an automated time window selection algorithm for seismic tomography we present flexwin an open source algorithm for the automated selection of time windows on pairs of observed and synthetic seismograms the algorithm was designed specifically to accommodate synthetic seismograms produced from 3 d wavefield simulations which capture complex phases that do not necessarily exist in 1 d simulations or traditional traveltime curves relying on signal processing tools and several user tuned parameters the algorithm is able to include these new phases and to maximize the number of measurements made on each seismic record while avoiding seismic noise our motivation is to use the algorithm for iterative tomographic inversions in which the synthetic seismograms change from one iteration to the next hence automation is needed to handle the volume of measurements and to allow for an increasing number of windows at each model iteration the algorithm is sufficiently flexible to be adapted to many tomographic applications and seismological scenarios including those based on synthetics generated from 1 d models we illustrate the algorithm using data sets from three distinct regions the entire globe the japan subduction zone and southern california

global upper mantle structure from finite frequency surface wave tomography 1 we report global shear wave velocity structure and radial anisotropy in the upper mantle obtained using finite frequency surface wave tomography based upon complete three dimensional born sensitivity kernels because wavefront healing effects are properly taken into account finite frequency surface wave tomography improves the resolution of small scale mantle heterogeneities especially for deep anomalies that are constrained by the longest period surface waves in our finite frequency model ffsw1 the globally averaged radial anisotropy shows a transition from positive sh sv to negative anisotropy sv sh at about 220 km consistent with a change in the dominant mantle circulation pattern from predominantly horizontal flow at shallow depths to vertical flow at greater depths the radial anisotropy beneath cratons and the old pacific plate agrees well with previous studies however our model exhibits a strong negative radial anisotropy at depths greater than 120 km beneath mid ocean ridges a feature that is not present in previous upper mantle models more interestingly the depth extent of the ridge anomalies is distinctly different beneath fast and slow spreading centers anomalies beneath fast spreading centers are stronger but the strength decreases rapidly below 250 km in contrast beneath slow spreading centers such as the northern mid atlantic ridge and the red sea anomalies extend down at least to the top of the transition zone the different depth extent of the ridge anomalies suggests that the primary driving force of slow spreading seafloor may be different from that of fast spreading seafloor and that active upwelling beneath slow spreading ridges may play a major role in the opening of the seafloor

automated seismic waveform location using multichannel coherency migration mcm ii application to induced and volcano tectonic seismicity locating microseismic events is essential for many areas of seismology including volcano and earthquake monitoring and reservoir engineering due to the large number of microseismic events in these settings an automated seismic location method is required to perform real time seismic monitoring the measurement environment requires a precise and noise resistant event location method for seismic monitoring in this paper we apply multichannel coherency migration mcm to automatically locate microseismic events of induced and volcano tectonic seismicity using sparse and irregular monitoring arrays compared to other migration based methods in spite of the often sparse and irregular distribution of the monitoring arrays the mcm can show better location performance and obtain more consistent location results with the catalogue obtained by manual picking our mcm method successfully locates many triggered volcano tectonic events with local magnitude smaller that 0 which demonstrates its applicability on locating very small earthquakes our synthetic event location example at a carbon capture and storage site shows that continuous and coherent drilling noise in industrial settings will pose great challenges for source imaging however automatic quality control techniques including filtering in the frequency domain and weighting are used to automatically select high quality data and can thus effectively reduce the effects of continuous drilling noise and improve source imaging quality the location performance of the mcm method for synthetic and real microseismic datasets demonstrates that the mcm method can perform as a reliable and automatic seismic waveform analysis tool to locate microseismic events

constraints on the correlation of p and s wave velocity heterogeneity in the mantle from p pp ppp and pkpab traveltimes we investigate the correlation of large scale p and s velocity heterogeneity in the mantle by determining how well 106 000 compressional p pp ppp and pkpab traveltimes can be explained by s wave velocity model s20rts scaled using a depth dependent factor and by a model in which the lateral p velocity variations are different we first assess the assumption that p wave traveltimes can be explained by a model in which lateral p velocity variations p are identical to s velocity variations s in model s20rts for a given depth we project s from s20rts into model s2p using a depth dependent scaling factor r defined as s r z x p we find by grid search that the highest reduction of data variance is obtained when r increases linearly from 1 25 at the surface to 3 0 at the core mantle boundary a comparison of s wave ss and p wave pp traveltimes for identical source receiver pairs also indicates that r increases with depth significantly higher variance reduction is not obtained when r is parametrized with an additional degree of freedom therefore the precise shape of r cannot be constrained by our data p and pp wave traveltime anomalies with respect to the scaled model s2p yield coherent geographic variations this indicates that there are large scale lateral p velocity variations in the mantle that are different from those in model s2p we estimate these variations by inverting p wave traveltime anomalies with respect to model s2p for a degree 12 model of p velocity heterogeneity this model p 12 s 2 p indicates where in the well sampled mantle regions we need to modify model s2p to further improve the fit to the traveltime data anomalies in p12 s 2 p exist throughout the mantle it is therefore not obvious that compositional heterogeneity is prominent in the lower 1000 km of the mantle only as suggested previously low p wave velocities in the upper mantle beneath oceans are the strongest anomalies in p12 s 2 p and explain better the delayed traveltimes of pp wave phases with oceanic surface refection points lower mantle anomalies include high and low p velocity structures beneath eastern asia and north america respectively the high p velocity anomaly in the lower mantle beneath the central pacific is consistent with the assertion made by other researchers that large scale lower mantle upwellings are not purely thermal in origin

pattern formation in a thin layer of sediment abstract a stability analysis is performed to investigate the process which leads to the formation of bottom forms when a thin layer of sediment covers a rigid substratum subject to the oscillatory flow induced by a surface gravity wave the amplitude of the bottom perturbation is assumed to be so small to linearize the hydrodynamic problem and the flow field is determined by analytical means however nonlinear effects are significant and play a fundamental role into the morphodynamic problem when the rigid substratum is bared by the growth of the most unstable mode hence the development of the bottom profile is evaluated by a numerical approach the model results show that the wavelength of the morphological patterns which are generated when the rigid substratum is bared is longer than the wavelength of the bottom forms which appear when the rigid substratum is always covered by the sediment the results of the theoretical model are supported by some experimental observations made in our laboratory

frechet kernels for imaging regional earth structure based on three dimensional reference models high resolution images of three dimensional 3d seismicstructuresare not only of scientific interest but also of practical importance in predicting strong ground motion after large earthquakes given the source and station distributions resolutions in current regional seismic tomography studies have been limited by two types of simplifying practices the adoption of high frequency approximations such as the ray theory and the use of one dimensional 1d reference starting models we have developed a new approach to compute accurate finite frequency 3d frechet sensitivity kernels of observed travel time and amplitude anomalies relative to 3d reference models in our approach we use a fourth order staggered grid finite difference method to model the seismic wave propagation in 3d media and the reciprocity property of the green s tensor to reduce the number of numerical simu lations this approach accounts for the perturbations in compressional and shear wave speeds in the same way leading to a capability of inverting for the shear wave speed directly from seismic data the algorithm is readily parallelized to allow for realistic regional high resolution 3d tomography inversions we have implemented the algorithm for the southern california earthquake center scec community velocity model scec cvm 3 0 a complex 3d model for southern california in cluding a number of sedimentary basins by enabling the inversion of 3d structural perturbations to 3d reference models our approach provides a practical means of iteratively solving the nonlinear regional tomography problems

seismic attenuation beneath europe and the north atlantic implications for water in the mantle abstract it is well known that anelasticity has significant effects on the propagation of seismic waves as manifested by physical dispersion and dissipation investigations of anelasticity provide complementary constraints on the physical properties of earth materials but contrary to imaging with elastic waves progress in mapping earth s anelasticity has been relatively slow and there is only limited agreement between different studies or methodologies here within the framework of adjoint tomography we use frequency dependent phase and amplitude anomalies between observed and simulated seismograms to simultaneously constrain upper mantle wavespeeds and attenuation beneath the european continent and the north atlantic ocean in the sea floor spreading environment beneath the north atlantic we find enhanced attenuation in the asthenosphere and within the mantle transition zone mtz in subduction zone settings for example beneath the hellenic arc elevated attenuation is observed along the top of the subducting slab down to the mtz no prominent reductions in wavespeeds are correlated with these distinct attenuation features suggesting that non thermal effects may play an important role in these environments a plausible explanation invokes the transport of water into the deep earth by relatively cold subducting slabs leading to a hydrated mtz as previously suggested by mineral physics and geodynamics studies

global adjoint tomography first generation model we present the first generation global tomographic model constructed based on adjoint tomography an iterative full waveform inversion technique synthetic seismograms were calculated using gpu accelerated spectral element simulations of global seismic wave propagation accommodating effects due to 3d anelastic crust mantle structure topography bathymetry the ocean load ellipticity rotation and self gravitation frechet derivatives were calculated in 3d anelastic models based on an adjoint state method the simulations were performed on the cray xk7 named titan a computer with 18 688 gpu accelerators housed at oak ridge national laboratory the transversely isotropic global model is the result of 15 tomographic iterations which systematically reduced differences between observed and simulated three component seismograms our starting model combined 3d mantle model s362ani kustowski et al 2008 with 3d crustal model crust2 0 bassin et al 2000 we simultaneously inverted for structure in the crust and mantle thereby eliminating the need for widely used crustal corrections we used data from 253 earthquakes in the magnitude range 5 8 mw 7 0 for the first 12 iterations we combined 30 s body wave data with 60 s surface wave data the shortest period of the surface waves was gradually decreased and in the last three iterations we combined 17 s body waves with 45 s surface waves we started using 180 min long seismograms after the 12th iteration and assimilated minor and major arc body and surface waves the 15th iteration model features enhancements of well known slabs an enhanced image of the samoa tahiti plume as well as various other plumes and hotspots such as caroline galapagos yellowstone and erebus furthermore we see clear improvements in slab resolution along the hellenic and japan arcs as well as subduction along the east of scotia plate which does not exist in the starting model point spread function tests demonstrate that we are approaching the resolution of continental scale studies in some areas for example underneath yellowstone this is a consequence of our multi scale smoothing strategy in which we define our smoothing operator as a function of the approximate hessian kernel thereby smoothing gradients less wherever we have good ray coverage such as underneath north america

continuous kurtosis based migration for seismic event detection and location with application to piton de la fournaise volcano la reunion abstract we present an automatic earthquake detection and location technique based on migration of continuous waveform data data are preprocessed using a kurtosis estimator in order to enhance the first arrival information then migrated onto a predefined search grid using precalculated p wave travel times and finally stacked local maxima in the resulting 4d space time grid indicate the locations and origin times of seismic events we applied our technique to earthquake swarms occurring on piton de la fournaise volcano la reunion france we located 5000 events from 12 different swarms that occurred between 2009 and 2011 our automated locations are consistent with those performed using manual picks and indicate that the seismicity concentrates around sea level multiplet analysis of the detected events and subsequent double difference relocation produce sharper images of the earthquake swarms our code waveloc is released in open source online material figures of seismicity distributions from waveloc synthetic test and stack amplitude values versus magnitudes

crustal structure and seismicity distribution adjacent to the pacific and north america plate boundary in southern california new three dimensional 3 d v p and v p v s models are determined for southern california using p and s p travel times from local earthquakes and controlled sources these models confirm existing tectonic interpretations and provide new insights into the configuration of geological structures at the pacific north america plate boundary the models extend from the u s mexico border in the south to the southernmost coast ranges and sierra nevada in the north and have a 15 km horizontal grid spacing and an average vertical grid spacing of 4 km down to 22 km depth the heterogeneity of the crustal structure as imaged by v p and v p v s models is larger within the pacific plate than the north american plate similarly the relocated seismicity deepens and shows more complex 3 d distribution in areas of the pacific plate exhibiting compressional tectonics the models reflect mapped changes in the lithology across major geological terranes such as the mojave desert the peninsular ranges and the transverse ranges the interface between the shallow mono of the continental borderland and the deep moho of onshore california forms a broad zone to the north beneath the western transverse ranges ventura basin and the los angeles basin and a narrow zone to the south along the peninsular ranges the near surface increase in velocity from the surface to up to 8 km depth is rapid and has a logarithmic shape for stable blocks and mountain ranges but is slow with a linear shape for sedimentary basins at midcrustal depths a rapid increase in v p is imaged beneath the sediments of the large sedimentary basins while beneath the adjacent mountain ranges the increase is small or absent

adjoint tomography of the southern california crust using an inversion strategy based on adjoint methods we developed a three dimensional seismological model of the southern california crust the resulting model involved 16 tomographic iterations which required 6800 wavefield simulations and a total of 0 8 million central processing unit hours the new crustal model reveals strong heterogeneity including local changes of 30 with respect to the initial three dimensional model provided by the southern california earthquake center the model illuminates shallow features such as sedimentary basins and compositional contrasts across faults it also reveals crustal features at depth that aid in the tectonic reconstruction of southern california such as subduction captured oceanic crustal fragments the new model enables more realistic and accurate assessments of seismic hazard

using seismic waves to image earth s internal structure seismic waves generated in earth s interior provide images that help us to better understand the pattern of mantle convection that drives plate motions

a quantitative comparison between 1d and 3d source inversion methodologies application to the middle east we present a quantitative comparison between seismic moment tensor mt inversion solutions using 1d and 3d synthetic seismograms at two frequency bands for events in the middle east to assess the effects of 3d models on source studies complex geology associated with the active continental convergent margin leads to a scarcity of reliable available data necessitating a thorough examination of solution stability and robustness to assure an accurate description of sources with well characterized source parameters solutions were calculated for 195 events m w 5 5 using a full waveform mt inversion matching both phase and amplitude seismic data processed at two frequency bands compares short and long period performance for 1d and 3d synthetic seismograms an improvement in fit between data and synthetics is seen using 3d over 1d synthetic seismograms especially for complex body wave propagation and surface wave dispersion at short periods 3d synthetics provide a more robust solution compared with 1d showing a reduction in error of the source mechanism the percentage of double couple components increases with the addition of 3d structure and suggests the percentage of non double couple components is a result of poorly constrained earth structure event solutions contained in the catalog graphic 1 table s1 in the electronic supplement to this paper have an average cross correlation value of 0 87 with good amplitude ratios and are improved i e increased variance reduction yet consistent with longer period solutions from the global centroid moment tensor cmt catalog online material table of 184 event solutions from 3d moment tensor inversion 1 embed inline graphic 1 gif

seismic tomography of the southern california crust based on spectral element and adjoint methods we iteratively improve a 3 d tomographic model of the southern california crust using numerical simulations of seismic wave propagation based on a spectral element method sem in combination with an adjoint method the initial 3 d model is provided by the southern california earthquake center the data set comprises three component seismic waveforms i e both body and surface waves filtered over the period range 2 30 s from 143 local earthquakes recorded by a network of 203 stations time windows for measurements are automatically selected by the flexwin algorithm the misfit function in the tomographic inversion is based on frequency dependent multitaper traveltime differences the gradient of the misfit function and related finite frequency sensitivity kernels for each earthquake are computed using an adjoint technique the kernels are combined using a source subspace projection method to compute a model update at each iteration of a gradient based minimization algorithm the inversion involved 16 iterations which required 6800 wavefield simulations the new crustal model m 16 is described in terms of independent shear v s and bulk sound v b wave speed variations it exhibits strong heterogeneity including local changes of 30 per cent with respect to the initial 3 d model the model reveals several features that relate to geological observations such as sedimentary basins exhumed batholiths and contrasting lithologies across faults the quality of the new model is validated by quantifying waveform misfits of full length seismograms from 91 earthquakes that were not used in the tomographic inversion the new model provides more accurate synthetic seismograms that will benefit seismic hazard assessment

long period body wave traveltimes through the crust implication for crustal corrections and seismic tomography summary the traveltimes of p and sh waves through the crust depend strongly on wave period at periods longer than 10 15 s where traveltime measurements for indirect e g surface reflected and core reflected waves are typically made the traveltimes are shorter than predicted by ray theory crustal corrections often used in global mantle tomography to isolate the effects of the crust on teleseismic traveltimes may have a complex frequency dependence and influence finite frequency inversions crustal corrections for profiles of crust2 0 and the prem reference model for the mantle may be several seconds larger or smaller than ray theoretical values depending on crustal thickness crustal velocities and wave period this variability is observed in the difference times between the seismic phases ss and s and between pp and p it is therefore important to incorporate the effects of the crust on traveltimes in finite frequency tomography in order to take full advantage of the variable mantle sensitivity of body waves at different periods

simulations of ground motion in the los angeles basin based upon the spectral element method we use the spectral element method to simulate ground motion generated by two recent and well recorded small earthquakes in the los angeles basin simulations are performed using a new sedimentary basin model that is constrained by hundreds of petroleum industry well logs and more than 20 000 km of seismic reflection profiles the numerical simulations account for 3d variations of seismic wave speeds and density topography and bathymetry and attenuation simulations for the 9 september 2001 m w 4 2 hollywood earthquake and the 3 september 2002 m w 4 2 yorba linda earthquake demonstrate that the combination of a detailed sedimentary basin model and an accurate numerical technique facilitates the simulation of ground motion at periods of 2 sec and longer inside the basin model and 6 sec and longer in the regional model peak ground displacement velocity and acceleration maps illustrate that significant amplification occurs in the basin

a three dimensional radially anisotropic model of shear velocity in the whole mantle summary we present a 3 d radially anisotropic s velocity model of the whole mantle saw642an obtained using a large three component surface and body waveform data set and an iterative inversion for structure and source parameters based on non linear asymptotic coupling theory nact the model is parametrized in level 4 spherical splines which have a spacing of 8 the model shows a link between mantle flow and anisotropy in a variety of depth ranges in the uppermost mantle we confirm observations of regions with vsh vsv starting at 80 km under oceanic regions and 200 km under stable continental lithosphere suggesting horizontal flow beneath the lithosphere we also observe a vsv vsh signature at 150 300 km depth beneath major ridge systems with amplitude correlated with spreading rate for fast spreading segments in the transition zone 400 700 km depth regions of subducted slab material are associated with vsv vsh while the ridge signal decreases whilethemid mantlehasloweramplitudeanisotropy vsv in the lowermost 300 km which appears to be a robust conclusion despite an error in our previous paper which has been corrected here the 3 d deviations from this signature are associated with the large scale low velocity superplumes underthecentralpacificandafrica suggestingthatvsh vsv isgeneratedinthepredominant horizontal flow of a mechanical boundary layer with a change in signature related to transition to upwelling at the superplumes

waveform modeling of the slab beneath japan 1 the tomographic p wave model for the japan subduction zone derived by zhao et al 1994 has two very striking features a slab about 90 km thick with p wave velocities 3 6 higher than the surrounding mantle and a mantle wedge with 6 low velocity anomalies we study three component seismograms from more than 600 hi net stations produced by two earthquakes which occurred in the downgoing pacific plate at depths greater than 400 km we simulate body wave propagation in the three dimensional 3 d p wave model using 2 d finite difference fdm and 3 d spectral element sem methods as measured by cross correlation between synthetics and data the p wave model typically explains about half of the traveltime anomaly and some of the waveform complexity but fails to predict the extended sh wave train in this study we take advantage of the densely distributed hi net stations and use 2 d fdm modeling to simulate the p sv and sh waveforms our 2 d model suggests that a thin elongated low velocity zone exists atop the slab extending down to a depth of 300 km with an s wave velocity reduction of 14 if a thickness of 20 km is assumed further 3 d sem simulations confirm that this model explains a strong secondary arrival which cannot easily be imaged with standard tomographic techniques the low velocity layer could explain the relatively weak coupling associated with most subduction zones at shallow depths 50 km generally involving abundant volcanic activity and silent earthquakes and it may also help to further our understanding of the water related phase transition of ultramafic rocks and the nature of seismicity at intermediate depths 70 300 km

partitioned waveform inversion and two dimensional structure under the network of autonomously recording seismographs nonlinear optimization methods are very effective in finding models that predict optimal waveform fits to observed seismograms provided the number of model parameters is small to reduce the size of the large scale two or three dimensional seismic modelling problem path integrals over seismic velocities may be defined as model parameters instead of the seismic velocities themselves this partitions the large scale optimization problem into a number of independent small scale problems and reduces the computational effort by several orders of magnitude the path integral parameters are transformed such that their correlation matrix becomes diagonal a linear inversion performs the mapping from the space of path integral parameters into the model space of seismic velocities and makes backus gilbert resolution analysis possible the method has been applied to body wave and surface wave data from the broadband portable network of autonomously recording seismographs nars in western europe using a surface wave ray approximation to generate synthetics by mode summation waveforms were fitted for frequencies as high as 50 mhz variations in s velocity as large as 6 1 have been established with a vertical resolution of 100 150 km and a horizontal resolution as small as 400 km in parts of the model although a low velocity layer is present under the southern part of the nars array such layer is very weak or absent north of the paris basin horizontal velocity gradients are well resolved down to 400 km depth

a structural vp model of the salton trough california and its implications for seismic hazard we present a high resolution three dimensional p wave seismic veloc ity model of the sedimentary basin in the salton trough southern california and use the model for spectral element method sem wave propagation and ground motion simulations to quantitatively assess seismic hazard in the region the basin geometry is defined by a surface representing the top of crystalline basement which was constrained by seismic refraction profiles and free air gravity data sonic logs from petroleum wells in the imperial valley and isovelocity surfaces defined by seismic refraction studies were used to define p wave velocity within the sedimentary basin as a function of two variables 1 absolute depth and 2 depth of the underlying crystalline basement surface cbs this velocity function was used to populate cells of a three dimensional spatial array voxet defining the p wave velocity structure in the basin the new model was then resampled in a computational mesh used for earthquake wave propagation and strong ground motion simulations based upon the sem komatitsch et al 2004 simulation of the 3 november 2002 mw 4 2 yorba linda earthquake demonstrates that the new model provides accurate simulation of strong ground motion amplification effects in the salton trough sedimentary basin offering substantial improvements over previous models a hypothetical mw 7 9 earthquake on the southern san andreas fault was then simulated in an effort to better understand the seismic hazard associated with the basin structure these sim ulations indicate that great amplification will occur during large earthquakes in the region due to the low seismic velocity of the sediments and the basin shape and depth

applying a three dimensional velocity model waveform cross correlation and cluster analysis to locate southern california seismicity from 1981 to 2005 we compute high precision earthquake locations using southern california pick and waveform data from 1981 to 2005 our latest results are significantly improved compared to our previous catalog by the following 1 we locate events with respect to a new crustal p and s velocity model using three dimensional ray tracing 2 we examine six more years of waveform data and compute cross correlation results for many more pairs than our last analysis and 3 we compute locations within similar event clusters using a new method that applies a robust fitting method to obtain the best locations satisfying all the differential time constraints from the waveform cross correlation these results build on the relocated catalogs of hauksson and shearer 2005 and shearer et al 2005 and provide additional insight regarding the fine scale fault structure in southern california and the relationship between the san andreas fault saf and nearby seismicity in particular we present results for two regions in which the seismicity near the southern saf seems to align on dipping faults

shear and compressional velocity models of the mantle from cluster analysis of long period waveforms summary we present a new technique for the efficient measurement of the traveltimes of long period body wave phases the technique is based on the fact that all arrivals of a particular seismic phase are remarkably similar in shape for a single event this allows the application of cross correlation techniques that are usually used in a regional context to measure precise global differential times the analysis is enhanced by the inclusion of a clustering algorithm that automatically clusters waveforms by their degree of similarity this allows the algorithm to discriminate against unusual or distorted waveforms and makes for an extremely efficient measurement technique this technique can be applied to any seismic phase that is observed over a reasonably large distance range here we present the results of applying the algorithm to the long period channels of all data archived at the iris dmc from 1976 to 2005 for the seismic phases s and p from 23 to 100 and ss and pp from 50 to 170 the resulting large data sets are inverted along with existing surface wave and updated differential traveltime measurements for new mantle models of s and p velocity the resolution of the new model is enhanced particularly in the mid mantle where ss and pp turn we find that slow anomalies in the central pacific and africa extend from the core mantle boundary to the upper mantle but their direct connection to surface hotspots is beyond our resolution furthermore we find that fast anomalies that are likely associated with subducting slabs disappear between 1700 and 2500 km and thus are not continuous features from the upper to lower mantle despite our extensive coverage and high resolution of the mid mantle

automated detection extraction and measurement of regional surface waves our goal is to develop and test an effective method to detect identify extract and quantify surface wave signals for weak events observed at regional stations we describe an automated surface wave detector and extractor designed to work on weak surface wave signals across eurasia at intermediate periods 8 s 40 s the method is based on phase matched filters defined by the rayleigh wave group travel time predictions from the broadband group velocity maps presented by ritzwoller and levshin 1998 and ritzwoller et al 1998 and proceeds in three steps signal compression signal extraction or cleaning and measurement first the dispersed surface wave signals are compressed in time by applying an anti dispersion or phase matched filter defined from the group velocity maps we refer to this as the compressed signal second the surface wave is then extracted by filtering noise temporally isolated from the time compressed signal this filtered signal is then redispersed by applying the inverse of the phase matched filter finally we adaptively estimate spectral amplitude as well as group and phase velocity on the filtered signal the method is naturally used as a detector by allowing origin time to slide along the time axis we describe preliminary results of the application of this method to a set of nuclear explosions and earthquakes that occurred on or near the chinese lop nor test site from 1992 through 1996 and one explosion on the indian rajasthan test site that occurred in may of 1998

seismic velocity structure of the crust beneath the japan islands abstract more than 13 000 arrival times of 562 local shallow earthquakes selected from the japan university network earthquake catalog are used to investigate the seismic velocity structure of the crust beneath the japan islands we simultaneously determined the hypocenter parameters p and s wave station corrections and depth distributions of the conrad and moho discontinuities beneath the whole of the japan islands by applying an inversion method the p and s wave station corrections show similar distribution patterns they are negative relatively late arrivals of seismic waves in hokkaido and positive relatively early arrivals of seismic waves in western japan in eastern honshu they are positive along the coast of the pacific ocean and negative in the land area and along the coast of the japan sea the conrad discontinuity is located at a depth range from 12 to 22 km in hokkaido the conrad is shallow in the eastern pan and becomes deep toward the west in ne honshu the conrad is deep beneath the land area and becomes shallow toward the surrounding seas in western japan the conrad is shallow in the northern part and becomes deep toward the south the moho is located in a depth range from 25 to 40 km in hokkaido the moho has the shape of a circular cone with a maximum depth of 36 km in most parts of the japan islands the moho is deep beneath the land area and becomes shallow toward the surrounding seas the moho is deepest up to 40 km beneath the central part of the chubu district

lithospheric architecture of the south western alps revealed by multiparameter teleseismic full waveform inversion the western alps although being intensively investigated remains elusive when it comes to determining its lithospheric structure new inferences on the latter are important for the understanding of processes and mechanisms of orogeny needed to unravel the dynamic evolution of the alps this situation led to the deployment of the cifalps temporary experiment conducted to address the lack of seismological data amenable to high resolution seismic imaging of the crust and the upper mantle we perform a 3 d isotropic full waveform inversion fwi of nine teleseismic events recorded by the cifalps experiment to infer 3 d models of both density and p and s wave velocities of the alpine lithosphere here by fwi is meant the inversion of the full seismograms including phase and amplitude effects within a time window following the first arrival up to a frequency of 0 2 hz we show that the application of the fwi at the lithospheric scale is able to generate images of the lithosphere with unprecedented resolution and can furnish a reliable density model of the upper lithosphere in the shallowest part of the crust we retrieve the shape of the fast dense ivrea body anomaly and detect the low velocities of the po and se france sedimentary basins the geometry of the ivrea body as revealed by our density model is consistent with the bouguer anomaly a sharp moho transition is followed from the external part 30 km depth to the internal part of the alps 70 80 km depth giving clear evidence of a continental subduction event during the formation of the alpine belt a low velocity zone in the lower lithosphere of the s wave velocity model supports the hypothesis of a slab detachment in the western part of the alps that is followed by asthenospheric upwelling the application of fwi to teleseismic data helps to fill the gap of resolution between traditional imaging techniques and enables integrated interpretations of both upper and lower lithospheric structures

global love wave overtone measurements 1 love wave phase velocities for fundamental and higher modes are difficult to measure because the different modes cannot easily be separated following yoshizawa and kennett 2002 we generate suites of path specific onedimensional shear wave velocity profiles using the neighbourhood algorithm of sambridge 1999a from this family of o 10 4 models both fundamental and higher mode phase velocities with mutually consistent uncertainties are calculated we have fully automated the method and analysed over forty thousand love wave seismograms from the gdsn and geoscope global networks from 1994 2004 our phase velocity measurements agree remarkably well with previous studies but we have been able to enlarge the available dataset dramatically we present global love wave phase velocity maps up to the fifth overtone with unprecedented resolution due to the improved path coverage comparing these maps to existing tomographic models we discern evidence of significant anisotropy inthe lower mantlearound a depth of 1000 km in the pacific citation visser k s lebedev j trampert and b l n kennett 2007 global love wave overtone measurements geophys res lett 34 l03302

unveiling the hydrothermal mineralogy of the chapi chiara gold prospect peru through reflectance spectroscopy geochemical and petrographic data abstract southern peru contains important epithermal au ag base metals deposits such as canahuire tucari santa rosa caylloma shila and paula the chapi chiara gold prospect is located in this region and is part of a paleo stratovolcano of the upper miocene pliocene the hydrothermal alteration of the prospect was characterized based on spectroradiometric data geochemistry and petrography the mineralogical data interpreted based on reflectance spectroscopy were spatialized using the sequential indicator simulation technique for producing probabilistic maps of alteration the inner part of the paleo stratovolcano sw sector is marked by three main cores of advanced argillic alteration aaa quartz alunite supergroup minerals kaolinite dickite topaz pyrophyllite diaspore associated with topographic highs the aaa1 core is surrounded by argillic alteration quartz illite paragonitic illite smectite pyrite and propylitic alteration quartz plagioclase chlorite calcite epidote smectite kaolinite pyrite chalcopyrite magnetite the central sector of the prospect situated in the ne flank of the paleo stratovolcano is characterized by hydrothermal breccias structured towards n65e the main mineral phases comprise quartz and abundant pyrite sometimes with traces of as anomalous geochemical values of ag as bi hg se sb and te coincide with high gold contents in this sector of the prospect jarosite and goethite are evidence of a subsequent supergene event based on the mineralogical characterization we conclude the existence of a high sulfidation epithermal system in chapi chiara hypogene minerals of higher temperature in the sw sector of the prospect such as diaspore pyrophyllite and topaz in the aaa zone and epidote in the propylitic alteration zone can reveal that the system is currently in a relatively deep erosion level suggesting its proximity in relation to the interface between a deep epithermal system and a mesothermal system

a three dimensional crustal seismic velocity model for southern california from a composite event method we present a new crustal seismic velocity model for southern california derived from p and s arrival times from local earthquakes and explosions to reduce the volume of data and ensure a more uniform source distribution we compute composite event picks for 2597 distributed master events that include pick information for other events within spheres of 2 km radius the approach reduces random picking error and maximizes the number of s wave picks to constrain absolute event locations and shallow velocity structure we also use times from controlled sources including both refraction shots and quarries we implement the simulps tomography algorithm to obtain three dimensional 3 d v p and v p v s structure and hypocenter locations of the composite events our new velocity model in general agrees with previous studies resolving low velocity features at shallow depths in the basins and some high velocity features in the midcrust using our velocity model and 3 d ray tracing we relocate about 450 000 earthquakes from 1981 to 2005 we observe a weak correlation between seismic velocities and earthquake occurrence with shallow earthquakes mostly occurring in high p velocity regions and midcrustal earthquakes occurring in low p velocity regions in addition most seismicity occurs in regions with relatively low v p v s ratios although aftershock sequences following large earthquakes are often an exception to this pattern

upper mantle beneath southeast asia from s velocity tomography 1 we present a three dimensional s velocity model of the se asian western pacific upper mantle with 400 km lateral resolution using the novel automated multimode inversion technique we processed 4038 vertical component seismograms and extracted 22 708 linear equations with uncorrelated uncertainties that constrain upper mantle structure we used time frequency windows to select signal with negligible proportion of scattered energy the windows included the fundamental rayleigh mode and s and multiple s waves the observed range of s velocity variations is the widest 17 18 in the upper 150 km of the mantle high velocity continental roots can reach beyond the present extent of the overlying archean proterozoic crust by 500 km beneath some precambrian units the roots are absent which can be attributed to deformation and gradual destruction of the ancient lithosphere at 120 150 km s velocity beneath some cratons reaches 4 8 km s this can be accounted for by thermal and compositional effects beneath the hainan island area a low velocity anomaly is observed from near the surface to the bottom of our model the hot spot type volcanism here may be caused by the deep mantle hainan plume a low velocity mantle domain underlies the south central sea of japan surrounded on the surface by intraplate volcanoes a deep seismicity gap is present near 40 n in the pacific slab subducting below and may result from a plume slab interaction a high velocity anomaly is present in the transition zone beneath the northern boundary of the yangtze craton we propose that the anomaly corresponds to subducted continental lithosphere stagnant atop the 660 km discontinuity

imaging mantle transition zone thickness with sds ss finite frequency sensitivity kernels summary we invert differential sds ss traveltime residuals measured from stacked waveforms and finitefrequency sensitivity kernels for topography on the 410 and 660 km discontinuities this approach yields higher resolution images of transition zone thickness than previous stacking methods which simply average smooth over topographic features apparent structure measured using simple stacking is highly dependent upon the bin size of each stack by inverting for discontinuity topography with a variety of bin sizes we can more accurately calculate the true structure the inverted transition zone model is similar to simple stack models with an average thickness of 242 km but the lateral variations in thickness are larger in amplitude and smaller in scale fast seismic velocities in 3 d mantle models such as sb4l18 correlate with areas of thicker transition zone the elongated curvilinear regions of thickened transition zone that occur near subduction zones are narrow and high amplitude which suggests relatively little lateral spreading and warming of subducted lithosphere within the transition zone the anomalously thin transition zone regions are laterally narrow and not broadly continuous if these variations in transition zone thickness are interpreted as thermal in nature then this model suggests significant temperature variations on small lateral scales

full 3d tomography for the crustal structure of the los angeles region we apply full 3d tomography f3dt to a regional dataset in the los angeles area in f3dt the starting model as well as the model perturbation is three dimensional and the sensitivity frechet kernels are computed using numerical schemes that account for the full physics of 3d wave propagation f3dt can account for the nonlinearity of structural inverse problem through iteration thus providing the most efficient means for assimilating seismic observations into dynamic ground motion models we have successfully applied a scattering integral si formulation of f3dt to improve a 3d elastic structure model the southern california earthquake center scec community velocity model version 3 0 cvm3 0 with lowest shear velocity clamped at 1 km sec in the los angeles region our data are time and frequency localized measurements of phase delay anomalies relative to synthetics computed from the 3d elastic starting model the frechet kernels for our measurements were computed by convolving the earthquake wave fields generated by point earthquake sources with the receiver green tensors rgts which are the spatial temporal fields produced by three orthogonal unit impulsive point forces acting at the receiver locations we inverted 7364 phase delay measurements of p and s body waves by using the lsqr method the revised 3d model laf3d provides substantially better fit to the observed waveform data than the 3d starting model to our knowledge this study is the first successful application of f3dt using real data in structural seismology

deep structure of japan subduction zone as derived from local regional and teleseismic events we have determined a detailed three dimensional p wave velocity structure of the japan subduction zone to 500 km depth by inverting local regional and teleseismic data simultaneously we used 45 318 p wave arrivals from 1241 shallow and deep earthquakes which occurred in and around the japan islands the arrival times are recorded by the japan university seismic network which covers the entire japan islands densely and uniformly we also used 4211 travel time residuals from 100 teleseismic events which are read from seismograms recorded by seismic stations in northeastern japan in comparison with the previous results obtained from only local and regional events the present result for the area around the lower plate boundary and the mantle below the plate is determined more reliably because of the addition of 7035 data from 100 teleseismic events and 41 very deep earthquakes in the crust and uppermost mantle low velocity zones are clearly visible beneath active volcanoes in the mantle wedge the low velocity zones generally parallel with the slab and exist continuously to a depth of about 200 km which is consistent with the petrological geochemical and geodynamic studies we consider that the existence of volcanism related low velocity anomalies in the mantle wedge is a general seismological characteristic of subduction zones in light of all the available tomographic results for many subduction zones in the world the pacific slab beneath japan is imaged more clearly than in previous studies as a high velocity zone with a thickness of 80 90 km and a p wave velocity 4 6 higher than the normal mantle lower velocity anomalies are found in the mantle below the slab

sv wave azimuthal anisotropy in the australian upper mantle preliminary results from automated rayleigh waveform inversion summary the pattern of azimuthal anisotropy for sv waves in the upper mantle beneath australia has been determined using a two stage tomographic procedure for rayleigh waves the inversion exploits an automated procedure based on the waveform inversion method of cara leve que 1987 to allow the analysis of 668 vertical component seismograms within a few weeks the automated procedure provides an eiective choice of the secondary observables used in the waveform inversion for both fundamental and higher modes allowing the construction of a set of radially strati ed upper mantle models which represent the average structures on paths criss crossing the australian continent the 668 path average models are then combined in a 3 d velocity model which describes the lateral variation of the sv velocity and its azimuthal anisotropy the lateral variations in wave speed show a good overall agreement with previous results for shear wave speed variations in australia but are accompanied by signi cant azimuthal anisotropy at 150 km depth the anisotropy displays a simple pattern with most of the directions of fast sv velocities dominated by a north south component close to the present day absolute plate motion nevertheless in the regions with the highest shear wave speed anisotropy is not aligned with the current plate motion suggesting a local resistance to mantle ow

full waveform tomography of the upper mantle in the south atlantic region imaging a westward fluxing shallow asthenosphere abstract a prominent feature of the south atlantic region is its strongly asymmetric residual bathymetry across the ocean basin it has been suggested that the residual bathymetry is dynamic in nature arising from the large slow velocity seismic anomaly located in the lower mantle beneath the african plate unfortunately the pattern of mantle heterogeneity particularly in the upper mantle is not well known owing to the sparsity of seismic stations and the existence of large aseismic regions on the african and south american plates here we present a new seismic tomographic study of the south atlantic upper mantle our model is based on a full seismic waveform inversion of 4000 high quality seismograms for isotropic 3 d seismic structure using a powerful adjoint methodology capable of extracting maximum information from each seismogram the theory requires simulation of seismic wave propagation in 3 d heterogeneous earth models computed with a spectral element method where the differences between observed and synthetic seismograms are quantified using phase misfits obtained through a time frequency transform the model images a continuous channel of pronounced slow seismic velocity in the shallow sublithospheric mantle between 150 and 300 km depth that branches in between the cratonic roots under the african and south american continents at greater depth below 300 350 km the slow anomalies are less pronounced and a change in the convective planform is indicated by isolated round shaped patches in an overall faster mantle it is possible that the depthwise change of the convective planform from vertical to horizontal advection of hot buoyant material in a low viscosity asthenosphere can reconcile the anomalous residual bathymetry in the region and we present a simple fluid dynamic model of pressure driven flow to assess the feasibility of this scenario

an evaluation of the scsn moment tensor solutions robustness of the mw magnitude scale style of faulting and automation of the method we have generated moment tensor solutions and moment magnitudes m w for 1700 earthquakes of local magnitude m l 3 0 that occurred from september 1999 to november 2005 in southern california the method is running as an automated real time component of the southern california seismic network scsn with solutions available within 12 min of event nucleation for local events the method can reliably obtain good quality solutions for m w with m l 3 5 and for the moment tensor for events with m l 4 0 the method uses the 1d time domain inverse code tdmt invc software package dreger 2003 the green s functions have been predetermined for various velocity profiles in southern california which are used in the inversion of observed three component broadband waveforms 10 100 sec using data from at least four stations moment tensor solutions have an assigned quality factor dependent on the number of stations in the inversion and the goodness of fit between synthetic and observed data if a minimum quality factor is attained the m l or m w is 5 0 or greater and if the event is in the southern california reporting regions the m w will be the official scsn cisn magnitude the m w from the high quality solutions determined from our method generally correlate very well with reviewed m l except in regions at the perimeter of the network the m w reported here indicates the scsn m l systematically underestimates the magnitude in the mexicali region of baja california mono lakes area coso region and the brawley seismic zone and overestimates the magnitude in the coastal ranges comparisons of the moment tensors determined using this model are made with harvard centroid moment tensors generated for larger earthquakes in the california region and recent 3d models for events in the los angeles region with excellent correlation most of the earthquakes with good quality solutions exhibit strike slip faulting in particular along the major late quaternary strike slip faults thrust faulting on east west striking planes is observed along the southern edge of the transverse ranges while northwest striking thrust faulting is observed in the coastal ranges normal faulting is most common in baja california and southern sierra nevada including the western basin and range region poor quality solutions with unreliable m w are caused by excessive background noise in the waveforms small events m l 4 0 can be affected by ambient noise or teleseisms but larger events can also have unreliable solutions if they follow a recent large regional event

waveform inversion using secondary observables a new method is proposed for inverting single station surface wave seismograms instead of inverting directly the time signal use is made of secondary observables built up from a set of time frequency images this allows us to enhance the signal to noise ratio and to make more linear the relationship between the model parameters and the inverted observables the feasibility of the method is checked on multimode synthetics prior to present the inversion of a long period multimode seismogram related to the pacific ocean