Initiation of Tectonic Earthquakes Caused by Surface Mining

Resumo

The influence of surface mining on the initiation of large seismic event is considered. The conditions of shearing-type dynamic events are described. A surface mine with the similar parameters as the Bachatsky open pit mine in Kuzbass is adduced as an example for quantifying the mining-induced change in the stress state in the plane of a future rupture as a result of an induced tectonic earthquake nearby a fault plane is quantified. The calculations are performed for different geometrical parameters of the fault zone: the changes are more observable in the zones of gently dipping thrust faulting and less appreciable in the area of steep normal faulting and strike-slip. In case of large surface mines, the zone of positive change in the Coulomb stresses higher than several tenths mega pascals has a considerable dimension and an area markedly larger than the area of nucleation zone of earthquakes of the magnitude M ≤ 6. In such conditions, even a small variability at the level of first percentage points of the natural stresses can be sufficient for the initiation of seismicity-generating shearing along the high-stress faults. It is found that, as against underground mining, the surface mining activities have no influence on localization of large earthquake sources but can draw the event nearer.