New Insight into the Deep Structure of Antarctic Peninsula Continental Margin by Methods of 2d Gravity/Magnetic Modelling and 3d Seismic Tomography

The Antarctic Peninsula, one of several terrains of Western Antarctica, is a Mesozoic magmatic arc at the southeastern Pacific margin. In order to investigate the structure of the crust and uppermost mantle of Antarctic Peninsula continental margin we have developed joint geophysical models by 2D gravity and magnetic modelling along two most representative and lengthy seismic refraction lines, acquired by Polish Academy of Sciences in 1980-1990th

The structure of the Kerch peninsula and north-eastern part of the Black sea crust according to the results of local seismic tomography

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

The high-speed structure of the upper floors of the mantle of the Black Sea basin

Lateral velocity variations in the mantle lithosphere of the Black Sea basin down to the depth of 80 km were estimated from travel time residuals of P-waves recorded at the coastal stations from earthquakes within and around the Black Sea. The observed data were corrected for the crust structure that allowed us to get more accurate information on the velocity distribution in the mantle lid. We applied the tomography method in which the 3D region under study was divided by cells and velocity correction in each cell was estimated. Some new features of the mantle lid structure have been found which reflect history of formation and evolution of the Black Sea depression. It has been shown that the Black Sea basin is not a single block: it consists of two different depressions distinguished by the velocity structure and orientation. They are separated by a low-velocity zone, western and eastern parts of which coincide with the West-Crimean fault and the Trans-Black Sea fault correspondingly

Collision processes at the northern margin of the Black Sea,

International audienceExtended along the Crimea–Caucasus coast of the Black Sea, the Crimean Seismic Zone (CSZ) is an 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 Coast), and Sevastopol subzones have also been recognized. Generalization of the focal mechanisms of 31 strong earthquakes during 1927–2013 has demonstrated the predominance of reverse and reverse–normal-faulting deformation regimes. This ongoing tectonic process occurs under the settings 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, this process is complicated by the East Black Sea Microplate frontal part wedging into the marginal part of the Scythian Plate crust. The indentation mechanism explains the strong gravity anomaly in the Crimean Mountains and their uplift