role of geological structure in the occurrence of earthquake induced landslides the case of the 2007 mid niigata offshore earthquake japan abstract the landslides induced by the mid niigata offshore earthquake in 2007 m jma 6 8 occurred mostly along the shore of the japan sea this study focused on the landslides that occurred near the hijirigahana cape yoneyama town in the niigata prefecture the study area is located in the western region of the central niigata prefecture along the japan sea the geology of the landslide area is dominated by late miocene sandstone rich member of alternating beds of sandstone and siltstone these strata gently dip to the north at approximately 25 to 30 and form cataclinal and orthoclinal slopes on the north and west facing slopes respectively the central niigata region is one of the most landslide prone areas in japan the study area is located approximately 30 km from the epicenter of the earthquake with an estimated intensity of 6 lower in the jma japan meteorological agency scale a group of landslides occurred in the study area the area contains the most concentrated set of landslides from this earthquake even though it is located far from the epicenter most of the landslides occurred on north facing slopes but two occurred on west facing slopes the landslides on the north facing slopes are characterized as translational slides the largest rock slide in the study area unit d width 100 m length 230 m slipped along the bedding plane of the strata observations from slickenlines from the slip surface and outcrop in the upper portion of unit d suggest that before this earthquake landslides frequently occurred on the north facing slopes and were controlled by the bedding plane with the exception of the largest one other landslides on north facing slopes were mostly debris slides indicating that sediments from older landslides exist the second largest landslide occurred on a west facing orthoclinal slope a rotational rock slide unit a was 80 m wide and 100 m long during the excavation after the landslide a high angle fault with a sw dip was identified behind the crushed zone based on field observation the fault was considered to be a non tectonic fault and created by gravitational movement during the excavation the crushed zone was identified on the cutting wall of the slope these results revealed that the relatively larger rotational rock slides occurred because of the existence of the crushed zone due to older events that caused the slippage along a non tectonic fault

regional scale co seismic landslide assessment using limit equilibrium analysis abstract traditionally regional assessment of seismic slope stability has been done using the infinite slope rigid sliding block analysis a major disadvantage of this approach is the resulting overestimation of the critical acceleration of the slope due to the underlying assumption of a predefined slope failure plane and consequently the underestimation of hazard areas prone to sliding in this paper we present a modified approach for assessing seismic slope instabilities using a model based on limit equilibrium analysis and circular slip surfaces with no restriction to any predefined slope failure plane for this purpose we conduct a parametric study to identify the relationship between the critical acceleration of the slope the slope angle and the slope shear strength parameters we model typical slopes in the rocscience software slide using bishop s limit equilibrium method to identify the critical accelerations that corresponds to a failure plane with factor of safety equal to one the critical accelerations were plotted against the variables in the parametric study and the best fit equations were obtained the proposed approach was developed for global application but it was tested using the well documented co seismic landslide database of the 1994 northridge ca earthquake the predicted sliding areas were compared to the inventory of landslides that were triggered in the val verde region in los angeles by the earthquake qualitative and quantitative assessments of the proposed model clearly show its advantages in predicting potential sliding areas

case history of landslide movement during the northridge earthquake we document a case history of northridge earthquake induced movement of a coherent landslide mass comprised principally of weathered previously sheared siltstone information on the residual shear strength of the material through which the sliding occurred is available both from backanalysis of a static rainfall induced failure on the same slope and laboratory test data postearthquake field reconnaissance data establishes the seismic slope displacements near the slope crest a yield coefficient is estimated for the slope based on residual shear strengths and measured groundwater levels at the time of the northridge earthquake this yield coefficient is used with four horizontal equivalent acceleration time histories that approximate the seismic demand within the slide mass in newmark sliding block displacement analyses the calculated displacements range from approximately 20 to 90 mm which compares well with observed displacements at the slide scarp of approximately 50 mm

empirical predictive models for earthquake induced sliding displacements of slopes earthquake induced sliding displacement is the parameter most often used to assess the seismic stability of slopes the expected displacement can be predicted as a function of the characteristics of the slope yield acceleration and the ground motion e g peak ground acceleration yet there is significant aleatory variability associated with the displacement prediction using multiple ground motion parameters to characterize the earthquake shaking can significantly reduce the variability in the prediction empirical predictive models for rigid block sliding displacements are developed using displacements calculated from over 2 000 acceleration time histories and four values of yield acceleration these empirical models consider various single ground motion parameters and vectors of ground motion parameters to predict the sliding displacement with the goal of minimizing the standard deviation of the displacement prediction the combination of peak ground acceleration and peak ground velocity is the tw

landslides triggered by the 22 july 2013 minxian zhangxian china mw 5 9 earthquake inventory compiling and spatial distribution analysis abstract on july 22 2013 an earthquake of ms 6 6 occurred at the junction area of minxian and zhangxian counties gansu province china this earthquake triggered many landslides of various types dominated by small scale soil falls slides and topples on loess scarps there were also a few deep seated landslides large scale soil avalanches and fissure developing slopes in this paper an inventory of landslides triggered by this event is prepared based on field investigations and visual interpretation of high resolution satellite images the spatial distribution of the landslides is then analyzed the inventory indicates that at least 2330 landslides were triggered by the earthquake a correlation statistics of the landslides with topographic geologic and earthquake factors is performed based on the gis platform the results show that the largest number of landslides and the highest landslide density are at 2400 m 2600 m of absolute elevation and 200 m 300 m of relative elevation respectively the landslide density does not always increase with slope gradient as previously suggested the slopes most prone to landslides are in s sw w and nw directions concave slopes register higher landslide density and larger number of landslides than convex slopes the largest number of landslides occurs on topographic position with middle slopes whereas the highest landslide density corresponds to valleys and lower slopes the underlying bedrocks consisting of conglomerate and sandstone of lower paleogene eb register both the largest number and area of landslides and the highest landslide number and area density values correlations of landslide number and landslide density with perpendicular and along strike distance from the epicenter show an obvious spatial intensifying character of the co seismic landslides the spatial pattern of the co seismic landslides is strongly controlled by a branch of the lintan dangchang fault which indicates the effect of seismogenic fault on co seismic landslides in addition the area affected by landslides related to the earthquake is compared to the relationship of area affected by landslides vs earthquake magnitude constructed based on earthquakes worldwide and it is shown that the area affected by landslides triggered by the minxian zhangxian earthquake is larger than that of almost all other events with similar magnitudes

using multiple logistic regression and gis technology to predict landslide hazard in northeast kansas usa abstract landslides in the hilly terrain along the kansas and missouri rivers in northeastern kansas have caused millions of dollars in property damage during the last decade to address this problem a statistical method called multiple logistic regression has been used to create a landslide hazard map for atchison kansas and surrounding areas data included digitized geology slopes and landslides manipulated using arcview gis logistic regression relates predictor variables to the occurrence or nonoccurrence of landslides within geographic cells and uses the relationship to produce a map showing the probability of future landslides given local slopes and geologic units results indicated that slope is the most important variable for estimating landslide hazard in the study area geologic units consisting mostly of shale siltstone and sandstone were most susceptible to landslides soil type and aspect ratio were considered but excluded from the final analysis because these variables did not significantly add to the predictive power of the logistic regression soil types were highly correlated with the geologic units and no significant relationships existed between landslides and slope aspect

spatial distribution of landslides triggered by the 2008 ms 8 0 wenchuan earthquake china abstract the ms 8 0 wenchuan earthquake of may 12 2008 is one of the most disastrous earthquakes in china the earthquake triggered tens of thousands of landslides over a broad area including shallow disrupted landslides rock falls deep seated landslides and rock avalanches some of which buried large sections of some towns and dammed the rivers the purpose of this study is to investigate correlations between the occurrence of landslides with geologic and geomorphologic conditions and seismic parameters over 56 000 earthquake triggered landslides with a total area of 811 km 2 are interpreted using aerial photographs and remote sensing images taken following the earthquake the spatial distribution of these landslides is analyzed statistically using both landslide point density lpd defined as the number of landslides per square kilometer and landslide area density lad the percentage of the area affected by landslides to determine how the occurrence of landslides correlates with distance from the epicenter distance from the major surface rupture seismic intensity and peak ground acceleration pga slope angle slope aspect elevation and lithology it is found that both lad and lpd have strong positive correlations with slope steepness distance from the major surface rupture and seismic intensity and that pre sinian schist and cambrian sandstone and siltstone intercalated with slate have the most concentrated landslide activities followed by the permian limestone intercalated with shale and devonian limestone statistical analyses also indicate that the major surface rupture has influence on the spatial distribution of landslides because lad and lpd are relatively higher on the hanging wall than on the footwall however the correlation between the occurrence of landslides with distance from the epicenter of the earthquake is complicated rather than a relatively simple negative correlation as found from other reported cases of earthquakes this is possibly due to complicated rupture processes of the earthquake

modeling study of variable upwelling circulation in the east china sea response to a coastal promontory abstracta three dimensional high resolution numerical model is used to investigate processes and dynamics of an intensified upwelling that is induced by a coastal promontory over the east china sea ecs shelf the center of the intensified upwelling around the promontory has been constantly observed but so far it has been dynamically unexplained forced by an idealized southeasterly wind stress the model results well capture the observed upwelling at the lee of the coastal promontory the intensified upwelling is formed by a strengthened shoreward transport downstream of the promontory as the upwelling jet veers shoreward the jet is mainly controlled by a cross shore geostrophic balance and is largely modulated by both centrifugal acceleration associated with nonlinear advection and by bottom stress the strengthened shoreward transport is mainly attributed to the cross shore geostrophic current that is induced by a countercurrent negative pressure gradient force pgf and partly attributed to th

landslides induced by the wenchuan earthquake and the subsequent strong rainfall event a case study in the beichuan area of china abstract the wenchuan earthquake on may 12 2008 triggered massive landslides and a subsequent strong rainfall prompted the development of new landslides as well as the reactivation of some pre existing landslides the highest seismic intensity zone of the wenchuan earthquake in beichuan china was selected as a case study to analyze the influence of the earthquake and the subsequent heavy rains on landslide evolution we selected this study area 414 km 2 since it was close to the coseismic surface rupture and because it suffered strong ground motion based on the interpretation of high resolution aerial photographs and remote sensing imagery combined with field investigation 40 pre earthquake landslides and 2221 coseismic landslides were identified with total landslide areas of 2 68 km 2 and 30 81 km 2 respectively there were 134 large over 50 000 m 2 co seismic landslides that covered a surface area of 15 54 km 2 and represented approximately 50 4 of the total area of the co seismic landslides the coseismic landslides were mainly located on the hanging wall of the causative fault and on the steep valley sides of the jian river and its tributaries a strong rainfall event occurred four months after the wenchuan earthquake and induced 969 new landslides which covered a 6 90 km 2 area and enlarged 169 existing landslides 2 48 km 2 the landslides were identified in spot5 images ultimately we found that earthquake tremors and the subsequent rainstorm severely disturbed the surface strata resulting in a large number of landslides

spatial and temporal analysis of landslides in central taiwan after 1999 chi chi earthquake abstract the hilly western foothill of taiwan island is highly prone to landslides especially during the typhoon season in the summer of 1999 the chi chi earthquake mw 7 6 resulted in tremendous amount of landslides in central taiwan the impact of this earthquake not only makes the geology more fractured but also changes the morphology in the western foothill area the geohazards in this area including debris flows and flooding after 1999 are closely related to the spatial and temporal behavior of these landslides focusing on the ta chia river wu river and chuo shuei river this study investigated the behavior of landslides in central taiwan after 1999 four major typhoon events i e toraji 2001 mindulle 2004 sinlaku 2008 and morakot 2009 were included in this study the study comprises two major parts i e the analysis of catchment landslides and the study of time effects the first part includes correlation analysis with rainfall and geology and the second part consists of time effects modeling of the impact of 1999 chi chi earthquake compared to typhoon toraji fewer and fewer reactivated landslides were induced by the subsequent typhoon events this finding reveals the self healing effect after the 1999 chi chi earthquake however the results show a close correlation between the distribution of landslides and the distribution of rainfall a conceptual model was developed to investigate the time effects of earthquake impact on the correlation of rainfall and landslides the analysis results suggest that the impact of the 1999 chi chi earthquake decays to 50 in about 1 3 years and to 10 in about 10 years this study can provide helpful details of the landslide investigation as an aid to hazard estimation and catchment management

dynamics of intensified downwelling circulation over a widened shelf in the northeastern south china sea abstractthis study reveals the dynamics behind the intensified downslope cross isobath transport over a widened shelf narrowing downwave in the northeastern south china sea nscs during a downwelling event utilizing a three dimensional numerical model over an idealized nscs shelf this study identified the forcing process and derived an analytical understanding of the invoked dynamics for the intensified downslope cross isobath transport this study found that the transport was formed by an amplified geostrophic transport because of an increased positive along isobath pressure gradient force pgf py and by an enhanced bottom ekman transport due to converging flow over the widened shelf based on the depth integrated vorticity dynamics py was linked with net frictional stress curl in the water column and the curl was primarily associated with the shear vorticity field induced by downwelling jet the increased positive vorticity seaside of the jet provided positive py for the downslope geostrop

progress on upwelling studies in the china seas east asian marginal seas surrounding china exhibit rich ocean upwelling mostly in response to the southwesterly summer monsoon upwelling in the china seas namely the south china sea the taiwan strait the east china sea the yellow sea and the bohai sea has become increasingly important because the potential changes in the upwelling may have dramatic ecosystem socioeconomic and climate impacts this paper reviews the progress of upwelling studies in the china seas since the year 2000 by presenting the principal characteristics and new understanding of 12 major upwelling regions in the china seas upwelling exhibits long term variability at intraseasonal to multi decadal scales as well as short term variability frequently caused by tropical cyclones it is also associated with the el nino southern oscillation local environmental variation and biogeochemical factors the coastal upwelling around hainan island and the upwelling or cold dome northeast of taiwan island are specifically highlighted because they have attracted great interest for decades this paper summarizes upwelling mechanisms in terms of wind topography tide stratification and background flow with applications mostly to the china seas finally we propose some topics for future upwelling research i e potential intensification of coastal upwelling under global climate change downwelling intrusion of upwelling into coastal embayments and the influence of upwelling on fishery and biogeochemical processes

controls of earthquake faulting style on near field landslide triggering the role of coseismic slip 1 we compare the spatial distributions of seven databases of landslides triggered by mw 5 6 7 9 earthquakes using distances normalized by the earthquake fault length we show that the normalized landslide distance distributions collapse i e the normalized distance distributions overlap whatever the size of the earthquake separately for the events associated with dip slip buried faulting earthquakes and surface faulting earthquakes the dip slip earthquakes triggered landslides at larger normalized distances than the oblique slip event of loma prieta we further identify that the surface faulting earthquakes of wenchuan chi chi and kashmir triggered landslides at normalized distances smaller than the ones expected from their mw 7 6 magnitudes these results support a control of the seismic slip through amplitude rake and surface versus buried slip on the distances at which landslides are triggered in terms of coseismic landslide management in mountainous areas our results allow us to propose distances at which 95 and 75 of landslides will be triggered as a function of the earthquake focal mechanism

upwelling off yangtze river estuary in summer 1 the mechanisms of upwelling off the yangtze river estuary yre and in the adjacent waters in boreal summer are studied using numerical modeling first the persistent feature of this phenomenon is confirmed using cruise observations satellite sea surface temperature sst and sst climatologic data then the masnum marine science and numerical modeling wave tide circulation coupled numerical model is employed to simulate the upwelling patterns on the basis of the simulation a set of numerical experiments are designed to explore the main mechanisms inducing the upwelling the results suggest that tidal mixing plays a predominant role in inducing the upwelling in offshore waters strong tidal mixing results in considerable horizontal density gradient across tidal fronts upwelling is induced as a branch of the secondary circulation which is stimulated by the cross frontal density gradient topography also exerts profound influences on upwelling by steering bottom currents to ascend upward and regulating tidal fronts in both location and intensity besides the tides and topography other dynamical factors also alter the strength of upwelling locally the yangtze river discharge yrd and taiwan warm current twc account partly for the upwelling off the yre and near zhoushan islands respectively the influence of wind on upwelling is small in the coastal waters near zhoushan islands the wind forcing exerts negative influences on upwelling by weakening the encroachment of twc onto the continental shelf which may exceed the positive effects of ekman pumping

dynamics of advection driven upwelling over a shelf break submarine canyon 1 the response over a submarine canyon to a several day upwelling event can be separated into three phases an initial transient response a later much longer steady advection driven response and a final relaxation phase for the advection driven phase over realistically steep deep and narrow canyons with near uniform flow and stratification at rim depth we have derived scale estimates for four key quantities observations from 5 real world canyon studies and 3 laboratory studies are used to validate the scaling and estimate the scalar constant for each scale based on 4 geometric parameters of the canyon the background stratification the coriolis parameter and the incoming current we can estimate 1 the depth of upwelling in the canyon to within 15 m 2 the deep vorticity to within 15 and 3 the presence absence of a rim depth eddy can be determined based on laboratory data 4 the total upwelling flux can also be estimated the scaling analysis shows the importance of a rossby number based on the radius of curvature of isobaths at the upstream mouth of the canyon this rossby number determines the ability of the flow to cross the canyon isobaths and generate the pressure gradient that drives upwelling in the canyon other important scales are a rossby number based on the length of the canyon which measures the ability of the flow to lift isopycnals and a burger number based on the width of the canyon that determines the likelihood of an eddy at rim depth generally long canyons with sharply turning upstream isobaths strong incoming flow small coriolis parameter and weak stratification have the strongest upwelling response

wind driven circulation in a shelf valley part i mechanism of the asymmetrical response to along shelf winds in opposite directions abstractmotivated by observations in hudson shelf valley showing stronger onshore than offshore flows this study investigates wind driven flows in idealized shallow shelf valleys this first part of a two part sequence focuses on the mechanism of the asymmetrical flow response in a valley to along shelf winds of opposite directions model simulations show that i when the wind is in the opposite direction to coastal trapped wave ctw phase propagation the shelf flow turns onshore in the valley and generates strong up valley transport and a standing meander on the upstream side in the sense of ctw phase propagation of the valley and ii when the wind is in the same direction as ctw phase propagation the flow forms a symmetric onshore detour pattern over the valley with negligible down valley transport comparison of the modeled upstream meanders in the first scenario with ctw characteristics confirms that the up valley flow results from ctws being arrested by the wind driven shelf flow establishin

dynamics of wind driven upwelling off the northeastern coast of hainan island both observational and reanalysis sea surface temperature data reveal that upwelling occurs frequently off the northeastern coast of hainan island downstream of the change in topography off tongluo cape which cannot be attributed to the along shelf wind alone to identify dynamics of the upwelling we conduct a numerical experiment using an idealized topography that is simplified from the actual topography off the eastern and northeastern coasts of hainan island the result indicates that the upwelling downstream of the change in topography is associated with onshore cross isobath transport analysis of the vertically integrated momentum balance shows that the upwelling linked onshore transport is primarily intensified by the along isobath barotropic pressure gradient force pgt but is weakened by the along isobath baroclinic pressure gradient force pgc the along isobath pgt is linked to the advection of relative vorticity the bottom stress curl and the gradient of momentum flux in vorticity equation on the other hand the pgc related process is diagnosed by potential vorticity pv balance similar to the negative pv term from wind stress the negative pv terms of the joint effect of baroclinicity and relief and the baroclinic bottom pressure torque weaken the upwelling linked onshore transport downstream of the change in topography the onshore transport is enhanced by the positive pv from bottom stress in addition the cross isobath forces play an important role in upwelling intensification in the shallow nearshore region

circulation near submarine canyons a modeling study circulation near a submarine canyon is analyzed with a numerical model previous theoretical work indicated that stratification controlled the interaction of coastal flow with canyons specifically the ratio of canyon width to the internal radius of deformation a wide canyon was thought to merely steer the flow while a narrow canyon would create substantial cross shelf exchange four cases are analyzed considering two directions of alongshore flow and two choices of initial stratification the weakly stratified case has an internal radius about equal to the canyon width while the strongly stratified case has one about 3 times the canyon width the direction of the alongshore flow is shown in this study to be the more important of the two factors in particular right bounded flow flow with the coast on the right looking downstream in the northern hemisphere leads to shallow downwelling in the canyon and weak exchange across the shelf break while left bounded flow creates upwelling at the head of the canyon and strong exchange between the ocean and shelf in left bounded flow upwelling dense water is pumped onto the shelf even for strong stratification however the stratification limits the vertical extent of the topographic influence so that the alongshore flow above the canyon is only weakly affected in the strongly stratified case with any level of stratification the surface temperature density is not modified at all by the flow interaction with the submarine canyon the important dynamics involve pressure gradients and coriolis acceleration and how they interact with the bathymetric gradients but not advection of momentum advection of density is clearly important in the upwelling cases finally continued upwelling onto the shelf acts as a drag mechanism and retards the alongshore coastal flow

spatial distribution analysis of landslides triggered by 2008 5 12 wenchuan earthquake china abstract the 2008 5 12 wenchuan earthquake seismic magnitude mw 7 9 according to the usgs triggered a great number of landslides a spatial database of landslides is built by interpreting the remote sensing rs data which covers 11 counties severely damaged by the earthquake with area of about 31 686 12 km2 the geological settings of the study area are detailed mapped including geologic structure and lithology the digital elevation model dem of the study area with resolution of 30 m 30 m is presented to address the topographic characteristics correlations between the occurrence of landslides with geological settings i e active faults the coseismic surface ruptures geological unit slope gradient slope elevation as well as slope aspect are analyzed using spatial modeling in gis with the aids of field investigations it can be concluded that the distance to the causative faults and slope gradient are much more important than other factors landslides are clustered distributed along the causative faults of f2 and f3 and landslides incidence are dramatically decreasing with the increasing of the distance to the causative faults the landslides incidence has an obvious increase near the active faults i e f1 landslide concentration lc landslides km2 has an obvious exponent increase with slope gradient however lc has no obvious relationship with geological unit and slope elevation the difference of lc value in each geological unit each slope elevation category maybe have been the result affected by slope gradient for each geological unit each slope elevation category and distance of each geological unit each slope elevation category to causative fault zone isoseismal map reflects the incidence of landslides in some degree and lc increases dramatically with intensity increasing almost all landslides occurred in the region above vi degree statistics result also indicates that in the near field of causative faults landslides tend to have the initial sliding direction similar to the movement of the causative faults and preliminary study shows that landslides incidence varies in different slopes with different structure and consequent slopes and obsequent slopes have a higher landslides incidence than other layered slopes

rock type control on erosion induced uplift eastern swiss alps abstract there is growing evidence that quaternary rock uplift in parts of the european alps is a consequence of climate and erosion driven isostatic rebound contemporary rates of rock uplift u in the swiss alps show two distinctive dome like peak regions that attain 1 6 mm yr 1 we focus on the alpenrhein catchment and its surroundings where one of these peak regions spatially coincides with widely exposed cretaceous bundner schist and lower tertiary flysch field assessments and analyses of hillslope gradient distributions quantitatively demonstrate the low rock mass strength and high erodibility of these rocks this is reflected in mean postglacial catchment erosion rates d 4 mm yr 1 as opposed to 0 7 mm yr 1 in more resistant crystalline rocks though largely inferred from landslide and debris flow prone tributary catchments 2 the localised erosion rates in bundner schist and flysch are among the highest documented for the alps and corroborated by historic suspended sediment yields and thus export from the region we further find that the steepness of bedrock rivers the density of large landslides and d correlate with the highest values of u our observations highlight the possibility that erosion of mechanically weak bundner schist and flysch enhanced by large landslides may have contributed to regional crustal unloading and concomitant rock uplift irrespective of whether this is betraying a coupling between long term uplift and erosion modulated by rock type our findings indicate that long term 10 3 to 10 4 yr geomorphic signals contained in bedrock river steepness spatial density of large landslides and postglacial erosion rates strikingly correlate with regional gradients of historic 10 1 yr rock uplift rates

a nested grid model of the oregon coastal transition zone simulations and comparisons with observations during the 2001 upwelling season 1 the oregon coastal transition zone octz extends several hundred kilometers offshore where shelf flows interact with the northern california current a primitive equation numerical ocean model is used to study the upwelling circulation in this region from 1 may to 1 november 2001 this octz model obtains initial and boundary conditions from a larger scale model of the california current system and forcing from a regional atmospheric model product the model results are compared with extensive in situ and remotely sensed data and the model is found to provide a realistic representation of flows both over the shelf and in the broader octz simulation of coastal sea level and shelf currents over the complex topography of the central oregon coast is improved quantitatively relative to previous regional models a particularly significant qualitative improvement is realistic representation of coastal jet separation and eddy formation offshore of cape blanco three dimensional lagrangian analysis of water parcel displacement shows that the surface waters inshore of the separated jet are upwelled from near the bottom along the shelf as far north as 45 5 n a large eddy which incorporates some of this upwelled water and carries it farther westward forms offshore in the late summer ensemble simulations show a distinction between the strongly deterministic response to wind forcing over the shelf and the more unstable less predictable jet separation and offshore eddy formation processes in the region near cape blanco

a conservative and consistent lagrangian gradient smoothing method for earthquake induced landslide simulation abstract numerical study of earthquake induced landslides plays an important role in the disaster prevention and post earthquake managements thanks to its mesh free feature the sph smoothed particle hydrodynamics method has significant advantages over the traditional grid based methods in dealing with extremely large deformation problems such as high speed fluid like landslides however sph is unstable when the material is in tension which is widely known as the tensile instability problem in sph although the instability issue can be removed to certain stand by particular ad hoc techniques the root cause of the problem is not addressed in addition such ad hoc techniques require additional user defined parameters which is difficult to make universally applicable in this study a conservative and consistent lagrangian gradient smoothing method l gsm is proposed for fluid like landslide simulations based on the recently developed meshfree l gsm in the present l gsm the strong form of governing equations is discretized using the gsm gradient operator in a conservative and consistent manner moreover a simple and accurate boundary treatment for free surface and solid boundary is newly proposed for l gsm to handle the complicated free surface and solid boundary existed in the landslide problems finally the proposed conservative and consistent l gsm framework is validated by a soil column collapse benchmark and three real landslide problems results show that our l gsm can give an accurate and reliable solution to the fluid like landslide problem with a high efficiency the treatments for free surface and solid boundary are also proven very effective in producing desired boundary conditions both cohesive soil column collapse example and wangjiayan landslide example demonstrate that l gsm is indeed free from the tensile instability problem

coastal upwelling in the east china sea in winter 1 the dynamic mechanisms of the upwelling off the east china sea ecs coast in wintertime are studied first the upwelling signals off the ecs coast are identified by the observed temperature salinity nutrients and dissolved oxygen data obtained during the cruises in january 1999 the masnum wave tide circulation coupled model is then employed to simulate the hydrography of the ecs comparisons between the simulations and observations show that the model performance is satisfactory on the basis of successful simulation four numerical experiments are conducted to investigate the upwelling mechanisms the results suggest that the density or salinity front which separates the inshore low salinity coastal water and the offshore taiwan warm current twc is the primary inducement for the upwelling owing to strong density gradient the baroclinic pressure gradient force pgf is quite large near the frontal zone and this pgf elicits an upwelling branch along the topography slope wind twc and tide affect the density front in extension and intensity thus exerting subsidiary influences on the upwelling according to ekman s theory the northerly monsoon is downwelling favorable however the net effects of wind on the upwelling off the ecs coast in winter are positive because it drives the changjiang river diluted water cdw flowing southward and forms the density front similarly the resultant effects of twc on the upwelling are negative for obstructing the pathway of cdw tide contributes to the upwelling because tidal mixing facilitates the expansion of cdw

earthquake induced chains of geologic hazards patterns mechanisms and impacts large earthquakes initiate chains of surface processes that last much longer than the brief moments of strong shaking most moderate and large magnitude earthquakes trigger landslides ranging from small failures in the soil cover to massive devastating rock avalanches some landslides dam rivers and impound lakes which can collapse days to centuries later and flood mountain valleys for hundreds of kilometers downstream landslide deposits on slopes can remobilize during heavy rainfall and evolve into debris flows cracks and fractures can form and widen on mountain crests and flanks promoting increased frequency of landslides that lasts for decades more gradual impacts involve the flushing of excess debris downstream by rivers which can generate bank erosion and floodplain accretion as well as channel avulsions that affect flooding frequency settlements ecosystems and infrastructure ultimately earthquake sequences and their geomorphic consequences alter mountain landscapes over both human and geologic time scales two recent events have attracted intense research into earthquake induced landslides and their consequences the magnitude m 7 6 chi chi taiwan earthquake of 1999 and the m 7 9 wenchuan china earthquake of 2008 using data and insights from these and several other earthquakes we analyze how such events initiate processes that change mountain landscapes highlight research gaps and suggest pathways toward a more complete understanding of the seismic effects on the earth s surface

upwelling induced by the frictional stress curl and vertical squeezing of the vortex tube over a submerged valley in the east china sea we conducted a process oriented modeling study to investigate the characteristics and dynamics of the prominent upwelling over a vast submerged valley in the east china sea ecs the valley is inversely funnel shaped with the west bank and the east bank oriented in the north south direction a cross bank upward transport occurred along the west bank it intensified northward and peaked around the head of the valley an along bank southward pressure gradient force pgf formed the cross bank geostrophic transport for the upwelling over the valley the pgf reached its maxima at the head of the valley our momentum and vorticity dynamic analyses revealed that a bottom stress curl mainly contributed the pgf along the west bank at the same time both the bottom stress curl and the nonlinear vorticity advection contributed to the pgf around the head the bottom stress curl was due to the bottom shear vorticity of the coastal current and the curvature vorticity around the head the nonlinear vorticity advection formed because of the vertical squeezing of vortex tube as the current flowed over the valley the nonlinearity mainly affected the pgf around the head whereas the bottom stress curl contributed to the pgf over the entire valley the ratio of the nonlinear to frictional contributions to the pgf increased as the coastal current intensified our study demonstrates that the pgf that drives the upwelling over the valley is the combined result of the nonlinearity due to vertical squeezing of vortex tube and bottom frictional effects

database and spatial distribution of landslides triggered by the lushan china mw 6 6 earthquake of 20 april 2013 abstract on 20 april 2013 an earthquake with mw 6 6 ms 7 0 hit lushan county sichuan province of china 30 3 n 103 e only 85 km southwest of the 2008 wenchuan mw 7 9 event the lushan shock triggered a large number of landslides with various types including highly disrupted shallow slides and rock falls deep seated landslides and large scale rock avalanches post earthquake high resolution aerial photographs and satellite images as well as a series of pre earthquake high resolution satellite images were collected to construct a detailed accurate objective and complete coseismic landslide database inventory which was validated by field investigation in selected areas based on the aerial photographs 0 2 or 0 6 m resolution that partly cover the affected area and pre earthquake satellite images 14 580 coseismic landslides were recognized and mapped in those areas without post earthquake aerial photographs coverage we mapped 7 948 more coseismic landslides based on post earthquake satellite images rapideye images with 5 m resolution and zy 3 images including panchromatic images with 2 1 m resolution and multi spectral images with 5 8 m resolution and pre earthquake satellite images the 22 528 coseismic landslides with a horizontal projection area of 18 88 km 2 and an estimated total volume of 41 56 10 6 m 3 were distributed in a nearly elliptic area of about 5 400 km 2 correlations between coseismic landslide abundances and topographic geologic and seismic factors were analyzed on 15 546 landslides of area 100 m 2 scatter plots between regional slope angle and landslide abundances in generalized homogeneous lithology combinations show no obvious relationship is present between them which challenges the conclusions of previous studies combining the lushan earthquake triggered landslides with other events on reverse and or thrust faults such as the 1999 chi chi and 2008 wenchuan shocks we found that coseismic landslides tend to occur in areas enveloped by two or more imbricated reverse and or thrust faults rather than only along the seismogenic fault the lushan event shows a higher ability of triggering landslides compared with other earthquakes of similar magnitudes which is likely due to the steep and rugged topography and fractured and densely jointed lithology resulted from long term tectonic activity the blind reverse seismogenic fault is likely also another significant factor based on detailed coseismic landslide inventory maps and databases of several recent major earthquakes such as the 2008 wenchuan 2010 haiti 2010 yushu and 2013 lushan temblors we suggest that the empirical correlations between earthquake magnitude and coseismic landslides need to be updated

assessment of the effects of historical strong earthquakes on large scale landslide groupings in the wei river midstream abstract regional active tectonics and historical earthquake records indicate the importance of the triggering effects of historical strong earthquakes on groups of large scale landslide occurrences in the wei river midstream section in this study a method to assess the triggering effects of historical earthquakes on regional large scale landslides is presented the greatest epicentral distances of seismically induced landslides were calculated the triggering effects of four key historical strong earthquakes with epicenters within 300 km of the wei river midstream section were analyzed these are the ms 7 0 qishan earthquake of 780 bce the ms 8 0 tianshui earthquake of 1654 ce the ms 8 25 huaxian earthquake of 1556 ce and the ms 8 5 haiyuan earthquake of 1920 ce taking the qishan earthquake as an example a seismically induced landslide displacement and hazard assessment method based on the newmark displacement model was developed the degree of spatial matching of the results for historical earthquake triggered landslides and the distribution of actual large scale landslide deposits were compared quantitatively using the success rate curve method the results show that of the four historical earthquakes the tianshui earthquake had the strongest effect of inducing large scale landslides regionally along the wei river midstream section

seismically induced landslide displacements a predictive model newmark s model for predicting earthquake induced landslide displacements provides a simple way to predict the coseismic displacements affecting a sliding mass subject to earthquake loading in this model seismic slope stability is measured in terms of critical acceleration which depends on the mechanical soil properties pore pressure distribution and slope geometry the triggering seismic forces are investigated in terms of energy radiation from the source propagation and site effects based on 190 accelerometric recordings from 17 italian earthquakes with magnitudes between 4 5 and 6 8 the method is based on the calibration of relations having the general form of an attenuation law that relates the energy of the seismic forces to the dynamic shear resistances of the sliding mass to propagate the expected landslide displacements as an inverse function of the distance from the fault rupture the amount of displacement computed through these relations provides a criterion to predict the occurrence of slope failures finally maps showing in a deterministic and a probabilistic way the potential of seismically induced landslide displacements are displayed as a tool to provide seismic landslide scenarios and earthquake induced landslide hazard maps respectively

methods for assessing the stability of slopes during earthquakes a retrospective abstract during the twentieth century several methods to assess the stability of slopes during earthquakes were developed pseudostatic analysis was the earliest method it involved simply adding a permanent body force representing the earthquake shaking to a static limit equilibrium analysis stress deformation analysis a later development involved much more complex modeling of slopes using a mesh in which the internal stresses and strains within elements are computed based on the applied external loads including gravity and seismic loads stress deformation analysis provided the most realistic model of slope behavior but it is very complex and requires a high density of high quality soil property data as well as an accurate model of soil behavior in 1965 newmark developed a method that effectively bridges the gap between these two types of analysis his sliding block model is easy to apply and provides a useful index of co seismic slope performance subsequent modifications to sliding block analysis have made it applicable to a wider range of landslide types sliding block analysis provides perhaps the greatest utility of all the types of analysis it is far easier to apply than stress deformation analysis and it yields much more useful information than does pseudostatic analysis

upwelling flow dynamics in long canyons at low rossby number 1 submarine canyons topographic features incising the continental slope vary in both shape and size the dynamics of short canyons have been observed and described in the field in the laboratory and with numerical simulations flow within long canyons such as juan de fuca canyon located between vancouver island and washington state in the pacific northwest is less well understood physical models of both long and short canyons have been constructed to understand the upwelling dynamics in long canyons and how upwelling changes as compared with the dynamics of short canyons at low rossby number stratification and rotation both important parameters in determining the dynamics in canyons can be controlled and scaled accordingly for replication of oceanic conditions the physical model is spun up to an initial rotation rate and the flow is forced by increasing the rotation rate over the equivalent of several days flow visualization is used to determine the strength and location of upwelling the strength and mechanisms generating vorticity as well as the differences between the flow within the long and short canyons the pattern of upwelling between the two canyons is significantly different in the horizontal with upwelling occurring through the canyon head in the short canyon and upwelling occurring close to the mouth along the downstream rim in the long canyon at high rossby number upwelling is similar in both the long and short canyon and is driven by advection however as rossby number decreases the flow in the long canyon is more strongly affected by the strong convergence of the isobaths near the canyon than by advection alone

landslides triggered by the 1994 northridge california earthquake abstract the 17 january 1994 northridge california earthquake m w 6 7 triggered more than 11 000 landslides over an area of about 10 000 km 2 most of the landslides were concentrated in a 1000 km 2 area that included the santa susana mountains and the mountains north of the santa clara river valley we mapped landslides triggered by the earthquake in the field and from 1 60 000 nominal scale aerial photography provided by the u s air force and taken the morning of the earthquake these mapped landslides were subsequently digitized and plotted in a gis based format most of the triggered landslides were shallow 1 to 5 m thick highly disrupted falls and slides within weakly cemented tertiary to pleistocene clastic sediment average volumes of these types of landslides were less than 1000 m 3 but many had volumes exceeding 100 000 m 3 the larger disrupted slides commonly had runout paths of more than 50 m and a few traveled as far as 200 m from the bases of steep parent slopes deeper 5 m thick rotational slumps and block slides numbered in the tens to perhaps hundreds a few of which exceeded 100 000 m 3 in volume most of these were reactivations of previously existing landslides the largest single landslide triggered by the earthquake was a rotational slump block slide having a volume of 8 10 6 m 3 analysis of the mapped landslide distribution with respect to variations in 1 landslide susceptibility and 2 strong shaking recorded by hundreds of instruments will form the basis of a seismic landslide hazard analysis of the los angeles area

landslide hazard evaluation a review of current techniques and their application in a multi scale study central italy in recent years growing population and expansion of settlements and life lines over hazardous areas have largely increased the impact of natural disasters both in industrialized and developing countries third world countries have difficulty meeting the high costs of controlling natural hazards through major engineering works and rational land use planning industrialized societies are increasingly reluctant to invest money in structural measures that can reduce natural risks hence the new issue is to implement warning systems and land utilization regulations aimed at minimizing the loss of lives and property without investing in long term costly projects of ground stabilization government and research institutions worldwide have long attempted to assess landslide hazard and risks and to portray its spatial distribution in maps several different methods for assessing landslide hazard were proposed or implemented the reliability of these maps and the criteria behind these hazard evaluations are ill formalized or poorly documented geomorphological information remains largely descriptive and subjective it is hence somewhat unsuitable to engineers policy makers or developers when planning land resources and mitigating the effects of geological hazards in the umbria and marche regions of central italy attempts at testing the proficiency and limitations of multivariate statistical techniques and of different methodologies for dividing the territory into suitable areas for landslide hazard assessment have been completed or are in progress at various scales these experiments showed that despite the operational and conceptual limitations landslide hazard assessment may indeed constitute a suitable cost effective aid to land use planning within this framework engineering geomorphology may play a renewed role in assessing areas at high landslide hazard and helping mitigate the associated risk

seismically induced landslides by a low magnitude earthquake the mw 4 7 ossa de montiel event central spain this work has been funded by spanish ministry of economy and competitiveness research project cgl2011 30153 c02 02 and by the research groups rnm 374 junta de andalucia tectac ucm 910368 and vigrob 184 universidad de alicante mr loffredo acknowledges funding of the universita di roma la sapienza post graduate grant concorso a n 480 area cun 04

post earthquake landsliding and long term impacts in the wenchuan earthquake area china abstract the ms 8 0 wenchuan earthquake on may 12 2008 triggered tens of thousands of landslides and produced large amounts of loose material the loose material accumulated in gullies or on slopes provides abundant sources for the consequent debris flows which will endanger resettled residents and destroy urban reconstruction during the 5 years following the wenchuan earthquake event heavy rainfalls have already induced a great number of debris flows in the earthquake damaged area resulting in serious casualties and property losses the co seismic landslides and the debris flows induced by rainfalls in the mianyuan river basin are analyzed using multi temporal remote sensing images more than 2000 landslides were triggered and about 4 0 108 m3 of loose material was generated in the mianyuan river basin and the volume of erodible material is 6 0 107 1 6 108 m3 there were 1 27 107 m3 of bed load sediments and 6 3 105 m3 suspended load sediments transported into the river system in the past 5 years the active mass movements will last for a long period in the mianyuan river basin

solution convergence of flow over steep topography in a numerical model of canyon upwelling 1 the convergence as resolution is increased is examined for a numerical model simulation of upwelling over a continental shelf canyon a series of idealized one and two dimensional models are used to plot the dependence of bottom ekman layer velocity structure and transport on model resolution using these results as a guide a bottom ekman layer resolving three dimensional numerical model is constructed this model is used to simulate a laboratory model of canyon upwelling alongshore velocity volume of fluid upwelled through the canyon onto the shelf and change in depth of the canyon water are examined at three grid resolutions numerical model particle trajectories are compared with a laboratory model of canyon upwelling to validate the model the results suggest that current computational cluster power is sufficient to accurately simulate all aspects of upwelling in a steep canyon with the exception of flow separation from the canyon wall

effects of directionality and vertical component of ground motions on seismic slope displacements in newmark sliding block analysis abstract the newmark sliding block model is widely used in the evaluation of seismic slope stability when using this model the horizontal acceleration is usually considered to act parallel to the slope downslope and the vertical component of ground motions is commonly ignored this study investigates the effect of vertical accelerations on the results of sliding displacement and quantitatively compares the difference of the displacement dn calculated from the original newmark s approach with the displacement dhv calculated from a more realistic case horizontal and vertical accelerations properly considered for this purpose 4136 ground motion recordings are selected from the nga west2 database and 2000 hypothetic slopes are simulated with critical accelerations ac ranging from 0 to 0 8 g comparison of dhv and dh shows that the incorporation of vertical accelerations only slightly increases the displacement besides the calculated dhv dn ratios are generally in the range of 1 to 5 indicating that dn significantly underestimates the slope displacement due to the simplification of seismic excitations the dhv dn ratios generally increase as ac increases simple predictive models are proposed to quantify the correction factor kd kd dhv dn they can be easily used in seismic landslide hazard assessment to improve the performance of the original newmark s approach

open boundary conditions for tidally and subtidally forced circulation in a limited area coastal model using the regional ocean modeling system roms in limited area ocean models open boundary conditions obcs often create dynamic inconsistencies and perform poorly in resolving tidal or subtidal flow when both forces exist orlanski type radiation obcs are reasonably efficient at treating the subtidally forced flow and flather type obcs are commonly adapted for the tidally forced flow however neither of them performs well when tidal and subtidal forces simultaneously drive the flows we have developed a novel obc that integrates the active obc in gan and allen 2005 and a flather type obc this new obc accommodates the concurrent tidal and subtidal tst forcing and the respective tidal or subtidal forcing at the open boundary of a limited area model this new tst obc treats the tidal component with a flather type obc and it separates subtidal barotropic and baroclinic components into local forced and global unforced components then an unforced orlanski type obc can be applied to the global part we applied the tst obc to all model variables to reduce dynamic inconsistence using the regional ocean modeling system we applied the tst obc to the shallow east china sea shelf where strong tidal and subtidal forces over complex topography govern the circulation our numerical experiments and analyses suggest that the tst obc was robust for both concurrent tidal subtidal forcing and solely tidal or subtidal forcing at the open boundary it reduced spurious energy reflection and overall it performed better than an orlanski type or flather type obc in reproducing realistic tidal and subtidal shelf circulation

uncertainty in seismic slope deformation model predictions in this article we examine how variability in driving and resisting force parameters together translate into uncertainty in seismic slope deformation predictions predictive uncertainty of the newmark rigid block and makdisi seed decoupled deformation based methods was evaluated by performing a series of probabilistic monte carlo simulations for two idealized slope models results from these analyses demonstrate that the highly non linear relationship between acceleration ratio and displacement associated with the deformation models dictates the way in which parametric variability is propagated through the analysis and can lead to varying degrees of uncertainty in the deformation predictions based on this observation three zones along the displacement acceleration ratio relationship were identified according to their relative degree of non linearity and correlated with their relative influence on predictive uncertainty these are i highly uncertain ii moderately uncertain and iii low uncertainty using this framework the widely held notion of a generic order of magnitude estimate for deformation predictions is a misnomer based on this it is recommended that realistic levels of parametric variability be incorporated in the seismic slope deformation analysis to establish the operating conditions of the slope system slopes identified as highly uncertain or moderately uncertain require a more robust probabilistic analyses to meaningfully interpret poorly constrained deformation predictions

circulation over a submarine canyon in the nw mediterranean 1 the circulation in blanes canyon an interruption in the nw mediterranean continental shelf north of barcelona was investigated the study employs data from oceanographic surveys carried out in the summer and fall of 2003 velocity data show that in the vicinity of the shelf break the flow is deflected along the canyon walls a cyclonic mean flow can be seen over the canyon mouth owing to vortex stretching of fluid parcels advected across the shelf break field observations are in qualitative agreement with fundamental fluid dynamic considerations based on potential vorticity conservation and friction effects at lateral boundaries evidence is given that upwelling is found near the shelf break inside the canyon in the two field experiments this upwelling extends vertically from the seasonal thermocline at about 100 m to the shelf slope front at about 200 m there is no evidence that upwelled water can reach the continental shelf

transient wind driven upwelling in a submarine canyon a process oriented modeling study 1 a hydrodynamic model is employed to study flow near a submarine canyon during conditions of upwelling favorable coastal winds findings reveal that up canyon flow is the rapid geostrophic adjustment to barotropic pressure gradients establishing across the canyon stratification leads to the formation of a cyclonic eddy within the canyon trapping neutrally buoyant matter and limits the upwelling depth only when a strong seasonal pycnocline is located below shelf break depth typical speeds of up canyon flow are 10 30 cm s constrained by the timescale of synoptic weather patterns 5 days only stronger events high upwelling index can move slope water from a depth 300 m onto the continental shelf and close toward the coast where it can be lifted into surface layers during a subsequent upwelling event

secondary geological hazard analysis in beichuan after the wenchuan earthquake and recommendations for reconstruction the wenchuan earthquake also known as 2008 sichuan earthquake occurred along the longmenshan fault zone on 12 may 2008 at 14 28 01 42 cst 06 28 01 42 utc it caused serious damage to structures in the region beichuan is a town which is within these severely damaged areas according to the earthquake intensity distribution map of 2008 wenchuan earthquake officially released by the china earthquake administration the earthquake intensity in beichuan was xi on the china seismic intensity scale as the earthquake occurred in a mountainous area there were thousands of landslides rockfalls debris flows and surface ruptures triggered by the earthquake over a broad area these secondary geological hazards substantially increased the human social and economic impact of the earthquake this paper presents a post earthquake analysis on the secondary geological hazards in beichuan the risk analyses associated with construction of the national earthquake memorial museum in beichuan are assessed and recommendations on risk mitigations for the mass reconstruction over the ruins are also provided based on this field study

regression models for estimating coseismic landslide displacement newmark s sliding block model is widely used to estimate coseismic slope performance early efforts to develop simple regression models to estimate newmark displacement were based on analysis of the small number of strong motion records then available the current availability of a much larger set of strong motion records dictates that these regression equations be updated regression equations were generated using data derived from a collection of 2270 strong motion records from 30 worldwide earthquakes the regression equations predict newmark displacement in terms of 1 critical acceleration ratio 2 critical acceleration ratio and earthquake magnitude 3 arias intensity and critical acceleration and 4 arias intensity and critical acceleration ratio these equations are well constrained and fit the data well 71 br 2 b88 but they have standard deviations of about 0 5 log units such that the range defined by the mean one standard deviation spans about an order of magnitude these regression models therefore are not recommended for use in site specific design but rather for regional scale seismic landslide hazard mapping or for rapid preliminary screening of sites 2007 elsevier b v all rights reserved

regional seismic slope assessment improvements considering slope aspect and vertical ground motion abstract seismic slope stability assessments in active fault zones are very important prior to designing and constructing large engineering structures however in most previous regional scale analyses ground motion records are either used directly or replaced by empirical regression equations in this paper we present an improved regional seismic slope stability assessment method considering the vertical slope aspect and ground motion based on limit equilibrium models and finite element models best fit equations are obtained to calculate the sliding angle and factor of safety fos then a two stage integration process is applied to obtain the permanent displacement the new model has been tested in the chenghai active fault zone china under a seismic precautionary intensity of 9 and the results of the new model are compared with those of traditional infinite slope models the results show that ignoring the vertical ground motion and slope aspect leads to underestimation of co seismic landslide hazards on regional scales and the new model provides a more accurate index to evaluate co seismic slope behaviours in large areas

intensified upwelling over a widened shelf in the northeastern south china sea 1 observational and three dimensional modeling studies reveal that the intensified upwelling in the northeastern south china sea nscs is formed as a result of intensified upslope advection of dense deep waters that cross the middle shelf toward the inner shelf over a distinctly eastward widened shelf the strongest advection occurs over the converging isobaths near the head of the widened shelf as these dense deep waters advance shoreward they are advected downstream by the quickly developed upwelling current over the inner shelf and eventually outcropped at the lee of a coastal cape dynamically the shoreward cross isobath transport over the widened shelf is geostrophically enhanced by a quasi barotropic negative westward along isobath pressure gradient force as a result of the net rate of the momentum influx and by an intensified bottom frictional transport owing to the flow confluence near the head of the widened shelf a negative pressure gradient also exists at the lee of the coastal cape over the inner shelf and locally amplifies shoreward motion induced by the respective widened shelf and the coastal promontory the along isobath variations of cross isobath transport in the water column over the middle and inner shelves interactively characterize intensified upwelling in the nscs

numerical study on the pattern and origins of kuroshio branches in the bottom water of southern east china sea in summer pattern and origins of kuroshio branches in the bottom water of southern east china sea ecs were carefully examined by numerical simulations based on the regional ocean modeling system roms together with observations model results show that in the bottom water of ecs the intrusion pattern of kuroshio is mainly composed of an offshore kuroshio branch current okbc which bifurcated from the kuroshio northeast of taiwan flows nearly along the isobath of similar to 100 m and a nearshore kuroshio branch current nkbc which originated from the kuroshio northeast of taiwan upwells northwestward gradually from similar to 250 m to similar to 60 m then turns to northeast around 27 5 degrees n 122 e thereafter flows northeastward along the isobath of similar to 60 m and finally reaches at 30 5 degrees n where it turns to east furthermore we found that the nkbc mostly originated in the kuroshio subsurface water 120 250 m east of taiwan whereas the okbc mainly stemmed from the kuroshio water 60 120 m east of taiwan this pattern and origins of okbc and nkbc well addressed the observational phenomena that off the coast of zhejiang province china there were colder less saline and more phosphate rich bottom water near the isobath of similar to 60 m rather than near the isobath of similar to 100 m in august 2009 finally it is proposed that on southern ecs continental shelf kuroshio exhibits its intrusion branches by an anticyclonical stair structure bottom stair nkbc middle stair okbc and top stair kuroshio surface branch kbc

simplified procedure for estimating earthquake induced deviatoric slope displacements a simplified semiempirical predictive relationship for estimating permanent displacements due to earthquake induced deviatoric deformations is presented it utilizes a nonlinear fully coupled stick slip sliding block model to capture the dynamic performance of an earth dam natural slope compacted earth fill or municipal solid waste landfill the primary source of uncertainty in assessing the likely performance of an earth waste system during an earthquake is the input ground motion hence a comprehensive database containing 688 recorded ground motions is used to compute seismic displacements a seismic displacement model is developed that captures the primary influence of the system s yield coefficient ky its initial fundamental period ts and the ground motion s spectral acceleration at a degraded period equal to 1 5 ts the model separates the probability of zero displacement i e 1 cm occurring from the distribution of nonzero displacement so that very low values of calculated

the response of a steep sided narrow canyon to time variable wind forcing abstract the response of a relatively narrow 7 km wide and deep 450 m deep steep sided up to 45 bottom slope submarine canyon to strong wind forcing is explored using data from an 18 element moored array as well as ctd surveys in the vicinity of astoria submarine canyon the data are used to describe spatial patterns and phase relationships between lateral velocity vertical velocity temperature relative and stretching vorticity alongshelf wind and the flow incident on the canyon upwelling within the canyon is simultaneous and spatially uniform to zero order and vertical velocity is highly correlated and in phase with alongshelf wind vertical velocity within the canyon is not related to flow incident on the canyon except during strong upwelling above the canyon temperature rather than vertical velocity time rate of change of temperature is in phase with wind estimated vertical velocities within the canyon were as great as 50 m d 1 upward during upwelling and 90 m d 1 downward du

spatial distribution of landslides triggered from the 2007 niigata chuetsu oki japan earthquake abstract understanding the spatial distribution of earthquake induced landslides from specific earthquakes provides an opportunity to recognize what to expect from future events the july 16 2007 mw 6 6 mjma 6 8 niigata chuetsu oki japan earthquake triggered hundreds of landslides in the area surrounding the coastal city of kashiwazaki and provides one such opportunity to evaluate the impacts of an offshore magnitude 6 earthquake on a steep coastal region as part of a larger effort to document all forms of geotechnical damage from this earthquake we performed landslide inventory mapping throughout the epicentral area and analyzed the resulting data for spatial seismic motion and geologic correlations to describe the pattern of landsliding coupled with examination of a third party aerial photo based landslide inventory our analyses reveal several areas of high landslide concentration that are not readily explained by either traditional epicentral and fault plane distance metrics or by recorded and inferred ground motions whereas average landslide concentrations averaged less than 1 landslide per square kilometer ls km2 some areas reached up to 2 ls km2 in the nishiyama hills to the northeast of kashiwazaki and between 2 and 11 ls km2 in coastal areas to the north and south of the city correlation with seismometer based and monument overturning back calculated ground motions suggests that a minimum peak ground acceleration pga of approximately 0 2 g was necessary for landsliding throughout the region but does not explain the subregional areas of high landslide concentration however analysis of topographic slope and the distribution of generally weak dip slope geologic units does sufficiently explain why on a sub regional scale high landslide concentrations occurred where they did these include 1 an inland region of steep dip slope anticlinal sedimentary strata with associated fold belt compression and uplift of the anticline and 2 coastal areas with generally weaker weathered outcrop lithology and steeper slopes resulting from active marine and terrestrial cliff processes the results offer lessons for understanding the effects of earthquakes on both regional and subregional scales with regard to the spatial distribution of landsliding

a method for producing digital probabilistic seismic landslide hazard maps abstract the 1994 northridge california earthquake is the first earthquake for which we have all of the data sets needed to conduct a rigorous regional analysis of seismic slope instability these data sets include 1 a comprehensive inventory of triggered landslides 2 about 200 strong motion records of the mainshock 3 1 24 000 scale geologic mapping of the region 4 extensive data on engineering properties of geologic units and 5 high resolution digital elevation models of the topography all of these data sets have been digitized and rasterized at 10 m grid spacing using arc info gis software on a unix computer combining these data sets in a dynamic model based on newmark s permanent deformation sliding block analysis yields estimates of coseismic landslide displacement in each grid cell from the northridge earthquake the modeled displacements are then compared with the digital inventory of landslides triggered by the northridge earthquake to construct a probability curve relating predicted displacement to probability of failure this probability function can be applied to predict and map the spatial variability in failure probability in any ground shaking conditions of interest we anticipate that this mapping procedure will be used to construct seismic landslide hazard maps that will assist in emergency preparedness planning and in making rational decisions regarding development and construction in areas susceptible to seismic slope failure

comment on spatial distribution analysis of landslides triggered by 2008 5 12 wenchuan earthquake china by shengwen qi qiang xu hengxing lan bing zhang jianyou liu engineering geology 116 2010 95 108

a modeling study of shelf circulation off northern california in the region of the coastal ocean dynamics experiment response to relaxation of upwelling winds 1 a two part modeling study of the wind forced flow on the continental shelf off northern california in the region 37 40 n of the coastal ocean dynamics experiment code is pursued this paper involves a process oriented study with idealized wind stress forcing gan and allen 2002 involves forcing with observed winds and heat flux for april may 1982 and comparison of model results with code observations a characteristic but previously unexplained response observed during code following the weakening or relaxation of southward upwelling favorable winds is the time dependent development of northward currents over the inner shelf next to the coast the presence of northward winds is not necessary for this occurrence the objective in this paper is to investigate the dynamics of the shelf flow response to upwelling wind relaxation events under idealized conditions in the basic case experiment a spatially uniform upwelling favorable southward wind stress of 0 1 pa is applied to the ocean initially at rest the stress is held constant for 10 days and then decreased linearly to zero over 3 days in response to the southward wind stress southward alongshore currents develop on the shelf accompanied by upwelling of cold dense water near the coast considerable spatial variability in the shelf flow clearly related to the alongshore variations in coastline and bottom topography is found the alongshore currents tend to separate from the coast south of capes and the coldest surface water is found at those locations as the winds decrease northward currents similar to those observed develop on the inner shelf next to the coast at many alongshore locations examination of the alongshore momentum balances shows that the northward currents are forced by a northward pressure gradient force associated with negative alongshore pressure gradients these pressure gradients are set up by the interaction of the wind forced flow with the alongshore variations in shelf topography in general negative alongshore pressure gradients intensified off pt reyes and pt arena by the gradient wind balance are found south of capes the negative pressure gradients geostrophically balance onshore flow at depth and upwelling is strengthened in these locations north of capes positive pressure gradients that are primarily in balance with nonlinear advective effects are found after the winds cease the forced across shelf circulation weakens and the resulting unbalanced negative pressure gradients south of the capes accelerate the alongshore currents northward processes with similar dynamics are found embedded in the more complex coastal ocean response to observed time varying winds by gan and allen 2002

geodynamics of the yellowstone hotspot and mantle plume seismic and gps imaging kinematics and mantle flow abstract integration of geophysical and geological data show that the yellowstone hotspot resulted from a mantle plume interacting with the overriding north america plate a process that has highly modified continental lithosphere by magmatic and tectonic processes and produced the 16 17 ma 700 km long yellowstone snake river plain ysrp silicic volcanic system accessibility of the ysrp allowed large scale geophysical projects to seismically image the hotspot and evaluate its kinematic properties using geodetic measurements seismic tomography reveals a crustal magma reservoir of 8 to 15 melt 6 km to 16 km deep beneath the yellowstone caldera an upper mantle low p wave velocity body extends vertically from 80 km to 250 km beneath yellowstone but the anomalous body tilts 60 wnw and extends to 660 km depth into the mantle transition zone we interpret this conduit shaped low velocity body as a plume of up to 3 5 vp and 5 5 vs perturbation that corresponds to a 1 2 partial melt models of whole mantle convection reveal eastward upper mantle flow beneath yellowstone at relatively high rates of 5 cm yr that deflects the ascending plume into its west tilted geometry a geodynamic model of the yellowstone plume constrained by vp and vs velocities and attenuation parameters suggests low excess temperatures of up to 120 k corresponding to a maximum 2 5 melt and a small buoyancy flux of 0 25 mg s i e properties of a cool weak plume the buoyancy flux is many times smaller than for oceanic plumes nonetheless plume buoyancy has produced a 400 km wide 500 m high topographic swell centered on the yellowstone plateau contemporary deformation derived from gps measurements reveals sw extension of 2 3 mm yr across the yellowstone plateau one fourth of the total basin range opening rate which we consider to be part of basin range intraplate extension locally decadal episodes of subsidence and uplift averaging 2 cm yr characterize the 80 year yellowstone caldera monitored history and are modeled as hydrothermal magmatic sources moreover a recent episode 2004 2009 of accelerated uplift of the yellowstone caldera at rates up to 7 cm yr has been modeled as resulting from magmatic recharge of a 10 km deep sill at the top of the crustal magma reservoir regionally gravitational potential energy of the yellowstone swell drives the lithosphere southwest and downhill from the yellowstone plateau 400 km where it coalesces with basin range province wide westward extension based on the geometry and its assumed 660 km depth we extrapolate the plume source southwest to its original location at 17 ma and 600 km southwest and 200 km north of the ysrp importantly this location is beneath the southern part of the columbia plateau flood basalt field of the same age and implies that the yellowstone mantle plume may be the common source for both of these large volcanic fields our time progression model suggests that the original plume head rose vertically behind the juan de fuca plate but at 12 ma it lost the protection of the subducting plate from eastward mantle flow and encountered cooler thicker continental lithosphere becoming entrained in eastward upper mantle flow these results reveal that yellowstone plume plate processes have had a profound effect on late cenozoic geologic evolution and topography of a large part of the western u s

coastal wind driven circulation in the vicinity of a bank part i modeling flow over idealized symmetric banks abstract this study examines how coastal banks influence wind driven circulation along stratified continental shelves numerical experiments are conducted for idealized symmetric banks the standard bank 200 km long and 50 km wide has dimensions similar to the heceta bank complex along the oregon shelf model runs are forced with 10 days of steady winds 0 1 pa upwelling and downwelling cases are compared the bank introduces significant alongshelf variability in the currents and density fields upwelling favorable winds create an upwelling front and a baroclinic jet flowing opposite coastal trapped wave propagation that bend around the standard bank approximately centered on the 90 m isobath the upwelling jet is strongest over the upstream bank half where it advects a tongue of dense water over the bank there is a current reversal shoreward of the main jet at the bank center upwelling is most intense over the upstream part of the bank while there is reduced upwelling and even downwelling over

a large landslide triggered by the 2008 wenchuan m8 0 earthquake in donghekou area phenomena and mechanisms abstract during the 2008 wenchuan earthquake more than 60 000 landslides were triggered resulting in about 20 000 casualties among these landslides a catastrophic one occurred in donghekou area of qingchuan county donghekou landslide had a volume of about 1 107 m3 traveled fast for approximately 2 km killing about 780 people the source area consisted of unstable sedimentary strata and the runout path was made of colluvial deposits during the earthquake the colluvial deposits started to move first before the arrival of the displaced landslide debris from the main source area we performed undrained cyclic ring shear tests on samples taken from the runout path and concluded that liquefaction of the runout path material enhanced the mobility of the debris material a fumarole was identified on the upper part of the runout path 6 months later we analyzed the gas and water venting out and concluded that the fumarole was not the result of fault movement it resulted instead from the weathering of slate from the source area the long travel landslide materials blocked two rivers forming two landslide dams that breached with the occurrence of overtopping to better understand the internal structure of the landslide deposits and then provide evidence for a rational plan of countermeasures to stabilize the landslide dams we measured the shear wave velocity of the landslide deposits by a surface wave technique called multichannel analysis of surface waves masw the results revealed that the landslide dams consisted of loosely deposited debris suggesting that the landslide dams were mechanically weak and prone to erosion by overtopping

the application of gis based logistic regression for landslide susceptibility mapping in the kakuda yahiko mountains central japan as a first step forward in regional hazard management multivariate statistical analysis in the form of logistic regression was used to produce a landslide susceptibility map in the kakuda yahiko mountains of central japan there are different methods to prepare landslide susceptibility maps the use of logistic regression in this study stemmed not only from the fact that this approach relaxes the strict assumptions required by other multivariate statistical methods but also to demonstrate that it can be combined with bivariate statistical analyses bsa to simplify the interpretation of the model obtained at the end in susceptibility mapping the use of logistic regression is to find the best fitting function to describe the relationship between the presence or absence of landslides dependent variable and a set of independent parameters such as slope angle and lithology here an inventory map of 87 landslides was used to produce a dependent variable which takes a value of 0 for the absence and 1 for the presence of slope failures lithology bed rock slope relationship lineaments slope gradient aspect elevation and road network were taken as independent parameters the effect of each parameter on landslide occurrence was assessed from the corresponding coefficient that appears in the logistic regression function the interpretations of the coefficients showed that road network plays a major role in determining landslide occurrence and distribution among the geomorphological parameters aspect and slope gradient have a more significant contribution than elevation although field observations showed that the latter is a good estimator of the approximate location of slope cuts using a predicted map of probability the study area was classified into five categories of landslide susceptibility extremely low very low low medium and high the medium and high susceptibility zones make up 8 87 of the total study area and involve mid altitude slopes in the eastern part of kakuda mountain and the central and southern parts of yahiko mountain

shaking table modeling of seismically induced deformations in slopes physical model experiments were performed on a 1 g shaking table with the principal goals of 1 investigating the mechanisms of seismically induced permanent deformations in slopes and 2 assessing the accuracy and applicability of the newmark sliding block procedure for estimating seismically induced deformations in slopes each of the clayey slope models deformed in response to strong shaking with the principal mode of deformation being deep rotational translational sliding displacement deformations were principally focused along one or more highly localized shear surfaces though a significant amount of additional deformation was also distributed over a relatively wide region of the models the newmark analyses generally provided moderately accurate although somewhat unconservative estimates of deformations displacements computed using the rigid sliding block analysis ranged from 27 to 225 of maximum measured displacements and averaged about 75 of measured displacements for the test series the newmark type analyses were most reliable for those model tests that experienced large deformations where the sliding resistance was controlled principally by postpeak to residual strengths

landslides triggered by the 1949 khait earthquake tajikistan and associated loss of life abstract earthquake triggered landslides are a major geological hazard in central asia in july 1949 the m7 4 khait earthquake triggered many hundreds of landslides in a mountainous region near the southern limit of the tien shan mountains central tajikistan these landslides involved widespread rock slope failure as well as large numbers of flowslides in loess that mantles the steep slopes of the region in the yasman valley hundreds of loess landslides coalesced to form a massive loess flow est vol 245 mm 3 that travelled up to 20 km on a slope of only 2 in an adjacent valley the khait landslide involved transformation of an earthquake triggered rockslide into a very rapid flow by the entrainment of saturated loess into its movement it travelled 7 41 km over a vertical distance of 1421 m with an estimated average velocity of 30 m s we estimate its volume as 75 mm 3 an order of magnitude less that previously published estimates the khait landslide was simulated using dan the number of casualties due to earthquake triggered landslides in the epicentral region was considerable approximately 4000 people were killed in the yasman valley loess flow as 20 villages kishlaks were overwhelmed in the khait landslide alone we estimate ca 800 people lost their lives when the villages of khait and khisorak were overrun by rapidly moving debris our data indicates that a total of approximately 7200 people were killed by earthquake triggered landslides in the epicentral region of the khait earthquake and that in terms of loss of life the 1949 yasman valley loess flow was one of the most destructive landslides in recent history

landslides triggered by the 20 april 2013 lushan earthquake sichuan province china abstract the 20 april 2013 lushan earthquake with a magnitude of m s 7 0 induced widespread landsliding along the southern segment of the longmen shan fault zone this paper presents a preliminary analysis of the characteristics of these co seismic landslides triggered in an area of 13 323 km 2 a total of 3810 individual landslide points were identified through an intensive field investigation and from digital aerial photographs taken after the lushan earthquake to facilitate the more detailed analysis on the areal frequency of co seismic landslides as polygons we selected an area of 732 km 2 around the epicenter that had the highest density of co seismic landslides the sizes of the landslides are in general much smaller than those that were triggered by the 2008 wenchuan earthquake the most common types of landslides in the study area were rock falls and shallow disrupted landslides from steep slopes which typically involved the top few meters of weathered bedrock and colluvium in this study the relation between the landslide distribution and five main factors was analyzed fault proximity epicenter proximity peak ground acceleration pga slope angle and lithology our study results show that the landslide concentration tends to decrease with distance from the seismogenic fault and the highest landslide concentration is located within a distance of 5 km regarding the distance to the epicenter the largest landslide density is found at a distance between 5 and 10 km the landslide concentration also increases with increasing slope angle until a maximum for the slope class 45 55 in addition results show that slopes consisting of deeply weathered and fractured sandstones and mudstones were the most susceptible to co seismic landslides in this study we found that the location of the hanging wall and the footwall of the fault did not seem to have an important effect on the landslide distribution this is in contradiction to what has been reported in other earthquake areas such as the wenchuan area

nonlinear coupled seismic sliding analysis of earth structures earthquake induced sliding displacements of earth structures are generally evaluated using simplified sliding block analyses that do not accurately model the seismic response of the sliding mass nor the seismic forces along the slide plane the decoupled approximation introduced to capture each of these effects separately is generally believed to be conservative however recent studies using linear viscoelastic sliding mass models have revealed instances where the decoupled approximation is unconservative in this paper a coupled analytical model that captures simultaneously the fully nonlinear response of the sliding mass necessary for intense motions and the nonlinear stick slip sliding response along the slide plane is presented the proposed sliding model is validated against shaking table experiments of deformable soil columns sliding down an inclined plane the effect of sliding on the response of earth structures is evaluated and comparisons are made between sliding displacements calculated us

the geological evolution of the tibetan plateau the geological evolution of the tibetan plateau is best viewed in a context broader than the india eurasia collision zone after collision about 50 million years ago crust was shortened in western and central tibet while large fragments of lithosphere moved from the collision zone toward areas of trench rollback in the western pacific and indonesia cessation of rapid pacific trench migration 15 to 20 million years ago coincided with a slowing of fragment extrusion beyond the plateau and probably contributed to the onset of rapid surface uplift and crustal thickening in eastern tibet the latter appear to result from rapid eastward flow of the deep crust probably within crustal channels imaged seismically beneath eastern tibet these events mark a transition to the modern structural system that currently accommodates deformation within tibet

widespread landslides induced by the mw 5 1 earthquake of 11 may 2011 in lorca se spain abstract on 11 may 2011 a moderate magnitude mw 5 1 earthquake struck the city of lorca se spain and nearby areas causing notable damage injuries and fatalities field inspection of the area affected allowed the location and characterization of more than 250 induced landslides mainly of disrupted type rock soil falls disrupted soil slides and rock avalanches this number was very high when compared with the inventories of previous events of similar magnitude mw 4 7 to 5 0 in the zone and with the results of previous models for predicting slope behavior during earthquakes several factors are proposed here to explain the observed differences i the comparatively high magnitude mw 4 5 of a foreshock of the seismic series that may have weakened the slopes ii the high peak ground motion values recorded for these events and iii the occurrence of topographic site effects the results of this study point out the importance of including such effects as improvements in the models for studying the regional behavior of slopes

on subinertial flow in submarine canyons effect of geometry shelf break canyons on the west coast of canada and the united states have been observed to be regions of enhanced upwelling during southward currents compared to the surrounding shelf break most shelf break canyons from oregon north cross only part of the continental shelf cutting from the shelf break toward the coast but end on the continental shelf well below the mixed layer juan de fuca canyon on the other hand cuts the continental shelf from the slope to and actually continues into the strait of juan de fuca this difference in geometry has a very strong effect on the subinertial flow around the canyon model canyon shapes which include convergent bathymetric contours are constructed and motivated for juan de fuca canyon and a typical shelf break canyon geostrophic analytic solutions show that the in canyon flow in juan de fuca canyon is generated by first order geostrophic dynamics whereas in the majority of canyons of which astoria is an example in canyon flow is generated by higher order effects this difference is postulated to lead to the observed very deep upwelling over juan de fuca canyon compared to more moderate episodic upwelling over astoria canyon

the influence of different simplified sliding block models and input parameters on regional predictions of seismic landslides triggered by the northridge earthquake abstract regional seismic landslide hazard maps are based on predictions of rigid sliding block displacement derived from estimates of earthquake ground shaking topography geology and shear strength the confidence in these predictions requires comparisons with field observations of landslide occurrence during previous well documented earthquakes this paper presents a comparison between observed landslides from the 1994 northridge california earthquake and predicted landslides based on sliding block displacement estimates seven empirical displacement models each of which uses a different combination of ground motion parameters are investigated to evaluate which models and associated ground motion parameters best predict seismic landslides using best estimates of ground shaking and shear strength properties from the northridge earthquake sliding displacements are calculated and compared with the locations of observed landslides only 20 40 of the observed landslides are captured and the total area of predicted landslides is much larger than observed the ability to predict landslide occurrence accurately depends less on the displacement model and associated ground motion parameters and more on the uncertainty in the model parameters particularly the assigned shear strengths because current approaches do not take into account the spatial variability of shear strength within individual geologic units the accuracy of the predictive models is controlled predominantly by the distribution of slope angles within a geologic unit assigning overly conservative low shear strength values results in a higher percentage of landslides accurately identified but also results in a large over estimation of the total landslide area making more accurate maps of seismic landslide hazards will require methods to define intra formational variations in shear strength

characteristics of earthquake and rain induced landslides near the epicenter of wenchuan earthquake abstract numerous landslides were triggered by the 12 may 2008 wenchuan earthquake in china particularly near the epicenter during the rainy season in 2010 after the earthquake much of the landslide debris was reactivated causing a large number of fatalities the earthquake has a significant impact on the subsequent rain induced landslides based on interpretation of satellite images taken in 2008 and 2010 combined with yearly field investigations this paper attempts to 1 map the earthquake induced landslides near the epicenter 2 present the distribution of the landslides occurring during a subsequent extreme storm in the same area and 3 compare the distribution characteristics of the earthquake induced landslides and the rain induced landslides through this study the following findings were obtained 1 the internal relief of the landslides in the study area is much higher than that in other affected regions of the wenchuan earthquake zone 2 the landslide area in hard rocks i e the granite and diorite zones is much larger than that in alluvium 3 the volume of hill slope loose deposits decreased while the volume of channel deposits increased during the process of mass transportation caused by rainfall after the earthquake 4 during the rainy seasons after the earthquake the density of landslides increased while the area of landslides decreased significantly and the type of landslides transformed from debris slides to debris flows and 5 the rain induced landslides are less steeper than the earthquake induced landslides

cross shelf exchange driven by oscillatory barotropic currents at an idealized coastal canyon abstract numerical simulations are used to study on shelf transport of dense water by oscillatory barotropic currents incident upon an isolated coastal canyon the physical system is a laboratory scale annulus in which forcing is provided by an oscillatory modulation in the rotation rate and for which the external nondimensional parameters match those from an appropriate oceanic analog the numerical simulations were conducted for comparison with a companion set of laboratory experiments and these prior studies have shown good qualitative and quantitative agreement between the two here the numerical simulations are examined in further detail to determine the three dimensional structure of the time mean currents and density field on the shelf to quantify the resulting onshore transport of dense water and to expose the underlying nondimensional parameter dependencies the incident barotropic currents produce in equilibrium an extensive pool of anomalously dense fluid on the shelf surrounding the canyo

statistical analysis of an earthquake induced landslide distribution the 1989 loma prieta california event the 1989 loma prieta california earthquake moment magnitude m 6 9 generated landslides throughout an area of about 15 000 km2 in central california most of these landslides occurred in an area of about 2000 km2 in the mountainous terrain around the epicenter where they were mapped during field investigations immediately following the earthquake the distribution of these landslides is investigated statistically using regression and one way analysis of variance anova techniques to determine how the occurrence of landslides correlates with distance from the earthquake source slope steepness and rock type the landslide concentration defined as the number of landslide sources per unit area has a strong inverse correlation with distance from the earthquake source and a strong positive correlation with slope steepness the landslide concentration differs substantially among the various geologic units in the area the differences correlate to some degree with differences in lithology and degree of induration but this correlation is less clear suggesting a more complex relationship between landslide occurrence and rock properties

landslides in eastern honshu induced by the 2011 tohoku earthquake in this article we discuss the character and spatial pattern of coseismic landslides from the eastern honshu region of japan which was strongly shaken in the 2011 tohoku earthquake we developed a detailed geospatial database of 3477 landslides based on postearthquake field surveys and examination of high resolution satellite imagery across a 28 380 km2 landslide study area analysis of the database shows that a substantial majority 80 of landslides occurred in quaternary soil and neogene rock units despite their abundance in the study area relatively few landslides occurred in pre neogene rocks i e older than 23 ma further examination of the data showed that the most common types of landslides were 1 disrupted landslides in neogene sedimentary rocks and 2 lateral spreading in quaternary sediments however we found that coseismic landslide erosion i e debris mobilization was almost fully dominated by lateral spreading within quaternary sediments when comparing the landslide inventory with ground motions recorded by dense regional seismic arrays we found no statistically significant correlation between landslide intensity and ground motion within the study area online material derivation of empirical parameters used in the area to volume transformations for lateral spreads

inclined plane studies of the newmark sliding block procedure this study considers the shaking induced displacement and dynamic response of a rigid block and deformable columns of soil on an inclined plane this work demonstrates that because of the coupled d

dynamics of cross shelf water exchanges off pearl river estuary in summer abstract dynamics regulating the cross isobath momentum and water exchanges over the shelf in the vicinity of the pearl river estuary pre in july 2015 and 2017 are examined using comprehensive observations and multiple level nested high resolution numerical simulations although driven by the upwelling and downwelling favorable winds in july 2015 and 2017 respectively the shelf currents and the cross isobath exchanges illustrate great similarity during these two periods this study finds that the southwesterly induced flow downstream in the taiwan strait maintained the northeastward upwelling currents in the vicinity of the pre that caused the extensive upslope invasion of the deep shelf waters the cross shelf exchanges of the shelf and coastal waters mainly occur over the irregular topography off the entrance of the huangmaohai estuary to the west of the dangan island and over a shallow trough to the east of hong kong it is also rationalized that the intensified exchange flow is established by an along shelf pressure gradient force that notably exceeds the contributions from the bottom and surface ekman transport as well as the nonlinearity of the shelf current in the water column the baroclinicity of the shelf and coastal waters plays minimal roles in altering this along shore pressure gradient force especially when upwelling favorable winds prevail the exchange flows in the water column thereby show great similarity with those in the bottom layer where the bottom along shore pressure gradient force is jointly imposed by the nonlinear advection of relative vorticity and frictional stress curl in both the surface and bottom layers the spatial variation of these terms is regulated by the intensity of the shelf current and along shelf variation of bottom topography

statistical analysis of landslide susceptibility at yongin korea the aim of this study is to evaluate the susceptibility of landslides at yongin korea using a geographic information system gis landslide locations were identified in the yongin area from interpretation of aerial photographs field surveys and maps of the topography soil type timber cover and geology these data were collected and constructed into a spatial database using gis the factors that influence landslide occurrence such as slope aspect and curvature of topography were calculated from the topographic database texture material drainage and effective soil thickness were extracted from the soil database and type age diameter and density of timber were extracted from the forest database lithology was extracted from the geological database and land use was classified from the landsat tm satellite image landslide susceptibility was analyzed using the landslide occurrence factors by probability and logistic regression methods the results of the analysis were verified using the landslide location data the validation results showed satisfactory agreement between the susceptibility map and the existing data on landslide location the gis was used to analyze the vast amount of data efficiently and statistical programs were used to maintain specificity and accuracy the results can be used to reduce associated hazards and to plan land use and construction

dynamic analysis of a slope failure from the 6 august 1979 coyote lake california earthquake abstract the coyote lake california earthquake of 6 august 1979 m l 5 7 provided a rare opportunity to perform a dynamic numerical analysis of a seismically induced slope failure using actual strong motion records the earthquake displaced a preexisting slump on the northeast shore of lake anderson and formed a fissure 20 m long offsets of 9 mm vertically and 18 mm horizontally were measured across the fissure the slump is 9 km northwest of the located epicenter but within 100 m of the mapped trace of the calaveras fault two strong motion records were written in the vicinity of the slump coyote creek 5 km to the southeast and gilroy 6 15 km to the southeast these records combined with field measurements of the slope estimates of the material properties and a dynamic numerical model based on the newmark analysis of seismic slope stability to calculate a predicted displacement for the landslide a displacement of 27 mm calculated using the n50 e component of the gilroy 6 record is in excellent agreement with the displacement measured in the field 21 mm however displacements of only 0 12 mm calculated using the 250 component of the coyote creek strong motion record reflect significant local variations in seismic shaking intensity because strong motion records and slope failures rarely coincide this landslide provides an important test case for our understanding of the dynamics of seismically induced landslides as well as a warning that local seismologic variations need to be considered in any design applications

repeating earthquakes in the yellowstone volcanic field implications for rupture dynamics ground deformation and migration in earthquake swarms abstract we evaluated properties of yellowstone earthquake swarms employing waveform multiplet analysis thirty seven percent of the earthquakes in the yellowstone caldera occur in multiplets and generally intensify in areas undergoing crustal subsidence outside the caldera in the hedgen lake tectonic area the clustering rate is higher up to 75 the yellowstone seismicity follows a succession of two phases of earthquake sequence the first phase is defined between swarms it is characterized by a decay of clustering rate and by foreshock aftershock sequences the second phase is confined to swarms and is characterized by an increase in clustering rate and dominant aftershock sequences this phase reflects tectonic swarms that occur on short segments of optimally oriented faults for example the largest recorded swarm in yellowstone occurred in autumn 1985 on the northwest side of the yellowstone plateau which was initiated as a tectonic source sequence fitting experimental dependence of fluid injection with intrusion migration suggests that the 1985 swarm involved after 10 days hydrothermal fluids flowing outward from the caldera the 2008 2009 yellowstone lake swarm exhibited a high migration rate of 1 km day a decrease in clustering rate without a main shock and appears to be associated with magma injection of 1 to 5 m 3 s in a succession of migrating magma fronts that incrementally solidify and fracture at its brittle edges the 2010 madison plateau earthquake swarm on the west side of the caldera initiated as a tectonic sequence but the expansion of the swarm front was associated with hydrothermal fluid migration

landslide characteristics and slope instability modeling using gis lantau island hong kong steep terrain and high a frequency of tropical rainstorms make landslide occurrence on natural terrain a common phenomenon in hong kong this paper reports on the use of a geographical information systems gis database compiled primarily from existing digital maps and aerial photographs to describe the physical characteristics of landslides and the statistical relations of landslide frequency with the physical parameters contributing to the initiation of landslides on lantau island in hong kong the horizontal travel length and the angle of reach defined as the angle of the line connecting the head of the landslide source to the distal margin of the displaced mass are used to describe runout behavior of landslide mass for all landslides studied the horizontal travel length of landslide mass ranges from 5 to 785 m with a mean value of 43 m and the average angle of reach is 27 7 this gis database is then used to obtain a logistic multiple regression model for predicting slope instability it is indicated that slope gradient lithology elevation slope aspect and land use are statistically significant in predicting slope instability while slope morphology and proximity to drainage lines are not important and thus excluded from the model this model is then imported back into the gis to produce a map of predicted slope instability the results of this study demonstrate that slope instability can be effectively modeled by using gis technology and logistic multiple regression analysis