shallow creep on the haiyuan fault gansu china revealed by sar interferometry interferometric synthetic aperture radar data are used to map the interseismic velocity field along the haiyuan fault system hfs at the north eastern boundary of the tibetan plateau two m 8 earthquakes ruptured the hfs in 1920 and 1927 but its 260 km long central section known as the tianzhu seismic gap remains unbroken since 1000 years the envisat sar data spanning the 2003 2009 period cover about 200 300 km2 along three descending and two ascending tracks interferograms are processed using an adapted version of roi pac the signal due to stratified atmospheric phase delay is empirically corrected together with orbital residuals mean line of sight velocity maps are computed using a constrained time series analysis after selection of interferograms with low atmospheric noise these maps show a dominant left lateral motion across the hfs and reveal a narrow 35 km long zone of high velocity gradient across the fault in between the tianzhu gap and the 1920 rupture we model the observed velocity field using a discretized fault creeping at shallow depth and a least squares inversion the inferred shallow slip rate distribution reveals aseismic slip in between two fully locked segments the average creep rate is 5 mm yr 1 comparable in magnitude with the estimated loading rate at depth suggesting no strain accumulation on this segment the modeled creep rate locally exceeds the long term rate reaching 8 mm yr 1 suggesting transient creep episodes the present study emphasizes the need for continuous monitoring of the surface velocity in the vicinity of major seismic gaps in terms of seismic hazard assessment

seismotectonic and seismicity of makran a bimodal subduction zone se iran abstract the present study combined spatial distribution and mechanism of seismicity seismicity parameters geomorphology in satellite imagery and tectonic features in makran inland to show that the makran low angle thrust fault is divided into two separate segments depth dispersal of earthquakes especially relocated events shows that the sinking plate is steeper in the west than in the east of makran significant facts were identified from the variation of moho depth between west and east slip rates of the inland faults and crustal shortenings in the north of makran the sistan suture zone plays a significant role in dividing the overriding plate into a non deforming helmand block and a less deforming lut block these blocks have different resistances against the northward subduction large and great events such as the 1989 chabahar mw 5 5 and 1945 gwadur mw 8 1 occurred in the south of subduction fronts of the western and eastern makran respectively they occurred in shallow depth and were the pieces of evidence of weak and strong coupling between the oceanic and continental crusts on a low angle and a very low angle reverse faults respectively spectral analysis and depth determination of the instrumental and pre instrumental earthquakes respectively helped to separate some plate boundary and intraplate events this separation geometry and non characteristic behavior of the subduction zone revealed from spatial and temporal distribution of the earthquakes probably dedicate a mature aleutian type for the subduction zone in the east missing great m 6 1 earthquakes less slip rate of the continental faults and steeper dipping of the sinking plate in the west probably indicate a kurile type for the iranian part of subduction makran is a bimodal subduction because geomorphological and seismic pieces of evidence indicate a nnw surficial and right lateral fracture zone in the continental crust and a nw deep and left lateral fracture zone in the oceanic crust respectively the fractures and geometry of subductions showed that the eastern makran has seismotectonically a wider area for potential coupling of a larger earthquake than the western makran

great thrust earthquakes and aseismic slip along the plate boundary of the makran subduction zone the makran subduction zone of iran and pakistan exhibits strong variation in seismicity between its eastern and western segments and has one of the world s largest forearcs we determine the source parameters for 14 earthquakes at makran including the great mw 8 1 earthquake of 1945 the only instrumentally recorded great earthquake at makran we determine the loci of seismic and aseismic slip along the plate boundary and we assess the effects of the large forearc and accretionary wedge on the style of plate boundary slip we apply body waveform inversions and for small magnitude events use first motions of p waves to estimate earthquake source parameters for the 1945 event we also employ dislocation modeling of uplift data we find that the earthquake of 1945 in eastern makran is an interplate thrust event that ruptured approximately one fifth the length of the subduction zone nine smaller events in eastern makran that are also located at or close to the plate interface have thrust mechanisms similar to that of the 1945 shock seaward of these thrust earthquakes lies the shallowest 70 80 km of the plate boundary we find that this segment and the overlying accretionary wedge remain aseismic both during and between great earthquakes this aseismic zone as in other subduction zones lies within that part of the accretionary wedge that consists of largely uconsolidated sediments seismic velocities less than 4 0 km s the existence of thrust earthquakes indicates that either the sediments along the plate boundary in eastern makran become sufficiently well consolidated and de watered about 70 km from the deformation front or older lithified rocks are present within the forearc so that stick slip sliding behavior becomes possible this study shows that a large quantity of unconsolidated sediment does not necessarily indicate a low potential for great thrust earthquakes in contrast to the east the plate boundary in western makran has no clear record of historic great events nor has modem instrumentation detected any shallow thrust events for at least the past 25 years most earthquakes in western makran occur within the downgoing plate at intermediate depths the large change in seismicity between eastern and western makran along with two shallow events that exhibit right lateral strike slip motion in central makran suggest segmentation of the subduction zone two paleozoic continental blocks dominate the overriding plate the boundary between them is approximately coincident with the transition in seismicity although relative motion between these blocks may account for some of the differing seismic behavior the continuity of the deformation front and of other tectonic features along the subduction zone suggests that the rate of subduction does not change appreciably from east to west the absence of plate boundary events in western makran indicates either that entirely aseismic subduction occurs or that the plate boundary is currently locked and experiences great earthquakes with long repeat times evidence is presently inconclusive concerning which of these two hypotheses is most correct the presence of well defined late holocene marine terraces along portions of the coasts of eastern and western makran could be interpreted as evidence that both sections of the arc are capable of generating large plate boundary earthquakes if that hypothesis is correct then western makran could produce a great earthquake or it could rupture as a number of segments in somewhat smaller magnitude events alternatively it is possible that western makran is significantly different from eastern makran and experiences largely aseismic slip at all times a knowledge of the velocity structure and nature of the state of consolidation or lithification of rocks at depth in the interior portion of the forearc of western makran should help to ascertain whether that portion of the plate boundary moves aseismically or ruptures in large to great earthquakes a resolution of this question has important implications for seismic hazard not only for western makran but also for other margins such as the cascadia subduction zone of western north america where historical thrust events have not occurred

focal mechanisms of earthquakes related to the 29 november 1975 kalapana hawaii earthquake the effect of structure models initial focal mechanism determinations for the 29 november 1975 kalapana hawaii earthquake indicated discrepancy between the mechanism determined from teleseismic data by ando and the mechanism determined using data from the local u s geological survey network surrounding the epicenter region the resolution of this difference is crucial to correctly understand this earthquake as well as to understand the tectonics of the south flank of kilauea volcano when a model with a low velocity layer at the base of the crust is used for projection back to the focal sphere for the local network mechanisms the discrepancy vanishes to further investigate this result focal mechanisms were determined using several contrasting models for a set of well recorded earthquakes a large number of these earthquakes have mechanisms identical to the main shock when the low velocity layer model is used dispersion of p and t axes is also minimized by use of this model a low angle slip direction favored for the main shock and typical of most other solutions exhibits remarkable stability normal to the east rift zone of kilauea our results suggest a tectonic model similar in nature to that proposed by ando in which the south flank of kilauea consists of a mobile block of crust which is relatively free to move laterally on a low strength zone at about 10 km depth forceful injection of magma along the rift zones provides the loading stress which is released by catastrophic failure in the weak horizontal layer in a cycle of perhaps 100 yr

the structure and fault activity of the makran accretionary prism the makran subduction zone has the highest incoming sediment thickness up to 7 5 km of any subduction zone these sediments have formed a wide accretionary prism 400 km seismicity in the makran is generally low however the margin experienced an mw 8 1 earthquake in 1945 which generated a significant regional tsunami seismic reflection data and swath bathymetry data from offshore pakistan are used to analyze the structure and fault activity of the outer accretionary prism the outer prism has a simple structure of seaward verging imbricate thrust faults many continuous for over 100 km along strike fault activity is analyzed using basin stratigraphy and fault geometry revealing a frontal continuously active zone a central intermittently active zone and a landward inactive zone over 75 of the faults in the seaward 70 km of the prism show evidence for recent activity the decollement occurs within the lower sediment section but steps onto the top basement surface in regions of elevated basement topography fault spacing 6 km and taper 4 5 are comparable to other margins such as s hikurangi cascadia and nankai suggesting that high sediment input is not leading to an unusual prism structure the decollement is unreflective which is unexpected considering other prism characteristics predicting a weak surface and may suggest a potentially stronger decollement than previously predicted this study provides a significant advance in our understanding of the structure of an end member convergent margin and demonstrates that systematic analyses of accretionary prism structure can help to elucidate subduction zone dynamics with ultimate relevance to seismogenic potential

the 2013 mw 7 7 balochistan earthquake seismic potential of an accretionary wedge great earthquakes rarely occur within active accretionary prisms despite the intense long term deformation associated with the formation of these geologic structures this paucity of earthquakes is often attributed to partitioning of deformation across multiple structures as well as aseismic deformation within and at the base of the prism davis et al 1983 we use teleseismic data and satellite optical and radar imaging of the 2013 m w 7 7 earthquake that occurred on the southeastern edge of the makran plate boundary zone to study this unexpected earthquake we first compute a multiple point source solution from w phase waveforms to estimate fault geometry and rupture duration and timing we then derive the distribution of subsurface fault slip from geodetic coseismic offsets we sample for the slip posterior probability density function using a bayesian approach including a full description of the data covariance and accounting for errors in the elastic structure of the crust the rupture nucleated on a subvertical segment branching out of the chaman fault system and grew into a major earthquake along a 50 north dipping thrust fault with significant along strike curvature fault slip propagated at an average speed of 3 0 km s for about 180 km and is concentrated in the top 10 km with no displacement on the underlying decollement this earthquake does not exhibit significant slip deficit near the surface nor is there significant segmentation of the rupture we propose that complex interaction between the subduction accommodating the arabia eurasia convergence to the south and the ornach nal fault plate boundary between india and eurasia resulted in the significant strain gradient observed prior to this earthquake convergence in this region is accommodated both along the subduction megathrust and as internal deformation of the accretionary wedge

interseismic strain accumulation along the western boundary of the indian subcontinent 1 despite an overall sinistral slip rate of 3 cm yr few major earthquakes have occurred in the past 200 years along the chaman fault system the western boundary of the india plate with the eurasia plate gps and insar data reported here indicate sinistral shear velocities of 8 17 mm yr across the westernmost branches of the fault system suggesting that a significant fraction of the plate boundary slip is distributed in the fold and fault belt to the east at its southernmost on land segment 26 n near the triple junction between the arabia eurasia and india plates we find the velocity across the ornach nal fault is 15 1 13 4 16 9 mm yr with a locking depth probably less than 3 km at latitude 30 n near the town of chaman pakistan where a m6 5 earthquake occurred in 1892 the velocity is 8 5 6 8 10 3mm yr and the fault is locked at approximately 3 4 km depth at latitude 33 n and further north insar data indicate a velocity across the chaman fault of 16 8 2 7 mm yr the width of the plate boundary varies from several km in the south where we observe 2 mm yr of convergence near the westernmost strike slip faults to a few hundreds of km in the north where we observe 6 9 mm yr of convergence and where the faulting becomes distinctly transpressional the shallow locking depth along much of the transform system suggests that earthquakes larger than those that have occurred in the historical record would be unexpected and that the recurrence interval of those earthquakes that have occurred is of the order of one or two centuries similar in length to the known historical record

the 2012 sumatra great earthquake sequence the equatorial indian ocean is a well known place of active intraplate deformation defying the conventional view of rigid plates separated by narrow boundaries where deformation is confined on 11 april 2012 this region was hit in a couple of hours by two of the largest strike slip earthquakes ever recorded moment magnitudes mw 8 6 and 8 2 broadband seismological observations of the mw 8 6 mainshock indicate a large centroid depth 30 km and remarkable rupture complexity detailed study of the surface wave directivity and moment rate functions clearly indicates the partition of the rupture into at least two distinct subevents to account for these observations we developed a procedure to invert for multiple point source parameters the optimum source model at long period consists of two point sources separated by about 209 km with magnitudes mw 8 5 and 8 3 to explain the remaining discrepancies between predicted and observed surface waves we can refine this model by adding directivity along the wnw ese axis however we do not exclude more complicated models to analyze the mw 8 2 aftershock we removed the perturbation due to large surface wave arrivals of the mw 8 6 mainshock by subtracting the corresponding synthetics computed for the two subevent model analysis of the surface wave amplitudes suggests that the mw 8 2 aftershock had a large centroid depth between 30 km and 40 km this major earthquake sequence brings a new perspective to the seismotectonics of the equatorial indian ocean and reveals active deep lithospheric deformation

ball and socket tectonic rotation during the 2013 mw7 7 balochistan earthquake abstract the september 2013 m w 7 7 balochistan earthquake ruptured a 200 km long segment of the curved hoshab fault in southern pakistan with 10 0 2 m of peak sinistral and 1 7 0 8 m of dip slip this rupture is unusual because the fault dips 60 15 towards the focus of a small circle centered in northwest pakistan and despite a 30 increase in obliquity along strike the ratios of strike and dip slip remain relatively uniform surface displacements and geodetic and teleseismic source inversions quantify a bilateral rupture that propagated rapidly at shallow depths from a transtensional jog near the northern end of the rupture static friction prior to rupture was unusually weak 0 05 and friction may have approached zero during dynamic rupture here we show that the inward dipping hoshab fault defines the northern rim of a structural unit in southeast makran that rotates akin to a 2 d ball and socket joint counter clockwise in response to india s penetration into the eurasian plate this rotation accounts for complexity in the chaman fault system and in principle reduces seismic potential near karachi nonetheless these findings highlight deficiencies in strong ground motion equations and tectonic models that invoke anderson byerlee faulting predictions

the 2 look tops mode design and demonstration with terrasar x burst mode acquisition schemes achieve wide coverage at the expense of a degraded azimuth resolution reducing therefore the performance on the retrieval of ground displacements in the azimuth direction when interferometric acquisitions are combined moreover the azimuth varying line of sight can induce discontinuities in the interferometric phase when local azimuth displacements are present e g due to ground deformation in this contribution we propose the interferometric 2 look terrain observation by progressive scans tops mode a sustaining innovation which records bursts of radar echoes of two separated slices of the doppler spectrum the spectral separation allows to exploit spectral diversity techniques achieving sensitivities to azimuth displacements better than with stripmap and eliminating discontinuities in the interferometric phase moreover some limitations of the tops mode to compensate ionospheric perturbations in terms of data gaps or restricted sensitivity to azimuth shifts are overcome the design of 2 look tops acquisitions will be provided taking the terrasar x system as reference to derive achievable performances the methodology for the retrieval of the azimuth displacement is exposed for the case of using pairs of images as well as for the calculation of mean azimuth velocities when working with stacks we include results with experimental terrasar x acquisitions demonstrating its applicability for both scenarios

convergence rate across the nepal himalaya and interseismic coupling on the main himalayan thrust implications for seismic hazard we document geodetic strain across the nepal himalaya using gps times series from 30 stations in nepal and southern tibet in addition to previously published campaign gps points and leveling data and determine the pattern of interseismic coupling on the main himalayan thrust fault mht the noise on the daily gps positions is modeled as a combination of white and colored noise in order to infer secular velocities at the stations with consistent uncertainties we then locate the pole of rotation of the indian plate in the itrf 2005 reference frame at longitude 1 34 3 31 latitude 51 4 0 3 with an angular velocity of 0 5029 0 0072 myr the pattern of coupling on the mht is computed on a fault dipping 10 to the north and whose strike roughly follows the arcuate shape of the himalaya the model indicates that the mht is locked from the surface to a distance of approximately 100 km down dip corresponding to a depth of 15 to 20 km in map view the transition zone between the locked portion of the mht and the portion which is creeping at the long term slip rate seems to be at the most a few tens of kilometers wide and coincides with the belt of midcrustal microseismicity underneath the himalaya according to a previous study based on thermokinematic modeling of thermochronological and thermobarometric data this transition seems to happen in a zone where the temperature reaches 350 c the convergence between india and south tibet proceeds at a rate of 17 8 0 5 mm yr in central and eastern nepal and 20 5 1 mm yr in western nepal the moment deficit due to locking of the mht in the interseismic period accrues at a rate of 6 6 0 4 10 19 nm yr on the mht underneath nepal for comparison the moment released by the seismicity over the past 500 years including 14 m w 7 earthquakes with moment magnitudes up to 8 5 amounts to only 0 9 10 19 nm yr indicating a large deficit of seismic slip over that period or very infrequent large slow slip events no large slow slip event has been observed however over the 20 years covered by geodetic measurements in the nepal himalaya we discuss the magnitude and return period of m 8 earthquakes required to balance the long term slip budget on the mht

surface slip and off fault deformation patterns in the 2013 mw 7 7 balochistan pakistan earthquake implications for controls on the distribution of near surface coseismic slip comparison of 398 fault offsets measured by visual analysis of worldview high resolution satellite imagery with deformation maps produced by cosi corr subpixel image correlation of landsat 8 and spot5 imagery reveals significant complexity and distributed deformation along the 2013 mw 7 7 balochistan pakistan earthquake average slip along the main trace of the fault was 4 2 m with local maximum offsets up to 11 4 m comparison of slip measured from offset geomorphic features which record localized slip along the main strand of the fault to the total displacement across the entire width of the surface deformation zone from cosi corr reveals 45 off fault deformation while previous studies have shown that the structural maturity of the fault exerts a primary control on the total percentage of off fault surface deformation large along strike variations in the percentage of strain localization observed in the 2013 rupture imply the influence of important secondary controls one such possible secondary control is the type of near surface material through which the rupture propagated we therefore compared the percentage off fault deformation to the type of material bedrock old alluvium and young alluvium at the surface and the distance of the fault to the nearest bedrock outcrop a proxy for sediment thickness along this hybrid strike slip reverse slip fault we find significantly more off fault deformation in younger and or thicker sediments accounting for and predicting such off fault deformation patterns has important implications for the interpretation of geologic slip rates especially for their use in probabilistic seismic hazard assessments the behavior of near surface materials during coseismic deformation and the future development of microzonation protocols for the built environment

accounting for uncertain fault geometry in earthquake source inversions i theory and simplified application the ill posed nature of earthquake source estimation derives from several factors including the quality and quantity of available observations and the fidelity of our forward theory observational errors are usually accounted for in the inversion process epistemic errors which stem from our simplified description of the forward problem are rarely dealt with despite their potential to bias the estimate of a source model in this study we explore the impact of uncertainties related to the choice of a fault geometry in source inversion problems the geometry of a fault structure is generally reduced to a set of parameters such as position strike and dip for one or a few planar fault segments while some of these parameters can be solved for more often they are fixed to an uncertain value we propose a practical framework to address this limitation by following a previously implemented method exploring the impact of uncertainties on the elastic properties of our models we develop a sensitivity analysis to small perturbations of fault dip and position the uncertainties of our fixed fault geometry are included in the inverse problem under the formulation of the misfit covariance matrix that combines both prediction and observation uncertainties we validate this approach with the simplified case of a fault that extends infinitely along strike using both bayesian and optimization formulations of a static slip inversion if epistemic errors are ignored predictions are overconfident in the data and slip parameters are not reliably estimated in contrast inclusion of uncertainties in fault geometry allows us to infer a robust posterior slip model epistemic uncertainties can be many orders of magnitude larger than observational errors for great earthquakes mw 8 not accounting for uncertainties in fault geometry may partly explain observed shallow slip deficits for continental earthquakes similarly ignoring the impact of epistemic errors can also bias estimates of near surface slip and predictions of tsunamis induced by megathrust earthquakes

horizontal coseismic deformation of the 1999 chi chi earthquake measured from spot satellite images implications for the seismic cycle along the western foothills of central taiwan 1 the 1999 chi chi earthquake mw 7 6 broke a major thrust fault along the western foothills of the central range of taiwan we have measured the horizontal coseismic displacement field by correlating optical satellite images acquired before and after the earthquake these data reveal the fault trace and a clockwise rotation of surface displacements toward the north with much larger displacements and strain in the hanging wall at the surface coseismic slip increases from 5 6 m near the epicenter to 10 11 m to the north in the epicentral area we observe a left lateral strike slip zone trending n125 e and farther north a fault zone trending n s with a right lateral component the data were modeled using elastic dislocations the fault geometry consists of a shallow

fault creep rates of the chaman fault afghanistan and pakistan inferred from insar the chaman fault is the major strike slip structural boundary between the india and eurasia plates despite sinistral slip rates similar to the north america pacific plate boundary no major m7 earthquakes have been documented along the chaman fault indicating that the fault either creeps aseismically or is at a late stage in its seismic cycle recent work with remotely sensed interferometric synthetic aperture radar insar time series documented a heterogeneous distribution of fault creep and interseismic coupling along the entire length of the chaman fault including an 125 km long creeping segment and an 95 km long locked segment within the region documented in this study here i present additional insar time series results from the envisat and alos radar missions spanning the southern and central chaman fault in an effort to constrain the locking depth dip and slip direction of the chaman fault i find that the fault deviates little from a vertical geometry and accommodates little to no fault normal displacements peak documented creep rates on the fault are 9 12 mm yr accounting for 25 33 of the total motion between india and eurasia and locking depths in creeping segments are commonly shallower than 500 m the magnitude of the 1892 chaman earthquake is well predicted by the total area of the 95 km long coupled segment to a first order the heterogeneous distribution of aseismic creep combined with consistently shallow locking depths suggests that the southern and central chaman fault may only produce small to moderate earthquakes m7

source inversion of w phase speeding up seismic tsunami warning w phase is a long period phase arriving before s wave it can be interpreted as superposition of the fundamental first second and third overtones of spheroidal modes or rayleigh waves and has a group velocity from 4 5 to 9 km s 1 over a period range of 100 1000 s the amplitude of long period waves better represents the tsunami potential of an earthquake because of the fast group velocity of w phase most of w phase energy is contained within a short time window after the arrival of the p wave at a distance of 50 w phase energy is contained within 23 min after the origin time which is the distinct advantage of using w phase for rapid tsunami warning purposes we use a time domain deconvolution method to extract w phases from the broad band records of global seismic networks the bandwidth of w phase is approximately from 0 001 to 0 01 hz and we bandpass filter the data from 0 001 to 0 005 hz in most cases having extracted w phase from the vertical component records we perform a linear inversion using a point source to determine mw and the source mechanism for several large earthquakes including the 2004 sumatra andaman earthquake the 2005 nias earthquake the 2006 kuril is earthquake and the 2007 sumatra earthquake w phase inversion yields reliable solutions and holds promise of the use of w phase for rapid assessment of tsunami potential

coseismic deformation of the 2001 mw 7 8 kokoxili earthquake in tibet measured by synthetic aperture radar interferometry the 14 november 2001 m w 7 8 kokoxili earthquake ruptured more than 400 km of the westernmost stretch of the left lateral kunlun fault in northern tibet interferometric synthetic aperture radar data from descending orbits along four adjacent tracks covering almost the entire rupture and 1 m pixel ikonos satellite images are used to map the rupture geometry and the surface displacements produced by the event interferograms are then inverted to solve for coseismic slip on the fault at depth the radar data show that the rupture connected the heituo fault where the earthquake initiated to the main kunlun fault cutting across a pull apart trough in between the two strike slip faults the fault model includes two vertical sections extending to a depth of 20 km and discretized into 5 km 5 km patches using a nonnegative least squares method that includes an appropriate degree of smoothing we solve for the left lateral slip on each fault patch our solution shows that the largest slip occurred at depths between 0 and 5 km reaching 8 m in two areas 200 and 250 km east of the earthquake epicenter significant slip took place below 10 km at both ends of the rupture slip appears to have been highly variable along the fault defining six sections of major moment release these sections correspond to six subsegments of the kunlun fault system defined from the surface morphology of the fault this suggests that fault geometry exerted a predominant influence on controlling the rupture propagation

on and off fault deformation associated with the september 2013 mw 7 7 balochistan earthquake implications for geologic slip rate measurements abstract the 24 september 2013 mw7 7 balochistan pakistan earthquake ruptured a 200 km long stretch of the hoshab fault in southern pakistan and produced the second largest lateral surface displacement observed for a continental strike slip earthquake we remotely measured surface deformation associated with this event using high resolution 0 5 m pre and post event satellite optical imagery we document left lateral near field on fault offsets 10 m from fault using 309 laterally offset piercing points such as streams terrace risers and roads peak near field displacement is 13 6 2 5 3 4 m we characterize off fault deformation by measuring medium 350 m from fault displacement using manual 259 measurements and automated image cross correlation methods respectively off fault peak lateral displacement values are 15 m and exceed on fault displacement magnitudes for 85 of the rupture length our observations suggest that for this rupture coseismic surface displacement typically increases with distance away from the surface trace of the fault however nearly 100 of total surface displacement occurs within a few hundred meters of the primary fault trace furthermore off fault displacement accounts for on average 28 of the total displacement but exhibits a highly heterogeneous along strike pattern the best agreement between near field and far field displacements generally corresponds to the narrowest fault zone widths our analysis demonstrates significant and heterogeneous mismatches between on and off fault coseismic deformation and we conclude that this phenomenon should be considered in hazard models based on geologically determined on fault slip rates

hierarchical interlocked orthogonal faulting in the 2019 ridgecrest earthquake sequence a nearly 20 year hiatus in major seismic activity in southern california ended on 4 july 2019 with a sequence of intersecting earthquakes near the city of ridgecrest california this sequence included a foreshock with a moment magnitude mw of 6 4 followed by a mw 7 1 mainshock nearly 34 hours later geodetic seismic and seismicity data provided an integrative view of this sequence which ruptured an unmapped multiscale network of interlaced orthogonal faults this complex fault geometry persists over the entire seismogenic depth range the rupture of the mainshock terminated only a few kilometers from the major regional garlock fault triggering shallow creep and a substantial earthquake swarm the repeated occurrence of multifault ruptures as revealed by modern instrumentation and analysis techniques poses a formidable challenge in quantifying regional seismic hazards

relation between continental strike slip earthquake segmentation and thickness of the crust 1 high resolution maps of large continental strike slip earthquake surface ruptures show that they are formed of fault segments these segments are bounded by fault bends step overs or combinations of the two the lowest limit in size for such segments may not be relevant in the understanding of earthquake mechanics as it pertains to the granular properties of fault zones the maximum limit in segment length however is important as it is directly relates to the maximum extent of seismic rupture to measure the length of the segments a new quantitative method based on piecewise linear fitting is developed and is used to automatically retrieve segments from earthquake rupture maps next this approach is tested against a set of ten continental strike slip earthquake ruptures derived from similar high quality maps the test suggests that segments have a maximum length of 18 km independent of regional tectonic setting slip inversions for earthquakes based on seismological and or geodetic data most often are not unique and can show some variability even for one particular event some basic characteristics however such as total moment release or general source geometry seem to persist that are relevant to earthquake mechanics measurements of the maximum horizontal extent of individual slip patches derived from seismic source inversion for strike slip ruptures show that their strike dimension does not increase infinitely with magnitude but instead reaches a maximum value of 25 km these two independent lines of observations complemented by earlier data and analog experiments suggest that it is the thickness of the seismogenic crust that controls the structural scaling of the length of seismic segments and that it is independent of the ultimate size of individual earthquakes

slip rates along the chaman fault implication for transient strain accumulation and strain partitioning along the western indian plate margin abstract the chaman fault in western pakistan marks the western collision boundary between the indian and eurasian plates and connects the makran subduction zone to the himalayan convergence zone geomorphic scale slip rates along an active strand of the chaman fault are added to the sporadic data set of this poorly investigated transform system field investigations coupled with high resolution geoeye 1 satellite data of an alluvial fan surface bostankaul alluvial fan show 1150 m left lateral offset by the fault since the formation of the alluvial fan surface a weighted mean 10be exposure age of 34 8 3 kyr for the bostankaul alluvial surface yields a slip rate of 33 3 3 0 mm yr this rate agrees with the geologically defined slip rates along the chaman fault but is approximately twice as large as that inferred from the decade long global positioning system measurements of 18 1 mm yr the contrast in geomorphic and geodetic slip rates along the chaman fault like other major intra continental strike slip faults has two major implications 1 the geodetic rates might represent a period of reduced displacement as compared to the averaged late pleistocene rate because of transient variations in rates of elastic strain accumulation or 2 strain partitioning within the plate boundary zone while strain partitioning could be the reason of slip rate variations within the western indian plate boundary zone transient strain accumulation could explain contrasting slip rates along the chaman fault at this stage in its poorly understood seismic cycle

an indian ocean tsunami triggered remotely by an onshore earthquake in balochistan pakistan this paper describes and documents instrumentally recorded tsunami waves that are interpreted as secondary effects of a 7 7 magnitude earthquake in southern pakistan on 24 september 2013 the tsunami waves were almost unnoticed because the wave heights were low and the tsunami occurred at low tide the historical record of tsunami events within the arabian sea northern indian ocean is fragmentary large tsunamigenic earthquakes are known to be generated in the makran subduction zone the area that forms the boundary of the arabian and eurasian plates submarine sliding is reported along the owen fracture zone which marks the boundary between the arabian and indian plates hence the tsunami hazard potential within the arabian sea is enigmatic our analysis is based on sea level oscillations recorded at various tide gauge stations along the coastlines of oman pakistan and iran as well as eyewitness accounts of the event in oman our results indicate that the waves were in the range of 1 m or less in height they were first recorded along the eastern coast of oman and propagated toward the west we suggest that the waves must have been triggered by a submarine slide on the makran margin cascading effects resulting in large submarine slope failures within the arabian sea are more frequent than postulated the hazard potential is underestimated as such secondary effects of distant ruptures onshore were previously not taken into account

over 100 years of faults interaction stress accumulation and creeping implications on chaman fault system pakistan the curve shaped chaman transform fault between pakistan and afghanistan demarks the western boundary of the indian plate which is the locus of many catastrophic earthquakes and this is poorly studied region to understand the earthquake fault interaction and hazard assessment based on earthquake triggering theory we investigate a sequence of earthquakes comprising five earthquakes that occurred in the chaman fault system since 1892 our results elucidate that three out of four earthquakes are triggered by the preceding earthquakes the 1935 earthquake of magnitude mw 7 7 is somewhat an independent earthquake in this sequence slightly influenced by the 1892 event the 1935 earthquake significantly loaded either terminus of its rupture with positive stress which later triggered the 1975 earthquake with 35 of its rupture length where cfs is above triggering threshold value and 1990 earthquake with 44 of its rupture length in positive stress lobe on ghazaband fault in the south lobe since the 1935 earthquake significantly increased the cfs on either terminus of its rupture the 2013 earthquake with magnitude mw 7 7 occurred on hoshab fault in the positive stress zone with 23 of its rupture length where cfs is positive moreover the northern locked segment of cf the southern segment of gbf southeastern segment of hf and paf demonstrate a high value of cfs it could trigger seismicity in these regions thus requiring arrangements to mitigate any seismic hazards in future

mapping 3d fault geometry in earthquakes using high resolution topography examples from the 2010 el mayor cucapah mexico and 2013 balochistan pakistan earthquakes fault dips are usually measured from outcrops in the field or inferred through geodetic or seismological modeling here we apply the classic structural geology approach of calculating dip from a fault s 3 d surface trace using recent high resolution topography a test study applied to the 2010 el mayor cucapah earthquake shows very good agreement between our results and those previously determined from field measurements to obtain a reliable estimate a fault segment 120 m long with a topographic variation 15 m is suggested we then applied this method to the 2013 balochistan earthquake getting dips similar to previous estimates our dip estimates show a switch from north to south dipping at the southern end of the main trace which appears to be a response to local extension within a stepover we suggest that this previously unidentified geometrical complexity may act as the endpoint of earthquake ruptures for the southern end of the hoshab fault

adaptive regularization of earthquake slip distribution inversion abstract regularization is a routine approach used in earthquake slip distribution inversion to avoid numerically abnormal solutions to date most slip inversion studies have imposed uniform regularization on all the fault patches however adaptive regularization where each retrieved parameter is regularized differently has exhibited better performances in other research fields such as image restoration in this paper we implement an investigation into adaptive regularization for earthquake slip distribution inversion it is found that adaptive regularization can achieve a significantly smaller mean square error mse than uniform regularization if it is set properly we propose an adaptive regularization method based on weighted total least squares wtls this approach assumes that errors exist in both the regularization matrix and observation and an iterative algorithm is used to solve the solution a weight coefficient is used to balance the regularization matrix residual and the observation residual an experiment using four slip patterns was carried out to validate the proposed method the results show that the proposed regularization method can derive a smaller mse than uniform regularization and resolution based adaptive regularization and the improvement in mse is more significant for slip patterns with low resolution slip patches in this paper we apply the proposed regularization method to study the slip distribution of the 2011 mw 9 0 tohoku earthquake the retrieved slip distribution is less smooth and more detailed than the one retrieved with the uniform regularization method and is closer to the existing slip model from joint inversion of the geodetic and seismic data

some thoughts on the use of insar data to constrain models of surface deformation noise structure and data downsampling repeat pass interferometric synthetic aperture radar insar provides spatially dense maps of surface deformation with potentially tens of millions of data points here we estimate the actual covariance structure of noise in insar data we compare the results for several independent interferograms with a large ensemble of gps observations of tropospheric delay and discuss how the common approaches used during processing of insar data affects the inferred covariance structure motivated by computational concerns associated with numerical modeling of deformation sources we then combine the data covariance information with the inherent resolution of an assumed source model to develop an efficient algorithm for spatially variable data resampling or averaging we illustrate these technical developments with two earthquake scenarios at different ends of the earthquake magnitude spectrum for the larger events our goal is to invert for the coseismic fault slip distribution for smaller events we infer the hypocenter location and moment we compare the results of inversions using several different resampling algorithms and we assess the importance of using the full noise covariance matrix

stick slip advance of the kohat plateau in pakistan in the westernmost himalaya the indian plate is thought to slip beneath the potwar and kohat plateaux on a layer of viscous material in an entirely aseismic manner analysis of insar data from 1992 shows that slip occurred during a rare mw 6 0 earthquake implying that the kohat plateau is locally grounded

extended nucleation of the 1999 mw 7 6 izmit earthquake laboratory and theoretical studies suggest that earthquakes are preceded by a phase of developing slip instability in which the fault slips slowly before accelerating to dynamic rupture we report here that one of the best recorded large earthquakes to date the 1999 moment magnitude mw 7 6 izmit turkey earthquake was preceded by a seismic signal of long duration that originated from the hypocenter the signal consisted of a succession of repetitive seismic bursts accelerating with time and increased low frequency seismic noise these observations show that the earthquake was preceded for 44 minutes by a phase of slow slip occurring at the base of the brittle crust this slip accelerated slowly initially and then rapidly accelerated in the 2 minutes preceding the earthquake

earthquakes and associated deformation in northern baluchistan 1892 2001 we examine a century of seismicity and earthquake related deformation on the western margin of the indian plate in the pakistan region of northern baluchistan several catalogs of earthquakes for this region currently exist but early catalogs in particular suffer from errors incompleteness inhomogeneity and location bias we form a new catalog of more than 1000 earthquakes using original sources to confirm macroseismic locations and assign m s magnitudes to earthquakes since 1892 in doing so we reveal a systematic east northeast bias in locations caused largely by the uneven global distribution of seismic stations used in their determination an appendix provides narrative accounts and historical references to 34 significant earthquakes in the region the pattern of seismicity in the past century shows activity over a 700 km long 200 km wide segment of the plate boundary with predominantly strike slip faulting to the west and thrust faulting to the east at its narrowest near 29 n transpression of the plate boundary is partitioned into reverse and strike slip components separated by approximately 100 km the m 7 3 1931 mach earthquake slip 1 1 m on a 40 east southeast dipping reverse fault released fault normal stresses that may have unclamped the subsequent m 7 7 left lateral quetta earthquake 4 years later the northern chaman fault system in the past century has been largely inactive suggesting that this time period is not representative of long term activity in the region and that up to 4 m of potential slip is currently available to drive one or more future m 7 earthquakes despite triangulation installed in the late nineteenth and early twentieth centuries no recent geodetic data are available to permit plate boundary velocities to be measured directly

high interseismic coupling in the eastern makran pakistan subduction zone estimating the extent of interseismic coupling along subduction zone megathrusts is essential for quantitative assessments of seismic and tsunami hazards up to now quantifying the seismogenic potential of the eastern makran subduction zone at the northern edge of the indian ocean has remained elusive due to a paucity of geodetic observations furthermore non tectonic processes obscure the signature of accumulating elastic strain historical earthquakes of magnitudes greater than 7 have been reported in particular the 1945 mw 8 1 earthquake resulted in a significant tsunami that swept the shores of the arabian sea and the indian ocean a quantitative estimate of elastic strain accumulation along the subduction plate boundary in eastern makran is needed to confront previous indirect and contradictory conclusions about the seismic potential in the region here we infer the distribution of interseismic coupling on the eastern makran megathrust from time series of satellite interferometric synthetic aperture radar insar images acquired between 2003 and 2010 applying a consistent series of corrections to extract the low amplitude long wavelength deformation signal associated with elastic strain on the megathrust we find high interseismic coupling i e the megathrust does not slip and elastic strain accumulates in the central section of eastern makran where the 1945 earthquake occurred while lower coupling coincides spatially with the subduction of the sonne fault zone the inferred accumulation of elastic strain since the 1945 earthquake is consistent with the future occurrence of magnitude 7 earthquakes and we cannot exclude the possibility of a multi segment rupture mw 8 however the likelihood for such scenarios might be modulated by partitioning of plate convergence between slip on the megathrust and internal deformation of the overlying actively deforming accretionary wedge

surface waveform tomography of the turkish iranian plateau summary the middle east is a tectonically complex region consisting of terrains as diverse as precam brian shields and young orogens the dominant tectonic feature is the turkish iranian plateau a recently elevated seismically active region along the zagros bitlis suture which results from the collision of the arabian plate with eurasia in this study we use surface waveform tomography to elucidate the upper mantle shear wave velocity structure beneath the turkish iranian plateau and adjacent regions the main large scale feature in the tomographic model is a low shear wave velocity anomaly in the uppermost mantle beneath the plateau this low velocity feature correlates with a long wavelength free air gravity anomaly and with recent volcanism whose geochemistry has a lower lithospheric mantle signature seismology gravity and volcanism all suggest the presence of a thin lithosphere and warm upper mantle beneath the turkish iranian plateau the upper mantle low shear wave velocity zone the high free air gravity and the deep lithospheric source depth for the basaltic volcanism are all consistent with a partial delamination of the lithosphere as a result of earlier lithospheric thickening resulting from the continental collision

megathrust and accretionary wedge properties and behaviour in the makran subduction zone this work forms part of the nerc and esrc funded project earthquakes without frontiers and was partially supported by the nerc large grant looking inside the continents from space cp is funded by an nerc studentship the facilities of iris data services and specifically the iris data management center were used for access to waveforms related metadata and or derived products used in this study iris data services are funded through the seismological facilities for the advancement of geoscience and earthscope sage proposal of the national science foundation under cooperative agreement ear 1261681

coseismic slip distribution of the 2002 mw7 9 denali fault earthquake alaska determined from gps measurements 1 on 3 november 2002 an mw7 9 earthquake occurred in central alaska the earthquake ruptured portions of the susitna glacier denali and totschunda faults inversion of the gps measured displacement field indicates that the event was dominated by a complex right lateral strike slip rupture along the denali fault gps sites closest to the epicenter show the effect of thrust motion on the susitna glacier fault the preferred coseismic slip model with m w 7 8 indicates relatively low slip on the western part of the rupture and high slip from about 60 km east of the hypocenter extending to the junction of the denali and totschunda faults we find mostly shallow slip from the surface to 15 km depth but the inversion suggests one large deep slip patch about 110 km east of the hypocenter our model predicts surface slip in good agreement with surface geological observations where model resolution is good

a new multilayered visco elasto plastic experimental model to study strike slip fault seismic cycle nowadays technological advances in satellite imagery measurements as well as the development of dense geodetic and seismologic networks allow for a detailed analysis of surface deformation associated with active fault seismic cycle however the study of earthquake dynamics faces several limiting factors related to the difficulty to access the deep source of earthquake and to integrate the characteristic time scales of deformation processes that extend from seconds to thousands of years to overcome part of these limitations and better constrain the role and couplings between kinematic and mechanical parameters we have developed a new experimental approach allowing for the simulation of strike slip fault earthquakes and analyze in detail hundreds of successive seismic cycle model rheology is made of multilayered visco elasto plastic analog materials to account for the mechanical behavior of the upper and lower crust and to allow simulating brittle ductile coupling postseismic deformation phase and far field stress transfers the kinematic evolution of the model surface is monitored using an optical system based on subpixel spectral correlation of high resolution digital images first results show that the model succeed in reproducing the deformation mechanisms and surface kinematics associated to the main phases of the seismic cycle indicating that model scaling is satisfactory these results are comforted by using numerical algorithms to study the strain and stress distribution at the surface and at depth along the fault plane our analog modeling approach appears then as an efficient complementary approach to investigate earthquake dynamics

empirical constraints on magnitude distance relationships for seismically induced submarine tsunamigenic landslides abstract seismically induced submarine landslide tsunamis here called silts attract growing attention due to their unique setting damage potential and short warning time a question of key importance especially for tsunami early warning is how far can an earthquake trigger a tsunamigenic slump here we investigate the relationships between earthquake magnitude and the maximal distance between the seismogenic fault and the tsunamigenic slumps rf and between the earthquake epicenter and the slump re and propose empirical constraints on these magnitude distance m d relations the 49 identified silts are spread in various seismotectonic and bathymetric settings in different seas around the globe we found that the maximal distance of the tsunamigenic submarine landslide from the parent earthquake grows with the magnitude and is bounded by an envelope constrained by mw as low as 4 9 for several kilometers the 1968 liguria coast italy and as far as 250 km for mw 7 7 the 1819 rann of kachchh india higher earthquake magnitudes also produce silts seemingly distances lower than 250 km however it is suspected that the available data is limited and unable to reflect the true nature of silt s generation generalized empirical relations between the earthquake magnitude mw and the maximal distance from the seismogenic fault to its generated silt rf in km are log rf 1 17 0 49 mw r2 0 78 the empirical distance between the earthquake epicenter and the corresponding tsunamigenic slump re in km is log re 0 87 0 45 mw r2 0 83 although many earthquakes within the m d bounding envelope did not produce tsunamis the successful events still enable the delineation of the m d zone vulnerable to tsunami generation which in turn can be applied to tsunami early warning procedures this is particularly important for near coast inland earthquakes as their tsunamigenic potential might be overlooked

w phase source inversion for moderate to large earthquakes 1990 2010 rapid characterization of the earthquake source and of its effects is a growing field of interest until recently it still took several hours to determine the first order attributes of a great earthquake e g m w 7 5 even in a well instrumented region the main limiting factors were data saturation the interference of different phases and the time duration and spatial extent of the source rupture to accelerate centroid moment tensor cmt determinations we have developed a source inversion algorithm based on modelling of the w phase a very long period phase 100 1000 s arriving at the same time as the p wave the purpose of this work is to finely tune and validate the algorithm for large to moderate sized earthquakes using three components of w phase ground motion at teleseismic distances to that end the point source parameters of all m w 6 5 earthquakes that occurred between 1990 and 2010 815 events are determined using federation of digital seismograph networks global seismographic network broad band stations and sts1 global virtual networks of the incorporated research institutions for seismology data management center for each event a preliminary magnitude obtained from w phase amplitudes is used to estimate the initial moment rate function half duration and to define the corner frequencies of the passband filter that will be applied to the waveforms starting from these initial parameters the seismic moment tensor is calculated using a preliminary location as a first approximation of the centroid a full cmt inversion is then conducted for centroid timing and location determination comparisons with harvard and global cmt solutions highlight the robustness of w phase cmt solutions at teleseismic distances the differences in m w rarely exceed 0 2 and the source mechanisms are very similar to one another difficulties arise when a target earthquake is shortly e g within 10 hr preceded by another large earthquake which disturbs the waveforms of the target event to deal with such difficult situations we remove the perturbation caused by earlier disturbing events by subtracting the corresponding synthetics from the data the cmt parameters for the disturbed event can then be retrieved using the residual seismograms we also explore the feasibility of obtaining source parameters of smaller earthquakes in the range 6 0 mw 6 5 results suggest that the w phase inversion can be implemented reliably for the majority of earthquakes of mw 6 or larger

the 2005 mw 7 6 kashmir earthquake sub pixel correlation of aster images and seismic waveforms analysis we analyze the m w 7 6 kashmir earthquake of october 8 2005 using sub pixel correlation of aster images to measure ground deformation and modeling seismic waveforms the surface rupture is continuous over a distance of 75 km and cuts across the hazara syntaxis reactivating the tanda and the muzaffarabad faults north of muzaffarabad the surface rupture coincides approximately with the mbt on the southwestern flank of the syntaxis although the two faults have opposite dip angles the rupture terminates abruptly at the hairpin turn of the mbt showing a strong structural control the fault offset is 4 m on average and peaks to 7 m northwest of muzaffarabad the rupture lasted about 25 s and propagated updip and bi laterally 2 km s with a rise time of 2 5 s the shallowness and compactness of the rupture both in time and space provide an explanation for the intensity of destructions this kind of analysis could be achieved as soon as a post earthquake image is available and would provide key information for early assessment of damages the study sheds some light on seismic hazard in the himalaya and raises concern regarding the possibility of a repetition of the 1555 event which presumably ruptured the himalayan front south of the kashmir basin and may have reached a magnitude m w 8

gps constraints on continental deformation in the africa arabia eurasia continental collision zone and implications for the dynamics of plate interactions 1 the gps derived velocity field 1988 2005 for the zone of interaction of the arabian african nubian somalian and eurasian plates indicates counterclockwise rotation of a broad area of the earth s surface including the arabian plate adjacent parts of the zagros and central iran turkey and the aegean peloponnesus relative to eurasia at rates in the range of 20 30 mm yr this relatively rapid motion occurs within the framework of the slow moving 5 mm yr relative motions eurasian nubian and somalian plates the circulatory pattern of motion increases in rate toward the hellenic trench system we develop an elastic block model to constrain present day plate motions relative euler vectors regional deformation within the interplate zone and slip rates for major faults substantial areas of continental lithosphere within the region of plate interaction show coherent motion with internal deformations below 1 2 mm yr including central and eastern anatolia turkey the southwestern aegean peloponnesus the lesser caucasus and central iran geodetic slip rates for major block bounding structures are mostly comparable to geologic rates estimated for the most recent geological period 3 5 myr we find that the convergence of arabia with eurasia is accommodated in large part by lateral transport within the interior part of the collision zone and lithospheric shortening along the caucasus and zagros mountain belts around the periphery of the collision zone in addition we find that the principal boundary between the westerly moving anatolian plate and arabia east anatolian fault is presently characterized by pure left lateral strike slip with no fault normal convergence this implies that extrusion is not presently inducing westward motion of anatolia on the basis of the observed kinematics we hypothesize that deformation in the africa arabia eurasia collision zone is driven in large part by rollback of the subducting african lithosphere beneath the hellenic and cyprus trenches aided by slab pull on the southeastern side of the subducting arabian plate along the makran subduction zone we further suggest that the separation of arabia from africa is a response to plate motions induced by active subduction

coseismic and early post seismic slip associated with the 1999 izmit earthquake turkey from sar interferometry and tectonic field observations summary we use combined tectonic field observations and sar data to determine an improved model of the slip associated with the 1999 izmit earthquake which ruptured the north anatolian fault at the eastern end of the sea of marmara the leading goal is to understand the main features of the coseismic and post seismic deformation which are captured together in the sar data to achieve this we make a critical analysis of the ers1 2 sar data which allows atmospheric effects to be identified and removed we also use detailed field mapping and measurements of the earthquake surface rupture dislocations in elastic half space and a forward modelling strategy allow us to obtain a slip model by steps a trial and error approach is combined with conventional inversion techniques to determine the slip in the different regions of the fault the sar data are well explained with three main zones of high slip along the fault releasing a total moment of 2 3 10 20 nm mw 7 6 which is higher than the seismological estimates 1 7 2 0 10 20 n m the inhomogeneous slip distribution correlates with fault segments identified at the surface the izmit rupture appears to have extended 30 km west of the hersek peninsula into the sea of marmara with slip tapering fro m2mt ozero the western end of the rupture is located 40 km sse from istanbul we show that some features seen near to mudurnu and gevye and previously interpreted as slip on secondary faults are explained mostly as atmospheric effects correlated with the topography using our approach and the available gps data we obtain a slip model that represents the coseismic slip alone which suggests that the moment release during the main shock was 1 9 10 20 nm mw 7 5 consistent with the seismological estimates we conclude that the sar data include the effects of 2 m of fast after slip during the month following the main shock within a zone of the fault located 12 24 km below the epicentral region near the hypocentre at a depth of 18 km the fault appears to have experienced dynamic slip of 1 m associated with the main shock followed by 2 m of rapidly decelerating post seismic shear during the following month we suggest that the distribution of heterogeneous slip and loading along the different fault segments may be important factors controlling the propagation of large earthquake ruptures along the north anatolian fault

coseismic deformation from the 1999 mw 7 1 hector mine california earthquake as inferred from insar and gps observations we use interferometric synthetic aperture radar insar and global positioning system gps observations to investigate static deformation due to the 1999 m w 7 1 hector mine earthquake that occurred in the eastern california shear zone interferometric decorrelation phase and azimuth offset measurements indicate regions of surface and near surface slip which we use to constrain the geometry of surface rupture the inferred geometry is spatially complex with multiple strands the southern third of the rupture zone consists of three subparallel segments extending about 20 km in length in a n45 w direction the central segment is the simplest with a single strand crossing the bullion mountains and a strike of n10 w the northern third of the rupture zone is characterized by multiple splays with directions subparallel to strikes in the southern and central the average strike for the entire rupture is about n30 w the interferograms indicate significant along strike variations in strain which are consistent with variations in the ground based slip measurements using a variable resolution data sampling routine to reduce the computational burden we invert the insar and gps data for the fault geometry and distribution of slip we compare results from assuming an elastic half space and a layered elastic space results from these two elastic models are similar although the layered space model predicts more slip at depth than does the half space model the layered model predicts a maximum coseismic slip of more than 5 m at a depth of 3 to 6 km contrary to preliminary reports the northern part of the hector mine rupture accommodates the maximum slip our model predictions for the surface fault offset and total seismic moment agree with both field mapping results and recent seismic models the inferred shallow slip deficit is enigmatic and may suggest that distributed inelastic yielding occurred in the uppermost few kilometers of the crust during or soon after the earthquake

the 2013 mw 7 7 balochistan earthquake energetic strike slip reactivation of a thrust fault we analyse the mw 7 7 balochistan earthquake of 09 24 2013 based on ground surface deformation measured from sub pixel correlation of landsat 8 images combined with back projection and finite source modeling of teleseismic waveforms the earthquake nucleated south of the chaman strike slip fault and propagated southwestward along the hoshab fault at the front of the kech band the rupture was mostly unilateral propagated at 3 km s on average and produced a 200 km surface fault trace with purely strike slip displacement peaking to 10 m and averaging around 6 m the finite source model shows that slip was maximum near the surface although the hoshab fault is dipping by 45 to the north in accordance with its origin as a thrust fault within the makran accretionary prism slip was nearly purely strike slip during that earthquake large seismic slip on such a non optimally oriented fault was enhanced possibly due to the influence of the free surface on dynamic stresses or to particular properties of the fault zone allowing for strong dynamic weakening strike slip faulting on thrust fault within the eastern makran is interpreted as due to eastward extrusion of the accretionary prism as it bulges out over the indian plate portions of the makran megathrust some thrust faults in the kirthar range and strike slip faults within the chaman fault system have been brought closer to failure by this earthquake aftershocks cluster within the chaman fault system north of the epicenter opposite to the direction of rupture propagation by contrast few aftershocks were detected in the area of maximum moment release in this example aftershocks cannot be used to infer earthquake characteristics

three dimensional boundary integral modeling of spontaneous earthquake sequences and aseismic slip 1 fault processes involve complex patterns of seismic events and aseismic slip this work develops a three dimensional 3 d methodology for simulating long term history of spontaneous seismic and aseismic slip on a vertical planar strike slip fault subjected to slow tectonic loading our approach reproduces all stages of earthquake cycles from accelerating slip before dynamic instability to rapid dynamic propagation of earthquake rupture to postseismic slip and to interseismic creep including aseismic transients we use the developed 3 d methodology to study interaction of fault slip with a small patch of higher normal stress over long term slip history for uniform initial prestress dynamic rupture is significantly affected by the stronger patch in the first simulated event but not in subsequent ones the change in behavior is due to redistribution of shear stress by prior slip which demonstrates that distributions of fault strength and stress are related and illustrates the importance of simulating long slip histories even in studies of dynamic rupture despite no long term effect on dynamic rupture the small patch of higher normal stress influences nucleation processes and hence long term slip patterns in the model comparison of the fully dynamic simulations and a widely used quasi dynamic approach shows that the quasi dynamic approach modifies long term slip patterns in addition to resulting in much smaller slip velocities and rupture speeds during dynamic events we show that the response of quasi dynamic formulations with reduced radiation damping terms can be scaled to match the results of the standard quasi dynamic formulation and hence cannot improve the comparison

a bayesian method for incorporating self similarity into earthquake slip inversions distributions of coseismic slip help illuminate many properties of earthquakes including fault geometry stress changes frictional properties and potential future hazard slip inversions take observations and calculate slip at depth but there are a number of commonly adopted assumptions such as minimizing the second spatial derivative of slip the laplacian that have little physical basis and potentially bias the result in light of growing evidence that fault slip shows fractal properties we suggest that this information should be incorporated into slip inversions as a form of regularization instead of laplacian smoothing we have developed a bayesian approach to efficiently solve for slip incorporating von karman regularization in synthetic tests our approach retrieves fractal slip better than laplacian regularization as expected but even performs comparably or better when the input slip is not fractal we apply this to the 2014 mw 6 0 napa valley earthquake on a two segment fault using interferometric synthetic aperture radar insar and global positioning system gps data we find the von karman and laplacian inversions give similar slip magnitude but in different locations and the von karman solution has much tighter confidence bounds on slip than the laplacian solution differences in earthquake slip due to the regularization technique could have important implications for the interpretation and modeling of stress changes on the causative and neighboring faults we therefore recommend that choice of regularization method should be routinely made explicit and justified and that von karman regularization is a better default than laplacian