inverse kinematic and forward dynamic models of the 2002 denali fault earthquake alaska we perform inverse kinematic and forward dynamic models of the m 7 9 2002 denali fault alaska earthquake to shed light on the rupture process and dynamics of this event which took place on a geometrically complex fault system in central alaska we use a combination of local seismic and global positioning system gps data for our kinematic inversion and find that the slip distribution of this event is characterized by three major asperities on the denali fault the rupture nucleated on the susitna glacier thrust fault and after a pause propagated onto the strike slip denali fault approximately 216 km to the east the rupture abandoned the denali fault in favor of the more southwesterly directed totschunda fault three dimensional dynamic models of this event indicate that the abandonment of the denali fault for the totschunda fault can be explained by the totschunda fault s more favorable orientation with respect to the local stress field however a uniform tectonic stress field cannot explain the complex slip pattern in this event we also find that our dynamic models predict discontinuous rupture from the denali to totschunda fault segments such discontinuous rupture helps to qualitatively improve our kinematic inverse models two principal implications of our study are 1 a combination of inverse and forward modeling can bring insight into earthquake processes that are not possible with either technique alone and 2 the stress field on geometrically complex fault systems is most likely not due to a uniform tectonic stress field that is resolved onto fault segments of different orientations rather other forms of stress heterogeneity must be invoked to explain the observed slip patterns

influence of focal mechanism in probabilistic seismic hazard analysis an extension of probabilistic seismic hazard analysis is proposed to introduce a priori information about seismic source parameters in particular faulting style is taken into account with a theoretical corrective coefficient applied to the attenuation law the validity of this correction is assessed through a comparison with observed data attenuation law predictions corrected and not corrected and the results of attenuation laws containing faulting style parameters the probabilistic nature of the analysis is maintained introducing into the classical hazard formulation a 2d probability density function describing the most probable focal mechanisms associated with each seismic source zone this new expression may also be used in the framework of deaggregation analysis thus the design earthquake resulting from the deaggregation is characterized by a focal mechanism an application to a site located in the southern apennines italy is shown the result of the analysis emphasizes the importance of strike slip events in the seismic hazard context compared with normal faulting seismic activity in this region

an integrated geophysical investigation of the upper crust in the epicentral area of the 1980 ms 6 9 irpinia earthquake southern italy in this paper we investigate the upper crustal structure of the irpinia region southern apennines thrust belt italy through analysis and joint interpretation of gravity data seismic reflection lines and subsurface information from many deep wells the investigated region includes the epicentral area of the 1980 ms 6 9 irpinia earthquake and is one of the italian regions with the highest seismic hazard the upper crustal structure is imaged by modeling a series of 15 sw trending gravity profiles spaced about 5 km apart plentifully constrained by seismic reflection lines and wells thus reducing the inherent ambiguity of the gravity modeling despite of the complexity of the modeled bouguer anomalies the application of a calibrating procedure to constrain the range of variability of the density values as well as the use of geometric constraints results in a good level of stability in the final density cross sections which in fact appear coherent both in the density values and in the geometrical features the inferred model shows important lateral density variations that can be mostly related to nw trending geologic structures high density bodies delineate carbonate platform thrust sheets and broad antiforms involving mesozoic basinal rocks while low density shallow bodies are associated with pliocene basins in addition important density i e lithological variations are evident along the strike of the range the most relevant being an abrupt deepening of the apulia carbonate platform in the southeastern part of the investigated region in the epicentral region of the 1980 event we find that the geometry of the high density high velocity carbonates of the apulia platform appears correlated with the distribution of the aftershocks and with the p wave velocity anomaly pattern as inferred from a previous local earthquake tomography the structural highs of the apulia platform correspond to high velocity regions where aftershocks and coseismic slip of the mainshock are concentrated this correlation suggests that the apulia carbonate platform geometry played an important role in the rupture propagation and in the aftershock distribution

parkfield earthquakes characteristic or complementary we model the two most recent mw 6 parkfield california earthquakes which occurred in 1966 and 2004 from a nonlinear global inversion of near fault strong motion seismograms our rupture models are characterized by spatially variable slip amplitude and rake rupture velocity and risetime the rupture models indicate that the two earthquakes generated slip in regions of the fault that are not identical as earlier suggested given the sparse seismic data set available for the 1966 earthquake we conduct a series of tests to verify our results 1 we perform synthetic tests in order to study the resolution of the 1966 seismic data set 2 we perform an inversion of the 2004 earthquake using a data set equivalent to the 1966 earthquake and 3 we model the 1966 data set under the a priori assumption that it was similar to the 2004 earthquake all of the tests as well as independent observations indicate that slip during the 1966 and 2004 parkfield earthquakes occurred in different regions of the fault this result implies that regions of a fault that are frictionally locked may remain locked even during a main shock moderate size earthquake in this scenario large earthquakes occur when all the locked regions of a fault are synchronized and ready to slip at the same time

the dependence of traction evolution on the earthquake source time function adopted in kinematic rupture models 1 we compute the temporal evolution of traction by solving the elasto dynamic equation and by using the slip velocity history as a boundary condition on the fault plane we use different source time functions to derive a suite of kinematic source models to image the spatial distribution of dynamic and breakdown stress drop strength excess and critical slip weakening distance d c our results show that the source time functions adopted in kinematic source models affect the inferred dynamic parameters the critical slip weakening distance characterizing the constitutive relation ranges between 30 and 80 of the total slip the ratio between d c and total slip depends on the adopted source time functions and in these applications is nearly constant over the fault we propose that source time functions compatible with earthquake dynamics should be used to inter the traction time history

sensitivity of ground motion simulations to earthquake source parameters a case study for istanbul turkey following the disastrous earthquakes in izmit and duzce along the north anatolian fault in 1999 the earthquake hazard in the istanbul area became a great concern in this study we simulate strong ground motions caused by a scenario earthquake m 7 5 in the marmara sea and investigate the effect of varying the input parameters on the broadband frequency ground motion simulations are based on a multiasperity source model that involves the combined rupture of the north anatolian fault segments beneath the marmara sea we use a hybrid model combin ing a deterministic simulation of the low frequencies 0 1 1 0 hz with a semisto chastic simulation of the high frequencies 1 0 10 0 hz computation at each fre quency range is performed separately and the total ground motion is combined in the time domain computations are linear and are performed at bedrock level thereby not taking any effect of local geological conditions into account we calculate a total of 17 earthquake scenarios corresponding to different source and attenuation param eters to study their effect on the ground motion the most significant parameters in terms of ground shaking level are the rise time rupture velocity rupture initiation point and stress drop the largest variability of strong ground motions is observed in regions adjacent to asperities and is associated with frequencies higher than 5 hz for lower frequencies our simulated velocity spectra within the istanbul area are fairly stable among scenarios the average standard deviations of all ground motion measures are less than 35 of the mean online material figures of peak ground acceleration and peak ground velocity and their differences to the reference scenario values

variability of near field ground motion from dynamic earthquake rupture simulations this study investigates near field ground motion variability due to dynamic rupture models with heterogeneity in the initial shear stress ground velocity seismograms are synthesized by convolving the time histories of slip velocity obtained from spontaneous dynamic rupture models with green s functions of the medium calculated with a discrete wavenumber finite element method peak ground velocity pgv estimated on the synthetics generally matches well with an empirically derived attenuation relation whereas spectral acceleration sa shows only an acceptable match at periods longer than 1 sec using the geometric mean to average the two orthogonal components leads to a systematic bias for the synthetics in particular at the stations closest to the fault this bias is avoided by using measures of ground motion that are independent of the sensor orientation the contribution from stress heterogeneity to the overall ground motion variability is found to be strongest close to the fault and in the backward directivity region of unilaterally propagating ruptures in general the intraevent variability originating from the radiation pattern and the effect of directivity is on the same order or larger than the interevent variability the interevent ground motion variability itself is dominated by the hypocenter station configuration and is influenced only to a lesser extent by the differences in the dynamic rupture process due to the stress heterogeneity in our modeling approach the hypocenter location is not picked arbitrarily but is determined to be mechanically consistent with the stress heterogeneity through a procedure emulating tectonic stress loading of the fault and nucleation compared to the peak ground motion recorded during the 2004 parkfield california earthquake our simulated seismograms show enhanced spatial correlation that may be attributed to the simplicity of the assumed crustal model or to an incomplete representation of the spatial heterogeneity of dynamic rupture parameters nevertheless the intraevent pgv variability in the near fault region determined for the parkfield dataset is of the same order of magnitude as for our simulations

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

rupture model of the 1999 duzce turkey earthquake deduced from high and low frequency strong motion data 1 we investigated the rupture process of the 1999 duzce earthquake by applying the multi time window linear waveform inversion method to low frequency ground motions 0 5 hz in the near source area then we performed theforwardmodellingofhigherfrequencyground motions 0 3 10 0 hz by the empirical green s function egf method to image the strong motion generation area smga we also examined the source model to check whether the supershear phenomenon occurred inside the asperities or not slip distribution model from the inversion suggests 2 asperities the maximum slip is obtained as 5 m near the hypocenter the high first time window front propagation velocity ftwfpv and consequently high apparent rupture velocity found from the investigation of rupture progression indicated that eastern propagation partially showed supershear behaviour the egf simulation which identifies an average rupture velocity vr in smga supports this finding index terms 7212 seismology earthquake ground motions and engineering 7215 seismology earthquake parameters 7223 seismology seismic hazard assessment and prediction citation birgoren g h sekiguchi and k irikura 2004 rupture model of the 1999 duzce turkey earthquake deduced from high and low frequency strong motion data geophys res lett 31 l05610 doi 10 1029 2003gl019194

deterministic ground motion scenarios for engineering applications the case of thessaloniki greece abstract in this article we present a deterministic study to estimate seismic ground motions expected in urban areas located near active faults the purpose was to generate bedrock synthetic time series to be used as seismic input into site effects evaluation analysis and loss estimates for the urban area and infrastructures of thessaloniki northern greece two simulation techniques a full wave method to generate low frequency seismograms 1 hz were used to compute time series associated with four different reference earthquakes having magnitudes from 5 9 to 6 5 and located within 30 km of thessaloniki the propagation medium and different source parameters were tested through the modeling of the 1978 thessaloniki earthquake m 6 5 moreover two different nucleation points were considered for each fault in order to introduce additional variability in the ground motion estimates between the two cases the quasi unilateral rupture propagation toward the city produces both higher median peak ground acceleration pga and peak ground velocity pgv values and higher variability than bilateral ones conversely the low frequency ground motion that is peak ground displacement pgd is slightly influenced by the position of the nucleation point and its variability is related to the final slip distribution on the faults of the reference earthquakes and to the location of the sites with respect to the nodal planes of the radiation pattern to validate our deterministic shaking scenarios we verified that the synthetic peak ground motions pga and pgv and spectral ordinates are within one standard deviation of several ground motion prediction equations valid for the region at specific sites we combined the low and high frequency synthetics to obtain broadband time series that cover the entire frequency band of engineering interest 0 25 hz the use of synthetic seismograms instead of empirical equations in the hazard estimates provides a complete evaluation of the expected ground motions both in frequency and time domains including predictions at short distances from the fault 0 10 km and at periods larger than 2 3 sec

variability of kinematic source parameters and its implication on the choice of the design scenario abstract near fault seismic recordings for recent earthquakes chi chi earthquake 1999 and parkfield earthquake 2004 show the high spatial heterogeneity of ground motion this variability is controlled by fault geometry rupture complexity and also by wave propagation and site effects nowadays the number of available records in the near source region is still not enough to infer a robust parameterization of the ground motion and to retrieve multiparametric predictive equations valid at close distances from the fault the use of a synthetic approach may help to overcome this limitation and to study the strong ground motion variability in this article we focus on ground motion dependence on different earthquakes breaking the same fault as it has been rarely recorded by instruments we model seismic scenarios from different rupture models of a fault similar to the 1980 irpinia italy earthquake source m w 6 9 a discrete wavenumber finite element technique is used to compute full wave displacement and velocity time series in the low frequency band up to 2 hz we investigate the variability of the ground motion as a function of different source parameters rupture velocity slip distribution nucleation point and source time function whose values depend on the state of knowledge of the physical model driving the process the probability density functions of the simulated ground motion parameters such as displacement response spectrum and peak ground velocity are used to identify particular scenarios that match specific engineering requests

source related variations of ground motions in 3 d media application to the newport inglewood fault los angeles basin summary deterministic earthquake scenario simulations are playing an increasingly important role in seismic hazard and risk estimation our aim is to calculate a substantial number of different finite source scenarios embedded in a 3 d structure for a particular fault or fault system by pre calculating numerical green s functions ngfs a large seismic fault is divided into subfaults of appropriate size for which synthetic green s functions at the surface are calculated and stored consequently ground motions from arbitrary kinematic sources can be simulated for the whole fault or parts of it by superposition to illustrate this approach and its functionalities we simulate m 7 up to 0 5 hz scenario earthquakes for a simplified model of the newport inglewood ni fault in the los angeles la basin we quantify the variations of surface ground motion e g peak ground velocity pgv and synthetic seismograms due to source parameters e g hypocentre location and corresponding slip history the results show a complex behaviour with dependence of absolute pgv and its variation on asperity location source directionality and local structure and demonstrate the necessity to combine 3 d structural and finite source effects to quantify ground motion characteristics and their variations

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

crustal scale duplexing beneath the yarlung zangbo suture in the western himalaya the fate of the indian plate during collision with asia is debated seismic images of the western himalaya reveal large scale thrust faults that transfer indian crust upwards into the overriding asian plate

slip accumulation and lateral propagation of active normal faults in afar we investigate fault growth in afar where normal fault systems are known to be currently growing fast and most are propagating to the northwest using digital elevation models we have examined the cumulative slip distribution along 255 faults with lengths ranging from 0 3 to 60 km faults exhibiting the elliptical or bell shaped slip profiles predicted by simple linear elastic fracture mechanics or elastic plastic theories are rare most slip profiles are roughly linear for more than half of their length with overall slopes always 0 035 for the dominant population of nw striking faults and fault systems longer than 2 km the slip profiles are asymmetric with slip being maximum near the eastern ends of the profiles where it drops abruptly to zero whereas slip decreases roughly linearly and tapers in the direction of overall aden rift propagation at a more detailed level most faults appear to be composed of distinct shorter subfaults or segments whose slip profiles while different from one to the next combine to produce the roughly linear overall slip decrease along the entire fault on a larger scale faults cluster into kinematically coupled systems along which the slip on any scale individual fault or fault system complements that of its neighbors so that the total slip of the whole system is roughly linearly related to its length with an average slope again 0 035 we discuss the origin of these quasilinear asymmetric profiles in terms of initiation points where slip starts and barriers where fault propagation is arrested in the absence of a barrier slip apparently extends with a roughly linear profile tapered in the direction of fault propagation

linearized inversion for fault rupture behavior application to the 1984 morgan hill california earthquake we present a technique to infer the rupture history of an earthquake from near source records of ground motion unlike most previous studies each point on the fault is assumed to slip only once when the rupture front passes with a spatially variable slip intensity in this parameterization the data are linearly related to slip intensity but nonlinearly related to rupture time we perform a linearized inversion for slip intensity and rupture time by iteratively perturbing an assumed starting model the inverse problem for the model perturbation is solved using a tomographic back projection technique smoothing and inequality constraints are applied to ensure that the resulting solution is stable and feasible asymptotic ray theory is used to calculate theoretical seismograms and partial derivatives with respect to model parameters in test cases with noisy synthetic data sets we found that it is possible to distinguish between rupture models having variable slip amplitude and models having variable rupture velocity provided the station coverage is adequate we apply the technique to recordings of the april 24 1984 morgan hill earthquake the results indicate that slip amplitude on the fault plane was extremely variable and that the rupture front did not propagate uniformly away from the hypocenter in particular rupture was delayed on a 12 km2 section of the fault approximately 14 km to the southeast of the hypocenter the rupture front surrounded the region which subsequently failed with a component of rupture propagation back toward the hypocenter similar behavior has been observed in dynamic rupture models with stress or strength inhomogeneities this segment of the fault ruptured with a large slip amplitude releasing 12 of the total seismic moment from 4 of the total area of the aftershock zone the surface trace of this section of the fault is characterized by a complex left step that could act to increase the normal stress acting across the fault however the distribution of aftershocks suggests that the fault at depth is simpler and that it may bend to the right in either case our rupture model suggests that this segment of the fault represents an asperity which initially resisted rupture but eventually ruptured massively we estimate the shear fracture energy for this earthquake to be 2 106 j m2

introduction to the special issue on the 2004 parkfield earthquake and the parkfield earthquake prediction experiment the 28 september 2004 m 6 0 parkfield earthquake a long anticipated event on the san andreas fault is the world s best recorded earthquake to date with state of the art data obtained from geologic geodetic seismic magnetic and electrical field networks this has allowed the preearthquake and postearthquake states of the san andreas fault in this region to be analyzed in detail analyses of these data provide views into the san andreas fault that show a complex geologic history fault geometry rheology and response of the nearby region to the earthquake induced ground movement although aspects of san andreas fault zone behavior in the parkfield region can be modeled simply over geological time frames the parkfield earthquake prediction experiment and the 2004 parkfield earthquake indicate that predicting the fine details of future earthquakes is still a challenge instead of a deterministic approach forecasting future damaging behavior such as that caused by strong ground motions will likely continue to require probabilistic methods however the parkfield earthquake prediction experiment and the 2004 parkfield earthquake have provided ample data to understand most of what did occur in 2004 culminating in significant scientific advances

dependence of slip weakening distance dc on final slip during dynamic rupture of earthquakes summary in this study we aim to understand the dependence of the critical slip weakening distance d c on the final slip d tot during the propagation of a dynamic rupture and the consistency of their inferred correlation to achieve this goal we have performed a series of numerical tests suitably designed to validate the adopted numerical procedure and to verify the actual capability in measuring d c we have retrieved two kinematic rupture histories from spontaneous dynamic rupture models governed by a slip weakening law in which a constant d c distribution on the fault plane as well as a constant d c d tot ratio are assumed respectively the slip velocity and the shear traction time histories represent the synthetic real target data which we aim to reproduce we use a 3 d traction at split nodes numerical procedure to image the dynamic traction evolution by assuming our modelled slip velocity as a boundary condition on the fault plane we assume a regularized yoffe function as source time function in our modelling attempts and we measure the critical slip weakening distance from the inferred traction versus slip curves at each point on the fault we compare the inferred values with those of the target dynamic models our numerical tests show that fitting the slip velocity functions of the target models at each point on the fault plane is not enough to retrieve good traction evolution curves and to obtain reliable measures of d c we find that the estimation of d c is very sensitive to any small variation of the slip velocity function an artificial correlation between d c d tot is obtained when a fixed shape of slip velocity is assumed on the fault i e constant rise time and constant time for positive acceleration which differs from that of the target model we point out that the estimation of fracture energy breakdown work on the fault is not affected by biases in measuring d c

a composite source model for computing realistic synthetic strong ground motions a composite source model is presented for convolution with synthetic green s functions in order to synthesize strong ground motions due to a complex rupture process of a large earthquake subevents with a power law distribution of sizes are located randomly on the fault each subevent radiates a displacement pulse with the shape of a brune s pulse in the far field at a time determined by a constant rupture velocity propagating from the hypocenter thus all the input parameters have a physical basis we simulate strong ground motions for event station pairs that correspond to records obtained in mexico by the guerrero accelerograph network the synthetic accelerations velocities and displacements have realistic amplitudes durations and fourier spectra

seismic hazard assessment for a characteristic earthquake scenario an integrated probabilistic deterministic method probabilistic seismic hazard analysis psha is classically performed through the cornell approach by using a uniform earthquake distribution over the source area and a given magnitude range this study aims at extending the psha approach to the case of a characteristic earthquake scenario associated with an active fault the approach integrates psha with a high frequency deterministic technique for the prediction of peak and spectral ground motion parameters in a characteristic earthquake the method is based on the site dependent evaluation of the probability of exceedance for the chosen strong motion parameter the latter is obtained from the statistical analysis of the synthetic waveform database produced for a large number of possible rupture histories occurring on the characteristic earthquake fault the method has been applied to a hazard evaluation in the umbria region where the threat is represented by a fault having the same geometry and mechanism as the 26 september 1997 colfiorito earthquake central italy moment magnitude m w 6

evidence for and implications of self healing pulses of slip in earthquake rupture dislocation time histories of models derived from waveforms of seven earthquakes are discussed in each model dislocation rise times the duration of slip for a given point on the fault are found to be short compared to the overall duration of the earthquake 10 however in many crack like numerical models of dynamic rupture the slip duration at a given point is comparable to the overall duration of the rupture i e slip at a given point continues until information is received that the rupture has stopped propagating alternative explanations for the discrepancy between the short slip durations used to model waveforms and the long slip durations inferred from dynamic crack models are 1 the dislocation models are unable to resolve the relatively slow parts of earthquake slip and have seriously underestimated the dislocations for these earthquakes 2 earthquakes are composed of a sequence of small dimension short duration events that are separated by locked regions barriers 3 rupture occurs in a narrow self healing pulse of slip that travels along the fault surface evidence is discussed that suggests that slip durations are indeed short and that the self healing slip pulse model is the most appropriate explanation a qualitative model is presented that produces self healing slip pulses the key feature of the model is the assumption that friction on the fault surface is inversely related to the local slip velocity the model has the following features high static strength of materials kilobar range low static stress drops in the range of tens of bars and relatively low frictional stress during slip less than several hundreds of bars it is suggested that the reason that the average dislocation scales with fault length is because large amplitude slip pulses are difficult to stop and hence tend to propagate large distances this model may explain why seismicity and ambient stress are low along fault segments that have experienced large earthquakes it also qualitatively explains why the recurrence time for large earthquakes may be irregular

effects of supershear rupture speed on the high frequency content of s waves investigated using spontaneous dynamic rupture models and isochrone theory 1 in this paper we achieve three goals 1 we demonstrate that crack tips governed by friction laws including slip weakening rate and state dependent laws and thermal pressurization of pore fluids propagating at supershear speed have slip velocity functions with reduced high frequency content compared to crack tips traveling at subshear speeds this is demonstrated using a fully dynamic spontaneous three dimensional earthquake model in which we calculate fault slip velocity at nine points locations distributed along a quarter circle on the fault where the rupture is traveling at supershear speed in the in plane direction and subshear speed in the antiplane direction this holds for a fault governed by the linear slip weakening constitutive equation by slip weakening with thermal pressurization of pore fluid and by rate and state dependent laws with thermal pressurization the same is also true even assuming a highly heterogeneous initial shear stress field on the fault 2 using isochrone theory we derive a general expression for the spectral characteristics and geometric spreading of two pulses arising from supershear rupture the well known mach wave and a second lesser known pulse caused by rupture acceleration 3 we demonstrate that the mach cone amplification of high frequencies overwhelms the de amplification of high frequency content in the slip velocity functions in supershear ruptures consequently when earthquake ruptures travel at supershear speed a net enhancement of high frequency radiation is expected and the alleged low peak accelerations observed for the 2002 denali and other large earthquakes are probably not caused by diminished high frequency content in the slip velocity function as has been speculated

a new nonlinear finite fault inversion with three dimensional green s functions application to the 1989 loma prieta california earthquake 1 we present a new procedure to invert for kinematic source parameters on a finite fault on the basis of the reciprocity relation of the green s functions we use a newly developed fourth order viscoelastic finite difference algorithm to calculate three dimensional 3 d green s functions actually the tractions on the fault we invert the data for the unknown source parameters at the nodes or corners of the subfaults the source parameters within a subfault area are allowed to vary this variation is calculated through bilinear interpolation of the four nodal quantities we have developed a global nonlinear inversion algorithm that is based on simulated annealing methods to solve efficiently for the nodal parameters we apply this method to the 1989 loma prieta california m 6 9 earthquake for both a 1 d and 3 d velocity structure we show 1 the bilinear interpolation technique reduces the dependence of inversion results on the subfault size by naturally including the effects of nearby subfaults 2 while the number of synthetic seismograms that must be computed is greatly increased by the bilinear interpolation the structure of the inversion method minimizes the actual numbers of computations 3 as expected complexity in the velocity structure is mapped into the source parameters that describe the rupture process there are significant differences between faulting models derived from 1 d and 3 d structural models

high frequency spectral falloff of earthquakes fractal dimension of complex rupture b value and the scaling of strength on faults the high frequency falloff omega sup minus gamma of earthquake displacement spectra and the b value of aftershock sequences are attributed to the character of spatially varying strength along fault zones the author assumes that the high frequency energy of a main shock is produced by a self similar distribution of subevents where the number of subevents with radii greated than r is proportional to r sup minus d d being the fractal dimension in this model an earthquake is composed of a hierarchical set of smaller earthquakes the static stress drop is parameterized to be proportional to r sup eta and strength is assumed to be proportional to static stress drop he finds that a distribution of subevents with d 2 and stress drop independent of seismic moment eta 0 produces a main shock with an omega sup minus 2 falloff if the subevent areas fill the rupture area of the main shock by equating subevents to islands of high stress of a random self similar stress field on a fault he relates d to the scaling of strength on a fault such that d 2 minus eta thus d 2 corresponds to constant stress drop scaling eta 0 and scale invariant fault strength amore self similar model of aftershock rupture zones on a fault is used to determine the relationship between the b value the size distribution of aftershock rupture zones and the scaling of strength on a fault the b value for aftershock sequences on a fault is found to equal 3 minus 1 5 eta 3 eta therefore this model indicates that the typically observed spectral falloffs of omega sup minus 2 and b values of 1 can be entirely caused by scale invariant strength eta 0 along fault zones less

relative and absolute dating of land surfaces abstract the dating of land surfaces has long posed problems for geomorphologists relative methods stratigraphic geomorphic topographic are sound and convincing exhumed forms may complicate identification and relationships for both epigene and etch forms have been buried and exhumed but in tectonically undisturbed areas the higher surfaces are older than those preserved at lower levels also surfaces have an age range the relationship of surfaces with volcanic deposits old shorelines and genetically related sedimentary sequences provides sound ages and correlation with dated duricrusts and faults is also useful there are no temporal limits to relative dating for the methods are equally applicable to the dating say of proterozoic surfaces as of those of pleistocene age the disadvantage of such methods is that the necessary evidence is frequently either not preserved or not exposed the so called absolute physical numerical methods and especially those based on exposure age dating with in situ cosmogenic radionuclides are appealing because they produce direct numerical ages and appear to be widely applicable but there are severe temporal limitations and sampling problems complicate and may invalidate interpretation absolute age determinations must be consistent with the stratigraphic and geomorphologic settings the best results are obtained when physicists and earth scientists pool their knowledge and experience a background in local and regional geology is especially important

the rupture process of the 1980 irpinia italy earthquake from the inversion of strong motion waveforms abstract the distribution of slip and the behaviour of rupture propagation during the 23rd november 1980 irpinia earthquake ms 6 9 was investigated by analysing strong motion accelerograms the rupture was assumed to develop on a two dimensional purely normal fault whose geometry was constrained by geologic and geodetic data and by the aftershock space distribution theoretical seismograms have been computed using the isochron approach with a spatially variable slip intensity the asymptotic ray theory is used to evaluate the far field green functions the rupture model was updated following a trial and error approach the fit of observed waveforms with synthetic seismograms allowed several peculiarities in the rupture history to be pointed out the source model resulting from the solution of the forward waveform modelling was then used as starting model for the inversion of ground velocities therefore we performed a linearized inversion for slip velocity and rupture times on the fault by iteratively perturbing the assumed starting model the inverse problem is solved by means of a tomographic back projection technique the inferred source model shows a bilateral rupture which does not propagate uniformly away from the hypocentre the rupture velocity and the slip distribution on the fault plane are rather variable the solution confirms the shallow dislocation gap in the central part of the fault suggested by the behaviour of the surface rupture the results indicate that the rupture propagated northwestward along a further fault fragment for which no surface evidence is observed the aftershocks occurred mostly inside of or near to the edges of the source areas of maximum co seismic slip

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

rupture process of the 2007 niigata ken chuetsu oki earthquake by non linear joint inversion of strong motion and gps data 1 we image the rupture history of the 2007 niigata ken chuestu oki japan earthquake by a nonlinear joint inversion of strong motion and gps data retrieving peak slip velocity rupture time rise time and slip direction the inferred rupture model contains two asperities a small patch near the nucleation and a larger one located 10 15 km to the south west the maximum slip ranges between 2 0 and 2 5 m and the total seismic moment is 1 6 1019 nm the inferred rupture history is characterized by rupture acceleration and directivity effects which are stable features of the inverted models these features as well as the source to receiver geometry are discussed to interpret the high peak ground motions observed pga is 1200 gals at the kashiwazaki kariwa nuclear power plant kknpp situated on the hanging wall of the causative fault despite the evident source effects predicted pgv underestimates the observed values at kknpp by nearly a factor of 10

spatial slip distribution of the september 20 1999 chi chi taiwan earthquake mw7 6 inverted from teleseismic data the teleseismic waveforms of the mw7 6 september 20 1999 chi chi earthquake were examined to obtain the quick information on the fault rupture process the deconvolution results show the fault ruptured from south to the north and revealed the west movement of the hanging wall to the footwall on the eastern dipping plane the spatial slip distribution shows that the earthquake was mainly composed by a large asperity with a dimension of about 45km 15km the maximum slip was about 8 m located at about 45 km to the north of the epicenter the slip distributions obtained in this study have a good agreement with the observed surface breaks the comparable static and the dynamic stress drops of about 11 mpa in the large slip region indicate that the melting fluid pressurization might have taken place in this earthquake it reduces the dynamic friction and results in the large slip observed

a global search inversion for earthquake kinematic rupture history application to the 2000 western tottori japan earthquake 1 we present a two stage nonlinear technique to invert strong motions records and geodetic data to retrieve the rupture history of an earthquake on a finite fault to account for the actual rupture complexity the fault parameters are spatially variable peak slip velocity slip direction rupture time and risetime the unknown parameters are given at the nodes of the subfaults whereas the parameters within a subfault are allowed to vary through a bilinear interpolation of the nodal values the forward modeling is performed with a discrete wave number technique whose green s functions include the complete response of the vertically varying earth structure during the first stage an algorithm based on the heat bath simulated annealing generates an ensemble of models that efficiently sample the good data fitting regions of parameter space in the second stage appraisal the algorithm performs a statistical analysis of the model ensemble and computes a weighted mean model and its standard deviation this technique rather than simply looking at the best model extracts the most stable features of the earthquake rupture that are consistent with the data and gives an estimate of the variability of each model parameter we present some synthetic tests to show the effectiveness of the method and its robustness to uncertainty of the adopted crustal model finally we apply this inverse technique to the well recorded 2000 western tottori japan earthquake mw 6 6 we confirm that the rupture process is characterized by large slip 3 4 m at very shallow depths but differently from previous studies we imaged a new slip patch 2 2 5 m located deeper between 14 and 18 km depth

physical limits on ground motion at yucca mountain abstract physical limits on possible maximum ground motion at yucca mountain nevada the designated site of a high level radioactive waste repository are set by the shear stress available in the seismogenic depth of the crust and by limits on stress change that can propagate through the medium we find in dynamic deterministic 2d calculations that maximum possible horizontal peak ground velocity pgv at the underground repository site is 3 6 m sec which is smaller than the mean pgv predicted by the probabilistic seismic hazard analysis psha at annual exceedance probabilities less than 10 6 per year the physical limit on vertical pgv 5 7 m sec arises from supershear rupture and is larger than that from the psha down to 10 8 per year in addition to these physical limits we also calculate the maximum ground motion subject to the constraint of known fault slip at the surface as inferred from paleoseismic studies using a published probabilistic fault displacement hazard curve these calculations provide a probabilistic hazard curve for horizontal pgv that is lower than that from the psha in all cases the maximum ground motion at the repository site is found by maximizing constructive interference of signals from the rupture front for physically realizable rupture velocity from all parts of the fault vertical pgv is maximized for ruptures propagating near the p wave speed and horizontal pgv is maximized for ruptures propagating near the rayleigh wave speed yielding in shear with a mohr coulomb yield condition reduces ground motion only a modest amount in events with supershear rupture velocity because ground motion consists primarily of p waves in that case the possibility of compaction of the porous unsaturated tuffs at the higher ground motion levels is another attenuating mechanism that needs to be investigated

scaling of the shear rupture process from nucleation to dynamic propagation implications of geometric irregularity of the rupturing surfaces a series of systematic high resolution laboratory experiments have been performed on the nucleation of propagating slip failure on preexisting faults having different surface roughnesses to demonstrate how the size scale and duration of shear rupture nucleation are affected by geometric irregularity of the rupturing surfaces on the basis of the experimental results it has been discussed theoretically how consistently scale dependent physical quantities inherent in shear rupture are scaled the experiments led to conclusive results that the nucleation process consists of two phases phase i an initial quasi static phase and phase ii a subsequent accelerating phase and that the nucleation process is greatly affected by geometric irregularities on the rupturing surfaces in phase i the rupture grows at a slow steady speed which is independent of the rupture growth length l in contrast during phase ii the rupture develops at accelerating speeds v which increase with an increase in l obeying a power law v vs l c n where vs is the shear wave velocity c is the characteristic length representing the geometric irregularity of the fault surfaces and and n are constants 8 87 10 29 and n 7 31 scale dependency of scale dependent physical quantities including the nucleation zone size and its duration is commonly ascribed to scale dependency of the slip dependent constitutive law parameter dc which is in turn governed by c it has been discussed that a unified comprehension can be provided for shear rupture of any size scale if the constitutive law for shear rupture is formulated as a slip dependent law

correlation migration using gaussian beams of scattered teleseismic body waves correlation migration for structural imaging using gaussian beams is described for the inversion of passively recorded teleseismic waves gaussian beam migration is based on an overcomplete frame based representation of the seismic wave field and uses localized slant stack windows of the data paraxial gaussian beams are then utilized for the backpropagation of the seismic waves into the me dium the method can provide stable imaging of seismic data in smoothly varying background media where caustics and triplicated arrivals exist we develop gaussian beam migration for structural imaging which allows for incident teleseismic waves from beneath the structure using directly scattered or surface reflected phases the method is applied to synthetic data computed for a collisional zone model and the inversions show that the gaussian beam migration can image structure using passive teleseismic data the method is next applied to synthetic data that have been con volved with an observed pulse from the 1993 cascadia experiment the autocorre lation is computed and the autocorrelated data are migrated by using gausian beams for direct p to s scattered waves and surface reflected waves although the migra tions of the autocorrelation data with the source pulse included have more noise than the migrations of the impulsive source data the subduction zone structure can still be clearly identified in the migrated results without removal of the source pulses

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