HR: 0800h
AN: NS31A-04    [Abstracts]
TI: Comparison of 1D, 2D and 2.5D Constrained Inversion of Electrical Resistivity Data
AU: * Catt, L M
EM: l.catt@see.leeds.ac.uk
AF: School of Earth and Environment, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, United Kingdom
AU: West, J
EM: l.j.west@leeds.ac.uk
AF: School of Earth and Environment, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, United Kingdom
AU: Clark, R A
EM: roger@earth.leeds.ac.uk
AF: School of Earth and Environment, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, United Kingdom
AB: Clay-rich till plains cover much of the UK. Such sites are attractive locations for landfills, since the till cover lowers the risk of landfill leachate entering groundwater. However, such tills often contain discrete sand and gravel bodies that can act as leachate flow routes. Such bodies may not be detected by conventional site investigation techniques such as drilling boreholes and trial pitting. A combined geoelectrical survey was carried out at a study site typical of such till plains and close to cliff exposures, which allowed direct mapping of sand bodies. Electrical resistivity tomography (ERT), resistivity cone penetrometry (RCPT) and frequency-domain electromagnetic data were collected. In a previous study, the electromagnetic and RCPT data were used to construct reference models for 2D inversion of the ERT data. The use of these reference models improved the solution models produced by inversion. We showed that the best solution model produced by inversion with a range of reference models could be determined without a priori knowledge of the true geoelectrical structure. This was done by using the area-weighted L2 norm between the solution models and associated reference models as a proxy for the misfit between the solution models and the true geoelectrical structure of the ground. In order to assess the most suitable method for combining invasive and non-invasive measurements, we compare both constrained and unconstrained 1D, 2D and 2.5D inversions of resistivity data collected at the study site. Preliminary results suggest that for 2.5D inversion the true 3D geoelectrical structure of the ground at the field study site is not sufficiently well known for comparison between the solution models and the true geoelectrical structure of the ground to be made. The results of work in progress evaluating layer-depth- constrained 1D inversion will be presented at the meeting.
DE: 0910 Data processing
DE: 3260 Inverse theory
SC: Near-Surface Geophysics [NS]
MN: 2007 Joint Assembly