equivalent point source modeling of moderate to large magnitude earthquakes and associated ground motion saturation effects we modeled the source and attenuation attributes of well recorded m6 earthquakes based on the equivalent point source approach with the goal of determin ing how to treat ground motion saturation effects within this context we consider ground motions as originating from an equivalent point source and mimic finite fault effects by treating the motion as emanating from a virtual point not a real point on the fault rupture such that ground motions are correctly predicted at close distances this is achieved by using an effective distance metric r d 2 h 2 0 5 in which drup is the closest distance to the rupture and h is a pseudodepth term that accounts for sat uration effects we found that the distance saturation effect is magnitude dependent extending to further distances with increasing magnitude for earthquakes of m 6 we model the saturation term as logh 1 72 0 43 m with a standard deviation of 0 19 in log10 units based on the values obtained from the study earthquakes the apparent source spectra of most m6 earthquakes can be modeled using a simple brune point source model for a few of the m6 earthquakes notably those in california we observed a spectral sag at intermediate frequencies for such earth quakes a two corner point source model provides a better match than the brune model we conclude that an equivalent point source model based on the effective distance concept can successfully predict the average ground motions from m6 earthquakes over a wide distance range including close distances 20 km

acceleration source spectra anticipated for large earthquakes in northeastern north america a set of 16 large intraplate earthquakes are considered on the basis of their tectonic settings compressive focal mechanisms and shallow focal depths as possible analogs for large earthquakes that may be anticipated to occur in northeastern north america the earthquakes range in seismic moment from 5 1023 to 3 1026 dyne cm and include the mainshocks and largest aftershocks of the 1982 miramichi canada the 1985 to 1988 nahanni canada and the 1988 tennant creek australia earthquake sequences the teleseismic recordings of these earthquakes are spectrally analyzed by correcting the logarithmically averaged acceleration spectra for the frequency dependent effects of attenuation and interference of the depth and direct phases the resulting acceleration source spectra are generally flat at high frequencies the mainshock spectra exhibit intermediate spectral falloffs that is u where 1 over frequencies that characteristically extend from 0 1 to 0 5 hz in contrast the largest aftershocks of the three sequences named above exhibit 2 spectral shapes the high frequency source spectral levels increase with seismic moment approximately as ru m 1 3 the 1988 saguenay canada earthquake which occurred significantly deeper than the other earthquakes exhibits an anomalous spectral shape combining the teleseismic data with strong motion recordings indicates that the intermediate spectral falloff for this earthquake extends from 0 2 to 3 hz the spectral amplitude at 3 hz is a factor of 3 higher than the amplitude anticipated for an earthquake of this size from the other 15 earthquakes

a ground motion predictive model for iran and turkey for horizontal pga pgv and 5 damped response spectrum investigation of possible regional effects we present a ground motion prediction equation gmpe for turkey and iran to investigate the possible regional effects on ground motion amplitudes in shallow active crustal earthquakes the proposed gmpe is developed from a subset of the recently compiled strong motion database of the earthquake model of the middle east region project see data and resources 1 a total of 670 turkish and 528 iranian accelerograms with depths down to 35 km are used to estimate peak ground acceleration peak ground velocity and 5 damped elastic pseudospectral acceleration ordinates of 0 01 s t 4 s the moment magnitude range of the model is 4 m w 8 and the maximum joyner boore distance is r jb 200 km the functional form considers three major fault mechanisms strike slip normal and reverse the nonlinear soil behavior is a function of v s 30 average shear wave velocity in the upper 30 m of soil profile our observations from empirical and estimated ground motion trends advocate regional differences in the territories covered by iran and turkey that originate from the differences in q factors kappa and near surface velocity profiles these factors eventually affect the magnitude and distance dependent scaling of spectral amplitudes in iran and turkey in essence the ground motion amplitudes of these two neighboring countries would draw patterns different than the ground motion estimates of gmpes developed from the strong motion databases of shallow active crustal earthquakes from multiple countries online material matlab code and regression coefficients for computing the response spectrum and distance scaling 1 sec 7

ground motion simulation by the empirical green s function method with a source defined by two corner frequencies and a two stage summation schemeground motion simulation by the egf method

ground motion relations for eastern north america predictive relations are developed for ground motions from eastern north american earthquakes of 4 0 m 7 25 at distances of 10 r 500 km the predicted parameters are response spectra at frequencies of 0 5 to 20 hz and peak ground acceleration and velocity the predictions are derived from an empirically based stochastic ground motion model the relations differ from previous work in the improved empirical definition of input parameters and em pirical validation of results the relations are in demonstrable agreement with ground motions from earthquakes of m 4 to 5 there are insufficient data to adequately judge the relations at larger magnitudes although they are consistent with data from the saguenay m 5 8 and nahanni m 6 8 earthquakes the underlying model parameters are constrained by empirical data for events as large as m 6 8

empirical ground motion relations for subduction zone earthquakes and their application to cascadia and other regions ground motion relations for earthquakes that occur in subduction zones are an important input to seismic hazard analyses in many parts of the world in the cascadia region washington oregon northern california and british columbia for example there is a significant hazard from megathrust earthquakes along the subduction interface and from large events within the subducting slab these hazards are in addition to the hazard from shallow earthquakes in the overlying crust we have compiled a response spectra database from thousands of strong motion record ings from events of moment magnitude m 5 8 3 occurring in subduction zones around the world including both interface and in slab events the 2001 m 6 8 nis qually and 1999 m 5 9 satsop earthquakes are included in the database as are many records from subduction zones in japan kyoshin net data mexico guerrero data and central america the size of the database is four times larger than that available for previous empirical regressions to determine ground motion relations for subduc tion zone earthquakes the large dataset enables improved determination of attenu ation parameters and magnitude scaling for both interface and in slab events soil response parameters are also better determined by the data we use the database to develop global ground motion relations for interface and in slab earthquakes using a maximum likelihood regression method we analyze regional variability of ground motion amplitudes across the global database and find that there are significant regional differences in particular amplitudes in cascadia differ by more than a factor of 2 from those in japan for the same magnitude distance event type and national earthquake hazards reduction program nehrp soil class this is believed to be due to regional differences in the depth of the soil profile which are not captured by the nehrp site classification scheme regional correction factors to account for these differences are proposed for cascadia and japan the results of this study differ significantly from previous analyses based on more limited data and have important implications for seismic hazard analysis the ground motion relations predict that a great megathrust earthquake m 8 at a fault distance of about 100 km would produce pseudoacceleration psa 5 damped horizontal component on soil sites of about 110 cm sec 2 at 0 5 hz 660 cm sec 2 at 2 5 hz and 410 cm sec 2 at 5 hz with a peak ground acceleration of about 180 cm sec 2 these damaging levels of motion would be experienced over a very large area corresponding to a rectangular area about 300 km wide by 500 km long large in slab events m 7 5 would produce even higher psa values within 100 km of the fault but the in slab motions attenuate much more rapidly with distance thus the hazard posed by moderate to large in slab events such as the 2001 nisqually earth quake is modest compared to that of a cascadia megathrust earthquake of m 8 in terms of the area that would experience damaging levels of ground motion

estimation of moment magnitude and stress parameter from shakemap ground motion parameters we describe an efficient method to determine moment magnitude and stress parameter in near real time in the immediate aftermath of a small to moderate earthquake m 3 6 from shakemap ground motion parameters 5 damped pseudospectral acceleration at 1 hz 0 33 hz 10 hz and or peak ground acceleration the methodology is based on relating shakemap parameters to source and attenuation parameters within the context of a generic stochastic point source model to provide an event specific ground motion prediction equation gmpe that will reliably predict amplitudes it is an approach that has been optimized for applications in regions with sparse networks an example is provided for southern ontario in brief we initially develop a simulation guided generic gmpe model based on the available database in the region we derive the applicable regional anelastic attenuation stress parameter and site amplification models then using the estimated regional models we show how to invert shakemaps parameters to estimate moment magnitude and stress parameter in near real time to define an event specific gmpe for an event that just happened the event specific gmpe can be used to provide robust calibrated shakemaps that are fully consistent with ground motion observations

ground motion prediction equation for small to moderate events at short hypocentral distances with application to induced seismicity hazards abstract the evaluation of seismic hazard from induced seismicity requires the development of ground motion prediction equations gmpes that are tuned to the key magnitude distance range for such applications i use events of m 3 6 at hypocentral distances less than 40 km drawn from the next generation attenuation west 2 nga west 2 database to develop a gmpe that accounts correctly for point source scaling in both magnitude and distance space for such events the developed gmpe is in demonstrable agreement with the nga west 2 database and with the predictions of a stochastic point source simulation model the database is sparse at close distances implying epistemic uncertainty of as much as a factor of 2 in ground motion amplitudes within 10 km of the hypocenter an important conclusion from this study is that the ground motion amplitudes for moderate induced events could be much larger near the epicenter than predicted by most of the nga west 2 gmpes the potential for large motions is a consequence of the shallow depth of induced events which places the earthquake fault only a short distance beneath the epicenter

regionally adjustable generic ground motion prediction equation based on equivalent point source simulations application to central and eastern north america abstract we develop a generic ground motion prediction equation gmpe that can be adjusted for use in any region by modifying a few key model parameters the basis of the gmpe is an equivalent point source simulation model whose parameters have been calibrated to empirical data in california in such a way as to determine the decoupled effects of basic source and attenuation parameters on ground motion amplitudes we formulate the generic gmpe as a function of magnitude distance stress parameter geometrical spreading rate and anelastic attenuation this provides a fully adjustable predictive model allowing users to calibrate its parameters using observed motions in the target region we also include an empirical calibration factor to account for residual effects that are different from and or missing in simulations compared to observed motions in the target region as an example we show how the generic gmpe can be adjusted for use in central and eastern north america cena and calibrated with the next generation attenuation east database we provide median predictions of ground motions in cena for average horizontal component peak ground motions and 5 damped pseudospectral acceleration periods up to t 10 s for magnitudes m 3 8 and distances up to 600 km

site amplifications for generic rock sites seismic shear wave velocity as a function of depth for generic rock sites has been estimated from borehole data and studies of crustal velocities and these velocities have been used to compute frequency dependent amplifications for zero attenuation for use in simulations of strong ground motion we define a genetic rock site as one whose velocity at shallow depths equals the average of those from the rock sites sampled by the borehole data most of the boreholes are in populated areas for that reason the rock sites sampled are of particular engineering significance we consider two genetic rock sites rock corresponding to the bulk of the borehole data and very hard rock such as is found in glaciated regions in large areas of eastern north america or in portions of western north america the amplifications on rock sites can be in excess of 3 5 at high frequencies in contrast to the amplifications of less than 1 2 on very hard rock sites the consideration of unattenuated amplification alone is computationally convenient but what matters for ground motion estimation is the combined effect of amplification and attenuation for reasonable values of the attenuation parameter k 0 the combined effect of attenuation and amplification for rock sites peaks between about 2 and 5 hz with a maximum level of less than 1 8 the combined effect is about a factor of 1 5 at 1 hz and is less than unity for frequencies in the range of 10 to 20 hz depending on t using these amplifications we find provisional values of about ao 70 bars and k 0 0 035 sec for rock sites in western north america by fitting our empirically determined response spectra for an m 6 5 event to simulated values the borehole data yield shear velocities 033o of 618 and 306 rrdsec for rock and soil sites respectively when averaged over the upper 30 m from this we recommend that v30 equals 620 and 310 m sec for applications requiring the average velocity for rock and soil sites in western north america by combining the amplifications for rock sites and the site factors obtained from our analysis of strong motion data we derive amplifications for sites with 17 3o 520 m sec nehrp class c corresponding to a mix of rock and soil sites and v3o 310 and 255 m sec average soil and nehrp class d sites respectively for the average soil site the combined effect of amplification and attenuation exceeds a factor of 2 0 for frequencies between 0 4 and about 4 hz with a peak site effect of 2 4 the peak of the nehrp class d site effect is 2 7

comparisons of ground motions from the 1999 chi chi earthquake with empirical predictions largely based on data from california this article has the modest goal of comparing the ground motions recorded during the 1999 chi chi taiwan mainshock with predictions from four empirical based equations commonly used for western north america these empirical predictions are largely based on data from california comparisons are made for peak acceleration and 5 damped response spectra at periods between 0 1 and 4 sec the general finding is that the chi chi ground motions are smaller than those predicted from the empirically based equations for periods less than about 1 sec by factors averaging about 0 4 but as small as 0 26 depending on period on which equation is used and on whether the sites are assumed to be rock or soil there is a trend for the observed motions to approach or even exceed the predicted motions for longer periods motions at similar distances 30 60 km to the east and to the west of the fault differ dramatically at periods between about 2 and 20 sec long duration wave trains are present on the motions to the west and when normalized to similar amplitudes at short periods the response spectra of the motions at the western stations are as much as five times larger than those of motions from eastern stations the explanation for the difference is probably related to site and propagation effects the western stations are on the coastal plain whereas the eastern stations are at the foot of young and steep mountains either in the relatively narrow longitudinal valley or along the eastern coast the sediments underlying the eastern stations are probably shallower and have higher velocity than those under the western stations manuscript received 1 december 2000

simulation of strong ground motions recorded during the 1985 michoacan mexico and valparaiso chile earthquakes abstract the purpose of this study is to develop and test a procedure for simulating acceleration time histories of large subduction earthquakes the ground motions of the large event are obtained by summing contributions from fault elements to simulate the propagation of rupture over the fault surface the radiation from the fault elements is represented by empirical source functions derived from near source strong motion recordings of m w 7 aftershocks and gross aspects of wave propagation are modeled by calculated green9s functions the procedure has been tested against the recorded strong ground motions of the m w 8 0 michoacan mexico and valparaiso chile earthquakes of 1985 we find that models of heterogeneous slip in these events derived by other investigators from the analysis of teleseismic and near source velocity seismograms also explain the shorter period motions of the recorded accelerograms the response spectra of the simulated motions generally have little or no significant bias in the period range of 0 05 to 2 sec for both earthquakes also the peak accelerations durations and envelope shapes of the time histories are in good agreement with the recorded motions the uncertainty associated with the modeling procedure estimated from the misfit between recorded and simulated response spectra shows a dependence on period and site conditions this uncertainty estimate includes the uncertainty involved in using empirical source functions derived from one subduction zone to simulate strong ground motions in another subduction zone the procedure is applied in a companion paper cohee et al 1991 to estimate strong ground motion characteristics in the pacific northwest region of the united states from hypothesized m w 8 subduction earthquakes on the cascadia plate interface

the effect of crustal structure on strong ground motion attenuation relations in eastern north america strong ground motion attenuation relations are usually described by smoothly decreasing functions of distance however consideration of wave propagation in the crust suggests that attenuation relations should be more complex such complexity may be present in strong ground motion data for eastern north american earthquakes which show amplitudes in the distance range of 60 to 150 km that lie above the trends at smaller and greater distances using a wavenumber integration method to compute green s functions and close in recordings of several earthquakes as empirical source functions we have generated synthetic seismograms that are in good agreement with regional and strong motion recordings of eastern north american earthquakes from these synthetic seismograms we have shown that the observed interval of relatively high amplitudes may be attributable to postcritically reflected s waves from the moho the presence and location of the interval of relatively high amplitudes is highly dependent on the crustal velocity structure and may therefore be expected to show regional variation however for any realistic structure model there will be a transition in the attenuation relation from an interval at shorter distances less than about 100 km that is dominated by direct waves to an interval at greater distances that is dominated by postcritically reflected waves the synthetic seismograms have response spectral velocities that match those of the recorded data and their m blg values are in good agreement with observed values

a predictive equation for vertical to horizontal response spectral ratios in northern iran abstract the importance of the vertical component of ground motion in damage infliction on a variety of structural systems has been shown in recent years however the available models for ground motion prediction equations gmpes for this component of earthquakes are limited and most of the existing gmpes have been specifically developed for the horizontal component of ground motion alternatively in some cases it is proposed to scale the horizontal spectrum of the earthquake to the vertical one using vertical to horizontal response spectral ratios vhsrs in this work the applicability of some global and regional vhsr models for northern iran are evaluated using several existing statistical approaches the results of these evaluations show inadequate correlation between these models and the observed vhsrs in this region consequently a new vhsr model has been proposed to convert the horizontal earthquake spectrum to the vertical one in the studied region in order to determine the regression coefficients for the proposed vhsr model some 712 three component records with distances less than 300 km from the source from 79 earthquakes with the magnitude ranging from m w 4 1 to 7 3 were used regression coefficients for peak ground acceleration and pseudospectral acceleration for 5 damped systems are determined using a random effect approach a series of comparative studies on the proposed model with respect to the existing vhsrs was performed using the median residuals for the spectral periods in the 0 1 3 s range the results of such investigation show significant reduction of the variability for the proposed model at least 50 compared with the other vhsrs online material database of strong motion records

empirical attenuation of ground motion spectral amplitudes in southeastern canada and the northeastern united states a database of 1700 digital seismograms from 186 earthquakes of mag nitude mn 2 5 5 6 that occurred in southeastern canada and the northeastern united states from 1990 to 2003 was compiled maximum likelihood regression analysis of the database was performed to determine a model for the attenuation of fourier spectral amplitudes for the shear window for the vertical and horizontal component of motion for frequencies from 0 2 to 20 hz fourier amplitudes follow a hinged trilinear attenuation model fourier spectral amplitudes decay as r 1 3 where r is hypocentral distance within 70 km of the source there is a transition zone from 70 to 140 km as the direct waves are joined by strong postcritical reflections where the attenuation is described as r 0 2 spectral amplitudes actually increase with distance in this range for low frequencies beyond 140 km the attenuation is well described by r 0 5 corresponding to geometric spreading in two dimensions the associated model for the regional quality factor for frequencies greater than 1 hz can be ex pressed as q 893f 032 q can be better modeled over a wider frequency range 0 2 20 hz by a polynomial expression log q 3 052 0 393 log f 0 945 log f 2 0 327 log f 3 the polynomial expression accommodates the observation that q values are at a minimum about 1000 near 1 hz and rise at both lower and higher frequencies correction factors for the spectral amplitude model that describe the effects of focal depth on the amplitudes and their attenuation are developed using the subset of events with known focal depth the attenuation model is similar to that determined from an earlier study with more limited data atkinson and mereu 1992 but the enlarged database indicates more rapid near source amplitude decay and higher q the attenuation model is used to play back attenuation effects to determine the apparent source spectrum for each earthquake in the database and hence determine moment magnitude m and brune stress drop the events have moment magnitude in the range from 2 5 to 5 stress drop increases with moment magnitude for events of m 4 3 then appears to attain a relatively constant level in the range from 100 to 200 bars for the larger events as previously noted in atkinson 1993b the results of this study provide a useful framework for improving regional ground motion relations in eastern north america they further our understanding of attenuation in the region through analysis of an enlarged ground motion database in particular the inclusion of the three component broadband data gathered over the last decade allows extension of attenuation models to both horizontal and vertical components over a broad frequency range 0 2 20 hz

the interface between empirical and simulation based ground motion models ground motion models gmms are a key driver for the results of probabilistic seismic hazard analyses and their uncertainty gmms that bridge seismological and empirical approaches are an effective tool to represent the distribution of ground motion and its uncertainty in seismic hazard assessment a methodology is presented that uses ground motion data recorded at seismograph sites in eastern north america and shows how they can be used to calibrate simple scalable seismological models of ground motion generation and propagation such gmms can directly account for the gross features of source scaling magnitude and stress parameter attenuation site response and kappa effects it is shown that by application of appropriate gmm strategies sigma aleatory uncertainty could be greatly reduced resulting in lower calculated hazard for nuclear plants founded on rock this reduction in sigma requires that high quality seismic monitoring e g broadband seismograph stations be installed and operated over a period of years in addition to strong motion stations and that an ongoing investment be made in data analysis and targeted gmm development using the data

the shape of ground motion attenuation curves in southeastern canada the shape of the attenuation curve of the fourier spectrum of acceleration is established for southeastern canada from empirical data the dataset is comprised of 1200 digital vertical component seismograms from 100 earthquakes recorded on 30 stations of the eastern canada telemetered network the distance range of the observations is 10 to 1700 km focal depths are from 5 to 30 km results indicate that the attenuation curve has three distinct sections at distances less than 70 km corresponding to attenuation of the direct wave amplitudes decay slightly more rapidly than 1 r r 1 1 between 70 and 130 km where the direct wave is joined by sms spectral amplitudes are approximately constant beyond 130 km corresponding to the lg phase amplitudes decay at a rate that is consistent with r 0 5 and q 670 f 0 33 the findings support the hypothesis of burger et al 1987 that postcritical reflections from the moho discontinuity play an important role in determining the shape of the attenuation curve however the influence of sms is subtle allowing the shape to be approximated by simple functional forms for example the commonly assumed bilinear form r 1 r 0 5 with frequency dependent q fits well if the transition from direct wave to lg spreading is placed at approximately 60 km a linear form r 1 over all distances with constant q 2000 also provides a satisfactory fit overall we find little evidence for the dependence of attenuation on focal depth or tectonic province

ground motions for induced earthquakes in oklahoma we examine ground motions for a sequence of earthquakes in oklahoma where assessment of hazard contributions from induced seismicity is of particular interest we aim to empirically calibrate a model driven equation that was derived for central and eastern north america cena so that it will match the observed ground motions of the 2011 prague oklahoma sequence we first show that ground motions in oklahoma decay at a rate similar to the average attenuation observed in the stable continental region of cena we then search for any needed adjustments to the cena source model to match ground motions from the induced seismicity sequence that occurred near prague in 2011 an interesting feature noted in the ground motion analysis is that the stress parameters for the prague mainshock events m 5 are notably higher than those for aftershocks moreover the stress parameter that characterizes the high frequency ground motion decays in both time and space relative to the three largest events the largest events in the prague sequence have similar source parameters to natural cena events of the same magnitude and focal depth but their aftershocks have weaker motions

intraevent spatial correlation characteristics of stochastic finite fault simulations spatially correlated strong ground motions can cause severe seismic da mage to spatially distributed buildings and infrastructure empirical spatial correlation models for ground motion measures such as peak ground acceleration and spectral acceleration have been developed using strong ground motion records from california taiwan and japan in this paper we compare an empirical spatial correla tion model for the 1999 chi chi taiwan earthquake with that obtained from stochas tic finite fault simulations the stochastic finite fault method is a widely used technique to generate synthetic ground motion records for engineering applications and hazard assessment we show that the stochastic records do not reproduce the ob served intraevent spatial correlation characteristics and comment on what would be required to make them do so

a constant stress drop model for producing broadband synthetic seismograms comparison with the next generation attenuation relations broadband 0 1 20 hz synthetic seismograms for finite fault sources were produced for a model where stress drop is constant with seismic moment to see if they can match the magnitude dependence and distance decay of response spec tral amplitudes found in the next generation attenuation nga relations recently developed from strong motion data of crustal earthquakes in tectonically active re gions the broadband synthetics were constructed for earthquakes of m 5 5 6 5 and 7 5 by combining deterministic synthetics for plane layered models at low fre quencies with stochastic synthetics at high frequencies the stochastic portion used a source model where the brune stress drop of 100 bars is constant with seismic mo ment the deterministic synthetics were calculated using an average slip velocity and hence dynamic stress drop on the fault that is uniform with magnitude one novel aspect of this procedure is that the transition frequency between the deterministic and stochastic portions varied with magnitude so that the transition frequency is inversely related to the rise time of slip on the fault the spectral accelerations at 0 2 1 0 and 3 0 sec periods from the synthetics generally agreed with those from the set of nga relations for m 5 5 7 5 for distances of 2 100 km at distances of 100 200 km some of the nga relations for 0 2 sec spectral acceleration were substantially larger than the values of the synthetics for m 7 5 and m 6 5 earthquakes because these relations do not have a term accounting for q at 3 and 5 sec periods the synthetics for m 7 5 earth quakes generally had larger spectral accelerations than the nga relations although there was large scatter in the results from the synthetics the synthetics showed a sag in response spectra at close in distances for m 5 5 between 0 3 and 0 7 sec that is not predicted from the nga relations

earthquake ground motion prediction equations for eastern north america new earthquake ground motion relations for hard rock and soil sites in eastern north america ena including estimates of their aleatory uncertainty vari ability have been developed based on a stochastic finite fault model the model incorporates new information obtained from ena seismographic data gathered over the past 10 years including three component broadband data that provide new in formation on ena source and path effects our new prediction equations are similar to the previous ground motion prediction equations of atkinson and boore 1995 which were based on a stochastic point source model the main difference is that high frequency amplitudes f 5 hz are less than previously predicted by about a factor of 1 6 within 100 km because of a slightly lower average stress parameter 140 bars versus 180 bars and a steeper near source attenuation at frequencies less than 5 hz the predicted ground motions from the new equations are generally within 25 of those predicted by atkinson and boore 1995 the prediction equations agree well with available ena ground motion data as evidenced by near zero average residuals within a factor of 1 2 for all frequencies and the lack of any significant residual trends with distance however there is a tendency to positive residuals for moderate events at high frequencies in the distance range from 30 to 100 km by as much as a factor of 2 this indicates epistemic uncertainty in the prediction model the positive residuals for moderate events at 100 km could be eliminated by an increased stress parameter at the cost of producing negative residuals in other magnitude distance ranges adjustment factors to the equations are provided that may be used to model this effect

stochastic finite fault modeling of ground motions from the 1999 chi chi taiwan earthquake application to rock and soil sites with implications for nonlinear site response the stochastic method for simulating strong ground motions from finite faults is applied to the records of the 1999 chi chi taiwan earthquake the method involves discretization of the fault plane into smaller subfaults each of which is assigned an x 2 spectrum the contributions from all subfaults are empirically atten uated to the observation site and summed to produce the synthetic acceleration time history the method is initially calibrated against the data recorded at 24 rock sites located within 7 120 km from the mainshock hypocenter and providing a broad azimuthal coverage of the fault plane the accuracy of the simulations is quantified through the model bias defined as the logarithm of the ratio of the observed to simulated spectrum averaged over all stations the calibrated model for the chi chi event has a near zero average bias in reproducing the ground motions at rock sites in the frequency range from 0 1 to 20 hz an unusually low value is found for the radiation strength factor s controlling the high frequency radiation level and directly related to the maximum slip velocity on the fault compared with the mean value found for north american earthquakes this result reflects the observed low peak ground ac celerations of the chi chi mainshock and physically its lower than usual slip ve locities the calibrated model is then used to simulate soil site site class d records using the linear response assumption the simulated soil site input motions are amplified by the weak motion amplification functions estimated by the spectral ratio technique from available aftershock records this analysis reveals an average reduction in strong motion amplification to about 0 5 0 6 of that in weak motions with an ac celeration threshold for detectable nonlinearity near 200 300 cm sec 2 however the derivation of soil site specific weak motion amplification was limited by the amount of aftershock data available further improvement in the quantification of nonlinear soil response during the chi chi earthquake may be possible with the release of additional aftershock datasets

xigaze forearc basin revisited south tibet provenance changes and origin of the xigaze ophiolite our new stratigraphic sedimentological and micropaleontological analysis integrated with basalt geochemistry sandstone petrography and detrital zircon u pb and hf isotope data suggests the revision of current models for the geological evolution of the asian active margin during the cretaceous the xigaze forearc basin began to form in the late early cretaceous south of the gangdese arc during the initial subduction of the neotethyan oceanic lithosphere under the lhasa terrane well preserved stratigraphic successions document the classical upwardshallowing pattern of the forearc basin strata and elucidate the origin of the associated oceanic magmatic rocks the normal midocean ridge basalt n morb geochemical signature and stratigraphic contact with the overlying abyssal cherts chongdui formation indicate that the xigaze ophiolite formed by forearc spreading and represents the basement of the forearc sedimentary sequence volcaniclastic sedimentation began with thick turbiditic sandstones and interbedded shales in the late albian santonian ngamring formation followed by shelfal deltaic and fl uvial strata padana formation with fi nal fi lling of the basin by the campanian age forearc sandstones do not show the classical trend from feldspatholithic volcaniclastic to quartzo feldspathic plutoniclastic compositions indicating limited unroofi ng of the gangdese arc prior to collision u pb age spectra of detrital zircons are unimodal with a 107 ma peak in the lower ngamring formation 104 99 ma bimodal with a subordinate additional peak at 157 ma in the middle ngamring formation 99 88 ma and multimodal with more abundant pre mesozoic ages in the upper ngamring and padana formations 88 76 ma these three petrofacies with distinct provenances document the progressive erosional evolution of the gangdese arc with uplift of the central lhasa terrane and expanding river catchments to include the central lhasa terrane during the late cretaceous

surface waves in the western taiwan coastal plain from an aftershock of the 1999 chi chi taiwan earthquake significant surface waves were recorded in the western coastal plain wcp of taiwan during the 1999 chi chi taiwan earthquake and its series of aftershocks we study in detail the surface waves produced by one aftershock 20 september 1999 18hr 03m 41 16sec m 6 2 in this paper we take the chelungpu chukou fault to be the eastern edge of the wcp because it marks a distinct lateral contrast in seismic wave velocities in the upper few kilometers of the surface for many records from stations within the wcp body waves and surface waves separate well in both the time domain and the period domain long period e g 2 sec ground motions in the plain are dominated by surface waves significant prograde rayleigh wave particle motions were observed in the wcp the observed peak ground velocities are about 3 5 times larger than standard predictions in the central and western part of the plain observed response spectra at 3 sec 4 sec and 5 sec at the center of the plain can be 15 times larger than standard predictions and 10 times larger than the predictions of joyner 2000 based on surface wave data from the los angeles basin the strong surface waves were probably generated at the boundary of the wcp and then propagated toward the west largely along radial directions relative to the epicenter the geometry of the boundary may have had a slight effect on propagation directions of surface waves group velocities of funda mental mode rayleigh and love waves are estimated using the multiple filter analysis mfa technique and are refined with phase matched filtering pmf group velocities of fundamental mode surface waves range from about 0 7 km sec to 1 5 km sec for the phases at periods from 3 sec to 10 sec one important observation from this study is that the strongest surface waves were recorded in the center of the plain the specific location of the strongest motions depends largely on the period of surface waves rather than on specific site conditions or plain structures accordingly we conjecture that surface waves could be generated in a wide area close to boundaries of low velocity sedimentary wave guides in the case studied in this article the area can be as wide as 30 km from the chelungpu fault to the center of the plain surface waves converted by p and s waves at different locations would overlap each other and add constructively along their propagation paths as a result the surface waves would get stronger and stronger beyond a certain distance to the boundary no more surface waves would be generated consequently no more local surface waves would be superimposed into the invasive surface waves and the surface waves would tend to decay in amplitude with distance

calibration of the specific barrier model to earthquakes of different tectonic regions the specific barrier model proposed and developed by papageorgiou and aki 1983a b 1985 provides the most complete yet parsimonious self consis tent description of the faulting process it applies both in the near fault and in the far field region thus allowing for consistent ground motion simulations over the entire frequency range and for all distances of engineering interest the model has been implemented in the stochastic method and calibrated with extended databases of response spectral amplitudes from earthquakes of intraplate regions mainly east ern north america events interplate regions and regions of tectonic extension spu dich et al 1999 database the ensemble average value of a key parameter of the specific barrier model the local stress drop dr l i s 161 bars for interplate earth quakes 114 bars for extensional regime earthquakes and 180 bars for intraplate earthquakes the high frequency source spectral levels of interplate and extensional regime earthquakes deviate significantly from self similar scaling the deviation is most likely caused by the effective source area and or irregularities in the rupture kinematics we account for their overall effects through a high frequency source complexity factor f in the source spectrum of the specific barrier model as a result inter and intraplate source spectra show similar high frequency levels at moderate magnitudes but intraplate earthquakes have higher spectral levels at the larger mag nitudes the interplate soil residuals show clear signs of nonlinear site response whereas only slight signs of such nonlinearity are observed for the extensional data set the regional models calibrated in this study are in reasonably good agreement with other regional attenuation relationships and provide a reliable and physically realistic yet computationally efficient way to model strong ground motions with implications for seismic hazard and risk analysis online material strong motion station and event station pair information

an empirical study of earthquake source spectra for california earthquakes we generalize source path and site effects for california earthquakes as functions of magnitude and distance based on regression analysis of 1000 fourier acceleration spectra from 43 california earthquakes in the moment magnitude range from 4 4 to 7 4 recorded at rupture distances from 1 to 200 km empirically derived source spectra for california earthquakes are generally inconsistent with the spectral shape implied by a brune omega squared point source model this is manifested by magnitude and frequency dependence of the brune model parameters for ex ample the brune stress parameter that best matches the data at high frequencies decreases from a value of about 120 bars at m5 5 to a value near 50 bars at m7 5 at frequencies below 1 hz though source spectra have much lower spectral ampli tudes than predicted by the brune point source model for these values of stress this discrepancy grows with increasing magnitude finite fault simulations indicate that this is a consequence of the breakdown of the validity of the point source approxi mation for large ruptures a stochastic finite fault model in which the fault is dis cretized as a number of subfaults each of which is represented by a brune omega squared point source correctly matches the observed spectral shapes and amplitudes the spectral decay parameter kappa representing average near surface attenuation of high frequency motion at rock sites increases with increasing magnitude from values near 0 035 sec at m5 5 to 0 050 sec at m7 5 magnitude dependence of kappa may be interpreted as evidence of nonlinearity for typical california sites subjected to strong ground motion comparisons of our empirical source spectra for california to corresponding spec tra for eastern north america suggest that the spectral amplitudes are similar in the two regions for low frequency motions f 2 hz for m5 5 f 0 5 hz for m7 5 for equivalent crustal conditions the eastern events appear to have enhanced high frequency near source amplitudes relative to the california events this is particularly pronounced for large magnitude earthquakes

source spectral properties of small to moderate earthquakes in southern kansas the source spectral properties of injection induced earthquakes give insight into their nucleation rupture processes and influence on ground motion here we apply a spectral decomposition approach to analyze p wave spectra and estimate brune type stress drop for more than 2000 ml1 5 5 2 earthquakes occurring in southern kansas from 2014 to 2016 we find that these earthquakes are characterized by low stress drop values median 0 4mpa compared to natural seismicity in california we observe a significant increase in stress drop as a function of depth but the shallow depth distribution of these events is not by itself sufficient to explain their lower stress drop stress drop increases with magnitude from m1 5 m3 5 but this scaling trend may weaken above m4 and also depends on the assumed source model although we observe a nonstationary sequence specific temporal evolution in stress drop we find no clear systematic relation with the activity of nearby injection wells

site effect evaluation using spectral ratios with only one station the spectral ratio technique is a common useful way to estimate empirical transfer function to evaluate site effects in regions of moderate to high seismicity the purpose of this paper is to show that it is possible to estimate empirical transfer function using spectral ratios between horizontal and vertical components of motion without a reference station the technique originally proposed by nakamura to analyze rayleigh waves in the microtremor records is presented briefly and it is discussed why it may be applicable to study the intense s wave part in earthquake records results are presented for three different cities in mexico oaxaca oax acapulco gro and mexico city these cities are very different by their geological and tectonic contexts and also by the very different epicentral distances to the main seismogenic zones affecting each city each time we compare the results of nakamura s technique with standard spectral ratios in all three cases the results are very encouraging we conclude that if site effects are caused by simple geology a first estimate of dominant period and local amplification level can be obtained using records of only one station

developing an application specific ground motion model for induced seismicity abstract a key element of quantifying both the hazard and risk due to induced earthquakes is a suite of appropriate ground motion prediction equations gmpes that encompass the possible shaking levels due to such events induced earthquakes are likely to be of smaller magnitude and shallower focal depth than the tectonic earthquakes for which most gmpes are derived furthermore whereas gmpes for moderate to large magnitude earthquakes are usually derived to be transportable to different locations and applications taking advantage of the limited regional dependence observed for such events the characteristics of induced earthquakes warrant the development of application specific models a preliminary ground motion model for induced seismicity in the groningen gas field in the netherlands is presented as an illustration of a possible approach to the development of these equations the gmpe is calibrated to local recordings of small magnitude events and captures the epistemic uncertainty in the extrapolation to larger magnitude considered in the assessment of the resulting hazard and risk

determination of stress parameters for eight well recorded earthquakes in eastern north america we determined the stress parameter for the eight earthquakes stud ied by atkinson and boore 2006 using an updated dataset and a revised point source stochastic model that captures the effect of a finite fault we consider four geometrical spreading functions ranging from 1 r at all distances to two or three part functions the values are sensitive to the rate of geometrical spreading at close distances with 1 r 1 3 spreading implying much higher than models with 1 r spreading the important difference in ground motions of most engineering con cern however arises not from whether the geometrical spreading is 1 r 1 3 or 1 r at close distances but from whether a region of flat or increasing geometrical spreading at intermediate distances is present as long as is constrained by data that are largely at distances of 100 km 800 km the simple 1 r model fits the sparse data for the eight events as well as do more complex models determined from larger datasets where the larger datasets were used in our previous ground motion predic tion equations this suggests that uncertainty in attenuation rates is an important com ponent of epistemic uncertainty in ground motion modeling for the attenuation model used by atkinson and boore 2006 the average value of from the point source model ranges from 180 bars to 250 bars depending on whether or not the stress parameter from the 1988 saguenay earthquake is included in the average we also find that for a given earthquake is sensitive to its moment magnitude m with a change of 0 1 magnitude units producing a factor of 1 3 change in the derived

attenuation of ground motion spectral amplitudes in southeastern australia a dataset comprising some 1200 weak and strong motion records from 84 earthquakes is compiled to develop a regional ground motion model for southeastern australia sea events were recorded from 1993 to 2004 and range in size from moment magnitude 2 0 m 4 7 the decay of vertical component fourier spectral amplitudes is modeled by trilinear geometrical spreading the decay of low frequency spectral amplitudes can be approximated by the coefficient of r 1 3 where r is hypocentral distance within 90 km of the seismic source from approximately 90 to 160 km we observe a transition zone in which the seismic coda are affected by postcritical reflections from midcrustal and moho discontinuities in this hypocentral distance range geometrical spreading is approximately r 0 1 beyond 160 km low frequency seismic energy attenuates rapidly with source receiver distance having a geometrical spreading coefficient of r 1 6 the associated regional seismic quality factor can be expressed by the polynomial log q f 3 66 1 44 log f 0 768 log f 2 0 058 log f 3 for frequencies 0 78 f 19 9 hz fourier spectral amplitudes corrected for geometrical spreading and anelastic attenuation are regressed with m to obtain quadratic source scaling coefficients modeled vertical component displacement spectra fit the observed data well amplitude residuals are on average relatively small and do not vary with hypocentral distance predicted source spectra i e at r 1 km are consistent with eastern north american ena models at low frequencies f less than approximately 2 hz indicating that moment magnitudes calculated for sea earthquakes are consistent with moment magnitude scales used in ena over the observed magnitude range the models presented represent the first spectral ground motion prediction equations developed for the southeastern australian region this work provides a useful framework for the development of regional ground motion relations for earthquake hazard and risk assessment in sea

modeling geometrical spreading and the relative amplitudes of vertical and horizontal high frequency ground motions in eastern north america abstract horizontally layered velocity models were used with point source and finite fault sources to investigate geometrical spreading and the relative amplitudes of vertical and horizontal ground acceleration within 120 km of the source full wave field simulations were done for a range of focal depths and for strike slip and reverse focal mechanisms the attenuation of the geometric mean of randomly oriented horizontal component maximum acceleration amplitudes averaged over all azimuths significantly exceeds the theoretical geometrical spreading for far field body waves in a homogeneous whole space for hypocentral distances less than approximately 60 km the behavior of the vertical component is different from the horizontal vertical attenuation near the epicenter is greater and is more dependent on source mechanism and depth because of the rapid near source decay of the direct s wave reflections from the mid lower crust and moho control the maximum amplitude of the vertical component acceleration in the 60 120 km hypocenter distance range resulting in a flattening of the vertical amplitude distance relation near source vertical maximum amplitudes averaged over all source receiver azimuths tend to be less than the geometric mean horizontal amplitude for strike slip focal mechanisms but near the source for reverse faults the azimuthally averaged vertical component amplitude exceeds that of the geometric mean horizontal the modeling indicates that similar vertical and horizontal component geometrical spreading and approximately constant horizontal vertical amplitude ratios observed in connection with the lg phase at distances greater than approximately 100 km in eastern north america may not hold at smaller distances ground motion prediction models for the vertical component near the source may need to incorporate strong geometrical spreading and dependence on radiation pattern

a generalization of the stochastic summation scheme of small earthquakes to simulate strong ground motions a generalization of the stochastic summation scheme of small earthquakes following a general form of the source spectrum n model is developed to estimate the proper probability density functions for rupture propagation over the fault and to simulate site specific strong ground motions in two independent stages the probability density functions for rupture propagation are first developed for a single corner frequency source model and then extended to multiplicative and additive double corner frequency source models to partially account for the effects of finite fault rupture such as fault geometry rise time and rupture time on ground motions and to better match observed fourier amplitude spectra fas the generalized two stage stochastic summation scheme developed in this study can be used to simulate realistic strong ground motion time histories from small events represented as empirical green s functions egfs by specifying only two source parameters of the seismic moment and stress drop for a given site the proposed two stage stochastic summation schemes are tested using numerical examples following the theoretical source models as well as observed ground motions of the 2011 mw 9 0 tohoku earthquake in japan and the 1994 mw 6 7 northridge earthquake in california to verify the applicability of the approach comparisons between the observed and simulated time histories for these two earthquakes their response spectra and fas show satisfactory performance of the proposed approach for engineering purposes the results of these comparisons indicate that the proposed stochastic summation of small events as egfs can adequately replicate observed ground motions and evaluate uncertainties in ground motions with the generation of many time history realizations corresponding to a multitude of possible rupture processes the proposed approach can also be used to generate multiple realistic acceleration time histories matched on average to the target response spectra for use in earthquake performance design and to develop ground motion models for low seismicity regions where there is a lack of recording of strong ground motions

parallel psm fdm hybrid simulation of ground motions from the 1999 chi chi taiwan earthquake a new technique for the parallel computing of 3 d seismic wave propagation simulation is developed by hybridizing the fourier pseudospectral method psm and the finite difference method fdm this psm fdm hybrid offers a good speed up rate using a large number of processors to show the feasibility of the hybrid a numerical 3 d simulation of strong ground motion was conducted for the 1999 chi chi taiwan earthquake mw 7 6 comparisons between the simulation results and observed waveforms from a dense strong ground motion network in taiwan clearly demonstrate that the variation of the subsurface structure and the complex fault slip distribution greatly affect the damage during the chi chi earthquake the directivity effect of the fault rupture produced large s wave pulses along the direction of the rupture propagation slips in the shallow part of the fault generate significant surface waves in coastal plain along the western coast a large velocity gradient in the upper crust can propagate seismic waves to longer distances with minimum attenuation the s waves and surface waves were finally amplified further by the site effect of low velocity sediments in basins and caused the significant disasters

a statistical model for ground motion produced by earthquakes at local and regional distances to adapt random process theory techniques for statistical estimation of peak ground motion to more realistic earth models we constrain the parameters of duration geometrical spreading and spectral shape by modeling the main ground motion as being the result of major contributions by the direct s wave and supercritically reflected s waves the results of our modeling are constrained to be consistent with values from full wave synthetics for the test models the combination of estimation theory and theoretical amplitude spectrum of the main ground motion within the ergodic window successfully predicts the mean peak vertical ground displacements velocities and accelerations of the 1982 miramichi earthquakes in new brunswick canada in addition upon considering the effects of source depth and crustal structure for the november 25 1988 saguenay earthquake m 5 8 in quebec canada the predicted mean peak horizontal ground accelerations match the observed data very well the effects of source depth and crustal structure on the peak ground motion are complicated for different source sizes and at different epicentral distance ranges

the 25 november 1988 saguenay quebec earthquake source parameters and the attenuation of strong ground motion the saguenay earthquake of 25 november 1988 occurred close to the southern margin of the saguenay graben in southern quebec it was caused by almost purely dip slip faulting centered at a depth of 26 km with a p axis oriented northeast southwest this faulting mechanism is similar to those of the larger historical earthquakes in eastern north america but the focal depth is substantially greater than all but one of these events the seismic moment estimated from regional pni waves and teleseismic long period body waves is 5 10 24 dyne cm corresponding to a moment magnitude of 5 8 the source duration of the earthquake is estimated to be 1 8 sec corresponding to a stress drop of 160 bars which is not significantly higher than the average stress drop of 120 bars estimated from previous large earthquakes in eastern north america in order to simultaneously match the recorded ground motion amplitudes of strong motion acceleration strong motion velocity and teleseismic short period and long period body waves it is necessary to use a source function having a complex shape that implies the presence of asperities and larger local stress drops the large set of strong motion recordings of the saguenay earthquake has been used to validate a procedure for estimating strong ground motion attenuation based on a simple wave propagation model the most important feature of the recorded strong motions is that their peak amplitudes do not decay significantly with distance inside 120 km but then decay abruptly beyond 120 km profiles of recorded accelerograms with absolute times indicate that at distances beyond 64 km the peak ground motions are due to strong postcritical reflections from velocity gradients in the lower crust the principal shear wave arrivals and the variation of their peak amplitudes with distance were reproduced in synthetic seismograms generated using a regional crustal structure model the critical distances for the postcritical reflections were short because of the deep focal depth of the event causing the elevation of ground motion amplitudes out to 120 km similar studies of earthquakes in other regions of eastern north america indicate that the strength of the postcritical reflections and the distance ranges over which they are dominant are controlled by the focal depth and crustal structure regional variations in crustal structure thus give rise to predictable regional variations in strong ground motion attenuation

evaluation of functional forms for the attenuation of small to moderate earthquake response spectral amplitudes in north america abstract we studied several attenuation forms to evaluate their ability to describe the decay of response spectral amplitudes in eastern canada northeastern united states central united states pacific northwest british columbia northern california and southern california linear bilinear and trilinear regression forms with different combinations of geometric spreading coefficients were tested to assess their ability to describe spectral amplitude decay from 0 33 to 10 hz in the distance range from 10 to 400 km the residual trends and the shapes of the attenuation forms do not show significant differences in goodness of fit between these trial forms making it difficult to see a meaningful distinction between them furthermore statistical measures such as the akaike information criterion are not particularly helpful in drawing such distinctions a simple linear model as well as more complex forms can fit the data in almost every region however this linear model has steeper slope in the west 1 3 than in the east 1 and may not extend well over large distances the linear model effectively smoothes through complications in functional form such as the moho bounce or the transition to surface wave spreading at regional distances a trilinear model has the best statistical fit in most cases but the added complications in shape and parameterization do not appear warranted by the marginal improvement in residuals the bilinear form offers a good compromise between simplicity and the ability to model amplitude decay appropriately at both near and regional distances

glacier response in the european alps to heinrich event 1 cooling the gschnitz stadial the gschnitz stadial was a period of regionally extensive glacier advance in the european alps that lies temporally between the breakdown of the last glacial maximum piedmont lobes and the beginning of the bolling warm interval moraines of the gschnitz stadial are found in medium to small catchments are steep walled and blocky and reflect a snowline lowering of 650 700 m in comparison to the little ice age reference snowline 10 be surface exposure dating of boulders from the moraine at the type locality at trins gschnitz valley tyrol austria shows that it stabilised no later than 15 400 1400 yr ago the overall morphological situation and the long reaction time of the glacier suggest that the climatic downturn lasted about 500 300 yr indicating that the gschnitz cold period began approximately 15 900 1400 yr ago if not somewhat earlier this is consistent with published radiocarbon dates that imply that the stadial occurred sometime between 15 400 14 c yr bp 18 020 19 100 cal yr and 13 250 14 c yr bp 15 360 16 015 cal yr a palaeoclimatic interpretation of the gschnitz glacier based on a simple glacier flow model and statistical glacier climate models shows that precipitation was about one third of modern day precipitation and summer temperatures were about 10 k lower than today in comparison during the younger dryas precipitation in this area was only about 10 less and ts summer temperature was only 3 5 4 k lower than modern values based on the age of the moraine and the cold and dry climate at that time we suggest that the gschnitz stadial was the response of alpine glaciers to cooling of the north atlantic ocean associated with heinrich event 1 copyright 2005 john wiley sons ltd