nonlinear soil response of a borehole station based on one dimensional inversion during the 2005 fukuoka prefecture western offshore earthquake the objective of this article is to present the nonlinear response of a soft sedimentary site based on a one dimensional inversion by a genetic algorithm of the shear wave velocity structure and damping factors of a borehole soil column during the 2005 fukuoka prefecture western offshore earthquake first we confirm that according to the source rupture mechanism the major and minor axes in the horizontal plane at the borehole station are the transverse and radial directions respectively then in order to corroborate in the linear domain the s wave transfer function of the borehole s logging we perform time dependent spectral ratios analyses on small aftershocks finally we show qualitative evidence of nonlinearity during the main shock associated with a significant shift toward low frequencies of several resonant modes and we evaluate the degree of nonlinearity by inverting the shear wave veloc ity structure and damping factors because of a directional effect present only in the major axis around 8 hz which prevents the use of the conventional objective function that minimizes the integrated residuals between observed and theoretical ratios we introduce a simple objective function that depends only on peaks frequency and amplitude the efficiency of the objective function and the robustness of the inversion are shown by performing eight independent inversions converging to very similar minima

borehole response studies at the garner valley downhole array southern california the garner valley downhole array gvda consists of a set of seven downhole strong motion instruments ranging from 0 to 500 m depth one of the objectives of this experiment is to estimate site response and study wave propagation as the energy travels from the bedrock underneath the site up through the soil column the gvda velocity structure is studied by computing synthetic accelerograms for a small event located at an epicentral distance of 10 km these synthetics simulate well the data recorded at the borehole stations in addition theoretical transfer functions are calculated using the obtained velocity model and compare well with the empirical transfer functions from 54 recorded events it is also observed that the downgoing wave effect is predominant in the first 87 m and is strongly reduced at depth using the velocity structure at gvda and the transfer function results it has also been possible to develop a simple method to compute the incident wave field which is needed in nonlinear site response for instance recently there have been many comparative studies between horizontal to vertical h v spectral ratios and traditional spectral ratios although many of these studies show that h v spectral ratios can reproduce the shape of the site response curve most show differences in the amplitude level in the case of garner valley where we have both surface and multiple borehole instruments we find that this discrepancy in amplitude of the site response estimates is because the vertical component has significant site response associated with it due to s to p conversions that begin in the weathered granite boundary at 87 m depth manuscript received 27 august 2001

incompletely compacted equilibrated ordinary chondrites we document the size distributions and locations of voids present within five highly porous equilibrated ordinary chondrites using high resolution synchrotron x ray microtomography ct and helium pycnometry we found total porosities ranging from 10 to 20 within these chondrites and with ct we show that up to 64 of the void space is located within intergranular voids within the rock given the low s1 s2 shock stages of the samples and the large voids between mineral grains we conclude that these samples experienced unusually low amounts of compaction and shock loading throughout their entire post accretionary history with fe metal and fes metal abundances and grain size distributions we show that these chondrites formed naturally with greater than average porosities prior to parent body metamorphism these materials were not fluffed on their parent body by impact related regolith gardening or events caused by seismic vibrations samples of all three chemical types of ordinary chondrites ll l h are represented in this study and we conclude that incomplete compaction is common within the asteroid belt

elastic finite difference modeling of the 1971 san fernando california earthquake finite difference seismograms calculated for the 1971 san fernando earthquake show strong effects due to lateral variation in sediment thickness in the san fernando valley and the los angeles basin using basin structure derived mostly from well logs and teleseismically determined source parameters two dimensional sh and p sv finite difference calculations reproduce the amplitude and duration of the strong motion velocities recorded across the los angeles and san fernando basins for the period range of 2 to 10 sec the edges of basins nearest the seismic source show ground motion amplification up to a factor of 3 over the case without the basin and tend to convert direct shear waves into love and rayleigh waves that travel within the basins

high frequency site effects at two parkfield downhole and surface stations abstract using stacked ratios of microearthquake source spectra recorded at the surface and 200 m downhole we have established the p and s wave site effect at two locations in parkfield california the frequency responses of both sites are bimodal being completely dominated by multiples and amplification below 10 hz and by attenuation above 30 hz the low frequency amplification factors show roughly three to five times more uphole motion compared to that downhole the multiples produce peaks with a maximum of nearly 10 times more uphole motion above 50 hz the downhole motion is always larger approaching a factor of 5 at the high frequency limits of our study when fit with a linear attenuation model the high frequency ratios yield compressional and shear q values between 6 and 19 the data were divided into subsets based on event location and time of year statistical comparison of these subsets shows no systematic variation with azimuth or season the results of our study accounts for the lack of high frequency surface reflections in the parkfield downhole data but not for the lack of source scaling of parkfield microearthquakes

nonlinearity liquefaction and velocity variation of soft soil layers in port island kobe during the hyogo ken nanbu earthquake clear nonlinear behavior is analyzed from the acceleration records of the 1995 hyogo ken nanbu earthquake at port island kobe from four triaxial in struments placed at four different depths the surficial effects during strong ground motions were compared with those during weak motions before and after the main shock we used a spectral ratio technique and a nonlinear inversion for velocity structure to analyze the data from the spectral analysis we observed a large variation of the spectral ratios between the surface and different depths during the strong ground motions and during the liquefied state the spectral ratios after the mainshock i e after the liquefied state are different from those before the mainshock the peak frequencies in the spectral ratios after the mainshock are shifted to lower fre quencies with respect to those in the spectral ratios before the mainshock we in verted the s wave velocities using a genetic algorithm technique to determine the velocity structure before during and after the mainshock the s wave velocity struc ture before and after the mainshock was found to be different specifically the s wave velocity of the second layer 5 m to 16 m depth after the mainshock was 20 lower than before our analysis shows that the liquefied state remains at least 3 hr after the mainshock but no more than 24 hr the rigidity of the soil decreased close to zero when liquefaction happened and later increases gradually following a trend that resembles a consolidation curve the strong influence of nonlinearity during the mainshock yielded a big reduction of the horizontal surface ground motions so that the observed horizontal peak acceleration was only about 25 of the peak acceler ation expected from the linear theory however the nonlinear effects in the vertical peak acceleration were not significant

nonlinear behavior of soil sediments identified by using borehole records observed at the ashigra valley japan abstract we evaluate the nonlinear behavior of soil sediments during strong ground shaking based on the identification of their s wave velocities and damping factors for both the weak and strong motions observed on the surface and in a borehole at kuno in the ashigara valley japan first we calculate spectral ratios between the surface station ks2 and the borehole station kd2 at 97 6 m below the surface for the main part of weak and strong motions the predominant period for the strong motion is apparently longer than those for the weak motions this fact suggests the nonlinearity of soil during the strong ground shaking to quantify the nonlinear behavior of soil sediments we identify their s wave velocities and damping factors by minimizing the residual between the observed spectral ratio and the theoretical amplification factor calculated from the one dimensional wave propagation theory the s wave velocity and the damping factor h 2 q 1 of the surface alluvial layer identified from the main part of the strong motion are about 10 smaller and 50 greater respectively than those identified from weak motions the relationships between the effective shear strain 65 of the maximum shear strain calculated from the one dimensional wave propagation theory and the shear modulus reduction ratios or the damping factors estimated by the identification method agree well with the laboratory test results we also confirm that the soil model identified from a weak motion overestimates the observed strong motion at ks2 while that identified from the strong motion reproduces the observed thus we conclude that the main part of the strong motion whose maximum acceleration at ks2 is 220 cm sec 2 and whose duration is 3 sec has the potential of making the surface soil nonlinear at an effective shear strain on the order of 0 1 the s wave velocity in the surface alluvial layer identified from the part just after the main part of the strong motion is close to that identified from weak motions this result suggests that the shear modulus recovers quickly as the shear strain level decreases

field measurements of wave overtopping at the rubble mound breakwater of rome ostia yacht harbour abstract this paper describes a new station for full scale measurement of wave overtopping at the rome yacht harbour rubble mound breakwater in ostia italy and the results of the successful first measurement campaign carried out during the winter season 2003 2004 the equipment and the research activities were supported by the eu project clash focusing on scale effects for wave overtopping at coastal structures the site is characterized by a very small tidal range a long shallow foreshore and depth limited breaking waves which interact with a shallow sloping porous rock structure overtopping water is collected by a steel tank installed on the crown slab behind the parapet wall the measurement of water level variation inside the tank by means of two pressure transducers allows the calculation of individual overtopping volumes incident waves sea levels and wind are also measured during seven independent storms more than 400 individual overtopping events were recorded and about 86 h of valid data are available this extensive dataset is presented discussed and then used for comparison with two commonly used overtopping prediction formulae based on small scale model tests showing their tendency to underestimate the prototype results a strong correlation between the hourly mean overtopping discharge and corresponding maximum volume is also presented the paper generally confirms the validity of the approach used in troch et al 2004 troch p geeraets j van de walle b de rouck j van damme l allsop w franco l 2004 full scale wave overtopping measurements on the zeebrugge rubble mound breakwater coastal engineering 51 609 628 for field measurement of wave overtopping

three dimensional finite difference waveform modeling of strong motions observed in the sendai basin japan we perform three dimensional 3d finite difference fd waveform modeling of strong motions in the frequency range 0 2 to 1 67 hz observed in the sendai basin japan during the japan meteorological agency magnitude m j 5 0 1998 miyagiken nanbu earthquake in a previous we estimated s wave velocity structures above the pre tertiary bedrock at six sites in the sendai basin based on array records of microtremors to interpolate these velocity structures in space we conduct single station microtremor measurements at a total of 61 locations and estimate the s wave velocity structure at each site by modeling the horizontal to vertical spectral ratio of fundamental mode rayleigh waves an initial 3d model of the basin is constructed using the velocity structures estimated from both array and single station microtremor measurements along with other information such as surface geology this model encompasses a region 33 km long 30 km wide and 19 km deep the final model is obtained through a trial and error process by fitting 3d fd synthetic waveforms to the bandpass filtered 0 2 hz to 1 67 hz displacement records 12 stations for the 1998 miyagiken nanbu earthquake we compute the synthetics using a fourth order staggered grid 3d fd method with variable grid spacing as the 3d model is modified the source parameters strike dip rake and seismic moment are estimated by a grid search method using 1d site specific models derived from the modified 3d model the observed waveforms are reproduced well at most stations by the final 3d basin model this agreement suggests the validity of the final 3d basin model for theoretical strong motion prediction of large earthquakes in the frequency range from 0 2 to 1 67 hz manuscript received 7 june 2000

the porosities of ordinary chondrites models and interpretation densities and porosities for 285 ordinary chondrites have been assembled and analyzed measured chondrite porosities are bimodal finds have an average porosity of 30 we conclude that mild degrees of weathering fill pore spaces lowering grain densities and porosities without significantly changing the bulk size or mass of the sample by assuming an original pristine grain density as a function of the meteorite s mineralogy determined by its class we can derive model pristine porosities these model porosities cluster around an average value of 10 for all classes of ordinary chondrites ordinary chondrites do not show any correlation of porosity model or measured with petrographic grade or sample size over a range from 0 2 g to 2 kg however we do see a correlation between shock state and porosity shock blackened meteorites are less porous than other meteorites furthermore less severely shocked meteorites show a much broader range of porosities with the maximum porosity seen among meteorites of a given shock class falling linearly as a function of that shock class this is consistent with the idea that shock compresses and closes pore space analysis of meteorite porosity provides a lower bound to the fine scale porosity of asteroids our densities even with 10 primordial porosity are significantly higher than inferred densities of possible asteroid parent bodies these asteroids are probably loose piles of rubble

evaluation of local site effects and their removal from borehole records observed in the sendai region japan abstract we present results from a borehole observation network composed of 12 borehole sites deployed in a 20 20 km area in the sendai region japan the subsurface quaternary layers vary with each site but a pliocene layer is commonly underlying at a depth of 0 to 80 m throughout the sendai region we define this pliocene layer whose s wave velocity is larger than 500 m sec and whose n value of the standard penetration test is greater than 50 as an engineering bedrock in the region once we characterize ground motions at the engineering bedrock we can either use these motions directly in the response analysis of whole soil building systems or use them in the nonlinear analysis of soft soil layers as an input the purpose of this study is to evaluate the local site effects due to surface layers overlying the engineering bedrock and to remove them by using one dimensional 1d soil models whose properties are determined by weak motion records of 18 events first we identify s wave velocities and frequency dependent quality factors q from amplification factors between surface records and borehole records observed at 10 sites at depths of several tens of meters the identified s wave velocities are very close to s wave logging values the identified q values show strong frequency dependence proportional to f 0 46 to 1 16 where f is frequency we confirm that the observed amplification factors in the frequency range from about 0 1 to 20 hz can be explained well by the theoretical ones based on the 1d wave propagation theory with the identified s wave velocities and q then we estimate the so called engineering bedrock waves which are supposed to be observed on the outcrop of the engineering bedrock from borehole records by using the 1d models with these identified soil constants we confirm that local site effects due to surface layers overlying the engineering bedrock are properly removed so that we have similar characteristics in the resultant engineering bedrock waves from records at different sites

site response of strong motion stations in the umbria central italy region we used near field and regional records from 16 earthquakes m l 4 6 5 9 located in the epicentral area of the 1997 umbria marche sequence to estimate the site response of 40 strong motion stations the distribution of hypocenters covers a distance range from 5 to 100 km we estimated site amplification factors using two techniques namely a generalized spectral inversion method and horizontal to vertical component spectral ratios hvsrs of ground acceleration for the first approach we inverted observed spectral amplitudes for site q and source using a reference site since the site response estimated using hvsrs assumes that the vertical component of motion is amplification free we also separated source and site effects by inverting the vertical component of the acceleration spectra we found that although most of the stations do not show important amplifications on the vertical component a few of them have a significant vertical amplification at low frequencies f q representative of the s wave train shows a frequency dependence that can be approximated by the relation q s 31 2 f 1 2 between 0 3 and 9 5 hz however at high frequencies f 10 hz this dependence weakens and q s takes an approximately constant value of 438

differences between site characteristics obtained from microtremors s waves p waves and codas we examine differences of empirical site characteristics among s waves p waves coda and microtremors using records at 20 sites in and around the sendai basin japan and interpret the differences theoretically at soft soil sites the horizontal to vertical spectral ratios hvrs for early p coda become different from hvrs for a p wave with increasing time and eventually converge on hvrs for microtremors the hvrs for an s coda become similar to hvrs for microtremors with increasing time in the frequency range lower than 3 hz at soft soil sites by contrast at a rock site and two hard soil sites hvrs for s coda agree well with hvrs for an s wave the soil to rock spectral ratios for horizontal hhrs and vertical vvrs components for early s coda are larger than those for an s wave at soft soil sites when we use the deep sedimentary structures above the bedrock before tertiary age theoretical hvr for the fundamental mode of rayleigh waves is consistent with observed hvr for microtremors and theoretical hvr for an obliquely incident sv wave is consistent with observed hvr for an s wave theoretical s wave site amplification factor explains well observed hhr for s wave but does not coincide with hvr for microtremors in general the frequencies of maximum peaks of hvrs for microtremors do not coincide with those of hvrs and hhrs for s wave however if we select hvrs with peak frequencies lower than 1 hz and peak amplitudes larger than three the peak frequencies of hvrs for microtremors roughly coincide with those of hvrs and hhrs for s wave even under these constraints their amplitudes do not coincide with each other concerning coda we conclude that the rayleigh wave contamination in coda is significant in the frequency range lower than 3 hz at soft soil sites

oxygen isotopes in asteroidal materials measurement of the variation of the 17o 16o and 18o 16o ratios of extraterrestrial materials has proven to be a key tool in understanding the formation and evolution of the solar system this chapter attempts to collate the huge data set of oxygen isotopic measurements of asteroidal material as sampled by meteorites in order to understand some of the processes involved in the formation of these primitive bodies and how such events have affected the oxygen isotopic ratios ultimately offering a window back to the very origin of solar system and its primordialoxygen isotopic heterogeneity oxygen is generally a major element in the gas liquid and solid phases that have interacted throughout the evolution of the solar system its chemical properties ensuring that there is abundant opportunity for reactions and exchange the details of which can be recorded in the isotopic ratios of the products such processes can be crudely subdivided into the following six categories early solar nebular isotopic heterogeneity high temperature modifi cation of nebular components metamorphism and melting in asteroids aqueous alteration in asteroids mixing of components brecciation terrestrial weathering it is clear from the isotopic variation in the earliest formed nebular components such as refractory inclusions and chondrules that there was considerable oxygen isotopic heterogeneity in the early solar nebula spanning over 50 and perhaps much greater in both 17o and 18o the origin of this variation is discussed elsewhere in this volume however isotopic exchange between the 16o rich solids and 17o and 18o rich gas phase s resulted in a wide range of isotopic variation in these early formed components offering insight into the conditions of these processes and the evolution of the reservoirs with time and or space once accreted onto the early planetisemals much of the primitive nebular components experienced considerable modification the metamorphism and melting experienced by some of these bodies most probably the result of heating from the decay of short lived radionuclides e g 26al resulted in progressive homogenization within individual bodies of any original isotopic heterogeneity complete homogenization appears to have been achieved in the hed parent body indicating very high levels of melting and the development of a large magma ocean the carbonaceous and ordinary chondrite parent bodies experienced more modest heating sufficient to mobilize water ice that accreted along with the more refractory materials the subsequent reactions between the liquid and solid phases at low temperature imparted large isotopic fractionations which record some of the conditions of this alteration such as water rock ratio temperature and isotopic signature and thus potentially the origin of the water ice the evolution of the asteroidal bodies has been far from simple and an important use of oxygen isotope measurements has been in the identifi cation of the components present in some meteorites the result of breakup reassembly and mixing of different bodies during impact processing the final oxygen isotopic signatures imparted into meteorite samples are those associated with terrestrial weathering the isotopic compositions of the weathering products depend on location primarily latitude while the magnitude of the weathering is dependent on many factors with some meteorites e g highly reduced enstatite chondrites and the matrix rich co3s particularly susceptible to such effects

influence of offshore topography on infragravity period oscillations in two rocks marina western australia abstract infragravity ig period oscillations in harbours and marinas can often lead to interruption in harbour operations due to excessive vessel movements field measurements in two rocks marina in south west australia have shown that ig period oscillations were always present and the amplitude of the oscillations was related to incident swell climate and was enhanced during storm events the marina is fronted by two shallow shore parallel reef systems located 3 2 and 4 7 km from the shoreline the area experiences continuous swell and frequent storm systems particularly during winter months this paper describes the application of a boussinesq wave model validated using field data to examine 1 source of the ig waves incident on the marina and 2 modal characteristics of the ig period oscillations inside the marina the cross shore evolution of the ig wave energy was examined using simulations with different contrasting incident wave conditions which included measured and idealised wave spectra the model results indicated that free ig waves were generated as the wind swell waves propagated over the offshore reef systems independent of the external forcing during stormy sea condition the ig energy over the primary and secondary reefs increased by a factor 10 and 8 respectively compared to the ig energy at offshore the ig wave spectrum near the marina entrance did not contain any major energy peaks and has an almost constant energy distribution across the ig wave frequencies however the frequencies similar to the marina s natural oscillation periods were excited within the marina the predicted energy distribution maps and water level snapshots inside the marina identified different oscillation modes which included mode 1 and mode 2 oscillations corresponding to a partially enclosed water body and zeroth mode corresponding to an open ended water body this study showed that in coastal regions characterised by complex offshore topography ig waves are generated independent of offshore wave conditions and harbours located in such environment are at risk of ig period oscillations depending on their geometry

site effects on large ground motions at kik net iwase station ibrh11 during the 2011 tohoku earthquake abstract large horizontal ground motions with peak ground accelerations pgas of more than 800 cm s 2 and peak ground velocities of nearly 60 cm s were observed at a kik net station iwase ibrh11 during the 2011 m w 9 0 tohoku japan earthquake we investigated site effects on the large ground motions by inverting the subsurface structure and simulating ground motions considering soil nonlinearity the structure from the seismic bedrock to the surface in the linear regime was inverted from 1 array records of microtremors using rayleigh wave inversion 2 surface to borehole spectral ratios of weak motions using s wave inversion based on the 1d wave propagation theory and 3 horizontal to vertical spectral ratios of weak motions using the inversion based on the diffuse field theory for plane waves the main cause of the large ground motions was found to be a strong impedance contrast between soft layers with an s wave velocity v s of less than 381 m s and a layer with v s 2371 m s at a depth of 30 m the strong motions at the surface during the 2011 tohoku earthquake simulated by equivalent linear analysis using borehole records at a depth of 103 m are in reasonable agreement with the observed records whereas those simulated using linear analysis were approximately twice as large as the observed values the results showed that the nonlinearity of the surface soils reduced the amplification factors and the pgas by half compared with the values for the linear regime the pgas of the bedrock motions with v s 2371 m s were estimated using equivalent linear analysis to have reached approximately 500 cm s 2

a stochastic method for investigating site effects by means of a borehole array sh and love waves abstract a stochastic method for investigating site effects by means of borehole array observation is proposed this method is based on a stochastic time series model that is derived from haskell9s matrix procedure for a layered medium and is applicable to transverse component recordings simultaneously obtained on the ground surface and at a depth the time series model not only accounts for the amplitude but also for the phase characteristics of the recordings by applying this method to actual downhole array recordings the following aspects of site effects can be investigated 1 an estimation of the wave transfer function for sh waves 2 the separation of upcoming and downgoing waves on a borehole seismogram at a depth that is an estimation of purely incident waves and 3 the enhancement of fundamental mode love waves on a surface seismogram are examined by applying this method to two borehole array recordings obtained at the fuchu observatory in japan a noteworthy point is that these aspects of site effects are examined using this method without any knowledge of the velocity structure beneath the site

a natural seismic isolating system the buried mangrove effects the belleplaine test site located in the island of guadeloupe french lesser antilles includes a three accelerometer vertical array designed for liquefac tion studies the seismic response of the soil column at the test site is computed using three methods the spectral ratio method using the vertical array data a numerical method using the geotechnical properties of the soil column and an operative fre quency domain decomposition fdd modal analysis method the belleplaine test site is characterized by a mangrove layer overlaid by a stiff sandy deposit this con figuration is widely found at the border coast of the caribbean region which is exposed to high seismic hazard we show that the buried mangrove layer plays the role of an isolation system equivalent to those usually employed in earthquake engineering aimed at reducing the seismic shear forces by reducing the internal stress within the structure in our case the flexibility of the mangrove layer reduces the distortion and the stress in the sandy upper layer and consequently reduces the potential of liquefaction of the site

analysis of borehole broadband recordings test site in the po basin northern italy we analyze the broadband recordings from a borehole station installed in the bedrock underneath the po basin northern italy and from a second station temporarily deployed on the surface at the same site to determine the surface sedimentary layer response and test the robustness of the different empirical techniques used to estimate local site effects we investigate the site amplification by evaluating the surface to downhole spectral ratios and the horizontal to vertical spectral ratios on both weak motion events and microtremors all the different empirical methods except the horizontal to vertical spectral ratios on weak motions reveal the main amplification peak at about 0 8 hz although the amplification factors are not always in agreement the 0 8 hz peak is the fundamental mode of the site due to the upper 130 m quaternary alluvium column v s 300 m sec we compare these experimental spectral functions with the theoretical 1d site response including and not including the borehole site response first we evaluate the theoretical transfer function at the surface then at depth and take the smoothed ratio the shallow velocity and attenuation structure at this site is assumed from previous studies we attempt to account for the effect of the reflected wave field in the borehole recordings in two different ways first we include the reflected wave field in the theoretical response function taking the theoretical transfer function9s ratio hst hbt and comparing it to the experimental earthquake ratios of horizontal components recorded at surface and at depth hs hb alternatively we multiply the hs hb earthquake ratio by the coherence and compare it to the surface response function this second approach does not provide a good fit to the amplitude of model response even if the shape of the ratio is in agreement with the theoretic response suggesting that multiplying by the coherence is not a good way to correct for the effect of reflected phases to further understand the goodness of our theoretical 1d model hst hbt theoretical evaluations we simulate the propagation through the shallower soil structure of the seismic waveforms recorded by the borehole sensor for a couple of events obtaining reasonably good agreement with the surface time histories both in phase and amplitude this test site and the results of this study are useful for understanding the influence of sedimentary layers on the ground shaking in the po basin the largest and most populated alluvial basin in italy

transient response of harbours to long waves under resonance conditions abstract this paper presents the results of a study aimed at quantifying the time response of harbour basins to long waves under resonance conditions on the basis of numerical simulations reproducing long waves in the yacht harbour of rome ostia italy it shows that the results valid for periodic forcing waves acting for an infinitely long time as those provided by models based on elliptic equations like the helmoltz and the mild slope equations can be misleading with respect to the more realistic ones that can be obtained using time varying wave equations taking advantage of the similarity between the processes studied here and a simple one dimensional resonator a method is also proposed to roughly estimate a time response parameter of each mode of the harbour using results from steady state numerical model results commonly applied for studying harbour resonance in engineering practice on the basis of further numerical simulations aimed at reproducing schematic harbour layouts the effect on resonance of the position of the entrance and of an outer harbour is studied the results indicate that the effects of design solutions to reduce resonance by placing the entrance at the middle of the harbour or using the outer harbour as a resonator can be correctly evaluated only when considering the time needed for the oscillations to fully develop

evaluation of methods for estimating linear site response amplifications in the los angeles region we have evaluated two methods of estimating linear site response amplifications and the standard index for classifying sites by comparing the results of each technique to observed ground motions at 33 sites in the los angeles region using velocity and density profiles from 33 boreholes we evaluated the use of the average 30 m shear wave velocity and associated site classifications the quarter wavelength method and the haskell propagator matrix method we correlated the average 30 m shear wave velocity and nehrp site classification at the borehole sites colocated within 290 m of a site with observed ground motion the observed data follow the expected trend of higher ground motion amplifications for lower average shear wave velocities but there is a significant degree of variability also there is a great deal of scatter in the observed amplifications within each national earthquake hazards reduction program nehrp class we used the velocity and density information in the database to calculate the average frequency dependent site response in the frequency ranges 1 3 hz 3 5 hz and 5 7 hz for a one dimensional flat layered structure using the haskell propagator matrix method and the quarter wavelength method there is a general correlation with the ground motion data however once again there is a great degree of scatter although slightly less for the quarter wavelength method we note that both the observed and predicted amplifications can change dramatically over a distance as small as 1 km or less even though all techniques considered give results that follow the expected trend of higher amplifications for softer sediments the predicted site response at any particular site with the current level of information may not be representative of the shaking that will actually occur during an earthquake the disparity between observed and predicted amplifications appears to be a result of oversimplification inherent in the amplificationestimation methods such as the use of average or assumed values for the site conditions in the absence of measured values the smoothing effect of using an average velocity limiting the properties considered to the uppermost 30 m of material and complexities in the wave propagation that are not addressed by these methods

the el asnam 1980 october 10 inland earthquake a new hypothesis of tsunami generation summary the western mediterranean sea is not considered as a high seismic region only several earthquakes with magnitude above five occur each year and only a handful have consequences on human beings and infrastructure the el asnam algeria earthquake of 1980 october 10 with an estimated magnitude ms 7 3 is one of the most destructive earthquakes recorded in northern africa and more largely in the western mediterranean basin although it is located inland it is known to have been followed by a small tsunami recorded on several tide gauges along the southeastern spanish coast in 1954 a similar earthquake having occurred at the same location induced a turbidity current associated to a submarine landslide which is widely known to have cut submarine phone cables far from the coast this event was followed by a small tsunami attributed to the landslide thus the origin of the tsunami of 1980 was promptly attributed to the same kind of submarine slide as no evidence of such mass movement was highlighted and because the tsunami wave periods does not match with a landslide origin in both cases 1954 and 1980 this study considers two rupture scenarios that the coseismic deformation itself of about 10 cm off the algerian coast near tenes is sufficient to produce a low amplitude several centimetres tsunami able to reach the spanish southeastern coast from alicante to algeciras gibraltar strait to the west after a discussion concerning the proposed rupture scenarios and their respective parameters numerical tsunami modelling is performed on a set of bathymetric grids then the results of wave propagation and amplification maximum wave height maps are discussed with a special attention to alicante spain harbour where the location of two historical tide gauges allows the comparison between synthetic mareograms and historical records showing sufficient signal amplitude this study is part of the active tsunami hazard assessment in mediterranean sea especially concerning its occidental part that is the algerian spanish and french coasts

inversion of strain dependent nonlinear characteristics of soils using weak and strong motions observed by borehole sites in japan during the 1995 hyogo ken nanbu earthquake strong motions with horizontal peak ground accelerations of 507 cm sec 2 or more 187 cm sec 2 and 126 cm sec 2 were observed at surface stations of borehole sites at amagasaki takasago and nanko in japan respectively we showed qualitative evidence of nonlinear soil response during strong motions at amgasaki and takasago but not at nanko using cross correlation and spectral ratio analyses of weak and strong motions we evaluated soil nonlinearity by inversion for s wave velocities and frequency dependent damping factors the strain dependence of shear modulus ratios inverted for gravel is larger than that for clay which is consistent with laboratory test results in the shear strain range from about 10 4 to 10 3 the strain dependence of shear modulus ratios inverted for clay and gravel at amagasaki and takasago is consistent with empirical relations based on laboratory test results for clay and gravel respectively these results support using laboratory estimates of shear modulus ratios to simulate strong motions at clay and gravel sites the damping factors for gravel inverted from the mainshock at amagasaki are the largest among the others but the strain dependence of damping factors are not as significant as that of shear modulus ratios the reason why the strain dependence of damping factors is not so significant may be because scattering attenuation is relatively dominated in the low strain range

strong ground motion in the 2011 tohoku earthquake a one directional three component modeling local wave amplification due to strong seismic motions in surficial multilayered soil is influenced by several parameters such as the wavefield polarization and the dynamic properties and impedance contrast between soil layers the present research aims at investigating seismic motion amplification in the 2011 tohoku earthquake through a one directional three component 1d 3c wave propagation model a 3d nonlinear constitutive relation for dry soils under cyclic loading is implemented in a quadratic line finite element model the soil rheology is modeled by mean of a multi surface cyclic plasticity model of the masing prandtl ishlinskii iwan mpii type its major advantage is that the rheology is characterized by few commonly measured parameters ground motions are computed at the surface of soil profiles in the tohoku area japan by propagating 3c signals recorded at rock outcrops during the 2011 tohoku earthquake computed surface ground motions are compared to the tohoku earthquake records at alluvial sites and the reliability of the 1d 3c model is corroborated the 1d 3c approach is compared with the combination of three separate one directional analyses of one motion component propagated independently 1d 1c approach the 3d loading path due to the 3c polarization leads to multiaxial stress interaction that reduces soil strength and increases nonlinear effects time histories and spectral amplitudes for the tohoku earthquake are numerically reproduced the 1d 3c approach allows the evaluation of various parameters of the 3c motion and 3d stress and strain evolution all over the soil profile

the combined role of bay and shelf modes in tsunami amplification along the coast 1 the role of free modes of oscillation of coastal areas in tsunami amplification at the coast is investigated here a finite element numerical model for modal analysis was applied and the numerically calculated natural frequencies were compared to those resulting from the spectra of measured sea level time series two case studies have been selected that of poverty bay new zealand and that of kuluk bay adak island alaska usa the natural modes of the sea areas that extend in front of these locations are shown to play an important role in tsunami amplification at both the considered bays in fact the enhancement of wave height is found to be related to both the small scale resonance controlled by the coastal shape and the large scale one governed by the continental shelf bathymetry in particular the model application to poverty bay reveals that some of the continental shelf modes are more energetic and occur at frequencies higher than the bay fundamental one these modes are identified as both cross shelf modes and trapped edge waves on the other hand the application to kuluk bay shows that geographical entrapment can be relevant for chain islands making the bay and the continental shelf modes almost coincident

dense array recordings in the san bernardino valley of landers big bear aftershocks basin surface waves moho reflections and three dimensional simulations abstract fourteen geos seismic recorders were deployed in the san bernardino valley to study the propagation of short period t 1 to 3 sec surface waves and moho reflections three dense arrays were used to determine the direction and speed of propagation of arrivals in the seismograms the seismograms for a shallow d 1 km m 4 9 aftershock of the big bear earthquake exhibit a very long duration 60 sec of sustained shaking at periods of about 2 sec array analysis indicates that these late arrivals are dominated by surface waves traveling in various directions across the valley some energy is arriving from a direction 180 from the epicenter and was apparently reflected from the edge of the valley opposite the source a close in aftershock 25 km depth 7 km displays substantial short period surface waves at deep soil sites a three dimensional 3d finite difference simulation produces synthetic seismograms with durations similar to those of the observed records for this event indicating the importance of s wave to surface wave conversion near the edge of the basin flat layered models severely underpredict the duration and spectral amplification of this deep soil site i show an example where the coda wave amplitude ratio at 1 to 2 hz between a deep soil and a rock site does not equal the s wave amplitude ratio because of the presence of surface waves in the coda of the deep soil site for one of the events studied 90 km there are sizable phases that are critically reflected from the moho pmp and sms at one of the rock sites the sms phase has a more peaked spectrum that the direct s wave

a systematic method for analyzing borehole recordings to estimate the wavefield in the lakebed zone of mexico city during the 1985 michoacan earthquake m s 8 1 large amplitude seismograms with extremely long duration hundreds of seconds were recorded in the lakebed zone of mexico city in spite of numerous studies the lakebed seismograms are not well understood in the present study we develop a systematic method for analyzing borehole recordings and apply it to recordings at depths of 0 and 102 m at the roma station to interpret the wavefield in the lakebed zone the target frequency period range is between 0 2 and 3 3 hz 0 3 and 5 0 sec we cross correlate the surface and borehole strong motion seismograms and identify body and surface wave portions in the main motions then we interpret the surface waves as fundamental mode love waves by calculating theoretical amplitude ratios for different scale structures using a statistical time series model with an information criterion we separate s and love wave portions from the surface recordings love waves are dominant and are recognized even in the early time section finally we attempt to explain s wave transfer functions between the surface and borehole recordings by considering subsidence of soft surficial deposits for several years on the basis of a three dimensional finite element technique this simulation demonstrates effects of the subsidence on amplification of s waves

simultaneous study of the source path and site effects on strong ground motion during the 1989 loma prieta earthquake a preliminary result on pervasive nonlinear site effects we considered the effects of source propagation path and local site conditions on strong ground motion from the loma prieta earthquake in the following steps first the local site effect was removed from the strong motion records applying the weak motion amplification factors estimated from nearby stations of usgs regional network using the coda method then we confirmed the approximate validity of the 1 r law of geometrical spreading factor for the crustal model applicable to the region and we determined the attenuation parameter q f and source spectrum s f empirically from the site effect corrected spectral amplitude both q f and s f are consistent with the results obtained earlier for major california earthquakes we then synthesized the time history of ground acceleration by applying the stochastic simulation technique the agreement between the observed and predicted records was good for duration and spectral content we found however a strong systematic discrepancy with regard to peak acceleration namely for distances less than 50 km the predicted peak acceleration consistently overestimated the observed for sediment sites and underestimated it for the franciscan formation sites since the above systematic discrepancy applies to all the available stations within about 50 km from the hypocenter it is unlikely that the effect is due to the radiation pattern near source structure or topography it appears that the strong difference in the amplification factor between the franciscan and the sediment sites observed for weak motion disappears at acceleration levels higher than about 0 1 to 0 3 g if this is due to the nonlinear response of the sediment sites it is in the range expected from geotechnical engineering studies

inversion of borehole weak motion records observed in istanbul turkey summary the estimation of shear wave velocity and attenuation in near surface geology is of primary importance in engineering seismology in fact such knowledge is essential for site response studies when preparing improved seismic hazard scenarios in this study we propose a linear inversion of the spectra of a deconvolved wavefield collected by a borehole array in istanbul turkey the spectra are calculated using as a reference the recordings collected by a sensor at the surface this allows us to minimize the effect of the deconvolution filter on the peaks amplitudes the feasibility of the proposed inversion scheme and the parametrization of the velocity and attenuation models were tested and assessed using synthetic data the real data inversion is carried out using observation from three weak motion events several starting models are used for each event changing the values of the quality factor qs whereas the starting vs profiles are fixed to what was obtained by the analysis of the deconvolved wavefield in the time domain our results showed that fairly well constrained vs models can be obtained while the variability of the qs profile both between different inversions of the same data set and between the inversions of different data sets might be large this indicates that qs variations observed in models derived by strong motion data inversions should be considered with care however the high agreement of the estimated soil profiles in the uppermost layer both when using different events and different starting models suggests that any variation in the s wave velocity that might be estimated when using strong motion data should be reliable

h l chondrite lapaz icefield 031047 a feather of icarus abstract antarctic meteorite lap 031047 is an ordinary chondrite composed of loosely consolidated chondritic fragments its petrography oxygen isotopic composition and geochemical inventory are ambiguous and indicate an intermediate character between h and l chondrites petrographic indicators suggest lap 031047 suffered a shock metamorphic overprint below 10 gpa which did not destroy its unusually high porosity of 27 vol metallographic textures in lap 031047 indicate heating above 700 c and subsequent cooling which caused massive transformation of taenite to kamacite the depletion of thermally labile trace elements the crystallization of chondritic glass to microcrystalline plagioclase of unusual composition and the occurrence of coarsely crystallized chondrule fragments is further evidence for post metamorphic heating to 700 750 c however this heating event had a transient character because olivine and low ca pyroxene did not equilibrate nearly complete degassing up to very high temperatures is indicated by the thorough resetting of lap 031047 s ar ar reservoir 100 55 ma ago a noble gas cosmic ray exposure age indicates it was reduced to a meter size fragment at

a study on the response of a soft basin for incident s p and rayleigh waves with special reference to the long duration observed in mexico city abstract the responses of two types of soft basins for incident sh sv p and rayleigh waves in a 2 d elastic half space are investigated with special reference to the long duration of strong motions observed in mexico city during the michoacan mexico earthquake of 1985 first the difficulty for simple 1 d models to reproduce the later part of the accelerogram observed in mexico city is shown then the effect of a 2 d deep basin structure of a relatively large scale 10 km wide and 1 km deep and a moderate impedance ratio 2 5 is studied the results show that surface waves generated at the edges of the basin are clearly propagating inside the basin back and forth however the increase in duration by these surface waves is 20 sec at most introducing another much softer layer inside the basin we found that the calculated durations and envelop shapes become very similar to the observed ones because of the slowness of surface wave propagation these theoretical studies suggest that the exceptionally long duration observed in mexico city might be caused by a strong constructive interaction of soft surface layers with a deep basin structure beneath the city

site amplification and attenuation of strong ground motion abstract at the mcgee creek california site three component strong motion accelerometers are located at depths of 166 m 35 m and 0 m the surface material is glacial moraine to a depth of 30 5 m overlying hornfels accelerations were recorded from two california earthquakes round valley m l 5 8 23 november 1984 18 08 utc and chalfant valley m l 6 4 21 july 1986 14 42 utc anti plane shear strains for the round valley and chalfant valley events are less than 1 8 10 5 and 1 2 10 5 respectively by separating out the sh components of acceleration we were able to determine the orientations of the downhole instruments peak sh accelerations at the surface were 5 7 times greater than those at 166 m in both earthquakes a constant phase velocity haskell thomson model was applied to generate synthetic sh seismograms at the surface using the accelerations recorded at 166 m in the frequency band 0 10 to 10 0 hz we compared the filtered synthetic records to the filtered surface data the onset of the sh pulse and the reflections from the interface at 30 5 m are clearly seen in both the synthetics and the recorded data the synthetic records closely match the data in both amplitude and phase the fit between the synthetic accelerograms and the data indicates that the seismic amplification at the surface is a result of the resonance of the surface layers and the contrast of the impedances shear stiffness of the near surface materials the impedance contrast of the materials does not account for all of the amplification of the peak accelerations at the surface the resonances of the layer system below 10 hz contribute the most to this amplification we find that a linear model predicts the soil response for frequencies up to 10 hz material damping is added to the soil layers of the model in the form of a quality factor q the damping moderates the strong resonance effects by allowing energy to radiate into the half space the quality factor q 10 is constant in this frequency range but does not accurately model the attenuation at frequencies above 10 hz

nonlinear soil behavior at the kashiwazaki kariwa nuclear power plant during the niigata chuetsu oki earthquake july 16 2007 records of the niigata chuetsu oki earthquake july 16 2007 mw 6 6 depth 17 km and its aftershocks from seismic vertical arrays deployed at the territory of the kashiwazaki kariwa nuclear power plant 15 km from the fault are used to study the soil behavior down to 250 m during strong ground motion nonlinear models of soil behavior during the main shock and six aftershocks are constructed and stresses and strains induced by the strong motion in the soil layers at various depths are estimated the data are processed using the method developed by pavlenko and irikura bull seismol soc am 96 6 2131 2145 2003 and previously applied for studying the soil behavior in near fault zones during the 1995 kobe and 2000 tottori earthquakes a rather good agreement between the recorded and simulated acceleration time histories testifies to the validity of the obtained vertical distributions of stresses and strains in soil layers in the upper softer layers 45 m at the territory of the plant the shear moduli were reduced by 30 35 during the main shock and by 1 5 3 during the aftershocks the constructed models of soil behavior can be used in scenario earthquake shaking maps of japan where based on source modeling parameters the level of strong motion can be evaluated for the territory of the power plant in future earthquakes with various magnitudes and fault planes using methods of stochastic finite fault modeling of ground motions from the chuetsu oki earthquake we estimated input motion to the soil layers during the main shock and found that it differs from the imposed motion recorded by the deepest sensor of the vertical array by slightly decreased by a factor of 1 2 low frequency f 10 hz spectral components

vulnerability of the dover strait to coseismic tsunami hazards insights from numerical modelling summary on 1580 april 6 a large earthquake shook the eastern english channel and its shores with numerous casualties and significant destruction documented some reports suggest that it was followed by a tsunami meanwhile earthquake magnitudes of mw 7 have been deemed possible on intraplate fault systems in neighbouring benelux this study aims to determine the possibilityofamw 5 5magnitudeearthquakegeneratingatsunamiinthedoverstrait oneof the world s busiest seaways in a series of numerical models focusing on sensitivity analysis earthquake source parameters for the dover strait are constrained by palaeoseismological evidence and historical accounts producing maps of wave heights and analysis of frequencies based on six strategically located virtual tide gauges of potential concern to engineering geologists a maximum credible scenario is also tested for mw 6 9 for earthquakes with mw of 5 5 none of the fault models we tested produced a tsunami on neighbouring shores however forearthquakeswithmw 6 9 bothextensionalandthrustingeventsproducedtsunami waves with open water amplitudes of up to 1 5 m and higher amplitudes might be expected in regions where waves are amplified by regional nearshore bathymetry sensitivity to parameter choice is emphasized but a pattern of densely inhabited coastal hotspots liable to tsunamirelated damage because of bathymetric forcing factors is consistently obtained

assessment of seismic site conditions a case study from guwahati city northeast india the 1897 great shillong earthquake revealed considerable seismic susceptibility in guwahati city such as soil liquefaction landslides and surface fissures in an attempt to quantify the seismic vulnerability of the city based on geological seismological and geotechnical aspects concerning seismic site characterization in depth analysis was performed using a microtremor survey with recordings of five small to moderate magnitude 4 8 mb 5 4 earthquakes that occurred in 2006 and geotechnical investigations using the standard penetration test spt additionally the basement topography was established using vertical electrical resistivity sounding and selected drill hole information region specific relationships are derived by correlating the estimated values of predominant frequency shear wave velocity and basement depth indicating conformity with the predominant frequency distribution and the basin topography underlain by a hard granitic basement most parts of the city adhere to the predominant frequency range of 0 5 3 5 hz setting aside areas of deep sediment fills or hilly tracts suggesting that the existing moderate rise rc buildings in the territory are seismically vulnerable furthermore the geotechnical assessment of the soil liquefaction potential reveals widespread susceptibility across the terrain eventually a site classification map of the city is prepared following the national earthquake hazard program nehrp provision the average site amplification factor from geotechnical modeling for site class d is about 3 in the frequency range of 2 4 hz in addition earthquake data yield an average site amplification factor of 4 6 in the frequency range of 1 2 5 0 hz at the seismic stations located in site class e and f high site amplifications of around 5 5 and 7 5 at 2 hz respectively are observed at amtron and irrig seismic stations which are located in the proximity of precambrian rocks indicating probable basin edge effects scattering and diffraction of incident energy interplay of dispersed valleys surrounded by small hillocks in the study region is likely to induce micro basin effects where the sediment thickness depth vis a vis predominant frequency and basin geometry in conjunction play pivotal roles in the augmentation of site response

3d analysis of s wave propagation in soft deposits during the 1985 michoacan earthquake surface wave magnitude 8 1 large amplitude seismograms of extremely long duration were recorded in the lake bed zone of mexico city large amplification in soft surficial deposits has not been well understood ground subsidence of the soft clay deposits might heavily influence s wave propagation in the present study we attempt to explain both s wave amplification and propagation time between surface and borehole recordings under the action of gravity on the basis of a 3d nonlinear finite element fe technique where a bilinear model with a mohr coulomb criterion is used we identify body wave s wave time sections in the recordings with a cross correlation analysis the fe simulation successfully predicts the s wave amplification and propagation time which cannot be explained by a purely 1d linear model although subsidence changes s wave linear amplification s wave propagation time decreases little

the dependency of inshore long waves on the characteristics of offshore short waves abstract this paper pursues the feasibility of establishing workable site specific relationships between concurrent inshore long wave characteristics and offshore short wave characteristics such relationships would have immediate relevance to the design of wave climate date collection systems for proposed ship mooring facilities a strong dependency was shown to exist between inshore long wave height and the height and frequency of the offshore short waves but no similar dependency was found for long wave frequency the possibility of a dependency between inshore long wave frequency and the group frequency of the offshore short waves was also pursued this proved inconclusive because wave group frequencies in a quasi stationary sea state were shown to be an extremely variable quantity such that the wave records to which the authors had access were too short to provide stable statistical descriptions of the characteristic group frequencies this leads to recommendations regarding the required minimum lengths of wave records when seeking data on wave group frequencies

attenuation and velocity structure for site response analyses via downhole seismogram inversion a seismic waveform inversion algorithm is proposed for the estimation of elastic soil properties using low amplitude downhole array recordings based on a global optimization scheme in the wavelet domain complemented by a local least square s fit operator in the frequency domain the hybrid scheme can efficiently identify the optimal solution vicinity in the stochastic search space whereas the best fit model detection is substantially accelerated through the local deterministic inversion results presented for selected aftershocks of the mw 7 0 sanriku minami earthquake in japan recorded by the kik net strong motion network illustrate robustness of the impedance structure estimation by contrast the attenuation structure is shown to be sensitive to the frequency content of seismic input data attributed to the deterministic description of the continuum in the forward model that cannot simulate late arrivals of multiple scattered energy sensitivity analyses illustrate that for the same forward model results can be substantially different based on the definition of the objective function it is concluded that even for engineering purposes inversion should aim to decouple intrinsic and scattering attenuation mechanisms

modeling three dimensional site response effects in the marina district basin san francisco california abstract loma prieta aftershock data recorded in the marina district of san francisco clearly show a large amplification in ground motion and a much longer duration of shaking relative to the response recorded at nearby rock sites for frequencies between 1 and 10 hz some of the amplification can be explained by the difference in impedance between the marina sites and the rock sites however 1d models underpredict the amplification in the range 1 to 3 hz and cannot account for the increased durations the available geologic information within the marina district indicates lateral variations in sediment thickness and composition our previous experience with modeling wave propagation in these types of basin environments has shown that these structures can greatly amplify and prolong the duration of the signals observed at sites within the basin in this study the seismic response of the marina basin is modeled with a 3d finite difference wave field simulation technique results from the numerical simulations at the basin sites indicate that the large amplitude arrivals following the direct s wave are surface waves traveling at relatively slow apparent velocities in general the surface waves contain the strongest recorded motions and produce the long duration of shaking observed at these sites in addition spectral ground motions from the 3d basin models do fairly well in reproducing the observed spectral amplification near 1 hz that is characteristic of the basin sites the simulation results suggest that focusing effects due to the geometry of the basin structure itself have a significant impact in determining the resonant periods at these basin sites

long waves induced by short wave groups over an uneven bottom unidirectional and periodically modulated short waves on a horizontal or very nearly horizontal bottom are known to be accompanied by long waves which propagate together with the envelope of the short waves at their group velocity however for variable depth with a horizontal lengthscale which is not too great compared with the group length long waves of another kind are further induced if the variation of depth is only one dimensional and localized in a finite region then the additional long waves can radiate away from this region in directions which differ from those of the short waves and their envelopes there are also critical depths which define caustics for these new long waves but not for the short waves thus while obliquely incident short waves can pass over a topography these second order long waves may be trapped on a ridge or away from a canyon

the ar ar age and petrology of miller range 05029 evidence for a large impact in the very early solar system abstract miller range mil 05029 is a slowly cooled melt rock with metal sulfide depletion and an ar ar age of 4517 11 ma oxygen isotopes and mineral composition indicate that it is an l chondrite impact melt and a well equilibrated igneous rock texture with a lack of clasts favors a melt pool over a melt dike as its probable depositional setting a metallographic cooling rate of approximately 14 c ma 1 indicates that the impact occurred at least approximately 20 ma before the ar ar closure age of 4517 ma possibly even shortly after accretion of its parent body a metal grain with a widmanstatten like pattern further substantiates slow cooling the formation age of mil 05029 is at least as old as the ar ar age of unshocked l and h chondrites indicating that endogenous metamorphism on the parent asteroid was still ongoing at the time of impact its metallographic cooling rate of approximately 14 c ma 1 is similar to that typical for l6 chondrites suggesting a collisional event on the l chondrite asteroid that produced impact melt at a minimum depth of 5 12 km the inferred minimum crater diameter of 25 60 km may have shattered the 100 200 km diameter l chondrite asteroid therefore mil 05029 could record the timing and petrogenetic setting for the observed lack of correlation of cooling rates with metamorphic grades in many l chondrites

nonlinear site models derived from 1d analyses for ground motion prediction equations using site class as the site parameter nonlinear site models are an important part of ground motion prediction equations gmpes and can be constructed in a number of ways if numerous soil site strong motion records contain the effect of strong nonlinear soil response the parameters for the nonlinear model can be a part of the regression parameters for gmpes it is also possible to derive nonlinear site models by numerical simulation however the number of strong motion records from japan that contain the effect of strong nonlinear soil response is still too small to derive nonlinear site terms we present a model of nonlinear site terms using site class as the site parameter in gmpes based on a 1d equivalent linear model the 1d model was constructed based on the shear wave velocity profiles from the kik net strong motion stations with a wide range of site periods soil depth and impedance ratios the rock site strong motion records were from different earthquake categories in japan and the pacific earthquake engineering research center dataset those records had a wide range of earthquake magnitudes source distances and peak ground accelerations a random effects regression model was fitted to the calculated spectral amplification ratios accounting for the effect of site impedance ratios earthquake magnitudes and source distances of the rock site records we also designed a method to adjust the 1d model so it can be used in a gmpe accounting for the fact that a 1d model is an overly simplistic assumption for many real strong motion recording stations in many parts of the world online material tables of nonlinear site model parameters

a nearshore long term infragravity wave analysis for open harbours abstract this study presents a comprehensive methodology for the reanalysis characterization and propagation of wave bound infragravity waves 1 300 hz to 1 30 hz in the nearshore a deep water short wave reanalysis has been modified analytically to include the energy input associated with infragravity waves full spectrum through the decomposition and energy balance of the radiation stress of waves in deep water a hybrid clustering numerical wave propagation downscaling technique was used forced by the modified full wave spectra previously obtained resulting in hourly series of high spatial resolution nearshore ocean waves including short and bound long waves the methodology has been applied to the northern coast of spain and validated by comparing buoy and pressure gauge records in the coast for short wave agitation and infragravity wave resonance responses in open harbours with very satisfactory results

explaining extreme ground motion in osaka basin during the 2011 tohoku earthquake despite being 770 km away from the epicenter observed ground motions due to the tohoku earthquake in the osaka basin were unexpectedly large with an amplification of more than a factor of 20 compared to immediately outside the basin and including 2 7 m peak to peak roof displacements at one high rise building the local ground motions exceeded expectations based on standard computations of site response by a factor of 3 predicted frequencies of peak acceleration were off by at least 50 and such discrepancies have not yet been explained quantitatively here we show that utilizing semianalytic theory for surface wave amplification we are able to accurately predict both the amplitudes and frequencies of large ground amplification in the osaka basin using only knowledge of the local one dimensional structure comparison between this simple prediction and observed amplification was not expected to be so favorable and suggests that simple one dimensional surface wave site amplification factors can be useful in the absence of full three dimensional wave propagation simulations such surface wave amplification factors can be included in addition to the standard measures of site specific site amplification and should help explain strong ground motion variability in future large earthquakes that shake osaka basin and elsewhere in the world

estimation of s wave velocity structures in and around the sendai basin japan using array records of microtremors we conducted array measurements of microtremors at six sites in and around the sendai basin to estimate deep s wave velocity structures above the seismological bedrock pre tertiary bedrock after estimating phase velocities of microtremors in the frequency range from about 0 5 to 3 hz we succeeded to estimate the deep structures above the pre tertiary bedrock at four soil sites kata okin arah and myg15 and only the upper part just beneath the pliocene layer at the other soil site trma using a rayleigh wave inversion technique at trma and a rock site tama we roughly estimate the deep s wave velocity structures using empirical site amplification factors derived from strong motion records the deepest bedrock depth is 1 km and the shallowest depth is 200 m among these six sites the difference of the bedrock depth between the eastern side and the western side of an active thrust fault the nagamachi rifu line is only 120 m the difference of the bedrock depth between two sites in the east of the basin reaches about 500 m although any geological boundaries or buried faults have not been mapped since the deep s wave velocity structure of the sendai basin had been basically unknown we delineate it for the first time in this article using array measurement of microtremors

an experiment in systematic study of global seismicity centroid moment tensor solutions for 201 moderate and large earthquakes of 1981 data from the global digital seismograph network were used to obtain centroid moment tensor solutions using the method of dziewonski et al 1981 results were obtained for 201 earthquakes ranging in seismic moment from 7 1023 to 3 1027 dyne cm the wide dynamic range of the sro asro stations allows us to investigate using the same algorithm series of events among which the smallest and the largest may differ in moment by a factor as large as 1000 among the events studied is a particularly interesting series in january 1981 off the island of honshu the main shock was preceded by three foreshocks and followed by four aftershocks all falling within the range of our analysis there is an indication that the source mechanism changes with the size of the event statistical analysis of the results for all earthquakes reveals that the half duration of shallow and intermediate events is approximated by 1 6 10 8 m01 3 the shifts in origin time for deep focus earthquakes are indicative of the general complexity of these events which depends only weakly on the seismic moment the extreme departures from a double couple mechanism seem to depend both on the moment and on the focal depth while for shallow earthquakes these departures decrease from a maximum at about 1025 dyne cm with increasing moment the reverse appears to be true with respect to deep focus earthquakes shallow earthquakes north of new guinea and along the solomon islands show systematic and substantial departures from the double couple mechanism

constraints on the role of impact heating and melting in asteroids received 1996 august 30 accepted in revised form 1997 january 30 abstract imaging of asteroids gaspra and ida and laboratory studies of asteroidal meteorites show that im pacts undoubtedly played an important role in the histories of asteroids and resulted in shock metamorphism and the formation of breccias and melt rocks however in recent years impact has also been called upon by numerous authors as the heat source for some of the major geological processes that took place on asteroids such as global thermal metamorphism of chondrite parent bodies and a variety of melting and igneous events the latter were proposed to explain the origin of ureilites aubrites mesosiderites the eagle station pallasites acapulcoites lodranites and the iab iiicd and iie irons we considered fundamental observations from terrestrial impact craters combined with results from laboratory shock experiments and theoretical consider ations to evaluate the efficiency of impact heating and melting of asteroids studies of terrestrial impact craters and relevant shock experiments suggest that impact heating of aster oids will produce two types of impact melts 1 large scale whole rock melts total melts not partial melts at high shock pressure and 2 localized melts formed at the scale of the mineral constituents mineral specific or grain boundary melting at intermediate shock pressures the localized melts form minuscule amounts of melt that quench and solidify in sifu thus preventing them from pooling into larger melt bodies partial melting as defined in petrology has not been observed in natural and experimental shock metamor phism and is thermodynamically impossible in a shock wave induced transient compression of rocks the total impact melts produced represent a minuscule portion of the displaced rock volume of the parent crater internal differentiation by fractional crystallization is absent in impact melt sheets of craters of sizes that can be tolerated by asteroids and impact melt rocks are usually clast laden thermal metamorphism of country rocks by impact is extremely minor experimental and theoretical considerations suggest that 1 single dis ruptive impacts cannot raise the average global temperature of strength or gravity dominated asteroids by more than a few degrees 2 cumulative global heating of asteroids by multiple impacts is ineffective for asteroids less than a few hundred kilometers in diameter 3 small crater size low gravity and low impact velocity suggest that impact melt volume in single asteroidal impacts is a very small 0 014 1 fraction of the total displaced crater volume 4 total impact melt volume formed during the typical lifetime of an asteroid is a small fraction 0 001 of the volume of impact generated debris and 5 much of the impact melt generated on asteroidal targets is ejected from craters with velocities greater than escape velocity and thus not retained on the asteroid the inescapable conclusion from these observations and calculations is that impacts cannot have been the heat source for the origin of the meteorite types listed above and we must turn to processes other than impact such as decay of short lived radionuclides or electromagnetic induction during an early t tauri phase of the sun to explain heating and melting of the parent bodies of these meteorites

a modal decomposition method for the analysis of long waves amplification at coastal areas abstract this paper presents a model for the evaluation of long waves amplification at coastal areas based on a modal decomposition method it is able of modelling the growth and the decay of the natural modes of the area under investigation and their contribution to the total wave field the model is an improvement of that developed by bellotti et al 2012b that was able of calculating the frequencies and the shapes of the natural modes but not their amplification under the action of forcing waves three test cases are used for the validation and to show the capabilities of the model the first considers the long waves resonance into a long and narrow harbour bay over a constant water depth it is a case for which a high degree of wave trapping into the semi enclosed coastal area is induced by the specific shape of the coastline the second test deals with the propagation of a group of edge waves along a straight coast with a constant sloping bottom generated in proximity of the shoreline by a special wave maker the model in this case properly evaluates what are the edge waves modes that contribute to the total wave field the third case involves the interaction of a solitary wave with a conical island for which laboratory data are available in this test a low degree of trapping exists but it is interesting for the present aims as the propagation of the waves around the island is expected to occur under the form of wave modes partially trapped by the bathymetry i e edge waves excited by the transient wave arriving from offshore on the basis of the tests results it is shown what is the role of the more relevant natural modes in the formation of the total surface elevation

statistical spectral model of earthquakes in the eastern tohoku district japan based on the surface and borehole records observed in sendai strong motions of 18 earthquakes 3 4 mj 7 1 mj jma magnitude in the eastern tohoku district japan have been observed at 12 borehole sites within a 20 20 km region in sendai in our previous study we defined a pliocene layer whose s wave velocity vs is greater than 500 m sec and whose n value of the standard penetration test is greater than 50 as engineering bedrock in sendai and calculated 304 engineering bedrock waves hypocentral distance x 15 to 300 km by removing the site response between the engineering bedrock and the surface as the second stage of our study toward a quantitative prediction of strong ground motions of horizontal components we propose here a statistical spectral model of the engineering bedrock waves by introducing the site response between the pre tertiary bedrock vs 3000 m sec and the engineering bedrock vs 500 to 700 m sec and a frequency dependent q into boore s spectral model we separate the site response between the pre tertiary bedrock and the engineering bedrock an attenuation function and source spectra from the engineering bedrock spectra by assuming an 2 model with the seismic moment m from the harvard cmt solution estimated for earthquakes of mj 5 3 initial values of corner frequency f are determined based on a previous empirical m f relationship in this district using six moderate sized earthquakes 5 3 mj 6 0 we first estimate frequency dependent q to be q 110 f 0 69 f frequency by minimizing the standard deviation of the site response which is defined as the ratio of observed engineering bedrock spectra with respect to the estimated attenuation and the assumed source spectra the averaged site response is simultaneously estimated to be 1 at 0 1 hz 5 at 1 hz and 3 at 20 hz we then invert f and cutoff frequencies f max for all 18 earthquakes and m for seven small sized earthquakes of mj 5 3 by minimizing the difference between the model and observed spectra the average brune stress drop obtained from an m f relationship estimated from 17 earthquakes except for the smallest earthquake with m less than 1021 dyne cm is 200 bars the estimated m f relationship is identical to the one used to calculate initial values of f so that we do not need to perform the inversion iteratively the obtained stress drop for subduction zone earthquakes in the eastern tohoku district is consistent with other previous studies the dependence of the inverted f max on m is not significant and the logarithmic average of f max is found to be 13 5 hz by using these controlling parameters and the m f relationship obtained from a regression analysis acceleration spectra on the engineering bedrock in sendai can be predicted statistically from x and m or mj by considering standard deviations of the site response f and f max