upper mantle anisotropy beneath the geoscope stations seismic anisotropy has been widely studied this last decade particularly by measuring splitting of vertically propagating core shear waves the main interest in this technique is to characterize upper mantle flow beneath seismic stations on the other hand the major restriction in this method is that a single station gives a single anisotropy measurement alternative methods have been developed in order to avoid this restriction an accurate determination of upper mantle seismic anisotropy beneath a seismic station may allow one by doing anisotropy correction to characterize remote or deeper anisotropy the geoscope network is ideal for this purpose because it is composed of a large set about 26 of high quality broadband seismometers globally distributed and because some of these stations have run for more than 10 years and most of them for more than 5 years we selected about 100 events at each site generally of magnitude mb 6 0 and we performed systematic measurements of the splitting parameters fast polarization direction and delay time t on sks skks and pks phases splitting on oceanic islands has been difficult to observe owing to the low quality of the signal but also perhaps owing to complex upper mantle structures beneath the stations station kip kipapa hawaii in the pacific is the only oceanic geoscope station with a clear anisotropy we determined well constrained splitting parameters for 10 of the 17 continental stations that may be explained by a single anisotropic layer the poor correlation between fast polarization directions and the absolute plate motion together with the apparent incoherence between the plate velocities and the observed delay times suggest that a simple drag induced asthenospheric flow alone fails to explain most of the observations for some stations located on or near major lithospheric structures tam tamanrasset algeria for instance we observe a good correlation between fast polarization directions and regional structures at station scz santa cruz california we found clear variations of the splitting parameters as a function of the event backazimuth compatible with two layers of anisotropy three stations can canberra hyb hyderabad india and ssb saint sauveur badole france seem to be devoid of detectable anisotropy

identifying global seismic anisotropy patterns by correlating shear wave splitting and surface wave data we compare a global compilation of shear wave splitting measurements with azimuthal seismic anisotropy parameters inferred from surface wave tomography the currently available splitting dataset is taken from a novel comprehensive collection of available publications that is updated interactively online the comparison between the two types of data is made by calculating predicted splitting parameters from the anisotropic tomography model comparing these predicted splitting parameters with the observed ones we find a considerable correlation between the two datasets at global scale this result is noteworthy since such correlation did not seem to exist in previous studies the spatial resolution associated with the two types of methods is rather different while surface waves have good vertical resolution and poor lateral resolution of several hundreds of kilometers sks splitting measurements have good lateral but poor vertical resolution the correlation can be understood in light of recent propositions that anisotropy seen by sks splitting constrains mostly the upper mantle and therefore a similar depth region as surface waves the correlation also confirms the generally good quality of the shear wave measurements as well as that of the anisotropic tomography model

mapping upper mantle flow beneath french polynesia from broadband ocean bottom seismic observations upper mantle structures and flow related to the south pacific superswell and to the associated short lived hotspots are investigated using seismic stations deployed in french polynesia beside island stations broadband ocean bottom seismometers bbobs have been deployed between the various polynesian archipelagos to investigate the oceanic upper mantle unperturbed by thickened crust or hotspot activity we investigate seismic anisotropy measured at bbobs stations and found it rather similar to that from island stations this confirms the ability of obs to be used for anisotropy purposes and suggests some homogeneity in the upper mantle pervasive deformation the two obs installed on the head of the society hotspot provide different anisotropy signatures than most of the other french polynesian stations one is isotropic to sks waves and the other provides a fast split direction normal to the average value observed in this area suggesting a more complex mantle flow induced by the plume upwelling

upper mantle anisotropy in se and central brazil from sks splitting evidence of asthenospheric flow around a cratonic keel abstract we present results of upper mantle anisotropy derived from measurements of core refracted shear wave splitting mainly sks phases recorded at 48 stations covering the major tectonic provinces in central and se brazil such as the tocantins province paraguay araguaia and brasilia belts between the amazon and sao francisco cratons the parana intracratonic basin the southern part of the sao francisco craton and the mantiqueira province with the coastal ribeira belt although the fast polarization directions vary across the region consistent orientations are observed over hundreds of kilometers the fast polarization directions tend to be close to the absolute plate motion given by the hot spot reference model hs3 nuvel1a however correlations with geological structures are also observed in the southern brasilia belt and in the ribeira belt respectively located sw and s of the sao francisco craton on the other hand in the northern tocantins province the fast shear wave direction n60 s is oblique to the sw ne trend of the geological units and faults and no anisotropy contribution from lithospheric sources can be clearly identified overall the fast polarization directions show a fan shaped pattern strongly suggesting asthenosperic flow around a thick and stiff keel in the southern part of the sao francisco craton consistent with the high velocity anomaly revealed by recent surface wave tomography the observed nw se directions in the southern part of the brasilia belt may also be interpreted as resulting from asthenospheric flow channeled between the sao francisco craton and a cratonic block beneath the parana basin the largest splitting delays observed in the southern brasilia belt and in the ribeira belt up to 2 4 s suggest contributions from both lithospheric and asthenospheric sources in those two areas our preferred model for the anisotropy causing the observed pattern of sks splitting consists of flow induced deformation in the asthenosphere caused by the absolute plate motion roughly towards w or wsw with flow channeled around a thick cratonic keel in the southern brasilia and in the ribeira fold belts the large delays and the parallelism with geological structures indicate additional anisotropy contribution from lithospheric sources

shear wave splitting and subcontinental mantle deformation splitting observations are interpreted in terms of the strain induced lattice preferred orientation of mantle minerals especially olivine we consider three hypotheses concerning the origin of the continental anlsotropy 1 strain associated with absolute plate motion as in the oceanic upper mantle 2 crustal stress and 3 the past and present internal deformation of the subcontinental upper mantle by tectonic episodes it is found that the last hypothesis is the most successful namely that the most recent significant episode of internal deformation appears to be the best predictor of q for stable continental regions this is interpreted as fossil anisotropy whereas for presently active regions such as alaska the anisotropy reflects present day tectonic activity in the stable portion of north america there is a good correlation between delay time and lithospheric thickness this is consistent with the anisotropy being localized in the subcontinental lithosphere and suggests that intrinsic anisotropy is approximately constant the acceptance of this hypothesis has several implications for subcontinental mantle deformation first it argues for coherent deformation of the continental lithosphere crust and mantle during orogenies this implies that the anisotropic portion of the lithosphere was present since the deformational episode and rules out the addition of undeformed material to this layer by subsequent underplating or conductive growth of the thermal boundary layer one of the most important issues in the study of orogenies is the need to reconcile the formation of thickened lithosphere with the paradoxically high mantle temperatures often associated with orogenic episodes most efforts to date have focussed on modes of deformation whereby the cold lithospheric mantle is removed by convective instability or delamination and replaced by warm asthenosphere these models however are incompatible with the evidence for preserved coherent lithospheric deformation rather the deformed mantle appears to have been heated in place we suggest that the elevated mantle temperatures may be due to the strain heating accompanying the deformation

evidence for ancient lithospheric deformation in the east european craton based on mantle seismic anisotropy and crustal magnetics abstract we present new shear wave splitting measurements performed at 16 stations on the east european craton and discuss their implications in terms of upper mantle anisotropy for this geophysically poorly known region previous investigations of mantle anisotropy in central europe have shown fast directions aligning smoothly with the craton s margin and various suggestions have been proposed to explain their origin such as asthenospheric flow or lithospheric frozen in deformation here we aim at investigating the continuation of this shear wave splitting pattern further to the east into the east european craton for the craton the interpretation appears to be less ambiguous than for central europe since several arguments support lithospheric anisotropy in this region 1 the large scale coherence within either of the four constituting blocks and the significant variations between the blocks on a small scale 2 the weak correlation with absolute plate motion vectors and 3 the good correlation between anisotropy and crustal features for which we use magnetic field alignments as a proxy rather good correlation of these magnetic features with seismic fast orientations strongly supports the idea of vertically coherent deformation throughout upper mantle and crust the observed splitting orientations thus reflect the last tectonic events of each block frozen in into the lithosphere for hundreds of millions of years

mantle flow in subduction systems the subslab flow field and implications for mantle dynamics 1 the character of the mantle flow field in subduction zones remains poorly understood despite its importance for our understanding of subduction dynamics in particular little attention has been paid to mantle flow beneath subducting slabs in order to identify processes that make first order contributions to the global pattern of subslab mantle flow we have compiled shear wave splitting measurements from subduction zones worldwide from previously published studies and estimated average splitting parameters for the subslab region globally the subslab region is overwhelmingly dominated by trench parallel fast splitting directions we tested for relationships between splitting delay time a measure of the strength of anisotropy and parameters that are indicators of tectonic processes such as trench migration velocity convergence velocity and obliquity age of subducting lithosphere and slab dip curvature seismicity and thickness we used several different plate motion models to describe plate and trench motions and evaluated the differences among the models we find that only one parameter namely the trench migration velocity in a pacific hot spot reference frame appears to correlate well with the strength of the subslab splitting signal this finding supports a model in which the mantle beneath subducting slabs is dominated by three dimensional flow induced by trench migration we explore several implications of our model for various aspects of mantle dynamics including the choice of a suitable reference frame s for mantle flow the existence of a thin decoupling zone between slabs and the subslab mantle and consequences for mass transfer between the upper and lower mantle

seismic anisotropy from the variscan core of iberia to the western african craton new constrains on upper mantle flow at regional scales abstract the regional mantle flow beneath the westernmost mediterranean basin and its transition to the atlantic domain is addressed by inspecting the anisotropic properties of the mantle more than 100 new sites from the variscan core of iberia to the northern rim of the western african craton are now investigated using the data provided by different temporary and permanent broad band seismic arrays our main objective is to provide a larger regional framework to the results recently presented along the gibraltar arc in order to check the validity of the different geodynamic interpretations proposed so far the significant variations in the retrieved anisotropic parameters suggest that different processes must be invoked to explain the origin of the observed anisotropy beneath the variscan units of the central iberian massif the new results show a moderate amount of anisotropy with fast polarization directions fpd oriented close to e w those results can only be explained in terms of global mantle flow if models accounting for contributions from surface plate motion net lithosphere rotation and density variations are taken into consideration one of the major results presented is the significant number of good quality data without evidence of anisotropy nulls observed beneath permanent stations in southern portugal those nulls can be explained by the presence of a predominantly vertical mantle flow associated to large variations in the lithospheric thickness beneath the gibraltar arc the fpd show a spectacular rotation evidenced by the results presented by diaz et al 2010 and miller et al 2013 those results are reviewed here taking also into consideration the geodynamic modeling presented recently by alpert et al 2013 and other geophysical and geodetic results further south the analysis of new broad band stations installed in the moroccan meseta and the high atlas show a small degree on anisotropy and a large number of null events pointing again to the presence of vertical flow in the mantle the results favor an asthenospheric origin related to present day mantle flow for the anisotropy observed from the variscan core of iberia to the northern rim of the west african craton this flow is deflected around the high velocity slab beneath the gibraltar arc and seems affected locally by vertical flow associated to edge driven convective cells the presence of significant backazimuthal variations in the anisotropic parameters retrieved from single events suggests that a second order contribution from an anisotropic layer within the lithosphere may also exist

seismic anisotropy and velocity structure beneath the southern half of the iberian peninsula travel times of 11 612 pn arrivals collected from 7675 earthquakes are inverted to image the uppermost mantle velocity and anisotropy structure beneath the southern half of the iberian peninsula and surrounding regions pn phases are routinely identified and picked for epicentral distances from 200 to 1200 km the method used in this study allows simultaneous imaging of variations of pn velocity and anisotropy the results show an average uppermost mantle velocity beneath the study area of 8 0 km s the peninsular area covered by the iberian massif is characterized by high pn velocity as expected in tectonically stable regions indicating areas of the hercynian belt that have not recently been reactivated the margins of the iberian peninsula have undergone a great number of recent tectonic events and are characterized by a pronouncedly low pn velocity as is common in areas greatly affected by recent tectonic and magmatic activity our model indicates that the betic crustal root might be underlined by a negative anomaly beneath the southeastern iberian peninsula in the atlantic ocean we find a sharp variation in the uppermost mantle velocities that coincides with the structural complexity of the european and african plate boundary in the gulf of cadiz our results show a very pronounced low velocity anomaly offshore from cape san vicente whereas high velocities are distributed along the coast in the gulf of cadiz in the alboran sea and northern morocco the direction of the fastest pn velocity found is almost parallel to the africa eurasia plate convergence vector northwest southeast whereas to the north this direction is almost parallel to the main trend of the betic cordillera i e east west in its central part and north south in the curvature of the arc of gibraltar this suggests that a significant portion of the uppermost mantle has been involved in the orogenic deformation that produced the arcuate structure of the betic cordillera however we assume that the neogene extension had no major influence on a lithospheric scale in the alboran sea our results also show a quite complex pattern of anisotropy in the southwest iberian lithospheric mantle since the relationship between the direction of fastest pn velocity and major hercynian tectonic trends cannot be directly established 2004 elsevier b v all rights reserved

delay times and shear wave splitting in the mediterranean region summary we measure sks splitting parameters and p and s delay times in the mediterranean region using broad band recordings from the temporary midsea array and permanent networks the midsea seismic array has substantially improved data coverage along the european mediterranean margins and in northern africa shear wave splitting is observed for 95 per cent of the stations with splitting times up to 2 s we propose five anisotropic domains based on the characteristics of the observations in the western part of the region we observe an alignment with plate motion suggesting an asthenospheric origin for anisotropy in the central and near eastern part the fast directions are less coherent laterally and influenced by extension and subduction processes along the dead sea fault the fast directions are parallel to the relative motion between arabia and africa which we attribute in part to coherent vertical deformation our measurements of teleseismic relative p and s wave delay times within the mediterranean region reach peak to peak values of 2 5 and 8 s respectively consistent with international seismological centre isc delay times we observe the earliest arrivals along the hellenic subduction zone and some of the latest along the dead sea fault we find that s wave delays are roughly three times as large as those of p waves from a slight frequency dependence of our cross correlation based delay time measurements we estimate mediterranean lateral heterogeneity to have a dominant size of one or more hundred kilometres we further determine that the anisotropy implied by our sks splitting measurements does not significantly bias the pattern of teleseismic delay times

influence of depositional processes on the geotechnical parameters of chicago glacial clays abstract the effects of depositional environment on properties stress history and undrained and drained shear strength parameters are evaluated for chicago glacial clay recent geology and basic depositional environments are described both laboratory and in situ shear strength evaluations have been conducted at several sites in the study area results of the investigations indicate that while depositional environment has a large impact on the engineering properties of these clays identification of the depositional environment is in itself insufficient to strength parameters post depositional events are shown to alter the stress history imparted during deposition and thus impact shear strength parameters

characteristics of wall deflections and ground surface settlements in shanghai the characteristics of wall deflections and surface ground settlements at six deep multi strutted excavations in shanghai soft soils were studied and compared with those of similar case histories reported worldwide particularly in taipei and singapore the measured wall deflections at the six metro stations of the pearl ii circle line show a typical bulging profile or deep seated shape at the end of the excavation the ratio between the measured maximum wall deflection and the depth of the excavation hm h in shanghai was 0 007 which was similar to the ratio measured in taipei but it was substantially smaller than the peck bounding limit of 0 01 at each station the measured maximum displacement was 0 45 of the final excavation depth because of the large aspect ratios of the underground excavations no significant three dimensional effects or corner effects were observed the measured maximum settlements of the six metro excavations fell within zone i of the peck classical normalized settleme

kinematics of the western africa eurasia plate boundary from focal mechanisms and gps data summary the western mediterranean displays a complex pattern of crustal deformation distributed along tectonically active belts developed in the framework of slow oblique plate convergence we used earthquake and global positioning system gps data to study the present day kinematics and tectonics of the africa eurasia plate boundary in this region crustal seismicity and focal mechanisms analysed in terms of seismic moment release and seismic deformation outline the geometry of major seismic belts and characterize their tectonics and kinematics continuous gps data have been analysed to determine euler vectors for the nubian and eurasian plates and to provide the global frame for a new mediterranean gps velocity field obtained by merging continuous and campaign observations collected in the 1991 2005 time span gps velocities and displacements predicted by the nubia eurasia rotation pole provide estimates of the deformation accommodated across the tectonically active belts the rather simple deformation occurring in the atlantic region characterized by extension about perpendicular to the middle atlantic and terceira ridges and right lateral motion along the gloria transform fault turns into a complex pattern of deformation occurring along broader seismic belts where continental lithosphere is involved our analysis reveals a more complex fragmentation of the plate boundary than previously proposed the roughly e w trending mainly compressive segments i e southwestern iberia northern algeria and southern tyrrhenian where plate convergence is largely accomodated across rather localized deformation zones and partially transferred northward to the adjacent domains i e the algero balearic and tyrrhenian basins are interrupted by regions of more distributed deformation i e the rif alboran betics tunisia libya and eastern sicily or limited seismicity i e the strait of sicily which are characterized by less homogeneous tectonics regimes mainly transcurrent to extensional in correspondence of the observed breaks tectonic structures with different orientation interfere and we find belts with only limited deformation i e the high and middle atlas the tunisian atlas and the offshore tunisia libya belt that extends from the plate boundary into the nubian plate along pre existing tectonic lineaments our analysis suggest that the sicilian pelagian domain is moving independently from nubia according to the presence of a right lateral and extensional decoupling zone corresponding to the tunisia libya and strait of sicily deformation zone despite the space variability of active tectonic regimes plate convergence still governs most of the seismotectonic and kinematic setting up to the central aeolian region in general local complexities derive from pre existing structural features inherited from the tectonic evolution of the mediterranean region on the contrary along calabria and the apennines the contribution of the subducted ionian oceanic lithosphere and the occurrence of microplates i e adria appear to substantially modify both tectonics and kinematics finally gps data across the gibraltar arc and the tyrrhenian calabria domain support the hypothesis that slab rollback in these regions is mostly slowed down or stopped

moment tensor solutions for small and moderate earthquakes in the ibero maghreb region 1 we applied time domain moment tensor inversion of local and regional waveforms to small and moderate mw 3 5 5 7 shallow earthquakes from the iberian peninsula northern morocco and northern algeria for the 6 years period from november 1995 to march 2002 and the previous network of autonomously recording seismograms nars experiment moment tensor solutions were obtained for 58 events considerably increasing the total number of available solutions in the study area for each event we performed a moment tensor inversion and a double couple grid search for simple faulting events the grid search is valuable as a quality test for its ability to reveal potential ambiguities of the solutions and to assess confidence limits of fault plane parameters or principal axes orientation the computed mechanisms show regional consistency a large part of the iberian peninsula is characterized by normal faulting mechanisms with sw ne oriented t axes thrusting and se nw compression is dominant in algeria in the alboran sea the westernmost part of the mediterranean and the transition between both regimes strike slip mechanisms dominate with approximately n s oriented p axes this pattern suggests a regional anomaly characterized by clockwise rotation of the principal horizontal stress orientations

accelerated pacific plate movements and climatic changes on time scales of 102 103 years in the late quaternary a synthesis abstract sea level curves constructed for the japan region for the period 14 000 to 10 000 years b p reveal inconsistencies in sea level during the intervals 10 000 10 500 11 500 12 000 and 13 000 13 500 years b p these intervals correspond to episodes of global climatic deterioration and catastrophic volcanic activity in japan these inconsistencies are explained on the basis of field observation by geoidal change and reactivation of the pacific plate movements from a glacio eustatic sea level curve it is supposed that the reactivation of the pacific plate movements was induced by mass redistribution within the earth due to rapid melting of polar ice furthermore the rapid spreading within the ocean basins greatly increased upwelling and this change in the ocean circulation resulted in abrupt global climatic cooling similar phenomena are recognized after 8000 and 130 000 years b p

shear wave splitting in the upper mantle wedge above the tonga subduction zone summary intermediate period seismograms of shear waves from deep earthquakes are examined for shear wave splitting diagnostic of seismic velocity anisotropy in the upper mantle wedge between the subducting tonga slab and stations in the fiji islands earthquakes with near vertical incidence angles are selected to minimize complications of converted phases and the free surface horizontal component seismograms for 25 deep earthquakes recorded at station lak on the lau ridge show splitting of up to 0 9 s with an average of 0 45 0 25 s between fast and slow s wave components anisotropy in the upper mantle is the most likely cause of the splitting the ese orientation of the fast velocity direction at station lak corresponds to an axis of symmetry of the anisotropic mantle and is approximately perpendicular to magnetic lineations in the lau basin and the northeastern portion of the south iiji basin the observations are consistent with a model of flow alignment of olivine 100 and orthopyroxene 001 axes parallel to the direction of basin extension seismograms for eight deep earthquakes at station sva on viti levu show up to 1 0 s splitting with an average of 0 65 0 29 s and a weak nne preferred orientation of fast velocity polarizations of shear wave particle motions corrected for anisotropy are within 36 5 26 of polarixations predicted for nine moment tensor solutions the magnitude of shearwave splitting and estimates of the thickness of the lithosphere in the fiji region imply that the anisotropy cannot be contained in the lithosphere alone either the anisotropy is distributed in both the lithosphere and asthenosphere or the asthenosphere alone is anisotropic

shear wave polarization anisotropy and subduction induced flow in the mantle wedge of northeastern japan abstract shear wave polarization anisotropy in the central part of northeastern ne japan was investigated we analyzed s phases of 293 intermediate depth earthquakes recorded at 77 stations and obtained 1286 splitting parameters the obtained results show the systematic variation in splitting parameters across the arc the leading shear wave polarization directions fast direction obtained at stations in the western side of the study area are oriented nearly e w which is sub parallel to the direction of relative plate motion between the pacific plate and the north american okhotsk plate in contrast fast directions obtained at stations in the eastern side of the study area are oriented approximately n s stations in the western side have a larger average delay time compared to those in the eastern side these variations suggest that the nature of anisotropy is quite different between the eastern and the western sides both experimental studies on the deformation of olivine and numerical simulations of plate driven flow predict that the lattice preferred orientation of olivine causes the fast direction sub parallel to the flow direction for the conditions in the mantle wedge of ne japan we thus infer that the lattice preferred orientation of olivine generated by flow induced strain is the most likely candidate for anisotropy that produces splitting with e w fast direction three possible causes of anisotropy in the eastern side are considered deformation of water rich olivine in the mantle wedge trench parallel flow in the mantle wedge due to along strike dip variations in the slab and anisotropy in the crust and the slab we could not however determine which causes are dominant further systematic study is required to reveal the cause of anisotropy in the eastern side

detection of upper mantle flow associated with the african superplume a continental scale low seismic velocity anomaly in the mid to lower mantle beneath africa is a robust feature of global tomographic models assuming the low velocities are associated with warm less dense material the african seismic anomaly has been ascribed to a long lived thermal upwelling from the lower mantle such a large scale upwelling should also affect the regional horizontal flow field in the upper mantle to test this model we compare seismic anisotropy inferred from shear wave splitting measurements with instantaneous flow calculations that incorporate mantle density structure inferred from seismic tomography we calculate splitting parameters at 13 ocean island stations surrounding africa splitting measurements from island stations are ideal for interpreting anisotropy induced by asthenospheric flow because they lack a thick overlying lithosphere that may also contribute to the observed anisotropy we tested for a possible lithospheric contribution by comparing the splitting measurements with the fossil spreading directions we find that although the fossil lithospheric fabric closely matches the observed fast polarization directions at stations 500 km from a ridge axis they are a poor fit to the data at stations located farther off axis thus we conclude that far from a ridge axis the observed anisotropy is dominated by asthenospheric flow to test for an active component of mantle upwelling we considered several models with varying assumptions about the velocity at the base of the asthenosphere that it is 1 stationary below plates moving in the no net rotation nnr or hotspot reference frames 2 driven by plate motions at the earth s surface or 3 driven by a combination of plate motion and mantle density heterogeneity inferred from either seismic tomography or the history of subduction we find that the best fitting flow field is generated by plate motions and density heterogeneity associated with large scale upwelling originating in the lower mantle beneath southern africa and is manifest as a radial pattern of flow at the base of the asthenosphere this model provides a significantly better fit to the observed anisotropy than a model in which mantle flow is driven through a passive response to subduction the resulting sub asthenospheric flow field is estimated to have velocities of 0 3 cm year and an asthenospheric viscosity of 3 1019 pa s is found to be most consistent with the regional anisotropy geoid height and dynamic topography

upper mantle flow beneath french polynesia from shear wave splitting summary upper mantle flow beneath the south pacific is investigated by analysing shear wave splitting parameters at eight permanent long period and broad band seismic stations and 10 broad band stations deployed in french polynesia from 2001 to 2005 in the framework of the polynesian lithosphere and upper mantle experiment plume despite the small number of events and the rather poor backazimuthal coverage due to the geographical distribution of the natural seismicity upper mantle seismic anisotropy has been detected at all stations except at tahiti where two permanent stations with 15 yr of data show an apparent isotropy the median value of fast polarization azimuths n67 5 w is parallel to the present pacific absolute plate motion direction in french polynesia apm n67 w this suggests that the observed sks fast polarization directions result mainly from olivine crystal preferred orientations produced by deformation in the sublithospheric mantle due to viscous entrainment by the moving pacific plate and preserved in the lithosphere as the plate cools however analysis of individual measurements highlights variations of splitting parameters with event backazimuth that imply an actual upper mantle structure more complex than a single anisotropic layer with horizontal fast axis a forward approach shows that a two layer structure of anisotropy beneath french polynesia better explains the splitting observations than a single anisotropic layer secondorder variations in the measurements may also indicate the presence of small scale lateral heterogeneities the influence of plumes or fracture zones within the studied area does not appear to dominate the large scale anisotropy pattern but may explain these second order splitting variations across the network

a back analysis method using an intelligent multi objective optimization for predicting slope deformation induced by excavation abstract a multi objective inverse analysis method for slope excavation was proposed in which orthogonal design numerical simulation back propagation neural network bpnn and elitist non dominated sorting genetic algorithm nsga ii were integrated the multi objective model is constructed by minimizing a set of multi objective error functions between the time series of observations and corresponding calculated values compared with the back analysis methods that uses traditional algorithms the proposed method is validated by a numerical example to be more effective for multi objective optimization the methodology is also applied to the excavation of a right bank slope at the dagangshan hydropower station located in the sichuan province china the obtained inversion parameters are used in forward analysis to predict displacements in this case application three types of field observations are used simultaneously in the back analysis which include displacements in the dadu river water flow y direction transverse x direction and vertical z direction compared with the field displacement data the trend of the predicted displacements agrees well with the measurements the results indicate that the proposed method can more precisely and reliably predict the slope deformation induced by excavation

shear wave splitting in eastern and central china implications for upper mantle deformation beneath continental margin eastern china located at the east margin of the eurasia plate is an ideal place to study the deformation pattern of upper mantle beneath continental margin we investigated the upper mantle anisotropy beneath eastern china by applying teleseismic shear wave splitting measurements we examined shear wave splitting measurements at 33 permanent stations from cdsn and gsn iris networks in eastern and central china as well as splitting parameters from a previous regional study the splitting observations are characterized by apparent diversity of anisotropy pattern in adjacent tectonic domains including the southeast china orogenic belt and the yangtze craton and the eastern and central north china craton based upon the straightforward relationships between seismic anisotropy and the development of lattice preferred orientation of mineral in upper mantle rocks we interpret the splitting results in terms of tectonic fabric within the upper mantle our interpretation implies that the upper mantle anisotropy beneath eastern china remained the effects of tectonic rejuvenation occurred during the late mesozoic to cenozoic we proposed that there are possibly two kinds of mechanisms involved in the upper mantle deformation beneath eastern china depending on the roles of thick root of cratonic lithosphere one mechanism is the deflecting the asthenospheric flow by the thick root of craton and the other one is the extensional asthenospheric flow causing the craton lost part of its thick root 2007 elsevier b v all rights reserved

base stability of grout pile reinforced excavations in soft clay grout piles are used to reinforce base soil to increase the base stability of excavations in soft clay and to reduce excavation induced ground movements to propose a model for the base undrained stability of deep excavation in clay reinforced with grout piles this paper presents an anisotropic strength criterion for clay reinforced with grout piles and the upper bound bearing capacity theory for excavation the proposed model is capable of determining the factor of safety against base heave for an excavation with or without ground improvement for various strength anisotropy ratios of clay and clay reinforced with grout piles the suitability of the model is verified with five field excavation cases among them four were with no ground improvement and one was with ground improvement generally the larger the ground improvement rate the more the material strength of a grout pile can be mobilized the factor of safety also becomes larger when the ground improvement rate is higher however the factor o

shear wave splitting beneath the galapagos archipelago shear wave splitting measurements in the galapagos archipelago show a rapid change from consistently oriented anisotropy to no measurable anisotropy at the western edge of the archipelago delay times are 0 4 0 9 s and fast polarization directions are 81 109 e these directions are consistent with anisotropy resulting from shear of the asthenosphere by the overlying plate there is no indication of fossil lithospheric anisotropy in the plate spreading direction in contrast beneath the center of the archipelago the upper mantle is isotropic or weakly anisotropic the isotropic region coincides approximately with a volume of anomalously low upper mantle velocities suggesting that the presence of melt may weaken the effects of fabric on anisotropy or that melt preferred orientation generates a vertical fast polarization direction alternatively the complex flow field associated with a near ridge hotspot may result in apparent isotropy

subduction zones an introduction to comparative subductology abstract the subduction model for trench arc back arc systems was deduced more or less as a logical consequence of sea floor spreading many features in these systems such as thrust type inter plate earthquakes and deep earthquakes along wadati benioff zones are readily explained by the subduction model but other features such as extensional spreading and high heat flow in back arc regions and arc volcanism are difficult to explain an approach to solve these problems may be to recognize the existence of the two basically different modes of subduction one chilean type causing a compressional stress regime in the arc and back arc regions the other mariana type causing a tensional stress regime implications of the two types of the mode of subduction for some tectonic problems such as vertical movement and sediment accretion at trenches are discussed with special reference to the results of recent dsdp active margin drilling in discussing the possible causes of the two modes it is suggested that the large scale thermal and stress regimes in the back arc areas may not be the direct products of simple subduction but of some additional factors involving much greater energy such as mantle flow associated with the motion of major plates finally the possible great importance of various types of collision accretion and erosion at subduction zones is emphasized

crustal movements and geodynamics in fennoscandia abstract morner n a 1981 crustal movements and geodynamics in fennoscandia in p vyskocil r green and h malzer editors recent crustal movements 1979 tectonophysics 71 241 251 the fennoscandian shield the classical area of glacial isostasy has been subjected to a complex sequence of motions throughout the late cenozoic still the geometry of the areas deformed has been roughly the same an asthenosphere of low viscosity 1020 1021 poises and a lithosphere of high flexural rigidity are established the present uplift represents an other mechanism than the rapid glacial isostatic readjustment of the low viscosity asthenosphere and seems to originate from mesospheric motions at around 1900 1910 there was a distinct geodynamic change which seems to be controlled by changes in the earth s rate of rotation the postglacial uplift of fennoscandia is found to be associated with intensive neotectonism faulting fracturing and seismicity

inverse analysis based interpretation of sand behavior from triaxial compression tests subjected to full end restraint current laboratory testing often imposes or assumes uniform stress and strain distribution in a specimen for convenient data reduction to interpret soil behavior this paper presents an inverse analysis framework self learning simulations selfsim to interpret the drained behavior of sand from triaxial compression tests with fully frictional loading platens the frictional platens result in significant bulging of and nonuniform stresses and strains within sand specimens selfsim treats the specimen as a boundary value problem bvp and extracts these nonuniform stresses and strains from within each specimen using external load and displacement measurements the extracted behavior shows significant principal stress rotation variation of intermediate principal stress and nonuniform volume change throughout the specimen mobilized friction angles are interpreted on the two dimensional slip surface associated with the mohr coulomb failure criterion on the octahedral plane associated with the drucker pra

wall and ground movements associated with deep excavations supported by cast in situ wall in mixed ground conditions field monitoring data on lateral wall deflection and ground settlement from 14 deep excavation case histories in hong kong involving cast in situ concrete wall were collected and analyzed mixed ground conditions consisted of successive layers of fill marine deposit and or alluvium and decomposed geomaterials the measured data were differentiated into two groups based on the standard penetration test n values of the ground n 30 group a and n 30 group b at half of the excavation depth the mean values of the maximum wall deflection hm and ground settlement vm in the excavations in group a are 0 23 and 0 12 of the excavation depth h respectively for the excavations in group b the mean value of hm is 0 13 h which is similar to other excavations in predominantly other stiff soils hm h 0 10 0 16 but vm is only 0 02 h which is small when compared to other similar database hm h 0 1 0 2 the settlement influence zone of the excavations in both groups reaches a distance of

physical modelling of pile drilling in sand drilling for foundation piles and tieback anchors through soils using a continuous casing to support the borehole is often referred to as overburden drilling monitoring data from several case st

seismic anisotropy beneath southern iberia from sks splitting abstract seismic anisotropy of the south iberian upper mantle is investigated using shear wave splitting of sks phases we analyzed teleseismic events recorded by sixteen permanent broadband stations installed on the southern iberian peninsula and in northern africa and we determined fast polarization directions and delay times t between fast and slow components the area of investigation extends across two important geological structures in the variscan iberian peninsula the variscan iberian massif in its center and the gibraltar arc in the southeast that represents the most westerly alpine belt in the western mediterranean shear wave splitting measurements from stations in the betic domain show homogeneous ene wsw fast directions nearly parallel to the trend of the mountain belt and smooth spatial variations stations in the north toward the southern part of the variscan iberian massif show homogeneous fast directions however trending ns to ne sw different from those recorded in the betic these observations may reflect a post hercynian variscan deformation of the ossa morena zone related to the main stages in the tectonic evolution of this part namely transpressional stage transtensional stage and shortening episode or a deformation related to the posterior alpine orogeny along the gibraltar arc we observe a smoothly varying trend changing from ene wsw in the eastern betics to ns in the area of gibraltar and ceuta following more or less the general trend of the mountain belt around the alboran sea and the coastline since a similar rotation is also visible in results from pn anisotropy this suggests that the anisotropy is vertically coherent starting from just below the moho comparing the anisotropy pattern expected from various geodynamic models with the observed sks splitting suggests that the anisotropy is best explained by a model of slab rollback rather than by delamination models

prediction of movements for braced cuts in clay a simplified method is presented for the prediction of wall and soil movements for braced excavations in soft to medium clay deposits the method is developed by combining the results of field data performance and finite element analyses a careful review of 130 published and unpublished case histories was carried out to select well documented projects with similar support systems and free of unusual construction effects the finite element analyses were directed toward the evaluation of effects of variation of soil shear strength soil stiffness support stiffness and system geometry both the field data and the finite element results show that a strong correlation exists between system movements and the factor of safety against basal heave based on the established behavior trends nondimensional plots are developed for predicting maximum magnitudes and distributions of wall deflections and ground settlements as a function of the factor of safety against basal heave and the other important parameters of the soil and structural system

geodetic measurements of crustal deformation in the western mediterranean and europe geodetic measurements of crustal deformation over large areas deforming at slow rates 5 mm yr over more than 1000 km such as the western mediterranean and western europe are still a challenge because 1 these rates are close to the current resolution of the geodetic techniques 2 inaccuracies in the reference frame implementation may be on the same order as the tectonic velocities we present a new velocity field for western europe and the western mediterranean derived from a rigorous combination of 1 a selection of sites from the itrf2000 solution 2 a subset of sites from the european permanent gps network solution 3 a solution of the french national geodetic permanent gps network rgp and 4 a solution of a permanent gps network in the western alps regal the resulting velocity field describes horizontal crustal motion at 64 sites in western europe with an accuracy on the order of 1 mm yr or better its analysis shows that central europe behaves rigidly at a 0 4 mm yr level and can therefore be used to define a stable europe reference frame in that reference frame we find that most of europe including areas west of the rhine graben the iberian peninsula the ligurian basin and the corsica sardinian block behaves rigidly at a 0 5 mm yr level in a second step we map recently published geodetic results in the reference frame previously defined geodetic data confirm a counterclockwise rotation of the adriatic microplate with respect to stable europe that appears to control the strain pattern along its boundaries active deformation in the alps apennines and dinarides is probably driven by the independent motion of the adriatic plate rather than by the africa eurasia convergence the analysis of a global gps solution and recently published new estimates for the african plate kinematics indicate that the africa eurasia plate motion may be significantly different from the nuvel1a values in particular geodetic solutions show that the convergence rate between africa and stable europe may be 30 60 slower than the nuvelia prediction and rotated 10 30 counterclockwise in the mediterranean

crust and upper mantle shear wave structure of northeast algeria from rayleigh wave dispersion analysis abstract we resolve the crust and upper mantle structure beneath northeast algeria at depths of 0 400 km using inversion of fundamental mode rayleigh wave our data set consists of 490 earthquakes recorded between 2007 and 2014 by five permanent broadband seismic stations in the study area applying a combination of different filtering technics and inversion method shear wave velocities structure were determined as functions of depth the resolved changes in vs at 50 km depth are in perfect agreement with crustal thickness estimates which reflect the study area s orogenic setting partly overlying the collision zone between the african and eurasian plates the inferred moho discontinuity depths are close to those estimated for other convergent areas in addition there is good agreement between our results and variations in orientations of regional seismic anisotropy at depths of 80 180 km negative vs anomalies at station cbbr suggest the existence of a failed subduction slab

shape of ground surface settlement profiles caused by excavation there are two general types of settlement profiles induced by excavation the spandrel type and the concave type based on a regression analysis of the field observations of settlement curves with

novel approach to integration of numerical modeling and field observations for deep excavations precedent and observation of performance are an essential part of the design and construction process in geotechnical engineering for deep urban excavations designers rely on empirical data to estimate potential deformations and impact on surrounding structures numerical simulations are also employed to estimate induced ground deformations significant resources are dedicated to monitor construction activities and control induced ground deformations while engineers are able to learn from observations numerical simulations have been unable to fully benefit from information gained at a given site or prior excavation case histories in the same area a novel analysis method self learning in engineering simulations selfsim is introduced to integrate precedent into numerical simulations selfsim is an inverse analysis technique that combines finite element method biologically inspired material models and field measurements selfsim extracts relevant constitutive soil information from field measurements of excavation response such as lateral wall deformations and surface settlement the resulting soil model used in a numerical analysis provides correct ground deformations and can be used in estimating deformations of similar excavations the soil model can continuously evolve using additional field information selfsim is demonstrated using two excavation case histories in boston and chicago

pollen and oxygen isotope analyses on late and post glacial sediments of the tourbiere de chirens dauphine france the sequence of vegetation phases in the late glacial was studied in a sediment section from the bog tourbiere de chirens by means of pollen analysis 18o16o ratios of samples of lacustrine marl obtained from the same profile reflect variations of 18o16o in precipitation and thus provide an additional independent paleoclimatic record the observed 18o16o variations agree well with the climatic history as deduced from pollen analysis the climatic transition from the oldest dryas to the bolling period sensu lato as well as the beginning and end of the younger dryas cold phase is marked by abrupt changes in the 18o16o ratio which were observed also in other regions of the alps these drastic climatic changes probably took place simultaneously over large areas of central europe and occurred within short time spans

responses of retaining wall and surrounding ground to pre excavation dewatering in an alternated multi aquifer aquitard system abstract pre excavation dewatering ped is an important construction stage in deep excavation field measurements show that retaining walls can develop obvious deflections during ped which has been rarely considered in the past the characteristics of ped induced wall deflection and the relationship of this deflection to surrounding ground deformation are still unclear in this study a ped test is simulated by a numerical model the model is verified by field observations and used to investigate the responses of retaining wall and surrounding ground to ped results indicate that the maximum wall defection hm and surface settlement vm can all reach centimeter level under common conditions of ped the ratio of vm to hm varies at the range of 0 45 0 67 wall and soil deformations will be more obvious if the soils within the dewatering depth hd have better permeability the relative positions between hd and strata i e aquifer or aquitard have great influence on the ped induced deformations if an aquifer appears below hd further increasing hd can induce a rapid growth of wall and soil deformations if thick aquitard appears below hd the deformation increments by further increasing hd are not apparent however once hd exceeds the center of the thick aquitard and reaches a thick confined aquifer the wall deflections and soil deformation zones behind the wall will enlarge significantly meanwhile a large bending moment in the retaining wall will arise around the bottom of the confined aquifer the designers should consider this condition and allocate enough steel rebars there preventing the appearance of wall cracks in the confined aquifer

shear wave splitting continental keels and patterns of mantle flow in this study we investigated the origin of seismic anisotropy in the mantle beneath north america in particular we evaluated whether shear wave splitting patterns in eastern north america are better explained by anisotropy caused by lithospheric deformation anisotropy due to mantle flow beneath the lithosphere or a combination of both we examined new measurements of shear wave splitting from the missouri to massachusetts broadband seismometer array moma the north american mantle anisotropy and discontinuity experiment nomad as well as splitting parameters from several previous studies we developed a simple finite difference model that approximates mantle flow around a complex three dimensional continental lithospheric keel to evaluate potential anisotropy from mantle flow beneath the lithosphere in eastern north america we compared shear wave splitting observations to predicted splitting parameters calculated using this mantle flow model our results indicate that a significant portion of observed shear wave splitting in eastern north america can be explained by mantle flow around the continental keel however shear wave splitting patterns in a few regions of eastern north america indicate that a component of lithospheric anisotropy must exist particularly in regions containing the largest keel thicknesses for eastern north america as well as for splitting observations in australia europe and south america we favor a model in which anisotropy is controlled by a combination of both lithospheric deformation and subcontinental mantle flow

sks splitting measurements in the apenninic tyrrhenian domain italy and their relation with lithospheric subduction and mantle convection 1 we present a compilation of singular shear wave splitting measurements in the italian region we used the method of silver and chan 1991 to determine the splitting parameters of fast direction and delay time from broadband sks waveforms the stations analyzed were mainly deployed in temporary experiments a few are permanent mednet broadband stations the splitting parameters reveal the presence of strong seismic anisotropy in the mantle beneath italy the fast polarization directions define two anisotropic domains a tyrrhenian domain with e w prevalent fast directions and an apennines adriatic domain with nw se to nnw sse prevalent fast directions the stations along the boundary between these two main domains show fast polarization directions that vary for earthquakes coming from different back azimuths this variability is a sign of a complex upper mantle structure also shown by seismic tomography but allows us to constrain the depth of the anisotropic layer in the 100 250 km range at least in the boundary zone between the two domains data at station vsl sardinia suggest the presence of depth dependent anisotropic structure where the shallower signature is consistent with the tyrrhenian domain results and the deeper one is possibly related to the presence of a subhorizontal slab laying on the 670 km discontinuity we argue that the complex pattern of fast directions is strictly related to the upper mantle structure and is caused by asthenospheric flows induced by slab rollback and contemporary deformation of the overriding tyrrhenian plate

continental scale shear wave splitting analysis investigation of seismic anisotropy underneath the australian continent the structure of the upper mantle beneath the australian continent is investigated using teleseismic shear wave splitting to extract seismic anisotropy measurements have been performed on data recorded at 190 sites with portable broadband seismic recorders spanning almost the entire surface of the continent since 1992 the average time span of the various deployments primarily designed for surface wave tomography is 6 months which is rather limited for shear wave splitting analysis however the data set provides a full continental scale survey using the reasonably favourable distribution of seismicity to australia seismic anisotropy has the potential to provide insights into the lithospheric structure and the possible mechanical coupling between the crust and the upper mantle but prior results for australia have indicated relatively small levels of splitting and a complex pattern these results are confirmed with our new and far more extensive measurements across the whole continent the pattern of seismic anisotropy from shear wave splitting beneath australia is rather complex and is not correlated with the almost north south absolute plate motion apm from recent models deviation of the asthenospheric mantle flow around the lithospheric roots associated with the extensive archaean and proterozoic zones of central and western australia could be occurring and so mantle flow related anisotropy cannot be completely ruled out despite the limited geological outcrop especially in phanerozoic eastern australia that is almost entirely covered by sedimentary basins some relationships can be highlighted between the orientation of the polarization plane of the fast s waves and structural trends along for instance the halls creek orogen bordering the eastern edge of the kimberley basin or along the new england and lachlan fold belts in the southeastern part of the continent such relationships might account for anisotropy frozen in the lithosphere during post tectonic thermal relaxation along the poorly constrained and controversial tasman line tl the geological boundary between precambrian and phanerozoic australia directions of anisotropy measured at some stations located in the close vicinity of the line appear to exhibit a curvilinear trend somewhat similar to that of the tl suggesting that fossil deformation associated with the tl might be recorded in the pattern of seismic anisotropy

effect of support characteristics on the earth pressure in a jointed rock mass this study examines the magnitude and distribution of earth pressures against a support system in a jointed rock mass according to the support characteristics strut stiffness and spacing differe

shear wave splitting beneath the snake river plain suggests a mantle upwelling beneath eastern nevada usa the snake river plain srp a 90 km wide topographic depression in southern idaho is a topographically anomalous feature in the western u s previous seismic studies focused on the northeastern srp to study its relationship with the yellowstone hotspot we present new teleseismic shear wave splitting data from six broadband seismic stations deployed along the axis of the srp from june 2000 to september 2001 we also analyze splitting at hlid a permanent station of the national seismic network located f100 km north of the plain splitting of individual teleseismic phases is consistent at all stations within 2r errors and we favor the interpretation of anisotropy with a single horizontal fast axis although a dipping axis interpretation is statistically permitted at two of the stations our station fast directions as well as shear wave splitting data from numerous other stations throughout the basin and range are best explained by a lattice preferred orientation of olivine due to horizontal shear along the base of the plate associated with the gravitational spreading of buoyant plume like upwelling material beneath eastern nevada into a southwestward flowing asthenosphere with respect to a fixed hotspot reference frame this parabolic asthenospheric flow paf model for the great basin is attractive because it explains the observed high elevations high mantle buoyancy low velocity anomaly beneath eastern nevada high heat flow and depleted geochemistry of some erupted basalts the lack of pliocene recent major volcanism in eastern nevada suggests that a significant amount of the buoyancy flux is due to compositional buoyancy our splitting station delay times vary in a way not predicted by the paf model and can be explained by a zone of aligned magma filled lenses and or partially molten dikes beneath the srp lithosphere a depleted olivine rich residuum underneath the sides of the eastern srp and or the effect of lateral lower crustal flow from beneath the esrp toward its adjacent flanks d 2004 elsevier b v all rights reserved

seismic sources on the iberia african plate boundary and their tectonic implications the plate boundary between iberia and africa has been studied using data on seismicity and focal mechanisms the region has been divided into three areas a the gulf of cadiz b the betics alboran sea and northern morocco and c algeria seismicity shows a complex behavior large shallow earthquakes h 30 km occur in areas a and c and moderate shocks in area b intermediate depth activity 30 h 150 km is located in area b the depth earthquakes h 650 km are located to the south of granada moment rate slip velocity andhvalues have been estimated for shallow shocks and show similar characteristics for the gulf of cadiz and algeria and quite different ones for the central region focal mechanisms of 80 selected shallow earthquakes 8 mb 4 show thrust faulting in the gulf of cadiz and algeria with horizontal nnw sse compression and normal faulting in the alboran sea with e w extension focal mechanisms of 26 intermediate depth earthquakes in the alboran sea display vertical motions with a predominant plane trending e w solutions for very deep shocks correspond to vertical dip slip along n s trends frohlich diagrams and seismic moment tensors show different behavior in the gulf of cadiz betic alboran sea and northern morocco and northern algeria for shallow events the stress pattern of intermediate depth and very deep earthquakes has different directions vertical extension in the nw se direction for intermediate depth earthquakes and tension and pressure axes dipping about 45 o for very deep earthquakes regional stress pattern may result from the collision between the african plate and iberia with extension and subduction of lithospheric material in the alboran sea at intermediate depth the very deep seismicity may be correlated with older subduction processes

studies of the influence of non linear stress strain characteristics in soil structure interaction recent field and laboratory studies have shown that even at very small strains many soils exhibit non linear stress strain behaviour nevertheless because of its convenience linear elasticity will continue to play an important role in the analysis of such problems as settlement deformation and soil structure interaction in this paper the measured non liqear stress strain properties of a low plasticity clay are used in the finite element analysis of footings piles excavations and pressuremeter tests to assess the influence of small strain non linearity in comparison with linear elastic behaviour in all cases non linear behaviour results in the concentration of strain and deformation towards the loading boundaries this is shown to have important consequences for soil structure interaction problems such as settlement profiles pile group interaction and contact stress distributions small strain non linearity also has a significant influence on the interpretation in terms of equivalent elastic modu

mantle dynamics beneath the gibraltar arc western mediterranean from shear wave splitting measurements on a dense seismic array 1 controversial evolutionary models have been proposed for the gibraltar arc system a complex interaction zone between the eurasia and african plates here we derive new mantle anisotropic constraints from sks splitting measurements on a dense network of about 90 broad band stations deployed over south iberia and north morocco the inferred fast polarization directions fpd clearly show a spectacular rotation along the arc following the curvature of the rif betic chain while stations located at the south and south east edges show distinct patterns these results support geodynamical processes invoking a fast retreating slab rather than convective removal and delamination models the fpd variations along the gibraltar arc can be explained by fossil anisotropy acquired during the western mediterranean eocene subduction while changes to the south and south east of the rif betic chain could be the imprint of a flow episode around an alboran high velocity slab during its miocene fragmentation from the algerian slab

lithospheric anisotropy beneath the pyrenees from shear wave splitting we investigate upper mantle anisotropy beneath the pyrenean range along three n s profiles across the mountain belt the results of a first profile that operated in 1993 in the central part of the belt have been presented elsewhere we present the results of two other profiles that ran in 1995 1996 and 1996 1997 in the eastern and western part of the belt respectively and propose an interpretation of the whole results teleseismic shear waves sks skks and pks are used to determine splitting parameters the fast polarization direction and the delay time t teleseismic shear wave splitting in the eastern pyrenees displays homogeneous values trending n100 e and t values in the range 1 1 to 1 5 s a station located in the southern massif central 100 km north of the range is characterized by different splitting parameters n70 e t 0 7 s in the western part of the belt anisotropy parameters are similar across the whole belt n110 e and t 1 3 to 1 5 s most of the measured delay times including those obtained in the central part of the range are above the global average of the sks splitting around 1 s at the belt scale is generally poorly correlated with recent estimations of the absolute plate motion which predicts a fast direction ranging between n50 e and n80 e instead the orientation of n100 e is parallel to the trend of the pyrenean belt but also to hercynian preexisting structures this parallelism supports an anisotropy primarily related to frozen or active lithospheric structures we show that a signature related to the pyrenean orogeny is likely for the stations located in the internal domains of the belt by contrast the anisotropy measured at the stations located on the external parts of the belt could reflect a pre pyrenean hercynian deformation we suggest that a late hercynian strike slip deformation is responsible for this frozen upper mantle anisotropy and that the pyrenean tectonic fabric developped parallel to this preexisting fabric finally no particularly strong splitting is related to the north pyrenean fault commonly believed to represent the plate boundary between iberia and eurasia

wall and ground movements due to deep excavations in shanghai soft soils an extensive database of 300 case histories of wall displacements and ground settlements due to deep excavations in shanghai soft soils were collected and analyzed the mean values of the maximum lateral displacements of walls constructed by the top down method walls constructed by the bottom up method including diaphragm walls contiguous pile walls and compound deep soil mixing walls sheet pile walls compound soil nail walls and deep soil mixing walls are 0 27 h 0 4 h 1 5 h 0 55 h and 0 91 h respectively where h is the excavation depth the mean value of the maximum ground surface settlement is 0 42 h the settlement influence zone reaches to a distance of about 1 5h to 3 5h from the excavation the ratio between the maximum ground surface settlement and the maximum lateral displacement of a wall generally ranges from 0 4 to 2 0 with an average value of 0 9 the factors affecting the deformation of the wall were analyzed it shows that there is a slight evidence of a trend for decreasing wall displacement with increasing system stiffness and the factor of safety against basal heave wall and ground movements were also compared with that observed in worldwide case histories

shear wave splitting around the eifel hotspot evidence for a mantle upwelling summary we present the results of a shear wave splitting analysis across the eifel hotspot in westcentral europe our data set includes 18 permanent european broadband stations and 102 temporary eifel broadband and short period stations we observe variations in splitting at most permanent stations but are not able to model them reliably with unique dipping axis or two layer anisotropy models we prefer instead a single layer model with a horizontal fast axis to approximate the first order anisotropy which varies smoothly between stations we observe a first order parabolic pattern in fast polarization azimuth around the hotspot which suggests that a lattice preferred orientation lpo of olivine fast axes exists in the asthenosphere as a result of the interaction between the slowly wsw moving eurasian plate and a mantle upwelling beneath the eifel volcanic fields the minority of the variation not explained by this model correlates with rapid lateral changes in splitting and is interpreted as a result of additional anisotropy and or the effects of dynamic recrystallization associated with lpo development in the region of corner flow near the conduit our parabolic asthenospheric flow paf interpretation is consistent with eifel geological tomographic receiver function global absolute plate motion electrical conductivity anisotropy and geochemical studies as well as with splitting studies in the great basin and around hawaii we suggest that the eifel upwelling is sporadic and a result of a low excess upwelling temperature and or varying crustal stresses that periodically shift and facilitate eruption the paf pattern we observe neither suggests nor rules out anisotropy in the conduit associated with a wet eifel upwelling we use our optimum pa f model parameters to calculate a eurasian plate speed of 12 km ma 1 w hich is consistent with the recent hs3 nuvel1a speed of 19 14 km ma 1

upper mantle flow beneath and around the hangay dome central mongolia mongolia represents the northernmost area affected by the india asia collision and it is actively deformed along transpressive belts closely associated with large scale strike slip faults the active and past mantle flow beneath this region is however poorly known in order to investigate deep mantle deformation beneath central mongolia and its relation with the surrounding major structures such as the siberian craton the gobi altay belt and the baikal rift a ns trending profile of broadband seismic stations has been deployed in the summer 2003 from the southern siberian craton to the gobi altay range crossing the entire hangay dome mantle flow is deduced from the splitting of teleseismic shear waves such as sks phases in eastern mongolia the permanent station uln in ulaanbaatar reveals the presence of two anisotropic layers the upper one being oriented ne sw close to the trend of lithospheric structures and the lower one nw se close to the trend of eurasia absolute plate motion along the ns profile in central mongolia seismic anisotropy deduced from sks splitting reveals a homogeneous nw se trending structure fully consistent with the observations made in the altay sayan in western mongolia the observed delay times of 1 5 to more than 2 0 s favor consistent mantle flow over large mantle thicknesses since the lithosphere is less than 100 km thick beneath central mongolia and since the observed fast directions are parallel to the trend of the lithospheric structures but also close to the trend of the absolute plate motion we propose that both the lithosphere and the asthenosphere may join their anisotropic effects beneath central mongolia to explain the large delay times although gps vectors represent the instantaneous displacement of the earth s surface and sks splitting the time and vertical integration of finite strain at depth we use the opportunity of the dense geodetic measurements available in this region to discuss the anisotropy pattern in term of present day deformation in the eurasia fixed reference frame gps and sks both depict a similar trend beneath central mongolia suggesting a lithospheric block escaping toward the east that could orient olivine a axes in the upper mantle within a transpressive tectonic regime a different behaviour is observed in western mongolia the gps vectors trend ns close to the regional compression direction whereas the fast sks directions trend ew suggesting a tectonic regime close to a mode of axial shortening generating the development of an ew trending foliation at depth we therefore propose that mongolia is a place where active and frozen lithospheric deformation may add their effects together with the sublithospheric flow in the three sources of anisotropy inferred a fundamental role is played by the siberian craton that acted as an undeformable core of the continent through time the frozen paleozoic and mesozoic structures wrap around the craton building up the fast anisotropic direction pattern the present day sublithospheric flow induced by the plate motion is likely deflecting around its deep roots finally the present day tectonic regime appears to be controlled by the presence of the craton to the north

supported excavations observational method and inverse modeling an inverse analysis procedure that uses construction monitoring data to update predictions of deformations for supported excavation systems is presented the numerical procedure is used to optimize the finite element model of a 12 2 m deep excavation through chicago glacial clays by minimizing the errors between monitoring data and computed displacements the field observations are obtained from inclinometer data that measured lateral movements of the soil behind the supporting walls on opposite sides of the excavation throughout construction five construction stages are defined for the inverse analysis at every new construction stage the inclinometer data relative to that stage are added to the observations already available to recalibrate the model of the excavation the constitutive responses of the soils are represented by the hardening soil h s model of the six basic h s input parameters only one parameter per layer is optimized while the other parameters are either kept constant or related

seismic anisotropy beneath stable continental interiors a robust knowledge of seismic anisotropy beneath the continents is essential to our understanding of plate tectonic theory as anisotropy provides a unique constraint on the character of past and present deformation in the lithosphere and sublithospheric mantle this review paper summarizes the range of techniques currently available to image seismic anisotropy with passive source seismic data and addresses current issues surrounding the observation and interpretation of continental seismic anisotropy to this end we present case studies for four regions where seismic anisotropy has been extensively investigated in recent years eastern north america the canadian shield australia and southern africa based on this full suite of results we infer that stable continental regions generally contain seismic anisotropy that is clearly located within both the lithosphere and the sublithospheric mantle usually to depths of at least 200 km and perhaps more an implication of these results is that tectonic plates are at most only partially coupled to the underlying mantle the results from these case studies also demonstrate that while remarkable progress in seismic anisotropy imaging has been achieved in recent years it is clear that much more work will be required to adequately understand the origin of continental seismic anisotropy we suggest that a more robust characterization of anisotropic parameters can only be achieved by integrating complementary seismic datasets and by incorporating constraints from key related datasets from mineral physics magnetotellurics gravity and geodesy

finite element analysis of lateral earth pressure on sheet pile walls abstract sheet pile walls providing lateral earth support are widely employed as excavation supporting systems for cutting slopes along the high speed railway in this study a validated three dimensional finite element fe model based on field measurements was used to explore lateral earth pressure distribution on sheet pile walls aiming to provide guidelines and recommendations for design of the sheet pile walls to this end the influence of pile length sheet s location pile s stiffness and soil properties on the pile performance were investigated the results showed that the optimum pile length was about 14 m for the sheet pile walls at a china high speed railway the sheet s location could affect the formation of soil arching and the mechanism of earth pressure distribution the moment of inertia of sheet pile walls was found to be effective in controlling pile displacement and earth pressure compared to young s modulus of the pile variations of soil parameters led to negligible changes in the earth pressure distribution furthermore a proposed simplified straight line form for earth pressure diagram based upon the fe analysis was developed compared with traditional earth pressure methods the proposed diagram considers the sheet effect overall the conducted study provided useful help toward the process of safer design and more economical sheet pile walls

sks splitting beneath continental rift zones we present measurements of sks splitting at 28 digital seismic stations and 35 analog stations in the baikal rift zone siberia and adjacent areas and at 17 stations in the east african rift in kenya and compare them with previous measurements from the rio grande rift of north america fast directions in the inner region of the baikal rift zone are distributed in two orthogonal directions ne and nw approximately parallel and perpendicular to the ne strike of the rift in the adjacent siberian platform and northern mongolian fold belt only the rift orthogonal fast direction is observed in southcentral mongolia the dominant fast direction changes to rift parallel again although a small number of measurements are still rift orthogonal for the axial zones of the east african and rio grande rifts fast directions are oriented on average nne that is rotated clockwise from the n s trending rift all three rifts are underlain by low velocity upper mantle as determined from teleseismic tomography rift related mantle flow provides a plausible interpretation for the rift orthogonal fast directions the rift parallel fast directions near the rift axes can be interpreted by oriented magmatic cracks in the mantle or small scale mantle convection with rift parallel flow the agreement between stress estimates and corresponding crack orientations lends some weight to the suggestion that the rift parallel fast directions are caused by oriented magmatic cracks

holocene tectonism in eastern asia and geoidal changes abstract there have been eight major tectonic movements along the east margins of asia during the holocene they are correlated with intervals of volcanic eruptions in japan and glacio eustatic falls which are believed to be worldwide at the same time the tectonic activities migrate from south to north the facts suggest that geoidal changes occurred at times of global cooling furthermore it is thought that the geoidal changes and the tectonic movements induced abrupt climatic cooling on a worldwide basis

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

seismic anisotropy and large scale deformation of the eastern alps abstract mountain chains at the earth s surface result from deformation processes within the earth such deformation processes can be observed by seismic anisotropy via the preferred alignment of elastically anisotropic minerals the alps show complex deformation at the earth s surface in contrast we show here that observations of seismic anisotropy suggest a relatively simple pattern of internal deformation together with earlier observations from the western alps the sks shear wave splitting observations presented here show one of the clearest examples yet of mountain chain parallel fast orientations worldwide with a simple pattern nearly parallel to the trend of the mountain chain in the eastern alps the fast orientations do not connect with neighboring mountain chains neither the present day carpathians nor the present day dinarides in that region the lithosphere is thin and the observed anisotropy thus resides within the asthenosphere the deformation is consistent with the eastward extrusion toward the pannonian basin that was previously suggested based on seismicity and surface geology

the origin of intraplate deformation in the atlas system of western and central algeria from jurassic rifting to cenozoic quaternary inversion abstract analysis of petroleum exploration data supplemented by paleostress data enabled discussion of the origin of the deformation in the western and central saharan atlas algeria this intraplate area has recorded the breakup of pangea late triassic the opening of the maghrebian tethys since the dogger and subsequently its closure oligocene to present however the two periods of strong coupling between europe and africa late lutetian and pleistocene which correspond to rapid uplifts of the atlas system and important deformations are not collision related they can be correlated to the beginning and the end of the development of the western mediterranean sea

seismic anisotropy in the eastern united states deep structure of a complex continental plate we have analyzed shear wave splitting recorded by portable and permanent broadband and long period stations located in the eastern united states teleseismic shear waves sks skks and pks were used to retrieve the splitting parameters the orientation of the fast wave polarization plane and the delay time t in total 120 seismic events were processed allowing for more than 600 splitting measurements within the appalachians stations located in the western external part are characterized by t 1s and trending n50 70 e in the south and central regions and n30 40 e in the north closely following the trend of the orogenic belt in these areas the transition region between north and central is characterized by t 1 1 3 s and by e w trending that are at a high angle to the regional geologic trend measurements at two stations located in the eastern internal part of the belt indicate very weak anisotropy the large scale pattern of anisotropy is not consistent with that predicted for simple asthenospheric flow beneath the plate splitting along the southern and eastern margins of the continent is consistent with that expected for grenvillian deformation an alternative model of asthenospheric flow around the cratonic keel cannot be ruled out within the cratonic core the correlation between t and lithospheric thickness suggests a lithospheric anisotropy smaller length scale variations also argue for a significant contribution of lithospheric structures the fabric responsible for shear wave splitting may have formed during tectonic episodes that affected the eastern united states i e the grenville and appalachian orogenies and the subsequent rifting of the north atlantic ocean our observations in the western appalachians suggest that the anisotropy may be preserved since the grenvillian orogeny the absence of detectable splitting in the two stations in the eastern appalachians is attributed to the igneous intrusions related to the atlantic rifting the measurements in the transition between the northern and central southern appalachians constitute an intriguing anomaly whose e w have little obvious relation to the regional surface geology we suggest two possible causes 1 the local dominance of asthenospheric flow motivated by the proximity of a pervasive low velocity anomaly and 2 lithospheric deformation in a transcontinental strike slip fault zone active during the appalachian collision

a tertiary asthenospheric flow beneath the southern french massif central indicated by upper mantle seismic anisotropy and related to the west mediterranean extension abstract upper mantle flow beneath the french massif central is investigated using teleseismic shear wave splitting induced by seismic anisotropy about 25 three component stations short period intermediate and broadband were installed during the period 1998 1999 in the southern massif central from the clermont ferrand volcanic area to the mediterranean sea teleseismic shear waves sks skks and pks were used to determine the splitting parameters the fast polarization direction and the delay time delay times ranging between 0 7 and 1 5 s have been observed at most of the sites the azimuths of the fast split shear waves trend homogeneously nw se in the southern massif central suggesting a homogeneous mantle flow beneath this area the observed nw se direction differs from the n100 e pyrenean anisotropy further south it does not appear to be correlated to hercynian structures nor to the present day motion of the plate but is well correlated to the tertiary extension direction we propose that the opening of the western mediterranean induced by the rotation of the corsica sardinia lithospheric block and the roll back to the se of the tethys slab may have generated a large asthenospheric mantle flow beneath the southern massif central and a deflection of the up going plume centered beneath the northern massif central toward the se

mantle upwellings melt migration and the rifting of africa insights from seismic anisotropy the rifting of continents and eventual formation of ocean basins is a fundamental component of plate tectonics yet the mechanism for break up is poorly understood the east african rift system ears is an ideal place to study this process as it captures the initiation of a rift in the south through to incipient oceanic spreading in north eastern ethiopia measurements of seismic anisotropy can be used to test models of rifting here we summarize observations of anisotropy beneath the ears from local and teleseismic body waves and azimuthal variations in surface wave velocities special attention is given to the ethiopian part of the rift where the recent eagle project has provided a detailed image of anisotropy in the portion of the ethiopian rift that spans the transition from continental rifting to incipient oceanic spreading analyses of regional surface waves show sub lithospheric fast shear waves coherently oriented in a north eastward direction from southern kenya to the red sea this parallels the trend of the deeper african superplume which originates at the core mantle boundary beneath southern africa and rises towards the base of the lithosphere beneath afar the pattern of shear wave anisotropy is more variable above depths of 150 km analyses of splitting in teleseismic phases sks and local shear waves within the rift valley consistently show rift parallel orientations the magnitude of the splitting correlates with the degree of magmatism and the polarizations of the shear waves align with magmatic segmentation along the rift valley analysis of surface wave propagation across the rift valley confirms that anisotropy in the uppermost 75 km is primarily due to melt alignment away from the rift valley the anisotropy agrees reasonably well within the pre existing pan african lithospheric fabric an exception is the region beneath the ethiopian plateau where the anisotropy is variable and may correspond to pre existing fabric and ongoing melt migration processes these observations support models of magma assisted rifting rather than those of simple mechanical stretching upwellings which most probably originate from the larger superplume thermally erode the lithosphere along sites of pre existing weaknesses or topographic highs decompression leads to magmatism and dyke injection that weakens the lithosphere enough for rifting and the strain appears to be localized to plate boundaries rather than wider zones of deformation

seismic anisotropy in the south western pacific region from shear wave splitting 1 we perform shear wave splitting measurements to determine seismic anisotropy in the upper mantle under the remote and still not well understood south western pacific region more precisely the new hebrides subduction zone we obtained 29 good and 35 fair splitting measurements at 8 stations and 93 good and fair null measurements from the data provided by various networks according to the splitting parameters the seismic stations are grouped into eastern and western stations anisotropy of the subducting plate western stations appears to be the result of absolute plate motion apm of the australian plate from fast orientations alone it would be difficult to judge which process is responsible for the anisotropic structure either the absolute plate motion or trench parallel toroidal flow their delay times reveal that these anisotropic parameters can be explained without the presence of the subduction zone and the apm provides a simple explanation for the observed anisotropy on the other hand delay times at eastern stations are higher than that of western stations these stations are located close to the subduction zone and the nearly trench parallel orientation of fast polarization axes and their higher splitting delay times indicate the presence of subduction zone anisotropy at eastern stations is apparently due to the additional effect from toroidal flow near the subduction zone which increases the total anisotropy

azimuthal anisotropy in the earth from observations of sks at geoscope and nars broadband stations abstract we have analyzed observations of low frequency sks waves recorded on horizontal components at several broadband stations of the geoscope and nars arrays splitting of sks is consistently observed and in good agreement with a hypothesis of azimuthal anisotropy due to transverse anisotropy with a horizontal axis in the upper mantle beneath the receivers we have designed an inversion method which takes advantage of observations made simultaneously at different azimuths and which permits us to obtain estimates of the direction of fast axis of anisotropy as well as the time delay between the orthogonal quasi shear waves in general the directions of fast velocity obtained both for stations around the atlantic and around the pacific appear to be related to directions of past and present plate motions

evidence for a post 3 16 ma change in nubia eurasia north america plate motions we combine updated gps velocities from the nubian nu eurasian eu and north american na plates with 500 new 3 16 myr average seafloor spreading rates and nine transform fault azimuths from the northern atlantic and arctic basin seafloor spreading centers to estimate and test for changes in the relative motion between these plates the numerous new seafloor spreading rates and gps velocities improve our ability to detect recent changes in the relative motions of these plates the angular velocity vector that best fits the eu na gps velocities lies significantly north of the 3 ma average pole in accord with previously published geologic evidence that the eu na pole has migrated northward since v3 ma although we also find evidence for a significant post 3 ma change in nu na motion it is less compelling because the nubian plate gps velocity field is sparse and nu na seafloor spreading rates appear to have remained steady within the 1 mm yr 31 uncertainties if we systematically decrease the seafloor spreading rates to correct for outward displacement of seafloor spreading magnetic lineations the nu eu pole derived from gps site velocities lies more than 30 angular degrees south of the tightly constrained 3 ma average estimate and predicts significantly slower and more oblique present day nu eu convergence in the mediterranean both models for nu eu motion pass a key test for their accuracy namely they correctly predict strike slip motion along the well mapped gloria fault east of the azores the change to more oblique nu eu motion may reflect increasing difficulty in maintaining margin normal convergence within this continent continent collision zone 8 2003 published by elsevier b v

kinematics of the iberia maghreb plate contact from seismic moment tensors and gps observations the iberian peninsula and the maghreb experience moderate earthquake activity and oblique nw se convergence between africa and eurasia at a rate of 5 mm yr coeval extension in the alboran basin and a n35 e trending band of active left lateral shear deformation in the alboran betic region are not straightforward to understand in the context of regional shortening and evidence complexity of deformation at the plate contact we estimate 86 seismic moment tensors mw 3 3 to 6 9 from time domain inversion of near regional waveforms in an intermediate period band those and previous moment tensors are used to describe regional faulting style and calculate average stress tensors the solutions associated to the trans alboran shear zone show predominantly strike slip faulting and indicate a clockwise rotation of the largest principal stress orientation compared to the regional convergence direction 1 at n350 e at the n algerian and sw iberian margins reverse faulting solutions dominate corresponding to n350 e and n310 e compression respectively over most of the betic range and intraplate iberia we observe predominately normal faulting and wsw ene extension 3 at n240 e from gps observations we estimate that more than 3 mm yr of african nubian eurasian plate convergence are currently accommodated at the n algerian margin 2 mm yr in the moroccan atlas and 2 mm yr at the sw iberian margin 2 mm yr is a reasonable estimate for convergence within the alboran region while alboran extension can be quantified as 2 5 mm yr along the stretching direction n240 e superposition of both motions explains the observed left lateral transtensional regime in the trans alboran shear zone two potential driving mechanisms of differential motion of the alboran betic gibraltar domain may coexist in the region a secondary stress source other than plate convergence related to regional scale dynamic processes in the upper mantle of the alboran region as well as drag from the continental scale motion of the nubian plate along the southern limit of the region in the atlantic ocean the 3 5 mm yr westward motion of the gibraltar arc relative to intraplate iberia can be accommodated at the transpressive sw iberian margin while available gps observations do not support an active subduction process in this area

three dimensional s velocity of the mantle in the africa eurasia plate boundary region from phase arrival times and regional waveforms 1 a new model of the three dimensional shear velocity structure of the africa eurasia plate boundary is presented the new model is derived by jointly inverting different types of seismic data the two main sources of information are regional waveforms and teleseismic s wave arrival times we show that it is possible to find a model that fit the different data types nearly as well as when inverting solely one type of data the main improvement in resolving power is achieved between depths of 300 and 700 km though the improvements are not limited to this depth range our model reflects the complicated evolution of this plate boundary area the transition zone is dominated by high velocity anomalies which we infer to represent a mix of lithosphere that subducted relatively recently or is not sufficiently cold and dense to traverse the 660 km discontinuity the only low velocity zone in the transition zone is beneath the ionian sea the high velocity hellenic slab is continuous throughout the upper mantle and into the lower mantle to about 1200 km most likely representing subducted neo tethys lithosphere the uppermost mantle is dominated by low velocities consistent with the high level of tectonic activity low velocity regions are relatively strong beneath the mid atlantic ridge turkey and the dead sea region the region s current lithosphere is relatively thin except beneath the adriatic and ionian seas and the easternmost atlantic ocean

detailed mapping of seismic anisotropy with local shear waves in southeastern kamchatka summary the kamchatka peninsula lies over a vigorous subduction zone where pacific and north american plates converge at a rate of almost 80 mm yr 1 earthquakes associated with the subduction process provide an excellent source of seismic data for the study of anisotropic properties of the upper mantle and crust overlying the downgoing lithospheric slab we collected a large set of shear waves from events within the slab recorded by a variety of seismic stations in kamchatka data from permanent and temporary networks cover the entire 700 km length of the subduction zone with 50 200 km spacing between observing sites resulting in an unprecedented coverage of the supraslab mantle wedge we estimated shear wave splitting in selected s waves using two techniques and applied quality tests to ensure measurement stability fast directions vary from station to station and they can vary with backazimuth at individual stations and with direction of propagation for individual sources in over 350 measurements we recovered meaningful splitting delays up to 1 s with most delays in the 0 2 0 6 s range additionally in nearly 200 measurements splitting could not be resolved yielding null observations anisotropic properties of the kamchatka supraslab mantle wedge vary greatly along the volcanic arc and forearc of the subduction zone observed anisotropic indicators in the arc and forearc correlate spatially with some tectonic features e g volcanoes inland of the volcanic arc most splitting values indicate trench parallel fast polarization we do not observe depth dependence in local s wave splitting delays consistent with a shallow coherence of anisotropic texture in the vicinity of petropavlovsk kamchatsky observed anisotropic indicators are coherently trench normal and thus consistent with 2 d corner flow however splitting above the fragmented slab edge near the klyuchevskoy volcanic centre is variable and trench oblique birefringence between petropavlovsk and klyuchevskoy is weak overall our observations are incompatible with a regional slab driven corner flow regime

mantle dynamics and seismic anisotropy abstract observations of seismic anisotropy yield some of the most direct constraints available on both past and present day deformation in the earth s mantle insight into the character of mantle flow can also be gained from the geodynamical modeling of mantle processes on both global and regional scales we highlight recent progress toward understanding mantle flow from both observations and modeling and discuss outstanding problems and avenues for progress particularly in the integration of seismological and geodynamical constraints to understand seismic anisotropy and the deformation that produces it to first order the predictions of upper mantle anisotropy made by global mantle circulation models match seismological observations well beneath the ocean basins but the fit is poorer in regions of greater tectonic complexity such as beneath continental interiors and within subduction systems in many regions of the upper mantle models of anisotropy derived from surface waves are seemingly inconsistent with shear wave splitting observations which suggests that our understanding of complex anisotropic regions remains incomplete observations of anisotropy in the d layer hold promise for improving our understanding of dynamic processes in the deep earth but much progress remains to be made in characterizing anisotropic structure and relating it to the geometry of flow geochemical heterogeneity or phase transitions major outstanding problems related to understanding mantle anisotropy remain particularly regarding the deformation and evolution of continents the nature of the asthenosphere subduction zone geodynamics and the thermo chemical state of the lowermost mantle however we expect that new seismological deployments and closer integration of observations with geodynamical models will yield rapid progress in these areas

on the relationship between azimuthal anisotropy from shear wave splitting and surface wave tomography 1 seismic anisotropy provides essential constraints on mantle dynamics and continental evolution one particular question concerns the depth distribution and coherence of azimuthal anisotropy which is key for understanding force transmission between the lithosphere and asthenosphere here we reevaluate the degree of coherence between the predicted shear wave splitting derived from tomographic models of azimuthal anisotropy and that from actual observations of splitting significant differences between the two types of models have been reported and such discrepancies may be due to differences in averaging properties or due to approximations used in previous comparisons we find that elaborate full waveform methods to estimate splitting from tomography yield generally similar results to the more common simplified approaches this validates previous comparisons and structural inversions however full waveform methods may be required for regional studies and they allow exploiting the back azimuthal variations in splitting that are expected for depth variable anisotropy applying our analysis to a global set ofskssplitting measurements and two recent surface wave models of upper mantle azimuthal anisotropy we show that the measures of anisotropy inferred from the two types of data are in substantial agreement provided that the splitting data is spatially averaged so as to bring it to the scale of long wavelength tomographic models and reduce spatial aliasing observed and tomography predicted delay times are significantly correlated and global angular misfits between predicted and actual splits are relatively low regional anisotropy complexity notwithstanding our findings imply that splitting and tomography yield a consistent signal that can be used for geodynamic interpretation

shear wave splitting to test mantle deformation models around hawaii seismic anisotropy allows us to study mantle deformation and it can thus help to constrain mantle flow in the vicinity of hotspots hypotheses for the cause of seismic anisotropy in this environment include the parabolic asthenospheric flow paf model radial flow from a mantle plume impinging on a moving lithosphere is dragged by the plate in the direction of absolute plate motion in map view this gives a parabolic pattern of flow opening in the direction of plate motion we present new shear wave splitting observations from land and ocean stations around the hawaiian islands that can be explained by the parabolic flow model the observations suggest asthenospheric anisotropy under the hawaiian islands which may be explained if dislocation creep persists to deeper depths there than in other regions perhaps due to the higher temperatures near hotspots

interplay between field measurements and soil behavior for capturing supported excavation response instruments are installed during the construction of urban excavations to monitor ground response at discrete locations to various construction activities to verify design assumptions and to effectively apply the observational approach inverse analysis approaches are often used to develop improved soil models suitable for representing soil response during excavation from these measurements we propose that through the integration of inverse analysis and instrument measurements it is possible to provide information on excavation performance at locations where no instrumentation is available therefore this study examines the relationship between various instruments typically used on an excavation project and the quality of information that can be extracted for excavation modeling a synthetically generated set of instrument measurements that include inclinometers surface settlement points extensometers heave gauges piezometers and strain gauges using an idealized soil profile are initially used the analyses show that in addition to the measurements of lateral wall deflections and surface settlement inclinometers placed some distance behind the wall and measured forces in the struts significantly improve the quality of the extracted soil behavior these findings are further demonstrated with a well instrumented deep excavation case study in taipei the inclinometers at the wall and at farther distance from the wall are used to extract the soil behavior the extracted soil model used in a numerical analysis provides a good prediction of excavation behavior elsewhere around the excavation including surface settlements

teleseismic arrivals at a mid ocean ridge effects of mantle melt and anisotropy recent observational evidence of upwelling mantle anisotropy at a slow spreading center has motivated the modeling of teleseismic arrivals at mid ocean ridges the models consider a variety of types of anisotropy and heterogeneity where the emphasis is to ascertain whether or not travel times can be used to discriminate between the existence of partial melt and anisotropy two mechanisms for anisotropy in the upwelling asthenosphere are considered one due to the preferential alignment of the fast axes of olivine crystals in the direction of mantle flow and the other due to the preferential alignment of cracks that feed melt towards the spreading axis the results indicate that p waves are most sensitive to even modest amounts of flowinduced asthenospheric anisotropy while s waves are most sensitive to the presence of mantle melt multiple s wave arrivals are predicted for many models most notably the ones with anisotropy due to crack alignment where very large s wave separations develop the model which best fits existing data requires a higher degree of crystal alignment anisotropy in the upwelling asthenosphere than in the lithosphere this effect has been predicted in studies of the evolution of crystal alignment anisotropy in polycrystalline aggregates

seismic anisotropy of northeastern algeria from shear wave splitting analysis abstract there are few studies of internal deformation under northern africa here we present such a study we analyze teleseismic shear wave splitting for northeast algeria to improve our knowledge of lithospheric and asthenospheric deformation mechanisms in this region we study waveform data generated by tens of teleseismic events recorded at five recently installed broadband bb stations in algeria these stations cover an area 2 across extending from the tellian geological units in the north to the saharan atlas units in the south analysis of sks wave splitting results insignificant spatial variations in fast polarization orientation over a scale length of at most 100 km the seismic anisotropy shows three clear spatial patterns a general ene wsw orientation is observed under the stations in the north this polarization orientation follows the direction of the tell atlas mountain chain which is perpendicular to the convergence direction between africa and eurasia delay times vary significantly across the region between 0 6 and 2 0 s at several stations there is an indication of a wnw ese polarization orientation which is apparently related to a later geodynamic evolutionary phase in this region a third pattern of seismic anisotropy emerges in the south with an orientation of roughly n s we discuss these observations in light of geodynamic models and present day geodetic motion

propagation of regional seismic phases lg and sn and pn velocity structure along the africa iberia plate boundary zone tectonic implications we used over 1000 regional waveforms recorded by 60 seismic stations located in northwest africa and iberia to map the efficiency of l g and sn wave propagation beneath the gulf of cadiz alboran sea and bounding betic rif and atlas mountain belts crustal attenuation is inferred from the tomographic inversion of l g pg amplitude ratios upper mantle attenuation is inferred from maps of sn propagation efficiency derived by inversion of well defined qualitative efficiency assignments based on waveform characteristics regions of l g attenuation correlate well with areas of thinned continental or oceanic crust significant sedimentary basins and lateral crustal variations comparison of the sn efficiency results with velocities obtained from an anisotropic pn traveltime inversion shows a fairly good correlation between regions of poor sn efficiency and low pn velocity a low pn velocity 7 6 7 8 km s 1 and significant sn attenuation in the uppermost mantle is imaged beneath the betics in southern spain in sharp contrast to the relatively normal pn velocity 8 0 8 1 km s 1 and efficient sn imaged beneath the alboran sea slow pn velocity anomalies are also imaged beneath the rif and middle atlas in morocco we do not identify any conclusive evidence of lithospheric scale upper mantle attenuation beneath the rif although the crust in the gibraltar region appears highly attenuating making observations at stations in this region ambiguous paths crossing the gulf of cadiz eastern atlantic and the moroccan and iberian mesetas show very efficient sn propagation and are imaged with high pn velocities 8 1 8 2 km s 1 the spatial distribution of attenuation and velocity anomalies lead us to conclude that some recovery of the mantle lid beneath the alboran sea must have occurred since the early miocene episode of extension and volcanism we interpret the low velocity and attenuating regions beneath the betics and possibly the rif as indicating the presence of partial melt in the uppermost mantle which may be underlain by faster less attenuating mantle in the light of observations from other geophysical and geological studies the presence of melt at the base of the betic crust may be an indication that delamination of continental lithosphere has played a role in the neogene evolution of the alboran sea region

constraining the extent of crust mantle coupling in central asia using gps geologic and shear wave splitting data abstract we have obtained constraints on mechanical crust mantle coupling for tibet and yunnan indo china by comparing the observed surface deformation field inferred from gps and quaternary fault slip rate data with the mantle deformation field inferred from several sks shear wave splitting data sets we first determined whether the anisotropy is dominantly asthenospheric or lithospheric by testing simple models of both types against the observed values of the fast polarization direction which is assumed to be parallel to the horizontal projection of the direction of maximum shear for asthenospheric flow we solved for a best fitting uniform sub asthenospheric velocity model for eurasia the fit however was not satisfactory rms misfit 20 solving for separate uniform flow fields in each region improves the fit 15 for tibet 11 for yunnan although the resulting flow fields are inconsistent with several geophysical and geological constraints and thus considered unlikely we then considered lithospheric models for tibet vertically coherent deformation i e maximum shear direction from surface deformation is parallel to yields an improved match 11 for left lateral shear both the goodness of fit and the dominance of left lateral surface faulting in tibet argue for a lithospheric source of anisotropy the misfit for yunnan is large for either right 53 or left lateral 49 shear which argues for complete crust mantle decoupling in yunnan we show that the fast polarization directions throughout both the tibet and yunnan region can be fit by a single lithospheric dynamic model in which there is strong coupling between crust and mantle beneath tibet but a complete decoupling between crust and mantle beneath yunnan crust this dynamic model predicts left lateral maximum shear directions within the mantle that align with fast polarization directions in both regions 9 these maximum shear directions within the mantle align with the left lateral maximum shear directions in the crustal deformation field in tibet but are not in yunnan our results have the following implications first the coherence between crust and mantle deformation in tibet implies strong crust mantle mechanical coupling since this is the only way that crustal buoyancy forces required to account for the surface deformation field can be transmitted into the mantle this behavior is consistent with a uniform strength lithosphere or strong crust but not with a substantially weaker crust for example it is inconsistent with the popular jelly sandwich rheology and thus precludes behavior such as large scale lower crustal flow in tibet the crust mantle coherence is also incompatible with mantle delamination second crust mantle decoupling within the yunnan lithosphere argues that mantle deformation there is controlled only by boundary conditions crustal buoyancy forces are not transmitted into the mantle beneath yunnan moreover the dynamic model for the mantle shows that the yunnan crust is moving south with respect to the mantle at rates as high as 30 mm yr third there is a fundamental rheological lithospheric transition between tibet and yunnan that may provide a key to understanding this significant orogen