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

flow modeling and permeability estimation using borehole flow logs in heterogeneous fractured formations a numerical model of flow in the vicinity of a borehole is used to analyze flowmeter data obtained with high resolution flowmeters the model is designed to 1 precisely compute flow in a borehole 2 approximate the effects of flow in surrounding aquifers on the measured borehole flow 3 allow for an arbitrary number n of entry exit points connected to m n far field aquifers and 4 be consistent with the practical limitations of flowmeter measurements such as limits of resolution typical measurement error and finite measurement periods the model is used in three modes 1 a quasi steady pumping mode where there is no ambient flow 2 a steady flow mode where ambient differences in far field water levels drive flow between fracture zones in the borehole and 3 a cross borehole test mode where pumping in an adjacent borehole drives flow in the observation borehole the model gives estimates of transmissivity for any number of fractures in steady or quasi steady flow experiments that agree with straddle packer test data field examples show how these cross borehole type curves can be used to estimate the storage coefficient of fractures and bedding planes and to determine whether fractures intersecting a borehole at different locations are hydraulically connected in the surrounding rock mass

crustal deformation of the eastern tibetan plateau revealed by magnetotelluric imaging the ongoing collision of the indian and asian continents has created the himalaya and tibetan plateau through a range of deformation processes these include crustal thickening detachment of the lower lithosphere from the plate delamination and flow in a weakened lower crust 1 6 debate continues as to which of these processes are most significant 7 in eastern tibet large scale motion of the surface occurs but the nature of deformation at depth remains unresolved a large scale crustal flow channel has been proposed as an explanation for regional uplift in eastern tibet 6 8 9 but existing geophysical data 10 11 do not constrain the pattern of flow magnetotellurics uses naturally occurring electromagnetic waves to image the earth s subsurface here we present magnetotelluric data that image two major zones or channels of high electrical conductivity at a depth of 20 40 km the channels extend horizontally more than 800 km from the tibetan plateau into southwest china the electrical properties of the channels imply an elevated fluid content consistent with a weak crust 12 13 that permits flow on a geological timescale these findings support the hypothesis that crustal flow can occur in orogenic belts and contribute to uplift of plateaux our results reveal the previously unknown complexities of these patterns of crustal flow many previous studies of the indiaasia

cross hole fracture connectivity assessed using hydraulic responses during liner installations in crystalline bedrock boreholes abstract in order to continually improve the current understanding of flow and transport in crystalline bedrock environments developing and improving fracture system characterization techniques is an important area of study the presented research examines the installation of flexible impermeable flute liners as a means for assessing cross hole fracture connectivity flute liners are used to generate a new style of hydraulic pulse with pressure response monitored in a nearby network of open boreholes drilled in gneissic rock of the canadian shield in eastern ontario canada borehole liners were installed in six existing 10 15 cm diameter boreholes located 10 35 m apart and drilled to depths ranging between 25 45 m liner installation tests were completed consecutively with the number of observation wells available for each test ranging between one and six the collected pressure response data have been analyzed to identify significant groundwater flow paths between source and observation boreholes as well as to estimate inter well transmissivity and storativity using a conventional type curve analysis while the applied solution relies on a number of general assumptions it has been found that reasonable comparison can be made to previously completed pulse interference and pumping tests results of this research indicate areas where method refinement is necessary but nonetheless highlight the potential for use in crystalline bedrock environments this method may provide value to future site characterization efforts given that it is complementary to and can be used in conjunction with other currently employed borehole liner applications such as the removal of cross connection at contaminated sites and the assessment of discrete fracture distributions when boreholes are sealed recreating natural hydraulic gradient conditions

plate tectonic history basin development and petroleum source rock deposition onshore china abstract china comprises a mosaic of distinct continental fragments separated by fold belts these fold belts are suture zones resulting from the accretion of various fragments formerly separated by intervening areas of oceanic crust the major sedimentary basins onshore china can be classified into four groups those in western china are flexural developing as a result of north south compression in contrast those in the east are extensional and related to development of the pacific oceanic margin in central china basins have a more problematic origin those of north central china ordos sichuan are flexural basins controlled by eastward directed thrusting along their western margin in contrast basins further south chuxiong shiwandashan are predominantly extensional and related to major strike slip movements by synthesizing basin stratigraphies across china in tectonostratigraphic terms and in particular comparing the nature and timing of unconformities it is possible to formulate a coherent model for the palaeoreconstruction of china we identify five major tectonostratigraphic breaks which equate with the collision of the following continental fragments tarim north china carboniferous permian south china block permian triassic qiantang late triassic early jurassic lhasa block late jurassic early cretaceous and india early tertiary prior to permian times the southern margin of eurasia ran approximately along the northern border of modern china the late carboniferous collision of tarim north china with eurasia resulted in the development of a flexural basin junggar and deposition of non marine clastics to the south of the suture shallow marine deposition continued in the late permian early triassic the progressive collision from east to west of the south china block with the north china block resulted in a change to fluvial lacutrine sedimentation across the entire north china tarim block open marine carbonate deposition in the north of the south china block passed southward into a deeper marine clastic sequence deposited in a backarc basin further south a subduction zone existed along the southeastern margin of the south china block in western china northward subduction throughout the triassic resulted in the development of the songban ganzi accretionary prism with retroarc thrusting resulting in flexure and the first development of the tarim basin oblique collision of the qiantang block in the late triassic along the east of the south china block resulted in east west directed thrusting which initiated the suchuan and ordos basins continued strike slip deformation along the south western margin of the south china block resulted in the development of basins with a significant extensional component such as chuxiong the collision of the qiantang block with the southern edge of the tarim basin early jurassic resulted in a renewed clastic influx in both the tarim and junggar basins along the eastern pacific margin a compressional arc and retroarc basin in the south passed northwards into an extensional arc system subduction rollback of the extensional arc initiated rifting in the late jurassic in the eren and songliao basins the late jurassic early cretaceous collision of the lhasa block in the west rejuvenated the thrust systems bordering the western basin and resulted in a renewed clastic influx in the southeast the compressional arc phase culminated in widespread thrusting and folding of early cretaceous age in the northeast extension continued with the progressive migration of the rift system southward with time the arrival of the indian block in the early tertiary rejuvenated the bounding thrust belts of all the western basins in the east the change in convergence of the pacific plate to a more westerly direction is marked by extension and widespread rifting along the entire length of eastern china throughout most of china mesozoic and cenozoic deposition occurred in predominantly non marine environments source rocks in such settings comprise principally mudstones deposited in lakes organic rich mudstones these can accumulate in both deep and shallow lakes in order to accumulate substantial volumes the lake must be significant in space and time in china lacustrine orms occur in both rift and flexural basins lacustrine orms deposited under humid climatic conditions are restricted to the period of maximum tectonic subsidence in the flexural basins of western china source rock deposition follows basin initiation by 20 30 ma in the extensional basins of eastern china source rock deposition takes place 5 15 ma after basin initiation by contrast semi arid and arid climate lacustrine orms whilst being best developed during the period of maximum tectonic subsidence occur at all stages in the basin history

interpretation of field tracer tests of a single fracture using a transient solute storage model the results and interpretation of five induced gradient tracer tests performed at five different average interborehole fluid velocities in a single fracture in monzonitic gneiss are described the experiments were conducted using radioactive 82br and a fluorescent dye as conservative tracers where the tracers were pulse injected into radial convergent and injection withdrawal flow fields the flow fields were established between straddle packers isolating the fracture in three boreholes over distances of 12 7 29 8 m the tracer breakthrough curves were determined from samples of the withdrawn groundwater and were interpreted using residence time distribution rtd theory and two deterministic simulation models the rtd curves of the tracer experiments were interpreted by fitting to the field data a simple advection dispersion model and an advection dispersion model with transient solute storage in immobile fluid zones both models consider the different flow field geometries associated with injection withdrawal and radial convergent tests comparison of the fits obtained by the simulation models suggest that the initial period of solute transport in single fractures is advection dominated and with increasing tracer residence time or decreasing fluid velocity transport progresses toward more fickian like behavior during the advective dominated period the transient solute storage model is shown to adequately describe the asymmetries and long tails characteristic of the fracture rtds interpretation of the tracer experiments using both simulation models further suggests that induced gradient tracer experiments are likely to underestimate the dispersive characteristics of single fractures under natural flow conditions

motion of the pacific plate relative to eurasia and its potential relation to cenozoic extension along the eastern margin of eurasia extension along the eastern margin of eurasia has been regarded commonly as a far field effect of the india eurasia collision however some aspects of the timing and location of this extension make a link between the collision and extension difficult we suggest that some extensional features commonly interpreted as effects of the collision may be related more simply to changes in plate convergence rates along the eastern plate boundary of eurasia an analysis of the motion of the pacific plate relative to eurasia suggests that the rate of pacific eurasia convergence varied significantly during the tertiary period from a late cretaceous convergence rate of 120 140 mm yr the rate declined substantially during early tertiary time and reached a minimum in eocene time of 30 40 mm yr in oligocene to earliest miocene time the average convergence rate increased moderately to 70 95 mm yr then decreased again to 65 70 mm yr during early to middle miocene time from late miocene to the present the rate of convergence increased to an average of 100 110 mm yr the paleocene through middle miocene episode of relatively slow convergence correlates with a period of widespread extension along the eastern margin of eurasia decreased convergence may have been related to a net reduction in horizontal compressional stress transmitted between the pacific and eurasian plates which resulted in widespread extension adjacent to the margin of eurasia

hydraulic tests in highly permeable aquifers 1 a semianalytical solution is presented for a mathematical model describing the flow of groundwater in response to a slug or pumping test in a highly permeable confined aquifer this solution which is appropriate for wells of any degree of penetration and incorporates inertial mechanisms at both the test and observation wells can be used to gain new insights into hydraulic tests in highly permeable settings the oscillatory character of slug and pumping induced responses will vary considerably across a site even in an essentially homogeneous formation when wells of different radii depths and screen lengths are used thus variations in the oscillatory character of responses do not necessarily indicate variations in hydraulic conductivity k existing models for slug tests in partially penetrating wells in high k aquifers neglect the storage properties of the media that assumption however appears reasonable for a wide range of common conditions unlike in less permeable formations drawdown at an observation well in a high k aquifer will be affected by head losses in the pumping well those losses which affect the form of the pumping induced oscillations can be difficult to characterize thus analyses of observation well drawdown should utilize data from the period after the oscillations have dissipated whenever possible although inertial mechanisms can have a large impact on early time drawdown that impact decreases rapidly with duration of pumping and distance to the observation well conventional methods that do not consider inertial mechanisms should therefore be viable options for the analysis of drawdown data at moderate to large times

spice benchmark for global tomographic methods the existing global tomographic methods result in different models due to different parametrization scale resolution and theoretical approach to test how current imaging techniques are limited by approximations in theory and by the inadequacy of data quality and coverage it is necessary to perform a global scale benchmark to understand the resolving properties of each specific imaging algorithm in the framework of the seismic wave propagation and imaging in complex media a eu ropean network spice project it was decided to perform a benchmark experiment of global inversion algorithms first a preliminary benchmark with a simple isotropic model is carried out to check the feasibility in terms of acquisition geometry and numerical accuracy then to fully validate tomographic schemes with a challenging synthetic data set we constructed one complex anisotropic global model which is characterized by 21 elastic constants and includes 3 d heterogeneities in velocity anisotropy radial and azimuthal anisotropy attenuation density as well as surface topography and bathymetry the intermediate period 32 s high fidelity anisotropic modelling was performed by using state of the art anisotropic anelastic modelling code that is coupled spectral element method csem on modern massively parallel computing resources the benchmark data set consists of 29 events and three component seismograms are recorded by 256 stations because of the limitation of the available computing power synthetic seismograms have a minimum period of 32s and a length of 10500s the inversion of the benchmark data set demonstrates several well known problems of classical surface wave tomography such as the importance of crustal correction to recover the shallow structures the loss of resolution with depth the smearing effect both horizontal and vertical the inaccuracy of amplitude of isotropic s wave velocity variation the difficulty of retrieving the magnitude of azimuthal anisotropy and so on the synthetic data set can be used to validate and calibrate new processing methodologies and has been made available to the scientific community at the institut de physique du globe de paris ipgp website www ipgp jussieu fr qyl any group wishing to test their tomographic algorithm is encouraged to download the synthetic data

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

the black sand placer deposits of kerala beach southwest india abstract heavy mineral concentrates known as black sands occur in layers and patches along the kerala beaches situated on the southwest coast of india detailed microscopic studies of 28 beach samples and 32 river bed samples from 16 west flowing rivers of kerala were examined the heavy mineral suite consists of opaques hornblende tremolite actinolite hypersthene clinopyroxene zircon monazite garnet sillimanite epidote staurolite apatite etc distribution maps of these minerals on the beaches and in river sediments have been prepared opaques as high as 96 were noted in some samples on the beach the minerals are derived mainly from the charnockites khondalites granite gneisses pegmatites or retrograde charnockites from the drainage basins of the different rivers a combination of two or more characteristic minerals was also identified for the major rivers of kerala five heavy mineral provinces on the beach were recognised from north to south they are 1 mixed mineral province with opaques zircon hornblende garnet sillimanite epidote 2 garnet hypersthene province 3 opaque zircon province 4 hornblende hypersthene province and 5 opaque zircon monazite province vigorous wave activity during the southwest monsoon the longshore current and onshore offshore movements played an important role in sorting the heavy mineral placer sands a three stage depositional model of the heavy mineral placer sands corresponding to the initial transgressive and regressive stages influenced by wave and current activity is suggested

asthenospheric imprints on the lithosphere in central mongolia and southern siberia from a joint inversion of gravity and seismology mobal experiment summary we present a joint inversion of gravity and teleseismic data to enlighten the lithospheric structures of the baikal mongolia region an area characterized by high topographic contrasts sporadic cenozoic volcanism extension and large transcurrent faulting in the vicinity of the baikal rift central asia the study uses a 1000 km long seismic transect that cross cuts the main tectonic structures from north to south namely the siberian platform tunka basin hangay dome and gobi altai belt the siberian platform depicts a high velocity lithosphere down to about 150 km we evidence strong velocity contrasts within the crust below the hangay dome and the tunka depression interpreted as a thickened crust a low velocity density region is located at various depths below the hangay dome thanks to the dense spatial coverage of gravity data we are able to define the 3 d geometry of this particular low velocity density anomaly the hangay dome anomalous body extends from 60 to 225 km depth at his largest point and slightly thins to no more than 40 km at its easternmost end a deep low velocity zone below 150 km with only a weak negative density contrast is observed on the eastern part of the transect we propose that the late cenozoic uplift of the whole mongolian plateau and associated rifting magmatism high heat flow and lithospheric thinning are not externally driven by the india asia collision but results from the interaction of two mantle plumes with the overlying lithosphere conversely recent faulting may be the major expression of the india asia collision in this region as well as n s striking rift basins that connect and interact with major strike slip faults such as the bolnai fault the comparison between time residuals of this experiment and the baikal rift seismic data shows an undeniable disproportion for the hangay anomaly the hangay time residuals are far more positive than through the baikal arguing for an asthenospheric signature that is not seen beneath the baikal rift furthermore the southern edge of the thick siberian cratonic lithosphere may favour the rise of a sublithospheric mantle flow at the contact with the baikal mongolia lithosphere

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

full waveform tomography for radially anisotropic structure new insights into present and past states of the australasian upper mantle article i nfo we combine spectral element simulations and adjoint techniques in a non linear full seismic waveform tomography for the radially anisotropic structure of the australasian upper mantle our method allows us to explain 30 s waveforms in detail and it yields tomographic images with locally 2 lateral resolution in the course of 19 conjugate gradient iterations the total number of exploitable waveforms increased from 2200 to nearly 3000 the final model amsan 19 thus explains data that were not initially included in the inversion this is strong evidence for the effectiveness of the inversion scheme and the physical consistency of the tomographic model amsan 19 confirms long wavelength heterogeneities found in previous studies and it allows us to draw the following inferences concerning the past and present states of the australian upper mantle and the formation of seismic anisotropy 1 small scale neutral to low velocity patches beneath central australia are likely to be related to localised paleozoic intraplate deformation 2 increasing seismic velocities between the moho and 150 km depth are found beneath parts of proterozoic australia suggesting thermochemical variations related to the formation and fragmentation of a centralian superbasin 3 radial anisotropy above 150 km depth reveals a clear ocean continent dichotomy we find strong vshnvsv beneath the coral and tasman seas the anisotropy is strongest at the top of the inferred asthenospheric flow channel where strain is expected to be largest radial anisotropy beneath the continent is weaker but more variable localised patches with vshbvsv appear in accord with small scale intraplate deformation 4 the ocean continent dichotomy disappears gradually between 150 and 250 km depth where the continental lithospheric mantle and the oceanic asthenosphere pass into the underlying convecting mantle 5 significant anisotropy exists below 250 km depth its character can be explained by sublithospheric small scale convection and a change in the dominant glide system of olivine

effects of three dimensional earth structure on cmt earthquake parameters abstract we investigate errors in centroid earthquake parameters due to unmodeled structural heterogeneity we generate a simulated dataset consisting of synthetic seismograms for 50 earthquakes and 150 stations distributed globally to generate the synthetic seismograms we use a spectral element wave propagation package specfem3d globe that accounts for the earth s three dimensional structure an established centroid moment tensor inversion algorithm from the global cmt project is used to invert the synthetic dataset with and without added noise for earthquake source parameters this algorithm uses a one dimensional earth structure together with approximate corrections for three dimensional structure to model the seismograms we interpret the differences between the estimated source parameters and the parameters used to compute the synthetic dataset as errors due to unmodeled structural heterogeneity and the presence of noise we expect that the errors obtained in this study are representative of the errors in the global cmt catalogue we find that the errors in scalar moment moment tensor elements and location are small on average the depth and centroid time are however biased by a small amount we find that the error in depth can be reduced significantly by applying corrections for the difference in the velocity structure at the source and receiver locations from the earth s average structure in the cmt inversions this modification has a minimal effect on the errors in centroid time we do not find large errors in scalar moments even where the crustal thickness at the source is very different from the earth s average crustal thickness

global shear speed structure of the upper mantle and transition zone s u m m a r y the rapid expansion of broad band seismic networks over the last decade has paved the way for a new generation of global tomographic models significantly improved resolution of global upper mantle and crustal structure can now be achieved provided that structural information is extracted effectively from both surface and body waves and that the effects of errors in the data are controlled and minimized here we present a new global vertically polarized shear speed model that yields considerable improvements in resolution compared to previous ones for a variety of features in the upper mantle and crust the model sl2013sv is constrained by an unprecedentedly large set of waveform fits 3 4 of a million broad band seismograms computed in seismogram dependent frequency bands up to a maximum period range of 11 450 s automated multimode inversion of surface and s wave forms was used to extract a set of linear equations with uncorrelated uncertainties from each seismogram the equations described perturbations in elastic structure within approximate sensitivity volumes between sources and receivers going beyond ray theory we calculated the phase of every mode at every frequency and its derivative with respect to sand p velocity perturbations by integration over a sensitivity area in a 3 d reference model the normally small perturbations of the 3 d model required to fit the waveforms were then linearized using these accurate derivatives the equations yielded by the waveform inversion of all the seismograms were simultaneously inverted for a 3 d model of shear and compressional speeds and azimuthal anisotropy within the crust and upper mantle elaborate outlier analysis was used to control the propagation of errors in the data source parameters timing at the stations etc the selection of only the most mutually consistent equations exploited the data redundancy provided by our data set and strongly reduced the effect of the errors increasing the resolution of the imaging our new shear speed model is parametrized on a triangular grid with a 280 km spacing in well sampled continental domains lateral resolution approaches or exceeds that of regionalscale studies the close match of known surface expressions of deep structure with the distribution of anomalies in the model provides a useful benchmark in oceanic regions spreading ridges are very well resolved with narrow anomalies in the shallow mantle closely confined near the ridge axis and those deeper down to 100 120 km showing variability in their width and location with respect to the ridge major subduction zones worldwide are well captured extending from shallow depths down to the transition zone the large size of our waveform fit data set also provides a strong statistical foundation to re examine the validity field of the jwkb approximation and surface wave ray theory our analysis shows that the approximations are likely to be valid within certain time frequency portions of most seismograms with high signal to noise ratios and these portions can be identified using a set of consistent criteria that we apply in the course of waveform fitting

coastal zone management programme in kerala india the physiographic setting of kerala state india is unique a narrow strip of the state contains a chain of lagoons and estuaries with a very high population density the strip is subjected to severe coastal erosion during the monsoon season a number of other problems are also associated with the coastal zone of kerala such as irregular dredging of black sands from the beaches coastal flooding hazards due to developmental activities etc a coastal zone management programme was developed and administered by the centre for earth science studies trivandrum to provide efficient coastal management and solve some of these problems various programmes included under the coastal zone management are the following 1 sedimentological bathymetric and geochemical studies of lagoons and estuaries 2 monitoring of planimetric changes of beaches by profiling beaches during different seasons all along the coast 3 studies of the nature distribution and provenance of black sand deposits from beaches 4 studies of the peculiar occurrence of patchy calm turbid areas of water in the offshore containing high suspended sediment concentrate known as mud banks 5 wave studies involving continuous monitoring of wave data all along the coast in order to understand wave climate and erosion 6 sediment movement studies using fluorescent tracer to aid in the development of ports and harbors 7 studies on various aspects of offshore the outlines of the various programmes discussed in this article will help other states and countries to develop a coastal zone management programme according to the needs of the state or country and the nature of the problem occurring in the coastal zone

geophysical geological and hydrogeological characterization of a tributary buried bedrock valley in southern ontario buried bedrock valleys infilled with quaternary aged sediment have the potential to become productive aquifers owing to prevalent sand and gravel deposits often associated with these topographic lo

flow bearing structures of fractured rocks insights from hydraulic property scalings revealed by a pumping test abstract a long duration pumping test conducted over 151 days in a fractured sandstone and shale formation displays a nonstandard drawdown response and anomalous pressure diffusion which cannot be properly interpreted using existing frameworks e g homogeneous double porosity boundary conditions and fractal models an alternative framework with simple geometry and more complex hydraulic properties is thus proposed to interpret such kind of drawdown responses the analytical development allows first to demonstrate all scaling relations in this interpretation framework then and most importantly the multi scale hydraulic test provides consistent scalings of transmissivity t to storativity s over distances ranging from 83 to 383 m in a faulted area drawdown analysis in several monitoring wells shows persistent decrease of transmissivity in highly channelized fracture flow structures in one structure the cubic dependency of transmissivity to storativity identifies a well defined fault and also demonstrates the validity of poiseuille flow at a scale rarely investigated in the other structure the linear dependency of transmissivity to storativity indicates that the flow bearing structure is the surrounding fracture network well designed pumping tests combined with scaling analysis driven by geological evidence thus provide essential information on flow bearing structures for site characterization and modeling tasks at least for moderate to low permeable fractured rocks the scaling of transmissivity to storativity appears to be more informative than any separate interpretation of hydraulic property scaling exponents

structure and evolution of the himalaya tibet orogenic belt the 1981 french chinese expedition to tibet focused on the lhasa block extending earlier coverage 400 km north of the tsangpo suture the lhasa block stood between 10 and 15 n latitude over most of the upper cretaceous and eocene and if gondwanian in origin had detached from gondwana by early permian seismic profiles reveal a complex moho topography resulting both from multiple continental thrusting and large scale strike slip faulting subduction related granitoids representing mixtures of mantle and crustal components and anatectic granitoids have been analysed and dated this study emphasizes the role of smaller blocks in the accretion of the continental mosaic

seismic wavespeed images across the iapetus and tornquist suture zones 1 closures of the iapetus ocean and the tornquist sea lead to the collision of the paleocontinents of laurentia baltica and eastern avalonia during the caledonian orogeny it has been speculated that relicts of these two closures may be preserved within the crust or upper mantle over the past decades numerous wide angle seismic profiles were gathered in northwestern europe to search for related subsurface features although active source studies revealed detailed crustal structures across the iapetus and tornquist suture zones there are relatively few clear three dimensional upper mantle images beneath this region we use a new european crust and upper mantle model eu30 determined based on continental scale nonlinear adjoint tomography to explore upper mantle structures across these two suture zones model eu30 reveals two fast anomalies within the upper mantle one dips in a northwesterly direction down to approximately 400 km beneath the north sea and the other dips in a southwesterly direction down to nearly 250 km across the tornquist suture zone in addition we observe a gap between the lithospheres of laurentia and eastern avalonia across the iapetus suture zone beneath the central british isles these seismic images suggest that heterogeneity related to the closures of the iapetus ocean and the tornquist sea have been preserved within the upper mantle over hundreds of millions of years

seismic imaging of the downwelling indian lithosphere beneath central tibet a tomographic image of the upper mantle beneath central tibet from indepth data has revealed a subvertical high velocity zone from 100 to 400 kilometers depth located approximately south of the bangong nujiang suture we interpret this zone to be downwelling indian mantle lithosphere this additional lithosphere would account for the total amount of shortening in the himalayas and tibet a consequence of this downwelling would be a deficit of asthenosphere which should be balanced by an upwelling counterflow and thus could explain the presence of warm mantle beneath north central tibet

anisotropic shear wave velocity structure of the earth s mantle a global model 1 we combine a new large data set of surface wave phase anomalies long period waveforms and body wave travel times to construct a three dimensional model of the anisotropic shear wave velocity in the earth s mantle our modeling approach is improved and more comprehensive compared to our earlier studies and involves the development and implementation of a new spherically symmetric reference model simultaneous inversion for velocity and anisotropy as well as discontinuity topographies and implementation of nonlinear crustal corrections for waveforms a comparison of our new three dimensional model s362ani with two other models derived from comparable data sets but using different techniques reveals persistent features 1 strong 200 km thick high velocity anomalies beneath cratons likely representing the continental lithosphere underlain by weaker fast anomalies extending below 250 km which may represent continental roots 2 weak velocity heterogeneity between 250 and 400 km depths 3 fast anomalies extending horizontally up to 2000 3000 km in the mantle transition zone beneath subduction zones 4 lack of strong long wavelength heterogeneity below 650 km suggesting inhibiting character of the upper mantle lower mantle boundary and 5 slow velocity superplumes beneath the pacific and africa the shear wave radial anisotropy is strongest at 120 km depth in particular beneath the central pacific lateral anisotropic variations appreciably improve the fit to data that are predominantly sensitive to the uppermost and lowermost mantle but not to the waveforms that control the transition zone and midmantle depths tradeoffs between lateral variations in velocity and anisotropy are negligible in the uppermost mantle but noticeable at the bottom of the mantle

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

low wave speed zones in the crust beneath se tibet revealed by ambient noise adjoint tomography we present a refined 3d crustal model beneath se tibet from ambient noise adjoint tomography different from ray theory based tomography adjoint tomography in this study incorporates a spectral element method sem and takes empirical green s functions egfs of rayleigh waves from ambient noise interferometry as the direct observation the frequency dependent traveltime misfits between sem synthetic green s functions and egfs are minimized with a preconditioned conjugate gradient method meanwhile the 3d model gets improved iteratively utilizing 3d finite frequency kernels the new model shows 3 6 shear wave speed increasing beneath the western sichuan basin scb depth 15 km and the central chuan dian block cdb and 6 12 shear wave speed reduction in the mid lower crust beneath the northern and the southern cdb the inferred spatial pattern of low wave speed zones consistent with possible partial melt suggests more complex and disconnected geometry than the pervasive narrow zone from the channel flow models

partial melt in the upper middle crust of the northwest himalaya revealed by rayleigh wave dispersion article i nfo seismic shear wave velocities are sensitive to the partial melts that should be present in the himalayan orogen if low viscosity channel flow is active at the present day we analyzed regional earthquakes in the western himalaya and tibet recorded on 16 broadband seismometers deployed across the nw indian himalaya from the indian platform to the karakoram range we used a multiple filter technique to calculate the group velocity dispersion of fundamental mode rayleigh waves and then inverted the dispersion records to obtain separate one dimensional shear wave velocity models for five geologic provinces the tibetan plateau ladakh arc complex indus tsangpo suture zone tethyan himalaya and himalayan thrust belt our velocity models show a low velocity layer lvl with 7 17 velocity reduction centered at 30 km depth and apparently continuous from the tethyan himalaya to the tibetan plateau this lvl shows good spatial correspondence with observations of low resistivity from magnetotelluric studies along the same profile of the possible explanations for low velocity and low resistivity in the mid crust only the presence of melts or aqueous fluids or both satisfactorily explains both sets of observations elevated heat flow observed in the nw himalaya implies that if aqueous fluids are present in the mid crust then the mid crust is well above its solidus comparison of our results with laboratory measurements and theoretical models suggests 3 7 melt is present in a channel in the upper middle crust of the nw himalaya at the present day and the physical conditions to enable active channel flow may be present

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

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

east asia mantle tomography new insight into plate subduction and intraplate volcanism abstract we present a new p wave tomographic model beneath east asia by inverting 1 401 797 arrival time data recorded by the regional seismic networks in east asia and temporary seismic arrays deployed on the tibetan plateau our high resolution tomography shows that the subducted pacific slab is revealed clearly as a high velocity high v zone and it becomes stagnant in the mantle transition zone beneath eastern china prominent high v anomalies atop the 410 km discontinuity are detected beneath the eastern north china craton and northeast china suggesting that lithospheric delamination may have occurred and greatly affected the thermal state intraplate magmatism and surface topography of this region the indian lithosphere is characterized by a high v anomaly and it is subducting nearly horizontally beneath the entire or most parts of western tibet and with a small dipping angle to the southernmost part of eastern tibet the intraplate magmatism in different parts of east asia has different origins the active tengchong volcano is underlain by a prominent low velocity low v anomaly in the shallow mantle which may be caused by the subduction and dehydration of the burma microplate plate or indian plate the hainan volcano is underlain by a plume like low v anomaly that extends down to at least 1000 km depth and seems to be related to the deep subductions of the burma microplate or indian plate in the west and the philippine sea plate in the east prominent low v anomalies are detected beneath the changbai longgang and xianjindao volcanoes in northeast asia which may be related to the rollback of the subducting pacific slab as well as the convective circulation process in the big mantle wedge above the stagnant slab the origin of the wudalianchi volcano in northeast china seems associated with the upwelling of asthenospheric materials caused by the subduction induced lithospheric delamination

shear wave tomography of china using joint inversion of body and surface wave constraints 1 the india eurasia collision and the decratonization of the north china craton have drawn much attention from the scientific community here we provide the first large scale s wave velocity model for china ch11 s based on constraints from both teleseismic surface and body waves we take advantage of the recent deployment of the 140 permanent stations of the chinese digital seismic network and temporary network deployments to resolve both the lithospheric and deeper mantle structure slow velocities are widespread in the crust and upper mantle deeply rooted fast anomalies are located beneath the stable yangtze craton and the western ordos block of the north china craton an upper mantle fast anomaly is observed beneath the eastern block of the north china craton and could represent thermally eroded or delaminated precambrian lithosphere another flat and fast feature appears beneath the tibetan plateau from 50 to 250 km depth this may represent the indian slab stalled in the mantle due to its buoyancy or a lithospheric instability triggered by the india eurasia collision a large fast anomaly apparently stagnant in the transition zone is observed beneath the yangtze craton and may play a role in the stability of this block in contrast on both sides of the south china block active and reactivated areas coincide with oceanic slab material that has already sunk into the lower mantle and that may have enhanced tectonic activity by forcing convection finally the upper mantle beneath tibet seems almost completely surrounded by adjacent high velocity and presumably strong blocks

structural and statistical characterization of joints and multi scale faults in an alternating sandstone and shale turbidite sequence at the santa susana field laboratory implications for their effects on groundwater flow and contaminant transport abstract this paper describes the properties of faults and fractures in the upper cretaceous chatsworth formation exposed at santa susana field laboratory and its surroundings simi hills california where groundwater flow and contamination have been studied for over three decades the complex depositional architecture of this turbidite consisting of alternating sandstones and shales interacting with formative stress conditions are responsible for multi scale fault hierarchies and permeable fractures in which nearly all groundwater flow occurs intensity and distribution of background fractures and their relation to bedding thickness are established for sandstones the dominant lithology the architecture of faults with increasing displacement is described and relationships among fault dimensional parameters captured data from 400 boreholes and piezometers reveal the effect of faults and fractures on groundwater flow large hydraulic head differences observed across fault zones with shale rich cores indicate these structures as cross flow barriers moreover hydraulic head profiles under ambient conditions and pumping tests suggest strong hydraulic connectivity in all directions to depth of hundreds of meters this outcrop based structural characterization relates the horizontal hydraulic conductivity to the observed well connected fracture network and explains the strong vertical connectivity across low hydraulic conductivity shales as faults and sheared fractures provide flow pathways

waveform tomography reveals channeled flow at the base of the oceanic asthenosphere understanding the relationship between different scales of convection that drive plate motions and hotspot volcanism still eludes geophysicists using full waveform seismic tomography we imaged a pattern of horizontally elongated bands of low shear velocity most prominent between 200 and 350 kilometers depth which extends below the well developed low velocity zone these quasi periodic fingerlike structures of wavelength 2000 kilometers align parallel to the direction of absolute plate motion for thousands of kilometers below 400 kilometers depth velocity structure is organized into fewer undulating but vertically coherent low velocity plumelike features which appear rooted in the lower mantle this suggests the presence of a dynamic interplay between plate driven flow in the low velocity zone and active influx of low rigidity material from deep mantle sources deflected horizontally beneath the moving top boundary layer

surface wave tomography and azimuthal anisotropy of the philippine sea plate abstract long period and broadband waveform data from 1984 to 2007 extracted mainly from the iris data center with additional data from 1997 to 2007 extracted from the ocean hemisphere project is used to perform a detailed mapping of rayleigh wave group velocity and anisotropic structures of the philippine sea plate psp our results show prominent high rayleigh wave group velocity anomalies and heterogeneity in three marginal basins of the psp at period up to 30 s the convergent boundaries around the psp are associated with low velocity anomalies heterogeneity of velocity distribution at deep depths along the ryukyu trench is also observed our results indicate that the azimuthal anisotropy in the psp is depth dependent the fast direction in the west philippine basin and the shikoku basin is in ne sw at shorter periods which is correlated with fossilized fabric produced by final phase of deformation whereas the fast direction in the parece vela basin is complex at shorter periods and becomes uniformly ne sw oriented at longer periods at the depths near the lithosphere asthenosphere boundary the fast directions become parallel to the absolute plate motion for various parts of the psp the fast directions along subduction zones around the psp are predominately trench normal the relatively simple patterns of azimuthal anisotropy may imply that the observed anisotropy originates from the a type lpo of olivine fabric at shallow depths in the back arc region and with slab entrained mantle flow at deep depths

groundwater flow characterization in a fractured bedrock aquifer using active dts tests in sealed boreholes summary in recent years wireline temperature profiling methods have evolved to offer new insight into fractured rock hydrogeology important advances in wireline temperature logging in boreholes make use of active line source heating alone and then in combination with temporary borehole sealing with flexible impervious fabric liners to eliminate the effects of borehole cross connection and recreate natural flow conditions here a characterization technique was developed based on combining fiber optic distributed temperature sensing dts with active heating within boreholes sealed with flexible borehole liners dts systems provide a temperature profiling method that offers significantly enhanced temporal resolution when compared with conventional wireline trolling based techniques that obtain a temperature depth profile every few hours the ability to rapidly and continuously collect temperature profiles can better our understanding of transient processes allowing for improved identification of hydraulically active fractures and determination of relative rates of groundwater flow the advantage of a sealed borehole environment for dts based investigations is demonstrated through a comparison of dts data from open and lined conditions for the same borehole evidence for many depth discrete active groundwater flow features under natural gradient conditions using active dts heat pulse testing is presented along with high resolution geologic and geophysical logging and hydraulic datasets implications for field implementation are discussed

a field example of measuring hydrodynamic dispersion in a single fracture a field example of measuring the dispersive properties of a single fracture in fractured plutonic rock is presented the experimental technique involves injecting a slug of conservative tracer into a steady groundwater flow field established between a pumping and recharging borehole and monitoring the tracer breakthrough by sampling the withdrawal water directly the breakthrough curves from two experiments were analyzed with a model which describes the flow field geometry either analytically or numerically and solves for hydrodynamic dispersion analytically a longitudinal dispersivity of 1 40 m was estimated by fitting the model to each set of field data the magnitude of the dispersion was determined to be independent of dispersive effects created by flow through the borehole instrumentation and thought to be purely hydrodynamic in nature

mongolian plateau evidence for a late cenozoic mantle plume under central asia the 2500 x 700 km mongolian plateau average elevation 2000 m is situated between the altai orogen and the siberian craton and occupies much of mongolia and transbaikalia in russia the plateau is characterized by 1 basin and range topography and two major domes hentai 600 x 300 km and hangai 800 x 550 km where altitudes reach 3905 m 2 lithosphere that is thinner than adjacent areas minimum 50 km 3 elevated heat flow up to 120 mw m2 4 dominantly alkaline basaltic volcanism in the form of cones lava fields and volcanic plateaus mostly of miocene quaternary age and 5 rifts including baikal main evolution in the pliocene quaternary tunka oligocene early miocene and hobsogol pliocene quaternary existing models explain these features in terms of diapiric upwelling of a mantle asthenolith below the main rifts and or as a long distance effect of the india asia collision we propose that the late cenozoic uplift of the whole mongolian plateau and associated rifting magmatism high heat flow and lithospherec thinning are not externally driven by the india asia collision but are the expression of the interaction of a mantle plume with overlying lithosphere some rifts link and interact with major strike slip faults such as the bolnai such faults may be the major expression of the india asia collision in this region

structure of the european upper mantle revealed by adjoint tomography the structure of the european crust and upper mantle is precisely known only in limited regions a new tomographic model for the entire european upper mantle identifies northeastward subduction of the adria plate beneath the dinarides mountains volcanism related to the upwelling eifel hotspot and mantle delamination beneath scandinavia

micromorphology of some placer minerals from kerala beach india abstract scanning electron microscopic studies of placer minerals such as ilmenite rutile sillimanite zircon monazite and garnet from beach sediments of kerala indicate a number of microfeatures these features are mainly produced by mechanical impact or solution activity of chemicals an attempt has been made to identify the common grain micro textures of the placer minerals and the processes responsible for their formation impact features result in blocks fracture plates steps pits and v shaped marks solution activity results in irregular marks etch v s oriented and unoriented etch pits grooves etc the environmental significance of these features is discussed

groundwater recharge assessment in an upland sandstone aquifer of southern california abstract the chloride mass balance cmb method was used to obtain long term recharge values for the santa susana field laboratory ssfl site which features a groundwater flow system beneath an upland ridge formed of sandstone and shale beds in the simi hills ventura county southern california this application relied on the availability of on site measurements of bulk atmospheric chloride deposition comprised of dry fallout and wet concentration a large number of groundwater samples 1490 collected over three decades from 206 wells spanning a depth range from 10 to 360 m and measurements of chloride in surface runoff during rain events the use of the cmb method is suited to the assessment of recharge for the study area because the mean chloride values in groundwater show minimal spatial trends indicating no sources other than atmospheric in addition the cl br ratio was used to exclude wells with possible anthropogenic chloride the site wide average recharge ranges between 1 8 and 9 5 of the mean annual precipitation 455 mm with a mean value of 4 2 the measured surface runoff varies from 2 3 to 10 2 with mean value of 6 1 28 mm and therefore the volume of water lost to evapotranspiration is between 95 9 and 80 3 with a mean value of 89 6 408 mm the long term recharge calculated using the cmb method is consistent with tritium distribution based on a subset of groundwater monitoring wells and with an analysis of steady flow in the groundwater mound beneath the ssfl furthermore the recharge value matches those in the literature for sandstone aquifers in arid and semi arid climates this recharge estimate has important relevance for site characterization in terms of constraining the volumetric groundwater flow rates and water balance and understanding the mechanisms of transport towards the water table moreover this is the first application of the cmb in an upland area of california hence the method is demonstrated to be robust and applicable to many upland bedrock areas in southern california and similar regions around the world and can be used to quantify groundwater flow rates and supplies relevant to water resource management

formation of arcs and backarc basins inferred from the tectonic evolution of southeast asia since the late cretaceous abstract results of the geological and geophysical surveys in the daito ridges and basin in the northern west philippine basin suggest that the daito ridge was an arc facing toward the south from the late cretaceous to the early tertiary the late cretaceous and tertiary history of southeast asia is evaluated based on these data in the daito ridges and basins and reconstructed based on overall plate kinematics that have operated in this area during the late cretaceous the daito ridge and the east philippine islands were positioned along the boundary between the indian and pacific plates the western half of the philippines setting on the indian plate approached from the south and collided with the east philippine daito arc either during the latest paleocene or the earliest eocene it is inferred that the bulk of the philippine archipelago rotated clockwise and borneo spun counterclockwise during the tertiary from the reconstruction the formation of backarc basins and their spreading direction are assessed as a result some primary causes and significant characteristics are suggested for the opening of backarc basins in southeast asia first opening of some backarc basins commenced with or was triggered by collisions second backarc basins opened approximately parallel to oceanic plate motion third the formation of some backarc basins was triggered by the approach of a hot spreading center fourth the spreading mode or direction of backarc basins was greatly affected by the configuration of the surrounding continent and was also rearranged to spread approximately parallel to oceanic plate motion the formation of backarc basins and their spreading direction can be reasonably explained by plate kinematics however the generative force responsible for their formation is possibly within the subduction system particularly to form horizontal tensional force in backarc side

high resolution mantle tomography of china and surrounding regions 1 a high resolution p wave tomographic model of the crust and mantle down to 1100 km depth under china and surrounding regions is determined by using about one million arrival times of p pp pp and pcp waves from 19 361 earthquakes recorded by 1012 seismic stations the subducting pacific slab is imaged clearly as a high velocity zone from the oceanic trenches down to about 600 km depth and intermediate depth and deep earthquakes are located within the slab the pacific slab becomes stagnant in the mantle transition zone under east china the western edge of the stagnant slab is roughly coincident with a surface topographic boundary in east china the active changbai and wudalianchi intraplate volcanoes in northeast china are underlain by significant slow anomalies in the upper mantle above the stagnant pacific slab these results suggest that the active intraplate volcanoes in ne china are not hot spots but a kind of back arc volcano associated with the deep subduction of the pacific slab and its stagnancy in the transition zone under the mariana arc however the pacific slab penetrates directly down to the lower mantle the active tengchong volcano in southwest china is related to the eastward subduction of the burma microplate the subducting indian and philippine sea plates are also imaged clearly the indian plate has subducted down to 200 300 km depth under the tibetan plateau with a horizontal moving distance of about 500 km high velocity anomalies are revealed in the upper mantle under the tarim basin ordos and sichuan basin which are three stable blocks in china

microplate capture rotation of the western transverse ranges and initiation of the san andreas transform as a low angle fault system tectonic rotation of the western transverse ranges block is explained by capture of the partially subducted monterey microplate by the pacific plate at about anomaly 6 time ca 20 ma as pacific monterey spreading slowed and eventually ceased the slip vector along the gently northeast dipping subduction interface beneath the california margin changed from slightly oblique subduction to transtensional dextral transform motion this change in slip vector and a shift of pacific plate motion eastward along the already subducted monterey plate interface imply that the san andreas transform began as a system of low angle faults that locally subjected the overriding continental margin to distributed basal shear and crustal extension this basal shear produced the rotated western transverse ranges this model helps explain the timing of initial rotation and basin formation the sudden appearance of widely distributed transform motion well inland of the margin in early miocene time why the western transverse ranges uniquely rotated as a large coherent crustal block and several fundamental structural characteristics of central and southern california the model also provides major constraints on the amount of pacific north america strike slip motion the position through time of offshore oceanic plates relative to onshore geology and a general explanation for what may happen as a spreading ridge approaches a trench and the subduction zone evolves into a transform system

combined use of straddle packer testing and flute profiling for hydraulic testing in fractured rock boreholes summary a combination of high resolution hydraulic tests using straddle packers and transmissivity t profiling using the flute flexible liner method liner profiling in densely fractured rock boreholes is shown to be efficient for the determination of the vertical distribution of t along the entire hole the liner t profiling method takes a few hours or less to scan the entire borehole length resulting in a t profile under favorable conditions this method has good reliability for identifying the highest t zones identified by distinct decreases in liner velocity when these zones are covered by the descending liner in contrast for one short test interval e g 1 2 m the multiple test straddle packer method takes a few hours to measure t with good precision and accuracy using a combination of steady state and transient tests e g constant head step tests slug tests and constant rate pumping tests because of the time consuming aspect of this multiple test method it is most efficient in each borehole to conduct straddle packer testing only in priority zones selected after assessment of other borehole data collected prior to packer testing the t profile from the liner method is instrumental in selecting high permeable zones for application of the multiple test method using straddle packers which in turn refines the t estimation from the liner profile results from three boreholes in densely fractured sandstone demonstrate this approach showing the synergistic use of the methods with emphasis on information important for determining hydraulic apertures

high resolution body wave tomography models of the upper mantle beneath eastern china and the adjacent areas 1 we present new 3 d tomographic models of vp vs and vp vsratio anomalies in the upper mantle beneath ec and adjacent areas this data was collected and interpreted with the goal of clarifying geodynamic processes that caused spatially variable event histories throughout eastern china ec during mesozoic to cenozoic time the tomographic images were constructed by inverting body wave travel times recorded at 1300 stations within the upgraded china national seismic network and 9 temporary arrays resolution tests for different depths and the featured velocity anomalies verify that the tomographic images capture the velocity heterogeneities in the upper mantle to depths of 700 km the salient features of vp vs and vp vsratio anomalies can be clearly identified these include strong multiscale heterogeneities occupying the upper mantle beneath ec and differences in the spatial scale of anomalies found beneath northern and southern areas of ec these features demonstrate a degree of spatial variability in the geodynamic evolution of ec we propose two mechanisms to explain these patterns first the western front of the subducted slab may have imparted greater horizontal compressional stress in areas where it impinged further eastward into ec these areas would experience stronger convection and an altered stress regime in the upper mantle creating significant thermal anomalies beneath the south china block scb relative to the eastern north china craton ncc second differing thermal states and viscosities for the eastern ncc and the cathaysia block cab resulted in differing responses to regional deformation the archean hinterland of the eastern ncc specifically has a colder thermal state and higher viscosity and therefore exhibits only small scale heterogeneities due to the effect of shear localization the neoproterozoic cab has a relatively warm thermal state with lower viscosity and thus deformed more continuously

identifying hydraulically conductive fractures with a slow velocity borehole flowmeter the u s geological survey used a recently developed heat pulse flowmeter to measure very slow borehole axial water velocities in granitic rock at a site near lac du bonnet manitoba canada the flowmeter was used with other geophysical measurements to locate and identify hydraulically conducting fractures contributing to the very slow vertical water flow in the two boreholes selected for study the heat pulse flowmeter has no moving parts and operates on the tag trace principle it is an improved version of the flowmeter developed by the water research centre in england in 1975 the u s geological survey s heat pulse flowmeter has a flow measuring range in water of 0 06 6 m min and can resolve velocity differences as slow as 0 01 m min this is an order of magnitude slower than the stall speed of spinner flowmeters the flowmeter is 1 16 m long and 44 mm in diameter it was calibrated in columns of 76 and 152 mm diameter to correspond to the boreholes studied the heat pulse flowmeter system is evalu

a no lid zone in the central chang thang platform of tibet evidence from pure path phase velocity measurements of long period rayleigh waves pure path phase velocities of fundamental mode rayleigh waves in the period range 30 80s are obtained for different paths across the tibet plateau using a two event method with events located in tibet and aligned with world wide standard seismograph network stations at teleseismic distance evidence is found for significant lateral variations of structure of the crust and uppermost mantle in tibet in particular phase velocities obtained on paths contained in the chang thang platform are higher than average in tibet at periods shorter than 60s while remaining very low at longer periods when interpreting these phase velocities in terms of simple layered s velocity models it is found that contrary to other areas in tibet they are incompatible with the existence of a high velocity lid s velocities of 4 4 4 5 km s are found immediately beneath the moho and the crust is somewhat thinner 50 60 km than average in tibet this indicates a possible upwelling of hot asthenospheric material compatible with landsat evidence for subrecent basaltic volcanism and independent seismic evidence such as inefficient transmission of sn waves on the other hand a 70 km thick crust and very high upper mantle s velocities are found on the western border of tibet karakorum hindu kush compatible with previous finer scale results concerning the associated zone of intermediate depth seismicity

subduction of the indian lithosphere beneath the tibetan plateau and burma abstract subduction of the indian lithosphere under eurasia plays an important role in the tectonic evolution of the tibetan plateau and surrounding regions to improve our knowledge of pertinent mantle structures through tomographic imaging we combine p wave arrival time data from temporary arrays in tibet and stations of the chinese seismograph network with reprocessed data from the international seismological centre the new images reveal considerable spatial variations in mantle structure along the collision zone and the horizontal distance over which presumed continental indian lithosphere slides northward beneath the plateau decreases from west where it underlies the himalayas and the entire plateau to east where no indication is found for present day underthrusting beyond the himalayan block and indus tsangpo suture p wavespeed appears low in the shallow mantle beneath much of central and eastern tibet these observations suggest that indian lithosphere underlies only the southwestern part of the plateau and that the central and northeastern part is underlain by lithosphere of asian origin the continental parts of the indian plate that currently underthrust or subduct below the plateau appear generally detached from the oceanic slab fragments that subducted longer ago and that have been detected deeper in the mantle except perhaps in the central part of the collision zone 80 90 e this suggests that ongoing india eurasia collision must increasingly be driven by other forces such as subduction of the indian plate further west and east e g beneath indochina our images reveal structures associated with eastward subduction along the burmese arc southeast of the eastern himalayan syntaxis the tengchong volcanic complex in southwest china is marked by slow wave propagation to 150 km depth suggesting a causal link to subduction along the burmese arc the low velocities beneath the red river fault region extend to greater depth and may be related to upper mantle processes further southeast

assessing the validity of the channel model of fracture aperture under field conditions in recent investigations of fluid and solute movement in discrete fractures spatial heterogeneity of the fracture aperture has been conceptualized as a series of noninterconnecting constant aperture flow paths or channels two methods of estimating the distribution of the aperture sizes are presented using information from a single hole pumping test and a radially converging tracer test the first method uses the transmissivity of the fracture and mean arrival time of the tracer while the second method uses the mean and variance of the solute arrival time if the fracture can be conceptualized as a series of nonintersecting flow paths of constant aperture the two methods should yield identical estimates for the parameters of the distribution the validity of the channel model can be assessed by comparing the parameters of the distribution that are estimated by the two methods this technique was demonstrated using hydraulic and tracer tests conducted in a discrete areally extensive horizontal fracture in the silurian dolomite in the northeastern illinois a lognormal and a truncated gamma distribution were used to describe the distribution of constant aperture flow paths the lognormal distribution could not reproduce the abrupt rising limb and maximum rate of mass arrival that characterized the tracer tests the gamma distribution more accurately predicted the shape of the breakthrough curves however the two methods of estimating the parameters of the distribution provided significantly different estimates of the variances of the aperture sizes the mean aperture as estimated by the two methods was similar the difference in the variance of the aperture as estimated by the two methods indicates that alternative conceptual models of aperture heterogeneity are required to more accurately describe both fluid and solute movement in this field situation

global seismicity of 2003 centroid moment tensor solutions for 1087 earthquakes abstract centroid moment tensor cmt solutions are presented for 1087 earthquakes that occurred during 2003 the solutions are obtained using the method of dziewonski et al dziewonski a m chou t a woodward j h 1981 determination of earthquake source parameters from waveform data for studies of global and regional seismicity j geophys res 86 2825 2852 and applying corrections for aspherical earth structure as represented by the whole mantle shear velocity model sh8 u4l8 of dziewonski and woodward dziewonski a m woodward r l 1992 acoustic imaging at the planetary scale in emert h harjes h p eds acoustical imaging vol 19 plenum press new york pp 785 797 the model of inelastic attenuation of durek and ekstrom durek j j ekstrom g 1996 a radial model of inelasticity consistent with long period surface wave attenuation bull seism soc am 86 144 158 is used to predict the decay of the waveforms the focal mechanisms of the largest or otherwise significant earthquakes of 2003 are reviewed

enhanced detection of hydraulically active fractures by temperature profiling in lined heated bedrock boreholes summary the effectiveness of borehole profiling using a temperature probe for identifying hydraulically active fractures in rock has improved due to the combination of two advances improved temperature sensors with resolution on the order of 0 001 c and temperature profiling within water inflated flexible impermeable liners used to temporarily seal boreholes from hydraulic cross connection the open hole cross connection effects dissipate after inflation so that both the groundwater flow regime and the temperature distribution return to the ambient background condition this paper introduces a third advancement the use of an electrical heating cable that quickly increases the temperature of the entire static water column within the lined hole and thus places the entire borehole and its immediate vicinity into thermal disequilibrium with the broader rock mass after heating for 4 6 h profiling is conducted several times over a 24 h period as the temperature returns to background conditions this procedure referred to as the active line source als method offers two key improvements over prior methods first there is no depth limit for detection of fractures with flow second both identification and qualitative comparison of evidence for ambient groundwater flow in fractures is improved throughout the entire test interval the benefits of the als method are demonstrated by comparing results from two boreholes tested to depths of 90 and 120 m in a dolostone aquifer used for municipal water supply and in which most groundwater flow occurs in fractures temperature logging in the lined holes shows many fractures in the heterothermic zone both with and without heating but only the als method shows many hydraulically active fractures in the deeper homothermic portion of the hole the identification of discrete groundwater flow at many depths is supported by additional evidence concerning fracture occurrence including continuous core visual inspection acoustic televiewer logs and tests for hydraulic conductivity using straddle packers as well as rock core voc data where available that show deep penetration and many migration pathways confidence in the use of temperature profiles and the conceptual model is provided by numerical simulation and the demonstrated reproducibility of the evolution of the temperature signal measured in the lined holes with and without heating this approach for using temperature profiling in lined holes with heating is a practical advance in fractured rock hydrogeology because the liners are readily available the equipment needed for heating is low cost and rugged and the time needed to obtain the profiles is not excessive for most projects

crust and upper mantle tomography in tibet using surface waves we have obtained maps of lateral variations of structure in the crust and lithosphere in tibet and surrounding regions by inversion of single station measurements of fundamental mode rayleigh wave phase velocities in the period range 25 100 sec for earthquakes located in central asia and observed at teleseismic digital stations in eurasia phase velocity maps are obtained using a tomographic method without a priori constraints on region boundaries the lateral variations of s velocity reveal a symmetric pattern on each side of crustal low velocity zone centered on the chang tang region north central tibet this zone is bounded by rather steep velocity gradients to the south and east about 250 and 400 km north and west of the frontal thrusts of the himalayas and lungmen shan respectively the northern boundary of the zone crosses the northern limit of the tibet plateau altyn tagh and kunlun extending into the southwest tarim and qaidam basins the low crustal velocities are consistent with a thick hot crust in the central part of tibet consistent with quaternary volcanism in chang tang the steep gradients towards higher velocities in the south and in the north are compatible with the documented continental subduction in the south and suggest that a similar situation might exist in the north

subduction triggered magmatic pulses a new class of plumes article i nfo a variety of atypical plume like structures and focused upwellings that are not rooted in the lower mantle have recently been discussed and seismological imaging has shown ubiquitous small scale convection in the uppermost mantle in regions such as the mediterranean region the western us and around the western pacific we argue that the three dimensional return flow and slab fragmentation associated with complex oceanic subduction trajectories within the upper mantle can generate focused upwellings and that these may play a significant role in regional tectonics the testable surface expressions of this process are the outside arc alkaline volcanism topographic swell and low velocity seismic anomalies associated with partial melt using three dimensional simplified numerical subduction models we show that focused upwellings can be generated both ahead of the slab in the back arc region though five times further inward from the trench than arc volcanism and around the lateral edges of the slab in the order of 100 km away from slab edges vertical mass transport and by inference the associated decompression melting in these regions appears strongly correlated with the interplay between relative trench motion and subduction velocities the upward flux of material from the depths is expected to be most pronounced during the first phase of slab descent into the upper mantle or during slab fragmentation we discuss representative case histories from the pacific and the mediterranean where we find possible evidence for such slab related volcanism

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

savani a variable resolution whole mantle model of anisotropic shear velocity variations based on multiple data sets we present a tomographic model of radially anisotropic shear velocity variations in the earth s mantle based on a new compilation of previously published data sets and a variable block parameterization adapted to local raypath density we employ ray theoretical sensitivity functions to relate surface wave and body wave data with radially anisotropic velocity perturbations our database includes surface wave phase delays from fundamental modes up to the sixth overtone measured at periods between 25 and 350 s as well as cross correlation traveltimes of major body wave phases before inversion we apply crustal corrections using the crustal model crust2 0 and we account for azimuthal anisotropy in the upper mantle using ray theoretical corrections based on a global model of azimuthal anisotropy while being well correlated with earlier models at long spatial wavelength our preferred solution savani additionally delineates a number of previously unidentified structures due to its improved resolution in areas of dense coverage this is because the density of the inverse grid ranges between 1 25 in well sampled and 5 in poorly sampled regions allowing us to resolve regional structure better than it is typically the case in global s wave tomography our model highlights i a distinct ocean continent anisotropic signature in the uppermost mantle ii an oceanic peak in above average 1 which is shallower than in previous models and thus in better agreement with estimates of lithosphere thickness and iii a long wavelength pattern of 1 associated with the large low shear velocity provinces in the lowermost mantle

heterogeneity and anisotropy of the lithosphere of se tibet from surface wave array tomography 1 understanding the geotectonic evolution of the southeastern tibetan plateau requires knowledge about the structure of the lithosphere using data from 77 broadband stations in sw china we invert rayleigh wave phase velocity dispersion curves from ambient noise interferometry t 1 0 40 s and teleseismic surface waves t 2 0 150 s for 3 d heterogeneity and azimuthal anisotropy in the lithosphere to 150 km depth our surface wave array tomography reveals 1 deep crustal zones of anomalously low shear wave speed and 2 substantial variations with depth of the pattern of azimuthal anisotropy upper crustal azimuthal anisotropy reveals a curvilinear pattern around the eastern himalayan syntaxis with fast directions generally parallel to the main strike slip faults the mantle pattern of azimuthal anisotropy is different from that in the crust and varies from north to south the tomographically inferred 3 d variation in azimuthal anisotropy helps constrain the source region of shear wave splitting south of 26 n off the high plateau most of the observed splitting can be accounted for by upper mantle anisotropy but for stations on the plateau proper with thick crust crustal anisotropy cannot be ignored on long wavelengths the pattern of azimuthal anisotropy in the crust differs from that in the mantle this is easiest explained if deformation varies with depth the deep crustal zones of low shear wave speed and presumably mechanical strength may represent loci of ductile deformation but their lateral variation suggests that in se tibet localized crustal channel flow and motion along the major strike slip faults are both important

non linear 3 d born shear waveform tomography in southeast asia s u m m a r ysoutheast se asia is a tectonically complex region surrounded by many active source re gions thus an ideal test bed for developments in seismic tomography much recent develop ment in tomography has been based on 3d sensitivity kernels based on the rst order bornapproximation but there are potential problems with this approach when applied to waveformdata in this study we develop a radially anisotropic model of se asia using long period multi mode waveforms we use a theoretical cascade approach starting with a large scale eurasianmodel developed using 2d nact sensitivity kernels and then using a modi ed born approxi mation nborn shown to be more accurate at modeling waveforms in order to invert a subsetof the data for structure in a subregion longitude 75

spectral element moment tensor inversions for earthquakes in southern california we have developed and implemented an automated moment tensor inversion procedure to determine source parameters for southern california earthquakes the method is based upon spectral element simulations of regional seismic wave propagation in an integrated 3d southern california velocity model sensitivity to source parameters is determined by numerically calculating the frechet derivatives required for the moment tensor inversion we minimize a waveform misfit function and allow limited time shifts between data and corresponding synthetics to accommodate additional 3d heterogeneity not included in our model the technique is applied to three recent southern california earthquakes the 9 september 2001 m l 4 2 hollywood event the 22 february 2003 m l 5 4 big bear event and the 14 december 2001 m l 4 0 diamond bar event using about half of the available three component data at periods of 6 sec and longer we obtain focal mechanisms depths and moment magnitudes that are generally in good agreement with estimates based upon traditional body wave and surface wave inversions

changbaishan volcanism in northeast china linked to subduction induced mantle upwelling the changbaishan volcanic complex in china cannot be easily explained as the consequence of a mantle plume seismic images from the region identify buoyant mantle material that may have been entrained and dragged downwards by the subducting pacific plate but is now escaping upwards through a gap in the plate and producing the intraplate volcanism

cenozoic normal faulting and regional doming in the southern hangay region central mongolia implications for the origin of the baikal rift province abstract the hangay dome in central mongolia is a mountainous region covering more than 200 000 km2 with numerous flat topped peaks over 3000 m that preserve a late cretaceous paleogene erosion surface doming began in the middle oligocene producing more than 2000 m of regional topographic uplift the range represents an important kinematic link between the baikal rift province to the north and altai transpressional ranges to the south and west structural field investigations of major faults visible on satellite imagery indicate that the southern hangay dome region is dominated by late cenozoic normal faults that bound small half graben most faults are ne striking and faults at the highest elevations are the most recently active most graben appear to be isolated systems that constitute small sediment sinks perched on the flanks and crests of the dome the first order feature is the dome itself and most sediment eroded off of the dome is deposited in the mongolian valley of lakes or is carried northwards by the selenga river and its extensive tributaries the basement of the dome is a precambrian craton although the shape and dimensions of the craton are poorly constrained to the north and east late cenozoic uplift of the southern dome region appears to be confined to the area underlain by cratonic basement whereas the altai region to the south and west is underlain by mechanically weaker palaeozoic arc and accretionary belts with respect to the regional northeast directed shmax the hangay craton appears to have acted as a rigid passive indentor focusing late cenozoic transpressional deformation around its west and southern margins models invoking a late cenozoic plume as the driving force for doming and widespread alkaline volcanism on the dome are not strongly supported by geochemical and isotopic data on neogene recent volcanics and the spatial correlation between areas that are domed and older cratonic crust appears too coincidental to be ignored convective removal of an overthickened lithospheric root leading to adiabatically decompressed asthenosphere could explain regional doming and volcanism however major crustal thickening last occurred in the permian in the southern hangay region and the time lag between thickening and postulated root removal and plateau uplift 200 myr appears too long an alternative model is explored based on speculated lithospheric mantle flow patterns driven by india s continued northeastward indentation it is suggested that lithospheric mantle flow diversion around the overthickened hangay craton crustal keel could cause lithospheric thinning beneath the craton and passive asthenospheric upwarp leading to regional topographic uplift and decompression melting alkali volcanism in general the angular relationship between precambrian craton boundaries and the prevailing northeasterly shmax appears to control the kinematics of late cenozoic deformation throughout the hangay altai sayan and baikal regions

seismic anisotropy and mantle flow seismic anisotropy in the mantle is primarily due to deformation induced lattice preferred orientation lpo of olivine crystals the aim of this paper is to better understand how such lpo is produced by flow and to learn whether observations of seismic anisotropy can be used to infer the local direction of flow within the mantle the basis of the work is a two dimensional theory which describes how lpo evolves during an arbitrary time dependent deformation ribe 1989 i investigate the evolution of lpo beneath ocean ridges above subducted slabs and in thermal convective flows the ocean ridge model predicts that the seismic anisotropy produced at a fast spreading ridge should be greater in magnitude than that produced at a slow spreading ridge and that the fast axis should be more nearly horizontal the subduction zone model predicts that strong seismic anisotropy should be produced above subducted slabs with the fast axis aligned with the slab regardless of the subduction angle the evolution of lpo in typical convective flows is extremely complex and depends strongly on such factors as the mode of heating and the surface boundary conditions in general there is no simple relation between the lpo and the local flow direction in any of the models considered the attempt to use seismic anisotropy to map flow patterns on a global scale is therefore probably unwarranted however the lpo does become aligned with the flow direction when the flow is a progressive simple shear such a flow occurs in limited portions of the mantle beneath the lithosphere at a fast spreading ridge above subducted slabs and in boundary layers beneath rigid surfaces such as continents observations of seismic anisotropy may therefore indicate the sense of shear at shallow depths in the mantle

tibetan and indian lithospheres in the upper mantle beneath tibet evidence from broadband surface wave dispersion broadband seismic experiments over the last two decades have produced dense data coverage across tibet yet the mechanism of the india asia lithospheric convergence beneath it remains a puzzle with even its basic features debated and with very different end member models advocated today we measured highly accurate rayleigh and love wave phase velocity curves in broad period ranges up to 5 200 s for a few tens of pairs and groups of stations across tibet combining in each case hundreds to thousands of interstation measurements made with cross correlation and waveform inversion methods robust shear velocity profiles were then determined by extensive series of nonlinear inversions of the data designed to constrain the depth dependent ranges of isotropic average shear speeds and radial anisotropy temperature anomalies in the upper mantle were estimated from shear velocities using accurate petrophysical relationships our results reveal strong heterogeneity in the upper mantle beneath tibet very large high velocity anomalies in the upper mantle are consistent with the presence of underthrust beneath southwestern tibet and subducted beneath central and eastern tibet indian lithosphere the corresponding thermal anomalies match those estimated for subducted indian lithosphere in contrast to the indian lithosphere tibetan lithosphere and asthenosphere display low to normal shear speeds tibetan lithosphere is thus warm and thin radial anisotropy in the upper mantle is weak in central and strong in northeastern tibet possibly reflecting asthenospheric flow above the subducting indian lithospheric slab

seismic image and origin of the changbai intraplate volcano in east asia role of big mantle wedge above the stagnant pacific slab abstract we determined p wave tomography of the crust and upper mantle under the changbai volcanic area in northeast asia by using 289 318 arrival time data from 4802 local earthquakes and 9599 teleseismic events a prominent low velocity anomaly is clearly imaged in the crust and upper mantle down to about 410 km depth beneath the changbai volcano a broad high velocity anomaly is revealed in the mantle transition zone and deep earthquakes occurred actively there suggesting that the subducting pacific slab is stagnating in the mantle transition zone under east asia our results suggest that the formation of the changbai and other intraplate volcanoes in northeast asia is related to the upwelling of hot and wet asthenospheric materials in the big mantle wedge above the stagnant pacific slab hence the active intraplate volcanoes in northeast asia are not hotspots related to deep mantle plumes but are caused by plate tectonic processes in the upper mantle

intrinsic versus extrinsic seismic anisotropy the radial anisotropy in reference earth models 1 seismic anisotropy usually arises from different mechanisms which include lattice or crystallographic preferred orientation lpo cpo alignment of cracks with or without fluid inclusions fine layering or partial melting this makes the interpretation of anisotropy in terms of intrinsic produced by lpo cpo versus extrinsic produced by other mechanisms properties difficult and nonunique the radial anisotropy in the one dimensional global spherically symmetric reference earth is usually claimed to be intrinsic here we explore whether the radial anisotropy in one dimensional reference earth models including preliminary reference earth model prem and the constrained reference earth model acy400 contains extrinsic anisotropy especially in relation to fine layering we conclude that as well as intrinsic anisotropy extrinsic anisotropy introduced by finely layered models can be considered to explain the lithospheric anisotropy in prem but cannot explain alone its asthenospheric anisotropy we also find that radial anisotropy in model acy400 is mainly intrinsic due to its petrological constraints

using earth tide induced water pressure changes to measure in situ permeability a comparison with long term pumping tests good constraints on hydrogeological properties are an important first step in any quantitative model of groundwater flow field estimation of permeability is difficult as it varies over orders of magnitude in natural systems and is scale dependent here we directly compare permeabilities inferred from tidal responses with conventional large scale long term pumping tests at the same site tidally induced water pressure changes recorded in wells are used to infer permeability at ten locations in a densely fractured sandstone unit each location is either an open hole well or a port in a multilevel monitoring well tidal response is compared at each location to the results of two conventional long term and large scale pumping tests performed at the same site we obtained consistent values between the methods for a range of site specific permeabilities varying from 10 15 m2 to 10 13 m2 for both open wells with large open intervals and multilevel monitoring well we conclude that the tidal analysis is able to capture passive and accurate estimates of permeability

global upper mantle tomography with the automated multimode inversion of surface and s wave forms summary we apply the automated multimode inversion of surface and s wave forms to a large global data set verify the accuracy of the method and assumptions behind it and compute an s vvelocity model of the upper mantle crust 660 km the model is constrained with 51 000 seismograms recorded at 368 permanent and temporary broadband seismic stations structure of the mantle and crust is constrained by waveform information both from the fundamentalmode rayleigh waves periods from 20 to 400 s and from s and multiple s waves higher modes in order to enhance the validity of the path average approximation we implement the automated inversion of surface and s wave forms with a three dimensional 3 d reference model linear equations obtained from the processing of all the seismograms of the data set are inverted for seismic velocity variations also relative to a 3 d reference in this study composed of a 3 d model of the crust and a one dimensional 1 d global average depth profile in the mantle below waveform information is related to shear and compressional velocity structure within approximate waveform sensitivity areas we use two global triangular grids of knots with approximately equal interknot spacing within each a finely spaced grid for integration over sensitivity areas and a rougher spaced one for the model parametrization for the tomographic inversion we use lsqr with horizontal and vertical smoothing and norm damping we invert for isotropic variations in s and p wave velocities but also allow for s wave azimuthal anisotropy in order to minimize errors due to possible mapping of anisotropy into isotropic heterogeneity the lateral resolution of the resulting isotropic upper mantle images is a few hundred kilometres varying with data sampling we validate the imaging technique with a spectral element resolution test inverting a published global synthetic data set computed with the spectral element method using a laterally heterogeneous mantle model we are able to reconstruct the synthetic model accurately this test confirms both the accuracy of the implementation of the method and the validity of the jwkb and path average approximations as applied in it reviewing the tomographic model we observe that low s v velocity anomalies beneath mid ocean ridges and backarc basins extend down to 100 km depth only shallower than according to some previous tomographic models this presents a close match to published estimates of primary melt production depth ranges there in the seismic lithosphere beneath cratons unambiguous high velocity anomalies extend to 200 km pronounced low velocity zones beneath cratonic lithosphere are rare where present south america tanzania they are neighboured by volcanic areas near cratonic boundaries the images of these low velocity zones may indicate hot material possibly of mantle plume origin trapped or spreading beneath the thick cratonic lithosphere

the role of the east asian active margin in widespread extensional and strike slip deformation in east asia east asia is a region of widespread deformation dominated by normal and strike slip faults deformation has been interpreted to result from extrusion tectonics related to the india eurasia collision which started in the early eocene in east and se china however deformation started earlier than the collision latest cretaceous to palaeocene suggesting that extrusion tectonics is not the only driving mechanism for east asia deformation it is suggested that the east asian active margin has influenced deformation in east asia significantly along the margin cenozoic back arc extension took place behind several adjoining arcs implying eastward rollback of the subducting slab and collapse of the overriding plate towards the retreating hinge line we show that extension took place along a c 7400 km long stretch of the east asian margin during most of the cenozoic physical models are presented simulating overriding plate collapse and back arc extension the models reproduce important aspects of the strain field in east asia for geometrical and rheological conditions scaled to represent east asia modelling shows that the active margin can be held responsible for deformation in east asia as far west as the baikal rift zone located c 3300 km from the margin

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

mechanisms of recharge in a fractured porous rock aquifer in a semi arid region abstract eleven porewater profiles in rock core from an upland exposed sandstone vadose zone in southern california with thickness varying between 10 and 62 m were analyzed for chloride cl concentration to examine recharge mechanisms estimate travel times in the vadose zone assess spatial and temporal variability of recharge and determine effects of land use changes on recharge as a function of their location and the local terrain the profiles were classified into four groups reflecting the range of site characteristics century to millennium average recharge varied from 4 to 23 mm y 1 corresponding to 1 moreover the temporal variability of recharge was estimated and along each profile past recharge rates calculated based on the sequence of cl concentrations in the vadose zone recharge rates increased at specific times coincident with historical changes in land use the consistency between the timing of land use modifications and changes in cl concentration and the match between observed and simulated cl concentration values in the vadose zone provide confidence in porewater age estimates travel times recharge estimates and reconstruction of recharge histories this study represents an advancement of the application of the chloride mass balance method to simultaneously determine recharge mechanisms and reconstruct location specific recharge histories in fractured porous rock aquifers the proposed approach can be applied worldwide at sites with similar climatic and geologic characteristics

structure of the upper mantle and transition zone beneath southeast asia from traveltime tomography 1 tomographic images of the mantle beneath east asia were obtained from the inversion of traveltime data from global and regional seismograph networks and from temporary arrays on and around the tibetan plateau our results are consistent with previous studies but the unprecedented resolution of mantle heterogeneity provides new insight into the large scale tectonic framework of the continental india asia collision in the western part of the study region and subduction of the oceanic lithosphere in the east in the realm of continental collision west of 100 e a relatively slow p wave speed characterizes the upper mantle beneath much of the tibetan plateau but the wave speed is high beneath cratonic india the southern and western part of the tibetan plateau hindu kush and the tian shan in the subduction realm east of 110 e the main structures are i pronounced low wave speed anomalies at a depth of between 100 and 400 km beneath asia s southeastern seaboard and the back arc regions of ongoing subduction ii narrow fast anomalies in the upper mantle beneath major subduction zones and iii widespread fast anomalies at a depth of 500 700 km beneath the sea of japan the northern part of the philippine sea plate and southeastern china if the latter anomalies represent stagnant slabs their fragmented nature and large lateral extent suggest that they are produced by different episodes of subduction beneath western pacific island arcs along the old se margin of asia or during the mesozoic collision of cratonic units in southeast asia attribution to ancient subduction systems implies that slab fragments can reside in the transition zone for at least several tens of millions of years shallow slow anomalies beneath the red river fault region connect to deep anomalies beneath the south china fold belt and south china sea suggesting a causal relationship between the evolution of the continental lithosphere of sw china and deeper mantle processes between the collision and the subduction realms tomography reveals high wave speed continental roots beneath the western part of the north china craton ordos block and the south china or yangtze craton sichuan basin to a depth of 300 km

finite frequency whole mantle p wave tomography improvement of subducted slab images received 23 july 2013 revised 14 october 2013 accepted 17 october 2013 1 we present a new whole mantle p wave tomographic model gap p4 we used two data groups short period data of more than 10 million picked up onset times and long period data of more than 20 thousand differential travel times measured by waveform cross correlation finite frequency kernels were calculated at the corresponding frequency bands for both long and short period data with respect to an earlier model gap p2 we find important improvements especially in the transition zone and uppermost lower mantle beneath the south china sea and the southern philippine sea owing to broadband ocean bottom seismometers bbobss deployed in the western pacific ocean where station coverage is poor this new model is different from a model in which the full data set is interpreted with classical ray theory bbobs observations should be more useful to sharpen images of subducted slabs than expected from simple raypath coverage arguments citation obayashi m j yoshimitsu g nolet y fukao h shiobara h sugioka h miyamachi and y gao 2013 finite frequency whole mantle p wave tomography improvement of subducted slab images geophys res lett 40 doi 10 1002 2013gl057401

p wave tomography and origin of the changbai intraplate volcano in northeast asia abstract we present the first seismic image of the upper mantle beneath the active intraplate changbai volcano in northeast asia determined by teleseismic travel time tomography the data are measured at a new seismic network consisting of 19 portable stations and 3 permanent stations our results show a columnar low velocity anomaly extending to 400 km depth with a p wave velocity reduction of up to 3 high velocity anomalies are visible in the mantle transition zone and deep focus earthquakes occur at depths of 500 600 km under the region suggesting that the subducting pacific slab is stagnant in the transition zone as imaged clearly by global tomography these results suggest that the intraplate changbai volcano is not a hotspot like hawaii but a kind of back arc volcano related to the deep subduction and stagnancy of the pacific slab under northeast asia

beach erosion and acceretion an example from kerala southwest coast of india the thickly populated coastal zone of kerala india is facing severe problems due to attack of high waves during the southwest monsoon systematic beach profiling at 5 km intervals was carried out along the 560 km stretch of the kerala coast during the pre and postmonsoon seasons in 1984 beach volume changes were calculated at each profile station and the erosional and accretional trends for the entire coastal tract were demarcated in a map total erosion along 55 stations is 1276 m3 m the general erosional and acceretional trends were also found to coincide with diverging and converging littoral currents deduced from the wave refraction diagrams such study at periodic intervals will be highly useful for proper management of the coastal zone