Interpretation of Geoelectric Pseudo Section and Seismic Refraction Tomography with Borehole Logs Carried out across a Functional Borehole at Garaje-Kagoro Area of Kaduna Northwestern Nigeria

Abstract

Electrical resistivity and Seismic refraction surveys were carried out
at Garaje Kagoro area of Kaduna State across a high yielding
borehole to characterize the subsurface structures responsible for
the high yield. Both the electrical resistivity method and the seismic
refraction method show that the borehole location is underlain by
four individual layers in agreement with the borehole log. The topsoil
with a resistivity range of 50-140Ωm constitutes of wet brown sand
and sandy clay which correlates well with the borehole log. The
weathered basement which is the second layer constitutes of
coarse/medium grain sand which correlates well with the borehole
log. The resistivity value of the weathered basement layer ranges
from 100-250Ωm. The depth to basement varies along the profile;
however, averagely it is about 65m. Generally, the geophysical
results revealed that the high yielding aquifer is a heterogeneous
unconfined aquifer with a good yielding potential which have thick
overburden deposition of fine-medium coarse grain sands. The
electrical resistivity method show that the resistivity values of
individual layers increases with depth. The seismic refraction method
show that the velocity of individual layers increases with depth.