Subbotin Institute of Geophysics of the NAS of Ukraine
Abstract
Local seismic tomographic study has been conducted according to the data of 200 weak earthquakes occurred in 1975-2010 and registered by seven seismic stations in the area of the Kerch peninsula and adjacent northern part of the Black Sea. Application of Backus-Gilbert method for the three-dimensional case allowed to study the velocity structure by P- and S-waves at the depths of 15-40 km and to calculate the ratio VP/VS. Two high velocity blocks have been revealed in the middle and lower crust of the region. The first one includes the P-velocity anomaly of the Kerch peninsula in the area of the western part of the Indol-Kuban trough. The other one is characterized by the S-velocity anomaly of the Shatsky swell and the Tuapse depression. The third high-velocity domain situated in the Black sea water area to the south from the Kerch peninsula belongs most probably to the uppermost mantle that underlie the thin sub-oceanic crust of the East-Black sea basin. Performed petrologic and geodynamic interpretation of the obtained anomalies makes possible to conclude the presence of active processes of thrusting the sub-oceanic crust of the East-Black sea basin under the continental crust of the Scythian plate and the southern part of the East-European platform. The transition area is controlled by a zone of high seismic activity, where the earthquake foci deepen northward that can be an additional evidence of on going underthrusting processes in the study region
