Abstract
The probability of earthquake occurrence in the Niger Delta region of Nigeria was studied in this research. The resonant column/bender element tests were used for the study. Series of analysis were carried out on compacted silt in subsoil strata obtained from various locations in Rivers, Bayelsa, Delta and Akwa Ibom States. The effects of confinement on frequency, shear modulus, shear velocity and damping ratio were studied. The tests results revealed that confinement has effects on the investigated parameters. Thus, frequency response increases with increase in confinement pressure. Also, the resonance column test at various confinements revealed changes in shear modulus, accelerometer output and damping ratio. Accordingly, there was high disparity in the tested parameters as confinement pressure was increased. Similarly, the bender element tests also showed that pressure has effect on shear wave-velocity, shear modulus and damping ratio confinement. The shear modulus and shear wave-velocity generally increased as confinement pressure was increased, while damping ratio decreases as confinement pressure was increased. The variations in Resonance Column/Bender Element test parameters showed that the silty soil in the Niger Delta region, an oil and gas rich area, is likely to experience earthquake in the future. Therefore, geological data should be collated for monitoring, especially as several geological activities take place in the region.
Highlights
The management and analysis of earthquake activities have been proposed as a good technique for understanding the susceptibility of earthquake event (Hudyma and Potvin, 2010)
The Niger Delta region is characterized by tropical rain forest, with average annual rainfall from 2000mm within the fresh zone to over 4000mm at the coast that accounts for nearly 85% of the annual rainfall; the coastal and Angiospermous tree zones contain nearly 70% of marshes and swamps that occupy, which are sometimes submerged throughout the wet season (April to October)
The effects of confinement pressure on frequency, shear modulus Gmax, shear velocity and damping ratio Dmin of silt samples was studied in selected States of the Niger Delta region of Nigeria using the resonant column and bender elements (RC/bender Element (BE)) tests
Summary
The management and analysis of earthquake activities have been proposed as a good technique for understanding the susceptibility of earthquake event (Hudyma and Potvin, 2010). Establishing an understanding of spatial and temporal characteristics of seismicity is fundamental for the effective management of seismic risk (Hudyma and Potvin, 2010; Cho et al, 2010). Malek and Leslie (2006) suggested that the non-linear behaviour of rock mass failure is indicative of critical phenomena and is evidence of unstable conditions. This concept is discussed in detail by Mendecki and Lynch (2004), giving a theoretical basis for system excitability as a model of self-organized criticality. Other studies have shown that the spatial and temporal characteristics of mining-induced seismicity following large events are comparable to characteristics of earthquake main and aftershock responses (Hills and Penney, 2008; Kgarume et al, 2010; Vallejos and McKinnon, 2010)
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