impacts of non plane waves on two station measurements of phase velocities summary to determine the regional shear wave velocities in the lithosphere it is frequently necessary to use two station dispersion curves we investigate the influence of non plane wave energy on such dispersion curves and compare them to two other better known sources of error deviations from great circle paths and uncorrelated noise to study the influence of nonplane waves created from distant heterogeneities we create complex wavefields in a laterally homogeneous medium by adding interfering waves to a main plane wave we then calculate the apparent phase velocity between two seismic stations located 100 400 km apart using realistic values for the sources of error we conclude that the contribution of each is similar for 200 km long profiles our conclusions on non plane waves are made under the assumption that non plane energy from distant heterogeneities varies randomly with hypocentre location if this is correct then only five to 10 events with different hypocentres are required to obtain a stable dispersion curve with less than 1 per cent error the influence of uncorrelated noise and non plane waves diminish for longer profiles while the errors due to great circle deviations are independent of profile length and systematically bias the dispersion curve to higher velocities we recommend the inclusion of some off profile broad band stations for surface wave studies on a regional scale because such supplementary stations make it possible to apply first order corrections for off great circle propagation the strong influence from the different sources of error combined with our lack of precise knowledge of the nature and amplitude of non plane energy implies that the interpretation of two station measurements should be restricted to major changes in regional earth structure

imaging crustal discontinuities and the downgoing slab beneath western crete the migration of teleseismic receiver functions yields high resolution images of the crustal structure of western crete data were collected during two field campaigns in 1996 and 1997 by networks of six and 47 short period three component seismic stations respectively a total of 1288 seismograms from 97 teleseismic events were restituted to true ground displacement within a period range from 0 5 to 7 s the application of a noise adaptive deconvolution filter and a new polarization analysis technique helped to overcome problems with local coda and noise conditions the computation and migration of receiver functions results in images of local crustal structures with unprecedented spatial resolution for this region the crust under crete consists of a continental top layer of 15 20 km thickness above a 20 30 km thick subducted fossil accretionary wedge with a characteristic en echelon fault sequence the downgoing oceanic moho lies at a depth of 40 60 km and shows a topography or undulation with an amplitude of several kilometres as a consequence of slab depth and distribution of local seismicity the mediterranean ridge is interpreted as the recent accretionary wedge

multiscale finite frequency rayleigh wave tomography of the kaapvaal craton summary we have measured phase delays of fundamental mode rayleigh waves for 12 events recorded by the southern africa seismic experiment at frequencies between 0 005 and 0 035 hz a novel multiscale finite frequency tomographic method based on wavelet decomposition of 3 d sensitivity kernels for the phase of rayleigh waves is used to map the shear velocities in the upper mantle beneath southern africa the kernels are computed by summing coupled normal modes over a very fine grid surrounding the seismic array to estimate and minimize the biases in the model resulting from structures outside the tomographic grid a jackknife inversion method is implemented the contribution of heterogeneities outside the target volume is significant but produces artefacts in the tomographic model that are easily identified and discarded before interpretation with structures on length scales as short as 100 km retrieved beneath the array the deep structure of the kaapvaal craton is revealed with unprecedented detail outside the array the corresponding resolution is 200 km high velocity cratonic roots are confined to the archean craton and extend to depths of at least 250 km confirming earlier surface structural studies we recognize two distinct units in the kaapvaal craton the eastern witwatersrand block and the western kimberley block are separated by a major near vertical translithospheric boundary which coincides with the colesberg lineament lower than average velocities south and east of the kaapvaal craton reveal extensive metasomatism and heating of the lithosphere probably related to the karoo magmatic event and to the opening of the south atlantic ocean

lithospheric structure of the central andes based on surface wave dispersion 1 shear wave velocity is very sensitive to temperature anomalies and partial melt and can provide important insights on the state of the lithosphere with that aim in mind phase velocities of rayleigh and love waves have been inverted for the regionalized shear wave velocity structure of the lithosphere across the central andes this inversion reveals strong lateral variations of vs both across the range and along strike in the altiplano crust in the upper crust the main features of our models are prominent low velocity anomalies probably related to partial melt below the los frailes ignimbrite complex and the southern altiplano at lower crustal level the altiplano is characterized by lower vs than the surrounding regions we find that the transition from the altiplano to the puna is associated with a 7 km thickening of the crust at mantle depths the nazca plate is found to be overlaid by a dipping low velocity zone with decreasing intensity with depth our results favor the idea of a cold mantle lid underlying the whole central andes

shear velocity structure in the aegean area obtained by inversion of rayleigh waves summary the purpose of this work is to derive a 3 d tomographic image of the shear wave velocity structure of the crust uppermost mantle in the aegean area using the group velocities of rayleigh wave fundamental mode the database consists of 185 regional earthquakes recorded at broad band stations that were installed for a period of 6 month in the aegean area within the framework of a large scale experiment in a previous work karagianni et al 2002 an averaged group velocity has been determined using the method of frequency time analysis ftan for each epicentre station ray path and the data were used in order to determine the local group velocities for different periods over the area covered by the seismic ray paths taking into account additional resolution results obtained for the local group velocities a grid of 0 5 was adopted for the aegean area and a local dispersion curve was defined for each gridpoint more than 80 local dispersion curves were finally inverted using a non linear inversion approach deriving the corresponding 1 d shear velocity models the interpolation of these models resulted in a 3 d s wave tomographic image of the crust and uppermost mantle in the broader aegean area as expected as a result of the complex tectonic setting of the aegean area strong lateral variations of the s wave velocities of the crust and uppermost mantle of the studied area are found in the southern aegean sea as well as in a large part of the central aegean sea a thin crust of approximately 20 22 km is observed whereas the remaining aegean sea area exhibits a crustal thickness less than 28 30 km on the contrary a crustal thickness of 40 46 km is observed in western greece along the hellenides mountain range whereas in the eastern continental greece the crust has a typical thickness of approximately 30 34 km for shallow depths 10 km low s wave velocities are observed under the sedimentary basins of the north aegean sea the gulf of thermaikos axios basin and western greece at depths ranging from 10 to 20 km low s wave velocities are mainly found in western greece under peloponnesus as well as in rhodes this low velocity zone seems to extend along the hellenic arc and can be correlated to the hellenides mountain range and the alpine orogenesis in agreement with previous p wave tomographic results in the southern aegean sea very low s wave velocities 3 6 4 0 km s 1 are observed at depths of approximately 30 40 km just below the moho discontinuity while in the rest of the inner aegean sea and continental greece the uppermost mantle is characterized by velocities around 4 3 4 4 km s 1 this low velocity zone in the southern aegean sea can be associated with the high temperatures and the presence of significant percentage partial melt in the mantle wedge of the southern aegean subduction zone in agreement with previous studies

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

segmented african lithosphere beneath the anatolian region inferred from teleseismic p wave tomography summary lithospheric deformation throughout anatolia a part of the alpine himalayan orogenic belt is controlled mainly by collision related tectonic escape of the anatolian plate and subduction roll back along the aegean subduction zone we study the deeper lithosphere and mantle structure of anatolia using teleseismic finite frequency p wave traveltime tomography we use data from several temporary and permanent seismic networks deployed in the region approximately 34 000 p wave relative traveltime residuals measured in multiple frequency bands are inverted using approximate finite frequency sensitivity kernels our tomograms reveal segmented fast seismic anomalies beneath anatolia that corresponds to the subducted portion of the african lithosphere along the cyprean and the aegean trenches we identify these anomalies as the subducted aegean and the cyprus slabs that are separated from each other by a gap as wide as 300 km beneath western anatolia this gap is occupied by slow velocity perturbations that we interpret as hot upwelling asthenosphere the eastern termination of the subducting african lithosphere is located near the transition from central anatolia to the eastern anatolian plateau or arabian eurasian collision front that is underlain by large volumes of hot underplating asthenosphere marked by slow velocity perturbations our tomograms also show fast velocity perturbations at shallow depths beneath northwestern anatolia that sharply terminates towards the south at the north anatolian fault zone nafz the associated velocity contrast across the nafz persists down to a depth of 100 150 km hence our study is the first to investigate and interpret the vertical extent of deformation along this nascent transform plate boundary overall the resolved upper mantle structure of anatolia is directly related with the geology and tectonic features observed at the surface of the anatolian plate and suggest that the segmented nature of the subducted african lithosphere plays an important role in the evolution of anatolia and distribution of its tectonic provinces

10be records of sediment cores from high northern latitudes implications for environmental and climatic changes the 10be records of four sediment cores forming a transect from the norwegian sea at 70 n core 23059 via the fram strait core 23235 to the arctic ocean at 86 n cores 1533 and 1524 were measured at a high depth resolution although the material in all the cores was controlled by different sedimentological regimes the 10be records of these cores were superimposed by glacial interglacial changes in the sedimentary environment core sections with high 10be concentrations 1 109 at g are related to interglacial stages and core sections with low10be concentrations 0 5 109 at g are related to glacial stages climatic transitions e g termination ii 5 6 are marked by drastic changes in the 10be concentrations of up to one order of magnitude the average 10be concentrations for each climatic stage show an inverse relationship to their corresponding sedimentation rates indicating that the 10be records are the result of dilution with more or less terrigenous ice rafted material however there are strong changes in the 10be fluxes e g termination ii into the sediments which may also account for the observed oscillations most likely both processes affected the 10be records equally amplifying the contrast between lower glacials and higher interglacials 10be concentrations the sharp contrast of high and low 10be concentrations at climatic stage boundaries are an independent proxy for climatic and sedimentary change in the nordic seas and can be applied for stratigraphic dating 10be stratigraphy of sediment cores from the northern north atlantic and the arctic ocean

aegean crustal thickness inferred from gravity inversion geodynamical implications since oligo miocene times the aegean domain has undergone regional extension due to the southward retreat of the hellenic subduction zone boundary conditions have been more recently modified by the westward extrusion of anatolia a new map of the aegean crustal thickness inferred from gravity inversion is proposed here to better constrain the variations in space and time of crustal thinning that has accumulated since oligo miocene times moho topography is obtained by inversion of satellite marine gravity data data are first corrected for terrain anomalies and deep mantle effects african subducting slab they are then filtered between 50 and 300 km to avoid short wavelength intracrustal effects results are consistent with previous 2d geophysical studies seismic refraction receiver functions and show that an overall regional isostatic compensation of the crust holds for the aegean area with a mean crustal thickness of 25 km three different provinces north aegean cyclades and cretan sea can be identified thinner crust is observed both in the north aegean region ne sw trending of thinning with crustal thickness lower than 24 km and in the cretan sea crustal thickness of 22 23 km between these two regions the cyclades are marked by a rather flat moho at 25 km a two stage model of the aegean extension could well explain the observed crustal thickness variation from oligocene to middle miocene gravitational collapse of the hellenides due to the southward retreat of the african slab reduced the aegean continental crust from 50 km by reference to continental greece and anatolia to a mean value of 25 km at the scale of the whole aegean from upper miocene to present the westward extrusion of anatolia modified the extension and the associated crustal thinning in the north aegean domain during this second episode crustal thinning related to the southward retreat of the african slab tends to localize in the cretan sea the cyclades likely behave as a rigid block translated toward the south west without significant deformation in agreement with the gps velocity field and the lack of major earthquakes d 2004 elsevier b v all rights reserved

wave theoretical inversion of teleseismic surface waves in a regional network phase velocity maps and a three dimensional upper mantle shear wave velocity model for southern germany summary using teleseimic surface wave data from 110 selected earthquakes recorded at 10broad band stations in southern germany we construct phase velocity maps of rayleigh waves for southern germany in a further step these maps are inverted for a three dimensional model of the sv velocity of the upper 200 km of the mantle we attempt to take into account the effect of heterogeneous structure outside the study region by jointly inverting the data for heterogeneous phase velocity inside the study region and the distortion of the incoming wavefields by the surrounding structure the total wavefield in the study region is computed with a scattering formalism which includes multiple forward scattering and single backscattering since in principle the data can be perfectly fit by the incoming wavefields without any heterogeneous structure inside the study area we impose additional constraints on the incoming wavefields to reduce the non uniqueness the most important constraint is an energy criterion which states that the energy of the modelled wavefield in the study area averaged over many events should be equal to the energy sampled by the stations we demonstrate that enforcing this criterion generates phase velocity maps with heterogeneous structure nevertheless we are able to satisfy the energy criterion without any heterogeneous structure at the price of an only slightly increased data misfit hence it must be concluded that a seismic network of size and station density such as the one used in this study is still insufficient to demonstrate convincingly the existence of heterogeneities in the network area using teleseismic surface waves any reasonable structure combined with the appropriate incoming wavefields would allow an acceptable fit of our data this frustrating conclusion of course applies to all other comparable studies which use teleseismic surface waves although we cannot convincingly show that any phase velocity map we find should be preferred over others we are able to obtain good reconstructions of test structures from realistic synthetic data with the same station and event distribution as the real data moreover we find that the geometric pattern of the phase velocity maps obtained from real data depends only weakly on the constraints applied in the inversion while the amplitude of the phase velocity perturbations is almost completely determined by the constraints for all periods considered the fit to the data is extremely good the reduction of the quadratic misfit relative to the case of plane incoming waves and no structure is dramatic for the shorter periods the 3 d model of vertical shear wave velocity down to a depth of 200 km exhibits a basic division into four quadrants separated by a vertical plane intersecting the surface along a nearly west east line and a horizontal plane at about 130 km depth the northern rants show high velocities in the top 120 km and low velocities below 140 km the opposite is the case for the southern quadrants an exception to this general feature is a pronounced low velocity zone in the northwestern corner of the region

boundary scavenging in the pacific ocean a comparison of 10be and 231pa concentrations of u th 231pa and 10be were measured in holocene sediments from two cores collected off the west coast of south america two cores from the east pacific rise two from the equatorial pacific and one from the south pacific central gyre our results together with data from 5 cores reported in the literature show that boundary scavenging plays a major role in the removal of 10be from the pacific ocean deposition rates of 10be at three margin sites are more than an order of magnitude greater than at sites of red clay accumulation in the deep central pacific deposition of 231pa is 4 to 5 fold greater at the margin sites the residence time of 10be with respect to chemical scavenging defined as its inventory in the water column divided by its rate of removal to the sediments varies regionally from 1000 years at the red clay sites in the deep central pacific to 100 years at the margin sites different factors control boundary scavenging of pa and be for example scavenging of 231pa is enhanced by metal oxide coatings of particles whereas this seems to have little influence on the scavenging of 10be 1990

constraints on absolute s velocities beneath the aegean sea from surface wave analysis summary the 3 d structure of the lithosphere beneath the aegean sea is investigated through surface wave dispersion analysis rayleigh and love waves recorded by 12 broad band stations installed for a duration of 6 months in the aegean region are processed through array analysis and wiener filtering data from three geofon stations in the area of crete were also used the resulting two station phase velocities are used to determine lateral variations of rayleigh wave phase velocities between periods of 20 and 100 s by a 2 d ray tomography method the obtained phase velocities are inverted to calculate variation of s wave velocity with depth using a combination of linearized inversion and a monte carlo based non linear inversion the absolute s wave velocity is resolved to a depth of approximately 200 km a highvelocity anomaly of 3 per cent is observed in the southern aegean attributed to the hellenic subduction in the northern part of the aegean in the prolongation of the north anatolian fault which is influenced by strong extensional movements we found low absolute s wave velocities at 50 100 km depth this supports a model of a distributed deformation of the upper mantle in the area separate rayleigh and love wave phase velocity inversions along common profiles reveal a strong love rayleigh discrepancy in the northern aegean down to at least 150 km depth i e most probably including the top of the asthenosphere

beryllium 10 in australasian tektites constraints on the location of the source crater abstract by using accelerator mass spectrometry we have measured the 10be concentrations of 86 australasian tektites corrected to the time of tektite production 0 8 my ago the 10be concentrations 106 atom g range from 59 for a layered tektite from huai sai thailand to 280 for an australite from new south wales australia the average value is 143 50 when tektites are sorted by country their average measured 10be concentrations increase slowly with increasing distance from southeast asia the probable location of the tektite producing event from 59 9 for 6 layered tektites from laos to 136 20 for 20 splash form tektites from australia the lowest 10be concentrations for tektites fall on or within a contour centered off the shore of vietnam south of the gulf of tonkin 107 e 17 n but also encompassing two other locations in the area of northeastern thailand previously proposed for the site of a single tektite producing impact the 10be concentrations of layered tektites show only a weak anticorrelation r 0 3 with the numbers of relict crystalline inclusions loosely consolidated fine grained terrestrial sediments or recently consolidated sedimentary rocks are the most likely precursor materials dilution of sediments with other kinds of rock raises problems in mixing and is not supported by petrographic data sedimentary columns that have the right range of 10be concentrations occur off the coasts of places where sedimentation rates are high relative to those in the deep sea a single impact into such a region 15 to 300 m thick could have propelled near surface high 10be material farthest to australia while keeping the deeper lying low 10be layers closer to home we do not rule out however other proposed mechanisms for tektite formation

joint inversion for three dimensional s velocity mantle structure along the tethyan margin abstract for purposes of studying the lateral heterogeneity as well as for ultimately predicting seismograms for this region we construct a new 3 d s velocity model by jointly inverting a variety of different seismic data we jointly invert regional waveforms surface wave group velocity measurements teleseismic s arrival times and crustal thickness estimates from receiver functions refraction lines and gravity surveys these data types have complementary resolving power for crust and mantle structures vertical and lateral variations shallow and deep mantle features local and global structure therefore a joint inversion of these data sets might help unravel the complexity of this tectonically diverse area these measurements are made from a combination of mantle investigation of the deep suture between europe and africa midsea program for array seismic studies of the continental lithosphere passcal geoscope geofon global seismographic network gsn international deployment of accelerometeres ida mednet national networks and local deployments throughout the study region which extends from the western mediterranean region to the hindu kush and encompasses northeastern africa the arabian peninsula the middle east and part of the atlantic ocean for reference we have fitted the waveforms of regional s and rayleigh waves from over 3800 seismograms using partitioned waveform inversion we include over 3000 crustal thickness estimates from receiver functions gravity measurements and refraction profiles we include rayleigh wave group velocities for hundred thousands of paths transecting the region we have over 3000 teleseismic s arrival times measured through cross correlation and over 170000 from picks originally reported to the international seismological centre isc

measuring surface wave phase velocities beneath small broad band arrays tests of an improved algorithm and application to the french alps the local measurement of dispersion curves of intermediate period surface waves is particularly difficult because of the long wavelengths involved we suggest an improved procedure for measuring dispersion curves using small aperture broad band arrays the method is based on the hypotheses of plane incoming waves and that averaging over a set of events with a good backazimuth distribution will suppress the effects of diffraction outside the array none of the elements of the processing are new in themselves but each step is optimized so we can obtain a reliable dispersion curve with a well defined uncertainty the method is based on the inversion for the slowness vector at each event and frequency using time delays between pairs of stations where the time delays deltat are obtained by frequency domain wiener filtering the interstation distance projected on to the slowness vector d is then calculated the final dispersion curve is found by at each frequency calculating the inverse of the slope of the best fitting line of all d deltat points to test the algorithm it is applied to synthetic seismograms of fundamental mode rayleigh waves in different configurations 1 the sum of several incident waves 2 an array located next to or above a crustal thickening and 3 added white noise using regular and irregular backazimuth distributions in each case a circular array of 23 km diameter and composed of six stations is used the algorithm is stable over a large range of wavelengths between half and a tenth of the array size depending on the configuration the situations of several simultaneously incoming waves or neighbouring heterogeneities are well handled and the inferred dispersion curve corresponds to that of the underlying medium above a strong lateral heterogeneity the inferred dispersion curve corresponds to that of the underlying medium up to wavelengths of eight times the array size in the configuration considered but further work is needed to better understand the limits under which the obtained dispersion curve is not biased in the case of 5 per cent spectral amplitude white noise the dispersion curve is also stable for wavelengths up to approximately eight times the array size but this limit depends of course strongly on the noise level the method is finally applied to data from two arrays in the french alps located 50 km apart it is possible to measure the dispersion curves up to wavelengths approximately ten times bigger than the array diameter the difference in the dispersion curves is compatible with a crustal and lithospheric thickening under the alps however the observed errors are large which result in severe limits on the interpretation in terms of lithospheric structure longer recording periods may help to reduce the errors otherwise the algorithm is likely to be of use mainly in areas where the lateral variations outside the array are smaller than those of the french alps

complex lithospheric structure under the central baltic shield from surface wave tomography complex lithospheric structure under the central baltic shield from surface wave tomography

moho topography under central greece and its compensation by pn time terms for the accurate location of hypocenters the example of the gulf of corinth 1995 aigion earthquake abstract in this paper we expand over the whole of central greece the moho map centered on the gulf of corinth from tomographic inversion of pmp traveltime profile data recorded by several tens of temporary stations our approach is based on pn moho refracted waves from a large regional earthquake recorded by both temporary stations and the permanent hellenic network the moho map shows the large moho depth under the hellenides belt it also highlights the shallower moho domain towards the aegean sea south and east of the corinth gulf the domain of shallow moho is limited along a ne sw prolongation ahead of the north anatolian fault from the north aegean trough to the western tip of the gulf of corinth towards the gulf of patras the pn time terms provide corrections for the permanent stations that can be used together with the 1d velocity depth model for a first order compensation of lateral heterogeneity and contribute to the accurate and fast location of earthquake hypocenters as a test we relocated the 1995 aigion earthquake in this way using only the sparse data of the permanent stations hypocentral coordinates then shift close to those derived by a dedicated dense array deployed after the earthquake implying improvement of the routine location

off great circle propagation of intermediate period surface waves observed on a dense array in the french alps array analysis is performed on surface waves recorded in the french alps using a small aperture 25 km temporary array of six broad band stations the analysis shows that both rayleigh and love waves deviate relative to the great circle path the deviations are particularly strong up to 30 between 20 and 40 s period to interpret these observations we first study the effect of large scale structures using ray tracing in a smooth laterally heterogeneous model of the earth second we evaluate the local effect by considering a model for the french alps including strong lateral heterogeneities around the array that were not taken into account in the ray tracing by combining these two possible causes of the observed deviations we propose an explanation for the general trend in the observed deviations finally we show that by taking into account azimuthal deviations phase velocities measured at a regional scale can be significantly improved

p and s deep velocity structure of the hellenic area obtained by robust nonlinear inversion of travel times we derived a new model for the p and s velocity structure of the lithosphere in the subduction area of the hellenic arc and the aegean sea from the inversion of travel times of local events the inversion technique applied is nonlinear since three dimensional ray tracing is incorporated at the same time an appropriate preconditioning of the final linearized system is used in order to reduce ray density effects on the results the p s coherency is controlled by an additional damping of the vp vs ratio the study focuses mainly on the structure of the hellenic subduction in the southern aegean region interesting features and details of the subducted slab can be recognized in the final tomographic images on the western part the shallower section of the slab is dipping at a very small angle 10 this changes to approximately 25 for the deeper part of the subduction resulting in a prominent kink at a depth of about 70 km which is in accordance with the general characteristics of the associated benioff zone the smaller eastern part of the slab is not resolved with the same detail but a clearly steeper subduction zone can be recognized moreover detailed information about the crustal thickness variations are inferred from the velocity structure and correlate very well with the existing results from refraction experiments finally the results confirm the recent suggestion concerning the existence of a low velocity crustal layer at shallow depths 10 15 km in the accretionary prism of the alpine belt

high resolution seismic imaging of the western hellenic subduction zone using teleseismic scattered waves summary the active hellenic subduction system has long been considered an ideal setting for studying subduction dynamics because it is easily accessible and of limited spatial extent it has been the focus of numerous seismological studies over the last few decades but nonetheless the detailed structure of both the slab and the surrounding mantle remain poorly constrained in an intermediate depth range from 30 to 150 km the objective of this paper is to fill this gap the intermediate depth regime is of particular interest because it is pivotal for improving our understanding of the dynamic interaction between subducting lithosphere and the surrounding mantle an interdisciplinary effort aimed at addressing this challenge is currently undertaken by the multidisciplinary experiments for dynamic understanding of subduction under the aegean sea medusa project as part of the medusa initiative a temporary array consisting of 40 densely spaced broad band seismometers from the iris passcal pool has been deployed in southern greece we process the teleseismic data recorded by this array with a migration algorithm based on the generalized radon transform to obtain high resolution images of the subduction zone in 2 d the images reveal a sharp mohoroviy discontinuity moho at depths ranging from 30 km beneath the western margin of the aegean sea to 40 km beneath the central peloponnesus where it outlines the crustal root of the hellenides to the west of the hellenides the continental moho is not identified but we interpret a pronounced discontinuity imaged at 20 km depth as the contact between low velocity sediments and high velocity crystalline basement the images also show the subducted oceanic crust as a low velocity layer that plunges at a constant angle of 21 from west to east the oceanic crust exhibits low velocities to at least 90 km depth indicating that the bulk of fluid transfer from the subducted slab into the mantle wedge occurs below this depth a detailed comparison of images constructed for distinct backazimuthal illuminations reveals deviations in the geometry of the subducted slab these deviations are attributed to structural and or compositional changes taking place directly to the north of the medusa array and are consistent with the existence of a slab tear beneath the central hellenic shear zone

10 be profiles in seawater a knowledge of the marine geochemical cycle of 10be is basic to the use of this long lived cosmogenic radioisotope half life 1 5 myr in geochronological and geophysical studies1 3 the first attempts at measuring 10be in seawater were made only recently using nuclear accelerator spectrometry and six concentration values from four locations have been reported4 6 this data base must be expanded to include detailed water column profiles so that the behaviour of 10be in the ocean can be more fully described a parallel case in point is the recent measurement7 of a detailed oceanic profile for the stable 9be we report here two water column profiles of 10be one in the drake passage near antarctica and the other in the san nicolas basin about 100 km off the coast of southern california the san nicolas basin profile clearly demonstrates the regulation of 10be distribution by particulate cycling the data confirm the earlier suggestion4 of particle uptake of 10be in the surface ocean they also furnish evidence for regeneration of 10be across the thermocline and near the sea floor and for mid water scavenging

fluxes of uranium and thorium series isotopes in the santa barbara basin abstract samples from the manop santa barbara basin sediment trap intercomparison were analyzed for the isotopes of uranium thorium radium lead and polonium all of the traps showed approximately the same compositions and isotopic ratios indicating that they trapped similar materials the234th flux via falling particles was very close to the flux predicted from the production and scavenging rates of234th from the water column the210pb content of the trapped particles and the surface sediments were the same however the measured flux of210pb was seven times greater than the predicted flux predicted and measured fluxes of228th and210po were similarly out of balance to explain this apparent inconsistency we suggest as others have done that the santa barbara basin is an area where scavenging from the water column is intensified and where sediments deposited initially on the margins may be physically remobilized on a short time scale these two effects increase the apparent area from which the basin derives the longer lived isotopes but does not increase significantly the supply of the short lived234th

receiver function study of the hellenic subduction zone imaging crustal thickness variations and the oceanic moho of the descending african lithosphere summary we use data from recently installed broad band seismographs on the islands of crete gavdos santorini naxos and samos in the hellenic subduction zone to construct receiver function images of the crust and upper mantle from south of crete into the aegean sea the stations are equipped with sts 2 seismometers and they are operated by gfz potsdam university of chania and eth zurich teleseismic earthquakes recorded by these stations at epicentral distances between 35 and 95 have been used to calculate receiver functions the receiver function method is a routinely used tool to detect crustal and upper mantle discontinuities beneath a seismic station by isolating the p s converted waves from the coda of the p wave converted p s energy from the oceanic moho of the subducted african plate is clearly observed beneath gavdos and crete at a depth ranging from 44 to 69 km this boundary continues to the north to nearly 100 km depth beneath santorini island because of a lack of data the correlation of this phase is uncertain north of santorini beneath the aegean sea moho depths were calculated from primary converted waves and multiply reflected waves between the moho and the earth s surface beneath southern and eastern crete the moho lies between 31 and 34 km depth beneath western and northern crete the moho is located at 32 and 39 km depth respectively and behaves as a reversed crust mantle velocity contrast possibly caused by hydration and serpentinization of the forearc mantle peridotite the moho beneath gavdos island located south of crete in the libyan sea is at 26 km depth indicating that the crust south of the crete microcontinent is also thinning towards the mediterranean ridge this makes it unlikely that part of the crust in crete consists of accreted sediments transported there during the present day subduction process which began approximately 15 ma because the backstop i e the boundary between the current accretionary wedge of the mediterranean ridge and the crete microcontinent is located approximately 100 km south of gavdos a seismic boundary at 32 km depth beneath santorini island probably marks the crustal base of the crete microcontinent a shallower seismic interface beneath santorini at 20 25 km depth may mark the depth of the detachment between the crete microcontinent and the overlying aegean subplate the moho in the central and northern aegean at naxos and samos is observed at 25 and 28 km depth respectively assuming a stretching factor of 1 2 1 3 crustal thickness in the aegean was 30 35 km at the inception of the extensional regime in the middle miocene

azimuthal anisotropy from array analysis of rayleigh waves in southern california summary direct detection of rayleigh wave azimuthal anisotropy is reported by applying an array analysis to broad band seismic data in southern california usa our approach has excellent resolution for frequencies between 30 and 60 mhz and good resolution between 10 and 30 mhz limitation from array size limits accuracy below 10 mhz and complicated wave propagation effects lead to difficulty above 60 mhz between 30 and 60 mhz azimuthal anisotropy of rayleigh wave phase velocity is detected cleanly phase velocity results show that the 2 components dominate the 4 components strength of anisotropy hovers around 1 per cent for the 2 components with standard error 1 of about 0 4 per cent fast axes orientations show stable orientation in the direction 110 clockwise from north and its opposite direction 290 depth sensitivity kernels for p wave and s wave anisotropy indicate that anisotropy is confined to depths in the upper 100 km and may even be to shallower depths we speculate that the fast axes alignment may be associated with a strong shearing process over the thickness of lithosphere due to obliquely collisional motions between the pacific plate and the north america plate in the region

p wave tomography of the mantle under the alpine mediterranean area 1 we study the upper mantle p wave velocity structure below the euro mediterranean area down to 1000 km depth by seismic travel time tomography we invert summary residuals constructed with both regional and teleseismic first arrival data reported by the international seismological centre isc 1964 1995 introducing some alternative strategies in the travel time tomographic approach and a new scheme to correct teleseismic data for global mantle structure our high resolution model pm0 5 is parameterized with three dimensional 3 d linear splines on a grid of nodes with 0 5 spacing in both horizontal directions and 50 km vertical spacing we obtain about 26 root mean square rms reduction of residuals by inversion in addition to roughly 31 reduction after summary rays formation and selection sensitivity analyses are performed through several test inversions to explore the resolution characteristics of the model at different spatial scales the distribution of large scale fast anomalies suggests that two different stages of a convection process presently coexist in very close regions the mantle dynamics of western central europe is dominated by blockage of subducted slabs at the 660 km discontinuity and ponding of seismically fast material in the transition zone contrarily in the eastern mediterranean fast velocity material sinks into the lower mantle suggesting that the flow of the cold downwelling here is not blocked by the 660 km discontinuity on a smaller scale the existence of tears in the subducted slab lithospheric detachment all along both margins of the adriatic plate as proposed by some authors is not supported by our tomographic images

the mechanical interaction between the propagating north anatolian fault and the back arc extension in the aegean we use fracture mechanics concepts to analyse the large scale deformation of anatolia and the aegean our purpose is to characterize the process of propagation of the north anatolian fault naf our approach incorporates long term geological constraints in dislocation modelling of present day gps velocities that allows for internal deformation in regions between major structures unravelling the superposition of two deformation fields now interacting in the aegean propagating naf and back arc extension permits us to characterise the large scale damage zone at the western end of the naf and to determine slip rates for the main structures the contemporary slip rate profile of the naf shows that it apparently behaves like a transform fault for 75 of its length the process zone corresponds to a rapid southwestward tapering of the naf slip rate modelling slip rate distributions for the naf under stress free conditions shows that the development of the process zone depends on the boundary conditions imposed at the hellenic arc our stress free modelling suggests a scenario for the evolution of the naf 1 at an earlier stage before the naf had reached the aegean it was not under the influence of hellenic arc pull its slip rate profile is modelled to have a half elliptical shape corresponding to a crack in elastic solid and an elastically strained anatolian lithosphere 2 the present day naf penetrates the aegean and a large process zone has developed due to interaction with the aegean extension and the hellenic arc pull elastic strains in the anatolian lithosphere are relaxed and the naf resembles a transform fault the models that we present suggest that changes in subduction zone behaviour should influence all of the boundaries associated with anatolian extrusion

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

anomalous isotopic concentrations in the sea off southern california measurements are reported of the 10be concentrations in 15 sediments from the sea off southern california the sedimentation patterns are modelled with a two component system one component having the high 10be concentration of pelagic sediment and the other the low concentration of continental runoff the pelagic component brought to the region by the california current with the pacific ocean as reservoir is very likely the source not only of anomalously high 10be deposition but also of similar effects with 2101pb 239 240pu and 241pu

beryllium 10 in continental sediments abstract the concentration of 10 be has been measured in 10 samples taken from a transect of surface sediments beginning in the atchafalaya river and extending across the bay 136 km into the gulf of mexico if corrected for a lower retentivity of sand for be they have a concentration that is constant within 13 this concentration is about an order of magnitude smaller than that of deep ocean sediments for comparison measurements of 10 be in rainwater in a sample of soil and in a deep ocean core were made

regional velocity structure in northern california from inversion of scattered seismic surface waves seismic surface waves recorded by the berkeley digital seismic network have been analyzed in order to constrain three dimensional lateral heterogeneity of the upper mantle under northern california a total of 2164 seismograms from 173 teleseismic events were windowed for the fundamental mode rayleigh wave followed by estimation of complex amplitude spectra over the period range 16 to 100 s using a multiple taper method since rayleigh waves at shorter periods particularly below 35 s suffer from serious multipathing or non plane wave arrivals these amplitude spectra have been interpreted as the product of wavefront distortion along the teleseismic propagation path and seismic structure beneath the network the amplitude spectra are first modeled in terms of non plane incoming wavefields and structural phase velocity perturbations period by period after corrections for moho and surface topography the phase velocity maps are inverted for three dimensional shear velocity perturbations s down to a depth of 200 km the s maps are in good agreement with the results of body studies over a broad spatial scale the dominant signals are associated with the thermal effects of the active gorda and fossil farallon subducted slab stretching from mount shasta through the western sierran foothills to the southern great valley and asthenospheric upwelling beneath the northern coast ranges the southern sierra nevada range is characterized by fast s down to 50 km and slow velocities between 60 and 120 km depth in agreement with independent inferences of a cold crust and warm upper mantle which may provide the buoyancy forces necessary to support the elevation of the range

be isotopes in rivers estuaries and their oceanic budgets 10be and 9be have been determined in several north american rivers and in the estuaries of san francisco bay and the pearl river china the average fluvial concentration of dissolved 10be in the rivers is 3220 1960 1 atoms g almost an order of magnitude higher than the observed estuarine values and slightly higher than the 10be concentration in the ocean 1700 atoms g for dissolved 9be a similar order of magnitude drop in concentration also occurs in going from rivers 750 740 pm to estuaries 80 140 pm however in contrast to the 10be situation there appears another order of magnitude drop from estuaries to the ocean which has 9be concentrations of 5 30 pm in spite of the wide range of concentrations for both isotopes in river and estuarine waters 10be 9be ratios range mostly from 2 to 12 10 9 with a median value of 7 10 9 atom atom and are much lower than the seawater ratio of 10 7 in the rivers studied a given volume of water contains roughly equal amounts of particulate and dissolved 10be the 10be concentration in particulate matter ranges from 2 106 to 1 109 atoms g particulate with a median value of about 5 107 atoms g particulate a two box model calculation shows that coastal regions play an important role in the removal of be isotopes from the ocean and that eolian dusts may be the chief source of oceanic 9be because of the marginal removal effect the overall oceanic residence time of be should be shorter than the residence time of 500 1200 yr estimated for the open ocean

asymmetric slip partitioning in the sea of marmara pull apart a clue to propagation processes of the north anatolian fault between 1939 and 1999 the north anatolian fault naf experienced a westward progression of eight large earthquakes over 800 km of its morphological trace the 2000 km long north anatolian transform fault has also grown by westward propagation through continental lithosphere over a much longer timescale 10 myr the sea of marmara is a large pull apart that appears to have been a geometrical mechanical obstacle encountered by the naf during its propagation the present paper focuses on new high resolution data on the submarine fault system that forms a smaller pull apart beneath the northern sea of marmara between two well known strike slip faults on land izmit and ganos faults the outstandingly clear submarine morphology reveals a segmented fault system including pull apart features at a range of scales which indicate a dominant transtensional tectonic regime there is no evidence for a single continuous purely strike slip fault this result is critical to understanding of the seismic behaviour of this region of the naf close to istanbul additionally morphological and geological evidence is found for a stable kinematics consistent both with the long term displacement field determined for the past 5 myr and with present day anatolia eurasia motion determined with gps however within the sea of marmara region the fault kinematics involves asymmetric slip partitioning that appears to have extended throughout the evolution of the pull apart the loading associated with the westward propagation process of the naf may have provided a favourable initial geometry for such a slip separation

eurasian fundamental mode surface wave phase velocities and their relationship with tectonic structures we automatically analyzed 32 000 fundamental mode love and rayleigh wave signals with earthquake station paths traversing eurasia and indonesia and obtained robust average phase velocity measurements between 20 s and 170 s periods along 4389 love and 4020 rayleigh paths these were inverted to give phase velocity maps at 14 fixed periods resolution tests suggest that features with diameter 750 km and 500 km are resolved over most of eurasia and central se asia respectively low period love waves image areas with thick sedimentary cover as low velocity zones and almost all periods image mountainous regions since these have thick crust and hence low average lithospheric shear velocity at long periods both love and rayleigh waves define high phase velocity zones across shield and cratonic areas reflecting their deep lithospheric roots we observe significant along strike heterogeneity in the zagros fold belt and tien shan altai system taking sections across eurasian phase velocity space allows us to make approximate interpretations in terms of shear velocity structure directly for example the red river and east vietnam boundary faults are traced on their eastern side by low velocities which extend at depth into indonesia we relate this to mantle upwelling associated with early eocene rotation of indochina and reversal of the sense of shear across the red river fault post 20 ma we observe dipping subduction of the mediterranean beneath the aegean of the philippine sea beneath indonesia and of the indian shield beneath tibet we also image a fossil subducted plate beneath ne borneo which we associate with subduction of the proto south china sea between 50 ma and 15 ma

high resolution surface wave tomography beneath the aegean anatolia region constraints on upper mantle structure summary this study provides new constraints on the upper mantle structure from western greece to central anatolia using seismic data of permanent broad band networks recently installed in greece and turkey and from a two year temporary array simbaad experiment we used 200 seismic events recorded at 146 broad band stations with a typical interstation distance of 60 100 km across the study area the high resolution 3 d shear wave velocity model of the mantle is obtained by inversion of fundamental mode rayleigh wave phase velocity maps for periods between 20 and 195 s the tomography is based on ray tracing in heterogeneous media taking into account external propagation effects the horizontal resolution is approximately 100 km however small heterogeneities may suffer from some horizontal smearing and damping the vertical resolution is approximately 100 km the vertical smoothing is necessary to avoid unresolved spurious shear wave velocity oscillations in the upper mantle the errors on shear wave velocities in our 3 d model 0 02 0 1 km s 1 are significantly smaller than the amplitude of vs variations 0 3 0 5 km s 1 in spite of the vertical and horizontal smoothing our model shows details in the upper mantle structure never reached at regional scale in the area the overall structure is characterized by a low velocity zone 80 200 km depth reflecting a slow and warm asthenosphere underlying a thin lithosphere the southwesternmost termination of the low velocity anomaly corresponds to the northward dipping hellenic slab the detailed shear velocity structure of the upper mantle beneath anatolia appears to be far more geometrically complex than revealed in previous tomographic studies of the area at depths larger than or equal to 160 km velocities are overall high beneath anatolia partly due to the presence of dipping high velocity anomalies which we tentatively interpret as remnant slabs the southernmost high velocity anomaly beneath anatolia is separated from the eastern edge of the hellenic slab by a major low velocity anomaly which we interpret as the trace of asthenospheric mantle material rising inside a vertical slab tear beneath southwestern anatolia

the eruption of komatiites and picrites in preference to primitive basalts abstract many archaean greenstone and post archaean flood basalt provinces exhibit flows of komatiites or picrites in close spatial and temporal association with fractionated basalts it follows that picrites and komatiites can erupt through the same crustal sections in which basaltic magmas apparently pond and fractionate this is surprising since considerations of melt density alone would suggest that komatiites and picrites should be trapped and fractionated more easily than basalts some of the factors that control the ascent of magmas through the crust are examined from a theoretical viewpoint with particular reference to the eruption of komatiites and archaean basalts ascent in dykes is characterized by a local balance between the viscous pressure drop due to flow and the buoyancy forces due to the local difference in density between the melt and the host rock the level of neutral buoyancy of the magma and solidification in the dyke tip are identified as the key controls for the trapping of mafic melts in solid crust and the formation of crustal magma chambers it is suggested that komatiites and picrites can erupt in preference to basalts because they are less prone to freezing at the dyke tip during dyke propagation

upper mantle structure in southern norway from beamforming of rayleigh wave data presenting multipathing summary a model for the upper mantle sv wave velocity under southern norway is obtained by depth inversion of the average phase velocity of the rayleigh wave fundamental mode in the area the average dispersion curve is obtained in the period range 22 200 s by beamforming of 190 rayleigh waves recorded by the magnus network a temporary regional network of 41 broad band stations resolution of the beamforming procedure is increased by deconvolving the original beams from the array response function using the lucy richardson algorithm in addition to an average phase velocity beamforming gives us some information concerning the nature of the incoming wavefield we detect deviations of the wave propagation direction from the great circle paths which commonly reach 10 at a period of 25 s for the teleseismic events the amplitude of the deviations decreases with increasing period and with decreasing epicentral distance as expected the phase velocity measured by beamforming does not show any correlation with the deviation from great circle path suggesting that deviation does not bias phase velocity measurements we detect also significant multipathing with characteristics that vary rapidly with frequency the obtained sv wave velocity profile clearly shows that southern norway is underlain by a low velocity zone in the upper mantle and does not have shield like characteristics despite its location in the baltic shield these findings support the hypothesis that the high topography of southern norway is sustained by anomalous upper mantle material

lithospheric structure of the aegean obtained from p and s receiver functions combined p and s receiver functions from seismograms of teleseismic events recorded at 65 temporary and permanent stations in the aegean region are used to map the geometry of the subducted african and the overriding aegean plates we image the moho of the subducting african plate at depths ranging from 40 km beneath southern crete and the western peloponnesus to 160 km beneath the volcanic arc and 220 km beneath northern greece however the dip of the moho of the subducting african plate is shallower beneath the peloponnesus than beneath crete and rhodes and flattens out beneath the northern aegean observed p to s conversions at stations located in the forearc indicate a reversed velocity contrast at the moho boundary of the aegean plate whereas this boundary is observed as a normal velocity contrast by the s to p conversions our modeling suggests that the presence of a large amount of serpentinite more than 30 in the forearc mantle wedge which generally occurs in the subduction zones may be the reason for the reverse sign of the p to s conversion coefficient moho depths for the aegean plate show that the southern part of the aegean crustal thickness of 20 22 km has been strongly influenced by extension while the northern aegean sea which at present undergoes the highest crustal deformation shows a relatively thicker crust 25 28 km this may imply a recent initiation of the present kinematics in the aegean western greece crustal thickness of 32 40 km is unaffected by the recent extension but underwent crustal thickening during the hellenides mountains building event the depths of the aegean moho beneath the margin of the peloponnesus and crete 25 28 and 25 33 km respectively show that these areas are also likely to be affected by the aegean extension even though the cyclades crustal thickness of 26 30 km were not significantly involved in this episode the aegean lithosphere asthenosphere boundary lab mapped with s receiver functions is about 150 km deep beneath mainland greece whereas the lab of the subducted african plate dips from 100 km beneath crete and the southern aegean sea to about 225 km under the volcanic arc this implies a thickness of 60 65 km for the subducted african lithosphere suggesting that the aegean lithosphere was not significantly affected by the extensional process associated with the exhumation of metamorphic core complexes in the cyclades

east anatolian high plateau as a mantle supported north south shortened domal structure an edited version of this paper was published by the american geophysical union agu copyright 2003 agu see also http www agu org pubs crossref 2003 2003gl017858 shtml http atlas geo cornell edu turkey publications sengor et al 2003 htm

anisotropic pn tomography of turkey and adjacent regions summary this study presents an analysis of pn traveltimes to determine lateral variations of velocity anisotropy of uppermost mantle and crustal thickness beneath turkey and adjacent regions from 1999 to 2010 more than 50 000 pn arrivals are compiled from 700 regional earthquakes and 832 stations of permanent and temporary networks operated in the study area we used a regularized least squares inversion to estimate the uppermost mantle parameters the results reveal features that correlate well with the geology and the active tectonics of the region overall thepnvelocitiesshowveryfast 8 4kms 1 andveryslow 8 3 km s 1 western black sea basin 8 3 km s 1 adriatic sea 8 3 km s 1 and zagros suture 8 3 km s 1 pn anisotropy has maximum amplitude of 0 6 km s 1 in the study area the largest and coherent anisotropic anomalies are observed in the western anatolia aegean sea and cyprian arc pn anisotropy in western anatolia aegean sea and greece correlate well with the present deformation of n s regional extension no clear correlation between anisotropy and the shear deformation along the north anatolian fault was observed the majority of the stations in central anatolia show small station residuals indicating the average crustal thickness of 35 2 km western anatolia and the aegean sea have crustal thicknesses between 28 2 and 33 2 km in greece the crustal thicknesses are increasing from 33 3 km from the western coast to a maximum of 48 3k m beneath dinarides hellenides the large crustal thicknesses are also observed along southern coast of anatolia 40 48 km

multiple resolution surface wave tomography the mediterranean basin summary from a large set of fundamental mode surface wave phase velocity observations we map the transversely isotropic lateral heterogeneities in the upper mantle shear velocity structure we design a multiple resolution inversion procedure which allows us to parametrize any selected region more finely than the rest of the globe we choose as a high resolution region the upper mantle underlying the mediterranean basin we formulate the inverse problem as in a

closing the gap between regional and global travel time tomography recent global travel time tomography studies by zhou 1996 and van der hilst et al 1997 have been performed with cell parameterizations of the order of those frequently used in regional tomography studies i e with cell sizes of 1 2 these new global models constitute a considerable improvement over previous results that were obtained with rather coarse parameterizations 5 cells the inferred structures are however of larger scale than is usually obtained in regional models and it is not clear where and if individual cells are actually resolved this study aims at resolving lateral heterogeneity on scales as small as 0 6 in the upper mantle and 1 2 3 in the lower mantle this allows for the adequate mapping of expected small scale structures induced by for example lithosphere subduction deep mantle upwellings and mid ocean ridges there are three major contributions that allow for this advancement first we employ an irregular grid of nonoverlapping cells adapted to the heterogeneous sampling of the earth s mantle by seismic waves spakman and bijwaard 1998 second we exploit the global data set of engdahl et al 1998 which is a reprocessed version of the global data set of the international seismological centre their reprocessing included hypocenter redetermination and phase reidentification finally we combine all data used p pp and pwp phases into nearly 5 million ray bundles with a limited spatial extent such that averaging over large mantle volumes is prevented while the signal to noise ratio is improved in the approximate solution of the huge inverse problem we obtain a variance reduction of 57 1 synthetic sensitivity tests indicate horizontal resolution on the scale of the smallest cells 0 6 or 1 2 in the shallow parts of subduction zones decreasing to approximately 2 3 resolution in well sampled regions in the lower mantle vertical resolution can be worse up to several hundreds of kilometers in subduction zones with rays predominantly pointing along dip important features of the solution are as follows 100 200 km thick high velocity slabs beneath all major subduction zones sometimes flattening in the transition zone and sometimes directly penetrating into the lower mantle large high velocity anomalies in the lower mantle that have been attributed to subduction of the tethys ocean and the farallon plate and low velocity anomalies continuing across the 660 km discontinuity to hotspots at the surface under iceland east africa the canary islands yellowstone and the society islands our findings corroborate that the 660 km boundary may resist but not prevent present day large scale mass transfer from upper to lower mantle or vice versa this observation confirms the results of previous global mantle studies that employed coarser parameterizations

s velocity structure and radial anisotropy in the aegean region from surface wave dispersion summary the lithospheric structure of the aegean region is investigated by analysis of rayleigh wave fundamental mode dispersion measurements isotropic 1 d models for almost 100 two station ray paths across the region display distinct variations in the moho depth and crustal s wave velocities the descending slab of the subducting african plate can be resolved down to 120 km depth beneath the volcanic arc three different regions are distinguished in terms of moho depth 1 the forearc with large crustal thicknesses between 38 and 48 km and an average of 43 km 2 the northern aegean with an average moho depth of 28 km and 3 the southern aegean central volcanic arc i e cyclades and sea of crete with an even thinner crust of around 25 km lateral variations in structure between 25 and 55 km depth indicate a marked difference between the western and eastern forearc collocated with pronounced changes in trench and slab geometry as well as published deformation rates s velocities between 25 and 55 km depth are low everywhere beneath the forearc but increase from the peleponnesus to crete an abrupt change occurs between western and central crete in terms of the visibility of the aegean moho and the seismic structure of the lithospheric mantle wedge an aegean mantle wedge with s velocities above 4 4 km s 1 is only observed to the east of central crete whereas to the west velocities of less than 4 0 km s 1 occur down to the plate contact these low velocities above the slab may indicate the presence of a melange of metamorphic rocks at the depths a low velocity asthenospheric layer is observed beneath the sea of crete and the cyclades below 40 km depth between the thinned lithosphere above and the slab below the observed radial anisotropy in the northern part of the aegean is likely to be due to preferred orientation of anisotropic minerals within the lower crust possibly caused by lateral ductile flow associated with recent lithospheric extension

the geological significance of cosmogenic nuclides in large lowland river basins abstract measured from a bag of sand taken in large rivers the concentration of cosmogenic nuclides such as in situ produced 10be 26al and 14c can be used to constrain the mean sediment flux of the headwaters and assess the duration of sediment storage from source to sink we revisit these principles with examples from the amazon and ganga basins we identify two end member cases controlling the concentration of cosmogenic nuclides in lowland river sediment 1 if the time scale of floodplain sediment storage is short compared to the half life of the nuclide in situ cosmogenic nuclide concentrations are not significantly altered in lowland basins in this case the concentration of e g in situ produced 10be in the sediment taken in the lowland basin equals in most cases that exported from the sediment source area but the variability in nuclide concentrations between headwater streams is significantly averaged out thus to convert the measured river sediments in situ cosmogenic nuclide concentration into a catchment wide denudation rate production rates are scaled to include those of the sediment producing mountainous areas only rather than the entire catchment area nuclide production in the lowlands where no sediment is being produced is hence excluded this correction is termed floodplain correction 2 if sediment buried for periods of the order of the nuclides half life is episodically re entrained into the active river paired nuclides for example the ratio of 26al 10be through the differential decay of these isotopes constrain the the storage duration and re mixing of floodplain sediment as in situ cosmogenic nuclides measure denudation rates over longer time scales typically integrating between 103 and 105 years their combination with modern estimates of sediment fluxes from river load gauging offers a rich potential of deciphering the controls of earth surface fluxes across large basins from this combination we can assess how river systems react to external perturbations such as climate change or human interference and how such signals are transmitted through the alluvial reaches of lowland basins the most important results in both basins are that i lowland amazon and ganga nuclide concentrations indeed broadly reflect the spatial average of andean and himalayan denudation respectively ii the thus calculated sediment fluxes are within uncertainty of modern fluxes from sediment gauging indicating complete sediment delivery to the sea without net loss into the basin and iii only the amazon basin given its size contains a substantial fraction of sediment buried temporarily in the quaternary finally we provide a short introduction to the use of meteoric cosmogenic nuclide 10be and its ratio to stable 9be released by rock weathering in lowlands in the amazon basin we show that 10be concentrations in fine grained suspended loads depth integrated over the water column using al si ratios provide erosion rates whereas the 10be 9be ratio on be adsorbed to particles provides the denudation rate both are similar to denudation rates from in situ 10be we show that this system responds more sensitively to sediment storage than the in situ system and both accumulation and decay of meteoric concentrations may thus be used to determine sediment residence time

love wave group velocity maps of turkey and surrounding regions summary we present the analysis of a love wave dispersion study performed across turkey and the surroundings group velocity dispersion curves were obtained from the local and regional earthquakes recorded at both permanent and temporary stations operated in the region lovewave group velocity maps in the period range of 10 50 s were computed using a tomographic inversion method the study shows the existence of significantly different crustal types in the area the group velocity anomalies are associated with the major geological structures in the region low group velocities at shorter periods 10 20 s are observed in the local sedimentary basins the eastern mediterranean and the black sea the eastern anatolia region is also characterized by low group velocities while pontides and bitlis p ot urge massif display higher group velocities the central anatolia exhibits uniform velocity distribution indicating more homogenous crust the isparta angle is marked by a wedge shaped low group velocity anomaly the low velocities observed in the isparta angle are related to crustal thickening and subduction related complex high velocities observed on the maps are associated with metamorphics magmatic arcs along the orogenic belts of pontides p

love rayleigh wave incompatibility and possible deep upper mantle anisotropy in the iberian peninsula love and rayleigh wave phase velocities are analyzed with the goal of retrieving information about the anisotropic structure of the iberian lithosphere the cross correlation method is used to measure the interstation phase velocities between diverse stations of the iliha network at periods between 20 and 120 s despite the 2 d structure of the network the love wave data are too few to enable an analysis of phase velocity azimuthal variations azimuthal averages of love and rayleigh wave phase velocities are calculated and inverted both in terms of isotropic and anisotropic structures realistic isotropic models explain the rayleigh wave and short period love wave phase velocities therefore no significant anisotropy needs to be introduced in the crust and down to 100 km depth in the upper mantle to explain our data a discrepancy is observed only at long periods where the data are less reliable love wave data at periods between 80 and 120 s remain 0 15 km s faster than predicted by isotropic models explaining the long period rayleigh wave data possibilities of biases in the measurements due to interferences with higher modes are examined but seem unlikely a transversely isotropic model with 8 of s wave velocity anisotropy in the upper mantle at depths larger than 100 km can explain the whole set of data in terms of a classical model of mantle anisotropy this corresponds to 100 of the crystals perfectly oriented in the horizontal plane in a pyrolitic mantle this is a rather extreme model which predicts at time delay between 0 and 2 seconds for split sks

the moho depth map of the european plate summary the european plate has a 4 5 gy long and complex tectonic history this is reflected in the present day large scale crustal structures a new digital moho depth map is compiled from more than 250 data sets of individual seismic profiles 3 d models obtained by body and surface waves receiver function results and maps of seismic and or gravity data compilations we have compiled the first digital high resolution map of the moho depth for the whole european plate extending from the mid atlantic ridge in the west to the ural mountains in the east and from the mediterranean sea in the south to the barents sea and spitsbergen in the arctic in the north in general three large domains within the european plate crust are visible the oldest archean and proterozoic crust has a thickness of 40 60 km the continental variscan and alpine crust has a thickness of 20 40 km and the youngest oceanic atlantic crust has a thickness of 10 20 km

global azimuthal seismic anisotropy and the unique plate motion deformation of australia differences in the thickness of the high velocity lid underlying continents as imaged by seismic tomography have fuelled a long debate on the origin of the roots of continents1 2 3 4 5 some of these differences may be reconciled by observations of radial anisotropy between 250 and 300 km depth with horizontally polarized shear waves travelling faster than vertically polarized ones2 this azimuthally averaged anisotropy could arise from present day deformation at the base of the plate as has been found for shallower depths beneath ocean basins6 such deformation would also produce significant azimuthal variation owing to the preferred alignment of highly anisotropic minerals7 here we report global observations of surface wave azimuthal anisotropy which indicate that only the continental portion of the australian plate displays significant azimuthal anisotropy and strong correlation with present day plate motion in the depth range 175 300 km beneath other continents azimuthal anisotropy is only weakly correlated with plate motion and its depth location is similar to that found beneath oceans we infer that the fast moving australian plate contains the only continental region with a sufficiently large deformation at its base to be transformed into azimuthal anisotropy simple shear leading to anisotropy with a plunging axis of symmetry may explain the smaller azimuthal anisotropy beneath other continents

high pressure metasediments in central turkey constraints on the neotethyan closure history 1 the distribution of oceanic domains and continental blocks in central anatolia remains a challenge in understanding the alpine geodynamic evolution of the tethys realm the consumption of a neotethys oceanic branch at the mesozoic cenozoic boundary welded the central anatolian crystalline complex in central turkey and the anatolide tauride block in western turkey with the northerly eurasian margin whether those two regions constituted a single or two distinct continental masses is still matter of debate high pressure metamorphism has been locally evidenced in the afyon zone which was however defined as a greenschist facies metamorphic zone of the anatolide tauride block since the afyon zone composes a metamorphic equivalent of a continental margin exposed far south of the izmir ankara suture zone this encouraged us to reevaluate its metamorphic evolution in order to better understand the relation between western and central turkey our investigations reveal that the high pressure minerals fe mg carpholite and glaucophane are present in the entire afyon zone which we reconsider as a blueschist facies zone we additionally present a tectonic reconstruction stripping off the postcollisional tectonics it reveals that today s bending of the high pressure belt is consistent with an eocene collision of the anatolide tauride block around the southern edge of the central anatolian crystalline complex we argue that the central anatolian crystalline complex and the anatolide tauride block were two distinct continental masses separated by a neotethyan oceanic stripe the closure of which engendered subduction related metamorphism in the latter and arc volcanism and high grade metamorphism in the former by late cretaceous to early cenozoic

45 m y of aegean crust and mantle flow driven by trench retreat the available seismic anisotropy data in the aegean shallow mantle and their relationship with crustal deformation are used for deciphering the lithosphere scale flow pattern driven by rollback of the hellenic subduction slab in the north and central aegean the directions of mantle seismic anisotropy trend parallel to stretching lineations in core complexes of the overlying crust suggesting that crust and mantle have undergone the same direction of flow at the scale of the entire aegean crustal extension is controlled by dextral rotation around a pole located at scutary pec albania that is related to the hellenic trench retreat the intensity of mantle anisotropy increases as a function of distance from the pole and of amount of rotation surface geology reveals that this rotating flow pattern resulted in strains accumulated since 45 ma a slab tear model is suggested to integrate the observed variations of geological events in time and space to subduction dynamics

10be spikes in plio pleistocene cyclothems wanganui basin new zealand identification of the local flooding surface lfs marine shelf sediments of the wanganui basin castlecliff section spanning oxygen isotope stages 21 17 ca 920 680 ka contain spikes of enriched 10be concentrations and enhanced 10be 9be ratios up to 10 background values the 10be spikes do not coincide precisely with peaks in carbonate content and grainsize or with changes in bulk rock chemical composition rather they appear in the sequence a little above the base of each cyclothem at the presumed location of the local flooding surface lfs they therefore originated in response to seafloor sediment starvation during transgression and not from ice sheet melting biogenic scavenging or geomagnetic intensity changes as has been suggested previously for 10be spikes in some deep sea or continental margin sequences

transuranic nuclides in two coastal marine sediments off peru the fluxes of plutonium isotopes as well as their depth profiles are similar for northern and southern hemispheric varved sediments taken off western american coasts the inventories are in excess of the values predicted for atmospheric fallout in these anoxic sediments there is a general increase in concentration from depths to the near surface these observations are explainable on the bases that anoxic deposits have a substantially higher retentivity of sedimented materials compared to that of their bioturbated oxic counterparts and that there are inputs of resuspended materials previously deposited in the marine environment the 241am distributions are explained by ingrowth from 241pu assuming a substantial input of the parent from the u s thermonuclear tests during the 1950 s and the immobilization of both pu and am in the deposits

lithosphere tearing at step faults response to edges of subduction zones abstract slab edges are a relatively common feature in plate tectonics two prominent examples are the northern end of the tonga subduction zone and the southern end of the new hebrides subduction zone near such horizontal terminations of subduction trenches ongoing tearing of oceanic lithosphere is a geometric consequence we refer to such kinks in the plate boundary as a subduction transform edge propagator or step other steps are the north and south ends of the lesser antilles trench the north end of the south sandwich trench the south end of the vrancea trench and both ends of the calabria trench volcanism near steps is distinct from typical arc volcanism in some cases slab edges appear to coincide with mantle plumes using 3d mechanical models we establish that step faults are stable plate tectonic features in most circumstances in the probably rare cases that the resistance to fault propagation is high slab break off will occur relative motion along the transform segment of the plate boundary often is non uniform and the step is not a transform plate boundary in the rigid plate tectonics sense of the phrase step propagation may result in substantial deformation rotation topography and sedimentary basins with a very specific time space evolution surface velocities are substantially affected by nearby steps

surface waveform tomography of the turkish iranian plateau summary the middle east is a tectonically complex region consisting of terrains as diverse as precam brian shields and young orogens the dominant tectonic feature is the turkish iranian plateau a recently elevated seismically active region along the zagros bitlis suture which results from the collision of the arabian plate with eurasia in this study we use surface waveform tomography to elucidate the upper mantle shear wave velocity structure beneath the turkish iranian plateau and adjacent regions the main large scale feature in the tomographic model is a low shear wave velocity anomaly in the uppermost mantle beneath the plateau this low velocity feature correlates with a long wavelength free air gravity anomaly and with recent volcanism whose geochemistry has a lower lithospheric mantle signature seismology gravity and volcanism all suggest the presence of a thin lithosphere and warm upper mantle beneath the turkish iranian plateau the upper mantle low shear wave velocity zone the high free air gravity and the deep lithospheric source depth for the basaltic volcanism are all consistent with a partial delamination of the lithosphere as a result of earlier lithospheric thickening resulting from the continental collision

increased production of cosmogenic 10be during the last glacial maximum beryllium 10 half life 1 5 myr is produced by spallation of nitrogen and oxygen atoms by cosmic rays in the upper atmosphere its production rate is proportional to the flux of cosmic rays which is modulated by solar activity and the strength of the earth s magnetic field1 2 weakening of the magnetic field allows more cosmic rays to impinge on the earth s atmosphere thereby increasing 10be production here we report that the ocean wide average accumulation rate of 10be in pacific sediments which reflects the global average production rate of 10be ref 3 was at least 25 greater during the height of the most recent ice age 24 000 16 000 yr ago than during the holocene the past 10 000 yr the higher production rate of 10be records the lower intensity of the geomagnetic field during that period and is consistent with the hypothesis developed to explain the younger 14c ages of fossil corals compared with ages obtained by u th dating4 these results also point to a more general need to consider variations in production rate in geochronological studies using other cosmogenic nuclides

10be study of rapid erosion in taiwan cosmogenic 10be was measured using accelerator mass spectrometry in soils and sediments to study the erosion of taiwan which has the highest denudation rate in the world the river sediments in taiwan have very low 10be concentrations around 5 million atoms per gram about 145 the world wide average this is the direct consequence of its high sediment yield of more than 1000 mg cm2 yr 70 times the world average combining these values we found that for taiwan as a whole the 10be output to the sea only slightly exceeds the input from the rain a situation typical of many areas around the world therefore even in this example of extremely rapid erosion 10be seems to remain a useful indicator for erosion status the total 10be inventory found in a soil profile from a geologically stable area is at least 18 of the maximum possible inventory the minimum age thus estimated for the soil is 0 11 ma in reasonable agreement with estimates from other means the maximum erosion rate for this area thus estimated is at most 0 14 mg cm2 yr four orders of magnitude slower than the average value observed for taiwan we also demonstrate that the shelf sediments around taiwan have received the admixing of a 10be rich component from the ocean and would give a poor estimate for material eroded from taiwan

upper mantle s velocity structure of north america we have inverted fundamental and higher mode rayleigh waveforms from 685 vertical component broadband seismograms with wave paths over north america to obtain an image of the upper mantle s velocity structure down to 660 km among the well resolved features of the new model are 1 a high velocity root beneath the north american craton which extends no deeper than 250 km except near the archean core of the craton where depths of 350 km are reached 2 a weak band of low velocity along the eastern margin of the north american craton which reaches into the transition zone 3 a low velocity slab window beneath the western united states down to a depth of 300 km 4 areas of low uppermost mantle velocity beneath the cascade volcanoes the yellowstone hotspot track the colorado plateau the sierra madre occidental and the grabens bordering the jalisco block and 5 a pronounced band of high velocities in the transition zone coinciding with the expected location of the subducted trailing fragments of the farallon plate we introduce several improvements to the method of partitioned waveform inversion which was used to compute the new model rather than to correct for an estimated depth to the mohorovicic discontinuity we leave the crustal thickness as a free though yet poorly resolved parameter in the inversion we also improve the windowing and filtering operator used to select uncontaminated waveforms

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

a first deep seismic survey in the sea of marmara deep basins and whole crust architecture and evolution abstract increased source strength streamer length and dense spatial coverage of seismic reflection profiles of the seismarmara leg 1 allow to image the deep structure of the marine north marmara trough nmt on the strike slip north anatolian fault naf west of the destructive izmit 1999 earthquake a reflective lower crust and the moho boundary are detected they appear upwarped on an e w profile from the southern central basin eastwards towards more internal parts of the deformed region thinning of the upper crust could use a detachment suggested from an imaged dipping intracrustal reflector that would allow upper crustal material to be dragged from beneath it and above the lower crust accounting for the extensional component but also southwest motion of the southern margin of the nmt sections across the eastern half of the nmt crossing the cinarcik and imrali basins reveal several faults that are active reaching into the basement and have varying strike and proportions of normal and strike slip displacement they might be viewed as petals of a large scale negative flower structure that spreads over a width of 30 km at surface and is rooted deeper in the lithosphere under the central basin a very thick sediment infill is revealed and its extensional bounding faults are active and imaged as much as 8 km apart down to 6 km depth we interpret them as two deep rooted faults encompassing a foundering basement block rather than being merely pulled apart from a jog in a strike slip above a decollement the deep basin lengthening would account for only a modest part of the proposed 60 km finite motion since 4 myr along the same direction oblique to the nmt that sidesteps the shear motion from its two ends thus differential motion occurred much beyond the deep basins like subsidence involving the nmt bounding faults and the intracrustal detachments the complex partitioned motion localized on active faults with diverse natures and orientations is suggested to represent the overburden deformation induced from horizontal plane simple shear occurring in depth at lithospheric scale and in front of the north anatolian fault when it propagated through the region

lithospheric structure of the arabian and eurasian collision zone in eastern turkey from s wave receiver functions summary crustal and upper mantle seismic discontinuities beneath eastern turkey are imaged using teleseismic s to p converted phases three crustal phases are observed the moho with depth ranging between 30 and 55 km indicating variable tectonic regimes within this continental collision zone an upper crustal discontinuity at approximately 10 km depth and various crustal low velocity zones possibly associated with recent quaternary volcanism imaging of the upper mantle is complicated by the 3 d geometry of the region in particular due to the bitlis zagros suture zone however several upper mantle s to p converted phase are identified as being the signature of the lithosphere asthenosphere boundary lab the inferred lab for the eastern anatolian accretionary complex indicates that eastern turkey has an anomalously thin between 60 and 80 km lithosphere which is consistent with an oceanic slab detachment model the observed lab phases for the arabian shield and iranian plateau indicate that lithospheric thickness for these stable regions is on the order of 100 to 125 km thick which is typical of continental margins

moho crustal architecture and deep deformation under the north marmara trough from the seismarmara leg 1 offshore onshore reflection refraction survey abstract understanding further the nature and evolution at lithospheric scale of the sea of marmara on the north anatolian fault needs constraints on the deep crustal and moho spatial variation this has been probed here with offshore onshore and obs ocean bottom seismometer refraction seismics in addition to coincident mcs marine multichannel reflection seismic profiles over the whole north marmara trough the diverse strikes of mcs profiles in a dense grid allow to avoid misinterpretation of late echoes in the deep basin as moho reflections and attribute them to sidesweeps moho is instead positively identified from reversed observations of first arrival head and refracted waves at the top of the mantle obtained at large offset by land stations a significant and sharp reduction in its depth on the order of 5 km occurs beneath both the eastern and western rims of the north marmara trough with a more progressive crustal thinning from the south the wide angle reflections on obs and land stations document in addition to moho the top of a lower crustal reflective layer which is also sampled by mcs profiles and appears to follow moho topography the dense grid of mcs profiles along the southwestern margin of the north marmara trough reveals a dipping reflector through the upper crust with tilted basement blocks on top this low angle fault is suggested as a normal sense detachment extending in depth towards the reflective lower crust the upwarp of the moho and lower crustal layer towards the north marmara trough suggests that crustal thinning occurs mostly in the upper crustal part with lateral transport of the material towards wsw in the footwall of the detachment and possibly other features to the south in the motion of anatolia with respect to stable eurasia oblique to the north marmara trough thinning can be accommodated in an asymmetric partitioning of the displacement on several branching faults at lithospheric scale

southern california inner basin sediment trap calibration the deployment of particle interceptor traps pits in the three inner basins of the southern california bight santa barbara santa monica and san pedro where preserved laminated bottom sediments occur provides a natural calibration between the parameters determined with the pits and those derived from the historical sedimentary deposits the accumulation rates and chemical composition of the pit materials compare favorably with these recently deposited bottom sediments the ratio of the measured particle collection rate to the sediment accumulation rate for these three basins averaged0 93 0 20 radionuclide 210pb 228th 232th and trace element fe cu zn cd pb compositions of the pit materials and surface sediments agree within generally 30 in each basin an application of pits as a sampling system in an outer basin san nicolas where the sedimentary record has been obscured by bioturbation is also presented to further demonstrate the utility of pits for spatial and temporal studies of various aspects of particle transport and sediment deposition based on the calibration of the pits in the three inner basins we conclude from the comparison of the radionuclide and trace element compositions between the pit materials and surface sediments from the san nicolas basin that recently deposited sedimentary material has been mixed by bioturbation with older material from the last several hundred years excess210pb and the228th 232th activity ratio in the pit material are 6 and 15 times higher than in the surface sediment total pb and1n hno3 leachable pb are 4 and 8 fold higher in the pit material

theoretical background for continental and global scale full waveform inversion in the time frequency domain summary we propose a new approach to full seismic waveform inversion on continental and global scales this is based on the time frequency transform of both data and synthetic seismograms with the use of time and frequency dependent phase and envelope misfits these misfits allow us to provide a complete quantification of the differences between data and synthetics while separating phase and amplitude information the result is an efficient exploitation of waveform information that is robust and quasi linearly related to earth s structure thus the phase and envelope misfits are usable for continental and global scale tomography that is in a scenario where the seismic wavefield is spatially undersampled and where a 3 d reference model is usually unavailable body waves surface waves and interfering phases are naturally included in the analysis we discuss and illustrate technical details of phase measurements such as the treatment of phase jumps and instability in the case of small amplitudes the frechet kernels for phase and envelope misfits can be expressed in terms of their corresponding adjoint wavefields and the forward wavefield the adjoint wavefields are uniquely determined by their respective adjoint source time functions we derive the adjoint source time functions for phase and envelope misfits the adjoint sources can be expressed as inverse time frequency transforms of a weighted phase difference or a weighted envelope difference in a comparative study we establish connections between the phase and envelope misfits and the following widely used measures of seismic waveform differences 1 cross correlation time shifts 2 relative rms amplitude differences 3 generalized seismological data functionals and 4 the l2 distance between data and synthetics used in time domain full waveform inversion we illustrate the computation of frechet kernels for phase and envelope misfits with data from an event in the west irian region of indonesia recorded on the australian continent the synthetic seismograms are computed for a heterogeneous 3 d velocity model of the australian upper mantle with a spectral element method the examples include p body waves rayleigh waves and s waves interfering with higher mode surface waves all the kernels differ from the more familar kernels for cross correlation time shifts or relative rms amplitude differences the differences arise from interference effects 3 d earth s structure and waveform dissimilarities that are due to waveform dispersion in the heterogeneous earth

10be concentrations and the long term fate of particle reactive nuclides in five soil profiles from california concentration depth profiles of cosmic ray produced 10 be t 1 2 1 5m y have been measured by accelerator mass spectrometry in five soil profiles these measurements were made in an effort 1 to understand the retentivity of soil surfaces for particle reactive tracers depositing from the atmosphere on time scales of 10 4 10 6 years and 2 to explore the application of 10 be as a chronometer of geomorphic surface age the profiles sampled are from two wave cut terraces located near mendocino california a table mountain top and an alluvial fan both located near friant california the ages of the mendocino terraces are inferred to be 1 5 10 5 years based on amino stratigraphic correlations and models of terrace evolution those of the table mountain top and alluvial fan are 9 5 10 6 years and 6 0 10 5 years respectively based on k ar analyses all the surfaces sampled are nearly flat and exhibit few erosional features in addition to 10 be we measured 210 pb 239 240 pu and 7 be to ascertain the retentivity of the soils for particle reactive nuclides and to assess the present day delivery rate of nuclides from the atmosphere the 7 be inventory is 4 0 dpm cm 2 similar to those observed at nearby locations the inventories of 210 pb and pu isotopes conform to those predicted from model calculations and suggest that the soil surfaces sampled retain the entire burden of particle reactive nuclides delivered to them over short time scales 100 years the 10 be concentrations in the sample range between 0 2 and 7 10 8 atoms g soil and show strong correlations with leachable fe and or al the inventory of 10 be in the soil domain sampled is 1 2 orders of magnitude lower than that expected from the geological age of the surface and an average delivery rate of 10 be from the atmosphere 5 2 10 5 atoms cm 2 yr the low inventory of 10 be is attributed to its loss from the soil domain sampled by solution transport based on a simple model type calculation with a first order removal process for 10 be the residence time of 10 be in the soil domains sampled is determined to be of the order of 10 4 years the low residence time of 10 be in the soil domains sampled requires that it be found either deeper in the regolith or in ground waters in either case the application of 10 be as a chronometer of geomorphic surface age is severely constrained however the study of 10 be in soils provides the only entry into the long term 10 4 10 6 years behavior of particle reactive nuclides in soils and hence could be important for understanding the behavior of analogous nuclides introduced into soils by natural and anthropogenic processes

epmantle a 3 d transversely isotropic model of the upper mantle under the european plate summary we present a new 3 d transversely isotropic shear wave velocity model of the european and mediterraneanuppermantleobtainedbyanalysisofsurfacewaves datausedarefundamentalmode rayleigh and love group velocity measurements in the period range 35 170 s taken on seismograms recorded by european stations for regional earthquakes the tomographic inversion to map the 3 d earth structure is split into two steps first we regionalize the group velocity dispersion measurements obtaining distinct geographical group velocity maps at different periods then each local dispersion curve is inverted separately to find the shear wave velocity structure at depth the inversion benefits from using ap rioriinformation from a 3 d global mantle model s20rts and a new detailed european crustal model epcrust to constrain the shallower layers the inversion scheme follows a non linear iterative algorithm by which rayleigh and love group slowness are inverted simultaneously for the best fitting isotropic voigt shear wave speed 2 vsv 1 vsh and radial anisotropy parameter vsh vsv final merging of the vs profiles results in a new higher resolution 3 d model of european upper mantle we find that western europe and mediterranean sea are mainly characterized by relatively low velocities strongly contrasting with the fast roots of the eastern european craton many regional scale structures are also evident in the model thus providing insights into the complex geodynamic framework of the european continent most prominent are the low velocity west mediterranean spreading basins and european cenozoic rift system and seismically fast features connected to subduction of adria microplate hellenic arc and calabrian arc radial anisotropy does not vary very significantly with respect to the prem profile as available data only resolve lateral variations to a limited degree due to trade off with velocity epmantle has the potential to provide a reliable seismological reference for the upper mantle structure in the broad european region

interpretation of seismic surface waves in regional networks joint estimation of wavefield geometry and local phase velocity method and numerical tests summary teleseismic surface waves in general strongly deviate from plane waves as is evident from the analysis of surface wave data recorded with dense networks this causes conventional ray based tomographic techniques to break down if applied to network surface wave data we present a new inversion method based on the acoustic wave equation and applicable to vertical component surface wave data which successfully deals with non plane wavefield geometries the basic idea of the method is a joint estimation of the incoming wavefield and heterogeneous structure within the network region crucial to the success of the method is an adequate parametrization of the incoming wavefield which is realized using hermite gaussian basis functions additionally we apply a constraint on the wavefield parameters that expresses the idea that the samples of the wavefield taken at the station locations should be representative for the wavefield in the whole network region in this way wavefields that show stronger fluctuations in spectral amplitude than observed at the stations are rejected to represent heterogeneous structure within the network region we use an expansion into 2 d hermite gaussian functions provided that the density of stations is sufficient the proposed method retrieves heterogeneous structure in the network region very well it is not sensitive to noise or non uniform azimuthal coverage of earthquakes moreover it yields smoothed versions of the true model if the roughness of the latter has been underestimated in the inversion conversely if the true model is much smoother than anticipated inspection of the trade off between model smoothness and data misfit allows us to find the correct model the limiting factor for the inversion is the density of stations which must allow for a reliable interpolation of the observed wavefield within the network therefore in order to perform regional surface wave studies it is essential to deploy seismic stations in the region of interest itself

non plane geometries of seismic surface wavefields and their implications for regional surface wave tomography summary seismic surface waves exhibit much more complicated wavefields than is commonly assumed we are led to this conclusion after analysing 90 teleseismic events recorded at on average eight broad band stations in southern germany large amplitude and phase fluctuations across the network are observed which as we show are definitely not due to instrument response or calibration problems in order to give an impression of how surface wavefields may look in reality we fit wavefields to the observed network data using basis wavefields derived from hermite gaussian functions we show both amplitude and phase distributions of several events synthetic wavefields generated by acoustic finite difference computations in a random medium with realistic correlation length and rms velocity fluctuations support the interpretation that most of the observed wavefield anomalies have accumulated on the path of the wave from the source to the network even if no lateral heterogeneities existed in the region of the network the large scale features of the observed wavefields would remain nearly unaltered we also model the synthetic wavefields using hermite gaussian wavefields and achieve extremely good fits in view of the large anomalies of the wavefields we investigate their implications for the regional surface wave tomography in this method one infers regional structure from a set of measurements of phase traveltime between pairs of stations the basic assumption of the method is that the wavefield incident on the network be plane thus all observed phase traveltime anomalies are interpreted in terms of regional heterogeneous structure the consequence is a seemingly highly inconsistent data set we perform several tomographic experiments with realistic synthetic data sets our experiments indicate that regional surface wave tomography may work if there is an excellent coverage of paths crossing the region and if each path is sampled several times under realistic conditions that is on a sparse network with not much more than one velocity value per path the imaging power of surface wave tomography is very poor owing to the seeming inconsistency of the phase traveltimes variance reduction is generally low with an increasing number of traveltime data it further decreases while at the same time the imaging power increases the opposite behaviour is observed if the number of data is reduced variance reduction increases but imaging power decreases hence in connection with regional surface wave tomography high variance reduction indicates a lack of data rather than the goodness of reconstruction

the shear wave velocity structure in the upper mantle beneath eurasia summary we develop an approach that allows us to invert for the mantle velocity structure within a finely parametrized region as a perturbation with respect to a low resolution global tomographic model we implement this technique to investigate the upper mantle structure beneath eurasia and present a new model of shear wave velocity parametrized laterally using spherical splines with 2 9 spacing in eurasia and 11 5 spacing elsewhere the model is obtained from a combined data set of surface wave phase velocities long period waveforms and body wave traveltimes we identify many features as narrow as few hundred kilometres in diameter such as subducting slabs in eastern eurasia and slow velocity anomalies beneath tectonically active regions in contrast to regional studies in which these features have been identified our model encompasses the structure of the entire eurasian continent furthermore including mantleand body wave waveforms helped us constrain structures at depths larger than 250 km which are poorly resolved in earlier models we find that up to 9 per cent faster than average anomalies within the uppermost 200 km of the mantle beneath cratons and some orogenic regions are separated by a sharp gradient zone from deeper 1t o 2 per cent anomalies we speculate that this gradient zone may represent a boundary separating the lithosphere from the continental root which might be compositionally distinct from the overlying lithosphere and remain stable either due to its compositional buoyancy or due to higher viscosity compared with the suboceanic mantle our regional model of anisotropy is not significantly different from the global one

non linear surface wave phase velocity inversion based on ray theory summary the development of temporary and permanent broad band seismic arrays reinforces the need for advanced interpretation techniques in surface wave analysis we present a new method based on 2 d paraxial ray theory of inverting teleseismic surface wave phase information and constructing phase velocity maps on a regional scale measurements of local phase velocities and propagation directions of rayleigh waves taken from full waveform synthetic seismograms are used to validate the ray theory for smooth structures on a regional scale curved wavefronts created by heterogeneous structure outside the study area are taken into account through joint inversion for the phase velocity field and the shape of the incoming wavefronts in the forward ray tracing procedure the curved wavefronts are introduced through the boundary conditions by equating the slowness vector of the ray at the edge of the study region with the known gradient of the arrival time of the wave to make the inverse problem non singular we constrain the parameters in the inversion primarily by applying a smoothness criteria on the velocity field and on the incoming wave field inversions of synthetic data sets computed by direct ray tracing and by full waveform modelling show that for 100 km spacing between stations the minimum size of structure that we can image is approximately 150 km heterogeneities with a size approximately equal to the wavelength are reconstructed by the ray based inversion even though velocity variations are underestimated due to the wave field smoothing of the structures a minimum signal to noise ratio of 3 5 is necessary in order to correctly retrieve the phase velocity field inversion of a subset of the svekalapko data for 60 s period demonstrates the applicability of the method on real 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

travel time tomography of the european mediterranean mantle down to 1400 km abstract the 3 d p wave velocity structure of the mantle below europe the mediterranean region and a part of asia minor is investigated this study is a considerable extension of an earlier tomographic experiment that was limited to imaging upper mantle structure only here the earth s volume under study encompasses the mantle to a depth of 1400 km and we increase the number of international seismological centre isc data for inversion by a factor of four by taking more years of observation and by including data from teleseismic events the most important departure from the earlier study is that we do not use the jeffreys bullen model as a reference model but an improved radially symmetric velocity model the pm2 model which is appropriate for the european mediterranean mantle our inversion procedure consists of two steps first the radial model pm2 is determined from the isc delay times by a nonlinear trial and error inversion of the data as opposed to the jeffreys bullen model the new reference model has a high velocity lithosphere a low velocity zone and seismic discontinuities at depths of 400 and 670 km next the isc data are corrected for effects related to the change in reference model and inverted for 3 d heterogeneity relative to the pm2 model we follow this two step approach to attain a better linearizable tomographic problem in which ray paths computed in the pm2 model provide a better approximation of the actual ray paths than those computed from the jeffreys bullen model hence the two step scheme leads to a more credible application of fermat s principle in linearizing the tomographic equations inversion results for the 3 d heterogeneity are computed for both the uncorrected isc data and for the pm2 data the data fit obtained in the two step approach is slightly better than in the inversion of isc data using the jeffreys bullen reference model a comparison of the tomographic results demonstrates that the pm2 data inversion is to be preferred to assess the spatial resolution an analysis is given of hit count patterns sampling of the mantle by ray paths and results of sensitivity tests with 3 d synthetic velocity models the spatial resolution obtained varies with position in the mantle and is studied both in map view and in cross section in the well sampled regions of the mantle the spatial resolution for larger scale structure can qualitatively be denoted as reasonable to good and at least sufficient to allow interpretation of larger scale anomalies a comparison is made of the results of this study with independent models of s velocity heterogeneity obtained in a number of investigations and with a prediction of the seismic velocity structure of the mantle computed from tectonic reconstructions of the mediterranean region in the context of this comparison interpretations of large scale positive anomalies found in the mediterranean upper mantle in terms of subducted lithosphere are given specifically addressed are subduction below southern spain below the western mediterranean and italy and below the aegean in the last region a slab anomaly is mapped down to depths of 800 km

mobilization of beryllium in the sedimentary column at convergent margins studies of be distributions in subduction zone sediments will help to understand questions regarding the enrichments of cosmogenic be 10 in arc volcanic rocks analyses of be 10 and be 9 in sediments of ocean drilling program site 808 nankai trough and be 9 in porewaters of site 808 and sites 671 and 672 barbados ridge complex show significant decreases in solid phase be 10 and large increases of porewater be 9 at the location of the decollement zone and below or at potential flow conduits these data imply the potential mobilization of be during pore fluid expulsion upon sediment burial experiments involving reaction between a decollement sediment and a synthetic nacl cacl2 solution at elevated pressure and temperatures were conducted in an attempt to mimic early subduction zone processes the results demonstrate that be is mobilized under elevated pressure and temperature with a strong ph dependence the be mobilization provides an explanation of be 10 enrichment in arc volcanic rocks and supports the argument of the importance of the fluid processes in subduction zones at convergent margins