Source Mechanisms of Mining-related Seismic Events in the Far West Rand, South Africa

The Far West Rand mining district is known for its deep gold mines and the associated high levels of seismic activity. Thousands of tremors are recorded every day by geophones installed in the mine workings. These events range in local magnitude ML from -1 to 4. Some of the biggest events (ML>3) are external to the network deployed on a single mine. We combined data from three mines (Savuka, Tautona and Mponeng) to improve the location of these events. Source mechanisms were calculated by minimizing the L2 norm of the difference between the observed and predicted P, SV and SH spectral amplitudes, with visually assigned polarities. The preliminary results from the Savuka mine show that the major principal stress is compressional, oriented near to the vertical, and with a significant isotropic component in the moment tensor solution.