Seismic Hazard Assessment of the Lake Chad Basin Region, Borno State

The Lake Chad Basin, spanning portions of Borno State in North East Nigeria, is traversed by reactivated Precambrian basement faults and Mesozoic rifts that represent potential seismic sources, yet the region's seismic hazard remains inadequately quantified in national risk assessments. This study undertakes a preliminary seismic hazard assessment of the Nigerian portion of the Lake Chad Basin, compiling an updated earthquake catalogue from national and global seismograph networks and evaluating historical seismicity patterns. The earthquake catalogue was assembled from the records of the Nigerian Meteorological Agency, United States Geological Survey, and International Seismological Centre, spanning a period of sixty years. Completeness of the catalogue was evaluated using Stepp's method and Gutenberg-Richter recurrence relationships were established for defined seismogenic zones. Attenuation relationships appropriate for cratonic and rift settings in West Africa were reviewed and applied in the hazard computation framework. Probabilistic seismic hazard analysis was conducted for a representative site in Maiduguri to derive peak ground acceleration and spectral acceleration values at ten percent and two percent probability of exceedance in fifty years. Results are compared against national building code seismic zone maps to evaluate their adequacy for North East Nigeria. Findings support evidence-based updates to the national seismic hazard zonation map. Keywords: seismic hazard, Lake Chad Basin, Borno State, Gutenberg-Richter, probabilistic assessment.