Seismotectonics of South Africa

Abstract

Assessment of seismic hazard is challenging especially for low seismicity regions like southern Africa. There is very little knowledge in terms of the coupling between the seismicity and active faults leading to an incomplete dataset in terms of recurrence times and seismic zonation. Concerted efforts have been made to compile a seismotectonic map of South Africa that will assist in delineating seismic hotspots in order to carry out a proper seismic hazard assessment using state of the art methodologies. In preparing the map, a homogeneous earthquake catalogue was compiled from local, regional and international databases. Fault plane solutions and stress information were obtained from publications, reports and international organisations such as the ISC, USGS and Harvard CMT. Though few such data are available for South Africa, all collected information is vital in the effort to understand the tectonics and stress modelling of the region. Several faults have been identified as possibly active, though some of them have no significant seismicity associated with them. Through these efforts, a seismotectonic map of South Africa has now been prepared. It is hoped that the information in the seismotectonic map will contribute to the preparation of more accurate hazard assessments for South Africa. However, efforts continue to collect and improve collection methods of historical and instrumental seismicity data, as well as geological information to improve the available seismotectonic data for this region.