assessment of teleseismically determined source parameters for the april 25 2015 mw 7 9 gorkha nepal earthquake and the may 12 2015 mw 7 2 aftershock on april 25 2015 a major m w 7 9 thrust earthquake ruptured the deeper portion of the seismogenic plate boundary beneath nepal along which india is underthrusting eurasia an m w 7 2 aftershock on may 12 2015 extended the eastern down dip edge of the rupture these destructive events caused about 9000 fatalities and 23 000 injuries the overall rupture zone is about 170 km long and 40 80 km wide this region of the plate boundary previously experienced a large earthquake in 1833 and in 1934 a larger m s 8 0 event located to the east ruptured all the way to the surface the main himalayan thrust mht on which slip occurred in 2015 has a very low dip angle of 6 and the depth of the mainshock slip distribution is very shallow extending from 7 to 18 km the shallow dip and depth present challenges for resolving faulting characteristics using teleseismic data we analyze global teleseismic signals for the mainshock and aftershock to estimate source parameters evaluating the stability of various procedures used for remotely characterizing kinematics of such shallow faulting back projection and finite fault slip inversion are used to assess the spatio temporal rupture history and evidence for frequency dependent radiation along dip slip zone width constraints from near field geodetic observations are imposed on the preferred models to overcome some limitations of purely teleseismic methods radiated energy stress drop and moment rate functions are determined for both events

source parameters of the 2014 mw 6 1 south napa earthquake estimated from the sentinel 1a cosmo skymed and gps data abstract using the combination of two insar and one gps data sets we present the detailed source model of the 2014 mw 6 1 south napa earthquake the biggest tremor to hit the san francisco bay area since the 1989 mw 6 9 loma prieta earthquake the insar data are from the sentinel 1a s1a and cosmo skymed cs satellites and gps data are provided by nevada geodetic laboratory we firstly obtain the complete coseismic deformation fields of this event and estimate the insar data errors then using the s1a data to construct the fault geometry one main and two short parallel sub faults which haven t been identified by field investigation as expected the geometry is in good agreement with the aftershock distribution by inverting the insar and gps data we derive a three segment slip and rake models our model indicates that this event was a right lateral strike slip earthquake with a slight reverse component in the west napa fault as we estimated the fault is 30 km long and more than 80 of the seismic moment was released at the center of the fault segment where the slip reached its maximum up to 1 m we also find that our geodetic moment magnitude is 2 07 1018 nm corresponding to mw 6 18 larger than that of usgs mw 6 0 and gcmt mw 6 1 this difference may partly be explained by our insar data including about one week s postseismic deformation and aftershocks the results also demonstrate high snr and great ability of the newly launched sentinel 1a in earthquake study furthermore this study suggests that this earthquake has potential to trigger nearby faults especially the green valley fault where the coulomb stress was imparted by the 2014 south napa earthquake

primary surface ruptures of the great himalayan earthquakes in 1934 and 1255 it is unclear where plate boundary thrusts generate giant rather than great earthquakes along the himalayas the source sizes and recurrence times of large seismic events are particularly uncertain since no surface signatures were found for those that shook the range in the twentieth century here we challenge the consensus that these events remained blind and did not rupture the surface we use geomorphological mapping of fluvial deposits palaeo seismological logging of river cut cliffs and trench walls and modelling of calibrated 14c ages to show that the mw 8 2 bihar nepal earthquake on 15 january 1934 did break the surface traces of the rupture are clear along at least 150 km of the main frontal thrust fault in nepal between 85 50 and 87 20 e furthermore we date collapse wedges in the sir valley and find that the 7 june ad 1255 earthquake an event that devastated kathmandu and mortally wounded the nepalese king abhaya malla also ruptured the surface along this stretch of the mega thrust thus in the past 1 000 years two great earthquakes 679 years apart rather than one giant eleventh century ad event contributed to the frontal uplift of young river terraces in eastern nepal the rare surface expression of these earthquakes implies that surface ruptures of other reputedly blind great himalayan events might exist the recurrence times of great himalayan earthquakes are difficult to assess because they rarely rupture the surface field mapping and 14c dating of offset fluvial deposits are used to identify two great himalayan quakes that ruptured the surface along the main plate boundary fault in ad 1255 and 1934

early palaeozoic palaeobiogeography of the variscan regions abstract the palaeobiogeographic method appears to be an attractive alternative for reconstruction of the palaeogeography of the variscan regions during the palaeozoic the evolution of faunal assemblages and climatic characteristics from the cambrian up to the end of the devonian demonstrates that baltica and north gondwana represent two major and independent palaeogeographic entities separated by a mid european rheic ocean which opened as early as the cambrian and closed progressively from the devonian the south armorican ocean whose closure generated the so called ligerian orogen is regarded as a branch of the rheic ocean both a tornquist s sea separating baltica from its western extension avalonia during the ordovician and a proto tethys ocean extending between southwestern europe and north africa during the devonian are excluded from our reconstructions

convergence rate across the nepal himalaya and interseismic coupling on the main himalayan thrust implications for seismic hazard we document geodetic strain across the nepal himalaya using gps times series from 30 stations in nepal and southern tibet in addition to previously published campaign gps points and leveling data and determine the pattern of interseismic coupling on the main himalayan thrust fault mht the noise on the daily gps positions is modeled as a combination of white and colored noise in order to infer secular velocities at the stations with consistent uncertainties we then locate the pole of rotation of the indian plate in the itrf 2005 reference frame at longitude 1 34 3 31 latitude 51 4 0 3 with an angular velocity of 0 5029 0 0072 myr the pattern of coupling on the mht is computed on a fault dipping 10 to the north and whose strike roughly follows the arcuate shape of the himalaya the model indicates that the mht is locked from the surface to a distance of approximately 100 km down dip corresponding to a depth of 15 to 20 km in map view the transition zone between the locked portion of the mht and the portion which is creeping at the long term slip rate seems to be at the most a few tens of kilometers wide and coincides with the belt of midcrustal microseismicity underneath the himalaya according to a previous study based on thermokinematic modeling of thermochronological and thermobarometric data this transition seems to happen in a zone where the temperature reaches 350 c the convergence between india and south tibet proceeds at a rate of 17 8 0 5 mm yr in central and eastern nepal and 20 5 1 mm yr in western nepal the moment deficit due to locking of the mht in the interseismic period accrues at a rate of 6 6 0 4 10 19 nm yr on the mht underneath nepal for comparison the moment released by the seismicity over the past 500 years including 14 m w 7 earthquakes with moment magnitudes up to 8 5 amounts to only 0 9 10 19 nm yr indicating a large deficit of seismic slip over that period or very infrequent large slow slip events no large slow slip event has been observed however over the 20 years covered by geodetic measurements in the nepal himalaya we discuss the magnitude and return period of m 8 earthquakes required to balance the long term slip budget on the mht

impact of topography on earthquake static slip estimates abstract our understanding of earthquakes is limited by our knowledge and our description of the physics of the earth when solving for subsurface fault slip it is common practice to assume minimum complexity for characteristics such as topography fault geometry and elastic properties these characteristics are rarely accounted for because our knowledge of them is often partial and they can be difficult to include in simulations however topography and bathymetry are known all over the earth s surface and recently developed software packages such as specfem x have simplified the process of including them in calculations here we explore the impact of topography on static slip estimates we also investigate whether the influence of topography can be accounted for with a zeroth order correction which accounts for variations in distance between subfaults and the surface of the domain to this end we analyze the 2015 mw 7 5 gorkha nepal and the 2010 mw 8 8 maule chile earthquakes within a bayesian framework the regions affected by these events represent different types of topography chile which contains both a deep trench and a major orogen the andes has a greater overall elevation range and steeper gradients than nepal where the primary topographic feature is the himalayan mountain range additionally the slip of the continental nepal event is well constrained whereas observations are less informative in a subduction context we show that topography has a non negligible impact on inferred slip models our results suggest that the effect of topography on slip estimates increases with limited observational constraints and high elevation gradients in particular we find that accounting for topography improves slip estimates where topographic gradients are large when topography has a significant impact on slip the zeroth order correction is not sufficient

three dimensional information extraction from gaofen 1 satellite images for landslide monitoring abstract to more efficiently use gaofen 1 gf 1 satellite images for landslide emergency monitoring a digital surface model dsm can be generated from gf 1 across track stereo image pairs to build a terrain dataset this study proposes a landslide 3d information extraction method based on the terrain changes of slope objects the slope objects are mergences of segmented image objects which have similar aspects and the terrain changes are calculated from the post disaster digital elevation model dem from gf 1 and the pre disaster dem from gdem v2 a high mountain landslide that occurred in wenchuan county sichuan province is used to conduct a 3d information extraction test the extracted total area of the landslide is 22 58 ha the displaced earth volume is 652 100 m3 and the average sliding direction is 263 83 the accuracies of them are 0 89 0 87 and 0 95 respectively thus the proposed method expands the application of gf 1 satellite images to the field of landslide emergency monitoring

joint inversion of gps insar and teleseismic data sets for the rupture process of the 2015 gorkha nepal earthquake using a generalized abic method abstract various observations are made to invert for the source model of the 2015 gorkha earthquake previously published slip models involve different slip distributions and slip amplitudes to obtain a robust model we jointly invert for the rupture process of the gorkha earthquake using three types of observations global positioning system gps interferometric synthetic aperture radar insar and teleseismic p wave data three constraints i e spatial and temporal smoothness and minimum moment constraints are applied to regulate the rupture process the weight ratios between data sets and prior constraints are determined from a new developed generalized akaike s bayesian information criterion gabic weight determination method this gabic method can simultaneously and objectively weigh various kinds of observations and prior constraints rather than being limited to the two types in the traditional abic method the inverted slip model reveals the seismic moment of the earthquake is 9 40 10 20 n m released primarily in the first 60 s equivalent to mw 7 92 the rupture front propagates unilaterally along the strike direction and spreads in both the strike and dip directions the slip distribution shows one large slip patch with two peaks along the strike direction with a maximum slip amplitude of approximately 7 6 m and identifies large slips 2 m that occur in the updip section of the main himalayan thrust mht fault plane our results indicate that the released slip amplitude is larger than the accumulated slip amplitude since 1833 so the 2015 earthquake likely does not overlap with the 1833 earthquake

ionospheric phase screen compensation for the sentinel 1 tops and alos 2 scansar modes variations of the ionosphere can significantly disrupt synthetic aperture radar sar acquisitions and interferometric measurements of ground deformation in this paper we show how the ionosphere can also strongly modify c band interferograms despite its smaller influence at higher frequencies thus ionospheric phase screens should not be neglected their compensation improves the estimation of ground deformation maps the split spectrum method is able to estimate the dispersive ionospheric component of the interferometric phase we describe the implementation of this method for the burst modes tops and scansar to estimate and remove ionospheric phase screens we present sentinel 1 interferograms of the 2016 taiwan earthquake and alos 2 interferograms of the 2015 nepal earthquake which show strong ionospheric phase gradients and their corrected versions finally to validate the results and better understand the origin of these ionospheric variations we compare the estimated differential ionosphere with global total electron content maps and local global positioning system measurements

line of sight displacement from alos 2 interferometry mw 7 8 gorkha earthquake and mw 7 3 aftershock interferometric synthetic aperture radar insar is a key tool for the analysis of displacement and stress changes caused by large crustal earthquakes particularly in remote areas a challenge for traditional insar has been its limited spatial and temporal coverage especially for very large events whose dimensions exceed the typical swath width of 70 100 km this problem is addressed by the alos 2 satellite whose palsar 2 instrument operates in scansar mode enabling a repeat time of 2 weeks and a swath width of 350 km here we present insar line of sight displacement data from alos 2 palsar 2 observations covering the mw 7 8 gorkha nepal earthquake and its mw 7 3 aftershock that were acquired within 1 week of each event the data are made freely available and we encourage their use in models of the fault slip and associated stress changes the mw 7 3 aftershock not only extended the rupture area of the main shock toward the east but also left a 20 km gap where the fault has little or no coseismic slip we estimate this unslipped fault patch has the potential to generate a mw 6 9 event

rupture processes of the 2015 mw 7 9 gorkha earthquake and its mw 7 3 aftershock and their implications on the seismic risk abstract the rupture processes of the 2015 april 25 gorkha earthquake and its strongest aftershock occurred on may 12 in nepal are investigated by joint inversion of seismological and geodetic data synthetic test shows that the sedimentary layers in the source region play an important role in the rupture process inversion our optimized model of the mainshock shows that the rupture has a unilateral propagation pattern the dominant mechanism is pure thrust with maximum slip of 5 8 m the rupture scale extends 60 km along dip and 150 km along strike and the largest static stress change is 7 6 mpa the total seismic moment is 7 87 1020 n m equivalent to mw 7 9 most seismic moment was released within 80 s and the majority seismic moment was released at the first 40 s the rupture propagated in main slip asperity with a velocity of 3 0 km s the strong aftershock magnitude is about mw 7 3 and the peak slip is about 5 0 m close to the peak slip of the mainshock moreover the slips of the mainshock and the aftershocks are in good complementary suggesting a triggering relationship between them considering the strain accumulation the gorkha earthquake ruptured only part of the seismic gap alone thus still poses high earthquake risk especially in the west side of the mainshock rupture zone

source parameters and triggering links of the earthquake sequence in central italy from 2009 to 2016 analyzed with gps and insar data abstract from 2009 to 2016 four earthquakes mw 6 occurred in central italy which are the apr 6th 2009 earthquake aug 24th 2016 earthquake oct 26th 2016 earthquake and oct 30th 2016 earthquake to investigate their seismic mechanism triggering relationships and impacts on the surrounding areas we obtained their coseismic deformation fields using the data of interferometric synthetic aperture radar insar and global positioning system gps we constructed three variable strike fault models for the four events which can be more consistent with the actual fault and improve the overall fitting precision on this basis we calculated the coseismic slips of the first two earthquakes respectively and obtained that of the last two earthquakes by a joint inversion method then the coulomb stress changes of those four earthquakes were calculated the results show that these earthquakes are mainly caused by normal faults that strike approximately nw se or nnw sse and dips to sw or wsw with angles between 33 and 47 all these events are shallow earthquakes and the main fault slips are located in the area with depth of 0 10 km accompanied by some surface ruptures the maximal slip with a value of 3 44 m at 4 km depth was caused by the oct 30th 2016 earthquake the inverted magnitudes of the four earthquakes are mw 6 26 mw 6 20 mw 6 19 and mw 6 60 the stress changes indicate that the former earthquake accelerated the latter one successively moreover there is a seismic gap between the regions of the apr 6th 2009 and aug 24th 2016 earthquakes and a high stress accumulating area in the south of the apr 6th 2009 earthquake region so the montereale fault in the gap and the barisciano fault located on the southeast of the paganica fault might have great earthquake risks due to the massive accumulated stress

transpressional rupture cascade of the 2016 mw 7 8 kaikoura earthquake new zealand large earthquakes often do not occur on a simple planar fault but involve rupture of multiple geometrically complex faults the 2016 m w 7 8 kaikoura earthquake new zealand involved the rupture of at least 21 faults propagating from southwest to northeast for about 180 km here we combine space geodesy and seismology techniques to study subsurface fault geometry slip distribution and the kinematics of the rupture our finite fault slip model indicates that the fault motion changes from predominantly right lateral slip near the epicenter to transpressional slip in the northeast with a maximum coseismic surface displacement of about 10 m near the intersection between the kekerengu and papatea faults teleseismic back projection imaging shows that rupture speed was overall slow 1 4 km s but faster on individual fault segments approximately 2 km s and that the conjugate oblique reverse north striking faults released the largest high frequency energy we show that the linking conway charwell faults aided in propagation of rupture across the step over from the humps fault zone to the hope fault fault slip cascaded along the jordan thrust kekerengu and needles faults causing stress perturbations that activated two major conjugate faults the hundalee and papatea faults our results shed important light on the study of earthquakes and seismic hazard evaluation in geometrically complex fault systems

palaeomagnetism palaeogeography and the multicomponent analysis of middle and upper cambrian rocks of the barrandian in the bohemian massif abstract with a view to the importance of the barrandian in the bohemian massif for global palaeogeographic reconstructions considerable attention has been devoted to palaeomagnetic stability tests and multicomponent analysis of rocks of the pre variscan formations using substantially improved laboratory techniques this study is devoted to samples of upper cambrian andesite and middle cambrian sediments alternating and thermal fields were used for magnetic cleaning a thermal demagnetizer fitted with a newly developed inductor of high sensitivity the rocoma rotating coil magnetometer with a sensitivity of 0 1 to 0 2 nt was used the whole newly built and fully tested mavacs system magnetic vacuum control system guaranteed a high degree of compensation of the magnetic field in a volume of 5 1 to a value not exceeding 2 nt as numerous laboratory experiments have shown the high magnetic vacuum was necessary to derive the palaeomagnetic directions of rocks of the older formations affected significantly by the variscan orogenic phase the position of the upper cambrian pole 28 6 s 131 2 e should be considered tentative because it was derived using samples from only three andesite outcrops two other andesite outcrops preserved carboniferous or permo carboniferous palaeomagnetic directions the position of the middle cambrian pole 11 3 s 154 0 e was determined using samples of sediments mainly greywackes and shales from ten outcrops some of which represent extensive rock cross sections by combining multicomponent analysis with fold tests the mean direction of the pre variscan magnetization could be derived the very low values of the moduli of the natural remanent magnetization of the middle cambrian sediments and the considerable amount of magnetically soft components required special care to be taken in the laboratory procedures the palaeozoogeographic zones of the barrandian are related to palaeogeographic latitudes of about 40 s derived from palaeomagnetic data cold water is characteristic for the bohemian fauna but arctic conditions can be ruled out due to the amount of primary red sediments mostly of continental origin

geodetic model of the 2015 april 25 mw 7 8 gorkha nepal earthquake and mw 7 3 aftershock estimated from insar and gps data

the early palaeozoic of the north atlantic region as a test case for the use of fossils in continental reconstruction abstract fossils have an important contribution to make in the reconstruction of early palaeozoic palaeogeography the north atlantic regions include well known early palaeozoic fossil faunas which should relate to the dispositions of continental plates during the period however different versions of ordovician palaeogeography based on fossils are described in the literature and in this paper we evaluate the influences which produce these discrepancies the most reliable results are obtained by combining analysis of faunal similarity especially shelf faunas with mapping the distribution of those biofacies which relate to former deep water sites planktic organisms may not be reliable palaeocontinent discriminants cladistic analyses of different groups of organisms living at the same early ordovician time point to the usefulness of trilobite data for palaeogeographic reconstruction such data indicate a three fold division of the north atlantic region into baltica laurentia and gondwana from the cambrian to at least the mid ordovician paris and robardet 1990 denied the existence of a tornquist s sea separating baltica from gondwana in the early ordovician it is considered that their different reconstruction was because the planktic organisms on which they based their maps were not affected by this important oceanic separation to the same extent as shelly benthos on the other hand there is no evidence of deeper water biofacies along the supposed line of rheic ocean separation of avalonia from gondwana until the late ordovician however there is some evidence of deeper biofacies along the nantes sardic line new term extending from southern armorica to sardinia

paleomagnetic constraints on the assembly of the old red continent abstract a model is proposed on the basis of paleomagnetic and geological arguments for the assembly of the old red continent which in the devonian comprised north america the baltic shield and russian platform as well as a third element called armorica the latter is thought to have included most of hercynian europe and southern england and wales as well as possibly the avalonian terranes of northeastern north america and perhaps some parts of the atlas ranges and moroccan meseta the model envisions a late ordovician taconic collision of north america and armorica which are joined in the late silurian by the baltic shield and russian platform not until the late early carboniferous did gondwana join the old red continent in a collision responsible for a large internal megashear parallel to the caledonian orogenic belt as well as the hercynian alleghenian orogeny subduction of the large siluro devonian ocean between gondwana and the old red continent is held responsible for the mid devonian acadian orogeny

seismotectonic perspectives on the himalayan arc and contiguous areas inferences from past and recent earthquakes abstract spread over countries including pakistan india nepal bhutan and china the himalayan mountain chain the most spectacular result of the indo eurasian plate collision is a locus of destructive earthquakes past earthquakes from this region have impacted vast swathes of frontal himalaya and stretches of alluvial plains south of the range front risk from future earthquakes has increased considering the burgeoning population and an ever expanding built environment in the region while considerable ambiguities exist on the locations ruptures and sizes of the earthquakes during the first half of the last millennium 1255 1344 and 1505 ce those during the latter half 1803 and 1833 ce are quite well documented all reported from the central himalayan segment comprising eastern nepal kumaun and garhwal while dormancy prevailed in the central segment in the intervening period the himalayan arc elsewhere witnessed three large great earthquakes in the last century namely 1905 kangra mw 7 8 1934 bihar nepal mw 8 2 and 1950 upper assam mw 8 6 the last one being the largest intra continental earthquake in the recorded history the april 25 gorkha nepal earthquake mw 7 8 located in the central seismic gap terminated the period of low level seismic productivity that followed the 1950 event the himalayan arc and its contiguous regions are now being investigated using various tools including paleoseismology quite understandably the interpretations and tectonic models do not always converge given the diverse quality and type of data the data from variously sized modern day earthquakes sourced in the diverse structural settings of the himalaya provide better constraints on the source properties of the himalayan earthquakes the source complexity and diversity is a striking point of interest for the post 1950 events and at least some of them seem to deviate from the generally accepted model of great ruptures on a shallow dipping detachment a prime example of such anomalies is the 2005 kashmir earthquake mw 7 6 sourced on an out of sequence thrust the sources of the 1991 uttarkashi mw 6 8 1999 chamoli mw 6 6 and the 2015 gorkha nepal mw 7 8 earthquakes all in the central himalayan segment are attributed to the ramp flat on the down dip part of the main himalayan thrust mht in contrast the 2011 sikkim mw 6 9 and the 2016 imphal mw 6 7 earthquakes are intraplate events sourced within the subducting slab source models of modern day earthquakes 1991 2016 discussed in this paper bring out this plurality of mechanisms expected of a complex subduction cum collisional boundary this review presents the status of current seismotectonic understanding of the himalaya from the analyses of significant earthquakes from the past as well as recent events with a focus on the central himalayan segment

coseismic and early postseismic deformation due to the 25 april 2015 mw 7 8 gorkha nepal earthquake from insar and gps measurements analysis of interferometric synthetic aperture radar insar and global positioning system gps data reveals coseismic and early postseismic 4 88 days surface displacements associated with the 25 april 2015 mw 7 8 gorkha nepal earthquake the pattern of early postseismic surface uplift and subsidence is found to be opposite to that of the coseismic motion insar and gps data were jointly inverted for coseismic and postseismic slip on the main himalayan thrust mht we consider a complex ramp flat ramp flat subsurface structure of the mht with four connected fault planes dipping toward north from the main frontal thrust mft the inverted coseismic slip distribution follows an elliptical pattern extending east southeastward from the hypocenter with maximum amplitude of 5 7 m above the upper edge of the midcrustal ramp we infer early postseismic afterslip 4 16 days of 0 2 0 47 m toward downdip of the coseismic slip asperity and another patch with 0 1 0 2 m slip toward east the shallow portion of the mht toward south is found to have remained unruptured during the earthquake nor did it slip aseismically after the earthquake suggesting possibility of large events in the future

a paleomagnetic study of piedmont metamorphic rocks in northern delaware it has been suggested that during the lower paleozoic the appalachian piedmont province formed not as part of north america but on the south or east side of the iapetus ocean the results of a previous paleomagnetic study of the arden pluton from the piedmont of northern delaware are in agreement with this hypothesis for the present study several metamorphic and igneous rocks were sampled across a wide area of the northern delaware piedmont the late ordovician poles determined in this study like the arden pluton pole lie close to their sites and do not agree with ordovician paleopoles for cratonic north america tilting of the sampled rocks after the acquisition of magnetization is considered unlikely because the same steep direction is found in rocks collected over a wide area the interpretation of these results is that the piedmont of northern delaware formed as part of the african plate and later became sutured to north america when the iapetus ocean closed and pangea was assembled

fault dip angle determination with the jℛi criterion and coulomb stress changes associated with the 2015 mw 7 9 gorkha nepal earthquake revealed by insar and gps data abstract minimizing data misfit has been widely used in geodetic determination of fault dip angle however it ignores the contribution from data noise here we use the j i criterion which takes into account both data misfit and the contribution from data noise to determine dip angle synthetic tests show dip angle estimates with the j i criterion are more accurate and robust than those with data misfit minimization we applied this j i criterion to the determination of the dip angle of the 2015 mw 7 9 gorkha nepal earthquake using interferometric synthetic aperture radar insar and global positioning system gps data the results show that the event ruptured to the north of kathmandu with a maximum slip value of 5 8 m and a dip angle of 9 5 we also calculated the coulomb failure stress changes resolved onto the receiver faults that are generally consistent with the fault geometry of this event suggesting the possible triggering relation to aftershocks with low dip angles and a zone of seismic potential located to the west of the rupture zone

monitoring surface deformation over permafrost with an improved sbas insar algorithm with emphasis on climatic factors modeling abstract changes of permafrost not only affect regional and global water circulation carbon deposit and climate warming but also influence ground ecological geophysical and biogeochemical processes in cold region monitoring surface deformation over permafrost will help to understand the dynamics of these processes assess climate changes and prevent potential damages to engineering structures underlain by permafrost this article employs an improved small baseline subset interferometric synthetic aperture radar sbas insar technique to monitor the surface deformation over the danxiong yangbajing area in the southern qinghai tibet plateau qtp with emphasis on climatic factors modeling a new deformation model considering both the external mainly climatic and internal factors such as tectonic activities and thermal character of frozen soil is constructed and introduced into the sbas insar to estimate the surface deformation over permafrost the results show that the peak to peak annual deformation over natural surface is 3 6 5 0 cm while that along the qinghai tibet highway qth and the qinghai tibet railway qtr is 2 8 3 7 cm we also find that the surface deformation over frozen soil is negatively correlated to air temperature and precipitation with the correlation being 0 80 to 0 45 and 0 95 to 0 75 respectively the root mean squares rmss of the residual un modeled deformation got by the proposed method are much smaller than that by the existing methods we also successfully examine a time lag of about 60 days between the retrieved maximal subsidence and the highest air temperature in warm seasons from may to september after compensating for this time lag the rmss of the residual deformation reduce significantly and the correlation between the deformation and the temperature rises considerably varying from 0 95 to 0 65 the method presented in this paper is more suitable to model and analyze the surface deformation in permafrost areas

stress triggering in thrust and subduction earthquakes and stress interaction between the southern san andreas and nearby thrust and strike slip faults 1 we argue that key features of thrust earthquake triggering inhibition and clustering can be explained by coulomb stress changes which we illustrate by a suite of representative models and by detailed examples whereas slip on surface cutting thrust faults drops the stress in most of the adjacent crust slip on blind thrust faults increases the stress on some nearby zones particularly above the source fault blind thrusts can thus trigger slip on secondary faults at shallow depth and typically produce broadly distributed aftershocks short thrust ruptures are particularly efficient at triggering earthquakes of similar size on adjacent thrust faults we calculate that during a progressive thrust sequence in central california the 1983 mw 6 7 coalinga earthquake brought the subsequent 1983 mw 6 0 nunez and 1985 mw 6 0 kettleman hills ruptures 10 bars and 1 bar closer to coulomb failure the idealized stress change calculations also reconcile the distribution of seismicity accompanying large subduction events in agreement with findings of prior investigations subduction zone ruptures are calculated to promote normal faulting events in the outer rise and to promote thrust faulting events on the periphery of the seismic rupture and its downdip extension these features are evident in aftershocks of the 1957 mw 9 1 aleutian and other large subduction earthquakes we further examine stress changes on the rupture surface imparted by the 1960 mw 9 5 and 1995 mw 8 1 chile earthquakes for which detailed slip models are available calculated coulomb stress increases of 2 20 bars correspond closely to sites of aftershocks and postseismic slip whereas aftershocks are absent where the stress drops by more than 10 bars we also argue that slip on major strike slip systems modulates the stress acting on nearby thrust and strike slip faults we calculate that the 1857 mw 7 9 fort tejon earthquake on the san andreas fault and subsequent interseismic slip brought the coalinga fault 1 bar closer to failure but inhibited failure elsewhere on the coast ranges thrust faults the 1857 earthquake also promoted failure on the white wolf reverse fault by 8 bars which ruptured in the 1952 mw 7 3 kern county shock but inhibited slip on the left lateral garlock fault which has not ruptured since 1857 we thus contend that stress transfer exerts a control on the seismicity of thrust faults across a broad spectrum of spatial and temporal scales

new palaeomagnetic constraints on the position of central bohemia during early ordovician times summary apparently conflicting data within the palaeomagnetic database suggest that bohemia was at much shallower palaeolatitudes than the armorican and iberian massifs in ordovician times in order to resolve this controversy a palaeomagnetic study of arenig and llanvirn volcanic and sedimentary rocks from the barrandfan basin central bohemia has been carried out this basin comprises a sequence of unmetamorphosed lower palaeozoic rocks the main folding of which occurred in late devonian to early carboniferous times the samples collected l sites 153 samples were subjected to stepwise thermal and alternating field treatment eleven sites yielded reliable magnetic directions with analysis of the results using standard principal component and great circle analyses up to three directions of magnetiza tion can be identified in these rocks the first termed a is generally removed below 200 c although in some cases it persists up to 450 oc in the volcanic rocks it is approximately parallel to the present day earth s magnetic field in the study area dec inc 360 67 and is thus thought to be of recent origin the second direction identified termed b is isolated at intermediate blocking temperatures 150 350 c and yields an overall in situ mean direction of 195 8 k 22 3 a 95 13 1 seven sites these directions fail the fold test of mcfadden 1990 and correspond to a palaeopole position of 34 s 356 e this coincides with the late carboniferous sector of the european apparent polar wander path and thus the b direction is interpreted as being a secondary overprint of this age the highest blocking temperature direction termed c is identified at temperatures between 350 and 450 600 c it passes the fold test resulting in an overall mean direction of 312 83 k 21 9 a 95 14 6 six sites after bedding correction this direction is interpreted as being representative of the early ordovician palaeomagnetic field direction in the bohemian massif and yields a palaeopole position of 58 n 355 e this translates into palaeolatitudes of 76 s for bohemia thus demonstrating that the bohemian massif was at similar peri polar latitudes to the rest of armorica during early mid ordovician times and formed part of the northern margin of gondwana

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

postseismic deformation associated with the 2015 mw 7 8 gorkha earthquake nepal investigating ongoing afterslip and constraining crustal rheology abstract the 2015 mw 7 8 gorkha earthquake has not only imposed effective constraints on the geometrical structures friction behaviours and seismogenic patterns of the nepal himalaya thrust systems but has also provided valuable insights into the uplift mechanism and lithosphere rheology of the tibetan plateau here 1 6 year gps observations are used to reveal the postseismic deformation characteristics following the gorkha earthquake investigate the ongoing aseismic afterslip on the main himalayan thrust mht fault and constrain the crustal rheology of the southern tibetan plateau first afterslip is considered to be solely responsible for the postseismic deformation afterslip only model the results show that afterslip is anticorrelated with peak coseismic slip areas one high afterslip concentration area with a peak of 24 cm is distributed downdip of the coseismic rupture as well as in two other regions one partially overlapping the mainshock rupture and the other next to the mw 7 3 aftershock area second the gps postseismic observations are inverted to jointly investigate afterslip and viscoelastic deformation multiple mechanism model the afterslip inversion results of the above two models are highly consistent indicating the dominant contribution of afterslip to surface deformation during the 1 6 year postseismic period considering the interseismic fault coupling and historical seismicity no appreciable fault slip associated with the gorkha earthquake is found to occur both updip and west of the mainshock rupture areas this reveals that the gorkha earthquake only unzipped the lower edge of the locked portion of the mht leaving the shallow portion and western segment of the seismogenic zone still locked and the nepal region under high seismic risk the viscoelastic mechanism contributes minorly to surface deformation during the 1 6 year postseismic period the middle lower crust is assumed to comprise maxwell material beneath an elastic 25 km thick upper crust and the optimal viscosity is conservatively estimated to be 1 6 1019 pa s beneath the southern tibetan plateau which should be robustly constrained with more long term observations more effective spatial constraints and more detailed crustal models

palaeomagnetism of the ibero armorican arc and the hercynian orogeny in western europe van der voo1 has pointed out that further advances in the understanding of the hercynian orogeny require palaeomagnetic data from well studied orogenic areas we report here palaeomagnetic results of palaeozoic rocks taken in brittany portugal and spain in the ibero armorican arc iaa a large geological feature considered to be a key area for the hercynian orogeny in western europe they show evidence that the iaa formed in two stages extending results obtained in spain by ries et al 2 giving precise constraints for the former shape of the arc we can use pre hercynian palaeomagnetic directions found in spain and portugal to follow its evolution during palaeozoic times this megastructure linking brittany to iberia squeezed between gondwana and the northern continents during the carboniferous did break away from the former block during ordovician times

monitoring activity at the daguangbao mega landslide china using sentinel 1 tops time series interferometry abstract the daguangbao mega landslide china induced by the 2008 wenchuan earthquake m w 7 9 with an area of approximately 8 km 2 is one of the largest landslides in the world experts predicted that the potential risk and instability of the landslide might remain for many decades or even longer monitoring the activity of such a large landslide is hence critical terrain observation by progressive scans tops mode from the sentinel 1 satellite provides us with up to date high quality synthetic aperture radar sar images over a wide ground coverage 250 250 km enabling full exploitation of various insar applications however the tops mode introduces azimuth dependent doppler variations to radar signals which requires an additional processing step especially for sar interferometry sentinel 1 tops data have been widely applied to earthquakes but the performance of tops data based time series analysis requires further exploitation in this study sentinel 1 tops data were employed to investigate landslide post seismic activities for the first time to deal with the azimuth dependent doppler variations a processing chain of tops time series interferometry approach was developed since the daguangbao landslide is as a result of the collapse of a whole mountain caused by the 2008 mw 7 9 wenchuan earthquake the existing digital elevation models dems e g srtm and aster exhibit height differences of up to approximately 500 m tandem x images acquired after the earthquake were used to generate a high resolution post seismic dem the high gradient topographic errors of the srtm dem i e the differences between the pre seismic srtm and the actual post seismic elevation together with low coherence in mountainous areas make it difficult to derive a precise dem using the traditional insar processing procedure a re flattening iterative method was hence developed to generate a precise tandem x dem in this study the volume of the coseismic daguangbao landslide was estimated to be of 1 189 0 110 10 9 m 3 by comparing the postseismic tandem x dem with the preseismic srtm dem which is consistent with the engineering geological survey result the time series results from sentinel 1 show that some sectors of the daguangbao landslide are still active and displaying four sliding zones and exhibiting a maximum displacement rate of 8 cm year even eight years after the wenchuan earthquake the good performance of tops in this time series analysis indicates that up to date high quality tops data with spatiotemporal baselines offer significant potential in terms of future insar applications

baltica a synopsis of vendian permian palaeomagnetic data and their palaeotectonic implications torsvlk t h smethurst m a van der voo r trench a abrahamsen n and halvorsen e 1992 baltlca a synopsis of vendlan permmn palaeomagnetic data and their palaeotectonlc implications earth sci rev 33 133 152 in light of recent additions to the palaeozoic palaeo magnetlc data base particularly for the ordovlclan era a revised apparent polar wander apw path for baltica has been constructed following a rigorous synthesis of all late precambrlan perm lan data the apw path is characterized by two prominent loops firstly a late precambrlan camb rlan loop probably relating to a rifting event and secondly a younger loop relating to a mid silurian scandlan colhsion event these features imply major change in plate tectonic reconfiguratlon baltlca probably represented an individual continental unit m early palaeozoic times and was positioned m high southerly latitudes in an inverted geographic orientation in such a reconstruction baltlca was separated from the northern margin of gondwana by the tornqulst sea and from laurentla by the iapetus ocean the tornqulst zone is thus interpreted as a passive or dextral transform margin during the early palaeozoic while undergoing counter clockwise rotations up to 1 6 ma baltica drifted northward through most ol the palaeozoic except for a short period of southerly movement in late silurian early devonian times after colhslon with laurentla rapid movements in latitude up to 9 cm yr are noted m late precambrlan earl y palaeozoic times and slgmficant decrease in velocities throughout palaeozoic time probably reflect the progressive amalgamation of a larger continent by early devonian euramerlca and permian pangea times the tornqulst sea had a principal component of palaeo east west orientation hence it is difficult to be precise in the timing of when micro continents such as eastern avalonla and the european masslfs ultimately collided along the southwestern margin of baltica these micro continents are considered to have been peripheral to gondwana m high southerly latitudes during the early ordovlclan eastern avalonla clearly had rifted off gondwana by llanvlrn llanded o times and may have collided with baltlca during late ordovlclan times although the present available sdunan palaeomagnetlc data from eastern avalonia may suggest colhslon in late silurian times across the lapetus facing margin of baltica laurentla was s tuated in equatorml to southerly latitudes during most of the lower palaeozoic these continents collided in mid silurian times l e a first collision between southwestern norway and greenland scotla nd which gave rise to the early scandlan orogeny 425 ma in southwestern norway possible followed by a later but less dramatic scandlan event in northern norway at around 410 ma since baltlca was geographically reverted m early palaeozoic times the colhsional margin could not have been a margin that once rifted off laurentm as assumed in a number of plate tectonic models

paleozoic evolution of the armorica plate on the basis of paleomagnetic data new paleomagnetic data support the contention that armorica and gondwana formed a coherent block until ordovician time however by early devonian time armorica collided with the north american northern european assembly to form the old red continent and the collision itself was responsible for the acadian orogeny not for the earlier taconic orogeny as postulated previously the carboniferous collision of gondwana with the old red continent subsequently formed pangaea and produced the appalachian hercynian orogeny

ordovician provincial signals from appalachian caledonian terranes statistical analysis of mainly mid to deep shelf ordovician brachiopod faunas from localities within and marginal to the appalachian caledonian orogen reveals biogeographical patterns not entirely consistent with those presumed for the progressive orthogonal closure of the iapetus ocean correspondence analysis of faunas of late arenig early llanvirn late llandeilo earliest caradoc and late ashgill age emphasize the importance of marginal and island faunas the role of regressions and transgressions on faunal distributions and the effects of climatic change in the definition of biogeographical trends during the ordovician

are some fossils better than others for inferring palaeogeography the early ordovician of the north atlantic region as an example different kinds of fossils have different patterns of palaeogeographical distribution this has led to differing palaeocontinental reconstructions in the early palaeozoic we take the early ordovician of the north atlantic region as a test case to investigate the influence of taxonomic group upon palaeogeographical interpretation using both single linkage duster analysis and parsimony methods of biogeographical analysis on fossil faunas and floras of various groups within this region it is shown that the patterns of similarity obtained and their relationship to supposed oceanic separations vary widely from one group to another some planktic fossils graptolites acritarchs do not see a separation between gondwana and baltica which is strongly supported by evidence from other groups trilobites and ostracodes in particular reveal patterns which conform well with other geological and geomagnetic evidence at least in the arenig uanvirn time period geographical separation is seen as a more important control on faunal composition than was biofacies considering the better fossil groups for biogeographical discrimination different analytical methods produce similar biogeographical results

the 2015 gorkha nepal earthquake sequence i source modeling and deterministic 3d ground shaking to better quantify the relatively long period 0 3 hz shaking experienced during the 2015 gorkha nepal earthquake sequence we study the finite rupture processes and the associated 3d ground motion of the mw7 8 mainshock and the mw7 2 aftershock the 3d synthetics are then used in the broadband ground shaking in kathmandu with a hybrid approach summarized in a companion paper chen and wei 2017 submitted together we determined the coseismic rupture process of the mainshock by joint inversion of insar sar gps static and high rate strong motion and teleseismic waveforms our inversion for the mainshock indicates unilateral rupture towards the ese with an average rupture speed of 3 0 km s and a total duration of 60 s additionally we find that the beginning part of the rupture 5 18 s has about 40 longer rise time than the rest of the rupture as well as slower rupture velocity our model shows two strong asperities occurring 24 s and 36 s after the origin and located 30 km to the northwest and northeast of the kathmandu valley respectively in contrast the mw7 2 aftershock is more compact both in time and space as revealed by joint inversion of teleseismic body waves and insar data the different rupture features between the mainshock and the aftershock could be related to difference in fault zone structure the mainshock and aftershock ground motions in the kathmandu valley recorded by both strong motion and high rate gps stations exhibited strong amplification around 0 2 hz a simplified 3d basin model calibrated by an mw5 2 aftershock can match the observed waveforms reasonably well at 0 3 hz and lower frequency the 3d simulations indicate that the basin structure trapped the wavefield and produced an extensive ground vibration our study suggests that the combination of rupture characteristics and propagational complexity are required to understand the ground shaking produced by hazardous earthquakes such as the gorkha event

hybrid stochastic ground motion modeling of the mw 7 8 gorkha nepal earthquake of 2015 based on insar inversion abstract we derive the coseismic slip distribution on a fault for the 2015 m w 7 8 gorkha earthquake based on alos 2 wide scan data and the inversion code sdm steepest descend method the results show that the maximum slip is 4 7 m and the total released seismic moment is 6 02 10 20 n m equivalent to an earthquake of m w 7 82 static stress and slip heterogeneity analyses show that both the average stress drop and corner wavenumber are at a low level additionally we model the observed impulsive behavior at the near source katnp station using a hybrid stochastic approach which combines an analytical approach at low frequencies with a stochastic approach at high frequencies the good agreement between the hybrid modeling and observed records reveals that the input parameters such as stress drop or slip distribution are suitable for the gorkha earthquake the success of the modeling indicates that in addition to the smooth onset of stf slip rate time function the low stress drop and low degree of slip heterogeneity are also responsible for the low level of high frequency ground motion during the gorkha earthquake

the occurrence and origin of late paleozoic remagnetization in the sedimentary rocks of north america although it has been known for 25 years that some paleozoic sedimentary rock units in europe and north america were remagnetized during pennsylvanian or permian time it is only very recently that the complex and widespread nature of the late paleozoic remagnetization phenomenon has been generally acknowledged it is now recognized that many paleozoic paleomagnetic poles for north america that were once considered reliable are in fact the result of remagnetization and as a consequence the paleomagnetic data base for the paleozoic is undergoing rapid and drastic revision the causes of late paleozoic remagnetization in north america are currently the focus of much interest and active research the remagnetization can reside in either hematite or magnetite and different remagnetization mechanisms have been important in different settings chemical remagnetization processes some related to specific diagenetic events are dominant in hematite bearing sandstones and carbonates in magnetite bearing carbonates both chemical and thermoviscous remagnetization processes appear to have been important but it is difficult to determine which process is the dominant one in some settings some of the observed remagnetizations can be linked to the migration of chemically active and perhaps hot fluids during the mountain building events that affected much of the continent during the late paleozoic paleomagnetic studies promise to be important in assessing the role of orogeny in driving fluid migrations within sedimentary basins and in constraining the age of the migrations and the nature of the fluids

coseismic and postseismic displacements from the 1978 mw 7 3 tabas e golshan earthquake in eastern iran abstract we use optical image correlation of historical aerial photographs and modern satellite images to investigate the 1978 m w 7 3 tabas e golshan thrust earthquake in eastern iran correlation of images between 1974 and 1991 reveals a near surface shortening component of 2 9 m across the margin of the tabas fold which is a combination of coseismic and postseismic deformation correlation of images between 1991 and 2013 shows a further 0 3 m of postseismic shortening using six pre earthquake aerial photographs acquired in 1956 and stereo spot 6 imagery from 2013 we also generate pre and post earthquake digital elevation models dems for one of the main fold segments differencing of the two dems reveals a height change of 4 7 m elastic dislocation modelling of the 1974 2013 displacement field requires 7 m slip on a 50 dipping fault extending from a depth of 0 1 km to 6 km at its base the majority of slip 6 5 m occurred prior to 1991 our results combined with previous insar observations indicate time decaying shallow postseismic afterslip it is likely that most of the afterslip occurred prior to 1991 the slip appears to dissipate in the near surface and is accommodated as a narrow band of flexural slip on bedding planes comparison of the fault slip model with terrace heights measured from the spot 6 dem suggests that the tabas fold system may exhibit characteristic slip behaviour such behaviour would require a magnitude m w 7 3 earthquake every 3500 years based on the previously estimated shortening rate of 1 0 mm yr this study highlights the usefulness of historical imagery in investigating past earthquakes thus providing new information about historical faulting in continental regions

coseismic deformations of the 2015 mw 7 8 gorkha earthquake and interseismic strain accumulation in the himalayan tectonic belt and tibetan plateau abstract the principal strain rate derived from gps velocities from the tibetan plateau and the india plate shows that the himalayan tectonic belt exhibits compression deformation in a ne ns ne direction from the west to the east the gps velocity profiles reflect that the distribution of strain accumulation is uneven there is a 17 1 mm yr compressive deformation distributed over 400 km along 85 e longitude a 20 9 22 2 mm yr compressive deformation dispersed across 400 500 km along 79 e longitude and a 15 3 16 9 mm yr compressive deformation spread across 500 600 km along 91 e longitude the mw 7 8 gorkha earthquake occurred at the edge of an intense compression deformation zone of about 6 0 10 8 yr in a north south direction and an about 90 compressive strain is absorbed in the 300 km region near the main frontal thrust mft coseismic displacements larger than three standard deviations 3sd are mainly concentrated within 360 km from the epicenter the nodal plane of the main shock divides the areas where tensile strain release in an exponential attenuation pattern is dominant to the north and where compressive strain with upward movement is dominant to the south the results inversed by the sdm program reveal that the maximal slip of the gorkha earthquake is 5 33 m and its moment magnitude is mw 7 85 and the largest stress drop is 4 21 mpa slips larger than 0 5 m are mainly distributed in a region approximately 135 km 105 km which show that the rupture of the gorkha earthquake does not reach the surface finally we estimate that the recurrence period of this earthquake is about 166 20 years according to the strain accumulation before the earthquake and the coseismic release feature

physics based scenario of earthquake cycles on the ventura thrust system california the effect of variable friction and fault geometry the ventura thrust system in california is capable of producing large magnitude earthquakes geological studies suggest that the fault geometry is complex composed of multiple segments at different dips thrust ramps dipping 30 50 linked with bed parallel decollements dipping 10 these latter types of gently dipping faults form due to preexisting weaknesses in the crust and therefore have different frictional parameters from thrust ramps the faults also experience different stresses because of how stresses are resolved onto the fault planes here we use a two dimensional fault model to assess how geometry and frictional properties of the ramp decollement system should affect the seismic cycle we test velocity strengthening velocity weakening and conditionally stable decollements and in addition explore how the dip angle of the decollement changes the earthquake behavior a velocity strengthening decollement cannot replicate the through going earthquake ruptures that have been inferred for the ventura fault system we therefore suggest that this and other decollements may be better represented using a velocity weakening or conditionally stable response our results show that minor variations in fault geometry produce slip amounts and recurrence intervals that differ only by 10 20 but do not fundamentally alter the types of earthquakes and interseismic slip we conclude that geological constraints on fault geometry are typically sufficient to produce modeled earthquake sequences that are statistically consistent with paleoseismic records however both frictional parameters along the fault and effective normal stress influence earthquake rupture patterns significantly more research is needed to adequately constrain these quantities in order for earthquake rupture models to work as effective predictors of fault behavior

faunal evidence for oceanic separations in the palaeozoic of britain the faunal criteria for the recognition of the relative separation of old continents are 1 the contrast between shallow not deep water faunas off opposite shorelines 2 the recognition of deeper water facies surrounding the edges of continents and 3 the recognition of the disposition of ancient climatic belts these criteria are defined and used to assess the relative position of the various parts of what is now britain in the palaeozoic the iapetus ocean is well characterized by faunal differences from the cambrian until the lower ordovician but from caradoc times onwards these differences dwindle until by the latest silurian only the distribution of the ostracods separates the two sides of the ocean on faunal grounds in the early ordovician s british faunas are comparable with those from bohemia france and elsewhere to the s indicating connection with gondwanaland and these faunas differ from those in the baltic area a distribution which we attribute to a true ocean tornquist9s sea between n and s europe tornquist9s sea probably closed in the upper ordovician and from ashgill times onwards the s british and baltic faunas remained similar during the middle and late silurian there is evidence of increasing faunal distinction between britain the baltic area and north america on the one hand and southern europe and gondwanaland on the other indicating an opening rheic ocean which appears to have persisted until late carboniferous times

characteristic ground motions of the 25th april 2015 nepal earthquake mw 7 9 and its implications for the structural design codes for the border areas of india to nepal abstract the 25th april 2015 nepal earthquake was found associated with a series of aftershocks and the mainshock rupture propagated predominantly towards se direction where a major aftershock mw 7 3 rocked on 12th may 2015 to the east of the mainshock that enhanced the rate of occurrence of aftershocks in the affected region we conducted a rigorous analysis of strong motion data to understand the characteristics of ground motion and their bearing on the structural design codes responsible for the damage to the structures in the border area of india to nepal the effect of ground geology on the acceleration response spectra are also evaluated using main shock and its associated strong earthquakes all the sites used in the present analysis are located on alluvium deposits showing a predominant period of 0 242 sec for horizontal components and at 0 193 sec for vertical components our results demonstrated that observed peak ground acceleration pga has prominent distribution in the border cities of up and bihar pga ranges from 3 to 80 cm sec 2 in the study region for the epicentral distance varying from 120 km to 495 km with respect to the source zone mainshock the peak ground velocity pgv varies from 1 to 16 cm sec while the peak ground displacement pgd lies in between 1 cm and 20 cm for the same area our study shows that variation of pgd pgv and pga are controlled and dictated by the geo morphological constraints besides the nature and extent of structural heterogeneities of the sub surface geological formation materials the obtained normalised spectral amplifications are compared with the bureau of indian standard code for construction of buildings which shows that the current indian building design code is within the structural limits proposed for the seismic forces at all periods for alluvium sites suggesting that the structural heterogeneity has the strong role contributing towards the intrinsic attenuation in the seismic wave propagating medium our analysis also shows a good correspondence with the nonlinearity of the seismic waves which in turn controls the degree of damage in an area we infer that extent of damage to the structures in the border cities of india vicinity to the rupture zone can be avoided if the existing building design code could have been implemented as the earthquake risk resilient mitigation plan

paleozoic accretionary orogenesis in the paleo asian ocean insights from detrital zircons from silurian to carboniferous strata at the northwestern margin of the tarim craton a detrital zircon u pb and lu hf isotopic study was carried out in the middle silurian to late carboniferous sedimentary strata of the northwestern tarim craton in order to understand accretionary processes in the southern part of the central asian orogenic belt detrital zircons from these strata yielded u pb ages clustering around 2 8 2 3 ga 2 0 1 7 ga 1 3 0 9 ga 880 600 ma and 500 400 ma with age populations and hf isotopic signatures matching those of magmatic rocks in the tarim craton and the central tianshan block abundant 500 400 ma detrital zircons most likely reflect deposition in a retroarc foreland basin inboard of an andean type magmatic arc to the north supporting the northern tarim central tianshan connection during early paleozoic time the absence of 380 310 ma zircon population in the carboniferous siliciclastic rocks suggests that the central tianshan block may have been separated from the tarim craton in the early devonian caused by the interarc back arc opening of the south tianshan ocean we propose an accretionary orogenic model switching from advancing to retreating mode during paleozoic time in the southwestern part of the paleo asian ocean this transition most likely occurred coevally with the rifting of southeast asian blocks from the northeastern margin of gondwana

shortcomings of insar for studying megathrust earthquakes the case of the mw9 0 tohoku oki earthquake 1 interferometric synthetic aperture radar insar observations are sometimes the only geodetic data of large subduction zone earthquakes however these data usually suffer from spatially long wavelength orbital and atmospheric errors that can be difficult to distinguish from the coseismic deformation and may therefore result in biased fault slip inversions to study how well insar constrains fault slip of large subduction zone earthquakes we use data of the 11 march 2011 tohoku oki earthquake mw9 0 and test insar derived fault slip models against models constrained by gps data from the extensive nationwide network in japan the coseismic deformation field was mapped using insar data acquired from multiple ascending and descending passes of the alos and envisat satellites we then estimated several fault slip distribution models that were constrained using the insar data alone onland and seafloor gps acoustic data or combinations of the different data sets based on comparisons of the slip models we find that there is no real gain by including insar observations for determining the fault slip distribution of this earthquake that said however some of the main fault slip patterns can be retrieved using the insar data alone when estimating long wavelength orbital atmospheric ramps as a part of the modeling our final preferred fault slip solution of the tohoku oki earthquake is based only on the gps data and has maximum reverse and strike slip of 36 0 m and 6 0 m respectively located northeast of the epicenter at a depth of 6 km and has a total geodetic moment is 3 6 1022 nm mw 9 01 similar to seismological estimates

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

estimating the return times of great himalayan earthquakes in eastern nepal evidence from the patu and bardibas strands of the main frontal thrust the return times of large himalayan earthquakes are poorly constrained despite historical devastation of cities along the mountain range definitive links between events and specific segments of the main frontal thrust mft are not established and paleoseismological records have not documented the occurrence of several similar events at the same location in east central nepal however recently discovered primary surface ruptures of that megathrust in the a d 1255 and 1934 earthquakes are associated with flights of tectonically uplifted terraces we present here a refined longer slip history of the mft s two overlapping strands patu and bardibas thrusts in that region based on updated geomorphic neotectonic mapping of active faulting two 1 3 km long shallow seismic profiles and logging of two river cut cliffs three paleoseismological trenches and several pits with constraints from 74 detrital charcoals and 14 cosmogenic nuclide ages the amount of hanging wall uplift on the patu thrust since 3650 450 years requires three more events than the two aforementioned the uplift rate 8 5 1 5mm yr thrust dip 25 5 n and apparent characteristic behavior imply 12 17 5m of slip per event on the bardibas thrust discrete pulses of colluvial deposition resulting from the coseismic growth of a flexural fold scarp suggest the occurrence of six or seven paleo earthquakes in the last 4500 50 years the coeval rupture of both strands during great himalayan earthquakes implies that in eastern nepal the late holocene return times of such earthquakes probably ranged between 750 140 and 870 350 years

which fault segments ruptured in the 2008 wenchuan earthquake and which did not new evidence from near fault 3d surface displacements derived from sar image offsets the 2008 m w 7 9 wenchuan earthquake ruptured a complex thrust faulting system at the eastern edge of the tibetan plateau and west of sichuan basin though the earthquake has been extensively studied several details about the earthquake such as which fault segments were activated in the earthquake are still not clear this is in part due to difficult field access to the fault zone and in part due to limited near fault observations in interferometric synthetic aperture radar insar observations because of decorrelation in this study we address this problem by estimating sar image offsets that provide near fault ground displacement information and exhibit clear displacement discontinuities across activated fault segments we begin by reanalyzing the coseismic insar observations of the earthquake and then mostly eliminate the strong ionospheric signals that were plaguing previous studies by using additional postevent images we also estimate the sar image offsets and use their results to retrieve the full 3d coseismic surface displacement field the coseismic deformation from the insar and image offset measurements are compared with both global positioning system and field observations the results indicate that our observations provide significantly better information than previous insar studies that were affected by ionospheric disturbances we use the results to present details of the surface faulting offsets along the beichuan fault from the southwest to the northeast and find that there is an obvious right lateral strike slip component as well as thrust faulting along the southern beichuan fault in yingxiu county which was strongly underestimated in earlier studies based on the results we provide new evidence to show that the qingchuan fault was not ruptured in the 2008 wenchuan earthquake a topic debated in field observation studies but show instead that surface faulting occurred on a northward extension of the beichuan fault during or immediately following the mainshock electronic supplement 1 parallel ascending orbit track coseismic deformation 1 http www bssaonline org lookup suppl doi 10 1785 0120160126 dc1

blind thrust rupture of the 2015 mw 6 4 pishan earthquake in the northwest tibetan plateau by joint inversion of insar and seismic data abstract the july 3rd 2015 pishan china mw 6 4 earthquake occurred within the hetian fold belt a frontal thrust region between the northwestern tibetan plateau and the tarim basin we investigate the fault geometry and the rupture process of the pishan earthquake based on joint inversion of teleseismic body waves and insar measurements our results show that the top of the fault that ruptured in the pishan earthquake is buried 5 2 km beneath the surface and that the earthquake ruptured only a segment of a deeply seated detachment lying under the hetian fold belt our inferred coseismic slip model shows two slip asperities located in the depth range of about 7 9 km and 10 11 km additionally we resolve a slip deficit region between the slip asperities which might indicate friction heterogeneity on the fault plane the earthquake ruptured for 15 s releasing a total seismic moment of 4 7 10 18 n m we also show that the latest pishan earthquake caused positive coulomb stress changes on back thrust faults potentially decreasing the time to the next earthquake on those faults based on our pishan coseismic slip model along with both the trend of the anticline system and the pattern of coseismic deformation we envision an ongoing east west extensional growth of the anticlines in the western kunlun frontal thrust region in addition to the northern underthrusting of the northwestern tibetan plateau below the tarim basin

source characteristics of the 2015 m w 7 8 gorkha nepal earthquake and its m w 7 2 aftershock from space geodesy abstract on april 25 2015 a destructive m w 7 8 earthquake struck the capital of nepal kathmandu killing more than 8800 people and destroying numerous historical structures we analyze six coseismic interferograms from several satellites alos 2 sentinel 1 a and radarsat 2 as well as three dimensional displacements at six gps stations to investigate fault structure and slip distribution of the gorkha earthquake using a layered crustal structure the best fit slip model shows that the preferred dip angle of the mainshock fault is 6 3 5 and the major slip is concentrated within depths of 8 15 km the maximum slip of 6 0 m occurs at a depth of 11 km 70 km south east of the epicenter the coseismic rupture extends 150 km eastward of the epicentre with a cumulative geodetic moment of 7 8 10 20 nm equivalent to an earthquake of m w 7 84 we also investigate the m w 7 2 aftershock on 12 may 2015 using another three postseismic interferograms from alos2 radarsat 2 and sentinel 1 a the insar based best fit slip model of the largest aftershock implies that its major slip is next to the eastern lower end of the mainshock rupture with a similar maximum slip of 6 m at a depth of 13 km this study generates various coseismic geodetic measurements to determine the source parameters of the m w 7 8 gorkha earthquake and 12 may m w 7 2 afershock providing an additional chance to understand the local fault structure and slip extent

the 2005 mw 7 6 kashmir earthquake sub pixel correlation of aster images and seismic waveforms analysis we analyze the m w 7 6 kashmir earthquake of october 8 2005 using sub pixel correlation of aster images to measure ground deformation and modeling seismic waveforms the surface rupture is continuous over a distance of 75 km and cuts across the hazara syntaxis reactivating the tanda and the muzaffarabad faults north of muzaffarabad the surface rupture coincides approximately with the mbt on the southwestern flank of the syntaxis although the two faults have opposite dip angles the rupture terminates abruptly at the hairpin turn of the mbt showing a strong structural control the fault offset is 4 m on average and peaks to 7 m northwest of muzaffarabad the rupture lasted about 25 s and propagated updip and bi laterally 2 km s with a rise time of 2 5 s the shallowness and compactness of the rupture both in time and space provide an explanation for the intensity of destructions this kind of analysis could be achieved as soon as a post earthquake image is available and would provide key information for early assessment of damages the study sheds some light on seismic hazard in the himalaya and raises concern regarding the possibility of a repetition of the 1555 event which presumably ruptured the himalayan front south of the kashmir basin and may have reached a magnitude m w 8

paleomagnetism of the late ordovician thouars massif vendee province france a paleomagnetic study of the late ordovician thouars massif reveals very steep components of magnetization directed upward and downward and with thermally discrete blocking temperatures of 550 to 580 c this characteristic magnetization yields a mean direction with declination inclination 340 83 with k 27 and 95 7 based on 15 sites the south paleopole is located at 34 n 5 e a partial magnetic overprint of hercynian age is observed in sites close to the south armorican shear zone the 15 sites are spread over some 20 by 30 km and the internal consistency of the site mean directions indicates that differential tilting of parts of the massif has not occurred since it appears to be unlikely that the entire massif was tilted we infer that the characteristic direction is primary and that the paleopole adequately represents the local magnetic field in the late ordovician the paleopole for the thouars massif supports previously obtained results from other ordovician rocks in hercynian europe but it is the first result to pass modern reliability criteria the high ordovician paleolatitudes of the armorican massif other areas in hercynian europe and north western africa indicate that gondwana and armorica were adjacent until late ordovician time low paleolatitudes for late devonian time suggest that armorica underwent rapid northward motion at a rate of about 10 cm yr during the silurian and earliest devonian armorica is thought to have collided with north america and the baltic shield russian platform before or during the early devonian forming the old red continent the collisions produced the caledonian and acadian orogenic belts

caradoc brachiopods from the leinster terrane se ireland a lost piece of the lapetus puzzle the recent re collection and examination of brachiopod dominated faunas from many localities in the duncannon group of the leinster terrane of se ireland has resulted in an improved age definition of the assemblages and a reassessment of their biogeographical affinities the assemblages are almost all soudleyan to longvillian caradoc in age and provide some constraint on the duration of volcanism related to subduction which may have ceased in the mid caradoc at this time they were part of a single anglo welsh province which occupied the seas around the eastern avalonia plate the province was composed of well established species from earlier baltic immigrations together with endemics connections with the scoto appalachian and mediterranean provinces are evident also

paleozoic paleogeography of north america gondwana and intervening displaced terranes comparisons of paleomagnetism with paleoclimatology and biogeographical patterns new paleomagnetic data have become available in the past 5 yr that require modifications in previously published paleogeographic reconstructions for the silurian and devonian in this paper the new paleopoles are compared to published paleogeographic models based on paleoclimatologic and biogeographic data the data from the three fields of paleomagnetism paleoclimatology and biogeography are generally in excellent agreement and an internally consistent paleogeographic evolutionary picture of the interactions between north america gondwana and intervening displaced terranes is emerging during the interval of the ordovician silurian and devonian north america stayed in equatorial paleoposition while rotating counter clockwise the northwest african part of gondwana was in high southerly latitudes during the late ordovician and was fringed by peri gondwanide terranes such as southern europe armorica and avalonian basement blocks now found in eastern newfoundland nova scotia the boston basin the appalachian piedmont and northern florida subsequently gondwana and the peri gondwanide terranes displayed rapid drift with respect to the pole this drift translates into the following pattern of movement for northwest africa during the latest ordovician early silurian this area moved rapidly northward from polar to subtropical latitudes followed by equally rapid southward motion from subtropical to intermediate about 50 s paleolatitudes during the late silurian middle devonian it is likely that significant east to west motion accompanied the latter shift in paleolatitudes with the caledonian acadian orogeny the result of silurian to early devonian convergence and collision between gondwana and north america this collision sandwiched several of the intervening displaced terranes between gondwana and north america subsequent to this collision gondwana was separated in the late devonian by a medium width ocean from north america and the avalonian and southern european blocks which were left behind adjacent to north america this new ocean closed during the carboniferous and the resulting convergence and collision were the cause of the hercynian alleghanian orogenic belt problems remaining for future research besides the further gathering of reliable paleopoles involve the uncertain pre devonian position of the southern british isles in this scenario and the very rapid velocity with respect to the pole that results from the rapid late ordovician silurian apparent polar wander for gondwana