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

the cowichan fold and thrust system vancouver island southwestern british columbia the cowichan fold and thrust system is a southwest verging linked thrust system formed by northeast southwest large scale crustal contraction involving the upper cretaceous nanaimo group and its wrangellian basement the geometry of the thrust system from plan and profile perspectives illustrates its thick skinned structural style the thrust system is interpreted to be a leading imbricate fan thrusting was most likely in sequence creating an estimated minimum 20 30 shortening at the basement cover interface both fault propagation and fault bend folding are evident the former being more common kinematic indicators and the geometry of the thrust system show no evidence of significant transpressional or transtensional displacement fields contraction postdates deposition of the nanaimo group and is indirectly dated as late eocene the sole fault of the thrust system is interpreted to rise from northwest to southeast on a series of deep lateral to oblique ramps and merge with the san juan fault system this explains the rapidly westward thickening wedge of thrusted wrangellian basement in the study area in the east the sole fault is interpreted to have locally permitted the nanaimo group to overthrust the san juan terrane investigation of the cowichan fold and thrust system reveals how shortening during westward progressing terrane accretion is accommodated in a forearc region dominated by a large slab of rigid semicontinental crust

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

the resolving power of cross borehole tomography the data collected in a cross borehole tomography problem is inherently incomplete since the boreholes do not completely surround the media under study the ability of the experiment to resolve structure is therefore limited by poor experimental geometry we use the method of backus and gilbert to investigate the ability of this technique to resolve variations in acoustic velocity and attenuation between the two boreholes both integrals that appear in the backus gilbert formulation can be performed analytically thus expediting the calculations the resolving kernels have significant horizontal width demonstrating that the horizontal position of structures can be only poorly resolved

the role of compressive stresses in jointing on vancouver island british columbia this study demonstrates that joint parallel compressive stresses were integral to the development of joint sets on vancouver island british columbia the mapped study area contains paleostress indicators in the form of calcareous concretions which have multiple internal fractures in precisely the same orientation as one of the surrounding joint sets in the sandstone matrix field and laboratory tests indicate that the stiffest concretions are the most likely to be fractured however results from numerical simulations using measured rock properties preclude an origin for the concretion fractures from either a far field uniaxial tensile or compressive stress fracturing is only found to be possible if the concretions possessed a lower poisson s ratio than the sandstone at the time of fracturing in the latter case a far field uniaxial compressive stress may have generated tensile effective stresses in the vicinity of high modulus concretions seeding the field site with an initial population of concretion fractures and joints given the close spacing of some joints their extension cannot be satisfactorily explained without invoking grain scale compression driven tensile fracturing mechanisms

the vertical profile of radar reflectivity of convective cells a strong indicator of storm intensity and lightning probability abstract reflectivity data from doppler radars are used to construct vertical profiles of radar reflectivity vprr of convective cells in mesoscale convective systems mcss in three different environmental regimes the national center for atmospheric research cp 3 and cp 4 radars are used to calculate median vprr for mcss in the oklahoma kansas preliminary regional experiment for storm central in 1985 the national oceanic and atmospheric administration tropical ocean global atmosphere radar in darwin australia is used to calculate vprr for mcss observed both in oceanic monsoon regimes and in continental break period regimes during the wet seasons of 1987 88 and 1988 89 the midlatitude and tropical continental vprrs both exhibit maximum reflectivity somewhat above the surface and have a gradual decrease in reflectivity with height above the freezing level in sharp contrast the tropical oceanic profile has a maximum reflectivity at the lowest level and a very rapid decrease in reflectivity with he

seismic tomography in boreholes summary synthetic seismic tomographic data sets for cross hole and hole to surface arrays are computed and inverted inversion imaging is performed through an iterative projection solution to a matrix equation the orientation as well as the position of an anomaly relative to the source and recorder arrays affects both the rate of convergence of the solution and the resolution obtained data density and distribution determine the physical validity of the image obtained at convergence borehole tomography is apparently a viable method for imaging inter hole structure

anisotropic velocity tomography a case study in a near surface rock mass cross borehole data were acquired in the surface crown pillar of a massive sulfide ore mine the data consist of five two dimensional 2 d cross borehole panels each with approximately 900 source receiver pairs the panels were located within the crown pillar at either side of and within a major subvertical fault zone that intersects the orebody an initial analysis of the data indicates that the bedrock containing the orebody is seismically anisotropic a rigorous analysis of the traveltimes using anisotropic velocity tomography confirms the initial assessment that anisotropy exists within the crown pillar rock mass anisotropic velocity tomography is the generalization of tomographic methods to anisotropic media as in any geophysical problem the data are insufficient to completely resolve the distributions of the rock properties at all scale lengths we use external constraints on the roughness of the final solution to ensure an algebraically well posed problem plots of the data residuals the t

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

thunderstorms above frontal surfaces in environments without positive cape part i a climatology abstract the first of two papers describing thunderstorms that occur above frontal surfaces frequently in environments without positive convective available potential energy cape focuses on the climatology of such storms for the conterminous united states the dataset used consists of 1093 observations made over a 4 year period the events were selected using conventional network data and a set of criteria that eliminated thunderstorms rooted in the boundary layer a composite of the dataset shows that the typical elevated thunderstorm occurs northeast of an associated surface low pressure center and north of a surface warm front in a region with northeasterly surface winds the planetary boundary layer is generally very stable as determined by comparisons with both the 50 kpa and 85 kpa air the thunderstorms are usually found in the left exit region of a low level wind maximum an area of horizontal deformation the large scale environment is strongly baroclinic with large vertical wind shear an

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

probabilistic models for estimating lithology abstract the estimation of lithology within a volume of rock from surface mapping and borehole logging has been achieved using probabilistic models the application of two geostatistical techniques indicator kriging and conditional simulation allows the incorporation of observed lithologies taking cognisance of their statistical and spatial distributions the newly developed probabilistic bayes markov method additionally allows for the sequences of lithologies to be modelled by the calculation of transition probabilities and markov chains verification of the estimates produced by these three methods has been enabled using the rocks actually exposed during the driving of an access tunnel into the aspo hard rock laboratory in south east sweden

determination of lithology from well logs using a neural network we have developed a computer program to automatically determine lithologies from well logs using a back propagation neural network unlike a conventional serial computer a neural network is a computational system composed of nodes sometimes called neurons neurodes or units and the connections between these nodes neural computing attempts to emulate the functions of the mammalian brain thus mimicking thought processes the neural network approach differs from previous pattern recognition methods in its ability to learn from examples unlike conventional statistical methods this new approach does not require sophisticated mathematics and a large amount of statistical data this paper discusses the application of neural networks to a pattern recognition problem in eology the determination of lithology from well logs the neural network determined the lithologies limestone dolomite sandstone shale sandy and dolomitic limestones sandy dolomite and shale sandstone from selected well logs in a fraction of the time required by an experienced human log analyst

microphysical properties of convectively generated fall streaks within the stratiform comma head region of continental winter cyclones abstractthis paper presents analyses of the microphysical structure of comma head stratiform precipitation in 14 continental cyclones focusing on fall streaks of hydrometeors produced by cloud top convective generating cells data were obtained at temperatures between 4 and 45 c using in situ instrumentation and the w band university of wyoming cloud radar all operated aboard the national science foundation national center for atmospheric research c 130 analyses are presented first for a case study of one cyclone followed by statistical analyses of the full dataset using radar based objective classifications the statistical percentile number concentrations averaged 1 9 times larger within the fall streaks compared to the regions between them and the corresponding ice water content and median mass diameter values averaged 2 2 and 1 1 times larger ice phase conditions were predominant within the stratiform precipitation with deposition and aggregation the primary ice growth mechanisms no distinc

instability characteristics of radar derived mesoscale organization modes within cool season precipitation near portland oregon abstractthe instability characteristics associated with different radar derived mesoscale organization modes are examined using six cool seasons of operational scanning radar data near portland oregon and operational sounding data from salem oregon additionally several years of microwave rain radar ka band vertically pointing radar data from portland and merwin washington are used to characterize the nature and occurrence of generating cells and fall streaks the combination of a new metric convective stratiform intermittency with the classification of radar reflectivity maps into convective and stratiform precipitation types was applied to periods when the freezing level was 1 4 km altitude this method distinguishes periods with embedded convective within stratiform mesoscale organization from those that were mostly convective or mostly stratiform mesoscale organization occurs in a continuum of states with predominantly stratiform structure occurring most frequently generating cells in the s

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

the north american lightning detection network naldn analysis of flash data 2001 09 abstractcloud to ground cg lightning data have been analyzed for the years 2001 09 for north america which includes alaska canada and the lower 48 u s states flashes recorded within the north american lightning detection network naldn are examined no corrections for detection efficiency variability are made over the 9 yr of the dataset or over the large geographical area comprising north america there were network changes in the naldn during the 9 yr but these changes have not been corrected for nor have the recorded data been altered in any way with the exception that all positive lightning reports with peak currents less than 15 ka have been deleted thus the reader should be aware that secular changes are not just climatological in nature all data were analyzed with a spatial resolution of 20 km the analyses presented in this work provide a synoptic view of the interannual variability of lightning observations in north america including the impacts of physical changes in the network dur

elevated potential instability in the comma head distribution and development abstractthe development of elevated potential instability within the comma head of a continental winter cyclone over the north central united states is examined using a 63 h weather research and forecasting wrf model simulation the simulation is first compared to the observed cyclone the distribution of most unstable convective available potential energy mucape within the comma head is then analyzed the region with positive mucape was based from 2 to 4 km altitude with mucape values up to 93 j kg 1 backward trajectories from five sublayers within the region of elevated convection in the comma head were calculated to investigate how elevated potential instability developed air in the lowest sublayer the source air for convective cells originated 63 h earlier near baja california at elevations between 2 25 and 2 75 km altitude air atop the layer where convection occurred originated at altitudes between 9 25 and 9 75 km in the arctic 5000 km away from the origin of air in the lowest sublayer

high resolution aquifer characterization using seismic cross hole tomography an evaluation experiment in a gravel delta we performed field experiments at a well studied aquifer test site to evaluate the geophysical method of seismic cross hole tomography for high resolution aquifer characterization we address the challenge of finding meaningful relationships between seismic velocity and hydraulic conductivity at the field scale for hydraulic conductivity estimation the resolution of seismic cross hole data is limited by inversion ambiguities and diffraction effects which are not accounted for using conventional ray based inversion algorithms for velocity reconstruction we investigate the impact of diffraction effects on seismic velocity inversion and implications for hydraulic modelling our ray based seismic tomograms correlate well with sedimentary cores and hydraulic conductivity logs allowing us to interpret a zone model with distinct geophysical hydraulic zones we use this zone model to constrain seismic inversions using two approaches for forward modelling ray tracing infinite frequency approximation and wavefield modelling at a realistic frequency which accounts for diffraction we show that using the common ray tracing approach seismic velocities in low velocity zones may be significantly overestimated based on the available data we observe a negative linear relationship between logarithmic hydraulic conductivity and seismic velocity this relationship is used to parameterize hydraulic models based on seismic velocity models computer simulations of advective contaminant transport demonstrate that their results are extremely sensitive to an accurate determination of seismic low velocity zones we conclude that seismic tomography is indeed very useful for high resolution aquifer characterization however an inversion approach that accounts for diffraction effects a priori knowledge of the subsurface structure and additional well data should be applied for quantitative interpretations

the role of moist processes in the formation and evolution of mesoscale snowbands within the comma head of northeast u s cyclones abstract the role of moist processes in regulating mesoscale snowband life cycle within the comma head portion of three northeast u s cyclones is investigated using piecewise potential vorticity pv inversion modeling experiments and potential temperature tendency budgets snowband formation in each case occurred along a mesoscale trough that extended poleward of a 700 hpa low this 700 hpa trough was associated with intense frontogenetical forcing for ascent a variety of pv evolutions among the cases contributed to midlevel trough formation and associated frontogenesis however in each case the induced flow from diabatic pv anomalies accounted for a majority of the midlevel frontogenesis during the band s life cycle highlighting the important role that latent heat release plays in band evolution simulations with varying degrees of latent heating show that diabatic processes associated with the band itself were critical to the development and maintenance of the band however changes in the meso

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

spatial variability in river sediments and its link with river channel geometry 1 this study explores the link between spatial variability within fluvial sedimentary strata and river channel geometry this link is then used to determine the macrodispersion coefficients for solute transport in groundwater flow in river deposits in doing that we combine concepts from sedimentology geostatistics and the stochastic lagrangian theory of subsurface transport it is proposed to analyze the spatial variability of river sediments in terms of transition probabilities the transition probabilities can be determined from the averages and variances of the lengths of stratasets and their volumetric fractions using concepts developed by carle and fogg 1996 and ritzi 2000 strataset length scales are shown to correlate well with the geometry of the river channel and its bed forms and can be determined indirectly from aerial photogrammetry and more directly through surface ground penetrating radar surveys stratal dimensions can also be related using lagrangian transport analysis to macrodispersivity of subsurface transport this allows relationships between the geometry of river channels and subsurface transport parameters of associated fluvial deposits for demonstration the longitudinal macrodispersivity in a compound bar deposit in the gravelly braided sagavanirktok river was investigated

the role of the interbed thickness on the step over fracture under overburden pressure multilayer jointing in tight oil and gas reservoirs is a useful indicator for the prediction of fluid mobility since pore pressure balances the principal minor horizontal stress at depth joint nucleations considered as sub vertical are mainly driven by the overburden pressure we demonstrate with a mixed criterion combining necessary conditions of stress and energy how heterogeneity such as an interbed promotes initiation of a fracture by a step over mechanism referring to critical characteristics such as the interbed thickness a specific initiation criterion emerges giving rise to a size effect due to the interbed thickness and is compared to a typical homogeneous rock failure criterion jointing over an interbed is enhanced by large interbed thicknesses even for moderate effective confining stresses size effect is reversed according to the relative importance of singular effects effective minor stress normal to the fracture plane and structural effect parallel loading effective conditions

vertical velocity and physical structure of generating cells and convection in the comma head region of continental winter cyclones abstractthe vertical motion and physical structure of elevated convection and generating cells within the comma heads of three continental winter cyclones are investigated using the wyoming w band cloud radar mounted on the national science foundation national center for atmospheric research nsf ncar c 130 supplemented by analyses from the rapid update cycle model and weather surveillance radar 1988 doppler wsr 88d data the cyclones followed three distinct archetypical tracks and were typical of those producing winter weather in the midwestern united states in two of the cyclones dry air in the middle and upper troposphere behind the pacific cold front intruded over moist gulf of mexico air at lower altitudes within the comma head separating the comma head into two zones elevated convection in the southern zone extended from the cold frontal surface to the tropopause the stronger convective updrafts ranged from 2 to 7 m s 1 and downdrafts ranged from 2 to 6 m s 1 the horizontal scale of the

dynamics of cloud top generating cells in winter cyclones part iii shear and convective organization abstractcloud top generating cells gcs are a common feature atop stratiform clouds within the comma head of winter cyclones the dynamics of cloud top gcs are investigated using very high resolution idealized wrf model simulations to examine the role of shear in modulating the structure and intensity of gcs simulations were run for the same combinations of radiative forcing and instability as in part ii of this series but with six different shear profiles ranging from 0 to 10 m s 1 km 1 within the layer encompassing the gcs the primary role of shear was to modulate the organization of gcs which organized as closed convective cells in simulations with radiative forcing and no shear in simulations with shear and radiative forcing gcs organized in linear streets parallel to the wind no gcs developed in the initially stable simulations with no radiative forcing in the initially unstable and neutral simulations with no radiative forcing or shear gcs were exceptionally weak with no clear organization

high resolution observations of the trowal warm frontal region of two continental winter cyclones abstract this paper compares the structure of the trough of warm air aloft trowal warm frontal region of two continental wintertime cyclones the cyclones were observed over the central great lakes region during the lake induced convection experiment snowband dynamics project field campaign the cyclones had different origins with the first forming east of the colorado rockies and the second forming over the gulf of mexico they were associated with different upper level flow regimes one located just north of a nearly zonal jet and the other located just west of a nearly meridional jet both storms produced heavy swaths of snow across the states of illinois wisconsin and michigan high resolution observations of frontal structure were made during flights of the national center for atmospheric research electra aircraft using dropsondes and the electra doppler radar tail radar system the high resolution observations suggest a different arrangement of air masses in the trowal region compared with the

lithologic tomography an application to geophysical data from the cadomian belt of northern brittany france abstract a probabilistic description of subsurface lithologic structures can be established by inverting multidisciplinary geophysical data constrained by geological and geostatistical priors the methodology is based on the joint modelling of several media properties and on a statistical description of the relationships between them the information provided by the geophysical data and the geological and geostatistical priors is represented by probability density functions pdf that are combined into a posterior pdf composed by 1 a prior pdf in the space of the primary lithologic model parameters 2 a pdf of the secondary physical model parameters conditional to the primary model parameters and 3 a joint likelihood function that is the product of the independent likelihood functions for each observed geophysical field applying a markov chain sampling method enables a large sample of joint models to be generated from the posterior pdf the true configuration of the media is then determined from the representation of models pulled from the chain and the elaboration of statistics from the large sample of posterior joint models the method was used to invert gravity and magnetic data jointly characterising the mass density field the magnetic susceptibility field and the lithotype field along two 2 d sections of the geological units in the cadomian belt of northern brittany besides generating 10 6 joint models consistent with the observations and priors some features of the joint models and the statistical tomographic images provided additional insights to the geologic configuration of the area for example the main cadomian thrust shows an irregular geometry that could have resulted from the belt emplacement and or from variscan tectonism and the hercynian granitic intrusion shows a deep subsurface continuation the cosimulation of magnetic susceptibility and mass density inside each lithologic region was performed according to a multivariate gaussian model or a mixed multivariate gaussian functions model that was developed specially to describe multimodal distributed properties

acoustic velocities in heated block of granite subjected to uniaxial stress acoustic velocities have been measured within a 38 cm cubic block of granite isolated from the surrounding rock the block was subjected to uniaxial stresses in the range 0 24 mpa and to heating in the range 14 sup 0 to 98 sup 0 c an increase in temperature from 14 sup 0 to 72 sup 0 c in the unstressed block resulted in an increase in velocities in directions parallel and perpendicular to the applied stress a further increase in temperature to 98 sup 0 c in the unstressed block resulted in a decrease in velocities application of uniaxial stress with the block at a temperature of 98 sup 0 c resulted first in uniform increases in velocity to an applied stress of mpa and then sharp decreases from 10 to 14 mpa followed by uniform increases in velocity to a maximum stress of 24 mpa a reduction in temperature to 16 sup 0 c resulted in a sharp reduction in velocity 25 percent less than originally measured at ambient temperature it is concluded that at temperatures rising to 72 sup 0 c anisotropic thermal expansion of the crystals comprising the granite causes the closure of microcracks present in the unheated rock between 72 sup 0 and 98 supmore 0 c particularly when stress was applied irreversible mechanical changes occurred in the block less

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

the mesoscale and microscale structure and organization of clouds and precipitation in midlatitude cyclones part xv a numerical modeling study of frontogenesis and cold frontal rainbands abstract a two dimensional hydrostatic primitive equation model is used to investigate the dynamics of frontogenesis in a moist atmosphere the development of a cold front is simulated through shear deformation associated with the non linear evolution of an eady wave simulations are performed with 5 10 40 and 80 km horizontal resolutions and 14 levels in the vertical four in the boundary layer compared to the dry case the inclusion of moisture in the model produces a stronger low level jet ahead of the front and a stronger upper level jet moisture also produces a stronger ageostrophic circulation across the front and a more concentrated updraft just ahead of the surface front the updraft develops a banded structure above and behind the surface front with a wavelength of about 70 km bands form near the back edge of the cloud shield and move toward the surface front with a relative velocity of 1 m s 1 these characteristics agree with observations of wide cold frontal rainbands the banded str

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

evolution of mesoscale precipitation band environments within the comma head of northeast u s cyclones abstract this paper explores the mesoscale forcing and stability evolution of intense precipitation bands in the comma head sector of extratropical cyclones using the 32 km north american regional reanalysis hourly 20 km rapid update cycle analyses and 2 km composite radar reflectivity data a statistical and composite analysis of 36 banded events occurring during the 2002 08 cool seasons reveals a common cyclone evolution and associated band life cycle a majority 61 of banded events develop along the northern portion of a hook shaped upper level potential vorticity pv anomaly during the 6 h leading up to band formation lower tropospheric frontogenesis nearly doubles and the conditional stability above the frontal zone is reduced the frontogenesis increase is primarily due to changes in the kinematic flow associated with the development of a mesoscale geopotential height trough this trough extends poleward of the 700 hpa low and is the vertical extension of the surface warm front and surface

crosshole seismology and seismic imaging in crystalline rocks a borehole to borehole audiofrequency seismic system using piezoelectric transducers as active elements has been developed and used to investigate crystalline rocks in canada high quality seismograms have been recorded for transmitter receiver distances of up to 230 meters it has been found that both travel times and signal amplitudes provide diagnostic information about rock quality two dimensional images of seismic velocity and transparency distributions between two boreholes derived from observed arrival times and amplitudes by simple back projection tomography reflect lithology and geological structure the results indicate the potential usefulness of crosshole seismic imaging as a tool for rock mass characterization

examining bacterial transport in intact cores from oyster virginia effect of sedimentary facies type on bacterial breakthrough and retention the effects of the physical7 chemical properties of sediment on the transport of bacteria were examined an adhesion deficient groundwater isolate was injected into intact cores of three different sedimentary facies total effluent recovery of bacteria varied with facies type and appeared to be most influenced by mean grain size and total metal hydroxide content bacterial concentrations within the core were highest near the point of injection but cell distribution exhibited considerable lateral and longitudinal variation calculations of the collision efficiency indicated that the bacterial inoculum injected into the cores was composed of a range of subpopulations of cells each possessing different values although predictions based on previously published research were generally correct this research highlights the need for further studies of bacterial transport under environmentally relevant conditions and the necessity of examining how the physiological heterogeneity of the injected organisms affects their transport in subsurface sediments

stability and charging characteristics of the comma head region of continental winter cyclones abstractthis paper presents analyses of the finescale structure of convection in the comma head of two continental winter cyclones and a 16 storm climatology analyzing the distribution of lightning within the comma head a case study of a deep cyclone is presented illustrating how upper tropospheric dry air associated with the dry slot can intrude over moist gulf air creating two zones of precipitation within the comma head a northern zone characterized by deep stratiform clouds topped by generating cells and a southern zone marked by elevated convection lightning when it occurred originated from the elevated convection a second case study of a cutoff low is presented to examine the relationship between lightning flashes and wintertime convection updrafts within convective cells in both storms approached 6 8 m s 1 and convective available potential energy in the cell environment reached approximately 50 250 j kg 1 radar measurements obtained in convective updraft regions showed enhanced spectral

the origin of tensile fracture lineaments abstract fracture controlled lineaments commonly seen where brittle basement is exposed at the earth s surface are generally restricted to a small number of sets with angles of 45 90 between sets the length frequency distribution of lineaments in each set follows a truncated poisson function such lineaments usually show almost no shearing offset suggesting a tensile origin a simple mechanical model of tensile fracturing is used to explain the spacing directions and length of lineaments as well as their depth frequency distribution results suggest that the penetration depth of tensile fractures which produce lineaments at the earth s surface is directly related to their length and that the fracture density is inversely proportional to fracture depth finally the angles between lineament sets may be controlled by the ratio of strength of unfractured rock to that of pre existing fractures which might heal with time the most likely source of tension is tectonic uplift fractures due to typical uplifts of 0 5 1 km over distances of 10 100 km may penetrate as brittle fractures to several kilometres into the crust perhaps to the depth at which seismic activity ceases

changes in the sorption capacity of coastal plain sediments due to redox alteration of mineral surfaces chemical characteristics of grain coatings in a coastal plain sandy aquifer on the eastern shore of virginia were investigated where sediments have been exposed to distinct groundwater redox conditions dissolved o2 was 5 0 to 10 6 mg l 1 in the regionally extensive aerobic groundwater whereas in a narrow leachate plume it was only 0 001 to 0 9 mg l 1 the amount of dissolved fe in the aerobic groundwater was only 0 005 to 0 01 mg l 1 but it was 12 to 47 mg l 1 in the anaerobic zone the amount of extractable fe was an order of magnitude higher for the aerobic sediments than for the anaerobic sediments indicating that reductive dissolution removed the oxide coatings the capacity for anion sorption on the sediment surfaces as indicated by the sorption of 35so42 was an order of magnitude higher in the aerobic vs anaerobic sediments the presence of anaerobic groundwater did not significantly alter the amount of extractable al oxides on the surface of the sediments and those coatings helped to maintain a high surface area the removal of the fe oxides from the grain surfaces under anaerobic conditions was solely responsible for the significant reduction of so4 sorption observed this loss of capacity for anion sorption could lead to more extensive transport of negatively charged constituents such as some contaminant chemicals or bacteria that may be of concern in groundwater

a study of lightning flashes attending periods of banded snowfall 1 lightning flashes n 1088 associated with 24 thundersnow events in the central united states were analyzed to document flash polarity signal strength and multiplicity negative lightning flashes n 872 80 dominated positive flashes n 216 20 with wintry precipitation in this study which stands in contrast to the majority of the research done on winter thunderstorms primarily in japan otherwise limited work has been done although thundersnow has been documented in the mid latitudes of north america europe and asia statistics on peak amplitude were determined for negative positive flashes yielding mean and standard deviation values of 24 ka 22 ka 38 ka 34 ka a subset of winter lightning events n 16 were then sought that occurred with banded single or multiple snowfall as banding often denotes greater organization in the atmosphere e g a jet streak aloft to aid in ascent or a low level jet streak to aid with moisture and thermal transport and thus the potential for deeper snow totals radar reflectivity values were recorded at the location of each lightning flash as well as the maximum radar reflectivity within the associated snow band the location of the lightning activity within the snow band was also noted as being either leading edge le trailing edge te core c or not correlated nc with respect to the motion of the parent band the majority of lightning flashes were found downstream of areas of highest radar reflectivity with respect to the motion of the snow bands and not with the highest reflectivity values if one uses the highest reflectivity values in a snowband as a proxy for the greatest surface snowfall intensity then the ground terminus of a cloud to ground lightning cg flash is often not co located with the heaviest snowfall rates however the work completed here does place the location of the typical cg flash 15 km downstream of the snowband location so one could use the occurrence of lightning as a nowcasting tool for impending snow intensification at the site of the cg flash

the role of pressure solution seam and joint assemblages in the formation of strike slip and thrust faults in a compressive tectonic setting the variscan of south western ireland abstract the ross sandstone in county clare ireland was deformed by an approximately north south compression during the end carboniferous variscan orogeny the initial assemblage consists of mutually abutting orthogonal arrays of 170 oriented set 1 joints veins jvs and approximately 75 oriented set 1 pressure solution seams psss formed under the same stress conditions orientations of splay jvs and psss set 2 suggest a clockwise remote stress rotation of about 35 responsible for the contemporaneous shearing of the set 1 arrays among these nearly orthogonal strike slip faults the prominent set is sub parallel to set 1 jvs these faults are formed by the linkage of en echelon segments with broad damage zones responsible for right lateral offsets of hundreds of meters thrust faults with up to 30 m of offset initiate within shale horizons and follow either the psss in the sandstones or high angle shales within tilted sequences within the large thrust fault zones compartmentalised blocks of rocks are bounded by thrust faults segments with various dip angles strike slip and thrust faults are contemporaneous and owe their existence to initial weaknesses in the form of jvs and psss rather than by switching relative stress magnitudes and orientations associated with andersonian models of faults and related stress orientations

the role of cloud top generating cells and boundary layer circulations in the finescale radar structure of a winter cyclone over the great lakes abstractdata from airborne w band radar are used in conjunction with thermodynamic fields from the weather research and forecasting model and air parcel back trajectories from the hysplit model to investigate the finescale reflectivity vertical motion and airmass structure of the comma head of a winter cyclone in the vicinity of the great lakes cloud top generating cells formed along an upper level frontal boundary vertically separating dry air which 48 h earlier was located in the upper troposphere over south central canada from moist air which was located in the lower troposphere over the southeast united states the stronger updrafts within the generating cells had vertical velocities ranging from 1 to 3 m s 1 the generating cells were important to precipitation production within the comma head precipitation trails formed within the generating cells could sometimes be followed to the boundary layer before merging boundary layer air beneath the cyclone s comma head exhibited convective circulati

aquifer structure identification using stochastic inversion this study presents a stochastic inverse method for aquifer structure identification using sparse geophysical and hydraulic response data the method is based on updating structure parameters from a transition probability model to iteratively modify the aquifer structure and parameter zonation the method is extended to the adaptive parameterization of facies hydraulic parameters by including these parameters as optimization variables the stochastic nature of the statistical structure parameters leads to nonconvex objective functions a multi method genetically adaptive evolutionary approach amalgam so was selected to perform the inversion given its search capabilities results are obtained as a probabilistic assessment of facies distribution based on indicator cokriging simulation of the optimized structural parameters the method is illustrated by estimating the structure and facies hydraulic parameters of a synthetic example with a transient hydraulic response

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

numerical simulation of fracture set formation a fracture mechanics model consistent with experimental observations a physically based model for the evolution of a single set of planar parallel fractures subject to a constant remote stress is presented the model simulates the mechanical interaction between fractures using a recently developed approximation technique for stress analysis in elastic solids with many fractures a comparison between experimental and numerical results shows that the model can accurately simulate the development of experimentally generated fracture sets once the flaw geometry is specified only one parameter controls the geometric evolution of the fracture set this parameter the velocity exponent relates fracture propagation velocity to stress concentration at the fracture tip monte carlo sensitivity analyses suggest that this parameter also controls the extent to which fracture growth is concentrated within zones or clusters similar analyses suggest that the extent of fracture clustering is less sensitive to the flaw density

insights into the evolving microphysical and kinematic structure of northeastern u s winter storms from dual polarization doppler radar abstractthe recent weather surveillance radar 1988 doppler wsr 88d network upgrade to dual polarization capabilities allows for bulk characterization of microphysical processes in northeastern u s winter storms for the first time in this study the quasi vertical profile qvp technique wherein data from a given elevation angle scan are azimuthally averaged and the range coordinate is converted to height is extended and applied to polarimetric wsr 88d observations of six northeast winter storms to survey their evolving bulk vertical microphysical and kinematic structures these analyses are supplemented using hourly analyses from the rapid refresh rap model regions of ascent inferred from qvps were consistently associated with notable polarimetric signatures implying planar crystal growth when near 15 c and riming and secondary ice production at higher temperatures the heaviest snowfall occurred most often when ascent and enhanced propagation differential phase shift occurred near 15 c

the lagrangian parcel dynamics of moist symmetric instability abstract a simple model describing the slantwise ascent of a two dimensional horizontal air tube subject to moist symmetric instability is developed under the assumptions that the froude number is small and that mixing is absent it is shown that in general the horizontal velocities attained by the tube are comparable to those of the mean flow and that vertical velocities of up to a few meters per second are possible the tube ascends slantwise in such a way that its buoyancy remains nearly zero unless the environment is my very nearly moist adiabatic in which case ascent at an angle of 45 to the vertical is preferred results of the analysis support the contentions of bennetts and hoskins and emanual that moist symmetric instability is the cause of some mesoscale rainbands in a companion paper it is demonstrated that the stability of the moist baroclinic atmosphere to two dimensional slantwise displacements of arbitrary magnitude can be approximately assessed by reversibly lifting parcel along sur

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

influence of terrain resolution on banded convection in the lee of the rocky mountains abstracton 16 17 february 2007 snowbands formed in the lee of the rocky mountains in wyoming colorado and nebraska on the anticyclonic shear side of a midlevel jet streak two types of bands were prevalent a longer wider band associated with frontogenesis along an equatorward moving cold front major band and multiple shorter narrower bands farther poleward minor bands to understand how the upstream terrain affected the occurrence and intensity of the bands multiple mesoscale model simulations were performed in which the terrain was incrementally smoothed the evolutions of the synoptic patterns were similar in all simulations that included topography but the synoptic pattern differed and no bands developed in a simulation with a flat land surface these results allowed a focus on the changes to the banded precipitation due to the terrain resolution remarkably although the exact location of the bands differed from run to run the bands in all simulations with topography were in roughly the s

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

an integrated approach to lithologic inversion part i theory for the complex problem of lithologic inversion a new formalism is proposed using a spatial distribution of seismic velocities cp cs and densities as input at each subsurface grid point the inversion result consists of the most likely lithotype gas sand shale etc together with its related litho parameters frame strength porosity etc the inversion method is based on the bayesian theory of parameter estimation allowing specification of inaccuracies in the input and the incorporation of geological knowledge an important advantage of the proposed inversion method is that for each practical situation the necessary accuracy of cp cs and can be predetermined to distinguish between specific lithotypes or to estimate a specific litho parameter with a prespecified accuracy for instance inversion results show that water saturation can only be estimated for an unrealistic accurate input on the other hand for the estimation of porosities it is generally sufficient to have compressional ve

hierarchical bayesian method for mapping biogeochemical hot spots using induced polarization imaging author s wainwright hm flores orozco a bucker m dafflon b chen j hubbard ss williams kh abstract 2015 american geophysical union all rights reserved in floodplain environments a naturally reduced zone nrz is considered to be a common biogeochemical hot spot having distinct microbial and geochemical characteristics although important for understanding their role in mediating floodplain biogeochemical processes mapping the subsurface distribution of nrzs over the dimensions of a floodplain is challenging as conventional wellbore data are typically spatially limited and the distribution of nrzs is heterogeneous in this study we present an innovative methodology for the probabilistic mapping of nrzs within a three dimensional 3 d subsurface domain using induced polarization imaging which is a noninvasive geophysical technique measurements consist of surface geophysical surveys and drilling recovered sediments at the u s department of energy field site near rifle co usa inversion of surface time domain induced polarization tdip data yielded 3 d images of the complex electrical resistivity in terms of magnitude and phase which are associated with mineral precipitation and other lithological properties by extracting the tdip data values colocated with wellbore lithological logs we found that the nrzs have a different distribution of resistivity and polarization from the other aquifer sediments to estimate the spatial distribution of nrzs we developed a bayesian hierarchical model to integrate the geophysical and wellbore data in addition the resistivity images were used to estimate hydrostratigraphic interfaces under the floodplain validation results showed that the integration of electrical imaging and wellbore data using a bayesian hierarchical model was capable of mapping spatially heterogeneous interfaces and nrz distributions thereby providing a minimally invasive means to parameterize a hydrobiogeochemical model of the floodplain

mesoscale structure in the megalopolitan snowstorm of 11 12 february 1983 part iii a large amplitude gravity wave abstract a large amplitude singular gravity wave is studied through the analysis of hourly observations radar and satellite data and observations of cloud to ground lightning flashes the wave activity was initiated just ahead of and to the left of the track of the major atlantic coast cyclone of 11 12 february 1983 the initial wave of depression was followed by a wave of elevation and finally a wake depression pressure amplitudes were several millibars the system propagated northeastward at 15 m s 1 accelerating to more than 25 m s 1 against increasing northeasterly flow in the lower troposphere surface northeasterlies increased and became gusty with the approach of the first pressure falls reaching a maximum at the pressure trough then abruptly weakening and backing as strong pressure increases were observed strong fluctuations in column total condensation rate and radar reflectivity occurred with the passage of the wave clustered lightning activity accompanied wave passage principally near

the structure and evolution of a continental winter cyclone part ii frontal forcing of an extreme snow event abstract the production of a narrow heavy occasionally convective snowband that fell within a modest surface cyclone on 19 january 1995 is examined using gridded model output from a successful numerical simulation performed using the university of wisconsin nonhydrostatic modeling system it is found that the snowband was produced by a thermally direct vertical circulation forced by significant lower tropospheric warm frontogenesis in the presence of across front effective static stability differences as measured in terms of the equivalent potential vorticity pve the sometimes convective nature of the snowband resulted from the development of freely convective motions forced by frontal lifting of the environmental stratification model trajectories demonstrate that a stream of warm moist air ascended through the trowal portion of the warm occluded structure that developed during the cyclone life cycle the lifting of air in the trowal was in this case forced by lower tropospheric frontogenesis occ

improved extraction of hydrologic information from geophysical data through coupled hydrogeophysical inversion 1 there is increasing interest in the use of multiple measurement types including indirect geophysical methods to constrain hydrologic interpretations to date most examples integrating geophysical measurements in hydrology have followed a three step uncoupled inverse approach this approach begins with independent geophysical inversion to infer the spatial and or temporal distribution of a geophysical property e g electrical conductivity the geophysical property is then converted to a hydrologic property e g water content through a petrophysical relation the inferred hydrologic property is then used either independently or together with direct hydrologic observations to constrain a hydrologic inversion we present an alternative approach coupled inversion which relies on direct coupling of hydrologic models and geophysical models during inversion we compare the abilities of coupled and uncoupled inversion using a synthetic example where surface based electrical conductivity surveys are used to monitor one dimensional infiltration and redistribution through this illustrative example we show that the coupled approach can provide significant reductions in uncertainty for hydrologic properties and associated predictions if the underlying model is a faithful representation of the hydrologic processes however if the hydrologic model exhibits structural errors the coupled inversion may not improve the hydrologic interpretation despite this limitation our results support the use of coupled hydrogeophysical inversion both for the direct benefits of reduced errors during inversion and because of the secondary benefits that accrue because of the extensive communication and sharing of data necessary to produce a coupled model which will likely lead to more thoughtful use of geophysical data in hydrologic studies

convective snowbands downstream of the rocky mountains in an environment with conditional dry symmetric and inertial instabilities abstract convective snowbands moved slowly over wyoming and northern colorado on 16 17 february 2007 and produced up to 71 mm 2 8 in of snow that was unpredicted by operational numerical weather prediction models and human forecasters the northwest southeast oriented bands lasted for over 6 h comprising both a single major band more than 30 km wide and multiple minor bands about 10 km wide the convective bands initiated within the ascending branch of a secondary circulation associated with both near surface and elevated frontogenesis but the bands remained nearly stationary while the near surface frontogenesis moved quickly equatorward the bands occurred downstream of complex terrain on the anticyclonic shear side of a midlevel jet streak where conditional dry symmetric negative potential vorticity and inertial negative absolute vorticity instabilities were present to determine the mechanisms responsible for the development and organization of these bands simulations using a convectio

coupled hydrogeophysical inversion using time lapse magnetic resonance sounding and time lapse gravity data for hydraulic aquifer testing will it work in practice 1 temporal changes in water content can be directly related to the time lapse signals retrieved using magnetic resonance sounding tl mrs and relative gravimetry tl rg previous studies suggest that tl rg measurements can potentially provide accurate estimates of aquifer characteristics in an aquifer pumping test experiment when used in a coupled hydrogeophysical inversion approach however these studies considered highly idealized conditions the aim of this paper is twofold first we investigate three major issues which likely limit the practical utility of tl rg for pumping test monitoring partially penetrating pumping wells in anisotropic aquifers delayed drainage effects and typical data errors for tl rg second we introduce tl mrs in a similar coupled hydrogeophysical inversion framework and compare the performance of tl mrs and tl rg for pumping test monitoring for this purpose we consider a virtual pumping test for which we generate synthetic drawdown tl mrs and tl rg observations and subsequently determine the aquifer parameters in an inverse parameter estimation approach the inclusion of tl rg and tl mrs data did slightly improve parameter estimates for the specific yield and hydraulic conductivity when considering a fully penetrating well and minimal data error using more conservative tl rg and tl mrs data error estimates according our own field experience strongly limited the informative value of the tl rg data tl mrs data was less affected by this for a partially penetrating well under anisotropic conditions parameter uncertainty could be reduced more effectively compared to a fully penetrating well delayed drainage effects did not limit the ability of the tl mrs and tl rg data to reduce parameter uncertainty significantly the incorporation of representative measurement error correlation in the tl rg data did not affect its informative value a local sensitivity analysis showed that observations were most sensitive to the pumping rate and the thickness specific yield and hydraulic conductivity of the aquifer the inclusion of tl mrs data proved to be more effective to constrain the aquifer parameters compared with tl rg the inclusion of both tl rg and tl mrs had limited added value compared to tl mrs only we conclude that this particular application of coupled hydrogeophysical inversion has limited potential for tl rg while tl mrs appears to be a more promising method

winter lightning along the east coast more than 150 000 cloud to earth lightning flashes were recorded along the east coast during the period 15 january 15 march 1986 in the region bounded by 25 n 40 n and 90 w 70 w the majority of the flashes for the two month period occurred over the atlantic ocean in the vicinity of the gulf stream where a peak flash density of 0 7 flashes km2 was observed approximately 270 km from the carolina coast this relatively sharp peak in the spatial distribution of lightning flashes to earth over the gulf stream occurs with a width at half maximum of approximately 130 km in the february 1986 data a close correlation is observed of the maximum lightning flash density contours with the maximum sea surface temperature contours

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

multiscale structure and evolution of an oklahoma winter precipitation event abstract a significant winter precipitation event occurred on 8 9 march 1994 in oklahoma snow accumulations greater than 30 cm 12 in were measured within a narrow corridor in northern oklahoma on the synoptic scale and mesoscale a correspondence between large snow accumulations and 600 hpa frontogenesis was revealed the precipitation was formed above the cold frontal surface owing to midtropospheric ascent associated with the cross frontal circulation in a region of elevated conditional instability the location of such a narrow corridor of large accumulations was not however disclosed by any patterns in the radar reflectivity data indeed during this event an elongated maximum of snow accumulation was not associated with a persistent band of enhanced reflectivity and vice versa dual polarization and dual doppler radar data allowed for a novel analysis of winter precipitation processes and structures within the context of the larger scale diagnosis it was possible to identify in order of

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

reactive transport modeling an essential tool and a new research approach for the earth sciences abstract reactive transport modeling is an essential tool for the analysis of coupled physical chemical and biological processes in earth systems and has additional potential to better integrate the results from focused fundamental research on earth materials appropriately designed models can describe the interactions of competing processes at a range of spatial and time scales and hence are critical for connecting the advancing capabilities for materials characterization at the atomic scale with the macroscopic behavior of complex earth systems reactive transport modeling has had a significant impact on the treatment of contaminant retardation in the subsurface the description of elemental and nutrient fluxes between major earth reservoirs and in the treatment of deep earth processes such as metamorphism and magma transport active topics of research include the development of pore scale and hybrid or multiple continua models to capture the scale dependence of coupled reactive transport processes frontier research questions that are only now being addressed include the effects of chemical microenvironments coupled thermal mechanical chemical processes controls on mineral fluid reaction rates in natural media and scaling of reactive transport processes from the microscopic to pore to field scale

climatology of banded precipitation over the contiguous united states abstracta climatology of banded precipitation features over the contiguous united states from 2003 to 2014 is constructed a band is defined as a precipitation feature with a major axis of 100 km or greater and a ratio of major axis length to minor axis length hereafter aspect ratio of 3 1 or greater by applying an automated feature based detection algorithm to composite radar imagery a database of 48 916 844 precipitation features is created of which 7 213 505 14 8 are bands this algorithm produces the first climatology of precipitation bands over the contiguous united states banded precipitation occurrence is broadly similar to total precipitation occurrence with a maximum of 175 h of banded precipitation annually over the ohio river valley in the warm season there is a strong diurnal signature associated with convective storm development for both the precipitation feature area and total area covered by precipitation but little diurnal signature in aspect ratio strong west east gradients

regional fractures i a mechanism for the formation of regional fractures at depth in flat lying reservoirs 1 regional fractures may form slowly at depth in extension and parallel to regional horizontal tectonic compression such fracture sets can be common in reservoirs despite the absence of flexure of the strata and are commonly important contributors to reservoir permeability such fractures make good targets for deviated wells high formation pore pressure is crucial to creating low effective confining stresses and brittle rock properties in the reservoirs conditions conducive to fracturing despite deep burial but pore pressure does not exceed the least principal stress and does not cause tensile fracturing the mechanism of natural hydraulic fracturing is incompatible with the characteristics of most regional fracture sets rather many regional fractures form duri g far field compression initiate at locally induced tensile stresses caused by flaws in the rock and propagate in the plane of the maximum and intermediate compressive stresses the differential stress required for initiation and propagation of regional fractures is well below that necessary for shear failure in the presence of high pore pressure fractures can be held open at depth by a tectonic basinwide dilatancy of the strata and the open void space commonly becomes mineralized

reactive transport modeling of early burial dolomitization of carbonate platforms by geothermal convection reactive transport models rtms permit quantitative investigation of diagenesis and its effects on reservoir quality the rtm toughreact is used to investigate diagenesis in an isolated platform driven by geothermal kohout convection of seawater which has been invoked to explain dolomitization during early burial previous short 0 1 m y rtm simulations suggested that convection can drive dolomitization mostly at greater than 50c and anhydritization but complete dolomitization requires greater than 30 60 m y our more extended rtm simulations 30 m y indicate significant nonlinearities in the system consistent with high temperature experiments with parts of the platform completely dolomitized within 10 15 m y as dolomitization proceeds the process becomes predominantly flux controlled with development of a wedge shaped dolomite body which thins from the margin to the interior at considerably shallower depth and cooler temperatures 20 30c than suggested by short simulations dolomitization is relatively insensitive to boundary conditions such as relative sea level and platform geometry but is significantly slower in circular than elongate platforms sediment permeability and reactive surface area commonly inversely related are key controls dolomitization is limited to the margin of low permeability muddy platforms despite a high reactive surface area dolomitization of more permeable grainy platforms is limited by a lower reactive surface area occurring only in the platform core due to widespread cooling sedimentary layering produces a complex diagenetic stratigraphy dolomitization favoring more reactive beds at shallow depth where permeability is not limiting but switching to more permeable beds at depth bank marginal fracturing limits dolomitization of the platform interior whether the fractures are baffles or conduits for flow

formation and evolution of frontal rainbands and geostrophic potential vorticity anomalies abstract a viscous semigeostrophic model is developed and used to study the formation and evolution of frontal rainbands in association with the dry and moist geostrophic potential vorticity gpv anomalies the numerical results show that when moist gpv mgpv becomes negative in the saturated region but the flow is still stable to viscous symmetric perturbations banded substructures can be generated internally by a positive feedback between the moist circulation bands and geostrophic forcing anomalies in association with the generation of mesoscale gpv anomalies in addition to the previous diagnostic results for idealized forcings the new aspect here is that the large scale moist ascent evolves into much finer multiple moist bands as soon as the positive feedback begins to generate banded substructures in the forcing and gpv fields when mgpv is positive multiple rainbands can only be generated externally by preexisting gpv or mgpv anomalies these rainbands can be self maintained by a weak feedba

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

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

proximity soundings of thundersnow in the central united states 1 proximity balloon soundings for snow events with lightning and thunder during the period 1961 through 1990 reveal a less statically stable environment than similar nonthundering snow events when thundersnow is present a less stable environment and in some cases subsequent upright convection is found aloft in all of the thundering cases examined here all of the events feature their most unstable parcel originating above a frontal inversion in fact only events in the cold air north of an extratropical cyclone are included in this study events with a lake effect or orographic enhancement are eliminated from the sample the basic composite derived by averaging temperatures at an established interval reveals a nearly saturated lower atmosphere below 0 c throughout its depth with the frontal inversion present and its most unstable parcel occurring just above the top of the inversion the feature preserving composite approach of r a brown 1993 better defines the frontal inversion bottom and top as well as the level and temperature of the most unstable parcel these are the features in need of preservation and a less statically stable environment emerges by doing so other salient features include the most unstable parcel originating some 30 50 mbar above the top of the frontal inversion and significant drying 100 mbar above the level of the most unstable parcel the bulk sounding characteristics also favor the existence of lightning the composite temperature at the level of the most unstable parcel is 8 7 c which allows for enhanced amounts of supercooled water to enter any updraft that may form the temperature of the most unstable parcel at its origin is also warmer than the charge reversal temperature therefore convection of any appreciable depth will span that level moreover the height of the composited 10 c level is 2959 m above ground level which previous investigators have shown is sufficiently high to favor lightning production yet no convective available potential energy cape appears with either composite approach which concurs with previous studies while several of the composite members feature cape for elevated layers the majority do not suggesting that other processes e g the release of symmetric instability which are difficult to assess from a single sounding tend to be at work

three dimensional high resolution fluvio glacial aquifer analog part 1 field study summary describing the complex structures that exist in many sedimentary aquifers is crucial for reliable groundwater flow and transport simulation however hardly any aquifer can be inspected in such detail that all decimeter to meter heterogeneity is resolved aquifer analogs serve as surrogates to construct models of equivalent heterogeneity and thus imitate those features relevant for flow or transport processes gravel pits found in excavation show excellent sections of the sedimentary sequence and thus offer direct insight into the structural and textural composition of the subsoil this paper describes an approach to also inspect the third dimension by mapping during the ongoing excavation it is possible to obtain a three dimensional representation of the subsurface within a short period of time a detailed description of a case study is presented and the findings from sedimentological hydrogeological and geophysical analyses are compared the gravel pit is located near the town of herten in southwest germany where relatively young unconsolidated fluvio glacial and fluvial sediments in the rhine basin are mined the excavated gravel body is built up by architectural elements typical for braided river deposits the study generated a high resolution data set of lithofacies hydrofacies and ground penetrating radar gpr profiles it represents the basis for a full three dimensional geostatistical reconstruction presented in the second part comunian et al 2011

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

radar kinematic information as a surrogate for isentropes in stratiform precipitation systems abstractthis study illustrates that dual doppler derived wind shear vertical gradient of the horizontal wind in stratiform nonturbulent flow is structured in long thin striations the reason this has not been documented before is that scanning ground based radars have inadequate vertical resolution deteriorating with range here data from an airborne radar with a fine range independent vertical resolution are used a comparison of the radar derived wind shear with model output of isentropes in vertical transects in the comma head of two frontal disturbances suggests that the wind shear layers describe material surfaces model output itself further confirms the alignment of isentropes with wind shear in vertical transects thus doppler radar derived wind shear a kinematic conserved variable may serve as a suitable proxy for thermodynamic conserved variables such as equivalent potential temperature in stratiform precipitation furthermore the presence of shear striations in vertical transects can