slip rate measurements on the karakorum fault may imply secular variations in fault motion beryllium 10 surface exposure dating of offset moraines on one branch of the karakorum fault west of the gar basin yields a long term 140 to 20 thousand year right lateral slip rate of 10 7 0 7 millimeters per year this rate is 10 times larger than that inferred from recent insar analyses 1 3 millimeters per year that span 8 years and sample all branches of the fault the difference in slip rate determinations suggests that large rate fluctuations may exist over centennial or millennial time scales such fluctuations would be consistent with mechanical coupling between the seismogenic brittle creep and ductile shear sections of faults that reach deep into the crust

block models of crustal motion in southern california constrained by gps measurements 1 we estimate slip rates on major active faults in southern california using a block model constrained by global positioning system measurements of interseismic deformation the block model includes the effects of block rotation and elastic strain accumulation consistent with a simple model of the earthquake cycle our estimates of the right lateral strike slip rate on the san andreas fault vary by at least a factor of 5 from a high of 35 9 0 5 mm yr in the carrizo plain to a low of 5 1 1 5 mm yr through the san bernadino segment shortening across the puente hills thrust and left lateral slip on the raymond hill fault are consistent with both thickening and escape tectonics in the los angeles basin discrepancies between geodetic and geologic slip rate estimates along the san andreas and san jacinto faults as well as in the eastern california shear zone may be explained by a temporal change in fault system behavior we find no substantial evidence for long term postseismic relaxation and infer that the viscosity of the lower crust upper mantle may be relatively high 1019 pa s

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

edge driven mechanical microplate models of strike slip faulting in the tibetan plateau 1 the india asia collision zone accommodates the relative motion between india and eurasia through both shortening and pervasive strike slip faulting to gain a mechanical understanding of how fault slip rates are driven across the tibetan plateau we develop a two dimensional linear elastic two stage deformable microplate model for the upper crust based on the behavior of an idealized earthquake cycle we use this approach to develop a suite of simple india asia collision zone models differing only in boundary conditions to determine which combination of edge forces and displacements are consistent with both the slip rate measurements along major tibetan faults as well as the geodetically observed extrusion of crustal material toward southeast asia model predictions for the altyn tagh 1 14 mm yr kunlun 3 10 mm yr karakorum 5 12 mm yr and haiyuan 3 5 mm yr faults are in agreement with geologically and geodetically inferred slip rates further models that accurately reproduce observed slip rate gradients along the altyn tagh and kunlun faults feature two critical boundary conditions 1 oblique compressive displacement along the himalayan range front west of the shillong plateau and 2 forcing in southeast asia additionally the ratio of internal block potency rate to the total potency rate for each microplate ranges from 28 to 79 suggesting a hybrid view of deformation in tibet as simultaneously localized on major faults and distributed at length scales 500 km

impact of riser reconstructions on estimation of secular variation in rates of strike slip faulting revisiting the cherchen river site along the altyn tagh fault nw china abstract slip rates are heavily contested for many of the first order strike slip faults within the indo asian collision zone rates determined geodetically are generally lower than those reported using reconstructions of offset landforms and it is unclear if this discrepancy reflects true secular variation in slip history systematic errors in interpretation or both here i examine the methods used to derive slip rates from reconstructions of displaced fluvial risers and show that such rates are subject to potentially important uncertainties that have largely been overlooked review of published data demonstrates that the slip rate can vary by a factor of 1 2 to 5 for the same site depending on whether the reconstruction uses the age of the upper or lower terrace for the initiation of riser offset to reduce this epistemic uncertainty i have developed six geomorphic indices that can be used to identify the most accurate end member reconstruction 1 comparison of riser offset with inset channel width 2 similarity of riser and tread displacements 3 morphological analysis of the scarp profile 4 riser deflection in plan view 5 diachroneity of terrace abandonment and 6 whether riser crests or bases yield the slip vector without the use of these geomorphic observations the epistemic uncertainty associated with current methods for determining slip rate from offset fluvial risers is likely to be so large that there is no resolvable discrepancy between the gps and geologic rates within the indo asian collision zone application of three of these indices to new field mapping of the cherchen he river site 86 4 e along the central altyn tagh fault yields a revised slip rate of 9 4 2 3 mm yr equivalent within error to the rates previously derived from gps and paleoseismic studies although reinterpretation of published data from the sulamu tagh site 87 4 is consistent with this revised rate additional work is needed to reconcile this result with some of the rates reported near aksay 94 e

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

distribution of slip from 11 mw 6 earthquakes in the northern chile subduction zone we use interferometric synthetic aperture radar gps and teleseismic data to constrain the relative location of coseismic slip from 11 earthquakes on the subduction interface in northern chile 23 25 s between the years 1993 and 2000 we invert body wave waveforms and geodetic data both jointly and separately for the four largest earthquakes during this time period 1993 m w 6 8 1995 m w 8 1 1996 m w 6 7 1998 m w 7 1 while the location of slip in the teleseismic only geodetic only and joint slip inversions is similar for the small earthquakes there are differences for the 1995 m w 8 1 event probably related to nonuniqueness of models that fit the teleseismic data there is a consistent mislocation of the harvard centroid moment tensor locations of many of the 6 6 earthquakes as well as three m w 7 events from the 1980s all of these earthquakes appear to rupture different portions of the fault interface and do not rerupture a limited number of asperities

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

dynamics of the india eurasia collision zone we present simple new dynamic calculations of a vertically averaged deviatoric stress field over a depth average of 100 km for asia from geodetic geologic topographic and seismic data a first estimate of the minimum absolute magnitudes and directions of vertically averaged deviatoric stress is obtained by solving force balance equations for deviatoric stresses associated with gravitational potential energy differences within the lithosphere plus a first order contribution of deviatoric stresses associated with stress boundary conditions this initial estimate of the vertically averaged deviatoric stress field is obtained independent of assumptions about the rheology of the lithosphere absolute magnitudes of vertically averaged deviatoric stresses vary between 5 and 40 mpa assuming bulk viscous behavior for the lithosphere the magnitudes of deviatoric stresses together with the magnitudes of strain rates inferred from quaternary fault slip rate and gps data yield vertically averaged effective viscosities for tibet of 0 5 5 1022 pa s compared with 1 2 5 1023 pa s in more rigid areas elsewhere in the region a forward modeling method that solves force balance equations using velocity boundary conditions allows us to refine our estimates of the vertically averaged effective viscosity distribution and deviatoric stress field the total vertically averaged deviatoric stress and effective viscosity field are consistent with a weak lower crust in tibet they are consistent with some eastward motion of tibet and south china lithosphere relative to eurasia and they confirm that gravitational potential energy differences have a profound effect on the spatially varying style and magnitude of strain rate around the tibetan plateau our results for the vertically averaged deviatoric stress argue for a large portion of the strength of the lithosphere to reside within the seismogenic upper crust to get deviatoric stress magnitudes there to be as high as 100 300 mpa in accord with laboratory and theoretical friction experiments indicating that stress drops in earthquakes are small fractions of the total deviatoric stress

block kinematics of the pacific north america plate boundary in the southwestern united states from inversion of gps seismological and geologic data 1 the active deformation of the southwestern united states 30 41 n is represented by a finite number of rotating elastic plastic spherical caps gps derived horizontal velocities geologic fault slip rates transform fault azimuths and earthquake derived fault slip vector azimuths are inverted for block angular velocities creep on block bounding faults permanent strain rates within the blocks and the rotations of 11 published gps velocity fields into to a common north american reference frame gps velocities are considered to be a combination of rigid block rotations recoverable elastic strain rates resulting from friction on block bounding faults and nonrecoverable strain rates resulting from slip on faults within the blocks the resulting pacific north america angular velocity is similar to some published estimates and satisfies transform azimuths and one spreading rate in the gulf of california earthquake slip vectors in the gulf of california and alaska and gps velocities along coastal california and within the pacific basin published fault slip rates are satisfied except in the southern mojave desert where the motion of the mohave block relative to north america is faster than can be explained by mapped faults the largest blocks the sierra nevada great valley and the eastern basin and range show permanent strain rates after removing elastic strain of only a few nanostrain per year demonstrating approximately rigid behavior observed horizontal strain rates correlate strongly with predicted strain rates from known faults suggesting that the short term strains evident in gps velocities are largely elastic in only about 20 of the region is distributed deformation needed to match the data indicating that a plate tectonic style description of the deformation of the western united states is plausible most blocks rotate about vertical axes at approximately the same rate as the pacific relative to north america suggesting that locally spin rates are communicated from block to block arguing against both floating block and ball bearing mechanisms of block rotation the similarities of the blocks spin rates to that of the pacific suggests that the pacific strongly influences their motions through edge tractions however it is shown that the blocks cannot rotate about the pacific north america pole without spinning counter to the sense of pacific north america shear unlike some other broad plate boundaries in the western united states vertical axis rotations take up very little of the slip rate budget across the region

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

late quaternary to decadal velocity fields in asia 1 fields of crustal velocity and strain rate within asia averaged over horizontal distances of 300 km are calculated from estimates of quaternary slip rates on faults and rates of change of lengths of baselines between gps sites the calculated fields fit strain rate components estimated from quaternary slip rates within 95 confidence limits and fit the gps data with an rms residual of 2 5 mm yr 1 the strain rate field constrained only by quaternary slip rates of faults differs from the combined solution at the level of 20 nstrain yr 1 and the differences are explicable by the limited accuracy of geological estimates of slip rate therefore the strain rate fields determined by geodetic measurements taken on the 10 year timescale are consistent with geological observations on the 104 year timescale the combined solution for velocities shows plate or block like motion within deforming asia only in tarim south china and the amurian region elsewhere the kinematics of rigid blocks does not provide a useful description of the motion in particular velocities relative to eurasia point at high angles to contours of their magnitudes not parallel to them as they would if large regions moved as rigid blocks the axes of principal horizontal compressional strain align with topographic gradients in agreement with previous suggestions that asia deforms as a continuum under the influence of gravity

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

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

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

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

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

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

petrology geochemistry and mineralization of the las aguilas and virorco mafic ultramafic bodies san luis province argentina the layered mafic ultramafic rocks in the sierras de san luis argentina las aguilas las higueras and virorco constitute a 3 5 km wide belt that extends over 100 km from ne to sw they carry a sulphide mineralization consisting of pyrrhotite pentlandite and chalcopyrite in veins and as disseminated to massive ore disseminated spinels are frequently associated with the sulphide minerals as well as platinum group minerals a strong correlation between s ni co cu cr pt and pd indicates the presence of one to three levels of mineralization within the ultramafic units the maximum concentration of these elements coincides with the units containing platinum group minerals pgm and spinel group minerals this clear relationship constitutes a good prospecting guide in the search for layers with high grade ore probably associated with deeper stratigraphic levels where ultramafic rocks are dominant the bulk rock chemistry and concentrations of metals and platinum group elements as well as textural evidence suggest that the parental magma was mafic with tholeiitic affinities and mgo rich the las aguilas layered mafic ultramafic body and the remaining bodies in the area bear similar characteristics to well known stratified complexes developed in extensional tectonic regimes as it is the case of jinchuan china kabanga tanzania and fiambala argentina

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

comparison of geodetic and geologic data from the wasatch region utah and implications for the spectral character of earth deformation at periods of 10 to 10 million years the wasatch fault and adjacent fault zones provide an opportunity to compare present day deformation rate estimates obtained from space geodesy with geologic displacement rates over at least four temporal windows ranging from the last millennium up to 10 myr the three easternmost gps sites of the basin and range geodetic network bargen at this latitude define a 130 km wide region spanning three major normal faults extending east west at a total rate of 2 7 0 4 mm yr with an average regional strain rate estimated to be 21 4 nstrain yr about twice the basin and range average on the wasatch fault the vertical component of the geologic displacement rate is 1 7 0 5 mm yr since 6 ka 0 6 mm yr since 130 ka and 0 5 0 7 mm yr since 10 ma however it appears likely that at the longest timescale rates slowed over time from 1 0 to 1 4 mm yr between 10 and 6 ma to 0 2 to 0 3 mm yr since 6 ma the cumulative vertical displacement record across all three faults also shows time variable strain release ranging from 2 to 4 mm yr since 10 ka to 1 mm yr averaged over the past 130 kyr conventional earthquake recurrence models reid type behavior would require an accordingly large variation in strain accumulation or loading rate on a 10 kyr timescale for which there appears to be no obvious geophysical explanation alternatively seismic strain release given a wide range of plausible constitutive behaviors for frictional sliding may be clustered on the 10 kyr timescale resulting in the high holocene rates with comparatively low uniform strain accumulation rates on the 100 kyr timescale wallace type behavior the latter alternative combined with observations at the million year timescale and the likelihood of a significant contribution of postseismic transients implies maxima of spectral amplitude in the velocity field at periods of 10 myr variations in tectonic loading 10 kyr clustered strain release and of 100 years postseismic transients if so measurements of strain accumulation and strain release may be strongly timescale dependent for any given fault system

how the continents deform the evidence from tectonic geodesy space geodesy now provides quantitative maps of the surface velocity field within tectonically active regions supplying constraints on the spatial distribution of deformation the forces that drive it and the brittle and ductile properties of continental lithosphere deformation is usefully described as relative motions among elastic blocks and is block like because major faults are weaker than adjacent intact crust despite similarities continental block kinematics differs from global plate tectonics blocks are much smaller typically 100 1000 km in size departures from block rigidity are sometimes measurable and blocks evolve over 1 10 ma timescales particularly near their often geometrically irregular boundaries quantitatively relating deformation to the forces that drive it requires simplifying assumptions about the strength distribution in the lithosphere if brittle elastic crust is strongest interactions among blocks control the deformation if ductile lithosphere is the stronger its fl

crustal sources in lower palaeozoic rocks from nw iberia insights from laser ablation u pb ages of detrital zircons detrital zircons from greywackes belonging to an ordovician volcanosedimentary igneous complex in nw spain were dated using the laser ablation inductively coupled plasma mass spectrometry technique u pb results indicate the existence of three pre cambrian crustal sources in nw iberia the age grouping dated at c 590 620 ma confirms the presence of a cadomian avalonian basement in this zone the second age group c 1 1 1 2 ga is the first evidence for a grenvillean age crustal component in nw iberia the age grouping dated at c 1 9 2 0 ga corresponds to the age of the icartian igneous basement exposed in other areas of the european variscides

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

coseismic deformation of the 2001 mw 7 8 kokoxili earthquake in tibet measured by synthetic aperture radar interferometry the 14 november 2001 m w 7 8 kokoxili earthquake ruptured more than 400 km of the westernmost stretch of the left lateral kunlun fault in northern tibet interferometric synthetic aperture radar data from descending orbits along four adjacent tracks covering almost the entire rupture and 1 m pixel ikonos satellite images are used to map the rupture geometry and the surface displacements produced by the event interferograms are then inverted to solve for coseismic slip on the fault at depth the radar data show that the rupture connected the heituo fault where the earthquake initiated to the main kunlun fault cutting across a pull apart trough in between the two strike slip faults the fault model includes two vertical sections extending to a depth of 20 km and discretized into 5 km 5 km patches using a nonnegative least squares method that includes an appropriate degree of smoothing we solve for the left lateral slip on each fault patch our solution shows that the largest slip occurred at depths between 0 and 5 km reaching 8 m in two areas 200 and 250 km east of the earthquake epicenter significant slip took place below 10 km at both ends of the rupture slip appears to have been highly variable along the fault defining six sections of major moment release these sections correspond to six subsegments of the kunlun fault system defined from the surface morphology of the fault this suggests that fault geometry exerted a predominant influence on controlling the rupture propagation

gps measurements from the ladakh himalaya india preliminary tests of plate like or continuous deformation in tibet observations of relative motion in a geodetic network in ladakh india and across southern tibet indicate slow shear on the karakorum fault rapid east west extension across the whole of southern tibet and constant arc normal convergence between india and southern tibet along the himalayan arc measurements of ten campaign style and six permanent sites with global positioning system gps precise geodesy provide these bounds on the style and rates of the large scale deformation in the tibet himalaya region divergence between sites at leh ladakh india and shiquanhe western tibet as well as slow relative motion among sites within the ladakh network limit right lateral slip parallel to the karakorum fault to only 3 4 5 mm yr this low rate concurs with a recent estimate of 3 4 mm yr for late holocene time but disagrees with the much higher rate of 30 35 mm yr that has been used to argue for plate like behavior of the tibetan plateau convergence between ladakh and the indian subcontinent at 18 8 3 mm yr at 224 17 1 differs little from estimates of convergence across the central segment of the himalaya finally lengthening of the baseline between leh ladakh and lhasa in southeastern tibet at 17 8 1 mm yr or between leh and bayi farther to the southeast at 18 3 mm yr is consistent with an extrapolation of rates of east west extension of the tibetan plateau based both on shorter gps baselines e g lhasa simikot and on diverging slip vectors of earthquakes in the himalaya we interpret these results to indicate that tibet behaves more like a fl uid than like a plate

dislocation model for aseismic crustal deformation at hollister california geodetic observations at many active plate margins reveal relatively steady aseismic motion during the time between major earthquakes we model the aseismic motion by the relative motion between several blocks that suffer frictional resistance in the upper crust frictional drag is represented by uniform dislocation on a fault surface we assume that friction occurs only on the upper brittle zone of each block boundary and that frictionless sliding occurs below this zone using a bayesian inversion procedure we invert geodetic data to determine the parameters of the block and dislocation model parameters to be estimated include the two horizontal components of velocity for each block and the dislocation rate dip angle slip angle and width of each rectangular fault patch for hollister we assume five blocks and nine rectangular fault patches rates of length change on 92 lines observed by trilateration make up the data triangulation leveling very long baseline interferometry satellite ranging and global positioning system data can also be easily included in our model our inversion procedure uses prior estimates of all block and fault parameters based on geological and seismological data the block parameters are estimated from geological observations of fault displacement rates while the widths of the fault patches are estimated from earthquake hypocentral depths we choose prior estimates of the dislocation rate to match observed creep rates the estimated block motion is well resolved by the geodetic data and agrees well with the geological estimates this suggests that the block motion is steady on time scales from 10 years to 1 m y the net motion across the san andreas calaveras fault system is 38 3 mm yr oriented s38 e thus some additional displacement possibly offshore is needed to match the rate of 56 mm yr predicted by plate tectonic models the depth of the transition from frictional to free sliding varies considerably from 0 4 km on the southern calaveras to 11 km on the central san andreas fault two segments of the san andreas north of 36 50 and south of 36 40 have the greatest potential for moderate to large earthquakes

geodetic observations of interseismic strain segmentation at the sumatra subduction zone deformation above the sumatra subduction zone revealed by global positioning system gps geodetic surveys shows nearly complete coupling of the forearc to the subducting plate south of 0 5 s and half as much to the north the abrupt change in plate coupling coincides with the boundary between the rupture zones of the 1833 and 1861 mw 8 thrust earthquakes the rupture boundary appears as an abrupt change in strain accumulation well into the interseismic cycle suggesting that seismic segmentation is controlled by properties of the plate interface that persist through more than one earthquake cycle structural evidence indicates that differences in basal shear stress may be related to elevated pore pressure in the north

seismicity of central tibet from project indepth iii seismic recordings as part of project international deep profiling of tibet and the himalaya iii a 400 km long densely spaced array of 57 broadband and short period seismic stations was deployed in central tibet from august 1998 through may 1999 although originally designed to image the lithosphere with teleseismic events the array also recorded numerous local and regional seismic events more than 900 local and regional events were detected on at least 10 stations during the 1 year deployment and we were able to locate 267 local earthquakes a substantial number of the events were found to cluster in or near large grabens and along known strike slip faults while other events show no obvious correlation with known structures in addition to spatial clustering at least one of the large clusters also exhibits temporal clustering that may be associated with magmatic or geothermal activity in the upper crust the average v p and v s are estimated to be 5 85 and 3 35 km sec for the upper crust and 7 0 and 3 9 km sec for the lower crust respectively the 50 focal mechanisms computed from this set of events are consistent with north south shortening and east west extension there are no clear indications of significant local perturbations in the regional stress field induced by the collision between india and eurasia the majority of the focal mechanisms indicate normal and strike slip faulting at least six of the newly computed focal mechanisms however indicate thrust faulting which is a phenomenon not well documented previously ninety nine percent of the local earthquakes have focal depths shallower than 25 km and the locations of the few deeper events are poorly constrained the shallow earthquake focal depths are consistent with high temperatures and proposed ductile or aseismic behavior in the middle to lower crust of central tibet figure 6 1 figure 6 a earthquake locations computed from this study shown on shaded topographic data triangles are indepth iii seismic stations circles are events and are scaled by magnitude graphic 2 a color version of this figure is available online at the ssa web site b earthquake locations shown with major geologic structures from taylor et al 2003 3 reproduced with permission m h taylor personal comm 2002 triangles are indepth iii seismic stations geologic structures are as in figure 2 4 1 pending yes 2 f1 embed inline graphic 1 gif 3 ref 46 4 f3

present day crustal deformation in china constrained by global positioning system measurements global positioning system gps measurements in china indicate that crustal shortening accommodates most of india s penetration into eurasia deformation within the tibetan plateau and its margins the himalaya the altyn tagh and the qilian shan absorbs more than 90 of the relative motion between the indian and eurasian plates internal shortening of the tibetan plateau itself accounts for more than one third of the total convergence however the tibetan plateau south of the kunlun and ganzi mani faults is moving eastward relative to both india and eurasia this movement is accommodated through rotation of material around the eastern syntaxis the north china and south china blocks east of the tibetan plateau move coherently east southeastward at rates of 2 to 8 millimeters per year and 6 to 11 millimeters per year respectively with respect to the stable eurasia

thermochronologic constraints on the late cenozoic exhumation history of the gurla mandhata metamorphic core complex southwestern tibet how the tibetan plateau is geodynamically linked to the himalayas is a topic receiving considerable attention the karakoram fault plays key roles in describing the structural relationship between southern tibet and the himalayas in particular considerable debate exists at the southeastern end of the karakoram fault where its role is interpreted in two different ways one interpretation states that slip along the dextral karakoram fault extends eastward along the indus yalu suture zone bypassing the himalayas the other interprets that fault slip is fed southward into the himalayan thrust belt along the gurla mandhata detachment gmd to evaluate these competing models the late miocene history of the gmd was reconstructed from thermokinematic modeling of zircon u th he data three east west transects reveal rapid cooling of the gmd footwall from 8 0 1 3 ma to 2 6 0 7 ma model simulations show a southward decrease in slip magnitude and rate along the gmd in the north initiation of the gmd range between 14 and 11 ma with a mean fault slip rate of 5 0 0 9 mm yr the central transect shows an initiation age from 14 to 11 ma with a mean fault slip rate of 3 3 0 6 mm yr in the south initiation began between 15 and 8 ma with a mean fault slip rate of 3 2 1 6 mm yr the initiation ages and slip rates match the karakoram fault across several timescales supporting the idea that the two are kinematically linked specifically the data are consistent with the gmd acting as an extensional stepover with slip transferred southward into the himalayas of western nepal

present day crustal deformation around sagaing fault myanmar 1 global positioning system gps measurement campaigns in myanmar conducted in 1998 and 2000 allow quantifying the present day crustal deformation around the sagaing fault system in central myanmar both a regional network installed at four points within the country and a local 18 station network centered on the city of mandalay across the sagaing fault demonstrate that active deformation related to the northward motion of india is distributed across myanmar in a platelet that extends from the western edge of the shan plateau in the east to the andaman trench in the west in this platelet deformation is rather diffuse and distributed over distinct fault systems in the east the sagaing shan scarp fault system absorbs 10 mm yr this gps study combined with an on land geotectonic survey demonstrate that oblique slip of india along the rigid sundaland block is accommodated by a partitioned system characterized by distribution of deformation over a wide zone index terms 1206 geodesy and gravity crustal movements interplate 8155 1243 geodesy and gravity space geodetic surveys 8110 tectonophysics continental tectonics general 0905 8158 tectonophysics plate motions present and recent 3040 keywords tectonics gps fault southeast asia

continental deformation in asia from a combined gps solution 1 after decades of research on continental tectonics there is still no consensus on the mode of deformation of continents or on the forces that drive their deformation in asia the debate opposes edge driven block models requiring a strong lithosphere with strain localized on faults to buoyancy driven continuous models requiring a viscous lithosphere with pervasive strain discriminating between these models requires continent wide estimates of lithospheric strain rates previous efforts have relied on the resampling of heterogeneous geodetic and quaternary faulting data sets using interpolation techniques we present a new velocity field based on the rigorous combination of geodetic solutions with relatively homogeneous station spacing avoiding technique dependent biases inherent to interpolation methods we find 1 unresolvable strain rates 3 109 yr over a large part of asia with current motions well described by block or microplate rotations and 2 internal strain possibly continuous limited to high elevation areas

locations of selected small earthquakes in the zagros mountains the zagros mountains of southern iran are marked by a zone of high seismicity and accommodate a significant portion of the convergence between arabia and eurasia due to the lack of dense local seismic or geodetic networks the inferred kinematics of the collision in iran is mainly based on catalogs of teleseismically determined earthquake locations we surveyed all mw 4 5 earthquakes in the harvard centroid moment tensor hcmt and international seismological centre isc catalogs that occurred in the zagros mountains during the period 1992 2002 and that were spanned by interferometric synthetic aperture radar insar images from the ers 1 and 2 satellites we invert the observed deformation for the best fitting point source single fault plane and distributed fault slip for four earthquakes and one unexplained deformation event we find that we can precisely locate earthquakes that are too small to be well located by either the hcmt or isc catalogs allowing us to tie specific earthquakes to active geologic structures

independent active microplate tectonics of northeast asia from gps velocities and block modeling 1 independent okhotsk and amurian microplate motions are tested using velocities from 123 gps sites 80 from within the proposed okh and amu plate boundaries used to constrain the plate kinematics of northeast asia a block modeling approach is used to incorporate both rigid block rotation and near boundary elastic strain accumulation effects in a formal inversion of the gps velocities models include scenarios with and without independent okh and amu plate motion our modeling favors scenarios with independent okh and amu motion based on the application of f test statistics the independent okh plate rotates 0 231 deg myr clockwise with respect to north america about a pole located north of sakhalin the modeled amu plate rotates 0 298 deg myr counterclockwise with respect to nam about a pole located west of the magadan region the plate motion parameters of the independent plates are consistent with the kinematics inferred from earthquake focal mechanism solutions along their boundaries

surface deformation detected by alos palsar small baseline sar interferometry over permafrost environment of beiluhe section tibet plateau china abstract the evolution of permafrost and the active layer is highly related to biological diversity and climate change because of its feedback effects involving water and carbon storage in this study we firstly examined the relationship of active layer variation geomorphological processes and anthropogenic activities by means of small baseline synthetic aperture radar interferometry in beiluhe hoh xil natural reserve in tibet plateau tp china 3 5 yr observation span of l band alos palsar data june 2007 to december 2010 was used the estimated surface displacements primarily in the range of 20 mm yr 1 to 20 mm yr 1 and time series implied evolution of the active layer and permafrost beneath the motion trend along slopes was complicated due to the geomorphological processes and thus interdisciplinary interpretations were needed anthropogenic influences on this frail permafrost environment were significant as evident from the remarkable surface settlement along the embankment of qinghai tibet railway it is crucial and necessary to monitor this permafrost plateau owing to the consequences arising from a combination of factors related to climate change geo hazard prediction nature conservation and regional sustainable development

earthquake strain rates and instantaneous relative motions within central and eastern asia summary we use the spatial distribution of moment tensors of earthquakes in this century to estimate the velocity field in asia within a eurasian reference frame in a least squares inversion strain rates on the surface of the earth are matched with continuous spline functions in order to recover the velocity gradient tensor associated with the seismic moment release in asia earthquakes account for 40 60 per cent of the expected motion of india relative to eurasia with the missing component of strain rate equivalent to about 20 mm yr 1 of n s shortening between siberia and india in this solution south china rotates counterclockwise and moves eastwards relative to siberia using rigid plate constraints we next investigate the characteristics of the complete horizontal strain field in asia that accommodates plate motions our strain rate solutions are analogous to the response of a newtonian thin viscous sheet in which the rate of work done by the straining medium in accommodating the velocity boundary conditions is a minimum in these solutions the euler pole for india relative to eurasia is constrained nuvel 1a demets et al 1994 but in the process of fitting the vlbi velocity at shanghai china ward 1994 heki et al 1995 the euler pole for south china is determined in the inversion a solution that both fits the velocity at shanghai china and yields a strain rate field consistent with the earthquake mechanisms is one where the south china block has a motion relative to siberia described by the pole at 51 n 131 e 0 3 deg myr 1 comparison of the complete strain field that accommodates plate motion with the seismic strains indicates that earthquake moment release rates in this century within mongolia are about a factor of 4 larger than the long term rate within gansu ningxia the earthquake moment rates have been about a factor of 2 higher than the long term rate the strike slip faulting within mongolia gansu ningxia western sichuan and yunnan is possibly a direct result of velocity boundary conditions imposed on the south china block by forces unrelated to continental collision of india and eurasia such as forces associated with subduction along the margins of south eastern asia verification of this requires a better understanding of the role of pre existing zones of weakness within the asian continental lithosphere

coseismic fault slip of the 2008 mw 7 9 wenchuan earthquake estimated from insar and gps measurements 1 we infer co seismic fault slip during the 2008 mw 7 9 wenchuan earthquake from interferometric synthetic aperture radar insar and gps observations of ground deformation we use alos palsar data from ascending orbits on six tracks and we do not use data that are strongly affected by ionospheric perturbations we use a fault model composed of three planar fault segments of the beichuan fault and one planar segment representing the parallel pengguan fault maximum thrust slip is up to 6 7 m near the surface and occurs in two locations near yingxiu in the south and beichuan in the center of the rupture maximum strike slip is over 4 m and occurs near pingtong and nanba along the northern end of the rupture we find that the ratio of coseismic thrust to strike slip on the beichuan fault decreases from 1 5 to 0 7 from the sw to the ne citation feng g e a hetland x ding z li and l zhang 2010 coseismic fault slip of the 2008 mw 7 9 wenchuan earthquake estimated from insar and gps measurements geophys res lett 37 l01302 doi 10 1029 2009gl041213

coseismic reverse and oblique slip surface faulting generated by the 2008 mw 7 9 wenchuan earthquake china the mw 7 9 wenchuan china earthquake ruptured two large thrust faults along the long menshan thrust belt at the eastern margin of the tibetan plateau this earthquake generated a 240 km long surface rupture zone along the beichuan fault and an additional 72 km long surface rupture zone along the pengguan fault maximum vertical and horizontal offsets of 6 5 m and 4 9 m respectively were measured along the beichuan fault a maximum vertical offset of 3 5 m was measured along the pengguan fault coseismic surface ruptures integrated with aftershocks and industry seismic profiles show that two imbricate structures have ruptured simultaneously resulting in the largest continental thrust event ever documented large oblique thrusting observed during this earthquake indicates that crustal shortening is an important process responsible for the high topography in the region as everywhere along the edge of tibetan plateau

continuous deformation of the tibetan plateau from global positioning system data global positioning system velocities from 553 control points within the tibetan plateau and on its margins show that the present day tectonics in the plateau is best described as deformation of a continuous medium at least when averaged over distances of 100 km deformation occurs throughout the plateau interior by ese wnw extension and slightly slower nne ssw shortening relative to eurasia material within the plateau interior moves roughly eastward with speeds that increase toward the east and then flows southward around the eastern end of the himalaya crustal thickening on the northeast ern and eastern margins of the plateau occurs over a zone 400 km wide and cannot be the result of elastic strain on a single major thrust fault shortening there accommodates much of india s penetration into eurasia a description in terms of movements of rigid blocks with elastic strain associated with slip on faults between them cannot match the velocity field

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

characteristics of the active xiaojiang fault zone in yunnan china a slip boundary for the southeastward escaping sichuan yunnan block of the tibetan plateau abstract the xiaojiang fault zone within the yunnan province china is one of the most active fault zones of the southeastern edge of the tibetan plateau this n s trending 400 km long fault zone defines the southern part of the eastern boundary of the sichuan yunnan block which is escaping southeastward from the tibet plateau and rotating around the eastern himalayan syntaxis the middle section of the fault zone splits into two branches each branch fault consists of several en echelon faults basins of various ages have developed on the step overs between the secondary faults the left lateral strike slip rate along the eastern branch is up to 9 mm a and that on the western branch is 7 mm a more than 10 m 6 historic earthquakes have occurred along the fault zone the largest was the 1833 songming earthquake of m 8 four earthquake rupture zones were discovered along the fault zone 15 trenches have been excavated along every major segment of the fault zone and 4 5 paleoearthquakes have been distinguished along the xiaojiang fault zone the average strong earthquake recurrence interval is 2000 2500 years

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

himalayan seismic hazard the devastating earthquake in bhuj on 26 january 2001 highlighted the high earthquake risk in the indian region of gujarat in their perspective bilham et al warn that major earthquakes may be expected in another part of india the himalayan arc an analysis of historic earthquakes suggests that several major earthquakes are overdue in this region but that recent low activity has focused attention away from the himalayan arc projections from earlier earthquakes suggest that just one of the possibly overdue himalayan earthquakes may lead to 200 000 predictable fatalities

rapid slip along the central altyn tagh fault morphochronologic evidence from cherchen he and sulamu tagh consistent with the d 18 o record from the guliya ice cap in the west kunlun the features of interest were all formed by glacial and fluvial processes subsequent to marine isotope stage 5e with the youngest features having formed during the early holocene optimum this near field morphochronological slip rate is averaged over many earthquake cycles and is hence little affected by interseismic strain it is kinematically consistent with other somewhat lower geomorphic slip rate measurements to the east the average rate and lower bounds obtained from alternate interpretational models 18 4 mm yr cannot be reconciled with the most rece geodetic measurements 7 mm yr suggesting that interseismic strain and interactions with adjacent faults may lead to disparate geologic and geodetic rate estimates this late pleistocene holocene morphochronologic rate would imply that at this longitude the altyn tagh fault on the north edge of tibet might absorb almost as much of india s convergence relative to siberia as the himalayan main frontal thrust does on the southern edge of the plateau index terms 1035 geochemistry geochronology 1208 geodesy and gravity crustal movements intraplate 8110 8102 tectonophysics continental contractional orogenic belts 8107 tectonophysics continental neotectonics keywords slip rates cosmogenic dating indo asian collision

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

late cenozoic right lateral strike slip faulting in southern tibet field observations collected during the sino french himalaya tibet cooperation project 1980 1982 show that right lateral faulting between southern and northern tibet roughly along the chord joining the eastern and western syntaxes of the himalayan arc is a major component of the active tectonics north of the himalayas just north of the well developed rifts of southern tibet we studied three right lateral 100 200 km long strike slip faults forming an en echelon array along that chord evidence for earthquake surface breaks was found on each of these faults for the m 8 beng co or damxung strike slip earthquake of november 18 1951 rupture parameters could be constrained to be 8 2 m and l 90 km offset glacial and postglacial morphological markers 105 years and 104 years b p imply displacement rates of the order of 1 2 cm yr on the three faults the en echelon fault zone appears to extend westward 2000 km across the plateau to the karakorum fault and is thus referred to as the karakorum jiali fault zone kjfz fast rates of slip on it and on faults along the northern rim of tibet appear to contrast with the slower rates of deformations in the interior of the plateau our estimates of slip rates on the strike slip and normal faults of southeastern tibet suggest that eastward extrusion of north tibet between the right lateral kjfz and the left lateral altyn tagh and kun lun faults absorbs at least 30 of the present convergence between india and asia we propose an instantaneous velocity model of the active tectonics of asia compatible with such faulting rates and geometries evidence for tertiary right lateral strike slip movements in southern tibet and around the eastern syntaxis of the himalayas is also found in the structural record offsets of various large scale geological features imply that these movements have been large

the aksay segment of the northern altyn tagh fault tectonic geomorphology landscape evolution and holocene slip rate 1 millennial slip rates have been determined for the altyn tagh fault atf at three sites near aksay 94 e in northeastern tibet by dating fluvial channels and terrace riser offsets with radiocarbon and 10be 26al surface exposure dating up to nine main surfaces are defined on the basis of morphology elevation and dating the abandonment age of some surfaces is constrained by radiocarbon dating which typically coincides with the youngest cosmogenic ages for a particular surface older surface exposure ages are taken to represent the duration of terrace emplacement cumulative offsets range from 20 to 260 m and fall in distinct groups indicative of climatically modulated regional landscape formation most samples are younger than 14 ka and postdate the last glacial maximum the end of the early holocene optimum marks the boundary between the ages of the two main terrace levels at 5 6 ka at this longitude the atf is divided into a northern and southern branch the northern atf should thus yield a minimum rate for the atf system slip rate estimates using the abandonment age of the overlying level for fill terraces or channels and the emplacement of the underlying level for strath terraces give 30 consistent results yielding an average holocene rate of 17 8 3 6 mm yr it is 9 mm yr less than the long term rate obtained near tura at 87 e 26 9 6 9 mm yr in keeping with the inference of an eastward decreasing rate on the atf due to increased thrusting to the south however it remains twice the rate determined by gps studies

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

earthquake cycle deformation and fault slip rates in northern tibet fault slip rate estimates along the altyn tagh and kunlun strike slip faults in northern tibet vary considerably between short term geodetic and long term geologic studies here we reanalyze and model all global positioning system gps data from northern tibet to determine if these differences might be explained by previously unmodeled transient processes associated with the earthquake cycle which can bias slip rate estimates from geodetic data we find that these effects cannot reconcile the geodetic data with the lowest bounds on the geologic slip rates along these faults even in the presence of low 1018 pa s viscosities within the mid crust or crust and mantle lithosphere surface velocities derived from gps measurements are best reproduced with models with a high viscosity 1018 pa s middle to lower crust and mantle lithosphere

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

gps measurements of present day convergence across the nepal himalaya the high elevations of the himalaya and tibet result from the continuing collision between india and asia which started more than 60 million years ago1 4 from geological and seismic studies of the slip rate of faults in asia5 it is believed that approximately one third of the present day convergence rate between india and asia 58 4mmyr 1 is responsible for the shortening uplift and moderate seismicity of the himalaya great earthquakes also occur infrequently in this region releasing in minutes the elastic strain accumulated near the boundary zone over several centuries and accounting for most of the advance of the himalaya over the plains of india the recurrence time for these great earthquakes is determined by the rate of slip of india beneath tibet which has hitherto been estimated indirectly from global plate motions6 from the slip rates of faults in asia7 8 from seismic productivity9 and from the advance of sediments on the northern ganges plain10 here we report geodetic measurements using the global positioning system gps of the rate of contraction across the himalaya which we find to be 17 52 2 mm yr 1 from the form of the deformation field we estimate the rate of slip of india beneath tibet to be 20 5 2 mmyr 1 strain sufficient to drive one or more great himalayan earthquakes with slip similar to that accompanying the magnitude 8 1 bihar nepal 1934 earthquake may currently be available in western nepal

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

late holocene earthquake history of the central altyn tagh fault china the altyn tagh fault accommodates sinistral motion between the tibetan plateau and the tarim block within the india eurasia collision zone we used well preserved evidence for surface rupturing earthquakes to reconstruct the earthquake history for the central altyn tagh fault we identified three geometric fault segments bounded by left steps and a bend geomorphic offsets indicate that the most recent event had maximum surface displacement of 5 5 m in the west 38 58n 90 08e 7 m in the central part of our study area and 4 m in the east 38 88n 91 58e the 14 c dates and trench logs of disrupted sediments indicate that these offsets occurred either in a single earthquake with a surface rupture length 240 km dated as 680 6 108 yr b p or as two events if there were two events the westernmost recent event occurred 518 6 268 yr ago whereas the eastern event occurred 650 6 80 yr ago and had a surface rupture length 155 km we find two events in the past 0 8 2 2 k y in the west and two or three events in the east yielding recurrence intervals of 0 7 6 0 4 k y and 1 1 6 0 3 k y respectively these recurrence rates for major earthquakes are lower than expected if the long term fault slip rate is 20 mm yr explanations for the discrepancy include an overdue major earthquake or accelerated deformation elsewhere in the india eurasia orogen

spatial variations of flexure parameters over the tibet quinghai plateau we investigate the tibet quinghai plateau and the tarim basin in terms of spatial variations of the elastic thickness te in the frame of the thin plate flexure model the method of investigation makes use of a convolutive method which allows high spatial resolution of the flexure properties and overcomes some of the problems tied to the spectral admittance coherence methodologies we study the relation between the topographic and subsurface loads and the observed crust mantle interface cmi undulations the latter having been obtained from gravity inversion the gravity data used for the inversion are a unique set of high quality data available over the chinese part of the plateau and constitute the highest resolution grid today available in this impervious area the gravity inversion is constrained by results from the study of the propagation of seismic waves the two extensive sedimentary basins the tarim and the qaidam basins are modeled by forward gravity modeling the oscillations of the cmi obtained from the gravity inversion agree well with those expected by loading the thin plate model of spatially variably elastic thickness with the surface and subsurface loads it is found that the modeling of the sedimentary basins is essential in the flexure analysis the spatial variations of elastic thickness correlate with the extensions of the different terrains that constitute the plateau most of the tibet plateau has low te varying in the bounds 10 30 km with lower values in the qiangtang terrain where the te reaches 8 km the tarim and the qaidam basins precambrian platforms overlain by sediments are rigid and have a te of up to 110 km and 70 km respectively the flexural analysis distinctly discerns the tibet plateau with thick crust part of which is molten from the cratonic areas the tarim and qaidam basins which though of thinner crust act as undeformable rigid blocks

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

intraplate deformation of the indian subcontinent 1 while deformation at the earth s surface primarily occurs along tectonic plate boundaries major earthquakes have shaken regions deep within continental interiors three of the largest m 7 5 historic intraplate earthquakes occurred within the indian subcontinent suggesting the possibility of significant intraplate deformation we consider surface velocities determined from new gps data collected at 29 continuous gps stations and 41 survey mode gps stations in india between 1995 and 2007 to find a north south shortening rate of 0 3 0 05 nanostrain yr 1 which may be accommodated by 2 1 mm yr of more localized convergence across central india southward motions at 4 7 mm yr of sites on the shillong plateau in northeast india reflect rapid shortening and high earthquake hazard associated with active thrust faults bounding the plateau the width and magnitude of the elastic strain accumulation field across the himalaya varies little from 76 90 longitude but the strain is more broadly distributed and convergence rates are higher along the eastern 200 km of the range

long range and long term fault interactions in southern california paleoseismological data suggest the occurrence of four bursts of seismic moment release in the los angeles region during the past 12 000 yr the historic period appears to be part of an ongoing lull that has persisted for about the past 1000 yr these periods of rapid seismic displacement in the los angeles region have occurred during the lulls between similar bursts of activity observed on the eastern california shear zone in the mojave desert which is now seismically active a kinematic model in which the faults of the greater san andreas system suppress activity on faults in the eastern california shear zone and vice versa can explain the apparent switching of activity between the two fault networks combined with the observation that short term geodetic and longer term geologic rates co vary on major southern california fault systems this suggests that either 1 a temporal cluster of seismic displacements on upper crustal faults increases ductile deformation on their downward extensions or 2 rapid ductile slip in the lower crust beneath faults loads the upper crust driving a seismic cluster we suggest that alternating periods of rapid seismic displacement may be the expected mode of seismicity when two fault systems accommodate the same plate boundary motion and slip on one system suppresses slip on the other

current slip rates on conjugate strike slip faults in central tibet using synthetic aperture radar interferometry this is the published version copyright 2006 american geophysical union all rights reserved

bayesian inference of plastosphere viscosities near the kunlun fault northern tibet 1 flow of the mid crust in the tibetan plateau may strongly influence the patterns of deformation and topography within this area this flow requires the lower crust to have low viscosity and so quantifying this viscosity may be used to test the idea of channel flow an application of bayesian methods to geologic and geodetic data from north central tibet yields lower crustal viscosities assumed newtonian of 1 1019 pa s and 2 1021 pa s 95 bounds the lower bound is larger than the value of 1016 1018 pa s required by models of flow of the lower crust of tibet unless the entire lower crust participates in channel flow

revel a model for recent plate velocities from space geodesy 1 we present a new global model for recent plate velocities revel describing the relative velocities of 19 plates and continental blocks the model is derived from publicly available space geodetic primarily gps data for the period 1993 2000 we include an independent and rigorous estimate for gps velocity uncertainties to assess plate rigidity and propagate these uncertainties to the velocity estimates the velocity fields for north america eurasia and antarctica clearly show the effects of glacial isostatic adjustment and australia appears to depart from rigid plate behavior in a manner consistent with the mapped intraplate stress field two thirds of tested plate pairs agree with the nuvel 1a geologic 3 myr average velocities within uncertainties three plate pairs caribbean north america caribbean south america and north america pacific exhibit significant differences between the geodetic and geologic model that may reflect systematic errors in nuvel 1a due to the use of seafloor magnetic rate data that do not reflect the full plate rate because of tectonic complexities most other differences probably reflect real velocity changes over the last few million years several plate pairs arabia eurasia arabia nubia eurasia india move more slowly than the 3 myr nuvel 1a average perhaps reflecting long term deceleration associated with continental collision several other plate pairs including nazca pacific nazca south america and nubia south america are experiencing slowing that began 25 ma the beginning of the current phase of andean crustal shortening

continental tectonics in the aftermath of plate tectonics the success of plate tectonics required an acceptance of continental drift and thus a reinterpretation of the large scale geological history of most of the earth but the basic tenet of plate tectonics rigid body movements of large plates of lithosphere fails to apply to continental interiors where buoyant continental crust can detach from the underlying mantle to form mountain ranges and broad zones of diffuse tectonic activity

global positioning system constraints on fault slip rates in southern california and northern baja mexico we use global positioning system gps estimates of horizontal site velocity to constrain slip rates on faults comprising the pacific north america plate boundary in southern california and northern mexico we enlist a simple elastic block model to parameterize the distribution and sum of deformation within and across the plate boundary we estimate a pacific north america relative plate motion rate of 49 3 mm yr one standard deviation consistent with nuvel 1a estimates we are able to resolve robust slip rate estimates for the southernmost san andreas san jacinto and elsinore faults 26 2 9 2 and 6 2 mm yr respectively and for the imperial and cerro prieto faults 35 2 and 42 1 mm yr respectively accounting for about 86 of the total plate motion the remaining 14 appears to be accommodated to the west of these fault systems probably via slip along the san clemente fault and or the san miguel vallecitos rose canyon and newport inglewood fault systems these results are highly consistent with paleoseismic estimates for slip rates implying that off fault strain accumulation within the deforming zone of the plate boundary is largely elastic we estimate that the seismically quiescent southernmost san andreas fault has incurred about 8 2 m of slip deficit over the last few hundred years presumably to be recovered during a future large earthquake

inescapable slow slip on the altyn tagh fault 1 gps surveys conducted in 1994 1998 and 2002 on the central portion of the altyn tagh fault confirm left lateral slip rates of 9 4 mm yr significantly slower than geological estimates of slip rate for the past several thousand years the measurements were obtained on a 300 km long profile between 88 and 91 e within one fault dimension of the mw 7 6 and mw 7 8 kunlun earthquakes of 1997 and 2001 the inferred elastic displacements from these events are incorporated into the interpreted 1994 2002 velocity field the recent serendipitous occurrence of these two large earthquakes on a sub parallel fault system suggests that slip on the kunlun fault may have recently accelerated thereby reducing the slip rate on the altyn tagh fault however geodetic data from northern tibet prior to the 2001 earthquake indicate present day rates similar to long term rates this suggests that systematic errors may be present in published geologic slip rate estimates for the altyn tagh fault

slip rates of the karakorum fault ladakh india determined using cosmic ray exposure dating of debris flows and moraines most recent major glacial advance occurred at 90 15 ka this is consistent with the inference of others that alpine glaciers in this region have not necessarily expanded in concert with northern hemisphere continental ice sheets if features including lateral moraines that liu inferred to have been offset 300 350 m by the karakorum fault date from the same period they too imply a slip rate of 3 4 mm yr 1 this slip rate is comparable to rates of extension across grabens within tibet with recent evidence that slip along the altyn tagh fault occurs at 10 mm yr 1 our rate suggests that slip along the boundaries of tibet is not significantly more rapid than extension within the plateau hence plate tectonics in the strictest sense ought not be applied to tibet because tibet does not behave as a rigid plate index terms 1824 hydrology geomorphology 1625 1035 geochemistry geochronology 9320 information related to geographic region asia 8107 tectonophysics continental neotectonics keywords karakorum fault slip rate cosmic ray exposure age beryllium 10

quaternary rupture behavior of the karakoram fault and its relation to the dynamics of the continental lithosphere nw himalaya western tibet abstract the karakoram fault is a major strike slip system that partitions strain between the compressional regime of the nw himalaya and the translational and extensional fault systems of western tibet although seismic and geodetic observations suggest that the fault is currently locked a high millennial slip rate infers a dominant role in the deformation of western tibet we examine all quaternary data available for the karakoram fault and attempt to explain the temporal and spatial variability of fault slip rate we show that the karakoram fault stress level could be modulated by coulomb stress changes associated with varying seismicities on the subducting indian plate beneath western tibet our model has implications for the understanding of stress transfer between large fault systems and their interaction with lithosphere deformation we suggest that while the long term deformation of tibet may be modeled as a partially viscous medium the slip rates of major faults may vary by one order of magnitude during the quaternary our analysis may resolve the frequently observed discrepancy between millennial and decadal records of fault slip rates

on the temporal variability of the surface gulf stream and near bottom flows long 3 4 years time series of the surface gulf stream position and near bottom flow south of nova scotia support earlier findings of a barotropic semimonthly periodicity in the region a bimodal gulf stream path downstream of the new england seamount chain and a seasonal shift in the gulf stream position new results are 1 a marked reduction of the meridional shifts of the surface gulf stream when it is in its north position mode 2 the semimonthly periodicity seeming to be related at times to the mf tide the most energetic long period tide and 3 an energetic highly coherent but out of phase motion with a near 40 day period in the surface gulf stream position and near bottom flow

a deforming block model for the present day tectonics of tibet 1 we use gps data from 45 sites across the tibetan plateau surveyed between 1991 and 2001 to study the distribution of strain in that part of the india eurasia collision zone the plateau is cut by a few major rapidly slipping strike slip fault zones with broadly distributed strain between those zones the gps velocities can be fit well by a simple deforming block model that combines uniform strain with the motion of blocks separated by the major known fault zones within the plateau the boundaries of the four blocks in this model correspond to the major rapidly slipping faults a rigid block model with a smaller number of blocks fits the data poorly and can be rejected we estimate that 5 9 0 7 mm yr of extension in the n69 w direction occurs on the yadong gulu rift south of the plateau localized extension may extend as far north as the nyainqentanglha range we find 7 4 0 7 mm yr of right lateral slip on the karakorum jiali fault zone significantly slower than that previously estimated from offset geologic features our deforming block model and a two dimensional single fault screw dislocation model give lower and upper bounds of 4 4 1 1 and 10 3 0 4 mm yr on the slip rate on the kunlun fault respectively comparable in its highest to the long term slip rate observed geologically the distributed deformation is surprisingly uniform over the tibetan plateau qaidam basin and qilian shan and approximates a combination of pure shear and uniaxial contraction with the same axes of maximum contraction n32 e this strain field is a combination of shortening and extension that produces little net dilatation 1 area loss per million years at present the broadly distributed strain most likely represents slip on many faults each with a relatively low slip rate distributed conjugate strike slip faulting is the most plausible mechanism to produce the observed strains as supported by the record of medium to large earthquakes within the plateau the distributed deformation is just as important in the accommodation of the total india eurasia convergence as is slip on the major faults the eastward motion of central tibet is as large as 50 of the convergence rate between india and eurasia however this eastward motion is not motion of a relatively undeforming block bounded by rapidly moving strike slip faults as suggested by past extrusion models instead much of this eastward extrusion is driven by the internal extension of the plateau our inference is in agreement with the model of f shen et al 2001 that suggested east west extension north south contraction and eastward plateau growth dominate the present tectonics of the tibetan plateau

instantaneous global plate motion model from 12 years of continuous gps observations 1 we estimate a global plate motion model for 17 major and minor tectonic plates solely on the basis of analysis of data from 106 globally distributed continuous gps stations spanning the period from january 1991 to july 2003 site positions estimated from 24 hour segments of data are aligned day by day to the international gps service igs realization of the itrf2000 reference frame using a similarity transformation thereby ensuring that the itrf2000 no net rotation condition is preserved linear velocities of a carefully selected set of stations are estimated from the position time series along with annual and semiannual fluctuations and position offsets due to gps instrument changes a white noise plus flicker noise model is applied to estimate realistic uncertainties for the site velocities which are then propagated into the derived plate motion model parameters we also examine the vertical velocities in the site selection process at the scripps orbit and permanent array center we have implemented a procedure whereby the plate motion model is updated on a regular monthly basis to improve its precision and reliability as new data become available and as a baseline against which anomalous motions can be detected

modeling broadscale deformation in northern california and nevada from plate motions and elastic strain accumulation we present a first order method for modeling broadscale deformation consistent with both plate tectonic motions and elastic strain accumulation on plate boundary faults interseismic deformation is assumed to be a superposition of long term rigid body motions between faults defined by angular velocities of spherical plates and backslip on shallow locked portions of faults in an elastic half space this method is applied to 1993 2000 continuous gps data from 35 sites in a profile from the san francisco bay area northern california to eastern nevada deformation is consistent within the 1 mm yr 1 uncertainties of the estimated site velocities with a simple 10 parameter model using 6 rigid plates and 3 locked san andreas system faults

low quaternary slip rate reconciles geodetic and geologic rates along the altyn tagh fault northwestern tibet for more than two decades the slip rate along the active left slip altyn tagh fault of northwestern tibet has been disputed with millennial rates reported to be as much as three times faster than those determined geodetically this problem is significant because the total offset plate boundary length and age of the altyn tagh fault make it the most important single structure accommodating india asia convergence north of the himalayas here we show that the central altyn tagh fault slipped at only 14 9 mm a over the past 4 6 ka by tightly bracketing the age of a displaced fluvial terrace riser at yuemake 88 51 e 38 19 n this result contradicts previous latest quaternary rates and is consistent with those derived from geodetic paleoseismic and geologic measurements and thus resolves the long standing dispute over the latest quaternary slip rate along the longest active strike slip fault in tibet