Development of an Original Seismic Hazard Model for the Benue Trough and Middle Belt Region of Nigeria

The Benue Trough and Middle Belt region of Nigeria has experienced moderate-intensity earthquakes historically, and infrastructure in the region is designed without explicit seismic hazard quantification, creating unassessed structural risk. This study develops an original probabilistic seismic hazard model for the Benue Trough and Middle Belt region using a comprehensive re-evaluation of the regional seismotectonic framework. The study constructs an original Nigerian earthquake catalogue from 1900 to 2023, systematically compiling and magnitude-homogenising records from international seismological networks, historical reports, and new instrumental data from a six-station seismograph network deployed across the study area during the research period. Seismotectonic source zone models are developed through integration of the earthquake catalogue with geological fault mapping, satellite SAR interferometry, and focal mechanism analysis. Ground motion prediction equations from Africa and globally applicable models are evaluated against the limited Nigerian strong motion database. Hazard is computed using the OpenQuake engine under three seismotectonic model branches with logic tree uncertainty treatment. The spatial distribution of peak ground acceleration at 475-year and 2475-year return periods is mapped at 10 km grid resolution. Results indicate maximum PGA of 0.08g at the 475-year level and 0.14g at the 2475-year level in highest-hazard zones near the Jos Plateau escarpment. The study provides the first probabilistic seismic hazard model for the Benue Trough region, enabling seismic provisions to be introduced to building codes for the zone.

Keywords: probabilistic seismic hazard, Benue Trough, Middle Belt Nigeria, earthquake catalogue, ground motion