faulting of rocks in three dimensional strain fields i failure of rocks in polyaxial servo control experiments abstract the dependence of the number of sets of faults and their orientation on the intermediate strain axis is investigated through polyaxial tests reported here and theoretical analysis reported in an accompanying paper in the experiments cubic samples of berea sandstone sierra white and westerly granites and candoro and solnhofen limestones were loaded on their three pairs of faces by three independent mutually perpendicular presses at room temperature two of the presses were servo controlled and applied constant displacement rates throughout the experiment most samples display three or four sets of faults in orthorhombic symmetry these faults form in several yielding events that follow a stage of elastic deformation in many experiments the maximum and the intermediate compressive stresses interchange orientations during the yielding events where the corresponding strains are constant the final stage of most experiments is characterized by slip along the faults

localization of a coal seam fire using combined self potential and resistivity data abstract the remediation of coal seam fires requires as a first step the precise localization of the burning front various geophysical methods can be employed for this purpose but not all of them can provide an unambiguous localization of this type of target we propose a combined inversion of self potential and resistivity data and the use of joint attributes characterizing the target to localize the burning front of a coal seam fire this new methodology is applied to the 3d reconstruction of a shallow coal seam fire in boulder colorado the coal seam fire is located in the gorham subbituminous coal formation at a depth comprised between 10 and 15 m the self potential survey comprises 160 stations 5 profiles and 32 stations per profile located at the ground surface with self potential anomalies amounting 70 to 50 mv with respect to an arbitrary reference located further away from the burning front the resistivity survey comprises 5 resistivity profiles with 118 measurements per profile 590 measurements in total the burning front is associated with very low value of the electrical resistivity

numerical modelling of self potential signals associated with a pumping test experiment summary the study of electrical signals associated with groundwater flow is a powerful method to determine in a non invasive way the distribution of hydraulic heads in aquifers hence the distribution of the hydraulic conductivity and storativity experimental hydraulic heads and electrical self potential sp signals associated with a pumping test in an unconfined aquifer were reproduced with a numerical model based on the finite difference method for simplicity we assumed axial symmetry around the pumping well we assessed the equivalent hydraulic conductivity and specific storage of the aquifer by fitting the piezometric levels obtained in the course of the pumping against synthetic hydraulic heads produced by the model the current coupling coefficient is obtained from the best fit between the experimental and modelled sp signals at the end of the pumping phase then keeping the previously determined hydraulic parameters the relaxation of both the hydraulic heads and the sp signals were modelled and found to be consistent with the measured values the data show almost linear relationships between the hydraulic heads in the aquifer and the electrical signals recorded at the ground surface these results show that sp signals allow monitoring subsurface flow in the course of pumping experiments

saline tracer visualized with three dimensional electrical resistivity tomography field scale spatial moment analysis 1 cross well electrical resistivity tomography ert was used to monitor the migration of a saline tracer in a two well pumping injection experiment conducted at the massachusetts military reservation in cape cod massachusetts after injecting 2200 mg l of sodium chloride for 9 hours ert data sets were collected from four wells every 6 hours for 20 days more than 180 000 resistance measurements were collected during the tracer test each ert data set was inverted to produce a sequence of 3 d snapshot maps that track the plume in addition to the ert experiment a pumping test and an infiltration test were conducted to estimate horizontal and vertical hydraulic conductivity values using modified moment analysis of the electrical conductivity tomograms the mass center of mass and spatial variance of the imaged tracer plume were estimated although the tomograms provide valuable insights into field scale tracer migration behavior and aquifer heterogeneity standard tomographic inversion and application of archie s law to convert electrical conductivities to solute concentration results in underestimation of tracer mass such underestimation is attributed to 1 reduced measurement sensitivity to electrical conductivity values with distance from the electrodes and 2 spatial smoothing regularization from tomographic inversion the center of mass estimated from the ert inversions coincided with that given by migration of the tracer plume using 3 d advective dispersion simulation the 3 d plumes seen using ert exhibit greater apparent dispersion than the simulated plumes and greater temporal spreading than observed in field data of concentration breakthrough at the pumping well

mesoscale to microscale simulations over complex terrain with the immersed boundary method in the weather research and forecasting model abstractimprovements to the weather research and forecasting wrf model are made to enable multiscale simulations over highly complex terrain with dynamically downscaled boundary conditions from t

thrust sheet rotation and out of plane strains associated with oblique ramps an example from the wyoming salient u s a abstract movement over oblique thrust ramps results in local thrust sheet rotation and principal strains which deviate from the transport plane resulting folds faults and deformation fabrics are superposed on those associated with displacement on frontal ramps the south fork thrust a hangingwall imbricate of the absaroka thrust sheet sw wyoming has a steeply dipping 70 small displacement 300 m oblique ramp in the hangingwall and footwall which makes an angle of 25 to the regional transport direction two penetrative deformation events are recorded by folding stylolitic cleavage and calcite twinning strains in the deformed hangingwall and footwall the first is e to se directed layer parallel shortening prior to or during motion of the absaroka thrust sheet the second event indicates ne directed shortening unique to the oblique ramp at a high angle to ramp strike at the trailing frontal ramp oblique ramp intersection folds in the footwall and normal faults in the hangingwall reflect local strike parallel shortening and extension due to out of plane deflection of the wallrock during displacement the out of plane strains arc consistent with those predicted by kinematic and mechanical models in the hangingwall of the oblique ramp cross strike fractures and bedding are rotated 30 counterclockwise about a vertical axis with respect to structural domains to the north and south due to differential displacement on the south fork thrust stylolitic cleavage and caleite strains unique to the oblique ramp show a similar change in attitude indicating the rotation was the latest recorded stage of deformation in general if an oblique ramp is shallowly dipping the hangingwall may move from the lower flat up the ramp and onto the upper hat if an oblique ramp has a steep dip as in the case of the south fork thrust relatively greater sliding and bending resistance may impede displacement up the ramp and upper flat further transport of the thrust sheet is then accommodated by footwall deformation and hangingwall rotation

three dimensional kinematic history at an oblique ramp leamington zone sevier belt utah abstract differences in kinematics in adjoining salients in fold thrust belts are typically accommodated along bounding transverse zones the leamington zone is an oblique ramp that accommodates slip between structures in the provo salient and the central utah segment of the sevier fold thrust belt the leamington zone consists of the leamington canyon thrust associated second order asymmetric folds and an out of syncline reverse fault the leamington canyon thrust is a rotated se dipping thrust fault with top to southeast motion it represents an oblique ramp of the folded canyon range thrust fold tightening of the syncline se of the folded leamington canyon thrust trace during later emplacement of underlying structures caused out of syncline reverse faulting in the fold core analysis of the finite strain minor fault populations and conjugate fracture sets were used in interpreting the 3 d kinematic history along the leamington zone restored maximum stretching directions of finite strain ellipsoids trend eastward overall inferred motion planes from populations of slickenlines on minor faults are consistent with overall southeastward motion acute bisectors of conjugate fracture sets may reflect more southward directions later in the deformation history these superimposed deformations with local relative chronologies of plastic and brittle structures using cross cutting relationships indicate that the leamington zone area shows overall clockwise changes in kinematic directions from e to ese to sse during successive pulses of deformation the temporal changes in kinematic directions along the leamington zone most likely reflect variations in kinematics over the oblique ramp as the overall easterly displaced 3 d fold thrust belt wedge interacted with the pre existing oblique ramp structure with small magnitudes of superimposed local vertical axis rotations during later folding and fold tightening of the leamington canyon thrust

resistivity and self potential tomography applied to groundwater remediation and contaminant plumes sandbox and field experiments summary geophysical methods can be used to remotely characterize contaminated sites and monitor in situ enhanced remediation processes we have conducted one sandbox experiment and one contaminated field investigation to show the robustness of electrical resistivity tomography and self potential sp tomography for these applications in the sandbox experiment we injected permanganate in a trichloroethylene tce contaminated environment under a constant hydraulic gradient inverted resistivity tomograms are able to track the evolution of the permanganate plume in agreement with visual observations made on the side of the tank self potential measurements were also performed at the surface of the sandbox using non polarizing ag agcl electrodes these data were inverted to obtain the source density distribution with and without the resistivity information a compact horizontal dipole source located at the front of the plume was obtained from the inversion of these self potential data this current dipole may be related to the redox reaction occurring between tce and permanganate and the strong concentration gradient at the front of the plume we demonstrate that time lapse self potential signals can be used to track the kinetics of an advecting oxidizer plume with acceptable accuracy and if needed in real time but are unable to completely resolve the shape of the plume in the field investigation a 3d resistivity tomography is used to characterize an organic contaminant plume resistive domain and an overlying zone of solid waste materials conductive domain after removing the influence of the streaming potential the identified source current density had a magnitude of 0 5 a m 2 the strong source current density may be attributed to charge movement between the neighboring zones that encourage abiotic and microbially enhanced reduction and oxidation reactions in both cases the self potential source current density is located in the area of strong resistivity gradient

self potential monitoring of a salt plume nonintrusively monitoring the spread of contaminants in real time with a geophysical method is an important task in hydrogeophysics we have developed a sandbox experiment showing that the self potential method can locate both the source of leakage and the front of a contaminant plume we monitored the leakage of a plume of salty water from a hole at the bottom of a small tank located at the top of a main sandbox initially the sand was saturated by tap water at a given time a hole was opened at the bottom of the tank allowing the salty water to migrate by diffusion and buoyancy driven flow in the main sandbox the bottom of the sandbox contained a network of 32 nonpolarizing silver silver chloride electrodes with amplifiers connected to a multichannel voltmeter the self potential response associated withthe migration of the salt plume in the sandbox was recorded over time a self potential anomaly was observed with amplitude varying from a few millivolts at the start of the leak to a few tens of mi

structural evolution of connecting splay duplexes and their implications for critical taper an example based on geometry and kinematics of the canyon range culmination sevier belt central utah abstract critical taper in an evolving orogenic wedge can be maintained by structural thickening in the back of the wedge this is often achieved by folding and uplift of pre existing large internal thrust sheets by the continued growth and or reactivation of duplexes in the hinterland the growth of a blind imbricate complex off a lower thrust provides another mechanism for folding a higher thrust individual splays in a blind imbricate complex may have fault propagation folds and or fault bend folds associated with them if the splays reach the overlying thrust they serve as connecting splays between the lower thrust floor and the upper thrust roof thereby forming a connecting splay duplex csd this type of duplex geometry requires periodic reactivation of the pre existing roof thrust the canyon range thrust in central utah is an internal thrust that is folded into an overturned antiform synform pair and overrides its own synorogenic conglomerates the same conglomerates are infolded into the core of the synform and preserve critical timing information regarding the history of folding and thrust reactivation the folding is caused by the development of a footwall antiformal stack in the core of the canyon range antiformal culmination the geometry and timing relationships suggest that the structure grew as a csd regional timing relationships suggest that the growth of the csd and reactivation of the thrust took place during the later part of the evolution of the orogenic wedge and may have helped the wedge maintain critical taper during thrusting in the external fold and thrust belt

palaeomagnetic evidence for rotations and deformation in the nogueras zone central southern pyrenees spain a multicomponent palaeomagnetic remanence from the lower triassic buntsandstein redbeds of the central southern pyrenees has been interpreted as being composed of three components a low blocking temperature recent viscous magnetization l an intermediate blocking temperature eocene remagnetization i and a high blocking temperature lower triassic remanence h these palaeomagnetic results can be used in conjunction with structural evidence to identify poles of rotation during the development of the nogueras zone antiformal stack poles from individual sites reflect local deformation and folding including vertical rotation due to shearing between adjacent thrust sheets the i component was sometimes acquired syn tectonically during thrust motion and can be used to define intermediate stages of structural development results from sites located on a single thrust sheet no 7 indicate that it rotated by 45 clockwise during emplacement this is reflected in an easterly increase in displacement estimated from the construction of balanced cross sections thrust sheets appear to have been pinned close to the present day location of pont de suert during the later stages of structural development the arcuate path of thrust sheet motions and the potential movements in and out of cross section can lead to over and under estimates of minimum displacement when using line length cross section balancing techniques

structural framework of the zagros fold thrust belt iran abstract data gleaned from the literature on the zagros have been compiled and used in conjunction with new interpretations to provide a better picture of the structures sedimentation history and deformation of this hydrocarbon rich mountain belt the belt parallel mountain front the n s trending kazerun izeh and e w trending bala rud fault zones are defined as the master structural elements of the belt these fault zones divide the zagros basin into zones with different stratigraphic successions and different rheological profiles this resulted in different structural styles developing along the belt during the subsequent collision the kazerun and izeh fault zones acted as the depositional system transition zone between the lurestan and fars regions in jurassic cretaceous time and partly controlled the distribution of the kazhdumi formation one of the major source rocks by the end of the cretaceous the nw se trending mountain front fault divided the present folded belt of the zagros into a major foreland basin to the southwest and a piggyback basin to the northeast activity along other major transfer fault zones including the izeh kazerun and bala rud fault zones occurred at this time and controlled the sedimentation and subsidence of the dezful embayment the main target region for hydrocarbon exploration these fault zones controlled the thickness of the asmari formation one of the main reservoirs and also the considerable thickness and facies changes of the gachsaran formation the major seal to the asmari formation the present morphology of the mountain belt is interpreted as being mainly related to the pinning of the mountain front fault to the northwest of the dezful embayment and to the north of the strait of hormuz

case of the phantom foredeep early cretaceous in west central utah a reconstruction of the structure in west central utah shows that a major foredeep with sedimentary deposits possibly as thick as 6 km now eroded probably existed at the present site of the sevier desert during early cretaceous time and conceivably during late jurassic time concurrent emplacement and erosion of the canyon range thrust sheet provided the load and sediment much like the willard paris thrust sheet did for the better documented early cretaceous foredeep in northern utah and eastern idaho the onset of major thrusting in western utah may have been as early as callovian or as late as albian a 50 m y time span

folding kinematics expressed in fracture patterns an example from the anti atlas fold belt morocco the anti atlas fold belt morocco formed during the same variscan collisional event that produced the valley and ridge fold thrust belt of the appalachian mountains both are external belts of the appalachian ouachita mauritanides chain and at the map scale have very similar topographic expressions the anti atlas however consists of map scale folds that are buckle related detachment folds whereas the valley and ridge folds developed in response to imbricate thrusting for this reason the anti atlas is referred to as a fold belt rather than a fold thrust belt this paper examines variscan folding processes in the anti atlas mountains folding in some layers occurred by sliding along a penetrative network of mesoscale fractures i e cataclastic flow during buckling layer parallel shortening fractures were reactivated in the later stages of folding to accommodate limb rotation although boutonnieres i e basement uplifts punctuate the fold belt the fracture patterns indicate that the uplifts failed to provide any bending component folding is also interpreted to occur under low to moderate confining pressures because the fracture network includes conjugate shear fractures with very small 20 dihedral angles

structural evolution of a major appalachian salient recess junction consequences of oblique collisional convergence across a continental margin transform fault most orogenic belts exhibit broadly arcuate regional map view trends of structural patterns commonly the inflection between opposing curves recesses and salients is a transverse zone marking a linear array of along strike contrasts in regional structure and stratigraphy analysis of such transverse zones can provide insight into the processes affecting orogenic curvature curvature is especially distinctive along the west flank of the appalachians where the tightest salient recess juncture is a thinned skinned transverse zone in georgia separating the alabama recess and tennessee salient and extending entirely across the width of deformed laurentian cover rocks this zone s most notable feature is a large oblique hanging wall ramp within the frontal metamorphic allochthon formed during alleghanian collisional events the basal decollement steps several kilometers stratigraphically upward across this ramp from proterozoic basement and its overlying late proterozoic rift sequence tennessee salient southwestward into basal cambrian and younger rocks alabama recess this ramp resulted from oblique sinistral displacement of the allochthon against an earlier east facing dextral continental margin transform fault that initially separated adjacent rifted margins of opposite polarity differences in the distribution thickness and facies of units indicate that important variations in basin geometry existed across the curvature inflection before paleozoic deformation suggesting that the orogenic curvature in part results from an inherited basin architecture translation of the allochthon over the ramp caused deflection of the tectonic transport trajectory major cross folding and rotation of earlier structures associated out of plane deformation propagated outward across the foreland producing the array of thinned skinned transverse structures aligned into the transverse zone

deformation along a salient transverse zone junction an example from the leamington transverse zone utah sevier fold thrust belt usa abstract within fold thrust belts the junctions between salients and recesses may hold critical clues to the overall kinematic history of fold thrust belts the deformation history within these junctions is best preserved in areas where thrust sheets extend from a salient through an adjacent recess we examine one such junction within the sevier fold thrust belt western united states along the leamington transverse zone northern utah the canyon range thrust sheet can be traced continuously from the leamington transverse zone to its adjacent salient to the south the central utah segment deformation within the canyon range thrust sheet took place by faulting and cataclastic flow analyses of these fault networks preserved throughout the canyon range thrust sheet are used to develop a kinematic history of the leamington transverse zone field data is supplemented by analog sandbox experiments this study suggests that in detail deformation within the overlying thrust sheet may not directly reflect the underlying basement structure moreover these junctions may contain several types of accommodating structures that helped to maintain critical taper and that serve as potential targets for natural resource exploration

self potential signals associated with variations of the hydraulic head during an infiltration experiment 1 a field experiment was performed to monitor the variations of the hydraulic head in the vicinity of a ditch during a water infiltration experiment and using the self potential method the coupling between electric and hydraulic flows is electrokinetic in nature the electrical signals are measured at the ground surface with a set of ten non polarisable petiau pb pbcl2 electrodes over a section perpendicular to the ditch the electrical potential is linearly related to the depth of the water table which is here quite shallow between 1 to 2 m a rough estimate of the electrokinetic coupling coefficient obtained in the field is 10 mv per meter of hydraulic head 1000 mv mpa 1 of pore fluid pressure the order of magnitude of this estimate agrees with a laboratory experiment performed with a soil sample from the test site the good correlation found between electrical potential and hydraulic head variations opens the door to direct tomography of hydraulic head fluctuations with many innovative applications in hydrogeology especially because the potential depth to which this method could be applicable is high several hundred meters

new model for evolution of fold and thrust belt curvature based on integrated structural and paleomagnetic results from the pennsylvania salient in a number of curved fold and thrust belts worldwide such as the cantabrian arc and the wyoming idaho salient paleomagnetic data indicate vertical axis rotations inconsistent with structural findings this apparent conflict is especially pronounced in the pennsylvania salient where the paleomagnetically defined vertical axis rotations are opposite of the rotation sense indicated by structural studies we resolve this apparent disparity by developing an integrated and kinematically admissible model that has implications for other curved mountain belts the curvature of the pennsylvania salient may be explained by deformation partitioning in an initially laterally tapered basin between the cambrian ordovician carbonates and the overlying siliciclastic rocks earliest deformation occurred in the lowest strata and progressed toward the foreland and up section with time lateral differences in initial layer parallel shortening in the cambrian ordovician carbonates caused differential translation and rotations about a vertical axis in the cover sequence because of initial basin geometry the orogenic wedge developed a lateral taper with further shortening in the wedge and involvement of the cover rocks in the fold and thrust deformation gravitational driving forces became more important and the paleostress trajectories diverged in opposite directions on the two arms of the salient in response to the lateral taper

computerized tomographic analysis of displacement trajectories and three dimensional fold geometry above oblique thrust ramps computerized tomographic analysis of physical models of fold thrust structures permits nondestructive systematic analysis of variations in displacement trajectories and variations in three dimensional fold geometry as a function of thrust fault geometry the authors studied models in which sand layers with embedded transport parallel marker lines were shortened incrementally up to a maximum of 24 over rigid footwall fault templates these templates simulated a right stepping oblique ramp connecting two ramps perpendicular to the shortening direction in response to movement over the oblique ramp templates overturned folds formed and marker line deflections indicative of out of plane strains developed marker lines within layers originally truncated by fault templates were deflected leftward away from the right stepping oblique ramp during deformation whereas marker lines within sand layers that originally extended across the upper flat of the fault template were deflected in a more radial pattern differences in marker line deflections imply that displacement trajectories within natural thrust sheets may vary as a function of overburden and structural position furthermore their tomographic studies graphically demonstrate that out of plane strain and differential rotation of layers within thrust sheets occur in the vicinity of oblique ramps

hydrogeophysical investigations of the former s 3 ponds contaminant plumes oak ridge integrated field research challenge site tennessee abstractat the oak ridge integrated field research challenge site near oak ridge tennessee contaminants from the former s 3 ponds have infiltrated the shallow saprolite for over 60 years two and three dimensional dc resistivity tomography is used to characterize the number and location of the main contaminant plumes which include high concentration of nitrate these contaminant plumes have typically an electrical resistivity in the range 2 20 ohm m while the background saprolite resistivity is in the range 60 120 ohm m so the difference of resistivity can be easily mapped using dc resistivity tomography to locate the contaminant pathways we develop a relationship to derive the in situ nitrate concentrations from the 3d resistivity tomograms accounting for the effect of surface conductivity the footprint of the contamination upon the resistivity is found to be much stronger than the local variations associated with changes in the porosity and the clay content with this method we identified a tot

an immersed boundary method for the weather research and forecasting model this paper describes an immersed boundary method that facilitates the explicit resolution of complex terrain within the weather research and forecasting wrf model mesoscale models such as wrf are increasingly used for high resolution simulations particularly in complex terrain but errors associated with terrain following coordinates degrade the accuracy of the solution the use of an alternative gridding technique known as an immersed boundary method alleviates coordinate transformation errors and eliminates restrictions on terrain slope that currently limit mesoscale models to slowly varying terrain simulations are presented for canonical cases with shallow terrain slopes and comparisons between simulations with the native terrain following coordinates and those using the immersed boundary method show excellent agreement validation cases demonstrate the ability of the immersed boundary method to handle both dirichlet and neumann boundary conditions additionally realistic surface forcing can be provided at the immersed boundary by atmospheric physics parameterizations which are modified to include the effects of the immersed terrain using the immersed boundary method the wrf model is capable of simulating highly complex terrain as demonstrated by a simulation of flow over an urban skyline

sulfur iron and calcium cycling associated with natural electric currents running through marine sediment natural electric currents running through marine sediments have recently been found to couple oxygen reduction at the surface to sulfide oxidation in deeper anoxic layers here we show that such spatial separation of oxidation and reduction processes causes non conventional sulfur iron and calcium mobilization and reallocation reduced marine sediment was incubated with overlying oxic water and the vertical distribution of solutes and solids was analyzed after 45 150 days as much as 44 of sediment oxygen consumption was driven by electric currents and electrogenic oxidation of sulfide to sulfate with concurrent proton generation resulted in significant dissolution of iron sulfides and calcium carbonates in the anoxic layers of the sediment most of the mobilized iron diffused to the oxic zone where it formed oxidized iron minerals calcium precipitated in the oxic zone as magnesium calcite the electric coupling of biogeochemical processes in distant regions thus generates unique chemical conditions in marine sediments whereby key elements are mobilized and relocated probably along with trace elements and nutrients we suggest that such electrically coupled biogeochemistry flourishes in marine sediments after transient oxygen depletion leaving distinct signatures of such events in the geological record

significance of the deformation history within the hinge zone of the pennsylvania salient appalachian mountains abstracttwo competing models exist for the formation of the pennsylvania salient a widely studied area of pronounced curvature in the appalachian mountain belt the viability of these models can be tested by compiling and analyzing the patterns of structures within the general hinge zone of the pennsylvania salient one end member model suggests a nw directed maximum shortening direction and no rotation through time in the culmination an alternative model requires a two phase development of the culmination involving nnw directed maximum shortening overprinted by wnw directed maximum shortening structural analysis at 22 locations throughout the valley and ridge and southern appalachian plateau provinces of pennsylvania are used to constrain orientations of the maximum shortening direction and establish whether these orientations have rotated during progressive deformation in the pennsylvania salient s hinge outcrops of paleozoic sedimentary rocks contain several orders of folds conjugate faults steep

estimating specific yield and storage change in an unconfined aquifer using temporal gravity surveys 1 two high precision gravity surveys were conducted to determine groundwater mass changes at a managed groundwater recharge site in northeastern colorado gravity data were collected during pumping and two months after pumping ceased during pumping gravity was lower by as much as 46 gal near the pumping wells and higher by as much as 90 gal near the recharge ponds in comparison to data collected after pumping had ceased these differences are attributed to changes in groundwater mass associated with drawdown and infiltration inverse modeling of the gravity data indicates a 5 1 105 m3 decrease in storage beneath the recharge ponds between the two surveys which we attribute to dissipation of the groundwater mound created by recharge during pumping this estimate of the change in groundwater storage is made independently of assumptions of physical properties of the aquifer dividing the change in water volume per unit area determined from the gravity modeling by the change in water level measured in wells provides an estimate of specific yield sy of 0 21 0 03 which is within the range of specific yield estimates derived from aquifer tests at the site water level changes predicted from the gravity data agree on average to within 0 45 m of those measured which we take to be an estimate of the uncertainty in water table depth predictions that can be obtained from gravimetric data in unconfined aquifers the study covers a 3 2 km2 area providing a prototype for similar studies at larger scales

imaging and characterisation of subsurface solute transport using electrical resistivity tomography ert and equivalent transport models abstract we assess the usefulness of electrical resistivity tomography ert in imaging and characterising subsurface solute transport in heterogeneous unconfined aquifers a field tracer experiment was conducted at the krauthausen test site germany the spatial and temporal evolution of the injected nabr solute plume was monitored in a 2d ert image plane located downstream of the injection well for 90 days since ert maps changes in bulk electrical conductivity the reconstructed images at selected time intervals are first converted to solute concentration maps by postulating a linear relation the concentration maps are then analysed using an equivalent convection dispersion model cdm which conceptualises the aquifer as a homogeneous medium with a uniform mean flow velocity as demonstrated by associated synthetic model studies ert resolution in terms of recovered equivalent dispersivities is limited due to spatial smoothing inherent to the imaging algorithm since for heterogeneous media local concentrations within the plume deviate from those predicted by the equivalent cdm we also interpret the ert derived pixel breakthrough curves in terms of an equivalent stream tube model stm the stm represents transport in the aquifer by a set of 1d convection dispersion processes allowing the degree of mixing and the heterogeneity of transport within the plume to be quantified we believe that the observed tracer plume is satisfactorily described by the equivalent cdm probably because the tracer plume was small relative to the heterogeneity scale of the aquifer even though application of the stm revealed some deviation from the ideal homogeneous case the equivalent dispersivity in the stm matches the longitudinal dispersivity of the cdm closely consistent with predominantly homogeneous mixing however the stm analysis illustrates how ert results can be used to quantify the variability of parameters relevant to flow and transport in heterogeneous aquifers

diesel transport monitoring in simulated unconfined aquifers using miniature resistivity arrays the principal aim of this study is to assess the scope of monitoring diesel plume migration in a scaled aquifer model with a miniaturised electrical resistivity array respectively 1000 and 500 ml of diesel were injected in both the unsaturated and water saturated zones of a sand body overlying a clay aquitard and diesel migration was monitored with a miniature electrode array and an off the shelf resistivity meter inverted time lapse electrical resistivity tomography ert data reflect downward and lateral spreading of the diesel plume away from the injection point in the unsaturated zone diesel was also imaged to spread upwards and laterally away from the injection point in the saturated zone as controlled by capillary rise in both cases later time ert images reflected preferential pooling of diesel on the water table as well as vertical smearing of pooled diesel in response to simulated water table fluctuations repeat fluid electrical conductivity ec and dissolved oxygen do measurements validate the observed changes in bulk resistivity caused by both diesel injections artefacts introduced by 2d inversion of 3d contaminant transport were abound time lapse ert imaging of diesel transport is therefore inferred to be feasible and well suited to complementing conventional techniques of intrusive site investigation although time lapse 3d or 4d ert imaging is strongly advocated

mapping soil layers using electrical resistivity tomography and validation sandbox experiments abstract knowledge of the geologic structure at a field site is a useful piece of information for hydrologic modeling since it can serve as more site specific prior information about the hydraulic parameter patterns at the site than generic spatial statistics widely accepted electrical resistivity tomography ert survey for mapping subsurface anomalies could be a viable tool for acquiring this information however their ability to delineate geologic structures has not been thoroughly investigated in this study two dimensional ert numerical experiments were first conducted to study the effects of boundary conditions on the dipole dipole and pole pole array configurations an ert setup subsequently was implemented in a sandbox consisting of complex layers of different sands a continuous copper wire was installed along the sides of the sandbox to impose potential boundaries using data collected with the pole pole array in the sandbox under different degrees of drainage and the successive linear estimator sle algorithm we show that ert yields electrical conductivity estimates of complex layer structures with small uncertainties in addition using sle with physically meaningful correlation scales as prior information can lead to an electrical conductivity field that is consistent with visually observed layer structures the correlation scale concept also was demonstrated to provide guidance to the design of the electrode spacing in the surveys moreover the estimated field was validated by predicting electrical potential fields from two independent ert surveys using electrodes at different locations results of this study suggest that the combination of ert and sle is a viable geophysical survey tool for mapping geologic layer structures research significance this study develops a method to implement prescribed potential boundaries for enhancing the pole pole ert survey illustrates the importance of correlation scales and develops an approach for validating ert results

stochastic analysis of moisture plume dynamics of a field injection experiment 1 a vadose zone field injection experiment was conducted in the summer of 2000 at the hanford site washington the unique moisture content database is used to identify the lithology at the field site and to interpret visualize and quantify the spatiotemporal evolution of the three dimensional 3 d moisture plume created by the injection experiment we conducted a hierarchical geostatistical analysis to examine the large scale geologic structure for the entire field site and then investigated small scale features within different layers afterward variogram analysis was applied to the field measured for seven different days during the injection experiment temporal variations of sills and ranges are related to the observed moisture plume dynamics a visualization of the 3 d moisture plume evolution illustrates effects of media heterogeneity statistics of changes in moisture content as a function of distance reveal large variance near the wetting front the coefficient of variation increases with decreasing mean these findings support the gradient and mean dependent variability in the moisture content distribution as reported by existing stochastic theories spatial moment analysis is also conducted to quantify the rate and direction of movement of the plume mass center and its spatial spreading the ratio of horizontal to vertical spreading at varying moisture contents suggests moisture dependent anisotropy in effective unsaturated hydraulic conductivity confirming existing stochastic theories however the principal directions of the spatial moments are found to vary as the moisture plume evolves through local heterogeneity a feature that has not been recognized in the theories

practical techniques for 3d resistivity surveys and data inversion1 techniques to reduce the time needed to carry out 3d resistivity surveys with a moderate number 25 to 100 of electrodes and the computing time required to interpret the data have been developed the electrodes in a 3d survey are normally arranged in a square grid and the pole pole array is used to make the potential measurements the number of measurements required can be reduced to about one third of the maximum possible number without seriously degrading the resolution of the resulting inversion model by making measurements along the horizontal vertical and 45 diagonal rows of electrodes passing through the current electrode the smoothness constrained least squares inversion method is used for the data interpretation the computing time required by this technique can be greatly reduced by using a homogeneous half space as the starting model so that the jacobian matrix of partial derivatives can be calculated analytically a quasi newton updating method is then used to estimate the partial derivatives for subsequent iterations this inversion technique has been tested on synthetic and field data where a satisfactory model is obtained using a modest amount of computer time on an 80486dx2 66 microcomputer it takes about 20 minutes to invert the data from a 7 by 7 electrode survey grid using the techniques described below 3d resistivity surveys and data inversion can be carried out using commercially available field equipment and an inexpensive microcomputer

characterization of stress perturbations near major fault zones insights from 2 d distinct element numerical modelling and field studies jura mountains abstract we consider and discuss the presence of discontinuities in the crust as a major source of stress perturbations based on 2 d distinct element modelling we reconstruct the local stress field around a vertical discontinuity in various geological contexts the resulting stress distribution reveals that major directional stress changes occur near the tips of the discontinuity so that stress deviations can reach values as large as 50 we establish simple relationships controlling stress changes around a pre existing fault zone as a function of 1 the remote differential stress magnitude 1 3 2 the friction coefficient on the discontinuity and 3 the strike of the discontinuity relative to the far field stress as a geological example we present the morez fault zone in the internal jura paleostress reconstruction in forty two sites indicates that the trends of the mio pliocene compression are n110 on average near the fault whereas they are n130 in the surrounding areas a comparison between the results of the tectonic study and those of theoretical modelling suggests that the 20 counterclockwise deviation is directly related to the reactivation of this large weak zone we thus evaluate the role of mechanical decoupling along pre existing zones of weakness especially with consideration to the accommodation of the alpine deformation in the jura belt

mechanisms of up valley winds abstract the basic physical mechanisms governing the daytime evolution of up valley winds in mountain valleys are investigated using a series of numerical simulations of thermally driven flow over idealized three dimensional topography the three dimensional topography used in this study is composed of two two dimensional topographies one a slope connecting a plain with a plateau and the other a valley with a horizontal floor the present two dimensional simulations of the valley flow agree with results of previous investigations in that the heated sidewalls produce upslope flows that require a compensating subsidence in the valley core bringing down potentially warmer air from the stable free atmosphere in the context of the three dimensional valley plain simulations the authors find that this subsidence heating in the valley core is the main contributor to the valley plain temperature contrast which under the hydrostatic approximation is the main contributor to the valley plain pressure differe

structural geology of stewart peak culmination idaho wyoming thrust belt a structural culmination is the highest point along a structural axis or fold system away from which the folds plunge structural culminations are an important and predictable component of foreland fold thrust belts and are prime targets for oil and gas accumulations the stewart peak culmination is a doubly plunging anticlinorium in the absaroka thrust sheet of western wyoming located in the northern salt river range major thrust faults in the stewart peak culmination comprise a large scale duplex fault zone the roof fault of the duplex is the absaroka thrust the floor fault is the basal or regional decollement and the intervening murphy and firetrail thrusts are trailing edge imbricate faults in the darby plate that have locally uplifted and deformed the absaroka into an asymmetric breached anticlinorium or culmination in addition these major thrust faults subdivide the culmination into fault bound structural horses each with a characteristic style of deformation as a function of its stratigraphic and structural level in the duplex a recent exploratory test of the culmination provided data which suggest that the absaroka thrust fault locally cuts downsection in the transport direction this may be explained by initial folding and breaching of the firetrail anticline followed by main motion on the absaroka thrust which overrode the fold the available data suggest that the stewart peak culmination is the result of 1 polyphase uplift or arching of the absaroka thrust sheet by the murphy and firetrail thrust sheets 2 lateral imbrication and ramping and 3 arching of the precambrian basement complex beneath the northern salt river range in addition a basic kinematic model of deformation applicable to structural culminations includes emplacement of an allochthonous mass over a parautochthonous substratum closely followed by or contemporaneous with deformation and translation of the footwall section to produce a duplex fault zone that folds the overlying allochthon the stewart peak culmination bears many similarities in structural style and origin to polyphase folded fault domes in the canadian rocky mountains specifically the stewart peak area is compared to the savanna creek and moose mountain culminations

history of the sevier orogenic wedge in terms of critical taper models northeast utah and southwest wyoming problems with applying critical taper models to ancient orogenic wedges are overcome in the late cretaceous late paleocene sevier orogenic wedge in utah and wyoming by a symptomatic approach in which wedge behavior is inferred from the time space distribution of thrust faulting erosion and synorogenic sediment accumulation in association with the orogenic wedge in turn the causes of wedge behavior are interpreted in terms of features that are known about the sevier wedge such as the locations of major decollements and the lithologic constituents of major thrust sheets from coniacian through late paleocene time 35 m y basement and cover rocks in the sevier wedge were shortened by 100 km in three major and one minor events an overall eastward progression of thrusting was punctuated by several episodes of out of sequence and hinterland vergent thrusting over the long term wedge taper was controlled by internal wedge strength initial taper and changes in the durability of the upper surface of the wedge and its internal lithostratigraphy critical taper was maintained by the offsetting effects of basement duplexing in the rear of the wedge and forward imbrication at the front of the wedge while the basal decollement was mainly in basement rocks the wedge was highly tapered and thrust spacing was relatively close 15 km beginning ca 75 ma the basal decollement ramped upward and eastward into weak cambrian shale and jurassic salt thrust spacing increased to 25 45 km and wedge taper decreased drastically the highly tapered rear part of the wedge carried strong basement rocks above moderately weak mylonitic and cataclastic decollements whereas the frontal lower taper part of the wedge carried sedimentary rocks above extremely weak salt and shale decollements through time internal strength of the wedge decreased as it incorporated an increasing proportion of sedimentary rocks the thrust belt was able to advance eastward in spite of its decreasing internal strength and decreasing taper because the basal decollement of the wedge also became weaker through time both by strain softening beneath the rear of the wedge and by propagating along extremely weak rocks beneath the front of the wedge provenance data from associated synorogenic conglomerates indicate that the durability of the upper surface of the wedge probably increased over the long term history of the sevier wedge as an increasing proportion of the erosional surface became occupied by resistant precambrian quartzite and basement rocks this would have had the effect of decreasing the rate of erosion through time and maintaining a steeper surface slope which would have helped the wedge to remain at critical to supercritical taper the sevier wedge also exhibits several shorter term 10 km and 3 was subjected to regional erosion marked by major unconformities that ultimately caught up with tectonic thickening and caused the wedge to stall this cyclicity is attributed to the need for wedges to become supercritical before they can propagate forward over large distances and a lag time between wedge thickening and uplift and wedge erosion erosion eventually catches up to the rate of uplift the wedge stalls and the locus of deformation shifts to the rear of the wedge in order to rebuild taper this analysis suggests that orogenic wedges continually deform and find a way to maintain taper sufficient to allow forward propagation as long as a sufficient push from the rear exists the actual taper value may change substantially through time as lithostratigraphy internal strength upper surface durability and presence absence of weak potential stress guides conspire to maintain a critical taper

folding by cataclastic flow at shallow crustal levels in the canyon range sevier orogenic belt west central utah abstract folds form by ductile deformation typically involving continuous flow in the elastico frictional regime such deformation may be accomplished by cataclastic flow involving collective movement on a population of fractures and zones the canyon range cr syncline part of the cr thrust sheet in west central utah developed in this regime the cr syncline is composed of thick bedded quartzite units with a small material contrast between layers limiting limb rotation by flexural slip alone thus fracture populations developed to accommodate fold tightening by limb rotation and thinning and the formation of transverse zones across the fold several generations of fracture and deformation zone dz networks are recognized from mesoscopic and microscopic evidence and can be related to stages of folding the net result of the large number of distributed fractures and deformation zones is a continuous deformation that is homogeneous at the scale of the outcrop all these lines of evidence suggest that large scale cataclastic flow accommodated folding by allowing rigid mesoscopic blocks to slide along bounding dzs along its length the cr syncline consists of several segments bounded by transverse zones with different mechanisms accommodating fold tightening in adjacent segments in one segment fold tightening progressed by limb rotation and then out of the core thrusting in contrast fold tightening in the adjoining segments occurred by rotation and thinning of one limb and possible hinge migration with the steeply dipping to overturned limb showing progressive thinning of units on a megascopic scale and progressive increase in the thickness and density of deformation zones at all scales

salinity dependence of the thermoelectric coupling coefficient in brine saturated sandstones 1 we report measurements of the thermoelectric coupling coefficient in intact sandstone samples saturated with nacl brine at concentrations ranging from 1 10 4 to 1 m our measurements account for temperature dependent electrode effects we also present a model for the salinity dependence of the thermoelectric coupling coefficient which yields a close match to the experimental data at low salinity the measured coupling coefficient exhibits the salinity dependence predicted for a perfect membrane while at high salinity the coupling coefficient follows that predicted for an uncharged porous medium measured values of the coupling coefficient range from 0 370 mvk 1 at low salinity 1 10 4 m to 0 055 mvk 1 at high salinity 1 m

waveform tomography at a groundwater contamination site surface reflection data wehaveappliedacoustic waveformtomographyto452d seismic profiles to image the 3d geometry of a buried paleochannel at a groundwater contamination site at hill air force base in utah the paleochannel which is incised into an alluvium covered clay aquitard acts as a trap for dense nonaqueous phase liquids dnapls that contaminate the shallowest groundwater system in the study area the 2d profiles were extracted from a 3d surface reflection data set first arrival traveltime tomography provided initial velocity models for the waveform tomography we inverted for six frequency components in the band 30 90 hz of the direct and refracted waves to produce 45 2d velocity models the flanks and bottom of a channel with a maximum depth of about 15 m were well modeled in most of the 45 parallel 2d slices whichallowedustoconstructa3dimageofthechannel by combining and interpolating between the 45 image slices the 3d model of the channel will be useful for siting extraction wells within the site remediation program the alluvium that fills the channel showed marked vertical and lateral velocity heterogeneity traveltime tomography and waveform tomography can be complementary approaches used together they can provide high resolution images of complicatedshallowstructures

a microbial fuel cell in contaminated ground delineated by electrical self potential and normalized induced polarization data there is a growing interest in the use of geophysical methods to aid investigation and monitoring of complex biogeochemical environments for example delineation of contaminants and microbial activity related to land contamination we combined geophysical monitoring with chemical and microbiological analysis to create a conceptual biogeochemical model of processes around a contaminant plume within a manufactured gas plant site self potential induced polarization and electrical resistivity techniques were used to monitor the plume we propose that an exceptionally strong 800 mv peak to peak dipolar sp anomaly represents a microbial fuel cell operating in the subsurface the electromagnetic and electrical geophysical data delineated a shallow aerobic perched water body containing conductive gasworks waste which acts as the abiotic cathode of microbial fuel cell this is separated from the plume below by a thin clay layer across the site microbiological evidence suggests that degradation of organic contaminants in the plume is dominated by the presence of ammonium and its subsequent degradation we propose that the degradation of contaminants by microbial communities at the edge of the plume provides a source of electrons and acts as the anode of the fuel cell we hypothesize that ions and electrons are transferred through the clay layer that was punctured during the trial pitting phase of the investigation this is inferred to act as an electronic conductor connecting the biologically mediated anode to the abiotic cathode integrated electrical geophysical techniques appear well suited to act as rapid low cost sustainable tools to monitor biodegradation

stress deflection in a tectonic compressional field a model for the northwestern iberian chain spain by means of fault population analysis using the right dihedra y r diagram and etchecopar s methods the states of stress in a number of sites of the cameras massif northwestern iberian chain spain and nearby areas of the ebro basin have been determined these states of stress have been used as a framework in order to infer a model of the actual stress field in that area during the main stage of the alpine compression oligocene lower miocene the three main compression directions obtained nw se nne ne sw can be explained by a single compression field with horizontal 1 trending nne and vertical 2 whose primary trajectories are deflected due to 1 large scale strike slip faults or lateral ramps of thrusts or 2 frontal ramps of thrusts oblique to the main compressive axis the reliability of this scheme has been checked by means of a two dimensional mathematical model based upon the finite element method and applied on a sheet whose rheological properties are similar to those of a standard limestone this model simulates the main features of the regional stress field and it was constructed after determining the average parameters of the possible external or primary field and simulating the major faults that could deflect the stress trajectories

quantitative assessment of electrical resistivity tomography for monitoring dnapls migration comparison with high resolution light transmission visualization in laboratory sandbox abstract real time monitoring of dense non aqueous phase liquids dnapls migration and distribution is essential for the decision of an effective remediation strategy light transmission visualization ltv has shown its accuracy and efficiency for measuring dnapls saturation and water content in the laboratory but it cannot be implemented in three dimensional sandbox or field scale sites recently developed electrical resistivity tomography ert has been applied in monitoring the migration and distribution of dnapls in bench and field scale studies however the evaluation of the ability of ert for monitoring dnapls migration by a direct comparison of ert with high resolution techniques such as ltv within an experimental system is still lacking two sandbox experiments with different permeability conditions are conducted to quantitatively assess the capability of ert for monitoring the dnapls migration during the injections ltv method is used to visualize the dnapls migration and provide high resolution saturation data while ert method is applied to capture the change of resistivity the results from the comparison between ltv and ert methods show that ert is successful in detecting the accumulation and flow bypassing phenomenon around the low permeability lenses as well as the penetration through the high permeability lenses there is a fair correlation between the resistivity and saturation with overall correlation coefficients above 0 6 except at last stage however using classical regularization techniques based on smoothness the area of dnapls plume determined by ert is commonly overestimated compared to the plume around the low permeability lenses the plume around the high permeability lenses estimated by ert is more extensive due to larger resistivity contrasts in addition ert measurements indicate that the resistivity increase caused by the low saturation dnapls is not apparent enough which is likely to be covered up under the changing hydrogeochemical environments in field investigations

an immersed boundary method enabling large eddy simulations of flow over complex terrain in the wrf model abstractthis paper describes a three dimensional immersed boundary method ibm that facilitates the explicit resolution of complex terrain within the weather research and forecasting wrf model two interpolation methods trilinear and inverse distance weighting idw are used at the core of the ibm algorithm this work expands on the previous two dimensional ibm algorithm of lundquist et al which uses bilinear interpolation simulations of flow over a three dimensional hill are performed with wrf s native terrain following coordinate and with both ib methods comparisons of flow fields from the three simulations show excellent agreement indicating that both ib methods produce accurate results idw proves more adept at handling highly complex urban terrain where the trilinear interpolation algorithm fails this capability is demonstrated by using the idw core to model flow in oklahoma city oklahoma from intensive observation period 3 iop3 of the joint urban 2003 field campaign flow in oklahoma c

topographic effects on radiation in the wrf model with the immersed boundary method implementation validation and application to complex terrain abstracttopographic effects on radiation including both topographic shading and slope effects are included in the weather research and forecasting wrf model and here they are made compatible w

cross coupled flow modeling of coincident streaming and electrochemical potentials and application to subglacial self potential data 1 this study aims to demonstrate that self potential measurements can yield unique information about subglacial drainage conditions which has so far been doubtful at the bed of warm based glaciers arborescent and distributed drainage systems interact and streaming and electrochemical potentials coincide a key secondary aim of this study is therefore the development of a mathematical framework for the analysis of self potentials generated by such interacting flow systems we consider cross coupling between hydraulic electrical and chemical driving forces and apply the resulting model solution to self potential data recorded beneath haut glacier d arolla switzerland we find that 1 the streaming and electrochemical contributions to the total self potential signal can be separated mathematically 2 streaming potentials directly reflect the direction of water flow at the glacier bed 3 combination of streaming potentials with hydraulic conductivity estimates from slug tests allows estimation of in situ subglacial water flow velocities 4 the subglacial zeta potential calculated from estimated values of the streaming coupling coefficient is small 0 022 v due to systematic flushing of clay minerals from the channel area during the melt season and 5 uncertainties in exact electrode location in the borehole are unlikely to produce self potential noise self potential measurements may therefore yield unique information about subglacial drainage conditions and especially the direction and velocity of in situ subglacial water flow are difficult to obtain by other methods we further anticipate that our mathematical framework will be applicable to other areas of subsurface hydrology especially where spatially distributed seepage feeds preferential flow pathways

evaluating implementations of the immersed boundary method in the weather research and forecasting model abstractthe terrain following coordinate system used by many atmospheric models can cause numerical instabilities due to discretization errors as resolved terrain slopes increase and the grid becom

an application of the immersed boundary method for recovering the three dimensional wind fields over complex terrain using multiple doppler radar data abstractthis study develops an extension of a variational based multiple doppler radar synthesis method to construct the three dimensional wind field over complex topography the immersed boundary method ibm is implemented to take into account the influence imposed by a nonflat surface the ibm has the merit of providing realistic topographic forcing without the need to change the cartesian grid configuration into a terrain following coordinate system both dirichlet and neumann boundary conditions for the wind fields can be incorporated the wind fields above the terrain are obtained by variationally adjusting the solutions to satisfy a series of weak constraints which include the multiple radar radial velocity observations anelastic continuity equation vertical vorticity equation background wind and spatial smoothness terms experiments using model simulated data reveal that the flow structures over complex orography can be successfully retrieved using radial velocity measurements from multiple d

three dimensional inversion of self potential data used to constrain the pattern of groundwater flow in geothermal fields 1 we propose an algorithm to invert self potential signals measured at the ground surface of the earth to localize hydromechanical disturbances or to the pattern of groundwater flow in geothermal systems the self potential signals result from the divergence of the streaming current density groundwater flow can be either driven by topography of the water table free convection or deformation of the medium the algorithm includes the electrical resistivity distribution of the medium obtained independently by dc resistance tomography or electromagnetic methods or by coding the assumed geology in terms of distribution of the electrical resistivity accounting for the effect of the temperature and salinity distributions and possibly constraints from borehole measurements inversion of the distribution of the source current density from ground surface and borehole self potential measurements is achieved by solving the inverse problem using tikhonov regularization solutions that are compatible with the physics of the primary flow problem by introducing assumptions regarding the smoothness or the compactness of the source and the three dimensional distribution of the electrical resistivity of the system the inverse problem can be solved in obtaining the three dimensional distribution of the current source density in the ground however an annihilator can be added to the inverted source geometry without affecting the measured self potential field annihilators can be obtained from boundary conditions synthetic models and a sandbox experiment are discussed to demonstrate the validity of the algorithm an application is presented to the geothermal field of cerro prieto baja california mexico using literature data inversion of the self potential and resistivity data allows observing a plume of hot groundwater rising to the ground surface in the central part of the investigated area and discharging to the ground surface in the southwest part the temperature anomaly associated with the existence of this plume is independently observed by interpolating borehole temperature measurements we found a good agreement between the distribution of the temperature and the inverted source current density the proposed method appears therefore as a noninvasive method for remote detection and three dimensional mapping of subsurface groundwater flow

the heavy rainfall mechanism revealed by a terrain resolving 4dvar data assimilation system a case study abstractin this research a newly developed terrain resolving four dimensional variational 4dvar based data assimilation system immersed boundary method variational doppler radar analysis system

hydrogeological characterization of the south oyster bacterial transport site using geophysical data a multidisciplinary research team has conducted a field scale bacterial transport study within an uncontaminated sandy pleistocene aquifer near oyster virginia the overall goal of the project was to evaluate the importance of heterogeneities in controlling the field scale transport of bacteria that are injected into the ground for remediation purposes geochemical hydrological geological and geophysical data were collected to characterize the site prior to conducting chemical and bacterial injection experiments in this paper we focus on results of a hydrogeological characterization effort using geophysical data collected across a range of spatial scales the geophysical data employed include surface ground penetrating radar radar cross hole tomography seismic cross hole tomography cone penetrometer and borehole electromagnetic flowmeter these data were used to interpret the subregional and local stratigraphy to provide high resolution hydraulic conductivity estimates and to provide information about the log conductivity spatial correlation function the information from geophysical data was used to guide and assist the field operations and to constrain the numerical bacterial transport model although more field work of this nature is necessary to validate the usefulness and cost effectiveness of including geophysical data in the characterization effort qualitative and quantitative comparisons between tomographically obtained flow and transport parameter estimates with hydraulic well bore and bromide breakthrough measurements suggest that geophysical data can provide valuable high resolution information this information traditionally only partially obtainable by performing extensive and intrusive well bore sampling may help to reduce the ambiguity associated with hydrogeological heterogeneity that is often encountered when interpreting field scale bacterial transport data

controls on the geometry of fold thrust belt salients salients convex to the foreland curves in the map traces of orogens typically involve fold thrust belts formed along the foreland margin of orogens an examination of the map view shape degree of asymmetry dimensions and structural trend line patterns i e the variation in fold trend and fault strike along the length of the belt of 20 fold thrust belt salients worldwide illustrates relationships between salient geometry and the geologic setting in which the salient formed in order to understand these relationships we used simple sandbox models to simulate the formation of three of the several types of salients specifically we examined indenter controlled salients the geometry of which reflects interaction of a fold thrust belt with a hinterland indenter basin controlled salients the geometry of which reflects lateral variations in the thickness of predeformational basin fill and detachment controlled salients the geometry of which reflects lateral variations in the strength of a detachment surface our models demonstrate that thrusts in these three types of salients initiate with a curved shape and that rocks within thrust sheets on the limbs of salients can undergo a vertical axis rotation in response to simple shear without requiring major rotation of the fault trace furthermore trend line patterns distinguish basin controlled from indenter controlled salients specifically structural trend lines in basin controlled salients converge at the end points of the curve while in indenter controlled salients they diverge at the end points of the curve the asymmetry of a salient correlates with the asymmetry of the predeformational basin and or of the indenter and with the convergence direction thus our results explain geometric characteristics of individual salients and address controversies concerning paleomagnetic data in salients they also may help prioritize petroleum exploration targets in salients foreland basin oil fields concentrate at the apex of basin controlled salients because the geologic factors that generate the salient also contribute to localizing oil fields

thrust timing growth of structural culminations and synorogenic sedimentation in the type sevier orogenic belt western united states most of the regional shortening in the type area of the sevier orogenic belt in central utah was accommodated by displacement on the canyon range neocomian aptian pavant aptian albian paxton cenomanian campanian and gunnison late campanian paleocene thrust systems inception of each thrust system generated synorogenic sediment associated with frontal thrust tip anticlines or triangle zones and older thrust sheets that were elevated above major ramps farther toward the hinterland the sevier culmination a large antiformal duplex cored by crystalline basement rocks developed during paxton and gunnison thrusting west of and structurally beneath the canyon range and pavant thrusts growth of the sevier culmination was coeval with reactivation of the canyon range and pavant thrust systems and produced a second culmination in proterozoic lower cambrian rocks in the canyon range these structural highs provided much of the sediment to the adjacent foreland basin from late cenomanian to late paleocene time and may have helped to maintain critical taper in the thrust belt