the viscosity of fine grained sediments a comparison of low to medium activity and high activity clays abstract viscosity is generally recognized as an indicator of landslide mobilization viscous behavior at relatively low high shear rates is an important predictor of the motion of slow fast moving landslides the viscosity in a modified bingham model at low and high shear rates was examined the viscous characteristics are primarily dependent on the physico chemical properties of the materials in question e g grain size mineralogy salinity in this context the viscous characteristics of low to medium activity and high activity clays bentonite with different salinities were compared empirical relationships exist between the liquidity index and the plastic viscosity regardless of the mineralogical composition this study also demonstrated a positive relationship between the liquidity index and the viscosity in a modified bingham model with n 1 the results showed that low to medium activity and high activity clays fall into a similar range for fine grained sediments mixed with salt water 30 g l however an effect of salinity was evident when using high activity clays mixed with fresh water modified bingham model is a useful and powerful tool for describing pre and post yield viscosity in engineering practice by correlating the geotechnical and rheological properties of fine grained sediments index properties can help to estimate the appropriate values for the rheological parameters of these soils

automatic approach for increasing the location accuracy of slow moving landslide endogenous seismicity the apoloc method seismological observations offer valuable insights on the stress strain states the physical mechanisms and the possible precursory signs of activation of various earth surface processes i e volcanoes glaciers and landslides comprehensive catalogues of the endogenous landslide seismicity that is corresponding to seismic sources generated by the unstable slope from either mechanical or hydrological origins should include the typology and an estimate of the source parameters location magnitude of the event these advanced catalogues constitute a strong basis to better describe the slope deformation and its time evolution and better understand the controlling factors because the number of seismic events in landslide catalogues is generally large automatic approaches must be considered for defining both the typology and the location of the sources we propose here a new location approach called automatic picking optimization and location method apoloc for locating landslide endogenous seismic sources from seismological arrays located at close distance the approach is based on the automatic picking of the p waves arrivals by optimizing the intertrace correlations the method is tested on calibration shots realized at the super sauze landslide southeast french alps and compared to other location approaches by using a realistic velocity model obtained from a seismic tomography campaign apoloc reduces the epicentre errors to 23 m on average compared to ca 40 m for the other approaches apoloc is then applied for documenting the endogenous seismicity i e slopequakes and rockfalls at the landslide

finite fault bayesian inversion of teleseismic body waves abstract inverting geophysical data has provided fundamental information about the behavior of earthquake rupture however inferring kinematic source model parameters for finite fault ruptures is an intrinsically underdetermined problem the problem of nonuniqueness because we are restricted to finite noisy observations although many studies use least squares techniques to make the finite fault problem tractable these methods generally lack the ability to apply non gaussian error analysis and the imposition of nonlinear constraints however the bayesian approach can be employed to find a gaussian or non gaussian distribution of all probable model parameters while utilizing nonlinear constraints we present case studies to quantify the resolving power and associated uncertainties using only teleseismic body waves in a bayesian framework to infer the slip history for a synthetic case and two earthquakes the 2011 m w 7 1 van east turkey earthquake and the 2010 m w 7 2 el mayor cucapah baja california earthquake in implementing the bayesian method we further present two distinct solutions to investigate the uncertainties by performing the inversion with and without velocity structure perturbations we find that the posterior ensemble becomes broader when including velocity structure variability and introduces a spatial smearing of slip using the bayesian framework solely on teleseismic body waves we find rake is poorly constrained by the observations and rise time is poorly resolved when slip amplitude is low electronic supplement figures of histograms of slip and rise time waveform comparisons between data and synthetics and slip velocity along the fault plane for a synthetic case as well as for the 2011 m w 7 1 van east turkey earthquake and the 2010 m w 7 2 el mayor cucapah baja california earthquake

determination of the location of faulting beneath kobe during the 1995 hyogo ken nanbu japan earthquake from near source particle motion we constrained the location of faulting beneath kobe during the 1995 hyogo ken nanbu kobe japan earthquake by investigating the particle motion of strong motion records from sites close to the causative fault the intersection of the earth s surface and the extension of buried fault plane is consistent with known active fault lines but not with the severely damaged zone the intersection line also agrees with geodetic data

kinematic inversion of physically plausible earthquake source models obtained from dynamic rupture simulations one approach to investigate earthquake source processes is to produce kinematic source models from inversion of seismic records and geodetic data the setup of the inversion requires a variety of assumptions and constraints to restrict the range of possible models here we evaluate to what extent physically plausible earth quake scenarios are reliably restituted in spite of these restrictions we study which characteristics of ruptures such as rupture velocity slip distribution stress drop rise time and slip function can be reliably determined from the inversion of near field seismic and geodetic data using spontaneous dynamic rupture simulations we gen erate five earthquake scenarios each of which has different characteristics of the source process then we conduct a blind test by modeling the synthetic near source data using a standard inversion scheme that optimizes the fit to the observations while searching for solutions with minimum roughness the inversion procedure assumes a rupture front propagating away from the hypocenter with variable rupture velocity and a simple cosine slip time function our results show that overall slip distribution and stress drop are reasonably well determined even for input models with relatively complex histories such as a subshear rupture transitioning to supershear speeds depth averaged rupture velocities are also reasonably well resolved although their estimate progressively deteriorates away from the hypocenter the local rise time and slip function are not well resolved but there is some sensitivity to the rupture pulse width which can be used to differentiate between pulse like and crack like ruptures our test for understanding the inaccuracies in green s functions shows that random 3d perturbations of 5 standard deviation do not lead to significant degradation of the estimation of earthquake source parameters as remedies to the current limitations we propose smoothing slip function parameters and using more complicated inversion schemes only if data necessitates them online material figures showing snapshots of forward and inverse modeling of rupture l curves slip models and waveform fits

rupture model of the 1999 duzce turkey earthquake deduced from high and low frequency strong motion data 1 we investigated the rupture process of the 1999 duzce earthquake by applying the multi time window linear waveform inversion method to low frequency ground motions 0 5 hz in the near source area then we performed theforwardmodellingofhigherfrequencyground motions 0 3 10 0 hz by the empirical green s function egf method to image the strong motion generation area smga we also examined the source model to check whether the supershear phenomenon occurred inside the asperities or not slip distribution model from the inversion suggests 2 asperities the maximum slip is obtained as 5 m near the hypocenter the high first time window front propagation velocity ftwfpv and consequently high apparent rupture velocity found from the investigation of rupture progression indicated that eastern propagation partially showed supershear behaviour the egf simulation which identifies an average rupture velocity vr in smga supports this finding index terms 7212 seismology earthquake ground motions and engineering 7215 seismology earthquake parameters 7223 seismology seismic hazard assessment and prediction citation birgoren g h sekiguchi and k irikura 2004 rupture model of the 1999 duzce turkey earthquake deduced from high and low frequency strong motion data geophys res lett 31 l05610 doi 10 1029 2003gl019194

the effect of calcium ions in pore water on the residual shear strength of kaolinite and sodium montmorillonite this paper reviews the literature concerning the effects of pore water chemistry on residual shear strength it presents the results of index limit and residual shear strength testing undertaken on kaolinite and sodium montmorillonite using concentrations of calcium chloride similar to the calcium levels measured in groundwaters obtained from landslipped calcareous mudrock of the fuller s earth formation the residual shear strength of the sodium montmorillonite increased markedly for the sample treated and tested with 80 mg 1 cat compared with that tested with deionized water greater concentra tions of ca2 resulted in only a marginal further increase in the residual shear strength these changes were also reflected in the interpreted parameters or and c the liquid limit of the montmorillonite decreased dramatically when the samples were treated with 80 mg 1 ca2 and this effect persisted and or was slightly enhanced when the concentration of ca2 was increased the residual shear strength

some characteristics of the stress field of the 1995 hyogo ken nanbu kobe earthquake we investigate the characteristics of the stress field associated with the 1995 hyogo ken nanbu kobe earthquake we use for the study a tomographic model of the fault slip inferred from the numerous near field recordings and we calculate the space and time evolution of shear stress on the fault during the earthquake we show that the spatial distribution of stress drop is very heterogeneous the apparent strength of the fault at the onset of the earthquake is low of the order of 1 mpa or less which indicates that the pre earthquake tectonic shear stress was close to the static friction over most of the fault at many locations the stress drop rotates significantly during sliding as was originally proposed by spudich 1992 we use the requirement of colinearity between the directions of maximum shear stress and instantaneous slip to determine the initial stress on the fault at the onset of the earthquake the pre earthquake tectonic stress varies greatly over the fault and ranges from about 1 to 10 mpa average values of the initial and final shear stresses over the fault are 3 3 and 1 6 mpa respectively indicating that about half of the pre earthquake tectonic stress was released during the earthquake there is a relatively strong correlation between the initial and final stress distributions which suggests that intrinsic fault properties not modified by the earthquake control the spatial distribution of tectonic stress over the fault we show that on average over the fault the dynamic friction coefficient is equal to about 40 of the static friction coefficient diagrams depicting the evolution of shear stress as a function of slip are consistent with slip weakening behavior but their interpretation is questionable because of the poor resolution of the data at high frequency and because of the constraints imposed on the model to perform the inversion

slope stability and groundwater flow system in the area of lizzano in belvedere northern apennines italy abstract in northern apennines landslides involving weak rocks such as clay shales are widespread and often cause damage to public infrastructure and private properties these landslides mostly classifiable as earthflows generally exhibit continuous slow movements with temporary increases of velocity controlled both by groundwater and rainfall regime although the relationship between precipitation groundwater flow and displacement rate is evident its quantitative description remains problematic we use piezometric and slope movement continuous monitoring to investigate the groundwater flow system in the vicinity of the contact between clay shales and overlying more permeable units where the village of lizzano in belvedere is located our aim is to describe the groundwater flow and its relation to slope deformation in order to simulate the effect of possible drainage measures both on piezometric levels and expected displacement rates timing and magnitude of piezometric responses at different depths are related to observed deformations and used to calibrate a transient 3d groundwater flow model groundwater modeling validates the conceptual hydrogeological scheme and allows simulation of the impact of surface and deep drainages on piezometric levels results indicate that horizontal drains are more effective than infiltration reduction measures both in terms of drawdown and time effectiveness of action simulated hydraulic heads are then used to produce a probabilistic prediction of the expected displacement rates by means of an empirical method in the case of lizzano in belvedere according to our results the lowering of hydraulic heads operated by horizontal drains can reduce the velocity of slope movements from centimeters per year to millimeters per year

source rupture process of the 2007 noto hanto japan earthquake estimated by the joint inversion of strong motion and gps data abstract the source rupture process during the 2007 noto hanto earthquake which was a reverse faulting event located near the western coast of the noto peninsula in central japan was estimated by the kinematic linear waveform inversion method the waveform inversion was conducted by jointly using velocity waveforms recorded at 12 near source strong motion stations and static horizontal displacements recorded at 19 global positioning system gps stations in order to implement reliable green s functions into the inversion a one dimensional underground velocity structure for each individual strong motion station was modeled through waveform modeling of an aftershock the waveform inversion result showed the following image of the source rupture process the larger slip concentrated in the vicinity of the hypocenter and it extended to the shallow portion of the source fault with a maximum slip of 5 1 m the whole source process was characterized by the total seismic moment of 1 57 10 19 n m m w 6 7 with the rupture duration of approximately 9 s the obtained source model explained observed strong ground motions and gps measured static horizontal displacements well the slip distribution correlated well with the spatiotemporal aftershock distribution and the northeast end of the rupture was blocked by the resistive structure in the crust from these facts the 2007 noto hanto earthquake could be concluded as reactivation of preexisting seafloor active faults f14 and f15 which were reported by the previous geophysical and geological surveys off the shore of the noto peninsula

deglacial changes in ocean circulation from an extended radiocarbon calibration temporal variations in the atmospheric concentration of radiocarbon sometimes result in radiocarbon based age estimates of biogenic material that do not agree with true calendar age this problem is particularly severe beyond the limit of the high resolution radiocarbon calibration based on tree ring data which stretches back only to1 2 about 11 8 kyr before present bp near the termination of the younger dryas cold period if a wide range of palaeoclimate records are to be exploited for better understanding the rates and patterns of environmental change during the last deglaciation extending the well calibrated radiocarbon timescale back further in time is crucial several studies attempting such an extension using uranium thorium dated corals3 4 5 and laminae counts in varved sediments6 7 8 9 show conflicting results here we use radiocarbon data from varved sediments in the cariaco basin in the southern caribbean sea to construct an accurate and continuous radiocarbon calibration for the period 9 to 14 5 kyr bp nearly 3 000 years beyond the tree ring based calibration a simple model compared to the calculated atmospheric radiocarbon concentration and palaeoclimate data from the same sediment core suggests that north atlantic deep water formation shut down during the younger dryas period but was gradually replaced by an alternative mode of convection possibly via the formation of north atlantic intermediate water

geophysical investigation of a large landslide in glaciolacustrine clays in the trieves area french alps abstract slope movements in clay deposits are spread all over the world and result from complex deformation processes including internal strains in the landslide body and slipping along rupture surfaces such mass movements are likely to generate changes in the geophysical parameters characterizing the ground which can be used to map the landslide body in the last decade geophysical techniques have been increasingly used for landslide investigation purposes however the success of any geophysical technique is overall controlled by the existence of a geophysical contrast differentiating the body to be mapped for landslides affecting thick clay materials from soft clay to shale or marl electrical and seismic techniques have been mainly applied in the past in this study we attempt to physically characterize the deformation within a large slide avignonet affecting laminated clays which were deposited in a glacially dammed lake during the wurm period clay deposits which cover an area of 300 km2 south of grenoble french alps and have a maximum thickness of 200 m overlay compact alluvial layers and marly limestone of mesozoic age piezometric data at avignonet show that the water table is very shallow implying that the slide developed in saturated clay several seismic and electrical profiles were performed in order to tentatively correlate the variations of p wave vp velocity s wave velocity vs and electrical resistivity with geotechnical data and morphological observations in such saturated and fine material it turned out that only the s wave velocity exhibits significant variations with the displacement rates and the morphological features vs values at shallow depth were found to be inversely correlated with displacement rates measured by gps with a division by at least a factor of 2 between the zones unaffected and strongly deformed by the landslide these results suggest that vs mapping could provide valuable information on the deformation state of the clay material and that the evolution of vs with time could be used as an indicator for characterizing the landslide activity in the subsurface including the evolution into a flow

paleotopographic control of landslides in lacustrine deposits trieves plateau french western alps paleotopography in quaternary sedimentary environments can be an important factor that controls landslide movement this study investigates the relation between paleotopography and landslide activity in two adjacent landslides in glaciolacustrine sediments located in the trieves area french western alps although both are in slopes underlain by the same lacustrine deposits the avignonet and harmaliere landslides exhibit major differences in morphology and displacement rates through a combination of geological mapping airborne light detection and ranging lidar data aerial photographs global positioning system gps and seismic noise measurements a three dimensional impression was made of both landslides the analysis reveals that the difference in kinematics between the two mass movements can be traced back to at least 50 years ago the results show that the harmaliere slide which failed catastrophically in 1981 is still much more active than the avignonet landslide the fear was that the avignonet landslide might develop in a similar catastrophic manner threatening a number of houses constructed on the landslide a geophysical survey based on ambient noise measurements allowed us to map the base of the lacustrine clays and the results indicate the presence of a n s ridge of hard sediments jurassic bedrock and or compact alluvial layers on the eastern side of the avignonet landslide this ridge disappears when approaching the harmaliere landslide and makes a place to what can be interpreted as a nw se oriented paleovalley of the river drac we proposed that the ridge acts as a buttress that could mechanically prevent the avignonet landslide from evolving as fast as the harmaliere furthermore the nw se paleovalley located under the harmaliere landslide corresponds to the motion direction of the slide therefore the different behaviour of the two landslides is partly controlled by the paleotopographic setting of lake trieves during the last glacial maximum extension these results suggest a major influence of the bedrock paleotopography on the kinematics of the landslides

deep learning of aftershock patterns following large earthquakes aftershocks are a response to changes in stress generated by large earthquakes and represent the most common observations of the triggering of earthquakes the maximum magnitude of aftershocks and their temporal decay are well described by empirical laws such as bath s law1 and omori s law2 but explaining and forecasting the spatial distribution of aftershocks is more difficult coulomb failure stress change3 is perhaps the most widely used criterion to explain the spatial distributions of aftershocks4 8 but its applicability has been disputed9 11 here we use a deep learning approach to identify a static stress based criterion that forecasts aftershock locations without prior assumptions about fault orientation we show that a neural network trained on more than 131 000 mainshock aftershock pairs can predict the locations of aftershocks in an independent test dataset of more than 30 000 mainshock aftershock pairs more accurately area under curve of 0 849 than can classic coulomb failure stress change area under curve of 0 583 we find that the learned aftershock pattern is physically interpretable the maximum change in shear stress the von mises yield criterion a scaled version of the second invariant of the deviatoric stress change tensor and the sum of the absolute values of the independent components of the stress change tensor each explain more than 98 per cent of the variance in the neural network prediction this machine learning driven insight provides improved forecasts of aftershock locations and identifies physical quantities that may control earthquake triggering during the most active part of the seismic cycle neural networks trained on data from about 130 000 aftershocks from around 100 large earthquakes improve predictions of the spatial distribution of aftershocks and suggest physical quantities that may control earthquake triggering

clay slides in the malselv valley northern norway characteristics occurrence and triggering mechanisms abstract the distribution of a large number of clay slides in the malselv valley northern norway is analysed and put into context with the stratigraphic organization of the valley fill sediments about 32 of the landslides larger than 104 m3 occur close to the valley margins where mud is either exposed or at shallow depth about 57 of the landslides occur mid valley where relatively thin arcuate shaped bottleneck landslide scars ranging from c 104 to 107 m3 in size is the dominant morphological signature of the slides typical for quick clay slides or earth flows involving fluid mud their most common triggering mechanism is probably erosion at the toe slopes by the river malselv or its tributaries river erosion close to the valley margin where glaciomarine and marine sediments are present seems to give the most severe slides the overall valley fill organization controls the distribution of clay slides which may apply to other fjord valleys having similar sediment distribution

specific distribution of ground motion during the 1995 kobe earthquake and its generation mechanism the 1995 kobe hyogo ken nanbu earthquake mw 6 9 is the most damaging in the recent japanese history and its notable feature is that most of the damage and over 6000 casualties occurred in a narrow belt through kobe and neighboring cities the kobe hanshin area usually a fault rupture propagation generates strong ground motions along the direction of propagation and this directivity effect should be significant above the source faults and beyond its leading end however the damage zone of the kobe earthquake is migrated noticeably from the fault trace into the center of kobe city three dimensional 3 d simulations of ground motion in kobe show that this migration is due to the strong amplification and ray bending in the sedimentary basin below the city in cooperation with the multipathing effects at a basin bedrock boundary

positive feedback and momentum growth during debris flow entrainment of wet bed sediment debris flows typically occur when intense rainfall or snowmelt triggers landslides or extensive erosion on steep debris mantled slopes the flows can then grow dramatically in size and speed as they entrain material from their beds and banks but the mechanism of this growth is unclear indeed momentum conservation implies that entrainment of static material should retard the motion of the flows if friction remains unchanged here we use data from large scale experiments to assess the entrainment of bed material by debris flows we find that entrainment is accompanied by increased flow momentum and speed only if large positive pore pressures develop in wet bed sediments as the sediments are overridden by debris flows the increased pore pressure facilitates progressive scour of the bed reduces basal friction and instigates positive feedback that causes flow speed mass and momentum to increase if dryer bed sediment is entrained however the feedback becomes negative and flow momentum declines we infer that analogous feedbacks could operate in other types of gravity driven mass flow that interact with erodible beds the mechanisms by which debris flows acquire mass and momentum as they entrain material are unclear large scale experiments suggest that the pore pressure of wet bed sediment increases as the flow moves over the bed leading to reduced friction and progressive scouring of the base

seismic and geodetic signatures of fault slip at the slumgullion landslide natural laboratory 1 we tested the hypothesis that the slumgullion landslide is a useful natural laboratory for observing fault slip specifically that slip along its basal surface and side bounding strike slip faults occurs with comparable richness of aseismic and seismic modes as along crustal and plate scale boundaries our study provides new constraints on models governing landslide motion we monitored landslide deformation with temporary deployments of a 29 element prism array surveyed by a robotic theodolite and an 88 station seismic network that complemented permanent extensometers and environmental instrumentation aseismic deformation observations show that large blocks of the landslide move steadily at approximately centimeters per day possibly punctuated by variations of a few millimeters while localized transient slip episodes of blocks less than a few tens of meters across occur frequently we recorded a rich variety of seismic signals nearly all of which originated outside the monitoring network boundaries or from the side bounding strike slip faults the landslide basal surface beneath our seismic network likely slipped almost completely aseismically our results provide independent corroboration of previous inferences that dilatant strengthening along sections of the side bounding strike slip faults controls the overall landslide motion acting as seismically radiating brakes that limit acceleration of the aseismically slipping basal surface dilatant strengthening has also been invoked in recent models of transient slip and tremor sources along crustal and plate scale faults suggesting that the landslide may indeed be a useful natural laboratory for testing predictions of specific mechanisms that control fault slip at all scales

a review of the discrete wavenumber method we present a review of the discrete wavenumber dwn method the method introduced by bouchon and art 1977 allows the simple and accurate calculation of the complete green s functions for many problems in elastodynamics

shear wave velocity as an indicator for rheological changes in clay materials lessons from laboratory experiments 1 clay rich geological formations are responsible for many landslides the dynamics of which are still poorly understood and intensely debated analysis of landslide motion shows that slow clayey slope movements can suddenly accelerate and fluidize as a result of sudden loading or heavy rainfall this solid fluid transition which involves disorganization of the particle network is accompanied by a loss in rigidity that could potentially be monitored by s wave velocity vs variations to investigate this hypothesis two types of laboratory experiments were performed on clay samples originating from an area affected by numerous landslides trieves french alps first creep and oscillatory rheometric tests revealed the thixotropic behavior of the clay with a highly pronounced viscosity bifurcation at a critical stress c in relation with this reduction in apparent viscosity a significant drop in vs is also observed over c second at zero stress acoustic surface wave propagation experiments showed a rapid linear vs decrease with the gravimetric water content w in the plastic domain and a much lower decay in the liquid domain the geotechnically defined liquid limit then appears as a break in thevs wcurve for water contents in the liquid domain in particular both experiments gave consistent results these laboratory results demonstrate that rheological changes in clay can be revealed through vs variations offering the possibility of monitoring solid to fluid transitions in the field

rupture process of the 2008 northern iwate intraslab earthquake derived from strong motion records the rupture process of the 2008 northern iwate japan earthquake m 6 8 has been derived from strong motion records obtained at 22 regional stations by the multi time window linear waveform inversion method this event occurred in the lower plane of the double seismic zone in the subducting pacific slab at a depth of 115 km a preliminary inversion analysis revealed that a single planar fault plane model was insufficient to satisfactorily explain waveforms at stations in a specific azimuth a two segment fault plane model was then assumed in which the fault model consisted of the northern and southern segments with a 44 difference in strike direction which respectively followed the source mechanisms determined by moment tensor inversion and p wave polarity analysis the source model derived from the two segment fault plane model greatly improved the waveform fitting at stations for which there was a large discrepancy in the preliminary analysis with the single planar fault plane model the largest asperity was located on the northern segment which generated the main phase observed at most stations the amount of slip on the southern segment was smaller but contributed significantly to the first of the two pulses observed at the stations to the south of the source area the stress drop of the largest asperity for this intraslab earthquake was large in comparison with that predicted from empirical relations obtained for crustal earthquakes which may be one of the causes of the relatively large accelerations recorded during this earthquake

source process of the 1995 kobe earthquake determination of spatio temporal slip distribution by bayesian modeling the kobe hyogo ken nanbu earthquake ms 6 8 occurred on 16 january 1995 in western japan bringing about a tremendous disaster we constructed its source model by determining a spatio temporal slip distribution using strong motion seismograms recorded at a number of stations near the hypocenter the source area is expressed using both a rough and a detailed subfault discretization system and a source time function expanded with a finite number of basis functions at each subfault is determined to perform stable inversions with many parameters we construct a bayesian model with unknown hyperparameters incorporating prior constraints on the smoothness of spatio temporal slip distribution in the observation equation using akaike s bayesian information criterion abic the optimal set of hyperparameters are objectively determined from observed data which enables us to uniquely determine a spatio temporal slip distribution after rough analysis in which the actual rupture area is estimated as 45 20 km we carried out a detailed analysis with a finer subfault discretization system 5 5 km in our final source model most of the slip exists beneath awaji island and the rupture below the city of kobe where the damage was most serious is relatively smaller the large slips of about 2 m in the shallowest subfaults located southwest of the hypocenter correspond to the surface offsets observed along the nojima fault the overall focal mechanism of the source is right lateral strike slip with a small thrust component while total seismic moment is 2 0 1019 nm the source time functions at shallow subfaults show a longer duration than those at deeper ones being hypothesized to represent a possible combined effect of low rupture propagation velocity and varying friction behavior in shallow regions of crust

fault geometry at the rupture termination of the 1995 hyogo ken nanbu earthquake the source geometry and slip distribution at rupture termination of the 1995 hyogo ken nanbu earthquake were investigated using waveform inversion on the assumption of fault branching in the northeastern part of the rupture model possible branching of the okamoto fault is suggested both by the static displacement distribution and damage extension east of kobe nishinomiya area to exclude data contaminated by the basin edge diffracted wave in the waveform inversion process we examined the spatio temporal variation of its influence and from a comparison with a flat model we determined windows appropriate for the data three subevents were identified as was reported in previous works the largest was in the shallow part on the awaji side whereas the smaller two occurred at great depths 7km on the kobe side we found a smaller subevent in the deep part of the branch total variance reduction was larger and the abic value was smaller when we assumed the branch than when we did not which shows the superiority of the branching fault model resolution checks showed that the slips on proposed branched portions are physical and not caused by random data noise or systematic errors in green s func tions that arise from misestimation of velocity structures calculation of the relative static displacement between two leveling observation stations near the branching fault also showed the greater utility of the branching fault model the effect of slip on the branched fault has been shown in near source ground motion simulation using the 3d finite difference method iwata et al 1999 the characteristic distribution of ground motion in the near source region indicated by the damage distribution is well reproduced by the modeling of both the source process and wave propagation in the realistic 3d velocity structure slip on the branched fault affected the ground motion in eastern kobe nada and higashi nada wards ashiya and nishinomiya cities but its contribution is not dominant even in those regions about 30 to 50 maximum velocity in the frequency range of 0 1 to 1 0 hz we conclude that branching rupture of the okamoto fault during the hyogo ken nanbu earthquake is the preferable interpretation on the source process of this earth quake this supports the idea of a geometrical barrier suggested by geological ob servations

a new nonlinear finite fault inversion with three dimensional green s functions application to the 1989 loma prieta california earthquake 1 we present a new procedure to invert for kinematic source parameters on a finite fault on the basis of the reciprocity relation of the green s functions we use a newly developed fourth order viscoelastic finite difference algorithm to calculate three dimensional 3 d green s functions actually the tractions on the fault we invert the data for the unknown source parameters at the nodes or corners of the subfaults the source parameters within a subfault area are allowed to vary this variation is calculated through bilinear interpolation of the four nodal quantities we have developed a global nonlinear inversion algorithm that is based on simulated annealing methods to solve efficiently for the nodal parameters we apply this method to the 1989 loma prieta california m 6 9 earthquake for both a 1 d and 3 d velocity structure we show 1 the bilinear interpolation technique reduces the dependence of inversion results on the subfault size by naturally including the effects of nearby subfaults 2 while the number of synthetic seismograms that must be computed is greatly increased by the bilinear interpolation the structure of the inversion method minimizes the actual numbers of computations 3 as expected complexity in the velocity structure is mapped into the source parameters that describe the rupture process there are significant differences between faulting models derived from 1 d and 3 d structural models

a comparison between short term co seismic and long term one year slip for the landers earthquake measurements from strong motion and sar interferometry the long term relative displacements in the region of the landers earthquake were measured over a time interval of about one year using sar interferometry we have also evaluated the co seismic slip distribution through a strong motion inversion cotton and campillo 1995 and these results are used to compute the static displacement field associated with the co seismic slip we show that the synthetic static and the interferometry measurements are in very good agreement to give an evaluation of the magnitude of the pre and post seismic slip a residual interferogram between data and synthetic co seismic slip has been computed a simple analysis of the residual displacements gives a limiting value of the amplitude of pre and post seismic slip integrated over a period of one year and suggests that it is on the order of a few decimeters

synthetic aperture radar interferogram of the 1995 kobe earthquake and its geodetic inversion crustal deformation from the mw 6 9 january 17 jst 1995 kobe japan earthquake was detected by synthetic aperture radar interferometry sar more than four fringes with ellipsoidal shape were observed surrounding the nojima fault on northern awaji island suggesting a shortening in the range of more than 11 75 4 cm on the east side of this fault the sar sensor shows ellipsoidal fringes with an uplift zone in the rokko mountain range and sharp subsidence around the kobe area in addition to sar interferometry leveling and gps surveys were conducted by the geographical survey institute of japan gsi the permanent gps observation sites of the gsi monitored ground displacements from this earthquake with daily updates based on these geodetic data we estimated the faulting mechanism of the earthquake the analytical procedure was an iterative linearized least squares method a multi fault system consisting of six subfaults was constructed the locations of the estimated model faults were close to those of the active faults in this area running from the nojima fault on awaji island to the rokko faults in the kobe area with a change in strike angle near the ohtsuki fault in the kobe area the slip vectors of the nojima fault on awaji island had a large component of reverse dip slip of about 2 m and strike slip of about 2 m in the kobe area the amount of slip ranged from 0 3 to 1 2 m and was small compared with the slip on the nojima fault the results of these slip vectors agreed well with the results of other seismic geodetic and field studies

shear wave velocity drop prior to clayey mass movement in laboratory flume experiments abstract clay slopes are susceptible to suddenly liquefy into rapidly accelerating landslides thereby threatening people and facilities in mountainous areas because the shear wave velocity v s characterizes the medium stiffness this parameter can potentially be used to investigate the rheological behavior of clay materials before and during the solid to fluid transition associated to such landslide failures previous rheometrical studies performed on clay samples coming from trieves landslides french alps have established that this material behaves as a yield stress fluid with a marked viscosity bifurcation when the applied stress reaches a critical level the viscosity decreases abruptly along with v s which tends to zero in the fully fluidized material here we monitor the rayleigh wave velocity v r variations in a saturated clay layer placed in a flume and progressively brought to failure by tilting the device experiments performed on clay samples with different water contents show a significant relative drop in v r values and hence in v s before the onset of the mass movement additional rheometrical analyses point out that this precursory drop in v s is presumably due to a complex transient rheological response of the clay these new results confirm that v s variations constitute a good indicator for monitoring clay slope stability

geotechnical problems caused by glaciolacustrine clays in the french alps abstract after more than 10 years of observations and monitoring of several landslides in glaciolacustrine clays in the french alps the authors give an account of the physical and mechanical characteristics of these formations the physical and geomechanical properties of the clays are analysed in relation to the main types of instability observed on the natural slopes of the area studied the low plasticity indexes of these clays explain the rapid transformation of the clays into a liquid state leading to innummerable surface flows the clays show a strong anisotropy at peak strength conditions that disappears at residual strength c o o 16 18 natural slopes become unstable if the gradient exceeds 8 10 these types of movement can be distinguished at three different depths 0 5 m 5 10 m and greater than 10 m the displacement rates vary from 1 cm yr for the deep seated slides to as much as 1 m yr for the surficial slides displacement rates in these slides are limited by the viscous properties of the laminated clays however extreme rainfall may cause catastrophic failure in conclusion some recommendations are given from an engineering point of view

speculations on the geometry of the initiation and termination processes of earthquake rupture and its relation to morphology and geological structure earthquake initiation and termination processes are commonly described in terms of barriers and asperities barriers fall into two classes geometric barriers are associated with places where the orientation of a failure surface changes and relaxation barriers where stress is low because aseismic creep processes outpace tectonic loading geometric barriers fall into conservative and nonconservative subgroups according to whether finite fault motion can proceed without the creation of new structures or whether it demands the creation of new faulting or void space the multiple faulting or fragmentation associated with some nonconservative barriers can disrupt fault planes and form asperities by means of selected examples it is shown that a description in terms of these barriers can help one to visualise the processes of earthquake rupture and its relation to the geological environment

geologic evidence for multiple slip weakening mechanisms during seismic slip in crystalline rock we examine exhumed seismogenic faults to investigate the mechanisms that may have achieved dynamic fault weakening during ancient ruptures field and microscope observations imply more than one weakening mechanism must have been active during slip events on the faults pseudotachylytes that are continuous over the scale of field exposures are indicative of melt lubrication a fault breccia crosscutting earlier formed cataclasites was mobilized during faulting and possibly represents a pressurized fault rock that resulted from thermal pressurization or elastohydrodynamic lubrication in some faults pseudotachylytes are developed in patches several meters long cataclasites in which there is no evidence for melting are present immediately along strike from the pseudotachylyte patches by considering the energy required for melting we show that the pseudotachylytes must have formed during ruptures larger than the patches implying that the cataclasites also accommodated seismic slip the distribution of fault rock types shows that the frictional response to slip during a single event was spatially variable reworked pseudotachylytes also indicate that coseismic processes change over time at a point on a fault these observations emphasize that macroscopic dynamic fault weakening is a function of multiple coeval processes at microscales to mesoscales detailed observations of the discontinuous pseudotachylytes show that slip zone thickness is the critical parameter that controls active coseismic processes the frictional response of a fault to slip is therefore dependent on the internal structure of faults given the along strike heterogeneity of most mapped fault zones the coexistence of multiple slip weakening mechanisms in a single earthquake will be common

grain size segregation and levee formation in geophysical mass flows 1 data from large scale debris flow experiments are combined with modeling of particle size segregation to explain the formation of lateral levees enriched in coarse grains the experimental flows consisted of 10 m3 of water saturated sand and gravel which traveled 80 m down a steeply inclined flume before forming an elongated leveed deposit 10 m long on a nearly horizontal runout surface we measured the surface velocity field and observed the sequence of deposition by seeding tracers onto the flow surface and tracking them in video footage levees formed by progressive downslope accretion approximately 3 5 m behind the flow front which advanced steadily at 2 m s 1 during most of the runout segregation was measured by placing 600 coarse tracer pebbles on the bed which when entrained into the flow segregated upwards at 6 7 5 cm s 1 when excavated from the deposit these were distributed in a horseshoe shaped pattern that became increasingly elevated closer to the deposit termination although there was clear evidence for inverse grading during the flow transect sampling revealed that the resulting leveed deposit was strongly graded laterally with only weak vertical grading we construct an empirical three dimensional velocity field resembling the experimental observations and use this with a particle size segregation model to predict the segregation and transport of material through the flow we infer that coarse material segregates to the flow surface and is transported to the flow front by shear within the flow head coarse material is overridden then recirculates in spiral trajectories due to size segregation before being advected to the flow edges and deposited to form coarse particle enriched levees

waveform inversion using abic for the rupture process of the 1983 hindu kush earthquake abstract an inversion method was developed to infer earthquake rupture process from far field velocity waveforms we devise a source model that has variable slip and variable rupture velocity the fault plane is divided into many subfaults slip amplitude is assumed to be dependent on the subfaults and slip velocity at a point is assumed to be a triangle function of time rupture time is expressed by an interpolation equation using the rupture times at the corners of the subfaults the slip distribution and the rupture front motion are estimated by constrained least squares inversion we incorporate smoothing constraints on slip distribution and on rupture propagation into the observed data the degree of the constraints is controlled by hyperparameters the optimal values of the hyperparameters are determined by minimizing akaike s bayesian information criterion abic under the assumption of abic we can obtain a unique solution with reasonable resolution we apply this inversion method to the hindu kush earthquake of 30 december 1983 with a depth of 212 km we found that the rupture process of this earthquake was composed of two subevents the first subevent occurs near the initiation point of the rupture the centre of the second subevent region is approximately 20 km to the west of the first subevent the released moment of the second subevent is about seven times larger than that of the first subevent

inversion of strong ground motion and teleseismic waveform data for the fault rupture history of the 1979 imperial valley california earthquake a least squares point by point inversion of strong ground motion and teleseismic body waves is used to infer the fault rupture history of the 1979 imperial valley california earthquake the imperial fault is represented by a plane embedded in a half space where the elastic properties vary with depth the inversion yields both the spatial and temporal variations in dislocation on the fault plane for both right lateral strike slip and normal dip slip components of motion inversions are run for different fault dips and for both constant and variable rupture velocity models effects of different data sets are also investigated inversions are compared which use the strong ground motions alone the teleseismic body waves alone and simultaneously the strong ground motion and teleseismic records the inversions are stabilized by adding both smoothing and positivity constraints the moment is estimated to be 5 0 10 25 dyne cm and the fault dip 90 5 dislocation in the hypocentral region south of the united states mexican border is relatively small and almost dies out near the border dislocation then increases sharply north of the border to a maximum of about 2 m under interstate 8 dipslip motion is minor compared to strike slip motion and is concentrated in the sediments the best fitting constant rupture velocity is 80 per cent of the local shear wave velocity however there is a suggestion that the rupture front accelerated from the hypocenter northward the 1979 imperial valley earthquake can be characterized as a magnitude 5 earthquake at the hypocenter which then grew into or triggered a magnitude 6 earthquake north of the border

three dimensional simulation of the near fault ground motion for the 1995 hyogo ken nanbu kobe japan earthquake abstract the 17 january 1995 hyogo ken nanbu earthquake is a typical example showing that the ground motions along basin edge faults can be very destructive in this study we simulate the near fault ground motion from this earthquake based on a kinematic fault model and a simplified 3d velocity structure of the kobe area the kinematic earthquake rupture and the wave propagation are modeled using a 3d finite difference method fdm our simulation identifies the basin edge effect as an important factor that influenced the ground motion amplification pattern in the kobe area we found that the coupling of the source directivity and basin edge effects causes impulsive ground motions with extremely high amplitude at periods greater than 1 sec and in a narrow zone offset less than 1 km from the basin edge the combination of these effects acted to create a fairly continuous band of amplification that extends about 30 km in an elongated zone parallel to the basin edge boundary in some areas localized site effects might have been as important as the abovementioned effects but they cannot explain the continuity of the extended east west zone of damage

ambient seismic noise monitoring of a clay landslide toward failure prediction given that clay rich landslides may become mobilized leading to rapid mass movements earthflows and debris flows they pose critical problems in risk management worldwide the most widely proposed mechanism leading to such flow like movements is the increase in water pore pressure in the sliding mass generating partial or complete liquefaction this solid to liquid transition results in a dramatic reduction of mechanical rigidity in the liquefied zones which could be detected by monitoring shear wave velocity variations with this purpose in mind the ambient seismic noise correlation technique has been applied to measure the variation in the seismic surface wave velocity in the pont bourquin landslide swiss alps this small but active composite earthslide earthflow was equipped with continuously recording seismic sensors during spring and summer 2010 an earthslide of a few thousand cubic meters was triggered in mid august 2010 after a rainy period this article shows that the seismic velocity of the sliding material measured from daily noise correlograms decreased continuously and rapidly for several days prior to the catastrophic event from a spectral analysis of the velocity decrease it was possible to determine the location of the change at the base of the sliding layer these results demonstrate that ambient seismic noise can be used to detect rigidity variations before failure and could potentially be used to predict landslides

a new light on arresting mechanism of dynamic earthquake faulting classic analyses have shown that dynamic growth of a shear crack cannot be arrested in a uniformly stressed elastic medium with homogeneously distributed fracture strengths this leads to a general supposition that earthquake rupture growth is arrested by inhomogeneities in the distributions of strengths or stresses we propose a novel idea for arresting mechanism of dynamic crack growth in the simulation with no constraints on the crack geometry our analysis shows that the arresting occurs spontaneously soon after crack bending even in the homogeneous medium and that inhomogeneities are indispensable not for stopping crack growth but for its promotion