Modern Studies of Earthquake Focal Mechanisms in Eastern Kazakhstan

This study presents the results of a detailed investigation of earthquake focal zones in Eastern Kazakhstan using modern methodologies for determining focal parameters and focal mechanisms. The stress regime and the elastic stress field of the Earth’s crust were analyzed based on seismic events recorded during the period 1990–2020. An information base was established for the investigation of regional deformation conditions using earthquake focal mechanism catalogs and data acquired from the regional seismological monitoring network. The installation of new seismic stations along the perimeter of Kazakhstan has enabled a more detailed investigation of seismicity in Eastern Kazakhstan and an assessment of the stress–strain state of the deep layers of the Earth’s crust in the region and adjacent territories. An electronic database of stress tensor parameters and seismotectonic deformation increments was developed using the method of cataclastic analysis of seismic data implemented in the STRESS seismic software package. The stress–strain state of the Earth’s crust was analyzed based on the spatial distribution of stress tensor parameters and seismotectonic strain increments. Zones characterized by contrasting stress regimes were identified, along the boundaries of which strong earthquake sources are most likely to occur. Analysis of the orientations of the principal stress axes indicates a reset-type stress regime.