gis based landslide susceptibility mapping using bivariate statistical analysis in devrek zonguldak turkey devrek town with increasing population is located in a hillslope area where some landslides exist therefore landslide susceptibility map of the area is required the purpose of this study was to generate a landslide susceptibility map using a bivariate statistical index and evaluate and compare the results of the statistical analysis conducted with three different approaches in seed cell concept resulting in different data sets in geographical information systems gis based landslide susceptibility mapping applied to the devrek region the data sets are created from the seed cells of a crowns and flanks b only crowns and c only flanks of the landslides by using ten different causative parameters of the study area to increase the data dependency of the analysis all parameter maps are classified into equal frequency classes based directly on the percentile divisions of each corresponding seed cell data set the resultant maps of the landslide susceptibility analysis indicate that all data sets produce fairly acceptable results in each data set analysis elevation lithology slope aspect and drainage density parameters are found to be the most contributing factors in landslide occurrences the results of the three data sets are compared using seed cell area indexes scai this comparison shows that the crown data set produces the most accurate and successful landslide susceptibility map of the study area

the namibian and brazilian southern south atlantic petroleum systems are they comparable analogues tectonic reconstructions made across the southern south atlantic ocean indicate a diversity of rift and drift basin characteristics on the conjugate margins that define them as different stratigraphic and structural entities in terms of petroleum systems the basins are not as unlike as some characteristics suggest given the lack of significant hydrocarbon discoveries to date south of the walvis ridge doubts have been cast on the presence in this area of the prolific lower cretac eous lacustrine and marine source rock systems which are well known in the greater campos basin and offshore angola oils and condensates from the basins south and north of the walvis ridge exhibit geochemical similarities suggesting that comparable source rock systems are present in both areas the condensate geochemical analysis results from the kudu field in namibia are compared with oils from marine and lacustrine sources in brazil indicating that the kudu condensates are derived from at least two different source rocks these results suggest that the underexplored basins offshore namibia contain thermally mature lower cretaceous lacus trine and marine source rocks offering a new frontier for petroleum exploration in africa s southern south atlantic

using multiple logistic regression and gis technology to predict landslide hazard in northeast kansas usa abstract landslides in the hilly terrain along the kansas and missouri rivers in northeastern kansas have caused millions of dollars in property damage during the last decade to address this problem a statistical method called multiple logistic regression has been used to create a landslide hazard map for atchison kansas and surrounding areas data included digitized geology slopes and landslides manipulated using arcview gis logistic regression relates predictor variables to the occurrence or nonoccurrence of landslides within geographic cells and uses the relationship to produce a map showing the probability of future landslides given local slopes and geologic units results indicated that slope is the most important variable for estimating landslide hazard in the study area geologic units consisting mostly of shale siltstone and sandstone were most susceptible to landslides soil type and aspect ratio were considered but excluded from the final analysis because these variables did not significantly add to the predictive power of the logistic regression soil types were highly correlated with the geologic units and no significant relationships existed between landslides and slope aspect

the oleananes origin maturation and limits of occurence in southern nigeria sedimentary basins oleananes occur within well defined age and paleogeographic boundaries in the sedimentary province of southern nigeria thus signifying that the biomarkers may be analogous to index fossils in anambra syncline lower benue trough the biomarkers are found in rocks which are as old as late upper cretaceous in tertiary niger delta the concentration composition and distribution of the oleananes in rocks and oils are determined mainly by palaeodepositional environment and thermal history and are independent of age and geographical location of specific samples oleanane content varies with increasing burial depth with peak concentration coinciding within rm range 0 4 0 6 implying early generation of hydrocarbons from the basin s typically resin rich kerogens it is evident that the oleanane content parameter is superior to the hopane and sterane isomerisation indices for monitoring thermal maturation in the delta and for differentiating paralic from paralic marine source facies as well as early from late generated oils

applications and limitations of mango s light hydrocarbon parameters in petroleum correlation studies mango 1987 reported on the remarkable invariance of four isoheptanes in petroleums regardless of the absolute concentration the ratio of sums of concentration of 2 methylhexane 2 3 dimethylpentane 3 methylhexane 2 4 dimethylpentane remains constant the k1 ratio value being around unity gas chromatographic analyses of an additional 500 oils contradict this invariance as a suite of oils from the cretaceous northwest basin argentina deviate significantly by having a ratio of 1 67 still oils derived from the same structural kerogen have invariant ratios that can vary from a lowest value of 0 79 found for the midland oil set mango 1990 up to a highest value of 1 67 found for the cretaceous northwest basin mango 1990 postulated so called parent daughter schemes having an invariance in the ratio of isoheptanes and dimethylcyclopentanes an invariance unique for a homologous set of oils but possibly distinctly different from another suite of homologous oils it will be shown here that this difference in invariance can be used in oil oil correlation studies and that this technique is especially powerful for oil condensate correlation condensates in which the concentration of biological markers is quite often below the limit of detection further the concentration of light hydrocarbons needed for this approach can be determined from whole oil gas chromatography without any pre treatment thus providing a rapid and cheap tool for correlation studies

uncommon steranes in brazilian marginal crude oils dinoflagellate molecular fossils in the sergipe alagoas basin brazil comprehensive two dimensional gas chromatography with time of flight mass spectrometry gc gc tofms was used to identify unusual steranes in branched cyclic hydrocarbon fractions of crude oils from sergipe alagoas basin brazil and infer the geochemical settings of their cretaceous source rocks hopane sterane and sterane ratios and the presence of gammacerane and carotane in the oil samples indicates a saline source rock depositional environment and predominantly marine organic matter om input steroidal hydrocarbons were represented by alkyl steranes and several sterane series including abundant short chain steranes c21 and c22 regular steranes c27 c29 and diasteranes c21 c23 c27 c29 the ring a methyl sterane series contained 3 methyl steranes c22 and c23 c28 c30 abundant 3 methyldiginane c22 and 3 methyldiacholestanes c28 including 4 methyl steranes with abundant c30 4 23 24 trimethylcholestanes in the branched cyclic fraction of these crude oils the c29 sterane isomers 23 24 dimethylcholestane and 24 ethylcholestanes were resolved by gc gc tofms and a c29 dinosterane derivative was identified for the first time in brazilian crude oils the 23 24 dimethyl and 4 23 24 trimethyl steroids can be related to dinoflagellate om and abundant dinosteranes suggests dinoflagellate blooms during source rock deposition in this brazilian marginal basin additionally the detection of c28 c32 3 alkyl cholestanes c29 c33 3 alkyl 24 methylcholestanes and c30 c34 3 alkyl 24 ethylcholestane with ethyl to pentyl groups at c 3 resulted in a complex sterane fingerprint as expected for petroleum generated from source rocks deposited under predominantly marine saline conditions with high microalgal input these biomarker results provide additional insight into the character and geologic processes responsible for the source rocks of crude oils in the brazilian marginal basins this information will be a valuable exploration tool that can be used to constrain the distribution of different oil types in these basins

geochemical comparison of fluid inclusion and present day oil accumulations in the papuan foreland evidence for previously unrecognised petroleum source rocks abstract petroleum production in papua new guinea is limited to the papuan fold belt present day oil accumulations in fields such as iagifu hedinia and gobe are thought to be mainly derived from clay rich jurassic marine source rocks containing terrestrially derived organic matter that were deposited under oxic conditions in this study other generative source rocks in the papuan foreland are indicated using fluid inclusion fi oil data from three wildcat wells koko 1 bujon 1 and kimu 1 which were drilled on the bosavi arch detailed organic geochemistry of these fi oils and associated free oils or oil stains suggests that none of these were generated from the aforementioned jurassic source rocks instead at least three different generative source rocks are indicated firstly a marine probably late cretaceous or younger source rock deposited under reducing conditions is indicated by the bujon 1 fi oil this source rock had a moderate contribution from higher plant organic matter including oleanane and or lupane the bujon 1 fi oil has similarities with fi oils from the iagifu 7x and p nyang 2x wells in the papuan fold belt secondly an algal dominated lacustrine source rock is indicated by the biodegraded koko 1 rft crude oil the unbiodegraded fi oil from koko 1 and the bujon 1 oil stains from the toro and imburu formations these lacustrine oils have high abundances of tricyclic terpanes pregnane homopregnane and gammacerane contain carotane and have high c26 c25 tricyclic terpane ratios the source of the lacustrine oils is inferred to contain moderate amounts of terrestrial organic matter indicated by a dominance of c29 steranes and abundant aromatic higher plant biomarkers and could be gypsiferous shales embedded in oligocene miocene carbonates or triassic age sediments deposited on igneous basement during early rifting associated with the break up of gondwana the kimu 1 fi oil was generated from a mature marine suboxic source rock but has a different geochemical composition to free oil from a similar interval which was derived from a carbonate rich source rock none of the fi oils correlate well with oil families previously described in papua new guinea accordingly the oils recovered from fis in this part of the papuan basin support the presence of laterally varying source rock compositions and qualities and indicate that there are opportunities to develop new charge models for features across the papuan foreland furthermore koko 1 bujon 1 and kimu 1 fi oils have different geochemical compositions compared to the associated free oils or oil stains indicating that each of these localities has a multi phase charge history further work to lower exploration risk in the papuan foreland should be directed to understanding the distribution maturity and expulsion history of these newly recognised potential source rocks

methylhopanoids molecular indicators of ancient bacteria and a petroleum correlation tool abstract methylhopanoids are organic compounds synthesized by certain bacteria that when preserved in sediments act as molecular fossils or biomarkers for organic matter inputs from specific bacterial sources two series of methylhopanoids occur each mainly deriving from a distinct bacterial source cyanobacteria 2 methyl and methanotrophic bacteria 3 methyl the abundance and composition of methylhopanoids within sediments of modern depositional environments varies widely apparently due to different bacterial communities contributing to the sedimentary organic matter comparable molecular characteristics are found in oils and their source rocks consequently methylhopanoids are valuable in oil oil and oil source rock correlations distinguishing between samples related to different depositional environments in particular abundant 3 methylhopanoids from methanotrophic bacteria or an additional unknown bacterial source are characteristic of some modern alkaline saline lake environments comparable compositional features in the methylhopanes of oils allow the assignment of lacustrine oils offshore west africa to two distinct lacustrine source rock facies and to distinguish between different marine source facies thus refining oil source rock correlation

geochemical and biological marker assessment of depositional environments using brazilian offshore oils abstract a combined geochemical and molecular characterization of a wide selection of oils from the major brazilian offshore basins has been undertaken the elemental sulphur nickel and vanadium and bulk oapi and 13c properties of each sample been considered together with its molecular composition determined using liquid and gas chromatography and quantitative biological marker investigations using gas chromatography mass spectrometry for alkanes the results reveal significant differences in the chemical features of the various oils which enable them to be divided into five groups the distinction of the groups appears to reflect differences in the depositional environment of the source rocks of the oils each group is correlated tentatively with source rocks laid down in a specific depositional regime namely lacustrine freshwater lacustrine saline water marine evaporitic marine carbonate or marine deltaic the diagnostic features that allow this classification are the relative abundance and carbon number distributions of n alkanes pristane phytane ratios sulphur nickel and vanadium contents carbon isotope data the absolute concentrations of hopanes and steranes and their abundance relative to 4 methylsteranes and also the occurrence and abundance of several specific biological markers including 18 h oleanane gammacerane carotane tricyclic terpanes higher acyclic isoprenoids 28 30 bisnorhopane and 25 28 30 trisnorhopane this investigation shows the value of a combined geochemical and molecular approach in the assessment of the palaeoenvironment of deposition of the source rocks which gave rise to the oils

the potential impact of climate change on typhoon triggered landslides in taiwan 2010 2099 abstract in the western north pacific including taiwan typhoons tropical cyclones and rainfall rates are predicted to intensify as a result of climate change because typhoons are the major triggers of shallow landslides in taiwan landslide activity is expected to increase as global warming continues to assess the worst scenario of landslide occurrence in a mountainous watershed till the end of the century this study developed a method to select a global climate model gcm from 21 available gcms and correct its monthly precipitation data before downscaling annual maximum 24 h rainfall from the corrected gcm data as input to the factor of safety model for landslide prediction average annual maximum rainfall is expected to increase from 322 mm in 1960 2008 to 371 mm in 2010 2099 average total unstable area is expected to increase from 1135 ha in 1960 2008 to 1280 ha in 2010 2099 a 12 increase as a first attempt to assess landslide activity due to global warming this study is useful as a reference for watershed management in taiwan the results must be evaluated in light of uncertainties caused by the correction and downscaling of gcm data and the input parameters to the slope stability model

regional test of a model for shallow landsliding landslides mapped in 14 watershed analyses in oregon and washington provide a regional test of a model for shallow landsliding a total of 3224 landslides were mapped in watersheds covering 2993 km2 and underlain by a variety of lithologies including tertiary sedimentary rocks of the coast ranges volcanic rocks of the cascade range and quaternary glacial sediments in the puget lowlands gis geographical information system techniques were used to register each mapped landslide to critical rainfall values predicted from a theoretical model for the topographic control on shallow landsliding using 30 m dems digital elevation models a single set of parameter values appropriate for simulating slide hazards after forest clearing was used for all watersheds to assess the regional influence of topographic controls on shallow landsliding model performance varied widely between watersheds with the best performance generally in steep watersheds underlain by shallow bedrock and the worst performance in generally low gradient watersheds underlain by thick glacial deposits landslide frequency slides km2 varied between physiographic provinces but yielded consistent patterns of higher slide frequency in areas with lower critical rainfall values simulations with variable effective cohesion predicted that high root strength effectively limits shallow landsliding to topographic hollows with deep soils and locations that experience excess pore pressures but that low root strength leads to higher probabilities of failure across a greater proportion of the landscape 1998 john wiley sons ltd language en

generation and expulsion of oils from permian coals of the sydney basin australia abstract organic geochemical and petrological assessment of coals coaly shales and fine grained sediments coupled with organic geochemical analyses of oil samples all from permo triassic sections of the southern sydney basin australia have enabled identification of the source for the widely distributed oil shows and oil seeps in this region the permian coals have higher hydrogen indices higher liptinite contents and much higher total organic matter extract yields than the fine grained sediments a variety of source specific parameters obtained from n alkanes regular isoprenoids terpanes steranes and diasteranes indicate that the oil shows and seeps were generated and expelled predominantly from higher plant derived organic matter deposited in oxic environments the source and maturity related biomarkers and aromatic hydrocarbon distributions of the oils are similar to those of the coals the oil coal relationship also is demonstrated by similarities in the carbon isotopic composition of the total oils coal extracts and their individual n alkanes extracts from the permo triassic fine grained sediments on the other hand have organic geochemical signatures indicative of mixed terrestrial and prokaryotic organic matter deposited in suboxic environments which are significantly different from both the oils and coal extracts the molecular signatures indicating the presence of prokaryotic organic matter in some of the coal extracts and oils may be due to thin sections of possibly calcareous lithologies interbedded within the coal measures the genetic relationship between the oils and coals provides new evidence for the generation and expulsion of oils from the permian coals and raises the possibility for commercial oil accumulations in the permian and early triassic sandstones potentially in the deeper offshore part of the sydney basin

spatially and temporally distributed modeling of landslide susceptibility mapping of landslide susceptibility in forested watersheds is important for management decisions in forested watersheds especially in mountainous areas the spatial distribution of relevant parameters for landslide prediction is often unavailable this paper presents a gis based modeling approach that includes representation of the uncertainty and variability inherent in parameters in this approach grid based tools are used to integrate the soil moisture routing smr model and infinite slope model with probabilistic analysis the smr model is a daily water balance model that simulates the hydrology of forested watersheds by combining climate data a digital elevation model soil and land use data the infinite slope model is used for slope stability analysis and determining the factor of safety for a slope monte carlo simulation is used to incorporate the variability of input parameters and account for uncertainties associated with the evaluation of landslide susceptibility this integrated approach of dynamic slope stability analysis was applied to the 72 km2 pete king watershed located in the clearwater national forest in north central idaho usa where landslides have occurred a 30 year simulation was performed beginning with the existing vegetation covers that represented the watershed during the landslide year comparison of the gis based approach with existing models fsmet and shalstab showed better precision of landslides based on the ratio of correctly identified landslides to susceptible areas analysis of landslide susceptibility showed that 1 the proportion of susceptible and non susceptible cells changes spatially and temporally 2 changed cells were a function of effective precipitation and soil storage amount and 3 cell stability increased over time especially for clear cut areas as root strength increased and vegetation transitioned to regenerated forest our modeling results showed that landslide susceptibility is strongly influenced by natural processes and human activities in space and time while results from simulated outputs show the potential for decision making in effective forest planning by using various management scenarios and controlling factors that influence landslide susceptibility such a process based tool could be used to deal with real dynamic systems to help decision makers to answer complex landslide susceptibility questions

a physically based model for the topographic control on shallow landsliding a model for the topographic influence on shallow landslide initiation is developed by coupling digital terrain data with near surface through flow and slope stability models the hydrologic model topog o loughlin 1986 predicts the degree of soil saturation in response to a steady state rainfall for topographic elements defined by the intersection of contours and flow tube boundaries the slope stability component uses this relative soil saturation to analyze the stability of each topographic element for the case of cohesionless soils of spatially constant thickness and saturated conductivity the steady state rainfall predicted to cause instability in each topographic element provides a measure of the relative potential for shallow landsliding the spatial distribution of critical rainfall values is compared with landslide locations mapped from aerial photographs and in the field for three study basins where high resolution digital elevation data are available tennessee valley in marin county california mettman ridge in the oregon coast range and split creek on the olympic peninsula washington model predictions in each of these areas are consistent with spatial patterns of observed landslide scars although hydrologic complexities not accounted for in the model e g spatial variability of soil properties and bedrock flow control specific sites and timing of debris flow initiation within areas of similar topographic control

landslide detection and susceptibility mapping in the sagimakri area korea using kompsat 1 and weight of evidence technique the purpose of this study is to detect landslide locations from satellite images and use them for landslide susceptibility mapping in the sagimakri area korea using a geographic information system and a data driven weight of evidence model the landslide location areas were identified from korea multipurpose satellite images by means of change detection technique and further verified by extensive field survey subsequently landslide locations were randomly selected in a 70 30 ratio for training and validation of the model respectively a spatial database was constructed which is composed of topography forest soil and land cover and 14 landslide related factors were extracted from the database the relationships between the detected landslide locations and the factors were identified and quantified by weights of evidence model tests of conditional independence were performed for the selection of factors allowing five different combinations of factors to be analyzed the relationships were used as the contrast values w and w of factor ratings in the overlay analysis to create landslide susceptibility indexes and maps the results of the analysis were validated by comparison with known landslide locations that were not used directly in the analysis

paleoreconstruction by biological markers abstract during diagenesis and conversion of the original lipid fraction of biological systems to petroleum hydrocarbons the following four basic events needed for paleoreconstruction can be monitored by biological markets 1 sourcing 2 maturation 3 migration and 4 biodegradation actual cases of applying biological markers to petroleum exploration problems in different parts of the world are demonstrated cretaceous and phosphoria sourced oils in the wyoming thrust belt can clearly be distinguished from one another by high quality source fingerprinting of biomarker terpanes using gas chromatography mass spectrometry identification of recently discovered biological markers head to head isoprenoids allows subtle source differentiation between oils from sumatra the degree of crude oil maturation in basins from california alaska russia wyoming and louisiana can be assessed by specific novel biomarker ratios 20s 20r sterane epimers field evidence from such interpretation is confirmed by laboratory pyrolysis of the rock an example of immature sumatra rock is given extensive migration is documented by biomarkers in several oils the effect of biodegradation on biomarker steranes and terpanes is exemlified in a california basin all biological marker results are consistent with the geological setting and add a new dimension in assisting the petroleum explorationist toward paleo reconstruction

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

modeling the sediment yield from landslides in the shihmen reservoir watershed taiwan landslides generate enormous volumes of sediment in mountainous watersheds however quantifying the downstream transport of landslide derived sediment remains a challenge landslide erosion and sediment delivery to the shihmen reservoir watershed in taiwanwas estimated using empirical landslide frequency area and volume area relationships empirical landslide runout models and the hydrological simulation programfortran hspf landslide erosion rates ranged from 0 4mmyr to 2 2mmyr during the period 1986 2003 but increased to 7 9mmyr following typhoon aere in 2004 the percentage of landslide sediment delivered to streams decreased from 78 during the period 1986 1997 to 55 in 2004 although the delivery ratio was lower the volume of landslide sediment delivered to streams was 2 81 10mgyr in 1986 1997 and 8 60 10mgyr in 2004 model simulations indicate that only a small proportion of the landslidematerial was delivered downstream an average of 13 of the landslide material delivered to rivers was moved downstream during the period 1986 1997 in 2004 the period including typhoon aere the annual fluvial sediment yield accounted for approximately 23 of the landslide material delivered to streams in general the transfer of sediment in the fluvial system in the shihmen reservoir watershed is dominantly transport limited the imbalance between sediment supply and transport capacity has resulted in a considerable quantity of landslide material remaining in the upper stream regions of the watershed copyright 2012 john wiley sons ltd

depositional environment organic matter sources and variable 17α h diahopane distribution in early permian samples southern sydney basin australia abstract early permian strata exposed in the southern part of the sydney basin nsw australia include the pebbley beach formation the snapper point formation and the wandrawandian siltstone these formations were deposited during the late paleozoic ice age when australia was close to the south pole the pebbley beach and snapper point formations were deposited in shallow marine to coastal environments while the wandrawandian siltstone was deposited in deeper water following a marine transgression however opinions differ on the precise environmental and climatic conditions that prevailed during their deposition sixteen outcrop samples from these formations were collected and analysed to determine their depositional conditions and the source s of their organic matter the biomarker and aromatic hydrocarbon distributions show that the rocks are in the early to mid oil window some aromatic parameters show that the stratigraphically younger wandrawandian siltstone is more thermally mature than the older pebbley beach formation which is interpreted to be due to the geographic position of these outcrops in the sydney basin the samples have low to intermediate pristane phytane ratios from 1 4 to 3 4 showing variation from oxic to suboxic depositional conditions most of the mudstones and siltstones sampled were deposited in a marine environment with some fluvial deltaic or estuarine influence and contain mixed type ii and type iii organic matter the pebbley beach formation is characterised by terpane distributions dominated by the c24 tetracyclic terpane and to a lesser extent the c19 tricyclic terpane the snapper point formation has a mix of c19 and c23 tricyclic terpanes and c24 tetracyclic terpane while the wandrawandian siltstone is dominated by c19 c21 and c23 tricyclic terpanes the sterane distribution follows a c29 c28 c27 pattern in the majority of the samples including in the marine deposited wandrawandian siltstone the three formations have very variable relative amounts of diahopanes and other rearranged hopanes with the highest c30 c30 hopane ratio 6 9 in the wandrawandian siltstone this formation also has high amounts of diasteranes compared to the other two formations but the relative amounts of diasteranes are not as high as for the diahopanes classically this suggests a clay rich sediment in an oxic or suboxic acid catalysed depositional environment with enhanced diagenetic alteration of the biomarkers the wandrawandian siltstone was deposited in suboxic conditions not unusual to many rocks that contain much less rearranged hopanes unusual characteristics of the wandrawandian siltstone include significant slumping and soft sediment deformation and deposition under periglacial glacial conditions the occurrence of the slumps on the continental slope led to significant sediment overturn and this may have resulted in enhanced diagenetic and catalytic rearrangement reactions leading to the elevated levels of diahopanes and other rearranged hopanes the disequilibrium between the relative abundances of diahopanes and diasteranes suggests different formation mechanisms for these biomarkers

origin of nama basin bitumen seeps petroleum derived from a permian lacustrine source rock traversing southwestern gondwana abstract biodegraded bitumens associated with quartz and calcite veins in the cambrian fish river subgroup sediments of the nama group of southern namibia have a geochemical signature diagnostic for organic matter that was deposited in a saline lacustrine palaeoenvironment in particular they contain abundant gammacerane carotane and 3 methylhopanes while 24 isopropyl cholestanes and dinosteroids are not detectable sealed tube hydrous pyrolysis of asphaltene and polar fractions yielded saturated hydrocarbons amenable to c isotopic analysis and these analyses show unusually low 13 c values these combined characteristics are also present in immature bitumens from the permian irati formation of brazil and a saline lacustrine facies of the whitehill formation in the karoo basin south africa we conclude that the bitumens originated from whitehill equivalent strata of the kalahari basin deposited in what was an extensive saline lacustrine basin in southwestern gondwana during the early permian in southern africa source rocks of the whitehill formation are generally immature for petroleum generation and it is therefore likely that the nama bitumens were expelled by contact metamorphism during emplacement of karoo dolerite sills and dykes in the jurassic

susceptibility assessments of shallow earthflows triggered by heavy rainfall at three catchments by logistic regression analyses abstract sometimes regional meteorological anomalies trigger different types of mass movements in may 1998 the western black sea region of turkey experienced such a meteorological anomaly numerous residential and agricultural areas and engineering lifelines were buried under the flood waters besides the reactivation of many previously delineated landslides thousands of small scale landslides mostly the earthflow type occurred all over the region the earthflows were mainly developed in flysch type units which have already presented high landslide concentrations in this study three different catchments namely agustu egerci and kelemen were selected because they have the most landslide prone geological units of the region the purposes of the present study are to put forward the spatial distributions of the shallow earthflows triggered to describe the possible factors conditioning the earthflows and to produce the shallow earthflow susceptibility maps of the three catchments the unique condition units ucu were employed during the production of susceptibility maps and during statistical analyses the unique condition units numbered 4052 for the agustu catchment 13 241 for the egerci catchment and 12 314 for the kelemen catchment the earthflow intensity is the highest in the agustu catchment 0 038 flow ucu and lowest in the egerci catchment 0 0035 flow ucu logistic regression analyses were also employed however during the analyses some difficulties were encountered to overcome the difficulties a series of sensitivity analyses were performed based on some decision rules introduced in the present study considering the decision rules the proper ratios of ucu free from earthflow 0 ucu including the earthflow 1 for the agustu egerci and kelemen catchments were obtained as 3 6 and 5 respectively also a chart for the proper ratio selection was developed the regression equations from the selected ratios were then applied to the entire catchment and the earthflow susceptibility maps were produced the landslide susceptibility maps revealed that 15 of the agustu catchment 8 of the egerci catchment and 7 of the kelemen catchment have very high earthflow susceptibility and most of the earthflows triggered by the may 1998 meteorological event were found in the very high susceptibility zones

triggering threshold precipitation and soil hydrological characteristics of shallow landslides in granitic landscapes abstract sierra de gredos a mountain range in central spain is prone to the occurrence of shallow landslides which can transform into sediment laden flows as demonstrated by geomorphologic evidence the analyses of these complex processes require reliable design tools for predicting thresholds of triggering precipitation in order to assess the susceptibility characteristics in the sierra de gredos there is a lack of knowledge concerning how weathering mantle properties vary spatially and what effects these spatial patterns have on infiltration surface runoff and shallow subsurface flow in this context this paper is focused on the hydrogeomorphic characterization of a shallow landslide that occurred on december 17 1997 the generalized quasi dynamic model gqdm was implemented to approach the critical rainfall intensity set for different durations and to establish the intensity duration id threshold to this purpose field and laboratory methods such as seismic refraction tomography srt time domain reflectometry tdr and geotechnical tests were applied the use of these field investigations and their combination with the gqdm have allowed us to provide a detailed description of the behavior of the catchment and reproduce the pattern of instability generated by an intense storm which triggered the 1997 shallow landslide furthermore this threshold can be used as a predictive tool for hazard prevention

application of biological markers in the recognition of palaeohypersaline environments the hydrocarbon fractions of a marl sample from a messinian basin in the northern appenines and four oils rozel point oil utah and three seep oils from sicily were studied

organic geochemical characterisation of depositional palaeoenvironments of source rocks and oils in brazilian marginal basins abstract an investigation of bulk isotopic and molecular features of a wide selection of source rocks and oils from brazilian marginal basins ranging from lower cretaceous to tertiary in age provides a number of organic geochemical criteria that characterise and distinguish their depositional palaeo environments the methods employed include evaluation of organic carbon contents rock eval pyrolysis vitrinite reflectance measurements determination of carbon isotope ratios elemental and visual kerogen analysis assessment of oils and solvent extracts by liquid and gas chromatography and quantitative biological marker investigations using gc ms for aliphatic hydrocarbons and uv vis spectrophotometry for metalloporphyrins selected data were evaluated using principal component analysis the results enable the recognition and differentiation of seven depositional regimes lacustrine freshwater lacustrine saline water marine evaporitic marine carbonate marine deltaic marine highly anoxic with a predominance of calcareous mudstone lithology and marine anoxic with predominance of siliciclastic lithology diagnostic features in the biological markers from these depositional environments include the carbon number distributions of n alkanes pristane phytane ratios absolute concentrations of carotane higher acyclic isoprenoids c 30 hopane and steranes and the abundance of the latter relative to 4 methylsteranes the occurrence and abundance of particular biological markers such as gammacerane tricyclic and tetracyclic terpanes 18 h oleanane 28 30 bisnorhopane and 25 28 30 trisnorhopane and the relative abundances of nickel and vanadyl porphyrins

origin of oils in the eastern papuan basin papua new guinea the geochemical characteristics of 16 oils condensates seep oil oil shows collectively called oils from the eastern papuan basin epb and one seep oil from the western papuan basin wpb are integrated with data from previous studies of oils fluid inclusion oils and solid bitumens from the epb and wpb papua new guinea the combined set of samples can be divided in two major families of hydrocarbons the family a oils mostly occurring in the wpb region were generated from clay rich marine source rocks containing predominantly terrigenous higher plant derived organic matter om deposited in a sub oxic to oxic environment source rock s for family a oils are likely to be of middle to upper jurassic e g the upper jurassic imburu formation the family b oils distributed mainly in the epb region were generated from cretaceous or younger marine carbonate source rock s deposited under anoxic to sub oxic conditions and containing predominantly prokaryotic om with some terrigenous higher plant inputs the epb natural gases analyzed in this study may be co genetic to the co occurring family b oils in the epb both family a and b oils were generated at similar thermal maturities of 1 0 1 3 vitrinite reflectance equivalent although no source interval to date has been firmly identified in the epb post jurassic strata are a viable option because 1 late cretaceous and paleogene carbonate and clastic marine sediments including possible source lithologies are present and 2 this section of the papuan basin sustained rapid sedimentation and tectonic loading particularly in the cenozoic

petroleum geochemistry and depositional setting of lacustrine source rocks abstract lacustrine sequences are increasingly being recognised as hosts for commercial reserves of petroleum petroleum source rocks in lacustrine sequences have organic carbon contents ranging from 20 and kerogen types range from type i to type iii the organic matter can be of land plant algal or bacterial origin most undegraded lacustrine oils are extremely paraffinic and waxy but a few are asphaltic and rich in sulphur the crude oils and source rocks contain a wide diversity of biological marker compounds reflecting different source inputs the diversity of chemistries displayed by lacustrine source rocks and crude oils reflect the wide variety of organic source materials and depositional conditions operative in lakes lacustrine sequences preserved in the geological record represent sediments deposited in fluvial lakes on humid flood plains and tectonic lakes in humid semi arid and arid environments preservation of organic matter in lakes is dependent on the formation of anoxic or micro oxic bottom waters this is favoured by stratification of lake waters brought about by temperature and salinity contrasts organic material preserved in oligotrophic lakes is largely of land plant origin which has been extensively modified by bacteria under mildly oxidizing conditions and supplemented by the bacterial remains source rocks of this type are found in 1 fluvial lacustrine settings e g jurassic of eromanga basin australia and 2 the oligotrophic phase of larger tectonic lakes e g early stages of green river formation uinta basin usa as these freshwater lakes become productive algal remains are contributed to the sediment and anoxic bottom waters can become more firmly established the green algae pediastrum and botryococcus appear to be particularly important although land plant detritus is still significant e g cretaceous source rocks songliao basin china saline lakes conditions tend to restrict the diversity of the source biota although preservation may be enhanced through anoxia brought about by salinity stratification and inhibition of bacterial decay e g later stages green river formation uinta basin usa sulphate rich and hypersaline lacustrine systems result in the formation of sulphur rich sources and oils e g jianghan basin china because of the diversity of organic matter types maturation criteria for hydrocarbon generation in lacustrine sequences also vary however in most cases higher maturation levels are required for significant hydrocarbon generation at present it is uncertain the extent to which algal and bacterial organic matter contribute to the source for the waxy hydrocarbons which are characteristic of lacustrine oils organic rich rocks formed in large freshwater and saline lakes are the most productive type of lacustrine source rock although sources formed in lakes of flood plains and deltas are also widespread

genetic classification of petroleum systems our genetic classification of petroleum systems is founded on a simple working nomenclature that consists of combining qualifiers from each of the following three categories 1 charge factor supercharged normally charged or undercharged 2 migration drainage style vertically drained or laterally drained and 3 entrapment style high impedance or low impedance the charge factor is estimated on the basis of the richness and volumetrics of mature source rocks the source potential index spi which combines source rock richness and thickness into a single parameter is a convenient shortcut for comparing the petroleum potential of diverse source rocks containing dissimilar kerogen types and for rapidly estimating regional charging capacity in extensively explored basins a positive correlation exists between the magnitude of spi and basin wide petroleum reserves the migration drainage style is determined from the structural and stratigraphic framework of a basin vertical migration drainage which occurs mainly through faults and fracture systems breaching a seal is characteristic of petroleum systems contained within rift basins deltaic sequences salt dome provinces wrench basins and fold and thrust belts in contrast lateral migration drainage is dominant wherever stratigraphically continuous seal reservoir doublets extend over a very large area in a tectonically stable province e g commonly foreland or intracratonic platform basins recognition of the dominant migration style helps to predict the location of zones of petroleum occurrence in relation to the hydrocarbon kitchens the entrapment style which is also dependent on the structural framework and the presence and effectiveness of seals describes the degree of resistance i e impedance working against dispersion of the petroleum charge application of these working concepts should help to significantly reduce geologic risk particularly in new ventures type exploration

petroleum isotopic and biomarker composition related to source rock organic matter and depositional environment abstract a multivariate approach has been developed that separates oils derived from organic matter in nonmarine shales marine shales and marine carbonates some or all of the following analyses were completed on 43 oils from known source rocks 1 c30 sterane and monoaromatic steroid biomarker ratios and 2 stable carbon and hydrogen isotope compositions of whole oil saturates and aromatics three group discriminant analysis of the 28 oils whereall biomarker and isotopic data are available results in no misclassifications at a significance level of 99 using only carbon and hydroogen isotopic data for whole oils saturates and aromatics results in correct classifications of 82 for oils derived from marine shale organic matter and 100 for oils from the other two sources triangular plots probabilities can be used to distinguish oils derived from the three source rock organic matter end members several publications describe classifications of marine vs nonmarine oils using stable carbon isotope ratios of the whole oil or the saturate and aromatic fractions our results confirm that these methods do not completely differentiate oils by source

a distributed slope stability model for steep forested basins a distributed physically based slope stability model dslam based on an infinite slope model a kinematic wave groundwater model and a continuous change vegetation root strength model is presented it is integrated with a contour line based topographic analysis and a geographic information system gis for spatial data extraction and display the model can be run with either individual rainfall events or long term sequences of storms these inputs can be either actual storm records or synthesized random events based on monte carlo simulation the model is designed to analyze rapid shallow landslides and the spatial distribution of safety factor fs in steep forested areas it can investigate the slope stability problem in both temporal and spatial dimensions for example the impact of timber harvesting on slope stability either at a given time or through an extended management period the probability of landslide occurrence for a given year and the delivery of landslide sediments to headwater streams the dslam model was applied in a steep forested drainage of cedar creek in the oregon coast ranges using actual spatial patterns of timber harvesting and measured rainfall during a major storm which triggered widespread landslides in that area in 1975 simulated volume and number of failures were 733 m3 and 4 respectively these values agreed closely with field measurements following the 1975 storm however the effect of parameter uncertainty may complicate this comparison for example when soil cohesion values of 2 0 and 3 0 kpa were used the failure volume changed by factors of 2 04 and 0 41 respectively compared with the average condition of 2 5 kpa used in the simulation for soil depths 30 higher and lower than the standard condition the failure volume changed by factors of 2 0 and 0 27 respectively when maximum root cohesion changed from 12 5 kpa average condition to 10 kpa the failure volume increased 1 73 fold for the case of 15 kpa the failure volume changed by a factor of 0 55 the simulated failures caused by the storm were mostly in hollows the simulations show that the spatial distribution of fs is controlled mainly by topography and timber harvesting patterns and is greatly affected by groundwater flow patterns during major rainstorms most areas with fs 3 0 corresponded with the distribution of blocks clear cut in 1968 and all elements with fs 2 0 were in areas clear cut in 1968 areas with low fs 1 0 1 6 expanded dramatically during the rainstorm and decreased at a slow rate after the storm factors of safety in hollows declined sharply during the storm

sediment yield during typhoon events in relation to landslides rainfall and catchment areas in taiwan abstract debris sourced from landslides will result in environmental problems such as increased sediment discharge in rivers this study analyzed the sediment discharge of 17 main rivers in taiwan during 14 typhoon events selected from the catchment area and river length that caused landslides according to government reports the measured suspended sediment and water discharge collected from hydrometric stations of the water resources agency of taiwan were used to establish rating curve relationships a power law relation between them then sediment discharge during typhoon events was estimated using the rating curve method and the measured data of daily water discharge positive correlations between sediment discharge and rainfall conditions for each river indicate that sediment discharge increases when a greater amount of rainfall or a higher intensity of rainfall falls during a typhoon event in addition the amount of sediment discharge during a typhoon event is mainly controlled by the total amount of rainfall not by peak rainfall differences in correlation equations among the rivers suggest that catchments with larger areas produce more sediment catchments with relatively low sediment discharge show more distinct increases in sediment discharge in response to increases in rainfall owing to the little opportunity for deposition in small catchments with high connectivity to rivers and the transportation of the majority of landslide debris to rivers during typhoon events also differences in geomorphic and geologic conditions among catchments around taiwan lead to a variety of suspended sediment dynamics and the sediment budget positive correlation between average sediment discharge and average area of landslides during typhoon events indicates that when larger landslides are caused by heavier rainfall during a typhoon event more loose materials from the most recent landslide debris are flushed into rivers resulting in higher sediment discharge the high proportion of large landslides in taiwan contributes significantly to the high annual sediment yield which is among the world s highest despite the small area of taiwan

mineralogical and geochemical evidence for coupled bacterial uranium mineralization and hydrocarbon oxidation in the shashagetai deposit nw china unusual mineral structures have recently been found in a sandstone hosted roll type uranium deposit in the middle jurassic zhiluo formation in the shashagetai deposit the northern ordos basin nw china the structures possess a chemical composition and crystal structure characteristic of mineral coffinite usio4 1 x oh 4x which occurs as nanoparticles with size ranging from 5 to 25 nm these structures are interpreted to be fossilized microorganisms based on mineralogical biosignatures including morphology size occurrence of biogenic coffinite as nano crystals and biological elements such as p the intimate intergrowth of coffinite with secondary pyrite of bacterial origin as defined by low 34 s values and calcite cements with petroleum derived carbon supports its biogenic origin oil inclusions in the host sandstone are characterized by abundant n alkanes slightly increased pr nc17 and ph nc18 ratios significant amounts of demethylated hopanes and tricyclic terpanes and the existence of unresolved complex mixtures these characteristics are interpreted to be a result of mixing of an earlier heavily degraded oil with a later charged fresh oil subsequently the oils were slightly degraded these lines of evidence lead to the proposal that the reduction of sulfate and oxidization of petroleum are likely synchronous with reduction of hexavalent u vi to tetravalent u iv uranium by sulfate reducing bacteria srb the discovery of a natural association of microorganism like structures a uranium mineral and biodegraded petroleum has implications for uranium biomineralization and fossil fuel exploration

comparing models of debris flow susceptibility in the alpine environment abstract debris flows are widespread in val di fassa trento province eastern italian alps where they constitute one of the most dangerous gravity induced surface processes from a large set of environmental characteristics and a detailed inventory of debris flows we developed five models to predict location of debris flow source areas the models differ in approach statistical vs physically based and type of terrain unit of reference slope unit vs grid cell in the statistical models a mix of several environmental factors classified areas with different debris flow susceptibility however the factors that exert a strong discriminant power reduce to conditions of high slope gradient pasture or no vegetation cover availability of detrital material and active erosional processes since slope and land use are also used in the physically based approach all model results are largely controlled by the same leading variables overlaying susceptibility maps produced by the different methods statistical vs physically based for the same terrain unit of reference grid cell reveals a large difference nearly 25 spatial mismatch the spatial discrepancy exceeds 30 for susceptibility maps generated by the same method discriminant analysis but different terrain units slope unit vs grid cell the size of the terrain unit also led to different susceptibility maps almost 20 spatial mismatch maps based on different statistical tools discriminant analysis vs logistic regression differed least less than 10 hence method and terrain unit proved to be equally important in mapping susceptibility model performance was evaluated from the percentages of terrain units that each model correctly classifies the number of debris flow falling within the area classified as unstable by each model and through the metric of roc curves although all techniques implemented yielded results essentially comparable the discriminant model based on the partition of the study area into small slope units may constitute the most suitable approach to regional debris flow assessment in the alpine environment

calibration and resolution effects on model performance for predicting shallow landslide locations in taiwan in this paper we optimise the spatially explicit prediction of landslide hazard landslide triggering and subsequent movement downslope of materials for a mountainous catchment in taiwan the location prediction is optimised by subsequently adding three location parameters rainfall distribution land use classes and dem derived slopes then the three most important model parameters are calibrated to find the best prediction for both stable and unstable areas the landslides predicted by the lapsus ls model are compared with a landslide inventory to validate the output the optimal model settings for the calibration area are then applied to a validation area results show that model performance can be improved by adding the spatial distribution of rainfall and by stratifying according to land use classes landslide prediction is better with fine resolution dems mainly because the local topography is smoothed in coarser resolutions although in general the amount of landslides is over predicted the overall performance indicates that the model is able to capture the important factors determining landslide location additional spatially distributed data such as regolith or soil depth and regeneration rates of the legacy effect can further enhance the model s prediction

depositional environment and factors controlling β carotane accumulation a case study from the jimsar sag junggar basin northwestern china abstract a combined investigation of bulk geochemistry and molecular geochemistry was carried out on 31 source rock samples from the lower permian lucaogou formation in the jimsar sag of the junggar basin northwestern china geochemical characterization reveals the depositional environments and other factors favorable for the generation and accumulation of carotane an important hydrocarbon precursor many core samples have a total organic carbon content 1 and rock eval s2 values 2 mg hc g rock suggesting relatively high hydrocarbon generation potential biomarkers in the lucaogou source rock extracts are characterized by short to long chain n alkanes a wide range of pr ph ratios 0 74 1 42 and carotane index values carotane cmax 0 16 1 92 high concentrations of c29 sterane relatively low tricyclic terpane content and moderate gammacerane index values 0 14 0 29 this is consistent with a weakly oxidizing to weakly reducing depositional environment with fresh to brackish water conditions rapid input of terrigenous organic matter and a relatively small contribution of aquatic algal bacterial organic matter cross plots of biomarker parameters and the carotane index show that carotane in the lucaogou source rocks is mainly derived from terrigenous organic matter and is found predominantly in sediments deposited in weakly reducing brackish environments it does not appear to have been affected by thermal maturation

sediment flux from a mountain belt derived by landslide mapping in humid uplands landsliding is the dominant mass wasting process in the western southern alps of new zealand landslides are scale invariant and have a power law magnitude frequency distribution independent studies from other regions suggest that this is a general property of landsliding this observation is of critical importance to the evaluation of the impact of events of different length scales over different time intervals on landscape evolution it is particularly useful when estimating regional geomorphic rates because it constrains the frequency and overall significance of extreme events which cannot otherwise be evaluated by integrating the complete response of the system we estimate the regional denudation rate due to landsliding to be 9 4 mm yr 1 sediment discharge from the western southern alps is dominated by landslide derived material

the application of gis based logistic regression for landslide susceptibility mapping in the kakuda yahiko mountains central japan as a first step forward in regional hazard management multivariate statistical analysis in the form of logistic regression was used to produce a landslide susceptibility map in the kakuda yahiko mountains of central japan there are different methods to prepare landslide susceptibility maps the use of logistic regression in this study stemmed not only from the fact that this approach relaxes the strict assumptions required by other multivariate statistical methods but also to demonstrate that it can be combined with bivariate statistical analyses bsa to simplify the interpretation of the model obtained at the end in susceptibility mapping the use of logistic regression is to find the best fitting function to describe the relationship between the presence or absence of landslides dependent variable and a set of independent parameters such as slope angle and lithology here an inventory map of 87 landslides was used to produce a dependent variable which takes a value of 0 for the absence and 1 for the presence of slope failures lithology bed rock slope relationship lineaments slope gradient aspect elevation and road network were taken as independent parameters the effect of each parameter on landslide occurrence was assessed from the corresponding coefficient that appears in the logistic regression function the interpretations of the coefficients showed that road network plays a major role in determining landslide occurrence and distribution among the geomorphological parameters aspect and slope gradient have a more significant contribution than elevation although field observations showed that the latter is a good estimator of the approximate location of slope cuts using a predicted map of probability the study area was classified into five categories of landslide susceptibility extremely low very low low medium and high the medium and high susceptibility zones make up 8 87 of the total study area and involve mid altitude slopes in the eastern part of kakuda mountain and the central and southern parts of yahiko mountain

biomarker distributions in crude oils and source rocks from different sedimentary environments abstract the saturated and aromatic hydrocarbons from a significant number of oils and source rocks derived from terrestrial and marine organic matter have been analysed by gc and gc ms results show that certain classes of biomarkers including bicyclic sesquiterpanes tricyclic terpanes pregnanes methylsteranes rearranged steranes hopane sulfides benzohopanes long chain alkylbenzenes and pentacyclic triterpanes can be used to distinguish differences in source input and or depositional environments variations in the distributions of the naphthalenes phenanthrenes fluorenes dibenzofurans dibenzothiophenes naphthobenzothiophenes and triaromatic steroid hydrocarbons may also reflect disparities in source input or sedimentary environments

prediction of source rock characteristics based on terpane biomarkers in crude oils a multivariate statistical approach abstract the distributions of eight tricyclic and eight pentacyclic terpanes were determined for 216 crude oils located worldwide with subsequent simultaneous rq mode factor analysis and stepwise discriminate analysis for the purpose of predicting source rock features or depositional environments five categories of source rocks are evident nearshore marine i e paralic deltaic deeper water marine lacustrine phosphaticrich source beds and ordovician age source rocks the first two factors of the rq mode factor analysis describe 45 percent of the variation in the data set the tricyclic terpanes appear to be twice as significant as pentacyclic terpanes in determining the variation among samples lacustrine oils are characterized by greater relative abundances of c 21 diterpane and gammacerane nearshore marine sources by c 19 and c 20 diterpanes and oleanane deeper water marine facies by c 24 and c 25 tricyclic and c 31 plus c 32 extended hopanes and ordovician age oils by c 27 and c 29 pentacyclic terpanes although thermal maturity trends can be observed in factor space the trends do not necessarily obscure the source rock interpretations also since bacterial degradation of crude oils rarely affects tricyclic terpanes biodegraded oils can be used in predicting source rock features the precision to which source rock depositional environments are determined might be increased with the addition of other biomarker e g steranes and stable isotope data using multivariate statistical techniques

a spatiotemporal probabilistic modelling of storm induced shallow landsliding using aerial photographs and logistic regression landslides constitute one of the major natural hazards that could cause significant losses of life and property mapping or delineating areas prone to landsliding is therefore essential for land use activities and management decision making in hilly or mountainous regions a landslide hazard map can be constructed by a qualitative combination of maps of site conditions including geology topography and geomorphology by statistical methods through correlating landslide occurrence with geologic and geomorphic factors or by using safety factors from stability analysis a landslide hazard map should provide information on both the spatial and temporal probabilities of landsliding in a certain area however most previous studies have focused on susceptibility mapping rather than on hazard mapping in a spatiotemporal context this study aims at developing a predictive model based on both quasi static and dynamic variables to determine the probability of landsliding in terms of space and time the study area selected is about 13 km 2 in north lantau hong kong the source areas of the landslides caused by the rainstorms of 18 july 1992 and 4 5 november 1993 were interpreted from multi temporal aerial photographs landslide data lithology digital elevation model data land cover and rainfall data were digitized into a geographic information system database a logistic regression model was developed using lithology slope gradient slope aspect elevation slope shape land cover and rolling 24 it rainfall as independent variables since the dependent variable could be expressed in a dichotomous way this model achieved an overall accuracy of 87 2 with 89 5 of landslide grid cells correctly classified and found to be performing satisfactorily the model was then applied to rainfalls of a variety of periods of return to predict the probability of landsliding on natural slopes in space and time it is observed that the modelling techniques described here are useful for predicting the spatiotemporal probability of landsliding and can be used by land use planners to develop effective management strategies copyright 0 2003 john wiley sons ltd

landslides triggered by the 23 november 2000 rainfall event in the imperia province western liguria italy from mid october to 22 november 2000 the western liguria region of italy experienced prolonged and intense rainfall with cumulative values exceeding 1000 mm in 45 days the severe rainfall sequence ended on november 23 with a high intensity storm that dumped more than 180 mm of rain in 24 h the high intensity event caused flooding and triggered more than 1000 soils slips and debris flows and a few large complex landslides slope failures caused three fatalities and severe damage to roads private homes and agriculture large 1 13 000 and very large 1 5000 scale colour aerial photographs were taken 45 days after the event over the areas most affected by the landslides through the interpretation of the 334 photographs covering an area of 500 km2 we prepared a landslide inventory map that shows 1204 landslides for a total landslide area of 1 6 km2 we identified the rainfall conditions that triggered landslides in the armea valley using cumulative and continuous rainfall data combined with detailed information on the time of landslide occurrence landslide activity initiated 8 to 10 h after the beginning of the storm and the most abundant activity occurred in response to rainfall intensities of 8 to 10 mm per hour for the ceriana municipality an area where the landslides were numerous in november 2000 we also collected information about a historical event that occurred on 8 11 december 1910 and triggered abundant landslides resulting in severe economic damage a comparison of the damage caused by the historical and the recent landslide events indicated that damage caused by the 1910 historical event was more diffused but less costly than the damage caused by the 2000 event

integrating physical and empirical landslide susceptibility models using generalized additive models physically based models are commonly used as an integral step in landslide hazard assessment geomorphic principles can be applied to a broad area resulting in first order assessment of landslide susceptibility new techniques are now available that may result in the increased accuracy of such models we investigate the possibility to enhance landslide susceptibility modeling by integrating two physically based landslide models the factor of safety fs and the shallow stability model shalstab with traditional empirical statistical methods that utilize terrain attribute information derived from a digital elevation model and land use characteristics related to forest harvesting the model performance is measured by the area under the receiver operating characteristic curve auroc and sensitivity at 90 and 80 specificity both estimated by bootstrap resampling our study examines 278 landslide initiation points in the klanawa watershed located on vancouver island british columbia canada we use a generalized additive model gam and a logistic regression model glm combining physical landslide models terrain attributes and land use data and gams and glms using only subsets of these variables in this study all empirical and combined physical empirical models outperform the physically based models with gams often performing significantly better than glms the strongest predictive performance is achieved by the gams using terrain attributes in combination with land use data variables representing physically based models do not significantly improve the empirical models but they may allow for a better physical interpretation of empirical models also based on bootstrap variable selection frequencies land use data fs slope and plan profile curvature are relatively the most important predictor variables

assessment of shallow landsliding by using a physically based model of hillslope stability a model for the simulation of shallow landsliding triggered by heavy rainstorms is analysed and discussed the model is applied in two mountainous catchments in the dolomites eastern italian alps the cordon catchment 5 km2 and the vauz catchment 1 9 km2 where field surveys provided a description of hydraulic and geotechnical properties of soils and an inventory of landslide scars is available the stability mapping procedure which is similar to that proposed by montgomery and dietrich 1994 water resources research30 1153 combines steady state hydrologic concepts with the infinite slope stability model the model provides an estimate of the spatial distribution of the critical rainfall which is the minimum steady state rainfall predicted to cause instability the comparison of the landslides observed in the study basins with model predictions shows that the distribution of critical rainfall obtained from the model provides a surrogate for failure initiation probability as a function of topographic location copyright 2002 john wiley sons ltd language en

a warning system for rainfall induced shallow failures abstract it is widely recognised that soil slips and debris flows are triggered by short intense storms owing its geologic geomorphologic and climatic settings the piedmont region nw italy is highly prone to the occurrence of this kind of landslides in the last two centuries in fact a total of 105 severe meteoric events which triggered shallow failures occurred and of these 18 events took place from 1990 to 2002 a fair number of rainfall thresholds have been proposed in the literature defined both on empirical or on physical bases empirical thresholds are defined collecting rainfall data for landslide meteoric events and for events without landslides while physical thresholds are based on numerical models that consider the relation between rainfall pore pressure and slope stability the main objective of this paper is the identification of the empirical triggering thresholds for the piedmont region four meteoric events were selected and analysed november 4 5 1994 july 7 8 1996 april 27 30 2000 october 13 16 2000 because they supply a wide range of variation for both rainfall parameters duration intensity cumulative rainfalls and the number of induced landslides in the intensity duration plot the critical limit is described by the equation i 19d 0 50 where i rainfall intensity expressed in mm h and d rainfall duration expressed in hours such a limit is traced to envelop 90 of the points on the graph in the ni d diagram the triggering thresholds are given by the equations ni 0 76d 0 33 and ni 4 62d 0 79 where ni normalised intensity with respect to the annual precipitation map expressed in mm h pma 100 in the article the different meaning of these thresholds is discussed finally the diagram ni ncr is proposed the triggering threshold is given by the expression ni 0 09ln ncr 0 54 where ncr is the normalised cumulative critical rainfall mm pma 100 the application of the triggering thresholds as a fundamental element in a warning system dedicated to the safeguarding of population in landslide prone areas is discussed in detail an operating procedure which is presently being verified and tested in the studied area is described

an integrated model for predicting rainfall induced landslides this study proposes a novel method that combines a deterministic slope stability model and a statistical model for predicting rainfall induced landslides the method first uses the deterministic model to derive the rainfall rate critical to induce slope failure for each land unit then it calculates the difference between the critical rainfall threshold and estimated rainfall intensity using the difference and estimated rainfall duration as explanatory variables the method derives a logit integrated model to compute landslide occurrence probabilities to demonstrate the effectiveness of this method the study used radar rainfall estimates and landslides associated with a typhoon tropical cyclone to develop the integrated model and the same types of data associated with another typhoon to validate the model the model had a modified success rate of 84 0 for predicting landslides and stable areas and model validation yielded a modified success rate of 87 4 both rates were better than those from the critical rainfall model the main advantage of the integrated model lies in its use of rainfall variables that are not included in calculating the critical rainfall also as a probabilistic model the integrated model is better suited for decision making in watershed management this study has advanced the method for predicting rainfall triggered landslides

modeling typhoon and earthquake induced landslides in a mountainous watershed using logistic regression landslides can be caused by storms and earthquakes most logistic regression models proposed in recent years have been targeted at rainfall induced landslides in areas such as taiwan where landslides can be triggered by typhoons tropical cyclones and earthquakes a rainfall induced model is insufficient because it provides only a partial explanation of landslide occurrence and overlooks the potential effect of earthquakes on typhoon triggered landslides this study used landslides triggered by a major earthquake and a typhoon prior to the earthquake to develop an earthquake induced model and a typhoon induced model the models were then validated by using landslides triggered by three typhoons after the earthquake according to the results typhoon triggered landslides tended to be near stream channels and earthquake triggered landslides were more likely to be near ridge lines moreover a major earthquake could still affect the locations of typhoon triggered landslides 6 years after the earthquake this study therefore demonstrates that an earthquake induced model both sheds light on the environmental factors for triggering landslides and augments a rainfall induced model in its predictive capability in areas such as taiwan

a new hierarchical bayesian approach to analyse environmental and climatic influences on debris flow occurrence abstract how can debris flow occurrences be modelled at regional scale and take both environmental and climatic conditions into account and of the two which has the most influence on debris flow activity in this paper we try to answer these questions with an innovative bayesian hierarchical probabilistic model that simultaneously accounts for how debris flows respond to environmental and climatic variables in it full decomposition of space and time effects in occurrence probabilities is assumed revealing an environmental and a climatic trend shared by all years catchments respectively clearly distinguished from residual random effects the resulting regional and annual occurrence probabilities evaluated as functions of the covariates make it possible to weight the respective contribution of the different terms and more generally to check the model performances at different spatio temporal scales after suitable validation the model can be used to make predictions at undocumented sites and could be used in further studies for predictions under future climate conditions also the bayesian paradigm easily copes with missing data thus making it possible to account for events that may have been missed during surveys as a case study we extract 124 debris flow event triggered between 1970 and 2005 in 27 catchments located in the french alps from the french national natural hazard survey and model their variability of occurrence considering environmental and climatic predictors at the same time we document the environmental characteristics of each debris flow catchment morphometry lithology land cover and the presence of permafrost we also compute 15 climate variables including mean temperature and precipitation between may and october and the number of rainy days with daily cumulative rainfall greater than 10 15 20 25 30 40 mm day 1 application of our model shows that the combination of environmental and climatic predictors explained 77 of the overall variability of debris flow occurrences in this data set occurrence probabilities depend mainly on climatic variables which explain 44 of the overall variability through the number of rainy days and maximum daily temperature this important time component in the variability of overall debris flow occurrence is shown to be responsible for a significant increase in debris flow activity between 1970 and 2005 at regional scale environmental variables which account for 33 of the overall variability includes mostly the morphometric variables of the debris flow catchments

organic geochemical evaluation of cretaceous shale samples from the orange basin south africa abstract organic geochemical evaluation of thirty two aptian to campanian shale samples from seven wells drilled on the shelf of the orange basin southwestern atlantic margin was carried out in order to determine their origin depositional environment thermal maturity and hydrocarbon potential the shale samples selected to represent highstand lowstand and transgressive systems tracts were analysed by rock eval pyrolysis for total organic c characteristics and by gas chromatography gc and gas chromatography mass spectrometry gc ms for n alkanes aliphatic isoprenoid hydrocarbons and biomarkers steranes hopanes and tricylic terpanes for most of the shale samples rock eval data hydrogen hi and oxygen index oi point to mainly type iii terrigenous organic matter only a few samples of turonian age reveal a higher proportion of marine organic matter being classified as type ii iii or type ii biomarker parameters suggest that the samples are deposited under suboxic to oxic environmental conditions rock eval data and biomarker maturity parameters assign for most of the samples a maturity level at the beginning of the oil window with some more mature samples of aptian albian and cenomanian age the hydrocarbon generation potential is low for most of the shelf shales as indicated by the s2 s3 ratio and hi values exceptions are some samples of turonian and aptian age

modelling the location of shallow landslides and their effects on landscape dynamics in large watersheds an application for northern new zealand in this study we propose a model to assess the location of shallow landslides and their impact on landscape development within a timeframe of years to decades processes that need to be incorporated in the model are reviewed then followed by the proposed modelling framework the capabilities of the model are explored through an application for a forested 17 km2 study catchment in northern new zealand for which digital elevation data are available with a grid resolution of 25 25 m the model predicts the spatial pattern of landslide susceptibility within the simulated catchment and subsequently applies a spatial algorithm for the redistribution of failed material by effectively changing the corresponding digital elevation data after each timestep on the basis of a scenario of triggering rainfall events relative landslide hazard and trajectories with runout criteria for failed slope material the resulting model will form a landslide module within the dynamic landscape evolution model lapsus the model forms a spatially explicit method to address the effects of shallow landslide erosion and sedimentation because digital elevation data are adapted between timesteps and on and off site effects over the years can be simulated in this way by visualization of the modelling results in a gis environment the shifting pattern of upslope and downslope in stability triggering of new landslides and the resulting slope retreat by soil material redistribution due to former mass movements can be simulated and assessed

modeling shallow landsliding susceptibility by incorporating heavy rainfall statistical properties abstract we present an index based shallow landsliding susceptibility model which allows explicit incorporation of local heavy rainfall statistical properties the model called quasi dynamic shallow landsliding model qd slam is developed upon a theory for coupled shallow subsurface flow and landsliding of the soil mantle the model uses a quasi dynamic wetness index to predict the spatial distribution of soil saturation in response to a rainfall of specified duration and can take into account the spatial variability of soil properties the rainfall predicted to cause instability in each topographic element is characterized by intensity and duration the incorporation of a scaling model for the rainfall frequency duration relationship provides a parsimonious and robust way to include heavy rainfall statistical properties into shallow landsliding modeling the model is used to determine the return period of the critical rainfall needed to cause instability for each topographic element the model is validated over six different study sites where detailed inventories of shallow landslides are available two study sites are located in the north of taiwan and four are located in the italian alps the sites are characterized by different climates and by different duration of the landslide triggering storms model results are evaluated against the surveyed landslides and compared to those obtained by using a steady state model resembling shalstab it is shown that qd slam improves significantly over the steady state approach in predicting existing landslides as represented in the considered landslide inventory moreover the improvement is higher for the cases where the landslide triggering storm duration is short with respect to the length of time required for every point on a catchment to reach subsurface drainage equilibrium the results of our work highlight the capability of the model to incorporate a robust description of the heavy rainfall properties in the analysis and mapping of shallow landsliding susceptibility by using an index style approach