Deep-Focus Mantle Earthquakes in the Eastern Part of the Caucasian Isthmus

Abstract—Based on the distribution of mantle seismicity and the sets of focal mechanisms of the earthquakes, the existence and deformation type of an allantoid mantle body within the eastern part of the Caucasus Isthmus is established. The body is inclined and plunges from the southeast to the northwest to a depth of 160 km. The shape of the mantle body and the type of its stress state which is fundamentally different from that for the Earth’s crust in the region precludes us from accepting plate-tectonic interpretation of this formation in the form of a concept implying the subsidence of the subducting part of the Arabian lithospheric plate underneath the Eurasian plate. We hypothesize that this phenomenon is associated with the tectogenesis process developing in the subcrustal mantle of the Caucasus irrespective of the collision processes.