Recent research in earth structure, earthquake and mine seismology, and seismic hazard evaluation in South Africa

Abstract

Research in earth structure, earthquake and mine seismology, and seismic hazard evaluation in South Africa is summarized for the last four years. Improvements to the South African National Seismograph Network (SANSN) include the gradual replacement of short-period by broad-band instruments. New regional travel-time curves for P and S waves, and models of the structure of the crust and mantle beneath southern Africa to depths of 800 km, have been constructed by South African seismologists using earthquake data recorded by the temporary Kaapvaal broad-band seismic network and SANSN. A significant increase in crustal thickness of about 10km was also identified between the southern part of the Kaapvaal craton and the northern region affected by the Bushveld magmatism. The Kaapvaal network has also been used to relocate mine tremors and tectonic earthquakes in South Africa to compare its location capability with SANSN. In mine seismology, research has focused on the understanding of rock behaviour in response to deep mining activities, assessment of seismic risk, prediction of seismicity, and controlling rock burst damage. A major emphasis has been on the integration of numerical modelling and seismicity. Developments in probabilistic seismic hazard analysis have emphasized improved estimates of the maximum regional magnitude, of peak ground acceleration attenuation values, and on providing uncertainties in model parameters.