Dynamic Response of Soils Influenced by Seismic Activities

Abstract The study investigated the dynamic soil properties of Delta and Akwa Ibom States in Niger Delta region of Nigeria as a function of seismic activities. The down-hole seismic test was used to determine the response of the soils. The results showed that young modulus increases with increase in depth, which ranged from 2817.5 to 3178.27kPa across the sites at depth of 30m. Also, shear wave velocity generally increases with increase in depth. The shear wave velocity results obtained from the experiment across the sites ranged from 130-283m/s, 139-262m/s,141-247m/s, 128-261m/s and 124-289m/s for Ikot Abasi, Ibagwa, Ibiaku Offot, Aboh and Afor Ogbodigbo respectively. Like the shear wave velocity, P-wave velocity generally increases with increase in depth, which is over twice the values of shear wave velocity. The P-wave velocity ranged from 326-676m/s across the sites. The void ratio was observed to be constant at certain range of depth in the soil strata, and in most cases, it does not increase correspondingly with depth. The void ratio results ranged from 0.655-0.813, 0.652-0.805, 0.664-0.794, 0.65-0.82 and 0.651-0.798 for Ikot Abasi, Ibagwa, Ibiaku Offot, Aboh and Afor Ogbodigbo sites respectively. Unlike void ratio, Poisson’s ratio fluctuates with depth, with values ranging from 0.249-0.353, 0.253-0.351, 0.308-0.357, 0.254-0.371 and 0.241-0.370 for Ikot Abasi, Ibagwa, Ibiaku Offot, Aboh and Afor Ogbodigbo sites respectively. Based on the observations on the dynamic response of the soils, the Niger Delta region, being an oil hub center, is susceptible to earthquake, which could be triggered with time if over stressed by heavy load and seismic activities.