Geophysical processes and biosphere: article

Аnnotation: The subject of the research is the dynamic movements along large faults initiated by industrial activity - «the fault-slip rock bursts». As a rule, focuses of such events are located at appreciable distances from the fronts of ongoing mining operations and at depths of several kilometers. In addition to the recognized types of trigger effects, such as fluid injection or seismic vibrations, the paper discusses the possible trigger effect of rock extraction and displacement during mining. The paper shows that a dynamic sliding can be initiated only on those faults, for which three geomechanical conditions for the occurrence of instability are fulfilled: (i) closeness of the Coulomb stresses on the fault plane to the local strength limit; (ii) the condition of weakening frictional contact with increasing sliding speed and relative movement of fault sides; (iii) realization of a certain ratio between the stiffness of the enclosing rock and the rate of reduction of the resistance to friction. Features of formation of a dynamic slip along a fault were considered in the series of laboratory and numerical experiments. As a result, it is shown that the rupture always begins in the section with the property of velocity weakening, regardless of the location of such a section relative to the direction of load application. With the help of analytical and numerical calculations, it became possible to demonstrate that excavation of rock in a large mining quarry leads to a change of about 1 MPa in the Coulomb stresses on fault plane in such areas that significantly exceed the size of the nucleation zone of earthquakes with M ≤ 6. This may turn to be enough to initiate seismogenic slips along stressed faults.