[S07-P] Poster

[S07-P-06] The Probabilistic Seismic Hazard Assessment of South Africa

^○Vunganai Midzi^{1, 2}, Brassnavy Manzunzu¹, Thifhelimbilu Mulabisana¹, Brian Zulu^1,2, Tebogo Pule¹, Sinovuyo Myendeki¹, Ganesh Rathod¹ (1.Council for Geoscience, Pretoria, South Africa, 2.University of the Witwatersrand, Johannesburg, South Africa)

More than 10 years has passed since previous national seismic hazard maps were prepared for South Africa. In those maps, zone-less techniques were applied. The availability of more reliable seismicity and geological data has made it possible to update those maps using probabilistic assessments that take into consideration all available data. Presented in this report, is a summary of the work conducted to produce the latest hazard maps for South Africa. This involved the systematic compilation and homogenisation of an earthquake catalogue, which comprised both historical and instrumental events.Work conducted in another project IGCP-601 to prepare a seismotectonic map of Africa, contributed much to the preparation of a corresponding seismotectonic map of southern Africa. The map consisted of major faults including possibly active faults in the region, focal mechanisms and seismicity. This information was also used in the preparation of seismic source zones for the hazard assessment. Two GMPEs were identified from available international models for regions that are tectonically similar to South Africa. These two models were then implemented in the hazard calculations, which were done using the OPENQUAKE software. Uncertainties associated with input parameters in both the seismic source and ground motion models were taken into account and implemented using the logic tree technique. Maps showing distribution of acceleration at three periods (PGA, 0.15s and 2.0s) computed for 10% probability of exceedance in 50 years were produced. The maps showed a strong influence of source zones associated with mining activity on the hazard of the country. The same mining regions were also observed to have the highest hazard. These maps constitute a valuable product of this study that can be useful in the mitigation of earthquake risks in South Africa especially considering the growth of its cities and also the location of major cities close to areas of high hazard.