BROAD-BAND SEISMIC STUDIES IN SOUTHERN AFRICA

This report summarizes the recent work of scientists involved with bro ad-band seismic studies in South Africa. Eight portable broad-band sei smic stations were deployed throughout the Archaean Kaapvaal Craton fo r a period of eighteen months to assist in defining lateral variations in the underlying crust and upper mantle. The studies undertaken comp rised: spectral ratio analysis, delay time modelling waveform inversio n, shear-wave splitting, and mantle converted phases. All the data obt ained during the broad-band lithospheric project clearly indicate that within the Kaapvaal Craton there are major geological features sugges ting that the craton is not a homogeneous entity. The large-scale feat ures of the western portion of the craton show anomalous deep structur es, different from any structures that have yet been reported in areas of Archaean age.