DETERMINATION OF THE WEATHERED REGOLITH USING SEISMIC REFRACTION METHOD IN PARTS OF KADUNA SOUTH INDUSTRIAL AREA, KADUNA NIGERIA.

Seismic refraction method of geophysical survey was carried out in parts of Kaduna South Industrial Area, Kaduna North-West Nigeria. Nine shooting points were taken at various points of interest using an ABEM instrument (MK 6 Seismograph) outside cultural interferences. The readings were taken at about 1 to 2km apart. Twelve channel geophones were laid from the shot point at 5m separations along the profile to pick up the seismic wave. Quantitative data interpretation of the travel-time was done using computer processing package. The no of layers, velocities and the thicknesses of unconsolidated material above the bedrock (Depth to bedrock) in the area of study were determined. Three to four layers were encountered, consisting of the Topsoil (Dark brown laterite, lateritic clay), (silty clay, orange brown laterite to kaolinitic clay and saturated sand), (Biotite and granite gneiss) and fractured/weathered basement rock. The average depth to the basement was found to be about 13m, the shallowest and deepest depth to the basement was found to be about 10m and 16m respectively. The qualitative interpretations in terms of layer velocities, thicknesses and histogram/frequencies plots were deduced and drawn. Seismic sections were compared with existing geology which showed a good degree of correlation. The second layer from the study area being mostly clay (1020-1630) m/s could cause differential settlement in foundations hence the need to remove it prior to foundation is of paramount importance.