Deterministic properties of mine tremor aftershocks

Abstract

Mine tremor aftershock sequences from two deep mines in the Far West Rand goldfield, South Africa, were analysed in order to determine the influence of geological and mining parameters on the risk posed by aftershocks. Mainshocks were stacked in time and space and the aftershock productivity was calculated for various subsets. Contrary to our working hypothesis, no significant differences were found between the aftershock productivity of mainshocks located in high stress areas and those located in low stress areas, or between mainshocks located in high strain-rate areas and those located in low strain-rate areas, or between mainshocks located near to geological features and those located further away from geological features. Thus, while the incidence of mainshocks may be affected by stress, strain rate and proximity of geological features, these factors do not have significant influence on aftershock productivity. Consequently, guidelines governing the time period and distance from the mainshock in which hazard is considered to be elevated need not take variations in these geological and mining parameters into account.