The influence of anisotropy on the apparent resistivity tensor: A model study

The investigation of anisotropic structures within the subsurface using direct current resistivity methods (DCR) requires an array set up with measurements in different orientations. Displaying the data by the apparent resistivity tensor provides a powerful tool to easily identify anisotropic structures. In this study we present several characteristics of intrinsic electrical anisotropy and its effect on the apparent resistivity tensor. Above anisotropic anomalies the principle axes of the tensor exhibit a homogeneous pattern with orientation along the anisotropic strike and the aspect ratio related to the anisotropic properties of the medium. Contrary, outside the anomaly the ellipticity of the tensor and its apparent resistivity values are spatially highly variable depending on the location and the orientation of the source current dipole. Some of these features are in clear contrast to the behavior of the tensors above isotropic resistivity anomalies.