Crustal P- and S-velocity structure of the Serbomacedonian Massif (Northern Greece) obtained by non-linear inversion of traveltimes

In the present study, the P - and S -velocity structure of the crust and uppermost mantle in the area of central Macedonia (northern Greece) is presented, as derived from the inversion of traveltimes of local events. An appropriate preconditioning of the final linearized system is used in order to reduce ray density effects on the results. The study focuses mainly on the structure of the broader area of the Serbomacedonian Massif. Interesting features and details of the crustal structure can be recognized in the final tomographic images. The crustal thickness shows strong variations. Under the Serbomacedonian and western Rhodope massifs the crust has a thickness that exceeds 30  km. On the other hand, the North Aegean Trough exhibits a fairly thin crust (25–27  km). Moreover, the Serbomacedonian Massif is bounded by two regions that trend parallel to the Axios river–Thermaikos gulf and the Strymon river–Orfanou gulf, respectively, which show significant crustal thinning (25–28  km). The observed match between the direction of this crustal thinning and the basins' axes indicates that they have been generated by the same extensional deformation episode.