Seismic Parameters of Mining-Induced Aftershock Sequences for Re-entry Protocol Development

Abstract

A common characteristic of deep mines in hard rock is induced seismicity. This results from stress changes and rock failure around mining excavations. Following large seismic events, there is an increase in the levels of seismicity, which gradually decay with time. Restricting access to areas of a mine for enough time to allow this decay of seismic events is the main approach in re-entry strategies. The statistical properties of aftershock sequences can be studied with three scaling relations: (1) Gutenberg– Richter frequency magnitude, (2) the modified Omori’s law (MOL) for the temporal decay, and (3) Ba˚th’s law for the magnitude of the largest aftershock. In this paper, these three scaling relations, in addition to the stochastic Reasenberg–Jones model are applied to study the characteristic parameters of 11 large magnitude mininginduced aftershock sequences in four mines in Ontario, Canada. To provide guidelines for re-entry protocol development, the dependence of the scaling relation parameters on the magnitude of the main event are studied. Some relations between the parameters and the magnitude of the main event are found. Using these relationships and the scaling relations, a space–time–magnitude re-entry protocol is developed. These findings provide a first approximation to concise and well-justified guidelines for re-entry protocol development applicable to the range of mining conditions found in Ontario, Canada.