shallow fault zone dilatancy recovery after the 2003 bam earthquake in iran earthquakes radiate from slip on discrete faults but also commonly involve distributed deformation within a broader fault zone especially near the surface variations in rock strain during an earthquake are caused by heterogeneity in the elastic stress before the earthquake by variable material properties and geometry of the fault zones and by dynamic processes during the rupture stress changes due to the earthquake slip both dynamic and static have long been thought to cause dilatancy in the fault zone that recovers after the earthquake decreases in the velocity of seismic waves passing through the fault zone due to coseismic dilatancy have been observed followed by postseismic seismic velocity increases during healing dilatancy and its recovery have not previously been observed geodetically here we use interferometric analysis of synthetic aperture radar images to measure postseismic surface deformation after the 2003 bam iran earthquake and show reversal of coseismic dilatancy in the shallow fault zone that causes subsidence of the surface this compaction of the fault zone is directly above the patch of greatest coseismic slip at depth the dilatancy and compaction probably reflects distributed shear and damage to the material during the earthquake that heals afterwards coseismic and postseismic deformation spread through a fault zone volume may resolve the paradox of shallow slip deficits for some strike slip fault ruptures

lithospheric structure and along strike segmentation of the central andean plateau seismic q magmatism flexure topography and tectonics the central andean plateau is a 300 km wide nearly 4 km high plateau which is situated above a 30 e dipping segment of the subducted nazca plate systematic changes in the topography the upper mantle seismic attenuation q structure the lithospheric flexural rigidity and the distribution and chemistry of back arc lavas indicate that the upper mantle structure changes along strike beneath the plateau south of 23 s the upper mantle beneath the plateau becomes hotter and the lithosphere becomes thinner and weaker this lateral variation in upper mantle structure coincides with variations in the tectonic style and timing of deformation in two physiographically distinct segments of the plateau and its adjacent foreland thrust belt to the east the bolivian altiplano and subandean ranges in the north and the argentine puna and santa barbara system in the south the segments different mantle lid thicknesses result in an altiplano supported mainly by crustal thickening and a puna supported by a combination of a crustal root and a thermal mantle root a thicker stronger foreland lithosphere in the north favors thin skinned underthrusting of the foreland beneath the plateau while to the south the thinner weaker lithosphere allows more basement involved shortening within the foreland and less underthrusting beneath the plateau a weaker lithosphere results in a longer period of compressional deformation and greater local and structural relief in the puna than in the relatively stable altiplano to the north ultimately this observed n s directed segmentation on the plateau and in the foreland may reflect the different responses of strong and weak continental lithosphere to an andean type subduction margin

extension during continental convergence with application to the tibetan plateau the tibetan plateau is the product of crustal thickening caused by the collision between india and asia and is the largest active example of extensional tectonics in a zone of continental collision throughout most of the tertiary the tectonics of the plateau were dominated by north south shortening a significant proportion of which took place on east west striking thrust faults for the last 5 m y or so the plateau has been thinning by the mechanism of extension on north south trending normal faults previous investigations of the collision have been able to account for the large scale features of the tertiary deformation but have failed to explain the transition in the late tertiary to quaternary strain rate field of the plateau from north south compression to east west extension the transition could in principle be effected by a reduction in the rate of convergence between india and asia or by a uniform reduction in strength of the whole continental lithosphere of asia it could not however be effected by a reduction in strength of the elevated region alone this produces increased compressional strain rates in the weakened zone an alternative explanation for the transition to extension comes from considering the thermal evolution of thickened continental lithosphere the lower part of the lithosphere consists of a thermal boundary layer which when thickened by horizontal shortening is colder and denser than its surroundings convective instability of the thickened thermal boundary layer and its replacement by hot asthenosphere would rapidly raise the surface elevation and gravitational potential energy of the overlying part of the lithosphere the convective instability would happen in a time brief compared with the collision time scale 50 m y in the case of india and asia but would only occur after there had already been substantial thickening of the lithosphere numerical experiments show that for a range of lithospheric parameters the increase in surface height as much as 2 km and of potential energy 5 to 10 1012 n m 1 resulting from convective instability of the lower lithosphere are sufficient for east west extension to replace north south compression as the dominant feature of the stress field of the tibetan plateau

the lost inca plateau cause of flat subduction beneath peru abstract since flat subduction of the nazca plate beneath peru was first recognized in the 1970s and 1980s a satisfactory explanation has eluded researchers we present evidence that a lost oceanic plateau inca plateau has subducted beneath northern peru and propose that the combined buoyancy of inca plateau and nazca ridge in southern peru supports a 1500 km long segment of the downgoing slab and shuts off arc volcanism this conclusion is based on an analysis of the seismicity of the subducting nazca plate the structure and geochemistry of the marquesas plateau as well as tectonic reconstructions of the pacific farallon spreading center 34 to 43 ma these restore three sub parallel pacific oceanic plateaus the austral tuamotu and marquesas to two farallon plate counterparts the iquique and nazca ridges inca plateau is apparently the sixth and missing piece in an ensemble of v shaped hotspot tracks formed at on axis positions we argue the mirror image of the inca plateau the marquesas plateau is an ancient edifice overprinted by recent volcanism in disagreement with the widely accepted young

observations and modeling of coseismic and postseismic deformation due to the 2015 mw 7 8 gorkha nepal earthquake we use space geodetic data to investigate coseismic and postseismic deformation due to the 2015 mw 7 8 gorkha earthquake that occurred along the central himalayan arc because the earthquake area is characterized by strong variations in surface relief and material properties we developed finite element models that explicitly account for topography and 3 d elastic structure we computed the line of sight displacement histories from three tracks of the sentinel 1a b interferometric synthetic aperture radar insar satellites using persistent scatter method insar observations reveal an uplift of up to 70 mm over 20 months after the main shock concentrated primarily at the downdip edge of the ruptured asperity gps observations also show uplift as well as southward movement in the epicentral area qualitatively similar to the coseismic deformation pattern kinematic inversions of gps and insar data and forward models of stress driven creep suggest that the observed postseismic transient is dominated by afterslip on a downdip extension of the seismic rupture a poroelastic rebound may have contributed to the observed uplift and southward motion but the predicted surface displacements are small we also tested a wide range of viscoelastic relaxation models including 1 d and 3 d variations in the viscosity structure models of a low viscosity channel previously invoked to explain the long term uplift and variations in topography at the plateau margins predict opposite signs of horizontal and vertical displacements compared to those observed our results do not preclude a possibility of deep seated viscoelastic response beneath southern tibet with a characteristic relaxation time greater than the observation period 2 years

coseismic slip model of the 2007 august pisco earthquake peru as constrained by wide swath radar observations summary the pisco earthquake m w 8 0 2007 august 15 occurred offshore of peru s southern coast at the subduction interface between the nazca and south american plates it ruptured a previously identified seismic gap along the peruvian margin we use wide swath insar observations acquired by the envisat satellite in descending and ascending orbits to constrain coseismic slip distribution of this subduction earthquake the data show movement of the coastal regions by as much as 85 cm in the line of sight of the satellite distributed slip model indicates that the coseismic slip reaches values of about 5 5 m at a depth of 18 20 km the slip is confined to less than 40 km depth with most of the moment release located on the shallow parts of the interface above 30 km depth the region with maximum coseismic slip in the insar model is located offshore close to the seismic moment centroid location the geodetic estimate of seismic moment is 1 23 10 21 nm m w 8 06 consistent with seismic estimates the slip model inferred from the insar observations suggests that the pisco earthquake ruptured only a portion of the seismic gap zone in peru between 13 5 s and 14 5 s hence there is still a significant seismic gap to the south of the 2007 event that has not experienced a large earthquake since at least 1687

finite fault inversion of dinsar coseismic displacement of the 2009 l aquila earthquake central italy 1 we define the geometric and kinematic characteristics of the fault activated during the mw 6 3 6 april 2009 l aquila earthquake from the modeling of envisat and cosmo skymed the first ever x band interferogram inverted for a coseismic dislocation study dinsar interferograms our best fit solution for the main shock is represented by a normal fault 16 km long and 12 km wide with a small right lateral component dipping 47 sw with a maximum slip of 90 cm although the seismic dislocation probably ended at 1 km depth the updip projection of the fault plane corresponds to the northern segment of the mapped paganica s demetrio fault where alignment of surface breaks was observed in the field the absence of this fault in existing seismic source catalogues suggests that an improved approach involving detailed surface and subsurface geological and geophysical investigations is needed for a better assessment of the seismic hazard at the local scale

normal faulting sequence in the pumqu xainza rift constrained by insar and teleseismic body wave seismology normal faulting earthquakes play an important role in the deformation of continents and pose significant seismic hazard yet important questions remain about their mechanics we use insar and body wave seismology to compute dislocation models and centroid moment solutions for four normal faulting earthquakes mw 5 7 6 2 that occurred in the pumqu xainza rift pxr southern tibet a region where low angle normal faulting has previously been inferred we also use the fault locations and slip to investigate the correlation between earthquakes and surface topography and to calculate stress interactions between the earthquakes the insar and body wave models give consistent focal mechanisms except for the magnitude of the 1996 event which may be overestimated due to postseismic deformation in the long interval interferograms we calculate the static stress changes due to coseismic slip and find that the 1993 event was too distant to cause triggering of the later events but that the 1998 event pair occurred in regions of increased coulomb stress resulting from the 1996 event all the fault planes found here dip at 40 60 reinforcing the absence in observations for low angle normal faulting earthquakes dip 30 whose focal planes can be determined unambiguously the fault planes of the 1993 and 1996 events are not associated with any obvious surface geomorphology suggesting that sometimes it is unreliable to resolve the focal plane ambiguity by geomorphology even for mw 6 2 events furthermore these events occurred outside the center of the rift indicating that the active faulting is more distributed and over a length scale at least 25 50 km east west in extent rather than confined to the 20 km width seen in the current mapped faulting and topography these results suggest that seismic hazard in other extensional zones worldwide might also be more broadly distributed than suggested by geomorphology

interseismic coupling and seismic potential along the central andes subduction zone we use about two decades of geodetic measurements to characterize interseismic strain build up along the central andes subduction zone from lima peru to antofagasta chile these measurements are modeled assuming a 3 plate model nazca andean sliver and south america craton and spatially varying interseismic coupling isc on the nazca megathrust interface we also determine slip models of the 1996 m w 7 7 nazca the 2001 m w 8 4 arequipa the 2007 m w 8 0 pisco and the m w 7 7 tocopilla earthquakes we find that the data require a highly heterogeneous isc pattern and that overall areas with large seismic slip coincide with areas which remain locked in the interseismic period with high isc offshore lima where the isc is high a m w 8 6 8 8 earthquake occurred in 1746 this area ruptured again in a sequence of four m w 8 0 earthquakes in 1940 1966 1974 and 2007 but these events released only a small fraction of the elastic strain which has built up since 1746 so that enough elastic strain might be available there to generate a m w 8 5 earthquake the region where the nazca ridge subducts appears to be mostly creeping aseismically in the interseismic period low isc and seems to act as a permanent barrier as no large earthquake ruptured through it in the last 500 years in southern peru isc is relatively high and the deficit of moment accumulated since the m w 8 8 earthquake of 1868 is equivalent to a magnitude m w 8 4 earthquake two asperities separated by a subtle aseismic creeping patch are revealed there this aseismic patch may arrest some rupture as happened during the 2001 arequipa earthquake but the larger earthquakes of 1604 and 1868 were able to rupture through it in northern chile isc is very high and the rupture of the 2007 tocopilla earthquake has released only 4 of the elastic strain that has accumulated since 1877 the deficit of moment which has accumulated there is equivalent to a magnitude m w 8 7 earthquake this study thus provides elements to assess the location size and magnitude of future large megathurst earthquakes in the central andes subduction zone caveats of this study are that interseismic strain of the forearc is assumed time invariant and entirely elastic also a major source of uncertainty is due to fact that the available data place very little constraints on interseismic coupling at shallow depth near the trench except offshore lima where sea bottom geodetic measurements have been collected suggesting strong coupling

fold evolution matrices and axial surface analysis of fault bend folds application to the medina anticline eastern cordillera colombia the medina anticline is a fault bend fold located in the hanging wall of the aguaclara fault along the southeastern thrust front of the eastern cordillera of colombia a petroleum province with giant fields we employ a modified technique of axial surface analysis using fold evolution matrices which helps define the subsurface geometry and thereby provides important constraints on trap geometry modeling of hydrocarbon migration pathways and prediction of reservoir quality

shallow slip deficit due to large strike slip earthquakes in dynamic rupture simulations with elasto plastic off fault response summary slip inversions of geodetic data from several large magnitude 7 strike slip earthquakes point to coseismic slip deficit at shallow depths 3 4 km that is coseismic slip appears to decrease towards the earth surface while the inferred slip distribution may be consistent with laboratory derived rate and state friction laws suggesting that the uppermost brittle crust may be velocity strengthening there remains a question of how the coseismic slip deficit is accommodated throughout the earthquake cycle the consequence of velocity strengthening fault friction at shallow depths is that the deficit of coseismic slip is relieved by post seismic afterslip and interseismic creep however many seismic events with inferred shallow slip deficit were not associated with either resolvable shallow interseismic creep or robust shallow afterslip hence the origin of shallow slip deficit remains uncertain in this study we investigate whether inelastic failure in the shallow crust due to dynamic earthquake rupture can explain the inferred deficit of shallow slip evidence for such failure is emerging from geologic seismic and geodetic observations we find that the amount of shallow slip deficit is proportional to the amount of inelastic deformation near the earth surface such deformation occurs under a wide range of parameters that characterize rock strength in the upper crust however the largest magnitude of slip deficit in models accounting for off fault yielding is 2 4 times smaller than that inferred from kinematic inversions of geodetic data to explain this discrepancy we further explore to what extent assumptions in the kinematic inversions may bias the inferred slip distributions inelastic deformation in the shallow crust reduces coseismic strain near the fault introducing an additional artificial deficit of up to 10 per cent of the maximum slip in inversions of geodetic data that are based on purely elastic models the largest magnitude of slip deficit in our models combined with the bias in inversions accounts for up to 25 per cent of shallow slip deficit which is comparable but still smaller than 30 60 per cent deficit inferred from kinematic inversions we discuss potential mechanisms that may account for the remaining discrepancy between slip deficit predicted by elasto plastic rupture models and that inferred from inversions of space geodetic data

geometry and structural evolution of the central andean backthrust belt bolivia the central andean backthrust belt is a large scale west vergent thrust system along the western side of the eastern cordillera in the generally east vergent andean fold thrust belt of bolivia although west vergent structures in the central andes have been recognized previously we describe the backthrust belt at a regional scale emphasizing its implications for the kinematic development of the andes and the subsequent influence of these kinematics on amounts of tectonic shortening we use techniques such as line length balancing restorability and the viability of the progressive development of the structures to construct balanced cross sections across the backthrust belt and altiplano the cross sections are taken to a regional depth of detachment basement to examine the relationship between mapped surface structures and inferred subsurface structures the relationship of the backthrust belt to the altiplano suggests that the altiplano basin is a crustal scale piggyback basin created as a basement megathrust propagated up and over a half crustal scale ramp located just west of the physiographic boundary of the eastern cordillera this basement megathrust was the means by which a narrow paleocene fold thrust belt located to the west of the altiplano propagated eastward and emerged in the present eastern cordillera the relationship between the basement thrusts and the physiographic boundaries of the central andean plateau as defined by isacks 1988 suggests that extensive megathrust sheets involving crystalline basement or quartzite may play an important role in the formation of orogenic plateaus the kinematic development of the andean fold thrust belt indicates that the backthrust belt developed as a taper building mechanism after the basement megathrust overextended the system eastward the mechanism proposed in this study for the development of the central andean backthrust belt requires a minimum of 200 km of shortening within the altiplano eastern cordillera alone this increases minimum shortening estimates across the fold thrust belt in bolivia to as much as 300 340 km

accurate source depths and focal mechanisms of shallow earthquakes in western south america and in the new hebrides island arc synthetic seismograms are matched to long period p waveforms in order to obtain accurate depths of shallow earthquakes with known focal mechanisms accurate depths are obtained for a large sample of moderate sized 6 ms 7 events which produced relatively simple p waveforms and do not require intensive analysis the estimated error in the determination of depth is about 5 km or less for most of the events considered the procedure is applied to two suites of events one in south america 83 events and one in the new hebrides 61 events in these two areas of contrasting styles of subduction the accurate depths provide new information on the bending of descending plates near trenches the seismicity and tectonics of the upper plate and the geometry and structure of the zone of contact between the upper and descending plates depths of suboceanic earthquakes which occurred near the trench and which have either tensional and compressional horizontal stress axes agree well with chapple and forsyth s 1979 preferred model of a bending elastic perfectly plastic plate however an unusually deep event occurred beneath the fiji plateau in an area of young ocean floor supposed to have been formed by sea floor spreading processes only since late miocene time the calculated depth of the event 48 km places it below the lithosphere asthenosphere boundary derived from thermal models vertical cross sections through the shallow parts of the subduction zones show that most of the earthquakes with thrust faulting focal mechanisms can be interpreted to be interplate events located in a thin 10 km thick curved zone of contact dipping arcward or landward from the trench axis however a few events with focal mechanisms similar to the interplate events do not fit on the inferred thin zone of contact these events would be accommodated by an interplate zone 15 km thick in both subduction zones interplate events occur at depths between about 15 and 50 km however the downdip width of the south american interplate zone is 2 to 3 times larger than that in the new hebrides most of the intraplate events near the interplate boundary are located in the descending plate in the upper plate seismicity is more pronounced in the back arc regions of the two subduction zones thus our results support the generality of a relatively aseismic zone in the upper plate located trenchward of the magmatic arc depths of shallow earthquakes in the eastern andes and sub andean regions of south america range between about 9 and 36 km indicating that both the upper and middle crust are seismically active about 75 of the events occurred in the upper 25 km furthermore the focal mechanisms indicate that from ecuador to argentina the crust of the eastern side of the andean cordilleran is in a state of east west compression oriented nearly parallel to the direction of convergence between the nazca and south american plates the depths the orientations of the earthquake nodal planes and the close relationships to quaternary tectonics imply basement involved crustal shortening in much of the eastern andes and sub andean zones of peru and argentina

seismicity and shape of the subducted nazca plate an updated compilation of earthquake locations and focal mechanism solutions from the international seismological centre and preliminary determination of earthquakes is the basis of a comprehensive study of the geometry of the wadati benioff zone beneath western south america the new data support previous mapping of a sharp flexure rather than a tear in the subducted nazca plate beneath southern peru and provide evidence for a similar flexure in the southward transition from nearly horizontal subduction to a slab with 30 dip at latitude 33 s in contrast the transition from 30 slab dip beneath bolivia to a nearly horizontal dip in the region between 28 s 32 s is more gradual occurring over several hundred kilometers of along strike distance between 20 s and 32 s this southward flattening corresponds to a broadening of a horizontal benchlike part of the subducted plate formed between 100 and 125 km depth the transition in continental tectonic style near 27 s 28 s from a wide volcanically active plateau to a narrow nonvolcanic cordillera appears not to be associated with the main slab flattening which begins to the north of these latitudes but with a more abrupt change in curvature of the subducted slab from convex upward to concave upward immediately below the plate boundary interface the concept of gaussian curvature is applied to slab bending to explain how subduction geometry is affected by the shape of the south american plate we hypothesize that the polarity of vertical curvature in the subducting slab is governed by the orientation of lateral curvature of the plate margin focal mechanism solutions for intermediate and deep earthquakes are grouped by geographic region and inverted for the orientation and relative magnitudes of the principal stresses results of the inversion indicate that downdip extension dominates in the slab above 350 km while downdip compression dominates at greater depths

a comparison of groundwater dating with 81kr 36cl and 4he in four wells of the great artesian basin australia the isotopic ratios 81 kr kr and 36 cl cl and the 4 he concentrations measured in groundwater from four artesian wells in the western part of the great artesian basin gab in australia are discussed based on radioactive decay along a water flow path the 81 kr kr ratios are directly converted to groundwater residence times results are in a range of 225 400 kyr with error bars in the order of 15 primarily due to counting statistics in the cyclotron accelerator mass spectrometer measurement additional uncertainties from subsurface production and or exchange with stagnant porewaters in the confining shales appear to be of the same order of magnitude these 81 kr ages are then used to calibrate the 36 cl and the 4 he dating methods based on elemental analyses of rock samples from the sandstone aquifer as well as from the confining bulldog shale the in situ flux of thermal neutrons and the corresponding 3 he 4 he and 36 cl cl ratios are calculated from a comparison of i the 3 he 4 he ratios measured in the groundwater samples with the calculated in situ ratios in rocks and ii the measured n 37 cl ratios with the 4 he concentrations measured in groundwater it is concluded that both helium and chloride are most likely added to the aquifer from sources in the stagnant porewaters of the confining shale by diffusion and or mixing based on this working hypothesis the 36 cl transport equation in groundwater is solved taking into account i radioactive decay ii subsurface production in the sandstone aquifer with an in situ 36 cl cl ratio of 6u10 315 and iii addition of chloride from a source in the confining shale with a 36 cl cl ratio of 13u10 315 lacking better information it is assumed that the chloride concentration increased linearly with time from an unknown initial value ci to its

surface displacements and source parameters of the 2003 bam iran earthquake from envisat advanced synthetic aperture radar imagery 1 the mw 6 6 26 december 2003 bam iran earthquake was one of the first earthquakes for which envisat advanced synthetic aperture radar asar data were available using interferograms and azimuth offsets from ascending and descending tracks we construct a three dimensional displacement field of the deformation due to the earthquake elastic dislocation modeling shows that the observed deformation pattern cannot be explained by slip on a single planar fault which significantly underestimates eastward and upward motions se of bam we find that the deformation pattern observed can be best explained by slip on two subparallel faults eighty five percent of moment release occurred on a previously unknown strike slip fault running into the center of bam with peak slip of over 2 m occurring at a depth of 5 km the remainder occurred as a combination of strike slip and thrusting motion on a southward extension of the previously mapped bam fault 5 km to the east

tandem afterslip on connected fault planes following the 2008 nima gaize tibet earthquake 1 on 9 january 2008 a m 6 4 normal faulting earthquake occurred in central tibet near the border of nima and gaize counties and just north of the bangong nujiang suture zone a week later a m 5 9 aftershock occurred a few kilometers to the northwest of the main shock here we consider interferometric synthetic aperture radar insar data from the japanese alos and european envisat satellites covering both the coseismic phase and 9 months of postseismic deformation the coseismic interferograms clearly show surface deformation resulting from both main shock and aftershock ruptures and data inversions using elastic dislocation models suggest that two northwest dipping faults form a synthetic system with the more steeply dipping aftershock plane meeting the main shock plane at depth postseismic interferograms show first order similarities with their coseismic counterparts indicating that afterslip occurred on both main shock and aftershock rupture surfaces during the months following the earthquakes the afterslip occurred at comparable depths to the coseismic slip but the amount of slip was about an order of magnitude smaller a slip template method is used to obtain moment release estimates at different postseismic time intervals and hence document the time dependence of the postseismic transient the exponential decay time of the afterslip is 34 days and the moment release due to the afterslip was about 10 of the coseismic moment models of viscoelastic stress relaxation in a maxwell half space place a strong lower bound on midcrust to lower crustal viscosity of 3 1017 pa s postseismic data covering a longer time span have the potential to improve this constraint

probing the mechanical properties of seismically active crust with space geodesy study of the coseismic deformation due to the 1992 mw7 3 landers southern california earthquake 1 the coseismic deformation due to the 1992 m w 7 3 landers earthquake southern california is investigated using synthetic aperture radar sar and global positioning system gps measurements the ers 1 satellite data from the ascending and descending orbits are used to generate contiguous maps of three orthogonal components east north up of the coseismic surface displacement field the coseismic displacement field exhibits symmetries with respect to the rupture plane that are suggestive of a linear relationship between stress and strain in the crust interferometric synthetic aperture radar insar data show small scale deformation on nearby faults of the eastern california shear zone some of these faults in particular the calico rodman and pinto mountain faults were also subsequently strained by the 1999 m w 7 1 hector mine earthquake i test the hypothesis that the anomalous fault strain represents essentially an elastic response of kilometer scale compliant fault zones to stressing by nearby earthquakes fialko et al 2002 the coseismic stress perturbations due to the landers earthquake are computed using a slip model derived from inversions of the insar and gps data calculations are performed for both homogeneous and transversely isotropic half space models the compliant zone model that best explains the deformation on the calico and pinto mountain faults due to the hector mine earthquake successfully predicts the coseismic displacements on these faults induced by the landers earthquake deformation on the calico and pinto mountain faults implies about a factor of 2 reduction in the effective shear modulus within the similar to 2 km wide fault zones the depth extent of the low rigidity zones is poorly constrained but is likely in excess of a few kilometers the same type of structure is able to explain high gradients in the radar line of sight displacements observed on other faults adjacent to the landers rupture in particular the lenwood fault north of the soggy lake has likely experienced a few centimeters of left lateral motion across 1 km wide compliant fault zone having the rigidity reduction of more than a factor of 2 the inferred compliant fault zones are interpreted to be a result of extensive damage due to past earthquakes

deformation on nearby faults induced by the 1999 hector mine earthquake interferometric synthetic aperture radar observations of surface deformation due to the 1999 hector mine earthquake reveal motion on several nearby faults of the eastern california shear zone we document both vertical and horizontal displacements of several millimeters to several centimeters across kilometer wide zones centered on pre existing faults portions of some faults experienced retrograde that is opposite to their long term geologic slip motion during or shortly after the earthquake the observed deformation likely represents elastic response of compliant fault zones to the permanent co seismic stress changes the induced fault displacements imply decreases in the effective shear modulus within the kilometer wide fault zones indicating that the latter are mechanically distinct from the ambient crustal rocks

global compilation of interferometric synthetic aperture radar earthquake source models 1 comparisons with seismic catalogs 1 while many earthquakes have now been studied using interferometric synthetic aperture radar insar data a full assessment of the quality and additional value of insar source parameters compared to seismological techniques is still lacking we compile a catalog of source models obtained using insar and estimate the corresponding centroid moment tensor cmt parameters we refer to this compilation as the icmt archive we compare source parameters from over 70 insar studies of 57 global earthquakes with those in the global cmt gcmt international seismological centre isc and engdahl hilst buland ehb seismic catalogs we find an overall good agreement between fault strike dip and rake values in the gcmt and icmt archives likewise the differences in seismic moment between these two archives are relatively small and we do not find support for previously suggested trends of insar leading to larger moments than seismic data however epicentral locations show substantial discrepancies which are larger for the gcmt median differences of 21 km than for the ehb and isc catalogs median differences of 10 km since insar data have a high spatial resolution and thus should map epicentral locations accurately this allows us to obtain a first independent estimate of epicentral location errors in the seismic catalogs earthquake depths from insar are systematically shallower than those in the ehb catalog with a median of differences of 5 km while this trend may be partly due to unmodeled crustal complexity it is also compatible with the observation that the rupture of crustal earthquakes tends to propagate upward in the seismogenic layer

fault mechanics and post seismic deformation at bam se iran the extent to which aseismic deformation relaxes co seismic stress changes on a fault zone is fundamental to assessing the future seismic hazard following any earthquake and in understanding the mechanical behaviour of faults here we use models of stress driven afterslip and viscoelastic relaxation in conjunction with post seismic insar measurements to show that there has been minimal release of co seismic stress changes through post seismic deformation following the 2003 mw 6 6 bam earthquake our analysis indicates the faults at bam remain predominantly locked suggesting that the co plus interseismically accumulated elastic strain stored downdip of the 2003 rupture patch may be released in a future mw 6 earthquake our observations and models also provide an opportunity to probe the growth of topography at bam we find that for our modelled afterslip distribution to be consistent with forming the sharp step in the local topography over repeated earthquake cycles and also to be consistent with the geodetic observations requires either 1 far field tectonic loading equivalent to a 2 10 mpa deviatoric stress acting across the fault system which suggests it supports stresses 60 100 times less than classical views of static fault strength or 2 that the fault surface has some form of mechanical anisotropy potentially related to corrugations on the fault plane that controls the sense of slip

on the mechanics of earthquake afterslip we propose a model for earthquake afterslip based on rate and state variable friction laws in the model afterslip is attributed to the interaction of a velocity weakening region at depth within which earthquakes nucleate with an upper region of velocity strengthening frictional behavior the existence of this upper region is supported by independent seismologic observations and the results of laboratory friction experiments in our model afterslip is the result of relaxation of a stress perturbation within the velocity strengthening region which arises when an earthquake propagates into that region from below we derive the stress perturbation and its decay from the friction constitutive law using a simple 1 degree of freedom approximation for the elastic interaction between the fault and its surroundings this approximation is based on thickness averaged displacements and slip velocities within the velocity strengthening region which is assumed to slip as a rigid block coseismic and postseismic slip are coupled through the thickness averaged stiffness k of the velocity strengthening region we assume k to be inversely proportional to the thickness of this region which means that thicker velocity strengthening regions have a greater tendency to arrest coseismic slip we model the afterslip time histories of the 1966 parkfield and 1987 superstition hills earthquakes and relate the model parameters to physical parameters which may govern the rheologic behavior of the faults in accord with field observations our model predicts 1 that afterslip on some faults scales with the thickness of the unconsolidated sedimentary cover and 2 that proportionally more afterslip occurs for earthquakes in which coseismic surface slip is small compared with coseismic slip at depth velocity strengthening frictional behavior is to be expected for faults within poorly consolidated sediments and for those that contain significant gouge zones about 500 m within their shallow regions 3 5 km combining our results with those of recent laboratory friction studies indicates that relatively young faults with little accumulated fault gouge should exhibit little afterslip

the 2011 mw 6 8 burma earthquake fault constraints provided by multiple sar techniques we used two tracks of alos palsar images to investigate the focal mechanism and slip distribution of the 2011 march 24 m w 6 8 burma strike slip earthquake three different sar techniques namely conventional interferometry sar pixel offsets spo and multiple aperture insar mai were employed to obtain the coseismic surface deformation fields along the 30 km length of the fault rupture along track measurements from spo and mai techniques show a high correlation and were subsequently used to precisely determine the location and extent of the surface fault trace the best fitting fault model geometry derived from an iterative inversion technique suggests that the rupture occurred on a near vertical sinistral strike slip fault west of the nam ma fault with a strike of 70 a maximum slip of 4 2 m occurs at a depth of 2 5 km with significant slip constrained only to the upper 10 km of the crust

coseismic slip distribution of the 2008 mw 7 9 wenchuan earthquake from joint inversion of gps and insar data on 12 may 2008 the m w 7 9 wenchuan earthquake occurred at the eastern margin of the tibetan plateau along the longmen shan fault based on previous geological and geophysical studies and offset maps from advanced land observing satellite phased array type l band synthetic aperture radar alos palsar data a layered crustal structure and a five segment rupture model are established to study the coseismic deformation of this event using the constrained least squares method a preferred coseismic slip model is derived from global positioning system gps and interferometric synthetic aperture radar insar data in particular the helmert variance component estimation hvce method is used to determine the relative weight ratio between the gps and insar data in contrast to the initial weight ratio 0 752 0 246 0 002 among three type observations gps horizontal gps vertical and insar los displacement the final optimal weight ratio is found to be 0 473 0 279 0 248 and the overall root mean square rms misfit for all three datasets decreases from 9 15 cm without hvce to 5 46 cm with hvce as revealed by the preferred slip the slip changes obviously along the strike direction from southwest to northeast and exhibits four asperities close to hongkou town yuejiashan town beichuan county and nanba town respectively two major asperities are located on the hongkou and beichuan segments with the maximum slip close to 10 m the slips of hongkou yuejiashan and beichuan segments are dominated by the thrust movement with a significant right lateral strike slip component the qingchuan segment experiences a dominant right lateral strike slip with an average magnitude of 1 2 m most of the slip asperities are shallower than 10 km depth except for the southwest part near the hypocenter where the slip may exceed 20 km the seismic moment of the wenchuan earthquake is 8 19 1020 n m m w 7 91 based on the layered crust model which is slightly larger than that using a corresponding homogeneous crust model m w 7 87

uplift of the central andean plateau and bending of the bolivian orocline the topography of the central andes can be considered the primary tectonic signal of late cenozoic mountain building in an arid region where the effects of uplift and magmatism are little obscured by denudation the spatial coverage of the topographic signal is more complete than that for sparsely sampled geological and geophysical data a color coded image of digitized topography between 12 s and 37 s highlights the altiplano puna one of the world s most remarkable plateaus and reveals important physiographic clues about the formation of that major feature the topographic data combined with information on structure magmatism seismicity and paleomagnetism support a simple kinematical model for the late cenozoic evolution of the central andes the model does not require collisional effects or enormous volumes of intrusive additions to the crust but instead calls upon plausible amounts of crustal shortening and lithospheric thinning the model interrelates andean uplift a changing geometry of the subducted nazca plate and a changing outline in map view of the leading edge of the south american plate crustal shortening has accommodated convergence between the chilean peruvian forearc and the south american foreland the altiplano puna plateau can be constructed by a combination of crustal shortening and thickening and lithospheric thinning above a shallow dipping 20 30 subducted plate the seawardly concave bend of western south america the bolivian orocline was enhanced but not completely produced by an along strike variation in the amount of late cenozoic shortening maximum shortening in bolivia both produced the widest part of the plateau and increased the seaward concavity of the bolivian orocline the along strike variations of shortening are hypothesized to result from corresponding along strike variations in the width of a weakened zone in the overriding plate weakening occurs above the wedge of asthenosphere located between the subducted and overriding plates hence the width of the zone of weakening depends upon the dip of the subducted plate two types of shortening are recognized 1 a widespread basin and range laramide like shortening that characterizes modem activity in the sierras pampeanas and late miocene deformation of the altiplano puna and 2 on the eastern side of the cordilleras and plateau an east verging foreland fold thrust belt in which the underthrust foreland compresses and thickens the ductile lower crust and produces a plateau uplift of the upper crust the second type of shortening can be applied to plio quaternary deformations throughout the central andes but with a substantial narrowing of the region of plateau uplift in peru and south of 28 s a proposed monoclinal flexure of the upper crust on the western side of the plateau uplift explains the remarkably simple and regular morphology of the main western slope of the central andes the monocline is located above the tip of the asthenospheric wedge between the converging plates it is postulated to occur above the western limit of lower crustal thickening in the regions of horizontal subduction the monocline can be associated with a late miocene asthenospheric wedge tip

postseismic rebound in fault step overs caused by pore fluid flow near field strain induced by large crustal earthquakes results in changes in pore fluid pressure that dissipate with time and produce surface deformation synthetic aperture radar sar interferometry revealed several centimeters of postseismic uplift in pull apart structures and subsidence in a compressive jog along the landers california 1992 earthquake surface rupture with a relaxation time of 270 45 days such a postseismic rebound may be explained by the transition of the poisson s ratio of the deformed volumes of rock from undrained to drained conditions as pore fluid flow allows pore pressure to return to hydrostatic equilibrium

geodetic investigation of the 13 may 1995 kozani grevena greece earthquake the ms 6 6 13 may 1995 kozani grevena earthquake struck a region of low historical seismic activity which includes a 10 year old triangulation network in northern greece after the earthquake monuments from this network were occupied with gps to measure co seismic displacements inversion of the co seismic displacement field to yield a source mechanism is achieved by use of a hybrid simplex monte carlo method which requires no a priori constraints the model focal mechanism agrees well with the global cmt solution and locally observed aftershocks but implies a significantly higher scalar moment than do seismological or sar interferometry studies and has a longer fault length than the model based on sar interferometry

dem error correction in insar time series we present a mathematical formulation for the phase due to the errors in digital elevation models dems in synthetic aperture radar sar interferometry insar time series obtained by the small baseline sb or the small baseline subset method we show that the effect of the dem error in the estimated displacement is proportional to the perpendicular baseline history of the set of sar acquisitions this effect at a given epoch is proportional to the perpendicular baseline between the sar acquisition at that epoch and the reference acquisition therefore the dem error can significantly affect the time series results even if sb interferograms are used we propose a new method for dem error correction of insar time series which operates in the time domain after inversion of the network of interferograms for the displacement time series this is in contrast to the method of berardino 2002 in which the dem error is estimated in the interferogram domain we show the effectiveness of this method using simulated insar data we apply the new method to fernandina volcano in the galapagos islands and show that the proposed dem error correction improves the estimated displacement significantly

the 1994 sefidabeh eastern iran earthquakes revisited new evidence from satellite radar interferometry and carbonate dating about the growth of an active fold above a blind thrust fault in 1994 three shallow earthquakes of mw 6 occurred close together on blind thrusts near sefidabeh in eastern iran in an earlier study of the teleseismic waveforms the geomorphology and the faulting in the epicentral region it was suggested that these earthquakes were associated with the growth of a ridge above a blind thrust fault system whose activity could be detected by its effect on the surface drainage in this study we present a sar interferogram that precisely determines the location and amount of coseismic surface displacements showing that the earthquakes in the sefidabeh sequence probably occurred on en echelon fault segments associated with three stepping ridges we also present u th dates of 100 ka for lake deposits uplifted by the growing ridge from the cumulative dated uplift and knowledge of the surface displacements due to an earthquake sequence we estimate that 120 such events have occurred in the past 100 ka with an average recurrence interval of 830 yr and an average convergence rate of 1 5 mm yr 1 on the sefidabeh thrust each estimate has an uncertainty of a factor of two either way we argue that the sefidabeh fault originally formed by coalescence of many small fault segments and has grown in length at about 2 cm yr 1 in the past 100 ka though the coseismic surface deformation observed in the sar interferogram closely resembles folding the overall topography does not because of inherited topography associated with earlier geological deformation in spite of this the activity of the buried thrust fault can easily be detected by its effect on the surface drainage a significant lesson when interpreting landscapes that are not entirely due to the present day deformation

unexpected earthquake hazard revealed by holocene rupture on the kenchreai fault central greece implications for weak sub fault shear zones this work forms part of the nercand esrc funded project earthquakes without frontiers and was partly funded by the nerc grant looking inside the continents from space

stress triggering in thrust and subduction earthquakes and stress interaction between the southern san andreas and nearby thrust and strike slip faults 1 we argue that key features of thrust earthquake triggering inhibition and clustering can be explained by coulomb stress changes which we illustrate by a suite of representative models and by detailed examples whereas slip on surface cutting thrust faults drops the stress in most of the adjacent crust slip on blind thrust faults increases the stress on some nearby zones particularly above the source fault blind thrusts can thus trigger slip on secondary faults at shallow depth and typically produce broadly distributed aftershocks short thrust ruptures are particularly efficient at triggering earthquakes of similar size on adjacent thrust faults we calculate that during a progressive thrust sequence in central california the 1983 mw 6 7 coalinga earthquake brought the subsequent 1983 mw 6 0 nunez and 1985 mw 6 0 kettleman hills ruptures 10 bars and 1 bar closer to coulomb failure the idealized stress change calculations also reconcile the distribution of seismicity accompanying large subduction events in agreement with findings of prior investigations subduction zone ruptures are calculated to promote normal faulting events in the outer rise and to promote thrust faulting events on the periphery of the seismic rupture and its downdip extension these features are evident in aftershocks of the 1957 mw 9 1 aleutian and other large subduction earthquakes we further examine stress changes on the rupture surface imparted by the 1960 mw 9 5 and 1995 mw 8 1 chile earthquakes for which detailed slip models are available calculated coulomb stress increases of 2 20 bars correspond closely to sites of aftershocks and postseismic slip whereas aftershocks are absent where the stress drops by more than 10 bars we also argue that slip on major strike slip systems modulates the stress acting on nearby thrust and strike slip faults we calculate that the 1857 mw 7 9 fort tejon earthquake on the san andreas fault and subsequent interseismic slip brought the coalinga fault 1 bar closer to failure but inhibited failure elsewhere on the coast ranges thrust faults the 1857 earthquake also promoted failure on the white wolf reverse fault by 8 bars which ruptured in the 1952 mw 7 3 kern county shock but inhibited slip on the left lateral garlock fault which has not ruptured since 1857 we thus contend that stress transfer exerts a control on the seismicity of thrust faults across a broad spectrum of spatial and temporal scales

slip complexity in earthquake fault models we summarize studies of earthquake fault models that give rise to slip complexities like those in natural earthquakes for models of smooth faults between elastically deformable continua it is critical that the friction laws involve a characteristic distance for slip weakening or evolution of surface state that results in a finite nucleation size or coherent slip patch size h models of smooth faults using numerical cell size properly small compared to h show periodic response or complex and apparently chaotic histories of large events but have not been found to show small event complexity like the self similar power law gutenberg richter frequency size statistics this conclusion is supported in the present paper by fully inertial elastodynamic modeling of earthquake sequences in contrast some models of locally heterogeneous faults with quasi independent fault segments represented approximately by simulations with cell size larger than h so that the model becomes inherently discrete do show small event complexity of the gutenberg richter type models based on classical friction laws without a weakening length scale or for which the numerical procedure imposes an abrupt strength drop at the onset of slip have h 0 and hence always fall into the inherently discrete class we suggest that the small event complexity that some such models show will not survive regularization of the constitutive description by inclusion of an appropriate length scale leading to a finite h and a corresponding reduction of numerical grid size

postseismic motion after the 2001 mw 7 8 kokoxili earthquake in tibet observed by insar time series 1 on november 14th 2001 a mw 7 8 earthquake occurred in the kokoxili region of northern tibet the earthquake ruptured more than 400 km along the western part of the kunlun fault with a maximum of 8 m left lateral slip in this paper we use a multitemporal interferometric sar insar time series technique to map the postseismic motion following the large kokoxili event sar data from envisat descending orbits along five adjacent tracks covering almost the entire ruptured fault length are used to calculate the displacement time series for a period between 2 and 6 years after the earthquake a peak to trough signal of 8 cm in the radar line of sight is observed during the period between 2003 and 2008 two different mechanisms are employed to explain the observed surface displacements namely afterslip and viscoelastic relaxation the observations inverted for afterslip on and below the coseismic rupture plane shows that the maximum slip in the afterslip model is 0 6 m the position of the maximum postseismic slip is located in the middle of two relatively high coseismic slip patches which suggests that afterslip is a plausible mechanism models of viscoelastic stress relaxation in a maxwell half space give a best fitting viscosity for the mid to lower crust of 2 5 1019 pa s and the principal postseismic relaxation process is due to viscous flow in the lower crust to upper mantle however the insar observations are incapable of distinguishing between localized afterslip and distributed viscoelastic relaxation deformation and the lowest misfits are produced by mixed models of viscoelastic relaxation in the mantle below 70 km and afterslip in the crust modeling of viscoelastic relaxation in a maxwell half space and also a mixed mechanism model enables us to place an effective viscosity of 2 1019 pa s on the lower crust to mantle of northern tibet

variability in the mean latitude of the atlantic intertropical convergence zone as recorded by riverine input of sediments to the cariaco basin venezuela abstract changes in the strength and position of the intertropical convergence zone itcz are an important component of climate variability in the tropical atlantic the cariaco basin located on the northern margin of venezuela is sensitive to tropical atlantic climate change and its sediments provide a record of past itcz behavior today the cariaco basin experiences two distinct seasons that reflect the annual migration of the atlantic itcz between january and march when the itcz lies south of the equator northeasterly trade winds sit directly over cariaco basin and strong coastal upwelling and dry conditions dominate beginning in june july as the itcz moves north local rainfall reaches a maximum and the upwelling diminishes or disappears here we summarize new and previously published data on the river derived terrigenous fraction of cariaco basin sediments as well as comparisons to other paleoclimate records which together suggest a coherent climatologic response in the tropical atlantic triggered by a pattern of itcz migration that mimics the seasonal cycle during periods of cooler north atlantic ssts on time scales ranging from the little ice age to the younger dryas to the cold stadials of the last glacial decreased detrital delivery to cariaco basin from local rivers suggests a southward shift in the mean latitudinal position of the itcz during warm interstadials and periods of holocene and deglacial warmth northward shifts in itcz position and its belt of convective rainfall are inferred from increased detrital delivery to the basin whether the rapid shifts in itcz position and precipitation recorded by cariaco basin sediments and other regional records reflect a response to forcing originating in the high latitude atlantic or to forcing potentially sourced in the tropics is a key question yet to be fully answered

insar observations of strain accumulation and fault creep along the chaman fault system pakistan and afghanistan we use 2004 2011 envisat synthetic aperture radar imagery and insar time series methods to estimate the contemporary rates of strain accumulation in the chaman fault system in pakistan and afghanistan at 29 n we find long term slip rates of 16 2 3 mm yr for the ghazaband fault and of 8 3 1 mm yr for the chaman fault this makes the ghazaband fault one of the most hazardous faults of the plate boundary zone we further identify a 340 km long segment displaying aseismic surface creep along the chaman fault with maximum surface creep rate of 8 1 2 mm yr the observation that the chaman fault accommodates only 30 of the relative plate motion between india and eurasia implies that the remainder is accommodated south and east of the katawaz block microplate

refining the shallow slip deficit geodetic slip inversions for three major m w 7 strike slip earthquakes 1992 landers 1999 hector mine and 2010 el mayor cucapah show a 15 60 per cent reduction in slip near the surface depth 2 km relative to the slip at deeper depths 4 6 km this significant difference between surface coseismic slip and slip at depth has been termed the shallow slip deficit ssd the large magnitude of this deficit has been an enigma since it cannot be explained by shallow creep during the interseismic period or by triggered slip from nearby earthquakes one potential explanation for the ssd is that the previous geodetic inversions lack data coverage close to surface rupture such that the shallow portions of the slip models are poorly resolved and generally underestimated in this study we improve the static coseismic slip inversion for these three earthquakes especially at shallow depths by 1 including data capturing the near fault deformation from optical imagery and sar azimuth offsets 2 refining the interferometric synthetic aperture radar processing with non boxcar phase filtering model dependent range corrections more complete phase unwrapping by snaphu statistical non linear approach for phase unwrapping assuming a maximum discontinuity and an on fault correlation mask 3 using more detailed geologically constrained fault geometries and 4 incorporating additional campaign global positioning system gps data the refined slip models result in much smaller ssds of 3 19 per cent we suspect that the remaining minor ssd for these earthquakes likely reflects a combination of our elastic model s inability to fully account for near surface deformation which will render our estimates of shallow slip minima and potentially small amounts of interseismic fault creep or triggered slip which could make up a small percentages of the coseismic ssd during the interseismic period our results indicate that it is imperative that slip inversions include accurate measurements of near fault surface deformation to reliably constrain spatial patterns of slip during major strike slip earthquakes

rapid late miocene rise of the bolivian altiplano evidence for removal of mantle lithosphere abstract the oxygen isotopic compositions of carbonates deposited in the northern altiplano demonstrate a rapid change in late miocene time which we attribute to an increase in elevation rainfall samples over an elevation transect adjacent to the altiplano of northern bolivia display a systematic decrease in mean annual 18 o values and define a local 18 o vs altitude gradient r gonfiantini m a roche j c olivry j c fontes g m zuppi the altitude effect on the isotopic composition of tropical rains chem geol 181 2001 147 167 which we apply to paleo meteoric water values determined from carbonates age constraints from magnetostragraphy and paleoelevation estimates suggest surface uplift of 2 5 to 3 5 km occurred between 10 3 ma and 6 8 0 4 ma when the altiplano rose to its current elevation only the removal of dense eclogitic lower crust and mantle lithosphere can generate a change of this magnitude and rapidity this change coincides with an 30 decrease in the rate of convergence between the south america and nazca plates and the propagation of deformation into the eastern subandean zone which we infer to have resulted from the increase in the force per unit length applied by the elevated andean plateau to the surrounding lowlands

great earthquakes and subduction along the peru trench subduction along the peru trench between 9 and 15 s involves both large interplate underthrusting earthquakes and intraplate normal fault earthquakes the four largest earthquakes along the peru trench are from north to south the 1970 m 7 9 intraplate normal fault earthquake and the interplate underthrusting earthquakes in 1966 m 8 0 1940 m 8 and 1974 m 8 0 we have studied the rupture process of these earthquakes and can locate spatial concentrations of moment release through directivity analysis of source time functions deconvolved from long period p wave seismograms the 1966 earthquake has a source duration of 45 s with most of the moment release concentrated near the epicenter two intraplate normal fault events occurred in 1963 m 6 7 and 7 0 at the down dip edge of the 1966 dominant asperity the 1940 earthquake is an underthrusting event with a simple source time function of 30 s duration that represents the rupture of a single asperity near the epicenter the 1974 earthquake has a source duration of 45 50s and two pulses of moment release this earthquake has a bilateral rupture with the first pulse of moment release located northwest of the epicenter and the second pulse of moment release located southeast of the epicenter both pulses of moment release occur on the northern half of the aftershock area the 1970 earthquake is one of the largest intraplate normal fault earthquakes to occur in a subduction zone and has a moment release comparable with many large underthrusting events the aftershocks for the 1970 earthquake form two distinct clusters the smaller cluster near the epicenter has focal mechanisms characterized by down dip tension but the second aftershock cluster located 80 km southeast of the epicenter has focal mechanisms characterized by down dip compression the p waves for the main shock can be modeled as two sources with different focal mechanisms and depths similar to the two clusters of aftershocks the first event has a down dip tensional focal mechanism and is followed 40 s later by a distinct second event located 80 km southeast of the epicenter with a down dip compressional focal mechanism and a somewhat shallower depth than the first event the observable directivity indicates that the second source is located at the second cluster of aftershocks that have down dip compressional focal mechanisms the occurrence of both down dip tensional and compressional focal mechanisms may be explained by extreme unbending stresses associated with the anomalous slab geometry the unusually large size of the 1970 earthquake may also be related to the subduction of the mendana fracture zone the historic earthquake record along the peru trench indicates that the previous event in 1746 was much larger than any of the three underthrusting earthquakes this century the 1746 earthquake may have ruptured the entire segment in a multiple asperity earthquake thus the mode of rupture along the peru coast has changed between successive earthquake cycles

frictional slip of granite at hydrothermal conditions sliding on faults in much of the continental crust likely occurs at hydrothermal conditions i e at elevated temperature and elevated pressure of aqueous pore fluids yet there have been few relevant laboratory studies to measure the strength sliding behavior and friction constitutive properties of faults at hydrothermal conditions we slid laboratory granite faults containing a layer of granite powder simulated gouge velocity stepping experiments were performed at temperatures of 23 to 600 c pore fluid pressures ph2o of 0 dry and 100 mpa wet effective normal stress of 400 mpa and sliding velocities v of 0 01 to 1 m s 0 32 to 32 m yr conditions were similar to those in earlier tests on dry granite to 845 c by lockner et al 1986 the mechanical results define two regimes the first regime includes dry granite up to at least 845 and wet granite below 250 c in this regime the coefficient of friction is high 0 7 to 0 8 and depends only modestly on temperature slip rate and ph2o the second regime includes wet granite above 350 c in this regime friction decreases considerably with increasing temperature temperature weakening and with decreasing slip rate velocity strengthening these regimes correspond well to those identified in sliding tests on ultrafine quartz we infer that one or more fluid assisted deformation mechanisms are activated in the second hydrothermal regime and operate concurrently with cataclastic flow slip in the first cool and or dry regime is characterized by pervasive shearing and particle size reduction slip in the second hot and wet regime is localized primarily onto narrow shear bands adjacent to the gouge rock interfaces weakness of these boundary shears may result either from an abundance of phyllosilicates preferentially aligned for easy dislocation glide or from a dependence of strength on gouge particle size major features of the granite data set can be fit reasonably well by a rate and temperature dependent three regime friction constitutive model chester this issue we extrapolate the experimental data and model fit in order to estimate steady state shear strength versus depth along natural slipping faults for sliding rates as low as 31 mm yr we do this for two end member cases in the first case pore pressure is assumed hydrostatic at all depths shallow crustal strength in this case is similar to that calculated in previous work from room temperature friction data while at depths below about 9 13 km depending on slip rate strength becomes less sensitive to depth but sensitive to slip rate in the second case pore pressure is assumed to be near lithostatic at depths below 5 km strength is low at all depths in this case 20 mpa in agreement with observations of weak faults such as the san andreas the predicted depth of transition from velocity weakening to velocity strengthening lies at about 13 km depth for a slip rate of 31 mm yr in rough agreement with the seismic aseismic transition depth observed on mature continental faults these results highlight the importance of fluid assisted deformation processes active in faults at depth and the need for laboratory studies on the roles of additional factors such as fluid chemistry large displacements higher concentrations of phyllosilicates and time dependent fault healing

fault slip distribution of the 1999 mw 7 1 hector mine california earthquake estimated from satellite radar and gps measurements we use a combination of satellite radar and gps data to estimate the slip distribution of the 1999 m w 7 1 hector mine earthquake a right lateral strikeslip earthquake that occurred on a northwest southeast striking fault in the southern california mojave desert the data include synthetic aperture radar interferograms insar from both ascending and descending orbits radar amplitude image offset fields sario for both ascending and descending azimuth directions and campaign gps observations from 55 stations provided by agnew et al 2002 we model the fault with nine segments derived from the field mapped fault rupture the sario data and aftershock locations we first estimate the dip of each fault segment as well as a single constant strike slip component across each segment resulting in an average dip of 83 to the northeast and slip of up to 5 6 m then we fix the optimal fault segment dip discretize the fault segments into 1 5 km 1 5 km patches and solve for the variable slip distribution using a nonnegative least squares method that includes an appropriate degree of smoothing our preferred solution has both right lateral strike slip and reverse faulting the estimated geodetic moment is 5 93 10 19 n m m w 7 1 similar to seismological estimates indicating that there are insignificant interseismic and postseismic deformation signals in the data we find strike slip displacements of up to 6 0 m and reverse faulting of up to 1 6 m with the maximum slip located just northwest of the epicenter most of the slip is concentrated northwest and south of the epicenter little slip is found on the northeastern branch of the fault the sario data and our modeling indicate that the amount and extent of surface fault rupture were underestimated in the field

lithospheric structure beneath the northern central andean plateau from the joint inversion of ambient noise and earthquake generated surface waves the central andean plateau cap as defined by elevations in excess of 3 km extends over 1 800 km along the active south american cordilleran margin making it the second largest active orogenic plateau on earth the uplift history of this high plateau with an average elevation around 4 km above sea level remains uncertain as paleoelevation studies along the cap suggest a complex non uniform uplift history as part of the central andean uplift and the geodynamics of high topography caught project we image the s wave velocity structure of the crust and upper mantle using surface waves measured from ambient noise and teleseismic earthquakes to investigate the upper mantle component of plateau uplift we observe three main features in our s wave velocity model including 1 a positive velocity perturbation associated with the subducting nazca slab 2 a negative velocity perturbation below the subandean crust that we interpret as anisotropic brazilian cratonic lithosphere and 3 a high velocity feature in the mantle above the slab that extends along the length of the altiplano from the base of the moho to a depth of 120 km a strong spatial correlation exists between the lateral extent of this high velocity feature and the relatively lower elevations of the altiplano basin suggesting a potential relationship determining if this high velocity feature represents a small lithospheric root or foundering of orogenic lithosphere requires more integration of observations but either interpretation implies a strong geodynamic connection with the uppermost mantle and the current topography of the northern cap

source model of the 2015 mw 6 4 pishan earthquake constrained by interferometric synthetic aperture radar and gps insight into blind rupture in the western kunlun shan the pishan xinjiang earthquake on 3 july 2015 is the one of largest events mw 6 7 that has occurred along the western kunlun shan northwestern edge of the tibetan plateau in recent time it involved blind thrusting at a shallow depth beneath the range front providing a rare chance to gain insights into the interaction between the tarim basin and the tibetan plateau here we present coseismic ground displacements acquired by high resolution alos 2 sar imagery and derived from gps resurveys on several near field geodetic markers after the event we observed a maximum displacement exceeding 10 cm in the epicentral region analysis of the data based on a finite fault model indicates that coseismic slip occurred on a subsurface plane of 22 km 8 km in size with a dip of about 27 to the north and a strike of 114 representing partial break of one ramp fault buried in paleozoic strata at 8 16 km depths beneath the foothill of the western kunlun shan this blind rupture is characterized largely by a compact thrusting patch with a peak slip of 0 63 m resulting in a stress drop of 2 3 mpa the source model yields a geodetic moment of 5 05 1018 n m corresponding to mw 6 4 the pishan earthquake suggests a northward migration of deformation front of the tibetan plateau onto the tarim basin our finding highlights slip along ramp decollement faults to build up the western kunlun shan as the tarim slab is subducting beneath western tibet

time dependent distributed afterslip on and deep below the izmit earthquake rupture surface deformation transients measured with the global positioning system during the 87 days between the 17 august 1999 izmit earthquake and the 12 november 1999 duzce earthquake indicate rapidly decaying aseismic fault slip on and well below the coseismic rupture elastic model inversions for time dependent distributed fault slip using a network inversion filter approach show that afterslip was highest between and below the regions of maximum coseismic slip and propa gated downward to or even below the base of the crust maximum afterslip rates decayed from greater than 2 m yr immediately after the i zmit earthquake to about 1 2 m yr just prior to the duzce earthquake maximum afterslip occurred below the eastern karadere rupture segment and near the i zmit hypocenter afterslip in the upper 16 km decayed more rapidly than that below the seismogenic zone these observations are consistent with a phase of rapid aseismic fault slip concentrated near the base of the seismogenic zone continued loading from the rapid deep afterslip along the eastern rupture zone is a plausible mechanism that helped trigger the nearby mw 7 2 12 november duzce earthquake

space geodetic observations and models of postseismic deformation due to the 2005 m7 6 kashmir pakistan earthquake we use the l band advanced land observing satellite alos and c band envisat interferometric synthetic aperture data and campaign gps observations to study the postseismic deformation due to the 2005 magnitude 7 6 kashmir pakistan earthquake that occurred in the northwestern himalaya envisat data are available from both the descending and ascending orbits and span a time period of 4 5 years immediately following the earthquake 2005 2010 with nearly monthly acquisitions however the envisat data are highly decorrelated due to high topography and snow cover alos data are available from the ascending orbit and span a time period of 2 5 years between 2007 and 2009 over which they remain reasonably well correlated we derive the mean line of sight los postseismic velocity maps in the epicentral area of the kashmir earthquake using persistent scatterer method for envisat data and selective stacking for alos data los velocities from all data sets indicate an uplift decrease in radar range primarily in the hanging wall of the earthquake rupture over the entire period of synthetic aperture radar observations 2005 2010 models of poroelastic relaxation predict uplift of both the footwall and the hanging wall while models of viscoelastic relaxation below the brittle ductile transition predict subsidence increase in radar range in both the footwall and the hanging wall therefore the observed pattern of surface velocities indicates that the early several years of postseismic deformation were dominated by afterslip on the fault plane possibly with a minor contribution from poroelastic rebound kinematic inversions of interferometric synthetic aperture radar and gps data confirm that the observed deformation is consistent with afterslip primarily downdip of the seismic asperity to place constraints on the effective viscosity of the ductile substrate in the study area we subtract the surface deformation predicted by stress driven afterslip model from the mean los velocities and compare the residuals to models of viscoelastic relaxation for a range of assumed viscosities we show that in order to prevent surface subsidence the effective viscosity has to be greater than 1019 pa s

the complete 3 d surface displacement field in the epicentral area of the 1999 mw7 1 hector mine earthquake california from space geodetic observations we use interferometric synthetic aperture radar insar data to derive continuous maps for three orthogonal components of the co seismic surface displacement field due to the 1999 m w7 1 hector mine earthquake in southern california vertical and horizontal displacements are both predominantly antisymmetric with respect to the fault plane consistent with predictions of linear elastic models of deformation for a strike slip fault some deviations from symmetry apparent in the surface displacement data may result from complexity in the fault geometry

depths and focal mechanisms of crustal earthquakes in the central andes determined from teleseismic waveform analysis and insar 1 we investigate the depths of crustal earthquakes mw 5 5 earthquakes from the global cmt catalog and previous work spanning 1944 2007 for 38 well recorded events we use teleseismic p and sh waveforms to model the strike dip rake focal depth and source time function we use insar observations of surface deformation from 9 earthquakes to compare inferred fault parameters with the waveform inversions and global catalogs to assess their accuracies while the depths from the insar and waveform analyses generally agree within error horizontal and depth errors in global catalogs are 10 to 50 km as found elsewhere as noted in previous work the majority of crustal earthquakes occur in the eastern cordillera and foreland regions of the central andes although a few normal and strike slip earthquakes occur beneath the altiplano plateau and in the forearc in southern peru and northernmost chile we propose a new interpretation of one of the basement thrusts shira mountain peru as a pop up block on the basis of our new earthquake depths we confirm that earthquakes in the flat slab areas of peru and argentina are within the sometimes aseismic lower crust lower crustal earthquakes are globally found in all types of tectonic settings only when the thermal lithosphere is more than 80 km thick and the amount of recent shortening extension is 30

rise of the andes the surface uplift of mountain belts is generally assumed to reflect progressive shortening and crustal thickening leading to their gradual rise recent studies of the andes indicate that their elevation remained relatively stable for long periods tens of millions of years separated by rapid 1 to 4 million years changes of 1 5 kilometers or more periodic punctuated surface uplift of mountain belts probably reflects the rapid removal of unstable dense lower lithosphere after long term thickening of the crust and lithospheric mantle

slab1 0 a three dimensional model of global subduction zone geometries 1 we describe and present a new model of global subduction zone geometries called slab1 0 an extension of previous efforts to constrain the two dimensional non planar geometry of subduction zones around the focus of large earthquakes slab1 0 describes the detailed non planar three dimensional geometry of approximately 85 of subduction zones worldwide while the model focuses on the detailed form of each slab from their trenches through the seismogenic zone where it combines data sets from active source and passive seismology it also continues to the limits of their seismic extent in the upper mid mantle providing a uniform approach to the definition of the entire seismically active slab geometry examples are shown for two well constrained global locations models for many other regions are available and can be freely downloaded in several formats from our new slab1 0 website http on doi gov d9arbs we describe improvements in our two dimensional geometry constraint inversion including the use of average active source seismic data profiles in the shallow trench regions where data are otherwise lacking derived from the interpolation between other active source seismic data along strike in the same subduction zone we include several analyses of the uncertainty and robustness of our three dimensional interpolation methods in addition we use the filtered subduction related earthquake data sets compiled to build slab1 0 in a reassessment of previous analyses of the deep limit of the thrust interface seismogenic zone for all subduction zones included in our global model thus far concluding that the width of these seismogenic zones is on average 30 larger than previous studies have suggested

extension on the tibetan plateau recent normal faulting measured by insar and body wave seismology we use insar and body wave modelling to determine the faulting parameters for a series of five mw 5 9 7 1 normal faulting earthquakes that occurred during 2008 including the march 20 yutian earthquake mw 7 1 one of the largest normal faulting events to have occurred recently on the continents we also study three earlier normal faulting earthquakes that occurred in southern tibet between 1992 and 2005 coseismic deformation for each of these eight events is measured with ascending and descending interferograms from envisat ers and alos sar data elastic dislocation modelling of the line of sight insar displacements and body wave seismological modelling of p and sh waves are used to estimate fault parameters and are found to be in good agreement for all the events studied the use of insar to measure deformation allows a relatively precise determination of the fault location in addition to resolving the focal plane ambiguity only five of the eight events are associated with a clear surface topographic feature suggesting that an underestimation of the amount of extension would result from using the surface expressions of normal faulting alone the observations in all cases are consistent with slip on planar surfaces with dips in the range 40 50 that penetrates the uppermost crust to a depth of 10 15 km we find no evidence for active low angle dip less than 30 normal faulting the contribution of the normal faulting to overall extension estimated by summing seismic moments over earthquakes for the past 43 yr is 3 4 mm yr 1 or 15 20 per cent of the rates of extension measured across the plateau using gps 85 per cent of the moment release in normal faulting over the past 43 yr has occurred in regions whose surface height exceeds 5 km this observation adds weight to the suggestions that the widespread normal faulting on the plateau is the result of variations in the gravitational potential energy of the lithosphere

changes in the tectonic regime above a subduction zone of andean type the andes of peru and bolivia during the pliocene pleistocene this paper adresses the changes in the tectonic regime in the peruvian and bolivian andes that have occurred since the upper miocene when the present day elevation of the cordillera above sea level has been almost reached the stress patterns are deduced essentially from a field study of fault kinematics and a numerical inversion of the slip vector data measured on the fault planes the cuzco fault system in southern peru is chosen as an example to illustrate the methodology used in this region striations on both active and holocene faults are in agreement with a n s extension but faults affecting early pleistocene deposits exhibit two families of striations the younger results from the previous n s extension the older involving reverse motions results from either an e w or a n s compression faults affecting pliocene formations often show an oldest family of striations resulting from a ne sw or an e w trending extension thus three tectonic regimes are demonstrated which are also supported by regional unconformities and sedimentological data 1 a pliocene extensional regime 2 a lower pleistocene compressional regime and 3 a mid pleistocene present day extensional regime similar analyses conducted in the pacific and sub andean lowlands allow sketching of the successive pliocene pleistocene stress patterns in the central andes the quaternary and present day stress pattern is characterized by a n s extension in the high andes and in the pacific lowlands and by an e w compression in the sub andean lowlands and at the contact between the nazca and south american plates this stress pattern is interpreted at a large wavelength 100 km as an effect of compensated topography this model supposes that the vertical lithospheric stress zz increases with the topography the crustal thickness and the low density mantle beneath and that the lithospheric maximum compressional horizontal stress hmax trending e w roughly parallel to the convergence is fairly constant on both edges of the andes the tectonics being compressional zz is 3 and hmax is 1 in the high andes zz becomes 1 then the e w trending hmax is 2 and hmin trending n s is 3 allowing extension to occur in this direction the pliocene stress pattern was characterized by a ne sw or an e w trending extension in the high andes in the pacific lowlands and possibly in the sub andean lowlands this stress pattern was clearly different from the present day one because the e w trending stress was hmin this required a weak push or eventually tractional boundary forces acting on the south american lithosphere it is suggested that this might result from a strong slab pull due to a long steeply dipping slab which decreased the value of the xx stress transmitted to the overriding plate the early pleistocene state of stress was compressional since the elevation of the andes had not markedly decreased during this period this required an increase of the e w trending stress value this resulted from a strong coupling between the two lithospheric plates possibly due to a rupture of a long slab under its own weight other spatial changes in the stress pattern are related to the particular situation of the forearc to the subduction of the buoyant nazca ridge and to the different dips of the slab extension in the high andes is of small magnitude of the order of 1 during the last 1 2 m y in a few basins it may have attained 40 during the pliocene 5 3 m y

source parameters of the 1 october 1995 dinar turkey earthquake from sar interferometry and seismic bodywave modelling abstract the 1 october 1995 m s 6 1 dinar earthquake ruptured a 10 km section of the nw se dinar civril fault there are discrepancies between the published source parameters from seismic data with seismic moments in disagreement by over a factor of two we use both sar interferometry and seismic bodywave modelling to determine earthquake source parameters an interferogram generated from ers 1 2 sar imagery spanning the event and separated by 5 months is used to derive source parameters by a downhill simplex inversion with multiple monte carlo restarts we model the displacements in the satellite line of sight initially using uniform slip on a rectangular dislocation in an elastic half space the resultant model fault plane agrees in strike and location with the observed surface break but systematic residuals exist in the line of sight deformation field resulting in a r m s residual of 20 mm in the interferogram the residuals are reduced if the depth distribution of slip is allowed to vary spatially in four segments along a continuous fault plane our best fitting solution with a r m s misfit of 8 mm reveals two distinct areas of slip on the fault plane strike 145 dip 49 rake 270 a main rupture slipping by 1 44 m between depths of 1 and 8 km becoming deeper to the se and matching the observed surface rupture and an along strike continuation to the nw of the same fault plane but between depths of 8 and 13 km and not associated with a surface break the total geodetic moment 4 5 0 1 10 18 nm is more than twice as large as published seismic moments based on the inversion of p waveforms alone but close to the harvard cmt moment 4 7 10 18 nm we use sh waveforms in addition to the p waves used previously to determine an alternative seismic source mechanism sh waves constrain the depth to be shallower than solutions based on p waves alone agreeing with the depths from the interferometric inversion and resulting in a larger moment 3 1 0 4 10 18 nm than the previous bodywave estimates 2 2 1 10 18 nm the cmt moment reduces in magnitude to a similar size 3 3 10 18 nm if the centroid depth and fault dip are constrained to the values determined from bodywave modelling and interferometry thus the geodetic moment is 40 bigger than the moment determined from seismology

earthquake nucleation on faults with rate and state dependent strength abstract 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 earthquakes in a region provide an upper limit for the size of the nucleation patch

the crust and uppermost mantle structure of southern peru from ambient noise and earthquake surface wave analysis abstract southern peru is located in the northern central andes which is the highest plateau along an active subduction zone in this region the nazca slab changes from normal to flat subduction with the associated holocene volcanism ceasing above the flat subduction regime we use 6 s to 67 s period surface wave signals from ambient noise cross correlations and earthquake data to image the shear wave velocity v s v structure to a depth of 140 km a mid crust low velocity zone is revealed and is interpreted as partially molten rocks that are part of the andean low velocity zone it is oblique to the present trench and possibly indicates the location of the volcanic arcs formed during the steepening of the oligocene flat slab beneath the altiplano plateau the recently subducted slab beneath the forearc shows a decrease in velocity from the normal to flat subduction regime that might be related to hydration during the formation of the nazca ridge which in turn may contribute to the buoyancy of the flat slab the mantle above the flat slab has a comparatively high velocity which indicates the lack of melting and thus explains the cessation of the volcanism above a velocity contrast from crust to uppermost mantle is imaged across the cusco vilcanota fault system and is interpreted as the boundary between two lithospheric blocks

source characteristics of the 2015 m w 7 8 gorkha nepal earthquake and its m w 7 2 aftershock from space geodesy abstract on april 25 2015 a destructive m w 7 8 earthquake struck the capital of nepal kathmandu killing more than 8800 people and destroying numerous historical structures we analyze six coseismic interferograms from several satellites alos 2 sentinel 1 a and radarsat 2 as well as three dimensional displacements at six gps stations to investigate fault structure and slip distribution of the gorkha earthquake using a layered crustal structure the best fit slip model shows that the preferred dip angle of the mainshock fault is 6 3 5 and the major slip is concentrated within depths of 8 15 km the maximum slip of 6 0 m occurs at a depth of 11 km 70 km south east of the epicenter the coseismic rupture extends 150 km eastward of the epicentre with a cumulative geodetic moment of 7 8 10 20 nm equivalent to an earthquake of m w 7 84 we also investigate the m w 7 2 aftershock on 12 may 2015 using another three postseismic interferograms from alos2 radarsat 2 and sentinel 1 a the insar based best fit slip model of the largest aftershock implies that its major slip is next to the eastern lower end of the mainshock rupture with a similar maximum slip of 6 m at a depth of 13 km this study generates various coseismic geodetic measurements to determine the source parameters of the m w 7 8 gorkha earthquake and 12 may m w 7 2 afershock providing an additional chance to understand the local fault structure and slip extent

geometric kinematic and erosional history of the central andean plateau bolivia 15 17 s 1 latitudinal changes in topography climate and thrust belt geometry in the central andes have led to conflicting hypotheses that climate or tectonics exert a first order control on orogen evolution the relative roles of climate and tectonics in the evolution of the andean orogen are difficult to quantify because of a lack of detailed observations for both the long term deformation and erosion history of the andean fold thrust belt we contribute to the resolution of this problem by presenting a sequentially restored balanced cross section based on new mapping across the northern bolivia portion of the thrust belt 15 17 s the timing and magnitude of exhumation across the cross section are determined by synthesizing 10 new and 70 previously published mineral cooling ages once balanced and restored the section was sequentially forward modeled using stratigraphic and cooling age constraints results indicate the eastern cordillera ec records the highest magnitudes of shortening 123 km or 55 the interandean zone ia has shortened 48 km or 30 in both the ec and ia individual thrust sheets are tightly folded and have minor offsets of 1 5 km the subandes sa has multiple levels of detachments allowing for thrust sheets with relatively large offsets 6 17 km total shortening in the sa is 66 km or 40 total magnitude of shortening for the entire fold thrust belt in this region is 276 km 40 new apatite and zircon fission track cooling ages in conjunction with published ages indicate two phases of rapid exhumation an earlier phase from 40 to 25 ma in the ec and one prior to 25 ma in the ia followed by distributed exhumation of the entire fold thrust belt from 15 0 ma combined exhumation estimates from the balanced cross section and thermochronology suggest 9 11 km of exhumation in the ec 5 9 km in the ia and 3 4 km in the sa long term shortening rates are 7 mm a for the ec and ia and 4 8 mm a for the sa the sa shortening rates are based on a 15 0 ma or 8 0 ma deformation window by linking cooling ages to location and magnitude of shortening we suggest an 10 17 ma pause or a dramatic deceleration in the rate of deformation and propagation of the fold thrust belt between 25 and 15 or 8 ma

radar interferogram filtering for geophysical applications the use of sar interferometry is often impeded by decorrelation from thermal noise temporal change and baseline geometry power spectra of interferograms are typically the sum of a narrow band component combined with broad band noise we describe a new adaptive filtering algorithm that dramatically lowers phase noise improving both measurement accuracy and phase unwrapping while demonstrating graceful degradation in regions of pure noise the performance of the filter is demonstrated with sar data from the ers satellites over the jakobshavns glacier of greenland

andean tectonics related to geometry of subducted nazca plate seismological and geological data show that tectonic segmentation of the andes coincides with segmentation of the subducted nazca plate which has nearly horizontal segments and 30 east dipping segments andean tectonics above a flat subducting segment between 28 s to 33 s are characterized by from west to east 1 a steady topographic rise from the coast to the crest of the andes 2 no significant quaternary and possibly neogene magmatism 3 a narrow belt of eastward migrating apparently thin skinned neogene to quaternary shortening of the andes and 4 plio pleistocene uplift of the crystalline basement on reverse faults in the pampeanas ranges from about 15 to 24 s over a 30 dipping subducted plate a west to east andes cross section includes 1 a longitudinal valley east of coastal mountains 2 an active neogene and holocene andesitic volcanic axis 3 the altiplano puna high plateau 4 a high neogene but inactive thrust belt eastern cordillera and 5 an active eastward migrating subandean thin skinned thrust belt tectonics above a steeply subducting segment south of 33 s are similar west of the volcanic axis but quite different to the east early cenozoic tectonics of western north america were quite similar to the neogene andes however duration of segmentation was longer and the width of deformation was greater in the western united states patterns of crustal seismicity are systematically related to plio quaternary structural provinces implying that current deformational processes have persisted since at least the pliocene horizontal compression parallel to the plate convergence direction is indicated to a distance of 800 km from the trench above flat subducting segments crustal seismicity occurs over a broad region whereas over steep segments it is confined to the narrow thrust belt strain patterns in the forearc region are complex and perhaps extensional and a broad region of the altiplano puna and eastern cordillera appears to be aseismic

2 5 d surface deformation of m6 1 earthquake near mt iwate detected by sar interferometry the two dimensional displacement vector field on the earth s surface associated with a large earthquake near iwate volcano in japan was mapped by combining satellite radar interferometry images from two different track directions the displacement reveals not only large main ruptures but details of many small faults movement of aftershocks and volcanic earthquakes the displacements of the aftershock faults coincide with a stress field reorganized by the main earthquake that accelerated the aftershock fault movements the displacements mimic the topography suggesting that repeated movements of the same faults in the quaternary have led to the presently existing topography

elastodynamic analysis for slow tectonic loading with spontaneous rupture episodes on faults with rate and state dependent friction we present an efficient and rigorous numerical procedure for calculating the elastodynamic response of a fault subjected to slow tectonic loading processes of long duration within which there are episodes of rapid earthquake failure this is done for a general class of rate and state dependent friction laws with positive direct velocity effect the algorithm allows us to treat accurately within a single computational procedure loading intervals of thousands of years and to calculate for each earthquake episode initially aseismic accelerating slip prior to dynamic rupture the rupture propagation itself rapid post seismic deformation which follows and also ongoing creep slippage throughout the loading period in velocity strengthening fault regions the methodology is presented using the two dimensional 2 d antiplane spectral formulation and can be readily extended to the 2 d in plane and 3 d spectral formulations and with certain modifications to the space time boundary integral formulations as well as to their discretized development using finite difference or finite element methods the methodology can be used to address a number of important issues such as fault operation under low overall stress interaction of dynamic rupture propagation with pore pressure development patterns of rupture propagation in events nucleated naturally as a part of a sequence the earthquake nucleation process earthquake sequences on faults with heterogeneous frictional properties and or normal stress and others the procedure is illustrated for a 2 d crustal strike slip fault model with depth variable properties for lower values of the state evolution distance of the friction law small events appear the nucleation phases of the small and large events are very similar suggesting that the size of an event is determined by the conditions on the fault segments the event is propagating into rather than by the nucleation process itself we demonstrate the importance of incorporating slow tectonic loading with elastodynamics by evaluating two simplified approaches one with the slow tectonic loading but no wave effects and the other with all dynamic effects included but much higher loading rate

coseismic and postseismic deformation of the 2016 mw 6 2 lampa earthquake southern peru constrained by interferometric synthetic aperture radar

afterslip and only afterslip following the 2004 parkfield california earthquake 1 an analysis of the first two years of postseismic surface deformations from gps reveals that afterslip is the only mechanism significantly contributing to postseismic deformation following the 2004 m6 parkfield california earthquake finite element modeling shows this event to have been too small to significantly stress the lower crust and upper mantle thus viscoelastic relaxation did not lead to detectable surface displacements similarly coseismically induced pressure changes in the upper crust were not sufficient to induce a measurable poroelastic response from 10 days to two years after the parkfield earthquake postseismic displacements at all gps stations experience the same characteristic decay time 2 weeks this suggests that only afterslip was activated and the distribution of slip remained unchanged in this time period afterslip was found to be broadly distributed in the upper 15 km of the crust and associated with a moment release of much greater magnitude than the coseismic rupture

the nature of orogenic crust in the central andes 1 the central andes 16 22 s are part of an active continental margin mountain belt and the result of shortening of the weak western edge of south america between the strong lithospheres of the subducting nazca plate and the underthrusting brazilian shield we have combined receiver function and surface wave dispersion results from the banjo seda project with other geophysical studies to characterize the nature of the continental crust and mantle lithospheric structure the major results are as follows 1 the crust supporting the high elevations is thick and has a felsic to intermediate bulk composition 2 the relatively strong brazilian lithosphere is underthrusting as far west 65 5 w as the high elevations of the western part of the eastern cordillera ec but does not underthrust the entire altiplano 3 the subcrustal lithosphere is delaminating piecemeal under the altiplano ec boundary but is not completely removed beneath the central altiplano the altiplano crust is characterized by a brittle upper crust decoupled from a very weak lower crust that is dominated by ductile deformation leading to lower crustal flow and flat topography in contrast in the high relief inland sloping regions of the ec and sub andean zone the upper crust is still strongly coupled across the basal thrust of the fold thrust belt to the underthrusting brazilian shield lithosphere subcrustal shortening between the altiplano and brazilian lithosphere appears to be accommodated by delamination near the altiplano ec boundary our study suggests that orogenic reworking may be an important part of the felsification of continental crust

lithospheric evolution of the andean fold thrust belt bolivia and the origin of the central andean plateau we combine geological and geophysical data to develop a generalized model for the lithospheric evolution of the central andean plateau between 188 and 208 s from late cretaceous to present by integrating geophysical results of upper mantle structure crustal thickness and composition with recently published structural stratigraphic and thermochronologic data we emphasize the importance of both the crust and upper mantle in the evolution of the central andean plateau four key steps in the evolution of the andean plateau are as follows 1 initiation of mountain building by 70 ma suggested by the associated foreland basin depositional history 2 eastward jump of a narrow early fold thrust belt at 40 ma through the eastward propagation of a 200 400 km long basement thrust sheet 3 continued shortening within the eastern cordillera from 40 to 15 ma which thickened the crust and mantle and established the eastern boundary of the modern central andean plateau removal of excess mantle through lithospheric delamination at the eastern cordillera altiplano boundary during the early miocene appears necessary to accommodate underthrusting of the brazilian shield replacement of mantle lithosphere by hot asthenosphere may have provided the heat source for a pulse of mafic volcanism in the eastern cordillera and altiplano at 24 23 ma and further volcanism recorded by 12 7 ma crustal ignimbrites 4 after 20 ma deformation waned in the eastern cordillera and interandean zone and began to be transferred into the subandean zone long term rates of shortening in the fold thrust belt indicate that the average shortening rate has remained fairly constant 8 10 mm year through time with possible slowing 5 7 mm year in the last 15 20 myr we suggest that cenozoic deformation within the mantle lithosphere has been focused at the eastern cordillera altiplano boundary where the mantle most likely continues to be removed through piecemeal delamination d 2005 elsevier b v all rights reserved

seismic and aseismic slip evolution and deformation associated with the 2009 2010 northern malawi earthquake swarm east african rift summary interferometric synthetic aperture radar insar measurements field observations and elastic modelling of the 2009 2010 karonga northern malawi earthquake swarm reveal widespread coseismic and localized post seismic deformation in a period of about 1 5 months starting on november 5 29 m 4 earthquakes struck the region culminating in an mw 6 peak event on december 19 the next few months were characterized by significant localized deformation with a very low seismic moment release we find a very good agreement between insar and field observations of surface ruptures our best fitted coseismic models indicate dip slip displacements on a fault dipping 40 to the southwest with maximum slip of about 120 cm at 3 5 km depth fault activity continued until 2010 august as shallow aseismic afterslip mostly above the maximum coseismic slip patches although the swarm occurred within a coastal plain covered by porous quaternary sediments and a high water table the effect of poroelastic relaxation on the post seismic deformation was found to be negligibly small in contrast with other recent earthquake swarms along the east african rift the karonga swarm shows no evidence for dike intrusion

postseismic deformation due to the mw 6 0 2004 parkfield earthquake stress driven creep on a fault with spatially variable rate and state friction parameters 1 we investigate the coseismic and postseismic deformation due to the m w 6 0 2004 parkfield california earthquake we produce coseismic and postseismic slip models by inverting data from an array of 14 continuous gps stations from the scign network kinematic inversions of postseismic gps data over a time period of 3 years show that afterslip occurred in areas of low seismicity and low coseismic slip predominantly at a depth of 5 km inversions suggest that coseismic stress increases were relaxed by predominantly aseismic afterslip on a fault plane the kinetics of afterslip is consistent with a velocity strengthening friction generalized to include the case of infinitesimal velocities we performed simulations of stress driven creep using a numerical model that evaluates the time dependent deformation due to coseismic stress changes in a viscoelastoplastic half space starting with a coseismic slip distribution we compute the time dependent evolution of afterslip on a fault plane and the associated displacements at the gps stations data are best explained by a rate strengthening model with frictional parameter a b 7 x 10 3 at a high end of values observed in laboratory experiments we also find that the geodetic moment due to creep is a factor of 100 greater than the cumulative seismic moment of aftershocks the rate of aftershocks in the top 10 km of the seismogenic zone mirrors the kinetics of afterslip suggesting that postearthquake seismicity is governed by loading from the nearby aseismic creep the san andreas fault around parkfield is deduced to have large along strike variations in rate and state frictional properties velocity strengthening areas may be responsible for the separation of the coseismic slip in two distinct asperities and for the ongoing aseismic creep occurring between the velocity weakening patches after the 2004 rupture

scardec a new technique for the rapid determination of seismic moment magnitude focal mechanism and source time functions for large earthquakes using body wave deconvolution accurate and fast magnitude determination for large shallow earthquakes is of key importance for post seismic response and tsumami alert purposes when no local real time data are available which is today the case for most subduction earthquakes the first information comes from teleseismic body waves standard body wave methods give accurate magnitudes for earthquakes up to mw 7 7 5 for larger earthquakes the analysis is more complex because of the non validity of the point source approximation and of the interaction between direct and surface reflected phases the latter effect acts as a strong high pass filter which complicates the magnitude determination we here propose an automated deconvolutive approach which does not impose any simplifying assumptions about the rupture process thus being well adapted to large earthquakes we first determine the source duration based on the length of the high frequency 1 3 hz signal content the deconvolution of synthetic double couple point source signals depending on the four earthquake parameters strike dip rake and depth from the windowed real data body wave signals including p pcp pp sh and scs waves gives the apparent source time function stf we search the optimal combination of these four parameters that respects the physical features of any stf causality positivity and stability of the seismic moment at all stations once this combination is retrieved the integration of the stfs gives directly the moment magnitude we apply this new approach referred as the scardec method to most of the major subduction earthquakes in the period 1990 2010 magnitude differences between the global centroid moment tensor cmt and the scardec method may reach 0 2 but values are found consistent if we take into account that the global cmt solutions for large shallow earthquakes suffer from a known trade off between dip and seismic moment we show by modelling long period surface waves of these events that the source parameters retrieved using the scardec method explain the observed surface waves as well as the global cmt parameters thus confirming the existing trade off for some well instrumented earthquakes our results are also supported by independent studies based on local geodetic or strong motion data this study is mainly focused on moment determination however the scardec method also informs us about the focal mechanism and source depth and can be a starting point to study systematically the complexity of the stf

the regional intraplate stress field in south america a compilation of lithospheric stress directions for continental south america and the inferred major patterns of the regional intraplate stress field are presented stress orientations are based primarily on earthquake focal mechanisms and quaternary fault slip inversion published in the literature four new focal mechanisms based on short period p wave modeling and selected centroid moment tensor solutions published by u s geological survey consistent with p wave first motions at south american and other world wide standard seismograph network stations are also included in the data base the observed patterns of intraplate stresses may be useful in constraining numerical models of the plate driving forces in the south american plate in the andean plateau altitudes greater than 3000 m n s extensional stresses predominate e w compressional stresses are observed in the sub andean and platform regions extending up to about 1000 km east of the andes the maximum horizontal stress shmax is uniformly oriented in the e w direction throughout western south america averages of the shmax direction at grid points spaced 2 5 o were taken as representing the regional field the e w direction of this regional field is not affected by the change of strike of the andean chain nor by the contact of a flat subducted slab underneath the regional shmax direction is oriented 15 o more clockwise than the direction of the nazca plate convergence the difference between the regional shmax orientations and the absolute plate motion may be only about 6 o this may indicate that contact forces with the nazca plate may not be the only major contributor to the intraplate stresses in western south america the eastern limit of this andean stress province seems to coincide with aseismic regions in the upper amazon basin and in the paraml basin in the central amazonian region seismicity and stress data suggest a seismic province with n s compressional stresses the origin of these stresses is not yet clearly understood but could possibly be related to lower crustal loading along the middle amazon basin in northeastern brazil seismicity is characterized by upper crustal strike slip earthquakes bordering the potiguar marginal basin a model is proposed for this region in which the stress field is the result of a superposition of regional e w compressional stresses and local extensional stresses oriented perpendicular to the continental margin possibly related to density contrasts and sediment loading in the continental shelf

evaluating models of coulomb stress transfer is variable fault geometry important to determine the importance of receiver fault geometry in coulomb stress calculations a new methodology is presented to model faults with variable geometry although most models use planar faults it is known that these are inaccurate representations of faults observed in the field the central italian apennines are chosen as a straightforward tectonic system with well exposed normal faults to investigate the effect of variable geometry it is shown that the static coulomb stress transfer is most sensitive to changes in strike of the receiver faults rather than changes in dip and rake therefore a novel methodology to generate strike variable faults composed of discrete rectangular patches is developed using the 2009 l aquila earthquake mw 6 3 the calculated stress transferred to planar versus variable faults is assessed the stress transferred to variable faults is sufficiently different when compared to planar cases to merit other earthquake sequences being reassessed with available fault geometry

patterns and mechanisms of coseismic and postseismic slips of the 2011 mw 7 1 van turkey earthquake revealed by multi platform synthetic aperture radar interferometry on 23rd october 2011 a mw 7 1 reverse slip earthquake occurred in the bardakci saray thrust fault zone in the van region eastern turkey earlier geodetic studies have found different slip distributions in terms of both magnitude and pattern in this paper we present several cosmo skymed csk envisat asar and radarsat 2 interferograms spanning different time intervals showing that significant postseismic signals can be observed in the first three days after the mainshock using observations that combine coseismic and postseismic signals is shown to significantly underestimate coseismic slip we hence employed the csk pair with the minimum postseismic signals to generate one conventional interferogram and one along track interferogram for further coseismic modelling our best fit coseismic slip model suggests that 1 this event is associated with a buried nnw dipping fault with a preferable dip angle of 49 and a maximum slip of 6 5 m at a depth of 12 km and 2 two unequal asperities can be observed consistent with previous seismic solutions significant oblique aseismic slip with predominant left lateral slip components above the coseismic rupture zone within the first 3 days after the mainshock is also revealed by a postseismic csk interferogram indicating that the greatest principal stress axis might have rotated due to a significant stress drop during the coseismic rupture

tectonic development southeastern border of the puna plateau northwestern argentine andes the puna altiplano a 500 000 km2 area at an average elevation of 3 7 km in the central andes occurs in a non collisional plate setting over a 30 east dipping segment of the benioff zone and is bounded to the north and south by nearly flat segments of the subducted nazca plate a 120 km long portion of the southeastern boundary of the puna in northwestern argentina was studied to gain insight into the structures associated with uplift of the plateau and into the nature of structures over the transition from flat to steeper subduction the structural geometry and kinematic evolution of the region was determined from geologic mapping and kinematic analysis of minor fault arrays the present southeastern margin of the puna was uplifted between 5 10 and 2 ma northwest southeast horizontal shortening and vertical extension during uplift were produced by northeast striking en echelon thrust faults dipping 17 55 northwest four to seven en echelon structural blocks each 20 30 km long constitute the border of the puna their structural geometry precludes large scale overthrusting as an important mechanism of plateau uplift along the studied segment in the past 2 m y there has been a 45 change in the direction of shortening and locally a 90 change in the extension direction indicating that the structures accompanying uplift are no longer active this change could be due to a change either in the geometry of the subducted plate or in convergence directions although neither of these hypotheses is testable given presently available data