lateral stress changes and shaft friction for model displacement piles in sand the paper describes a series of tests performed in a drum centrifuge on instrumented model displacement piles in normally consolidated sand these tests examined the influence of the pile installation method the stress level and the pile aspect ratio on the increase in lateral effective stress on the pile shaft during static load testing to failure a parallel series of constant normal load and constant normal stiffness cns laboratory interface shear experiments was performed to assist interpretation of the centrifuge tests it is shown that although the cycling associated with pile installation results in a progressive reduction in the stationary horizontal effective stress acting on a pile shaft and densification of the sand in a shear band close to the pile shaft this sand dilates strongly during subsequent shearing to failure in a static load test the dilation the amount of which depends on the cyclic history is constrained by the sur rounding soil and therefore leads to large increases in lateral effective stresses and hence to large increases in mobi lized shaft friction the increase in lateral stress is shown to be related to the radial stiffness of the soil mass constraining dilation of the shear band and to be consistent with measurements made in appropriate cns interface shear tests the paper s findings assist in the extrapolation of model scale pile test results to full scale conditions

kinematic model of active deformation in central asia the velocity field of present day deformation in central asia is modelled using a set of four rotating blocks siberia tarim tibet india on a spherical earth a best fit is inverted on the basis of estimated shortening rates across the main thrust zones himalayas tien shan and measured slip rates along the principal strike slip faults altyn tagh and karakorum separating those blocks the fit to the data implies that nearly all the present convergence between india and asia can be accounted for by slip partitioning on these four zones with as much as 50 absorbed by northeastwards extrusion of tibet this suggests that localised deformation governs the present mechanical behaviour of the central asian lithosphere

block modeling with connected fault network geometries and a linear elastic coupling estimator in spherical coordinates geodetic observations of interseismic deformation provide constraints on the partitioning of fault slip across plate boundary zones the spatial distribution of both elastic and inelastic strain accumulation and the nature of the fault system evolution here we describe linear block theory which decomposes surface velocity fields into four components 1 plate rotations 2 elastic deformation from faults with kinematically consistent slip rates 3 elastic deformation from faults with spatially variable coupling and 4 homogeneous intrablock strain elastic deformation rates are computed for each fault segment in a homogeneous elastic half space using multiple optimal planar cartesian coordinate systems to minimize areal distortion and triangular dislocation elements to accurately represent complex fault system geometry block motions fault slip rates elastic coupling and internal block strain rates are determined simultaneously using a linear estimator with constraints from both geodetically determined velocity fields and geologic fault slip rate estimates we also introduce algorithms for efficiently implementing alternative fault network geometries to quantify parameter sensitivity to nonlinear perturbations in model geometry

uniform postglacial slip rate along the central 600 km of the kunlun fault tibet from 26al 10be and 14c dating of riser offsets and climatic origin of the regional morphology late pleistocene holocene sinistral slip rates on several segments of the kunlun fault in northeastern tibet have been determined these determinations are based on the measured displacement of alluvial surfaces whose surface ages were determined by cosmogenic 2 6 al and 1 0 be dating of quartz pebbles and by 1 4 c dating of charcoal in the west at three sites along the xidatan dongdatan segment of the fault near 94 e terrace riser offsets ranging from 24 to 110 m with cosmogenic ages ranging from 1800 to 8200 yr yield a mean left lateral slip rate of 11 7 1 5 mm yr 1 field observations indicate minimum offsets of 9 12 m this offset when combined with the long term slip rate indicates that great earthquakes m 8 rupture this segment of the fault with a recurrence interval of 800 1000 yr at two sites along the dongxi anyemaqin segment of the fault near 99 e terrace riser offsets ranging from 57 to 400 m with 1 4 c ages ranging from 5400 to 37 000 yr bp yield a minimum slip rate of 10 mm yr 1 at one site the 1937 january 7 m 7 5 and the penultimate earthquakes produced 4 m of left slip and 0 4 m of reverse slip the maximum recurrence interval of earthquakes with such characteristic slip is thus 400 yr farther east near 100 5 e along the maqen segment of the fault the 180 m offset of a lateral moraine emplaced between the last glacial maximum 20 ka and 11 100 yr bp yields a mean slip rate of 12 5 2 5 mm yr 1 the slip rates are constant within uncertainty throughout the 600 km of the kunlun fault that we studied the average slip rate is 11 5 2 0 mm yr 1 extrapolating this rate to the reminder of the fault we conclude that most 80 per cent of the 300 morphological offsets measured in the field or on spot satellite images post date the last glacial maximum most of the terraces we studied were deposited during the humid period of the early holocene optimum 9 5 ka the formation of younger terraces reflects late holocene climate change

contemporary crustal deformation of northeast tibet from geodetic investigations and a comparison between the seismic and geodetic moment release rates abstract we processed the data recorded by 32 continuous gps stations from the crustal movement observation network of china and combined them with published gps observations in a common geodetic reference frame to better depict the ongoing crustal velocities and deformation field of northeast tibet the derived velocity field indicates that the deformation of northeast tibet is characterized mainly by crustal shortening coupled with the eastward extrusion of crustal material and clockwise block rotation we further used the gps velocity field to evaluate the strain rate tensors by the method of sandwell and wessel 2016 the strain rate field shows an obvious transition of the contraction rate from ne sw to nee sww and a decrease in the maximum shear strain rate from west to east was observed along the east kunlun fault and haiyuan fault indicating that the block rotation and lateral extrusion therein may be partitioned by ne sw oriented compression to some extent the inhomogeneity of the rotation strain rate implies that northeast tibet does not behave like a single rigid block but instead resembles a left lateral shear zone supporting the hypothesis that the northward transfer of motion along the east kunlun fault may play a significant role in the deformation style of this area the dilatation rate verified that most of northeast tibet experiences crustal thickening which coincides with the average uplift rate of 1 mm y revealed by gps velocities and channel steepness indices we also estimated the geodetic moment rates and compared them with the seismic moment rates estimated using the truncated gutenberg richter earthquake distribution the ratio of the seismic strain rate to the geodetic strain rate in the regions near the altyn tagh fault the qaidam basin adjoining the qilian mountains the haiyuan fault and the central part of the east kunlun fault are near unity indicating that the deformation in these areas is dominated by seismic release and may represent fully coupled seismogenic zones the occurrence of large earthquakes in the past estimated magnitudes m 6 coupled with a high geodetic deformation rate in these regions could indicate overdue m 6 earthquakes however other factors including the occurrence of creep and the long recurrence time of mw 8 0 earthquakes should be taken into consideration along the haiyuan fault by contrast in other regions including the southern and eastern parts of the haiyuan fault along the elashan fault and the northern qilian mountains the geodetic moment rate is higher than the seismic moment rate by a factor between 3 and 9 we propose that this phenomenon is related to the undersampling of long term earthquake rates within the seismic catalogue long term aseismic crustal deformation or a combination of these factors our study has implications for better comprehending the current seismotectonic pattern of northeast tibet

short term vertical velocity field in the apennines italy revealed by geodetic levelling data we estimate current vertical movements along the apennines italy through repeatedly measured high precision levelling routes in order to highlight regional crustal deformation the analysis of a geodetic database with a minimum benchmark density of 0 7 bm km 1943 2003 time period is carried out we evaluate systematic and random error and their propagation along the levelling routes tests on original raw height data have been carried out to define error propagation the computed relative vertical rates stand significantly above error propagation a series of traverses along and across the apennines and a map of relative vertical velocities reveal a geodetic signal characterised by values up to 2 5 3 0 mm a and by wavelengths up to 100 km

contemporary crustal deformation around the southeast borderland of the tibetan plateau 1 we derive a detailed horizontal velocity field for the southeast borderland of the tibetan plateau using gps data collected from the crustal motion observation network of china between 1998 and 2004 our results reveal a complex deformation field that indicates that the crust is fragmented into tectonic blocks of various sizes separated by strike slip and transtensional faults most notably the regional deformation includes 10 11 mm yr left slip across the xianshuihe fault 7 mm yr left slip across the anninghe zemuhe xiaojiang fault zone 2 mm yr right slip across a shear zone trending northwest near the southern segment of the lancang river fault and 3 mm yr left slip across the lijiang fault deformation along the southern segment of the red river fault appears not significant at present time the region south and west of the xianshuihexiaojiang fault system whose eastward motion is resisted by the stable south china block to the east turns from eastward to southward motion with respect to south china resulting in clockwise rotation of its internal subblocks active deformation is detected across two previously unknown deformation zones one is located 150 km northwest of and in parallel with the longmenshan fault with 4 6 mm yr right slip and another is continued south southwestward from the xiaojiang fault abutting the red river fault with 7 mm yr left slip while both of these zones are seismically active the exact locations of faults responsible for such deformation are yet to be mapped by field geology comparing our gps results with predictions of various models proposed for tibetan plateau deformation we find that the relatively small sizes of the inferred microblocks and their rotation pattern lend support to a model with a mechanically weak lower crust experiencing distributed deformation underlying a stronger highly fragmented upper crust

present day kinematics at the india asia collision zone the collision of the indian subcontinent with asia drives the growth and evolution of the greater tibetan plateau region fault slip rates resulting from the relative motion between crustal blocks can provide a kinematic description of the distribution of presentday deformation i construct a three dimensional regional scale elastic block model of the india asia collision zone that is consistent with geodetic observations of interseismic deforma tion mapped fault system geometry historical seismicity and the mechanics of the earthquake cycle this mechanical model of the elastic upper crust yields a set of kinematically consistent fault slip rates and block motions that may serve to constrain dynamic models of continental crustal dynamics

slip rates and seismic moment deficits on major active faults in mainland china 1 the chinese mainland features widespread active faults and intensive seismic activity both can be described in terms of slip rates on these faults previous studies of fault slip rates in mainland china have focused on individual faults or fault segments and large discrepancies exist among results derived from different methods here we derive a self consistent estimate of the slip rates on all major faults in mainland china using the recently updated gps data and an elastic block model the predicted slip rates are high in western and low in eastern china ranging from 25 1 2 0 mm yr in the himalayan thrust system to less than 1 0 mm yr in north china using these slip rates we estimated the rates of moment accumulation on the major fault zones and compared them with the seismic moment released on each fault zone using the chinese historical earthquake catalog that extends for more than 2000 years in many regions the results show nine seismic zones with large moment deficits unreleased moment future refinement of gps measurements and earthquake history will allow better estimates of slip rates on individual faults and better assessment of earthquake hazard on these faults in mainland china

dissipation of fast strike slip faulting within and beyond northeastern tibet structural patterns global positioning system gps velocities and quaternary fault slip rates in northeastern tibet indicate a transfer of left lateral slip from the kunlun fault northeast to the haiyuan fault and minor crustal shortening and rotation within a 200 km wide stepover zone related deformation also continues at least a few hundred kilometers north of the haiyuan fault into a region of diffuse extensional shear or rotation underlain by average thickness crust fast localized slip along the central kunlun fault transforms into distributed deformation across a 500 km wide zone where the lower crust is weak the distribution of fault parallel gps velocities across this region suggests a decrease in fault slip toward eastern fault tips and progressive dissipation of slip to the north rather than east of the tibetan plateau as previously suggested

three dimensional velocity field of present day crustal motion of the tibetan plateau derived from gps measurements 1 using the measurements of 750 gps stations around the tibetan plateau for over 10 years since 1999 we derived a high resolution 3 d velocity field for the present day crustal movement of the plateau the horizontal velocity field relative to stable eurasia displays in details the crustal movement and tectonic deformation features of the india eurasia continental collision zone with thrust compression lateral extrusion and clockwise rotation the vertical velocity field reveals that the tibetan plateau is continuing to rise as a whole relative to its stable north neighbor however in some subregions uplift is insignificant or even negative the main features of the vertical crustal deformation of the plateau are the following a the himalayan range is still rising at a rate of 2 mm yr the uplift rate is 6 mm yr with respect to the south foot of the himalayan range b the middle eastern plateau has a typical uplift rate between 1 and 2 mm yr and some high mountain ranges in this area like the longmen shan and gongga shan have surprising uplift rates as large as 2 3mm yr c in the middle southern plateau there is a basin and endorheic subregion with a series of ns striking normal faults showing obvious sinking with the rates between 0 and 3 mm yr d the present day rising and sinking subregions generally correspond well to the cenozoic orogenic belts and basins respectively e at the southeastern corner of the plateau there is an apparent trend that the uplift rate is gradually decreasing from between 0 8 and 2 3 mm yr in the inner plateau to between 0 5 and 1 6 mm yr outside the plateau with the decrease of terrain height

present day crustal motion within the tibetan plateau inferred from gps measurements 1 using the measurements of 726 gps stations around the tibetan plateau we determine the rigid rotation of the entire plateau in a eurasia fixed reference frame which can be best described by an euler vector of 24 38 0 42 n 102 37 0 42 e 0 7096 0 0206 ma the rigid rotational component accommodates at least 50 of the northeastward thrust from india and dominates the eastward extrusion of the northern plateau after removing the rigid rotation to highlight the interior deformation within the plateau we find that the most remarkable interior deformation of the plateau is a glacier like flow zone which starts at somewhere between the middle and western plateau goes clockwise around the eastern himalayan syntaxis ehs and ends at the southeast corner of the plateau with a fan like front the deformation feature of the southern plateau especially the emergence of the flow zone could be attributed to an eastward escape of highly plastic upper crustal material driven by a lower crust viscous channel flow generated by lateral compression and gravitational buoyancy at the later developmental stage of the plateau the first order feature of crustal deformation of the northeastern plateau can be well explained by a three dimensional elastic half space dislocation model with rates of dislocation segments comparable to the ones from geological observations in the eastern plateau although gps data show no significant convergence between the eastern margin of the plateau and the sichuan basin a small but significant compressional strain rate component of 10 5 2 8 nstrain yr exists in a relatively narrow region around the eastern margin in addition a large part of the eastern plateau northeast of the ehs is not undergoing shortening along the northeastward convergence direction of the ehs but is stretching

millennial slip rates of the tazang fault the eastern termination of kunlun fault implications for strain partitioning in eastern tibet abstract the way of slip transformation and strain partitioning at the eastern termination of the kunlun fault system remains unclear and the question of whether this fault system is an important part for lateral extrusion of tibetan crust is debatable the tazang fault is regarded as the easternmost continuation of the kunlun fault system and its late quaternary activity is unknown in this paper we use displaced geomorphic features combined with radiocarbon and optically stimulated luminescence osl dating to determine millennial slip rates along the tazang fault our data yield a 1 4 3 2 mm yr left slip rate on the western tazang fault similar to that on the maqu segment of the kunlun fault tectonic geomorphology proposes that displacement on the kunlun fault is probably transferred to the tazang fault via a pull apart basin the eastern tazang fault has a dominant reverse motion that decreases eastward from 1 5 mm yr to 0 2 0 3 mm yr at the easternmost part displaced terraces indicate that the eastern strand of the northern longriba fault is active in the holocene and has a 0 8 mm yr right lateral slip rate with a 0 3 mm yr reverse component millennial slip rates and geodetic results show that the decrease of left lateral motion along the tazang fault is mainly transformed into crustal shortening along the nearly n s trending longriba minjiang and huya faults probably resulting in uplift of the min shan our results also indicate that the deformation along the tazang fault is not transferred to beyond the border of the plateau and the kunlun fault is not an important tectonics for tibetan extrusion

neotectonics of the min shan china implications for mechanisms driving quaternary deformation along the eastern margin of the tibetan plateau the min shan region located along the eastern margin of the tibetan plateau north of the sichuan basin provides an important natural laboratory in which to study the rates and patterns of deformation and their relationship to mountain building at the margin of the plateau the topographic margin of the plateau is coincident with a north trending mountain range the min shan that stands nearly 2 km above the mean elevation of the plateau 3500 m in this region we exploit the preservation of a series of variably deformed quaternary sediments along the western flank of the range to investigate the pleistocene holocene deformation field within the min shan region mapping and field observations of remnant alluvial fans of late pleistocene age indicate that deformation within the min shan involved substantial 10 rapid down to the northwest tilting the geometry of the deposits and the partial preservation of an erosion surface beneath the basin suggest that much of the modern relief of the min shan relative to the tibetan plateau is a consequence of this late pleistocene tilting rates of tilting inferred from luminescence dating of interbedded loess have been remarkably rapid 10 8 rad yr similarly rapid rates of holocene differential rock uplift are inferred from tilted lacustrine sediments in the southwestern part of the range the range is bounded on the west by the min jiang fault zone an east vergent reverse fault however holocene alluvial terraces in headwaters of the min river are preserved across the fault in several places indicating that displacement rates on the min jiang fault are 1 mm yr active faulting only occurs along the eastern foot of the range huya fault for a short distance 60 km despite 3 km of relief on the eastern range front the relationship between these structures and the tilting observed in the min jiang basin is enigmatic the faults do not appear to exert a strong control on the rates and pattern of deformation within the basin a simple flexural model demonstrates that rates of tilting on the western flank of the min shan are too high to be simply attributed to an isostatic response to surficial loading and unloading of the lithosphere present day horizontal shortening across the min shan is geodetically determined to be less than 2 3 mm yr suggesting that only a small part of the observed tilting can be attributed to horizontal shortening thus tilting and concomitant differential rock uplift in the min shan appear to require an additional driving component we suggest that quaternary deformation along the western min shan may reflect the surface response to thickening of a weak lower crust at the margin of the tibetan plateau

active deformation of asia from kinematics to dynamics using estimated strain rates across the actively deforming region of asia to infer variations in viscous stress it is shown that gradients of stress point uphill toward the center of tibet where gravitational potential energy per unit surface area reaches a maximum thus the dynamics of the deformation seem to obey the equation of creeping flow which expresses a balance between gradients in stress and the gravitational body force this balance in the region of the tibetan plateau yields an estimate of 10 22 pascal second for the average viscosity of the tibetan lithosphere which is only about 10 to 100 times greater than the viscosity of the convecting upper mantle

co2 storage potential of south african coals and gas entrapment enhancement due to igneous intrusions abstract methane outburst events have occurred in some underground coal mines of south africa such as those in twistdraai mine in the highveld coalfield in the early 1990s occurrences of methane outbursts suggest that high gas content in adsorbed and free phase might be present in some sections of the coal seams coal seams might also be friable in those sections allowing pulverisation during outburst the survey of gas outburst events indicates that the locations of high gas emissions were mainly in the vicinity of the igneous intrusions mainly dolerite intrusions these intrusions are a result of post depositional volcanism into coal seams in some major coalfields of south africa such as the highveld coalfield this study was undertaken firstly to investigate potential locations for the occurrence of coal seam gas in south african coal seams with respect to the igneous intrusions and their enhancement effect on gas release and storage of these coals secondly it was thought that as the metamorphosed coals with high ash content were not economically viable for mining they might be potentially suitable for co 2 disposal measurements on 14 coal samples taken in an underground coal mine at various distances from a dolerite dyke show that the adsorption and porosity properties of metamorphosed coals have been enhanced thus increasing their gas storage capacity diffusivity results show that dolerite intrusions would act as enclosures and gas traps for storage of gas gas diffusivity was greater in coals near the dyke by a factor of two in general it is expected that the co 2 storage and gas flow properties of such coals be enhanced due to the heating effect of intrusions making the coals more appealing for possible future sequestration of co 2 from anthropogenic sources

empirical approach based on centrifuge testing for cyclic deformations of laterally loaded piles in sand a systematic study into the response of monopiles to lateral cyclic loading in medium dense and dense sand was performed in beam and drum centrifuge tests the centrifuge tests were carried out at different cyclic load and magnitude ratios while the cyclic load sequence was also varied the instrumentation on the piles provides fresh insights into the ongoing development of net stresses bending moments and deflections as cycling progresses parallels between the test results and corresponding cyclic triaxial tests are drawn the paper combines the results from this study with those from previous experimental investigations to provide empirical design recommendations for monopiles subjected to unidirectional cyclic loading

contrasting crustal deformation mechanisms in the longmenshan and west qinling orogenic belts ne tibet revealed by magnetotelluric data abstract the northeastern margin of tibet is the youngest risen part and key area for understanding the growth mechanism of the tibetan plateau new broadband magnetotelluric mt data are conducted at the conjunction of the longmenshan and west qinling orogenic belts in ne tibet the preferred resistivity model obtained using 3 d inversion method shows a dramatic resistivity contrast from the sichuan basin sb to the west qinling orogenic belt wqob beneath the sb and longmenshan orogenic belt lmsob several low resistivity zones are distributed in the upper crust underlain by an intact resistive lower crust indicating the upper crustal deformation is responsible for the uplift of the lmsob while to the north a prominently conductive lower crust is observed favoring the ductile deformation of the weak lower crust plays a significant role in the crustal thickening of the wqob therefore we suggest contrasting crustal deformation mechanisms work in the lmsob and wqob and diversified crustal deformations together contribute to the marginal growth of the plateau moreover combining with other studies we propose the deep conductive bodies beneath the wqob would be induced by the hot upwelling related to the asthenospheric flow from the plateau

variations in locking along the east kunlun fault tibetan plateau china using gps and leveling data the east kunlun fault ekf is one of the largest and most active sinistral strike slip faults in the qinghai tibet plateau since 1900 many earthquakes of magnitude 7 have occurred in this region the maqin maqu segment mms a seismic gap underlying a densely populated zone is particularly important while the area has been extensively researched to assess seismic risk refined asperity geodetic imaging is deficient we combined multiple sets of gps and leveling observations to obtain spatial temporal distributions of locking along the ekf we delineated the probable asperity ranges according to the fault plane locking and the distribution of small earthquakes long term observations on gps velocity 1999 2013 and leveling 1970 2013 indicate that the dulan maduo segment dms of the ekf has a 140 km long strong coupling section and both the mms and the eastern ruoergai segments have a 40 km long locking range the 2013 2015 gps velocity observations show that from maqu to maqin the locked dms and mms lengths increased to 200 km and 240 km respectively while the locked eastern ruoergai segment decreased and migrated 60 km to the west this change in locking over time implies that the post seismic effects of surrounding earthquakes have had significant impacts on the ekf the locking area derived from 2015 to 2017 gps velocity shows a growing trend and indicates the connectedness between the two speculative asperities combining the distribution of historical earthquakes and the precision positioning of small earthquakes we conclude that the geodetic imaging of the ekf indicates that the mms and dms are high risk zones for destructive earthquakes

present day crustal deformation and strain transfer in northeastern tibetan plateau abstract the three dimensional present day crustal deformation and strain partitioning in northeastern tibetan plateau are analyzed using available gps and precise leveling data we used the multi scale wavelet method to analyze strain rates and the elastic block model to estimate slip rates on the major faults and internal strain within each block our results show that shear strain is strongly localized along major strike slip faults as expected in the tectonic extrusion model however extrusion ends and transfers to crustal contraction near the eastern margin of the tibetan plateau the strain transfer is abrupt along the haiyuan fault and diffusive along the east kunlun fault crustal contraction is spatially correlated with active uplifting the present day strain is concentrated along major fault zones however within many terranes bounded by these faults intra block strain is detectable terranes having high intra block strain rates also show strong seismicity on average the ordos and sichuan blocks show no intra block strain but localized strain on the southwestern corner of the ordos block indicates tectonic encroachment

lithospheric structure across the northeastern margin of the tibetan plateau implications for the plateau s lateral growth abstract variations of lithospheric structure across the northeastern tibetan plateau and its bounding asian blocks the alxa block to the north and the ordos block to the east are crucial for understanding the rise and lateral growth of the tibetan plateau using waveforms from high density seismic arrays in northeastern tibetan plateau and the surrounding regions we investigated the lithospheric structure with s and p wave receiver functions the results show strong and relatively simple negative velocity gradients in the depth range of mantle lithosphere 70 150 km under the ordos and alxa blocks similar to those under typical stable continental lithosphere in contrast under northeastern tibetan plateau including its marginal regions the velocity gradients are weak and diffusive for the mantle lithosphere which may be explained by elevated temperature and presence of partial melts the changes of lithospheric structures are sharp between the tibetan plateau and the bounding ordos and alxa blocks suggesting that these two blocks have restricted the lateral growth of the tibetan plateau as rigid boundaries however across the northeastern corner of the tibetan plateau to the yinchuan rift the lithospheric mantle structures are similar suggesting a lateral mantle flow from the tibetan plateau to the gap between the ordos and the alxa blocks the crustal structures along this transition show evidence of lateral growth of the tibetan plateau in particular the edge of thickened crust and evidence of moho superposition are found between the haiyuan fault and the tianjin shan fault which may have replaced the haiyuan fault as the front boundary of the laterally growing tibetan plateau in its northeastern corner

northeastward growth of the tibet plateau deduced from balanced reconstruction of two depositional areas the qaidam and hexi corridor basins china we address the problem of late cenozoic uplift erosion and growth of northeastern tibet by reconstructing from isopach maps and drill holes the volumes and masses of sediments deposited in the qaidam and hexi corridor basins since 35 myr ago the mass budget is based on simple geometrical assumptions such as regional similarity of the thickness ratios between strata of different ages in the qaidam where our record extends back to the oligocene the budget shows a huge rise of the accumulation rates after the beginning of the pliocene 5 3 ma the early pliocene seems to be the period of maximum deposition with accumulation rates in excess of 1 mm yr 1 2 7 kg m 2 yr 1 of compacted rocks throughout the basin there also seems to be a southeastward shift of the largest depocenters between the upper pliocene 3 4 1 6 ma and the quaternary in the hexi corridor sedimentation is confined to small foreland flexural depressions associated with the frontal thrusts of the qilian shan and occurs at an average rate one order of magnitude smaller than in the qaidam basin the accumulation rate is maximum in the quaternary the sedimentation history appears to support a plateau building mechanism resulting from the combination of two geologicallly common processes crustal scale thrusting and sedimentary basin infilling the time needed to completely fill the qaidam basin and make its catchment a plateau closely resembling that of the highest part of tibet qangtang is of the order of 9 myr the mechanism now at work north of the kunlun which involves rapid infilling of broad flat areas separated by relatively narrow mountain ranges has thus probably been important in producing the high smooth topography that characterizes much of central tibet

cenozoic tectonic evolution of the qaidam basin and its surrounding regions part 3 structural geology sedimentation and regional tectonic reconstruction the qaidam basin is the largest topographic depression inside the tibetan plateau because of its central position understanding the tectonic origin of the qaidam basin has important implications for unraveling the formation mechanism and growth history of the tibetan plateau in order to achieve this goal we analyzed regional seismic reflection profiles across the basin and a series of thickness distribution patterns of cenozoic strata at different time slices the first order structure of the basin is a broad cenozoic synclinorium which has an amplitude ranging from 16 km in the west to 48 in the west to 15 s 1 to 1 3 10 17 s 1 the eastward decrease in upper crustal shortening requires a progressive shift in crustal thickening mechanisms across qaidam basin from dominantly upper crustal shortening in the west to dominantly lower crustal shortening in the east although sedimentation began synchronously at 65 50 ma across the entire basin the initiation ages of the southern and northern basin bounding structures are significantly different deformation started at 65 50 ma in the north and at 29 24 ma in the south this information and the existing inference that the uplift of the eastern kunlun range south of qaidam basin began after 30 20 ma imply that the paleogene 65 24 ma qaidam and hoh xil basins on both sides of the eastern kunlun range may have been parts of a single topographic depression 500 km wide in the north south direction between the qilian shan and fenghuo shan thrust belts in the north and south the development of this large paleogene basin in central tibet and its subsequent destruction and partitioning by the neogene uplift of the eastern kunlun range requires a highly irregular sequence of deformation possibly controlled by preexist ing weakness in the tibetan lithosphere

active fold deformation and crustal shortening rates of the qilian shan foreland thrust belt ne tibet since the late pleistocene abstract quantification of crustal shortening rates across foreland fold and thrust belts is essential for evaluating how convergence is accommodated throughout the orogenic belt and analyzing seismic hazard in neighboring cities in this study we focused on active fold along the western portion of the qilian shan foreland thrust belt in ne tibet the shortening rate across the hujiatai anticline ha along the eastern segment of the fodongmiao hongyazi fault fhf is 0 8 0 2 mm a based on terrestrial cosmogenic nuclide tcn dating of deformed late pleistocene fluvial terrace when this rate is combined with the shortening rates of 1 1 1 4 mm a and 0 7 1 2 mm a along the western and central segments obtained by previous studies it is apparent that crustal shortening rates along the fhf gradually decrease to the east this eastward decrease in fault activity may be a result of the northward propagation of the fhf or partitioning of strain off to nearby faults or folds furthermore tectonic geomorphology and trenching suggest that several thrust faults around the ha ruptured during the historical 1609 earthquake combining the shortening rate of 0 6 0 8 mm a across the north side of the jiudong basin with our rate we suggest that the total crustal shortening rate across the basin is about 1 3 2 2 mm a assuming little internal deformation which accounts for roughly 20 40 of the amount of crustal shortening deformation across the qilian block these results demonstrate that the qilian shan foreland basin plays an important role in accommodating the crustal deformation of northeastern tibet

rayleigh wave tomography of the northeastern margin of the tibetan plateau abstract the convergence between the indian continent and the southern margin of eurasia has eventually led to the growth of the tibetan plateau eastward various models have suggested that a large scale flow in the lower crust or and the asthenosphere is responsible for the uplift of eastern tibet it has also been suggested that the continental flow may move around the thick lithosphere of the ordos plateau and the sichuan basin in order to investigate the validity of the crust mantle flow and its possible path we have used rayleigh wave tomography with sensitivity kernels to estimate both the phase velocity structure 20 143 s and the shear wave velocity structure 0 200 km across the northeastern margin of the tibetan plateau from the surface to 100 km our shear wave velocity model shows a prominent low velocity anomaly beneath northeastern tibet suggestive of a warm lithosphere its boundary lies at 105 e longitude which borders the western ordos plateau and sichuan basin from 125 km to 200 km our shear wave velocity model shows a low velocity channel beneath the qilian qinling orogen that lies between the ordos and sichuan blocks this channel may represent the asthenosphere given the fact that the lithosphere is 120 150 km thick in northeastern tibet and the qinling orogen we also inverted for the anisotropy parameters in the study area simultaneously with the velocity parameters the dominant fast direction is nww see generally consistent with the sks splitting results the calculated shear strain from gps and the fault slip rate measurements furthermore the fast directions in our anisotropic model vary only slightly with periods and the anisotropy magnitudes at long periods 100 143 s are large and exceed those at short medium periods 20 80 s indicating potentially although not necessarily vertically coherent deformation from the crust to the asthenosphere and possibly large deformation in the asthenosphere the deformation seems to be linked to the southeastward extrusion tectonics caused by the collision boundary force

piles under cyclic axial loading study of the friction fatigue and its importance in pile behavior the main point of this paper is to identify the key features and load transfer mechanisms controlling friction fatigue of piles under cyclic loading numerical modeling makes use of an advanced ela

lateral growth of ne tibetan plateau restricted by the asian lithosphere results from a dense seismic profile abstract we present high resolution receiver function images along a 700 km long dense seismic array extending from northern tibetan plateau to the alxa block crossing the entire qilian thrust belt qtb the dense stations with less than 2 km station intervals allow the receiver functions to unveil unprecedented details of crustal structures across the northern frontier of the growing tibetan plateau the migration image shows a thickened and strongly deformed qtb crust with an uneven moho and complex internal structures that are indicative of pure shear shortening the alxa block in contrast has a thinner crust a flat moho and little internal crustal deformation these results suggest that the lateral growth of ne tibetan plateau is restricted by the strong asian lithosphere which shows no visible subduction beneath the tibetan plateau as previously suggested

finite strain calculations of continental deformation 2 comparison with the india asia collision zone numerical experiments on a thin viscous sheet model for deformation of continental lithosphere subjected to an indenting boundary condition yield distributions of crustal thickness of stress and strain rate and of latitudinal displacements that may be compared with observations in the india asia collision zone a simple indenting boundary condition applied to initially laterally homogeneous sheets obeying a power law rheology produces results that are in broad agreement with the observations provided that the power law exponent is three or greater and the sheet can support vertically integrated stress differences of 2 1013 5 1012 n m 1 in regions in front of the indenter under these conditions the calculated deformation shows accommodation of convergence primarily by crustal thickening to produce a plateau in front of the indenter palaeomagnetic data from india and tibet and the observed distribution of topography suggest that much of the post eocene convergence of india with asia has been taken up by deformation within asia that involved crustal thickening the principal difference between calculation and observation is the absence from the calculated strain rate fields of east west extension of the plateau in front of the indenting boundary the calculations show that once such a plateau is formed the buoyancy force associated with the crustal thickness contrast inhibits further thickening and the plateau strains at less than half the rate of its immediate surroundings seismically determined regional strain rates exhibit a similar distribution with the tibetan plateau straining at about one quarter the rate of the tien shan and ningxia gansu regions calculated principal compressive stress orientations and regional strain rates agree with the seismically determined quantities in the mongolia baikal tien shan tibet and ningxia gansu regions of asia to within the uncertainty of the latter the vertically integrated stresses that are calculated for the viscous sheet are comparable with those that can be supported by a theologically stratified continental lithosphere obeying laboratory determined flow laws we suggest that the thin viscous sheet model described in this paper and its companion gives a simple and physically plausible description of the observed deformation in central asia in this description the predominant mechanism of accommodation of continental convergence is diffuse crustal thickening with shear on vertical planes playing a subsidiary role once large crustal thickness contrasts have been established

oblique stepwise rise and growth of the tibet plateau two end member models of how the high elevations in tibet formed are i continuous thickening and widespread viscous flow of the crust and mantle of the entire plateau and ii time dependent localized shear between coherent lithospheric blocks recent studies of cenozoic deformation magmatism and seismic structure lend support to the latter since india collided with asia 55 million years ago the rise of the high tibetan plateau likely occurred in three main steps by successive growth and uplift of 300 to 500 kilometer wide crustal thrust wedges the crust thickened while the mantle decoupled beneath gently dipping shear zones did not sediment infilling bathtub like of dammed intermontane basins formed flat high plains at each step the existence of magmatic belts younging northward implies that slabs of asian mantle subducted one after another under ranges north of the himalayas subduction was oblique and accompanied by extrusion along the left lateral strike slip faults that slice tibet s east side these mechanisms akin to plate tectonics hidden by thickening crust with slip partitioning account for the dominant growth of the tibet plateau toward the east and northeast

active crustal deformation in southeastern tibetan plateau the kinematics and dynamics abstract crustal deformation in southeastern tibetan plateau has been attributed to tectonic extrusion and gravitational spreading here we analyzed the present day strain partitioning in this region using gps data the results show highly localized shear strain along the xianshuihe anninghe xiaojiang strike slip faults as expected by the model of tectonic extrusion however the localized shear strain along strike slip faults ends in southern yunnan and transfers to crustal extension in yunnan and contraction in myanmar we developed three dimensional visco elastoplastic finite element models to investigate the causes of the observed crustal deformation our results indicate that the present day crustal deformation in southeastern tibetan plateau can be largely explained by gravitational spreading

late quaternary right lateral slip rates of faults adjacent to the lake qinghai northeastern margin of the tibetan plateau by combining terrace riser offsets with terrace ages dated by 14 c optically stimulated luminescence osl and 10 be techniques we determine average slip rates of 1 1 0 3 mm yr and 1 2 0 4 mm yr for the elashan and riyueshan faults two north northwest trending right lateral strike slip faults west and east of the lake qinghai in the northeastern margin of the tibetan plateau these faults are conjugate to the major easterly trending left lateral altyn tagh haiyuan qilianshan and kunlun faults and they contribute to the subdivision of the region between the haiyuan qilianshan and kunlun faults into small blocks tens to 100 km in dimension the relatively low slip rates in this region reflect distributed deformation the total right lateral offsets of geological contacts are 9 12 km along the elashan fault and 11 12 km for the northern segment of the riyueshan fault if long term slip rates were constant during late cenozoic time dates of initiation of dextral movement would be 9 or 10 3 ma for the two strike slip faults concurrent with onsets or acceleration of tectonic deformation in cenozoic basins nearby our study highlights a stage of tectonic deformation in the northeastern margin of the tibetan plateau beginning since ca 8 12 ma tens of millions of years after the collision between india and eurasia began

late quaternary left lateral slip rate of the haiyuan fault northeastern margin of the tibetan plateau 1 slip rates of major active strike slip faults within and around the tibetan plateau provide constraints for understanding the dynamics of continental deformation in general because large slip rates can be taken to imply localized deformation between rigid blocks and low slip rates on faults are more consistent with distributed deformation several major strike slip faults have been studied during the last 3 decades as one of important active strike slip faults in and around the tibetan plateau the slip rate of the haiyuan fault has been discrepantly estimated to be high by proponents of escape tectonics or low by others and gps observations to better constrain its slip rate and then to better understand the mechanics of intracontinental deformation we try to more carefully consider offset geomorphic features and age constraints along the haiyuan fault in this paper we select three sites where both upper and lower bounds of slip rate can be obtained we find that slip rates are 4 2 0 8 mm yr at the shaomayin 4 5 0 7 mm yr at gaowanzi and 5 0 2 5 mm yr at huangliangtan site combinations of these rates with those published previously yield an average slip rate of 4 5 1 0 mm yr on the haiyuan fault this rate agrees with the present day slip rate of 4 3 1 5 mm yr measured by gps 4 2 8 mm yr by interferometric synthetic aperture radar and 5 mm yr through paleoseismological studies the temporal consistency suggests a steady state process of strain accumulation and release along the haiyuan fault the low slip rate suggests that the haiyuan fault similar to the altyn tagh fault does not transfer a significant portion of the convergence between india and asia out of india s path into eurasia but merely redistributes crustal thickening

differential strain transfer longmen shan thrust belt eastern tibetan plateau margin implications for seismic hazards abstract southeastward strain transfer in the middle southern longmen shan lms thrust belt not only can promote the development of fault related folds and earthquakes in the piedmont but also affect the seismogenic capacity of the middle southern lms thrust belt however the detailed transfer process remains elusive in this work we combine structural profile re analysis sandbox modeling and seismic statistics to illustrate the strain transfer process our main results indicate that 1 the thickness of the shallow detachment e g middle lower triassic gypsum salt strata is probably the main factor for differences in southeastward strain transfer within the domain between the middle southern lms thrust belt and weiyuan moxi anticline this is also supported by our sandbox model 2 the seismogenic capacity in the southern lms thrust belt is probably proportional to the corresponding shortening of the range front blind thrust rfbt thus seismogenic capacity in the seismic gap zone is weaker than those of other segments of the southern lms thrust belt which is probably

tertiary basin evolution along the northeastern margin of the tibetan plateau evidence for basin formation during oligocene transtension the development of high topography associated with the indo asian collision plays a central role in ongoing debates over the linkages between development of the tibetan plateau and climate in northeastern tibet the widespread appearance of coarse terrestrial sediment during the oligocene is commonly interpreted to herald the development of a foreland basin in response to crustal thickening along the present day margin of the plateau however a lack of direct observations relating sediment accumulation to fault activity leaves this interpretation uncertain here we present new stratigraphic observations along the northern margin of the longzhong basin that provide insight into the tectonic setting of basin development a combination of field and subsurface observations including the geometry of basin bounding faults sedimentary provenance paleoflow direction isopach and sedimentary facies distribution patterns constrains basin evolution from the middle tertiary through quaternary time our results suggest that ne sw extension across normal faults controlled development of accommodation space in the northern longzhong basin during the oligocene to early miocene continued sediment accumulation from the mid miocene through pliocene occurred in a broad shallow basin consistent with thermal subsidence following extension basin inversion initiated between 10 ma and 6 ma associated with the development of the modern haiyuan fault system our results imply that the onset of tertiary sedimentation in the longzhong basin does not represent a developing foredeep associated with a nascent tibetan plateau but rather reflects transtensional deformation inboard of extensional basins along the east asian margin

balance of seismic moment in the songpan ganze region eastern tibet implications for the 2008 great wenchuan earthquake abstract the 12 may 2008 wenchuan earthquake ms 8 0 occurred on the longmen shan fault zone where slip rates are low and earthquakes are infrequent in comparison with other major fault zones in the songpan ganze region eastern tibet we have investigated the evolution of strain energy along major faults in this region by comparing the accumulation and release of seismic moment first we calculated the slip rates on the longmen shan and other major faults in the region using a three dimensional regional scale block model constrained by the latest gps data on the longmen shan fault the predicted right lateral and dip slip rates are respectively 1 7 0 8 mm year and 1 2 1 0 mm year along the southwestern segments and 1 4 1 1 mm year and 3 3 1 3 mm year on the northeastern segments these slip rates are one order of magnitude lower than those on the xianshuihe fault and other faults in the region second using the earthquake catalog we estimated the scalar moment released on major faults in the songpan ganze region between 1879 and 2007 the released seismic moment was 63 of the regional scalar moment accumulated during this period the moment deficits were found mainly on the western xianshuihe and eastern kunlun faults the eastern xianshuihe fault has been a focus of studies because of the high slip rates and frequent earthquakes but a sequence of major quakes there since 1893 has reduced the moment deficit to 3 68 1019 n m barely enough for a mw 7 0 event it takes the longmen shan fault more than 1000 years to accumulate the seismic moment 1 15 1021 n m released during the 2008 great wenchuan earthquake hence we conclude that a repeat of great earthquakes on the ruptured segment of the longmen shan fault is unlikely in the next few hundred years but the unruptured southwestern segment of the longmen shan fault is capable of producing a mw 7 7 earthquake in the next 50 years

active thrusting and folding in the qilian shan and decoupling between upper crust and mantle in northeastern tibet fieldwork south of the city of gaotai gansu province china shows that active shortening of surface sediments in the foothills of the yumu shan a large fore mountain of the qilian shan at the northeastern edge of tibet involves both overthrusting and flexural slip folding north of this mountain we found and mapped a prominent north facing thrust scarp that offsets a holocene fan sloping gently 3 4 to the north part of this scarp appears to be related to the m 7 5 180 a d earthquake that may have led to the demise of the han dynasty city of luo tuo chen in the hexi corridor a set of 10 100 150 m long profiles measured across this scarp 3 2 m high on the average can be made to fit the diffusion degraded morphology of a surface break related to the 180 a d event using a value of about 3 3 m 2 10 3 yr for the mass diffusivity of fanglomerates in this part of gansu province smaller mountain facing scarps on a terrace capped foothill result from bedding slip concurrent with active folding of underlying steeply northdipping plioquaternary sandstone and conglomerate beds holocene uplift rates along the yumu shan which is only one of the qilian shan ranges are estimated to be between 0 4 and 1 9 mm yr which implies that much of the mountain formed in the quaternary the periclinal structure of the plioquaternary envelope under which the paleozoic core of the yumu shan plunges towards the west suggests that the whole 3200 m high mountain is a basement ramp anticline mountains striking parallel to the yumu shan with similar structure and comparable or greater sizes north and south of the hexi corridor probably also correspond to recent crustal ramp anticlines this implies that the wide mountainous upper crustal wedge making the northeastern edge of the tibet qinghai plateau is detached from the underlying lower crust and upper mantle

cenozoic shortening budget for the northeastern edge of the tibetan plateau is lower crustal flow necessary 1 two of the most popular mechanisms for thickening the crust beneath the tibetan plateau are 1 pure shear with faulting and folding in the upper crust and horizontal shortening below and 2 flow of lower or middle crust without significant shortening of the upper crust to help discriminate between the relative contributions of these two mechanisms well constrained estimates of upper crustal shortening are needed here we document the cenozoic shortening budget across the northeastern tibetan plateau margin with several balanced cross sections that exploit thermochronological and magnetostratigraphic constraints these sections indicate 11 2 1 east west shortening since middle miocene time and 9 2 3 nne ssw shortening between middle eocene and middle miocene times with little subsequent shortening of this orientation shortening rates accelerate fivefold after middle miocene time given the present day crustal thickness of 56 4 km in northeastern tibet crustal restorations that remove cenozoic shortening suggest that the northeastern tibetan crust was 45 5 km thick prior to the india asia continental collision this precollision thickness estimate is equivalent to average continental crustal thicknesses both adjacent to the tibetan plateau 44 4 km and globally 41 6 km and suggests that pure shear alone may account for cenozoic crustal thickening in northeastern tibet in contrast to eastern tibet where in the absence of significant shortening structures crustal flow has been invoked to explain the addition of crustal material since middle miocene time our results may obviate lower crustal flow as a necessary crustal thickening agent in northeastern tibet

long hole destress blasting for rockburst control during deep underground coal mining abstract the lazy colliery in the ostrava karvina coalfield of the upper silesian coal basin adopted modern longwall technology for an underground extraction of coal seam no 504 this coal seam is located at a cover depth of around 700 m the seam thickness varied from 3 1 m to 5 0 m in the selected longwall panel two overlying coal seams nos 512 and 530 experienced mining at average heights of 58 m and 75 m respectively from the planned working horizon of the seam no 504 the proposed longwall panel was adversely situated below goaf edges of the workings in these two overlying extracted seams an analysis of the inter burden rock mass among these coal seams showed the presence of strong massive strata of sandstones and conglomerates with uniaxial compressive strength values between 70 mpa and 120 mpa the stress is measured at different mining stages by compact conical ended borehole monitoring ccbm a simple laboratory test of the coal sample found a high value of the ratio of the elastic deformation to the total deformation 0 8 indicating the energy storing characteristic prone to burst bump of the coal seam under the existing geo mining conditions of the site a suitable destress blasting long hole drilling and blasting design is adopted to pre fracture the identified competent strata from both gate roads in advance the total length of the panel could be extracted without any bump rockburst after the destress blasting the efficiency of the adopted destress blasting at the different mining stages is evaluated in terms seismic effect se which is calculated through the available seismic monitoring data and weight of the charged explosive a systematic adoption of the destress rock blasting led the 300 m long longwall panel to be smoothly extracted without any further rockbursts

cenozoic tectonic evolution of asia a preliminary synthesis abstract asia has been a major testing ground for various competing models of continental deformation due to its relatively well understood plate boundary conditions in the cenozoic exceptional exposure of active structures and strain distribution and widespread syn collisional igneous activity as a proxy for the thermal state of the mantle and crust two cenozoic orogens dominate the continent the himalayan tibetan orogen in the east induced by the india asia collision and the turkish iranian caucasus orogen in the west induced by the arabia asia collision the development of the two orogens was accomplished by shortening in the early stage followed by strike slip faulting and extension in the late stage in the himalayan tibetan orogen shortening across two discrete thrust belts at 55 30 ma in southern and northern tibet created a large intracontinental basin the paleo qaidam basin in between subsequent crustal thickening and a possible thermal event in the mantle e g convective removal of central tibetan mantle lithosphere may have raised the elevation of this early intra plateau basin up to 2 3 km to its current height collision between india and asia also caused lateral extrusion of southeast asia between 32 ma and 17 ma the latest stage of the india asia collision was expressed by north trending rifting and the development of trench facing v shaped conjugate strike slip faults in central mongolia central tibet eastern afghanistan and southeast asia in the turkish iranian caucasus orogen early crustal thickening in the orogenic interior began at or prior to 30 20 ma this style of deformation was replaced by strike slip faulting at 15 5 ma associated with further northward penetration of arabia into asia westward extrusion of the anatolia turkey block and rapid extension across the sea of crete and sea of aegean the late stage extension in both orogens was locally related to extensional core complex development the continental margin extension of east asia was developed in two stages initially in a widely distributed zone that has an east west width of 500 800 km during 65 35 ma which was followed by localized extension and opening of back arc basins associated with the development of spreading centers at 32 17 ma e g japan sea or east korea sea bohai bay and south china sea opening of the back arc basins could be induced by 1 rapid eastward migration of the western pacific trench system or 2 oblique subduction of pacific plate beneath asia that had produced a series of en echelon right slip primary shear zones linking with back arc spreading centers oriented obliquely to the strike of the nearby trench since 15 ma the eastern margin of asia became contractional in the east west direction as indicated by the collapse of back arc basins in the western pacific and the development of fold thrust belts along the eastern continental margin coeval with the contraction is widespread east west extension in siberia north china and the tibetan plateau the above observations can be explained by a change in boundary condition along the eastern margin of asia that allowed the thickened asian continent to spread eastward causing east west extension in its trailing edge and east west compression in its leading edge in west asia continental margin extension started at about 25 20 ma in the aegean and cretan regions which was associated with a rapid southward retreat of the hellenic arc the complex evolution of cenozoic deformation in asia may be explained by a combined effect of temporal changes in plate boundary conditions thermal evolution of the upper mantle perturbed by collisional tectonics and the built up of gravitational energy through crustal thickening and thermal heating although the past research in asia has treated the india asia and arabia asia convergence as separate collisional processes their interaction may have controlled the far field cenozoic deformation in asia the most pronounced result of this interaction is the creation of a northeast trending 300 400 km wide and 1500 km long zone of northwest striking right slip faults which extends from the zagros thrust belt in the south to western mongolia in the north and links with the active tian shan and altai shan intracontinental orogens cenozoic deformation and coeval igneous activity spatially overlap with one another in the himalayan tibetan and turkish iranian caucasus orogens a large cenozoic magmatic gap exists between tibet in the south and mongolia in the north where cenozoic deformation has not been associated with any coeval igneous activity finally cenozoic igneous activity is always associated with jurassic cretaceous magmatic arcs suggesting a causal relationship between the early arc magmatism and later syn collisional magmatism

the geological evolution of the tibetan plateau the geological evolution of the tibetan plateau is best viewed in a context broader than the india eurasia collision zone after collision about 50 million years ago crust was shortened in western and central tibet while large fragments of lithosphere moved from the collision zone toward areas of trench rollback in the western pacific and indonesia cessation of rapid pacific trench migration 15 to 20 million years ago coincided with a slowing of fragment extrusion beyond the plateau and probably contributed to the onset of rapid surface uplift and crustal thickening in eastern tibet the latter appear to result from rapid eastward flow of the deep crust probably within crustal channels imaged seismically beneath eastern tibet these events mark a transition to the modern structural system that currently accommodates deformation within tibet

lithospheric structure of the ordos block and its boundary areas inferred from rayleigh wave dispersion abstract we have measured rayleigh wave phase velocities of the ordos block and its southern and western boundary areas and inverted these data to describe the upper mantle structure the ordos block was found to be characterized by distinctly high seismic velocities at depths commonly associated with a low velocity asthenosphere to the south abnormally slow velocity anomalies appeared in the weihe rift probably indicating subsolidus grain boundary weakening effect under high temperatures near solidus instead of partial melt in the asthenosphere an intermediate seismic velocity structure was observed beneath the northern qinling orogen nql to the south of the weihe rift a thin high velocity lid which was probably a cratonic relic was found under the haiyuan arcuate tectonic region hatr west of the ordos block a thick lithosphere was present beneath the ordos block 200 km and the nql 140 km while a thinner lithosphere 100 km was found beneath the hatr and the weihe rift the observed structural differences were likely associated with different lithospheric tectonics in the study region whereas the weihe rift and the hatr had been strongly affected by cenozoic lithospheric modification and thinning the ordos block and the nql appeared to have been much less influenced combined with previous studies our results suggested that the far field effect of the indo asia collision may have played an important role in the unique lithospheric process in the study region such as the extension of the weihe rift the preservation of a cratonic relic under the hatr and the localized intense lithospheric modification of these two regions the substantial variations of deep structure and thus contrasting rheological properties between the ordos block and the surrounding notable seismic belts the hatr and weihe rift may be a candidate mechanism for the contrasting seismicity of the region the lateral variations in the lithospheric structure estimated here generally agreed with changes in upper mantle deformation patterns previously derived from sks splitting measurements

microplate model for the present day deformation of tibet 1 site velocities from 349 global positioning system gps stations are used to construct an 11 element quasi rigid block model of the tibetan plateau and its surroundings rigid rotations of five major blocks are well determined and average translation velocities of six smaller blocks can be constrained where data are well distributed the velocity field can be explained well by rigid block motion and fault slip across block boundaries residual misfits average 1 6 mm yr compared to typical one standard deviation velocity uncertainties of 1 3 mm yr any residual internal straining of the blocks is small and heterogeneous however residual substructure might well represent currently unresolved motions of smaller blocks although any smaller blocks must move at nearly the same rate as the larger blocks within which they lie undetected relative motions between them could be significant particularly where there are gaps in gps coverage predicted relative motions between major blocks agree with the observed sense of slip and along strike partitioning of motion across major faults however predicted slip rates across tibet s major strike slip faults are low only 5 12 mm yr a factor of 2 3 smaller than most rates estimated from fault offset features dated by radiometric methods as 2000 to 100 000 year old previous work has suggested that both gps data and low fault slip rates are incompatible with rigid block motions of tibet the results reported here overcome these objections

soil flow mechanisms of full flow penetrometers in layered clays through particle image velocimetry analysis in centrifuge test this paper reports the soil flow mechanisms observed in centrifuge tests around full flow t bar and ball penetrometers in layered clays the layered clay samples consisted of soft stiff stiff so

present day crustal vertical movement inferred from precise leveling data in eastern margin of tibetan plateau abstract we collect precise leveling data observed in the period of 1970 to 2012 around the eastern margin of the tibetan plateau and process the data to acquire present day crustal vertical velocity field vertical rates of 9 gps sites are employed as a priori constraints to define the reference frame the velocity field shows that most of the regions in the eastern margin of the tibetan plateau are undergoing uplift the gongga shan and west qinling are uplifting at maximum rates of 5 8 1 0 mm a and 6 0 1 3 mm a respectively a 2 d buried dislocation model is used to infer normal or reverse dip slip rates the result indicates that the reverse slip rate along the longmen shan fault is 4 2 0 5 mm a followed by the daliangshan and longriba faults with the rates of 3 7 0 5 mm a and 2 8 0 3 mm a respectively thezemuhe and northern section of the xiaojiang fault have the normal slip rates of 2 3 1 0 mm a and 2 9 0 4 mm a respectively combining vertical velocity field with gps derived horizontal velocity field we investigate the characteristics of crustal movement and dynamic mechanism the 3d velocity field indicates that the helan shan is uplifting and the yinchuan graben is subsiding the 3d crustal movement of the liupan shan region is segmented with the area in the vicinity of the northern liupan shan fault uplifting and the area in the vicinity of southern liupan shan fault subsiding respectively the subsidence of the central and southern sichuan yunnan terrain is caused by the near east west extension the budget of horizontal material influx suggests that movements of the upper and lower crust are rather different in most of the region excessive material influx into the lower crust upper mantle underneath most of the sub blocks seems required to maintain the uplift rates inferred from leveling providing evidence for the existence of lower crustal flow in this region

the growth of northeastern tibet and its relevance to large scale continental geodynamics a review of recent studies recent studies of the northeastern part of the tibetan plateau have called attention to two emerging views of how the tibetan plateau has grown first deformation in northern tibet began essentially at the time of collision with india not 10 20 myr later as might be expected if the locus of activity migrated northward as india penetrated the rest of eurasia thus the north south dimensions of the tibetan plateau were set mainly by differences in lithospheric strength with strong lithosphere beneath india and the tarim and qaidam basins steadily encroaching on one another as the region between them the present day tibetan plateau deformed and its north south dimension became narrower second abundant evidence calls for acceleration of deformation including the formation of new faults in northeastern tibet since 15 ma and a less precisely dated change in orientation of crustal shortening since 20 ma this reorientation of crustal shortening and roughly concurrent outward growth of high terrain which swings from nne ssw in northern tibet to more ne sw and even ene wsw in the easternmost part of northeastern tibet are likely to be in part a consequence of crustal thickening within the high tibetan plateau reaching a limit and the locus of continued shortening then migrating to the northeastern and eastern flanks these changes in rates and orientation also could result from removal of some or all mantle lithosphere and increased gravitational potential energy per unit area and from a weakening of crustal material so that it could flow in response to pressure gradients set by evolving differences in elevation

low temperature thermochronometry along the kunlun and haiyuan faults ne tibetan plateau evidence for kinematic change during late stage orogenesis the tibetan plateau is a prime example of a collisional orogen with widespread strike slip faults whose age and tectonic significance remain controversial we present new low temperature thermochronometry to date periods of exhumation associated with kunlun and haiyuan faulting two major strike slip faults within the northeastern margin of tibet apatite and zircon u th he and apatite fission track ages which record exhumation from 2 to 6 km crustal depths provide minimum bounds on fault timing results from kunlun samples show increased exhumation rates along the western fault segment at circa 12 8 ma with a possible earlier phase of motion from 30 20 ma along the central fault segment at circa 20 15 ma and along the eastern fault segment at circa 8 5 ma combined with previous studies our results suggest that motion along the haiyuan fault may have occurred as early as 15 ma along the western central fault segment before initiating at least by 10 8 ma along the eastern fault tip we relate an 250 km wide zone of transpressional shear to synchronous kunlun and haiyuan fault motion and suggest that the present day configuration of active faults along the northeastern margin of tibet was likely established since middle miocene time we interpret the onset of transpression to relate to the progressive confinement of tibet against rigid crustal blocks to the north and expansion of crustal thickening to the east during the later stages of orogen development

bounds on the holocene slip rate of the haiyuan fault north central china abstract we measured the offsets of six stream valleys of 30 to 90 m along the northwest southeast trending left lateral haiyuan strike slip fault in north central china minimum ages of these offsets were determined to estimate lower bounds for the holocene slip rate the most reliable bounds are 7 6 1 0 and 6 7 1 0 mm yr with three others that are smaller 3 4 0 7 3 5 0 9 and 4 1 0 4 mm yr and one large value 16 4 5 9 mm yr that we doubt thus the average holocene slip rate of the haiyuan fault is larger than 6 mm yr and probably exceeds 7 mm yr if the average slip rate of 5 to 10 mm yr for the quaternary period is applicable to the holocene epoch the average rate is 8 2 mm yr

outward growth of the tibetan plateau during the cenozoic a review abstract the surface uplift history of the tibetan plateau tp offers a key testing ground for evaluating models of collisional tectonics and holds important implications for processes ranging from global cooling to the onset of the asian monsoon various models have been proposed to reveal the surface uplift history of the tp but controversies remain we evaluate these models using data from sedimentology and stratigraphy structural geology magmatism exhumation and paleoaltimetry studies structural analyses indicate that thrust belts which spread from the central tp outward toward its surrounding margins accommodated most of the india asia convergence and facilitated crustal shortening and thickening in the central tp eocene adakitic rocks located in the qiangtang and the lhasa blocks likely were generated by partial melting of an eclogitic source paleogene 50 30 ma potassic rocks only occur in the qiangtang block whereas late oligocene late miocene 26 8 ma potassic rocks occur both in the qiangtang and lhasa blocks low temperature thermochronologic ages in the central tp are older than 40 35 ma whereas those in the margins are younger than 20 ma mostly late miocene and pliocene pleistocene in age independent paleoaltimetry estimates suggest that the lhasa and qiangtang terranes attained their current elevations during the eocene most likely due to the initial collision between india and lhasa whereas the hoh xil basin area to the north and himalayas to the south were still low even below sea level in the latter case we argue for an inside out growth pattern for the tibetan plateau the tp grew southward and northward from a nucleus of high topography and is likely to continue expanding along the mazar tagh fault to the northwest the kuantai shan hei shan longshou shan to the northeast the longquan shan to the east and the shillong plateau to the south if the northward force of india would not diminished

slip rate gradients along the eastern kunlun fault 1 whether strike slip fault systems in eurasia accomplish eastward extrusion of tibetan crust and lithosphere depends largely on the kinematics of deformation at the fault tip here we present new slip rate determinations using millennial scale geomorphic markers from sites along the easternmost segment of the kunlun fault in north central tibet this fault system represents one of the major strike slip faults within the indo asian collision zone has been argued to exhibit uniform slip rates along much of its length and plays a central role in models for eastward extrusion of tibetan lithosphere displaced fluvial terrace risers along tributaries of the yellow river coupled with 14c ages of terrace material provide constraints on slip rates over late pleistocene to holocene time results indicate that slip rates decrease systematically along the eastern 150 km of the fault from 10 to 2 mm yr these data challenge the view that slip along the kunlun fault remains uniform along the entire length of the fault and instead reveal gradients in displacement similar to those expected at fault tips moreover slip along the fault appears to terminate within the thickened crust of the plateau and therefore any extrusion of tibetan lithosphere accomplished by slip along the kunlun fault must be absorbed by internal deformation of the plateau surrounding the fault tip

crustal shortening in the andes why do gps rates differ from geological rates gps data indicate 30 40 mm yr 1 present day crustal shortening across the andes whereas geological evidence shows crustal shortening concentrated in the sub andean thrust belt at a much lower rate 15 mm yr 1 we reconcile the discrepancy between the geodetic and the geological crustal shortening using geodynamic modeling that includes timescale dependent crustal deformation the gps velocities reflect the instantaneous deformation in the andes that includes both permanent deformation and elastic deformation that will be recovered during future earthquakes whereas the lower geological rates reflect only the permanent deformation the three dimensional viscoelastic model predicts nearly uniform short term velocity gradients across the andes similar to the gps results and concentrated long term crustal shortening in the sub andean thrust zone consistent with geological observations

multiscale estimation of gps velocity fields we present a spherical wavelet based multiscale approach for estimating a spatial velocity field on the sphere from a set of irregularly spaced geodetic displacement observations because the adopted spherical wavelets are analytically differentiable spatial gradient tensor quantities such as dilatation rate strain rate and rotation rate can be directly computed using the same coefficients in a series of synthetic and real examples we illustrate the benefit of themultiscale approach in particular the inherent ability of the method to localize a given deformation field in space and scale as well as to detect outliers in the set of observations this approach has the added benefit of being able to locally match the smallest resolved process to the local spatial density of observations thereby both maximizing the amount of derived information while also allowing the comparison of derived quantities at the same scale but in different regions we also consider the vertical component of the velocity field in our synthetic and real examples showing that in some cases the spatial gradients of the vertical velocity field may constitute a significant part of the deformation this formulation may be easily applied either regionally or globally and is ideally suited as the spatial parametrization used in any automatic time dependent geodetic transient detector

slip rate on the kunlun fault at hongshui gou and recurrence time of great events comparable to the 14 11 2001 mw 7 9 kokoxili earthquake abstract a field study of the surface rupture of the 14 november 2001 mw 7 9 kokoxili or kunlun shan earthquake near hongshui gou 35 9 n 92 2 e a site with exceptional geomorphic offsets long identified on spot images yields bounds on this earthquake return time and on the slip rate along the kusai hu segment of the kunlun fault measurements of the sinistral coseismic and cumulative offsets of four distinct strath terrace risers and of rill channels incised in the adjacent fan bajada complemented by post earthquake metric resolution satellite image restoration are 3 0 5 m 6 1 m 31 2 m 63 5 m and 110 10 m the smallest offset is unambiguously that of the 14 11 2001 earthquake the 31 and 63 m riser offsets which have thermoluminescence ages of 2885 285 and 5960 450 yr respectively imply an average slip rate of 10 0 1 5 mm yr almost identical to that found 200 km eastwards in xidatan using 10 be cosmogenic dating of surface pebbles the repetitive seismic slip 3 m implies an average recurrence time of 300 50 yrs for earthquakes comparable to the 14 11 2001 event this new data increases the body of evidence suggestive of local characteristic slip during large earthquakes and firmly corroborates the millennial eastward extrusion rate 1 cm yr of north central tibet relative to the qaidam

direct dating of eocene reverse faulting in northeastern tibet using ar dating of fault clays and low temperature thermochronometry abstract paired together fault gouge dating and low temperature thermochronometry overcome the limitations and assumptions inherent in each independent technique here we establish timing of brittle faulting along the west qinling fault of northeastern tibet by dating several size fractions of fault gouge clay that represent variable populations of illite polytypes results show that the authigenic or fault generated component of illite formed at 50 8 ma and that the detrital component formed at 236 7 ma indicating a middle eocene age of faulting and a middle triassic age of the wall rocks comparing this dataset with published thermochronology from hanging wall rocks supports the interpretation that the west qinling fault initiated at 50 ma and continued until at least middle miocene time and that authigenic clay growth occurred at ambient temperatures of 110 c lack of overprinting of younger clay ages at this site may indicate that rocks were out of the thermal window for authigenic clay formation during later faulting episodes the potential for temperature to control illite growth has implications for interpretation of authigenic illite ages and their relationship to deformation episodes within fault zones

partitioning of localized and diffuse deformation in the tibetan plateau from joint inversions of geologic and geodetic observations abstract the spatial complexity of continental deformation in the greater tibetan plateau region can be defined as the extent to which relative motion of the indian and asian plates is partitioned between localized slip on major faults and distributed deformation potency rates provide a quantitative metric for determining the magnitudes of diffuse and on fault crustal deformation which are proportional to strain rates within crustal micro plates and fault slip rates respectively we simultaneously estimate micro plate rotation rates interseismic elastic strain accumulation fault slip rates on major structures and strain rates within 24 tectonic micro plates inferred from active fault maps in the greater tibetan plateau region using quasi static block models constrained by interseismic surface velocities at 731 gps sites and 9 holocene late quaternary geologic fault slip rates the joint geodetic geologic inversion indicates that geologic slip rates are kinematically consistent with differential micro plate motions estimated left lateral slip rates on the altyn tagh west central kunlun and xianshuihe faults are relatively homogeneous along strike 11 5 10 5 and 11 mm yr respectively while segmentation of the eastern kunlun fault by the intersecting elashan and riyueshan faults results in a decreased slip rate consistent with geologic observations the fraction of total potency rate associated with intrablock strain uncorrected for observational noise ranges from 0 27 in the himalayan range block to 0 91 in the aksai chin block monte carlo simulations are used to quantify the likelihood that internal deformation is statistically distinguishable from the uncertainties in geodetic velocities these simulations indicate that internal block deformation is statistically significant only within the himalayan range front where internal deformation accounts for id 0 11 of block potency rate budget west central plateau id 0 68 ganzi yushu xianshuihe 0 58 burma 0 09 jiali 0 38 and aksai chin 0 68 blocks in the other 18 tectonic micro plates within the plateau region estimated internal block potency is not currently distinguishable from the expected contribution of observational noise to residual velocities of the total potency budget within the tibetan plateau 85 is taken up by slip on major faults with the remaining 15 accommodated by internal processes at sub block scale distinguishable from observational noise the localization of the majority of plate boundary activity is also supported by the spatial distribution of modern and historical crustal earthquakes sixty seven percent of the total moment released by earthquakes in the cmt catalog and 90 of historical moment since 1900 have been released within 25 km of the major faults included in the block model representing only 12 of the characteristic half block length scale of 215 km the localization of deformation inferred from geologic geodetic and seismic observations suggests that forces applied to tectonic micro plates drive fault system activity at the india asia collision zone over decadal to quaternary time scales

crustal structures across the western weihe graben north china implications for extrusion tectonics at the northeast margin of tibetan plateau the stable ordos plateau extensional weihe graben and qinling orogenic belt are located at the northeast margin of the tibetan plateau they have been thought to play different roles in the eastward expanding of the tibetan plateau peking university deployed a linear seismic array across the western end of the weihe graben to investigate the crustal structures of the tectonic provinces of this structure receiver function analyses revealed low to moderate poisson s ratios and anticorrelations between poisson s ratios and topography beneath the qinling orogen these features may indicate a tectonic thickening of the felsic upper crust by folding and thrusting within the qinling orogen we observed a strong horizontal negative signal at the midcrust beneath the ordos plateau which may indicate a low velocity zone this observation would suggest the stable cratonic ordos plateau had been modified due to the compression between the tibetan plateau and the ordos plateau we also observed an abrupt 4 km moho offset across the weihe fault changing from 44 km beneath the ordos plateau to 40 km beneath the qinling orogen we conclude that the weihe fault is a lithosphere scale fault shear zone which extends into the upper mantle beneath the weihe graben it acts as the major boundary separating the stable ordos plateau and the active qinling orogen

geometry and late pleistocene slip rates of the liangdang jiangluo fault in the western qinling mountains nw china abstract two groups of faults striking in different direction nww trending and nee trending within the western qinling mountains play important roles in the tectonic deformation and the transference slip along the east end of the east kunlun fault we investigated the fault geometry and kinematics properties in the area based on the displacements of landforms and optically stimulated luminescence osl dating techniques the late pleistocene slip rates along the liangdang jiangluo fault were determined to be 0 43 0 13 mm a thrust and 0 71 0 18 mm a left lateral strike slip we also investigated some other faults and obtained characteristically low slip rates these slip rates are consistent with decadal gps observations despite previous studies that point to a systematic decrease in the left lateral slip rates from 10 mm a to

crustal shear s velocity and poisson s ratio structure along the indepth iv profile in northeast tibet as derived from wide angle seismic data summary from the s wave data collected along a 270 km long profile spanning the kunlun mountains in ne tibet 14595 sg phase arrivals and 21 sms phase arrivals were utilized to derive a whole crustal s velocity model and together with a previously derived p velocity model a poisson s ratio model beneath the profile the final tomogram for the upper 10 15 km of the crust reveals the lower velocities associated with the predominantly neogene quaternary sediments of the qaidam basin to the north and the higher velocities associated with the predominantly palaeozoic and mesozoic upper crustal sequences of the songpan ganzi terrane and kunlun mountains to the south this study finds no evidence that the kunlun mountains are involved in large scale northward overriding of the qaidam basin along a shallow south dipping thrust the in the upper 10 15 km of the crust are often lower than 0 25 indicating a preponderance of quartz rich rocks in the upper crust beneath the profile below 10 15 km depth the remainder of the crust down to the moho has an average of 0 24 beneath the songpan ganzi terrane and kunlun mountains and 0 25 below the qaidam basin these low are similar to other low found along other profiles in the northeastern part of the plateau assuming an isotropic situation and no significant variation in between 10 15 km depth and the moho then the lower crust between 25 30 km depth below sea level and the moho with p velocities varying from 6 6 km s 1 at the top to around 6 9 km s 1 at the base and of 0 24 0 25 should comprise intermediate granulites in the upper part transitioning to granulite facies metapelites in the lower part as the pre cenozoic qaidam basin crust has probably not lost any of its lower crust during the present himalayan orogenic cycle in the cenozoic and only has a of 0 245 0 25 then it appears that the pre cenozoic qaidam basin crust involved in the collision is more felsic and thus weaker and more easily deformable than normal continental crust with a global average of 0 265 0 27 and the tarim and sichuan basin crusts this situation then probably facilitates the collision and promotes the formation of new high plateau crust at the ne margin of tibet south of the qaidam basin the crust of the songpan ganzi terrane and kunlun mountains has an even lower average crustal of 0 23 0 24 and is thus presumably even weaker and more easily deformable than the crust beneath the qaidam basin this then supports the hypothesis of karplus et al that the high tibetan plateau may be thickening northward into south qaidam as its weak thickened lower crust is injected beneath stronger qaidam crust

localization of mining induced horizontal fractures along rock layer interfaces in overburden field measurements and prediction the locations of mining induced horizontal fractures along rock interfaces in the overburden of donetsk coal basin were identified using an original experimental device the device traps methane from horizontal fracture zone 100 fold coal seam thickness over an active longwall mining excavation presence or absence of horizontal fractures along rock layer interfaces is correlated with physical characteristics of the overburden such as thickness uniaxial compressive strength of overburden rock layers location of rock layer interfaces and thickness of extracted coal seams as a result a combined criterion based on these physical characteristics is proposed to predict the presence of overburden horizontal fracturing in coal mine operations

magnetostratigraphy and depositional history of the miocene wushan basin on the ne tibetan plateau china implications for middle miocene tectonics of the west qinling fault zone abstract based on field mapping section measurement and magnetostratigraphy 1700 m of sedimentary rocks have accumulated in the wushan basin between 16 ma and 6 ma basin geometry sedimentation characteristics and the early syn depositional deformation along the northern margin of the basin indicate that formation of the wushan basin was related to tectonic deformation along the west qinling fault zone during the middle miocene a series of basins of similar age to the wushan basin were generated along and to the south of the west qinling fault zone while basalts also erupted in this region at this time we suggest that the middle miocene 16 ma may represent a change in kinematics and deformation style in the region along and to the south of the west qinling fault zone at this time there was a transition from nne ssw compressional deformation that dominated the region since the late paleogene to the development of wnw ese and or e w trending strike slip movement and associated transpressional and transtensional activity that continues today the miocene wushan basin may have developed in association with transpression along the west qinling fault zone whether this transition was related to the onset of strike slip along the east kunlun fault and related deformation transfer lower crustal flow or removal of mantle lithosphere the middle miocene provides direct evidence for a change in the kinematic style along the plateau margin

transformation of displacement between strike slip and crustal shortening in the northern margin of the tibetan plateau evidence from decadal gps measurements and late quaternary slip rates on faults abstract studies of late quaternary geological slip rates and the gps decadal slip rates along the major strike slip faults in the northern margin of the tibetan plateau show that slip rates remain relatively constant along the middle sections of each fault and decrease rapidly toward the ends our recent studies suggest that the slip rates are low

distribution of active rock uplift along the eastern margin of the tibetan plateau inferences from bedrock channel longitudinal profiles 1 current models of long term river incision into bedrock suggest that the local rate of differential rock uplift should exert a primary control on the gradient of channel longitudinal profiles however discrimination of this effect from the influence of variations in substrate erodibility sediment flux precipitation and transient changes in profile shape has proved difficult in practice here we investigate the controls on the spatial distribution of bedrock channel gradients adjacent to the sichuan basin in an effort to assess the degree and nature of active deformation along this margin of the tibetan plateau analysis of river longitudinal profiles utilizing a channel steepness index a measure of profile gradient normalized for drainage area reveals a zone of anomalously steep channels adjacent to the topographic front of the plateau margin channel profiles are systematically less steep in their headwater reaches on the plateau and in their lower reaches east of the plateau margin comparison of steepness indices to mapped lithologic variations reveals that lithology has only a limited influence on channel gradient in this field area we observe no systematic relationship between steepness indices and upstream drainage area channels of all size are steeper near the plateau margin we argue that these systematic changes are not readily explained as a consequence of increased sediment flux or of orographic precipitation we are led to conclude that steep channel profiles along the topographic front of the plateau reflect active differential rock uplift between this region and the foreland

dynamic disaster control under a massive igneous sill by grouting from surface boreholes abstract an overlying 140 m thick massive igneous sill has adversely affected mining activities considerably in the haizi coal mine china a coal and gas outburst disaster occurred during the drivage for a subsequent longwall after the extraction of two faces in the ii102 mining area the massive sill was determined to be primarily responsible for this outburst owing to the bed separation that occurred below the sill due to the sill s large span this is because such separation meant the massive sill was not supported by the gob as in a general case but it was supported by the solid coal instead resulting in a long load transfer distance that caused the drivage gate to collapse unexpectedly into the abutment thus it was determined that the high abutment pressure primarily triggered the outburst such disaster risk would have remained had the drivage in the gate continued and a wide area and sudden roof fall could have occurred during the extraction of the next longwall had the igneous sill broken suddenly as the critical span was reached with these risks in mind a field trial of a method of grouting into the overburden of the abandoned faces from surface boreholes was conducted for dynamic disaster control this technique alleviates the abutment pressures and restrains the igneous sill deflection by eliminating fractures and voids in the overburden using grouting the adoption of this grouting method led to the subsequent drivage and mining of a further 510 m without occurrence of any further dynamic disasters