Abstract:
Seismic refraction shooting and Electrical resistivity depth sounding have been carried out at Igbogbo (Ikorodu area, Southwest Nigeria) to determine the structural setting of the subsurface materials and groundwater potential.
A total of eighteen vertical electrical sounding using the schlumberger array of 500m maximum spread and twenty-seven seismic refraction data using forward and reverse shooting methods of lateral distance 42m along each profile were acquired within the study area.
The results indicate the presence of three seismic refraction layers with the first layer having velocity 150-366m/s and thickness 1.0-3.3m, representing topsoil. The second refraction layer is composed of lateritic clay with thickness 4.5-10.5m and velocity 578-878m/s. The third refraction layer consists of sandy clay with velocity 1000- 2500m/s. The delineated refraction layers are characterized by increase in velocity with depth. The geoelectric sounding clearly show that the subsurface layers are characterized by topsoil, laterite, sandy clay, clayey sand, sand and clay with sand acting as aquifer units. The two thick aquifer units mapped are capable of sustainable industrial development in the area.
The seismic refraction shooting was able to delineate three layers because of the energy source used which is consistent with the first three layers in geoelectric sounding. To attain deeper depths of penetration using seismic refraction method, a stronger energy source is recommended.
