The Influence of Non-Collinear Electrodes Arrangement on a Two-dimensional Resistivity Survey Using Wenner Array

Abstract

Conventional protocols employed by various multi-electrode resistivity systems are designed with the assumption that the survey lines are straight to ensure collinear electrode pairs. However, as most survey areas are characterized by surface constraints, it is rarely possible to carry out two-dimensional electrical resistivity tomography (2-DERT) measurement on a straight line. Therefore, 2-DERT surveys conducted on a surface constraint field requires shifting of some electrodes off the survey line, which implies a non-collinear electrodes arrangement. Hence, the result of such a survey is prone to false anomalies and in turn, wrong interpretation. This article aims to uncover the potential effect of non-collinear electrodes arrangement on 2-D resistivity survey. To achieve this goal, the data was acquired in four phases using Wenner array with all electrodes inline, one offline, two offline and three offline at stepwise distances, respectively. The inverse resistivity models obtained revealed slight to distinct variation of anomalies as two or more electrodes are offline at a distance >½ the minimum electrode spacing.