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

monitoring soil water and displacement conditions leading to landslide occurrence in partially saturated clays abstract shallow landslides frequently occur during transient rainfall infiltration and under partially saturated conditions however a detailed analysis of what triggers them particularly in clayey soils is often hindered by the lack of field measurements it is uncommon in fact to capture their occurrence in an instrumented natural slope this paper presents results from an integrated field experiment monitoring the soil water and displacement conditions that lead to the occurrence of a shallow landslide in partially saturated clays the integration of a variety of experimental techniques allowed for the examination of interplay between soil hydrological and mechanical properties this research also evaluates a slope stability model based on the suction stress concept since the model was applied after the occurrence of the landslide the results are interpreted as a hind casting technique for model evaluation nevertheless the detailed field measurements acquired during the monitoring activity and the occurrence of a landslide during the experiment provided significant information on model parameters and data interpretation the station provides remote satellite monitoring of data on weather variables soil water content and soil suction a time domain reflectometry cable was installed vertically to detect potential soil failure the experimental area had a high probability of landslide occurrence indeed slope failure occurred during the observation period showing the effectiveness of the station in detecting the occurrence time and depth of landslides the landslide was triggered in consequence of changes in suction stress the failure plane occurred at a depth of 1 4 m corresponding to the interface between a superficial layer of higher permeability of 1 to 1 45 m thickness slipping over a compacted substrate having lower permeability the analysis allowed for testing of the validity of the model and the description of the triggering mechanisms of the observed shallow landslide in unsaturated conditions indicating that oscillations in soil matric suction were the dominant variables determining soil failure

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

critical slip surface and landslide volume of a soil slope under random earthquake ground motions finding the critical slip surface and estimating the landslide volume are of primary importance for slope seismic design however this may be difficult due to the uncertainty of ground motions to address this problem a new method for calculating uncertainties is recommended in this paper especially for the critical slip surface and landslide volume under random earthquake ground motions firstly a series of intensity frequency nonstationary random earthquake ground motions were generated based on an improved orthogonal expansion method a given number of potential slip surfaces were set in a soil slope subsequently the factor of safety fos of each slip surface for all ground motions was calculated and the minimum fos curves were obtained it was found that the critical slip surfaces and failure times are uncertain under different earthquakes the monte carlo method was used to verify the accuracy of probability density evolution method pdem and the results of the pdem and the monte carlo method are consistent meaning that the pedm has higher computational efficiency moreover the distributions of earthquake triggered landslide volume and landslide depth were analyzed by considering equivalent extreme events both landslide volume and depth exhibit a normal distribution for a homogeneous soil slope the framework of this study is meaningful for slope seismic design in engineering for example the location of critical slip surface can be used for slope reinforcement and the distribution of sliding volume can be used for disaster assessment

development of a loess mudstone landslide in a fault fracture zone a landslide occurred on the morning of december 16 2013 in liujiabao village tianshui city gansu province china the 260 000 m3 of landslide material traveled a distance of 190 m downslope and damaged a village road and several farmhouses before it stopped on the middle of the slope these landslide materials are still threatening the lives and property of people in the downslope residential areas a field survey revealed that this landslide was strongly affected by the geological setting six normal faults that extend from east to west developed in the neogene mudstone of this region these faults form a fault fracture zone with a width of 80 m the authors performed a detailed investigation of the geological features of these six normal faults and their spatial and faulting relationships to the landslide were examined finally the evolutionary progress of the loess mudstone landslide controlled by the fault fracture zone is discussed

ground motion relations for eastern north america predictive relations are developed for ground motions from eastern north american earthquakes of 4 0 m 7 25 at distances of 10 r 500 km the predicted parameters are response spectra at frequencies of 0 5 to 20 hz and peak ground acceleration and velocity the predictions are derived from an empirically based stochastic ground motion model the relations differ from previous work in the improved empirical definition of input parameters and em pirical validation of results the relations are in demonstrable agreement with ground motions from earthquakes of m 4 to 5 there are insufficient data to adequately judge the relations at larger magnitudes although they are consistent with data from the saguenay m 5 8 and nahanni m 6 8 earthquakes the underlying model parameters are constrained by empirical data for events as large as m 6 8

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

distribution and genetic types of loess landslides in china abstract in this study 14 544 loess landslides collected from the loess plateau of china are used to reveal their distribution and origins main factors considered include landslide density regional tectonics soil properties geomorphic structure rainfall distribution seismic activity and human activity based on these factors the loess plateau is divided into eight zones with high possibilities of landslides that are classified into six genetic types the first genetic type of clustering distribution of loess landslides is related to several main regional active faults the second type is related to broken pieces of loess geomorphic structures the third type is considered to be due to unloading of the geomorphic peripheral slope that can cause the internal structural plane to open and thus controls the prototype and scale of the loess landslide change of hydrogeological conditions in the slope softens the loess pedestal and the slippery layer forming a softening zone and thus controlling the shear crack and slip model of the fourth type of loess landslides the fifth type is due to seismic activities that can generate additional stress to the earth s surface and landform slopes causing the opening of joints and seismic liquefaction the last type of landslides is caused by human activities by changing the geological structure hydrogeological conditions and the inner stress balance of slopes

three dimensional geological structures and sliding factors and modes of loess landslides loess environments such as the chinese loess plateau are geologically fragile because of their great thickness loose structure crisscrossing ravines and gullies broken terrain dry climate severe erosion and unevenly distributed rainfall as a consequence loess areas are highly prone to environmental problems and geological hazards the geological structure of the loess is one of the main factors that controls occurrence of these geohazards this study investigated the mechanism of loess landslides and their sliding control mode from the perspective of their geological structure using this mechanism a three dimensional geological model of loess landslides was established the study shows that the structural planes in loess divide a complete slope into separate blocks which enables the fast and deep infiltration of surface water via seepage channels and reduces the shear strength of the soil mass inducing landslides the development and formation of loess landslides are primarily controlled by structural planes and influenced by infiltrated water softening the structural plains various types of structural planes may combine and form structural bodies of different types and scales which control the type depth and scale of loess landslides

felt intensity versus instrumental ground motion a difference between california and eastern north america we examine the question of whether a single ground motion intensity correlation equation gmice is applicable to both eastern north america ena intraplate and california interplate we initially address this issue with the datasets from previous studies and separate them into central united states cus california and canada datasets we then add data from the 2008 m 5 2 mt carmel illinois and the 2005 m 4 7 riviere du loup earthquakes to the cus and canada datasets respectively for each dataset the median of ground motion values at each modified mercalli intensity mmi level and their 95 confidence limits are calculated for peak ground velocity pgv peak ground acceleration pga and spectral acceleration sa at 0 3 1 0 and 2 0 s the california median value is relatively higher than the cus and canada for pgv and sa at 1 0 and 2 0 s based on the median values and the associated uncertainty we combine all datasets for pga and 0 3 s sa in order to determine a gmice the cus and canada datasets are combined separately from california for pgv 1 0 s sa and 2 0 s sa ena earthquakes have a different spectral shape than those in california particularly at intermediate periods 1 0 s where ena spectral amplitudes are reduced which may explain the difference we see at longer periods finally a log linear fit of mmi to the median values of ground motion is used to determine gmice

ground motion to intensity conversion equations gmices a global relationship and evaluation of regional dependency we analyzed the regional dependence of ground motion to intensity conversion equations and derived a new global relationship to improve ground motion and intensity estimates for earthquake hazard applications including those related to the shakemap system for this purpose we merged several databases collected by other authors in different geographical regions to highlight any systematic regional effects in the relationship between macroseismic intensities and both peak ground velocity and peak ground acceleration our database contains macroseismic intensities derived from expert assignments or from the did you feel it database paired with peak ground motions pgm from seismic stations we constrain our intensity ground motion pairs to those with a maximum 2 km separation for each region we derived invertible relationships between intensities and ground motion using an orthogonal regression we also derived a global relationship to quantify the regional differences we investigated the dependence of intensity on predictor variables such as pgm magnitude and hypocentral distance our analyses indicate that pgm is the most robust predictor variable of intensity within one standard deviation our regional and global results are in agreement with the relations of worden et al 2012 for california faenza and michelini 2010 for italy tselentis and danciu 2008 for greece and atkinson and kaka 2007 for central eastern united states the earthquakes in the study ranged in magnitude from 2 5 to 7 3 and the distances ranged from less than a kilometer to about 200 km from the epicenter online material table summarizing published relationships and figures showing the relationship between peak ground acceleration and intensity

site amplifications for generic rock sites seismic shear wave velocity as a function of depth for generic rock sites has been estimated from borehole data and studies of crustal velocities and these velocities have been used to compute frequency dependent amplifications for zero attenuation for use in simulations of strong ground motion we define a genetic rock site as one whose velocity at shallow depths equals the average of those from the rock sites sampled by the borehole data most of the boreholes are in populated areas for that reason the rock sites sampled are of particular engineering significance we consider two genetic rock sites rock corresponding to the bulk of the borehole data and very hard rock such as is found in glaciated regions in large areas of eastern north america or in portions of western north america the amplifications on rock sites can be in excess of 3 5 at high frequencies in contrast to the amplifications of less than 1 2 on very hard rock sites the consideration of unattenuated amplification alone is computationally convenient but what matters for ground motion estimation is the combined effect of amplification and attenuation for reasonable values of the attenuation parameter k 0 the combined effect of attenuation and amplification for rock sites peaks between about 2 and 5 hz with a maximum level of less than 1 8 the combined effect is about a factor of 1 5 at 1 hz and is less than unity for frequencies in the range of 10 to 20 hz depending on t using these amplifications we find provisional values of about ao 70 bars and k 0 0 035 sec for rock sites in western north america by fitting our empirically determined response spectra for an m 6 5 event to simulated values the borehole data yield shear velocities 033o of 618 and 306 rrdsec for rock and soil sites respectively when averaged over the upper 30 m from this we recommend that v30 equals 620 and 310 m sec for applications requiring the average velocity for rock and soil sites in western north america by combining the amplifications for rock sites and the site factors obtained from our analysis of strong motion data we derive amplifications for sites with 17 3o 520 m sec nehrp class c corresponding to a mix of rock and soil sites and v3o 310 and 255 m sec average soil and nehrp class d sites respectively for the average soil site the combined effect of amplification and attenuation exceeds a factor of 2 0 for frequencies between 0 4 and about 4 hz with a peak site effect of 2 4 the peak of the nehrp class d site effect is 2 7

mass movements along a rapidly uplifting river valley an example from the upper jinsha river southeast margin of the tibetan plateau because of the rapid uplift of the tibetan plateau since the middle and late pleistocene the surrounding mountainous areas of the tibetan plateau also show a rapid uplift trend the study area is located in the upper reaches of the jinsha river southeastern tibetan plateau tectonically the study area is located in the eastern segment of the jinshajiang suture zone which is the weak belt of the lithosphere affected by the rapid uplift steep slopes are formed by the rapid vertical down cutting of rivers in the studied reach under the sustained action of the gravitational field the deformation and failure of slopes readily occur to better formulate development and risk mitigation plans a mass movement inventory map at the scale of 1 50 000 was prepared for the 100 km long reach a total of 247 mass movements of different types sizes and relative ages were mapped via image interpretation and detailed field survey the statistical analysis of their spatial distributions was performed using two relative concentration indexes the correlations between the spatial distribution and six common factors were analyzed elevation slope angle slope aspect lithology active fault and river system the geomorphological survey shows that the mass movements locally play an important role in the present day landscape evolution in addition the geomorphic features indicate that the mapped giant landslides can be classified as very old landslides and they very likely occurred under a different morphoclimatic environment than that of the present

large deep seated landslides controlled by geologic structures prehistoric and modern examples in a jurassic subduction accretion complex on the kii peninsula central japan abstract the relationship between large deep seated landslides and geologic structures characteristic of accretionary complexes were examined in the chichibu belt on the eastern part of the kii peninsula central japan in the chichibu belt bedrock consists of jurassic accretionary complexes composed of basalt limestone chert permian triassic boundary siliceous shale ptbs mudstone sandstone and melanges with sheared shale matrices the landslides treated in this paper include prehistoric examples involving volumes greater than one million cubic meters located in the karako sono kasagi and aso areas and the modern kasugadani landslide that was triggered by the typhoon meari on 29 30 september 2004 the age of the landslide in the sono area was estimated at 20 440 70 bp and 20 820 70 bp based on ams 14c ages of wood fragments embedded in the dammed lake sediments while ages of the other prehistoric slides are not known all of the landslides occurred on dip slopes the bedding foliation and fault planes of the rocks in the area generally trend e w and dip to the north although those in the kasugadani area dip to the south as a result of local folding the landslides selectively slid along the planes of 1 ptbs horizons that were less strong than those of underlying chert 2 lithologic boundaries with physical contrasts or 3 boundary faults between melange units these geologic structures including the north dipping bedding cleavage fault planes were formed during jurassic subduction accretion and later uplift processes the movement directions estimated for the 269 landslides and unstable slopes in this region are also n nne and their slip planes are subparallel to the general bedding cleavage planes in this area thus future slides are also likely to occur on north facing slopes

loess geohazards research in china advances and challenges for mega engineering projects 2019 loess is a meta stable cemented assemblage of mainly silt and clay sized particles of low plasticity when dry it behaves like a brittle material but when wetted up the fabric rapidly collapses unique geomorphological features include extensive surface erosion soil piping loess karst catastrophic landslides and widespread collapse hydro consolidation the chinese loess plateau is a more or less continuous drape of thick loess covering some 440 000 km2 it is one of china s regions that is most prone to geohazards this paper reviews advances in the research related to loess geohazards drawing particular attention to the need to apply research findings to recent very large mega construction projects in loess terrain such as the mountain excavation and city construction in yan an levelling 78 km2 for urban expansion the lanzhou new district creating 246 km2 of new level ground for construction and large engineered interventions in the landscape for gully control and land reclamation such as those in shaanxi and gansu generating agricultural land covering an area of some 8000 km2 these projects are in response to increasing pressures to facilitate expansion of urban centres their interconnecting infrastructures and their agricultural support systems it is argued that where proper application of scientific knowledge for engineering control e g densification drainage of these new landscapes is absent these projects could generate a substantial and costly geohazard legacy for future generations

relationship between peak ground acceleration peak ground velocity and macroseismic intensity in western chinarelationship between pga pgv and macroseismic intensity in western china

on the modified mercalli intensities and magnitudes of the 1811 1812 new madrid earthquakes we reexamine original felt reports from the 1811 1812 new madrid earthquakes and determine revised isoseismal maps for the three principal mainshocks in many cases we interpret lower values than those assigned by earlier studies in some cases the revisions result from an interpretation of original felt reports with an appreciation for site response issues additionally earlier studies had assigned modified mercalli intensity mmi values of v vii to a substantial number of reports that we conclude do not describe damage commensurate with intensities this high we investigate several approaches to contouring the mmi values using both analytical and subjective methods for the first mainshock on 02 15 lt december 16 1811 our preferred contouring yields m 7 2 7 3 using the area moment regressions of johnston 1996 for the 08 00 lt on january 23 1812 and 03 45 lt on february 7 1812 mainshocks we obtain m 7 0 and m 7 4 7 5 respectively our magnitude for the february mainshock is consistent with the established geometry of the reelfoot fault which all evidence suggests to have been the causative structure for this event we note that the inference of lower magnitudes for the new madrid events implies that site response plays a significant role in controlling seismic hazard at alluvial sites in the central and eastern united states we also note that our results suggest that thrusting may have been the dominant mechanism of faulting associated with the 1811 1812 sequence

empirical attenuation of ground motion spectral amplitudes in southeastern canada and the northeastern united states a database of 1700 digital seismograms from 186 earthquakes of mag nitude mn 2 5 5 6 that occurred in southeastern canada and the northeastern united states from 1990 to 2003 was compiled maximum likelihood regression analysis of the database was performed to determine a model for the attenuation of fourier spectral amplitudes for the shear window for the vertical and horizontal component of motion for frequencies from 0 2 to 20 hz fourier amplitudes follow a hinged trilinear attenuation model fourier spectral amplitudes decay as r 1 3 where r is hypocentral distance within 70 km of the source there is a transition zone from 70 to 140 km as the direct waves are joined by strong postcritical reflections where the attenuation is described as r 0 2 spectral amplitudes actually increase with distance in this range for low frequencies beyond 140 km the attenuation is well described by r 0 5 corresponding to geometric spreading in two dimensions the associated model for the regional quality factor for frequencies greater than 1 hz can be ex pressed as q 893f 032 q can be better modeled over a wider frequency range 0 2 20 hz by a polynomial expression log q 3 052 0 393 log f 0 945 log f 2 0 327 log f 3 the polynomial expression accommodates the observation that q values are at a minimum about 1000 near 1 hz and rise at both lower and higher frequencies correction factors for the spectral amplitude model that describe the effects of focal depth on the amplitudes and their attenuation are developed using the subset of events with known focal depth the attenuation model is similar to that determined from an earlier study with more limited data atkinson and mereu 1992 but the enlarged database indicates more rapid near source amplitude decay and higher q the attenuation model is used to play back attenuation effects to determine the apparent source spectrum for each earthquake in the database and hence determine moment magnitude m and brune stress drop the events have moment magnitude in the range from 2 5 to 5 stress drop increases with moment magnitude for events of m 4 3 then appears to attain a relatively constant level in the range from 100 to 200 bars for the larger events as previously noted in atkinson 1993b the results of this study provide a useful framework for improving regional ground motion relations in eastern north america they further our understanding of attenuation in the region through analysis of an enlarged ground motion database in particular the inclusion of the three component broadband data gathered over the last decade allows extension of attenuation models to both horizontal and vertical components over a broad frequency range 0 2 20 hz

the shape of ground motion attenuation curves in southeastern canada the shape of the attenuation curve of the fourier spectrum of acceleration is established for southeastern canada from empirical data the dataset is comprised of 1200 digital vertical component seismograms from 100 earthquakes recorded on 30 stations of the eastern canada telemetered network the distance range of the observations is 10 to 1700 km focal depths are from 5 to 30 km results indicate that the attenuation curve has three distinct sections at distances less than 70 km corresponding to attenuation of the direct wave amplitudes decay slightly more rapidly than 1 r r 1 1 between 70 and 130 km where the direct wave is joined by sms spectral amplitudes are approximately constant beyond 130 km corresponding to the lg phase amplitudes decay at a rate that is consistent with r 0 5 and q 670 f 0 33 the findings support the hypothesis of burger et al 1987 that postcritical reflections from the moho discontinuity play an important role in determining the shape of the attenuation curve however the influence of sms is subtle allowing the shape to be approximated by simple functional forms for example the commonly assumed bilinear form r 1 r 0 5 with frequency dependent q fits well if the transition from direct wave to lg spreading is placed at approximately 60 km a linear form r 1 over all distances with constant q 2000 also provides a satisfactory fit overall we find little evidence for the dependence of attenuation on focal depth or tectonic province

landslide dam deformation analysis under aftershocks using large scale shaking table tests measured by videogrammetric technique abstract the ms 8 0 wenchuan earthquake triggered at least 257 landslide dams more than 849 aftershocks with magnitudes higher than ms 4 0 occurred after the wenchuan earthquake by 12 march 2012 shen et al 2013 which might largely influence the structure and soil properties of these dams this paper aims to study the dynamic deformation of landslide dams under aftershocks through larger scale shaking table tests videogrammetric technique was applied to measure the dynamic deformation of the model dams two groups of shaking table tests were conducted with two types of landslide dam materials one with quartz sands containing 10 kaolin dam i and the other with only quartz sands dam ii the dam deformation and its influencing factors were analyzed with the results measured by videogrammetric technique the deformations were generally higher on the surface of the dams either on the crest or on the both upstream and downstream slopes higher peak ground acceleration pga resulted in larger dam deformations due to higher seismic force the deformations under the combination of x and z directional shakings were larger than those under x directional shaking for sufficient vibratory compaction water rising led to the increase of dam deformations because that the water seepage reduced the effective soil stress especially reduced the matric suction the settlements of the dam composed of more fine particles were larger than that composed of large particle size because that the soil pores in the former were filled more sufficiently with fine particles the aftershocks may not directly trigger the failures of landslide dams but accelerate the overtopping failures by lowering the dam crest with settlement and cracking

earthquake source spectra in eastern north america source spectra for earthquakes of 3 m 7 in eastern north america ena are determined from regional seismograph recordings strong motion records teleseismic data and modified mercalli intensity data the inclusion of mmi data is made possible by the finding that the felt area of an earthquake is an accurate measure of its high frequency spectral level at the source current ground motion relations for ena are based on a brune source model with a stress parameter of 100 bars this model is a poor fit to ena source spectra for events of m 4 at high frequencies 5 to 10 hz observed spectral amplitudes are more nearly matched by a brune stress parameter of 200 bars intermediate frequency amplitudes near 1 hz are matched by a stress parameter of approximately 50 bars an empirical two corner source model is proposed to describe ena source spectra for events of 4 m 7

reservoir processes and fluid origins in the baca geothermal system valles caldera new mexico at the baca geothermal field in the valles caldera new mexico 19 deep wells were drilled in an attempt to develop a 50 mwe megawatts electric power plant the chemical and isotopic compositions of steam and water samples have been used to indicate uniquely the origin of reservoir fluids and natural reservoir processes two distinct reservoir fluids exist at baca these fluids originate from the same deep high temperature 335 c saline 2500 mg kg cl parent water but have had different histories during upflow one fluid from wells 4 and 13 is isotopically light high in radiogenic noble gases co2 and hco3 and low in ca it has a temperature of 290 295 c and a reservoir chloride near 1900 mg kg this fluid resulted from rapid upward flow through 1 1 to 1 4 m y old bandelier tuff reservoir rocks after long residence in pre bandelier 7 m y sediments and precambrian basement rocks and 25 dilution with high altitude cold groundwater from redondo peak the other water from wells 15 19 and 24 moved slowly through the bandelier tuff and cooled conductively with minor steam loss for well 19 from 335 c to 280 260 c apparently short residence in old basement rocks has left this water with low radiogenic gases conductive cooling without mixing has kept the original chloride and relatively heavy isotope composition of the deep water the recharge to the deep parent water is not well understood but may be from lower elevation precipitation outside the valles caldera area gases are in equilibrium in all liquid reservoir fluids at near reservoir temperatures and the concentrations of atmospheric gases are similar to those of air saturated water indicating little boiling and steam loss all water solutes and gases in the reservoir fluids originate from air saturated meteoric recharge water watermineral reactions and rock leaching with the possible exception of excess 3he that must have an ultimate mantle source this gas could originate directly from magma or from leaching of intrusive volcanic rocks beneath the bandelier

the attenuation of seismic intensity in italy part i theoretical and empirical backgrounds abstract we critically analyze the results on seismic intensity attenuation in italy derived by albarello and d amico 2004 and gasperini 2001 we demonstrate that due to the inadequacy of certain underlying assumptions the empirical relationships determined in those studies did not best reproduce the decay of intensity as the distance from the source increases we reconsidered some of the relevant concepts and assumptions used in these intensity attenuation studies macroseismic epicenter epicentral intensity data completeness to suggest some useful recipes for obtaining unbiased estimates in particular we suggest that 1 data for distances from the source at which an intensity below the limit of diffuse perceptibility iv is expected should be excluded from attenuation computations because such data are clearly incomplete 2 attenuation equations that include a term proportional to the epicentral intensity i 0 with a coefficient different from 1 0 must not be used because they imply a variable offset between i 0 and the intensity expected at the epicenter and 3 epicentral intensities must be recomputed consistently with the attenuation equation because those reported by the italian catalog do not generally correspond with the intensity predicted at the epicenter by the attenuation relationships so far proposed following these suggestions produces a significant reduction in the standard deviation of the model that might lead to a corresponding reduction of the estimates of seismic hazard

earthquakes as collapse precursors at the han sur lesse cave in the belgian ardennes abstract collapse activation is an ongoing process in the evolution of karstic networks related to the weakening of cave vaults because collapses are infrequent few have been directly observed making it challenging to evaluate the role of external processes in their initiation and triggering here we study the two most recent collapses in the dome chamber of the han sur lesse cave belgian ardenne that occurred on or shortly after 3rd december 1828 and between the 13th and 14th of march 1984 because of the low probability that the two earthquakes that generated the strongest ground motions in han sur lesse since 1800 on 23rd february 1828 mw 5 1 in central belgium and 8th november 1983 mw 4 8 in liege occurred by coincidence less than one year before these collapses we suggest that the collapses are related to these earthquakes we argue that the earthquakes accelerated the cave vault instability leading to the collapses by the action of other factors weakening the host rock in particular the 1828 collapse was likely triggered by a smaller mw 4 2 nearby earthquake the 1984 collapse followed two months of heavy rainfall that would have increased water infiltration and pressure in the rock mass favoring destabilization of the cave ceiling lamina counting of a stalagmite growing on the 1828 debris dates the collapse at 1826 9 ce demonstrating the possibility of dating previous collapses with a few years of uncertainty furthermore our study opens new perspectives for studying collapses and their chronology both in the han sur lesse cave and in other karstic networks we suggest that earthquake activity could play a stronger role than previously thought in initiating cave collapses

anatomy of landslides along the dead sea transform fault system in nw jordan abstract in the mountainous region north of amman jordan cenomanian calcareous rocks are being monitored constantly for their mass wasting processes which occasionally cause severe damage to the amman irbid highway satellite remote sensing data landsat tm aster and srtm and ground measurements are applied to investigate the anatomy of landslides along the dead sea transform fault system dstfs a prominent strike slip fault the joints and faults pertinent to the dstfs match the architectural elements identified in landslides of different size this similarity attests to a close genetic relation between the tectonic setting of one of the most prominent fault zones on the earth and modern geomorphologic processes six indicators stand out in particular 1 the fractures developing in n s and splay faults represent the n s lateral movement of the dstfs they governed the position of the landslides 2 cracks and faults aligned in ne sw to nnw ssw were caused by compressional strength they were subsequently reactivated during extensional processes and used in some cases as slip planes during mass wasting 3 minor landslides with ne sw straight scarps were derived from compressional features which were turned into slip planes during the incipient stages of mass wasting they occur mainly along the slopes in small wadis or where a wide wadi narrows upstream 4 major landslides with curved instead of straight scarps and rotational slides are representative of a more advanced level of mass wasting these areas have to be marked in the maps and during land management projects as high risk area mainly and may be encountered in large wadis with steep slopes or longitudinal slopes undercut by road construction works 5 the spatial relation between minor faults and slope angle is crucial as to the vulnerability of the areas in terms of mass wasting 6 springs lined up along faults cause serious problems to engineering geology in that they step up the behavior of marly interbeds to accelerate sliding during mass wasting the most vulnerable areas prone to slope instabilities are those with compressional tectonics followed by extensional movements with fault bound springs and smectite bearing marly layers interbedded with pure massive limestones the semi arid to arid climate with periodic rainfalls combined with subsurface water circulation along the joints and faults can trigger mass wasting

laboratory study on soil behavior in loess slope subjected to infiltration abstract in recent years heifangtai plateau in gansu province china has received significant attention as a loess region in which landslides frequently occur this study aims to examine the soil behavior and failure mechanism s of loess slopes subjected to water infiltration high quality samples were retrieved behind the failure plane of a landslide in heifangtai three sets of stress path tests were conducted to mimic the process of loess slope failures these tests include undrained compression on anisotropically consolidated saturated samples drained shear by decreasing mean effective stress at constant axial load on saturated samples and wetting by decreasing matric suction at constant axial load on unsaturated samples loess behavior was evaluated in terms of shear strength deformation upon shearing critical state state parameter and soil water characteristic curve three major observations were drawn from the test results first the anisotropically consolidated saturated loess exhibits a noticeable strain softening behavior upon undrained compression the peak shear strength is mobilized at less than 1 axial strain the ultimate shear strength is only 20 30 of the peak value second when subjected to shear by decreasing mean effective stress at constant axial load the saturated loess exhibits sudden failure when the confining stress is low at higher stresses the soil exhibits progressive failure third unsaturated loess deforms progressively when subjected to a reduction in matric suction i e wetting at constant axial load the failure mechanisms of the loess slopes are discussed based on the experimental findings

probabilistic stability analysis of rainfall induced landslides considering spatial variability of permeability abstract many regions around the world are vulnerable to rainfall induced landslides a variety of methods have been proposed for revealing the mechanism of landslide initiation current analysis methods however do not consider the effects of non homogeneous soil profiles and variable hydraulic responses on rainfall induced slope failures in korea where the depth of weathering is very shallow many slope failures occur in the layer of weathered residual soil that overlays the bedrock these failures are characterized by shallow failure surfaces located near the interface between the weathered soil and the underlying bedrock in this study probabilistic stability analyses were conducted for a weathered residual soil slope with shallow impermeable bedrock to study the failure mechanism of rainfall related landslides a series of seepage and stability analyses of an infinite slope based on one dimensional random fields were performed to study the effects of uncertainty due to the spatial heterogeneity of hydraulic conductivity on the failure of unsaturated slopes due to rainfall infiltration the results showed that a probabilistic framework can be used to efficiently consider various failure patterns caused by spatial variability of hydraulic conductivity in rainfall infiltration assessment for a shallow infinite slope

shaking scenarios from multiple source models shed light on the 8 september 1905 mw 7 calabria earthquake southern italy project istege indagine sismotettonica del terremoto dell 8 settembre 1905 mw 7 4 nel golfo di sant eufemia offshore tirrenico calabrese supported by ogs istituto nazionale di oceanografia e di geofisica sperimentale project ritmare funded by dipartimento della protezione civile italy s national civil protection

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

isoseismal map of the 2015 nepal earthquake and its relationships with ground motion parameters distance and magnitude abstract a devastating earthquake of mw 7 8 struck central nepal on 25th april 2015 6 11 25 ut which resulted in more than 9000 deaths and destroyed millions of houses standing buildings roads and electrical installations worth 25 30 billions of dollars are reduced to rubbles the earthquake was widely felt in the northern parts of india and moderate damage have been observed in the northern part of up and bihar region of india maximum intensity ix according to the usgs report was observed in the meizoseismal zone surrounding the kathmandu region in the present study we have compiled available information from the print electronic media and various reports of damages and other effects caused by the event and interpreted them to obtain modified mercalli intensities mmi at over 175 locations spread over nepal and surrounding indian and tibet region we have also obtained a number of strong motion recordings from india and nepal seismic network and developed an empirical relationship between the mmi and peak ground acceleration pga peak ground velocity pgv we have used least square regression technique to derive the empirical relation between the mmi and ground motion parameters and compared them with the empirical relationships available for other regions of the world further seismic intensity information available for historical earthquakes which have occurred in the nepal himalaya along with the present intensity data has been utilized for developing an attenuation relationship for the studied region using two step regression analyses the derived attenuation relationship is useful for assessing damage of a potential future large earthquake earthquake scenario based planning purposes in the region

unsaturated soil mechanics in rainfall induced flow landslides abstract rainfall induced flow landslides in coarse grained soils pose significant threats to populations and structures due to their high velocities long travel distance and the absence of definite warning signs during the pre failure stage the triggering phase of these phenomena is frequently related to rainfall events which significantly reduce matric suction in the shallower soil layers in this paper the processes leading to the onset of such phenomena are illustrated and some observations on their modelling are briefly recalled the failure stage at different scales is then modelled with reference to a case study from southern italy which draws on high quality experimental data sets from extensive in situ and laboratory investigation

relationships between instrumental ground motion parameters and modified mercalli intensity in eastern north america a new relationship between modified mercalli intensity mmi and peak ground velocity pgv is developed by comparing instrumentally recorded and inferred historical pgv values to observed mmi for 18 significant earthquakes from eastern north america ena of moment magnitude 3 6 7 25 this pgv mmi relationship is implemented in shakemaps in ontario to estimate ground shaking intensity instrumentally derived mmi given instrumental recordings of pgv corresponding relationships for 5 damped pseudoacceleration psa at frequencies of 1 5 and 10 hz are also developed we compare the results with previous relationships between mmi and ground motion parameters developed for california by wald et al 1999a and atkinson and sonley 2000 we conclude that empirical relationships between mmi and ground motion are significantly different in eastern north america than in california thus such relationships should be assessed for each region where shakemaps are implemented manuscript received 24 october 2003

ground motion simulations of a major historical earthquake 1660 in the french pyrenees using recent moderate size earthquakes summary in regions where only small to moderate size events have been recorded it is important to be able to anticipate the effects of a large event by simulating the ground motion it may generate using the very good records of two small earthquakes that occurred in the central french pyrenees 2007 november 15 mw 3 6 and 2006 november 17 mw 4 5 we simulated the ground motions generated by a magnitude 6 1 earthquake equivalent to a historical event that struck the region in 1660 this major earthquake caused severe damage and reached a maximum macroseismic intensity of ix on the msk scale the simulation is based on the empirical green s function egf method which allows simulations in a broad frequency range and accounts for both propagation and site effects we first validated the method by reproducing the records of the mw 4 5 earthquake using the mw 3 6 earthquake as an egf a careful analysis of corner frequencies and spectral ratios revealed a clear directivity effect of the rupture process for the larger event mw 4 5 when this directivity is taken into account in the simulation a very good reproduction of the mw 4 5 ground motion parameters is obtained at all the stations we then used the records of the mw 3 6 earthquake as an egf for simulating the historical event at 11 stations we computed a large number of synthetic accelerograms that aim to account for the possible source variability of an mw 6 1 earthquake the comparison between the computed ground accelerations and those given by three different empirical ground motion prediction equations gmpes reveals that simulation is quite successful finally our simulation results are compared with intensity data of the 1660 event by use of three different ground motion intensity conversion equations gmices we found that the intensity levels predicted from ground motion simulations are systematically lower than the reported macroseismic intensities to explain this difference the hypothesis of a possible underestimation of the magnitude of the 1660 event is discussed

the role of seismic triggering in a deep seated mudstone landslide china historical reconstruction and mechanism analysis abstract deep seated mudstone landslides are widely distributed in northwest china the zhengjiamo landslide occurred in 734 ce near taijing tianshui region it was triggered by the main shock of the historical ms 7 0734 ce earthquake the earthquake also induced a wide range of landslides in this area with hundreds of fatalities and many houses destroyed by landslide debris based on a detailed field survey borehole data and mapping a detailed geological reconstruction of the slope was achieved and the geo mechanical features of the claystone involved in the landslide were obtained using the particle flow code to simulate the mechanism of the zhengjiamo landslide the features of the landslide dynamics were obtained using a 5 stage model during the landslide process the slip mass at the front and upper edges exhibited higher mobility than at the rear and bottom edges furthermore the contact bond strength of the sliding body gradually weakened the model indicates that the particle bond strength has a larger influence on the maximum runout distance and landslide debris morphology than the type of weak intercalated layers the slip mass presented a rotational slide pattern and remained on the slip plane throughout the sliding process finally the earthquake uplifted the slope toe which prevented the slip mass from gliding the modelled scenario provided a reasonably good fit to the actual topography verifying the modelling results after the historical earthquake with the clay minerals swelling and shrinking under rainfall and efflorescence conditions the structure of the soft rock changed contributing to the weakening of the sliding rock mass the landslide gradually crept and evolved to its current topography

real time generation of shakemaps in the southeastern alps abstract the aim of this study is the real time generation of shakemaps in the southeastern alps area the shakemap software has been adapted to the southeastern alps region and implemented to obtain a stable interface with the antelope acquisition system in order to extract the ground motion parameters from the waveforms and to generate shakemaps within 5 min of the earthquake occurrence to evaluate the influence of the station density synthetic seismograms are computed for the bovec northwest slovenia 2004 earthquake and various shakemaps are generated by varying the grid size of the simulated recording stations the results indicate that a dense and uniform spatial distribution of stations in the field is essential to produce accurate shakemaps and the present density of stations in central friuli is sufficient for a reliable estimate of the extent of the area of strongest shaking the related maps are generated in real time or quasi real time using the region specific ground motion predictive equations and empirical relations that predict the macroseismic intensity from the recorded ground motion the model is validated by comparison between observed data and shakemap results for both weak motions claut 2007 earthquake and strong motions bovec 1998 earthquake

probabilistic seismic hazard assessment for portugal the probabilistic seismic hazard of portugal is analyzed with a logic tree approach a critical part of the work was the review of the seismic catalog and the moment magnitude m estimation for historical earthquakes to produce a cat alog with a uniform magnitude scale the instrumental magnitudes were converted to m through empirical relations two seismic zonations were considered each in cluding two broad tectonic zones and a set of smaller seismicity zones catalog completeness and the b value for the truncated exponential recurrence model were calculated for the broad sources defined by tectonic criteria the smaller seismicity sources were used to calculate the a value using the fixed b value of the correspond ing tectonic zone this approach allows for a larger amount of data to estimate the most critical parameters by statistical methods without compromising the spatial detail of hazard results three published attenuation relations were used in the logic tree with weights that were based on tectonic considerations and on the comparison with macroseismic data converted to horizontal peak ground acceleration pga the ambraseys et al 1996 attenuation model for pga used by most previous hazard studies of the region seems to underestimate considerably the ground motion for mainland portugal a total of 96 hazard curves were calculated with seisrisk iii for each point of the map the resulting mean hazard map for 10 exceedence probability in 50 years displays pga values that range from 0 05g to 0 20g these mean values are slightly higher than in previous pga studies the hazard patterns obtained display a maximum related to intraplate onshore seismicity whereas pre vious studies using intensities highlighted the southwest offshore contribution fur ther work on ground motion attenuation in western iberia is necessary to improve the seismic hazard assessment

ground motion amplification at rock sites across canada as determined from the horizontal to vertical component ratio we determine the frequency dependent amplification inherent in hard rock sites across canada under the assumption that it can be estimated from the ratio of the horizontal to vertical h v components of ground motion the use of h v as an estimate of amplification was originally proposed by nakamura 1989 for microtremors and then generalized to earthquake ground motions by lermo and chavez garcia 1993 the h v method was applied to a fourier spectra database compiled from 424 earthquakes of magnitude greater than or equal to 2 recorded on 32 three component stations of the canadian national seismograph network cnsn all sited on rock shear wave velocity 1500 m sec in each case we analyzed the s wave portion of the seismograms including the direct s and other strong s phases such as lg the average amplification h v for rock sites does not vary significantly across the country it is weakly frequency dependent increasing from a factor near unity at 0 5 hz to a maximum in the range from 1 2 to 1 6 at 10 hz this amplification is consistent with what would be expected from a gradual decrease in shear wave velocity as the seismic waves approach the surface due to factors such as near surface weathering the interpretation of the h v ratio as a measure of site response is consistent with the general geological conditions of the recording sites in particular the 5 hz h v ratio can be correlated with local geological conditions the central canada sites have the lowest estimated site amplification this is consistent with competent hard rock site conditions with high near surface shear wave velocities there are two stations that show anomalous h v ratios that suggest significant local site effects these are edm near edmonton which may be influenced by topographic amplification and a61 a station in the charlevoix seismic zone

dynamics characteristic of red clay in a deep seated landslide northwest china an experiment study abstract the red mudstone sediments are widely encountered in earthquake region northwestern china which is vulnerable to the occurrence of landslides previous studies focused on rain induced shallow landslides some deep seated landslides in red clay with a gentle inclination are still not well understood a fatal landslide named as zhengjiamo landslide located in tianshui china was investigated the aim of this study was to study mechanism of shear surface development under earthquake using a series of cyclic triaxial tests the test results of the red clay from the zhengjiamo landslide revealed that the undrained shear strength and excess pore pressure increase with increasing confining stresses 3 and ocr it is also observed that those stress strain behaviors on the deviatoric stress axial strain and pore water pressure subsequent to the initial contractive response the saturated clay exhibited dilation upon continued shearing the dilated tendency of the clay becomes more prevalent with increasing confining stresses 3 and ocr during the dynamic response the reduction of shear strength of the red clay is substantially caused by the increasing number of cycles n under earthquakes the sliding zone may behave in a brittle ductile pattern

stability analysis of rock slopes subjected to seepage forces using the modified hoek brown criterion abstract the paper deals with the stability analysis of a water saturated rock slope by means of the kinematic approach of limit analysis theory particular emphasis is first given to the effects of pore water pressure on the global stability of geotechnical structures the rock strength properties being formulated in terms of effective stresses it is shown how the effect of seepage flow may be accounted for such an analysis through driving body forces derived from the gradient of excess pore pressure distribution is shown the latter is obtained as the solution to a hydraulic boundary value problem and then incorporated as external loading in the subsequent stability analysis the rock strength properties are modeled by a modified hoek brown failure criterion for which closed form expressions of the support functions have been derived in a previous paper the approach is then applied to investigate the stability of rock slopes computational results are given providing ample evidence of the destablizing effects induced by the seepage forces the influence of relevant geometrical strength and loading parameters is also discussed

heavy rainfall triggered loess mudstone landslide and subsequent debris flow in tianshui china abstract continuous and heavy precipitation triggered a large loess landslide at the southern dagou village of mapaoquan town tianshui city gansu province of china on july 21 2013 the landslide debris rapidly turned into a debris flow that was deposited in the ravine mouth with the volume of 1 9 105 m3 detailed field mapping three dimensional laser scanning aerial photograph interpretation and laboratory tests were carried out to study the formation and moving characteristics of the landslide and subsequent debris flow the results showed that 1 the peak flow velocity and peak discharge of the debris flow were estimated to be approximately 7 2 m s and 730 m3 s respectively the velocity had a tendency to first increase and then decrease from the head to entrance in the dagou gully 2 the analysis of rainfall conditions showed that the effective antecedent rainfall within 7 days and hourly rainfall intensity which triggered the slide debris flows was 239 mm and 20 mm h respectively compared with the critical rainfall in this area the effective antecedent rainfall was found to be more significant in triggering this event 3 the mean and effective particle sizes were approximately 0 73 1 3 mm and 0 036 0 087 mm respectively and had the same distribution along the gully as the velocity which confirmed the process of the variation in the flow velocity 4 the scale amplification was very obvious in the formation and moving process of the slide debris flows

ground motion to intensity conversion equations for iran new empirical relations between macroseismic intensity and ground motion parameters including peak ground acceleration and velocity are developed using strong ground motion data and modified mercalli intensity mmi information from earthquakes within iran plateau the strong motion data consists of 116 three component waveforms of 23 earthquakes with mw 5 1 7 3 occurred from 1977 to 2017 the intensity values for each ground motion record were assigned considering the location of accelerograph stations on the isoseismal maps simple predictive equations are obtained by fitting a linear model to the mean peak ground motion values applying least squares regression however visual inspection of residuals shows magnitude and distance dependency for this set of equations improved relationships between ground motion and intensity are derived by comprising magnitude and distance terms as predictive variables the refined ground motion to intensity conversion equations show smaller variability than simple linear equations in predicting mmi values both proposed models are compared with similar relationships in iran and other regions of the world the observed discrepancies in relationships may reflect the differences in input data especially the macroseismic intensity assignments as well as regional variability the proposed relations can be used for rapid hazard assessments and loss estimation in iran and surrounding regions