an experimental study of the relationship between joint spacing and layer thickness abstract two methods for measuring joint spacing are described and compared the area method is a constant for a given outcrop area and is not affected by joint distribution within that area in contrast the line method depends on the location of the linear traverse two kinds of joint sets are distinguished on bedding surfaces 1 a poorly developed set represents the early stages of development when typical joint lengths are less than typical spacing 2 a well developed set represents later stages when lengths are much greater than spacing the area method is applicable to both poorly and well developed sets whereas the line method produces inconsistent results for poorly developed joint sets surface textures on many joints indicate point fracture origins and propagation parallel to bedding whereas most numerical model studies of spacing assume linear origins and propagation perpendicular to bedding the laboratory experiments described in this paper do not suffer from these restrictions an important concept confirmed during these experiments is fracture saturation when the applied strain reaches a certain value fracture spacing stops evolving and remains nearly constant these fracture sets are well developed spacing at saturation is a function of layer thickness but is independent of strain whereas spacing before saturation varies strongly with applied strain thus plotting spacing vs thickness and comparing the slopes of lines fit to such data for poorly developed joint sets in different layers is unlikely to be a diagnostic test for differences in material properties on the other hand spacing may be a sensitive indicator of strain for layers with poorly developed joint sets assessing fracture saturation is a lirst order consideration when gathering spacing data

lower silurian aeronian megafaunal and conodont biofacies of the northwestern michigan basin lower silurian llandovery aeronian carbonates of the burnt bluff group northwestern michigan basin represent a transect along a southward dipping ramp that extends from tidal flat to basin environments benthic megafaunas include an ostracod biofacies tidal flat stromatoporoid coral biofacies very shallow subtidal pentamerid crinozoan and crinozoan stromatoporoid biofacies deeper subtidal and a crinozoan sponge biofacies distal ramp and basin the crinozoan sponge biofacies which includes diverse small crinozoan ossicles 19 types of siliceous sponge spicules and at least 65 other taxa has a biota that is similar to those of silurian continental margins megafaunal biofacies indicate an early silurian gradient going from a shoreline in the north to water depths of perhaps 60 m in the south the burnt bluff group contains conodonts of the icriodella discreta icriodella deflecta zone as an onshore biofacies with panderodus kockelella ozarkodina icriodella and oulodus and an offshore biofacies with panderodus walliserodus and aspelundia rcsumc les carbonates du silurien infkrieur llandovery aeronien du groupe de burnt bluff dans la rcgion nord ouest du bassin de michigan rephentent un transect le long d une rampe inclince vers le sud s ktalant d un environnement d estran tidal a celui d un bassin les mkgafaunes benthiques incluent un biofaciks a ostracodes estran tidal un biofaciks a stromatoporoi des coraux infratidal trks peu profond des biofaciks a pentamkrides crinozoaires et crinozoaires stromatoporoi des infratidal profond et un biofaciks a crinozoaires cponges rampe distale et bassin le biofaciks a crinozoaires cponges qui inclut diverses petites plaques de crinozoaires 19 types de spicules d cponges siliceux et au moins 65 autres taxons posskde un biote qui est similaire a ceux des marges continentales siluriennes les biofaciks mkgafauniques indiquent un gradient au silurien prccoce allant d une ligne de rivage dans le nord jusqu a des profondeurs d eau atteignant peut etre 60 m dans le sud le groupe de burnt bluff contient des conodontes de la zone a icriodella discreta icriodella deflecta comme biofaciks intracdtier accompagncs de panderodus kockelella ozarkodina icriodella et oulodus et un biofaciks extrac6tier avec panderodus walliserodus et aspelundia traduit par la rcdaction

velocity field of the la clapiere landslide measured by the correlation of aerial and quickbird satellite images 1 two displacement maps of the la clapiere landslide france have been derived over two periods of 4 years 1995 1999 and 1999 2003 by correlation of aerial photographs and a quickbird satellite image the movement of the landslide ranges from 2 5 m to 20 m per year those values have been validated over 13 points monitored by conventional tacheometric measurements three areas with significant differences in velocity field have been mapped limits of those areas are in good agreement with in situ observations velocity maps show the low long term temporal variability of the landslide movement and its spatial variability the optical correlation method using images derived from various sensors airborne and spatial is a promising technique for improving the spatial resolution of velocity field observation of landslides over several years

geomechanical modeling of hydraulic fracturing why mechanical stratigraphy stress state and pre existing structure matter the increasing exploration and production in unconventional resource plays in the past decade has been accompanied by a greater need for understanding the effectiveness of multistage hydraulic fracturing programs particularly in long 1500 m or 5000 ft subhorizontal boreholes laterals traditional analytical analysis techniques for estimating the size and orientation of fractures induced by fluid injection typically result in predictions of relatively long and planar extension mode i bi wing fractures which may not be representative of natural systems although these traditional approaches offer the advantage of rapid analysis neglect of key features of the natural system e g realistic mechanical stratigraphy pre existing natural faults and fractures and heterogeneity of in situ stresses may render results unrealistic for planning executing and interpreting multimillion dollar hydraulic stimulation programs numerical geomechanical modeling provides a means of including key aspects of natural complexity in simulations of hydraulic fracturing in this study we present the results of two dimensional finite element modeling of fluid injection induced rock deformation that combines a coupled stress pore pressure analysis with a continuum damage mechanics based constitutive relationship the models include both the natural mechanical stratigraphic variability as well as the in situ stress state anisotropy and permit tracking of the temporal and spatial development of shear and tensile permanent strains that develop in response to fluid injection our results show that simple long planar fractures are unlikely to be induced in most mechanically layered natural systems under typical in situ stress conditions analyses that assume this type of fracture geometry may significantly overestimate the reach of hydraulically induced fractures and or effectively stimulated rock volume

earthquake driven acceleration of slow moving landslides in the colca valley peru detected from pleiades images abstract major earthquakes in mountainous areas often trigger rapid landslides some observations also suggest that earthquakes can damage landslide prone areas or cause slow moving landslides to accelerate with a risk of evolution to rapid landslides in the following months after the earthquake here we use optical images from the pleiades satellites to detect slow moving landslides and quantify the effect of earthquakes on the landslide motion we process multi temporal pleiades images acquired in march april and july 2013 over an area of 210 km2 in the colca valley south peru to obtain two digital elevation models dem and three displacement fields of the area the processed dems have an uncertainty of 0 6 m 1 an order of magnitude better than two global and freely available dems gdem v2 and srtm whereas the displacement fields have an uncertainty of between 0 11 and 0 18 m 1 in both horizontal directions using these data we detect 9 slow moving landslides and compare their velocities during the march april and april july periods we find that landslide velocities are highest during the wet season which suggests a strong groundwater control and we also highlight a landslide acceleration caused by a regional mw 6 0 earthquake the major parameters controlling the acceleration of the slow moving landslides are the rock type and the distance to the source suggesting that friction at the basal interface in the weeks after the earthquake is dependent on the shaking intensity

interseismic coupling and seismic potential along the central andes subduction zone we use about two decades of geodetic measurements to characterize interseismic strain build up along the central andes subduction zone from lima peru to antofagasta chile these measurements are modeled assuming a 3 plate model nazca andean sliver and south america craton and spatially varying interseismic coupling isc on the nazca megathrust interface we also determine slip models of the 1996 m w 7 7 nazca the 2001 m w 8 4 arequipa the 2007 m w 8 0 pisco and the m w 7 7 tocopilla earthquakes we find that the data require a highly heterogeneous isc pattern and that overall areas with large seismic slip coincide with areas which remain locked in the interseismic period with high isc offshore lima where the isc is high a m w 8 6 8 8 earthquake occurred in 1746 this area ruptured again in a sequence of four m w 8 0 earthquakes in 1940 1966 1974 and 2007 but these events released only a small fraction of the elastic strain which has built up since 1746 so that enough elastic strain might be available there to generate a m w 8 5 earthquake the region where the nazca ridge subducts appears to be mostly creeping aseismically in the interseismic period low isc and seems to act as a permanent barrier as no large earthquake ruptured through it in the last 500 years in southern peru isc is relatively high and the deficit of moment accumulated since the m w 8 8 earthquake of 1868 is equivalent to a magnitude m w 8 4 earthquake two asperities separated by a subtle aseismic creeping patch are revealed there this aseismic patch may arrest some rupture as happened during the 2001 arequipa earthquake but the larger earthquakes of 1604 and 1868 were able to rupture through it in northern chile isc is very high and the rupture of the 2007 tocopilla earthquake has released only 4 of the elastic strain that has accumulated since 1877 the deficit of moment which has accumulated there is equivalent to a magnitude m w 8 7 earthquake this study thus provides elements to assess the location size and magnitude of future large megathurst earthquakes in the central andes subduction zone caveats of this study are that interseismic strain of the forearc is assumed time invariant and entirely elastic also a major source of uncertainty is due to fact that the available data place very little constraints on interseismic coupling at shallow depth near the trench except offshore lima where sea bottom geodetic measurements have been collected suggesting strong coupling

lithologic and structural controls on natural fracture distribution and behavior within the lisburne group northeastern brooks range and north slope subsurface alaska the carboniferous lisburne group of northern alaska has been deformed into a variety of map scale structures in both compressional and extensional structural settings thus providing a series of natural experiments for observing the formation distribution and behavior of fractures in this thick carbonate unit two fracture sets dominate the lisburne group carbonates of the north slope subsurface and the nearby northeastern brooks range fold and thrust belt north northwest striking regional extension fractures probably formed in front of the northeastern brooks range fold and thrust belt in the north slope subsurface this fracture set overprints east northeast striking fractures related to earlier extensional deformation in contrast in the fold and thrust belt the north northwest striking fracture set is overprinted by younger east northeast striking fractures related to subsequent contractional deformation lithology is the primary control on the fracture density of both sets in mildly deformed lisburne copyright 1997 the american association of petroleum geologists all rights reserved 1manuscript received february 20 1996 revised manuscript received november 25 1996 final acceptance june 5 1997 2geophysical institute university of alaska fairbanks fairbanks alaska 99775 3sandia national laboratories ms 0705 albuquerque new mexico 87185 4department of petroleum natural gas engineering new mexico institute of mining technology socorro new mexico 87801 and sandla national laboratories ms 0705 albuquerque new mexico 87185 this study was supported by a department of energy subcontract administered by sandia national laboratories additional support was provided by arco alaska bp alaska chevron exxon mobil and japan national oil company we would like to thank arco alaska and bp alaska for giving us permission to view selected lisburne group cores w wallace for helpful discussions on deformational styles of detachment folds a j mansure for help in interpreting the interference tests and w wallace k biddle w belfield n hurley and j kelley for helpful reviews of the manuscript

geological and mechanical study of argillaceous north sea chalk implications for the characterisation of fractured reservoirs abstract argillaceous chalk intervals from the north sea are characterised by matrix permeabilities lower than 0 2 md and therefore they are defined as tight chalks hence fracture networks within these chalks are of major importance to predict fluid flow and reservoir or seal behaviour this study aims to understand the geological parameters controlling the chalk petrophysical and mechanical properties using the outcrop analogue of the cenomanian chalk at cap blanc nez northern france sedimentological petrographic and petrophysical analyses were performed and show that the combination of the depositional environment and diagenetic imprint control the microtexture non carbonate content is ranging from 5 to 40 within the studied samples and is critical for the diagenetic imprint the fracture behaviour of the chalk was studied using a mechanical stratigraphy approach throughout the 70 m thick succession where a transition between lower cenomanian argillaceous chalk and middle upper cenomanian pure chalk is exposed twenty two mechanical units are distinguished and the amount of fractures crosscutting initiating and terminating on mechanical interfaces quantified manual scanlines show that fracture spacing ranges from 17 to 232 cm mechanical interfaces are associated with lithological heterogeneities with strong microtextural contrasts related to the non carbonate content and or degree of cementation the mechanical units are thus defined either by deposition or diagenesis the fracturing behaviour of about 10 m homogeneous pure chalk interval units defined as dfz densely fractured zones differs significantly from the rest of the succession large sigmoidal shaped fractures are confined to those intervals and a dense fracture network developed because of their plastic behaviour clay layers are able to accommodate part of the stress whereas homogeneous pure chalk show a more brittle behaviour

detailed measurement of the magnitude and orientation of thermal gradients in lined boreholes for characterizing groundwater flow in fractured rock summary recent developments have led to revitalization of the use of temperature logging for characterizing flow through fractured rock the sealing of boreholes using water filled flexible impermeable liners prevents vertical cross connection between fractures intersecting the hole and establishes a static water column with a temperature stratification that mimics that in the surrounding formation measurement of the temperature profile of the lined hole water column using a high sensitivity single point probe achieving resolution on the order of 0 001 c has identified fractures with active flow under ambient groundwater conditions without cross connecting flow along the borehole detection of flow in fractures was further improved with the use of a heater to create thermal disequilibrium in the active line source als technique and eliminate normal depth limitations in the process this paper presents another advancement detailed measurement of the magnitude and direction of the thermal gradient to characterize flow through fractured rock the temperature within the water column is measured along the length of the lined hole using a temperature vector probe tvp four high sensitivity sensors arranged in a tetrahedral pattern oriented using three directional magnetometers based on these data the horizontal and vertical components of the thermal field as well as the direction of temperature gradient are determined typically at depth intervals of less than 0 01 m this probe was assessed and refined by trials in over 30 lined boreholes the results from two holes through a fractured dolostone aquifer in guelph ontario are used as exampled since no other device exists for measuring flow magnitude and direction under the ambient flow condition created by lined holes the performance of the tvp is assessed by examining the reproducibility of the temperature measurements through an als test and by the consistency of the results relative to other types of larger scale information from the study area temperature profiles were measured in lined holes under both ambient thermal conditions and subject to als heating of the entire length of the holes to demonstrate resolution and reproducibility the hydraulic gradient in three dimensional space based on pressure measurements from three depth discrete multilevel monitoring systems in nearby holes was used to independently estimate variations in groundwater flow directions the characteristics of the hydraulic and thermal regimes are compared to assess response to changes in flow in a fractured rock system when used in the lined holes the level of detail provided by this multi sensor probe is much greater than that provided by a single sensor probe and this detail strongly supports inferences concerning the relative magnitude and direction of the flow the results of this study indicate that the details of the thermal gradient can be measured and provides superior results compared to a conventional one dimensional temperature profile thereby substantially enhancing the characterization of groundwater flow in fractured rock

deformation due to the 17 august 1999 izmit turkey earthquake measured from spot images the geometry of the ruptured areas and the coseismic slip distribution data are key to highlighting the behavior of seismic faults this information is generally retrieved from field investigations and geodetic measurements or synthetic aperture radar sar interferometry here we show that spot images can also be used to accurately map the fault zone and to determine the slip distribution by subpixel correlation of images acquired before and after an earthquake the measured slip includes the contribution of possible distributed shear that might not be clearly expressed in surface ruptures and smoothes out possible along strike variability due to near surface fault complexities we apply the technique to the m s 7 4 1999 izmit earthquake our results reveal a 100 m wide and very linear fault zone that can be traced for 70 km from golcuk to akyazi along which supershear rupture has been inferred the obtained slip distribution compares well with the field measurements and is consistent with ground deformation measured at some distance from the fault zone using sar images very little deformation was accommodated off the main fault plane maximum slip is observed near sapanca lake at a small fault jog that has probably influenced rupture propagation

landslide movement in southwest colorado triggered by atmospheric tides the slumgullion landslide in the western united states has been moving almost continuously for over 100 years observations and numerical modelling show that air pressure changes from atmospheric tides trigger daily movement

influence of typhoons and earthquakes on rainfall induced landslides and suspended sediments discharge abstract the aim of this paper is to present data on the occurrence of landslides triggered by typhoon and earthquake events and to discuss the basic earthquake triggering mechanisms involved four events of typhoon and earthquake triggered landslides in the chenyoulan river catchment of central taiwan during 1996 to 2004 were studied in order to identify their controlling factors the landslides areas were measured by comparing aerial photos taken over the past 18 years and sediment discharge was counted at hydrometric stations investigation results demonstrate that hillslope geomaterials that had been disturbed by strong seismic shaking induced expansion of landslide areas during subsequent events analysis of normalized difference vegetation index ndvi also registered the changes of uncovered conditions on the hillslope caused by landsliding when flow discharge is lower than 100 m 3 s 1 post seismic sediment concentration is roughly four times higher than pre seismic concentration with the same flow discharge this fate indicates that the amount of sediment discharge at normal flow discharge is affected by supplied sediment volume which tends to increase with seismic activity

analysis of large seismically induced gravitational deformations imaged by high resolution cosmo skymed synthetic aperture radar using differential synthetic aperture radar interferometry dinsar on cosmo skymed constellation of small satellites for the mediterranean basin observation data we obtain an accurate and spatially continuous measure of the coseismic ground displacement due to the mw 6 3 l9aquila central italy earthquake we identify two local deformation patterns associated with long term gravitational mass movements and interpret the deformation mechanisms by integrating geological analysis and simple analytical modeling these subtle deformations the role of which in landscape evolution and earthquake induced hazard needs to be fully assessed may only be identified using high resolution dinsar

inversion of deformation fields time series from optical images and application to the long term kinematics of slow moving landslides in peru abstract slow moving landslides are numerous in mountainous areas and pose a large threat to populations many observations show that their kinematics is driven by climatic forcings and earthquakes in this study we document the complex interaction between those two forcings on the slow moving landslide kinematics based on the retrieval of landslide displacements over 28 years using optical satellite images to overcome the decorrelation effect over this large time span and possible misalignment between images we develop a method that uses the redundancy of displacement fields from image pairs to derive a robust time series of displacement the method is tested on the 28 year long spot1 5 pleiades archive over an area in peru affected by both earthquakes and rainfall errors are estimated on stable areas and by comparison with one 13 year long and eleven 3 year long gps time series on the maca landslide the methodology diminishes by up to 30 the uncertainty and reduces significantly the gaps due to decorrelation the data set allows detecting 3 major landslides moving at a rate of 35 to 50 m over 28 years and smaller landslides with lower displacement rates time series obtained over the three main landslides provide interesting results of their long term kinematics primarily driven by precipitation we propose simple statistical hydro kinematic models relating yearly motion to seasonal rainfall to explain the observed time series we found that annual precipitation is controlling the landslide displacements after a certain rainfall threshold is reached besides this control we show the possible impact of a local mw 5 4 earthquake in 1991 on the kinematics of the maca landslide our results suggest that the earthquake accelerated the landslide and has an effect during several years on the precipitation threshold required for triggering a motion these results suggest that the rainfall threshold can vary in time following strong earthquakes shaking

vein spacing in extending layered rock the effect of synkinematic cementation cemented fractures veins commonly show mm scale spacing even in layerbound arrangements in beds of cm to dm scale thickness the relief of tension around such layerbound fractures should preclude nearby fracture propagation and result in cm to dm scale fracture spacing we hypothesize that cement precipitated during vein opening could re establish tension across veins and lessen the effects of relieved tension thus decreasing fracture spacing we test this hypothesis using a computer based numerical model the model consists of a 2d triangular lattice of nodes connected by elastic springs the lattice is stretched by holding the left boundary stationary and moving the right boundary to the right at constant velocity the lattice consists of three layers springs within the middle fracturing layer fail upon stretching past a given critical length springs within the upper and lower matrix layers are indestructible we tune the model parameters to produce the familiar regular spacing of barren fractures joints then we perturb this system by adding cement within fractures as the fractures propagate and widen cementation is simulated by extending failed springs across the space between the nodes on which they are rooted and re attaching springs once they reach across re attached springs are assigned a new neutral length equal to their current length on re attachment the primary effect of cementation is to make fractures narrower and more closely spaced thus the model highlights the resistance to fracture widening by cement as a potential reason why veins can be more closely spaced than joints individual fractures open and seal multiple times when the stiffness of cemented springs is lower than that of the host rock springs suggesting that natural crack seal vein opening is associated with persistent mechanical weakness at extant fractures modeled veins are more irregularly spaced than modeled joints but the vein patterns remain more regularly spaced than would be expected for a random arrangement therefore the model does not explain systematic clustering of natural veins

dual porosity fractured miocene syn rift dolomite reservoir in the issaran field gulf of suez egypt a case history of the zonal isolation of highly fractured water carrier bed

rate weakening friction characterizes both slow sliding and catastrophic failure of landslides abstract catastrophic landslides cause billions of dollars in damages and claim thousands of lives annually whereas slow moving landslides with negligible inertia dominate sediment transport on many weathered hillslopes surprisingly both failure modes are displayed by nearby landslides and individual landslides in different years subjected to almost identical environmental conditions such observations have motivated the search for mechanisms that can cause slow moving landslides to transition via runaway acceleration to catastrophic failure a similarly diverse range of sliding behavior including earthquakes and slow slip events occurs along tectonic faults our understanding of these phenomena has benefitted from mechanical treatments that rely upon key ingredients that are notably absent from previous landslide descriptions here we describe landslide motion using a rate and state dependent frictional model that incorporates a nonlocal stress balance to account for the elastic response to gradients in slip our idealized one dimensional model reproduces both the displacement patterns observed in slow moving landslides and the acceleration toward failure exhibited by catastrophic events catastrophic failure occurs only when the slip surface is characterized by rate weakening friction and its lateral dimensions exceed a critical nucleation length h h that is shorter for higher effective stresses however landslides that are extensive enough to fall within this regime can nevertheless slide slowly for months or years before catastrophic failure our results suggest that the diversity of slip behavior observed during landslides can be described with a single model adapted from standard fault mechanics treatments

spacing and distribution of bed perpendicular joints throughout layered shallow marine carbonates granada basin southern spain abstract this contribution focuses on the controls exerted by sedimentological petrographic and mechanical rock properties on the distribution of bed perpendicular joints throughout layered carbonates the study was conducted on tortonian shallow marine skeletal grainstones and rudstones cropping out in the granada basin southern spain the results of combined field and laboratory analyses are consistent with the rock grain size of the studied carbonates exerting a key control on distribution of the bed perpendicular joints a positive correlation between joint spacing and mechanical unit thickness is computed for the grainstones whereas joints are almost absent in rudstones the rock grain size affected the diagenetic processes such as cementation and dissolution and therefore the resulting porosity and uniaxial compressive strength ucs values quantitative data show that higher ucs values are commonly associated with greater calcite amounts lower values of porosity and finer grain sizes and hence denser bed perpendicular joint sets in conclusion this study documents that it is possible to infer the density of bed perpendicular joints in layered carbonates based on the sedimentological petrographic and mechanical parameters considering the impact that this type of joints has on subsurface fluid flow the acquired knowledge can help the management of geofluids as well as the overall prediction of carbonate reservoir quality

fracture characterization in tight carbonates an example from the ozark plateau arkansas outcrop studies of fracture development used as analogs for subsurface fracture patterns are critical because of the importance of fractures as fluid flow pathways and the fact that most fracture networks exist at a smaller resolution than current seismic data can resolve fracture networks in carbonate units are typically controlled by the mechanical properties of the unit indicating that the mechanical stratigraphy as well as the fracture stratigraphy should be considered this study presents the results of a fracture analysis in the mississippian carbonates of the ozark plateau considering both mechanical and fracture network characteristics mechanical characteristics of the succession were defined using a combination of rebound values and thin section petrography fracture characteristics included orientation and intensity together with abutting relationships results indicate that fracture orientations show a distinct evolution throughout the measured succession including the appearance of early systematic sets followed by pervasive systematic fracture sets related to existing basement features fracture orientation changes do not correspond to changes in mechanical stratigraphy fracture intensity however is related to the thickness of the mechanical unit instead of the bed thickness and is greatest in less competent units mechanical control influences the fracture network on a smaller scale than that of regional tectonic stresses thus evaluations of carbonate reservoirs must account for both the large scale and the small scale investigations into fracture characteristic controls outcrop evaluations are of critical importance to properly assess characteristics that are challenging to recover from conventional subsurface data sets such as core and seismic reflection volumes

deriving large scale glacier velocities from a complete satellite archive application to the pamir karakoram himalaya mountain glaciers are pertinent indicators of climate change and their dynamics in particular surface velocity change is an essential climate variable in order to retrieve the climatic signature from surface velocity large scale study of temporal trends spanning multiple decades is required satellite image feature tracking has been successfully used to derive mountain glacier surface velocities but most studies rely on manually selected pairs of images which is not adequate for large datasets in this paper we propose a processing strategy to exploit complete satellite archives in a semi automated way in order to derive robust and spatially complete glacier velocities and their uncertainties on a large spatial scale in this approach all available pairs within a defined time span are analysed preprocessed to improve image quality and features are tracked to produce a velocity stack the final velocity is obtained by selecting measures from the stack with the statistically higher level of confidence this approach allows to compute statistical uncertainty level associated with each measured image pixel this strategy is applied to 1536 pairs of landsat 5 and 7 images covering the 3000 km long pamir karakoram himalaya range for the period of 1999 2001 to produce glacier annual velocity fields we obtain a velocity estimate for 76 000 km2 or 92 of the glacierized areas of this region we then discuss the impact of coregistration errors and variability of glacier flow on the final velocity the median 95 confidence interval ranges from 2 0 m year on the average in stable areas and 4 4 m year on the average over glaciers with variability related to data density surface conditions and strain rate these performances highlight the benefits of processing of a complete satellite archive to produce glacier velocity fields and to analyse glacier dynamics at regional scales

combined observations of rock mass movements using satellite sar interferometry differential gps airborne digital photogrammetry and airborne photography interpretation 1 recent global warming through the related retreat of mountain glaciers causes a growing number of different slope instabilities requiring accurate and cost effective monitoring we investigate the potential of combined remote sensing observations from satellite and airborne microwave and optical sensors for an efficient survey of mountainous ground displacements the evolution of a paraglacial deep seated rock mass movement due to glacier retreat in the swiss alps has been observed between 1976 and 2008 with satellite synthetic aperture radar sar interferometry differential gps and airborne digital photogrammetry analysis of differential sar interferograms revealed an acceleration of the landslide from 4 cm yr in the slope parallel direction during the mid 1990s to more than 30 cm yr in the summer of 2008 differential gps surveys performed between the summers of 2007 and 2008 indicate seasonal variations of the landslide activity the photogrammetric analysis revealed no significant movement i e 1 cm yr between 1976 and 1995 and provides an overview of the total displacement between 1995 and 2006 with high spatial resolution in situ and airborne photography interpretation suggests that the landslide was activated at earliest by the end of the last glaciation but without any significant long lasting activity during the holocene and that the exponentially increasing reactivation since the 1990s is the result of ongoing debutressing of the valley flank due to the glacier retreat in combination with strong precipitation and snowmelt events we conclude that the employed remote sensing techniques complement each other well within a landslide hazard assessment procedure

geochronologic and stratigraphic constraints on canyon incision and miocene uplift of the central andes in peru the deepest valleys of the andes have been cut in southern peru by the rios cotahuasi ocona and colca majes these canyons are late miocene landforms based on a new ignimbrite stratigraphy supported by 42 new 40ar 39ar age determinations obtained on plateau forming and valley filling ignimbrites between 19 and 13 ma a gently sloping surface bevelling the clastic wedge southeast of the developing mountain front was mantled by widespread ignimbrites after 13 ma this paleosurface was tilted up from 2 2 km a s l at the mountain front to 4 3 km a s l at the base of the pliocene and pleistocene volcanoes that crown the southwestern edge of the altiplano the canyons incised this topography after 9 ma while the dated base of younger ignimbrite valley fills suggests that these canyons had been cut down to near their present depths as early as 3 8 ma by 1 4 ma however the canyons had been almost completely refilled by 1 3 km thick unwelded pyroclastic deposits which were subsequently eroded valley incision since 9 ma at an average rate of 0 2 mm yr 1 is the response to topographic uplift after 13 ma combined with increasing runoff due to a wetter climate recorded after 7 ma although long term aridity generated an imbalance between high long term uplift rates and low plateau denudation rates the combination of aridity and volcanism still promoted canyon incision because episodic volcanic fills maintained a cycle of catastrophic debris avalanches and subsequent dam breakouts

fracture characteristics in cretaceous platform and overlying ramp carbonates an outcrop study from maiella mountain central italy abstract this article focuses on field and laboratory based characterization of vertically persistent fractures that are part of oblique slip normal fault zones and crosscut the cretaceous platform and overlaying ramp carbonates outcropping at maiella mountain central italy the achieved results show that i fault damage zones are wider and more densely fractured in the platform carbonates than in the ramp ones ii joints and sheared joints composing the fault damage zones are taller better connected and less spaced within the former rocks than in the ramp carbonates the aforementioned structural differences are interpreted to be a consequence of the different mechanical properties of the platform and ramp carbonates during failure at maiella mountain platform carbonates are indeed made up of overall stiffer higher uniaxial compressive strength values and less porous rocks due to more abundant intergranular void filling cement and presence of matrix in terms of hydrocarbon flow and recovery geometric and dimensional attributes of fractures suggest that the well connected network of closely spaced fractures cutting across the platform carbonates may form efficient pathways for both vertical and horizontal hydrocarbon flow in contrast the relatively poorly connected and low density fracture network affecting the ramp carbonates is likely less efficient in providing fairways for flowing hydrocarbons

assessing the flow regime in a contaminated fractured and karstic dolostone aquifer supplying municipal water the silurian dolostone bedrock in ontario canada is a broad 400 km long swath northward from niagara falls through the bruce peninsula that represents an important water source for municipal industrial and agricultural uses where the quaternary overburden is thin or absent karst is common this study concerns an urban area where the dolostone aquifer is 100 m thick beneath up to 50 m thick quaternary deposits and where karst features identified by borehole information are common hydraulic tests show moderate to large bulk rock hydraulic conductivity and rock core tests indicate much smaller matrix hydraulic conductivity than the bulk rock values therefore the aquifer is essentially a dual permeability fully saturated system in which conduits occur within a network of ubiquitous extensive horizontally and vertically interconnected fractures karst features are concentrated in a thin zone at the top of rock likely representing former epikarst and also in a thicker zone in the middle of the aquifer some pumping test results and large yields of some municipal wells are consistent with conduit occurrences however atmospheric tritium distributed source contamination cl view the mathml source and a point source pesticide plume metolachlor show detailed concentration distributions lacking influence of flow in conduits detailed hydraulic head profiles also show no influence of conduit flow this study shows that when designing monitoring networks for groundwater quality and source water protection in similar contexts locating conduits is not necessary because contaminant distributions are governed by the combined influences of the rock matrix fractures and conduits the hydraulic boundary conditions and the interconnected fracture network with only minimal conduit effects prior to glaciations an integrated karstic aquifer could develop with flow controlled by conduits however this original converging flow system became non functional when the quaternary sediments drastically modified the boundary hydrologic conditions and the head distribution

surface motion of mountain glaciers derived from satellite optical imagery a complete and detailed map of the ice velocity field on mountain glaciers is obtained by cross correlating spot5 optical images this approach offers an alternative to sar interferometry because no present or planned radar satellite mission provides data with a temporal separation short enough to derive the displacements of glaciers the methodology presented in this study does not require ground control points gcps the key step is a precise relative orientation of the two images obtained by adjusting the stereo model of one slave image assuming that the other master image is well georeferenced it is performed with numerous precisely located homologous points extracted automatically the strong ablation occurring during summer time on the glaciers requires a correction to obtain unbiased displacements the accuracy of our measurement is assessed based on a comparison with nearly simultaneous differential gps surveys performed on two glaciers of the mont blanc area alps if the images have similar incidence angles and correlate well the accuracy is on the order of 0 5 m or 1 5 of the pixel size similar results are also obtained without gcps an acceleration event observed in early august for the mer de glace glacier is interpreted in term of an increase in basal sliding our methodology applied to spot5 images can potentially be used to derive the displacements of the earth s surface caused by landslides earthquakes and volcanoes

stratigraphic controls on vertical fracture patterns in silurian dolomite northeastern wisconsin vertical opening mode fractures are mapped on quarry walls to assess the stratigraphic controls on fracture patterns in the relatively undeformed silurian dolomite of northeastern wisconsin our two stage study uses maps of vertical fractures to assess the effectiveness of various types of stratigraphic horizons e g organic partings or cycle bounding mud horizons in terminating opening mode fractures first the mechanical stratigraphy of the exposures is interpreted from the observed fracture pattern both visual inspection and a newly developed quantitative method are employed to identify effective mechanical interfaces the two methods show similar results confirming the validity of qualitative visual inspection the second stage of our study stochastically predicts mechanical stratigraphy and subsequent fracture pattern from empirical relationships between the observed sedimentary stratigraphy and the interpreted mechanical stratigraphy for example 63 of cycle bounding mud horizons within the inner middle and middle shelf facies associations serve as mechanical interfaces these empirical percentages are input to a monte carlo analysis of 50 stochastic realizations of mechanical stratigraphy comparisons of the stochastically predicted and interpreted mechanical stratigraphy yield errors ranging from 13 to 33 this method yields far better results than assuming that all stratigraphic horizons act as mechanical interfaces the methodology presented in this article demonstrates an improved prediction of fracture pattern within relatively undeformed strata from both complete characterization of sedimentary stratigraphy and understanding mechanical controls on fracturing

structural and statistical characterization of joints and multi scale faults in an alternating sandstone and shale turbidite sequence at the santa susana field laboratory implications for their effects on groundwater flow and contaminant transport abstract this paper describes the properties of faults and fractures in the upper cretaceous chatsworth formation exposed at santa susana field laboratory and its surroundings simi hills california where groundwater flow and contamination have been studied for over three decades the complex depositional architecture of this turbidite consisting of alternating sandstones and shales interacting with formative stress conditions are responsible for multi scale fault hierarchies and permeable fractures in which nearly all groundwater flow occurs intensity and distribution of background fractures and their relation to bedding thickness are established for sandstones the dominant lithology the architecture of faults with increasing displacement is described and relationships among fault dimensional parameters captured data from 400 boreholes and piezometers reveal the effect of faults and fractures on groundwater flow large hydraulic head differences observed across fault zones with shale rich cores indicate these structures as cross flow barriers moreover hydraulic head profiles under ambient conditions and pumping tests suggest strong hydraulic connectivity in all directions to depth of hundreds of meters this outcrop based structural characterization relates the horizontal hydraulic conductivity to the observed well connected fracture network and explains the strong vertical connectivity across low hydraulic conductivity shales as faults and sheared fractures provide flow pathways

relating background fractures to diagenesis and rock physical properties in a platform slope transect example of the maiella mountain central italy abstract fractured reservoirs are of prime interest as fracture networks control most of the fluid flow and or accumulation however characterizing 3d fracture patterns from subsurface data remains challenging studying fractures on outcrops is a good substitution to 1d data from subsurface exploration tools in addition outcrops allow deciphering the nature origin and conditions for fracture formation through the geodynamic history in this paper we aim at characterizing the true 3d fracture patterns and determining the genetic role of facies diagenesis and rock physical properties we targeted a platform slope transect within a carbonate reservoir analog the maiella mountain in central italy where implications for analog hydrocarbon reservoir can be discussed fracture patterns are sorted based on geometric and kinematic criteria from field measurements and petrographic analyzes on thin sections sedimentary facies pore types and rock physical properties have been characterized in order to establish the impact of early diagenesis on rock evolution diagenetic sequences have been unraveled and correlated to the fractures fracture sequences have been determined considering the cross cutting relationships and compared with burial uplift history in the two studied formations platform and slope carbonates we interpret a stage of fracturing perpendicular to bedding formed at shallow depth and occurring prior to major regional tectonic events the studied carbonates have undergone early diagenesis during fast and shallow burial conferring early brittle behavior the amount of stylolites is not correlated to burial depth but to fracture density porosity and free air p wave velocity it means that fracture development mechanical and petrophysical properties are acquired during early diagenesis both studied formations have undergone the same geodynamic history and their brittle response is different and not related to folding but to burial and early cementation deciphering the close relationship between sedimentary facies diagenetic and geodynamic history has allowed unraveling the controling factors on rock properties and therefore on fracture pattern

characterizing carbonate reservoir fracturing from borehole data a case study of the visean in northern belgium abstract fractured carbonate rocks are widely used as hydrocarbon or geothermal reservoirs to provide a better understanding of the distribution and characteristics of such fractures a general workflow will be presented for the characterization of fracturing from borehole data by exploration and statistical analyses of integrated datasets in a case study of visean limestones in a belgian borehole both cores and geophysical well logs were used to investigate which factors control the characteristics of partially open veins which contribute to permeability relationships between multiple variables were tested statistically lithology geochemistry and geophysical well log values were taken into account as well as quantified veins vugs and stylolites from cores although natural joint frequencies appeared hard to quantify from the available data partially open vein characteristics could be well quantified the results show that differential compaction controlled the development of fractures fracturing occurred preferentially in massive reefal buildup boundstones in contrast to layered wacke to grainstones layer parallel slip along bedding surfaces could also have reduced fracture development in the latter limestones frequencies of cemented veins and partially open veins are positively correlated which suggests that the partially open veins result from either re opening by dissolution or re opening due to a later fracturation phase in summary this multi source study provides a workflow for fracture characterization from boreholes as well as insights into the factors controlling the distribution and characteristics of partially open veins which enhance reservoir permeability

lacunarity analysis of fracture networks evidence for scale dependent clustering abstract previous studies on fracture networks have shown that fractures contained within distinct mechanical units stratabound are regularly spaced while those that terminate within the rock mass are clustered non stratabound lacunarity is a parameter which can quantify the distribution of spaces between rock fractures when normalized to account for differences in fracture abundance lacunarity characterizes the distribution of spaces as the degree of clustering in the fracture network normalized lacunarity curves l r computed using the gliding box algorithm and plotted as a function of box size r were constructed for natural fracture patterns from telpyn point wales and the hornelen basin norway the results from analysis of the telpyn point fractures indicate that such curves are sensitive to differences in the clustering of different fracture sets at the same scale for fracture networks mapped at different scales from the hornelen basin our analysis shows that clustering increases with decreasing spatial scale this trend is attributed to the transition from a stratabound system at the scale of sedimentary cycles 100 200 m that act as distinct mechanical units to a non stratabound fracture system geometry at the finer 10 s of meters thick bedding scale

horizontal coseismic deformation of the 2003 bam iran earthquake measured from spot 5 thr satellite imagery 1 on 26 december 2003 a destructive mw 6 5 earthquake occurred in kerman province iran killing more than 30 000 people around the ancient city of bam we map the fault zone and determine the slip distribution using sub pixel correlation of images taken by the spot 5 thr sensor before and after the main shock our results show that the surface displacement occurred on a blind fault oriented n174 and located south of bam a 15 km along strike profile depicts a distribution with a maximum displacement of 1 2 0 15 m near the centre of the fault the mean slip that we infer 0 77 0 05 m is much higher than the ground displacement measured in the field 0 2 m we suggest that field measured displacements are underestimated due to slip accommodation within an 500 m wide shear zone furthermore we demonstrate for the first time the relevancy of 2 5 m spot 5 thr images for sub pixel ground displacement measurements

fracture development and mechanical stratigraphy of austin chalk texas the mechanical stratigraphy of the upper cretaceous austin chalk is established from study of fracture intensity along its outcrop trend from dallas to san antonio and westward to langtry texas and in the subsurface from study of cores and or fracture identification logs from 30 wells three mechanical stratigraphic units are recognized 1 an upper fractured massive chalk corresponding to the big house chalk member 2 a middle ductile chalk marl corresponding to the dessau chalk and burditt marl members and 3 a lower fractured massive chalk corresponding to the atco chalk member representative samples from the three mechanical stratigraphic units were experimentally shortened dry at 10 17 34 and 70 mpa confining pressure at 24 c and at a strain rate of 2 5 10 4 sec 1 to determine if the relative mechanical behavior observed at the surface could be extrapolated into the subsurface at different simulated burial depths the experimentally determined ductilities parallel those determined from outcrop and subsurface studies multiple linear regression analysis indicates that porosity is most strongly correlated with fracture strength smectite content has the second strongest correlation for low porosity specimens 9 13 5 the strength of specimens with 4 smectite is reduced 30 42 compared to specimens with no smectite the coefficient of internal friction at 17 mpa confining pressure decreases from 1 66 to 0 61 as smectite content increases from 0 to 4 sem photomicrographs of undeformed specimens show that smectite and other clays are distributed as large 30 m discrete amorphous concentrated masses throughout the chalk they are comminuted along the induced fracture surfaces where their grain size is 0 5 m or less these observations suggest that smectite acts as a soft inclusion localizing shear failure and correspondingly weakening the material

clay slides in the malselv valley northern norway characteristics occurrence and triggering mechanisms abstract the distribution of a large number of clay slides in the malselv valley northern norway is analysed and put into context with the stratigraphic organization of the valley fill sediments about 32 of the landslides larger than 104 m3 occur close to the valley margins where mud is either exposed or at shallow depth about 57 of the landslides occur mid valley where relatively thin arcuate shaped bottleneck landslide scars ranging from c 104 to 107 m3 in size is the dominant morphological signature of the slides typical for quick clay slides or earth flows involving fluid mud their most common triggering mechanism is probably erosion at the toe slopes by the river malselv or its tributaries river erosion close to the valley margin where glaciomarine and marine sediments are present seems to give the most severe slides the overall valley fill organization controls the distribution of clay slides which may apply to other fjord valleys having similar sediment distribution

geophysical investigation of a large landslide in glaciolacustrine clays in the trieves area french alps abstract slope movements in clay deposits are spread all over the world and result from complex deformation processes including internal strains in the landslide body and slipping along rupture surfaces such mass movements are likely to generate changes in the geophysical parameters characterizing the ground which can be used to map the landslide body in the last decade geophysical techniques have been increasingly used for landslide investigation purposes however the success of any geophysical technique is overall controlled by the existence of a geophysical contrast differentiating the body to be mapped for landslides affecting thick clay materials from soft clay to shale or marl electrical and seismic techniques have been mainly applied in the past in this study we attempt to physically characterize the deformation within a large slide avignonet affecting laminated clays which were deposited in a glacially dammed lake during the wurm period clay deposits which cover an area of 300 km2 south of grenoble french alps and have a maximum thickness of 200 m overlay compact alluvial layers and marly limestone of mesozoic age piezometric data at avignonet show that the water table is very shallow implying that the slide developed in saturated clay several seismic and electrical profiles were performed in order to tentatively correlate the variations of p wave vp velocity s wave velocity vs and electrical resistivity with geotechnical data and morphological observations in such saturated and fine material it turned out that only the s wave velocity exhibits significant variations with the displacement rates and the morphological features vs values at shallow depth were found to be inversely correlated with displacement rates measured by gps with a division by at least a factor of 2 between the zones unaffected and strongly deformed by the landslide these results suggest that vs mapping could provide valuable information on the deformation state of the clay material and that the evolution of vs with time could be used as an indicator for characterizing the landslide activity in the subsurface including the evolution into a flow

patterns of movement in rotational and translational landslides the movement of rotational and translational landslides occurs as a result of either sliding on discrete shear surfaces or ductile deformation within a shear zone in this paper we examine the movement histories of a number of landslides that occurred in a variety of materials in a range of settings and demonstrate that one of two movement styles is evident during accelerating phases for all landslides observed the first style which has previously been noted has a linear form in a plot of 1 v against time v is velocity the second style has an asymptotic form in the same plot trending toward steady state movement rates we propose that the linear form occurs in landslides in which crack propagation i e shear surface generation is the dominant process whereas the second style occurs where movement is taking place across existing planes of weakness or as a result of ductile deformation processes this study demonstrates that the evaluation of plots of 1 v against time for landslides is a useful technique for forecasting movement styles and rates and for interpreting ongoing deformation processes in real time

historic drought puts the brakes on earthflows in northern california california s ongoing unprecedented drought is having profound impacts on the state s resources here we assess its impact on 98 deep seated slow moving landslides in northern california we used aerial photograph analysis satellite interferometry and satellite pixel tracking to measure earthflow velocities spanning 1944 2015 and compared these trends with the palmer drought severity index a proxy for soil moisture and pore pressure that governs landslide motion we find that earthflow velocities reached a historical low in the 2012 2015 drought but that their deceleration began at the turn of the century in response to a longer term moisture deficit our analysis implies depth dependent sensitivity of earthflows to climate forcing with thicker earthflows reflecting longer term climate trends and thinner earthflows exhibiting less systematic velocity variations these findings have implications for mechanical hydrologic interactions that link landslide movement with climate change as well as sediment delivery in the region

a view on some hydrological triggering systems in landslides abstract in this paper different types of hydrological triggering systems for debris flows shallow and deeper landslides are described the generation of surface run off and high peak discharges in first order alpine catchments is an important triggering mechanism for debris flows failure conditions in shallow landslides can occur when at a critical depth which is determined by the cohesion of the soil and the slope angle the moisture content in the soil becomes close to saturation resulting in a considerable reduction of soil strength deeper landslides 5 20 m depth are in most cases triggered by positive pore pressures on the slip plane induced by a rising ground water level the assessment of meteorological threshold conditions for shallow landslides 1 2 m needs more detailed meteorological information than for deeper landslides in the analyses of the hydrological triggering systems of deeper landslides the presence of a permeable top layer and fissures has to be taken into consideration

mechanism for joint saturation in mechanically layered rocks an example from southern israel abstract over 700 joint spacings were measured along a 190 m scanline within a single limestone bed of the turonian gerofit formation southern israel by investigating joints belonging to a single systematic set confined to a bed of uniform thickness one can factor out the major influences of bed thickness lithology and mechanical properties on joint set development joint spacing distributions and fracture spacing ratios fsr vary dramatically along the length of the scanline and correlate directly with throughgoing fracture zones belonging to the same tectonic stress regime regions cross cut by fracture zones display narrower median joint spacings fsr of 1 3 and unimodal joint spacing distributions where fracture zones are absent joint spacings have wider medians fsr of 0 8 and multimodal distributions because fracture zones most likely represent areas of high strain and laboratory experiments demonstrate a systematic decrease in fracture spacing with increasing strain regions of the bed cross cut by fracture zones are likely at a more advanced stage of joint set development and hence closer to saturation than other regions joint saturation in the gerofit formation may be achieved by a shift in scale from single layer to multi layer jointing as the development of throughgoing joints prevents the formation of additional bedding confined joints

dynamic depositional and early diagenetic processes in a deep water shelf setting upper cretaceous austin chalk north texas abstract the austin chalk of north texas was deposited on a deep water shelf north of the san marcos platform during a worldwide coniacian and santonian sea level highstand transgressive lowermost lower austin chalk highstand uppermost lower austin chalk and regressive middle and upper austin chalk phases of cyclic chalk and marl sedimentation are recognized in core and outcrop and on log cross sections sedimentary structures in excellent exposures in excavations and tunnels created in ellis county for the superconducting super collider provide new evidence of sediment transport during austin chalk deposition during transgression bottom currents syndepositionally reworked nannoplankton oozes incising channels as much as 120 ft across and 8 ft deep weakly burrowed channel fills having preservation of fine lamination document rapid infilling channel fills are composed of pyritized and carbonized wood and inoceramus lag deposits pellets echinoderm fragments and globigerinid grainstones and coccolith ooze during maximum highstand bottom reworking was suppressed detrital content of highstand marls is low 20 percent organic content is high 1 4 to 3 5 percent coccolith preservation is excellent because of minimal diagenetic alteration regression is marked by resumed channel cutting and storm bed winnowing in the middle and upper austin chalk suppressed resistivity log response and recessive weathering characteristics of the middle austin chalk are not primarily related to depositional environment but rather to increased input of volcanic ash during the accumulation of this interval early stabilization of ash produced clay coated microfabrics in sediments that are otherwise similar to the transgressive deposits

impact of mechanical heterogeneity on joint density in a welded ignimbrite joints are conduits for groundwater hydrocarbons and hydrothermal fluids robust fluid flow models rely on accurate characterisation of joint networks in particular joint density it is generally assumed that the predominant factor controlling joint density in layered stratigraphy is the thickness of the mechanical layer where the joints occur mechanical heterogeneity within the layer is considered a lesser influence on joint formation we analysed the frequency and distribution of joints within a single 12 m thick ignimbrite layer to identify the controls on joint geometry and distribution the observed joint distribution is not related to the thickness of the ignimbrite layer rather joint initiation propagation and termination are controlled by the shape spatial distribution and mechanical properties of fiamme which are present within the ignimbrite the observations and analysis presented here demonstrate that models of joint distribution particularly in thicker layers that do not fully account for mechanical heterogeneity are likely to underestimate joint density the spatial variability of joint distribution and the complex joint geometries that result consequently we recommend that characterisation of a layer s compositional and material properties improves predictions of subsurface joint density in rock layers that are mechanically heterogeneous

morphology structure and kinematics of a rainfall controlled slow moving andean landslide peru the large slow moving landslide of maca is located in the upper colca valley southern peru a region characterized by a well pronounced rainy period and intense and recurrent sustained seismicity the landslide developed in deep lacustrine deposits has recently accelerated threatening the maca village this work aims at understanding the rupture mechanism and the causes of the recent landslide reactivation acceleration we present a multidisciplinary characterization of the maca landslide that includes i geological and morphological mapping in the field ii remote sensing analysis using an historical aerial photograph of 1955 and the pleiades satellite images 2013 iii global positioning system gps including time series of surveys over 13 years and continuous measurements over 14 months iv a geophysical campaign with deep electrical resistivity tomography profiles acquired across the landslide mass our study shows that this 60 mm3 landslide which can be classified as a clay silt compound landslide moved by 15 m between 2001 and 2014 with a large inter annual velocity variation up to a factor of 500 depending on the rainfall intensity we suggest that these dramatic changes in velocity are the result of the combination of a threshold mechanism and the short intense rainy season in peru this study reveals three main driving factors acting at different timescales i over several decades the river course has significantly changed causing the maca landslide reactivation in the 1980s due to the erosion of its toe ii at the year scale a minimum amount of rainfall is required to trigger the motion and this amount controls the landslide velocity iii transient changes in slide velocity may occur anytime due to earthquakes this study particularly highlights the non linear behaviour of the motion with rainfall copyright 2016 john wiley sons ltd

seventeen years of the la clapiere landslide evolution analysed from ortho rectified aerial photographs we present a new method of digital elevation model dem calculation from aerial photographs and apply this method to the la clapiere landslide in the mercantour massif in eastern france the method uses new techniques of image correlation and of restitution of camera parameters the calculated dems are used to ortho rectify three aerial photographs acquired between 1983 and 1999 measurements made from these ortho rectified images show that the average velocity of the landslide was of 1 7 cm day with the rate of the headscarp retreat of 4 1 cm day and the toe of the landslide advancing at 1 7 cm day between 1983 and 1999 within the landslide the velocity field is are relatively homogeneous although their directions are locally heterogeneous scree slopes and scarps develop in an heterogeneous way within the landslide because the headscarp moves faster than the front of the landslide material spreads laterally at the scree slopes and or is eroded at the front of the landslide by the river and or is accumulated within the landslide on a low slope area located above a competent bar called igliere bar d 2002 elsevier science b v all rights reserved

detecting co seismic displacements in glaciated regions an example from the great november 2002 denali earthquake using spot horizontal offsets we use spot image pairs to determine horizontal offsets associated with the mw 7 9 november 2002 denali earthquake in the vicinity of slate creek ak field measurements and aerial photographs are used to further characterize the geometry of the surface rupture aerial photographs show that shear localization occurs where the rupture trace is linear and distributed off fault deformation is common at fault bends and step overs or at geologic contacts between rock glacial sediments and ice the displacement field is generated using a sub pixel cross correlation technique between spot images taken before and after the earthquake we identify the effects of glacier motion in order to isolate the tectonic displacements associated with the denali earthquake the resulting horizontal displacement field shows an along strike variation in dextral shear with a maximum of approximately 7 5 m in the east near 144 52 w which decreases to about 5 m to the west near 145 45 w if the november 2002 earthquake represents the long term behavior of the denali fault it implies a westward decrease in the long term dextral slip rate a possible mechanism to accommodate the westward decreasing slip on the denali fault is to transfer fault slip to adjacent east trending contractional structures in the western region of the central alaskan range

staircase fractures in microbialites and the role of lamination related mechanical anisotropy the example of the acquasanta terme travertine deposits central italy this study describes a peculiar yet common type of fracture showing a staircase trajectory which forms in rocks with moderately weak planar anisotropies the staircase fracture trajectory is given by alternating fracture segments oriented parallel to lap or at an angle ramp with respect to the lamination layering the analyses has been accomplished on travertines which are continental microbial hydrothermal deposits having a typical poorly stratified yet strongly laminated texture in these rocks porosity and permeability have a high across lamination variability and are mostly controlled by an interconnected and locally corroded array of permeable layers fractures and faults structural analysis integrated with analytical modeling provided a conceptual model of staircase fracture localization as a function of the travertine lamination dip lamination parallel fracture segments localize within the porous laminae mostly at the interface with tight laminae ramp type fracture segments cut the lamination connecting lamination parallel segments two types of staircase fracture can be modeled the first group develops in subhorizontal to gently dipping deposits lamination dip 30 and corresponds to high energy environments major discoveries of hydrocarbon have been recently made in continental lacustrine microbial carbonates in the brazilian south atlantic margin some of which exhibit a texture similar to those usually observed in travertines understanding of the lacustrine carbonates is still at an early stage given that in modern rift settings vent related thermal travertine and nonthermal tufa carbonates are a major component the proposed conceptual model of staircase fracture localization contributes to the preparation of a model for the potential occurrence of high permeability pathways in hydrocarbon and geothermal microbial reservoirs

interpretation of ancient epikarst features in carbonate successions a note of caution abstract in shallow marine carbonate successions of the phanerozoic evidence for shorter lived subaerial exposure stages of ancient carbonate seafloors is commonly found in the presence of small scale epi karst solution pits in discontinuity surfaces under favorable conditions these solution features are accompanied by soil features including calcretes or root traces alveolar septal structures petrographic evidence such as pendant cements circumgranular cracks or pisoliths bleaching and staining of carbonate rocks or circumstantial geochemical evidence perhaps more often however ancient carbonate successions lack undisputable evidence for meteoric karsting using a well exposed case example from the aptian of oman we here document that the superficial visual field inspection of solution pits in discontinuity surfaces may lead to erroneous interpretations outcrops at jabal madar a diapiric structure allow for an in depth analysis of dissolution features in the regionally extensive top shu aiba discontinuity the solution pits discussed here were investigated for their stratigraphic position their orientation relative to bedding planes diagenetic and petrographic features and their potential relation to extensional fractures related to the updoming of jabal madar the main message brought forward is that under burial conditions spatially localized hypogenic carbonate leaching may form features that are easily mistaken for ancient meteoric epikarst these features preferentially form in interstratal positions where fractured massive carbonate rocks are capped by a major discontinuity surface overlain by non fractured argillaceous sediments thus while dissolution reprecipitation processes in the burial phreatic realm are omni directional in permeable carbonates low permeability argillaceous fines are not or to a much lesser extent prone to chemical corrosion as a consequence carbonate aggressive burial fluids leach out pits at the carbonate shale interface these appear to protrude perpendicular as bowl shaped depressions into the underlying limestones and are in the case examples documented here preferentially aligned along factures these findings have significance for the interpretation of ancient epikarst features in shallow marine carbonate successions

characterization of complex groundwater flows in the environment of singular buildings by combining hydrogeological and non destructive geophysical ground penetrating radar techniques punta begona galleries getxo spain locating and quantifying groundwater flow in many built up areas are a priority with regard to its complete restoration in this work a hydrogeological survey of the surroundings of the punta begona galleries getxo bizkaia built on a coastal cliff was completed by using ground penetrating radar gpr testing thus the preliminary characterization of soils and rocks in accessible areas of the cliff was first improved by hydrogeological information gathered from a single survey borehole including permeability measurements by low pressure injection tests lpts and continuous water level monitoring as a complementary method the non destructive gpr technique was performed during both dry and wet hydrological periods and in tandem with the injection tests providing more complete spatial and temporal images of water flows specifically gpr allows mapping of flow paths in soils and assessing the continuity of fractures in rock masses altogether this complementary approach provides greater knowledge of complex underground flow dynamics in built environments thus making it easier to make decisions for their management

rapid large area mapping of ice flow using landsat 8 abstract we report on the maturation of optical satellite image based ice velocity mapping over the ice sheets and large glacierized areas enabled by the high radiometric resolution and internal geometric accuracy of landsat 8 s operational land imager oli detailed large area single season mosaics and time series maps of ice flow were created using data spanning june 2013 to june 2015 the 12 bit radiometric quantization and 15 m pixel scale resolution of oli band 8 enable displacement tracking of subtle snow drift patterns on ice sheet surfaces at 1 m precision ice sheet and snowfield snow drift features persist for typically 16 to 64 days and up to 432 days depending primarily on snow accumulation rates this results in spatially continuous mapping of ice flow extending the mapping capability beyond crevassed areas our method uses image chip cross correlation and sub pixel peak fitting in matching landsat path row pairs high pass filtering is applied to the imagery to enhance local surface texture the current high image acquisition rates of landsat 8 725 scenes per day globally reduces the impact of high cloudiness in polar and mountain terrain and allows rapid compilation of large areas or dense temporal coverage of seasonal ice flow variations the results rival the coverage and accuracy of interferometric synthetic aperture radar insar mapping

role of heterogeneity in elastic properties and layer thickness in the jointing of layered sedimentary rocks 1 we investigate how overburden weight acts in conjunction with heterogeneity in elastic properties between sedimentary layers to induce the tensile stress necessary for regional jointing model results are supported by data from a new experimental design in which an aluminum loading frame sandwiches a tabular specimen of brittle material of varying thickness between two layers of rubber load is applied perpendicular to the layering the aluminum load frame only permits the rubber layers to expand in one direction leading to the formation of a system of parallel fractures in the brittle layer as the rubber extends uniaxially the initiation of the first fractures is independent of the layer thickness as fracture spacing decreases below the layer thickness mechanical interaction between closely spaced fractures limits the initiation of additional fractures the onset of mechanical inhibition of additional fracture growth occurs at greater normalized fracture spacings in thinner layers

combining high resolution vertical gradients and sequence stratigraphy to delineate hydrogeologic units for a contaminated sedimentary rock aquifer system summary hydrogeologic units hgus representing subsurface contrasts in hydraulic conductivity form the basis for all conceptual and numerical models of groundwater flow however conventionally delineation of these units relies heavily on data sets indirect with respect to hydraulic properties here we use the spatial and temporal characteristics of the vertical component of hydraulic gradient i e vertical gradient as the primary line of evidence for delineating hgus for cambrian ordovician sedimentary rocks at a site in dane county wisconsin the site includes a 16 km2 area encompassing a 3 km long mixed organic contaminants plume the vertical gradients are derived from hydraulic head profiles obtained using high resolution westbay multilevel systems installed at 7 locations along two orthogonal 4 km long cross sections and monitoring to depths between 90 and 146 m with an average of 3 4 monitoring zones per 10 m these vertical gradient cross sections reveal 11 laterally extensive hgus with contrasting vertical hydraulic conductivity kv the position and thickness of the kv contrasts are consistently associated with sequence stratigraphic features maximum flooding intervals and sequence boundaries distinguished at the site using cores and borehole geophysical logs the same sequence stratigraphic features are also traceable across much of the cambrian ordovician aquifer system of the midwest us the vertical gradients and sequence stratigraphy were arrived at independently and when combined provide a hydraulically calibrated sequence stratigraphic framework for the site this framework provides increased confidence in the precise delineation and description of the nature of hgu contacts in each borehole reduced uncertainty in interpolation of the hgus between boreholes and some capability to predict hgu boundaries and thickness in offsite areas where high resolution hydraulic data sets are not available consequently this hgu conceptual model will serve as a better basis for numerical simulations of groundwater flow and contaminant transport needed for continued risk assessment and to evaluate potential remedial technologies for the site more broadly the association between kv contrasts and sequence stratigraphy demonstrated at this site provides valuable insight into the relationship between geology and hydraulic contrasts that can be transferred to other areas of the upper midwest us and perhaps elsewhere to strata deposited in similar settings

mechanical stratigraphic controls on fracture patterns within carbonates and implications for groundwater flow abstract groundwater flow in low matrix permeability carbonate rocks is largely controlled by fracture networks the stratigraphic features that control fracture initiation and termination within a sequence of sedimentary rock strata define the mechanical stratigraphy of the sequence we investigate the effectiveness of various types of stratigraphic horizons in terminating opening mode fractures in two different carbonate rock sequences a relatively homogeneous dolomite sequence in door county wi and an interbedded chalk and marl sequence within the austin chalk tx additionally we present analog and numerical modeling results that delineate the specific mechanisms that facilitate fracture termination the combination of model results and empirical relationships between observed sedimentary features and mechanical stratigraphy shows 1 fractures terminate at weak contacts e g thin organic layers shallowly buried contacts or thick fine grained units adjacent to thin fractured beds 2 fractures propagate across strong contacts e g intracycle contacts between different lithology and thin fine grained units adjacent to thick fractured beds and 3 fractures step over at moderate strength contacts we use these guidelines to predict fracture network from sedimentary stratigraphy by qualitatively assessing the mechanical stratigraphy of a portion of the relatively complex cretaceous shelf margin sequence at sant corneli spain this predictive demonstration illustrates the utility of assessing the mechanical stratigraphy of subsurface strata within which fractures are not directly observable we conclude that for a variety of carbonate mechanical stratigraphic sequences dominant fluid flow characteristics such as horizontal high flow zones and flow compartmentalization can be evaluated using fracture spacing and connectivity within fracture networks that is predicted from sedimentary stratigraphy although the resulting heterogeneous flow networks do not rely on every fracture present they are highly dependent on the mechanical stratigraphy

role of shale thickness on vertical connectivity of fractures application of crack bridging theory to the austin chalk texas abstract contrasting material properties of alternating chalk and shale layers control vertical connectivity of fractures our field observations within the austin chalk texas indicate that 1 the majority of vertical fractures occur in chalk layers and abut against contacts with shale layers 2 thicker shale layers have greater resistance to fracture propagation than thinner shale layers from these observations we hypothesize both the resistance of shale to fracturing and the thickness of shale layers may inhibit fracture propagation across the shale and into the next chalk layer we model crack propagation within a three layered system brittle chalk fracture resistant shale brittle chalk the modeled crack extends across the shale but closing tractions applied to the crack segment within the shale layer simulate resistance of shale to fracturing the crack tip lies a short distance within the unfractured chalk layer simulating a coplanar flaw with potential to propagate if the stress intensity factor at the flaw exceeds the chalk fracture toughness the crack propagates thereby bridging and eventually rupturing the shale layer for any chalk thickness there is a critical shale thickness above which fractures cross the shale layer and below which fractures arrest at shale finite element method fem analysis evaluates the influence of shale ductility within the chalk shale chalk system although remote and fluid pressure driven fractures produce identical stress intensity factors in elastic chalk shale systems lower driving stresses are required to propagate fluid pressure driven fractures through a system ductile shale layers than fractures under remote tension

fracture intersections as integrators for unsaturated flow 1 a simple experiment finds that fracture intersections can act to integrate unsaturated flows such that regular low flows entering the intersection from above are transformed into large less frequent pulses below at low flows our simple intersection forms two capillary barriers water from above pools at the intersection until sufficient pressure builds to breach the barriers and discharge stored fluid the barriers then reform and the process is repeated at low flows the volume discharged from the intersection remains relatively uniform across a range of flow rates at higher flows discharge volume is highly variable and a viscous stabilized non pulsating regime occurs at the highest flow rate that we considered

controls on fracture distribution in cretaceous sedimentary rocks from the isfahan region iran in this study relationships between fracture patterns lithology thickness diagenetic processes and grain size are evaluated within cretaceous sediments in two sections of dizlu and kolah ghazi of isfahan this study area was selected based on its outcrops of different rock units and its well developed tectonic fractures the fracture patterns within stratigraphic units of these sections are studied using geometrical and statistical analyses this study finds that variable fracture spacing and fracture spacing ratios can be affected by lithology thickness grain size of sediments and diagenetic processes a study of fracture stratigraphy based on fracture pattern evaluation within different cropped out sedimentary rocks can be used to improve understanding of the same types of sedimentary rock units below the surface or throughout other sedimentary basins consequently this could improve information regarding storage and fluid flow pattern throughout sedimentary rocks in different regions even for subsurface purposes

detailed hydraulic head profiles as essential data for defining hydrogeologic units in layered fractured sedimentary rock this paper describes a study in southern wisconsin where vertical hydraulic head profiles measured in exceptional detail provided the key data for defining hydrogeologic units hgus in a layered sequence of sandstone siltstone shale and dolostone the most important data were obtained from corehole mp 6 which was cored 131 m into bedrock and instrumented using a westbay multilevel system with 36 depth discrete monitoring intervals the resulting head profile is consistant over time and shows eight distinct inflections in hydraulic head several of the inflections occur between adjacent permeable units and are likely due to poor vertical connectivity of fracture sets rather than distinct lower permeability layers or aquitards in the conventional sense no other type of data was capable of identifying the position of such distinct hydrogeologic features these zones of abrupt head loss provide the primary dataset for delineation of eleven hgus at mp 6 and are supported by less detailed head profiles at other locations although the detailed head profiles are essential core logs and geophysical logs from other boreholes are nessessary to fully establish the lateral continuity of the hgus

sedimentary and diagenetic controls on the multiscale fracturing pattern of a carbonate reservoir the madison formation sheep mountain wyoming usa a multidisciplinary approach has been applied to characterize the madison formation in the sheep mountain anticline at different scales in order to illustrate the relationship between sedimentology diagenesis and fracturing pattern sedimentary facies are organized into three types of elementary facies sequences showing different vertical evolutions of their petrophysical properties this is controlled by the double influence of the initial sedimentary facies and the diagenetic evolution three main sets of fractures related to the sevier and laramide compressive phases and to the folding of sheep mountain have been described at three orders of scale at small scale the sevier related set i and folding related set iii are the most abundant set ii dated from the early stage of the laramide compression exhibits the highest fracture intensity there is also a clear faciologic control on the fracture intensity small scale mechanical units correspond to entire facies sequences when no or little petrophysical property contrasts between beds are observed conversely small scale mechanical units correspond to each bed of a facies sequence in the case of high contrasts of petrophysical properties between beds at intermediate scale set ii is not present and sets i and iii show the highest fracture intensities the latter are partly controlled by the mechanical unit thickness intermediate and large scale mechanical unit distribution is mainly controlled by the overall faciologic vertical stacking pattern and by the position across the sheep mountain anticline forelimb or backlimb sheep mountain outcrops provide a good spatial representation of the carbonate reservoir heterogeneities from the micro to the field scale illustrating the complexity of fractured carbonate reservoirs

deformation time series generation in areas characterized by large displacement dynamics the sar amplitude pixel offset sbas technique we exploit the amplitude information of a sequence of synthetic aperture radar sar images acquired at different times in order to generate displacement time series in areas characterized by large and or rapid deformation the size of which is on the order of the image s pixel dimensions we follow the same rationale of the small baseline subset sbas differential sar interferometry dinsar approach by coupling the available sar images into pairs characterized by a small separation between the acquisition orbits we exploit the amplitudes of the selected image pairs in order to calculate the relative across track range and along track azimuth pixel offsets po finally we apply the sbas inversion strategy to retrieve the range and azimuth displacement time series this approach referred to as pixel offset po sbas technique has been applied to a set of 25 envisat sar observations of the sierra negra caldera galapagos islands spanning the 2003 2007 time interval the retrieved deformation time series show the capability of the technique to detect and measure the large displacements affecting the inner part of the caldera that in correspondence to the october 2005 eruption reached several meters moreover by comparing the po sbas results to continuous gps measurements we estimate that the accuracy of the po sbas time series is on the order of 1 30th of a pixel for both range and azimuth directions

the nature and distribution of flowing features in a weakly karstified porous limestone aquifer the nature and distribution of flowing features in boreholes in an area of approximately 400 km2 in a weakly karstic porous limestone aquifer the chalk was investigated using single borehole dilution tests sbdts and borehole imaging one hundred and twenty flowing features identified from sbdts in 24 boreholes have densities which decrease from 0 3 m 1 near the water table to 0 07 m 1 at depths of more than 40 m below the water table the average density is 0 20 m 1 there is some evidence of regional lithological control and borehole imaging of three boreholes indicated that most flowing features are associated with marls hardgrounds and flints that may be developed at a more local scale borehole imaging also demonstrated that many flowing features are solutionally enlarged fractures suggesting that even in carbonate aquifers where surface karst is developed on only a small scale groundwater flow is still strongly influenced by dissolution fully connected solutional pathways can occur over 100s sometimes 1000s of metres however conduits tubules and fissures may not always be individually persistent along a flowpath instead being connected together and also connected to unmodified fractures to create a relatively dense network of voids with variable apertures 15 cm groundwater therefore moves along flowpaths made up of voids with varying shape and character local solutional development of fractures at significant depths below the surface suggests that mixing corrosion and in situ sources of acidity may contribute to solutional enhancement of fractures the study demonstrates that single borehole dilution testing is a useful method of obtaining a large dataset of flowing features at catchment regional scales the chalk is a carbonate aquifer with small scale surface karst development and this study raises the question of whether other carbonate aquifers with small scale surface karst have similar characteristics and what hydrological role small scale dissolutional features play in highly karstic aquifers

olivinites in the angrite d orbigny vestiges of pristine reducing conditions during angrite formation abstract olivinites together with olivine megacrysts are the most magnesian phases found in angrites their chemical composition mg 90 is out of equilibrium with the groundmass and far away from that of possible precipitates from angrite parent melts therefore olivinites as well as olivine megacrysts were considered as xenoliths and xenocrysts we report here a detailed study of five olivinites from the angrite d orbigny our results indicate that d orbigny experienced metasomatic alteration processes which led to enrichments in feo and mno relative to the original composition changing the initial mg rich composition of the olivines to the one seen now as this process took place in equilibrium with a chondritic reservoir e g fe mn ratios spreading around primitive values the primitive mg rich olivine chemical composition was changed towards a more fayalitic one while preserving a chondritic signature this chondritic signature was preserved in the fe mn ratio of the olivinites olivine megacrysts augite grains in olivinites and groundmass olivine of d orbigny therefore the fayalite content of about 35 mol that characterizes the groundmass olivine of this rock as well as other angrites does not correspond to its original composition but may be the result of a late metasomatic process that affected these rocks if so olivinites and mg rich olivines might not be compositionally exotic phases but are an early constituent phase that retained the pristine more reducing conditions that have been preserved in some angrites where they form either a small part of the rock e g asuka 881371 and d orbigny or the majority of it nwa 8535

characterizing the influence of interlayers on the development and distribution of fractures in deep tight sandstones using finite element method abstract understanding and interpreting the location intensity and aperture of tectonic fractures within deep geological structure are important to hydrocarbon exploration and development taken the paleogene tight sandstones interbedded with mudstone interlayers in tarim basin as an example we explored a novel finite element based geomechanical modeling to quantitatively predict fracture development and distribution and effectively evaluate the vertical penetration of fractures through mudstone layers this approach is based on the concept that fractures can be inferred from the redistribution of stress and strain with combination of certain failure criterion we established several sets of sand shale interbedded geological models and compared simulation results with observed core data it was found that in tight sandstone reservoirs with few ductile interlayers the elastic parameter is main factor affecting development of fractures in contrast the sand mud thickness ratio is the most important factor controlling the development of fractures for sandstone interbedded with multiple mudstone layers furthermore the lithology of interface boundary was shown to strongly control the fracture penetration into mudstone interlayers when the mudstone interlayer is thin enough it is easily penetrated by fractures generated in sandstones and fractures are more likely to develop around lithological interface such results were explained by the differences in rock mechanics properties and inconsistent deformation between layers and its derived tensile stress the modeling results on fracture density and aperture showed good agreement with the core observation and micro imaging interpretation and the average simulation accuracy of single wells has reached more than 80

mechanical stratigraphy and palaeo karstification of the murge area apulia southern italy the cretaceous apulia platform exposed in the murge area southern italy suffered intense palaeo karstification this study focuses on the controlling factors of karstification with emphasis on fracturing mechanical stratigraphy was used to calculate the fracture density withindifferent sedimentarysequences several mechanical unitswere defined and a characteristic relationship was found between unit thicknesses and fracture density that is fracture density increases if layer thickness decreases in some of the quarries studied sedimentary cycles are clearly present that are also reflected in the fracture density logs the degree of karstification withina mechanical unit is proportional to the mean fracture spacing based on fracture orientation data extracted from lidar scans different orientation clusters were observed between fractures thatarekarstifiedandfracturesthatarenotkarstified post datingkarstification theclustersofkar stified fractures are related to the compression of the southern apennines the fractures became dissolution enlarged during the pleistocene uplift caused by bulging of the apulia platform this main karstification phase occurred prior to late pleistocene deposition and before the for mation of orthogonal fracture sets

ground penetrating radar and structural geological mapping investigation of karst and tectonic features in flyschoid rocks as geological hazard for exploitation abstract we evaluated the use of ground penetrating radar gpr in detecting karst cavities and discontinuities that could form potential landslide surfaces in flyschoid rocks of the rode open pit mine in anhovo w slovenia we recorded 21 gpr profiles in three consecutive benches with the unshielded 50 mhz rough terrain antenna rta system and correlated them with the results of detailed structural and lithological mapping of the area we located several karst cavities and confirmed the presence of discontinuities with the interpretation of gpr profiles alone however their correlation with geological and structural data gave a more precise insight into the structural setting of the studied area the different discontinuity families specified in the rode open pit mine are mainly the result of the strike slip tectonics and gradual anisotropic lithology the complexity of the intersections of structural discontinuities and the mechanical properties of rocks contribute to the formation of sliding surfaces and the developing of karst features cavities and phreatic channels develop in the vadose zone in calcarenites and result from complex structural deformation and karstification factors at the open joints or larger structural fractures

earthquake triggered increase in sediment delivery from an active mountain belt in tectonically active mountain belts earthquake triggered landslides deliver large amounts of sediment to rivers we quantify the geomorphic impact of the 1999 mw 7 6 chi chi earthquake in taiwan which triggered 20 000 landslides coseismic weakening of substrate material caused increased landsliding during subsequent typhoons most coseismic landslides remained confined to hillslopes downslope transport of sediment into the channel network occurred during later storms the sequential processes have led to a factor of four increase in unit sediment concentration in rivers draining the epicentral area and increased the magnitude and frequency of hyperpycnal sediment delivery to the ocean four years after the earthquake rates of hillslope mass wasting remain elevated in the epicentral area

ground motion measurement in the lake mead area nevada by differential synthetic aperture radar interferometry time series analysis probing the lithosphere rheological structure 1 we measure ground motion around the lake mead nevada using synthetic aperture radar interferometry the lake water level has fluctuated through time since impoundment in 1935 to quantify the deformation due to water level variations over the past decade and to constrain the crust and mantle rheological parameters in the lake area we analyze 241 interferograms based on 43 ers images acquired between 1992 and 2002 all interferograms have a high coherence due to arid conditions most of them show strong atmospheric artefacts tropospheric phase delays are estimated and corrected for each interferogram by analyzing the phase elevation correlation corrections are validated using data from the era40 global atmospheric reanalysis corrected interferograms are inverted pixel by pixel to solve for the time series of ground motion in the lake area temporal smoothing is added to reduce random atmospheric artefacts the observed deformation is nonlinear in time and spreads over a 50 50 km2 area we observe a 16 mm subsidence between 1995 and 1998 due to an 11 m water level increase followed by an uplift due to the water level drop after 2000 we model the deformation taking into account the loading history of the lake since 1935 a simple elastic model with parameters constrained by seismic wave velocities does not explain the amplitude of the observed motion the two layer viscoelastic model proposed by kaufmann and amelung 2000 with a mantle viscosity of 1018 pa s adjusts well the data amplitude and its spatiotemporal shape

glacier surface velocities in alpine terrain from optical satellite imagery accuracy improvement and quality assessment the worldwide retreat of mountain glaciers has important consequences for the water food and power supply of large and densely populated areas in south and central asia successful mitigation of the hydrological impacts on societies as well as assessing glacier related hazards require large scale monitoring of glacier dynamics however detailed glaciological data from the asian highlands are lacking due to its size and difficult accessibility we have applied a novel technique for precise orthorectification co registration and sub pixel correlation of advanced spaceborne thermal emission and reflection radiometer aster satellite imagery to derive surface velocities of himalayan glaciers our approach allows for the correction of offsets due to attitude effects and sensor distortions as well as elevation errors if a digital elevation model dem from the shuttle radar topography mission srtm was used for orthorectification after post processing the error on the displacements is on the order of 2 4 m per correlation translated into annual velocities this error is reduced increased when the correlated images are more less than a year apart through application of a filtering procedure and several quality tests the consistency of the results is validated to provide confidence in the remotely sensed velocity measurements despite the lack of ground control this novel approach allows fast easy and economically viable acquisition of detailed glaciological data in areas of difficult access and provides a means for large scale monitoring of glaciers in high mountainous terrain

mechanical and fracture stratigraphy using examples from core studies this article shows that separate identification of mechanical stratigraphy and fracture stratigraphy leads to a clearer understanding of fracture patterns and more accurate prediction of fracture attributes away from the wellbore mechanical stratigraphy subdivides stratified rock into discrete mechanical units defined by properties such as tensile strength elastic stiffness brittleness and fracture mechanics properties fracture stratigraphy subdivides rock into fracture units according to extent intensity or some other observed fracture attribute mechanical stratigraphy is the by product of depositional composition and structure and chemical and mechanical changes superimposed on rock composition texture and interfaces after deposition fracture stratigraphy reflects a specific loading history and mechanical stratigraphy during failure because mechanical property changes reflect diagenesis and fractures evolve with loading history mechanical stratigraphy and fracture stratigraphy need not coincide in subsurface studies current mechanical stratigraphy is generally measurable but because of inherent limitations of sampling fracture stratigraphy is commonly incompletely known to accurately predict fractures in diagenetically and structurally complex settings we need to use evidence of loading and mechanical property history as well as current mechanical states

controls on the seasonal deformation of slow moving landslides article history precipitation drives seasonal velocity changes in slow moving landslides by increasing pore water pressure and reducing the effective normal stress along basal shear zones this pressure change is often modeled as a pore water pressure wave that diffuses through the landslide body such that the minimum time required for landslides to respond to rainfall should vary as the square of landslide depth which often approximates the saturated thickness and inversely with hydraulic diffusivity here we assess this model with new observations from the landslide prone eel river catchment northern california using satellite radar interferometry insar time series precipitation data and high resolution topographic data from airborne lidar we quantify the seasonal dynamics of 10 slow moving landslides which share the same lithologic tectonic and mediterranean climate conditions these slope failures have areas ranging from 0 16 to 3 1 km 2

linear to non linear relationship between vein spacing and layer thickness in centimetre to decimetre scale siliciclastic multilayers from the high ardenne slate belt belgium germany abstract typical spacing distributions have frequently been described for fractures in thin sedimentary layers 40 cm vein spacing tends to increase to a maximum value becoming more or less independent of layer thickness the resemblance with fracture spacing suggests that in an unfractured rock vein saturation can occur high fluid pressures are responsible for vein nucleation but the stress state around the initial veins controls the spacing pattern subsequently in a vein saturated rock or the existing veins will thicken by the process of crack sealing or a new cross cutting vein generation will develop in case the regional stress field changes relatively with respect to the existing veins

nature and origin of collapse breccias in the zechstein of ne england local observations with cross border petroleum exploration and production significance across the north sea

correlation of satellite image time series for the detection and monitoring of slow moving landslides abstract slow moving landslides are widespread in many landscapes with significant impacts on the topographic relief sediment transfer and human settlements their area wide mapping and monitoring in mountainous terrain however is still challenging the growing archives of optical remote sensing images offer great potential for the operational detection and monitoring of surface motion in such areas this study proposes a multiple pairwise image correlation mpic technique to obtain a series of redundant horizontal displacement fields and different multi temporal indicators for a more accurate detection and quantification of surface displacement the technique is developed and tested on a series of monoscopic and stereoscopic pleiades satellite images at a test site in the south french alps empirical tests confirm that mpic significantly increased detection accuracy f measure 0 85 and that the measurement error can be reduced by averaging velocities from all pair combinations covering a given time step i e when stereo pairs are available for at least one date the derived inventory and displacement fields of 169 slow moving landslides show a positive relationship between the landslide size and velocities as well as a seasonal acceleration of the largest landslides in response to an increase in effective precipitation the processing technique can be adapted to better exploit increasingly available time series from a variety of optical satellites for the detection and monitoring of landslide displacement

evolution of fracture and fault controlled fluid pathways in carbonates of the albanides fold thrust belt the process of fracture and fault formation in carbonates of the albanides fold thrust belt has been systematically documented using hierarchical development of structural elements from hand sample outcrop and geologic map scales the function of fractures and faults in fluid migration was elucidated using calcite cement and bitumen in these structures as a paleoflow indicator two prefolding pressure solution and vein assemblages were identified an overburden assemblage and a remote tectonic stress assemblage sheared layer parallel pressure solution surfaces of the overburden assemblage define mechanical layers shearing of mechanical layers associated with folding resulted in the formation of a series of folding assemblage fractures at different orientations depending on the slip direction of individual mechanical layers prefolding and folding related fracture assemblages together formed fragmentation zones in mechanical layers and are the sites of incipient fault localization further deformation along these sites was accommodated by rotation and translation of fragmented rock which formed breccia and facilitated fault offset across multiple mechanical layers strike slip faults formed by this process are organized in two sets in an apparent conjugate pattern calcite cement and bitumen that accumulated along fractures and faults are evidence of localized fluid flow along fault zones by systematic identification of fractures and faults their evolution and their fluid and bitumen contents along with subsurface core and well log data we identify northeast southwest trending strike slip faults and the associated structures as dominant fluid pathways in the albanides fold thrust belt

flow modeling and permeability estimation using borehole flow logs in heterogeneous fractured formations a numerical model of flow in the vicinity of a borehole is used to analyze flowmeter data obtained with high resolution flowmeters the model is designed to 1 precisely compute flow in a borehole 2 approximate the effects of flow in surrounding aquifers on the measured borehole flow 3 allow for an arbitrary number n of entry exit points connected to m n far field aquifers and 4 be consistent with the practical limitations of flowmeter measurements such as limits of resolution typical measurement error and finite measurement periods the model is used in three modes 1 a quasi steady pumping mode where there is no ambient flow 2 a steady flow mode where ambient differences in far field water levels drive flow between fracture zones in the borehole and 3 a cross borehole test mode where pumping in an adjacent borehole drives flow in the observation borehole the model gives estimates of transmissivity for any number of fractures in steady or quasi steady flow experiments that agree with straddle packer test data field examples show how these cross borehole type curves can be used to estimate the storage coefficient of fractures and bedding planes and to determine whether fractures intersecting a borehole at different locations are hydraulically connected in the surrounding rock mass