Geophysical Characterisation of the Benue Rift System Using Teleseismic Receiver Function Analysis

The Benue Trough is interpreted as a failed rift arm of the South Atlantic opening, yet its crustal thickness and lithospheric structure are poorly constrained by seismic methods compared to the main Atlantic rift basins, limiting understanding of rift initiation processes in the West African Precambrian craton. This study analyses teleseismic P-wave receiver functions recorded at seven broadband seismic stations of the AfricaArray network in Nigeria to determine crustal thickness and Vp/Vs ratio beneath the Benue Trough and flanking basement provinces. Teleseismic P-wave records from earthquakes with magnitudes exceeding 5.8 at epicentral distances of 30 to 90 degrees were selected from three years of continuous recording. Receiver functions were computed using the iterative deconvolution method and stacked using the H-kappa grid search technique to estimate Moho depth and Vp/Vs ratio. Results show that crustal thickness beneath the Benue Trough ranges from 28 to 34 kilometres, significantly thinner than the 38 to 44 kilometres observed beneath the flanking Jos Plateau and Cameroon Highlands. The Vp/Vs ratio of 1.78 to 1.82 beneath the trough suggests an intermediate to mafic crustal composition consistent with rift-related mafic underplating or intrusion. The Moho shallowing beneath the trough is consistent with crustal thinning during Cretaceous rifting, and the elevated Vp/Vs ratio indicates that partial basaltic underplating accompanied the rifting episode. The results provide quantitative constraints for geodynamic modelling of the Benue rift system. Keywords: receiver function, crustal structure, Benue Trough, Moho, rift system