Improved 3D pole‐dipole resistivity surveys using radial measurement pairs

Abstract

For convenience in the field, multielectrode arrays used to collect 3D resistivity data are typically laid out in a Cartesian grid with potential measurements made using electrode pairs oriented in the X and Y axis directions. The current flow away from a given injection electrode, however, has radial symmetry in the case of a homogeneous, isotropic half‐space, and near‐radial symmetry otherwise, unless the ground is extremely heterogeneous or anisotropic. Consequently, many of the voltage measurements made using standard electrode combinations are tangential or nearly‐tangential to the voltage equipotentials, resulting in a poor signal‐to‐noise ratio. We compare data collected using a standard pole‐dipole configuration with measurements made using the same Cartesian array, but choosing electrode pairs that lie along lines radiating away from the injection electrode. The remarkable improvement in data quality using a radial data acquisition pattern illustrates the importance of considering the potential gradient when designing resistivity data collection schemes.