Modern Collision Processes at the Northern Coast of the Black Sea
Stretching along the Crimea–Caucasus coast of the Black Sea, the Crimean Seismic Zone (CSZ) is evidence of active tectonic processes at the junction of the Scythian Plate and Black Sea Microplate. A relocation procedure applied to weak earthquakes (mb < 3) recorded by ten local stations during 1970–2013 helped to determine more accurately the parameters of hypocenters in the CSZ. The Kerch–Taman, Sudak, Yuzhnoberezhnaya (South Shore), and Sevastopol subzones have also been recognized. Summarization of the mechanisms in the foci of 31 strong earthquakes during 1927–2013 has demonstrated the predominance of reverse and reverse–normal-faulting deformation regimes. This modern tectonic process occurs under conditions of compression and transpression. The earthquake foci with strike-slip component mechanisms concentrate in the west of the CSZ. Comparison of deformation modes in the western and eastern Crimean Mountains according to tectonophysical data has demonstrated that the western part is dominated by strike-slip and normal-faulting, while in the eastern part, reverse-fault and strike-slip deformation regimes prevail. Comparison of the seismicity and gravity field and modes of deformation suggests underthusting of the East Black Sea Microplate with thin suboceanic crust under the Scythian Plate. In the Yuzhnoberezhnaya Subzone, the subduction process is complicated by wedging in the frontal part of the East Black Sea Microplate into the marginal part of the crust of the Scythian Plate. The pushing-in indentation mechanism explains the strong gravity anomaly in the Crimean Mountains and their modern uplift.  Keywords: Crimea, Black Sea, seismicity, earthquake mechanisms, collision processes, kinematic analysis, deformation regimes