itrf2008 plate motion model 1 the itrf2008 velocity field is demonstrated to be of higher quality and more precise than past itrf solutions we estimated an absolute tectonic plate motion model made up of 14 major plates using velocities of 206 sites of high geodetic quality far from plate boundaries deformation zones and glacial isostatic adjustment gia regions derived from and consistent with itrf2008 the precision of the estimated model is evaluated to be at the level of 0 3 mm a wrms no gia corrections were applied to site velocities prior to estimating plate rotation poles as our selected sites are outside the fennoscandia regions where the gia models we tested are performing reasonably well and far from gia areas where the models would degrade the fit antarctica and north america our selected velocity field has small origin rate bias components following the three axis x y z respectively 0 41 0 54 0 22 0 64 and 0 41 0 60 95 per cent confidence limits comparing our model to nnr nuvel 1a and the newly available nnr morvel56 we found better agreement with nnr morvel56 than with nnr nuvel 1a for all plates except for australia where we observe an average residual rotation rate of 4 mm a using our selection of sites we found large global x rotation rates between the two models 0 016 ma and between our model and nnr morvel56 of 0 023 ma equivalent to 2 5 mm a at the earth surface

rupture process of the 2010 mw 7 8 mentawai tsunami earthquake from joint inversion of near field hr gps and teleseismic body wave recordings constrained by tsunami observations the 25 october 2010 mentawai tsunami earthquake mw 7 8 ruptured the shallow portion of the sunda megathrust seaward of the mentawai islands offshore of sumatra indonesia generating a strong tsunami that took 509 lives the rupture zone was updip of those of the 12 september 2007 mw 8 5 and 7 9 underthrusting earthquakes high rate 1 s sampling gps instruments of the sumatra gps array network deployed on the mentawai islands and sumatra mainland recorded time varying and static ground displacements at epicentral distances from 49 to 322 km azimuthally distributed tsunami recordings from two deepwater sensors and two tide gauges that have local high resolution bathymetric information provide additional constraints on the source process finite fault rupture models obtained by joint inversion of the high rate hr gps time series and numerous teleseismic broadband p and s wave seismograms together with iterative forward modeling of the tsunami recordings indicate rupture propagation 50 km up dip and 100 km northwest along strike from the hypocenter with a rupture velocity of 1 8 km s subregions with large slip extend from 7 to 10 km depth 80 km northwest from the hypocenter with a maximum slip of 8 m and from 5 km depth to beneath thin horizontal sedimentary layers beyond the prism deformation front for 100 km along strike with a localized region having 15 m of slip the seismic moment is 7 2 1020 n m the rupture model indicates that local heterogeneities in the shallow megathrust can accumulate strain that allows some regions near the toe of accretionary prisms to fail in tsunami earthquakes

earthquake supercycles inferred from sea level changes recorded in the corals of west sumatra records of relative sea level change extracted from corals of the mentawai islands sumatra imply that this 700 kilometer long section of the sunda megathrust has generated broadly similar sequences of great earthquakes about every two centuries for at least the past 700 years the moment magnitude 8 4 earthquake of september 2007 represents the first in a series of large partial failures of the mentawai section that will probably be completed within the next several decades

structure and seismogenic properties of the mentawai segment of the sumatra subduction zone revealed by local earthquake traveltime tomography 1 on 12 september 2007 an mw8 4 earthquake occurred within the southern section of the mentawai segment of the sumatra subduction zone where the subduction thrust had previously ruptured in 1833 and 1797 traveltime data obtained from a temporary local seismic network deployed between december 2007 and october 2008 to record the aftershocks of the 2007 event was used to determine two dimensional 2 d and three dimensional 3 d velocity models of the mentawai segment the seismicity distribution reveals significant activity along the subduction interface and within two clusters in the overriding plate either side of the forearc basin the downgoing slab is clearly distinguished by a dipping region of highvp 8 0 km s which can be a traced to 50 km depth with an increased vp vs ratio 1 75 to 1 90 beneath the islands and the western side of the forearc basin suggesting hydrated oceanic crust above the slab a shallow continental moho of less than 30 km depth can be inferred suggesting that the intersection of the continental mantle with the subducting slab is much shallower than the downdip limit of the seismogenic zone despite localized serpentinization being present at the toe of the mantle wedge the outer arc islands are characterized by low vp 4 5 5 8 km s and high vp vs greater than 2 0 suggesting that they consist of fluid saturated sediments the very low rigidity of the outer forearc contributed to the slow rupture of the mw 7 7 mentawai tsunami earthquake on 25 october 2010

tsunami earthquakes the quest for a regional signal using the technique developed by newman and okal j geophys res 103 1998 26885 a dataset of digital records from 84 earthquakes is analyzed to investigate their source slowness in the quest for a possible regional signal in three subduction zones which experienced recent tsunami earthquakes nicaragua 1992 java 1994 peru 1996 the dataset is augmented by analog seismograms from historical events including major tsunamigenic earthquakes of the past 65 years we fail to detect a regional trend for slowness which suggests that the latter may be controlled on a more local scale by morphological structures of the subducting plate no correlation is found between slowness and either depth focal mechanism or seismic moment in nicaragua we document two slow historical earthquakes located on the slab down dip from the 1992 shock the most interesting results are in peru where a local area of slowness is tentatively defined around the source of the 1960 tsunami earthquake and where both the 1996 and 1960 tsunami earthquakes occur at the intersection of the trench with major topographic features on the nazca plate the mendana fracture zone and the trujillo trough respectively 2001 elsevier science b v all rights reserved

footprints of past earthquakes revealed in the afterslip of the 2010 mw 7 8 mentawai tsunami earthquake the 2010 mw 7 8 mentawai tsunami earthquake marks one of the first tsunami earthquakes to have postseismic deformation observed by geodetic instruments the sumatran gps array sugar has recorded the postseismic deformation following this event continuously for 5 years the spatio temporal evolution of the postseismic deformation is well explained by velocity strengthening frictional sliding on the sunda megathrust our results show that the 2010 afterslip progressed downdip relative to the 2010 coseismic rupture the southeastern portion of the afterslip region overlaps the area that slipped during the mainshock and afterslip of the 2007 mw 8 4 bengkulu earthquake while the northwestern portion slipped an area without recent large earthquakes by incorporating pre earthquake stress conditions into quasi dynamic models we demonstrate that the preceding cumulative slip from the 2007 sequence might have caused a 0 1 mpa difference in pre earthquake coulomb stress between the southeastern and northwestern portions of the afterslip region

tsunami source of the 2010 mentawai indonesia earthquake inferred from tsunami field survey and waveform modeling the 2010 mentawai earthquake magnitude 7 7 generated a destructive tsunami that caused more than 500 casualties in the mentawai islands west of sumatra indonesia seismological analyses indicate that this earthquake was an unusual tsunami earthquake which produces much larger tsunamis than expected from the seismic magnitude we carried out a field survey to measure tsunami heights and inundation distances an inversion of tsunami waveforms to estimate the slip distribution on the fault and inundation modeling to compare the measured and simulated tsunami heights the measured tsunami heights at eight locations on the west coasts of north and south pagai island ranged from 2 5 to 9 3 m but were mostly in the 4 7 m range at three villages the tsunami inundation extended more than 300 m interviews of local residents indicated that the earthquake ground shaking was less intense than during previous large earthquakes and did not cause any damage inversion of tsunami waveforms recorded at nine coastal tide gauges a nearby gps buoy and a dart station indicated a large slip maximum 6 1 m on a shallower part of the fault near the trench axis a distribution similar to other tsunami earthquakes the total seismic moment estimated from tsunami waveform inversion was 1 0 1021 nm which corresponded to mw 7 9 computed coastal tsunami heights from this tsunami source model using linear equations are similar to the measured tsunami heights the inundation heights computed by using detailed bathymetry and topography data and nonlinear equations including inundation were smaller than the measured ones this may have been partly due to the limited resolution and accuracy of publically available bathymetry and topography data one dimensional run up computations using our surveyed topography profiles showed that the computed heights were roughly similar to the measured ones

postseismic deformation following the 2010 m 7 2 el mayor cucapah earthquake observations kinematic inversions and dynamic models due to its location on a transtensional section of the pacific north american plate boundary the salton trough is a region featuring large strike slip earthquakes within a regime of shallow asthenosphere high heat flow and complex faulting and so postseismic deformation there may feature enhanced viscoelastic relaxation and afterslip that is particularly detectable at the surface the 2010 m 7 2 el mayor cucapah earthquake was the largest shock in the salton trough since 1892 and occurred close to the us mexico border and so the postseismic deformation recorded by the continuous gps network of southern california provides an opportunity to study the rheology of this region three year postseismic transients extracted from gps displacement time series show four key features 1 1 2 cm of cumulative uplift in the imperial valley and sim 1 cm of subsidence in the peninsular ranges 2 relatively large cumulative horizontal displacements 150 km from the rupture in the peninsular ranges 3 rapidly decaying horizontal displacement rates in the first few months after the earthquake in the imperial valley and 4 sustained horizontal velocities following the rapid early motions that were still visibly ongoing 3 years after the earthquake kinematic inversions show that the cumulative 3 year postseismic displacement field can be well fit by afterslip on and below the coseismic rupture though these solutions require afterslip with a total moment equivalent to at least a m 7 2 earthquake and higher slip magnitudes than those predicted by coseismic stress changes forward modeling shows that stress driven afterslip and viscoelastic relaxation in various configurations within the lithosphere can reproduce the early and later horizontal velocities in the imperial valley while newtonian viscoelastic relaxation in the asthenosphere can reproduce the uplift in the imperial valley and the subsidence and large westward displacements in the peninsular ranges we present two forward models of dynamically coupled deformation mechanisms that fit the postseismic transient well a model combining afterslip in the lower crust newtonian viscoelastic relaxation in a localized zone in the lower crust beneath areas of high heat flow and geothermal activity and newtonian viscoelastic relaxation in the asthenosphere and a second model that replaces the afterslip in the first model with viscoelastic relaxation with a stress dependent viscosity in the mantle the rheology of this high heat flow high strain rate region may incorporate elements of both these models and may well be more complex than either of them

heterogeneous coupling of the sumatran megathrust constrained by geodetic and paleogeodetic measurements geodetic and paleogeodetic measurements of interseismic strain above the sumatran portion of the sunda subduction zone reveal a heterogeneous pattern of coupling annual banding in corals provides vertical rates of deformation spanning the last half of the 20th century and repeated gps surveys between 1991 and 2001 and continuous measurements at gps stations operated since 2002 provide horizontal velocities near the equator the megathrust is locked over a narrow width of only a few tens of kilometers in contrast the locked fault zone is up to about 175 km wide in areas where great interplate earthquakes have occurred in the past formal inversion of the data reveals that these strongly coupled patches are roughly coincident with asperities that ruptured during these events the correlation is most spectacular for rupture of the m w 8 7 nias simeulue earthquake of 2005 which released half of the moment deficit that had accumulated since its previous rupture in 1861 suggesting that this earthquake was overdue beneath the mentawai islands strong coupling is observed within the overlapping rupture areas of the great earthquakes of 1797 and 1833 the accumulated slip deficit since these events is slowly reaching the amount of slip that occurred during the 1833 earthquake but already exceeds the slip that occurred during the 1797 earthquake thus rerupture of part of the mentawai patch in september 2007 was not a surprise in contrast coupling is low below the batu islands near the equator and around enggano island at about 5 s where only moderate earthquakes m w 8 0 have occurred in the past two centuries the correlation of large seismic asperities with patches that are locked during the interseismic period suggests that they are persistent features this interpretation is reinforced by the fact that the large locked patches and great ruptures occur beneath persistent geomorphologic features the largest outer arc islands depth and convergence rate dependent temperature might influence the pattern of coupling through its effect on the rheology of the plate interface but other influences are required to account for the observed along strike heterogeneity of coupling in particular subduction of the investigator fracture zone could be the cause for the low coupling near the equator

the 25 october 2010 sumatra tsunami earthquake slip in a slow patch 1 various models for the generation of tsunami earthquakes have been proposed including shallow earthquake slip through low strength materials because these physical fault conditions would likely affect other earthquakes in the same rupture zone source properties of other events may provide a guide to locations of tsunami earthquakes the 25 october 2010 mw 7 8 mentawai tsunami earthquake and surrounding events provide a test of this hypothesis we determine slip patterns for the mainshock and relocate aftershocks with the majority occurring in the near trench region the two largest magnitude aftershocks occurred within the downdip end of the mainshock rupture area and have long moment normalized rupture duration likely related to fault zone conditions several older relocated earthquakes at the northern edge of the 2010 rupture area also have long duration character suggesting both spatial and temporal consistency in the conditions needed to produce slow seismic processes along this margin

frictional afterslip following the 2005 nias simeulue earthquake sumatra continuously recording global positioning system stations near the 28 march 2005 rupture of the sunda megathrust moment magnitude m w 8 7 show that the earthquake triggered aseismic frictional afterslip on the subduction megathrust with a major fraction of this slip in the up dip direction from the main rupture eleven months after the main shock afterslip continues at rates several times the average interseismic rate resulting in deformation equivalent to at least a m w 8 2 earthquake in general along strike variations in frictional behavior appear to persist over multiple earthquake cycles aftershocks cluster along the boundary between the region of coseismic slip and the up dip creeping zone we observe that the cumulative number of aftershocks increases linearly with postseismic displacements this finding suggests that the temporal evolution of aftershocks is governed by afterslip

the 25 october 2010 mentawai tsunami earthquake mw 7 8 and the tsunami hazard presented by shallow megathrust ruptures the 25 october 2010 mentawai indonesia earthquake m w 7 8 ruptured the shallow portion of the subduction zone seaward of the mentawai islands off shore of sumatra generating 3 to 9 m tsunami run up along southwestern coasts of the pagai islands that took at least 431 lives analyses of teleseismic p sh and rayleigh waves for finite fault source rupture characteristics indicate 90 s rupture duration with a low rupture velocity of 1 5 km s on the 10 dipping megathrust with total slip of 2 4 m over an 100 km long source region the seismic moment scaled energy release is 1 4 10 6 lower than 2 4 10 6 found for the 17 july 2006 java tsunami earthquake m w 7 8 the mentawai event ruptured up dip of the slip region of the 12 september 2007 kepulauan earthquake m w 7 9 and together with the 4 january 1907 m 7 6 tsunami earthquake located seaward of simeulue island to the northwest along the arc demonstrates the significant tsunami generation potential for shallow megathrust ruptures in regions up dip of great underthrusting events in indonesia and elsewhere

postseismic deformation following the 1999 chi chi earthquake taiwan implication for lower crust rheology on 1999 september 21 the mw 7 6 chi chi earthquake ruptured a segment of the chelungpu fault a frontal thrust fault of the western foothills of taiwan the stress perturbation induced by the rupture triggered a transient deformation across the island which was well recorded by a wide network of continuously operating gps stations the analysis of more than ten years of these data reveals a heterogeneous pattern of postseismic displacements with relaxation times varying by a factor of more than ten and large cumulative displacements at great distances in particular along the longitudinal valley in eastern taiwan where relaxation times are also longer we show that while afterslip is the dominant relaxation process in the epicentral area viscoelastic relaxation is needed to explain the pattern and time evolution of displacements at the larger scale we model the spatiotemporal behavior of the transient deformation as the result of afterslip on the decollement that extends downdip of the chelungpu thrust and viscoelastic flow in the lower crust and in the mid crust below the central range we construct a model of deformation driven by coseismic stress change where afterslip and viscoelastic flow are fully coupled the model is compatible with the shorter relaxation times observed in the near field which are due to continued fault slip and the longer characteristic relaxation times and the reversed polarity of vertical displacements observed east of the central range our preferred model shows a viscosity of 0 5 1 x 10 19 pa s at lower crustal depths and 5 x 10 17 pa s in the mid crust below the central range between 10 and 30 km depth the low viscosity zone at mid crustal depth below the central range coincides with a region of low seismicity where rapid advection of heat due to surface erosion coupled with underplating maintain high temperatures estimated to be between 300 c and 600 c from the modeling of thermo chronology and surface heat flow data

frictional properties on the san andreas fault near parkfield california inferred from models of afterslip following the 2004 earthquake the abundance of geodetic and seismic data recording postseismic deformation following the 2004 parkfield earthquake provides an unprecedented opportunity to resolve frictional properties on the parkfield section of the san andreas fault the parkfield segment is a transition between the locked section to the southeast that last ruptured in the 1857 fort tejon earthquake and the creeping section to the northwest we develop three dimensional rate and state dependent friction models of afterslip following the 2004 earthquake to investigate the frictional behavior of the fault it is assumed that the coseismic rupture occurred on an area of the fault surrounded by aseismic creep that accelerated after the earthquake we estimate the distribution of coseismic slip afterslip and rate state frictional parameters by inverting a two step slip model in the model we 1 estimate the coseismic slip distribution from 1 hz global positioning system gps data and 2 use the corresponding coseismic shear stress change on the fault as input into a numerical afterslip model governed by rate state friction we find the rate state frictional parameter a b an indicator of frictional stability is in the range 10 4 10 3 at 50 mpa normal stress which is near the transition from potentially unstable negative a b to nominally stable positive a b friction the estimate of a b values falls within a wide range of experimental values reported for serpentinite which crops out along the san andreas fault zone the critical slip distance d c which characterizes the distance over which strength breaks down during a slip event is in the range 0 01 0 1 m consistent with seismic estimates and a fault gouge thickness of 1 10 m the afterslip model reproduces most features observed in the gps time series data including high surface velocities in the first few months after the earthquake and lower rates at later times as well as the cumulative postseismic displacement the model tends to underpredict the displacement data at later times suggesting that perhaps the modeled afterslip period ends too quickly or an unmodeled deformation process dominates the signal at later times

partial rupture of a locked patch of the sumatra megathrust during the 2007 earthquake sequence the great sumatra andaman earthquake and tsunami of 2004 was a dramatic reminder of the importance of understanding the seismic and tsunami hazards of subduction zones 1 2 3 4 in march 2005 the sunda megathrust ruptured again producing an event 5 of moment magnitude mw 8 6 south of the 2004 rupture area which was the site of a similar event in 1861 ref 6 concern was then focused on the mentawai area where large earthquakes had occurred in 1797 mw 8 8 and 1833 mw 9 0 6 7 two earthquakes one of mw 8 4 and twelve hours later one of mw 7 9 indeed occurred there on 12 september 2007 here we show that these earthquakes ruptured only a fraction of the area ruptured in 1833 and consist of distinct asperities within a patch of the megathrust that had remained locked in the interseismic period this indicates that the same portion of a megathrust can rupture in different patterns depending on whether asperities break as isolated seismic events or cooperate to produce a larger rupture this variability probably arises from the influence of non permanent barriers zones with locally lower pre stress due to the past earthquakes the stress state of the portion of the sunda megathrust that had ruptured in 1833 and 1797 was probably not adequate for the development of a single large rupture in 2007 the moment released in 2007 amounts to only a fraction both of that released in 1833 and of the deficit of moment that had accumulated as a result of interseismic strain since 1833 the potential for a large megathrust event in the mentawai area thus remains large

inverting geodetic time series with a principal component analysis based inversion method 1 the global positioning system gps system now makes it possible to monitor deformation of the earth s surface along plate boundaries with unprecedented accuracy in theory the spatiotemporal evolution of slip on the plate boundary at depth associated with either seismic or aseismic slip can be inferred from these measurements through some inversion procedure based on the theory of dislocations in an elastic half space we describe and test a principal component analysis based inversion method pcaim an inversion strategy that relies on principal component analysis of the surface displacement time series we prove that the fault slip history can be recovered from the inversion of each principal component because pcaim does not require externally imposed temporal filtering it can deal with any kind of time variation of fault slip we test the approach by applying the technique to synthetic geodetic time series to show that a complicated slip history combining coseismic postseismic and nonstationary interseismic slip can be retrieved from this approach pcaim produces slip models comparable to those obtained from standard inversion techniques with less computational complexity we also compare an afterslip model derived from the pcaim inversion of postseismic displacements following the 2005 8 6 nias earthquake with another solution obtained from the extended network inversion filter enif we introduce several extensions of the algorithm to allow statistically rigorous integration of multiple data sources e g both gps and interferometric synthetic aperture radar time series over multiple timescales pcaim can be generalized to any linear inversion algorithm

a unified gps based earthquake catalog for the sumatran plate boundary between 2002 and 2013 we have compiled the first self consistent gps based earthquake catalog for the sumatran plate boundary using continuous daily position time series from the sumatran gps array sugar we document 30 earthquakes which occurred within or outside the sugar network from august 2002 through the end of 2013 and we provide estimates of both vertical and horizontal coseismic offsets associated with 1 m9 2 3 m8 6 m7 19 m6 and 1 m5 9 earthquakes as well as postseismic decay amplitudes and times associated with 9 m 7 earthquakes and 1 m6 7 earthquake for most of the previously studied earthquakes our geodetic catalog provides more complete coseismic displacements than those published showing consistent patterns of motion across a large range of distances for many of the moderate to large earthquakes we publish their coseismic displacements for the first time providing new constraints on their locations and slip distributions for the postseismic time series we have tackled the challenge of separating the signals for individual events from the overlapping effects of many other earthquakes as a result we have obtained either new or much longer time series than previously published based on our long time series we find logarithmic decay times ranging from several days to more than 20 years and sometimes a second decay time is needed suggesting that when studying large to great sumatran earthquakes we need to consider multiple postseismic mechanisms our geodetic catalog provides rich spatial and temporal sumatran earthquake cycle information for future studies of the physics and dynamics of the sumatran plate boundary

the 25 october 2010 mentawai tsunami earthquake from real time discriminants finite fault rupture and tsunami excitation 1 the moment magnitude 7 8 earthquake that struck offshore the mentawai islands in western indonesia on 25 october 2010 created a locally large tsunami that caused more than 400 human causalities we identify this earthquake as a rare slow source tsunami earthquake based on 1 disproportionately large tsunami waves 2 excessive rupture duration near 125 s 3 predominantly shallow near trench slip determined through finite fault modeling and 4 deficiencies in energy to moment and energy to duration cubed ratios the latter in near real time we detail the real time solutions that identified the slow nature of this event and evaluate how regional reductions in crustal rigidity along the shallow trench as determined by reduced rupture velocity contributed to increased slip causing the 5 9 m local tsunami runup and observed transoceanic wave heights observed 1600 km to the southeast

coulomb stress perturbation after great earthquakes in the sumatran subduction zone potential impacts in the surrounding region abstract the sumatran subduction zone has been seismically very active compared with other major subduction zones in the world since 2004 a sequence of large earthquakes ruptured along the trench including the 2004 mw 9 2 sumatra andaman the 2005 mw 8 6 nias simeulue the 2007 mw 8 4 bengkulu the 2010 mw 7 8 mentawai tsunami earthquakes and numerous moderate and small events these earthquakes released stress over tens of seconds to minutes disturbing the lithosphere and asthenosphere across a broad region as earthquake introduced stress disturbance can trigger tremendous aftershocks and sometimes precipitate large earthquakes in their vicinity gaining a detailed picture of spatial and temporal stress evolution on the fault and its neighboring faults is crucial for seismic forecasting here we have developed spatiotemporal coulomb stress models for the sumatran region which includes the sumatran subduction zone and the sumatran fault using a well studied postseismic model this postseismic model is constrained by decade long time series of geodetic observations from the sumatran gps array sugar and from tide gauge data in southeast asia we show that coulomb stress changes imparted by co and post seismic processes of previous great ruptures could well explain the temporal and spatial connection between seismicity and stress evolution most importantly our results reveal that the stress in the mentawai seismic gap of the sumatran subduction zone was loaded by more than two bars these stress perturbations could potentially trigger the rupture of the mentawai seismic gap which was already overdue in the last seismic cycle now the likelihood for the failure of this gap is even higher than before 2004 we also find that along the sumatran fault stress has increased to more than one bar which may explain the surrounding seismicity consequently we highlight the considerable seismic hazard and associated tsunami threat to the neighboring regions

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

challenging the rate state asperity model afterslip following the 2011 m9 tohoku oki japan earthquake 1 prior to the 2011 m9 tohoku oki earthquake subduction at the japan trench was characterized by m7 8 earthquakes sometimes rupturing the same source regions seismic asperities followed by extensive afterslip detected by gps measurements a physically based model consisting of velocity weakening asperities surrounded by aseismic creep on velocity strengthening regions the rate state asperity model became the prevailing conceptual model for earthquakes in this region theory and numerical simulation indicates that velocity weakening areas do not exhibit sustained afterslip while velocity strengthening regions do not accumulate stress interseismically here we demonstrate that the rate state asperity model is contradicted by models of postseismic deformation following the tohoku oki earthquake afterslip in the first eight months either occurred on historical seismic asperities or stress accumulated in regions surrounding the asperities unsmoothed inversions of cumulative 8 month postseismic gps displacements that restrict afterslip to areas outside of historical ruptures cannot fit the data without afterslip exceeding the slip that fully relaxes the coseismic stress change in contrast similarly constrained inversions allowing slip within historical ruptures can satisfactorily fit the postseismic displacements these results require a modification of the rate state asperity model and raise new questions about physical processes and properties of the subduction interface

transition flow in step pool systems pressure distributions and drag forces abstractstep pool systems occur naturally in steep mountain streams and as man made structures in steep channel sections where they serve as energy dissipating structures three different flow regimes may occur the dominant flow regime is the cascading nappe flow regime at higher discharges the skimming flow regime develops with an almost plane water surface in between these flow regimes a transition flow regime occurs a physical model was used to measure the pressure distribution around a single step for a particular step pool geometry and for different flow regimes nappe transition skimming to achieve this 14 simultaneously recording piezoresistive pressure transducers were distributed around the step the results showed that the regime change from nappe to transition flow is associated with a discontinuity of the average froude number of a step pool unit as well as drops in pressures and water depth relative instantaneous drag forces reached a maximum for this regime change this implies

geodetic observations of an earthquake cycle at the sumatra subduction zone role of interseismic strain segmentation 1 we use survey mode and continuous gps data from 1991 to 2007 to examine fault segmentation in the earthquake cycle at the sumatra megathrust site of the 26 december 2004 mw 9 1 sumatra andaman the 28 march 2005 mw 8 7 nias simeulue and the 12 september 2007 mw 8 4 mentawai earthquakes these data including new observations from 2006 and 2007 allow us to observe the final few years of one earthquake cycle and the beginning of the next our analysis reveals that the megathrust is segmented a characteristic that may persist through multiple earthquake cycles the nias simeulue earthquake ruptured approximately the same region that broke in 1861 a 300 km long segment abutting the sumatra andaman rupture zone farther southeast the mentawai segment of the megathrust 0 5 s 5 s which produced m 8 earthquakes in 1797 and 1833 is fully locked in the interseismic period but is flanked by two freely slipping regions the batu islands in the nw and enggano in the se the 12 september 2007 mentawai earthquake sequence ruptured only the southern one third of the 1833 rupture zone we model postseismic deformation from the sumatra andaman and nias simeulue earthquakes and find that afterslip was concentrated updip and downdip respectively from the main shocks comparing the velocity fields before and after 2001 we find the subduction zone underneath the batu islands and enggano which prior to the earthquakes was partially to fully coupled appears now to be slipping freely thus while the segmentation of the subduction zone is preserved interseismic coupling on the subduction fault may vary with time

validation of linearity assumptions for using tsunami waveforms in joint inversion of kinematic rupture models application to the 2010 mentawai mw 7 8 tsunami earthquake tsunami observations have particular importance for resolving shallow offshore slip in finite fault rupture model inversions for large subduction zone earthquakes however validations of amplitude linearity and choice of subfault discretization of tsunami green s functions are essential when inverting tsunami waveforms we explore such validations using four tsunami recordings of the 25 october 2010 mentawai m w 7 8 tsunami earthquake jointly inverted with teleseismic body waves and 1 hz gps high rate gps observations the tsunami observations include near field and far field deep water recordings as well as coastal and island tide gauge recordings a nonlinear dispersive modeling code neowave is used to construct tsunami green s functions from seafloor excitation for the linear inversions along with performing full scale calculations of the tsunami for the inverted models we explore linearity and finiteness effects with respect to slip magnitude variable rake determination and subfault dimensions the linearity assumption is generally robust for the deep water recordings and wave dispersion from seafloor excitation is important for accurate description of near field green s functions breakdown of linearity produces substantial misfits for short wavelength signals in tide gauge recordings with large wave heights including the tsunami observations in joint inversions provides improved resolution of near trench slip compared with inversions of only seismic and geodetic data two rupture models with fine grid 15 km and coarse grid 30 km spacing are inverted for the mentawai event stronger regularization is required for the fine model representation both models indicate a shallow concentration of large slip near the trench with peak slip of 15 m fully nonlinear forward modeling of tsunami waveforms confirms the validity of these two models for matching the tsunami recordings along with the other data

spatially variable fault friction derived from dynamic modeling of aseismic afterslip due to the 2004 parkfield earthquake we investigate fault friction from dynamic modeling of fault slip prior to and following the m w 6 0 earthquake which ruptured the parkfield segment of the san andreas fault in 2004 the dynamic modeling assumes a purely rate strengthening friction law with a logarithmic dependency on sliding rate a b ln v v the initial state of stress is explicitly taken into account and afterslip is triggered by the stress change induced by the earthquake source model given a priori we consider different initial stress states and two coseismic models and invert for the other model parameters using a nonlinear inversion scheme the model parameters include the reference friction the friction rate dependency characterized by the quantity a b assumed to be either uniform or depth dependent the model parameters are determined from fitting the transient postseismic geodetic signal measured at continuous gps stations our study provides a view of frictional properties at the kilometers scale over the 0 15 km depth illuminated by the coseismic stress change induced by the parkfield earthquake the reference friction is estimated to be between 0 1 and 0 5 with independent a priori constraints on the amplitude of differential stress the range of possible values narrows down to 0 1 0 17 the friction rate coefficient a b is estimated to be 10 3 10 2 with a hint that it increases upward from about 1 3 10 3 at 3 7 km depth to about 4 7 10 3 at 0 1 km depth it is remarkable that our results are consistent with frictional properties measured on rock samples recovered from the fault zone thanks to the san andreas fault observatory at depth experiment

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

glacimarine sedimentation in kangerdluk disko fjord west greenland in response to a surging glacier abstract beginning in 1995 a large outlet glacier of the sermersauq ice cap on disko island surged 10 5 km downvalley to within 10 km of the head of the fjord kuannersuit sulluat reaching its maximum extent in summer 1999 before beginning to retreat sediment discharge to the fjord increased from 13 10 3 t day 1 in 1997 to 38 10 3 t day 1 in 1999 ctd results sediment traps and cores from the 2000 melt season document the impact of the surge on the glacimarine environment of the fjord within 4 km of the inflow sedimentation rates increased by 30 times over those before the surge reaching an estimated maximum value of 29 cm a 1 up to 4 2 mm day 1 between 24 july and 9 september 2000 fine grained deposits from suspension in the water column displayed diurnal laminations in response to the interaction of tidal cycles with the sediment plume these are not found in the sediments deposited before surging thin beds of sandy turbidites from turbidity currents originating from slope failures on the delta front occurred at about 20 day intervals during the melt season each of these effects was limited to within several kilometres of the point of inflow but provide a unique signal significantly different from those generated by normal hydroclimatically induced events

the 2010 mw 7 8 mentawai earthquake very shallow source of a rare tsunami earthquake determined from tsunami field survey and near field gps data 1 the mw 7 8 october 2010mentawai indonesia earthquake was a tsunami earthquake a rare type of earthquake that generates a tsunami much larger than expected based on the seismicmagnitude itproducedalocallydevastatingtsunami withrunupcommonlyinexcess of 6 m we examine this event using a combination of high rate gps data from instruments located on the nearby islands and a tsunami field survey the gps displacement time series are deficient in high frequency energy and show small coseismic displacements 16 m our modeling results show that the combination of the small gps displacements and large tsunami can only be explained by high fault slip at very shallow depths far from the islands and close to the oceanic trench inelastic uplift of trench sediments likely contributed to the size of the tsunami recent results for the 2011 mw 9 0 tohoko oki earthquake have also shown shallow fault slip but the results from our study which involves a smaller earthquake provide much stronger constraints on how shallow the rupture can be with the majority of slip for the mentawai earthquake occurring at depths of 6 km this result challenges the conventional wisdom that the shallow tips of subduction megathrusts are aseismic and therefore raises important questions both about the mechanical properties of the shallow fault zone and the potential seismic and tsunami hazard of this shallow region

modeling afterslip and aftershocks following the 1992 landers earthquake one way to probe the rheology of the lithosphere and fault zones is to analyze the temporal evolution of deformation following a large earthquake in such a case the lithosphere responds to a known stress change that can be assessed from earthquake slip models constrained from seismology and geodesy here we model the postseismic response of a fault zone that is assumed to obey a rate strengthening rheology where the frictional stress varies as a ln e e being the deformation rate and a 0 a rheological parameter the model is simple enough that these parameters can be estimated by inversion of postseismic geodetic data we apply this approach to the analysis of geodetic displacements following the m w 7 3 1992 landers earthquake the model adjusts well the measured displacements and implies a 0 47 0 53 mpa in addition we show that aftershocks and afterslip follow the same temporal evolution and that the spatiotemporal distribution of aftershocks is consistent with the idea that they are driven by reloading of the seismogenic zone resulting from frictional afterslip