TOMOGRAPHY OF THE CRUST AND UPPER-MANTLE IN SOUTHEAST EUROPE

Compressional velocity structure of the crust and-the upper mantle in southeastern Europe (broader Aegean area) is studied by inverting resi duals of the first P arrivals from earthquakes in this region (16 degr ees E-31 degrees E, 34 degrees N-43 degrees N). The data used are from regional events recorded by the permanent network of stations during the period 1971-1987, enriched with data from experiments with portabl e seismographs in four regions of this broad area. This study confirms the strong variations of crustal thickness in this area as well as th e subduction of the eastern Mediterranean lithosphere under the southe rn Aegean and gives further detailed information on the crustal and up per mantle structure of the area. Important new information is the exi stence of a low-velocity crustal layer in western Greece and Albania a nd that the velocity anomaly in the mantle under the southern Aegean e xtends much farther and deeper to the northeast than the Benioff zone of the intermediate depth earthquakes indicates. Furthermore, evidence is presented about the possible existence of older subduction in the northern Aegean and about the influence of the tectonic regime on the velocity field.