Field evaluation of 3D geo-electrical resistivity imaging for environmental and engineering studies using parallel 2D profiles

Eight parallel two-dimensional (2D) geo-electrical resistivity profiles were generated in hard-rock (Pulivendla) area of Andhra Pradesh, India using a Lund imaging multi-electrode system adopting Wenner array. The aim of the survey was to experimentally evaluate the effectiveness of using parallel 2D profiles for three-dimensional (3D) geo-electrical resistivity imaging for better understanding of aquifer geometry and its characteristics. The observed 2D apparent resistivity data were independently inverted, and then collated to 3D data set. The inversion of the resulting 3D data set was carried out using a full 3D inversion code. The 3D inverse model of resistivity images obtained are presented as horizontal depth slices. The 2D images extracted from 3D inverse models showed no distortions that are observed in 2D models obtained by 2D inversion. The 3D inverse model resistivity appears to be more realistic, considering the hydrogeology of the area. The unusually high resistivity values observed in the 2D inverse models were not observed in the 3D inverse models. The very low near-surface inverse model resistivity observed is thought to be structurally influenced. The results, which are consistent with numerical evaluation, show that high resolution 3D geoelectrical resistivity imaging can be successfully conducted using parallel 2D profiles if appropriate survey parameters are carefully chosen.