oxygen isotope analyses and pleistocene ice volumes abstract the oxygen isotope record from fossil foraminifera in deep sea sediments is commonly used as a proxy for global ice volume the linkage between 18 o and ice volume however is probably nonlinear we have developed a simple numerical model of the isotopic response of the oceans to ice volume change the major features it simulates are 1 the changing mean isotopic composition of snow as a function of ice volume colder snow temperatures forced by climate change and higher elevation accumulation areas imply more negative mean 18 o 2 the nonequilibrium isotopic composition of ice sheets the past history of an ice sheet is integrated into its mean isotopic composition which introduces a lag of isotopic ice volume i e the measured 18 o record scaled to ice volume units behind true ice volume 3 selective preservation of isotopically more negative colder higher latitude ice this geographic effect can selectively amplify or dampen the isotopic response to the ice volume signal we illustrate the response of our model to simple hypothetical ice volume transitions of ice growth and ice decay sensitivity tests are illustrated for all model parameters the results suggest that oxygen isotope records reproduce the general patterns of ice volume change fairly accurately the foraminiferal isotope record however may misrepresent the true amplitude of the ice volume signal and lag true ice volume by 1000 to 3000 yr

state of the art of modelling two phase flow in fractured rock two phase flow in fractured rock is an important phenomenon for a range of practical problems not the least of which is non aqueous phase liquid napl contamination of groundwater although multiphase systems have long been studied in the petroleum field in the hydrogeological field progress has only just reaches the point where models are being developed scale effect is one of the main issues of concern although models presented in this paper have the potential to provide useful predictions they can only be used to investigate a variety of possible scenarios with parameters being specified in the form of distribution of values the calibration and validation of all but the simplest of these models poses a formidable task with great demands on hydrogeologists and geophysicists to provide adequate data

field determination of the three dimensional hydraulic conductivity tensor of anisotropic media 2 methodology and application to fractured rocks the analytical solutions developed in the first paper can be used to interpret the results of cross hole tests conducted in anisotropic porous or fractured media in the particular case where the injection and monitoring intervals are short relative to the distance between them the test results can be analyzed graphically from the transient variation of hydraulic head in a given monitoring interval one can determine the directional hydraulic diffusivity kd e ss and the quantity d ss by curve matching here kd e is directional hydraulic conductivity parallel to the unit vector e pointing from the injection to the monitoring interval ss is specific storage and d is the determinant of the hydraulic conductivity tensor k the principal values and directions of k together with ss can then be evaluated by fitting an ellipsoid to the square roots of the directional diffusivities ideally six directional measurements are required in practice a larger number of measurements is often necessary to enable fitting an ellipsoid to the data by least squares if the computed kd e ss values fluctuate so severely that a meaningful least squares fit is not possible one has a direct indication that the subsurface does not behave as a uniform anisotropic medium on the scale of the test test results from a granitic rock near oracle in southern arizona are presented to illustrate how the method works for fractured rocks at the site the oracle granite is shown to respond as a near uniform anisotropic medium the hydraulic conductivity of which is strongly controlled by the orientations of major fracture sets the cross hole test results are shown to be consistent with the results of more than 100 single hole packer tests conducted at the site

recovery of injected freshwater to differentiate fracture flow in a low permeability brackish aquifer summary a low permeability weathered siltstone sandstone aquifer containing brackish water was investigated to measure recoverability of injected freshwater with the aim of determining the significance of secondary porosity in contributing to groundwater flow and transport examination of the core borehole geophysics radon 222 electromagnetic flowmeter emf profiles and step drawdown pumping tests did not identify whether fractures contribute to groundwater flow a number of injection and recovery tests lasting from 3 days to 3 months using potable water showed a large degree of mixing with native groundwater withdrawal greater than 12 17 of the injected volume resulted in recovered water containing more native groundwater than injected water a finite element solute transport model was set up to reproduce the observed salinity in recovered water without the inclusion of discrete fractures in the model it was not possible to get a fit between the observed and modelled salinity of recovered water within a realistic range of dispersivity values the model was subsequently verified by using data from long term injection and recovery trials this evaluation of mixing conclusively demonstrated that the aquifer behaved as a fractured rock aquifer and not as an aquifer with primary porosity alone therefore aquifer storage and recovery can be a very useful hydrogeological method to identify the occurrence of fracture flow in aquifers where there is a measurable concentration difference between the injected water and ambient groundwater

scale dependent resistivity measurements of oracle granite a series of cross hole and single hole electrical conductivity measurements were made within saturated oracle granite the tests performed with point source and point reference electrodes pole pole or normal array were designed to examine the equivalent homogeneous conductivity as a function of the rock volume by increasing the interelectrode separation the length scale of the tests ranged from 8 inches to over 100 feet analysis of the data showed that 1 a power law relationship was observed where the electrical conductivity increased resistivity decreased with electrode separation 2 exponential variograms were derived for all distance classes thus no finite variance was attained 3 conductivity can be approximated as a nonhomogeneous locally isotropic variable and 4 the log of the apparent resistivity for a particular scale of measurement i e at constant current potential electrode distances can be fit to a fractional brownian motion fbm process and thus interpreted as a fractal process overall cross hole and single hole electrical resistivity measurements proved to be an efficient technique to assess the electrical behavior of the fractured rock mass at the oracle site

variations of the snow physical parameters and their effects on albedo in sapporo japan continuous measurements of the radiation budget and meteorological components along with frequent snow pit work were performed in sapporo hokkaido japan during two winters from 2003 to 2005 the measured relationships between broadband albedos and the mass concentration of snow impurities were compared with theoretically predicted relationships calculated using a radiative transfer model for the atmosphere snow system in which different types in light absorption of impurity models based on mineral dust and soot were assumed the result suggests that the snow in sapporo was contaminated not only with mineral dust but also with more absorptive soot a comparison of the measured relationships between broadband albedos and snow grain size for two different layers with the theoretically predicted relationships revealed that the visible albedo contains information about the snow grain size in deeper snow layers 10 cm and the near infrared albedo contains only surface information this is due to the difference in penetration depth of solar radiation into snow between the visible and the near infrared wavelengths

transient hydraulic tomography in a fractured dolostone laboratory rock block experiments 1 the accurate characterization of fractured geologic medium imaging of fracture patterns and their connectivity have been a challenge for decades recently hydraulic tomography has been proposed as a new method for imaging the hydraulic conductivity k and specific storage ss distributions of fractured geologic media while encouraging results have been obtained in the field the method has not been rigorously assessed in a controlled laboratory setting in this study we assess the performance of transient hydraulic tomography tht in a fractured dolomitic rock block the block is characterized through flow through tests and multiple pumping tests the pumping test data were then analyzed with the tht code of zhu and yeh 2005 to image the fracture patterns and their connectivity through the delineation of k and ss distributions or tomograms results show that the tht analysis of pumping tests yields high k and low ss zones that capture the fracture pattern and their connectivity quite well and those patterns become more vivid as additional pumping test data are added to the inverse model the performance of the estimated k and ss tomograms are then assessed by 1 comparing the tomograms obtained from synthetic to real data 2 comparing the tomograms from two different pumping configurations 3 comparing the estimated geometric mean of the hydraulic conductivity kg from the k tomogram to the effective hydraulic conductivity keff estimated from the flow through tests and 4 predicting five independent pumping tests not used in the construction of the k and ss tomograms the performance assessment of the k and ss tomograms reveals that tht is able to image high k and low ss zones that correspond to fracture locations in the fractured rock block and that the tomograms can be used to predict drawdowns from pumping tests not used in the construction of the tomograms with reasonable fidelity

retrieving snow and ice characteristics by remotely sensed emissivity using the multi view brightness temperature within 8 μm to 14 μm abstract this study provides a method determining the characteristics of snow and ice with remote sensing by converting top of atmosphere brightness temperature to surface emissivity which depends on wavelength and observation angle with respect to snow and ice properties envisat s advanced along track spectral radiometer aatsr features dual view thermal infrared measured brightness temperature using bands 11 m and 12 m in nadir and forward 55 view and a total column water vapour tcwv product from medium resolution imaging spectrometer meris we obtain four measurements per pixel we retrieve three surface emissivities e per pixel calculated from simulated surface temperatures related to 11 m nadir view values we define emissivity classes for different snow grain sizes from angular and spectral field measurements of snow grain size and emissivity above snow and ice from hori et al 2006 2007 fine medium coarse suncrust and ice remaining pixels are either indistinct between classes unclassified or invalid temperatures above the freezing point label pixels as wet analysing 26 aatsr scenes in 2007 and 2008 we retrieve a high portion of classification in greenland antarctica and the sea ice of the hudson bay steep and heterogeneous topography may cause invalid and unclassified pixels in eurasia close to coasts we generally find a higher snow temperature and a large number of wet pixels

what does hydraulic tomography tell us about fractured geological media a field study and synthetic experiments abstract between 2005 and 2010 japan atomic energy agency conducted four long term independent pumping tests in a fractured granite formation at the mizunami underground research laboratory miu site in mizunami city central japan during these tests drawdowns were monitored at different depths along several deep boreholes these tests become one of the few if not the only hydraulic tomographic survey conducted in the world over thousands of meters in a fractured geologic medium with several fault zones we analyzed the drawdown time data set associated with each pumping test independently and then the data sets from all pumping tests jointly to derive the spatial distributions of hydraulic conductivity k and specific storage s s of the medium these estimated distributions revealed some large scale high k and low k zones while the low k zones corroborated well with known low permeable layers and fault based on geological investigations there were no clear geological features that can be related to the large scale high k zones in order to understand and substantiate these high and low k zones we simulated a hydraulic tomographic survey in a synthetic fractured aquifer which bears similar geologic features i e formations fractures and faults at the miu site with exception that the hydraulic properties fracture and fault distributions were known exactly results of the simulation show that not only are the identified high k zones related to fracture networks connected with pumping and observation locations of each pumping test but also their values reflect the degree of connectivity of the network afterward we investigated the extent of the improvement of characterization of the fault and fractures through the use of deploying dense monitoring intervals and late time flux measurements

monitoring ice sheet behavior from space satellite remote sensing has revolutionized ice sheet research a variety of instruments sensitive to different parts of the electromagnetic spectrum take what the human eye detects as a flat white desert and provide data sets rich in scientific information image based maps of ice sheets are becoming commonplace and have become an integral component of field work more than a pretty picture the digital character of the satellite data from these instruments has become fundamental to the production of elevation motion accumulation and reflectance data sets visible imagery shows the scientist a wealth of features that offer clues to the history and current behavior of the ice sheet radar and microwave imagery provide information from beneath the surface and have been used to estimate snow accumulation rates interferometry principles have recently been applied to measure surface topography and ice motion with unparalleled precision nonimaging instruments also keep a watchful eye monitoring the ice sheet for indications of growth or shrinkage further expansion of the uses of satellite data is anticipated in the future

comparison between the results of a snow metamorphism model and remote sensing derived snow parameters in the alps abstract the numerical snow metamorphism model crocus derives a complete description of the snow cover according to its geographical location range elevation slope and orientation from the remote sensing data snow parameters that were comparable to the model results were derived the lower elevation of the snow cover the surface grain size and the surface temperature the landsat thematic mapper sensor was used because it has a good spatial resolution a short wave infrared channel which is sensitive to grain size and a thermal infrared channel a first landsat tm thematic mapper scene was acquired on 24 april 1992 and a second one on 11 december 1992 a dem digital elevation model was used to obtain the local incidence angles and the elevation of each snow pixel the pixels were then grouped according to the crocus classification range elevation slope orientation and the mean snow characteristics for each class were compared with the crocus results the lower limit of snow and the surface grain size derived from tm data compared favorably with the model results even if those parameters were not always easy to define larger differences were found for the temperature because it varies rapidly and is very sensitive to shadowing by surrounding mountains and also because its remote measurement is dependent on atmospheric conditions

cave sediments constrain the latest pleistocene advance of the laurentide ice sheet in the champlain valley vermont usa laurentide ice sheet advance vermont usa

groundwater in fractured bedrock environments managing catchment and subsurface resources an introduction hard rocks including crystalline igneous metamorphic and strongly cemented sedimentary and carbonate rocks cover about 50 of the earth s land surface singhal gupta 2010 globally the volume of groundwater contained in hard rock aquifers is not well constrained comte et al 2012 but locally they can be important aquifers macdonald et al 2012 albeit with low groundwater storage and poor primary porosity and permeability groundwater flow in these hard rocks is commonly observed to be associated with water bearing discontinuities such as fractures joints and faults mazurek 2000 berkowitz 2002 font capo et al 2012 and in the weathered regolith wright 1992 chilton foster 1995 deyassa et al 2014 structural elements such as fault zones also strongly govern the behaviour of these systems forster evans 1991 lopez smith 1995 bense et al 2013 the nature abundance orientation and connectivity of these water bearing features are largely governed by the history and nature of structural deformation of the bedrock and commonly impose strong anisotropic flow and transport parameters on these bedrock aquifers hsieh et al 1985 bour davy 1997 mortimer et al 2011 weathering processes furthermore lead to an alteration of bedrock composition and associated aquifer properties resulting in enhanced fracture connectivity and an overall vertical stratification zonation of bulk aquifer properties ranging from highly altered shallow regolith horizons to more competent sparsely fractured bedrock at depth dewandel et al 2006 krasn sharp 2007 lachassagne et al 2011

222rn transport in a fractured crystalline rock aquifer results from numerical simulations abstract dissolved 222 rn concentrations in ground water from a small wellfield underlain by fractured middle proterozoic pikes peak granite southwest of denver colorado range from 124 to 840 kbq m 3 3360 22700 pci l 1 numerical simulations of flow and transport between two wells show that differences in equivalent hydraulic aperture of transmissive fractures assuming a simplified two fracture system and the parallel plate model can account for the different 222 rn concentrations in each well under steady state conditions transient flow and transport simulations show that 222 rn concentrations along the fracture profile are influenced by 222 rn concentrations in the adjoining fracture and depend on boundary conditions proximity of the pumping well to the fracture intersection transmissivity of the conductive fractures and pumping rate non homogeneous distribution point sources of 222 rn parent radionuclides uranium and 226 ra can strongly perturb the dissolved 222 rn concentrations in a fracture system without detailed information on the geometry and hydraulic properties of the connected fracture system it may be impossible to distinguish the influence of factors controlling 222 rn distribution or to determine location of 222 rn point sources in the field in areas where ground water exhibits moderate 222 rn concentrations flow and transport simulations of a hypothetical multifracture system consisting of ten connected fractures each 10 m in length with fracture apertures ranging from 0 1 to 1 0 mm show that 222 rn concentrations at the pumping well can vary significantly over time assuming parallel plate flow transmissivities of the hypothetical system vary over four orders of magnitude because transmissivity varies with the cube of fracture aperture the extreme hydraulic heterogeneity of the simple hypothetical system leads to widely ranging 222 rn values even assuming homogeneous distribution of uranium and 226 ra along fracture walls consequently it is concluded that 222 rn concentrations vary not only with the geometric and stress factors noted above but also according to local fracture aperture distribution local groundwater residence time and flux of 222 rn from parent radionuclides along fracture walls

a dual fracture model to simulate large scale flow through fractured rocks discrete fracture network models can be used to study groundwater flow in fractured rock masses however one may find that it is not easy to apply such models to practical projects as it is diffic

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

understanding of hydraulic properties from configurations of stochastically distributed fracture networks a systematic investigation of the effect of configurations of stochastically distributed fracture networks on hydraulic behaviour for fractured rock masses could provide either quantitative or qualitative correlation between the structural configuration of the fracture network and its corresponding hydraulic behaviour and enhance our understanding of appropriate application of groundwater flow and contaminant transport modelling in fractured rock masses in this study the effect of block sizes intersection angles of fracture sets standard deviations of fracture orientation and fracture densities on directional block hydraulic conductivity and representative elementary volume is systematically investigated in two dimensions by implementing a numerical discrete fracture fluid flow model and incorporating stochastically distributed fracture configurations it is shown from this investigation that the configuration of a stochastically distributed fracture network has a significant quantitative or qualitative effect on the hydraulic behaviour of fractured rock masses compared with the deterministic fracture configurations that have been extensively dealt with in a previous study this investigation is expected to be more practical and adequate since fracture geometry parameters are inherently stochastically distributed in the field moreover the methodology and approach presented in this study may be generally applied to any fracture system in investigating the hydraulic behaviours from configurations of the fracture system while establishing a bridge from the discrete fracture network flow modelling to equivalent continuum modelling in fractured rock masses copyright 2007 john wiley sons ltd

the fernbank interglacial site near ithaca new york usa abstract the fernbank interglacial site on the west side of cayuga lake new york has been recently subjected to more detailed study to a lengthened mollusc list are added ostracodes insects fish pollen and plant macrofossils of these plants are well preserved and diverse whereas other groups are poorly preserved and incomplete nevertheless all support the interglacial assignment sangamon which is further supported by minimum age radiocarbon dates 50 000 14 c yr bp and a tl date of 81 11 ka in the plant record near the top of the sequence abundant tree charcoal indicates forest fires like the toronto interglacial record the plants show a declining july mean temperature from 24 to 18 c according to transfer functions through the sequence from mixed deciduous forest to boreal forest

a pollen study of a late quaternary peat bog south central adirondack mountains new york a series of cores from a 7 ha glacial kettle 600 m above sea level provides information on the development of a sphagnum peat bog and the late quaternary vegetation and climate history of the south central adirondack mountains new york within the kettle stratified drift that dates to about 11 000 yr b p is overlain by varved glacial lake sediment gyttja and peat the fossil pollen samples at brandreth bog were compared with 1 618 modern pollen samples using squared chord distance the degree of similarity between fossil and modern pollen samples was calibrated using comparisons among modern samples from different vegetation regions modern pollen analogs were identified for all of the fossil samples at brandreth bog and the vegetation and climate associated with these modern analogs were used to interpret the vegetation and climate history near the site the numerically derived pollen assemblage zones at brandreth bog are broadly similar to those for other sites in the region a forest similar to the current boreal forest succeeded treeless vegetation and spruce woodland around brandreth bog before about 10 200 yr b p a pine dominated forest was present by 9 600 yr b p continued warming of the climate allowed a hemlock rich mixed conifer hardwood forest to grow around brandreth bog after 7 000 yr b p and spruce and fir became less plentiful after a sharp decline in the amount of hemlock around brandreth bog at 4 700 yr b p birch maple beech and pine became the primary forest constituents spruce and fir trees increased in number near brandreth bog after 4 000 yr b p a development indicative of a reversal of the general warming trend that typified the early holocene by 2 000 yr b p a bog mat had closed over the lake basin a rise in the abundance of ragweed pollen about 125 yr b p reflected european settlement probably to the south correlation among five cores at the study site provided evidence of sediment focusing in the former lake basin

characterization of horizontal transmissivity anisotropy using cross hole slug tests abstract traditional methods for characterizing horizontally anisotropic aquifers are all based on pumping tests in this paper we present a new method for the identification of horizontal anisotropy using cross hole slug tests which is much more easily accessible comparing to pumping tests through scaler transform an anisotropic medium was converted into an equivalent isotropic medium when applying the analytical solutions derived for isotropic media to interpret cross hole slug tests performed in anisotropic media the estimated transmissivity is the geometrical mean of the anisotropic transmissivity tensor regardless of sampling direction however the apparent storativity calculated from different observation wells is equal to the true storativity scaled by a factor defined by the formation anisotropy thus anisotropy can be resolved through apparent storativity that bears directional information the proposed method was first validated by a numerical experiment and then applied to field data it was found that the tensor results obtained by this new method with cross hole slug tests are consistent with that obtained by applying the classical papadopulos method with cross hole pumping tests conducted in the same wells when applied to heterogeneous media tensor results produced by the new method may be subject to considerable errors this is because the results are strongly sensitive to the connectivity between measurement boreholes and the formation medium to reduce the error level responses from a large number of observation wells located in various directions around the source well are needed in addition to the adopted kgs solution for confined aquifers the proposed methodology can be applied to incorporate other analytical methods for a variety of aquifer types as long as the characteristic relationship between the measure scale and the aquifer storativity can be established

fracture characterization using earth tide analysis summary wells tapping confined aquifer systems are known to commonly produce water level fluctuations caused by strain induced earth tides in this investigation a straightforward methodology is presented for quantifying the specific storage and secondary porosity of a fractured fault zone aquifer system using earth tides water level and barometric pressure head data are smoothed and then filtered to remove low frequency responses the resulting tidal signals are used in the program baytap g to yield amplitude and phase shifts of all the major tidal groups the resulting tidal parameters can be used to compute the time dependent volumetric strain caused by the m 2 and o 1 tides stress strain hysteresis loops are produced when the reduced water levels are compared to the volumetric strain induced by these tides for amplification factors near unity representing the ratio of pressure response to tidal loading in the fracture to water level response in the well the slopes of the loops represent the specific storage of the fracture the barometric efficiency and specific storage can then be used to estimate a secondary porosity and other parameters of the aquifer system this analysis was carried out at the fractured rock research site frs in the blue ridge physiographic province in floyd county virginia

which empirical model is best suited to simulate glacier mass balances based on an extensive dataset of surface mass balances smb from four glaciers in the french alps for the period 1995 2012 and in the framework of enhanced temperature index models we investigate the sensitivity of seasonal glacier smb to temperature solar radiation precipitation and topographical variables our results reveal strong correlations between winter smb and precipitation although the precipitation gradient cannot explain the high accumulation rates based on the available point measurements we found no relevant relationship between winter smb and topographical variables temperature was found to be the main driver of ice snow ablation while solar radiation was found to strongly influence the spatial distribution of summer smb we compared the ability of several enhanced temperature index models to accurately simulate point smb and glacier wide mb our analyses revealed that the uncertainties in the simulated annual smb due to winter smb uncertainties are larger than differences between models and prevented us from concluding which model is the most suitable in contrast with results of previous studies including solar radiation in melt models did not improve the performances when modelling glacier wide mb we conclude that a classical degree day model is sufficient to simulate the long term glacier wide mb if the underlying processes are not required to be resolved

correlation between groundwater flow and deformation in the fractured carbonate gran sasso aquifer infn underground laboratories central italy the gran sasso massif is a carbonate fractured aquifer with a spring discharge of more than 18 m3 s 1 the water table has been partially drained by two motorway tunnels and an underground laboratory ul located into the core aquifer karst features have limited role below the water table where groundwater flow is mainly regulated by the fracture network two paired laser extensometers ba and bc recorded ground deformation in the ul changes in deformation correlate with the seasonal recharge discharge cycle of groundwater flow and its long term changes hydrostatic conditions prevail during the recharge phases because of the low permeability of local fractures favoring compression and hydraulic gradient increase above the ul fast groundwater flow through the high permeability fault outcropping in the ul can enhance local dilatation for short periods spring discharge during exhaustion periods is fed by the low permeability fracture network fostering hydrodynamic conditions by hydraulic gradient decrease diminishing compression and consequently favoring dilatation independent support to this conceptual model comes from local tests and a numerical model which highlights the hydromechanical strain effects induced by the hydrological cycle on the jointed rock mass along ba and the role of the hydraulic gradient on the rock mass deformation

effect of faults on fluid flow and chloride contamination in a carbonate aquifer system abstract a unified multidiscipline hypothesis is proposed to explain the anomalous pattern by which chloride has been found in water of the upper floridan aquifer in brunswick glynn county georgia analyses of geophysical hydraulic water chemistry and aquifer test data using the equivalent porous medium epm approach are used to support the hypothesis and to improve further the understanding of the fracture flow system in this area using the data presented herein we show that 1 four major northeast southwest trending faults capable of affecting the flow system of the upper floridan aquifer can be inferred from structural analysis of geophysical data and from regional fault patterns 2 the proposed faults account for the anomalous northeastward elongation of the potentiometric surface of the upper floridan aquifer 3 the faults breach the nearly impermeable units that confine the upper floridan aquifer from below allowing substantial quantities of water to leak vertically upward as a result aquifer transmissivity need not be excessively large as previously reported to sustain the heavy long term pumpage at brunswick without developing a steep cone of depression in the potentiometric surface 4 increased fracturing at the intersection of the faults enhances the development of conduits that allow the upward migration of high chloride water in response to pumping from the upper floridan aquifer and 5 the anomalous movement of the chloride plume is almost entirely controlled by the faults

hydrogeologic role of geologic structures part 2 analytical models abstract this paper is the second of two papers that address the influence of geologic structures on ground water flow at various scales in fractured rocks the ultimate purpose of this research is to investigate the feasibility of grouting preferentially permeable zones as a strategy to minimize the production of acid mine drainage in underground hard rock mines in which the major permeability is structure and fracture controlled the aim of grouting is to reduce permeability around mined out openings to minimize the rate of inflow of ground water into such openings via the structurally controlled preferentially permeable pathways a series of hydraulic stress tests were conducted to help characterize the role of geologic structures in controlling the ground water flow system in the vicinity of the bunker hill mine in north idaho the results of these tests indicate that most of the ground water that flows from the underground drillholes used for hydraulic stress testing is derived from a few discrete structurally produced fracture zones that are more or less connected through smaller scale fractures four types of analytical models are considered as a means of analyzing the results of multiple drillhole hydraulic stress tests as follows cross hole equivalent porous media double porosity equivalent porous media a solution to flow in and around a single vertical fracture leaky equivalent porous media partial penetration the estimation of hydraulic coefficients in complex fractured rock environments involves the combined application of a number of deterministic analytical models the models to be used are selected dependent on the location of the drawdown observations relative to the water producing zone and the length of the test the result of the tests can be related to the permeability hierarchy discussed in our first paper

a new determination method for the permeability tensor of fractured rock masses abstract hydraulic characteristics are important fundamental properties of fractured rock masses and involve various geoscience and engineering disciplines the determination of the permeability tensor is the basic input of the equivalent continuum ec model for hydraulic behavior analysis an analytical method to determine the permeability tensor of fractured rock masses is developed based on the orientation and linear frequency of fractures along with a value of the permeability in any direction the orientation and linear frequency of fractures can be easily sampled in practice and the value of the permeability in some direction can be tested by a relatively cheap single well pumping test the key step of this method is to derive the theoretical relationship between the permeabilities in two different directions in addition an anisotropy index of permeability aip is defined to quantitatively describe the permeability anisotropy some numerical experiments were conducted with the universal distinct element code udec to validate the developed method the results show that a the predicted values are very close to the real ones b for all cases of rock masses with equal aperture fracture sets the mean error rate of the permeabilities in 23 different directions is approximately 10 c for rock masses with different aperture fracture sets the mean error rate increases from 8 6 to 28 9 as the aperture ratio increases from 1 to 4 and d therefore the estimation method for directional permeability proposed in this study is valid especially for those rock masses in which the aperture ratios of the fracture sets are small e g less than 3

quaternary climates and sea levels of the u s atlantic coastal plain uranium series dating of corals from marine deposits of the u s atlantic coastal plain coupled with paleoclimatic reconstructions based on ostracode marine and pollen continent data document at least five relatively warm intervals during the last 500 000 years on the basis of multiple paleoenvironmental criteria we determined relative sea level positions during the warm intervals relative to present mean sea level were 7 5 meters at 188 000 years ago 7 5 1 5 meters at 120 000 years ago 6 5 3 5 meters at 94 000 years ago and 7 3 meters at 72 000 years ago the composite sea level chronology for the atlantic coastal plain is inconsistent with independent estimates of eustatic sea level positions during interglacial intervals of the last 200 000 years hydroisostatic adjustment from glacial interglacial sea level fluctuations lithospheric flexure and isostatic uplift from sediment unloading due to erosion provide possible mechanisms to account for the discrepancies alternatively current eustatic sea level estimates for the middle and late quaternary may require revision

snow grain size measurements in antarctica grain size is an important but not well known characteristics of snow at the surface of antarctica in the past grain size has been reported using various methods the reliability reproducibility and inter comparability of which is not warranted in this paper we present and recommend depending on available logistical support 3 techniques of snow grain sampling and or imaging in the field as well as an ariginal digital image processing method which we have proved to provide reproducible and intercomparable measures of a snow grain size parameter the mean convex radius results from more than 500 samples and 3000 images of snow grains presented which yield a still spatially limited yet unprecendtedly wide picture of near surface snow grain size distribution from field work in antarctica in particular except at sites affected by a very particular meteorology surface grains in the interior of the ice sheet are uniformly small o 1 to 0 2 mm the climate related increase of grain size with depth through metamorphism is as expected not spatially uniform our antarctic snow grain size database will continue to grow as field investigators bring new samples images and measures of snow grain size

a numerical model to simulate snow cover stratigraphy for operational avalanche forecasting laws of snow metamorphism have been introduced in a numerical model which simulates the evolution of temperature density and liquid water profiles of snow cover as a function of weather conditions to establish these laws the authors have summarized previous studies on temperature gradient and on wet snow metamorphism and they have also conducted metamorphism experiments on dry or wet fresh snow samples an original formalism was developed to allow a description of snow with parameters evolving continuously throughout time the introduction of laws of metamorphism has improved significantly the derivation of the settlement of internal layers and of snow covered albedo which depend on the simulated stratigraphy i e the type and size of snow grains of different layers of the snow cover the model was tested during a whole winter season without any re initialization comparison between the simulated characteristics of the snow cover and the observations made in the field are described in detail the model proved itself to be very efficient in simulating accurately the evolution of the snow cover stratigraphy throughout the whole winter season

application of fracture network model with crack permeability tensor on flow and transport in fractured rock article i nfo very efficient and practical models that use a crack tensor in terms of fracture geometry parameters for field rock mass are proposed a framework of the crack tensor approach combined with the identifying fracture controlled characteristics was successively used in a hypothetical hydro geological field for determining the dynamics of flow and transport of nuclides in fractured rock the modeling results and site specific data of lan yu island in taiwan reveal the characteristics associated with the geometry of fracture networks under the prescribed boundaries the simulated fracture networks were transformed into a grid based simulation procedure under consideration of the delaying effect in matrix owing to particle migration synthetic flow results indicate that the flowing vector is very sensitive to fracture intensity p32 high fracture intensity leads to high velocity heterogeneity generated by fractures field will result in the shortest and the longest transmission distance of 12 fold difference while taking into consideration of the ingrowth decay transport the plumes of the daughter product were relatively tortuous and anomalous to predict

an energy and mass model of snow cover suitable for operational avalanche forecasting a numerical model has been developed to simulate energy and mass evolution of snow cover at a given location as a function of meteorological conditions precipitation air temperature humidity wind velocity and incoming short wave and long wave radiation this model named crocus was first tested on a well instrumented field during a whole winter showing its ability to simulate the important phenomena affecting the evolution of the snow layers high temperature gradients wetting compaction and melting freezing cycles a second test was conducted at two locations in the french network used for operational avalanche forecasting though the weather observations are made there only twice daily the snow profiles calculated by the model were very close to those obtained once a week by a pit observation crocus proved itself sufficient to be considered now as a useful objective tool for operational avalanche forecasting

snow dunes and glazed surfaces in antarctica new field and remote sensing data as part of the international trans antarctic scientific expedition project the italian antarctic programme undertook two traverses from the terra nova station to talos dome and to dome c along the traverses the party carried out several tasks drilling glaciological and geophysical exploration the difference in spectral response between glazed surfaces and snow makes it simple to identify these areas on visible near infrared satellite images integration of field observation and remotely sensed data allows the description of different mega morphologic features wide glazed surfaces sastrugi glazed surface fields transverse dunes and megadunes topography global positioning system ground penetrating radar and detailed snow surface surveys have been carried out providing new information about the formation and evolution of mega morphologic features the extensive presence up to 30 of glazed surface caused by a long hiatus in accumulation with an accumulation rate of nil or slightly negative has a significant impact on the surface mass balance of a wide area of the interior part of east antarctica the aeolian processes creating these features have important implications for the selection of optimum sites for ice coring because orographic variations of even a few metres per kilometre have a significant impact on the snow accumulation process remote sensing surveys of aeolian macro morphology provide a proven high quality method for detailed mapping of the interior of the ice sheet s prevalent wind direction and could provide a relative indication of wind intensity

transport of magnetite and ilmenite by glaciers in the adirondack mountains of new york till collected from surface exposures within the valley of the hudson river south of the sanford hill magnetite ilmenite ore deposit in the adirondack mountains of new york is composed primarily of plagio clase pyroxene garnet magnetite and ilmenite the concentrations of magnetite and ilmenite in bulk till both decrease exponentially with increasing distance south of the ore bodies because of dilution by the entrainment of plagioclase and garnet pyroxene from the bedrock and from older till deposits in the valley evidence for comminution of magnetite and ilmenite is provided by decreasing abundances of these minerals in the coarse fractions 1000 125 m and corresponding increases in the fine fractions 125 m the apparent rate of comminution of ilmenite as a function of transport distance is significantly greater than that of magnetite which causes ilmenite to be concentrated in the fine fraction of till compared to magnetite the weight ratios of magnetite and ilmenite in the fine to coarse

use of variable scale pressure test data to estimate the log hydraulic conductivity covariance and dispersivity of fractured granites near oracle arizona abstract application of modern stochastic theories to nonuniform geologic media requires among other things knowing the principal directions and correlation lengths of the log hydraulic conductivity covariance to infer this information by standard geostatistical methods directly from point measurements of hydraulic conductivity in three dimensional space is seldom possible due to a ubiquitous scarcity of data to show how this difficulty can be overcome we use an example of fractured granitic rocks near oracle arizona at this site hydraulic conductivities were measured on a small scale by packer tests and on a larger scale by cross hole tests the test results suggest that the measured hydraulic conductivities can be viewed as quantities defined over a continuum which are scalar on a local scale but exhibit large scale anisotropy due to spatial nonuniformity and the effect of fracture orientations based on this observation the two sets of hydraulic conductivity data are related theoretically and the resulting expression is used to estimate the anisotropic covariance function of log hydraulic conductivities at the oracle site we then employ these parameters to calculate a fickian dispersivity tensor for the oracle granite by relying on the recent theory of neuman et al 1987a our results highlight the need to extend available stochastic theories to the domain of strongly nonuniform media the properties of which fluctuate with large amplitudes

estimating spatially variable representative elementary scales in fractured architecture using hydraulic head observations 1 water resources within large scale fractured aquifers are typically evaluated using continuum models while any arbitrary scale of continuum can be imposed to represent fracture architecture using the representative elementary volume eliminates errors that result from estimating network connectivity in traditional theory representative elementary scales res are equal in magnitude and geometry throughout a domain and are normally determined using a structural indicator such as porosity or effective hydraulic conductivity we present a fluid based methodology analyzing scale dependent energy variation to estimate res using relatively low cost readily available hydraulic head data hydraulic head predictions of res hyres reveal a spatial variation in elementary scale consistent with the flow field and fracture architecture porosity predictions of res porres incorporate the structural effect of disconnected fracture regions but do not account for fluid behavior res estimated from hydraulic conductivity kres are sensitive to fracture connectivity which controls fluid movement but are difficult to quantify because of scale and spatial variability hyres may be the superior approach for evaluating water resources because it is sensitive to fracture connectivity and avoids complications with scale and spatially dependent averaging our method is sensitive to fracture density clustering connectivity and flow direction but is insensitive to the magnitude of hydraulic gradient hyres is a novel approach to estimating spatially variable res that improves water resource evaluation and flow characterization in fractured aquifers

estimation of permeability for the rock mass around the shiplocks of the three gorges project china changes in the bulk permeability of the fractured rock mass around the shiplocks of the three gorges project china during excavation have been investigated using a numerical modelling technique the numerical model took into account both the effect of fractures on the in situ bulk permeability and the increase in permeability resulting from the stress relief and opening of the fractures caused by excavation fracture patterns were estimated on the basis of field exposures in three orthogonal planes the numerical model was calibrated for the in situ condition by varying the fracture stiffness until a close match in terms of both magnitude and direction was obtained with the equivalent permeabilities estimated on the basis of field pumping tests excavation of the shiplocks both with and without the use of temporary supports was modelled and the resulting changes in stress and permeability in the surrounding rock mass calculated in both cases the opening of fractures subparallel to the shiplock channels resulted in an increase in the permeability of the ground but when the vertical sidewalls were supported during excavation the increase in permeability was less marked the results of the analyses highlight the effects of engineering activities on the permeability of fractured rock masses and demonstrate that these effects can be controlled through the judicious choice of construction techniques and procedures

modelling of the densification of polar firn characterization of the snow firn transition the transformation of dry snow to firn is described by the transition between densification by deformationless restacking and densification by power law creep the observed decrease with temperature of the density at the snow firn transition seems to result from the competition between grain boundary sliding and power law creep these two densification processess occur concurrenlly in snow although there are probably micro regions in which sliding alone occurs validation ofa geometrical densifi cation model developed for ceramics has been obtained from densification data from several antarctic and greenland sites and from the characterization of the structure of polar firn

estimation of rev size and three dimensional hydraulic conductivity tensor for a fractured rock mass through a single well packer test and discrete fracture fluid flow modeling abstract a new methodology is presented to determine the representative elementary volume rev size and three dimensional 3 d hydraulic conductivity tensor for a fractured rock mass first a 3 d stochastic fracture network model was built and validated for a gneissic rock mass based on the fracture data mapped from scanline surveys at the site this validated fracture network model was combined with the fracture data observed on a borehole to generate a stochastic deterministic fracture network system in a cubic block around each packer test conducted at a different depth region in the same borehole each packer test was simulated numerically applying a developed discrete fracture fluid flow model to estimate the influenced region or effective range for the packer test a cubic block of size 18 m with the packer test interval of length about 6 5 m located at the centre of this block was found to be suitable to represent the influenced region using this block size the average flow rate per unit hydraulic gradient defined as the transmissivity multiplied by mean width of flow paths field for fractures was calibrated at different depth regions around the borehole by numerically simulating the packer tests conducted at different depth regions the average flow rate per unit hydraulic gradient of the fractures that intersect the borehole was considered to be quite different to the average flow rate per unit hydraulic gradient of the fractures that do not intersect the borehole a relation was developed to quantify the ratio between these two parameters by studying the directional hydraulic conductivity behaviour of different cubic block sizes having the validated stochastic fracture network and calibrated hydraulic parameters a rev for the hydraulic behaviour of the rock mass was estimated to be a block size of 15 m the hydraulic conductivity tensor in 3 d computed through regression analysis using the calculated directional hydraulic conductivity values in many directions was found to be significantly anisotropic the principal directions of the hydraulic conductivity tensor were found to be agreeable with the existing fracture system of the site further the geometric hydraulic conductivity calculated was found to be comparable to the hydraulic conductivity estimated through the radial flow assumption in continuum porous media

spectral bi directional reflectance of snow and glacier ice measured in dronning maud land antarctica visible and near infrared spectral reflectances of snow and superimposed ice were measured in dronning maud land antarctica during the 1992 93 austral summer spectral reflectance curves of both snow and superimposed ice remain high 80 in the visible region a pronounced decrease in reflectance appears in the near infrared especially for superimposed ice superimposed ice with a 1 cm thick surface layer of ice bound snow crystals had a considerably higher reflectance than superimposed ice containing only a few snow crystals furthermore these data prove that snow and superimposed ice reflect solar radiation specularly and suggest that the anisotropy strengthens with increasing wavelengths integrated in situ reflectances corresponding to landsat tm bands 1 4 show that tm band 1 is least affected whereas tm band 4 is most affected by anisotropy furthermore the anisotropy increases with increasing off nadir viewing angles up to an angle corresponding to 90 s s solar elevation for a 15 off nadir sensor observation angle the average snow reflectance for tm bands 1 4 is about 10 higher than at nadir similarly the apparent reflectance can be more than 50 higher than the nadir reflectance for larger observation angles consequently if satellite derived reflectances are going to be considered as absolute values a topographic correction model is needed to correct for the effects of anisotropy

stratigraphic evidence of a pre wisconsinan interglaciation in the adirondack mountains new york abstract multiple tills separated by interbedded lake sediments were temporarily exposed during open pit mining at sanford hill near newcomb in the central adirondack mountains of northeastern new york radiocarbon ages of wood fragments from brown clay between two tills at that site indicate an age older than 55 000 yr b p a pollen profile in the brown pond clay tahawus clay records a transition from initial domination by pine spruce and birch to an oak pollen zone the upward disappearance of spruce and decrease of pine and birch are accompanied by diversification and increase in hardwood pollen this assemblage includes several warm climate hardwood species that are not represented in the postglacial flora of the region suggesting that the biota existed during an interglacial or interstadial interval that was warmer and or longer than postglacial time accordingly the tahawus clay is tentatively assigned to the sangamon interglaciation and probably to marine oxygen isotope substage 5e truncation of the tahawus clay by glacial erosion may account for the absence of a sangamon paleosol

a comparative study of discrete fracture network and equivalent continuum models for simulating flow and transport in the far field of a hypothetical nuclear waste repository in crystalline host rock abstract one of the major challenges of simulating flow and transport in the far field of a geologic repository in crystalline host rock is related to reproducing the properties of the fracture network over the large volume of rock with sparse fracture characterization data various approaches have been developed to simulate flow and transport through the fractured rock the approaches can be broadly divided into discrete fracture network dfn and equivalent continuum model ecm the dfn explicitly represents individual fractures while the ecm uses fracture properties to determine equivalent continuum parameters we compare dfn and ecm in terms of upscaled observed transport properties through generic fracture networks the major effort was directed on making the dfn and ecm approaches similar in their conceptual representations this allows for separating differences related to the interpretation of the test conditions and parameters from the differences between the dfn and ecm approaches the two models are compared using a benchmark test problem that is constructed to represent the far field 1 1 1 km 3 of a hypothetical repository in fractured crystalline rock the test problem setting uses generic fracture properties that can be expected in crystalline rocks the models are compared in terms of the 1 effective permeability of the domain and 2 nonreactive solute breakthrough curves through the domain the principal differences between the models are mesh size network connectivity matrix diffusion and anisotropy we demonstrate how these differences affect the flow and transport we identify the factors that should be taken in consideration when selecting an approach most suitable for the site specific conditions

high resolution non destructive measurement and characterization of fracture apertures abstract we measure at high resolution the fracture aperture of several consolidated materials and statistically characterize the aperture distribution for future studies on single and multiphase flow and transport through fractured porous media the images of the real fractures in granite and sandstone rocks are obtained with a computer aided tomography cat x ray scanner the minimum pixel size is 0 27 0 27 mm but fractures as small as 35 m can be accurately measured using a calibration standard for the variation in ct number due to the missing rock mass in a given pixel the distribution of fracture apertures is best described by a lognormal function this was also corroborated by comparing the theoretical to actual ratio of geometric mean to arithmetic mean apertures the mechanical roughness of the fractures ranged from 0 17 to 1 5 the variability in fracture aperture displayed only short range structure with correlation lengths of 0 8 to 7 mm at maximum which is at most one tenth of the minimum dimension width of the fracture plane fracture aperture distribution is rather heterogeneous potential flow channels can be deduced from the fracture aperture distribution