examination of the repeatability of two ms6 4 menyuan earthquakes in qilian haiyuan fault zone ne tibetan plateau based on source parameters abstract repeating earthquakes are key evidence for understanding earthquake recurrence and help improve long term seismic risk assessment in 1986 and 2016 two ms6 4 earthquakes occurred in menyuan region near the middle segment of qilian haiyuan fault zone ne tibetan plateau long period waveforms of the two events at teleseismic stations show high degree of similarity however previous solutions on earthquake location and focal mechanism show remarkable discrepancies especially for the 1986 event as well the ruptured faults also remain ambiguous in this study we determined the source parameters of these two earthquakes including the relative location focal depth focal mechanism source duration and rupture directivity the results show that two earthquakes are thrust events in shallow crust and are located within 15 km and the 2016 earthquake ruptured down dip for 6 km along the southwest dipping plane combing the source parameters geological data and deep seismic reflection profiles we infer that these two earthquakes occurred on the same secondary fault of lenglong ling fault the middle segment of qilian haiyuan fault but they ruptured on different sections of the fault although the two events are probably not repeating earthquakes of qilian haiyuan fault zone the seismic risk of m6 thrust earthquake on these secondary faults and even larger strike slip earthquake on lenglong ling fault are not negligible based on the source parameters and ten year gps observations

shallow creep on the haiyuan fault gansu china revealed by sar interferometry interferometric synthetic aperture radar data are used to map the interseismic velocity field along the haiyuan fault system hfs at the north eastern boundary of the tibetan plateau two m 8 earthquakes ruptured the hfs in 1920 and 1927 but its 260 km long central section known as the tianzhu seismic gap remains unbroken since 1000 years the envisat sar data spanning the 2003 2009 period cover about 200 300 km2 along three descending and two ascending tracks interferograms are processed using an adapted version of roi pac the signal due to stratified atmospheric phase delay is empirically corrected together with orbital residuals mean line of sight velocity maps are computed using a constrained time series analysis after selection of interferograms with low atmospheric noise these maps show a dominant left lateral motion across the hfs and reveal a narrow 35 km long zone of high velocity gradient across the fault in between the tianzhu gap and the 1920 rupture we model the observed velocity field using a discretized fault creeping at shallow depth and a least squares inversion the inferred shallow slip rate distribution reveals aseismic slip in between two fully locked segments the average creep rate is 5 mm yr 1 comparable in magnitude with the estimated loading rate at depth suggesting no strain accumulation on this segment the modeled creep rate locally exceeds the long term rate reaching 8 mm yr 1 suggesting transient creep episodes the present study emphasizes the need for continuous monitoring of the surface velocity in the vicinity of major seismic gaps in terms of seismic hazard assessment

late quaternary river incision rates and rock uplift pattern of the eastern qilian shan mountain china abstract the uplift rate and pattern of the qilian shan mountain which lies in the northeast margin of the tibetan plateau are key to understanding the dynamics of crustal deformation in the northeastern tibetan plateau in this work late quaternary terraces in seven river valley sections in the eastern qilian shan mountain are studied to determine terrace abandonment ages by osl optical simulating luminescence and terrace heights by gps global positioning system surveys river incision rates since 76 ka bp are calculated ranging from 0 37 mm a to 1 49 mm a distribution of river incision rates shows that higher river incision rates 0 85 1 49 mm a are located at the rivers upstream reaches where mean mountain elevation is 4000 m and relatively lower incision rates 0 32 0 62 mm a are located at the mountain front where the mean mountain elevation is

holocene rate of slip and tentative recurrence interval for large earthquakes on the san andreas fault cajon pass southern california abstract detailed mapping of the san andreas fault zone where it crosses cajon creek southern california has revealed a number of late quaternary deposits and geomorphological features offset by the fault radiocarbon dates from alluvial and swamp deposits provide a detailed chronology with which to characterize the activity of the san andreas fault four independent determinations of the slip rate on the san andreas fault yield an average rate of 24 5 3 5 mm yr for the past 14 400 years the similarity of the four values which span different intervals of time from 5900 to 14 400 years ago suggest that the slip rate has been constant during this period the slip rate confirms that the san andreas fault is accumulating slip faster than any other fault in the plate boundary throughout california also the sum of the slip rates on the san andreas 24 5 mm yr and the san jacinto 10 mm yr faults south of their junction is the same as the san andreas north of their junction 35 mm yr an excavation provided evidence for at least two and up to four earthquakes that caused rupture on the fault between 1290 and 1805 a d and tentative evidence for six earthquakes in about the last 1000 years both lines of evidence imply an average recurrence interval for large earthquakes of about 1 to 2 centuries combined with the historic record this investigation indicates that the last major earthquake at cajon creek was probably at the beginning or middle of the 18th century while the record at cajon creek may suggest that the next major earthquake on the san andreas fault is overdue the data can be interpreted to indicate that the recurrence interval for earthquakes on the san andreas south of the 1857 rupture is 3 to 4 centuries and that the anticipated event should not be expected until the next century

along strike variations of the partitioning of convergence across the haiyuan fault system detected by insar oblique convergence across tibet leads to slip partitioning with the coexistence of strike slip normal and thrust motion on major fault systems a key point is to understand and model how faults interact and accumulate strain at depth here we extract ground deformation across the haiyuan fault restraining bend at the northeastern boundary of the tibetan plateau from envisat radar data spanning the 2001 textendash2011 period we show that the complexity of the surface displacement field can be explained by the partitioning of a uniform deep seated convergence mountains and sand dunes in the study area make the radar data processing challenging and require the latest developments in processing procedures for synthetic aperture radar interferometry the processing strategy is based on a small baseline approach before unwrapping we correct for atmospheric phase delays from global atmospheric models and digital elevation model errors a series of filtering steps is applied to improve the signal to noise ratio across high ranges of the tibetan plateau and the phase unwrapping capability across the fault required for reliable estimate of fault movement we then jointly invert our insar time series together with published gps displacements to test a proposed long term slip partitioning model between the haiyuan and gulang left lateral faults and the qilian shan thrusts we explore the geometry of the fault system at depth and associated slip rates using a bayesian approach and test the consistency of present day geodetic surface displacements with a long term tectonic model we determine a uniform convergence rate of 10 8 6 textendash11 5 mm yr 1 with an n89 81 textendash97 e across the whole fault system with a variable partitioning west and east of a major extensional fault jog the tianzhu pull apart basin our 2 d model of two profiles perpendicular to the fault system gives a quantitative understanding of how crustal deformation is accommodated by the various branches of this thrust strike slip fault system and demonstrates how the geometry of the haiyuan fault system controls the partitioning of the deep secular motion

cosmic ray labeling of erosion surfaces in situ nuclide production rates and erosion models a number of in situ cosmogenic radionuclides and stable nuclides have been measured in natural exposed rock surfaces with a view to study their in situ production and rock erosion rates 1 the in situ radionuclides can be used for a high resolution tomography of the erosional history of an exposed surface two stable nuclides 3he 21ne and five radionuclides 10be 26al 36cl 14c 39ar having half lives in the range of 300 1 5 106 yr half life are measurable in many rock types a prerequisite for the application of the in situ nuclides for the study of erosional histories of surfaces is a knowledge of their production rates under different irradiation conditions altitude latitude irradiation geometry and shielding relative nuclide production rates can be determined fairly accurately using the extensive available data on cosmic ray neutrons 2 absolute nuclide production rates cannot generally be predicted with any accuracy because of lack of data on excitation functions of nuclides unless some normalization is possible as was done in the case of several cosmic ray produced isotopes in the atmosphere 3 based on a recent natural calibration experiment in which erosion free surfaces exposed to cosmic radiation for 11 000 yrs were sampled the absolute production rates of 10be and 26al in quartz have been accurately estimated for mountain altitudes in sierra nevada 4 the absolute production rates of 10be and 26al in quartz can therefore be estimated fairly accurately for any given latitude and altitude some measurements of 14c in rocks of low erosion rate 5 similarly allow an estimate of its production rate attempts made to measure the in situ production rates of 3he in rocks have not yet led to a convergent production rate in view of the importance of knowing the production rates of isotopes of he ne and ar i present here theoretical estimates of their production rates based on available cross section data i discuss the information that can be extracted from the study of the in situ nuclides in rocks useful parameters characterizing the exposure history of a rock surface are 1 the effective surface exposure age and 2 the time averaged erosion rate the implications of these parameters for single and multiple nuclide studies are discussed in terms of the erosion models considered

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

late cenozoic river system reorganization and its origin within the qilian shan ne tibet abstract the northward growth of the tibetan plateau has reshaped the qilian shan orogen with prolonged history along two large strike slip faults the altyn tagh fault on the west and the haiyuan fault on the east this orogen with its high elevation is referred to as the water tower of the northeastern margin of the tibetan plateau shedding many rivers into the surrounding arid areas in a way different from all other orogens within the plateau the factors that control the evolution of these rivers in this highly active region particularly their relative contribution through time are not well known our study presents evidence that the left lateral movement of the haiyuan fault one of the largest active strike slip faults within the tibetan plateau since 13 8 ma created a series of nw trending linear thrust fold belts aligned in an en echelon pattern along the trace of the fault this completely reconfigured the flow direction of the rivers within the qilian shan range from n s rivers that flowed into the hexi corridor and qaidam basin to today s w e rivers flowing into the tarim basin and longxi basin along a series of nw trending linear thrust folds belt aligned in an en echelon pattern along the trace of the haiyuan fault on the north and south this river system reorganization event is corroborated by sedimentary and geochronologic evidence within the intermountain basins where these rivers flow the longxi basin the largest intermountain basin surrounding the qilian shan on the east was drained by rivers flowing east which were dammed by the uplift of the liupan shan since 10 8 ma to form a large lake the second river system reorganization again occurred through climate change in 1 8 ma it included the incision of the yellow river capturing major rivers and halting their flow to the southeast it is concluded that the haiyuan fault plays a crucial role not only in the lateral growth of the tibetan plateau but also in the uplift of the qilian shan which led to the river system reorganization

paleoglaciation of the tibetan plateau and surrounding mountains based on exposure ages and ela depression estimates the tibetan plateau holds an ample record of past glaciations and there is an extensive set of glacial deposits dated by exposure dating here a compilation is presented of 10be exposure ages from 485 glacial deposits with 1855 individual samples on the tibetan plateau and ela depression estimates for the glacial deposits based on a simple toe to headwall ratio approach to recalculate the tibetan plateau exposure ages 10be production rates from 24 calibration sites across the world are compiled and recalibrated yielding an updated global reference 10be production rate the recalculated exposure ages from the tibetan plateau glacial deposits are then divided into three groups based on exposure age clustering to discriminate good well clustered from poor scattered deglaciation ages a major part of the glacial deposits have exposure ages affected by prior or incomplete exposure complicating exposure age interpretations the well clustered deglaciation ages are primarily from mountain ranges along the margins of the tibetan plateau with a main peak between 10 and 30 ka indicating glacial advances during the global lgm a large number of deglaciation ages older than 30 ka indicates maximum glaciation predating the lgm but the exposure age scatter generally prohibits accurate definition of the glacial chronology the ela depression estimates scatter significantly but the main part is remarkably low average ela depressions of 337 197 m for the lgm and 494 280 m for the pre lgm indicate restricted glacier expansion

paleogene clockwise tectonic rotation of the xining lanzhou region northeastern tibetan plateau 1 to help understand the deformational history of the northeastern tibetan plateau paleomagnetic samples were collected from 177 sites and two magnetostratigraphic sections at 16 localities distributed among upper jurassic lower cretaceous to pliocene sedimentary and subordinate volcanic rocks within the xining lanzhou region 34 37 n 101 105 e a total of 127 sites at 12 localities yielded primary magnetizations confirmed by fold reversal and conglomerate tests age control on sedimentary rocks is provided by regional synthesis of chronostratigraphic data and our own biostratigraphic and magnetostratigraphic analysis presented in the companion paper by horton et al 2004 analysis of paleomagnetic declination combined with results from previous studies yield a remarkably consistent trend of vertical axis tectonic rotations across the studied region whereas 19 0 7 2 to 37 8 10 6 clockwise rotations are recorded consistently in all paleomagnetic localities in lower cretaceous to eocene rocks all paleomagnetic localities in oligocene to pliocene rocks have recorded minor to insignificant rotations indicating that the xining lanzhou region has undergone a wholesale regional clockwise rotation during late paleogene time consistent with regional chronostratigraphic and thermochronologic results this late paleogene tectonic rotation confirms that deformation reached regions of the northern tibetan plateau shortly after the initial collision of india with asia when compared to rotational paleomagnetic results from adjacent regions several mechanisms can be proposed to explain the clockwise rotation on the basis of consistency with geologic data we prefer a model involving clockwise rotation of the xining lanzhou region through right lateral shear and associated shortening related to northward indentation of the qaidam basin index terms 1525 geomagnetism and paleomagnetism paleomagnetism applied to tectonics regional global 8102 tectonophysics continental contractional orogenic belts 9320 information related to geographic region asia 9604 information related to geologic time cenozoic keywords tectonics paleomagnetism tibetan plateau

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

postglacial left slip rate and past occurrence of m 8 earthquakes on the western haiyuan fault gansu china high resolution hr air photographs and a 1 m horizontal and 2 m vertical resolution digital elevation model derived from them by stereophotogrammetry provide new constraints on the behavior of the western stretch of the active haiyuan fault in gansu province china the photographs cover three swaths along the fault each about 2 km long and at least 500 m wide near the village of songshan at 103 5oe this high resolution data set is used to map and measure cumulative horizontal offsets of alluvial terraces and risers that range between 115 and la 135 m and 70 and 90 m at two sites dating these terraces with 14c yields minimum and maximum ages of 8400 and 7600 and 14 200 years b p respectively this leads to a postglacial slip rate of 12 4 mm yr with a most likely minimum value of 11 6 1 1 mm yr the smallest stream offsets observed on the hr photographs range between 8 and 16 m and are interpreted as coseismic displacements of the last few earthquakes with m 8 that ruptured the 220 km long tianzhu gap of the fault west of the yellow river earthquakes of that size within this gap which has been quiescent for at least 800 years would recur at intervals of 1050 450 years

a pollen record of holocene climatic changes from the dunde ice cap qinghai tibetan plateau pollen preserved in ice cores from the dunde ice cap provides a sensitive record of holocene climatic changes and vegetational response in the northern qinghai tibetan plateau at time scales ranging from millennia to centuries and decades pollen analysis of the annually resolvable ice layers for a 30 yr period 1957 1986 suggests that total pollen concentration is correlated positively with summer precipitation and negatively with summer temperature thus it is a sensitive indicator of moisture availability and vegetation density in the steppe and desert regions around dunde high pollen concentrations between 10 000 and 4800 yr b p suggest that the summer monsoon probably extended beyond its present limit to reach dunde and westernmost tibet in response to orbital forcing the summer monsoon retreated time transgressively across the qinghai tibetan plateau during the middle holocene relatively humid periods occurred at 2700 2200 1500 800 and 600 80 yr b p probably as a result of neoglacial cooling prominent pollen changes during the medieval warm period 790 620 yr b p and the little ice age 330 80 yr b p suggest that the vegetation in the qinghai tibetan plateau region is sensitive to abrupt century scale climatic changes such as those anticipated in scenarios of greenhouse warming

uniform slip rate along the kunlun fault implications for seismic behaviour and large scale tectonics a long term slip rate is derived from concordant 10 be 26 al and 14 c dating of cumulativeoffse ts along much of the length of the kunlun fault values at 6 sites indi cateuniform slip 11 5 2 0 mm yr since 40 kyr bp this relatively high slip rate corresponds to a first order discon tinuity in the asian crustal velocity field m 8a nd m 7 5 earthquakes on 2 segments of the fault recur with charac teristic slip 10 2ma nd 4 4 0 4m ev e ry 850 and 420 yrs respectively

surface rupture and slip distribution along the lenglongling fault in the ne tibetan plateau implications for faulting behavior abstract the lenglongling fault lllf is located in the western section of the tianzhu seismic gap along the qilian haiyuan fault zone in the ne tibetan plateau between the 1920 m8 5 haiyuan and the 1927 m8 0 gulang earthquakes there is little information about the paleoseismic history of the lllf and understanding the faulting history of the lllf is important for determining the seismic hazards of both the fault and the seismic gap using uav based photogrammetry high resolution satellite imagery and field investigations we mapped the surface trace of the fault in detail and measured 192 left lateral offsets of geomorphic markers along the fault trace a binned cumulative offset probability density copd distribution was calculated to analyze single event and multi event cumulative offsets as a result we find that the lllf has fresh scarps along the entire 120 km length indicating that the most recent event might have ruptured the full segment of the fault the coseismic offset of the most recent event changes along the fault trace and has an asymmetrical bell shaped distribution the maximum offset was 7 m located in the middle eastern section of the fault and the offset decreases progressively towards both ends the minimum offset located at the western end was 3 0 m and the average coseismic offset was 4 8 m the cumulative offsets of the four most recent paleoearthquakes are multiples of the coseismic offset of the most recent event and show similar slip distributions indicating that the fault ruptures with a characteristic slip the fault slip distribution estimated recurrence interval and estimated moment magnitude imply that the lllf releases accumulated strain energy mainly by repeatedly producing mw 7 5 7 8 earthquakes every 1000 200 years we also show that the binned copd technique performs well to separate single event and multi event cumulative offsets

fast late pleistocene slip rate on the leng long ling segment of the haiyuan fault qinghai china 1 fieldwork along the western haiyuan fault where it cuts young glacial landforms in the leng long ling range qinghai northeastern tibet yields new constraints on its long term left slip rate our mapping near 101 85 e based on aerial photographs 1 50 000 topographic maps and spot images shows glacial valley edges and lateral moraines offset 200 m by the fault quartz rich cobbles were sampled on top of one moraine for in situ 10be and 26al cosmogenic nuclide dating among 12 dated samples the 6 oldest show ages clustering at 10 300 339 years this age probably reflects the time of last reshaping of the moraine before the valley glacier withdrew south of the fault around the end of the younger dryas 11 000 years b p assuming that the 200 40 m moraine offset started to be recorded after glacial retreat across the fault constrains the late pleistocene slip rate on the leng long ling segment of the haiyuan fault to be 19 5 mm yr

improving in situ cosmogenic chronometers new radiocarbon ages for sierra nevada deglaciation the first 10 be measurements from the laurentide terminal moraine and calculations based on paleomagnetic field strength have the potential to substantially improve the accuracy of cosmogenic age estimates specifically three new constraints apply to the interpretation of measured abundances of in situ produced cosmogenic 10be and 26al 1 a suite of minimum limiting radiocarbon dates indicates that the sierra nevada was deglaciated at least several thousand years earlier than assumed when nishiizumi et al 1989 first calibrated 10be and 26 al production rates based on polished bedrock surfaces in the range with retreat beginning by 18 000 cal yr b p and completed by 13 000 cal yr b p 2 concentrations of 10be in moraine boulders and glacier polished bedrock in new jersey show little variance 10 1 and can be used to calculate a preliminary 10be production rate integrated over the past 21 000 22 000 cal yr b p at 41 200 300 m altitude that is about 20 lower than currently accepted 3 calculations of the effect of past geomagnetic field strength variations on production rates suggest that the use of temporally averaged production rates may generate age errors of 20 however cosmogenic exposure ages can be corrected for this effect although the corrections currently are imprecise many previously reported late pleistocene 10be and 26al exposure ages are probably too young and are less accurate and less precise than implied by reported uncertainties the discrepancy between accepted production rates and those calculated from laurentide exposures when considered together with the sierran deglacial chronology and the model results suggest that correlations between cosmogenic and other numerical ages especially for brief events like the younger dryas and heinrich events will not be robust until temporal variations and the altitude latitude scaling of production rates are fully understood and quantified at levels comparable to current analytic uncertainties 3

geodetic evidence for a low slip rate in the altyn tagh fault system the collision between india and asia has been simulated with a variety of computational models that describe or predict the motions of the main faults of east asia geological slip rate estimates of 20 30 mm yr 1 suggest that the largest of these faults the 2 000 km long altyn tagh fault system on the northern edge of the tibetan plateau absorbs as much of the indo asian convergence signal as do the himalayas partly by oblique slip and partly by contraction and mountain growth however the predictions of dynamic models for asian deformation and the lower bounds of some geological slip rates estimates 3 9 mm yr 1 refs 7 8 suggest that the altyn tagh system is less active here we report geodetic data from 89 91 degrees e that indicate left lateral shear of 9 5 mm yr 1 and contraction of 3 1 mm yr 1 across the altyn tagh system this result combined with our finding that at 90 degrees e tibet contracts north south at 9 1 mm yr 1 supports the predictions of dynamic models of asian deformation

crustal lithospheric structure and continental extrusion of tibet crustal shortening and thickening to c 70 85 km in the tibetan plateau occurred both before and mainly after the c 50 ma india asia collision potassic ultrapotassic shoshonitic and adakitic lavas erupted across the qiangtang c 50 29 ma and lhasa blocks c 30 10 ma indicate a hot mantle thick crust and eclogitic root during that period the progressive northward underthrusting of cold indian mantle lithosphere since collision shut off the source in the lhasa block at c 10 ma late miocene pleistocene shoshonitic volcanic rocks in northern tibet require hot mantle we review the major tectonic processes proposed for tibet including rigid block continuum and crustal flow as well as the geological history of the major strike slip faults we examine controversies concerning the cumulative geological offsets and the discrepancies between geological quaternary and geodetic slip rates low present day slip rates measured from global positioning system and insar along the karakoram and altyn tagh faults in addition to slow long term geological rates can only account for limited eastward extrusion of tibet since mid miocene time we conclude that despite being prominent geomorphological features sometimes with wide mylonite zones the faults cut earlier formed metamorphic and igneous rocks and show limited offsets concentrated strain at the surface is dissipated deeper into wide ductile shear zones

4 d evolution of se asia s mantle from geological reconstructions and seismic tomography abstract how the collision between india and asia is related to processes deeper in the mantle is unclear here we compare geological reconstructions of block motions within asia since 50 ma with the tomographically imaged three dimensional 3 d morphology of subducted lithosphere to obtain insight into the spatiotemporal evolution of mantle structure past positions of the convergent margin show remarkable similarities with slab geometry at specific depths the striking change in slab geometry from a linear structure beneath 1100 km to an increasingly distorted shape at depths of less than 700 km results from collision the slab contours match the progressive deformation of asia s margin including india s indentation and sundaland s extrusion ever since the onset of collision the indian plate appears to have overridden its own sinking mantle and it does not seem at present to underthrust tibet significantly north of the zangbo suture if correct this observation would provide further evidence against models of plateau build up involving indian lithosphere the tomographic images beneath india confirm that asian deformation has absorbed at least 1500 km of convergence since collision began from the match between the southeastward motion of sundaland between 40 and 20 ma and the principal change in slab structure between 700 and 1100 km depths we infer that lateral advection in the mantle is small and that the sinking rate beneath sunda was 2 cm yr in the lower mantle and 5 cm yr above the transition zone

mesozoic cenozoic evolution of the xining minhe and dangchang basins northeastern tibetan plateau magnetostratigraphic and biostratigraphic results 1 accurate stratigraphic ages are crucial to understanding the deformation history of the tibetan plateau prior to and during the indo asian collision efforts to quantify mesozoiccenozoic ages are hindered by limited fossils and a paucity of volcanic horizons and regionally correlative strata magnetostratigraphic and biostratigraphic results from the xining minhe longzhong basin complex and dangchang basin provide an improved chronology of nonmarine basin development over a large region of the northeastern tibetan plateau 34 37 n 101 105 e analyses of 171 magnetostratigraphic levels and 24 palynological assemblages 120 species indicate late jurassic early cretaceous to mid tertiary deposition although magnetic polarity zonation is incomplete independent palynological age control partially restricts possible correlations to the geomagnetic polarity timescale the sediment accumulation record basin provenance structural geology and published thermochronological data support a history of jurassic exhumation late jurassic early cretaceous fault related basin initiation and cretaceous paleogene reduced accumulation these patterns which are compatible with late jurassic early cretaceous extension and cretaceous paleogene postrift thermal subsidence were disrupted at about 40 30 ma when shortening related to the indo asian collision induced localized range uplift vertical axis rotation and amplified subsidence indexterms 1520 geomagnetism and paleomagnetism magnetostratigraphy 8102 tectonophysics continental contractional orogenic belts 9320 information related to geographic region asia 9604 information related to geologic time cenozoic 9609 information related to geologic time mesozoic keywords tectonics magnetostratigraphy tibetan plateau cenozoic mesozoic sedimentary basins

deriving fault slip histories to test for secular variation in slip with examples from the kunlun and awatere faults abstract although offset and age data from displaced landforms are essential for identifying earthquake clusters and thus testing whether faults slip at uniform or secularly varying rates it is not clear how the uncertainties in such measurements should be propagated so as to yield a robust fault slip history i e record of fault displacement over time here we develop a monte carlo approach for estimating the distribution of geologically reasonable fault slip histories that fit the offset and age data from a population of dated and displaced landforms the model assumes that the landforms share common faulting histories the offset and age constraints are correct and the fault has not reversed shear sense analysis of the model results yields both a precise average slip rate in the case where a linear fit is applied to the data and a best fit fault slip history in the case where the linear constraint is removed the method can be used to test for secular variation in slip because the uncertainty on this best fit history is quantified by applying the method to previously published morphochronologic data from faulted late quaternary terrace risers along the kunlun fault in china and the awatere fault in new zealand we have assessed the extent to which our modeled average slip rates match previously reported values and the data support previous interpretations of uniform slip rate the kunlun data set yields average slip rates of 8 7 3 6 2 1 mm yr and 5 1 1 6 1 2 mm yr 68 27 confidence for the central and eastern reaches of the fault respectively both of which match previously published slip rates our analysis further indicates that these fault reaches have both slipped uniformly over the latest quaternary in contrast analysis of data from the saxton river site along the awatere fault reveals a mid holocene deceleration in slip rate from 6 2 1 6 1 4 mm yr to 2 8 1 0 0 6 mm yr this result contradicts previous interpretations of uniform slip along the awatere fault the monte carlo method we present here for quantifying fault slip histories using the offset and age data from a population of faulted landforms provides an important tool for distinguishing temporally uniform from secularly varying fault slip

measurement of interseismic strain across the haiyuan fault gansu china by insar the haiyuan fault is part of a major left lateral fault system at the northeastern edge of the tibet qinghai plateau two m8 earthquakes 1920 and 1927 occurred along the fault bracketing an unbroken section of the fault identified as the tianzhu seismic gap we use interferometric synthetic aperture radar data from descending orbits of the ers satellites acquired between 1993 and 1998 along two adjacent tracks covering the gap to measure the current surface movements and better understand the present day mechanical behavior of this fault section the analysis of the radar data involves first the combined correction of orbital errors and errors associated with the phase delay through the troposphere a subset of the data is then selected based on the analysis of the residual noise spectra for each pair of data the selected interferograms are stacked and the average phase change rate is converted in fault parallel velocity assuming that the ground movement is horizontal and parallel to the fault velocity maps from both tracks show a zone of high velocity gradient across the fault a few kilometers wide consistent with left lateral slip on the haiyuan fault the average velocity field from the two tracks in their overlapping area is well fit with a single screw dislocation model in an elastic half space the derived fault slip rate at depth 4 2 8 mm yr is consistent with recent gps results the corresponding shallow apparent locking depth 0 4 2 km can be explained by a current low stress accumulation on the fault due to creep almost on the entire fault plane however unless it is transient this creep would be paradoxical with the occurrence of past large earthquakes along this fault section as revealed by paleoseismology an alternative model implying both shallow creep in the brittle upper crust and deep aseismic slip beneath the seismogenic layer separated by a locked section would be consistent with insar observations and with the potential for large earthquakes on the fault as well a two dislocation model with slip at 5 mm yr beneath 15 km and a transient creep rate of 11 mm yr between 2 and 7 km fits the insar data however the width and creep rate of the shallow creeping zone and their possible along strike variations are still poorly resolved with the present data set

source parameters of the 2016 menyuan earthquake in the northeastern tibetan plateau determined from regional seismic waveforms and insar measurements abstract on january 21st 2016 a ms 6 4 earthquake hit menyuan county qinghai province china the nearest known fault is the leng long ling lll fault which is located approximately 7 km north of the epicenter this fault has mainly shown sinistral strike slip movement since the late quaternary period however the focal mechanism indicates that it is a thrust earthquake which is different from the well known strike slip feature of the lll fault in this study we determined the focal mechanism and primary nodal plane through multi step inversions in the frequency and time domain by using the broadband regional seismic waveforms recorded by the china digital seismic network cdsn our results show that the rupture duration was short within 0 2 s after the earthquake and the rupture expanded upwards along the fault plane based on these fault parameters we then solve for variable slip distribution on the fault plane using the insar data we applied a three segment fault model to simulate the arc shaped structure of the northern lll fault and obtained a detailed slip distribution on the fault plane the inversion results show that the maximum slip is 0 43 m and the average slip angle is 78 8 with a magnitude of mw 6 0 and a focal depth of 9 38 km with the geological structure and the inversion results taken into consideration it can be suggested that this earthquake was caused by the arc shaped secondary fault located at the north side of the lll fault the secondary fault together with the lll fault forms a normal flower structure the main lll fault extends almost vertically into the base rock and the rocks between the two faults form a bulging fault block therefore we infer that this earthquake is the manifestation of a neotectonics movement in which the bulging fault block is lifted further up under the compresso shear action caused by the tibetan plateau pushing towards the northwest direction

irregular earthquake cycle along the southern tianshan front aksu area china 1 a long deformation record 16 5 ka showing nonsteady earthquake recurrence is established for the aksu thrust tianshan china on the basis of cosmogenic 10be dating of faulted surfaces topographic leveling across the aksu fault scarp indicates up to 10 m uplift across a moraine abandoned 16 5 ka and similar uplift of 6 m across two inset surfaces yielding ages of 12 5 and 5 ka successively smaller uplifts of terraces younger than 5 ka indicate that three or more major earthquakes occurred during this period these data show that the aksu thrust fault was quiet for at least 7500 years and active in the last 5000 years and probably in the interval 16 5 12 5 ka the seismic cycle along the aksu thrust fault over the last 16 500 years was thus strongly irregular showing long quiescence and clustering which is a challenge for paleoseismology and hazard assessment this irregularity also makes it more difficult to estimate long term shortening rates nevertheless we are able to constrain a minimum total shortening rate 7 mm yr across the southern tianshan front for the last 12 500 years that is about a third of the total geodetic rate for the western tianshan 20 mm yr

global positioning system measurements from eastern tibet and their implications for india eurasia intercontinental deformation we present and interpret global positioning system gps measurements of crustal motions for the period 1991 1998 for a network encompassing the eastern part of the tibetan plateau and its foreland relative to a eurasian frame defined by minimizing the velocities of 16 gps stations in europe central asia and siberia stations within all parts of the plateau foreland in south china move 6 10 mm yr east southeast indicating that the eastward movement within the plateau is part of a broader eastward movement that involves the plateau and its eastern and northern foreland north of the plateau foreland stations move northeastward at 10 mm yr indicating that the northern boundary of the deformation zone lies north of the plateau with this realization of a eurasian frame the velocity of the gps station at bangalore in southern india implies that the northward motion of india is 5 12 mm yr slower than that predicted from the nuvel 1a plate reconstruction viewed relative to the south china block stations of the northeast plateau bounded on the north by the qilian shan and the altyn tagh fault move nne to ne with velocities ranging from 19 mm yr within the plateau to 5 11 mm yr in its foreland the altyn tagh fault shows left lateral slip of 10 mm yr at 95 e and shortening across the fault of 5 mm yr stations south and west of the xianshuihe xiaojiang fault system define a crustal fragment rotating clockwise at 10 mm yr relative to the south china block around the eastern himalayan syntaxis the gps measurements indicate no significant shortening 3 mm yr within the longmen shan of the central eastern plateau and its adjacent foreland although the longmen shan rise over 6 km in 100 km horizontal distance geological studies indicate that the deformational field was established diachronously in late miocene to pliocene time was characterized by no east west shortening of tibetan crust and has an inhomogeneous style of deformation resulting from a balance of different tectonic processes

using 10be exposure dating to constrain glacial advances during the late glacial and holocene on mount xuebaoding eastern tibetan plateau moraines preserved around mount xuebaoding 5588 m above sea level on the eastern margin of the tibetan plateau represent past glacial activity in this area the chronology of these moraines was established using 10be exposure dating the dating results revealed multiple glacial events prior to the late glacial 14 1 2 2 ka the late glacial 15 6 1 6 to 11 2 3 0 ka the early middle holocene 9 1 0 9 to 6 7 0 7 ka and the neoglacial periods 2 5 0 5 to 1 5 0 1 ka these glacial stages are consistent with the recalculated ages from surrounding areas throughout the indian and east asian monsoon influenced region on the eastern tibetan plateau comparing with other paleoclimate indexes we suggest that the late glacial event was mainly driven by low temperature the early middle holocene event by high precipitation and the late holocene neoglacial event by low temperature

nature and timing of quaternary glaciation in the himalayan tibetan orogen abstract much effort has been made in recent years to define the timing and extent of quaternary glaciation throughout the himalayan tibetan orogen these studies are challenging because of the logistical and political inaccessibility of the region and the inherent problems associated with the application of numerical dating techniques nevertheless the studies are providing abundant evidence for significant glacial advances throughout the last several glacial cycles and are beginning to accurately define the extent and timing of glaciation in selected regions studies are showing that himalayan tibetan glaciers in arid regions during the last glacial cycle reached their maximum extent early in the cycle and that global last glacial maximum glacier advances were significantly less extensive however along the more monsoonal influenced greater himalaya there is increasing evidence to suggest that glaciation was more extensive later in the last glacial cycle but this has yet to be fully assessed in addition the new studies are showing that throughout most himalayan tibetan regions significant glacier advances occurred during the lateglacial and early holocene with minor advances in some regions during the mid holocene the still relatively poor chronological control in the himalayan tibetan orogen however makes it difficult to construct correlations across the region and with regions elsewhere in the world this in turn makes it hard to assess the relative importance of the different climatic mechanisms that force glaciation across the himalayan tibetan orogen and to quantify paleoclimate change in this high altitude subtropical region the lateglacial and holocene glacial records however are particularly well preserved in several himalayan tibetan regions glacial successions such as these have the greatest potential to be examined in detail using newly developing numerical dating and geomorphic and sedimentologic methods to derive high resolution terrestrial records of glaciation that will help in paleoclimatic reconstruction for high altitude subtropical regions

latest pleistocene to holocene thrusting recorded by a flight of strath terraces in the eastern qilian shan ne tibetan plateau

effect of orogeny plate motion and land sea distribution on eurasian climate change over the past 30 million years the eurasian climates of today 10 million and 3o million years ago are simulated using an atmospheric general circulation model that incorporates realistic continental geography and epicontinental sea distributions the resulting climates compare well with various palaeoclimate records the retreat of the paratethys an epicontinental sea shifts the central asian climate from temperate to continental conditions and plays as important a role as uplift of the himalayan tibetan plateau in driving the asian monsoon changes

tropical climate instability the last glacial cycle from a qinghai tibetan ice core an ice core record from the guliya ice cap on the qinghai tibetan plateau provides evidence of regional climatic conditions over the last glacial cycle 36 cl data suggest that the deepest 20 meters of the core may be more than 500 000 years old the 18 o change across termination i is 5 4 per mil similar to that in the huascaran peru and polar ice cores three guliya interstadials stages 3 5a and 5c are marked by increases in 18 o values similar to that of the holocene and eemian 124 000 years ago the similarity of this pattern to that of ch 4 records from polar ice cores indicates that global ch 4 levels and the tropical hydrological cycle are linked the late glacial stage record contains numerous 200 year oscillations in 18 o values and in dust nh 4 and no 3 levels

elastic block and strain modeling of gps data around the haiyuan liupanshan fault northeastern tibetan plateau abstract based on the dense gps velocity field in the northeastern margin of the tibetan plateau from 1999 to 2016 we have produced the deformation and strain characteristics of the haiyuan fault and the liupanshan fault estimated long term slip rate along the haiyuan liupanshan fault zones show a gradual decrease from 6 4 1 6 mm yr at the tuolaishan fault to 2 9 1 2 mm yr at the southern liupanshan fault left lateral thrusting movement was inverted for the xiangshan tianjingshan fault xs tjs which has an average slip rate of 2 1 3 4 mm yr during the study period we also calculated the heterogeneous distribution of interseismic coupling along the fault zones our result also shows the locking depth of the tianzhu seismic gap is 22 km the slip rate deficit the seismic moment accumulation rate and the coulomb stress accumulation rate are high on the fault planes whereas the second invariant of the strain rate is low at the surface the liupanshan fault is locked to a depth of 23 km and the corresponding seismic moment accumulation rate on the fault plane is high while the strain rate at the surface is low the accumulated strain along the tianzhu seismic gap and the liupanshan fault could be balanced by earthquakes with magnitudes of mw7 9 and mw7 4 considering the absence of large earthquakes over the last 1000 years and 1400 years respectively the haiyuan segments had ruptured during 1920 haiyuan earthquake and the estimated locking depth for period 1999 2016 is 5 10 km its seismic moment accumulation rate at depth is low and the strain rate at the surface is high our result indicates that 70 of the strike slip along the haiyuan segments transforms into thrusting along the liupanshan fault while the remaining 30 is related to the orogeny of the liupanshan for slip between the haiyuan fault and the xs tjs about 27 34 of the slip is partitioned on the xs tjs

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

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

present day kinematics of asia derived from geologic fault rates active fault geometry available quaternary rates on major faults and the far field plate motion are used to determine crustal kinematics in the collision zone between india and asia using a finite element formalism to construct a spherical shell model of the asian continent with embedded faults we seek a velocity solution approaching the motion of rigid blocks by minimizing the elastic strain energy in the fault bounded blocks by doing so we test the assumption that long term deformation within continents is mostly localized into major faults in the solution fault motion accounts for more than 80 of the deformation allowing us to describe our velocity model in terms of quasi rigid block rotations on the sphere south china is rotating clockwise about a pole located southwest of borneo implying an e ese velocity vector of 11 mm yr for a point at shanghai in agreement with the velocity vector determined by very long baseline interferometry heki et al 1995 the eastward movement of south china is accommodated by oblique extension along the red river fault at a rate of 10 5 mm yr in the south and by the combination of left lateral strike slip motion on the qinling dabie shan fault and the counterclockwise rotation of the ordos and adjacent blocks in the north the tarim rotates clockwise with respect to dzungaria about a pole located at 44 n 92 e consistent with increasing crustal shortening toward the west throughout the tien shan assuming incompressibility a crustal volume budget over a domain encompassing the tertiary mountain ranges in asia shows that over the last 10 000 years 73 4 of the north south shortening between india and asia has been absorbed by thickening of the lithosphere and 27 has been accommodated by lateral extrusion of continental blocks the present day predominance of thickening in asia results from the relatively slow eastward motion of south china controlled by strike slip faulting in the qinling shan and oblique extension in northeastern china

the tectonics of the western ordos plateau ningxia china slip rates on the luoshan and east helanshan faults analysis of the locus style and rate of faulting is fundamental to understanding the kinematics of continental deformation the ordos plateau lies to the northeast of tibet within the india eurasia collision zone previous studies have suggested that it behaves rigidly and rotates anticlockwise within a large scale zone of ene wsw left lateral shearing for this rotation to be accommodated the eastern and western margins of the ordos plateau should be undergoing right lateral shearing and yet the dominant faulting style appears to be extensional we focus specifically on the kinematics of the faults bounding the western margin of the ordos plateau and make new slip rate estimates for two of the major faults in the region the right lateral strike slip luoshan fault and the normal slip east helanshan fault we use a combination of infrared stimulated luminescence dating of offset landforms with high resolution imagery and topography from the pleiades satellites to determine an average right lateral slip rate of 4 3 0 4 mm a 1 uncertainty on the luoshan fault similarly we use 10be exposure dating to determine a vertical throw rate on the east helanshan fault of 0 6 0 1 mm a corresponding to an extension rate of 0 7 0 1 mm a 1 uncertainty both of these results agree well with slip rates determined from the latest campaign gps data we therefore conclude that right lateral shearing is the dominant motion occurring in the western ordos region supporting a kinematic model of large scale anticlockwise rotation of the whole ordos plateau

rates and kinematics of active shortening along the eastern qilian shan china inferred from deformed fluvial terraces in the eastern qilian shan a flight of fluvial terraces developed along the jinta river valley are deformed across the nanying anticline four individual fluvial terraces are preserved at different elevations above the river and higher terrace treads are draped by systematically thicker aeolian loess optically stimulated luminescence dating of deposits at the base of the loess provides constraints on the timing of surface abandonment terraces were abandoned at 69 4 ka b p t4 57 4 ka b p t3 and between 34 3 ka b p t2 respectively differential gps measurement of the terrace profile across the anticline allows reconstruction of subsurface fault geometry we model terrace deformation above a listric thrust fault with a tip line at 2 2 0 1 km depth and whose dip shallows systematically to 23 3 degrees at depth of 5 8 1 1 km combining terrace ages with this model of fault geometry we estimate a shortening rate of 0 8 0 2 mm a across the nanying fold and a shortening rate of similar to 0 1 mm a across the mountain front fault since similar to 70 ka b p this rate suggests that the frontal fault system along the eastern qilian shan accomplishes crustal shortening at rates of approximately 0 9 0 3 mm a during late pleistocene time

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

cosmogenic nuclide constraints on late quaternary glacial chronology on the dalijia shan northeastern tibetan plateau abstract cosmogenic nuclide cn apparent exposure dating has become a widely used method for determining the age of glacial landforms on the tibetan plateau with 1200 published ages we present the first 10be exposure ages from the dalijia shan the most northeastern formerly glaciated mountain range on the tibetan plateau the moraine groups identified from field and remote sensing imagery mapping record four glacial events at 37 07 3 70 to 52 96 4 70 ka mis 3 20 17 1 79 to 26 99 2 47 ka mis 2 16 92 1 49 to 18 76 1 88 ka mis 2 and 11 56 1 03 to 11 89 1 06 ka younger dryas these ages indicate that glaciation in the northeastern tibetan plateau is much younger than previously thought in addition this record is consistent with many other regions on the tibetan plateau with a local last glacial maximum during mis 3 asynchronous with northern hemisphere last glacial maximum during mis 2 the dalijia shan might also include an event of younger dryas age but this needs to be tested in future studies

holocene left slip rate determined by cosmogenic surface dating on the xidatan segment of the kunlun fault qinghai china cosmogenic dating using in situ sup 26 al and sup 10 be in quartz pebbles from alluvial terrace surfaces constrains the late holocene slip rate on the xidatan segment of the kunlun fault in northeastern tibet two terrace risers offset by 24 3 and 33 4 m having respective ages of 1799 388 and 2914 471 yr imply a slip rate of 12 1 2 6 mm yr the full range of ages obtained le 22 8 k y most of them between 6 7 and 1 4 k y confirm that terrace deposition and incision hence landform evolution are modulated by post glacial climate change coupled with minimum offsets of 9 12 m this slip rate implies that great earthquakes m approximately 8 with a recurrence time of 800 1000 yr rupture the kunlun fault near 94 e

paleoseismology and slip rate of the western tianjingshan fault of ne tibet china abstract we present results from a detailed investigation of the horizontal displacement distribution timing of paleoearthquakes and left lateral slip rate on the western tianjingshan fault measurements of 240 offset streams and ridges confirm that the fault is left lateral and record evidence of repeated 3 4 m coseismic offsets along the 60 km long fault this suggests that 6 earthquakes may have occurred along the entire western tianjingshan fault with repeated occurrence of earthquakes of mw 7 2 7 5 structural and stratigraphic relationships exposed in our five trenches in combination with previously reported studies further indicate that the fault has ruptured in as many as six paleoearthquakes since the late quaternary paleoseismic data show that the average recurrence interval for holocene earthquakes is approximately 5 000 yr the most recent earthquake along the western tianjingshan fault occurred 1 2 0 1 kyr bp indicating that this fault segment did not rupture in the m 7 5 historical earthquake of 1709 that ruptured the central tianjingshan fault we estimate that the holocene slip rate of the western tianjingshan fault is 1 1 1 2 mm yr based on measurements of the age and offset of stream channels compared with the relatively fast slip rate of the haiyuan fault 4 6 mm yr we suggest that the tianjingshan fault acts as an essential active fault accommodating the sinistral displacement and crustal shortening deformation in ne tibet

constraints on the late quaternary glaciations in tibet from cosmogenic exposure ages of moraine surfaces abstract this contribution provides new constraints on the timing of tibetan glacial recessions recorded by the abandonment of moraines we present cosmogenic radionuclide 10 be inventories at 17 sites in southern and western tibet 32 crests 249 samples and infer the range of permissible emplacement ages based on these analyses individual large embedded rock and boulder samples were collected from the crests of moraine surfaces and analyzed for 10 be abundance we consider two scenarios to interpret the age of glacial recession leading to the moraine surface formation from these sample exposure ages 1 erosion of the moraine surface is insignificant and so the emplacement age of the moraines is reflected by the mean sample age and 2 erosion progressively exposes large boulders with little prior exposure and so the oldest sample age records the minimum moraine emplacement age we found that depending on the scenario chosen the moraine emplacement age can vary by 50 for 100 ka old samples we consider two scaling models for estimating the production rates of 10 be in tibet which has an important although lesser effect on inferred moraine ages while the data presented herein effectively increase the database of sample exposure ages from tibet by 20 we find that uncertainties related to the interpretation of the 10 be abundance within individual samples in terms of moraine emplacement ages are sufficient to accommodate either a view in which glacial advances are associated with temperature minima or precipitation maxima that are recorded by independent paleoclimate proxies a reanalysis of published data from moraines throughout tibet shows that the variation we observe is not unique to our dataset but rather is a robust feature of the tibetan moraine age database thus when viewed in a similar way with other samples collected from this area uncertainties within moraine exposure ages obscure attribution of tibetan glacial advances to temperature minima or precipitation maxima our work suggests that more reliable chronologies of tibetan glaciations will come from improvements in production rate models for this portion of the world as well as a better understanding of the processes that form and modify these geomorphic surfaces

late pleistocene slip rate of the central haiyuan fault constrained from optically stimulated luminescence 14c and cosmogenic isotope dating and high resolution topography the haiyuan fault is a major left lateral active fault of the india asia collision zone while the 1000 km long fault between hala lake in the west to liupan shan in the east accommodates eastward displacement of northeast tibet relative to the gobi alashan to the north the amount of slip accumulated and its slip rate remain debated we revisit the site of daqing or sangedun at 102 7 e in gaudemer et al 1995 to better constrain the long term slip rate of the haiyuan fault in its central part we used terrestrial lidar to build a high resolution dem and unmanned aerial vehicle to build an aerial photomosaic with 0 1 m resolution to survey the offset terraces their geomorphology and the fault trace we refine the geomorphological interpretation of the site measure riser offsets and determine their relation to terrace formation the well constrained age of the highest terrace t3 at 13 7 1 5 ka determined from the combination of surface and sub surface osl 14 c and terrestrial in situ 10 be cosmogenic nuclide dating associated with the maximum lower terrace riser offset of 88 m yield a minimum slip rate of 6 4 1 2 mm yr over the late pleistocene the age of the intermediate terrace t2 is bracketed between 8 0 ka 14 c and 12 ka 10 be the ages and vertical offsets of the 2 highest terraces is used to infer the age of t2 offset vertically 5 7 m at 5 4 1 ka its 29 2 m offset is consistent with a rate of 6 5 mm yr given the vertical offset youngest terrace t1 of 1 3 0 2 m its age is estimated at 1 2 0 2 ka in agreement with the youngest surface exposure age overall a slip rate of 5 8 mm yr fits all offset and age data at the daqing site the smallest offset of a gully incised into t1 of 6 0 0 5 m is potentially associated with the most recent slip event that occurred in the last millennia

quaternary glaciation of tibet the geological evidence the question of the number and extent of pleistocene glaciations on the qinghai xizang tibet plateau remains contentious there has been considerable research activity in tibet by chinese scientists since the late 1950s and their principal findings including data on glacial and periglacial geomorphology sedimentology tectonics stratigraphy and lake history have been used to reconstruct ice margins and palaeosnowlines three and in places four distinct glaciations have been recognised the most extensive occurring in the later middle pleistocene valley and piedmont glacial systems with some mountain ice caps and a small ice sheet on the upper reaches of the huang he have been recognised but there is no evidence of a single tibetan ice sheet as the plateau and the himalaya karakoram underwent accelerating uplift through the quaternary there occurred progressive desiccation in the interior as the influx of indian ocean moisture was constrained equilibrium line elevations in the last glacial maximum were 4000 m in the south east and northeast plateau margins rising to 5500 m in the northwest interior the heat island provided by the plateau the progressive reduction in precipitation most marked during the glacials and the strong southeast to northwest precipitation gradients produced a glacier distribution pattern dominated by the trans tibetan mountain ranges tectonics and periglacial including aeolian processes have played an equal role with glaciation in generating the plateau s quaternary sedimentary succession

continental deformation accommodated by non rigid passive bookshelf faulting an example from the cenozoic tectonic development of northern tibet abstract collision induced continental deformation commonly involves complex interactions between strike slip faulting and off fault deformation yet this relationship has rarely been quantified in northern tibet cenozoic deformation is expressed by the development of the 1000 km long east striking left slip kunlun qinling and haiyuan faults each have a maximum slip in the central fault segment exceeding 10s to 100 km but a much smaller slip magnitude

tectonic geomorphology of the qilian shan in the northeastern tibetan plateau insights into the plateau formation processes abstract we examined the regional scale topography of the qilian shan on the northeastern margin of the tibetan plateau longitudinal profiles and geomorphometric indices such as slope local relief and channel steepness reveal that the qilian shan was developed as a local plateau with high relief steep marginal ranges and interior low relief topography landscape mapping across this local plateau revealed spatially varied origins of the low relief landscape in the qilian shan north of the haiyuan fault universal massive intermontane aggradation was identified however the low relief plateau to the south of the haiyuan fault was dominated by relict erosional surfaces even though accompany basin filling still contributes the geomorphologic contrasts led us to integrate both the basin filling processes and antecedent low relief erosional surfaces into a new insight into the development of the qilian shan plateau in the northeastern tibet our present study highlights that explanation for the low relief plateau formation needs to consider the complex geological evolution of the qilian shan and the tibetan plateau itself

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

late quaternary glacial advances in the eastern qilianshan north eastern tibet as inferred from luminescence dating of fluvioglacial sediments

characteristics and transition mechanism of late cenozoic structural deformation within the niushoushan luoshan fault zone at the northeastern margin of the tibetan plateau abstract the niushoushan luoshan fault zone nlf separates two major tectonic units the ordos block and the northeastern margin of the tibetan plateau the deformational processes within this fault zone recorded the uplift and expansion of the northeastern margin of the plateau however the tectonic transition mechanisms during the end miocene pleistocene and the characteristics of deformation at the end pliocene and their tectonic significances remain unclear in this study a detailed survey of structural deformation within the fault zone was carried out the measurements were combined with regional tectonic analysis and geochronology to determine the effects of changing tectonic stress fields and proposed the following late cenozoic tectonic evolution of the nlf nw se compression and left lateral strike slip deformation in the late miocene pliocene ne sw compression and right lateral strike slip movement in late pliocene middle pleistocene and e w extensional tectonics since the late pleistocene although the late miocene deformation indicates that expansion of the northeastern margin of the tibetan plateau had already reached this fault zone at this time the most intense tectonic deformation did not commence until the end of the pliocene this indicates that the margin of the plateau was expanding at this time the results show that the tectonic evolution of the nlf was closely related to collision between the indian and eurasian plates and to uplift of the tibetan plateau the fault zone also records the expansion of the northeastern margin of the tibetan plateau and the cenozoic tectonic transition of the ordos block from westward extrusion to clockwise rotation

cosmic ray production rates of 10be and 26al in quartz from glacially polished rocks we have studied the concentrations of 10be and 26al in quartz crystals extracted from glacially polished granitic surfaces from the sierra nevada range these surfaces were identified with the glacial advance during the tioga period 11 000 years ago our measurements yield the most accurate estimates to date for the absolute production rates of these nuclides in sio2 due to cosmic ray nucleons and muons for geomagnetic latitudes 43 8 44 6 n and altitudes 2 1 3 6 km the estimates are relatively free from uncertainties in snow cover since we studied a suite of rock surfaces inclined 0 75 with respect to the horizontal the principal uncertainty arises due to the lack of a precise date for the glacial retreat event about 10 the 26al 10be ratio at production 6 0 is determined more accurately since the exposure age of the samples is 2 orders of magnitude smaller than the mean lives of the two nuclides production rates of 10be and 26al in quartz at other latitudes and altitudes in the troposphere can be determined from the present measurements by scaling using the known altitude and latitude dependence of cosmic ray fluxes of nucleons and negative muons knowledge of the production rates of these nuclides is a prerequisite for their application in erosion and geomorphological studies

displacement along the haiyuan fault associated with the great 1920 haiyuan china earthquake abstract we used a plane table and an alidade to construct detailed topographic maps of offset features stream channels dry gullies and old terrace walls along the fault zone that ruptured during the 1920 haiyuan earthquake m 8 7 in ningxia and gansu china the maximum displacement appears to have reached 10 m at shikaguangou between the salt lake and xianzhou basins in southern ningxia the average displacement along the 100 km of the fault that we studied was about 8 m assuming that the average slip rate to be between 5 and 10 mm yr the recurrence interval for events similar to that in 1920 would be about 800 to 1600 yr

paleoearthquakes and rupture behavior of the lenglongling fault implications for seismic hazards of the northeastern margin of the tibetan plateau

late pleistocene holocene slip rate along the hasi shan restraining bend of the haiyuan fault implication for faulting dynamics of a complex fault system we thank the associate editor and an anonymous reviewer for their insightful comments that greatly improve this manuscript we are grateful to rene boutin at laboratoire d hydrologie et geochimie de la surface and aster team g aumaitre d bourles and k keddadouche at aster cerege for icp aes and ams measurements respectively part of this work was supported by insu cnrs france and the university of strasbourg j van der woerd for the al and be concentration analyses at lhyges and ipgs and for 10be 9be and 26al 27al ratios measurements on the aster ams facility gerege aix en provence france supported by insu cnrs and ird we thank yang ye for his help with the chi square modeling of the depth profile data and a s meriaux for her help with error propagation and mean age calculations part of this work has been supported by the cnrs pics program france chine all slip rate data discussed in the paper but the ones derived in this study are extracted from the published literature listed in the reference list pleiades imagery is available for purchase from airbus industry https www intelligence airbusds com en 8692 pleiades this is ipgp contribution 4090

timing of multiple late quaternary glaciations in the hunza valley karakoram mountains northern pakistan defined by cosmogenic radionuclide dating of moraines moraines and associated landforms in the upper hunza valley karakoram mountains northern pakistan provide an excellent record of multiple glaciations during the late quaternary glaciers advanced at least eight times by using 10 be and 26 al surface exposure dating on moraine boulders and scoured bedrock we determined the timing of glaciation for four of these glacial advances ca 54 7 43 2 ka borit jheel glacial stage ca 25 7 21 8 ka ghulkin i glacial stage ca 18 4 15 3 ka ghulkin ii glacial stage and ca 10 8 9 0 ka batura glacial stage for two of the older advances the yunz and shanoz glacial stages our data set a limit of 60 ka although at present the uncertainties in dating make it impossible to describe unequivocally the climate processes controlling glaciations in the hunza valley the results suggest that precipitation changes related to oscillations in the southwest asian monsoonal system combine with cooling that is broadly associated with heinrich events to cause glacial advances in this region

insight into the 2016 menyuan m w 5 9 earthquake with insar a blind reverse event promoted by historical earthquakes in 2016 the mw 5 9 menyuan earthquake occurred at the western end of the tianzhu seismic gap in the middle segment of the left lateral strike slip haiyuan fault system studying the focal mechanism of the menyuan earthquake and its correlation with historical seismicity is of great significance in understanding the tectonic style of the haiyuan fault system and assessing the tianzhu gap seismic risk using sentinel 1a radar imagery we obtain the coseismic deformation field of the menyuan earthquake in the los direction and invert the deformation field slip distribution model based on the interseismic deformation field reflected by gps data and the relocated results of aftershocks provided by previous studies we then analyze the seismogenic nodal plane of the menyuan earthquake and consider the west dipping model to be the most likely seismogenic solution the west dipping model indicates that the average slip of the menyuan earthquake is 0 41 m and the average rake angle is 68 with a magnitude of mw 5 905 considering the historical strong earthquakes and viscoelastic layered crust the results from coulomb failure stress modeling indicate that the coulomb stress loading caused by the historical strong events promoted the occurrence of the 2016 menyuan earthquake both the low seismicity within the tianzhu gap and the cluster phenomenon of medium earthquakes on the lao hu shan lhs and leng long ling lll faults have strong correlations with the stress change distribution resulting from the historical strong earthquakes a series of medium events occurring on the north side of the lll fault represented by the 2016 menyuan earthquake would raise the seismic risk on the western end of the tianzhu gap

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

kinematic behavior of southern alaska constrained by westward decreasing postglacial slip rates on the denali fault alaska long term slip rates for the denali fault in southern alaska are derived using 10 be cosmogenic radionuclide crn dating of offset glacial moraines at two sites correction of 10 be crn model ages for the effect of snow shielding uses historical regional snow cover data scaled to the site altitudes to integrate the time variation of snow cover we included the relative changes in effective wetness over the last 11 ka derived from lake level records and 18 o variations from alaskan lakes the moraine crn model ages are normally distributed around an average of 12 1 1 0 ka n 22 1 the slip rate decreases westward from 13 mm a at 144 49 w to about 7 mm a at 149 26 w the data are consistent with a kinematic model in which southern alaska translates northwestward at a rate of 14 mm a relative to a stable northern alaska with no rotation this suggests progressive slip partitioning between the denali fault and the active fold and thrust belt at the northern front of the alaska range with convergence rates increasing westward from 4 mm a to 11 mm a between 149 w and 145 w as the two moraines sampled for this study were emplaced synchronously our suggestion of a westward decrease in the slip rate of the denali fault relies largely upon the measured offsets at both sites regardless of any potential systematic uncertainty in the crn model ages

three dimensional mechanical modeling of the gps velocity field around the northeastern tibetan plateau and surrounding regions article i nfo the northeastern corner of the tibetan plateau is a complex tectonic region with different fault mechanisms from left lateral thrusting of the qilian shan left lateral strike slipping of the haiyuan fault along the plateau edge and right lateral extension across the alashan and the ordos out of the northeastern tibetan plateau here we use 3d finite element models incorporating fault as coulomb type friction zone to investigate mechanical relation between crustal rheology and long term deformation of the main active fault systems models are constrained with gps velocity field and available geological slip rates crustal rheology is simplified as an elastobrittle upper part underlying with viscoelastic crust we test models with fault frictions from 0 4 to 0 02 on different fault systems and mean viscosities of the lower crust from