analysis of landslide frequencies and characteristics in a natural system coastal british columbia two hundred and one debris slides and debris ows were analyzed in a 286 km2 study area on the west coast of vancouver island british columbia canada the study area remains essentially untouched by humans and therefore affords a natural setting in which to examine slope processes landslides were identi ed and characterized on aerial photographs from 1 15 000 to 1 31 680 and were then mapped and transferred to a gis for analysis based on detailed landslide surveys we propose a new method to accurately determine volume of landslides of this type by measured total area results indicate average denudation rates of 56 m3 y 1 km 2 and higher natural rates of failure than analogous regions in coastal british columbia in contrast the landslide rates are substantially less than those from forested watersheds landslide distribution is spatially clustered in air photograph epochs and we propose intense storm cells within regional events as the causal mechanism further failures occurred preferentially over the west coast crystalline complex by 1 4 times a metamorphic assemblage of gabbros schists and amphibolites but 1 5 times less often over the island plutonic suite a granitic intrusive formation the former result represents a new nding while the latter corroborates ndings of previous authors we examined magnitude frequency relationships of the data set and present for the rst time a strong argument that the rollover effect is not merely an artefact but is instead a consequence of the physical characteristics of the landslides themselves we subsequently analyzed magnitude frequency relationships from two other complete data sets from coastal british columbia and produced a family of curves corroborating this result copyright 2004 john wiley sons ltd

a multi proxy study of holocene environmental change recorded in alluvial deposits along the southern coast of the pampa region argentina analyses of fossil records of molluscs stable isotopes of carbon and oxygen diatoms and palynomorphs from alluvial deposits at arroyo claromeco in the southern pampa region of argentina provide an integrated reconstruction of rapid holocene environmental change related to marine and palaeoclimate influences the major events recorded include i disturbances produced by marine influences in close proximity to the coast before ca 7700 cal a bp ii a short term decrease in salinity associated with freshwater influx between ca 7700 and 7400 cal a bp in response to eustatic adjustment as sea level rose iii an increasing input of marine water related to the holocene sea level highstand and greater evaporative conditions between 7400 and 6450 cal a bp and iv evaporative processes linked to a pronounced climatic variability that triggered changes in water chemistry during the last ca 6000 cal a bp concurrently with the late holocene sea level fall a comparison of coastal and continental stable isotope records from the pampa region reveals that evaporation and a negative precipitation evaporation p e ratio balance strongly influenced water chemistry in the coastal region and was as important an influence as marine water during the period of maximum sea level highstand copyright 2014 john wiley sons ltd

holocene vegetation changes along the southeastern coast of the argentinean pampa grasslands in relation to sea level fluctuations and climatic variability palynological analysis of alluvial sequences from arroyo claromeco abstract here we present palynological records from alluvial deposits in four outcrop sequences along the lower reaches of arroyo claromeco buenos aires province argentina 38 50 s latitude 60 05 w longitude these data indicate development of soils and grasslands with associated halophytic vegetation in the higher elevations of the floodplains between ca 7200 and 6000 14 c yr bp ca 8000 and 7000 cal yr bp at lower elevations halophytic saltmarsh vegetation was replaced by wetland communities sedges in response to a sea level highstand at 6500 14 c yr bp ca 7400 cal yr bp soils were buried by expanding wetlands at ca 6000 14 c yr bp a trend that persisted until ca 3400 14 c yr bp ca 3700 cal yr bp over this interval we observe repeated fluctuations between grassland and halophytic vegetation in response to variations in water level and physical chemical conditions resulting from desiccation or flooding events these variations are caused by hydrologic variability in a subhumid dry climatic mean state channel incision occurred between ca 3400 and 2500 14 c yr bp ca 3700 3200 cal yr bp concurrent with sporadic and intermittent sediment deposition at higher elevations of the floodplain the pollen record from the paleochannel infilling indicate grasses accompanied by halophytic taxa between ca 2500 and 800 14 c yr bp 3200 and 700 cal yr bp deposited in a shallow brackish to fresh water body the palynological spectra from sediments deposited sporadically at higher elevations show halophytic vegetation and a trend toward wetland desiccation followed by development of psammophytic communities after ca 1100 14 c yr bp the tops of the alluvial sequences are covered by sand dunes whose modern spectra are characterized by psammophytic vegetation along with exotic tree taxa our results and inferences are consistent with previous studies and provide more detailed insights into the impacts of holocene sea level and climatic variations aspects that are relevant for the coastal pampa grasslands under various scenarios in a warming world

the frequency and distribution of recent landslides in three montane tropical regions of puerto rico landslides are common in steep mountainous areas of puerto rico where mean annual rainfall and the frequency of intense storms are high each year landslides cause extensive damage to property and occasionally result in loss of life average population density is high 422 people km2 and is increasing this increase in population density is accompanied by growing stress on the natural environment and physical infrastructure as a result human populations are more vulnerable to landslide hazards the blanco cibuco and coamo study areas range in surface area from 276 to 350 km2 and represent the climatologic geographic and geologic conditions that typify puerto rico maps of recent landslides developed from 1 20 000 scale aerial photographs in combination with a computerized geographic information system were used to evaluate the frequency and distribution of shallow landslides in these areas several types of landslides were documented rainfall triggered debris flows shallow soil slips and slumps were most abundant hillslopes in the study area that have been anthropogenically modified exceed 12 in gradient are greater than 300 m in elevation and face the east northeast are most prone to landsliding a set of simplified matrices representing geographic conditions in the three study areas was developed and provides a basis for the estimation of the spatial controls on the frequency of landslides in puerto rico this approach is an example of an analysis of the frequency of landslides that is computationally simple and therefore may be easily transferable to other settings

basement configuration of on land kutch basin from seismic refraction studies and modeling of first arrival travel time skips abstract the kutch basin is one of the three narmada cambay and kutch major marginal rift basins that are close to each other in mid western part of the indian subcontinent the seismic refraction and wide angle reflection data were acquired and a first order velocity structure of the kutch sedimentary basin along jakhau mandvi mandvi mundra mundra adesar and hamirpur halvad profiles is derived the travel time skip phenomenon has been noticed in the travel time plots and record sections indicating presence of low velocity sediments derived two dimensional velocity depth models revealed a mesozoic sedimentary sequence sandwiched between trap and limestone layers in some of the profiles two thick low velocity layers that corresponds early to late mesozoic era have been identified these are dipping towards mandvi along jakhau mandvi profile the early mesozoic layer that is thinning towards southeast is completely missing in mandvi mundra profile it is also noticed that the early mesozoic bhuj formation exists in the northern parts of the mundra adesar and hamirpur halvad profiles where it directly overlies the granitic basement the derived velocity depth model suggests that the basement is about 3 km deep near jakhau and reaches a depth of about 6 km near mandvi the layered structure may correspond to the tertiary trap late mesozoic sediments and mesozoic limestone the velocity depth model obtained in kutch is very similar to earlier derived model for jamnagar and dwarka sub basins of northwestern saurashtra peninsula suggesting probable continuity linkage between southern on land kutch and across the gulf of kutch to saurashtra peninunsula we also conclude that the evolution of kutch basin as a peri cratonic rift basin is essentially controlled by the four f1 f4 faults inferred from obvious abrupt changes in layer thickness velocity along the seismic refraction profiles

the influence of loess cave development upon landslides and geomorphologic evolution a case study from the northwest loess plateau china abstract loess caves landslides collapses bank erosion and soil erosion which are independently and interactively shaping the modern loess landscape are widely distributed across the chinese loess plateau the study area is located in a small watershed in huining county gansu province which is one of the areas with the strongest development of loess caves across the loess plateau this area is an ideal site for studying geological hazards and geomorphic evolution on the loess plateau seventeen landslides and 176 loess caves with a density of 887 units km2 were investigated with a uav unmanned aerial vehicle and mapped by gis geographic information system using high resolution uav images and topographic data we carried out an interpretation of loess caves bank erosion and landslides studied the spatial distribution and developmental patterns of loess caves landform morphology and the relationship between loess caves and landslides based on gis spatial analysis mathematical statistics and field surveys and analyzed the influence of loess microtopography on slope landforms finally six typical evolutionary models of soil erosion loess cave development landslide occurrence barrier dam formation are preliminarily proposed the primary slope stage early cave stage accelerated cave stage cave connecting stage landslide creeping stage and landslide dam forming stage this study is a useful exploration and an attempt to reveal the influence of loess cave development on slope stability and disaster chain effects

rift basins in western margin of india and their hydrocarbon prospects with special reference to kutch basin the western continental margin of india can be classed as a divergent or passive margin the western continental shelf is an extensive carbonate bank bombay offshore basin passing into clastic sediments on the north and south three craton margin embayed basins kutch cambay and narmada in the northern part of the shelf are filled predominantly with clastic sediments these basins occupy grabens bounded by faults diverging seaward the grabens were formed by three rift systems along major precambrian tectonic trends the rifting developed sequentially from north to south around the saurashtra horst kutch basin was formed in the early jurassic followed by cambay basin in early cretaceous time and the narmada in the late cretaceous it appears that these rifting ev nts occurred at successive stages during the northward migration of the indian plate after its break from gondwanaland in late triassic or early jurassic it is inferred that these rift basins opened up successively as a result of the counterclockwise drift of the indian craton bombay offshore and cambay are two major oil producing basins in the western margin these basins are characterized by high geothermal gradients attributed to the shallowness of the mantle in this region oil has not been found in kutch basin which is mainly an onshore mesozoic basin the basin depocenter shifted offshore at the northwestern part of the continental shelf where the shelf is wide

geological hazards in loess terrain with particular reference to the loess regions of china abstract the considerable morphodynamic energy provided by the continuing tectonic evolution of asia is expressed in high erosional potentials and very high rates of sediment production that make this continent unequalled as a terrestrial source of primary silt many of these environments are hazardous threatening human occupation health and livelihood especially in regions of dense population such as the loess lands of north china dry loess can sustain nearly vertical slopes being perennially under saturated however when locally saturated it disaggregates instantaneously such hydrocompaction is a key process in many slope failures made worse by an underlying mountainous terrain of low porosity rocks gully erosion of loess may yield very high sediment concentrations 60 by weight characteristic vertical jointing in loess influences the hydrology enlarged joints develop into natural sub surface piping systems which on collapse produce a loess karst terrain collapsible loess up to 20 m thick is common on the western loess plateau foundation collapse and cracked walls are common many rapid events following periods of unusually heavy monsoonal rain slope failure is a major engineering problem in thick loess terrain flow slide and spread types being common the results are often devastating in both urban and rural areas an associated hazard is the damming of streams by landslides the human population increases the landslide risk in china notably through imprudent land use practices including careless water management a number of environmentally related endemic diseases arise from the geochemistry of loess and its groundwaters including fluorosis cretinism kaschin beck disease keshan disease and goitre the chinese desert margins also have a major atmospheric dust problem the effect of such dust upon human health in these extensive regions including many large cities has yet to be evaluated but pneumoconiosis is thought to affect several million people in north and west china

gully and tunnel erosion in the hilly loess plateau region china article i nfo article history although gully development is frequently observed to be associated with piping and tunnel erosion in many parts of the world there is a lack of detailed studies on their spatial interactions such studies not only con tribute to developing geomorphic theories on the evolution of both hillslopes and drainage networks but also are useful to design effective control measures of erosion the present study aims to examine the interactions between gully development and tunnel erosion in the hilly loess plateau region of northern china firstly gullies tunnel inlets and mass movements in the 9 1 km 2 wangjiagou watershed were mapped through ae rial photo interpretation and reconnaissance surveys secondly detailed field studies were carried out to in vestigate the interactions between gully development and tunnel formation processes in the selected gullies thirdly the physiographic variables of gullies derived from gis and field measurements were analyzed to identify differences between tunneled and untunneled gullies a total of 704 channels 967 tunnel inlets and 547 mass movements were identified in the study watershed on the basis of their location and morphology all the channels were classified into four types headwater gullies hillside gullies valleyside gullies and ephemeral river channels tunnels are associated with 79 of headwater gullies 48 of hillside gullies 3 of valleyside gullies and none of ephemeral river channels mass movements are dominated by falls in headwater gullies falls and slides in hillside gullies and soil creeps in ephemeral stream channels statistical tests indicate that there are significant differences in phys iographic variables between tunneled and untunneled gullies tunnel formation in gullies is intricately affect ed by topographic conditions land uses knickpoint distribution soil materials and mass movements published by elsevier b v

pedosedimentary and palaeoenvironmental significance of a holocene alluvial sequence in the southern pampas argentina a representative section of the holocene alluvial record of the southern pampas argentina com prises a sequence of clastic sediments a diatomite and two palaeosols detailed macro and micromorphological descriptions provide the basis for the reconstruction of its pedosedimentary history combining the pedosedi mentary reconstruction with palaeoecological data allows a detailed overview of alluvial landscape development and associated palaeoenvironmental change in the region during the holocene the early holocene shift from a subhumid dry to humid climate was marked initially by a diminution in clastic sedimentation the development of the puesto callejon viejo soil and then re establishment of fluvial aggradation with a dominance of bioclastic sedimentation loess inputs increased during the mid holocene as the climate reverted to subhumid dry and temporary subaerial exposure of the sediments led to the formation of the puesto berrondo soil more variable environmental conditions followed with natur

pleistocene and holocene beaches and estuaries along the southern barrier of buenos aires argentina abstract the buenos aires aggradation plain has a good record of quaternary sea level fluctuations to the east of the tandilia range the elevations of the pleistocene beaches respond to the tectonic behaviour of the salado basin holocene beaches indicate a maximum transgression higher than 2 m the low relief permitted an extended horizontal record of beach chenier plains interfingered with estuarine environments coastal lagoons marshes covered by a sandy eastern barrier between the tandilia and ventania ranges the location of pleistocene and holocene beaches are related to a former higher relief i e they are attached to low altitude cliffs and underneath cliff top dunes composing the southern barrier at claromeco pleistocene gravel beaches mostly composed of caliche pebbles occur at heights between 4 and 7 m and are overlying estuarine pleistocene environments beaches of the same age are at a level of 10 m at mar del plata harbour and arroyo sotelo west of mar chiquita lagoon holocene beaches found at punta mogotes and costa bonita are at higher altitudes than on the eastern barrier ca 2 4 m the holocene estuarine sequences are related laterally to present operating inlets las brusquitas la ballenera quequen grande claromeco quequen salado they are seldon thicker than 2 4 m and comprise basal layers of black muds towards the top the layers are thinner of coarser grain size and white colours grain size analyses were performed comparatively on pleistocene mid holocene and present beaches sangamonian beaches aregravelly or coarser than medium sand mean holocene beaches are usually coarser than medium sand but dominantly shelly to the north of mar del plata and composed of volcanic clasts to the south of this city modern beaches are dominated by fine sand except at some erosive beaches between the mar del plata capes they have a lesser content of shells than those of mid holocene

geological and geotechnical characteristics of some loess and loessic soils from china and britain a comparison abstract derbyshire e and mellors t w 1988 geological and geotechnical characteristics of some loess and loessic soils from china and britain a comparison eng geol 25 135 175 loess and loessic deposits cover some 630 000 km 2 of the surface of mainland china the loess plateau of shanxi shaanxi gansu and ningxia being the type region of this formation loess thickness generally exceeds 100 m over large areas of the loess plateau the maximum recorded thickness being 335 m in eastern gansu province near the city of lanzhou in britain loess and loessic deposits form part of a group of materials collectively known as brickearth they occur predominantly as sporadic accumulations in the southeast of england and rarely attain a thickness of more than four metres despite their geographical separation the deposits from china and britain have a remarkable similarity in some of their physical and geotechnical characteristics samples from both locations have been examined and tested in the laboratory and the results are presented the scope of the testing programme involved mineralogical analyses soil microfabric studies using a scanning electron microscope index testing including plasticity grading and density measurements and the investigation of the compressibility characteristics of the soils with particular reference to their susceptibility to collapse a soil structure model based on scanning electron microscope studies is presented and discussed in relation to the perceived mode of formation of the soils and their postdepositional history

the post last glacial maximum transgression in the de la plata river and adjacent inner continental shelf argentina abstract deposits resulting from the last glacial maximum transgression have been studied in the lowermost regions of the del plata fluvial basin in eastern argentina which include the de la plata river and adjacent inner shelf and coastal plains after applying the concepts of sequence stratigraphy those deposits were considered as a unit and defined as a depositional sequence composed of two systems tracts respectively representing the transgressive event and the highstand of sea level the sequence was deposited in different but genetically linked depositional environments such as high and low energy coasts with coastal barriers beach ridges coastal plains estuaries and deltas as well as inner shelf the boundary between the sequence and the underlying pre transgressive units is represented by the transgressive surface or unconformity modeled by the ravinement process which extends from the outer edge of the shelf to the coast this surface is time transgressive and can be recognized by distinct physical characteristics above and below it depending on the successive sedimentary environments developed in deep shallow or coastal waters as sea level fluctuated

interaction between landsliding materials and the underlying erodible bed in a loess flowslide abstract loess landslides exhibit strong interactions with the terrace sediments of the jing river on the south jingyang platform jingyang xi an china analysis of past landslide events revealed that the sand layer of this terrace was thrust up to the surface accompanied by other terrace sediments of carrying this led to the formation of a thrust nappe structure over a long distance we performed ring shear tests to examine the shear behavior of this sand layer with the finding that saturated sand was highly susceptible to liquefaction induced failure the groundwater level of the study area is high resulting in near saturation of the sand layer therefore topographic interferences contributed additional variables and increased interaction complexities simulations indicated that the liquefied sand layer was compressed and forced due to the absence of constraints the sand layer near the bottom of the slope was sheared out over a relatively short distance on the other hand particle interia and constraints of the stable layer resulted in the sand layer near the distal part of the deposits being sheared upward to the ground finally an initiation movement model of loess flowslides is proposed it describes static liquefaction of the loess layer of the slope resulted in occurrence of flowslides collisions between the deposits from the platform edge slope and terrace sediments resulted in the shear liquefaction of sands the landslide experienced four stages as they moved scraping collisions floating scrapes folded thrusts and nappe accumulation

modelling the erosional susceptibility of landslide catchments in thick loess chinese variations on a theme by jan de ploey abstract in his 1990 paper catena 17 175 183 jan de ploey proposed a system whereby catchments are viewed as functional units in which geomorphic work results from the combined effects of water erosion and mass movements his measure of erosional susceptibility of catchments es introduced the gravitational potential in addition to the kinetic energy of the eroding agents this modelling of the erosional susceptibility of catchments in terms of energy was being used to explore time dependent variations of es when jan de ploey died also at this time he extended an invitation to the present authors to test and extend his model using our data base on the landslide dominated catchments in the thick loess country of north central china this paper presents a series of new equations expressing variations in es using a data base for over 200 landslides in the loess covered mountainous terrain relative relief up to 1500 m of the lanzhou region of eastern gansu province these equations express the loss of potential energy of the landslide mass in relation to the relative relief and the pressure energy input in the form of rainfall these indices of erosional susceptibility can be used to analyse the differences in response from one catchment to another and through time between the characteristics of vegetation cover including land use hydrology geomechanical behaviour and mechanisms of movement on slopes using certain assumptions on percentage area of catchments affected by mass movement and long term mean annual precipitation in the lanzhou region the es equation suggests an estimate for non clayey materials of about 10 4 m 2 s 2 which is a significantly higher susceptibility value than the mean worldwide value for non clayey materials obtained by de ploey

failure mechanisms in loess and the effects of moisture content changes on remoulded strength abstract investigations into the failure mechanisms of loess slopes in the loess region of north central china have shown that a majority of mass movements are associated with shallow slab slides predominantly moving under tension the effects of soil moisture content are of paramount importance when dry vertical slopes in loess may exceed 15 m in height but under conditions close to saturation the structural strength of loess rapidly decreases causing failure of the slopes mass failure of loess occurs as collapse due to hydroconsolidation and disintegration of the loess fabric as a result of liquefaction or fluidization and can be associated with progressive failure processes local destruction of the openwork fabric of the loess can lead to small plastic movements within the loess deposits this is as close as loess can come to creep

vegetational history of the late glacial holocene transition in the grasslands of eastern argentina abstract palynological records from eight sites located in the eastern plains of argentina from the humid pampa in the east to the xerophytic woodland dry pampa ecotone in the west allow a regional reconstruction of the vegetation of late glacial holocene transition fossil pollen records were interpreted in terms of palaeoenvironmental information using the modern pollen vegetation climate relationship as an analogue although an exact analogue does not exist today late glacial vegetation consisted mostly of psammophytic steppe in large areas of the central and south western pampa grassland which in the south west is associated with a shrub steppe suggesting subhumid dry to semi arid climatic conditions the replacement of dry steppe by humid grassland and the rapid evolution of pond environments during the early holocene starting during the late glacial holocene transition suggests a shift towards subhumid to humid climate conditions the late glacial holocene transition is indicated in the pollen records by repeated abrupt changes in the proportions and concentrations of some taxa such as brassicaceae asteraceae and carduus type in the modern vegetation they represent species of common occurrence in human induced disturbance habitats suggesting an environment that was subject to frequent natural disturbance such as rapid and repeated flooding episodes that inundated the depressions along the valley floodplains caused by unusual rainfall events some species of carduus may have been native and not introduced by the europeans suggesting that late glacial vegetation of the pampa grasslands may account for the abundance of ruderal species of special interest is the presence of myrtaceae in some pollen assemblages between 11 000 and 9000 yr b p at present myrtaceae are not part of the natural vegetation in the pampa grassland their presence in the fossil pollen records may be interpreted as local deposition instead of extra regional origin myrtaceae formed part of the psammophytic steppe and after late glacial holocene transition they disappeared from the regional flora perhaps due to the climatic change that occurred at the beginning of the holocene it is the most significant cause of extending the area of some pampa grassland taxa but it may have reduced the area for others of the late glacial vegetation at least myrtaceae were probably not able to adapt to the new habitats and hence disappeared from the regional flora at the pleistocene holocene transition although other plants may have disappeared as well these cannot be identified because pollen from these plants cannot be differentiated morphologically during the late glacial holocene transition communities with no modern counterparts probably formed and disappeared

investigating landslide related cracks along the edge of two loess platforms in northwest china cracks are widely developed along the edge of loess platforms in northwest china field surveys reveal that these cracks can be grouped into shallow and deeply penetrating ones the former occur at a small distance from the platform edge normally penetrate into the top unsaturated loess with the penetration depth being controlled by the joints in loess the latter penetrate deeper into the saturated loess farther away from the platform edge these cracks control the inflow and drainage of irrigation water the shallow penetrating crack can fail as a slide or fall with a volume of up to hundreds of cubic meters the deeply penetrating crack can fail as a flow like landslide with a volume of thousands of cubic meters or more a full scale field test simulating irrigation on the platform surface was conducted the two types of crack can be interconnected so that the water applied in the test finally flowed into the deep crack and was discharged from the platform analysis of soil stress states and the results of field test show that the deeply penetrating cracks could have both positive as well as negative effects on slope stability on the one hand water can flow more freely in the cracks and the loess could be saturated and trigger a landslide on the other hand the water can drain more easily along the crack and slope stability could be enhanced as the groundwater level is suppressed copyright 2012 john wiley sons ltd

size distribution of loess slides in relation to local slope height within different slope morphologies abstract loess slides are widespread and dangerous gravity induced surface processes on the loess plateau of north central china the local slope height and slope morphology have been considered as important conditioning factors for landslide susceptibility mapping however the quantitative relationship between landslide size and local slope height within different slope morphologies is not very clear in this study an inventory of 155 loess slides was developed based on detailed field investigation and remote sensing image interpretation statistical analysis and gis were applied to find the quantitative relationships between the size of these loess slides and local slope height in different types of slope morphologies the analysis shows that the relationship between the loess slides volume and area exhibits a similar trend within different types of slope morphologies in addition the analysis demonstrated that loess slides are more frequent on local slope height from 40 to 100 m stepped slopes with higher pore water pressure are prone to sliding and approximate 34 19 of total loess slides occur in these stepped slopes moreover the analysis shows that the mean loess slide area and volume rapidly increase with increasing local slope height furthermore the result underlines the fact that both the local slope height and the slope morphology are two fundamental factors that control the occurrence as well as size distribution of loess slides the loess slide size remarkably increases with increasing local slope height within every type of slope morphologies these findings indicate that local slope height can limit the loess slide size and their spatial extent moreover we quantified the correlation between the loess slide size and local slope height using power law form and the scaling exponents of the correlations are different within different slope morphologies

magnetotellurics study to identify subsurface resistivity structure in the eastern part of kachchh little rann area of gujarat india a magnetotelluric mt survey has been conducted in the eastern part of the kachchh region of gujarat state crossing little rann starting from adesar village in the north to enjar village in the south where limited geophysical data is available the profile has been acquired in the n s direction having a total length of 52 km with the interstation spacing of 3 4 km from two dimensional 2d inversion of the mt data four conductive zones are identified the analysis reveals that the depth of the basement varies from 1 2 km in the south to 1 8 km in the north the first conductive zone is found at a distance of 3 km in the south of adesar and is identified at the location of the kanmer fault kf the eastern extension of south wagad fault swf and might be the kf the second conductive zone is found at a distance of 42 km in the south of adesar and 13 km north of enjar village and is located at the contact zone of kachchh and saurashtra peninsula at the location of the north kathiawar fault nkf it is inferred as the nkf the third conductive zone at a distance of 27 km in the south of adesar is found between the first and second conductor this is interpreted as a step fault formed during the rifting process of kachchh the lower crust below 20 km is found conductive 120 m and might indicate the presence of fluid filled mafic ultramafic rocks in the lower crust

the liquefaction of sands a collapse surface approach recent large scale slides occurring during the hydraulic placement of an artificial island berm in the beaufort sea resulted from the liquefaction of the berm sand subsequent laboratory tests and

a view on some hydrological triggering systems in landslides abstract in this paper different types of hydrological triggering systems for debris flows shallow and deeper landslides are described the generation of surface run off and high peak discharges in first order alpine catchments is an important triggering mechanism for debris flows failure conditions in shallow landslides can occur when at a critical depth which is determined by the cohesion of the soil and the slope angle the moisture content in the soil becomes close to saturation resulting in a considerable reduction of soil strength deeper landslides 5 20 m depth are in most cases triggered by positive pore pressures on the slip plane induced by a rising ground water level the assessment of meteorological threshold conditions for shallow landslides 1 2 m needs more detailed meteorological information than for deeper landslides in the analyses of the hydrological triggering systems of deeper landslides the presence of a permeable top layer and fissures has to be taken into consideration

experimental case study of seismically induced loess liquefaction and landslide abstract the 1920 haiyuan ms 8 5 earthquake induced a large number of fluidized loess landslides in china characterized by low slope angles long run out distances and fluidized movement the mechanism of these landslides has aroused considerable interest although additional research is needed to understand more fully the behavior of the loess and the failure mechanism field investigation was conducted on the shibeiyuan landslide and loess samples collected for later laboratory analysis by conventional geotechnical tests triaxial compression tests and ring shear tests the field survey revealed that the shibeiyuan landslide occurred on a concave slope

controlling factors of loess landslides in western china based on detailed field data from recent geo hazards surveys in the loess plateau region of western china this study analyzes the key factors that control loess landslides the evolution phase of river valleys the geological structure of slopes and the geometry of slopes are all found to play a role in determining the occurrence distribution and other characteristics of loess landslides groundwater and vegetation also contribute to their formation a combination of human engineering activities and precipitation events are the principal triggering factors for the instability of loess slopes

size distribution of submarine landslides along the u s atlantic margin abstract assessment of the probability for destructive landslide generated tsunamis depends on the knowledge of the number size and frequency of large submarine landslides this paper investigates the size distribution of submarine landslides along the u s atlantic continental slope and rise using the size of the landslide source regions landslide failure scars landslide scars along the margin identified in a detailed bathymetric digital elevation model dem have areas that range between 0 89 km2 and 2410 km2 and volumes between 0 002 km3 and 179 km3 the area to volume relationship of these failure scars is almost linear inverse power law exponent close to 1 suggesting a fairly uniform failure thickness of a few 10s of meters in each event with only rare deep excavating landslides the cumulative volume distribution of the failure scars is very well described by a log normal distribution rather than by an inverse power law the most commonly used distribution for both subaerial and submarine landslides a log normal distribution centered on a volume of 0 86 km3 may indicate that landslides preferentially mobilize a moderate amount of material on the order of 1 km3 rather than large landslides or very small ones alternatively the log normal distribution may reflect an inverse power law distribution modified by a size dependent probability of observing landslide scars in the bathymetry data if the latter is the case an inverse power law distribution with an exponent of 1 3 0 3 modified by a size dependent conditional probability of identifying more failure scars with increasing landslide size fits the observed size distribution this exponent value is similar to the predicted exponent of 1 2 0 3 for subaerial landslides in unconsolidated material both the log normal and modified inverse power law distributions of the observed failure scar volumes suggest that large landslides which have the greatest potential to generate damaging tsunamis occur infrequently along the margin

collapsibility and deformation characteristics of deep seated loess in china abstract lin z g and wang s j 1988 collapsibility and deformation characteristics of deep seated loess in china eng geol 25 271 282 as part of a comprehensive research program laboratory tests were conducted on samples of deep seated loess from different locations of the loessial regions of northern china including shaanxi gansu shanxi and honan provinces the information thus acquired on some aspects of the engineering properties of the samples such as the unit collapse pressure relationships the initial collapse pressure versus the preconsolidation pressure and deformation pressure characteristics is interesting and may prove useful to geotechnical engineers who work on projects on water poor plateaux or high river terraces in loessial regions throughout the world

deep seated gravitational slope deformation dsgsd and slow moving landslides in the southern tien shan mountains new insights from insar tectonic and geomorphic analysis we investigated deep seated gravitational slope deformation dsgsd and slow mass movements in the southern tien shan mountains front using synthetic aperture radar sar time series data obtained by the alos palsar satellite dsgsd evolves with a variety of geomorphological changes e g valley erosion incision of slope drainage networks over time that affect earth surfaces and therefore often remain unexplored we analysed 118 interferograms generated from 20 sar images that covered about 900 km2 to understand the spatial pattern of the slope movements and to identify triggering parameters we correlated surface dynamics with the tectono geomorphic processes and lithologic conditions of the active front of the alai range we observed spatially continuous constant hillslope movements with a downslope speed of approximately 71 mm year 1 velocity our findings suggest that the lithological and structural framework defined by protracted deformation was the main controlling factor for sustained relief and consequently downslope mass movements the analysed structures revealed integration of a geological structural setting with the superposition of cretaceous paleogene alternating carbonatic and clastic sedimentary structures as the substratum for younger less consolidated sediments this type of structural setting causes the development of large scale gravity driven dsgsd and slow mass movement surface deformations with clear scarps and multiple crest lines triggered planes for large scale deep mass creeps and these were related directly to active faults and folds in the geologic structures our study offers a new combination of insar techniques and structural field observations along with morphometric and seismologic correlations to identify and quantify slope instability phenomena along a tectonically active mountain front these results contribute to an improved natural risk assessment in these structures

scaling relationships between bed load volumes transport distances and stream power in steep mountain channels bed load transport during storm events is both an agent of geomorphic change and a significant natural hazard in mountain regions thus predicting bed load transport is a central challenge in fluvial geomorphology and natural hazard risk assessment bed load transport during storm events depends on the width and depth of bed scour as well as the transport distances of individual sediment grains we traced individual gravels in two steep mountain streams the erlenbach switzerland and rio cordon italy using magnetic and radio frequency identification tags and measured their bed load transport rates using calibrated geophone bed load sensors in the erlenbach and a bed load trap in the rio cordon tracer transport distances and bed load volumes exhibited approximate power law scaling with both the peak stream power and the cumulative stream energy of individual hydrologic events bed load volumes scaled much more steeply with peak stream power and cumulative stream energy than tracer transport distances did and bed load volumes scaled as roughly the third power of transport distances these observations imply that large bed load transport events become large primarily by scouring the bed deeper and wider and only secondarily by transporting the mobilized sediment farther using the sediment continuity equation we can estimate the mean effective thickness of the actively transported layer averaged over the entire channel width and the duration of individual flow events this active layer thickness also followed approximate power law scaling with peak streampower and cumulative stream energy and ranged up to 0 57min the erlenbach broadly consistent with independent measurements

three dimensional gravity modelling of kutch region india abstract understanding the crustal architecture of kutch rift region india is important due to the presence of thick mesozoic sediments and also due to occurrence of earthquakes we present here three dimensional gravity models the major features of our shallow crustal model are 1 thickness of deccan traps is almost negligible towards northern side of vigodi fault and katrol hill fault 2 mesozoic sediment thickness is about 3 km on the southern side and 3 several undulations in the basement on the wagad uplift the model is consistent with the geological observation that the basin slopes towards southwest the observed bouguer gravity anomalies are explained by 10 km thick granitic upper crust of 2 7 g cm 3 10 km thick intermediate mid crust of 2 82 g cm 3 15 km thick mafic lower crust of 2 91 g cm 3 density crustal thickness is about 40 45 km on wagad uplift and near katrol hill fault the modelled gravity data do not require presence of anomalous amount of fluids melts and or magma chambers in the deep crust of kutch region

sensitivity of rainstorm triggered shallow mass movements on gully slopes to topographical factors on the chinese loess plateau abstract topographical factor is one of the most important factors in understanding the formation mechanism of shallow mass movements on gully slopes on the loess plateau china however the sensitivity of shallow mass movements on gully slopes to topography is poorly understood here a series of rainfall simulation experiments was performed to quantitatively explore the influences of slope height 1 0 and 1 5 m and gradient 60 and 70 on shallow mass movements on the natural loess slopes on the loess plateau our research observed shallow mass movement processes on undisturbed slopes by using a topography meter and collected data that well reflected the nature of the processes the conducted study has advantageous over traditional methods that are usually used in laboratory tests of backfilled soil results showed that the amount of shallow mass movement increased with increased slope height and gradient the shallow mass movement rates i e gravity erosion rates increased by approximately 3 8 times with increased slope height from 1 0 m to 1 5 m and increased by 148 525 with increased slope gradient from 60 to 70 the sensitivity coefficient of slope gradients for shallow mass movements was 2 1 times larger than that of slope heights for the shallow mass movements slope heights had the greatest effect on earthflow relative to slide and avalanche whereas slope gradients had the greatest effect on slide our results provided insights into natural hazard susceptibility assessment and control erosion processes

paleolimnological record of the pampean plains argentina as a natural archive of south american hydroclimatic variability since the lgm to the current warm period abstract laguna mar chiquita lmc 30 54 s 62 51 w is a highly variable and shallow saline lake located in the pampean plains of argentina the paleolimnological record of lmc contains information on the environmental variability that occurred in a large area of southern south america since the last glacial maximum lgm until the present as inferred from the diatom assemblages sedimentary features and geochemical proxies prolonged intervals of high and lowstands have caused variations in water salinity trophic state and sedimentary processes this is the first paleolimnological reconstruction covering the hydroclimatic variability that occurred over the last 25 000 cal yr bp in the argentinean pampean region results are in accordance with well known global climatic phases the late pleistocene record is characterized by a scenario dominated by lowstands hypersaline and oligotrophic lake conditions radiocarbon ages 25 000 19 000 cal yr bp indicate that the onset of the record is coeval with the lgm later a progressive lake water level increase was registered at 17 000 cal yr bp which can be assigned to the heinrich stadial 1 a shift toward comparatively drier conditions identified in the record between 14 700 and 13 000 cal yr bp can be chronologically related to the antarctic cold reversal the transition from the late pleistocene to the holocene 13 500 10 500 cal yr bp is recorded by highstand phases while the early holocene record is characterized by high to intermediate water levels the hydrological reconstruction corresponding to the mid holocene is characterized by alternating phases of high lowstands the onset of the late holocene record is marked by the development of dry conditions and thus lowstand phases while around 1300 cal yr bp a distinct water lake level increase is recognized this humid phase ascribed to the medieval climatic anomaly is followed by the record of lowstands between 500 and 1000 cal yr bp being coeval with the little ice age the uppermost part of the record of lmc encompasses the current warm period showing a marked shift towards high lake water level conditions the hydrological variability registered in the paleolimnological record highlights the importance of laguna mar chiquita as an outstanding paleoclimate sensor of hydroclimatic variations for a large area of south eastern south america

gravity erosion on the steep loess slope behavior trigger and sensitivity abstract gravity erosion is a dominant geomorphic process on the widespread steep loess slopes yet it is not well understood due to the complexity of failure occurrence and behavior this study conducted a series of experiments in the laboratory to test the stability of different slope geometries and rainfalls and then performed a sensitivity analysis to quantitatively explore the triggering mechanisms of mass failure on the steep loess slope a topography meter designed by the authors was used to quantitatively measure the process of gravity erosion and the increase rate analysis method presented by the authors was also used to analyze the sensitivity of gravity erosion the following three types of gravity erosion were observed landslide avalanche and mudslide in an event of rainfall various types of gravity erosion might emerge in the same period and mass failures with the same mode and similar size often adjacently appeared sometimes a group of mass failures might happen on a large slowly slipping block then the increase rate analysis method was used to evaluate variations in the gravity erosion with respect to changes in other causal parameters of rainfall duration intensity and slope height gradient climate driven factors and topography triggers had prominent influences on gravity erosion whether for the total amount or the peak amount in an experiment the largest sensitivity parameter on both landslides and mudslides was that of rainfall duration in comparison topography was relatively less influential for the total amount in an experiment the sensitivity parameters of rainfall duration on the landslide and mudslide were 24 9 and 19 5 respectively while the sensitivity parameter of rainfall intensity on the avalanche was 2 2 for the peak amount in an experiment the sensitivity parameter of rainfall duration on the landslide and mudslide were 5 5 and 15 6 respectively meanwhile the sensitivity parameter of slope gradient on the avalanche was 4 6 the experimental results obtained here provide an insight into the pre failure mechanisms and processes of steep loess slopes

palaeoenvironmental evolution and sea level fluctuations along the southeastern pampa grasslands coast of argentina during the holocene holocene pollen and diatom analyses and complementary data from 18o and 13c malacology and sedimentology have provided a detailed record of vegetation history and palaeoenvironmental change at arroyo las brusquitas on the southeastern coast of the pampas of argentina especially in relation to past sea levels holocene palaeosalinity trends were estimated by detrended correspondence analysis and by salinity indexes based on pollen and diatom data as a consequence of sea level rise from the postglacial an extensive wave cut platform formed over which holocene infilling sequences were deposited unconformably in these sequences variation in pollen and diatom assemblages occurred in agreement with changes in mollusc diversity and abundance isotope values and sediment deposits between ca 6700 and 6190 14c yr bp 6279 6998 cal yr bp saline conditions predominated in an environment highly influenced by tides and salt water during the holocene sea level highstand between ca 6200 and 3900 14c yr bp 4235 4608 cal yr bp shallow brackish water bodies formed surrounded by saltmarsh vegetation that became more widespread from 5180 14c yr bp 5830 6173 cal yr bp to 3900 14c yr bp in relation to a sea level stabilisation period within the regression phase less saline conditions marked by frequent variations in salinity predominated between ca 3900 and 2040 yr 14c bp 1830 2160 cal yr bp the intertidal saltmarsh environment changed into a brackish marsh dominated by freshwater conditions and sporadic tidal influence halophytic vegetation increased towards ca 200014c yr bp indicating that saline conditions may be due to either desiccation or an unusually high tide range with rare frequency after ca 2000 14c yr bp the sedimentary sequences were buried by aeolian sand dunes changes in holocene vegetation and environments in las brusquitas area are in agreement with data obtained from various southeastern coastal sites of the pampa grasslands copyright 2005 john wiley sons ltd

a study of a flowslide with significant entrainment in loess areas in china flowslides are a frequent type of natural disaster in loess areas and may result in the significant loss of properties and or casualties the dagou flowslide is a typical event in a loess area and is accompanied by significant sediment entrainment to analyze the mechanisms responsible for flowslides and to obtain the parameters for a runout analysis a field investigation was conducted specimens were sampled on site to carry out laboratory tests including a triaxial test sieve analysis and chemical component analysis the parameters were used in the runout study employing an energy based runout model an analytical entrainment model was adopted to calculate the entrainment after considering physical properties and the mechanism of the entrainment process of the loess finally the entrainment model was incorporated into the runout model to simulate the post failure process of this case energy dissipation due to the deformation of slices was considered as it was thought to be important for a slide with a significant deformation the simulation results were compared with the measurements including runout distance total volume erosion depth deposition height at different sections and velocities at specific locations the results indicate that the energy based runout model together with the entrainment model can capture the kinematic characteristics of the dagou flowslide therefore it is feasible to use this model to predict the runout characteristics of flowslides in similar areas copyright c 2017 john wiley sons ltd

late pleistocene sea level variations derived from the argentine shelf 1 neritic littoral marine sedimentary deposits from the argentine shelf provide a record of late pleistocene sea level variation sediments interpreted to reflect the last glacial maximum low stand are 150 m below present using a simple airy isostatic model for hydroisostatic compensation and correcting for a minor tectonic component yields a local eustatic sea level lowering of 105 m at the last glacial maximum the deglacial sea level curve records two rapid sea level rises consistent with mwp1 a and 1 b as documented by the barbados coral based sea level curve comparison with relative sea level variations predicted by the ice4g vm2 viscoelastic model have highlighted a deficiency in the model s predicted sea level history for this region detailed data model comparisons of late pleistocene sea level variations are necessary in the face of climate change induced sea level perturbations to determine regional and or systematic biases in the treatment of lithosphere viscosity and accurate predictions of future sea level

temporal patterns of nonseismically triggered landslides in shaanxi province china abstract examination of the temporal patterns of landslide events provides valuable insights into the baseline information used to determine landslide activity and perform risk assessment in a given area we collected a catalog of historical nonseismically triggered landslides that occurred over 22 years in shaanxi province china we found that the annual number of slides was significantly related to the annual number of falls the average annual numbers of slides and falls were approximately 17 and 10 respectively the active and nonactive periods of landslides alternated within the time series of the annual number of landslides an empirical power law correlation exists between the complementary cumulative frequency and the annual number of landslides the monthly distribution of landslide events is significantly associated with monthly rainfall most landslide events occurred in the rainy season between july and october the average time intervals of falls and slides from july to october were approximately 12 days and 8 days respectively moreover the temporal distribution of landslide events is clustered owing to the impact of nonuniformly distributed rainfall activities most of the landslides concentrated in one or two months of a year furthermore the nonzero values in the landslide time series are nonuniformly spaced the complementary cumulative frequency distribution of the time intervals between landslide events can be adequately fitted by an exponential function based on these equations the temporal probabilities of landslide events can be predicted in addition most of the nonseismically triggered landslides in shaanxi province were triggered by long term antecedent rainfall and high intensity intraday rainfall

late quaternary vegetational and climatic changes in the pampa grassland of argentina abstract the vegetation and climate of the pampa grassland argentina during the late quaternary are reconstructed from pollen recovered from dated stratigraphic sections from arroyo walls and from archaelogical excavations prior to 10 500 yr b p herbaceous psammophytic steppe existed in the central part of the pampa grassland while xerophytic woodland associated with psammophytic and halophytic steppe occurred in the southwestern part of the pampa these types of vegetation and the continental conditions that prevailed in the area of the present day coast 38 s indicate subhumid dry climate and annual precipitation 100 mm lower than present a subsequent change toward a vegetation characteristic of ponds swamps and foodplains or toward environments with locally more effective moisture occurred ca 10 500 yr b p suggesting annual precipitation close to modern levels or a higher availability of water in the central part of the pampa grassland this type of vegetation existed until 8000 yr b p when it was replaced by grassland communities that lasted until 7000 yr b p in the southwestern part of the pampa grassland this vegetation developed before 7000 yr b p and persisted until ca 5000 yr b p sea level higher than the present ca 6200 yr b p is consistent with sharp modification of the vegetation and development of local halophytic communities dominant at 38 s a return to subhumid dry conditions occurred after 5000 yr b p the late holocene vegetation is characterized by pollen assemblages similar to the psammophytic and halophytic communities of the southern pampa grassland associated with communities with more edaphic conditions at the same time at 38 s a sea level regression is suggested by the dominance of fresh water pollen assemblages and micropaleontological remains the trend toward humid temperate conditions ca 1000 yr b p suggested by vertebrate remains characteristic of temperate and humid conditions as well as a very short but dry episode during the 18th century suggested by the geology are not clearly evidenced in the pollen sequences vegetational and climatic changes are explained by the latitudinal shifts and changes in intensity of the southern atmospheric circulation and changes in sea level

tropical salt marsh succession as sea level indicator during heinrich events abstract centennial millennial dynamics of tropical salt marsh vegetation are documented in the pollen record from marine core md03 2622 cariaco basin venezuela which spans the glacial period between 63 and 29 ka five rapid and abrupt expansions of salt marsh vegetation are linked with north atlantic heinrich events hes within each event a recurrent pattern starting with species of chenopodiaceae followed by grasses and subsequently by cyperaceae species suggests a successional process that is determined by the close relationship between sea level and community dynamics the salt tolerant chenopodiaceae at the base of each sequence indicate hypersaline intertidal environments which were most likely promoted by extremely dry atmospheric conditions rapid sea level rise characterizes the onset of he stadials causing erosion of marsh sediments and continued recruitment of pioneer species chenopodiaceae which are the only ones capable of tolerating the rapid rate of disturbance once as sea level drops or as rise decelerates marsh plants are able to trap and stabilize sediments favouring the establishment of more competitive species graminoids the increment of marsh height as a result of autochthonous sediment accumulation reduces the extent of hypersaline environments and allows the establishment of mesohaline species these results add to the scarce knowledge on tropical salt marsh ecosystems and provide independent paleoclimatic evidence on sea level changes occurring simultaneously with antarctica climate variations

landslide volumes and landslide mobilization rates in umbria central italy abstract a catalogue of 677 landslides of the slide type was selected from a global database of geometrical measurements of individual landslides including landslide area al and volume vl the measurements were used to establish an empirical relationship to link al in m2 to vl in m3 the relationship takes the form of a power law with a scaling exponent 1 450 covers eight orders of magnitude of al and twelve orders of magnitude of vl and is in general agreement with existing relationships published in the literature the reduced scatter of the experiential data around the dependency line and the fact that the considered landslides occurred in multiple physiographic and climatic environments and were caused by different triggers indicate that the relationship between vl and al is largely independent of the physiographical setting the new relationship was used to determine the volume of individual landslides of the slide type in the collazzone area central italy a 78 9 km2 area for which a multi temporal landslide inventory covering the 69 year period from 1937 to 2005 is available in the observation period the total volume of landslide material was vlt 4 78 107 m3 corresponding to an average rate of landslide mobilization l 8 8 mm yr 1 exploiting the temporal information in the landslide inventory the volume of material produced during different periods by new and reactivated landslides was singled out the wet period from 1937 to 1941 was recognized as an episode of accelerated landslide production during this 5 year period approximately 45 of the total landslide material inventoried in the collazzone area was produced corresponding to an average rate of landslide mobilization l 54 mm yr 1 six times higher than the long term rate the volume of landslide material in an event or period was used as a proxy for the magnitude of the event or period defined as the logarithm base 10 of the total landslide volume produced during the event or period with this respect the new relationship to link al and vl is a starting point for the adoption of a quantitative process based landslide magnitude scale for landslide events

spatial patterns causes and consequences of landslides in the gilgel gibe catchment sw ethiopia abstract the gilgel gibe catchment in sw ethiopia is one of the areas in east africa affected by landslides to better understand the patterns and the causal factors of these landslides all landslides in a small study area 14 km in the hilly parts of the gilgel gibe catchment were mapped and analyzed in total 60 landslides were mapped these landslides caused a displacement of 1 million m slope material which corresponds to a mean displaced volume of 50 ton ha 1 y 1 in the last 20 years moreover many landslides deliver directly sediment to the rivers and hence increase the sediment load in the rivers this soil loss to the rivers was estimated at 11 ton ha 1 y 1 during the same period high annual rainfall ca 2000 mm y 1 lithological and pedological properties and to a lesser extent steep 16 slopes turn the area into an inherent unstable situation and can be indicated as preconditions for the landslides in the study area distance to rivers is significantly the most important precondition as slopes near rivers are less stable than slopes further away from the rivers this is mainly caused by river incision and bank erosion which often occur in the area and which can be attributed to increased runoff due to deforestation over the past 20 years therefore recent deforestation caused more shallow landslides but also indirectly more deep seated landslides close to the rivers heavy rainfall is indicated as the main triggering factor for almost all landslides

landslide hazard mapping based on geological attributes abstract a landslide susceptibility zoning technique is proposed and has been tested in a catchment area of 317 km 2 along the aglar river a tributary of the river yamuna in the himalayas the aglar catchment is characterised by varied rock types mostly sedimentary an active fault landslides moderate to intense seismic activity and moderate human influence very little is known about this terrain except for one previous study this study focusses on the relationship between the terrain parameters and landslide hazard mapping a landslide susceptibility map is presented which can serve as first generation map on which subsequent detailed information can be incorported it is the first map of this kind from the himalayas based on quantitative evaluation of geomorphological and geological parameters on a classified terrain database map the study is in two stages first the terrain has been classified into several homogeneous patterns followed by small physiographic units which are uniform in their characteristics throughout second each unit acquires a score from a rating system based on the degree of mutual relationship between landslides and geological attributes such as slope distance from fault relief dip slope relationship etc each of which has been given weighting according to the strength of this relationship the aim is to frame a practical database system rationally which can be imported into a geographical information system for rapid digital handling of the data a positive relationship established between landslide and sediment yield indicates that long term sediment production in the catchment area comes from the ongoing geological and geomorphological activity the work may have applications in various parts of the himalayas especially the ungauged and unknown catchments falling in similar geological areas and latitudes

landslide inventory in a rugged forested watershed a comparison between air photo and field survey data abstract landslide inventories are routinely compiled by means of aerial photo interpretation api when examining photo pairs the forest canopy notably in old growth forest hides a population of not visible landslides in the present study we attempt to estimate how important is the contribution of landslides not detectable from aerial photographs to the global mass of sediment production from mass failures on forested terrain of the capilano basin coastal british columbia api was coupled with intensive fieldwork for identification and measurement of all landslides a 30 year framework was adopted we show that not visible landslides can represent up to 85 of the total number of failures and account for 30 of the volume of debris mobilised such percentages display high sub basin variability with rates of sediment production varying by one order of magnitude between two sub basins of the study area this is explained qualitatively by gis based analysis of slope frequency distributions drainage density and spatial distribution of surficial materials such observations find further support in the definitions of transport limited and supply limited basins as a practical consideration to land managers we envisage that supplementary fieldwork for landslide identification is mandatory in transport limited systems only fieldwork has demonstrated that gully related failures have a greater importance than one could expect from api

loessic silt deposits in the western himalayas their sedimentology genesis and age abstract loess is abundant in the foreland basins of the himalayas however it is poorly developed within the intermontane basins of the western himalayas and karaloram selected sections were studied from the swat himalaya and the karakoram mountains fieldwork and sedimentological analysis including grain size mineralogy and microfabric showed that the loessic sediments have been reworked and some have undergone weak pedogeneses these silts are not true loess rather a loessic colluvium thermoluminescence tl dates from the loessic sediments in sections from the swat valley provided younger ages than earlier workers had suggested this is consistent with reworking of the loess in these areas it is concluded that care must be taken when using loessic silts for tl in similar mountainous terranes

formation and development of the structure of collapsing loess in china abstract gao g 1988 formation and development of the structure of collapsing loess in china eng geol 25 235 245 it is well known that in china the regional variations in microstructure of loess are in phase with the overall tendency for collapsibility gradually decreasing from the northwest to the southeast these differences are consistent with variations in climatic conditions this indicates that the structure of collapsing loess is closely related to the climatic condition and geological environment based on the microstructure analyses it can be assumed that the formation and development of the structure of collapsing loess in china has undergone five stages the loessization stage the formation stage the development stage the degeneration stage and the clayization stage the five stages of loess regularly exist in different regions of the loess plateau this also shows that under the modern climatic condition the collapsing loess in the northwest of the loess plateau in china is still developing however the feature of collapsing loess is gradually disappearing in the southeast of the loess plateau

estimating the quality of landslide susceptibility models we present a landslide susceptibility model for the collazzone area central italy and we propose a framework for evaluating the model reliability and prediction skill the landslide susceptibility model was obtained through discriminant analysis of 46 thematic environmental variables and using the presence of shallow landslides obtained from a multi temporal inventory map as the dependent variable for statistical analysis by comparing the number of correctly and incorrectly classified mapping units it is established that the model classifies 77 0 of 894 mapping units correctly model fitting performance is investigated by comparing the proportion of the study area in each probability class with the corresponding proportion of landslide area we then prepare an ensemble of 350 landslide susceptibility models using the same landslide and thematic information but different numbers of mapping units this ensemble is exploited to investigate the model reliability including the role of the thematic variables used to construct the model and the model sensitivity to changes in the input data by studying the variation of the model s susceptibility estimate the error associated with the susceptibility assessment for each mapping unit is determined this result is shown on a map that complements the landslide susceptibility map prediction skill of the susceptibility model is then estimated by comparing the forecast with two recent event inventory maps the susceptibility model is found capable of predicting the newly triggered landslides a general framework for testing a susceptibility model is proposed including a scheme for ranking the quality of the susceptibility assessment

giant landslides topography and erosion abstract distributions of slope angles in tectonically active mountain belts point to the development of threshold conditions where hillslopes attain a critical inclination or height at which they fail readily because of limitations in material strength it has been proposed that hillslopes adjust to rapid uplift and bedrock incision through an increase in the rate of relief limiting landsliding rather than gradual slope steepening here we test this concept by investigating the relationship between mean local relief h which we take to be a proxy of long term erosion rates e and the occurrence of over 300 of the largest v 10 8 m 3 terrestrial landslides on earth we find that nearly two thirds of these giant landslides have occurred in the steepest 5 of the earth s land surface where relief is close to its proposed upper strength limit they are primarily located in deeply incised valleys along fault bounded fringes of active mountain belts and in volcanic arcs this distribution coincides with areas of high long term erosion rates 4 mm yr 1 confirming that giant landslides contribute to rapid denudation of mountains most of the eroded volume is concentrated in the smallest but steepest parts of mountain belts and volcanic arcs first order estimates of minimum erosion rates accomplished by the largest landslides are 0 01 mm yr 1 these rates are between 1 and 10 of the late pleistocene to holocene mean erosion rates in a given area importantly the landslide erosion rates show a nonlinear increase with mean local relief suggesting that the contribution of giant landslides in total and per event increases significantly with increasing overall erosion rates however giant landslides also occur in areas of lower than average relief h 300 700 m irrespective of whether threshold hillslopes have developed or not factors contributing to these failures include soft rocks extensive low angle discontinuities high rates of fluvial bedrock incision and tectonically driven deformation and slope loading

occurrence of landsliding on slopes where flowsliding had previously occurred an investigation in a loess platform north west china abstract loess slides in south jingyang platform shaanxi province usually occur on slopes where loess flowslides had previously occurred numerical modeling shows that flowslide occurrence causes conditions that increase shear stress and water content in the subsequent slopes both of these factors move the soil stress states towards its theoretical failure line under these conditions only small increases in water content can cause soil collapse this leads to the backscarps of former flowslides being much more prone to landsliding wetting test results show that the loess can collapse suddenly as the water content gradually increases therefore the wetting process induced by continued irrigation may result in the subsequent slides during constant water content tests of the loess material soil shear strength increases with the development of specimen deformation therefore slide mobilization which may be a relatively slow process is dependent on whether the wetting conditions exist finally a slope evolution model for loess platforms is proposed in this study

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 erosion controlled by hillslope material landslide erosion is a primary control of landscape relief a wide ranging analysis of landslide geometry shows that soil based landslides are generally less voluminous than landslides that involve the failure of bedrock and provides refined metrics for estimating the volume of a landslide from the area of the failure

influence of topography and volume on mobility of loess slides within different slip surfaces mobility of loess slides has been evaluated using an empirical approach based on a detailed field investigation and remote sensing image interpretation for all the loess slides the affected area increases with increasing loess slides volume from the statistical analysis it is seen that the travel distance has an increasing trend while the coefficient of friction has a decreasing trend with the increase in landslide volume landslide volume determine its travel distance and coefficient of friction that can be shown with a regression equation having simple power law form which indicates that the mobility of loess slides increases with increasing volumes by analogy the greater the energy of the sliding loess mass the stronger is the mobility of loess slide a plot of the travel distance of loess slide versus fall height shows a significant positive power law correlation indicating the increase in mobility of loess slide with fall height the negative power law correlation observed between the travel distance and slope inclination implies that the mobility decreases with the increase of slope inclination three datasets of loess slides characterized by different slip surfaces were distinguished the red clay contact landslides have the strong mobility than landslides in loess and bedrock contact

environmental history since 11 000 14c yr b p of the northeastern pampas argentina from alluvial sequences of the lujan river abstract sedimentological malacological and pollen analyses from 14c dated alluvial sections from the lujan river provide a detailed record of environmental changes during the holocene in the northeastern pampas of argentina from 11 200 to 9000 14c yr b p both sedimentary and biological components suggest that the depositional environment was eutrophic alkaline and freshwater to brackish shallow water bodies without significant water circulation during this time bioclastic sedimentation was dominant and the shallow water bodies reached maximum development as the climate became more humid suggesting an increase in precipitation short term fluctuations in climate during the last stage of this interval may have been sufficient to initiate changes in the water bodies as reduction of the volume alternated with periods of flooding the beginning of the evolution of shallow swamps in the wide floodplain or huge wetlands was contemporaneous with a sea level lower than the present one from 9000 and 7000 14c yr b p mesotrophic alkaline brackish probably anoxic swamps existed between 7000 and 3000 14c yr b p anoxic calcareous swamps were formed with subaerial exposure and development of the puesto berrondo soil 3500 2900 14c yr b p a trend to a reduction of water bodies is recorded from 9000 to ca 3000 14c yr b p with a significant reduction after ca 7000 14c yr b p a shift to subhumid dry climate after 7000 14c yr b p appears to be the main cause during this time an additional external forcing toward higher groundwater levels was caused by holocene marine transgression causing changes in the water bodies levels the climate became drier during the late holocene ca 3000 yr b p when clastic sedimentation increased under subhumid dry conditions flood events increased in frequency during this time from ca a d 1790 to present the pollen record reflects widespread disturbance of the vegetation during the european settlement

regional tectonic framework structure and evolution of the western marginal basins of india abstract the kutch saurashtra cambay and narmada basins are pericontinental rift basins in the western margin of the indian craton these basins were formed by rifting along precambrian tectonic trends interplay of three major precambrian tectonic trends of western india dharwar nnw sse aravalli delhi ne sw and satpura ene wsw controlled the tectonic style of the basins the geological history of the basins indicates that these basins were formed by sequential reactivation of primordial faults the kutch basin opened up first in the early jurassic rifting was initiated in late triassic along the delhi trend followed by the cambay basin in the early cretaceous along the dharwar trend and the narmada basin in late cretaceous time along the satpura trend the evolution of the basins took place in four stages these stages are synchronous with the important events in the evolution of the indian sub continent its breakup from gondwanaland in the late triassic early jurassic its northward drifting during the jurassic cretaceous and collision with the asian continent in the early tertiary the most important tectonic events occurred in late cretaceous time the present style of the continental margins of india evolved during early tertiary time the saurashtra arch the extension of the aravalli range across the western continental shelf subsided along the eastern margin fault of the cambay basin during the early cretaceous it formed an extensive depositional platform continuous with the kutch shelf for the accumulation of thick deltaic sediments a part of the saurashtra arch was uplifted as a horst during the main tectonic phase in the late cretaceous the present high thermal regime of the cambay bombay high region is suggestive of a renewed rifting phase

a new hypothesis for the deep subsurface structures near the bhuj 2001 earthquake mw 7 6 hypocentre zone and its tectonic implications summary we provide a new hypothesis for the deep subsurface structures near the bhuj 2001 earthquake region based on magnetotelluric mt investigations carried out close to the epicentre zone 2 d inversion of broad band mt data of two profiles of lengths 32 km aa and 52 km bb revealed a thick 3 km highly conductive 1 4 m surface layer of fluvio marine mesozoic cenozoic sediments the models delineate the hypocentre zone located at 20 25 km depth that manifests the high resistivity conductivity transition zone the accumulation of compressive stresses post rifting along this weak zone has resulted in the reverse slip of bhuj 2001 earthquake the reverse fault f1 associated with the earthquake is believed to be an ancient normal fault formed during the rifting phase contrary to earlier suggested theories we suggest that f1 got initiated along the high resistivity conductivity transition zone causing the bhuj 2001 event the geoelectric models revealed a laterally extending partially resistive zone at 20 30 km depth range showing a tendency to extend further deep model calculations using synthetic data also support this observation therefore we hypothesize the presence of a basal detachment marking the transition zone between the continental crust and the lithospheric upper mantle at 40 km depth intersected by the f1 the geoelectric models suggest that the crustal thinning caused the asthenospheric upwelling and or serpentinization leading to the ascent of volatiles and melts the subsurface geometry in kachchh basin suggests the thick skinned deformation

crustal structure of the gujarat region india new constraints from the analysis of teleseismic receiver functions abstract in this study receiver function analysis is carried out at 32 broadband stations spread all over the gujarat region located in the western part of india to image the sedimentary structure and investigate the crustal composition for the entire region the powerful genetic algorithm technique is applied to the receiver functions to derive s velocity structure beneath each site a detail image in terms of basement depths and moho thickness for the entire gujarat region is obtained for the first time gujarat comprises of three distinct regions kachchh saurashtra and mainland in kachchh region depth of the basement varies from around 1 5 km in the eastern part to 6 km in the western part and around 2 3 km in the northern part to 4 5 km in the southern part in the saurashtra region there is not much variation in the depth of the basement and is between 3 km and 4 km in gujarat mainland part the basement depth is 5 8 km in the cambay basin and western edge of narmada basin in other parts of the mainland it is 3 4 km the depth of moho beneath each site is obtained using stacking algorithm approach the moho is at shallower depth 26 30 km in the western part of kachchh region in the eastern part and epicentral zone of the 2001 bhuj earthquake large variation in the moho depths is noticed 36 46 km in the saurashtra region the crust is more thick in the northern part it varies from 36 38 km in the southern part to 42 44 km in the northern part in the mainland region the crust is more thick 40 44 km in the northern and southern part and is shallow in cambay and narmada basins 32 36 km the large variations of poisson s ratio across gujarat region may be interpreted as heterogeneity in crustal composition high values of 0 30 at many sites in kachchh and few sites in saurashtra and mainland regions may be related to the existence of high velocity lower crust with a mafic ultramafic composition and locally to the presence of partial melt the existing tectono sedimentary models proposed by various researchers were also examined

a low dimensional physically based model of hydrologic control of shallow landsliding on complex hillslopes hillslopes have complex three dimensional shapes that are characterized by their plan shape profile curvature of surface and bedrock and soil depth to investigate the stability of complex hillslopes with different slope curvatures and plan shapes we combine the hillslope storage boussinesq hsb model with the infinite slope stability method the hsb model is based on the continuity and darcy equations expressed in terms of storage along the hillslope solutions of the hsb equation account explicitly for plan shape by introducing the hillslope width function and for profile curvature through the bedrock slope angle and the hillslope soil depth function the presented model is composed of three parts a topography model conceptualizing three dimensional soil mantled landscapes a dynamic hydrology model for shallow subsurface flow and water table depth hsb model and an infinite slope stability method based on the mohr coulomb failure law the resulting hillslope storage boussinesq stability model hsb sm is able to simulate rain induced shallow landsliding on hillslopes with non constant bedrock slope and non parallel plan shape we apply the model to nine characteristic hillslope types with three different profile curvatures concave straight convex and three different plan shapes convergent parallel divergent in the presented model the unsaturated storage has been calculated based on the unit head gradient assumption to relax this assumption and to investigate the effect of neglecting the variations of unsaturated storage on the assessment of slope stability in the transient case we also combine a coupled model of saturated and unsaturated storage and the infinite slope stability method the results show that the variations of the unsaturated zone storage do not play a critical role in hillslope stability therefore it can be concluded that the presented dynamic slope stability model hsb sm can be used safely for slope stability analysis on complex hillslopes our results show that after a certain period of rainfall the convergent hillslopes with concave and straight profiles become unstable more quickly than others whilst divergent convex hillslopes remain stable even after intense rainfall in addition the relation between subsurface flow and hillslope stability has been investigated our analyses show that the minimum safety factor fs occurs when the rate of subsurface flow is a maximum in fact by increasing the subsurface flow stability decreases for all hillslope shapes copyright 2008 john wiley sons ltd

representing the landslide magnitude frequency relation capilano river basin british columbia we use magnitude frequency analysis as a statistical tool to quantify the erosion caused by landslides and debris ows using air photo and ground derived data we show that the departure from power law distribution customarily observed for small magnitude is an artefact of sampling de ciencies nonetheless the total distribution is not sensitive to the frequency of small slides and total erosion remains adequately represented in the air photo derived data our data also demonstrate a real departure from simple scaling at much larger magnitudes the cause of which is not de nitively established copyright 2004 john wiley sons ltd

the tectonic evolution of western india and its impact on hydrocarbon occurrences an overview abstract the largest hydrocarbon accumulations of india were localized in western india by a unique convergence of tectonic events mesozoic rifting along the structural trends of proterozoic mobile belts formed the passive margin basins of the indian coast during the campanian rifting of madagascar from india north south striking normal faults propagated into the area of the cambay graben late maastrichtian doming over the incipient deccan reunion hotspot imparted extensional stresses to the northwestern indian coast and formed the fault block that became the bombay high after eruption of the deccan flood basalts in early paleocene extension continued in the weakened crust this resulted in enhanced subsidence of the cambay graben and surat danahu depression rifting of the seychelles microcontinent from india and reactivation of normal faults on the emergent bombay high the cambay graben and the surat danahu depression filled with organic rich source shales as they underwent thermal subsidence shallow water eocene to miocene carbonates developed on the slowly subsiding bombay platform and sea level oscillations fostered secondary porosity development late tertiary maturation of the surat danahu depression shales generated hydrocarbons that migrated into the carbonate reservoirs on the bombay high konkan kerala and the older basins of the east coast of india were unaffected by the post campanian tectonic events and lack the favorable play elements that characterize the giant fields

landslide susceptibility analysis in central vietnam based on an incomplete landslide inventory comparison of a new method to calculate weighting factors by means of bivariate statistics abstract vietnam is regarded as a country strongly impacted by climate change population and economic growth result in additional pressures on the ecosystems in the region in particular changes in landuse and precipitation extremes lead to a higher landslide susceptibility in the study area approx 12 400 km 2 located in central vietnam and impacted by a tropical monsoon climate hence this natural hazard is a serious problem in the study area a probability assessment of landslides is therefore undertaken through the use of bivariate statistics however the landslide inventory based only on field campaigns does not cover the whole area to avoid a systematic bias due to the limited mapping area the investigated regions are depicted as the viewshed in the calculations on this basis the distribution of the landslides is evaluated in relation to the maps of 13 parameters showing the strongest correlation to distance to roads and precipitation increase an additional weighting of the input parameters leads to better results since some parameters contribute more to landslides than others the method developed in this work is based on the validation of different parameter sets used within the statistical index method it is called omit error because always omitting another parameter leads to the weightings which describe how strong every single parameter improves or reduces the objective function furthermore this approach is used to find a better input parameter set by excluding some parameters after this optimization nine input parameters are left and they are weighted by the omit error method providing the best susceptibility map with a success rate of 92 9 and a prediction rate of 92 3 this is an improvement of 4 4 and 4 2 respectively compared to the basic statistical index method with the 13 input parameters

comparison of landslide susceptibility based on a decision tree model and actual landslide occurrence the akaishi mountains japan abstract this paper proposes a statistical decision tree model to analyze landslide susceptibility in a wide area of the akaishi mountains japan the objectives of this study were to validate the decision tree model by comparing landslide susceptibility and actual landslide occurrence and to reveal the relationships among landslide occurrence topography and geology landslide susceptibility was examined through ensemble learning with a decision tree decision trees are advantageous in that estimation processes and order of important explanatory variables are explicitly represented by the tree structures topographic characteristics elevation slope angle profile curvature plan curvature and dissection and undissection height and geological data were used as the explanatory variables these topographic characteristics were calculated from digital elevation models dems the objective variables were landslide occurrence and reactivation data between 1992 and 2002 that were depicted by satellite image analysis landslide susceptibility was validated by comparing actual data on landslides that occurred and reactivated after the model was constructed between 2002 and 2004 this study revealed that from 2002 to 2004 landslides tended to occur and reactivate in catchments with high landslide susceptibility the landslide susceptibility map thus depicts the actual landslide occurrence and reactivation in the akaishi mountains this result indicates that the decision tree model has appropriate accuracy for estimating the probabilities of future landslides the tree structure indicates that landslides occurred and reactivated frequently in the catchments that had an average slope angle exceeding ca 29 and a mode of slope angle exceeding 33 which agree well with previous studies a decision tree also quantitatively expresses important explanatory variables at the higher order of the tree structure

undrained shear behavior of loess saturated with different concentrations of sodium chloride solution abstract a series of ring shear tests was conducted on saturated loess to investigate the effects of nacl concentration in pore water and desalinization on the shear behavior under undrained conditions the loess samples were taken from the ground surface of a frequently active landslide in china were saturated by de aired distilled water with different concentrations of nacl and then were sheared undrained after that the samples were retrieved remolded re set into the shear box and re saturated by passing through de aired distilled water such that the samples were desalinized and then were sheared undrained again through comparing the undrained shear behavior the effects of nacl in the pore water and desalinization on the undrained shear behavior of loess were examined the results showed that the variation of nacl concentration in pore water can strongly affect the shear behavior of saturated loess both the peak shear strength and steady state strength increased with increase of nacl concentration until a certain value after which they decreased with further increase of nacl concentration meanwhile the peak shear strength and steady state strength of the desalinized samples recovered to those of the original sample hence the effects of salinization are reversible these findings may be of practical importance to better understand the repeated occurrence of some irrigation induced loess landslides in china

on slope instability induced by seepage erosion this paper is focused on seepage erosion causing liquefaction processes and rapid slope failures one case history which occurred along an old fluvial terrace in the po plain northern italy is