Dispersion of Surface Waves in Southern Africa from Inter-station Measurements

We measured Rayleigh and Love wave dispersion across southern Africa using a combination of cross-correlation and waveform inversion approaches. Phase-velocity averages between pairs of stations of the SASE array were obtained in period ranges of at least 5-200 s for Rayleigh and 5-50 s for Love waves. The new data confirm the thinning of the crust from the Limpopo Belt and northern Kaapvaal Craton towards the southern part of the craton, as observed perviously. A reduction in S-wave velocity at the bottom of the lithosphere at 150-200 km is required by the data both beneath the Kaapvaal Craton and the Limpopo Belt, although this reduction is less pronounced beneath the latter. The new data should also enable direct measurements of the depth of the lithosphere-asthenosphere boundary.