HR: 1340h
AN: H23A-1116    [Abstracts]
TI: Combining Core and Geophysical Data Using Spatial Statistics to Infer the Permeability Structure of Glacial Sediments
AU: Kilner, M
EM: mkilner@fugro.co.uk
AF: formerly 1, now Fugro Engineering Services Limited, 18 Frogmore Road , Hemel Hempstead, Her HP3 9RT United Kingdom
AU: * West, J
EM: jared@earth.leeds.ac.uk
AF: Institute of Earth and Biosphere, School of Earth and Environment, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT United Kingdom
AU: Murray, T
EM: tavi@geography.leeds.ac.uk
AF: School of Geography, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT United Kingdom
AB: Geophysical surveys, such as resistivity and electromagnetic surveys, are a valuable tool in characterization of the permeability structure of aquifer confining layers for the purpose of pollution vulnerability assessment. However, these geophysical techniques suffer from a range of limitations associated with sampling volume or data inversion process. For example, when characterizing glacial sequences comprising sands and clays, resistivity inversions often mis-place the depths of layer boundaries, and fail to relatively detect thin layers at depth, or those below conductive overburden. These problems seriously compromise our ability to generate accurate permeability fields directly from geophysical data. We present an approach aimed at overcoming these limitations by combining geophysical data with core data using co-kriging. Normally, geophysical datasets are accompanied by relatively sparse direct geological data (e.g. borehole logs). These data can be used to identify where geophysical datasets fail to adequately reflect geological structure; they can also identify areas where the structure is more adequately reflected in the geophysical data. Here, we present an attempt to use the spatial structure of areas of a glacial cover sequence where good geophysical data are available to interpolate geological structure between sparse boreholes. The spatial structure of the geophysical data is first characterized using semi-variograms; co-kriging of the spatially dense geophysical and sparse borehole data enables the interpolation of a more complete geological cross section. The permeability fields produced by this approach are compared with those generated by direct conversion of resistivity profiling data, in order to ascertain the significance of the proposed approach for groundwater vulnerability assessment.
DE: 1827 Glaciology (1863)
DE: 1832 Groundwater transport
DE: 1875 Unsaturated zone
DE: 1894 Instruments and techniques
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting