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Due to the advancement in technology being applied in geophysics, it is of importance that a geophysical test site center is established for calibration, training, and demonstration of such equipment. An integrated geophysical survey of the area has been conducted, with the aim of characterizing the subsurface structures and lithology. Thereafter, different types of objects that respond to all geophysical techniques will be buried at different depths in the site. Seismic refraction and electrical resistivity tomography were used, using the seistronix RAS 24 seismograph and SAS 4000 ABEM Terameter equipment. These two survey methods were adopted due to the pictorial image they give of the subsurface, enabling a clear view of subsurface structures. A total of five profiles were taken at a total length of 300 m and an inter-profile spacing of 45 m. The results of this survey in correlation with borehole data revealed three distinct layers; overburden, weathered and fresh basement. The overburden consists of the topsoil and lateritic clay, averaging a depth of 3 to 6 m and having a seismic velocity of 100 to 700 m/s and resistivity range of 370 to 750 Ωm. Underneath the overburden is the weathered basement, consisting of brownish fine to medium grained coarse sand, gravel and some disintegrated schistose material, averaging a depth of 6 to 30 m and having a seismic velocity of 700 to 2100 m/s and resistivity range of 56 to 370 Ωm. The depth to the third layer (fresh basement) suggested less compact subsurface of depth >45 m. A close examination of the velocities with depth shows higher velocities at deeper depths (2100 to 3200 m/s) and resistivity > 1500 Ωm.

global journal of earth and environmental science

Two-dimensional image of seismic refraction tomography and electrical resistivity tomography survey in a proposed geophysical test site at Shika, Ahmadu Bello University Zaria, Nigeria