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

the state of stress on some faults of the san andreas system as inferred from near field strong motion data we present a simple method to calculate the stress produced on an earthquake fault during rupture this method allows the complete evaluation of the stress spatio temporal history over the fault we apply this approach to study the changes in shear stress produced during four of the largest earthquakes which occurred along the san andreas fault system over the last 20 years the imperial valley earthquake of 1979 the morgan hill earthquake of 1984 the loma prieta earthquake of 1989 and the northridge earthquake of 1994 we use for this study the tomographic models of the fault rupture obtained from the inversion of the near field seismic data recorded during these earthquakes the results obtained show that the static and the dynamic stress drops vary greatly over the fault the peak values obtained for the four earthquakes studied range from about 20 to 100 mpa these high values imply that the initial shear stress level on the fault at the onset of the earthquake was high on at least a significant portion of the fault the regions of the fault which break with a high stress drop are also the regions where slip is large this suggests that most of the slip produced in a large earthquake takes place over the strong areas of the fault low slip regions tend to break with low stress drops after the earthquake the shear stress is increased over a significant portion of the fault which corresponds to low slip regions aftershock activity tends to be concentrated in these areas of stress increase the apparent strength of the fault before the earthquake that is the local shear stress increase which is required for rupture is also extremely heterogeneous the rupture velocity seems to be inversely correlated with this apparent fault strength the rupture accelerating over the weak areas of the fault and slowing down over the high strength areas

estimation of source rupture process and strong ground motion simulation of the 2002 denali alaska earthquake a m w 7 9 inland crustal earthquake occurred in the denali fault system alaska on 3 november 2002 at 22 12 utc in this study we estimated the source process of the 2002 denali earthquake by a multiple time window linear kinematic waveform inversion using strong motion and global positioning system gps measured static displacement data the obtained source model could explain both the observed strong motion waveforms and gps measured static displacements large slips on the fault plane are observed at approximately 80 90 km and 150 200 km east from the hypocenter these features are consistent with the observed surface rupture distribution and the other inversion results obtained using teleseismic body waves we also observed some portions of the whole fault with a local rupture propagation velocity of more than 4 0 km sec that exceeded the shear wave velocity of the source region the relation between the rupture area and seismic moment of this earthquake seems to follow the bilinear l model scaling rather than the self similar source scaling model the combined area of asperities is somewhat smaller than that expected from the empirical scaling relationship with seismic moments developed by compiling inverted source models finally we conducted a forward ground motion simulation using the finite difference method to estimate the influence of the heterogeneous source process obtained here on the spatial distribution of strong ground motions the calculated ground motions are relatively large above and around the large slip areas and also in the region east of the fault area because of the forward directivity effect of unilateral rupture propagation

three dimensional dynamic simulation of the 1992 landers earthquake the 1992 landers california earthquake magnitude 7 3 was modeled as the propagation of a spontaneous rupture controlled by a realistic prestress distribution with the use of a three dimensional finite difference method the dynamic rupture reproduces the general slip pattern used to compute the initial stress distribution and generates near fault ground motions at the surface similar to observations the simulated rupture propagates on the fault along a complex path with highly variable speed and rise time changing the magnitude and pattern of the stress significantly the method provides the framework to estimate earthquake rupture parameters from recorded seismic and geodetic data

strong shaking in los angeles expected from southern san andreas earthquake 1 the southernmost san andreas fault has a high probability of rupturing in a large greater than magnitude 7 5 earthquake sometime during the next few decades new simulations show that the chain of sedimentary basins between san bernardino and downtown los angeles form an effective waveguide that channels love waves along the southern edge of the san bernardino and san gabriel mountains earthquake scenarios with northward rupture in which the guided wave is efficiently excited produce unusually high long period ground motions over much of the greater los angeles region including intense localized amplitude modulations arising from variations in waveguide cross section

distribution of dynamic and static stress changes during 2000 tottori japan earthquake brief interpretation of the earthquake sequences foreshocks mainshock and aftershocks 1 the dynamic and static stress changes during the 2000 tottori earthquake have been recovered from the results of waveform inversion we use the dem to solve the elastodynamic equation specifying the slip along the fault obtained by a kinematic fault model the resulting shear stress distribution suggests an explanation of the foreshock and aftershock distributions we conclude that the fault zone heterogeneity is strong and most of the foreshocks and aftershocks were located in the zone of negative stress drop and mainly in the area surrounding the asperity this suggests that the asperity behaved as a barrier during the foreshocks and after the main shock the stress in the area surrounding the asperity increased and triggered most of the aftershocks the foreshock distribution was confined to a finite localized zone in the central part of the fault suggesting that this zone was bordered by barriers

hypocenter locations in finite source rupture models we use a database of more than 80 finite source rupture models for more than 50 earthquakes m w 4 1 8 1 with different faulting styles occurring in both tectonic and subduction environments to analyze the location of the hypocenter within the fault and to consider the correlation between hypocenter location and regions of large slip rupture in strike slip and crustal dip slip earthquakes tends to nucleate in the deeper sections of the fault subduction earthquakes do not show this tendency ratios of the hypocentral slip to either the average or the maximum slip show that rupture can nucleate at locations with any level of relative displacement rupture nucleates in regions of very large slip d 2 3 d max in only 16 of the events in regions of large slip 1 3 d max d d max in 35 of the events and in regions of low slip d 1 3 d max in 48 of the events these percentages significantly exceed the percentages of fault area with very large 7 and large 28 slip ruptures that nucleate in regions of low slip however tend to nucleate close to regions of large slip and encounter a zone of very large slip within half the total rupture length applying several statistical tests we conclude that hypocenters are not randomly located on a fault but are located either within or close to regions of large slip

evaluating a kinematic method for generating broadband ground motions for great subduction zone earthquakes application to the 2003 mw 8 3 tokachi oki earthquake abstract we compare broadband synthetic seismograms with recordings of the 2003 m w 8 3 tokachi oki earthquake to evaluate a compound rupture model in which slip on the fault consists of multiple high stress drop asperities superimposed on a background slip distribution with longer rise times low frequency synthetics 1 hz stochastic synthetics using a matched filter at 1 hz we show that this compound rupture model and overall approach accurately reproduces waveform envelopes and observed response spectral accelerations sas from the tokachi oki event we find that sufficiently short subfault rise times i e electronic supplement additional waveforms and subevent slip distributions

surface rupturing and buried dynamic rupture models calibrated with statistical observations of past earthquakes in the context of the slip weakening friction model and simplified asper ity models for stress state we calibrate dynamic rupture models for buried and surface rupturing earthquakes constrained with statistical observations of past earth quakes these observations are the kinematic source models derived from source in versions of ground motion and empirical source models of seismic moment and rupture area the calibrated parameters are the stress drop distribution on the fault and average stress drop we develop a set of dynamic rupture models that consist of asperities and surrounding background areas the distribution of dynamic stress drop outside the asperity is characterized by a fraction of the stress drop on the as perity from this set of models we identify dynamic fault models with defined stress drop characteristics that satisfy the observations the selected dynamic fault models show that surface rupturing earthquakes are characterized by a large area of negative stress drop surrounding the asperities while buried earthquakes present positive or zero stress drop in addition the calibrated fault models that match the observations show that the average stress drop is independent of earthquake size for buried earth quakes but scale dependent for surface rupturing earthquakes this suggests that in the context of our parameterization buried earthquakes follow self similarity scaling and surface rupturing earthquakes break this self similarity we apply the calibrated dynamic models to simulate near source ground motion consistent with observations that suggest that buried earthquakes generate stronger ground motion than surface rupturing earthquakes at high frequency we propose possible mechanisms that satisfy this observation as follows buried rupture has a hypocenter location below the as perity this can produce strong directivity of the slip velocity function toward the free surface that effect in addition to a reduced fault area and low fracture energy during rupture may be significant in enhancing high frequency ground motion on the other hand surface rupturing earthquakes have a shallow hypocenter large fracture energy on the asperities and enhanced energy absorption due to large areas of negative stress drop in the background area these characteristics of large earthquakes inhibit severe directivity effects on the slip velocity function directly toward the free surface redu cing the high frequency ground motion

ground motion simulations of 1811 1812 new madrid earthquakes central united states we performed a suite of numerical simulations based on the 1811 1812 new madrid seismic zone nmsz earthquakes which demonstrate the importance of 3d geologic structure and rupture directivity on the ground motion response throughout a broad region of the central united states cus for these events our simulation set consists of 20 hypothetical earthquakes located along two faults associated with the current seismicity trends in the nmsz the hypothetical scenarios range in magnitude from m 7 0 to 7 7 and consider various epicenters slip distributions and rupture characterization approaches the low frequency component of our simulations was computed deterministically up to a frequency of 1 hz using a regional 3d seismic velocity model and was combined with higher frequency motions calculated for a 1d medium to generate broadband synthetics 0 40 hz in some cases for strike slip earthquakes located on the southwest northeast striking nmsz axial arm of seismicity our simulations show 2 10 s period energy channeling along the trend of the reelfoot rift and focusing strong shaking northeast toward paducah kentucky and evansville indiana and southwest toward little rock arkansas these waveguide effects are further accentuated by rupture directivity such that an event with a western epicenter creates strong amplification toward the northeast whereas an eastern epicenter creates strong amplification toward the southwest these effects are not as prevalent for simulations on the reverse mechanism reelfoot fault and large peak ground velocities 40 cm s are typically confined to the near source region along the up dip projection of the fault nonetheless these basin response and rupture directivity effects have a significant impact on the pattern and level of the estimated intensities which leads to additional uncertainty not previously considered in magnitude estimates of the 1811 1812 sequence based only on historical reports the region covered by our simulation domain encompasses a large portion of the cus centered on the nmsz including several major metropolitan areas based on our simulations more than eight million people living and working near the nmsz would experience potentially damaging ground motion and modified mercalli intensities ranging from vi to viii if a repeat of the 1811 1812 earthquakes occurred today moreover the duration of strong ground shaking in the greater memphis metropolitan area could last from 30 to more than 60 s depending on the magnitude and epicenter online material tables of 1d velocity models used to generate the high frequency synthetics and figures of source models and peak ground motion synthetics

evaluating the compatibility of dynamic rupture based synthetic ground motion with empirical ground motion prediction equation we performed an assessment of a database of synthetic ground motion generated by a suite of dynamic rupture simulations to verify compatibility of the peak ground amplitudes with respect to empirical ground motion prediction equations gmpes the dynamic rupture model database developed by dalguer and mai 2011 is composed of 360 earthquake scenarios with moment magnitudes in the range of 5 5 7 for three mechanisms of faulting reverse normal and strike slip and for both buried faults and surface rupturing faults having depth and non depth dependent normal stresses initial shear stress distribution follows a von karman stochastic distribution overall we show quantitatively that the upper frequency limit of the suite of simulations is 1 0 hz up to this frequency the synthetic data are compatible with the empirical model which means that the residuals defined as the differences between observed and predicted ground motions fall in the range of of the empirical gmpe characteristics of the mean values along distance 10 45 km and period t 1 0 s including standard deviation of the synthetic response spectra and peak ground velocity are comparable to their counterpart empirical gmpe at very near source 1 2 km synthetics show supersaturation of the mean peak values which is different from the saturation features predicted by the gmpes the effect of source parameters such as stress drop peak slip velocity and rupture speed and of surface and buried rupture as well as hanging wall and footwall are highly sensitive to ground motion suggesting that these effects contribute to the variability of ground motion near the source and that inclusion of them in the source terms may contribute to reducing uncertainties in gmpes

surface rupture effects on earthquake moment area scaling relations empirical earthquake scaling relations play a central role in fundamental studies of earthquake physics and in current practice of earthquake hazard assessment and are being refined by advances in earthquake source analysis a scaling relation between seismic moment m0 and rupture area a currently in use for ground motion prediction in japan features a transition regime of the form m0 a2 between the well recognized small self similar and very large w model earthquake regimes which has counterintuitive attributes and uncertain theoretical underpinnings here we investigate the mechanical origin of this transition regime via earthquake cycle simulations analytical dislocation models and numerical crack models on strike slip faults we find that even if stress drop is assumed constant the properties of the transition regime are controlled by surface rupture effects comprising an effective rupture elongation along dip due to a mirror effect and systematic changes of the shape factor relating slip to stress drop based on this physical insight we propose a simplified formula to account for these effects in m0 a scaling relations for strike slip earthquakes

estimation of dynamic rupture parameters from the radiated seismic energy and apparent stress we propose a new procedure for estimating the critical slip weakening distance dc by evaluating the spatio temporal distribution of the apparent stress calculated from the spatio temporal distribution of the slip velocity function on the fault plane obtained from a kinematic inversion of the earthquake source the idea is based on the fact that the apparent stress can be related to the difference between the earthquake average stress and the frictional dynamical stress on the fault plane during the rupture process from the cumulative slip apparent stress relationship we estimate the critical slip dc of the 1992 landers earthquake we find that the critical slip weakening plays an important role in controlling the rupture velocity in the case of the landers earthquake the very low rupture velocity in the central segment could be explained by the large dc value obtained for the main asperity on that segment

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

some characteristics of the stress field of the 1995 hyogo ken nanbu kobe earthquake we investigate the characteristics of the stress field associated with the 1995 hyogo ken nanbu kobe earthquake we use for the study a tomographic model of the fault slip inferred from the numerous near field recordings and we calculate the space and time evolution of shear stress on the fault during the earthquake we show that the spatial distribution of stress drop is very heterogeneous the apparent strength of the fault at the onset of the earthquake is low of the order of 1 mpa or less which indicates that the pre earthquake tectonic shear stress was close to the static friction over most of the fault at many locations the stress drop rotates significantly during sliding as was originally proposed by spudich 1992 we use the requirement of colinearity between the directions of maximum shear stress and instantaneous slip to determine the initial stress on the fault at the onset of the earthquake the pre earthquake tectonic stress varies greatly over the fault and ranges from about 1 to 10 mpa average values of the initial and final shear stresses over the fault are 3 3 and 1 6 mpa respectively indicating that about half of the pre earthquake tectonic stress was released during the earthquake there is a relatively strong correlation between the initial and final stress distributions which suggests that intrinsic fault properties not modified by the earthquake control the spatial distribution of tectonic stress over the fault we show that on average over the fault the dynamic friction coefficient is equal to about 40 of the static friction coefficient diagrams depicting the evolution of shear stress as a function of slip are consistent with slip weakening behavior but their interpretation is questionable because of the poor resolution of the data at high frequency and because of the constraints imposed on the model to perform the inversion

recipe for predicting strong ground motion from crustal earthquake scenarios we developed a recipe for predicting strong ground motions based on a characterization of the source model for future crustal earthquakes from recent developments of waveform inversion of strong motion data used to estimate the rupture process we have inferred that strong ground motion is primarily related to the slip heterogeneity inside the source rather than average slip in the entire rupture area asperities are characterized as regions that have large slip relative to the average slip on the rupture area the asperity areas as well as the total rupture area scale with seismic moment we determined that the areas of strong motion generation approximately coincide with the asperity areas based on the scaling relationships the deductive source model for the prediction of strong ground motions is characterized by three kinds of parameters outer inner and extra fault parameters the outer fault parameters are defined as entire rupture area and total seismic moment the inner fault parameters are defined as slip heterogeneity inside the source area of asperities and stress drop on each asperity based on the multiple asperity model the pattern of rupture nucleation and termination are the extra fault parameters that are related to geomorphology of active faults we have examined the validity of the earthquake sources constructed by our recipe by comparing simulated and observed ground motions from recent inland crustal earthquakes such as the 1995 kobe and 2005 fukuoka earthquakes

the importance of the dynamic source effects on strong ground motion during the 1999 chi chi taiwan earthquake brief interpretation of the damage distribution on buildings the 1999 chi chi taiwan earthquake that originated on a low angle reverse fault showed complexity and uncommon characteristics the records show that the hanging wall side is characterized by larger particle motions than the foot wall and the ground motion is stronger in the northern part than in the southern part of the causative fault although the strongest ground motion occurred near the north ern part of the trace structural damage was heavier in the southern part in order to get a better understanding of the complex damage distribution caused by this earth quake the dynamic rupture process was numerically simulated because of the dif ferences between the observed features of the rupture process in the northern and southern parts of the fault each part was modeled independently by using a 2d discrete element model dem the principal results of the simulation show that the velocity ground motions in the northern part in the frequency range of 0 5 2 hz natural frequency range of standard structures are small near the surface break thus light structural damage might be predicted near the surface rupture moreover in the northern part the fault rupture propagation reaches the surface with a very slow velocity about 1 2 km sec however in the southern part the rupture propa gation reaches the surface with higher velocity about 3 0 km sec these differences between the models could explain why the ground motion near the surface rupture in the northern part caused less damage in structures than the ground motion in the southern part

prediction of total organic carbon at rumaila oil field southern iraq using conventional well logs and machine learning algorithms abstract total organic carbon toc is an important parameter for assessing the hydrocarbon potential of source rocks the standard method for analysis of toc is the rock eval pyrolysis on cutting and core samples the coring process is always expensive and time consuming therefore researchers around the world focused on developing techniques to estimate toc and other organic parameters from readily available well logs data that are almost available in all wells in this study we evaluated the use of three machine learning models namely random forest rf rotation forest rf k nearest neighbors knn to estimate toc based on conventional well logs data the well logs involved gamma ray acoustic density neutron and deep resistivity the efficacy of the models was tested against the most widely used backpropagation artificial neutral network bpann and support vector regression svr models north rumaila oilfield in southern iraq was taken as a case study the models were trained and tested using data from two wells in the field namely r 167 and r 172 the number of toc measurements used for training and testing were 40 r 167 and 18 r 172 respectively the efficacy of the used algorithms was evaluated using mean absolute error mae root mean squared error rmse and correlation of determination r2 the models are also visually compared using taylor diagram and violin plot to distinguish the best performance model results indicated the knn was the best followed by rf and then rf the worst performance models were bpann and svr models this study confirmed the ability of machine learning models for building efficient model for estimating toc from readily available borehole logs data without the need for very expensive coring process

terashake2 spontaneous rupture simulations of mw 7 7 earthquakes on the southern san andreas fault abstract previous numerical simulations terashake1 of large m w 7 7 southern san andreas fault earthquakes predicted localized areas of strong amplification in the los angeles area associated with directivity and wave guide effects from northwestward propagating rupture scenarios the terashake1 source was derived from inversions of the 2002 m w 7 9 denali alaska earthquake that source was relatively smooth in its slip distribution and rupture characteristics owing both to resolution limits of the inversions and simplifications imposed by the kinematic parameterization new simulations terashake2 with a more complex source derived from spontaneous rupture modeling with small scale stress drop heterogeneity predict a similar spatial pattern of peak ground velocity pgv but with the pgv extremes decreased by factors of 2 3 relative to terashake1 the terashake2 source excites a less coherent wave field with reduced along strike directivity accompanied by streaks of elevated ground motion extending away from the fault trace the source complexity entails abrupt changes in the direction and speed of rupture correlated to changes in slip velocity amplitude and waveform features that might prove challenging to capture in a purely kinematic parameterization despite the reduced pgv extremes northwest rupturing terashake2 simulations still predict entrainment by basin structure of a strong directivity pulse with pgvs in los angeles and san gabriel basins that are much higher than predicted by empirical methods significant areas of those basins have predicted pgv above the 2 probability of exceedance poe level relative to current attenuation relationships even when the latter includes a site term to account for local sediment depth and wave guide focusing produces localized areas with pgv at roughly 0 1 0 2 poe about a factor of 4 5 above the median in contrast at rock sites in the 0 100 km distance range the median terashake2 pgvs are in very close agreement with the median empirical prediction and extremes nowhere reach the 2 poe level the rock site agreement lends credibility to some of our source modeling assumptions including overall stress drop level and the manner in which we assigned dynamic parameters to represent the mechanical weakness of near surface material future efforts should focus on validating and refining these findings assessing their probabilities of occurrence relative to alternative rupture scenarios for the southern san andreas fault and incorporating them into seismic hazard estimation for southern california

rupture dynamics with energy loss outside the slip zone 1 energy loss in a fault damage zone outside the slip zone contributes to the fracture energy that determines rupture velocity of an earthquake a nonelastic two dimensional dynamic calculation is done in which the slip zone is modeled as a fault plane and material off the fault is subject to a coulomb yield condition in a mode 2 crack like solution in which an abrupt uniform drop of shear traction on the fault spreads from a point coulomb yielding occurs on the extensional side of the fault plastic strain is distributed with uniform magnitude along the fault and it has a thickness normal to the fault proportional to propagation distance energy loss off the fault is also proportional to propagation distance and it can become much larger than energy loss on the fault specified by the fault constitutive relation the slip velocity function could be produced in an equivalent elastic problem by a slip weakening friction law with breakdown slip dc increasing with distance fracture energy g and equivalent dc will be different in ruptures with different initiation points and stress drops so they are not constitutive properties they are determined by the dynamic solution that arrives at a particular point peak slip velocity is however a property of a fault location nonelastic response can be mimicked by imposing a limit on slip velocity on a fault in an elastic medium

a comparison of recorded response spectra from the 2008 wenchuan china earthquake with modern ground motion prediction models we compared response spectra from the m w 7 9 2008 wenchuan earthquake with five modern ground motion prediction equations gmpes ninety three strong motion records within 300 km of the fault plane were selected for comparison with the gmpe models of zhao zhang et al 2006 abrahamson and silva 2008 boore and atkinson 2008 campbell and bozorgnia 2008 and chiou and youngs 2008 for spectral periods up to 5 0 s the site class of the recording stations used for the zhao zhang et al 2006 model was inferred from response spectral ratios of the horizontal and vertical components h v computed from the strong motion records in moving and overlapping time windows the average shear wave velocity of the top 30 m v s 30 was only available for two stations v s 30 was extrapolated from the average of the top 20 m v s 20 when possible and inferred from the h v response spectral ratios when necessary the average predictions of all models were acceptable the zhao zhang et al 2006 model gave the best predictions for peak ground acceleration and short spectral periods especially up to 100 km of the source distance all next generation attenuation nga models predicted the recorded spectra very well for periods of 0 5 1 0 s and at 5 0 s the chiou and youngs 2008 model gave the best overall predictions the standard deviations of all attenuation models were similar at a 5 significance level however differences between spectra estimated by various nga models were statistically and practically significant with the largest difference between the average predictions being nearly a factor of 1 4 at the 0 1 s period and 2 3 at the 5 0 s period for data within a source distance of 100 km although one earthquake did not produce median ground motions that the gmpes are designed to predict such a large difference represents a challenge for empirical models when estimating spectra from very large crustal earthquakes

earthquake source scaling relationships from 1 to 5 ml using seismograms recorded at 2 5 km depth the scaling relationships of earthquake sources less than about magnitude 3 have been the subject of considerable controversy over the last two decades studies of such events have shown a tendency for the constant stress drop self similarity of larger earthquakes to breakdown at small magnitudes and an apparent minimum source dimension of about 100 m has been observed other studies showed that this apparent breakdown in scaling could be an artifact of severe near surface attenuation limiting the spatial resolution of surface data in this study source parameters are determined for over 100 nearby tectonic earthquakes from recordings at a depth of 2 5 km in granite in the cajon pass scientific drill hole southern california comparison of the seismograms recorded at this depth with those at the wellhead clearly demonstrates the effect of the severe attenuation in the upper kilometers of the earth s crust source parameters are calculated by spectral modeling of three component p and s waves assuming four source models based on the brune 2 n 2 model in model l n 2 is fixed and q of p and s waves is determined to be 912 581 1433 and 1078 879 1323 respectively the numbers in parentheses are 1 standard deviation in model 2 qp qs 1000 is assumed and n is allowed to vary the 2 model is a good average for the data set but there is some real scatter supported by the data in model 3 qp qs 1000 is also assumed and 2 is constrained and in model 4 attenuation is ignored and n is allowed to vary source dimensions of less than 10m are observed for all four models 10 times smaller than the proposed minimum no breakdown in constant stress drop scaling is seen in the downhole data approximately ml 1 to 5 5 m0 109 1016 nm the ratio between radiated seismic energy estimated by integrating the velocity squared spectra with adequate signal bandwidth and seismic moment appears to decrease gradually with decreasing moment in the magnitude range 1 to 7 this is not incompatible with a constant stress drop but could result from errors in calculating energy the ratio of the s wave energy to that radiated by the p waves is about 14 after correction for attenuation this low value is consistent with the corner frequency shift of about 1 3 this corner frequency shift is observed for all four source models and therefore is interpreted as being source controlled

development of dynamic asperity models to predict surface fault displacement caused by earthquakes asperity models for ground motion prediction is widely used in japan here we expand the application of these asperity models to predict fault displacement caused by surface rupture the proposed approach is rather simple and practical for the use in fault displacement hazard analysis in nuclear installations and other critical infrastructures as it is the emphasis of the current topical issue the proposed method mainly consists of two steps the first step consists in the characterization of asperities at the seismogenic zone based on the kinematic asperity source model following irikura s recipe irikura and miyake in pure applied geophysics 168 85 104 2011 for strong ground motion prediction since the kinematic model does not take into account surface rupture mechanism this first step assumes that the fault is buried and then by trial and error procedure the stress drop on the asperities are estimated so that the average slip at each asperity be consistent with the ones from the kinematic model at this stage the dynamic model predicts strong ground motion consistent with those from the kinematic model in the second step the surface rupture is included by calibrating the shallow layer sl with stress drop strength excess and critical slip distance so that the final fault displacement along the fault be consistent with observations the 2010 mw 7 0 darfield new zealand earthquake is used to test the proposed method surface rupturing was observed in several sites along the main fault reaching values of fault displacement larger than 5 m the main fault of this earthquake is strike slip almost vertical therefore a simplified planar fault asperity model to capture the main features of the fault displacement is assumed the fault dimensions are assumed to have a length of 60 km and a width of 24 km with three asperities the preferred model of the first step predicts average slip for each asperity of 2 7 2 7 and 2 m corresponding respectively to stress drops of 6 0 mpa 8 5 mpa and 7 0 mpa in the second step the surface rupture is calibrated assuming a sl zone of 3 km depth we found that negative stress drop is not necessary in the sl because this strongly inhibits surface rupturing our preferred model produces fault displacement distribution closer to the observed ones but average slip at each asperity increases to 3 4 m 3 2 and 2 8 m this increase in average slip is due to the contribution of surface rupturing ground motion differences between fault surface rupturing and buried models are negligible except at the very near source these differences are attributed to the sl rupture that mainly affect the ground motion at the very near source overall our simple asperity model captures the main features of the observed fault displacement and near source ground motion proving that the proposed simple and practical two step procedure provides meaningful estimate of fault displacement and near source ground motion consistent with observations as such this method has the potential to be used in practical fault displacement hazard analysis

simulation of tensile crack generation by three dimensional dynamic shear rupture propagation during an earthquake 1 as there is no evidence that cracks are created directly in modes ii and iii shear cracks probably occur only along a weakness plane as in a preexisting fault mode i fracture therefore may be an important factor in crack formation during shallow earthquakes a three dimensional shear dynamic rupture process was simulated on the assumption that shear slip occurs only in a preexisting fault and the possibility of introducing new internal cracks that propagate under tensile stress as a consequence of the dynamic process of shear slip propagation the discrete element method dem was used to solve this problem because it can introduce internal tensile cracks the simple slip weakening model was used as the friction law on the preexisting fault for shear rupture propagation for new tensile cracks fracture follows classical griffith theory when the critical value for tensile fracture surface energy is reached the proposed model was used to simulate the rupture process of a strike slip shallow fault results show that the generation of new cracks is affected by rupture directivity in terms of the hypocenter and asperity location as well as by fault geometry with respect to the free surface cracks develop a flower like structure that surrounds the preexisting fault when the asperity is located at less than a certain depth the flower like structure that originates from the top of the fault reaches the free surface we consider that this is the mechanism for forming the flower structure near surface during a strike slip shallow earthquake

quantification of fault zone plasticity effects with spontaneous rupture simulations previous studies have shown that plastic yielding in crustal rocks in the fault zone may impose a physical limit to extreme ground motions we explore the effects of fault zone non linearity on peak ground velocities pgvs by simulating a suite of surface rupturing strike slip earthquakes in a medium governed by drucker prager plasticity using the awp odc finite difference code our simulations cover magnitudes ranging from 6 5 to 8 0 three different rock strength models and average stress drops of 3 5 and 7 0 mpa with a maximum frequency of 1 hz and a minimum shear wave velocity of 500 m s friction angles and cohesions in our rock models are based on strength criteria which are frequently used for fractured rock masses in civil and mining engineering for an average stress drop of 3 5 mpa plastic yielding reduces near fault pgvs by 15 30 in pre fractured low strength rock but less than 1 in massive high quality rock these reductions are almost insensitive to magnitude if the stress drop is doubled plasticity reduces near fault pgvs by 38 45 and 5 15 in rocks of low and high strength respectively because non linearity reduces slip rates and static slip near the surface plasticity acts in addition to and may partially be emulated by a shallow velocity strengthening layer the effects of plasticity are exacerbated if a fault damage zone with reduced shear wave velocities and reduced rock strength is present in the linear case fault zone trapped waves result in higher near surface peak slip rates and ground velocities compared to simulations without a low velocity zone these amplifications are balanced out by fault zone plasticity if rocks in the damage zone exhibit low to moderate strength throughout the depth extent of the low velocity zone sim 5 km we also perform dynamic non linear simulations of a high stress drop 8 mpa m 7 8 earthquake rupturing the southern san andreas fault along 250 km from indio to lake hughes non linearity in the fault damage zone and in near surface deposits would reduce peak ground velocities in the los angeles basin by 15 50 depending on the strength of crustal rocks and shallow sediments these results show that non linear effects may be relevant even at long periods in particular in earthquakes with high stress drop and in the presence of a low velocity fault damage zone

compositional change of majoritic garnet in a morb composition from 7 to 17 gpa and 1400 to 1600 c experimental phase relations of an average normal mid ocean ridge basalt n morb composition from 7 gpa to 17 gpa and 1400 to 1600 c reveal the compositional variation of garnet in equilibrium with pyroxene the na2o content of majoritic garnet in equilibrium with pyroxene and stishovite increases up to 2 5 wt with increasing pressure and temperature na enters the garnet structure via the substitution mg fe ca al na si ti the pyroxene garnet partition coefficient dcp ga for na decreases with increasing pressure however clinopyroxene coexisting with garnet becomes more na rich as pressure increases these relationships are independent of the feo content in garnet our experiments confirm that rare majoritic and na rich garnet inclusions in diamonds have formed at transition zone pressure in lithologies of basaltic bulk composition

generation of microcracks by dynamic shear rupture and its effects on rupture growth and elastic wave radiation laboratory and field observations suggest that dynamically propagating earthquake faults generate a large number of tensile microcracks in their vicinity which will contribute to the formation of fault zones intense interactions are expected to occur between such microcracks and a dynamically propagating fault which will complicate the fault growth near field seismic waves will also be affected by the generation of microcracks we numerically study how such tensile microcracks are generated and how dynamic growth of a macroscopic shear rupture and near field elastic waves are affected by the distribution of generated microcracks it is essential to consider a large number of microcracks in such studies so that it is impractical to consider each microcrack individually from the viewpoint of computation time and memory we overcome this difficulty by representing the microcrack distribution by anisotropic properties of the overall elastic coefficients on the basis of hudson s 1980 study our simulations show that the decrease in the microcrack density is approximated well by a logarithmic function of the distance from the rupture plane microcracks on the dilational side of the rupture plane are shown to make larger angles to the rupture plane than on the compressive side these are consistent with field and laboratory observations it is also shown that dynamically generated microcracks tend to reduce the rupture tip shear stress this implies that the dynamic growth of a shear rupture is more decelerated when microcracks are generated than when the shear rupture is isolated in an isotropic and homogeneous medium if the dynamic rupture growth is arrested suddenly an abrupt expansion of the distribution zone of microcracks is shown to occur near the arrested rupture tip aftershocks are expected to cluster in this zone because of the shear stress enhancement there and the high density of distributed microcracks which facilitates aftershock occurrence due to dynamic coalescence of microcracks our simulations also show that the component of radiated displacement waves perpendicular to the rupture plane is much more affected by the generation of microcracks than the parallel component

magnitude scaling of the near fault rupture directivity pulse abstract current ground motion models all assume monotonically increasing spectral amplitude at all periods with increasing magnitude however near fault recordings from recent earthquakes confirm that the near fault fault normal forward rupture directivity velocity pulse is a narrow band pulse whose period increases with magnitude this magnitude dependence of the period of the near fault pulse is expected from theory because the period of the pulse is related to source parameters such as the rise time duration of slip at a point on the fault and the fault dimensions which generally increase with magnitude this magnitude dependence of the pulse period causes the response spectrum to have a peak whose period increases with magnitude such that the near fault ground motions from smaller earthquakes may exceed those of larger earthquakes at intermediate periods around 1 s this paper presents preliminary equations relating the period of the fault normal component of the forward rupture directivity velocity pulse to the earthquake magnitude and a preliminary model for the acceleration response spectra of near fault fault normal ground motions that includes the magnitude dependence of the period of the response spectral peak

determination of earthquake energy release and ml using terrascope we estimated the energy radiated by earthquakes in southern california using on scale very broadband recordings from terrascope the method we used involves time integration of the squared ground motion velocity and empirical determination of the distance attenuation function and the station corrections the time integral is typically taken over a duration of 2 min after the p wave arrival the attenuation curve for the energy integral we obtained is given by q r cr n exp kr r 2 2 h ref 2 with c 0 49710 n 1 0322 k 0 0035 km 1 and h ref 8 km where is the epicentral distance a similar method was used to determine m l using terrascope data the station corrections for m l are determined such that the m l values determined from terrascope agree with those from the traditional optical wood anderson seismographs for 1 5 6 5 m l saturates the ratio e s m 0 m 0 seismic moment a measure of the average stress drop for six earthquakes the 1989 montebello earthquake m l 4 6 the 1989 pasadena earthquake m l 4 9 the 1990 upland earthquake m l 5 2 the 1991 sierra madre earthquake m l 5 8 the 1992 joshua tree earthquake m l 6 1 and the 1992 landers earthquake m w 7 3 are about 10 times larger than those of the others that include the aftershocks of the 1987 whittier narrows earthquake the sierra madre earthquake the joshua tree earthquake and the two earthquakes on the san jacinto fault the difference in the stress drop between the mainshock and their large aftershocks may be similar to that between earthquakes on a fault with long and short repeat times the aftershocks which occurred on the fault plane where the mainshock slippage occurred had a very short time to heal hence a low stress drop the repeat time of the major earthquakes on the frontal fault systems in the transverse ranges in southern california is believed to be very long a few thousand years hence the events in the transverse ranges may have higher stress drops than those of the events occurring on faults with shorter repeat times such as the san andreas fault and the san jacinto fault the observation that very high stress drop events occur in the transverse ranges and the los angeles basin has important implications for the regional seismic potential the occurrence of these high stress drop events near the bottom of the seismogenic zone strongly suggests that these fault systems are capable of supporting high stress that will eventually be released in major seismic events characterization of earthquakes in terms of the e s m 0 ratio using broadband data will help delineate the spatial distribution of seismogenic stresses in the los angeles basin and the transverse ranges

3d simulations of m 7 earthquakes on the wasatch fault utah part i long period 0 1 hz ground motion abstract we predict ground motions in the salt lake basin slb during m 7 earthquakes on the salt lake city segment of the wasatch fault wfslc first we generate a suite of realistic source representations by simulating the spontaneous rupture process on a planar vertical fault with the staggered grid split node finite difference fd method the initial distribution of shear stress is the sum of both a regional depth dependent shear stress appropriate for a dipping normal fault and a stochastically generated residual shear stress field associated with previous ruptures the slip rate histories from the spontaneous rupture scenarios are projected onto a detailed 3d model geometry of the wfslc that we developed based on geological observations next we simulate 0 to 1 hz wave propagation from six source models with a 3dfd code using the most recent version of the wasatch front community velocity model horizontal spectral accelerations at two seconds 2 s sas reveal strong along strike rupture direction effects for unilateral ruptures as well as significant amplifications by the low velocity sediments on the hanging wall side of the fault for ruptures nucleating near the southern end of the segment we obtain 2 s sas of up to 1 4 g near downtown slc caused by a combination of rupture direction and basin edge effects average 3 s sas and 2 s sas from the six scenarios are generally consistent with values predicted by four next generation attenuation models

estimation of the high frequency radiation of the 2000 tottori japan earthquake based on a dynamic model of fault rupture application to the strong ground motion simulation abstract in the present study we investigate the high frequency hf radiation mechanism of the 2000 tottori earthquake in japan based on a 3d spontaneous fault rupture dynamic model we generalize the model of hf radiation of a suddenly stopping circular crack madariaga 1977 boatwright 1982 to the radiation from a general 3d rupture in a planar fault where hf is radiated during gradual changes of rupture velocity at the rupture front local rupture velocity changes are expressed as the divergence of local rupture velocity vectors that are derived from gradients of rupture times from the dynamic model our numerical model of the tottori earthquake indicates that rupture velocity changes are largely induced by barriers locally stronger fault sections across the fault plane and that hf radiation mainly originates within asperities large stress drop regions in areas where the product of dynamic stress drop and rupture velocity changes is maximum we develop a strong ground motion simulation methodology that incorporates hf radiation inferred from a dynamic fault rupture model using this methodology we investigate the hf radiation of the tottori earthquake by inverting observed near source acceleration envelopes of the earthquake our inversion results corroborate that hf radiation originates within asperities and show that significant hf radiation represents no more than a 20 of the total asperity area our results show that the incorporation of a directivity factor on the basis of a well defined physical rupture model to the radiation pattern leads to a significant improvement in fitting of observed ground motions our simulated near source strong ground motions of the tottori earthquake are also able to reproduce the 2 radiation theoretically predicted in 2d dynamic fault rupture models

dynamic modeling of the 1992 landers earthquake we have used observed band pass filtered accelerograms and a previously determined slip distribution to invert for the dynamic rupture propagation of the 1992 landers earthquake in our simulations dynamic rupture grows under the simultaneous control of initial stress and rupture resistance by friction which we modeled using a simple slip weakening law we used a simplified landers fault model where the fault segments were combined into a single vertical planar fault by trial and error we modified an initial stress field inferred from the kinematic slip distribution proposed by wald and heaton 1994 until dynamic rupture generated a rupture history and final slip distribution that approximately matched those determined by the kinematic inversion we found that rupture propagation was extremely sensitive to small changes in the distribution of prestress and that a delicate balance with energy release rate controls the average rupture speed for the inversion we generated synthetic 0 5 hz ground displacements using an efficient green s function propagator method axitra this method enables us to propagate the radiation generated by the dynamic rupture to distances greater than those feasible using the finite difference method the dynamic model built by trial and error inversion provides a very satisfactory fit between synthetics and strong motion data we validated this model using records from stations used in the slip inversion as well as some which were not included we also inverted for a complementary model that fits the data just as well but in which the initial stress was perfectly uniform while rupture resistance was heterogeneous this demonstrates that inversion of ground motion is nonunique

dynamic stress changes during earthquake rupture we assess two competing dynamic interpretations that have been pro posed for the short slip durations characteristic of kinematic earthquake models de rived by inversion of earthquake waveform and geodetic data the first interpretation would require a fault constitutive relationship in which rapid dynamic restrengthen ing of the fault surface occurs after passage of the rupture front a hypothesized mechanical behavior that has been referred to as self healing the second inter pretation would require sufficient spatial heterogeneity of stress drop to permit rapid equilibration of elastic stresses with the residual dynamic friction level a condition we refer to as geometrical constraint these interpretations imply contrasting pre dictions for the time dependence of the fault plane shear stresses we compare these predictions with dynamic shear stress changes for the 1992 landers m 7 3 1994 northridge m 6 7 and 1995 kobe m 6 9 earthquakes stress changes are com puted from kinematic slip models of these earthquakes using a finite difference method for each event static stress drop is highly variable spatially with high stress drop patches embedded in a background of low and largely negative stress drop the time histories of stress change show predominantly monotonic stress change after passage of the rupture front settling to a residual level without significant evidence for dynamic restrengthening the stress change at the rupture front is usu ally gradual rather than abrupt probably reflecting the limited resolution inherent in the underlying kinematic inversions on the basis of this analysis as well as recent similar results obtained independently for the kobe and morgan hill earthquakes we conclude that at the present time the self healing hypothesis is unnecessary to explain earthquake kinematics

source characterization for broadband ground motion simulation kinematic heterogeneous source model and strong motion generation area we estimate strong motion generation areas that reproduce near source ground motions in a broadband frequency range 0 2 10 hz using the empirical green s function technique the strong motion generation areas are defined as extended areas with relatively large slip velocities within a total rupture area four m 6 class the 1997 kagoshima on march and may 1997 yamaguchi and 1998 iwate and several moderate size earthquakes in japan were analyzed we examine the relationship between the strong motion generation area and the area of asperities which is characterized based on heterogeneous slip distributions estimated from low frequency 1 hz waveform inversions somerville et al 1999 we performed waveform fitting in acceleration velocity and displacement then obtained the strong motion generation area occupying about a quarter of the total rupture area the size and position of the strong motion generation area coincide with those of characterized asperities we find self similar scaling of seismic moment to both the size of the strong motion generation area and the rise time for a magnitude range of analyzed earthquakes based on our results we propose a characterized source model for the broadband ground motion simulation which consists of strong motion generation areas with large slip velocities and a background slip area with a small slip velocity waveform modeling of the characterized source model suggests that the strong motion generation areas play important roles in simulating broadband ground motions and have the potential to be an about 10 mpa stress release area on the fault manuscript received 22 august 2002

expected seismic shaking in los angeles reduced by san andreas fault zone plasticity computer simulations of large m 7 8 earthquakes rupturing the southern san andreas fault from se to nw e g shakeout widely used for earthquake drills have predicted strong long period ground motions in the densely populated los angeles basin due to channeling of waves through a series of interconnected sedimentary basins recently the importance of this waveguide amplification effect for seismic shaking in the los angeles basin has also been confirmed from observations of the ambient seismic field by simulating the shakeout earthquake scenario based on a kinematic source description for a medium governed by drucker prager plasticity we show that nonlinear material behavior could reduce the earlier predictions of large long period ground motions in the los angeles basin by up to 70 as compared to viscoelastic solutions these reductions are primarily due to yielding near the fault although yielding may also occur in the shallow low velocity deposits of the los angeles basin if cohesions are close to zero fault zone plasticity remains important even for conservative values of cohesions suggesting that current simulations assuming a linear response of rocks are overpredicting ground motions during future large earthquakes on the southern san andreas fault

broadband kinematic stochastic simulation of an earthquake source a refined procedure for application in seismic hazard studies to carry out a realistic simulation of earthquake strong ground motion for applied studies one needs an earthquake fault source simulator that can integrate most relevant features of observed earthquake ruptures a procedure of this kind is proposed that creates a broadband kinematic source model at lower frequencies the source is described as propagating slip pulse with locally variable velocity the final slip is assumed to be a two dimensional 2d random function at higher frequencies radiation from the same running strip is assumed to be random and incoherent in space the model is discretized in space as a grid of point subsources with certain time histories at lower frequencies a realistic shape of source spectrum is generated implicitly by simulated kinematics of slip pulse propagation at higher frequencies the original approach is used to generate signals with spectra that plausibly approximate the prescribed smooth far field source spectrum this spectrum is set on the basis of the assumedly known regional empirical spectral scaling law and subsource moment rate time histories are conditioned so as to fit this expected spectrum for the random function that describes final slip over the fault area lognormal probability distribution of amplitudes is assumed on the basis of exploratory analysis of inverted slip distributions similarly random functions that describe local slip rate time histories are assumed to have lognormal distribution of envelope amplitudes in this way one can effectively emulate expressed asperities of final slip and occasional occurrence of large spikes on near source accelerograms a special procedure is proposed to simulate the spatial coherence of high frequency fault motion this approach permits the simulation of fault motion plausibly at high spatial resolution fulfilling the prerequisite for simulation of strong motion in the vicinity of a fault a particular realization sample of a source created in a simulation run depends on several random seeds and also on a considerable number of parameters their values can be selected so as to take into account expected source features they can also be perturbed to examine the source related component of uncertainty of strong motion the proposed approach to earthquake source specification is well adapted to the study of deterministic seismic hazard it may be used for simulation of individual scenario events or suites of such events as well as for analysis of uncertainty for expected ground motion parameters from a particular class of events examples are given of application of the proposed approach to strong motion simulations and related uncertainty estimation

stress breakdown time and slip weakening distance inferred from slip velocity functions on earthquake faults we estimate the critical slip weakening distance on earthquake faults by using a new approach which is independent of the estimate of fracture energy or radiated seismic energy the approach is to find a physically based relation between the breakdown time of shear stress tb the time of peak slip velocity tpv and the slip weakening distance dc from the time histories of shear stress slip and slip velocity at each point on the fault which can be obtained from dynamic rupture calculations using a simple slip weakening friction law numerical calculations are carried out for a dynamic shear crack propagating either spontaneously or at a fixed rupture velocity on a vertical fault located in a 3d half space and a more realistic horizontally layered structure with finite difference schemes the results show that tpv is well correlated with tb for faults even with a heterogeneous stress drop dis tribution except at locations near strong barriers and the fault edges we also inves tigate this relation for different types of slip weakening behavior we have applied the method to two recent strike slip earthquakes in western japan the 2000 tottori and the 1995 kobe events we integrated the slip velocity functions on the vertical fault obtained from kinematic waveform inversion of strong motion and teleseismic records from the arrival time of rupture tr to the time of the peak slip velocity tpv and we then corrected the slip obtained at tpv for the errors expected from the dynamic calculations it was found that the slip weakening dis tance d c estimated in the frequency window between 0 05 and 0 5 hz ranges between 40 and 90 cm on the two earthquake faults however if we consider the limited frequency resolution of the observed waveforms probable time errors in the slip velocity functions obtained from kinematic inversion and the uncertainty of the slip weakening behavior the above estimates may be those located between the minimum resolvable limit and the upper bound of their real values the estimated dc values do not necessarily seem to indicate larger values in the shallower part and smaller values in the deeper part of the fault but rather a spatially heterogeneous distribution that appears to be dependent on the local maximum slip this possible dependence might be interpreted by the frictional properties of the fault such as the degree of roughness or the thickness of gouge layers in addition to stress heterogeneities

performance of irikura recipe rupture model generator in earthquake ground motion simulations with graves and pitarka hybrid approach we analyzed the performance of the irikura and miyake pure and applied geophysics 168 2011 85 104 2011 im2011 asperity based kinematic rupture model generator as implemented in the hybrid broadband ground motion simulation methodology of graves and pitarka bulletin of the seismological society of america 100 5a 2095 2123 2010 for simulating ground motion from crustal earthquakes of intermediate size the primary objective of our study is to investigate the transportability of im2011 into the framework used by the southern california earthquake center broadband simulation platform in our analysis we performed broadband 0 20 hz ground motion simulations for a suite of m6 7 crustal scenario earthquakes in a hard rock seismic velocity structure using rupture models produced with both im2011 and the rupture generation method of graves and pitarka bulletin of the seismological society of america 2016 gp2016 the level of simulated ground motions for the two approaches compare favorably with median estimates obtained from the 2014 next generation attenuation west2 project nga west2 ground motion prediction equations gmpes over the frequency band 0 1 10 hz and for distances out to 22 km from the fault we also found that compared to gp2016 im2011 generates ground motion with larger variability particularly at near fault distances 1 s for this specific scenario the largest systematic difference in ground motion level for the two approaches occurs in the period band 1 3 s where the im2011 motions are about 20 30 lower than those for gp2016 we found that increasing the rupture speed by 20 on the asperities in im2011 produced ground motions in the 1 3 s bandwidth that are in much closer agreement with the gmpe medians and similar to those obtained with gp2016 the potential implications of this modification for other rupture mechanisms and magnitudes are not yet fully understood and this topic is the subject of ongoing study we concluded that im2011 rupture generator performs well in ground motion simulations using graves and pitarka hybrid method therefore we recommend it to be considered for inclusion into the framework used by the southern california earthquake center broadband simulation platform

scale model and numerical simulations of near fault seismic directivity foam rubber experiments simulating unilaterally propagating strike slip earthquakes provide a means to explore the sensitivity of near fault ground motions to rupture geometry subsurface accelerometers on the model fault plane show rupture propagation that approaches a limiting velocity close to the rayleigh velocity the slip velocity waveform at depth is cracklike slip duration of the order of narrower fault dimension w divided by s wave speed surface accelerometers record near fault ground motion enhanced along strike by rupture induced directivity most experimental features initiation time shape duration and absolute amplitude of acceleration pulses are successfully reproduced by a 3d spontaneous rupture numerical model of the experiments numerical and experimental model acceleration pulses show similar decay with distance away from the fault and fault normal components in both models show similar large amplitude growth with distance along fault strike this forward directivity effect is also evident in response spectra the fault normal spectral response peak at period w 3 increases approximately sixfold along strike on average in the experiments with similar increase about fivefold in the corresponding numerical simulation the experimental and numerical model response spectra agree with an empirical directivity model for natural earthquakes at long periods near w and both overpredict shorter period empirical directivity effects with the amount of overprediction increasing systematically with diminishing period we attribute this difference to rupture and wavefront incoherence in natural earthquakes due to fault zone heterogeneities in stress frictional resistance and elastic properties present in the earth but absent or minimal in the experimental and numerical models rupture front incoherence is an important component of source models for ground motion prediction but finding an effective kinematic parameterization may be challenging

heterogeneous distribution of the dynamic source parameters of the 1999 chi chi taiwan earthquake 1 the spatial and temporal distribution of the stress on the fault plane of the 1999 chi chi taiwan earthquake is calculated from kinematic inversion results using a three dimensional finite difference method for solving the elastodynamic equations we analyze the relations between stress and slip for all grid positions on the fault and use these relations to infer the friction law for the rupture the dynamic source parameters were also determined our results show that for most of the points on the fault the relation between stress and slip was consistent with the slip weakening law during the rupture process especially for those points with large slip however consistency with the velocity weakening law is not clear from the observed relation between stress and slip velocity the distributions of the dynamic parameters on the fault are very heterogeneous the peak value of the static stress drop is 35 mpa in general high stress drop occurred in the areas with large slip the estimated strength excesses are generally small suggesting that the tectonic shear stress had reached the level of the fault strength before the main shock the slip weakening distance dc and the fracture energy gc are proportional to the final slip the aftershock activity correlates with the spatial distribution of dynamic source parameters usually the aftershocks near the fault plane are concentrated in regions with small or negative static stress drop and there were few aftershocks in regions which had large values of critical slip weakening distance dc

spatial and temporal distribution of slip for the 1992 landers california earthquake we have determined a source rupture model for the 1992 landers earthquake m w 7 2 compatible with multiple data sets spanning a frequency range from zero to 0 5 hz geodetic survey displacements near field and regional strong motions broadband teleseismic waveforms and surface offset measurements have been used explicitly to constrain both the spatial and temporal slip variations along the model fault surface our fault parameterization involves a variable slip multiple segment finite fault model which treats the diverse data sets in a self consistent manner allowing them to be inverted both independently and in unison the high quality data available for the landers earthquake provide an unprecedented opportunity for direct comparison of rupture models determined from independent data sets that sample both a wide frequency range and a diverse spatial station orientation with respect to the earthquake slip and radiation pattern in all models consistent features include the following 1 similar overall dislocation patterns and amplitudes with seismic moments of 7 to 8 10 26 dyne cm seismic potency of 2 3 to 2 7 km 3 2 very heterogeneous unilateral strike slip distributed over a fault length of 65 km and over a width of at least 15 km though slip is limited to shallower regions in some areas 3 a total rupture duration of 24 sec and an average rupture velocity of 2 7 km sec and 4 substantial variations of slip with depth relative to measured surface offsets the extended rupture length and duration of the landers earthquake also allowed imaging of the propagating rupture front with better resolution than for those of prior shorter duration strike slip events our imaging allows visualization of the rupture evolution including local differences in slip durations and variations in rupture velocity rupture velocity decreases markedly at shallow depths as well as near regions of slip transfer from one fault segment to the next as rupture propagates northwestward along the multiply segmented fault length the rupture front slows as it reaches the northern limit of the johnson valley landers faults where slip is transferred to the southern homestead valley fault an abrupt acceleration is apparent following the transfer this process is repeated and is more pronounced as slip is again passed from the northern homestead valley fault to the emerson fault although the largest surface offsets were observed at the northern end of the rupture our modeling indicates that substantial rupture was also relatively shallow less than 10 km in this region

generation of new cracks accompanied by the dynamic shear rupture propagation of the 2000 tottori japan earthquake the 2000 tottori japan earthquake caused fracture zones of surface rupture at some places away from the trace of the main causative fault in order to explain this observation the 3d dynamic rupture process of the 2000 tottori japan earthquake was simulated the attractive feature of the problem under consideration is the possibility of introducing internal new cracks that propagate under tensile stress as a consequence of the dynamic process of shear slip propagation the discrete element method was used to solve this problem because it can introduce internal tensile cracks for the shear rupture propagation the simple slip weakening model was used as a friction law on the fault the new tensile cracks occur following the classical griffith theory when the critical value of tensile fracture surface energy has been reached the first step to solve the problem was the estimation of the dynamic parameters such as stress drop strength excess and critical slip which were recov ered from the results of waveform inversion in the second step a shear dynamic rupture process was simulated assuming that shear slip occurs only on the pre existing fault and the tensile stress concentration resulting from shear slip causes the new cracks that propagate away from the pre existing fault the results which are consistent with the observations show a free surface rupture caused by the new cracks and the development of a flowerlike structure springing from the borders of the pre existing fault and main asperity

dynamic rupture modelling of the 1999 duzce turkey earthquake the dynamic rupture process and near source ground motion of the 1999 mw 7 1 duzce earthquake are simulated the fault rupture is governed by the slip weakening friction model coupled to a three dimensional viscoelastic wave equation the problem is solved numerically by a 3 d dynamic rupture code that uses a generalized finite difference method initial parameterization of stress drop delta tau and strength excess s text e for dynamic rupture calculations is obtained from the slip velocity distribution of a kinematic waveform inversion ki model by solving the elastodynamic equation with the kinematic slip as a boundary condition using the kinematic slip distribution and observed ground motion as constraints a trial and error procedure was followed to define the stress parameterization preferred model describes the source in terms of stress with three asperities located respectively at the deep middle and shallow and strong barriers between asperities s text e is as high as 19 mpa at barriers between the three asperities and delta tau is maximum about 40 mpa at the deepest asperity this heterogeneity in stress distribution produces abrupt jumps in rupture velocity exhibiting locally apparent rupture speed exceeding the p wave velocity at the borders between barriers and asperities due to sharp changes of fault strength and stress drop at those areas overall consistent with other studies the rupture propagation is dominated by supershear speed toward the eastern asperities and at shallow surface simulated surface rupture at the eastern fault is consistent with other studies nevertheless the western shallower parts did not rupture during the simulation suggesting that those regions may have already broken during the 1999 kocaeli event which occurred three months earlier ground motion simulation catches the major characteristics of the observed waveforms distribution of simulated peak ground velocity pgv in low frequency 0 1 0 5 hz inside the study area reveals the propagation pattern on the field with pgv reaching to 1 2 and 2 2 m s in the ns and ew components respectively

estimation of radiated energy of finite source earthquake models we estimated seismically radiated energy for kinematic earthquake rupture models instead of integrating far field waveforms we used an expression for radiated energy with slip and stress on the fault plane using an analytic crack model of sato and hirasawa 1973 we show that the finite difference method can estimate the radiated energy fairly well however if the rupture propagation velocity is near the s wave velocity and the grid interval is coarse we may underestimate the radiated energy substantially we analyzed five models of three earthquakes of m w 5 7 for the 1995 kobe earthquake we used three different kinematic models and obtained consistent values of radiated energy of 2 4 3 6 1014 j there are common features among the three models 1 more efficient energy radiation from the deeper regions of the fault and 2 little energy radiation beneath the city of kobe the models of the kobe earthquake and the other two earthquakes show that energy radiation is concentrated near the hypocenter and the initiation point of asperities we also find the area of negative energy radiation energy absorption near the edge of large slipped areas although our estimates tend to be smaller by about a factor of 3 than previous estimates the difference is reasonable because the frequency range is not complete and we cannot deal with detailed rupture behavior such as rapid rupture acceleration and deceleration manuscript received 18 january 2002

earthquakes on dipping faults the effects of broken symmetry dynamic simulations of earthquakes on dipping faults show asymmetric near source ground motion caused by the asymmetric geometry of such faults the ground motion from a thrust or reverse fault is larger than that of a normal fault by a factor of 2 or more given identical initial stress magnitudes the motion of the hanging wall is larger than that of the footwall in both thrust reverse and normal earthquakes the asymmetry between normal and thrust reverse faults results from time dependent normal stress caused by the interaction of the earthquake generated stress field with earth s free surface the asymmetry between hanging wall and footwall results from the asymmetric mass and geometry on the two sides of the fault

testing long period ground motion simulations of scenario earthquakes using the mw 7 2 el mayor cucapah mainshock evaluation of finite fault rupture characterization and 3d seismic velocity models using a suite of five hypothetical finite fault rupture models we test the ability of long period t 2 0 s ground motion simulations of scenario earthquakes to produce waveforms throughout southern california consistent with those recorded during the 4 april 2010 m w 7 2 el mayor cucapah earthquake the hypothetical ruptures are generated using the methodology proposed by graves and pitarka 2010 and require as inputs only a general description of the fault location and geometry event magnitude and hypocenter as would be done for a scenario event for each rupture model two southern california earthquake center three dimensional community seismic velocity models cvm 4m and cvm h62 are used resulting in a total of 10 ground motion simulations which we compare with recorded ground motions while the details of the motions vary across the simulations the median levels match the observed peak ground velocities reasonably well with the standard deviation of the residuals generally within 50 of the median simulations with the cvm 4m model yield somewhat lower variance than those with the cvm h62 model both models tend to overpredict motions in the san diego region and underpredict motions in the mojave desert within the greater los angeles basin the cvm 4m model generally matches the level of observed motions whereas the cvm h62 model tends to overpredict the motions particularly in the southern portion of the basin the variance in the peak velocity residuals is lowest for a rupture that has significant shallow slip 5 km depth whereas the variance in the residuals is greatest for ruptures with large asperities below 10 km depth overall these results are encouraging and provide confidence in the predictive capabilities of the simulation methodology while also suggesting some regions in which the seismic velocity models may need improvement

dynamic shear rupture interactions with fault bends and off axis secondary faulting 1 on the basis of elastodynamic stress fields for singular crack and nonsingular slip weakening models of propagating rupture we develop preliminary answers to such questions as follows if a rupturing fault is intersected by another providing a possible bend in the failure path when will stressing be consistent with rupture along the bend what secondary fault locations and orientations in a damaged region bordering a major fault will be stressed to failure by the main rupture stresses that could initiate rupture on a bend are shown to increase dramatically with crack speed especially near the limiting speed rayleigh for mode ii shear for mode iii whether a bend path once begun can be continued to larger scales depends on principal stress directions and ratios in the prestress field conditions should often be met in mode ii for which bend paths encouraged by stressing very near the rupture tip are discouraged by the larger scale stressing a basis for intermittent rupture propagation and spontaneous arrest secondary failure in the damage zone likewise increases markedly as the limiting speed is approached such may make the fracture energy much greater than for slip on a single surface the extent of secondary faulting is strongly affected by prestress directions and the ratio of residual to peak strength for mode ii prestress controls whether activation occurs primarily on the extensional side which we show to be the typical case or on the compressional side too natural examples are consistent with the concepts developed

can observations of earthquake scaling constrain slip weakening summary we use observations of earthquake source parameters over a wide magnitude range m w 0 7 to place constraints on constitutive fault weakening the data suggest a scale dependence of apparent stress and stress drop both may increase slightly with earthquake size we show that this scale dependence need not imply any difference in fault zone properties for different sized earthquakes we select 30 earthquakes well recorded at 2 5 km depth at cajon pass california we use individual and empirical green s function spectral analysis to improve the resolution of source parameters including static stress drop and total slip s we also measure radiated energy e s w ecompare the cajon pass results with those from larger california earthquakes including aftershocks of the 1994 northridge earthquake and confirm the results of abercrombie 1995 e s m 0 where rigidity and both e s m 0 and increase as m 0 and s increases uncertainties remain large due to model assumptions and variations between possible models and earthquake scale independence is possible within the resolution assuming that the average trends are real we define a quantity g 2 es m 0 s 2w hich is the total energy dissipation in friction and fracture minus 1 s w here 1 is the final static stress if 1 d the dynamic shear strength during the last increments of seismic slip then g g the fracture energy in a slip weakening interpretation of dissipation

determination of constitutive relations of fault slip based on seismic wave analysis constitutive laws define the boundary conditions on fault plane and govern many aspects of earthquake failure although several constitutive laws have been formulated based on laboratory rock experiments and applied to theoretical studies in various fields no actual relation during a natural earthquake has been determined the 1995 kobe earthquake is suitable for detailed kinematic analysis and this enables the first evaluation of constitutive relations for a natural earthquake in this study we determine spatiotemporal slip distribution on an assumed fault plane of the 1995 kobe earthquake by waveform inversion and then solve elastodynamic equations using a finite difference method to determine the stress distribution and constitutive relations on the fault plane an inversion method based on bayes theorem is employed to obtain a spatiotemporal slip distribution and enables us to ensure the objective uniqueness of the solution with numerous parameters and smoothing constraints this slip distribution is then used as part of the boundary condition in the finite difference calculation the time histories of slip and shear stress obtained then provide a constitutive relation at each point on the fault plane they show slip weakening relations almost everywhere on the fault plane while slip rate dependency is not clear the slip weakening behavior has a clear depth dependency indicating that the slip weakening rate d du is smaller in the shallow crust than that in the deep crust this may be associated with the paucity of shallow seismicity observed in the source region of this earthquake as reported for many mature fault systems

spatial variation of seismogenic depths of crustal earthquakes in the taiwan region implications for seismic hazard assessment abstract this paper presents the first whole taiwan scale spatial variation of the seismogenic zone using a high quality crustal seismicity catalog the seismicity onset and cutoff depths i e seismogenic depths are determined by the earthquake depth moment distribution and used to define the upper and lower boundaries of the seismogenic zone respectively together with the published fault geometries and fault area moment magnitude relations the depth difference in the onset and cutoff depths i e seismogenic thickness is used as the fault width to determine the moment magnitudes of potential earthquakes for the major seismogenic faults results show that the largest mw7 9 8 0 potential earthquake may occur along the changhua fault in western taiwan where the seismic risk is relatively high and seismic hazard mitigation should be a matter of urgent concern in addition the first motion focal mechanism catalog is used to examine the relation between the seismogenic depths and earthquake source parameters for crustal earthquakes 50 km the shallowest onset and cutoff depths are observed for normal and strike slip events respectively this observation is different from the prediction of the conventional continental rheology model which states that thrust events have the shallowest cutoff depth thus a more sophisticated rheology model is necessary to explain our observed dependence of the seismogenic depths on faulting types meanwhile for intermediate to large crustal mw 4 depth 50 km earthquakes thrust events tend to occur at the bottom region of the seismogenic zone but normal and strike slip events distribute at a large depth range

earthquake fracture energy inferred from kinematic rupture models on extended faults 1 we estimate fracture energy on extended faults for several recent earthquakes by retrieving dynamic traction evolution at each point on the fault plane from slip history imaged by inverting ground motion waveforms we define the breakdown work wb as the excess of work over some minimum traction level achieved during slip wb is equivalent to seismological fracture energy g in previous investigations our numerical approach uses slip velocity as a boundary condition on the fault we employ a three dimensional finite difference algorithm to compute the dynamic traction evolution in the time domain during the earthquake rupture we estimate wb by calculating the scalar product between dynamic traction and slip velocity vectors this approach does not require specifying a constitutive law and assuming dynamic traction to be collinear with slip velocity if these vectors are not collinear the inferred breakdown work depends on the initial traction level we show that breakdown work depends on the square of slip the spatial distribution of breakdown work in a single earthquake is strongly correlated with the slip distribution breakdown work density and its integral over the fault breakdown energy scale with seismic moment according to a power law with exponent 0 59 and 1 18 respectively our estimates of breakdown work range between 4 105 and 2 107 j m2 for earthquakes having moment magnitudes between 5 6 and 7 2 we also compare our inferred values with geologic surface energies this comparison might suggest that breakdown work for large earthquakes goes primarily into heat production

characterization of stress drops on asperities estimated from the heterogeneous kinematic slip model for strong motion prediction for inland crustal earthquakes in japan dense strong motion observation networks provided us with valuable data for studying strong motion generation from large earthquakes from kinematic waveform inversion of seismic data the slip distribution on the fault surface of large earthquakes is known to be spatially heterogeneous because heterogeneities in the slip and stress drop distributions control the generation of near source ground motion it is important to characterize these heterogeneities for past earthquakes in constructing a source model for reliable prediction of strong ground motion the stress changes during large earthquakes on the faults recently occurring in japan are estimated from the detailed slip models obtained by the kinematic waveform inversion the stress drops on and off asperities are summarized on the basis of the stress change distributions obtained here in this paper we define the asperity to be a rectangular area whose slip is 1 5 or more times larger than the average slip over the fault according to the previous study for inland crustal earthquakes the average static stress drops on the asperities of the earthquakes studied here are in the range 6 23 mpa whereas those off the asperities are below 3 mpa we compiled the stress drop on the asperities together with a data set from previous studies of other inland earthquakes in japan and elsewhere the static stress drop on the asperity depends on its depth and we obtained an empirical relationship between the static stress drop and the asperity s depth moreover surface breaking asperities seemed to have smaller stress drops than buried asperities simple ground motion simulations using the characterized asperity source models reveal that deep asperities generate larger ground motion than shallow asperities because of the different stress drops of the asperities these characteristics can be used for advanced source modeling in strong ground motion prediction for inland crustal earthquakes

rupture process of the 1999 kocaeli turkey earthquake estimated from strong motion waveforms the multiple time window linear waveform inversion is applied to study the source process of the 1999 kocaeli turkey earthquake using strong motion data two peculiar observations characterize this event the first one is a conflicting observation of the long surface ruptures and short source duration resulting from the observed strong motion waveforms the second is an anomalously short s p time observed at a station skr considering its hypocentral distance a supershear rupture propagation ellsworth and celebi 1999 and the p wave triggering of an asperity anderson et al 2000 were both proposed to explain the record at skr our waveform inversion study is aimed to examine these possibilities in order to clarify the relation between the spatial distribution of the surface ruptures and coseismic slips we divide the assumed fault plane into three parts and look for the first time window front propagation velocity propagation velocity of triggering front of the first time window at each subfault in each part by performing numerous inversions changing the first time window front propagation velocity separately in each part and selecting the best first time window propagation velocities that give largest variance reduction at the same time appropriate smoothness of spatiotemporal slip distribution is searched for by performing inversions with different strength of smoothing constraints against the observational equations and judging the relative appropriateness of inversion results in terms of the akaike s bayesian information criterion the best source model is characterized by an asperity that is about 35 km east of the epicenter and near a segment boundary at sapanca lake triggered by the first time window front with 5 8 km sec close to p wave velocity the time progression of the rupture suggests a scenario where a p wave arriving from the hypocenter or somewhere around the hypocenter triggered the second largest asperity near the junction of the segments at sapanca lake which is a preferable interpretation the first time window propagation velocities west of the hypocenter and east of skr are expected to be 3 0 km sec manuscript received 20 august 2000

three dimensional finite difference simulation of fault dynamics rectangular faults with fixed rupture velocity we analyze three dimensional finite difference solutions for a simple shear crack model of faulting to determine the effects of fault length and width on the earthquake slip function the fault model is dynamic with only rupture velocity fault dimensions and dynamic stress drop prescribed the numerical solutions are accurate for frequencies up to 5 hz and are combined with asymptotic results for shear cracks in order to characterize the slip function at higher frequencies near the hypocenter the slip velocity exhibits a square root singularity whose intensity increases with hypocentral distance at distances greater than the fault width w growth of the velocity intensity ceases and the slip function becomes nearly invariant with distance along the fault length closed form expressions are developed for the dependence of static slip s slip rise time tr and slip velocity intensity v on fault geometry along the center line of a long narrow fault at hypocentral distances exceeding w these expressions reduce to s w tr 0 5 w vr and v w 2 vr where is the dynamic stress drop the shear modulus and vr the rupture velocity the numerical results imply that uniform dislocation kinematic earthquake models in which slip is represented by a ramp time function will underpredict high frequency ground motion relative to low frequency ground motion a further implication of the numerical solutions is that the nature of inelastic processes at the advancing edge of a long fault will depend on fault width but will be independent of rupture length

numerical study of ground motion differences between buried rupturing and surface rupturing earthquakes recent ground motion observations suggest that surface rupturing earth quakes generate weaker near fault ground motion than buried earthquakes this dif ference is significant in the period range of 0 3 3 sec contributing factors to this phenomenon may include the effect of fault zone weakness at shallow depth on rup ture dynamics and rupture directivity during earthquakes we present results from numerical experiments of spontaneous dynamic rupture and near source ground motion simulations of surface rupturing and buried earth quakes and discuss mechanisms for the observed ground motion differences the surface rupturing earthquake is modeled with a shallow zone of 5 km thickness con taining areas of negative stress drop within the framework of the slip weakening fric tion model and lower rigidity surface rupturing models with this weak zone generate lower amplitude ground velocity than do models without this modification observed ground motion differences between surface and buried events are qual itatively reproduced by imposing higher stress drop in the buried earthquakes than in the surface earthquakes combined with introducing a deeper rupture initiation for buried rupture enhancing upward rupture directivity effects for the latter events in the context of our simplified model parameterization then the observed differences in ground motion could arise from combined effects of relative weakness of the shal low layer of faults the relatively larger stress drops of buried ruptures and a tendency of near fault sites to record strong upward directivity from buried ruptures