Reducing Ambiguity with Geoelectric Investigations: Implications for Near-Surface Cavities

Abstract

Aims: The purpose of this study include to evaluate the theoretical and practical aspects of the 1D and 2D resistivity data types, especially with respect to precision as they pertain to cavity depth investigation for site characterization in Ogbunike community, Southeastern Nigeria. Study Design: The results of geoelectrical survey carried out at the Ogbunike community, Southeastern Nigeria where underground cavities exist are presented and discussed. Place and Duration of Study: The study was carried out at Ogbunike community, Southeastern Nigeria and it lasted for about six months from November 2011 to April 2012. Methodology: The 1D and 2D electrical resistivity method using schlumberger array and dipole-dipole array respectively were applied in the course of the geophysical investigation of known and unknown cavities. Anomalous zones of the cavities were distinguishable by the zones with very high resistivity, surrounded by the lower background resistivity zones. Results: The 1D resistivity method revealed the depth to the subsurface cavities only while the 2D resistivity method gave a more precise definition of the size of the cavities including the width and depth to the target. From the results obtained, the 2D electrical method interprets depth to known cavity to be deeper than the actual depth while the 1D electrical method interprets the depth to known cavity to be less than the actual depth to the cavity. Also, from the results of the geoelectrical survey an unknown cave was detected.