On the Initiation of Dynamic Slips on Faults by Man-Made Impacts

Аннотация

The subject of research is dynamic slips on large faults initiated by man-made impacts. In addition to recognized types of man-made impacts such as fluid injection or seismic vibrations, the possible trigger effect of rock extraction and displacement during mining operations is considered. It is shown that dynamic sliding can be initiated only on faults in which three geomechanical conditions for the occurrence of instability are fulfilled: closeness of the value of Coulomb stresses in the fault plane to the local ultimate tensile strength; the condition of weakening of frictional contact with an increasing sliding velocity and relative movement of fault sides; and the implementation of a certain ratio between the stiffness of the enclosing massif and the rate of reduction of resistance to friction. Features of formation of a dynamic slip on a fault are considered in the series of laboratory and numerical experiments. It is shown that the movement always begins in the segment with the property of velocity weakening, regardless of the location of such a segment relative to the load application. According to the calculations, the excavation of rock in a large mining quarry leads to a change of about 1 MPa in the Coulomb stresses in the fault plane in areas that significantly exceed the size of the nucleation zone of earthquakes with \(M \leqslant 6\). This may turn out to be sufficient to initiate seismogenic slips on stressed faults.