Assessment and Characterization of Site Response Parameters in the Lower Benue Trough of Nigeria using HVSR Microtremor measurements

Abstract

The aim of this study therefore, is to estimate site response parameters namely: predominant frequency (fr), amplification factor (Ao), vulnerability index (Kg) and average Shear-wave Velocity (V ), to assist in seismic site S classification in the Lower Benue Trough (LBT), Nigeria. The noise data used were collected from seismic stations in Nigeria and seismic noise acquired randomly in parts of LBT. Secondly, known values of sediment thickness were acquired from boreholes and publications within the LBT. The data were screened to remove earthquakes and other trends, like instrument response. The soil response parameters were determined using the horizontal-to-vertical ratio (HVSR) method. The results of Fr and V range from 0.1Hz to 9.0 Hz and 598m/s to 4368m/s; and known data on S sediment thickness range from 100m to 1410m. The Vs and kg beneath Ife, Nsukka, Awka and Abakaliki stations were computed to be 288m/s, 1019m/s, 940.6m/s, 255.02m/s and 15, 38, 39, 34 respectively. The values of Fr, Vs and h are indicative of the presence of soft, stiff soil, very dense soil, soft rock and hard rock profiles. High Ao and kg values in parts of LBT indicate high probability of ground deformation and vulnerability index to structures if an earthquake occurs in the area. However, further site studies are encouraged for comprehensive soil classification. Apart from the site response parameters computed to estimate the earthquake hazards potential in the region covered, a model for future determination of sediments' thicknesses was also developed in this research.

Publication Info:

Author: Kadiri, A.U , Ezomo, F.O. , Osahon, O.D. , Isogun, A.M. and Muhammed, H.A.

Volume: 57

Issue: September

Published By: Journal of Mining and Geology, 2024-09-01