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

gutenberg s surface wave magnitude calibrating function theoretical basis from synthetic seismograms the surface wave magnitude as originally defined by gutenberg 1945 appears to be the most stable quantity rating the strengths of seismic sources it is based on the ground displacement produced by a nearly monochromatic wave train the calibrating function underlying the magnitude definition was obtained from observations of the amplitudes as a function of epicentral distance for a wealth of earthquakes no distinction was made as to focal depths thus the calibrating function depends on one parameter the epicentral distance only subsequent attempts to introduce a focal depth correction were not successful in practice and one and the same calibrating function continues to be applied to events with focal depths ranging from 0 to about 70 km assuming a strike slip point source located inside a standard earth model synthetic seismograms of the fundamental mode sh love wave are computed for a range of focal depths and azimuths amplitude distance curves are obtained and averaged over the azimuths the curves are the basis for improved calibrating functions average depth corrections are obtained and applied to some populations of seismic events the corrected surface wave magnitudes are internally more consistent than the uncorrected ones usually published applying the depth correction to published surface wave magnitudes and considering themb ms relation for a sample of earthquakes and explosions it has been established that for a given intensity of short periodic radiation the 20 s radiation intensity can vary by orders of magnitude while it is known that the 20 s radiation intensity is generally lower for explosions than for earthquakes it turns out to be even lower if the depth correction is applied yielding a clearer separation between both classes of seismic events

on the variation of slip direction during earthquake rupture supporting and conflicting evidence from the 1989 loma prieta earthquake abstract the direction of the slip can change during a rupture episode as a function of time and or of the position on the fault plane in this work we focus on the spatial variations of slip direction during an earthquake theoretically the spatial variations of rake are caused by changes in the direction of the static and dynamic traction the 1989 loma prieta earthquake provides one of the most striking examples of slip direction rotation during the coseismic rupture all the source models obtained by using different inversion procedures show strong spatial partitioning of slip into strike slip motion se of the epicenter and dip slip motion in the nw section in this study we perform both forward waveform modeling and waveform inversion tests to check if the previously observed variations of rake are constrained by seismological data we use the isochrone approach and a tomographic back projection algorithm to solve the forward modeling and the inverse problem respectively results show that observed ground velocities can be well reproduced by source models having spatial slip distribution similar to the beroza9s 1991 inversion solution but having constant rake synthetic inversion tests point out that the inversion procedure does not constrain the slip direction we have analyzed the s wave polarization in order to constrain the direction of slip along the fault this analysis confirms that a predominant strike component rake 160 characterizes the slip direction in the southeastern section while an increase of the reverse component in the northwest section of the fault allows one to explain the observed polarization well an oblique mechanism is consistent with the fault plane solution confirming a spatial variation of the slip direction during the earthquake if the rake actually varied then a nonuniform prestress condition due to a change in fault geometry or to a redistribution of static stress or a spatially inhomogeneous stress release should be proposed in order to explain the observed changes of slip direction we conclude that a nonuniform prestress is a likely explanation for the inferred rake rotations these variations of the direction of slip involve a low value of the initial stress

seismic moment catalog of large shallow earthquakes 1900 to 1989 we compile a worldwide catalog of shallow depth 70 km and large ms 7 earthquakes recorded between 1900 and 1989 the catalog is shown to be complete and uniform at the 20 sec surface wave magnitude ms 7 0 we base our catalog on those of abe 1981 1984 and abe and noguchi 1983a b for events with ms 7 0 those catalogs however are not homogeneous in seismicity rates for the entire 90 year period we assume that global rates of seismicity are constant on a time scale of decades and most inhomogeneities arise from changes in instrumentation and or reporting we correct the magnitudes to produce a homogeneous catalog the catalog is accompanied by a reference list for all the events with seismic moment determined at periods longer than 20 sec using these seismic moments for great and giant earthquakes and a moment magnitude relationship for smaller events we produce a seismic moment catalog for large earthquakes from 1900 to 1989 the catalog is used to study the distribution of moment released worldwide although we assumed a constant rate of seismicity on a global basis the rate of moment release has not been constant for the 90 year period because the latter is dominated by the few largest earthquakes we find that the seismic moment released at subduction zones during this century constitutes 90 of all the moment released by large shallow earthquakes on a global basis the seismic moment released in the largest event that occurred during this century the 1960 southern chile earthquake represents about 30 to 45 of the total moment released from 1900 through 1989 a frequency size distribution of earthquakes with seismic moment yields an average slope b value that changes from 1 04 for magnitudes between 7 0 and 7 5 to b 1 51 for magnitudes between 7 6 and 8 0 this change in the b value is attributed to different scaling relationships between bounded large and unbounded small earthquakes thus the earthquake process does have a characteristic length scale that is set by the downdip width over which rupture in earthquakes can occur that width is typically greater for thrust events at subduction zones than for earthquakes along transform faults and other tectonic environments

surface deformation and lower crustal flow in eastern tibet field observations and satellite geodesy indicate that little crustal shortening has occurred along the central to southern margin of the eastern tibetan plateau since about 4 million years ago instead central eastern tibet has been nearly stationary relative to southeastern china southeastern tibet has rotated clockwise without major crustal shortening and the crust along portions of the eastern plateau margin has been extended modeling suggests that these phenomena are the result of continental convergence where the lower crust is so weak that upper crustal deformation is decoupled from the motion of the underlying mantle this model also predicts east west extension on the high plateau without convective removal of tibetan lithosphere and without eastward movement of the crust east of the plateau

effect of source depth correction on the estimation of earthquake size the relationship between surface wave magnitude ms and seismic moment mo of earthquakes is essential for the estimation of seismic risk in any region in the hypothesis of constant stress drop theoretical models predict that log mo and ms are related by a linear law the slope most commonly found in the literature is around 1 5 here we show that the application to the ms values of the necessary correction for the focal depth gives a general increment of the correlation coefficient and that a slope around 1 0 is consistent with the global data while for regionalized data it can vary from about 1 0 to 2 0

microseismic rupture propagation imaging abstractwe have developed a method for tracing the rupture propagation of microseismic events we referred to it as microseismic rupture propagation imaging mrpi which is an adaptation of the back projection technique from global seismology hence we shifted back recorded waveforms to a grid of possible source locations and obtained a coherent phase stack that migrated according to the migration of the rupture front using synthetic ruptures and the corresponding waveforms obtained by finite difference modeling we tested the viability of the approach for a reservoir model with the properties and geometry of the monitoring system of the basel 1 geothermal reservoir first we found that an estimation of the rupture location orientation direction and length was feasible in this environment the method was then applied to the four largest events ml 3 1 3 4 recorded at the basel 1 reservoir we found that the obtained rupture lengths and orientations were reasonably consistent with independent estim

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

present day kinematics at the india asia collision zone the collision of the indian subcontinent with asia drives the growth and evolution of the greater tibetan plateau region fault slip rates resulting from the relative motion between crustal blocks can provide a kinematic description of the distribution of presentday deformation i construct a three dimensional regional scale elastic block model of the india asia collision zone that is consistent with geodetic observations of interseismic deforma tion mapped fault system geometry historical seismicity and the mechanics of the earthquake cycle this mechanical model of the elastic upper crust yields a set of kinematically consistent fault slip rates and block motions that may serve to constrain dynamic models of continental crustal dynamics

seismology energy radiation from the sumatra earthquake we determined the duration of high frequency energy radiation from indonesia s great sumatra andaman earthquake 26 december 2004 to be about 500 seconds this duration can be translated into a rupture length of about 1 200 km which is more than twice as long as that inferred from body wave analyses performed soon after the event our analysis was able rapidly to define the extent of rupture thereby aiding the assessment of seismic hazard in the immediate future

surface deformation related to the 2008 wenchuan earthquake and mountain building of the longmen shan eastern tibetan plateau abstract the 12 may 2008 ms 8 0 wenchuan earthquake china was one of largest continental thrusting events worldwide based on interpretations of post earthquake high resolution remote sensing images and field surveys we investigated the geometry geomorphology and kinematics of co seismic surface ruptures as well as seismic and geologic hazards along the longmen shan fold and thrust belt our results indicate that the wenchuan earthquake occurred along the ne sw trending yingxiu beichuan and guanxian anxian faults in the longmen shan fold and thrust belt the main surface rupture zones along the yingxiu beichuan and guanxian anxian fault zones are approximately 235 and 72 km in length respectively these sub parallel ruptures may merge at depth the yingxiu donghekou surface rupture zone can be divided into four segments separated by discontinuities that appear as step overs or bends in map view surface deformation is characterized by oblique reverse faulting with a maximum vertical displacement of approximately 10 m in areas around beichuan county earthquake related disasters e g landslides are linearly distributed along the surface rupture zones and associated river valleys the wenchuan earthquake provides new insights into the nature of mountain building within the longmen shan eastern tibetan plateau the total crustal shortening accommodated by this great earthquake was as much as 8 5 m with a maximum vertical uplift of approximately 10 m the present results suggest that ongoing mountain building of the longmen shan is driven mainly by crustal shortening and uplift related to repeated large seismic events such as the 2008 wenchuan earthquake furthermore rapid erosion within the longmen shan fold and thrust belt occurs along deep valleys and rupture zones following the occurrence of large scale landslides triggered by earthquakes consequently we suggest that crustal shortening related to repeated great seismic events together with isostatic rebound induced by rapid erosion related unloading is a key component of the geodynamics that drive ongoing mountain building on the eastern tibetan plateau

lessons learned from the 2004 sumatra andaman megathrust rupture the 2004 sumatra andaman earthquake has been extensively studied because of its great size and devastating consequences large amounts of highquality seismic geodetic and geologic data have led to a number of proposed models for its length duration fault geometry rupture velocity and slip history the latest of these models vary in their details but now largely agree in their large scale features which include significant coseismic slip along the entire 1300 to 1500 km rupture the bulk of which occurred fast enough to radiate seismic waves the earthquake s enormous size has challenged conventional processing approaches and stimulated the development of new analysis and inversion methods including multiple source inversions highfrequency body wave imaging and satellite observations of tsunami heights and gravity changes the sumatra megathrust earthquake was the largest in 40 years and is by far the best documented but it does not seem fundamentally different in its properties from other large subduction zone earthquakes

the 16 april 2016 mw 7 8 ms 7 5 ecuador earthquake a quasi repeat of the 1942 ms 7 5 earthquake and partial re rupture of the 1906 ms 8 6 colombia ecuador earthquake the 2016 ecuador m w 7 8 earthquake ruptured the subduction zone boundary between the nazca and south american plates joint modeling of seismic and tsunami observations indicates an 120 km long rupture area beneath the coastline north of the 1998 m w 7 2 rupture the slip distribution reveals two discrete asperities near the hypocenter and around the equator their locations and the patchy pattern are consistent with the prior interseismic geodetic strain which showed highly locked patches also beneath the coastline aftershocks cluster along two streaks one aligned nearly parallel to the plate convergence direction up dip of the main slip patches and the other on a trench perpendicular lineation south of the 1958 rupture zone comparisons of seismic waveforms and magnitudes show that the 2016 event and 1942 earthquakes have similar surface wave magnitude m s 7 5 overlapping rupture areas and similar main pulses of moment rate the same area ruptured as the southernmost portion of the larger earthquake of 1906 m w 8 6 m s 8 6 the seismic behavior reflects persistent heterogeneous frictional properties of the colombia ecuador megathrust

present day crustal motion within the tibetan plateau inferred from gps measurements 1 using the measurements of 726 gps stations around the tibetan plateau we determine the rigid rotation of the entire plateau in a eurasia fixed reference frame which can be best described by an euler vector of 24 38 0 42 n 102 37 0 42 e 0 7096 0 0206 ma the rigid rotational component accommodates at least 50 of the northeastward thrust from india and dominates the eastward extrusion of the northern plateau after removing the rigid rotation to highlight the interior deformation within the plateau we find that the most remarkable interior deformation of the plateau is a glacier like flow zone which starts at somewhere between the middle and western plateau goes clockwise around the eastern himalayan syntaxis ehs and ends at the southeast corner of the plateau with a fan like front the deformation feature of the southern plateau especially the emergence of the flow zone could be attributed to an eastward escape of highly plastic upper crustal material driven by a lower crust viscous channel flow generated by lateral compression and gravitational buoyancy at the later developmental stage of the plateau the first order feature of crustal deformation of the northeastern plateau can be well explained by a three dimensional elastic half space dislocation model with rates of dislocation segments comparable to the ones from geological observations in the eastern plateau although gps data show no significant convergence between the eastern margin of the plateau and the sichuan basin a small but significant compressional strain rate component of 10 5 2 8 nstrain yr exists in a relatively narrow region around the eastern margin in addition a large part of the eastern plateau northeast of the ehs is not undergoing shortening along the northeastward convergence direction of the ehs but is stretching

tracking unilateral earthquake rupture by p wave polarization analysis summary rapid estimation of earthquake rupture propagation is essential to declare an early warning for tsunami generating earthquakes an increasing number of seismological methods have been developed to determine rupture parameters such as length velocity and propagation direction especially since the occurrence of the sumatra andaman earthquake that resulted in a devastating tsunami in the indian ocean region here we present a new method to follow the rupture process in near real time by a polarization analysis of local and regional p phases that permits a faster determination of rupture properties than using teleseismic records the new technique has the capability to provide detailed information in less than 10 min originally the method stems from a single station earthquake location method and is expanded here to monitor p phase polarization variations through time as the earthquake source moves away from the hypocentre the backazimuth of an incoming p phase is expected to change accordingly with polarization analysis we may be able to monitor the temporal change in p wave backazimuth to follow the rupture process in near real time three component p phases are scanned to determine the azimuthal variation as a function of time the backazimuth of a moving rupture front is determined by the first eigenvector of the covariance matrix the linearity of the particle motion is used as a measure of the quality of the data seismic stations at local and regional distances are used we tested the new method with a theoretical simulation and observed seismograms of the sumatra andaman earthquake 2004 december 26 mw 9 3 and we were able to follow the rupture for the first 200 s for larger ruptures stations at more than 30 epicentral distances would be required the method is also successfully applied to the wenchuan earthquake 2008 may 12 mw 8 0

complex polarization analysis of particle motion knowledge of particle motion polarization aids in identifying phases on three component seismograms the scheme of montalbetti and kanasewich 1970 is extended to analytic three component seismograms where the imaginary part of the signal is the hilbert transform of the real part this scheme has only one free parameter the length of the time window over which the polarization parameters are estimated so it can be applied in a routine way to three component data the azimuth and dip of the direction of maximum polarization and the degree of elliptical polarization as a function of time for the seismograms are obtained polarization analysis of strong motion data from the 1971 san fernando earthquake aids in the discrimination between wave types which is important for the understanding of the complicated earthquake induced shaking observed in basins most arrivals are incident on the receivers in the direction of the back azimuth to the epicenter which suggests that despite the complicated motions two dimensional finite difference methods are sufficient to understand the effect on seismic waves of the los angeles and san fernando basins vidale and helmberger 1986b

rupture process of the 2004 sumatra andaman earthquake the 26 december 2004 sumatra andaman earthquake initiated slowly with small slip and a slow rupture speed for the first 40 to 60 seconds then the rupture expanded at a speed of about 2 5 kilometers per second toward the north northwest extending 1200 to 1300 kilometers along the andaman trough peak displacements reached 15 meters along a 600 kilometer segment of the plate boundary offshore of northwestern sumatra and the southern nicobar islands slip was less in the northern 400 to 500 kilometers of the aftershock zone and at least some slip in that region may have occurred on a time scale beyond the seismic band

capillary moisture flow and the origin of cavernous weathering in dolerites of bull pass antarctica flow of water through joint blocks that exhibit cavernous weathering was modeled for the ferrar dolerite in bull pass antarctica a peculiar moisture regime allows an analytical solution under steady state saturated conditions the presence of surface coatings on the top surface of the blocks causes the matric potential gradient within the blocks to be horizontal near the surface deflecting the flow of migrating water toward the uncoated sides during evaporation because weathering of the rock interior is proportional to the moisture flux the extent of rock weathering will be similar along similar contours of the matric potential gradient as granular disintegration occurs it will also follow the lines of equipotennal and cavernous weathering will result if those lines are concave

the interpretation of the b and the b0 values and its implications on the regional deformation of the crust summary after reviewing the model and the interpretation of the negative power laws which represent the statistical distributions of the linear dimension of faults l and of the stress drops p of the earthquakes it is seen that the coefficient of the law log m0 m increases with m for smaller m it is verified that the parameters l and p of california earthquakes are independent and also it is suggested that one may consider a fractal dimension of earthquakes associated with p it is shown how these statistical distributions may allow distribution of slips in the seismic regions to be inferred where all the slips occur approximately in the same horizontal direction from the density distribution of the length of the faults it is found that in california 50 per cent of the regional displacement is due to the faults with linear lengths larger than 63 per cent of the maximum linear length of the faults similar results are obtained using the seismic moment m0 or the magnitude m instead of l in these cases however the density distribution of p is also needed for the exact computation of the displacement assuming that in california the regional displacement has been 5 cm yr 1 as measured with ground observations and space techniques it is tentatively estimated that the displacement due to earthquakes with m0 larger than 1027 1 may be as large as 4 2 cm yr 1 and that a cumulative displacement of at least 170 cm due to earthquakes with m0 larger than 1027 1 may have not been released since the great 1906 san francisco earthquake it is finally discussed how the variation in the density distribution of stress drops may be a precursor to earthquakes

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

teleseismic inversion for rupture process of the 27 february 2010 chile mw 8 8 earthquake the 27 february 2010 chile m w 8 8 earthquake is the fifth largest earthquake to strike during the age of seismological instrumentation the faulting geometry slip distribution seismic moment and moment rate function are estimated from broadband teleseismic p sh and rayleigh wave signals we explore some of the trade offs in the rupture process estimation due to model parameterizations limited teleseismic sampling of seismic phase velocities and uncertainty in fault geometry the average slip over the 81 500 km 2 rupture area is about 5 m with slip concentrations down dip up dip and southwest and up dip and north of the hypocenter relatively little slip occurred up dip offshore of the hypocenter the average rupture velocity is 2 0 2 5 km s

evidence of bias in estimations of earthquake size magnitudes of earthquakes determined using traditional methods show systematic deviations dependent on tectonic setting from accurate estimates of earthquake size magnitudes are overestimated for most of the continental earthquakes underestimated for mid oceanic ridges and differences of varying sign are obtained for subduction zones this is important in evaluating the seismic risk or consideration of effects such as the seismic versus aseismic strain release as seismic moments determined from magnitudes can be wrong by as much as a factor of four

single station location of seismic events a review and a plea for more research abstract traveltime based location methods are ineffective for locating regional seismic events which are recorded by few stations however the comprehensive test ban treaty ctbt makes it imperative that we monitor sparsely observed events this paper reviews the current status of single station location ssl methods the location of seismic events using records from one three component broadband digital station we argue here that ssl methods may ultimately provide the most effective and economical means for monitoring small magnitude m 3 seismic events over most of the earth potentially station event distance and focal depth may be determined accurately by utilizing broadband three component data and matching observed and synthetic waveforms station event azimuth is determinable from the polarization of the p wave arrival and p coda however more research is required before ssl methods become a practical alternative to traveltime based methods currently the most significant problem is that regional seismograms are strongly dependent on regional crustal structure thus future research efforts should focus both on determining appropriate crustal models in specific regions and also on improved methods for dealing with regional variations in crustal structure a second important problem concerns location errors with ssl they may involve 180 errors in station event azimuth or other highly non gaussian blunders

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

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

the 1997 umbria marche central italy earthquake sequence insights on the mainshock ruptures from near source strong motion records a small size foreshock and the two mainshocks of the umbria marche earthquake sequence which occurred on september 26 1997 have been recorded by two digital 3c accelerometers located at near source distances the close epicentral distance and azimuthal location relative to the fault orientation and geometry make these records relevant to look at the detail of the rupture kinematics s wave polarizations apparent source time duration and waveforms from strong motion records are used to constrain the location of the fracture origin point the fault geometry the final slip distribution size and mechanism of the events the final model shows that the seismic ruptures occurred along two adjacent sub parallel low angle dipping normal faults the relative timing location and geometry of the mainshock faults suggest the presence of a transfer zone barrier which has probably controlled the amplitude increase of local stress released by the first rupture at its nw edge which triggered about 9 hours later the second rupture

rupture details of the 28 march 2005 sumatra mw 8 6 earthquake imaged with teleseismic p waves 1 we image the rupture of the 28 march 2005 sumatra mw 8 6 earthquake by back projecting teleseismic p waves recorded by the global seismic network and the japanese hi net to their source the back projected energy suggests that the rupture started slowly had a total duration of about 120 s and propagated at 2 9 to 3 3 km s from the hypocenter in two different directions first toward the north for 100 km and then after a 40 s delay toward the southeast for 200 km our images are consistent with a rupture area of 40 000 km2 the locations of the first day of aftershocks and the harvard cmt mw of 8 6 which implies an average slip of 6 m the earthquake is similar in its location size and geometry to a mw 8 5 event in 1861 our estimated average slip is consistent with a partially coupled subduction interface gps forearc velocities and the 59 mm yr convergence rate if the 2005 earthquake released elastic strain that accumulated over many hundreds of years rather than just since the last 1861 event

field experiments on physical weathering and wind erosion in an antarctic cold desert field experiments were carried out over a five year period with the aim of understanding contemporary weathering and erosional environments in the sor rondane mountains an antarctic cold desert region these include observations of 1 scaling from rockwalls 2 disintegration of tuff blocks with or without saline solutions and 3 abrasion of artificial walls by wind monitoring was also made of rock surface temperature and wind speed despite frequent temperature oscillations across 0 c rock scaling due to frost action was generally very slow because of low moisture content in the rockwalls exposure to the cold dry climate led to the rapid disintegration of porous tuff blocks including soluble salts like halite and thenardite this indicates that rates of weathering are increased greatly with the accumulation of such salts in the bedrock although gypsum did not cause any visible damage over four years its widespread occurrence in heavily damaged rocks demonstrates that increasing gypsum contents may also intensify rock breakdown the snow laden katabatic wind resulted in rapid wearing of the windward face of an asbestos board with the peak erosion at 30 40 cm above the ground nonetheless the landforms expected from the unidirectional wind characteristics are by no means common features because of lack of abrasive materials such as snow and sand particles these experiments suggest that frost weathering and wind erosion are only locally effective where plenty of moisture or an abrasive material is available whilst salt weathering and removal of the waste by wind play a major role in constructing erosional landforms over the mountains

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

beno gutenberg contribution to seismic hazard assessment and recent progress in the european mediterranean region abstract the fundamental work of beno gutenberg has inspired and guided an appreciable part of research in modern seismology both from the experimental and the theoretical point of view among the several topics of seismology that have benefited from the fundamental contribution of gutenberg we consider particularly relevant the description of the asthenospheric low velocity channel the definition of the surface waves magnitude and the gutenberg richter law since they are pivotal tools for seismic hazard assessment the quite revolutionary model for the lithosphere asthenosphere system in the european area predicts the existence of almost aseismic lithospheric roots these roots are located in correspondence of most of the orogenic belts and interrupt the asthenosphere low velocity channel that has been identified by beno gutenberg in 1948 the model of the european upper mantle proposed for the first time in 1979 and subsequently refined has stimulated a considerable amount of research which has nicely confirmed the major innovative features of the early model at present the subduction of the lithosphere at continent continent collisions supported not only by seismological data is a widely accepted concept within the community of earth scientists even if it contradicts one of the basic dogmas of the original formulation of plate tectonics the proposed model for the alpine apennines area supplies a new and unifying framework for the interpretation of the quaternary magmatism at present generally accepted by petrologists and geochemists the theoretical basis for the gutenberg s surface wave magnitude calibration function has been supplied by the use of complete synthetic seismograms and thus it has been possible to formulate the theoretical m s depth correction the introduction of the depth correction for m s enables the computation of surface wave magnitude for all earthquakes regardless of their focal depth this is especially important for the quantification of subcrustal historical earthquakes for which the seismic moment may be difficult to estimate from recordings of early mechanical seismographs the new m s calibrating function yield both distance and depth independent magnitude estimates the analysis of the global seismicity using the seismotectonic regionalization in subduction zones mid oceanic ridge zones island arcs shows that a single gutenberg richter gr relation is not universally applicable and that a multiscale seismicity model can reconcile two apparently conflicting paradigms the self organized criticality mechanism and the characteristic earthquake concept the multiscale representation has been applied to italy where the zones at the space scale of 400 500 km quite well reproduce the shapes of the regions used to apply the globally tested cn intermediate term earthquake prediction algorithm

imaging the 2016 mw 7 8 kaikoura new zealand earthquake with teleseismic p waves a cascading rupture across multiple faults the 13 november 2016 mw 7 8 kaikoura new zealand earthquake was investigated using teleseismic p waves backprojection of high frequency p waves from two regional arrays shows unilateral rupture of at least two southwest northeast striking faults with an average rupture speed of 1 4 1 6 km s and total duration of 100 s guided by these backprojection results 33 globally distributed low frequency p waves were inverted for a finite fault model ffm of slip the ffm showed evidence of several subevents however it lacked significant moment release near the epicenter where a large burst of high frequency energy was observed a local strong motion network recorded strong shaking near the epicenter hence for this earthquake the distribution of backprojection energy is superior to the ffm as a guide of strong shaking for future large earthquakes that occur in regions without strong motion networks initial shaking estimates could benefit from backprojection constraints

source spectra of great earthquakes teleseismic constraints on rupture process and strong motion short period body waves recorded at teleseismic distances from great earthquakes provide information about source rupture processes and strong motions first we examine mostly wwssn records of 19 earthquakes of moment magnitude m w of 6 5 to 9 5 four parameters are measured from the short period p wave train the maximum amplitude the period at maximum amplitude the time between the first arrival and when the maximum amplitude is attained and coda length an extension m b of the teleseismic magnitude m b is defined using the maximum amplitude of the entire short period p wave rather than the amplitude achieved in the first few p wave cycles a least squares fit to the data yields the following relationship between m b and m w m b 0 53 m w 2 70 for m w 6 5 to 9 5 the time from the first arrival until the maximum amplitude is achieved and the coda length are roughly proportional to m w but are further interpreted by a simple asperity model of the rupture process these data support that short period waves are on average generated preferentially in the same regions of the fault plane as long period waves with periods of 10 to 50 sec we analyze the spectra of short and intermediate period teleseismic gdsn records for seven earthquakes with m w s of 6 4 to 7 8 and hand digitized short period wwssn records of the 1971 san fernando earthquake significant differences exist between the spectra of different events due partly to variations in tectonic setting or seismic coupling using the digital data we also investigate the relationship between time domain amplitude and spectral amplitude for short period p waves from our empirical relation between spectral amplitude and time domain amplitude we estimate the spectral amplitudes implied by the m b data we compare our results to the 2 and gusev spectral models neither model can completely represent the data nevertheless we consider the 2 model a useful reference model for comparing different events the average source spectrum of six large events with m w 7 4 to 7 8 does not have the spectral structure suggested by gusev an application to strong motion modeling is presented in which a 1971 san fernando teleseismic short period record is summed up to simulate teleseismic records produced by five great earthquakes the summation procedure matches the moment of the event to be simulated and includes rupture propagation fault plane roughness and randomness the m b data provide an important constraint on the summation procedures thus constrained this summation procedure can be more confidently used with near field strong motion records as green s functions to predict strong motions from great earthquakes

coseismic radiation of the 2008 m w 7 9 wenchuan earthquake and its relationship to fault complexities the long rupture length and complex fault geometries of the 2008 mw 7 9 wenchuan earthquake offer a great opportunity to investigate the relationship between coseismic radiation and fault complexities in this study we first improved the compressive sensing back projection method cs bp with window time adjustment and parallel computation to enhance its spatial temporal resolution and computational efficiency then we applied the cs bp to invert for the coseismic radiation of the wenchuan earthquake in multiple frequency bands our results show that the coseismic radiation of the wenchuan earthquake is frequency dependent and strongly associated with the fault geometries low frequency radiation sources are concentrated on smooth fault segments with large coseismic slip while higher frequency sources are mainly related to fault complexities e g xiaoyudong fault gaochuan fault bend leigu fault bend and nanba fault step over an acceleration of rupture speed from 1 5 to 3 0 km s is also observed the near xiaoyudong fault where strong high frequency energies were radiated finally we discuss the role of rupture speed in mediating the relationship between coseismic radiation and fault complexities on one hand sudden changes of rupture speeds contribute to strong high frequency radiation on the other hand fault complexities can also strongly affect the rupture speed a sudden break of a large asperity is able to propel the acceleration while rupture front may decelerate when it jumps across geometric barriers

tracking the rupture of the mw 9 3 sumatra earthquake over 1 150 km at teleseismic distance on 26 december 2004 a moment magnitude mw 9 3 earthquake occurred along northern sumatra the nicobar and andaman islands resulting in a devastating tsunami in the indian ocean region the rapid and accurate estimation of the rupture length and direction of such tsunami generating earthquakes is crucial for constraining both tsunami wave height models as well as the seismic moment of the events compressional seismic waves generated at the hypocentre of the sumatra earthquake arrived after about 12 min at the broadband seismic stations of the german regional seismic network grsn located approximately 9 000 km from the event here we present a modification of a standard array seismological approach and show that it is possible to track the propagating rupture front of the sumatra earthquake over a total rupture length of 1 150 km we estimate the average rupture speed to be 2 3 2 7 km s 1 and the total duration of rupture to be at least 430 s and probably between 480 and 500 s

rupture imaging of the mw 7 9 12 may 2008 wenchuan earthquake from back projection of teleseismic p waves 1 the mw 7 9 wenchuan earthquake of 12 may 2008 was the most destructive chinese earthquake since the 1976 tangshan event tens of thousands of people were killed hundreds of thousands were injured and millions were left homeless here we infer the detailed rupture process of the wenchuan earthquake by back projecting teleseismic p energy from several arrays of seismometers this technique has only recently become feasible and is potentially faster than traditional finite fault inversion of teleseismic body waves therefore it may reduce the notification time to emergency response agencies using the iris dmc we collected 255 vertical component broadband p waves at 30 95 from the epicenter we found that at periods of 5 s and greater nearly all of these p waves were coherent enough to be used in a global array we applied a simple down sampling heuristic to define a global subarray of 70 stations that reduced the asymmetry and sidelobes of the array response function arf we also considered three regional subarrays of seismometers in alaska australia and europe that had apertures less than 30 and p waves that were coherent to periods as short as 1 s individual arfs for these subarrays were skewed toward the subarrays however the linear sum of the regional subarray beams at 1 s produced a symmetric arf similar to that of the groomed global subarray at 5 s for both configurations we obtained the same rupture direction rupture length and rupture time we found that the wenchuan earthquake had three distinct pulses of high beam power at 0 23 and 57 s after the origin time with the pulse at 23 s being highest and that it ruptured unilaterally to the northeast for about 300 km and 110 s with an average speed of 2 8 km s it is possible that similar results can be determined for future large dip slip earthquakes within 20 30 min of the origin time using relatively sparse global networks of seismometers such as those the usgs uses to locate earthquakes in near real time

decay and preservation of stone in modern environments stone objects decay in all environments but the modes of decay vary from one region to another in the modern industrial countries acid deposition has accelerated the decay of stone many objects that survived centuries of weathering without serious damage have in the present century decomposed beyond recognition the black crusts seen on stone structures mostly contain gypsum formed by so2 reactions with calcareous minerals these crusts exfoliate destroying the sculptural form because of the absence of proven technology to treat and restore these objects the caryatids at the acropolis had to be moved indoors to save them from further disfiguration

seismicity of oceanic and continental rifts a geodynamic approach abstract two major kinds of divergent structures oceanic and intracontinental rifts were compared in principal seismic and tectonic characteristics first the role of main components of the mid oceanic ridges mor was estimated for the whole earth we considered two levels of the mor segmentation the first order structures are the segments of mor between triple junctions and the second order structures are a transform faults and rift parts of mor the seismic catalogues neic and cmt were used to assess the seismic moment release the seismic moment release was calculated another way using the global plate tectonic model nuvel 1 and brune s formulae comparison of these two values shows that the seismic coupling coefficient varies from 1 to 10 for most of mor and is always higher for transform faults most of the deformation therefore is aseismic slip most seismicity of mor is confined to transform faults the energy contribution of transform faults is one to two orders magnitude higher than that of the rift and increases with the spreading rate there is a strong correlation between the seismic moment release of strike slip faults and their total lengths the correlation shows that the seismic moment release depends on the total transform area and confirms the simple thermal model of transform seismicity that was given by burr and solomon the seismic moment release and the spreading rate have opposite patterns for the rifts there is an inverse correlation between the seismic moment of normal faults and spreading velocity while it seems for transforms that these parameters are independent finally these results show that the seismicity of transforms and rifts depends first of all on the thermal structure of oceanic lithosphere in the case of continental rifts one can distinguish in the degree of seismic activity depending on the stage of rifting hence analysis of the continental seismicity requires the consideration of factors of a geological evolution that play practically no role in the case of oceanic lithosphere the comparison of geological and seismic data for the east african region has allowed us to outline the regular changes of the seismic regime during development of the rift zone from the stage of incipient rift to mature oceanic rift in the evolutionary series intracontinental incipient rift intracontinental mature rift intercontinental rift oceanic slow spreading rift oceanic fast spreading rift there is a gradual decrease of the role of rifts sensu stricto as tension structures and increase of the role of strike slip faults epicenters concentrate along major faults as well the level of seismic energy becomes lower although the rate of deformation increases

along dip seismic radiation segmentation during the 2007 mw 8 0 pisco peru earthquake 1 the short period 0 5 2 s seismic radiation properties of the august 15 23 40 57 utc 2007 mw 8 0 pisco peru earthquake are imaged by back projecting p waves recorded at 374 elements of usarray deployed in western north america at distances of 54 74 from the source region the coherent short period seismic energy release has two main intervals similar to moment rate functions determined by inversion of longer period teleseismic body waves however the spatial locations of the coherent bursts of short period energyrelease are located northanddown dip of the region of major slip the contrast between short and long period seismic radiation properties of the pisco earthquake is more subtle than for the 2011 mw 9 0 tohoku earthquake but provides further support for the idea of depth dependent changes in sliding behavior during megathrust ruptures citation sufri o k d koper and t lay 2012 along dip seismic radiation segmentation during the 2007 mw 8 0 pisco peru earthquake geophys res lett 39 l08311 doi 10 1029 2012gl051316

rapid estimation of rupture extent for large earthquakes application to the 2004 m9 sumatra andaman mega thrust 1 rapid estimation of the rupture extent of large earthquakes is critical for tsunami warning and emergency response the hypocenter of a distant earthquake is determined from the first seismic p waves within about 15 minutes after the event however methods for determining the size and rupture extent of very large earthquakes rely on long period recordings and aftershock locations which are not available until several hours or more after the event here we introduce a method for rapid estimation of the rupture termination location for large earthquakes based on short period p wave recordings available about 30 minutes after an event the hypocenter and the rupture termination location provide estimates of the extent of rupture and the event size application to the 2004 m9 sumatra andaman earthquake gives a rupture termination location near the andaman islands about 1100 km north of the hypocenter and a rupture duration of about 8 minutes

global creepex distribution and its relation to earthquake source geometry and tectonic origin summary the ms mb ratio conventionally used for the discrimination of earthquakes and underground nuclear explosions has been studied for a pure earthquake catalogue in an attempt to classify earthquakes into two categories one related to extremely lowfrequency events of creep and the other to relatively high frequency explosions ms and mb measured at 20 s and 1 s respectively are considered as estimates of source spectra at two separate points thus allowing one to compare large samples of earthquakes from the spectral point of view creepex or the deviation of ms mfc points from the orthogonal regression of ms on mb is by definition a parameter independent of the size of seismic events it has been estimated from neic magnitudes and is studied in relation to parameters of central moment tensor solutions of the harvard group for this purpose the parameters of central moment tensors have been factorized to make classes of equivalence of events with the same dip and rake and arbitrary strike and size the resulting triangle representation of source mechanisms has been used to correct the global distribution of creepex for the type of source mechanism dip slip events have consistently lower creepex than strike slip ones however the global distribution of creepex either corrected or uncorrected for source mechanism has a clear tectonic pattern negative values in most of the subduction zones and positive ones in mid ocean ridges the dependence of creepex on focal depth is negligible according to empirical data for events shallower than 40 km limitation of the sample by considering only events in this depth range does not diminish considerably the amount of data and does not change the tectonic pattern of the creepex