integration of ground based radar and satellite insar data for the analysis of an unexpected slope failure in an open pit mine abstract on 17 november 2016 an unexpected slope failure occurred in an undisclosed copper open pit mine the nature of the event urged for a thorough back analysis of slope monitoring data in order to assess its size and temporal evolution and to determine whether precursors potentially able to anticipate the failure were present to this aim satellite insar data spanning over the final 9 months before the event were in retrospect acquired and coupled with measurements from a ground based radar that was in use at the time of the failure although progressive deformation was detected by the ground based radar in correspondence of the two uppermost benches in the pit the satellite insar data revealed that the vast majority of the instability actually involved a large part of natural slope above the mine crest this sector was not visible by the ground based radar thanks to the short revisit time of the sentinel 1 mission clear slope accelerating creep was observed for the first time in satellite insar measurements over an open pit mine the delimitation of the area featuring accelerating creep behavior matched remarkably the source area of the failure as mapped in the field after the event considerations on the volume of the instability and on the development of the failure process both in space and time were consequently derived the results provided a clear example of the value of jointly using ground based and satellite interferometry to reduce the uncertainties inherent to the identification and characterization of impending catastrophic slope failures

oxygen isotopic composition of multiple species of planktonic foraminifera recorders of the modern photic zone temperature gradient abundances of 12 species of planktonic foraminifera collected in two plankton tows from the east tropical atlantic are compared to the chlorophyll content and the temperature of the sea water from which they were collected as expected from previous work in the tropics all dominant tropical species occur in greatest abundance within the photic zone many species occur in greatest abundances in the seasonal thermocline in association with the maximum chlorophyll concentration while a few algal symbiont bearing species occur in greatest abundance in the mixed layer the 18o measurements of planktonic foraminifera shells from core top sediment samples confirm the vertical stratification within the photic zone that is suggested by the relationship between hydrography and abundances found in the plankton tows and found in the statistical study by ravelo et al 1990 comparison between the measured 18o values of planktonic foraminifera with the predicted 18o profiles of the overlying water column at three core locations indicate that species abundances in the sediment record the seasonally integrated conditions of the photic zone and suggests that the abundance of a species in the sediment depends on whether the preferred ecological conditions of that species may be found within the photic zone of the overlying water column sometime during the year species which calcify below the photic zone have only trace relative abundances finally it appears that the total range of 18o values of the dominant species approximates the predicted annual 18o of calcite range in the upper 80 m of the water column

process of slip surface development and formation of slip surface clay in landslides in tertiary volcanic rocks japan abstract once landslide movement has been initiated the sliding mass tends to move toward a more stable position however landslides that have occurred in some tertiary volcanic rocks in japan show recurrent movement a possible reason for this behavior is that the mineral composition and properties of slip surface materials results in better lubrication along the slip surface as movement continues in order to determine the causes five landslides in japanese tertiary volcanics with different movement histories were studied based on geological investigation the results presented in this paper were obtained by studying the development process and formation of slip surfaces and clays in landslides in these volcanics for rocks of similar types and mineralogies the clay content of slip surface materials can be directly related to the displacement and history of slide movement this study indicates that the type of slip surface ranges from 1 striation type showing only striations on bedrock without clay to 2 brecciated type clayey breccia 3 mylonite type clay with breccia and to 4 clay type clay without breccia if the slip surface occurs in tuff or tuffaceous materials and is subjected to increasing slide movement the smectite content in the slip surface clay increases while the silicate mineral content decreases furthermore the smectite content is observed to increase within the same landslide from the head to the toe portion of the landslide direction of groundwater flow the groundwater along the slip surface above the impervious zone contains an increased concentration of ca ions as the concentration of hco3 ions exceeds 40 mg l an environment is created that promotes the formation of smectite this process indicates that there is an active ion exchange within the groundwater near the slip surface that forms smectite thus the formation of smectite in the slip surface requires the presence of tuff and a sufficient concentration of hco3 ions in the groundwater the study results presented here indicate that frictional resistance decreases as clay content increases the reason for repeated movement of japanese landslides in tertiary tuffs or tuffaceous rocks at or in the immediate vicinity of the slip surface is attributed to 1 an increase in clay materials along the slip surface as the slide movement is repeated and 2 the presence of groundwater that promotes the formation of smectite as is commonly known smectite is one of the clay minerals that has lowest frictional resistance

reevaluation of the oxygen isotopic composition of planktonic foraminifera experimental results and revised paleotemperature equations cultured planktonic foraminifera orbulina universa symbiotic and globigerina bulloides nonsymbiotic are used to reexamine temperature 18o relationships at 15 25 c relationships for both species can be described by linear equations equations for o universa grown under low light ll and high light hl share a slope of 4 80 0 21 c 1 with a hl ll offset of 0 33 due to symbiont photosynthetic activity the effect of co32 on o universa is 0 002 mol 1 kg 1 and is insensitive to temperature for g bulloides ontogenetic effects produce size related trends in temperature 18o whereby larger shells are enriched in 18o relative to smaller specimens the o universa temperature 18o relationships are more accurate than previously published equations for describing plankton tow data our equations do not explain planktonic core top data with the same precision but provide a good fit to benthic cibicidoides data below 10 c temperature 18o relationships for g bulloides provide good agreement with field data for this species from the northeast pacific

terrestrial laser scanning of rock slope instabilities this manuscript presents a review on the application of a remote sensing technique terrestrial laser scanning tls to a well known topic rock slope characterization and monitoring although the number of publications on the use of tls in rock slope studies has rapidly increased in the last 5 10 years little effort has been made to review the key developments establish a code of best practice and unify future research approaches the acquisition of dense 3d terrain information with high accuracy high data acquisition speed and increasingly efficient post processing workflows is helping to better quantify key parameters of rock slope instabilities across spatial and temporal scales ranging from cubic decimetres to millions of cubic metres and from hours to years respectively key insights into the use of tls in rock slope investigations include a the capability of remotely obtaining the orientation of slope discontinuities which constitutes a great step forward in rock mechanics b the possibility to monitor rock slopes which allows not only the accurate quantification of rockfall rates across wide areas but also the spatio temporal modelling of rock slope deformation with an unprecedented level of detail studying rock slopes using tls presents a series of key challenges from accounting for the fractal character of rock surface to detecting the precursory deformation that may help in the future prediction of rock failures further investigation on the development of new algorithms for point cloud filtering segmentation feature extraction deformation tracking and change detection will significantly improve our understanding on how rock slopes behave and evolve perspectives include the use of new 3d sensing devices and the adaptation of techniques and methods recently developed in other disciplines as robotics and 3d computer vision to rock slope instabilities research

rainy periods and bottom water stagnation initiating brine accumulation and metal concentrations 1 the late quaternary a working hypothesis is proposed to account for the present accumulation of brines in isolated pockets of the ocean floor and for the formation of the underlying organic and metal rich sediments these are the tyro and bannock basins in the east mediterranean the red sea deeps and the orca basin in the northern gulf of mexico initiation of brine derived deposition in the red sea deeps and orca basin occurred between 12 000 and 8000 years b p this time bracket also encompasses the formation of the latest east mediterranean sapropel and the wettest global climate since the last glacial maximum this wet period first appeared in the tropics around 12 000 years b p then in the subtropical and middle latitudes during the same period the 23 000 year precession cycle brought the summer insolation of the northern hemisphere to its peak at 11 000 years b p with retreating northern hemisphere ice sheets the red sea deeps and the orca basin became anoxic during this humid period and metal rich sapropel deposition then began in contrast the tyro and bannock basins began accumulating a brine long before and persisted beyond this climatic stage the hypothesis involves two propositions 1 as in the eastern mediterranean sea marine anoxia was mainly the consequence of the large influx of continental runoff and local precipitation longer residence time of bottom waters so called stagnation in silled rimmed basins would have resulted from lower salinity at the sea surface in areas of deep water formation in the eastern mediterranean the red sea and the gulf of mexico and 2 miocene or older evaporites underlie these basins or outcrop on their flanks leaching from these evaporites was an ongoing process before the quasi stagnation phase but the initial leachate much less saline than the present brines was continuously flushed by bottom circulation the climate induced quiescence of bottom waters in these basins enabled the leachate to accumulate the feedback of stagnation by increased density progressively raised the salinity of entrapped bottom waters to the present brine concentration the high density has resisted brine removal by bottom circulation until present time long after cessation of the initiating wet period the brines therefore are stagnant fossil waters

persistent solar influence on north atlantic climate during the holocene surface winds and surface ocean hydrography in the subpolar north atlantic appear to have been influenced by variations in solar output through the entire holocene the evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon 14 and beryllium 10 and centennial to millennial time scale changes in proxies of drift ice measured in deep sea sediment cores a solar forcing mechanism therefore may underlie at least the holocene segment of the north atlantic9s 1500 year cycle the surface hydrographic changes may have affected production of north atlantic deep water potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally

using a discrete element approach to model lava dome emplacement and collapse abstract lava dome collapses can lead to explosive activity and pyroclastic flow generation which makes them one of the most deadly consequences of volcanic activity the mechanisms linked to a collapse are however still poorly understood and very few numerical models exist that investigate the actual collapse of a lava dome after emplacement we use a discrete element method implemented in the modelling software particle flow code to investigate lava dome growth but also go further to test the stability of the dome under the following conditions increased internal pressure switch in extrusion direction caused by partial cooling of the dome and extrusion of lava onto variable underlying topography we initially show the morphology development of a growing lava dome and how the rheological boundary between core and talus evolves throughout the lifetime of a dome and with varied solidus pressures through visualisation of strain accumulation within the lava dome we show superficial rockfall development due to interaction with topography whereas large deep seated failures occur when the dome is exposed to internal overpressures we find that a switch in extrusion direction promotes a transition from endogenous to exogenous dome growth and leads to lava lobe formation we demonstrate that lava dome collapse exhibits many features similar to common landslides and by investigating strain patterns within the dome we can use numerical modelling to understand features that elude field observations

renewal of deep water in the red sea during 1982 1987 between october 1982 and may 1983 the deep water in the northern red sea was ventilated through slope convection the deep water became cooler fresher and more oxygenated dense bottom water formed in the gulf of suez during winter cooling sank down the continental slope thereby entraining near surface and intermediate depth waters from the application of a one dimensional plume model a vertical transport of 0 58 106 m3 s 1 over a period of 7 months was estimated long term time series of atmospheric heat fluxes show that such a major convection event can occur every 4 7 years the corresponding renewal time of the red sea deep water is thus of the order of 40 90 years in agreement with previous estimates

load redistribution rules for progressive failure in shallow landslides threshold mechanical models rainfall induced landslides are often preceded by progressive failures that culminate in abrupt mass release local failure progression is captured by a landslide hydro mechanical triggering lht model that represents the soil mantle as interacting columns linked by tensile and compressive mechanical bonds mechanical bonds may fail at a prescribed threshold leaving a modeling challenge of how to redistribute their load to neighboring intact soil columns we employed an elastic spring block model to analytically derive redistribution rules defined by the stiffness ratio of compressive to tensile bonds these linear elastic rules were generalized to real soil using measurable young s modulus and poisson s ratio results indicate that local failure characteristics of ductile like soils e g clay are reproduced by low stiffness ratios whereas global failure of brittle sandy soils corresponds to large stiffness ratios systematic analyses yield guidelines for selecting load redistribution rules for failure of geological materials and mass movement phenomena represented by discrete threshold mechanics

carbonate preservation and climatic changes in the central red sea during the last 380 kyr as recorded by pteropods abstract numerical abundances of pteropods and planktic foraminifera and the mode of pteropod preservation were determined in core kl 11 taken from the central part of the red sea the abundance of pteropods shells g dry sediment was compared to that of planktic foraminifera pt pf pt a technique that permits detection of changes in carbonate preservation for the last 380 kyr the numerical abundance of pteropods is influenced by the properties of the water column and preservation is influenced by the bottom water during the last 200 kyr except during isotope stage 5 5 carbonates are in general well preserved during this period the abundance pattern of the pteropods and planktic foraminifera is very similar and follows the climatic signal of the red sea with high numbers during the interglacial stages changing to very low numbers during glacial maximum conditions the similar abundance trends of the two groups and between them and the 18o curve indicates abundance is strongly linked to salinity from isotope stage 6 to the bottom of the core the pteropods occur in low numbers unlike the planktic foraminifera which continue to display the high amplitude glacial interglacial cyclicity the deviations mainly during interglacial stages between the abundance pattern of the two groups and the low pt pf pt values indicate a significant change in carbonate preservation distinctive carbonate dissolution intervals are recognized in the red sea correlating to large scale deep water dissolution events of the mid brunhes dissolution cycle in the indian ocean the anti estuarine circulation pattern of the red sea prevents a direct connection between the deep water masses of the two oceans and rules out the likelihood that changes in the deep water circulation caused these carbonate dissolution events the numerical variations between nonmigratory epipelagic and migratory mesopelagic pteropods were used to evaluate changes in the structure of the water column abundance maxima of mesopelagic pteropods as in the recent red sea indicate an aerated water column with 0 5 ml o2 l oxygen concentrations at the minimum zone mesopelagic abundance maxima coincide commonly with negative monsoonal index values indicating a more aerated water column connected to increasing aridity in the red sea region abundance maxima of epipelagic pteropods indicate a strongly stratified water column at times causing severe depletion in oxygen at intermediate water depths epipelagic peak events coincide often with positive monsoon index values implying an overall milder and more humid climate in the red sea probably associated with enhanced precessional controlled southwest monsoon activity

inversion of deformation fields time series from optical images and application to the long term kinematics of slow moving landslides in peru abstract slow moving landslides are numerous in mountainous areas and pose a large threat to populations many observations show that their kinematics is driven by climatic forcings and earthquakes in this study we document the complex interaction between those two forcings on the slow moving landslide kinematics based on the retrieval of landslide displacements over 28 years using optical satellite images to overcome the decorrelation effect over this large time span and possible misalignment between images we develop a method that uses the redundancy of displacement fields from image pairs to derive a robust time series of displacement the method is tested on the 28 year long spot1 5 pleiades archive over an area in peru affected by both earthquakes and rainfall errors are estimated on stable areas and by comparison with one 13 year long and eleven 3 year long gps time series on the maca landslide the methodology diminishes by up to 30 the uncertainty and reduces significantly the gaps due to decorrelation the data set allows detecting 3 major landslides moving at a rate of 35 to 50 m over 28 years and smaller landslides with lower displacement rates time series obtained over the three main landslides provide interesting results of their long term kinematics primarily driven by precipitation we propose simple statistical hydro kinematic models relating yearly motion to seasonal rainfall to explain the observed time series we found that annual precipitation is controlling the landslide displacements after a certain rainfall threshold is reached besides this control we show the possible impact of a local mw 5 4 earthquake in 1991 on the kinematics of the maca landslide our results suggest that the earthquake accelerated the landslide and has an effect during several years on the precipitation threshold required for triggering a motion these results suggest that the rainfall threshold can vary in time following strong earthquakes shaking

geostatistical analysis in weathering studies case study for stanton moor building sandstone geostatistical techniques for spatial prediction and spatial simulation have been used in an innovative application to the study of weathering of natural building stone the study investigates the differences in the spatial variation of permeability characteristics between fine and coarse grained stanton moor building sandstone non destructive permeability measurements using an unsteady state portable probe permeameter were made on three adjacent faces of two cubic blocks representative of fine to medium grained and medium to coarse grained stanton moor sandstone the findings provide greater understanding in the investigation of the durability characteristics of the stanton moor sandstone and show that the spatial distribution and variability of permeability is more important in predicting the overall strength and weathering properties than mean permeability and absolute minimum and maximum values the results suggest that both primary textural characteristics such as grain size and extent of cementation appear to be important factors in determining the overall durability properties of stanton moor sandstone as a building stone geostatistical analysis has been shown to be an important tool in the characterization of spatial variation for the investigation of weathering of building stones copyright 2006 john wiley sons ltd

a coral oxygen isotope record from the northern red sea documenting nao enso and north pacific teleconnections on middle east climate variability since the year 1750 a 245 year coral oxygen isotope record from the northern red sea ras umm sidd egypt 28 n in bimonthly resolution is presented the mean annual coral 18o signal apparently reflects varying proportions of both sea surface temperature and 18oseawater variability in conjunction with instrumental observations of climate the coral record suggests for interannual and longer timescales that colder periods are accompanied by more arid conditions in the northern red sea but increased rainfall in the southeastern mediterranean whereas warmer periods are accompanied by decreased rainfall in the latter and less arid conditions in the northern red sea a 70 year oscillation of probably north atlantic origin dominates the coral time series interannual to interdecadal variability is correlated with instrumental indices of the north atlantic oscillation nao the el nino southern oscillation enso and north pacific climate variability the results suggest that these modes contributed consistently to middle east climate variability since at least 1750 preferentially at a period of 5 7 years

multicentennial scale hydrological changes in the black sea and northern red sea during the holocene and the arctic north atlantic oscillation 1 paleoenvironmental proxy data for ocean properties eolian sediment input and continental rainfall based on high resolution analyses of sediment cores from the southwestern black sea and the northernmost gulf of aqaba were used to infer hydroclimatic changes in northern anatolia and the northern red sea region during the last 7500 years pronounced and coherent multicentennial variations in these records reveal patterns that strongly resemble modern temperature and rainfall anomalies related to the arctic oscillation north atlantic oscillation ao nao these patterns suggest a prominent role of ao nao like atmospheric variability during the holocene beyond interannual to interdecadal timescales most likely originating from solar output changes

analogue modeling of the collapse of non homogeneous granular slopes along weak horizons abstract in this study we use results of analogue models to investigate the effect of the dip location and thickness of a weak horizon on the stability failure kinematics and internal deformation of a granular slope the models are systematically designed to simulate the collapse of non homogeneous granular slopes by focusing on the spatial and temporal distribution of their internal deformation model results show that the presence of a weak horizon embedded within the granular slope has a significant influence on the granular failure which is accommodated through different generation pulses that successively decrease in volume however the dip and stratigraphic location of the weak horizon dictate whether the weak horizon play a role during the failure or not when the main failure surface is contained within a weak horizon the dip and thickness of the weak horizon have a positive effect on the displacement of the failure mass whereas a shallow located weak horizon causes larger displacement of the failure mass during the collapse of granular slopes in addition the collapse of granular slopes results in the formation of different generation normal faults and shortening structures folds and thrusts within the failure mass the first generation normal faults with a steep dip about 60 cut across the entire stratigraphy of the slope whereas the later generation normal faults with a gentle dip about 40 cut across the shallow units the distribution of these internal structures within the failure mass is affected significantly by the dip location and thickness of the weak horizon

seismic precursory patterns before a cliff collapse and critical point phenomena 1 we analyse the statistical pattern of seismicity before a 1 2 103 m3 chalk cliff collapse on the normandie ocean shore western france we show that a power law acceleration of seismicity rate and energy in both 40 hz 1 5 khz and 2 hz 10khz frequency range is defined on 3 orders of magnitude within 2 hours from the collapse time simultaneously the average size of the seismic events increases toward the time to failure these in situ results are derived from the only station located within one rupture length distance from the rock fall rupture plane they mimic the critical point like behavior recovered from physical and numerical experiments before brittle failures and tertiary creep failures our analysis of this first seismic monitoring data of a cliff collapse suggests that the thermodynamic phase transition models for failure may apply for cliff collapse

controls on the size and geometry of landslides insights from discrete element numerical simulations abstract we use numerical two dimensional discrete element method dem to study the controls on the size and geometry of an individual landslide this method allows us to analyze the temporal and spatial evolution of slope failure and landsliding from the intact pre failure slope to the restabilized post failure slope the size of our simulated landslides reflects the amount of disintegrated material available for sliding which is controlled by the peak strength of the slope material and to a lesser degree by the pre failure slope angle the observed size of natural landslides therefore reflects mainly the local natural material strengths we hypothesize that the observed global characteristic landslide size is a result of the limited thickness generally up to a few meters of disintegrated and weathered material that exists on hillslopes poised and ready for sliding the primary controls on the landslide geometry quantified as the ratio of their thickness to length t l prove to be the residual friction angle of the slope material and the original slope angle the t l is observed to be unchanged for a given initial slope angle and independent of the slope material peak strength or the slope height we suggest that the narrow range of observed natural t l is a result of narrow ranges of mechanical properties and initial slope geometries involved in natural slope failure

identifying rock slope failure precursors using lidar for transportation corridor hazard management abstract in the thompson and fraser river valleys rockfall and rockslides are a hazard for railway traffic in the region in june 2013 a 2600 m 3 rockslide occurred in the white canyon causing damage to infrastructure and interruption to service in the year preceding this failure the slope was monitored using terrestrial light detection and ranging lidar as part of the railway ground hazards research program initiative the purpose of this study is to evaluate a hazard management strategy for transportation corridors exposed to steep slopes involving the identification of rockfall precursors prior to significant slope failures for this failure deformation was observed in the seven months preceding collapse with an accelerating period occurring in the final 28 days a distinct pattern of smaller rockfalls was observed around the perimeter of the deforming rock block as well as loss of surficial material over the slides tension crack this study shows that with lidar monitoring precursors to rock slope failures can be identified allowing for better rock slope hazard management by focusing attention on areas with the highest probability of failure

the use of surface monitoring data for the interpretation of landslide movement patterns the tessina landslide is a large seasonally active slope failure located on the southern slopes of mt teverone in the alpago valley of ne italy consisting of a complex system that has developed in tertiary flysch deposits the landslide which first became active in 1960 threatens two villages and is hence subject to detailed monitoring with high quality data being collected using piezometers inclinometers extensometers and through the use of a highly innovative automated electronic distance measurement edm system which surveys the location of a large number of reflector targets once every 6 h these systems form the basis of a warning system that protects the villages but they also provide a very valuable insight into the patterns of movement of the landslide in this paper analysis is presented of the movement of the landslide concentrating on the edm dataset which provides a remarkable record of surface displacement patterns it is proposed that four distinct movement patterns can be established which correspond closely to independently defined morphological assessments of the landslide complex any given block of material transitions through the four phases of movement as it progresses down the landslide with the style of movement being controlled primarily by the groundwater conditions the analysis is augmented with modelling of the landslide undertaken using the itasca flac code the modelling suggests that different landslide patterns are observed for different parts of the landslide primarily as a result of variations in the groundwater conditions the model suggests that when a movement event occurs displacements occur initially at the toe of the landslide then retrogress upslope

forecasting giant catastrophic slope collapse lessons from vajont northern italy rapid giant landslides or sturzstroms are among the most powerful natural hazards on earth they have minimum volumes of similar to10 6 10 7 m 3 and normally preceded by prolonged intervals of accelerating creep are produced by catastrophic and deep seated slope collapse loads similar to1 10 mpa conventional analyses attribute rapid collapse to unusual mechanisms such as the vaporization of ground water during sliding here catastrophic collapse is related to self accelerating rock fracture common in crustal rocks at loads similar to1 10 mpa and readily catalysed by circulating fluids fracturing produces an abrupt drop in resisting stress measured stress drops in crustal rock account for minimum sturzstrom volumes and rapid collapse accelerations fracturing also provides a physical basis for quantitatively forecasting catastrophic slope failure c 2003 elsevier science b v all rights reserved

ice core palaeoclimate records in tropical south america since the last glacial maximum ice core records spanning the last 25 000 yr from the tropical andes of south america are reviewed these records from quelccaya huascaran and sajama present a high temporal resolution picture of both the late glacial stage lgs and the holocene climatic and environmental conditions in the south american andes late glacial stage conditions at high elevations appear to have been cooler than today although the magnitude of the inferred cooling differs with the particular proxy used e g snowline depression pollen ice cores insoluble dust and anion concentrations in the ice cores reveal that lgs hydrological conditions in the tropics 9 s were much drier than today whereas in the subtropics 18 s lgs conditions were much wetter this probably reflects the migration of the tropical hadley cell in response to a different meridional temperature gradient low nitrate concentrations in the lgs ice from both huascaran and sajama suggest that the amazon basin forest cover may have been much less extensive discussed is the conundrum surrounding the use of d 18 o as a palaeothermometer in the tropics where temperatures exhibit little seasonal variation yet the ice core records suggest that d 18 o records temperature variations on decadal to millennial time scales finally evidence is presented for a strong twentieth century warming copyright 2000 john wiley sons ltd

monsoons and the dynamics of deserts the existence of subtropical deserts such as the sahara has often been attributed to the annual mean zonal mean hadley circulation which shows strong descent in the subtropics however the zonal mean hadley circulation shows considerable evolution over the course of the year with very strong subtropical descent during winter but practically no zonal mean subtropical descent during summer when rainfall over the eastern sahara and the mediterranean is least charney 1975 proposed a biosphere albedo feedback mechanism whereby local anthropogenic effects related to over grazing could affect the radiative balance enhancing summertime diabatic descent and leading to desertification of the subtropics in general the present study which uses an idealized model suggests a monsoon desert mechanism for desertification whereby remote diabatic heating in the asian monsoon region can induce a rossby wave pattern to the west integral with the rossby wave solution is a warm thermal structure that interacts with air on the southern flank of the mid latitude westerlies causing it to descend this adiabatic descent is localized over the eastern sahara and mediterranean and over the kyzylkum desert to the south east of the aral sea by the mountains of north africa and south west asia trajectories indicate that the monsoon desert mechanism does not represent a simple walker type overturning cell instead the descending air is seen to be mainly of mid latitude origin it is speculated that the monsoon forced adiabatic descent may result in clear air and therefore a local diabatic enhancement which effectively doubles the strength of descent with this mechanism desertification can be forced by remote changes in monsoon strength rather than by local effects this conclusion is supported by the observed dramatic strengthening of descent over the mediterranean and east sahara during the onset of the asian monsoon and on the longer timescale by relating prehistoric lake levels to milankovitch monsoon forcing the latter may help to explain the perceived discrepancies between the palaeoclimate of the eastern sahara and the strength of a tropic wide monsoon the monsoon desert mechanism may not be confined to the asian monsoon alone and the existence of other monsoon climate regions over the globe may in a similar way explain the observed summertime strengthening of the oceanic sub tropical anticyclones and the existence of western continental deserts and mediterranean type climate regions

multiple fluid generations in the sudbury igneous complex fluid inclusion ar o h rb and sr evidence abstract the elliptically zoned sudbury structure in northern ontario is host to world class nickel copper pge deposits which are generally regarded as the products of a single magmatic event however there is increasing evidence of multi episodic fluid rock including ni cu sulphide interactions in the sudbury structure that range from early remobilization of the cooling ores ca 1850 ma through metamorphism and deformation related to the penokean orogeny to neotectonic fracturing ca 5 13 ma previous fluid inclusion studies have identified an h2o nacl co2 kcl fluid of highly variable phase ratios intimately associated with the ores and a distinct population of primary two phase fluid inclusions associated with post intrusion metasomatic alteration this study introduces two new distinct populations of fluid inclusions 1 a population represented by two phase co2 bearing fluid inclusions hosted along healed fracture planes in quartz that offset ore minerals that was trapped between 280 340 c and 1750 to 3500 bars pressure as the fluid inclusion trails offset and therefore post date the ore their genesis is consistent with a late penokean 1 83 1 89 ga or later ca 1450 contractional event 2 a two phase highly saline 16 wt nacl equivalent fluid hosted within neotectonic 5 13 ma rb sr galena sphalerite calcite quartz chlorite veins inclusions of this fluid were trapped at temperatures ranging from 60 to 135 c and maximum confining pressures of 950 bars stable isotope data o d from biotite amphibole and epidote from the alteration assemblages of remobilized veins within the sudbury structure show distinct evidence of a mixing trend of fluids originating within or near the magmatic water box and trending towards a metamorphic fluid of isotopic composition similar to an evolved sudbury structure groundwater ar ar data from the amphiboles within sudbury intrusive complex sic footwall breccia from the craig mine are consistent with a mixed ar ar spectrum the step heating ar release spectrum yields ages ranging from ca 1800 ma at the low temperature end to approximately 2640 ma for high temperature steps these dates are in agreement with the ca 1850 and 2647 ma ages for the sic and levack gneisses respectively and are interpreted as the reinjection of country rocks partially melted by the sic back into the sudbury structure the isotopic evidence for mixed fluids derived from a combination of a magmatic fluid and a regional groundwater metamorphic fluid suggests that the highly variable phase ratio fluid inclusions associated with the ore may be divided into two end member fluids represented by an exsolved sic fluid and a regional groundwater metamorphic fluid this is consistent with at least five distinct fluids being present during the evolution of the sudbury structure

stability analysis of a typical landslide mass in the three gorges reservoir under varying reservoir water levels water level change upstream of a reservoir highlights the risk of a landslide prone area on the banks of a reservoir this paper conducted a study on the deformation mechanism of a selected landslide that occurred in the three gorges reservoir tgr after the water level of the reservoir changed the long monitored surface deformation of the slide mass revealed that the deformation of the landslide was related to the water level changes in the reservoir especially of the change between flood and floodless seasons the measured internal lateral displacements in the landslide showed that such a landslide was characterized by a trail mode flac3d was adopted to model the landslide by examining the plastic zone factor of safety and the displacement in the x direction in consideration of four conditions the natural state of a landslide in the tgr the initial impoundment the subsequent rise of water level and the drawdown of water level the numerical results indicated that the landslide mass tended to be unstable during the initial impoundment the subsequent rise of water level had a limited effect on the landslide happening but the drawdown of water level directly triggered the landslide the landslide changed from push mode to trail mode it is strongly recommended that drawdown of the water level in the reservoir be carefully controlled to mitigate the effect on landslide mass

development of progressive landslide failure in cohesive materials the development of progressive failure in slopes is a poorly understood process and relatively few advances in terms of the mechanics of the development of failure have been made since 1967 however advances in the understanding of the development of fractures in brittle materials provide new insights into landslide mechanics in addition the link between the deformation mechanism and movement type allows interpretation of displacement records to determine the mechanisms acting within a slope this paper utilizes these insights into deformation processes combined with reinflation stress path triaxial experiments to propose a new model for the development of a progressive first time failure within a slope this model is able to explain the development of failure when the factor of safety is greater than unity the existence of saito linearity a linear trend when the reciprocal of velocity prior to failure is plotted against time during tertiary creep and the development of failures during periods of apparently increasing normal effective stress

long term dynamics of rockslides and damage propagation inferred from mechanical modeling 1 long term observations of large active rockslides show accelerating deformation over many thousands of years since the last deglaciation the effect of deglaciation on slope stability is however poorly understood due to 1 limited long term observations and 2 a complex interaction between glacier retreat and hydrogeological mechanical and morphological processes to assess the sensitivity of rockslide dynamics to these different processes a model of progressive damage through intact rock mass is developed in this study based on the finite element method this model uses time to failure laws based on rock laboratory creep experiments it is able to reproduce progressive damage localization along shear bands associated with strain rate acceleration as observed during tertiary creep the model reproduces the different phases of deformation associated with morphologies typical of large rockslides this model is thus suitable for simulating the dynamics of large rockslides and the transition from initiation to rapid sliding the sensitivity of rockslide kinematics and morphology to different mechanical properties is analyzed this analysis shows that the time evolution of the rockslide can be inferred with the knowledge of only one time parameter independent of the knowledge of the mechanical properties of the rock mass this parameter is here chosen as the time when the summit slope displacement has reached 10 m a parameter that can be estimated with cosmogenic dating the model is then used to study the effects of deglaciation on the valley flank stability and the formation of large rockslides this study shows that the deglaciation velocity can affect the morphology of the rockslide with the shear band of the rockslide emerging at higher elevation as the velocity decreases we also show that the response to the deglaciation can last several thousands of years after the glacier retreat

patterns of movement in rotational and translational landslides the movement of rotational and translational landslides occurs as a result of either sliding on discrete shear surfaces or ductile deformation within a shear zone in this paper we examine the movement histories of a number of landslides that occurred in a variety of materials in a range of settings and demonstrate that one of two movement styles is evident during accelerating phases for all landslides observed the first style which has previously been noted has a linear form in a plot of 1 v against time v is velocity the second style has an asymptotic form in the same plot trending toward steady state movement rates we propose that the linear form occurs in landslides in which crack propagation i e shear surface generation is the dominant process whereas the second style occurs where movement is taking place across existing planes of weakness or as a result of ductile deformation processes this study demonstrates that the evaluation of plots of 1 v against time for landslides is a useful technique for forecasting movement styles and rates and for interpreting ongoing deformation processes in real time

scaling law of average failure rate and steady state rate in rocks the evolution properties in the steady stage of a rock specimen are reflective of the damage or weakening growth within and thus are used to determine whether an unstable transition occurs in this paper we report the experimental results for rock granite and marble specimens tested at room temperature and room humidity under three typical loading modes quasi static monotonic loading brittle creep and brittle creep relaxation deformed rock specimens in current experiments exhibit an apparent steady stage characterized by a nearly constant evolution rate which dominates the lifetime of the rock specimens the average failure rate presents a common power law relationship with the evolution rate in the steady stage although the exponent is different for different loading modes the results indicate that a lower ratio of the slope of the secondary stage with respect to the average rate of the entire lifetime implies a more brittle failure

predicting the sliding behavior of rotational landslides based on the tilting measurement of the slope surface abstract the surface displacements of slopes have been considered as a significant indicator in landslide investigations in last several decades while in recent years the tilting of slope surfaces is also being recognized as an important index in landslide monitoring however the slope surface tilting has been rarely examined so far and requires detailed investigations in this paper a series of laboratory tests and a field test were performed to investigate the surface tilting in rotational landslides as well as the correlation between tilt angles and displacements of slope surfaces in the laboratory tests slope models were constructed with different shapes of pre designed slip surfaces and tested under varying test conditions the tilting behavior of the slope surfaces in laboratory tests was measured using tilt sensors embedded into the slopes while the surface displacement was obtained by tracing the movement of marked points set on the slope surfaces near to the tilt sensors the test results revealed a linear relationship between the tilt angles and displacements of slope surfaces in the process of slope failure and this linear relationship was validated by a field test in which the slope failure was triggered by artificial rainfall the test results also indicated that the coefficient of the linear relation is consistent with the value of real distance between the locations of tilt sensors and the centers of slip surfaces an equation that relates the slope surface tilting and displacements was proposed in this study furthermore a method to estimate the geometry of the slip surface was also developed which was deduced from the observation that the path of the sliding masses was parallel to the slip surface according to the results of laboratory tests additionally an acceleration stage of surface tilting was observed in slope failure induced by artificial rainfall which implies that the surface tilting measurement can be used to predict the potential development of a rotational landslide or its reactivation

use of sentinel 2 images for the detection of precursory motions before landslide failures abstract the sentinel 2 optical satellites provide a global coverage of land surfaces with a 5 day revisit time at the equator we investigate the ability of these freely available optical images to detect precursory motions before rapid landslides a 9 month time series of displacement is derived from sentinel 2 data over a major landslide in the french alps which exhibited a sudden reactivation in june 2016 this analysis reveals a 7 month period of low activity 1 m followed by a sudden acceleration of 3 2 1 2 m in 3 days before the failure of a mass of about 2 to 3 6 106 m3 the location of this precursory motion is consistent with that of the slow motions occurring since 2001 about 1 m year as revealed by aerial photographs and lidar analysis this change in activity over a very short period of time days emphasizes the value of the frequent revisit time of sentinel 2 despite its medium resolution of 10 m we finally simulate the ability of sentinel 2 for detecting these precursory patterns before a rapid landslide occurs based on typical voight s laws for creeping materials characterized by a power law exponent based on this analysis and on global cloud cover maps we compute the probability to detect pre failure motions of landslides using the sentinel 2 constellation this probability is highly heterogeneous at the global scale affected by the revisit time of the satellite and the cloud cover however the main factors controlling this detection ability are the properties of the landslide itself its size and the parameter with almost 100 of detection probability for 1 3 and 0 for 1 8 despite all these limitations probability to detect a motion before a landslide failure often reaches 50 for classical landslide parameters these results open new perspectives for the early warning of large landslide motion from global and open source remote sensing data

management of a typhoon induced landslide in otomura japan abstract late in january 2004 slope instability evidence such as cracks and subsidence appeared on a retaining wall along national highway 168 near otomura nara prefecture japan this road plays a strategic role as a long distance route for passenger vehicles and trucks therefore detailed investigations and constant surveillance have to be carried out in order to manage the induced risk situations six months later on august 10th a large landslide occurred due to heavy rainfalls related to typhoons 10 and 11 that hit japan on the first week of august field and aerial surveys of the site were carried out soon after the appearance of the first geomorphologic evidence of landslide movements and a monitoring system was immediately set up landslide displacements have been measured since the early stage of movement and road traffic was strictly controlled in order to minimize possible damage this paper illustrates the effects of landslide activation and the investigations carried out in order to assess landslide hazard and predict the time of failure suitable methods for risk management oriented to increase the public safety and including risk control and crisis mitigation acts are also discussed

morphology structure and kinematics of a rainfall controlled slow moving andean landslide peru the large slow moving landslide of maca is located in the upper colca valley southern peru a region characterized by a well pronounced rainy period and intense and recurrent sustained seismicity the landslide developed in deep lacustrine deposits has recently accelerated threatening the maca village this work aims at understanding the rupture mechanism and the causes of the recent landslide reactivation acceleration we present a multidisciplinary characterization of the maca landslide that includes i geological and morphological mapping in the field ii remote sensing analysis using an historical aerial photograph of 1955 and the pleiades satellite images 2013 iii global positioning system gps including time series of surveys over 13 years and continuous measurements over 14 months iv a geophysical campaign with deep electrical resistivity tomography profiles acquired across the landslide mass our study shows that this 60 mm3 landslide which can be classified as a clay silt compound landslide moved by 15 m between 2001 and 2014 with a large inter annual velocity variation up to a factor of 500 depending on the rainfall intensity we suggest that these dramatic changes in velocity are the result of the combination of a threshold mechanism and the short intense rainy season in peru this study reveals three main driving factors acting at different timescales i over several decades the river course has significantly changed causing the maca landslide reactivation in the 1980s due to the erosion of its toe ii at the year scale a minimum amount of rainfall is required to trigger the motion and this amount controls the landslide velocity iii transient changes in slide velocity may occur anytime due to earthquakes this study particularly highlights the non linear behaviour of the motion with rainfall copyright 2016 john wiley sons ltd

the impact of a weak horizon on kinematics and internal deformation of a failure mass using discrete element method abstract weak horizons within slopes may induce and or accelerate failure of slopes in this study we focus on the effect of orientation location and dimension of a weak horizon on the mode and kinematics of downslope movement of a failure mass using discrete element method two kinds of cases with weak horizons were studied one unstable homogeneous slope with low shear strength c 50 kpa 0 57 and two stable homogeneous slopes with high shear strength c 60 kpa 0 57 or c 50 kpa 0 7 in the three sets of slope models there was a weak horizon with a finite thickness embedded within the slope in each set of slope models two different thicknesses and locations for the weak horizons were considered to systematically investigate the effect of these parameters on the mass movement in addition the dip of the weak horizon was changed where in some models it was parallel to the slope and in others it was dipping either steeper or gentler than the slope we analyzed both kinematics and internal deformation of the failure mass in all models and conclude that the presence and geometry i e thickness location and dip of a weak horizon changes the mode and kinematics of mass movement and governs the location of the failure surface

submarine landslides triggered by destabilization of high saturation hydrate anomalies submarine landslides occur along continental margins at depths that often intersect the gas hydrate stability zone prompting suggestions that slope stability may be affected by perturbations that arise from changes in hydrate stability here we develop a numerical model to identify the conditions under which the destabilization of hydrates results in slope failure specifically we focus on high saturation hydrate anomalies at fine grained to coarse grained stratigraphic boundaries that can transmit bridging stresses that decrease the effective stress at sediment contacts and disrupt normal sediment consolidation we evaluate slope stability before and after hydrate destabilization hydrate anomalies act to significantly increase the overall slope stability due to large increases in effective cohesion however when hydrate anomalies destabilize there is a loss of cohesion and increase in effective stress that causes the sediment grains to rapidly consolidate and generate pore pressures that can either trigger immediate slope failure or weaken the surrounding sediment until the pore pressure diffuses away in cases where failure does not occur the sediment can remain weakened for months in cases where failure does occur we quantify landslide dynamics using a rate and state frictional model and find that landslides can display either slow or dynamic i e catastrophic motion depending on the rate dependent properties size of the stress perturbation and the size of the slip patch relative to a critical nucleation length scale our results illustrate the fundamental mechanisms through which the destabilization of gas hydrates can pose a significant geohazard

the mechanics of deep seated landslides results are presented of a sequence of laboratory tests undertaken to elucidate the behaviour of deep seated landslides in deep seated failures deformation has been reported at depths of up to 250 m in the movement zone owing to the weight of the overburden and the surrounding stress environment conventional soil mechanics cannot be used to explain effectively associations between the landslip activity and the deformation mechanisms operating within the moving mass a series of experiments has been undertaken on london clay using a high pressure servohydraulically controlled triaxial deformation system to replicate the stresses acting at the base of a large deep seated landslide a number of tests were undertaken the most significant focusing on the transition between ductile and brittle behaviour although sediments usually behave in a brittle manner at low effective stresses common to many geomorphological studies and in a ductile manner at high effective stresses the results presented here identify for the first time in mudrocks a transitional phase of behaviour in which creep like movement will manifest itself at the base of a deep seated landslide as the growth of microcracks the microcracks may eventually coalesce to form a shear surface a consequence of which is likely to be sudden failure the results thus have important implications in the understanding of movement mechanisms in large deep seated failures rates of displacement and how they may change through time 1997 by john wiley sons ltd

recent rainfall induced landslides and debris flow in northern taiwan this paper discusses the factors initiating landslides and a large scale debris flow in the chonho area of taipei county northern taiwan which resulted from heavy rainfall during typhoon xangsane in november 2000 the morphology and triggering mechanism of the landslides and the debris flow were investigated using aerial photographs taken over the past 20 years field measurement of channel cross sections laboratory assessment of slope material properties and slope stability analysis a large landslide that occurred in the source area was the initial source of material for the debris flow the majority of the landslide debris entered the main stream where it mixed with water and became a debris flow eroding the sidewalls of the stream the debris flow entrained additional material and traveled downstream into chonho village our findings indicate that the november 2000 landslides and the debris flow were strongly influenced by the physical properties of the underlying pyroclastic substrate and the pattern of bedrock discontinuities within the valleys

geology of the melas chasma landing site for the mars exploration rover mission 1 the melas chasma landing site was considered a high priority site for the mars exploration rover mer mission because of the opportunity to land on and study potential layered sedimentary deposits though no longer considered a candidate site because of safety concerns the site remains a scientifically interesting area that provides insight into the geologic history of valles marineris within the landing ellipse are dunes landslide material and unusual blocky deposits the blocky deposits are composed of rounded blocks some of which have meter scale layering and they show evidence of ductile deformation including bending and distortion of coherent blocks around each other the morphologic characteristics of the blocks are unique and they appear to have no terrestrial analogue however the gross morphology of these blocky deposits and their superposition on adjacent wallrock is consistent with the blocks having been transported downslope given the existence of other large mass failures in the area we propose the blocky deposits may also have originated from mass movement events the size of the blocks coupled with the distances they traveled indicates high mobility the distances the blocks were transported and their rounded irregular shapes suggest either water in the source material or deposition in a subaqueous environment the source for the main blocky deposit inside the landing ellipse is considered to be the wallrock to the south while the other two blocky deposits have source regions along the northern canyon walls the southern wallrock of melas chasma contains numerous valleys not seen elsewhere in valles marineris the identification of valley networks along the southern wallrock suggests that a source of water existed below the surface of the plateau and produced the valleys after intersecting the edge of the exposed canyon walls

rotational translational landslides in the neogene basins at the northeast margin of the tibetan plateau abstract rotational translational landslides are common in neogene basins throughout the world and are of high risk to the public to understand the mechanism of rotational translational failure the spatial distribution and deformation of rotational translational landslides in the northeast of the tibetan plateau are investigated in this study the spatial distribution of these landslides is dependent on the regional tectonics and geomorphology crustal stresses and lithological properties the rotational translational landslides are concentrated in the neogene mudstone basins and the intensities of these landslides are observed to gradually decrease from the hinterland of the plateau to the marginal basins the bedding parallel shear zones within the location of the rotational translational landslides are present in the overconsolidated neogene mudstones with high clay content nearly horizontal tectonic stresses and erosion cause the formation of horizontal shear stresses in the sliding masses in this stress environment materials with low internal friction angle

an accelerating precursor to predict time to failure in creep and volcanic eruptions real time prediction by monitoring of the evolution of response variables is a central goal in predicting rock failure a linear relation omega omega similar to 1 c t f t has been developed to describe the time to failure where li represents a response quantity c is a constant and tf represents the failure time observations from laboratory creep failure experiments and precursors to volcanic eruptions are used to test the validity of the approach both cumulative and simple moving window techniques are developed to perform predictions and to illustrate the effects of data selection on the results laboratory creep failure experiments on granites show that the linear relation works well during the final approach to failure for blind prediction the simple moving window technique is preferred because it always uses the most recent data and excludes effects of early data deviating significantly from the predicted trend when the predicted results show only small fluctuations failure is imminent c 2017 elsevier b v all rights reserved

reassessing landslide deformation in ganges chasma mars 1 high resolution images of landslide aprons in ganges chasma show extensive scarps rock chutes and talus accumulations on the canyon rim below these exists a topographic bench formed of multiple terraces ridges and scarps the terrace slopes are talus covered similar to the canyon rim small volume lobes and sheets originate from talus accumulations and extend downslope while previously determined to be the result of large volume catastrophic landslides the characteristics and dimensions of the terraces forming the topographic bench can be explained by deep seated gravitational creep of the ancient rock mass gravity driven movements over millions of years can also account for the morphology and dimensions of talus lobes thus offering an alternative to catastrophic long runout landslide mechanisms the movement of lobes is suggested to be analogous to terrestrial periglacial rock glaciers

landslide deformation monitoring with alos palsar imagery a d insar geomorphological interpretation method the objective of this work is to propose a geomorphologically guided method for the interpretation of l band alos palsar interferograms created by differential interferometric synthetic aperture radar d insar the interferograms are used to estimate the deformation pattern of two rapid and large landslides poche la valette south east france the wrapped and unwrapped phase values are interpreted for different movement types rotational translational and complex sliding and two ranges of surface displacement rates kinematic sub units are detected for both landslides and zones affected by enlargement or retrogression are identified the insar derived displacement rates are consistent with ground based measurements and with remote estimates of the displacement from c band and x band satellite sar sensors the results demonstrate the potential of l band alos palsar imagery for the monitoring of active landslides with important changes in the soil surface state and covered by vegetation

a pronounced dry event recorded around 4 2 ka in brine sediments from the northern red sea partly laminated sediments were sampled from the brine filled anoxic shaban deep basin in the northern red sea at about 4200 cal yr bp more than two millennia of anoxic sedimentation is replaced by a sub oxic facies strongly suggesting the episodic absence of the brine at the same time stable oxygen isotopes from surface dwelling foraminifera show a sharp increase within less than 100 yr pointing to a strong positive salinity anomaly at the sea surface this major evaporation event significantly enhanced the renewal of deep water and the subsequent ventilation of the small shaban deep basin the timing and strength of the reconstructed environmental changes around 4200 cal yr bp suggest that this event is the regional expression of a major drought event which is widely observed in the neighboring regions and which strongly affected middle east agricultural civilizations

controls on the seasonal deformation of slow moving landslides article history precipitation drives seasonal velocity changes in slow moving landslides by increasing pore water pressure and reducing the effective normal stress along basal shear zones this pressure change is often modeled as a pore water pressure wave that diffuses through the landslide body such that the minimum time required for landslides to respond to rainfall should vary as the square of landslide depth which often approximates the saturated thickness and inversely with hydraulic diffusivity here we assess this model with new observations from the landslide prone eel river catchment northern california using satellite radar interferometry insar time series precipitation data and high resolution topographic data from airborne lidar we quantify the seasonal dynamics of 10 slow moving landslides which share the same lithologic tectonic and mediterranean climate conditions these slope failures have areas ranging from 0 16 to 3 1 km 2

earthquake rupture as a critical point consequences for telluric precursors abstract earthquakes are related to rupture phenomena in complex statistical systems of cracks we first review some available information suggesting that rupture in earthquakes is a critical point the consequences of this hypothesis on several phenomena are then discussed in particular we focus our attention on a simple theory of electroseismic activity based on mechano electrical transduction effects such as the piezoelectric or the pressure induced polarization effect the neighbourhood of the rupture threshold is characterized by a specific response which could correspond to telluric wave activity observed as precursors of earthquakes

influence of northern hemisphere climate and global sea level rise on the restricted red sea marine environment during termination i 1 we present high resolution paleoceanographic records of surface and deep water conditions within the northern red sea covering the last glacial maximum and termination i using alkenone paleothermometry stable oxygen isotopes and sediment compositional data paleoceanographic records in the restricted desert surrounded northern red sea are strongly affected by the stepwise sea level rise and appear to record and amplify well known millennial scale climate events from the north atlantic realm during the last glacial maximum lgm sea surface temperatures were about 4 c cooler than the late holocene pronounced coolings associated with heinrich event 1 2 c below the lgm level and the younger dryas imply strong atmospheric teleconnections to the north atlantic owing to the restricted exchange with the indian ocean red sea salinity is particularly sensitive to changes in global sea level paleosalinities exceeded 50 psu during the lgm a pronounced freshening of the surface waters is associated with the meltwater peaks mwp1a and mwp1b owing to an increased surface near inflow of normal saline water from the indian ocean vertical 18o gradients are also increased during these phases indicating stronger surface water stratification the combined effect of deglacial changes in sea surface temperature and salinity on water column stratification initiated the formation of two sapropel layers which were deposited under almost anoxic condition in a stagnant water body

the selborne cutting stability experiment the paper describes a field experiment in which a 9 m deep cut slope in gault clay was brought to failure by pore pressure recharge the geology of the site is described and the procedures used to

detecting slope deformation using two pass differential interferometry implications for landslide studies on earth and other planetary bodies landslide features have been identified on earth and the moon mars venus as well on the jovian moons by focusing on a terrestrial landslide complex we test the operational parameters of radarsat 1 and the use of two pass differential interferometry to detect change to map its extent and to measure the amount of movement over a given time period radarsat 1 was chosen because of its variable imaging modes and geometry for investigations of landslide motions using remote sensing techniques repeat pass data are required synthetic aperture radar sar interferometry insar can ideally monitor movements across the whole surface of a landslide to a millimeteric precision yielding a coverage significantly better than that obtained by ground instrumentation obtaining optimal data for insar analysis requires controlled orbital characteristics and imaging geometries an understanding of the landslide characteristics and behavior a cooperative surface and mitigation of the factors that can affect phase using two pass differential interferometry a slope deformation map has been generated from radarsat 1 data for part of the black ven landslide 2 52 w 50 40 n on the south coast of england four months separate the insar pair during which time 0 03 m of subsidence was measured from this a movement rate of 0 09 m yr can be calculated this agrees well with ground observations and an in situ record of movement thus demonstrating that the technique can be used to investigate landslides with further refinement it can provide more direct measurements of landslide deformation on earth and other planetary bodies than are currently available

progressive shear surface development in cohesive materials implications for landslide behaviour the aim of this study was to investigate mechanisms of progressive shear surface development using a series of specialised triaxial cell tests intact and remoulded samples of gault clay from the ventnor undercliff on the isle of wight in southern england were subjected to pore pressure reinflation ppr testing in a triaxial cell in which failure is generated by increasing pore pressure under a constant total stress state in addition a novel very long term 500 days creep test was undertaken in which the sample eventually failed at a constant stress state below the failure envelope the experiments showed that undisturbed samples of the gault clay failed in a brittle manner generating a linear trend when plotted using the saito technique on the other hand remoulded samples showed ductile behaviour as indicated by a non linear saito trend a number of otherwise identical ppr tests were conducted in which the rate of increase in pore water pressure was varied these tests showed that strain rate generated at any point in the ppr tests depended on both the effective stress and the rate of change of effective stress the latter is important because a change in stress generates a change in strain thus whilst tests at different rates of change of effective stress are similar when plotted in q p space and in strain p space they are markedly different in strain rate p space the long term creep test failed when the stress state had been constant for over 80 days this mechanism was reminiscent of creep rupture occurring below the failure envelope defined in the conventional experiments we conclude that first time failure in the gault clay is a progressive mechanism dominated by the development of micro cracking which leads to strain localisation and the development of one or more shear surfaces at failure whilst this mechanism may usually occur in response to a change in stress the study indicates that failure can develop progressively in the remoulded gault clay shear strains cannot localise along a singular shear surface the results provide new insight into the mechanisms of landslide movement operating within the ventnor landslide complex and indicate that present movements are likely to be occurring on a pre existing shear surface the lab tests suggest that this material is unlikely to undergo catastrophic failure