wind and thermodynamic retrieval from single doppler measurements of a gust front observed during phoenix ii abstract the adjoint method to retrieve the three dimensional wind and thermodynamic fields is applied to single doppler observations of a gust front measured during the phoenix ii experiment this method uses a fluid dynamics model and its adjoint and combines the retrieval with data assimilation into the prediction model the wind and thermodynamic variables are determined by minimizing the difference between the model solution and the observations experiments are conducted first with radial velocity alone and then with both radial velocity and reflectivity to examine the quality of the retrieval with respect to radar location boundary conditions length of assimilation data filtering smoothing enforced by penalty functions and model accuracy verification of these experiments is provided by a dual doppler analysis test results show that the adjoint method is able to retrieve the wind and thermodynamic fields of the gust front the retrieved horizontal wind agrees very well with the dual doppler

the mesoscale and microscale structure and organization of clouds and precipitation in midlatitude cyclones viii a model for the seeder feeder process in warm frontal rainbands abstract previous field studies have indicated that warm frontal rainbands form when ice particles from a seeder cloud grow as they fall through a lower level feeder cloud in this paper we present results from a parameterized numerical model of the growth processes that can lead to the enhancement of precipitation in a seeder feeder type situation the model is applied to two types of warm frontal rainbands in the first type 1 situation the vertical air motions are typical of those associated with slow widespread lifting in the vicinity of warm fronts in the second type 2 situation the vertical air motions are stronger and more characteristic of the mesoscale the model simulations show that in the type 1 situations the growth of the seed ice crystals within the feeder zone is due to vapor deposition the feeder zone in this case is slightly sub saturated with respect to water due to the presence of the seed crystals in regions where the feeder zone is not seeded from aloft snow cryst

effects of strength properties of discontinuities on the unstable lower slope in the chiu fen erh shan landslide taiwan abstract the chiu fen erh shan landslide was a huge dip slope avalanche triggered by the devastating chi chi earthquake in central taiwan in 1999 anomalous geomorphic precursors such as ground subsidence and thrust which are signs of slope instability were subsequently observed on the lower slope of the chiu fen erh shan landslide in november 2002 post failure behavior and affected area of the lower part of the landslide must be investigated to provide adequate countermeasures this study presents the results of the post failure behavior simulation of the lower slope of the chiu fen erh shan landslide using discontinuous deformation analysis dda the simulation results show that the surface rocks in the sliding mass move faster and further than the rocks at great depth the angle of internal friction is found to have a great influence on the failure process than does the cohesion the sliding rocks are accumulated in the depression in front of the toe of the landslide except under the conditions of very low internal friction the depression performs as a buffer zone when the lower slope fails

numerical analysis of the mobility of the palos verdes debris avalanche california and its implication for the generation of tsunamis abstract analysis of morphology failure and post failure stages of the palos verdes debris avalanche reveals that it may have triggered a significant tsunami wave our analysis of the failure itself indicates that the slope is stable under aseismic conditions but that a major earthquake with a magnitude around 7 could have triggered the slide a post failure analysis considering the debris avalanche as a bi linear flow shows that peak velocities of up to 45 m s could have been reached and that the initial movement involved a mass of rock less than 10 km wide 1 km long and about 50 80 m thick initial wave height estimates vary from 10 to 50 m tsunami waves propagating to the local shoreline would be significantly smaller such a range demonstrates our lack of proper knowledge of the transition from failure to post failure behavior related to mass movements further investigations and analyses of terrestrial and submarine evidence are required for a proper hazard assessment related to tsunami generation in the los angeles area

acoustic fluidization and the extraordinary mobility of sturzstroms 1 sturzstroms are a rare category of rock avalanche that travel vast horizontal distances with only a comparatively small vertical drop in height their extraordinary mobility appears to be a consequence of sustained fluid like behavior during motion which persists even for driving stresses well below those normally associated with granular flows one mechanism that may explain this temporary increase in the mobility of rock debris is acoustic fluidization where transient high frequency pressure fluctuations generated during the initial collapse and subsequent flow of a mass of rock debris may locally relieve overburden stresses in the rock mass and thus reduce the frictional resistance to slip between fragments in this paper we develop the acoustic fluidization model for the mechanics of sturzstroms and discuss the conditions under which this process may sustain fluid like flow of large rock avalanches at low driving stresses

a theory for strong long lived squall lines abstract we study herein the mechanics of long lived line oriented precipitating cumulus convection squall lines using two and three dimensional numerical models of moist convection these models used in juxtaposition enable us to address the important theoretical issue of whether a squall line is a system of special long lived cells or whether it is a long lived system of ordinary short lived cells our review of the observational literature indicates that the latter is the most consistent paradigm for the vast majority of cases but on occasion a squall line may be composed of essentially steady supercell thunderstorms the numerical experiments presented herein show that either type of squall line may develop from an initial line like disturbance depending on the magnitude and orientation of the environmental shear with respect to the line with shallow shear oriented perpendicular to the line a long lived line evolves containing individually short lived cells our analysis of this type o

simulated supercells in nontornadic and tornadic vortex2 environments abstractthe composite near storm environments of nontornadic and tornadic supercells sampled during the second verification of the origins of rotation in tornadoes experiment vortex2 both appear to be generally favorable for supercells and tornadoes it has not been clear whether small differences between the two environments e g more streamwise horizontal vorticity in the lowest few hundred meters above the ground in the tornadic composite are actually determinative of storms tornadic potential from the vortex2 composite environments simulations of a nontornadic and a tornadic supercell are used to investigate storm scale differences that ultimately favor tornadogenesis or tornadogenesis failure both environments produce strong supercells with robust midlevel mesocyclones and hook echoes though the tornadic supercell has a more intense low level updraft and develops a tornado like vortex exceeding the ef3 wind speed threshold in contrast the nontornadic supercell only produces shallow vortic

buoyancy and pressure perturbations derived from dual doppler radar observations of the planetary boundary layer applications for matching models with observations abstract the technique developed by gal chen in 1978 is used to derive vertical velocities buoyancy and pressure perturbations from dual doppler radar observations of the planetary boundary layer pbl several approaches to verification are pursued they include a scan to scan temporal continuity of the derived fields b an objective test to find out how well the derived pressure perturbations balance the dynamical equations c comparison of dual doppler derived horizontally averaged fluxes of heat versus in situ measurements and other data sets and d a noteworthy improvement in the quality of the retrieved pressure when tendencies are included previous studies indicate that in order for the method to be viable the radars have to resolve the pbl with at least ten vertical levels one such event occurred on 27 september 1978 during project phoenix conducted at the boulder atmospheric observatory bao 300 m tower an inversion above a shallow boundary layer of height around 800 m was eroded

an analysis of cold season supercell storms using the synthetic dual doppler technique abstractcold season tornadic outbreaks occur with regularity in the southeastern united states however detailed analyses of parent supercell storms in the cold season environment often low cape high shear are scarce this is often because storms do not always move close enough to radars for a comprehensive single doppler analysis and significant topography or trees in the southeast make it difficult for mobile radars to operate thus limiting dual doppler coverage however during the super tuesday tornado outbreak of 5 6 february 2008 two tornadic supercell storms passed within 30 40 km of the weather surveillance radar 1988 doppler wsr 88d sites in memphis and nashville tennessee knqa and kohx respectively the relative steadiness of these storms during passage along with the large motion vector from the southwest at 20 25 m s 1 allowed the application of a synthetic dual doppler sdd analysis as such a detailed analysis of these storms was completed including examinations of low lev

the structure and classification of numerically simulated convective storms in directionally varying wind shears abstract using a three dimensional numerical cloud model we investigate the effects of directionally varying wind shear on convective storm structure and evolution over a wide range of shear magnitudes as with a previous series of experiments using unidirectional wind shear profiles weisman and klemp the current results evince a spectrum of storm types ranging from short lived single cells at low shears multicells at intermediate shears to supercells at high shears with a clockwise curved hodograph the supercellular growth is confined to the right flank of the storm system while multicellular growth is favored on the left flank an analysis of the dynamic structure of the various cells reveals that the quasi steady supercell updrafts are strongly enhanced by dynamically induced pressure gradients on the right flank of the storm system we use this feature along with other related storm characteristics such as updraft rotation to propose a dynamically based storm classification scheme following

effects of the vertical component of ground shaking on earthquake induced landslide displacements using generalized newmark analysis abstract the popular newmark method calculates the cumulative permanent displacement of a landslide having a known critical acceleration as it is subjected to the effects of an earthquake acceleration time history for an infinite slope this method considers ground acceleration as parallel to the slope and downslope which results in two important limitations 1 vertical downslope acceleration only is considered 2 the ratio of vertical to horizontal acceleration only depends on the inclination of the slope surface in the model developed herein the ground acceleration is not parallel to the slope the ratio of vertical to horizontal acceleration called the vertical accelerometric parameter depends on the seismic situation of the slope magnitude earthquake source distance style of faulting and the vertical acceleration acts alternately upslope and downslope application of the principles of classical mechanics leads to the pseudo static factor of safety and hence to the seismic horizontal critical acceleration of a potential landslide which depends not only on its static factor of safety geometry geotechnical properties and hydrogeologic conditions but also on its seismic situation it is shown that newmark s model is in fact a particular case of the general model and in most cases the seismic horizontal critical acceleration results from vertical upslope acceleration and is lower than newmark s critical acceleration as a consequence the displacements d resulting from the model developed herein will be greater than the displacements dn calculated from newmark s approach for some potential landslides the difference d dn is considerable and results in significant consequences in the seismic stability analysis of the affected slopes which justifies the importance of the effects of vertical ground shaking

simulation and analysis of tornado development and decay within a three dimensional supercell thunderstorm abstract a three dimensional numerical simulation using a two way interactive nested grid is to study tornado genesis within a supercell during a 40 minute period two tornadoes grow and decay within the storm s mesocyclone the tornadoes have life spans of approximately 10 minutes maximum ground relative surface wind speeds exceed 60 m s 1 during both tornadoes and horizontal pressure gradients reach 18 hpa km 1 during the second tornado comparison of the simulated storm evolution with doppler and field observations of supercells and tornadoes shows many similar features vertical vorticity in the mesocyclone and the tornado vortex at low levels is initially created by the tilting of the environmental vorticity and baroclinically generated vorticity along the forward gland gust front of the storm tornadogenesis is initiated when mesocyclone rotation increase above cloud base the increased rotation generates lower pressure in the mesocyclone increasing the upward pressure gradient forces the upwar

three dimensional numerical modeling of convection produced by interacting thunderstorm outflows part i control simulation and low level moisture variations abstract the klemp wilhelmson three dimensional numerical cloud model is used to investigate cloud development along intersecting thunderstorm outflow boundaries the model initial environment is characterized by a temperature and moisture profile typically found in strong convective situations and the initial wind field is prescribed by a constant unidirectional shear 2 9 m s 1 km 1 from 0 8 to 8 9 km with a constant wind everywhere else the wind shear vector is perpendicular to the line containing the two initial outflow producing clouds which are spaced 16 km apart and are triggered by thermal impulses centered at the top of the boundary layer the dynamics of the outflow collision are documented using time dependent kinematic air parcel trajectories and thermodynamic data we find that ambient air in the outflow collision region is literally squeezed out of the way as the two outflows collide some of this air is lifted to saturation triggering two convective clouds the upshear member of the

rock and soil avalanches theory and simulation 1 we present a 2 d contact dynamics discrete element model for simulating initiation and motion of rock avalanches integrating hillslope geometry mohr coulomb rock behavior pore pressure before avalanche triggering and avalanche trigger avalanche motion is modeled as a dense granular flow of dry frictional and cohesive particles on the basis of granular physics and shear experiments we review some of the theories for the unexpectedly long runout of rock avalanches different causes are evoked according to the strength strong or weak of the slip surface relative to the bulk mechanical fluidization and acoustic fluidization theories state that agitation of rock particles reduces frictional strength increasing runout conversely granular mechanics suggests that as shear strain rate increases granular material becomes more agitated more dissipative and more resistant another theory states that dynamic fragmentation of clasts creates an isotropic pressure that drives longer runout in contrast granular mechanics suggests that fragmentation may induce fluidization and strengthening of the granular material while particle size reduction among others induces weakening of the granular flow and enhances long runout runout is also enhanced for column like rock masses collapsing from steep hillslopes long runout may also be linked to thermal weakening mechanisms at the slip surface e g thermal pressurization and shear melting which may lower drastically the shear strength the model is illustrated with a hypothetical example of a rain triggered avalanche mobilizing shallowly dipping layers several phases are identified including slope failure avalanche triggering resulting from slip weakening and avalanche motion in which rocks are folded and sheared

structural geodetic and seismological evidence for tectonic escape in sw taiwan abstract recent structural geodetic and seismological data in sw taiwan are analysed and discussed in terms of present day tectonic escape occurring in response to the active n100 collisional shortening the escaping area corresponds to the onland extension of the manila accretionary wedge this region comprises a rheologically weak thick muddy cover which is decoupled from the underlying basement by a decollement and which deforms mainly by aseismic creep it is separated from the northern actual collisional area by a major wnw to nw trending structural and kinematic transition zone oblique to the structural grain of the belt the chishan transfer fault zone geodetic data are further used to define several poorly deforming blocks undergoing nearly uniform displacement velocities and bounded by kinematic discontinuities that fit the major faults and to determine the present day across strike and along strike motions on these major faults although direct onland structural evidence of tectonic escape is poor reconstruction of quaternary paleostress patterns demonstrate that this escape probably began during the late pleistocene later than in northeastern taiwan as a result of the southward migration of the collision through time offshore structural data help to constrain the geometry and the southern extension of the escaping blocks finally a tentative model of lateral extrusion in sw taiwan is proposed

geological and geomorphological precursors of the chiu fen erh shan landslide triggered by the chi chi earthquake in central taiwan abstract special features were correlated to the geological causes of the chiu fen erh shan landslide a gigantic rockslide on a dip slope induced by the chi chi earthquake ml 7 3 in central taiwan in 1999 an aerial photo interpretation and the succeeding geological mapping of the failure were employed in this study a linear depression a steep step and a low drainage density in the landslide area were detected from the aerial photos taken in 1998 the gravitational creep was believed to result in the features of the linear depression and the low drainage density the steep step represented a buckling feature found in the field the landslide area is composed of stratified sandstone and shale with dip angles ranging 20 36 the slip surface developed along a pre existing bedding fault that resulted from flexural slip folding before the chi chi earthquake the rock on the upslope side buckled and was retained by a thick bedded sandstone downslope the earthquake shock seriously damaged the sandstone support and led to the catastrophic landslide this type of landslide is likely to occur on the moderately dipping slope of stratified rocks that were previously deformed by flexural slip folding

dynamic adjustment in a numerically simulated mesoscale convective system impact of the velocity field abstract an identical twin methodology is applied to a three dimensional cloud model to study the dynamics of adjustment in deep convective storms the principal goal is to diagnose how mass and velocity fields mutually adjust in order to better understand the relative information content value of observations the physical interdependency among variables and to help in the design of dynamically consistent analyses to ensure smooth startup of numerical prediction models using a control simulation truth or nature run of an idealized long lived bow echo convective system a series of adjustment experiments is created by resetting in various combinations the horizontal and vertical velocity components of the control run to their undisturbed base state values during the mature stage of storm system evolution the integrations then are continued for comparison against the control this strategy represents a methodology for studying transient response to an impulsive perturbation in a manner concept

ensemble based data assimilation for thermally forced circulations 1 the effectiveness of the ensemble kalman filter enkf for thermally forced circulations is investigated with simulated observations a two dimensional nonlinear hydrostatic non rotating and incompressible sea breeze model is developed for this purpose with buoyancy and vorticity as the prognostic variables model resolution is 4 km horizontally and 50 m vertically forcing is maintained through an explicit heating function with additive stochastic noise pure forecast experiments reveal that the model exhibits moderate nonlinearity the strongest nonlinearity occurs along the sea breeze front at the time of peak sea breeze phase considerable small scale error growth occurs at this phase for vorticity while buoyancy is dominated by large scale error as the direct result of the initial condition uncertainty in the enkf experiments simulated buoyancy observations with assumed error of 10 3 ms 2 on land surface with 40 km spacing are assimilated every 3 hours as a result of their resolution the observations naturally sample the larger scale flow structure at the first analysis step the filter is found to remove most of the large scale error resulting from the initial conditions and the domainaveraged error of buoyancy and vorticity is reduced by about 83 and 42 respectively subsequent analyses continue to remove error at a progressively slower rate and the error ultimately stabilizes within about 24 hours for both variables at later model times while mostly large scale buoyancy errors due to the stochastic heating uncertainty are effectively removed the filter also performs well at reducing smaller scale vorticity errors associated with the sea breeze front this is an indication that observations also contain useful small scale information relevant at the scales of frontal convergence

velocity field of gps stations in the taiwan area abstract the 131 stations of the taiwan gps network were surveyed 4 6 times from 1990 to 1995 with dual frequency geodetic receivers the standard deviation of an observed baseline length with its linear trend removed is in the range of 6 10 mm for a 3 120 km long baseline the average rates of length change for all baselines of the network and those from nine continuously monitoring permanent stations are used in a least squares adjustment to estimate the velocities of the gps stations relative to paisha penghu situated at the chinese continental margin to the south of fengping in the northern coastal range the velocity vectors of stations in lanhsu lutao and the coastal range trend in the directions of 306 322 with rates of 56 82 mm yr in contrast there is a dramatic decrease in the rates to the north of fengping this may be caused by the motion along the ne sw trending thrusts which obliquely cut the northern coastal range a discontinuity of about 30 mm yr in the rates along with a remarkable change in the directions of station velocity is observed across the longitudinal valley then the moving directions gradually shift to the west for the stations in the western foothills in the kaohsiung pingtung coastal area the station velocities are even directed toward the southwest to the north of the peikang high the velocity vectors of the stations change direction from the west gradually to the north and finally to the east and southeast significant nw se extensional deformation is found in the ilan plain and northern taiwan in general the pattern of the velocity field for gps stations in the taiwan area is quite consistent with the directions of present day tectonic stress

pressure and buoyancy fields derived from doppler radar data in a tornadic thunderstorm abstract a method for retrieval of pressure and buoyancy distributions in deep convection is applied to doppler radar data collected at two analysis times during the tornadic del city oklahoma thunderstorm of 20 may 1977 change of a previous version of the technique necessitated by application to real data include procedures for handling irregularly bounded volumes and missing data and new assumptions to include reflectivity data and turbulent effects in the equations internal consistency cheeks on the quality of retrieved pressure fields imply that the input data are generally of good quality and point out times and heights within the storm at which greater confidence can be placed in the derived fields in the pretornadic stage the pressure distribution includes at each level a high low couplet across the updraft with the maximum pressure gradient generally oriented along the environmental shear vector at that altitude these results are in agreement with predictions of linear theory locations of

entrainment of debris in rock avalanches an analysis of a long run out mechanism many rock avalanches entrain and liquefy saturated soil from their paths evidence for this includes mud displaced from the margins of rock avalanche deposits substrate material smeared along the base of deposits extrusion of liquefied soil upward through the deposits and increases of volume a hypothesis first suggested in 1881 and since reinforced by several authors suggests that entrainment of substrate material increases mobility although the process has been discussed in the literature for more than 100 years few detailed and quantitative descriptions exist the main purpose of this paper is to describe two recent cases from british columbia canada where rockslides entrained substrate on a very large scale influencing the character of the events estimated volume balance curves based on detailed field mapping are provided for both cases dynamic analyses are carried out using a numerical model and using the same set of rheological parameters the mechanism of material entrainment and displacement is discussed the data suggest that rapid rock failures entraining very large quantities of saturated substrate material represent a special type of landslide transitional between rock avalanche and debris avalanche many rock avalanches can thus be seen as end members of a continuum of phenomena involving rock failure followed by interaction with saturated substrate

forecasting landslide hazard by the 3d discrete element method a case study of the unstable slope in the lushan hot spring district central taiwan abstract catastrophic landslides and related phenomena are commonly facilitated by the subtropical climate with frequent typhoons and recurrent earthquakes in taiwan s mountainous areas one area susceptible to potentially catastrophic landslides is located at lushan in central taiwan which is famous for its hot springs and tourism the northern slope above the hot spring district slips gradually and frequently due to heavy rainfall for safety reasons the slip affected area has been under constant borehole monitoring by government agencies and a controversial public debate has arisen over permanent evacuation of the hot spring district in this study we attempt to simulate possible scenarios of catastrophic slope failure using slip geometries derived from the monitoring data and assess potential landslide impact areas by a discrete element method using the pfc3d code in the worst case scenario the lushan hot spring district is predicted to be destroyed by debris in 20 s besides the planned regional emergency refuge is rapidly jeopardized by flooding resulted from landslide dammed lakes this study addresses catastrophic slope failure under heavy rainfall conditions given a range of friction coefficients and varied continuity of the failure surfaces it is noted that the pfc3d code has limitations in modeling all complex mechanisms of landslide particularly in modeling loss of material shear strength due to increases in pore pressure nevertheless the numerical simulation results by the 3d discrete element method provide scenario based runout paths particle velocities and landslide affected areas which are useful information for decision support and future landslide hazard assessment

retrieval of model initial fields from single doppler observations of a supercell thunderstorm part ii thermodynamic retrieval and numerical prediction in this two part study a single doppler parameter retrieval technique is developed and applied to a real data case to provide model initial conditions for a short range prediction of a supercell thunderstorm the technique consists of the sequential application of a single doppler velocity retrieval sdvr followed by a variational velocity adjustment a thermodynamic retrieval and a moisture specification step in part i the sdvr procedure is described and results from its application to a supercell thunderstorm are presented in part ii results from the thermodynamic retrieval and the numerical model prediction for this same case are presented for comparison results from parallel sets of experiments using dual doppler derived winds and winds obtained from the simplified velocity retrieval described in part i are also shown following the sdvr the retrieved wind fields available only within the storm volume are blended with a base state background field obtained from a proximity sounding the blended fields are then variationally adjusted to preserve anelastic mass conservation and the observed radial velocity a gal chen type thermodynamic retrieval procedure is then applied to the adjusted wind fields for all experiments full retrieval simplified retrieval and dual doppler the resultant perturbation pressure and potential temperature fields agree qualitatively with expectations for a deep convective storm an analysis of the magnitude of the various terms in the vertical momentum equation for both the full retrieval and dual doppler experiments indicates a reasonable agreement with predictions from linear theory in addition the perturbation pressure and vorticity fields for both the full retrieval and dual doppler experiments are in reasonable agreement with linear theory predictions for deep convection in sheared flow following a simple moisture specification step short range numerical predictions are initiated for both retrieval experiments and the dual doppler experiment in the full single doppler retrieval and dual doppler cases the general storm evolution and deviant storm motion are reasonably well predicted for a period of about 35 minutes in contrast the storm initialized using the simplified wind retrieval decays too rapidly indicating that the additional information obtained by the full wind retrieval primarily low level polar vorticity is vital to the success of the numerical prediction sensitivity experiments using the initial fields from the full retrieval indicate that the predicted storm evolution is strongly dependent on the initial moisture fields overall the numerical prediction results suggest at least some degree of short term predictability for this storm and provide an impetus for continued development of single doppler retrieval procedures

thermoporomechanics of creeping landslides the 1963 vaiont slide northern italy 1 the catastrophic vaiont landslide southern alps italy of 9 october 1963 moved 2 7 108 m3 of rock that collapsed in an artificial lake causing a giant wave that killed 1917 people the landslide was preceded by 2 3 years of creep that ended with the final collapse of the rock mass slipping at about 30 m s 1 assuming that creep was localized in a clay rich water saturated layer in this study we propose shear heating as the primary mechanism for the long term phase of accelerating creep we study only the creeping phase of the slide and we model this phase using a rigid block moving over a thin zone of high shear strain rates introducing a thermal softening and velocity strengthening law for the basal material we reformulate the governing equations of a water saturated porous material obtaining an estimate for the collapse time of the slide our model is calibrated upon real velocity measurements from the vaiont landslide and provides an estimation of the critical time of failure up to 169 days before the collapse we also show that the slide became critical 21 days before the collapse when shear heating started localizing in the clay rich layer inducing a tendency for slip localization and thermal runaway instability in a plane the total loss of strength in the slipping zone during the last minutes prior to the slide is explained by the onset of thermal pressurization triggered by the temperature rise within the clay rich layer

stress tensor inversion for the chi chi earthquake sequence and its implications on regional collision we study the stress regime associated with the 1999 chi chi taiwan earthquake sequence broadband waveforms of 115 events recorded by the broadband array in taiwan for seismology bats are analyzed to determine their focal mechanisms depths and seismic moments these solutions are then used to invert for the reduced stress tensor using the algorithm of angelier 1998 we perform the stress inversion in three different ways first we aim at defining in the first approximation a uniform stress field by taking the entire dataset as a whole the inversion result shows a stress regime with the maximum compression along the direction of n119 e remarkably consistent with the direction of the relative motion between the philippine sea plate and eurasia this solution is stable and varies little in terms of the orientations of stress axes within 8 and the ratio of stress differences between 0 26 and 0 44 in the second approximation we aim at explaining more subtle features of our observations by considering differently built subsets we divide the dataset according to different seismogenic structures as identified by kao and chen 2000 our results yield rather similar results axes of maximum compressive stress fall in the range of n99 138 e in terms of trends and in the range of 1 17 in plunges for all subsets except a small group in the footwall furthermore we observe a systematic clockwise change in the direction of compression from south to north representing the more general fan shaped pattern of stress trajectories that characterizes the whole collision zone finally the inversion is performed for the three main types of faulting that is reverse strike slip and normal types the axis of maximum compression for the reverse mechanisms has the same direction as that for the strike slip whereas the normal type subset yields a n54 e extension that trends obliquely to the compression the fact that the stress regime associated with the chi chi aftershock sequence is similar to that derived from geological and seismic data in the region implies that the stress regime corresponding to the regional collision in taiwan is responsible for the occurrence of the chi chi earthquake moreover systematic secondary variation in the state of stress is observed for different types of focal mechanisms and seismogenic structures such variation may play an important role in producing local stress concentration that leads to the nucleation of disastrous earthquakes in central taiwan manuscript received 12 january 2001

the impact of spatial variations of low level stability on the life cycle of a simulated supercell storm abstract this study reports on the dynamical evolution of simulated long lived right moving supercell storms in a high cape strongly sheared mesoscale environment which initiate in a weakly capped region and subsequently move into a cold boundary layer bl and inversion region before dissipating the storm simulations realistically approximate the main morphological features and evolution of the 22 may 1981 binger oklahoma supercell storm by employing time varying inflow lateral boundary conditions for the storm relative moving grid which in turn are prescribed from a parent fixed steady state mesoscale analysis to approximate the observed inversion region to the east of the dryline on that day a series of full life cycle storm simulations have been performed in which the magnitude of boundary layer coldness and the convective inhibition are varied to examine the ability of the storm to regenerate and sustain its main updraft as it moves into environments with increasing convective stability the

analysis of the chiufengershan landslide triggered by the 1999 chi chi earthquake in taiwan abstract a disastrous earthquake rocked taiwan on september 21 1999 with magnitude m l 7 3 and an epicenter near the small town of chi chi in central taiwan the chi chi earthquake triggered landslide on the dip slope at the chiufengershan in this study a review of the topography and geology of this area was followed by field investigations laboratory testing was applied to understand the geomaterial composing the slope then based on a series of limit equilibrium analyses the failure mechanism of this landslide and the risk of the residual slope were studied according to the stability analyses the pre quake slope is quite stable with factor of safety of 1 77 dry to 1 35 full groundwater level explaining why there is no written record of a landslide here for the past 100 years in contrast a back analysis shows that the chi chi earthquake induced dynamic loading is far more than the dip slope can sustain due in part to the short distance to the epicenter a monte carlo type probability analysis suggests that the residual slope is more dangerous than the pre quake slope and needs more attention

assimilation of high resolution tropical cyclone observations with an ensemble kalman filter using noaa aoml hrd s hedas evaluation of the 2008 11 vortex scale analyses abstractthe hurricane weather research and forecasting hwrf ensemble data assimilation system hedas is developed to assimilate tropical cyclone inner core observations for high resolution vortex initialization it is based on a serial implementation of the square root ensemble kalman filter enkf in this study hwrf is used in an experimental configuration with horizontal grid spacing of 9 3 km on the outer inner domain hedas is applied to 83 cases from years 2008 to 2011 with the exception of two hurricane hilary 2011 cases in the eastern north pacific basin all cases are observed in the atlantic basin observed storm intensity for these cases ranges from tropical depression to category 4 hurricane overall it is found that high resolution tropical cyclone observations when assimilated with an advanced data assimilation technique such as the enkf result in analyses of the primary circulation that are realistic in terms of intensity wavenumber 0 radial structure as well as wavenumber 1

analysis of landsliding by earthquake shaking using a block on slope thermo mechanical model example of jiufengershan landslide central taiwan the jiufengershan rock and soil avalanche is one of the largest landslides triggered by the chi chi taiwan earthquake september 21 1999 in order to study landslide triggering and propagation by seismic shaking we propose a method that combines features of the classic newmark approach with mechanical relations involving mohr coulomb failure criteria pore water pressure and shear heating during the sliding process the effective shear strength is affected by shear heating and by pore pressure variations during the sliding process the shaking process was simulated using strong motion accelerograms of the three nearest free field stations which surrounded the landslide the initiation and propagation of earthquake induced landslides are mainly controlled by the peak and residual shear strengths respectively the increase in temperature in the shear zone increases the pore water pressure and weakens the shear strength rock avalanches are generated when mechanical parameters achieve critical threshold values such that the residual shear strength is less than the tangential projection of body forces

dynamic disintegration processes accompanying transport of the holocene flims sturzstrom swiss alps abstract a sturzstrom is a large scale landslide that evolves during transport into a rapid granular flow rock avalanche by a dynamic disintegration process numerous theoretical hypotheses have been proposed to explain the excessive mobility of these catastrophic mass movements but the role of disintegration processes remains poorly understood exceptional outcrop conditions at the giant 12 km3 flims sturzstrom swiss alps permit the analysis of disintegration processes that result from shearing during transport in confined zones of the rock mass shearing is concentrated along preferred surfaces originating as bedding planes which evolve into shear band layers differential velocities of slabs separated by these shear layers induce oblique fractures in the slabs by accommodation contacts between grains are maintained in the shear layers in unconfined zones near the top and the lateral margins shearing generates dilatancy the rock mass is affected by anisotropic dispersion without mixing and disintegrated material is preferentially produced to the top due to inflation the rock slide then evolves to a granular flow the consequence of these processes is the formation of two distinct depositional facies in the sturzstrom the structured facies exhibits a stratified aspect close to the base reflecting confined slab on slab shearing motion towards the top and distally it evolves into a chaotic facies with some isolated pockets of the structured facies reduction of confining forces on the moving sturzstrom allows transformation of the structured facies into the chaotic facies this characteristic transition observable in many sturzstrom deposits seems to be necessary for the rock avalanche process to occur and offers insights into the long runout characteristics of these catastrophic mass movements

an investigation of the goshen county wyoming tornadic supercell of 5 june 2009 using enkf assimilation of mobile mesonet and radar observations collected during vortex2 part i experiment design and verification of the enkf analyses abstracthigh resolution doppler radar velocities and in situ surface observations collected in a tornadic supercell on 5 june 2009 during the second verification of the origins of rotation in tornadoes experiment vortex2 are assimilated into a simulated convective storm using an ensemble kalman filter enkf a series of enkf experiments using a 1 km horizontal model grid spacing demonstrates the sensitivity of the cold pool and kinematic structure of the storm to the assimilation of these observations and to different model microphysics parameterizations an experiment is performed using a finer grid spacing 500 m and the most optimal data assimilation and model configurations from the sensitivity tests to produce a realistically evolving storm analyses from this experiment are verified against dual doppler and in situ observations and are evaluated for their potential to confidently evaluate mesocyclone scale processes in the storm using trajectory analysis and calculations of lagrangian vorticity

tornado resolving ensemble and probabilistic predictions of the 20 may 2013 newcastle moore ef5 tornado abstractan ensemble of 10 forecasts is produced for the 20 may 2013 newcastle moore ef5 tornado and its parent supercell using a horizontal grid spacing of 50 m nested within ensemble forecasts wi

wind and temperature retrievals in the 17 may 1981 arcadia oklahoma supercell ensemble kalman filter experiments abstract the feasibility of using an ensemble kalman filter enkf to retrieve the wind and temperature fields in an isolated convective storm has been tested by applying the technique to observations of the 17 may 1981 arcadia oklahoma tornadic supercell radial velocity and reflectivity observations from a single radar were assimilated into a nonhydrostatic anelastic numerical model initialized with an idealized horizontally homogeneous base state the assimilation results were compared to observations from another doppler radar the results of dual doppler wind syntheses and in situ measurements from an instrumented tower observation errors make it more difficult to assess enkf performance than in previous storm scale enkf experiments that employed synthetic observations and a perfect model nevertheless the comparisons in this case indicate that the locations of the main updraft and mesocyclone in the arcadia storm were determined rather accurately especially at midlevels the magnitudes of v

sea level changes versus hydrothermal diagenesis origin of triassic carbonate platform cycles in the dolomites italy abstract the triassic platform carbonate cycles of the dolomites best developed and studied at the latemar have been considered key examples for the documentation of eustatic sea level changes the cycles appear to reflect a low energy lagoonal environment which is however difficult to reconcile with the small platforms lacking marginal energy barriers in a tropical stormy climate an alternative interpretation to eustatically controlled cyclicity and repeated subaerial exposure is provided by diagenesis in a hydrothermal field elevated heat flow 0 2 ma before the onset of the mafic igneous activity triggered the circulation of diagenetic fluids with a composition similar to seawater by intermittent opening of fractures through some platforms this caused tepee formation by precipitation of displacive cement pendant cement and pisolite formation and favoured cyanobacterial mat formation and their early dolomitization the abundance of cycles correlates with that of the somewhat younger volcanic dikes crosscutting some platforms diffuse venting or seeping in the upper unconsolidated sediment layers explains the stratiform occurrence of the diagenetic features and alternation with normal marine deposition in deep but photic water at the wave base

large scale landslide simulations global deformation velocities and basal friction the cause of the apparent small friction exhibited by long runout landslides has long been speculated upon in an attempt to provide some insight into the matter this paper describes results obtained from a discrete particle computer simulation of landslides composed of up to 1 000 000 two dimensional discs while simplified the results show many of the characteristics of field data the volumetric effect on runout preserved strata etc and with allowances made for the two dimensional nature of the simulation the runouts compare well with those of actual landslides the results challenge the current view that landslides travel as a nearly solid block riding atop a low friction basal layer instead they show that the mass is completely shearing and indicate that the apparent friction coefficient is an increasing function of shear rate the volumetric effect can then be understood with all other conditions being equal different size slides appear to travel with nearly the same average velocity however as the larger landslides are thicker they experience smaller shear rates and correspondingly smaller fractional resistance

frictional fusion due to coseismic landsliding during the 1999 chi chi taiwan ml 7 3 earthquake fused materials pseudotachylytes generated from landsliding during the 1999 chi chi taiwan ml7 3 earthquake are found on the glide plane in mio pliocene interbedded shale and siltstone the pseudotachylytes occur as thin layers on the glide plane and as veins injected into cracks in the host rocks which are a few mm to 1 cm in thickness typical melting textures within the pseudotachylyte include vesicles glassy matrices flow structures and rounded and embayed clast shapes powder x ray diffraction analysis has revealed a glass content of up to 50 wt within the pseudotachylyte physical conditions of pseudotachylyte formation are estimated to have been 1 5 mpa corresponding to ca 40 m depth at a temperature of at least 1100 1600 c the geological and petrological data suggests that these pseudotachylytes formed by frictional melting generated from coseismic landsliding during the chi chi earthquake

modeling failure of jointed rock slope with two main joint sets using a novel dem bond contact model abstract in order to investigate the failure processes and mechanisms of jointed rock slopes distinct element method dem was applied with a novel bond contact model the bond contact model is validated by a series of numerical direct shear tests on jointed models and the comparisons to laboratory test results dem jointed rock slope models were then generated and two arrangements of joint sets and two types of slope surface were chosen to test the capabilities of the bond contact model the slope models were destabilized progressively by the critical gravity approach and both the failure onset and the slope collapse process were analyzed microscopic information reveals that the initiation of slope failure can be divided into three phases and is induced from stress concentration within the rock bridges occurrence of tension cracks and their propagation and coalescence the slope surface properties reflected by different damping affect both post failure configuration and propagation distance of the rock slope the study demonstrates that the novel bond contact model implemented in the dem code is able to tackle the fundamental problems of jointed rock slope failure and helps to better understand the slope failure mechanisms from a macroscopic and microscopic level

two dimensional convection in non constant shear a model of mid latitude squall lines numerical simulations of two dimensional deep convection are analysed using analytical models extended to include shallow downdraughts and non constant shear the cumulonimbus are initiated by low level convergence created by a finite amplitude downdraught these experiments have constant low level shear and differ only in the profile of mid and upper level winds quasi steady convenction is produced if the mid and upper level flow has small shear and the low level shear is large the surface precipitation ismaximized for no intial relative relative flow aloft if stationary this storm p o can give prodigious locilized rainfall p o is the two dimentisonal equivalent of the supercell these results are placed in context with previous two dimensional simulations attention is drawn to the similiarity with previous two dimensional simulations attention is drawn to the similarity with squall lines in central and eastern u s a storm p o is analysed by construction of time averaged fields of streamfunction vorticity teperature and height deviation the smoothness of these fields suggests a conceptual model of the storm dynamics which involves cooperation between distinct charcteristic flows an overturning updraught a jump type updraught a shallow downdraught a low level rotor and a boundary layer an idealized analytical model is described by solution of the equations for steady convection these solutions for the remote flow are derived from energy conversation mass continuity and a momentum budget and they give relationships between the non dimensional parameteres of the problem it is apparent that the convection is a high froude or low richardson number flow demanding the existence of a cross storm pressure gradient inherent in this idealized model is a vortex sheet between updraught and down draught and it is considered that the dynamical instability of this sheet is related to complexities in the numerical simulation furthermore these results show that in two dimensions both non constant shear and a shallow downdraught are necessary to maintain steady convection

dynamic response characteristics and deformation evolution of loess slopes under seismic loads abstract the loess plateau is one of the most seismically and geologically active regions in china the related catastrophic earthquakes and geological disasters have caused more than 1 4 million deaths in the plateau in this study the slopes on the edge of the loess tableland in pingliang city gansu province the core area of the loess plateau are investigated based on large scale shaking table model tests and discrete element numerical simulation particle flow code pfc 2d the dynamic response characteristics and deformation evolution process of fissured and non fissured loess slopes under different seismic loads are studied the test results show that with increasing seismic load input the peak ground displacement pgd of the loess slopes increases gradually with increasing slope height for the two types of slopes the acceleration amplification effects in the slope with horizontal direction load are larger than those of the vertical direction load the amplification factor of the peak ground acceleration pga at the shoulder of the fissured slope is significantly larger than that of the non fissured slope according to the numerical simulation results of the fissured slope when the seismic load is small the bond failures are distributed densely in the initial fissured structural plane and at the model bottom regarding the non fissured slope the bond failures in the slope are mainly distributed at the bottom of the model with increasing acceleration amplitude the number of bond failures in the slopes increases rapidly when the input load increases to 0 40 g two potential slip surfaces occur in the shallow surface of the fissured slope and a potential slip surface appears at the back edge of the non fissured slope

single doppler velocity retrievals with phoenix ii data clear air and microburst wind retrievals in the planetary boundary layer abstract a new three dimensional single doppler velocity retrieval is introduced and tested with reflectivity and radial velocity data gathered during the phoenix ii field program near boulder colorado this retrieval is based on reflectivity conservation with provision for raindrop fall speed the incompressibility condition and a temporal constraint on the velocity field two temporal constraints are considered velocity stationarity and taylor s frozen turbulence approximation velocity stationarity in a moving reference frame it is demonstrated that either of these temporal constraints can be used to derive a second conserved scalar from the original conserved scalar reflectivity this two scalar system is in general overdetermined but a least squares formulation reduces the problem to a poisson equation for a pseudostreamfunction the requisite boundary conditions arise naturally from the least squares formulation and require only single doppler measurements for their evaluation the new r

earthquake triggered increase in sediment delivery from an active mountain belt in tectonically active mountain belts earthquake triggered landslides deliver large amounts of sediment to rivers we quantify the geomorphic impact of the 1999 mw 7 6 chi chi earthquake in taiwan which triggered 20 000 landslides coseismic weakening of substrate material caused increased landsliding during subsequent typhoons most coseismic landslides remained confined to hillslopes downslope transport of sediment into the channel network occurred during later storms the sequential processes have led to a factor of four increase in unit sediment concentration in rivers draining the epicentral area and increased the magnitude and frequency of hyperpycnal sediment delivery to the ocean four years after the earthquake rates of hillslope mass wasting remain elevated in the epicentral area

effect of baseline corrections on displacements and response spectra for several recordings of the 1999 chi chi taiwan earthquake displacements derived from many of the accelerogram recordings of the 1999 chi chi taiwan earthquake show drifts when only a simple baseline de rived from the pre event portion of the record is removed from the records the appearance of the velocity and displacement records suggests that changes in the zero level of the acceleration are responsible for these drifts the source of the shifts in zero level are unknown but in at least one case it is almost certainly due to tilting of the ground this article illustrates the effect on the ground velocity ground dis placement and response spectra of several schemes for accounting for these baseline shifts a wide range of final displacements can be obtained for various choices of baseline correction and comparison with nearby gps stations none of which are colocated with the accelerograph stations do not help in choosing the appropriate baseline correction the results suggest that final displacements estimated from the records should be used with caution the most important conclusion for earthquake engineering purposes however is that the response spectra for periods less than about 20 sec are usually unaffected by the baseline correction although limited to the analysis of only a small number of recordings the results may have more general significance both for the many other recordings of this earthquake and for data that will be obtained in the future from similar high quality accelerograph networks now being installed or soon to be installed in many parts of the world

geological and morphological study of the jiufengershan landslide triggered by the chi chi taiwan earthquake the jiufengershan rock and soil avalanche is one of the largest landslides triggered by the chi chi earthquake taiwan 1999 the landslide destabilized the western limb of the taanshan syncline along a weak stratigraphic layer it involved a flatiron remnant which was almost entirely mobilized during the earthquake the avalanche was slowed down by ns trending ridges located downstream along the jiutsaihu creek the landslide affected a 60 m thick and 1 5 km long sedimentary pile composed of shales and sandstones which dip 228se toward a transverse valley the triggering mechanism and the sliding process were analyzed by means of geological and morphological data from aerial photographs and observed in the field a high resolution airborne light detection and ranging lidar image taken 2 5 years after the landslide allows the identification of morphological structures along the sliding surface and the landslide accumulation the sliding surface shows several deformation structures such as fault scarps and folds these structures are interpreted in terms of basal shear stresses created during the avalanche three major joint sets were identified at the sliding surface the isopach map of the landslide was calculated from the comparison between elevation models before and after the earthquake the coseismic volume of mobilized material and landslide deposit data are 4210 6 m 3 and 5010 6 m 3 respectively the geometry of the landslide accumulation in the field has an irregular star shape the morphology of the deposit area shows a sequence of smooth reliefs and depressions that contrast with the neighboring ridges d 2005 elsevier b v all rights reserved

the arcadia oklahoma storm of 17 may 1981 analysis of a supercell during tornadogenesis abstract on 17 may 1981 an extensive dataset was collected for a supercell thunderstorm that produced an f2 tornado near arcadia in central oklahoma coordinated dual doppler scans of the storm by 10 cm research radars were collected at approximately 5 min intervals from 30 min before the tornado touched down until 15 min after the tornado had dissipated the arcadia storm was also well sampled by a 444 m tall instrumented tower the low level inflow updraft mesocyclone and rear precipitation core of the supercell all passed across the tower a comparison of the instrumented tower measurements with a dual doppler synthesis reveals that the latter qualitatively resolved the low level flow however the magnitudes of the low level horizontal winds and updraft speed were underestimated in addition the vertical shear of the horizontal wind in the lowest kilometer was unresolved in the doppler winds in the storm environment horizontal vorticity was strong 1 5 10 2 s 1 and approximately streamwise

tornado maintenance investigated with high resolution dual doppler and enkf analysis abstractdual doppler wind synthesis and ensemble kalman filter analyses produced by assimilating doppler on wheels velocity data collected in four tornadic supercells are examined in order to further understand the maintenance of tornadoes although tornado scale features are not resolved in these analyses larger scale processes involved with tornado maintenance are well represented the longest lived tornado is maintained underneath the midlevel updraft within a zone of low level horizontal convergence along a rear flank gust front for a considerable time and dissipates when horizontally displaced from the midlevel updraft the shortest lived tornado resides in a similar zone of low level convergence briefly but dissipates underneath the location of the midlevel updraft when the updraft becomes tilted and low level convergence is displaced several kilometers from the tornado this suggests that a location beneath the midlevel updraft is not always a sufficient condition for tornado maintenance particu

the tornadic supercell on the kanto plain on 6 may 2012 polarimetric radar and surface data assimilation with enkf and ensemble based sensitivity analysis abstracta tornadic supercell and associated low level mesocyclone lmc observed on the kanto plain japan on 6 may 2012 were predicted with a nonhydrostatic mesoscale model with a horizontal resolution of 350 m through assimilation of surface meteorological data horizontal wind temperature and relative humidity of high spatial density and c band doppler radar data radial velocity and rainwater estimated from reflectivity and specific differential phase with a local ensemble transform kalman filter with assimilation of both surface and radar data a strong lmc was successfully predicted near the path of the actual tornado when either surface or radar data were not assimilated however the lmc was not predicted therefore both surface and radar data were essential for successful lmc forecasts the factors controlling the strength of the predicted lmc defined as a low level maximum vertical vorticity were clarified by an ensemble based sensitivity analysis esa which is a new approach for ana

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

deformation history of the southwestern taiwan foreland thrust belt insights from tectono sedimentary analyses and balanced cross sections abstract analysis of the basin scale and local deformation history and estimates of shortening rates are performed in the southwestern foreland thrust belt of the plio pleistocene taiwan orogen timing of deformational events is constrained using both syntectonic unconformities and other markers of syndepositional tectonic activity three cross sections are investigated and balanced intermediate shortening rates are estimated based on balanced and restored cross sections the total amount of shortening along studied balanced sections results from superimposed thin skinned and thick skinned styles a shallow aseismic thick decollement is located to depth of 6 8 km at the base of thick late miocene shales that behaves as ductile layer the occurrence of a deep seismic decollement to depth of 12 15 km is confirmed by seismicity fault plane solutions of focal mechanisms and a seismic reflection profile providing evidence of reactivated and inverted inherited extensional features beneath the coastal plain three major tectonic stages are recognized within the southwestern foothills which are correlated with local thrusting events the first stage begins at 5 ma with the onset of the taiwan collision and ends at 2 1 6 ma it reflects an initial submarine accretionary stage associated with moderate tectonic activity the second major stage occurs during late pliocene early pleistocene this intermediate collision stage sealed the evolution of the southern foreland thrust wedge from submarine to continental environment in relation with exhumation and denudation of the central range the last stage of deformation begins in the middle pleistocene and continues until present it is associated with high rates of sedimentation and most of the thrusts are activated or reactivated at that time and out of sequence thrusting occurs the collision started synchronously near 5 ma throughout the southwestern taiwan total and intermediate shortening rates are more or less constant through time in studied sections that may suggest that long term deformation in the taiwan foreland thrust belt occurred more or less at steady state since 5 ma the southward decrease of rates of shortening from 3 6 to 4 8 mm year in northern sections to 2 2 mm year in southern section might be related to both influence of indentation by the peikang high to the north and southward transition at the scale of the southwestern foothills from collision to subduction setting the effect of the obliquity of the convergence resulting in regional southward migration of the collision cannot be definitely inferred from this analysis our results place new kinematic and time constraints which must be taken into account in forthcoming geodynamic models of the taiwan collision

evolution of the large landslide induced by typhoon morakot a case study in the butangbunasi river southern taiwan using the discrete element method abstract in 2009 typhoon morakot delivered high intensity rainfall and triggered many sites of large landslide which projected areas were larger than 10 000 m 2 from the satellite image especially in southern taiwan according to dtm analysis the material volume of the large landslide in butangbunasi river was more than four times larger than that of the nearly famous landslide disaster in hsiaolin village nevertheless the different movement of these two large landslides led to different disaster impacts based on literatures and field works the large hsiaolin landslide was a catastrophic landslide which had high velocity and less energy loss in the kinematic process the source area of the large landslide in the butangbunasi river on the other hand was composed of several landslide events and the kinetic energy dissipated when the landslide materials attained to riverbed in sequence in this study we divided the butangbunasi river large landslide into five slope units namely a b c d and e landslide events to recognize the mechanism of the large landslide and the simulation by using the particle flow code 3d pfc3d which is based on the discrete element method provided the kinematic process of the large landslide in the butangbunasi river it is noticed that most of the initial energy dissipated during the movement which the fist happening landslide event counteracted the crash of the follow up events and the residual energy gradually declined by the collision interaction of landslide blocks until the end of the large landslide the result helps to reconstruct the evolution of the large landslide from small scale landslide events and contributes to predict the affected region of the disaster it also reveals that even though the impact of the large landslide is reduced by sequent small scale landslide events there still remain secondary disasters such as landslide dam which show a high potential risk in the river valley and midstream

influence of surface normal ground acceleration on the initiation of the jih feng erh shan landslide during the 1999 chi chi taiwan earthquake the 1999 chi chi taiwan earthquake triggered numerous landslides throughout a large area in the central range to the east southeast and south of the fault rupture among them are two large rock avalanches at tsaoling and at jih feng erh shan at jih feng erh shan the entire thickness 30 50 m of the mio cene changhukeng shale over an area of 1 km 2 slid down its bedding plane for a distance of about 1 km initial movement of the landslide was nearly purely trans lational we investigate the effect of surface normal acceleration on the initiation of the jih feng erh shan landslide using a block slide model we show that this ac celeration currently not considered by dynamic slope stability analysis methods significantly influences the initiation of the landslide

the impact of data assimilation length scales on analysis and prediction of convective storms abstractan idealized convective test bed for the local ensemble transform kalman filter letkf is set up to perform storm scale data assimilation of simulated doppler radar observations convective systems with lifetimes exceeding 6 h are triggered in a doubly periodic domain perfect model experiments are used to investigate the limited predictability in precipitation forecasts by comparing analysis schemes that resolve different length scales starting from a high resolution reference scheme with 8 km covariance localization and observations with 2 km resolution on a 5 min cycle an experimental hierarchy is set up by successively choosing a larger covariance localization radius of 32 km observations that are horizontally averaged by a factor of 4 a coarser resolution in the calculation of the analysis weights and a cycling interval of 20 min after 3 h of assimilation the high resolution analysis scheme is clearly superior to the configurations with coarser scales in terms of rms error and field o

discrete element simulation of the jiufengershan rock and soil avalanche triggered by the 1999 chi chi earthquake taiwan we present contact dynamics discrete element simulations of the earthquake triggered jiufengershan avalanche which mobilized a 60 m thick 1 5 km long sedimentary layer dipping similar to 22 degrees se toward a valley the dynamic behavior of the avalanche is simulated under different assumptions about rock behavior water table height and boundary shear strength additionally seismic shaking is introduced using strong motion records from nearby stations we assume that seismic shaking generates shearing and frictional heating along the surface of rupture which in turn may induce dynamic weakening and avalanche triggering a simple slip weakening criterion was adopted to simulate shear strength drop along the rupture surface we investigate the mechanical processes occurring during triggering and propagation of an avalanche mobilizing shallowly dipping layers incipient deformation forms a pop up structure at the toe of the dip slope as the avalanche propagates the pop up deforms into an overturned fold which overrides the surface of separation along a decollement simultaneously uphill layers slide at high velocity 125 km h and are folded and disrupted as they reach the toe of the dip slope the avalanche foot forms a wedge that is pushed forward as deformed rocks accrete at its rear we simulated five cross sections across the jiufengershan avalanche which differ in the geometry of the surface of separation topographic and simulated surface profiles are similar the friction coefficient at the surface of separation determined from back analysis is abnormally low mu ss 0 2 possibly due to lubrication by liquefied soils the granular deposits of simulated earthquake and rain triggered avalanches are similar