Can mine tremors be predicted? Observational studies of earthquake nucleation, triggering and rupture in South African mines

Abstract

Mining-induced earthquakes pose a risk to workers in deep mines, while natural earthquakes pose a risk to people living close to plate boundaries and even in stable continental regions. A five-year ca. US$3 million Japan-SA collaborative project "Observational studies to mitigate seismic risks in mines" was launched in August 2010. The project has three main aims: (1) to learn more about earthquake preparation and triggering mechanisms by deploying arrays of sensitive instruments in mines where mining-related stresses are likely to induce significant seismic activity; (2) to learn more about earthquake rupture and damage phenomena by deploying strong ground motion sensors close to potential rupture zones and on the walls of stopes; and (3) to upgrade the South African national surface seismic network in the mining districts. Acoustic emission sensors, accelerometers, strainmeters, and controlled seismic sources are being installed at sites in Ezulwini, Moab-Khotsong and Driefontein gold mines to monitor the deformation of the rock mass, the accumulation of damage during the earthquake preparation phase, and dynamic stress as the rupture front propagates. These data will be integrated with measurements of stress, stope closure, stope strong motion, and seismic data recorded by the mine-wide network. Here we describe the design of experiments that seek to identify reliable precursors of damaging seismic events.