detailed rupture imaging of the 25 april 2015 nepal earthquake using teleseismic p waves we analyze the rupture process of the 25 april 2015 nepal earthquake with globally recorded teleseismic p waves the rupture propagated east southeast from the hypocenter for about 160 km with a duration of 55 s backprojection of both high frequency hf 0 2 to 3 hz and low frequency lf 0 05 to 0 2 hz p waves suggest a multistage rupture process from the low frequency images we resolve an initial slow downdip northward rupture near the nucleation area for the first 20 s stage 1 followed by two faster updip ruptures 20 to 40 s for stage 2 and 40 to 55 s for stage 3 which released most of the radiated energy northeast of kathmandu the centroid rupture power from lf backprojection agrees well with the global centroid moment tensor solution the spatial resolution of the backprojection images is validated by applying similar analysis to nearby aftershocks the overall rupture pattern agrees well with the aftershock distribution a multiple asperity model could explain the observed multistage rupture and aftershock distribution

smooth and rapid slip near the japan trench during the 2011 tohoku oki earthquake revealed by a hybrid back projection method abstract we developed a new back projection method that uses teleseismic p waveforms to integrate the direct p phase with reflected phases from structural discontinuities near the source and used it to estimate the spatiotemporal distribution of the seismic energy release of the 2011 tohoku oki earthquake we projected a normalized cross correlation of observed waveforms with corresponding green s functions onto the seismic source region to obtain a high resolution image of the seismic energy release applying this method to teleseismic p waveform data of the 2011 tohoku oki earthquake we obtained spatiotemporal distributions of seismic energy release for two frequency bands a low frequency dataset and a high frequency dataset we showed that the energy radiated in the dip direction was strongly frequency dependent the area of major high frequency seismic radiation extended only downdip from the hypocenter whereas the area of major low frequency seismic radiation propagated both downdip and updip from the hypocenter we detected a large release of seismic energy near the japan trench in the area of maximum slip which was also the source area of the gigantic tsunami when we used only the low frequency dataset the timing of this large seismic energy release corresponded to an episode of smooth and rapid slip near the japan trench and reflects the strong dependence of the seismic energy distribution obtained on the frequency band of the input waveform dataset the episode of smooth and rapid slip may have been the trigger for a release of roughly all of the accumulated elastic strain in the seismic source region of the 2011 tohoku oki earthquake

coseismic temporal changes of slip direction the effect of absolute stress on dynamic rupture abstract we investigate the dynamics of rupture at low stress level we show that one main difference between the dynamics of high and low stress events is the amount of coseismic temporal rake rotation occurring at given points on the fault curved striations on exposed fault surfaces and earthquake dislocation models derived from ground motion inversion indicate that the slip direction may change with time at a point on the fault during dynamic rupture we use a 3d boundary integral method to model temporal rake variations during dynamic rupture propagation assuming a slip weakening friction law and isotropic friction the points at which the slip rotates most are characterized by an initial shear stress direction substantially different from the average stress direction over the fault plane we show that for a given value of stress drop the level of initial shear stress i e the fractional stress drop determines the amount of rotation in slip direction we infer that seismic events that show evidence of temporal rake rotations are characterized by a low initial shear stress level with spatially variable direction on the fault possibly due to changes in fault surface geometry and an almost complete stress drop our models motivate a new interpretation of curved and cross cutting striations and put new constraints on their analysis the initial rake is in general collinear with the initial stress at the hypocentral zone supporting the assumptions made in stress tensor inversion from first motion analysis at other points on the fault especially away from the hypocenter the initial slip rake may not be collinear with the initial shear stress contradicting a common assumption of structural geology on the other hand the later part of slip in our models is systematically more aligned with the average stress direction than the early slip our modeling suggests that the length of the straight part of curved striations is usually an upper bound of the slip weakening distance if this parameter is uniform over the fault plane and the direction of the late part of slip of curved striations should have more weight in the estimate of initial stress direction

deformation due to the 17 august 1999 izmit turkey earthquake measured from spot images the geometry of the ruptured areas and the coseismic slip distribution data are key to highlighting the behavior of seismic faults this information is generally retrieved from field investigations and geodetic measurements or synthetic aperture radar sar interferometry here we show that spot images can also be used to accurately map the fault zone and to determine the slip distribution by subpixel correlation of images acquired before and after an earthquake the measured slip includes the contribution of possible distributed shear that might not be clearly expressed in surface ruptures and smoothes out possible along strike variability due to near surface fault complexities we apply the technique to the m s 7 4 1999 izmit earthquake our results reveal a 100 m wide and very linear fault zone that can be traced for 70 km from golcuk to akyazi along which supershear rupture has been inferred the obtained slip distribution compares well with the field measurements and is consistent with ground deformation measured at some distance from the fault zone using sar images very little deformation was accommodated off the main fault plane maximum slip is observed near sapanca lake at a small fault jog that has probably influenced rupture propagation

earthquake ruptures with strongly rate weakening friction and off fault plasticity part 1 planar faults abstract observations demonstrate that faults are fractal surfaces with deviations from planarity at all scales we study dynamic rupture propagation on self similar faults having root mean square rms height fluctuations of order 10 3 to 10 2 times the profile length our 2d plane strain models feature strongly rate weakening fault friction and off fault drucker prager viscoplasticity the latter bounds otherwise unreasonably large stress concentrations in the vicinity of bends our choice of a cohesionless yield function prevents tensile stress states and thus fault opening a consequence of strongly rate weakening friction is the existence of a critical background stress level above which self sustaining rupture propagation in the form of self healing slip pulses first becomes possible around this level at which natural faults are expected to operate ruptures become extremely sensitive to fault roughness and exhibit substantial fluctuations in rupture velocity except for shallow inclinations of the maximum compressive stress to the fault less than about 20 the fluctuations are anticorrelated with the local fault slope these accelerations and decelerations of the rupture together with naturally emerging slip heterogeneity excite waves of all wavelengths and result in ground acceleration spectra that are flat at high frequency consistent with observed strong motion records

factors controlling the field settling velocity of cohesive sediment in estuaries abstract it has long been recognized that the suspended sediment concentration ssc is one of the major determinants for the flocculation of cohesive particles into sediment flocs in estuaries it is furthermore well known that the turbulent shear of the water significantly influences the flocculation process and the equilibrium settling velocity of flocculated sediment in a turbulent flow a vast number of authors have reported algorithms relating the median settling velocity w 50 to suspended sediment concentration however only a few studies have dealt with the impact of the turbulent shear in this paper expressed as the root mean square rms velocity gradient g in the water on the w 50 in situ there is a strong need to establish algorithms based on in situ measurements describing the dual impact of both ssc and g on the flocculation process and hence w 50 the present paper addresses this topic field settling velocities of suspended cohesive sediment have been measured in micro meso and macro tidal estuaries regression analyses between the w 50 ssc and g are presented it is shown that by including both g and ssc in the regression analyses a significant increase in the correlation of the description of w 50 and the controlling parameters from each area can be obtained a generic algorithm describing the data from all the investigated areas is suggested it works well within specific tidal areas but fails to give a generic description of the field settling velocity

spontaneous rupture processes on a bending fault 1 we simulated spontaneous rupture processes on a vertical bending strike slip fault in a three dimensional half space using a finite difference method rupture area and overall slip distribution on the fault vary with the initial stress field which depends on strike change at the bend rupture velocity and detailed slip distribution around the bend on the other hand are affected by time dependent normal stress change caused by rupture this dynamic stress change plays an important role in the rupture process ahead of the bend as well as in the resulting ground motion the numerical simulation method demonstrated here in a simplified geometry is equally applicable to modeling strong ground motion from geometrically complex ruptures in realistic earth models

the calibration of optical backscatter sensors for suspended sediment of varying darkness levels a series of calibration experiments were run in order to determine the effect of the colour of suspended sediment on the response of optical backscatter sensors obs munsell notation describes the properties of soil and sediment colour using the three parameters hue chroma and value which represent respectively the spectral position lightness level and amount of pure chromatic colour present the exposure of the obs to munsell soil chart patches revealed that the obs is sensitive to variations in munsell value and not munsell hue or chroma since obs output decreased with darkness level and increased with lightness level and munsell value it is suggested that the level of blackness of particles acts to absorb the near infrared ir signal of the obs modifying its output a strong correlation r2 0 984 was found between the observed and predicted obs outputs of varying concentrations and ratios of black and white suspended sediment the obs output was predicted using a linear mixture model incorporating end member calibrations of black and white sediment similar to green and boon green m o boon j d iii 1993 the measurement of constituent concentrations in nonhomogeneous sediment suspensions using optical backscatter sensors marine geology 110 pp 73 81 a strong correlation r2 0 907 was also observed between luminance factor and ir reflectance for various minerals suggesting a link between munsell notation and obs output formulae were developed to predict the ir reflectance of sediment of known munsell value concentration and size models predicting sediment transport should consider the effect of the level of blackness of particles on the obs response

structural setting of the 2008 mw 7 9 wenchuan china earthquake the 2008 m w 7 9 wenchuan earthquake ruptured an imbricate thrust system in the longmen shan range which forms the eastern boundary of the tibetan plateau we use seismic reflection data and surface geology to construct geologic cross sections and a three dimensional 3d fault model in the range front the rupture was complex with slip on both the steeply dipping beichuan fault and the more shallowly dipping pengguan fault which appear to merge at depth in contrast only the beichuan fault ruptured in the north with the transition near a lateral fault offset thus the earthquake involved multiple thrust splays and breached a significant segment boundary to investigate the tectonic setting of the earthquake we extend our previous measurements of crustal shortening hubbard and shaw 2009 into the interior of the range and show that shortening correlates with topography this suggests that upper crustal shortening can produce the high topography of the longmen shan without calling on other uplift mechanisms based on this understanding we model the thrust belt as a critical taper wedge to assess what rock and fault strengths are required to explain the topographic slopes within the range front and basin the low taper within the basin is consistent with a weak detachment f 0 1 while a slightly stronger f 0 3 0 4 detachment is necessary to explain the higher taper of the range front this difference may relate to the localization of the detachment within a triassic evaporite sequence within the basin while the faults beneath the range front are rooted in precambrian metasedimentary or igneous rocks critical taper theory implies that shortening in the range front where the 2008 wenchuan earthquake occurred is many times greater than in the basin consistent with our shortening measurements we examine the implications of these findings for seismic hazard assessment in the region and in other active mountain belts around the world

earthquakes as multiscale dynamic ruptures with heterogeneous fracture surface energy 1 we propose a model of the wide scale growth of dynamic rupture during an earthquake based on our multiscale simulation of a planar crack in a three dimensional homogeneous elastic space a simple slip weakening law governs the fracture friction processes and its characteristic parameters slip weakening distance and fracture surface energy have multiscale heterogeneous distributions we consider a set of randomly distributed circular patches whose diameter is proportional to the fracture surface energy each patch represents an asperity between irregular fault surfaces and the size number relation of the patches obeys power law statistics we assess rupture propagation from a small instability using a boundary integral equation method with a renormalization technique although most events stop shortly after their initiation some grow triggering neighboring patches of similar size small and large events show statistically self similar properties of rupture growth and stop spontaneously without requiring a special stopping mechanism the rupture velocity locally exceeds the shear wave speed but globally remains subshear speed due to the increase of the average fracture energy as the rupture grows the relation between size and frequency of events is a power law which is explained by the triggering probability between patches as a consequence of statistically self similar random triggering growth we observe a distinct main phase in seismic waves similar to those of natural earthquakes but we cannot estimate the final size of the event from the initial part of the seismic waves if this is true for the real earthquakes predicting the size of a future earthquake would be quite difficult

integrated seismic source model of the 2015 gorkha nepal earthquake we compared spatiotemporal slip rate and high frequency around 1 hz radiation distributions from teleseismic p wave data to infer the seismic rupture process of the 2015 gorkha nepal earthquake for these estimates we applied a novel waveform inversion formulation that mitigates the effect of green s functions uncertainty and a hybrid backprojection method that mitigates contamination by depth phases our model showed that the dynamic rupture front propagated eastward from the hypocenter at 3 0 km s and triggered a large slip event centered about 50 km to the east it also showed that the large slip event included a rapid rupture acceleration event and an irregular deceleration of rupture propagation before the rupture termination heterogeneity of the stress drop or fracture energy in the eastern part of the rupture area where aftershock activity was high inhibited rupture growth high frequency radiation sources tended to be in the deeper part of the large slip area which suggests that heterogeneity of the stress drop or fracture energy there may have contributed to the damage in and around kathmandu

the role of algae in fine sediment flocculation in situ and laboratory measurements abstract the precise interactions between organic and inorganic particles in the context of flocculation is an on going topic of research the suspended particulate matter spm found in estuaries is composed of both organic and inorganic particles with specific particle size distributions psd s these psd s are a function of the hydrodynamic conditions suspended sediment concentration ssc organic matter composition salinity and seasonal variations a field campaign was carried out in august 2015 in the turbidity maximum zone of the yangtze estuary where the spm dynamics were recorded the concentration of algae in the water column was indirectly measured through the chlorophyll a concentration cc we show that there is a strong correlation between ssc and cc in the whole water column for the whole tidal cycle additional flocculation experiments in the laboratory confirm that the largest observed flocs are predominantly organic based and that salinity alone could not induce the flocculation of the yangtze mineral particles a key parameter for the maximal floc size is the algae concentration to sediment concentration ratio when this ratio is high the d50 is high and vice versa

mapping of the high frequency source radiation for the loma prieta earthquake california waveform inversion has been successfully applied to map the spatial distribution of earthquake fault slip from strong motion records but its application has been restricted to a relatively lower frequency range of the data 5 hz generation is incoherent between neighboring patches on the fault we formulated an analytical model for calculating the envelope time history of the squared high frequency displacement seismogram this envelope time history is found through the line integration of the squared energy radiation intensity over the isochron using a recursive stochastic inversion scheme we determined both the lower frequency slip distributions from the low pass filtered strong motion displacement data and the higher frequency energy radiation intensity from the envelope of the squared high frequency displacement data on an extended fault for the 1989 loma prieta earthquake respectively our resulting lower frequency slip model shows that there are two main slip patches and little slip directly updip of the hypocenter one major slip zone located 10 km northwest of the hypocenter with predominant dip slip and the other located 12 km southeast of the hypocenter with predominant oblique slip our preliminary results of the high frequency energy radiation intensity inversion indicate three large high frequency sources and few smaller ones located on the outer periphery of the large slip zones this suggests that the high frequency energy sources are located along or near the boundaries of large slip zones which is consistent with the theoretical consideration that high frequencies are primarily generated from the rupture stopping areas or places with large slip variation

laboratory evaluation of two lisst 25x using river sediments abstract there are different methods to determine particle size most of them are only applicable in the laboratory in order to describe the suspended fine sediment sizes where flocs may be part of the suspension in situ measurements are essential this work shows the results of sediment size measurements done in the laboratory using two lisst 25x diffractometers developed for in situ measurements and a malvern mastersizer 2000 diffractometer for laboratory use the two lisst 25x models characterize the sample size through the sauter mean diameter smd besides the smd the malvern diffractometer determines the granulometric distributions of the samples the tested samples are from different fluvial and estuarine environments parana salado and the amazon rivers and their sizes smd range from 4 to 300 m the relationship between smd obtained with the two lisst 25x and the malvern diffractometers gave a determination coefficient of r2 0 98 compared to the malvern instrument used as a reference it was observed that the lisst instruments tend to overestimate the measured smd for diameters lower than 20 m and to underestimate the values of samples with larger diameters 20 m aiming to obtain other characteristic diameters of the granulometric distribution from smd measurements obtained with lisst 25x diffractometers correlations between smd and d10 d50 and d90 were established the dependency of the measurement of sediment mass concentration obtained with lisst instruments with the particle size is also addressed

rupture termination and jump on parallel offset faults proper evaluation of seismic hazard depends on accurate estimates of potential earthquake size in areas with complex multisegment fault systems such an estimate in turn depends on an ability to predict the circumstances under which rupture may jump between fault segments many observational and numerical studies have analyzed the phenomenon of jumping rupture but none has focused on how the process of rupture termination on the primary nucleating fault segment affects the ability of rupture to jump to a secondary fault segment in the current study i model the dynamics of a simple 2d strike slip fault system with two parallel segments arranged with either a compressional or extensional stepover i vary the suddenness with which the initial shear stress tapers to zero on the primary section if the initial shear stress goes to zero over a very small 100 m distance rupture readily jumps both compressional and extensional stepovers of 1 km if the initial shear stress tapers to zero over 1 km rupture can jump the compressional stepover but not the extensional stepover if the initial shear stress tapers to zero over 2 5 km rupture cannot jump either the compressional or the extensional stepover the results illustrate the importance of the slip gradient and the resultant static stress field and the acceleration of the rupture front and the resultant generation of stopping phases in determining the probability of jumping rupture

spatio temporal distribution of fault slip and high frequency radiation of the 2010 el mayor cucapah mexico earthquake 1 earthquake slip history and moment release are best resolved using long period seismic waves but details in the rupture process such as sharp changes in rupture velocity or direction can be imaged more clearly using higher frequency waves here we investigate the slip and the high frequency radiation histories of the 2010 el mayor cucapah baja california mexico earthquake mw 7 2 the slip distribution inferred from inversion of strong motion data between 0 02 and 0 25 hz indicates northwest propagating rupture followed by bilateral rupture for 40 s the sources of high frequency radiation between 0 3 and 2 hz inferred from back projection analysis using teleseismic data are adjacent to but not within the high slip patches from the finite slip model in time and space this implies relatively smooth rupture during the times and regions of maximum moment release as theoretical models have predicted high frequency radiation seems mostly associated with changes in rupture velocity or slip magnitude strong high frequency radiation is also found where the rupture propagated to a branch fault 50 km northwest of the hypocenter complementary constraints on both fault slip and high frequency radiation provide increased understanding of earthquake rupture mechanics and may help improve strong motion evaluation at high frequencies

a high frequency secondary event during the 2004 parkfield earthquake by using seismic records of the 2004 magnitude 6 0 parkfield earthquake we identified a burst of high frequency seismic radiation that occurred about 13 kilometers northwest of the hypocenter and 5 seconds after rupture initiation we imaged this event in three dimensions by using a waveform back projection method as well as by timing distinct arrivals visible on many of the seismograms the high frequency event is located near the south edge of a large slip patch seen in most seismic and geodetic inversions indicating that slip may have grown abruptly at this point the time history obtained from full waveform back projection suggests a rupture velocity of 2 5 kilometers per second energy estimates for the subevent together with long period slip inversions indicate a lower average stress drop for the northern part of the parkfield earthquake compared with that for the region near its hypocenter which is in agreement with stress drop estimates obtained from small magnitude aftershocks

triggered slip observations of the 17 august 1999 izmit turkey earthquake using radar interferometry we use synthetic aperture radar interferometry insar to map the displacement field of the 17 august 1999 izmit earthquake which largely conforms to that predicted for an elastic upper crust we determine the earthquake source parameters and show that slip continues farther west than the mapped fault ruptures we also show that additional sub surface displacements occurred on parallel strands of the north anatolian fault zone we argue that this was caused by changes in static stress accompanying the mainshock or by the dynamic release of regional stresses

dongfang 1 1 gas field in the mud diapir belt of the yinggehai basin south china sea abstract the dongfang 1 1 df1 1 mud diapir field is the largest gas field discovered in the yinggehai basin up to now with a proven gas reserve of 99 68 10 9 m 3 the gas pay zones are within the pliocene fine sandstones and siltstones of the littoral and sand bar facies with normal pressure regimes the gases include variable amounts of co 2 and n 2 in addition to hydrocarbon gases the hydrocarbon gases with the exception of biogenic methane and nitrogen originated from the marine source rocks within the overpressured lower to middle miocene strata while co 2 is most likely the product of thermal decomposition of the tertiary calcareous mudstones and pre tertiary carbonates through relatively long distance vertical migration the field has received at least four phases of natural gas charging occurring relatively late most likely during the post pliocene himalayan orogeny diapiric faults act as the main conduit for upward movement of fluids released from the deep high pressure system with abnormally high pressures providing the significant driving force for gas migration because of the episodic nature of the deep high pressured fluid release and the diapir fault activity this shallow diapir gas field is characterized by multiple gas sources and episodic fluid accumulation

surface ruptures on the transverse xiaoyudong fault a significant segment boundary breached during the 2008 wenchuan earthquake china abstract the 220 km long rupture of the 2008 mw 7 9 wenchuan earthquake breached several km scale geometric discontinuities along strike including the previously un mapped nw trending xiaoyudong fault connecting between the two major ne trending rupture planes on the beichuan and pengguan faults in this paper we present high resolution mapping of the 8 km long surface breaks and sinistral oblique thrusting coseismic slip on the xiaoyudong fault scarp height is the largest at the nw end reaching 3 5 m and decreases southward in steps to less than 0 2 m with an average slip gradient of 6 10 3 at a few tens of meters length scale but up to 50 10 3 locally left lateral offsets co vary with the vertical component the largest sinistral slip vector we observed is 2 2 m geological and geophysical evidence suggests that the xiaoyudong fault is likely a 30 sw dipping lateral ramp that soles into the pengguan fault and at its northwestern end intersects with the beichuan fault where the latter has a step in the fault plane kinematically the xiaoyudong fault functions as a tear and conjugate fault and coincides with significant coseismic slip rake rotations on both the beichuan and pengguan faults similar correlation of fault bends with sharp changes in faulting style occurs at other steps along the wenchuan rupture the xiaoyudong fault may have played a positive role in linking coseismic slip partitioning between parallel reverse fault planes facilitating the growth of a longer and more destructive rupture this highlights the role of tear faults in bridging ruptures between segments such that reverse type ruptures can breach steps wider than anticipated from strike slip fault examples transfer faults are common and perhaps poorly documented features in reverse fault systems and their roles in ruptures may increase the maximum potential earthquake magnitude for fold and thrust belts

high resolution backprojection at regional distance application to the haiti m7 0 earthquake and comparisons with finite source studies a catastrophic m w7 earthquake ruptured on 12 january 2010 on a complex fault system near port au prince haiti offshore rupture is suggested by aftershock locations and marine geophysics studies but its extent remains difficult to define using geodetic and teleseismic observations here we perform the multitaper multiple signal classification music analysis a high resolution array technique at regional distance with recordings from the venezuela national seismic network to resolve high frequency about 0 4 hz aspects of the earthquake process our results indicate westward rupture with two subevents roughly 35 km apart in comparison a lower frequency finite source inversion with fault geometry based on new geologic and aftershock data shows two slip patches with centroids 21 km apart apparent source time functions from usarray further constrain the intersubevent time delay implying a rupture speed of 3 3 km s the tips of the slip zones coincide with subevents imaged by backprojections the different subevent locations found by backprojection and source inversion suggest spatial complementarity between high and low frequency source radiation consistent with high frequency radiation originating from rupture arrest phases at the edges of main slip areas the centroid moment tensor cmt solution and a geodetic only inversion have similar moment indicating most of the moment released is captured by geodetic observations and no additional rupture is required beyond where it is imaged in our preferred model our results demonstrate the contribution of backprojections of regional seismic array data for earthquakes down to m 7 especially when incomplete coverage of seismic and geodetic data implies large uncertainties in source inversions

seismogram envelope inversion for the spatial distribution of high frequency energy radiation from the earthquake fault application to the 1994 far east off sanriku earthquake japan incoherency of high frequency seismic waves leads to the idea to analyze seismogram envelopes disregarding phase information for the source study we develop an inversion method for estimating high frequency above 1 hz energy radiation from the earthquake fault and site amplification factors from observed mean square s wave seismogram envelopes the inversion is executed by using the s wave envelope green function from the onset to coda for a point shear dislocation source in a scattering medium which is formulated based on an extended version of the radiative transfer theory the use of the envelope green function enables us to estimate the spatial distribution of high frequency energy radiation on a fault plane this has been difficult by conventional waveform inversion methods the rupture velocity and the duration time of energy radiation on each subfault are also estimated by grid search method we apply this new method to the 1994 far east off sanriku northeastern japan earthquake mw 7 7 which ruptured a 90 km segment of the plate boundary along the japan trench inverting observed seismogram envelopes at 10 strong motion stations in japan it is concluded that above 90 of the high frequency energy was radiated from the western half of the fault with the largest energy radiation near the deep side edge the rupture velocity is estimated to be 2 7 km s the estimated site amplification factors ranging between 0 3 and 15 are consistent with those independently estimated by the coda normalization method

coseismic deformation from the 2008 wenchuan china earthquake derived from alos palsar images abstract we analyzed alos palsar images along eight paths acquired before and after the mainshock of an earthquake in wenchuan in the sichuan province of china may 12 2008 we found entire coseismic deformation features and detected many fringes in an approximately 100 km wide region surrounding the longmen shan fault zone we found 6 7 broad elliptic fringes north of the epicenter which indicated around 70 80 cm increase in range distance between the ground and satellite this pattern corresponded to subsidence or eastward shift of ground which is often seen above the lower margin of a low angled thrust we also counted 8 9 fringes i e 90 100 cm range decrease between the fault zone and chengdu chengdu is located roughly 50 km away from the pengguan fault which is the southernmost trace of the longmen shan fault zone as this area is located on the footwall side the pattern suggested a westward shift of the earth s surface however we could not obtain high correlations due to large displacements in the about 240 km long belt along the surface faults several concentric fringes were found along the beichuan fault which is the central trace of the longmen shan fault zone this implied that the rupture process of this earthquake was complicated we also performed pixel matching to estimate offsets in the region of low correlation positive and negative range offsets larger than 2 m were found on the north and south sides of the beichuan fault respectively we observed a belt of negative range and azimuth offsets between the beichuan and pengguan faults we calculated an interferogram using a multi segment fault model with uniform slip along the beichuan and pengguan faults and estimated the slip distribution based on previous seismological studies we assumed that the southwestern part dipped toward the northwest by 33 degrees whereas the central and northeastern parts had a much steeper dip angle we found two regions of slips larger than 4 m in the southwest and central parts of the beichuan fault the pengguan segments may have much smaller slips around 1 m the southwestern segments of the beichuan fault and the entire pengguan fault had dominant thrust components whereas dextral slip prevailed in the central and northeastern segments of the beichuan fault the estimated geodetic moment was 5 87 1020nm mw 7 78

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

an integrated optic and acoustic ioa approach for measuring suspended sediment concentration in highly turbid environments abstracts accurate measurement of suspended sediment concentration ssc in highly turbid environments has been a problem due to optical or acoustic signal saturation and attenuation the saturation returns a limited measurement range and the attenuation raises an ambiguity problem that a low optical or acoustic output could mean a low or a high ssc in this study an integrated optic and acoustic ioa approach is proposed to i overcome the ambiguity problem ii increase the measurement range to high ssc values and iii obtain high resolution ssc profiles the ioa approach is a combination of argus suspension meter asm optical backscatter sensor obs and acoustic doppler velocimeter adv in this approach the asm derived ssc is preferred because of its lowest relative error followed by obs and adv the asm can produce high resolution 1 cm interval ssc profiles when it is not saturated usually ssc

a study of in situ sediment flocculation in the turbidity maxima of the yangtze estuary abstract in order to improve our understandings of temporal and vertical variations of sediment flocculation dynamics within the turbidity maxima tm of the highly turbid yangtze estuary ye we deployed lisst 100c a laser instrument for in situ monitor of the sizes and concentrations of flocculated particles in a wet season field data in terms of vertical profiles of flow velocity suspended sediment concentration ssc salinity flocculated particle size distribution and volume concentration were obtained based on field works conducted at consecutive spring moderate and neap tides data analyses show that the mean floc diameters d m were in the range of 14 95 m and flocculation exhibited strong temporal and vertical variations within a tidal cycle and between spring neap cycles larger d m were observed during high and low slack waters and the averaged floc size at neap tide was found 57 larger than at spring tide effective density of flocs decreased with the increase of floc size and fractal dimension of flocs in the ye was mainly between 1 5 and 2 1 we also estimated the settling velocity of flocs by 0 04 0 6 mm s 1 and the largest settling velocity occurred also at slack waters moreover it is found that turbulence plays a dominant role in the flocculation process floc size decreases significantly when the shear rate parameter g is 2 3 s 1 suggesting the turbulence breaking force combined effects of fine sediment flocculation enhanced settling process and high sediment concentration resulted in a large settling flux around high water which can in part explain the severe siltation in the tm of the ye thus shedding lights on the navigation channel management

modelling flocculation towards an integration in large scale sediment transport models abstract despite recent advancement in the field of sediment transport the integration of cohesive sediment properties in large scale transport models remain a challenging task in order to model adequately the change in particle size that occurs in different environmental conditions flocculation models based on the so called population balance equations pbe are often used these models have to be efficient enough to be implemented in numerical transport models and as full pbe s are time expensive to run and depend on a huge amount of a priori unknown parameters simplifications have to be made these simplifications comes unavoidably at the cost of properly accounting for the complex particle particle and particle fluid interactions in order to stay as close as possible to the physical processes we propose a different approach based on a logistic growth model that mimics the particle size distribution psd measured over time for all size classes the parameters of the model can easily be found from laboratory measurements in contrast to most models the particle classes we propose are not defined by particle size but in terms of mineral sediment composition one class is composed of unflocculated mineral sediment particles another of flocculated sediment particles and a third one of organic particles the mass balance between classes and the way to obtain their corresponding average settling velocity are given mass balance and settling velocities are the required input parameters for all sediment transport models the simplicity of the derived expressions and their link with measurable variables makes them good candidates for future implementation in such models

rupture dynamics and ground motion from 3 d rough fault simulations 1 we perform three dimensional 3 d numerical calculations of dynamic rupture along non planar faults to study the effects of fault roughness on rupture propagation and resultant ground motion the fault roughness model follows a self similar fractal distribution over length scales spanning three orders of magnitude from 102 to 105 m the fault is governed by a strongly rate weakening friction and the bulk material is subject to drucker prager viscoplasticity fault roughness promotes the development of self healing rupture pulses and a heterogeneous distribution of fault slip at the free surface and at depth the inelastic deformation generated by the large dynamic stress near rupture fronts occurs in a narrow volume around the fault with heterogeneous thickness correlated to local roughness slopes inelastic deformation near the free surface however is induced by the stress waves originated from dynamic rupture at depth and spreads to large distances 10 km away from the fault the present simulations model seismic wave excitation up to 10 hz with rupture lengths of 100 km permitting comparisons with empirical studies of ground motion intensity measures of engineering interest characteristics of site averaged synthetic response spectra including the distance and period dependence of the median values absolute level and intra event standard deviation are comparable to appropriate empirical estimates throughout the period range 0 1 3 0 s this class of model may provide a viable representation of the ground motion excitation process over a wide frequency range in a large spatial domain with potential applications to the numerical prediction of source and path specific effects on earthquake ground motion

factors controlling floc settling velocity along a longitudinal estuarine transect a 147 km longitudinal transect of flocculated cohesive sediment properties in san francisco bay sfb was conducted on june 17th 2008 our aim was to determine the factors that control floc settling velocity along the longitudinal axis of the estuary the inssev lf video system was used to measure floc diameters and settling velocities at 30 stations at a distance of 0 7 m above the estuary bed floc sizes d ranged from 22 m to 639 m and settling velocities ws ranged between 0 04 mm s 1 and 15 8 mm s 1 during the longitudinal transect nearbed turbulent shear stresses throughout the transect duration were within the 0 2 0 5 pa range which typically stimulates flocculation growth the individual d ws floc density plots suggest the suspended sediments encountered throughout sfb were composed of both muddy cohesive sediment and mixed sediments flocs mass weighted population mean settling velocity wsmass ranged from 0 5 mm s 1 to 10 mm s 1 the macrofloc and microfloc demarcation at 160 m sub populations demonstrated parameterised settling velocities which spanned nearly double the range of the sample mean settling velocities wsmean the macroflocs tended to dominate the suspended mass up to 77 of the ambient suspended solid concentration ssc from san pablo bay to carquinez strait the vicinity of the turbidity maximum zone microfloc mass was particularly significant typically 60 100 of the ssc in the northern section of south bay and most of central bay the transect took eleven hours to complete and was not fully synoptic during slack tide larger and faster settling flocs deposited accounting for most of the longitudinal variability the best single predictor of settling velocity was water velocity 39 min prior to sampling not suspended sediment concentration or salinity resuspension and settling lags are likely responsible for the lagged response of settling velocity to water velocity the distribution of individual floc diameters and settling velocities indicates that floc density for a given floc diameter varies greatly a small portion a few percent of suspended sediment mass in sfb is sand sized and inclusion of sand in flocs appears likely fractal theory for cohesive sediment assumes that there is a single primary particle size that flocculates which is not the case for these types of mixed sediment flocs the wide variability in the physical biological and chemical processes which contribute to flocculation within sfb means that spatial floc data is required in order to accurately represent the diverse floc dynamics present in the bay system the importance in determining accurate estimates of floc density has been highlighted by the sfb data as these provide the basis for realistic distributions of floc dry mass and the mass settling flux across a floc population however although video floc sampling devices can produce the various floc property trends observed in sfb good survey practice is still paramount one can see that if the sampling coverage i e data collection frequency is poor this could lead to potential mis interpretations of the data and only limited conclusions may be drawn from such a restricted survey for example a limited survey i e only 3 stations compared to the 10 stations in the full survey in south bay produces an under estimate in both the macrofloc sscmacro distribution by a factor of four and the wsmacro by a factor of two to develop sediment transport numerical models for sfb high quality floc size and settling data are needed to understand and simulate the depositional qualities of both suspended cohesive sediment and mixed sediments in san francisco bay this study has shown that the most pragmatic solution is a physically based approach whereby the detailed flocs d vs ws spectra are parameterised in terms of their macrofloc and microfloc properties this aids in model calibration whilst retaining more of the dynamical aspects of the floc populations all forms of flocculation are dynamically active processes therefore it is important to also include both ssc and turbulence functions together with the floc data

rupture process of the mw 7 9 2015 gorkha earthquake nepal insights into himalayan megathrust segmentation we investigate the rupture process of the 25 april 2015 gorkha earthquake mw 7 9 using a kinematic joint inversion of teleseismic waves strong motion data high rate gps static gps and synthetic aperture radar sar data the rupture is found to be simple in terms of coseismic slip and even more in terms of rupture velocity as both inversion results and a complementing back projection analysis show that the main slip patch broke unilaterally at a steady velocity of 3 1 3 3 km s this feature likely contributes to the moderate peak ground acceleration 0 2 g observed in kathmandu the 15 km deep rupture occurs along the base of the coupled portion of the main himalayan thrust and does not break the area ranging from kathmandu to the front the limitation in length and width of the rupture cannot be identified in the preearthquake interseismic coupling distribution and is therefore discussed in light of the structural architecture of the megathrust

a laboratory examination of floc characteristics with regard to turbulent shearing abstract turbulent shear generated within the water column is recognised as having a controlling influence over both the flocculation of fine grained cohesive sediments within estuarine waters and their respective aggregate break up this study examines the inter relationships between floc characteristics over increasing turbidity 80 200 mg l 1 and turbulent shear 0 0 6 n m 2 environments by the use of a laboratory flume within which a suspension can be sheared at a controlled rate and with an unintrusive macro lens miniature video camera mounted in a viewing port on the flume channel wall the camera enables the direct simultaneous measurement of both floc size and settling velocity from which accurate estimates of floc effective density and porosity can be made measurements were made 120 s after the induced turbulence has ceased the instrument has an upper viewing turbidity limit of 210 mg l 1 and a lower resolution of 20 m the sediment was collected from the inter tidal mudflats at weir quay on the tamar estuary in devon southwest england the results indicated that increasing turbidity at low shear levels encouraged floc growth but the effect of the increasing turbulent shear 0 35 n m 2 together with increasing concentration in suspension causes disruption rather than enhancing the flocculation process at shears up to 0 35 n m 2 the largest size and settling velocity flocs were produced at high concentrations whereas above 0 35 n m 2 disruption caused smaller flocs at higher concentrations the use of algorithms which were based either on a single floc characteristic i e size or settling velocity or a mean fractal dimension were seen not to accurately approximate the experimental data a multiple regression analysis of the experimental data produced the following formula based on mean values of the 20 largest flocs sampled under each of the imposed environmental conditions referred to as max20size mean values settling velocity 0 301 0 00337 rms of the gradient in turbulent velocity fluctuations 0 000606 spm 0 00335 floc size which proved to be the most accurate representation with an r 2 value of 0 95 a similar formula was determined for the average value of the four fastest settling flocs within each sample group max4w s this highlights the importance of modelling algorithms that are developed from data that take into account effective density variations i e simultaneous size and settling velocity measurement