inversion of the rupture process and high frequency radiation of the 2017 jiuzhaigou earthquake northeastern tibetan plateau abstract we studied the low and high frequency source processes of the 2017 jiuzhaigou earthquake and focused on when and where the high frequency 2 0 10 0 hz seismic energy was radiated in relation to the low frequency 0 02 0 5 hz seismic energy the low frequency source processes were jointly inverted using teleseismic p and sh broadband waves combined with near field strong motion data a three dimensional model considering real topography was used to compute the near field green s function the high frequency wave radiation was inversed using the envelope of acceleration seismograms of near field records and the empirical green s function by the differential evolution algorithm the results showed the 2017 jiuzhaigou earthquake was a typical strike slip earthquake with a seismic moment of about 6 9 1018 n m and maximum slip of about 1 5 m during the 2 s following the initial rupture the earthquake radiated large high frequency waves but small low frequency waves then the rupture broke the high stress drop area in the up dip direction of the hypocenter generating an obvious asperity located just above the hypocenter about 60 of the seismic moment of the earthquake was released during about 2 6 s after initiation of the rupture the high frequency radiation areas were mostly located on the lower periphery of the asperity in accordance with the complementary relationship between the distribution of high frequency waves and zones of large slip which might be attributable to both the initiation of the rupture and the breaking of the high stress drop area parts of the high frequency radiation areas overlapped the lower part of the asperity where the high frequency radiation occurred about 2 s earlier than the low frequency radiation the stress drop of the 2017 jiuzhaigou earthquake was considerably lower than average for global intraplate earthquakes but similar to that of the 2013 lushan earthquake

anisotropic upper crust above the aftershock zone of the 2013 ms 7 0 lushan earthquake from the shear wave splitting analysis we have conducted a systematic shear wave splitting analysis using 1000 selected aftershocks with m 2 from the 2013 ms 7 0 lushan earthquake along the longmenshan fault system in southwest china polarization directions of fast shear waves show a bimodal distribution with one dominant direction approximately parallel to the fault strike and the other close to the regional maximum horizontal compressive stress direction this indicates that in this area mechanisms causing crustal seismic anisotropy are both stress induced and fault zone structure controlled delay times between fast and slow shear waves do not show a clear trend of increase for deeper events suggesting the anisotropic zone is mostly above the aftershocks which are generally located below 8 km we further applied a shear wave splitting tomography method to measured delay times to characterize the spatial distribution of seismic anisotropy the three dimensional anisotropic percentage model shows strong anisotropy above 8 km but low anisotropy below it the mainshock slip zone and its aftershocks are associated with very low or negligible anisotropy and high velocity indicating that the zones with high anisotropy and low velocity above 8 km are mechanically weak and it is difficult for stress to accumulate there the main and back reverse fault zones are associated with high anisotropic anomalies above 8 km likely caused by shear fabric or microfractures aligned parallel to the fault zone

3d geometry of range front blind ramp and its effects on structural segmentation of the southern longmen shan front eastern tibet abstract a 3d fault morphology model has been constructed from seismic profiles covering the piedmont of the southern longmen shan lms eastern margin of the tibetan plateau it reveals a spatial correlation between an 3 5 km high geometrical bump on the range front blind ramp rfbr and the gap between the 2008 m w 7 9 wenchuan and 2013 m w 6 6 lushan earthquakes sandbox modeling is then used to probe the effects of the geometrical irregularity of the rfbr on fault behaviors and the lms range front deformation sand wedges are designed to thrust over artificial blind ramps analogous to the thrusting of the lms orogenic wedge toward the sichuan basin through the rfbr the experiments reproduce the first order deformation features presented in the southern lms range front confirming that along strike geometrical variations of the rfbr have induced the segmentation of both fault motion and the range front deformation their results also suggest that the gap between the wenchuan and lushan earthquakes is located directly within the structural transition zone originating from the geometrical bump on the rfbr additionally there is a duplex structure occurring in the hanging wall of the geometrical bump which localizes significant shear strain with progressive shortening and represents a fracture zone corresponding to the observed geophysical anomaly low seismic velocity underneath the seismic gap it is likely that this fractured body protected the gap from the ruptures of the wenchuan and lushan earthquakes

rupture directivity from strong motion recordings of the 2013 lushan aftershocks abstract the observed directivity effects of ground motion have extensive implications for both earthquake source physics and earthquake hazard analyses on active fault zones in general it is still difficult to determine the rupture directivity in detail for smaller earthquakes because of limited azimuthal coverage four lushan aftershocks that occurred on 20 and 21 april 2013 events i ii iii and iv were well recorded by the national strong motion observation network system of china an interesting phenomenon was clearly observed the distributions of the triggered stations for the four aftershocks which had adjacent hypocenters and similar magnitudes differed significantly from each other the analyses of ground motion parameters including the peak ground motion parameters response spectra and durations indicate that the directivity of the ground motion was significant for events ii and iii the fourier spectral ratio method was used to imprint the rupture directivity we calculated the rupture direction and rupture velocity by inverting the peak parameters random realizations in many times were utilized to consider the uncertainty in the results of the inversion the results indicate that the four events shared the similar northeast southwest trending fault plane and had similar rupture velocities of approximately 2 1km s event i was more likely to be a perfectly symmetric bilateral rupture though there was large uncertainty in the results of the inversion the rupture for events ii and iii propagated predominantly toward the southwest however event iv was observed to have an approximately symmetric bilateral propagation slightly inclining to the northeast we also confirmed the period dependent directivity effect by inverting the response spectra at different periods

rupture history of the 2013 mw 6 6 lushan earthquake constrained with local strong motion and teleseismic body and surface waves 1 the rupture history of the 20 april 2013 mw 6 6 lushan china earthquake is constrained by inverting waveforms of local strong motion teleseismic broadband body waves and long period surface waves this earthquake ruptured a blind thrust fault oriented n210 e along the longmenshan fault zone and dipping 40 to the nw the inverted slip distribution is heterogeneous dominated by a slip patch with a roughly right triangular shape which spans a depth range of 5 20 km and accounts for two thirds of the total seismic moment 8 9 1018 n m the rupture initiated roughly at the middle of the triangle s hypotenuse and during the first 4 s propagated mainly in along strike and downdip directions toward a peak slip of 1 2 m despite a large number of fatalities and economic loss the estimated static and apparent stress drops of the lushan earthquake are 1 5 mpa and 0 35 mpa considerably low with respect to other similar intraplate earthquakes

observational constraints on the fracture energy of subduction zone earthquakes we relate seismologically observable parameters such as radiated energy seismic moment rupture area and rupture speed to the dynamics of faulting to achieve this objective we computed the radiated energy for 23 subduction zone earthquakes recorded between 1992 and 2001 most of these earthquakes have a magnitude m w 7 5 but we also included some smaller m w 6 7 well studied subduction zone earthquakes and six crustal earthquakes we compiled static stress drop estimates for these 29 earthquakes from literature and used a slip weakening model to determine the radiation efficiency of these earthquakes we also determined the rupture speed of these earthquakes from literature from fracture mechanics fracture energy and hence radiation efficiency can be related to the rupture speed the radiation efficiencies estimated from the partitioning of energy as given by the slip weakening model are consistent with the rupture speed estimated for these earthquakes most earthquakes have radiation efficiencies between 0 25 and 1 and are hence efficient in generating seismic waves but tsunami earthquakes and two deep earthquakes the 1994 bolivia and the 1999 russia china border earthquakes have very small radiation efficiencies 0 25 and hence dissipate a large amount of energy during faulting we suggest that differences in the radiation efficiencies of different types of earthquakes could be due to fundamental differences in their rupture mechanics in deep events the energy is probably dissipated in thermal processes in the fault zone while it is possible that the morphology of the trench causes large energy dissipation during the rupture process of tsunami earthquakes

a new strategy of finite fault inversion using multiscale waveforms and its application to the 2015 gorkha nepal earthquakefinite fault inversion using multiscale waveforms and its application to the 2015 gorkha earthquake

radiosonde observations of gravity waves in the lower stratosphere over davis antarctica radiosonde observations made from davis station antarctica 68 6 s 78 0 e between 2001 and 2012 are used to compile a climatology of lower stratosphere inertial gravity wave characteristics wavelet analysis extracts single wave packets from the wind and temperature perturbations wavelet parameters combined with linear gravity wave theory allow for the derivation of a wide range of wave characteristics observational filtering associated with this analysis preferentially selects inertial gravity waves with vertical wavelengths less than 2 3 km the vertical propagation statistics show strong temporal and height variations the waves propagate close to the horizontal and are strongly advected by the background wind in the wintertime notably around half of the waves observed in the stratosphere above davis between early may and mid october propagate downward this feature is distributed over the observed stratospheric height range based on the similarity between the upward and downward propagating waves and on the vertical structure of the nonlinear balance residual in the polar winter stratosphere it is concluded that a source due to imbalanced flow that is distributed across the winter lower stratosphere best explains the observations calculations of kinetic and potential energies and momentum fluxes highlight the potential for variations in results due to different analysis techniques

bedrock temperature as a potential method for monitoring change in crustal stress theory in situ measurement and a case history abstract experimental studies have confirmed that temperature is notably affected by rock deformation therefore change in crustal stress should be indicated by measurable changes in bedrock temperature in this work we investigated the possibility that the bedrock temperature might be used to explore the state of crustal stress in situ measurement of bedrock temperature at three stations from 2011 to 2013 was used as the basis for the theoretical analysis of this approach we began with theoretical analyses of temperature response to change in crustal stress and of the effect of heat conduction this allowed distinction between temperature changes produced by crustal stress stress temperature from temperature changes caused by conduction from the land surface conduction temperature stress temperature has two properties synchronous response and a high frequency feature that allow it to be distinguished from conduction temperature the in situ measurements confirmed that apparently synchronous changes in the stress temperature of the bedrock occur and that there exist obvious short term components of the in situ bedrock temperature which agrees with theory on 20 april 2013 an earthquake occurred 95 km away from the stations fortuitously providing a case study by which to verify our method for obtaining the state of crustal stress using temperature the results indicated that the level of local or regional seismic activity representing the level of stress adjustment largely accords with the stress temperature this means that the bedrock temperature is a tool that might be applied to understand the state of stress during seismogenic tectonics therefore it is possible to record changes in the state of crustal stress in a typical tectonic position by long term observation of bedrock temperature hereby the measurement of bedrock temperature has become a new tool for gaining insight into changes in the status of shallow crustal stress

the energy release in earthquakes energy calculations are generally made through an empirical application of the familiar gutenberg richter energy magnitude relationships the precise physical significance of these relationships is somewhat uncertain we make use here of the recent improvements in knowledge about the earthquake source to place energy measurements on a sounder physical basis for a simple trapezoidal far field displacement source time function with a ratio x of rise time to total duration t 0 the seismic energy e is proportional to 1 x 1 x 2 m 0 2 t 0 3 where m 0 is seismic moment as long as x is greater than 0 1 or so the effect of rise time is not important the dynamic energies thus calculated for shallow events are in reasonable agreement with the estimate e 5 10 5 m 0 based on elastostatic considerations deep events despite their possibly different seismological character yield dynamic energies which are compatible with a static prediction similar to that for shallow events studies of strong motion velocity traces obtained near the sources of the 1971 san fernando 1966 parkfield and 1979 imperial valley earthquakes suggest that even in the distance range of 1 to 5 km most of the radiated energy is below 1 to 2 hz in frequency far field energy determinations using long period wwssn instruments are probably not in gross error despite their band limited nature the strong motion record for the intermediate depth bucharest earthquake of 1977 also suggests little teleseismic energy outside the pass band of a long period wwssn instrument

provenance of the murihiku terrane new zealand evidence from the jurassic conglomerates and sandstones in southland abstract sedimentary petrological geochemical and geochronological studies were carried out to reveal the provenance of the murihiku terrane southland new zealand the murihiku terrane comprises late permian to early cretaceous volcaniclastic sediments that were deposited at the fore arc or back arc basin of the eastern gondwana margin the strata in the waikawa district southland are middle or early late jurassic and comprise sandstones interbedded with conglomerates and mudstones the sediments can be petrologically classified into two groups one dominated by intermediate mafic volcanic detritus type a and the other more quartz bearing 15 20 in qfl dominated by felsic volcanic and plutonic detritus type b the chemistry of detrital clinopyroxene in type a sediments is compatible with their derivation from island arc volcanics whole rock major and trace element analyses suggest that granitoid and gabbroid clasts associated with type b sediments are also of volcanic arc origin geochemical characteristics of the plutonic clasts can be compared closely with the median batholith median tectonic zone whole rock k ar ages of the clasts 156 8 and 177 9 ma for gabbroid clasts and 156 8 and 212 11 ma for alkali feldspar granite clasts are consistent with the median batholith magma cooling small quantities of grandite and pyrope bearing garnet grains in type b sediments might be derived from metamorphosed intermediate mafic volcanic rocks to amphibolite facies granitic cataclasite and hornfels are also compatible with derivation from the median batholith that was accreted to the brook street terrane

upper crustal folding of the 2013 lushan earthquake area in southern longmen shan china insights from late quaternary fluvial terraces abstract a thrust earthquake of mw6 6 occurred on april 20 2013 near lushan county in the southern longmen shan at the east margin of tibetan plateau this earthquake did not produce a surface rupture zone and the late quaternary activities of the outcropped faults in the earthquake area were not obvious which increased the difficulty of studying the seismogenic structure this article took as the research target the middle reach of the qingyijiang river which traverses the earthquake area by surveying correlating the fluvial terraces studied quantitatively the late quaternary tectonic deformation and further discussed the seismotectonics the longitudinal profile of river terraces along the middle reach of the qingyijiang river reveals that the principal deformation style in the late quaternary was anticline type folding the folding is a typical fault bend fold involving the basement which is controlled by the newest flat ramp flat structure possibly formed in the pliocene or the early pleistocene across the fold the average shortening rate in the late quaternary is 0 6 1 3 mm yr about one third of the crustal shortening rate by gps data across the longmen shan fold and thrust belt and its foreland the foreland thin skinned structure developed in the cretaceous to paleogene strata in the earthquake area was passively involved into the fault bend folding in the late quaternary which commend the thrust ramp developing in a piggyback style the newest ramp appears to have controlled the rupture and the surface deformation of the 2013 lushan earthquake in the process of thrust sheet sliding toward foreland along the flat ramp flat detachment the ramp acts as a locking structure where earthquake ruptures the coseismic surface deformation seems to be passive folding of the thrust sheet climbing the ramp

stress shadow on the southwest portion of the longmen shan fault impacted the 2008 wenchuan earthquake rupture the 2008 wenchuan earthquake mw7 9 unilaterally ruptured the longmen shan fault lmsf along eastern tibet the earthquake rupture propagated about 270km northeastward whereas it propagated only about 20km southwestward along the strike of the fault although a significant attention has been paid to the question of predominantly unilateral propagation the primary reasons for this type of propagation remain unclear in this research we examined the change of coulomb stress along the lmsf caused by the historical earthquakes near and on the lmsf from 1725 to 2008 we found that the 14 preceding large earthquakes m6 5 on the xianshui he fault cast a stress shadow on the sw segment of the lmsf which was not activated by the 2008 wenchuan earthquake rupture the 1970 dayi earthquake on the sw segment of the lmsf contributed significantly to this stress shadow compared with the segment of the 2008 wenchuan earthquake rupture this stress shadow caused strong stress contrasts of 214 22 and 80kpa in the seismic gap of the very sw segment of the lmsf the rupture zone of the 2013 lushan earthquake and the seismic gap between the 2008 wenchuan and 2013 lushan earthquake ruptures respectively stress contrasts in these values were consistent with tectonic loading over 165 17 and 62years respectively by integrating an interseismic stress loading rate of 1 3kpa a we proposed that this stress shadow might have created a barrier at the sw segment preventing the earthquake rupture propagating southwestward

simulating ground motion directivity using stochastic empirical green s function method first strong motion recordings from an m w 4 4 earthquake with symmetrical rupture were regarded as empirical green s functions egfs to simulate ground motions produced by the 2013 m w 6 6 lushan mainshock using the two step stochastic egf method proposed by kohrs sansorny et al 2005 in this simulation the source of the lushan mainshock was set to consist only of an asperity in the vicinity of the hypocenter which was determined according to the statistical properties of asperity the good agreement between the simulated ground motions and the observed recordings at short periods 2 0 s validates this method furthermore recordings from an m w 4 5 earthquake with significant rupture directivity were used as egfs to simulate ground motions of the lushan mainshock the rupture directivity mainly exerts significant effects on the simulated short period ground motions which result in large discrepancies with the observed recordings simulated ground motions are much higher than the observed ones at directive stations but lower at antidirective stations more significant effects are observed at directive stations than antidirective stations using the azimuthal apparent corner frequency to consider the rupture directivity in the two step stochastic egf method the good reproductions of the observed recordings are obtained at short periods which indicates that the rupture directivity at short periods can be simulated well finally ground motions from a series of lushan like earthquakes assuming various rupture directivities were simulated by adjusting the apparent corner frequency the simulated ground motions show significant directivity effects the two step stochastic egf method provides an effective approach to predicting ground motions for future earthquakes because far fewer source parameters are required

what the exercise of the spice source inversion validation blindtest 1 did not tell you summary uncertainties of earthquake finite fault inversions based upon strong motion data are investigated using the source inversion validation blindtest 1 exercise of the spice seismic wave propagation and imaging in complex media a european network project motivated by previous counterintuitive results the distribution of slip and the shapes of asymmetric slip rate functions are simultaneously inverted by matching 10 or 33 broad band three component velocity waveforms within the period ranging from 0 02 to 2hz using a finite fault method that carries out the waveform inversion in the wavelet domain the effects of subfault size data noise and the number of stations have been explored our results suggest 1 although there are inevitable discrepancies between the inverted model and the target model because of ignoring the spatial slip variations within individual subfaults the fault slip and rise time distributions can be well constrained even with the data including large gaussian noise 2 it is crucial for source studies to develop new inversion schemes that can properly honour the frequency and time dependent energy distribution of seismic radiation and data noise for instance inversions using the variance reduction function of velocity waveforms as the objective function have low sensitivities to the total seismic moment and peak slip 3 although the relative value of the objective function is guided in the inversion the absolute value of the objective function cannot be used to evaluate the quality of an inverted model 4 because the source inversion is based on surface observations the spatiotemporal resolution of source inversion is affected not only by the data quality but also by the earthquake itself for vertical strike slip faults the along strike resolution is better than that along the downdip direction

upper ocean inertial currents forced by a strong storm part i data and comparisons with linear theory abstract a strong isolated october storm generated 0 35 0 7 m s 1 inertia frequency currents in the 40 m deep mixed layer of a 300 km 300 km region of the northeast pacific ocean the authors describe the evolution of these currents and the background flow in which they evolve for nearly a month following the storm instruments included ctd profilers 36 surface drifters an array of 7 moorings and air deployed velocity profilers the authors then test whether the theory of linear internal waves propagating in a homogeneous ocean can explain the observed evolution of the inertial frequency currents the subinertial frequency flow is weak with typical currents of 5 cm s 1 and steady over the period of interest the storm generates inertial frequency currents in and somewhat below the mixed layer with a horizontal scale much larger than the rossby radius of deformation reflecting the large scale and rapid translation speed of the storm this scale is too large for significant linear propagation of the

active thrusting of the longquan fault in the central sichuan basin china and the seismotectonic behavior in the longmen shan fold and thrust belt present day convergence within the longmen shan fold and thrust belt lsftb was released by the 2008 mw 7 9 wenchuan earthquake which ruptured multiple thrust ramps beneath the range front structures however it is still unclear whether fault slip propagated eastward into the foreland closer to densely populated areas around chengdu in this study we provide constraints on the 3 d subsurface structure fault activity and seismic hazards of the longquan fault located in the central sichuan basin 100 km east of the range front structures of the lsftb we develop a seismotectonic model and assess the activity of the longquan fault by a combination of methods including interpretation of seismic reflection profiles analysis of satellite images field mapping trench logging and radiocarbon dating our survey reveals that at least two surface rupturing events occurred on the longquan fault in the holocene our 3 d structural model and evidence for late holocene faulting events on the longquan fault reveals that upper crustal shortening in the sichuan basin is accommodated by a frontal thrust system that is linked to the recently active range front blind structures by a shallow detachment we suggest that dynamic weakening following fault activity at the longmen shan range front might unlock the up dip portion of this shallow detachment sending slip eastward into the foreland and to the surface along the longquan thrust ramps our results have important implications for seismic hazards assessment of active frontal thrusts linked by upper crustal detachments in active fold and thrust belts around the world

regional w phase source inversion for moderate to large earthquakes in china and neighboring areas earthquake source characterization has been significantly speeded up in the last decade with the development of rapid inversion techniques in seismology among these techniques the w phase source inversion method quickly provides point source parameters of large earthquakes using very long period seismic waves recorded at teleseismic distances although the w phase method was initially developed to work at global scale within 20 to 30 min after the origin time faster results can be obtained when seismological data are available at regional distances i e 12 in this study we assess the use and reliability of regional w phase source estimates in china and neighboring areas our implementation uses broadband records from the chinese network supplemented by global seismological stations installed in the region using this data set and minor modifications to the w phase algorithm we show that reliable solutions can be retrieved automatically within 4 to 7 min after the earthquake origin time moreover the method yields stable results down to mw 5 0 events which is well below the size of earthquakes that are rapidly characterized using w phase inversions at teleseismic distances

gravity waves appearing in a high resolution gcm simulation global characteristics of gravity waves in the lower stratosphere are examined using a gcm with high resolution in both the horizontal t106 corresponding to about 120 km and the vertical 600 m the bottom boundary condition of the model is that of an aquaplanet with perpetual february sea surface temperature the simulated gravity waves are in good agreement with mesosphere stratosphere troposphere mst radar observations at a middle latitude on the gravity wave structure and on the frequency spectra as a function of height the frequency spectra of simulated wind and temperature fluctuations are also examined as a function of latitude large values of spectral density are observed at frequencies higher than the inertial frequency f in a weak wind region around 20 km which is consistent with the characteristics of internal gravity waves an isolated peak is observed near f for horizontal wind spectra at latitudes higher than 108 while the energy is distributed in a wide range of frequency at lower latitudes where f approaches zero further analysis is performed of those fluctuations having periods shorter than 24 h and those having vertical wavelengths smaller than 5 km these are frequently analyzed as gravity waves using observation data the distribution of energy and momentum fluxes in the latitude height section is examined the result indicates that short period waves mostly propagate upward and poleward from the equatorial region the wave energy reaches about 508 lat at the 27 km altitude a negative positive maximum of vertical flux of meridional momentum y9w9 is seen above the subtropical jet in the northern southern hemisphere for small vertical scale gravity waves this is consistent with the preferred equatorward propagation of the wave indicated by a statistical analysis based on mst radar observations the ratio of potential to kinetic energy maximizes over the equator and decreases poleward the eliassen palm flux divergence associated with gravity waves is decelerative above the subtropical jet albeit small

triggered slip on a back reverse fault in the mw6 8 2013 lushan china earthquake revealed by joint inversion of local strong motion accelerograms and geodetic measurements abstract the 2013 mw6 8 lushan china earthquake occurred in the southwestern end of the longmenshan fault zone we jointly invert local strong motion data and geodetic measurements of coseismic surface deformation including gps and insar to obtain a robust model of the rupture process of the 2013 lushan earthquake our joint inversion best model involves the rupture of two opposing faults during the lushan earthquake a main fault and a secondary fault it is only when the secondary fault is included that both the gps and insar measurements are fit along with the near field strong motion over 75 of the computed moment was released in slip on the main fault segment a northwest dipping listric thrust fault with buried thrust and dextral strike slip at hypocenter depths and with only minor slip closer to the surface the secondary fault mainly involved oblique thrust slip or pure dextral strike slip at shallower depths and accounts for just under 24 of the moment released in the lushan earthquake coulomb stress changes of about 0 5 mpa on the secondary fault segment at the time coseismic slip initiated on that fault indicate that slip was likely triggered by the coseismic slip on the main blind thrust fault our coseismic slip model is consistent with a sub horizontal and east west to southeast northwest trending most compressive stress our inferred coseismic slip model is also consistent with previous gps derived models of strain accumulation on the longmenshan fault system

assessment of the accuracy of re analyses in the equatorial lower stratosphere the accuracy of horizontal winds and temperature in the equatorial lower stratosphere is evaluated in different re analyses european centre for medium range weather forecasts ecmwf operational analysis era interim and modern era retrospective analysis for research and applications using an independent data set collected at low latitudes during long duration balloon flights in early 2010 the three analyzed wind products are found significantly less accurate than in the extratropics with periods of 10m sdisagreement with the observations lasting several days to highlight the dynamical context in which the major disagreement events occur case studies are carried out the events are shown to be related to an improper representation of large scale equatorial kelvin and yanai wave packets with vertical wavelengths smaller than 5 km such events can induce large errors on trajectories computed with analyzed winds relatively to the actual balloon trajectory 4000 km separation after 5 days of calculation reasons for analyses inaccuracy are discussed the vertical resolution of the underlying model likely plays a role but the main factor responsible for deficiencies appears to be the lack of wind observations indeed errors in analyzed winds during the campaign have a strong longitudinal structure with root mean square errors twice as large over the indian ocean and western pacific poorly covered by radiosounding stations as over the maritime continent or south america for the ecmwf analysis this structure mirrors that of the analysis increments which have largest amplitudes over observed regions we argue that the reported events are more likely to happen during maximum shear phases of the quasi biennial oscillation

global variations of stress drop for moderate to large earthquakes 1 we investigate the global variation of earthquake stress drops using spectra of about 2000 events of mb 5 5 between 1990 and 2007 we use an iterative least squares method to isolate source displacement spectra from travel path and receiver contributions based on a convolutional model the observed p wave source spectra are corrected with a globally averaged empirical correction spectrum and estimates of near source attenuation assuming a brune type source model we estimate corner frequencies and compute stress drops stress drop estimates for individual earthquakes range from about 0 3 to 50 mpa but the median stress drop of about 4 mpa does not vary with moment implying earthquake self similarity over the mw 5 2 to 8 3 range of our data a comparison of our results with previous studies confirms this observation over most of the instrumentally observable magnitude range while the absolute values of our estimated stress drops depend upon the assumed source model we identify relative regional variations of stress drop that are robust with respect to the processing parameters and modeling assumptions which includes an inherent assumption of constant rupture velocity we find a dependence of median stress drop on focal mechanism with a factor of 3 5 times higher stress drops for strike slip earthquakes and also find a factor of 2 times higher stress drops for intraplate earthquakes compared to interplate earthquakes

long aftershock sequences within continents and implications for earthquake hazard assessment one of the most powerful features of plate tectonics is that the known plate motions give insight into both the locations and average recurrence interval of future large earthquakes on plate boundaries plate tectonics gives no insight however into where and when earthquakes will occur within plates because the interiors of ideal plates should not deform as a result within plate interiors assessments of earthquake hazards rely heavily on the assumption that the locations of small earthquakes shown by the short historical record reflect continuing deformation that will cause future large earthquakes here however we show that many of these recent earthquakes are probably aftershocks of large earthquakes that occurred hundreds of years ago we present a simple model predicting that the length of aftershock sequences varies inversely with the rate at which faults are loaded aftershock sequences within the slowly deforming continents are predicted to be significantly longer than the decade typically observed at rapidly loaded plate boundaries these predictions are in accord with observations so the common practice of treating continental earthquakes as steady state seismicity overestimates the hazard in presently active areas and underestimates it elsewhere

a comparative study of source complexity of two moderate sized earthquakes in southern taiwan 2016 mw6 4 and 2010 mw6 2 earthquakes we study the complex rupture history of the 2016 mw6 4 meinong earthquake and the 2010 mw6 2 jiaxian earthquake in southern taiwan by simultaneously inverting near field strong motion records local and teleseismic broadband waveforms along with long period surface waves the focal mechanism results reveal that both earthquakes may rupture two different blind faults the rupture of the 2016 event is dominated by the strike slip motion with minor thrust faulting while the 2010 event is a relatively high angle thrust earthquake our preferred finite fault source models suggest that the coseismic rupture history of the 2016 event should be relatively more complex than the 2010 event during the 2016 event two main patches of slip characterize the coseismic slip history the cumulative seismic moment within 12 s of rupture is about 5 36 1018 n m which is 1 9 times of the moment of the 2010 event the slip of the 2016 event is associated with relatively larger perk slip of 0 7 m at shallower depth 18 19 km higher average slip of 0 3 m and faster slip rate with the maximum value of 3 4 m s our kinematic models can shed some light on the cause of the difference in seismic hazard between these two earthquakes and will be further applied to analyze the deep blind fault structure in southern taiwan

spatial temporal evolutions of early aftershocks following the 2013 mw 6 6 lushan earthquake in sichuan china we perform a comprehensive detection of early aftershocks following the 2013 mw 6 6 lushan earthquake which occurred in the southern longmenshan fault zone in sichuan province china about 5 years after the 2008 mw 7 9 wenchuan earthquake we use events in both standard and relocated catalogs as templates to scan through continuous waveforms 2 days before and 3 days after the main shock we successfully reduce the magnitude of completeness mc by more than 1 order and obtain up to 6 times more events than listed in both catalogs aftershocks in the first hour mostly occur around the main shock slip region and aftershocks at later times show systematic expansions in the along strike perpendicular strike and updip directions although postseismic deformation following the lushan main shock has not been clearly identified we suggest that early aftershock expansions are likely driven by afterslip of the lushan main shock this is consistent with the observations that most aftershocks were in the stress shadow of the lushan main shock and that there was significant slip deficit in the top 10 km of the crust we also find that seismicity on the back thrust fault was activated as soon as 20 min after the main shock earlier than previously reported we are unable to detect any clear foreshocks in the last 2 days before the lushan main shock

the slip history of the 1994 northridge california earthquake determined from strong motion teleseismic gps and leveling data we present a rupture model of the northridge earthquake determined from the joint inversion of near source strong ground motion recordings p and sh teleseismic body waves global positioning system gps displacement vectors and permanent uplift measured along leveling lines the fault is defined to strike 122 and dip 40 to the south southwest the average rake vector is determined to be 101 and average slip is 1 3 m the peak slip reaches about 3 m our estimate of the seismic moment is 1 3 0 2 10 26 dyne cm potency of 0 4 km3 the rupture area is small relative to the overall aftershock dimensions and is approximately 15 km along strike nearly 20 km in the dip direction and there is no indication of slip shallower than about 5 to 6 km the up dip strong motion velocity waveforms are dominated by large s wave pulses attributed to source directivity and are comprised of at least 2 to 3 distinct arrivals a few seconds apart stations at southern azimuths indicate two main s wave arrivals separated longer in time about 4 to 5 sec these observations are best modeled with a complex distribution of subevents the initial s wave arrival comes from an asperity that begins at the hypocenter and extends up dip and to the north where a second larger subevent is centered about 12 km away the secondary s arrivals at southern azimuths are best fit with additional energy radiation from another high slip region at a depth of 19 km 8 km west of the hypocenter the resolving power of the individual data sets is examined by predicting the geodetic gps and leveling displacements with the dislocation model determined from the waveform data and vice versa and also by analyzing how well the teleseismic solution predicts the recorded strong motions the general features of the geodetic displacements are not well predicted from the model determined independently from the strong motion data likewise the slip model determined from geodetic data does not adequately reproduce the strong motion characteristics whereas a particularly smooth slip pattern is sufficient to satisfy the geodetic data the strong motion and teleseismic data require a more heterogeneous slip distribution in order to reproduce the velocity amplitudes and frequency content although the teleseismic model can adequately reproduce the overall amplitude and frequency content of the strong motion velocity recordings it does a poor job of predicting the geodetic data consequently a robust representation of the slip history and heterogeneity requires a combined analysis of these data sets

depth dependence of post seismic velocity changes in and near source area of the 2013 m7 0 lushan earthquake revealed by s coda of repeating events abstract i investigated postseismic velocity changes within focal area of the 2013 m 7 0 lushan earthquake using coda wave data of repeating small earthquakes i employed template matching and grid search methods to identify well defined repeating earthquakes in order to minimize artifacts induced by variations in source location i identified a total of 3 isolated patches in a two month period after the m 7 0 mainshock i applied the coda wave interferometry technique to the waveform data of the identified repeating earthquakes to estimate velocity changes between the first and subsequent events in each cluster up to 0 1 0 2 velocity increase is observed from the s coda of repeating events occurred at regions surrounding the large coseismic slip area at seismogenic depths my observations suggest that a large percent of velocity changes may occur at surface near the stations or shallow however healing along the propagation paths in the deep 5 20 km is likely have contributed to the amount of velocity changes observed after the lushan earthquake

re evaluating seismic hazard along the southern longmen shan china insights from the 1970 dayi and 2013 lushan earthquakes abstract competing hypotheses have been proposed to explain the seismic hazard i e whether earthquakes with m 7 occur of the southern longmen shan lms this region did not rupture during the 2008 mw 7 9 wenchuan earthquake but later generated the 2013 mw 6 6 lushan earthquake currently the maximum possible earthquake magnitude its average recurrence interval and the seismogenic structure of the southern lms remain poorly documented this study aims to re evaluate seismogenic structures and seismic hazard along the southern lms we first describe the sub surface structural geometry as well as the total slip and quaternary activity of the range front blind thrust rfbt using high resolution seismic reflection profiles borehole data and intensity derived macroscopic epicenters this thrust which generated the 1970 ms 6 2 dayi and 2013 mw 6 6 lushan earthquakes extends for 250 km along the lms range front integrating new evidence of active faulting and folding and previous quantitative horizontal shortening rate results we estimate that the quaternary slip rate of the rfbt is nearly 1 mm yr with a minimum total slip of 5 km since 8 5 ma furthermore we calculate the accumulation rate of seismic moment 8 04 2 09 1017 n m yr for the main active thrusts on the southern lms to compare with the moment release rate for earthquakes in the region when we combine this with the gutenberg richter distribution obtained from historical and instrumental catalogs we estimate that the potential maximum moment magnitude of an earthquake in the southern lms is 7 7 finally we conclude that the entire southern lms is capable of generating much larger earthquakes mw 7 3 7 7 than seen recently with an average frequency of once every 1000 1400 years therefore our findings confirm that there is potential for large earthquakes in the southern lms especially on the rfbt which extends beneath the densely populated chengdu plain

fault geometry and slip distribution of the 2013 mw 6 6 lushan earthquake in china constrained by gps insar leveling and strong motion data

the 2013 lushan earthquake implications for seismic hazards posed by the range front blind thrust in the sichuan basin china thrust and reverse faults pose significant earthquake hazards in convergent plate margins around the world but have proven difficult to study given the complex nature of their ruptures which often involve multiple along strike and vertically stacked fault segments the 2013 mw 6 6 lushan earthquake exemplified this complexity rupturing a blind thrust fault in the southern longmen shan which border the western sichuan basin in china this event occurred 80 km south of the epicenter of the destructive 2008 mw 7 9 wenchuan earthquake the wenchuan earthquake produced surface ruptures on two parallel fault splays the pengguan and beichuan faults in contrast the lushan earthquake was generated by a ramp in the range front blind thrust rfbt which is in the footwall of the wenchuan rupture we use seismic reflection profiles petroleum wells and relocated seismicity to construct a three dimensional model of this imbricated fault system our model illustrates that the 2013 lushan earthquake ruptured 10 of the rfbt which extends for 250 km along the longmen shan range front and into the western sichuan basin analysis of growth strata in structures above the rfbt fault along strike shows clear evidence of quaternary activity and constrains the middle pleistocene to current slip rate at two locations on the fault single segment and multisegment fault rupture scenarios involving the rfbt suggest the potential for large earthquakes m7 8 that would affect the densely populated western sichuan basin assessing the hazards posed by such complex thrust systems which occur in convergent margins worldwide requires subsurface characterization of fault segments that can be independently associated with geologic and seismologic evidence of fault activity

slip history and dynamic implications of the 1999 chi chi taiwan earthquake we investigate the rupture process of the 1999 chi chi taiwan earthquake using extensive near source observations including three component velocity waveforms at 36 strong motion stations and 119 gps measurements a three plane fault geometry derived from our previous inversion using only static data ji et al 2001 is applied the slip amplitude rake angle rupture initiation time and risetime function are inverted simultaneously with a recently developed finite fault inverse method that combines a wavelet transform approach with a simulated annealing algorithm ji et al 2002b the inversion results are validated by the forward prediction of an independent data set the teleseismic p and sh ground velocities with notable agreement the results show that the total seismic moment release of this earthquake is 2 7 10 20 n m and that most of the slip occurred in a triangular shaped asperity involving two fault segments which is consistent with our previous static inversion the rupture front propagates with an average rupture velocity of 2 0 km s 1 and the average slip duration risetime is 7 2 s several interesting observations related to the temporal evolution of the chi chi earthquake are also investigated including 1 the strong effect of the sinuous fault plane of the chelungpu fault on spatial and temporal variations in slip history 2 the intersection of fault 1 and fault 2 not being a strong impediment to the rupture propagation and 3 the observation that the peak slip velocity near the surface is in general higher than on the deeper portion of the fault plane as predicted by dynamic modeling