Integrated Satellite Geodesy and Geophysical Modelling of Active Deformation in the Lake Chad Basin, North East Nigeria

The Lake Chad Basin is one of Africa's most dynamic geomorphological systems, experiencing the interaction of active tectonic deformation in the West African Rift System, compaction of unconsolidated Quaternary sediments under changing groundwater head conditions, and aeolian and hydrological modifications to the land surface, all of which produce complex patterns of ground displacement detectable by space geodetic methods. This research develops an integrated framework combining Interferometric SAR time-series analysis with geophysical modelling of tectonic, hydrological, and sediment compaction deformation sources to decompose observed surface displacement fields in the Nigerian Chad Basin. A ten-year Sentinel-1 SAR archive covering Borno, Yobe, and Adamawa states is processed using the Small Baseline Subset method to produce spatially continuous mean velocity maps and displacement time-series at approximately 80-metre resolution. The observed displacement field is decomposed into contributions from viscoelastic postseismic relaxation following the 2012 MW 5.3 Maiduguri earthquake sequence, elastic groundwater withdrawal deformation modelled using a Mogi source framework, and non-linear compaction of Chad Formation clay layers quantified using a one-dimensional consolidation model calibrated to borehole clay thickness data. Residual velocities after model subtraction identify two previously unrecognised zones of anomalous uplift in the Bama Ridge area, tentatively attributed to deep igneous intrusion. The research establishes the first geophysically decomposed deformation model for the Nigerian Chad Basin, with implications for earthquake hazard, groundwater management, and infrastructure design. Keywords: InSAR, active deformation, Lake Chad Basin, geodesy, geodynamics