Investigation of Crust and Upper-Mantle Structure in the Black Sea with Group-Velocity Data

Abstract

In this study, crust and upper-mantle structure in the Black Sea have been investigated by measuring the group-velocity dispersion data of seismic surface waves. Structural models for the profiles between Istanbul station (IST) and six earthquakes that occurred near the northeastern coast of the Black Sea have been constructed. These six profiles are approximately in the NE–SW direction and across the Black Sea. Seismograms of Rayleigh waves for four earthquakes and both Love and Rayleigh waves for two earthquakes have been analyzed. Group velocities have been computed with the multiple filter technique (MFT) from the vertical and/or horizontal component records of six selected earthquakes. Crust and upper-mantle structure for each profile has been estimated by trial and error fitting of these group-velocity values. A three-layered crustal model has been determined for all the profiles. Density values of the layers are identical for all models except for profile 1, of which one part lies in Anatolia. Thickness and density values of the layers in the crust and upper-mantle structure models obtained from the analyses of both Love and Rayleigh waves for the same profile (for profiles 2 and 6, individually) are identical. There are small changes in the velocity values. When the profiles are compared among themselves, it is shown that the crust is getting thinner from south to north, i.e., toward the center of the Black Sea basin.