lake volume and groundwater storage variations in tibetan plateau s endorheic basin the tibetan plateau tp the highest and largest plateau in the world with complex and competing cryospheric hydrologic geodynamic processes is particularly sensitive to anthropogenic warming the quantitative water mass budget in the tp is poorly known here we examine annual changes in lake area level and volume during 1970s 2015 we find that a complex pattern of lake volume changes during 1970s 2015 a slight decrease of 2 78 gt yr 1 during 1970s 1995 followed by a rapid increase of 12 53 gt yr 1 during 1996 2010 and then a recent deceleration 1 46 gt yr 1 during 2011 2015 we then estimated the recent water mass budget for the inner tp 2003 2009 including changes in terrestrial water storage lake volume glacier mass snow water equivalent swe soil moisture and permafrost the dominant components of water mass budget namely changes in lake volume 7 72 0 63 gt yr 1 and groundwater storage 5 01 1 59 gt yr 1 increased at similar rates we find that increased net precipitation contributes the majority of water supply 74 for the lake volume increase followed by glacier mass loss 13 and ground ice melt due to permafrost degradation 12 other term such as swe 1 makes a relatively small contribution these results suggest that the hydrologic cycle in the tp has intensified remarkably during recent decades

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

holocene paleoearthquake history on the qingchuan fault in the northeastern segment of the longmenshan thrust zone and its implications abstract although much work has been performed for faults with high slip rates little attention has been paid to low slip rate faults such as the longmenshan thrust zone ltz on which the wenchuan earthquake occurred the ltz is a long and matured fault that evolved during the mesozoic as a structural boundary but its quaternary activity had been considered insignificant the wenchuan earthquake on the central segment of the ltz and the following lushan earthquake on the southwestern segment illustrate the necessity of assessing the regional seismic potential around the northeastern extension of the ltz however little is known about its activity and paleoearthquake history to solve these problems we conducted paleoseismological trench excavations at two sites on the qingchuan fault to establish its paleoearthquake history only one and the latest event that occurred in the holocene is identified based on the radiocarbon dating the faulting event is constrained to occur between 4115 and 3820 b c and a long recurrence interval of greater than 6000 years is thus estimated judging from the matured fault structure of the qingchuan fault the latest event was likely to have ruptured the full length of the fault according to the empirical scaling laws between magnitude and rupture length the magnitude of the event is estimated to be mw 7 6 7 9 on the basis of the slip rate from gps measurements and the elapsed time since the last event it is estimated that a seismic moment equivalent to mw 7 5 has been accumulated on the qingchuan fault considering the increased coulomb failure stress and the shortened time of earthquake recurrence triggered by the wenchuan earthquake it is suggested a high seismic risk along the qingchuan fault and its neighboring area furthermore the slow strain buildup unadapted geometry and matured fault structure of the ltz may be the reason why it produces rare but large intraplate earthquakes

a study of the coulomb stress and seismicity rate changes induced by the 2008 m w 7 9 wenchuan earthquake sw china abstract correlations between the calculated coulomb stress changes and observed seismicity rate changes after the wenchuan earthquake are investigated in this article three improvements are made in the calculation of static stress change including employing a dislocation method with triangular elements rather than traditional rectangular elements setting up a more realistic source slip model and a more complete receiver fault model and resolving stress changes on assumed receiver faults with spatially variable focal mechanisms based on well determined focal mechanisms at different calculation points the recorded aftershocks are mapped for comparison with the spatial distribution of stress changes the results indicate that the wenchuan earthquake encourages not only three major fault systems the east kunlun south of xianshuihe and west of qinling southern frontal but also several other regions including tazang north of min jiang north of pingwu qingchuan and west of chongqing in particular the eastern segment of longriba is shown to be quite dangerous with dramatic stress increase the influence of depth and frictional coefficient is analyzed the depth of calculation beyond the depth range of the source model will make a significant difference to the stress change map and thus cannot be neglected many aftershocks occurring in the stress shadow zone near the main rupture can be attributed to dynamic stress triggering and the fractal structure of the main fault the observed seismicity rate changes are compared with the static stress changes the results show that high background seismicity rates will amplify the effect of stress change the observed seismicity rate changes support the forecast rate of 10 year seismicity after the wenchuan earthquake based on the rate and state dependent friction model coulomb stresses increase on the focal mechanisms away from the main rupture which demonstrates the influence of the wenchuan earthquake over a wide range especially the focal mechanism for lushan earthquake undergoes a stress increase by more than 2 0 bars which suggests that the lushan earthquake has been effectively promoted by the wenchuan earthquake

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

the implications of regional microseismic activities a lesson from 2008 ms 8 0 wenchuan earthquake abstract the ms 8 0 wenchuan earthquake has greatly perturbed the crustal stress in longmenshan fault zone lfz and its neighboring regions and hence significantly changed the regional seismicity pattern convectional coulomb stress change model based on half space dislocation source of layered elastic or viscoelastic crust can only provide brief reference to estimate the after shock sequences roughly in this study we apply the z test statistical method to examine the earthquake catalogue five years before and after this event to detect the changes of regional seismicity intensity and their statistical significance in lfz and its neighboring regions we analyze changes of the z values with respect to time and seismic magnitude in each region our results reveal that after the wenchuan earthquake seismicity intensity has significantly increased in eastern kunlun fault southern longmenshan fault longquanshan fault and huayingshan fault in sichuan basin but has significantly decreased in northern and central longmenshan fault vicinity of the songpan minjiang fault and fubianhe fault in bayankala block respectively seismicity rate change in northern and central anninghe zemuhe fault zone is not correlated with the wenchuan earthquake these results remain within 99 confidence level of the z test statistical method we compare our statistical analysis results with calculations of coseismic coulomb failure stress change due to the wenchuan earthquake from previous studies in most of the regions and fault zones the sign of the seismicity rate change agrees with the sign of the coulomb stress change

effect of crustal layering upon dislocation modeling slip distribution at depth on a fault may be inferred from the deformation observed on the surface in inverting the surface deformation data to obtain the slip distribution the earth is generally approximated by an elastic half space slip distributions inferred from a half space model may contain artifacts including zones of reversed slip due solely to effects of layering in the real earth this effect is demonstrated for a vertical strike slip fault in an earth consisting of an elastic layer overlying an elastic half space slip on the fault is taken to be independent of the along strike coordinate i e antiplane strain is assumed for a given slip distribution in this model the slip distribution on a similar fault in an elastic half space is found that produces the identical surface deformation comparison of the two slip distributions reveals structure introduced into the half space equivalent slip profile by crustal layering the comparisons suggest that low resolution inversion schemes e g single screw dislocation models are not drastically affected by earth structure but attempts at detailed inversion are likely to produce profiles contaminated by artifacts of earth structure

static coulomb stress changes on faults caused by the 2008 mw 7 9 wenchuan china earthquake abstract the 12 may 2008 mw 7 9 wenchuan earthquake has changed the regional tectonic stress field significantly it is important to know how such a change affects the tectonic loading processes of the faults and therefore the seismic potential of the region utilizing the slip distribution of the wenchuan earthquake as the driving source we compute the changes of coulomb failure stress cfs on the neighborhood faults assuming a friction coefficient of 0 4 our results show that the cfss have increased on average 1 6 104 and 1 8 104 pa at the sw and ne ends of the longmen shan 2 6 104 pa at the western segment of the qinling southern frontal 2 0 104 pa at the northernmost part of the longriba 1 4 104 pa at the southernmost part of the xianshuihe 1 3 104 pa at the southeast end of the east kunlun 9 0 103 pa at the southernmost part of the minjiang 2 9 103 pa at the baiyu and 3 5 103 pa at the longxian baoji faults recurring times of these faults are advanced about 39 and 230 years for the sw and ne segments of the longmen shan 5 5 years toward the east end of the east kunlun and 1 6 years for the se segments of the xianshuihe faults the quake also relaxed the cfs significantly on most part of the minjiang southwest segment of the longriba northwest segment of the xianshuihe southeast segment of the yushu maqu north part of the xiaojinhe daliangshan and anninghe faults with the cfs reductions ranging on average of 1 8 104 2 5 104 7 1 103 2 4 103 1 0 103 1 0 103 and 1 6 103 pa respectively recurring times of these faults are delayed up to 185 years for the south segment of the minjiang up to 18 years for the northeast of the longriba up to 9 8 years for the west qinling northern frontal and up to 2 7 years for the northwest segment of the xianshuihe faults respectively we test sensitivity of the changes of cfs to variations of apparent fiction coefficient and find that the senses of cfs change are almost invariant with except at the minjiang longriba and qinling southern frontal faults where large normal stresses on faults induced by the wenchuan earthquake could play an important role in manifesting cfs change when is large the cfs changes vary slowly along seismogenic depth on most of the receiver faults

did the 2008 mw 7 9 wenchuan earthquake trigger the occurrence of the 2017 mw 6 5 jiuzhaigou earthquake in sichuan china

late quaternary paleoearthquakes along the northern segment of the nantinghe fault on the southeastern margin of the tibetan plateau abstract the strong earthquake behaviors of faults are significant for learning crustal deformation mechanisms and for assessing regional seismic risk to date faults that bound tectonic blocks have attracted considerable concern and many studies however scant attention has been paid to faults within blocks that can also host devastating earthquakes the nantinghe fault is a left lateral strike slip fault within the southwestern yunnan block and it slips at 4 mm yr suggesting strong activity in the late quaternary nevertheless no earthquake greater than 6 has ever been recorded along it except for the 1941 m 7 earthquake near the myanmar china border region in contrast many earthquakes have occurred in the near region delineating a seismic gap near the nantinghe fault although several studies have been conducted upon it the activity of its northern segment is confusing and whether this fault segment has loaded sufficient stress to fail remains debatable furthermore previous work failed to conduct any paleoseismological studies bringing out great uncertainty in learning its activity and faulting behavior as well as in assessing the regional seismic risk to solve these problems we mapped the fault traces utilizing high resolution satellite images and aerial photographs and conducted three paleoseismological trenches along the northern segment of the nantinghe fault the trench excavations revealed a 45 000 year incomplete paleoearthquake history and confirmed that this fault segment has been active since the late pleistocene but was not ruptured during the 1941 earthquake additionally at least five paleoearthquakes are identified with their respective age ranges of before 39 030 bce 38 500 37 220 bce 28 475 5445 bce 3535 bce 800 ce and 1320 1435 ce based on radiocarbon dating among the paleoearthquakes the latest is suggested to have generated a surface rupture much longer than 14 km with a magnitude likely up to ms 7 0 furthermore based on the elapsed time since the latest paleoearthquake and the sinistral slip rate along the fault it is proposed that the northern segment of the nantinghe fault has accumulated a seismic energy equivalent to ms 7 0 and it is in a high seismic risk along this fault segment and in the neighboring area

locations and types of ruptures involved in the 2008 sichuan earthquake inferred from sar image matching 1 we have detected detailed ground displacements in the proximity of the longmen shan fault zone lmsfz by applying a sar offset tracking method in the analysis of the 2008 sichuan earthquake an elevation dependent correction is indispensable for achieving sub meter accuracy a sharp displacement discontinuity with a relative motion of 1 2 m appears over a length of 200 km along the lmsfz which demonstrates that the main rupture has proceeded on the beichuan fault bf among several active faults composing the lmsfz and a new active fault is detected on the northeastward extension of the bf the rupture on the bf is characterized by a right lateral motion in the northeast while in the southwest an oblique right lateral thrust slip is suggested in contrast to the northeast where a major rupture proceeded on the bf only in the southwest multiple thrust ruptures have occurred in the southeastern foot of the pengguan massif

modeling the holocene slip history of the wasatch fault utah coseismic and postseismic coulomb stress changes and implications for paleoseismicity and seismic hazard

viscoelastic flow in the lower crust after the 1992 landers california earthquake space geodesy showed that broad scale postseismic deformation occurred after the 1992 landers earthquake three dimensional modeling shows that afterslip can only explain one horizontal component of the postseismic deformation whereas viscoelastic flow can explain the horizontal and near vertical displacements the viscosity of a weak about 10 km thick layer in the lower crust beneath the rupture zone that controls the rebound is about 10 18 pascal seconds the viscoelastic behavior of the lower crust may help to explain the extensional structures observed in the basin and range province and it may be used for the analysis of earthquake hazard

characteristics of focal mechanisms and the stress field in the southeastern margin of the tibetan plateau crustal earthquake focal mechanisms are investigated in the southeastern margin of the tibetan plateau where the tibetan plateau and stable south china block merge an updated database of focal mechanisms has been compiled by selecting 132 global centroid moment tensor solutions and by adding the 173 new solutions 3 5 ms 7 4 estimated by waveform inversion in this study a total of 305 mechanisms are included in this database these solutions show regionally specific distributions with dominant strike slip faulting and some normal and reverse faulting focal mechanism solutions have also been inverted for the stress tensor orientation to obtain the principal stress axes over the study region results show that the horizontal maximum principal 1 axes rotate clockwise with a wider range than the geodetically measured surface motion in the east which is not limited to the xianshuihe xiaojiang fault but has some overlap with the zhaotong lianfeng fault localized normal faulting stress regimes are observed in the jinshajiang litang fault areas and the baoshan sub block the minimum principal axes are oriented with a gradually changing trend from north south to northwest southeast from north to south indicating diverse compression stress patterns significant changes in the crustal stress field after the wenchuan earthquake are preliminarily observed in the baoshan sub block where orientations of two principal axes have changed and in the jinggu ximeng sub block areas where the strike slip faulting stress pattern has transformed to normal faulting

the co seismic coulomb stress change and expected seismicity rate caused by 14 april 2010 ms 7 1 yushu china earthquake a moderate and widely felt earthquake of ms7 1 mw6 9 occurred on april 14 2010 in yushu district of qinghai province china which destroyed a large number of buildings and killed more than two thousand people the distribution of the aftershock sequence is sparse but with relatively large magnitudes ms6 3 and ms5 7 aftershocks were recorded strong aftershocks are still highly potential to occur in the near future therefore it is critical to delineate areas where potential aftershocks could occur based on static stress triggering theory we calculated the coseismic stress changes induced by the mainshock in yushu county and its surrounding regions by adopting elastic dislocation theory and a multilayered crustal model according to the rate and state variable friction law we calculated the expected seismicity rate and probability of occurrences of m 5 0 earthquake in the next ten years it is observed that the coulomb stress changes increase apparently on the segment of the wudaoliang qumalai fault the batang luoxu and dangjiang longbao segments of the ganzi yushu fault and the whole wulanwula lake yushu fault based on the theory of coulomb stress triggering the probability of earthquake occurrence on these faults would increase in the near future considering the historical seismicity the strain accumulation and the coulomb stress changes the probability of m 5 earthquake and m 6 earthquake occurrence in the entire study area in the next 10 years are 79 87 and 26 7 33 6 respectively actually a moderate earthquake of ms5 3 occurred to the northwest of the nangqian county on june 26 2011

slip maxima at fault junctions and rupturing of barriers during the 2008 wenchuan earthquake the devastating wenchuan earthquake in 2008 struck along a fault zone that showed low rates of deformation analysis of gps and insar data suggests that as structural barriers failed during a single earthquake the rupture cascaded across multiple fault segments which may explain the high magnitude of the event

local stress perturbations associated with the 2008 wenchuan m 8 0 earthquake near the longmenshan fault zone in the eastern margin of the tibetan plateau abstract the 2008 wenchuan m 8 0 earthquake induced local stress perturbations near the longmenshan lms fault zone using in situ measurements and stress tensor inversions from focal mechanisms we investigated the post earthquake perturbed stress field at shallow depths 1 2 km in the upper crust above a basal attachment 5 18 km as well as in the middle crust beneath a basal attachment 19 32 km at shallow depths in the beichuan jiangyou section the maximum principal stress 1 orientations changed from a pre earthquake orientation of nww to a post earthquake orientation of nee however near the baoxing an xian and qingchuan mianxian sections the pre earthquake 1 orientation of nw nww was largely unaltered before the mainshock in the upper crust above the basal detachment the entire lms fault zone exhibited a consistent 1 orientation of nw nww however after the earthquake some sections such as the beichuan nanba section achieved 1 orientations of nee that were distinctly different from the pre seismic stress field in the middle crust beneath the basal detachment the stress field was mostly unchanged the crust beneath the basal detachment along the eastern margin of the tibetan plateau is dominated by nww oriented maximum principle stress and strain directions and a thrust faulting stress regime along the entire lms fault zone these observations are representative of the southeastward motion of the bayan har block and its ongoing collision with the south china block along the lms thrust belt the spatially heterogeneous stress field that occurred in the upper crust 18 km after the mainshock was most likely caused by the co seismic static stress changes associated with the wenchuan earthquake prior to the onset of seismic activity the deviatoric stress magnitudes were estimated at less than 22 mpa and 4 mpa at depths of 10 km and 20 km respectively suggesting that the mainshock fault zone has a relatively low fault strength to overcome in order to initiate significant co seismic rupture and aftershocks especially in the crust beneath the basal detachment these smaller deviatoric magnitudes are indicative of the weaker fault materials that resides in the lms region

influence of the 2008 wenchuan earthquake mw 7 9 on the occurrence probability of future earthquakes on neighboring faults abstract the longquan shan fault and the huya fault are two major neighboring faults of the longmen shan fault zone where the 12 may 2008 wenchuan earthquake m w 7 9 occurred to study the influence of the wenchuan event on these two active faults we calculate changes of coulomb stress on the longquan shan fault and the huya fault caused by the wenchuan mainshock our results indicate that the coulomb stress in the northern section zone a of the longquan shan fault is increased by 0 07 0 10 bars that in the middle section zone b by 0 04 0 11 bars and that in the southern section zone c shows almost no change for the huya fault the coulomb stress is decreased by 0 01 0 03 bars in the northern section zone a 0 10 0 35 bars in the middle section zone b and nearly 0 5 bars in the southern section zone c the epicenter distribution of small earthquakes m l 1 5 on the longquan shan fault and the huya fault after the wenchuan earthquake is consistent with the distribution of the coulomb stress change this implies that the wenchuan earthquake may have triggered small events on the longquan shan fault but inhibited those on the huya fault we then use the rate state friction law to calculate the occurrence probability of future earthquakes in the study region for the next decade they include the distribution of b values magnitude of completeness m c the background seismicity rate a value of a n and the duration for the transient effect t a in the study region we also estimate the earthquake occurrence probabilities on the neighboring faults after the wenchuan earthquake our results show that the occurrence probability of future earthquakes in the longquan shan has a slight increase being 7 for m 5 0 shocks during the next decade but the earthquake probability in the huya region is reduced obviously being 5 20 7 26 and 3 9 for m 5 0 shocks during the next decade in sections a b and c of the huya fault respectively

three dimensional velocity structure of crust and upper mantle in southwestern china and its tectonic implications using p and s arrival times from 4625 local and regional earthquakes recorded at 174 seismic stations and associated geophysical investigations this paper presents a three dimensional crustal and upper mantle velocity structure of southwestern china 21 34 n 97 105 e southwestern china lies in the transition zone between the uplifted tibetan plateau to the west and the yangtze continental platform to the east in the upper crust a positive velocity anomaly exists in the sichuan basin whereas a large scale negative velocity anomaly exists in the western sichuan plateau consistent with the upper crustal structure under the southern tibetan plateau the boundary between these two anomaly zones is the longmen shan fault the negative velocity anomalies at 50 km depth in the tengchong volcanic area and the panxi tectonic zone appear to be associated with temperature and composition variations in the upper mantle the red river fault is the boundary between the positive and negative velocity anomalies at 50 km depth the overall features of the crustal and the upper mantle structures in southwestern china are a low average velocity large crustal thickness variations the existence of a high conductivity layer in the crust or and upper mantle and a high heat flow value all these features are closely related to the collision between the indian and the asian plates

surface wave array tomography in se tibet from ambient seismic noise and two station analysis ii crustal and upper mantle structure summary we determine the 3 d shear wave speed variations in the crust and upper mantle in the southeastern borderland of the tibetan plateau sw china with data from 25 temporary broad band stations and one permanent station interstation rayleigh wave phase velocity dispersion curves were obtained at periods from 10 to 50 s from empirical green s function egf derived from ambient noise interferometry and from 20 to 150 s from traditional two station ts analysis here we use these measurements to construct phase velocity maps from 10 to 150 s using the average interstation dispersion from the egf and ts methods between 20 and 50 s and estimate from them with the neighbourhood algorithm the 3 d wave speed variations and their uncertainty the crust structure parametrized in three layers can be well resolved with a horizontal resolution about of 100 km or less because of the possible effect of mechanically weak layers on regional deformation of particular interest is the existence and geometry of low shear velocity layers lvls in some regions prominent lvls occur in the middle crust in others they may appear in the lower crust in some cases the lateral transition of shear wave speed coincides with major fault zones the spatial variation in strength and depth of crustal lvls suggests that the 3 d geometry of weak layers is complex and that unhindered crustal flow over large regions may not occur consideration of such complexity may be the key to a better understanding of relative block motion and patterns of seismicity

more major earthquakes at the nepal himalaya study on coulomb stress perspective abstract on april 2015 a major earthquake of 7 9 mw occurred in the nepal himalaya followed by 553 earthquakes of local magnitude greater than 4 0 within the first 43 days including another major event of 7 3 mw we resolve the static coulomb failure stress cfs change onto the finite fault models of 7 9 mw after elliott et al 2016 and galezka et al 2015 and its effect on associated receiver faults correlation of aftershocks with the enhanced cfs condition shows that the elliott et al 2016 model explains 60 4 and the galezka et al 2015 model explains about 47 7 of the aftershocks in high stress regions aftershocks were poorly spatially correlated with the enhanced cfs condition after the 7 9 mw main shock and can be explained by correlation with release of seismic energy from the associated secondarily stressed prominent thrust planes and transverse faults stress resolved on the associated receiver faults show increased stress on both transverse and thrust fault systems with the potential of triggering significant aftershocks or subsequent main shocks

indonesian earthquake earthquake risk from co seismic stress last year s indonesian earthquake has increased seismic hazard in the region the scale of death and destruction caused by the recent sumatra andaman islands earthquake and its tsunami has raised concerns that another earthquake might be triggered on the contiguous sunda trench subduction zone a new calculation of stress distribution here and on the neighbouring sumatra fault reveals stress build up on both structures severe enough to increase the already high earthquake hazard this finding makes the need for an indian ocean tsunami warning system all the more pressing following the massive loss of life caused by the sumatra andaman earthquake in indonesia and its tsunami the possibility of a triggered earthquake on the contiguous sunda trench subduction zone is a real concern we have calculated the distributions of co seismic stress on this zone as well as on the neighbouring vertical strike slip sumatra fault and find an increase in stress on both structures that significantly boosts the already considerable earthquake hazard posed by them in particular the increased potential for a large subduction zone event in this region with the concomitant risk of another tsunami makes the need for a tsunami warning system in the indian ocean all the more urgent

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

faulting associated with large earthquakes and the average rate of deformation in central and eastern asia we determine approximate average rates of deformation in portions of eastern and central asia for the last 80 years these rates are based on estimates of source dimensions average displacements seismic moments and orientations of faults of all large earthquakes m 7 5 and as many other major earthquakes m 7 0 as possible in asia since 1900 a major part of this study is the compilation of these data for separate parts of asia we combine seismic moment tensors to estimate the average rotational strain or deformation tensors for these regions for the last 80 years we estimate that shortening across the tien shan has occurred at 11 mm yr between 5 and 19 mm yr left lateral shear on easterly trending planes in mongolia in northwestern tibet gansu and ningxia and on the xianshuihe fault in western sichuan has been very rapid more than 10 mm yr in each region and apparently as rapid as 40 mm yr in northwestern tibet gansu and ningxia slower rates of a few to 10 mm yr appear to characterize east west extension and conjugate north south shortening of tibet the earthquake history of the himalaya is consistent with rates of underthrusting of more than 10 mm yr but is probably less than the convergence rate of india with eurasia of about 50 mm yr the overall strain field is consistent with a large part of india s penetration into eurasia being absorbed by the extrusion of material out of india s way as a result southeast china moved at about 21 mm yr east southeast with respect to eurasia in the last 80 years with an uncertainty of about a factor of 2 in this estimated rate

coseismic and postseismic vertical movements associated with the 1940 m7 1 imperial valley california earthquake elevation changes derived from precise leveling surveys conducted by the national geodetic survey in 1931 1941 1972 and 1974 along two routes crossing the imperial fault in southern california represent the first documented examples of spatially coherent vertical movements associtated with strike slip faulting in the united states the leveling routes cross the northern section of the fault that broke at the time of the 1940 m7 1 imperial valley earthquake the observed vertical movements which extend approximately 25 km east and west of the fault are among the largest observed anywhere in the united states these movements are consistent with simple elastic models of coseismic and postseismic secondary vertical deformation due to right lateral strike slip movement along a finite length fault the spatial and temporal patterns of deformation suggest a simple scenario consisting of large coseismic slip on the southern part of the imperial fault which transferred stresses to the northern part of the imperial fault and the brawley fault en echelon fault northeast of imperial fault these stresses were subsequently released primarily by aseismic creep the estimates of coseismic faulting determined from the leveling observations are roughly consistent with field observations of horizontal surface offset made after the earthquake as well as with some estimates derived from triangulation measurements the postseismic fault offsets reported here suggest slip to shallower levels than previous estimates of postseismic slip determined from repeated triangulation measurements the overall shallow slip coseismic plus postseismic required by the leveling observations is larger on the southern part of the imperial fault than on the northern part of this fault or on the brawley fault the 1979 m6 6 imperial valley earthquake apparently eliminated some of this difference in overall shallow slip by causing surface offsets on the northern part of the imperial fault and the southern brawley fault even though the epicenter for the 1979 event was located on the southern imperial fault other geophysical observations in this part of the imperial valley fault creep seismicity seismic faulting suggest that stick slip on the southern part of the imperial fault and creep on the northern part of this fault and on the brawley fault may characterize the long term fault behavior in the imperial valley

stress evolution before and after the 2008 wenchuan china earthquake abstract we examine the distribution of coulomb stress before and following the m 7 9 wenchuan earthquake and model the time dependent components of the stress field into the future our modelling shows that the combined coseismic plus postseismic viscoelastic stress change due to the preceding large events m 6 7 at the hypocentral area of the wenchuan earthquake is negative which may have led to a delay on its occurrence between 16 and 95 yr depending on the rake of the rupture on the other hand coseismic stress modelling of the wenchuan earthquake shows strong interaction particularly with the faults close to its sw and ne ends such interactions have previously been shown to trigger further large earthquakes in addition redistribution of stresses due to continuing postseismic deformation will potentially increase the stress levels not only on these faults but also on the distant faults such as the xianshuihe kunlun and tazang faults postseismic viscoelastic stress load on these distant faults over the next 22 yr since the earthquake could be up to 2 5 times larger than that of the coseismic stress increase alone this would potentially advance these faults in their seismic cycle and thereby encourage future earthquakes resulting in clustering of large earthquakes in the region this behaviour however strongly depends on the stage that these faults are in their seismic cycle which is not known currently given the high density of population in the area with several cities chengdu guangyuan and hanzhong of more than 1 million inhabitants our results indicate a need for detailed paleoseismic studies to help elucidate the state of the stressed faults

coseismic surface ruptures and crustal deformations of the 2008 wenchuan earthquake mw7 9 china 1 the irregularly distributed surface fault ruptures of the wenchuan earthquake spanned over 200 km along the longmen shan lms fault zone through field investigations we found over 10 coseismic surface ruptures with maximum vertical displacements of approximately 6 m on the yingxiu beichuan fault and 2 m on the guanxian anxian fault however the entire fault rupture movement was still not clearly understood since high topographic areas were inaccessible thus we used interferometric synthetic aperture radar insar satellite observations to capture whole coseismic surface ruptures and crustal deformations across the lms faults we created a novel bi fault slip model to invert fault slips using insar information which yielded that thrust fault slips were dominant at yingxiu houshenggou and bajiaomiao in the near epicenter segment while the dextral fault slips were dominant at pingtong and nanba along the northeast segment the combination of field investigations and simulations suggested that the two coseismic fault zones ruptured with an irregular surface distribution accompanied by crustal deformations