Crustal structure of the Mediterranean sea by surface waves. Part I: Group velocity

abstract The purpose of this paper is to obtain an approximation to the crust-mantle structure of the Mediterranean Region, using only group-velocity data. Earthquakes whose seismic paths cross totally or partially the Mediterranean Sea have been used. Forty-eight earthquakes have been selected and their corresponding Rayleigh and Love group-velocity dispersion curves were calculated. Most of the records belong to the standard seismological stations installed in the borders of the Mediterranean Sea. The Rayleigh and Love wave dispersion curves obtained have been classified in five different groups which show the same dispersive character. There is a correlation of such classification with the oceanic percentage and geographic region crossed by the paths, i.e., with the corresponding type of crustal structure. Crust-mantle theoretical models have been computed for both Rayleigh and Love waves. The dispersion curves of these models fit acceptably into an average of the data of each group. They show a remarkable difference between the eastern and western Mediterranean crust, which is considered as one of the main results of this investigation. The crust to the south of the Ionian and Aegean Seas shows somewhat smaller velocities and larger thicknesses, for the uppermost crustal layers, than that of the western Mediterranean, which seems to be of a more oceanic character.