the characteristics and formation mechanism of a regional fault in shale strata insights from the middle upper yangtze china abstract shale is a type of fracture prone rock but few regional faults are observed in shale strata here we investigate a regional detachment fault in the middle upper yangtze muy to understand the formation mechanism of a special regional fault in shale strata based on a lithological mineralogical and mechanical study as well as semi quantitative model of displacement we found that the formation of this detachment fault is closely related to the lithological association and flexural slip processes the lithological association of this detachment fault is characterized by two thick competent layers separated by a thin weak interlayer at both the macroscopic and microscopic scales when these layers are folded the detachment fault zone is commonly present in a thin weak interlayer namely the wufeng formation at the macroscopic scale and primarily along interfaces in laminar siliceous shales lss and secondarily in k bentonite interlayers within the lss at the microscopic scale the regional fault zone is characterized by parallel to strata surfaces and abrupt contacts with the protolith the fabric of the fault core is obviously controlled by the flexural slip intensity and the number of slip events as well as their direction and structural position the natural shale gas obtained from well hd 1 has proven that this regional detachment fault in shale strata is not only a migration pathway for hydrocarbons but also acts as an adsorption state reservoir for free gas from other areas this regional detachment fault in shale strata is likely to advance the shale gas industry and to expand the exploration of conventional gas

the puguang gas field new giant discovery in the mature sichuan basin southwest china the giant puguang gas field with a proven original in place gas volume of 350 109 m3 12 36 tcfg was discovered in 2003 in the eastern sichuan fold thrust belt of the mature sichuan basin southwest china the field is a combination structural stratigraphic trap closed by lateral depositional change and fault closure the trap evolved from a paleo oil reservoir originating in the triassic jurassic the entrapment of thermal gas which was derived from lower middle silurian and permian source rocks occurred during deep burial in the jurassic cretaceous tertiary quaternary compression transformed the paleotrap into the present gas reservoir gas is contained in the lower triassic feixianguan and the upper permian changxing reservoirs which consist predominantly of dolomitized oolites deposited in shelf and platform margin shoal and backreef environments reservoir quality is characterized by porosity of 1 29 and permeability of 0 01 9664 md with buried depth greater than 5000 m 16 400 ft the discovery of the puguang field exemplifies the successful application of a new play concept and new technology in a mature basin the discovery resulted from a shift in exploration strategy from structures to stratigraphic traps in reef and shoal dolomites and benefited from advanced high resolution seismic techniques the discovery will not only broaden the exploration scope in the sichuan basin but also provide an excellent analog for exploration in other fold thrust belts worldwide

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

deep water depositional mechanisms and significance for unconventional hydrocarbon exploration a case study from the lower silurian longmaxi shale in the southeastern sichuan basin the purpose of this work was to study the depositional mechanisms and significance of the longmaxi shale in the sichuan basin in southern china seven lithofacies were identified based on the detailed observation of outcrops and cores using petrographic and scanning electron microscope examination of thin sections and other data analyses 1 laminated calcareous mudstone 2 laminated carbonaceous mudstone 3 laminated silty mudstone 4 laminated claystone 5 laminated siliceous shale 6 siltstone and 7 massive mudstone the laminated mudstone and laminated claystone originated from suspension deposition and siliceous shale is associated with ocean upwelling whereas massive mudstone and siltstone were primarily deposited by turbidity currents the depositional mechanisms have a great effect on the source rock and reservoir properties suspension deposition near oceanic upwelling zones can provide favorable conditions for the production and preservation of organic matter and are thus conducive to the formation of high quality source rocks total organic carbon content up to 5 4 the reservoir storage spaces are primarily interlaminated fractures and organic pores with good physical reservoir properties high porosity permeability and brittle mineral content turbidity currents may carry a large quantity of oxygen to the seafloor resulting in the oxidation of organic matter which is unfavorable for its preservation the lithofacies formed by turbidity currents have relatively low total organic carbon contents average 1 structural fractures and intergranular pores are the primary storage spaces that are present in the reservoir in summary organic rich shale and siliceous shale that was deposited from suspension near upwelling zones are key exploration targets for shale oil and gas the widely distributed multilayer tight sandstone is important in the exploration for tight oil a better understanding of the deposition mechanism and its effect on oil reservoirs may assist in identification of favorable areas for exploration

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

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

gis based landslide susceptibility mapping using analytical hierarchy process and bivariate statistics in ardesen turkey comparisons of results and confirmations abstract the ardesen area is prone to landslides because of the climate conditions geologic and geomorphologic characteristics of the region as in previous years in 2001 due to heavy rainfall there were many landslides resulting in damage and human casualties there is still a great danger of further landslides in the region therefore it is vitally important to prepare a landslide susceptibility map of the region in this study the analytical hierarchy process ahp the statistical index wi and weighting factor wf methods were used to produce and later compare three susceptibility maps for this purpose thematic layers including landslide inventory lithology weathering slope aspect land cover distance to stream drainage density and distance to road were used in this study area 98 of landslides occurred in highly or completely weathered units lithology weathering land cover and slope data layers were found to be important factors in the study area to confirm the practicality of the three susceptibility maps were compared with a landslide activity map containing 16 active landslide zones the outcome was that the active landslide zones do not completely fit into the high and very high susceptibility classes but 81 3 of these landslide zones fall into the high and very high susceptibility zones of the ahp method while this is 62 5 in the case of wi method and 68 8 with the wf method in spite of the results obtained in this study the development of a susceptibility map is usually determined by the needs and available resources the results showed that the ahp method gave a more realistic picture of the actual distribution of landslide susceptibility than the wi and wf methods

a range of fault slip styles on progressively misoriented planes during flexural slip folding cape fold belt south africa flexural slip folds are distinctive of mixed continuous discontinuous deformation in the upper crust as folding is accommodated by continuous bending of layers and localized discontinuous slip along layer interfaces the mechanism of localized layer parallel slip and the stress and fluid pressure conditions at which flexural slip occurs are therefore distinctive of shear localization during distributed deformation in the prince albert formation mudstone sequence of the karoo basin the foreland basin to the cape fold belt folds are well developed and associated with incrementally developed bedding parallel quartz veins with slickenfibers oriented perpendicular to fold hinge lines locally cross cutting axial planar cleavage and showing hanging wall motion toward the fold hinge bedding parallel slickenfiber coated veins dip at angles from 18 to 83 implying that late increments of bedding parallel shear occurred along unfavorably oriented planes the local presence of tensile veins in mutually cross cutting relationship with bedding parallel slickenfiber coated veins indicate local fluid pressures in excess of the least compressive stress slickenfiber vein microstructures include a range of quartz morphologies dominantly blocky to elongate blocky but in places euhedral to subhedral the veins are commonly laminated with layers of quartz separated by bedding parallel slip surfaces characterized by a quartz phyllosilicate cataclasite crack seal bands imply incremental slickenfiber growth in increments from tens of micrometers to a few millimeters in some places whereas other vein layers lack evidence for incremental growth and likely formed in single slip events single slip events however also involved quartz growth into open space and are inferred to have formed by stick slip faulting overall therefore flexural slip in this location involved bedding parallel faulting along progressively misoriented weak planes with a range of slip increments

a gis based landslide susceptibility evaluation using bivariate and multivariate statistical analyses bivariate and multivariate statistical analyses were used to predict the spatial distribution of landslides in the cuyahoga river watershed northeastern ohio u s a the relationship between landslides and various instability factors contributing to their occurrence was evaluated using a geographic information system gis based investigation a landslide inventory map was prepared using landslide locations identified from aerial photographs field checks and existing literature instability factors such as slope angle soil type soil erodibility soil liquidity index landcover pattern precipitation and proximity to stream responsible for the occurrence of landslides were imported as raster data layers in arcgis and ranked using a numerical scale corresponding to the physical conditions of the region in order to investigate the role of each instability factor in controlling the spatial distribution of landslides both bivariate and multivariate models were used to analyze the digital dataset the logistic regression approach was used in the multivariate model analysis both models helped produce landslide susceptibility maps and the suitability of each model was evaluated by the area under the curve method and by comparing the maps with the known landslide locations the multivariate logistic regression model was found to be the better model in predicting landslide susceptibility of this area the logistic regression model produced a landslide susceptibility map at a scale of 1 24 000 that classified susceptibility into four categories low moderate high and very high the results also indicated that slope angle proximity to stream soil erodibility and soil type were statistically significant in controlling the slope movement

a comparison of the gis based landslide susceptibility assessment methods multivariate versus bivariate the purpose of this study is to evaluate and to compare the results of multivariate logical regression and bivariate landslide susceptibility methods in geographical information system gis based landslide susceptibility assessment procedures in order to achieve this goal the asarsuyu catchment in nw turkey was selected as a test zone because of its well known landslide occurrences interfering with the e 5 highway mountain pass

magnitude based scaling of tsunami propagation 1 most current operational tsunami prediction systems are based upon databases of precomputed tsunami scenarios where some form of linear scaling is applied to the precomputed model runs in order to represent specific earthquake magnitudes this can introduce errors due to assumptions made about the rupture width and possible effects on dispersion in this paper we perform a series of numerical experiments on uniform depth domains using the method of splitting tsunamis most model and develop estimates of the maximum error that an assumed discrepancy in the width of a rupture will produce in the resulting field of maximum tsunami amplitude this estimate was produced from fitting the decay of maximum amplitude with normalized distance for various resolutions of the source widths to the grid size resulting in a simple power law whose coefficients effectively vary with wavelength resolution this provides a quantification of the effect that linear scaling of precomputed scenarios will have on forecasts of tsunami amplitude this estimate of scaling bias is investigated in relation to the scenario database that is currently in use within the joint australian tsunami warning centre

propagation of distant tsunamis over slowly varying topography 1 a new two dimensional finite difference numerical scheme is developed to simulate the propagation of distant tsunamis over slowly varying topography with improved dispersion effect of waves the new scheme solves the shallow water equations on a uniform grid system however the actual computation is made on a hidden grid system whose grid size is adjustable according to the condition required to satisfy local dispersion relationships of waves for varying water depth the present model is tested for the cases of two dimensional propagation of an initial gaussian hump over various uniform water depth regions for a varying topography a one dimensional test is conducted the tests show that accuracy of the numerical model is improved significantly over that of the conventional finite difference models finally the present model is applied to the simulation of a historical tsunami event the numerical result shows that the submerged rise and ridge play an important role of a waveguide for the tsunamis propagating over that topography

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

gis based landslide susceptibility mapping for a problematic segment of the natural gas pipeline hendek turkey a segment of natural gas pipeline was damaged due to landsliding near hendek re routing of the pipeline is planned but it requires the preparation of a landslide susceptibility map in this study the statistical index wi and weighting factor wf methods have been used with gis to prepare a landslide susceptibility map of the problematic segment of the pipeline for this purpose thematic layers including landslide inventory lithology slope aspect elevation land use land cover distance to stream and drainage density were used in the study area landslides occur in the unconsolidated to semi consolidated clayey unit and regolith the wf method gives better results than the wi method lithology is found to be the most important aspect in the study area based on the findings obtained in this study the unconsolidated to semi consolidated clayey unit and alluvium should be avoided during re routing agricultural activities should not be allowed in the close vicinity of the pipeline

impact of interlayer slip on fracture prediction from geomechanical models of fault related folds understanding and interpreting the timing location orientation and intensity of natural fractures within a geologic structure are commonly important to both exploration and production planning activities here we explore the application of finite element based geomechanical models to fracture prediction our approach is based on the idea that natural fractures can be interpreted or inferred from the geomechanical model derived permanent strains for this analysis we model an extensional fault tip monocline developed in a mechanically stratified limestone and shale sequence because field data exist that can be directly compared with model results the approach and our conclusions however are independent of the specific structural geometry the presence or absence of interlayer slip is shown to strongly control the distribution and evolution of strain and this control has important implications for interpreting fractures from geomechanical models

natural fractures in shale a review and new observations natural fractures have long been suspected as a factor in production from shale reservoirs because gas and oil production commonly exceeds the rates expected from low porosity and low permeability shale host rock many shale outcrops cores and image logs contain fractures or fracture traces and microseismic event patterns associated with hydraulic fracture stimulation have been ascribed to natural fracture reactivation here we review previous work and present new core and outcrop data from 18 shale plays that reveal common types of shale fractures and their mineralization orientation and size patterns a wide range of shales have a common suite of types and configurations of fractures those at high angle to bedding faults bed parallel fractures early compacted fractures and fractures associated with concretions these fractures differ markedly in their prevalence and arrangement within each shale play however constituting different fracture stratigraphies differences that depend on interface and mechanical properties governed by depositional diagenetic and structural setting several mechanisms may act independently or in combination to cause fracture growth including differential compaction local and regional stress changes associated with tectonic events strain accommodation around large structures catagenesis and uplift fracture systems in shales are heterogeneous they can enhance or detract from producibility augment or reduce rock strength and the propensity to interact with hydraulic fracture stimulation burial history and fracture diagenesis influence fracture attributes and may provide more information for fracture prediction than is commonly appreciated the role of microfractures in production from shale is currently poorly understood yet potentially critical we identify a need for further work in this field and on the role of natural fractures generally

tectonics of the middle triassic intracontinental xuefengshan belt south china new insights from structural and chronological constraints on the basal decollement zone in orogenic belts a basal decollement zone often develops at depth to accommodate the shortening due to folding and thrusting of the sedimentary cover in the early mesozoic intracontinental xuefengshan belt of south china such a decollement zone is exposed in the core of anticlines formed by the emplacement of the late orogenic granitic plutons our detailed multi scale structural analysis documents a synmetamorphic ductile deformation in the basal decollement the neoproterozoic pelite and sandstone and the intruding early paleozoic granites were deformed and metamorphosed into mylonites and orthogneiss respectively the metamorphic foliation contains a nw se stretching lineation associated with top to the nw kinematic indicators the ductile shearing of these high strained rocks can be correlated with nw verging folds and thrusts recognized in the neoproterozoic to early triassic sedimentary cover monazite u th pbtot chemical dating and zircon sims u pb dating provide age constraints of the ductile shearing between 243 and 226 ma and late orogenic granite emplacement around 235 215 ma in agreement with recent geochronological data these new results show that the xuefengshan belt is an early mesozoic orogen dominated by the nw directed shearing and thrusting at the southeastern boundary of the xuefengshan belt the chenzhou linwu fault separates the early mesozoic domain to the nw from the early paleozoic domain to the se the tectonic architecture of this belt was possibly originated from the continental underthrusting to the se of the south china block in response to northwest directed subduction of the paleo pacific plate

prediction of the occurrence of slope instability phenomenal through gis based hazard zonation slope instability hazard assessment is based on the analysis of the terrain conditions at sites where slope failures occurred in the past for the analysis of the causative factors the application of geographic information systems gis is an essential tool in the data analysis and subsequent hazard assessment three scale levels of hazard mapping are defined a direct experience driven mapping at reconnaissance level a statistical approach to determine the causative factors in a quantitative susceptibility mapping and a methodology at large scale making using of deterministic models

the flexural slip mechanism abstract detailed field studies of turbiditic sequences from south georgia south atlantic north devon england and cardigan bay wales show that flexural slip occurs on discrete movement horizons between rock packets in which the beds have welded contacts stair stepping displacements of sedimentary dykes and of early quartz veins show that the movement horizons generally have a decimetre to metre spacing and are marked by bedding parallel quartz veins these veins are from 1 mm to several cm thick and can be used to identify movement horizons in the absence of displaced markers they consist of several sheets of quartz fibres which each carry a slickenfibre lineation and which together preserve a record of the displacements on an individual surface complex slickenfibre patterns and departures from ideal behaviour in which slip occurs orthogonal to the fold hinge probably result from changes in slip vector on the limbs of growing non cylindrical folds movement horizons show many of the features associated with large scale thrusting such as ramps duplexes and imbricate structures and the shear sense given by fibre steps on these surfaces and by duplexes within stratigraphically restricted packages changes across fold hinges chevron folds are thought to develop mainly by flexural flow in the early stages with flexural slip becoming dominant later as the beds become lithified new slip surfaces are generated as the dip of the fold limbs increases

facies patterns and geography of the yangtze region south china through the ordovician and silurian transition abstract lithofacies and biofacies changes through the ordovician and silurian transition on the yangtze platform are coincident with stepwise mass extinctions recovery events global sea level changes and regional palaeogeographic configurations facies patterns through three intervals the late mid ashgill hirnantian and early rhuddanian indicate that black shale occupied most of the yangtze platform region during the late mid ashgill and early rhuddanian while the hirnantian possesses more diverse facies types the black shale was replaced by carbonate facies during the hirnantian coincident with a global sea level low stand biofacies changes from the late mid ashgill graptolitic to the hirnantian shelly facies were apparently signalled by gradual and diachronous existence of a mixed facies the manosia facies in the yangtze region however the biofacies change was abrupt from the hirnantian to the early rhuddanian when graptolitic facies occupied most areas on the yangtze platform leaving only a very narrow limited belt of shelly facies along the southern margin of the platform in northern guizhou the early rhuddanian unified biofacies pattern is a result of a global sea level rise which may be synchronized with a recovery bioevent of graptolites after hirnantian mass extinction

mechanisms of shale gas storage implications for shale gas exploration in china this article reviews the mechanisms of shale gas storage and discusses the major risks or uncertainties for shale gas exploration in china at a given temperature and pressure the gas sorption capacities of organic rich shales are primarily controlled by the organic matter richness but may be significantly influenced by the type and maturity of the organic matter mineral composition especially clay content moisture content pore volume and structure resulting in different ratios of gas sorption capacity gsc to total organic carbon content for different shales in laboratory experiments the gsc of organic rich shales increases with increasing pressure and decreases with increasing temperature under geologic conditions assuming hydrostatic pressure gradient and constant thermal gradient the gsc increases initially with depth due to the predominating effect of pressure passes through a maximum and then decreases because of the influence of increasing temperature at greater depth this pattern of variation is quite similar to that observed for coals and is of great significance for understanding the changes in gsc of organic rich shales over geologic time as a function of burial history at an elevated temperature and pressure and with the presence of moisture the gas sorption capacities of organic rich shales are quite low as a result adsorption alone cannot protect sufficient gas for high maturity organic rich shales to be commercial gas reservoirs two models are proposed to predict the variation of gsc and total gas content over geologic time as a function of burial history high contents of free gas in organic rich shales can be preserved in relatively closed systems loss of free gas during postgeneration uplift and erosion may result in undersaturation the total gas contents lower than the sorption capacity and is the major risk for gas exploration in marine organic rich shales in china

diagnosis of landslide risk for individual buildings insights from prahova subcarpathians romania the aim of this study is to quantify the landslide risk for individual buildings using spatial data in a gis environment a landslide prone area from prahova rivers subcarpathian valley was chosen because of its associated landslide hazards and its impact upon human settlements and activities the bivariate landslide susceptibility index lsi was applied to calculate the spatial probability of landslides occurrence the landslide susceptibility index map was produced by numerically adding the weighted thematic maps for slope gradient and aspect water table soil texture lithology built environment and land use validation curves were obtained using the random split strategy for two combinations of variables a all seven variables and b three variables which showed highest individual success rates with respect to landslides occurrences slope gradient water table and land use the principal pre disposing factors were found to be slope steepness and groundwater table vulnerability was established as the degree of loss to individual buildings resulting from a potential damaging landslide with a given return period in an area risk was calculated by multiplying the spatial probability of landslides by the vulnerability for each building and summing up the losses for the selected return period

reactivation characteristics and dynamic hazard prediction of an ancient landslide in the east margin of tibetan plateau the increasing human engineering activities and frequent extreme weather events have caused extensive reactivation of ancient landslides which are widely developed in the east margin of tibetan plateau the shangyaogou landslide as a typical ancient landslide example in this area was investigated to reveal the reactivation characteristics and its stability was calculated under the continuous rainfall condition with the intensity 30 mm day using the finite element software geo studio the whole movement process and hazard prediction under the different triggering conditions were simulated using the numerical software dan3d the study results showed that 1 under the joint influence of mw 7 9 wenchuan earthquake toe erosion and intensive rainfall multi stage deformations occurred to the front part of the shangyaogou landslide in multiple periods and also indicated a significant potential instability 2 under the continuous rainfall condition when the single effective total infiltration reached about 65 mm the reactivation part will become unstable while the single effective total infiltration reached about 120 mm both reactivation part and posterior part became instability 3 the maximum run out distance of the reactivation part was calculated to be 350 m and the forefront of the accumulation deposit would not reach the residential area when both parts failed simultaneously the maximum run out distance was calculated to be 550 m by considering the thickness and dynamic energy of the accumulation deposits and the vulnerable elements inside the fan area with radius of 150 m would be severely threatened 4 abundant earthquake triggered landslides have been developing in history or in recent years in the eastern margin of tibetan plateau some of them have been partly reactivated due to the increasing human engineering activities and extreme rainfall events and they have a potential for further deformation and failure the presented study methods can provide guidance for local disaster prevention and mitigation and can be used as a reference for the hazard prediction of the similar ancient landslides which have been reactivated

landslide susceptibility delineation in the ar rayth area jizan kingdom of saudi arabia using analytical hierarchy process frequency ratio and logistic regression models mountain areas in the southern western corner of the kingdom of saudi arabia ksa frequently suffer from various types of landsides induced by rainstorms and anthropogenic activities to mitigate these problems landslide susceptibility mapping and classification is important to develop quick and safe mitigation or remediation measures and to help the decision making in future planning by identifying the most vulnerable areas this paper summarizes the findings of a landslide susceptibility analysis in the ar rayth area jizan ksa using an analytical hierarchy process ahp frequency ratio fr and logistic regression lr models with the aid of gis tools and remote sensing data the landslide inventory map was prepared according to historical data interpretation of high resolution satellite images geo eye 0 5 m resolution and quickbird 0 6 m resolution topographic maps 1 10 000 and verified by field investigations an inventory map with 253 landslides locations was extracted from many sources the landslide inventory was randomly divided into two datasets 75 for training the models and 25 for validation an enhanced thematic mapper plus 15 m satellite image acquired in 2006 was used for determining the normalized difference vegetation index a contour map 1 10 000 with a 10 m contour interval was converted to digital elevation model 10 m resolution and subsequently converted to slope slope aspect curvature elevation and drainage networks geological data obtained with the help of satellite images were used to prepare lithological units and lineaments roads were digitized from the high resolution image and a rainfall map was prepared from the rainfall gauges distributed throughout the study area all these data were used to construct a spatial database using gis and image processing three landslide susceptibility maps were constructed one on the basis of a heuristic method using an ahp the other two on the basis of landslide inventories and causative factors using fr and lr furthermore each causative factor s weight was determined according to these three models and landslide susceptibility indices were calculated for verification receiver operating characteristic curves were calculated and the areas under the curve auc for success rate are 0 755 0 828 and 0 749 and for prediction rate are 0 708 0 781 and 0 727 for the ahp fr and lr respectively in addition the percentage of existing training landslides data in high and very high zones of the susceptibility maps is of 73 2 85 31 and 88 59 and for the validation landslides data is 73 2 85 31 and 88 59 for the ahp fr and lr respectively the findings indicated that the values of auc are above 0 7 for both success and prediction rate which indicate these three models are suitable for susceptibility analysis also percent of training and validation landslides data of high and very high zones indicate that lr model is more accurate followed by fr model and ahp model

meganodular limestone of the pagoda formation a time specific carbonate facies in the upper ordovician of south china abstract the decimeter scale 3 d network structure of the upper ordovician pagoda formation in south china has been an enigmatic sedimentary feature and a case of non uniformitarian carbonate depositional system without modern analog the network bands are developed pervasively throughout the entire pagoda formation superficially resembling desiccation or syneresis cracks especially in bedding plane view with decimeter scale sub polygonal to irregularly sinuous patterns detailed petrographic analysis however shows that the crack like network bands have the same carbonate matrix skeletal grains and overall fabrics as the rock they surround in this study we demonstrate that the network structure is not generated by shrinkage cracks but is rather a time specific lithofacies it originated from prolonged growth of nodular carbonate controlled by the convergence of several geological and paleoclimatic factors including a a protracted sea level highstand lasting for about 5 myr b an interval of tectonic quiescence favoring the dominance of carbonate production with minimal siliciclastic input and c location of the south china paleoplate in the hurricane free paleoequatorial zone devoid of severe storm disturbances between the fairweather and maximum storm wave bases normally 15 120 m depths favoring long term uninterrupted growth of caco3 meganodules on a mid shelf substrate this study corroborates recent paleogeographic reconstructions that position the south china paleoplate on the equator during the late ordovician

large scale climatic fluctuations in the latest ordovician on the yangtze block south china likely under warm and humid conditions low cia values however indicate the near absence of chemical weathering thereby refl ecting cool and or arid conditions in this paper the paleo climatic changes during the ordovician silurian transition were reconstructed in the light of cia values derived from the chemical composition of fi ne grained siliciclastic rocks in the mid upper yangtze river region china the infl u ences of paleoclimatic changes on biota are also discussed abstract the ordovician silurian transition was a critical interval in earth s history marked by dramatic climatic oceanic and biological turnovers here we present the chemical index of alteration cia as a proxy of changes in intensity of chemical weathering and its varia tions across the ordovician silurian boundaries wufeng through guanyinqiao to longmaxi formations from wangjiawan and nanbazi on the yangtze block south china in order to explore the climatic changes our data show that the cia values of sediments commonly range from 75 to 90 in the wufeng and longmaxi formations indicating a high degree of chemical weathering and thus a hot and humid climate during deposition in contrast a sharp drop in cia values most 60 70 in the guanyinqiao formation or hirnantian suggests an overall cold and arid climate interrupted by several intervals of warm climate when deposited the temporal coincidence of two phases of massive biotic extinctions with the beginning and end of the cold climate epoch respectively suggests that the large climatic changes could be one of the main controls on the mass extinctions although other factors may also have played a role

fractured shale gas systems the first commercial united states natural gas production 1821 came from an organic rich devonian shale in the appalachian basin understanding the geological and geochemical nature of organic shale formations and improving their gas producibility have subsequently been the challenge of millions of dollars worth of research since the 1970s shale gas systems essentially are continuous type biogenic predominant thermogenic or combined biogenic thermogenic gas accumulations characterized by widespread gas saturation subtle trapping mechanisms seals of variable lithology and relatively short hydrocarbon migration distances shale gas may be stored as free gas in natural fractures and intergranular porosity as gas sorbed onto kerogen and clay particle surfaces or as gas dissolved in kerogen and bitumen five united states shale formations that presently produce gas commercially exhibit an unexpectedly wide variation in the values of five key parameters thermal maturity expressed as vitrinite reflectance sorbed gas fraction reservoir thickness total organic carbon content and volume of gas in place the degree of natural fracture development in an otherwise low matrix permeability shale reservoir is a controlling factor in gas producibility to date unstimulated commercial production has been achievable in only a small proportion of shale wells those that intercept natural fracture networks in most other cases a successful shale gas well requires hydraulic stimulation together the devonian antrim shale of the michigan basin and devonian ohio shale of the appalachian basin accounted for about 84 of the total 380 bcf of shale gas produced in 1999 however annual gas production is steadily increasing from three other major organic shale formations that subsequently have been explored and developed the devonian new albany shale in the illinois basin the mississippian barnett shale in the fort worth basin and the cretaceous lewis shale in the san juan basin in the basins for which estimates have been made shale gas resources are substantial with in place volumes of 497 783 tcf the estimated technically recoverable resource exclusive of the lewis shale ranges from 31 to 76 tcf in both cases the ohio shale accounts for the largest share