wave field estimated by borehole recordings in the reclaimed zone of tokyo bay we estimate the wave field in the reclaimed zone of tokyo bay by analyzing the three components of surface and downhole strong motion accelerograms recorded at two borehole stations during five medium earthquakes the target period range is between 0 1 and 2 0 sec first wave types of observed seismic motions are identified by calculating theoretical amplification of body waves and surface waves and cross correlation functions between the surface and downhole recordings then the horizontal components of the surface and downhole recordings are separated into s wave and surface wave accelerograms finally 2d wave propagation simulations for basin structures are performed to interpret the recordings the conclusions are as follows 1 main seismic motions are composed of not only s waves but also love waves surface waves are found to be more dominant than s waves in the period range of more than 1 0 sec 2 love waves are more heavily amplified than s waves at the theoretical predominant periods of ground in the soft surficial deposits 3 the large surface wave amplification is excited by the surficial deposits together with a deep basin 4 in the surficial deposits quality factors are found to be about 10 around the theoretical predominant periods of ground 5 the wave propagation simulations suggest strong heterogeneities near the ground surface and can explain observed seismic motions qualitatively

the current state of knowledge about shatter cones introduction to the special issue shatter cones are a fracture phenomenon that is exclusively associated with shock metamorphism and has also been produced in the laboratory in several shock experiments the occurrence of shatter cones is the only accepted meso to macroscopic recognition criterion for impact structures shatter cones exhibit a number of geometric characteristics orientation apical angles striation angles sizes that can be best described as varied from case to case possible links between geometric properties with impact or crater parameters have remained controversial and the lack of understanding of the mechanism of formation of shatter cones does not offer a physical framework to discuss or understand them a database of shatter cone occurrences has been produced for this introduction paper to the special issue of meteoritics and planetary science on shatter cones distribution of shatter cones with respect to crater size and lithology suggests that shatter cones do not occur in impact craters less than a few kilometers in diameter with a few currently questionable exceptions all pertinent hypotheses of formation are presented and discussed several may be discarded in light of the most recent observations the branching fracture mechanism and the interference models proposed respectively by sagy et al 2002 and baratoux and melosh 2003 require further evaluation new observations experiments or theoretical considerations presented in this special issue promise an important step forward based on a renewed effort to resolve the enigmatic origin of these important features

stacked pile solution for axial load settlement analysis of driven piles in multi layered soils the load settlement q s response of deep foundations is influenced by the soil stiffness one of the most common methods of installing these foundations is the process of driving which changes t

surface wave dispersion analysis in mexico city abstract in this article we present an observational investigation of ground motion at mexico city focused on surface waves our purpose is 2 fold first to understand incident ground motion during the great michoacan earthquake of 19 september 1985 and second to characterize surface waves propagating in the lake bed zone to this end we analyze the strong motion records obtained at mexico city for the large m s 8 1 earthquake of 19 september 1985 it is shown that in the low frequency range we observe the rayleigh fundamental mode in both the vertical and the radial components and the love fundamental mode in the transverse component at all the strong motion stations the vertical component also shows the first higher mode of rayleigh waves we use a very broadband record obtained at station cu for the smaller m s 6 7 earthquake of 14 may 1993 to verify that the dispersion computed from the model of campillo et al 1989 represents well the average surface wave propagation between the coast and mexico city in the 7 to 10 sec period range we use this result to assign absolute times to the strong motion records of the michoacan event this allowed us to identify additional wave trains that propagate laterally in directions other than great circle in the 3 to 5 sec period range these wave trains are identified as love waves in a second analysis we study a set of refraction data obtained during a small scale 250 m experiment on the virgin clay of the lake bed zone phase velocity dispersion curves for several modes of rayleigh waves are identified in the refraction data and inverted to obtain an s wave velocity profile this profile is used as the uppermost layering in a 2d model of mexico city valley the results of numerical simulation show that surface waves generated by lateral finiteness of the clay layer suffer large dispersion and attenuation we conclude that surface waves generated by the lateral heterogeneity of the upper most stratigraphy very significantly affect ground motion near the edge of the valley but their importance is negligible for distances larger than 1 5 km from the edge thus locally generated surface waves propagating through the clay layer cannot explain late arrivals observed for the 1985 event we suggest that the long duration of strong motion is due to the interaction between lateral propagation of waves guided by deep layers 1 to 4 km and the surficial clay layer this interaction is possible by the coincidence of the dominant frequency of the uppermost layers and the frequency of the deeply guided waves

frequency dependent attenuation of shear waves in the crust of the southern kanto area japan the attenuation characteristics of shear waves in the crust of the southern kanto area central japan were estimated using strong motion data including acceleration data recorded in the pre tertiary basement rocks by means of downhole observation the quality factor qs f was determined for a range of discrete frequencies from 0 5 to 16 hz from the analysis of data from 13 local earthquakes with focal depths of less than about 50 km that occurred in the philippine sea plate and in the boundary zone between the lower part of the eurasian plate and the upper part of the philippine sea plate the estimated 1 qs f shows a peaked structure in this frequency range on the assumption that the geometrical spreading exponent is 1 body waves the estimated peak 1 qs f is of the order of 10 2 at 0 8 hz

excitation of high frequency surface waves with long duration in the valley of mexico during the 1985 michoacan earthquake ms 8 1 large amplitude seismograms with extremely long duration were recorded in the lake bed zone of mexico city we interpret high frequency seismic wave fields in the three geotechnical zones the hill the transition and the lake bed zones in the valley of mexico on the basis of a systematic analysis for borehole strong motion recordings we make identification of wave types for real seismograms first amplitude ratios between surface and underground seismograms indicate that predominant periods of the surface seismograms are largely controlled by the wave field incident into surficial layers in the valley of mexico we interpret recorded surface waves as fundamental mode love waves excited in the mexican volcanic belt by calculating theoretical amplification for different scale structures second according to a cross correlation analysis the hill and transition seismograms are mostly surface waves in the lake bed zone while early portions are noisy body waves late portions are mostly surface waves third using two kinds of surface arrays with different station intervals we investigate high frequency surface wave propagation in the lake bed zone the wave propagation is very complicated depending upon the time section and the frequency band finally on the basis of a statistical time series model with an information criterion we separate s and surface wave portions from lake bed seismograms surface waves are dominant and are recognized even in the early time section thus high frequency surface waves with long duration in the valley of mexico are excited by the mexican volcanic belt

shatter cones and shocked rocks in southwestern montana the beaverhead impact structure shatter cones that point steeply upward are present in abundance over an area 100 km sup 2 in belt supergroup sandstone outcrops in beaverhead county southwestern montana crushed sandstone with fragments dispersed in a fluidal textured cryptocrystalline matrix of similar chemical composition has also been found absence of cones in adjacent units of mississippian and younger are suggests a late precambrian early paleozoic age for the formation of this newly discovered impact structure only a small part of which is preserved in the complexly faulted terrain

the mesoproterozoic beaverhead impact structure and its tectonic setting montana idaho 40ar 39ar and u pb isotopic constraints abstract new 40ar 39ar and uranium lead u pb zircon data from the beaverhead impact structure first identified by extensive shatter coning of proterozoic quartzite and gneiss from the beaverhead mountains near the montana idaho border indicate that the structure formed at or after 900 ma the 40ar 39ar age spectra from fine grained muscovite and biotite from a breccia zone in high grade gneiss show significant argon loss but yield dates for highest temperature steps that cluster between 899 and 908 ma the dated minerals probably formed by recrystallization of impact glass so on both geologic and isotopic grounds the dates probably represent the minimum age of impact u pb data for zircons from the same breccia are strongly discordant and yield an upper intercept apparent age of documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepac

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

effect of aging on the penetration resistance of sands the main objective of this study was to understand the effect of aging on the penetration resistance of freshly deposited sands two types of sand locally available river sand used as masonry sand and beaufort sea sand were selected for the study the sands were allowed to age under a constant stress of 100 kpa in a specially designed apparatus in a dry state as well as submerged in distilled water and in simulated sea water penetration resistance of the sand beds was measured periodically by pushing 4 probes into the sand bed mineralogical and fabric studies on freshly deposited and aged sand samples were conducted to detect the effect of aging if any on sand grains the results indicate that aging significantly increases the penetration resistance of sands the rate of increase in penetration resistance was higher for the submerged sand as compared with the dry sand the increase in penetration resistance of the sand in a dry state was attributed to rearrangement of sand grains in the submerged

liquefaction lateral stress consolidation state and aging abstractin 1986 1989 jackson lake dam wyoming was removed after standard penetration tests indicated that the foundation soil was subject to liquefaction part of a subsequent research program involved measuring lateral in situ stresses at various depths in the foundation soil by use of the ko stepped blade a device that introduces a stepwise lateral displacement of soil so contact pressures can be extrapolated to give the hypothetical pressure on a zero thickness step the foundation soil was cohesionless mix of alluvial and deltaic silts and sands with some sharp edged gravel the lateral stress measurements established relationships between the four topics in the title of this paper a normal consolidation state meaning that a soil is in equilibrium with its own weight can be established when ko is constant with depth and lateral effective stresses extrapolate to zero at the ground surface on this basis three stress zones were identified 1 based on limited data an uppermost zone to a depth

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

mexico 1985 the case for gravity waves summary the argument for the existence of gravity waves in sedimentary layers during strong earthquakes such as the 1985 mexico earthquake is based on a theory which predicts a discontinuity in surface wave propagation at a finite strain value b effects of stress strain non linearity in sediments and c observations suggesting the presence of ultra short wavelengths in soils during the 1985 mexico earthquake

accounting for soil aging when assessing liquefaction potential it has been recognized that liquefaction resistance of sand increases with age due to processes such as cementation at particle contacts and increasing frictional resistance resulting from particle rearrangement and interlocking as such the currently available empirical correlations derived from liquefaction of young holocene sand deposits and used to determine liquefaction resistance of sand deposits from in situ soil indices standard penetration test spt cone penetration test cpt shear wave velocity test vs are not applicable for old sand deposits to overcome this limitation a methodology was developed to account for the effect of aging on the liquefaction resistance of old sand deposits the methodology is based upon the currently existing empirical boundary curves for holocene age soils and utilizes correction factors presented in the literature that comprise the effect of aging on the in situ soil indices as well as on the field cyclic strength crr this paper describes how to combine currently recorded spt cpt and vs values with corresponding crr values derived for aged soil deposits to generate new empirical boundary curves for aged soils the method is illustrated using existing geotechnical data from four sites in the south carolina coastal plain sccp where sand boils associated with prehistoric earthquakes have been found these sites involve sand deposits that are 200 000 to 450 000 years in age this work shows that accounting for aging of soils in the sccp yields less conservative results regarding the current liquefaction potential than when age is not considered the modified boundary curves indicate that old sand deposits are more resistant to liquefaction than indicated by the existing empirical curves and can be used to evaluate the liquefaction potential at a specific site directly from the current in situ properties of the soil

3 d simulations of surface wave propagation in the kanto sedimentary basin japan part 2 application of the surface wave bem abstract the 3 d surface wave boundary element method is applied to the same set of strong motion records as those of part 1 kato et al 1993 namely the long period strong motion with periods around 8 sec recorded at the jma japan meteorological agency stations in yokohama and tokyo during the 1980 izu hanto toho oki earthquake this method simulates exact love and rayleigh waves in a laterally heterogeneous medium including 3 d basin structures the needed computer memory and cpu time are made manageable by assuming the inside and outside of the basin to consist of horizontal flat layers in addition vertical interfaces are assumed between the basin and the outside bedrock for simplicity in this study after checking the range of validity of the flat layer approximation for the kanto sedimentary basin the generation and propagation of surface waves in the basin are numerically investigated in particular our investigation places special emphasis on the cause of the observed long duration which could not be explained in part 1 using the surface wave gaussian beam method when the bedrock outside the western margin of the kanto basin is incorporated into the model the observed long duration at the tokyo station is successfully reproduced this can be explained by the strong surface waves generated by the surface wave to surface wave conversion at the margin and appearing in tokyo after the direct surface waves from the epicenter this result agrees with kinoshita et al 1992 who studied records from an array of seismographs in tokyo moreover when a sedimentary basin of sagami bay is included as was done in part 1 the simulations are greatly improved particularly at the yokohama station which corresponds to the node in the radiation pattern of the source this is due to the fact that the radiation pattern is strongly affected by the near source heterogeneity of the sagami basin all these results together with direct comparisons to 2 d modelings clearly show the strong 3 d effects of the basin structures on the generation and propagation of surface waves for this earthquake

estimation of the wave fields in the three geotechnical zones of tokyo we estimate the wave fields in the three geotechnical zones the hill alluvial and reclaimed zones of tokyo by analyzing the three components of surface and downhole strong motion accelerograms recorded at six borehole stations although the wave field of the reclaimed zone was already estimated in a recent study it is partly re estimated by an improved technique the target period range is mainly between 0 1 and 2 0 sec the wave types of observed ground motions are identified by calculating the theoretical vertical amplitude ratios of body waves and surface waves and the cross correlation functions between the surface and downhole recordings in the calculation of the theoretical amplitude ratios the damping for wave propagation and the damping for the eigenfunctions of surface waves are separately considered further the horizontal components of the surface and downhole recordings are separated into s wave and surface wave accelerograms the main conclusions are summarized as follows 1 the ground motions observed in the alluvial and reclaimed zones are mostly composed of s waves and love waves 2 the love wave amplitude ratios are larger than the s wave ratios in a soft surficial deposit around the theoretical predominant period the large love wave amplitude ratios are excited by the surficial deposit and a deep sedimentary basin and 3 quality factors near 10 are obtained for the soft deposit around the predominant period

three dimensional topography of the sediment basement interface in the tokyo metropolitan area central japan abstract an extensive seismic refraction experiment was conducted in the tokyo metropolitan area central japan to reveal the three dimensional basin structure in this area sixty three explosions were fired over 14 years and more than 2000 travel times were picked for several phases for our inversion the basement is divided into two homogeneous regions where the sediment is assumed to be of uniform velocity the interface separating the sediment and basement is then parameterized by bi cubic b splines and a smoothness constraint is imposed to avoid oscillatory artifacts in the solution the relative weight of the constraint to data residuals is determined by minimizing akaike9s bayesian information criterion about 1500 travel times of refracted p waves are inverted tomographically and the interface shape determined agrees well with the results of other geophysical surveys such as borehole measurements and gravimetric observations the basement velocities in the northern and southern regions are 5 7 and 5 4 km sec respectively previous two dimensional analyses suggested there is a 4 5 km sec layer in the uppermost part of the southern basement but we ignore it for simplicity so that estimated depths are likely underestimated by 1 2 km in the southern region nevertheless this study provides the first detailed image of the basin structure in the area which will help strong motion and earthquake hazard studies as additional constraints

3 d simulations of surface wave propagation in the kanto sedimentary basin japan part 1 application of the surface wave gaussian beam method abstract the goal of this study is to simulate the displacement waveforms of 8 sec period love waves observed at tokyo and yokohama stations in the kanto sedimentary basin during the izu hanto toho oki earthquake of 29 june 1980 m 0 7 10 25 dyne cm the surface wave gaussian beam method is applied for this purpose on the basis of the 3 d seismic velocity and density structure of the kanto basin and assuming that the earth medium is laterally homogeneous outside the kanto basin waveforms of love waves are synthesized the synthesized seismograms underestimate the observed peak amplitudes at yokohama station this is primarily because the station is located in the direction of the nodal plane of the love wave radiation as indicated by yamanaka et al 1992 a quaternary basin exists in the sagami bay between the source location and the kanto basin we include the sagami basin in our model by the approximation of a circular low velocity region excellent agreement between observed and synthesized waveforms was achieved not only for amplitude but also for phase for the early parts of the wave trains at both stations we conclude that the low velocity quaternary basin in the sagami bay acts like a lens to focus surface wave energy resulting in high amplitudes the later arriving waves in particular the long duration observed at tokyo station however cannot be adequately explained by this method one possible reason for the failure of simulating the later phases is that this method disregards the secondary love waves converted from s waves and or surface waves at a laterally discontinuous boundary although the surface wave gaussian beam method cannot adequately predict the duration of observed seismograms it provides us with a satisfactory prediction of amplitudes and phases for early arrivals in laterally slowly varying media at drastically lower computation costs and less memory requirements than does other methods

sand grain crushing and interface shearing during displacement pile installation in sand particle crushing shear banding interface abrasion and migration of crushing products all have the potential to influence the behaviour of displacement piles in sands this paper considers these particulate processes reporting experiments with model displacement piles installed in uniform pressurised sand and parallel interface ring shear tests the findings offer new insights into the mechanics of displacement piles in sands

resonant response models for the valley of mexico i the elastic inclusion approach summary the model developed by bard and bouchon to study the earthquake response of open ended 2 d sediment filled valleys with simple geometries is generalized to describe completely enclosed basins with arbitrary geometries by solving the basin form that corresponds to the valley of mexico it is possible to understand via a two step process model several of the observed features of the 1985 september 19 earthquake that devastated downtown mexico city here a general approach that allows the treatment of the particular seismic behaviour of the valley of mexico which is a large sediment filled valley containing an extremely soft ground urban area with a very high water content using collective resonance methods that vary from elastic to acoustic models is established this will lead through a series of papers to a theory that takes into account the role played by any valley s collective modes for microzonation and seismic damage predictions

pseudotachylite in impact structures generation by friction melting and shock brecciation a review and discussion abstract fault related pseudotachylites are generated as the result of brittle or brittle ductile deformation related to seismic faulting it is generally accepted among tectonic workers that while cataclasis plays a role in pseudotachylite formation friction melting is involved in addition pseudotachylite and pseudotachylite like breccias have been repeatedly described from the basement exposures of impact and cryptoexplosion structures and as veinlets in shocked meteorites and lunar samples the relevant literature is reviewed with regard to controversial usage of the term pseudotachylite and attention is drawn to several problematic aspects 1 the term pseudotachylite is currently used both as a purely descriptive term and with genetic implications 2 no unambiguous criteria for comparison and distinction of tectonically and impact generated pseudotachylites have been identified 3 it needs to be considered that in impact structures pseudotachylite could be generated by two distinct processes namely by shock brecciation melting and by friction melting pseudotachylite in impact structures could be the result of either of these two processes or of both 4 it is recommended to adhere more stringently when describing breccias from impact or cryptoexplosion structures to nomenclature accepted for the description of fault rocks in tectonic environments this would help to avoid confusion when discriminating between melt rocks pseudotachylite impact melt rock fragmental breccias cataclasite fragmental impact breccia and mylonitic rocks 5 no criteria for the distinction of melt bearing impact breccias impact melt rock and pseudotachylite have been established either in order to solve these problems close interaction between structural geologists and impact workers is warranted it is suggested that the understanding of breccias in impact structures would be improved by paying particular attention to the temporal relationships between different breccia types this would facilitate recognition of possibly different formational processes for impact produced melt and fragmental breccias and their distinction from pre and post shock deformation products

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

concretion morphology classification and genesis abstract a discussion of the most relevant morphological features of concretionary bodies and the different classifications and the criteria involved in these classifications is presented together with suggestions for improvements to the various classification schemes the meaning of syngenetic diagenetic and epigenetic related to the relative timing and environment of growth of concretionary bodies is also reviewed and discussed the replacement of mixed morphogenetic classifications which lead to conflicting results by classification categories based on textural features is proposed because the identification of the genetic environment of a concretionary body tells little about its history i recommend defining growth patterns in which the successive steps associated with changes in composition and or texture and the development of new structures are recorded a new path is presented that accounts for the contradiction between textural and isotope features which suggests respectively syngenetic and diagenetic or even epigenetic signatures this new path is characterized by the preservation of large porosities over very long time spans and down to depths that are somewhat greater than expected due to the inhibition of normal compaction caused by early overpressuring this overpressuring is the result of the development of hydraulic seals since approximately the syngenetic phase times the concepts of force of crystallization and displacive growth are also reviewed it is being suggested to discard some controversial interpretations of their actual importance for true concretionary displacive growth under epigenetic conditions in accordance with other authors the conclusion is reached that displacive growth is only possible if the shear strength of the host is very low and the stress field within the host is almost hydrostatic a new model the symcompactional concretionary growth model is proposed which explains how a concretionary body generally a nodule can grow while its host thins down by compaction this overpressured undercompacted model will be useful for the interpretation of an assemblage of features such as injection dikes hydraulic breccias cone in cone structures among others that are thought to be representative of the former presence of overpressured horizons these overpressured horizons could serve as detachment planes in paleotectonically active basins seals that could have controlled the movement of brines and hydrocarbons during the diagenetic evolution of the basin can also be assessed this is relevant for the identification of maturation conditions the potential development of secondary fracture permeability due to hydraulic fracturing in buried areas of the basin can also be evaluated based on the identification of formerly overpressured horizons in outcrops the origin of concretions is generally a geological puzzle clifton 1957

effect of friction fatigue on pile capacity in dense sand the paper presents the results of a series of field tests performed to study the causes of friction fatigue experienced by displacement piles four instrumented model piles were installed at a dense sand test bed site the test series was designed to impose different levels of cyclic loading during pile installation static and cyclic load tests were subsequently performed to study the differences in the axial capacities developed for ostensibly monotonic and cyclic installations the test results indicated that the mobilized horizontal effective stress regime that controls pile side friction primarily depends on the in situ sand state as reflected by the cone penetration test cpt qc resistance a zone of highly stressed sand that produced a concentration of high shear resistance was mobilized in the vicinity of the pile base the horizontal effective stress that acted on the pile shaft reduced in response to cyclic loading with the largest reductions occurring for high intensity cyclic loading or when the pile had experienced only a few load cycles during installation although cyclic loading caused a reduction in the horizontal effective stress that acted on the pile shaft the elevated stress built up in the vicinity of the pile base during installation remained higher than that remote from the base the elevated stress in the vicinity of the pile base only dissipated after cyclic tension loading had been applied

compaction of alluvial sands by deep blasting the jebba hydroelectric development nigeria presently under construction features a 42 m high zoned rockfill embankment founded on river alluvium up to 70 m in depth the riverbed alluvium comprises fine to medium to coarse grained quartzitic sands with traces of gravel the relative densities of the sands vary appreciably in both the vertical and horizontal directions during the dam design it was found that it would be necessary to densify the loose to medium dense portion of the river sands to maintain settlements within acceptable limits and to withstand design earthquake forces the top 25 m of the river alluvium is densified by the vibrocompaction method and below this level down to depths of 40 m the alluvium is densified by blasting there is no precedent found in the literature for densification by blasting at such depth this paper presents details of a test program and the production work test results conclusively show increases in static cone penetration resistance in loose sand layers

evaluation of installation effects on set up of field displacement piles in sand the paper presents results from a new series of tests on displacement piles in sand involving different installation modes and combines these with results from previous tests at the same site as

static response of monopile to lateral load in overconsolidated dense sand abstractlarge diameter rigid monopile foundations have been extensively used in the fast growing offshore wind energy industry over the last two decades in view of the offshore environment later

time lapsed shear wave velocity vs tomographic images and stress in sand surrounding displacement pile during setup this study reports model pile tests designed to characterize the underlying mechanisms of driven pile setup in dry sand by means of stress measurement with the tactile pressure sensors and spatio t

gravity waves in mexico city i gravity perturbed waves in an elastic solid abstract local site effects caused unprecedented damage at mexico city during the 19 september 1985 michoacan earthquake notwithstanding significant efforts observed long duration strong ground motion in the lake zone has not yet received a truly satisfactory explanation following the suggestions of gilbert 1967 and lomnitz 1988 1989 we explore in this paper the possibility of explaining this long duration in terms of gravity perturbed waves in an elastic solid after a brief review of gilbert9s model and of its limitations we use a linearization of the free surface boundary condition for nonnegligeable vertical displacements to introduce gravity in our equations we consider modifications due to gravity in rayleigh9s function and in free surface reflection coefficients and we find that rayleigh9s pole is significantly affected by gravity for very high poisson9s ratios finally we present results for the problem of ground motion simulation on the surface of an irregular thin layer of very soft clay our results show that gravity may affect rayleigh9s wave velocity by a factor larger than 2 only in the case of an extremely soft surface layer poisson9s ratio larger than 0 499999 but that the transition between rayleigh waves in solids and gravity waves in fluids suggested by lomnitz 1991 does not exist regarding mexico city we show that gravity perturbations in an elastic solid do not affect either the character of surface motion or amplitudes or duration of ground motion and thus do not provide an explanation for the long duration of strong motion in mexico city

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

gravity waves in mexico city ii coupling between an anelastic solid and a fluid layer abstract this paper completes a previous study of the role of gravity during the 19 september 1985 michoacan earthquake at mexico city it is assumed as suggested by lomnitz 1989 1990 that nonlinear mechanisms could bring the rheology of the mexico city soft clay layer nearer to a fluid than to a solid in order to test whether gravity waves in a viscous fluid could provide an explanation of exceedingly long duration observed at mexico city we have studied the motion on the surface of an irregular viscous fluid layer overlaying an elastic half space our formulation takes into account vertical displacement at the free surface of the fluid layer but requires a linearization of the corresponding boundary condition a decomposition of diffracted fields in terms of plane waves allows the use of aki larner9s method excitation is given by vertically incident sv waves we present results both for nonviscous and viscous fluids and show that an adequate free boundary condition is essential for this problem lacking data we have performed several simulations for values of viscosity going from 300 to 30 000 pa s in the case of a nonviscous fluid gravity surface waves are generated efficiently by diffraction of elastic waves on the irregular interface but attenuate rapidly when including viscosity and are not significant for viscosities above 3000 pa s the results presented in our companion paper and here allow us to conclude that gravity is not a likely explanation to the long duration of ground motion observed at mexico city in a more general context our model may be useful to study the interaction of seismic waves with water reservoirs such as dams

a comprehensive interpretation of strong motions in the mexican volcanic belt large amplitude seismograms with extremely long duration have been recorded in the valley of mexico recently we came to recognize important effects of the mexican volcanic belt mvb on the seismograms we interpret strong motions observed in the mvb by analyzing the three components of surface and borehole accelerograms recorded during the 14 september 1995 earthquake m s 7 3 the target period range is between 0 1 and 10 0 sec with emphasis on a 2 0 to 3 0 sec period range in the lake bed zone inside the valley wave types of seismic motions are identified by calculating theoretical amplification of various seismic waves and cross correlation functions between surface and borehole recordings in the mvb propagation velocities of dominant surface waves are estimated by analyses of recordings and are compared with theoretical velocities and 2d 3d wave propagation simulations for the mvb and the mexico city basin are performed our conclusions are the following 1 we suggest that while strong motions observed in the lake bed zone are a mixture of p s love and rayleigh waves fundamental mode love waves are dominant 2 surface waves are found to be much more heavily amplified than s waves in the soft lake bed deposit 3 we confirm that the mvb is an important structure to amplify seismic motions the lake bed deposit together with the basin structure proves to remarkably amplify surface waves 4 in the lake bed deposit quality factors are found to be about 3 in the long period range of more than 1 5 sec manuscript received 24 march 2003

cpt based evaluation of liquefaction and lateral spreading in centrifuge two series of centrifuge model tests were conducted using nevada sand four saturated models placed in a mildly inclined laminar box and simulating a 6 m thick deposit were shaken inducing liquefaction effects and lateral spreading the sand was deposited at a relative density dr 45 or 75 two of the 45 models were subjected to overconsolidation or preshaking the second series involved in flight measurements of static cone tip penetration resistance qc simulating the standard cone penetration test cpt 36 mm cone values of qc increased with dr overconsolidation and preshaking a normalized resistance qc1n was assigned to each of the four liquefaction lateral spreading models increases in dr overconsolidation and preshaking decreased liquefaction and ground deformation but relative density alone captured these effects rather poorly conversely qc1n predicted extremely well the liquefaction and lateral spreading response of the four models confirming seed s hypothesis to explain the s

measurement of q 1 for s waves in mudstone at chikura japan comparison of incident and reflected phases in borehole seismograms seismograms from small events in the southern kanto region have been recorded by a seismometer installed in a 732 m deep borehole at chikura observatory japan where mudstone of early pliocene age is found from the ground surface to the bottom of the borehole strong phases occurring 1 5 1 6 sec after the s wave arrival were interpreted as reflections at the ground surface ray path directions of the incident s waves were determined from the minimum principal axis of the three dimensional trajectory ellipsoid which represents the particle motion for a head wave of s phase transverse horizontal sh components were used to estimate the q 1 value for s waves assuming the free surface acted as an 100 reflector for the sh waves and the incident sh phase as an input and the reflected phase as an output we calculated system functions the q 1 value was measured from the transfer characteristics between the incident and the reflected phases in a single seismogram thus no corrections were necessary for source or site including instrument effects if we applied a power law model the following relationship was obtained from the regression analyses of 20 events log 10 q 1 0 52 0 48 log 10 f 1 28 0 22 1 0 f 5 0 hz where f is frequency in hz and error values are the 95 confidence levels of the regression coefficients

piles under cyclic axial loading study of the friction fatigue and its importance in pile behavior the main point of this paper is to identify the key features and load transfer mechanisms controlling friction fatigue of piles under cyclic loading numerical modeling makes use of an advanced ela

shatter cone and microscopic shock alteration evidence for a post paleoproterozoic terrestrial impact structure near santa fe new mexico usa article i nfo field mapping morphologic description and petrographic analysis of recently discovered shatter cones within paleoproterozoic crystalline rocks exposed over an area n 5k m 2 located 8 km northeast of santa fe new mexico usa give robust evidence of a previously unrecognized terrestrial impact structure herein we provisionally name this the santa fe impact structure the shatter cones are composed of nested sub conical curviplanar and flat joint surfaces bearing abundant curved and bifurcating striations that strongly resemble the multiply striated joint surfaces msjs documented from shatter cones at vredefort dome the cones occur as a penetrative feature in intrusive igneous and supracrustal metamorphic rocks are unusually large up to 2 m long and 0 5 m wide at the base display upward pointing apices and have subvertical northeastward plunging axes that crosscut regional host rock fabrics key characteristics of superficially similar but non shock generated conical and striated features are inconsistent with the properties of the santa fe cones in thin section sub millimeter scale dark semi opaque to isotropic veneers on cone surfaces and veinlets within cone interiors closely resemble previously described shock induced melt features microscopic grain alteration restricted generally to within 1 mm of the cone surfaces includes random fractures fluid micro inclusions sericite replacement in feldspar rare kink bands in mica optical mosaicism and decorated planar fractures pfs and planar deformation features pdfs in quartz the pfs and pdfs are dominated by a basal 0001 crystallographic orientation which indicate a peak shock pressure of 5 10 gpa that is consistent with shatter cone formation regional structural and exhumation models together with anomalous breccia units that overlie and crosscut the shatter cone bearing rocks may provide additional age constraints for the impact event the observed shatter cone outcrop area suggests that the minimum final crater diameter of the santa fe impact structure was 6 13 km

suction caissons in dense sand part ii vertical cyclic loading into tension suction caissons have been used for numerous oil and gas installations and are increasingly considered as a foundation solution for offshore wind turbines owts there can be significant differenc

seismic coupling of interface modes in sedimentary basins a recipe for disaster abstract coupling between an evanescent p wave and a rayleigh wave can occur when the two modes share the same phase velocity at an interface the result is a new distinctive monochromatic mode of large amplitude and finite duration that may reverberate in a bounded layer generating stationary patterns due to constructive and destructive interference such modes may be responsible for earthquake damage in the valley of mexico and perhaps in other sedimentary basins vulnerable to seismic disasters on soft ground

probability of wave slamming and the magnitude of slamming loads on offshore wind turbine foundations abstract physical model tests were analyzed with the objective to establish a formulae for the probability of wave slamming on offshore wind turbine foundations and the associated slamming force furthermore the effect of wave slamming is analyzed for a monopile wind turbine foundation using a state of the art aeroelastic model the laboratory measurements were carried out in deltares atlantic basin as part of the joint industry project wave impacts on fixed turbines in short jip wifi long crested and irregular waves typical for the north sea were applied and more than 130 design storms and 500 slamming impacts were analyzed a simple closed form expression for the probability of wave slamming is presented and a reasonable agreement with the laboratory measurements shown a criterion for when wave slamming should be included in design computations is formulated based on the sea state steepness it is observed that wave slamming occurs during tests with a flat seabed and that seabed features such as sand waves significantly increase the probability of wave slamming furthermore a simplified slamming load formulation is proposed based on observations from a subset of the laboratory tests the magnitude of the slamming load is validated against the remaining part of the laboratory measurements and compared with existing slamming load formulations the new formulation is in better agreement with the underlying measurements than existing formulations and is of a simpler form which makes it easier to apply the new slamming load formulation is applied in design computations for a realistic wind turbine with the offshore wind farm gemini as base case the computations show that wave slamming at this specific location is not governing the structural design however wave slamming may introduce high accelerations in the transition piece located in the free surface zone where waves are impacting the structure

frequency effects in the dynamic lateral stiffness of monopiles in sand insight from field tests and 3d fe modelling with the offshore wind industry rapidly expanding worldwide geotechnical research is being devoted to foundation optimisation most intensively for large diameter monopiles the analysis and desi

basin induced love waves observed using the strong motion array at fuchu japan phases have been observed in the s wave coda of local earthquakes recorded at the fuchu strong motion array located in the kanto basin in the western suburbs of tokyo japan these phases are often larger than the direct s wave at a period of 1 sec because these phases are observed only on horizontal components at surface sites and are weakly observed at only the shallowest 150 m of a number of borehole sites they are interpreted as love waves particle motions indicate significantly off azimuth travel directions the fuchu array is too sparse to allow the application of standard array analysis to determine the origin of these phases instead we use a combination of three component polarization enveloping and slant stack techniques that allows propagation directions to be reasonably well determined 10 however group slownesses are more difficult to obtain precisely 1 to 2 sec km using these results and assuming that the love waves are generated by the scattering of s waves at the earth s surface we estimate locations of scattering points we find that the scattering occurs along a short segment of the kanto basin boundary for widely distributed earthquake source locations we believe that this segment is important because it is the closest part of the basin boundary to the observation sites the existence of these basin induced love waves violates backscattering models for the generation of the coda of local earthquakes this must be kept in mind when applying coda techniques to sediment basin sites at periods of 1 sec or more

the terrestrial impact cratering record approximately 130 terrestrial hypervelocity impact craters are currently known due to variations in preservation and in geologic knowledge this sample is biased towards young x 20 km craters on the cratons of australia europe including the former u s s r and north america the rate of discovery of new craters is 3 5 craters per year although modified by erosion terrestrial impact craters exhibit the range of morphologies observed for craters on other terrestrial planetary bodies such as the moon terrestrial craters provide essential ground truth data on the geologic effects of impact and the subsurface structure of impact craters which can be used to constrain interpretations of lunar samples and models of crater formation due to erosion and its effects on form terrestrial craters are recognized primarily by the occurrence of shock metamorphic effects these include shatter cones microscopic planar deformation features solid state and fusion glasses high pressure polymorphs and whole rock melting and vaporization shock recovery experiments indicate that these features occur over shock pressures of 5 gpa to x 100 gpa terrestrial craters have a set of geophysical characteristics which are largely the result of the passage of a shock wave and impact induced fracturing they include gravity and magnetic lows and reductions in seismic velocity the gravity anomalies are seldom greater than 30 mgal due to the limiting effects of lithostatic pressure on fracturing at large complex craters the gravity signature may include a central relative gravity high due to uplift and short wavelength central magnetic anomalies due to a variety of processes much current work is focused on the effects of impact on earth evolution previous work on shock metamorphism and the contamination of impact melt rocks by meteoritic siderophile elements provides a basis for the interpretation of the physical and chemical evidence from cretaceous tertiary boundary sites as resulting from a major impact suggestions that other biological boundaries in the stratigraphie record are due to periodic impacts are not supported by time series analysis of the terrestrial cratering record by analogy with the lunar record and modelling of the effects of very large impacts it has been proposed that biological and atmospheric evolution of the earth could not stabilize before the end of the late heavy bombardment 3 8 ga ago the present terrestrial cratering rate is 5 4 2 7 10 15 km 2a 1 for a diameter 20 km this represents a local threat on historic time scales on a global scale a major impact sufficient to cripple human civilization severely will occur on time scales of 106 a

effects of hydromechanical loading history and antecedent soil mechanical damage on shallow landslide triggering evidence suggests that the sudden triggering of rainfall induced shallow landslides is preceded by accumulation of local internal failures in the soil mantle before their abrupt coalescence into a landslide failure plane the mechanical status of a hillslope at any given time reflects competition between local damage accumulated during antecedent rainfall events and rates of mechanical healing e g rebonding of microcracks and root regrowth this dynamic interplay between damage accumulation and healing rates determines the initial mechanical state for landslide modeling we evaluated the roles of these dynamic processes on landslide characteristics and patterns using a hydromechanical landslide triggering model for a sequence of rainfall scenarios the progressive nature of soil failure was represented by the fiber bundle model formalism that considers threshold strength of mechanical bonds linking adjacent soil columns and bedrock the antecedent damage induced by prior rainfall events was expressed by the fraction of broken fibers that gradually regain strength or mechanically heal at rates specific to soil and roots results indicate that antecedent damage accelerates landslide initiation relative to pristine undamaged hillslopes the volumes of first triggered landslides increase with increasing antecedent damage however for heavily damaged hillslopes landslide volumes tend to decrease elapsed time between rainfall events allows mechanical healing that reduces the effects of antecedent damage this study proposed a quantitative framework for systematically incorporating hydromechanical loading history and information on precursor events e g such as recorded by acoustic emissions into shallow landslide hazard assessment

the agoudal high atlas mountains morocco shatter cone conundrum a recent meteorite fall onto the remnant of an impact site associations between impact structures and meteorite occurrences are rare and restricted to very young structures meteorite fragments are often disrupted in the atmosphere and in most cases meteorite falls that have been decelerated by atmospheric drag do not form a crater furthermore meteorites are rapidly weathered in this context the finding of shatter cones in jurassic marly limestone in the same location as a recent 105 40 ka iron meteorite fall near the village of agoudal high atlas mountains morocco is enigmatic the shatter cones are the only piece of evidence of a meteorite impact in the area the overlap of a meteorite strewn field with the area of occurrence of shatter cones led previous researchers to consider that the meteorite fall was responsible for the formation of shatter cones in the context of formation of one or several small 100 m impact craters that had since been eroded shatter cones are generally not reported in association with subkilometer diameter impact craters here we present new field observations and an analysis of the distribution and characteristics of shatter cones breccia and meteorites in the agoudal area evidence for local deformation not related to the structural high atlas tectonics has been observed such as a vertical to overturned stratum trending n150 n160 new outcrops with exposures of shatter cones are reported and extend the previously known area of occurrence the area of in situ shatter cones 0 15 km2 and the strewn field of meteorites are distinct although they show some overlap the alleged impact breccia is revealed as calcrete formations no evidence for a genetic relationship between the shatter cones and the meteorites can be inferred from field observations the extent of the area where in situ shatter cones and macrodeformation not corresponding to atlas tectonic deformation are observed suggest that the original diameter of an impact structure could have been between at least 1 3 km for typical erosion rates in the atlas region 0 08 cm yr 1 the period of time required for the erosion of such a structure 1 25 3 75 ma is much larger than the age of the meteorite fall this line of reasoning excludes a genetic link between the shatter cones and the meteorite fall and indicates that the observed shatter cones belong to an ancient impact structure that has been almost entirely eroded

field experiments at three sites to investigate the effects of age on steel piles driven in sand this paper investigates the influences that steel type in situ soil properties water table depth pile diameter roughness and driving procedures have on the ageing behaviour of piles driven in s

field trials of suction caissons in clay for offshore wind turbine foundations a programme of testing on suction caisson foundations in an artificially prepared sand test bed near luce bay in scotland is described the tests are relevant to the design of either monopod or quadruped foundations for offshore wind turbines records are presented for suction installation of the caissons cyclic moment loading under both quasi static and dynamic conditions to simulate the behaviour of a monopod foundation and cyclic vertical loading and pullout of caissons to simulate one footing in a quadruped foundation variations of stiffness with loading level of the foundation are observed with high initial stiffness followed by hysteretic behaviour at moderate loads and degradation of response at high loads some implications for the design of wind turbine foundations are briefly discussed

effects of geologic time on the initial stiffness of clays abstract the paper addresses the effect of geologic aging on the initial stiffness of clays through the analysis of in situ shear stiffness data obtained using a seismic cone penetrometer at three sites in boston blue clay bbc a 12 000 14 000 year old post glacial marine clay deposit the effects of this aging period are estimated using as reference for the unaged behavior the results of over 90 triaxial shear phases conducted on specimens of resedimented boston blue clay rbbc a soil prepared in the laboratory from natural bbc and tested after 1 day of laboratory aging at the same ocr and effective stress level the natural clay displays an initial stiffness which on the average is approximately 50 greater than that of the laboratory resedimented clay based on the estimated age of the natural deposit this corresponds to an increase of the stiffness per log cycle of time of 7 this value of the aging coefficient ng is at the low end of values presented in the literature for clays which are however all based on shorter aging durations days to weeks

analytical estimation of short period ground motions in mexico city for engineering applications in previous studies short period 0 2 5 0 s ground motions in mexico city were investigated by a systematic analysis of surface and downhole accelerograms and it was found that short period love waves were very dominant at the predominant periods of grounds although the average vertical amplification of ground motions with long duration was interpreted fairly well at soft soil sites the large time variations in the vertical amplification remain unexplained the present study addresses two issues on the vertical amplification at two soft soil sites which are important for engineering applications the first issue is the interpretation of the large time variations in the vertical amplification of ground motions and the influence of the depth of the structure in which surface waves are trapped is examined the second issue is the interpretation of inertial force excitation which is usually used in the engineering community in terms of seismic waves the second issue is also estimated by the vertical amplification the conclusions are as follows 1 the large time variations in the vertical amplification of ground motions can be explained sufficiently by both the mixture of s waves and love waves and the depth of the structure in which love waves are trapped the structure corresponds to the mexico city basin 2 although inertial force excitation is considered to be valid for s waves it proves to be invalid for love waves

dynamic deformations of shallow sediments in the valley of mexico part i three dimensional strains and rotations recorded on a seismic array abstract we study the spatial variation in earthquake ground motions or equivalently the dynamic displacement gradient field using a novel analysis procedure borrowed from geodesy seismic data recorded in the valley of mexico by a microarray of three three component surface accelerographs and two three component accelerographs at depths of 30 m and 102 m constrain our estimates of the dynamic displacement gradient field from which strains and rotations derive for four moderate earthquakes at distances of 250 to 300 km our study focuses on the effects of low velocity surface materials on the deformation at the surface the gradients corresponding to deformation across vertical planes dominate and vertical axis rotations are of similar magnitudes as strains the greatest peak surface gradient we observed was 206 strain for the 14 september 1995 m w 7 5 earthquake at a distance of 300 km however much larger gradients occur across horizontal planes u z where u is a horizontal displacement and z is depth at some depth between 0 and 30 m these values are about a factor 10 greater than the corresponding gradient components at the surface u z for the 14 september earthquake equaled or exceeded 665 strain at depth the dynamic deformations experienced in mexico city undoubtedly have occurred before and will occur again in other densely populated areas however in many other regions the sediment response will not remain linear and elastic resulting instead in liquefaction and ground failure