stress fields and fault reactivation angles of the 2000 western tottori aftershocks and the 2001 northern hyogo swarm in southwest japan abstract we estimated the stress fields of the aftershocks of the 2000 western tottori earthquake m w 6 6 and the northern hyogo swarm max m w 5 2 by a stress tensor inversion of moment tensor solutions reported from the national research institute for earth science and disaster prevention japan the maximum principal stress direction of the western tottori sequence was estimated as n107 e with a strike slip regime in the northern hyogo swarm the orientations of the principal stress directions could not be well constrained by the observed data but after examining the detailed characteristics of the solution we obtained a most probable solution of n113 e for the 1 direction these solutions are consistent with the maximum horizontal directions roughly estimated from the strike directions of large earthquakes occurring geographically between these two seismic activities we measured the angle between each fault slip direction and maximum principal stress direction to investigate the frictional properties of earthquakes the distribution of the angles was forward modeled to estimate the coefficient of friction and the stress ratio assuming uniformly distributed fault orientations for the western tottori sequence a homogeneous stress field with a coefficient of friction less than 0 4 was estimated a high stress level was also suggested because very little change occurred in the stress field during the mainshock for the northern hyogo sequence the coefficient of friction was estimated to be between 0 5 and 1 0

a nonlinear method to estimate source parameters amplitude and travel times of teleseismic body waves abstract we present a nonlinear waveform inversion method to determine source parameters under point source approximation depth source time function centroid moment tensor and seismic moment and also travel times and amplitudes of body waves from teleseismic records we demonstrate that our source time function estimates significantly improve correlation between observed and synthetics broadband seismograms the scaling of source dimensions with seismic moment is similar for deep and shallow events in the japanese subduction area for moment magnitudes between 6 1 and 7 5 we compare event depths and moment tensors obtained with our method to those reported by different institutions for a set of japanese earthquakes this comparison reveals that our method gives hypocentral depths closer to those obtained with regional arrays than other teleseismic methods the seismic moment is properly recovered but data weighting strongly influences the moment tensor solution focal mechanisms are biased by high frequency body wave amplitude variations due to crustal structure below the stations and by errors on the instrument responses body wave differential travel times are improved compared with phase picking measurements the high quality travel times will be exploited to obtain more precise event locations and higher resolution tomographic models online material coordinates of japanese earthquakes processed in this study

effects of biological crust coverage on soil hydraulic properties for the loess plateau of china biological soil crusts bscs are ubiquitous living covers that have been allowed to grow on abandoned farmlands over the loess plateau because the grain for green project was implemented in 1999 to control serious soil erosion however few studies have been conducted to quantify the effects of bsc coverage on soil hydraulic properties this study was performed to assess the effects of bsc coverage on soil hydraulic properties which are reflected by the soil sorptivity under an applied pressure of 0 s and 3 s cm saturated hydraulic conductivity k wetting front depth wfd and mean pore radius for the loess plateau of china five classes of bsc coverage i e 1 20 20 40 40 60 60 80 and 80 100 and a bare control were selected at both cyanobacteria and moss covered sites to measure soil hydraulic properties using a disc infiltrometer under 2 consecutive pressure heads of 0 and 3 cm allowing the direct calculation of s s k and the wfd was measured onsite using a ruler immediately after the experiments of infiltration the results indicated that both cyanobacteria and moss crusts were effective in changing the soil properties and impeding soil infiltration the effects of moss were greater than those of cyanobacteria compared to those of the control the s s k wfd and values of cyanobacteria covered soils were reduced by 13 7 11 0 13 3 10 6 and 12 6 on average and those of moss covered soils were reduced by 27 6 22 1 29 5 22 2 and 25 9 respectively the relative soil sorptivity under pressures of 0 rs and 3 rs cm the relative saturated hydraulic conductivity rk the relative wetting front depth rwfd and the relative mean pore radius r decreased exponentially with coverage for both cyanobacteria and moss covered soils the rates of decrease in rs rs rk rwfd and r of cyanobacteria were significantly slower than those of moss especially for the coverage of 0 40 with smaller ranges the variations of soil hydraulic properties with bsc coverage were closely related to the change in soil clay content driven by the bsc coverage on the loess plateau the results are useful for simulating the hydraulic parameters of bsc covered soils in arid and semiarid areas

joint earthquake source inversions using seismo geodesy and 3 d earth models a joint earthquake source inversion technique is presented that uses insar and long period teleseismic data and for the first time takes 3 d earth structure into account when modelling seismic surface and body waves ten average source parameters moment latitude longitude depth strike dip rake length width and slip are estimated hence the technique is potentially useful for rapid source inversions of moderate magnitude earthquakes using multiple data sets unwrapped interferograms and long period seismic data are jointly inverted for the location fault geometry and seismic moment using a hybrid downhill powell monte carlo algorithm while the insar data are modelled assuming a rectangular dislocation in a homogeneous halfspace seismic data are modelled using the spectral element method for a 3 d earth model the effect of noise and lateral heterogeneity on the inversions is investigated by carrying out realistic synthetic tests for various earthquakes with different faulting mechanisms and magnitude mw 6 0 6 6 synthetic tests highlight the improvement in the constraint of fault geometry strike dip and rake and moment when insar and seismic data are combined tests comparing the effect of using a 1 d or 3 d earth model show that long period surface waves are more sensitive than long period body waves to the change in earth model incorrect source parameters particularly incorrect fault dip angles can compensate for systematic errors in the assumed earth structure leading to an acceptable data fit despite large discrepancies in source parameters three real earthquakes are also investigated eureka valley california 1993 may 17 mw 6 0 aiquile bolivia 1998 february 22 mw 6 6 and zarand iran 2005 may 22 mw 6 5 these events are located in different tectonic environments and show large discrepancies between insar and seismically determined source models despite the 40 50 km discrepancies in location between previous geodetic and seismic estimates for the eureka valley and aiquile earthquakes the seismic data are found to be compatible with the insar location a 30 difference in strike between insar and seismic derived source models is also resolved when taking 3 d earth structure into account in the analysis of the eureka valley earthquake the combination of both insar and seismic data further constrains the dip for the zarand earthquake and in all cases the seismic moment is more robustly constrained in the joint inversions than in the individual data set inversions unmodelled lateral heterogeneities in earth and the models could partly explain some of the observed source parameter discrepancies related to the seismic data the authors 2014 published by oxford university press on behalf of the royal astronomical society

very low frequency earthquakes related to small asperities on the plate boundary interface at the locked to aseismic transition 1 very low frequency vlf seismic signals observed in southwestern japan are evidently radiated from shear slips on the upper surface of the subducting philippine sea plate we used grid moment tensor inversion and centroid moment tensor inversion to calculate 242 moment tensor solutions with moment magnitudes between 3 1 and 3 8 from continuous seismograms recorded over a 5 year period by using a very dense broadband seismic network at least 5 10 sequences of repetitive activity were observed during the 5 years the vlf events formed clustered distributions along the 35 km isodepth contour of the subducting plate surface the nodal planes which dip landward of moment tensor solutions of the vlf events reflected the configuration of the subducting plate interface the slip vectors were consistent with the direction of movement of the subducting plate the dip and strike of the slip vectors clearly reflected the configuration of the upper surface of the subducting plate we found that the rates of seismic moment release per unit area associated with five major vlf clusters were very similar although both the seismic magnitudes and sizes of the clusters varied considerably the rate of seismic moment released from detectable vlf sources was 0 1 of the rates of short term slow slip events suggesting that the source areas occupied only 0 1 of the fault segment on which the short term slow slip events occurred

on the geometric complexity of earthquake focal zone and fault systems a statistical study we discuss various methods used to investigate the geometric complexity of earthquakes and earthquake faults based both on a point source representation and the study of interrelations between earthquake focal mechanisms we briefly review the seismic moment tensor formalism and discuss in some detail the representation of double couple dc earthquake sources by normalized quaternions non dc earthquake sources like the clvd focal mechanism are also considered we obtain the characterization of the earthquake complex source caused by summation of disoriented dc sources we show that commonly defined geometrical fault barriers correspond to sources without any clvd component we analyze the cmt global earthquake catalog to examine whether the focal mechanism distribution suggests that the clvd component is likely to be zero in tectonic earthquakes although some indications support this conjecture we need more extensive and significantly more accurate data to answer this question fully

3 d rotation of double couple earthquake sources summary we discuss 3 d rotations by which one double couple earthquake source can be rotated into another arbitrary double couple due to the symmetry of double couple sources there are four such rotations an algorithm is obtained in analytical form which is also available as a computer program solving the inverse problem of 3 d rotation of double couple earthquake sources i e for each pair of focal mechanisms or seismic moment tensor solutions the program finds all four rotations which rotate one mechanism into another this algorithm may be used in a wide variety of studies of stress field causing earthquakes investigations of the relationship between the focal mechanisms and the tectonic features of a seismogenic region etc the same inversion algorithm can be used to study the 3 d rotation of any symmetric second rank tensor such as the stress or strain tensor

source mechanism of mining induced seismic events resolution of double couple and non double couple models abstract traditional assumption about a seismic source as a double couple dc can represent a serious limitation for describing mechanisms of mining induced seismic events in mining conditions more general process than a shear slip can occur due to stress concentration on mined out areas we assume both non dc components within the dipole description of the source the moment tensor and a single force we processed five seismic events recorded at driefontein gold mine in south africa to demonstrate that waveform modeling is not successful enough due to poor information about the medium inversion of amplitudes of direct p and s waves is more prospective due to their smaller sensitivity to detail of the medium and possibility to correct them for ray bending and shear wave splitting prior to the inversion moreover we are able to estimate the error of the resulting mechanism due to neglect of ray bending all five events processed display non dc mechanisms which are significant at 95 considering the mismodelling of the rock mass by a homogeneous isotropic medium the source mechanisms are in agreement with the underground mining and geological structures one event has a sub vertical pressure single dipole complemented by an implosion which is the body force equivalent of a collapsing horizontal crack or a burst of a pillar supporting the hangingwall of a mined out area two events have mechanisms close to a pressure single couple all three events are located on pillars two out of these three events can be assigned with a downward single force as an alternative mechanism which matches the amplitude data successfully it is the force equivalent of a mined out area collapse when a rock mass falls from the hangingwall to the footwall the events are however rather strong which would require too large rock mass fallen one of the remaining events is a nearly horizontal tensile single couple corresponding to a vertical tensional fault it could be originated by a break of the hangingwall of a mined out area however the hypocenter of this event is deep into the footwall were there is no mining taking place the last event is mostly dc accompanied by a compensated compressive dipole which may be associated to nearly vertical dip slip along a fault in the hangingwall this event is located on the margin of a wide pillar which supports the interpretation

a long flume study of the dynamic factors affecting the resistance of a loamy soil to concentrated flow erosion experiments were carried out in a 20 m long flume to assess the variation of the runoff erosion resistance of a loamy soil as a function of initial moisture content and compaction the results of seven experimental runs show that the runoff erosion resistance of a loamy material is extremely sensitive to variations in initial moisture content and to a somewhat lesser extent in bulk density the very low resistance to runoff erosion of initially dry material is explained by structural changes which take place at the time of wetting slaking and microfissuration cause a considerable decrease of the soil s shear strength and therefore of its resistance to runoff erosion a first analysis shows that during a given rainfall event initially dry soils may well show significantly more erosion than initially wet soils despite the increase of infiltration with decreasing initial moisture content

nied seismic moment tensor catalogue for regional earthquakes around japan quality test and application abstract we have examined the quality of the national research institute for earth science and disaster prevention nied seismic moment tensor mt catalogue obtained using a regional broadband seismic network freesia first we examined using synthetic waveforms the robustness of the solutions with regard to data noise as well as to errors in the velocity structure and focal location then to estimate the reliability robustness and validity of the catalogue we compared it with the harvard centroid moment tensor cmt catalogue as well as the japan meteorological agency jma focal mechanism catalogue we found out that the nied catalogue is consistent with harvard and jma catalogues within the uncertainty of 0 1 in moment magnitude 10 km in depth and 15 in direction of the stress axes the nied mt catalogue succeeded in reducing to 3 5 the lower limit of moment magnitude above which the moment tensor could be reliably estimated finally we estimated the stress tensors in several different regions by using the nied mt catalogue this enables us to elucidate the stress deformation field in and around the japanese islands to understand the mode of deformation and applied stress moreover we identified a region of abnormal stress in a swarm area from stress tensor estimates

back arc extension in the okinawa trough the okinawa trough lying to the east of china is a back arc basin formed by extension within continental lithosphere behind the ryukyu trench arc system middle to late miocene uplift associated with normal faulting of the initially adjacent ryukyu nonvolcanic arc and the taiwan sinzi folded belt corresponds to the first rifting phase the timing of rifting is supported by the presence of marine sediments of corresponding age drilled in the northern okinawa trough the rifting occurred after a major early miocene change in the motion of the philippine plate with respect to eurasia and ceased during the pliocene a second rifting phase started about 2 m y ago at the plio pleistocene boundary and has continued until the present time it has proceeded to a more advanced stage in the middle and southern okinawa trough than it has farther north detailed bathymetric sea beam seismic reflection and magnetics data collected during the pop 1 cruise of the r v jean charcot reveal the principal features of the extensional processes the back arc spreading phase started very recently in the southern and middle okinawa trough as exemplified by several en echelon and in some cases overlapping active central graben oriented n70 e n80 e some of these depressions are intruded by volcanic ridges of fresh back arc basalt with associated large magnetic anomalies transform faults between these en echelon active rifts are not obvious we suggest that the major part of the southern okinawa trough is underlain by a thinned continental crust and that except for the system of en echelon rifts of the southern okinawa trough the back arc basin oceanic domain is limited to a width of a few tens of kilometers or less in the axial portion of the trough the system of axial back arc volcanic ridges that occur in the rifts ends at the latitude of okinawa island whereas active volcanoes in the ryukyu arc occur only north of okinawa island we refer to this transition between active arc and back arc volcanism as the volcanic arc rift migration phenomenon vamp globally back arc volcanism propagated from the southern okinawa trough to the okinawa vamp area rifting continues to occur in the northern okinawa trough but is not yet accompanied by associated volcanism the okinawa vamp area is characterized by a series of parallel basaltic ridges oriented n75 e with associated linear magnetic anomalies characteristic of dyke intrusions we suggest that the formation of the back arc oceanic domain took place along the axial back arc extensional zone trending n75 e and that this zone presently ends at the southern extremity of the active volcanic chain the initial phase of formation of back arc basin oceanic crust is non steady state and is characterized by the lack of a developed fracture zone pattern the termination of the vamp area in the direction of the volcanic zone of the arc is consistent with the suggestion of molnar and atwater that the volcanic arc is a fundamental line of weakness which determines where initial back arc spreading occurs apparently back arc extension initially occurred within the continental lithosphere located westward of the ryukyu arc along its whole length but the subsequent back arc volcanism was initiated in the southernmost portion of the region and then moved northward this migration was accompanied by the shutting down of volcanic activity along the abandoned portions of the arc it is this transfer of volcanism that we call the vamp process thus arc and back arc basin volcanism seem to be associated in such a manner that spreading tends to migrate simultaneously with a cessation in volcanic activity along the arc this interplay of arc and back arc activity is probably linked to changes in the parameters of plate convergence since the plate motion in the phillippine sea is oblique to the trench at least in the southern part of the okinawa trough we suggest that the oblique resisting force applied to the edge of the overriding plate engenders the development of en echelon extensional features within and behind the arc the motion of the ryukyu platelet with respect to eurasia is consequently an extensional strike slip motion trending roughly parallel to the okinawa trough

on the effect of the 3 d regional geology on the seismic design of critical structures the case of the kashiwazaki kariwa nuclear power plant

source complexity of the 1988 armenian earthquake evidence for a slow after slip event we analyzed teleseismic p and s waves using a multiple event deconvolution method to investigate the source process of the spitak armenia earthquake of december 7 1988 teleseismic long period body waves exhibit complex waveforms significantly more complex than those normally seen for an event of this size we identified two groups of subevents one is a group of strike slip events during the first 20 s the other is a dip slip event initiating at about 30 s after the initial rupture the tensor sum of all the subevents is essentially strike slip strike 302 dip 59 rake 143 with a scalar moment of 1 47 10 19 n m the seismic moment of the dip slip event strike 89 dip 60 rake 88 is 5 6 10 18 n m nearly 40 of the total and the moment release rate is slower than the other subevents with a strike slip mechanism we call this event a slow after slip event the mechanism of the after sup event is consistent with the present day deformation pattern in the caucasus where north south compression is predominant due to the continental collision between the arabian plate and the russian platform this result suggests that in a region where both strike slip motion and crustal shortening are taking place like southern california a large strike slip event may accompany large thrust events and vice versa in order to determine the total coseismic deformation pattern it is essential to resolve these multiple events in time space and mechanism

modified frequency wavenumber algorithm for regional seismograms using filon s quadrature modelling of lg waves in eastern north america summary the main focus of this study is to develop an efficient frequency wavenumber code to synthesize high frequency say 10 hz regional seismograms up to a distance of more than 1000 km in a medium consisting of a large number of crustal layers and investigate effects of regional waveguides on lg waves in this newly developed code the frequency wavenumber response is evaluated by using the filon s quadrature at high frequency and the polynomial approximation of bessei s functions implementing trapezoidal integration at low frequency this has reduced the computation time by several folds compared to the time needed for the trapezoidal integration using this algorithm both broad band seismograms at harvard and short period ectn eastern canadian telemetered network seismograms from 1988 november 25 saguenay earthquake were successfully modelled a moment magnitude of 5 9 was used initially an average waveguide was calibrated to successfully excite the regional pnl and snl waves at hrv its near surface structure constrained by matching the recorded frequency content the crust mantle transition zone was constrained by modelling the strength of the broad band snl waves consisting of sn ssmsnsmssms and ssmssms phases relative to the initial pnl waves the model was modified to consist of thin layers with an alternating high and low velocity distribution to match the high frequency ectn lg waves observed from 300 to 600 km away in addition the effect of a near surface irregular receiver structure on the duration of lg waves was also investigated by convolving its response with the regional lg seismograms initial study suggests this method as viable for modelling the entire lg waves including the coda numerical studies suggest that the shapes and peak amplitudes on lg seismograms depend more strongly on the source depth anelasticity and crustal waveguide than do the pnl seismograms

effects of biological soil crusts on surface roughness and implications for runoff and erosion abstract soil surface roughness has a strong influence on runoff and erosion affecting surface storage capacity water flow routing and velocity and modifying runoff rates it also reduces soil detachment by raindrops and the shear effect of water flow on the soil surface in arid and semiarid ecosystems biological soil crusts bscs commonly appear in clearings between plants depending on the dominant component in the bsc community the roughness of the soil surface may vary considerably changing the hydrologic and erosive response of the soil the aim of this study is to determine the effect of physical and biological crusts on soil surface roughness and their influence on runoff and erosion for this purpose we set up open plots containing different bsc types and treatments and recorded runoff and total erosion from all the events for 18 months micro topographic indexes were calculated from high resolution digital surface models of the plots built from terrestrial laser scanner height data after comparing different spatial resolutions and indexes we concluded that only the local random roughness index in a 40 mm moving window provided a precise estimation of the roughness induced by bscs though it did not have a direct effect on runoff response the best relationship between microtopography and runoff on biologically crusted soils was found for surface storage capacity which appears as a powerful predictor of the runoff coefficient on long temporal scales sediment yield was not well predicted by any of the micro topographic indexes studied the only index that was significantly related to sediment yield was the local random roughness in a 40 mm moving window but even this explained only a third of the erosion variance

spatial variation of the crustal stress field along the ryukyu taiwan luzon convergent boundary 1 we applied an improved stress inversion method to a comprehensive data set of earthquake focal mechanisms to depict the pattern of crustal stress along the western convergent boundary of the philippine sea plate our results indicate that the crustal stress along the ryukyu fore arc is segmented with boundaries at or near the places of seamount subduction including the tokara channel an extensional stress regime is observed along the entire ryukyu back arc implying that back arc rifting may have extended northward to kyushu a triangular area near the southernmost terminus of the ryukyu arc is characterized by a unique stress signature the eastern boundary of this ryukyu taiwan stress transition coincides with the 123 e meridian where the gagua ridge intercepts the ryukyu trench whereas its western boundary agrees remarkably well with the border between the postcollision and waning collision domains in northern taiwan the taiwan collision zone is dominated by compression that rotates locally according to the structural configuration of the lukang magnetization high lmh suggesting that the lmh may be critical in controlling the local stress distribution the stress signature of the luzon arc taiwan collision reaches as far south as 19 5 n the tectonic stress along the manila trench luzon fore arc is dominated by a complex regime of extension that cannot be explained by simple plate bending or in slab membrane stress since this extensional regime is observed only south of 22 n it probably marks the northern limit of the contemporary boundary between the subduction along the manila trench and the collision in taiwan

effect of a change in the state of stress on the likelihood of inland fault failure during the mw 6 6 iwaki earthquake resulting from the mw 9 0 2011 tohoku earthquake japan abstract a mw 6 6 earthquake occurred on 11 april 2011 in the iwaki area northeastern honshu arc inland japan hereafter the 2011 iwaki earthquake this event occurred just one month after the 2011 mw 9 0 off the pacific coast of tohoku earthquake 11 march 2011 hereafter the 2011 tohoku earthquake the 2011 iwaki earthquake was produced by near simultaneous slip on two faults the itozawa and yunodake faults here we examine the failure on the itozawa and yunodake faults with respect to the change in the state of stress in the iwaki area produced by the 2011 tohoku earthquake furthermore we quantitatively evaluate the excess fluid pressure our analysis reveals that the antecedent state of stress played an important role in the occurrence of the 2011 iwaki earthquake we demonstrate the importance of excess fluid pressure in terms of the initiation of the 2011 iwaki earthquake three end member models of failure were identified based on our modeling with different friction coefficients 1 high friction coefficients 0 75 in which case triggering of the iwaki earthquake would have required fluid pressure levels greater than those of 3 these pressures should have been regulated by fault valve action and evidence for such action should appear in the seismic record 2 low friction coefficients

a synthetic seismicity model for the middle america trench this paper develops a new iterative technique based on the concept of fault segmentation and computed using two dimensional static dislocation theory to build models of seismicity and fault interaction which are physically acceptable and geometrically and kinematically correct the technique is applied in two steps to seismicity observed at the middle america trench the first step constructs generic models which randomly draw segment strengths and lengths from a two dimensional probability distribution the second step constructs predictive models in which segment lengths and strengths are adjusted to mimic the actual geography and timing of large historical earthquakes both types of models not only reproduce the statistics of seismicity over five units of magnitude but also duplicate other aspects including foreshock and aftershock sequences migration of foci and the capacity to produce both characteristic when an isolated segment fails and noncharacteristic earthquakes when several adjacent or nearby segments fail in concert over a period of about 150 years the complex interaction of fault segments and the nonlinear failure conditions conspire to transform an apparently deterministic model into a chaotic one in that small changes in initial conditions ultimately lead to very different patterns of events at least for the middle america trench it seems doubtful that successful predictive models of earthquakes could span a much longer duration

automated near realtime cmt inversion the earthquake research institute eri of the university of tokyo has completely automated the process of determining source mechanisms of earthquakes using waveform data the solutions are automatically distributed using the internet without being checked the process is initiated by receipt of e mail giving the origin time and location of an earthquake to determine the source mechanism we apply the harvard centroid moment tensor cmt inversion method to long period body wave data the portion of the seismogram from the first arrival to the initial surface wave the method has been successfully applied since october 1993 to all of the major earthquakes in the world for which we received event e mail 108 of the 242 cmt solutions in 1994 were determined within 6 hours of the event with an average delay of 3 8 hours for local events e g events around japan it is also possible to determine cmt solutions within 30 minutes from the occurrence of the earthquakes using an efficient dialup data retrieval system operated by eri

stress and the direction of slip on fault planes the shear stress direction on a fault plane depends only on four of the six components of the stress tensor assuming only that the slip direction marks the shear stress direction on any fault plane and that stress is homogeneous it is possible to estimate these four stress parameters from populations of fault planes with known slip directions as several workers have observed different formulations of the problem may yield varying best fitting stresses and estimates of uncertainty in the simplest case no assumptions are made regarding the orientations of fault planes relative to the stress tensor thus the technique allows for the possibility that the fault planes may be very weak here we present simple analytical and graphical descriptions of the field of admissible fault geometries relative to any four parameter stress model which can be used to illustrate the significance of various inverse strategies in particular this paper explores the effects of using two alternative measures of misfit between an observed fault datum and stress model 1 the pole rotation the angle between the observed and predicted slip direction on the observed fault plane and 2 the minimum rotation the smallest angle between the observed fault geometry and any fault geometry which is consistent with the model by allowing for variation of the fault plane as well as the slip vector the minimum rotation procedure generally achieves a more stable and presumably realistic estimate of the actual discrepancy between a fault observation and stress model than the pole rotation procedure in a test case using 17 earthquake focal mechanisms from the yuii region of eastern taiwan separate inversions based on the two misfit criteria yield different optimum stress models and uncertainty estimates additional constraints on the stress tensor such as the effect of friction can be superimposed on the ones used here

metastable olivine wedge beneath the japan sea imaged by seismic interferometry the metastable olivine wedge mow within subducted slabs has long been hypothesized to host deep focus earthquakes 300 km its presence would also rule out hydrous slabs being subducted into the mantle transition zone however the existence and dimensions of mow remain debatable here we apply inter source interferometry which converts deep earthquakes into virtual seismometers to detect the seismic signature of mow without influence from shallow heterogeneities with data from the hi net we confirm the existence of mow beneath the japan sea and constrain its geometry to be 30 km thick at 410 km depth and gradually thinning to a depth of 580 km at least our result supports transformational faulting of metastable olivine as the initiation mechanism of deep earthquakes although large events m7 0 probably rupture beyond the wedge furthermore the slab core must be dehydrated at shallower depth and only transports negligible amount of water into the transition zone

hydrological responses and soil erosion potential of abandoned cropland in the loess plateau china recent changes in hydrological processes and soil erosion in the loess plateau china are immediate responses to cropland abandonment for revegetation which lead to a long term decrease in runoff generation and soil erosion however detailed hydrological responses and soil erosion changes have not been clearly evaluated in this study two issues were focused on the plot scale the first issue relates to changes in vegetation cover and soil properties during the early stages of revegetation given the occurrence of soil compaction it was hypothesized that runoff increased during this period and the soil erosion did not significantly decline even though vegetation increased the second issue is the effect of scale on runoff and soil erosion three plot groups of three vegetation types and two restoration stages were established for comparative experiments the results from these experiments confirmed that the soil compaction occurred during revegetation in this region greater runoff was produced in plot group that experienced both a longer restoration time and with higher vegetation cover such as groups 2 and 3 in this study than that with a shorter restoration time and lower vegetation cover group 1 in addition the total soil loss rates of all plot groups were rather low and did not significantly differ from each other this indicates that a reduction in runoff generation and soil erosion as a result of revegetation was limited in the early stages of restoration following the cropland abandonment with increasing plot area the runoff coefficient decreased for the plot group with a longer revegetation time groups 2 and 3 but gently increased for the one with a shorter restoration time group 1 in groups 2 and 3 soil loss rate decreased when plot area enlarged in group 1 it decreased before a plot area threshold of 18 m 2 was exceeded however the increase occurred when plot area crossed the threshold value in conclusion the high vegetation cover alone did not lead to reduction in the runoff coefficient during the early stages of revegetation when evaluating hydrological and soil erosion responses to revegetation the soil compaction processes should be considered additionally the effect of scale on runoff and soil erosion was found to be dependent on restoration extent and thus on restoration time c 2011 elsevier by all rights reserved

update of regional moment tensor analysis for earthquakes in new zealand and adjacent offshore regions abstract new zealand is one of the more seismically active countries in the world with over 15 000 earthquakes each year in new zealand and the adjacent offshore region routine regional moment tensor rmt analysis was implemented by geonet in 2007 and nearly 1300 rmt solutions have been calculated for the new zealand region from august 2003 through early september 2012 the new zealand rmt catalog contains events with moment magnitude m w 3 2 7 3 and centroid depth 2 375 km and includes rmt solutions from aftershock sequences for two major earthquakes 15 july 2009 m w 7 8 dusky sound and 3 september 2010 m w 7 1 darfield the rmt solutions provide important constraints on the active tectonics of new zealand including stress and strain and the rmt catalog along with 155 global centroid moment tensor project solutions is used to examine the relationship between m w and local magnitude m l for shallow focus 33 km depth the m l m w relationship is found to be similar across new zealand except for the fiordland region for all of new zealand except fiordland m l 0 93 0 06 m w 0 54 0 24 and for fiordland m l 0 83 0 04 m w 1 09 0 13 for deep focus earthquakes 33 km depth m l is consistently larger than m w by more than a full magnitude unit for some events the discrepancy between m l and m w is found to be depth dependent with m l m w 0 94exp h 75 37 0 80 where h is focal depth in km

precambrian to modern manganese mineralization changes in ore type and depositional environment manganese mineralization is diverse in occurrence origin mineralogy and geochemistry these variations reflect differences in the processes of formation and depositional environments which in turn are a response to changes in the land ocean atmosphere system over geological time as such manganese deposits can act as markers of major events in the dynamic evolution of the earth s surface modern manganese accumulations provide insights into key factors controlling manganese deposition that cannot readily be determined from examination of ancient ores a knowledge of oceanic currents ocean chemistry or small scale variations in physicochemical patterns of recent basins for example may extend our understanding of depositional processes in the past equally the study of precambrian deposits not only elucidates ancient mechanisms of manganese metallogenesis but also helps to unravel the impact of comprehensive environmental changes on metal deposition on a scale not realized in younger geological times

soil erosion by surface water flow on a stony semiarid hillslope soil erosion on hillslopes occurs by processes of soil splash from raindrop impacts and sediment entrainment by surface water flows this study investigates the process of soil erosion by surface water flow on a stony soil in a semiarid environment a field experimental method was developed whereby erosion by concentrated flow could be measured in predefined flow areas without disturbing the soil surface the method allowed for measurements in this study of flow erosion at a much wider range of slopes 2 6 to 30 1 per cent and unit discharge rates 0 0007 to 0 007 m2 s 1 than have been previously feasible flow velocities were correlated to discharge and hydraulic radius but not to slope the lack of correlation between velocity and slope might have been due to the greater rock cover on the steeper slopes which caused the surface to be hydraulically rougher and thus counteract the expected effect of slope on flow velocity the detachment data illustrated limitations in applying a linear hydraulic shear stress model over the entire range of the data collected flow detachment rates were better correlated to a power function of either shear stress r2 0 51 or stream power r2 0 59 published in 1999 by john wiley sons ltd

seismic moment tensor resolution on a local scale simulated rockburst and mine induced seismic events in the kopanang gold mine south africa seismic records contain information about the effect of the source as well as the effect of wave propagation through the rock mass the effect of wave propagation is usually not well known as only simplified models of geological structures are available therefore the information about the source retrieved by inverting seismograms may include errors due to incomplete knowledge of the rock mass along the propagation path which in turn cause a distortion in the calculated moment tensor mt the distortion of the mt on a local scale was observed by inverting records of a simulated rockburst conducted at the kopanang gold mine in south africa a dominant isotropic component of the explosive characteristics was found from the inversion the deviatoric components retrieved from the blast are spurious a test of their stability indicated that they are not significant assuming an uncertainty above 5 for velocities and 10 for attenuation within the homogeneous model available for the mine thus the retrieval of the mt from records of local networks in mines using a homogeneous model of the rock mass seems to be feasible however the homogeneous model of the rock mass can only be applied to close stations within a few kilometers of the source the seismic records from distant stations were too complex to be modelled by a homogeneous rock mass records of six mine induced seismic events recorded at the kopanang gold mine were also inverted a vertical linear dipole along the pressure p axis was found for three of the events suggesting a pillar burst the mechanism of two events contains an isotropic implosion together with a nearly vertical dip slip and seems to indicate a combination of a cavity collapse with a down dip slip along a nearly vertical fault one event corresponds to a dipole along the tensional t axis however it is vertical thus its association with tensile faulting of the hangingwall is uncertain

modeling of long period ground motions in the nankai subduction zone model simulation using the accretionary prism derived from oceanfloor local s wave velocity structures the accretionary prism in the subduction zone which consists of thick low velocity oceanic sediments significantly affects the propagation of seismic waves for shallow offshore earthquakes including large interplate earthquakes in order to simulate long period 5 s ground motions in the nankai subduction zone we constructed a three dimensional 3d seismic velocity structure model of the accretionary prism by interpolation extrapolation of local s wave velocity structures beneath 46 oceanfloor seismic stations donet which are deployed just above the accretionary prism off the southern kii and eastern shikoku regions we modeled local s wave velocity structures using a simple two parameter depth varying velocity function to investigate the effects of the accretionary prism on ground and seafloor motions we conducted numerical simulations of seismic wave propagation for three local earthquakes that occurred in southwestern japan the simulations reasonably reproduced the observed seismograms not only for the period ranges of the moment tensor inversion 50 s but also for the strong long period ground motions in the sedimentary basins 5 s especially in the region where donet stations are densely deployed since depth varying local s wave structures significantly improve the reproducibility of long period ground motions our modeling procedure is useful for modeling long period ground motions of local and regional offshore subduction zone earthquakes

the 12 july 1993 hokkaido nansei oki japan earthquake effects of source complexity on surface wave radiation abstract we present an analysis of the data dependency of surface wave inversions for source parameters of the 12 july 1993 hokkaido nansei oki japan earthquake this dependency is demonstrated by differences between source mechanisms obtained from different data sets particularly from rayleigh waves or love waves although inversions of various data sets yield unanimously thrust fault mechanisms for the inversion of rayleigh waves the mechanism is characterized by a shallow dipping west plunging nodal plane which is consistent with p wave first motion data and the distribution of aftershocks close to the hypocenter however for the inversion of both rayleigh and love waves the mechanism is characterized by a shallow dipping east plunging nodal plane several numerical experiments were carried out to test a hypothesis that the data dependency is attributed to the effects of source complexity on the surface wave radiation with the source complexity being characterized by tempo spatial changes in focal mechanism and moment release during the rupture process the experiments show that source parameters obtained from inversions of surface waves with periods as long as a few hundred seconds can be largely affected by using various models of source complexity proposed previously for the hokkaido earthquake and the effects on love waves tend to be systematically different from those on rayleigh waves our preferred source model is characterized by significant tempo spatial changes in focal mechanism the experiments based on this model provide a good explanation for the data dependency although our analysis cannot completely reject the alternative explanation that attributes the dependency to the manifestation of errors in modeling the surface wave propagation and or inversion instability the model is consistent with the data of body waves and long period surface waves for a very broad frequency band implying the existence of weak zones with various fault geometries along the eastern margin of the japan sea

spatial heterogeneity of soil detachment capacity by overland flow at a hillslope with ephemeral gullies on the loess plateau abstract ephemeral gullies are typical erosional landforms and widespread on the chinese loess plateau to better understand the spatial variability in soil detachment capacity dc by overland flow and its influence at a hillslope with an ephemeral gully this study investigates a hillslope on the loess plateau using classical statistics geostatistical analysis and principal component analysis undisturbed soil samples were collected from 202 sites along nine 90 m transects in two completely developed ephemeral gullies and were scoured in a laboratory flume under consistent hydraulic conditions the results indicate that dc varied widely from 0 0004 to 1 25 kg m 2 s 1 with a mean of 0 22 kg m 2 s 1 the coefficient of variation also shows a high variability in dc the ephemeral gullies were divided into four sections uppermost upper middle and lower slopes and dc differed significantly among the four sections a semivariogram of dc indicated a moderate spatial dependence the sampling interval significantly affects the spatial pattern of dc when the sampling interval decreased from 10 to 2 m the nugget variance decreased whereas structured variance spatial dependence and range increased distribution maps of dc derived from kriging interpolation showed that samples in the lower slope position have greater dc than the other positions dc significantly correlates with clay content sand content median soil grain size bulk density cohesion water stable aggregate and litter mass density principal component analysis pca and a minimum data set mds method identified that the median soil grain size bulk density and litter mass density were the major factors affecting the spatial variability in dc

iranian regional centroid moment tensor catalog solutions for 2012 2017 abstract in 2012 the installation of broadband seismic stations in iran allowed the beginning of the moment tensor project of iranian earthquakes by the iranian seismological center irsc in a period of five years 194 moment tensors with 3 7 mw 7 6 were computed based on analysis of seismograms recorded at local and regional distances included in the catalog are the moment tensors of 83 events not modeled by gcmt a reasonable consistency exists between the mechanisms of common events in the two catalogs the average moment magnitude difference is 0 1 and the kagan angle is below 20 for 61 of the earthquakes the p b and t axes difference is up to 15 the moment tensor catalog of iran shows a decrease of the magnitude of completeness by 0 3 after this study the number of accepted solutions as a fraction of attempts of the project with the average of 55 increased from 40 in 2012 to 68 in 2016 due to the expansions of the seismic networks in iran the dataset includes earthquakes from all seismic zones in iran with the dominance of thrust faulting the calculated depths in this study are consistent with the subregion seismotectonic conditions of iran the information on seven earthquakes with mw 6 0 and 53 events with 5 0 mw

shallow intraplate seismicity related to the illapel 2015 mw 8 4 earthquake implications from the seismic source abstract the september 16 2015 mw 8 4 illapel chile earthquake is the first large event occurring in north central chile after the 1943 earthquake filling a known seismic gap in the region the earthquake took place in a complex tectonic region nearby an area where transition from erosive to accretionary margin occurs due to the collision of juan fernandez ridge jfr along the chilean margin we inverted the kinematic rupture process of the 2015 mw 8 4 illapel earthquake from the joint inversion of teleseismic body waves and near field data the relative weighting between datasets and the weighting of spatial temporal constraints are objectively estimated by applying the akaike s bayesian information criterion the coseismic slip model yields a total seismic moment of 4 92 1021 nm occurred over 120 s the rupture shows both downdip and updip propagation with slip extending along the thrust interface from 50 km depth to shallow near trench depths

okinawa trough backarc basin early tectonic and magmatic evolution the okinawa trough lying between japan and taiwan is a backarc basin formed by extension within the continental lithosphere behind the ryukyu trench arc system stress directions associated with the two last extensional phases in the southwestern okinawa trough have been deduced from a comparison with analog modeling the direction of extension is n 150 o for the pleistocene phase of extension 2 0 1 ma and n 170 o for the late pleistocene holocene phase of extension 0 1 0 ma the present day ryukyu volcanic arc a narrow continuous feature extending from japan to taiwan is located on the eastern side of the okinawa trough 80 100 km above the wadati benioff zone the minimum depth for emplacement of arc magmatism scarce present day backarc volcanism appears in the middle and southern okinawa trough within linear en echelon bathymetric depressions a n045 o oriented seamount volcanic chain cuts across obliquely the southwestern okinawa trough and lies in the direct line of extension of the gagua ridge a n s linear volcanic feature of the philippine sea plate associated with this extension of the gagua ridge a large reentrant located at the base of the ryukyu prism the uplift of part of the nanao forearc basin and the deformation of the sedimentary arc suggest that the voluminous cross backarc volcanism could be tied to the subduction of the gagua ridge located there at a depth of 80 100 km beneath the backarc basin a second area of anomalous volcanism has been identified in the middle okinawa trough in the ene extension of the daito ridge a wnw ese 400 km long volcanic feature of the philippine sea plate we suggest that the gagua and daito ridges initially induced stress at the base of the arc which is still brittle and cracks propagated through the overlying brittle lithosphere allowing magmas with arc affinities to erupt at the seafloor this excessive magmatism reaches the seafloor through conduits which preferentially follow in their shallowest portion the crustal normal faults of the backarc rifts the okinawa trough is consequently still in an early stage of evolving from arc type to backarc activity

creeping subduction zones are weaker than locked subduction zones faults that are fully or partially locked pose the greatest seismic hazard because they accumulate stress that can then be released in large earthquakes in contrast other faults continuously creep the creeping versus locked behaviour is probably related to the frictional properties of the fault and the effective normal stress on the fault but it is unclear whether locked faults are weaker or stronger than creeping faults here we use stress orientations in subduction zones from inversion of earthquake moment tensors and find that geodetically determined creeping versus locked behaviour is correlated with the orientation of the subduction zone plate boundary fault relative to the principal stress axes globally locked subduction zones appear well oriented for failure assuming a typical laboratory friction coefficient creeping subduction zones are more poorly oriented implying a lower apparent friction coefficient due to either low intrinsic friction or reduced effective normal stress the spatial variations of stress orientation on the japan trench are similarly correlated with spatial variations in coupling with creeping regions having a lower apparent friction coefficient than locked regions the absolute strength of faults is influenced by the ambient fluid pressure which is often elevated in subduction zones this suggests low overall strength for locked subduction zone faults and additional strength reduction in creeping zones that may be due to transient elevated fluid pressures the faults in creeping segments of subduction zones are weaker than those in locked segments according to analyses of stress orientations and gps data from subduction zones globally

earthquakes along the ryukyu kyushu arc strain segmentation lateral compression and the thermomechanical state of the plate interface we systematically determined the focal depths and mechanisms of 49 large to moderate sized earthquakes mb 5 4 that occurred along the ryukyu kyushu arc since 1963 by inverting the waveforms and amplitudes of p and sh wave trains at teleseismic distances the results are sufficiently precise to delineate seismogenic structures near the plate interface in detail revealing features not predicted by plate kinematics in contrast to previous studies of this arc and those along other subduction zones shallow seismicity along the plate interface is systematic showing two distinct layers of activities the second layer of seismicity is delineated by a few earthquakes that occurred at depths between 50 and 65 km some 10 20 km directly beneath the seismogenic portion of the interplate thrust zone these earthquakes indicate lateral compressional strain within the subducted slab as their p axes are subparallel to the local strike of the arc not perpendicular to the arc as one would expect from the direction of plate convergence the occurrence of these events cannot be accounted for by membrane stress due to the geometry of the subducted slab to our knowledge similar earthquakes occurred only beneath the northern indoburman ranges and along the banda arc where subducted slabs as part of the indian plate are being dragged northward with their northern edges bumping into east west trending collision zones nearby by drawing an analogy between the tectonic settings of these three regions we interpret events beneath the plate interface along the ryukyu kyushu arc as a consequence of ongoing collision between the philippine sea plate and eurasia near taiwan the interplate thrust zone is largely aseismic down to a depth of approximately 30 km a large number of earthquakes showing low angle thrust faulting commence at this depth and are accompanied by two events that show antithetic thrust faulting at a slightly shallower depth of 20 25 km these observations suggest that the strength of the plate interface increases significantly below the depth of proximately 25 5 km based upon available heat flow measurements between the trench axis and the volcanic arc we estimated the temperature field and magnitude of shear traction along the interplate thrust zone the deepest interplate earthquakes 40 50 km correspond to temperatures of approximately 730 980 c comparable to the limiting temperature of intraplate mantle earthquakes 800 c and that of intermediate and deep focus earthquakes at wadati benioff zones potential temperature 900 k therefore the cessation of seismicity in general is probably controlled by similar temperature conditions regardless of the tectonic settings of source regions the magnitude of shear traction along the seismogenic portion 40 50 km depth of the interplate thrust zone seems to be of the order of 100 mpa which in turn implies a low average coefficient of friction of only 0 10 0 05 considerably less than those observed for laboratory specimens the inception of intermediate focus earthquakes within the subducted slab is at a depth of about 100 km whereas shallow earthquakes show no apparent variations along the entire arc intermediate depth earthquakes indicate downdip extension along the northern end of the arc near kyushu but abruptly change to downdip compression along the rest of the arc all available evidence indicates that this is a spatial pattern unrelated to earthquake cycles at the moment tectonic interpretation of such a distinct strain segmentation along the arc is enigmatic without the presence of clear discontinuities in the age of the subducted slab the sudden switch in the strain field of the slab is difficult to explain by the continuously varying rate of subduction along the arc in any case this pattern of strain segmentation requires the presence of a major accommodation structure such as a tear fault in the subducted slab near the tokara channel appendix is available with entire article on microfiche order from american geophysical union 2000 florida ave n w washington dc 20009 document b91 004 2 50 payment must accompany order

an improved method for determining the regional stress tensor using earthquake focal mechanism data application to the san fernando earthquake sequence the orientations of fault planes and slip directions indicated by a population of earthquake focal mechanisms can be used to determine best fit regional principal stress directions and r 2 1 3 1 a measure of relative stress magnitudes under the assumption of uniform stress in the source region this analysis allows for the possibility that failure occurs on preexisting zones of weakness of any orientation in the inversion we perform a grid search of stress models to find the one which requires the smallest total rotation of all the fault planes that is needed to match the observed and predicted slip directions the method allows for errors in orientations of both the fault planes and slip directions we have an objective means for identifying the more likely of the two possible fault planes from each focal mechanism relative to a given stress model thus we do not face the problem of ambiguity of nodal planes which plagues other analyses of this kind by using a grid search of stress models rather than a linearization scheme we are able to perform a realistic error analysis and thus establish confidence limits for the preferred regional stresses the method can be used to investigate possible stress inhomogeneities during earthquake sequences by analyzing subsets of the data population the technique has been applied to 76 events from the san fernando earthquake sequence for which we have found best fit stresses plunge and azimuth 1 7 187 2 27 281 3 62 84 and r 0 65 the average misfit between this stress model and all the data is about 8 and all but eight of the aftershocks have misfits of less than 20 these values are considerably less than the uncertainty of the focal mechanism determinations therefore significant stress inhomogeneities are not required by the data our analysis does not support the suggestion of a change in stresses during the aftershock sequence as proposed by others on the basis of an apparent change in focal mechanisms

effects of grass roots on the erodibility of topsoils during concentrated flow abstract traditional vegetative techniques to control gully development rely mainly on the effects of above ground biomass whereas little attention has been given to the role of below ground biomass yet in a context where above ground biomass may temporarily or spatially disappear e g due to fire or grazing roots can play an important role in protecting soil against erosion few studies have investigated the impacts of roots of natural vegetation such as grass on the resistance of topsoils in concentrated flow erosion zones although grasses grow in many environments therefore the objective of this study is to investigate the impact of root density and root length density of grass on the erodibility of root permeated saturated topsoils three plots were established on a sandy loam their treatments were 1 bare 2 low density drilled grass and 3 high density drilled grass simulating different root densities after one month topsoil samples were taken and subjected to concentrated flow using a hydraulic flume in the laboratory slope flow discharge mean velocity water temperature and sediment concentration were measured root density and root length density values were assessed relative soil detachment rates and mean flow shear stresses were calculated the results indicate a negative exponential relation between the relative soil detachment rate and root density as well as root length density independent of the applied flow shear stresses however the best relationship fitting the data is the hill curve indicating that relative soil detachment rates decrease to very low values 0 05 with an increase in root density from 0 to 4 kg m 3 or root length density from 0 to 400 km m 3 a comparison between the effects of vegetation cover on sheet and rill erosion rates and those of the root area ratio of grass roots on relative soil detachment rates reveals that grass roots are very effective in reducing soil detachment rates the equations obtained can be used to predict the effect of grass roots on soil erosion rates during concentrated runoff and to evaluate the ability of roots to increase topsoil resistance against erosion by concentrated flow calculations of relative erosion rates using the equations from the rusle and wepp models indicate that the observed trend is better predicted with the rusle model and the wepp model for croplands than with the wepp model for rangelands

centroid moment tensor catalogue for indonesia abstract we developed a centroid moment tensor cmt catalogue of earthquakes in and around indonesia inacmt using data from the nationwide broadband seismograph network in indonesia we obtained cmt solutions for about 500 earthquakes that occurred in and around indonesia between 2006 and 2009 the moment magnitudes ranged from 4 5 to 8 3 we examined the accuracy of the cmt solutions of the inacmt catalogue by comparing them with those obtained by the global cmt gcmt project the seismic moments and focal mechanisms of these catalogues were highly consistent with each other but we found systematic differences between the catalogues in the source centroid locations of earthquakes off sumatra the inacmt source centroid locations were closer to the hypocenter locations in the preliminary determination of earthquakes pde of the u s geological survey compared to those of gcmt the systematic deviations in the gcmt source centroid locations may mainly reflect insufficient azimuthal coverage of the stations used for the inversions as well as uncertainties in the earth model using the inacmt catalogue we investigated seismic activity related to the off bengkulu seismic sequence on 12 september 2007 mw 8 3 7 9 and 6 8 southwest of sumatra and the earthquakes northwest of the island of new guinea on 3 january 2009 mw 7 7 and 7 4 in the aftershock activity of the 2007 off bengkulu seismic sequence we found that shallow earthquakes were aligned along the eastern coast of siberut island located between the sunda trench and sumatra these earthquakes may have occurred along the mentawai fault or another unknown fault the focal mechanisms of the earthquakes were dominantly reverse slip although the mentawai fault has been considered to be a strike slip fault shallow large earthquakes along this fault may cause damage above the source region and generate large tsunamis we found that the 2009 earthquakes northwest of new guinea occurred along the manokwari trough and that the aftershocks were aligned along a plane dipping about 30 to the south indicating that the pacific and or philippine sea plate subducts below the australian plate at the manokwari trough the inacmt catalogue enables us to perform detailed analyses of seismic activity in and around indonesia which contributes to better understanding of tectonic features and potential seismic and tsunami hazards in indonesia as well as the coastal regions of the pacific and indian oceans

broadband analysis of the 21 september 1993 klamath falls earthquake sequence the source characteristics of the klamath falls earthquake sequence were estimated from broadband seismograms recorded by the berkeley digital seismic network bdsn terrascope and western united states iris stations solutions were obtained for events ranging in size from mw 3 8 to mw 6 0 an empirical green s function inverse approach was used to estimate kinematic source parameters of the two mw 6 0 mainshocks both events were found to have ruptured northwest on adjacent segments of the lake of the woods system of normal faults the two main shocks abut where there is a pronounced 10 to 20 clockwise rotation of strike which may have initially acted as a barrier to a through going mw 6 2 event

real time determination of seismic moment tensor for the italian region this work has been funded by the 2005 2007 dpc s4 and 2008 2010 dpc s3 italian civil protection contracts

automatic regional moment tensor inversion in the european mediterranean region summary we produce fast and automatic moment tensor solutions for all moderate to strong earthquakes in the european mediterranean region the procedure automatically screens near real time earthquake alerts provided by a large number of agencies each event with magnitude m 4 7 triggers an automatic request for near real time data at several national and international data centres moment tensor inversion is performed using complete regional long period 50 100 s waveforms initially the data are inverted for a fixed depth to remove traces with a low signal tonoise ratio the remaining data are then inverted for several trial depths to find the best fitting depth solutions are produced within 90 min of an earthquake we analyse the results for the period 2000 april to 2002 april to evaluate the performance of the procedure for quality assessment we compared the results with the independent swiss regional moment tensor catalogue srmt and divided the 87 moment tensor solutions into three groups 38 a quality solutions with well resolved m w depth and focal mechanism 21 b quality solutions with wellresolved m w and 28 unreliable c quality solutions the non homogeneous station and event distributions varying noise level and inaccurate earthquake locations affected solution quality for larger events m w 5 5 we consistently obtained a quality solutions for m w 4 5 5 5 we obtained a and b quality solutions solutions that pass empirical rules mimicking the a posteriori quality for our data set are automatically disseminated

outer rise seismicity boosted by the maule 2010 mw 8 8 megathrust earthquake abstract the maule 2010 megathrust earthquake mw 8 8 has been characterized by two coseismic high slip patches asperities north and south of the epicenter separated by a region of lower slip here we invert full broadband waveforms to obtain regional moment tensors yielding precise centroid depth and source parameters of outer rise events mw 4 5 including a large mw 7 4 event that occurred just 1 5 h after the maule mainshock outer rise seismicity occurred mainly in two clusters 1 a large number of outer rise events in the subducting plate located just seaward of the northern asperity of the maule earthquake and 2 a second cluster with fewer events seaward of the southern edge of the maule rupture area thus the outer rise seismicity is correlated with the coseismic rupture of the maule earthquake reflecting the stress state of the interplate coupled zone the moment tensor results indicate similar extensional focal mechanisms for all outer rise events in the northern zone in the southern region most of the outer rise events are also extensional except for one strike slip event located near the oceanic mocha fracture zone the centroid depths vary from 5 to 20 km depth and present similar magnitudes many of the outer rise events nucleated near the mocha fracture zone including the mw 7 4 event and one strike slip event the calculated yield strength envelope for the oceanic nazca lithosphere suggests that the centroid depths of intraplate tensional events span almost the entire upper brittle part of the oceanic lithosphere

effect of natural restoration time of abandoned farmland on soil detachment by overland flow in the loess plateau of china vegetation restoration has significant effects on soil properties and vegetation cover and thus affects soil detachment by overland flow few studies have been conducted to evaluate this effect in the loess plateau where a great green project was implemented in the past decade this study was carried out to quantify the effects of age of abandoned farmland under natural vegetation restoration on soil detachment by overland flow and soil resistance to erosion as reflected by soil erodibility and critical shear stress the undisturbed soil samples were collected from five abandoned farmlands with natural restoration age varying from 3 to 37 years the samples were subjected to flow scouring in a 4 0 m long by 0 35 m wide hydraulic flume under six different shear stresses ranging from 5 60 to 18 15 pa the results showed that the measured soil detachment capacities in currently cultivated farmland were 24 1 to 35 4 times greater than those of the abandoned farmlands for the abandoned farmlands soil detachment capacities fluctuated greatly due to the complex effects of root density and biological crust thickness and could be simulated well by flow shear stress and biological crust thickness with a power function nse 0 851 soil erodibility of abandoned farmlands decreased gradually with restoration age and reached a steady stage when restoration age was greater than 28 years the critical shear stress of the natural abandoned farmlands declined when restoration age was less than 18 years and then increased due to the episodic influences of vegetation recovery and biological crust development more studies in the loess plateau are necessary to quantify the relationship between soil detachment capacity and biological crust thickness for better understanding the mechanism of soil detachment under natural vegetation restoration copyright 2013 john wiley sons ltd

moment tensor inversions for local earthquakes using surface waves recorded at terrascope we have developed a method to determine moment tensors for local earthquakes using short period 10 to 50 sec surface waves recorded at terrascope stations to correct for the substantial lateral variations in crustal structure we applied phase corrections to the data using a regionalized phase velocity model we have determined moment tensors for over 180 events in the last 3 yr in southern california for magnitudes as small as 3 2 and as large as 6 5 the results are consistent with those obtained from first motion data as well as other waveform inversions when continuous data telemetry from the stations becomes available this method can yield moment tensors for earthquakes in southern california and adjacent regions within minutes after the occurrence of an event our results confirm the relation log m o seismic moment 1 5m l local magnitude obtained by an earlier study

crustal and upper mantle structure in the ryukyu island arc deduced from deep seismic sounding summary in 1984 an extensive geophysical investigation was conducted in the northernmost part of the ryukyu island arc south of kyushu island japan the aim of this investigation was to obtain new information on the nature of crust and upper mantle at the continental margin through various geophysical measurements seismic profiling gravity magnetism sea beam and heat flow this paper presents the crust and upper mantle structure deduced from ocean bottom seismographic profiling conducted along two lines one line 190 km long was taken behind the northernmost part of the ryukyu island arc parallel to the major tectonic units i e the okinawa trough ryukyu arc and ryukyu trench the other 295 km long was perpendicular to the tectonic units along these profiles we deployed ocean bottom seismograms spaced 10 20km apart as a controlled source we used both explosives and an airgun array the experiment was successful and provided quite important information on the tectonics of a trenchisland arc back arc system the velocity structure obtained for the profile behind the ryukyu islands has continental properties the sediment thickness is 3 4 km although it shows lateral variations due to basement undulation the velocities of the upper and lower crust are 5 8 6 2 and 6 6 6 8 km s respectively the total crustal thickness decreases southwestward from 27 30 to 23 24 km this is direct evidence for crustal thinning associated with the process of back arc spreading the velocity structure along the profile from the trench to the island arc clearly shows the subduction accretion and deformation at this margin the crust beneath the trench has oceanic properties the sediment thickness is 1 3 3 0 km beneath which the igneous basement shows severe undulation the total crustal thickness is 7 8 km the p velocity is slightly less than 8 0 km s our seismic data revealed a huge sedimentary wedge located 50 150 km landward of the trench the maximum thickness of this wedge exceeds 12 km the origin of this wedge may be oceanic because the p wave velocity in its eastern half is almost comparable to that obtained for the trench area the velocity structure landward of the wedge is continental and similar to that obtained for the profile behind the island arc

quantifying the surface covering binding and bonding effects of biological soil crusts on soil detachment by overland flow biological soil crusts bscs have impacts on soil detachment process through surface covering and binding and bonding b b mechanisms which might vary with successional stages of bscs this study was conducted to quantify the effects of surface covering binding and bonding of bscs on soil detachment capacity by overland flow in a 4 m long hydraulic flume with fixed bed two dominant bsc types developed well in the loess plateau the early successional cyanobacteria and the later successional moss were tested using natural undisturbed soil samples collected from the abandoned farmlands two treatments of undisturbed crusts and one treatment of removing the above ground tissue of bscs were designed for each bsc type for comparison bare loess soil was used as the baseline the collected soil samples were subjected to flow scouring under six different shear stresses ranging from 6 7 to 21 2 pa the results showed that soil detachment capacity dc and rill erodibility kr decrease with bsc succession and the presence of bscs obviously increased the critical shear stress especially for the later successional moss crust for the early successional cyanobacteria crust dc was reduced by 69 2 compared to the bare loess soil where 37 7 and 31 5 are attributed to the surface covering and b b respectively for the later successional moss crust dc decreased by 89 8 compared to the bare loess soil where 68 9 and 20 9 contributed to the surface covering and b b respectively these results are helpful in understanding the influencing mechanism of bscs on soil erosion and in developing the process based erosion models for grassland and forestland copyright 2017 john wiley sons ltd

monitoring of strain release in central and northern california using broadband data systematic cataloguing of seismic moment depth and mechanism of regional earthquakes down to magnitude m 4 can now be achieved in close to real time using data from sparse networks of digital broadband stations the procedure we have developed relies on 3 independent methods for the determination of moment tensor providing confidence limits on the results we show the results of application to the seismicity in central and northern california for a one year period starting in march 1992 and illustrate how patterns of stress and strain release can now be monitored systematically and reliably in a timely fashion

comparison of centroid moment tensor and first motion solutions for western mediterranean earthquakes abstract comparison of centroid moment tensor and first motion solutions shows that the two different methods give compatible solutions for moderate sized earthquakes in the western mediterranean while the centroid moment tensor solution provides a good indication of the general style of deformation occurring in an area careful consideration of the first motion solution is still necessary for detailed study of source mechanics there is no obvious character of the centroid moment tensor solution such as small values of moment or large non double couple contribution that can be used as diagnostic of a significantly different first motion solution

topographic zonation of infiltration in the hilly loess region north china field infiltration tests using portable rainfall infiltrometers were conducted in the wangjiagou experimental basin in the hilly loess region of north china based on data collected at 27 sites a topographic zonation of infiltration characteristics was observed the average steady infiltration rate and the average ponding time decreased from the hilltop to the hillslope and further decreased to the gully wall such a zonation is closely related to the variations of topography soil and land use conditions in the study area a general infiltration model is proposed collected field data are used to establish the applicability of the proposed model in the study area

detailed fault structure of the 2000 western tottori japan earthquake sequence we investigate the faulting process of the aftershock region of the 2000 western tottori earthquake m w 6 6 by combining aftershock hypocenters and moment tensor solutions aftershock locations were precisely determined by the double difference method using p and s phase arrival data of the japan meteorological agency unified catalog by combining the relocated hypocenters and moment tensor solutions of aftershocks by broadband waveform inversion of freesia f net we successfully resolved very detailed fault structures activated by the mainshock the estimated fault model resolves 15 individual fault segments that are consistent with both aftershock distribution and focal mechanism solutions rupture in the mainshock was principally confined to the three fault elements in the southern half of the zone which is also where the earliest aftershocks concentrate with time the northern part of the zone becomes activated which is also reflected in the postseismic deformation field from the stress tensor analysis of aftershock focal mechanisms we found a rather uniform stress field in the aftershock region although fault strikes were scattered the maximum stress direction is n107 e which is consistent with the tectonic stress field in this region in the northern part of the fault where no slip occurred during the mainshock but postseismic slip was observed the maximum stress direction of n130 e was possible as an alternative solution of stress tensor inversion

rupture process of the april 24 2017 mw 6 9 valparaiso earthquake from the joint inversion of teleseismic body waves and near field data abstract the central chilean margin 32 33 s is characterized by the subduction of the juan fernandez ridge jfr beneath the continental south american plate the jfr corresponds to a hotspot track composed by seamounts typically 3 3 5 km high above the surrounding seafloor with a ridge trench collision zone underlying the prominent valparaiso forearc basin vfb this region has been affected by several large and mega earthquakes where the last event corresponds to a complex seismic sequence that took place at the southern edge of vfb in april 2017 the spatio temporal distribution of the seismic events is characterized by a predominant southeast migration of the seismicity an mw 6 9 earthquake triggered two days after the sequence started and occurred at the northern end of the rupture area of the 1985 mw 8 0 valparaiso earthquake we compute the kinematic rupture process of the 2017 mw 6 9 valparaiso earthquake from the joint inversion of teleseismic body waves and near field data the akaike s bayesian information criterion was used to objectively estimate both the relative weighting between datasets and the weighting of spatial and temporal constraints used as a priori information the coseismic slip is distributed over an area of dimensions 35 10 km2 with a maximum slip of 1 5 m the rupture propagated unilaterally downdip the source duration from the moment rate solution is 20 s with a total seismic moment of 3 05 1019 nm mw 6 9 the analysis of the seismicity shows that most of the events occurred along the plate interface foreshock clustered northern from the mainshock epicenter and the aftershocks occurred to the southeast at a deeper location the inverted regional moment tensors show similar faulting mechanism than the mainshock the seismic sequence started two days before the mainshock and lasted for about two weeks and a migration pattern of the seismicity was observed the rupture of the 2017 mw 6 9 earthquake nucleated where the san antonio seamount belonging to the jfr is subducting and propagated downwards along a zone that presents high interseismic coupling the complex seismic sequence might be explained by an aseismic slip transient in the zone and the influence of the downdip migration of fluids from the accretionary prism along the subduction channel the erosive and tunneling effect left by the sudden slip of the subducting seamount might provide the cavity for downdip migration of fluids and subsequent swarm seismicity