Earthquake Focal Mechanisms and Geodynamic Modeling of the North and Central Caucasus

The question of the existence of foci of deep earthquakes in the Caucasus is extremely important both from the viewpoint of geodynamics and seismic hazard and seismic zoning of the region. Earlier, it was believed that earthquakes with depths not exceeding 150 km could occur in the Caucasus. The existence of deeper earthquakes in the Caucasus has not previously been discussed in the scientific literature. In recent years, discussion of this issue has found reflection in works by various authors. However, consideration of the existence of deep foci based only on seismological data gives no idea of the geodynamic reasons that could cause the accumulation and discharge of energy in the form of earthquakes at great depths in the Caucasus. The article discusses the geodynamics of the Caucasus with the involvement of modern studies on seismic tomography and deformation conditions for recording movements of the crust at reference GPS stations. Analysis of the focal mechanisms of earthquakes in the North and Central Caucasus obtained for different depths, data on the distribution of hypocenters, seismic tomography sections, and geodynamic conditions have made it possible to choose the optimal versions of geodynamic models and draw appropriate conclusions about the causes of earthquakes both at great depths and in the crust of the region under study.