lithospheric and upper mantle structure of southern tibet from a seismological passive source experiment fifteen seismic stations were operated with about 20 km spacing in southern tibet across the zangbo suture the collision zone between india and asia between may and october 1994 as part of the international deep profiling of tibet and the himalaya project indepth ii for wide angle recording of the controlled source experiment and for passive earthquake recording in addition a dense deployment 4 km spacing of stations within the german depth profiling of tibet and the himalayas gedepth project also recorded a number of teleseismic earthquakes the third data source used in this study is the records of the permanent broadband station at lhasa teleseismic records have been obtained in sufficient quantity and quality to derive an image of the structure of the lithosphere and upper mantle from p to s converted phases important results are as follows the moho at 70 80 km and a second discontinuity at 50 60 km depth are observed over the entire profile south and north of the zangbo suture the data from the gedepth dense array enable the detection of inclined structures penetrating the crust at the zangbo suture a pronounced low velocity zone exists north of the zangbo suture at about 10 20 km depth the locations of the upper mantle discontinuities at 410 and 660 km depth are in agreement with the global reference model iasp91 kennett 1991 over a large region of the himalaya and southern tibet

prediction of the behaviour of landslide dams using a geomorphological dimensionless index landslide dams are a common phenomenon they form when a landslide reaches the bottom of a river valley causing a blockage the first effect of such a dam is the infilling of a lake that inundates the areas upstream while the possibility of a sudden dam collapse with a rapid release of the impounded waters poses a higher flood risk to the downstream areas the results of the main inventories carried out to date on landslide dams have been examined to determine criteria for forecasting landslide dam evolution with particular emphasis on the assessment of dam stability not all landslides result in the blockage of a river channel this only occurs with ones that can move a large amount of material with moderate or high velocities in most cases these landslides are triggered by rainfall events or high magnitude earthquakes a relationship also exists between the volume of the displaced material and the landslide dam stability several authors have proposed that landslide dam behaviour can be forecast by defining various geomorphological indexes that result from the combination of variables identifying both the dam and the dammed river channel further developments of this geomorphological approach are presented in this paper by the definition of a dimensionless blockage index starting with an analysis of 84 episodes selected worldwide it proved to be a useful tool for making accurate predictions concerning the fate of a landslide dam copyright 2002 john wiley sons ltd

turning ray tomography using a low spatial frequency model parameterization a linear least squares inversion is applied to the turning ray first arrival times of a shallow marine seismic reflection data set to estimate the slowly varying laterally and vertically components of the near surface velocity field the velocity model is represented with a low spatial frequency parameterization 2d cubic b splines designed specifically for the predicted components of the data this model parameterization effectively decouples the slowly varying background from the higher spatial frequency component of the velocity field produced by shallow low velocity gas charged sands and allows the solution to be obtained in a single iteration the observed first arrival times background and shallow anomaly induced perturbations and the slowly varying first arrival times related to the background velocity are inverted separately similar velocity model estimates result demonstrating the decoupling imposed by the b spline model parameterization the background velocity and the low velocity anomalies are best treated as separate inverse problems using very different model parameterizations ray tracing a synthetic model containing local low velocity anomalies embedded in a smooth background does not accurately predict the anomaly induced first arrival time perturbations seen in the field data acoustic finite difference waveform modeling shows that reflections and diffractions from the anomalies interfere with the diving wave first arrivals first arrival times picked from the full waveform synthetics more accurately predict the field data first arrival times

continental crust composition constrained by measurements of crustal poisson s ratio deciphering the geological evolution of the earth s continental crust requires knowledge of its bulk composition and global variability the main uncertainties are associated with the composition of the lower crust seismic measurements probe the elastic properties of the crust at depth from which composition can be inferred of particular note is poisson s ratio this elastic parameter can be determined uniquely from the ratio of p to s wave seismic velocity and provides a better diagnostic of crustal composition than either p or s wave velocity alone1 previous attempts to measure have been limited by difficulties in obtaining coincident p and s wave data sampling the entire crust2 here we report 76 new estimates of crustal spanning all of the continents except antarctica we find that on average increases with the age of the crust our results strongly support the presence of a mafic lower crust beneath cratons and suggest either a uniformitarian craton formation process involving delamination of the lower crust during continental collisions followed by magmatic underplating or a model in which crust formation processes have changed since the precambrian era

using multiple logistic regression and gis technology to predict landslide hazard in northeast kansas usa abstract landslides in the hilly terrain along the kansas and missouri rivers in northeastern kansas have caused millions of dollars in property damage during the last decade to address this problem a statistical method called multiple logistic regression has been used to create a landslide hazard map for atchison kansas and surrounding areas data included digitized geology slopes and landslides manipulated using arcview gis logistic regression relates predictor variables to the occurrence or nonoccurrence of landslides within geographic cells and uses the relationship to produce a map showing the probability of future landslides given local slopes and geologic units results indicated that slope is the most important variable for estimating landslide hazard in the study area geologic units consisting mostly of shale siltstone and sandstone were most susceptible to landslides soil type and aspect ratio were considered but excluded from the final analysis because these variables did not significantly add to the predictive power of the logistic regression soil types were highly correlated with the geologic units and no significant relationships existed between landslides and slope aspect

spectral matrix filtering applied to explosion seismology data examples from the western alps abstract a multichannel filtering method is described and its application to explosion seismology data presented the processing method uses the information contained in the eigenelements of the spectral matrix and allows enhancement of the most coherent signal by improvement of the signal to noise ratio the processing of synthetic data shows the performance of the method when the noise level of the section varies and when the reflected signal is differently time shifted the signal to noise ratio always increases allowing better determination of arrival times on real data it is shown that after processing the picking of events is easier and reflectors which were previously invisible may become visible

crustal structure beneath aso caldera southwest japan as derived from receiver function analysis abstract aso volcano experienced a huge pyroclastic eruption 90 thousand years ago and formed a large caldera 18 km 25 km in order to test the hypothesis of a magma body in the mid and lower crust that has been suggested geophysically and geochemically we investigated seismic velocity discontinuities and velocity structure beneath aso caldera using receiver functions and a genetic algorithm inversion we confirm the existence of the moho at depths between 30 km and 35 km and a large velocity anomaly should exist in the deep portion of the crust beneath aso caldera from imaging of receiver functions observed only at stations outside the caldera as a result of a more detailed examination with ga inversion a low velocity layer is detected at depths between 10 km and 24 km beneath the western part of the caldera s wave velocity of the layer is estimated to be 2 0 2 4 km s we estimate that the low velocity layer contains at most 15 melt or 30 aqueous fluid the layer exists near the conrad and at the same depths as the swarm of the low frequency earthquakes and a compressional and dilatational deformation source which are expected to be caused by fluid movement beneath the middle eastern part of the caldera fluid contained in the layer might be related with huge pyroclastic eruptions of aso volcano

discriminant analysis of the geomorphic characteristics and stability of landslide dams article i nfo landslides can cause the formation of dams but these dams often fail soon after lake formation thus rapidly evaluating the stability of a landslide dam is crucial for effective hazard mitigation this study utilizes discriminant analysis based on a japanese dataset consisting of 43 well documented landslide dams to determine the significant variables including log transformed peak flow or catchment area and log transformed dam height width and length in hierarchical order which affect the stability of a landslide dam the high overall prediction power 88 4 of the 43 training cases are correctly classified and the high cross validation accuracy 86 demonstrate the robustness of the proposed discriminant models phwl with variables including log transformed peak flow and log transformed dam height width and length and ahwl with variables including log transformed catchment area and log transformed dam height width and length compared to a previously proposed dbi index based graphic approach the discriminant model ahv which uses the log transformed catchment area dam height and dam volume as relevant variables shows better ability to evaluate the stability of landslide dams although these discriminant models are established using a japanese dataset only the present multivariate statistical approach can be applied for an expanded dataset without any difficulty when more completely documented worldwide landslide dam data are available

gis techniques and statistical models in evaluating landslide hazard geographical information systems gis and numerical cartography may greatly facilitate the development and use of statistical models for the assessment of regional landslide hazard from a small drainage basin located in central italy relevant geological and geomorphological factors were collected and processed by applying gis technology in particular modules were used which both generate high fidelity digital terrain models and automatically partition the terrain into main slope units the resulting information was then analysed by discriminant analysis which enabled landslide hazard and risk to be evaluated in each slope unit although not lacking drawbacks the method proved to be a feasible and cost effective approach to landslide susceptibility assessment and mapping

imaging the moho and subducted oceanic crust at the isthmus of tehuantepec mexico from receiver functions using teleseismic data recorded along a transect which we call veox for veracruz oaxaca seismic line of 46 broadband stations installed across the isthmus of tehuantepec in southern mexico we obtained receiver functions and stacked them to study the moho topography and back projected them to visualize the subducted slab geometry beneath the isthmus we observed a back azimuth dependent moho thickness across the transect particularly beneath the los tuxtlas volcanic field also we observed the cocos plate which subducts with an angle of 26 between 140 and 310 km from the trench comparison with regional seismicity indicates that it occurs below the oceanic crust

shear wave anisotropy of the upper and lower crusts estimated by stripping analysis of ps converted waves abstract the anisotropic structure of the crust is investigated by measuring the shear wave polarization anisotropy of the ps phases converted at the conrad and moho discontinuities the ps converted phases are identified on the p wave receiver functions which are constructed from teleseismic records at the f net and hi net stations in the kinki chugoku shikoku and kyushu districts in southwest japan the ps phase traveling through an anisotropic layer undergoes shear wave splitting which is described by splitting parameters fast polarization direction fpd and split time the upper and lower crustal anisotropies are estimated from the splitting parameters of the conrad and moho ps phases respectively which are determined by a waveform cross correlation method to reliably estimate the lower crustal anisotropy the moho ps phase is corrected for the shear wave splitting effect in the upper crust by a stripping method because the upper crustal anisotropy masks the anisotropic behavior of the ps phase in the lower crust the split times estimated for the upper and lower crusts are less than 0 2 s but their fpd characteristics differ from each other the fpds in the upper crust are predominantly in the e w direction the fpds in the lower crust range from nw se to ne sw in the region with the philippine sea phs slab subduction but from ne sw to se nw in the region without slab subduction thus seismic anisotropy exists in both the lower and upper crusts and slab subduction significantly influences the lower crustal anisotropy the most likely cause for the upper crustal anisotropy is the alignment of vertical cracks induced in the upper crust by the tectonic stress while the lower crustal anisotropy is attributed to the lattice preferred orientation of rock forming minerals along with ductile deformation of the lower crust

statistical approach to earthquake induced landslide susceptibility susceptibility analysis for predicting earthquake induced landslides has most frequently been done using deterministic methods multivariate statistical methods have not previously been applied in this study however we introduce a statistical methodology that uses the intensity of earthquake shaking as a landslide triggering factor this methodology is applied in a study of shallow earthquake induced landslides in central western taiwan the results show that we can accurately interpret landslide distribution in the study area and predict the occurrence of landslides in neighboring regions this susceptibility model is capable of predicting shallow landslides induced during an earthquake scenario with similar range of ground shaking without requiring the use of geotechnical groundwater or failure depth data

receiver functions of seismic waves in layered anisotropic media application to the estimate of seismic anisotropy abstract we investigate the effect of seismic anisotropy on p wave receiver functions calculating synthetic seismograms for p wave incidence on multilayered anisotropic structure with hexagonal symmetry the main characteristics of the receiver functions affected by the anisotropy are summarized as 1 appearance of seismic energy on radial and transverse receiver functions 2 systematic change of p to s ps converted waveforms on receiver functions as ray back azimuth increases and 3 reversal of the ps phase polarity on the radial receiver function in a range of the back azimuth another important influence is shear wave splitting of the ps converted waves and other later phases reverberated as s wave by numerical experiments using synthetic receiver functions we demonstrate that the waveform cross correlation analysis is applicable to splitting ps phases on receiver functions to estimate the seismic anisotropy of layer structure advantages to utilizing the ps phases are 1 they appear more clearly on receiver functions than on seismograms and 2 they inform us about what place along the seismic ray path is anisotropic real analysis of shear wave splitting is executed to the moho generated ps phases that are identified on receiver functions at six seismic stations in the chugoku district southwest japan the time lags between the two arrivals of the split ps phases are estimated at 0 2 0 7 sec and the polarization directions of the fast arrival components are from north south to northeast southwest this result is consistent with recent results of shear wave splitting measurements and the trend of linear epicenter distributions of crustal earthquakes and active fault strikes in the chugoku district

logistic regression model for predicting the failure probability of a landslide dam landslides may obstruct river flow and result in landslide dams they occur in many regions of the world the formation and disappearance of natural lakes involve a complex earth surface process according to the lessons learned from many historical cases landslide dams usually break down rapidly soon after the formation of the lake regarding hazard mitigation prompt evaluation of the stability of the landslide dam is crucial based on a japanese dataset this study utilized the logistic regression method and the jack knife technique to identify the important geomorphic variables including peak flow or catchment area dam height width and length in sequence affecting the stability of landslide dams the resulting high overall prediction power demonstrates the robustness of the proposed logistic regression models accordingly the failure probability of a landslide dam can also be evaluated based on this approach ten landslide dams formed after the 1999 chi chi earthquake the 2008 wenchuan earthquake and 2009 typhoon morakot with complete dam geometry records were adopted as examples of evaluating the failure probability the stable tsao ling landslide dam which was induced by the chi chi earthquake has a failure probability of 27 68 using a model incorporating the catchment area and dam geometry on the contrary the tangjiashan landslide dam which was artificially breached soon after its formation during the wenchuan earthquake has a failure probability as high as 99 54 typhoon morakot induced the siaolin landslide dam which was breached within one hour after its formation and has a failure probability of 71 09 notably the failure probability of the earthquake induced cases is reduced if the catchment area in the prediction model is replaced by the peak flow of the dammed stream for these cases in contrast the predicted failure probability of the heavy rainfall induced case increases if the high flow rate of the dammed stream is incorporated into the prediction model consequently it is suggested that the prediction model using the peak flow as causative factor should be used to evaluate the stability of a landslide dam if the peak flow is available together with an estimation of the impact of an outburst flood from a landslide dammed lake the failure probability of the landslide dam predicted by the proposed logistic regression model could be useful for evaluating the related risk

regional variations of the shear wave polarization anisotropy in the crust and mantle wedge beneath the tohoku district abstract we investigated the regional variations of the shear wave polarization anisotropy in the upper crust lower crust and mantle wedge beneath the tohoku district in the northeast japan arc the shear wave splitting parameters fast polarization direction fpd and split time for the upper and lower crusts are estimated by shear wave splitting analysis of the ps phases which are generated by the conversion of a p wave into an s wave at the conrad and moho discontinuity interfaces the splitting parameters for the mantle wedge are determined by splitting analysis of the slab ps phase converted at the oceanic crust on the subducting pacific slab and the direct s waves from deep focus earthquakes located just below seismic stations the ps phases are identified on the p wave receiver functions constructed from the teleseismic records to accurately determine the splitting parameters for the lower crust from the moho ps phase the ps phase should be corrected for the shear wave splitting effect in the upper crust similarly to estimate the mantle wedge anisotropy the direct s wave and slab ps phase must be corrected for the splitting effect in the crust the anisotropies of the crust and mantle wedge are estimated from the corrected ps phases and direct s waves the anisotropy of the upper crust exhibits a regional variation where fpd of the split shear wave is predominant in the n s direction in the pacific coast area and in the e w direction in the rest of the tohoku district the split time is less than 0 2 s the upper crustal anisotropy is attributed to the alignment of vertical cracks induced in the upper crust by tectonic stress in the lower crust fpd is predominant in the e w direction with a split time similar to that in the upper crust and the anisotropy of the lower crust is due to the lattice preferred orientation of rock forming minerals in the mantle wedge fpd is predominant in the n s direction trench parallel in the fore arc side of the volcanic front but in the e w direction trench perpendicular in the back arc side the split time in the mantle wedge is similar to that of the upper crust the most likely cause for the trench perpendicular anisotropy in the back arc mantle wedge is the lattice preferred orientation of a type olivine along flows of the secondary mantle convection for trench parallel anisotropy in the fore arc mantle wedge we considered two possible causes the preferred orientation of b type olivine along the secondary mantle convection and that of dry olivine along the trench parallel flow produced by the along strike dip variation of the pacific slab however we could not determine which one is the origin

from mountain summits to roots crustal structure of the eastern alps and bohemian massif along longitude 13 3 e abstract the crustal structure of the eastern alps and adjacent tectonic units investigated in this work sheds new light on the relationship of surface geology to geodynamic processes operating at depth of particular interest are the nature of a previously proposed moho gap south and east of the tauern window the plate tectonic affinity of the steeply dipping eastern alpine slab and the relationship of the alps to the neogene sedimentary basins and the bohemian massif to address these questions we use various seismological approaches based on converted waves from the temporary passive experiment easi eastern alpine seismic investigation a complementary experiment of the alparray project the easi is a densely spaced 540 km long seismic network along 13 3 e we operated for more than a year the uppermost crustal structures in and near the alps exhibit dipping layers and or tilted anisotropy that correlate well with surface geology observations the moho despite its variable appearance is clearly identified along most of the swath the variscan lithospheric blocks beneath the bohemian massif are imaged with sub vertical boundaries beneath the eastern alps the shape of the moho is consistent with bi vergent orogenic thickening with a steeper and deeper reaching adriatic plate plunging northwards beneath the european plate in the north at the junction of these plates at depth around the previously proposed moho gap the root of the eastern alps is a broad trough characterized by a zone of low velocity gradient that is up to 20 km thick transitioning between crust and mantle our receiver function results corroborate earlier lithosphere upper mantle seismic tomography images and highlight the adriatic affinity of the eastern alpine slab the zigzag deployment pattern of stations in the easi experiment also allows distinction of short wavelength variations perpendicular to the profile both within the shallow and the deep crust this underlines the importance of applying 3d imaging in complex geodynamic systems

archean and proterozoic crustal evolution evidence from crustal seismology seismic velocity models for archean and proterozoic provinces throughout the world are analyzed the thickness of the crust in archean provinces is generally found to be about 35 km except at collisional boundaries whereas proterozoic crust has a significantly greater thickness of about 45 km and has a substantially thicker high velocity 7 0 km s layer at the base we consider two models that may explain these differences the first model attributes the difference to a change in the composition of the upper mantle the higher temperatures in the archean mantle led to the eruption of komatiitic lavas resulting in an ultradepleted lithosphere unable to produce significant volumes of basaltic melt proterozoic crust developed above fertile mantle and subsequent partial melting resulted in basaltic underplating and crustal inflation in the second model convection in the hot archean mantle is considered to have been too turbulent to sustain stable long lived subduction zones by the proterozoic the mantle had cooled sufficiently for substantial island and continental arcs to be constructed and the high velocity basal layer was formed by basaltic underplating

regional variation in shear wave polarization anisotropy of the crust in southwest japan as estimated by splitting analysis of ps converted waves on receiver functions abstract regional variation in shear wave polarization anisotropy of the crust is investigated in the kyushu chugoku shikoku and kinki districts southwest japan using ps converted phases generated at the moho discontinuity the ps phases on radial and transverse receiver functions are analyzed to determine shear wave splitting parameters of fast polarization direction and time lag by waveform cross correction analysis as a result the fast polarization directions are shown to be obviously different between the chugoku district and the kyushu and shikoku districts which are separated from each other by the seto inland sea in the kyushu shikoku and south kinki districts the ps phases exhibit fast polarization directions ranging from e w to nw se the polarization directions are not only consistent with those of s waves from shallow crustal earthquakes but also parallel to the direction of maximum horizontal compression acting on southwest japan and the strike directions of metamorphic belts accretionary zones and rift zones thus the polarization anisotropy is understood to reflect mainly the upper crustal anisotropy that is attributable to stress induced vertical cracks and geological lineament structure on the other hand in the chugoku and north kinki districts fast polarization directions are in a range from n s to ne sw they are not consistent with the tectonic stress field and the s wave splitting observed for shallow crustal earthquakes the disagreement between the fast polarization directions estimated from the s waves and the ps converted phases is interpreted as arising because the lower crustal anisotropy attributed to mineral preferred orientation has a significant influence on the ps phase splitting the regional variation in ps phase polarization anisotropy of the crust in southwest japan is dependent on which anisotropy of the upper and lower crust is prominently reflected in the moho ps phase splitting

crust and mantle structure across the basin and range colorado plateau boundary at 37 n latitude and implications for cenozoic extensional mechanism we present new evidence on the seismic velocity and density of the crust and upper mantle along a 200 km long transect across the eastern basin and range and western colorado plateau at 37 n latitude receiver functions computed from the p waveforms recorded with 10 portable broadband stations deployed along the transect were used to estimate crustal thickness variations the crust is 30 35 km thick within the eastern basin and range and increases over a distance of 100 km at the western edge of the colorado plateau reaching a maximum of approximately 45 km east of the hurricane fault the timing of crustal multiples within the reciever functions were used to estimate the v p v s of the crust along the profile and we found that the western colorado plateau crust is characterized by a high poisson s ratio 0 28 0 29 indicative of a crust with an average mafic composition we estimated the upper mantle lid thickness along our profile based on teleseismic p wave travel times and constraints provided by gravity data our data and available geophysical constraints are most consistent with a lithosphere that thickens from an average thickness of 60 km beneath the basin and range to 100 km beneath the western colorado plateau although the basin and range lithosphere may have significant thickness variations the thick strong mafic crust and thicker mantle lid under the colorado plateau can account for the relative geologic stability and subdued magmatism of the plateau during laramide compression and cenozoic extension compared to surrounding regions the crustal and lithospheric thinning across the tectonic boundary occurs over a short distance 100 km suggesting it is a geologically young feature produced by a predominantly mechanical response to late cenozoic extension our new lithosphere model at 37 n latitude is consistent with the existence in early cenozoic time of a flat subducted slab at 100 km depth and a relict sevier laramide 50 60 km thick crustal welt and 60 100 pure shear extension values of 1 6 2 0 during the late cenozoic

global scale analysis of the mantle pds phases a global scale analysis of travel times of the mantle pds phases converted from p to s from the discontinuity at a depth d beneath the receiver is presented most of the data are related to p 410 s and p 660 s recorded by the broadband stations of geoscope incorporated research institutions for seismology iris and other networks in order to provide a good global scale coverage published measurements at 37 stations are complemented by our measurements at 45 stations lateral resolution of our data is many times higher than that of ss and its precursors previously used for similar purposes but we have fewer data in the oceans lateral variations of travel times of the major pds phases are strongly correlated with the lateral p and s velocity variations in the uppermost mantle as revealed by tomographic studies the scaling coefficient between the teleseismic s and p residuals as found from the variations of travel times of the major pds phases is around 3 7 for north america and around 3 3 for the rest of the world almost all the differential travel times t p 660 s t p 410 s are in the range of 1 s relative to the average value of 24 0 s if the lateral variations of the velocities within the mantle transition zone mtz can be neglected the corresponding variations of thickness of the mtz are in the range of 10 km relative to the standard depth of 250 km and do not show significant correlation with either velocities in the upper mantle above the mtz or with the variations of thickness of the mtz as found in some recent studies of precursors to ss there is a weak but marginally significant positive correlation between the variations of thickness of the mtz inferred from our data and the s velocity variations in the mtz as given by su et al 1994 this correlation suggests that both variables contain temperature dependent components lateral variability of the mtz is also manifested by extreme weakness of p 410 s at several locations this may indicate either anomalous topography on 410 km discontinuity or strong broadening of the otherwise sharp discontinuity at some stations there are arrivals that can be interpreted as p 520 s this interpretation implies that the strengh and or sharpness of 520 km discontinuity as well as its depth are laterally variable in a broad range

anisotropy of the mantle inferred from observations of p to s converted waves summary seismic anisotropy has been previously studied at depths usually not exceeding 100 or 150 km in this paper we present a method of analysis of seismic records which is very sensitive to azimuthal anisotropy and is applicable at almost any depth range the idea of the method is to detect and analyse the sh component of the waves converted from p to s in the mantle the procedure of record processing includes frequency filtering axis rotation transformation of the record to a standard form stacking the standardized sh component records of many seismic events and the harmonic analysis of amplitude as a function of the direction of wave propagation when applied to the long period records of norsar the procedure detected a converted wave with the properties implying the possibility of its propagation in a transversely isotropic medium with a horizontal axis of symmetry our preferred model postulates anisotropy of 1 per cent in a layer 50 km thick at the base of the upper mantle

azimuthal shear wave velocity anisotropy in the basin and range province using moho ps converted phases an eight station large aperture seismometer array was deployed in the basin and range province of west central nevada for the 1988 1989 program for array seismic studies of the continental lithosphere passcal passive source seismic experiment during the 10 months of data collection a total of 100 teleseismic events were recorded 30 source equalized p wave receiver functions show waveform variations in timing amplitude and polarity in the moho ps phase that is diagnostic of shear wave velocity anisotropy information regarding the crustal anisotropic component can be recovered through the ps phase since it is generated at the moho and is sensitive to shear wave splitting in the crust only we utilize single event stacked and array beam formed receiver functions to minimize the influence of structural variations and scattering on the observed converted phases analysis of shear wave splitting of the ps conversion from the crust mantle boundary indicates a fast azimuth of anisotropy oriented approximately nw se with observed time delays of 0 20 s this strongly suggests coherent crustal anisotropy with a fast direction perpendicular to the strike of fault block mountain ranges this fabric is most likely due to the preferred crystallographic orientation of seismically anisotropic minerals in the middle to lower crust rather than the distribution of basin and range upper crustal fracture systems

on the detection and identification of converted and reflected phases from receiver functions summary we develop a simple methodology to extract information related to crustal structure such as the mean vp vs ratio the magnitude of lateral variations and the presence of discontinuities from a selection of receiver functions we show that crustal phases can be detected and exploited on individual receiver functions two filtering techniques based on singular value decomposition and spectral matrix filtering are proposed to enhance the coherent phases in receiver functions additionally the relative traveltimes and slownesses between the different phases are utilized for a more reliable phase identification we apply these methods to data of station pru czech republic and compare the results with a classical time domain waveform inversion we find a good qualitative agreement between the simple crustal models inferred from the two approaches waveform modelling suggests that the identification of converted phases can still be ambiguous and other geophysical or geological constraints are needed

anisotropic upper mantle stratigraphy and architecture of the slave craton the earth s physical properties show a dominantly radial structure which is the result of compositional differentiation isochemical phase changes1 and rheological layering2 rheological layering is perhaps the most difficult to investigate using conventional seismological techniques because the seismic manifestation of this property elastic anisotropy may closely mimic the effects of isotropic heterogeneity3 nonetheless an improved characterization of earth s rheological structure promises important insights into such processes as plate dynamics and continental evolution here i present a methodology for effectively characterizing sharp transitions in anisotropic upper mantle structure using the coda of teleseismic p waves application to seismograms from the slave craton reveals a well developed stratigraphy at least in part anisotropic with major boundaries occurring at nominal depths of 75 135 and 195 km the geometry and sharpness of these discontinuities suggest a structural origin perhaps involving shallow subduction

the poisson ratio of the australian crust geological and geophysical implications the poisson ratio which depends on the vp vs ratio provides much tighter constraints on the crustal composition than either the compressional or the shear velocity alone the crustal poisson ratio can be determined from the joint analysis of the travel times of waves converted at the moho and of crustal multiples reflected at the top of the moho we have analyzed the records of the permanent stations installed on the australian continent complemented by the data of the skippy experiment the results reveal substantial variations in the poisson ratio in the different tectonic units for the proterozoic crust an increase of the poisson ratio with increasing crustal thickness is systematically observed while for the phanerozoic crust the poisson ratio tends to decrease for increasing crustal thicknesses these observations are in remarkable agreement with the results of the deep seismic soundings that were performed in the former soviet union the variations observed in the proterozoic provinces can perhaps be explained by underplating of mafic materials at the base of the crust fl 2000 elsevier science b v all rights reserved

examining the interior of llaima volcano with receiver functions abstract llaima volcano in chile is one of the largest and most active volcanoes in the southern andes with over 50 eruptions since the 1600s after years of persistent degassing llaima most recently erupted in a series of violent strombolian eruptions in 2007 2009 this period had few precursory signals which highlights the need to obtain accurate magma storage information while petrologic advancements have been made in understanding magma degassing and crystallization trends a comprehensive seismic study has yet to be completed here we present results of a receiver function survey utilizing a dense seismic array surrounding llaima volcano application of h stacking and common conversion point stacking techniques reveals a new moho estimate and two structural anomalies beneath llaima volcano we interpret a low velocity zone between 8 and 13 km depth as a newly imaged magma body

shallow structure effects on broadband teleseismic p waveforms the first 5 sec of source equalized p wave receiver functions from an array of broadband portable instruments located about 50 km from the coast in western washington are strongly influenced by very shallow structure depths less than 3 km these data display behavior associated with a dipping high velocity contrast interface at shallow depths the direct p wave and the p to s converted phase vary strongly with backazimuth producing an apparent delay in first arriving energy at western backazimuths these patterns are attributed to a shallow contact between low velocity sandstones at the surface and an underlying high velocity volcanic unit this shallow structure influences even the original unprocessed teleseismic p waves suggesting that such shallow structure could affect other studies such as seismic source analysis utilizing broadband data

the application of gis based logistic regression for landslide susceptibility mapping in the kakuda yahiko mountains central japan as a first step forward in regional hazard management multivariate statistical analysis in the form of logistic regression was used to produce a landslide susceptibility map in the kakuda yahiko mountains of central japan there are different methods to prepare landslide susceptibility maps the use of logistic regression in this study stemmed not only from the fact that this approach relaxes the strict assumptions required by other multivariate statistical methods but also to demonstrate that it can be combined with bivariate statistical analyses bsa to simplify the interpretation of the model obtained at the end in susceptibility mapping the use of logistic regression is to find the best fitting function to describe the relationship between the presence or absence of landslides dependent variable and a set of independent parameters such as slope angle and lithology here an inventory map of 87 landslides was used to produce a dependent variable which takes a value of 0 for the absence and 1 for the presence of slope failures lithology bed rock slope relationship lineaments slope gradient aspect elevation and road network were taken as independent parameters the effect of each parameter on landslide occurrence was assessed from the corresponding coefficient that appears in the logistic regression function the interpretations of the coefficients showed that road network plays a major role in determining landslide occurrence and distribution among the geomorphological parameters aspect and slope gradient have a more significant contribution than elevation although field observations showed that the latter is a good estimator of the approximate location of slope cuts using a predicted map of probability the study area was classified into five categories of landslide susceptibility extremely low very low low medium and high the medium and high susceptibility zones make up 8 87 of the total study area and involve mid altitude slopes in the eastern part of kakuda mountain and the central and southern parts of yahiko mountain

configuration of the continental moho and philippine sea slab in southwest japan derived from receiver function analysis relation to subcrustal earthquakes abstract we carried out receiver function imaging to estimate detailed configurations of the continental moho discontinuity and the philippine sea phs slab beneath southwest japan we calculated the receiver functions by an extended time multiple taper method a clear discontinuity at about 30 km depth was found beneath northern chugoku and kinki and we interpreted this as the continental moho we also found a northward dipping discontinuity at about 20 40 km depth beneath shikoku part of chugoku and the southern kii peninsula we present a new interpretation that this clear boundary is the upper part of the phs slab furthermore a less prominent northward dipping discontinuity is thought to be the aseismic phs slab at the depth of about 60 km beneath northern chugoku and kinki most subcrustal earthquakes occur at the plate boundary and or within the oceanic crust and their p axes tend to be oriented at high angles to the strike of the phs slab in northern chugoku existence of the aseismic phs slab is consistent with the adakitic rocks which are generated by the melting of younger slabs

simulation of the parma river blockage by the corniglio landslide northern italy abstract near the village of corniglio in the northern apennines about 40 km sw of parma a big landslide was recently 1994 1996 subjected to reactivation damaging many buildings and partially obstructing the parma river in this work we have carried out a quantitative analysis of the recent evolution of the landslide with the help of a geographic information system gis in order to predict the most plausible future developments then various simulations of landslide descent were carried out and above all to evaluate the possibility of blockage formation to this purpose two computer programs that simulate the material descent through a cellular automata model and define blockage characteristics were written many different simulations were carried out 16 of which are presented here for each of them the computer output consists of a table defining the quantity of displaced material area and volume of the dam and lake and of a map showing the areas involved in the landslide movement and upstream flooding in order to assess the probability of blockage formation and dam stability we applied the simulation results to some empirical rules defined by preceding authors through statistical analysis carried out on a high number of analogous phenomena these rules suggest that it is very unlikely that blockage takes place as the result of very slow landslide velocity riverbed width and high erodibility of the material if it were to occur the size and shape of the dam seem sufficient to guarantee a considerable degree of stability making a sudden failure improbable

a hybrid method to compute short period synthetic seismograms of teleseismic body waves in a 3 d regional model we present a hybrid method to simulate the propagation of short period teleseismic body waves through 3 d regional models the incident wavefield is computed in an spherically symmetric reference earth model based on the direct solution method the global and regional wavefields are matched at the boundaries of the regional mesh in the regional domain we implement a spectral element method with absorbing boundaries to cancel the outgoing scattered wavefield the hybrid method is successfully benchmarked against the direct solution method in the reference earth model iasp91 the potential of the method is illustrated by computing short period p wave synthetic seismograms in a 3 d model with a 20 km moho offset and or topography on the free surface focusing on the actual example of the pyrenees

crustal thickness variations in the margins of the gulf of california from receiver functions receiver functions rfs from teleseismic events recorded by the nars baja array were used to map crustal thickness in the continental margins of the gulf of california a newly forming ocean basin although the upper crust is known to have split apart simultaneously along the entire length of the gulf little is known about the behaviour of the lower crust in this region the rfs show clear p to s wave conversions from the moho beneath the stations the delay times between the direct p and p to s waves indicate thinner crust closer to the gulf along the entire baja california peninsula the thinner crust is associated with the eastern peninsular ranges batholith prb crustal thickness is uncorrelated with topography in the prb and the moho is not flat suggesting mantle compensation by a weaker than normal mantle based on seismological evidence the approximately w e shallowing in moho depths is significant with extremes in crustal thickness of 21 and 37 km similar results have been obtained at the northern end of the gulf by lewis et al who proposed a mechanism of lower crustal flow associated with rifting in the gulf extensional province for thinning of the crust based on the amount of pre pliocene extension possible in the continental margins if the lower crust did thin in concert with the upper crust it is possible that the crust was thinned during the early stages of rifting before the opening of the ocean basin in this case we suggest that when breakup occurred the lower crust in the margins of the gulf was still behaving ductilely alternatively the lower crust may have thinned after the gulf opened the implications of these mechanisms are discussed

seismic evidence for an ancient rift beneath the cumberland plateau tennessee a detailed analysis of broadband teleseismic p waveforms broadband receiver functions developed from teleseismic p waveforms recorded on the midperiod passband of regional seismic test network station rscp are inverted for vertical velocity structure beneath the cumberland plateau tennessee the detailed broadband receiver functions are obtained by stacking source equalizd horizontal components of teleseismic p waveforms the resulting receiver functions are most sensitive to the shear velocity structure near the station a time domain inversion routine utilizes the radial receiver function to determine this structure assuming a crustal model parameterized by many thin flat lying homogeneous layers lateral changes in structure are identified by examining azimuthal variations in the vertical structure the results reveal significant rapid lateral changes in the midcrustal structure beneath the station that are interpreted in relation to the origin of the east continent gravity high located northeast of rscp the results from events arriving from the northeast show a high velocity midcrustal layer not present in results from the southeast azimuth this velocity structure can be shown to support the idea that this feature is part of a keweenawan rift system another interesting feature of the derived velocity models is the indication that the crust mantle boundary beneath the cumberland plateau is a thick probably laminated transition zonemore between the depths of 40 and 55 km a result consistent with interpretations of early refraction work in the area less

the lithosphere in central europe seismological and petrological aspects abstract the lithosphere thickness in the variscan belt of central europe varies between about 60 and 150 km with typical values of 100 120 km our estimates derived from directionally independent representative p wave residuals are in good agreement with magnetotelluric determinations of a layer with increased conductivity in the upper mantle the large scale anisotropies of the subcrustal lithosphere beneath four seismological stations determined from spatial variations of relative p residuals vary between 6 5 and 15 2 for p velocities the s wave anisotropies determined from sks polarizations vary between 2 2 and 6 7 these values are in reasonable agreement with the anisotropies of peridotites determined in laboratory systematic spatial variations of the directional terms of relative residuals in dependence on azimuths and incidence angles suggest the existence of large dipping anisotropic structures in the subcrustal lithosphere the residual patterns at most stations in the saxothuringicum rhenohercynicum and in the massif central imply northwesterly orientated dips of the anisotropic structures while stations in the moldanubicum the alpine foredeep and most of the alps north of the insubric line suggest southeasterly orientated dips in our interpretation the dipping anisotropic structures may represent paleosubductions which retain olivine preferred orientations originating from an ancient oceanic lithosphere the variscides of central europe may thus represent a collision zone characterized by two systems of paleosubductions divergent relative to the suture between the moldanubicum and the saxothuringicum

receiver functions for the tien shan analog broadband network contrasts in the evolution of structures across the talasso fergana fault we determined the structure of the crust beneath the central and western tien shan by analyzing broadband 1 20 s analog seismograms of converted p sv phases generated by earthquakes at teleseismic distances and recorded by 14 seismograph stations the one dimensional structures that best explain the waveforms reveal pronounced differences in crustal velocities east and west of the talasso fergana fault specifically the transition zone between the crust and the mantle east of the fault is about 2 times broader than that west of the fault also velocities at depths between 10 and 35 km are about 10 lower in the east although the depth range of these lower velocities is not well resolved the talasso fergana fault is an important boundary for other observables in addition to the structural discontinuities observed at the surface the areas east of the talasso fergana fault are associated with abnormally low mantle velocities outcrops of basalt low q and short wavelength variations in anisotropy integrating these observations we interpret the broad mantle gradient as being due to vertical intrusions of mantle material into the lower crust likewise the low velocities in the midcrust could be thermally induced or due to the introduction of magmatically derived fluids the gross contrast in structure east and west of the talasso fergana fault could reflect a contrast in the dynamics of mountain building in these two regions we postulate that while crustal shortening is the dominant mechanism controlling topography west of the talasso fergana fault vertical uplift caused by a mass deficiency in the upper mantle may contribute significantly to the generation and maintenance of the high elevations east of the fault