The Structure on the Western Flank of the Gregory Rift (Kenya). Part I. The Crust

Durham University's seismic array at Kaptagat was set up on the western flank of the Kenya Rift. Analysis of the first arrivals of local and regional earthquakes recorded at the array has provided a crustal model across the Rift margin. It is concluded that a steep structural boundary separates normal shield crust and sub-Moho material beneath the western flank of the Gregory Rift from a mantle derived crustal intrusion beneath the Rift axis. A detailed model of the shield crust is presented and an indication is given of the complex structure which probably exists beneath the Rift itself.