NUMERICAL MODELING OF THE STRESSED STATE OF THE EARTHS CRUST AND CONDITIONS OF DYNAMIC INSTABILITY OF SEISMOACTIVE FAULTS DURING RIFTING

To receive insight into conditions of origin and process of earthquake preparation, the stressed state of the Earth's crust and its variatio ns was investigated. With this aim, a detailed two-dimensional elastic model for a vertical section of the Earth's crust has been developed. A model prototype is the central part of the Baikal Rift Zone. The mo del takes into account the distribution of elastic properties and dens ity in the Earth's crust, determined from data of seismic soundings an d includes a number of tectonic disturbances: the depth central fault and a number of peripheral faults including listric one. The boundary conditions were specified on the basis of a complex of geologo-geophys ical data, first of all, on mechanisms of earthquake foci and their sp atial distribution. The conditions adopted chiefly correspond to a mod el for passive rifting. Numerical modeling of a stressed state by the method of finite elements has revealed potentially seismic places of a nomalous concentrations of stresses. Modeling of the effect of externa l and internal additional factors (stress variations on the regional l evel, rigidity variations at the contact with fault sides) has reveale d the most sensitive zones with a quantitative estimation of the effec t of increased stresses in them.