Application of 3D resistivity tomography to delineate subsurface structures

Abstract

We have developed a three-dimensional (3D) resistivity inversion code for resistivity tomography, where resistivity data are measured using electrodes installed in several boreholes as well as at the Earth surface. The algorithm is based on finite element approximations for forward modelling, and the ACB (Active Constraint Balancing) algorithm is adopted to enhance the resolving power of the smoothness-constrained least-squares inversion. Resolution analysis with numerical examples shows that 3D resistivity tomography is a promising tool to construct high-resolution 3D images of subsurface structures. We have also shown that topography effects should be incorporated in the inversion to get accurate 3D images without artefacts. In the application of the method to a field data set acquired at a granite quarry, we could successfully delineate the 3D attitude of faults or fractures in the site.