Deformation characteristics of strike-slip fault zones

A theoretical study of the temporal variation and spatial distribution of deformation characteristics in tectonic zones of such structures as the San Andreas fault in California was carried out. The fault is modeled by a rupture in the crust subjected to gravitational lithostatic pressure and constant tectonic compressional and shear stresses. Scenarios of the deformation process are classified in accordance with the level of tectonic stresses, frictional forces on the fault, and resistance to fracture. The cases of regional deformation and creep are examined. A focus is placed on the process of seismotectonic deformation. A relationship between the temporal variation of deformations, on the one hand, and faulting and seismicity, on the other, is discussed. In fact, this relationship characterizes various aspects of the general fracturing process in the medium. It is noted that, in order to construct an adequate deformation model of the seismotectonic process, one should know either the temporal variation of the faulting process or the law of seismicity migration. These aspects of the fracturing process are assumed to be known [Molchanov, 1993] and provide the basis for determining deformations. Temporal variations of displacements and shear strain at the Earth's surface, as well as their rates, are calculated and plotted for specific cases in a form that can be easily compared with iii situ observations. The effects of tectonic stresses, penetration depth of the initial rupture, and brittle strength of the medium art: studied. The characteristic features of the strain evolution due to swarm seismicity and in processes that involve a single catastrophic earthquake are elucidated. It is shown that the duration of the deformation stage preceding an earthquake substantially shortens with increasing earthquake intensity.