Numerical analysis of ground motion in a South African mine using SPECFEM3D

Abstract

Intensive seismicity was often observed in the front of tabular stopes in South African gold mines. The seismicity was usually caused by high stress concentration due to excavation, and some of the seismic events were fault rupture events. This study focuses on numerical modelling of seismic wave propagation resulted from a moment magnitude Mw = 1.4 seismic event occurring on 9 July 1996 at Mponeng mine in South Africa, using an advanced numerical tool called SPECFEM3D. Both point and non-point source models are considered and ground motions along a haulage tunnel at a depth of 2,650 m are analysed and compared with field monitoring data. It is found that the non-point source model produces better results than the point source model in near-source field. The haulage tunnel and the mined-out areas have a large influence on the ground motions. In the modelling results, strong ground motion localisation is observed at certain areas of the haulage tunnel and in the mined-out areas. Most of the simulated seismograms agree with the field recorded ones. It is seen that SPECFEM3D is a useful tool for modelling seismic wave propagation in underground mines.