Broad-band seismic studies in southern Africa

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