The effect of structure and anisotropy on resistivity measurements

When conducting resistivity investigations over steeply dipping geologic structures, large orientational variations in resistivity response are commonly encountered. These variations can arise from resistivity contrasts between constituent layers or from anisotropy within the beds. When such structures are concealed, a thorough sampling of these orientational variations must be conducted. Field experience and model studies have shown that such sampling can be conveniently conducted using the crossed‐square array and that the orientational variations encountered can be adequately summarized by the anisotropically defined parameters of apparent resistivity, anisotropy, and strike derived from these array measurements.