q of the indian shield we analyze spectral attenuation of lg waves to determine q of the indian shield the dataset consists of four earthquakes recorded in the distance range of 240 2400 km the new estimate q f 800f 0 42 0 1 hz f 20 hz is based on a larger dataset than a previous estimate q f 508f 0 48 1 hz f 20 hz the new q f of the indian shield is comparable to the q in regions of eastern north america where its value is relatively high for example the adirondack mountains it is also in agreement with previously reported lg coda q at f 1 hz for the indian subcontinent the revised q f has important implications for the estimation of ground motions in the indian shield region using the stochastic method since the recorded data presently come mostly from large distances

theoretical study of the excitation spectral characteristics and geometrical attenuation of regional seismic phases abstract we present a theoretical study of the generation and geometrical attenuation of regional crustal phases we do this through the computation of seismograms in the epicentral distance range from 60 to 500 km the geometrical attenuation of lg waves with epicentral distance is of the form r 0 83 pg wave amplitudes display a much stronger decay of the form r 1 5 the spectral density of the crustal transfer function for pg waves is relatively flat for frequencies between 0 1 and 5 hz while lg wave spectra strongly fall off beyond 2 to 3 hz the excitation of pg wave is insensitive to the depth of the source within the crust while the lg amplitude is about 50 per cent higher for a source in the upper and middle crust than in the lower crust the amplitudes of these two phases drastically decrease when the source is below the moho these results illustrate the important role of wave guide played by the crust for the propagation of lg and pg we find that the geometrical attenuation of pg and lg waves is independent of source mechanisms in the case of an explosion the excitation of pg is insensitive to the source depth the lg wave amplitude is small in comparison to pg and rayleigh waves and depends on the closeness of the source to an interface or to the free surface

geometrical spreading and attenuation of lg waves a comparison between western anatolia turkey and southern spain abstract we compared the attenuation and geometrical spreading coefficient of lg waves for crustal paths in western anatolia and southern spain at source receiver distances between 80 and 400 km we used the coda normalization method which is based on the elimination of the source and site effects from observed spectra of lg waves q for lg waves in the crust was determined as a function of frequency in the range 1 5 10 0 hz for western anatolia and in the range 1 5 12 hz for southern spain we found that qlg shows a strong frequency dependence in both regions in western anatolia the frequency dependence of qlg is qlg f 82 f1 0 and the geometrical spreading coefficient ranges from 0 6 to 0 9 we found qlg 83 f0 88 and a geometrical spreading coefficient close to 0 5 in southern spain comparing our results with coda q values obtained in both regions qlg qc are similar qlg is close to qi in all frequency bands we interpret the geometrical spreading coefficient higher than 0 5 for western anatolia as due to a strong layered and heterogeneous crustal structure

attenuation of coda waves in new england abstract seismic wave attenuation was measured in new england from the time domain decay of coda wave amplitudes on narrow bandpass filtered seismograms of local earthquakes the frequency band of interest was 0 75 to 10 hz q c f was found to increase with frequency across this band but there was also a difference between the q c f values for short t t 100 sec lapse times of coda wave propagation for the short lapse time data corresponding to wave paths primarily in the upper crust q c f increases from 400 at 3 hz to 1300 at 10 hz for the large lapse time data corresponding to wave paths in the lower crust and upper mantle q c f was found to vary from 660 at 1 hz to 1500 at 10 hz if we interpret this dataset in terms of a model incorporating both scattering and anelastic attenuation we find that the mean free path of seismic waves over this frequency band is 80 km for short lapse times and 400 km for long lapse times if we assume that scattering is entirely responsible for the observed attenuation we find that the minimum mean free path for short lapse times is about 75 km over all frequencies whereas for long lapse times the minimum mean free path decreases from 400 km at 0 75 hz to 90 km at 10 hz

mineralogy and petrology of chondrules and inclusions in the mokoia cv3 chondrite all objects 100 m in apparent diameter in five polished thin sections of the mokoia cv3 chondrite were studied and classified number and volume percentages and mean apparent size of each type of chondrule and inclusion were determined three major types of olivine chondrules were observed igneous chondrules recrystallized chondrules and chondrules that appear to be accretional aggregates coarse grained cai s have igneous textures and mineral parageneses while fine grained cai s are aggregates containing varying proportions of al rich concentric objects ca rich chaotic material and inclusion matrix chondrules and refractory inclusions in mokoia and allende are broadly similar in texture and mineral chemistry but mokoia refractory inclusions contain phyllosilicates rather than feldspathoids and melilite rich cai s are more abundant in allende we think that most cai s formed during the metamorphism partial melting and incomplete distillation of primitive dust aggregates when they were heated in the solar nebula in the process ca rich melt appears to have been physically separated from al rich residues producing the observed fractionation of ca from al into distinct constituents of cai s some cai s may be aggregates of devitrified amorphous metastable condensates inclusion matrix may have condensed from silicate rich vapors produced during distillation mokoia inclusion matrix contains phyllosilicates that are probably primitive nebular material

frequency dependent attenuation in eastern kazakhstan and implications for seismic detection thresholds in the soviet union abstract the frequency dependent attenuation of regional seismic phases recorded by three stations near the nuclear explosion test site in eastern kazakhstan is estimated by inverting spectra from 21 events with magnitudes between 2 3 and 4 6 at distances between 200 and 1300 km the pn spectra are inverted between 1 and 10 hz and the lg spectra are inverted between 0 5 and 2 5 hz the motivation for this study is that previous estimates of detection capability in the soviet union are based on data recorded in other regions eastern north america and scandinavia and therefore have large uncertainty the data recently recorded in eastern kazakhstan provide an excellent opportunity to compare regional wave propagation and noise characteristics at these sites to conditions assumed in previous detection capability simulations it is found that attenuation in eastern kazakhstan is not much different from attenuation in scandinavia but it is greater than attenuation in eastern north america this implies that estimates of detection thresholds that assume attenuation like that observed in eastern north america will be lower than estimates of detection thresholds that assume attenuation like that observed in eastern kazakhstan or scandinavia however it is not known how well data recorded in eastern kazakhstan represent conditions in other areas of the soviet union

coda q in the southern appalachians the attenuation of seismic coda waves in the southern appalachian region was studied signal sources were five local and regional earthquakes and one explosion located in ohio virginia and south carolina the data were recorded digitally by a network of seven stations in western virginia joint least squares estimates of the quality factor q relative recording site responses and coda source amplitudes were obtained in five frequency bands using the single scattering model and assuming body wave geometrical spreading the results indicate a frequency dependent coda q represented by q 811 f0 42 1 5 f 12 hz for lapse times in the range 15 to 250 seconds site responses determined relative to the average network response differ by less than a factor of 2 in the range 3 to 12 hz at five of the seven stations however the differences in the response of the other two sites increase with frequency amounting to a factor of 5 at 12 hz estimated relative coda source amplitude spectra exhibit similar shapes consistent with the assumption that the scattering process is independent of path in the study region

propagation of lg waves in the north australian craton influence of crustal velocity gradients abstract aftershocks of three large earthquakes near tennant creek in the northern territory of australia provide a unique opportunity to study regional seismic phases in the north australian craton three portable digital seismographs were operated near the source zone to provide control on earthquake locations and seven recorders formed a line between tennant creek and the seismic array at alice springs which is 430 km to the south eleven earthquakes of sufficient size for analysis were recorded during a one week deployment two months following the main shocks the group velocity observed for lg waves along this profile of 3 7 km sec is at the high end of the normal range and appropriate for a stable continental interior we estimate attenuation in discrete frequency bands by measuring the decay of amplitude as a function of distance from the source and assuming the common r 5 6 relationship for geometrical spreading however this assumption leads to frequency dependent q values q 230 36 f 0 66 0 12 that are abnormally low for a stable continental region the apparent q is also not consistent with other observations such as the high lg group velocity the positive bias in m l estimates obtained for other parts of australia using standard attenuation relations the size of felt areas for large central australian earthquakes nor with the high frequency content of seismic reflection data collected near our profile some crustal models for northern australia derived from seismic refraction work show a gradient zone between 30 and 55 km rather than a sharp moho discontinuity we therefore investigate the effect of gradient zones at the crust mantle transition on the decay of lg amplitudes using synthetic seismograms calculated with the wavenumber integral method the modeling suggests that some of the s wave energy that would be trapped in a crustal wave guide with a sharp lower boundary can leak out in the presence of a gradient and so enhance the attenuation in addition there are focusing effects due to the formation of caustics from the gradient zones which cannot be represented by a single analytic amplitude correction

chemical compositions of refractory inclusions in the murchison c2 chondrite abstract samples from ten refractory inclusions in murchison some of which are splits of inclusions whose mineralogical and petrographic characteristics are known have been analysed for thirty six elements by neutron activation six inclusions have group ii or group iii patterns or variants of such patterns two inclusions bb 5 and much 1 have large negative yb anomalies unaccompanied by correspondingly large negative eu anomalies it is possible that the latter condensed originally with group iii patterns and preferentially took up eu in later exchange processes under reducing conditions one inclusion sh 2 has heavy ree enrichment factors that increase with the refractoriness of the ree indicating the presence of an extremely high temperature or ultrarefractory ree condensate but it also has a heavy ree light ree ratio that indicates mixing of that component with a lower temperature ree condensate the frequency of highly fractionated ree patterns and absence of group i patterns suggest that refractory inclusions in murchison stopped equilibrating with the nebular gas at higher temperatures than most allende coarse grained inclusions the lower ir os and ru re ratios of some murchison inclusions compared to those of allende coarse grained inclusions indicate that condensate alloys that contributed noble metals to the former also stopped equilibrating with the nebular gas at higher temperatures than those that contributed noble metals to the latter murchison inclusions tend to be lower in non refractory elements than allende coarse grained inclusions suggesting that on average the former underwent less severe secondary alteration than the latter

the abundance and relative volatility of refractory trace elements in allende ca al rich inclusions implications for chemical and physical processes in the solar nebula abstract we have determined the relative volatility of lithophile refractory trace elements lrte in the solar nebula by first calculating 50 condensation temperatures for 26 lrte oxides assuming ideal solid solution in perovskite and where appropriate in hibonite and melilite the measured abundances of 25 lrte and six siderophile refractory trace elements in 97 group i 11 111 and v allende ca al rich inclusions cai s and in ultra refractory inclusions then are used to empirically modify lrte and refractory siderophile volatility sequences that are based on condensation temperatures alone sc is significantly less depleted in group ii allende cai s than are other lrte e g zr hf y that also have very high oxide condensation temperatures ba sr and eu three moderately volatile lrte are significantly more enriched in ca rich group ii and group iii allende cai s than they are in spinel rich varieties of these inclusions we explain these observations and several others by invoking dust fractionation s and crystal chemical and diffusion effects during the formation of allende cai s that overprinted volatility based on solid gas reactions alone for example we show that hibonite probably was not the carrier of the super refractory lithophile component that is missing from group ii allende inclusions anomalous hf depletions relative to zr and y that are common in group i iii and v allende cai s can be partly explained if anders and ebihara 38 overestimated the cosmic abundance of hf by approximately 10

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

characteristics of short period wave propagation in regions of fennoscandia with emphasis on lg abstract wave propagation of crustal phases in particular lg near the arcess array in northern norway is examined and compared to propagation characteristics near the noress array in southern norway relying on array analysis we show that ray theory explanations of arrivals in local and regional seismograms are very useful in deducing the composition of the crustal wave trains frequency wavenumber analysis is applied to the array data to identify the arrivals then a composite of array beams is used to approximate each event record sections of composite seismograms are constructed for different directions from arcess to study propagational characteristics with distance and azimuth and then compared to composite seismogram record sections from noress to study different regional characteristics to model the observed character of lg and rg synthetic record sections are constructed by wavenumber integration in velocity models representative of structure in the different regions the results show that rg propagation distance varies significantly between regions and that the velocity gradient in the lower crust is the dominant factor in specifying lg characteristics in the baltic shield region lg is dominated by several discrete arrivals representing multiple moho reflections or by multiple moho reflections and turning waves with each multiple confined to a small distance range so that only one multiple set dominates at each distance furthermore we demonstrate that incomplete knowledge of the propagation characteristics leads to mislocations of local and regional events and inhibits source depth discrimination of events we identify three earthquakes in the arcess data set based on source depths these are constrained by phase velocities and depth phases none of which were properly identified by the automatic array detection software

shear wave attenuation characteristics over the central india tectonic zone and its surroundings abstract the study area lies between latitude 18 26 n and longitude 73 83 e and mainly covers the central india tectonic zone citz the frequency dependent shear wave quality factor qs has been estimated over the citz and its surroundings using double spectral ratio dsr method we have considered 25 local earthquakes with magnitude ml varies from 3 0 to 4 7 recorded at 11 stations running under national seismic network the fast fourier transformed fft spectra were computed from the recorded waveform having time window from onset of s phase to 1 0 s and for a frequency band of 0 1 10 hz three different shear wave velocities i e 3 87 3 39 and 3 96 km s were obtained over the study area based on a pair of earthquakes recorded at a pair of stations the low qs values of 51 96 at 1 hz i e qs 51f0 49 qs 90f0 488 and qs 96f0 53 were found in the area covering the son narmada tapti sonata lineament citz eastern part of the satpura fold belt vindhyan and gondwana basins godavari and mahanadi grabens and southern part of gangetic plain intermediate qs values of the order of 204 277 i e qs 204f0 56 and qs 277f0 55 were noted in the cartonic areas namely bundelkhand dharwar bhandara and bastar while the higher qs values of 391 628 at 1 hz i e qs 391f0 49 qs 409f0 48 qs 417f0 48 qs 500f0 66 qs 585f0 65 and qs 628f0 69 were found in the eastern part of the sonata citz and the northeastern part of the satpura fold belt the low qs values might be attributing to the more heterogeneous sonata rift system low qs values further may presumably be associated with lower level of seismicity and apparently account for higher tectonic stress accumulation over long duration the long term accumulated stress is generally released through occasional triggering of moderate magnitude earthquakes in the sonata zone surrounding the sonata region the higher qs values possibly accounts for a more homogeneous subsurface structure along the sonata zone

effects of irregular structure of the mississippi embayment on ground motion amplification the objective of this study is to evaluate effects of the presently available 3d velocity model of the mississippi embayment structure on the amplification of seismic waves by using simulated finite difference seismograms effects of both 2d and 3d embayment basement structures were considered the 3d model included information of the near surface velocities that were derived from the existing 1d velocity models the 2d crustal model was taken from catchings 1999 which extended from saint louis missouri to memphis tennessee finite difference seismograms were simulated for point sources embedded at both ends of the 2d structure these seismograms were examined to distinguish features like peak amplitude amplifications and duration of seismograms when the seismic waves propagated from the mississippi embayment toward the illinois basin and vice versa to establish a working 3d structure model of the embayment we compiled geologic information of the region on material properties of the shallow structure and used the 3d model developed at the center of earthquake research institute ceri memphis as the starting model the 3d model was used to generate finite difference seismograms along several profiles for a m w 7 2 scenario earthquake occurring on the new madrid fault zone an equivalent 1d model which included the basin materials was also used to compare the 3d versus equivalent 1d ground motions simulated using the finite difference method to establish the amplification factors due to the surface sediments in the 3d model finite difference seismograms were also computed for a 1d hard rock reference model these 1d and 3d responses of the mississippi embayment were used for estimating ground motion amplification at sites where the depth to the basement is deeper than 500 m our investigation suggests that the deep structure of the mississippi embayment has little impact on long period ground motion amplitudes t 2 sec for large earthquakes that rupture in the central part of the basin this supports the hypothesis that for engineering purposes ground motions simulated based on the equivalent 1d crustal model are adequate for representing ground motions from future large earthquakes m w 7 occurring in the new madrid seismic zone

the effect of crustal structure on the regional phases pg and lg at the nevada test site the effect of local structure on the characteristics of the regional phases pg and lg was investigated by analyzing events at epicentral distances less than 10 from the nevada test site the stations used are on markedly different geological structures three on granitic intrusions two on pahute mesa a feature overlaying a buried volcanic caldera and finally four on yucca flats a deep alluvial valley the crustal effect on amplitudes is quite significant for both lg and pg yucca flats gives amplitudes as much as a full order of magnitude higher than the stations on granite while pahute mesa stations are 0 7 0 8 magnitude units higher in amplitude than the granite sites besides gross amplitude effects the local crust also induces prolonged ringing at yucca flats resulting in the lengthening of the signal wave trains the observed site amplification effects show no clear dependence on the azimuths of arrivals indicating that the phenomenon is due to local structures and is not caused by lateral refraction of surface wave modes the observed amplification is similar in magnitude for the vertical component of both pg and lg thus not affecting the pg lg amplitude ratio a possible discriminant between earthquakes and explosions at regional distances finite difference theoretical simulations using two dimensional models of the yucca basin reproduce in a qualitative sense the ringing effect observed at the yucca flats any attempt at matching characteristics of pg and lg with synthetic seismograms computed for laterally homogeneous layered structures is apt to lead to false conclusions about the source and path properties unless the recording sites used are carefully chosen for small crustal effects

regional spectral scaling relations of source parameters for earthquakes in the baltic shield abstract spectral analysis of regionally recorded lg waves is performed to determine source parameters such as seismic moment source radius and stress drop of earthquakes in the baltic shield and to derive regional spectral scaling relations the data consist of about 350 lg phases on short period vertical component analog seismograms from earthquakes with magnitude m l ranging from 2 to 5 2 source radii estimated from the corner frequency show only a slight increase with increasing seismic moment in the range 3 10 18 to 5 10 20 dyn cm while the increase is more rapid for larger events baltic shield earthquakes show increasing stress drops ranging from about 0 1 to 10 bars for increasing seismic moment the relatively low stress drops could in part be explained by bias due to band limited analog data the slope of the curve relating seismic moment to corner frequency is steeper than 3 which suggests a departure from a constant stress drop scaling relation proposed for large earthquakes the derived relationship between the seismic moment m o and magnitude m l is log m o 16 93 1 01 m l for 2 m l 5 2

linking bedrock discontinuities to glacial quarrying quarrying and abrasion are the two principal processes responsible for glacial erosion of bedrock the morphologies of glacier hard beds depend on the relative effectiveness of these two processes as abrasion tends to smooth bedrock surfaces and quarrying tends to roughen them here we analyze concentrations of bedrock discontinuities in the tsanfleuron forefield switzerland to help determine the geologic conditions that favor glacial quarrying over abrasion aerial discontinuity concentrations are measured from scaled drone based photos where fractures and bedding planes in the bedrock are manually mapped a tukey honest significant difference test indicates that aerial concentration of bed normal bedrock discontinuities is not significantly different between quarried and non quarried areas of the forefield thus an alternative explanation is needed to account for the spatial variability of quarried areas to investigate the role that bed parallel discontinuities might play in quarrying we use a finite element model to simulate bed normal fracture propagation within a stepped bed with different step heights results indicate that higher steps larger spacing of bed parallel discontinuities propagate bed normal fractures more readily than smaller steps thus the spacing of bed parallel discontinuities could exert strong control on quarrying by determining the rate that blocks can be loosened from the host rock

attenuation of 1 6 s lg waves in eurasia we report our investigation of the lg attenuation characteristics in eurasia using digital recordings from the incorporated research institutions for seismology chinese digital seismic network broadband stations to maximize the utilization of the current station and source distribution in the region we have derived a new technique known as the source pair receiver pair sprp method for lg attenuation measurement the procedure eliminates seismic source and site effects leaving behind decontaminated amplitude data from which regional wave attenuation is estimated for lg attenuation studies the sprp method is more flexible and of greater general applicability than its predecessor the reversed two station method chun et al 1987 the application of the sprp method to our time domain analysis of 33 regional and far regional seismic events has provided stable regional average for lg attenuation in periods of 1 6 s our time domain analysis aided by a damped least squares inversion algorithm has led to robust measurements of lg attenuation q and its frequency dependence in nine subregions of tectonic significance regions of active tectonics and seismicity generally have lower q0 than that in the stable continental interior subregional q and are found compatible with the published results in areas of relatively uniform geology values are comparatively poorly determined suggesting that they are susceptible to the presence of crustal heterogeneities along the wave paths

an assessment of the impact of the 2003 epri ground motion prediction models on the usgs national seismic hazard maps ground motion attenuation relations have an important impact on seismic hazard analyses ground motion modeling is particularly sensitive to assumptions about wave propagation attenuation crustal q and geometrical spreading as well as source and site conditions studies of path attenuation from earthquakes in eastern north america ena provide insights into the appropriateness of specific attenuation relations an electric power research institute epri 2003 2004 study combines published ena ground motion attenuation relations into four model forms single corner double corner hybrid empirical and finite fault when substituted in the u s geological survey 2002 national seismic hazard maps for the five ena relations originally used in those hazard calculations the epri 2003 relations predict similar ground motions and hazard at short periods 0 5 sec relative to the 2002 national maps a major reason for this difference is due to the crustal seismic wave attenuation model assumed in a few of the ena relations combined into the epri 2003 2004 models although appropriate differences in geometrical spreading models among ena relations can also be significant a few ena relations have 1 hz q values q that are below the epri 1993 consensus range for q when coupled with a geometrical spreading of r 0 5 the epri 2003 2004 single corner relation is strongly influenced by the inclusion of ena relations with assumed q below the epri 1993 range which explains much of the discrepancy in predictions at longer periods

a study of variations in the horizontal to vertical lg amplitude ratio in the eastern united states abstract three component short period data on lg in the eastern united states show unusually large regional variations in the average value of the ratio of the largest horizontal h to the largest vertical z component of ground motion this ratio is found to have a value of about 3 or larger for most sites in the central platform and the coastal plains regions and less than 2 for the hard rock sites in the appalachian mountains region large values of h z in the region of coastal plains sediments can be explained as being due to the presence of low velocity overburden but such an explanation is probably not valid for sites in the central platform region large variations in h z from one site to another are of special importance in earthquake engineering since most damage to structures is generally caused by the horizontal components of ground motion

attenuation of high frequency shear waves in the crust measurements from new york state south africa and southern california we compare the attenuation of high frequency 3 30 hz shear waves for crustal paths in new york state south africa and southern california over source receiver distances of about 10 400 km the data consist of digital recordings of s waves 5 100 km and lg waves 100 400 km produced by earthquakes we use a coda normalization method to remove the effects of site amplification and source excitation from the amplitudes of the s and lg waves over the entire distance range studied 10 400 km the amplitude decay of 3 hz shear wave energy is considerably less for the tectonicaily stable areas of new york and south africa than for the tectonicaily active region of southern california high frequency 30 hz s wave attenuation is significantly less for new york and south africa than for southern california for distances between 15 and 90 km we parameterize the decay with distance r of coda normalized shear wave amplitudes with a frequency independent q and geometrical spreading exponent where geometrical spreading is proportional to r for new york state the s wave amplitude decay 3 30 hz is well described by a frequency independent q of 2100 330 490 and of 1 3 0 1 the decay of lg wave amplitudes from 3 to 15 hz in the new york state region is fit with a frequency independent q of 1600 280 330 of 0 70 0 2 the s wave amplitudes 3 30hz in south africa yield a q of 1500 190 380 and of 1 3 0 1 fixing the geometrical spreading at r 0 5 produces an lg wave q estimate at 3 hz in south africa of 360 50 80 this lg wave q is low considering that south africa is a cratonic tectonicaily stable area the s wave amplitudes from southern california are described with a frequency independent q of 800 150 240 and a large geometrical spreading exponent of of 1 9 0 2 we find an lg wave q at 3 hz of 260 30 for southern california after constraining the geometrical spreading at r 0 5

attenuation of ground motion in the eastern united states abstract frequency dependent attenuation of ground motion in the eastern united states is investigated for both vertical and horizontal components of motion this is accomplished by digitizing and analyzing three component short period long range seismic measurements data from over 200 earthquake station pairs with epicentral distances less than about 1000 km pseudo relative velocity as well as velocity response spectra for 5 per cent damping are obtained for the frequency range of 0 5 to 7 hz a multi variate least squares inversion is used to derive the station and source terms as well as the mean q analysis of data for the entire eastern united states indicates q values for the vertical and horizontal components to be indistinguishable substantial increase in q with frequency a factor of about 2 from 1 to 7 hz large as much as a factor of 20 in amplitude site terms for both the vertical and horizontal components and the mean ratio of the peak horizontal to peak vertical component to be a stable characteristic of the site large regional variations in q are also indicated by subsets of data such as for the central united states and the appalachian mountains region

an ultra refractory inclusion from the ornans carbonaceous chondrite a small refractory inclusion 1 g was found in the ornans carbonaceous chondrite the inclusion is extremely enriched in the most refractory ree lu er ho the more volatile light ree having more than two orders of magnitude lower concentrations refractory metals are fractionated in a similar way high abundances of the most refractory metals os re low content of more volatile metals such as ru and pt gas solid equilibrium at high temperatures can easily account for the observed relative abundances of refractory elements independent temperature estimates from ree abundances and refractory metal contents suggest an equilibrium temperature of about 1670 k at 10 3 atm the trace element pattern of the inclusion is complementary to the pattern of fine grained allende inclusions the inclusion may either represent a first condensate from a cooling gas of approximately solar composition or the very last residue from an evaporation process only the low contents of w and mo do not fit the pattern of refractory elements predicted from condensation calculations both elements however readily form volatile oxides therefore this depletion could be taken as indication of an evaporative origin of the inclusion the metal phase consists of small os rich grains in a comparatively os poor matrix grains and matrix appear to be a mechanical mixture this textural evidence cannot be easily reconciled with an evaporative origin a condensation origin of the inclusion would require that w and mo were lost at a later time in a more oxidising environment without affecting the metallic ta found in some of the metal grains

regionalization of crustal coda q in the continental united states a contour map of crustal q sub 0 values for the entire united states is presented based on a scattering model to explain the coda waves of local and near regional earthquakes these coda q sub 0 values are in good agreement with q of lg waves data are obtained from over 250 local earthquakes with most magnitudes between 3 0 and 5 0 recorded by 25 wwssn and 27 lrsm stations throughout the continental united states these two sets of data provide a range of frequencies from 0 5 to 3 5 hz a frequency dependence of q is observed in the range of frequencies considered a power law dependence of the form q q sub 0 f f sub 0 sup eta is assumed the value of frequency dependence eta is found to be maximum in the tectonically active western united states and least in the stable regions of the central and south central united states the lowest q sub 0 values are obtained in the western united states with values ranging from 140 to 200 in the coastal plains average crustal q sub 0 values for the basin and range province vary from 200 to 300 increasing gradually to 400 in the colorado plateau region q sub 0 valuesmore in the columbia plateau vary from 200 to 400 q sub 0 values increase very rapidly along the central and southern rocky mountains from 400 to 800 east of the rocky mountains q sub 0 values increase gradually in the interior plains to a maximum value of around 1300 in the mississippi embayment region farther east q sub 0 values decrease gradually to an almost constant value of 1000 along the appalachian mountains coastal regions of eastern and northeastern united states have a crustal q sub 0 value between 900 to 700 regions of north central and gulf coastal plains show low q sub 0 values ranging from 600 to 400 and less the source factor b f sub p a measure of the intensity of scattering was obtained for several different regions of the continental united states regions of high q sub 0 values exhibit low intensity of scattering less

mapping of coda wave attenuation and its frequency dependency over eastern indian shield the study area comprises two tectonic blocks namely the chotanagpur microplate and the singhbhum microplate waveform data of 112 local earthquakes of magnitude mw 2 5 were considered for the present analysis coda q qc for each event at eight different central frequencies 1 14 hz and four different coda windows was estimated using back projection algorithm the average q0 qc at 1 hz and exponent values were regionalized by projecting each value in selected square grid of dimension 0 1 0 1 back projection algorithm was used for inversion of qc and the final values were computed after ten iterations when the residual error was reduced to acceptable level inversion was stabilized by a nine point spatial smoothening gaussian filter to compute the qc values for each frequency and subsequently combined values of q0 and were also computed the final power law equation of the coda wave attenuation for the concerned region was found to be qc 336 38 16 50 f 0 83 0 036 q0 varies from 180 to 255 270 to 360 297 to 386 and 340 to 420 and vary from 0 9 to 1 02 0 79 to 0 89 0 79 to 0 88 and 0 79 to 0 86 for 30 35 40 and 45 s coda windows increase in q0 and decrease in values with increase of coda window length shows the depth dependency of seismic wave attenuation at 1 hz frequency the central part surrounding the receiver lying at the junction of the chotanagpur and the singhbhum tectonic provinces documents lower q0 and higher values and presumably caused by more heterogeneities present in the area the higher concentration of lower magnitude earthquakes in this area support this observation the mapping values of attenuation can be utilized for hazard assessment of the area

observed variations of earthquake motion across a sediment filled valley the response to earthquake motion of a site in one sediment filled valley was observed to depend strongly on frequency and the position of the site within the valley and weakly on the input signal s azimuth and incidence angles the observed input motion was weak varying between 10 5 and 10 3 g measurements of ground velocity were made on profiles across and along the valley and simultaneously on two nearby rock sites the valley was 400 m wide and 700 m long with a maximum sediment thickness of 60 m the average seismic impedance contrast between the sediments and underlying basement rock was about 6 1 ratios of fourier spectra from soil sites to spectra from nearby rock sites showed apparent site amplifications of as much as a factor of ten depending strongly on frequency and the distance of the site from the valley edge the scatter in spectral ratios for earthquakes with different azimuths and angles of incidence was about a factor of two thus local site effects that changed the amplitude of incident motion by a factor of two or more could be identified in the records of most earthquakes ground motion at valley edge and mid valley sites separated by less than 100 m differed by as much as a factor of five this difference could cause large differential motion in structures spanning these sites a theoretical flat layer model of sediment response predicts the average behavior of the middle of the valley but not that of the valley edge the lowest frequency responance apparently involves the sediments across the width of the valley not just the vertical column of soil beneath each site

a spectral analysis of the 21 may 1997 jabalpur india earthquake mw 5 8 and estimation of ground motion from future earthquakes in the indian shield region the jabalpur earthquake 23 08 n 80 06 e h 36 km is the first event in the indian peninsular shield region to be well recorded by a newly installed 10 station broadband seismographic network using these data we estimate q of lg wave in the indian shield region as q 508 0 48 1 20 hz the corrected source spectrum with m 5 4 1024 dyne cm reported in the harvard cmt catalog and an 2 source model requires a stress parameter p of 420 bar to explain high frequency spectral level the computed seismic energy from the records is 7 4 1020 erg which yields an apparent stress and brune stress drop of 62 and 270 bars respectively the analysis of the jabalpur earthquake provides some elements for the estimation of ground motions during future earthquakes in the indian shield region based on the results of the jabalpur earthquake and on studies of tectonically similar region of eastern north america we assume that 1 the sources follow an 2 model 2 s waves dominate at r 100 km and lg waves dominate at r 100 km 3 q f 508 0 48 4 the ground motion is a bandlimited finite duration gaussian white noise and 5 the effective duration of the ground motion equals 1 c 0 05 r where fc is the corner frequency we apply random vibration theory rvt to compute various measures of ground motion such as a max and v max at near source distances the source finiteness is approximately taken into account the attenuation curves for 5 5 mw 7 and for p of 100 400 bar are presented as expected the predicted values with p 420 bar agree reasonably well with the limited jabalpur data an a max of 150 gal is predicted in the epicentral region of this earthquake the predicted curves imply p 100 bar for the latur earthquake of 1993 mw 6 1 h 2 5 km to explain a max 1 g and the reported isoseismal intensities in the epicentral region for koyna earthquake of 1967 mw 6 3 the inferred a max and v max from isoseismal intensities and the recorded strong motions at the koyna dam site are in agreement with the prediction curves for p 100 bar the rvt predictions seem reasonable but need validation from more strong motion data which is presently lacking

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

an investigation into earthquake ground motion characteristics in eastern north america abstract a random vibration model of the hanks mcguire type is used to predict peak ground motions at rock sites in eastern north america the assumed geometric decay and distance dependent duration approximate the propagation of direct body waves at short distances and lg waves at regional distances the model predicts peak acceleration and velocities as well as response spectra and magnitude for a given seismic moment and corner frequency to predict ground motions for a given lg magnitude m lg the model is first used to calculate the seismic moment corresponding to that magnitude assuming a source scaling law then knowing the moment and corner frequency the model is used to calculate peak ground motions available data from strong motion recordings and from the ectn and lrsm networks modified to estimate horizontal ground motions on rock where appropriate are used to verify the model9s assumption and predictions modified mercalli intensity data are also used ground motions predicted by the model with a stress drop of 50 to 200 bars agree with the ground motion data but the m lg values computed by the model for given seismic moments do not agree with nuttli9s 1983 moment versus m lg data for large earthquakes resolution of the latter disagreement awaits the collection of instrumental data from large events in eastern north america

the high frequency shape of the source spectrum for earthquakes in eastern and western canada abstract the high frequency shape of the earthquake spectrum strongly influences the amplitude of the peak ground acceleration and of the response spectrum at frequencies of 10 hz and greater a key parameter for the description of high frequency ground motions is kappa which is the decay slope of the fourier spectrum of acceleration at near source distances anderson and hough 1984 note anderson and hough originally referred to this parameter as kappa 0 kappa may be attributed to site effects f max hanks 1982 source processes papageorgiou and aki 1983 or both seismographic data place weak but significant constraints on kappa values on average there is no resolved kappa effect on spectra recorded at rock sites in eastern canada in the frequency range f 30 hz four firm soil sites in southwestern ontario also show no kappa effect an implied upper bound for kappa is 0 004 or lower bound of 30 hz for f max by contrast source spectra from earthquakes in the cascadia region recorded on hard rock sites in southwestern british columbia b c appear to be well described by a kappa of 0 011 0 002 the b c spectra are thus intermediate to the eastern case with zero apparent kappa and the typical california case for which kappa is about 0 04