dynamic earthquake rupture modelled with an unstructured 3 d spectral element method applied to the 2011 m9 tohoku earthquake an important goal of computational seismology is to simulate dynamic earthquake rupture and strong ground motion in realistic models that include crustal heterogeneities and complex fault geometries to accomplish this we incorporate dynamic rupture modelling capabilities in a spectral element solver on unstructured meshes the 3 d open source code specfem3d and employ state of the art software for the generation of unstructured meshes of hexahedral elements these tools provide high flexibility in representing fault systems with complex geometries including faults with branches and non planar faults the domain size is extended with progressive mesh coarsening to maintain an accurate resolution of the static field our implementation of dynamic rupture does not affect the parallel scalability of the code we verify our implementation by comparing our results to those of two finite element codes on benchmark problems including branched faults finally we present a preliminary dynamic rupture model of the 2011 m w 9 0 tohoku earthquake including a non planar plate interface with heterogeneous frictional properties and initial stresses our simulation reproduces qualitatively the depth dependent frequency content of the source and the large slip close to the trench observed for this earthquake

rupture process of the 2011 tohoku oki mega thrust earthquake m9 0 inverted from strong motion data 1 we investigate the rupture process of the m9 0 tohoku oki mega thrust earthquake using the relatively low frequency strong motion records 0 01 0 125 hz observed at 36 k net and kik net stations the epicentral distances of which range from 120 km to 400 km the fault model is a rectangular plane the length and width of which are 510 km along the japan trench and 210 km along subducting direction of the pacific plate respectively we perform the multi time window inversion analysis with a 30 30 km2 subfault the derived slip model has one large slip area this area extends from the region around the hypocenter to the shallow part of the fault plane and further to the north and south along the trench axis located far off southern iwate miyagi and northern fukushima prefectures the seismic moment is 4 42 1022 nm mw 9 0 and the maximum slip is 48 m the slips near the coast are relatively small except off miyagi prefecture which experienced a slip greater than 5 m the shallow large slip area which continuously ruptured from 60 s to 100 s after the initial break radiated seismic waves rich in very low frequency content 0 02 hz the rupture after 100 s propagating to the southern fault area contributes to the distinct phases observed for fukushima and ibaraki prefectures the relationship between the proposed rupture model and the feature of the acceleration waveforms is not straightforward and suggests the frequency dependency of the seismic wave radiation

finite faults and inverse theory with applications to the 1979 imperial valley earthquake abstract using a representation theorem from elastodynamics subsurface slip on a known fault is formulated as the solution to an inverse problem in which recorded surface ground motion is the data two methods of solution are presented the least squares method which minimizes the squared differences between theory and data and the constrained least squares method which simultaneously maintains a set of linear inequalities instabilities in the solution are effectively eliminated in both methods and the sensitivity of the solution to small changes in the data is quantitatively stated the inversion methodology is applied to 77 components of near field ground acceleration recorded during the 15 october 1979 imperial valley earthquake the faulting is constrained to propagate bilaterally away from the epicenter at an average velocity of 90 per cent of the shear wave speed on a vertical fault plane extending from the surface to 10 km depth inequality constraints are used to keep the faulting sequence physically reasonable by maintaining right lateral motion and positive slip velocity the preferred solution is stable and provides a good fit to the data it is also realistic and consistent with observed surface offsets and independent estimates of seismic moment

high frequency source radiation during the 2011 tohoku oki earthquake japan inferred from kik net strong motion seismograms 1 to investigate source processes of the 2011 tohoku oki earthquake we utilized a source location method using high frequency 5 10 hz seismic amplitudes in this method we assumed far field isotropic radiation of s waves and conducted a spatial grid search to find the best fitting source locations along the subducted slab in each successive time window our application of the method to the tohoku oki earthquake resulted in artifact source locations at shallow depths near the trench caused by limited station coverage and noise effects we then assumed various source node distributions along the plate and found that the observed seismograms were most reasonably explained when assuming deep source nodes this result suggests that the high frequency seismic waves were radiated at deeper depths during the earthquake a feature which is consistent with results obtained from teleseismic back projection and strong motion source model studies we identified three high frequency subevents and compared them with the moment rate function estimated from low frequency seismograms our comparison indicated that no significant moment release occurred during the first high frequency subevent and the largest moment release pulse occurred almost simultaneously with the second high frequency subevent we speculated that the initial slow rupture propagated bilaterally from the hypocenter toward the land and trench the landward subshear rupture propagation consisted of three successive high frequency subevents the trenchward propagation ruptured the strong asperity and released the largest moment near the trench

seismic structure of the northeastern japan convergent margin a synthesis many studies recently made on the basis of seismic observations have revealed a detailed structure of the crust and the upper mantle beneath the northeastern japan arc and its relationship to seismic and volcanic activity spatial distributions of the depths to the conrad and the moho discontinuities estimated from shallow earthquake data and seismic explosion data show that both discontinuities are deep in the middle of the land area and shallow toward the coastlines of the japan sea and the pacific ocean the pn velocity has a lateral variation it is as low as 7 5 km s beneath the land area while that beneath the japan sea and the pacific ocean is 8 0 8 2 km s it changes abruptly at the transition zones which are located along the coastlines precise structure and location of the subducted pacific plate beneath the land area is inferred from converted or reflected seismic waves at the top or bottom of the plate the pacific plate is composed of a thin 5 km low velocity upper layer and a thick high velocity lower layer its total thickness being 80 90 km the upper plane seismicity of the double seismic zone is confined to the thin low velocity upper layer which probably corresponds to the subducted former oceanic crust the lower plane seismicity lies at the middle of the high velocity lower layer and the lower half of the plate below it is incapable of generating earthquakes the shallower portion of the upper surface of the plate beneath the pacific ocean along which major seismicity with low angle thrust faultings is actually occurring is also located by seismic observations on land and in the sea the pacific plate subducts at an extremely low angle of 5 for the first 25 km depth and then the dip steepens rather abruptly to 30 normal fault type events at the top of the plate have not been detected in the portion where the downward bending is the largest but have been ditected near the trench axis where it is rather small tomographic inversions for seismic velocity structure clearly delineate the inclined high velocity pacific plate with a thickness of 80 90 km and low velocity zones in the crust and the mantle wedge beneath active volcanoes seismic attenuation tomography also shows similar zones of low q value beneath active volcanoes although its spatial resolution is much lower the low velocity zones with 2 6 velocity lows are continuously distributed from the upper crust just beneath active volcanoes to a depth of 100 150 km in the mantle wedge and are approximately parallel to the dip of the underlying pacific plate these low velocity zones probably reflect the pathway of magma ascent from a depth in the mantle wedge to the earth s surface corresponding to a portion of the subduction induced secondary mantle wedge flow

fluid transport properties in sediments and their role in large slip near the surface of the plate boundary fault in the japan trench abstract fluid transport properties such as permeability and porosity are significant parameters that affect earthquake generation we measured the transport properties of shallow sediments sampled around the plate boundary near the japan trench during iodp expedition 343 at confining pressures up to 40 mpa the permeabilities of samples from the shallow plate boundary fault were very low at 10 20 m 2 equivalent to a hydraulic diffusivity of 10 10 m 2 s 1 permeability and porosity in the core of the fault zone at the plate boundary were lower than those in the immediately overlying sediments and the surrounding intact sediment suggesting that the plate boundary fault can act as a barrier for fluid flow low permeability and high pore compressibility in the shallow plate boundary fault create a strong potential for dynamic fault weakening due to fluid pressurization with frictional heating even when the initial shear stress is low our investigation supports the hypothesis that thermal pressurization on the fault plane helped facilitate the extremely large slip in the shallow part of the subduction zone during the tohoku earthquake as the fault zone has a lower permeability than the surrounding sediments and a higher clay content pore pressure generation at depth by dehydration of clay minerals can explain formation of the shallow strong patch on the fault more reasonably than continuous fluid influx from the subducting oceanic crust which does not affect pore pressure at depth in the fault zone although there are many possible mechanisms of fault weakening thermal pressurization can act relatively efficiently as slip begins even at shallow depths therefore our results support the role of thermal pressurization in shallow slip during the tohoku earthquake

dynamic rupture scenarios of anticipated nankai tonankai earthquakes southwest japan 1 we investigated dynamic rupture scenarios of anticipated megathrust earthquakes on the nankai tonankai subduction zone southwest japan to improve the scenario reliability the model parameters should be constrained by available data or derived from their analysis we employed the three dimensional plate interface geometry and the slip deficit rate on the interface accumulated slip deficit was used to obtain the stress drop distribution of anticipated earthquakes the estimated stress drop distribution is consistent with the seismogenic asperity locations known from the analysis of past earthquakes fault friction constitutive parameters however had to be assumed from indirect observations because they cannot be constrained directly by the data based on various geophysical observations we defined three regions where larger fracture energy is required these are the eastern edge of the tonankai area the western edge of the nankai area and the region between the tonankai and nankai areas beneath the kii peninsula such lateral heterogeneity promoted the segmented rupture along the nankai trough with predefined stress drop and constitutive parameters various rupture scenarios for tonankai and nankai asperities were obtained for different initiation locations in some cases a single segment is ruptured while in other cases all the segments are broken due to dynamic linkage at the segment boundary causing a giant earthquake the initiation location is a critical parameter that controls the rupture propagation across the segment boundary these scenarios will be extremely useful to evaluate deterministically the strong ground motions and tsunami hazards caused by the next major earthquakes in southwest japan

detection of ground motions using high rate gps time series monitoring surface deformation in real time help at planning and protecting infrastructures and populations manage sensitive production i e seveso type and mitigate long term consequences of modifications implemented we present rt shake an algorithm developed to detect ground motions associated with landslides sub surface collapses subsidences earthquakes or rock falls rt shake detects first transient changes in individual gps time series before investigating for spatial correlation s of observations made at neighbouring gps sites and eventually issue a motion warning in order to assess our algorithm on fast seconds to minute large from 1cm to meters and spatially consistent surface motions we use the 1hz geonet gnss network data of the tohoku oki mw9 0 2011 as a test scenario we show the delay of detection of seismic wave arrival by gps records is of 10 seconds with respect to an identical analysis based on strong motion data and this time delay depends on the level of the time variable noise nevertheless based on the analysis of the gps network noise level and ground motion stochastic model we show that rt shake can narrow the range of earthquake magnitude by setting a lower threshold of detected earthquakes to mw6 5 7 if associated with a real time automatic earthquake location system

application of horizontal to vertical spectral ratios of earthquake ground motions to identify subsurface structures at and around the k net site in tohoku japan abstract we propose an optimal way to use horizontal to vertical spectral ratios hvrs for subsurface structure exploration based on the diffuse field concept kawase et al 2011 sanchez sesma et al 2011 this approach is applicable to both earthquake and microtremor ground motions we show here analyses of the observed ground motion data at and around a k net station in miyagi prefecture japan where very large peak horizontal ground acceleration was observed during the earthquake of 11 march 2011 off the pacific coast of tohoku japan we compare hvrs of the strong motions for the mainshock and the largest peak acceleration aftershock with those averaged over tens of weak motions to observe soil nonlinearity effects on the hvrs then we determine detailed velocity profiles from the hvrs at the k net tsukidate station and the temporary aftershock observation sites we find that hvrs can be explained quite well by the identified velocity profiles at all the target sites the observed peak at 9 hz for the averaged weak motion data originates in the topmost layers lying over the engineering bedrock

broadband seismic wave radiation process of the 2000 western tottori japan earthquake revealed from wavelet domain inversion 1 we develop a new inversion method to obtain the low and high frequency wave radiation processes whose border is 1 hz in this method we adopt a consecutive approach to evaluate the fitness between the observed and synthetic strong motions and to synthesize the waveforms a new feature of our inversion is an evaluation of the fitness of broadband strong motions including the high frequency range using the wavelet coefficient of velocity waveforms based on the frequency dependent characteristics of seismic waves another new feature is the introduction into the source inversion of a hybrid green s function which is constructed from theoretical and empirical green s functions for the low and high frequency ranges respectively in order to reach the global minimum by nonlinear inversion we introduce a multiscale approach for the low frequency inversion after a synthetic test the inversion method was applied to the 2000 western tottori earthquake for three frequency bands the low frequency inversion 0 0625 1 hz reveals that the asperity extends from the southeast of the hypocenter to the shallow part of the fault above the hypocenter the waves of 1 2 hz are radiated most intensely from the rupture starting area of the southeast asperity on the other hand the higher frequency waves of 2 4 hz are radiated most strongly from the edge of the southeast asperity the inversion result suggests a possibility that broadband strong motions are generated from the asperities and the high frequency wave radiations are particularly related to the initiation and termination of the asperity rupture

rupture process of the 2008 iwate miyagi nairiku japan earthquake derived from near source strong motion records abstract we derive the rupture process of the 2008 iwate miyagi nairiku japan earthquake m jma 7 2 during which the largest ground acceleration to date namely 4022 cm sec 2 was recorded at a hanging wall station iwth25 station of kik net just above the hypocenter velocity waveform data 0 1 1 hz at 14 strong motion stations of k net and kik net including the borehole records of iwth25 are inverted using the multi time window linear waveform inversion method we assume a horizontally layered velocity structure model having low velocity subsurface layers for each station in order to calculate the green s functions the waveform inversion indicates that there are two major slip patches one patch extends from the hypocenter to the southern shallower part of the fault a particularly large slip area in this patch is centered approximately 8 km to the south of the hypocenter with a maximum slip of 6 2 m the area ruptured between 4 and 9 sec after the initial break the other patch with smaller slip is located in the northern part which broke after the rupture of the southern slip patch the initial 0 4 sec rupture occurred beneath iwth25 contributing to the synthesis of a distinctive upward velocity pulse at this station examination of the slip contribution to the synthetic velocity waveforms and comparison of the isochrones with the slip distribution suggest that a peak acceleration greater than 4000 cm sec 2 observed at iwth25 was generated from the area that is closest to the hypocenter in the southern particularly large slip area

dynamic source model for the 2011 tohoku earthquake in a wide period range combining slip reactivation with the short period ground motion generation process this paper describes a validated dynamic rupture model of the 2011 tohoku earthquake that reproduces both long period 20 100 s and short period 3 20 s ground motions in order to reproduce the observed large slip area slip asperity we assign a large dc slip critical distance area following kinematic source inversion results sufficiently large slip is achieved through rupture reactivation by the double slip weakening friction model in order to reproduce the strong motion generation areas smgas we assign short dc and large stress drop areas following empirical green s function egf simulation results which indicate that although more distant from the hypocenter smga1 ruptured earlier than smga2 or smga3 which are closer to the hypocenter this observation is confirmed by the backprojection method in order to reproduce this important feature in dynamic simulation results we introduce a chain of small high stress drop patches between the hypocenter and smga1 by systematic adjustment of stress drops and dc the rupture reproduces the observed sequence and timing of smga ruptures and the final slip derived by kinematic models this model also reproduces the multiseismic wavefront observed from strong ground motion data recorded along the pacific coast of the tohoku region we compare the velocity waveforms recorded at rock sites along the coastline with one dimensional 1d synthetic seismograms for periods of 20 100 s the fit is very good at stations in the northern and central areas of tohoku we also perform finite difference method fdm simulations for periods of 3 20 s and confirm that our dynamic model also reproduces wave envelopes overall we are able to validate the rupture process of the tohoku earthquake

modeling strong motion recordings of the 2010 mw 8 8 maule chile earthquake with high stress drop subevents and background slip strong motion recordings of the m w 8 8 maule earthquake were modeled using a compound rupture model consisting of 1 a background slip distribution with large correlation lengths relatively low slip velocity and long peak rise time of slip of about 10 s and 2 high stress drop subevents asperities on the deeper portion of the rupture with moment magnitudes 7 9 8 2 high slip velocity and rise times of slip of about 2 s in this model the high frequency energy is not produced in the same location as the peak coseismic slip but is generated in the deeper part of the rupture zone using synthetic seismograms generated for a plane layered velocity model i find that the high stress drop subevents explain the observed fourier spectral amplitude from about 0 1 to 1 0 hz broadband synthetics 0 10 hz were calculated by combining deterministic synthetics derived from the background slip and asperities 1 hz with stochastic synthetics generated only at the asperities 1 hz the broadband synthetics produced response spectral accelerations with low bias compared to the data for periods of 0 1 10 s a subevent stress drop of 200 350 bars for the high frequency stochastic synthetics was found to bracket the observed spectral accelerations at frequencies greater than 1 hz for most of the stations the synthetics had durations of the arias intensity similar to the observed records

a rapid and nondestructive method to determine normal and shear stiffness of a single rock joint based on 1d wave propagation theory abstractdetermination of joint stiffness one of the most important mechanical properties of rock joints is of great significance however joint stiffness is often difficult to complete and accurate determine because of the 3d nature of joints and limited budgets and visible exposure wave attenuation in a rock mass is mainly attributed to the presence of joints based on 1d plane wave theory a rapid and nondestructive method namely the rapid evaluation method is proposed to calculate normal and shear stiffness of joints the joint is viewed as a boundary condition modeled by the displacement discontinuity model by solving wave equations with reasonable approximation joint stiffness can be inversely solved which is dependent on the seismic impedance transmission or reflection coefficient and dominant frequency of transmitted waves ultrasonic laboratory tests were carried out to record incident reflected and transmitted waveforms as input to the rapid evaluation method it was found that the

determination of megathrust rupture processes using plate interface based fault models and 3d green s functions an application to the 2011 mw 9 1 tohoku earthquake in order to understand physical processes of megathrust earthquakes and thus to analyze hazards of the regions proper information of the rupture processes is essential in this study we develop a technique for determination of large spatial scale rupture processes on megathrust faults in subduction zones as soon as possible based on teleseismic broadband full waveform inversions using realistic models of finite fault geometries and 3d global velocity structures finite fault geometry models are constructed for eleven subduction zones of the circum pacific area utilizing the 3d plate interface model slab 1 0 of usgs green s functions for available pairs of subfaults and globally distributed stations to be used in the inversions are computed in the global 3d velocity model using spectral element method rather than in a 1d velocity model this scheme accommodates synthetic waves with lateral velocity variations especially for surface waves which is useful in estimations of large spatial scale slip distributions the data utilized are teleseismic broadband full waveform records including body waves and surface waves at the epicentral distance of 30o 80o the observed data are inverted for fault rupture processes based on the non negative least square technique with a multiple source time window scheme for each subfault the applicability of the method is tested for the 2011 mw 9 0 tohoku oki earthquake and the result shows that the proposed scheme of the finite fault inversion produces reasonable results of slip distributions

fault geometry at the rupture termination of the 1995 hyogo ken nanbu earthquake the source geometry and slip distribution at rupture termination of the 1995 hyogo ken nanbu earthquake were investigated using waveform inversion on the assumption of fault branching in the northeastern part of the rupture model possible branching of the okamoto fault is suggested both by the static displacement distribution and damage extension east of kobe nishinomiya area to exclude data contaminated by the basin edge diffracted wave in the waveform inversion process we examined the spatio temporal variation of its influence and from a comparison with a flat model we determined windows appropriate for the data three subevents were identified as was reported in previous works the largest was in the shallow part on the awaji side whereas the smaller two occurred at great depths 7km on the kobe side we found a smaller subevent in the deep part of the branch total variance reduction was larger and the abic value was smaller when we assumed the branch than when we did not which shows the superiority of the branching fault model resolution checks showed that the slips on proposed branched portions are physical and not caused by random data noise or systematic errors in green s func tions that arise from misestimation of velocity structures calculation of the relative static displacement between two leveling observation stations near the branching fault also showed the greater utility of the branching fault model the effect of slip on the branched fault has been shown in near source ground motion simulation using the 3d finite difference method iwata et al 1999 the characteristic distribution of ground motion in the near source region indicated by the damage distribution is well reproduced by the modeling of both the source process and wave propagation in the realistic 3d velocity structure slip on the branched fault affected the ground motion in eastern kobe nada and higashi nada wards ashiya and nishinomiya cities but its contribution is not dominant even in those regions about 30 to 50 maximum velocity in the frequency range of 0 1 to 1 0 hz we conclude that branching rupture of the okamoto fault during the hyogo ken nanbu earthquake is the preferable interpretation on the source process of this earth quake this supports the idea of a geometrical barrier suggested by geological ob servations

the coseismic slip distribution of a shallow subduction fault constrained by prior information the example of 2011 tohoku mw 9 0 megathrust earthquake

pre and postseismic slow slip surrounding the 2011 tohoku oki earthquake rupture abstract slow aseismic slip that accommodates part of the long term plate motion on subduction megathrusts is thought to be strongly related to the occurrence of large earthquakes on the same fault zone however the temporal evolution and spatial distribution of the aseismic slip before major earthquakes and of accelerated postseismic afterslip are largely unconstrained we estimate cumulative offsets of small repeating earthquakes that are interpreted to reflect the in situ aseismic slip history on the subduction zone offshore northeastern japan these data reveal contrasting aseismic slip patterns between the coseismic rupture area of the mw 9 0 tohoku oki earthquake and surrounding portions of the subduction thrust the rupture area is characterised by low and variable slip rates before 2008 and the slip stopped almost completely after the earthquake the region surrounding the rupture area exhibited higher aseismic fault slip rates before the earthquake and clear postseismic slip of up to 1 6 m within 9 months following the main shock the frictional fault properties and complete relief of ambient stress in the central rupture zone of the main shock probably control the observed distribution the postseismic slip shows a more abrupt increase in the region closer to the source suggesting outwards propagation of afterslip small but distinct increases in the slip rate in the 3 yr before the earthquake near the area of large coseismic slip suggests preseismic unfastening of the locked area in the last stage of the earthquake cycle

groundwater pressure changes in central japan induced by the 2011 off the pacific coast of tohoku earthquake 1 in the 2011 off the pacific coast of tohoku earthquake groundwater pressure changes were observed in and around the mizunami underground research laboratory miu in central japan where two vertical shafts and horizontal research galleries are excavated in the granitic rock mass coseismic changes of groundwater pressure are believed to correspond to crustal dilation contraction induced by earthquakes in this study we calculated volumetric strain changes due to the tohoku earthquake based on previously reported fault slip models the calculation indicates approximately 2 10 7 of dilational strain around the miu based on the strain sensitivities calculated from tidal responses at the monitoring boreholes the dilation corresponds to drawdowns of several tens of centimeters and is almost the same as the drawdown observed in the boreholes at distances greater than 1 km from the miu in contrast rapid elevation of groundwater pressures associated with the earthquake was observed in the boreholes within the 500 m vicinity of the miu the anomalous elevation is explained by a temporary recovery of the drawdown due to excavation of the shafts and a unique permeability increase induced by the coseismic dilation of heterogeneous local geological structures such as impervious faults controlling the hydrogeological environment

propagation of an earthquake triggering front from the 2011 tohoku oki earthquake 1 increases in seismicity have been widely observed at varying distances from the source area following large earthquakes the increased number of earthquakes are usually called aftershocks if the area is within a rupture length of the mainshock and called remotely triggered events if they are well beyond that distance these earthquakes can be explained as being induced by static and or dynamic stress changes due to the mainshock however clear observations of dynamic triggering have been inadequate to differentiate between the two mechanisms this study shows that early post seismic events triggered by the 2011 mw 9 0 tohoku oki earthquake systematically propagated over japan in a southwestern direction associated with the strong seismic waves from the source the propagation front was consistent with the arrivals of large amplitude surface waves traveling at 3 1 to 3 3 km s and extending to a distance of 1 350 km there were no observations of triggered earthquakes in the northern direction dynamic stress changes toward the north were comparable to or smaller than those necessary for triggering in the southwestern direction static stress changes were one to two orders smaller than dynamic stress changes at remote distance indicating that static stress was not the main mechanism of the triggering furthermore the dynamic stress strain changes play an important role for remote triggering if the value is more than 500 kpa in stress or 10 6 in strain

frontal wedge deformation near the source region of the 2011 tohoku oki earthquake 1 we report an uplift of 5 m with a horizontal displacement of more than 60 m due to the 2011 tohoku oki earthquake the uplift was measured by an ocean bottom pressure gauge installed before the earthquake on a frontal wedge which formed an uplift system near the japan trench horizontal displacements of the frontal wedge were measured using local benchmark displacements obtained by acoustic ranging before and after the earthquake the average displacements at the frontal wedge were 58 m east and 74 m east southeast these results strongly suggest a huge coseismic slip beneath the frontal wedge on the plate boundary the estimated magnitude of the slip along the main fault was 80 m near the trench our results suggest that the horizontal and vertical deformations of the frontal wedge due to the slip generated the tremendous tsunami that struck the coastal area of northeastern japan

simple crack models explain deformation induced by subduction zone megathrust earthquakes following the 2010 maule and 2011 tohoku earthquakes many studies have examined the relation between megathrust earthquakes and subsequent deformation here we apply simple models based on mode ii shear cracks including approximated effects of the free surface to study induced deformation during coseismic and early postseismic stages we distinguish between buried and surface ruptures represented by a full crack and a half crack model respectively we adopt an analogy based approach to interpret the half crack model from well known results of the full crack model which is also validated by our numerical simulations with transferable knowledge between the two models we provide easy ways to understand 1 the contrasting deformation patterns in the frontal wedge of the overriding plate between buried ruptures and surface ruptures 2 the correlation between triggered outer rise normal faulting and surface ruptures and 3 the similar deformation patterns for both buried and surface ruptures toward the down dip end with a preference for normal faulting in the overriding plate and for reverse faulting in the subducting plate these model outcomes are consistent with several recent observations on aftershocks and veins in a paleoaccretionary wedge we further investigate some important transient features during rupture propagation which show that a transition from compressional to extensional deformation in the frontal wedge of the overriding plate is possible even during a single rupture event our work provides alternative views for understanding various aspects of subduction zone megathrust earthquakes and raises the issue of important transient features that were typically ignored in previous studies

inversion of strong ground motion and teleseismic waveform data for the fault rupture history of the 1979 imperial valley california earthquake a least squares point by point inversion of strong ground motion and teleseismic body waves is used to infer the fault rupture history of the 1979 imperial valley california earthquake the imperial fault is represented by a plane embedded in a half space where the elastic properties vary with depth the inversion yields both the spatial and temporal variations in dislocation on the fault plane for both right lateral strike slip and normal dip slip components of motion inversions are run for different fault dips and for both constant and variable rupture velocity models effects of different data sets are also investigated inversions are compared which use the strong ground motions alone the teleseismic body waves alone and simultaneously the strong ground motion and teleseismic records the inversions are stabilized by adding both smoothing and positivity constraints the moment is estimated to be 5 0 10 25 dyne cm and the fault dip 90 5 dislocation in the hypocentral region south of the united states mexican border is relatively small and almost dies out near the border dislocation then increases sharply north of the border to a maximum of about 2 m under interstate 8 dipslip motion is minor compared to strike slip motion and is concentrated in the sediments the best fitting constant rupture velocity is 80 per cent of the local shear wave velocity however there is a suggestion that the rupture front accelerated from the hypocenter northward the 1979 imperial valley earthquake can be characterized as a magnitude 5 earthquake at the hypocenter which then grew into or triggered a magnitude 6 earthquake north of the border

ground motion attenuation from the 1995 kobe earthquake based on simulations using the hybrid green s function method because of the limited number of strong motion stations in the kobe area at the time of the 1995 kobe earthquake information about the characteristics of the near fault ground motion acceleration in bedrock is sparse in this study we estimated the near fault ground motion and derived characteristics of its attenuation on rock using an hybrid broadband technique and a source model that have been validated against data we found that at high frequencies the near fault ground motion produced by the kobe earthquake was of the same level as that predicted by the empirical attenuation relation for japanese crustal earthquakes the areas with the largest peak horizontal acceleration are located at the extremities of the fault and include most of the kobe city

source inversion for estimating the continuous slip distribution on a fault introduction of green s functions convolved with a correction function to give moving dislocation effects in subfaults summary in order to obtain knowledge concerning the physics of earthquake rupturing more precisely and to obtain reliable source process for near source ground motion simulation we introduced a convolution method that incorporates the effect of a moving dislocation over a rectangular area to a synthetic point source into computing the element source waves for the waveform inversion therefore the rupture directivity effect over the entire fault area is considered fully in the waveform inversion the rupture process inverted using this technique has a continuous slip distribution inside the subfaults the moment release history obtained for each subfault directly reflects a slip time function on the subfault because the rupture propagation effect inside each subfault is separated the validity of this technique is based on the following approximation the green s functions from two point sources are approximately the same after a phase correction when the distances between two point sources is much smaller than the distance between the sources and an observation station the condition for valid usage of this technique has been found through numerical tests we applied this technique in the waveform inversion of strong motion records for the source process of the 1995 hyogo ken nanbu earthquake the global characteristics of moment release distributions are similar between two inversion results one inverted with point source element waveforms and the other with element source waves considering the finite moving dislocation effects inside each subfault however the details are different e g the locations of local maxima of the total moment release are different between these inversion results a positive correlation between final slip and peak slip velocity is observed