variation of slip and creep along the levant rift over the past 4500 years frequency magnitude relations were established for a fault system embedded in a shear zone with dimensions 1000 km 200 km that extends from the gulf of elat to the east anatolian fault the resulting frequency magnitude relations were found to be in good agreement with both the documented instrumental earthquake statistics for ml 4 5 in the present century and microearthquake activity for ml 1 5 recorded in israel and some adjacent territories during 1976 1979 when these frequency magnitude relations are extended to 2500 b c one can account for the maximal magnitude earthquakes that echo in the bible and are manifested in archaeological excavations it is found that seismic slip rates increase significantly from south toward north in such a way that in north central israel and lebanon seismic slip constitutes only 13 of the motion the rest being attributed to visco elastic processes further north as one approaches the collision zone with the turkish plate aseismicity tends to disappear and the slip is purely seismic

potential earthquake risk estimations by application of a simulation process abstract potential earthquake risks are defined here in terms of the annual probability of exceeding a peak ground acceleration level at the free surface of a site potential earthquake risks in israel were estimated by shapira 1981 1982 by considering the apparent seismicity of the region during the last 145 years in this paper a simulation process has been applied in order to examine the reliability of previous estimations and to provide another general tool for earthquake risk evaluation a relatively simple monte carlo procedure was developed and has been used for estimating as an example the potential earthquake risk in jerusalem israel the estimated probabilities obtained by the simulation procedure are for all practical purposes similar to the apparent probabilities previously determined by the author however a re evaluation of the potential earthquake risks in israel will be required when an attenuation equation based on local and regional acceleration measurements has been developed

characterization of the 3 d fracture setting of an unstable rock mass from surface and seismic investigations to numerical modeling the characterization of the fracturing state of a potentially unstable rock cliff is a crucial requirement for stability assessments and mitigation purposes classical measurements of fracture location and orientation can however be limited by inaccessible rock exposures the steep topography and high rise morphology of these cliffs together with the widespread presence of fractures can additionally condition the success of geophysical prospecting on these sites in order to mitigate these limitations an innovative approach combining non contact geomechanical measurements active and passive seismic surveys and 3 d numerical modeling is proposed in this work to characterize the 3 d fracture setting of an unstable rock mass located in nw italian alps madonna del sasso vb the 3 d fracture geometry was achieved through a combination of field observations and non contact geomechanical measurements on oriented pictures of the cliff resulting from a previous laser scanning and photogrammetric survey the estimation of fracture persistence within the rock mass was obtained from surface active seismic surveys ambient seismic noise and earthquakes recordings were used to assess the fracture control on the site response processing of both datasets highlighted the resonance properties of the unstable rock volume decoupling from the stable massif a finite element 3 d model of the site including all the retrieved fracture information enabled both validation and interpretation of the field measurements the integration of these different methodologies applied for the first time to a complex 3 d prone to fall mass provided consistent information on the internal fracturing conditions supplying key parameters for future monitoring purposes and mitigation strategies

high temperature and pressure seismic properties of a lower crustal prograde shear zone from the kohistan arc pakistan anastomosing shear zones exposed in the lower crust of the kohistan palaeoisland arc in pakistan have parageneses indicating increasing pressure during deformation therefore they represent a rare example of strain localization during crustal thickening we investigated the seismic properties of a sheared gabbro with constant bulk chemistry across one of these shear zones the compressional wave velocity was measured at confining pressures of up to 0 5 gpa and temperatures of up to 600 8c the density the average vp compressional p wave velocity and the acoustic impedance at room temperature increase from the undeformed protolith through the strain gradient to the intensely sheared mylonite the seismic anisotropy is largest for the strain gradient the vp dependence of the velocities on temperature is much higher in the mylonite than in the protolith the acoustic impedance contrast between protolith and mylonite is high enough to generate seismic reflections at low temperatures but not at high temperatures this suggests that the seismic reflectivity may also depend on the temperature consequently ductile shear zones can be detected in reflection profiles of crusts with low geothermal gradients and may be transparent in crusts with high geothermal gradients

a probabilistic approach for evaluating earthquake risks with application to the afro eurasian junction abstract earthquake risks may be quantified in terms of the annual probability of exceeding peak ground accelerations on the free surface accordingly a direct method for estimating these probabilities is developed the probabilistic approach is mainly based on seismographic data and follows the assumption that the known seismicity of the region during the last t years would not dramatically change in the future t years the method was applied to the region of the afro eurasian junction for estimating the apparent annual probabilities of exceeding peak ground accelerations in jerusalem tel aviv and haifa the reliability of the suggested approach is examined by means of comparison between the obtained results for jerusalem and the seismic history of the city in the last 1000 years

mapping brittle fracture zones in three dimensions high resolution traveltime seismic tomography in a granitic pluton summary fractured and altered zones within a granitic pluton are mapped in three dimensions by means of high resolution seismic traveltime tomography the input traveltimes were picked from offset and azimuth variable vertical seismic profiles ovsp acquired in three boreholes and from seismic shot gathers of four cdp high resolution seismic reflection profiles recorded on the surface for the ovsp data a hydrophone streamer placed in the boreholes recorded the acoustic energy generated a signal with a frequency content between 15 to 150 hz by a vibroseis truck at source points distributed every 30 m in a rectangular grid of 620 m by 150 m the combination of borehole and surface seismic data resulted in an increase in the ray density of the shallow subsurface the tomographic algorithm uses a variable model grid with a finer grid spacing close to the surface were ray density is highest and the velocity variations are strongest therefore the resulting velocity models feature more detail at shallow levels a simple and smooth starting velocity model was derived from p wave velocity logs careful surface geological mapping and borehole geophysical data p and s wave velocity logs and poisson s ratio depth functions provided key constraints for a physically reasonable 3 d interpretation of the tomograms the low velocity anomalies constrained by the tomographic images were interpreted as unconsolidated rock fractures and altered zones which correlate with structures mapped at the surface or velocity anomalies identified in the logs subsequent resolution analysis revealed that the derived velocity model is well constrained to depths of 60 m

modeling source zone boundary uncertainty in seismic hazard analysis most probabilistic seismic hazard studies assume that future earthquakes will occur in clearly defined seismically homogeneous areal source zones this assumption means that modeled seismic rates change abruptly at source zone boundaries with the result that predicted acceleration levels may differ considerably at sites a few kilometers apart near a boundary e g changes of 50 to 80 per cent or more at sites 20 km apart however homogeneous source zones are at best an approximation and the areal extent of such zones is usually not well determined i propose modifying the model so that the seismicity originally associated with each point in a source zone instead be regarded as normally distributed with standard deviation about that point this permits seismicity to vary smoothly across source zone boundaries when this variability is modeled if is 25 per cent or less of the width of the source zone acceleration levels calculated at sites at the center of the zone and at sites on the boundary are about the same as those calculated when no location variability 0 is assumed however calculated levels decrease at sites between the center and the boundary and increase at sites outside the boundary the changes tend to become larger at the higher accelerations corresponding to longer exposure times when earthquakes are modeled as ruptures along well defined linear faults predicted accelerations also increase significantly as the site location approaches the fault however in many cases neither the location of a fault nor the definitions of its end points can be precisely stated acceleration as a function of site location will vary more smoothly if possible fault locations are regarded as either normally or uniformly distributed

verification of velocity resistivity relationships derived from structural joint inversion with borehole data we present results of three dimensional joint inversion of seismic magnetotelluric and gravity data over a marine salt dome such structures are difficult to image with a single method and our results demonstrate how combining different techniques can yield improved results more importantly we examine the reliability of velocity conductivity relationships derived from structure coupled joint inversion approaches comparison with a seismic reflection section shows that our models match the upper limit of the salt furthermore velocity and resistivity logs from a borehole drilled into the salt dome s flank match within error those recovered by the inversion the good match suggests that the difference in length scale does not have a significant effect in this case this provides a strong incentive to incorporate borehole data into the joint inversion in the future and substantiates approaches that use the relationships derived from joint inversion models for lithological classification

micro and macroseismicity of the dead sea rift and off coast eastern mediterranean abstract the seismicity of israel has been evaluated from documented earthquake records of the present century and two years of routine monitoring of microearthquake activity by means of eleven stations spreading from the gulf of elat to northern galilee the dead sea rift asserts itself as the tectonic feature that accounts for the seismicity of our region the activity peaks at zones where the fault branches sideways or at a junction with other fault systems in particular the crescent fault of wadi faria seems to be a zone of high strain accumulation this is probably the site of many historical earthquakes which caused inland and coastal damage it is thus found that the most active fault today which constitutes the greatest seismic risk to israeli metropolitan areas extends along the dead sea rift from 31 2 n to 33 4 n the seismicity around the dead sea conforms with the proposed movement along en echelon faults while the southwest segment is presently inactive most of the seismic activity there is limited to the neighbourhood of its eastern shore with extreme seismicity at its southern tip near the prehistorical site of bab a dara a the seismicity of the arava is much lower than the jordan dead sea section the seismicity of the israeli coast was found to be somewhat higher than that of the arava

neotectonic activity in caesarea the mediterranean coast of central israel abstract evidence for neotectonic activity along the coast of the southern levant exists in the ancient harbor of caesarea in central israel where large herodian breakwaters are presently submerged 5 8 m below sealevel whereas other contemporary coastal installations in the same area remain at sealevel high resolution seismic reflection surveys on the very shallow continental shelf encountered a series of coast parallel faults that displace both the eolianite which crops out along the coastal zone and the submerged breakwaters the faults have 1 3 m of offsets downthrowing their seaward flank and leaving their landward flank stable we suggest that the subsidence of the ancient breakwaters was caused by neotectonic displacements on these faults and enhanced by solifluction records of historical earthquakes in the coastal levant region and archaeological evidence of faulting are compatible with the geophysical findings the neotectonic activity of the mediterranean coast of israel which is a consequence of the plio quaternary subsidence of the southeastern mediterranean basin has shaped the coast of the southern levant even during the past 2000 years

acquisition and processing strategies for 3d georadar surveying a region characterized by rugged topography efficiently performing 3d ground penetrating radar gpr or georadar surveys across rugged terrain and then processing the resultant data are challenging tasks conventional approaches using unconnected gpr and topographic surveying equipment are excessively time consuming for such environments and special migration schemes may be required to produce meaningful images we have collected gpr data across an unstable craggy mountain slope in the swiss alps using a novel acquisition system that records gpr and coincident coordinate information simultaneously undulating topography dips of 8 to 16 and boulders with diameters up to about 2 m complicated the field campaign after standard processing the data were found to be plagued by time shifts associated with minor coordinate inaccuracies uneven antenna ground coupling and numerous small gaps in data coverage these problems were resolved by passing the data sequentially through an adaptive f xy deconvolution routine and f kx and f ky filters this filtering also reduced incoherent noise finally the data were migrated using a 3d algorithm that accounted for the undulating topography the nonmigrated and migrated images contained gently and moderately dipping reflections from lithological boundaries and actively opening fracture zones a suite of prominent diffraction patterns was generated at a steeply dipping fracture zone that projected to the surface through this case history we introduce a general strategy for 3d gpr studies of topographically rugged land

3d seismic traveltime tomography imaging of the shallow subsurface at the c o2 sink project site ketzin germany a 3d reflection seismic survey was performed in 2005 at the ketzin carbon dioxide c o2 pilot geological storage site the c o2 sink project near berlin germany to image the geological structure of the site to depths of about 1 km because of the acquisition geometry frequency limitations of the source and artefacts of the data processing detailed structures shallower than about 150 m were unclear to obtain structural images of the shallow subsurface we applied 3d traveltime tomography to data near the top of the ketzin anticline where faulting is present understanding the shallow subsurface structure is important for long term monitoring aspects of the project after c o2 has been injected into a saline aquifer at about 650 m depth we used a 3d traveltime tomography algorithm based on a combination ofsolving for 3d velocity structure and static corrections in the inversion process to account for artefacts in the velocity structure because of smearing effects from the unconsolidated cover th

site effect analysis around the seismically induced ananevo rockslide kyrgyzstan in 1911 the surface wave magnitude 8 2 kemin earthquake hit northeastern tien shan kyrgyzstan close to the cities of bishkek and almaty the capitals of kyrgyzstan and kazakhstan respectively several hundreds of people were killed by the earthquake some by indirect effects such as landslides and mudflows a particular but nonfatal landslide triggered by the kemin event was a rockslide in the vicinity of ananevo north of lake issyk kul kyrgyzstan rockslide located above the fault zone activated in 1911 in the summer of 1999 a geophysical seismological field trip was organized to study geology and to record seismic ground motions on and around the ananevo rockslide the work was part of project assessing seismogenic landslide hazard in northern kyrgyzstan based on various case studies of slope failures in connection with site specific ground motion dynamics the geophysical investigations consisted of seismic refraction tests processed as 2d seismic tomographies and surface wave inversion which were combined to build a 3d geophysical model of the landslide site ground motions from small earthquakes were analyzed using several techniques to define site effects over the mountain massif both h v and standard spectral ratios indicated lower dominant frequencies with stronger amplification in the crest region with respect to the mountain slope these effects could be partially simulated by 1d 2d and 3d finite element modeling by comparing the numerical results with the experimental data the presence of a surficial low velocity layer of varying thickness appeared to be the key factor controlling the ground motion around the rockslide

probabilistic appraisal of earthquake hazard parameters deduced from a bayesian approach in the northwest frontier of the himalayas a straightforward bayesian statistic is applied in five broad seismogenic source zones of the northwest frontier of the himalayas to estimate the earthquake hazard parameters maximum regional magnitude mmax value of g r relationship and seismic activity rate or intensity for this purpose a reliable earthquake catalogue which is homogeneous for mw 5 0 and complete during the period 1900 to 2010 is compiled the hindukush pamir himalaya zone has been further divided into two seismic zones of shallow h 70 km and intermediate depth h 70 km according to the variation of seismicity with depth in the subduction zone the estimated earthquake hazard parameters by bayesian approach are more stable and reliable with low standard deviations than other approaches but the technique is more time consuming in this study quantiles of functions of distributions of true and apparent magnitudes for future time intervals of 5 10 20 50 and 100 years are calculated with confidence limits for probability levels of 50 70 and 90 in all seismogenic source zones the zones of estimated mmax greater than 8 0 are related to the sulaiman kirthar ranges hindukush pamir himalaya and himalayan frontal thrusts belt suggesting more seismically hazardous regions in the examined area the lowest value of mmax 6 44 has been calculated in northern pakistan and hazara syntaxis zone which have estimated lowest activity rate 0 0023 events day as compared to other zones the himalayan frontal thrusts belt exhibits higher earthquake magnitude 8 01 in next 100 years with 90 probability level as compared to other zones which reveals that this zone is more vulnerable to occurrence of a great earthquake the obtained results in this study are directly useful for the probabilistic seismic hazard assessment in the examined region of himalaya

characterizing an unstable mountain slope using shallow 2d and 3d seismic tomography as transport routes and population centers in mountainous areas expand risks associated with rockfalls and rockslides grow at an alarming rate as a consequence there is an urgent need to delineate mountain slopes susceptible to catastrophic collapse in a safe and noninvasive manner for this purpose we have developed a 3d tomographic seismic refraction technique and applied it to an unstable alpine mountain slope a significant segment of which is moving at 0 01 0 02 m year toward the adjacent valley floor first arrivals recorded across an extensive region of the exposed gneissic rock mass have extraordinarily low apparent velocities at short 0 2 m to long 100 m shot receiver offsets inversion of the first arrival traveltimes produces a 3d tomogram that reveals the presence of a huge volume of very low quality rock with ultralow to very low p wave velocities of 500 2700 m s these values are astonishingly low compared to the average horizontal p wave velocity of 5400 m s determined from labora

tectonic implications of recent microearthquake data from israel and adjacent areas a recently installed seismograph network in israel enables for the first time a systematic examination of the microearthquake activity and its relation to the regional tectonics the observed microearthquake activity is widespread and not limited to the dead sea rift plate boundary in the rift itself the more seismically active parts are north of the sea of galilee and in the dead sea basin a possible seismic quiescence appears in the jordan valley to the north of the dead sea basin and may be associated with that segment of the plate boundary which broke recently 1927 thus indicating a low strain level inside israel the active nature of the carmel farah fault systems was determined its present level of seismicity appears to be comparable to that of the rift itself indicating the significance of this fault system in the active tectonics of the area the high microseismic activity on these faults and their location in densely populated areas mark them as possibly important sources of seismic hazards diffused seismicity is observed throughout much of israel although the nature of these earthquakes is not yet understood the small magnitude earthquakes near the rift are most probably part of a seismic halo around the plate boundary pronounced seismicity is also observed in the mediterranean sea off the coast of southern lebanon and northern israel this microearthquake activity decreases from north to south and to some extent from east to west whereas near the coast of northern israel and southern lebanon the microearthquake activity is relatively high in the south near the coast of the sinai peninsula it is very low this difference is attributed to a possible combination of a higher strain level in the african plate as it approaches the africa eurasia plate boundary and hinge faulting near the coast

air circulation in deep fractures and the temperature field of an alpine rock slope the subsurface temperature field of a rock slope is a key variable influencing both bedrock fracturing and slope stability however significant unknowns remain relating to the effect of air and water fracture flow which can rapidly transmit temperature changes to appreciable depths in this work we analyze a unique set of temperature measurements from an alpine rock slope at 2400 m a s l in southern switzerland the monitored area encompasses part of an active slope instability above the village of randa vs and is traversed by a network of open cracks some of which have been traced to 80 m depth we first describe distributed temperature measurements and borehole profiles highlighting deep steady temperatures and different transient effects and then use these data to approximate the conductive temperature field at the site in a second step we analyze the impact of air and water circulation in deep open fractures on the subsurface thermal field on multiple visits to the study site in winter we consistently noted the presence of warm air vents in the snowpack following the trace of deep tension cracks measurements showed that venting air changed temperature gradually from 3 to 2 c between december and may which is similar to the rock temperature at around 50 m depth comparison with ambient air temperature suggests that winter conditions favor buoyancy driven convective air flow in these fractures which acts to cool the deep subsurface as the rock gives up heat to incoming air the potential impact of this process on the local thermal field is revealed by a disturbed temperature profile in one borehole and transient signals observed at depths well below the thermal active layer seasonal water infiltration during snowmelt appears to have little impact on the temperature field in the monitored area copyright 2011 john wiley sons ltd

active faulting in the dead sea rift abstract manifestations of late quaternary and holocene faulting were studied in a 500 km long segment of the dead sea transform rift most prominent are left slip faults whose characteristic physiographic features are recognizable along most of the studied segment where these faults bend or are stepped to the left rhomb shaped grabens or pull aparts are produced forming depressions in the reverse situation compressional features such as pressure ridges domes and folds form positive topographic features such structures are combined on a variety of scales ranging from a few hundred meters long to tens of kilometers normal faults sub parallel to the left slip faults produce a trough like valley along much of the dead sea transform but are most prominent along the margins of the large rhomb grabens e g the dead sea trough they apparently record a small component of transverse extension generally their motion is slow young slip did not occur along some segments during the last few 10 4 y elsewhere throws of 10 20 m at least occurred in this period the dead sea transform is seismically active the instrumental and historic records indicate a seismic slip rate of 0 15 0 35 cm y during the last 1000 1500 y while estimates of the average pliocene pleistocene rate are 0 7 1 0 cm y either much creep takes place or the slip rate varies over periods of a few 10 3 y

microseismicity of three locations along the jordan rift abstract from september 1981 until june 1984 a portable seismograph station array was in operation at three different locations along the jordan rift system covering a the dead sea area b the hula valley area and c the southern part of the arava valley based on the seismological data obtained by these arrays a comparison of the microseismic activity in these areas is made these observations are also compared with the data from the countrywide network issn some preliminary conclusions regarding the seismicity of the investigated areas and the performance of the arrays are suggested

reconnaissance geophysical methods in landslide investigations abstract landslides are a natural hazard in many countries and often affect civil engineering structures and projects three aspects in particular require examination in a geotechnical appraisal of a landslide s stability in engineering terms 1 the definition of its three dimensional shape with particular reference to shear surfaces and failure planes 2 the definition of the hydrogeological regime with regard to water input to the landslide and its distribution within the slip mass 3 the detection of movement by or within the slip mass and the characterisation of such movements the site investigation costs may be very high since landslides may be extremely large structurally complex and topographically severe it is therefore advantageous in suitable circumstances to carry out reconnaissance geophysical surveys to define the structure and to guide optimum siting of boreholes and pits and ultimately the installation of piezometers inclinometers etc standard surface geophysical techniques including the seismic electrical resistivity acoustic emission and borehole methods have all been applied with varying success to look at a landslide before a major site investigation commences in recent years electromagnetic methods have been the subject of considerable research in this field and significant advances have been made in this paper the application of the above geophysical methods at the reconnaissance stage in a landslide investigation has been reviewed and illustrated with several case histories taken from different geological settings

probabilistic assessment of earthquake hazard in israel abstract the earthquake hazard in israel is assessed on the basis of the cornell mcguire probabilistic approach using the available set of instrumental and historical regional earthquake data a horizontal peak ground acceleration probability map is presented based on a proposed seismicity model earthquake source zonation and the application of the joyner boore attenuation relationship the present results differ from those previously obtained owing to the technique used the incorporation of a greater amount of instrumental data and the use of a more appropriate attenuation relationship for the first time regional earthquake hazard analysis incorporates the active carmel and farah faults this alters the risk estimate and is important considering their proximity to densely populated and industrialized areas an approximate sensitivity analysis is carried out for main model input parameters with inherent uncertainties

internal structure and deformation of an unstable crystalline rock mass above randa switzerland part i internal structure from integrated geological and geophysical investigations 6m 3 of material occurred in fractured gneissic rock whose principal foliation faults and fracture zones dip into the slope above the scarp of the second rockslide the mountain continues to move at rates of up to 2 cm year in an attempt to understand failure mechanisms in fractured crystalline rock masses we have carried out a comprehensive multidisciplinary study that included detailed geological mapping borehole logging and imaging and surface and borehole geophysical surveys an integrated interpretation of the resultant data has revealed the presence of three prominent fault and fracture zone sets that define the internal structure of the rock mass some faults and fracture zones could be traced up to 85 m into the subsurface using borehole radar reflection methods the dips of the faults and fracture zones estimated from surface mapping matched those from radar reflection and borehole televiewer surveys no evidence was found for significant faults or persistent weakness planes that paralleled the 1991 rockslide failure surfaces instead the new observations were consistent with dominant failure mechanisms that involve the progressive development of major shear and brittle fracturezones and the eventual destruction of intact rock bridges immediately prior to catastrophic collapse this integrated study provides the first reliable model of the 3 d fault structure associated with and contributing to a large rock slope instability in a brittle crystalline rock mass

tectonic conditioning revealed by seismic refraction facilitates deep seated landslides in the western escarpment of the main ethiopian rift abstract landslide is a geo hazard phenomenon that has been taking lives and causing severe property damages all over the world mostly in mountainous areas the main ethiopian rift has a unique tectonic setting with complex geological and geomorphological features coupled with continuously deteriorating environmental conditions which made its escarpments vulnerable for landslides the study area is located near the debre sina town within the yizaba wein locality which has been severely affected by frequent landslide problems this work was carried out using a multidisciplinary approach based on geological geomorphological kinematic analysis and geophysical survey seismic refraction investigations were carried out along the yizaba wein landslide main scarp to determine the depth to the bedrock and to the failure plane to assess the stability of the slope to locate possible structural features and to identify the extent of recent landslide activity and to study the subsurface situation the seismic measurements were made along three nearly orthogonal survey lines in the recently affected area a high resolution 2d p wave survey was conducted using a 24 channel seismic unit the seismic refraction results revealed four layers of geomaterials with distinct physical characteristics that contained a subsurface landslide anomaly within the layers the layers were interpreted according to the major lithological units from top to bottom i clay loosely cemented colluvial sediments and highly weathered agglomeratic basalt ii highly to moderately fractured porphyritic basalt ignimbrite volcanic ash and rhyolite trachyte iii moderately to slightly fractured ignimbrite rhyolite trachyte and basalt and iv very strong massive fresh rock bedrock faults and weak zones have also been identified in the bedrock based on the abundance of fractures and subsidiary faults resulting from damage of rocks and change of lithology due to variable fault rock formation strongly influencing the wavefield distribution which usually causes a local decrease of the velocity value the main findings show that the landslide in the yizaba wein locality was caused by its complex geological structural setting and downslope movement of the underlying pyroclastic sediment facilitated by heavy rainfall considering the similar geological and tectonic settings similar mechanisms can be assumed for other landslides along the rift margins and associated highlands of ethiopia

p and sv velocity structure of the south portuguese zone fold and thrust belt sw iberia from traveltime tomography imaging the architecture of the shallow crust of the south portuguese zone fold and thrust belt is essential to extend surface mapped geological information to depth and to help in developing model

multiscale geophysical characterization of an unstable rock mass abstract hazard mitigation from rockfalls and landslides is a priority in densely populated areas a proper characterization of the inner structure of the rock mass is key to the comprehension of the mechanisms enhancing the slope instabilities to this aim multi scale geophysical methods can provide a novel and valuable tool for a high resolution imaging of the internal structure of the rock mass and unique constraints on the physical state of the medium we present here a cross hole seismic tomography survey coupled with laboratory ultrasonic velocity measurements and physical properties determination on rock samples to characterize the damaged and potentially unstable granitic cliff of madonna del sasso nw italy results allowed to obtain i a lithological interpretation of the velocity field obtained at the site ii a systematic correlation of the measured velocities with physical properties density and porosity and macroscopic features of the granite weathering and anisotropy of the cliff the multi scale approach adopted within this study revealed to be crucial for the imaging at depth of the main fractures affecting the cliff site scale seismic tests and for the understanding of the variations in the seismic velocity between altered and intact rock laboratory scale tests similar approaches can be potentially used in further microseismic monitoring studies

fault behavior and characteristic earthquakes examples from the wasatch and san andreas fault zones paleoseismological data for the wasatch and san andreas fault zones have led to the formulation of the characteristic earthquake model which postulates that individual faults and fault segments tend to generate essentially same size or characteristic earthquakes having a relatively narrow range of magnitudes near the maximum analysis of scarp derived colluvium in trench exposures across the wasatch fault provides estimates of the timing and displacement associated with individual surface faulting earthquakes at all of the sites studied the displacement per event has been consistently large measured values range from 1 6 to 2 6 m and the average is about 2 m on the basis of variability in the timing of individual events as well as changes in scarp morphology and fault geometry six major segments are recognized along the wasatch fault on the basis of the most likely number of surface faulting events 18 that have occurred on segments of the wasatch fault zone during the past 8000 years an average recurrence interval of 400 666 years with a preferred average of 444 years is calculated for the entire zone geologic data on the distribution of slip associated with prehistoric earthquakes and slip rates along the south central segment of the san andreas fault suggest that the m 8 1857 earthquake is a characteristic earthquake for this segment comparisons of earthquake recurrence relationships on both the wasatch and san andreas faults based on historical seismicity data and geologic data show that a linear constant b value extrapolation of the cumulative recurrence curve from the smaller magnitudes leads to gross underestimates of the frequency of occurrence of the large or characteristic earthquakes only by assuming a low b value in the moderate magnitude range can the seismicity data on small earthquakes be reconciled with geologic data on large earthquakes the characteristic earthquake appears to be a fundamental aspect of the behavior of the wasatch and san andreas faults and may apply to many other faults as well

constraining regional paleo peak ground acceleration from back analysis of prehistoric landslides example from sea of galilee dead sea transform article i nfo accurate estimation of expected peak ground acceleration pga in seismically active regions is a challenging task the best way to estimate quantitatively expected pga is by investigating instrumental data of past strong earthquakes in a given area in some regions of the world however recorded data are scarce and if they exist they are typically available only since the late 19th century as such they are hardly representative of the true seismicity in the studied region we propose here an analytical approach to constrain the lower threshold of paleoseismic pga on the basis of back analysis of old landslides to perform the analysis we need a mapped landslide with geomorphic features that have been preserved in the field the slip surface a good reconstruction of the slope geometry and ground water level prior to failure and the mechanical properties of the sheared material we perform static and pseudo static limit equilibrium analyses using standard solution procedures to obtain lower bounds of paleoseismic pga back analyses of three different landslides around the sea of galilee sog return similar results that range between 0 15 and 0 5 g thus constraining the threshold paleoseismic pga range for this region the analytically inferred regional pga is supported by results of an independent numerical analysis of toppled columns in a nearby byzantine church using results from a recent paleoseismic trenching study performed on one of the studied landslides and a modified attenuation relationship for the study area we localize the loci of moment magnitude mw 7 0 earthquakes that can explain the studied failures along the boundaries of the sog and find that they coincide with traces of the eastern and western margin faults of the dead sea transform the temporal relationships between the observed failures are discussed on the basis of dated colluvial sediments geomorphologic constraints and archeological evidence

2d electrical resistivity imaging of some complex landslides in lucanian apennine chain southern italy we use high resolution electrical resistivity imaging to delineate the geometry of complex landslides in the lucanian apennine chain of southern italy to identify the discontinuity between the landslide material and bedrock and to locate possible surfaces of reactivation the lucanian apennine chain is characterized by high hydrogeological hazard and shows a complete panorama of mass movements in this area all typologies of landslides markedly predisposed and tightly controlled by the geostructural characteristics are found rotational and translational slides rototranslational slides earth and mudflows as well as deep seated gravitational slope phenomena with a predominance of rototranslational slides evolving as earthflow slides three test sites characterized by complex geology and a high hydrogeologic hazard are studied the giarrossa and varco izzo earthflow slides are located to the west and east of the town of potenza whereas the latronico slide is located close to the town of latronico

palaeoseismicity of the oquirrh fault utah from shallow seismic tomography the magnitude and frequency of normal fault palaeoearthquakes are usually determined by trenching studies that ascertain the size and number of colluvial wedges along the fault such information can be invaluable in predicting the seismic hazard and potential for a future earthquake in that region digging trenches across normal faults however is environmentally intrusive expensive and limited in the penetration depth to overcome these problems we propose the use of 3 d seismic tomography as a means to identify the shapes and sizes of colluvial wedges along normal faults as an example 2 d and 3 d seismic surveys were conducted across the oquirrh fault utah with the purpose of imaging the normal fault structure to a depth of about 10 m results show that the 3 d tomogram clearly delineates the fault zone and a colluvial wedge both of which correlate extremely well with the geological cross section interpreted from an adjacent trench the thickness of the colluvial wedge image is used in conjunction with a seismic section to compute an estimate of a 6 8 moment magnitude earthquake for the most recent event on this fault which is in close agreement with the 7 0 estimate based on a nearby trenching study these tomographic results demonstrate for the first time that seismic imaging methods can be used in some cases to estimate unambiguously the shapes of colluvial wedges and the sizes of prehistoric earthquakes thus seismic tomography has the possibility of providing cheaper deeper and wider but less resolved images of fault systems than the intrusive excavation of trenches across faults

chemical alteration of fine grained sedimentary rocks at gale crater abstract from sol 750 to 1550 the curiosity rover documented 100 m thick stack of fine grained sedimentary rocks making up part of the murray formation at the base of mt sharp gale crater here we use data collected by the chemcam instrument to estimate the level of chemical weathering in these sedimentary rocks both the chemical index of alteration cia and the weathering index scale wis indicate a progressive increase in alteration up section reaching values of cia of 63 and wis of 25 the increase in cia and wis values is coupled with a decrease in calcium abundance suggesting partial dissolution of ca bearing minerals clinopyroxene and plagioclase mineralogy from the chemin x ray diffraction instrument indicates a decrease in mafic minerals compared with previously analyzed strata and a significant proportion of phyllosilicates consistent with this interpretation these observations suggest that the sediments were predominantly altered in an open system before or during their emplacement contrasting with the rock dominated conditions inferred in sedimentary deposits analyzed at yellowknife bay

refraction tomography over a buried waste disposal site determining the depth and geometry of a landfill s lower boundary is a difficult task potential field methods generally lack the necessary depth resolution and seismic reflection data are usually contaminated by source generated noise in the time range of interest 50 ms to address this problem we have developed a surface 2 d tomographic refraction scheme that is based on a fast finite difference eikonal solver and an inversion method that incorporates appropriate damping and smoothing constraints this new scheme has been applied to a first arrival traveltime data set collected across adjacent landfills in northern switzerland high quality seismic data were collected along five profiles that crossed the landfills and two that sampled undisturbed natural sediments seismic waves generated from multiple shots were recorded on large numbers of closely spaced receivers during quiet evening periods reliability of the resultant velocity tomograms was estimated on the basis of 1 ray diagrams 2 plot

quantifying bedrock fracture patterns within the shallow subsurface implications for rock mass strength bedrock landslides and erodibility 1 the role of bedrock fractures and rock mass strength is often considered a primary influence on the efficiency of surface processes and the morphology of landscapes quantifying bedrock characteristics at hillslope scales however has proven difficult here we present a new field based method for quantifying the depth and apparent density of bedrock fractures within the shallow subsurface based on seismic refraction surveys we examine variations in subsurface fracture patterns in both fiordland and the southern alps of new zealand to better constrain the influence of bedrock properties in governing rates and patterns of landslides as well as the morphology of threshold landscapes we argue that intense tectonic deformation produces uniform bedrock fracturing with depth whereas geomorphic processes produce strong fracture gradients focused within the shallow subsurface additionally we argue that hillslope strength and stability are functions of both the intact rock strength and the density of bedrock fractures such that for a given intact rock strength a threshold fracture density exists that delineates between stable and unstable rock masses in the southern alps tectonic forces have pervasively fractured intrinsically weak rock to the verge of instability such that the entire rock mass is susceptible to failure and landslides can potentially extend to great depths conversely in fiordland tectonic fracturing of the strong intact rock has produced fracture densities less than the regional stability threshold therefore bedrock failure in fiordland generally occurs only after geomorphic fracturing has further reduced the rock mass strength this dependence on geomorphic fracturing limits the depths of bedrock landslides to within this geomorphically weakened zone

holocene seismic and tectonic activity in the dead sea area abstract the dead sea is a large active graben within the dead sea rift which is bounded by two major strike slip faults the jericho and the arava faults we investigated the young tectonic activity along the jericho fault by excavating trenches up to 3 5 m deep across its trace the trenches penetrate through late pleistocene and holocene sediments we found that a zone up to 15 m wide of disturbed sediments exists along the fault these disturbed sediments provide evidence for two periods of intensive activity or more likely for two major earthquakes that occurred during the last 2000 years the earthquakes are evident in small faults vertical throw of a few layers cracks unconformities and wide fissures we further documented evidence for recent sinistral shear along the jericho fault in deformed sediments and damage to an 8th century palace on a subsidiary fault we suggest that the two earthquakes may be correlated with the 31 b c earthquake and the 748 a d earthquake reported by the ancients