DOBRE-99: The crust structure of the Donets basin along the Mariupol-Belovodsk profile

Seismic experiments on a profile crossing the Donets basin (the Donets fold structure) were conducted by an international expedition (Ukraine, Poland, Denmark, the United States, and the Netherlands) within the framework of the DOBRE project of the EUROPROBE Pro-ram in 1999. The experiments were intended to study the deep lithospheric structure of the Donets basin and the surrounding Ukrainian Shield (the Azov region) and the southern slope of the Voronezh massif, the geometry of crustal and mantle structures (including the structure of the crust-mantle transition zone), and their relation to rifting and the subsequent inversion of the basin. The preliminary results showed that the velocity structure of the sedimentary basin is well expressed in the wavefield and indicate an asymmetric shape of the basement surface dipping toward the basin center in the south more steeply than in the north. The thickness of the sedimentary cover in the studied part of the Donets basin reaches 20 km. A thick (>10 km) high-velocity (>6.9 km/s) body located under the basin proper and slightly inclined northward relative to the center of the downwarp is identified in the lower crust. Crustal velocities under the Ukrainian Shield (the Azov region) are, on the whole, higher than under the Voronezh massif. The Moho lies at depths of 40 to 42 km and is characterized by P wave velocities varying from 8 to 8.3 km/s.