Record broadband seismic data from teleseismic regional and local quakes that sample rifted Proterozoic and unrifted Archean lithosphere in East Africa. This will enable us to image upper mantle structure beneath both the Tanzania craton and the rifted mobile belts in order to examine deep continental structure as it evolves within a modem extensional regime. Determination of whether the Cenozoic extensional event which has clearly disrupted lithospheric structure beneath the Proterzoic mobile belts has similarly modified deep structure under the Tanzanian Craton has important implications for understanding the dynamic evolution of continental lithosphere.