neogene tectonostratigraphy and kinematics of calabrian basins implications for the geodynamics of the central mediterranean abstract a new structural model for the calabrian arc southern italy is presented based on a systematic analysis of basin kinematics combined with a review of the literature on basement structure three tectonic patterns can be distinguished a nw se trending oblique thrust zones determining a set of n130 trending segments b sw ne to e w trending thrust zones and c radial and concentric tensional fault systems in the southern tyrrhenian back arc area these faults combined with dome shaped uplift centres determine the actual arc patterns a and b can be regarded as the on shore representation of the calabrian accretionary wedge system the kinematics of various types of basins such as piggy back pull apart and complex oblique strike slip basins are connected to these patterns the patterns a and b can be linked to the middle miocene early pliocene development of oblique convergent crustal shear zones strike slip cycle whereas pattern c can be linked to the pleistocene collapse of the southern tyrrhenian basin and concentric uplift of the arc our structural model has considerable implications for the understanding of the kinematic evolution of the central mediterranean we propose a model in which the evolution is characterized by an alternation of the translation of the calabrian lithosphere element either to the southeast gravitationally or to the northeast compression combining a our analyses of basin evolution b the structural model and c some considerations concerning kinematics of the central mediterranean with the geodynamic mechanisms as proposed in literature we present a model which consists of a geodynamic cycle comprising the following three stages 1 a tension stage with back arc basin opening related to the diapiric inflow of asthenosphere material and roll back of the subducted ionian slab resulting in gravitational displacement of the calabrian element to the southeast 2 a transpression stage with oblique overthrusting towards the northeast upon the southern apennines and 3 a compression stage with ne sw compression due to oblique dextral shear along the north african margin plate rupture lithosphere split and back arc basin collapse

autologistic modelling of susceptibility to landsliding in the central apennines italy in previous research a logistic regression of landslide occurrence on several explanatory variables was fitted and used to map landslide susceptibility for a small area in the central apennines italy here the spatial dependence or spatial correlation in the residuals from the fitted regression model was accounted for by inserting an autocovariate into the model the autocovariate was estimated by applying a gibbs sampler to the susceptibilities for neighbouring pixels as in any landslide susceptibility analysis accuracy was difficult to assess because of the requirement for data on future landslides however by comparing the ordinary logistic model to the autologistic model obtained on the same set of data it was possible to assess the influence of the autocovariate the autocovariate rendered the model simpler because several variables lost their significance and were therefore omitted from the model further areas of high landslide susceptibility estimated from the autologistic model were geographically clustered as one would expect and this may be advantageous in terms of i interpreting the model and ii displaying the results to non experts

gis techniques and statistical models in evaluating landslide hazard geographical information systems gis and numerical cartography may greatly facilitate the development and use of statistical models for the assessment of regional landslide hazard from a small drainage basin located in central italy relevant geological and geomorphological factors were collected and processed by applying gis technology in particular modules were used which both generate high fidelity digital terrain models and automatically partition the terrain into main slope units the resulting information was then analysed by discriminant analysis which enabled landslide hazard and risk to be evaluated in each slope unit although not lacking drawbacks the method proved to be a feasible and cost effective approach to landslide susceptibility assessment and mapping

gis based weights of evidence modelling of rainfall induced landslides in small catchments for landslide susceptibility mapping landslide susceptibility mapping is a vital tool for disaster management and planning development activ ities in mountainous terrains of tropical and subtropical environments in this paper the weights of evidence modelling was applied within a geographical information system gis to derive landslide susceptibility map of two small catchments of shikoku japan the objective of this paper is to evaluate the importance of weights of evidence modelling in the generation of landslide susceptibility maps in relatively small catchments having an area less than 4 sq km for the study area in moriyuki and monnyu catchments northeast shikoku island in west japan a data set was generated at scale 1 5 000 relevant thematic maps representing various factors e g slope aspect relief flow accumulation soil depth soil type land use and distance to road that are related to landslide activity were generated using field data and gis techniques both catchments have homogeneous geology and only consist of cretaceous granitic rock thus bedrock geology was not considered in data layering during gis analysis success rates were also estimated to evaluate the accuracy of landslide suscepti bility maps and the weights of evidence modelling was found useful in landslide susceptibility mapping of small catchments

river profiles along the himalayan arc as indicators of active tectonics abstract longitudinal profiles along sixteen major transverse himalayan rivers add important constraints to models of active continental subduction and its evolution these profiles are characterized by a zone of relatively high gradient that cannot be associated with differential resistence to erosion in all cases the base of the zone of increased gradients correlates with 1 the topographic front between the lesser and high himalayas 2 the narrow belt of intermediate magnitude thrust earthquakes 3 the main central thrust zone mct these features define a small circle in the central portion of the himalayan arc these correlations suggest that the discontinuity in the river profiles and the other features are controlled by a major tectonic boundary between the rising high himalayas and the lesser himalayas no sharp increases in gradient are observed near the main boundary thrust mbt except on a few rivers such as the jhelum or kundar where the mbt lies close to both the mct and the seismic belt thus it is unlikely that the mbt is a major tectonic boundary the diversion of river courses along the mbt and around anticlines in the sub himalayas has probably been caused by aggradation near the rosion deposition boundary upstream of uplifts in the mahabharat range and sub himalayas a parallel is drawn between the himalayas and new guinea based on the hypothesis that continent arc collision of the type occurring in northern australia preceded continent continent collision in the himalayas the present sedimentary tectonic phase in new guinea resembles the subathu paleocene eocene phase in the himalayas incipient counterparts of the major himalayan structures including the mct and the mbt are recognized in new guinea the drainage patterns in the himalayas and in new guinea bear a similar relation to major structures this suggests that 1 the tectonic evolution of the himalayas has been rather uniform since early stages of collision and 2 the himalayan drainage was also formed at these early stages and is therefore antecedent to the rise of the high himalayas

artificial neural networks applied to landslide susceptibility assessment abstract landslide hazard mapping is often performed through the identification and analysis of hillslope instability factors usually managed as thematic data within geographic information systems gis in heuristic approaches these factors are rated by the attribution of scores based on the assumed role played by each of them in controlling the development of a sliding process other more refined methods based on the principle that the present and the past are keys to the future have also been developed thus allowing less subjective analyses in which landslide susceptibility is assessed by statistical relationships between past landslide events and hillslope instability factors the objective of this research is to define a method with the ability to forecast landslide susceptibility through the application of artificial neural networks anns the riomaggiore catchment a subwatershed of the reno river basin located in the northern apennines italy was chosen as an ideal test site as it is representative of many of the geomorphological settings within this region in the present application two different anns used in classification problems were set up and applied one belonging to the category of multi layered perceptron mlp and the other to the probabilistic neural network pnn family the hillslope factors that have been taken into account in the analysis were the following a lithology b slope angle c profile curvature d land cover and e upslope contributing area these factors have been classified on nominal scales and their intersection allowed 3342 homogeneous domains unique condition unit ucu to be singled out which correspond to the terrain units utilized in this analysis the model vector used to train the anns is a subset of that derived from the production of unique condition units and consists of 3342 records organized in input and output variable vectors in particular the hillslope factors once classified on nominal scales as binary numbers represent the 19 input variables while the presence absence of a landslide in a given terrain unit is assumed to be the output variable the comparison between the most up to date landslide inventory of the riomaggiore catchment and the hazardous areas as predicted by the anns showed satisfactory results with a slight preference for the mlp for this reason this is an encouraging preliminary approach towards a systematic introduction of ann based statistical methods in landslide hazard assessment and mapping

assessment of shallow landslide susceptibility by means of multivariate statistical techniques several multivariate statistical analyses have been performed to identify the most influential geological and geomorphological parameters on shallow landsliding and to quantify their relative contribution a data set was first prepared including more than 30 attributes of 230 failed and unfailed slopes the performance of principal component analysis t test and one way test allowed a preliminary selection of the most significant variables which were used as input variables for the discriminant analysis the function obtained has classified successfully 88 5 per cent of the overall slope population and 95 6 per cent of the failed slopes slope gradient watershed area and land use appeared as the most powerful discriminant factors a landslide susceptibility map based on the scores of the discriminant function has been prepared for ensija range in the eastern pyrenees an index of relative landslide density shows that the results of the map are consistent copyright 2001 john wiley sons ltd language en

constraints on the structure of the himalaya from an analysis of gravity anomalies and a flexural model of the lithosphere the intracontinental subduction of india beneath the himalaya presents several similarities to that occurring at island arcs we study one of those similarities by analyzing gravity anomalies across the himalaya assuming that the topography is supported by the indian elastic plate flexed under the weight of both the overthrust mountains and the sediments in the ganga basin we first examine in detail the effects of each of the following parameters on the configuration of the elastic plate and on the gravity anomalies the flexural rigidity the position of the northern end of the elastic plate the amount of underthrusting of such a plate beneath the range and the density contrasts between the crust and mantle and between the sediments and the crust a plate with a constant flexural rigidity of about 0 7 1025 n m between 0 2 and 2 0 1025 n m allows a good fit to the data from the lesser himalaya and the ganga basin such a plate however cannot underthrust the entire himalaya instead the gravity anomalies show that the moho steepens from only about 3 beneath the lesser himalaya to about 15 beneath the greater himalaya this implies a smaller flexural rigidity beneath the greater himalaya 0 1 to 1 0 1023 n m than beneath the ganga basin and the lesser himalaya even with a thin weak plate beneath the greater himalaya the weight of the mountains depresses the plate too much unless an additional force or moment is applied to the plate the application of a bending moment unit length to the end of the plate of about 0 6 1018 n m is adequate to elevate the indian plate and to bring the calculated gravity anomalies in agreement with those observed both the smaller flexural rigidity and the bending moment can be understood if we assume that part or all of the indian crust has been detached from the lower lithosphere that underthrusts the greater himalaya we study the tectonic implications of these results by means of a series of idealized balanced cross sections from the collision to the present that reproduce several important features of the geology of the himalaya and predict an amount of eroded material comparable to that in the ganga basin and the bay of bengal these cross sections include high grade metamorphic rocks near the main central thrust and a steeper dip of it there than in the lesser himalaya they predict rapid uplift only in the greater himalaya and at the foot of the lesser himalaya

seismotectonics of the himalayan collision zone geometry of the underthrusting indian plate beneath the himalaya fault plane solutions and well determined focal depths of medium sized earthquakes topography and landsat imagery in conjunction with seismicity maps cross sections and available geological information are used to investigate the present tectonics of the himalayan continental collision zone most of the accurately located epicenters of events along the himalayan arc 78 e 95 e that occurred between 1961 and 1981 are concentrated in a narrow zone about 50 km wide lying between the northerly dipping main boundary mbt and main central mct thrusts most of these events are located just south of the mct though the epicenters of the events are in general well located their depths as determined by teleseismic travel time data are very unreliable events with accurately determined depths obtained from identification of surface reflected phases define a simple planar zone from about 10 km and 20 km depth with an apparent dip of about 15 this result is all the more remarkable considering that the events used were located along about an 1800 km length of the himalyan arc except for one all available focal mechanisms of events within this zone indicate shallow 30 north dipping thrusts this shallow north dipping zone apparently defines a part of the detachment that separates the underthrusting indian plate from the lesser himalayan crustal block the spatial extent and the geometry of this interplate thrust zone strongly indicate that the mbt and nearby subsidiary surface and blind thrusts rather than the mct are currently the most active structures of the himalayan arc we suggest that the great himalayan earthquakes m 8 occur along the same detachment surface as defined by the thrust type medium sized events events located to the south of the mbt and beneath the ganges foredeep show normal faulting with t axes perpendicular to the himalayan trend the above results suggest that the indian continental plate is underthrusting the himalayan crustal blocks in a relatively coherent and simple geometry and that this geometry is not much different from that observed along oceanic subduction zones the november 19 1980 earthquake that occurred near the mct near 88 5 e shows a predominantly strike slip focal mechanism one of the nodal planes of this mechanism is transverse to the himalayan structural grain and moreover this plane has a trend similar to that of the recently mapped yadong gulu rift in the tethyan himalaya and in southern tibet just northeast of the earthquake we interpret this predominantly left lateral strike slip mechanism to indicate a possible genetic relationship between transverse structural features in the underthrusting indian plate the kishangang basement fault and the upper himalayan blocks and tibet

susceptibility zoning of shallow landslides in fine grained soils by statistical methods abstract the paper proposes a methodology in two successive steps to zone the susceptibility to shallow landslides in fine grained soils by means of statistical methods the first step of the methodology aiming at defining calibrating and validating the statistical analysis ends with a landslide susceptibility computational map the second step of the methodology is employed to produce a susceptibility map for zoning purposes this structured methodology arises from the need to distinguish at any given scale of analysis between the spatial discretization needed to perform the statistical computations terrain computational units and terrain units useful for zoning purposes terrain zoning units the applicability of the proposed methodology is tested at two different scales 1 25 000 and 1 5000 in two areas of southern italy the test area for the larger scale being a portion of the test area used for the analysis at the smaller scale this allows for the generalization of the obtained results through the comparison for the same phenomena in the same geo environmental context of the predisposing factors at two scales of analysis in both analyses the relevant variables for the susceptibility assessment are elevation zone slope gradient slope curvature and geology in the analysis at large scale also the weathered rock thickness available only at this scale assumes a relevant role in both cases the aggregation of multiple terrain computational units tcu into a larger terrain zoning unit tzu works best when focal statistic techniques are used with a characteristic dimension of the area of influence equal to 16 tcus

landslide susceptibility assessment using weights of evidence applied to a study area at the jurassic escarpment sw germany a gis based model for the assessment of the landslide susceptibility in a selected area of the jurassic escarpment in the swabian alb sw germany is described using the weights of evidence method a quantitative model applied to landslides and their causative factors was created and illustrated in susceptibility maps while previous research work in this area concentrated on large scale investigations the present study was carried out at a regional level with a target scale of 1 150 000 the method is based on the assumption that future landslides will occur under the conditions similar or equal to those of past comparable landslides of the same type therefore the analysis was limited to one single type of landslides where the causative factors can be assumed as stable over a period of time due to uncertainties in the model mainly because of variances of the weights assigned to the causative factors the derived probability values representing the susceptibility for future landslides have to be considered relative however potential susceptible areas can be delineated and landslide indicators can be identified from the available data set slopes with angles from 11 to 26 composed of the oxford limestone marls as well as strongly argillaceous and silty colluvial material such as solifluction layers and colluvial cones are susceptible the main soil type of the escarpment and the other steep slopes of the swabian alb valleys are rendzinas formed in solifluction layers rendzina profiles including rock debris and clay which are superimposed on marl debris were also identified as landslide indicators these findings are in agreement with previous geomorphological studies in the same area the methodology seems to have widespread applicability beyond this local research area with the limitation that the knowledge of past landslides input to the model affects the absolute value of the final probability

landslide susceptibility assessment by bivariate methods at large scales application to a complex mountainous environment statistical assessment of landslide susceptibility has become a major topic of research in the last decade most progress has been accomplished on producing susceptibility maps at meso scales 1 50 000 1 25 000 at 1 10 000 scale which is the scale of production of most regulatory landslide hazard and risk maps in europe few tests on the performance of these methods have been performed this paper presents a procedure to identify the best variables for landslide susceptibility assessment through a bivariate technique weights of evidence woe and discusses the best way to minimize conditional independence ci between the predictive variables indeed violating ci can severely bias the simulated maps by over or under estimating landslide probabilities the proposed strategy includes four steps i identification of the best response variable rv to represent landslide events ii identification of the best combination of predictive variables pvs and neo predictive variables npvs to increase the performance of the statistical model iii evaluation of the performance of the simulations by appropriate tests and iv evaluation of the statistical model by expert judgment the study site is the north facing hillslope of the barcelonnette basin france affected by several types of landslides and characterized by a complex morphology results indicate that bivariate methods are powerful to assess landslide susceptibility at 1 10 000 scale however the method is limited from a geomorphological viewpoint when rvs and pvs are complex or poorly informative it is demonstrated that expert knowledge has still to be introduced in statistical models to produce reliable landslide susceptibility maps

landslide hazard evaluation a review of current techniques and their application in a multi scale study central italy in recent years growing population and expansion of settlements and life lines over hazardous areas have largely increased the impact of natural disasters both in industrialized and developing countries third world countries have difficulty meeting the high costs of controlling natural hazards through major engineering works and rational land use planning industrialized societies are increasingly reluctant to invest money in structural measures that can reduce natural risks hence the new issue is to implement warning systems and land utilization regulations aimed at minimizing the loss of lives and property without investing in long term costly projects of ground stabilization government and research institutions worldwide have long attempted to assess landslide hazard and risks and to portray its spatial distribution in maps several different methods for assessing landslide hazard were proposed or implemented the reliability of these maps and the criteria behind these hazard evaluations are ill formalized or poorly documented geomorphological information remains largely descriptive and subjective it is hence somewhat unsuitable to engineers policy makers or developers when planning land resources and mitigating the effects of geological hazards in the umbria and marche regions of central italy attempts at testing the proficiency and limitations of multivariate statistical techniques and of different methodologies for dividing the territory into suitable areas for landslide hazard assessment have been completed or are in progress at various scales these experiments showed that despite the operational and conceptual limitations landslide hazard assessment may indeed constitute a suitable cost effective aid to land use planning within this framework engineering geomorphology may play a renewed role in assessing areas at high landslide hazard and helping mitigate the associated risk

the role of the 1999 chamoli earthquake in the formation of ground cracks abstract the moderate magnitude chamoli earthquake that occurred in the garhwal higher himalaya in the early hours of march 29 1999 caused intense damage to the ground and mountain slopes of the alaknanda mandakini river valley and adjoining region a systematic survey of this induced damage was conducted immediately after the earthquake occurred prominent shallow cracks of significant length negligible width and indeterminate vertical extent conspicuously tensile in nature with little or no slip across the crack planes were observed in the ground at several places along the surveyed route these cracks had formed in the dynamic phase of the chamoli earthquake process that is in the period of time during which the earthquake generated seismic waves were passing through the geographic region of interest however we use the theory of earthquake induced static or long time stress changes to visualize such cracks at some selected sites where ground damage was relatively more intense and varied to suggest lower bound estimates of the dynamic stress contributions of the main shock for their formation based on the results of our analysis we conclude that just prior to the earthquake occurrence under the influence of the local ambient stress field the ground at these sites was already near failure in tension to this in its dynamic phase the chamoli earthquake induced stress perturbations having across the planes of the cracks i shear components which were nearly equal and opposite to similar components of the ambient stress field and ii normal tensile components necessary for triggering tensile failure of the ground the 3 or minimum principal stress component of the resultant perturbed failure stress field thus became sufficiently tensile while the transverse stresses became sufficiently insignificant this facilitated formation of major tensile cracks in the ground there our static estimates of the tensile stress changes at the different sites are in essence estimates of the minimal triggering stress perturbations that was provided by the chamoli earthquake in the dynamic state for the formation of the tensile cracks there

a new old approach for shallow landslide analysis and susceptibility zoning in fine grained weathered soils of southern italy abstract rainfall induced shallow landslides involve several geo environmental contexts and different types of soils in clayey soils they affect the most superficial layer which is generally constituted by physically weathered soils characterised by a diffuse pattern of cracks this type of landslide most commonly occurs in the form of multiple occurrence landslide phenomena simultaneously involving large areas and thus has several consequences in terms of environmental and economic damage indeed landslide susceptibility zoning is a relevant issue for land use planning and or design purposes this study proposes a multi scale approach to reach this goal the proposed approach is tested and validated over an area in southern italy affected by widespread shallow landslides that can be classified as earth slides and earth slide flows specifically by moving from a small 1 100 000 to a medium scale 1 25 000 with the aid of heuristic and statistical methods the approach identifies the main factors leading to landslide occurrence and effectively detects the areas potentially affected by these phenomena finally at a larger scale 1 5000 deterministic methods i e physically based models trigrs and trigrs unsaturated allow quantitative landslide susceptibility assessment starting from sample areas representative of those that can be affected by shallow landslides considering the reliability of the obtained results the proposed approach seems useful for analysing other case studies in similar geological contexts

great earthquakes seismicity gaps and potential for earthquake disaster along the himalaya plate boundary abstract analysis of the space time patterns of seismicity in the himalaya plate boundary has established the existence of three seismic gaps 1 1 the kashmir gap lying west of the 1905 kangra earthquake 2 2 the central gap situated between the 1905 kangra and the 1934 bihar earthquakes 3 3 the assam gap between the 1897 and 1950 assam earthquakes this study has shown that the above great earthquakes were preceded as well as followed by long periods 19 years of decreased levels of seismic activity in the epicentral regions remarkable decrease in the seismicity following the year 1970 has been observed in the western half of the central gap as well as in the assam gap local seismic investigation in the assam gap confirms this feature and the seismicity suggests the existence there of an asperity the local seismic investigations in garhwal himalaya have shown that the small earthquakes are confined to the upper 6 8 km of the crust and may have strike slip motions these earthquakes occur in a region where teleseismically recorded events were few

landslide inventory maps new tools for an old problem landslides are present in all continents and play an important role in the evolution of landscapes they also represent a serious hazard in many areas of the world despite their importance we estimate that landslide maps cover less than 1 of the slopes in the landmasses and systematic information on the type abundance and distribution of landslides is lacking preparing landslide maps is important to document the extent of landslide phenomena in a region to investigate the distribution types pattern recurrence and statistics of slope failures to determine landslide susceptibility hazard vulnerability and risk and to study the evolution of landscapes dominated by mass wasting processes conventional methods for the production of landslide maps rely chiefly on the visual interpretation of stereoscopic aerial photography aided by field surveys these methods are time consuming and resource intensive new and emerging techniques based on satellite airborne and terrestrial remote sensing technologies promise to facilitate the production of landslide maps reducing the time and resources required for their compilation and systematic update in this work we first outline the principles for landslide mapping and we review the conventional methods for the preparation of landslide maps including geomorphological event seasonal and multi temporal inventories next we examine recent and new technologies for landslide mapping considering i the exploitation of very high resolution digital elevation models to analyze surface morphology ii the visual interpretation and semi automatic analysis of different types of satellite images including panchromatic multispectral and synthetic aperture radar images and iii tools that facilitate landslide field mapping next we discuss the advantages and the limitations of the new remote sensing data and technology for the production of geomorphological event seasonal and multi temporal inventory maps we conclude by arguing that the new tools will help to improve the quality of landslide maps with positive effects on all derivative products and analyses including erosion studies and landscape modeling susceptibility and hazard assessments and risk evaluations

on the damage caused by the chamoli earthquake of 29 march 1999 abstract the moderate magnitude chamoli earthquake which occurred on 29 march 1999 in the alkananda river valley region of garhwal himalaya caused considerable loss to human life and property from a systematic field survey of the damage conducted for five continuous days immediately after the earthquake the following could be noted i the consequences of the damage are most pronounced near the main central thrust mct ii the maximum damage is between chamoli and the 40 km2 area to the its north and was probably caused by major uplift iii distinct radial cracks accompanied by considerable ground subsidence due to this earthquake could be observed north of the completely devastated village of mawana situated 4 km northwest of chamoli iv the intensity of damage in the meisoseismal zone covering approx 580 km2 area suggests a value of 0 2 g for the ground acceleration

interpretation of observed ground level changes due to the 1905 kangra earthquake northwest himalaya the kangra earthquake of 1905 in the northwest himalaya was the first indian earthquake for which coseismic ground elevation changes were measured through repeat precision levelling the levelling une from saharanpur to mussoorie via dehra dun was situated near the southeastern extremity of the nw se trending meizoseismal area maximum uplift of 14 3 cm was measured at a bench mark in dehra dun some details of the levelling data having been published recently data for eight bench marks were considered for interpretation in this study in principle these are sufficient for us to estimate eight parameters of a rectangular rupture buried in a homogeneous poisson solid but because of some uncertainties regarding the bench mark positions and also the relatively small amounts of uplift measured at the bench marks we have preferred to use the data as a means to check the reasonableness of rupture models proposed on other grounds rather than to propose a new model independently the observed elevation changes are not in accord with the view that the kangra earthquake was caused by a single 100 km long rupture along the shahpur mandi sector of the northwest himalaya however the data can be explained if in addition a second smaller rupture extending on either side of the levelling une near dehra dun is assumed the data can also be explained if the rupture during the earthquake had 1 a length of 280 km parallel to the general strike of the himalaya from around kangra up to a short distance about 10 15 km northwest of the levelling une near dehra dun 2 a breadth of 80 km perpendicular to the strike of the himalaya 3 a northeasterly dip of about 5 and 4 a depth of 10 15 km along its sw edge finally the elevation data rule out any role for the main boundary thrust in the occurrence of the kangra earthquake this major tectonic feature demarcating the geological boundary between the outer and the lesser himalaya thus appears to be unimportant in the current seismotectonics of the region and the subduction of the indian lithospheric plate under the mountains

landslide zoning over large areas from a sample inventory by means of scale dependent terrain units abstract a procedure is proposed to produce landslide distribution zoning maps to be considered preparatory to susceptibility hazard and risk zoning maps based on 1 the results from a statistical multivariate analysis of a landslide inventory which must be available for only a portion of the territory to be zoned and 2 the use of appropriately defined terrain mapping units the units are divided into terrain computational units tcus and terrain zoning units tzus whose size is related to the scale of zoning the procedure comprises three phases calibration validation and prediction the purpose of the prediction phase is the application of a calibrated and validated statistical model in a territory previously recognized as viable on the basis of a priori applicability maps for which no information is available regarding the distribution of landslides or where the information provided by the landslides inventory is unreliable or heterogeneous the proposed procedure is applied to two case studies in southern italy for the analysis and zoning of slow moving landslides at 1 25 000 and 1 100 000 scales respectively the first case study illustrates the applicability of the procedure the aim of the second case study is to address the part of the procedure related to the evaluation of the computational maps at the end of the calibration and validation phases

combining spatial data in landslide reactivation susceptibility mapping a likelihood ratio based approach in w belgium a key issue in landslide susceptibility mapping concerns the relevance of the spatial data combination used in the prediction various combinations of high resolution predictor variables and possibilities of selecting them from a larger dataset are analysed the scarp reactivation of several landslides in a hilly region of w belgium is investigated at the pixel scale the susceptibility modelling uses the reactivated scarp segments as the dependent variable and 13 factors at a 2 m resolution related to topography hydrology land use and lithology as potential independent variables the modelling uses a likelihood ratio approach based on the comparison for each independent variable between two empirical distribution functions edfs respectively for the reactivated and non reactivated areas it uses these edfs as favourability values to build membership values and combine them with a fuzzy gamma operator five different data combinations are tested and compared by analysing the prediction rate curves obtained by cross validation the geomorphological value of the resulting susceptibility maps is also discussed this research shows relevant results for predicting the susceptibility to scarp reactivation we highlight the need for testing several data combinations and underline that combining quantitative criteria with expert opinion is an asset for reliable predictions

a comparative study of dempster shafer and fuzzy models for landslide susceptibility mapping using a gis an experience from zagros mountains sw iran abstract a catchment area at the zagros mountains nw shiraz iran is selected as a test site to comparing the output results of the dempster shafer d s and fuzzy models in landslide hazard mapping lithology slope angle slope aspect land cover and soil depth were considered as landslide causal factors the factor maps were input into a gis and a modified landslide hazard evaluation factor mlhef rating and fuzzy membership functions as well as belief function values were assessed for each class of the factor maps the fuzzy sum product and gamma combination approaches were examined and output maps were assessed based on the known landslides the outputs of fuzzy sum and product combination rules were not reasonable because these approaches classified the area into very high or very low susceptibility zones respectively which were not compatible to the field and factor maps criteria a value of 0 94 yielded the most reliable susceptibility for landslides overlay of the known landslides with the output favorability map showed that the identified landslides were located in the high and very high susceptible zones the output results of the dempster shafer model plausibility belief and uncertainty images were also evaluated based on the known landslides the results of this approach revealed that although it was expected that most of the known landslides correspond the plausibility or the belief map only a few of them supported the case and some landslides were coincided into the disbelief or uncertainty maps it is concluded that in comparison to the fuzzy model the d s model obtains less reliable results for landslide hazard mapping since the belief functions were assigned based on the fuzzy membership functions this might be due to the integration equations used by the model or the number of evidence maps used as input layers

a comparison of statistical and deterministic methods for shallow landslide susceptibility zoning in clayey soils abstract shallow landslides are widespread in different geological contexts and generally occur as multiple events over large areas when these phenomena involve fine grained soils they may cause serious consequences in terms of environmental and property damages and thus their spatial forecasting becomes a relevant issue for land use planning and design purposes the existing literature provides several methods for landslide susceptibility assessment categorized in qualitative and quantitative methods when dealing with analyses at large scale 1 5000 quantitative methods are generally preferred in this paper landslide susceptibility maps are produced for a study area prone to shallow landsliding located in catanzaro southern italy to this aim two quantitative methods are implemented the statistical information value method and the deterministic trigrs model the two approaches are compared by means of two indicators of the grade of correctness of the landslide susceptibility maps the area under curve of the roc curve auc and the overestimation index oi the results of the analyses in terms of auc values demonstrate the effectiveness and consistency of both methods in performing the susceptibility mapping of the study area when the oi values are considered the results provided by the deterministic model are slightly better than the ones resulting from the statistical analysis this does not come as a surprise for the case study at hand and it can be ascribed to the availability within the study area of a reliable database of soil properties and an in depth knowledge of the behaviour of the considered landslides

verification of landslide susceptibility mapping a case study a methodology is proposed for mapping susceptibility to landsliding and validating the results heavy rains in late 1996 and early 1997 led to a large number of landslids in the rute sector cordoba southern spain where landslide susceptibility mapping had previously been carried out using a matrix method developed with a geographical information system gis analysis of the distribution of the new landslides or reactivated earlier ones enabled the methodology to be validated by calculating association coefficients and determining the closeness of the match between subsequent field evidence and the previously defined susceptibility levels from the data obtained it can be concluded that the susceptibility mapping effectively explained the spatial distribution of landslides thus providing valuable information on stability conditions over a widespread area copyright 1999 john wiley sons ltd

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

susceptibility and triggering scenarios at a regional scale for shallow landslides abstract the work aims at identifying susceptible areas and pluviometric triggering scenarios at a regional scale in calabria italy with reference to shallow landsliding events the proposed methodology follows a statistical approach and uses a database linked to a gis that has been created to support the various steps of spatial data management and manipulation the shallow landslide predisposing factors taken into account are derived from i the 40 m digital terrain model of the region an 15 075 km2 extension ii outcropping lithology iii soils and iv land use more precisely a map of the slopes has been drawn from the digital terrain model two kinds of covers prevalently coarse grained cg cover or fine grained fg cover were identified referring to the geotechnical characteristics of geomaterial covers and to the lithology map soilscapes were drawn from soil maps and finally the land use map was employed without any prior processing subsequently the inventory maps of some shallow landsliding events totaling more than 30 000 instabilities of the past and detected by field surveys and photo aerial restitution were employed to calibrate the relative importance of these predisposing factors the use of single factors first level analysis therefore provides three different susceptibility maps second level analysis however enables better location of areas susceptible to shallow landsliding events by crossing the single susceptibility maps on the basis of the susceptibility map obtained by the second level analysis five different classes of susceptibility to shallow landsliding events have been outlined over the regional territory 8 9 of the regional territory shows very high susceptibility 14 3 high susceptibility 15 moderate susceptibility 3 6 low susceptibility and finally about 58 very low susceptibility finally the maps of two significant shallow landsliding events of the past and their related rainfalls have been utilized to identify the relevant pluviometric triggering scenarios by using 205 daily rainfall series different triggering pluviometric scenarios have been identified with reference to cg and fg covers a value of 365 mm of the total rainfall of the event and or 170 mm d of the rainfall maximum intensity and a value of 325 mm of the total rainfall of the event and or 158 mm d of the rainfall maximum intensity are able to trigger shallow landsliding events for cg and fg covers respectively the results obtained from this study can help administrative authorities to plan future development activities and mitigation measures in shallow landslide prone areas in addition the proposed methodology can be useful in managing emergency situations at a regional scale for shallow landsliding events triggered by intense rainfalls through this approach the susceptibility and the pluviometric triggering scenario maps will be improved by means of finer calibration of the involved factors

life history of a cyclonic ring detached from the kuroshio extension as seen by the geosat altimeter the sea surface dynamic topography ssdt sea surface height relative to the geoid is approximately estimated by combining the temporal fluctuation of ssdt determined from altimetry data with the climatological mean ssdt calculated from hydrographic data this approximated ssdt or composite ssdt is obtained in the area southeast of japan for the first year 1986 1987 of the geosat exact repeat mission variations in the kuroshio current system are well described by the composite ssdt in particular a complete life history of a cyclonic ring is observed for the first time in this region namely westward propagation of a southward meander of the kuroshio extension its pinching off to form a cyclonic ring the ring s westward movement its coalescence with the kuroshio and its eastward advection all available hydrographic data and cloud free satellite infrared images support the existence of this series of phenomena

strong ground motion from the uttarkashi himalaya india earthquake comparison of observations with synthetics using the composite source model the uttarkashi earthquake of 19 october 1991 ms 7 0 occurred in the greater himalayan region north of the main central thrust at an estimated depth of 12 km the fault plane solution indicates a low angle thrust mechanism striking northwest consistent with the tectonic pattern of thrusting in the region aftershocks define a belt parallel to and north of the surface trace of the main central thrust roughly 10 km wide and 30 km long the mainshock is located at the northeast edge of this zone the earthquake was recorded on 13 strong motion accelerographs at distances ranging from 25 to 150 km from the epicenter one station at bhatwari peak horizontal acceleration of 272 cm sec 2 is above the aftershock zone the maximum peak horizontal acceleration was about 313 cm sec 2 at uttarkashi at an epicentral distance of 36 km the amplitudes and frequency content of the strong ground motions are more or less consistent with expectations for an earthquake of this magnitude in california synthetics generated using the composite source model and synthetic green s functions zeng et al 1994a b are successful in producing acceleration velocity and displacement with a realistic appearance and the correct statistical properties of the two accelerograms recorded nearest the fault bhatwari and uttarkashi to produce these we introduced trial and error modifications of the layered medium velocity model within uncertainties at more distant stations we first used the velocity structure that worked for the two nearest stations differences emphasize the large potential role of unknown site and wave propagation effects for the station at tehri we explored different velocity models and found one there that was also quite successful we then used these two velocity models to predict strong ground motions at bhatwari and tehri from a potential magnitude 8 5 earthquake filling part of the seismic gap along the himalayan frontal faults the synthetics show peak accelerations that are only somewhat larger than those in the uttarkashi event but much longer durations and increased amplitudes of response spectra at long periods

landslide characteristics and slope instability modeling using gis lantau island hong kong steep terrain and high a frequency of tropical rainstorms make landslide occurrence on natural terrain a common phenomenon in hong kong this paper reports on the use of a geographical information systems gis database compiled primarily from existing digital maps and aerial photographs to describe the physical characteristics of landslides and the statistical relations of landslide frequency with the physical parameters contributing to the initiation of landslides on lantau island in hong kong the horizontal travel length and the angle of reach defined as the angle of the line connecting the head of the landslide source to the distal margin of the displaced mass are used to describe runout behavior of landslide mass for all landslides studied the horizontal travel length of landslide mass ranges from 5 to 785 m with a mean value of 43 m and the average angle of reach is 27 7 this gis database is then used to obtain a logistic multiple regression model for predicting slope instability it is indicated that slope gradient lithology elevation slope aspect and land use are statistically significant in predicting slope instability while slope morphology and proximity to drainage lines are not important and thus excluded from the model this model is then imported back into the gis to produce a map of predicted slope instability the results of this study demonstrate that slope instability can be effectively modeled by using gis technology and logistic multiple regression analysis