Seismic Refraction Profiling For Groundwater in a Basement Terrain: The Case of Akamkpa, Southeast Nigeria.

Abstract

Weathering induces secondary porosity on (otherwise) crystalline basement rocks; forming a wide range of regolith. Groundwater accumulates at the base of this regolith and the thicker the regolith, the higher the possibility of locating groundwater occurrence. Nine (9) seismic refraction profiles were survey using the hammer-plate striking system in various parts of Akamkpa with the intent of locating aquifers. The interpretation of the time – distance graph reveal a typical two layer model. The top layer, with mean seismic velocity of 931m/s with thickness between 3.39m and 19.23m from the surface is within the range of velocities for loose and porous material whereas, the lower layer with mean seismic velocity of 2284m/s compares well with those of fissured to fresh (transitional) basement rocks. This shows that the weathered overburden material of the basement complex is thick enough (3.39 – 18.23m) to support shallow to medium depth borehole development in the area.

Keywords: Basement, Porosity, Regolith, Seismic Velocity, Weathering.