f Seismic Structure of Southern Africa: New Constraints from Surface Waves

Continental-scale seismic tomography shows the lithospheric keels beneath the cratons of Africa as pronounced high-velocity anomalies, bottoming at depths of up to about 200 km. A pronounced sub-cratonic low-velocity zone is observed only in Tanzania, where it is neighboured by volcanic areas and may be showing hot material—possibly of mantle-plume origin—trapped or spreading beneath the thick cratonic lithosphere. Regional-scale, surface-wave array analysis in South Africa shows variations in lithospheric structure across the Kaapvaal Craton and the Limpopo Belt. A reduction in S-velocity at the bottom of the lithosphere (150-200 km depths) is required by the data both beneath the Kaapvaal Craton and the Limpopo Belt, being less pronounced beneath the latter.