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

gis based support vector machine modeling of earthquake triggered landslide susceptibility in the jianjiang river watershed china abstract support vector machine svm modeling is based on statistical learning theory it involves a training phase with associated input and target output values in recent years the method has become increasingly popular the main purpose of this study is to evaluate the mapping power of svm modeling in earthquake triggered landslide susceptibility mapping for a section of the jianjiang river watershed using a geographic information system gis software the river was affected by the wenchuan earthquake of may 12 2008 visual interpretation of colored aerial photographs of 1 m resolution and extensive field surveys provided a detailed landslide inventory map containing 3147 landslides related to the 2008 wenchuan earthquake elevation slope angle slope aspect distance from seismogenic faults distance from drainages and lithology were used as the controlling parameters for modeling three groups of positive and negative training samples were used in concert with four different kernel functions positive training samples include the centroids of 500 large landslides those of all 3147 landslides and 5000 randomly selected points in landslide polygons negative training samples include 500 3147 and 5000 randomly selected points on slopes that remained stable during the wenchuan earthquake the four kernel functions are linear polynomial radial basis and sigmoid in total 12 cases of landslide susceptibility were mapped comparative analyses of landslide susceptibility probability and area relation curves show that both the polynomial and radial basis functions suitably classified the input data as either landslide positive or negative though the radial basis function was more successful the 12 generated landslide susceptibility maps were compared with known landslide centroid locations and landslide polygons to verify the success rate and predictive accuracy of each model the 12 results were further validated using area under curve analysis group 3 with 5000 randomly selected points on the landslide polygons and 5000 randomly selected points along stable slopes gave the best results with a success rate of 79 20 and predictive accuracy of 79 13 under the radial basis function of all the results the sigmoid kernel function was the least skillful when used in concert with the centroid data of all 3147 landslides as positive training samples and the negative training samples of 3147 randomly selected points in regions of stable slope success rate 54 95 predictive accuracy 61 85 this paper also provides suggestions and reference data for selecting appropriate training samples and kernel function types for earthquake triggered landslide susceptibility mapping using svm modeling predictive landslide susceptibility maps could be useful in hazard mitigation by helping planners understand the probability of landslides in different regions

structure of the crust beneath the southeastern tibetan plateau from teleseismic receiver functions abstract southeastern tibet marks the site of presumed clockwise rotation of the crust due to the india eurasian collision and abutment against the stable sichuan basin and south china block knowing the structure of the crust is a key to better understanding of crustal deformation and seismicity in this region here we analyze recordings of teleseismic earthquakes from 25 temporary broadband seismic stations and one permanent station using the receiver function method we find that the crustal thickness decreases gradually from the tibetan plateau proper to the sichuan basin and yangtze platform but that significant intra crustal heterogeneity exists on shorter lateral scales 0 30 are detected beneath the southeastern margin of tibet but in the sichuan basin and southeastern yangtze platform the values are close to the global average combined with high regional heat flow and independent evidence for mid crustal layers of high electric conductivity the large intra crustal s wave velocity reduction 12 19 and the intermediate to high average crustal poisson s ratios are consistent with partial melt in the crust beneath parts of southeastern tibet these results could be used in support of deformation models involving intra crustal flow with the caveat that significant lateral variation in location and strength of this flow may occur

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

analysis of landslide dams induced by the 2008 wenchuan earthquake abstract landslide dams caused by earthquakes are extremely hazardous disruptions of the flow of water and sediment in mountain rivers capable of delivering large outburst floods that may devastate downstream areas we analyzed a unique inventory of 828 landslide dams triggered by the m w 7 9 2008 wenchuan tectonic earthquake china constituting 1 4 of the 60 000 coseismic slope failures mapped and attributed to this event while 501 landslides blocked the rivers completely the remainder caused only partial damming or channel diversion the spatial distribution of landslide dams follows the same trend of that of the total landslide distribution with landslide dams being most abundant in the steep watersheds of the hanging wall of the yingxiu beichuan thrust fault and in the northeastern part of the strike slip fault near qingchuan besides the co seismic landslide density the river width also played a key role in determining the landslide dam formation narrow rivers are more prone to be dammed than the wide rivers the correlation between river width and landslide dam volume follows a linear relation which can be used to roughly estimate the dam formation possibility however the applicability of this correlation needs to be validated in other regions the decay failure rate of dams defined here as the percentage of the number and area of landslide dams that have failed over time shows that 25 of dams accounting for 30 of total landslide dam area failed one week after the earthquake these percentages increased to 60 within 1 month and to 90 within 1 year the geomorphometric parameters were analyzed revealing power law relations between landslide area and dam width landslide source area and dam area as well as lake area and lake volume the inventory presented in this study will enrich the worldwide earthquake induced landslide dam database and will also contribute to a better understanding of the post earthquake dam decay

statistical analysis of seismic data from north western and western argentina due to the process of subduction of the nazca plate high seismic activity is observed near the argentine andean range between 21 s and 36 s the new version of the argentine seismic catalogue which includes well defined events during the period 1964 1989 allows us to perform an analysis of seismic risk

frequency and hazard of large rock avalanches in the central southern alps new zealand forty two rock avalanche deposits with volumes ranging from a chosen lower threshold of 1 10 6 m 3 up to 500 10 6 m 3 have been identified in a 10 000 km 2 area of the central southern alps new zealand the observed frequency of one per 244 yr over 10 250 yr is biased by erosion a nearly complete sample of the past 1 700 yr indicates a frequency of 1 per 94 yr on the average the largest rock avalanche in any century is 56 10 6 m 3 and in any millennium 103 10 6 m 3 at about one per century most large rock avalanches are probably triggered by large earthquakes and only a few by large storms the risk of rock avalanche debris reaching a specified distance from a source of known elevation is given by a simple stochastic model locally calibrated to assess rock avalanche hazard

co seismic ruptures of the 12 may 2008 ms 8 0 wenchuan earthquake sichuan east west crustal shortening on oblique parallel thrusts along the eastern edge of tibet abstract the m s 8 0 wenchuan earthquake which devastated the mountainous western rim of the sichuan basin in central china produced a surface rupture over 200 km long with oblique thrust dextral slip and maximum scarp heights of 10 m it thus ranks as one of the world s largest continental mega thrust events in the last 150 yrs field investigation shows clear surface breaks along two of the main branches of the ne trending longmen shan thrust fault system the principal rupture on the nw dipping beichuan fault displays nearly equal amounts of thrust and right lateral slip basin ward of this rupture another continuous surface break is observed for over 70 km on the parallel more shallowly nw dipping pengguan fault slip on this latter fault was pure thrusting with a maximum scarp height of 3 5 m this is one of the very few reported instances of crustal scale co seismic slip partitioning on parallel thrusts this out of sequence event with distributed surface breaks on crustal mega thrusts highlights regional ew directed present day crustal shortening oblique to the longmen shan margin of tibet the long rupture and large offsets with strong horizontal shortening that characterize the wenchuan earthquake herald a re evaluation of tectonic models anticipating little or no active shortening of the upper crust along this edge of the plateau and require a re assessment of seismic hazard along potentially under rated active faults across the densely populated western sichuan basin and mountains

surface deformation related to the 2008 wenchuan earthquake and mountain building of the longmen shan eastern tibetan plateau abstract the 12 may 2008 ms 8 0 wenchuan earthquake china was one of largest continental thrusting events worldwide based on interpretations of post earthquake high resolution remote sensing images and field surveys we investigated the geometry geomorphology and kinematics of co seismic surface ruptures as well as seismic and geologic hazards along the longmen shan fold and thrust belt our results indicate that the wenchuan earthquake occurred along the ne sw trending yingxiu beichuan and guanxian anxian faults in the longmen shan fold and thrust belt the main surface rupture zones along the yingxiu beichuan and guanxian anxian fault zones are approximately 235 and 72 km in length respectively these sub parallel ruptures may merge at depth the yingxiu donghekou surface rupture zone can be divided into four segments separated by discontinuities that appear as step overs or bends in map view surface deformation is characterized by oblique reverse faulting with a maximum vertical displacement of approximately 10 m in areas around beichuan county earthquake related disasters e g landslides are linearly distributed along the surface rupture zones and associated river valleys the wenchuan earthquake provides new insights into the nature of mountain building within the longmen shan eastern tibetan plateau the total crustal shortening accommodated by this great earthquake was as much as 8 5 m with a maximum vertical uplift of approximately 10 m the present results suggest that ongoing mountain building of the longmen shan is driven mainly by crustal shortening and uplift related to repeated large seismic events such as the 2008 wenchuan earthquake furthermore rapid erosion within the longmen shan fold and thrust belt occurs along deep valleys and rupture zones following the occurrence of large scale landslides triggered by earthquakes consequently we suggest that crustal shortening related to repeated great seismic events together with isostatic rebound induced by rapid erosion related unloading is a key component of the geodynamics that drive ongoing mountain building on the eastern tibetan plateau

active tectonics of the beichuan and pengguan faults at the eastern margin of the tibetan plateau the steep high relief eastern margin of the tibetan plateau has undergone rapid cenozoic cooling and denudation yet shows little evidence for large magnitude shortening or accommodation generation in the foreland basin we address this paradox by using a variety of geomorphic observations to place constraints on the kinematics and slip rates of several large faults that parallel the plateau margin the beichuan and pengguan faults are active dominantly dextral slip structures that can be traced continuously for up to 200 km along the plateau margin both faults offset fluvial fill terraces that yield inheritance corrected cosmogenic 10be exposure ages of 15 kyr indicating latest pleistocene activity the pengguan fault appears to have been active in the holocene at two sites along strike latest quaternary apparent throw rates on both faults are variable along strike but are typically 1 mm yr 1 rates of strike slip displacement are likely to be several times higher probably 1 10 mm yr 1 but remain poorly constrained late quaternary folding and dextral strike slip has also occurred along the western margin of the sichuan basin particularly associated with the present day mountain front these observations support models for the formation and maintenance of the eastern plateau margin that do not involve major upper crustal shortening they also suggest that activity on the margin parallel faults in eastern tibet may represent a significant seismic hazard to the densely populated sichuan basin

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

evaluation of factors controlling earthquake induced landslides caused by chi chi earthquake and comparison with the northridge and loma prieta events over 10 000 landslides were triggered by the september 21 1999 chi chi earthquake a large number of these landslides have been mapped from spot images and a smaller number were described in a detailed field investigation geographic information systems gis was used to conduct a spatial characterization of the slope failures including distribution of type size slope angle bedrock geology ground motion and distance from earthquake source the most abundant landslides were shallow disaggregated rock and soil slides landslides occurred primarily in tertiary sedimentary rocks which are well known for their susceptibility to landsliding in many parts of the world landslide concentration values diminish beyond epicentral distances of 40 and 70 km from the epicenter and the surface projection of the fault plane respectively ground motion was found to be the most significant factor in triggering the shallow landslides in the chi chi earthquake overall 74 of all slope failures occurred in regions with vertical ground motions greater than 0 2g and 81 of all slope failures occurred in the region with mean horizontal peak ground accelerations pga greater than 0 15g these factors were used to compare landslides generated by the chi chi earthquake to the landslides triggered by the 1989 loma prieta earthquake and the 1994 northridge earthquake the major difference in distribution of landslides between the chi chi earthquake and the two california earthquakes was the distribution of slope angles in the chi chi earthquake 90 of the failures occurred on slopes steeper than 45 while more than 80 of failures occurred on slopes less than 50 in california apparently reflecting much steeper and tectonically more active geologic setting in taiwan

global positioning system measurements from eastern tibet and their implications for india eurasia intercontinental deformation we present and interpret global positioning system gps measurements of crustal motions for the period 1991 1998 for a network encompassing the eastern part of the tibetan plateau and its foreland relative to a eurasian frame defined by minimizing the velocities of 16 gps stations in europe central asia and siberia stations within all parts of the plateau foreland in south china move 6 10 mm yr east southeast indicating that the eastward movement within the plateau is part of a broader eastward movement that involves the plateau and its eastern and northern foreland north of the plateau foreland stations move northeastward at 10 mm yr indicating that the northern boundary of the deformation zone lies north of the plateau with this realization of a eurasian frame the velocity of the gps station at bangalore in southern india implies that the northward motion of india is 5 12 mm yr slower than that predicted from the nuvel 1a plate reconstruction viewed relative to the south china block stations of the northeast plateau bounded on the north by the qilian shan and the altyn tagh fault move nne to ne with velocities ranging from 19 mm yr within the plateau to 5 11 mm yr in its foreland the altyn tagh fault shows left lateral slip of 10 mm yr at 95 e and shortening across the fault of 5 mm yr stations south and west of the xianshuihe xiaojiang fault system define a crustal fragment rotating clockwise at 10 mm yr relative to the south china block around the eastern himalayan syntaxis the gps measurements indicate no significant shortening 3 mm yr within the longmen shan of the central eastern plateau and its adjacent foreland although the longmen shan rise over 6 km in 100 km horizontal distance geological studies indicate that the deformational field was established diachronously in late miocene to pliocene time was characterized by no east west shortening of tibetan crust and has an inhomogeneous style of deformation resulting from a balance of different tectonic processes

geological and geomorphological characteristics of landslides triggered by the 2004 mid niigta prefecture earthquake in japan abstract the 2004 mid niigta prefecture earthquake mjma 6 8 triggered more than one thousand landslides in the miocene to quaternary sedimentary rocks in japan the most common landslides were shallow disrupted landslides on steep slopes which has been common in many previous disastrous earthquakes in the world the mid niigta prefecture earthquake also triggered more than one hundred deep landslides providing valuable information on the conditions for their occurrence a field investigation and the interpretation of aerial photographs taken before and after the earthquake suggest that reactivation of existing landslides and undercutting of slopes are the most important factors for deep landslides to be triggered by earthquakes in addition planar sliding surfaces seem to be essential for the generation of catastrophic landslides triggered by this earthquake planar bedding parallel sliding surfaces were formed at the boundary between the overlying permeable sandstone and underlying siltstone or along the bedding planes of alternating beds of sandstone and siltstone sliding surfaces along the slope parallel oxidation front were formed in the area of black mudstone new landslides rockslide avalanches occurred with the sliding surfaces in a several cm thick tuff interbedded in siltstone one rockslide avalanche occurred on a slope where buckling deformation preceded the earthquake gentle valley bottom sediments were mobilized in many locations probably because they were saturated and partial liquefaction had occurred due to the earthquake shaking

the effect of the wenchuan earthquake on the fluvial morphology in the longmen shan eastern tibetan plateau discussion and speculation abstract although large earthquakes can have significant impacts on the geomorphology of mountain rivers the consequences of such impacts remain poorly understood the ms 8 0 wenchuan earthquake of 12 may 2008 created knickpoints waterfalls in the river systems of the longmen shan eastern tibet plateau in addition to numerous landslides along rivers in this study we use high resolution remote sensing images and field surveys to examine how the baisha and jianjiang river channels responded to the wenchuan earthquake the morphological response along the baisha river was a knickpoint with a height of 4 5 m which was studied from 2008 to 2012 however the river did not show rapid incision via knickpoint migration during the post earthquake period in fact post seismic flooding destroyed the face of the co seismic knickpoint the rapid removal of the knickpoint suggests that the abrupt vertical displacement associated with the earthquake did not exceed the adjustment threshold of the fluvial dynamic equilibrium and so was unable to drive rapid morphological change at the local scale along the jianjiang river the average meander migration rate of the beichuan reach was 2 8 m yr between 2001 and 2008 but increased to 51 1 m yr during the five years following the 2008 wenchuan earthquake this rapid increase in the meander migration rate is attributed to excess sediment supplied to the river as a consequence of the earthquake these two case studies indicate that the wenchuan earthquake caused channel aggradation rather than a significant increase in river incision by locally generating relief across the river

ground motions at the outermost limits of seismically triggered landslides abstract over the last few decades we and our colleagues have conducted field investigations in which we mapped the outermost limits of triggered landslides in four earthquakes 1987 whittier narrows california m 5 9 1987 superstition hills california m 6 5 1994 northridge california m 6 7 and 2011 mineral virginia m 5 8 in an additional two earthquakes 1976 guatemala m 7 5 and 1983 coalinga california m 6 5 we determined limits using high resolution aerial photographic interpretation in conjunction with more limited ground investigation limits in these earthquakes were defined by the locations of the very smallest failures 3 from the most susceptible slopes that can be identified positively as having been triggered by earthquake shaking because we and our colleagues conducted all of these investigations consistent methodology and criteria were used in determining limits in the six earthquakes examined we correlated the outermost landslide limits with peak ground accelerations pgas from shakemap models of each earthquake for the four earthquakes studied by field investigation the minimum pga values associated with farthest landslide limits ranged from 0 02 g to 0 08 g the range for the two earthquakes investigated using aerial photographic interpretations was 0 05 0 11 g although pga values at landslide limits depend on several factors including material strength topographic amplification and hydrologic conditions these values provide an empirically useful lower limiting range of pga needed to trigger the smallest failures on very susceptible slopes in a well recorded earthquake this pga range can be used to identify an outer boundary within which we might expect to find landsliding in earthquakes that are not well recorded mapping the outermost landslide limits provides a useful clue about ground motion levels at the mapped limits

paleoseismological events in the seismic gap between the 2008 wenchuan and the 2013 lushan earthquakes and implications for future seismic potential abstract the aftershocks of the 2008 wenchuan and 2013 lushan earthquakes delineated a prominent 60 km long seismic gap the uncertainty regarding the near future seismic potential of this seismic gap has become of increasing importance to both the scientific community and the public using paleoseismology this study investigated the occurrence of the last major event in the seismic gap and then considered the future seismic potential based on image interpretation trench excavation radiocarbon and optically stimulated luminescence dating and comparisons with historical earthquake rupture lengths the most recent paleoearthquake estimated magnitude m6 5 7 0 along the shuangshi dachuan fault sdf which is the southern segment of the longmen shan fault was constrained to 640 1330 ce very possibly 876 ce according to the most recent geological and geophysical findings we suggest that the seismic gap i e the sdf could be capable of generating m6 0 7 0 earthquakes but that the likelihood of such an occurrence in the near future is not very high

coseismic reverse and oblique slip surface faulting generated by the 2008 mw 7 9 wenchuan earthquake china the mw 7 9 wenchuan china earthquake ruptured two large thrust faults along the long menshan thrust belt at the eastern margin of the tibetan plateau this earthquake generated a 240 km long surface rupture zone along the beichuan fault and an additional 72 km long surface rupture zone along the pengguan fault maximum vertical and horizontal offsets of 6 5 m and 4 9 m respectively were measured along the beichuan fault a maximum vertical offset of 3 5 m was measured along the pengguan fault coseismic surface ruptures integrated with aftershocks and industry seismic profiles show that two imbricate structures have ruptured simultaneously resulting in the largest continental thrust event ever documented large oblique thrusting observed during this earthquake indicates that crustal shortening is an important process responsible for the high topography in the region as everywhere along the edge of tibetan plateau

continuous deformation of the tibetan plateau from global positioning system data global positioning system velocities from 553 control points within the tibetan plateau and on its margins show that the present day tectonics in the plateau is best described as deformation of a continuous medium at least when averaged over distances of 100 km deformation occurs throughout the plateau interior by ese wnw extension and slightly slower nne ssw shortening relative to eurasia material within the plateau interior moves roughly eastward with speeds that increase toward the east and then flows southward around the eastern end of the himalaya crustal thickening on the northeast ern and eastern margins of the plateau occurs over a zone 400 km wide and cannot be the result of elastic strain on a single major thrust fault shortening there accommodates much of india s penetration into eurasia a description in terms of movements of rigid blocks with elastic strain associated with slip on faults between them cannot match the velocity field

earthquake induced rockfall hazard zoning abstract a methodology for quantitative probabilistic hazard zonation for earthquake induced rockfalls is presented and demonstrated in the area of friuli eastern italian alps affected by the 1976 mw 6 5 earthquake four rockfall datasets have been prepared both from historical data analysis and field surveys the methodology relies on a three dimensional hazard vector whose components include the rockfall kinetic energy the fly height and the annual frequency the values of the first two components are calculated for each location along the slope using the 3d rockfall runout simulator hy stone the rockfall annual frequency is assessed by multiplying the annual onset frequency by the simulated transit frequency the annual onset frequency is calculated through a procedure that combines the extent of unstable areas calculated for 10 different seismic hazard scenarios with different annual frequencies of occurrence and the magnitude relative frequency relationship of blocks as derived from the collected field data for each annual frequency of occurrence the unstable area is calculated as a function of morphometric and earthquake characteristics a series of discriminant analysis models using the rockfall datasets and dems of different resolution 1 and 10 m identified the controlling variables and verified the model robustness in contrast with previously published relationships we show that the slope curvature plays a relevant role in the computation of the unstable area

effects of entrainment phenomenon on the rapid and long runout movement of landslides in wenjia gully sichuan china as a common phenomenon in landslides entrainment of loose bed material along the sliding path can enhance both the volume and mobility of the sliding mass posing a great threat to the life and property safety of people in the affected area for the purpose of revealing the mechanism of entrainment phenomenon of sliding material in the runout process a dynamic slice based model was firstly proposed in the present study in this model the motion of landslide body is assumed to follow the rheological law proposed by voellmy additionally through voellmy model the increase in kinetic energy mass and volume of landslide body and entrainment depth caused by the entrainment phenomenon were taken into consideration subsequently on the basis of the dynamic slice based model back analyses were performed on the wenjia gully landslide the effect of entrainment phenomenon on the post failure motion was analyzed the calculated results shows that the travel distance obtained from proposed model is closer to field data than that resulted from scheidegger s empirical method moreover the peak value of the maximum velocity calculated by this model is in good agreement with that get from the dynamic analysis model dan3d when considering the entrainment phenomenon the volume of sliding mass increases greatly in post failure motion this paper provides a new method for analyzing the entrainment phenomenon in landslide motion

sediment flux from a mountain belt derived by landslide mapping in humid uplands landsliding is the dominant mass wasting process in the western southern alps of new zealand landslides are scale invariant and have a power law magnitude frequency distribution independent studies from other regions suggest that this is a general property of landsliding this observation is of critical importance to the evaluation of the impact of events of different length scales over different time intervals on landscape evolution it is particularly useful when estimating regional geomorphic rates because it constrains the frequency and overall significance of extreme events which cannot otherwise be evaluated by integrating the complete response of the system we estimate the regional denudation rate due to landsliding to be 9 4 mm yr 1 sediment discharge from the western southern alps is dominated by landslide derived material

a seismic landslide susceptibility rating of geologic units based on analysis of characteristics of landslides triggered by the 17 january 1994 northridge california earthquake abstract one of the most significant effects of the 17 january 1994 northridge california earthquake m 6 7 was the triggering of thousands of landslides over a broad area some of these landslides damaged and destroyed homes and other structures blocked roads disrupted pipelines and caused other serious damage analysis of the distribution and characteristics of these landslides is important in understanding what areas may be susceptible to landsliding in future earthquakes we analyzed the frequency distribution and geometries of triggered landslides in the santa susana 7 5 quadrangle an area of intense seismic landslide activity near the earthquake epicenter landslides occurred primarily in young late miocene through pleistocene uncemented or very weakly cemented sediment that has been repeatedly folded faulted and uplifted in the past 1 5 million years the most common types of landslide triggered by the earthquake were highly disrupted shallow falls and slides of rock and debris far less numerous were deeper more coherent slumps and block slides primarily occurring in more cohesive or competent materials the landslides in the santa susana quadrangle were divided into two samples single landslides 1502 and landslide complexes 60 which involved multiple coalescing failures of surficial material we described landslide morphologies by computing simple morphometric parameters area length width aspect ratio slope angle to quantify and rank the relative susceptibility of each geologic unit to seismic landsliding we calculated two indices 1 the susceptibility index which is the ratio given as a percentage of the area covered by landslide sources within a geologic unit to the total outcrop area of that unit and 2 the frequency index given in landslides per square kilometer ls km2 which is the total number of landslides within each geologic unit divided by the outcrop area of that unit susceptibility categories include very high 2 5 landslide area or 30 ls km2 high 1 0 2 5 landslide area or 10 30 ls km2 moderate 0 5 1 0 landslide area or 3 10 ls km2 and low

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

provenance and earthquake signature of the last deglacial xinmocun lacustrine sediments at diexi east tibet abstract well preserved lacustrine sediments are found in some areas in east tibet this region is characterized by a windy and semi arid climate alpine valleys and frequent earthquakes measurements of rare earth elements observations from a scanning electron microscope and a high resolution record of grain size measurements allowed us to compare fine sediments from the xinmocun section in the diexi lake with loess from the chinese loess plateau and south china results indicate that fine grains of the xinmocun lacustrine sediments were transported by wind and trapped in the lake whereas the 16 m fraction was likely from local sources the grain size changes within the section repeatedly show abrupt coarsening and upward fining probably due to palaeoearthquake events large earthquakes in the study area often caused rockfalls and landslides exposing fine sediments that had accumulated on mountains slopes the fine grains were then retransported by wind to the diexi lake optically stimulated luminescence dating of the xinmocun section indicates continuous deposition from 18 65 to 10 63 ka these results indicate that palaeoearthquakes in the study area had a mean recurrence interval of 0 32 ka therefore we propose that lacustrine sediments in a tectonically active region have the potential to record a continuous history of palaeoearthquakes palaeoearthquakes probably produced numerous rockfalls and landslides in alpine valleys and provided significant sources of regional eolian dust

magnitude and frequency of rock falls and rock slides along the main transportation corridors of southwestern british columbia the two main transportation corridors of southwestern british columbia are subject to a range of rock slope movements rock falls rock slides and rock avalanches that pose significant risks to r

influence of a tectonically active mountain belt on its foreland basin evidence from detrital zircon dating of bedrocks and sediments from the eastern tibetan plateau and sichuan basin sw china abstract the tectonically active eastern tibetan plateau tp impacts the populous sichuan basin in the form of dust and exhumed detrital materials to better understand a detailed transport process of detrital material from the eastern tp to the sichuan basin eight samples were collected from the upper reaches of the min river in the eastern tp to the sichuan basin for zircon u pb chronological and grain size analysis the results are compared with those of previously studies zircon grains are comparatively coarse in three bedrock samples one fluvial sand sample and one dust sample but are distinctly fine in three lacustrine samples intriguingly the zircon grain size parameters from the fluvial sand and dust samples are similar to each other consistent with previous studies of this area the analysis of our u pb zircon ages indicates five major age populations at 180 350 ma 350 550 ma 700 1000 ma 1600 2000 ma and 2200 2600 ma which broadly correspond to five known granitoid magmatic events within the yangtze block the min river links lacustrine sediments from lixian fluvial sands from wenchuan leshan yibin and from the dadu river and the dayi conglomerate implying the dayi conglomerate was transported by fluvial rather than glacial processes the denuded detrital material mainly generated by seismic events in the eastern tp was transported by water flow into the western sichuan basin where two thick sedimentary depocenters developed and the relatively fine grains were then transported by wind to the northern sichuan basin thus the thick sediments in the western sichuan basin mainly transported by the min river probably exerted a major influence on dust deposition in the northern sichuan basin in contrast the jialing and dadu rivers made a minor contribution

monitoring co2 saturation using time lapse amplitude versus offset analysis of 3d seismic data from the ketzin co2 storage pilot site germany the injection of co2 at the ketzin pilot site commenced in june 2008 and was terminated in august 2013 after 67 kt had been injected into a saline formation at a depth of 630 650 m as part of the site monitoring program four 3d surface seismic surveys have been acquired to date one baseline and three repeats of which two were conducted during the injection period and one during the post injection phase the surveys have provided the most comprehensive images of the spreading co2 plume within the reservoir layer both petrophysical experiments on core samples from the ketzin reservoir and spectral decomposition of the 3d time lapse seismic data show that the reservoir pore pressure change due to co2 injection has a rather minor impact on the seismic amplitudes therefore the observed amplitude anomaly is interpreted to be mainly due to co2 saturation in this study amplitude versus offset analysis has been applied to investigate the amplitude versus offset response from the top of the sandstone reservoir during the injection and post injection phases and utilize it to obtain a more quantitative assessment of the co2 gaseous saturation changes based on the amplitude versus offset modelling a prominent decrease in the intercept values imaged at the top of the reservoir around the injection well is indeed associated solely with the co2 saturation increase any change in the gradient values which would in case it was positive be the only signature induced by the reservoir pressure variations has not been observed the amplitude versus offset intercept change is therefore entirely ascribed to co2 saturation and used for its quantitative assessment the estimated co2 saturation values around the injection area in the range of 40 60 are similar to those obtained earlier from pulsed neutron gamma logging the highest values of 80 are found in the second seismic repeat in close vicinity to the injection and observation wells