Systematic multi-technique mapping of the Southern flank of Iwaraja fault

Abstract

A geophysical study of Iwaraja segment of Ifewara-Zungeru fault zone in Nigeria was conducted using remote sensing and geoelectric techniques to analyse and identify the structural elements and fractures. The Omo Forest Reserve area, Abata Egba (along Ondo-Ife highway), and Iwaraja fault zones were selected for the study. Wenner electrode profiling was undertaken at electrode separations of 10, 20 and 30 m on diplines perpendicul-ar to trend of the fault, while Schlumberger electrode configuration was adopted for vertical electrical sounding on points delineated by resistivity profiles. At Omo Forest Reserve, 3 fault signatures of falling resistivity profi-les in uniformly high resistivity environment were identified. Deep fracturing manifested in consistently decrea-sing resistivity values at large electrode separations. At Olode area, 4 signatures were identified. The profiles at Iwaraja area showed the net resistivity decreased in Western direction. The overburden materials were variably thick and underlain by bedrock that had been partially weathered and fractured, but were not infinitely resistive as usually observed in crystalline Precambrian basement complex environment. The study area was characteriz-ed by a series of faults, which were oriented in the North North East - South South West ((NNE-SSW) directio-ns, and inclined towards the East.