LITHOLOGY DISCRIMINATION USING SHEAR AND COMPRESSIONAL WAVES IN UYO AND ITS ENVIRON, SOUTHEASTERN NIGERIA
Journal: Malaysian Journal of Geosciences (MJG)
Author: Akaninyene O. Akankpo, Ubong E. Essien, Magnus U. Igboekwe
This is an open access article distributed under the Creative Commons Attribution License CC BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited
Compressional and shear wave velocities reveal vital information about the physical properties of rocks and their lithology contrast. In this study, we have applied the seismic refraction method to investigate the dynamic elastic modulus of subsurface layers in our study area. Electromagnetic geophones were firmly coupled to the ground to transform generated seismic energy at the source to electrical voltage which is a function of velocity. A total of twenty-seven P-wave refraction shootings were performed and measured P-wave velocity ranged from 218.00 ms-1 to 749.30 ms-1. The S-wave velocity obtained in the field ranged from 98.30 ms-1 to 340.70 ms-1. These values indicate that both layers 1 and 2 are weathered zones characterized by fine and lateritic sands which are capable of withstanding little or no mechanically related load or stress / pressure applied on the surface. In terms of Vp-Vs ratio, the first layer indicated a range of 2.2071 to 2.2183 with a mean value of 2.2108 for the area while the second layer produced a Vp-Vs ratio ranging from 2.1993 to 2.2055 with a mean value of 2.2023. The near constant Vp-Vs ratio of 2.2 obtained in the study shows a similarity in the formation grains in the shallow layers penetrated by the seismic waves.