dynamics of the 1984 rock avalanche and associated distal debris flow on mount cayley british columbia canada implications for landslide hazard assessment on dissected volcanoes abstract in 1984 a mass of quaternary pyroclastic rock est vol 0 74 106m3 slid from the western flank of mount cayley volcano in southwest british columbia the disintegrating rock mass entrained a further 0 20 106 m3 and formed a rock avalanche that travelled a horizontal distance of 3 46 km from its source over a vertical elevation difference of 1 18 km equivalent to a fahrboschung of 19 from the superelevation of the debris trimline in the mid path it is estimated that velocities reached at least 42 m s in the upper part of its path velocities may have approached 70 m s the rock avalanche was partially transformed into a distal debris flow that travelled a further 2 6 km down turbid creek in a narrow channelised path to the squamish river temporarily blocking it the motion of the rock avalanche including the production of a distal debris flow was successfully simulated using a dynamic analytical model both the results of this analysis and field evidence indicate that the rock avalanche did not come to a halt in the upper part of its path as suggested by cruden and lu 1992 but travelled to its distal limit in one uninterrupted movement this finding has important implications for landslide hazard assessment at mount cayley and similar sites the landslide is typical of those which occur on the steep slopes of dissected volcanoes and is one of seven high velocity rock avalanches that have occurred in the garibaldi volcanic belt of southwest british columbia since 1855

retrieval of super virtual refraction by cross correlation topography and severe variations of near surface layers lead to travel time perturbations for the events in seismic exploration usually these perturbations could be estimated and eliminated by refraction technology the virtual refraction method is a relatively new technique for retrieval of refraction information from seismic records contaminated by noise based on the virtual refraction this paper proposes supervirtual refraction interferometry by cross correlation to retrieve refraction wavefields by summing the cross correlation of raw refraction wavefields and virtual refraction wavefields over all receivers located outside the retrieved source and receiver pair this method can enhance refraction signal gradually as the source receiver offset decreases for further enhancement of refracted waves a scheme of hybrid virtual refraction wavefields is applied by stacking of correlation type and convolution type super virtual refractions our new method does not need any information about the near surface velocity model which can solve the problem of directly unmeasured virtual refraction energy from the virtual source at the surface and extend the acquisition aperture to its maximum extent in raw seismic records it can also reduce random noise influence in raw seismic records effectively and improve refracted waves signal to noise ratio by a factor proportional to the square root of the number of receivers positioned at stationary phase points based on the improvement of virtual refraction s signal to noise ratio using results from synthetic and field data we show that our new method is effective to retrieve refraction information from raw seismic records and improve the accuracy of first arrival picks

application of super virtual seismic refraction interferometry to enhance first arrivals a case study from saudi arabia complex near surface anomalies are one of the main onshore challenges facing seismic data processors refraction tomography is becoming a common technology to estimate an accurate near surface velocity model this process involves picking the first arrivals of refracted waves one of the main challenges with refraction tomography is the low signal to noise ratio characterizing the first break waveform arrivals especially for the far offset receivers this is especially evident in data recorded using reflection acquisition geometry this low signal to noise ratio is caused by signal attenuation due to geometrical spreading of the seismic wavefield near surface generated noise and amplitude absorption super virtual refraction interferometry improves the quality of the first break picks by enhancing the amplitude of the refracted waves and attenuating the amplitude of the random noise

on a plane wave based crosscorrelation type seismic interferometry we explored a new approach to retrieve virtual seismic responses from crosscorrelating acquired seismic data in the plane wave domain using this method slant stacking is first performed over shot or receiver locations of observed seismic data to produce plane wave transformed gathers crosscorrelation is then performed by selecting traces with the same ray parameters from different shot or receiver locations of the plane wave gathers unlike traditional crosscorrelation type time space domain interferometry where full range of ray parameters is used for each survey location this method directly selects common ray parameters to cancel overlapping raypaths this approach can be used to retrieve reflections in the presence of dispersive waves and to select certain ranges of ray parameters with directional wave paths for retrieval it can avoid spurious arrivals in supervirtual interferometry when unwanted arrivals such as reflections break the requirement of conventional interferometry in addition computation time can be saved with this approach because plane wave transform usually results in a reduction of the original data volume we demonstrate this method with synthetic and ocean bottom seismometer data examples

surface features of uniaxial tensile fractures and their relation to rock anisotropy in inada granite abstract uniaxial tensile fractures parallel to the rift grain and hardway planes were formed in inada granite most of the fractures split the rock forming mineral grains as transgranular paths under microscopic observations the surface topography of the fractures was measured by the stereo photogrammetric technique and is different in different orientations the rift parallel uniaxial fracture has the smoothest surface and the grain parallel fractures are smoother than hardway parallel fractures the mineral compositions are also different on the failed surfaces of different directions the rift parallel fractures have almost the same constituent mineral ratio as the parent rock however the grain parallel fractures pass preferentially through feldspar grains and contain less quartz grains as compared to the bulk composition of the parent rock in addition it is remarkable on hardway parallel fractures it is considered that the differences of surface topography and mineral compositions are caused by preferred orientations and spatial distributions of pre existing microcracks in inada granite

a new practical method for prediction of geomechanical failure time abstract predicting the failure time of geo hazards is an important rock mechanics problem we first evaluated the validity of the inverse velocity inv method to predict failure time of rock mass and landslides this method utilizes rates of displacement or strain to predict the actual failure time tf so the value of total displacement or strain before failure is not crucial second we developed a new method for computing failure time predictions based on the slope gradient to predict tf termed the slo method finally a simple conceptualised model representing safe and unsafe predictions was proposed to validate these hypotheses prediction of rock mass failure in the asamushi and vaiont landslides in situ studies was conducted furthermore laboratory conditions were incorporated into the research which include predictions using circumferential strain and axial strain from uniaxial compression creep test on shikotsu welded tuff swt and predictions of failure time for inada granite under brazilian creep tests it was found that the slo method is better than the inv method slo gave safe predictions in all the cases in contrast inv tends to give unsafe predictions predicted failure time tfp tf our findings reveal that predictions using circumferential strain are better than those made using axial strain for swt and notably given failure with very short tertiary creep the methods tend to show limited reliability however the slo method could find extensive application in predicting failure time of geo hazards for instance roof wall failure in mines etc

coseismic and postseismic deformation of the 2016 m w 6 6 aketao earthquake from insar observations and modelling on november 25 2016 the mw 6 6 aketao earthquake occurred in xinjiang western china we used the combination of ascending sentinel 1a descending sentinel 1b and ascending alos 2 palsar data to measure the coseismic deformation the line of sight los coseismic deformation implies that the earthquake was dominated by right lateral strike slip ignoring the fault perpendicular deformation the fault parallel and up down deformation was extracted based on the combination of sentinel 1a and 1b observations results show that the maximum fault parallel deformation is 13 7 cm at the north wall and the minimum is 16 5 cm at the south wall of the muji fault then coseismic slip distribution was derived using the steepest descent method sdm based on a single segment fault model using the three insar los observations as constraints the slip distribution reveals two slip centers the maximum slip of the eastern center is 0 5 m at a depth of 8 8 km where the rake angle is 181 2 the maximum slip of the western center is 0 6 m at a depth of 10 8 km where the rake angle is 181 1 the derived seismic moment obtained equals the mw 6 6 earthquake in this study postseismic deformation time series in 1 5 years after the earthquake were retrieved from 26 multi temporal sentinel 1 descending scenes the postseismic los deformation at the north and south walls of muji fault both increases with time but in opposite directions the cumulative deformation is 60 80 mm at the north wall and 30 to 20 mm at the south wall the postseismic deformation shows similar patterns with the coseismic deformation and has the same mechanism there is no obvious lock at the unbroken gap

source receiver interferometric redatuming using sparse buried receivers to address complex near surface environments a case study of seismic imaging quality and time lapse repeatability

seismic imaging of the olduvai basin tanzania abstract a 5 6 km long line of refraction and reflection seismic data spanning the pliocene pleistocene fill of the olduvai basin tanzania is presented the line is oriented along a northwest southeast profile through the position of olduvai gorge coring project ogcp borehole 2a our aims are to 1 delineate the geometry of the basin floor by tracing bedrock topography of the metaquartzitic and gneissic basement 2 map synsedimentary normal faults and trace individual strata at depth and 3 provide context for the sequence observed in ogcp cores results with refraction tomography and poststack migration show that the maximum basin depth is around 405 m 25 m in the deepest portion which quadruples the thickness of the basin fill previously known from outcrops variations in seismic velocities show the positions of lower density lake claystones and higher density well cemented sedimentary sequences the bed i basalt lava is a prominent marker in the refraction seismic results bottom most sediments are dated to 2 2 ma near where borehole 2a bottoms out at the depth of 245 m however the seismic line shows that the basin fill reaches a maximum stratigraphic thickness of around 380 m deep at borehole 2a in the western basin where the subsidence was greatest this further suggests that potential hominin palaeoenvironments were available and preserved within the basin fill possibly as far back as around 4 ma applying a temporal extrapolation using the average sediment accretion rate

using supervirtual first arrivals in controlled source hardrock seismic imaging well worth the effort varied applications of seismic interferometry have arisen in the last decade however the potential of the method to improve reflection seismic processing in hardrock environments has not explicitly been regarded therefore in this paper we investigate the potential of retrieving the first arrivals originally hindered by high noise level in the exploitation of controlled source data acquired over the iron oxide apatite rich deposit at grangesberg sweden and its mining induced structures the supervirtual first arrivals retrieved using interferometry methodologies allowed first breaks to be picked more extensively than in the original data revised static corrections significantly improved the linearity of the first arrivals and continuity of reflections in the source gathers especially reflections considerably enhanced in the source gathers stacked constructively in the final section comparison with geological data supported by traveltime forward modelling indicates that these reflections represent the unmined part of the deposit other reflections at shallower depth are interpreted as anthropogenic faults possibly located at lithological contacts tomographic inversion was also run using the augmented traveltime data the greater resolution and penetration of this new tomographic image allowed better bridging with the results of the reflection seismic section velocity anomalies depict the presence of mining induced structures and a potential brewery fault which is believed to put at risks an urban area even though the potential of first arrival retrieval seems to be case dependent this study illustrates that interferometry may substantially improve the accuracy of static corrections and subsequent stack for hardrock imaging as well as in the penetration and resolution of traveltime tomograms

inferred fault geometry and slip distribution of the 2010 jiashian taiwan earthquake is consistent with a thick skinned deformation model abstract we invert measurements of coseismic displacements from 139 continuously recorded gps sites from the 2010 jiashian taiwan earthquake to solve for fault geometry and slip distribution using an elastic uniform stress drop inversion the earthquake occurred at a depth of 23 km in an area between the western foothills fold and thrust belt and the crystalline high mountains of the central range providing an opportunity to examine the deep fault structure under taiwan the inferred rupture plane is oblique to the prominent orientation of thrust faults and parallel to several previously recognized nw striking transfer zones that appear to connect stepping thrusts we find that a fault striking 318 344 with dip of 26 41 fits the observations well with oblique reverse sinistral slip under a low stress drop of about 0 5 mpa the derived geodetic moment of 2 92 10 18 n m is equivalent to a m w 6 24 earthquake coseismic slip is largely concentrated within a circular patch with a 10 km radius at the depth between 10 and 24 km and maximum slip of 190 mm we suggest this earthquake ruptured the nw striking chishan transfer fault zone which we interpret as a listric ne dipping lateral ramp with oblique slip connecting stepping thrust faults ramps the inferred slip on the lateral ramp is considerably deeper than the 7 15 km deep detachment identified in previous studies of western taiwan we infer an active basal detachment under western taiwan at a depth of at least 20 23 km based on these inversion results the earthquake may have nucleated at the base of the lateral ramp near the intersection with the basal detachment coulomb stress change calculations suggest that this earthquake moved several ne striking active thrust faults in western taiwan nearer to failure

coseismic deformation of the 2016 taiwan mw6 3 earthquake using insar data and source slip inversion abstract an earthquake of seismic moment magnitude mw 6 3 occurred in southern taiwan on february 6th 2016 in this paper we use differential interferometric synthetic aperture radar d insar technology and data from the sentinel 1a s 1a iw radar satellite to estimate the coseismic deformation of this event on the basis of ascending data insar analysis reveals a circle like uplift area 45 km in diameter 20 km northwest of the epicenter that has a maximum line of sight los displacement of 12 cm south and east of this uplift area minor subsidence occurred while descending data indicated uplift in the west and sink in the east with maximum values of 8 0 cm and 6 0 cm respectively displacements are continuously distributed across the entire deformed region implying that the seismogenic fault did not pierce the earth s surface based on these insar displacements coupled with gps observations we inverted the distribution of source slip using an elastic half space fault model both separately and jointly four kinds of inversion results consistently show a slip concentration to the northwest of the epicenter with maximum slip in the range 0 35 0 55 m confined to depths of 6 15 km in the crust the source fault is dominated by thrust with left lateral strike slip joint inversion using insar ascending and descending data as well as gps data resulted in maximum slip of 0 44 m within the range determined by separate inversions inversion results show that this was a mw6 25 earthquake consistent with measurements collected by the united states geological survey usgs

theory of supervirtual refraction interferometry summary inverting for the subsurface velocity distribution by refraction traveltime tomography is a well accepted imaging method by both the exploration and earthquake seismology communities a significant drawback however is that the recorded traces become noisier with increasing offset from the source position and so accurate picking of traveltimes in far offset traces is often prevented to enhance the signal to noise ratio snr of the far offset traces we present the theory of supervirtual refraction interferometry where the snr of far offset head wave arrivals can be theoretically increased by a factor proportional to here n is the number of receiver or source positions associated with the recording and generation of the head wave arrival there are two steps to this methodology correlation and summation of the data to generate traces with virtual head wave arrivals followed by the convolution of the data with the virtual traces to create traces with supervirtual head wave arrivals this method is valid for any medium that generates head wave arrivals recorded by the geophones results with both synthetic traces and field data demonstrate the feasibility of this method there are at least four significant benefits of supervirtual interferometry 1 an enhanced snr of far offset traces so the first arrival traveltimes of the noisy far offset traces can be more reliably picked to extend the useful aperture of the data 2 the snr of head waves in a trace that arrive later than the first arrival can be enhanced for accurate traveltime picking and subsequent inversion by later arrival traveltime tomography 3 common receiver pair gathers can be analysed to detect the presence of diving waves in the first arrivals which can be used to assess the nature of the refracting boundary and 4 the source statics term is eliminated in the correlation operations so that the timing of the virtual traces is independent of the source excitation time this suggests the possibility of applying this method to earthquake data recorded by receivers that are inline with the refraction paths and source locations

understanding the kinematic behavior of the active gascons rockslide from in situ and satellite monitoring data abstract the monitoring of the 410 000 m3 coastal gascons rockslide began in 2009 this paper presents and analyzes combined in situ and satellite based monitoring data to interpret the kinematic behavior of the slide and the evolution of the rockslide and the possible mechanisms that can lead to an accelerating phase of movement the available data are 1 relative displacements measured by thirteen crackmeters and manually with an extensometer tape 2 absolute displacements obtained from inclinometers and vertical shape accelerometer arrays in boreholes total station surveys and satellite based point target analysis insar pta 3 the settlement of the railway ballast monitored by two horizontal shape accelerometer arrays 4 groundwater pressures from nine vibrating wire piezometers and 5 weather conditions the study indicates that the role of water on displacements varies spatially within the rockslide the rockslide s kinematic behavior enables us to develop evolution scenarios of the rockslide which could be useful to conduct a risk analysis this leads to the identification of critical zones for railroad safety the unique set of monitoring data helps to elucidate the complexity of the rockslide s behavior

static stress transferred by the 1999 chi chi taiwan earthquake effects on the stability of the surrounding fault systems and aftershock triggering with a 3d fault slip model we investigated the effect of changes in static stress caused by the 1999 m l 7 3 chi chi earthquake on the surrounding fault systems in taiwan we examined this problem from two perspectives first we applied a statistical test for the hypothesis of static stress triggering by comparing the distributions of the coulomb failure stress changes on the focal mechanism nodal planes both before and after the mainshock since preshocks could obviously not have been affected by the mainshock the deviation of these distributions determined the significance of static stress triggering second we calculated the coulomb failure stress changes on the chukou and meishan faults in specified slip directions to evaluate the stability of these two active faults after the chi chi earthquake the static stress changes were obtained by applying the theory of dislocation in an elastic half space to a 3d rupture model derived from the surface displacements associated with the chi chi earthquake our results showed that the distributions of the coulomb failure stress changes for events preceding and following the chi chi earthquake were significantly different yet consistent with the hypothesis of static stress triggering we also found that both the chukou and the meishan faults were in stress shadows at depths shallower than 10 km however because a number of aftershocks fell in these stress shadows it is possible that other mechanisms such as dynamic stress were responsible for triggering these events manuscript received 6 november 2000

a modified delay time method for statics estimation with the virtual refraction topography and near surface heterogeneities lead to traveltime perturbations in surface land seismic experiments usually these perturbations are estimated and removed prior to further processing of the data a common technique to estimate these perturbations is the delay time method we have developed the modified delay time method wherein we isolate the arrival times of the virtual refraction and estimate receiver side delay times the virtual refraction is a spurious arrival found in wavefields estimated by seismic interferometry the new method removes the source term from the delay time equation is more robust in the presence of noise and extends the lateral aperture compared to the conventional delay time method we tested this in an elastic 2d numerical example where we estimated the receiver delay times above a horizontal refractor taking advantage of reciprocity of the wave equation and rearranging the common shot gathers into common receiver gathers isolated source delay times could also be obtained

enhanced refractor imaging by supervirtual interferometry refraction surveys are a well established method of imaging subsurface velocities both in terms of the deep crustal structure at global scales and in the shallow near surface these surveys generally involve deploying an array of receivers on the surface or water bottom and recording arrivals from a seismic source initiated at or near the surface

circumferential strain behavior during creep tests of brittle rocks abstract creep tests were carried out on inada granite under confining pressure and on dry and wet specimens of kamisunagawa sandstone distinctive points qa the point where the axial strain rate reaches a minimum qc the point where the magnitude of circumferential strain rate reaches a minimum and rc the point where the magnitude of circumferential strain acceleration begins to increase were defined dependency of the strain values at the distinctive points on creep stress confining pressure and water presence was examined circumferential strain at qc or rc was not affected by creep stress for both rocks peak load points were observed in reloading stress strain curves when reloading was carried out before qc for kamisunagawa sandstone circumferential strain values at peak load during reloading coincided with critical extensile strain which is defined as circumferential strain value at peak load during constant strain rate tests and is insensitive to confining pressure water presence and anisotropy although slightly affected by strain rate load increased slightly or did not increase when reloading was carried out after rc for both rocks rc in creep tests scattered around unloading stress strain curves from peak load during constant strain rate tests for kamisunagawa sandstone these observations suggest that qc and rc in creep tests are closely related to the peak load points during constant strain rate tests circumferential strain would be used as a condition insensitive damage indicator of rock in creep tests as well as in constant strain rate tests

a dislocation model of strain accumulation and release at a subduction zone strain accumulation and release at a subduction zone are attributed to stick slip on the main thrust zone and steady aseismic slip on the remainder of the plate interface this process can be described as a superposition of steady state subduction and a repetitive cycle of slip on the main thrust zone consisting of steady normal slip at the plate convergence rate plus occasional thrust events that recover the accumulated normal slip because steady state subduction does not contribute to the deformation at the free surface deformation observed there is completely equivalent to that produced by the slip cycle alone the response to that slip is simply the response of a particular earth model to embedded dislocations for a purely elastic earth model the deformation cycle consists of a coseismic offset followed by a linear in time recovery to the initial value during the interval between earthquakes for an elastic viscoelastic earth model elastic lithosphere over a viscoelastic asthenosphere the postearthquake recovery is not linear in time records of local uplift as a function of time indicate that the long term postseimic recovery is approximately linear suggesting that elastic earth models are adequate to describe the deformation cycle however the deformation predicted for amore simple elastic half space earth does not reproduce the deformation observed along the subduction zones in japna at all well if stick slip is restricted to the main thrust zone as recognized earlier by shimazaki seno and kato the uplift profiles could be explained if stick slips were postulated to extend along the plate interface beyond the main thrust zone to a depth of perhaps 100 km but independent evidence suggests that stick slip at such depths if unlikely less

source complexity of the 4 march 2010 jiashian taiwan earthquake determined by joint inversion of teleseismic and near field data abstract the jiashian earthquake m l 6 4 occurred on 4 march 2010 it was the largest inland event in southern taiwan of 2010 the mainshock location was unexpected since it occurred in an area with relatively low background seismicity in addition reports of earthquake focal mechanisms do not fit with any known active fault geometry in order to understand the origin of this earthquake especially its rupture process we perform a joint source inversion by using teleseismic body wave gps coseismic displacements and near field ground motion data in this study we considered a northwest southeast trending fault with a northeast dip retrieved from gps coseismic data and aftershocks distribution to analyze the detailed slip distribution in space and time we used near field 3d green s functions provided by spectral element method and a full time space inversion technique we find a complex rupture process with several slip patches distributed inside two main asperities the slip map reveals a mean slip of 12 9 cm for a maximum slip of 27 3 cm leading to a m w 6 47 for this event the rupture initiates in the deepest portion of the fault at 20 km depth and propagated upward up to 2 km depth to form the two asperities the source time function of this event revealed two pulses corresponding to the two asperities for a total duration time of about 16 s most aftershocks occurred near the upper boundary of the deepest asperity while no aftershocks are located close to the shallowest one we infer that the locations of these slip patches are related to the surrounding fault systems that may have restricted the rupture propagation during the earthquake

increasing the number and signal to noise ratio of obs traces with supervirtual refraction interferometry and free surface multiples summary the theory of supervirtual interferometry is modified so that free surface related multiple refractions can be used to enhance the signal to noise ratio snr of primary refraction events by a factor proportional to ns where ns is the number of post critical sources for a specified refraction multiple we also show that refraction multiples can be transformed into primary refraction events recorded at virtual hydrophones located between the actual hydrophones thus data recorded by a coarse sampling of ocean bottom seismic obs stations can be transformed in principle into a virtual survey with p times more obs stations where p is the order of the visible free surface related multiple refractions the key assumption is that the refraction arrivals are those of head waves not pure diving waves the effectiveness of this method is validated with both synthetic obs data and an obs data set recorded offshore from taiwan results show the successful reconstruction of far offset traces out to a source receiver offset of 120km the primary supervirtual traces increase the number of pickable first arrivals from approximately 1600 to more than 3100 for a subset of the obs data set where the source is only on one side of the recording stations in addition the head waves associated with the first order free surface refraction multiples allow for the creation of six new common receiver gathers recorded at virtual obs station located about half way between the actual obs stations this doubles the number of obs stations compared to the original survey and increases the total number of pickable traces from approximately 1600 to more than 6200 in summary our results with the obs data demonstrate that refraction interferometry can sometimes more than quadruple the number of usable traces increase the source receiver offsets fill in the receiver line with a denser distribution of obs stations and provide more reliable picking of first arrivals apotentialliabilityofthismethodisthatlong offsetrefractionarrivalsextractedbyinterferometry might not necessarily be head waves from deeper refraction interfaces the extracted arrivals might be from a shallower interface and so only supply redundant information about that portion of the subsurface nevertheless our tomography example shows the value of these arrivals in reducing artefacts and increasing resolution in the tomogram

extracting earth s elastic wave response from noise measurements recent research has shown that noise can be turned from a nuisance into a useful seismic source in seismology and other fields in science and engineering the estimation of the system response from noise measurements has proven to be a powerful technique to convey the essence of the method we first treat the simplest case of a homogeneous medium to show how noise measurements can be used to estimate waves that propagate between sensors we provide an overview of physics research dating back more than 100 years showing that random field fluctuations contain information about the system response this principle has found extensive use in surface wave seismology but can also be applied to the estimation of body waves because noise provides continuous illumination of the subsurface the extracted response is ideally suited for time lapse monitoring we present examples of time lapse monitoring as applied to the softening of soil after the 2011 tohoku oki earthquake the detection of a precursor to a landslide and temporal changes in the lunar soil

innovative consideration of a directional appraisal parameter as destabilized criterion of the colluvial landslide as the instability criteria of the singular dimension displacement of a landslide are limited and insufficient a new appraisal parameter the vertical displacement direction rate is considered in landslide stability model in this paper then the displacement directional rate variation at different evolutional stages of landslide stability and its significance in landslide forecasting are systematic analyzed on the basis of the different evolutional rules of the vertical displacement directional rate in the different deformation stages the destabilized criterion of this kind of parameter is established in terms of the principle of statistics furthermore according to the destabilized criterion a calculation and evaluation of the stability of xintan landslide is carried out by means of the appraisal parameter of the vertical displacement direction rate the result of analysis is basically consistent with the practical deforming law of the landslide the result above indicates that the vertical displacement direction rate is an effective appraisal parameter serving as an essential and stable criterion for the stability evaluation of a slope therefore this directional appraisal parameter is of very special significance and also suitable and effective in the prediction of landslides

the structure of the crust and uppermost mantle beneath south china from ambient noise and earthquake tomography summary two years of continuous recordings of ambient seismic noise observed at 354 stations in south china from 2009 to 2010 are used to estimate rayleigh wave group and phase velocity maps from 6 to 40 s period these results are merged with rayleigh wave phase velocity maps from 25 to 70 s period derived from earthquakes in the same time frame eikonal tomography generates the dispersion maps which by monte carlo inversion are used to estimate a 3 d vsv model of the crust and upper mantle down to a depth of 150 km across all of south china with attendant uncertainties a clear image emerges of the west yangtze block a region of the western yangtze craton characterized by relatively thick crust 40 km overlying a seismic mantle lithosphere that extends to at least 150 km that may have been the nucleus for the formation of the yangtze craton in the archean and may present a present day obstacle to the eastward expansion of tibet the west yangtze block contrasts with the thinner crust 30 km and mantle lithosphere 70 80 km beneath the eastern yangtze craton and south china foldbelt these observed differences are consistent with processes associated with flat slab subduction in the mesozoic that may have eroded the lithosphere of the eastern yangtze craton and the south china foldbelt

slope creep behavior observations and simulations rock slopes undergoing long term effects of weathering and gravity may gradually deform or creep downslope leading to geological structures such as bending bucking fracturing or even progressive failure this study uses geomechanics based numerical modeling to qualitatively explain the cause and evolution of slope creep behavior constitutive models used include the creep mohr coulomb and anisotropic models the last two models are used with the strength reduction in calculation first the results of field investigation around a landslide site occurring in slate are present the causes and modes of creep structures observed on slopes and underground are studied second the study investigates the influences of slope topography and anisotropy orientations on slope creep behavior finally progressive failure of slopes with different shapes is examined the simulated results show that the bending type of structures develops near slope surfaces and the buckling type of structures is associated with the deformation or slides of a slope the creep pattern varies with the orientation and position of an original planar structure the shear zone involves a joint or fracture along which displacement has taken place moreover creep behavior is more significant on slopes with greater height and inclination as well as on steeper portions whether on concave or convex slopes in addition with the same topographic conditions consequent slopes with coinciding cleavage and obsequent slopes with steep cleavage result in greater creep behavior without the effects of anisotropic cleavage concave and straight slopes develop failure surfaces from the crowns downwards whereas convex slopes develop failure surfaces from the toes upwards

3d velocity structure around the source area of the 1999 chi chi taiwan earthquake before and after the mainshock 3d v p and v p v s models for the source area before and after the chi chi earthquake are derived from a tomographic inversion of seismic travel time data from the taiwan central weather bureau seismic network cwbsn resulting 3d velocity models reveal a strong lateral variation in the crust particularly at a depth range of 5 to 25 km along the trend of the dipping chelungpu thrust in general low v p and high v p v s anomalies are found in and around the source volume of the chi chi earthquake a volume centered around the entire 100 km 40 km chelungpu rupture surface we pay special attention to the crustal properties and their changes due to the chi chi event and the association of the crustal anomalies with seismicity combining the results with those of other geological and geophysical surveys the crustal anomalies are interpreted as images of a highly fractured and fluid filled chi chi source region fluid overpressure is known to reduce the strength of the fault zone and in this case may have initiated the nucleation of the chi chi earthquake the v p models obtained before and after the chi chi event show some interesting heterogeneities regions of low v p anomaly appear to have further expanded with the occurrence of the chi chi earthquake the v p v s model shows high anomalies near the source rupture especially near where the rupture is believed to have nucleated after the chi chi event the v p v s model shows a substantial change that may reflect an outward shift of the fluid filled fractured source region this shift is shown by a general expansion in v p v s anomalies to a broader region e g where two intensive aftershock clusters occurred and a significant v p v s reduction to more normal values near the chelungpu rupture we attribute these changes in v p and v p v s anomalies as well as the expansion and shift of the anomalous regions to be a response to the localized stress change caused by the slip of the chi chi rupture the location of the seismic events is correlated with that of the crustal v p and v p v s anomalies large events appear to occur in the transition zones of both v p and v p v s anomalies this finding may be of use in the identification of weakened crustal regions in a seismic zone thus suggesting where impending large earthquakes are likely to occur all input data and initial and final models of this article are given as electronic files in the cd attached to the end of this issue

failure forecast for large rock slides by surface displacement measurements forecasting the failure of large rock slides is difficult because of nonlinear time dependency and seasonal effects which affect the displacements starting from the accelerating creep theory prop