Application of Seismic Methods in Civil Engineering Projects in South East Nigeria

This study examines the professional application of seismic geophysical methods in civil engineering projects in South East Nigeria, documenting case studies and evaluating the value added by seismic investigations to project outcomes. The South East's Cretaceous-Paleocene sedimentary terrain and deeply weathered basement complex create variable foundation conditions that benefit significantly from seismic characterisation. This study compiles and analyses 20 civil engineering geophysical survey projects conducted in Anambra, Enugu, Imo, Abia, and Ebonyi States from 2020 to 2023, covering bridge foundations, road construction, dam sites, and building developments. For each project, the seismic method deployed (MASW, seismic refraction, or seismic reflection), survey objectives, data quality, interpretation accuracy, and influence on engineering decisions are assessed. Post-construction performance data where available are used to validate geophysical predictions. Findings reveal that seismic refraction is the most commonly applied method, used in 14 of 20 projects, primarily for depth to competent bedrock estimation. MASW is used in 9 projects for shear wave velocity profiling. Multi-method surveys are used in only 6 projects despite evidence that combined seismic and resistivity investigations improve characterisation accuracy. Geophysical recommendations are fully implemented in engineering design in only 65 percent of projects, with budget constraints and scepticism from some structural engineers identified as barriers. The study concludes that professional development of structural engineers in geophysical method interpretation would improve the utilisation of geophysical investigations in the region. It recommends joint geophysicist-engineer training workshops.

Keywords: seismic methods, civil engineering geophysics, South East Nigeria, MASW, engineering site investigation.