Interpretation of resistivity data using 3D Euler deconvolution and Radially Averaged Power Spectrum

Abstract

Different electrode configuration in resistivity measurements over the same geologic structures generally produce different anomaly patterns. This is related to the position of the structure concerning the electrodes. Given the above, a unified approach has been proposed using the concept of analytical signal to interpret the resistivity data as electric potential follows Laplace’s equation. We interpret the data sets using Euler deconvolution and Radially Averaged Power Spectrum (RAPS) to determine both lithological boundaries and units and compare the results with inverted resistivity section. We analysed the resistivity data using electrical resistivity tomography (ERT) technique over conducting dyke and vertical fault for Wenner and dipole–dipole arrays, respectively. The obtained structural indices for dyke and fault are 1.0 and 0.6, respectively. The results from Euler depth solutions match well with the inverted resistivity section. Subsequently, two field examples one each over ground water and mineral exploration were analysed. The delineated lineaments over ground water exploration matches fairly well with the available results. In addition, some additional lineaments are also mapped. These new features could be a zone of interest for a detailed survey. The depths from Euler depth solutions and RAPS are in agreement. However, no depth information was available earlier. The data for mineral exploration have been acquired by ERT technique with a profile length of ~500 m over Dhanjori Basin, Jharkhand, India. The Euler depth solution and RAPS indicated the presence of two interfaces at an average depth of 8 and 20 m and 7 and 21 m, respectively. The first interface is present all along the profile, whereas the second interface lies between a part of the profile. The location and depth of these are in broad agreement with the resistivity sections obtained from ERT/AMT and borehole data. A borehole in the vicinity of the survey area indicated the presence of two interfaces. The first interface coincides with the soil depth and the second interface coincides with the sulphide mineralization.