Assessment of Seismic Site Response and Liquefaction Potential for Seismic Site Classification in the Niger Delta Region

Abstract A comprehensive seismic site characterization of Igbogene in the Niger Delta region of Nigeria was conducted to evaluate the site response and liquefaction potential. Field investigations included borehole drilling, Standard Penetration Testing (SPT), and Multi-Channel Analysis of Surface Waves (MASW) testing to obtain soil samples and characterize subsurface properties. Laboratory tests determined soil classification, index properties, density, and geotechnical parameters per ASTM standards. Mathematical correlations were developed through regression modelling to estimate SPT N-values, shear wave velocity (Vs), and liquefaction and safety factor factor based on soil depth, composition, moisture content, and effective stress. The correlations demonstrated strong agreement with measured field and laboratory data, outperforming existing empirical models. Subsurface conditions comprised predominantly loose to dense silty sands and soft compressible clays within the upper 30 m. Shear wave velocity profiles matched closely with the developed velocity correlation, averaging 5.2% error. Site response analyses and simplified liquefaction evaluations were conducted to assess seismic hazards. The results showed amplification factors ranging from 1.5 to over 3 for the loose sandy soils, demonstrating their ability to significantly amplify ground shaking. Liquefaction potential maps were generated based on spatial variations in geologic conditions. This comprehensive site characterization provided reliable input for seismic microzonation and geotechnical earthquake engineering design as per international codes. This study's results can aid in stimulating infrastructure resilience against seismic activity throughout the Niger Delta region.