a study of planetary waves in the southern winter troposphere and stratosphere part i wave structure and vertical propagation abstract planetary wave propagation in the southern winter troposphere and stratosphere is studied in an attempt to trace the origins of upward propagating disturbance daily geopotential girds from 1000 to 1 mb are analyzed for two 120 day winter seasons a cross correlation analysis technique is developed which allows coherent wave structure to be traced in time significant correlations are observed between the troposphere and stratosphere at finite time lags indicative of vertically propagating waves the observed vertical propagation time scales between the middle troposphere and middle stratosphere are on the order of 4 days for zonal wavenumber 1 k 1 1 2 days for k 2 and 1 day for k 3 the cross correlation analysis also delineates the meridional and vertical structures of the transient in time planetary waves zonal wavenumber 1 fluctuations exhibit a vertical out of phase relationship between the midlatitude troposphere and atmosphere three out of phase maxima in latitude are observed in

two sources of nonisotropic radiation from underground explosions in granite significant tangential ground motion observed during underground explosions makes it difficult to distinguish them from natural earthquakes such motion can be generated by the source geometry and emplacement conditions by the heterogeneous nature of the rock mass mechanical properties may vary in space due to the presence of cracks joints faults and various geologic layers and also by the nonuniform in situ stress state the last mechanism is increasingly important with depth when the difference in main principal stresses becomes significant this paper is focused on the role of material strength of the rock mass in generation of non radial motion during explosions in pre stressed media numerical modeling of underground chemical explosions in granite at various depths have been conducted to compare two possible mechanisms of shear wave generation the first caused by rock mass anisotropy is important at shallow depth the second is related to elastic plastic relaxation around the cavity created by the explosion tangential motions for these two mechanisms have different signatures

numerical modeling of liquefaction and comparison with centrifuge tests the prediction of liquefaction and resulting displacements is a major concern for earth structures located in regions of moderate to high seismicity conventional procedures used to assess liquefac

radiation from point sources in general anisotropic media summary a procedure to evaluate the geometrical properties of the slowness surface for arbitrary anisotropic media is presented this allows us to use results for computing the displacement field from point sources in general anisotropic media utilizing the gaussian curvature of the slowness surface of the considered waves since the formulae used are based on high frequency asymptotics the procedure gives reliable results as long as no parabolic points of the slowness surface are encountered radiation patterns of point sources for models representing rocks in the crust and upper mantle are presented and discussed the radiation from point sources in anisotropic models is compared with the radiation from point sources in average isotropic models to emphasize the differences anisotropy is either caused by aligned cracks crustal rocks or by aligned olivine crystals upper mantle rocks considering models of aligned cracks differing only in the physical parameters of the crack material water or gas significantly different radiation patterns are obtained models with wet cracks exhibit focusing of quasi s wave energy for some directions whereas this effect is not observed for the corresponding model with dry cracks the quasi s wave radiation pattern from explosions are multilobed and the wet crack models exhibit more lobes than the dry crack models the radiation of single forces in olivine shows strong energy focusing wave tuning of quasi s waves however for realistic compositions of upper mantle rocks with some 10 per cent of preferentially orientated olivine this wave tuning is less pronounced

centrifuge modeling of seismically induced uplift for the bart transbay tube the bart transbay tube tbt is an immersed cut and cover subway tunnel that runs from oakland to san francisco california the loose sand and gravel backfills placed around the tunnel are considered to be liquefiable and the clays under the backfill are soft in some zones along the alignment these conditions could potentially result in uplift of the tunnel during strong earthquake shaking this paper describes centrifuge model tests performed to verify numerical methods used to assess the stability and to evaluate the potential uplift mechanisms of the tbt the observed mechanisms of uplift were a ratcheting mechanism sand migrating under the tunnel with each cycle of relative movement a pore water migration mechanism water flowing under the tunnel and a bottom heave mechanism involving soft soils below the base of the trench a fourth potential mechanism viscous flow of liquefied soil was not observed the volume of the tunnel relative to the volume of the trench and the densities and permea

elliptical diagnostics of stratospheric polar vortices diagnostics based on the spatial moments of isopleths of a long lived tracer or of potential vorticity are presented that enable the structure and evolution of stratospheric polar vortices to be concisely summarized and quantified the area centre aspect ratio and orientation of the equivalent ellipse of the vortex on an isentropic surface are defined using the second and lower order spatial moments of contours within the vortex edge region by examining the variations of these elliptical diagnostics with time and altitude the temporal evolution and vertical structure of the polar vortices can be quantified the usefulness of the diagnostics is assessed by examining nitrous oxide data from the geophysical fluid dynamics laboratory skyhi general circulation model the diagnostics show and quantify several differences between the arctic and antarctic vortices in the skyhi model the arctic vortex moves further off the pole is generally more elongated and has a more complicated vertical structure than the antarctic vortex with larger variations of both the vortex centre and elongation with height the elliptical diagnostics also identify the occurrence of large scale rossby wave breaking events both at the vortex edge and in the subtropics in the model

improvements to regional explosion identification using attenuation models of the lithosphere 1 regional p s amplitudes have been recognized as an effective discriminant between earthquakes and explosions while closely spaced events generally discriminate easily the application of this technique to broad regions has been hampered by large variations in the amplitude of phases due to the attenuation of the crust and upper mantle making use of a recent p wave and s wave attenuation model of the lithosphere we have found that correcting the events using our amplitude methodology significantly reduces the scattering in the earthquake population we demonstrate an application of this technique to station nil using broad area earthquakes and the 1998 indian nuclear explosion using the pn lg discriminant in the 1 2 hz passband we find that the explosion which is lost in the scatter of the earthquakes in the uncorrected discriminant clearly separates by correcting for attenuation structure we see a similar reduction in scatter and separation for the pn sn and pg lg discriminants

phenomenology and modeling of explosion generated shear energy for the source physics experiments abstract we present a mechanism for shear wave generation from buried explosions as part of the source physics experiment spe series the spe series includes sensitized heavy ammonium nitrate fuel oil sources of various sizes detonated in a borehole in the jointed climax stock granite the cylinder shaped shots were grouted in the borehole to couple the energy to the rock a high fidelity site model with explicit inclusion of the cylindrical explosive the grout filled borehole and site joint sets was included in a numerical simulation that mimics the near field velocity environment measured by an array of in ground accelerometers this approach was accommodated through a coupled euler lagrange code that allows simultaneous solving of a euler domain to model the high deformation source region and a lagrange domain that includes the complex geology with full contact specific laboratory measured geomechanical properties for the rock and the joint sets were included in the model the simulations compare favorably to the data and provide a possible physical mechanism for unexpected shear motion through the release of stored shear strain on the joints this research will advance our understanding of explosion generated shear wave energy from low yield nuclear tests

critical state based interpretation of the monotonic behavior of hostun sand abstracta series of bender element tests and drained and undrained monotonic triaxial compression and extension tests were performed on air pluviated samples of hostun sand samples were prepared t

numerical model verification and calibration of george massey tunnel using centrifuge models dynamic soil structure interaction analyses were carried out for the seismic retrofit design of the immersed george massey tunnel both to predict and study soil liquefaction and related tunnel mov

simulation of topographic effects on seismic waves from shallow explosions near the north korean nuclear test site with emphasis on shear wave generation 1 we performed high resolution 8 hz three dimensional simulations of ground motions from shallow explosions in the presence of rough surface topography near the north korean nuclear test site to study elastic propagation effects with emphasis on theoretical aspects of shear wave generation interaction with rough topography causes significant p to rg scattering along the surface with amplification of high frequency 2 8 hz shear waves relative to the flat earth case shear waves of different polarizations are coupled by topographic scattering rg precursors composed of p to rg conversions traveling as surface waves have the spectral amplitudes comparable to the p wave while the rg phase has the low frequency 0 5 3 hz spectral shape of the rg from the flat case plus the high frequency 3 8 hz p wave spectra motions at near vertical takeoff angles corresponding to teleseismic propagation are increased or decreased indicating that waves are focused or defocused by topographic features above the source topographic roughness has a dramatic effect as short wavelength features 2 5 km are included higher frequencies are amplified by topography including frequencies corresponding to wavelengths shorter than the shortest topographic scale length overall topography enhances energy propagating along the surface near the source amplifies surface waves and tends to balance sv and sh polarized motions all of which impact shear wave observations used for nuclear explosion monitoring further simulation studies could elucidate how the wavefield emerging from a topographically rough area ultimately propagates to regional and or teleseismic distances

seismic decoupling with chemical and nuclear explosions in salt an extensive series of simulations was performed of underground explosions in salt using both chemical and nuclear explosives in both cases the radius of the initial emplacement cavity was varied from the fully tamped configuration to as large as 80 m kt sup 1 3 when not fully tamped the cavity was assumed initially to contain air at ambient temperature and pressure in the nuclear source case the simulations are shown to be in good agreement with the salmon sterling events conducted by the united states and with recently released russian data on a similar pair of explosions in an azgir salt dome simulation of the us cowboy series of chemical explosions in a louisiana salt mine are also shown to be in very good agreement with the experimental data however the constitutive model for the salt that best explains these data is different from that derived for salmon both salt models are amply supported by laboratory and field data the main result of these simulations is that cavity decoupling with chemical explosives is much less efficient than with nuclear explosives although maximum decoupling factors f sub max near 200 may be attainable with either of the two sources the cavity size required to achievemore this value appears to be 40 m kt sup 1 3 for cavity radii half as large f sub max is roughly 4 times lower with nuclear explosives and lower by another factor of 4 with chemical sources moreover if the initial cavity radius is a more modest 10 m kt sup 1 3 f sub max 3 even with a nuclear source 24 refs 8 figs less

mechanism for postliquefaction water film generation in layered sand soil investigations at two sites demonstrate that layered structure or stratification in sand deposits is prevalent not only in reclaimed ground but also in natural alluvial ground one dimensional liquefaction tests in a lucite tube are then carried out for models of several types of layered sand indicating that water films will develop under most circumstances beneath or within less permeable sublayers a basic mechanism for the water film generation is discussed based on the measurements of soil settlement and excess pore pressure the development of the water film and the associated soil settlement are numerically simulated by a simple sedimentation analysis and a rational explanation of the test results is found thus a significant involvement of water films in liquefied sand deposits and their basic mechanism are clarified it is highly probable that water films are involved as a part of a sliding surface and play a significant role in a seismically induced flow failure in loose and layered sand deposits during liquefaction

an observational study of traveling planetary waves in the southern hemisphere abstract southern hemisphere analyses from the surface to 2 mb and from 20 to 80 s for the period may september 1979 have been used to study the structure of traveling planetary waves space time cross spectral analysis of the height field has been employed to define the amplitude and phase for both the eastward and westward moving components of particular combinations of zonal wavenumber and frequency band latitude height contour plots of power phase and coherence squared show that westward moving waves have structure characteristic of barotropic external modes and are coherent across a broad range of latitudes and from the surface to 2 mb the highest level analyzed eastward moving waves on the other hand have more rapid phase variations especially in the troposphere and appear more baroclinic the tropospheric structure of the moving components of wavenumbers 1 4 is as one would expect for baroclinically unstable modes of the charney type wavenumbers 1 and 2 both have double amplitude maxima i

effects of rock damage on seismic waves generated by explosions in studying the physical processes involved in the generation of seismic waves by explosions it is important to understand what happens in the region of high stresses immediately surrounding the explosion this paper examines one of the processes that takes place in this region the growth of pre existing cracks which is described quantitatively as an increase in rock damage an equivalent elastic method is used to approximate the stress field surrounding the explosion and a micro mechanical model of damage is used to calculate the increase in damage simulations for a 1 kt explosion reveal that the region of increased damage can be quite large up to ten times the cavity radius the damage is initiated on a damage front that propagates outward behind the explosive stress wave with a velocity intermediate between that of p and s waves calculations suggest that the amount of increased damage is controlled primarily by the initial damage and the extent of the region of increased damage is controlled primarily by the initial crack radius the motions that occur on individual cracks when damage increases are converted to seismic moment tensors which are then used to calculate secondary elastic waves which radiate into the far field it is found that while the contribution from an individual crack is small the combined effect of many cracks in a large region of increased damage can generate secondary waves that are comparable in amplitude to the primary waves generated by the explosion provided that there is asymmetry in the damage pattern this process is quite effective in generating s waves thus providing a quantitative explanation of how s waves can be generated by an explosion two types of asymmetry are investigated a shear pre stress and a preferred orientation of cracks and it is found that both produce similar effects

multi scale fracture damage associated with underground chemical explosions abstract understanding rock damage induced by explosions is critical for a number of applications including the monitoring and verification of underground nuclear explosions mine safety issues and modeling fluid flow through fractured rock we use core observations televiewer logs and thin section observations to investigate fracture damage associated with two successive underground chemical explosions spe2 and spe3 in granitic rock at both the mesoscale and microscale we compare the frequency and orientations of core scale fractures and the frequency of microfractures between a pre experiment core and three post experiment cores natural fault zones and explosion induced fractures in the vicinity of the explosive source are readily apparent in recovered core and in thin sections damage from faults and explosions is not always apparent in fracture frequency plots from televiewer logs although orientation data from these logs suggests explosion induced fracturing may not align with the pre existing fracture sets core scale observations indicate the extent of explosion induced damage is 10 0 m after spe2 and 6 8 m after spe3 despite both a similar size and location for both explosions at the microscale damage is observed to a range distance of 10 2 0 9 m after spe2 and 16 6 0 9 and 11 2 0 6 in two different cores collected after spe3 additional explosion induced damage interpreted to be the result of spalling is readily apparent near the surface but only in the microfracture data this depth extent and intensity of damage in the near surface region also increased after an additional explosion this study highlights the importance of evaluating structural damage at multiple scales for a more complete characterization of the damage and particularly shows the importance of microscale observations for identifying spallation induced damage

soil parameters for deformation analysis of sand masses meaningful stress and deformation analysis of soil structures requires an adequate stress strain law herein are presented guidelines for selection of parameters for a simple incremental hyperbolic stress strain law for sand based upon a tangent stiffness that varies with stress level the parameters are obtained from an examination of laboratory and field measurements available in the literature and are presented in terms of both penetration value and relative density the laboratory results indicate the importance of first time or primary loading versus repeated loading on modulus values back analysis of field observations for monotonic loading conditions indicates that primary loading modulus values obtained from triaxial tests are appropriate at low relative density whereas perhaps higher values in the repeated loading range are appropriate at high relative densities key words sand deformation analysis hyperbolic tangent stiffness modulus relative density monotonic loading repeated loading

observations of wave mean flow interaction in the southern hemisphere abstract variations of zonal mean and eddy properties in the southern hemisphere during the winter of 1979 are studied several periods of enhanced wave activity and rapid zonal mean changes are observed during these periods of rapid change both the actual zonal wind tendency and the eliassen palm flux divergence have a dipole pattern in the upper stratosphere with positive values in high latitudes and negative values in middle and low latitudes the positive values of e p flux divergence near the pole are particularly interesting since they suggest a possible source of wave activity in this region the stationary component of wavenumber 1 and the eastward traveling component of wavenumber 2 contribute most to the dipole pattern of wave driving in the stratosphere a nearly uniform deceleration of the mean flow in the troposphere is contributed to by all zonal wavenumbers from 1 to 10 the lower wavenumbers contribute most to the driving in high latitudes while the driving in lower latitudes is contri

cyclic loading response of loose air pluviated fraser river sand for validation of numerical models simulating centrifuge tests cyclic loading response of loose fraser river sand was investigated as input to numerical simulation of centrifuge physical models using constant volume direct simple shear tests conducted with a

cyclic shear response of fine grained mine tailings the mechanical response of three different types of fine grained mine tailings is examined using data from constant volume cyclic direct simple shear dss tests under cyclic dss loading fine grained tailings typically exhibit a cumulative decrease in effective stress along with progressive degradation of shear stiffness the observed shear strain development due to cyclic mobility is similar in form to that of the previously observed cyclic shear response for natural silts the cyclic resistance ratio crr of laterite tailings is observed to increase with an increase in the initial effective confining stress vc for this material the dilative tendency due to stress densification seems to have overridden the contractive tendency due to the increase in confining stress in contrast the crr of copper gold zinc tailings is insensitive to the initial effective confining stress suggesting a response similar to that of normally consolidated clay the postcyclic maximum shear strength ratio su pc v

deformation characteristics and control techniques at the shiziping earth core rockfill dam abstractthis paper presents a representative engineering case the shiziping dam to illustrate deformation controls of highrise earth core rockfill dams in seismic areas techniques for controlling dam deformation including structure design foundation treatment material properties and construction are discussed in detail field monitoring data and deformation characteristics were reviewed to verify control effectiveness the deformation during the construction and initial impoundment period accounted for 70 85 of the overall deformation the deformation was primarily influenced by weight wetting behavior and creep creep stabilized 7 or 8 months after the completion of construction the total deformation is caused by fill and foundation materials uneven deformation is mainly caused by foundation shape foundation compression symmetry and uniformity of fill materials uneven deformation may be improved by using reasonable dam zone and fill material designs and appropriately increasing core wall c

fault rupture propagation through previously ruptured soil abstractsurface fault rupture during recent earthquakes has significantly damaged structures although several researchers have studied surface fault rupture the effects of fault rupture propagating through soil that has been ruptured previously have not been investigated yet faults rupture multiple times so that native soil deposits will have likely undergone previous ruptures that would have developed shear bands within the soil and the stress state of the soil will have evolved because of these events in addition the predominant modes of soil shearing during the fault rupture process have not been characterized fully numerical simulations are performed to analyze the mechanics of dip slip surface fault rupture and to explore the effects of previously ruptured soil the numerical results demonstrate that the soil rupture process occurs in two distinct stages first broad deformation occurs before strain localization which is followed by more localized deformation after shear band formation str

climatology and interannual variability of wave mean flow interaction in the southern hemisphere abstract the climatology and interannual variability of wave mean flow interaction in the southern hemisphere 20 80 s 0 55 km is described for the winter months of june september based on a sample of four years 1979 82 the stratospheric jet stream shifts downward and poleward over the course of the winter in response to seasonal variations in thermal forcing the shift occurs at different times in different years however so that the months of july and august show substantial interannual variability of monthly mean zonal winds the poleward and downward shift of the jet axis in an individual year is usually abrupt and occurs in association with a burst of upwardly propagating planetary waves the driving of the mean flow in the stratosphere generally has a dipolar structure with easterly accelerations near 40 s and westerly accelerations in polar latitudes the structure of the wave driving is consistent with the structure of the observed mean flow accelerations

can the fisk conjecture be explained by rock damage around explosions we investigate the possibility that rock damage ashby and sammis 1990 johnson and sammis 2001 can explain recent observations of fisk 2006 2007 that p and s wave corner frequencies from explosions differ by a factor approximately related to the ratio of near source compressional and shear velocities the fisk conjecture the observation of differing p and s wave corner frequencies from explosions forms the basis for the success of the high frequency p s discriminant using first order considerations we find that the damage mechanics model can indeed explain the fisk conjecture although this is certainly not a unique explanation the key to our argument is that although the radius of rock damage is less than that of the so called elastic radius the slow velocity of the outward propagating damage front can reduce shear wave corner frequencies this explanation differs slightly from that of fisk 2006 2007 who states that s waves from explosions occur at a similar length scale comparable to the elastic radius as for p waves because of the significant reduction in v s caused by rock damage we suggest that the shear waves generated within the damage region can have a radius significantly less than the elastic radius for a p wave additionally because rock damage is controlled by the difference of the maximum and minimum principal stress first order considerations suggest that lithospheric overburden does not shut off rock damage until scaled depths of burial of up to graphic 1 thus effects due to rock damage may be an important source of shear waves for nearly all tamped nuclear explosions for which we have experience 1 embed inline graphic 1 gif

centrifugal modeling of seismic behavior of large diameter pipe in liquefiable soil this study focused on the behavior of a large diameter burial pipe with special reference to its stability against flotation subject to soil liquefaction centrifugal modeling technique was used where the results are presented for a total of eight shaking table tests conducted on the burial pipe in a laminar box under 30g gravitational field the ground was prepared with nevada sand at a relative density of 38 and shaken with a sinusoidal wave at an amplitude of 0 5g the use of a viscous fluid in a saturated soil deposit satisfied the time scaling relationships of both dynamic and dissipation phenomena the centrifugal modeling technique simulated flotation of pipeline as the soil liquefied a technique that used gravels and geosynthetic material was used to mitigate flotation the response of the soil deposit in terms of acceleration and excess pore pressure was investigated the uplifting of the pipe earth pressure response and ground surface deformation were also presented based on the test results a design procedure was proposed for the burial pipe in resisting flotation due to soil liquefaction the deadweight and stiffness of the gravel unit which was confined by geosynthetic were important items in design

numerical and centrifuge modeling of seismic soil foundation structure interaction on liquefiable ground abstractthe effective mitigation of the liquefaction hazard requires an improved understanding of the consequences of liquefaction in terms of ground shaking permanent displacement and building performance in this paper results from centrifuge experiments of a shallow founded structure on liquefiable sand are used to evaluate the predictive capabilities of a state of the art numerical tool solid fluid fully coupled 3d nonlinear numerical simulations were performed using the pdmy02 soil model implemented in a software modeling domain the numerical model captured excess pore pressures and accelerations well in the free field but largely underestimated volumetric settlements due to loss of water during shaking this was associated with the drastic increase in soil hydraulic conductivity when approaching liquefaction which was not taken into account numerically as well as the underestimation of soil volumetric compressibility the contribution of volumetric strains to total building settlement was

canlex full scale experiment and modelling a major aim of the canadian liquefaction experiment canlex was to verify analysis procedures for pre dicting liquefaction phenomena towards this purpose two loading events were carried out a field event comprising a clay embankment built over a loose sand foundation layer and a centrifuge test performed on a model of a sand em bankment structure both the field event and the centrifuge model were planned so as to induce a static liquefaction failure and were instrumented to observe their response in terms of displacement and pore pressure the fundamental mechanical characteristics of the foundation layer were determined from laboratory element tests triaxial and simple shear these tests formed the basis for the stress strain modelling used in the numerical analyses two fundamentally different modelling techniques were used one involved a fully coupled plasticity model and the other involved a model based on a collapse surface approach the model and prototype structures were then analyzed and the predicted results in terms of displacements and pore pressures were compared with the measured values the results from both approaches were found to be in reasonable agreement with the measurements provided allowance was made for direc tion of loading and drainage effects were accounted for resume un but principal du canadian liquefaction experiment canlex etait de verifier les procedures d analyse pour predire les phenomenes de liquefaction a cette fin deux cas de chargement ont ete realises un chargement sur le terrain comprenant la construction d un remblai d argile sur une couche de fondation de sable meuble et un essai au centrifuge realise sur un modele d une structure de remblai de sable tant le remblai sur le terrain que le modele dans le centrifuge ont ete planifies de facon a induire une rupture par liquefaction statique et ont ete instrumentes pour ob server leurs reponses en termes de deplacement et de pression interstitielle les caracteristiques mecaniques

liquefaction susceptibility criteria for silts and clays new liquefaction susceptibility criteria for saturated silts and clays are presented that are based on the mechanics of their stress strain behavior and which provide improved guidance for selecting engineering procedures for estimating potential strains and strength loss during seismic loading monotonic and cyclic undrained loading test data for silts and clays show that they transition over a fairly narrow range of plasticity indices pi from soils that behave more fundamentally like sands sand like behavior to soils that behave more fundamentally like clays clay like behavior with the distinction having a direct correspondence to the type of engineering procedures that are best suited to evaluating their seismic behavior it is recommended that the term liquefaction be reserved for describing the development of significant strains or strength loss in fine grained soils exhibiting sand like behavior whereas the term cyclic softening failure be used to describe similar phenomena in fine grained soils exhibiting clay like behavior for practical purposes clay like behavior can be expected for fine grained soils that have pi 7 although a slightly lower transition point for soils with a cl ml classification perhaps pi 5 or 6 would be equally consistent with the available data issues related to the practical application of these criteria are discussed

a source model for induced earthquakes at the geysers geothermal reservoir the results of a previous study on source mechanisms of small earthquakes at the geysers geothermal reservoir in northern california are used to investigate an extended crack model for seismic events the seismic events are characterized by their first degree moment tensors and interpreted in terms of a model that is a combination of a shear crack and wing cracks solutions to both forward and inverse problems are obtained that can be used with either dynamic or static moment tensors the model contains failure criteria explains isotropic parts that are commonly observed in induced earthquakes and produces estimates of crack dimensions and maximum amount of slip effects of fluid pressure are easily incorporated into the model as an effective stress the model is applied to static moment tensors of 20 earthquakes that occurred during a controlled injection project in the northwest geysers for earthquakes in the moment magnitude range of 0 9 2 8 the model predicts shear crack radii in the range of 10 150 m wing crack lengths in the range of 2 25 m and maximum slips in the range of 0 3 1 1 cm only limited results are obtained for the time dependence of the earthquake process but the model is consistent with corner frequencies of the isotropic part of the moment tensor being greater than the deviatoric part and waveforms of direct p waves that become more emergent for larger events

interannual variability of the stratospheric circulation in the southern hemisphere the variability from year to year of the seasonal evolution in the southern hemisphere stratosphere over a period of 10 years from 1980 to 1989 is investigated using the global geopotential height derived from the data from the stratospheric sounding unit on board the tiros noaa satellites as a measures of interannual variability the variance of the zonal mean geostrophic wind over the 10 years was calculated for each day although the major warming hardly occurs in the southern hemisphere stratosphere large variances can be observed during the winter and spring the maximum variances appear at low latitudes in late autumn move towards mid latitudes in midwinter and remain near 60 s in spring the seasonal movement of the zonal mean westerly jet in the southern hemisphere stratosphere can be classified into two categories in terms of the location of the maximum westerlies at the 1 mb level in midwinter namely hlj high latitude jet years with maximum westerlies around 50 s llj low latitude jet years with maximum westerlies around 40 s during the late winter the core of the westerly jet moves polewards earlier in hlj years in llj years in association with this earlier movement the growth of the amplitudes of planetary waves 1 and 2 during the period from winter to spring occurs earlier in hlj years than in llj years in autumn however the wave 1 amplitude only for llj years develops vigorously in the stratosphere and even the troposphere before the seasonal movement of the zonal mean westerly jet branches off into the two categories the appearances of hlj and llj years occur in groups of a few years this is quite different from the behaviour of the equatorial quasi biennial oscillation

liquefaction flow of submarine slopes under partially undrained conditions an effective stress approach the stability of submarine slopes is commonly assessed based on undrained soil response liquefaction flow may occur when pore pressure rise in soil elements under constant shear stress causes a reduction in effective stresses recent experimental studies have shown that a small net flow of water into an element results in additional pore pressure generation and further reduces its strength as a result soil elements can liquefy due to expansive volumetric strains that cannot be predicted by undrained analysis submarine deposits of the fraser river delta are known to contain high concentrations of methane gas tidal variations can cause unequal pore pressure generation with depth and time in these soils such changes reduce the effective stresses during low tides and may induce liquefaction flow of slopes due to partial drainage conditions an effective stress approach based on an elastic plastic stress strain relationship is presented to model liquefaction flow of sand a fully coupled analysis is carr

uplift of immersed tunnel in liquefiable seabed under wave and current propagation abstract in ocean environments wave usually propagates in association with a current the paper presents a cyclic characterization framework for elastoplastic consolidating behavior of liquefiable seabed around the immersed tunnel under combined wave and current loading based on the biot dynamic consolidation theory special attention is placed on modeling the nonlinear wave current interaction the cyclic plasticity behavior of marine deposits and the soil structure contact effect the paper extends an existing masing model to large strain regime in the order of 10 2 in the framework of cyclic plasticity for capturing the liquefaction induced nonlinear behavior of marine deposits then the proposed cyclic plasticity model is implanted into an explicit time matching finite difference analysis platform permitting a comprehensive simulation of the intensive response of the immersed tunnel in the seabed experiencing the excess pore pressure accumulation and residual liquefaction retrospective simulation of a well documented centrifuge test by the proposed framework indicates satisfactory agreement validating the reliability for capturing the excess pore pressure accumulation and residual liquefaction during wave propagation finally the influences of current on the wave induced liquefaction in the vicinity of an immersed tunnel are investigated by a numerical example the results indicate that the ocean current significantly changes the original characteristics of wave induced liquefaction as well as the induced uplift of the immersed tunnel especially with consideration of the cyclic plasticity behavior of marine deposits the mechanisms of seabed liquefaction and the induced uplift of the immersed tunnel under wave and current actions are also interpreted

liquefaction limit during earthquakes and underground explosions implications on ground motion attenuation liquefaction of saturated soils and sediments documented during earthquakes shows an empirical relation log r max 2 05 0 10 0 45 m where r max is the liquefaction limit in meters i e the maximum distance from liquefaction site to the hypocenter and m is the earthquake magnitude combining this with an empirical relation between m and the seismic energy of an earthquake we obtain a relation between the liquefaction limit and the seismic energy e a r max the prefactor corresponds to a threshold energy for liquefaction ranging from 0 004 to 0 1 j m3 the exponent ranging from 3 2 to 3 3 implies that the energy density of ground motion attenuates with distance according to 1 r 3 2 3 3 where r is the distance from the hypocenter the value of the threshold energy suggests a preliquefaction degradation of the shear modulus of soils by more than 3 orders of magnitude liquefaction documented during underground explosions is characterized by a threshold energy several orders of magnitude greater than that for liquefaction during earthquakes but shows a similar functional relation between e and r max as that for liquefaction during earthquakes and implies a similar attenuation relation between ground motion energy density and distance

stress densification and its evaluation stress densification occurs in natural soils as well as manmade embankments and physical model tests such densification can increase stability and liquefaction resistance one dimensional compress

a climatology of stratospheric polar vortices and anticyclones 1 united kingdom meteorological office global analyses from 1991 to 2001 are used to create a global climatology of stratospheric polar vortices and anticyclones new methodologies are developed that identify vortices in terms of evolving three dimensional 3 d air masses a case study illustrates the performance of the identification schemes during february and march of 1999 when a merger of anticyclones led to a stratospheric warming that split the arctic polar vortex the 3 d structure and temporal evolution of the arctic vortex and identified anticyclones demonstrates the algorithm s ability to capture complicated phenomena the mean geographical distribution of polar vortex and anticyclone frequency is shown for each season the frequency distributions illustrate the climatological location and persistence of polar vortices and anticyclones a counterpart to the aleutian high is documented in the southern hemisphere the australian high the temporal evolution of the area occupied by polar vortices and anticyclones in each hemisphere is shown as a function of potential temperature large polar vortex area leads to an increase in anticyclone area which in turn results in a decrease in the size of the polar vortex during northern winter and southern spring 9 years of daily anticyclone movement are shown on the 1200 k 36 km 4 hpa isentropic surface preferred locations of anticyclogenesis are related to cross equatorial flow and weak inertial stability regimes of traveling and stationary anticyclones are discussed index terms 3309 meteorology and atmospheric dynamics climatology 1620 3319 meteorology and atmospheric dynamics general circulation 3334 meteorology and atmospheric dynamics middle atmosphere dynamics 0341 0342 keywords polar vortex stratospheric anticyclones

asperity model of an earthquake dynamic problem a previous study that presented the static solution for an asperity model of an earthquake is extended to solve the dynamic problem that develops when failure occurs on the boundary of an asperity patch and then spreads over the surrounding displacement shadow region the boundary integral equation method is coupled with basic constitutive equations for failure and friction to solve the dynamic problem with different parameters used for the strong asperity patch and weak shadow region no friction displacement weakening friction and velocity strengthening friction are all investigated depending on the type and amount of friction that is present the dynamic solutions for slip on the fault exhibit a range of different features including overshoot of the static solution and oscillation rupture front velocities that may be greater than or less than the s velocity and change with position and either total or partial release of the static moment common characteristics of the solutions are that failure on the asperity patch is almost independent of failure on the shadow region and that the displacement deficit on the shadow region is released by propagating slip pulses the stress concentrations of the asperity model are sufficient to produce nonlinear elastic effects in a region extending outward from the fault to distances comparable with the dimensions of the shadow region beginning with the solutions for slip on the fault waveforms are simulated for an earthquake of magnitude m w 1 44 and compared with data recorded at a distance of 8 65 km simulations that contain both source and propagation effects are capable of explaining most of the basic features of the observational data including general agreement with the shape of the waveforms in the time domain the levels and slopes of the spectra at low frequencies less than 10 hz and at high frequencies greater than 100 hz and some of the interference effects present in both the time and frequency domains

seismic liquefaction lateral spreading and flow slides a numerical investigation into void redistribution experience from past earthquakes indicates that seismically induced large lateral spreads and flow slides in alluvial sand deposits have taken place in coastal and river areas in many parts of the world the ground slope in these slides was often not very steep gentler than a few percent recent research indicates that the presence of low permeability silt or clay sublayers within the sand deposits is responsible for this behaviour such layers form a barrier to upward flow of water associated with earthquake generated pore pressures this causes an accumulation of pore water at the base of the layers resulting in greatly reduced strength and possible slope instability this paper uses an effective stress coupled stress flow dynamic analyses procedure to demonstrate the effects of a low permeability barrier layer on ground deformations from an earthquake event the analyses show that an expansion zone develops at the base of barrier layers in stratified soil deposits under seismic loading which can grea

seismic imaging of santorini subsurface constraints on caldera collapse and present day magma recharge abstract volcanic calderas are surface depressions formed by roof collapse following evacuation of magma from an underlying reservoir the mechanisms of caldera formation are debated and predict differences in the evolution of the caldera floor and distinct styles of magma recharge here we use a dense active source seismic tomography study to reveal the sub surface physical properties of the santorini caldera in order to understand caldera formation we find a 3 km wide cylindrical low velocity anomaly in the upper 3 km beneath the north central portion of the caldera that lies directly above the pressure source of the 2011 2012 inflation we interpret this anomaly as a low density volume caused by excess porosities of between 4 and 28 with pore spaces filled with hot seawater vents that were formed during the first three phases of the 3 6 ka late bronze age lba eruption are located close to the edge of the imaged structure the correlation between older volcanic vents and the low velocity anomaly suggests that this feature may be long lived we infer that collapse of a limited area of the caldera floor resulted in a high porosity low density cylindrical volume which formed by either chaotic collapse along reverse faults wholesale subsidence and infilling with tuffs and ignimbrites phreatomagmatic fracturing or a combination of these processes phase 4 eruptive vents are located along the margins of the topographic caldera and the velocity structure indicates that coherent down drop of the wider topographic caldera followed the more limited collapse in the northern caldera this progressive collapse sequence is consistent with models for multi stage formation of nested calderas along conjugate reverse and normal faults the upper crustal density differences inferred from the seismic velocity model predict differences in subsurface gravitational loading that correlate with the location of 2011 2012 edifice inflation this result supports the hypothesis that sub surface density anomalies may influence present day magma recharge events we postulate that past collapses and the resulting topographical and density variations at santorini influence magma focusing between eruptive cycles a feedback process that may be important in other volcanoes

compressional waves guided between parallel fractures abstract we have performed experiments on the laboratory scale to image seismic wavefronts of compressional waves that are guided between parallel fractures the wavefronts are detected using water coupled 1 mhz piezoelectric transducers the stiffness of the fractures is controlled by applying radial stress in a hydraulic stress apparatus that leaves the observation face of the fractured sample open to measurement the two fractures form a waveguide in isotropic homogeneous aluminum and act as parallel displacement discontinuity boundary conditions separated by a distance d 2 the compressional wave is a leaky guided mode that sheds energy into the medium beyond the fractures however the fractures provide sufficiently strong energy confinement inside the central waveguide for a sample length l of approximately l 15 to observe the guided wave fractures with low fracture specific stifffness produce strong energy confinement in the guided compressional mode wave

experimental observations on the response of loose sand under simultaneous increase in stress ratio and rotation of principal stresses the drained response of loose sand relative density of 30 under simultaneous increase in principal stress ra tio r 1 3 and the inclination of major principal stress to the vertical is examined using data from hollow cylin der torsional shear testing the study specifically pertains to the behaviour of loose sand subject to monotonic linear stress path loadings in the r space within the domain of r 2 4 58 while intermediate principal stress parameter b and effective mean normal stress m are held constant the relationship between horizontal shear stress zt and hori zontal shear strain zt of loose sand under such loadings is shown to be unique and stress path independent at any stress state the horizontal shear stiffness dzt dzt for a given m depends only on the current value ofzt and not on the value of individual components of normal effective stress or their increments when r and are increased simultaneously in a linear manner loose sand initially exhibits linear strain paths suggesting no significant changes to the inherent anisotropy during the early stages of such loading the directions of principal stress increment and principal strain increment 3 are found coincident when 4 58 an approach to predict the response of loose sand under simultaneous in crease in r and with constant b and m has been developed based on these findings

climatology of arctic and antarctic polar vortices using elliptical diagnostics abstract the climatological structure and interannual variability of the arctic and antarctic stratospheric polar vortices are examined by analysis of elliptical diagnostics applied to over 19 yr of potential vorticity data the elliptical diagnostics define the area center elongation and orientation of each vortex and are used to quantify their structure and evolution the diagnostics offer a novel view of the well known differences in the climatological structure of the polar vortices although both vortices form in autumn to early winter the arctic vortex has a shorter life span and breaks down over a month before the antarctic vortex there are substantial differences in the distortion of the vortices from zonal symmetry the arctic vortex is displaced farther off the pole and is more elongated than the antarctic vortex while there is a midwinter minimum in the distortion of the antarctic vortex the distortion of the arctic vortex increases during its life cycle there are also large differenc

fracture channel waves the properties of guided waves which propagate between two parallel fractures are examined plane wave analysis is used to obtain a dispersion equation for the velocities of fracture channel waves analysis of this equation demonstrates that parallel fractures form an elastic waveguide that supports two symmetric and two antisymmetric dispersive rayleigh channel waves each with particle motions and velocities that are sensitive to the normal and tangential stiffnesses of the fractures these fracture channel waves degenerate to shear waves when the fracture stiffnesses are large to rayleigh waves and rayleigh lamb plate waves when the fracture stiffnesses are low and to fracture interface waves when the fractures are either very closely spaced or widely separated for intermediate fracture stiffnesses typical of fractured rock masses fracture channel waves are dispersive and exhibit moderate to strong localization of guided wave energy between the fractures the existence of these waves is examined using laboratory acoustic measurements on a fractured marble plate this experiment confirms the distinct particle motion of the fundamental antisymmetric fracture channel wave a sub 0 mode and demonstrates the ease with which a fracture channel wave can be generated and detected copyright 1999 american geophysical union

planetary wave mean flow interaction in the stratosphere a comparison between northern and southern hemispheres by the use of stratospheric height and temperature field data obtained from the tiros satellite dynamical interaction between planetary waves and mean zonal winds in the stratosphere is investigated special attention is paid to differences between northern and southern hemispheres an analysis is made for pressure levels from 70 to 0 4 mb during the period from june 1981 to may 1982 eliassen palm e p flux diagnostics are used as a powerful and useful tool to investigate the wave mean flow interaction from winter to summer the seasonal marches of wave activity measured by the e p flux and of mean zonal wind are different between the two hemispheres in the nh wave activity varies intermittently with a characteristic timescale of about two weeks once the core of the stratospheric westerly jet shifts poleward due to a minor warming the subsequent wave activity breaks the westerlies dramatically to replace them by the easterlies in association with the sudden warming whilst in the sh wave activity in mid winter is quiet corresponding to small time variations of the maximum westerly speed in late winter the core of the stratospheric westerly jet suddenly shifts poleward and downward due to a wavenumber 2 minor warming after the shifting of the westerly jet the wave activity of wavenumber 1 is enhanced and continues until early summer on the basis of this observational evidence we discuss i the seasonal evolutions of wave activity and the mean zonal wind ii the interannual variability of the stratospheric circulations and iii the time variation of wave activity

an observational study of high latitude stratospheric planetary waves in winter abstract nimbus 4 and 5 radiances representing temperatures in the upper and lower stratosphere are analyzed to obtain power and coherence squared spectra at high latitudes during the winters of both hemispheres the spectra for zonal wavenumbers 1 3 are presented indicating a variety of wave features which exist in the upper stratosphere an eastward moving wavenumber 1 feature with 4 day period is described in greater detail the possible nature of this wave is briefly discussed a second wave observed only in the southern hemisphere wavenumber 2 field is found to be westward moving with period near 2 3 days

soil liquefaction induced uplift of underground structures physical and numerical modeling abstractunderground structures located in liquefiable soil deposits are susceptible to floatation following a major earthquake event such failure phenomenon generally occurs when the soil liquefies and loses its shear resistance against the uplift force from the buoyancy of the underground structure numerical modeling accompanied with centrifuge experiments with shallow circular structures has been carried out to investigate the floatation failure at different buried depths of the structure the influence of the magnitude of input sinusoidal earthquake shaking was also studied both numerical and experimental results showed matching uplift response of the structures and acceleration and pore pressure measurements in the liquefied soil deposit a higher uplift displacement of the structure was observed for shallower buried depth thereby indicating the influence of overlying soil weight against floatation results also showed that the structures commenced floatation in the presence of high excess pore pr

effect of shaking strength on the seismic response of liquefiable level ground abstract shaking strength is one of the most important parameters that characterize earthquake events in the past it was common to apply shaking of different strengths consecutively on a soil model to investigate the effect of shaking level on seismic ground response without considering the effect of loading history in this study a series of dynamic centrifuge tests under different shaking levels was performed on fresh saturated sand models with the same initial conditions to investigate the effect of shaking strength on the seismic response of liquefiable level ground the experimental observations indicate the following effects 1 shaking strength has pronounced effect on the excess pore pressure buildup in the saturated sand deposit the maximum excess pore pressure at the deep part of the deposit increased by 184 and 109 as the peak input acceleration along the x direction increased from approximately 0 064 g to 0 098 g and from 0 098 g to 0 189 g respectively 2 shaking strength has significant effect on the development of shear strain in soil however the permanent settlement is sensitive to the shaking strength at low shaking level but the increment rate tends to slow down as the shaking strength becomes stronger 3 the peak acceleration along the x direction at the ground surface was 0 126 0 079 and 0 087 g at peak input accelerations of 0 064 0 098 and 0 189 g respectively the peak acceleration at the ground surface under slight shaking was greater than that under strong shaking 4 the amplification pattern of acceleration varied continuously during shaking the amplification factor decreased quickly as the excess pore pressure accumulated under strong shaking but continued to increase at an early stage under low strength earthquake the natural frequency of the soil column also evolved with the development of the shaking induced excess pore pressure which had adversely affected the wave propagation and ground response the data presented in this paper enrich the ground response database and can be used to validate the current site response analysis methods

equivalent linear computation of response spectra for liquefiable sites the spectral envelope method abstracta simplified methodology is proposed for the computation of elastic response spectra at liquefiable sites based on the widely used equivalent linear frequency domain site response analysis method the actual response spectrum is obtained as the upper bound envelope of the thus calculated response spectra corresponding to the preliquefaction and the postliquefaction segments of the seismic excitation the former computed for the natural soil properties and the latter for the properties of the liquefied soil the time of liquefaction onset which separates the two seismic excitation segments is defined in terms of the minimum factor of safety against liquefaction within the liquefiable layer additional guidelines are provided for the estimation of the excess pore pressure buildup and the associated soil softening during the preliquefaction segment of the seismic excitation as well as for the definition of the liquefied soil stiffness and the hysteretic damping ratio the proposed methodology h

lower stratospheric rossby wave trains in the southern hemisphere a case study for late winter of 1997 behaviour of quasi stationary circulation anomalies observed in the lower stratosphere of the extratropical southern hemisphere during austral late winter of 1997 is studied the anomalies are defined as daily low pass filtered departures from the circulation varying slowly with the seasonal cycle a wave activity flux and refractive index for stationary rossby waves are utilized in the analysis each of which is defined locally for the zonally varying westerlies subseasonal fluctuations in the lower stratosphere were often associated with zonally confined wave trains emanating upward from localized quasi stationary anomalies in the troposphere including blocking ridges the three dimensional propagation of the waves was found sensitive to the structure of a local waveguide upward injection of rossby wave activity into the stratosphere tended to occur slightly upstream or just beneath of a lower stratospheric waveguide associated with the developed polar night jet pnj which led to the subsequent formation of a well defined wave train downstream along that jet the distribution of the lower stratospheric subseasonal variability thus exhibits significant zonal asymmetries reflecting those in the pnj structure and the distribution of tropospheric disturbances seasonal evolution of the pnj and that of the tropospheric intraseasonal variability substantially modulated the lower stratospheric activity of subseasonal fluctuations copyright 2004 royal meteorological society

inverting ground motion from a seismometer array to obtain the vertical component of rotation a test using data from explosions to study factors that affect reliability of the derived vertical rotational ground motions about vertical axis from translational array waveforms we have conducted a field test using explosion the dataset was collected on march 4 2008 from an active source experiment of the taiwan geodynamics research project taiger 2008 in which 750 kg of explosives were set off about 500 m away from a specially designed seismic array in free field consisting of 8 tri axial rotational sensors 13 tri axial accelerometers and 12 six channel 24 bit dataloggers with gps receivers our results show that the waveform fits were greatly improved when the explosion induced crustal strains were less than 2 10 5 for our station configuration as a result our modeling for the large amplitude part of the mainshock was not entirely successful however we have successfully recovered the first order features of the later part of the vertical rotational ground motions using translational velocity waveforms in the 0 5 20 hz bandwidth using the spudich and fletcher s procedure 2009 moreover we used a modified jaeger s 1969 formula and derived similar rotational synthetics we found that the best rotational rate waveform fits were derived using a station configuration of a dense small aperture translational array combined with a few largeoffset stations a small aperture array is needed to fulfill the uniform rotation assumption however inverting data from an array of small spatial dimension requires waveforms of high signal to noise ratio and high sampling rates surprisingly large offset translation stations provided additional constraints in time and space helping to fit the low frequency waveforms using the inverted result we forward predicted the vertical translational waveforms not used in the inversion and got excellent fits this suggests that the inverted results are of good quality for predicting the complete translational ground motions even though only horizontal components were used in the inversion array derived or directly measured rotational ground motions can be used to predict translational ground motions in the near by region lessons learned from this study could be helpful for future studies using translational ground motions to derive dynamic ground strains tilts and torsions

estimation of liquefaction induced manhole uplift displacements and trench backfill settlements abstracta simple method to predict the uplift displacement of a manhole and trench backfill settlement due to liquefaction is proposed the conventional equilibrium of vertical forces acting on a manhole is solely a function of such forces acting and is incapable of predicting the uplift displacement in this paper the proposed method adds variables including the uplift displacement f and settlements of backfill s under the condition that the volume of an uplifted portion of a manhole is equal to a settled volume of a trench backfill to date the method is verified through comparison with the results of 1 g and centrifuge model tests a new safety factor which takes into account the amount of manhole uplift and backfill settlement is also derived

cyclic characterization of wave induced oscillatory and residual response of liquefiable seabed the paper presents a robust modeling method for a fully coupled effective stress analysis of the wave induced liquefaction scenarios based on the biot consolidation theory in this context emphasis is placed on the implementation of a well calibrated cyclic soil model and an empirical shear volume coupling equation which links the increment of volumetric strain per cycle of wave with the shear strain occurring during that particular cycle unlike most of the previous investigations using the amplitude of shear stress over the wave period or the phase resolved oscillatory shear stresses as the source term for calculating the residual pore pressure in this study the source term is related to the rate of plastic volumetric deformation and implemented into the biot consolidation equation to consider both generation and partial dissipation of excess pore pressure during wave propagation then the proposed modeling method is incorporated into a dynamic finite difference analysis procedure model calibrations are carried out in terms of individual soil element behavior and seabed response under progressive waves respectively overall good agreement demonstrates the reliability of the modeling method for the prediction of wave induced seabed response finally the paper highlights the potentials of proposed modeling framework to simulate the basic features of wave induced seabed response i e the coupling of progressive buildup of pore pressure and cyclic softening of soil skeleton by means of numerical examples the obtained results show that the cyclic behavior of liquefiable seabed under wave actions can be well captured by the proposed model

the micromechanics of westerley granite at large compressive loads the micromechanical damage mechanics formulated by ashby and sammis pure appl geophys 133 3 489 521 1990 has been shown to give an adequate description of the triaxial failure surface for a wide variety of rocks at low confining pressure however it does not produce the large negative curvature in the failure surface observed in westerly granite at high confining pressure we show that this discrepancy between theory and data is not caused by the two most basic simplifying assumptions in the damage model 1 that all the initial flaws are the same size or 2 that they all have the same orientation relative to the largest compressive stress we also show that the stress strain curve calculated from the strain energy density significantly underestimates the nonlinear strain near failure in westerly granite both the observed curvature in the failure surface and the nonlinear strain at failure observed in westerly granite can be quantitatively fit using a simple bi mineral model in which the feldspar grains have a lower flow stress than do the quartz grains the conclusion is that nonlinearity in the failure surface and stress strain curves observed in triaxial experiments on westerly granite at low loading rates is probably due to low temperature dislocation flow and not simplifying assumptions in the damage mechanics the important implication is that discrepancies between experiment and theory should decrease with increased loading rates and therefore the micromechanical damage mechanics as formulated can be expected to give an adequate description of high strain rate phenomena like earthquake rupture underground explosions and meteorite impact

shear waves from isotropically dominated sources comparison of the 2013 rudna poland and 2007 crandall canyon utah mine collapses comparison of observed and synthetic radiation patterns suggests that love waves generated by the 2007 crandall canyon mine collapse m w 4 1 are the result of shear waves generated by a relatively large compensated linear vector dipole component at the source whereas the love waves associated with a 2013 rudna mine collapse m w 4 2 are minimal except where amplified by a deep sedimentary basin we examine the source of the 19 march 2013 rudna mine poland collapse with a full moment tensor inversion method using the complete waveforms of regional distance seismic data the computed source is primarily composed of a dominant and statistically significant implosive component the rudna source is more similar to previous mine collapses than to double couple tectonic earthquakes although source mechanisms are similar there are clear differences in love wave amplitudes online material tables of velocity models and figures of moment tensors and waveform fits

corner frequency scaling of regional seismic phases for underground nuclear explosions at the nevada test site model fits are used to estimate source spectral corner frequencies of regional seismic phases pn pg and lg from underground nuclear explosions unes at the nevada test site nts based on recordings by lawrence livermore national laboratory llnl nts network stations the spectra are corrected for instrument response distance and station effects and then network averaged explicit information regarding geophysical working point properties depth of burial and some announced yields for nts explosions springer et al 2002 is utilized for the spectral modeling scaling of pn pg and lg corner frequencies with source yield is examined for sets of explosions at yucca flat pahute mesa and rainier mesa with similar material properties medium type density velocities and gas porosity the unes are limited to those in media with gas porosity of 10 or less so that a source spectral model with a rolloff of f 2 is applicable model comparisons are also examined for regional p lg discriminants a key result is that lg corner frequencies for ntsunes exhibit similar scaling with source size as for p waves but shifted lower analogous to observations by fisk 2006 for the lop nor semipalatinsk and novaya zemlya test sites this appears to corroborate an important effect that is that major contributions to s wave generation by explosions occur near the source with a similar length scale comparable to the elastic radius as for p waves from explosions although the explicit physical mechanism is not yet understood the implications are important regarding where and perhaps how s waves are predominantly generated by explosions a related key result is that the increasing separation of p lg at higher frequencies between nts explosions and earthquakes has a consistent model based explanation as at other nuclear test sites in terms of the difference between explosion p and s corner frequencies

study on liquefaction mechanism of saturated sand considering stress redistribution abstract most of the saturated soil in actual condition is anisotropically consolidated and can liquefy during minor earthquake based on the analysis of stress state in actual soil the present paper considers that the stress redistributed during loading process which result in the liquefaction however in present conventional element tests the liquefaction in anisotropically consolidated saturated sands acs cannot be induced under dynamic cyclic loading without stress reversal it contributes to the uncertainty about the liquefaction resistance of soil and the development model of excess pore water pressure pwp a brief theoretical interpretation within the theory of limit state of soils is given to explain why the liquefaction in acs could not be induced using the conventional element test under dynamic cyclic load with low or moderate amplitude and the validity of the theoretical analysis is verified by experiments the stress redistribution is realized by confining the lateral deformation based on the conventional test and the liquefaction in acs under minor cyclic load is realized furthermore a new concept called continued liquefaction is proposed apart from transient liquefaction the pwp the total confining pressure and the total vertical stress are always at the same level and the mean effective stress of sands is always zero in the continued liquefaction stage finally a suggestion that the development model of pwp should be established on the basis of the ratio of the pwp to the initial vertical stress is recommended

geotechnical mitigation strategies for earthquake surface fault rupture abstractsurface fault rupture can be damaging to structures built on or near active faults if the hazard is not addressed properly fault induced angular distortion and lateral ground strain can cause beams to yield and eventually lead to structural collapse when avoidance is not possible geotechnical mitigation strategies can be used these strategies include spreading fault displacement over a large area causing the structure to respond with rigid body movement and diverting the fault rupture around the structure the effectiveness of these strategies can vary from protecting life safety to preventing significant damage and can be effective for a range of dip slip fault displacements earth fills should be sufficiently thick and ductile to prevent the underlying fault dislocation from developing at the ground surface thick rc mat foundations proved to be especially effective in shielding the superstructure from the damaging effects of the underlying ground movements although more challenging to im

dilation angle and liquefaction potential its proposed that the dilation angle or expansion rate of the sand during shear is a measurement describing the initial state of the sand which could be obtained in both the laboratory and the field and which could give a measure of liquefaction resistance the dilation angle can be readily obtained in the laboratory from drained triaxial or simple shear tests and in the field it can be obtained from self boring pressuremeter tests a liquefaction resistance chart based on dilation angle rather than on corrected blow count is presented from this chart an estimate of the field liquefaction resistance of saturated sands can be obtained from dilation angles from self boring pressuremeter tests details are given of the analysis procedure in which the dilation angle was obtained as a function of relative density by performing drained static simple shear tests on the same sand over a range of relative densities and observing volume change characteristics the relations between liquefaction resistance relative density and dilation angle are discussed liquefaction resistance can be correlated with relative density corrected dilation angle or corrected blow count and a chart showing liquefaction resistance in terms of these three parameters is shown the latter indicates that liquefaction is not likely to occur regardless of the stress level provided the relative density is in excess of 75 the corrected dilation angle is greater than 16 degress or the corrected blow count exceeds 20

numerical simulation of building response on liquefiable sand abstractthe effective design of earthquake resistant structures and liquefaction mitigation techniques requires an improved understanding of the development and consequences of liquefaction in this paper the results from centrifuge experiments of structures with shallow foundations on liquefiable sand were used to evaluate the predictive capabilities of a state of the practice numerical tool fully coupled numerical simulations with the ubcsand model implemented in flac 2d captured building settlements measured in these experiments reasonably well for one scaled input motion mostly within factors of 0 7 and 1 8 the soil model captured the overall contribution of deviatoric displacement mechanisms and localized volumetric strains during partially drained cyclic loading the primary limitation of the model became evident for slower rates of earthquake energy buildup when the extent of soil softening and building displacement was overestimated by up to a factor of 4 the observations from recent case hi

eastward travelling waves in the southern hemisphere stratosphere during the spring of 1983 this paper presents a case study of planetary waves in the southern hemisphere stratosphere during the spring of 1983 using the global temperature and geopotential height data provided by the united states national meteorological center nmc the eastward travelling wave of zonal wavenumber 2 with a period of 9 2 days persisted from mid september to early november it had a phase structure which showed only slight tilt with height and latitude while the quasi stationary wave 1 tilted westwards with increasing height and towards the equator during the vigorous period of the eastward travelling wave 2 the amplitude of the quasi stationary wave 1 varied with a period of about 10 days this variation was due to a coincidence between the phases of the stationary wave 1 and the eastward travelling wave 2 when the ridges of waves 1 and 2 overlap wave 1 amplitude reaches its maximum the active period of the travelling wave 2 is closely related to the seasonal change in the mean zonal winds in 1983 the eastward travelling wave 2 became vigorous after the zonal mean westerly jet moved rapidly poleward and downward compared with the other 5 years for which we have data the wind structure for the month of september 1983 was peculiar because of the stronger meridional curvature of the westerly jet

phase and spectral ratio discrimination between nts earthquakes and explosions part i empirical observations seismic discrimination of small magnitude mb 0 5 hz regional measurements in this study we evaluate the most promising short period discriminants p wave to s wave phase amplitude ratios and low to high frequency spectral amplitude ratios for a data set from the nevada test site the data consist of 130 underground nuclear explosions one very large chemical explosion and 50 earthquakes ranging from magnitude 2 to 6 recorded at two broadband digital seismic stations operated by lawrence livermore national laboratory in contrast with much previous discrimination work in the western united states the common stations and paths for all the events in this study allow the discriminants to be evaluated without applying propagation corrections and differences between events can be ascribed to very near source effects the source effects found to have the most influence on the discriminants in this study are depth for the earthquakes and the source medium properties of gas porosity density and velocity for the explosions the phase amplitude ratio discriminants tested are pn lg and pg lg both show little dependence on magnitude and work better at higher frequencies and when averaged over the two stations at 6 to 8 hz pn lg discriminates all except the shallowest earthquakes while pg lg discriminates all but the high gas porosity explosions low to high frequency spectral amplitude ratio discriminants were tested in each of the phases pn pg lg and lg coda the explosions show significant dependence on source material properties such as gas porosity all the spectral ratios show dependence on magnitude and for 1 2 hz 6 8 hz none performs well below magnitude 3 5 of the spectral ratios lg coda performs the best at least in part because of its extremely small interstation variability discriminating all but the low gasporosity explosions the best discriminant performance is given by combining phase and spectral ratios a sum of the logarithmic values of pn lg pg lg and the lg coda discriminates all but two of the shallowest earthquakes the source medium dependence of the discriminants suggests that discrimination performance differences between the western united states and other regions of the world may be due more to source property differences than differences in the regional path simply put western united states discriminant studies differ from those in the rest of the world because of the lack of explosions in very high gas porosity low velocity materials outside of the nevada test site

on near source earthquake triggering 1 when one earthquake triggers others nearby what connects them two processes are observed static stress change from fault offset and dynamic stress changes from passing seismic waves in the near source region r 50 km for m 5 sources both processes may be operating and since both mechanisms are expected to raise earthquake rates it is difficult to isolate them we thus compare explosions with earthquakes because only earthquakes cause significant static stress changes we find that large explosions at the nevada test site do not trigger earthquakes at rates comparable to similar magnitude earthquakes surface waves are associated with regional and long range dynamic triggering but we note that surface waves with low enough frequency to penetrate to depths where most aftershocks of the 1992 m 5 7 little skull mountain main shock occurred 12 km would not have developed significant amplitude within a 50 km radius we therefore focus on the best candidate phases to cause local dynamic triggering direct waves that pass through observed near source aftershock clusters we examine these phases which arrived at the nearest 200 270 km broadband station before the surface wave train and could thus be isolated for study direct comparison of spectral amplitudes of presurface wave arrivals shows that m 5 explosions and earthquakes deliver the same peak dynamic stresses into the near source crust we conclude that a static stress change model can readily explain observed aftershock patterns whereas it is difficult to attribute near source triggering to a dynamic process because of the dearth of aftershocks near large explosions

effect of waste rock inclusions on the seismic stability of an upstream raised tailings impoundment a numerical investigation over the years seismic activity has been a relatively common cause of tailings impoundment failure the flow of liquefied tailings from such ruptures can result in very severe consequences includ

shear waves produced by explosive sources shear waves s waves created by an explosion at or near an interface have been observed in experimental field studies and in mathematical model studies but the observations have been separated so widely in time place and publication that their relation has not been apparent recent papers on the s wave are referenced here and study of their implications for field work is recommended from earlier papers illustrations of s waves designated source shear waves at three gulf coast sites were selected for examples the source shear wave was found to be strong directional and the likely cause of downgoing compressional waves by wave conversion the mathematical s wave and the source shear waves are sv waves at observation points along any line through the source position if the line has an inclination of 45 degrees along a vertical line through the source the wave is not detected because of difficulties in assembling observations at points both deep and of large offset it is highly desirable to

seismic source theory in stratified anisotropic media we extend seismic source theory to general anisotropic media for the numerical evaluation of spectral amplitudes of point sources in multilayered anisotropic crustal models first we obtain an explicit representation of the spectral elastodynamic green s tensor in general homogeneous anisotropic media as a sum of three integrals over the corresponding three slowness surfaces the multidimensional stationary phase principle is then applied to derive an asymptotic approximation at the far field in the case of azimuthally isotropic media we offer an alternative representation of the green s tensor and its ensuing displacements fields in the form of an exact hankel transform over the horizontal wave number variable the total field is specified here in terms of two potentials an sh potential and a mixed quasi transverse quasi longitudinal potential both of which assume the role of two scalar green s functions the availability of the green s tensor in analytical form enables one to obtain readily numerical solutions for a wide selection of media and sources it is shown that the radiation field of an explosion has the following new features 1 quasi transverse waves are created with four and eight lobe patterns 2 quasi longitudinal waves are generated for the collatitudinal displacement with four lobe patterns 3 the energy ratio sv p may reach the value of 20 for more than 50 of the azimuths in crustal structures such as tuff and shales and 4 radiation patterns for vertical shear waves are created which are indistinguishable from corresponding waves produced by earthquake faults our formalism allows us to establish a haskell type matrix algorithm for a multilayered azimuthally isotropic half space which enables us to calculate body waves and surface waves in real earth crustal models

analysis of canlex liquefaction embankments prototype and centrifuge models un objectif principal du projet canadien d etude de la liquefaction canadian liquefaction experiment canlex etait de verifier les procedures d analyse pour la prediction des phenomenes de liquefaction a cette fin deux cas de chargement ont ete realises un chargement sur le terrain comprenant un remblai construit sur une couche de fondation de sable l che et un essai au centrifuge realise sur un modele de la structure prototype tant l essai sur le terrain que l essai au centrifuge ont ete planifies de facon a induire une rupture par liquefaction statique les caracteristiques mecaniques fondamentales de la couche de fondation ont ete determinees dans des essais en laboratoire sur des elements triaxiaux et cisaillement simple ces caracteristiques ont ete d abord obtenues sur un element en utilisant un modele de comportement contrainte deformation elasto plastique le prototype et les structures a l echelle ont alors ete modelises comme un ensemble de tels elements le drainage etait un facteur tres important durant le chargement et etait directement incorpore dans la procedure de l analyse les resultats predits concordent bien tant avec l essai au centrifuge qu avec les mesures sur le terrain

water film in liquefied sand and its effect on lateral spread a one dimensional 1d saturated sand layer of 2 m in thickness in which a silt seam is sandwiched is liquefied by an instant shock it is found that a water film is easily formed beneath the silt seam with a thickness as thin as a few millimeters just after liquefaction in loose sand and that the film lasts longer than the postliquefaction settlement the effect of the water film on pore pressure distribution and sand settlement is intensively studied one gram shake table tests are then carried out for 2d models with or without seams of silt within a saturated sand layer in the former case water films formed beneath silt seams just after liquefaction enable the soil mass above them to glide because of an unbalanced force along the water films not only during but also after shaking in the latter case the soil deforms continuously mostly during shaking and stops afterward thus a significnat effect of water films formed beneath thin low permeability sublayers in a liquefied loose sand on the failure mode and timing in lateral spread is clearly demonstrated by these simple model tests

midwinter warmings in the southern hemisphere stratosphere in 1988 an analysis was made of intense midwinter warmings which took place in the southern hemisphere stratosphere during august september 1988 by using the southern hemispheric data set up to the 1 mb level provided by the japan meteorological agency it is found that the 30mb temperature increase over eastern antarctica about 60 k for 10 days from 22 august to 1 september is associated with the amplification of a quasi stationary planetary wave of zonal wavenumber 1 the enhancement of wave 1 appears quasi periodically with a period of about 2 weeks during the midwinter of 1988 clear evidence is presented to show that the quasi periodic amplification of wave 1 is due to the wave wave interaction between the quasi stationary forced wave of wavenumber 1 and the eastward travelling wave of wavenumber 2 it is emphasized therefore that the mechanism of warming in this case is quite different from that of the transient vertical propagation of a planetary wave forced from below as observed in the northern hemisphere winter

two dimensional array measurements of near source ground accelerations abstract two dimensional array measurements of near source accelerations have been conducted 6 km from the 5 6 m l explosion colwick at pahute mesa nevada test site the three component nine station array measured 400 m across with interstation spacing of 100 m wavenumber spectra and beam forming stacking were used to measure apparent velocities and directions of propagation of acceleration waveforms the robustness of individual station accelerograms was measured with frequency domain coherency estimates and cross correlation functions the dependence of interstation coherency upon station spacing and frequency band was also examined wave propagation in pahute mesa can be characterized by p sv and sh wave motion in a horizontally homogeneous medium for frequencies below 5 hz strong incoherent scattered signals are present above 5 hz on all components the fraction of scattered energy can be estimated and treated as signal generated noise a strong sh pulse was observed to propagate across the array measured phase velocity arrival time and direction of propagation require cogeneration of sh with p sv energy by the explosion colwick weaker and more diffuse transverse acceleration signals arrive coincident with the p wave and during the time prior to s these arrivals are interpreted as forward scattered energy from the p wave the small array permitted a refinement of the horizontally averaged s wave velocity model for pahute mesa the mesa is characterized by a low velocity layer 600 m thick above the water table with a steep velocity gradient immediately below the coherency measurements indicate the upper 1 km or more of pahute mesa is heterogeneous at scale lengths less than 1 km

propagation velocity of shockwaves and pressure waves in soil and rock a variable pressure wave propagation velocity is developed and analyzed in ground materials which may be characterized by an exponential density pressure relationship the peak overpressure dependence is minor in the low pressure range and the propagation velocity of the pressure wave is essentially a constant in fact it is the seismic p wave propagation velocity pressure dependence becomes increasingly more significant at peak overpressures exceeding 1 kbar 108 pa at very high pressure levels encountered only in shockwaves at and above 10 kbar 109 pa the initial mechanical characteristics of the ground materials become less significant and the propagation velocity depends primarily upon the peak overpressure

transmission of seismic waves across single natural fractures fractures and other nonwelded contacts are important mechanical and hydrological features of rock masses their effects on seismic wave propagation can be modeled as a boundary condition in the seismic wave equation seismic stress is continuous across such a boundary but seismic particle displacement and seismic particle velocity are not the complete solutions for seismic wave reflection conversion and transmission across a displacement and velocity discontinuity between two half spaces with different densities and elastic properties are derived for all angles of the incident wave the ratio between the seismic stress across this boundary and the seismic particle displacement and velocity are described by a specific stiffness and a specific viscosity respectively a displacement discontinuity results in frequency dependent reflection and transmission coefficients and a frequency dependent group time delay the velocity discontinuity results in frequency independent coefficients and zero delay results of laboratory experiments on compressional and shear wave transmission across three different natural fractures in a quartz monzonite are described measurements were made at different effective stresses under dry and saturated conditions at room temperature it is shown that the effect of these fractures on the spectral amplitudes for compressional and shear pulses transmitted across these fractures are described well by a displacement discontinuity for compressional pulses under dry and saturated conditions and by a combined displacement and velocity discontinuity for shear wave pulses under dry and saturated conditions values of specific stiffness and specific viscosity vary between fractures and increase with increasing effective stress as does the static specific stiffness of these fractures changes in the spectral amplitudes of transmitted pulses are also analyzed in terms of attenuation using the seismic quality factor q which is found to be a function of frequency

lg coda methods applied to nevada test site events spectral peaking and yield estimation abstract we have applied the regional s wave coda calibration technique of mayeda et al 2003 to earthquake data in and around the nevada test site nts using four regional broadband stations from the lawrence livermore national laboratory llnl seismic network we applied the same path and site corrections to tamped nuclear explosion data and averaged the source spectra over the four stations narrowband coda amplitudes from the spectra were then regressed against inferred yield based on the regional m b pn magnitude of denny et al 1987 along with the yield formulation of vergino and mensing 1990 we find the following 1 the coda derived spectra show a peak that is dependent upon emplacement depth not event size 2 source size estimates are stable for the coda and show a dependence upon the near source strength and gas porosity 3 for explosions with the same m b pn or inferred yield those in weaker material have lower coda amplitudes at 1 3 hz

seismic deformation analysis of tuttle creek dam to facilitate the design of seismic remediation for tuttle creek dam in east central kansas a seismic finite difference analysis of the dam was performed using the software flac and the ubcsand and ubctot soil constitutive models the flac software has a key advantage because it can use calibrated site specific constitutive models earlier deformation analyses using a hyperbolic constitutive model for the foundation fine grained materials did not properly represent the modulus and strength reduction and predicted extremely large permanent deformations cyclic triaxial laboratory tests using high quality samples and in situ vane shear tests were used to calibrate the flac constitutive model herein the resulting flac analysis of the unremediated dam predicted an upstream slope toe deformation of about 0 6 m a crest settlement of about 0 6 m and a downstream slope toe deformation of about 1 5 m using the design ground motion based on the estimated permanent deformations and other factors it was decided

permeability and stiffness of sands at very low effective stresses loose saturated sandy soils may undergo liquefaction under cyclic loading generating positive excess pore pressures due to their contractile nature and inability to dissipate pore pressures rapidly during earthquake loading these liquefied soils have a near zero effective stress state and hence have very low strength and stiffness causing severe damage to structures founded upon them the duration for which this near zero effective stress state persists is a function of the rate of reconsolidation of the liquefied soil which in turn is a function of the permeability and stiffness of the soil at this very low effective stress existing literature based on observation of physical model tests suggests that the consolidation coefficient cv associated with this reconsolidation of liquefied sand is significantly lower than that of the same soil at moderate stress levels in this paper the results of a series of novel fluidisation tests in which permeability k and coefficient of consolidation cv were indep