Deep velocity structure of crust and upper mantle in the central parts of Balkan Region

Abstract

Some velocity characteristics of the crust and upper mantle in the central part of the Balkan region are studied on the basis of about 1000 local and teleseismic earthquakes, registered on the 32 seismic stations. An approach for estimation of the large anisotropic structures effects is used together with the general consideration about the connection between the time residuals and velocity inhomogeneities. The main features of the inhomogeneities in the crust and upper mantle are drscussed in relation with some gravity, heat flow and seismotectonic data. The distribution of the crustal inhomogeneities in general corresponds to the configuration of the morphotectonic structures in Bulgaria. The subcrustal inhomogeneities are discordant with the surface structures, but their orientation is in coincidence with the Trans-Balkan seismolineament system. This fact indicates that the crustal seismicity in the region is probably controlled by the upper mantle structures. The high-velocity structures in the deep upper mantle beneath the Rhodope massif probably represent a paleosubduction at a depth more than 300 km.