Geophysical research: article

Аnnotation: In this work we study the high-speed structure of the upper crust of the Gulf of Finland region and its surroundings using the method of noise surface-wave tomography. For this, noise records of 16 broadband seismic stations located in the region and its vicinity were used. The cross-correlation functions of ambient noise calculated for station pairs allowed us to construct the dispersion curves in a period range of 2-20 s. The maps of group velocity distribution for separate periods were obtained using a 2D-tomography method. Then the inverse problem of reconstruction the S-wave velocity from the dispersion curve of the surface wave was solved. The initial approximation was chosen on the basis of the analysis of the Sovetsk-Kohtla-Jarve velocity profile obtained by the DSS method. The velocity sections were searched in the form of a piecewise-constant function, the number of layers for the crust was set equal to five, the thickness of the layers and the velocity in them varied. The resulting vertical velocity sections were presented in the form of lateral variations of the velocity for some depth ranges. As a result of the work, the structure of the crust in the area of transition from the Fennoscandian shield to the Russian plate to the depths of 16 km was refined. On the map for a depth interval of 0-2 km, the change in the velocity V