Seismicity and deep tectonics of the Black Sea depression and its margins

Seismicity has been detected within the central "granite-free" part of the Black Sea depression, which earlier was considered aseismic.   The seismicity defines specific zones in the depression and its margins. In the depression, epicenters are grouped into diagonal linear chains separating large blocks.   The vertical distribution of seismicity has allowed us to distinguish four main levels in the Black Sea tectonosphere, which differ in elastic and strength properties: sedimentary layers, brittle crystalline crust, plastic upper mantle, and deeper mantle which is considerably more homogenous. At various levels, structures show azimuthal discordance. The plastic upper mantle appears to be connected with the asthenosphere.  It is most uplifted under the "granite-free" part of the Black Sea depression and is apparently responsible for its formation. A mantle asthenolith (or asthenolithes) probably occur there.