deep seated gravitational slope deformations related landslides and tectonics abstract deep seated gravitational slope deformations and their relationships with tectonic deformation of rocks is considered to examine the viewpoint of tectonics as a causative factor in slope deformation first a distinction is made between the different types of deep seated gravitational slope deformation then the geomorphological and structural effects of the different macrostructural deformations induced by tectonics on the scale of the whole deforming ridge is briefly discussed finally some case studies that represent either verified or possible cases of gravity deformation in response to tectonic activity are used as illustration

joint inversion of full waveform ground penetrating radar and electrical resistivity data part 2 enhancing low frequencies with the envelope transform and cross gradientsjoint inversion of gpr and er data recovering material properties of the subsurface using ground penetrating radar gpr data of finite bandwidth with missing low frequencies and in the presence of strong attenuation is a challengi

diagenesis in north sea hpht clastic reservoirs consequences for porosity and overpressure prediction upper jurassic clastic reservoirs of the fulmar formation in the central north sea possess anomalously high porosities for their present day depth of burial reservoirs with the highest overpressures have the highest porosities possess less macroquartz cement and have significant secondary porosity quartz cementation in hpht high pressure high temperature reservoirs has been inhibited by a combination of factors high overpressure limited fluid movement presence of early grain coating cements high pore fluid salinity and possibly petroleum migration secondary porosity has contributed to reservoir quality with an average of 4vol extra porosity created quantitative prediction of porosity would require an improved depositional model for the fulmar accurate thermal and pressure modelling and detailed knowledge of field filling and leakage histories theoretical calculations indicate that diagenetic reactions occurring in the fulmar formation smectite illitisation and quartz cementation did not generate significant overpressure because seal permeabilities were too high and the rate of volume increase associated with the reactions too small therefore diagenetic reactions can effectively be ignored when modelling overpressure generation in the central north sea although cementation will affect rock permeability and rates of fluid dissipation

internal structure of an alpine rock glacier based on crosshole georadar traveltimes and amplitudes rapid melting of permafrost in many alpine areas has increased the probability of catastrophic rock slides in an attempt to provide critical structural information needed for the design and implementation of suitable mitigation procedures we have acquired low frequency 22 mhz cross hole radar data from within a fast moving rock glacier an important form of alpine permafrost since the ice rock and pockets of water and air found in the underground of high alpine areas have very different dielectric permittivities and electrical conductivities the radar method was well suited for investigating the structure and state of the rock glacier our interpretation of the radar velocities and attenuations was constrained by geomorphological observations borehole lithological logs and the results of a surface seismic survey the radar data revealed the existence of a discontinuous 7 11 m thick ice rich zone distinguished by high velocities 0 14 0 17 m ns and low attenuations 0 04 0 09 m 1 and a thin underlying ice free zone characterized by moderate velocities 0 11 0 12 m ns and low attenuations 0 04 0 09 m 1 beneath these two zones we observed a prominent band of high velocities 0 14 0 17 m ns and moderately high attenuations 0 10 0 20 m 1 associated with unconsolidated glacial sediments and numerous large air filled voids which in the past were probably filled with ice at greater depths the variably dry to water saturated sediments were represented by generally lower velocities 0 08 0 10 m ns and higher attenuations 0 16 0 24 m 1 the bedrock surface was represented by an abrupt 0 03 m ns velocity increase we speculate that the disappearance of ice both laterally and with depth occurred during the past one to two decades

detection of spatially limited high porosity layers using crosshole gpr signal analysis and full waveform inversion high permittivity layers related to high porosity layers or impermeable clay lenses can act as low velocity electromagnetic waveguides electromagnetic wave phenomena associated with these features are complicated not well known and not easy to interpret in borehole gpr data recently a novel amplitude analysis approach was developed that is able to detect continuous low velocity waveguides and their boundaries between boreholes by using maximum and minimum positions of the trace energy profiles in measured gpr data by analyzing waveguide models of different thickness dip extent permittivity and conductivity parameters we extend the amplitude analysis to detect spatially limited or terminated waveguides waveguides that show high amplitude elongated wave trains are most probably caused by a change in porosity rather than a change in clay content in a crosshole gpr data set from the boise hydrogeophysical research site two terminated wave guiding structures were detected using the extended amplitude analysis information gained from the amplitude analysis improved the starting model for full waveform inversion which imaged the lateral extent and thickness of terminated waveguides with high resolution synthetic data calculated using the inverted permittivity and conductivity models show similar amplitudes and phases as observed in the measured data which indicates the reliability of the obtained models neutron neutron logging data from three boreholes confirm the changes in porosity and indicate that these layers were high porosity sand units within low porosity poorly sorted sand and gravel units

improved characterization of fine texture soils using on ground gpr full waveform inversion ground penetrating radar gpr uses the recording of electromagnetic waves and is increasingly applied for a wide range of applications traditionally the main focus was on the analysis of the medium permittivity since estimates of the conductivity using the far field approximation contain relatively large errors and cannot be interpreted quantitatively recently a full waveform inversion fwi scheme has been developed that is able to reliably estimate permittivity and conductivity values by analyzing reflected waves present in on ground gpr data it is based on a frequency domain solution of maxwell s equations including far intermediate and near fields assuming a 3 d subsurface here we adapt the fwi scheme for on ground gpr to invert the direct ground wave traveling through the shallow subsurface due to possible interference with the airwaves and other reflections an automated time domain filter needed to be included in the inversion in addition to the obtained permittivity and conductivity values also the wavelet center frequency and amplitude return valuable information that can be used for soil characterization combined geophysical measurements were carried out over a silty loam with significant variability in the soil texture the obtained medium properties are consistent with theta probe electromagnetic resistivity tomography and electromagnetic induction results and enable the formulation of an empirical relationship between soil texture and soil properties the permittivities and conductivities increase with increasing clay and silt and decreasing skeleton content moreover with increasing permittivities and conductivities the wavelet center frequency decreases whereas the wavelet amplitude increases which is consistent with the radiation pattern and the antenna coupling characteristics

monitoring landslides and tectonic motions with the permanent scatterers technique spaceborne differential synthetic aperture radar interferometry dinsar has already proven its potential for mapping ground deformation phenomena e g volcano dynamics however atmospheric disturbances as well as phase decorrelation have prevented hitherto this technique from achieving full operational capability these drawbacks are overcome by carrying out measurements on a subset of image pixels corresponding to pointwise stable reflectors permanent scatterers ps and exploiting long temporal series of interferometric data results obtained by processing 55 images acquired by the european space agency esa ers sar sensors over southern california show that the ps approach pushes measurement accuracy very close to its theoretical limit about 1 mm allowing the description of millimetric deformation phenomena occurring in a complex fault system a comparison with corresponding displacement time series relative to permanent gps stations of the southern california integrated gps network scign is carried out moreover the pixel by pixel character of the ps analysis allows the exploitation of individual phase stable radar targets in low coherence areas this makes spaceborne interferometric measurements possible in vegetated areas as long as a sufficient spatial density of individual isolated man made structures or exposed rocks is available the evolution of the ancona landslide central italy was analysed by processing 61 ers images acquired in the time span between june 1992 and december 2000 the results have been compared with deformation values detected during optical levelling campaigns ordered by the municipality of ancona the characteristics of ps gps and optical levelling surveying are to some extent complementary a synergistic use of the three techniques could strongly enhance quality and reliability of ground deformation monitoring d 2002 elsevier science b v all rights reserved

origin and significance of redistributional secondary porosity abstract redistributional secondary rds porosity is created by the dissolution of framework grains and cements and the simultaneous precipitation of reaction products in the nearby pore space aluminosilicate minerals and in particular feldspars are the usual precursors of rds porosity in sandstones common product minerals are authigenic quartz and clay minerals usually kaolinite this type of secondary porosity is almost ubiquitous in sandstones rds porosity has little effect on the total porosity of reservoir rocks and contrary to popular opinion cannot give rise to higher than expected porosities at depth petrographic criteria alone are an insufficient measure that the rock has undergone leaching resulting in porosity enhancement to demonstrate porosity enhancement due to leaching it is necessary to show that the porosity of the rock is statistically higher than would otherwise be the case for a rock of similar characteristics that has not been leached the dissolution precipitation reactions that give rise to rds arise from the inherent thermodynamic instability of minerals such as the feldspars and other aluminosilicates which formed under magmatic or metamorphic conditions when these minerals dissolve they add aluminium and silica to the pore fluid however the concentration of aluminium and silica in the pore fluid is buffered by clay minerals and quartz respectively during burial diagenesis thus any increase in the concentration of these components leads to the precipitation of an authigenic clay mineral and authigenic quartz carboxylic acids are claimed to have the capacity to complex aluminium and so increase the solubility of aluminium and eliminate the precipitation of a clay phase however they are unlikely to have any major effect on aluminium solubility in natural i e complex pore fluids in fact dissolution will occur in acid neutral or alkaline conditions at a rate that is kinetically controlled reaction rates speed up exponentially with increasing temperature and therefore depth resulting in the destruction of more and more unstable components this increase in the rate of destruction of unstable components at depth can give rise to what appears to be a late leaching event what is seen in fact is the natural culmination of the destruction of thermodynamically unstable phases at an ever increasing rate during burial thus for a rock of a given composition the fraction of the total porosity that is secondary will increase with burial depth until all labile components are consumed the behaviour of mineral mixtures in the presence of a moving pore fluid is an additional contributing factor to the ubiquity of rds porosity where two or more minerals add the same ion to the pore fluid then the steady state concentration of that ion which is reached at some distance down the flow path theoretically an infinite distance is a weighted average of the equilibrium solubilities of that ion with respect to the minerals that contribute the ion thus as the pore fluid approaches a steady state concentration of the ion it will be undersaturated with respect to the least stable minerals and oversaturated with respect to the most stable mineral hence rds porosity must form as a result of the dissolution of the least stable mineral and the precipitation of the most stable mineral although kaolinite is the most common dissolution product of feldspars with increasing temperature its stability field shrinks with respect to other clay minerals such as illite thus it is possible for feldspars and other aluminosilicates to decompose at depth to give illite and authigenic quartz the growth of fibrous illite together with the change from a dominantly primary to a dominantly secondary pore structure can give rise to a rapid loss of permeability with depth where changes in the clay mineral type do not occur the impact of rds porosity on the porosity permeability behaviour of sandstones is minimal up to secondary porosities of about 10 beyond this figure there is at present too little data to make a clear statement

3d aquifer characterization of the hermalle sous argenteau test site using crosshole ground penetrating radar amplitude analysis and full waveform inversion to improve the understanding of flow and transport processes in the critical zone high resolution and accurate estimation of the small scale heterogeneity is essential preferential flow paths related to high porosity layers and clay lenses in gravel aquifers greatly affect flow and transport processes in the subsurface and their high electrical contrast to their surrounding matrix and limited extent can act as low velocity electromagnetic waveguides in the past decade time domain full waveform inversion fwi of crosshole ground penetrating radar gpr data has shown to provide 2d decimeter scale resolution images of relative permittivity and electrical conductivity of the subsurface which can be related to porosity and soil texture most studies using crosshole gpr fwi resolved high porosity zones that were identified by an amplitude analysis approach but clay lenses or zones with higher electrical conductivity that act as low velocity waveguides are hard to distinguish in the measured data and amplitude analysis because of the absence of characteristic wave propagation features we have investigated a set of nine crosshole gpr data sets from a test site in hermalle sous argenteau near the meuse river in belgium to characterize the aquifer within a decimeter scale resolution and to improve the understanding of a previously performed heat tracer experiment thereby we extend the amplitude analysis to identify two different types of low velocity waveguides either caused by an increased porosity or a higher electrical conductivity and higher porosity combining the gpr amplitude analysis for low velocity waveguide zones with the standard fwi results provided information on waveguide zones which modified the starting models and further improved the fwi results moreover an updated effective source wavelet is estimated based on the updated permittivity starting models in comparison with the traditional fwi results the updated fwi results present smaller gradient of the medium properties and smaller root mean squared error values in the final inversion results the nine crosshole sections are used to generate a 3d image of the aquifer and allowed a detailed analysis of the porosity distribution along the different sections consistent structures of the permittivity and electrical conductivity show the robustness of the updated fwi results the aquifer structures obtained by the fwi results agree with those results of the heat tracer experiment

modeling 3d porosity and permeability from gpr data in the ellenburger dolomite central texas three dimensional porosity and permeability were modeled in an ellenburger carbonate reservoir analog from 2d crosshole and 3d surface survey ground penetrating radar gpr data two dimensional gpr crosshole velocity tomography 3d migration of the gpr surface data and porosity and permeability calibration to gpr attributes results in 3d porosity and permeability predictions that provide a consistent model of the paleocave structures and facies distributions picking the maximum instantaneous amplitude of the direct arrival wavelet for velocity tomography reduces uncertainties caused by a low signal to noise ratio uncorrelated noise and the interference between reflections and critical refractions at the earth air interface the gpr velocity is anisotropic with an average vertical to horizontal velocity ratio of 0 93 which is attributed to the dominance of the relatively horizontal orientation of the maximum porosity and permeability porosity and permeability trends are influenced by regional northe

amorphous silica nanofilms result in growth of misoriented microcrystalline quartz cement maintaining porosity in deeply buried sandstones deeply buried sandstones in sedimentary basins typically have low porosity due to cementation and compaction there are several known causes of anomalously high porosity in sandstones one of which is microquartz coatings on sand grains that seem to inhibit growth of quartz cement however there has been no mechanistic understanding of why or how microquartz grows or why it maintains high porosity in sandstones here we have used high resolution scanning electron microscopy electron backscattered diffraction and transmission electron microscopy to study the microquartz cemented late cretaceous heidelberg formation germany we have revealed that a nanofilm of amorphous silica 50 100 nm and a layer of chalcedony are between the detrital grain and microquartz cement the amorphous silica insulates the detrital quartz grains and prevents syntaxial growth while microquartz adopts the orientation of the underlying chalcedony with its fast growth c axis parallel to the grain surface thus preventing growth into the pore now that we know what controls microquartz growth and why it preserves porosity it can be used to help identify rank and appraise deeply buried petroleum accumulations

capacitive conductivity logging and electrical stratigraphy in a high resistivity aquifer boise hydrogeophysical research site we tested a prototype capacitive conductivity borehole tool in a shallow unconfined aquifer with coarse unconsolidated sediments and very low conductivity water at the boise hydrogeophysical research site bhrs examining suchahigh resistivitysystemprovidesagoodtestforthecapacitive conductivity tool because the conventional induction conductivity tool known to have limited effectiveness in high resistivity systems did not generate expressive well logs at the bhrs the capacitive conductivity tool demonstrated highly repeatable low noise behavior but poor correlation with the induction tool in the lower conductivity portions of the stratigraphy where the induction tool was relatively unresponsive singular spectrum analysis of capacitive conductivity logs reveals similar vertical length scales ofstructurestoporositylogsatthebhrs also majorstratigraphic units identified with porosity logs are evident in the capacitive conductivity logs however a previously unrecognized subdivision in the upper portion of one of the major stratigraphicunitscanbeidentifiedconsistentlyasarelatively low conductivity body i e an electrostratigraphic unit between the overlying stratigraphic unit and the relatively high conductivity lower portion despite similar porosity and lithology in adjacent units the high repeatability and resolutionandthewidedynamicrangeofthecapacitive conductivity tool are demonstrated here to extend to high resistivity unconsolidatedsedimentaryaquiferenvironments

the hydrogeologic information in cross borehole complex conductivity data from an unconsolidated conglomeratic sedimentary aquifer abstractaccurate estimation of the hydrological properties of near surface aquifers is important because these properties strongly influence groundwater flow and solute transport laboratory based investigations have indicated that induced polarization ip properties of porous media may be linked through either semiempirical or fully mechanistic models to hydrological properties including hydraulic conductivity therefore there is a need for field assessments of the value of ip measurements in providing insights into the hydrological properties of aquifers a cross borehole ip survey was carried out at the boise hydrogeophysical research site bhrs an unconsolidated fluvial aquifer that has previously been well studied with a variety of geophysical and hydrogeologic techniques high quality ip measurements were inverted with careful consideration of the data error structure to provide a 3d distribution of complex electrical conductivity values the inverted distribution was further simplified usin

targeted reflection waveform inversion of experimental ground penetrating radar data for quantification of oil spills under sea ice abstractrapid spill detection and mapping are needed with increasing levels of oil exploration and production in the arctic previous work has found that ground penetrating radar gpr is effective for qualitative identification of oil spills under and encapsulated within sea ice quantifying the spill distribution will aid effective spill response to this end we have developed a targeted gpr reflection waveform inversion algorithm to quantify the geometry of oil spills under and within sea ice with known electric properties of the ice and oil we have inverted for oil thickness and variations in ice thickness we have tested the algorithm with data collected during a controlled spill experiment using 500 mhz radar reflection data the algorithm simultaneously recovered the thickness of a 5 cm thick oil layer at the base of the ice to within 8 of the control value estimated the thickness of a 1 cm thick oil layer encapsulated within the ice to within 30 of the control value and accurately mapped

high resolution water content estimation from surface based ground penetrating radar reflection data by impedance inversion 1 mapping hydrological parameter distributions in high resolution is essential to understand and simulate groundwater flow and contaminant transport of particular interest is surface based ground penetrating radar gpr reflection imaging in electrically resistive sediments because of the expected close link between the subsurface water content and the dielectric permittivity which controls gpr wave velocity and reflectivity conventional tools like common midpoint cmp velocity analysis provide physical parameter models of limited resolution only we present a novel reflection amplitude inversion workflow for surface based gpr data capable of resolving the subsurface dielectric permittivity and related water content distribution with markedly improved resolution our scheme is an adaptation of a seismic reflection impedance inversion scheme to surface based gpr data key is relative amplitude preserving data preconditioning including gpr deconvolution which results in traces with the source wavelet distortions and propagation effects largely removed the subsequent inversion for the underlying dielectric permittivity and water content structure is constrained by in situ dielectric permittivity data obtained by direct push logging after demonstrating the potential of our novel scheme on a realistic synthetic data set we apply it to two 2 d 100 mhz gpr profiles acquired over a shallow sedimentary aquifer resulting in water content images of the shallow 3 7 m depth saturated zone having decimeter resolution

petroleum emplacement inhibits quartz cementation and feldspar dissolution in a deeply buried sandstone abstract whether the emplacement of petroleum in sandstone reservoirs can preserve porosity during burial remains controversial in the kessog field uk central north sea average porosities of the crestal sections of the fluvial deltaic pentland formation reservoir can exceed 25 despite burial to 4 km or more the predicted porosity for the reservoir at this depth is only around 14 based on regional data oil saturation data thin section point counts grain size and sorting measurements reservoir pressure and sem images were combined to analyze the cause of the high reservoir porosity petroleum emplacement preventing cementation is the most likely mechanism for porosity preservation facies variation is not responsible as the high porosity sandstones from the crestal well are in terms of average grain size fine grained and sorting coefficient moderately well sorted nearly the same as the lower porosity sandstones from the flanks of the field average porosity 13 15 other potential porosity preservation mechanisms such as overpressure grain coats and feldspar dissolution can be discounted the sandstones with high oil saturations are characterized by 1 most porosity being primary as opposed to secondary 2 there being 2 5 less quartz cement than in the water saturated sandstones 3 there being 2 3 more k feldspar and 2 6 less kaolin than the water saturated counterparts this study demonstrates that petroleum emplacement can effectively inhibit quartz cementation and k feldspar transformation to kaolin in sandstone reservoirs

landslide activity as a geoindicator in italy significance and new perspectives from remote sensing landslide activity responds to rapid environmental changes and represents a relevant geoindicator in mountainous or hilly areas this paper discusses the socio economic relevance of landslide hazard in italy and the problems encountered in establishing relationships between landslide frequency climate and vegetation changes at different time scales landslides blocking a river channel have been carefully taken into account because they are usually characterized by high intensities with regard to the involved masses and movement velocities and their occurrences are often datable via radiocarbon dating this is due to the recovery of organic matter in the landslide dammed lakes for these reasons they can be considered important geoindicators in the wider category of slope failures the marked effects of the anthropogenic activity on slope instability processes in the last 50 years are discussed with reference to two case histories the chianti hills in tuscany and the cinque terre national park in liguria finally two novel techniques of remote sensing are proposed as tools for a systematic monitoring of slope instability at different time and spatial scales both techniques are based on the interferometric synthetic aperture radar sar technology and differ on the type of platform satellite and ground based used to acquire data

deep burial dissolution of k feldspars in a fluvial sandstone pentland formation uk central north sea the pentland formation of the uk central north sea is a quartzite in a sequence of more arkosic sandstones provenance sensitive heavy mineral indices are interpreted to indicate that it was probably derived by erosion of arkosic sediments which also supplied the arkosic marine sandstones of the contemporaneous fulmar formation a lack of apatite within the pentland formation suggests that the feldspars could have dissolved during exposure to groundwaters during very shallow burial however petrographic and geochemical evidence supports survival of at least some of the feldspar to burial depths in excess of at least 2 km when the sandstones had been stabilized against compaction by quartz cements or overpressure abundant kaolin which has not reacted to form illite is preserved at burial depths in excess of 4000 m suggesting an unusual lack of available potassium there is a strong contrast in diagenetic pathways with the overlying marine fulmar formation which most probably had the same initial composition but in which kaolin is absent and fibrous illite is present it is suggested that a lower concentration of potassium and aluminium within the pentland formation compared with the probable source and the comparably sourced fulmar formation represents export of k from the sands on a metre scale

waveform inversion of crosshole georadar data influence of source wavelet variability and the suitability of a single wavelet assumption waveform based tomographic imaging of crosshole georadar data is a powerful method to investigate the shallow subsurface because of its ability to provide images of electrical properties in near surface environments with unprecedented spatial resolution a critical issue with waveform inversion is the a priori unknown source signal indeed the estimation of the source pulse is notoriously difficult but essential for the effective application of this method here we explore the viability and robustness of a recently proposed deconvolution based procedure to estimate the source pulse during waveform inversion of crosshole georadar data where changes in wavelet shape with location as a result of varying near field conditions and differences in antenna coupling may be significant specifically we examine whether a single average estimated source current function can adequately represent the pulses radiated at all transmitter locations during a crosshole georadar survey or whether a separate source wavelet estimation should be performed for each transmitter gather tests with synthetic and field data indicate that remarkably good tomographic reconstructions can be obtained using a single estimated source pulse when moderate to strong variability exists in the true source signal with antenna location only in the case of very strong variability in the true source pulse are tomographic reconstructions clearly improved by estimating a different source wavelet for each transmitter location

receiver coupling effects in seismic waveform inversions seismic waveform inversion offers opportunities for detailed characterization of the subsurface however its full potential can only be exploited when any systematic source and receiver effects are either carefully avoided or appropriately accounted for during the inversions repeated crosshole measurements in the mont terri switzerland underground laboratory have revealed that receiver coupling may significantly affect the seismic waveforms more seriously coupling conditions may vary during the course of a monitoring experiment to address this problem we have developed a novel scheme that estimates medium properties frequency dependent source functions and frequency dependent receiver coupling factors we demonstrate the efficacy of the new scheme via a synthetic 2d crosshole experiment in which realistic receiver coupling factors are incorporated because determination of medium parameters and estimation of source functions and receiver coupling factors are largely separated the method can be

application of diffraction tomography to fracture detection two diffraction tomography techniques are applied to crosshole field data to detect fractures in granitic rock the techniques used are the conventional back propagation method and a new quadratic programming method incorporating constraints in this formulation the born approximation is used for linearization of the inverse problem two dimensional 2 d pseudo spectral finite difference synthetic data are generated to demonstrate the inversion methods and justify use of the born approximation also using 2 d born synthetic data the velocity sensitivity of the inversion algorithm and reduction of fracture generated tube waves and s waves are investigated the inversion methods are applied to field data from the grimsel test site in switzerland the data are collected from a 10 21 5m rectangular area where fractures are known to exist data acquisition with 0 5 m spacing of three component receivers and a piezoelectric source is carried out so as to obtain a nearly complete coverage of the region cros

nonlinear subsidence rate estimation using permanent scatterers in differential sar interferometry discrete and temporarily stable natural reflectors or permanent scatterers ps can be identified from long temporal series of interferometric sar images even with baselines larger than the so called critical baseline this subset of image pixels can be exploited successfully for high accuracy differential measurements the authors discuss the use of ps in urban areas like pomona ca showing subsidence and absidence effects a new approach to the estimation of the atmospheric phase contributions and the local displacement field is proposed based on simple statistical assumptions new solutions are presented in order to cope with nonlinear motion of the targets

hydraulic conductivity imaging from 3 d transient hydraulic tomography at several pumping observation densities 1 3 d hydraulic tomography 3 d ht is a method for aquifer characterization whereby the 3 d spatial distribution of aquifer flow parameters primarily hydraulic conductivity k is estimated by joint inversion of head change data from multiple partially penetrating pumping tests while performance of 3 d ht has been studied extensively in numerical experiments few field studies have demonstrated the real world performance of 3 d ht here we report on a 3 d transient hydraulic tomography 3 d tht field experiment at the boise hydrogeophysical research site which is different from prior approaches in that it represents a baseline analysis of 3 d tht performance using only a single arrangement of a central pumping well and five observation wells with nearly complete pumping and observation coverage at 1 m intervals we jointly analyze all pumping tests using a geostatistical approach based on the quasi linear estimator of kitanidis 1995 we reanalyze the system after progressively removing pumping and or observation intervals significant progressive loss of information about heterogeneity is quantified as reduced variance of the k field overall reduced correlation with slug test k estimates at wells and reduced ability to accurately predict independent pumping tests we verify that imaging accuracy is strongly improved by pumping and observational densities comparable to the aquifer heterogeneity geostatistical correlation lengths discrepancies between k profiles at wells as obtained from ht and slug tests are greatest at the tops and bottoms of wells where ht observation coverage was lacking

effect of antennas on velocity estimates obtained from crosshole gpr data to obtain tomographic images with the highest possible resolution from crosshole ground penetrating radar gpr data raypaths covering a wide range of angles between the boreholes are required in practice however the inclusion of high angle ray data in crosshole gpr inversions often leads to tomograms so dominated by inversion artifacts that they contain little reliable subsurface information here we investigate the problems that arise from the standard assumption that all first arriving energy travels directly between the centers of the antennas through numerical modeling we show that this assumption is often incorrect at high transmitter receiver angles and can lead to significant errors in tomographic velocity estimates when the antenna length is a significant fraction of the borehole spacing

borehole radar applied to the characterization of hydraulically conductive fracture zones in crystalline rock1 this paper discusses the borehole radar system ramac developed within the framework of the international stripa project which can be used in three different measuring modes single hole reflection cross hole reflection and cross hole tomography the reflection modes basically provide geometrical data on features located at some distance from the borehole in addition the strength of the reflections indicate the contrast in electrical properties single hole reflection data are cylindrically symmetrical with respect to the borehole which means that a unique fracture orientation cannot be obtained a method has been devised where absolute orientation of fracture zones is obtained by combining single hole reflection data from adjacent holes similar methods for the analysis of cross hole reflection data have also been developed and found to be efficient the radar operates in the frequency range 20 60 mhz which gives a resolution of 1 3 m in crystalline rock the investigation range obtained in the stripa granite is approximately 100 m in the single hole mode and 200 300 m in the cross hole model variations in the arrival time and amplitude of the direct wave between transmitter and receiver have been used for cross hole tomographic imaging to yield maps of radar velocity and attenuation the cross hole measurement configuration coupled withmore tomographic inversion has less resolution than the reflection methods but provides better quantitative estimates of the values of measured properties the analysis of the radar data has provided a consistent description of the fracture zones at the stripa cross hole site in agreement with both geological and geophysical observations less

numerical modeling of borehole georadar data high frequency electromagnetic em wave propagation phenomena associated with borehole georadar experiments are complex to improve our understanding of the governing physical processes we present a finite difference solution of maxwell s equations in cylindrical coordinates this approach allows us to model the full em wavefield associated with borehole georadar experiments and to assess the adequacy of ray based methods currently used to interpret the observed amplitudes our results indicate that because shallow boreholes are often water filled the finite length of the boreholes as well as changes in material properties along a borehole wall can have major effects on the amplitude behavior of borehole georadar data as a result of waveguide phenomena the radiation pattern of a vertical electric dipole source located in a water filled borehole may be distorted significantly with respect to the corresponding reference radiation pattern in a homogeneous medium even greater distortions of the radiation pattern result when the electric dipole source is located near material boundaries or near the upper or lower end of a borehole this study indicates that some of the basic assumptions of conventional ray based amplitude tomography often are not fulfilled for borehole georadar data and that the derived constraints on the attenuation and conductivity structure should be regarded as qualitative in nature the algorithm and the results presented in this study do however offer the perspective to alleviate some of these inherent problems and thus help to make ray based georadar attenuation tomography a more reliable and effective tool for probing the shallow subsurface

appraisal of waveform repeatability for crosshole and hole to tunnel seismic monitoring of radioactive waste repositories countries worldwide are seeking solutions for the permanent removal of high level radioactive waste from the environment surrounding the waste with multiple engineered barriers and emplacement in deep geological repositories is widely accepted as a safe means of isolating it from the biosphere for the necessary 105 106 years as a precautionary measure society demands that repositories be monitored for 100 300 years after they are backfilled and sealed effective monitoring that does not compromise the engineered and natural barriers is challenging to address this issue we investigate the viability of crosshole and hole to tunnel seismic methods for remotely monitoring high level radioactive waste repositories measurements are made at two underground rock laboratories in switzerland one within granitic rock and one within clay rich sediments numerical simulations demonstrate that temporal changes of the monitored features i e bentonite plug excavation damage zone sand filled microtunnel sh

mapping small elevation changes over large areas differential radar interferometry a technique that uses synthetic aperture radar sar images to measure very small 1 cm or less surface motions with good resolution 10 m over large swaths 50 km is presented along with experimental results the method could be used for accurate measurements of many geophysical phenomena including swelling and buckling in fault zones residual displacements from seismic events and prevolcanic swelling the method is based on sar interferometry where two images are made of a scene by simultaneously flying two physically separated antennas then the phases of corresponding pixels are differenced and altitude formation is deduced from some simple computation and image rectification it is also possible to use one antenna flown twice over the same scene then if the second flight exactly duplicates the track of the first an interesting possibility occurs there would be no phase changes between the images at all unless there was a physical change in the scene such as ground swelling that would alter the distance from some resolution element to the antenna since the phase changes all occur at the short carrier wavelength the basic limitation on sensitivity is only the phase noise in the system when the two imaging passes are made from flight tracks that are separated which is the case with the seasat images used here it is no longer possible to distinguish surface changes from the parallax caused by topography however with some additional computation a third image made at some other baseline may be used to remove the topography and leave only the surface changes this method was applied using seasat data to an imaging site in imperial valley california where motion effects were observed that were ascribed to the expansion of water absorbing clays phase change images of this area are shown along with associated ground truth about the presence of water problems with the technique are explored along with a discussion of future experimental possibilities on upcoming sar missions like earth observing system eos earth resources satellite ers 1 sir c and the venus imaging radar magellan

lack of inhibiting effect of oil emplacement on quartz cementation evidence from cambrian reservoir sandstones paleozoic baltic basin currently the question of whether or not the presence of oil in sandstone inhibits quartz cementation and preserves porosity is still debated data from a number of cambrian sandstone oil fields and dry fields have been studied to determine the effects of oil emplacement on quartz cementation the data show that the porosity distribution is not affected by the presence of oil in sandstones from oil fields and dry fields with similar porosity distribution from this it can be concluded that oil emplacement does not lead to preservation of primary porosity and silica supply for quartz cementation is derived from internal sources rather in spite of large variation in porosity and quartz cement content a regular pattern of porosity decrease is related to increasing temperature or depth the observed heterogeneity is due to local factors that influence the precipitation of quartz cement including sandstone architecture i e distribution of shales within the sandstone bodies and sandstone thickness heterogeneity is inherent to sandstone architecture and to the fact that silica for quartz cementation is derived from heterogeneously distributed local pressure solution models predicting reservoir properties should encompass facies and architecture as important independent factors

diagenesis of the safaniya sandstone member mid cretaceous in saudi arabia abstract safaniya member of the mid cretaceous wasia formation was deposited as fluvio marine deltaic sediments in northeastern saudi arabia and the northwestern arabian gulf after its deposition and initial burial the mid cretaceous sequence was uplifted during late cretaceous structural movements structural traps in the region also started forming at this time but structural growth continued during the eocene and new structures developed during the plio pleistocene the diagenetic mineral assemblage in the safaniya sandstones includes kaolinite illite glauconite pyrite quartz and carbonate cements kaolinite and illite occur both as authigenic and detrital minerals authigenic kaolinite exists as skeletal and euhedral plates forming vermicules and aggregates of booklets infilling the pore spaces authigenic illite occurs as overgrowths of projecting laths quartz cement is present as syntaxial overgrowths and as microcrystalline quartz carbonates occur as patches and show replacement textures early diagenetic events include the formation of calcite siderite glauconite and pyrite at or close to the sediment water interface vermicular kaolinite and microcrystalline quartz probably formed by meteoric water diagenesis during the late cretaceous uplift quartz overgrowths and the bulk of the euhedral kaolinite may have formed during the late cretaceous early tertiary burial illite and ankerite were precipitated during deep burial probably from fluids expelled from the basinal kazhdumi shales to the east and northeast the precipitation of authigenic minerals in the clean quartz sandstones has reduced the primary interparticle porosity by an average of about 9 of the rocks because the clays occur mainly as pore filling cements their precipitation has caused only a small reduction in the permeability of these rocks

use of differential sar interferometry in monitoring and modelling large slope instability at maratea basilicata italy abstract differential synthetic aperture radar sar interferometry diffsar allows in principle to measure very small movements of the ground and to cover in continuity large areas so that it can be considered as a potentially ideal tool to investigate landslides and other slope instability in this paper we explore the use of this technique to improve our knowledge of the slope instability of a well investigated area the maratea valley affected by continuous slow movements producing an impressive sackung type phenomenon which poses several unanswered questions in particular by using this technique we analyse the time evolution of ground movements from 1997 to 2000 the slope movements during this same time interval have also been monitored in the past by using other techniques such as electronic distance meter edm and gps measurements gps and diffsar results are here compared in our implementation of the diffsar technique the problem of decorrelation noise is faced by using a phase unwrapping approach that allows to process sparse data and the impact of atmospheric artefacts is reduced by performing a temporal analysis of the deformations observed in successive interferograms in this study we also show that it is possible to perform a temporal analysis of continuous slow landslide movements by using a limited number of ers sar data sets and low precision topographic information all the acquired data edm gps and diffsar are consistent and allow a kinematic model of instability within the investigated time interval to be proposed a map of slopes subject to different velocities of vertical displacements was delineated modifying previous knowledge within the valley progressive and almost linear displacements over time were confirmed

multivariate analysis of cross hole georadar velocity and attenuation tomograms for aquifer zonation 1 we have investigated the potential of combining cross hole georadar velocity and attenuation tomography as a method for characterizing heterogeneous alluvial aquifers a multivariate statistical technique known as k means cluster analysis is used to correlate and integrate information contained in velocity and attenuation tomograms cluster analysis allows us to identify objectively the major common trends in the tomographic data and thus to reduce the information to a limited number of characteristic parameter combinations the application of this procedure to two synthetic data sets indicates that it is a powerful tool for converting the complex relationships between the tomographically derived velocity and attenuation structures into a lithologically and hydrologically meaningful zonation of the probed region in addition these synthetic examples allow us to evaluate the reliability of further petrophysical parameter estimates we find that although absolute values of the tomographically inferred petrophysical parameters often differ significantly from the actual parameters the clustering approach enables us to reliably identify the major trends in the petrophysical properties finally we have applied the approach to a cross hole georadar data set collected in a well studied alluvial aquifer a comparison of the clustered tomographic section with well log data demonstrates that our approach delineates the hydrostratigraphic zonation

inverse theory applied to multi source cross hole tomography part 1 acoustic wave equation method1 frequency domain methods are well suited to the imaging of wide aperture cross hole data however although the combination of the frequency domain with the wavenumber domain has facilitated the development of rapid algorithms such as diffraction tomography this has also required linearization with respect to homogeneous reference media this restriction and association restrictions on source receiver geometries are overcome by applying inverse techniques that operate in the frequency space domain in order to incorporate the rigorous modelling technique of finite differences into the inverse procedure a nonlinear approach is used to reduce computational costs the method of finite differences is applied directly to the frequency domain wave equation the use of high speed high capacity vector computers allow the resultant finite difference equations to be factored in place in this way wavefields can be computed for additional source positions at minimal extra cost allowing inversions to be generated using data from a very large number of source positions synthetic studies show that where weak scatter approximations are valid diffraction tomography performs slightly better than a single iteration of non linear inversion however if the background velocities increase systematically with depth diffraction tomography is ineffective whereas non linear inversion yields useful images from one frequency component of the data after a single iteration further synthetic studies indicate the efficacy of the method in the time lapse monitoring of injection fluids in tertiary hydrocarbon recovery projects

crosshole gpr full waveform inversion of waveguides acting as preferential flow paths within aquifer systems high contrast layers caused by porosity or clay content changes can have a dominant effect on hydraulic processes within an aquifer these layers can act as low velocity waveguides for gpr waves we used a field example from a hydrological test site in switzerland to show that fullwaveform inversion of crosshole gpr signals could image a subwavelength thickness low velocity waveguiding layer we exploited the full information content of the data whereas ray based inversion techniques are not able to image such thin waveguide layers because they only exploit the first arrival times and first cycle amplitudes this lowvelocity waveguide layer is caused by an increase in porosity and indicates a preferential flow path within the aquifer the waveguide trapping causes anomalously high amplitudes and elongated wavetrains to be observed for a transmitter within thewaveguide and receivers straddling thewaveguide depth range the excellent fit of amplitudes and phase between the measured and modeled data confirms its presence this new method enables detailed aquifer characterization to accurately predict transport and flow and can be applied to a wide range of geologic hydrological and engineering investigations

open system chemical behavior in deep wilcox group mudstones texas gulf coast usa abstract wilcox group mudstones have been mechanically and geochemically transformed over a temperature range of 20 200 c our research controlled for provenance and age by sampling from five wells parallel to the paleodepositional axis all within the houston delta system across the sampled depths mudstone porosity has been reduced from 25 to

seismic waveform inversion in the frequency domain part 2 fault delineation in sediments using crosshole data a crosshole experiment was carried out in a layered sedimentary environment in which a normal fault is known to cut through the section initial traveltime inversions produced stable but low resolution images from which the fault could be only vaguely inferred to image the fault wavefield inversion was used to produce a velocity model consistent with the detailed phase and amplitude of the data at a number of frequencies our wavefield inversion scheme uses a classical descent type algorithm for decreasing the data misfit by iteratively computing the gradient of this misfit by repeated forward and backward propagations our propagator is a full wave equation frequency domain acoustic finite difference method the use of the frequency space domain yields computational advantages for multisource data and allows an easy incorporation of viscous effects by running wavefield inversion on the field data a quantitative velocity image was produced that yielded a significantly improved image of the fault when compared with the original traveltime inversions because the original field data were noisy and contained a high degree of multiple scattering from the layering of the sediments the transmitted arrivals were selectively windowed to enhance the image the sediments at the site were strongly attenuating we therefore used a viscoacoustic model during the modeling and the inversion that correctly simulated the observed decrease in amplitude with increasing frequency and source receiver offset furthermore since the traveltime inversion indicated a high degree of anisotropy at the site a fixed homogeneous level of anisotropy was used during the inversion tests at varying levels of anisotropy confirmed the improvement in image quality and in data fit when anisotropy was incorporated the final image was verified by examining the distribution of the residuals in the frequency domain by comparing time domain modeled wavefields with the observed data and by direct comparison with borehole logs

phase and amplitude inversion of crosswell radar data phase and amplitude inversion of crosswell radar data estimates the logarithm of complex slowness for a 2 5d heterogeneous model the inversion is formulated in the frequency domain using the vector helmholtz equation the objective function is minimized using a back propagation method that is suitable for a 2 5d model and that accounts for the near intermediate and far field regions of the antennas the inversion is tested with crosswell radar data collected in a laboratory tank the model anomalies are consistent with the known heterogeneity in the tank the model s relative dielectric permittivity which is calculated from the real part of the estimated complex slowness is consistent with independent laboratory measurements the methodologies developed for this inversion can be adapted readily to inversions of seismic data e g crosswell seismic and vertical seismic profiling data

estimation of the 3d correlation structure of an alluvial aquifer from surface based multi frequency ground penetrating radar reflection data knowledge about the stochastic nature of heterogeneity in subsurface hydraulic properties is critical for aquifer characterization and the corresponding prediction of groundwater flow and contaminant transport whereas the vertical correlation structure of the heterogeneity is often well constrained by borehole information the lateral correlation structure is generally unknown because the spacing between boreholes is too large to allow for its meaningful inference there is however evidence to suggest that information on the lateral correlation structure may be extracted from the correlation statistics of the subsurface reflectivity structure imaged by surface based ground penetrating radar measurements to date case studies involving this approach have been limited to 2d profiles acquired at a single antenna centre frequency in areas with limited complementary information as a result the practical reliability of this methodology has been difficult to assess here we extend previous work to 3d and consider reflection ground penetrating radar data acquired using two antenna centre frequencies at the extensively explored and well constrained boise hydrogeophysical research site we find that the results obtained using the two ground penetrating radar frequencies are consistent with each other as well as with information from a number of other studies at the boise hydrogeophysical research site in addition contrary to previous 2d work our results indicate that the surface based reflection ground penetrating radar data are not only sensitive to the aspect ratio of the underlying heterogeneity but also albeit to a lesser extent to the so called hurst number which is a key parameter characterizing the local variability of the fine scale structure

application of a new 2d time domain full waveform inversion scheme to crosshole radar data crosshole radar tomography is a useful tool in diverse investigations in geology hydrogeology and engineering conventional tomograms provided by standard ray based techniques have limited resolution primarily because only a fraction of the information contained in the radar data i e thefirst arrivaltimesandmaximumfirst cycleamplitudesis included in the inversion to increase the resolution of radar tomograms wehavedevelopedaversatilefull waveforminversion scheme that is based on a finite difference time domain solution of maxwell s equations this scheme largely accountsforthe3dnatureofradar wavepropagationandincludes an efficient method for extracting the source wavelet from the radar data after demonstrating the potential of the newschemeontworealisticsyntheticdatasets weapplyitto two crosshole field data sets acquired in very different geologic hydrogeologic environments these are the first applications of full waveform tomography to observed crosshole radar data the resolution of all full waveform tomograms is showntobemarkedlysuperiortothatoftheassociatedraytomograms small subsurface features a fraction of the dominant radar wavelength and boundaries between distinct geological hydrological units are sharply imaged in the fullwaveformtomograms

use of permanent scatterers technique for large scale mass movement investigation abstract in the oltrepo pavese northern italy several areas subjected to risk assessment according to italian law are located around a highly fractured sandstone slabs m vallassa sandstone lying on a deformable clayey substratum epiligurian sequence the structural and geomorphologic surveys and comparison with results obtained by some authors in similar geological contexts indicate the possible presence of deep seated gravitational deformations which could be classified as lateral spread the potentiality of the permanent scatterers technique has been explored by the authors for investigating large slope displacements in the oltrepo pavese the permanent scatterers analysis was combined with in situ conventional geomorphological structural and geotechnical studies test sites corresponding to sandstone slabs and areas classified at high risk from the institutional authorities were selected a geological model of each test area was obtained from the integration of the geological geomorphological character of the site with the geotechnical data boreholes piezometers and laboratory tests the ps technique allows to detect and delimit the unstable area and to identify some zones within the mass movement characterized by different displacements rates and thus different degree of hazard

geostatistical inference using crosshole ground penetrating radar high resolution tomographic images obtained from crosshole geophysical measurements have the potential to provide valu able information about the geostatistical properties of unsaturat ed zonehydrologic statevariablessuchasmoisturecontent un der drained or quasi steady state conditions the moisture con tentwillreflectthevariationofthephysicalpropertiesofthesub surface which determine the flow patterns in the unsaturated zone deterministicleast squaresinversionofcrossholeground penetrating radargprtraveltimesresultinsmooth minimum variance estimates of the subsurface radar wave velocity struc ture whichmaydiminishtheutilityoftheseimagesforgeostatis tical inference we have used a linearized stochastic inversion technique to infer the geostatistical properties of the subsurface radar wave velocity distribution using crosshole gpr travel times directly expanding on a previous study we have deter minedthatitispossibletoobtainestimatesofglobalvarianceand mean velocity values of the subsurface as well as the correlation lengths describing the subsurface velocity structures accurate estimation of the global variance is crucial if stochastic realiza tions of the subsurface are used to evaluate the uncertainty of the inversion estimate we have explored the full potential of the geostatisticalinferencemethodusingseveralsyntheticmodelsof varying correlation structures and have tested the influence of different assumptions concerning the choice of covariance func tionanddatanoiselevel inaddition wehavetestedthemethod ology on traveltime data collected at a field site in denmark there inferred correlation structures indicate that structural dif ferences exist between two areas located approximately 10 m apart anobservationconfirmedbyagprreflectionprofile fur thermore the inferred values of the subsurface global variance and the mean velocity have been corroborated with moisture content measurements obtained gravimetrically from samples collectedatthefieldsite

quartz cement volumes across oil water contacts in oil fields from petrography and wireline logs preliminary results from the magnus field northern north sea

radio tomography and borehole radar delineation of the mcconnell nickel sulfide deposit sudbury ontario canada in an effort to reduce costs and increase revenues at mines there is a strong incentive to develop high resolution techniques both for near mine exploration and for delineation of known orebodies to investigate the potential of high frequency em techniques for exploration and delineation of massive sulfide orebodies radio frequency electromagnetic rfem and ground penetrating radar gpr surveys were conducted in boreholes through the mcconnell massive nickel copper sulfide body near sudbury ontario from 1993 1996 crosshole rfem data were acquired with a jw 4 electric dipole system between two boreholes on section 2720w ten frequencies between 0 5 and 5 0 mhz were recorded radio signals propagated through the sudbury breccia over ranges of at least 150 m at all frequencies the resulting radio absorption tomogram clearly imaged the mcconnell deposit over 110 m downdip signal was extinguished when either antenna entered the sulfide body however the expected radio shadow did not eventuate when transmitter and receiver were on opposite sides of the deposit two dimensional modeling suggested that diffraction around the edges of the sulfide body could not account for the observed held amplitudes it was concluded at the time that the sulfide body is discontinuous according to modeling a gap as small as 5 m could have explained the observations subsequent investigations by inco established that pick up in the metal cored downhole cables was actually responsible for the elevated signal levels both single hole reflection profiles and crosshole measurements were acquired using ramac borehole radar systems operating at 60 mhz detection of radar reflections from the sulfide contact was problematic one coherent reflection was observed from the hanging wall contact in single hole reflection mode this reflection could be traced about 25 m uphole from the contact in addition to unfavorable survey geometry factors which may have suppressed reflections included host rock heterogeneity disseminated sulfides and contact irregularity velocity and absorption tomograms were generated in the sudbury breccia host rock from the crosshole radar radar velocity was variable averaging 125 m mus while absorption was typically 0 8 db m at 60 mhz kirchhoff style 2 d migration of later arrivals in the crosshole radargrams defined reflective zones that roughly parallel the inferred edge of the sulfide body the mcconnell high frequency em surveys established that radio tomography and simple radio shadowing are potentially valuable for near and in mine exploration and orebody delineation in the sudbury breccia the effectiveness of borehole radar in this particular environment is less certain

hierarchical geostatistics and multifacies systems boise hydrogeophysical research site boise idaho 1 the geostatistical structure of a heterogeneous coarse fluvial aquifer is investigated with porosity data derived from neutron logs at a research well field boise hydrogeophysical research site or bhrs that was designed in part to support three dimensional geostatistical analysis of hydrologic and geophysical parameters recognizing that the coarse fluvial deposits include subdivisions units between bounding surfaces we adopt a hierarchical approach and examine the porosity geostatistics of the aquifer at three scales at the bhrs the saturated fluvial deposits as a whole maximum interwell spacing 80 m thickness 16 18 m are at hierarchical level 1 five subhorizontal units within these deposits four cobble dominated units and a channel sand can be traced across the central area of the bhrs and are at hierarchical level 2 and subunits patches or lenses in one of the level 2 units unit 4 are at hierarchical level 3 we use variography and porosity statistics to recognize nonstationarity at hierarchical level 1 and in one of the level 2 units unit 4 where the means and variances of porosity differences as a function of lag are not constant between distinct units and subunits respectively the geostatistical structure at level 1 is modeled with different horizontal and vertical structures that have different sills vertical sill greater than horizontal sill the difference in sills can be explained quantitatively by the summing of weighted sills from all individual units and combined units i e a given pair of different units where the weights are the proportions of data pairs contributing to the sills at each lag from the individual and combined units extension of this analysis leads to a weighted multistructure form of the variogram function whereby a global experimental variogram in a hierarchical system can be decomposed quantitatively into weighted component individual and combined unit or facies structures for any number of units or hierarchical levels such decomposition of the global horizontal variogram from the bhrs indicates that short range periodicity in that structure is due to both 1 combined unit structures associated with patches or lenses at hierarchical level 3 in unit 4 and 2 variations in thickness of unit 2 for hierarchical multifacies systems structure models fit to global horizontal and vertical experimental variograms may not be useful for subsequent stochastic modeling if the system on which the structure models are based is nonstationary

sinkhole detection using 2d full seismic waveform tomography we have developed an application of 2d time domain waveform tomography for detection of embedded sinkholes and anomalies the measured seismic surface wavefields were inverted using a full waveform inversion fwi technique based on a finite difference solution of 2d elastic wave equations and the gauss newton inversion method the key advantage of this approach is the ability to generate all possible wave propagation modes of seismic wavefields body waves and rayleigh waves that are then compared with measured data to infer complex subsurface properties the pressure wave p wave and shear wave s wave velocities are inverted independently and simultaneously the fwi was applied to one synthetic and two real experimental data sets the inversion results of synthetic data showed the useful capability of the waveform analysis in identifying an embedded void the inversion results of real data sets showed that the waveform analysis was able to delineate 1 an embedded concrete culvert and 2 a complex profile with an embedded void and highly variable bedrock laterally and vertically an independent invasive test standard penetration test was also conducted to verify the seismic test results

estimating porosity with ground penetrating radar reflection tomography a controlled 3 d experiment at the boise hydrogeophysical research site 1 to evaluate the uncertainty of water saturated sediment velocity and porosity estimates derived from surface based ground penetrating radar reflection tomography we conducted a controlled field experiment at the boise hydrogeophysical research site bhrs the bhrs is an experimental well field located near boise idaho the experimental data set consisted of 3 d multioffset radar acquired on an orthogonal 20 30 m surface grid that encompassed a set of 13 boreholes experimental control included 1 1 d vertical velocity functions determined from traveltime inversion of vertical radar profiles vrp and 2 neutron porosity logs we estimated the porosity distribution in the saturated zone using both the topp and complex refractive index method crim equations and found the crim estimates in better agreement with the neutron logs we found that when averaged over the length of the borehole surface derived velocity measurements were within 5 of the vrp velocities and that the porosity differed from the neutron log by less than 0 05 the uncertainty however is scale dependent we found that the standard deviation of differences between ground penetrating radar derived and neutron log derived porosity values was as high as 0 06 at an averaging length of 0 25 m but decreased to less than 0 02 at length scale of 11 m additionally we used the 3 d porosity distribution to identify a relatively high porosity anomaly i e local sedimentary body within a lower porosity unit and verified the presence of the anomaly using the neutron porosity logs since the reflection tomography approach requires only surface data it can provide rapid assessment of bulk hydrologic properties identify meter scale anomalies of hydrologic significance and may provide input for other higher resolution measurement methods

significance of porosity for stratigraphy and textural composition in subsurface coarse fluvial deposits boise hydrogeophysical research site recognition and quantitative characterization of subsurface stratigraphic units in coarse unconsolidated fluvial deposits are difficult because large grain size and the large scale of sedimentary structures make direct interpretation from core difficult or impossible in this paper we use porosity data from well logs and grain size distribution gsd data from core to investigate four pebble and cobble dominated units that have been identified in porosity logs in deposits at a research well field boise hydrogeophysical research site lacking direct observation at an appropriate scale questions about distribution of parameters and textural composition in these units are analyzed with statistical tests the four pebble and cobble dominated porosity stratigraphic units may be grouped into two types 1 units 1 and 3 have low porosity mean 0 17 0 18 and low porosity variance and 2 units 2 and 4 have higher porosity mean 0 23 0 24 and higher porosity variance based on gsd data core samples are subdivided into five lithotypes the five lithotypes occur in different proportions and have different vertical transition probability characteristics in the two types of units 1 units 1 and 3 have only framework gravel dominated lithotypes and have random vertical transition probability between these two lithotypes and 2 units 2 and 4 consist of both framework gravel dominated and sand or matrix dominated lithotypes and have structured vertical transition probability the two framework gravel dominated lithotypes occur in all four stratigraphic units but have distinctly lower porosity in units 1 and 3 i e tighter packing than in units 2 and 4 looser packing considering the repeated stratigraphic occurrence of and the statistical significance of differences between the two types of units both the individual unit distinctions and the two unit groupings appear to be valid it is reasonable to interpret that the observed packing differences associated with units 1 and 3 compared with units 2 and 4 are related to different sedimentary processes that produce different bedforms or grain fabrics perhaps under different bedload transport rates

imaging and characterization of facies heterogeneity in an alluvial aquifer using gpr full waveform inversion and cone penetration tests summary spatially highly resolved mapping of aquifer heterogeneities is critical for the accurate prediction of groundwater flow and contaminant transport here we demonstrate the value of using full waveform inversion of crosshole ground penetrating radar gpr data for aquifer characterization we analyze field data from the krauthausen test site where crosshole gpr data were acquired along a transect of 20 m length and 10 m depth densely spaced cone penetration tests cpt located close to the gpr transect were used to validate and interpret the tomographic images obtained from gpr a strong correlation was observed between cpt porosity logs and porosity estimates derived from gpr using the complex refractive index model crim a less pronounced correlation was observed between electrical conductivity data derived from gpr and cpt cluster analysis of the gpr data defined three different subsurface facies which were found to correspond to sediments with different grain size and porosity in conclusion our study suggests that full waveform inversion of crosshole gpr data followed by cluster analysis is an applicable approach to identify hydrogeological facies in alluvial aquifers and to map their architecture and connectivity such facies maps provide valuable information about the subsurface heterogeneity and can be used to construct geologically realistic subsurface models for numerical flow and transport prediction

inference of multi gaussian relative permittivity fields by probabilistic inversion of crosshole ground penetrating radar data abstractin contrast to deterministic inversion probabilistic bayesian inversion provides an ensemble of solutions that can be used to quantify model uncertainty we have developed a probabilistic inversion approach that uses crosshole first arrival traveltimes to estimate an underlying geostatistical model the subsurface structure and the standard deviation of the data error simultaneously the subsurface is assumed to be represented by a multi gaussian field which allows us to reduce the dimensionality of the problem significantly compared with previous applications in hydrogeology novelties of this study include an improvement of the dimensionality reduction algorithm to avoid streaking artifacts it is the first application to geophysics and the first application to field data the results of a synthetic example show that the model domain enclosed by one borehole pair is generally too small to provide reliable estimates of geostatistical variables a real data example based on two borehole pairs

integration of diverse physical property models subsurface zonation and petrophysical parameter estimation based on fuzzy c means cluster analyses inversions of an individual geophysical data set can be highly nonunique and it is generally difficult to determine petrophysical parameters from geophysical data we show that both issues can be addressed by adopting a statistical multiparameter approach that requires the acquisition processing and separate inversion of two or more types of geophysical data to combine information contained in the physical property models that result from inverting the individual data sets and to estimate the spatial distribution of petrophysical parameters in regions where they are known at only a few locations we demonstrate the potential of the fuzzy c means fcm clustering technique after testing this new approach on synthetic data we apply it to limited crosshole georadar crosshole seismic gamma log and slug test data acquired within a shallow alluvial aquifer the derived multiparameter model effectively outlines the major sedimentary units observed in numerous boreholes and provides plausible estimates

sar monitoring of progressive and seasonal ground deformation using the permanent scatterers technique spaceborne differential radar interferometry has proven a remarkable potential for mapping ground deformation phenomena e g urban subsidence volcano dynamics coseismic and postseismic displacements along faults as well as slope instability however a full operational capability has not been achieved yet due to atmospheric disturbances and phase decorrelation phenomena these drawbacks can often be at least partially overcome by carrying out measurements on a subset of image pixels corresponding to natural or artificial stable reflectors permanent scatterers ps and exploiting long temporal series of interferometric data this approach allows one to push the measurement precision very close to its theoretical limit in the order of spl sim 1 mm for c band european remote sensing ers like sensors in this paper the detection of both time uniform and seasonal deformation phenomena is addressed and a first assessment of the precision achievable by means of the ps technique is discussed results highlighting deformation phenomena occurring in two test sites in california are reported fremont in the southern bay area and san jose in the santa clara valley

a synthetic study to assess the applicability of full waveform inversion to infer snow stratigraphy from upward looking ground penetrating radar data snow stratigraphy and liquid water content are key contributing factors to avalanche formation upward looking groundpenetrating radar upgpr systems allow nondestructive monitoring of the snowpack but deriving density and liquid water content profiles is not yet possible based on the direct analysis of the reflection response we have investigated the feasibility of deducing these quantities using full waveform inversion fwi techniques applied to upgpr data for that purpose we have developed a frequency domain fwi algorithm in which we additionally took advantage of time domain features such as the arrival times of reflected waves our results indicated that fwi applied to upgpr data is generally feasible more specifically we could show that in the case of a dry snowpack it is possible to derive snow densities and layer thicknesses if sufficient a priori information is available in case of a wet snowpack in which it also needs to be inverted for the liquid water content the algorithm might fail even if sufficient a priori information is available particularly in the presence of realistic noise finally we have investigated the capability of fwi to resolve thin layers that play a key role in snow stability evaluation our simulations indicate that layers with thicknesses well below the gpr wavelengths can be identified but in the presence of significant liquid water the thin layer properties may be prone to inaccuracies these results are encouraging and motivate applications to field data but significant issues remain to be resolved such as the determination of the generally unknown upgpr source function and identifying the optimal number of layers in the inversion models furthermore a relatively high level of prior knowledge is required to let the algorithm converge however we feel these are not insurmountable and the new technology has significant potential to improve field data analysis