Abstract

Acquisition geometry for 3D geoelectrical resistivity imaging in which apparent resistivity data of a set of parallel 2D profiles are collated to 3D data set was evaluated. A set of parallel 2D apparent resistivity data were generated over two model structures. The models, horst and trough structures, simulates the geological environment of a weathered profile and refuse dump site in a crystalline basement complex, respectively.  The apparent resistivity data were generated for Wenner-alpha (WA), Wenner-beta (WB), Wenner-Schlumberger (WSC), dipole-dipole (DDP), pole-dipole (PDP), and pole-pole (PP) arrays with minimum electrode separations (a = 2, 4, 5 and 10 m ) and inter-line spacing (L = a, 2a, 2.5a, 4a, 5a and 10a). The 2D apparent resistivity data for each of the arrays were collated to 3D data set and inverted using a full 3D inversion code. The 3D imaging capability and resolution of the arrays for the set of parallel 2D profiles are presented. Grid orientation effects, which decrease with decreasing inter-line spacing, are observed in the inversion images. Inter-line spacing of not greater than four times the minimum electrode separation gives reasonable inverse models. The resolution of the inverse models can be greatly improved if the 3D data set is built by collating sets of orthogonal 2D profiles.

Key words: Acquisition geometry, parallel 2D profiles, 3D surveys, geoelectrical resistivity, 3D imaging, inversion.