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

tectonothermal evolution of the mayuan assemblage in the cathaysia block implications for neoproterozoic collision related assembly of the south china craton the mayuan assemblage in the cathaysia block southeast china consists of felsic paragneiss pelitic schist greenschist amphibolite marble calcsilicate and quartzite that underwent three episodes of deformation d1 d3 and four episodes of metamorphism m1 m4 in the early neoproterozoic the m1 assemblage consists of mineral inclusions defining an early foliation s1 within porphyroblasts represented by chlorite muscovite biotite plagioclase quartz in pelitic schist and actinolite chlorite epidote albite quartz enclosed in amphibolite m2 coincides with the development of the regional schistosity s2 and represents the formation of the porphyroblasts and growth of matrix minerals resulting in development of prograde metamorphic zones chlorite biotite garnet staurolite and kyanite zones m3 is simultaneous with the third phase of deformation d3 and produced sillimanite bearing mineral assemblages in pelitic schist and hornblende bearing assemblages in amphibo lite the last metamorphic episode m4 gave rise to the retrogressive assemblage chlorite muscovite in pelitic rock and actinolite chlorite epidote in amphibolite the sequence of mineral assemblages and history of metamorphic reactions built from the petrogenetic grid of pelites suggest a near isothermal decompression clockwise p t path for the mayuan pelitic schists using the tweequ software program the garnet biotite thermometer and garnet muscovite biotite plagioclase barometer yield p t conditions for m1 of 5 5 to 6 0 kb and 450 to 500 c and conditions for the garnet staurolite and kyanite zones of m2 of 6 0 to 7 0 kb and 550 to 600 c 6 0 to 7 5 kb and 600 c and 11 0 to 11 5 kb and 600 c the p t conditions of m3 were estimated at 570 to 625 c and 4 0 to 4 5 kb using the muscovite biotite thermometer and hornblende plagioclase geothermo barometer the garnet chlorite thermometer yields temperatures of 300 to 400 c for m4 but the pressures of m4 cannot be quantitatively estimated because of the lack of a suitable geobarometer these p t estimates also define an near isothermal decompression clockwise p t path which is involved in initial crustal thickening followed by rapid exhumation and final cooling and is related to amalgamation of the cathaysia and yangtze blocks to form the south china craton

an early miocene age for a high temperature event in gneisses from zabargad island red sea egypt mantle diapirism in the last decade much attention has been focused on the tectonothermal and geochemical evolution of rocks outcropping on zabargad island red sea egypt this island though of limited size 4 km has an almost unique geodynamic setting 50 kmwest of the red sea axis and reveals a close association of mafic ultramafic rocks with a metamorphic gneiss complex understanding the geodynamic evolution of the island was expected to elucidate the processes operating in a young rift setting environment and crust mantle interface tectonics since the first work of bonatti et al 1981 however genetic models have been limited by the the scant data on the timing of juxtaposition between the peridotites and the gneisses as well as the nature of the mafic ultramafic rocks one interpretation considers the peridotites as an asthenospheric mantle diapir intruding a pan african continental crust during the early stages of the red sea opening e g nicolas et al 1987 the fewattempts todate the time of intrusion of the peridotites are consistent with this view nicolas et al 1985 for example inferred a k ar age of 23 7 myr for amphiboles extracted fromanamphibolite this value concurs with the more precise ar ar age 18 7 1 3 myr given by hornblende extracted from a pegmatoidal pocket of a coarse grained hornblendite in harzburgite trieloff et al 1997 both ages are identical within errors of a 18 4 1 0myr zircon age obtained by oberli et al 1987 although there is a good agreement between the three methods oberli s zircon value has been presented only in an abstract thus making it difficult to properly evaluate k ar and ar ar ages have also been questioned for decoupling of parent and daughter nuclides villa 1990 or for their meaning in terms of a geological event uplift hydrothermalism or emplacement age due to their known susceptibility to low grade events an alternative interpretation considers the peridotites and the gneisses to be panafrican brueckner et al 1988 1995 and that juxtaposition of both rock types occurred shortly after differentiation from a common depleted mantle source 700 ma this is apparently supported by the so called slap errorchron resulting from alignment of whole rock peridotite samples and cpx separates in the sm nd isochron diagram brueckner et al 1988 this model however has been challenged in two recent papers on the grounds of fluid inclusion boullier et al 1997 and noble gases and argon chronological studies trieloff et al 1997 in both models gneisses are seen to represent remnants of the pan african continental deep crust left behind during opening of the red sea rift pan african ages for the metamorphic gneiss complex are well established by sm nd and rb srmineral isochrons lancelot and bosch 1991 brueckner et al 1995 as well as by a zircon pb pb evaporation date brueckner et al 1995 from a felsic gneiss located a few hundred metres from the contact zone between the central peridotite body and the gneisses these ages however provide no constraints on the timing of juxtaposition of gneisses and peridotites in order to solve this fundamental problem and because of the known resistance to alteration of the mineral zircon we focused on the u pb dating of single zircon grains extracted from a felsic gneiss located at the contact zone with the central peridotite body

no direct correlation of mantle flow beneath the north china craton to the india eurasia collision constraints from new sks wave splitting measurements summary the long range effects of the ongoing india eurasia collision and their role in the cenozoic tectonic evolution of eastern china are not well understood here we investigate deformation beneath the north china craton and the qilian mountain region between the haiyuan and kunlun faults both of which are located immediately to the northeast of the tibetan plateau we present teleseismic shear wave splitting parameters from 299 broad band stations these stations provided good spatial coverage in mapping upper mantle deformation beneath the north china craton and the qilian mountain the backazimuth dependence of fast directions fromstationslocatedwithintheqilianmountainregionindicatesacomplexanisotropypattern a multilayer anisotropy and or anisotropy with a dipping symmetry axis may exist beneath the qilian mountain the overlapping or underthrusting of material evident in anisotropy from this region may be a long range effect of the india eurasia collision the central north china craton showed spatially coherent fast directions and the shear wave velocity anomalies within the upper mantle these patterns suggest horizontal deflection of a regional mantle upwelling possibly originating from the mantle transition zone anisotropy with large delay times was observed in the vicinity of shanxi rift system high lnvs lnvp values for the upper mantle indicate that anisotropy in this area is enhanced by vertically aligned melt filled fissures our results suggest that the dynamic processes beneath the central north china craton are not directly related to the india eurasia collision

crustal and uppermost mantle velocity structure and its relationship with the formation of ore districts in the middle lower yangtze river region abstract in this study we conduct ambient noise tomography and teleseismic two plane wave tomography to probe the crustal and uppermost mantle structures in the middle lower yangtze river region the data used include 14 months from july 2012 to august 2013 of continuous vertical component ambient noise data and 219 teleseismic earthquakes recorded at 138 broadband seismic stations from chinese provincial networks and 19 temporary seismic stations deployed by china university of geosciences beijing first we apply ambient noise tomography to the collected ambient noise data to generate rayleigh wave group and phase velocity maps at 5 42 s periods and two plane wave tomography method to earthquake data to generate intermediate to long period phase velocity maps at 20 143 s periods we then combine the short to intermediate period velocity maps from ambient noise and the intermediate to long period phase velocity maps from earthquake data to generate broadband phase velocity maps at periods from 5 to 143 s by inverting these 5 143 s rayleigh wave velocity maps we construct a 3 d shear wave velocity model from the surface to 250 km depth in the middle lower yangtze river region the 3 d model shows that in the upper crust the basin regions including the jianghan hehuai subei hefei and nanyang basins are all featured with low velocities and the mountain regions with high velocities in the uppermost mantle a low velocity zone at 100 200 km depth is observed beneath the middle lower yangtze river metallogenic belt moreover our tomographic results show that the ningwu and ningzhen ore districts are clearly characterized by the strongest low velocity anomaly in the uppermost mantle at 70 200 km depth the depth extent of the low velocity zone becomes shallower and the amplitude of low velocity anomaly becomes larger from the southwest jiurui ore district to northeast ningwu ore districts the change pattern of the low velocity zone in the depth extent and the amplitude is consistent with the fact that peak ages of magmatic events along the middle lower yangtze river metallogenic belt progressively become younger and younger from 148 ma in the southwest to 125 ma in the northeast the observed low velocity zone may represent the cooling hot upper mantle which was partially molten in the past resulting from partial melting of the paleo pacific plate or of an enriched mantle source induced by the westward subduction of the paleo pacific plate the upwelling of the mantle derived magmas may result in the formation of these granitic rocks and coeval ores deposits along the middle lower yangtze river metallogenic belt

components and episodic growth of precambrian crust in the cathaysia block south china evidence from u pb ages and hf isotopes of zircons in neoproterozoic sediments abstract detailed lam icpms u pb dating and lam mc icpms lu hf isotope analysis were carried out on zircons from nine samples of basement metamorphic rocks in the southern cathaysia block south china the chemical compositions of these metamorphic rocks and zircon morphology indicate that their protoliths were sedimentary zircon u pb dating results show they mainly formed during the late neoproterozoic the precambrian crust of the cathaysia block can be divided into two distinct tectonic domains the wuyishan terrane to the northeast and the nanling yunkai terrane to the southwest the nearly e w boundary between these two terranes is also supported by geophysical petrological and geochemical evidence and the basement rocks of the two terranes are comprised of different components the wuyishan terrane is characterized by dominant paleoproterozoic 1 86 ga and lesser neoarchean magmatism and the southern central part of the terrane suffered strong neoproterozoic and early paleozoic tectonothermal reworking the zircon data suggest that there were five important episodes of juvenile crust generation 3 6 ga 2 8 ga 2 6 2 4 ga 1 85 ga and 0 8 0 7 ga in the wuyishan terrane strong paleoproterozoic 1 85 ga magmatism in northern wuyishan and neoproterozoic 0 8 0 7 ga magmatism in central and southern wuyishan both principally involved the remelting of old crust with minor input of juvenile material in contrast the nanling yunkai terrane contains abundant neoarchean and grenvillian zircons some evidence of mesoproterozoic activity and rare paleo to meso archean and neoproterozoic zircons u pb ages and hf isotopic compositions of the detrital zircons from the late neoproterozoic to early paleozoic meta sedimentary rocks in the nanling yunkai area suggest that the growth of juvenile crust mainly occurred at 3 6 ga 3 3 ga 2 5 2 6 ga 1 6 ga 1 0 ga and 0 8 0 7 ga neoarchaean 2 6 2 5 ga grenvillian 1 0 ga and neoproterozoic 0 8 0 7 ga magmatism mainly involved the recycling of old crust minor remnants of 4 1 ga crust may remain in the terrane this crustal history is distinct from that of the wuyishan terrane and analogous to those recorded for the eastern india east antarctic domain of northern gondwanaland suggesting that they probably were once linked

crustal structure and geodynamics of the middle and lower reaches of yangtze metallogenic belt and neighboring areas insights from deep seismic reflection profiling abstract a 300 km long seismic reflection profile was acquired across the middle and lower reaches of the yangtze river mly metallogenic belt and its adjacent areas the objective of the survey was to establish the deep architecture and geodynamic framework of the region results based on the interpretation of the deep seismic data include 1 tan lu fault appears as a subvertical thrust fault or transpression fault with its deep portion dipping toward the southeast 2 the zhangbaling uplift is squeezed out along this fault 3 complex upper crustal deformation structures beneath the chuquan depression include both kink bands thrusts imbrication and fold structures reflecting contraction deformation and detachment fault and normal fault structures reflecting extensional deformation 4 the crocodile reflection structure emerging beneath the tan lu fault and ningwu lishui volcanic basin which represents the decoupled deformation process of the upper and lower crust associated with intra continental subduction 5 further to the southeast the upper crust deformation shows a large scale wave form pattern making crustal scale syncline and anticline 6 the entire section of the reflection moho is clearly discernible at depth of 30 0 34 5 km and the moho beneath the middle and lower reaches of yangtze river metallogenic belt is shallowest while the moho beneath the north china block is deeper than that beneath the yangtze block the moho offsets could be seen beneath the ningwu volcanic basin the seismic reflection data suggest that lithosphere delamination and asthenosphere upwelling that may result from the mesozoic intra continental orogenesis is responsible for the formation of large scale magmatism and mineralization in the mly metallogenic belt

crustal and uppermost mantle s velocity structure under hi climb seismic array in central tibetan plateau from joint inversion of surface wave dispersion and receiver function data abstract trade off between the depth of an interface and the average velocity above the interface is well known in receiver function inversion to resolve model ambiguity surface wave dispersion data which are sensitive to vertical shear velocity average are commonly combined with p receiver functions in the inversion in this paper we design a joint inversion scheme using the neighborhood searching algorithm to solve shear velocity structure of the crust and uppermost mantle with receiver function and surface wave dispersion data two sets of stretched splines are implemented in the inversion to obtain smooth velocity profiles separated by a specifically defined moho discontinuity we apply this method to the dense hi climb seismic array in the central tibetan plateau tp the indian crust is observed to subduct and underplate the tibetan crust between the yarlung zangbo suture and the bangong nujiang suture at the latitude of about 31 5 n the crust thickens from about 50 km below the indian foreland to over 75 km south of bangong nujiang suture and turns shallower at around 65 km under the qiangtang block we identify two zones with complicated moho structure beneath the northern lhasa block and southern qiangtang block indicating highly deformed moho morphology and beneath the himalaya block associated with the underthrusting of the indian plate respectively a low velocity zone is present in the mid crust in most parts of the profile under the tp with up to more than 10 velocity reduction the low velocity structure is not continuous forming discontinuous patches rather than channels calling for a revision of the channel flow model

stiffness method for anticipating earthquakes in strain softening earthquake models the single variable r kf ks measures the nearness to earthquake instability kf and ks are stiffnesses of the fault zone and elastic surroundings instability occurs when increasing r reaches unity for a simple two dimensional antiplane model r is a function of d e du and h where e is shear strain at the ground surface and u is remote displacement observed at a distance h from the fault r is independent of the fault zone constitutive law crustal rigidity and shear stress magnitude

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

crustal structure beneath china from receiver function analysis 1 we collected and processed a large amount of high quality broadband teleseismic waveform data recorded by the 48 chinese national digital seismic network stations to estimate large scale lateral variations of crustal thickness and vp vs ratio hence poisson s ratio beneath china a statistical method was used to select mutually coherent receiver functions at each station which yielded over 200 traces for most of the stations with the conventional h the crustal thickness and vp vs ratio approach there is a large trade off between h and consequently multiple maxima are frequently observed in the h domain we introduced a weight function that measures the coherence between the p to s conversion and the reverberation phases at each h grid to reduce the trade off a 4th root stacking method was further applied to reduce uncorrelated noise relative to the linear stack these modifications turned out to be very effective in reducing the h trade off and yielded reliable estimates of crustal thickness and vp vs ratio the crust beneath eastern china is as thin as 31 33 km and the underlying moho is relatively flat and sharp in the western part of china the crust is considerably thicker and shows large variations the moho is observed at about 51 km depth along the tian shan fold system and about 84 km deep beneath the central part of the tibetan plateau the transition occurs at the so called n s belt between about 100 and 110 e which is featured by unusually high seismicity and large gravity anomalies the average vp vs ratio over the mainland china crust is about 1 730 0 249 significantly lower than the global average 1 78 0 27 of the continental crust this lower vp vs ratio may suggest a general absence of mafic lowermost crustal layer beneath china

crustal structure beneath the dabie orogenic belt from ambient noise tomography abstract the qinling dabie sulu orogenic belt in east central china is the largest high and ultrahigh pressure hp and uhp metamorphic zone in the world the dabie mountains are the central segment of this orogenic belt between the north china and yangtze cratons this work studies the nature of the crustal structure beneath the dabie orogenic belt to better understand the orogeny to do that we apply ambient noise tomography to the dabie orogenic belt using ambient noise data from 40 stations of the china national seismic network cnsn between january 2008 and december 2009 we retrieve high signal noise ratio snr rayleigh waves by cross correlating ambient noise data between most of the station pairs and then extract phase velocity dispersion measurements from those cross correlations using a spectral method taking those dispersion measurements we obtain high resolution phase velocity maps at 8 35 second periods by inverting rayleigh wave phase velocity maps we construct a high resolution 3d shear velocity model of the crust in the dabie orogenic belt the resulting 3d model reveals interesting crustal features related to the orogeny high shear wave velocities are imaged beneath the hp uhp metaphoric zones at depths shallower than 9 km suggesting that hp uhp metaphoric rocks are primarily concentrated in the upper crust underlying the high velocity hp uhp metamorphic zones low shear velocities are observed in the middle crust probably representing ductile shear zones and or brittle fracture zones developed during the exhumation of the hp uhp metamorphic rocks strong high velocities are present beneath the northern dabie complex unit in the middle crust possibly related to cooling and crystallization of intrusive igneous rocks in the middle crust resulting from the post collisional lithosphere delamination and subsequent magmatism a north dipping moho is revealed in the eastern dabie with the deepest moho appearing beneath the northern dabie complex unit consistent with the model of triassic northward subduction of the yangtze craton beneath the north china craton

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

detailed moho geometry beneath southeastern china and its implications on thinning of continental crust abstract we used teleseismic p wave receiver functions and the h stacking method to obtain crustal thicknesses beneath 121 permanent stations in the middle lower yangtze craton and its adjacent areas using nearly 700 teleseismic events in 2009 and 2010 we then combined them with results of previous work to map detailed moho geometry in the region the results show that in addition to overall thin crust of 30 km in thickness throughout southeastern china there are two ns oriented narrow zones of extensive crustal thinning in the region the western zone passes through the xiangzhong basin the jianghan basin and the nanxiang basin while the eastern zone follows the tanlu fault the two merge in the south forming a v shaped thin crust area in southeastern china we suggest different geodynamic mechanisms of crustal thinning north and south of the 29 n parallel crustal thinning in the northern part was caused by the westward subduction of the pacific plate and its eastward migration of the trench crustal thinning in the southern part is mainly controlled by the interaction between the philippine and the eurasia plates the change of subduction polarity from the northward subduction of the philippine plate under eurasia to the eastward high angle subduction of the eurasian plate under the philippine plate in taiwan is responsible for diverse extensional stress regime in south china the v shape crustal thinning zone was formed due to a mantle corner flow in the rear of subducting eurasia plate in a form of hot fingers growing from the mantle corner flow to cause the moho uplift in the southern part of the region

petrogenesis of the late yanshanian mantle derived intrusions in southeastern china response to the geodynamics of paleo pacific plate subduction abstract several late yanshanian syenitic and gabbroic rocks from the coastal area of southeastern se china have been studied to determine zircon u pb ages and hf isotopic compositions as well as whole rock elemental and sr nd isotopic compositions to constrain their sources and tectonic settings the systematic la icp ms zircon u pb dating results indicate that they can be divided into two main stages the early stage 141 118 ma and the late stage 98 86 ma which temporally correspond to the regional lower and upper volcanic series respectively the early stage syenitic and gabbroic rocks are accompanied by vast rhyolitic and dacitic volcanic rocks with minor granites their parental magma was derived from an enriched mantle metasomatized by subducted sedimentary materials the late stage syenitic rocks mainly occur as the central intrusion of the caldera with ages close to the accompanied volcanics forming a caldera related volcanic intrusive ring complex they were produced by magma mixing between depleted asthenosphere melts and subduction related enriched mantle melts it is suggested that the late yanshanian tectonic settings of se china transformed from a compressional environment to an extensional environment corresponding to the transformation from forward to rollback subduction of the paleo pacific plate at approximately 110 ma

geologic framework and tectonic evolution of the qinling orogen central china abstract the geologic framework of the qinling orogen was built up through interplay of three blocks the north china block including the north qinling the south qinling and the south china block separated by the shangdan and mianlue sutures the shangdan suture resulted from middle paleozoic collision of the north china block and the south qinling the mianlue suture resulted from late triassic collision of the south qinling and the south china block present upper crust of the qinling is structured dominantly by thrust fold systems the north qinling displays thick skinned deformation with crystalline basement involved whilst the south qinling is characterized by thin skinned thrusts and folds detached above the lower sinian two types of precambrian basement crystalline and transitional are defined according to lithology and metamorphic grade and different in age stratigraphic and sedimentary architecture is characterized by distinct zonation the qinling orogen experienced a prolonged continental divergence and convergence between blocks during the period from late neoproterozoic to early paleozoic times the south qinling was the northern margin of the south china block and the north qinling was the southern margin of the north china block separated by a proto tethyan qinling ocean the north qinling evolved into an active margin when the proto tethyan qinling ocean subducted northward during ordovician time collision of the south and north qinling took place in middle paleozoic along the shangdan suture synchronous with the collision rifting occurred at the southern rim of the south qinling and was followed by the opening of the paleo tethyan qinling ocean during the late paleozoic resulting in the splitting of the south china block from the south qinling collision of the south qinling and the south china block came about in the late triassic along the mianlue suture the late triassic collisional orogeny caused extensive fold and thrust deformation and granitoid intrusions throughout the qinling and led to final amalgamation of the north and south china blocks

slab like high velocity anomaly in the uppermost mantle beneath the dabie sulu orogen seismic tomography is used to determine three dimensional velocity structure of the dabie sulu orogen in eastern china the high resolution image of the p waves velocity structure is obtained for the uppermost mantle to a depth of at least 150 km along the latitudes of 30 38 n and longitudes of 114 122 e results of this inversion reveal a slab like high velocity anomaly under this orogen in the depth from moho discontinuity to at least 110 km it may represent a remnant of the subducted yangtze block during the period of triassic continent continent collision

distinct upper mantle deformation of cratons in response to subduction constraints from sks wave splitting measurements in eastern china abstract interaction between the subducting slab the overriding continental lithosphere and mantle flow are fundamental geodynamic processes of subduction systems eastern china is an ideal natural laboratory to investigate the behavior and evolution of cratonic blocks within a subduction system in this study we investigate deformation of the upper mantle beneath eastern china we present seismic shear wave splitting measurements from three networks consisting of over 483 broadband stations with 157 stations giving a total of 516 results the splitting parameters exhibit complex regional patterns but are relatively coherent within individual tectonic units tectonic blocks exhibited distinctive fast directions relative to regional features the dominant attitude of fast directions for the north china craton was subparallel to the direction of subduction whereas fast directions for southeastern china were perpendicular to the direction of subduction the shear wave splitting measurements were interpreted according to a high resolution tomographic body wave velocity model combining these two datasets showed that the predominant geodynamic models for the region mantle plume mantle wedge and flat slab subduction models are incompatible with the observations presented here we suggest that the north china craton yangtze craton and the cathaysia block have undergone different deformational events due to differing mantle flow patterns and distinct spatial and temporal subduction histories of the pacific and philippine sea plates