multistep modelling of receiver based seismic and ambient noise data from wombat array crustal structure beneath southeast australia summary a limitation of most forms of passive seismic tomography using distant earthquakes lies in the fact that crustal structure is poorly resolved an attempt is made here to address this issue by modelling teleseismic receiver functions rfs and dispersion curves derived from ambient noise through a multistep approach the seal3 experiment in central and southern new south wales nsw used here represents one of 13 array deployments that so far comprise the large wombat project which aims to cover a significant portion of the australian continent with a rolling array of seismometers an interactive forward modelling software package irffm2 is introduced and applied to the observed rfs and surface wave dispersion curves to define a prior physically acceptable range of elastic parameters in the lithosphere which is combined with a grid search and a linearized inversion our results emphasize the importance of a joint treatment of rfs and dispersion data as the predictions from 1 d velocity models at individual stations derived from only rfs display large departures from the observed ambient noise dispersion curves in total 27 jointly constrained 1 d shear wave models are produced which provide sufficient sampling of the crust beneath seal3 to permit detailed inferences about lateral variations in structure to be made of particular note is the observation that the moho deepens towards the mountainous southeast where it exceeds 50 km in depth beneath the southern highlands of nsw thus marking out some of the thickest crust in australia the complex lateral variations in mid lower crustal velocity that we observe probably reflect the manifold interactions of a thinning lithosphere associated igneous underplating recent hot spot related volcanism and uplift our results image an important part of the lithosphere that is poorly constrained by regional and teleseismic tomography and contribute to the understanding of the formation of the southern highlands and the palaeozoic lachlan orogen

continental vs oceanic lithosphere beneath the eastern mediterranean sea implications from rayleigh wave dispersion measurements abstract tectonics of the eastern mediterranean are strongly influenced by subduction of oceanic lithosphere with slab pull as a prominent driving force the current distribution of remnants of oceanic lithosphere and the properties of african mantle lithosphere beneath the eastern mediterranean basin have been a matter of debate previous studies variously found continental as well as oceanic lithosphere in this region a set of 1 d s wave velocity models is determined in order to characterize the mantle lithosphere in the area between crete and the middle east for seven paths starting from cyprus and running to crete to anatolia as well as to the middle east broad band average phase velocity curves of the fundamental rayleigh mode are obtained in the frequency range of about 3 mhz to 90 mhz by a two station method in addition an east west oriented path crossing southern anatolia and a path running parallel to the dead sea fault zone are considered phase velocity curves are inverted for path average 1 d s wave velocity models resolution is investigated with the neighbourhood algorithm comparing the resulting 1 d models cold oceanic mantle lithosphere showing s wave velocities above 4 6 km s 1 can be distinguished from mantle lithosphere with low s wave velocities oceanic lithosphere is found west of cyprus beneath the herodotus basin as indicated by benioff zones it is subducting towards northwest in the southeastern aegean and towards northeast beneath southwestern anatolia to the east of cyprus the mantle lithosphere beneath the easternmost mediterranean sea shows low s wave velocities no indications for cold oceanic mantle lithosphere are found beneath the levant basin in the region of the dead sea fault zone and the levant basin the lithosphere asthenosphere boundary is located at shallow depths of about 60 km to 80 km the dsfz is situated in a region of thinned lithosphere underlain by an asthenosphere with anomalous low s wave velocities low s wave velocities beneath southern anatolia extend down to at least 150 km depth as expected for a back arc setting inferred moho depths vary for the different paths between 28 km and 41 km

crustal anisotropy beneath hudson bay from ambient noise tomography evidence for post orogenic lower crustal flow the crust underlying hudson bay canada records a long and complex tectonic history in this study we investigate this region using tomographic inversion based on continuous ambient noise recordings from 37 broadband seismograph stations that encircle hudson bay the ambient noise data were processed to obtain group velocity dispersion measurements from 10 35 s period which were inverted using an algorithm that incorporates the effects of anisotropy this work is among the first in which ambient noise data have been used to investigate azimuthal anisotropy the inversion method uses smoothing and damping to regularize the solution due to the significantly increased number of model parameters relative to the isotropic case we performed a careful analysis for parameter selection to determine whether leakage occurs between isotropic and anisotropic model parameters we observe a robust pattern of anisotropic fast directions in the mid crust that are consistent with large scale tectonic trends based on magnetic anomaly patterns in particular a distinctive double indentor shape for the superior craton is clearly expressed in both data sets this pattern breaks down deeper in the crust suggesting that some degree of lithospheric decoupling in the lower crust such as channel flow occurred during orogenesis given regional evidence for vertically coherent deformation in the crust and underlying mantle we interpret this pattern in the lower crust as a tectonic overprint that post dates the main phase of trans hudson deformation at most levels in the crust we observe a profound change in direction of anisotropic fast direction across an inferred suture beneath hudson bay

crustal shear wave velocity structure of the western united states inferred from ambient seismic noise and earthquake data 1 surface wave dispersion measurements from ambient seismic noise and array based measurements from teleseismic earthquakes observed with the earthscope usarray transportable array ta are inverted using a monte carlo method for a 3 d vs model of the crust and uppermost mantle beneath the western united states the combination of data from these methods produces exceptionally broadband dispersion information from 6 to 100 s period which constrains shear wave velocity structures in the crust and uppermost mantle to a depth of more than 100 km the high lateral resolution produced by the ta network and the broadbandedness of the dispersion information motivate the question of the appropriate parameterization for a 3 d model particularly for the crustal part of the model we show that a relatively simple model in which vs increases monotonically with depth in the crust can fit the data well across more than 90 of the study region except in eight discrete areas where greater crustal complexity apparently exists the regions of greater crustal complexity are the olympic peninsula the mendocinotriple junction the yakima fold belt the southern cascadia back arc the great central valley of california the salton trough the snake river plain and the wasatch mountains we also show that a strong rayleigh love discrepancy exists across much of the western united states which can be resolved by introducing radial anisotropy in both the mantle and notably the crust we focus our analysis on demonstrating the existence of crustal radial anisotropy and primarily discuss the crustal part of the isotropic model that results from the radially anisotropic model by voigt averaging model uncertainties from the monte carlo inversion are used to identify robust isotropic features in the model the uppermost mantle beneath the western united states is principally composed of four large scale shear wave velocity features but lower crustal velocity structure exhibits far greater heterogeneity we argue that these lower crustal structures are predominantly caused by interactions with the uppermost mantle including the intrusion and underplating of mafic mantle materials and the thermal depression of wave speeds caused by conductive heating from the mantle upper and middle crustal wave speeds are generally correlated and notable anomalies are inferred to result from terrane accretion at the continental margin and volcanic intrusions

influence of sand on hydraulics and gravel transport in a braided gravel bed river measurements in a braided reach of the proglacial white river washington are used to compare the bed load capacity and competence of flow over the predominant gravel bed and over a narrow ribbon of mobile sand which extended alongside the talweg analysis of 144 velocity profiles and 222 bed load samples shows that shear stress and roughness height were significantly lower over sand than gravel but maximum bed load diameter and total gravel transport rate significantly higher as were transport rates of given size fractions at similar shear stresses these differences in competence and capacity are explained by relative size effects on the threshold shear stress for entrainment the influence on gravel transport of local variation in bed material size may explain the self sorting of bed load sheets described by other workers however in channels like that described here the continuous longitudinal ribbon of sand allows the flow to develop a lower shear stress over the smoother bed which partly offsets the relative size effects on competence and capacity

global crustal thickness from neural network inversion of surface wave data summary we present a neural network approach to invert surface wave data for a global model of crustal thickness with corresponding uncertainties we model the a posteriori probability distribution of moho depth as a mixture of gaussians and let the various parameters of the mixture model be given by the outputs of a conventional neural network we show how such a network can be trained on a set of random samples to give a continuous approximation to the inverse relation in a compact and computationally efficient form the trained networks are applied to real data consisting of fundamental mode love and rayleigh phase and group velocity maps for each inversion performed on a 2 2 grid globally we obtain the a posteriori probability distribution of moho depth from this distribution any desired statistic such as mean and variance can be computed the obtained results are compared with current knowledge of crustal structure generally our results are in good agreement with other crustal models however in certain regions such as central africa and the backarc of the rocky mountains we observe a thinner crust than the other models propose we also see evidence for thickening of oceanic crust with increasing age in applications characterized by repeated inversion of similar data the neural network approach proves to be very efficient in particular the speed of the individual inversions and the possibility of modelling the whole a posteriori probability distribution of the model parameters make neural networks a promising tool in seismic tomography

surface wave tomography of the gulf of california 1 we measured interstation fundamental mode rayleigh wave phase velocities using data from the nars baja seismic network located around the gulf of california a region average shear velocity model and a set of azimuthally anisotropic phase velocity maps are obtained from these data the average shear velocity structure shows a strong low velocity zone underlying a thin lid and the data are suggestive of low velocities down into the transition zone the phase velocity maps display signatures of sedimentary layers crustal thickness variations upwelling under the plate boundary and the presence of the subducted farallon microplate remnants beneath the gulf the upper mantle features inferred from this study provide new seismic evidence on the tectonic evolution of the region

mapping the moho with seismic surface waves a review resolution analysis and recommended inversion strategies abstract the strong sensitivity of seismic surface waves to the moho is evident from a mere visual inspection of their dispersion curves or waveforms rayleigh and love waves have been used to study the earth s crust since the early days of modern seismology yet strong trade offs between the moho depth and crustal and mantle structure in surface wave inversions prompted doubts regarding their capacity to resolve the moho here we review surface wave studies of the moho with a focus on early work and then use model space mapping to establish the waves sensitivity to the moho depth and the resolution of their inversion for it if seismic wavespeeds within the crust and upper mantle are known then moho depth variations of a few kilometres produce large 1 perturbations in phase velocities however in inversions of surface wave data with no a priori information wavespeeds not known strong moho depth shear speed trade offs will mask 90 of the moho depth signal with remaining phase velocity perturbations 0 1 only in order to resolve the moho with surface waves alone errors in the data must thus be small up to 0 2 for resolving continental moho with larger errors moho depth resolution is not warranted and depends on error distribution with period an effective strategy for the inversion of surface wave data alone for the moho depth is to first constrain the crustal and upper mantle structure by inversion in a broad period range and then determine the moho depth in inversion in a narrow period range most sensitive to it with the first step results used as reference prior information on crustal and mantle structure reduces the trade offs and thus enables resolving the moho depth with noisier data such information should be used whenever available joint analysis or inversion of surface wave and other data receiver functions topography gravity can reduce uncertainties further and facilitate moho mapping

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

peculiarities of surface wave propagation across central eurasia abstract the recent installation of six broadband digital iris ida seismic stations in the ussr has provided new opportunities for studying surface wave propagation across eurasia group velocities of fundamental rayleigh and love modes between epicenters and these stations were determined for 35 events that occurred since april 1989 to the middle of july 1990 near eurasia differential phase velocities were found for the same arrivals along paths between several pairs of stations group and phase velocities were obtained in the period range from 15 to 300 sec frequency time polarization analysis was used for studying polarization properties of surface waves in some cases significant anomalies in the particle motion for periods up to 100 sec were observed they are attributed to surface wave refraction and scattering due to lateral inhomogeneities at the boundaries and inside the eurasia continent

the upper mantle beneath the philippine sea region from waveform inversions we present a three dimensional s velocity model for the upper mantle beneath the philippine sea region it was derived from inversions of 281 broad band vertical component seismograms recorded in the area at the global seismological network gsn and skippy portable array stations we have been able to obtain high resolution tomographic images spanning the depths down to 200 300 km and locally down to the upper transition zone high velocity subducting slabs and low velocity volcanic arc regions are the dominant features of the model fast thin lithosphere of back arc basins is underlain by a prominent low velocity zone low velocities at lithospheric depths are observed beneath the extinct central basin ridge in the west philippine basin and close to the eauripik ridge that separates the east and west caroline basins high upper mantle heterogeneity and resulting scattering presents a difficulty and limits the resolution especially below 200 300 km explicit modeling of seismic wave diffraction may be necessary for a significant improvement in resolution

seismic evidence for olivine phase changes at the 410 and 660 kilometer discontinuities the view that the seismic discontinuities bounding the mantle transition zone at 410 and 660 kilometer depths are caused by isochemical phase transformations of the olivine structure is debated combining converted wave measurements in east asia and australia with seismic velocities from regional tomography studies we observe a correlation of the thickness of and wavespeed variations within the transition zone that is consistent with olivine structural transformations moreover the seismologically inferred clapeyron slopes are in agreement with the mineralogical clapeyron slopes of the mg fe 2sio4 spinel and postspinel transformations

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

anisotropic rayleigh wave tomography of ireland s crust implications for crustal accretion and evolution within the caledonian orogen 1 the irish landmass now at the western extremity of the eurasian plate was formed in the caledonian orogeny during the palaeozoic assembly of pangea the associated closure of the iapetus ocean is recorded in the ne sw structural trends that dominate the tectonic set up of ireland today the deep crustal dynamics of the orogeny and the effect on the crust of the subsequent extension and magmatism in the north atlantic are debated fabrics within deep crustal rocks preserve a record of deformation during and after the continental collisions here we measured rayleigh wave phase velocities using seismograms recorded by permanent and temporary intermediate band stations in ireland and inverted the data for phase velocity maps including azimuthal anisotropy the observed isotropic phase velocity heterogeneity reflects moderate crustal thickness and seismic velocity variations across ireland anisotropy of rayleigh waves at 10 20 s periods shows a ne sw fast propagation direction and is largest up to 2 at a 15 s period at which rayleigh waves sample primarily the middle and lower crust the ne sw trend of the deep crustal anisotropic fabric is parallel to tectonic trends in particular the iapetus suture zone which indicates that suture parallel flow in the middle and lower crust accommodated the continental collision the apparent preservation of the caledonian age fabric also shows that the deep crust of the eurasian margin in ireland was neither stretched by the nw se extension associated with the opening of the north atlantic nor modified significantly by the cenozoic magmatism in the region

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

underplating in the himalaya tibet collision zone revealed by the hi climb experiment we studied the formation of the himalayan mountain range and the tibetan plateau by investigating their lithospheric structure using an 800 kilometer long densely spaced seismic array we have constructed an image of the crust and upper mantle beneath the himalayas and the southern tibetan plateau the image reveals in a continuous fashion the main himalayan thrust fault as it extends from a shallow depth under nepal to the mid crust under southern tibet indian crust can be traced to 31 n the crust mantle interface beneath tibet is anisotropic indicating shearing during its formation the dipping mantle fabric suggests that the indian mantle is subducting in a diffuse fashion along several evolving subparallel structures

preservation ofδ18o values of fluid inclusion water in quartz over geological time in an epithermal environment beregovo deposit transcarpathia ukraine 18o and d values were measured for water in fluid inclusions in minerals from the beregovo epithermal deposit transcarpathia ukraine directly measured 18o values for the water in inclusions in quartz were compared to calculated 18oquartz values using fluid inclusion homogenization temperatures and published isotope equilibria constants on the basis of this comparison it was concluded that the 18o values of water in the fluid inclusions in quartz in epithermal environments are preserved over geological time further evidence for the lack of isotope exchange between fluid inclusion water and the quartz host is the similarity between the isotopic composition of water extracted from sulphides sphalerite 18o 3 5 and d 82 and galena 18o 2 5 and d 79 and water extracted from coexisting quartz 18o 2 8 and d 84

complex layered deformation within the aegean crust and mantle revealed by seismic anisotropy continental lithosphere can undergo pervasive internal deformation often distributed over broad zones near plate boundaries however because of the paucity of observational constraints on three dimensional movement at depth patterns of flow within the lithosphere remain uncertain endmember models for lithospheric flow invoke deformation localized on faults or deep shear zones or alternatively diffuse viscous fluid like flow here we determine seismic rayleigh wave anisotropy in the crust and mantle of the aegean region an archetypal example of continental deformation our data reveal a complex depth dependent flow pattern within the extending lithosphere beneath the northern aegean sea fast shear wave propagation is in a north south direction within the mantle lithosphere parallel to the extensional component of the current strain rate field in the south central aegean where deformation is weak at present anisotropic fabric in the lower crust runs parallel to the direction of palaeo extension in the miocene the close match of orientations of regional scale anisotropic fabric and the directions of extension during the last significant episodes of deformation implies that at least a large part of the extension in the aegean has been taken up by distributed viscous flow in the lower crust and lithospheric mantle

an inverted continental moho and serpentinization of the forearc mantle volatiles that are transported by subducting lithospheric plates to depths greater than 100 km are thought to induce partial melting in the overlying mantle wedge resulting in arc magmatism and the addition of significant quantities of material to the overlying lithosphere asthenospheric flow and upwelling within the wedge produce increased lithospheric temperatures in this back arc region but the forearc mantle in the corner of the wedge is thought to be significantly cooler here we explore the structure of the mantle wedge in the southern cascadia subduction zone using scattered teleseismic waves recorded on a dense portable array of broadband seismometers we find very low shear wave velocities in the cold forearc mantle indicated by the exceptional occurrence of an inverted continental moho which reverts to normal polarity seaward of the cascade arc this observation provides compelling evidence for a highly hydrated and serpentinized forearc region consistent with thermal and petrological models of the forearc mantle wedge this serpentinized material is thought to have low strength and may therefore control the down dip rupture limit of great thrust earthquakes as well as the nature of large scale flow in the mantle wedge

southern african crustal evolution and composition constraints from receiver function studies 1 stacking of approximately 1500 radial receiver functions recorded at about 80 broadband seismic stations deployed in southern africa reveals systematic spatial variations in the ratio of crustal p and s wave velocities crustal thickness h and the amplitude of the converted moho phases r the eastern zimbabwe and the southern kaapvaal cratons are characterized by small h 38 km small 1 73 and large r 0 15 values suggesting that the relatively undisturbed archean crust beneath southern africa is separated from the mantle by a sharp moho and is felsic in composition the limpopo belt which was created by a collisional event at 2 7 ga displays large h 43 km but similar and r values relative to the cratonic areas the bushveld mafic intrusion complex and its surrounding areas show large 1 78 large h 43 km and small r 0 11 values reflecting the intrusion of mafic material into the original crust as a result of the bushveld event at 2 05 ga excluding the bushveld the spatially consistent and age independent low accentuate the difference between felsic crustal composition and more mafic island arcs that are thought to be the likely source of continental material within such an island arc model our data combined with xenolith data excluding mantle delamination in cratonic environments suggest that the modification to a felsic composition e g by the partial melting of basalt and removal of residue by delamination is restricted to have occurred during the collision between the arcs and the continent

crustal thickness map of the western united states by partitioned waveform inversion the partitioned waveform inversion method nolet 1990 was used to obtain a new crustal thickness map of the western united states we fitted 200 seismograms containing higher and fundamental mode rayleigh waves for events and stations in the western united states which provided average crustal thickness constraints between each source receiver pair all these constraints were combined in a linear inversion to obtain a crustal thickness map local crustal thickness estimates from published seismic reflection refraction work were used as additional constraints to overcome deficiencies of path coverage in some areas the resulting crustal thickness map shows thicker 45 km crust beneath the cascades thick 40 km crust beneath the sierra nevada thin 30 km crust beneath the basin and range and thick greater than 45 km crust beneath the colorado plateau the boundary between the colorado plateau and the southern leg of the basin and range is a prominent feature of the model thick crust is seen at the bend of the san andreas fault near los angeles our model is broadly consistent with the crustal thickness map of mooney and weaver 1989 a quantitative comparison with the crustal thickness model 3smac nataf and ricard 1996 was performed by inverting for a model that deviates least from it results show that we are able to retain most of the features of that model while maintaining a good fit to the surface wave and point constraint data

eucrust 07 a new reference model for the european crust 1 we present a new digital model eucrust 07 for the crust of western and central europe and surroundings 35n 71n 25w 35e available results of seismic reflection refraction and receiver functions studies are assembled in an integrated model at a uniform grid 15 0 15 0 the model consists of three layers sediments and two layers of the crystalline crust besides depth to the boundaries we provide average p wave velocities in the upper and lower parts of the crystalline crust the new model demonstrates large differences in the moho depth compared to previous compilations over 10 km in some specific areas e g the baltic shield furthermore the velocity structure of the crust is much more heterogeneous than in previous maps eucrust 07 offers a starting point for numerical modeling of deeper structures by allowing correction for crustal effects beforehand and to resolve trade off with mantle heterogeneities citation tesauro m m k kaban and s a p l cloetingh 2008 eucrust 07 a new reference model for the european crust geophys res lett 35 l05313 doi 10 1029 2007gl032244

deep structure of the alps what do we really know abstract in the last five decades the deep structure of the alps has been probed by every geophysical method applicable and the resulting amount of data is unmatched for any other orogen in this study an attempt is made to review the data and the proposed structural models with the aim of separating the certain from the probable and from the speculative information this can be achieved by first reviewing the theoretical resolving power and ambiguity of the applied interpretation methods and then analysing the proposed models the methods reviewed are inversion of surface wave data teleseismic and local earthquake seismic tomography near vertical reflection seismology wide angle reflection and refraction seismology and gravity modelling all information about the moho rated as certain is combined to give a moho map of the alpine area the information rated as certain and probable and additional qualitative arguments are used to discuss a crustal model of the western and central alps represented by two cross sections major structural elements in this crustal model are a thick overthrust penninic nappe system wedging at mid to lower crustal levels a discontinuous moho and strong variations along the strike of the orogen whereas the structures of the european upper crust and of the penninic nappe system are well constrained only few and isolated lower crustal structural elements are rated as certain finally the shape of the lower lithosphere in the alps is discussed by review and comparison of the results from surface wave teleseismic travel time residual and tomographic studies qualitative arguments suggest the existence of a lithospheric root or slab beneath the alps probable tomographic information suggests a south vergent european lithospheric slab beneath the southern alps and the po plain despite the considerable number of studies aimed at resolving the deepest part of alpine orogeny the available quantitative information on the sub moho structure cannot be rated as certain

a synoptic view of the distribution and connectivity of the mid crustal low velocity zone beneath tibet 1 based on 1 2 years of continuous observations of seismic ambient noise data obtained at more than 600 stations in and around tibet rayleigh wave phase velocity maps are constructed from 10 s to 60 s period a 3 d vsv model of the crust and uppermost mantle is derived from these maps the 3 d model exhibits significant apparently inter connected low shear velocity features across most of the tibetan middle crust at depths between 20 and 40 km these low velocity zones lvzs do not conform to surface faults and significantly are most prominent near the periphery of tibet the observations support the internal deformation model in which strain is dispersed in the deeper crust into broad ductile shear zones rather than being localized horizontally near the edges of rigid blocks the prominent lvzs are coincident with strong mid crustal radial anisotropy in western and central tibet and probably result at least partially from anisotropic minerals aligned by deformation which mitigates the need to invoke partial melt to explain the observations irrespective of their cause in partial melt or mineral alignment mid crustal lvzs reflect deformation and their amplification near the periphery of tibet provides new information about the mode of deformation across tibet

new images of the earth s upper mantle from measurements of surface wave phase velocity anomalies 1 the sensitivity of a surface wave to the lateral structure of the earth s mantle depends on the local structure and thickness of the crust particularly at short periods the strong lateral heterogeneity of the crust has a significant nonlinear effect on the surface wave sensitivity functions thus far this effect has not been quantified and tomographic studies of the upper mantle based on surface wave observations have not taken it into account on the basis of a jeffreys wentzel kramers brillouin jwkb description of surface wave propagation we find and discuss the lateral variations of the sensitivity of love and rayleigh waves to mantle seismic anomalies associated with a realistic model of the crust mooney et al 1998 we then use the resulting laterally varying sensitivity kernels to determine a new tomographic image of horizontally and vertically polarized shear velocity in the upper mantle from love and rayleigh wave phase velocity measurements periods from 35 to 300 s in terms of large scale patterns of high and low velocity our model is similar to previously published ones confirming among other features the anomalous anisotropy underlying the central pacific ekstrom and dziewonski 1998 we find however that the lateral dependence of the surface wave sensitivity kernels has a significant effect on the absolute amplitude of the anomalies which should not be neglected as we attempt to obtain higher resolution images of the upper mantle