase the number of round tables on this topic and debate on the peculiarities of using faults in seismic hazard

Fault reactivation: The Picuris-Pecos fault system of north-central New Mexico

NASA Astrophysics Data System (ADS)

McDonald, David Wilson

The PPFS is a N-trending fault system extending over 80 km in the Sangre de Cristo Mountains of northern New Mexico. Precambrian basement rocks are offset 37 km in a right-lateral sense; however, this offset includes dextral strike-slip (Precambrian), mostly normal dip-slip (Pennsylvanian), mostly reverse dip-slip (Early Laramide), limited strike-slip (Late Laramide) and mostly normal dip-slip (Cenozoic). The PPFS is broken into at least 3 segments by the NE-trending Embudo fault and by several Laramide age NW-trending tear faults. These segments are (from N to S): the Taos, the Picuris, and the Pecos segments. On the east side of the Picuris segment in the Picuris Mountains, the Oligocene-Miocene age Miranda graben developed and represents a complex extension zone south of the Embudo fault. Regional analysis of remotely sensed data and geologic maps indicate that lineaments subparallel to the trace of the PPFS are longer and less frequent than lineaments that trend orthogonal to the PPFS. Significant cross cutting faults and subtle changes in fault trends in each segment are clear in the lineament data. Detailed mapping in the eastern Picuris Mountains showed that the favorably oriented Picuris segment was not reactivated in the Tertiary development of the Rio Grande rift. Segmentation of the PPFS and post-Laramide annealing of the Picuris segment are interpreted to have resulted in the development of the subparallel La Serna fault. The Picuris segment of the PPFS is offset by several E-ESE trending faults. These faults are Late Cenozoic in age and interpreted to be related to the uplift of the Picuris Mountains and the continuing sinistral motion on the Embudo fault. Differential subsidence within the Miranda graben caused the development of several synthetic and orthogonal faults between the bounding La Serna and Miranda faults. Analysis of over 10,000 outcrop scale brittle structures reveals a strong correlation between faults and fracture systems. The dominant

Fault architecture and deformation processes within poorly lithified rift sediments, Central Greece

NASA Astrophysics Data System (ADS)

Loveless, Sian; Bense, Victor; Turner, Jenni

2011-11-01

Deformation mechanisms and resultant fault architecture are primary controls on the permeability of faults in poorly lithified sediments. We characterise fault architecture using outcrop studies, hand samples, thin sections and grain-size data from a minor (1-10 m displacement) normal-fault array exposed within Gulf of Corinth rift sediments, Central Greece. These faults are dominated by mixed zones with poorly developed fault cores and damage zones. In poorly lithified sediment deformation is distributed across the mixed zone as beds are entrained and smeared. We find particulate flow aided by limited distributed cataclasis to be the primary deformation mechanism. Deformation may be localised in more competent sediments. Stratigraphic variations in sediment competency, and the subsequent alternating distributed and localised strain causes complexities within the mixed zone such as undeformed blocks or lenses of cohesive sediment, or asperities at the mixed zone/protolith boundary. Fault tip bifurcation and asperity removal are important processes in the evolution of these fault zones. Our results indicate that fault zone architecture and thus permeability is controlled by a range of factors including lithology, stratigraphy, cementation history and fault evolution, and that minor faults in poorly lithified sediment may significantly impact subsurface fluid flow.

Stafford fault system: 120 million year fault movement history of northern Virginia

USGS Publications Warehouse

Powars, David S.; Catchings, Rufus D.; Horton, J. Wright; Schindler, J. Stephen; Pavich, Milan J.

2015-01-01

The Stafford fault system, located in the mid-Atlantic coastal plain of the eastern United States, provides the most complete record of fault movement during the past ~120 m.y. across the Virginia, Washington, District of Columbia (D.C.), and Maryland region, including displacement of Pleistocene terrace gravels. The Stafford fault system is close to and aligned with the Piedmont Spotsylvania and Long Branch fault zones. The dominant southwest-northeast trend of strong shaking from the 23 August 2011, moment magnitude Mw 5.8 Mineral, Virginia, earthquake is consistent with the connectivity of these faults, as seismic energy appears to have traveled along the documented and proposed extensions of the Stafford fault system into the Washington, D.C., area. Some other faults documented in the nearby coastal plain are clearly rooted in crystalline basement faults, especially along terrane boundaries. These coastal plain faults are commonly assumed to have undergone relatively uniform movement through time, with average slip rates from 0.3 to 1.5 m/m.y. However, there were higher rates during the Paleocene–early Eocene and the Pliocene (4.4–27.4 m/m.y), suggesting that slip occurred primarily during large earthquakes. Further investigation of the Stafford fault system is needed to understand potential earthquake hazards for the Virginia, Maryland, and Washington, D.C., area. The combined Stafford fault system and aligned Piedmont faults are ~180 km long, so if the combined fault system ruptured in a single event, it would result in a significantly larger magnitude earthquake than the Mineral earthquake. Many structures most strongly affected during the Mineral earthquake are along or near the Stafford fault system and its proposed northeastward extension.

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

DOE PAGES

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

2015-03-01

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

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

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

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

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

Earthquake nucleation on faults with rate-and state-dependent strength

USGS Publications Warehouse

Dieterich, J.H.

1992-01-01

Dieterich, J.H., 1992. Earthquake nucleation on faults with rate- and state-dependent strength. In: T. Mikumo, K. Aki, M. Ohnaka, L.J. Ruff and P.K.P. Spudich (Editors), Earthquake Source Physics and Earthquake Precursors. Tectonophysics, 211: 115-134. Faults with rate- and state-dependent constitutive properties reproduce a range of observed fault slip phenomena including spontaneous nucleation of slip instabilities at stresses above some critical stress level and recovery of strength following slip instability. Calculations with a plane-strain fault model with spatially varying properties demonstrate that accelerating slip precedes instability and becomes localized to a fault patch. The dimensions of the fault patch follow scaling relations for the minimum critical length for unstable fault slip. The critical length is a function of normal stress, loading conditions and constitutive parameters which include Dc, the characteristic slip distance. If slip starts on a patch that exceeds the critical size, the length of the rapidly accelerating zone tends to shrink to the characteristic size as the time of instability approaches. Solutions have been obtained for a uniform, fixed-patch model that are in good agreement with results from the plane-strain model. Over a wide range of conditions, above the steady-state stress, the logarithm of the time to instability linearly decreases as the initial stress increases. Because nucleation patch length and premonitory displacement are proportional to Dc, the moment of premonitory slip scales by D3c. The scaling of Dc is currently an open question. Unless Dc for earthquake faults is significantly greater than that observed on laboratory faults, premonitory strain arising from the nucleation process for earthquakes may by too small to detect using current observation methods. Excluding the possibility that Dc in the nucleation zone controls the magnitude of the subsequent earthquake, then the source dimensions of the smallest

Fiber fault location utilizing traffic signal in optical network.

PubMed

Zhao, Tong; Wang, Anbang; Wang, Yuncai; Zhang, Mingjiang; Chang, Xiaoming; Xiong, Lijuan; Hao, Yi

2013-10-07

We propose and experimentally demonstrate a method for fault location in optical communication network. This method utilizes the traffic signal transmitted across the network as probe signal, and then locates the fault by correlation technique. Compared with conventional techniques, our method has a simple structure and low operation expenditure, because no additional device is used, such as light source, modulator and signal generator. The correlation detection in this method overcomes the tradeoff between spatial resolution and measurement range in pulse ranging technique. Moreover, signal extraction process can improve the location result considerably. Experimental results show that we achieve a spatial resolution of 8 cm and detection range of over 23 km with -8-dBm mean launched power in optical network based on synchronous digital hierarchy protocols.

Preliminary Pseudo 3-D Imagery of the State Line Fault, Stewart Valley, Nevada Using Seismic Reflection Data

NASA Astrophysics Data System (ADS)

Saldaña, S. C.; Snelson, C. M.; Taylor, W. J.; Beachly, M.; Cox, C. M.; Davis, R.; Stropky, M.; Phillips, R.; Robins, C.; Cothrun, C.

2007-12-01

The Pahrump Fault system is located in the central Basin and Range region and consists of three main fault zones: the Nopah range front fault zone, the State Line fault zone and the Spring Mountains range fault zone. The State Line fault zone is made up north-west trending dextral strike-slip faults that run parallel to the Nevada- California border. Previous geologic and geophysical studies conducted in and around Stewart Valley, located ~90 km from Las Vegas, Nevada, have constrained the location of the State Line fault zone to within a few kilometers. The goals of this project were to use seismic methods to definitively locate the northwestern most trace of the State Line fault and produce pseudo 3-D seismic cross-sections that can then be used to characterize the subsurface geometry and determine the slip of the State Line fault. During July 2007, four seismic lines were acquired in Stewart Valley: two normal and two parallel to the mapped traces of the State Line fault. Presented here are preliminary results from the two seismic lines acquired normal to the fault. These lines were acquired utilizing a 144-channel geode system with each of the 4.5 Hz vertical geophones set out at 5 m intervals to produce a 595 m long profile to the north and a 715 m long profile to the south. The vibroseis was programmed to produce an 8 s linear sweep from 20-160 Hz. These data returned excellent signal to noise and reveal subsurface lithology that will subsequently be used to resolve the subsurface geometry of the State Line fault. This knowledge will then enhance our understanding of the evolution of the State Line fault. Knowing how the State Line fault has evolved gives insight into the stick-slip fault evolution for the region and may improve understanding of how stress has been partitioned from larger strike-slip systems such as the San Andreas fault.

Modelling Fault Zone Evolution: Implications for fluid flow.

NASA Astrophysics Data System (ADS)

Moir, H.; Lunn, R. J.; Shipton, Z. K.

2009-04-01

which compare well to features observed in mapped exposures. For these simple simulations from a small number of pre-existing joints the fault zone evolves in a predictable way: fault linkage is governed by three key factors: Stress ratio of s1 (maximum compressive stress) to s3(minimum compressive stress), original geometry of the pre-existing structures (contractional vs. dilational geometries) and the orientation of the principle stress direction (σ1) to the pre-existing structures. In this paper we present numerical simulations of the temporal and spatial evolution of fault linkage structures from many pre-existing joints. The initial location, size and orientations of these joints are based on field observations of cooling joints in granite from the Sierra Nevada. We show that the constantly evolving geometry and local stress field perturbations contribute significantly to fault zone evolution. The location and orientations of linkage structures previously predicted by the simple simulations are consistent with the predicted geometries in the more complex fault zones, however, the exact location at which individual structures form is not easily predicted. Markedly different fault zone geometries are predicted when the pre-existing joints are rotated with respect to the maximum compressive stress. In particular, fault surfaces range from evolving smooth linear structures to producing complex ‘stepped' fault zone geometries. These geometries have a significant effect on simulations of along and across-fault flow.

Eastern Denali Fault surface trace map, eastern Alaska and Yukon, Canada

USGS Publications Warehouse

Bender, Adrian M.; Haeussler, Peter J.

2017-05-04

We map the 385-kilometer (km) long surface trace of the right-lateral, strike-slip Denali Fault between the Totschunda-Denali Fault intersection in Alaska, United States and the village of Haines Junction, Yukon, Canada. In Alaska, digital elevation models based on light detection and ranging and interferometric synthetic aperture radar data enabled our fault mapping at scales of 1:2,000 and 1:10,000, respectively. Lacking such resources in Yukon, we developed new structure-from-motion digital photogrammetry products from legacy aerial photos to map the fault surface trace at a scale of 1:10,000 east of the international border. The section of the fault that we map, referred to as the Eastern Denali Fault, did not rupture during the 2002 Denali Fault earthquake (moment magnitude 7.9). Seismologic, geodetic, and geomorphic evidence, along with a paleoseismic record of past ground-rupturing earthquakes, demonstrate Holocene and contemporary activity on the fault, however. This map of the Eastern Denali Fault surface trace complements other data sets by providing an openly accessible digital interpretation of the location, length, and continuity of the fault’s surface trace based on the accompanying digital topography dataset. Additionally, the digitized fault trace may provide geometric constraints useful for modeling earthquake scenarios and related seismic hazard.

Fault-scale controls on rift geometry: the Bilila-Mtakataka Fault, Malawi

NASA Astrophysics Data System (ADS)

Hodge, M.; Fagereng, A.; Biggs, J.; Mdala, H. S.

2017-12-01

Border faults that develop during initial stages of rifting determine the geometry of rifts and passive margins. At outcrop and regional scales, it has been suggested that border fault orientation may be controlled by reactivation of pre-existing weaknesses. Here, we perform a multi-scale investigation on the influence of anisotropic fabrics along a major developing border fault in the southern East African Rift, Malawi. The 130 km long Bilila-Mtakataka fault has been proposed to have slipped in a single MW 8 earthquake with 10 m of normal displacement. The fault is marked by an 11±7 m high scarp with an average trend that is oblique to the current plate motion. Variations in scarp height are greatest at lithological boundaries and where the scarp switches between following and cross-cutting high-grade metamorphic foliation. Based on the scarp's geometry and morphology, we define 6 geometrically distinct segments. We suggest that the segments link to at least one deeper structure that strikes parallel to the average scarp trend, an orientation consistent with the kinematics of an early phase of rift initiation. The slip required on a deep fault(s) to match the height of the current scarp suggests multiple earthquakes along the fault. We test this hypothesis by studying the scarp morphology using high-resolution satellite data. Our results suggest that during the earthquake(s) that formed the current scarp, the propagation of the fault toward the surface locally followed moderately-dipping foliation well oriented for reactivation. In conclusion, although well oriented pre-existing weaknesses locally influence shallow fault geometry, large-scale border fault geometry appears primarily controlled by the stress field at the time of fault initiation.

Tectono-stratigraphic evolution of normal fault zones: Thal Fault Zone, Suez Rift, Egypt

NASA Astrophysics Data System (ADS)

Leppard, Christopher William

The evolution of linkage of normal fault populations to form continuous, basin bounding normal fault zones is recognised as an important control on the stratigraphic evolution of rift-basins. This project aims to investigate the temporal and spatial evolution of normal fault populations and associated syn-rift deposits from the initiation of early-formed, isolated normal faults (rift-initiation) to the development of a through-going fault zone (rift-climax) by documenting the tectono-stratigraphic evolution of the Sarbut EI Gamal segment of the exceptionally well-exposed Thai fault zone, Suez Rift, Egypt. A number of dated stratal surfaces mapped around the syn-rift depocentre of the Sarbut El Gamal segment allow constraints to be placed on the timing and style of deformation, and the spatial variability of facies along this segment of the fault zone. Data collected indicates that during the first 3.5 My of rifting the structural style was characterised by numerous, closely spaced, short (< 3 km), low displacement (< 200 m) synthetic and antithetic normal faults within 1 - 2 km of the present-day fault segment trace, accommodating surface deformation associated with the development of a fault propagation monocline above the buried, pre-cursor strands of the Sarbut El Gamal fault segment. The progressive localisation of displacement onto the fault segment during rift-climax resulted in the development of a major, surface-breaking fault 3.5 - 5 My after the onset of rifting and is recorded by the death of early-formed synthetic and antithetic faults up-section, and thickening of syn-rift strata towards the fault segment. The influence of intrabasinal highs at the tips of the Sarbut EI Gamal fault segment on the pre-rift sub-crop level, combined with observations from the early-formed structures and coeval deposits suggest that the overall length of the fault segment was fixed from an early stage. The fault segment is interpreted to have grown through rapid lateral

From coseismic offsets to fault-block mountains

USGS Publications Warehouse

Thompson, George A.; Parsons, Thomas E.

2017-01-01

In the Basin and Range extensional province of the western United States, coseismic offsets, under the influence of gravity, display predominantly subsidence of the basin side (fault hanging wall), with comparatively little or no uplift of the mountainside (fault footwall). A few decades later, geodetic measurements [GPS and interferometric synthetic aperture radar (InSAR)] show broad (∼100 km) aseismic uplift symmetrically spanning the fault zone. Finally, after millions of years and hundreds of fault offsets, the mountain blocks display large uplift and tilting over a breadth of only about 10 km. These sparse but robust observations pose a problem in that the coesismic uplifts of the footwall are small and inadequate to raise the mountain blocks. To address this paradox we develop finite-element models subjected to extensional and gravitational forces to study time-varying deformation associated with normal faulting. Stretching the model under gravity demonstrates that asymmetric slip via collapse of the hanging wall is a natural consequence of coseismic deformation. Focused flow in the upper mantle imposed by deformation of the lower crust localizes uplift, which is predicted to take place within one to two decades after each large earthquake. Thus, the best-preserved topographic signature of earthquakes is expected to occur early in the postseismic period.

From coseismic offsets to fault-block mountains

PubMed Central

Thompson, George A.

2017-01-01

In the Basin and Range extensional province of the western United States, coseismic offsets, under the influence of gravity, display predominantly subsidence of the basin side (fault hanging wall), with comparatively little or no uplift of the mountainside (fault footwall). A few decades later, geodetic measurements [GPS and interferometric synthetic aperture radar (InSAR)] show broad (∼100 km) aseismic uplift symmetrically spanning the fault zone. Finally, after millions of years and hundreds of fault offsets, the mountain blocks display large uplift and tilting over a breadth of only about 10 km. These sparse but robust observations pose a problem in that the coesismic uplifts of the footwall are small and inadequate to raise the mountain blocks. To address this paradox we develop finite-element models subjected to extensional and gravitational forces to study time-varying deformation associated with normal faulting. Stretching the model under gravity demonstrates that asymmetric slip via collapse of the hanging wall is a natural consequence of coseismic deformation. Focused flow in the upper mantle imposed by deformation of the lower crust localizes uplift, which is predicted to take place within one to two decades after each large earthquake. Thus, the best-preserved topographic signature of earthquakes is expected to occur early in the postseismic period. PMID:28847962

From coseismic offsets to fault-block mountains.

PubMed

Thompson, George A; Parsons, Tom

2017-09-12

In the Basin and Range extensional province of the western United States, coseismic offsets, under the influence of gravity, display predominantly subsidence of the basin side (fault hanging wall), with comparatively little or no uplift of the mountainside (fault footwall). A few decades later, geodetic measurements [GPS and interferometric synthetic aperture radar (InSAR)] show broad (∼100 km) aseismic uplift symmetrically spanning the fault zone. Finally, after millions of years and hundreds of fault offsets, the mountain blocks display large uplift and tilting over a breadth of only about 10 km. These sparse but robust observations pose a problem in that the coesismic uplifts of the footwall are small and inadequate to raise the mountain blocks. To address this paradox we develop finite-element models subjected to extensional and gravitational forces to study time-varying deformation associated with normal faulting. Stretching the model under gravity demonstrates that asymmetric slip via collapse of the hanging wall is a natural consequence of coseismic deformation. Focused flow in the upper mantle imposed by deformation of the lower crust localizes uplift, which is predicted to take place within one to two decades after each large earthquake. Thus, the best-preserved topographic signature of earthquakes is expected to occur early in the postseismic period.

From coseismic offsets to fault-block mountains

NASA Astrophysics Data System (ADS)

Thompson, George A.; Parsons, Tom

2017-09-01

In the Basin and Range extensional province of the western United States, coseismic offsets, under the influence of gravity, display predominantly subsidence of the basin side (fault hanging wall), with comparatively little or no uplift of the mountainside (fault footwall). A few decades later, geodetic measurements [GPS and interferometric synthetic aperture radar (InSAR)] show broad (˜100 km) aseismic uplift symmetrically spanning the fault zone. Finally, after millions of years and hundreds of fault offsets, the mountain blocks display large uplift and tilting over a breadth of only about 10 km. These sparse but robust observations pose a problem in that the coesismic uplifts of the footwall are small and inadequate to raise the mountain blocks. To address this paradox we develop finite-element models subjected to extensional and gravitational forces to study time-varying deformation associated with normal faulting. Stretching the model under gravity demonstrates that asymmetric slip via collapse of the hanging wall is a natural consequence of coseismic deformation. Focused flow in the upper mantle imposed by deformation of the lower crust localizes uplift, which is predicted to take place within one to two decades after each large earthquake. Thus, the best-preserved topographic signature of earthquakes is expected to occur early in the postseismic period.

Fault kinematics and localised inversion within the Troms-Finnmark Fault Complex, SW Barents Sea

NASA Astrophysics Data System (ADS)

Zervas, I.; Omosanya, K. O.; Lippard, S. J.; Johansen, S. E.

2018-04-01

The areas bounding the Troms-Finnmark Fault Complex are affected by complex tectonic evolution. In this work, the history of fault growth, reactivation, and inversion of major faults in the Troms-Finnmark Fault Complex and the Ringvassøy Loppa Fault Complex is interpreted from three-dimensional seismic data, structural maps and fault displacement plots. Our results reveal eight normal faults bounding rotated fault blocks in the Troms-Finnmark Fault Complex. Both the throw-depth and displacement-distance plots show that the faults exhibit complex configurations of lateral and vertical segmentation with varied profiles. Some of the faults were reactivated by dip-linkages during the Late Jurassic and exhibit polycyclic fault growth, including radial, syn-sedimentary, and hybrid propagation. Localised positive inversion is the main mechanism of fault reactivation occurring at the Troms-Finnmark Fault Complex. The observed structural styles include folds associated with extensional faults, folded growth wedges and inverted depocentres. Localised inversion was intermittent with rifting during the Middle Jurassic-Early Cretaceous at the boundaries of the Troms-Finnmark Fault Complex to the Finnmark Platform. Additionally, tectonic inversion was more intense at the boundaries of the two fault complexes, affecting Middle Triassic to Early Cretaceous strata. Our study shows that localised folding is either a product of compressional forces or of lateral movements in the Troms-Finnmark Fault Complex. Regional stresses due to the uplift in the Loppa High and halokinesis in the Tromsø Basin are likely additional causes of inversion in the Troms-Finnmark Fault Complex.

Superimposed extension and shortening in the southern Salinas Basin and La Panza Range, California: A guide to Neogene deformation in the Salinian block of the central California Coast Ranges

USGS Publications Warehouse

Colgan, Joseph P.; McPhee, Darcy K.; McDougall, Kristin; Hourigan, Jeremy K.

2013-01-01

We synthesized data from geologic maps, wells, seismic-reflection profiles, potential-field interpretations, and low-temperature thermochronology to refine our understanding of late Cenozoic extension and shortening in the Salinian block of the central California Coast Ranges. Data from the La Panza Range and southern Salinas Basin document early to middle Miocene extension, followed by Pliocene and younger shortening after a period of little deformation in the late Miocene. Extension took place on high-angle normal faults that accommodated ∼2% strain at the scale of the ∼50-km-wide Salinian block (oriented perpendicular to the San Andreas fault). Shortening was accommodated by new reverse faults, reactivation of older normal faults, and strike-slip faulting that resulted in a map-view change in the width of the Salinian block. The overall magnitude of shortening was ∼10% strain, roughly 4–5 times greater than the amount of extension. The timing and magnitude of deformation in our study area are comparable to that documented in other Salinian block basins, and we suggest that the entire block deformed in a similar manner over a similar time span. The timing and relative magnitude of extension and shortening may be understood in the context of central Coast Range tectonic boundary conditions linked to rotation of the western Transverse Ranges at the south end of the Salinian block. Older models for Coast Range shortening based on balanced fault-bend fold-style cross sections are a poor approximation of Salinian block deformation, and may lead to mechanically improbable fault geometries that overestimate the amount of shortening.

Fluid flow and permeabilities in basement fault zones

NASA Astrophysics Data System (ADS)

Hollinsworth, Allan; Koehn, Daniel

2017-04-01

Fault zones are important sites for crustal fluid flow, specifically where they cross-cut low permeability host rocks such as granites and gneisses. Fluids migrating through fault zones can cause rheology changes, mineral precipitation and pore space closure, and may alter the physical and chemical properties of the host rock and deformation products. It is therefore essential to consider the evolution of permeability in fault zones at a range of pressure-temperature conditions to understand fluid migration throughout a fault's history, and how fluid-rock interaction modifies permeability and rheological characteristics. Field localities in the Rwenzori Mountains, western Uganda and the Outer Hebrides, north-west Scotland, have been selected for field work and sample collection. Here Archaean-age TTG gneisses have been faulted within the upper 15km of the crust and have experienced fluid ingress. The Rwenzori Mountains are an anomalously uplifted horst-block located in a transfer zone in the western rift of the East African Rift System. The north-western ridge is characterised by a tectonically simple western flank, where the partially mineralised Bwamba Fault has detached from the Congo craton. Mineralisation is associated with hydrothermal fluids heated by a thermal body beneath the Semliki rift, and has resulted in substantial iron oxide precipitation within porous cataclasites. Non-mineralised faults further north contain foliated gouges and show evidence of leaking fluids. These faults serve as an analogue for faults associated with the Lake Albert oil and gas prospects. The Outer Hebrides Fault Zone (OHFZ) was largely active during the Caledonian Orogeny (ca. 430-400 Ma) at a deeper crustal level than the Ugandan rift faults. Initial dry conditions were followed by fluid ingress during deformation that controlled its rheological behaviour. The transition also altered the existing permeability. The OHFZ is a natural laboratory in which to study brittle fault

Pseudo-fault signal assisted EMD for fault detection and isolation in rotating machines

NASA Astrophysics Data System (ADS)

Singh, Dheeraj Sharan; Zhao, Qing

2016-12-01

This paper presents a novel data driven technique for the detection and isolation of faults, which generate impacts in a rotating equipment. The technique is built upon the principles of empirical mode decomposition (EMD), envelope analysis and pseudo-fault signal for fault separation. Firstly, the most dominant intrinsic mode function (IMF) is identified using EMD of a raw signal, which contains all the necessary information about the faults. The envelope of this IMF is often modulated with multiple vibration sources and noise. A second level decomposition is performed by applying pseudo-fault signal (PFS) assisted EMD on the envelope. A pseudo-fault signal is constructed based on the known fault characteristic frequency of the particular machine. The objective of using external (pseudo-fault) signal is to isolate different fault frequencies, present in the envelope . The pseudo-fault signal serves dual purposes: (i) it solves the mode mixing problem inherent in EMD, (ii) it isolates and quantifies a particular fault frequency component. The proposed technique is suitable for real-time implementation, which has also been validated on simulated fault and experimental data corresponding to a bearing and a gear-box set-up, respectively.

Coulomb Fault Mechanics at Work in the Proterozoic: Strike-Slip Faults and Regional-Scale Veining in the Mt. Isa Inlier, Australia

NASA Astrophysics Data System (ADS)

Begbie, M. J.; Sibson, R. H.; Ghisetti, F. C.

2005-12-01

microbreccias and cataclasites containing vein fragments; (2) innumerable subvertical quartz veins (cm to m thick) lying subparallel to the bounding shear zones with textures ranging from pure dilation to multiply recemented breccias of wallrock and quartz fragments; (3) irregular non-systematic veins; and (4) occasional minor faults from the complementary set. Mutual cross-cutting relationships between all the structural components indicate penecontemporaneous development within the inferred stress field. Slickenfibers and striations along fault components indicate predominantly strike slip motion on subvertical planes. Homogenisation temperatures from quartz hosted fluid inclusions cluster at ~210°C while vein textures record histories of incremental hydrothermal deposition under low effective stress, probably in the epizonal environment (<1-2 km depth). This regional study demonstrates the existence of a rather uniform stress province, corresponding to an Andersonian regime and initiation of faults in accord with the coulomb failure criterion.

Seismic Velocity and Elastic Properties of Plate Boundary Faults

NASA Astrophysics Data System (ADS)

Jeppson, Tamara N.

The elastic properties of fault zone rock at depth play a key role in rupture nucleation, propagation, and the magnitude of fault slip. Materials that lie within major plate boundary fault zones often have very different material properties than standard crustal rock values. In order to understand the mechanics of faulting at plate boundaries, we need to both measure these properties and understand how they govern the behavior of different types of faults. Mature fault zones tend to be identified in large-scale geophysical field studies as zones with low seismic velocity and/or electrical resistivity. These anomalous properties are related to two important mechanisms: (1) mechanical or diagenetic alteration of the rock materials and/or (2) pore fluid pressure and stress effects. However, in remotely-sensed and large-length-scale data it is difficult to determine which of these mechanisms are affecting the measured properties. The objective of this dissertation research is to characterize the seismic velocity and elastic properties of fault zone rocks at a range of scales, with a focus on understanding why the fault zone properties are different from those of the surrounding rock and the potential effects on earthquake rupture and fault slip. To do this I performed ultrasonic velocity experiments under elevated pressure conditions on drill core and outcrops samples from three plate boundary fault zones: the San Andreas Fault, California, USA; the Alpine Fault, South Island, New Zealand; and the Japan Trench megathrust, Japan. Additionally, I compared laboratory measurements to sonic log and large-scale seismic data to examine the scale-dependence of the measured properties. The results of this study provide the most comprehensive characterization of the seismic velocities and elastic properties of fault zone rocks currently available. My work shows that fault zone rocks at mature plate boundary faults tend to be significantly more compliant than surrounding crustal

Did the Malaysian Main Range record a weak hot Mega Shear?

NASA Astrophysics Data System (ADS)

Sautter, Benjamin; Pubellier, Manuel

2015-04-01

The Main Range of Peninsular Malaysia is a batholith that extends over more than 500km from Malacca in the South to the Thailand border in the North. It results from the subduction/accretion history of the western margin of Sunda Plate by Late Triassic times. We present a structural analysis based on geomorphology, field observations and geochronological data. While most of the basement fabrics are characterized by N-S structures such as granitic plutons, sutures, and folds, a prominent oblique deformation occurred by the End of the Mesozoics synchronous with a widespread thermal anomaly (eg Tioman, Stong, Gunung Jerai, Khanom, Krabi plutons). Morphostructures and drainage anomalies from Digital Elevation Model (SRTM and ASTER), allow us to highlight 2 major groups of penetrative faults in the Central Range Batholith: early NW-SE (5km spaced faults some of which are identified as thrust faults) cross-cut and offset by NNE-SSW dextral normal faults. The regularly spaced NW-SE faults bend toward the flanks of the Batholith and tend to parallel both the Bentong Raub Suture Zone to the East and the strike slip Bok Bak Fault to the West, thus giving the overall fault network the aspect of a large C/S band. Hence, a ductile/brittle behavior can be proposed for the sigmoid faults in the core of the Batholith, whereas the NNE faults are clearly brittle, more linear and are found on the smaller outlying plutons. Radiogenic crystallization ages are homogenous at 190±20Ma (U-Pb Zircon, Tc>1000°C and K-Ar Muscovite, Tc350°C) whereas Zircon fission tracks(Tc=250°C) show specific spatial zoning of the data distribution with ages at 100±10Ma for the outlying plutons and ages at 70±10Ma for the Main Range. We propose a structural mechanism according to which the Main Range would be the ductile core of a Mega-Shear Zone exhumed via transpressive tectonics by the end of Mesozoic Times. A first stage between 100 and 70Ma (Upper Cretaceous) of dextral transpression affected

Research on Distribution Characteristics of Lunar Faults

NASA Astrophysics Data System (ADS)

Lu, T.; Chen, S.; Lu, P.

2017-12-01

Circular and linear tectonics are two major types of tectonics on lunar surface. Tectonic characteristics are of significance for researching about lunar geological evolution. Linear tectonics refers to those structures extending linearly on a lunar surface. Their distribution are closely related to the internal geological actions of the moon. Linear tectonics can integrally or locally express the structural feature and the stress status as well as showing the geological information of the interior of the moon. Faults are of the largest number and are of a certain distribution regularity among the linear tectonics, and are always the focus of domestic and overseas lunar tectonic research. Based on remote sensing geology and theory of traditional tectonic geology, We use a variety of remote sensing data processing to establish lunar linear tectonic interpretation keys with lunar spectral, terrain and gravity data. On this basis, interpretation of faults of the whole moon was primarily conducted from Chang'e-2 CCD image data and reference to wide-angle camera data of LROC, laser altimeter data of LOLA and gravity data of GRAIL. Statistical analysis of the number and distribution characteristics of whole lunar faults are counted from three latitude ranges of low, middle and high latitudes, then analyze the azimuth characteristics of the faults at different latitudes. We concluded that S-N direction is a relatively developed orientation at low latitudes. Middle latitudes reveal six preferred orientations of N-E, N-W, NN-E, NN-W, N-EE and N-WW directions. There are sparse faults of E-W direction distribution at low and middle latitudes. Meanwhile, the largest number of faults of E-W direction on lunar surface are mainly distributed along high latitudes with continuity and regularity. Analyzing faults of Mare Imbrium by the method of Euler deconvolution. The result show that there are two different properties of faults in Mare Imbrium. In conclusion, we suggest that the

The Fault Tree Compiler (FTC): Program and mathematics

NASA Technical Reports Server (NTRS)

Butler, Ricky W.; Martensen, Anna L.

1989-01-01

The Fault Tree Compiler Program is a new reliability tool used to predict the top-event probability for a fault tree. Five different gate types are allowed in the fault tree: AND, OR, EXCLUSIVE OR, INVERT, AND m OF n gates. The high-level input language is easy to understand and use when describing the system tree. In addition, the use of the hierarchical fault tree capability can simplify the tree description and decrease program execution time. The current solution technique provides an answer precisely (within the limits of double precision floating point arithmetic) within a user specified number of digits accuracy. The user may vary one failure rate or failure probability over a range of values and plot the results for sensitivity analyses. The solution technique is implemented in FORTRAN; the remaining program code is implemented in Pascal. The program is written to run on a Digital Equipment Corporation (DEC) VAX computer with the VMS operation system.

Investigation of lineaments on Skylab and ERTS images of Peninsular Ranges, Southwestern California

NASA Technical Reports Server (NTRS)

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

1974-01-01

The author has identified the following significant results. Northwest trending faults such as the Elsinore and San Jacinto are prominently displayed on Skylab and ERTS images of the Peninsular Ranges, southern California. Northeast, north-south, and west-north-west trending lineaments and faults are also apparent on satellite imagery. Several of the lineaments represent previously unmapped faults. Other lineaments are due to erosion along foliation directions and sharp bends in basement rock contacts rather than faulting. The northeast trending Thing Valley fault appears to be offset by the south branch of the Elsinore fault near Agua Caliente Hot Springs. Larger horizontal displacement along the Elsinore fault further northwest may be distributed along several faults which branch from the Elsinore fault in the Peninsular Ranges. The northeast and west-northwest trending faults are truncated by the major northwest trending faults and appear to be restricted to basement terrane. Limited data on displacement direction suggests that the northeast and west-northwest trending faults formed in response to an earlier period of east-northeast, west-southwest crustal shortening. Such a stress system is consistent with the plate tectonic model of a subduction zone parallel to the continental margin suggested in the late Mesozoic and early Tertiary.

Fault-Tree Compiler

NASA Technical Reports Server (NTRS)

Butler, Ricky W.; Boerschlein, David P.

1993-01-01

Fault-Tree Compiler (FTC) program, is software tool used to calculate probability of top event in fault tree. Gates of five different types allowed in fault tree: AND, OR, EXCLUSIVE OR, INVERT, and M OF N. High-level input language easy to understand and use. In addition, program supports hierarchical fault-tree definition feature, which simplifies tree-description process and reduces execution time. Set of programs created forming basis for reliability-analysis workstation: SURE, ASSIST, PAWS/STEM, and FTC fault-tree tool (LAR-14586). Written in PASCAL, ANSI-compliant C language, and FORTRAN 77. Other versions available upon request.

Geophysical and isotopic mapping of preexisting crustal structures that influenced the location and development of the San Jacinto fault zone, southern California

USGS Publications Warehouse

Langenheim, V.E.; Jachens, R.C.; Morton, D.M.; Kistler, R.W.; Matti, J.C.

2004-01-01

We examine the role of preexisting crustal structure within the Peninsular Ranges batholith on determining the location of the San Jacinto fault zone by analysis of geophysical anomalies and initial strontium ratio data. A 1000-km-long boundary within the Peninsular Ranges batholith, separating relatively mafic, dense, and magnetic rocks of the western Peninsular Ranges batholith from the more felsic, less dense, and weakly magnetic rocks of the eastern Peninsular Ranges batholith, strikes north-northwest toward the San Jacinto fault zone. Modeling of the gravity and magnetic field anomalies caused by this boundary indicates that it extends to depths of at least 20 km. The anomalies do not cross the San Jacinto fault zone, but instead trend northwesterly and coincide with the fault zone. A 75-km-long gradient in initial strontium ratios (Sri) in the eastern Peninsular Ranges batholith coincides with the San Jacinto fault zone. Here rocks east of the fault are characterized by Sri greater than 0.706, indicating a source of largely continental crust, sedimentary materials, or different lithosphere. We argue that the physical property contrast produced by the Peninsular Ranges batholith boundary provided a mechanically favorable path for the San Jacinto fault zone, bypassing the San Gorgonio structural knot as slip was transferred from the San Andreas fault 1.0-1.5 Ma. Two historical M6.7 earthquakes may have nucleated along the Peninsular Ranges batholith discontinuity in San Jacinto Valley, suggesting that Peninsular Ranges batholith crustal structure may continue to affect how strain is accommodated along the San Jacinto fault zone. ?? 2004 Geological Society of America.

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

NASA Technical Reports Server (NTRS)

Vouk, Mladen A.; Mcallister, David F.

1989-01-01

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

The Morelia-Acambay Fault System

NASA Astrophysics Data System (ADS)

Velázquez Bucio, M.; Soria-Caballero, D.; Garduño-Monroy, V.; Mennella, L.

2013-05-01

The Trans-Mexican Volcanic Belt (TMVB) is one of the most actives and representative zones of Mexico geologically speaking. Research carried out in this area gives stratigraphic, seismologic and historical evidence of its recent activity during the quaternary (Martinez and Nieto, 1990). Specifically the Morelia-Acambay faults system (MAFS) consist in a series of normal faults of dominant direction E - W, ENE - WSW y NE - SW which is cut in center west of the Trans-Mexican Volcanic Belt. This fault system appeared during the early Miocene although the north-south oriented structures are older and have been related to the activity of the tectonism inherited from the "Basin and Range" system, but that were reactivated by the east- west faults. It is believed that the activity of these faults has contributed to the creation and evolution of the longed lacustrine depressions such as: Chapala, Zacapu, Cuitzeo, Maravatio y Acambay also the location of monogenetic volcanoes that conformed the Michoacan-Guanajuato volcanic field (MGVF) and tend to align in the direction of the SFMA dominant effort. In a historical time different segments of the MAFS have been the epicenter of earthquakes from moderated to strong magnitude like the events of 1858 in Patzcuaro, Acambay in 1912, 1979 in Maravatio and 2007 in Morelia, among others. Several detailed analysis and semi-detailed analysis through a GIS platform based in the vectorial archives and thematic charts 1:50 000 scaled from the data base of the INEGI which has allowed to remark the influence of the MAFS segments about the morphology of the landscape and the identification of other structures related to the movement of the existent faults like fractures, alignments, collapses and others from the zone comprehended by the northwest of Morelia in Michoacán to the East of Acambay, Estado de México. Such analysis suggests that the fault segments possess a normal displacement plus a left component. In addition it can be

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

NASA Astrophysics Data System (ADS)

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.

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

NASA Astrophysics Data System (ADS)

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

2017-12-01

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

Spatial arrangement of faults and opening-mode fractures

NASA Astrophysics Data System (ADS)

Laubach, S. E.; Lamarche, J.; Gauthier, B. D. M.; Dunne, W. M.; Sanderson, David J.

2018-03-01

Spatial arrangement is a fundamental characteristic of fracture arrays. The pattern of fault and opening-mode fracture positions in space defines structural heterogeneity and anisotropy in a rock volume, governs how faults and fractures affect fluid flow, and impacts our understanding of the initiation, propagation and interactions during the formation of fracture patterns. This special issue highlights recent progress with respect to characterizing and understanding the spatial arrangements of fault and fracture patterns, providing examples over a wide range of scales and structural settings. Five papers describe new methods and improvements of existing techniques to quantify spatial arrangement. One study unravels the time evolution of opening-mode fracture spatial arrangement, which are data needed to compare natural patterns with progressive fracture growth in kinematic and mechanical models. Three papers investigate the role of evolving diagenesis in localizing fractures by mechanical stratigraphy and nine discuss opening-mode fracture spatial arrangement. Two papers show the relevance of complex cluster patterns to unconventional reservoirs through examples of fractures in tight gas sandstone horizontal wells, and a study of fracture arrangement in shale. Four papers demonstrate the roles of folds in fracture localization and the development spatial patterns. One paper models along-fault friction and fluid pressure and their effects on fault-related fracture arrangement. Contributions address deformation band patterns in carbonate rocks and fault size and arrangement above a detachment fault. Three papers describe fault and fracture arrangements in basement terrains, and three document fracture patterns in shale. This collection of papers points toward improvement in field methods, continuing improvements in computer-based data analysis and creation of synthetic fracture patterns, and opportunities for further understanding fault and fracture attributes in

A Log-Scaling Fault Tolerant Agreement Algorithm for a Fault Tolerant MPI

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

Hursey, Joshua J; Naughton, III, Thomas J; Vallee, Geoffroy R

The lack of fault tolerance is becoming a limiting factor for application scalability in HPC systems. The MPI does not provide standardized fault tolerance interfaces and semantics. The MPI Forum's Fault Tolerance Working Group is proposing a collective fault tolerant agreement algorithm for the next MPI standard. Such algorithms play a central role in many fault tolerant applications. This paper combines a log-scaling two-phase commit agreement algorithm with a reduction operation to provide the necessary functionality for the new collective without any additional messages. Error handling mechanisms are described that preserve the fault tolerance properties while maintaining overall scalability.

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

NASA Astrophysics Data System (ADS)

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

2007-12-01

The ENE-to NW-striking NTF is an active frontal thrust that delimits the Alborz Mountain range to the south with an up to 2000 m topographic break with respect to the adjacent Tehran plain. Eocene rocks of the Alborz range are thrusted over Neogene and Quaternary sediments of the alluvial Tehran embayment. The fault consists of right- stepping segments and merges to the east with the active Mosha-Fasham strike-slip fault (MFF). The complex tectonic history, involving changes in the direction of SHmax, has resulted in a composite tectonic landscape with inherited topographic and fault-kinematic fingerprints along the NTF. We therefore used a combination of fault-kinematic measurements and geomorphic observations to unravel the temporal tectonic evolution of this fault. Presently, the NTF is virtually inactive, although the tectonically overprinted landforms reflect tectonic activity on longer time scales during the Quaternary. Being located adjacent north of the Tehran megacity, there is thus considerable interest to decipher its youngest tectonic evolution and to better understand the relation with other fault systems. Our fault kinematic study has revealed an early dextral kinematic history for the NTF. Dextral strike-slip and oblique reverse faulting took place during NW-oriented shortening. The overall fault-geometry of the NTF suggests that it has evolved in relation to dextral transpression along the MFF. This early kinematic regime was superseded by NE-oriented shortening, associated with sinistral-oblique thrusting along the fault segments. Fault linkage between the semi-independent ENE-striking NTF-segments and NW-striking thrusts (Emamzadeh Davud Fault [EDF], Purkan Vardij Thrust [PVT], NTF-prolongation) point towards an evolution into a nascent transpressional duplex. In this scenario the NTF segments constitute lateral ramps and the NW-striking faults act as frontal ramps. Topographic residuals, as an expression of high-uplift zones, indicate that the

Experimental study on propagation of fault slip along a simulated rock fault

NASA Astrophysics Data System (ADS)

Mizoguchi, K.

2015-12-01

Around pre-existing geological faults in the crust, we have often observed off-fault damage zone where there are many fractures with various scales, from ~ mm to ~ m and their density typically increases with proximity to the fault. One of the fracture formation processes is considered to be dynamic shear rupture propagation on the faults, which leads to the occurrence of earthquakes. Here, I have conducted experiments on propagation of fault slip along a pre-cut rock surface to investigate the damaging behavior of rocks with slip propagation. For the experiments, I used a pair of metagabbro blocks from Tamil Nadu, India, of which the contacting surface simulates a fault of 35 cm in length and 1cm width. The experiments were done with the similar uniaxial loading configuration to Rosakis et al. (2007). Axial load σ is applied to the fault plane with an angle 60° to the loading direction. When σ is 5kN, normal and shear stresses on the fault are 1.25MPa and 0.72MPa, respectively. Timing and direction of slip propagation on the fault during the experiments were monitored with several strain gauges arrayed at an interval along the fault. The gauge data were digitally recorded with a 1MHz sampling rate and 16bit resolution. When σ is 4.8kN is applied, we observed some fault slip events where a slip nucleates spontaneously in a subsection of the fault and propagates to the whole fault. However, the propagation speed is about 1.2km/s, much lower than the S-wave velocity of the rock. This indicates that the slip events were not earthquake-like dynamic rupture ones. More efforts are needed to reproduce earthquake-like slip events in the experiments. This work is supported by the JSPS KAKENHI (26870912).

Surface Creep along the Chaman Fault on the Pakistan-Afghanistan Border imaged by SAR interferometry

NASA Astrophysics Data System (ADS)

Szeliga, W. M.; Furuya, M.; Satyabala, S.; Bilham, R.

2006-12-01

The Chaman fault system is an on-land transform separating the Indian and Asian plates. From the Arabia/Asia/India triple junction on the Makran coast it passes north through Baluchistan, trending NNE into Afghanistan before merging with the Himalayan arc in the North West Frontier province of Pakistan. Geological and plate closure estimates of slip on the system suggest sinistral slip of between 1.9 and 3.5 cm/yr over the last 25 Ma. Oblique convergence occurs near and north of Quetta, Pakistan where it is accommodated by thrust faulting in ranges to the east of the apparently pure strike-slip Chaman fault. We present InSAR analyses that suggest that a 110 km segment of the Chaman fault system north of Quetta may be experiencing shallow aseismic slip (creep). ERS-1/-2 data indicate a change in range along a 110 km segment of the Chaman fault by as much as 7.8 mm/yr. The absence of ascending pass scenes means that we cannot exclude the possibility that some or all of this sinistral slip occurs as vertical displacement, although we suspect that slip partitioning may rule out a substantial vertical component to the observed slip. The trend of the Chaman fault lies nearly perpendicular to the satellite range direction reducing the signal to noise ratio and rendering the data too noisy to assess the locking depth of creep on the fault, although it would appear to be locked at least 5 km beneath the surface. We note the length and rate of slip of the creeping segment of the Chaman fault is similar to that of the Hayward fault in California.

Surface faulting along the Superstition Hills fault zone and nearby faults associated with the earthquakes of 24 November 1987

USGS Publications Warehouse

Sharp, R.V.

1989-01-01

The M6.2 Elmore Desert Ranch earthquake of 24 November 1987 was associated spatially and probably temporally with left-lateral surface rupture on many northeast-trending faults in and near the Superstition Hills in western Imperial Valley. Three curving discontinuous principal zones of rupture among these breaks extended northeastward from near the Superstition Hills fault zone as far as 9km; the maximum observed surface slip, 12.5cm, was on the northern of the three, the Elmore Ranch fault, at a point near the epicenter. Twelve hours after the Elmore Ranch earthquake, the M6.6 Superstition Hills earthquake occurred near the northwest end of the right-lateral Superstition Hills fault zone. We measured displacements over 339 days at as many as 296 sites along the Superstition Hills fault zone, and repeated measurements at 49 sites provided sufficient data to fit with a simple power law. The overall distributions of right-lateral displacement at 1 day and the estimated final slip are nearly symmetrical about the midpoint of the surface rupture. The average estimated final right-lateral slip for the Superstition Hills fault zone is ~54cm. The average left-lateral slip for the conjugate faults trending northeastward is ~23cm. The southernmost ruptured member of the Superstition Hills fault zone, newly named the Wienert fault, extends the known length of the zone by about 4km. -from Authors

Map of the Rinconada and Reliz Fault Zones, Salinas River Valley, California

USGS Publications Warehouse

Rosenberg, Lewis I.; Clark, Joseph C.

2009-01-01

The Rinconada Fault and its related faults constitute a major structural element of the Salinas River valley, which is known regionally, and referred to herein, as the 'Salinas Valley'. The Rinconada Fault extends 230 km from King City in the north to the Big Pine Fault in the south. At the south end of the map area near Santa Margarita, the Rinconada Fault separates granitic and metamorphic crystalline rocks of the Salinian Block to the northeast from the subduction-zone assemblage of the Franciscan Complex to the southwest. Northwestward, the Rinconada Fault lies entirely within the Salinian Block and generally divides this region into two physiographically and structurally distinct areas, the Santa Lucia Range to the west and the Salinas Valley to the east. The Reliz Fault, which continues as a right stepover from the Rinconada Fault, trends northwestward along the northeastern base of the Sierra de Salinas of the Santa Lucia Range and beyond for 60 km to the vicinity of Spreckels, where it is largely concealed. Aeromagnetic data suggest that the Reliz Fault continues northwestward another 25 km into Monterey Bay, where it aligns with a high-definition magnetic boundary. Geomorphic evidence of late Quaternary movement along the Rinconada and Reliz Fault Zones has been documented by Tinsley (1975), Dibblee (1976, 1979), Hart (1976, 1985), and Klaus (1999). Although definitive geologic evidence of Holocene surface rupture has not been found on these faults, they were regarded as an earthquake source for the California Geological Survey [formerly, California Division of Mines and Geology]/U.S. Geological Survey (CGS/USGS) Probabilistic Seismic Hazards Assessment because of their postulated slip rate of 1+-1 mm/yr and their calculated maximum magnitude of 7.3. Except for published reports by Durham (1965, 1974), Dibblee (1976), and Hart (1976), most information on these faults is unpublished or is contained in theses, field trip guides, and other types of reports

Fault Management Metrics

NASA Technical Reports Server (NTRS)

Johnson, Stephen B.; Ghoshal, Sudipto; Haste, Deepak; Moore, Craig

2017-01-01

This paper describes the theory and considerations in the application of metrics to measure the effectiveness of fault management. Fault management refers here to the operational aspect of system health management, and as such is considered as a meta-control loop that operates to preserve or maximize the system's ability to achieve its goals in the face of current or prospective failure. As a suite of control loops, the metrics to estimate and measure the effectiveness of fault management are similar to those of classical control loops in being divided into two major classes: state estimation, and state control. State estimation metrics can be classified into lower-level subdivisions for detection coverage, detection effectiveness, fault isolation and fault identification (diagnostics), and failure prognosis. State control metrics can be classified into response determination effectiveness and response effectiveness. These metrics are applied to each and every fault management control loop in the system, for each failure to which they apply, and probabilistically summed to determine the effectiveness of these fault management control loops to preserve the relevant system goals that they are intended to protect.

Quaternary low-angle slip on detachment faults in Death Valley, California

USGS Publications Warehouse

Hayman, N.W.; Knott, J.R.; Cowan, D.S.; Nemser, E.; Sarna-Wojcicki, A. M.

2003-01-01

Detachment faults on the west flank of the Black Mountains (Nevada and California) dip 29??-36?? and cut subhorizontal layers of the 0.77 Ma Bishop ash. Steeply dipping normal faults confined to the hanging walls of the detachments offset layers of the 0.64 Ma Lava Creek B tephra and the base of 0.12-0.18 Ma Lake Manly gravel. These faults sole into and do not cut the low-angle detachments. Therefore the detachments accrued any measurable slip across the kinematically linked hanging-wall faults. An analysis of the orientations of hundreds of the hanging-wall faults shows that extension occurred at modest slip rates (<1 mm/yr) under a steep to vertically oriented maximum principal stress. The Black Mountain detachments are appropriately described as the basal detachments of near-critical Coulomb wedges. We infer that the formation of late Pleistocene and Holocene range-front fault scarps accompanied seismogenic slip on the detachments.

Denali fault slip rates and Holocene-late Pleistocene kinematics of central Alaska

USGS Publications Warehouse

Matmon, A.; Schwartz, D.P.; Haeussler, Peter J.; Finkel, R.; Lienkaemper, J.J.; Stenner, Heidi D.; Dawson, T.E.

2006-01-01

The Denali fault is the principal intracontinental strike-slip fault accommodating deformation of interior Alaska associated with the Yakutat plate convergence. We obtained the first quantitative late Pleistocene-Holocene slip rates on the Denali fault system from dating offset geomorphic features. Analysis of cosmogenic 10Be concentrations in boulders (n = 27) and sediment (n = 13) collected at seven sites, offset 25-170 m by the Denali and Totschunda faults, gives average ages that range from 2.4 ± 0.3 ka to 17.0 ± 1.8 ka. These offsets and ages yield late Pleistocene-Holocene average slip rates of 9.4 ± 1.6, 12.1 ± 1.7, and 8.4 ± 2.2 mm/yr-1 along the western, central, and eastern Denali fault, respectively, and 6.0 ± 1.2 mm/yr-1 along the Totschunda fault. Our results suggest a westward decrease in the mean Pleistocene-Holocene slip rate. This westward decrease likely results from partitioning of slip from the Denali fault system to thrust faults to the north and west. 2006 Geological Society of America.

Fault and joint measurements in Austin Chalk, Superconducting Super Collider Site, Texas

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

Nance, H.S.; Laubach, S.E.; Dutton, A.R.

1994-12-31

Structure maps of 9.4 mi of nearly continuous tunnel excavations and more than 10 mi of other exposures and excavations in Austin Chalk at the Superconducting Super Collider (SSC) site in Ellis County, Texas, record normal-fault and joint populations in the subsurface within the northern segment of the Balcones Fault Zone with unmatched resolution for such a long traverse. Small faults (<10 ft throw) occur in clusters or swarms that have as many as 24 faults. Fault swarms are as much as 2,000 ft wide, and spacing between swarms ranges from 800 to 2,000 ft, averaging about 1,000 ft. Predominantlymore » northeast-trending joints are in swarms spaced 500 to more than 21,000 ft apart.« less

Critical fault patterns determination in fault-tolerant computer systems

NASA Technical Reports Server (NTRS)

Mccluskey, E. J.; Losq, J.

1978-01-01

The method proposed tries to enumerate all the critical fault-patterns (successive occurrences of failures) without analyzing every single possible fault. The conditions for the system to be operating in a given mode can be expressed in terms of the static states. Thus, one can find all the system states that correspond to a given critical mode of operation. The next step consists in analyzing the fault-detection mechanisms, the diagnosis algorithm and the process of switch control. From them, one can find all the possible system configurations that can result from a failure occurrence. Thus, one can list all the characteristics, with respect to detection, diagnosis, and switch control, that failures must have to constitute critical fault-patterns. Such an enumeration of the critical fault-patterns can be directly used to evaluate the overall system tolerance to failures. Present research is focused on how to efficiently make use of these system-level characteristics to enumerate all the failures that verify these characteristics.

The Mechanics of Transient Fault Slip and Slow Earthquakes

NASA Astrophysics Data System (ADS)

Marone, C.; Leeman, J.; Scuderi, M.; Saffer, D. M.; Collettini, C.

2015-12-01

Earthquakes are understood as frictional stick-slip instabilities in which stored elastic energy is released suddenly, driving catastrophic failure. In normal (fast) earthquakes the rupture zone expands at a rate dictated by elastic wave speeds, a few km/s, and fault slip rates reach 1-10 m/s. However, tectonic faults also fail in slow earthquakes with rupture durations of months and fault slip speeds of ~100 micron/s or less. We know very little about the mechanics of slow earthquakes. What determines the rupture propagation velocity in slow earthquakes and in other forms of quasi-dynamic rupture? What processes limit stress drop and fault slip speed in slow earthquakes? Existing lab studies provide some help via observations of complex forms of stick-slip, creep-slip, or, in a few cases, slow slip. However, these are mainly anecdotal and rarely include examples of repetitive slow slip or systematic measurements that could be used to isolate the underlying mechanisms. Numerical studies based on rate and state friction also shed light on transiently accelerating slip, showing that slow slip can occur if: 1) fault rheology involves a change in friction rate dependence (a-b) with velocity or unusually large values of the frictional weakening distance Dc, or 2) fault zone elastic stiffness equals the critical frictional weakening rate kc = (b-a)/Dc. Recent laboratory work shows that the latter can occur much more commonly that previously thought. We document the complete spectrum of stick-slip behaviors from transient slow slip to fast stick-slip for a narrow range of conditions around k/kc = 1.0. Slow slip occurs near the threshold between stable and unstable failure, controlled by the interplay of fault zone frictional properties, normal stress, and elastic stiffness of the surrounding rock. Our results provide a generic mechanism for slow earthquakes, consistent with the wide range of conditions for which slow slip has been observed.

Eigenvector of gravity gradient tensor for estimating fault dips considering fault type

NASA Astrophysics Data System (ADS)

Kusumoto, Shigekazu

2017-12-01

The dips of boundaries in faults and caldera walls play an important role in understanding their formation mechanisms. The fault dip is a particularly important parameter in numerical simulations for hazard map creation as the fault dip affects estimations of the area of disaster occurrence. In this study, I introduce a technique for estimating the fault dip using the eigenvector of the observed or calculated gravity gradient tensor on a profile and investigating its properties through numerical simulations. From numerical simulations, it was found that the maximum eigenvector of the tensor points to the high-density causative body, and the dip of the maximum eigenvector closely follows the dip of the normal fault. It was also found that the minimum eigenvector of the tensor points to the low-density causative body and that the dip of the minimum eigenvector closely follows the dip of the reverse fault. It was shown that the eigenvector of the gravity gradient tensor for estimating fault dips is determined by fault type. As an application of this technique, I estimated the dip of the Kurehayama Fault located in Toyama, Japan, and obtained a result that corresponded to conventional fault dip estimations by geology and geomorphology. Because the gravity gradient tensor is required for this analysis, I present a technique that estimates the gravity gradient tensor from the gravity anomaly on a profile.

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

USGS Publications Warehouse

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.

Faulted terrace risers place new constraints on the late Quaternary slip rate for the central Altyn Tagh fault, northwest Tibet

USGS Publications Warehouse

Gold, R.D.; Cowgill, E.; Arrowsmith, J.R.; Chen, X.; Sharp, W.D.; Cooper, K.M.; Wang, X.-F.

2011-01-01

The active, left-lateral Altyn Tagh fault defines the northwestern margin of the Tibetan Plateau in western China. To clarify late Quaternary temporal and spatial variations in slip rate along the central portion of this fault system (85??-90??E), we have more than doubled the number of dated offset markers along the central Altyn Tagh fault. In particular, we determined offset-age relations for seven left-laterally faulted terrace risers at three sites (Kelutelage, Yukuang, and Keke Qiapu) spanning a 140-km-long fault reach by integrating surficial geologic mapping, topographic surveys (total station and tripod-light detection and ranging [T-LiDAR]), and geochronology (radiocarbon dating of organic samples, 230Th/U dating of pedogenic carbonate coatings on buried clasts, and terrestrial cosmogenic radionuclide exposure age dating applied to quartz-rich gravels). At Kelutelage, which is the westernmost site (37.72??N, 86.67??E), two faulted terrace risers are offset 58 ?? 3 m and 48 ?? 4 m, and formed at 6.2-6.1 ka and 5.9-3.7 ka, respectively. At the Yukuang site (38.00??N, 87.87??E), four faulted terrace risers are offset 92 ?? 12 m, 68 ?? 6 m, 55 ?? 13 m, and 59 ?? 9 m and formed at 24.2-9.5 ka, 6.4-5.0 ka, 5.1-3.9 ka, and 24.2-6.4 ka, respectively. At the easternmost site, Keke Qiapu (38.08??N, 88.12??E), a faulted terrace riser is offset 33 ?? 6 m and has an age of 17.1-2.2 ka. The displacement-age relationships derived from these markers can be satisfied by an approximately uniform slip rate of 8-12 mm/yr. However, additional analysis is required to test how much temporal variability in slip rate is permitted by this data set. ?? 2011 Geological Society of America.

Scissoring Fault Rupture Properties along the Median Tectonic Line Fault Zone, Southwest Japan

NASA Astrophysics Data System (ADS)

Ikeda, M.; Nishizaka, N.; Onishi, K.; Sakamoto, J.; Takahashi, K.

2017-12-01

The Median Tectonic Line fault zone (hereinafter MTLFZ) is the longest and most active fault zone in Japan. The MTLFZ is a 400-km-long trench parallel right-lateral strike-slip fault accommodating lateral slip components of the Philippine Sea plate oblique subduction beneath the Eurasian plate [Fitch, 1972; Yeats, 1996]. Complex fault geometry evolves along the MTLFZ. The geomorphic and geological characteristics show a remarkable change through the MTLFZ. Extensional step-overs and pull-apart basins and a pop-up structure develop in western and eastern parts of the MTLFZ, respectively. It is like a "scissoring fault properties". We can point out two main factors to form scissoring fault properties along the MTLFZ. One is a regional stress condition, and another is a preexisting fault. The direction of σ1 anticlockwise rotate from N170°E [Famin et al., 2014] in the eastern Shikoku to Kinki areas and N100°E [Research Group for Crustral Stress in Western Japan, 1980] in central Shikoku to N85°E [Onishi et al., 2016] in western Shikoku. According to the rotation of principal stress directions, the western and eastern parts of the MTLFZ are to be a transtension and compression regime, respectively. The MTLFZ formed as a terrain boundary at Cretaceous, and has evolved with a long active history. The fault style has changed variously, such as left-lateral, thrust, normal and right-lateral. Under the structural condition of a preexisting fault being, the rupture does not completely conform to Anderson's theory for a newly formed fault, as the theory would require either purely dip-slip motion on the 45° dipping fault or strike-slip motion on a vertical fault. The fault rupture of the 2013 Barochistan earthquake in Pakistan is a rare example of large strike-slip reactivation on a relatively low angle dipping fault (thrust fault), though many strike-slip faults have vertical plane generally [Avouac et al., 2014]. In this presentation, we, firstly, show deep subsurface

Slip Inversion Along Inner Fore-Arc Faults, Eastern Tohoku, Japan

NASA Astrophysics Data System (ADS)

Regalla, Christine; Fisher, Donald M.; Kirby, Eric; Oakley, David; Taylor, Stephanie

2017-11-01

The kinematics of deformation in the overriding plate of convergent margins may vary across timescales ranging from a single seismic cycle to many millions of years. In Northeast Japan, a network of active faults has accommodated contraction across the arc since the Pliocene, but several faults located along the inner fore arc experienced extensional aftershocks following the 2011 Tohoku-oki earthquake, opposite that predicted from the geologic record. This observation suggests that fore-arc faults may be favorable for stress triggering and slip inversion, but the geometry and deformation history of these fault systems are poorly constrained. Here we document the Neogene kinematics and subsurface geometry of three prominent fore-arc faults in Tohoku, Japan. Geologic mapping and dating of growth strata provide evidence for a 5.6-2.2 Ma initiation of Plio-Quaternary contraction along the Oritsume, Noheji, and Futaba Faults and an earlier phase of Miocene extension from 25 to 15 Ma along the Oritsume and Futaba Faults associated with the opening of the Sea of Japan. Kinematic modeling indicates that these faults have listric geometries, with ramps that dip 40-65°W and sole into subhorizontal detachments at 6-10 km depth. These fault systems can experience both normal and thrust sense slip if they are mechanically weak relative to the surrounding crust. We suggest that the inversion history of Northeast Japan primed the fore arc with a network of weak faults mechanically and geometrically favorable for slip inversion over geologic timescales and in response to secular variations in stress state associated with the megathrust seismic cycle.

Astypalaea Linea: A Large-Scale Strike-Slip Fault on Europa

NASA Astrophysics Data System (ADS)

Tufts, B. Randall; Greenberg, Richard; Hoppa, Gregory; Geissler, Paul

1999-09-01

Astypalaea Linea is an 810-km strike-slip fault, located near the south pole of Europa. In length, it rivals the San Andreas Fault in California, and it is the largest strike-slip fault yet known on Europa. The fault was discovered using Voyager 2 images, based upon the presence of familiar strike-slip features including linearity, pull-aparts, and possible braids, and upon the offset of multiple piercing points. Fault displacement is 42 km, right-lateral, in the southern and central parts and probably throughout. Pull-aparts present along the fault trace probably are gaps in the lithosphere bounded by vertical cracks, and which opened due to fault motion and filled with material from below. Crosscutting relationships suggest the fault to be of intermediate relative age. The fault may have initiated as a crack due to tension from combined diurnal tides and nonsynchronous rotation, according to the tectonic model of R. Greenberg et al. (1998a, Icarus135, 64-78). Under the influence of varying diurnal tides, strike-slip offset may have occurred through a process called “walking,” which depends upon an inelastic lithospheric response to displacement. Alternatively, fault displacement may have been driven by currents in the theorized Europan ocean, which may have created simple shear structures such as braids. The discovery of Astypalaea Linea extends the geographical range of lateral motion on Europa. Such motion requires the presence of a decoupling zone of ductile ice or liquid water, a sufficiently rigid lithosphere, and a mechanism to consume surface area.

Modelling earthquake ruptures with dynamic off-fault damage

NASA Astrophysics Data System (ADS)

Okubo, Kurama; Bhat, Harsha S.; Klinger, Yann; Rougier, Esteban

2017-04-01

Earthquake rupture modelling has been developed for producing scenario earthquakes. This includes understanding the source mechanisms and estimating far-field ground motion with given a priori constraints like fault geometry, constitutive law of the medium and friction law operating on the fault. It is necessary to consider all of the above complexities of a fault systems to conduct realistic earthquake rupture modelling. In addition to the complexity of the fault geometry in nature, coseismic off-fault damage, which is observed by a variety of geological and seismological methods, plays a considerable role on the resultant ground motion and its spectrum compared to a model with simple planer fault surrounded by purely elastic media. Ideally all of these complexities should be considered in earthquake modelling. State of the art techniques developed so far, however, cannot treat all of them simultaneously due to a variety of computational restrictions. Therefore, we adopt the combined finite-discrete element method (FDEM), which can effectively deal with pre-existing complex fault geometry such as fault branches and kinks and can describe coseismic off-fault damage generated during the dynamic rupture. The advantage of FDEM is that it can handle a wide range of length scales, from metric to kilometric scale, corresponding to the off-fault damage and complex fault geometry respectively. We used the FDEM-based software tool called HOSSedu (Hybrid Optimization Software Suite - Educational Version) for the earthquake rupture modelling, which was developed by Los Alamos National Laboratory. We firstly conducted the cross-validation of this new methodology against other conventional numerical schemes such as the finite difference method (FDM), the spectral element method (SEM) and the boundary integral equation method (BIEM), to evaluate the accuracy with various element sizes and artificial viscous damping values. We demonstrate the capability of the FDEM tool for

Hayward Fault rocks: porosity, density, and strength measurements

USGS Publications Warehouse

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

2001-01-01

Porosity, density and strength measurements were conducted on rock samples collected from the Hayward Fault region in Northern California as part of the Hayward Fault Working Group’s efforts to create a working model of the Hayward Fault. The rocks included in this study were both fine and coarse grained gabbros, altered keratophyre, basalt, sandstone, and serpentinite from various rock formations adjacent to the Hayward Fault. Densities ranged from a low of 2.25 gm/cc (altered keratophyre) to 3.05 gm/cc (fine gabbro), with an average of 2.6 gm/cc, typical of many other rocks. Porosities were generally around 1% or less, with the exception of the sandstone (7.6%) and altered keratophyre (13.5%). Failure and frictional sliding tests were conducted on intact rock cylinders at room temperature under effective pressure conditions of up to 192 MPa, simulating depths of burial to 12 km. Axial shortening of the samples progressed at a rate of 0.1 µm/sec (fine samples) or 0.2 µm/sec (porous samples) for 6 mm of displacement. Velocity stepping tests were then conducted for an additional 2 mm of displacement, for a total of 8 mm. Both peak strength (usually failure strength) and frictional strength, determined at 8 mm of displacement, increased systematically with effective pressure. Coefficients of friction, based on the observed fracture angles, ranged from 0.6 to 0.85, consistent with Byerlee’s Law. Possible secondary influences on the strength of the Hayward rock samples may be surface weathering, or a larger number of pre-existing fractures due to the proximity to the Hayward Fault. All samples showed velocity strengthening, so that the average a-b values were all strongly positive. There was no systematic relation between a-b values and effective pressure. Velocity strengthening behavior is associated with stable sliding (creep), as observed in the shallow portions of the Hayward Fault.

Taking apart the Big Pine fault: Redefining a major structural feature in southern California

USGS Publications Warehouse

Onderdonk, N.W.; Minor, S.A.; Kellogg, K.S.

2005-01-01

New mapping along the Big Pine fault trend in southern California indicates that this structural alignment is actually three separate faults, which exhibit different geometries, slip histories, and senses of offset since Miocene time. The easternmost fault, along the north side of Lockwood Valley, exhibits left-lateral reverse Quaternary displacement but was a north dipping normal fault in late Oligocene to early Miocene time. The eastern Big Pine fault that bounds the southern edge of the Cuyama Badlands is a south dipping reverse fault that is continuous with the San Guillermo fault. The western segment of the Big Pine fault trend is a north dipping thrust fault continuous with the Pine Mountain fault and delineates the northern boundary of the rotated western Transverse Ranges terrane. This redefinition of the Big Pine fault differs greatly from the previous interpretation and significantly alters regional tectonic models and seismic risk estimates. The outcome of this study also demonstrates that basic geologic mapping is still needed to support the development of geologic models. Copyright 2005 by the American Geophysical Union.

Identification of the Polaris Fault using lidar and shallow geophysical methods

USGS Publications Warehouse

Hunter, Lewis E.; Powers, Michael H.; Burton, Bethany L.

2017-01-01

As part of the U.S. Army Corps of Engineers' (USACE) Dam Safety Assurance Program, Martis Creek Dam near Truckee, CA, is under evaluation for earthquake and seepage hazards. The investigations to date have included LiDAR (Light Detection and Ranging) and a wide range of geophysical surveys. The LiDAR data led to the discovery of an important and previously unknown fault tracing very near and possibly under Martis Creek Dam. The geophysical surveys of the dam foundation area confirm evidence of the fault in the area.

Three-thrust fault system at the plate suture of arc-continent collision in the southernmost Longitudinal Valley, eastern Taiwan

NASA Astrophysics Data System (ADS)

Lee, J.; Chen, H.; Hsu, Y.; Yu, S.

2013-12-01

Active faults developed into a rather complex three-thrust fault system at the southern end of the narrow Longitudinal Valley in eastern Taiwan, a present-day on-land plate suture between the Philippine Sea plate and Eurasia. Based on more than ten years long geodetic data (including GPS and levelling), field geological investigation, seismological data, and regional tomography, this paper aims at elucidating the architecture of this three-thrust system and the associated surface deformation, as well as providing insights on fault kinematics, slip behaviors and implications of regional tectonics. Combining the results of interseismic (secular) horizontal and vertical velocities, we are able to map the surface traces of the three active faults in the Taitung area. The west-verging Longitudinal Valley Fault (LVF), along which the Coastal Range of the northern Luzon arc is thrusting over the Central Range of the Chinese continental margin, braches into two active strands bounding both sides of an uplifted, folded Quaternary fluvial deposits (Peinanshan massif) within the valley: the Lichi fault to the east and the Luyeh fault to the west. Both faults are creeping, to some extent, in the shallow surface level. However, while the Luyeh fault shows nearly pure thrust type, the Lichi fault reveals transpression regime in the north and transtension in the south end of the LVF in the Taitung plain. The results suggest that the deformation in the southern end of the Longitudinal Valley corresponds to a transition zone from present arc-collision to pre-collision zone in the offshore SE Taiwan. Concerning the Central Range, the third major fault in the area, the secular velocities indicate that the fault is mostly locked during the interseismic period and the accumulated strain would be able to produce a moderate earthquake, such as the example of the 2006 M6.1 Peinan earthquake, expressed by an oblique thrust (verging toward east) with significant left-lateral strike slip

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

NASA Technical Reports Server (NTRS)

Bergman, Eric A.; Solomon, Sean C.

1987-01-01

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

Modeling the Fault Tolerant Capability of a Flight Control System: An Exercise in SCR Specification

NASA Technical Reports Server (NTRS)

Alexander, Chris; Cortellessa, Vittorio; DelGobbo, Diego; Mili, Ali; Napolitano, Marcello

2000-01-01

In life-critical and mission-critical applications, it is important to make provisions for a wide range of contingencies, by providing means for fault tolerance. In this paper, we discuss the specification of a flight control system that is fault tolerant with respect to sensor faults. Redundancy is provided by analytical relations that hold between sensor readings; depending on the conditions, this redundancy can be used to detect, identify and accommodate sensor faults.

Slip accumulation and lateral propagation of active normal faults in Afar

NASA Astrophysics Data System (ADS)

Manighetti, I.; King, G. C. P.; Gaudemer, Y.; Scholz, C. H.; Doubre, C.

2001-01-01

We investigate fault growth in Afar, where normal fault systems are known to be currently growing fast and most are propagating to the northwest. Using digital elevation models, we have examined the cumulative slip distribution along 255 faults with lengths ranging from 0.3 to 60 km. Faults exhibiting the elliptical or "bell-shaped" slip profiles predicted by simple linear elastic fracture mechanics or elastic-plastic theories are rare. Most slip profiles are roughly linear for more than half of their length, with overall slopes always <0.035. For the dominant population of NW striking faults and fault systems longer than 2 km, the slip profiles are asymmetric, with slip being maximum near the eastern ends of the profiles where it drops abruptly to zero, whereas slip decreases roughly linearly and tapers in the direction of overall Aden rift propagation. At a more detailed level, most faults appear to be composed of distinct, shorter subfaults or segments, whose slip profiles, while different from one to the next, combine to produce the roughly linear overall slip decrease along the entire fault. On a larger scale, faults cluster into kinematically coupled systems, along which the slip on any scale individual fault or fault system complements that of its neighbors, so that the total slip of the whole system is roughly linearly related to its length, with an average slope again <0.035. We discuss the origin of these quasilinear, asymmetric profiles in terms of "initiation points" where slip starts, and "barriers" where fault propagation is arrested. In the absence of a barrier, slip apparently extends with a roughly linear profile, tapered in the direction of fault propagation.

Controls on fault zone structure and brittle fracturing in the foliated hanging wall of the Alpine Fault

NASA Astrophysics Data System (ADS)

Williams, Jack N.; Toy, Virginia G.; Massiot, Cécile; McNamara, David D.; Smith, Steven A. F.; Mills, Steven

2018-04-01

Three datasets are used to quantify fracture density, orientation, and fill in the foliated hanging wall of the Alpine Fault: (1) X-ray computed tomography (CT) images of drill core collected within 25 m of its principal slip zones (PSZs) during the first phase of the Deep Fault Drilling Project that were reoriented with respect to borehole televiewer images, (2) field measurements from creek sections up to 500 m from the PSZs, and (3) CT images of oriented drill core collected during the Amethyst Hydro Project at distances of ˜ 0.7-2 km from the PSZs. Results show that within 160 m of the PSZs in foliated cataclasites and ultramylonites, gouge-filled fractures exhibit a wide range of orientations. At these distances, fractures are interpreted to have formed at relatively high confining pressures and/or in rocks that had a weak mechanical anisotropy. Conversely, at distances greater than 160 m from the PSZs, fractures are typically open and subparallel to the mylonitic or schistose foliation, implying that fracturing occurred at low confining pressures and/or in rocks that were mechanically anisotropic. Fracture density is similar across the ˜ 500 m width of the field transects. By combining our datasets with measurements of permeability and seismic velocity around the Alpine Fault, we further develop the hierarchical model for hanging-wall damage structure that was proposed by Townend et al. (2017). The wider zone of foliation-parallel fractures represents an outer damage zone that forms at shallow depths. The distinct < 160 m wide interval of widely oriented gouge-filled fractures constitutes an inner damage zone. This zone is interpreted to extend towards the base of the seismogenic crust given that its width is comparable to (1) the Alpine Fault low-velocity zone detected by fault zone guided waves and (2) damage zones reported from other exhumed large-displacement faults. In summary, a narrow zone of fracturing at the base of the Alpine Fault

Earthquake Nucleation and Fault Slip: Possible Experiments on a Natural Fault

NASA Astrophysics Data System (ADS)

Germanovich, L. N.; Murdoch, L. C.; Garagash, D.; Reches, Z.; Martel, S. J.; Johnston, M. J.; Ebenhack, J.; Gwaba, D.

2011-12-01

High-resolution deformation and seismic observations are usually made only near the Earths' surface, kilometers away from where earthquake nucleate on active faults and are limited by inverse-cube-distance attenuation and ground noise. We have developed an experimental approach that aims at reactivating faults in-situ using thermal techniques and fluid injection, which modify in-situ stresses and the fault strength until the fault slips. Mines where in-situ stresses are sufficient to drive faulting present an opportunity to conduct such experiments. The former Homestake gold mine in South Dakota is a good example. During our recent field work in the Homestake mine, we found a large fault that intersects multiple mine levels. The size and distinct structure of this fault make it a promising target for in-situ reactivation, which would likely to be localized on a crack-like patch. Slow patch propagation, moderated by the injection rate and the rate of change of the background stresses, may become unstable, leading to the nucleation of a dynamic earthquake rupture. Our analyses for the Homestake fault conditions indicate that this transition occurs for a patch size ~1 m. This represents a fundamental limitation for laboratory experiments and necessitates larger-scale field tests ~10-100 m. The opportunity to observe earthquake nucleation on the Homestake Fault is feasible because slip could be initiated at a pre-defined location and time with instrumentation placed as close as a few meters from the nucleation site. Designing the experiment requires a detailed assessment of the state-of-stress in the vicinity of the fault. This is being conducted by simulating changes in pore pressure and effective stresses accompanying dewatering of the mine, and by evaluating in-situ stress measurements in light of a regional stress field modified by local perturbations caused by the mine workings.

PV System Component Fault and Failure Compilation and Analysis.

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

Klise, Geoffrey Taylor; Lavrova, Olga; Gooding, Renee Lynne

This report describes data collection and analysis of solar photovoltaic (PV) equipment events, which consist of faults and fa ilures that occur during the normal operation of a distributed PV system or PV power plant. We present summary statistics from locations w here maintenance data is being collected at various intervals, as well as reliability statistics gathered from that da ta, consisting of fault/failure distributions and repair distributions for a wide range of PV equipment types.

Fault-zone structure and weakening processes in basin-scale reverse faults: The Moonlight Fault Zone, South Island, New Zealand

NASA Astrophysics Data System (ADS)

Alder, S.; Smith, S. A. F.; Scott, J. M.

2016-10-01

The >200 km long Moonlight Fault Zone (MFZ) in southern New Zealand was an Oligocene basin-bounding normal fault zone that reactivated in the Miocene as a high-angle reverse fault (present dip angle 65°-75°). Regional exhumation in the last c. 5 Ma has resulted in deep exposures of the MFZ that present an opportunity to study the structure and deformation processes that were active in a basin-scale reverse fault at basement depths. Syn-rift sediments are preserved only as thin fault-bound slivers. The hanging wall and footwall of the MFZ are mainly greenschist facies quartzofeldspathic schists that have a steeply-dipping (55°-75°) foliation subparallel to the main fault trace. In more fissile lithologies (e.g. greyschists), hanging-wall deformation occurred by the development of foliation-parallel breccia layers up to a few centimetres thick. Greyschists in the footwall deformed mainly by folding and formation of tabular, foliation-parallel breccias up to 1 m wide. Where the hanging-wall contains more competent lithologies (e.g. greenschist facies metabasite) it is laced with networks of pseudotachylyte that formed parallel to the host rock foliation in a damage zone extending up to 500 m from the main fault trace. The fault core contains an up to 20 m thick sequence of breccias, cataclasites and foliated cataclasites preserving evidence for the progressive development of interconnected networks of (partly authigenic) chlorite and muscovite. Deformation in the fault core occurred by cataclasis of quartz and albite, frictional sliding of chlorite and muscovite grains, and dissolution-precipitation. Combined with published friction and permeability data, our observations suggest that: 1) host rock lithology and anisotropy were the primary controls on the structure of the MFZ at basement depths and 2) high-angle reverse slip was facilitated by the low frictional strength of fault core materials. Restriction of pseudotachylyte networks to the hanging-wall of the

Seismic interpretation of the deep structure of the Wabash Valley Fault System

USGS Publications Warehouse

Bear, G.W.; Rupp, J.A.; Rudman, A.J.

1997-01-01

Interpretations of newly available seismic reflection profiles near the center of the Illinois Basin indicate that the Wabash Valley Fault System is rooted in a series of basement-penetrating faults. The fault system is composed predominantly of north-northeast-trending high-angle normal faults. The largest faults in the system bound the 22-km wide 40-km long Grayville Graben. Structure contour maps drawn on the base of the Mount Simon Sandstone (Cambrian System) and a deeper pre-Mount Simon horizon show dip-slip displacements totaling at least 600 meters across the New Harmony fault. In contrast to previous interpretations, the N-S extent of significant fault offsets is restricted to a region north of 38?? latitude and south of 38.35?? latitude. This suggests that the graben is not a NE extension of the structural complex composed of the Rough Creek Fault System and the Reelfoot Rift as previously interpreted. Structural complexity on the graben floor also decreases to the south. Structural trends north of 38?? latitude are offset laterally across several large faults, indicating strike-slip motions of 2 to 4 km. Some of the major faults are interpreted to penetrate to depths of 7 km or more. Correlation of these faults with steep potential field gradients suggests that the fault positions are controlled by major lithologic contacts within the basement and that the faults may extend into the depth range where earthquakes are generated, revealing a potential link between specific faults and recently observed low-level seismicity in the area.

AGSM Functional Fault Models for Fault Isolation Project

NASA Technical Reports Server (NTRS)

Harp, Janicce Leshay

2014-01-01

This project implements functional fault models to automate the isolation of failures during ground systems operations. FFMs will also be used to recommend sensor placement to improve fault isolation capabilities. The project enables the delivery of system health advisories to ground system operators.

Distributed Fault-Tolerant Control of Networked Uncertain Euler-Lagrange Systems Under Actuator Faults.

PubMed

Chen, Gang; Song, Yongduan; Lewis, Frank L

2016-05-03

This paper investigates the distributed fault-tolerant control problem of networked Euler-Lagrange systems with actuator and communication link faults. An adaptive fault-tolerant cooperative control scheme is proposed to achieve the coordinated tracking control of networked uncertain Lagrange systems on a general directed communication topology, which contains a spanning tree with the root node being the active target system. The proposed algorithm is capable of compensating for the actuator bias fault, the partial loss of effectiveness actuation fault, the communication link fault, the model uncertainty, and the external disturbance simultaneously. The control scheme does not use any fault detection and isolation mechanism to detect, separate, and identify the actuator faults online, which largely reduces the online computation and expedites the responsiveness of the controller. To validate the effectiveness of the proposed method, a test-bed of multiple robot-arm cooperative control system is developed for real-time verification. Experiments on the networked robot-arms are conduced and the results confirm the benefits and the effectiveness of the proposed distributed fault-tolerant control algorithms.

Geodetic Measurement of Deformation East of the San Andreas Fault in Central California

NASA Technical Reports Server (NTRS)

Sauber, Jeanne M.; Lisowski, Michael; Solomon, Sean C.

1988-01-01

Triangulation and trilateration data from two geodetic networks located between the western edge of the Great Valley and the San Andreas fault have been used to calculate shear strain rates in the Diablo Range and to estimate the slip rate along the Calaveras and Paicines faults in Central California. Within the Diablo Range the average shear strain rate was determined for the time period between 1962 and 1982 to be 0.15 + or - 0.08 microrad/yr, with the orientation of the most compressive strain at N 16 deg E + or - 14 deg. The orientation of the principal compressive strain predicted from the azimuth of the major structures in the region is N 25 deg E. It is inferred that the measured strain is due to compression across the folds of this area: the average shear straining corresponds to a relative shortening rate of 4.5 + or - 2.4 mm/yr. From an examination of wellbore breakout orientations and the azimuths of P-axes from earthquake focal mechanisms the inferred orientation of maximum compressive stress was found to be similar to the direction of maximum compressive strain implied by the trend of local fold structures. Results do not support the hypothesis of uniform fault-normal compression within the Coast Ranges. From trilateration measurements made between 1972 and 1987 on lines that are within 10 km of the San Andreas fault, a slip rate of 10 to 12 mm/yr was calculated for the Calaveras-Paicines fault south of Hollister. The slip rate of the Paicines fault decreases to 4 mm/yr near Bitter.

A Discrete Element Modeling Approach to Exploring the Transition Between Fault-related Folding Styles

NASA Astrophysics Data System (ADS)

Hughes, A. N.; Benesh, N. P.; Alt, R. C., II; Shaw, J. H.

2011-12-01

development of a steep, narrow front-limb, characteristic of fault-propagation folding. We find that the boundary conditions imposed on the far wall of the model have the strongest influence on structural style, but that other factors, such as fault dip and mechanical strengths, play secondary roles. By testing a range of values for each of the parameters, we are able to identify the range of values under which the transition occurs. Additionally, we find that the transition between fault-bend and fault-propagation folding is gradual, with structures in the transitional regime showing evidence of each structural style during a portion of their history. The primary role that boundary conditions play in determining fault-related folding style implies that the growth of natural structures may be affected by the emergence of adjacent structures, or in distal variations in detachment strengths. We explore these relationships using natural examples from various fold-and-thrust belts.

Thrust-induced collapse of mountains-an example from the "Big Bend" region of the San Andreas Fault, western transverse ranges, California

USGS Publications Warehouse

Kellogg, Karl S.

2005-01-01

Mount Pinos and Frazier Mountain are two prominent mountains just south of the San Andreas fault in the western Transverse Ranges of southern California, a region that has undergone rapid Quaternary contraction and uplift. Both mountains are underlain, at least in part, by thrusts that place granitic and gneissic rocks over sedimentary rocks as young as Pliocene. Broad profiles and nearly flat summits of each mountain have previously been interpreted as relicts of a raised erosion surface. However, several features bring this interpretation into question. First, lag or stream gravels do not mantle the summit surfaces. Second, extensive landslide deposits, mostly pre?Holocene and deeply incised, mantle the flanks of both mountains. Third, a pervasive fracture and crushed?rock network pervades the crystalline rocks underlying both mountains. The orientation of the fractures, prominent in roadcuts on Mount Pinos, is essentially random. 'Hill?and?saddle' morphology characterizes ridges radiating from the summits, especially on Mount Pinos; outcrops are sparse on the hills and are nonexistent in the saddles, suggesting fractures are concentrated in the saddles. Latest movement on the thrusts underlying the two mountain massifs is probably early Quaternary, during which the mountains were uplifted to considerably higher (although unknown) elevations than at present. A model proposes that during thrusting, ground accelerations in the hanging wall, particularly near thrust tips, were high enough to pervasively fracture the hanging?wall rocks, thereby weakening them and producing essentially an assemblage of loose blocks. Movement over flexures in the fault surface accentuated fracturing. The lowered shear stresses necessary for failure, coupled with deep dissection and ongoing seismic activity, reduced gravitational potential by spreading the mountain massifs, triggering flanking landslides and producing broad, flat?topped mountains. This study developed from mapping in

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

NASA Technical Reports Server (NTRS)

Wilson, Edward (Inventor)

2008-01-01

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

Seismic Hazard and Fault Length

NASA Astrophysics Data System (ADS)

Black, N. M.; Jackson, D. D.; Mualchin, L.

2005-12-01

If mx is the largest earthquake magnitude that can occur on a fault, then what is mp, the largest magnitude that should be expected during the planned lifetime of a particular structure? Most approaches to these questions rely on an estimate of the Maximum Credible Earthquake, obtained by regression (e.g. Wells and Coppersmith, 1994) of fault length (or area) and magnitude. Our work differs in two ways. First, we modify the traditional approach to measuring fault length, to allow for hidden fault complexity and multi-fault rupture. Second, we use a magnitude-frequency relationship to calculate the largest magnitude expected to occur within a given time interval. Often fault length is poorly defined and multiple faults rupture together in a single event. Therefore, we need to expand the definition of a mapped fault length to obtain a more accurate estimate of the maximum magnitude. In previous work, we compared fault length vs. rupture length for post-1975 earthquakes in Southern California. In this study, we found that mapped fault length and rupture length are often unequal, and in several cases rupture broke beyond the previously mapped fault traces. To expand the geologic definition of fault length we outlined several guidelines: 1) if a fault truncates at young Quaternary alluvium, the fault line should be inferred underneath the younger sediments 2) faults striking within 45° of one another should be treated as a continuous fault line and 3) a step-over can link together faults at least 5 km apart. These definitions were applied to fault lines in Southern California. For example, many of the along-strike faults lines in the Mojave Desert are treated as a single fault trending from the Pinto Mountain to the Garlock fault. In addition, the Rose Canyon and Newport-Inglewood faults are treated as a single fault line. We used these more generous fault lengths, and the Wells and Coppersmith regression, to estimate the maximum magnitude (mx) for the major faults in

Wetland losses related to fault movement and hydrocarbon production, southeastern Texas coast

USGS Publications Warehouse

White, William A.; Morton, Robert A.

1997-01-01

Time series analyses of surface fault activity and nearby hydrocarbon production from the southeastern Texas coast show a high correlation among volume of produced fluids, timing of fault activation, rates of subsidence, and rates of wetland loss. Greater subsidence on the downthrown sides of faults contributes to more frequent flooding and generally wetter conditions, which are commonly reflected by changes in plant communities {e.g., Spartina patens to Spartina alterniflora) or progressive transformation of emergent vegetation to open water. Since the 1930s and 1950s, approximately 5,000 hectares of marsh habitat has been lost as a result of subsidence associated with faulting. Marsh- es have expanded locally along faults where hydrophytic vegetation has spread into former upland areas. Fault traces are linear to curvilinear and are visible because elevation differences across faults alter soil hydrology and vegetation. Fault lengths range from 1 to 13.4 km and average 3.8 km. Seventy-five percent of the faults visible on recent aerial photographs are not visible on photographs taken in the 1930's, indicating relatively recent fault movement. At least 80% of the surface faults correlate with extrapolated subsurface faults; the correlation increases to more than 90% when certain assumptions are made to compensate for mismatches in direction of displacement. Coastal wetlands loss in Texas associated with hydrocarbon extraction will likely increase where production in mature fields is prolonged without fiuid reinjection.

A study of tectonic activity in the Basin-Range Province and on the San Andreas Fault. No. 1: Kinematics of Basin-Range intraplate extension

NASA Technical Reports Server (NTRS)

Eddington, P. K.; Smith, R. B.; Renggli, C.

1986-01-01

Strain rates assessed from brittle fracture and total brittle-ductile deformation measured from geodetic data were compared to estimates of paleo-strain from Quaternary geology for the intraplate Great Basin part of the Basin-Range, western United States. These data provide an assessment of the kinematics and mode of lithospheric extension that the western U.S. Cordillera has experienced from the past few million years to the present. Strain and deformation rates were determined by the seismic moment tensor method using historic seismicity and fault plane solutions for sub-regions of homogeneous strain. Contemporary deformation in the Great Basin occurs principally along the active seismic zones. The integrated opening rate across the entire Great Basin is accommodated by E-E extension at 8 to 10 mm/a in the north that diminishes to NW-SE extension of 3.5 mm/a in the south. Zones of maximum lithospheric extension correspond to belts of thin crust, high heat flow, and Quaternary basaltic volcanism, suggesting that these parameters are related through mechanism of extension such as a stress relaxation, allowing bouyant uplift and ascension of magmas.

Frictional heterogeneities on carbonate-bearing normal faults: Insights from the Monte Maggio Fault, Italy

NASA Astrophysics Data System (ADS)

Carpenter, B. M.; Scuderi, M. M.; Collettini, C.; Marone, C.

2014-12-01

Observations of heterogeneous and complex fault slip are often attributed to the complexity of fault structure and/or spatial heterogeneity of fault frictional behavior. Such complex slip patterns have been observed for earthquakes on normal faults throughout central Italy, where many of the Mw 6 to 7 earthquakes in the Apennines nucleate at depths where the lithology is dominated by carbonate rocks. To explore the relationship between fault structure and heterogeneous frictional properties, we studied the exhumed Monte Maggio Fault, located in the northern Apennines. We collected intact specimens of the fault zone, including the principal slip surface and hanging wall cataclasite, and performed experiments at a normal stress of 10 MPa under saturated conditions. Experiments designed to reactivate slip between the cemented principal slip surface and cataclasite show a 3 MPa stress drop as the fault surface fails, then velocity-neutral frictional behavior and significant frictional healing. Overall, our results suggest that (1) earthquakes may readily nucleate in areas of the fault where the slip surface separates massive limestone and are likely to propagate in areas where fault gouge is in contact with the slip surface; (2) postseismic slip is more likely to occur in areas of the fault where gouge is present; and (3) high rates of frictional healing and low creep relaxation observed between solid fault surfaces could lead to significant aftershocks in areas of low stress drop.

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

USGS Publications Warehouse

Brogan, George E.; Kellogg, Karl; Slemmons, D. Burton; Terhune, Christina L.

1991-01-01

The Death Valley-Furnace Creek fault system, in California and Nevada, has a variety of impressive late Quaternary neotectonic features that record a long history of recurrent earthquake-induced faulting. Although no neotectonic features of unequivocal historical age are known, paleoseismic features from multiple late Quaternary events of surface faulting are well developed throughout the length of the system. Comparison of scarp heights to amount of horizontal offset of stream channels and the relationships of both scarps and channels to the ages of different geomorphic surfaces demonstrate that Quaternary faulting along the northwest-trending Furnace Creek fault zone is predominantly right lateral, whereas that along the north-trending Death Valley fault zone is predominantly normal. These observations are compatible with tectonic models of Death Valley as a northwest-trending pull-apart basin. The largest late Quaternary scarps along the Furnace Creek fault zone, with vertical separation of late Pleistocene surfaces of as much as 64 m (meters), are in Fish Lake Valley. Despite the predominance of normal faulting along the Death Valley fault zone, vertical offset of late Pleistocene surfaces along the Death Valley fault zone apparently does not exceed about 15 m. Evidence for four to six separate late Holocene faulting events along the Furnace Creek fault zone and three or more late Holocene events along the Death Valley fault zone are indicated by rupturing of Q1B (about 200-2,000 years old) geomorphic surfaces. Probably the youngest neotectonic feature observed along the Death Valley-Furnace Creek fault system, possibly historic in age, is vegetation lineaments in southernmost Fish Lake Valley. Near-historic faulting in Death Valley, within several kilometers south of Furnace Creek Ranch, is represented by (1) a 2,000-year-old lake shoreline that is cut by sinuous scarps, and (2) a system of young scarps with free-faceted faces (representing several faulting

The Honey Lake fault zone, northeastern California: Its nature, age, and displacement

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

Wagner, D.L.; Saucedo, G.J.; Grose, T.L.T.

The Honey Lake fault zone of northeastern California is composed of en echelon, northwest trending faults that form the boundary between the Sierra Nevada and the Basin Ranges provinces. As such the Honey Lake fault zone can be considered part of the Sierra Nevada frontal fault system. It is also part of the Walker Lane of Nevada. Faults of the Honey Lake zone are vertical with right-lateral oblique displacements. The cumulative vertical component of displacement along the fault zone is on the order of 800 m and right-lateral displacement is at least 10 km (6 miles) but could be considerablymore » more. Oligocene to Miocene (30 to 22 Ma) age rhyolite tuffs can be correlated across the zone, but mid-Miocene andesites do not appear to be correlative indicating the faulting began in early to mid-Miocene time. Volcanic rocks intruded along faults of the zone, dated at 16 to 8 Ma, further suggest that faulting in the Honey Lake zone was initiated during mid-Miocene time. Late Quaternary to Holocene activity is indicated by offset of the 12,000 year old Lake Lahontan high stand shoreline and the surface rupture associated with the 1950 Fort Sage earthquake.« less

The Effects of Fault Bends on Rupture Propagation: A Parameter Study

NASA Astrophysics Data System (ADS)

Lozos, J. C.; Oglesby, D. D.; Duan, B.; Wesnousky, S. G.

2008-12-01

Segmented faults with stepovers are ubiquitous, and occur at a variety of scales, ranging from small stepovers on the San Jacinto Fault, to the large-scale stepover on of the San Andreas Fault between Tejon Pass and San Gorgonio Pass. Because this type of fault geometry is so prevalent, understanding how rupture propagates through such systems is important for evaluating seismic hazard at different points along these faults. In the present study, we systematically investigate how far rupture will propagate through a fault with a linked (i.e., continuous fault) stepover, based on the length of the linking fault segment and the angle that connects the linking segment to adjacent segments. We conducted dynamic models of such systems using a two-dimensional finite element code (Duan and Oglesby 2007). The fault system in our models consists of three segments: two parallel 10km-long faults linked at a specified angle by a linking segment of between 500 m and 5 km. This geometry was run both as a extensional system and a compressional system. We observed several distinct rupture behaviors, with systematic differences between compressional and extensional cases. Both shear directions rupture straight through the stepover for very shallow stepover angles. In compressional systems with steeper angles, rupture may jump ahead from the stepover segment onto the far segment; whether or not rupture on this segment reaches critical patch size and slips fully is also a function of angle and stepover length. In some compressional cases, if the angle is steep enough and the stepover short enough, rupture may jump over the step entirely and propagate down the far segment without touching the linking segment. In extensional systems, rupture jumps from the nucleating segment onto the linking segment even at shallow angles, but at steeper angles, rupture propagates through without jumping. It is easier to propagate through a wider range of angles in extensional cases. In both

A High-Resolution Seismic Survey Across the State Line fault, NV

NASA Astrophysics Data System (ADS)

Beachly, M.; Cox, C. M.; Saldana, S. C.; Snelson, C. M.; Taylor, W. J.; Robins, C.; Davis, R.; Stropky, M.; Phillips, R.; Cothrun, C.

2007-12-01

During the summer of 2007, an investigation of the faulting in Stewart Valley was under taken, located within the central Basin and Range province ~90 km west of Las Vegas, Nevada. The goal of this study was to resolve the seismic hazard potential of the State Line fault, a right-lateral strike-slip fault that runs the length of Stewart Valley. Four seismic reflection lines were acquired, two perpendicular and two parallel to the State Line fault. What is presented is an analysis of the western and eastern seismic lines parallel to the State Line fault. The western line was acquired utilizing a 144-channel geode system with each of the 4.5 Hz vertical geophones set out at 5 m intervals to form a 715 m long profile. The eastern line employed 120 of these geophones in a 595 m long profile. A mini-vibroseis served as the seismic source every ten meters, between geophones. The vibroseis was programmed to produce an 8 s linear sweep from 20-160 Hz. Three sweeps were recorded at each shot location without acquisition filters at a sampling rate of 0.5 ms. The three shot gathers were then stacked at each location to reduce noise. The data collected had minimal noise, although; during the processing of the eastern line a notch filtered was used to remove the 60 Hz noise created by adjacent power line. These lines, acquired parallel to the State Line fault, contain matching features that serve to determine how much lateral displacement the fault has undergone. The amount of the displacement can indicate how active the fault is, and thus, what magnitude of earthquake can be expected in the future. This will in turn contribute to determining the seismic hazard potential for southern Nevada. A preliminary interpretation of the seismic reflection sections indicates an average displacement of about 20 - 38 m with greater displacement in the deeper sections of the image. The shallow depth displacement calculations are consistent with previous work in the area. The State Line fault

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

NASA Astrophysics Data System (ADS)

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

2010-04-01

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

Aftershocks of the 2014 South Napa, California, Earthquake: Complex faulting on secondary faults

USGS Publications Warehouse

Hardebeck, Jeanne L.; Shelly, David R.

2016-01-01

We investigate the aftershock sequence of the 2014 MW6.0 South Napa, California, earthquake. Low-magnitude aftershocks missing from the network catalog are detected by applying a matched-filter approach to continuous seismic data, with the catalog earthquakes serving as the waveform templates. We measure precise differential arrival times between events, which we use for double-difference event relocation in a 3D seismic velocity model. Most aftershocks are deeper than the mainshock slip, and most occur west of the mapped surface rupture. While the mainshock coseismic and postseismic slip appears to have occurred on the near-vertical, strike-slip West Napa fault, many of the aftershocks occur in a complex zone of secondary faulting. Earthquake locations in the main aftershock zone, near the mainshock hypocenter, delineate multiple dipping secondary faults. Composite focal mechanisms indicate strike-slip and oblique-reverse faulting on the secondary features. The secondary faults were moved towards failure by Coulomb stress changes from the mainshock slip. Clusters of aftershocks north and south of the main aftershock zone exhibit vertical strike-slip faulting more consistent with the West Napa Fault. The northern aftershocks correspond to the area of largest mainshock coseismic slip, while the main aftershock zone is adjacent to the fault area that has primarily slipped postseismically. Unlike most creeping faults, the zone of postseismic slip does not appear to contain embedded stick-slip patches that would have produced on-fault aftershocks. The lack of stick-slip patches along this portion of the fault may contribute to the low productivity of the South Napa aftershock sequence.

Fault linkage and continental breakup

NASA Astrophysics Data System (ADS)

Cresswell, Derren; Lymer, Gaël; Reston, Tim; Stevenson, Carl; Bull, Jonathan; Sawyer, Dale; Morgan, Julia

2017-04-01

The magma-poor rifted margin off the west coast of Galicia (NW Spain) has provided some of the key observations in the development of models describing the final stages of rifting and continental breakup. In 2013, we collected a 68 x 20 km 3D seismic survey across the Galicia margin, NE Atlantic. Processing through to 3D Pre-stack Time Migration (12.5 m bin-size) and 3D depth conversion reveals the key structures, including an underlying detachment fault (the S detachment), and the intra-block and inter-block faults. These data reveal multiple phases of faulting, which overlap spatially and temporally, have thinned the crust to between zero and a few km thickness, producing 'basement windows' where crustal basement has been completely pulled apart and sediments lie directly on the mantle. Two approximately N-S trending fault systems are observed: 1) a margin proximal system of two linked faults that are the upward extension (breakaway faults) of the S; in the south they form one surface that splays northward to form two faults with an intervening fault block. These faults were thus demonstrably active at one time rather than sequentially. 2) An oceanward relay structure that shows clear along strike linkage. Faults within the relay trend NE-SW and heavily dissect the basement. The main block bounding faults can be traced from the S detachment through the basement into, and heavily deforming, the syn-rift sediments where they die out, suggesting that the faults propagated up from the S detachment surface. Analysis of the fault heaves and associated maps at different structural levels show complementary fault systems. The pattern of faulting suggests a variation in main tectonic transport direction moving oceanward. This might be interpreted as a temporal change during sequential faulting, however the transfer of extension between faults and the lateral variability of fault blocks suggests that many of the faults across the 3D volume were active at least in part

Data-based fault-tolerant control for affine nonlinear systems with actuator faults.

PubMed

Xie, Chun-Hua; Yang, Guang-Hong

2016-09-01

This paper investigates the fault-tolerant control (FTC) problem for unknown nonlinear systems with actuator faults including stuck, outage, bias and loss of effectiveness. The upper bounds of stuck faults, bias faults and loss of effectiveness faults are unknown. A new data-based FTC scheme is proposed. It consists of the online estimations of the bounds and a state-dependent function. The estimations are adjusted online to compensate automatically the actuator faults. The state-dependent function solved by using real system data helps to stabilize the system. Furthermore, all signals in the resulting closed-loop system are uniformly bounded and the states converge asymptotically to zero. Compared with the existing results, the proposed approach is data-based. Finally, two simulation examples are provided to show the effectiveness of the proposed approach. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.

Post-Neogene tectonism along the Aravalli Range, Rajasthan, India

NASA Astrophysics Data System (ADS)

Sen, Deepawati; Sen, Saurindranath

1983-03-01

The Aravalli Range runs southwest from Delhi for a distance of about 700 km. Its western margin is well defined, but the eastern margin is diffuse. Five geomorphic provinces are recognized in the study area: the western piedmont plains; the ridge and valley province which in the Central Aravallis occurs at two different heights separated by a fault scarp; the plateau province demarcated from the former by a fault scarp, confined to the Southern Aravallis, and occurring for a short stretch at two heights across another fault scarp; the BGC rolling plains east of the Range; and the BGC uplands south of the above. The scarps coincide with Precambrian faults. A series of rapids and water-falls, together with deeply entrenched river courses across the scarps and the youthful aspects of the escarpments with no projecting spurs, or straight river courses along their feet, all point unmistakably to a recent or post-Neogene vertical uplift along pre-existing faults. Presence of knickpoints at a constant distance from the Range in all west-flowing rivers, the ubiquitous terraces, and river courses entrenched within their own flood-plain deposits of thick gritty to conglomeratic sand, are indicative of a constant disturbance with a gradual rise of the Range east of the knickpoint, wherefrom the coarse materials were carried by the fast west-flowing streams. There is a differential uplift across the plateau scarp together with a right-lateral offset. This epeirogenic tectonism is ascribed to the collision of the Eurasian and the subducting Indian plates and to a locking of their continental crusts. By early Pleistocene, with the MBT gradually dying off, continued plate movement caused a flexural bending of the plate by a moment generated at the back, and a possible delinking of the continental crust along the zone of subduction. The felexural bending ripped open the Precambrian regional faults. The differential uplift and the difference in the distances of the nodes on two

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

NASA Astrophysics Data System (ADS)

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

2006-12-01

Ten years have past since the first official assessment of the long-term seismic risks of the Itoigawa-Shizuoka tectonic line active fault system (ISTL) in 1996. The disaster caused by the1995 Kobe (Hyogo-ken-Nanbu) earthquake urged the Japanese government to initiated a national project to assess the long-term seismic risks of on-shore active faults using geologic information. ISTL was the first target of the 98 significant faults and the probability of a M7 to M8 event turned out to be the highest among them. After the 10 years of continued efforts to understand the ISTL, now it is getting ready to revise the assessment. Fault mapping and segmentation: The most active segment of the Gofukuji fault (~1 cm/yr left-lateral strike slip, R=500~800 yrs.) had been maped only for less than 10 km. Adjacent segments were much less active. This large slip on such a short segment was contradictory. However, detailed topographic study including Lidar survey revealed the length of the Gofukuji fault to be 25 km or more. High slip rate with frequent earthquakes may be restricted to the Gofukuji fault while the 1996 assessment modeled frequent >100 km rupture scenario. The geometry of the fault is controversial especially on the left-lateral strike-slip section of the ISTL. There are two models of high-angle Middel ISTL and low-angle Middle ISTL with slip partitioning. However, all geomorphic and shallow geologic data supports high-angle almost pure strike slip on the faults in the Middle ISTL. CRIEPI's 3- dimensional trenching in several sites as well as the previous results clearly demonstrated repeated pure strike-slip offset during past a few events. In Middle ISTL, there is no evidence of recent activity of pre-existing low-angle thrust faults that are inferred to be active from shallow seismic survey. Separation of high (~3000 m) mountain ranges and low (<1000 m) basin floor requires significant dip-slip component, but basin-fill sediments and geology of the range do not

On Identifiability of Bias-Type Actuator-Sensor Faults in Multiple-Model-Based Fault Detection and Identification

NASA Technical Reports Server (NTRS)

Joshi, Suresh M.

2012-01-01

This paper explores a class of multiple-model-based fault detection and identification (FDI) methods for bias-type faults in actuators and sensors. These methods employ banks of Kalman-Bucy filters to detect the faults, determine the fault pattern, and estimate the fault values, wherein each Kalman-Bucy filter is tuned to a different failure pattern. Necessary and sufficient conditions are presented for identifiability of actuator faults, sensor faults, and simultaneous actuator and sensor faults. It is shown that FDI of simultaneous actuator and sensor faults is not possible using these methods when all sensors have biases.

Late Quaternary faulting in the Sevier Desert driven by magmatism.

PubMed

Stahl, T; Niemi, N A

2017-03-14

Seismic hazard in continental rifts varies as a function of strain accommodation by tectonic or magmatic processes. The nature of faulting in the Sevier Desert, located in eastern Basin and Range of central Utah, and how this faulting relates to the Sevier Desert Detachment low-angle normal fault, have been debated for nearly four decades. Here, we show that the geodetic signal of extension across the eastern Sevier Desert is best explained by magma-assisted rifting associated with Plio-Pleistocene volcanism. GPS velocities from 14 continuous sites across the region are best-fit by interseismic strain accumulation on the southern Wasatch Fault at c. 3.4 mm yr -1 with a c. 0.5 mm yr -1 tensile dislocation opening in the eastern Sevier Desert. The characteristics of surface deformation from field surveys are consistent with dike-induced faulting and not with faults soling into an active detachment. Geologic extension rates of c. 0.6 mm yr -1 over the last c. 50 kyr in the eastern Sevier Desert are consistent with the rates estimated from the geodetic model. Together, these findings suggest that Plio-Pleistocene extension is not likely to have been accommodated by low-angle normal faulting on the Sevier Desert Detachment and is instead accomplished by strain localization in a zone of narrow, magma-assisted rifting.

Late Quaternary faulting in the Sevier Desert driven by magmatism

PubMed Central

Stahl, T.; Niemi, N. A.

2017-01-01

Seismic hazard in continental rifts varies as a function of strain accommodation by tectonic or magmatic processes. The nature of faulting in the Sevier Desert, located in eastern Basin and Range of central Utah, and how this faulting relates to the Sevier Desert Detachment low-angle normal fault, have been debated for nearly four decades. Here, we show that the geodetic signal of extension across the eastern Sevier Desert is best explained by magma-assisted rifting associated with Plio-Pleistocene volcanism. GPS velocities from 14 continuous sites across the region are best-fit by interseismic strain accumulation on the southern Wasatch Fault at c. 3.4 mm yr−1 with a c. 0.5 mm yr−1 tensile dislocation opening in the eastern Sevier Desert. The characteristics of surface deformation from field surveys are consistent with dike-induced faulting and not with faults soling into an active detachment. Geologic extension rates of c. 0.6 mm yr−1 over the last c. 50 kyr in the eastern Sevier Desert are consistent with the rates estimated from the geodetic model. Together, these findings suggest that Plio-Pleistocene extension is not likely to have been accommodated by low-angle normal faulting on the Sevier Desert Detachment and is instead accomplished by strain localization in a zone of narrow, magma-assisted rifting. PMID:28290529

Fault Injection Campaign for a Fault Tolerant Duplex Framework

NASA Technical Reports Server (NTRS)

Sacco, Gian Franco; Ferraro, Robert D.; von llmen, Paul; Rennels, Dave A.

2007-01-01

Fault tolerance is an efficient approach adopted to avoid or reduce the damage of a system failure. In this work we present the results of a fault injection campaign we conducted on the Duplex Framework (DF). The DF is a software developed by the UCLA group [1, 2] that uses a fault tolerant approach and allows to run two replicas of the same process on two different nodes of a commercial off-the-shelf (COTS) computer cluster. A third process running on a different node, constantly monitors the results computed by the two replicas, and eventually restarts the two replica processes if an inconsistency in their computation is detected. This approach is very cost efficient and can be adopted to control processes on spacecrafts where the fault rate produced by cosmic rays is not very high.

Centrifugal compressor fault diagnosis based on qualitative simulation and thermal parameters

NASA Astrophysics Data System (ADS)

Lu, Yunsong; Wang, Fuli; Jia, Mingxing; Qi, Yuanchen

2016-12-01

This paper concerns fault diagnosis of centrifugal compressor based on thermal parameters. An improved qualitative simulation (QSIM) based fault diagnosis method is proposed to diagnose the faults of centrifugal compressor in a gas-steam combined-cycle power plant (CCPP). The qualitative models under normal and two faulty conditions have been built through the analysis of the principle of centrifugal compressor. To solve the problem of qualitative description of the observations of system variables, a qualitative trend extraction algorithm is applied to extract the trends of the observations. For qualitative states matching, a sliding window based matching strategy which consists of variables operating ranges constraints and qualitative constraints is proposed. The matching results are used to determine which QSIM model is more consistent with the running state of system. The correct diagnosis of two typical faults: seal leakage and valve stuck in the centrifugal compressor has validated the targeted performance of the proposed method, showing the advantages of fault roots containing in thermal parameters.

Fault Wear by Damage Evolution During Steady-State Slip

NASA Astrophysics Data System (ADS)

Lyakhovsky, Vladimir; Sagy, Amir; Boneh, Yuval; Reches, Ze'ev

2014-11-01

Slip along faults generates wear products such as gouge layers and cataclasite zones that range in thickness from sub-millimeter to tens of meters. The properties of these zones apparently control fault strength and slip stability. Here we present a new model of wear in a three-body configuration that utilizes the damage rheology approach and considers the process as a microfracturing or damage front propagating from the gouge zone into the solid rock. The derivations for steady-state conditions lead to a scaling relation for the damage front velocity considered as the wear-rate. The model predicts that the wear-rate is a function of the shear-stress and may vanish when the shear-stress drops below the microfracturing strength of the fault host rock. The simulated results successfully fit the measured friction and wear during shear experiments along faults made of carbonate and tonalite. The model is also valid for relatively large confining pressures, small damage-induced change of the bulk modulus and significant degradation of the shear modulus, which are assumed for seismogenic zones of earthquake faults. The presented formulation indicates that wear dynamics in brittle materials in general and in natural faults in particular can be understood by the concept of a "propagating damage front" and the evolution of a third-body layer.

Fault Interaction and Stress Accumulation in Chaman Fault System, Balouchistan, Pakistan, Since 1892

NASA Astrophysics Data System (ADS)

Riaz, M. S.; Shan, B.; Xiong, X.; Xie, Z.

2017-12-01

The curved-shaped left-lateral Chaman fault is the Western boundary of the Indian plate, which is approximately 1000 km long. The Chaman fault is an active fault and also locus of many catastrophic earthquakes. Since the inception of strike-slip movement at 20-25Ma along the western collision boundary between Indian and Eurasian plates, the average geologically constrained slip rate of 24 to 35 mm/yr accounts for a total displacement of 460±10 km along the Chaman fault system (Beun et al., 1979; Lawrence et al., 1992). Based on earthquake triggering theory, the change in Coulomb Failure Stress (DCFS) either halted (shadow stress) or advances (positive stress) the occurrence of subsequent earthquakes. Several major earthquakes occurred in Chaman fault system, and this region is poorly studied to understand the earthquake/fault interaction and hazard assessment. In order to do so, we have analyzed the earthquakes catalog and collected significant earthquakes with M ≥6.2 since 1892. We then investigate the evolution of DCFS in the Chaman fault system is computed by integration of coseismic static and postseismic viscoelastic relaxation stress transfer since the 1892, using the codePSGRN/PSCMP (Wang et al., 2006). Moreover, for postseismic stress transfer simulation, we adopted linear Maxwell rheology to calculate the viscoelastic effects in this study. Our results elucidate that three out of four earthquakes are triggered by the preceding earthquakes. The 1892-earthquake with magnitude Mw6.8, which occurred on the North segment of Chaman fault has not influence the 1935-earthquake which occurred on Ghazaband fault, a parallel fault 20km east to Chaman fault. The 1935-earthquake with magnitude Mw7.7 significantly loaded the both ends of rupture with positive stress (CFS ≥0.01 Mpa), which later on triggered the 1975-earthquake with 23% of its rupture length where CFS ≥0.01 Mpa, on Chaman fault, and 1990-earthquke with 58% of its rupture length where CFS ≥0

Structural geology of western part of Lemhi Range, east-central Idaho

USGS Publications Warehouse

Tysdal, Russell G.

2002-01-01

The Poison Creek Anticline is a major fold that occupies a large part of the western part of the Lemhi Range. The fold is now broken by normal faults, but removal of displacement on the normal faults permitted reconstruction of the anticline. The fold formed during late Mesozoic compressional deformation in the hinterland of the Cordilleran thrust belt. It is in the hanging wall of the Poison Creek thrust fault, a major fault in east-central Idaho, that displaced Proterozoic strata over lower Paleozoic rocks.

Deciphering Stress State of Seismogenic Faults in Oklahoma and Kansas Based on High-resolution Stress Maps

NASA Astrophysics Data System (ADS)

Qin, Y.; Chen, X.; Haffener, J.; Trugman, D. T.; Carpenter, B.; Reches, Z.

2017-12-01

Induced seismicity in Oklahoma and Kansas delineates clear fault trends. It is assumed that fluid injection reactivates faults which are optimally oriented relative to the regional tectonic stress field. We utilized recently improved earthquake locations and more complete focal mechanism catalogs to quantitatively analyze the stress state of seismogenic faults with high-resolution stress maps. The steps of analysis are: (1) Mapping the faults by clustering seismicity using a nearest-neighbor approach, manually picking the fault in each cluster and calculating the fault geometry using principal component analysis. (2) Running a stress inversion with 0.2° grid spacing to produce an in-situ stress map. (3) The fault stress state is determined from fault geometry and a 3D Mohr circle. The parameter `understress' is calculated to quantify the criticalness of these faults. If it approaches 0, the fault is critically stressed; while understress=1 means there is no shear stress on the fault. Our results indicate that most of the active faults have a planar shape (planarity>0.8), and dip steeply (dip>70°). The fault trends are distributed mainly in conjugate set ranges of [50°,70°] and [100°,120°]. More importantly, these conjugate trends are consistent with mapped basement fractures in southern Oklahoma, suggesting similar basement features from regional tectonics. The fault length data shows a loglinear relationship with the maximum earthquake magnitude with an expected maximum magnitude range from 3.2 to 4.4 for most seismogenic faults. Based on 3D local Mohr circle, we find that 61% of the faults have low understress (<0.2); while several faults with high understress (>0.5) are located within highest-rate injection zones and therefore are likely to be influenced by high pore pressure. The faults that hosted the largest earthquakes, M5.7 Prague and M5.8 Pawnee are critically stressed (understress < 0.08), whereas the fault of M5 Fairview earthquake is only

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

USGS Publications Warehouse

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

2010-01-01

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

Pressure Monitoring to Detect Fault Rupture Due to CO 2 Injection

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

Keating, Elizabeth; Dempsey, David; Pawar, Rajesh

The capacity for fault systems to be reactivated by fluid injection is well-known. In the context of CO 2 sequestration, however, the consequence of reactivated faults with respect to leakage and monitoring is poorly understood. Using multi-phase fluid flow simulations, this study addresses key questions concerning the likelihood of ruptures, the timing of consequent upward leakage of CO 2, and the effectiveness of pressure monitoring in the reservoir and overlying zones for rupture detection. A range of injection scenarios was simulated using random sampling of uncertain parameters. These include the assumed distance between the injector and the vulnerable fault zone,more » the critical overpressure required for the fault to rupture, reservoir permeability, and the CO 2 injection rate. We assumed a conservative scenario, in which if at any time during the five-year simulations the critical fault overpressure is exceeded, the fault permeability is assumed to instantaneously increase. For the purposes of conservatism we assume that CO 2 injection continues ‘blindly’ after fault rupture. We show that, despite this assumption, in most cases the CO 2 plume does not reach the base of the ruptured fault after 5 years. As a result, one possible implication of this result is that leak mitigation strategies such as pressure management have a reasonable chance of preventing a CO 2 leak.« less

Pressure Monitoring to Detect Fault Rupture Due to CO 2 Injection

DOE PAGES

Keating, Elizabeth; Dempsey, David; Pawar, Rajesh

2017-08-18

The capacity for fault systems to be reactivated by fluid injection is well-known. In the context of CO 2 sequestration, however, the consequence of reactivated faults with respect to leakage and monitoring is poorly understood. Using multi-phase fluid flow simulations, this study addresses key questions concerning the likelihood of ruptures, the timing of consequent upward leakage of CO 2, and the effectiveness of pressure monitoring in the reservoir and overlying zones for rupture detection. A range of injection scenarios was simulated using random sampling of uncertain parameters. These include the assumed distance between the injector and the vulnerable fault zone,more » the critical overpressure required for the fault to rupture, reservoir permeability, and the CO 2 injection rate. We assumed a conservative scenario, in which if at any time during the five-year simulations the critical fault overpressure is exceeded, the fault permeability is assumed to instantaneously increase. For the purposes of conservatism we assume that CO 2 injection continues ‘blindly’ after fault rupture. We show that, despite this assumption, in most cases the CO 2 plume does not reach the base of the ruptured fault after 5 years. As a result, one possible implication of this result is that leak mitigation strategies such as pressure management have a reasonable chance of preventing a CO 2 leak.« less

Fault diagnosis of power transformer based on fault-tree analysis (FTA)

NASA Astrophysics Data System (ADS)

Wang, Yongliang; Li, Xiaoqiang; Ma, Jianwei; Li, SuoYu

2017-05-01

Power transformers is an important equipment in power plants and substations, power distribution transmission link is made an important hub of power systems. Its performance directly affects the quality and health of the power system reliability and stability. This paper summarizes the five parts according to the fault type power transformers, then from the time dimension divided into three stages of power transformer fault, use DGA routine analysis and infrared diagnostics criterion set power transformer running state, finally, according to the needs of power transformer fault diagnosis, by the general to the section by stepwise refinement of dendritic tree constructed power transformer fault

Large earthquakes and creeping faults

USGS Publications Warehouse

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.

A novel KFCM based fault diagnosis method for unknown faults in satellite reaction wheels.

PubMed

Hu, Di; Sarosh, Ali; Dong, Yun-Feng

2012-03-01

Reaction wheels are one of the most critical components of the satellite attitude control system, therefore correct diagnosis of their faults is quintessential for efficient operation of these spacecraft. The known faults in any of the subsystems are often diagnosed by supervised learning algorithms, however, this method fails to work correctly when a new or unknown fault occurs. In such cases an unsupervised learning algorithm becomes essential for obtaining the correct diagnosis. Kernel Fuzzy C-Means (KFCM) is one of the unsupervised algorithms, although it has its own limitations; however in this paper a novel method has been proposed for conditioning of KFCM method (C-KFCM) so that it can be effectively used for fault diagnosis of both known and unknown faults as in satellite reaction wheels. The C-KFCM approach involves determination of exact class centers from the data of known faults, in this way discrete number of fault classes are determined at the start. Similarity parameters are derived and determined for each of the fault data point. Thereafter depending on the similarity threshold each data point is issued with a class label. The high similarity points fall into one of the 'known-fault' classes while the low similarity points are labeled as 'unknown-faults'. Simulation results show that as compared to the supervised algorithm such as neural network, the C-KFCM method can effectively cluster historical fault data (as in reaction wheels) and diagnose the faults to an accuracy of more than 91%. Copyright © 2011 ISA. Published by Elsevier Ltd. All rights reserved.

The SCEC 3D Community Fault Model (CFM-v5): An updated and expanded fault set of oblique crustal deformation and complex fault interaction for southern California

NASA Astrophysics Data System (ADS)

Nicholson, C.; Plesch, A.; Sorlien, C. C.; Shaw, J. H.; Hauksson, E.

2014-12-01

Southern California represents an ideal natural laboratory to investigate oblique deformation in 3D owing to its comprehensive datasets, complex tectonic history, evolving components of oblique slip, and continued crustal rotations about horizontal and vertical axes. As the SCEC Community Fault Model (CFM) aims to accurately reflect this 3D deformation, we present the results of an extensive update to the model by using primarily detailed fault trace, seismic reflection, relocated hypocenter and focal mechanism nodal plane data to generate improved, more realistic digital 3D fault surfaces. The results document a wide variety of oblique strain accommodation, including various aspects of strain partitioning and fault-related folding, sets of both high-angle and low-angle faults that mutually interact, significant non-planar, multi-stranded faults with variable dip along strike and with depth, and active mid-crustal detachments. In places, closely-spaced fault strands or fault systems can remain surprisingly subparallel to seismogenic depths, while in other areas, major strike-slip to oblique-slip faults can merge, such as the S-dipping Arroyo Parida-Mission Ridge and Santa Ynez faults with the N-dipping North Channel-Pitas Point-Red Mountain fault system, or diverge with depth. Examples of the latter include the steep-to-west-dipping Laguna Salada-Indiviso faults with the steep-to-east-dipping Sierra Cucapah faults, and the steep southern San Andreas fault with the adjacent NE-dipping Mecca Hills-Hidden Springs fault system. In addition, overprinting by steep predominantly strike-slip faulting can segment which parts of intersecting inherited low-angle faults are reactivated, or result in mutual cross-cutting relationships. The updated CFM 3D fault surfaces thus help characterize a more complex pattern of fault interactions at depth between various fault sets and linked fault systems, and a more complex fault geometry than typically inferred or expected from

Cyclical Fault Permeability in the Lower Seismogenic Zone: Geological Evidence

NASA Astrophysics Data System (ADS)

Sibson, R. H.

2005-12-01

Syntectonic hydrothermal veining is widespread in ancient fault zones exhibiting mixed brittle-ductile behavior that are exhumed from subgreenschist to greenschist environments. The hydrothermal material (predominantly quartz ± carbonate) commonly occurs as fault-veins developed along principal slip surfaces, with textures recording intermittent deposition, sometimes in the form of repeated episodes of brecciation and recementation. Systematic sets of extension veins with histories of incremental dilation often occur in adjacent wallrocks. Conspicuous for their size and continuity among these fault-hosted vein systems are mesozonal Au-quartz lodes, which are most widespread in Archean granite-greenstone belts but also occur throughout the geological record. Most of these lode gold deposits developed at pressures of 1-5 kbar and temperatures of 200-450°C within the lower continental seismogenic zone. A notable characteristic is their vertical continuity: many `ribbon-texture' fault veins with thicknesses of the order of a meter extend over depth ranges approaching 2 km. The largest lodes are usually hosted by reverse or reverse- oblique fault zones with low finite displacement. Associated flat-lying extension veins in the wallrock may taper away from the shear zones over tens or hundreds of meters, and demonstrate repeated attainment of the ~lithostatic fluid overpressures needed for hydraulic extension fracturing. Where hosted by extensional-transtensional fault systems, lode systems tend to be less well developed. Mesozonal vein systems are inferred to be the product of extreme fault-valve behavior, whereby episodic accumulation of pore-fluid pressure to near-lithostatic values over the interseismic period leads to fault rupture, followed by postseismic discharge of substantial fluid volumes along the freshly permeable rupture zone inducing hydrothermal precipitation that seals the fracture permeability. Aqueous mineralizing fluids were generally low

Insurance Applications of Active Fault Maps Showing Epistemic Uncertainty

NASA Astrophysics Data System (ADS)

Woo, G.

2005-12-01

Insurance loss modeling for earthquakes utilizes available maps of active faulting produced by geoscientists. All such maps are subject to uncertainty, arising from lack of knowledge of fault geometry and rupture history. Field work to undertake geological fault investigations drains human and monetary resources, and this inevitably limits the resolution of fault parameters. Some areas are more accessible than others; some may be of greater social or economic importance than others; some areas may be investigated more rapidly or diligently than others; or funding restrictions may have curtailed the extent of the fault mapping program. In contrast with the aleatory uncertainty associated with the inherent variability in the dynamics of earthquake fault rupture, uncertainty associated with lack of knowledge of fault geometry and rupture history is epistemic. The extent of this epistemic uncertainty may vary substantially from one regional or national fault map to another. However aware the local cartographer may be, this uncertainty is generally not conveyed in detail to the international map user. For example, an area may be left blank for a variety of reasons, ranging from lack of sufficient investigation of a fault to lack of convincing evidence of activity. Epistemic uncertainty in fault parameters is of concern in any probabilistic assessment of seismic hazard, not least in insurance earthquake risk applications. A logic-tree framework is appropriate for incorporating epistemic uncertainty. Some insurance contracts cover specific high-value properties or transport infrastructure, and therefore are extremely sensitive to the geometry of active faulting. Alternative Risk Transfer (ART) to the capital markets may also be considered. In order for such insurance or ART contracts to be properly priced, uncertainty should be taken into account. Accordingly, an estimate is needed for the likelihood of surface rupture capable of causing severe damage. Especially where a

Influence of fault steps on rupture termination of strike-slip earthquake faults

NASA Astrophysics Data System (ADS)

Li, Zhengfang; Zhou, Bengang

2018-03-01

A statistical analysis was completed on the rupture data of 29 historical strike-slip earthquakes across the world. The purpose of this study is to examine the effects of fault steps on the rupture termination of these events. The results show good correlations between the type and length of steps with the seismic rupture and a poor correlation between the step number and seismic rupture. For different magnitude intervals, the smallest widths of the fault steps (Lt) that can terminate the rupture propagation are variable: Lt = 3 km for Ms 6.5 6.9, Lt = 4 km for Ms 7.0 7.5, Lt = 6 km for Ms 7.5 8.0, and Lt = 8 km for Ms 8.0 8.5. The dilational fault step is easier to rupture through than the compression fault step. The smallest widths of the fault step for the rupture arrest can be used as an indicator to judge the scale of the rupture termination of seismic faults. This is helpful for research on fault segmentation, as well as estimating the magnitude of potential earthquakes, and is thus of significance for the assessment of seismic risks.

Tectonic inheritance, reactivation and long term fault weakening processes

NASA Astrophysics Data System (ADS)

Holdsworth, Bob

2017-04-01

This talk gives a geological review of weakening processes in faults and their long-term effect on reactivation and tectonic inheritance during crustal deformation. Examples will be drawn from the Atlantic margins, N America, Japan and the Alps. Tectonic inheritance and reactivation are fundamentally controlled by the processes of stress concentration and shear localisation manifested at all scales in the continental lithosphere. Lithosphere-scale controls include crustal thickness, thermal age and the boundary conditions imposed by the causative plate tectonic processes during extension. At the other end of the scale range, grain-scale controls include local environmental controls (depth, stress, strain rate), rock composition, grainsize, fabric intensity and the presence of fluids or melt. Intermediate-scale geometric controls are largely related to the size, orientation and interconnectivity of pre-existing anisotropies. If reactivation of pre-existing structures occurs, it likely requires a combination of processes across all three scale ranges to be favourable. This can make the unequivocal recognition of inheritance and reactivation difficult. Large (e.g. crustal-scale) pre-existing structures are especially important due to their ability to efficiently concentrate stress and localise strain. For big faults (San Andreas, Great Glen, Median Tectonic Line), detailed studies of the associated exposed fault rocks indicate that reactivation is linked to the development of strongly anisotropic phyllosilicate-rich fault rocks that are weak (e.g. friction coefficients as low as 0.2 or less) under a broad range of deformation conditions. In the case of pre-existing regional dyke swarms (S Atlantic, NW Scotland) - which may themselves track deep mantle fabrics at depth - multiple reactivation of dyke margins is widespread and may preclude reactivation of favourably oriented local basement fabrics. In a majority of cases, pre-existing structures in the crust are

Frictional melting experiments investigate coseismic behaviour of pseudotachylyte-bearing faults in the Outer Hebrides Fault Zone, UK.

NASA Astrophysics Data System (ADS)

Campbell, L.; De Paola, N.; Nielsen, S. B.; Holdsworth, R.; Lloyd, G. E. E.; Phillips, R. J.; Walcott, R.

2015-12-01

Recent experimental studies, performed at seismic slip rates (≥ 1 m/s), suggest that the friction coefficient of seismic faults is significantly lower than at sub-seismic (< 1 mm/s) speeds. Microstructural observations, integrated with theoretical studies, suggest that the weakening of seismic faults could be due to a range of thermally-activated mechanisms (e.g. gel, nanopowder and melt lubrication, thermal pressurization, viscous flow), triggered by frictional heating in the slip zone. The presence of pseudotachylyte within both exhumed fault zones and experimental slip zones in crystalline rocks suggests that lubrication plays a key role in controlling dynamic weakening during rupture propagation. The Outer Hebrides Fault Zone (OHFZ), UK contains abundant pseudotachylyte along faults cutting varying gneissic lithologies. Our field observations suggest that the mineralogy of the protolith determines volume, composition and viscosity of the frictional melt, which then affects the coseismic weakening behaviour of the fault and has important implications for the magnitudes and distribution of stress drops during slip episodes. High velocity friction experiments at 18 MPa axial load, 1.3 ms-1 and up to 10 m slip were run on quartzo-feldspathic, metabasic and mylonitic samples, taken from the OHFZ in an attempt to replicate its coseismic frictional behaviour. These were configured in cores of a single lithology, or in mixed cores with two rock types juxtaposed. All lithologies produce a general trend of frictional evolution, where an initial peak followed by transient weakening precedes a second peak which then decays to a steady state. Metabasic and felsic single-lithology samples both produce sharper frictional peaks, at values of μ = 0.19 and μ= 0.37 respectively, than the broader and smaller (μ= 0.15) peak produced by a mixed basic-felsic sample. In addition, both single-lithology peaks occur within 0.2 m slip, whereas the combined-lithology sample displays a

Bouguer gravity and crustal structure of the Dead Sea transform fault and adjacent mountain belts in Lebanon

NASA Astrophysics Data System (ADS)

Kamal; Khawlie, Mohamad; Haddad, Fuad; Barazangi, Muawia; Seber, Dogan; Chaimov, Thomas

1993-08-01

The northern extension of the Dead Sea transform fault in southern Lebanon bifurcates into several faults that cross Lebanon from south to north. The main strand, the Yammouneh fault, marks the boundary between the Levantine (eastern Mediterranean) and Arabian plates and separates the western mountain range (Mount Lebanon) from the eastern mountain range (Anti-Lebanon). Bouguer gravity contours in Lebanon approximately follow topographic contours; i.e., positive Bouguer anomalies are associated with the Mount Lebanon and Anti-Lebanon ranges. This suggests that the region is not in simple isostatic compensation. Gravity observations based on 2.5-dimensional modeling and other available geological and geophysical information have produced the following interpretations. (1) The crust of Lebanon thins from ˜35 km beneath the Anti-Lebanon range, near the Syrian border, to ˜27 km beneath the Lebanese coast. No crustal roots exist beneath the Lebanese ranges. (2) The depth to basement is ˜3.5-6 km below sea level under the ranges and is ˜8-10 km beneath the Bekaa depression. (3) The Yammouneh fault bifurcates northward into two branches; one passes beneath the Yammouneh Lake through the eastern part of Mount Lebanon and another bisects the northern part of the Bekaa Valley (i.e., Mid-Bekaa fault). The Lebanese mountain ranges and the Bekaa depression were formed as a result of transtension and later transpression associated with the relative motion of a few crustal blocks in response to the northward movement of the Arabian plate relative to the Levantine plate.

Model-Based Fault Tolerant Control

NASA Technical Reports Server (NTRS)

Kumar, Aditya; Viassolo, Daniel

2008-01-01

The Model Based Fault Tolerant Control (MBFTC) task was conducted under the NASA Aviation Safety and Security Program. The goal of MBFTC is to develop and demonstrate real-time strategies to diagnose and accommodate anomalous aircraft engine events such as sensor faults, actuator faults, or turbine gas-path component damage that can lead to in-flight shutdowns, aborted take offs, asymmetric thrust/loss of thrust control, or engine surge/stall events. A suite of model-based fault detection algorithms were developed and evaluated. Based on the performance and maturity of the developed algorithms two approaches were selected for further analysis: (i) multiple-hypothesis testing, and (ii) neural networks; both used residuals from an Extended Kalman Filter to detect the occurrence of the selected faults. A simple fusion algorithm was implemented to combine the results from each algorithm to obtain an overall estimate of the identified fault type and magnitude. The identification of the fault type and magnitude enabled the use of an online fault accommodation strategy to correct for the adverse impact of these faults on engine operability thereby enabling continued engine operation in the presence of these faults. The performance of the fault detection and accommodation algorithm was extensively tested in a simulation environment.

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)

NASA Astrophysics Data System (ADS)

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.