on the spatial relationship between landslides and causative factors on lantau island hong kong abstract this paper presents a statistical approach to study the spatial relationship between landslides and their causative factors at the regional level the approach is based on digital databases and incorporates such methods as statistics spatial pattern analysis and interactive mapping firstly the authors propose an object oriented conceptual model for describing a landslide event and a combined database of landslides and environmental factors is constructed by integrating the various databases within such a conceptual framework the statistical histogram spatial overlay and dynamic mapping methods are linked together to interactively evaluate the spatial pattern of the relationship between landslides and their causative factors a case study of an extreme event in 1993 on lantau island indicates that rainfall intensity and the migration of the center of the rainstorm greatly influence the occurrence of landslides on lantau island a regional difference in the relationship between landslides and topography is identified most of the landslides in the middle and western parts of the island occurred on slopes with slope angles of 25 35 while in the eastern part the corresponding range is 30 35 overlaying landslide data with land cover reveals that a large number of landslides occurred in the bareland and shrub covered area and in the transition zones between different vegetation types the proposed approach can be used not only to analyze the general characteristics of such a relationship but also to depict its spatial distribution and variation thereby providing a sound basis for regional landslide prediction

transient reducing greenhouse warming on early mars the evidence for abundant liquid water on early mars despite the faint young sun is a long standing problem in planetary research here we present new ab initio spectroscopic and line by line climate calculations of the warming potential of reduced atmospheres on early mars we show that the strength of both co 2 h 2 and co 2 ch 4 collision induced absorption cia has previously been significantly underestimated contrary to previous expectations methane could have acted as a powerful greenhouse gas on early mars due to co 2 ch 4 cia in the critical 250 500 cm 1 spectral window region in atmospheres of 0 5 bar co 2 or more percent levels of h 2 or ch 4 raise annual mean surface temperatures by tens of degrees with temperatures reaching 273 k for pressures of 1 25 2 bars and 2 10 of h 2 and ch 4 methane and hydrogen produced following aqueous alteration of mars crust could have combined with volcanically outgassed co 2 to form transient atmospheres of this composition 4 5 3 5 ga our results also suggest that inhabited exoplanets could retain surface liquid water at significant distances from their host stars

detection of carbonates in martian weathering profiles noachian surfaces on mars exhibit vertical assemblages of weathering horizons termed as weathering profiles this indicates that surface water caused alteration of the rocks that required a different warmer climate than today evidence of this early martian climate with co 2 vapor as the main component causing greenhouse warming has been challenged by the lack of carbonate in these profiles here we report the analysis of compact reconnaissance imaging spectrometer for mars l detector data leading to the detections of carbonates using a spectral signature exclusively attributed to them the carbonates are collocated with hydroxylated minerals in weathering profiles over the martian surface the origin of co 2 for the formation of carbonates could be the atmosphere the widespread distribution of weathering profiles with carbonates over the surface of the planet suggest global interactions between fluids containing carbonate bicarbonate ions with the surface of mars in the presence of atmospheric water until around 3 7 billion years ago plain language summary the oldest surface of mars witnessed an impact of dense and humid atmosphere leading to the formation of hydrated minerals the analysis of remote sensing data allows identifying carbonates mixed with the hydrated minerals these associations of carbonates and hydrated minerals are widespread on the surface of the planet this indicates a planetary scale process of formation involving the presence of fluids containing inorganic carbon this finding allows a better understanding of the environment of mars during the period suspected to be the most likely to have host habitable environment on the planet

the timing of martian valley network activity constraints from buffered crater counting abstract valley networks concentrations of dendritic channels that often suggest widespread pluvial and fluvial activity have been cited as indicators that the climate of mars differed significantly in the past from the present hyperarid cold desert conditions some researchers suggest that the change in climate was abrupt while others favor a much more gradual transition thus the precise timing of valley network formation is critical to understanding the climate history on mars we examine thirty valley network incised regions on mars including both cratered upland valley networks and those outside the uplands and apply a buffered crater counting technique to directly constrain when valley network formation occurred the crater populations that we derive using this approach allow assessment of the timing of the last activity in a valley network independent of the mapping of specific geological units from these measurements we find that valley networks cluster into two subdivisions in terms characteristics and age 1 valley network activity in the cratered highlands has an average cessation age at the noachian hesperian boundary and all valleys that we crater counted are early hesperian or older no evidence is found for valley networks in the cratered uplands of late hesperian or amazonian age the timing of the cessation of cratered upland valley network activity at the noachian hesperian boundary also corresponds to a decline in the intensity of large crater formation and degradation and to the apparent end of phyllosilicate type weathering 2 a few valley network incised regions formed outside of the cratered uplands on volcanic edifices in association with younger impact craters and on the rim of valles marineris we applied our buffered crater counting technique to four such valleys on the volcanoes ceraunius tholus hecates tholus and alba patera and on the rim of echus chasma and find that each has distinctive and different late hesperian or early amazonian ages indicating that valley networks formed from time to time in the post noachian period unlike the cratered upland valley networks these isolated occurrences are very local and have been interpreted to represent local conditions e g snowpack melted during periods of intrusive volcanic activity in contrast to a gradual cessation in the formation of valley networks proposed by some workers our new buffered crater counting results indicate a relatively abrupt cessation in the formation of the widespread cratered upland valley networks at approximately the end of the noachian followed only by episodic and very localized valley network formation in later mars history very likely due to specific conditions e g local magmatic heating these valley network ages and correlations are thus consistent with a major change in the near surface aqueous environment on mars at approximately the noachian hesperian boundary the noachian environment supported surface running water and fluvial erosion across mars in the cratered uplands enhanced crater degradation and a weathering environment favoring the formation of phyllosilicates the hesperian amazonian environment was more similar to the hyperarid cold desert of today with valley networks forming only extremely rarely and confined to localized special conditions sources of water for these latter occurrences are likely to be related to periodic mobilization and equatorward migration of polar volatiles due to variations in spin axis orbital parameters and to periodic catastrophic emergence of groundwater

the case against vast glaciation in valles marineris mars abstract the valles marineris of mars form the largest system of interconnected canyons in the solar system where morphological mineralogical and structural evidence of widespread glaciation has been recently reported however neither precipitation models nor global water budgets can account for such a colossal fill and the hypothesis has thus far remained unchallenged by additional scrutiny here we present the first thorough case against a valles marineris glaciation by describing new evidence that precludes the existence of a glacier most crucially we review high resolution imaging science experiment hirise images of chaos terrain in candor chasma previously interpreted as remnant glacial ice and identify layered boulder rich scarps bearing no similarity to scarps of massive ice in promethei terra or the north polar layered deposits we also find no significant differences in the structure morphology and composition of chaos terrain in candor and the chryse planitia region which suggests candor s chaos like chryse s is fractured highland terrain we also review several other key supports for the glacial hypothesis including the coincidence of an apparent glacial trimline with the water bearing mineral jarosite and the apparent presence of glacial features including kettle holes and sandur plains these too are found to have more plausible explanations with non glacial origins including tectonic reorganisation groundwater sapping and chaotic fracturing we conclude that the valles marineris glacial hypothesis is inconsistent with both observed morphology and our understanding of the ancient martian climate and we find no evidence to support its existence

gis based support vector machine modeling of earthquake triggered landslide susceptibility in the jianjiang river watershed china abstract support vector machine svm modeling is based on statistical learning theory it involves a training phase with associated input and target output values in recent years the method has become increasingly popular the main purpose of this study is to evaluate the mapping power of svm modeling in earthquake triggered landslide susceptibility mapping for a section of the jianjiang river watershed using a geographic information system gis software the river was affected by the wenchuan earthquake of may 12 2008 visual interpretation of colored aerial photographs of 1 m resolution and extensive field surveys provided a detailed landslide inventory map containing 3147 landslides related to the 2008 wenchuan earthquake elevation slope angle slope aspect distance from seismogenic faults distance from drainages and lithology were used as the controlling parameters for modeling three groups of positive and negative training samples were used in concert with four different kernel functions positive training samples include the centroids of 500 large landslides those of all 3147 landslides and 5000 randomly selected points in landslide polygons negative training samples include 500 3147 and 5000 randomly selected points on slopes that remained stable during the wenchuan earthquake the four kernel functions are linear polynomial radial basis and sigmoid in total 12 cases of landslide susceptibility were mapped comparative analyses of landslide susceptibility probability and area relation curves show that both the polynomial and radial basis functions suitably classified the input data as either landslide positive or negative though the radial basis function was more successful the 12 generated landslide susceptibility maps were compared with known landslide centroid locations and landslide polygons to verify the success rate and predictive accuracy of each model the 12 results were further validated using area under curve analysis group 3 with 5000 randomly selected points on the landslide polygons and 5000 randomly selected points along stable slopes gave the best results with a success rate of 79 20 and predictive accuracy of 79 13 under the radial basis function of all the results the sigmoid kernel function was the least skillful when used in concert with the centroid data of all 3147 landslides as positive training samples and the negative training samples of 3147 randomly selected points in regions of stable slope success rate 54 95 predictive accuracy 61 85 this paper also provides suggestions and reference data for selecting appropriate training samples and kernel function types for earthquake triggered landslide susceptibility mapping using svm modeling predictive landslide susceptibility maps could be useful in hazard mitigation by helping planners understand the probability of landslides in different regions

effect of the greenhouse gases co2 h2o so2 on martian paleoclimate there is general agreement that certain surface features on mars are indicative of the presence of liquid water at various times in the geologic past in particular the valley networks are difficult to explain by a mechanism other than the flow of liquid water it has been suggested in several studies that a thick co2 atmosphere on mars early in its history could have provided a greenhouse warming that would have allowed the flow of water either on the surface or just below the surface however we have examined this effect with a detailed radiation model and have found that if reduced solar luminosity early in the history of the solar system is taken into account even three bars of co2 will not provide sufficient greenhouse warming the addition of water vapor and sulfur dioxide both plausible gases that may have been emitted by martian volcanoes to the atmosphere also fail to warm the surface above 273k for reduced solar luminosity conditions the increase in temperature may be large enough however for the formation of these features by brines

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

a brief survey of gis in mass movement studies with reflections on theory and methods this paper surveys the evolution and progress of landslide studies with particular reference to the use of geographic information systems gis in setting the agenda for research the article begins with a critical discussion of the mass movement classification problem and notes that it has been thornier and more complex than it has for many other types of extreme natural phenomena the evolution of slope instability studies is charted from its descriptive field based origins to recent higher levels of understanding on the one hand there has been a shift from static to dynamic modelling of slope processes using digital simulation and computer graphics while on the other hand automated cartography gis and remote sensing have enabled regional studies at last to predominate over site based ones however gis often tends to favour inductive study design and so does the continuing emphasis on classification the low level of insight generated by inductive studies has inhibited the development of more interdisciplinary frameworks for study it has also proved difficult to reorient landslide studies to tackle slope instability problems with greater sensitivity to the stakeholders needs finally although social administrative political cultural and perceptual aspects of landslides have been neglected there are signs of a new interest in these important aspects

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

formation timescales of large martian valley networks abstract assessing timescales for formation of the ancient martian valley networks is key to interpreting the early climate on mars we determined the likely formation times for seven of the largest ancient valley networks on mars using the darcy weisbach equation for average flow velocity three different sediment transport models and a range of input parameters to encompass possible formation conditions with runoff rates similar to intense storms in arid regions on earth the minimum formation timescales of these martian valley networks range from 10 5 to 10 7 yr depending on the specific valley network shorter formation timescales require hurricane scale flows that if minimized with assumptions of continuous formation unlike even terrestrial rates could complete large valley network formation in as little as 200 to 5000 yr though this is not the preferred interpretation while these results do not support impact induced climate change as the sole mechanism for creating precipitation sufficient to incise the large valley networks neither do they extend the amount of time required to form the networks beyond their range in age consistent with hypotheses that valley incision was constrained to a relatively short period of martian history near the noachian hesperian boundary approximately 3 6 to 3 8 ga

methane bursts as a trigger for intermittent lake forming climates on post noachian mars lakes existed on mars later than 3 6 billion years ago according to sedimentary evidence for deltaic deposition the observed fluviolacustrine deposits suggest that individual lake forming climates persisted for at least several thousand years assuming dilute flow but the lake watersheds little weathered soils indicate a largely dry climate history with intermittent runoff events here we show that these observational constraints although inconsistent with many previously proposed triggers for lake forming climates are consistent with a methane burst scenario in this scenario chaotic transitions in mean obliquity drive latitudinal shifts in temperature and ice loading that destabilize methane clathrate using numerical simulations we find that outgassed methane can build up to atmospheric levels sufficient for lake forming climates if methane clathrate initially occupies more than 4 of the total volume in which it is thermodynamically stable such occupancy fractions are consistent with methane production by water rock reactions due to hydrothermal circulation on early mars we further estimate that photochemical destruction of atmospheric methane curtails the duration of individual lake forming climates to less than a million years consistent with observations we conclude that methane bursts represent a potential pathway for intermittent excursions to a warm wet climate state on early mars

effect of mars atmospheric loss on snow melt potential in a 3 5 gyr mars climate evolution model post noachian martian paleochannels indicate the existence of liquid water on the surface of mars after about 3 5 gya irwin et al 2015 palucis et al 2016 in order to explore the effects of variations in co2 partial pressure and obliquity on the possibility of surface water we created a zero dimensional surface energy balance model we combine this model with physically consistent orbital histories to track conditions over the last 3 5 gyr of martian history we find that melting is allowed for atmospheric pressures corresponding to exponential loss rates of dp dt t 3 73 or faster but this rate is within 0 5 of the rate calculated from initial measurements made by the mars atmosphere and volatile evolution maven mission if we assume all the escaping oxygen measured by maven comes from atmospheric co2 lillis et al 2017 tu et al 2015 melting at this loss rate matches selected key geologic constraints on the formation of hesperian river networks assuming optimal melt conditions during the warmest part of each mars year irwin et al 2015 stopar et al 2006 kite et al 2017a b the atmospheric pressure has a larger effect on the surface energy than changes in mars s mean obliquity these results show that initial measurements of atmosphere loss by maven are consistent with atmospheric loss being the dominant process that switched mars from a melt permitting to a melt absent climate jakosky et al 2017 but non co2 warming will be required if 2 gya paleochannels are confirmed or if most of the escaping oxygen measured by maven comes from h2o

a warm or a cold early earth new insights from a 3 d climate carbon model abstract oxygen isotopes in marine cherts have been used to infer hot oceans during the archean with temperatures between 60 c 333 k and 80 c 353 k such climates are challenging for the early earth warmed by the faint young sun the interpretation of the data has therefore been controversial 1d climate modeling inferred that such hot climates would require very high levels of co2 2 6 bars previous carbon cycle modeling concluded that such stable hot climates were impossible and that the carbon cycle should lead to cold climates during the hadean and the archean here we revisit the climate and carbon cycle of the early earth at 3 8 ga using a 3d climate carbon model we find that co2 partial pressures of around 1 bar could have produced hot climates given a low land fraction and cloud feedback effects however such high co2 partial pressures should not have been stable because of the weathering of terrestrial and oceanic basalts producing an efficient stabilizing feedback moreover the weathering of impact ejecta during the late heavy bombardment lhb would have strongly reduced the co2 partial pressure leading to cold climates and potentially snowball earth events after large impacts our results therefore favor cold or temperate climates with global mean temperatures between around 8 c 281 k and 30 c 303 k and with 0 1 0 36 bar of co2 for the late hadean and early archean finally our model suggests that the carbon cycle was efficient for preserving clement conditions on the early earth without necessarily requiring any other greenhouse gas or warming process

experimental reproduction of the martian weathering profiles argues for a dense noachian co2 atmosphere abstract on mars mineral sequences have been detected and they are composed of a top layer of al rich clay minerals then al fe rich clay minerals and a bottom layer composed of mg fe rich clay minerals by analogy with earth such sequences are interpreted as weathering profiles formed by the interaction of acidic solutions in equilibrium with the atmosphere and the parent rock thus understanding of the aqueous solution composition leading to the above mineral description allows deciphering the atmosphere composition we designed an experimental column system with three levels containing powdered basaltic rock to test the influence of different acidic fluids on the mineralogical formation five solutions were used h 2 so 4 and hcl at ph 3 in equilibrium with n 2 atmosphere pure water in equilibrium with 0 1 and 1 atmospheric pressure co 2 leading to ph values of 3 9 and 4 4 respectively and a h 2 so 4 solution at ph 3 in equilibrium with 0 1 atmospheric pressure co 2 leading to a ph value of 2 98 the results obtained show that the content of al rich clay minerals and the evolution from al al fe to fe mg rich clay minerals formed are better reproduced with an originally high pco 2 hence we suggest that acidic alteration driven by a dense co 2 atmosphere reproduced better the observed martian weathering profiles the experiments involving co 2 led to the formation of carbonates their identification by near infrared nir detection methods is challenged because even the laboratory nir spectra acquired on the experimental products show that i the absorption bands related to carbonates are very weak and ii the strongest feature at 3 95 m is beyond the crism nir range such carbonate formation is consistent with the recent carbonate detection at a planetary scale in weathering profiles which goes toward that the weathering profiles could have been formed under a dense co 2 rich atmosphere as suggested also by climatic models

drainage density and relative relief in humid steep mountains with frequent slope failure previous studies in japanese mountains have shown that drainage density d correlates negatively with relief r and the erosion rate e whereas elsewhere both r and e correlate positively with d to investigate the inconsistency this paper compares two types of d r relations for eight mountain river basins in central japan r is computed from a digital elevation model for 1109 morphometric samples of area 0 5 km 0 5 km drainage networks in these cells were first constructed by map criteria applied previously in japan deeply notched v shaped contours with an angle 53 the resulting d correlates negatively with r confirming preceding studies when drainage lines along shallower hollows were added however the calculated d essentially constant these relations arise from active landsliding in high relief terrains which has eroded steep channel banks into gentle ones the decline of channel banks with increasing r is accelerated in terrains underlain by soft rocks because of rapid erosion the constant d for all the drainage lines indicates a uniform frequency or spacing of ridges and hollows on hillslopes in rugged humid mountains because the d r and d e relations for japan reflect a uniquely japanese physiographic setting characterized by frequent landsliding they differ from those relations for other regions where channelization by gullying predominates 1997 by john wiley sons ltd

updated global map of martian valley networks and implications for climate and hydrologic processes 1 martian valley networks have long been viewed as some of the best evidence of prolonged surface water on mars analysis from viking data showed that valleys were primarily contained on the ancient crust drainage networks were immature and large undissected regions occurred in between individual systems these observations led many to propose that they formed primarily by groundwater processes and limited or no climate change from the present state was required using more recent and higher resolution data sets including visible infrared and topographic data we have manually remapped valleys on a global scale more than eight times as many valleys have been identified on the surface and calculated drainage densities are on average higher by a factor of 2 further regions previously thought to be undissected have significant incision by fluvial processes most of these systems seem to have formed around the noachian hesperian boundary 3 8 3 6 ga minor valley formation continued through the hesperian and into the early amazonian epoch approximately 2 8 ga ago the new data reveal characteristics of sustained precipitation and surface runoff including inner braided channels terraces multiple periods of formation complex network morphology and correlation with other fluviosedimentary features and chloride salts on mars groundwater processes or a transient steam atmosphere generated by impacts played at most a minor role these new results imply that mars had a long lived period or periods of clement conditions toward the end of the noachian epoch that supported a hydrologic cycle and potentially a biosphere

an expert knowledge based approach to landslide susceptibility mapping using gis and fuzzy logic this paper presents an expert knowledge based approach to landslide susceptibility mapping in an effort to overcome the deficiencies of data driven approaches the proposed approach consists of three generic steps 1 extraction of knowledge on the relationship between landslide susceptibility and predisposing factors from domain experts 2 characterization of predisposing factors using gis techniques and 3 prediction of landslide susceptibility under fuzzy logic the approach was tested in two study areas in china the kaixian study area about 250 km 2 and the three gorges study area about 4600 km 2 the kaixian study area was used to develop the approach and to evaluate its validity the three gorges study area was used to test both the portability and the applicability of the developed approach for mapping landslide susceptibility over large study areas performance was evaluated by examining if the mean of the computed susceptibility values at landslide sites was statistically different from that of the entire study area a z score test was used to examine the statistical significance of the difference the computed z for the kaixian area was 3 70 and the corresponding p value was less than 0 001 this suggests that the computed landslide susceptibility values are good indicators of landslide occurrences in the three gorges study area the computed z was 10 75 and the corresponding p value was less than 0 001 in addition we divided the susceptibility value into four levels low 0 0 0 25 moderate 0 25 0 5 high 0 5 0 75 and very high 0 75 1 0 no landslides were found for areas of low susceptibility landslide density was about three times higher in areas of very high susceptibility than that in the moderate susceptibility areas and more than twice as high as that in the high susceptibility areas the results from the three gorge study area suggest that the extracted expert knowledge can be extrapolated to another study area and the developed approach can be used in large scale projects results from these case studies suggest that the expert knowledge based approach is effective in mapping landslide susceptibility and that its performance is maintained when it is moved to a new area from the model development area without changes to the knowledge base c 2014 elsevier b v all rights reserved

probabilistic landslide hazard assessment at the basin scale abstract we propose a probabilistic model to determine landslide hazard at the basin scale the model predicts where landslides will occur how frequently they will occur and how large they will be we test the model in the staffora river basin in the northern apennines italy for the study area we prepare a multi temporal inventory map through the interpretation of multiple sets of aerial photographs taken between 1955 and 1999 we partition the basin into 2243 geo morpho hydrological units and obtain the probability of spatial occurrence of landslides by discriminant analysis of thematic variables including morphological lithological structural and land use for each mapping unit we obtain the landslide recurrence by dividing the total number of landslide events inventoried in the unit by the time span of the investigated period assuming that landslide recurrence will remain the same in the future and adopting a poisson probability model we determine the exceedance probability of having one or more landslides in each mapping unit for different periods we obtain the probability of landslide size by analysing the frequency area statistics of landslides obtained from the multi temporal inventory map assuming independence we obtain a quantitative estimate of landslide hazard for each mapping unit as the joint probability of landslide size of landslide temporal occurrence and of landslide spatial occurrence

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

the fate of early mars lost water the role of serpentinization the fate of water which was present on early mars remains enigmatic we propose a simple model based on serpentinization a hydrothermal alteration process which may produce magnetite and store water our model invokes serpentinization during about 500 to 800 myr while a dynamo is active which may have continued after the formation of the crustal dichotomy we show that the present magnetic field measured by mgs in the southern hemisphere is consistent with a 500 m thick global equivalent layer of water trapped in serpentine serpentinization results in the release of h 2 the released h atoms are lost to space through thermal escape increasing the d h ratio in water reservoirs exchanging with atmosphere we show that the value of the d h ratio in the present atmosphere 5 is consistent with the serpentinization of a 500 m thick water gel we reassess the role of non thermal escape in removing water from the planet by considering an updated solar wind ionosphere interaction representation we show that the contribution of oxygen escape to h isotopic fractionation is negligible our results suggest that significant amounts of water up to a 330 1030 m thick gel present at the surface during the noachian similar to the quantity inferred from the morphological analysis of valley networks could be stored today in subsurface serpentine 1 the study like earth mars has been endowed with large amounts of water during accretion equivalent to the content of several terrestrial oceans corresponding to a several 10 km thick global equivalent layer the present inventory of observable water on mars mainly within the polar caps is quite smaller in the range from 20 30 m the mega regolith capacity is large with up to 500 gel m potentially trapped in the cryosphere and hypothetically several additional hundreds of meters up to 500 m of ground water surviving at depth below the cryosphere 1 a 500 m thick gel is generally assumed to be required to explain the formation of outflow channels 2 and most of this water could be trapped today as water ice and possibly deep liquid water in the subsurface and also possibly under the form of hydrated minerals

landslide susceptibility mapping by correlation between topography and geological structure the janghung area korea the purpose of this study is to develop and apply the technique for landslide susceptibility analysis using geological structure in a geographic information system gis in the study area the janghung area of korea landslide locations were detected from indian remote sensing irs satellite images by change detection where the geological structure of foliation was surveyed and analysed the landslide occurrence factors location of landslide geological structure and topography were constructed into a spatial database then strike and dip of the foliation and the aspect and slope of the topography were compared and the results which were verified using landslide location data show that foliation of gneiss has a geometrical relation to the joint or fault that leads to a landslide using the geometrical relations the landslide susceptibility was assessed and verified the verification results showed satisfactory agreement between the susceptibility map and the landslide location data

the methane cycle on titan despite titan s cold temperatures about 93 7 k at the equator fluvial and atmospheric processes are active on this moon of saturn with methane playing a similar role to water on earth however titan lacks a global methane ocean and rainfall appears to be episodic saturn s moon titan is the second largest natural satellite in the solar system and the only one that possesses a substantial atmosphere with a surface temperature of 93 7 k at the equator titan s water is almost completely frozen out of the atmosphere water ice comprises between 35 and 45 of the mass of titan depending on the interior model but methane seems to play many of the roles on titan that water does on earth clouds have been observed fluvial and dendritic features have been imaged suggesting episodic heavy rainfall and there is compelling but circumstantial evidence for near polar lakes or seas of methane and its atmospheric photochemical product ethane however whereas earth possesses a massive global ocean of water titan lacks a global methane ocean and on titan low latitude rainfall appears to be an occasional process limited by the small amount of available solar energy compared with that of earth titan is therefore distinct from the earth but is also different from venus in retaining an active cycle of precipitation and evaporation and from mars in the preponderance of active fluvial and pluvial processes in the present day

deep earthquakes and the thermal assimilation of subducting lithosphere two problematic aspects of deep seismic zones are investigated the maximum depth about 700 km of seismic activity and the relative maximum in seismic energy release in the 500 700 km depth range it is shown that both features can be accounted for by a model based on thermal assimilation this implies that no barrier is required at a depth of 650 700 km to explain the observations

zonation of the landslide hazards in the forereservoir region of the three gorges project on the yangtze river on the basis of the investigation and statistic analysis of the landslide hazards in the forereservoir region of the three gorges project on the yangtze river the major factors that are found to have affected the slope stabilities are outlined and a zonation of landslide hazards of the region is made using an integrated information model it is divided into destructive disastrous slightly disastrous likely disastrous and essentially non disastrous areas the first two cover an area of less than 5 of the total region and are at a distance of more than 20 km from the three gorges dam and so a landslide over there will impose no direct impact to the tgp but may effect to some degree the navigation of the yangtze river and nearby highway transportation reservoir slopes and building of cities and towns