INVESTIGATION OF SUBSURFACE LITHOLOGIES IN UNIBEN AREA, EDO STATE USING 2D (ERT) ELECTRICAL RESISITIVITY TOMOGRAPHY METHOD

ABSTRACT

This project article entails the use of 2D Electrical Resistivity Tomography Survey (ERT) for the investigation/probing of subsurface lithology in UNIBEN AREA, EDO STATE. As it is known, the accurate characterization of subsurface lithology is crucial for various geotechnical, environmental, and engineering applications. In this study, the use of the 2D ERT survey involved the deployment of an array of electrodes along a survey line, where electrical currents were injected into the ground, and corresponding voltages were measured. The data further acquired from the ERT survey were then processed and inverted with a software (Res2dinv) to produce a 2D resistivity (tomogram) model of the subsurface. However, the data’s that were acquired, processed and interpreted generated results which suggested four (4) major lithologic layers in various study locations of which are : The topmost layer (topsoil) consisting of very little portions of sand, clay and clayey sand. Also, there is an observable large portion (about 80%) of an aquifer deposited in various regions which is marked by a green color, again the last layer interpreted as a fractured basement consisting majorly of very dry coarse sand marked by a red color zone which is of high resistivity. These sub-surface lithologies were made possible to delineate from their inferred resistivity values.