Rupture propagation in strong earthquake sources and tectonic stress field

Abstract Problems of physical basis of earthquake source mechanics are discussed. Results of stress state reconstruction based on the cataclastic analysis of discontinuous dislocations in some seismotectonic active earth crust domains are presented. Common features of the stress state in areas of preparation of strong earthquake in this century are revealed. It is demonstrated that the distribution of the effective isotropic pressure and of the maximal shear stress in areas of earthquake source preparation is characterized by essential heterogeneity. The main part of the source is always associated to crust domain under low effective confining pressure. Specific role of crust domains characterized by high stress gradients is recognized. The nucleation point of the earthquake is usually associated to such domains. Based on some strong earthquake case studies it is demonstrated that usually the rupture propagates from the region of high gradients of stresses toward the crust domains characterized by low effective compression.

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