Statistical properties of mine tremor aftershocks

Abstract

Mine tremors and their aftershocks pose a risk to mine workers in the deep gold mines of South Africa. The statistical properties of mine-tremor aftershocks were investigated as part of an endeavour to assess the hazard and manage the risk. Data from two gold mines in the Carletonville mining district were used in the analysis. Main shocks were aligned in space and time and the aftershock sequences stacked and analysed. The aftershocks were found to satisfy Gutenberg–Richter scaling, with a b value close to 1. Aftershock activity diminished with time in accordance with the modified Omori law, with p values close to 1. However, the relationship between the main shock and its biggest aftershock violated Ba°ths law, with DML & 1.9 for main shocks with ML\3 and increasing for main shocks with ML[3. The aftershock density was found to fall-off with distance as r-1.3, suggesting triggering by dynamic stress