triggering and runaway processes of catastrophic tsaoling landslide induced by the 1999 taiwan chi chi earthquake as revealed by high velocity friction experiments pliocene sedimentary rocks of about 130 mm3 in volume slid along bedding planes dipping by 14 with an average speed of about 35 m s during the tsaoling landslide we conducted friction experiments to reproduce the initiation processes of this landslide by idealizing landslide movements during the earthquake as accelerating decelerating motion experiments were done on shale from the field at 3 mpa normal stress corresponding to the overburden pressure results indicate that the accelerating decelerating motion causes weakening and strengthening at each oscillation cycle and results in overall slip weakening which can be approximated as an exponential slip weakening behaviors during oscillatory slip are fairly similar to those during sliding at constant slip rates newmark analysis with measured frictional properties reveals that the landslide can be triggered with wet gouge properties but the landslide motion stops with parameters for dry shale gouge delayed initiation of the landslide is consistent with a survivor s witness

dynamic analysis and field investigation of a fluidized landslide in guanling guizhou china abstract on june 28 2010 a large catastrophic landslide was triggered by a heavy rainfall in guanling guizhou china this catastrophic event destroyed two villages and caused 99 casualties the landslide involved the failure of about 985 000 m 3 of sandstone from the source area the displaced materials traveled about 1300 m with a descent of about 400 m covering an area of 129 000 m 2 with the final volume being accumulated to be 1 840 000 m 3 approximately to provide information for hazard zonation of similar type of landslides in the same area we used a dynamic model dan3d to simulate the runout behavior of the displaced landslide materials and found that a combined frictional vollemy model could provide the best performance in simulating this landslide and the runout is precisely duplicated with a dynamic friction angle of 30 and a pore pressure ratio r u of 0 55 for the materials at the source area and with vollemy parameters of friction coefficient f 0 1 dimensionless and turbulent coefficient 400 m s 2 the simulated results indicated that the duration of the movement is estimated at about 60 s for a mean velocity 23 m s to examine the effectiveness of simulation by means of dan3d and also to evaluate the reactivation potential of these displaced landslide materials depositing on the valley we used electrical resistivity tomography ert method to survey the depth and internal structure of landslide deposits the ert results showed that dan3d gave a good prediction on the shape and runout distance of the landslide deposits although the predicted maximum depths of landslide deposit on some areas were differing from those obtained by ert method

influence of kinematics on landslide mobility and failure mode geometry of discontinuities greatly influences the kinematic behavior of slopes and landslides discontinuous deformation analysis dda is used here to analyze two typical examples of slope failure demonstrating that accurate representation of the geometry of the discontinuities is essential for identification of kinematically correct failure modes then static stability analyses of the vaiont italy landslide of october 9 1963 are used to show that the dda results compare favorably with previously published limit equilibrium studies using similar geometries and that the location and number of discontinuities have a significant effect on the predicted stability and failure velocities of the landslide dynamic dda simulations of the vaiont landslide show that the peak velocity increases up to 50 as the number of blocks increases indicating that internal disintegration of the landslide mass results in increasing acceleration and higher peak velocity dda analyses simulating pore pressure rise resulting from frictional heating of the basal slide plane show that the peak velocity similarly increases up to 50 as the number of blocks increases the magnitude of the increase in peak velocity as a result of disintegration i e increasing number of blocks suggests that as much attention should be paid to the geometry of discontinuities as is typically paid to shear strength and pore pressure

effects of near fault seismic loadings on run out of large scale landslide a case study this study presents the run out analysis of the daguangbao landslides subjected to near fault multi direction earthquake forces using discontinuous deformation analysis dda the daguangbao landslide is the largest landslide induced by the 2008 wenchuan earthquake in order to investigate the effects of near fault seismic force on landslide run out kinematic behavior of sliding mass is simulated by a dynamic discrete numerical analysis method called dda in this simulation based on the shape of failure surface and the feature of slope geology the whole slope is divided into three parts base block upper sliding mass and lower sliding mass then two sliding masses are divided into the smaller discrete deformable blocks based on pre existing discontinuities size effect of the huge landslide is also considered baseline corrected real horizontal and vertical ground motions are taken as volume force acting to the base block the results show that seismic force has a significant influence on the landslide progression sliding distance and shape of post failure results of the horizontal and vertical situation are in good agreement with those obtained from post earthquake field investigation remote sensing image and description from the survivors

monitoring numerical modelling and hazard mitigation of the moscardo landslide eastern italian alps abstract the moscardo torrent basin eastern italian alps is a high risk site since a large roto translational landslide might dam the torrent with the consequence of increasing the possibility of large debris flow events creating a threat for the infrastructures and the socio economic activities of the villages that dot the valley below the landslide whose volume is estimated 2 million m3 has been monitored since 2006 with inclinometers electric piezometers and a gps network the velocity along the entire body of the landslide averages 1 0 1 5 cm per month the shear surface develops at depths varying from 9 to 10 m to 55 62 m while the groundwater table is almost constant throughout the year despite a cumulative rainfall of the area that usually reaches 2000 mm year the movements were simulated in a numerical model in order to estimate the stabilization effect obtained by different types of possible countermeasures the simulation was carried out using flac 2d with creep modelling visco elasto plastic model of the medium in the sliding zone was assumed allowing to determine the relation between time and displacement a 10 year displacement trend starting from the initial situation of 2006 was simulated moreover seismic conditions were taken into consideration with a quasi static approach by applying a horizontal acceleration the numerical model was built and validated on the basis of the data retrieved from geological investigations as well as from inclinometric and gps measurements the results show that an accurate and well planned multidisciplinary approach can help the decision makers in the choice of the most effective engineering solution for the mitigation of landslide hazard and risk

distribution pattern of earthquake induced landslides triggered by the 12 may 2008 wenchuan earthquake abstract this paper presents the preliminary results of an extensive study of the mapping the distribution of landslides triggered by the wenchuan earthquake in sichuan province china on 12 may 2008 an extensive landslide interpretation was carried out using a large set of optical high resolution satellite images e g aster alos cartosat 1 spot 5 and ikonos as well as air photos for both the pre and post earthquake situation landslide scarps were mapped as points using multi temporal visual image interpretation taking into account shape tone texture pattern elevation and ridge and valley orientation nearly 60 000 individual landslide scarps were mapped the landslide distribution map was compared with the inventory map that was prepared directly after the earthquake which contains about 11 000 individual landslide points through the calculation of normalized landslide isopleths maps remarkable differences were observed as the earlier inventory mapping did not consider the pre earthquake situation and did not consider all individual landslides as part of the landslide inventory landslides were identified that had blocked the drainage and had formed landslide dams the landslide distribution was compared with a number of aspects such as the seismic parameters distance to epicenter distance to fault rupture co seismic fault geometry and co seismic slip distribution and geology the most remarkable correlation found was with the co seismic slip distribution and the fault geometry landslide distribution in the section of the fault that had mainly a thrust component with low angle fault plane was found to be much higher than the sections that had steeper fault angles and a major strike slip component

new dynamic procedure for back calculating the shear strength parameters of large landslides abstract case histories of the tsaoling landslide and the chiu fen erh shan landslide both located in taiwan are used in this study to validate the procedure proposed for the dynamic back calculation of the shear strength parameters of the sliding surfaces of large landslides this new procedure uses the newmark sliding model while simultaneously considering the critical displacement concept the premise of the new procedure is that in a stable slope back calculation tends to underestimate the shear strength however as the intensity of earthquake shaking increases and the slope approaches failure the back calculated shear strength will approach to the true value based on this concept the new procedure method is developed and validated with the two well documented case histories the shear strength parameters back calculated using the proposed method agree well with those reported in the literature the new dynamic back calculation procedure is especially suitable in the situation where groundwater monitoring data are unavailable thus the new method is complementary to the traditional groundwater based limiting equilibrium back calculation approach

longitudinal ridges in mass movement deposits prominent longitudinal features are often reported on the surfaces of mass movement deposits however the genesis and implications of these have not hitherto been considered and herein we present preliminary observations of their occurrence both in the field and in the laboratory elongated ridges are often oriented sub parallel to the flow direction and aligned radially from the source due to debris spreading they are particularly prominent in large 106m3 rock avalanches emplaced onto deformable substrates and are also found in the proximal reaches of volcanic debris avalanches flowbands which are longer and thinner expressions of longitudinal ridges are continuous along the entire flow length and are observed in rock avalanches emplaced onto glaciers in snow and some ice avalanches in pyroclastic flows and some block and ash flows in ejecta sheets in extraterrestrial landslides and in some volcanic debris avalanches other volcanic debris avalanches and the distal areas of rock avalanches often display hummocks that are aligned radially from the source we propose that these aligned hummocks are remnants of longitudinal ridges the formation of elongate ridges and their expressions as flowbands aligned hummocks or distal lobes and digits in qualitatively similar fashion in both laboratory and field environments suggests they represent an intrinsic tendency of granular flows in a wide range of situations

ejection landslide at northern terminus of beichuan rupture triggered by the 2008 mw 7 9 wenchuan earthquake on 12 may 2008 the mw 7 9 wenchuan earthquake triggered wide spread damaging landslides in many parts of the longmen shan area among these landslides the donghekou ejection landslide is quite special it is located at the north east end of the beichuan rupture and it has caused a great loss of life at the villages of donghekou qinchuan and sichuan provinces because of its special location this ejection landslide differs from landslides caused by gravity or rainstorms only the sliding surface is not uniformly continuous instead two sections can be distin guished an upper section with a step sliding surface and a lower section more gently dipping the landslide started with material ejection caused by large local seismic acceleration throwing rocks into the air with a parabolic trajectory before they fell back to the ground in this paper we analyze geologic and geomorphologic conditions that favored the occurrence of this landslide and we introduce a simple tectonic geomorphology model to explain the mechanism that led to the ejection landslide we find that the location of the landslide zone along with the domino like ground tension cracks observed on both sides of the beichuan rupture is controlled by the propagation of the rupture our result also suggests that in addition to local seismic shaking intensity horizontal acceleration and geomorphologic and geologic condi tions the vertical acceleration and the style of faulting could also play an important role in the occurrence of earthquake triggered landslides

unconventional pseudostatic stability analysis of the diezma landslide granada spain based on a high resolution engineering geological model abstract a novel unconventional pseudostatic analysis is proposed here to infer on the sensitivity of a landslide to earthquakes characterized by different physical properties several sine waves with different amplitudes frequencies and phases were applied to the landslide mass assuming limit equilibrium conditions the unconventional approach was used for the diezma landslide case study the landslide is located 25 km from the city of granada spain although the slope had repeatedly suffered small scale stability problems since the construction of the a 92 highway a larger failure occurred on 18 march 2001 and damaged the highway between kilometers 272 6 and 272 8 the landslide had an estimated volume of 1 2 mm 3 and involved a disordered deposit of silt and clay with heterometric blocks within the numidoide formation which outcrops along the contact between the malaguide and dorsal domains of the betic cordillera mountain range despite the 18 million euros spent since 1999 on geotechnical investigations and stabilization solutions the numerous reactivations that occurred through 2010 and 2013 demonstrate the persistent activity of the landslide the geometry of the large slope failure corresponding to the first activation of the diezma landslide was used to back analyze the stability of the slope based on a high resolution engineering geological model the model was developed from the analysis of numerous borehole logs as well as from geophysical investigations consisting of seismic noise measurements the results demonstrate that the safety factor sf of the diezma landslide varies significantly for frequencies less than 1 hz moreover unstable conditions are reached at frequency values between 0 5 and 1 hz for water pressure distributions corresponding to bishop factors r u between 0 and 0 36 to estimate the co seismic displacements the geometrical and mechanical properties of the landslide mass were used to derive its characteristic periods for thickness t s and length t l which were compared with the characteristic period of the earthquake t m the results indicate that the maximum expected co seismic displacements are up to 2 m for an earthquake with a t m value close to 1 s and an arias intensity on the order of 1 m s

granular flow experiments on the interaction with stationary runout path materials and comparison to rock avalanche events the central focus of this work is to study the processes acting well below the surface of a moving rock or debris avalanche during travel over stationary substrate material small scale physical models at a linear scale of 1 104 used coal as avalanche analogue material and different granular material simulating sedimentary substrates varying in frictional resistance thickness and relative basal boundary roughness as well as inerodible non deformable runout path conditions substrate materials with the least frictional resistance showed the greatest response to granular flow overriding becoming entirely mobilized beneath and ahead of the moving mass and producing the longest runout observed with a unique deposit profile shape with a smooth substrate basal contact failure occurred along this plane and avalanche and substrate became coupled during runout with a rough base however temporary force chains of grain contacts in the substrate prevailed longer imparted their resistance to motion shear into the granular flow and the flow rear section consequently halted earlier than when moving over substrates with a weak base reducing substrate thickness diminished the effect of basal contact roughness on granular flow runout and deposit length inerodible non deformable substrate conditions caused changes in granular flow behaviour from essentially en masse sliding on low friction surfaces to increasing granular agitation over rougher paths copyright 2012 john wiley sons ltd

evaluation of landslide mechanisms characterized by high speed mass ejection and long run out based on events following the wenchuan earthquake abstract in the 2008 wenchuan earthquake the mass ejection type of high speed and long run out landslide was an unusual hazard characterized by its dramatic phenomenon of a huge slope mass launching into the air and becoming airborne for a long distance quantitative and qualitative combined techniques were applied to reveal the formation mechanism of this type of landslide four prerequisites critical to form mass ejection are identified high position of the toe of the surface of rupture critical height and critical inclination of slope sufficient open space in the movement direction and adequate take off speed of ski jump like mass ejection these four area specific prerequisites provide a promising approach for screening and targeting the potential landslides subsequently a dynamic reliability analysis method that considers the feature of energy time distribution is proposed this site specific method provides a more credible evaluation by emphasizing the most significant period within the whole earthquake duration finally an aerodynamic inverse method combined with an energy conservation based method is applied in the quantitative evaluation to calculate take off speed of mass ejection this paper provides a viable solution for regional screening and site assessment for new potential targets of this type of landslide

landslide amplification by liquefaction of runout path material after the 2008 wenchuan m 8 0 earthquake china here we propose that an earthquake can trigger the failure of a landslide mass while simultaneously triggering liquefaction of runout path materials before the arrival of the landslide mass thus greatly increasing the size and mobility of an overriding landslide during the 2008 wenchuan earthquake about 60 000 landslides were triggered directly resulting in about 20 000 casualties while these landslides mainly originated from steep slopes some landslides with high mobility formed in colluvial valley deposits among these the most catastrophic was the xiejiadian landslide in pengzhou city which traveled hundreds of meters before coming to rest through field investigation and laboratory testing we conclude that this landslide primarily formed from colluvial deposits in the valley and secondarily from failure of slopes in granitic rock located uphill much of the granitic slope failure was deposited in the upper part of the travel path near the slide head the remainder was dispersed throughout the main landslide deposit superposition of deposits at the landslide toe indicates that landslide debris derived from colluvial soil was deposited first the deposits at the landslide toe displayed flow characteristics such as fine materials comprising basal layers and large boulders covering the deposit surface we hypothesize that the main part of the landslide resulted from seismogenic liquefaction of valley colluvium rather than from liquefaction potentially caused by undrained loading from the granitic slope failures impacting the colluvium to examine the likelihood that seismogenic liquefaction occurred we took samples from different areas of the landslide deposit and performed undrained cyclic shear tests on them in the laboratory the results showed that the sandy soils that comprise most of the deposit are highly liquefiable under seismic loading therefore we conclude that liquefaction of the colluvium in the valley during the earthquake was the main reason for this rapid 46 m s long runout 1 7 km landslide

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

dynamic simulation of the motion of fragmenting rock avalanches a mass referenced continuum model for dynamic analysis of rapid mass movement dan is verified by laboratory and field data increased earth pressure coefficients are used in this model to represent the dispersive pressures caused by fragmentation within a translating rock avalanche the numerical model demonstrates that increased runout in large rock avalanches can occur with normal friction coefficients if higher than normal internal pressures such as those believed to be generated by fragmentation are present the extent of the falling mountain rock avalanche deposit in new zealand is reproduced in the model with normal friction and high earth pressure coefficients to represent by analogy the additional internal pressures due to fragmentation it appears that if internal friction is changed by fragmentation it is only by a small amount and may increase rather than decrease to test this and to move beyond the present analogue model requires a better understanding of the rheology of fragmenting ro

erosion and mobility in granular collapse over sloping beds 1 we describe laboratory experiments of granular material flowing over an inclined plane covered by an erodible bed designed to mimic erosion processes of natural flows travelling over deposits built up by earlier events two controlling parameters are the inclination of the plane and the thickness of the erodible layer we show that erosion processes can increase the flow mobility i e runout over slopes with inclination close to the repose angle of the grains r by up to 40 even for very thin erodible beds erosion efficiency is shown to strongly depend on the slope of the topography entrainment begins to affect the flow at inclination angles exceeding a critical angle c r 2 runout distance increases almost linearly as a function of the thickness of the erodible bed suggesting that erosion is mainly supply dependent two regimes are observed during granular collapse a first spreading phase with high velocity followed by a slow thin flow provided either the slope or the thickness of the erodible bed is high enough surprisingly erosion affects the flow mostly during the deceleration phase and the slow regime the avalanche excavates the erodible layer immediately at the flow front waves are observed behind the front that help to remove grains from the erodible bed steep frontal surges are seen at high inclination angles over both rigid or erodible bed finally simple scaling laws are proposed making it possible to obtain a first estimate of the deposit and emplacement time of a granular collapse over a rigid or erodible inclined bed

ejection landslides triggered by the 2008 wenchuan earthquake and movement modelling using aerodynamic theory and artificial disintegration collision technique many ejection landslides in the 2008 wenchuan earthquake exhibited unusually dramatic behaviour in which a huge sliding mass was launched into the air and supported for a long distance because of the aerodynamic effect in this paper the formation conditions and movement characteristics of ejection landslides are analysed the flight behaviour of the centroid of the ejection mass is studied by numerical solution with and without the aerodynamic effect the impact and movement processes of the sliding mass are simulated by incorporating an advanced discretisation approach into discontinuous deformation analysis dda simulation results of the dayanke rock avalanche induced by the 2008 wenchuan earthquake show that the aerodynamic effect significantly affects its flight behaviour before collision simultaneously the colluvium on the slope surface remarkably reduces its traveling speed and runout moreover the initial angle between the velocity of the detached ejection mass and the horizontal direction strongly affects the flight distance and final deposition pattern of the avalanche

unusual july 10 1996 rock fall at happy isles yosemite national park california effects of the july 10 1996 rock fall at happy isles in yosemite national park california were unusual compared to most rock falls two main rock masses fell about 14 s apart from a 665 m high cliff southeast of glacier point onto a talus slope above happy isles in the eastern part of yosemite valley the two impacts were recorded by seismographs as much as 200 km away although the impact area of the rock falls was not particularly large the falls generated an airblast and an abrasive dense sandy cloud that devastated a larger area downslope of the impact sites toward the happy isles nature center immediately downslope of the impacts the airblast had velocities exceeding 110 m s and toppled or snapped about 1000 trees even at distances of 0 5 km from impact wind velocities snapped or toppled large trees causing one fatality and several serious injuries beyond the happy isles nature center a dense sandy cloud trailed the airblast and abraded fallen trunks and trees left standing the happy isles rock fall is one of the few known worldwide to have generated an airblast and abrasive dense sandy cloud the relatively high velocity of the rock fall at impact estimated to be 110 120 m s influenced the severity and areal extent of the airblast at happy isles specific geologic and topographic conditions typical of steep glaciated valleys and mountainous terrain contributed to the rock fall release and determined its travel path resulting in a high velocity at impact that generated the devastating airblast and sandy cloud the unusual effects of this rock fall emphasize the importance of considering collateral geologic hazards such as airblasts from rock falls in hazard assessment and planning development of mountainous areas

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

history of basin formation and tectonic evolution at the termination of a large transcurrent fault system deformation mode of central kyushu japana abstract the central part of the kyushu island is a locus of active arc volcanism associated with subduction of the philippine sea plate being located at a bend in the boundary between the philippine sea and eurasian plates a complicated lateral displacement has generated half grabens a zone of strike slip and rhomboidal basins filled with volcanic material in central kyushu initial northward subduction in latest miocene time activated the n s trending kokura tagawa tectonic line ktl as a left lateral slip fault that bounds the western margin of the area of volcano tectonic depression the hohi volcanic zone which was initially formed about 6 ma ago the depocenter which is now called kuju basin in the hohi volcanic zone was at the corner of the ktl and the e w trending median tectonic line mtl relative convergence direction of the philippine sea plate shifted counterclockwise at about 1 5 ma and active motion on the ktl declined at the same time west northwestward subduction enhanced right slip on the mtl geologic gravimetric and seismic data indicate that the mtl has shifted its active trace northward in central kyushu as far as 10 km as a result the depocenter adjacent to the transcurrent fault migrated northeastward in the hohi volcanic zone specifically from kuju basin pliocene via shonai basin early quaternary to beppu bay basin late quaternary the latest depocenter of the beppu bay is surrounded by active faults that clearly delineate a rhomboidal basin on the mtl central kyushu exemplifies the basin forming history and tectonic evolution at the termination of a large transcurrent fault system

interpretations of a middle miocene and late quaternary steady dextral transpression in sw japan and the opening tectonics for the japan sea abstract an internal rotation hypothesis for the deformation of sw japan for middle miocene and recent times is studied rotations are known to have occurred from paleomagnetic data for the earlier case two geodetic flow field estimates as well as another tectonic study suggest that the rotations are also taking place at present a further examination of the geodetic flow models suggests that the rotations contained in these flow models are intrinsic to the deformation of sw japan which occurs in an e w dextral transpressive simultaneous pure and simple shear tectonic regime maps of rotation rates one half of vorticity and shear gradients the n s variation of the e w velocity field constructed from the geodetic flow models resemble one another in pattern the estimates of the directions of the principal strain rates from the geodetic models are on the whole n s contractional and or e w extensional which match the geodetic reference coordinate system used in the adjustment of the geodetic data these observations suggest that the vortical flow contained in the geodetic flow models is a frame independent shear induced vorticity as the material is rotating with respect to the principal directions of the strain rates and that the oblique motion of the philippine sea plate is partitioned between shear and arc normal convergence components the rotation rate is 10 12 ma furthermore the kinematical vorticity number estimates from the geodetic data correlate well with the first order tectonic fabric patterns in sw japan super simple shear deformation for large parts of sw japan where the median tectonic line and other large strike slip faults are found is also indicated in the internal kinematical vorticity number estimates a new model for the formation of the japan sea is proposed extrusion of japan due to the okhotsk eurasia collision this model agrees with the fundamental observations of the early middle miocene deformation in the region the application of an indentation extrusion model to the okhotsk eurasia collision results in a better agreement between the predicted and observed structures and leads to simpler more reasonable and coherent interpretations for the origin and development of the structures compared with the achievements of the previous models the nne trending early middle miocene rifts lying along the continental margin of western hokkaido formed as pull apart basins along a sinistral fault related to the collision of the okhotsk plate which segmented in a left handed sense because the collision was oblique the n s trending rifts and the normal faults found in the back arc domain of the ne honshu arc formed by eastward extrusion under the influence of the mariana type subduction in the japan trench these rift basins were subsequently left laterally displaced by movement along nw trending sinistral strike slip faults the shikoku basin opened from the east toward the west and dextral shear was imparted to the sw margin from the nankai trough leading to clockwise rotations in the middle miocene in sw japan the paleomagnetic rotations are accommodated as fully internal structural rotations in the new model for the origin of the japan sea the current episode of deformation in sw japan began 1 5 million years ago after a hiatus during a 15 5 ma interval and is likely a continuation of the middle miocene style of tectonics

crustal scale strike slip deformation in hokkaido northern japan abstract field surveys in hokkaido reveal that the entire tectonic belt in northern japan was a right lateral shear zone from eocene to middle miocene time this zone of deformation can be followed northwards in sakhalin for more than 2000 km and formed at the same time as the opening of the japan sea a thrusting component during the strike slip deformation and later deformation stages led to the uplift of the deep parts of the shear zone exposing a complete section through the upper crust the stress field inferred from the analysis of fault sets is consistent with the non coaxial deformation observed in the deeper ductile parts of the shear zone there is a transition from west to east across the width of the belt 100 km from en echelon folds thrusts and nappes at upper structural levels through the brittle ductile transition with an incipient vertical schistosity into ductile deformation with a vertical foliation and metamorphic recrystallization in the amphibolite facies deep parts of the crust granulites were uplifted and retrogressed during the strike slip movement fault set analysis together with data concerning the direction and sense of nappe emplacement imply that thrusting west of the ductile deformation zone occurred during the strike slip deformation minor flat lying structures coexist with vertical pure strike slip structures this study and previous ones reveal a crustal scale half flower structure with superficial thrusting associated with a deep narrow ductile zone with a high gradient of deformation and temperature

dynamic process analysis for the initiation and movement of the donghekou landslide debris flow triggered by the wenchuan earthquake the donghekou landslide debris flow was a remarkable geological disaster triggered by the wenchuan earthquake in 2008 the dynamic process of a rapid landslide debris flow is very complicated and can be divided into two aspects the slope dynamic response of the earthquake and the mass movement and accumulation process a numerical method combined with a finite difference method fdm and discrete element method dem for simulation of landslide debris flow under seismic loading is presented the fdm and dem are coupled through the critical sliding surface initiation time and velocity the dynamic response of the slope is simulated by the finite difference method and critical sliding surface is determined using the earthquake response spectrum method the landslide initiation time and the velocity are determined by time history analysis the mass movement and accumulation process is simulated using the discrete element method simulation results demonstrate that the maximum amplification coefficient of dynamic acceleration for the donghekou slope is approximately 3 909 the initiation time of landslide is approximately 6 0 s and the average initial velocity of the sliding mass is approximately 0 85 m s the failure of the slope is the result of elevation orientated amplification effect and the sliding mass triggered with a small initial velocity the numerical simulated result of the maximum sliding velocity is approximately 66 35 m s and the mass is disintegrated rapidly because of collision and free fall the landslide velocity decreases when the flowing mass reaches a lower slope angle and gradually comes to a stop and the total travel distance is approximately 2400 m c 2013 elsevier ltd all rights reserved

undrained shear behaviour of sands subjected to large shear displacement and estimation of excess pore pressure generation from drained ring shear tests undrained shear behaviour of fine silica and weathered granitic sand subjected to large shear displacement is examined parallel experiments using ring shear and the triaxial compression tests on soil specimens through a wide range of initial void ratios were conducted to investigate undrained shear strength as the key factor in the flow like motion of landslides the steady state undrained shear strengths achieved in ring shear tests were in general smaller than those in the triaxial compression tests probably because of the excess pore pressure generation by grain crushing within the shear zone that occurred in ring shear very low steady state shear strengths were achieved however in triaxial compression tests on the dense silica sand in which well defined shear surfaces developed in the cylindrical specimens in these triaxial compression tests shear deformation must have been concentrated on these surfaces to generate excess pore pressure similar to that found in ring shear tests an attempt wa

a fragmentation spreading model for long runout rock avalanches based on the observation that deposits of large rock avalanches consist predominantly of intensely fragmented rock debris it is proposed that the processes of rock fragmentation are significant ca

dynamic discrete analysis of an earthquake induced large scale landslide abstract the chiu fen erh shan landslide estimated to have a volume of 36 million cubic meters was triggered by the m w 7 6 taiwan chi chi earthquake of 1999 the debris covered an area of 1 95 km 2 and claimed 36 lives during the sliding the landslide mass disintegrated with its debris acquiring high speeds to reach over 1 km of travel distance the main objectives of the study were to investigate if it was possible to numerically model the landslide progression including slope disintegration and to reproduce the post failure configuration toward these goals the study employed a discrete element method called discontinuous deformation analysis for the dynamic analysis by incorporating the spacing and orientation information of the joints and bedding planes the slope was modeled as an assemblage of discrete deformable blocks horizontal and vertical ground motions were simultaneously applied the near field digital strong records were affected by the large uplift of the hanging wall of the reverse thrust fault and corrections were made to address this issue the study showed that the methodology adopted was able to capture essential characteristics of the landslide and gave a post failure configuration resembling that observed in the field