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

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

late pleistocene holocene right slip rate and paleoseismology of the nayband fault western margin of the lut block iran the 290 km long nayband strike slip fault bounds the western margin of the lut block and cuts across a region thought to have been quiescent during the last few millennia cl 36 cosmic ray exposure cre and optically stimulated luminescence osl dating of cumulative geomorphic offsets are used to derive the long term slip rate the measured offsets at two sites along the fault range between 9 1 m and 195 15 m with ages from 6 8 0 6 ka to 100 ka yielding minimum and maximum bounds of late pleistocene and holocene slip rates of 1 08 and 2 45 mm yr 1 respectively this moderate slip rate of 1 8 0 7 mm yr 1 averaged over several earthquake cycles is compared to the paleoseismic record retrieved from the first trench excavated across the fault combining the paleoseismic evidence with 18 osl ages obtained from this trench site demonstrates the occurrence of at least four large m 7 earthquakes during the last 17 4 1 3 ka and of two older wearthquakes one before 23 ka and another before 70 5 ka the exposed sediment succession also indicates a significant gap at the end of mis 2 and the beginning of mis 1 the age of the most recent regional incision is accurately bracketed between 6 1 ka and 7 4 ka sediments from the last 7 ka contain evidence of the three younger earthquakes interestingly the penultimate and antepenultimate events occurred between 6 5 0 4 ka and 6 7 0 4 ka within a time interval lasting at most 1 ka whereas the most recent earthquake occurred within the last millennium such an irregular earthquake occurrence suggests the seismic behavior of the nayband fault is not strictly time dependent but possibly related to clustering from this and taking into account the occurrence of the most recent earthquake within the last 800 years the imminence of an earthquake along the nayband fault cannot be discarded although the most recent surface rupturing event seems to have occurred after ad 1200 this event went unnoticed in the historical records this provides a marked illustration of the incompleteness of the historical seismic catalogs in central iran challenging any assessment of regional seismic hazard without appropriate geologic and geochronological information large and infrequent earthquakes are characteristic of the seismic behavior of the slow slipping strike slip faults slicing central and eastern iran also the slip rates summed across central and eastern iran from the iran plateau up to the afghan lowlands appear in agreement with the most recent gps data

seismic velocity ratio in the crust and uppermost mantle in southeast wellington province new zealand the regional variation of the seismic velocity ratio over a 200 km long traverse has been studied by means of microearthquake surveys the wadati plot method is used with a minimum of four p and s arrivals for each of 49 earthquakes the area as a whole is found to be characterized by a value of 1 74 1 76 for earthquakes of depth 12 40 km except in a 50 km long section near wellington where is low at 1 60 this low has been attributed to the fault zones in the region a small change of is observed between the upper crust 5 km and lower crust 12 km but there is no change of between the lower crust and uppermost mantle

analysis of strong phases other than p and s from a microearthquake survey in the wellington region new zealand a few subcrustal earthquakes located by means of a microearthquake survey in the wellington region at the indian and pacific plate boundary exhibit strong phases between first p and first s arrivals these phases have been identified as having been converted from s to p sp or p to s ps at the mohorovicic discontinuities of the indian and pacific plates examples of these phases are shown here two events are selected and simple models are assumed to draw ray paths of these phases as possible explanations of mode conversion

comment on slip rate measurements on the karakorum fault may imply secular variations in fault motion chevalier et al 1 1 presented cosmic ray exposure dates for glacial deposits offset by movement along the karakorum fault they inferred a late quaternary slip rate on this fault 10 7 0 7 mm year that is higher than rates reported in recent field studies 2 2 the reported rate

revision of the age of magnetization of the montmartin red beds normandy france summary a new roadcut has enabled us to sample the south dipping limb of the montmartin syncline for a palaeomagnetic reevaluation of an earlier result published by jones van der voo bonhommet in combination with the results previously published in 1979 for the north dipping beds of the syncline a conclusively negative fold test is obtained the resulting magnetization declination inclination 206 3 95 12 palaeopole at 38 s 325 e is interpreted to be of late carboniferous age not late devonian as thought earlier simultaneously we have re evaluated the age of the rocks previously thought to be late devonian on the basis of acritarchs chitinozoans and spores it has not been possible to reconfirm these fossils not even in the same samples as studied originally in contrast the regional presence of early palaeozoic fossils suggests to us an age similar to that of other red beds in the arrnorican massif which have been dated as early ordovician the geodynamic implications of our finding that the montmartin rocks are completely remagnetized however are of no great consequence for the geodynamics of the hercynian belt pre folding magnetization obtained from silurian and devonian rocks in spain and germany argue for the same conclusion as reached erroneously in our earlier study namely that the armorican massif and adjacent parts of hercynian europe were adjointed to north america great britain the baltic shield and the russian platform since at least late devonian time if a medio european ocean existed during the palaeozoic it was virtually closed before the mid devonian and of insignificant width during culm deposition in early carboniferoirs time

a seismic structure study in the kaoping area southwestern taiwan the difference between s wave and s to p wave conversion s p phase arrival times is enhanced with rectilinear motion detector filtering to describe alluvial sediment thickness in the kaohsiung pingtung kaoping plains area a more complete understanding of the underground structures of the kaoping area is provided in this paper and explains why the surrounding regions in taiwan experience more earthquakes than the kaoping area data are based on seismic activity recorded by the portable array for numerical data acquisition panda for the period from 1995 to 1997 the difference between s wave and s p phase arrival times shows that the sedimentary layer is thicker along the west and southwest coasts p wave travel time residuals high frequency attenuation parameters kappa and quality factor q p q s and coda waves confirm this result we also determined the orientation of the chaochou fault using the first motion of p wave arrivals to the east of the chaochou fault stress trends southeast northwest while to the west it trends northeast southwest the change in stress trends east and west of chaochou fault suggests the presence of a highly fluid accretionary wedge in the kaoping area the chaochou fault forms a seismically active tectonic boundary with the uplift of the hanging wall leading to westward tilting of the basement of the kaoping plains we demonstrate that these features are the reason there are relatively few earthquakes in the kaoping area the presence of a highly fluid accretionary wedge is indicated by a thick alluvial layer in the west and southwest kaoping coasts the peikung high acts as the indenter that may allow seismic energy to escape and reduce the number of earthquakes in the region online material figures illustrating calculations of kappa q c p and s wave spectra q p and q s from ground motion data

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

a framework of holocene and late pleistocene environmental change in eastern iran inferred from the dating of periods of alluvial fan abandonment river terracing and lake deposition abstract we review studies of the holocene and late pleistocene stratigraphy of eastern iran to infer past changes in the environment within this presently arid region we build a scenario of widespread and presumably climatically driven evolution of the landscape through the holocene six sites covering a 10 range in latitude indicate a regional abandonment of alluvial fan surfaces at 10 3 ka with the younger 9 ka end of this age range supported by several of the best constrained studies incision of rivers into the fan surfaces has occurred in discrete stages in the early to mid holocene 9 7 ka leading to the formation of flights of river terraces detailed records of lakebed deposition in the presently arid interior of iran are rare though the available data indicate lake highstand conditions at

no late quaternary strike slip motion along the northern karakoram fault abstract models that treat long term evolution of the tibetan orogen in terms of interactions between rigid blocks require the right slip karakoram fault that bounds the western margin of the tibetan plateau to be a long lived stable high slip rate feature while the southern portion of the fault clearly remains active recent work has proposed that the northern half of the karakoram fault is currently inactive new field observations and geochronologic results from the northern end of the karakoram fault system confirm this interpretation and provide the first quantitative data on the minimum age for the termination of slip in the southeast pamir gravel that yields a u series age of 198 5 ka on secondary carbonate caps a non deformed strath terrace that extends across the main strand of the karakoram fault the secondary achiehkopai fault strand is overlain by undisturbed hangdi glacial stage 24 6 ka deposits and dabudar glacial stage penultimate glacial cycle 150 ka or older deposits which lack observable lateral displacement or deformation together these observations show that the northern portion of the karakoram fault system has not accommodated any detectable strike slip deformation since at least 24 6 ka and most likely since 200 ka or more these results show that the karakoram fault system no longer forms a continuous discrete kinematic boundary at the western margin of the tibetan plateau this suggests that even long 500 km strike slip faults within orogenic belts are inherently unstable features consistent with models of continental collision zones involving relatively weak crust and distributed deformation

the role of the indian summer monsoon and the mid latitude westerlies in himalayan glaciation review and speculative discussion new dates for late quaternary glaciations in the himalayas show that during the last glacial cycle glaciations were not synchronous throughout the region rather in some areas glaciers reached their maxima at the global glacial maximum of c 18 20 ka bp whereas in others glaciers were most extensive at c 60 30 ka bp comparison of these data with palaeoclimatic records from adjacent regions suggest that on millennial timescales himalayan glacier fluctuations are controlled by variations in both the south asian monsoon and the mid latitude westerlies

timing and style of late quaternary glaciation in northeastern tibet glacial successions in the anyemaqen and nianbaoyeze mountains of northeastern tibet are reassessed and new glacial chronologies are presented for these regions cosmogenic radionuclide and optically stimulated luminescence dating indicates that two glacial advances occurred in marine isotope stage mis 3 and mis 2 in the anyemaqen mountains a third advance occurred in the early holocene we suggest that glaciation was synchronous in the anyemaqen and nianbaoyeze mountains as well as in other glaciated areas of tibet and the himalaya that are influenced by the asian monsoon the maximum extent of glaciation occurred early in the last glacial cycle mis 3 during a time of increased insolation when the monsoon intensified and supplied abundant precipitation as snow at high altitude to feed high altitude glaciers this suggests that precipitation as snow is fundamental in controlling glaciation in these regions however the occurrence of glacial advances during the insolation minimum of mis 2 suggests that despite reduced precipitation at this time the annual temperatures were cold enough to maintain positive glacier mass balances the numerically defined chronologies for the anyemaqen and nianbaoyeze mountains presented here provide a framework for comparing glacial advances in other parts of high asia

short paper cadomian terrane tectonics and magmatism in the armorican massif the north armorican composite terrane nw france is a collage of displaced terranes which result from the amalgamation of cadomian continental arcs and marginal basin complexes by sinistral transpression along a continental margin above a subduction zone early cadomian arc activity occurred at c 700 650 ma but terrane accretion did not occur until c 540 ma and post tectonic magmatism persisted well into the palaeozoic cadomian events thus span a considerably greater period than previously supposed

shallow morphology of the subducted pacific plate along the hikurangi margin new zealand abstract along the east coast of the north island new zealand the pacific plate is subducted beneath the australian plate the seismicity associated with this subduction has been determined using the results from a number of temporary and permanent microearthquake networks a synthesis of the microearthquake seismicity the depths of thrust events the depth of s to p conversions and deep reflection seismic studies leads to a coherent picture of the subducting slab both in terms of its mechanical structure and in terms of the general morphology the slab is initially subducted at a low angle of a few degrees is bent through a circular arc of few hundred kilometre radius and then becomes planar again below 120 km depth the radius of curvature varies along strike from about 280 km just north of wellington to 240 km north of hawke bay the slab shape between depths of 15 45 km is thus approximately conical it also approximates within the errors of hypocentre location a surface of constant gaussian curvature as would be geometrically expected from the simple bending of a thin spherical lithospheric shell observed seismicity is primarily concentrated within what is interpreted as the subducted crust of the pacific plate with a lower level of activity within the subducted mantle normal fault mechanisms at the top of the plate probably reflect tensional stress associated with the plate bending whereas thrust events observed at the lower bound of the observed seismicity probably reflect compression below the neutral plane

beryllium 10 dating of mount everest moraines indicates a strong monsoon influence and glacial synchroneity throughout the himalaya moraine successions in glaciated valleys south of mount everest provide evidence for at least eight glacial advances during the late quaternary cosmogenic radionuclide crn surface exposure dating of moraine boulders defines the timing of each glacial advance and refines the previous glacial chronologies the crn data show that glaciation was most extensive during the early part of the last glacial marine oxygen isotype stage mis 3 and earlier but limited during mis 2 the global last glacial maximum and the holocene a previously assumed neoglacial advance is dated to 3 6 6 0 3 ka and the crn dates confirm a glacial advance ca 1 ka these results show that glaciations on the south side of everest were not synchronous with the advance of northern hemisphere ice sheets yet glaciations within the himalaya the world s highest mountain belt were synchronous during the late quaternary the existence of glacial advances during times of increased insolation suggests that enhanced moisture delivered by an active south asian summer monsoon is largely responsible for glacial advances in this part of the himalaya these data allow us to quantify the importance of global climate change and monsoon influence on glaciation in the himalaya

microseismicity and tectonics at the indian pacific plate boundary south east wellington province new zealand summary the seismicity structure and tectonics of part of the north island plate boundary have been studied by means of a microearthquake traverse in the south eastern part of wellington province the short term microseismicity observed in this survey is similar to the long term macroseismicity about 200 microearthquakes have been located in a four week survey microearthquakes occur mostly within the depth range 20 40 km defining a band of activity which is fairly continuous and uniform along the strike direction of the subducted pacific plate a break in seismic activity is observed below 40 km depth however in vertical sections along the direction of the dip of the subducted plate systematic differences in microearthquake activity are observed between the supposedly locked and unlocked regions of the subducted plate the sections show further how the foci deepen progressively towards the north west focal mechanisms of 115 well located microearthquakes are examined in relation to the structure and tectonics of the region the mechanisms are related to the plate interface geometry in a manner consistent with that found for other regions of plate convergence microearthquakes in the overriding plate are associated with thrust fault mechanisms while those in the subducted plate exhibit normal faulting the stress pattern is also consistent with the tectonics of the region the t axes of the normal fault mechanisms are parallel to the dip of the subducted plate whereas the p axes of the thrust fault mechanisms are nearly in the e w direction this is consistent with the suggestion that the plates are locked in the coastal part of the region in addition small but systematic differences in the thickness and dip of the benioff zone are observed in the sw the zone is about 5 km thinner and 6 less steep than in the ne on the landward side there is a bend in the benioff zone at 25 30 km depth the dip of the zone sharply increases below this depth where it enters the region of negative gravity anomaly

short term viscous effects on measurements of remanance summary the magnetic remanence of some rock specimens when measured in mu metal shielded magnetometers appear to include a rapidly acquired 100 s component that has a characteristic direction for each magnetometer which seems to be related to the sequence of specimen positions during measurement this spurious remanence can be mistaken for a stable linear geologically meaningful magnetic vector the effect can be partially reduced by passing a small current through a coil wound around the mu metal opening and largely but not completely eliminated by placing the magnetometer in field free space

uncertainties in slip rate estimates for the mission creek strand of the southern san andreas fault at biskra palms oasis southern california this study focuses on uncertainties in estimates of the geologic slip rate along the mission creek strand of the southern san andreas fault where it offsets an alluvial fan t2 at biskra palms oasis in southern california we provide new estimates of the amount of fault offset of the t2 fan based on trench excavations and new cosmogenic 10be age determinations from the tops of 12 boulders on the fan surface we present three alternative fan offset models a minimum a maximum and a preferred offset of 660 m 980 m and 770 m respectively we assign an age of between 45 and 54 ka to the t2 fan from the 10be data which is significantly older than previously reported but is consistent with both the degree of soil development associated with this surface and with ages from u series geochronology on pedogenic carbonate from t2 described in a companion paper by fletcher et al this volume these new constraints suggest a range of slip rates between 12 and 22 mm yr with a preferred estimate of 14 17 mm yr for the mission creek strand of the southern san andreas fault previous studies suggested that the geologic and geodetic slip rate estimates at biskra palms differed we find however that considerable uncertainty affects both the geologic and geodetic slip rate estimates such that if a real discrepancy between these rates exists for the southern san andreas fault at biskra palms it cannot be demonstrated with available data

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

improved moraine age interpretations through explicit matching of geomorphic process models to cosmogenic nuclide measurements from single landforms abstract the statistical distributions of cosmogenic nuclide measurements from moraine boulders contain previously unused information on moraine ages and they help determine whether moraine degradation or inheritance is more important on individual moraines here we present a method for extracting this information by fitting geomorphic process models to observed exposure ages from single moraines we also apply this method to 94 10 be apparent exposure ages from 11 moraines reported in four published studies our models represent 10 be accumulation in boulders that are exhumed over time by slope processes moraine degradation and the delivery of boulders with preexisting 10 be inventories to moraines inheritance for now we neglect boulder erosion and snow cover which are likely second order processes given a highly scattered data set we establish which model yields the better fit to the data and estimate the age of the moraine from the better model fit the process represented by the better fitting model is probably responsible for most of the scatter among the apparent ages our methods should help resolve controversies in exposure dating we reexamine the conclusions from two published studies based on our model fits

macrostructural and microstructural architecture of the karakoram fault relationship between magmatism and strike slip faulting a key factor in interpreting the significance of large scale strike slip faults in models of continental deformation is an understanding of the temporal relationship between faulting and magmatism knowledge of when a strike slip fault initiated is essential in order to determine its long term slip rate and its significance in accommodating strain we review key structural criteria that identify whether magmatism is prekinematic or synkinematic with faulting and apply these criteria to a major tibet bounding strike slip fault along the karakoram fault in western tibet opinion is divided between 1 those advocating that magmatism and shearing were coeval in which case the youngest u pb crystallization age provides a minimum age of shear and 2 those advocating that magmatism preceded strike slip shearing in which case the youngest u pb crystallization age provides a maximum age of shear fault zone rocks within the central segment of the fault are variably deformed displaying high to low temperature solid state fabrics mylonites indicate subsolidus noncoaxial deformation at temperatures that have not exceeded greenschist lower amphibolite facies there is no evidence for submagmatic deformation and there are no textural or structural indicators that suggest synkinematic magmatism consequently magmatism preceded shearing suggesting that the u pb age of proximal leucogranites sets a maximum age for shear coupled with a limited offset 150 km these data confirm a low long term slip rate for the karakoram fault 3 10 mm yr consequently the fault is unlikely to have played a significant role in accommodating strain during the indo asian collision and thus its role in suggested extrusion models of deformation is limited

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

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

active faulting mountain growth and erosion at the margins of the tibetan plateau constrained by in situ produced cosmogenic nuclides abstract the india asia collision zone is a key area for understanding continental plateau formation and mountain building two fundamental questions in this context are how the northeastward motion of india is partitioned between strike slip and thrust faults and how mountain building is counteracted by erosion cosmogenic nuclides allow us to address these questions because they provide age constraints on tectonically offset landforms and constraints on erosion rates after considerable debate on whether or not major strike slip faults move at high rates of up to 20 30 mm yr and absorb most of the continental deformation it now appears that the three largest faults altyn tagh haiyuan kunlun have millennial slip rates of no more than 8 13 mm yr consistent with rates of elastic strain accumulation determined by geodetic methods furthermore a significant portion of the lateral slip on these faults is transferred to thrust faults within the collision zone both observations indicate that the eastward tectonic escape of material along these faults is less important than often assumed with respect to mountain building and erosion cosmogenic nuclide studies show that thrust faults at the northeastern and eastern margins of tibet qilian shan longmen shan have vertical slip rates of 0 3 to 2 mm yr while catchment wide erosion rates vary from 0 02 to 1 0 mm yr with high relief areas eroding significantly faster than the plateau interior and growing mountains in the foreland the deeply incised regions have apparently reached an erosional steady state in which rock uplift is balanced by erosion river terraces at active mountain fronts document repeated changes between sediment deposition and fluvial incision during the quaternary incision and terrace formation occurred predominantly at glacial interglacial transitions but also during interglacial periods hence flights of terraces at the fault bounded mountain fronts record the interplay between sustained rock uplift and a temporally variable climate

pn velocity study using a temporary seismographic network in the shillong plateau northeast india abstract seismic p wave velocity pn of the uppermost mantle beneath the shillong plateau has been studied using a temporary seismographic network refracted pn arrivals of shallow distant earthquakes m 3 0 recorded at pairs of stations lying within 2 azimuthal differences with respect to a given epicenter are used in this study since the method is based on relative travel time differences the measurement is independent of origin time and location errors the average pn velocity is found to be 8 57 0 02 km sec which is higher than the average mantle velocity 8 13 km sec under other areas of the indian subcontinent the observed high pn velocity beneath the plateau may be attributed to the presence of high density material

accuracy of cosmogenic ages for moraines analyses of all published cosmogenic exposure ages for moraine boulders show an average age range of 38 between the oldest and youngest boulders from each moraine this range conflicts with the common assumption that ages of surface boulders are the same as the age of the landform the wide spread in boulder ages is caused by erosion of the moraine surface and consequent exhumation of fresh boulders a diffusion model of surface degradation explains the age range and shows that a randomly sampled small set of boulders n 3 7 will always yield a lower age limit for the moraine the model indicates that for identical dating accuracy six to seven boulders are needed from old and tall moraines 40 000 100 000 yr 50 100 m initial height but only one to four boulders from small moraines 20 000 100 000 yr 10 20 m by following these guidelines the oldest obtained boulder age will be 90 of the moraine age 95 probability this result is only weakly sensitive to a broad range of soil erosion rates our analysis of published boulder ages indicates that 3 of all moraine boulders have prior exposure and 85 of these boulders predate the dated moraine

too young or too old evaluating cosmogenic exposure dating based on an analysis of compiled boulder exposure ages cosmogenic exposure dating has greatly enhanced our ability to define glacial chronologies spanning several global cold periods and glacial boulder exposure ages are now routinely used to constrai

palaeomagnetism of late precambrian cambrian volcanics and intrusives from the armorican massif france samples of the keratophyre tuffs of treguier 640 12 myr of the upper brioverian series and the microgranite dykes of loguivy 548 24 myr have been collected from the north coast of brittany france the samples were progressively demagnetized with af and predominantly thermal methods blocking temperatures coercivities and acquisition of isothermal remanent magnetization irm indicate that the keratophyre remanence is variably carried in magnetite hematite or occasionally in both after removal of a soft viscous component two stable palaeomagnetic directions were found one in magnetite the other in hematite the characteristic magnetite direction tb 300 580 c is a pre folding primary thermoremanent magnetization trm which after structural correction has a mean declination inclination of 217 9 30 4 the younger hematite component has a mean in situ direction of 320 4 20 3 the microgranite natural remanent magnetization nrm intensity distribution is distinctly bimodal forming high and low 1 6 a m 1 intensity groups upon demagnetization a single stable remanence in magnetite was removed between 300 and 580 c or 20 and 100 mt two characteristic directions were found to be statistically related to the intensity groups at the 99 per cent confidence level low intensity samples have a mean direction of 201 9 2 3 and probably resulted from a late devonian early carboniferous local magnetization high intensity microgranites have a mean direction of 200 50 8 and this remanence is shown to be a primary trm palaeopoles obtained from the two keratophyre magnetizations magnetite 44 7 n 116 4 e hematite 39 5 n 233 6 e as well as the high intensity microgranite remanence 5 8 s 339 9 e show good agreement with similar age poles from the apparent polar wander path for the armorican massif comparison of these data to recent palaeomagnetic data from southern england and wales gives additional evidence to link that region with the armorica plate as proposed by van der voo and hagstrum et al

evidence against quaternary slip on the northern karakorum fault suggests kinematic reorganization at the western end of the himalayan tibetan orogen abstract while the right slip karakorum fault is one of the most prominent structures in the himalayan tibetan orogen its evolution and role in accommodating deformation related to the collision between india and asia is controversial different models interpret the karakorum fault as either 1 a long lived stable feature analogous to a plate boundary structure or 2 an evolving fault system with limited displacement 150 ka overly the trace of the two strands of the karakorum fault and show no evidence of tectonic disturbance 2 older late pliocene to early quaternary loess deposits which overlie the trace of the fault are either undisturbed or are cut by small normal fault scarps with no evidence of strike slip displacement 3 east west trending bedrock incised stream valleys up to 500 m deep cross both strands of the fault with no sign of lateral deflection i suggest that termination of slip along the northern segment of the karakorum fault occurred in the pliocene due to southward propagation of the altyn tagh fault system along the longmu co gozha co fault and impingement of the karakorum fault this study suggests that large intracontinental strike slip faults embedded within orogenic plateaus are transient features which should be expected to have complicated kinematic histories and short life spans relative to the life of an orogenic belt

reflected and mode converted seismic waves within the shallow aleutian subduction zone southern kenai peninsula alaska pronounced secondary phases observed in local recordings of quarry shots and earthquakes on the southern kenai peninsula alaska are identified as reflected p and s and converted s to p phases originating within four depth ranges in the upper few kilometers of the cook inlet tertiary basin at midcrustal depths within the overthrust north american plate at about 35 km depth near the top of the wadati benioff seismic zone in proximity to the inferred interplate megathrust and at about 5 10 km below the megathrust in the subducted pacific plate beneath the landward margin of the accreted chugach terrane the mid upper plate mup discontinuity dips as steeply as 20 degree 30 degree to the west northwest over the depth range 12 18 km at shallower depths it flattens and possibly arches with the crest at about 10 km depth similar midcrustal reflectors have been imaged about 125 km to the southwest and about 350 km to the northeast along the structural trend of the chugach terrane the extensive reflectors may have a common origin possibly caused by the presence of underplated rocks relative amplitudes and polarities of the secondary phases originating at mup depths provide few constraints on the nature of the discontinuity it appears that the mupmore discontinuity is seismically inactive and does not represent a brittle ductile transition zone within the upper plate the two converted s to p phases generated near the top of the subducted plate could indicate a low velocity zone associated with subducted oceanic crust less

contributions and unrealized potential contributions of cosmogenic nuclide exposure dating to glacier chronology 1990 2010 abstract this paper reviews the application of cosmogenic nuclide exposure dating to glacier chronology exposure dating of glacial landforms has made an outsize impact on this field because the technique filled an obvious need that had already been recognized by glacial geologists by now hundreds of studies have used cosmogenic nuclide exposure dating to date glacial deposits and in fact it is rare to find a study of glacial geology or glacier chronology or any paleoclimate synthesis that makes use of such studies that does not involve exposure dating these developments have resulted in major contributions to glacier chronology and paleoclimate in particular i reconstructing antarctic ice sheet change ii establishing the chronology of late pleistocene and holocene glacier change in mountain regions where it was previously unknown iii establishing the broad chronological outlines of mountain glaciations prior to the last glacial maximum and iv gaining insight into subglacial erosional processes through the observation that many glaciated surfaces preserve cosmogenic nuclide inventories from long past ice free periods as well as the present one an important potential future contribution will be the application of the large data set of exposure dated glacier chronologies to better understand global and regional climate dynamics during lateglacial and holocene millennial scale climate changes however this contribution cannot be realized without significant progress in two areas i understanding and accounting for geologic processes that cause apparent exposure ages on glacial landforms to differ from the true age of the landform and ii minimizing systematic uncertainties in exposure ages that stem from cosmogenic nuclide production rate estimates and scaling schemes at present there exists an enormous data set of exposure ages on glacial deposits but these data cannot be used to their full potential in paleoclimate syntheses due to an inadequate understanding of geologic scatter and production rate uncertainties the intent of this paper is to highlight this situation and suggest some strategies for realizing this potential

spatial variations in late quaternary slip rates along the doruneh fault system central iran the doruneh fault system dfs is one of the major active strike slip faults in the arabia eurasia collision zone despite its geological activity no large m 6 5 historical or instrumental earthquakes have been recorded along it to date the rate and distribution of slip as well as the seismic behavior of the dfs have been unknown we reconstructed 67 geomorphic offsets recorded by three successive alluvial abandonment surfaces q1 q2 and q3 displaced along the western wfz and central cfz fault zones the determined ages of 12 36 and 120 ka using in situ produced 10 be and 36 cl cosmogenic nuclides for theses surfaces allowed to estimate three sets of individual left lateral slip rates and consequently to describe the spatiotemporal distribution of slip along the cfz and wfz the slip rates averaged over time intervals of 36 and 120 ka reveal variable slip rates along length but similar slip rates at a point with a maximum rate of 8 2 mm yr during the holocene however the fault slip behavior appears more complex with a maximum rate of 5 3 mm yr the cfz is divided into two 4 km apart segments with symmetrical slip distributions relative to a persistent boundary which has not been ruptured over the last 12 ka the maximum length of seismic fault segments varies from 70 to 100 km which could produce earthquakes with a magnitude of m w 7 2 7 4 this emphasizes the necessity of segmentation models for long strike slip faults that may not necessarily rupture along their whole length during a single earthquake

holocene slip rate along the gyaring co fault central tibet although geodetic measurements of interseismic deformation in interior tibet suggest slow strain accumulation active slip along the right lateral gyaring co fault is suggested to be between 8 and 21 mm yr reliable geologic constraints on the slip rate along this fault are sparse here we document 12 2 m of right lateral displacement of lacustrine shorelines across the gyaring co fault optically stimulated luminescence ages of the shorelines are tightly clustered between 4 1 and 4 4 ka these data require an average slip rate of 2 2 3 2 mm yr along the central gyaring co fault during the latter half of the holocene consideration of seismic cycle effects allows the possibility of slightly higher average slip rates up to 2 2 4 5 mm yr overall our results suggest that the slip rate along the gyaring co fault is similar to other strike slip faults in interior tibet supporting the notion that active deformation in this region is distributed among numerous slowly moving faults

beryllium 10 dating of the duration and retreat of the last pinedale glacial sequence accurate terrestrial glacial chronologies are needed for comparison with the marine record to establish the dynamics of global climate change during transitions from glacial to interglacial regimes cosmogenic beryllium 10 measurements in the wind river range indicate that the last glacial maximum marine oxygen isotope stage 2 was achieved there by 21 700 700 beryllium 10 years and lasted 5900 years ages of a sequence of recessional moraines and striated bedrock surfaces show that the initial deglaciation was rapid and that the entire glacial system retreated 33 kilometers to the cirque basin by 12 100 500 beryllium 10 years

late quaternary slip rate along the central bangong chaxikang segment of the karakorum fault western tibet insight into the spatial and temporal changes of slip rate is essential to understand the kinematic role of large strike slip faults in continental collision zones geodetic and geologic rates from present to several million years ago along the karakorum fault range from 0 to 11 mm yr here we determine the first late quaternary slip rate at the southern end of the linear bangong chaxikang segment of the karakorum fault using cumulative offsets 20 200 m of fans and terraces at three sites as well as 74 new 10 be surface exposure ages to constrain the age of these offset geomorphic markers the rate is 3 mm yr at sites gun and chaxikang and it is 1 7 2 2 mm yr at the gar fan site together with rates obtained along the southernmost menshi kailas segment the karakorum fault slip rate seems to increase southeastward from south of bangong lake to kailas from 3 to 8 mm yr these karakorum fault slip rate data 3 8 mm yr together with the total length of the fault 1000 km and its initiation age 13 23 ma confirm that the karakorum fault is the major fault accommodating dextral strike slip motion ne of the western himalayas the dextral karakorum fault in the south and the conjugate left lateral longmu co altyn tagh fault system in the north are thus the major strike slip faults of western tibet which contribute to eastward extrusion of tibet

feeding the aneurysm orogen parallel mass transport into nanga parbat and the western himalayan syntaxis the nanga parbat haramosh massif nphm western himalayan syntaxis requires an influx of mass exceeding that in the adjacent himalayan arc to sustain high topography and rapid erosional exhumation rates what supplies this mass flux and feeds this tectonic aneurysm we show using a simple 3 d model of oblique orogen convergence that velocity strain partitioning results in horizontal orogen parallel op crustal transport and the same behavior is inferred for the himalaya with op transport diverting converging crust toward the syntaxis model results also show that the op flow rate decreases in the syntaxis thereby thickening the crust and forming a structure like the nphm the additional crustal thickening over and above that elsewhere in the himalayan arc sustains the rapid exhumation of this aneurysm normally velocity strain partitioning would be minimal for the himalayan arc where the convergence obliquity is no greater than 40 however we show analytically that the himalayan system can act both as a critical wedge and exhibit strain partitioning if both the detachment beneath the wedge and the bounding rear shear zone which accommodates op transport are very weak corresponding numerical results confirm this requirement and demonstrate that a nanga parbat type shortening structure can develop spontaneously if the orogenic wedge and bounding rear shear zone can strain rate soften while active these results lead us to question whether the position of nphm aneurysm is localized by river incision as previously suggested or by a priori focused tectonic shortening of the crust in the syntaxis region as demonstrated by our models

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

a kinematic model for the evolution of the eastern california shear zone and garlock fault mojave desert california abstract the eastern california shear zone in the mojave desert california accommodates nearly a quarter of pacific north america plate motion in south central mojave the shear zone consists of six active faults with the central calico fault having the fastest slip rate however faults to the east of the calico fault have larger total offsets we explain this pattern of slip rate and total offset with a model involving a crustal block the mojave block that migrates eastward relative to a shear zone at depth whose position and orientation is fixed by the coachella segment of the san andreas fault saf southwest of the transpressive big bend in the saf both the shear zone and the garlock fault are assumed to be a direct result of this restraining bend and consequent strain redistribution the model explains several aspects of local and regional tectonics may apply to other transpressive continental plate boundary zones and may improve seismic hazard estimates in these zones

first tectonic geomorphology study along the longmu gozha co fault system western tibet abstract the longmu gozha co left lateral strike slip fault system lgcf is located in remote western tibet forming a triple junction with both the altyn tagh fault atf and the karakorum fault kf the two major strike slip faults in the region the ashikule gozha co and longmu co faults are clear and distinct left stepping en echelon faults together forming the lgcf system although poorly documented quantifying its activity remains a key problem to understand the kinematics and the tectonic history of the westernmost tibetan plateau indeed the karakax fault nw segment of the atf lgcf and kf together control the tectonics of western tibet which itself controls the extrusion of tibet towards the east with the lgcf acting as a natural boundary for eastward motion of the tibetan plateau due to india s northward impingement the lgcf system shows clear and impressive morphological indications of left lateral active shear that we quantify using field measurements terrestrial lidar along with 10 be surface exposure dating our data suggest a slip rate 9 and 8 mm yr respectively yielding a few mm yr of extension accommodated most likely in the ashikule graben and surroundings located between the atf and karakax faults numerous evidences of recent tectonic related events are present in the vicinity such as the 1951 volcanic eruption as well as the 2008 and 2014 ms 7 3 yutian earthquakes attesting of its high activity in addition the lgcf s en echelon geometry and identical direction with the atf as well as smaller geological offsets and lower slip rate compared to those on the surrounding faults suggest that this segment of the atf may be the most recent

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

polarization filtering for automatic picking of seismic data and improved converted phase detection summary data adaptive polarization filtering is used to improve the detection of converted seismic phases both direct waves and mode converted ps and sp arrivals may be more easily picked on the filtered records an autopicking routine is applied that cuts the polarization filtered traces according to the modelled traveltime of each phase through an initial structure use of forward modelled source receiver times reduces the likelihood of an automatic pick being incorrectly made on spurious spikes in the polarization filtered trace it is therefore a realistic way of automatically picking multiphase data sets or more generally linearly polarized phases where low signal to noise ratios may be encountered the method is suitable for any three component seismic data and is here applied to local earthquakes recorded in north island new zealand intermediate energy is observed between the direct p and s arrivals due to phase conversion at the interface between the indo australian and subducting pacific plates the amplitudes of these converted arrivals are often too low for them to be identified above the p wave coda but polarization filtering of the records enables the yield of converted phase picks to be greatly increased

structural evolution of the neogene gar basin western tibet implications for releasing bend development and drainage patterns we investigated the interaction among basin bounding faults basin fi ll and geomorphic features of the southern gar basin one of only two known releasing double bend basins along the karakoram fault to better understand their structural evolution and role in basin development the southern gar basin is bounded by an 44 km long n20 wstriking central fault segment fl anked by two n40 w striking segments that parallel the regional strike of the karakoram fault system the central fault segment is composed of a system of strike slip and normal faults that young basinward and incorporate basin fi ll in their uplifted footwalls the oldest faults along the extensional portion of the bend are dominantly strike slip and they strike 15 w from the main strike of the karakoram fault basin fi ll is broadly folded about a nnwtrending axis and can be explained by e se directed slip along a listric normal fault cross sections across the basin and associated faults suggest the geometry is best described as an extensional fl ower structure forward structural modeling of the intrabasinal faults shows that the system has accommodated 8 km of east west extension we interpret the bend to have formed from linking of r and p shears into a through going principal displacement zone at shallow levels in the crust low confi ning pressures r shears are exploited at deeper levels these faults merge with the principal displacement zone forming the extensional fl ower structure geometry we estimate that the shear zone is 50 35 km wide based on the aerial distribution of p and r shears restoration of r shears on the west and east sides of the gar valley indicates 55 km of right lateral separation along the karakoram fault which is a minimum slip estimate for the karakoram fault system

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

shear wave velocity of the sedimentary basin in the upper mississippi embayment using s to p converted waves from mid october 1989 to august 1992 40 three component panda portable array for numerical data acquisition stations were deployed in the central new madrid seismic zone three component digital seismograms recorded by the panda stations in the region are characterized by 1 the very weak direct s arrivals on the vertical component which can be identified unambiguously from the two horizontal components and 2 at least two prominent secondary arrivals between the direct p and s arrivals one sp dominant on the vertical component and another ps with smaller amplitude on the two horizontal components travel time differences between the sp and s and between the p and ps are the same for different earthquakes recorded at the same station but are different at different stations even for the same event polarization analyses of three component seismograms and travel time measurements confirm the interpretation that these two secondary arrivals are the p to s ps and s to p sp converted waves that occur at the bottom of the sedimentary basin beneath each station since abundant well log data are available in the upper mississippi embayment the thickness of the sediments beneath each seismic station can be estimated travel time differences between the direct and the converted waves can be used to calculate average shear wave velocity for the sediments beneath each station the estimated shear wave velocities of the sediments beneath panda stations vary from 0 45 to 0 67 km sec the higher shear wave velocity associated with thicker sediments can be interpreted as a consequence of increasing compaction of unconsolidated sediments due to increasing overburden

scsp observed on north island new zealand implications for subducting plate structure seismic phase conversions provide important constraints on the layered nature of subduction zone structures recordings from digital stations in north island new zealand have been examined for converted scs to p scsp arrivals from deep 150 km tonga kermadec earthquakes to image layering in the underlying hikurangi subduction zone consistent p wave energy prior to scs has been identified from stations in eastern and southern north island where the subducted plate interface is at a depth of between 15 and 30 km two scs precursors are observed ray tracing indicates that the initial precursor scsp1 corresponds to conversion from the base of an 11 14 km thick subducting pacific crust the second precursor is interpreted as a conversion from the top of the subducting plate the amplitude ratio scsp1 scs increases from 0 10 to 0 19 from northern to southern north island this is within the range expected from a simple first order velocity discontinuity at an oceanic moho a 1 2 km thick layer of low velocity sediment at the top of the subducting plate is required to explain the remaining scsp waveform our results imply that the abnormally thick hikurangi chatham plateau has been subducting beneath new zealand for at least 2 9 myr thus explaining the high uplift rates observed across eastern north island

surface dating of dynamic landforms young boulders on aging moraines the dating of landforms is crucial to understanding the evolution history and stability of landscapes cosmogenic isotope analysis has recently been used to determine quantitative exposure ages for previously undatable landform surfaces a pioneering application of this technique to date moraines illustrated its considerable potential but suggested a chronology partially inconsistent with existing geological data consideration of the dynamic nature of landforms and of the ever present processes of erosion deposition and weathering leads to a resolution of this inconsistency and more generally offers guidance for realistic interpretation of exposure ages

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

insar observations of low slip rates on the major faults of western tibet two contrasting views of the active deformation of asia dominate the debate about how continents deform i the deformation is primarily localized on major faults separating crustal blocks or ii deformation is distributed throughout the continental lithosphere in the first model western tibet is being extruded eastward between the major faults bounding the region surface displacement measurements across the western tibetan plateau using satellite radar interferometry insar indicate that slip rates on the karakoram and altyn tagh faults are lower than would be expected for the extrusion model and suggest a significant amount of internal deformation in tibet

response to comment on slip rate measurements on the karakorum fault may imply secular variations in fault motion brown et al 1 1 argue that the dispersion in the exposure ages we obtained from the manikala glacier moraines 2 2 is influenced by postdepositional processes and that only the oldest boulder age on each moraine group can be used to assess its abandonment age determining the

review of gps and quaternary fault slip rates in the himalaya tibet orogen abstract previous studies related to the active deformation within the india asia collision zone have relied on slip rate data from major faults to test kinematic models for the region however estimated geodetic and quaternary slip rates demonstrate large variability for many of the major faults in the region e g altyn tagh and karakorum faults as a result several studies have challenged the assumption that geodetic slip rates are representative of quaternary slip rates in this review slip rate data from the quaternary fault database for central asia are used to determine the overall relationship between quaternary and global positioning system gps slip rates for 19 faults a least squares and pearson correlation analysis are applied to investigate this relationship to evaluate the sensitivity of the slip rate relationship to the presence absence of individual faults and different quaternary dating methods the slip rates were systematically re sampled to account for the range of published uncertainties for slip rates the monte carlo method was applied regression through 57 quaternary gps slip rate pairs yields an r2 value of 0 71 results from the re sampling analysis show that the inclusion or exclusion of slip rate data from specific faults e g the ganzi fault karakorum fault himalayan main frontal thrust and main pamir thrust have the highest influence on the strength of the correlation changing the pearson correlation coefficient by 0 08 0 05 0 06 and 0 06 respectively furthermore there appears to be a systematic bias in the agreement between rates such that quaternary rates tend to be higher than gps rates this bias is likely due to assumptions embedded in the geomorphic reconstructions of offset landforms used for estimating quaternary slip rates in the dataset taken together these results suggest that gps slip rates are more likely to represent quaternary slip rates when strict fault selection and geomorphic dating criteria are applied cases of inconsistencies in slip rates over different time scales may point to differences in the sensitivity of various fault slip measurement methods more often than secular rate changes

late cenozoic deformation of the kura fold thrust belt southern greater caucasus although the geometry and kinematics of the first order structures accommodating arabia eurasia convergence are relatively well known in turkey and iran major shortening structures remain poorly understood within the central portion of the collision zone in eastern anatolia and the caucasus new remotely sensed neotectonic mapping synthesis of regional geologic and stratigraphic data and balanced cross sections suggest that the kura fold thrust belt has accommodated the majority of arabia eurasia convergence since the early pliocene between the longitudes of 45 e and 49 e this belt lies southeast of the n80 w striking greater caucasus mountains and forms an eastward narrowing band of elevated topography that roughly parallels the range front for 400 km along strike the belt is separated from the greater caucasus to the north by the 10 to 25 km wide alazani basin and comprises a series of predominantly south verging folds deforming eocene quaternary flysch and molasse to document structural geometries within the kura fold thrust belt we have used the real time interactive mapping system rims software to analyze advanced spaceborne thermal emission and reflection radiometer aster visible to near infrared vnir and digital elevation model dem data this neotectonic mapping indicates an along strike eastward decrease in both structural complexity and the degree to which deformed geomorphic surfaces are dissected existing geologic maps indicate a corresponding eastward decrease in the depth of exposure by integrating the structural geometries determined in our analysis of remote sensing data with existing geologic data we have constructed two balanced cross sections which suggest these systematic along strike variations result from a west to east decrease in total shortening within the kura fold thrust belt we interpret this variable shortening to stem from eastward propagation of the kura fold thrust belt comparison of our preliminary total shortening estimates with those predicted by current plate motions suggest that the kura fold thrust belt has accommodated 30 40 25 km of total arabia eurasia convergence since 5 ma and thus forms a first order structural system within the central portion of the collision zone

asymmetrical erosion and morphological development of the central ladakh range northern india abstract variations in erosion were quantified across the topographically and morphometrically asymmetrical central ladakh range in nw india to elucidate erosion and sediment transfer processes across space and time and to gain insight into how mountains erode and evolve morphometric analysis and 10 be cosmogenic nuclide analysis of 14 fluvial sediment samples from active channels in six catchments conducted across the mountain range constrains 100 ka timescale erosion rates for catchments on the northern side of the mountain range and are between 56 12 and 74 11 m ma while catchments on the southern side of the mountain range to between 20 3 and 39 8 m ma for the last 300 ka maximum elevation from swath analysis across the range shows a strong correlation with the elas of 382 contemporary glaciers the higher erosion rate to the north likely relates to tectonic tilting of the central ladakh range and to active rock uplift on the northern side of the range along the karakoram fault morphometric analysis shows that the maximum and average elevations increase at nearly the same rate on a catchment scale across the central ladakh range with higher elevation on the northern side this suggests that greater erosion on the northern side of the range is not keeping pace with rock uplift moreover long term denudational unloading does not play a significant role in the tectonic tilting of the central ladakh range