Mining Activities and the Spatial-Temporal Variations of Earthquakes in Southern Africa

Abstract

Spatial-temporal variations in earthquake occurrence have been studied in many regions of the world but little can be said about the Southern Africa Region in this regard. Using earthquakes of magnitudes greater than or equal to one together with the FORTRAN language and Generic Mapping Tools (GMT), spatial variations of earthquakes spanning the period 1966 to 2014 were examined for the region. Similarly, the temporal variations with earthquakes of magnitudes greater than or equal to four were studied. The spatial analysis showed that the highest number of events (1438) in the period occurred at an average depth
of around 7.5 km representing approximately 79.9 % of the total earthquakes considered. The temporal distribution of events on the other hand showed that the highest number of events (590) were recorded in the year 1993. Three main issues were identified as potential factors responsible for the observed variations. Activities such as mining and failures in weak zones of the rock mass as well as increase in the number of stations were identified as the key factors responsible for the observed distributions. The third factor could not be independently verified. However, earlier studies suggest that this factor indeed have caused major earthquakes in the region.