the thermal structure of mantle plumes axisymmetric or triple junction summary a mantle plume is probably a complex 3 d thermal structure that possesses approximate axisymmetry as it approaches the base of the lithosphere from below but followed down towards the base of the layer probably consists of a triple junction or quadruple junction of connected hot sheets a relatively weak hot sheet rising only part way through the layer probably connects two neighbouring mantle plumes these conclusions are suggested by numerical experiments on a 3 d constant viscosity plane layer with stress free boundaries which detail the gradational change in the planform of a convecting layer from the top of the layer to its base the planform of a convecting layer is a map in the horizontal plane of the principal thermal anomalies in the layer these anomalies are the main sources of positive for hot fluid or negative for cold fluid buoyancy and therefore they drive the convective flow they may appear in cross section as structures with either axial symmetry columns planar symmetry sheets or some complex asymmetric form when convection is driven at least partially by basal heating the planform near the top of the layer may be described as a network of cold sinking sheets and isolated hot columns while near the base of the layer it appears as a network of hot rising sheets and isolated cold columns the hot columns near the upper surface arise from the vertices or nodes of the network of hot sheets on the lower surface and similarly the cold columns at the base of the layer form below the vertices of the network of cold sheets near the upper surface near the upper surface the apparent planform of this experiment is analogous to that of mantle convection the cold sheets compared to subduction zones and the hot columns compared to mantle plumes the hot plumes impinging on the upper surface produce approximately axisymmetric temperature anomalies surface uplift and extensional stress fields however the relatively minor deviations from axisymmetry of surface observables reflect the deep structure of the mantle plume formed by the junction of three or four hot sheets on the base of the layer it seems likely that the commonly occurring triple junction form of continental rifts may reflect an underlying structure that is implicit in the convective circulation of the mantle beneath

geological hazards vulnerability and risk assessment using gis model for glenwood springs colorado glenwood springs colorado lies at the junction of the roaring fork and colorado rivers surrounded by the steep peaks of the colorado rocky mountains large parts of the region have had intensive sheet erosion debris flows and hyperconcentrated floods triggered by landslides and slumps the latter come from unstable slopes in the many tributary channels on the mountainsides causing concentration of debris in channels and a large accumulation of sediment in colluvial wedges and debris fans that line the river valleys many of the landslide and debris flow deposits exist in a state resembling suspended animation ready to be destabilized by intense precipitation and or seismic activity during this century urban development in the roaring fork river valley has increased rapidly the city of glenwood springs continues to expand over unstable debris fans without any construction of hazard mitigation structures since 1900 glenwood springs has had at least 21 damaging debris flows and floods on july 24 1977 a heavy thunderstorm spread a debris flow over more than 80 ha of the city this paper presents a method that uses geographic information systems gis to assess geological hazards vulnerability and risk in the glenwood springs area the hazards evaluated include subsidence rockfall debris flows and floods and in this paper we focus on debris flows and subsidence information on topography hydrology precipitation geomorphic processes bedrock and surficial geology structural geology soils vegetation and land use was processed for hazard assessment using a series of algorithms arc info and grass gis softwares were used to produce maps and tables in a format accessible to urban planners after geological hazards were defined for the study area we estimated the vulnerability ve of various elements for an event of intensity i risk is assessed as a function of hazard and vulnerability we categorized the study area in 14 classes for planning procedures 7 classes defined as areas suitable for human settlement and 7 classes defined as unsuitable for building and most effectively reserved for parks and forests

model test study on monitoring dynamic process of slope failure through spatial sensor network landslides represent a major type of natural hazards worldwide for development of risk mitigation capabilities an effective system for monitoring dynamic process of slope failure capable of gathering spatially distributed information before during and after a landslide occurrence at real time manner is essential a spatial sensor network ssn which integrates the real time communication infrastructure and observations from in situ sensors and remote sensing platforms offers an efficient and effective approach for such purpose in this paper a ssn based landslide monitoring system was designed and evaluated through a model test study conducted at tongji university china this system munold multi sensor network for observing landslide disaster has been designed as a comprehensive monitoring framework including sensor observations multi channel wireless communication remote data storage visualization data processing and data analysis in this model test study initial experimentation demonstrated the capabilities of the munold system for collecting real time information about the dynamic process and propagation of slope failure innovatively generated from the high speed stereo images the sequential surface deformation vector field can be created and may exhibit the dynamic process during the extremely critical and short period of the slope failure after this model test study the munold system is going to be further improved and extended in a landslide prone region in sichuan province china

parameterization of soil properties for a model of topographic controls on shallow landsliding application to rio de janeiro a key problem in the use of physically based models of landslide hazards is how to parameterize the representation of soil properties we applied a physically based model for the topographic control on shallow landsliding shalstab to two catchments in rio de janeiro to investigate the accuracy of model results in relation to parameterization of soil properties in so doing we address the relevance of values derived from laboratory tests to the field problem as well as the trade offs inherent in model parameterization we ran the model for all combinations of reasonable cohesion bulk density and friction angle values and compared model predictions to mapped landslides scars we rank sorted model performance through the proportion of the total area of landslide scars correctly predicted as potentially unstable application of the model to an area where soil properties are not well known can be based on either a standard parameterization that emphasizes topographic controls or on local calibration of soil parameters against a map of known landslide locations our analysis suggests that in general acquisition of high quality digital elevation models dems is more important than generation of spatially detailed soil property values for reconnaissance level assessment of shallow landslide hazards

the fold test in palaeomagnetism summary the fold test suggested by mcelhinny is shown to be inappropriate more correctly one should determine whether the mean direction of a group of sites from one limb of a fold may be distinguished statistically from the mean direction of a group of sites from another limb details of the application of this test are given with examples it is shown that the test indicates significance under far less severe folding than does the test suggested by mcelhinny

on the suitability of refractory bricks from a mediaeval brass melting and working site near dinant belgium as geomagnetic field recorders directional field archaeomagnetic data from two oval shaped kilns of which still one was lined with refractory bricks unearthed in a brass melting and working site in bouvignes sur meuse in belgium confirm the archaeologic dating as 14 15th century a d for the main site activities the archaeomagnetic dates obtained using reference secular variation curves of the geomagnetic field direction for france and great britain lead to better time constraints for the cessation of kiln operations refractory bricks firebricks that are used for their chemical and thermal properties and in particular for their resistance to high temperatures and temperature changes are not unusual in metal melting and working sites the firebricks from the examined site are coarse grained and very porous inside but possess a very stable remanent magnetisation and revealed to be suitable magnetic field recorders although the firebricks have a single component remanent magnetization non random deviations in remanence direction in function of the relative azimuth from the centre of the kiln or with the position of the bricks in the kiln wall were observed several hypotheses for the origin of the deviations were considered anisotropy refraction magnetic interaction magnetic field distortion and the presence of a local disturbing magnetic source

on archeomagnetic secular variation curves and archeomagnetic dating abstract secular variation sv of the earth s magnetic field can be used for dating purposes by comparing archeomagnetic directions of unknown ages with a well dated reference curve in this study we propose a dating technique based on the statistics of mcfadden and mcelhinny geophys j int 103 1990 725 for testing the hypothesis that two fisherian distributions of individual directions share a common mean direction the statistics are adapted to test the degree of compatibility between one individual fisherian mean direction and a reference curve constructed using the bivariate extension of the fisher distribution furthermore as the density of the data which define the archeomagnetic reference curve varies in time we suggest that one computes the mean directions with moving windows of varying duration where both the window widths and the time shifts between successive mean directions are fixed when a minimum threshold density of data is reached within each time interval in our paper we apply this new procedure to the french archeomagnetic data set

quantitative risk assessment of landslides triggered by earthquakes and rainfall based on direct costs of urban buildings abstract this paper outlines a framework for risk assessment of landslides triggered by earthquakes and rainfall in urban buildings in the city of medellin colombia applying a model that uses a geographic information system gis we applied a computer model that includes topographic geological geotechnical and hydrological features of the study area to assess landslide hazards using the newmark s pseudo static method together with a probabilistic approach based on the first order and second moment method fosm the physical vulnerability assessment of buildings was conducted using structural fragility indexes as well as the definition of damage level of buildings via decision trees and using medellin s cadastral inventory data the probability of occurrence of a landslide was calculated assuming that an earthquake produces horizontal ground acceleration a h and considering the uncertainty of the geotechnical parameters and the soil saturation conditions of the ground the probability of occurrence was multiplied by the structural fragility index values and by the replacement value of structures the model implemented aims to quantify the risk caused by this kind of disaster in an area of the city of medellin based on different values of a h and an analysis of the damage costs of this disaster to buildings under different scenarios and structural conditions currently 62 of valle de aburra where the study area is located is under very low condition of landslide hazard and 38 is under low condition if all buildings in the study area fulfilled the requirements of the colombian building code the costs of a landslide would be reduced 63 compared with the current condition an earthquake with a return period of 475 years was used in this analysis according to the seismic microzonation study in 2002

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

frequency ratio model based landslide susceptibility mapping in lower mae chaem watershed northern thailand the purpose of this study is to produce a landslide susceptibility map for the lower mae chaem watershed northern thailand using a geographic information system gis and remotely sensed images for this purpose past landslide locations were identified from satellite images and aerial photographs accompanied by the field surveys to create a landslide inventory map ten landslide inducing factors were used in the susceptibility analysis elevation slope angle slope aspect lithology distance from lineament distance from drainage precipitation soil texture land use land cover lulc and ndvi the first eight factors were prepared from their associated database while lulc and ndvi maps were generated from landsat 5 tm images landslide susceptibility was analyzed and mapped using the frequency ratio fr model that determines the level of correlation between locations of past landslides and the chosen factors and describes it in terms of frequency ratio index finally the output map was validated using the area under the curve auc method where the success rate of 80 06 and the prediction rate of 84 82 were achieved the obtained map can be used to reduce landslide hazard and assist with proper planning of lulc in the future

mapping of risk and susceptibility of shallow landslide in the city of sao paulo brazil abstract in the city of sao paulo where about 11 million people live landslides and flooding occur frequently especially during the summer these landslides cause the destruction of houses and urban equipment economic damage and the loss of lives the number of areas threatened by landslides has been increasing each year the objective of this article is to analyze the probability of risk and susceptibility to shallow landslides in the limoeiro river basin which is located at the head of the aricanduva river basin one of the main hydrographic basins in the city of sao paulo to map areas of risk we created a cadastral survey form to evaluate landslide risk in the field risk was categorized into four levels based on natural and anthropogenic factors r1 low risk r2 average risk r3 high risk and r4 very high risk to analyze susceptibility to shallow landslides we used the shalstab shallow landsliding stability mathematical model and calculated the distribution frequency df of the susceptibility classes for the entire basin finally we performed a joint analysis of the average risk concentration rc and risk potential rp we mapped 14 risk sectors containing approximately 685 at risk homes more than half of which presented a high r3 or very high r4 probability of risk to the population in the susceptibility map 41 of the area was classified as stable and 20 as unconditionally unstable although the latter category accounted a smaller proportion of the total area it contained a concentration rc of 41 of the mapped risk areas with a risk potential rp of 12 we found that the locations of areas predicted to be unstable by the model coincided with the risk areas mapped in the field this combination of methods can be applied to evaluate the risk of shallow landslides in densely populated areas and can assist public managers in defining areas that are unstable and inappropriate for occupation

magnetic refraction studied on two experimental kilns summary experimental kilns in the form of shells half spheres and circular bottom plates inner radius 15 cm outer radius 17 cm were made from clay fire clay and less than 5 per cent by volume of fine grained haematite powder for the study of the effect of magnetic refraction in archaeological structures the haematite in the clay was reduced to a strongly magnetic phase maghematized magnetite the acquisition of trm was performed in a non magnetic gas heated furnace in the local geomagnetic field the kiln material has a maghemite ore content of about 2 per cent by volume and an apparent magnetic susceptibility at room temperature of about 4 x lo si units the deviations of the declination and inclination of the trm at different latitudes of the shells were respectively up to 40 and 15 and systematically dependent from the position of the specimens in the shell or bottom plate in agreement with model calculations however the classical approach for the magnetic refraction in materials with ferrimagnetic ore grains dispersed in a nonmagnetic rock matrix with simple assumptions for the demagnetizing fields of the ore grains and of the macroscopic sample was not able to explain the large refraction effects which have been observed an adequate theory for the magnetic refraction in rocks is still not available for archaeomagnetic studies some advice is offered for sampling and demagnetization treatment of the material in order to minimize refraction effects in archaeomagnetic data some consequences for palaeomagnetic studies are also discussed

characterization of the magnetic fabric of rocks abstract an inextensive system of magnetic susceptibility anisotropy factors is suggested which is sufficient in the majority of practical applications for characterizing the magnetic fabric of rocks the system involves three newly devised factors the corrected anisotropy degree the shape factor and the difference shape factor the first of these characterizes the quantity of anisotropy somewhat better than the commonly used anisotropy degree the shape factor characterizes the quality of anisotropy i e the shape of the susceptibility ellipsoid in a convenient way its definition is based on a certain analogy between the anisotropy ellipsoid and the strain ellipsoid the difference shape factor can replace the shape factor when only the differences between the principal susceptibilities are given while the mean susceptibility is unknown

the deep structure of ocean ridges in a convecting mantle abstract plate tectonic models have frequently assumed that mid ocean ridges are the surface expression of the hot rising limb of a convection cell measured half spreading rates show that in any reference frame the horizontal transverse velocity of some ridges is comparable to the individual plate velocities if the above assumption is correct this observation implies that the thermal structure beneath the ridge can adjust rapidly to the changing surface configuration of the plates numerical experiments in a two dimensional convecting layer of constant viscosity fluid show that such a rapid adjustment is probably unrealistic a symmetrically spreading ridge moving horizontally is simulated by specifying a velocity boundary condition on the upper surface of the layer the other boundary conditions are uncertain so several different combinations are used in the experiments including periodic or reflecting lateral boundaries and stress free or no slip lower boundary in all the experiments the rising sheets of the convection cells are anchored firmly in the mean horizontal flow of the layer unless the mean flow coincides approximately with the ridge velocity the ridge quickly moves away from a rising sheet which is initially beneath it if the aspect ratio width depth of the convection cells is significantly greater than one this conclusion is even more evident in the earth it seems unlikely that there is a systematic deep of the order of the convecting layer thickness structure beneath the worldwide network of ocean ridges

a physically based multi hazard risk assessment platform for regional rainfall induced slope failures and debris flows abstract rainfall induced slope failures and debris flows are two major hazards in mountainous areas a physically based multi hazard risk assessment platform for regional rainfall induced slope failures and debris flows has been developed in this study the platform enables prompt assessment of risks posed by regional rainfall induced slope failures and debris flows across multiple catchments which is required in landslide risk management in a large area it considers the contribution of slope failures to debris flows and the scenario of a location impacted by multiple slope failures or debris flows or both the contribution of slope failures to debris flows is considered by adding the increased amount of channel deposit from slope failures to the source material of debris flows the platform is applied to a highway near the epicentre of the 2008 wenchuan earthquake the platform predicts the impact areas and runout distances of regional debris flows reasonably well the risk assessment results indicate that both slope failures and debris flows pose a great danger to travellers along the road shortly after the earthquake due to the presence of a large amount of loose landslide deposits on steep terrains the materials from the slope failures triggered during a storm substantially increase the channel deposit volume leading to significantly increased debris flow volume and risk a multi hazard risk assessment approach is necessary to consider the scenario of a location impacted by multiple slope failures or debris flows or both since assessing risks of slope failures and debris flows separately may underestimate the risk

seasat derived gravity over the musicians seamounts the two dimensional gravity field over the musicians seamount province in the pacific ocean has been derived from seasat altimetry geoid maps were produced by fitting a minimum curvature surface to the sea surface height measurements as a check on the quality of this interpolation method we also gridded the data using weighted grid point averages fourier transforms of both the geoid and geoid gradient were used to determine the gravity field we have compared gravity maps produced these different ways in order to identify the problems involved in pushing seasat data to the limits of its spatial resolution and accuracy our minimum curvature interpolation scheme was determined to be the more accurate and cost effective mapping method while gravity obtained by transforming the geoid produced more reliable gravity maps the bathymetry of this area was used to predict the gravity field by filtering the bathymetry under the assumption that it is regionally compensated by a thin elastic plate gravity fields predicted for a variety of effective elastic thicknesses were compared to the seasat derived gravity particularly in areas with good track coverage the derived gravity tends to favor a thin plate with an effective elastic thickness of 5 km though the east west ridges in the south display a smaller signal more consistent with airy compensation this variation may be indicative of early fracturing of the lithosphere in the south or it may be a manifestation of the age difference and early thermal structure across the murray fracture zone which separates the seamount province into northern and southern sections neighboring seamounts with different flexural signatures particularly in the south may indicate that volcanism occurred in the same location over an extended period of time

estimate of the magnetic anisotropy effect on the archaeomagnetic inclination of ancient bricks abstract the magnetic fabric of 59 bricks coming from 5 ancient kilns has been studied by measuring the anisotropy of magnetic susceptibility ams and the anisotropy of isothermal airm anhysteretic aarm and thermal atrm remanent magnetization the bricks are characterized by a well developed magnetic fabric that matches their flat shape the shape of the anisotropy ellipsoids is in almost all cases oblate with the maximum and intermediate axes lying parallel to the large face of the brick and the minimum axis perpendicular to it the directions of the principal axes are almost the same irrespectively of the type of anisotropy measured whereas the degree of anisotropy of the airm aarm and atrm is much higher than the ams as the bricks lie horizontally within the kiln the planar magnetic fabric results in an inclination shallowing of the archaeomagnetic direction with respect to that of the earth s magnetic field at the time of their last cooling estimation of this effect on the grounds of atrm measurements yields a shallowing that varies from 4 to 10 for individual samples such inclination difference may significantly bias archeomagnetic dating for the case of the canosa late roman kiln it leads to a dating error of more than two centuries

investigating the expected archaeomagnetic dating precision in europe a temporal and spatial analysis based on the scha dif 3k geomagnetic field model abstract archaeomagnetic dating is a chronometric dating technique based on the ability of baked clay archaeological structures and artifacts to acquire a thermal remanent magnetization trm when heated at high temperatures and cooled in the presence of the earth s magnetic field the precision of archaeomagnetic dating depends on several factors among others the availability of a detailed reference secular variation sv curve for a given territory in this study we investigate the precision that archaeomagnetic dating can reach in europe we used the scha dif 3k european geomagnetic field model to calculate the dating uncertainties for the last 3000 years taking into consideration only the uncertainties depending on the change rate of the geomagnetic field in the past and the reference sv curve s uncertainty envelope such uncertainties were calculated both in time and space they are usually asymmetrically distributed around the considered year and it have been represented as dynamic maps of uncertainties the obtained results show that archaeomagnetic dating based solely on directional data declination and inclination can be very precise for the last four centuries with total uncertainties being almost always lower than 100 years all around europe inherent dating uncertainties are also low for the last millennium with values ranging from 50 to 300 years these results underline the great potential of archaeomagnetism on dating baked clays belonging to the last 1000 years for older periods the uncertainty maps show that the dating precision may importantly vary from place to place but with local non symmetric uncertainty ranges generally below 400 years the obtained maps also show that adding the intensity to the computation of the inherent uncertainties does not always reduce the uncertainty the temporal and spatial analysis presented here does not give the total dating imprecision of archaeomagnetic dating that definitely depends on numerous often uncontrollable factors but aims at offering a useful tool to archaeomagnetic and archaeological research to check the feasibility of archaeomagnetic dating for determining the age of an archaeological structure below a desired precision

improving sinkhole hazard models incorporating magnitude frequency relationships and nearest neighbor analysis abstract this work presents a methodology for elaborating sinkhole hazard models that incorporate the magnitude and frequency relationships of the subsidence process the proposed approach has been tested in a sector of the ebro valley mantled evaporite karst where sinkholes largely induced by irrigation practices have a very high occurrence rate 50 sinkholes km 2 yr in this area covering 10 km 2 a total of 943 new cover collapse sinkholes were inventoried in 2005 and 2006 multiple susceptibility models have been generated analyzing the statistical relationships between the 2005 sinkholes and different sets of variables including the nearest sinkhole distance the quantitative evaluation of the prediction capability of these models using the 2006 sinkhole population has allowed the identification of the method and variables that produce the most reliable predictions the incorporation of the indirect variable nearest sinkhole distance has contributed significantly to increase the quality of the models despite simplifying the modeling process by using categorical rather than continuous variables the best susceptibility model generated with the total sinkhole population and the selected method and variables has been transformed into a hazard model that provides minimum estimates of the spatial temporal probability of each pixel to be affected by sinkholes of different diameter ranges this transformation has been carried out combining two equations derived from the more complete 2006 sinkhole population one of them expressing the expected spatial temporal probability of sinkhole occurrence and the other the empirical magnitude and frequency relationships generated for two different types of land surfaces which control the strength of the surface layer and the size of the sinkholes the presented method could be applied to predict the spatial temporal probability of events with different magnitudes related to other geomorphic processes e g landslides

continuous and large sediment supply in a steep landslide scar southern japanese alps abstract continuous sediment supply in the aka kuzure landslide scar in the tectonically active alpine southern japanese alps was investigated using airborne light detection and ranging data in 2000 2003 2007 and 2012 in addition we focused on the spatial variability of denudation patterns based on topographical analyses using dems denudation volume for the past 12 years reached about 106 m3 and mean annual denudation rate ranged from 0 25 to 0 31 m yr topographical analyses revealed that sediment supply in the scar consists of a combination of two denudation types sporadic deep and wide thin these denudation types have different roles in the topographical development of the landslide scar sporadic deep type supplies less volume than wide thin type but still contributes to channel development as it mainly occurs on lower order streams and tends to change the convex slope into a concave slope in contrast although denudation depth of the wide thin type is thin the area affected by this type extends to the whole landslide scar consequently the wide thin type accounts for most of the total volume lost for which detachment by frost shattering is suggested as an important role

landslide temporal analysis and susceptibility assessment as bases for landslide mitigation machu picchu peru multi temporal landslide occurrence information acquired through aerial photo interpretation and field mapping was used to assess occurrence frequencies on the slopes around the unesco cultural world heritage site of machu picchu peru this showed that the coarse time resolution of the historical landslide information may lead to inaccurate interpretations regarding landslide occurrence frequencies in some parts of the study area in addition the assumption that the past landslide frequency can be used to describe the future landslide occurrence was not proved in the study area thereafter unique conditional analyses were undertaken to assess landslide susceptibility using a limited number of preparatory factor maps it showed that large majority of the inca city is located on least susceptible areas within the region the results of the susceptibility assessment combined with landslide occurrence frequencies may serve as a basis for the landslide hazard mitigation in the studied area for these purposes pixel based susceptibility maps were generalized into expert defined landslide management units these units provide site managers with easily understandable and applicable hence reliable information about future landslide occurrences an approach describing usage of the resulting susceptibility maps for onsite mitigation purposes was described with respect to the needs of machu picchu site managers

archaeomagnetic evidence for the age of a roman pottery kiln from calahorra spain summary the first report of a palaeomagnetic study of a roman pottery kiln is presented individual bricks from the walls of the heating chamber have been sampled and measured in order to determine their palaeomagnetic directions the measurements indicate that the innermost part of the structure was heated well above the curie point of haematite enabling the use of the palaeomagnetic declination and inclination after the axial dipole correction and fitting to the paris i t curve to infer the age of the last heating event

distribution anisotropy the cause of ams in igneous rocks understanding of ams in pristine basic igneous rocks in terms of flow orientation of ellipsoidal magnetite grains is thwarted by the fact that these grains 1 typically are irregularly equant or skeletal rather than distinctly ellipsoidal and 2 usually crystallize interstitially and late after magma flow has ceased however the distribution of such grains will be relatively anisotropic if they grew in residual liquid volumes within a preferredly oriented by flow silicate template this constraint may impose a slight preferred shape orientation to the irregular magnetite grains during their growth but in addition we suggest it is the anisotropic magnetic interaction between the grains which is the basic cause of ams experiments involving the casting of magnetite epoxy mixtures in various foliated or lineated glass templates have yielded samples with the expected ams symmetry i e k3 perpendicular to glass plates or k1 parallel to glass rods slicing of near isotropic synthetic blank and natural rock cores and interleaving with glass slides showed a progressive increase in anisotropy of the blank from 0 4 to 2 and the natural rock from 0 9 to 2 9 in both the k3 axis migrates to be perpendicular to the glass slides

human impact on geomorphic processes and hazards in mountain areas in northern spain abstract the temporal occurrence of slope movements their contribution to relief evolution and human influence on those processes in two study areas of northern spain are presented the work is based on temporal analyses covering 100 ka in one study area and 43 years in the other temporal analysis has been the basis for quantitatively assessing the magnitude of human influence and developing landslide susceptibility and hazard models with known independently tested prediction capability the results obtained in one study area show a relationship between landsliding periods and increasing precipitation during upper pleistocene and holocene significant increases of landslide frequency and mobilisation rate were also found around 5500 and 200 years ago those moments coincide with two periods of intensified human presence and activities neolithic and industrial revolutions the increase observed represents about one order of magnitude from pre neolithic to present a similar increase has been found between 1954 and 1997 in the other study area the latter increase shows no relationship with changes in climate parameters or seismic activity a fairly good correlation has been found between landslide frequency and socioeconomic indicators of human activity sedimentation rates in two neighbouring estuaries were determined and significant increases particularly in the second part of last century were also found evidence obtained suggest that the increases observed in the frequency of slope instability events and therefore hazard denudation and sedimentation rates are due to a greater extent to indirect geomorphologic changes caused by human action rather than climate change detailed analysis of landslide frequency during that 43 year period has also been used to produce and validate landslide susceptibility models and obtain landslide hazard maps with known prediction accuracy validation tests were carried out comparing susceptibility maps based on landslides that have occurred in the past with the ones occurring in several later periods prediction capability of models could thus be determined validation of susceptibility maps using data derived from the temporal analysis of landslides was used to obtain hazard maps expressed as probability of new ruptures in a given time period on the basis of past trends in terrain behaviour possible impacts of a growing influence of human activities on the terrain have been incorporated into the assessment of future hazards by considering different scenarios

archaeomagnetic dating of archaeological sites from switzerland and bulgaria baked materials from three archaeological sites in switzerland and one in bulgaria have been examined and dated archaeomagnetically the detailed rock magnetic properties of the burnt clay collected have already been studied therefore and have been published elsewhere geophysical journal international 153 2003 146 the main aim of this paper is to determine the terminus ante quem for the last firing of the clay collected from pottery kilns or burnt layers the directional and intensity results of the ancient geomagnetic field corresponding to the time of the structure s last firing are given for each site these geomagnetic parameters are then compared with reference curves to provide archaeomagnetic dates for the last use of the kilns application of archaeomagnetism as a dating tool is only possible for those regions that already have reference curves bulgaria is fortunate in having established reference curves covering almost the last 8000 years two swiss sites were dated using only directional results on the basis of existing palaeodirectional results for switzerland as well as the french directional reference curves the archaeomagnetic dates of three of the sites were then compared to archaeological evidence and available radiocarbon dates the palaeointensity data obtained from this study will enrich the existing archaeomagnetic database for western europe

evaluating and comparing methods of sinkhole susceptibility mapping in the ebro valley evaporite karst ne spain abstract multiple sinkhole susceptibility models have been generated in three study areas of the ebro valley evaporite karst ne spain applying different methods nearest neighbour distance sinkhole density heuristic scoring system and probabilistic analysis for each sinkhole type separately cover collapse sinkholes cover and bedrock collapse sinkholes and cover and bedrock sagging sinkholes the quantitative and independent evaluation of the predictive capability of the models reveals that 1 the most reliable susceptibility models are those derived from the nearest neighbour distance and sinkhole density these models can be generated in a simple and rapid way from detailed geomorphological maps 2 the reliability of the nearest neighbour distance and density models is conditioned by the degree of clustering of the sinkholes consequently the karst areas in which sinkholes show a higher clustering are a priori more favourable for predicting new occurrences 3 the predictive capability of the best models obtained in this research is significantly higher 12 5 82 5 than that of the heuristic sinkhole susceptibility model incorporated into the general urban plan for the municipality of zaragoza although the probabilistic approach provides lower quality results than the methods based on sinkhole proximity and density it helps to identify the most significant factors and select the most effective mitigation strategies and may be applied to model susceptibility in different future scenarios

a method for correcting geographically separated remanence directions for the purpose of archaeomagnetic dating summary spatial variations in the geomagnetic field must be taken into account if secular variation master curves and directional magnetic dates are to be optimized two methods for relocating remanence vectors have been proposed and in this paper their relative accuracies are compared using a numerical model based on the present day field a method which converts archaeomagnetic directions via a virtual geomagnetic pole is shown to be the more efficient transformation for an archaeomagnetic region the size of the british isles 900 km radius the maximum error in relocating vectors to a central location is predicted to be of the order of 1 2

quantitative landslide risk assessment and mapping on the basis of recent occurrences abstract a quantitative procedure for mapping landslide risk is developed from considerations of hazard vulnerability and valuation of exposed elements the approach based on former work by the authors is applied in the bajo deba area northern spain where a detailed study of landslide occurrence and damage in the recent past last 50 years was carried out analyses and mapping are implemented in a geographic information system gis the method is based on a susceptibility model developed previously from statistical relationships between past landslides and terrain parameters related to instability extrapolations based on past landslide behaviour were used to calculate failure frequency for the next 50 years a detailed inventory of direct damage due to landslides during the study period was carried out and the main elements at risk in the area identified and mapped past direct monetary losses per type of element were estimated and expressed as an average specific loss for events of a given magnitude corresponding to a specified scenario vulnerability was assessed by comparing losses with the actual value of the elements affected and expressed as a fraction of that value 0 1 from hazard vulnerability and monetary value risk was computed for each element considered direct risk maps pixel year were obtained and indirect losses from the disruption of economic activities due to landslides assessed the final result is a risk map and table combining all losses per pixel for a 50 year period total monetary value at risk for the bajo deba area in the next 50 years is about 2 4 106 euros

archaeointensity determinations from italy new data and the earth s magnetic field strength variation over the past three millennia summary three kilns and a collection of baked bricks from italian archaeological sites have been studied for archaeointensity determination using the thellier method as modified by coe all sites are dated based on archaeological information and their ages range from 500 to 800 ad and 1500 to 1700 ad rock magnetic studies identify magnetite ti magnetite and hematite as the main magnetic minerals and magnetic susceptibility versus temperature shows a good thermal stability of the samples the intensity results have been corrected for anisotropy of the thermoremanent magnetization and cooling rate effects the new data together with 136 previously published results are used to estimate the variation of the earth s magnetic field over the past three millennia the time distribution of the italian absolute intensity data is irregular with the majority of determinations concentrated during the last four centuries while older periods are very poorly covered most of the data come from volcanic rocks and show significant discrepancies all data have been compared with archaeointensity results from europe and regional and global models predictions this work indicates the need to obtain more high quality archaeointensity results in particular for the periods older than 200 bc and between 200 and 1000 ad in order to determine a robust italian intensity secular variation curve that in combination with directional data could be used for archaeomagnetic dating

a theoretical and experimental comparison of the anisotropies of magnetic susceptibility and remanence in rocks and minerals summary susceptibility thermo remanent magnetization trm and isothermal remanent magnetization irm anisotropy ellipsoids have been determined for several rock samples the results indicate that the ellipsoid of initial susceptibility is less anisotropic than the trm and low field irm ellipsoids which are found experimentally to be of identical shape this suggests that palaeomagnetic data for anisotropic rocks may be corrected by using the anisotropy ellipsoid determined from magnetically non destructive low field irm measurements such irm measurements can also be used to obtain anisotropy axes of samples which are inherently anisotropic but which have a susceptibility which is too weak to be accurately measured the results for a series of artificial anisotropic samples containing magnetite particles of different sizes in the range 0 2 90 m were very similar to those for the rocks in contrast a comparison of the susceptibility and irm ellipsoids for anisotropic samples containing particles from a magnetic tape gave very different results in accordance with theory such results imply that susceptibility and irm ellipsoids could be used to determine whether anisotropic rocks contain uniaxial single domain particles magnetization confined to the easy axis or whether the particles are essentially multidomain

trm deviations in anisotropic assemblages of multidomain magnetite anisotropic assemblages of multidomain magnetite particles develop an anisotropy of magnetic susceptibility ams which in turn induces deviations of thermo remanent magnetization trm from the field direction from the theories of multidomain trm acquisition it is shown that the trm anisotropy tensor has its eigenvalue ratios ti related to the principal weak field susceptibility ratios pi by the order of magnitude ti p2i this relation has been experimentally verified on two sets of highly anisotropic rock samples the exponent has been determined to be 1 94 in the samples from a peruvian gabbro and 1 81 in those from the granite of flamanville nw france accounting for experimental difficulties in determining the trm anisotropy tensors these exponents are judged to agree well with the expected one it is therefore stressed that ams measurements provide a good means of evaluating the magnetic field direction from deviated trm directions providing magnetic carriers are mainly multidomain magnetites

comparison of landslide susceptibility based on a decision tree model and actual landslide occurrence the akaishi mountains japan abstract this paper proposes a statistical decision tree model to analyze landslide susceptibility in a wide area of the akaishi mountains japan the objectives of this study were to validate the decision tree model by comparing landslide susceptibility and actual landslide occurrence and to reveal the relationships among landslide occurrence topography and geology landslide susceptibility was examined through ensemble learning with a decision tree decision trees are advantageous in that estimation processes and order of important explanatory variables are explicitly represented by the tree structures topographic characteristics elevation slope angle profile curvature plan curvature and dissection and undissection height and geological data were used as the explanatory variables these topographic characteristics were calculated from digital elevation models dems the objective variables were landslide occurrence and reactivation data between 1992 and 2002 that were depicted by satellite image analysis landslide susceptibility was validated by comparing actual data on landslides that occurred and reactivated after the model was constructed between 2002 and 2004 this study revealed that from 2002 to 2004 landslides tended to occur and reactivate in catchments with high landslide susceptibility the landslide susceptibility map thus depicts the actual landslide occurrence and reactivation in the akaishi mountains this result indicates that the decision tree model has appropriate accuracy for estimating the probabilities of future landslides the tree structure indicates that landslides occurred and reactivated frequently in the catchments that had an average slope angle exceeding ca 29 and a mode of slope angle exceeding 33 which agree well with previous studies a decision tree also quantitatively expresses important explanatory variables at the higher order of the tree structure

modelling of the gravity effects of flexurally compensating thin layers under the afanasy nikitin seamount abstract modelling of the gravity data over the afanasy nikitin seamount is carried out to estimate the variation of the crustal and flexural parameters along the strike of the seamount it is inferred that the compensation of the seamount is due to both the bending of a very thin elastic plate and the occurence of low density material at depth the elastic plate thickness is inferred as 2 km and does not change significantly along the strike of the seamount furthermore the crustal thicknesses range within 12 22 km not showing any systematic variation along the strike of the seamount it is suggested that the afanasy nikitin seamount was emplaced on thin and weak lithosphere very near to a slowly migrating ridge which trapped a hot rising plume resulting in a higher crustal thickness

flexure and gravity anomalies of the oceanic lithosphere beneath the louisville seamount abstract we have calculated the elastic thickness te flexural deflection and gravity anomaly of the oceanic crust beneath the louisville seamount lsc 03 near the kermadec trench a regional residual separation of the bathymetry was performed to remove the effect of other geologic features e g the trench we used the uniform density and dense core models to approximate the total mass of the seamount which was defined as the surface load required for flexural deformation from the flexure modeling results we found that more flexural depression was predicted by the uniform density model than by the dense core model however the uniform density model predicted a significantly smaller gravity anomaly than observed whereas the dense core model minimized the prediction misfits reasonably the best flexure model was found with a te of 16 km for the uniform density model and 6 km for the dense core model the flexure computed with the dense core model was consistent with the seismically detected moho the flexure modeling for lsc 03 thus indicates that the dense core model better approximates the inner structure of the lsc 03 based on the crustal age and geochronology of the given seamount the age of the oceanic crust at the time of seamount formation t is 20 ma if this is the case however the te estimates from both flexure models require some degree of lithospheric reheating by louisville hotspot activity alternatively considering the tectonic plate motion of the osbourn trough t becomes approximately 4 ma this younger lithosphere model is more consistent with the observed flexural deformation and the te estimate from the dense core model therefore the time that the seamount induced lithospheric deformation occurred may be far earlier than the age dated volcanism

gis based landslide susceptibility mapping for the 2005 kashmir earthquake region abstract the m w 7 6 october 8 2005 kashmir earthquake triggered several thousand landslides throughout the himalaya of northern pakistan and india these were concentrated in six different geomorphic geologic anthropogenic settings a spatial database which included 2252 landslides was developed and analyzed using aster satellite imagery and geographical information system gis technology a multi criterion evaluation was applied to determine the significance of event controlling parameters in triggering the landslides the parameters included lithology faults slope gradient slope aspect elevation land cover rivers and roads the results showed four classes of landslide susceptibility furthermore they indicated that lithology had the strongest influence on landsliding particularly when the rock is highly fractured such as in shale slate clastic sediments and limestone and dolomite moreover the proximity of the landslides to faults rivers and roads was also an important factor in helping to initiate failures in addition landslides occurred particularly in moderate elevations on south facing slopes shrub land grassland and also agricultural land were highly susceptible to failures while forested slopes had few landslides one third of the study area was highly or very highly susceptible to future landsliding and requires immediate mitigation action the rest of the region had a low or moderate susceptibility to landsliding and remains relatively stable this study supports the view that 1 earthquake triggered landslides are concentrated in specific zones associated with event controlling parameters and 2 in the western himalaya deforestation and road construction contributed significantly to landsliding during and shortly after earthquakes

an automated method to extract fluvial terraces from lidar based high resolution digital elevation models the oiartzun valley a case study in the cantabrian margin abstract combined climatic and tectonic conditions controlled the quaternary incision of rivers and the fluvial terraces are the most significant landforms to untangle their evolutionary history increasing availability of high resolution topography data over large areas offers an opportunity to increment greatly the quantity and the quality of information feasible for the development of semi automated techniques for identification and characterization of these features in this study we apply a methodology based on demoulin et al 2007 for the detection of fluvial terraces in digital elevation models dem with the novelty of using dems derived from high resolution lidar data that are processed using geographical information system gis routines the method is based on the recognition of slope variations and change of sign of profile curvature across the hillslopes considering scatter plots over valley segments of given length every minimum of slope value as a function of either distance to or elevation above the base of the valley is considered a possible terrace remnant the compilation of these slope minima retained within the successive segments covering the whole length of the valley will finally provide a two dimensional plot of terrace remnants in respect to the present day long profile of the river we successfully tested this method in the oiartzun valley in the eastern area of the cantabrian margin western pyrenees where terrace maps were previously developed via aerial photo interpretation and field mapping campaigns despite the highly erosive nature of the cantabrian fluvial systems the poor preservation of fluvial landforms and the abundant vegetation cover our method obtained good results due to its objectivity exhaustiveness and rapidity allowing fast and coherent analysis of fluvial valleys and their comparison

emplacement of the marion dufresne lena and ob seamounts south indian ocean from a study of isostasy abstract three gravity and topographic profiles over the ob lena and marion dufresne seamount chain southwest indian ocean are analysed in terms of the isostatic response of the lithosphere these seamounts are regionally supported by both the bending of an elastic plate which varies significantly in thickness along the chain and by the presence of light material at depth this variation is correlated with the age of the lithosphere at the time of loading by the seamounts which varies between 6 and 40 m y these ages when combined with the identification of magnetic anomalies yield absolute emplacement ages for each seamount these results favour a creation of the marion dufresne and lena seamounts near the active southeast indian ridge during the upper cretaceous their emplacement due to intraplate volcanism as the result of the displacement of the antartic plate over a hot spot is therefore considered very unlikely interpretation of the results over ob seamount are somewhat less conclusive but support a similar upper cretaceous emplacement near the southwest indian ridge

origin and tectonic evolution of the caroline ridge and the sorol trough western tropical pacific from admittance and a tectonic modeling analysis abstract an independent caroline sea plate surrounded by prominent seismotectonic features is said to exist in the western tropical pacific the caroline sea plate is a transient feature existing only when the caroline philippine sea plate boundary is jumping to the caroline pacific boundary the origin and the tectonic evolution of the caroline ridge sorol trough region which forms the northern part of the caroline pacific plate boundary are examined using a standard admittance analysis a tectonic modeling study and additional direct gravity and magnetic analyses the observed admittance function is fitted well by shallow airy model in the 250 125 km 0 025 k 1 wavelength region whose average crustal thickness t c is 20 km and also by thin plate flexure model of isostasy within the diagnostic waveband of 250 80 km 0 025 k 1 with an effective elastic thickness t e of 5 7 km a simple interpretation of the observed admittance function is that the local airy model of isostasy is the main support mechanism in the study region for the longer wavelength more fundamental topography corresponding to that of the caroline ridge the caroline ridge is inferred to have formed in a near ridge tectonic setting on top of oceanic lithosphere which was young thin and weak at the time of emplacement the tectonic model study after an explanation for rifting along the mendana fracture zone in the nazca plate suggests that the sorol trough formed in the 17 7 ma interval splitting the caroline ridge into two longitudinal halves the rifting along the sorol trough which took place in the manner described in weissel and karner 1989 flexural uplift of rift flanks due to mechanical unloading of the lithosphere during extension j geophys res 94 13 919 13 950 necking of unbroken lithosphere post dated the formation of the caroline ridge by 10 15 m y during which time t e in the region increased to 5 10 km the rifting necking along the sorol trough represents a second loading event in the region the combined gravity effects of the rifting as well as the increase in the t e in the region from essentially nil to 5 10 km is reflected in the agreement between the observed admittance and the regional model with a 5 7 km t e in the wavelength region 80 km these results are consistent with the findings and the suggestions of the previous investigators in the region in that 1 the caroline ridge was constructed in the late oligocene by hot spot volcanism on top of oligocene seafloor of the caroline sea back arc basin 2 the eauripik rise genetically related to the caroline ridge formed on young and weak caroline basin lithosphere and is supported by airy manner crustal thickening and that 3 the lithosphere of the caroline ridge was young at the time of rifting necking along the sorol trough on the basis of the current results and the findings of the previous workers a tentative hypothetical rheological model for the crustal density structure of the caroline ridge sorol trough is also given the caroline sea plate appears to be bounded in the north and south by e w trending boundaries that deform diffusely while more normal narrow n s trending boundaries exhibiting more localized albeit slow deformation bound the plate in the east and west

emplacement of afanasy nikitin seamount based on transfer function analysis of gravity and bathymetry data abstract the nature of compensation of the afanasy nikitin seamount in the central indian ocean lithosphere is examined through transfer function analysis of gravity and bathymetry data along five profiles across the seamount the seamount appears to be regionally compensated by the bending of an elastic plate of only 2 5 km thickness from this low elastic thickness it is inferred that the seamount is formed near a spreading axis transform junction

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