FRACTURE DELINEATION AND CHARACTERIZATION FOR GROUNDWATER STUDY USING AZIMUTHAL RESISTIVITY SURVEY: CASE STUDY OF PART OF UNIVERSITY OF ILORIN, SOUTHWESTERN, NIGERIA

Abstract

The usefulness of electrical resistivity anisotropy in rocks for improved geological mapping using electrical resistivity
survey could not be over emphasized. Electrical resistivity survey was employed in delineation and characterization
of the subsurface fractures within the migmatite and granite-gneiss rocks in a part of University of Ilorin, Nigeria.
Sixteen radial vertical electrical soundings were analyzed with the aim of using electrical resistivity anisotropy
properties to unravel the studied area geology or for groundwater exploration. Azimuthal resistivity soundings (ARS)
was carried out at four locations and at different distances. Four of such distances were analyzed, making a total of
sixteen points. Interpretations were both qualitative and quantitative involving radial plots, intensities of fracturing
and computer iterations. Electrical resistivity anisotropy is inherent in this area as observed from the electrical
resistivity data. The rose plot shows the preponderance of fractures in the N-S direction while the acquired data showed
the predominance of fractures in the N-S followed by the NE-SW and then the NW-SE directions which agree with
the geology of the study area and corroborate the fact that basement complex terrain of southwestern Nigeria is
characterized by NE-SW and NW-SE lineaments which cut across the earlier Pan-African structures. Result from this
study shows a fracture system that connote the study area as a reliable groundwater potential site. This is key to
sustainable groundwater resources and further planning in this environment.