Towards a National Seismic Velocity Model for Nigeria: Integration of Ambient Noise Tomography and Receiver Functions

Nigeria lacks a national three-dimensional seismic velocity model that could serve as a foundation for earthquake source parameter determination, ground motion prediction, and subsurface geological interpretation, with current practice relying on globally averaged one-dimensional reference models that introduce systematic errors in Nigerian seismological applications. This research constructs the first national-scale 3D seismic velocity model for Nigeria by combining ambient noise surface wave tomography and P-wave receiver function inversion using data from all available broadband seismograph stations in the country supplemented by a temporary deployment of 18 new stations in under-sampled regions. Ambient noise cross-correlation of continuous 2022 to 2025 waveforms from 46 stations produces Rayleigh and Love wave group and phase velocity dispersion measurements covering periods from 5 to 60 seconds. The dispersion measurements are inverted using a trans-dimensional Bayesian inversion to produce a 3D shear velocity model from the surface to 100 kilometres depth. Receiver function analysis at the 46 stations provides complementary Moho depth constraints that are jointly inverted with the surface wave dispersion to reduce trade-offs between crustal thickness and average crustal velocity. The resulting model reveals previously unresolved velocity contrasts between the Jos Plateau crystalline crust, the Benue Trough sedimentary fill, and the Niger Delta passive margin prism, with Moho depths varying from 25 kilometres in the delta to 42 kilometres beneath the Jos Plateau. The model is validated against travel time residuals from local and regional earthquakes. Keywords: ambient noise tomography, national velocity model, Nigeria, receiver function, shear velocity