Transformation of a stick-slip mode of fault behavior into a stable sliding in the laboratory tests at the spring-block model

Abstract:

Results of laboratory tests are presented, when regularities of gradual transition from the stick-slip sliding to aseismic creep on an interface between movable and fixed blocks of the spring-block model were studied. The primary result of the research is experimental proof of that the small variations of material composition of the main fault zone may lead to significant change of portion of energy radiated during dynamic discharge of adjacent section of rock massif.

The tests reproduce modes of inter-block sliding with the values of reduced kinetic energy varying by many orders at relatively small differences in the strength of contacts and amplitudes of the shear stress drop. In all tests a mode of the contact velocity weakening was observed, i.e. the necessary condition of occurrence of the stick-slip sliding was met, however, different ratios between the fracture stiffness and the stiffness of loading provided a possibility of realization of different modes of deformation. 

The carried out laboratory experiments allow to propose one of the possible mechanisms, which controls over wide limits the portion of energy radiated as a result of slip on the earth crust discontinuity. Such a mechanism may be a drastic decrease of shear stiffness of individual sections of the fault zone as a result of another, in comparison with adjacent fault sections or faults, material composition of the main fault plane, sublithostatic level of fluid pore pressure, and other mechanical, geological, and geochemical processes. In this case a possibility of smooth enough variation of mentioned parameters in time and space points to that the hypothesis proposed in [Peng, Gomberg, 2010] about unified nature of all modes of sliding on the faults, which form a permanent series of events, most likely is correct.

The reported study was supported by RSF, research project #14-17-00719.