region specific key seismic parameters for earthquakes in northern iran strong motion accelerograms recorded within northern iran are used to examine the propagation characteristics of shear wave including geometric spreading behavior q value j 0 and horizontal to vertical h v ratio these region specific key seismic parameters are estimated from 259 three component records of 22 earth quakes with magnitude ranging from m 4 9 to m 7 4 in northern iran the geometric spreading follows a trilinear behavior with a strong postcritical reflection from the moho the first and second hinges of the trilinear behavior are at 75 and 150 km respectively the associated q value based on the vertical component is q 87 f 1 46 j0 value for vertical and horizontal components are 0 03 and 0 05 respec tively because of lack of station specific site information the h v ratio is considered to be a rough estimation of generic site amplification the obtained region specific parameters are used to estimate the average stress drop based on three stochastic modeling approaches stochastic point source modeling suggests a brune stress drop of 125 bars whereas stochastic finite fault modeling based on static and dynamic corner frequency approaches suggests a stress drop of 68 bars

simulation of strong ground motion during the 1950 great assam earthquake in this paper ground motion during the independence day earthquake of august 15 1950 mw 8 6 ben menahem et al 1974 in the northeastern part of india is estimated by seismological approaches a hybrid simulation technique which combines the low frequency ground motion simulated from an analytical source mechanism model with the stochastically simulated high frequency components is used for obtaining the acceleration time histories a series of ground motion simulations are carried out to estimate the peak ground acceleration pga and spectral accelerations at important cities and towns in the epicentral region one sample pga distribution in the epicentral region encompassing the epicenter is also obtained it is found that pga in the epicentral region has exceeded 1 g during this earthquake the estimated pga s are validated to the extent possible using the mmi values the simulated acceleration time histories can be used for the assessment of important engineering structures in northeastern india

integrated use of seismograph and strong motion data to determine soil amplification response of the fraser river delta to the duvall and georgia strait earthquakes we present a new method to estimate site amplification in which re gional seismographic data are used to constrain the input motions to the soil profile the empirical inferred amplification is determined as the ratio of the fourier spec trum of the recorded motion on soil to the spectrum of the inferred input motion at the underlying bedrock interface the method is demonstrated for sites on the fraser river delta british columbia b c that recorded the 1996 m 5 1 duvall wash ington and 1997 m 4 3 georgia strait b c earthquakes regional seismographic recordings on rock sites are used to determine the apparent source spectra of these events these spectra are attenuated to sites in the fraser river delta then input to a specified soil profile we compare the empirical inferred amplification to alternative estimates of the soil amplification based on 1 the quarter wavelength approach and 2 the assumption that the amplification is approximately equal to the observed h v ratio the empirical inferred amplification estimates are grossly consistent with the theoretical amplification estimates but have larger peaks at specific frequencies probably due to resonant effects not accounted for in the quarter wavelength ap proach the h v ratio appears to be a simple and useful first approximation to the site response the fraser river delta amplifies weak motions by factors of three to six over a broad frequency range from 0 2 to 4 hz high frequency motions f 10 hz are attenuated the long period amplifications pose a serious concern in the event of strong earthquake shaking from large earthquakes a useful by product of the analysis is the determination of apparent source spectra for the events the apparent source spectrum of the georgia strait earthquake is in good agreement with the brune point source model with a stress drop of approxi mately 45 bars the apparent source spectrum of the slightly larger duvall earthquake is in reasonable agreement with the brune model with a stress drop of about 70 bars however for the duvall earthquake there is evidence of a sag in spectral amplitudes relative to the brune model at intermediate frequencies 0 3 to 1 hz this inter mediate frequency sag is an expected result of source complexity it is well dem onstrated by the broadband seismic data

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

dissolution and time dependent compaction of albite sand experiments at 100 c and 160 c in ph buffered organic acids and distilled water abstract aqueous fluids are important in the diagenesis and deformation of crustal rocks both chemical and physical interactions are involved and often they are strongly coupled for example pore waters not only dissolve transport and precipitate chemical species but they also substantially affect the mechanical behavior of the rocks that contain them stresses magnified at grain contacts by differences in pore fluid pressure p p and confining pressure p c can in turn influence the rate and extent of chemical exchange to begin investigation of these coupled systems compaction experiments were conducted using albite sand 250 500 m and distilled water ph 5 8 0 07 m acetate ph 4 7 and 0 07 m acetate 0 005 m citrate ph 4 4 solutions in a hydrothermal flow through system at conditions that simulate diagenesis pore fluid chemistry and pore volume loss were monitored to quantify the effects of organic acids on time dependent compaction rates the effects of stress and fluid chemistry on the dissolution kinetics were also examined albite dissolution rates monitored by steady state fluid chemistry increased when an effective pressure p e p c p p was applied probably due to increases in total surface area caused by grain breakage at contacts these effects were transient in distilled water however si and al concentrations remained elevated in the acetate pore fluid the average si based release rates indicate 35 increase in reactive surface area by application of p e 34 5 mpa at 100 c with p e 34 5 mpa steady state si concentrations were 2 3 times higher in 0 07 m acetate and 5 8 times higher in 0 07 m acetate 0 005 m citrate than in distilled water al increased by even larger factors 3 in the acetate buffer and 10 in the citrate solution these changes in fluid chemistry are attributed to both ph and ligand enhanced reactions albite dissolution appears to be controlled by surface complexation reactions at al sites rapid dissolution of albite in the organic acid solutions is probably due to the ability of organic acid ligands to selectively complex with aluminum time dependent compaction was observed at 100 and 160 c with p e 34 5 mpa strain rates increased with temperature from 10 9 s l at 100 c to 10 8 s l at 160 c and decreased with strain in all pore fluids especially at 100 c compaction rates in distilled water and in the acetate solution had similar magnitudes and strain dependencies however small amounts of citrate species apparently enhance compaction compared to the other fluids at similar strains textural data indicate that time dependent compaction of the albite sand occurred primarily by brittle mechanisms at these temperatures however the deformation is clearly thermally activated and may be chemically assisted by the aqueous pore fluid

source parameters of earthquakes in eastern and western north america based on finite fault modeling the ground motion from large earthquakes is often predicted based on finite fault modeling in which the fault plane is discretized into small independently rupturing subfaults the radiation from all subfaults is summed at the observation point despite the success of the method in matching observed ground motion char acteristics the physical interpretation of the subfaults has remained largely unclear and a rationale for the choice of the subfault attributes has been lacking two key parameters the subfault size and the maximum slip velocity on the fault govern the amplitude of the source spectrum at intermediate and high frequencies respec tively we determined these key source parameters on an event by event basis for all well recorded moderate to large earthquakes in western north america wna by fitting simulated to observed response spectra we compare the values of these source parameters with those obtained previously for eastern north america ena and the michoacan mexico earthquakes a total of 26 modeled events we find that the characteristic subevent size increases linearly with moment mag nitude in an apparently deterministic manner the subevent size relationship obtained for wna is not statistically different from that obtained for ena in both regions the subevent size follows the trend of log dl 2 0 4 m 4 m 8 where dl is the subfault size in km this trend agrees well with independent studies by somerville et al 1999 and aki 1992 in which the characteristic size of the patches asperities or barriers on earthquake faults was determined these results indi cate that large earthquakes should be viewed as a sequence of smaller events that comprise the large rupture interestingly the characteristic size of these constituent small events appears to be directly related to the size of the overall rupture the slip velocities determined for all 26 earthquakes vary in a narrow range from about 0 25 to 0 60 m sec with a mean of 0 40 m sec and standard deviation of 0 09 m sec the slip velocities for the ena events are distributed randomly over this range while those for the wna region appear to exhibit a decreasing trend with increasing magnitude our results indicate that a generic region independent earthquake source model for engineering prediction of strong ground motions can be developed

spectral decay parameter k of western iran using accelerograms recorded up to 2018 an important parameter that controls strong ground motion at high frequencies higher than 1 hz is the spectral decay or kappa k parameter this parameter is a linear decay factor for fourier spectrum of acceleration on a linear logarithmic scale within a certain frequency range which indicates the range of attenuation of high frequency energy this parameter is used as a key input for the simulation of strong ground motion through a random method this study aims to estimate the kappa parameter for the west of iran that has a high seismic activity hence 10 reference earthquakes as well as 76 accelerograms recorded from 1973 until 2018 are used including the 7 3 magnitude ezgeleh kermanshah earthquake on november 12 2017 the k is derived for the latest seismotectonic zoning map of iran to enhance the accuracy of calculations and only the records in which the reference earthquake and accelerograms occurred in the same zone are considered in the k equation the k parameter is calculated separately for each horizontal component and for the mean then the linear relationships between the kappa and distance are separately calculated and analyzed for each seismic zone an accumulative equation is also proposed for all zones the presented equations indicate that the near surface attenuation parameter k0 for the west seismic zones of iran varies from 0 0331 to 0 0398 this parameter can be used effectively to calculate the strong ground motion in the zones using synthetic methods

spectral analysis of seismic waves in the northern indian ocean region abstract attenuation of ground motion amplitudes away from the seismic source is recognized as a significant issue by researchers of particular interest is the attenuation or propagation of seismic waves from long distance sources regions like sri lanka have experienced tremors from events as far as 1500 km a recently identified diffusing plate boundary just around 300 km away from the southern tip of sri lanka poses significant seismic risk however a comprehensive study of the region with respect to the propagation or attenuation of seismic waves has generally been lacking with the availability of new archival data of 71 events recorded at three digital broadband stations we have estimated q value for the northern indian ocean region surrounding sri lanka multiple linear regression analysis of recorded vertical component fourier acceleration amplitudes yields a relatively higher q 0 value of about 389 2 35 for the subject region furthermore the combined effect of upper crustal amplification and attenuation has been assessed using the standard horizontal to vertical ratio method the negligible upper crustal modifications obtained from the analysis imply the presence of an older crustal rock stratigraphy at near source depths around the subject region source spectra of recorded events have also been derived by correcting the observed amplitudes for geometric and anelastic attenuation the source spectra analysis resulted in a typical stress drop value of about 50 bars which is consistent with brune s source spectra models stochastic modeling of a recent m w 8 6 event that occurred in the region was undertaken based on the parameters derived from the analysis and compared with the real recorded spectra results show a reliable match between the simulations and the recorded spectra which supports the validity of the estimated parameters seismological parameters derived from this study can provide reliable estimates of seismic hazard of sri lanka

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

site amplification and frequency dependent attenuation coefficient at rock sites of the himachal region in northwest himalaya india abstract the s wave fourier amplitude spectra from the strong motion network data in the himachal region of the northwest himalaya are used to estimate site amplification and s wave attenuation q for this analysis 60 three component records were used from eight earthquakes with magnitudes ranging from m 3 4 to 5 4 recorded at 13 stations over a hypocentral distance range of r 9 48 km the characteristics of the site amplification are analyzed using horizontal to vertical h v fourier spectral ratios of the s phase of the time history the average amplification is close to unity except in a narrow frequency range of 2 4 hz the overall behavior of the h v ratio is consistent with local geological conditions of the study region the s wave quality factor q f is estimated as 103 f 0 66 for 0 2 f 20 hz and the validity is checked by computing path attenuation functions derived from the new q f the estimated q f is also compared with results from previous studies of q for the himalayan region

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

a probabilistic procedure for scenario based seismic hazard maps of greater tehran abstract the seismic hazard assessment of tehran the capital of iran with a population of over 10 million is necessary in the decision making process for risk reduction the main objective of this paper is to present a procedure for obtaining maximum hazard maps in seismically active regions such as tehran with a history of destructive earthquakes but where the number of the instrumentally recorded large magnitude events is small the deterministic and probabilistic seismic hazard methods are two quantitative approaches with some practical limitations to overcome their limitations the bayesian statistics are used to estimate maximum earthquake magnitude by combining prior seismological information with the available limited data the bayesian approach is used to estimate maximum earthquakes corresponding to different individual ground motion scenarios at a specific hazard level the maximum hazard maps are obtained by merging different individual worst case ground motion scenarios at a specific hazard level the hazard analyses under different scenarios are conducted by the finite fault procedure which uses geological and seismological parameters for each seismic source the obtained results are in agreement with the observed intensities of historical earthquakes moreover the conventional approach of probabilistic seismic hazard analysis is presented to show the difference between the two procedures the findings provide information about the seismic design or retrofit of structures and infrastructures

stochastic finite fault modeling of ground motions from the 1994 northridge california earthquake i validation on rock sites the stochastic method of simulating ground motions from finite faults is validated against strong motion data from the m 6 7 1994 northridge california earthquake the finite fault plane is subdivided into elements each element is as signed a stochastic o92 spectrum and the delayed contributions from all subfaults are summed in the time domain simulated horizontal acceleration time histories and fourier spectra at 28 rock sites are compared with observations we first perform simulations using the slip distribution on the causative fault derived from strong motion teleseismic gps and leveling data wald et al 1996 we then test the performance of the method using quasi random distributions of slip and alternative hypocenter locations this is important because the rupture initiation point and slip distribution are in general not known for future earthquakes the model bias is calculated as the ratio of the simulated to the observed spectrum in the frequency band of 0 1 to 12 5 hz averaged over a suite of rock sites the mean bias is within the 95 confidence limits of unity showing that the model provides an accurate prediction of the spectral content of ground motions on average the maximum excursion of the model bias from the unity value when averaged over all 28 rock stations is a factor of approximately 1 6 at most frequencies it is below a factor of 1 4 interestingly the spectral bias and the standard deviation of the stochastic simu lations do not depend on whether the fault slip distribution and hypocenter location are based on data or are randomly generated this suggests that these parameters do not affect the accuracy of predicting the average characteristics of ground motion or they may have their predominant effect in the frequency range below about 0 1 hz below the range of this study the implication is that deterministic slip models are not necessary to produce reasonably accurate simulations of the spectral content of strong ground motions this is fortunate because such models are not available for forecasting motions from future earthquakes however the directivity effects controlled by the hypocenter location are important in determining peak ground ac celeration at individual sites although the method is unbiased when averaged over all rock sites the simulations at individual sites can have significant errors generally a factor of 2 to 3 which are also frequency dependent factors such as local geology site topography or basin propagation effects can profoundly affect the recordings at individual stations to generate more accurate site specific predictions empirical responses at each site could be established

stochastic finite fault modeling of subduction zone earthquakes in northeastern india in this article a stochastic finite fault source model is calibrated to estimate ground motion in northeastern india for intermediate depth events originating in the indo burmese tectonic domain a total of 47 three component accelerograms from eight events with magnitudes ranging from m w 4 8 6 4 are used to estimate the input source and site parameters of the finite fault source model key seismic parameters such as stress drop and site amplification function are determined from the recorded strong motion data the obtained stress drop of the eight recorded events lies in between 105 and 165 bars

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

new insights into path attenuation of ground motions in northeast india and northwest himalayas abstract we compile a data set of 585 weak broadband and strong ground motion recordings from 184 earthquakes covering hypocentral distances ranging from 9 to 436 km in northeast india and the northwest himalayas source normalized vertical component fourier amplitude s wave spectra are used to study path attenuation characteristics namely geometrical spreading and quality factor in the two regions a trilinear model of geometrical spreading of r 1 0 for hypocentral distance r r 0 0 for r between 125 km and 140 km and r 1 0 for r 140 km approximates the decay of low frequency 1 0 hz amplitudes in northeastern india better than the conventional theoretical bilinear geometrical spreading of r 1 0 for r r 0 5 otherwise in the northwestern himalayas the geometrical spreading is found to be r 1 0 which is the same as that of a bilinear model at hypocentral distances r f given by in the frequency range of 0 9 20 hz

subevent structure of large earthquakes a ground motion perspective our ability to predict ground motions from future earthquakes hinges on the accurate modeling of the radiation from the earthquake source a successful approach to modeling earthquake radiation has been to represent faults as a series of discrete independently rupturing subfaults although their physical interpretation has remained largely unclear our simulation of ground motions from twenty six well recorded moderate to large earthquakes substantiates the hypothesis that large ruptures are made up of a sequence of smaller subevents the size of a subevent follows a simple linear relationship with the size of the earthquake fault in an apparently deterministic manner the strength of the high frequency radiation is controlled by the maximum slip velocity which varies stochastically over a small range both the characteristic subevent size and the slip velocity appear to be region independent indicating a remarkable uniformity in earthquake source properties this observation helps to reduce the uncertainty in ground motion prediction by constraining its essential and previously ambiguous parameters

modeling of strong motion data in northeastern india q stress drop and site amplification abstract in this article point source seismological model is used to model the available strong motion accelerograms in northeastern india key seismic parameters such as quality factor q value kappa factor 0 site amplification and stress drop are derived from the strong motion data a total of 111 three component records coming from seven earthquakes with magnitudes ranging from m w 5 2 to 7 2 are used in obtaining the source and path parameters the q value of the indo burma tectonic domain which is a subduction zone is obtained as 431 f 0 7 for the bengal basin shillong plateau region the quality factor is estimated as 224 f 0 93 the kappa factors for vertical and horizontal components are obtained as 0 013 and 0 033 for soft rock type sites for firm ground sites 0 is estimated as 0 025 for vertical and 0 041 for horizontal components respectively the site amplification functions for soft rock and firm ground conditions are found from the horizontal to vertical ratio the obtained stress drops of the seven events lie between 128 and 282 bars the source parameters obtained in this study provide a useful framework for working out ground motion relations in northeastern india

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 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

modeling some empirical vertical component lg relations abstract higher mode surface wave theory is used to model the vertical component lg wave observed in eastern north america at regional distances tests of the model are made to determine whether it is capable of describing empirical spectral scaling laws spatial attenuation and peak time domain lg amplitudes it is found that a simple crustal model and a rough estimate of crustal qb are all that are required to accomplish this good results are obtained if the average crustal qp is equated to the coda q of the same frequency introduction the lg wave is a wave observed on short period seismograms of local and regional seismic events which travels with a group velocity of approximately 3 5 km sec in the central united states it is usually the largest arrival on the seismogram which makes it suitable for defining a magnitude scale nuttli 1973 herrmann and nuttli 1982 as part of developing the magnitude scale there have been many studies on the spatial attenuation of the lg wave nuttli 1973 street 1976 bollinger 1979 singh and herrmann 1982 the lg wave is usually thought of as a superposition of higher mode surface waves propagating within the crustal wave guide herrmann and nuttli 1975a b attempted to deterministically model observed lg amplitudes in terms of focal mechanism focal depth and seismic moment using surface wave techniques they were limited by their inability to compute surface wave eigenfunctions at frequencies greater than 0 5 hz however their results were encouraging harkrider 1979 drawing upon the work of apsel 1979 discovered a way to compute surface wave energy integrals of the higher modes very precisely bache

local and regional p wave spectral attenuation model for iran a robust frequency dependent local and regional p wave attenuation model is estimated for continental paths in the iranian plateau in order to calculate the average attenuation parameters 46 337 vertical component waveforms related to 9267 earthquakes which are recorded at the iranian seismological center irsc stations have been selected in the distance range 10 1000 km the majority of the event s magnitudes are less than 4 5 this collection of records provides high spatial ray path coverage results indicate that the shape of attenuation p wave curve versus distance is not uniform and has three distinct sections with hinges at 90 and 175 km a trilinear model for attenuation of p wave amplitude in the frequency range 1 10 hz is proposed in this study fourier spectral amplitudes are found to decay as r 1 2 where r is hypocentral distance corresponding to geometric spreading within 90 km from the source there is a section from 90 to 175 km where the attenuation is described as r 0 8 and the attenuation is described well beyond 175 km by r 1 3 moreover the average quality factor for pg and pn waves qpg and qpn related to anelastic attenuation is obtained as qpg 54 2 2 6 f 1 0096 0 07 and qpn 306 8 7 4 f 0 51 0 05 there is a good agreement between the results of the model and observations also the attenuation model shows compatibility with the recent regional studies from the results it turns out that the amplitude of p waves attenuates more rapidly in comparison with the global models in local distances

earthquake source spectra in eastern north america source spectra for earthquakes of 3 m 7 in eastern north america ena are determined from regional seismograph recordings strong motion records teleseismic data and modified mercalli intensity data the inclusion of mmi data is made possible by the finding that the felt area of an earthquake is an accurate measure of its high frequency spectral level at the source current ground motion relations for ena are based on a brune source model with a stress parameter of 100 bars this model is a poor fit to ena source spectra for events of m 4 at high frequencies 5 to 10 hz observed spectral amplitudes are more nearly matched by a brune stress parameter of 200 bars intermediate frequency amplitudes near 1 hz are matched by a stress parameter of approximately 50 bars an empirical two corner source model is proposed to describe ena source spectra for events of 4 m 7

simulation of strong ground motion in northern iran using the specific barrier model summary in this study based upon the calibrated specific barrier model sbm against the latest available strong motion data ground motion prediction equations for soil and rock sites in northern iran are developed the sbm may provide the most complete simple and self consistent description of the faulting process which is applicable in both near fault and far field regions consequently the sbm may provide consistent ground motion simulations over the entire necessary frequency range and for all distances of engineering interests to determine source parameters in this study we used 163 three component records of 32 earthquakes with magnitude ranging from mw 4 9 to 7 4 in northern iran in the database records with hypocentral distances less than 200 km are chosen and only earthquakes whose moment magnitude estimates are available have been used furthermore using the best available information recording sites are classified into two main geologic categories rock and soil because of the lack of site amplification information in the most regions of the world including iran we used the h v ratio method for estimating the site amplification moreover the kappa factor that shows diminishing the high frequency amplitude is determined in this study two data sets are considered for determining the source parameters g and l and the h v ratio and the kappa factor only s wave part of signals is used in each analysis regression analysis is performed using random effects method that considers both interseismic event to event and coseismic within event variabilities to effectively deal with the problem of weighting observations from different earthquakes the residuals are controlled against available northern iranian strong ground motion data to verify that the model predictions are unbiased and that there are no significant residual trends with magnitude and distance at first it is assumed that no sign of self similarity breakdown is observed between the source radius and its seismic moment after controlling the results the modified sbm should be used as some deviations have been observed to verify the robustness of the results the number of observations is changed by removing various randomly selected data sets from the original database which results in unchanged results of the model stochastic simulations are then implemented to predict peak ground motion and response spectra parameters the stochastic sbm predictions are in relatively good agreement with other available attenuation relationships proposed for iran europe and middle east it has been shown that the proposed sbm of this study provides unbiased ground motion estimates over the entire frequency range of most engineering applications it provides a reliable and physically realistic yet computationally efficient way to model strong ground motions

comparison of the taiwan chi chi earthquake strong motion data and ground motion assessment based on spectral model from smaller earthquakes in taiwan the design of buildings and structures in earthquake prone regions must be based on information relating to expected seismic effect estimations of time domain and spectral parameters of ground motion are obtained by empirical relations that connect these to earthquake magnitude distance and local soil conditions in the taiwan region the models for estimating ground motion parameters were obtained recently on the basis of recordings of small to moderate 5 0 m l 6 5 earthquakes a large collection of acceleration records from the recent m l 7 3 m w 7 6 chi chi earthquake and aftershocks makes it possible to test the applicability of the established models in the case of larger events we compared modeled fourier amplitude spectra and peak accelerations and response spectra which were calculated using the stochastic approach from the fourier spectra and the data obtained during the mainshock and the largest aftershocks m l 6 6 6 8 it has been shown that the previously established regional spectral model fourier spectra of ground acceleration may be applied for evaluation of ground motion parameters for earthquakes reverse faulting of magnitudes up to m l 6 8 7 0 and hypocentral depth more than 10 km to satisfy to the peculiarities of ground motion propagation during shallow depth less than 10 km events the model should be revised the analysis of accelerograms from the mainshock m l 7 3 depth 8 km 314 records and large shallow aftershock m l 6 8 depth 10 km 350 records allows the authors to obtain the revised spectral model for average soil conditions manuscript received 31 may 2001

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

stochastic strong ground motion simulation of the 12 november 1999 duzce turkey earthquake using a dynamic corner frequency approach on 12 november 1999 only three months after the 17 august 1999 kocaeli earthquake mw 7 4 an earthquake of mw 7 1 occurred immediately to the east of the kocaeli rupture in northwestern turkey resulting in extensive structural damage in the city of duzce and its surrounding area it was reported to be a right lateral strike slip event on the previously unbroken segment of the north anatolian fault zone with a north dipping fault plane this paper presents stochastic finite fault simulation of near field ground motions from this earthquake at selected near fault stations based on a dynamic corner frequency approach using the computer program exsim motazedian and atkinson 2005 the method requires region specific source path and site characterizations as input model parameters the source mech anism of the 1999 duzce event and regional path effects are well constrained from previous studies of the earthquake the local site effects at the selected stations are studied as a combination of the kappa operator and frequency dependent soil ampli fication the model parameters are validated against recordings and a stress drop value of 100 bars is estimated for the 1999 duzce earthquake the validated model is then used to compute synthetic records around the fault distribution of peak ground motion parameters is observed to be consistent with the building damage dis tribution in the near fault region most affected by the seismic shaking the attenuation of synthetic ground motion parameters is compared with recent ground motion pre diction equations proposed for the region by gulkan and kalkan 2002 ulusay et al 2004 and akkar and bommer 2007 as well as two next generation attenuation models by boore and atkinson 2007 and campbell and bozorgnia 2007 despite discrepancies at several stations stochastic finite fault modeling based on a dynamic corner frequency approach confirms to be a practical tool to reproduce the ground motions of large earthquakes

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

ground motion amplification at rock sites across canada as determined from the horizontal to vertical component ratio we determine the frequency dependent amplification inherent in hard rock sites across canada under the assumption that it can be estimated from the ratio of the horizontal to vertical h v components of ground motion the use of h v as an estimate of amplification was originally proposed by nakamura 1989 for microtremors and then generalized to earthquake ground motions by lermo and chavez garcia 1993 the h v method was applied to a fourier spectra database compiled from 424 earthquakes of magnitude greater than or equal to 2 recorded on 32 three component stations of the canadian national seismograph network cnsn all sited on rock shear wave velocity 1500 m sec in each case we analyzed the s wave portion of the seismograms including the direct s and other strong s phases such as lg the average amplification h v for rock sites does not vary significantly across the country it is weakly frequency dependent increasing from a factor near unity at 0 5 hz to a maximum in the range from 1 2 to 1 6 at 10 hz this amplification is consistent with what would be expected from a gradual decrease in shear wave velocity as the seismic waves approach the surface due to factors such as near surface weathering the interpretation of the h v ratio as a measure of site response is consistent with the general geological conditions of the recording sites in particular the 5 hz h v ratio can be correlated with local geological conditions the central canada sites have the lowest estimated site amplification this is consistent with competent hard rock site conditions with high near surface shear wave velocities there are two stations that show anomalous h v ratios that suggest significant local site effects these are edm near edmonton which may be influenced by topographic amplification and a61 a station in the charlevoix seismic zone

simulation of ground motion in the zagros region of iran using the specific barrier model and the stochastic method abstract physically based ground motion prediction equations for soil and rock sites in the zagros region have been developed based on the specific barrier model sbm used within the context of the stochastic model instead of direct time domain simulation random vibration theory was used to estimate measures of peak motion in terms of the pseudospectral velocity of anelastic harmonic oscillator with 5 viscous damping to avoid the uncertainties calibration of the source model uses a database of carefully selected strong motion data without ambiguity about the site condition therefore only rock sites are selected for determining source parameters also to avoid any inconsistencies caused by magnitude conversion formulas we restricted the dataset only to events with available moment magnitudes regression analysis is performed using the random effects model that considers both interevent and intraevent variabilities to effectively deal with the problem of an unequal number of records from different earthquakes no sign of self similarity breakdown is observed between the source radius and its seismic moment the local and global stress drops derived for the zagros region 39 and 116 bars respectively are more consistent with the values obtained by other authors for an interplate regime than the values for an intraplate region however from the viewpoint of source heterogeneity as the ratio of the stress drops is an indicator of the complexity of the source and heterogeneity of slip on the fault the zagros events which have a stress drop ratio of about three are more homogeneous than other interplate events stochastic simulations are then implemented to predict peak ground motion and response spectra parameters for rock and soil site conditions online material catalog tables of earthquakes and attenuation tables

analysis of accelerations from the 1 october 1995 dinar turkey earthquake the dinar earthquake 1 october 1995 occurred in southwestern turkey and had a moment magnitude of 6 4 and a normal faulting mechanism the earthquake caused 90 deaths over 200 injuries and a large amount of damage it was recorded by seven strong motion accelerographs the strong motion accelerograph at dinar is on the edge of the surface projection of the fault the record from dinar is possibly unique in its proximity to the causative fault for this type of mechanism the dinar strong motion station is in a small stiff building on soft sediments with a shallow water table the peak acceleration was 0 32 g on the horizontal component perpendicular to the fault trace the earthquake was caused by rupture on the dinar fault which is a normal fault trending generally toward the south southeast with the hanging wall on the west there was surface rupture along about a 12 km segment of this fault the dinar strong motion station is at the south end of the fault under 1 km from the nearest surface trace the hypocenter was at the south end beneath dinar with rupture propagating toward the north and away from the strong motion site a specific composite source model was found that reproduces the statistical characteristics of the ground motions and also approximately reproduces the low frequency waveform in the strong motion in this model the fault length l is 12 5 km the width w is 17 3 km and the moment m 0 is 4 72 10 25 dyne cm the fault strikes 130 and dips 45 toward the southwest from the surface to 12 km for the composite parameters the largest subevent r max is 4 0 km the rupture velocity is 1 5 km sec and the subevent stress drop is 60 bars after anderson 1997 the composite source model parameters imply that the static stress drop was 36 bars the radiated seismic energy in this event was 4 3 10 21 ergs the apparent stress was 18 bars and the savage wood ratio was 1 0 most of the seismic energy is released at depths greater than 2 km the major asperity is beneath the location where synthetic aperture radar interferometry found the maximum surface deformation