the 2010 maule chile earthquake downdip rupture limit revealed by space geodesy radar interferometry from the alos satellite captured the coseismic ground deformation associated with the 2010 mw 8 8 maule chile earthquake the alos interferograms reveal a sharp transition in fringe pattern at 150 km from the trench axis that is diagnostic of the downdip rupture limit of the maule earthquake an elastic dislocation model based on ascending and descending alos interferograms and 13 near field 3 component gps measurements reveals that the coseismic slip decreases more or less linearly from a maximum of 17 m along strike average of 6 5 m at 18 km depth to near zero at 43 48 km depth quantitatively indicating the downdip limit of the seismogenic zone the depth at which slip drops to near zero appears to be at the intersection of the subducting plate with the continental moho our model also suggests that the depth where coseismic slip vanishes is nearly uniform along the strike direction for a rupture length of 600 km the average coseismic slip vector and the interseismic velocity vector are not parallel which can be interpreted as a deficit in strike slip moment release

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

interseismic strain accumulation measured by gps in the seismic gap between constitucion and concepcion in chile the concepcion constitucion area 35 37 s in south central chile is very likely a mature seismic gap since no large subduction earthquake has occurred there since 1835 three campaigns of global positioning system gps measurements were carried out in this area in 1996 1999 and 2002 we observed a network of about 40 sites including two east west transects ranging from the coastal area to the argentina border and one north south profile along the coast our measurements are consistent with the nazca south america relative angular velocity 55 9 n 95 2 w 0 610 ma discussed by vigny et al 2008 this issue which predicts a convergence of 68 mm year oriented 79 n at the chilean trench near

earthquakes a chilean surprise initiation of the great 2010 chile earthquake occurred within the rupture zone of the 1835 event experienced by charles darwin however the peak fault slip was to the north of the epicentre not where it was expected to occur

finite element model predictions of static deformation from dislocation sources in a subduction zone sensitivities to homogeneous isotropic poisson solid and half space assumptions 1 dislocation models can simulate static deformation caused by slip along a fault these models usually take the form of a dislocation embedded in a homogeneous isotropic poisson solid half space hipshs however the widely accepted hipshs assumptions poorly approximate subduction zone systems of converging oceanic and continental crust this study uses three dimensional finite element models fems that allow for any combination including none of the hipshs assumptions to compute synthetic green s functions for displacement using the1995 mw 8 0 jalisco colima mexico subduction zone earthquake and associated measurements from a nearby gps array as an example fem generated synthetic green s functions are combined with standard linear inverse methods to estimate dislocation distributions along the subduction interface loading a forward hipshs model with dislocation distributions estimated from fems that sequentially relax the hipshs assumptions yields the sensitivity of predicted displacements to each of the hipshs assumptions for the subduction zone models tested and the specific field situation considered sensitivities to the individual poisson solid isotropy and homogeneity assumptions can be substantially greater than gps measurement uncertainties forward modeling quantifies stress coupling between the mw 8 0 earthquake and a nearby mw 6 3 earthquake that occurred 63 days later coulomb stress changes predicted from static hipshs models cannot account for the 63 day lag time between events alternatively an fem that includes a poroelastic oceanic crust which allows for postseismic pore fluid pressure recovery can account for the lag time the pore fluid pressure recovery rate puts an upper limit of 10 17 m2 on the bulk permeability of the oceanic crust

impact of topography on earthquake static slip estimates abstract our understanding of earthquakes is limited by our knowledge and our description of the physics of the earth when solving for subsurface fault slip it is common practice to assume minimum complexity for characteristics such as topography fault geometry and elastic properties these characteristics are rarely accounted for because our knowledge of them is often partial and they can be difficult to include in simulations however topography and bathymetry are known all over the earth s surface and recently developed software packages such as specfem x have simplified the process of including them in calculations here we explore the impact of topography on static slip estimates we also investigate whether the influence of topography can be accounted for with a zeroth order correction which accounts for variations in distance between subfaults and the surface of the domain to this end we analyze the 2015 mw 7 5 gorkha nepal and the 2010 mw 8 8 maule chile earthquakes within a bayesian framework the regions affected by these events represent different types of topography chile which contains both a deep trench and a major orogen the andes has a greater overall elevation range and steeper gradients than nepal where the primary topographic feature is the himalayan mountain range additionally the slip of the continental nepal event is well constrained whereas observations are less informative in a subduction context we show that topography has a non negligible impact on inferred slip models our results suggest that the effect of topography on slip estimates increases with limited observational constraints and high elevation gradients in particular we find that accounting for topography improves slip estimates where topographic gradients are large when topography has a significant impact on slip the zeroth order correction is not sufficient

brioverian volcanism and cadomian tectonics baie de st brieuc brittany stages in the evolution of a late precambrian ensialic basin

emplacement of lobate sheet flows with hyaloclastites onto soft sediment the erquy neoproterozoic lava pile armorican massif france abstract the neoproterozoic volcano sedimentary succession of the heussaye headland erquy belongs to the cadomian block located in the north east of the armorican massif france the volcanism dated at approximately 608 7 ma zircon u pb data occurred in a back arc basin this site exhibits a noteworthy verticalized pile of moderately metamorphosed greenschist facies basaltic andesite flows of arc back arc tholeiite affinity alternating with metasedimentary layers sandstones and siltstones a large range of volcanic facies characteristic of an underwater soft substrate environment can be continuously studied for over than 200 m parallel to the flow edges they include pillow lavas lava lobes fluidal peperites and sediment matrix hyaloclastites the presence of parallel lava lobes in a sector where one lava flow is capped by a variably thick hyaloclastite carapace together with the occurrence of asymmetric turbiditic folds in interbedded metasedimentary layers suggests the existence of an easterly facing gentle paleoslope the sudden thinning of this hyaloclastite carapace in two spots located approximately 60 m from each other is attributed to the synvolcanic activity of two conjugate normal paleofaults this hypothesis is supported by the observation of a hyaloclastite accumulation in one of the two spots close to a strike slip fault which may have been extensional at the time of the volcanism water entered the lava flow along the faults resulting in an interstitial network of hyaloclastites by quench fragmentation in the upper part of the hanging wall block all these observations are consistent with a model of lava emplacement along a subaqueous slope resulting from synmagmatic extensional faulting in a marginal basin context

the effects of topography on magma chamber deformation models application to mt etna and radar interferometry we have used a three dimensional elastic finite element model to examine the effects of topography on the surface deformation predicted by models of magma chamber deflation we used the topography of mt etna to control the geometry of our model and compared the finite element results to those predicted by an analytical solution for a pressurized sphere in an elastic half space topography has a significant effect on the predicted surface deformation for both displacement profiles and synthetic interferograms not only are the predicted displacement magnitudes significantly different but also the map view patterns of displacement it is possible to match the predicted displacement magnitudes fairly well by adjusting the elevation of a reference surface however the horizontal pattern of deformation is still significantly different thus inversions based on constant elevation reference surfaces may not properly estimate the horizontal position of a magma chamber we have investigated an approach where the elevation of the reference surface varies for each computation point corresponding to topography for vertical displacements and tilts this method provides a good fit to the finite element results and thus may form the basis for an inversion scheme for radial displacements a constant reference elevation provides a better fit to the numerical results

the cadomian granites of mancellia northeast armorican massif of france relationship to the st malo migmatite belt petrogenesis and tectonic setting abstract the north armorican shear zone nasz divides the cadomian belt of the armorican massif of france into two major terranes the north armorican composite terrane nact and the central armorican terrane cat the nact is a pastiche of displaced blocks and terranes st brieuc terrane st malo terrane and mancellian terrane which results from the amalgamation of cadomian continental arc and basin complexes by sinistral transpression along a continental margin above a southerly dipping subduction zone in the nact the neoproterozoic brioverian succession was deformed and metamorphosed during the cadomian orogeny and intruded by syn to post tectonic plutonic complexes the st malo migmatite belt is a syn tectonic suite of anatectic migmatites derived through partial melting of the brioverian succession using the t test on whole rock geochemical data there is no evidence to suggest that a sample of st malo diatexites comes from a population with a different mean than some samples of the brioverian succession sandstones resulting homogeneous diatexites anatectic granites of the core were emplaced syn kinematically into cadomian strike slip shear zones thus the age of anatexis of 540 ma is also the date of strike slip shearing and provides a minimum age for the sinistral transpression which amalgamated the terranes of the nact the mancellian granites to the southeast of the st malo migmatites were emplaced at 540 ma and are overlain unconformably by cambrian sediments overall geochemistry and a variety of specific geochemical parameters show that the mancellian granites are similar to the diatexites and anatectic granites of the st malo migmatite belt using the t test on whole rock geochemical data there is no evidence to suggest that the sample of mancellian granites comes from a population with a different mean than the sample of st malo diatexites additionally both suites of rocks are peraluminous they have similar distributions of rb sr and ba they have k rb ratios around 225 and they plot largely within the vag field using trace element discrimination diagrams for the interpretation of tectonic setting samples of the brioverian succession sandstones the st malo migmatites and the mancellian granites all exhibit similar primordial mantle normalized element patterns preliminary results of nd and sr isotope studies reveal a similar restricted range of values for nd between 4 0 and 7 3 and sr between 3 and 42 and depleted model ages in the range 1 7 to 1 5 ga tdmur for both mancellian granites and st malo migmatites isotopic features which set these rock types apart from other cadomian granites within the nact the st malo migmatite belt and the mancellian granites are coeval at 540 ma and both developed by anatexis at intermediate crustal depths of the brioverian succession within an inverted but only moderately overthickened behindarc basin in comparison with the st malo migmatites the mancellian granites represent farther travelled products of intracrustal melting but their geochemistry still preserves the characteristic signature of the source

geochemistry and geotectonic interpretation of the penthievre crystalline massif northern brittany france abstract in the armorican massif of brittany and normandy northern france and the channel islands u k an episode of crust formation spanning the period from 700 ma to the early palaeozoic can be recognized and is attributed to the cadomian orogenic cycle during the early part of this orogenic cycle the components of the penthievre crystalline massif were emplaced to produce the basement upon which local brioverian volcanism and sedimentation took place three separate episodes of crustal accretion have been recognised in the penthievre crystalline massif the first is represented by the yffiniac group which is dominantly of basic to intermediate composition with a minor acidic component this suite which was metamorphosed at amphibolite facies shows geochemical characteristics of island arc tholeiitic to continental calc alkaline igneous activity ree profiles are flat to lree enriched cen ybn in the range 1 18 4 89 incompatible element spidergrams show relative enrichment of for example th u lree and lil elements and depletion of ta nb and ti ta la and nb la ratios are low the second suite is represented by the port morvan group a linear belt of leucocratic orthogneisses containing net veined rafts of deformed yffiniac group rocks the port morvan group gneisses are trondhjemitic to quartz dioritic in composition with na2o k2o up to 32 9 the third assemblage comprises the jospinet group and the fort de la latte complex these are part of a compositionally expanded mantle derived plutonic suite ranging from ultrabasic to aplitic in composition flat chondritic ree profiles characterise gabbros whereas lree enriched profiles characterise calc alkaline and alkali calcic granitoid plutons there is evidence in penthievre for protracted destructive plate margin activity and associated plutonism of andean type the penthievre crystalline massif probably represents the roots of juxtaposed island arc and continental margin terranes produced in three crust forming episodes during the cadomian orogenic cycle brioverian sedimentation and volcanism took place in ensialic basins on rifted crust the closure of these brioverian basins was accompanied by the emplacement of calc alkaline plutons into the crystalline basement

micropaleontologie du proterozoique du massif armoricain france abstract upper proterozoic sediments brioverian of brittany and normandy france contain microfossils of algal affinities 1 1 assemblages of solitary and colonial vegetative cells and possibly sporulating cells which seem strikingly similar to sphaerocongregus variabilis reported from late precambrian sedimentary rocks in north america paleocryptidium described in brittany and reported from proterozoic rocks of bohemia is probably conspecific of sphaerocongregus in brittany and normandy these assemblages are particularly abundant in lower and middle brioverian sedimentary rocks 670 1000 ma 2 2 assemblages of solitary and colonial cells which can be compared with various species of favososphaera reported from the upper proterozoic of europe in brittany these assemblages have only been detected in upper brioverian sandstones and limestones 670 580 ma

integrated seismic source model of the 2015 gorkha nepal earthquake we compared spatiotemporal slip rate and high frequency around 1 hz radiation distributions from teleseismic p wave data to infer the seismic rupture process of the 2015 gorkha nepal earthquake for these estimates we applied a novel waveform inversion formulation that mitigates the effect of green s functions uncertainty and a hybrid backprojection method that mitigates contamination by depth phases our model showed that the dynamic rupture front propagated eastward from the hypocenter at 3 0 km s and triggered a large slip event centered about 50 km to the east it also showed that the large slip event included a rapid rupture acceleration event and an irregular deceleration of rupture propagation before the rupture termination heterogeneity of the stress drop or fracture energy in the eastern part of the rupture area where aftershock activity was high inhibited rupture growth high frequency radiation sources tended to be in the deeper part of the large slip area which suggests that heterogeneity of the stress drop or fracture energy there may have contributed to the damage in and around kathmandu

line of sight displacement from alos 2 interferometry mw 7 8 gorkha earthquake and mw 7 3 aftershock interferometric synthetic aperture radar insar is a key tool for the analysis of displacement and stress changes caused by large crustal earthquakes particularly in remote areas a challenge for traditional insar has been its limited spatial and temporal coverage especially for very large events whose dimensions exceed the typical swath width of 70 100 km this problem is addressed by the alos 2 satellite whose palsar 2 instrument operates in scansar mode enabling a repeat time of 2 weeks and a swath width of 350 km here we present insar line of sight displacement data from alos 2 palsar 2 observations covering the mw 7 8 gorkha nepal earthquake and its mw 7 3 aftershock that were acquired within 1 week of each event the data are made freely available and we encourage their use in models of the fault slip and associated stress changes the mw 7 3 aftershock not only extended the rupture area of the main shock toward the east but also left a 20 km gap where the fault has little or no coseismic slip we estimate this unslipped fault patch has the potential to generate a mw 6 9 event

localized fault slip to the trench in the 2010 maule chile mw 8 8 earthquake from joint inversion of high rate gps teleseismic body waves insar campaign gps and tsunami observations the 27 february 2010 mw 8 8 maule earthquake ruptured 500 km along the plate boundary offshore central chile between 34 s and 38 5 s establishing whether coseismic fault offset extended to the trench is important for interpreting both shallow frictional behavior and potential for tsunami earthquakes in the region joint inversion of high rate gps teleseismic body waves interferometric synthetic aperture radar insar campaign gps and tsunami observations yields a kinematic rupture model with improved resolution of slip near the trench bilateral rupture expansion is resolved in our model with relatively uniform slip of 5 10 m downdip beneath the coast and two near trench high slip patches with 12 m displacements the peak slip is 17 m at a depth of 15 km on the central megathrust located 200 km north from the hypocenter and overlapping the rupture zone of the 1928 m 8 event the updip slip is 16 m near the trench another shallow near trench patch is located 150 km southwest of the hypocenter with a peak slip of 12 m checkerboard resolution tests demonstrate that correctly modeled tsunami data are critical to resolution of slip near the trench with other data sets allowing but not requiring slip far offshore large interplate aftershocks have a complementary distribution to the coseismic slip pattern filling in gaps or outlining edges of large slip zones two clusters of normal faulting events locate seaward along the plate motion direction from the localized regions of large near trench slip suggesting that proximity of slip to the trench enhanced extensional faulting in the underthrusting plate

the 1985 central chile earthquake a repeat of previous great earthquakes in the region a great earthquake surface wave magnitude 7 8 occurred along the coast of central chile on 3 march 1985 causing heavy damage to coastal towns intense foreshock activity near the epicenter of the main shock occurred for 11 days before the earthquake the aftershocks of the 1985 earthquake define a rupture area of 170 by 110 square kilometers the earthquake was forecast on the basis of the nearly constant repeat time 83 9 years of great earthquakes in this region an analysis of previous earthquakes suggests that the rupture lengths of great shocks in the region vary by a factor of about 3 the nearly constant repeat time and variable rupture lengths cannot be reconciled with time or slip predictable models of earthquake recurrence the great earthquakes in the region seem to involve a variable rupture mode and yet for unknown reasons remain periodic historical data suggest that the region south of the 1985 rupture zone should now be considered a gap of high seismic potential that may rupture in a great earthquake in the next few tens of years

postseismic relaxation driven by brittle creep a possible mechanism to reconcile geodetic measurements and the decay rate of aftershocks application to the chi chi earthquake taiwan we evaluate the effect of coseismic stress changes on the fault slip at midcrustal depth assuming a velocity strengthening brittle creep rheology we show that this model can help reconcile the time evolution of afterslip as measured from geodesy with aftershocks decay we propose an analytical expression for slip of the brittle creeping fault zone bcfz that applies to any dynamic or static stress perturbation including shear stress and normal stress changes the model predicts an initial logarithmic increase of slip with time postseismic slip rate decays over a characteristic time t r a that does not depend on the amplitude of the stress perturbation and it asymptotically joins the long term creep imposed by interseismic stress buildup given that the seismicity rate might be considered proportional to the sliding velocity of the bcfz the model predicts a decay rate of aftershocks that follows omori s law with a mathematical formalism identical to that of dieterich 1994 although based on a different mechanical rationale our model also differs from dieterich s model in that it requires that aftershock sequences and deep afterslip as constrained from geodetic measurements should follow the same temporal evolution we test this for the 1999 chi chi earthquake m w 7 6 and find that both sets of data are consistent with a model of afterslip due to the response of the bcfz the inferred relaxation time t r 8 5 years requires a value for a log v being the coefficient of friction in the range between 1 3 10 3 and 10 2

effect of near fault terrain upon dislocation modeling coseismic surface deformation provides important information needed to determine source rupture geometry and slip distribution as well as to estimate seismic moment in this study numerical experiments were designed to analyze and classify how free surface topography affects surface deformation the investigation was performed by 3 d finite element modeling results of this study show that crustal deformation induced by near fault terrain is significant and can be measured with present geodetic survey techniques the characteristics of the terrain effects show that a hill structure produces more crustal deformation than a half space model and that the crustal deformation of a basin structure is less than that of the half space model the topographic correction is in the order of five percent of the fault dislocation on the basis of the relationship between fault offset and earthquake magnitude it is suggested that the terrain effects on the coseismic crustal deformation of shallow earthquakes with a magnitude greater than 5 6 should be considered as one of the major errors in coseismic deformation modeling which ignored the surface topography on the order of 300 meters

an accurate and efficient method for including the effects of topography in three dimensional elastic models of ground deformation with applications to radar interferometry topography has a large effect on the results predicted by elastic surface deformation models in regions of significant relief in some cases topography may have more influence on the predicted deformation field than do model source parameters we have developed an approximate analytical technique for including topographic effects that retains most of the computational simplicity of elastic half space models while providing an accurate representation of topographic effects we use a series expansion of the elastic half space solution with a small slope approximation yielding a set of higher order corrections the integrated effect of these corrections is evaluated using fourier methods we investigate the effectiveness of our method by comparing predicted results for a tilted triaxial ellipsoid with those predicted by finite element models the resulting displacements and displacement gradients are in good agreement with finite element results both for relatively smooth topography synthetically generated and for the greater relief in the vicinity of mount etna volcano we then compare the results of our method with those predicted by traditional elastic half space models using different reference elevations and with a previously proposed method of estimating topographic effects our new method provides a significantly better fit to the finite element results than do the other methods our method is able to accurately portray both the number and the horizontal pattern of fringes in a synthetic interferogram when compared with finite element results in particular the method accurately represents the broadening of fringes that is observed in regions of high relief as well as reproducing the location of the fringe center and the topographically induced deviation of the fringes from a regular pattern elastic half space models typically show a fringe center that is displaced with respect to the finite element results indicating that parameter inversions based on such a model would provide incorrect estimates of the horizontal source position the lack of topographically generated fringe distortions in elastic half space results would also likely lead to inaccuracies in the predicted magnitude and orientation of proposed deformation sources our new technique over comes these limitations and should be useful when evaluating either traditional geodetic results or the greater areal coverage provided by interferometric observations

interseismic megathrust coupling beneath the nicoya peninsula costa rica from the joint inversion of insar and gps data the nicoya peninsula costa rica was struck by a long anticipated and gap filling mw 7 6 earthquake in 2012 to study interseismic strain accumulation on the megathrust beneath the nicoya peninsula we present an improved interseismic coupling model by integrating interferometric synthetic aperture radar insar and gps data our model reveals three strongly coupled patches the first strongly coupled patch locates beneath the nicoya peninsula and ruptured during the 2012 earthquake the second strongly coupled patch locates offshore the central nicoya peninsula and remained largely unbroken however this region is close to and possibly intermingled with shallow slow slip and tremor suggesting that accumulated strain in this region may be released both seismically and aseismically the third strongly coupled patch offshore of the southeastern end of nicoya overlaps part of the coseismic rupture of the 1990 mw 7 0 nicoya gulf earthquake indicating that significant strain has re accumulated since this event incorporating insar data provides a more refined interseismic coupling model than using gps alone and allows for a more reliable comparison with local seismic and aseismic activities this comparison indicates that strongly locked regions during the interseismic stage are the loci of coseismic slip and deep slow slip and low frequency earthquakes occur in regions of low coupling or transition zones from low to high coupling while shallow slow slip and tremor commingle with strongly coupled regions our study demonstrates that insar data can be used to recover small long wavelength deformation signals with refined resolution in challenging subduction zone environments when integrated with gps observations

toward understanding tectonic control on the mw 8 8 2010 maule chile earthquake the maule earthquake of 27th february 2010 m w 8 8 affected similar to 500 km of the nazca south america plate boundary in south central chile producing spectacular crustal deformation here we present a detailed estimate of static coseismic surface offsets as measured by survey and continuous gps both in near and far field regions earthquake slip along the megathrust has been inferred from a joint inversion of our new data together with published gps insar and land level changes data using green s functions generated by a spherical finite element model with realistic subduction zone geometry the combination of the data sets provided a good resolution indicating that most of the slip was well resolved coseismic slip was concentrated north of the epicenter with up to 16 m of slip whereas to the south it reached over 10 m within two minor patches a comparison of coseismic slip with the slip deficit accumulated since the last great earthquake in 1835 suggests that the 2010 event closed a mature seismic gap slip deficit distribution shows an apparent local overshoot that highlight cycle to cycle variability which has to be taken into account when anticipating future events from interseismic observations rupture propagation was obviously not affected by bathymetric features of the incoming plate instead splay faults in the upper plate seem to have limited rupture propagation in the updip and along strike directions additionally we found that along strike gradients in slip are spatially correlated with geometrical inflections of the megathrust our study suggests that persistent tectonic features may control strain accumulation and release along subduction megathrusts c 2012 elsevier b v all rights reserved

effects of three dimensional crustal structure and smoothing constraint on earthquake slip inversions case study of the mw6 3 2009 l aquila earthquake earthquake slip inversions aiming to retrieve kinematic rupture characteristics typically assume 1 d velocity models and a flat earth surface however heterogeneous nature of the crust and presence of rough topography lead to seismic scattering and other wave propagation phenomena introducing complex 3 d effects on ground motions here we investigate how the use of imprecise green s functions achieved by including 3 d velocity perturbations and topography affect slip inversion results we create sets of synthetic seismograms including 3 d heterogeneous earth structure and topography and then invert these synthetics using green s functions computed for a horizontally layered 1 d earth model we apply a linear inversion regularized by smoothing and positivity constraint and examine in detail how smoothing effects perturb the solution among others our tests and resolution analyses demonstrate how imprecise green s functions introduce artificial slip rate multiples especially at shallow depths and that the timing of the peak slip rate is hardly affected by the chosen smoothing the investigation is extended to recordings of the 2009 mw6 3 l aquila earthquake considering both strong motion and high rate gps stations we interpret the inversion results taking into account the lessons learned from the synthetic tests the retrieved slip model resembles previously published solutions using geodetic data showing a large slip asperity southeast of the hypocenter in agreement with other studies we find evidence for fast but subshear rupture propagation in updip direction followed by a delayed propagation along strike we conjecture that rupture was partially inhibited by a deep localized velocity strengthening patch that subsequently experienced afterslip

3 d finite element modelling of deformation and stress associated with faulting effect of inhomogeneous crustal structures summary modelling of deformation and stress caused by earthquake faulting or fault motion based on a homogeneous elastic half space model does not include crustal rigidity layering and lateral variations geological data and seismic surveys indicate that the crust is elastically inhomogeneous and that rigidity layering and heterogeneities are likely to affect the magnitude and pattern of deformation and stress we use the finite element method fem to investigate deformation and stress generated by strike slip tensile and thrust faulting considering rigidity layering in the crust for a fault with a dimension of 25 10 km and a slip value of 0 5 m cutting through the top 10 km of the crust the deformation and stress change associated with the three modes of faulting are calculated for an island arc crustal structure represented by three models of rigidity layering the results indicate i the maximum effect in horizontal displacements due to crustal layering for the investigated models is 19 7 mm and 28 8 mm for strike slip and tensile faulting respectively for thrust faulting the effect is up to 58 3 mm this remarkable effect is due to the offset of layers by thrust faulting which dynamically changes the crustal structure both horizontally and vertically ii the maximum effect in vertical deformation due to crustal rigidity layering for strike slip and tensile faulting is 5 mm in contrast the effect for thrusting is 30 3 mm iii the effect in the shear stress change at a depth of 7 5 km for the different styles of faulting ranges from 0 02 mpa to 0 10 mpa an additional modelling analysis of subduction thrusting at the japan trench with a detailed structural model based on seismic surveys further confirms the significant distortion caused by a homogeneous model that ignores crustal structural information overall the effect of crustal rigidity layering is at least 20 per cent for surface deformation and 15 per cent for stress changes at depth in light of the present accuracy of global positioning system gps observations 2 mm and the estimate of stress change required for earthquake hazard analysis ca 0 01 mpa the results from the numerical experiments indicate that crust inhomogeneity rigidity layering and lateral variations should be included in any quantitative models of faulting

teleseismic inversion for rupture process of the 27 february 2010 chile mw 8 8 earthquake the 27 february 2010 chile m w 8 8 earthquake is the fifth largest earthquake to strike during the age of seismological instrumentation the faulting geometry slip distribution seismic moment and moment rate function are estimated from broadband teleseismic p sh and rayleigh wave signals we explore some of the trade offs in the rupture process estimation due to model parameterizations limited teleseismic sampling of seismic phase velocities and uncertainty in fault geometry the average slip over the 81 500 km 2 rupture area is about 5 m with slip concentrations down dip up dip and southwest and up dip and north of the hypocenter relatively little slip occurred up dip offshore of the hypocenter the average rupture velocity is 2 0 2 5 km s

a 2 d hybrid technique to model the effect of topography on coseismic displacements application to the umbria marche central italy 1997 earthquake sequence summary we face the problem of modelling the influence of the irregular topography of the earth s crust on coseismic displacements the modelling technique we propose is valid for a homogeneous elastic 2 d domain and is based on a two step approach that uses 1 the traditional analytical results valid for elastic spaces and elastic half spaces with a flat free surface ffs and 2 a finite element fe numerical code to compute the disturbance induced by the local topography attention is particularly focused on 1 the comparison between the results obtained through our method and the analytical formulae valid for ffs geometries which are used extensively today in both forward and inverse modelling even in the presence of irregular topography and 2 the advantages of our hybrid approach over pure fe models after discussing the theoretical experiment of a gaussian topography we present an application to modelling the displacement fields induced by selected events of the earthquake sequence that hit the umbriamarche region in the central apennines italy in 1997 devoting major attention to the effect of the apennines chain topography in the source region in all cases the topography is found to play an important role and to introduce non negligible corrections to the coseismic surface displacement components computed through the ffs approximation the main effect is that topography not only affects the magnitude of the surface signal but it may also lead to highfrequency disturbances that tend to grow with the shallowness of the fault

coseismic slip distribution of the february 27 2010 mw 8 8 maule chile earthquake 1 static offsets produced by the february 27 2010 mw 8 8 maule chile earthquake as measured by gps and insar constrain coseismic slip along a section of the andean megathrust of dimensions 650 km in length 180 km in width gps data have been collected from both campaign and continuous sites sampling both the near field and far field alos palsar data from several ascending and descending tracks constrain the near field crustal deformation inversions of the geodetic data for distributed slip on the megathrust reveal a pronounced slip maximum of order 15 m at 15 25 km depth on the megathrust offshore lloca indicating that seismic slip was greatest north of the epicenter of the bilaterally propagating rupture a secondary slip maximum appears at depth 25 km on the megathrust just west of concepcion coseismic slip is negligible below 35 km depth estimates of the seismic moment based on different datasets and modeling approaches vary from 1 8 to 2 6 1022 n m our study is the first to model the static displacement field using a layered spherical earth model allowing us to incorporate both near field and far field static displacements in a consistent manner the obtained seismic moment of 1 97 1022 n m corresponding to a moment magnitude of 8 8 is similar to that obtained by previous seismic and geodetic inversions

coseismic slip distribution for the mw 9 2011 tohoku oki earthquake derived from 3 d fe modeling 1 the coseismic slip distribution of the mw 9 0 2011 tohoku oki earthquake has been estimated by inverting near field onshore and offshore geodetic data using green s function calculated with a 3 d finite element fe model the fe model simulates several geophysical features of the subduction zone that hosted the rupture surface of the event these features include a 3 d geometric configuration and distribution of material properties of the tectonic system a precise geometric configuration of the irregular rupture surface and an irregular free surface according to the topography and bathymetry a model that simulates rupture along the interface between the relatively weak overriding okhotsk plate and stiff subducting slab of the pacific plate requires less slip to produce the observed surface deformation compared to a model having uniform material properties across the rupture interface furthermore the estimated slip of the heterogeneous model is more widely distributed over the shallow portion of the plate boundary whereas the estimated slip of the homogeneous model is more focused updip of the epicenter this demonstrates the sensitivity of inverse analyses of geodetic data for the 2011 tohoku oki earthquake to the simulated domain geometry and configuration of material properties

traveltime delay and initial phase reversal of distant tsunamis coupled with the self gravitating elastic earth systematic tsunami traveltime delays of up to 15 min relative to the numerically simulated long waves from the 2010 chilean and 2011 tohoku oki earthquakes were widely observed at deep ocean tsunamimeters enigmatic small negative phases appearing before the main peak were commonly found only at the trans oceanic locations the frequency dependence of the measured tsunami phase velocities shows reverse dispersions at long periods i e the tsunami speed becomes slower at periods beyond 1000 s this is consistent with the phase velocities of a tsunami mode coupled with a self gravitating elastic earth suggesting that the effects of compression and dilatation of seawater elastic tsunami loadings on a solid earth and the geopotential variations associated with the motion of mass during tsunami propagation are responsible for the traveltime delays and the initial negative phases simple 1 d tsunami propagation tests confirm that the reverse dispersion creates a small negative phase that precedes the main peak at large distances a new method to simulate tsunami waveforms on real ocean bathymetry that takes into account seawater compressibility the elasticity of the earth and geopotential perturbations has been developed by applying a phase correction to the simulated long waves the simulated waveforms in which phase corrections are applied for the dispersion effects accurately reproduce the observed waveforms including a small initial negative phase that appears at distant locations the traveltime difference between the observed and simulated waveforms has been decreased to less than 5 min and the waveform difference between them remarkably diminishes

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

three dimensional fem derived elastic green s functions for the coseismic deformation of the 2005 mw 8 7 nias simeulue sumatra earthquake using finite element models fems we examine the sensitivity of surface displacements to the location of fault slip topography and three dimensional variations in elastic moduli in the context of a 2 d infinite thrust fault we then evaluate the impact of these factors and fault geometry on surface displacements and estimates of the distribution of coseismic slip associated with the 2005 m w 8 7 nias simeulue sumatra earthquake topographic effects can be significant near the trench where bathymetric gradients are highest and the fault is closest to the free surface variations in young s modulus can significantly alter predicted deformation surface displacements are relatively insensitive to perturbations in poisson s ratio for shear sources but may play a stronger role when the source has a dilatational component if we generate synthetic displacements using a heterogeneous elastic model and then use an elastic half space or layered earth model to estimate the slip distribution and fault geometry we find systematic residuals of surface displacements and different slip patterns compared to the input fault slip model the coseismic slip distributions of the 2005 earthquake derived from the same fault geometry and different material models show that the rupture areas are narrower in all tested heterogeneous elastic models compared to that obtained using half space models this difference can be understood by the tendency to infer additional sources in elastic half space models to account for effects that are intrinsically due to the presence of rheological gradients although the fit to surface observations in our preferred 3 d fem model is similar to that from a simple half space model the resulting slip distribution may be a more accurate reflection the true fault slip behavior

the 2010 mw 8 8 maule megathrust earthquake of central chile monitored by gps large earthquakes produce crustal deformation that can be quantified by geodetic measurements allowing for the determination of the slip distribution on the fault we used data from global positioning system gps networks in central chile to infer the static deformation and the kinematics of the 2010 moment magnitude m w 8 8 maule megathrust earthquake from elastic modeling we found a total rupture length of 500 kilometers where slip up to 15 meters concentrated on two main asperities situated on both sides of the epicenter we found that rupture reached shallow depths probably extending up to the trench resolvable afterslip occurred in regions of low coseismic slip the low frequency hypocenter is relocated 40 kilometers southwest of initial estimates rupture propagated bilaterally at about 3 1 kilometers per second with possible but not fully resolved velocity variations

correlation of the rhenohercynian variscides recent structural and stratigraphical data from the rhenohercynian variscides of belgium germany and south cornwall indicate tectonic continuity within this zone prior to disruption along a late carboniferous dextral transcurrent fault this extends from the bristol channel to the vosges parallel to similar lineaments of variscan age in europe and north america consequently a tectonic model for south cornwall is extrapolated to europe and a plate tectonic setting for the evolution of the north european variscides by the closure of an oceanic basin is discussed

estimating the effect of earth elasticity and variable water density on tsunami speeds the speed of tsunami waves is typically calculated using the shallow water approximation over a rigid body earth recent comparisons of tsunami arrival times from the 11 march 2011 tsunami suggest however that the standard formulation has errors around the 1 level and it has been suggested that the elasticity of the earth can explain the discrepancy while previous work has indeed shown that such elastic deformation can modify tsunami speeds the effect has been neglected partly due to the difficulty in understanding how large this elastic effect is here we remedy this by providing a new derivation and expression for how to incorporate the first order effect that solid earth elasticity and ocean water compressibility have on tsunami speeds this result is shown to agree approximately with previous theory and helps to explain observed timing discrepancies from the 11 march 2011 tsunami the dispersive elastic correction and the non dispersive compressibility correction together may account for the majority of the observed discrepancy

circum pacific seismic potential 1989 1999 the seismic potential for 96 segments of simple plate boundaries around the circum pacific region is presented in terms of the conditional probability for the occurrence of either large or great interplate earthquakes during the next 5 10 and 20 years i e 1989 1994 1989 1999 and 1989 2009 this study represents the first probabilistic summary of seismic potential on this scale and involves the comparison of plate boundary segments that exhibit varying recurrence times magnitudes and tectonic regimes presenting these data in a probabilistic framework provides a basis for the uniform comparison of seismic hazard between these differing fault segments as well as accounting for individual variations in recurrence time along a specific fault segment and uncertainties in the determination of the average recurrence time

slip distribution of the february 27 2010 mw 8 8 maule earthquake central chile from static and high rate gps insar and broadband teleseismic data 1 the shallow depth underthrust earthquake of february 27 2010 mw 8 8 ruptured the subduction plate interface in central chile between 34 s and 38 s we retrieve the spatial and temporal distribution of slip during this mega earthquake through a joint inversion of teleseismic records insar and high rate gps hrgps data additionally our model is shown to agree with broadband surface waves rupture initiated at about 32 km depth and propagated bilaterally resulting in two main slip zones located ssw and nne of the hypocenter nucleation did not take place within or at the edge of one of these main asperities but in between during the first 30s slip propagated predominantly southwards later on the rupture evolved more slowly and more symmetrically eventually the northern asperity became predominant with maximum slip reaching about 20 m most of the seismic moment was released within 110s a relatively short time explained by the bilateral propagation the overall average rupture velocity is 2 6 km s but propagation occurred initially faster towards the south 3 2 km s large slip did not reach the trench a result consistent with the moderate size of the tsunami down dip rupture stopped at about 50 km depth in agreement with the lower limit of the locked zone inferred by ruegg et al 2009 from pre seismic gps data

u pb geochronological constraints on the timing of brioverian sedimentation and regional deformation in the st brieuc region of the neoproterozoic cadomian orogen northern france during the neoproterozoic cadomian orogeny in northern france supracrustal rocks of the brioverian supergroup were deposited in marginal and back arc basins and were subsequently variably deformed and metamorphosed new u pb analyses of single and small multigrain fractions of zircon from selected plutons from the baie de st brieuc region provide robust geochronological constraints on the timing of these events the jospinet granodiorite forms part of the local basement directly overlain by brioverian metasediments and basic volcanics and yields a u pb zircon date of 625 9 3 6 1 9 2 ma the pre tectonic port moguer tonalite which has been strongly sheared along with its amphibolite facies country rocks has a crystallization age of 600 4 0 9 ma emplacement ages of 576 3 1 5 1 2 ma for the syn tectonic fort la latte quartz diorite and 574 6 1 8 1 5 ma for the late tectonic st quay quartz diorite place limits on termination of deposition and timing of subsequent regional deformation of the brioverian sequence in the baie de st brieuc region the new dates constrain the age of brioverian sedimentation to the interval 626 575 ma a range consistent with a previously published pb pb zircon evaporation age of ca 58822 ma for brioverian volcanic rocks lanvollen formation deformation within this sector of the cadomian belt is believed to have occurred shortly before 575 ma revising previously published estimates for the age of this major tectonothermal cadomian event by 10 20 my 2002 elsevier science b v all rights reserved

correction to coseismic slip distribution of the february 27 2010 mw 8 8 maule chile earthquake 1 in the paper coseismic slip distribution of the february 27 2010 mw 8 8 maule chile earthquake by fred f pollitz et al geophysical research letters 38 l09309 doi 10 1029 2011gl047065 2011 the captions for figure 1 3 are ordered incorrectly the correct captions for figures 1 3 appear here 2 figure 1 rupture areas associated with historic earthquakes along the andean megathrust and aftershocks of the february 27 2010 event historical epicenters are provided by centro regional de sismologia para america del sur and aftershock locations are provided by the national earthquake information center white lines indicate the surface projection of the fault plane used to model the 2010 event nazca south america relative plate motion vector is from ruegg et al 2009 3 figure 2 observed coseismic gps offsets black vectors with 95 uncertainties compared with model horizontal offsets using the coseismic slip model obtained by the joint insar gps inversion which is contoured in gray values in meters white lines indicate the surface projection of the fault plane 4 figure 3 coseismic slip models derived from a insar data only b gps data only and c combined gps and insar data with seismic moment indicated for each model contour interval is 3 m star symbol indicates the global cmt epicenter

underplating in the himalaya tibet collision zone revealed by the hi climb experiment we studied the formation of the himalayan mountain range and the tibetan plateau by investigating their lithospheric structure using an 800 kilometer long densely spaced seismic array we have constructed an image of the crust and upper mantle beneath the himalayas and the southern tibetan plateau the image reveals in a continuous fashion the main himalayan thrust fault as it extends from a shallow depth under nepal to the mid crust under southern tibet indian crust can be traced to 31 n the crust mantle interface beneath tibet is anisotropic indicating shearing during its formation the dipping mantle fabric suggests that the indian mantle is subducting in a diffuse fashion along several evolving subparallel structures

timing of post obduction granitoids from intrusion through cooling to exhumation in central anatolia turkey abstract the middle to late cretaceous central anatolian granitoids intrude the supra subduction zone type central anatolian ophiolite and medium to high grade metasediments of central anatolian crystalline complex and are overlain by late palaeocene to early middle eocene sediments their single zircon 207 pb 206 pb evaporation ages define three clusters 1 cenomanian turonian weighted mean age 94 9 3 4 ma 2 turonian santonian 85 5 5 5 ma and 3 campanian 74 9 3 8 ma their hornblende and biotite 40 ar 39 ar and k ar cooling ages cluster around 80 65 ma the close hornblende and biotite ages reflect rapid exhumation of a mid crustal section during the campanian maastrichtian early to middle palaeocene 57 62 ma apatite fission track age clusters date the tail end of this exhumation episode it is proposed that the central anatolian granitoid melts were generated in a post collisional extensional setting following the docking of an oceanic island arc onto the tauride anatolide platform campanian maastrichtian to early middle palaeocene rapid exhumation event is considered to result from continent continent collisions between eurasian plate and the tauride anatolide platform along the izmir ankara erzincan suture zone

imaging short period seismic radiation from the 27 february 2010 chile mw 8 8 earthquake by back projection of p pp and pkikp waves 1 teleseismic short period 0 5 5 s p waves from the 27 february 2010 chile earthquake mw 8 8 are back projected to the source region to image locations of coherent short period seismic wave radiation several receiver array configurations are analyzed using different p wave arrivals including networks of stations in north america p japan pkikp and europe pp as well as a global configuration of stations with a broad azimuthal distribution and longer period p waves 5 20 s coherent bursts of short period radiation from the source are concentrated below the chilean coastline along the downdip portion of the megathrust the short period source region expands bilaterally with significant irregularity in the radiation comparison with finite fault slip models inverted from longer period seismic waves indicates that the regions of large slip on the megathrust are located updip of the regions of short period radiation a manifestation of frequency dependent seismic radiation similar to observations for the great 2011 tohoku earthquake mw 9 0 back projection of synthetic p waves generated from the finite fault models demonstrates that if the short period energy had radiated with the same space time distribution as the long period energy back projection analysis would image it in the correct location updip we conclude that back projection imaging of short period signals provides a distinct view of the seismic source that is missed by studies based only on long period seismic waves geodetic data and or tsunami observations

the cadomian active margin north armorican massif france a segment of the north atlantic panafrican belt abstract within the european variscan belt the armorican massif northwestern france contains an isolated fragment of the north atlantic panafrican belt the cadomian block mostly unaffected by variscan deformation this block is composed of neoproterozoic rocks ranging in age from 620 to 540 ma brioverian locally overlying a composite basement of icartian 2000 ma or pentevrian 750 ma age the cadomian tectonics the last magmatic manifestations of which are dated at around 540 ma were sealed by a cover of early cambrian rocks in normandy and early ordovician rocks in brittany five units are distinguished in this cadomian block tregor saint brieuc guingamp saint malo and fougeres although the units are bound by major faults the overall coherence of their different protolithic characteristics suggests that they can be fitted into a simple geodynamic model the tregor unit represented by the north tregor batholith of crustal affinity and its icartian host rock probably reflects an early cadomian evolution the saint brieuc unit essentially made up of magmatic rocks of juvenile affinity includes two assemblages juxtaposed by the cadomian tectonics 1 a volcanosedimentary succession formed in a typical island arc setting reflecting subduction around 610 ma and 2 a volcanic plutonic complex emplaced around 590 ma in an extensional active continental margin of pentevrian age the guingamp unit predominantly migmatitic includes a tectonic slice of deep origin the extrusion of which accompanied the exhumation of the migmatites it may represent the trace of a possible suture the saint malo unit is composed of brioverian detrital rocks the significance of which is uncertain passive continental margin or accretionary prism it is structured around a late migmatitic dome 540 ma the fougeres unit corresponds to the outer domain of the cadomian orogeny it was only weakly deformed by cadomian tectonics and is intruded by the large mancellian batholith of crustal origin dated at 540 ma together the structural units are interpreted in the framework of an evolving active margin juxtaposing continental margin marginal basin and volcanic arc before being shortened during the cadomian convergent tectonics

rupture process of the mw 7 9 2015 gorkha earthquake nepal insights into himalayan megathrust segmentation we investigate the rupture process of the 25 april 2015 gorkha earthquake mw 7 9 using a kinematic joint inversion of teleseismic waves strong motion data high rate gps static gps and synthetic aperture radar sar data the rupture is found to be simple in terms of coseismic slip and even more in terms of rupture velocity as both inversion results and a complementing back projection analysis show that the main slip patch broke unilaterally at a steady velocity of 3 1 3 3 km s this feature likely contributes to the moderate peak ground acceleration 0 2 g observed in kathmandu the 15 km deep rupture occurs along the base of the coupled portion of the main himalayan thrust and does not break the area ranging from kathmandu to the front the limitation in length and width of the rupture cannot be identified in the preearthquake interseismic coupling distribution and is therefore discussed in light of the structural architecture of the megathrust

central chile finally breaks chile is the site of some of the largest earthquakes in the world on average a magnitude 8 earthquake occurs there every 10 years or so these earthquakes take place in the subduction zone either as interplate ruptures at the interface between the south american and nazca plates or as intraplate events within the subducted nazca plate a few times in every century massive plate interface earthquakes break several hundred kilometers in a single shock this is what happened on 27 february 2010 when a major earthquake magnitude 8 8 occurred in the maule and biobio regions in central chile see the first figure this region had last experienced a major subduction earthquake in 1835 when darwin 1 visited the area as part of his voyage on the beagle his description of the earthquake inspired many seismologists and historians of chilean earthquakes 2 3

displacements and tilts from dip slip faults and magma chambers beneath irregular surface topography surface displacements and tilts due to buried deformation sources are influenced by topography the leading order corrections due to topography of arbitrary profile but small slope are determined for dip slip faults edge dislocations and magma bodies lines of inflation in a two dimensional elastic medium the vertical displacement correction is simply the product of the topography and the horizontal normal strain due to the source in a flat half space the correction for a normal fault beneath an idealized basin and range topography is a slight increase in the uplift on the range side the effect of topography for a line of inflation beneath a symmetric volcano is to reduce the central uplift failure to account for topographic influences can bias estimates of source depth and geometry

finite element inversion of dinsar data from the mw 6 3 l aquila earthquake 2009 italy 1 fault slip distribution is usually retrieved from geodetic data assuming that the local crust is an elastic homogeneous and isotropic half space in the last decades spatially dense geodetic data e g dinsar maps have highlighted complex patterns of coseismic deformation that require new modeling tools such as numerical methods able to represent rheological and geometrical complexities of the earth s crust in this work we develop a procedure to perform inversion of geodetic data based on the finite element method accounting for a more realistic description of the local crust the method is applied to the 2009 l aquila earthquake mw 6 3 using dinsar images of the coseismic displacement results highlight the non negligible influence of the medium structure homogeneous and heterogeneous models show discrepancies up to 20 in the fault slip distribution values furthermore in the heterogeneous models a new area of slip appears above the hypocenter we also perform a resolution study showing that the information about fault slip distributions retrieved from geodetic data should be considered as averaged on surrounding patches

joint estimation of afterslip rate and postseismic relaxation following the 1989 loma prieta earthquake global positioning system gps data from campaigns carried out over the 5 years following the 1989 loma prieta earthquake and leveling data measured in 1990 and 1992 define the postseismic velocity field around the loma prieta rupture zone subtraction of a background velocity field yields a residual velocity pattern which we interpret as the product of two physical processes 1 slow afterslip along distinct planes in the upper cru st and 2 viscoelastic relaxation of the lower crust and upper mantle biirgmann et al 1997 previously derived an afterslip model involving uniform afterslip on two optimally determined planes in cluding oblique reverse slip on the coseismic rupture and reverse slip on a shallow thrust fault to the northeast of the san andreas fault we further consider models of distributed slip on these two fault planes plus a viscoelastic relaxation pattern which depends on a suitable cose ismic rupture model and crust and mantle viscosities several fault models from the literature were considered for the 1989 coseismic rupture with nearly identical impact on the results simultaneous maximum likelihood inversion of the gps and leveling data for afterslip distri bution and viscosity yields the following results 1 a good fit to the data is obtained by smooth afterslip distributions without any viscoelastic relaxation being required 2 tangible broad scale viscoelastic relaxation of the lower crust and upper mantle are present in this data set at 97 confidence and a lower crustal viscosity of 1029 pa s is obtained however the viscosity of both the lower crust and upper mantle are poorly constrained 3 for a given misfit 20 less integrated afterslip and smoother afterslip distributions result when viscoelas tic relaxation is included 4 maximum slip rates on the slip distributed models are 3 5 crn yr the dominant patches estimated on the two planes fill in the entire depth range 4 13 km without significant overlap and deeper afterslip is not required the afterslip distribution on the coseismic rupture plane is strongly dominated by reverse slip immediately southeast of the main center of coseismic reverse slip

interseismic coupling on the main himalayan thrust we determine the slip rate and pattern of interseismic coupling on the main himalayan thrust along the entire himalayan arc based on a compilation of geodetic interferometric synthetic aperture radar and microseismicity data we show that convergence is perpendicular to the arc and increases eastwards from 13 3 1 7 mm yr to 21 2 2 0 mm yr these rates are comparable to geological and geomorphic estimates indicating an essentially elastic geodetic surface strain the interseismic uplift rate predicted from the coupling model closely mimics the topography suggesting that a small percentage of the interseismic strain is permanent we find that the fault is fully locked along its complete length over about 100 km width we don t find any resolvable aseismic barrier that could affect the seismic segmentation of the arc and limit the along strike propagation of seismic ruptures the moment deficit builds up at a rate of 15 1 1 10 19 n m yr for the entire length of the himalaya