Developments in Resistivity Inversion with Electrode Displacements for Landslide Monitoring
M.H. Loke, P.B. Wilkinson, J.E. Chambers, S. Uhlemann and P.I. Meldrum
Event name: 23rd European Meeting of Environmental and Engineering Geophysics
Session: Geoelectrics and Electromagnetics - Instrumentation, Theory and Applications I
Publication date: 03 September 2017
Info: Extended abstract, PDF ( 822.86Kb )
Price: € 20
Time-lapse resistivity surveys are being used to monitor changes in the subsurface that relate to landslide hydraulic processes and movements. In geologically unstable areas, not only does the subsurface resistivity change with time, but the positions of the electrodes also change due to ground movements. If direct measurements of the electrode positions are not available immediately after the ground movements, both the changes in electrode positions and the subsurface resistivity have to be estimated from the apparent resistivity measurements. We describe a modification to the smoothness-constrained least-squares optimization method that includes the electrode positions, together with the subsurface resistivity, as unknown variables to be determined. A fast adjoint-equation method is used to calculate the Jacobian matrices associated with the electrode positions from the finite-element capacitance matrix. Ground movements in a landslide zone normally occur in the downslope direction. This information is incorporated into the inversion algorithm using the method of transformations to reduce the ambiguity in the recovered electrode positions. Tests with a field data set from a landslide-prone area showed the error of the estimated electrode positions from the inversion algorithm is about 10%.