Numerical evaluation of 3D geoelectrical resistivity imaging for environmental and engineering investigations using orthogonal 2D profiles

Abstract

Field design for 3D data acquisition in geoelectrical resistivity imaging using a net of orthogonal sets of 2D profiles was numerically investigated. A series of 2D apparent resistivity pseudosections were generated over a synthetic horst structure representing the geological environment of a crystalline basement in low latitude areas using RES2DMOD code. Different minimum electrode separations and inter‐line spacing were used with a view of determining the optimum inter‐line spacing relative to the minimum electrode separation. The 2D apparent resistivity data were collated to 3D data set and then inverted using RES3DINV, a full 3D inversion code. The relative effectiveness and imaging capabilities of Wenner‐alpha (WA), Wenner‐beta (WB), Wenner‐Schlumberger (WSC), dipole‐dipole (DDP), pole‐dipole (PDP), and pole‐pole (PP) arrays to image the structure using a net of orthogonal set of 2D profiles are presented. The normalized average sensitivity of the inversion results show that WSC, DDP, and PDP arrays are more sensitive to the 3D structure investigated. Interline spacing of not greater than four times the minimum electrode separation gives reasonable resolution.