Continental vs. oceanic lithosphere beneath the Eastern Mediterranean Sea - Implications from Rayleigh wave dispersion measurements

Tectonics of the eastern Mediterranean are strongly influenced by subduction of oceanic lithosphere with slab pull as a prominent driving force. The current distribution of remnants of oceanic lithosphere and the properties of African mantle lithosphere beneath the eastern Mediterranean basin have been a matter of debate. Previous studies variously found continental as well as oceanic lithosphere in this region. A set of I-D S-wave velocity models is determined in order to characterize the mantle lithosphere in the area between Crete and the Middle East. For seven paths starting from Cyprus and running to Crete, to Anatolia as well as to the Middle East, broad-band average phase velocity curves of the fundamental Rayleigh mode are obtained in the frequency range of about 3 mHz to 90 mHz by a two-station method. In addition, an east-west oriented path crossing southern Anatolia and a path running parallel to the Dead Sea Fault Zone are considered. Phase velocity curves are inverted for path average 1-D S-wave velocity models. Resolution is investigated with the Neighbourhood Algorithm. Comparing the resulting 1-D models, cold oceanic mantle lithosphere showing S-wave velocities above 4.6 km s(-1) can be distinguished from mantle lithosphere with low S-wave velocities. Oceanic lithosphere is found west of Cyprus beneath the Herodotus basin. As indicated by Benioff zones, it is subducting towards northwest in the southeastern Aegean and towards northeast beneath southwestern Anatolia. To the east of Cyprus the mantle lithosphere beneath the easternmost Mediterranean Sea shows low S-wave velocities. No indications for cold oceanic mantle lithosphere are found beneath the Levant basin. In the region of the Dead Sea Fault Zone and the Levant basin the lithosphere-asthenosphere boundary is located at shallow depths of about 60 km to 80 km. The DSFZ is situated in a region of thinned lithosphere underlain by an asthenosphere with anomalous low S-wave velocities. Low S-wave velocities beneath southern Anatolia extend down to at least 150 km depth as expected for a back arc setting. inferred Moho depths vary for the different paths between 28 km and 41 km. Crown Copyright (C) 2008 Published by Elsevier B.V. All rights reserved.