Seismotectonic Model of the Northwest Caucasus: Geological-Geophysical Aspect

Abstract

In connection with the seismic hazard assessment of the Black Sea coast of Russia, the problem of the formation of seismicity in the Northwest Caucasus in the context of recent kinematics of the East Black Sea microplate is relevant, and the boundary of the microplate with the Scythian plate, in our opinion, should be considered among the most debatable issues. This problem is studied based on the tectonic scheme of the consolidated crustal layer of the Northwest Caucasus relying on the analysis of the geological and geophysical data. It is shown that the interplate boundary is represented by the Crimean and West Caucasian faults and that the crust of the Scythian plate is tectonically stratified in the region of the plate interaction which led to the overthrusting of its layers with the subsequent isostatic downwarping of the Moho to a depth of 55 to 60 km beneath the Greater Caucasus Orogen. The tectonic structure of the northeastern flank of the East Black Sea microplate is determined by the Anapa and Sochi blocks having significant excess density. The formation of seismicity of the Northwest Caucasus is mainly associated with the reverse stresses created by the seismogenic Anapa and Sochi blocks and with the tectonic stresses in the zone of the West Caucasian interplate fault. The area of the Anapa and Sochi blocks is at most 4000 square kilometers, which constrains the limiting source size and the maximum (6.0) magnitude of the earthquakes.