unsaturated zone characterization in soil through transient wetting and drying using gpr joint time frequency analysis and grayscale images summary this paper describes an experimental method to characterize the soil s unsaturated zone by constructing a scenario in which transient downward water infiltration took place from the topsoil to the bottom soil continuously during the water infiltration gpr waveforms and side view grayscale images of the soil column were simultaneously and continuously captured the gpr wavelets associated with the wetting front were analyzed using short time fourier transform stft algorithm the downward wetting front and the stretch of unsaturated transition zone decelerated and eased the wetting front s reflection in the time domain as well as reduced the peak frequency and attenuated the frequency spectra in the frequency domain the subsequent drying process further attenuated but accelerated the wetting front s reflection in both time and frequency domains these observations were correlated with the image pixel profiles from which gpr velocity profiles at different lapsed times were generated after computation via a complex refractive index model crim the crim method is entirely non invasive and not only offers very detailed measurement of the water saturation profile of the transition zone in laboratory scale but also is potentially useful for the further study of a variety of vadose zone properties

limnologic analysis of gusev crater paleolake mars abstract the survey of the hydrogeologic system formed by gusev crater and ma adim vallis aeolis subquadrangle of mars points out evidence for the existence of an ice covered lake in gusev crater a first lake was formed by the drainage of the aquifer in the region surrounding gusev before the entry of ma adim vallis in the crater the existence of a former lake in gusev is deduced from the morphology of the ma adim delta its comparison with terrestrial antarctic analogs argues for the presence of an ice covered lake in gusev at the time that the southern part of the crater s rampart was breached by ma adim first release and for a subice lacustrine construction of the valley s delta our survey shows that ma adim vallis may have entered gusev crater as late as late hesperian early amazonian as part of a second lake episode the relationship between the variation of the gusev lake water level the volume of the lake and the surface of the lake bed is established by our bathymetric model the elevation of the former lake is deduced from the elevation of the mesa like structures in the delta of ma adim vallis furthermore the correlation of the crater frequency of gusev rampart with mars stratigraphic age shows that lakes may have occupied gusev crater over a period of time covering 2 gyrs from the formation of the crater to the last episode of water release from ma adim vallis though it is most likely that the lake was episodical the recurrence of abundant water in gusev crater makes this site a high priority for missions either for martian resource exploration or for the search of life

ground penetrating radar assisted saturation and permeability estimation in bimodal systems near surface investigations often require characterization of vadose zone hydraulic parameters conventional sampling or borehole techniques for estimating these parameters are costly time consuming and invasive all of which limit collection of hydrogeological data at a spacing needed for detailed site characterization incorporation of two or three dimensional densely sampled geophysical data with conventional hydrological data increases the amount of data available for the characterization and thus has the potential to significantly improve the hydraulic parameter estimates over those obtained from borehole data alone the hydraulic estimation procedure can be greatly improved by incorporating dielectric information potentially available from ground penetrating radar gpr a noninvasive high resolution geophysical method the procedures for collecting and processing gpr data in the format needed for the proposed estimation technique are relatively new and still a topic of research our method requires as a starting point the ability to estimate dielectric constants from gpr data numerical experiments were performed to investigate the general utility of the gpr assisted estimation technique under a range of conditions three bimodal systems were investigated each system being composed of a sand facies together with another facies with a larger clay volume fraction each facies was defined using characteristic values of clay content porosity and permeability using dielectric information and petrophysical relations degree of saturation and intrinsic permeability values at each location within the three systems were identified for bimodal systems a dielectric constant measurement corresponds to two possible values of saturation and intrinsic permeability at each location single values of saturation and intrinsic permeability were estimated from these values using the principle of maximum likelihood results from case studies demonstrate that a combination of gpr data with conventional borehole data significantly improves the estimates of saturation and has the potential to improve the estimates of permeability over those obtained from well bore data alone the proposed method should be especially advantageous for vadose zone characterization in areas favorable for gpr data acquisition where detailed hydraulic parameter information is required but the drilling of numerous boreholes is prohibited

overbank sediment profiles evidence of early mining and smelting activities in the harz mountains germany abstract two overbank sediment cores to a depth of 5 6 m and 2 3 m respectively from the uferbach catchment on the western foothills of the harz mountains lower saxony germany revealed two anomalies of pb zn and cu at 30 130 cm and at 204 cm a pb zn anomaly at 280 cm and a pb anomaly at 410 cm evidence of four phases of mining and smelting activities in the catchment the geochemical major minor and trace elements and mineralogical investigations microscopy and microprobe analysis of matrix and slag particles allowed for a broad interpretation of the element behavior e g landuse and the source region of the processed ore hydrothermal deposits of the upper harz a simple calculation model based on 14 c data helped to estimate the time frame for the anomalies the most likely interpretation requires an increase of the sedimentation rates over time from 1 to 4 mm a 1 and suggests medieval 1140 1345 a d karolingian 82 890 ad roman germanic 425 500 a d and early historic 825 625 b c phases of smelting activities

pilot scale field validation of the long electrode electrical resistivity tomography method a validation experiment carried out in a scaled field setting was attempted for the long electrode electrical resistivity tomography method in order to demonstrate the performance of the technique in imaging a simple buried target the experiment was an approximately 1 17 scale mock up of a region encompassing a buried nuclear waste tank on the hanford site the target of focus was constructed by manually forming a simulated plume within the vadose zone using a tank waste simulant the long electrode results were compared to results from conventional point electrodes on the surface and buried within the survey domain using a pole pole array both point and long electrode imaging techniques identified the lateral extents of the pre formed plume with reasonable fidelity but the long electrode method was handicapped in reconstructing vertical boundaries the pole dipole and dipole dipole arrays were also tested with the long electrode method and were shown to have the least favourable target properties including the position of the reconstructed plume relativetotheknownplumeandtheintensityoffalsepositivetargets thepoorperformance of the pole dipole and dipole dipole arrays was attributed to an inexhaustive and non optimal coverage of data at key electrodes as well as an increased noise for electrode combinations with high geometric factors however when comparing the model resolution matrix among the different acquisition strategies the pole dipole and dipole dipole arrays using long electrodes were shown to have significantly higher average and maximum values within the matrix than any pole pole array the model resolution describes how well the inversion model resolves the subsurface given the model resolution performance of the pole dipole and dipole dipole arrays it may be worth investing in tools to understand the optimum subset of randomly distributed electrode pairs to produce maximum performance from the inversion model

overbank sediments from central mexico an evaluation of their use in regional geochemical mapping and in studies of contamination from modern and historical mining abstract overbank sediment sequences in central mexico display vertical changes in chemistry which can be related to both anthropogenic contamination and natural geological sources and processes they also show significant lateral chemical variation at both local and regional levels which makes the design of a sampling strategy for regional geochemical mapping or contamination studies difficult this variation is particularly pronounced in drainage basins which have been contaminated by mining activity and limits the use of overbank sediment as a systematic regional geochemical mapping medium to be used with confidence overbank sediments require detailed studies of fluvial geomorphology and history accompanied by accurate age dating active drainage sediments are a more viable alternative in areas of historical mining activity but must be examined carefully in the light of the regional background where levels of contamination are low or the contaminants are buried within the river floodplain

joint inversion of crosshole radar and seismic traveltimes acquired at the south oyster bacterial transport site the structural approach to joint inversion entailing common boundaries or gradients offers a flexible and effective way to invert diverse types of surface based and or crosshole geophysical data the cross gradients function has been introduced as a means to construct models in which spatial changes in two distinct physical property models are parallel or antiparallel inversion methods that use such structural constraints also provide estimates of nonlinear and nonunique field scale relationships between model parameters here we jointly invert crosshole radar and seismic traveltimes for structurally similar models using an iterative nonlinear traveltime tomography algorithm application of the inversion scheme to synthetic data demonstrates that it better resolves lithologic boundaries than the individual inversions alone tests of the scheme on gpr and seismic data acquired within a shallow aquifer illustrate that the resultant models have improved correlations with flowmeter data in comparison with models based on individual inversions the highest correlation with the flowmeter data is obtained when the joint inversion is combined with a stochastic regularization operator and the vertical integral scale is estimated from the flowmeter data point spread functions show that the most significant resolution improvements offered by the joint inversion are in the horizontal direction

integration of hydrological and geophysical data beyond the local scale application of bayesian sequential simulation to field data from the saint lambert de lauzon site quebec canada adequate characterization of aquifer heterogeneity is critically important for the sustainable use protection and remediation of groundwater resources the combined use of hydrological and geophysical measurements is arguably the most effective means of achieving this objective in this regard significant progress has been made on the quantitative integration of geophysical and hydrological data at the local scale however the extension of such approaches to larger more regional scales remains a major research challenge in this paper we demonstrate the application of a recently developed regional scale hydrogeophysical data integration approach which is based on bayesian sequential simulation to a field database from quebec canada consisting of low resolution surface based geoelectrical measurements as well as high resolution direct push and borehole based measurements of the electrical and hydraulic conductivities the results of our study which involved the integration of data along an approximately 250 m long survey line confirm that this novel methodology with suitable adaptation is fully applicable to field data and has the potential of providing realistic estimates of the spatial distribution of hydraulic target parameters at the regional scale equally importantly through the generation of multiple stochastic realizations the methodology allows for quantitative assessment of the uncertainty associated with the inferred subsurface models which in turn is essential for interpreting subsequent predictions of the flow and transport characteristics of the studied region

the timing of martian valley network activity constraints from buffered crater counting abstract valley networks concentrations of dendritic channels that often suggest widespread pluvial and fluvial activity have been cited as indicators that the climate of mars differed significantly in the past from the present hyperarid cold desert conditions some researchers suggest that the change in climate was abrupt while others favor a much more gradual transition thus the precise timing of valley network formation is critical to understanding the climate history on mars we examine thirty valley network incised regions on mars including both cratered upland valley networks and those outside the uplands and apply a buffered crater counting technique to directly constrain when valley network formation occurred the crater populations that we derive using this approach allow assessment of the timing of the last activity in a valley network independent of the mapping of specific geological units from these measurements we find that valley networks cluster into two subdivisions in terms characteristics and age 1 valley network activity in the cratered highlands has an average cessation age at the noachian hesperian boundary and all valleys that we crater counted are early hesperian or older no evidence is found for valley networks in the cratered uplands of late hesperian or amazonian age the timing of the cessation of cratered upland valley network activity at the noachian hesperian boundary also corresponds to a decline in the intensity of large crater formation and degradation and to the apparent end of phyllosilicate type weathering 2 a few valley network incised regions formed outside of the cratered uplands on volcanic edifices in association with younger impact craters and on the rim of valles marineris we applied our buffered crater counting technique to four such valleys on the volcanoes ceraunius tholus hecates tholus and alba patera and on the rim of echus chasma and find that each has distinctive and different late hesperian or early amazonian ages indicating that valley networks formed from time to time in the post noachian period unlike the cratered upland valley networks these isolated occurrences are very local and have been interpreted to represent local conditions e g snowpack melted during periods of intrusive volcanic activity in contrast to a gradual cessation in the formation of valley networks proposed by some workers our new buffered crater counting results indicate a relatively abrupt cessation in the formation of the widespread cratered upland valley networks at approximately the end of the noachian followed only by episodic and very localized valley network formation in later mars history very likely due to specific conditions e g local magmatic heating these valley network ages and correlations are thus consistent with a major change in the near surface aqueous environment on mars at approximately the noachian hesperian boundary the noachian environment supported surface running water and fluvial erosion across mars in the cratered uplands enhanced crater degradation and a weathering environment favoring the formation of phyllosilicates the hesperian amazonian environment was more similar to the hyperarid cold desert of today with valley networks forming only extremely rarely and confined to localized special conditions sources of water for these latter occurrences are likely to be related to periodic mobilization and equatorward migration of polar volatiles due to variations in spin axis orbital parameters and to periodic catastrophic emergence of groundwater

the roza member columbia river basalt group a gigantic pahoehoe lava flow field formed by endogenous processes we present studies on the physical volcanology of the 15 ma roza member of the wanapum formation in the columbia river basalt group the roza member represents a compound pahoehoe flood basalt lava flow field with an area of 40 300 km 2 and a volume of 1300 km 3 it consists of 4 major lava flows each composed of numerous decimeter to kilometer long pahoehoe lobes roza lavas feature a wide range of pahoehoe surface structures such as lava rise plateaus tumuli and surface breakouts and we illustrate that the lava morphology is inconsistent with previous proposals of rapid emplacement for these lavas an integral component of the roza flow field is the sheet lobe with internal structures identical to those of inflated pahoehoe sheet lobes from hawaii and iceland both at the same scale and at much larger scales we identify a three part division of the sheet lobes into basal crust lava core and lava crust which are interpreted as the equivalent to the bottom crust the liquid lava core and the surface crust of an active inflating pahoehoe lobe the upper lava crust grows continuously during lava emplacement and its growth rate can be approximated by conductive cooling this relationship is used to calculate the emplacement time for individual roza sheet lobes and to derive a first order estimate on the duration of the roza eruption the results indicate that the emplacement of individual roza lobes lasted for months to years and that the lava flow field was constructed over a period of at least 14 years we propose that the roza flows achieved great areal dimensions and thicknesses by inflation and endogenous growth as the lava flowed from vent to flow front it traveled under an insulating crust which maintained cooling rates of 0 1 c km and allowed for efficient transport of lava over distances up to 300 km

inversion of tracer test data using tomographic constraints 1 we have developed a methodology for inverting tracer test data using zonation information obtained from two dimensional radar tomograms to improve the typically overly smooth hydraulic conductivity fields obtained from conventional inversion of tracer test data the method simultaneously yields two dimensional estimates of hydraulic conductivity as well as petrophysical relationships that relate hydraulic conductivity to radar velocity these relationships can be assumed to be stationary throughout the area of investigation or to vary as a function of zonation using a synthetic three dimensional hydraulic conductivity field we apply the developed inversion methodology and explore the impact of the strength and stationarity of the petrophysical relationship as well as the impact of errors that are often associated with radar data acquisition such as unknown borehole deviation we find that adding radar tomographic data to tracer test data improves hydrogeological site characterization even in the presence of minor radar data errors the results are contingent on the assumption that a relationship between radar velocity and hydraulic conductivity exists therefore the applicability of the proposed method may be limited to field sites where this condition is partially or fully satisfied

use of high resolution geophysical data to characterize heterogeneous aquifers influence of data integration method on hydrological predictions 1 the integration of geophysical data into the subsurface characterization problem has been shown in many cases to significantly improve hydrological knowledge by providing information at spatial scales and locations that is unattainable using conventional hydrological measurement techniques the investigation of exactly how much benefit can be brought by geophysical data in terms of its effect on hydrological predictions however has received considerably less attention in the literature here we examine the potential hydrological benefits brought by a recently introduced simulated annealing sa conditional stochastic simulation method designed for the assimilation of diverse hydrogeophysical data sets we consider the specific case of integrating crosshole ground penetrating radar gpr and borehole porosity log data to characterize the porosity distribution in saturated heterogeneous aquifers in many cases porosity is linked to hydraulic conductivity and thus to flow and transport behavior to perform our evaluation we first generate a number of synthetic porosity fields exhibiting varying degrees of spatial continuity and structural complexity next we simulate the collection of crosshole gpr data between several boreholes in these fields and the collection of porosity log data at the borehole locations the inverted gpr data together with the porosity logs are then used to reconstruct the porosity field using the sa based method along with a number of other more elementary approaches assuming that the grid cell scale relationship between porosity and hydraulic conductivity is unique and known the porosity realizations are then used in groundwater flow and contaminant transport simulations to assess the benefits and limitations of the different approaches

bayesian method for hydrogeological site characterization using borehole and geophysical survey data theory and application to the lawrence livermore national laboratory superfund site a stochastic bayesian approach for combining well logs and geophysical surveys for enhancing subsurface characterization is presented the main challenge we face is in creating the bridge to link between ambiguously related geophysical surveys and well data the second challenge is imposed by the disparity between the scale of the geophysical survey and the scale of the well logs our approach is intended to integrate and transform the well log data to a form where it can be updated by the geophysical survey and this tends to be a convoluted process our approach starts with generating images of the lithology conditional to well logs each lithology image is then used as the basis for generating a series of shaliness images conditional to well log data shaliness images are converted to resistivity images using a site specific petrophysical model relating between shaliness resistivity and lithology to create the necessary interface with the cross well resistivity survey the lithology and resistivity images are then updated using cross well electromagnetic resistivity surveys we explored the limits of the approach through synthetic surveys of different resolutions and error levels employing the relationships between the geophysical and hydrological attributes which are weak nonlinear or both the synthetic surveys closely mimic the conditions at the llnl superfund site we show that the proposed stochastic bayesian approach improves hydrogeological site characterization even when using low resolution resistivity surveys

trace metal storage in recent floodplain sediments along the dill river central germany abstract trace metals are stored in near channel floodplain sediments along many rivers in industrial and mined watersheds of western european countries such as germany in this paper i document the distribution of cu pb and zn in 13 cores collected from near channel floodplain sediments along a 25 km reach of the dill river in central germany mean concentrations of the three trace metals exceed background concentrations an indication of anthropogenic enrichment along the study reach many individual samples have concentrations several times the background levels and exceed standards for trace metals contained in the german federal soil protection act metal concentrations generally peak at depths of 0 2 to 0 7 m below the floodplain surface and are assumed to represent the period of maximum metal releases to the environment through upstream industrial activity ore mining or both in eight of the cores radiocarbon ages obtained below the depth of peak metal concentrations provide maximum dates for sediment accumulation of between 90 and 1700 years ago with most ages clustering in the period of 90 to 300 years ago the ages and depth to peak metal concentrations indicate 0 6 to 1 0 m of floodplain sedimentation over the last 150 to 300 years 0 3 0 4 cm y 1 which exceed sedimentation amounts and rates found in surrounding watersheds surface sediments contain lower metal concentrations suggesting deposition recently of cleaner sediments trace metals stored along the dill river serve as a reminder that stores of contaminants exist in geomorphically sensitive locations of the fluvial system these legacy sediments bear the chemical imprint of industrial or mining activities that no longer occur in the watershed

two and three dimensional quantification of lead contamination in alluvial soils of a historic mining area using field portable x ray fluorescence fpxrf analysis abstract two and three dimensional element distributions in soils and sediments may be important for the identification of geomorphic processes and the reconstruction of landscape evolution field portable x ray fluorescence fpxrf analysers provide new possibilities in the detection and quantification of these element distributions results from a research project studying the heavy metal contamination of alluvial soils in a historic mining area at the vils river near freihung eastern bavaria germany exemplify how fpxrf can be applied to quantify two and three dimensional element distributions in a floodplain environment on different scales the results show that two dimensional lead distribution of topsoil bulk samples 0 to 20 cm depth clearly depends on the geomorphology of the study area concentrations of more than 1000 mg kg 1 lead are restricted to the river floodplain on a fluvial terrace lead concentrations of the topsoils are consistently far below 500 mg kg 1 within the floodplain environment the lead contamination is not homogeneously distributed but forms areas of higher and lower lead concentrations micro fluvial structures channels ridges are polluted on different levels depending on the composition of the sediments or the water contents this demonstrates that accurate assessments of floodplain metal contamination can only be made if small scale spatial variability has been considered analysis of the three dimensional lead distribution shows that concentrations of the in situ measurements range from 500 6000 mg kg 1 subject to depth geomorphology and distance from the vils river although the absolute contents are higher three dimensional lead distribution derived from laboratory measurements is identical with the plotted results of the in situ investigations by calculating a correction factor for further investigations water content as one of the main causes for differing results between field and laboratory analyses can be diminished in situ fpxrf analysis as a robust technique could be used to investigate metal contamination on floodplain soils at a range of spatial scales it allows detailed sampling which can yield important information on the geomorphological controls on metal contamination in such environments

volcanism on mars more than 15 years of planetary exploration of mars have given insight into the geologic processes that have shaped its surface the newly acquired viking data have shown that volcanism is one of the most important geologic processes operating on mars throughout its history in situ chemical analyses of martian soil by the viking lander spacecraft indicate mafic to ultramafic source rocks this is consistent both with available remote sensing data which indicate the presence of mafic minerals such as pyroxene and olivine and with petrologic modeling based on available geophysical data which suggest that martian lavas are probably iron rich and ultramafic these data strongly suggest that basaltic volcanism is widespread on mars and much of the photogeological data may be studied in this context photogeological analysis of the martian surface has shown two main types of volcanic morphologies the first type is central volcanoes which are volcanic landforms developed by continued and prolonged eruption from a point source vent this category includes 1 shields the classic low profile volcanic mountains of which olympus mons is the most spectacular example 2 domes steep sided constructs such as tharsis tholus that may represent lower rates of eruption than the shields or possibly more silicic lava compositions 3 highland patera radially textured low profile volcanoes that occur in the cratered terrain and are interpreted as ash shields 4 alba patera an apparently unique volcanic landform consisting of a vast volcanic center over 1500 km across with flank slopes of less than a tenth of a degree and 5 various small features such as cinder cones the second major category is volcanic plains which are units recognized by several criteria of which the presence of mare ridges and flow lobes are the most useful volcanic plains are subdivided into four main groups 1 simple flows broad smooth to rolling plains that contain numerous mare type ridges but no flow lobes interpreted as being composed of thick single cooling units 2 complex flows displaying multiple overlapping flow lobes interpreted to be indicative of thin multiple cooling units 3 undifierentiated flows plains that typically lack any morphologic identifying feature but are considered to be volcanic partly on the basis of their association with large volcanic centers and 4 questionable plains volcanic units heavily modified by other processes erosion tectonism etc so that their origins are uncertain when these categories of volcanic morphologies are combined with relative age data provided by crater statistics a volcanic history for mars can be derived as follows early heavy bombardment of mars was accompanied and followed by small scale fluvial channeling extensive flood volcanism the plateau plains and ash shield volcanism in the cratered terrain shortly after this time less extensive flood volcanism continued to resurface the planet during formation of the northern southern hemisphere dichotomy central volcanism became more prominent with the development of the alba patera center as well as the older shields and domes of the northern hemisphere early tharsis and elysium regions the development of the tharsis and elysium uplifts may have triggered the release of large scale catastrophic floods producing large channels continued uplift and lithospheric thinning concentrated volcanic activity in the tharsis region producing large shield volcanoes and extensive lava plains both central vent and plains volcanism have been active throughout martian history but the volumes of extrusion have gradually decreased with time this is consistent with a moonlike thermal history involving a lithosphere of increasing thickness with time gradually turning off the volcanism although many questions remain regarding martian volcanism the viking data have provided a remarkable detailed overview of the probable nature of the volcanic history of mars

high resolution shallow seismic experiments in sand part ii velocities in shallow unconsolidated sand we conducted a shallow high resolution seismic reflection and refraction experiment on a sandy beach the depth of investigation was about 2 m we interpret the data using the hertz mindlin contact theory combined with gassmann s equation these were used to obtain the vertical velocity profile then the profile was computed from seismic data using the turning rays approximation the normal moveout nmo velocity at the depth of 2 m matches the velocity profile as a result we developed a method to invert measured velocity from first arrivals i e velocity versus distance into velocity versus depth using only one adjustable parameter this parameter contains all the information about the internal structure and elasticity of the sand the lowest velocity observed was about 40 m s it is noteworthy that the theoretical lower bound for velocity in dry sand with air is as low as 13 m s we find that modeling sand as a quartz sphere pack does not quantitatively agree with the measured data however the the

geochemical characterization using geophysical data and markov chain monte carlo methods a case study at the south oyster bacterial transport site in virginia 1 the study demonstrates the use of ground penetrating radar gpr tomographic data for estimating sediment geochemical parameters using data collected at the department of energy south oyster bacterial transport site in virginia by exploiting the site specific mutual dependence of gpr attenuation and extractable fe ii and fe iii concentrations on lithofacies we develop a statistical model in which lithofacies and fe ii and fe iii concentrations at each pixel between the boreholes are considered as random variables the unknown variables are estimated by conditioning to the colocated gpr data and the lithofacies measurements along boreholes using a markov chain monte carlo method cross validation results show that the geophysical data constrained by lithofacies have the potential for providing high resolution multidimensional information on extractable fe ii and fe iii concentrations at the south oyster site

mapping permeability in heterogeneous aquifers using hydrologic and seismic data a new method is presented for identification of the permeability distribution in near surface aquifers in addition to using the usual sparsely sampled pressure and permeability data the method incorporates densely sampled seismic data as obtained from a reflection or tomography survey along with empirical relationships between seismic and hydraulic properties the procedure is to first estimate by hydrologic inversion a pressure field then the velocity permeability pressure relationship is used to map the inverted pressure and measured seismic data to multivalued estimates of the permeability of those the most probable value based on the hydrologic inversion is selected in synthetic case studies the tremendous increase in coverage offered by the seismic data leads to dramatically better results in terms of both accuracy and resolution an appealing feature is the use of relatively easy to acquire pressure data a second is the incorporation of geophysical data which can sample an entire aquifer remotely without the need for an expensive and invasive drilling program

a comparison of deterministic and stochastic approaches for regional scale inverse modeling on the mar del plata aquifer summary inversion of the spatial variability of transmissivity t in groundwater models can be handled using either stochastic or deterministic i e geology based zonation approaches while stochastic methods predominate in scientific literature they have never been formally compared to deterministic approaches preferred by practitioners for regional aquifer models we use both approaches to model groundwater flow and solute transport in the mar del plata aquifer where seawater intrusion is a major threat to freshwater resources the relative performance of the two approaches is evaluated in terms of i model fits to head and concentration data available for nearly a century ii geological plausibility of the estimated t fields and iii their ability to predict transport we also address the impact of conditioning the estimated fields on t data coming from either pumping tests interpreted with the theis method or specific capacity values from step drawdown tests we find that stochastic models based upon conditional estimation and simulation techniques identify some of the geological features river deposit channels and low transmissivity regions associated to quartzite outcrops and yield better fits to calibration data than the much simpler geology based deterministic model which cannot properly address model structure uncertainty however the latter demonstrates much greater robustness for predicting sea water intrusion and for incorporating concentrations as calibration data we attribute the poor performance and underestimated uncertainty of the stochastic simulations to estimation bias introduced by model errors qualitative geological information is extremely rich in identifying large scale variability patterns which are identified by stochastic models only in data rich areas and should be explicitly included in the calibration process

the use of overbank sediment for geochemical mapping and contamination assessment results from selected english and welsh floodplains abstract overbank sediment profiles from floodplains in england and wales contain a record of both natural geochemical patterns and those showing the influence of man s activities it has been suggested that this characteristic can be used to allow maps to be compiled which show human impact on the fluvial geochemical environment studies reviewed in this paper however show that a single overbank profile very rarely spans the period from before anthropogenic disturbance through to the industrial revolution and later significant lateral variations in metal concentrations occur also over a relatively small area in overbank sediments of the same general age these and the nature of vertical changes in chemistry make the choice of sample sites and sampling interval within a profile difficult even sediments which appear uncontaminated may record anthropogenic influences from activities such as deforestation and agriculture a means of dating the sediment and an appreciation of river erosion and sedimentation histories are shown to be essential in order to ensure that maps intended to depict natural geochemical variations are based on material deposited before disturbance of the catchment by human activity these considerations and associated costs may render overbank sediment non viable as a regional geochemical mapping medium

reactive facies an approach for parameterizing field scale reactive transport models using geophysical methods 1 developing a predictive understanding of subsurface contaminant plume evolution and natural attenuation capacity is hindered by the inability to tractably characterize controlling reactive transport properties over field relevant scales here we explore a concept of reactive facies which is based on the hypothesis that subsurface units exist that have unique distributions of properties that influence reactive transport we further hypothesize that geophysical methods can be used to identify and spatially distribute reactive facies and their associated parameters we test the reactive facies concept at a u s department of energy uranium contaminated groundwater site where we have analyzed the relationships between laboratory and field including radar and seismic tomographic data sets our analysis suggests that there are two reactive facies that have unique distributions of mineralogy texture hydraulic conductivity and geophysical attributes we use these correlations within a bayesian framework to integrate the dense geophysical data sets with the sparse core based measurements this yields high resolution 0 25 m 0 25 m estimates of reactive facies and their associated properties and uncertainties along the 2 d tomographic transects comparison with colocated samples shows that the estimated properties fall within 95 uncertainty bounds to illustrate the value of reactive facies characterization approach we used the geophysically estimated properties to parameterize reactive transport models which were then used to simulate migration of an acidic u plume through the domain modeling results suggest that each identified reactive facies exerts a unique control on plume evolution highlighting the usefulness of the reactive facies concept for spatially distributing properties that control reactive transport over field relevant scales

derivation of site specific relationships between hydraulic parameters and p wave velocities based on hydraulic and seismic tomography derivation of site specific relationships between hydraulic parameters and p wave velocities based on hydraulic and seismic tomography brauchler r 1 doetsch j 1 2 dietrich p 3 sauter m 4 eth zurich department of earth sciences sonneggstrasse 5 8092 zurich switzerland now at earth sciences division lawrence berkeley national laboratory one cyclotron road berkeley ca 94720 ufz helmholtz centre for environmental research department monitoring and exploration technologies permoserstrasse 15 04318 leipzig germany geoscientific centre university of gottingen goldschmidtstrase 3 37077 gottingen germany

an igneous origin for features of a candidate crater lake system in western memnonia mars the association of channels inner terraces and delta like features with martian impact craters has previously been interpreted as evidence in favor of the past existence of crater lakes on mars however examination of a candidate crater lake system in western memnonia suggests instead that its features may have formed through igneous processes involving the flow and ponding of lava accumulations of material in craters and other topographic lows throughout much of the study region have characteristics consistent with those of volcanic deposits and terraces found along the inner flanks of some of these craters are interpreted as having formed through drainage or subsidence of volcanic materials channels previously identified as inlets and outlets of the crater lake system are interpreted instead as volcanic rilles these results challenge previous interpretations of terrace and channel features in the study region and suggest that candidate crater lakes located elsewhere should be reexamined

quantitative integration of hydrogeophysical data conditional geostatistical simulation for characterizing heterogeneous alluvial aquifers high resolution geophysical parameter information as it can be provided for example by crosshole georadar and seismic tomography has proven to provide useful spatial information to complement traditional hydrological methods such as core analyses logging techniques and tracer or pumping tests quantitative integration of these diverse database components is one of the major challenges in the field of high resolution hydrogeophysics because of their different scales of measurement and the usually weak petrophysical relations among the measurements in this study we systematically explore the usefulness of a conditional stochastic simulation approach based on simulated annealing for this purpose first we generate a realistic model of an alluvial aquifer consisting of a 2d scale invariant porosity field on the basis of this model we generate synthetic neutron porosity logs and crosshole georadar tomographic surveys we then use the proposed geostatistical simulation approach to integrate this hydr

three dimensional stochastic estimation of porosity distribution benefits of using ground penetrating radar velocity tomograms in simulated annealing based or bayesian sequential simulation approaches 1 estimation of the three dimensional 3 d distribution of hydrologic properties and related uncertainty is a key for improved predictions of hydrologic processes in the subsurface however it is difficult to gain high quality and high density hydrologic information from the subsurface in this regard a promising strategy is to use highresolution geophysical data that are relatively sensitive to variations of a hydrologic parameter of interest to supplement direct hydrologic information from measurements in wells e g logs vertical profiles and then generate stochastic simulations of the distribution of the hydrologic property conditioned on the hydrologic and geophysical data in this study we develop and apply this strategy for a 3 d field experiment in the heterogeneous aquifer at the boise hydrogeophysical research site and we evaluate how much benefit the geophysical data provide we run high resolution 3 d conditional simulations of porosity with both simulated annealing based and bayesian sequential approaches using information from multiple intersecting crosshole gound penetrating radar gpr velocity tomograms and neutron porosity logs the benefit of using gpr data is assessed by investigating their ability when included in conditional simulation to predict porosity log data withheld from the simulation results show that the use of crosshole gpr data can significantly improve the estimation of porosity spatial distribution and reduce associated uncertainty compared to using only well log measurements for the estimation the amount of benefit depends primarily on the strength of the petrophysical relation between the gpr and porosity data the variability of this relation throughout the investigated site and lateral structural continuity at the site

origin of periodically spaced wrinkle ridges on the tharsis plateau of mars ridged plains are a major geologic unit on mars and are a predominant unit on the tharsis plateau a region that has undergone uplift extension and extensive shield and flood volcanism these units probably flood volcanic in origin are characterized by landforms classed as wrinkle ridges wrinkle ridges are interpreted to be folds resulting from buckling followed by reverse to thrust faulting flexure fracture a prominent characteristic of many of the wrinkle ridges on mars particularly those in the tharsis ridge system is the periodic nature of their spacing the periodic spacing has been evaluated in six major provinces on the tharsis plateau with regions further divided into domains based largely on variation in ridge orientation the average spacing of the tharsis ridges based on 2934 measurements is 30 km in an effort to account for the periodic nature of the wrinkle ridges the ridged plains material is modeled as both a single member and a multilayer with frictionless contacts that has buckled at a critical wavelength of folding free slip between layers is assumed based on the possible existence of mechanically weak interbeds in the ridged plains sequence separating groups of flows the near surface mechanical structure in the area of ridged plains is approximated by a strong layer or layers overlying a weak megaregolith of finite thickness overlying a strong basement buckling of the ridged plains is assumed to be decoupled from the basement by the weak megaregolith decoupling is enhanced if the megaregolith were water or ice rich at the time of deformation the rheologic behavior of the ridged plains and megaregolith is approximated by a linear elastic and linear viscous material the models are examined for a range in 1 the strength contrast between the ridged plains material and the underlying megaregolith 2 thickness of the ridged plains material 3 thickness of the megaregolith and 4 number of layers the elastic model can explain the observed ridge spacing only if the ridged plains are relatively thick 2400 m with multiple layers n 1 and relatively high contrasts in young s modulus e e0 100 the high e e0 required is possible only if the megaregolith was water rich at the time of deformation over the same range in values of the parameters viscous buckling is much less restricted the viscous model can explain the observed ridge spacing over a wide range in ridged plains thickness 250 m to several kilometers megaregolith thickness number of layers n 1 to 8 and contrasts in viscosity 0 10 in addition viscous buckling is viable if the megaregolith were dry water rich or ice rich at the time of deformation the absence of folds with a cross sectional geometry in the shape of a sinusoid anticline syncline pairs may be the result of initial deformation of the ridged plains material into low amplitude folds in infinitesimal strain followed by plastic yielding in the cores of the anticlines in finite strain initial elastic or viscous buckling coupled with plastic yielding confined to the hinge area followed by the development of reverse to thrust faulting could account for the asymmetric fold geometry of many of the wrinkle ridges

development of a joint hydrogeophysical inversion approach and application to a contaminated fractured aquifer this paper presents a joint inversion approach for combining crosshole seismic travel time and borehole flowmeter test data to estimate hydrogeological zonation the approach is applied to a complex fractured department of energy field site located at the oak ridge national laboratory in tennessee united states we consider seismic slowness the inverse of seismic velocity and hydrogeological zonation indicators as unknown variables and use a physically based model with unknown parameters to relate the seismic slowness to the zonation indicators we jointly estimate all the unknown parameters in the model by conditioning them to the crosshole seismic travel times as well as the borehole flowmeter data using a bayesian model and a markov chain monte carlo sampling method the fracture zonation estimates are qualitatively compared to bromide tracer breakthrough data and to uranium biostimulation experiment results the comparison suggests that the joint inversion approach adequately estimated the fractured zonation and that the fracture zonation influenced biostimulation efficacy our study suggests that the new joint hydrogeophysical inversion approach is flexible and effective for integrating various types of data sets within complex subsurface environments and that seismic travel time data have the potential to provide valuable information about fracture zonation

applications of algebraic reconstruction techniques to crosshole seismic data tomographic imaging techniques were applied to two crosshole data sets to determine the velocity structures and the reliability and resolution of the algorithms on real data the experiments were carried out at the retsoff salt mine in new york and at the underground radioactive waste study site at the stripa mine facility in sweden the traveltimes at restoff were high quality and were obtained over raypaths of up to 500 m in length the structure was quite complicated with velocity contrasts up to 50 percent the stripa site was in granitic rock with velocity contrasts of only a few percent the dimensions of the experiment were small with maximum ray lengths of just over 10 m the data at this site were collected with very high accuracy source and receiver locations were measured to better than 1 0 mm and traveltimes were read to 0 001 ms a number of algorithms similar to the algebraic reconstruction techniques art used in medical imaging have been applied to the data some modifications of the algorithms such as the application of weighting schemes damping parameters and curved raypaths were performed the resulting velocity fields were compared to the known fields and with each other to determine an optimal method the algorithms were found to be a rapid reliable means of reconstructing the slowness field of real data low velocity zones were recovered with accuracy in location and value it was also found that great care was necessary in application of the techniques to ensure that proper damping parameters are used and the proper number of iterations taken otherwise poor reconstructions will result

visual attributes of a rock and their relationship to permeability a comparison of digital image and minipermeameter data 1 what is the relationship between the visual attributes of a rock sample and its permeability and how might such information be used in aquifer reservoir characterization we investigated these questions by way of three meter scale blocks of rock two sandstones and one volcanic tuff each rock exhibits visual and permeability patterns that differ in geometry intensity and scale using a gas minipermeameter hundreds to thousands of permeability values were collected on grids at centimeter scale resolution from each block face and compared to the digital visual image of the same face we found no significant direct correlation between the permeability measurements and any objective textural measure drawn from the corresponding digital images despite the obvious resemblance of the permeability maps and visual images hypothesizing that the human eye relies on spatial correlation to synthesize information we calculated and compared semivariograms for both the maps and the images semivariogram shape anisotropy ratio and principal axes orientation were consistent for the maps and images of each rock but different between rocks to explore this similarity further we compared discrete features appearing in map image pairs using a difference of gaussian edge filter to segment i e delineate the spatial features the filter consistently colocated visually sharp features such as sedimentological bounding surfaces in both the map and the image additionally cumulative distribution functions characterizing the size shape and orientation of the segmented features were statistically indistinguishable between a permeability map and its corresponding visual image but statistically different between rocks these results suggest that it may not always be possible to use visual images photographs or scans of outcrops to directly map permeability even with a training set of punctual permeability data in particular defining such relations may be difficult where the scales of analysis and or intensity of heterogeneity are limited e g within a given facies as is the case here where direct mapping is not possible these results suggest that visual images can still be used to delineate spatial permeability patterns especially to locate boundaries where sharp permeability contrasts occur other surrogate measurements of permeability in particular the various geophysical methods may exhibit similar behavior

late hesperian to early amazonian midlatitude martian valleys evidence from newton and gorgonum basins 1 numerous shallowly incised valleys extend from the upper interior rims of newton and gorgonum basins across smooth interior basin deposits these valleys are a few meters to 300 m wide and may have experienced discharges over all or most of their width implying that they are in fact incised channels in newton crater these valleys extend up to 75 km to near the center of the basin floor in gorgonum basin the valleys terminate at what we interpret to be a former ice covered lake these valleys appear to be examples of scattered shallowly incised valleys found throughout the midlatitudes of mars superimposed upon the widespread mantling deposits within the region on the basis of crater count age dating the interior valleys in newton and gorgonum basins were formed at about the hesperian to amazonian transition the runoff through the valleys may have occurred due to episodic melting of snow and ice that had accumulated on the crater rims temperatures warm enough to cause extensive melting may have occurred during optimal orbital and obliquity configurations because of intensive volcanism releasing greenhouse gasses or as a result of a brief episode of warming from a large impact somewhere on mars the valleys were formed at about the same time as major outflow channels were active along the highlands lowlands boundary water delivered to the northern lowlands by the outflow channels may have been recycled as snow and ice deposits within the martian midlatitudes the episodic melting of such deposits may have formed the midlatitude valleys

on the value of lithofacies data for improving groundwater flow model accuracy in a three dimensional laboratory scale synthetic aquifer improvement of the prediction accuracy of groundwater flow models has been receiving substantial attention from many researchers through the development of enhanced characterizations of the structure of subsurface lithofacies and of the distribution of hydraulic conductivity in this study we investigated how incorporating increasing amounts of lithofacies data into the construction of a conceptual model of aquifer heterogeneity helps to reduce prediction error and uncertainty in groundwater flow models an approach based on both laboratory experiments and numerical simulations was tested using data from an intermediate scale synthetic heterogeneous aquifer the heterogeneous aquifer consisted of five lithofacies corresponding to five test sands three pumping tests were conducted and provided experimental data to perform groundwater flow model calibration and validation the pumping tests were also simulated numerically in order to provide a series of error free synthetic hydraulic data sets on the basis of markov chains models of transition probabilities a total of 901 random realizations of the heterogeneous distribution of lithofacies were created using varying amounts of conditioning lithofacies data sampled along randomly placed hypothetical boreholes for each realization and for two other simplified lithofacies models parameter estimation was performed to estimate the hydraulic conductivity of the lithofacies using the experimental and synthetic hydraulic data from the three pumping tests the results generally showed that the use of more lithofacies data in the construction of the lithofacies realizations led to an improvement in groundwater flow model prediction accuracy when using the error free synthetic hydraulic data the calibration prediction error and uncertainty decreased drastically when the mean borehole spacing was on the order of twice the horizontal correlation length or less when the experimental hydraulic data were used this drastic improvement in the calibration prediction error was somewhat obscured and in some cases exhibited a local minimum this local minimum although beyond practical limits corresponded to an optimal number of boreholes finally the effect of incorporating more lithofacies data for the construction of lithofacies realizations was found to have a similar impact on the quality of model calibration and on the quality of predictive simulations conducted using the calibrated model

combined effect of heterogeneity anisotropy and saturation on steady state flow and transport structure recognition and numerical simulation 1 natural soil profiles may be interpreted as an arrangement of parts which are characterized by properties like hydraulic conductivity and water retention function these parts form a complicated structure characterizing the soil structure is fundamental in subsurface hydrology because it has a crucial influence on flow and transport and defines the patterns of many ecological processes we applied an image analysis method for recognition and classification of visual soil attributes in order to model flow and transport through a man made soil profile modeled and measured saturation dependent effective parameters were compared we found that characterizing and describing conductivity patterns in soils with sharp conductivity contrasts is feasible differently solving flow and transport on the basis of these conductivity maps is difficult and in general requires special care for representation of small scale processes

a simultaneous inversion of seismic traveltimes and amplitudes for velocity and attenuation it is possible to efficiently use traveltime and amplitude information to infer variations in velocity and q with little additional computation terms accounting for source radiation pattern and receiver coupling may be included in the inversion the methodology is based upon a perturbation approach to paraxial ray theory the perturbation approach linearizes the relationship between velocity deviations and traveltime and amplitude anomalies using the technique we infer the velocity and attenuation structure at a fractured granitic site near raymond california a set of four well pairs are examined and each is found to contain two zones of strong attenuation the velocity variations contain an upper low velocity region corresponding to the uppermost attenuating zone the location of these zones agrees with independent well log and geophysical data the velocity and attenuation anomalies appear to coincide with extensively fractured sections of the borehole and may indicate fracture zones rather than individual fractures

stochastic inversion of tracer test and electrical geophysical data to estimate hydraulic conductivities 1 quantifying the spatial configuration of hydraulic conductivity k in heterogeneous geological environments is essential for accurate predictions of contaminant transport but is difficult because of the inherent limitations in resolution and coverage associated with traditional hydrological measurements to address this issue we consider crosshole and surface based electrical resistivity geophysical measurements collected in time during a saline tracer experiment we use a bayesian markov chain monte carlo mcmc methodology to jointly invert the dynamic resistivity data together with borehole tracer concentration data to generate multiple posterior realizations of k that are consistent with all available information we do this within a coupled inversion framework whereby the geophysical and hydrological forward models are linked through an uncertain relationship between electrical resistivity and concentration to minimize computational expense a facies based subsurface parameterization is developed the bayesian mcmc methodology allows us to explore the potential benefits of including the geophysical data into the inverse problem by examining their effect on our ability to identify fast flowpaths in the subsurface and their impact on hydrological prediction uncertainty using a complex geostatistically generated two dimensional numerical example representative of a fluvial environment we demonstrate that flow model calibration is improved and prediction error is decreased when the electrical resistivity data are included the worth of the geophysical data is found to be greatest for long spatial correlation lengths of subsurface heterogeneity with respect to wellbore separation where flow and transport are largely controlled by highly connected flowpaths

modeling the impact of solute recycling on groundwater salinization under irrigated lands a study of the alto piura aquifer peru summary studies of groundwater quality in arid and semi arid lands show that irrigation return flow is one of major factors contributing to aquifer salinization existing mathematical models do not account explicitly for solute recycling during irrigation on a daily scale which is considered as an important salinization input the main objective of this research was to develop a mathematical numerical model that can simulate impact of irrigation return flow by coupling water and solute fluxes at the soil surface with quality of water pumped from the aquifer this was obtained with a quasi 3d model representing flow in the vadose zone aquifer system by series of 1d richards equations in a variably saturated zone and by a 3d flow equation in groundwater the 3d advection dispersion equation is solved in the entire domain concentration of irrigation water is calculated at each time step as a function of concentration of both surface water and groundwater extracted at specific locations the model was applied to simulate the impact of irrigation on groundwater salinization of alto piura aquifer northern peru over thirty years three scenarios were considered i use of flood irrigation and groundwater extraction the present situation ii increase of groundwater pumping by 50 compared to the first scenario and iii transition from flood irrigation to drip irrigation thus decreasing irrigation volume by around 60 compared to the first scenario results indicate that in different irrigation areas the simulated increase rates of total dissolved solids in groundwater vary from 3 5 to 15 17 mg l year depending on hydrogeological and hydrochemical conditions volumes of water extracted and proportion between surface water and groundwater applied the transition from flood irrigation to drip irrigation decreases the negative impact of return flow on groundwater quality however drip irrigation causes faster soil salinization compared to flood irrigation irrigation return coefficients were calculated in the order of 21 23 and 22 24 for the first and second scenarios respectively

updated global map of martian valley networks and implications for climate and hydrologic processes 1 martian valley networks have long been viewed as some of the best evidence of prolonged surface water on mars analysis from viking data showed that valleys were primarily contained on the ancient crust drainage networks were immature and large undissected regions occurred in between individual systems these observations led many to propose that they formed primarily by groundwater processes and limited or no climate change from the present state was required using more recent and higher resolution data sets including visible infrared and topographic data we have manually remapped valleys on a global scale more than eight times as many valleys have been identified on the surface and calculated drainage densities are on average higher by a factor of 2 further regions previously thought to be undissected have significant incision by fluvial processes most of these systems seem to have formed around the noachian hesperian boundary 3 8 3 6 ga minor valley formation continued through the hesperian and into the early amazonian epoch approximately 2 8 ga ago the new data reveal characteristics of sustained precipitation and surface runoff including inner braided channels terraces multiple periods of formation complex network morphology and correlation with other fluviosedimentary features and chloride salts on mars groundwater processes or a transient steam atmosphere generated by impacts played at most a minor role these new results imply that mars had a long lived period or periods of clement conditions toward the end of the noachian epoch that supported a hydrologic cycle and potentially a biosphere

inversion of hydrological tracer test data using tomogrpahicconstraints a reasonable description of the hydraulic conductivity structure is a prerequisite for modeling contaminant transport however formulations of hydrogeological inverse problems utilizing hydrogeological data only often fail to reliably resolve features at a resolution required for accurately predicting transport incorporation of geophysical data into the inverse problem offers the potential to increase this resolution in this study we invert hydrological tracer test data using the shape and relative magnitude variations derived from geophysical tomographic data to regionalize a hydrogeological inverse problem in order to estimate the hydraulic conductivity structure our approach does not require that the petrophysical relationship be known a priori but that it is linear and stationary within each geophysical anomaly however tomograms are imperfect models of geophysical properties and geophysical properties are not necessarily strongly linked to hydraulic conductivity therefore we focus on synthetic examples where the correlation between radar velocity and hydraulic conductivity as well as the geophysical data acquisition errors are varied in order to assess what aspects of the hydraulic conductivity structure we can expect to resolve under different conditions the results indicate that regularization of the tracer inversion procedure using geophysical data improves estimates of hydraulic conductivity we find that even under conditions of corrupted geophysical data we can accurately estimate the effective hydraulic conductivity and areas of high and low hydraulic conductivity however given imperfect geophysical data our results suggest that we cannot expect accurate estimates of the variability of the hydraulic conductivity structure

overbank sediments from the surroundings of the russian nickel mining and smelting industry on the kola peninsula top and bottom samples of overbank sediments were collected at 43 sites within a 12 000 km2 area around the nickel smelter in nikel and the ore roasting plant at zapoljarnij in northwestern russia in addition three detailed overbank profiles were sampled in 10 cm sections from three catchments representing different levels of pollution all samples were analysed for more than 30 elements by icp aes following aqua regia extraction results obtained show that overbank sediments represent natural geogenic background levels rather well although the major pollutants co cu ni and s are strongly enriched at some places close to industry overbank sediment is not especially well suited for mapping the extent of airborne contamination in the area co cu ni and s are mobile within the profile collected from the most polluted catchment

a stochastic approach to the characterization of lithofacies from surface seismic and well data heterogeneity of natural geologic formations strongly influences groundwater flow and contaminant migration this study presents a formal stochastic approach for the integration of surface seismic data and well data into the identification of the spatial arrangement location geometry and interconnectedness of lithofacies and incorporating this information in the estimation of the log permeability probability density function pdf to achieve this goal normal move out nmo corrections are applied to the seismic reflection data to estimate interval seismic velocities calibration curves constructed from the well logs transform these velocity estimates into a lithology indicator prior probability field from the well data and the indicator prior probability field the indicator covariance function and its associated confidence limits are computed neighboring lithology logs and the indicator covariance function are then combined to update the indicator probability field the conditional log permeability pdf is finally computed by weighting the log permeability distribution of each lithology with respect to its indicator probability field the effectiveness of the proposed procedure is shown to depend on the quality of the seismic data and the degree of correlation between seismic and hydrogeologic soil properties a synthetic case study is performed which shows that the surface seismic and well data complement each other with optimal results achieved when both types of data are incorporated into a joint identification procedure

acoustic crosswell imaging using asymptotic waveforms seismic waveforms are inverted using an asymptotic method the asymptotic method models amplitudes correctly at the caustics and takes nonstationary raypaths into account when computing the waveforms and thus is an extension of geometrical ray theory using numerical differencing partial derivatives of the data with respect to the model are computed as expected these partial derivatives or sensitivity functions are concentrated along but not confined to raypaths the sensitivity functions enable the formulation of a waveform inversion algorithm which is applied to a synthetic crosswell experiment and a laboratory crosswell experiment the synthetic experiment shows the advantages of the waveform inversion method over conventional traveltime inversion methods boundaries of anomalies are better defined and smearing is reduced the waveform inversion produces a much lower misfit than the traveltime inversion the goal of the laboratory experiment was the detection of a nonaqueous phase liquid napl in water saturated sand the sand was imaged before and after injection of the napl using the waveform inversion method low velocity anomalies were imaged that correlate well with post experiment determination of napl concentrations the low velocity anomaly defocuses the seismic energy however the amplitude reduction due to the low velocity anomaly is not enough to explain the observed low amplitudes we suggest that other mechanisms such as multiple scattering 3 d effects or intrinsic attenuation not included in the asymptotic waveform modeling play an important role in decreasing the amplitude

in situ compositions of martian volcanics implications for the mantle the primary objective of this analysis is to determine the mineralogic composition of relatively pristine terrains exposed on the surface of mars this analysis is conducted using imaging spectrometer data acquired in 1989 by the imaging spectrometer for mars ism instrument that was onboard the phobos ii spacecraft the ism instrument acquired some of the highest spectral 64 channels between 0 77 and 3 14 m and spatial resolution 22 km pixel observations to date of mars focused on the equatorial region relatively unaltered surfaces were identified in these data on the basis of their spectral properties low albedo weak spectral slope absence of ferric absorptions and were found in volcanic terrains of syrtis major valles marineris ophir planum and sinus meridiani oxia palus spectra representative of the diversity among terrains were extracted for detailed analysis using the modified gaussian model to determine the primary mafic mineralogy it was determined that the mafic mineralogy of the regions investigated is dominated by low calcium and high calcium pyroxene lcp hcp and that there was homogeneity within a given region but some heterogeneity between regions in the relative abundance of lcp to hcp the two pyroxene mineralogy is consistent with the mineralogies of the basaltic snc meteorites believed to have originated on mars two pyroxene volcanic mineralogies are indicative of large degrees of partial melting e g komatiites or a mantle source depleted in aluminum integration of these findings with previous studies of mars and the snc meteorites indicates that 1 the snc mineralogies are representative of large volcanic regions of mars with surface ages as old as 2 3 ga 2 the martian mantle was depleted in aluminum at least as long ago as the oldest terrain analyzed ophir planum and 3 there has been little evolution in the composition of mantle source regions as the 180 ma snc mineralogies are comparable to those of the oldest terrains analyzed

human induced sedimentation patterns of a channelized lowland river channelization of the severely polluted odra and vistula rivers in poland induced intensive accumulation of fine grained deposits rich in organic matter and heavy metals these sediments have been identified in vertical profiles in a narrow zone along river banks both in groyne created basins and on the floodplain grain size organic matter zinc zn lead pb copper cu content and cesium 137 137cs was used for sediment dating and stratigraphy and chemistry have been diagnostic features for these deposits named industrial alluvium in the most polluted river reaches stabilized by bank reinforcements and groynes 2 m thick slack water groyne deposits are composed of uniform strata of polluted silts with organic matter content over 10 zn content over 1000 mg kg and average cu and pb over 100 mg kg the average rate of sediment accretion in groynes is higher than on the floodplain and reaches 5 cm yr stratification which appears at higher levels in the groyne fields and on the levees reflects a change from in channel to overbank deposition and is typified by dark layers separated by bright sandy and less polluted strata stratified 4 m thick sediment sequences have been found in groyne fields of incised river reaches the average rate of sediment accretion in these reaches is of the order of 5 cm yr in stable and relatively less polluted river reaches vertical accretion organic deposits are finely laminated and the average rate of deposition amounts to a few millimeters per year investigations indicate that groyne construction favors conditions for long term storage of sediments at channel banks for this reason groynes should be considered as structures that efficiently limit sudden release of sediment associated heavy metals stored in channels and in floodplains of the historically polluted rivers copyright 2014 john wiley sons ltd

an effective bayesian model for lithofacies estimation using geophysical data 1 a bayesian model coupled with a fuzzy neural network bfnn is developed to enhance the use of geophysical data in lithofacies estimation prior estimates are inferred from borehole lithofacies measurements using indicator kriging and posterior estimates are obtained by updating the prior using geophysical data the novelty of this study lies in the use of the fuzzy neural network for the inference of the likelihood function this allows spatial correlation of lithofacies as well as nonlinear cross correlation between lithofacies and geophysical attributes to be incorporated into lithofacies estimation the effectiveness of bfnn is demonstrated using synthetic data emulating measurements at the lawrence livermore national laboratory llnl site

apparent thermal inertia and the surface heterogeneity of mars abstract thermal inertia derivation techniques generally assume that surface properties are uniform at horizontal scales below the footprint of the observing instrument and to depths of several decimeters consequently surfaces with horizontal or vertical heterogeneity may yield apparent thermal inertia which varies with time of day and season to investigate these temporal variations we processed three mars years of mars global surveyor thermal emission spectrometer observations and produced global nightside and dayside seasonal maps of apparent thermal inertia these maps show broad regions with diurnal and seasonal differences up to 200 j m 2 k 1 s 1 2 at mid latitudes 60 s to 60 n and 600 j m 2 k 1 s 1 2 or greater in the polar regions we compared the seasonal mapping results with modeled apparent thermal inertia and created new maps of surface heterogeneity at 5 resolution delineating regions that have thermal characteristics consistent with horizontal mixtures or layers of two materials the thermal behavior of most regions on mars appears to be dominated by layering with upper layers of higher thermal inertia e g duricrusts or desert pavements over fines prevailing in mid latitudes and upper layers of lower thermal inertia e g dust covered rock soils with an ice table at shallow depths prevailing in polar regions less common are regions dominated by horizontal mixtures such as those containing differing proportions of rocks sand dust and duricrust or surfaces with divergent local slopes other regions show thermal behavior that is more complex and not well represented by two component surface models these results have important implications for mars surface geology climate modeling landing site selection and other endeavors that employ thermal inertia as a tool for characterizing surface properties

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

recent changes in heavy metal contamination at near channel positions of the lahn river central germany abstract short term monitoring of heavy metal concentrations along rivers affords the opportunity to examine the persistence of contaminants in the fluvial environment this paper examines changes in the concentrations of cu pb and zn at near channel positions along a 75 km reach of the lahn river an agrarian watershed in central germany between 2000 and 2007 thirty three sites sampled in 2000 were re sampled in 2007 in order to document changes in trace metal contamination the concentrations of cu and pb decreased between 2000 and 2007 whereas the concentration of zn was statistically unchanged the pb concentration decreased at 82 of the sample sites over the study period whereas cu concentrations decreased at 70 of the sites site to site variation in the concentrations of pb with distance downstream from potential source areas declined between 2000 and 2007 the downstream variation in cu also decreased over the study period albeit to a lesser degree the decrease in pb and to a lesser extent cu concentrations adjacent to the lahn river appears to reflect the recent reductions in the release of trace elements to the environment zinc concentrations were unchanged suggesting that it is derived from different sources than are cu and pb or is cycling through the watershed differently than cu and pb lower concentrations of cu and pb in channel bank sediments translate to a reduced risk of future downstream heavy metal pollution in the study area

heterogeneous aquifer characterization from ground penetrating radar tomography and borehole hydrogeophysical data using nonlinear bayesian simulations it is known that the heterogeneity of hydraulic conductivity drives the groundwater flow and the transport of contaminants however in conventional characterization methods the lack of densely sampled hydrological data does not permit us to describe the aquifer heterogeneity at an appropriate scale in this study we integrate ground penetrating radar gpr tomographic data with hydraulic conductivity logs to estimate the hydraulic conductivity of a heterogeneous unconsolidated aquifer at a decimetric scale between two boreholes the integration of these different data sets is achieved using a nonlinear bayesian simulation algorithm the prior hydraulic conductivity distribution is estimated under gaussian hypothesis by simple kriging of the hydraulic well data the likelihood of hydraulic conductivity given the relative permittivity and the electrical conductivity functions is obtained from a kernel probability density function estimator that describes the in situ relationship between the electric and the hydraulic properties measured along boreholes the proposed method is tested on a synthetic heterogeneous model of permeability to validate the methodology we show that permeability realizations obtained from the proposed algorithm present a higher correlation with the synthetic model than other classical simulation methods the method is then applied on data acquired over an unconsolidated aquifer located in saint lambert de lauzon quebec canada the data set consists of measurements from i gpr crosshole acquisition ii cone penetration testing with pressure measurement combined with soil moisture resistivity and iii a borehole electromagnetic flowmeter by using the presented bayesian approach we generated multiple hydraulic conductivity realizations that are in good agreement with the hydrogeological model of the area

relation of the spectroscopic reflectance of olivine to mineral chemistry and some remote sensing implications using high resolution visible and near infrared diffuse spectral reflectance we have systematically investigated apparent wavelength shifts as a function of mineral chemistry in the fe mg olivine series from fo11 to fo91 the study also shows that trace amounts of nickel can be spectrally detected in the olivine structure we show that significant compositional information can only be extracted at relatively high resolution because the overall spectral characteristics of the olivines change only subtly as a function of the fe mg ratio significant spectral variation as a function of grain size is also demonstrated adding a further complication to the interpretation of remotely sensed data from olivine rich surfaces this laboratory study is expected to aid in the interpretation of remotely sensed data from both terrestrial and extraterrestrial bodies terrestrial applications may include the recognition of ultramafic ultrabasic and basaltic terrains which in themselves may have mineral potential among extraterrestrial applications the asteroids are obvious candidates for further examination if instrumentation can provide the necessary wavelength coverage resolution and signal to noise ratio so that spectra can be compared to those laboratory data discussed here some permutations of fe mg ni relations in olivines are discussed as they apply to the interpretation of asteroid surfaces and other extraterrestrial bodies

hydrogeophysical data integration at larger scales application of bayesian sequential simulation for the characterization of heterogeneous alluvial aquifers knowledge of the spatial distribution of hydraulic conductivity k within an aquifer is critical for reliable predictions of solute transport and the development of effective groundwater management and or remediation strategies while core analyses and hydraulic logging can provide highly detailed information such information is inherently localized around boreholes that tend to be sparsely distributed throughout the aquifer volume conversely larger scale hydraulic experiments like pumping and tracer tests provide relatively low resolution estimates of k in the investigated subsurface region as a result traditional hydrogeological measurement techniques contain a gap in terms of spatial resolution and coverage and they are often alone inadequate for characterizing heterogeneous aquifers geophysical methods have the potential to bridge this gap the recent increased interest in the application of geophysical methods to hydrogeological problems is clearly evidenced by the formation and rapid growth

woodland history in the upper harz mountains revealed by kiln site soil sediment and peat charcoal analyses charcoal is abundant in various soils and soil sediments and is basically the result of either natural wildfires or of anthropogenic ignition compositions of charcoal assemblages are the result of several taphonomical processes beside this little is known about the influence of charcoal from anthropogenic origin like charcoal production sites kiln sites on soil charcoal assemblages to elucidate how human charcoal production as well as erosion of the relicts of kiln sites influenced charcoal assemblages in soils and mires a multi proxy approach was applied at two transects on the renneckenberg a steep slope in the low mountain range harz germany on this slope three types of archives soil soil sediments kiln sites and peatland were investigated each with different methods on a local scale soil charcoal analyses kiln site charcoal analyses peat macro micro charcoal and pollen analysis the kiln site charcoal records are taxonomically richer in wood taxa than those from colluvial assemblages especially regarding deciduous tree species fagus sylvatica and acer sp are rare or absent in the colluvial charcoal assemblages which are dominated by picea charcoal at the bottom of the slope the soil charcoal concentration is very high and indicates strong erosion of charcoal from the upper part of the slope significant taxonomical discrepancies between the colluvial and the kiln site charcoal assemblages may be related to different fire intensity throughout the holocene and to human woodland usage additionally changes in the run off intensity and fire frequency are detected in the peat macro charcoal record reflecting vegetation change in the early holocene the micro charcoal content coincides with the main mining phases in the late holocene and the 9 2 k climatic anomaly

vertical radar profiling combined analysis of traveltimes amplitudes and reflections abstractvertical radar profiling vrp is a single borehole geophysical technique in which the receiver antenna is located within a borehole and the transmitter antenna is placed at one or various offsets from the borehole today vrp surveying is primarily used to derive 1d velocity models by inverting the arrival times of direct waves using field data collected at a well constrained test site in germany we evaluated a vrp workflow relying on the analysis of direct arrival traveltimes and amplitudes as well as on imaging reflection events to invert our vrp traveltime data we used a global inversion strategy resulting in an ensemble of acceptable velocity models and thus it allowed us to appraise uncertainty issues in the estimated velocities as well as in porosity models derived via petrophysical translations in addition to traveltime inversion the analysis of direct wave amplitudes and reflection events provided further valuable information regarding subsurface properties and architecture the

predicting aquifer characteristics to enhance hydrogeophysical model in fractured karstified rocks of dammam formation at bahr al najaf basin iraq groundwater represents a major water source in bahr al najaf basin so the knowledge of the aquifer parameters is an essential goal to assess and manage groundwater resources a comprehensive view of the fractured and karstified aquifers within dammam formation at bahr al najaf basin is very important because the karstified environments are very complex this study is an attempt to extract mathematically empirical relationships between the hydraulic parameters and the geoelectrical properties to improve the construction of a hydrogeophysical model instead of using the conventional procedures of pumping tests or drill new well which need great effort and high cost the enhanced hydrogeophysical model shows that the main aquifer has a uniform lithology of carbonate rocks good water saturation and belongs to m dammam member the correlation between hydraulic conductivity k m day and aquifer resistivity rho 0 m gave a logical relationship in such kind of aquifer which has correlation coefficient r2 equals to 0 737 in addition the correlation between transmissivity t m2 day and both of transverse resistance tr m2 and longitudinal conductance sl 1 revealed the similarity in lithological characteristics of middle dammam aquifer due to the approximately equal values of strong r2 0 862 and 0 868 respectively this may be due to the nature of the studied area as a discharge zone which has a good porosity varphi of 22 and a high water saturation sw equals to 1 approximately the extracted relationship of direct proportionality between t m2 day and sl 1 is an important one therefore this relationship can be used directly to calculate t m2 day mathematically in the present study the relations between the hydraulic parameters and the geoelectrical properties are expressed as linear equations instead of nonlinear because we believe that it is mathematically more acceptable and reliable for hard rock aquifers that the m dammam aquifer is confined with a fully saturated thickness in addition the comparison between r2 of the linear and nonlinear relation of t m2 day with tr m2 and t m2 day with sl 1 appeared to have little divergence of r2 equal to 0 028 and 0 001 respectively

rootless cones on mars indicating the presence of shallow equatorial ground ice in recent times high resolution mars orbiter camera moc images have revealed the existence of clusters of small cones in the cerberus plains marte valles and amazonis planitia mars these cones are similar in both morphology and planar dimensions to the larger of icelandic rootless cones which form due to explosive interactions between surficial lavas and near surface groundwater impact crater size frequency relationships indicate that surfaces upon which the cones sit are no older than 10 ma if martian cones form in the same manner as terrestrial rootless cones then equatorial ground ice or ground water must have been present near the surface in geologically recent times

effect of obliteration on crater count chronologies for martian surfaces 1 the density of impact craters calibrated against lunar data is currently the only quantitative measure of surface age for terrestrial planetary surfaces unlike the moon however mars has been weathered and eroded obliterating some small 10 km diameter craters a phenomenon addressed in the mariner viking days of mars exploration but commonly overlooked in recent studies we present a quantitative model that extends this earlier work to assess the effect of erosion and infilling on surface ages inferred from crater frequency distributions our work affirms that small cratersizedistributionscanbeinterpretedquantitatively in terms of effects of erosion and crater infilling at rates comparable to those reported for mars a reanalysis of prior studies indicates that low to moderate long term rates of erosion and crater infilling can mask an ancient age and result in small crater populations similar to those offered as evidence for young and geologically significant surface activity citation smith m r a r gillespie and d r montgomery 2008 effect of obliteration on crater count chronologies for martian surfaces geophys res lett 35 l10202 doi 10 1029 2008gl033538

hydrodynamic parameters of a sandy soil determined by ground penetrating radar inside a single ring infiltrometer this study shows how mualem van genuchten m vg parameters can be obtained from gpr data acquired during water infiltration from a single ring infiltrometer in the case of a sandy soil water content profiles were generated at various time steps using hydrus 1d based on particular values of the m vg parameters and were converted to dielectric permittivity profiles using the complex refractive index method the gprmax suite of programs was used to generate radargrams and to follow the wetting front progression in depth using the arrival time of the electromagnetic waves recorded by a ground penetrating radar gpr theoretically the 1 d time convolution between reflectivity and gpr signal at any infiltration time step is related to the peak of the reflected signal recorded in the corresponding trace in the radargram we used this relationship to invert the m vg parameters for constant and falling head infiltrations using the shuffled complex evolution sce ua algorithm the method is presented on synthetic examples and on experiments carried out for a sandy soil the parameters inverted are compared with values obtained in laboratory on soil samples and with disk infiltrometer measurements

explosive lava water interactions ii self organization processes among volcanic rootless eruption sites in the 1783 1784 laki lava flow iceland we have applied quantitative geospatial analyses to rootless eruption sites in the hnuta and hrossatungur groups of the 1783 1784 laki lava flow to establish how patterns of spatial distribution can be used to obtain information about rootless cone emplacement processes and paleo environments this study utilizes sample size dependent nearest neighbor nn statistics and voronoi tessellations to quantify the spatial distribution of rootless eruption sites and validate the use of statistical nn analysis as a remote sensing tool our results show that rootless eruption sites cluster in environments with abundant lava and water resources but competition for limited groundwater in these clusters can cause rootless eruption sites to develop repelled distributions this pattern of self organization can be interpreted within the context of resource availability and depletion topography tends to concentrate lava fuel and water coolant within topographic lows thereby promoting explosive lava water interactions in these regions given an excess supply of lava within broad sheet lobes rootless eruption sites withdraw groundwater from their surroundings until there is insufficient water to maintain analogs to explosive molten fuel coolant interactions rootless eruption sites may be modeled as a network of water extraction wells that draw down the water table in their vicinity rootless eruptions at locations with insufficient groundwater may either fail to initiate or terminate before explosive activity has ceased at nearby locations with a greater supply of water thus imparting a repelled distribution to observed rootless eruption sites

geophysical hydrological identification of field permeabilities through bayesian updating a new bayesian method is developed to identify the spatial distribution of permeabilities in addition to sparsely sampled permeability and pressure data this approach incorporates densely sampled seismic velocity data along with semiempirical relationships between seismic and hydraulic soil properties the procedure consists first of performing a hydrological inversion based solely on the permeability and pressure data in light of the available seismic data the velocity permeability pressure relationships are then used to update in a bayesian sense the image of the permeability field to investigate the usefulness of this approach synthetic case studies are performed these studies demonstrate that even when the seismic data are corrupted by a significant level of error a joint geophysical hydrological inversion can produce improved images of permeability moreover this paper derives rigorously the bounds on the error that can be tolerated in seismic velocities such that they are still useful for hydrological purposes

ground penetrating radar for high resolution mapping of soil and rock stratigraphy ground penetrating radar is a technique which offers a new way of viewing shallow soil and rock conditions the need to better understanding overburden conditions for activities such as geochemical sampling geotechnical investigations and placer exploration as well as the factors controlling groundwater flow has generated an increasing demand for techniques which can image the subsurface with higher resolution than previously possible the areas of application for ground penetrating radar are diverse the method has been used successfully to map ice thickness water depth in lakes bedrock depth soil stratigraphy and water table depth it is also used to delineate rock fabric detect voids and identify karst features the effective application of the radar for the high resolution definition of soil stratigraphy and fractures in bedrock is highlighted the basic principles and practices involved in acquiring high quality radar data in the field are illustrated by selected case histories one example demonstrates how radar has been used to map the bedrock and delineate soil horizons to a depth of more than 20 m two case histories show how radar has been used to map fractures and changes of rock type to 40 m range from inside a mine another case history demonstrates how radar has also been used to detect and map the extent of groundwater contamination the corroboration of the radar results by borehole investigations demonstrates the power and utility of the high resolution radar method as an aid for interpolation and extrapolation of the information obtained with conventional coring programmes with the advent of new instrumentation and field procedures the routine application of the radar method is becoming economically viable and the method will see expanded use in the future

estimating the hydraulic conductivity at the south oyster site from geophysical tomographic data using bayesian techniques based on the normal linear regression model this study explores the use of ground penetrating radar gpr tomographic velocity gpr tomographic attenuation and seismic tomographic velocity for hydraulic conductivity estimation at the south oyster site using a bayesian framework since site specific relations between hydraulic conductivity and geophysical properties are often nonlinear and subject to a large degree of uncertainty such as at this site we developed a normal linear regression model that allows exploring these relationships systematically although the log conductivity displays a small variation s 2 5 0 30 and the geophysical data vary over only a small range results indicate that the geophysical data improve the estimates of the hydraulic conductivity the improvement is the most significant where prior information is limited among the geophysical data gpr and seismic velocity are more useful than gpr attenuation

constraints on the history of open basin lakes on mars from the composition and timing of volcanic resurfacing 1 abundant evidence exists for valley network related fluvial activity near the noachian hesperian transition on mars and areally significant quantities of volcanic ridged plains were emplaced during this period as well thus it is worthwhile to explore the hypothesis that lava water interaction occurred on the surface of mars at this time we analyzed the morphology physical properties composition and surface ages of thirty open basin lakes topographic lows with both an inlet valley and an outlet valley that were also resurfaced by volcanic flows hyperspectral imaging data from the compact reconnaissance imaging spectrometer for mars crism and observatoire pour la mineralogie l eau les glaces et l activite omega instruments indicate that of the 30 basins 12 exhibit the spectral properties of basaltic lithologies with diagnostic absorptions of olivine high calcium pyroxene and low calcium pyroxene an olivine high calcium pyroxene mixture is the most commonly identified mineral assemblage consistent with other hesperian aged volcanic units therefore our mineralogical results for over a third of the open basin lake floors analyzed support prior interpretations that the basins were resurfaced by volcanic flows supporting evidence for resurfacing by volcanic flows is also given by the observed morphology and physical properties e g surface roughness thermal inertia of the resurfaced open basin lake floors in these 30 examples however no evidence was found for lava water interaction the ages of emplacement derived through counts of superposed craters of all 30 of the open basin lake volcanic resurfacing units show that resurfacing began in the late noachian near the noachian hesperian boundary was concentrated in the hesperian and continued into the early amazonian the lack of geologic features indicative of lava water interaction suggests that the basins were likely to have been mostly devoid of water at the time of the latest phase of volcanic resurfacing we conclude that there is no geologic evidence that suggests the fluvial activity associated with the studied paleolakes was coeval with the emplacement of the observed volcanic resurfacing units several of which date to the late noachian early hesperian

a comparative review of upscaling methods for solute transport in heterogeneous porous media the classical fickian model for solute transport in porous media cannot correctly predict the spreading the dispersion of contaminant plumes in a heterogeneous subsurface unless its structure is completely characterized although the required precision is outside the reach of current field characterization methods the advection dispersion model remains the most widely used model among practitioners two approaches can be adopted to solve the effect of physical heterogeneity on transport first based on a given characterization of the spatial structure of the subsurface upscaling methods allow the computation of apparent scale dependent parameters especially longitudinal dispersivity to be used in the classical fickian model in the second approach upscaled non fickian transport equations with scale independent parameters are used in this paper efforts are made to classify and review upscaling methods for fickian transport parameters and non fickian upscaled transport equations for solute transport with an emphasis on their mathematical properties and their one dimensional analytical formulations in particular their capacity to mode scale effects in apparent longitudinal dispersion is investigated upscaling methods and upscaled models are illustrated in the case of two three dimensional synthetic aquifers with lognormal hydraulic conductivity distributions characterized by variance values of 2 and 8 c 2008 etsevier b v all rights reserved

correlation of geoelectric data with aquifer parameters to delineate the groundwater potential of hard rock terrain in central uganda knowledge of aquifer parameters is essential for management of groundwater resources conventionally these parameters are estimated through pumping tests carried out on water wells this paper presents a study that was conducted in three villages tumba kabazi and ndaiga of nakasongola district central uganda to investigate the hydrogeological characteristics of the basement aquifers our objective was to correlate surface resistivity data with aquifer properties in order to reveal the groundwater potential in the district existing electrical resistivity and borehole data from 20 villages in nakasongola district were used to correlate the aquifer apparent resistivity e with its hydraulic conductivity ke and aquifer transverse resistance tr with its transmissivity te ke was found to be related to e by text log k text e 0 002 rho text e 2 692 similarly tr was found to be related to t by text tr 0 07t text e 2260 using these expressions aquifer parameters tc and kc were extrapolated from measurements obtained from surface resistivity surveys our results show very low resistivities for the presumed water bearing aquifer zones possibly because of deteriorating quality of the groundwater and their packing and grain size drilling at the preferred ves spots was conducted before the pumping tests to reveal the aquifer characteristics aquifer parameters to and ko as obtained from pumping tests gave values 29 424 7 m2 day 374 3 m day 9 801 1 m2 day 437 0 m day 31 852 4 m2 day 392 9 m day the estimated aquifer parameter tc and kc when extrapolated from surface geoelectrical data gave 7 142 9 m2 day 381 9 m day 28 200 0 m2 day 463 4 m day 19 428 6 m2 day 459 2 m day for tumba kabazi and ndaiga villages respectively interestingly the similarity between the kc and ko pairs was not significantly different we observed no significant relationships between the tc and to pairs the root mean square errors were estimated to be 18 159 m2 day and 41 4 m day

seismic velocities and poisson s ratio of shallow unconsolidated sands we determined p and s wave velocity depth profiles in shallow unconsolidated beach sand by analyzing three component surface seismic data p and s wave velocity profiles were calculated from traveltime measurements of vertical and tangential component seismograms respectively the results reveal two discrepancies between theory and data whereas both velocities were found to be proportional to the pressure raised to the power of 1 6 as predicted by the hertz mindlin contact theory the actual values of the velocities are less than half of those calculated from this theory we attribute this discrepancy to the angularity of the sand grains assuming that the average radii of curvature at the grain contacts are smaller than the average radii of the grains we modify the hertz mindlin theory accordingly we found that the ratio of the contact radius to the grain radius is about 0 086 the second disparity is between the observed poisson s ratio of 0 15 and the theoretical value 0 008 for random pack of quartz spheres this discrepancy can be reconciled by assuming slip at the grain contacts because slip decreases the shearing between grains poisson s ratio increases

electrical resistivity hydraulic conductivity relationships in glacial outwash aquifers empirical field relationships between the apparent formation factors from surface resistivity soundings and hydraulic conductivity from pumping tests in fresh water granular aquifers usually show positive correlations these relationships can be adequately explained by theory if consideration is taken of in situ field conditions a sound theoretical basis for relating apparent formation factor to pertinent hydrogeophysical parameters in homogeneous isotropic sand is a three phase parallel resistor model which explicity includes parameters of porewater resistivity grain size and shape porosity tortuosity and intergranular surface conductance the veracity of the theoretical model is supported by data from laboratory tests the model demonstrates that intergranular surface conductance is an important factor at small grain sizes and high porewater resistivities operating to lower the apparent formation factor the model further shows that direct relationships between hydraulic conductivity and formation factor are weak in the normal range of porewater resistivity being strongly dependent on porosity when systematic variation of in situ porosity and aquifer layering effects are considered a simulated field curve relating the apparent formation factor to hydraulic conductivity is shown to compare favorably with the comparable curve from field data for thirteen pumping test sites in southern rhode island both theoretical and empirical results demonstrate a useful positive correlation between aquifer apparent formation factor and hydraulic conductivity quantitative interpretation however is imprecise because of nonuniqueness of interpretation and inherent variation in important aquifer parameters especially porosity

rootless cones on mars a consequence of lava ground ice interaction fields of small cratered cones on mars are interpreted to have formed by rootless eruptions due to explosive interaction of lava with ground ice contained within the regolith beneath the flow melting and vaporization of the ice and subsequent explosive expansion of the vapour act to excavate the lava and construct a rootless cone around the explosion site similar features are found in iceland where flowing lava encountered water saturated substrates the martian cones have basal diameters of c 30 1000 m and are located predominantly in the northern volcanic plains high resolution mars orbiter camera images offer significant improvements over viking data for interpretation of cone origins a new model of the dynamics of cone formation indicates that very modest amounts of water ice are required to initiate and sustain the explosive interactions that produced the observed features this is consistent with the likely low availability of water ice in the martian regolith the scarcity of impact craters on many of the host lava flows indicates very young ages suggesting that ground ice was present as recently as less than 10 l00 ma and may persist today rootless cones therefore act as a spatial and temporal probe of the distribution of ground ice on mars which is of key significance in understanding the evolution of the martian climate the location of water in liquid or solid form is of great importance to future robotic and human exploration strategies and to the search for extraterrestrial life

hydraulic properties of a model dike from coupled bayesian and multi criteria hydrogeophysical inversion coupled hydrogeophysical inversion aims to improve the use of geophysical data for hydrological model parameterization several numerical studies have illustrated the feasibility and advantages of a coupled approach however there is still a lack of studies that apply the coupled inversion approach to actual field data in this paper we test the feasibility of coupled hydrogeophysical inversion for determining the hydraulic properties of a model dike using measurements of electrical resistance tomography ert our analysis uses a two dimensional 2d finite element hydrological model hydrus 2d coupled to a 2 5d finite element electrical resistivity code crmod and includes explicit recognition of parameter uncertainty by using a bayesian and multiple criteria framework with the dream and amalgam population based search algorithms to benchmark our inversion results soil hydraulic properties determined from ert data are compared with those separately obtained from detailed in situ soil water content measurements using time domain reflectometry tdr our most important results are as follows 1 tdr and ert data theoretically contain sufficient information to resolve most of the soil hydraulic properties 2 the dream derived posterior distributions of the hydraulic parameters are quite similar when estimated separately using tdr and ert measurements for model calibration 3 among all parameters the saturated hydraulic conductivity of the dike material is best constrained 4 the saturation exponent of the petrophysical model is well defined and matches independently measured values 5 measured ert data sufficiently constrain model predictions of water table dynamics within the model dike this finding demonstrates an innate ability of ert data to provide accurate hydrogeophysical parameterizations for flooding events which is of particular relevance to dike management and 6 the amalgam derived pareto front demonstrates trade off in the fitting of ert and tdr measurements altogether we conclude that coupled hydrogeophysical inversion using a bayesian approach is especially powerful for hydrological model calibration the posterior probability density functions of the model parameters and model output predictions contain important information to determine if geophysical measurements provide constraints on hydrological predictions

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

spatial correlation structure estimation using geophysical and hydrogeological data the large spatial variability of hydraulic properties in natural geologic systems over a wide range of scales and the difficulty of collecting representative and sufficient hydraulic property measurements using conventional sampling techniques render estimation of spatial correlation parameters difficult further compounding the estimation problem is the observation that the integral scale estimate is a function of the measurement support scale to mitigate these problems we investigate the use of tomographic geophysical data in combination with hydrogeological data in the spatial correlation estimation procedure two synthetic case studies were investigated where the scale of the geophysical measurements were varied relative to the scale of the hydrogeological properties the spatial correlation structure parameter estimation procedure was performed in the spectral domain where analysis of data having different support scales and spatial sampling windows was facilitated comparison of the spatial correlation structure parameters estimated from measured data with those of the synthetic aquifers revealed which type of data tomographic hydrogeological or a combination of both was most effective for recovering spatial correlation statistics under different sampling heterogeneity conditions these synthetic case studies suggest that collection of a few tomographic profiles and interpretation of these profiles together with limited well bore data can yield correlation structure information that is otherwise obtainable only from extensive hydrological sampling

volcanic processes as alternative mechanisms of landform development at a candidate crater lake site near tyrrhena patera mars 1 palos crater a prominent candidate crater lake site in the hesperia region of mars is located at the mouth of a sinuous inlet channel that extends from the northern flanks of tyrrhena patera previous studies of this site have concluded that channels and basin infill units likely formed through aqueous processes that partly involved karst like removal of materials in the subsurface by the flow of groundwater as with many locales on mars the aqueous processes hypothesized to have been involved in the formation and evolution of terrain features are compelling however the characteristics of this site suggest that an alternative set of mechanisms for landform development should be considered alongside aqueous hypotheses the main attributes of channels and infill of the central crater include 1 an association with a very large volcanic rise to the south 2 the existence of roofed segments of the main inlet channel and 3 infill of the central crater and outlet channel by materials that have characteristics consistent with those expected of volcanic plains these general attributes are consistent with formation through or in association with processes that involved the flow of lava although a volcanic model may account for the presence and basic nature of landforms previously considered supportive of a paleolake interpretation of the site an overprint of dendritic valley networks on parts of the inlet system suggests that aqueous processes may have also acted in the evolution of the site a complex interrelation between past igneous and aqueous processes at this site is possible

regional scale integration of multiresolution hydrological and geophysical data using a two step bayesian sequential simulation approach significant progress has been made with regard to the quantitative integration of geophysical and hydrological data at the local scale for the purpose of improving predictions of groundwater flow and solute transport however extending corresponding approaches to the regional scale still represents one of the major challenges in the domain of hydrogeophysics to address this problem we have developed a regional scale data integration methodology based on a two step bayesian sequential simulation approach our objective is to generate high resolution stochastic realizations of the regional scale hydraulic conductivity field in the common case where there exist spatially exhaustive but poorly resolved measurements of a related geophysical parameter as well as highly resolved but spatially sparse collocated measurements of this geophysical parameter and the hydraulic conductivity to integrate this multi scale multi parameter database we first link the low and high resolution geophysical data via a stochastic downscaling procedure this is followed by relating the downscaled geophysical data to the high resolution hydraulic conductivity distribution after outlining the general methodology of the approach we demonstrate its application to a realistic synthetic example where we consider as data high resolution measurements of the hydraulic and electrical conductivities at a small number of borehole locations as well as spatially exhaustive low resolution estimates of the electrical conductivity obtained from surface based electrical resistivity tomography the different stochastic realizations of the hydraulic conductivity field obtained using our procedure are validated by comparing their solute transport behaviour with that of the underlying true hydraulic conductivity field we find that even in the presence of strong subsurface heterogeneity our proposed procedure allows for the generation of faithful representations of the regional scale hydraulic conductivity structure and reliable predictions of solute transport over long regional scale distances

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

estimation of the water table throughout a catchment using self potential and piezometric data in a bayesian framework information about spatial variations of the water table that occur throughout catchments is useful to infer large scale flow patterns but conventional mapping using piezometric data is invasive slow and expensive water flow in the subsurface generates an electrical current called the streaming current the resulting self potential sp electrostatic signals can be measured non intrusively quickly and inexpensively at the ground surface we considered two conceptual models to relate sp signals to the water table the infiltration model relates sp signals to the thickness of the vadose zone while the water table model relates sp signals to the distribution of the water table in unconfined aquifers these models are first calibrated against field data before a bayesian method is applied to update a kriged map of the water table obtained from piezometric observations using a kriged sp map the estimated water tables based on the two conceptual models were combined into one final model using concepts from bayesian model averaging the method was applied to a small agricultural catchment not vert similar1 km2 in southern france the posterior water table estimates were improved mainly on the slopes surrounding the basin understanding the variations in the water table on these slopes is important because infiltration in these areas feed the basin with groundwater flow the bayesian framework is useful to avoid overconfident predictions when using sp data in hydrogeological estimation because it provides realistic uncertainty estimates