Most of the recorded seismic activity in South Africa is induced by mining operation. Seismograms of rockbursts show well developed Rg waves, with the fundamental mode propagating at 3.1 km/s. Some records also display clear group velocity dispersion. Recognition of Rg waves on the seismograms indicates that the event has a shallow focal depth (0-5 km), and the large amplitudes and dispersion imply a heterogeneous crustal structure. Studies of the analytical attenuation of Rg waves in South Africa yield a specific quality factor, Q, of 195, which is much lower than the value of 495 obtained using coda waves. This discrepancy can be explained by the presence of a low-velocity upper-crustal layer and, hence, supports previous suggestions of a heterogeneous crust. Analysis of Rg waves therefore gives information on local crustal structure and may also, in some cases, provide a discriminator between rockbursts and earthquakes.
ASJC Scopus subject areas
- Earth-Surface Processes