a parametric numerical study of the interaction between seismic waves and landslides for the evaluation of the susceptibility to seismically induced displacements this study presents the results of a numerical analysis investigating the influence of the interaction between seismic waves and slopes on seismically induced displacements of existing landslides three step like slope geometries with dip angles varying from 10 degrees to 45 degrees and two landslide mechanisms were considered 54 multi frequential dynamic equivalent signals were applied to the models and were derived according to the lema des approach based on the accelerometric records of the european strong motion and cosmos databases the simulations were performed using a finite difference approach that assumed different viscous rheologies and considered different values for both the dynamic properties and the mechanical parameters the interaction between seismic waves and landslides was analyzed using frequency ratios defined for characteristic periods associated with the landslide dimensions i e thickness and length and the seismic input a regression analysis was also performed to derive correlations between seismically induced displacements and the frequency ratios the values of the arias intensity and the critical accelerations the obtained results reveal that a the seismically induced displacements increase with the seismic amplification induced by the landslide mass b the coupling of a 2d interaction between seismic waves and slope with the 1d resonance of the landslide mass which is strictly related to the high impedance contrasts between the landslide mass and the substratum significantly affects the seismically induced displacements and c the seismically induced displacements increase more intensely with increasing slope angle for a rototranslational mechanism with respect to a translational one moreover the seismically induced displacements that can be expected from the here obtained results can significantly differ from those computed by the sliding block stability analyses based on newmark s method

the importance of earthquake induced landslides to long term slope erosion and slope failure hazards in seismically active regions abstract this paper describes a general method for determining the amount of earthquake induced landsliding that occurs in a seismically active region over time this determination can be used as a quantitative measure of the long term hazard from seismically triggered landslides as well as a measure of the importance of this process to regional slope erosion rates and landscape evolution the method uses data from historical earthquakes to relate total volume of landslide material dislodged by an earthquake to the magnitude m and seismic moment m0 of the earthquake from worldwide data a linear regression relation between landslide volume v and m0 is determined as v m0 1018 9 0 13 where v is measured in m3 and m0 is in dyn cm to determine the amount of earthquake generated landsliding over time this relation is combined with data on seismic moment release for a particular region which may be derived from either earthquake history or fault slip data the form of the m0 v relation allows the rate of production of earthquake induced landslides over time to be determined from total rate of seismic moment release without regard to the distribution of individual events thus simplifying and generalizing the determination application of the method to twelve seismically active regions with areas ranging from 13 275 to 2 308 000 km2 shows that erosion rates from earthquake induced landslides vary significantly from region to region of the regions studied the highest rates were determined for the island of hawaii new zealand western new guinea and the san francisco bay region of california significantly lower rates were determined for iran tibet the sierra nevada great basin region of california and central japan for the time period from 715 ad to the present intermediate rates were determined for peru southern california onshore california turkey and central japan for the time period from 1586 ad to the present to determine the relative long term importance of seismically triggered landslides these erosion rates are compared to erosion rates calculated for other slope processes and to rates calculated from fluvial sediment discharge comparisons with other slope processes indicate that earthquake induced landslides are the predominant agents of slope erosion on the island of hawaii in the san francisco bay region and in western new guinea for hawaii the san francisco bay region and sierra nevada great basin region of california the erosion rates calculated for earthquake induced landslides also exceed the regional erosion rates calculated from fluvial sediment discharge

the effect of glaciation on the intensity of seismic ground motion seismicity is known to contribute to landscape denudation through its role in earthquake triggered slope failure but little is known about how the intensity of seismic ground motions and therefore triggering of slope failures may change through time topography influences the intensity of seismic shaking generally steep slopes amplify shaking more than flatter slopes and because glacial erosion typically steepens and enlarges slopes glaciation may increase the intensity of seismic shaking of some landforms however the effect of this may be limited until after glaciers retreat because valley ice or ice caps may damp seismic ground motions two dimensional numerical models flac 6 0 were used to explore how edifice shape rock stiffness and various levels of ice inundation affect edifice shaking intensity the modelling confirmed that earthquake shaking is enhanced with steeper topography and at ridge crests but it showed for the first time that total inundation by ice may reduce shaking intensity at hill crests to about 20 50 of that experienced when no ice is present the effect is diminished to about 80 95 if glacier ice level reduces to half of the mountain slope height in general ice cover reduced shaking most for the steepest sided edifices for wave frequencies higher than 3 hz and when ice was thickest and the rock had shear stiffness well in excess of the stiffness of ice if rock stiffness is low and shear wave velocity is similar to that of ice the presence of ice may amplify the shaking of rock protruding above the ice surface the modelling supports the idea that topographic amplification of earthquake shaking increases as a result of glacial erosion and deglaciation it is possible that the effect of this is sufficient to have influenced the distribution of post glacial slope failures in glaciated seismically active areas copyright 2012 john wiley sons ltd

seismically induced rock slope failures resulting from topographic amplification of strong ground motions the case of pacoima canyon california abstract the 1994 northridge earthquake mw 6 7 triggered extensive rock slope failures in pacoima canyon immediately north of los angeles california pacoima canyon is a narrow and steep canyon incised in gneissic and granitic rocks peak accelerations of nearly 1 6 g were recorded at a ridge that forms the left abutment of pacoima dam peak accelerations at the bottom of the canyon were less than 0 5 g suggesting the occurrence of topographic amplification topographic effects have been previously suggested to explain similarly high ground motions at the site during the 1971 mw 6 7 san fernando earthquake furthermore high landslide concentrations observed in the area have been attributed to unusually strong ground motions rather than higher susceptibility to sliding compared with nearby zones we conducted field investigations and slope stability back analyses to confirm the impact of topographic amplification on the triggering of landslides during the 1994 earthquake our results suggest that the observed extensive rock sliding and falling would have not been possible under unamplified seismic conditions which would have generated a significantly lower number of areas affected by landslides in contrast modelling slope stability using amplified ground shaking predicts slope failure distributions matching what occurred in 1994 this observation confirms a significant role for topographic amplification on the triggering of landslides at the site and emphasises the need to select carefully the inputs for seismic slope stability analyses

the effects of normal and shear stress wave phasing on coseismic landslide displacement predictive models used to assess the magnitude of coseismic landslide strain accumulation in response to earthquake ground shaking typically consider slope parallel ground accelerations only and ignore both the influence of coseismic slope normal ground accelerations and the phase relationship between dynamic slope normal and slope parallel accelerations we present results of a laboratory study designed to assess the significance of the phase offset between slope normal and slope parallel cyclic stresses on the generation of coseismic landslide displacements using a dynamic back pressured shearbox that is capable of simulating variably phased slope normal and slope parallel dynamic loads we subjected sediment samples to a range of dynamic loading scenarios indicative of earthquake induced ground shaking we detail the variations in strain accumulation observed when slope normal and slope parallel stresses occur independently and simultaneously both in and out of phase using a range of dynamic stress amplitudes our results show that the instantaneous phasing of dynamic stresses is critical in determining the amount of coseismic landslide displacement which may vary by up to an order of magnitude based solely on wave phasing effects instantaneous strain rate is an exponential function of the distance normal to the mohr coulomb failure envelope in plots of shear stress against normal effective stress this distance is strongly controlled by the phase offset between dynamic normal and shear stresses our results demonstrate that conditions considered by conventional coseismic slope stability models can either overestimate or underestimate earthquake induced landslide displacement by up to an order of magnitude this has important implications for accurate assessment of coseismic landslide hazard

trampoline effect in extreme ground motion in earthquake hazard assessment studies the focus is usually on horizontal ground motion however records from the 14 june 2008 iwate miyagi earthquake in japan a crustal event with a moment magnitude of 6 9 revealed an unprecedented vertical surface acceleration of nearly four times gravity more than twice its horizontal counterpart the vertical acceleration was distinctly asymmetric the waveform envelope was about 1 6 times as large in the upward direction as in the downward direction which is not explained by existing models of the soil response we present a simple model of a mass bouncing on a trampoline to account for this asymmetry and the large vertical amplitude the finding of a hitherto unknown mode of strong ground motion may prompt major progress in near source shaking assessments

the little red hill seismic experimental study topographic effects on ground motion at a bedrock dominated mountain edifice the kinematic response of a bedrock dominated mountain edifice to seismic shaking near lake coleridge in the southern alps of new zealand was examined a small elongated and bedrock dominated mountain ridge little red hill was equipped with a seismic array seven earss instruments mark l 4 3d seismometers were installed along the ridge crest the flank and at the base of the 210 m high 500 m wide and 800 m long mountain edifice from february to july 2006 seismic records of local and regional earthquakes were used to provide information on amplification and deamplification effects as well as on the frequency response at different parts on the edifice the ground motion records were analyzed using three different methods comparisons of peak ground accelerations power spectral density analysis and standard spectral ratio analysis time and frequency domain analyses show that site amplification is concentrated along the elongated crest of the edifice where amplifications of up to 1100 were measured relative to the motion at the flat base the field experiment also highlighted the extreme variations in amplification with regard to closely located sites but at contrasting topographic locations theoretical calculations and frequency analyses of field data indicate a maximum response along the ridge crest of little red hill for frequencies of about 5 hz which correlate to wavelengths approximately equal to the half width or height of the edifice the consequence of amplification effects on the stability and degradation of rock masses can be seen areas showing high amplification effects overlap with the spatial distribution of seismically generated block fields at little red hill it is concluded that topography geometry and distance to the seismic source play key roles in causing amplification effects of seismic ground motion and supporting dilation and degradation of rock mass across bedrock dominated mountain edifices

variable microstructural response of baddeleyite to shock metamorphism in young basaltic shergottite nwa 5298 and improved u pb dating of solar system events abstract the accurate dating of igneous and impact events is vital for the understanding of solar system evolution but has been hampered by limited knowledge of how shock metamorphism affects mineral and whole rock isotopic systems used for geochronology baddeleyite monoclinic zro2 is a refractory mineral chronometer of great potential to date these processes due to its widespread occurrence in achondrites and robust u pb isotopic systematics but there is little understanding of shock effects on this phase here we present new nano structural measurements of baddeleyite grains in a thin section of the highly shocked basaltic shergottite northwest africa nwa 5298 using high resolution electron backscattered diffraction ebsd and scanning transmission electron microscopy stem techniques to investigate shock effects and their linkage with u pb isotopic disturbance that has previously been documented by in situ u pb isotopic analyses the shock altered state of originally igneous baddeleyite grains is highly variable across the thin section and often within single grains analyzed grains range from those that preserve primary magmatic twinning and trace element zonation baddeleyite shock group 1 to quasi amorphous zro2 group 2 and to recrystallized micro granular domains of baddeleyite group 3 these groups correlate closely with measured u pb isotope compositions primary igneous features in group 1 baddeleyites n 5 are retained in high shock impedance grain environments and an average of these grains yields a revised late amazonian magmatic crystallization age of 175 30 ma for this shergottite the youngest u pb dates occur from group 3 recrystallized nano to micro granular baddeleyite grains indicating that it is post shock heating and new mineral growth that drives much of the isotopic disturbance rather than just shock deformation and phase transitions our data demonstrate that a systematic multi stage microstructural evolution in baddeleyite results from a single cycle of shock loading heating and cooling during transit to space and that this leads to variable disturbance of the u pb isotope system furthermore by linking in situ u pb isotopic measurements with detailed micro to nano structural analyses it is possible to resolve the timing of both endogenic crustal processes and impact events in highly shocked planetary materials using baddeleyite this opens up new opportunities to refine the timing of major events across the solar system

seismic triggering of catastrophic failures on shear surfaces in saturated cohesionless soils this paper is concerned with an analysis of the seismic performance of infinite slopes in undrained conditions the material assumed on the sliding surface is a loose saturated sand susceptible to a gradual loss in undrained shear strength after failure with the progress of unidirectional shear displacement the undrained monotonic and cyclic shear behavior of this sand was investigated through an experimental study based on ring shear tests with initial stresses corresponding to the static conditions on the sliding surface of the analyzed slopes these tests provide the experimental framework for a modified sliding block method to estimate the earthquake induced undrained shear displacements for conditions of no shear stress reversals on the sliding surface the proposed estimation procedure incorporates the shearing resistance obtained from undrained monotonic ring shear tests to approximate the undrained yield resistance at a certain displacement during an earthquake the term catastrophic failure is

the interaction of seismic waves with step like slopes and its influence on landslide movements abstract the interaction of seismic waves with slopes is a major factor influencing landslide movements that involve slope stability local site seismic amplification and topographic effects affecting ground motion the results of a numerical study of landslide movements induced by the interaction of seismic waves with step like slopes are presented here to investigate this input slope interaction a dynamic analysis was performed using the finite difference stress strain numerical code flac 6 0 under visco plastic conditions the dynamic signals were selected to be representative of different peak ground accelerations pgas arias intensities and frequency contents and they were used in a parametric study of different step like slopes with different geometrical configurations in terms of dip height and thickness of geological strata the derived outputs were processed for a seismic amplification analysis and to evaluate the induced stress strain effects in terms of progressive failure and resulting displacements the obtained results i describe a fundamental role of topography in amplifying or de amplifying the seismic ground motion ii demonstrate that the progressive failure of unsheared slopes influences the seismic amplification iii show that the strain effects on unsheared slopes in terms of progressive failure are more intense with increasing arias intensity and slope dip iv prove that amplification or de amplification processes can justify the values of displacements involving pre existing landslide masses which are significantly different with respect to those expected on the basis of sliding block approaches i e newmark s and flexible sliding block methods v highlight that in the geological setting considered here the seismically induced displacements arising from the reactivation of pre existing landslide masses can be significantly underestimated by sliding block approaches in the case of low angle slopes characterised by high k values i e the ratios between the critical pseudostatic threshold ky of the landslide and pgas of the applied seismic input

regression models for estimating coseismic landslide displacement newmark s sliding block model is widely used to estimate coseismic slope performance early efforts to develop simple regression models to estimate newmark displacement were based on analysis of the small number of strong motion records then available the current availability of a much larger set of strong motion records dictates that these regression equations be updated regression equations were generated using data derived from a collection of 2270 strong motion records from 30 worldwide earthquakes the regression equations predict newmark displacement in terms of 1 critical acceleration ratio 2 critical acceleration ratio and earthquake magnitude 3 arias intensity and critical acceleration and 4 arias intensity and critical acceleration ratio these equations are well constrained and fit the data well 71 br 2 b88 but they have standard deviations of about 0 5 log units such that the range defined by the mean one standard deviation spans about an order of magnitude these regression models therefore are not recommended for use in site specific design but rather for regional scale seismic landslide hazard mapping or for rapid preliminary screening of sites 2007 elsevier b v all rights reserved

instrumental evidence of normal mode rock slope vibration summary a unique field experiment was performed to constrain the seismic response of a large potentially unstable rock slope in the southern swiss alps small aperture seismic arrays were deployed to record ambient vibrations both inside and outside of the mapped instability boundary the recordings were analysed by means of the high resolution f k method site to reference spectral ratios and time frequency dependent polarization analysis all three methods indicated that the wavefield within the potentially unstable rock mass is dominated by normal mode motion standing waves rather than horizontal propagation of seismic waves both fundamental frequency and relative amplification could be recovered from ambient noise data the observed amplification is strongly directional and the maximum amplification is oriented perpendicular to open tension cracks mapped at the ground surface our results highlight site response characteristics relevant for analysis of earthquake triggered rock slope failures

landslides earthquakes and erosion this paper relates landslide inventories to erosion rates and provides quantitative estimates of the landslide hazard associated with earthquakes we do this by utilizing a three parameter inverse gamma distribution which fits the frequency area statistics of three substantially dcompletet landslide event inventories a consequence of this general distribution is that a landslide event magnitude ml lognlt can be introduced where nlt is the total number of landslides associated with the landslide event using this general distribution landslide event magnitudes ml can be obtained from incomplete landslide inventories and the total area and volume of associated landslides as well as the area and volume of the maximum landslides can be directly related to the landslide event magnitude using estimated recurrence intervals for three landslide events and the time span for two historical inventories we estimate regional erosion rates associated with landslides as typically 0 1 2 5 mm year 1 we next give an empirical correlation between the earthquake magnitude associated landslideevent magnitude and the total volume of associated landslides using these correlations we estimate that the minimum earthquake magnitudes that will generate landslides is m 4 3f0 4 finally using gutenberg richter frequency magnitude statistics for regional seismicity we relate the intensity of seismicity in an area and the magnitude of the largest regional earthquakes to erosion rates we find that typical seismically induced erosion rates in active subduction zones are 0 2 7 mm year 1 and adjacent to plate boundary strike slip fault zones are 0 01 0 7 mm year 1

residual shear strength variability as a primary control on movement of landslides reactivated by earthquake induced ground motion implications for coastal oregon u s most large seismogenic landslides are reactivations of preexisting landslides with basal shear zones in the residual strength condition residual shear strength often varies during rapid displacement but the response of residual shear zones to seismic loading is largely unknown we used a ring shear apparatus to perform simulated seismic loading tests constant displacement rate tests and tests during which shear stress was gradually varied on specimens from two landslides to improve understanding of coseismic landslide reactivation and to identify shear strength models valid for slow gravitational failure through rapid coseismic failure the landslides we studied represent many along the oregon u s coast seismic loading tests resulted in 1 catastrophic failure involving unbounded displacement when stresses represented those for the existing landslides and 2 limited to unbounded displacement when stresses represented those for hypothetical dormant landslides suggesting that coseismic landslide reactivation may be significant during future great earthquakes occurring near the oregon coast constant displacement rate tests indicated that shear strength decreased exponentially during the first few decimeters of displacement but increased logarithmically with increasing displacement rate when sheared at 0 001 cm s 1 or greater dynamic shear resistance estimated from shear strength models correlated well with stresses observed during seismic loading tests indicating that displacement rate and amount primarily controlled failure characteristics we developed a stress based approach to estimate coseismic landslide displacement that utilizes the variable shear strength model the approach produced results that compared favorably to observations made during seismic loading tests indicating its utility for application to landslides

regional patterns of earthquake triggered landslides and their relation to ground motion 1 we have documented patterns of landsliding associated with large earthquakes on three thrust faults the northridge earthquake in california chi chi earthquake in taiwan and two earthquakes on the ramu markham fault bounding the finisterre mountains of papua new guinea in each case landslide densities are shown to be greatest in the area of strongest ground acceleration and to decay with distance from the epicenter in california and taiwan the density of co seismic landslides is linearly and highly correlated with both the vertical and horizontal components of measured peak ground acceleration based on this observation we derive an expression for the spatial variation of landslide density analogous with regional seismic attenuation laws in its general form this expression applies to our three examples and we determine best fit values for individual cases our findings open a window on the construction of shake maps from geomorphic observations for earthquakes in non instrumented regions

determination of the shear strength parameters of an unsaturated soil using the direct shear test multistage direct shear tests have been performed on saturated and unsaturated specimens of a compacted glacial till a conventional direct shear apparatus was modified in order to use the axis tra

advances and problems in understanding the seismic response of potentially unstable slopes abstract the influence of site effects on landslide triggering during earthquakes has been inferred in several studies but its evaluation is made difficult by the complexity of factors controlling the dynamic response of potentially unstable slopes and also by the lack of local ground motion instrumental observations this work explores this problem and reports new findings based on an ongoing long term accelerometric monitoring conducted on a landslide prone test area in the apennine mountains italy where the presence of site effects enhancing seismic susceptibility of local slopes has been invoked on the basis of historic accounts of landsliding triggered at large epicentral distance the recordings relative to low to moderate magnitude earthquakes showed significant amplifications affecting hillslope portions covered by thick 5 m colluvia and pronounced amplification maxima oriented along the local maximum slope direction on a recent deep seated landslide while the amplifications seem most likely linked to high impedance contrast between surface materials and underlying substratum the causes of directivity are less clear the case of the monitored test site together with evidence of site response directivity identified on other hillslopes suggest that the directivity phenomena can result from a combination of topographic lithological and structural factors that act together to re distribute shaking energy focusing it on site specific directions thus it is difficult to single out the critical factors controlling such phenomena and no general criterion for the identification of sites affected by directivity is proposed here nevertheless the presence and orientation of site response directivity can be revealed through reconnaissance techniques by using recordings of seismic weak motion and or ambient microtremors and calculating azimuthal variation of shaking energy and horizontal to vertical ground motion spectral ratios a comparison with the recordings obtained during the recent m w 6 3 earthquake that hit the abruzzo region in april 2009 demonstrated that analysis relying on data from low energy events can furnish valid indications for slope behaviour also under stronger shaking provided the data are well differentiated in terms of distance azimuth and source characteristics furthermore the comparative analysis of the abruzzo earthquake recordings at a landslide and reference sites showed that directivity properties of strong shaking had been correctly anticipated using earlier weak motion observations however under the complex slope conditions the identification of resonance frequencies from horizontal to vertical spectral ratios estimated from weak motion accelerometric recordings does not seem reliable and better results have been obtained by velocimetric microtremor recordings

evidence for temporal variation of seismic velocity within the upper continental crust observations of systematic temporal variations of seismic anisotropy are presented for an induced seismicity experiment at 9 km depth these observations were made under particularly well controlled conditions in the german continental deep drilling program ktb borehole using shear wave splitting from similar events recorded at a three component instrument located at 4 km depth from a hydraulic fracturing experiment at 9 km depth in a large set of seismic events recorded during the experiment many can be associated with multiplets exhibiting essentially identical waveforms since they must have approximately the same source location and source radiation pattern these events are particularly useful for testing the hypothesis of time dependent anisotropy anisotropy itself is clearly a very prominent feature in the data a simple approach for waveform matching of split shear waves allows unprecedented resolution of variations in shear wave splitting importantly the variation of shear wave splitting with time is a relative measurement which can be performed with higher accuracy than the associated absolute measurement in particular the relative measurement is not affected by timing errors nor by event distance variations during the experiment the difference between shear wave velocities decreases by 2 within 12 hours after that the medium apparently approaches a state which is stable for at least 5 hours we suggest that the temporal variation is due to the tectonic stress release from seismic events caused by the fluid injection this model requires the presence of fluid filled cracks at depths larger than 4 kin

seismic loading impacts on excess pore water pressure maintain landslide triggered flowslides during the 2003 sanriku minami earthquake japan a flowslide was triggered on a slope of about 13 5o the displaced landslide mass developed into a flowslide and deposited on a horizontal rice paddy after traveling approximately 130 m to study the trigger and movement mechanisms of this landslide field investigation and laboratory ring shear tests were performed field investigation revealed that the landslide originated from a fill slope where a gully was buried for cultivation some decades ago and shallow ground water was present undrained monotonic and cyclic ring shear tests on a sample pyroclastic deposits taken from the source area revealed that the soil is highly liquefiable and its steady state shear strength can be little affected by overconsolidation using the seismic records of the earthquake probable seismic loadings on the sliding surface were synthesized and applied to the samples in ring shear tests which were performed under undrained or partially drained conditions the undrained and partially drained tests revealed that shear failure can be triggered by the introduction of seismic loading and formation of excess pore water pressure the generation of excess pore water pressure along with increase of shear displacement and the inhibited dissipation of excess pore water pressure due to the thickness of the saturated soil layer above the sliding surface probably enabled the continued post failure landsliding copyright 2008 john wiley sons ltd

numerical simulation of rock mass vibrations induced by nearby production blast it is of importance to understand the effect of production blasts on the surrounding rock formations in underground mines this study presents a numerical procedure to simulate stress waves resulting from nearby production blasts first the damping coefficient and peak borehole pressure are calibrated using a dynamic numerical model of a single blast hole the resulting time varying particle velocities in the surrounding rock mass at the specified points are calculated these are then used as input parameters in a three dimensional mine wide model considering a positional relationship between the blast hole and the specified points on the wall rock the mine wide model encompasses a fault running parallel to a steeply dipping tabular ore deposit dynamic analysis simulating the effect of production blasts is conducted after the extraction of mining blocks with static analysis in this study variations of stresses along the fault due to blast induced stress waves are examined results demonstrate that