P-wave tomography reveals a westward dipping low velocity zone beneath the Kenya Rift

Three teleseismic P-wave travel time data sets (KRISP 1985, 1989 - 1990; Kenya Broadband Seismic Experiment) have been inverted to obtain a new tomographic model of the upper mantle beneath the Kenya Rift. The model shows a 0.5 - 1.5% low velocity anomaly below the rift extending to about 150 km depth. Below similar to 150 km depth, the anomaly broadens to the west toward the Tanzania Craton, suggesting a westward dip to the structure. Tomographic images to the south in Tanzania and to the north in Ethiopia also show westward dipping low velocity anomalies below depths of similar to 150 - 200 km. The presence of westward dipping low velocity structures along much of the East African rift ( Ethiopia, Kenya and Tanzania) is difficult to explain with a plume model and is consistent with some models of the African Superplume showing anomalous lower and upper mantle structure connecting at mid-mantle depths under the western side of East Africa.