seismic microzonation based on large geotechnical database application to lisbon abstract historically portugal has suffered the effects of several strong earthquakes in particular lisbon and the south and southwestern portuguese coast were affected by the largest known european earthquake on november 1st 1755 it is well known that the local ground conditions strongly affect the seismic ground motion modifying the signal s amplitude duration and frequency content which induces large variability in the motion induced to buildings and infrastructures aware of this situation the lisbon municipality promoted the development of a project to elaborate a new seismic microzonation map based on a large geotechnical database and geological data the eurocode 8 ground classification based on the vs30 parameter was adopted as reference however the geotechnical database has a very small number of geophysical logs and is mainly composed of borehole data and spt blows number an expedited methodology was applied to determine the n30 parameter as a proxy of the vs30 parameter non invasive field experiments surface waves seismic profiles and hvsr performed with ambient vibrations and data collected from independent geophysical reports were also used to check and validate the classification based on n30 because the distribution of the classified profiles was not uniformly distributed the final microzonation map was obtained from the combination of the profile classification and the surface geology

late quaternary benthic foraminifera and deep water paleoceanography in the south china sea abstract recent and late quaternary deep sea benthic foraminifera in the south china sea scs have been quantitatively studied in order to approach some disputable questions about the glacial deep circulation of the pacific from the paleoceanographic records of a marginal sea for example whether or not there existed the north pacific deep water npdw during glacials based on the quantitative data of deep sea benthic foraminiferal faunas from sixty six surface sediment samples of the scs a q mode factor analysis indicates that the globocassidulina subglobosa assemblage the astrononion novozealandicum and bulimina aculeata assemblages and the eggerella bradyi assemblage are associated with the intermediate water mass iwm deep water mass dwm and the deep water below ccd in the scs respectively the factor assemblages resulted from surface sample data were then applied to the quantitative analysis of late quaternary deep sea benthic foraminifera in eight cores from the scs and western pacific the results show a generally increased contribution of the dwm assemblage relative to that of the iwm assemblage during glacials which implies that the influence of the dwm increased and that of the iwm decreased in the scs and western pacific however there were two major deep water paleoceanographic changes during the late quaternary 1 the deep sea carbonate dissolution of the scs and western pacific was intensified during 18 0 stages 4 5 evidenced by the higher arenaceous calcareous ratios of benthic foraminifera and relative abundance of eggerella bradyi 2 the influence of the pacific dwm above 2500 m greatly increased during the last glacial maximum lgm inferred from the increased abundances of the pacific dwm benthic foraminiferal assemblage as compared to those of the pacific iwm and pacific bottom water mass assemblages in the western pacific particularly the water in which favocassidulina favus was distributed could not enter the scs since the lgm meanwhile the great changes had taken place in the dwm of the scs during the lgm reflected in the occurrence of a clearly cooled and ventilated dwm and the replacement of a novozealandicum and b aculeata assemblages by b aculeata melonis barleeanum assemblage at water depths of 1000 2500 m these significant changes during the lgm may be related to the formation of the npdw

modern distribution patterns of planktonic foraminifera in the south china sea and western pacific a new transfer technique to estimate regional sea surface temperatures abstract we present 30 new planktonic foraminiferal census data of surface sediment samples from the south china sea recovered between 630 and 2883 m water depth these new data together with the 131 earlier published data sets from the western pacific are used for calibrating the simmax 28 transfer function to estimate past sea surface temperatures this regional simmax method offers a slightly better understanding of the marginal sea conditions of the south china sea than the linear transfer function fp 12e which is based only on open ocean data however both methods are biased toward the tropical temperature regime because of the very limited data from temperate to subpolar regions the simmax formula was applied to sediment core 17940 from the northeastern south china sea with sedimentation rates of 20 80 cm ka results revealed nearly unchanged summer temperatures around 28 c for the last 30 ky while winter temperatures varied between 19 5 c in the last glacial maximum and 26 c during the holocene during termination 1a the winter estimates show a younger dryas cooling by 3 c subsequent to a temperature optimum of 24 c during the bolling allerod estimates of winter temperature differences between 0 and 100 m water depth document the seasonal variations in the thickness of the mixed layer and provide a new proxy for estimating past changes in the strength of the winter monsoon

foraminiferal responses to upwelling variations in the south china sea over the last 220 000 years abstract late quaternary benthic and planktonic foraminiferal and isotopic data were obtained from two sediment cores in the present upwelling areas of the south china sea core 17928 off northwestern luzon and core 17954 off eastern vietnam quantitative analyses of foraminifera in the two cores revealed the foraminiferal responses to paleoceanographic changes over the last 220 000 years high productivity species such as neogloboquadrina dutertrei bulimina acculeata uvigerina peregrina melonis barleeanus and chilostomella oviodea displayed high abundance during interglacial periods in core 17954 and during glacial periods in core 17928 correspondingly variations in benthic foraminifera accumulation rates the ratio of infaunal to epifaunal benthic foraminifera and the presence of the benthic foraminifers cibicidoides miloilids and oridorsalis umbonatus all indicate that bottom water was oxygen rich and oligotrophic during glacial periods off vietnam core 17954 but such bottom conditions occurred during interglacial periods off luzon core 17928 sea surface temperature results from planktonic foraminifera transfer function and variations in the abundance of planktonic foraminifera typical tropical species globigerina sacculifer tropical subtropical species globorotalia menardii globigerinoides ruber and pulleniatina obliquiloculata transition species globorotalia inflata and arctic species neogloboquadrina pachyderma indicate an increase in cool waters during marine isotope stage mis 5 except for mis 5 5 and glacial intervals in the cores 17954 and 17928 respectively the ratios of mixed layer thermocline dwelling species and depth of thermocline dot estimates using transfer function suggest that the dot was shallower during the interglacial than the glacial periods off vietnam core 17954 but the dot was shallower during the glacial periods off luzon core 17928 our results show that in the glacial periods lower sea surface temperature shoaled thermocline and high productivity increased off northwestern luzon core 17928 and that on the contrary similar event occurred in the interglacial off vietnam core 17954 these differences in the upper water column structure and productivity in the two areas were induced by coastal upwelling which in turn is driven by monsoons the intensity of upwellings is also closely related to the evolution of the eastern asian monsoon therefore we conclude that differences in the upwelling intensity in the two sites indicate strengthening of winter and summer monsoon during the glacial and interglacial periods respectively

a comparison and test of various site response estimation techniques including three that are not reference site dependent abstract we compare various site response estimation techniques using after shock data of the 1989 loma prieta earthquake collected in oakland california because of recent interest in comparing results from weak and strong motion to infer any nonlinearity and between direct s and coda waves we pay particular attention to the uncertainties first sediment to bedrock spectral ratio estimates between pairs of sites are compared with those obtained from various generalized inversion approaches where the source and site effects of multiply recorded events are solved for simultaneously we find that the site amplification factors are very similar among these approaches but that the uncertainties can be significantly different depending on how the data are weighted we also examine and test three site response estimation techniques that do not rely on a reference site to estimate source and path effects the first involves a parameterized source and path effects inversion even when the bedrock data are excluded from consideration this approach is found to reveal the frequency dependence of site response at each of the sediment sites the second technique involves taking horizontal to vertical component spectral ratios receiver function type estimates of shear wave aftershock data these are also found to reveal the frequency dependence of site response at the sediment sites and the results for the bedrock site are relatively flat and near unity the third estimate is formed by taking horizontal to vertical component ratios of ambient seismic noise and these are shown to reveal the fundamental resonant frequency of the sediment sites unfortunately discrepancies exist among all of the site response estimates and with one dimensional predictions with respect to a frequency independent scaling factor nevertheless the highly frequency dependent character of site response is well constrained and the fact that non reference site dependent methods are capable of revealing this is promising for site specific hazard assessments in regions that lack adequate reference sites

ice volume forcing of winter monsoon climate in the south china sea high resolution studies of a planktonic foraminifer core record from the south china sea scs 31kl 18 45 4 n 115 52 4 e water depth 3360 m reveal changes driven by ice volume forcings in the climate of the east asian monsoon in the western pacific marginal sea during the late quaternary the analyses of planktonic foraminifer faunal abundance data from the core indicate significant variations in the relative abundances of the dominant taxa over the past 100 000 years since the isotope stage 5 the transfer function estimates of faunal sea surface temperatures sst correlate well with a long term 104 105 years trend of global glaciation about 65 000 years ago there was an observable change in the mode of sst variability as many low latitude records have shown these findings suggest that the scs surface circulation and the east asian winter monsoon systems are mainly driven by variations in global glaciation levels the association of surface ocean cooling in the scs with global climatic events suggests that fluctuations in the strength of the east asian winter monsoon may be linked to shifts in the latitudinal position of the westerly winds and the siberian high pressure system

glacial holocene biogenic sedimentation patterns in the south china sea productivity variations and surface water pco2 a bathymetric transect of cores in the south china sea extending from 4200 m to less than 1000 m water depth has been examined for glacial interglacial changes in carbonate and organic carbon sedimentation typical pacific carbonate cycles high carbonate content during glacials and low carbonate content during interglacials characterize cores from water depths deeper than 3500 m in contrast atlantic carbonate cycles low carbonate during glacials and high carbonate during interglacials are observed in cores from depths shallower than 3000 m as a result of increased dilution of carbonate by terrigenous material during glacial low stands of sea level glacial interglacial changes in the carbonate chemistry of south china sea intermediate and deep waters resulted in significant changes in the positions of the carbonate compensation depth ccd and the aragonite compensation depth acd during the last glacial the ccd and acd were at least 400 and 1200 m deeper respectively than at present organic carbon accumulation rates in the south china sea were approximately 2 times higher during the last glacial than the holocene carbon isotopic analyses and c n ratios of the organic matter indicate that only a small fraction of the increase in glacial organic carbon accumulation can be attributed to input of terrestrial carbon on the basis of this we conclude that surface water productivity in the south china sea was approximately 2 times higher during the last glacial maximum this is consistent with previous studies which have demonstrated that glacial productivity was higher in low to mid latitude regions of the atlantic and eastern pacific the deglacial decrease in organic carbon accumulation is accompanied by a decrease in 13corg using the relationship between 13corg and co2 aq developed by popp et al 1989 we estimate that surface water pco2 values in the south china sea during the last 25 000 years were very similar to atmospheric co2 concentrations

depth resolution of earthquakes in central asia by moment tensor inversion of long period rayleigh waves effects of phase velocity variations across eurasia and their calibration the moment tensor inversion method for long period rayleigh waves is discussed from the point of view of event depth resolution in this method depth is usually determined by finding the minima in appropriate least squares residuals versus depth curves we show that depth cannot be resolved if the data are sampled only at one frequency and a choice of frequencies spanning a wide range of values yields better resolution we also show that the variance reduction at the minimum depends strongly on biases in the data provided they are not simple periodic functions in azimuth from the source since such biases are introduced in particular when the propagation corrections are inaccurate this provides a means by which to study regional trends of phase velocities this method is then applied to obtain an estimate of lateral heterogeneity in central asia starting with a reference point in the pamir mountains and a set of accurately known phase velocities on paths to eurasian wwssn stations we study the rayleigh waves at these stations in the period range 30 to 90 s for eight events located in or near the tibet plateau at stances from the reference point heterogeneity in phase velocity is thus found to be about 1000 to 1500 km in this period range constraining the source parameters of the most distant events by body wave modeling we determine new phase velocities on paths to wwssn stations from the center of the tibet plateau the variation of phase velocity with source location reaches 1 to 2 and the low velocity within tibet clearly has a dominant effect we then discuss the regionalization of phase velocities as a possible way to determine a calibration curve for a given source to receiver path we find that although the regionalized phase velocities in eurasia are stable to first order they do not seem accurate enough to be used for moment tensor inversions with arbitrary source locations this may be due to non ray theoretical effects causing the breakdown of phase velocity additivity when higher order accuracy is needed on the other hand reference phase velocities on source receiver paths can be obtained reasonably fast for events large enough so that body wave modeling is possible to constrain depth and source mechanism we demonstrate that these phase velocity curves are accurate enough for the calibration of propagation effects for another event located as much as 400 to 500 km away this provides an encouraging approach to study both structure and source mechanisms of smaller events within a highly heterogeneous continental region the only constraint is to find several events with the right magnitude of both long period body waves and surface waves

effects of three dimensional earth structure on cmt earthquake parameters abstract we investigate errors in centroid earthquake parameters due to unmodeled structural heterogeneity we generate a simulated dataset consisting of synthetic seismograms for 50 earthquakes and 150 stations distributed globally to generate the synthetic seismograms we use a spectral element wave propagation package specfem3d globe that accounts for the earth s three dimensional structure an established centroid moment tensor inversion algorithm from the global cmt project is used to invert the synthetic dataset with and without added noise for earthquake source parameters this algorithm uses a one dimensional earth structure together with approximate corrections for three dimensional structure to model the seismograms we interpret the differences between the estimated source parameters and the parameters used to compute the synthetic dataset as errors due to unmodeled structural heterogeneity and the presence of noise we expect that the errors obtained in this study are representative of the errors in the global cmt catalogue we find that the errors in scalar moment moment tensor elements and location are small on average the depth and centroid time are however biased by a small amount we find that the error in depth can be reduced significantly by applying corrections for the difference in the velocity structure at the source and receiver locations from the earth s average structure in the cmt inversions this modification has a minimal effect on the errors in centroid time we do not find large errors in scalar moments even where the crustal thickness at the source is very different from the earth s average crustal thickness

seismic ground motion in napoli for the 1980 irpinia earthquake the seismic ground motion in the urban area of napoli has been computed for the 1980 earthquake m s 6 9 with a hybrid technique based on the mode summation and the finite difference methods the detailed geological setting of each quarter has been reconstructed from several stratigraphies and six geological zones have been recognized shear wave velocity profiles have been assigned based on hole tests and inversion of rayleigh group velocities artificially generated

astronomically tuned plio pleistocene benthic δ 18 o record from south china sea and atlantic pacific comparison based on benthic foraminiferal n 18 o from odp site 1143 a 5 myr astronomical timescale for the west pacific plio pleistocene was established using an automatic orbital tuning method the tuned brunhes matuyama paleomagnetic polarity reversal age agrees well with the previously published age of 0 78 ma the tuned ages for several planktonic foraminifer bio events also agree well with published dates and new ages for some other bio events in the south china sea were also estimated the benthic n 18 o from site 1143 is highly coherent with the earth s orbit etp both at the obliquity and precession bands for the last 5 myr and at the eccentricity band for the last 2 myr in general the 41 kyr cycle was dominant through the plio pleistocene although the 23 kyr cycle was also very strong the 100 kyr cycle became dominant only during the last 1 myr a comparison of the benthic n 18 o between the atlantic odp 659 and the east and west pacific 846 and 1143 reveals that the atlantic pacific benthic oxygen isotope difference ratio vn 18 oatlpac displays an increasing trend in three time intervals 3 6 2 7 ma 2 7 2 1 ma and 1 5 0 25 ma each of the intervals begins with a rapid negative shift in vn 18 oatlpac followed by a long period with an increasing trend corresponding to the growth of the northern hemisphere ice sheet this means that all three intervals of ice sheet growth in the northern hemisphere were accompanied at the beginning by a rapid relative warming of deep water in the atlantic as compared to that of the pacific followed by its gradual relative cooling this general trend superimposed on the frequent fluctuations with glacial cycles should yield insights into the processes leading to the boreal glaciation cross spectral analyses of the vn 18 oatlpac with the earth s orbit suggests that after the initiation of northern hemisphere glaciation at about 2 5 ma obliquity rather than precession had become the dominant force controlling the vertical structure or thermohaline circulation in the paleo ocean a 2002 elsevier science b v all rights reserved

seismic characterization of neapolitan soils detailed shear wave velocity profiles versus depth have been obtained in typical lithostratigraphies of napoli ftan and hedgehog methods have been applied to rayleigh surface waves recorded in refraction seismic surveys the comparison with literature measurements shows good agreement with nearby down and cross hole tests

forcing of atlantic equatorial and subpolar millennial cycles by precession abundance cycles of the marine alga florisphaera profunda centered on a period of 7600 carbon 14 years 8400 calendar years are present in high resolution records from the equatorial atlantic spanning 0 to 45 000 years ago these cycles correlate with heinrich events 1 through 5 which document rapid changes in continental ice melting around the subpolar north atlantic these variations in f profunda are a direct response to modulation in zonal wind driven divergence produced by a precessional component of orbital variation during a time of reduced eccentricity modulation

a detailed study of the site effects in the volcanic area of campi flegrei using empirical approaches summary campi flegrei is a highly populated active caldera in the south of italy several hundred thousand people live within this area which is characterized by seismicity and ground deformation episodes known as bradyseism for this reason this area falls into a high risk category and thus the italian civil defence requires a detailed site effect estimation to determine the local amplification of the seismic waves for a high number of sites we have analysed the seismic recordings of three seismic networks that have been deployed in the campi flegrei area over different time periods the first network was deployed during the bradyseismic crisis of 1982 1984 we selected 22 of the highest magnitude earthquakes that were recorded during this crisis an additional 22 seismic events were selected from those recorded by the mobile seismic network that has been in operation in the campi flegrei area since 2006 the third data set comprises noise recorded by 34 seismic stations that were deployed during the active serapis experiment in 2001 september the generalized inversion technique and the h v spectral ratio method were applied to the s waves and coda waves of the earthquakes recorded by the first two seismic networks to determine the site transfer functions of the recording stations the seismic noise recorded by the third network was analysed using the nakamura s technique the results show that the high topographical and geological heterogeneity of the sites located inside the caldera has an important influence on the seismic wave amplification consequently the site transfer functions can be different even at sites close to each other the transfer functions of the sites located outside the caldera are much more regular apparently due to the more regular topography and geology

estimating geophysical bedrock depth using single station analysis and geophysical data in the extra carpathian area of romania local site evaluation is an essential step in understanding the amplification of seismic motion induced by the complex geological structure and their estimation for future strong earthquakes in urban regions one of the critical parameters on evaluating amplification effects is the depth of the geophysical bedrock whose interface to soft sediments is responsible for the development of destructive resonance phenomena the present study is focused on the estimation of the geophysical bedrock depth along the extra carpathian area of romania moesian platform and surroundings by correlating and interpolating the results obtained from single station measurements with the available geological geophysical data each site was investigated through the computation of horizontal to vertical h v spectral ratios from three component single station measurements of ambient vibrations the geophysical bedrock depth was computed using a two step inversion scheme based on the retrieval of the rayleigh wave ellipticity peak at each seismic station using a regional generic velocity profile the fundamental frequency of resonance reaches the lowest value in the deepest side 0 07 hz and is rising to 13 hz in the south of the moesian platform where a shallow bedrock is present the computed bedrock depths from 30 to 3100 m show a dipping tendency towards the southern carpathians and complex features such as local outcrops and lateral depth variations superpose this gradually dipping trend in the carpathian foreland the bedrock is interpreted as the transition between different sediment layers of neogene while outside this area as the neogene cretaceous transition

quaternary surface water stable isotope signal from calcareous nannofossils at dsdp site 593 southern tasman sea oxygen isotope values from calcareous nannofossils in four cores spanning the quaternary from dsdp site 593 in tasman sea are compared with the 18o signal of planktonic and benthic foraminifers from the same samples the classic mid late quaternary isotope stages are exhibited with stage 12 particularly well developed when 18o values of nannofossils are adjusted for coccolithophore vital effects they indicate larger by 1 6 c surface to bottom paleotemperature gradients and greater by 1 3 c changes in mean sea surface temperature between full glacial and interglacial conditions than do 18o values from planktonic foraminifers along with the foraminifers the nannofossils record a bimodal distribution of 18o between the early and mid late quaternary indicating a significant change in global ice budget the 13c of nannofossils also shows a bimodal distribution but is opposite to that for the foraminifers nannofossil 18o values record a shift of 0 8 at isotope stage 8 corresponding to a major reduction in abundance of the previously dominant gephyrocapsids a shift in 13c of 1 5 also occurs at stage 8 and a shift in 13c of 1 2 at around stage 14 the 18o shift in nannofossils is at least a pacific wide phenomenon the 13c shifts are possibly global the 13c signal of nannofossils exhibits an antipathetic relationship to that of benthic foraminifers back to isotope stage 18 but no significant correlation beyond this level to the base of the quaternary this is interpreted as reflecting local productivity dominating global influences on 13c since stage 18 at dsdp site 593 the difference between nannofossil and benthic foraminifer 13c signals 13c tends to be maximum during glacial stages and minimum during interglacials throughout the section showing a strong correlation with the nannofossil 18o signal the increased partitioning of 13c between surface and bottom waters during the glacial periods may indicate heightened productivity in surface waters in the southern tasman sea at these times

a procedure for modelling shallow dislocation sources summary expressions for displacements on the surface of a layered half space due to an arbitrary oriented shear dislocation are given in terms of generalized ray expansions useful approximations of these expressions for shallow events as recorded at teleseismic distances for realistic earth models are presented the results of this procedure are used to generate synthetic p sv and sh waveforms for various assumptions of stress drop

on an improved method to obtain the moment tensor and depth of earthquakes from the amplitude spectrum of rayleigh waves abstract a new method is presented to invert for the moment tensor and depth using the amplitude spectra of vertical component rayleigh waves in the period range 20 to 100 sec the technique follows a similar approach to that suggested by romanowicz 1982a to invert for the moment tensor from the complex spectra of rayleigh waves and presents some distinct advantages to the method proposed originally by mendiguren 1977 it eliminates some biases and errors in the data arising for example from inaccurate propagation corrections furthermore it is substantially faster computationally and permits us to study independently the variance reduction as a function of depth of each of the momenttensor elements resulting in better focal depth resolution the method is applied to three earthquakes in the tien shan mountains of central asia the eastern cordillera of peru and the gibbs transform fault in the north atlantic in all three cases the results of the moment tensor inversion agree with those determined using long period body wave modeling

seismotectonics of the himalayan collision zone geometry of the underthrusting indian plate beneath the himalaya fault plane solutions and well determined focal depths of medium sized earthquakes topography and landsat imagery in conjunction with seismicity maps cross sections and available geological information are used to investigate the present tectonics of the himalayan continental collision zone most of the accurately located epicenters of events along the himalayan arc 78 e 95 e that occurred between 1961 and 1981 are concentrated in a narrow zone about 50 km wide lying between the northerly dipping main boundary mbt and main central mct thrusts most of these events are located just south of the mct though the epicenters of the events are in general well located their depths as determined by teleseismic travel time data are very unreliable events with accurately determined depths obtained from identification of surface reflected phases define a simple planar zone from about 10 km and 20 km depth with an apparent dip of about 15 this result is all the more remarkable considering that the events used were located along about an 1800 km length of the himalyan arc except for one all available focal mechanisms of events within this zone indicate shallow 30 north dipping thrusts this shallow north dipping zone apparently defines a part of the detachment that separates the underthrusting indian plate from the lesser himalayan crustal block the spatial extent and the geometry of this interplate thrust zone strongly indicate that the mbt and nearby subsidiary surface and blind thrusts rather than the mct are currently the most active structures of the himalayan arc we suggest that the great himalayan earthquakes m 8 occur along the same detachment surface as defined by the thrust type medium sized events events located to the south of the mbt and beneath the ganges foredeep show normal faulting with t axes perpendicular to the himalayan trend the above results suggest that the indian continental plate is underthrusting the himalayan crustal blocks in a relatively coherent and simple geometry and that this geometry is not much different from that observed along oceanic subduction zones the november 19 1980 earthquake that occurred near the mct near 88 5 e shows a predominantly strike slip focal mechanism one of the nodal planes of this mechanism is transverse to the himalayan structural grain and moreover this plane has a trend similar to that of the recently mapped yadong gulu rift in the tethyan himalaya and in southern tibet just northeast of the earthquake we interpret this predominantly left lateral strike slip mechanism to indicate a possible genetic relationship between transverse structural features in the underthrusting indian plate the kishangang basement fault and the upper himalayan blocks and tibet

distribution of calcareous nannoplankton in surface sediments from intertidal and shallow marine regimes of a marginal sea jason bay south china sea abstract the surface sediments collected from the intertidal and shallow marine 0 20 m regimes of jason bay south china sea contain calcareous nannoplankton assemblages in whichgephyrocapsa oceanica comprises 99 of the assemblage the calcareous nannoplankton diversity is very low and the abundance of species tends to increase with both depth and distance offshore and becomes abundant in samples from water depths of 18 m and 20 m emiliania huxleyi is absent from all studied samples the sediments from the intertidal regime contained rare calcareous nannoplankton

body wave moment tensor inversion of local earthquakes an application to the south iceland seismic zone the focal mechanisms and scalar seismic moments of four local earthquakes are determined using a seismic moment inversion method for frequencies larger than those of dominant oceanic noise and lowe

the depth of the october 1981 off chile outer rise earthquake ms 7 2 estimated by a comparison of several waveform inversion methods the determination of source depth of the october 1981 ms 7 2 outer rise earthquake off the chilean coast has important implications for the stress state of the subducting plate we analyze the chile earthquake using three different waveform inversion methods in order to check the consistency of these methods and to estimate the source depth the methods we used are 1 1 honda and seno s 1989 inversion method in which we incorporate both long period p waves and surface waves 2 2 nab lek s 1984 body wave inversion methods for long period p and sh waves 3 3 seno and honda s 1988 deconvolution method in which we assume vertically distributed point sources and use long period p waves these methods give consistent results which suggest that the centroid depth and depth extent of the chile earthquake lies between 20 to 45 km measured from the sea surface this conclusion is contradictory to those obtained by the previous workers who prefer a shallow 25 km source depth we found that the gdsn long period data alone cannot constrain the source depth well the shape of deconvolved source time function is found to be strongly dependent on the assumption of point and distributed sources and the crustal structure used in the deconvolution the source depth obtained in this study shows that the 1981 chile outer rise earthquake possibly occurred because of the compression associated with the bending of the subducting plate

isotopic and biostratigraphical records of calcareous nannofossils in a pleistocene core knowledge of the species composition is essential for the isotopic record of polyspecific coccolith assemblages in deep sea sediments to be interpreted properly we have determined the carbon and oxygen isotopic composition as well as the relative abundance of coccolith species on the 3 25 m fractions of the caribbean core p6304 4 the dominant taxon in all samples is well preserved gephyrocapsa spp oxygen isotope variations clearly define glacial interglacial oscillations except in the upper part of the core carbon isotopic compositions are not related to the oxygen isotope stratigraphy the occurrence of three coccolith datum levels in the core correlates almost exactly with globally synchronous horizons1 the amplitude of the coccolith 18o record 2 4 is significantly greater than that for the planktonic foraminifera globigerinoides sacculifer in p6304 4 and adjacent cores2 4 we suggest here that selective dissolution or deep calcification during interglacials reduced the amplitudes of g sacculifer in these cores and that the coccolith record is a more reliable indicator of temperature and 18o changes in surface seawater

globorotalia truncatulinoides as indicator of upper ocean thermal structure during the quaternary evidence from the south china sea and okinawa trough abstract globorotalia truncatulinoides is shown to be indicative of upper ocean thermal structure and sensitive to the thermocline fluctuations and the thickness of the north pacific subtropical mode water npstmw thermostads for the quaternary in the south china sea scs and okinawa trough during the last 1 5 ma the relative abundance percentage of g truncatulinoides displayed long term oscillations on a time scale longer than the glacial interglacial cycle but with two major changes around 550 400 ka and 115 55 ka bp it decreased to near zero during 550 400 ka bp and then disappeared from the equatorial indian and pacific oceans this suggests that the thermocline depth and the scale of winter deep mixing decreased at that time interval and since then the linkage between the scs and the equatorial oceans at intermediate depths remarkably weakened and the npstmw strongly influenced the scs the predominance of left coiling g truncatulinoides together with the occurrence of globoquadrina conglomerata in the western north pacific between 115 and 55 ka bp indicates a deep thermocline and very thick npstmw thermostads a decreasing trend in the relative abundance of g truncatulinoides from marine isotopic stages 7 to 1 is evident in the scs indicating a progressive reduction of the npstmw thermostads after the last glacial maximum g truncatulinoides increased in abundance but abruptly disappeared between 8 and 4 ka bp from the scs and okinawa trough implying a mid holocene reduction in the npstmw thermostad thickness

enso like forcing on oceanic primary production during the late pleistocene late pleistocene changes in oceanic primary productivity along the equator in the indian and pacific oceans are revealed by quantitative changes in nanoplankton communities preserved in nine deep sea cores we show that variations in equatorial productivity are primarily caused by glacial interglacial variability and by precession controlled changes in the east west thermocline slope of the indo pacific the precession controlled variations in productivity are linked to processes similar to the southern oscillation phenomenon and they precede changes in the oxygen isotopic ratio which indicates that they are not the result of ice sheet fluctuations the 30 000 year spectral peak in the tropical indo pacific ocean productivity records is also present in the antarctica atmospheric co2 record suggesting an important role for equatorial biological productivity in modifying atmospheric co2

late quaternary upwelling intensity and east asian monsoon forcing in the south china sea foraminifera from two cores off eastern vietnam and the northwestern philippines where modern summer and winter monsoon driven upwelling occurs in the south china sea respectively were analyzed to evaluate the changes in paleoproductivity and upper water structure over the last 220 000 yr we observed enhanced organic carbon flux and a shoaled thermocline when upwelling intensified off eastern vietnam during interglacial ages and off the northwestern philippines during glacial ages this indicates that the east asian summer monsoon increased while the winter monsoon decreased during interglacial ages particularly the upwelling reached a maximum off eastern vietnam during late marine isotopic stage mis 5 and off the northwestern philippines during mis 2 implying that the summer monsoon decreased gradually since mis 5 while the winter monsoon displayed an opposite trend the variations in upwelling proxies exhibit a distinct cyclicity with frequencies near 41 000 yr and 23 000 yr off eastern vietnam in contrast to a strong frequency peak near 100 000 yr off the northwestern philippines we suggest that the east asian summer monsoon has been forced by changes in solar insolation associated with precession and obliquity while ice volume forcing is probably a primary factor in determining the strength and timing of the east asian winter monsoon but with less important insolation forcing

peculiarities of surface wave propagation across central eurasia abstract the recent installation of six broadband digital iris ida seismic stations in the ussr has provided new opportunities for studying surface wave propagation across eurasia group velocities of fundamental rayleigh and love modes between epicenters and these stations were determined for 35 events that occurred since april 1989 to the middle of july 1990 near eurasia differential phase velocities were found for the same arrivals along paths between several pairs of stations group and phase velocities were obtained in the period range from 15 to 300 sec frequency time polarization analysis was used for studying polarization properties of surface waves in some cases significant anomalies in the particle motion for periods up to 100 sec were observed they are attributed to surface wave refraction and scattering due to lateral inhomogeneities at the boundaries and inside the eurasia continent

glacial holocene calcareous nannofossils and paleoceanography in the northern south china sea abstract last glacial to holocene paleoceanography of the northern south china sea was inferred from nannofossil variations and several hydrographic proxies from a piston core scs90 36 17 59 70 n 111 29 64 e water depth 2050 m the upper part of the sedimentary sequence dated 15 5 to 1 2 ka provided a high resolution record whereas part of the sediments older than 15 5 ka was lost due to erosion a correspondence analysis of the nannofossil succession suggests that the paleoceanography developed in four stages the first stage 26 13 3 ka has a fairly well preserved diverse nannoflora dominated by gephyrocapsa and florisphaera profunda the floral composition together with high concentration of ketones c37 and organic carbon indicates high surface water fertility the second stage the deglacial period 13 3 10 7 ka had an increased surface water turbidity and a stronger influence of pacific open ocean waters as evidenced by the decrease of florisphaera profunda and increase of emiliania huxleyi respectively a preservation peak of calcareous microfossils centered at 12 ka correlates to the global preservation event of termination i the third stage early holocene 10 7 4 4 ka is marked by a gradual increase of f profunda and small placolith taxa at the expense of e huxleyi the floral composition indicates that conditions were more oligotrophic compared to the pre holocene the preservation of nannofossils became progressively worse indicating a rise of the nannofossil lysocline in sediments deposited at 5 5 and 4 ka nannofossil preservation improves probably reflecting a local cooling event during the last stage from 4 4 to 1 2 ka e huxleyi umbilicosphaera and large reticulofenestra increased their relative abundance to replace small placoliths further stratification of the surface water column may have been responsible for this floral succession

characteristics of long period microtremors and their applicability in exploration of deep sedimentary layers abstract applicability of long period microtremors in inferring subsurface structure is examined using measurements of microtremors in the northwestern part of the kanto plain in japan short term continuous measurements of long period microtremors at both sediment and basement sites were taken a spectral peak at a period of 4 to 5 sec is stable with time while peaks at periods less than 2 sec are time variant suggesting a variation of microtremor sources however it was found that the spectral ratio between vertical and horizontal microtremors ellipticity at each site is stable with time good agreement was found between ellipticities of microtremors at the sediment site and those computed for rayleigh waves in which the structure of the sediments beneath the site was taken into account we also found that the ellipticities of rayleigh waves in earthquake ground motions were consistent with those of the microtremors these comparisons provide strong evidence that long period microtremors in the area studied consist mainly of rayleigh waves the ellipticity of microtremors was investigated by observing microtremors at temporary observation sites in the kanto plain where the sediment thickness varied from 0 to 1 km the subsurface structures were deduced by trial and error fitting of observed ellipticities with theoretical ellipticities that were calculated assuming rayleigh waves these results show that ellipticity of long period microtremors is effective for deducing structure from microtremor data at a single site

an intermediate depth earthquake beneath tibet source characteristics of the event of september 14 1976 this paper presents the results of a detailed study of an intermediate depth earthquake beneath southern tibet september 14 1976 0643 51 6 ut 29 8l n 89 57 e focal depth 90 10 km mb 5 4 from the differences in arrival times of p pp and sp and from rayleigh wave spectral densities the focus is estimated to be at depth of 90 10 km and therefore in the uppermost mantle from the polarities of the first motions of p waves inversion of the relative amplitudes of p pp and sp and synthesis of their waveforms the source mechanism is constrained to be predominantly normal faulting with the t axis approximately horizontal and trending east west this mechanism is similar to those of shallow earthquakes in tibet the occurrence of an earthquake at depth of 90 km is consistent with rapid deformation at a temperature of about 700 to 800 c in the mantle beneath the tibetan crust the seismic moment of an equivalent double couple point source is estimated to be about 9 1024 dyne cm with an uncertainty factor of 1 3 from the sp amplitudes in the period range near 10 s and 5 1024 dyne cm also with an uncertainty factor of 1 3 from the spectral density of rayleigh waves with periods of 50 s

a no lid zone in the central chang thang platform of tibet evidence from pure path phase velocity measurements of long period rayleigh waves pure path phase velocities of fundamental mode rayleigh waves in the period range 30 80s are obtained for different paths across the tibet plateau using a two event method with events located in tibet and aligned with world wide standard seismograph network stations at teleseismic distance evidence is found for significant lateral variations of structure of the crust and uppermost mantle in tibet in particular phase velocities obtained on paths contained in the chang thang platform are higher than average in tibet at periods shorter than 60s while remaining very low at longer periods when interpreting these phase velocities in terms of simple layered s velocity models it is found that contrary to other areas in tibet they are incompatible with the existence of a high velocity lid s velocities of 4 4 4 5 km s are found immediately beneath the moho and the crust is somewhat thinner 50 60 km than average in tibet this indicates a possible upwelling of hot asthenospheric material compatible with landsat evidence for subrecent basaltic volcanism and independent seismic evidence such as inefficient transmission of sn waves on the other hand a 70 km thick crust and very high upper mantle s velocities are found on the western border of tibet karakorum hindu kush compatible with previous finer scale results concerning the associated zone of intermediate depth seismicity

source mechanisms of twenty six large shallow earthquake ms 6 5 during 1980 from p wave first motion and long period rayleigh wave data source mechanisms of 26 large shallow earthquakes are determined in terms of a double couple point source with a correction for the nondirectional part of source finiteness by using p wave first motions and long period rayleigh wave spectra recorded on wwssn ida and gdsn networks the combined use of both data sets allows us to determine the double couple mechanism uniquely in most cases constrained linear moment tensor inversion m xz m yz 0 correctly determines the strike of the fault but fails to estimate the dip and underestimates the scalar moment all thrust events along the deep sea trenches analyzed in this study show nodal planes which dip perpendicular to the trench axis at an angle shallower than 45 the fit to data of the double couple inversion is comparable to that of the constrained moment tensor inversion using the phase spectra of surface waves we can detect a slow source process with an accuracy of about 10 to 20 sec

comment on low frequency microtremor anomalies at an oil and gas field in voitsdorf austria by marc andre lambert stefan schmalholz erik h saenger and brian steiner geophysical prospecting 57 393 411

seismic moment tensors and source depths determined by the simultaneous inversion of body and surface waves we present a linear moment tensor inversion method that incorporates both body and surface wave data the source coordinates are fixed during the inversion and the source depth is determined by applying the inversion at several depths and taking the depth that produces the minimum residual the inversion is carried out in the time domain for body wave data and in the frequency domain for surface wave data the fundamental rayleigh waves at the period of 256 s from ida stations and the long period p waves from wwssn and gdsn stations whose angular distances are from 30 to 90 are used as the data the simultaneous inversion of both body and surface wave data sets has several merits because of the body wave constraints the present method gives reasonable solutions at shallow depths 30 km where long period surface wave inversions become unstable although the inversion using only body wave data is unstable in the sense that it allows for a variety of solutions with a slight change in the assumed depth probably because of the noise present and poor coverage of body wave data to determine the source mechanisms the inclusion of surface wave data makes the solution stable this is because the surface wave data constrain nodal plane strikes we may also expect better resolution in source depth by including the body wave data because the local crustal structure above the source can be taken into account to generate the green s function we applied our method to two large earthquakes one occurring at the triple junction off boso peninsula central honshu on 18 september 1984 and another at the outer rise area off the chile trench on 16 october 1981 the scalar moments of the boso oki and chile earthquakes are estimated to be 3 2 1026 dyn cm and 6 3 1026 dyn cm respectively the ratio of the minimum absolute eigenvalue of the moment tensor to the maximum which may measure the non double couple component is less than 10 for both earthquakes this suggests that their sources are essentially a double couple the source depths of both events are determined as 30 km the boso oki event is indicative of hinge faulting within the pacific slab at the triple junction the chile event is consistent with compressional bending stress in the deeper part of the lithosphere at the trench outer rise area off chile

insolation cycles as a major control of equatorial indian ocean primary production analysis of a continuous sedimentary record taken in the maldives indicates that strong primary production fluctuations 70 to 390 grams of carbon per square meter per year have occurred in the equatorial indian ocean during the past 910 000 years the record of primary production is coherent and in phase with the february equatorial insolation whereas it shows diverse phase behavior with 18o depending on the orbital frequency eccentricity obliquity or precession examined these observations imply a direct control of productivity in the equatorial oceanic system by insolation in the equatorial indian ocean productivity is driven by the wind intensity of westerlies which is related to the southern oscillation therefore it is suggested that a precession forcing on the southern oscillation is responsible for the observed paleoproductivity dynamics

calcareous nannofossils and the origin of eastern mediterranean sapropels a quantitative analysis of calcareous nannofossil assemblages was carried out with an optical microscope on four deep sea cores raised from the eastern mediterranean and selected to form a nw se transect a total of 748 samples were studied including a very detailed analysis of sapropels s5 and s6 in two out of the four cores this paper is restricted to the discussion of the results obtained on florisphaera profunda which provided important insights on the mechanisms of sapropel formation an intricated and unravelled puzzle for the scientists of the last decades on the basis of abundance variations of f profunda the only species of calcareous nannoplankton which inhabits the lower part of the photic zone i suggest that sapropel formation was triggered by increased primary production either confined to a deep chlorophyll maximum dcm a concept previously introduced by rohling and gieskes 1989 or extended to a thicker layer of the photic zone when increased primary production was confined to the dcm sapropel s3 s4 s5 s7 and s1 this latter only in the eastern part of the basin the abundance of f profunda was enhanced greatly with respect to all other species living in the higher part of the photic zone on the contrary when the increased primary production was extended to a thicker layer of the photic zone glacial sapropels s6 and s8 the production of most nannoplankton species was favored decreasing the relative proportion of f profunda

late cenozoic tectonics of the kepingtage thrust zone interactions of the tien shan and tarim basin northwest china the kepingtage kalpin thrust zone northwest china is an actively deforming part of the india asia collision system it lies south of the tien shan has an area of 16 000 km2 and consists of arcuate emergent imbricates overall vergence is toward the interior of the tarim basin to the south thrust sheets typically expose upper cambrian to permian platformal strata thrusting is largely thin skinned thin upper cambrian evaporites are likely to be the main decollement horizon the kepingtage thrust zone is the only margin of the tarim basin to deform in this style in the cenozoic it is replaced to the east and west by thrust zones which have propagated shorter distances into the interior of the tarim basin thick up to 10 km mesozoic and cenozoic clastic successions are present and deformed in these regions such successions are not present in the kepingtage thrust zone or the adjacent bachu uplift within the tarim basin because of episodic activity on steep northwest southeast trending thrusts which define the margins of the bachu uplift these mesozoic cenozoic strata may have suppressed the ability of regions along strike from the kepingtage thrust zone to deform by thin skinned thrusting utilizing the upper cambrian decollement the along strike variation in active thrusting at the southern margin of the tien shan is an example of syntectonic sedimentation controlling thrust belt deformation style a balanced section across the thrust zone indicates 28 shortening equivalent to 35 km this is equivalent to an average slip rate of 1 8 mm yr 1 and a strain rate of 4 4 10 16 s 1 assuming deformation began at circa 20 ma active deformation is focused along the frontal thrust the kepingtage fault the northern boundary of the kepingtage thrust zone is formed by the south tien shan fault this major north dipping thrust is seismically active with published earthquake focal depths at midcrustal levels 14 and 18 km it juxtaposes upper carboniferous sedimentary rocks of different facies and different paleozoic deformation histories speculatively it represents a reactivation of a late paleozoic thrust which originated at the boundary between the platformal interior of the tarim block and a deeper water foreland basin to its north

benthic foraminiferal paleoceanography of the south china sea over the last 40 000 years benthic foraminifera in gravity and piston cores from two sites of the northern and southern slopes of the south china sea scs were analyzed to evaluate changes in surface productivity and deep water mass characteristics over the last 40 000 years our observations suggest that changes in organic carbon flux that is food supply and chemical and or physical properties of the ambient water mass may be the two primary and intercorrelated factors controlling the distribution patterns of benthic foraminifera when organic carbon flux increased above 3 5 g c m 2 yr 1 in the southern scs during the last glacial maximum and in the northern scs during the first part of the holocene around 10 ka b p a group of detritus feeders including bulimina aculeata and uvigerina peregrina dominated the benthic foraminiferal assemblage as shown by relative abundance and accumulation rates this may reflect episodes of increased surface productivity possibly induced by increased input of nutrients from nearby river runoff suspension feeders such as cibicidoides wuellerstorfiand a group of opportunistic species including oridorsalis umbonatus melonis barleeanum and chilostomella ovoidea gradually became more abundant than detritus feeders as soon as the organic carbon flux decreased to 2 5 3 5 g c m 2 yr 1 similar glacial to interglacial changes in relative abundance and accumulation rates were observed in both cores for a number of species including eggerella bradyi globocassidulina subglobosa astrononion novozealandicum sphaeroidina bulloidesand cibicidoides robertsonianus these changes were not correlated to the distribution patterns of organic carbon in both cores and may have been related to yet unspecified changes in chemical and or physical properties of the ambient water mass independent of changes in organic carbon flux 1999 elsevier science b v all rights reserved

v s profiles from noise cross correlation at local and small scale ambient noise measurements have been performed at local and small scales in the neapolitan and surrounding areas campania southern italy by employing two broad band kinemetrics q330 stations equipped with episensor es t three component accelerometers in both experiments frequency time analysis ftan method has been performed on the vertical and radial components of noise cross correlations to retrieve the rayleigh wave dispersion green s function at local scale over an interstation distance of about 26 km the group velocity dispersion values have been compared with those obtained from ftan analysis on recordings of two earthquakes with similar path at small scale measurements have been carried out over an interstation distance of about 440 m in the public gardens of scampia the northernmost quarter of naples the rayleigh wave group velocity dispersion data obtained from noise cross correlation have been combined with those from active seismic experiment along the same alignment but shorter 120 m offset the non linear inversion of such a dispersion curve has allowed the definition of v s models to depths of 100 m in agreement with nearby stratigraphy moreover a good agreement has resulted for the resonance frequency among the h v ratio the ellipticity of the fundamental mode computed for the chosen v s model and the average two dimensional 2d spectral amplification computed along a cross section representative of the scampia quarter

quantitative composition of benthic foraminiferal assemblages as a proxy indicator for organic carbon flux rates in the south china sea abstract the organic carbon flux signal embedded in the distribution data of benthic foraminifera from 43 box core surface samples from the south china sea scs is compared to data from two gravity cores on the northern core 17940 2 and southern core 17964 3 slope of the scs surface sampling stations cover almost the entire area of the south china sea including areas with preferential summer monsoonal upwelling or winter monsoonal upwelling as well as a wide range of water depths 300 4000 m we use correspondence analysis afc to examine the relation between the quantitative composition of benthic foraminiferal assemblages water depth and organic carbon flux rates we find a clear correlation between benthic foraminiferal assemblage composition factor 1 of the afc and organic carbon flux rates in the surface samples and use the same model to calculate paleo flux rates for the two cores significantly increased carbon flux rates are observed in the southern scs sunda shelf margin during the last glacial maximum lgm whereas the organic carbon flux rates along the northern slope of the scs seem to be highest during the early holocene

focal depths and fault plane solutions of earthquakes under the tibetan plateau we compare synthetic and recorded p wave forms to place constraints on the focal depths and fault plane solutions of 16 crustal earthquakes beneath the highest parts 4000 m of the tibetan plateau fault plane solutions for all 16 events show combinations of normal and strike slip faulting with t axes oriented approximately east west none of these solutions show thrust faulting thus the data corroborate previous inferences that the active tectonics are dominated by east west extension focal depths for all 16 events are less than 15 km and appear to be between 5 and 10 km this style of deformation and these depths of faulting are similar to those in the basin and range province of the western united states two intermediate depth events below the crust of southern tibet also show primarily normal faulting with east west t axes the solution for one discussed by chen et al 1981 is unambiguous the solution for the other the event of august 1 1973 27 59 n 89 17 e 85 10 km mb 4 9 is less certain both apparently occurred in the mantle beneath a thick aseismic lower crust and their occurrence suggests that brittle deformation occurs there in response to a stress field similar to that operating at shallow depths beneath tibet

evaluation of site effect within the tectonic basin in the northern side of ankara abstract this study mainly concentrates on the determination of site effects for the plio quaternary and especially alluvial soils of the cubuk district and its close vicinity in ankara turkey in the study area particularly in the vicinity of the asymmetric graben that has formed due to the tectonic activities along the ne sw trending normal faults a microtremor survey was implemented to identify the local site response under a possible seismic event the results were compared and correlated by using passive and active surface wave measurements engineering geological and geotechnical deep borehole logs along with information on local geology and geological tectonic setting regarding the microtremor results larger fundamental periods were acquired than expected over the area and the effect of the tectonic deformation on the stiffness of the soils was also observed at either the h v curves or the shear wave velocity profiles the results have demonstrated that geotechnical information down to a depth of 30 m may not be compared with the h v parameters the h v amplitudes were not always accompanied with the higher periods in the quaternary sediments this could be due to the basin and basin edge effects observed particularly at the center and boundary of the basin respectively additionally the microtremor survey showed that the spectral ratio amplitudes derived by the h v ratio are debatable and are not a direct indicator of local soil behavior under a seismic excitation

foraminiferal responses to major pleistocene paleoceanographic changes in the southern south china sea a detailed age model for core 17957 2 of the southern south china sea was developed based on delta 18 o coarse fraction magnetostratigraphy and biostratigraphy for the last 1500 kyr the delta 18 o record has clear similar to 100 kyr cycles after the mid pleistocene revolution mpr at the entrance of marine isotopic stage mis 22 planktonic foraminifera responded to the mpr immediately showing the increased sea surface temperature sst and dissolution after the mpr benthic foraminifera did not respond to it until the brunhes matuyama boundary since the mpr the depth of thermocline gradually became shallower until miss 6 5 this major change within miss 6 5 was also reflected in the decreased ssts and increased productivity and deep water mass thus two major pleistocene paleoceanographic changes were found one was around the mpr the other occurred within miss 6 5 which speculatively might be ascribed to the reorganization of surface and deep circulation possibly induced by tectonic forces

last glacial maximum in china comparison between land and sea abstract as a result of the sea level drop at the last glacial maximum about 100 120 m in the south china sea and 130 150 m in the east china sea the size and configurations of the china seas changed greatly the east china sea with the yellow sea and bohai gulf was reduced into an elongated trough while the south china sea became a semi enclosed gulf due to the southern shift of the polar front in the north pacific and the reorganization of the surface current system the winter temperature in the south china sea was 6 10 c colder and the seasonality was much stronger than it is now the reduced sea area and thus the increased distance to the coast together with the declined sea surface temperature led to intensified aridity on the land the enhanced eolian processes related to the intensification of the winter monsoon caused an expansion of the loess deposition area reaching the southeastern part of china to the south of the yangtze river and off the modern sea coast vegetation zones greatly shifted to the southeast in north china deserts and steppes were much more extensive than they are now and the modern areas of warm temperate broad leaved forests were occupied by steppes or woodland in south china the deciduous broadleaved forests were developed in areas now covered by evergreen forests and the monsoon rain forest completely disappeared the changes in the climate on land and the configurations of seas altered the sediment supply and sedimentation rate in the china seas giving rise to the atlantic type late quaternary caco3 curve there

molecular biomarker record of sea surface temperature and climatic change in the south china sea during the last 140 000 years the d 18 oa ndd 18 c isotopic composition of globigerinoides ruber the concentration of c37 alkenones n nonacosane and n hexacosan 1 ol and the populations of coccolith species in core 17961 2 have been used to characterize the climatic changes which occurred in the south china sea scs during the last climatic cycle the relative composition of diand triunsaturated c37 alkenones the u k index has been used to estimate the variation in sea surface temperatures the concentrations of the terrigenous markers n nonacosane and n hexacosan 1 ol have allowed to infer changes in continental water dynamics during the glacial and interglacial times the stratigraphic record of these compounds has shown that the influence of continental waters i e the molengraaff river and restricted water circulation in scs gave rise to a marginal system of higher but slower response to climatic change both in terminations i and ii the change from glacial to interglacial conditions involves a considerable reduction of continental water input into this semi enclosed system the high resolution study of the biomarker proxies in termination i has shown that the sst increase lagged about 2 3 ky the d 18 o isotopic decrease of cibicidoides wuellerstorfi probably the sst increase corresponds to the period of the sunda shelf inundation onset 1999 elsevier science b v all rights reserved

s waves profiles from noise cross correlation at small scale abstract cross correlations of ambient seismic noise recordings are studied to infer shear wave velocities vs profiles versus depth experiments are performed over inter station distances ranging from 60 m to about 400 m in the crowded and noisy historical centre of napoli where the conditions for the use of active controlled source seismic spreadings are prohibitive even for just one receiver from the noise cross correlation group velocity dispersion curves are extracted with ftan method and their non linear inversion supplies vs profiles versus depth the information of nearby stratigraphies and the range of vs variability for samples of neapolitan soils and rocks confirms the validity and reliability of the results obtained with our expeditious procedure if successfully tested in other geological settings the proposed approach is a low cost methodology to get reliable vs velocity profiles versus depth

late quaternary paleoceanography of the south china sea glacial interglacial contrasts in an enclosed basin the sea surface paleotemperature of the south china sea scs is estimated quantitatively based on the quantitative analysis of planktonic foraminiferal faunas recovered from piston cores v36 06 3 v36 06 5 and so49 kl8 on the northern continental slope the results lead to a reconstruction of the history of paleocirculation patterns during the last 200 000 years the postglacial and interglacial transbasinal circulation pattern was replaced by a semienclosed basin flow pattern during glacial episodes lowered sea level transformed the scs into a semienclosed basin with the only passageway to the open ocean in its northeastern corner the east asian monsoon which governs circulation patterns in the scs both today and during the late quaternary created both clockwise summer and counterclockwise winter surface gyres during glacials the inflow of tropical surface water masses from both the pacific and indian oceans decreased or was completely cut off from this marginal sea causing a greater decrease in glacial sea surface temperature than in the open ocean of the same latitude inferred increased influence of pacific temperate waters and decreased influence of tropical subtropical waters are confirmed by changes in the planktonic foraminiferal assemblages glacial interglacial fluctuation in sea surface temperature sst 6 8 9 3 c for winter and 2 3 c for summer as well as the seasonality 4 6 c for postglacial and interglacials and 9 10 c for glacials are much greater than the adjacent open western pacific reflecting the amplification of the climatic signal in the marginal sea

age dependence of oceanic intraplate seismicity and implications for lithospheric evolution we have determined depths for 16 oceanic intraplate earthquakes using body wave modeling a data set composed of these and 11 other well constrained depths shows that the maximum depth of seismicity deepens with increasing lithospheric age and appears to be bounded by a 700 800 c isotherm the maximum depth to which intraplate earthquakes occur is approximately equal to the flexural elastic thickness but much less than the seismic thickness from surface wave dispersion the maximum faulting depth is consistent with the predictions of rapid weakening at high temperatures for dry olivine rheologies determined by experimental rock mechanics oceanic intraplate earthquakes can occur at greater depths and temperatures than has previously been reported for continental crustal events presumably because oceanic lithosphere is stronger at high temperatures both the number of earthquakes and the cumulative seismic moment decrease with lithospheric age the cause of this trend is unclear possibilities include nonrandom location of preexisting weak zones with respect to the age provinces fault strengthening with age or a decrease in the stress level a decrease in intraplate stress with age is opposite that expected from ridge push stresses which increase with age but may result either from thermoelastic stresses which are greatest in young lithosphere or near ridge stress concentrations due to local heterogeneities in the spreading process

coccolithophores in the equatorial atlantic ocean response to seasonal and late quaternary surface water variability abstract the present study was initiated to ascertain the significance of coccolithophores as a proxy for paleoceanographic and paleoproductivity studies in the equatorial atlantic data from a range of different samples from the plankton surface sediments as well as sediment cores are shown and compared with each other in general the living coccolithophores in the surface and subsurface waters show considerable variation in cell numbers and distribution patterns cell densities reached a maximum of up to 300 103 coccospheres l in the upwelling area of the equatorial atlantic here emiliania huxleyi is the dominant species with relatively high cell numbers whereas umbellosphaera irregularis and umbellosphaera tenuis are characteristic for oligotrophic surface waters although they are observed in high relative abundances these species only occur in low absolute numbers the lower photic zone is dominated by high abundances and considerable cell numbers of florisphaera profunda the geographical distribution pattern of coccoliths in surface sediments reflects the conditions of the overlying surface water masses however abundances of the oligotrophic species umbellosphaera irregularis and umbellosphaera tenuis are strongly diminished causing an increase in relative abundance of the lower photic zone taxa florisphaera profunda and gladiolithus flabellatus during the past 140 000 years the surface water circulation of the equatorial atlantic has changed drastically as can be seen from changes in the coccolithophore species composition absolute coccolith numbers as well as coccolith accumulation rates significant increases in coccolith numbers and accumulation rates is observed in the southern equatorial atlantic during the last glacial interval oxygen isotope stages 2 4 which we attribute to enhanced upwelling intensities and advection of cool nutrient rich waters at this site in the western equatorial atlantic we observe an opposite trend with decreasing numbers of coccoliths during glacial periods which probably is caused by a deepening of the thermocline

late pleistocene nutrients and sea surface productivity in the south china sea a record of teleconnections with northern hemisphere events surface nutrient variations during the last 200 000 years have been reconstructed based on the cd ca ratios in the tests of planktonic foraminifera neogloboquadrina dutertrei and the biogenic opal content from two gravity cores retrieved from the northern and northwestern parts of the south china sea scs the cd ca ratios obtained from n dutertrei in recent sediments from fourteen box cores distributed over the scs basin reflect present nutrient levels in the overlying surface waters areas with relatively high cd ca values in the surface sediments are in the region of high chlorophyll a in the northern south china sea near the dongsha islands consistent with previous observation high values of cd ca found in sediments east of vietnam and east of the nansha islands may be a result of increased nutrients due to local upwelling induced by the summer monsoon core 17940 2 raised from the northern continental slope of the scs exhibits exceptional high sedimentation rates 25 85 cm kyr for the last 35 kyr the cd ca ratios in this core are relatively higher during the periods of late d 18 o stage 3 and the mid holocene core 17950 2 with an average sedimentation rate of 5 cm kyr offers a continuous long record back to d 18 o stage 7 in general cd ca values in the downcore records are higher during interglacials and progressively increase as the interglacials proceed values peak around the times of optimum climate conditions and correlate with periods of increased opal wt correlations in the interval of overlap between the two records support the interpretation that variations in cd ca ratios in core 17940 2 are not an individual signal but can be replicated of special interest in this study is the tentative correlation between cd ca peaks in the scs record and the timing of iceberg discharge events heinrich events in the north atlantic mass accumulation rate mar of opal data from core 17950 2 indicate high surface productivity during glacial intervals corresponding to oxygen isotope stages 6 4 and 2 the increase in surface productivity during glacials from the northern scs is contemporaneous with an intensified winter monsoon as recorded by the terrestrial loess deposits the agreement with wind strength recorded in the loess plateau from mainland china supports the

seismicity focal mechanisms and tectonics in the last four years there has been a tremendous increase in the detail of tectonic processes reported in the typical seismotectonic study new data from many local and regional networks of seismographs established during the previous four year period plus the now routine application of improved hypocentral location procedures long period body wave modelling and moment tensor inversion using digitally recorded data have increased resolution of both the hypocentral location and the nature of the faulting process consequently research emphasis has been on local tectonics or those aspects of regional and global tectonics requiring high resolution i briefly describe below some of the highlights of these studies

constraints on the structure of the tibet plateau from pure path phase velocities of love and rayleigh waves pure path phase velocities of love and rayleigh waves across the tibet plateau are determined for the period range 30 90 s and for two opposite directions of propagation along the length of the plateau the method used is a two event method similar in principle to the classical two station method where the roles of stations and events are interchanged the success of this method is due to a favorable geometry whereby events located at each end of the plateau align to within 1 of a great circle path with one wwssn station at teleseismic distance to the east and one to the west body wave modeling is used to constrain depth and source mechanism of the events in order to calculate the corresponding source phases for surface waves phase velocities are determined to within 0 02 km s or better for rayleigh waves and 0 007 km s for love waves the constraints added by these data to the crust and upper mantle structure beneath tibet are discussed in the light of previous studies the best fitting model has a 65 km thick crust with low average crustal velocities and an sn velocity of 4 65 km s the low velocity zone is limited to the depth range 100 150 km the interesting result of this study is that both love and rayleigh wave data can be matched to within 1 in phase velocity by a unique isotropic model this points to a similarity with a stable region upper mantle structure such as that of the canadian shield finally additional rayleigh wave phase velocity data are used to compare propagation on different paths in the vicinity of tibet the tarim basin to the north of tibet stands out as having a distinct crustal structure more similar to an average tectonic region structure moreover evidence is presented for the existence of a very low velocity region at the western end of tibet which correlates well with a pronounced gravity low observed in that area

florisphaera profunda a possible nannoplankton indicator of late quaternary changes in sea water turbidity at the northwestern margin of the pacific three piston cores from the ryukyu trench slope northwestern margin of the pacific ocean contain nearly continuous paleoceanographic records of the last 320 165 and 105 kyr ages of the cores are constrained by planktic 18o stratigraphy and roughly substantiated by the presence of two calcareous nannofossil events spectral analysis of the changes in relative abundance offlorisphaera profunda a nannoplankton species presently living in the lower euphotic zone reveals a maximum power at 0 01 cycles kyr corresponding to the 100 kyr cycle of orbital eccentricity much lower power is observed at the 23 kyr precessional band this differs from the equatorial atlantic ocean variations which show dominant power in the 23 kyr precessional band in the changes off profunda abundances molfino and mcintyre 1990a besides our cores were taken outside the equatorial divergence zone we also show a rather close relationship betweenf profunda abundance and sea water transparency secchi depth in the present northwest pacific based on data from 204 sites of surface sediment samples because sea water transparency is primarily affected by bio productivity change in open ocean stratigraphic changes off profunda abundances in our cores seem to have been caused by productivity change as well pointed out by molfino and mcintyre 1990a b a mechanism proposed by them for its change however is not applied to our cases due to differences in spectral analysis results and in geographic situation alternatively we suggest that geographic change of the northwestern margin of the pacific during the late quaternary causedf profunda abundance change through the sea water turbidity change which has been affected not only by bio productivity but also by land origin particles supply

millennial scale dynamics of the east asian winter monsoon during the last 200 000 years the primary productivity dynamics of the last 200 000 years in the sulu sea was reconstructed using the abundance of the coccolithophore florisphaera profunda in the images md97 2141 core we find that primary productivity was enhanced during glacial periods which we suggest is due to a stronger east asian winter monsoon during the last 80 kyr eight significant increases in primary productivity pp in the sulu sea are similar to east asian winter monsoon changes recorded in chinese loess the pp maxima are not linked with heinrich events he in the north atlantic although four pp peaks are synchronous with he the pp oscillations have frequencies near those of the dansgaard oeschger cycles in northern hemisphere ice records and indicate a teleconnection of the east asian winter monsoon with greenland climate in this sulu sea record the east asian winter monsoon oscillates with periodicities of6 4 2 3 4 2 3 and 1 5 kyr in particular the 1 5 kyr cycle exhibits a strong and pervasive signal from stage 6 to the holocene without any ice volume modulation this stationarity suggests that the 1 5 kyr cycle is not driven by some high latitude forcing

effects of lateral heterogeneity and source process time on the linear moment tensor inversion of long period rayleigh waves spectra of mantle rayleigh waves recorded on the ida network are inverted to determine the seismic moment tensor of the 9 june 1980 california mexico border earthquake the 29 july 1980 vanuatu islands earthquake and the 9 july 1980 santa cruz islands earthquake examinations are made to correct for phase velocity lateral heterogeneity and source process time a simple regionalization stable continent tectonic region young ocean and old ocean improves results of the linear inversion but the phase correction is not large enough and the discontinuous change of phase velocity across the boundary between regions causes an artificial rapid change in apparent phase velocity as a function of azimuth therefore a more detailed but gradual representation of the lateral heterogeneity is desirable to correct for the propagation effect in the linear inversion a source process time which consists of the nondirectional part of the apparent duration of main faulting and the delay time of the faulting from initial break is estimated by a phase analysis of rayleigh waves the source process time is generally proportional to the seismic moment on the log log scale but some earthquakes deviate considerably from the general relation therefore the measurement of the source process time should be made before the moment tensor inversion the phase errors introduced by the lateral heterogeneity and source process time may cause a bias to low scalar moment

lateral heterogeneity in continents moment tensor inversion of long period surface waves and depth resolution of crustal events body wave modeling and phase velocity calibrations

calcareous nannofossil biostratigraphy in the pearl river mouth basin south china sea and neogene reticulofenestrid coccoliths size distribution pattern abstract the calcareous nannofossil biostratigraphy of the pearl river mouth basin includes 26 bioevents and twenty zones combined zones from oligocene to early pleistocene and a middle eocene zone most zonal boundaries of other workers in other regions of the world are recognized especially those defined by last occurrences the nannofossil zones are placed within the lithostratigraphic units of the offshore basin the size distribution pattern of reticulofenestrids from middle miocene to pliocene can be used to further subdivide the neogene biostratigraphically bioevents can be used to recognize the neogene epoch boundaries in the area

are microtremors useful in site response evaluation we have reviewed the applicability of microtremor measurements to evaluate site response of soft soils to this end we evaluated three different techniques commonly used to estimate site effects from microtremor measurements interpretation of fourier amplitude spectra computation of spectral ratios relative to a firm reference station and finally computation of spectral ratios of horizontal components relative to the vertical component of ground motion nakamura s technique these techniques are applied to microtremor records obtained in three cities in mexico mexico city oaxaca and acapulco these cities differ in their local geological conditions and in their seismotectonic environment in order to evaluate the results obtained from microtremor measurements we compare them with standard spectral ratios of the intense s wave part of weak or strong motion records obtained at the same sites our results showed that microtremor measurements can be used to estimate the dominant period of a site with very acceptable reliability in the range 0 3 to 5 hz the best results were obtained with nakamura s technique which also gives a rough estimate of amplification of seismic waves when the local geology is relatively simple simple numerical simulations indicate that the underlying assumptions of nakamura s technique are consistent with the propagation of rayleigh waves these simple numerical simulations also explain why different researchers have been able to successfully characterize 1d site effects using microtremor records regardless of whether they consider microtremors to consist of surface or body waves our results strongly suggest that the technique by nakamura effectively compensates for source effects in microtremor measurements which eliminates a major limitation to their application in earthquake engineering

late quaternary paleoceanography of the south china sea surface circulation and carbonate cycles paleoceanographic information from 34 sediment cores is summarized to investigate the glacial interglacial variations in sea surface circulation and late quaternary carbonate cycles in the south china sea judging from the distribution pattern of deposition rates the enormous terrigenous supply by rivers is responsible for the high rate of hemipelagic sedimentation which was even higher during glacial periods paleotemperature maps based on transfer function temperature estimates have revealed a e w gradient of sst for glacial summer and a s n gradient for glacial winter and this agrees well with the clockwise surface circulation in summer and counterclockwise in winter during glacials as shown by a preliminary computer modelling the high resolution paleotemperature curves of core v36 3 from the northern slope show an abrupt cooling event which may belong to the younger dryas carbonate percentage in sediments and preservation of foraminifers and pteropods are used to study the carbonate cycles in the marginal sea it turns out that two mechanisms are functioning there being a basin with large drainage areas vast amount of river borne terrigenous input dilutes carbonate and its intensification during glacial decreases the glacial cac03 being a basin connected with the pacific the fluctuations of lysocline ccd and acd in the scs are related to those in the pacific ocean and dissolution is strengthened at interglacial thus above the present ccd the dilution factor predominates and the atlantic cycles are produced below the present ccd the dissolution factor prevails resulting in the pacific pattern of carbonate cycles

coccolith evidence for quaternary nutricline variations in the southern south china sea abstract nutricline variations during the last 1560 ka in the southern south china sea are reconstructed using the relative abundance of the coccolithophore florisphaera profunda in odp site 1143 nutricline depth shows both long term large magnitude variation and high frequency glacial interglacial variation on the long term scale the nutricline experienced four significant changes which occurred at 900 480 250 and 50 ka respectively according to these changes five stages could be recognized during the last 1560 ka from 1560 to 900 ka the nutricline depth increased gradually around 900 ka the nutricline abruptly shallowed and then remained stable until 480 ka the nutricline was shallow during the time interval between 480 and 250 ka at 250 ka it deepened again and increased gradually until 50 ka after 50 ka the nutricline depth decreased gradually to modern values on the glacial interglacial scale the variations in nutricline depth show different patterns before and after 900 ka before 900 ka the nutricline was deep during glacial periods and shallow during interglacials however after 900 ka the nutricline was deep during interglacials and shallow during glacials spectral analysis of the relative abundance of f profunda shows a similar trend in addition to the eccentricity 113 76 ka obliquity 55 39 ka and precession 24 19 ka we also find a 431 ka cycle the former three periods reflect glacial interglacial variations in nutricline and the period of 431 ka reflects long term variations in nutricline we suggested that the variations in nutricline in the southern south china sea were caused by global and regional climate changes glacial interglacial variations in nutricline are mainly controlled by the east asian monsoon and the long term variations might be related to the global climatic events such as the mid pleistocene revolution and the mid brunhes event

source characterization of two reykjanes ridge earthquakes surface waves and moment tensors p waveforms and nonorthogonal nodal planes well constrained fault plane solutions from p wave first motions for mid ocean ridge normal faulting earthquakes usually require nonorthogonal nodal planes local structural effects and or departures from a double couple source mechanism have been invoked to explain this phenomenon in order to obtain an independent determination of the source mechanisms for the april 24 1970 and april 3 1972 events on the southern reykjanes ridge we invert the rayleigh wave radiation pattern to obtain the source moment tensor the moment tensor formulation should be particularly well suited to this problem because it is not restricted a priori to a double couple source mechanism a potential drawback of the technique however is the requirement that phase velocities along the earthquake station paths be known very accurately in order to obtain the source phase from the observed phase and an objective of this study was to determine whether a regionalized phase velocity model compiled from published dispersion curves is adequate the results of the moment tensor inversion for both events indicate shallow normal faulting with the tension axis approximately horizontal and perpendicular to the local strike of the ridge apparent departures from a pure double couple source seem to result from errors in the data and the poor resolution of the mxz and myz components of the moment tensor for shallow sources after performing the inversion under a series of increasingly more stringent constraints we conclude that the data for both events are compatible with pure double couple sources with moments of 4 8 and 7 5 1024 dyn cm respectively we then show that interference between p pp and sp due to shallowness of the source can account for the observed nonorthogonality and match the observed p waveforms for the april 3 1972 event with theoretical seismograms calculated for a shear fault whose orientation is consistent with the surface wave solution the best fit to the data is obtained for a long narrow fault 13 km by 3 km with rupture initiating near the seafloor the moment indicated by the p waves is 7 5 1024 dyn cm these source parameters give an average displacement of about 60 cm and a stress drop of 30 60 bars taking into account various uncertainties although we might expect attentuation to be high in the mid ocean ridge environment the average attenuation required to fit the teleseismic data is not higher than normal t 1 s the p waves from the april 24 1970 earthquake were too small to be suitable for quantitative modeling by synthetic seismograms but are qualitatively consistent with a shallow fault model similar to that for the larger event we conclude that the faulting process described by these two earthquake mechanisms is directly related to the formation of rift valley topography

a physically sound way of using noise measurements in seismic microzonation applied to the urban area of napoli noise measurements have been done in the urban area of napoli italy a densely and crowded populated city of southern italy with historical architectonic heritage often damaged by tectonic earthquakes noise has been recorded by kinemetrics q330 station with a 3 component episensor broadband accelerometer the h v ratio between the mean of the fourier spectra of the horizontal components and the spectrum of the vertical component has been computed for 20 s windows and averaged on about 150 windows of noise data noise has been measured at sites with detailed shear wave velocity profiles obtained from the non linear inversion hedgehog method of the group velocity dispersion curve of rayleigh fundamental mode extracted with ftan method from active seismic surveys ellipticities of all modes rayleigh waves and spectral amplifications both with sophisticated algorithms like mode summation and finite difference techniques and simplified 1 d techniques have been computed it turns out that the fundamental and at times also higher modes rayleigh waves are present at the resonance frequency of the soil cover where the maximum spectral value of noise h v shows resemblance to the main peak of computed spectral amplifications although the match at the resonance frequency realistic computed amplifications must be assumed for seismic microzonation hence a novel use of noise measurements is proposed which consists of a rapid detailed mapping of the computed spectral amplifications and average physical properties starting from the fit of the main peak frequency 2007 elsevier b v all rights reserved

coccolithophore response to oceanographic changes in the equatorial atlantic during the last 200 000 years a deep sea core from the eastern equatorial atlantic meteor core 16772 1 21 s 11 58 w revealed strong primary productivity variations 70 230 gc m2 year based on the relative abundance of the deep living coccolithophore florisphaera profunda with productivity maxima following temperature minima during the last 200 000 years the response of the coccolithophore flora was investigated by relative and absolute abundance records of coccoliths the wind strength and the resulting equatorial upwelling intensity are thought to comprise the most important control of coccolith abundance and species composition which reflects the different abundance of coccolithophores living in the upper or lower photic zone relative abundances of the different species varies widely throughout the core although a wide range of species were present in the different samples three different taxa dominated the assemblage the lower photic zone species f profunda was the most abundant with a mean relative abundance of 49 4 throughout the core the upper photic zone flora were divided into three groups emiliania huxleyi together with small gephyrocapsa 3 m was the second most abundant species group mean 20 8 gephyrocapsa oceanica was the third most important species in the core and had a mean relative abundance of 16 8 all other species together represented a mean of 13 highest absolute abundance of coccoliths number gram sediment occurs in sediments deposited during periods of high sst mainly in warm isotope stages 1 and 5 the accumulation rates of coccoliths number cm2 ky show peaks in isotope stages 1 and 5 but also in some parts of cool isotope stages 4 and 6 high relative and absolute abundance of f profunda were found in warm isotope stages which suggests that a deep nutricline existed and that primary productivity was low absolute and relative abundance records of e huxleyi and small gephyrocapsa 3 m mainly showed higher values in sediments from warm periods the other upper photic zone coccolith species were generally more abundant during periods of low sst particularly in isotope stages 2 4 and 6 which were times of high primary productivity and a shallow nutricline this suggest that e huxleyi and small gephyrocapsa probably were able to live deeper in the water column than most other species during periods of low nutrient supply to the upper photic zone in summary the composition of the coccolith flora can be explained by the nutricline depth level with three different assemblages being recognized a deep photic zone assemblage consisting of f profunda a middle upper photic zone assemblage of e huxleyi and small gephyrocapsa and an upper photic zone assemblage consisting of all other species

an experiment in the retrieval of depth and source mechanism of large earthquakes using very long period rayleigh wave data abstract the possibility of obtaining an estimate of depth for large earthquakes from low frequency mantle wave data alone is investigated using moment tensor formalism after illustrating the sensitivity to depth of the eigenfunctions in the period range of 160 to 350 sec we give several examples of application of the two step inversion procedure proposed earlier for shorter period rayleigh wave data romanowicz 1982 we find that for earthquakes below a depth of about 50 km we are able to resolve depth even when a spherically symmetric average earth model is used for propagation corrections this is particularly interesting in the case of large subduction zone earthquakes for which an estimate of the vertical extent of faulting can thus be obtained independently of aftershock studies in a very fast and simple manner which does not involve any synthetic seismogram calculations or lateral heterogeneity modeling for shallower earthquakes especially those with one steeply dipping nodal plane the resolution of depth is less precise taking lateral heterogeneity into account by using available regionalized phase velocities improves the results marginally we anticipate that accounting more accurately for the low order harmonics in the worldwide phase velocity distribution should prove most helpful since these interfere the most with the theoretical radiation patterns of earthquakes the determination of depth depends more critically on the source process time which has to be accounted for especially for horizontally propagating faults