source characteristics of the 28 september 2018 m w 7 5 palu sulawesi indonesia se asia earthquake based on inversion of teleseismic bodywaves we study source characteristics of the september 28 2017 mw 7 5 palu sulawesi indonesia earthquake that occurred in central sulawesi and triggered devastating tsunami waves along the coastal plains of the island we apply point source teleseismic p and sh body waveform inversion and kinematic slip inversion techniques to obtain double couple source mechanism and comprehensive finite fault slip model of the source the overall results show a strike slip faulting mechanism strike 353 5 dip 65 5 and rake angles 4 5 with a small amount of dip slip component at a shallow focal depth of 16 2 km associated with the nw se trending left lateral palu koro strike slip fault in the central sulawesi region the p wave first motion polarity readings recorded at near field and regional seismic stations are found to be reasonably consistent with the source mechanism solution of the earthquake and estimated error limits we have extensively studied and considered the rupture velocity to be about 4 1 km s during the slip inversion as previously proposed by seismological and geodetic studies for this event the obtained finite fault slip distribution model displays a rupture starting from the hypocentre located at 16 km and then it propagated south accompanied by high amount of displacement and reached the surface the model has two slip patches of 2 0 4 0 m at north of the fault plane and 5 0 6 3 m at south near palu city which is very well matched with the observed damage and destruction related to the earthquake the fault length and width average slip and stress drop values are estimated to be 150 km 45 km 1 5 m and 13 bars respectively we have also obtained total source duration to be about 40 s with the most of seismic energy released at 10 s and 25 s furthermore a small dip slip component is evidently observed from both source models and we suggest that this oblique shear which reflects the bending of slip vector along the strike direction could be comparatively responsible for tsunami generation along the left lateral palu koro fault the validation of this hypothesis could be done by evaluating the results of the mathematical tsunami simulations based on the comprehensive non uniform slip models along with a high resolution bathymetry data which provides the details of the continental shelf in palu bay

systematic comparisons of earthquake source models determined using insar and seismic data abstract robust earthquake source parameters e g location seismic moment fault geometry are essential for reliable seismic hazard assessment and the investigation of large scale tectonics they are routinely estimated using a variety of data and techniques such as seismic data and more recently interferometric synthetic aperture radar insar comparisons between these two datasets are frequently made although not usually in a comprehensive way this review compares source parameters from global and regional seismic catalogues with those from a recent database of insar parameters which has been expanded with 18 additional source models for this study we show that moment magnitude mw estimates agree well between the two datasets with a trend for thrust events modelled using insar to have slightly larger mw estimates earthquake locations determined using insar agree well with those reported in regional catalogues with a median difference of 6 3 km between them which is smaller than for global seismic catalogues we also investigate the consistency of source parameters and source directivity by comparing isc hypocentres with gcmt and icmt centroid locations for earthquakes with mw 6 5 in some cases the source directivity is qualitatively comparable with previous studies especially when comparing isc and icmt locations the average difference between insar determined depths and those in the ehb catalogue is reduced if a layered half space is used in the inversion of insar data overall faulting geometry strike dip and rake angles remain in good agreement with values from the gcmt catalogue and any large discrepancies can be attributed to tradeoffs between parameters with continued investment in satellites for radar interferometry insar is a valuable technique for the estimation of earthquake source parameters the observed trends and discrepancies between insar and seismically determined source parameters are the result of issues with the data different inversion techniques and the assumed earth structure model

coseismic slip distribution of the 2015 mw7 8 gorkha nepal earthquake from joint inversion of gps and insar data for slip within a 3 d heterogeneous domain

inversion of complex body waves we have developed a method that inverts seismic body waves to determine the mechanism and rupture pattern of earthquakes the rupture pattern is represented as a sequence of subevents distributed on the fault plane this method is an extension of our earlier method in which the subevent mechanisms were fixed in the new method the subevent mechanisms are determined from the data and are allowed to vary during the sequence when subevent mechanisms are allowed to vary however the inversion often becomes unstable because of the complex trade offs between the mechanism the timing and the location of the subevents many different subevent sequences can explain the same data equally well and it is important to determine the range of allowable solutions some constraints must be imposed on the solution to stabilize the inversion we have developed a procedure to explore the range of allowable solutions and appropriate constraints in this procedure a network of grid points is constructed on the i plane where and i are respectively the onset time and the distance from the epicenter of a subevent the best fit subevent is determined at all grid points then the correlation is computed between the synthetic waveform for each subevent and the observed waveform the correlation as a function of and i and the best fit mechanisms computed at each i grid point depict the character of allowable solutions and facilitate a decision on the appropriate constraints to be imposed on the solution the method is illustrated using the data for the 1976 guatemala earthquake

magnitudes of future large earthquakes near istanbul quantified from 1500 years of historical earthquakes present day microseismicity and gps slip rates abstract in the past 1500 years seven sequences of significant earthquakes have occurred on a 160 km long segment of the north anatolian fault zone nafz centered on istanbul the most recent of these sequences will be complete with the future occurrence of one or more mw 7 0 earthquakes near the city from a summation of the seismic moment released by historical earthquakes between 500 and 2000 ce we calculate a mean slip deficit rate of 9 9 mm year our moment summation procedure sums the seismic moment associated with known historical earthquakes in the past 1500 years based on rupture length and assumed seismogenic depth we observed that in the 1999 izmit earthquake strongly coupled fault patches were associated with the highest co seismic slip in our calculated map of present day slip potential we recognize several such patches from their low present day rate of microseismicity e g segments beneath the kumburgaz and eastern cinarcik marmara basins in contrast intervening weakly coupled patches host high present day background seismicity e g the segment beneath the western tekirdag basin this lends credibility to an interpretation of future earthquakes occurring in three seismogenic segments of the nafz corresponding to three deep basins in the sea of marmara the present day slip deficits reach up to 1 7 m beneath the western tekirdag basin segment and 4 0 m and 5 4 m beneath the central central high and kumburgaz basin and eastern cinarcik basin segments respectively these segments most recently ruptured in august 1766 may 1766 and october 1509 and currently have a potential to generate mw 7 2 mw 7 4 and mw 7 5 earthquakes respectively although contiguous ruptures have not occurred historically ruptures of contiguous segments could occur as a mw 7 5 earthquake in the west or a mw 7 6 earthquake in the east or as a single through going mw 7 7 rupture

observational constraints on the fracture energy of subduction zone earthquakes we relate seismologically observable parameters such as radiated energy seismic moment rupture area and rupture speed to the dynamics of faulting to achieve this objective we computed the radiated energy for 23 subduction zone earthquakes recorded between 1992 and 2001 most of these earthquakes have a magnitude m w 7 5 but we also included some smaller m w 6 7 well studied subduction zone earthquakes and six crustal earthquakes we compiled static stress drop estimates for these 29 earthquakes from literature and used a slip weakening model to determine the radiation efficiency of these earthquakes we also determined the rupture speed of these earthquakes from literature from fracture mechanics fracture energy and hence radiation efficiency can be related to the rupture speed the radiation efficiencies estimated from the partitioning of energy as given by the slip weakening model are consistent with the rupture speed estimated for these earthquakes most earthquakes have radiation efficiencies between 0 25 and 1 and are hence efficient in generating seismic waves but tsunami earthquakes and two deep earthquakes the 1994 bolivia and the 1999 russia china border earthquakes have very small radiation efficiencies 0 25 and hence dissipate a large amount of energy during faulting we suggest that differences in the radiation efficiencies of different types of earthquakes could be due to fundamental differences in their rupture mechanics in deep events the energy is probably dissipated in thermal processes in the fault zone while it is possible that the morphology of the trench causes large energy dissipation during the rupture process of tsunami earthquakes

kinematic inversion of physically plausible earthquake source models obtained from dynamic rupture simulations one approach to investigate earthquake source processes is to produce kinematic source models from inversion of seismic records and geodetic data the setup of the inversion requires a variety of assumptions and constraints to restrict the range of possible models here we evaluate to what extent physically plausible earth quake scenarios are reliably restituted in spite of these restrictions we study which characteristics of ruptures such as rupture velocity slip distribution stress drop rise time and slip function can be reliably determined from the inversion of near field seismic and geodetic data using spontaneous dynamic rupture simulations we gen erate five earthquake scenarios each of which has different characteristics of the source process then we conduct a blind test by modeling the synthetic near source data using a standard inversion scheme that optimizes the fit to the observations while searching for solutions with minimum roughness the inversion procedure assumes a rupture front propagating away from the hypocenter with variable rupture velocity and a simple cosine slip time function our results show that overall slip distribution and stress drop are reasonably well determined even for input models with relatively complex histories such as a subshear rupture transitioning to supershear speeds depth averaged rupture velocities are also reasonably well resolved although their estimate progressively deteriorates away from the hypocenter the local rise time and slip function are not well resolved but there is some sensitivity to the rupture pulse width which can be used to differentiate between pulse like and crack like ruptures our test for understanding the inaccuracies in green s functions shows that random 3d perturbations of 5 standard deviation do not lead to significant degradation of the estimation of earthquake source parameters as remedies to the current limitations we propose smoothing slip function parameters and using more complicated inversion schemes only if data necessitates them online material figures showing snapshots of forward and inverse modeling of rupture l curves slip models and waveform fits

a hybrid method for simulating near source broadband seismograms application to the 2003 bam earthquake mw 6 5 the main objective of this article is to simulate the three components of near source ground shaking recorded at bam station close to the causative fault during the destructive the 2003 bam earthquake where were strongly influenced by rupture directivity effect a hybrid technique composed of the theoretical green s function finite element and finite difference method proposed by spudich et al 1987 2003 compsyn and a 2 based finite fault approach proposed by beresnev and atkinson 1998a finsim are used for generating seismograms at low and high frequencies respectively a genetic algorithm technique is developed for minimizing the differences between the recorded and simulated data incorporating parameters within a predefined upper lower bound s values previously estimated for main shock by other investigators two different faulting models consist of a straight line segment and a straight line segment followed by a slightly north eastward branch are used the simulated three component seismograms at bam station in terms of elastic response spectra are validated by comparing the simulated time series with those of the observed data moreover the pulses involved in the recorded time series due to the rupture directivity are estimated and compared with those of the observed data a sensitivity analysis is performed for recognizing the influence of model parameter changes such as focal mechanism strike dip and rake rise time rupture velocity and hypocenter location on the simulated seismograms relatively good match of the simulated and observed time series particularly the two faulting models confirm the potentiality of the proposed technique and the suitability of seismological model parameters used this technique can be used for specific site hazard analysis of the bam region and linear nonlinear dynamic analysis of structures where were damaged during the bam earthquake particularly for retrofitting the well known international adobe buildings of arg e bam

p wave velocity structure of the crust and its relationship to the occurrence of the 1999 izmit turkey earthquake and aftershocks we determined hypocenters and focal mechanism solutions of aftershocks and three dimensional p wave velocity structure in and around the focal area of the 1999 izmit earthquake m w 7 4 aftershocks form a 170 km long narrow zone trending in an east west direction along the northern branch of the north anatolian fault zone nafz they are not homogeneously distributed in the whole aftershock area but consist of several clusters there are three significant clusters in the aftershock activity 1 near the hypocenter of the mainshock 2 near 29 2 e in the marmara sea and 3 east of 30 4 e focal mechanism solutions of aftershocks have various types but they are similar to each other within each cluster the p wave velocity structure obtained has a distinct low velocity area to the west of the mainshock hypocenter the mainshock rupture area estimated by yagi and kikuchi 2000 lies outside this low velocity area there exists a high velocity anomaly to the east of 30 4 e this high velocity area lies below the aftershock cluster distributed to the east of 30 4 e this high velocity anomaly extends to the shallower depth of the southern branch iznik mekece fault of nafz the anatolian earthquake sequence that had migrated westward for the past 60 yr did not propagate into this southern branch this suggests the possibility that the anatolian earthquake sequence progressed to the west exploiting an area that might break more easily

earthquake source parameters along the hellenic subduction zone and numerical simulations of historical tsunamis in the eastern mediterranean abstract we studied source mechanism parameters and slip distributions of earthquakes with m w 5 0 occurred during 2000 2008 along the hellenic subduction zone by using teleseismic p and sh waveform inversion methods in addition the major and well known earthquake induced eastern mediterranean tsunamis e g 365 1222 1303 1481 1494 1822 and 1948 were numerically simulated and several hypothetical tsunami scenarios were proposed to demonstrate the characteristics of tsunami waves propagations and effects of coastal topography the analogy of current plate boundaries earthquake source mechanisms various earthquake moment tensor catalogues and several empirical self similarity equations valid for global or local scales were used to assume conceivable source parameters which constitute the initial and boundary conditions in simulations teleseismic inversion results showed that earthquakes along the hellenic subduction zone can be classified into three major categories 1 focal mechanisms of the earthquakes exhibiting e w extension within the overriding aegean plate 2 earthquakes related to the african aegean convergence and 3 focal mechanisms of earthquakes lying within the subducting african plate normal faulting mechanisms with left lateral strike slip components were observed at the eastern part of the hellenic subduction zone and we suggest that they were probably concerned with the overriding aegean plate however earthquakes involved in the convergence between the aegean and the eastern mediterranean lithospheres indicated thrust faulting mechanisms with strike slip components and they had shallow focal depths h

aftershock activity of the 1999 izmit turkey earthquake revealed from microearthquake observations an accurate aftershock distribution of the 1999 izmit turkey earthquake was obtained by using the data from a local seismic network izinet and 10 temporary seismic stations more than 2000 aftershocks were relocated for the period of about 2 months following the mainshock from this aftershock distribution we obtained several pieces of information on the characteristics of the mainshock first the mainshock initiated fault rupture from a place adjacent to an active swarm area where many microearthquakes had been occurring for more than 20 yr prior to the mainshock second the aftershock region extended in the east west direction along the north anatolian fault zone nafz this confirms that the mainshock was caused by a slip on the nafz third the western end of the rupture caused by the mainshock is likely to have reached up to about 29 2 e in the izmit bay and hence the total length of the fault rupture caused by the mainshock amounts to about 150 km as long as the estimate of the fault rupture length is based on the aftershock distribution this information is important for the discussion on the possibility of future large earthquakes in the west of the source region of the izmit earthquake we also found a clear tendency that aftershocks occur in clusters which implies strong heterogeneity in both the rupture process and the medium along the fault zone manuscript received 7 october 2000

scaling relationships of source parameters for slow slip events to better understand the physical mechanisms of slow slip events sses detected worldwide we explore the scaling relationships of various source parameters and compare them with similar scaling laws for earthquakes these scaling relationships highlight differences and similarities between slow slip events and earthquakes and hold implications for the degree of heterogeneity and fault healing characteristics the static stress drop remains constant for different sized events as is observed for earthquakes however the static stress drop of slow slip events is within a range of 0 01 1 0 mpa 1 2 orders of magnitude lower than that found for earthquakes which could be related to the low stress state on the fault the average rupture velocity ranging from kilometers per second to kilometers per day decreases linearly with increasing seismic moment in log log space unlike earthquakes that are nearly constant this inverse relationship of rupture velocity with seismic moment could be related to the heterogeneity of fault properties slow slip events typically have ratios of event duration over dislocation rise time less than 3 while earthquakes have ratios greater than 3 this indicates that slow slip events are less pulselike than earthquakes in their mode of propagation and suggests that the healing behind the rupture front is delayed the recurrence statistics of slow slip events on the northern cascadia subduction zone are weakly time predictable and moderately antislip predictable that is the event size and preevent recurrence interval are anticorrelated which may indicate that healing between events strengthens the fault with time online material table of source parameters and data sources

evidence for self similar triangular slip distributions on earthquakes implications for earthquake and fault mechanics we characterize average slip distributions on earthquakes beyond their individual heterogeneity for that we analyze a large number of seismic slip distributions both measured at the surface after earthquakes 44 profiles and derived from slip inversion models 76 models investigating the overall shape of these slip profiles we find that they are roughly triangular both along strike and dip and most of them 70 80 are asymmetric long linear slopes and high slip gradients therefore are the key ingredients to describe earthquake slip profiles the scaling relations between maximum displacement and length or width suggest furthermore that the triangular slip profiles are self similar such slip patterns make earthquakes dominated by one major zone of maximum slip hence one major asperity analyzing the position of hypocenters with respect to these asperities we find that earthquakes nucleate at a distance from them that averages 20 30 of their total length compiling observations on 56 earthquakes we show that this distance i e the asperity size is structurally defined we then compare the earthquake slip profiles to cumulative slip profiles measured on long term faults of various ages and sizes and find that all profiles have a similar shape triangular and asymmetric hence combining data for a large number of earthquakes leads to point out average generic characteristics of the coseismic slip that are similar to those that emerge from the accumulation of events with time on a single fault this suggests that these characteristics result from robust physical properties

a spatial random field model to characterize complexity in earthquake slip 1 finite fault source inversions reveal the spatial complexity of earthquake slip over the fault plane we develop a stochastic characterization of earthquake slip complexity based on published finite source rupture models in which we model the distribution of slip as a spatial random field the model most consistent with the data follows a von karman autocorrelation function acf for which the correlation lengths a increase with source dimension for earthquakes with large fault aspect ratios we observe substantial differences of the correlation length in the along strike a x and downdip a z directions increasing correlation length with increasing magnitude can be understood using concepts of dynamic rupture propagation the power spectrum of the slip distribution can also be well described with a power law decay i e a fractal distribution in which the fractal dimension d remains scale invariant with a median value d 2 29 0 23 while the comer wave number k c which is inversely proportional to source size decreases with earthquake magnitude accounting for larger slip patches for large magnitude events our stochastic slip model can be used to generate realizations of scenario earthquakes for near source ground motion simulations

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

the 1999 izmit turkey earthquake nonplanar fault structure dynamic rupture process and strong ground motion we simulated dynamic rupture propagation along various nonplanar fault models of the 1999 izmit turkey earthquake using a boundary integral equation method these models were inferred from geological and geodetic observations based on these results we modeled seismic wave propagation around the fault system using a finite difference method we focused on the effect of different fault geometries on the rupture process and seismic wave propagation numerical simulation results imply a rapid and continuous rupture propagation from the izmit sapanca lake segment to the sapanca akyazi segment the rupture under sapanca lake appears to have propagated not on a disconnected fault segment but along a smooth fault structure with a bend of only a few degrees the observational complexity of the surface breaks however can be best simulated by a highly segmented fault model this infers that fault geometric characters observed in the field reflect near surface structure and that seismological and geodetic features are controlled by global fault structure at depth then we investigated the effect of frictional parameters and the initial stress field in order to explain near field seismograms at station skr located a distance of a few kilometers from the fault we had to force the rupture to propagate at shallow depth close to the station in order to obtain this we had to introduce a finite cohesive force in the friction law that allows stress accumulation and release in the shallow crust the external stress field had to be large enough for the rupture to propagate at very rapid speed our simulation results show that it is important to include detailed fault geometry in the numerical simulation and to constrain frictional parameters and the initial stress field for understanding of the full dynamic process of an earthquake

slip distribution and stress changes associated with the 1999 november 12 duzce turkey earthquake mw 7 1 the 1999 november 12 duzce earthquake m w 7 1 was apparently the eastward extension of the august 17 izmit earthquake m w 7 4 the duzce event caused heavy damage and fatalities in the cities of duzce and bolu here a finite fault inversion method with five discrete time windows is applied to derive the co seismic slip distribution of the duzce earthquake the fault plane is best modelled as a 40 x 20 km 2 plane with a strike of 262degrees and a dip of 65degrees to the north and that the majority of slip occurred in two distinct patches on either side of the hypocentre implying bilateral rupture the possible triggering of this event by the izmit earthquake is investigated using coulomb stress modelling of all large events since 1943 with the inclusion of secular loading the results show that although the duzce rupture plane was in a stress shadow prior to the izmit earthquake that event caused a significant coulomb stress load taking the duzce fault out of the stress shadow which probably precipitated failure a comparison of the mapped coulomb stress change with the inferred slip shows no correlation between the two finally the stress modelling indicates that the northern branch of the north anatolian fault zone beneath the sea of marmara towards the city of istanbul is presently the most highly loaded segment of the north anatolian fault zone

source model of an earthquake doublet that occurred in a pull apart basin along the sumatran fault indonesia summary on 2007 march 6 an earthquake doublet occurred along the sumatran fault indonesia the epicentres were located near padang panjang central sumatra indonesia the first earthquake with a moment magnitude m w of 6 4 occurred at 03 49 utc and was followed two hours later 05 49 utc by an earthquake of similar size m w 6 3 we studied the earthquake doublet by a waveform inversion analysis using data from a broadband seismograph network in indonesia jisnet the focal mechanisms of the two earthquakes indicate almost identical rightlateral strike slip faults consistent with the geometry of the sumatran fault both earthquakes nucleated below the northern end of lake singkarak which is in a pull apart basin between the sumani and sianok segments of the sumatran fault system but the earthquakes ruptured different fault segments the first earthquake occurred along the southern sumani segment and its rupture propagated southeastward whereas the second one ruptured the northern sianok segment northwestward along these fault segments earthquake doublets in which the two adjacent fault segments rupture one after the other have occurred repeatedly we investigated the state of stress at a segment boundary of a fault system based on the coulomb stress changes the stress on faults increases during interseismic periods and is released by faulting at a segment boundary on the other hand the stress increases both interseismically and coseismically and may not be released unless new fractures are created accordingly ruptures may tend to initiate at a pull apart basin when an earthquake occurs on one of the fault segments the stress increases coseismically around the basin the stress changes caused by that earthquake may trigger a rupture on the other segment after a short time interval we also examined the mechanism of the delayed rupture based on a theory of a fluidsaturated poroelastic medium and dynamic rupture simulations incorporating a rheological velocity hardening effect these models of the delayed rupture can qualitatively explain the observations but further studies especially based on the rheological effect are required for quantitative studies

new constraints on the rupture process of the 1999 august 17 izmit earthquake deduced from estimates of stress glut rate moments summary this paper illustrates the use of integral estimates given by the stress glut rate moments of total degree 2 for constraining the rupture scenario of a large earthquake in the particular case of the 1999 izmit mainshock we determine the integral estimates of the geometry source duration and rupture propagation given by the stress glut rate moments of total degree 2 by inverting long period surface wave lpsw amplitude spectra kinematic and static models of the izmit earthquake published in the literature are quite different from one another in order to extract the characteristic features of this event we calculate the same integral estimates directly from those models and compare them with those deduced from our inversion while the equivalent rupture zone and the eastward directivity are consistent among all models the lpsw solution displays a strong unilateral character of the rupture associated with a short rupture duration that is not compatible with the solutions deduced from the published models with the aim of understand this discrepancy we use simple equivalent kinematic models to reproduce the integral estimates of the considered rupture processes including ours by adjusting a few free parameters controlling the western and eastern parts of the rupture we show that the joint analysis of the lpsw solution and source tomographies allows us to elucidate the scattering of source processes published for this earthquake and to discriminate between the models our results strongly suggest that 1 there was significant moment released on the eastern segment of the activated fault system during the izmit earthquake 2 the apparent rupture velocity decreases on this segment

deep learning of aftershock patterns following large earthquakes aftershocks are a response to changes in stress generated by large earthquakes and represent the most common observations of the triggering of earthquakes the maximum magnitude of aftershocks and their temporal decay are well described by empirical laws such as bath s law1 and omori s law2 but explaining and forecasting the spatial distribution of aftershocks is more difficult coulomb failure stress change3 is perhaps the most widely used criterion to explain the spatial distributions of aftershocks4 8 but its applicability has been disputed9 11 here we use a deep learning approach to identify a static stress based criterion that forecasts aftershock locations without prior assumptions about fault orientation we show that a neural network trained on more than 131 000 mainshock aftershock pairs can predict the locations of aftershocks in an independent test dataset of more than 30 000 mainshock aftershock pairs more accurately area under curve of 0 849 than can classic coulomb failure stress change area under curve of 0 583 we find that the learned aftershock pattern is physically interpretable the maximum change in shear stress the von mises yield criterion a scaled version of the second invariant of the deviatoric stress change tensor and the sum of the absolute values of the independent components of the stress change tensor each explain more than 98 per cent of the variance in the neural network prediction this machine learning driven insight provides improved forecasts of aftershock locations and identifies physical quantities that may control earthquake triggering during the most active part of the seismic cycle neural networks trained on data from about 130 000 aftershocks from around 100 large earthquakes improve predictions of the spatial distribution of aftershocks and suggest physical quantities that may control earthquake triggering

the resolving power of coseismic surface displacement data for fault slip distribution at depth 1 the spatial slip distribution of the august 17 1999 izmit turkey earthquake has previously been determined from both geodetic and seismological data though the models derived agree on a broad scale they are significantly different in detail these differences could be due to the inversion techniques applied and or additional constraints implemented and or be due to poor resolution it is also conceivable that the relative agreement at larger scales results in part from a resolution artifact common to all models to investigate this we perform a resolution analysis of fault slip models based on the inversion of surface displacement data assuming the theory of elastic dislocations in a half space and adopting a parameterization for which model predictions are capable of fitting the spatial variations of the data the inverse problem proves to be intrinsically ill conditioned

rupture length and velocity for earthquakes in the mid atlantic ridge from directivity effect in body and surface waves abstract the dimensions and rupture velocities of four earthquakes two in the mid atlantic ridge and two in iceland with strike slip mechanisms and magnitudes m w between 6 2 and 6 8 were studied using the directivity effects of rayleigh and body waves for rayleigh waves we used the directivity function for different pairs of stations and for body waves the waveforms of p and sh waves corresponding to a simple extended line source we have found that three have very shallow depths about 3 km and one 8 km fault lengths between 12 km and 21 km and a low rupture velocity of about 1 5 km s to 2 0 km s which supports the idea of the presence of slow earthquakes in transform faults

a joint analysis of gps motions and insar to infer the coseismic surface deformation of the izmit turkey earthquake summary from a joint analysis of gps and insar data we have determined the kinematic coseismic surface deformation of the 1999 august 17 izmit turkey earthquake in terms of strain rotation and fault slip the fault slip contribution shows two distinct peaks one of 4 m of slip at golcuk and a second of 2 9 m slip near sapanca lake the strain field portrays four distinct quadrants reflecting the earthquake focal mechanism the transition between the quadrants is not centred on the epicentre of the event but shifted eastwards north of the fault and westwards south of the fault this shift is the result of a two stage source rupture process caused by the step over features in the fault geometry this rupture process also induced a distinct asymmetry in the displacement field across the fault we obtain left lateral shear strains along the sakarya segment that is the result of a subsequent source nucleating at the akyazi gap inducing failure on the easternmost segments strong interaction is also observed from a consecutive source near hersek finally we deduce that the izmit earthquake has released most of the strain that has accmulated since the last main event on this stretch of the north anatolian fault in 1719

fault slip source models for the 2014 mw 6 9 samothraki gokceada earthquake north aegean trough combining geodetic and seismological observations the 24 may 2014 mw 6 9 samothraki gokceada shallow depth 11 km earthquake along the north aegean trough nat at the westward extension of the north anatolian fault zone nafz is investigated using constraints from seismological and geodetic data a point source solution based on teleseismic long period p and sh waveforms suggests an essentially strike slip faulting mechanism consisting of two subevents while from a finite fault inversion of broadband data the rupture area and slip history were estimated analysis of data from 11 permanent gps stations indicated significant coseismic horizontal displacement but no significant vertical or postseismic slip okada type inversion of horizontal slip vectors using the new topological inversion algorithm allowed precise modeling of the fault rupture both as single and preferably as double strike slip faulting reaching the surface variable slip models were also computed the independent seismological and geodetic fault rupture models are broadly consistent with each other and with structural and seismological data and indicate reactivation of two adjacent fault segments separated by a bend of the nat the 2014 earthquake was associated with remote clusters of low magnitude aftershocks produced low accelerations and filled a gap in seismicity along the nat in the last 50 years faulting in the nat seems not directly related to the sequence of recent faulting farther east along the nafz and the seismic gap in the marmara sea near istanbul

predominance of unilateral rupture for a global catalog of large earthquakes the manner in which an earthquake rupture propagates across a fault reflects both the initial properties of the fault and the dynamical stresses produced by the rupture we quantify the propagation of an earthquake rupture using the second moments of the earthquake space time distribution in particular the second moments provide a simple way to differentiate between approximately bilateral and predominantly unilateral ruptures we determined the second moments for a catalog of m w 7 earthquakes that have occurred since 1994 the results show that approximately 80 of large shallow ruptures are predominantly unilateral our result agrees well with strong motion inversions from previous studies on moderate and large earthquakes the predominance of unilateral propagation in large earthquakes is explained by a simple characteristic earthquake model in which large events rupture an entire structurally defined fault segment and nucleation points are uniformly distributed along the fault the predominance of unilateral rupture may also be enhanced by the dynamic stress field produced by contrasts in the elastic properties between the two sides of plate boundary faults manuscript received 16 november 2001

complex source process of the 17 august 1999 izmit turkey earthquake broadband teleseismic p wave data at epicentral distances of 30 90 are inverted to retrieve the complex source process of the 17 august 1999 izmit earthquake a comparison of the waveforms of the mainshock with those of the aftershocks suggests a spatially complex rupture process having a duration of more than 45 sec inversion and modeling of broadband p waveforms are performed in this time window incorporating a priori field observations of coseismic displacements both single point and multiple point source representations are determined we found that the rupture process can be divided into at least three steps in the first step rupture initiated from the hypocenter and extended bilaterally along the e w striking fault with an almost pure right lateral strike slip motion the eastern portion of the rupture front passed through the sapanca lake and stopped around akyazi whereas the western portion stopped near hersek this step lasted for 22 23 sec releasing a total moment of 1 43 1020 n m the dislocation was concentrated briefly at two areas one near golcuk and the other between the sapanca lake and akyazi slip in these two areas was concentrated in the upper 10 km of the crust after 1 2 sec a second source started possibly initiating on an underwater fault west of hersek although its rupture lasted for almost 20 sec its moment release was very low just 0 17 1020 n m another 8 9 sec later the easternmost fault segment between akyazi and the area west of duzce was triggered with a rupture lasting for more than 15 sec producing little energy in the short period band with slip concentrated in a zone extending vertically 25 km to the surface and with a moment of 0 61 1020 n m manuscript received 22 september 2000

earthquake mechanisms in the gulfs of gokova sigacik kusadasi and the simav region western turkey neotectonics seismotectonics and geodynamic implications abstract the mechanical behavior of continental lithosphere of aegean region and western turkey is one of the foremost interesting geological disputes in earth sciences this region provides complex tectonic events which produced a strong heterogeneity in the crust as such in among most continental regions the reasons of the ongoing lithospheric scale extension within the aegean region can be revealed by the correlation with the prevailing kinematic and dynamic factors such as roll back of the subduction slab and back arc extension westward extrusion of the anatolian micro plate block rotations and transtensional transform faults seismological studies of earthquake source mechanisms and slip inversions play important roles on deciphering the current deformation and seismotectonic characteristics of the region in recent years several moderate earthquakes have occurred in the gulfs of gokova sigacik kusadasi and simav graben we studied source mechanisms and rupture histories of those earthquakes to retrieve the geometry of active faulting source characteristics kinematic and dynamic fault parameters and current deformations in western turkey we used teleseismic body waveform inversions of long period p and sh and broad band p waveforms we also checked first motion polarities of p waves recorded at both regional and teleseismic stations inversion results revealed e w striking normal faulting mechanisms with small amount of left lateral strike slip components in the gulf of gokova and ne sw oriented right lateral strike slip faulting mechanisms in the gulf of sigacik in simav graben earthquake source parameters show dominantly normal faulting mechanisms with strike slip components our inversions resulted in focal depths for the earthquake ranging from 10 to 15 km and ne sw trending t axes directions the finite fault slip distribution and rupture propagation models exhibit seismic moment releases and large displacement values which essentially occurred at hypocenters of the earthquakes the overall results exhibited uniform and circular shaped rupture propagations along dip directions of fault planes although most of the focal mechanism solutions show dominantly normal faulting mechanisms associated with the e w oriented horst graben structures in western turkey there are also strike slip faulting mechanisms related to remarkable strike slip faults which are capable of generating damaging earthquakes particularly in the gulf of sigacik and karaburun peninsula thus we suggest that present day deformation in the gulfs of gokova sigacik kusadasi and simav graben western turkey is still mainly driven by the n s extensional tectonics but we tentatively further emphasize the importance of strike slip faults in shaping tectonic structures in the aegean region

multicycle dynamics of nonplanar strike slip faults 1 we perform two dimensional dynamic models of strike slip faults with a change in strike a bend over multiple earthquake cycles to examine the long term effects of nonplanar fault geometry a viscoelastic model a proxy for off fault deformation and tectonic loading is introduced for the interseismic process to avoid pathological stress buildup around the bend a finite element method with an elastodynamic model is used to simulate dynamic earthquake ruptures we find that stresses near the bend differ strongly from the regional stress field and that the fault develops a relatively steady state in which the stress level and the event pattern on the fault are stable reduced normal stress on the dilatational side and increased normal stress on the compressive side of the bend during dynamic ruptures result in the bend serving as an initiation and or a termination point s for rupture typical events on such a fault consist of two classes unilateral events that rupture only the favorable segment and bilateral events that rupture the favorable segment and part of or the entire unfavorable segment in the latter class of events a time delay in rupture around the bend results from a high yield stress on the compressive side of the bend other effects of the bent fault geometry include higher displacement on the inward wall than on the outward wall higher slip on the more favorable segment than on the less favorable segment and a large slip velocity on the compressive side of the bend

scaling relations of source parameters of earthquakes occurring on inland crustal mega fault systems we examined a new scaling relation between source area s and seismic moment m 0 for large crustal earthquakes on mega fault systems including earthquakes with magnitudes larger than m w7 4 we focused on earthquakes that occurred on inland crustal mega fault systems such as the 2008 wenchuan and 2002 denali earthquakes and compiled the source parameters using 11 inland crustal earthquakes which analyses of source rupture processes by waveform inversion as well as investigation of surface ruptures via geomorphological surveys we found that the maximum surface rupture displacement is two to three times larger than the average slip on the source fault and the length of the surface rupture is equivalent to the length of the source fault furthermore our compiled data shows the displacement of the surface rupture d saturates around 10 m when the length of the surface rupture l reaches 100 km assuming that the average width of the source fault w 18 km for japanese inland crustal earthquakes and the saturated surface displacement d 10 m we found that the scaling relations between rupture area s and seismic moment m 0 have three stages for the first stage s is proportional to m 0 2 3 for earthquakes smaller than m 0 7 5 1018 nm for the second stage s ranges from m 0 1 2 to m 0 2 3 depending on the thickness of the seismogenic zone for the third stage s is proportional to m 0 because of the saturation of the slip on the fault from our compiled data we derived the third scaling relation between source area s and seismic moment m 0 for inland crustal mega fault systems to be s km2 1 0 10 17 m 0 nm where m 0 1 8 1020 nm

disputable non double couple mechanisms of several strong earthquakes second degree moment approach the earthquake source mechanism description of the geometry of the source and its strength in terms of forces equivalent to rupturing of the rock mass is routinely modeled as a moment tensor mt describing the earthquake focus as a point however sometimes this approximation is not satisfied and seismic radiation keeps the directivity due to the finite extent of the source inversion into the mt then may yield a biased mechanism synthetic study in the adamova and silen 2010 demonstrated the appearance of spurious non double couple components in the mechanism even for a pure double couple dc source their method was designed to reduce the spurious source components by using the second degree moments to evaluate their contribution into the records and subtract it from the data here we applied the procedure to five moderate to large regional events with large nonshear components they are mostly located on large tectonic faults where predominantly pure shear slip is expected we studied one event on the prominent north anatolian fault three events in the pacific area and one event in bolivia in most cases the non dc components essentially were reduced and the geometry of the mechanism remained largely unchanged this confirms the hypothesis that part of the non dc components in regional mt solutions may be spurious due to the neglect of the source finiteness in the routine procedure of the mt retrieval in addition the geometrical and kinematical characteristics of the foci provided by the second degree moments the source ellipsoid and rupture velocity vector are mostly consistent with the fault geometry aftershock distribution and estimates of rupture speed from available previous studies

estimating slip distribution for the izmit mainshock from coseismic gps ers 1 radarsat and spot measurements we use four geodetic satellite systems global positioning system gps european remote sensing ers radarsat and satellite pour l9observation de la terre spot to measure the permanent deformation field produced by the izmit earthquake of 17 august 1999 we emphasize measurements from interferometric analysis of synthetic aperture radar sar images acquired by ers and radarsat and their geodetic uncertainties the primary seismological use of these data is to determine earthquake source parameters such as the distribution of slip and the fault geometry after accounting for one month9s postseismic deformation tropospheric delay and orbital gradients we use these data to estimate the distribution of slip at the time of the izmit mainshock the different data sets resolve different aspects of the distribution of slip at depth although these estimates agree to first order with those derived from surface faulting teleseismic recordings and strong motion careful comparison reveals differences of 40 in seismic moment we assume smooth parameterization for the fault geometry and a standard elastic dislocation model the root mean square residual scatter is 25 mm and 11 mm for the ers and radarsat range changes respectively our estimate of the moment from a joint inversion of the four geodetic data sets is m 0 1 84 10 20 n m a moment magnitude of m w 7 50 these values are lower than other estimates using more realistic layered earth models given the differences between the various models we conclude that the real errors in the estimated slip distributions are at the level of 1 m the prudent geophysical conclusion is that coseismic slip during the izmit earthquake tapers gradually from approximately 2 m under the hersek delta to 1 m at a point 10 km west of it we infer that the yalova segment west of the hersek delta may remain capable of significant slip in a future earthquake

comparison of the coseismic rupture with the aftershock distribution in the hyuga nada earthquakes of 1996 on october 19 1996 a large underthrusting earthquake ms 6 7 the hyuga nada japan earthquake occurred along the southern end of nankai trough about two months later a second large earthquake ms 6 7 occurred in the adjacent region we study the source process of the two large earthquakes in the hyuga nada region and compare the coseismic rupture area with aftershock distribution the main source parameters obtained for the first mainshock are strike dip rake 210 12 81 the seismic moment mo 2 3 1019 nm mw 6 8 the rupture area s 20 15 km and the source duration t 17 s for the second main shock strike dip rake 210 12 87 the seismic moment mo 1 5 1019 nm mw 6 7 the rupture area s 18 18 km and the source duration t 15 s the coseismic rupture areas do not overlap the aftershock area while the aftershock areas of the two main shocks mutually overlap this implies that the common aftershock region takes a role of barriers to dynamic rupture it is also seen that the aftershock area expanded during the first one day

rupture segmentation and process of the 2001 mw 7 8 central kunlun china earthquake field investigations allow us to constrain the coseismic surface rupture zone of 400 km with a strike slip up to 16 3 m associated with the 2001 m w 7 8 central kunlun earthquake that occurred along one of the western segments of the kunlun fault northern tibet the rupture zone may be divided into four segments based on the geological structures tectonic landform features spatial displacement distributions obtained from field observations and analysis of teleseismic waveforms the deformational characteristics of the surface ruptures and focal mechanism solutions reveal that the earthquake had a nearly pure strike slip mechanism the inversion results from seismic data show that the rupture started from the west near the epicentral area bilaterally and rapidly extended to the east in an unilateral manner for 380 km and that the largest slip region was limited in the subsegment 150 280 km east of the epicenter consistent with field observations the average stress drop is estimated to be 7 mpa in the area where the largest displacements occurred a value typical of intraplate earthquakes the geologic evidence and the inversion results from seismic data clearly show that temporal and spatial displacement distributions and the rupture process are restricted by the pre existing geological structures of the kunlun fault

strong ground motion estimation in the sea of marmara region turkey based on a scenario earthquake we perform a broadband frequency bedrock strong ground motion simulation in the marmara sea region turkey based on several fault rupture scenarios and a source asperity model the technique combines a deterministic simulation of seismic wave propagation at low frequencies with a semi stochastic procedure for the high frequencies to model the high frequencies we applied a frequency dependent radiation pattern model which efficiently removes the effective dependence of the pattern coefficient on the azimuth and take off angle as the frequency increases the earthquake scenarios considered consist of the rupture of the closest segments of the north anatolian fault system to the city of istanbul our scenario earthquakes involve the rupture of the entire north anatolian fault beneath the sea of marmara namely the combined rupture of the central marmara fault and north boundary fault segments we defined three fault rupture scenarios based on the location of the hypocenter selecting a preferred hypocentral location near a fault bend for each case we analysed the effect of location of the asperity within the central marmara fault on the subsequent ground motion as well as the influence of anelasticity on the highfrequency attenuation characteristics the fault and asperity parameters for each scenario were determined from empirical scalings and from results of kinematic and dynamic models of fault rupture we calculated the resulting time series and spectra for ground motion at istanbul and evaluated the sensitivity of the predictions to choice of model parameters the location of the hypocenter is thus shown to be a critical parameter for determining the worst scenario earthquake at istanbul we also found that anelasticity has a significant effect on the regional attenuation of peak ground accelerations our simulated ground motions result in large values of acceleration response spectra at long periods which could be critical for building damage at istanbul during an actual earthquake d 2004 elsevier b v all rights reserved

joint inversion of insar gps teleseismic and strong motion data for the spatial and temporal distribution of earthquake slip application to the 1999 izmit mainshock the space time distribution of slip of the 17 august 1999 izmit earthquake is investigated by inverting synthetic aperture radar sar interferometry and global positioning system gps data together with teleseismic broadband and near field strong motion records surface offsets are used as an added constraint special emphasis is given to analysis of the resolution of the different data sets we use a four segment finite fault model and a nonlinear inversion scheme allowing slip to vary in amplitude direction and duration as well as variable rupture velocity from the inversion of synthetic data we find that the best spatial resolution can be expected in the upper half of the fault model above 12 km where coverage of the interferometric sar data is good western half of the rupture and near the gps and strong motion stations teleseismic data are found to have a lower resolution that is more evenly distributed over the fault model the joint inversion of all the data sets has an increased resolving power compared with the separate inversions and gives a more robust description of the space and time distribution of slip our study shows the importance of resolution tests in evaluating the reliability of earthquake kinematic models and it confirms that an excellent fit of a single kind of data does not necessarily imply a good retrieval of the kinematic properties of an earthquake the izmit rupture which is almost pure right lateral strike slip faulting is dominated by the bilateral breaking of a central asperity located between 29 7 e about 10 km west of the city of golcuk and 30 4 e eastern margin of sapanka lake with slip reaching 6 8 m in the depth range 6 12 km the western termination of the rupture is found near the city of yalova but large slip ends around 29 7 e about 10 km east of hersek delta a second area of large slip is required by all the data sets further east toward the city of duzce between 30 7 e and 31 1 e karadere and duzce faults this eastern slip zone which is separated from the main central asperity by an area of greatly reduced slip is less well constrained by the data however a strong motion station near the city of duzce helps to locate a high slip patch near 31 1 e in the depth range 6 12 km the total seismic moment resulting from the joint inversion is 2 4 1027 dyne cm most of the energy release occurred in a short time less than 15 sec corresponding to the bilateral breaking of the central asperity rupture propagation is relatively uniform and fast toward the west with a rupture velocity close to 3 5 km sec propagation of large slip toward the east is initially slower but it accelerates during a short time interval about 10 sec after rupture nucleation eastward progression then slows down to less than 2 km sec after 15 sec and rupture almost vanishes in amplitude ca 20 sec after initiation rupture propagation then proceeds on the easternmost karadere and duzce fault segments east of 30 7 e from 22 to ca 50 sec supershear rupture propagation is not required for modeling the waveforms considered in this study the hypocenter of the duzce earthquake which occurred 3 months later 12 november 1999 m w 7 2 is located in the immediate vicinity of the easternmost slip patch of the izmit earthquake manuscript received 28 july 2000

source rupture process of the kocaeli turkey earthquake of august 17 1999 obtained by joint inversion of near field data and teleseismic data the rupture process of the 1999 turkey earthquake is examined using both near field strong motion data and teleseismic body wave data the derived source parameters are as follows strike dip slip 268 86 180 nearly pure strike slip the seismic moment mo 1 7 1020 nm mw 7 4 the source duration 20 sec the fault length 70 km the fault width 15 km the rupture process is characterized by an asymmetric bilateral rupture propagation and smooth slip it consists of two major fault segments a rupture propagating to the west and a second rupture propagating to the east the maximum dislocation and the maximum dislocation velocity are 6 3 m and 2 7 m s respectively both found at the former segment the average dislocation is about 4 m the extent of the coseismic rupture suggests that a considerable part of the anticipated seismic gap remains unruptured

normal mode constraints on shear and compressional wave velocity of the earth s inner core abstract free oscillation data are used to determine the average compressional and shear wave velocity structure of the earth s inner core and place tight constraints on their values the new data reinforce the argument for a solid inner core and the best data fit is obtained for average inner core velocities close to the prem reference model s 3 55 0 05 km s p 11 15 0 05 km s these values limit the time windows in which inner core shear waves like pkjkp may be observed inner core velocities for hcp and bcc iron at inner core conditions from ab initio molecular dynamics simulations and diamond anvil cell experiments are found to be incompatible with the seismological data in particular for the shear wave velocity when light elements are taken into account the misfit is worse than for a fluid inner core model the discrepancy between seismic and mineral physical values for the inner core shear wave velocity may be explained by an inner core temperature in excess of 6500 k the existence of fluid inclusions in the inner core the effect of viscoelastic weakening or crystal defects

seismic activity triggered by the 1999 izmit earthquake and its implications for the assessment of future seismic risk summary a serious question has remained as to the location of the western end of the main rupture zone associated with the 1999 izmit turkey earthquake a clear answer to this question is extremely important for the assessment of future seismic risk in the eastern marmara sea region turkey in this paper we show an effective approach to answering this important question unifying different kinds of information such as seismic activity focal mechanism solutions and stress changes caused by the main shock into a clear image we first point out that the major moment release is 1 6r10 20 n m and covered the area between 29 7ue and 30 5ue and we then claim that the enhanced seismic activity after the main shock in the eastern marmara sea region should be regarded as activity triggered by the increase of stress rather than as aftershock activity along the ruptured zone we propose three fault segments with an average stress increase on each in the western extension of the main shock rupture zone as potential sites for future large earthquakes namely i the 50 km long yalova hersek segment 0 45 mpa ii the nw setrending right lateral strike slip fault known as the princes islands segment 0 18 mpa

imaging coseismic rupture in far field by slip patches summary since the end of the 1970s teleseismic waves are used routinely to infer the first order characteristics of the event location depth duration focal mechanism but finding the second order kinematic parameters spatial distribution of slip rupture velocity and more basically the discrimination between the fault plane and the other nodal plane of distant events remains a difficult task classically these events are studied by two different methods either they are seen as a succession of subevents each of which is considered as a point source or like in near field as extended sources where the kinematic parameters are retrieved on a grid the first approach is not physically satisfactory and can lead to erroneous interpretations of the

stress tensor inversions along the westernmost north anatolian fault zone and its continuation into the north aegean sea summary gephart forsyth s method has been applied to estimate stress orientations from earthquake fault plane solutions of the westernmost north anatolian fault zone nafz its westward continuation in the northern aegean sea where it interacts with the normal faulting of central greece and of the western coastal parts of anatolia in total 163 fault plane solutions were used to invert for the stress tensor of 9 seismotectonic subregions magnitudes range from 1 1 to 7 4 all events have shallow focal depths most occurred in the uppermost 15 km and very few in the 15 to 40 km depth range the region studied is characterized by strike slip nafz by transtension central greece and western anatolia and by a strong signature of transpression in the marmara area from nafz to central greece the 3 axis changes continuously and smoothly its orientation from n35 e in the westernmost nafz to nearly north south in continental central greece and the maximum horizontal stress hmax changes from wnw ese to e w the total angle of lateral variation in the direction of either hmax or 3 is 40 in central western anatolia the orientation of 3 is nne ssw n10 e while in southern western anatolia it is nnw sse n33 w in both cases the development of the major grabens simav gediz menderes is in agreement with the resolved stress tensor at the termination of the nafz against central greece the regime is complex the dextral shear motion transferred from the east crosses the pilion peninsula and northern evia island where it interacts with the major normal faults of continental greece these faults have variable orientations the e w trending quaternary fault system and the nw se trending fault system which is inherited from the past the latter faults under the presently acting stress field are reactivated either as strike slip faults with sinistral strike slip component when oriented at small angle in respect to 3 or as normal faults with small sinistral strike slip component when oriented at high angle in respect to 3 the occurrence of the recent 2001 july 26 skyros event which was clearly connected to a nnw sse fault with sinistral strike slip motion provides strong seismological evidence that the old structures can equally well be reactivated under the presently active stress field

deeper penetration of large earthquakes on seismically quiescent faults why many major strike slip faults known to have had large earthquakes are silent in the interseismic period is a long standing enigma one would expect small earthquakes to occur at least at the bottom of the seismogenic zone where deeper aseismic deformation concentrates loading we suggest that the absence of such concentrated microseismicity indicates deep rupture past the seismogenic zone in previous large earthquakes we support this conclusion with numerical simulations of fault behavior and observations of recent major events our modeling implies that the 1857 fort tejon earthquake on the san andreas fault in southern california penetrated below the seismogenic zone by at least 3 to 5 kilometers our findings suggest that such deeper ruptures may occur on other major fault segments potentially increasing the associated seismic hazard

source models of the 2012 haida gwaii canada and 2015 illapel chile earthquakes and numerical simulations of related tsunamis seismological observations provide essential input parameters for numerical tsunami simulations here we present source mechanism parameters finite fault source rupture models and numerical tsunami simulation results for the destructive october 28 2012 haida gwaii canada mw 7 7 and september 16 2015 illapel chile mw 8 3 earthquakes and resulting tsunamis these two earthquakes were controlled by active tectonic features along the subduction zones that had developed in response to the convergent movements of lithospheric plates the faulting geometry strike dip and rake angles focal depth fault dimensions average and maximum slip values on the fault planes and seismic moments of the earthquakes are estimated by analyzing teleseismic long period p and sh waves and broadband p waveforms and using waveform inversion and hybrid back projection methods the obtained slip models of the earthquakes reveal heterogeneous slip distributions on fault planes with long source durations 80 s and 150 s and low stress drop values 10 15 bars numerical simulations of tsunami wave propagation are further performed using the uniform and non uniform slip models and nonlinear long wave equations in spherical coordinates the shape and arrival times of leading tsunami waves are adequately constrained particularly with the heterogeneous slip distribution models the general characteristics of synthetic tsunami waveforms e g amplitude shape arrival time calculated using the non uniform slip model are more consistent with the observed tsunami records than those of a uniform slip model it is further seen that simulation results using preliminary and fast slip models for both earthquakes give only approximate early tsunami estimates tsunami wave heights and arrival times to the coasts are mostly not well simulated the results indicate that tsunami simulations based on finite fault source slip models likely contribute to the determination of tsunamigenic coastal regions by revealing locations arrival times amplitudes and directions of tsunami waves within a close approximation to observed records off shore and far from the source region they provide sufficient information to facilitate tsunami warning and mitigation challenges after the destructive earthquakes we further suggest that joint inversions of gps tsunami teleseismic and strong ground motion records and higher resolution bathymetry data are needed in order to obtain better correlations between observed and synthetic tsunami data especially for the later arriving waves

extended fault inversion with random slipmaps a resolution test for the 2012 mw 7 6 nicoya costa rica earthquake inversions for the full slip distribution of earthquakes provide detailed models of earthquake sources but stability and non uniqueness of the inversions is a major concern the problem is underdetermined in any realistic setting and significantly different slip distributions may translate to fairly similar seismograms in such circumstances inverting for a single best model may become overly dependent on the details of the procedure instead we propose to perform extended fault inversion trough falsification we generate a representative set of heterogeneous slipmaps compute their forward predictions and falsify inappropriate trial models that do not reproduce the data within a reasonable level of mismodelling the remainder of surviving trial models forms our set of coequal solutions the solution set may contain only members with similar slip distributions or else uncover some fundamental ambiguity such as for example different patterns of main slip patches for a feasibility study we use teleseismic body wave recordings from the 2012 september 5 nicoya costa rica earthquake although the inversion strategy can be applied to any type of seismic geodetic or tsunami data for which we can handle the forward problem we generate 10 000 pseudo random heterogeneous slip distributions assuming a von karman autocorrelation function keeping the rake angle rupture velocity and slip velocity function fixed the slip distribution of the 2012 nicoya earthquake turns out to be relatively well constrained from 50 teleseismic waveforms two hundred fifty two slip models with normalized l1 fit within 5 per cent from the global minimum from our solution set they consistently show a single dominant slip patch around the hypocentre uncertainties are related to the details of the slip maximum including the amount of peak slip 2 3 5 m as well as the characteristics of peripheral slip below 1 m synthetic tests suggest that slip patterns such as nicoya may be a fortunate case while it may be more difficult to unambiguously reconstruct more distributed slip from teleseismic data

inversion for the physical parameters that control the source dynamics of the 2004 parkfield earthquake a fully dynamic inversion for the earthquake source process in which the geometry of the rupture area the stress conditions and frictional properties on the fault are obtained is carried out by inverting displacement records for the 2004 mw 6 0 parkfield california earthquake the rupture area of the earthquake is modeled using elliptical patches and seismograms from 10 near field digital stations are used synthetic tests to investigate the performance of the inversion in retrieving the rupture process demonstrate that we can reliably recover the large scale features of the spatiotemporal distribution of slip to investigate the stress conditions and frictional properties of the fault under which we produce a rupture model that fits the observed data we explore the parameter space using a monte carlo method and find an optimal region where the source models fit the data well the best fitting rupture process is shown to occur mainly within one horizontal elliptical region 22 km long along strike and 4 km wide along depth the seismic moment is 1 2 1018 n m and the stress drop over the ellipse is 4 mpa the rupture speed nearly constant during the entire rupture process is 2 9 km s the dimensionless quantity roughly the strain energy change per unit fault surface divided by the energy release rate which includes information on the stress and frictional properties on the fault is found to be 1 4 for the ellipse and strongly controls the rupture process along with the size of the initial circular patch that initiates the earthquake

the rupture process during the 1999 duzce turkey earthquake from joint inversion of teleseismic and strong motion data abstract teleseismic and strong motion data are inverted to determine the rupture process during the november 1999 duzce earthquake in nw turkey the fault geometry rise time and rupture velocity are determined from the aftershock distribution and preliminary inversions of the teleseismic data joint inversion of the teleseismic and strong motion data is then carried out for the slip distribution we obtain the strike 264 dip 64 rake 172 seismic moment 5 0 1019 n m mw 7 1 and average stress drop 7 mpa this earthquake was characterized by bilateral fault rupture and asymmetric slip distribution two asperities areas of large slip are identified the eastern one being 1 5 times larger than the western one the derived slip distribution is consistent with the aftershock distribution surface rupture and damage the point of rupture initiation in this duzce earthquake coincided with the eastern tip of the aftershock distribution of the august 1999 izmit earthquake

strike slip fault geometry in turkey and its influence on earthquake activity the geometry of turkish strike slip faults has been reviewed and described from this data set it appears that fault geometry the distribution of discontinuities such as bends and stepovers along the main fault trace plays an important role in controlling the location of large earthquake rupture segments along the fault zones large earthquake ruptures generally do not propagate past individual stepovers that are wider than 5 km or bends that have angles greater than about 30 more important than the size of each discontinuity however is the total geometric pattern i e the distribution of adjacent bends and stepovers based not only on distance from one another but also on relative discontinuity size certain geometric patterns restraining single or double bends are particularly common and can be viewed as responsible for strain accumulation along portions of the fault zone fault geometry not only plays a role in the extent of earthquake rupture but also in characteristics of earthquake behavior for example large earthquake epicenters often occur near restraining bends or double bends furthermore aftershocks and swarm activity can often be associated with releasing areas areas along the strike slip fault that are undergoing a relatively large amount of extension

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

aftershock patterns and main shock faulting we have compared aftershock patterns following several moderate to large earthquakes with the corresponding distributions of coseismic slip obtained from previous analyses of the recorded strong ground motion and teleseismic waveforms well located aftershock hypocenters are projected onto the main shock fault plane and their positions are examined relative to the zones of coseismic displacement indicated by the estimated distributions of main shock slip we also examine the aftershock focal mechanisms when these data are available in an attempt to identify possible patterns of secondary faulting within the aftershock zone our results are consistent with a hypothesis of aftershock occurrence that requires a secondary redistribution of stress following primary failure on the earthquake fault aftershocks following the earthquakes examined in this study occur mostly outside of or near the edges of the source areas indicated by the patterns of main shock slip the spatial distribution of aftershocks reflects either a continuation of slip in the outer regions of the areas of maximum coseismic displacement or the activation of subsidiary faults within the volume surrounding the boundaries of main shock rupture

influence of releasing step overs on surface fault rupture and fault segmentation examples from the 17 august 1999 izmit earthquake on the north anatolian fault turkey the 17 august 1999 izmit earthquake broke four distinct structural segments of the north anatolian fault from east to west the karadere sakarya sapanca and golcuk fault segments these segments are separated from one another and the adjoining yalova and duzce fault segments to the west and east respectively by distinct right releasing step over and or gaps in the fault trace these include from east to west the eften lake step over 2 4 km wide akyazi gap 6 13 km long sapanca step over 1 2 km wide golcuk step over 1 2 km wide and karamursel step over 4 5 km wide the earthquake nucleated within or near the golcuk step over with bilateral rupture propagation to the west and east to the west about 4 5 5 m of surface rupture up to 7 m of subsurface rupture on the golcuk segment was mostly if not entirely arrested by the 4 to 5 km wide karamursel step over to the east about 3 4 m of surface rupture about 4 m of subsurface rupture propagated through the 1 to 2 km wide sapanca step over triggering up to 4 5 5 5 m of surface rupture up to 5 6 m of subsurface rupture on the sakarya segment rupture on the sakarya segment stepped across the akyazi gap triggering 1 1 5 m of rupture on the karadere segment rupture on the karadere segment was arrested by the 2 to 4 km wide eften lake step over modeling of the transient stress field associated with the rupture propagation agrees well with the field observations the modeled fault rupture of 5 m on the golcuk segment appears to decrease the transient stress on the eastern tip of the adjoining yalova segment across the 4 to 5 km wide karamursel step over even if we allow rupture on the golcuk segment to extend along the entire southern margin of the step over our model shows that regardless of the amount of slip in a generic sense it is difficult to increase stress on the tip of an adjoining fault segment across a 5 km wide step over on the other hand fault rupture of 3 m on the western tip of the sapanca fault segment significantly increases the transient stress on the adjoining sakarya segment across the 1 to 2 km wide sapanca step over allowing rupture propagation across the basin an evaluation of 30 historical strike slip earthquakes involving 59 step over basins supports our field observations and stress modeling of the izmit fault rupture historical strike slip events with small to large displacements usually propagate through step overs less than 1 2 km wide with increasing displacement larger and larger step overs can be ruptured through the empirical data generally show a ratio ranging from 2 1 to 1 1 between step over width in kilometers and strike slip displacement in meters for a through going rupture however step overs of 4 to 5 km width appear to always arrest fault rupture regardless of the amount of displacement these results therefore provide important constraints for evaluating the probability of multisegment ruptures on segmented strike slip faults manuscript received 20 august 2000

the generating mechanisms of the august 17 1999 izmit bay turkey tsunami regional tectonic and local mass instabilities causes abstract the m w 7 4 earthquake that affected the northwestern part of turkey on august 17 1999 and in particular the gulf of izmit had dramatic consequences also as regards tsunami generation the main cause of the earthquake was a dextral strike slip rupture that took place along different segments of the western part of the north anatolian fault wnaf the rupture process involved not only a number of distinct strike slip fault segments but also dip slip ancillary faults connecting the main transcurrent segments the general picture was further complicated by the occurrence of subsidence and liquefaction phenomena especially along the coasts of the izmit bay and in the sapanca lake tsunami effects were observed and measured during post event surveys in several places along both the northern and the southern coasts of the bay the run up heights in most places were reported to lie in the interval 1 3 m but in the small town of degirmendere where a local slump occurred carrying underwater buildings and gardens of the waterfront sector eyewitnesses reported water waves higher than 15 m the purpose of this work is to investigate on the causes of the tsunami by means of numerical simulations of the water waves we show that the tsunami was a complex event consisting at least of the combination of a regional event due to tectonic causes and of a local event associated with the mass failure as to the first we are able to demonstrate that the observed tsunami cannot be explained only in terms of the sea bottom dislocation produced by the main right lateral dislocation but that the prominent contribution comes from the displacement associated with the secondary shallow normal faults furthermore the large waves and effects seen in degirmendere can be explained as the consequence of the slump by means of a stability analysis based on an original method making use of the limit equilibrium concept we show that the slump was highly stable before the earthquake and that it was triggered by seismic waves simulation of the tsunami induced by the slump was carried out by a two step numerical code that computes the landslide motion first and then the generated water wave propagation it is shown that the computed local tsunami matches the experimental data

magnetotelluric imaging of the fault rupture area of the 1999 izmit turkey earthquake abstract wide band 320 0 001 hz and long period 0 01 0 0001 hz magnetotelluric mt data were acquired along two profiles crossing the western part of the north anatolian fault zone nafz turkey which consists of two main fault branches the first profile izmit profile crosses the epicentral area of the 17 august 1999 izmit earthquake in fact the mt measurements along this profile started just a few weeks before the occurrence of the mainshock and four instruments happened to be in operation in the vicinity of the fault when the earthquake took place the second profile adapazari profile is located about 30 km east of the first profile two dimensional modeling shows the following results first the hypocenters of mainshock and aftershocks are located on the highly resistive side near the edge of a conductive zone second the long period mt data show a low resistivity zone extending down to 50 km between the two fault branches such a deep conductive zone is interpreted as representing partial melting resulted from the past complex tectonics in this region and it is related to the non seismic after slip in the layer below the seismogenic zone characterized by the highly resistive layer

how far did the surface rupture of the 1999 izmit earthquake reach in sea of marmara an open problem concerning the mw 7 4 1999 izmit earthquake along the north anatolian fault naf system is the apparent conflict between estimates of strike slip deformation based on field and remote sensing data this is due to the fact that the main strand of the naf west of the epicenter lies below the sea of marmara seismological evidence and models based on synthetic aperture radar interferometry suggest that coseismic and early postseismic displacement accumulated after the earthquake could have reached the western end of the izmit gulf and possibly the southern edge of the cinarcik basin tapering off along the northern coast of the armutlu peninsula more than 60 km from the epicenter this scenario is not confirmed by onshore field observations that point toward a termination of the surface rupture around 30 km to the east these discrepancies convey high uncertainties in the estimate of the tectonic load produced by the izmit earthquake on the adjacent fault segment toward istanbul we analyzed data from different sources including high resolution marine geophysical surveys and two nautile dives along the fault controlled canyon that connects izmit cinarcik basins our observations suggest that the surface rupture of the 1999 izmit earthquake propagated through the shallow gulf but did not reach the deep marmara basins in fact along the slope between cinarcik and the western end of the izmit gulf we do not observe fault related ruptures affecting the sea floor but rather a series of active gas seeps and black patches that mark the presence of known active faults our findings have implications for seismic risk assessment in the highly populated region of istanbul both for the estimate of tectonic load transferred to the next fault segments and the location of the next earthquake citation gasperini l a polonia g bortoluzzi p henry x le pichon m tryon n cagatay and l

was the 1899 menderes valley earthquake a double earthquake historical and paleosismological constraints abstract september 20 1899 menderes valley earthquake is the last destroying event in the buyuk menderes graben western turkey just proceeding the installation of the earliest seismograms in the world the previous geological studies revealed that this seismic event of estimated mw 6 5 6 7 caused a surface rupture of 50 km between aydin and kuyucak in the center of the graben based on the extremely different positioning of microseismic epicenter of this event in various historical documents we re evaluated the 1899 earthquake with a rather multidisciplinary perspective quantitative earthquake data including fatalities damage and various types of aids were gathered from daily journals and special commission reports of the time these data are corrected with the population statistics and georeferenced for exact determination of the position of the surface rupture we benefited the verbal description in historical documents and witnesses of elder local people furthermore morphological and palaeoseismological investigations were realized in the eastern part of the graben where surface deformations were made mention in historical documents different ground shake related indicators conformably revealed two distinct geographically separated damage zone one at yenipazar and the other at ortakci in the middle and east of the graben respectively trench studies in the west of the ortakci village indicated evidences of a seismic event presumably the 1899 earthquake with 180 cm vertical displacement bimodal distribution damage unrelated to basement lithology and building types and the incoherence between the total surface rupture length and the observed vertical offset and earthquake intensity lead us to conclude that the 1899 menderes valley earthquake was an earthquake doublet occurred in two neighboring segments in very close temporal proximity