modeling susceptibility to landslides using the weight of evidence approach western colorado usa abstract the paonia mcclure pass area of colorado is well known for active mass movements we examined 735 active shallow movement features including debris flows debris slides rock slides and soil slides in this area identification of the hazardous areas is a fundamental component of disaster management and an important basis for promoting safe human occupation and infrastructure development in landslide prone areas bayes theorem based on the weight of evidence woe was used to create a map of landslides that could be hazardous the modeling was accomplished by employing a geographical information system gis and a statistical package seventeen factors that cause landslides were measured and weighted using the woe method to create a map of areas susceptible to landslides the maps of weighted factors were summed on a pixel by pixel basis after performing chi square tests to determine factors that are conditionally independent of each other by combining factors that represent topography hydrology geology land cover and human influences six models were developed the performance of each model was evaluated by the distribution of the observed landslides the validity of the best map was checked against landslides which were not entered in the analysis the resulting map of areas susceptible to landslides has a prediction accuracy of 78

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

a hybrid fuzzy weight of evidence method in landslide susceptibility analysis on the wuyuan area china abstract the present study proposed a hybrid fuzzy weight of evidence model for constructing a landslide susceptibility map in the wuyuan area china where disastrous landslide events have occurred the model combines the knowledge of experts obtained through a fuzzy logic approach and a hybrid weight of evidence method the estimated knowledge based fuzzy membership value of each environmental variable is combined with data based conditional probabilities to derive fuzzy posterior probabilities and landslide susceptibility the developed model was compared with a landslide susceptibility map produced using the data driven weight of evidence method based on 510 landslide and non landslide sites the sites were identified by analyzing airborne imagery field investigation and previous studies landside susceptibility for these sites was analyzed using 10 geo environmental variables slope aspect lithology soil rainfall plan curvature the normalized difference vegetation index distance to roads distance to rivers and distance to faults the resultant hybrid fuzzy weight of evidence method showed high predictive power with the area under the success and predictive curves being 0 770 and 0 746 respectively additional analyses showed that the developed model could work effectively even with limited data

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

landslide susceptibility mapping by comparing the wlc and wofe multi criteria methods in the west crete island greece in the current research the weighted linear combination wlc and the weights of evidence wofe methods were applied for landslide susceptibility zonation mapping in the chania prefecture of crete island greece several thematic maps representing various landslide conditioning factors such as geology formations faults proximity altitude slope gradient aspect curvature rivers proximity precipitation roads proximity and land use types have been generated in a gis environment three landslide susceptibility maps were created one for each method and a combined one by applying the logistic regression approach to the wlc and wofe susceptibility maps the maps were evaluated and validated using the efficiency rate curve the receiver operator curve and the spatially agreed areas methods the resulting landslide susceptibility maps have uncertainties introduced due to the subjective knowledge of experts in the case of wlc method and to the quality of the recorded landslides sample in the case of the wofe method nevertheless the performance of the three approaches was found to be almost equal with all methods to produce quite satisfactory results besides the comparison of the applied methods the current study contributes to the risk management of the area providing the first landslide susceptibility maps for chania prefecture

landslide susceptibility mapping in injae korea using a decision tree a data mining classification technique can be applied to landslide susceptibility mapping because of its advantages a decision tree is one popular classification algorithm although hardly used previously to analyze landslide susceptibility because the obtained data assume a uniform class distribution whereas landslide spatial event data when represented on a grid raster layer are highly class imbalanced for this study of south korean landslides a decision tree was constructed using quinlan s algorithm c4 5 the susceptibility of landslide occurrence was then deduced using leaf node ranking or m branch smoothing the area studied at injae suffered substantial landslide damage after heavy rains in 2006 landslide related factors for nearly 600 landslides were extracted from local maps topographic including curvature slope distance to ridge and aspect forest providing age type density and diameter and soil texture drainage effective thickness and material for the quantitative assessment of landslide susceptibility the accuracy of the twofold cross validation was 86 08 accuracy using all known data was 89 26 based on a cumulative lift chart a decision tree can therefore be used efficiently for landslide susceptibility analysis and might be widely used for prediction of various spatial events

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

statistical approach to earthquake induced landslide susceptibility susceptibility analysis for predicting earthquake induced landslides has most frequently been done using deterministic methods multivariate statistical methods have not previously been applied in this study however we introduce a statistical methodology that uses the intensity of earthquake shaking as a landslide triggering factor this methodology is applied in a study of shallow earthquake induced landslides in central western taiwan the results show that we can accurately interpret landslide distribution in the study area and predict the occurrence of landslides in neighboring regions this susceptibility model is capable of predicting shallow landslides induced during an earthquake scenario with similar range of ground shaking without requiring the use of geotechnical groundwater or failure depth data

fractal dimension and b value on creeping and locked patches of the san andreas fault near parkfield california we tested the hypotheses 1 that the fractal dimension d of hypocenters are different in a locked and a creeping segment of the san andreas fault and 2 that the relationship d 2b holds approximately where b is the slope of the frequency magnitude relationship the test area was the 30 to 50 km fault segment north of park eld for which two earthquake catalogs exist the borehole high resolution seismic network data and the u s geological survey data which have a minimum magnitude of completeness of mc 0 4 and mc 1 0 1 2 respectively the relative location errors in the two catalogs are estimated as 0 25 km and less than 1 km respectively the periods of high quality data available extend from 1987 to 1998 5 and 1981 to 2000 2 respectively furnishing 2609 and 3775 events for analysis in the two catalogs in the locked part 0 5 b 0 7 and 0 96 d 1 14 whereas in the creeping segment 1 1 b 1 6 and 1 45 d 1 72 however the spatial distribution of the hypocenters in the creeping segment is not well approximated by a fractal distribution we conclude 1 that the frequency magnitude distribution as described by b as well as the fractal dimension d are different in the locked and creeping segments near park eld 2 that the spatial distribution in the creeping segment is not well approximated by a fractal distribution and 3 that the relationship d 2b holds in the locked segment where both parameters can be measured accurately thus we propose that the heterogeneity of seismogenic volumes lead to differences in d and b and that these differences where established by high quality data may furnish clues concerning properties of fault zones

the seismic cycle at subduction thrusts 1 insights from laboratory models 1 subduction megathrust earthquakes occur at the interface between the subducting and overriding plates these hazardous phenomena are only partially understood because of the absence of direct observations the restriction of the instrumental seismic record to the past century and the limited resolution completeness of historical to geological archives to overcome these restrictions modeling has become a key tool to study megathrust earthquakes we present a novel model to investigate the seismic cycle at subduction thrusts using complementary analog paper 1 and numerical paper 2 approaches here we introduce a simple scaled gelatin on sandpaper setup including realistic tectonic loading spontaneous rupture nucleation and viscoelastic response of the lithosphere particle image velocimetry allows to derive model deformation and earthquake source parameters analog earthquakes are characterized by quasi periodic recurrence consistent with elastic theory the interseismic stage shows rearward motion subsidence in the outer wedge and uplift of the coastal area as a response of locked plate interface at shallow depth the coseismic stage exhibits order of magnitude higher velocities and reversal of the interseismic deformation pattern in the seaward direction subsidence of the coastal area and uplift in the outer wedge like natural earthquakes analog earthquakes generally nucleate in the deeper portion of the rupture area and preferentially propagate upward in a crack like fashion scaled rupture width slip proportionality and seismic moment duration scaling verifies dynamic similarities with earthquakes experimental repeatability is statistically verified comparing analog results with natural observations we conclude that this technique is suitable for investigating the parameter space influencing the subduction interplate seismic cycle

the weakness of earthquake faults numerical experiments using the particle based lattice solid model produce simulated earthquakes model faults with a thin gouge layer are sufficiently weak relative to those without gouge to explain the heat flow paradox hfp stress drop statistics are in agreement with field estimates models with a thick granular fault zone exhibit a strong evolution effect results are initially similar to those of laboratory experiments but after a sufficient time the system self organizes into a weak state the long time required for self organization could explain why weak gouge has not been observed in the laboratory the new results suggest an hfp explanation without the so called fatal flaws of previously proposed solutions they demonstrate that fault friction potentially undergoes a strong evolution effect and could be dependent on gouge microstructure this raises questions about the extent to which laboratory derived friction laws can be used in macroscopic domain earthquake simulation studies

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

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

frictional resistance of a fault zone with strong rotors as a possible mechanism to explain the lack of a heat flow anomaly along the creeping section of the san andreas fault we have determined the effect of placing hard rotors along a surface between two deformable media in this case styrofoam balls between two blocks of foam rubber the probable presence of franciscan rocks at depth along the creeping section of the san andreas fault suggested this mechanism since the franciscan is characterized not only by basic serpentinous rocks which are weak but also by embedded more or less equidimensional blocks of very strong rocks knockers e g high grade blueschists and eclogites which might act as rotors the results suggest that knocker rotation may be a viable mechanism for reduction of friction on the creeping section of the san andreas fault and thus be at least a partial explanation of the lack of any observed frictional heat flow anomaly there

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

gis based landslide susceptibility for arsin yomra trabzon north turkey region the purpose of this study is to assess the susceptibility of landslides around yomra and arsin towns near trabzon in northeast of turkey using a geographical information system gis landslide inventory of the area was made by detailed field surveys and the analyses of the topographical map the landslide triggering factors are considered to be slope angle slope aspect distance from drainage distance from roads and the weathered lithological units which were called as geotechnical units in the study idrisi and arcgis packages manipulated all the collected data logistic regression lr and weighted linear combination wlc statistical methods were used to create a landslide susceptibility map for the study area the results were assessed within the scope of two different points a effectiveness of the methods used and b effectiveness of the environmental casual parameters influencing the landslides the results showed that the wlc model is more suitable than the lr model regarding the casual parameters geotechnical units and slopes were found to be the most important variables for estimating the landslide susceptibility in the study area

carbon elemental and isotopic composition in mantle xenoliths from spain insights on sources and petrogenetic processes abstract the carbon elemental concentration c wt and isotopic 13c composition of mantle xenoliths from the tallante and calatrava volcanic occurrences in south east and central spain respectively have been investigated to identify carbon sources and processes occurring in distinct geodynamic settings of the iberian peninsula the peridotitic mantle xenoliths from calatrava show elemental c ranging from 0 11 to 2 87 wt which is coupled with a continuous isotopic variation from very negative values 13c 26 1 to typical mantle values 13c 5 9 on the other hand the tallante mantle xenolith suite displays lower c contents 0 06 0 15 wt showing a tighter variation with 13c depleted values ranging between 20 1 and 23 7 higher elemental c up to 0 41 wt displaying distinctly less negative isotopic values 13c between 13 8 and 11 9 have been recorded in veins crosscutting tallante peridotites plausibly representing the product of metasomatic reactions the data from the two investigated xenolith suites invariably display a good correlation between elemental and isotopic composition suggesting a mantle origin for carbon and rayleigh type fractionation as the process responsible for the observed c 13c variation however the correlation between the carbon isotopic data with other isotopic tracers e g 87sr 86sr 3he 4he used to identify distinct mantle components and metasomatic reactions indicates systematic differences between the two xenolith suites suggesting that beneath the betic cordillera where tallante is located the deep c cycle involves recycling via subduction preceding accompanying continental collision of crustal components back in the mantle coherently geochemical trends observed in the tallante xenoliths seem to be influenced by metasomatic agents generated by melting of crustal lithologies that according to the analysis of a metasedimentary xenolith can contain c up to 1 2 wt having 13c of ca 18 0

landslide susceptibility mapping based on support vector machine a case study on natural slopes of hong kong china abstract the support vector machine svm is an increasingly popular learning procedure based on statistical learning theory and involves a training phase in which the model is trained by a training dataset of associated input and target output values the trained model is then used to evaluate a separate set of testing data there are two main ideas underlying the svm for discriminant type problems the first is an optimum linear separating hyperplane that separates the data patterns the second is the use of kernel functions to convert the original non linear data patterns into the format that is linearly separable in a high dimensional feature space in this paper an overview of the svm both one class and two class svm methods is first presented followed by its use in landslide susceptibility mapping a study area was selected from the natural terrain of hong kong and slope angle slope aspect elevation profile curvature of slope lithology vegetation cover and topographic wetness index twi were used as environmental parameters which influence the occurrence of landslides one class and two class svm models were trained and then used to map landslide susceptibility respectively the resulting susceptibility maps obtained by the methods were compared to that obtained by the logistic regression lr method it is concluded that two class svm possesses better prediction efficiency than logistic regression and one class svm however one class svm which only requires failed cases has an advantage over the other two methods as only failed case information is usually available in landslide susceptibility mapping

use of fuzzy relations to produce landslide susceptibility map of a landslide prone area west black sea region turkey abstract preparation of landslide susceptibility maps is important for engineering geologists and geomorphologists however due to complex nature of landslides producing a reliable susceptibility map is not easy for this reason many procedures have been used to produce such maps in this study a new attempt is tried to produce landslide susceptibility map of a part of west black sea region of turkey to obtain the fuzzy relations for producing the susceptibility map a landslide inventory database is compiled by both field surveys and airphoto studies a total of 266 landslides are identified in the study area and dominant mode of failure is rotational slide while the other mode of failures are soil flow and shallow translational slide the landslide inventory and the parameter maps are analyzed together using a computer program fullsa developed in this study the computer program utilizes the fuzzy relations and produces the landslide susceptibility map automatically according to this map 9 6 of the study area is classified as very high susceptibility 10 3 as high susceptibility 8 9 as moderate susceptibility 27 5 as low susceptibility and 43 8 as very low susceptibility or nonsusceptible areas the prediction performance of the susceptibility map is checked by considering actual landslides in the study area for this purpose strength of the relation rij and the root mean square error rmse values are calculated as 0 867 and 0 284 respectively these values show that the produced landslide susceptibility map in the present study has a sufficient reliability it is believed that the approach employed in this study mainly prevents the subjectivity sourced from the parameter selection and provides a support to improve the landslide susceptibility mapping studies

seismicity and stress rotation in a granular model of the brittle crust the basic mechanical process responsible for earthquakes and faulting is not known the intuitive notion of frictional slip on faults between elastic crustal blocks cannot be reconciled with laboratory measurements of the strength of rocks1 field observations of heat flow2 3 and stress orientation4 around the san andreas fault in california and seismological estimates of the energy radiated by earthquakes5 the weakening of large faults by elevated pore fluid pressure6 has been suggested as one solution to this paradox but places severe constraints on the hydrological conditions of the faults concerned here i propose an alternative model for earthquake mechanics in which the crust is treated as a system of many interlocking blocks divided by many faults7 the model combines this random granular structure with simple deterministic mechanical interactions numerical simulations of the deformation of an aggregate of rough grains under compressive stress show earthquake like elastodynamic failures without frictional heat production and substantial rotation of stresses across shear zones which mimics field observations there remain problems of scale in comparing these simulations with nature but a seismological test of the model may be possible

the seismic cycle at subduction thrusts insights from seismo thermo mechanical models 1 the underestimation of the size of recent megathrust earthquakes illustrates our limited understanding of their spatiotemporal occurrence and governing physics to unravel their relation to associated subduction dynamics and long term deformation we developed a 2 d continuum viscoelastoplastic model that uses an eulerian lagrangian finite difference framework with similar on and off fault physics we extend the validation of this numerical tool to a realistic subduction zone setting that resembles southern chile the resulting quasi periodic pattern of quasi characteristic m8 m9 megathrust events compares quantitatively with observed recurrence and earthquake source parameters albeit at very slow coseismic speeds without any data fitting surface displacements agree with gps data recorded before and during the 2010 m8 8 maule earthquake including the presence of a second order flexural bulge these surface displacements show cycle to cycle variations of slip deficits which overall accommodate 5 of permanent internal shortening we find that thermally and stress driven creep governs a spontaneous conditionally stable downdip transition zone between temperatures of 350 c and 450 c ruptures initiate above it and below the forearc moho propagate within it interspersed by small intermittent events and arrest below it as ductile shearing relaxes stresses ruptures typically propagate upward along lithological boundaries and widen as pressures drop the main thrust is constrained to be weak due to fluid induced weakening required to sustain regular subduction and to generate events with natural characteristics fluid pressures of 75 99 of solid pressures the agreement with a range of seismological geodetic and geological observations demonstrates the validity and strength of this physically consistent seismo thermo mechanical approach

strength of chrysotile serpentinite gouge under hydrothermal conditions can it explain a weak san andreas fault chrysotile bearing serpentinite is a constituent of the san andreas fault zone in central and northern california at room temperature chrysotile gouge has a very low coefficient of friction 0 2 raising the possibility that under hydrothermal conditions might be reduced sufficiently to 0 1 to explain the apparent weakness of the fault to test this hypothesis we measured the frictional strength of a pure chrysotile gouge at temperatures to 290 c and axial shortening velocities as low as 0 001 m s as temperature increases to 100 c the strength of the chrysotile gouge decreases slightly at low velocities but at temperatures 200 c it is substantially stronger and essentially independent of velocity at the lowest velocities tested we estimate that pure chrysotile gouge at hydrostatic fluid pressure and appropriate temperatures would have shear strength averaged over a depth of 14 km of 50 mpa thus on the sole basis of its strength chrysotile cannot be the cause of a weak san andreas fault however chrysotile may also contribute to low fault strength by forming mineral seals that promote the development of high fluid pressures

constraints on ground accelerations inferred from unfractured hoodoos near the garlock fault california abstract in the absence of long term instrumental data the presence of fragile geologic features near active faults can provide physical limits on the level of ground shaking that could potentially have significant implications for seismic hazards this paper introduces a multidisciplinary investigation that uses unfractured hoodoos in seismically active regions to constrain the level of ground accelerations at those locations although there is a large uncertainty associated with the age of the hoodoos because of their rapidly eroding nature they can still be useful in providing physical limits on ground motions associated with recent large events here we consider the fragilities of two hoodoos in the red rock canyon region within a few kilometers of the garlock fault which is an active strike slip fault in a transtensional region with at least a few large earthquakes in the holocene the hoodoos at these sites could be evidence of median or relatively low ground motions associated with large transtensional strike slip earthquakes results of our field and laboratory tests on two hoodoos provide constraints on peak ground accelerations pgas of and using the u s geological survey s usgs probabilistic seismic hazard psh deaggregation the dominant earthquake contributing to the hazard at the site of the hoodoos for the recurrence intervals of 475 975 and 2475 years is located at a distance of 4 8 km and has a magnitude of 7 63 consistent with the observed paleoearthquake evidence on the garlock fault the pgas corresponding to these three return periods are 0 26 0 40 and respectively therefore the survival of the more fragile hoodoo during a presumably large event on the garlock fault in the past 550 years would be consistent with the 2008 seismic hazard level if the ground motions during that event were below the median value

rupture mechanism and interface separation in foam rubber models of earthquakes a possible solution to the heat flow paradox and the paradox of large overthrusts abstract spontaneous stick slip along the interface between stressed foam rubber blocks is a simple analog of earthquake rupture and stick slip results from this model are used to elucidate the role of normal stress variations along the interface in the stick slip process observations indicate significant normal interface vibrations and separation during slip suggesting that dynamic changes in normal stress rather than a drop in the coefficient of friction may control stick slip as suggested for example by tolstoi oden and martins and brune and co workers observations of particle trajectories indicate that stick slip shear motion is associated with various degrees of fault separation for an asymmetric model the motion is consistent with slipping motion of the type suggested by schallamach and price for a symmetric model the motion is similar to that suggested by comninou and dundurs if interface waves of this type involving separation during slip occur in earthquakes they may be a solution to the heat flow paradox since a major part of the slip occurs during separation and during low normal stress thus frictional heat generation is reduced normal interface vibrations during stick slip may explain the high corner frequency of p wave spectra and the generally high levels of p wave spectra beyond the corner frequency schallamach comninou type waves are consistent with the partial stress drop abrupt locking self healing models of brune and heaton

precarious rock evidence for low near source accelerations for trans tensional strike slip earthquakes abstract this paper describes precarious rock evidence for low ground motions associated with extensional sections of strike slip faults recent evidence from physical and numerical models and data regressions has indicated that ground motion for extensional strike slip regions may be lower than for strike slip faults with a large fault normal tectonic stress component and for thrust faults in general data from compressional strike slip and thrust earthquakes dominates the database used in most regression curves for ground acceleration and in the calculation of current probabilistic seismic hazard maps therefore estimates of ground accelerations on these seismic hazard maps may be too high for sites near extensional sections of strike slip faults this paper discusses precariously balanced rock data from three areas near extensional sections of strike slip faulting 1 the region of the honey fault california with an active holocene fault 2 the red rock canyon region of the garlock fault near a dilatational step over and 3 the region just south of beaumont california near the hemet dilatational step over in the san jacinto fault these are all active strike slip faults with at least a few large earthquakes in the holocene and in the case of the san jacinto example historic large earthquakes m 7 thus the precarious rocks at these sites are evidence of relatively low ground motions associated with extensional strike slip faulting the results of this study could be very important in developing more detailed seismic hazard maps in the future

artificial neural networks and cluster analysis in landslide susceptibility zonation a landslide susceptibility analysis is performed by means of artificial neural network ann and cluster analysis ca this kind of analysis is aimed at using anns to model the complex non linear relationships between mass movements and conditioning factors for susceptibility zonation in order to identify unstable areas the proposed method adopts ca to improve the selection of training validation and test records from data managed within a geographic information system gis in particular we introduce a domain specific distance measure in cluster formation clustering is used in data pre processing to select non landslide records and is performed on the whole dataset excluding the test set landslides susceptibility analysis is carried out by means of anns on the so generated data and compared with the common strategy to select random non landslide samples from pixels without landslides the proposed method has been applied in the brembilla municipality a landslide prone area in the southern alps italy the results show significant differences between the two sampling methods the classification of the test set previously separated and excluded from the training data is always better when the non landslide patterns are obtained using the proposed cluster sampling the case study validates that by means of a domain specific distance measure in cluster formation it is possible to introduce expert knowledge into the black box modelling method implemented by anns to improve the predictive capability and the robustness of the models obtained

numerical simulation of earthquake faults with gouge toward a comprehensive explanation for the heat flow paradox the particle based lattice solid model is used to simulate transform faults with and without fault gouge stick slip frictional behavior is observed in two dimensional numerical experiments of model faults both with and without gouge when no gouge is present the fault is strong and the heat generation and stress drops are correspondingly high in disaccord with observations surrounding the heat flow paradox in contrast when a gouge is specified the fault is weak and the heat generation as well as stress drops are low in quantitative agreement with observational constraints the heat flow is low on average and during short periods of aseismic creep seismic efficiencies are compatible with observationally based bounds counter intuitively the fault strength decreases as the intrinsic friction between particles is increased beyond a given threshold the mechanism for low fault strength and heat is rolling and jostling of fault gouge grains during slip this allows macroscopic movement of the fault with only minimal slip between surfaces of the gouge grains as this dynamical mechanism operates during seismic and aseismic slip it provides an explanation for the lack of a heat flow anomaly in both the seismic and creeping parts of the san andreas fault the simulation results provide the first comprehensive and quantitative possible explanation of the heat flow paradox and suggest that fault gouge plays a fundamental role on the dynamics of earthquake faults whether rolling and jostling of fault gouge particles provides the explanation for the heat flow paradox in nature remains to be validated by observation evidence