gis analysis to assess landslide susceptibility in a fluvial basin of nw sicily italy abstract landslide hazard assessment effected by means of geostatistical methods is based on the analysis of the relationships between landslides and the spatial distributions of some instability factors frequently such analyses are based on landslide inventories in which each record represents the entire unstable area and is managed as a single instability landform in this research landslide susceptibility is evaluated through the study of a variety of instability landforms landslides scarps and areas uphill from crown the instability factors selected were bedrock lithology steepness topographic wetness index and stream power index the instability landform densities computed for all the factors which were arranged in unique condition unit allowed us to derive a total of three prediction images for each landslide typology the role of the instability factors and the effects generated by the use of different landforms were analyzed by means of a bivariate analysis of the relationships between factors and landslide density b predictive power validations of the prediction images based on a random partition strategy the test area was the iato river basin north western sicily whose slopes are moderately involved in flow and rotational slide landslides 219 and 28 respectively the area is mainly made up of the following complexes numidian flysch clays 19 1 terravecchia sandy clays 5 1 terravecchia clayey sands 3 0 3 and san cipirello marly clays 9 0 the steepness parameter shows the highest landslide density in the 11 19 class for both the typologies 8 1 even if the density distributions for rotational slides are right asymmetric and right shifted we obtained significant differences in shape when we used different instability landforms unlike scarps and areas uphill from crowns landslide areas produce left asymmetric and left shifted density distributions for both the typologies as far as the topographic wetness index is concerned much more pronounced differences were detected among the instability landforms of rotational slides in contrast the flow landslides produce normal like density distributions the latter and the rotational slide landslide areas produce the highest density values in the class 5 5 6 7 despite an abrupt decreasing trend starting from the first class 3 2 4 4 which is generated by the density values of the rotational slide scarps and areas uphill from crowns the stream power index at the foot of the slopes which was automatically derived using a gis procedure shows a positive correlation with the landslide densities marked by the maximum classes 4 8 6 0 for flows and 6 0 7 2 for rotational slides the validation procedure results confirmed that the choice of instability landform influences the results of the susceptibility analysis furthermore the validation procedure indicates that a the predictive models are generally satisfactory b scarps and zones uphill from crown areas are the most diagnostically unstable landforms for flow and rotational slide landslides respectively

a comparative study of suction stress between sand and silt under unsaturated conditions abstract the purpose of this study is to estimate and compare suction stress between sand and silt sampled from the coast of korea the water content and matric suction of sand joomunjin and silt saemangeum were first examined using an automated soil water characteristic curve swcc apparatus based on the axis translation technique swccs were then estimated from the test results using the van genuchten 1980 model at equal matric suction the corresponding water content of silt was higher than that of sand moreover the saturated water content and air entry value aev of silt were larger than those of sand using the fitting swcc parameters suction stress characteristic curves ssccs were estimated according to the method proposed by lu and likos 2006 the sscc behavior for sand and silt was different and significantly depended on the material properties particularly pore size and pore size distribution for sand the suction stress exhibited rapid variation with changes in matric suction but for silt the suction stress approached a constant value as the matric suction increased in addition when the matric suction was smaller than the aev of soil the suction stress was equal to the magnitude of the matric suction in contrast when the matric suction exceeded the aev of soil suction stress had a nonlinear shape with respect to the matric suction

landslide hazard assessment in the three gorges area china using aster imagery wushan badong abstract the objectives of this study are to develop a methodology for regional scale assessment of landslide hazard using remotely sensed data and to produce a landslide hazard map of the wushan badong area in the three gorges china from advanced spaceborne thermal emission and reflection radiometer aster images the area is undergoing rapid urban development with slope instability causing a widespread natural hazard landslide related parameters were largely estimated through image processing and visual interpretation of aster multi spectral and topographic data we used field measurements to define the quantification for three parameters a slope angle in relation to lithology b distance to drainage network in relation to stream order and c distance to tectonic lineament in relation to lineament length we employed a multi parameter elimination and characterization model based on estimation of the geometric mean to remove areas where landslides are not expected to occur and classify the remaining areas into landslide hazard categories our results show increased landslide hazard in and around wushan and badong towns as well as other populated areas along the yangtze and its tributaries we used field data on landslide distribution to identify typical geomorphological settings for different landslide types and to provide ground control for the hazard assessment the results indicate good correlation between classified high hazard areas and field confirmed slope failures and show the usefulness of aster imagery for landslide hazard assessment at a regional scale

numerical simulation of metamorphic pressure temperature time paths and fluid production in subducting slabs in order to investigate metamorphic reactions and fluid production in subduction zones a 2 dimensional finite difference model has been constructed the model simulates heat transfer in a subduction zone with a 27 dip a spatial resolution of 1 km is used in the region of the subduction thrust in order to carefully monitor metamorphic reactions elsewhere the spatial resolution is 5 km in these calculations the oceanic crust is assumed to contain 2 wt bound volatiles distributed homogeneously within the 7 5 km thick crust fluids are released by continuous and discontinuous end members of three different dehydration models pressure sensitive temperature sensitive and amphibole negative dp dt dehydration subduction zone pressure temperature time p t t paths predicted by the model intersect the wet basaltic solidus only at the initiation of subduction in mature subduction zones and in the absence of significant frictional heating and induced mantle convection p t t paths encounter subsolidus conditions at depths of 100 150 km beneath magmatic arcs suggesting that slab dehydration reactions play an important role in arc magma genesis metamorphic dehydration reactions that consume 50 kj kg result in p t t paths that are only 5 k cooler than models that neglect such reactions in both the temperature and amphibole dehydration models the fluid production region moves to greater depths over time as the subduction zone cools within the oceanic crust fluid production starts at the top of the crust and migrates downward in the temperature and amphibole dehydration models this phenomenon coupled with the weakening effect of devolatilization reactions may result in the accretion of oceanic crust to the hanging wall of the subduction zone for a convergence rate of 3 cm yr average fluid fluxes out of the subducting slab range from 0 1 kg fluid m yr for the continuous reaction models to 1 kg fluid m yr for the discontinuous pressure and amphibole dehydration models vertical fluid fluxes on the order of 1 kg fluid m yr can substantially perturb the thermal structure of overlying rocks and can cause large scale hydration and metasomatism of the overlying mantle wedge in contrast the thermal effect of fluid flow parallel to the subduction thrust zone is insignificant compared to the thermal effect of subducting oceanic lithosphere

partial transformation of gabbro to coesite bearing eclogite from yangkou the sulu terrane eastern china an ultra high pressure uhp metamorphic slab at yangkou beach near qingdao in the sulu region of china consists of blocks of eclogite facies metagabbro metagranitoid ultramafic rock and mylonitic orthogneisses enclosed in granitic gneiss a gradational sequence from incipiently metamorphosed gabbro to completely recrystallized coesite eclogite formed at ultra high pressures was identified in a single 30 m block metagabbro is preserved in the core whereas coesite eclogite occurs along the block margins the metagabbro contains an igneous assemblage of pl aug opx qtz bt ilm ti mag it shows relict magmatic textures and reaction coronas fine grained garnet developed along boundaries between plagioclase and other phases primary plagioclase broke down to ab ky ms zo grt amp augite is rimmed by sodic augite or omphacite whereas orthopyroxene is rimmed by a corona of cum act and omp qtz layers or only omp qtz in transitional rocks augite and orthopyroxene are totally replaced by omphacite and the lower pressure assemblage ab ky phn zo grt coexists with domains of omp jd70 73 ky phn in pseudomorphs after plagioclase both massive and weakly deformed coesite bearing eclogites contain omp ky grt phn coe qtz rt and preserve a faint gabbroic texture coesite inclusions in garnet and omphacite exhibit limited conversion to palisade quartz some intergranular coesite and quartz pseudomorphs after coesite also occur assemblages of the coronal stage transitional and uhp peak occurred at about 540 50 c at c 13 kbar 600 800 c at 15 25 kbar and 800 850 c at 30 kbar respectively garnet from the coronal through the transitional to the eclogite stage rocks show a decrease in almandine and an increase in grossular pyrope components garnet in low grade rocks contains higher mno and lower pyrope components the growth textures of garnet within pseudomorphs after plagioclase or along grain boundaries between plagioclase and other phases are complex the application of garnet zoning to estimate p t should be carried out with caution some garnet enclosing quartz aggregates as inclusions shows radial growth boundaries these quartz aggregates as well as other primary and low p phases persisted metastably at uhp conditions due to sluggish reactions resulting from the lack of fluid during prograde and retrograde p t evolution

an inverted double seismic zone in chile evidence of phase transformation in the subducted slab data from two microseismic field experiments in northern chile revealed an elongated cluster of earthquakes in the subducted nazca plate at a depth of about 100 kilometers in which down dip tensional events were consistently shallower than a family of compressional earthquakes this double seismic zone shows a distribution of stresses of opposite polarity relative to that observed in other double seismic zones in the world the distribution of stresses in northern chile supports the notion that at depths of between 90 to 150 kilometers the basalt to eclogite transformation of the subducting oceanic crust induces tensional deformation in the upper part of the subducted slab and compressional deformation in the underlying mantle

the geology of dunedin new zealand and the management of geological hazards abstract the city of dunedin is located on the remains of a miocene volcanic eruptive centre which is underlain by tertiary marine sediments and late cretaceous quartz gravel sand and clay with some coal seams these in turn rest on a basement of jurassic schist the geology and topography pose a number of geological hazards that must be considered in urban development these include landslide mine subsidence ground shaking amplification and liquefaction coastal erosion and tsunami a number of research policy and planning initiatives have been undertaken to assess and mitigate the effects of these hazards a gis based hazard information system for a part of the city was developed to assist in identifying and mitigating hazards under legislation the dunedin city council dcc is obliged to keep a register of known hazards in addition a lifelines project has been undertaken to identify hazards and related risks to emergency and utility services these studies may be used by asset managers to prioritise mitigation measures for critical facilities as well as to avoid hazards the dcc district plan includes policies to gather and maintain hazard information encourage research into hazards and control activities in areas that might be affected by hazards

garnets recording deep crustal earthquakes syn eclogite facies pseudotachylytes of the bergen arcs western norway were formed during co seismic faulting at a depth of 60 km during caledonian continent collision concurrent with fluid induced partial eclogitization of precambrian anorthositic granulites the pseudotachylytes contain the high pressure assemblage omphacite garnet and kyanite and formed in the metastable granulites at the border of eclogitized areas rock volumes corresponding to outcrops of 100 m2 in area were shattered by pseudotachylytes associated with ultramylonites cataclasites and shear zones the granulite facies garnets unzoned and inclusion free away from the pseudotachylyte veins display planar and curved fractures brecciation and melting with decreasing distance from the veins sieve textured garnet developed by the disintegration of granulite facies garnet crystallization of eclogite facies mineral inclusions and welding together of garnet fragments fractured granulite facies garnets trend to more almandine rich compositions with variable grossular contents in the pseudotachylyte veins a second generation of minute 10 200 m euhedral or dendritic garnets has a higher femg ratio than the granulite facies garnet and a wide range in grossular content grs11 grs89 suggesting rapid growth and cooling fracturing of garnet and its preferential disappearance in the pseudotachylyte show that garnet has a relatively low fracture toughness seismic faulting caused enhanced reaction rates during ongoing fluid induced eclogitization of the deep crust by increasing the surface to volume ratio of garnet and its dislocation density the sudden volume reduction associated with eclogitization of metastable crust may have nucleated further faulting and pseudotachylyte formation

accelerated hydration of the earth s deep crust induced by stress perturbations the metamorphic cycle associated with the formation of mountain belts produces a lower crust containing little or no free fluid1 2 the introduction of external fluids to dry and impermeable volumes of the earth s crust is thus a prerequisite for the retrogressive metamorphism later observed in such regimes such metamorphism can cause significant changes in the crust s physical properties including its density rheology and elastic properties3 4 on a large scale the introduction of fluids requires the presence of high permeability channels such as faults or fractures which are the result of external tectonic stresses but extensive interaction between externally derived fluids and the fractured rock requires efficient mass transport away from the initial fractures into the rock itself and this transport often occurs over distances much longer than expected from grain boundary diffusion here we present both field observations and a simple network model that demonstrate how the transport of fluids into initially dry rock can be accelerated by perturbations in the local stress field caused by reactions with fluids we also show that the morphology of reaction fronts separating dry from wet rocks depends on the anisotropy of the external stress field

the effect of fluid and deformation on zoning and inclusion patterns in poly metamorphic garnets within the bergen arcs of w norway caledonian eclogite facies assemblages t 650 c p 15 kbar have formed from grenvillian granulites t 800 900 c p 10 kbar along shear zones and fluid pathways garnets in the granulites grti pyr56 40 alm45 25gro19 14 are unzoned or display a weak ca 1 wt feo over 1000 m zoning the eclogite facies rocks contain garnets inherited from their granulite facies protoliths these relict garnets have certain areas with compositions identical to the garnets in their nearby granulite but can be crosscut by bands of a more almrich composition grtii pyr31 41alm40 47gro17 21 formed during the eclogite facies event these bands orientated preferentially parallel or perpendicular to the eclogite foliation may contain mineral filled veins or trails of eclogite facies minerals omphacite amphibole white mica kyanite quartz and dolomite steep compositional gradients up to 9 wt feo over 40 m separate the two generations of garnets indicating limited volume diffusion the bands are interpreted as fluid rich channels where element mobility must have been infinitely greater than it was for the temperature controlled volume diffusion at mineral interfaces in the granulites the re equilibration of granulite facies garnets during the eclogite facies event must therefore be a function of fracture density deformation and fluid availability the results cast doubts on modern petrological and geochronological methods that assume pure temperature controlled chemical re equilibration of garnets

a procedure for landslide susceptibility zonation by the conditional analysis method numerous methods have been proposed for landslide probability zonation of the landscape by means of a geographic information system gis among the multivariate methods i e those methods which simultaneously take into account all the factors contributing to instability the conditional analysis method applied to a subdivision of the territory into unique condition units is particularly straightforward from a conceptual point of view and particularly suited to the use of a gis in fact working on the principle that future landslides are more likely to occur under those conditions which led to past instability landslide susceptibility is defined by computing the landslide density in correspondence with different combinations of instability factors the conceptual simplicity of this method however does not necessarily imply that it is simple to implement especially as it requires rather complex operations and a high number of gis commands moreover there is the possibility that in order to achieve satisfactory results the procedure has to be repeated a few times changing the factors or modifying the class subdivision to solve this problem we created a shell program which by combining the shell commands the gis geographical research analysis support system grass commands and the gawk language commands carries out the whole procedure automatically this makes the construction of a landslide susceptibility map easy and fast for large areas too and even when a high spatial resolution is adopted as shown by application of the procedure to the parma river basin in the italian northern apennines

reaction enhanced ductility the role of solid solid univariant reactions in deformation of the crust and mantle abstract in collision belts and subduction zones penetrative deformation of thrust sheets may be catalyzed by metamorphic reactions if the reactions have a significant effect on the mechanical properties of rocks reaction enhanced ductility may result if a reaction produces a significant decrease in grain size thus allowing the rock to deform superplastically the product grain size of a reaction is a function of the ratio of nucleation and growth rates this ratio varies along any pressure temperature time ptt path and only attains a significant value at a certain distance from an equilibrium boundary a comparison of rates of change of p and t along typical segments of ptt paths for crustal rocks leads to the conclusion that a high nucleation rate a small grain size and resulting superplastic deformation are more likely to be achieved when reaction boundaries are crossed during underthrusting rather than during the thermal readjustments of a perturbed geotherm following crustal thickening or during uplift an example of reaction enhanced ductility occurs in eclogite facies metagranitoids in the sesia lanzo zone western alps where medium grained plagioclase reacted to fine grained jadeite quartz during early alpine underthrusting microstructural evidence from shear zones shows that the jadeite quartz aggregates were highly ductile and it is inferred that the small grain size allowed superplastic deformation further evidence suggests that this process operated during regional deformation of metagranitoids rubie 1982 the reaction of olivine to spinel or the beta phase by metastable overstepping of the two phase stability fields in a subducting plate ringwood 1975 may result in fine grained products and thus may be analogous to the albite jadeite quartz reaction the consequent decrease in effective viscosity is likely to have important consequences for plate dynamics at and below the depths of major phase transitions

infiltration induced seasonally reactivated instability of a highway embankment near the eisenhower tunnel colorado usa abstract infiltration induced landslides are major natural hazards when they occur along highways they can impede traffic damage infrastructure and threaten public safety this paper presents a case study of an active landslide on an embankment of interstate 70 west of the eisenhower tunnel in central colorado usa records indicate that the hillslope under i 70 has moved episodically over the previous 40 years in the previous two decades the road surface has been displaced vertically by more than 60 cm the objective of this work is to develop a conceptual model capable of quantifying the seasonally reactivated landslide movement at the site inclinometer data of subsurface deformation and geologic and hydrologic mapping are used to develop the conceptual model as well as to constrain a numerical model a two dimensional hydro mechanical numerical model is used to test the conceptual model under three different infiltration rates during the period of snowmelt in the spring the framework used in the numerical model accounts for the major physical processes driving instability of the slope time dependent variably saturated flow the resultant changes in stress and induced deformation when the snowmelt water infiltrates into the slope the soil water content and the water table level vary accordingly these time dependent variations result in changes in soil matric suction effective stress and consequently change in slope stability the model calculates pore water pressures suction stress and the distribution of effective stress in the embankment slope at different times global factors of safety as a function of time are calculated along the predetermined sliding surface using effective stresses calculated with finite elements the slope stability assessment quantitatively confirms the conceptual model and is consistent with the displacements monitored at the site during the years of 2007 2009 it is shown that annual snowmelt infiltration of 60 100 cm of water can reduce the factor of safety by 6 enough to sustain landslide movement for as long as 8 months each year

impact of chi chi earthquake on the occurrence of landslides and debris flows example from the chenyulan river watershed nantou taiwan abstract the chenyulan river watershed in central taiwan was chosen for evaluating the impact of the chi chi earthquake on the occurrence of landslides and for exploring the initial conditions triggering debris flows interpretations of aerial photographs and spot images as well as field investigations were used to identify landslide and debris flow occurrences precipitation data were then utilized to investigate critical conditions leading to the debris flow comparison of five spot images taken between june 1996 before the july 1996 typhoon herb and september 1999 before the chi chi earthquake shows that the landslide area increased from 7 1 106 to 7 5 106 m2 during that time however by january 2000 after the chi chi earthquake the landslide area almost tripled to 20 8 106 m2 measurement of images taken in march and august 2001 reveals that the landslide area had further expanded to 24 2 106 and 27 5 106 m2 respectively significant differences before and after the earthquake are also noticed in 1 the intensity and amount of precipitation required for triggering debris flow 2 the size of contributing drainage basin in which debris flows occurred and 3 the frequency of debris flows after the chi chi earthquake maximum hourly rainfall intensity and critical accumulated precipitation necessary to initiate debris flow reduced to as low as 1 3 of the pre earthquake figures prior to the chi chi earthquake most debris flows occurred in gullies with slopes greater than 10 and in drainage basins larger than 0 1 km2 conversely after the earthquake debris flows were observed even in gullies with effective drainage area smaller than 0 03 km2 furthermore before the earthquake the debris flow recurrence time in the study area was greater than 5 years whereas six debris flow events have been observed in the 2 years since the earthquake

a method for evaluating the stability of an unsaturated slope in natural terrain during rainfall abstract the stability of an unsaturated slope in natural terrain was evaluated based on the variation in the suction stress in the soil layer induced by rainfall a field monitoring site where landslides have occurred in the past was selected as the study area to apply the concept of slope stability analysis considering the suction stress in unsaturated soil the soil water characteristic curve swcc and the suction stress characteristic curve sscc of the unsaturated soil obtained from the study area were estimated using the van genuchten 1980 model and the lu and likos 2006 model respectively the phenomenon of ground saturation induced by the infiltration of rainfall into unsaturated soil is similar to the wetting path of the swcc the curve fit parameters estimated from the swcc wetting path were therefore used to determine the matric suction and suction stress in the unsaturated soil the amount of rainfall and the volumetric water content of the soil were measured using a rain gauge and time domain reflectometer tdr sensors respectively at the monitoring site an infinite slope was chosen as representative of the slope of the natural terrain in the study area because the slope length is very long but the depth of the soil layer over the rock is very shallow the stability of this unsaturated slope in natural terrain was evaluated based on the safety factor of an infinite slope considering the suction stress in the unsaturated soil layer the safety factor of the slope suddenly decreased during and just after a rainfall and then recovered notably the safety factor of this natural slope exhibited continuous fluctuations because of changes in the suction stress caused by the evaporation and infiltration of water in the unsaturated soil layer the variation in the suction stress in unsaturated soil induced by rainfall can be estimated from the results of laboratory tests performed to estimate the wetting process based on the swcc and sscc in combination with field monitoring data collected by sensors to measure the volumetric water content or matric suction in the soil therefore the infinite slope stability of a slope in natural terrain can be evaluated in real time by estimating the suction stress in the unsaturated soil due to rainfall when the volumetric water content or matric suction in the soil is being monitored in the field

landslides associated with the may 12 2008 wenchuan earthquake implications for the erosion and tectonic evolution of the longmen shan abstract satellite images and aerial photography following the wenchuan earthquake show that a broad area experienced severe landsliding in association with the main earthquake and aftershocks a zone of high density landsliding 10 landslide surface area affected stretches for 240 km along the earthquake region in proximity to the yingxiu beichuan and pennguan faults which ruptured during the earthquake the width of this severe landsliding zone varies along the strike from 25 30 km wide in the southwestern section of the earthquake region to 3 5 in the northeastern section these variations coincide with differences in hillslope gradients bedrock lithologies co seismic slip and ground shaking observed in these sections of the earthquake region in general there is good correlation between the magnitude and distribution of ground shaking experienced during the earthquake and mapped landslide density though limited data and varying fault models prevent any in depth comparison with high resolution maps of ground shaking experienced landslides associated with wenchuan earthquake highlight interesting aspects of erosion and tectonic evolution of the longmen shan short term erosion rates in the longmen shan region measured from cosmogenic nuclides prior to the earthquake were 0 2 0 3 mm yr reflecting the last 2000 3000 years a time period shorter than the estimated recurrence interval of large earthquakes along the fault that ruptured while long term erosion rates measured by low temperature thermochronology were higher 0 5 0 7 mm yr for the last 8 10 ma integrating the total amount of erosion associated the earthquake into the short term erosion rate estimates pushes the rate much higher this suggests that the earthquake and associated landslide erosion was necessary for the landscape to catch up and balance the long term tectonic growth of the longmen shan particularly in the southwestern section of the earthquake region taken together the earthquake and associated landslide erosion can be seen as the most recent expression of the rapid deformation uplift and erosion that previous geomorphic evidence and geodynamic models had argued for along longmen shan front

strain partitioning during partial melting and crystallizing felsic magmas abstract the rheology of partly molten felsic systems changes dramatically during the onset of melting and through crystallization solid to liquid and liquid to solid transitions are not rheologically identical contradicting the concept of a unique rheological critical melt percentage we use four thresholds separating the successive stages according to the melt fraction for the melting transition 1 the liquid percolation threshold connects the melt pockets at about 8 of melt thus allowing local magma displacement at the metric scale and 2 for greater melt percentages 20 25 a melt escape threshold corresponds to the onset of transport over large distances of the melt and part of the residual solid phase leading ultimately to granitic bodies for the solidification transition 3 the first formation of a rigid framework of crystals which can accumulate stress although the melt can still flow corresponds to the rigid percolation threshold 55 solids and 4 the system becomes totally locked at about 72 75 solid which corresponds to the particle locking threshold the present paper focuses on strain partitioning induced by the coexistence of two contrasting rheological phases between these thresholds on a variety of scales non coaxial deformation is preferentially accommodated by the lower viscosity melt which increases the vorticity in the melt phase and reinforces asymmetries in the flow pattern strain partitioning also increases the scale length of the weakest phase during melting and magma ascent whereas strain partitioning decreases the scale length during crystallizing strain partitioning also affects the migration of melt by raising the particle locking threshold and lowering the melt escape threshold for three dimensional deformations such as transpression the direction of melt segregation e g horizontal may differ from the direction of melt migration e g vertical

experimental study of dynamic bending failure of laurentian granite loading rate and pre load effects in deep underground rock engineering projects rocks are under static pre load and they may further experience dynamic load due to earthquakes or production blasts it is thus desirable to consider

processes leading to eclogitization densification of subducted and tectonically buried crust 1 the transformation of subducted and tectonically buried crustal rocks to denser eclogite plays a fundamental role in the dynamics of mountain building and crustal recycling however a complex of partially eclogitized granulites on the island of holsnoy in the western part of the norwegian caledonides reveals that such densification depends in part on the antecedent history of rock masses and that large bodies of untransformed rock can persist metastably even after long residence times in the lower crust the rocks on holsnoy suggest that conversion to eclogite was delayed until lower or subcrustal seismic events allowed aqueous fluids to enter the previously dry and unusually strong granulite complex metamorphism then occurred in a spatially heterogeneous manner with several distinct physical processes involving feedbacks between deformation fluid infiltration and chemical reactions operating simultaneously in different parts of the rock mass field relations show that the introduction of fluids and conversion to eclogite significantly weakened the rocks a reservoir flux systems model is used to represent the various processes contributing to eclogitization of the granulites which operated at vastly different rates over disparate intervals of time the model suggests that the metamorphic process may have been brief 1 myr and ultimately self limiting arrested by the change in rheology associated with the conversion of brittle granulite to ductile eclogite

unsaturated hydro mechanical behaviour of rainfall induced mass remobilization in post earthquake landslides abstract clarifying the hydro mechanical characteristics of the mechanism associated with mass remobilization is a major step towards landslide early warning but this clarification is usually hampered by a lack of in situ evidence in this study shallow rainfall triggered slope failures under partially saturated conditions were documented by combining instrumental evidence from field experiments on a natural co seismic landslide and hydro mechanical slope stability analysis in an earthquake affected region the results revealed the transient processes and unsaturated conditions associated with mass movement in response to rainfall and preferential flow paths were found to dominate the hydrological processes during rainfall infiltration in the landslide deposit the results also demonstrated the importance of certain hydrological parameters including soil matric suction and moisture content in landslide early warning this study reveals a partially saturated hydro mechanical behaviour to predict the initiation of rainfall induced landslides during post earthquake disaster relief

landslide hazard assessment of the 2008 wenchuan earthquake a case study in beichuan area the wenchuan earthquake magnitude ms 8 0 of 12 may 2008 triggered widespread and large scale landslides over an area of about 50 000 km2 a study was undertaken to determine the primary factors associated with seismic landslide occurrence an index based approach used to assess earthquake triggered landslide hazard in the central part of the wenchuan earthquake area affected is described slope gradient relief amplitude lithology bedding slope relations fault proximity stream proximity and antecedent rainfall are recognized as factors that may have had an important influence on landslide occurrence the assessment of the influence of each of these factors is presented through use of a series of maps showing areas of low moderate high and very high landslide hazard areas identified as having very high and high landslide hazard were located along the earthquake source fault and along both banks of the jian river the role of rainfall is very significant for future landslide occurrence in the

landslides triggered by the 8 october 2005 kashmir earthquake abstract the 8 october 2005 kashmir earthquake triggered several thousand landslides these were mainly rock falls and debris falls although translational rock and debris slides also occurred in addition a sturzstrom debris avalanche comprising 80 million m3 buried four villages and blocked streams to create two lakes although landsliding occurred throughout the region covering an area of 7500 km2 the failures were highly concentrated associated with six geomorphic geologic anthropogenic settings including natural failures in 1 highly fractured carbonate rocks comprising the lowest beds in the hanging wall of the likely earthquake fault 2 tertiary siliciclastic rocks along antecedent drainages that traverse the hazara kashmir syntaxis 3 steep 50 slopes comprising precambrian and lower paleozoic rocks 4 very steep 50 lower slopes of fluvially undercut quaternary valley fills and 5 ridges and spur crests the sixth setting was associated with road construction extensive fissuring in many of the valley slopes together with the freshly mobilized landslide debris constitutes a potential hazard in the coming snowmelt and monsoon seasons this study supports the view that earthquake triggered landslides are highly concentrated in specific zones associated with the lithology structure geomorphology topography and human presence

structural development and petrofabrics of eclogite facies shear zones bergen arcs western norway implications for deep crustal deformational processes caledonian eclogite facies shear zones developed from grenvillian garnet granulite facies anorthosites and gabbros in the bergen arcs of western norway allow direct investigation of the relations between macroscopic structures and crystallographic preferred orientation cpo in lower continental crust field relations on the island of holsnoy show that the eclogites formed locally from granulite facies rocks by progressive development of 1 eclogite adjacent to fractures 2 eclogite in discrete shear zones 2 m thick 3 eclogite breccia consisting of 80 well foliated eclogite that wraps around rotated granulite blocks and 4 anastomosing subparallel eclogite facies shear zones 30 100 m thick continuous over distances 1 km within the granulite terrane these shear zones deformed under eclogite facies conditions at an estimated temperature of 670 50 c and a minimum pressure of 1460 mpa which corresponds to depths of 55 km in the continental crust detailed investigation of the major shear zones shows the development of a strong foliation defined by the shape preferred orientation of omphacite and by alternating segregations of omphacite garnet rich and kyanite zoisite rich layers a consistent lineation throughout the shear zones is defined by elongate aggregates of garnet and omphacite the cpo of omphacite determined from five axis universal stage measurements shows a strong b axis maximum normal to foliation and a c axis girdle within the foliation plane with weak maxima parallel to the lineation direction these patterns are consistent with deformation of omphacite by slip parallel to 001 and suggest glide along 010 the lineation and cpo data reveal a consistent sense of shear zone movement although the displacement was small localized faulting of high grade rocks accompanied by fluid infiltration can be an important mode of failure in the lower continental crust field relations show that granulite facies rocks can exist in a metastable state under eclogite facies conditions and imply that the lower crust can host differing metamorphic facies at the same depth deformation of granulite and partial conversion to eclogite such as is exposed on holsnoy island may be an orogenic scale process in the lowermost crust of collisional orogens

triggering mechanism and reactivation probability of loess mudstone landslides induced by rainfall infiltration a case study in qinghai province northwestern china rainfall especially rainstorm is a major factor in inducing loess mudstone landslides and plays an essential role in landslide reactivation the aim of the paper is to study the triggering mechanism and reactivation probability of a loess mudstone landslide induced by rainfall infiltration in qinghai province northwestern china according to the numerical model of elastic plastic mechanics the triggering mechanism of loess mudstone landslides was revealed then the reactivation probability of the potential landslide was evaluated by the combination of the limit equilibrium and monte carlo methods for one thing the relationship between water content and shear strength of media was analyzed based on the mechanical test of materials for another the effects of rainfall conditions were analyzed on the distribution of water content in the aerated zone with the two dimensional coupling model of unsaturated saturated seepage the results show that the shear strength of media is very sensitive to water content because of water rock interaction including hydration and dissolution besides the water content significantly increases at the interface between the loess and mudstone after the rainstorm occurring owing to the permeability heterogeneous of media and topographic feature which leads to the strength deterioration although the whole landslide is stable in the rainstorm conditions its middle part can be reactivated along the original sliding zone with high probability by a geomechanical model of sliding tension therefore the landslide reactivation is controlled by the water sensitivity of media the permeability heterogeneous of media the topographic feature and the original sliding zone especially the original sliding zone this research provides a valuable reference for the occurrence and reactivation of similar landslides

subducting oceanic crust on the philippine sea plate in southwest japan abstract it is well known that subcrustal earthquakes occur in southwest japan owing to subduction of the philippine sea phs plate observing the earthquakes at a single station in the chugoku district we frequently find a distinct pair of later p and s phases after weak initial p and s phases respectively these later phases were observed only for earthquakes with particular source receiver geometries the events in the west seto inland sea epicentral distances from 120 km to 240 km and the source receiver direction almost parallel to the strike of the nankai trough the feature of initial and later phases was summarized as follows 1 the later phases are observed for subcrustal earthquakes occurring at depths between 40 km and 60 km but not for those below the depth 2 single station apparent velocities of initial p and s phases are 8 0 km s and 4 9 km s and they are somewhat higher than ordinary velocities of the uppermost mantle 3 single station apparent velocities of later p and s phases are on the other hand 6 6 km s and 3 8 km s and they are comparable to the velocities of the continental lower crust and the main layer of oceanic crust these features could not be explained unless the subcrustal earthquakes take place within the low velocity oceanic crust overlying the high velocity oceanic plate this suggests that the oceanic crust subducts beneath the west seto inland sea as a part of the phs plate

timescales and mechanisms of fluid infiltration in a marble an ion microprobe study using a recently developed ion microprobe technique a detailed oxygen isotope map of calcite grains in a coarse grained marble has been constructed supported by trace element mn sr fe analysis and cathodoluminescence cl imaging in order to constrain scales of oxygen isotope equilibrium timescales and mechanisms of metamorphic fluid infiltration and fluid sources and pathways results are compared with a previous study of this sample wada 1988 carried out using a cryo microtome technique and conventional oxygen isotope analysis the marble from the high temperature low pressure hida metamorphic belt in north central japan underwent granulite facies followed by amphibolite facies metamorphic events the latter associated with regional granite intrusion the cl imaging indicates two types of calcite a yellow luminescing ylc and a purple luminescing plc variety the ylc which occupies grain boundaries fractures replacement patches and most of the abundant deformation twin lamellae post dates the dominant plc calcite and maps out fluid pathways systematic relationships were established between oxygen isotope and trace element composition calcite type and texture based on 74 18o 16o and 17 trace element analyses with 20 30 m spatial resolution the ylc is enriched in mn and fe and depleted in 18o and sr compared to plc and is much more 18o depleted than is indicated from conventional analyses results are interpreted to indicate infiltration of 18o depleted metamorphic or magmatic fluid initial 18o 9 10 5 along grain boundaries fractures and deformation twin lamellae depleting calcite grains in sr and enriching them in mn and fe the sample is characterised by gross isotopic and elemental disequilibrium with important implications for the application of chromatographic theory to constrain fluid fluxes in metacarbonate rocks

the characteristics of the landslides triggered by the wenchuan ms 8 0 earthquake from anxian to beichuan abstract this paper presents a quantitative analysis of the number and area of the landslides triggered by the wenchuan ms 8 0 earthquake from anxian to beichuan in this study the controlling factors of landslides are obtained from geological maps relief amplitude slope and topographic roughness calculated from dem data in arcgis 9 2 a total of 4134 landslides are identified from digital aero image of 1 m resolution covering 19 7 km2 that accounts for 6 4 of the study area the number of landslides with areas less than 5000 m2 is up to 85 22 the smallest landslide is 6 m2 and the largest 1515 000 m2 the number of landslides which have occurred is 1 6 times more prevalent at hanging walls as opposed to foot walls also the relationship between the numbers of landslides and the distances to an earthquake rupture at a hanging wall is linear but exponential at a footwall these results prove that landslide activity is more severe at hanging walls than at foot walls the outcrop area of geologic unit is proportional to the number of landslides except the jurassic triassic and quaternary units r2 0 952 in the study area and landslide density is 19 meanwhile the area of a landslide is linearly proportional to outcrop area of geologic unit except jurassic lower cambrian and quaternary unit r2 0 8279 in the study area and appear to indicate that the lithology does not play an important role in landslides in the study area earthquake triggered landslides tend to be concentrated in specific zones associated with the event controlling parameters such as reliefs slopes and topographic roughness the landslides occurred particularly in the range of 600 1293 m relief amplitudes and the number in this range amounts to 90 of total slides in the studied region moreover landslides easily occurred in the curvature 1 15 with slope between 5 and 55 in addition landslides also usually occurred in the range of 1 1 5 topographic roughness therefore these correlations provide a way to assess regional landslide hazards and are of great significance to regional geohazard planning and prediction

earthquakes in the ductile regime pseudotachylytes from a crustal scale shear zone in central australia have developed in a cyclical manner once developed an individual pseudotachylyte is deformed in a ductile manner only to be overprinted at a later stage by a new generation of pseudotachylytes such cyclic generation and deformation of pseudotachylyte has been interpreted in the past as representing conditions at the brittleductile transition a different interpretation however is presented here it is proposed that psuedotachylytes and associated ultramylonites can develop entirely within the ductile regime as ductile instabilities such instabilities are different in nature to those previously discussed at length in the geophysical literature but are identical in principle with the instabilities that develop for velocity weakening frictional behavior in spring slider systems at a given strain rate a critical temperature tc is defined at which the transient work hardening equals the product of stress relaxation due to a thermal fluctuation and the heat generated by shearing a necessary condition for ductile instability at a given strain rate is that the temperature is belowtc then the rate of change of stress with respect to strain is negative an additional requirement is that this rate of change exceeds in magnitude the effective elastic stiffness of the loading system ductile instabilities are marginally possible at geological strain rates in quartzites but are possible at mid crustal temperatures in other rock types on the basis of these observations a new interpretation is presented for the base of the seismogenic zone in crustal regions

an objective method to rank the importance of the factors predisposing to landslides with the gis methodology application to an area of the apennines valnerina perugia italy the present work aims at contributing to further our knowledge on the predisposing factors to landslides as well as proposing a method that allows us to weigh up as objectively as possible the influence that the various factors have on landslides in order to construct a realistic map of potential landslide hazards in order to assess the differential incidence of very predisposing factor to landslides maps of the various factors considered were drawn up with the aid of idrisi software 1997 the factors were as follows the distance from faults parallelism between the fractures and the landslide scarps land use lithology distance from the streams orientation and steepness of slopes orientation of layers compared to the slope the global analysis of the different incidence of the factors analyzed on the landslides present in the study area was carried out by comparing the respective maps with that of the scarps in this way the number of pixels forming the scarps which fell into the various classes of the maps was calculated the result thus obtained can form the basis of an objective assignation of the different ratings to be attributed to the various factors under consideration in fact the analysis carried out in this study has shown that the factors act differently and for every factor only some of the classes considered have marked importance

evaluation of landslide mechanisms characterized by high speed mass ejection and long run out based on events following the wenchuan earthquake abstract in the 2008 wenchuan earthquake the mass ejection type of high speed and long run out landslide was an unusual hazard characterized by its dramatic phenomenon of a huge slope mass launching into the air and becoming airborne for a long distance quantitative and qualitative combined techniques were applied to reveal the formation mechanism of this type of landslide four prerequisites critical to form mass ejection are identified high position of the toe of the surface of rupture critical height and critical inclination of slope sufficient open space in the movement direction and adequate take off speed of ski jump like mass ejection these four area specific prerequisites provide a promising approach for screening and targeting the potential landslides subsequently a dynamic reliability analysis method that considers the feature of energy time distribution is proposed this site specific method provides a more credible evaluation by emphasizing the most significant period within the whole earthquake duration finally an aerodynamic inverse method combined with an energy conservation based method is applied in the quantitative evaluation to calculate take off speed of mass ejection this paper provides a viable solution for regional screening and site assessment for new potential targets of this type of landslide

low effective viscosity during high pressure metamorphism due to dissolution precipitation creep the record of hp lt metamorphic carbonates and siliciclastic rocks from crete the micro structural record of high pressure low temperature hp lt metamorphic rocks t 400 50 c p 10 2 kbar of the phyllite quartzite unit in western crete greece is interpreted in terms of deformation mechanisms and flow stress phyllites were deformed at low stress by dissolution precipitation creep governed by strongly enhanced dissolution along quartz mica 001 phase boundaries quartzites and quartz veins were deformed by dislocation creep at higher flow stress the contrasting effective viscosities caused stress concentration in the quartzites and quartz veins also microstructures from aragonite marbles indicate that dissolution precipitation creep was the dominant deformation mechanism and that dislocation creep has not been activated in these rocks pervasive ductile deformation was restricted to hp lt metamorphic conditions and the microstructural record of deformation at maximum depth has been preserved with all subsequent deformation localized and confined to the brittle field constraints on the timing of deformation allow an estimation of strain rates experimentally determined flow laws for dislocation creep are used to pose upper bounds on flow stress and bulk viscosities of rocks deformed by dissolution precipitation creep for the phyllites a conservative estimate is about 1019 pa s or below in contrast to 1020 pa s derived for the quartzites this compares well to the viscosity contrast of 1 2 orders of magnitude reflected by the mesoscopic structures since phyllites and carbonate rocks form large portions of the subducted sedimentary pile the low flow stress during rapid deformation of these rocks at hp lt metamorphic conditions and the lack of deformation along the burial and exhumation path imply very low strength of the plate boundary shear zones and negligible shear heating

temporal and tectonic evolution of the granulite eclogite association from the bergen arcs western norway the u pb and sm nd dating of deep crustal rocks from the bergen arcs system helps resolve enigmatic aspects of the tectonic evolution of the caledonian orogen in western norway and yields insights into the arrested stages of eclogite development within the granulites of the area the u pb dating of zircon from one of the eclogite facies shear zones yields an upper intercept age of 945 5 ma all errors two standard deviations 2 which is similar to other zircon ages from the granulite facies protolith the age is interpreted to represent the time of late proterozoic sveconorwegian granulite metamorphism the u pb ages of sphene and epidote show that the eclogites formed early in the evolution of the caledonian orogen pre scandian phase at about 460 ma an eclogite facies quartz vein yields a sm nd whole rock garnet isochron of 440 12 ma that may reflect the onset of cooling immediately after peak eclogite facies conditions although the sm nd systematics reveal some isotopic disequilibrium within the sample in tandem with previous 40ar39ar age determinations from an adjacent eclogite of 450 ma for hornblende and 430 ma for muscovite these data indicate that 30 ma elapsed between formation of the eclogites and the initial stages of cooling and exhumation to at least mid crustal levels this corresponds to minimum cooling rates of 14 c m y the timing relations suggest that the formation and exhumation of these eclogites from the overlying caledonian nappe wedge in western norway are related to an early phase of crustal subduction during or somewhat before the major phase of continent continent collision the short period of time between the formation of the eclogites and the initial stages of exhumation and rapid cooling is consistent with the only partial and localized transformation of the granulite to eclogite isolated occurrences of eclogite within the granulite the formation of eclogite along metasomatic fronts and the formation of hydrous eclogite facies minerals within the dry granulite all point to the importance of fluids in the transformation and re equilibration of the granulite to eclogite together field and isotopic data demonstrate that both the localized and limited access of fluids and the rapid cycling of continental crust through the deepest portions of the orogen to upper crustal levels resulted in the preservation of the arrested stages of eclogite formation and survival of the granulites metastably through eclogite facies conditions

gis based landslide susceptibility for arsin yomra trabzon north turkey region the purpose of this study is to assess the susceptibility of landslides around yomra and arsin towns near trabzon in northeast of turkey using a geographical information system gis landslide inventory of the area was made by detailed field surveys and the analyses of the topographical map the landslide triggering factors are considered to be slope angle slope aspect distance from drainage distance from roads and the weathered lithological units which were called as geotechnical units in the study idrisi and arcgis packages manipulated all the collected data logistic regression lr and weighted linear combination wlc statistical methods were used to create a landslide susceptibility map for the study area the results were assessed within the scope of two different points a effectiveness of the methods used and b effectiveness of the environmental casual parameters influencing the landslides the results showed that the wlc model is more suitable than the lr model regarding the casual parameters geotechnical units and slopes were found to be the most important variables for estimating the landslide susceptibility in the study area

high temperature rheology of enstatite implications for creep in the mantle high temperature deformation experiments have been performed on oriented single crystals of enstatite at 1 atm under controlled conditions of oxygen fugacity and silica activity the results indicate that creep on the weakest high temperature slip system in enstatite within the protoenstatite stability field is independent of oxygen fugacity and obeys a power law relation with a stress exponent of n 3 8 0 5 and activation energy of q 820 80 kj mol a decrease in creep rate with increasing aluminum and iron content suggests that aluminum or iron ions play an active role in maintaining charge neutrality within the crystals the single crystal strengths are greater than those reported for polycrystalline enstatite deforming predominantly on the same slip system suggesting that the polycrystalline samples may have been water weakened a comparison of the single crystal results with those for olivine deformed at 1 atm indicates that enstatite is probably stronger than olivine under upper mantle conditions unless the presence of water results in a greater weakening of enstatite than olivine

fracture geometry of pseudotachylyte generation zones a study of shear fractures formed during seismic events abstract the orientation and movement sense of shear fractures in pseudotachylyte generation zones developed in the ikertoq shear belt west greenland are described and the fracturing sequence is inferred the generation zones occur in strongly foliated gneisses and consist of concordant usually paired principal displacement shear fractures paired shears on which most melt was generated and a system of minor shear fractures minor shear fracturing was most intense between principal displacement shear fractures and most melt intruded from these paired shears inwards with respect to the zone intrusion of injection veins of pseudotachylyte off the principal displacement shear fractures is believed to be contemporaneous with minor shear fracturing in the generation zones generation zones affect intact rocks and individual principal displacement shear fractures have a maximum displacement of 4 6 m paired principal displacement shear fractures are up to 3 m apart and have a maximum observed length of 1 km in all the zones described the fracturing appears to be the result of a single episode of slip both dextral and sinistral generation zones occur within the study area and have different geometries in each case the displacement is strike slip

seismic waves guided by untransformed oceanic crust subducting into the mantle the case of the kanto district central japan a model of the subduction of oceanic crust is established through an analysis of the upper mantle earthquakes occurring beneath the kanto district central japan a distinct pair of later p and s phases xp and xs commonly observed at specific stations for these events in a depth range of 40 60 km and is considered to take place in association with the subducting motion of the philippine sea plate the xp phase is found from its particle motions to be a longitudinal seismic wave a principal component analysis of wavelets including the initial p and the xp phases shows that the latter arrives at the earth s surface with a slightly shallower angle relative to the former close agreement between the relative arrival time ratio of xs s xp p and the vp vs ratio of crustal or mantle rocks suggests that both xp and xs travel along the same path as longitudinal and tangential waves respectively one can clearly observe these later phases at stations located where the upper surface of the philippine sea plate is apparently in direct contact with the bottom of the crust of the honshu island apparent velocities of the xp and the xs phases are comparable to the seismic velocities of the main layer of the oceanic crust or the lower continental crust which are never expected for an upper mantle earthquake if the velocity structure is laterally homogeneous travel time curves for several earthquakes indicate that these apparent velocities can be directly related to the seismic velocity in the source region the hypocentral distribution of the events related to the subducting motion of the philippine sea plate does not form such a thin seismic zone as observed in southwest japan but extends over the entire thickness of the philippine sea plate the earthquakes from which the later phases are observed occur only in a shallower portion of this thick and contorted seismic zone the deeper portion does not generate such events these characteristics are best explained if these later phases are regarded as the seismic waves guided by the subducted portion of the gabbroic oceanic crust at the top of the philippine sea plate taking the result of our earlier work into account we conclude that the subducting oceanic crust remains in a gabbroic phase without transformation to eclogitic rocks at depths down to about 60 km along the entire northern boundary of the philippine sea plate

relationships among three repeated large scale debris flows at pubugou ravine in the wenchuan earthquake zone the 12 may 2008 wenchuan earthquake in china triggered numerous landslides loose landslide materials can easily evolve into deadly debris flows during wet seasons during the period from 2008 to 2011 three separate large scale debris flows occurred in the pubugou ravine near the epicentre of the earthquake that were among the largest repeated debris flows ever reported approximately 1 76 106 m3 of sediment was deposited during these three events this paper aims to i analyze the movements of solid materials during the repeated debris flows ii discuss the evolution of the initiation mechanisms of these debris flows and iii evaluate the changing depositional morphology of the debris flow fans and examine the particle sizes of the debris flow materials to achieve the above research objectives timely field investigations were undertaken in the past 5 years after each of these debris flow events satellite images were used to delineate the boundaries of the initiation areas the transportation c

aggregate properties of fracture populations abstract empirical studies indicate that the individual attributes of both faults and extension fractures follow power law scaling aggregate properties of fracture populations are important in a variety of problems and can be specified in terms of the scaling parameters of individual fracture attributes development of an expression for an aggregate property requires consideration of a number of independent factors including the topologic dimension of the aggregate property the topologic dimension of sampling and the possibility of scaling changes for fractures that span some mechanically significant layer the riemann zeta function provides an alternative to integration for the analytical and numerical solution of aggregate problems previous work regarding aggregate properties of fracture populations has focused on the strain due to faulting new expressions are developed here for other aggregate properties of interest fracture surface area fracture porosity fracture permeability and shear wave anisotropy a general characteristic of these aggregate properties is that for most values of scaling exponents the aggregate properties are dependent on the size of the sampling domain this implies that the aggregate properties are scale dependent additionally it appears that fracture surface area is concentrated in the smallest fractures of many populations fracture porosity is concentrated in the largest fractures of most populations but not as strongly as fracture permeability which probably derives almost entirely from the largest fractures in populations

landslides triggered by the avaj iran earthquake of june 22 2002 abstract the 2002 avaj iran earthquake mw 6 5 triggered many landslides over an area of about 3600 km 2 in this paper we describe a ground based field study conducted during several days immediately after the earthquake and pre and post earthquake landslide inventory maps that were prepared the landslides due to earthquake include 47 fall and topple zones 9 slides and 3 lateral spreads the largest slide is a rockslide 150 100 m which occurred southeast of the village of changureh the main results of this study are the density of earthquake triggered landslides decreases away from the fault zone in a manner that is asymmetric with respect to direction although several slides and lateral spreads were seen the most common types of triggered landslides are falls and topples the area throughout which landslides occurred and maximum epicentral and fault zone distances of landslides are comparable to similar data from other historical earthquakes landslides mostly occurred in the most susceptible geologic units in which there were many landslides before the earthquake new disrupted slides and falls generally occurred in ancient fall zones but no information about reactivation of coherent slides is available

coseismic reverse and oblique slip surface faulting generated by the 2008 mw 7 9 wenchuan earthquake china the mw 7 9 wenchuan china earthquake ruptured two large thrust faults along the long menshan thrust belt at the eastern margin of the tibetan plateau this earthquake generated a 240 km long surface rupture zone along the beichuan fault and an additional 72 km long surface rupture zone along the pengguan fault maximum vertical and horizontal offsets of 6 5 m and 4 9 m respectively were measured along the beichuan fault a maximum vertical offset of 3 5 m was measured along the pengguan fault coseismic surface ruptures integrated with aftershocks and industry seismic profiles show that two imbricate structures have ruptured simultaneously resulting in the largest continental thrust event ever documented large oblique thrusting observed during this earthquake indicates that crustal shortening is an important process responsible for the high topography in the region as everywhere along the edge of tibetan plateau

catastrophic debris flows on 13 august 2010 in the qingping area southwestern china the combined effects of a strong earthquake and subsequent rainstorms in the wenchuan area in sw china an abundance of loose co seismic landslide debris was present on the slopes after the wenchuan earthquake which in later years served as source material for rainfall induced debris flows or shallow landslides slopes composed of cambrian sandstones and siltstones intercalated with slates appeared to be most susceptible to co seismic landsliding a total of 20 debris flows are described in this paper all were triggered by heavy rainfall on 13th of august 2010 field reconnaissance and measurements supported by aerial photo interpretation were conducted to identify the locations and morphological characteristics of the debris flow gullies in order to obtain information about surface area and volume of landslides and the debris flows the debris flows in the study area were initiated by two processes a run off erosion on co seismic landslide material and concentrated erosion of landslide debris in steep channels b new landslides that transform into debris flows the volume of debris flow deposits on individual fans varies by many orders of magnitude the smallest deposit has a volume of from 5760 to 3 1 million m3 a comparison of the measured volumes deposited on the fan with the volumes of debris stored in the catchment shows the huge potential for future debris flow activity whilst there is a weakly significant positive correlation between these two volumes no significant statistical correlation could be established between volumes of debris flow deposits and other morphometric parameters of the catchment a catastrophic debris flow catchment the wenjia catchment was selected as an extreme case to show in detail the mechanism of debris flow formation as a result of intensive erosion in loose material which was deposited by a rock avalanche during the 2008 earthquake event analyses of the meteorological conditions that triggered these debris flows show one day antecedent precipitation varying between 67 7 and 137 6 mm with a mean rainfall intensity of about 7 3 to 22 5 mm h a rainfall event with peak intensity of 38 7 mm h triggered the largest debris flow event rainfall data related to five debris flow events in the wenjia torrent was used to establish a primary rainfall intensity duration relationship for the triggering of debris flows which was compared to other rainfall duration thresholds from other parts of the world in the discussion emphasis is laid on the need to unravel the process mechanisms which initiated the debris flows for a better understanding and assessment of meteorological thresholds

flume tests to study the initiation of huge debris flows after the wenchuan earthquake in s w china abstract in the wenchuan area in the southwest of china a huge amount of loose co seismic landslide material was deposited on slopes during the wenchuan earthquake of may 2008 these loose deposits formed the source material for rainfall induced debris flows or shallow landslides in the years after the earthquake on august 13 2010 about 20 large debris flows were triggered by heavy rainfall in the area around the epicenter of the wenchuan earthquake field reconnaissance revealed that the initiation of these post earthquake debris flows was closely related to severe erosion of the loose deposits flume tests were carried out to study the initiation mechanism of these post earthquake debris flows and the related influencing factors the flume was instrumented with ten combination sets of suction and pore pressure sensors these sensors were accompanied by tdr probes to measure the soil water content the flume has a length of 2 5 m and a width of 1 5 m a series of 26 tests was conducted to study the influence of slope gradient and discharge on the initiation mechanism and scale of the debris flows the amount of debris flow discharge was obtained by collecting the washed out deposits every 20 s the experimental results showed that the initiation mechanism of debris flows for gentle slopes and steep slopes was different on steeper slope incision by run off water was very rapid initiating directly the start of a debris flow the debris flow volume increased rapidly by a chain of subsequent cascading processes starting with collapses of the side walls damming and breaching leading to a rapid widening of the erosion channel at gentler slopes less intensive run off incision caused an accumulation of material down slope which after saturation failed as shallow slides transform in a second stage into debris flows it was demonstrated that the slope was the dominant factor in controlling the scale of the debris flows while the effect of discharge on erosion and the size of the debris flows was less clear

the significance of grain scale stresses in the kinetics of metamorphism during metamorphism phases grow and dissolve dominantly along grain boundaries bulk diffusion models for the development of metamorphic textures often assume that diffusion is homogeneous in regions of each phase rather than being localised along phase boundaries under isotropic stress chemical potentials of components involved in reactions are likely to be buffered along grain boundaries between phases thus inhibiting diffusion and growth motive forces must exist which overcome this and it is proposed here that local heterogeneous stresses will be important a mathematical theory for stress controlled growth is derived this theory predicts that the growth rates of two phases along their mutual interface will be linked in a quantifiable way it forms a basis for considering the important effects of stresses induced by local volumetric changes during metamorphism and it provides a link between these effects and those related to pressure solution in deforming rocks

impacts of the chi chi earthquake on subsequent rainfall induced landslides in central taiwan abstract the influence of the chi chi earthquake on subsequent rainfall induced landslides was evaluated by comparing the occurrence of landslides in the choushui river watershed through eight spot images that covered the period from 1996 to 2001 the chi chi earthquake not only triggered serious coseismic landslides itself but also extensively disturbed surface strata around the epicentral area after surface strata have been highly disturbed heavy rainfalls in 2000 and 2001 have triggered more landslides than the earthquake itself compared with the data obtained from images before the earthquake it is obvious that the density of rainfall induced landslides increased significantly after the earthquake and the places where landslides occurred changed as well although typhoon herb in 1996 brought more precipitation than typhoon toraji in 2001 only 9 77 km 2 landslides were induced by herb while 48 8 km 2 landslides almost five times larger than those caused by herb were triggered by toraji besides landslides induced by herb were mainly distributed in mid slope areas with slopes of 20 30 after the chi chi earthquake the rainfall induced landslides occurred mainly in places with slopes between 40 and 50

strength of slightly serpentinized peridotites implications for the tectonics of oceanic lithosphere we deformed cores of peridotite with 10 15 lizardite and chrysotile serpentine to determine the influence of serpentine content on the strength and the style of deformation the strength the pressure dependence of strength and the nominally nondilatant mode of brittle deformation of slightly serpentinized peridotites are comparable to those of pure serpentinites these results indicate that deformation is accommodated primarily by serpentine while olivine despite being the more abundant component remains nominally undeformed on the basis of these data and previous work we determine that the transition from a strong dilatant dunite rheology to a weak nondilatant serpentinite rheology is not a linear function of the degree of serpentinization instead an abrupt transition in strength is observed at low degrees of serpentinization the pressure of the transition from localized to distributed deformation also decreases abruptly from 1000 mpa to 150 350 mpa the change in rheological behavior occurs at a serpentine content of 10 15 or less which corresponds to published compressional seismic velocity of 7 8 7 5 km s at a pressure of 200 mpa the seismic velocity of the oceanic lithosphere particularly of that formed at slow spreading ridges can thus provide constraints on its mechanical properties at depth because slightly serpentinized peridotites have a rheology similar to that of pure serpentinite significant lithospheric weakening may occur after the onset of alteration near or at the ridge axis

shear deformation and eclogite formation within granulite facies anorthosites of the bergen arcs western norway the anorthosites of the bergen arcs contain two distinct metamorphic mineral assemblages which are stable under different p t conditions a granulite facies assemblage which equilibrated at t 800 900 c p 10 kbar is defined by the minerals plagioclase al rich diopside cpx i garnet gnt i scapolite orthopyroxene dark brown hornblende this assemblage is linked by corona structures to a primary magmatic mineralogy where coexistence of olivine and plagioclase limits the maximum crystallization pressure of the anorthosites to 8 kbar at 1200 c the anorthosites are transected by a series of fine grained shear zones in which the granulite facies assemblage is replaced by an eclogite mineralogy defined by omphacite cpx ii jd40 50 garnet kyanite epidote clinozoisite phengite quartz amphibole with plagioclase sometimes remaining in the marginal parts mineral compositions indicate equilibration conditions for the eclogite paragenesis of t 700 800 c p 16 19 kbar a series of textural and mineralogical changes which can be observed as the strain increases into the shear zones demonstrates that the eclogite mineralogy is formed at the expense of the granulite facies minerals during the early stages of shear zone development the eclogite mineralogy defines a strong mylonitic fabric which again is truncated by centimetres thick secondary shear zones containing clasts of both granulite and eclogite minerals these latter fine grained ultramylonites may be connected to uplift of this deep seated complex the eclogite shear zones are highly oblique to the granulite structures indicating that the eclogite shear zones formed under a new stress regime rb sr dating shows that the granulite facies assemblage formed in sveconorwegian time or earlier while minerals from shear zones define ages around 400 ma indicating a caledonian formation of the eclogites this work demonstrates the critical role of deformation in triggering metamorphic reactions whether the shear stress also was important in stabilizing the eclogite assemblages is not clear from the available data

infinite slope stability under steady unsaturated seepage conditions 1 we present a generalized framework for the stability of infinite slopes under steady unsaturated seepage conditions the analytical framework allows the water table to be located at any depth below the ground surface and variation of soil suction and moisture content above the water table under steady infiltration conditions the framework also explicitly considers the effect of weathering and porosity increase near the ground surface on changes in the friction angle of the soil the factor of safety is conceptualized as a function of the depth within the vadose zone and can be reduced to the classical analytical solution for subaerial infinite slopes in the saturated zone slope stability analyses with hypothetical sandy and silty soils are conducted to illustrate the effectiveness of the framework these analyses indicate that for hillslopes of both sandy and silty soils failure can occur above the water table under steady infiltration conditions which is consistent with some field observations that cannot be predicted by the classical infinite slope theory a case study of shallow slope failures of sandy colluvium on steep coastal hillslopes near seattle washington is presented to examine the predictive utility of the proposed framework

a seismic landslide susceptibility rating of geologic units based on analysis of characteristics of landslides triggered by the 17 january 1994 northridge california earthquake abstract one of the most significant effects of the 17 january 1994 northridge california earthquake m 6 7 was the triggering of thousands of landslides over a broad area some of these landslides damaged and destroyed homes and other structures blocked roads disrupted pipelines and caused other serious damage analysis of the distribution and characteristics of these landslides is important in understanding what areas may be susceptible to landsliding in future earthquakes we analyzed the frequency distribution and geometries of triggered landslides in the santa susana 7 5 quadrangle an area of intense seismic landslide activity near the earthquake epicenter landslides occurred primarily in young late miocene through pleistocene uncemented or very weakly cemented sediment that has been repeatedly folded faulted and uplifted in the past 1 5 million years the most common types of landslide triggered by the earthquake were highly disrupted shallow falls and slides of rock and debris far less numerous were deeper more coherent slumps and block slides primarily occurring in more cohesive or competent materials the landslides in the santa susana quadrangle were divided into two samples single landslides 1502 and landslide complexes 60 which involved multiple coalescing failures of surficial material we described landslide morphologies by computing simple morphometric parameters area length width aspect ratio slope angle to quantify and rank the relative susceptibility of each geologic unit to seismic landsliding we calculated two indices 1 the susceptibility index which is the ratio given as a percentage of the area covered by landslide sources within a geologic unit to the total outcrop area of that unit and 2 the frequency index given in landslides per square kilometer ls km2 which is the total number of landslides within each geologic unit divided by the outcrop area of that unit susceptibility categories include very high 2 5 landslide area or 30 ls km2 high 1 0 2 5 landslide area or 10 30 ls km2 moderate 0 5 1 0 landslide area or 3 10 ls km2 and low

landslides induced by the 2008 wenchuan earthquake sichuan china the 2008 wenchuan earthquake with a magnitude of mw 7 9 induced numerous slope movements on the hanging walls of fault surface ruptures and on steep inner valleys along the minjiang river landslide moving directions showed preferred orientations normal to the fault ruptures indicating the effect of the directivity of the seismic wave the most common landslides were of carbonate rocks which are easily dissolved and decrease the contact surfaces the largest non volcanic landslide in history was induced in bedded dolomite by the earthquake and was preceded by gravitational deformation with ridge top depressions valley fill materials were mobilized at 36 locations probably by pore water pressure build up

textural evolution of synthetic anhydrite halite mylonites the rheology and textural evolution of mylonites for both crustal and mantle rocks are generally poorly understood stress and strain partitioning between shear zones and wall rock foliation development flow mechanisms and constitutive relations are little known to address these problems we have begun an experimental study in which anhydrite and halite aggregates are deformed in simple shear homogeneous mixes at intervals of 10 vol of anhydrite and halite powders of 90 to 180 m grain size comprise the 1 mm thick zone between the 35 precut surfaces in 2 by 4 cm right circular cylinders of anhydrite all specimens are confined under 200 mpa pc and tested at 300 c t producing an aggregate of near zero porosity all specimens are shortened at an axial displacement rate of 5 l0 6 cm s to shear strains of about 2 0 most stress strain curves have a similar form they are characterized by an initial linear response that is followed by a work hardening region that leads to a plateau of constant stress whilst strain continues to accumulate this apparent steady state behavior is followed by a drop in stress to a second apparent steady state stress the strain at this stress drop and the magnitude of the drop increase with increasing anhydrite content the second lower steady state stress for all mixes approaches that of sheared pure halite optical examination of the fabrics shows that straining under the initial apparent steady state is accommodated by both mineral phases a foliation evolves as defined by mineral segregation and grain elongation of halite at 15 to 30 to the shear zone walls anhydrite grains rotate until their 001 010 slip system parallels the foliation the anhydrite also exhibits twin lamellae kinks and microfractures following the stress drop rheologic behavior is dominated by dynamic recovery in halite the recrystallized grain size increasing consistent with the lower stress level

susceptibility assessment of earthquake triggered landslides in el salvador using logistic regression abstract this work has evaluated the probability of earthquake triggered landslide occurrence in the whole of el salvador with a geographic information system gis and a logistic regression model slope gradient elevation aspect mean annual precipitation lithology land use and terrain roughness are the predictor variables used to determine the dependent variable of occurrence or non occurrence of landslides within an individual grid cell the results illustrate the importance of terrain roughness and soil type as key factors within the model using only these two variables the analysis returned a significance level of 89 4 the results obtained from the model within the gis were then used to produce a map of relative landslide susceptibility

are the lower planes of double seismic zones caused by serpentine dehydration in subducting oceanic mantle in a number of subduction zones earthquakes at 50 200 km depth define two dipping planes separated by 20 40 km that appear to merge downdip upper plane earthquakes are inferred to occur within the subducting oceanic crust whereas lower plane earthquakes occur in the subducting oceanic mantle beneath northeast japan the results of a new finite element heat transfer model suggest that the lower seismic plane cuts across isotherms at a shallow angle lower plane earthquakes occur at 550 800 c at 100 km depth and at 350 600 c at 160 km depth these conditions coincide with the dehydration reaction antigorite serpentine forsterite enstatite h 2 o which suggests that lower plane earthquakes may be triggered by dehydration embrittlement which in turn suggests that the subducting oceanic mantle is partially hydrated serpentinization may occur in the trench outer rise region where faulting may promote infiltration of seawater several tens of kilometers into the oceanic lithosphere if this hypothesis is correct current subduction zone h 2 o budgets may significantly underestimate the amount of bound h 2 o entering the subduction factory

evolution of debris flow activities in gaojiagou ravine during 2008 2016 after the wenchuan earthquake abstract the 2008 wenchuan earthquake in sichuan china triggered numerous landslides in the stricken area the loose landslide materials retained on mountain slopes and in gullies are prone to reactivation and may transform into debris flows in the rainy season nine years after the wenchuan earthquake debris flows are still active in gaojiagou ravine 16 5 km north of the epicentre on 14 august 2010 3 july 2011 13 july 2013 and 6 july 2016 four large scale debris flows were triggered by heavy storms in gaojiagou ravine the four debris flows blocked the minjiang river twice and caused severe damage to nearby villages and reconstruction sites several questions arise from these repeated debris flows did the level of triggering rainfall change in the four debris flow events how did the initiation mechanism evolve over time what are the differences in the runout characteristics in the four events how did the check dams constructed in 2012 function in the subsequent debris flows in this paper we evaluated the loose deposit volumes in gaojiagou ravine before and after each of the four debris flows and the runout volumes and analysed the triggering rainfall intensities initiation mechanisms and runout characteristics of the four debris flows the rainfall threshold for the debris flows in gaojiagou ravine increased over time and the initiation mechanisms evolved from landslides to channel bed failure and subsequently to channel bank erosion the mobility of the debris flows decreased from 2010 to 2016 as the initiation positions moved lower and the particle size of the runout materials became coarser

kinematic thermal and petrological model of the central alps lepontine metamorphism in the upper crust and eclogitisation of the lower crust abstract seismic and seismological studies as well as gravimetric models indicate that a slab of european lithospheric mantle and lower crust is currently underthrust below the apulian crust we assume a simple kinematic model in which the lower and upper subducted european crusts are decoupled along a decollement the lower crust goes into subduction without deformation the upper crust deforms by pure shear with a horizontal compressional axis the total erosional flux is adjusted to balance upper crust input so that the belt keeps the same geometry different distributions of erosion being used the computed temperature field is steady state if the kinematic model applies during a minimum time of 40 myr for a convergence rate of 8 mm yr equilibrium mineral assemblages and densities are determined from the computed p t conditions for a granodioritic chemical composition of the upper crust and an andesitic composition of the lower crust assuming local isostasy the density model fits the average topographic profile across the central alps the p t t paths obtained for the part of the upper crust initially at depths 10 to 16 km are compatible with the medium pressure oligocene metamorphism in the lepontine dome the peak calculated temperature for the deepest non subducted crustal rocks is 600 c for a pressure of 0 8 gpa near the lower limit of high pressure amphibolites we thus propose that the lepontine metamorphism corresponds to the steady state thermal regime however either faster erosion rates in the internal part of the belt or tectonic denudation are required for exhumation of the deeper portion of the belt the computed temperature field implies eclogitisation of the lower crust at a depth of 55 to 60 km we conclude that the moho limiting the deepest part of the root may correspond to the eclogitisation phase change lower crust eclogites have a density comparable to or higher than that of the mantle depending on their chemical composition 3 37 for andesitic eclogites 3 56 for gabbroic eclogites thus andesitic eclogites may stay in gravitational equilibrium in the mantle below the root whereas gabbroic eclogites are gravitationally unstable and should sink

development of an initiation criterion for debris flows based on local topographic properties and applicability assessment at a regional scale abstract damages caused by landslides have been increasing because of the greater frequency of localized heavy rain to prevent landslide disasters more efficiently more studies in relation to predicting the initiation areas of debris flows that cause large scale damage are necessary the main purpose of this study is to develop a criterion for detecting debris flow initiation areas by using an empirical method that was chosen from several types of approaches to debris flow initiation detection in this study ten gis based geomorphological datasets were obtained from slide and debris flow initiation areas located in seoul gyeonggi province and gangwon province the geomorphological characteristics of slide and debris flow occurrence areas were analyzed through a comparative analysis to identify relationships between debris flow initiation and each topographic index an initiation criterion for debris flows based on the geomorphological characteristics was suggested using an artificial neural network ann model combined with a modified threshold for the relationship between slope and upslope contributing area to validate the suitability of the initiation criterion for debris flow sequential applications of slope failure analysis and debris flow initiation analysis were conducted on a case study site to simulate the actual debris flow events as a result of the debris flow initiation analysis the prediction capture rate of the debris flow initiation criterion was determined to be 88 9 debris flow initiation areas totaling 143 300 m2 were identified among 1 935 400 m2 of slope failure areas predicted in the slope failure analysis it is efficient to apply the debris flow initiation criterion in the debris flow simulation because slope failure areas are only partly transformed into debris flows

gis modelling of earthquake damage zones using satellite remote sensing and dem data the devastating earthquake that occurred in wenchuan county sichuan province china on the 12th may 2008 caused widespread damage and devastation to rural communities and economy the terrain of the entire region has been weakened and is now highly susceptible to long term slope instability that will trouble this region for many years to come before the earthquake the maximum seismic intensity expected in the region was vi viii in the 12 degree liedu scale the intensity measure adopted in china however the actual intensity caused by the earthquake ranged between viii and xi the seismic intensity map is practical for regional guidance but lacks the detail to provide an adequate representation of the true damage level in terms of current status and future potential in such a seismically active and populated region especially when the hazards and risks are likely to be multiple and cascading in high relief areas this paper presents a gis based novel approach to earthquake damage zone modelling using satellite remote sensing and dem data the novelty is to take into account the co seismic ground deformation measured using differential sar interferometry as an important modulating factor in modelling the susceptibility of earthquake related geohazards together with conventional multi criteria factors which draw on geological and topographical variables such as rock competence slope proximity to drainage and fracture density the modulating effect of the earthquake greatly enhances the susceptibility in the areas where the majority of the ensuing landslides and debris flows actually took place when this susceptibility model is further modulated by the mapped surface disruption caused by the earthquake which encompasses all forms of mass movement and urban destruction it is directly linked to seismic intensity and we call it earthquake damage the output earthquake damage map represents both the current damage status as well as the future damage hazard potential the resulting earthquake damage map for the beichuan region clearly defines a series of zones of increasing seismic intensity approximately corresponding to liedu values viii xi but with great details

suction stress characteristics in granite red soils and their relationship with the collapsing gully in south china abstract the main goal of this research is to study the relationship between the soil suction stress and soil properties within four different soil profiles of collapsing gullies in the hilly granitic region of southern china large differences were found in the four soil layers between granite red soils which are manifested in terms of soil bulk density porosity particle composition clay minerals micromorphology organic matter cation exchange capacity permeability oxide and hydraulics properties the suction stress of the upper soils increases rapidly and almost linearly monotonously with the increase of matric suction whereas c layers increases rapidly first followed by a slow increase the suction stress of the lower soils is significantly smaller than the upper soils under the same matric suction these findings illustrate that the collapsing gully starts from the lower part of the granite red soil and finally caused the gravity collapse in the upper soils which is the main aspect that is different from the other types of soil erosion furthermore suction stress has a very significant correlation with soil properties with a positive correlation to the fine particle content iron and aluminum oxide and a negative correlation to coarse particles in addition suction stress can also be explained as being directly proportional to weathering degree our research provides a theoretical basis for the mass failures of the granite derived red soil in southern china

gis based landslide susceptibility mapping for the 2005 kashmir earthquake region abstract the m w 7 6 october 8 2005 kashmir earthquake triggered several thousand landslides throughout the himalaya of northern pakistan and india these were concentrated in six different geomorphic geologic anthropogenic settings a spatial database which included 2252 landslides was developed and analyzed using aster satellite imagery and geographical information system gis technology a multi criterion evaluation was applied to determine the significance of event controlling parameters in triggering the landslides the parameters included lithology faults slope gradient slope aspect elevation land cover rivers and roads the results showed four classes of landslide susceptibility furthermore they indicated that lithology had the strongest influence on landsliding particularly when the rock is highly fractured such as in shale slate clastic sediments and limestone and dolomite moreover the proximity of the landslides to faults rivers and roads was also an important factor in helping to initiate failures in addition landslides occurred particularly in moderate elevations on south facing slopes shrub land grassland and also agricultural land were highly susceptible to failures while forested slopes had few landslides one third of the study area was highly or very highly susceptible to future landsliding and requires immediate mitigation action the rest of the region had a low or moderate susceptibility to landsliding and remains relatively stable this study supports the view that 1 earthquake triggered landslides are concentrated in specific zones associated with event controlling parameters and 2 in the western himalaya deforestation and road construction contributed significantly to landsliding during and shortly after earthquakes

landslide susceptibility mapping of the slopes in the residual soils of the mengen region turkey by deterministic stability analyses and image processing techniques abstract the aim of the present study is to prepare a landslide susceptibility map of a region of about 120 km2 between gokcesu and pazarkoy around mengen nw turkey at approximately 10 km north of the north anatolian fault zone where frequent landslides occur for this purpose mechanisms of the landslides were studied by two dimensional stability analyses together with field observations and the parameters controlling the development of such slides were identified field observations indicated that the failures generally developed within the unconsolidated and or semiconsolidated soil units in forms of rotational successive shallow landslides within the weathered zone in mengen cukurca and sazlar formations although consisting of residual soils capak and gokdag formations do not exhibit landslides as the natural slopes formed on these do not exceed the critical slope angles statistical evaluations and distribution of the landslides on the topographical map showed that such parameters as cohesion angle of internal friction slope relative height orientation of slopes proximity to drainage pattern vegetation cover and proximity to major faults were the common features on the landslides digital images were obtained to represent all these parameters on gray scale on the spot image and on the digital elevation model dem of the area using image processing techniques soil mechanics tests were carried out on 36 representative samples collected from different units and parameters were determined for two dimensional stability analyses basing on sensitivity approach and for the preparation of digital shear strength map in order to determine the critical slope angle values for the residual soils a series of sensitivity analyses were realized by using two dimensional deterministic slope stability analyses techniques for varying values of cohesion angle of internal friction and slope height along with varying saturation conditions according to the results of the sensitivity analyses the mengen formation was found to be most susceptible unit to landslides covering about 33 5 of the region studied in terms of surface area the distribution of the critical slopes were determined by superimposing the critical slope values from sensitivity analyses on slope map of the study area on the other hand iso cohesion and iso friction maps were produced by locating the values of cohesion and internal friction angles in a geographic coordinate system such that they coincide with sample locations on the dem and by further interpolation of the values concerned the pixel values were evaluated in gray scale from 0 to 255 0 representing the lowest pixel value and 255 representing the highest sensitivity analyses on cohesion and angle of internal friction to investigate the effects of these parameters only on stability revealed that cohesion was effective at a rate of 70 by itself while angle of internal friction alone controlled the stability by a rate of 30 the iso cohesion and iso friction maps previously obtained were digitally combined in these rates and a shear strength map was prepared the geographic setting of the study area is such that northern slopes usually receive dense precipitation in relation to this fact about 42 of the landslides are due north thus a slope orientation map was prepared using the dem and slopes facing north were evaluated as being more susceptible to sliding proximity to the drainage pattern was another important factor in the evaluation as streams could adversely affect the stability by either eroding the toe or saturating the slope or both when considered together in conjunction with the field observations faults and landslides showed a close association in the area about 88 of the landslides were detected within an area closer than 250 m to major faults therefore a main discontinuity map was produced using the spot image of the region and proximity to major faults was evaluated as a parameter as most of the landslides developed in areas where the vegetation was rather sparse a vegetation cover map was therefore obtained from the spot image and the areas with denser vegetation were considered to be less susceptible to sliding with respect to the areas with less or no vegetation having prepared the maps accounting for the distribution of critical slopes shear strength properties relative height slope angle orientation of the slopes vegetation cover proximity to the drainage pattern geographic corrections were carried on each of these and a potential failure map was obtained for the residual soils by superimposing all these maps next a classification was performed on the final map and five relative zones of susceptibility were defined when compared with this map all of the landslides identified in the field were found to be located in the most susceptible zone the performance of the method used in processing the images appears to be quite high the zones determined on the map being the zones of relative susceptibility

landslide processes and landslide susceptibility analysis from an upland watershed a case study from st andrew jamaica west indies abstract rainfall induced landslides are common geomorphic events on the steeper slopes of upper st andrew and cause severe environmental engineering social and economic repercussions in the area a geotechnical study was initiated to identify a past present and potential landslide types and sites for landslides b to examine the nature of geological geomorphological and geotechnical conditions under which failures can take place and c the potential landslide hazard in the area 886 failures were mapped more than 80 of which were located in soils a total of 1 55 km2 9 80 of the total area had failed approximately 59 failures per km2 were mapped with the highest density within elastic sedimentary units and weathered granodiorite 789 failure were mapped on slopes between 20 45 with no failure on slope less than 10 481 failures were mapped along twelve major roadways 46 6 km of road with approximately 10 failures km of road analysis of eighteen geotechnical units within nine geological formations revealed that the highest susceptibility for failure was within old landslide deposits with granular nonplastic to low plasticity soils and on slopes between 20 and 30 the lowest susceptibility was found within white limestones and recent alluvium and terrace deposits granular nonplastic to low plasticity soils are generally more susceptible than fine soils especially on slopes between 30 and 45 while granular and expansive clay soils demonstrate similar susceptibilities but on slopes between 30 and 45 and 20 and 45 respectively clastic sedimentary rocks are more susceptible that igneous lithologies an increase in slope angle increases the susceptibility to failures but only on slopes up to 45 an increase in the degree of weathering of soils and bedrock and fracturing of bedrock as well as road construction increases the landslide susceptibility in the area

landslide susceptibility analysis with a heuristic approach in the eastern alps vorarlberg austria the aim of the study is landslide hazard assessment carried out on a working scale of 1 25 000 the study area within the northern calcareous alps was geologically and geotechnically mapped in order to identify causes and mechanisms of active mass movements the field surveys were digitised by a geographical information system and divided into data layers the geological units were classified according to their geotechnical properties all layers were converted into grids and spatially analysed together with a digital elevation model comparing the layers with the inventory of active landslides the prevailing factors leading to sliding movements were identified because of the complex tectonic setting and the small number of active landslides a statistical method of hazard assessment was not applicable using the heuristic approach of an index method the data layers of geotechnical class bedding conditions tectonic layouts slope angles slope orientations vegetation and erosion were analysed the susceptibility of each layer has been evaluated with help of bivariate statistics the layers have been weighted with indices due to their importance iteratively and were combined into a landslide susceptibility map

large scale hydration of the lithosphere above subducting slabs during subduction oceanic lithosphere capped by variably hydrated uppermost mantle oceanic crust and sediments undergoes progressive metamorphism and devolatilization the petrologic evolution of subducting oceanic lithosphere and the overriding continental oceanic lithosphere can be predicted by integrating thermal models with petrologic phase equilibria in mature subduction zones that have achieved thermal steady state the subducting slab lies at subsolidus conditions for depths 100 150 km most subducting oceanic crust passes through the blueschist to eclogite facies transition where large amounts of h2o are released by the breakdown of na amphibole lawsonite or clinozoisite and chlorite the large amounts of h2o released by continuous blueschist eclogite reactions can cause large scale hydration of the overriding lithosphere and can trigger partial melting of the mantle wedge lowermost lithosphere and asthenosphere upward migration of slab derived fluids add h2o co2 sio2 and incompatible elements to the overlying lithospheric plate that result in the formation of new phases e g serpentine amphibole and mica and chemical modification of existing phases e g trace element enrichment of clinopyroxene evidence for large scale lithospheric hydration above subducting slabs includes serpentinite diapirs observed in the marianas forearc low p wave velocities observed in the hanging wall of the alaskan and japanese subduction zones and studies of high pressure metamorphic terrains

spatial probabilistic modeling of slope failure using an integrated gis monte carlo simulation approach spatial probabilistic modeling of slope failure using a combined geographic information system gis infinite slope stability model and monte carlo simulation approach is proposed and applied in the landslide prone area of sasebo city southern japan a digital elevation model dem for the study area has been created at a scale of 1 2500 calculated results of slope angle and slope aspect derived from the dem are discussed through the spatial interpolation of the identified stream network the thickness distribution of the colluvium above tertiary strata is determined with precision finally by integrating an infinite slope stability model and monte carlo simulation with gis and applying spatial processing a slope failure probability distribution map is obtained for the case of both low and high water levels

pseudotachylytes generated during seismic faulting and eclogitization of the deep crust pseudotachylytes are typically interpreted to have formed by frictional melting during coseismic faulting within the upper to middle crust pseudotachylytes in the bergen arcs of western norway contain microlites including omphacite garnet plagioclase and quartz this eclogite facies assemblage is stable at temperatures of about 800 c and pressures of 18 to 19 kilobars corresponding to depths of 60 kilometers or more the pseudotachylytes are exposed in grenvillian granulites that locally underwent fluid induced eclogitization and corresponding volume reduction of approximately 10 percent during the caledonian continental collision the pseudotachylytes may have formed as a result of the rapid relaxation of stresses caused by the eclogitization process

landslide zoning in a part of the garhwal himalayas the himalayas are undergoing constant rupturing in the thrust belt zone in the garhwal himalayas due to which earthquake and mass movement activity is triggered these processes of mass movement and landslides have been constantly modifying the landscape landslides are one of the indicators of the geomorphological modifications taking place in this active and fragile terrain this work is aimed at providing another example of landslide susceptibility mapping based on geological and geomorphological attributes the data collected from aerial photographs topographic sheets and the image suggests that there is a correlation between the distribution of landslides and some of the geological and geomorphological factors for example the distance from an active fault relative relief and slope parameters like factor of safety altitude relief slope and the distance from the fault lineament have been included in the study a rating system has been applied to the factors for arriving at a quantitative estimate of landslide susceptibility for each physiographic unit since terrain classification forms the foundation of this work the entire study can be grouped into two sequential activities 1 the terrain classification and 2 landslide susceptibility mapping the result is the landslide susceptibility zoning map presented the landslides have not been classified with respect to time and may represent the final result of the on going geological geomorphological and seismic activity since the holocene period or late pleistocene time when the glaciers retreated