The Adriatic lithosphere is a promontory of the African plate: Evidence of a continuous mantle lid in the Ionian Sea from efficient Sn propagation

Abstract

Evidence of a continuous lithosphere between the northern margin of Africa and Italy is given from the analysis of regional waveforms recorded by the Italian Seismic Network. Frequency and amplitude of shear waves Sn propagating over the Ionian Sea and the western part of the Levantine Sea are examined in this study. An important observation is that Sn waves are efficiently transmitted without exception at epicentral distances ranging from 3˚ to 22.5˚. The very efficient propagation of uppermost mantle shear waves implies that mantle lithosphere is continuous in this part of the Mediterranean region. This in turn implies that the lithosphere underlying the Adriatic Sea is attached to the African lithosphere and can be considered a promontory of the major African plate. The regional shear phase Lg, that typically propagates within the continental crust, is not transmitted in this area. This observation is consistent with the presence of oceanic crust in the eastern Mediterranean, as hypothesized by previous studies.