{The 3-D structure of the lithosphere beneath the Aegean Sea is investigated through surface wave dispersion analysis. Rayleigh and Love waves recorded by 12 broad-band stations installed for a duration of 6 months in the Aegean region are processed through array analysis and Wiener filtering. Data from three GEOFON stations in the area of Crete were also used. The resulting two-station phase velocities are used to determine lateral variations of Rayleigh wave phase velocities between periods of 20 and 100 s by a 2-D ray tomography method. The obtained phase velocities are inverted to calculate variation of S-wave velocity with depth using a combination of linearized inversion and a Monte Carlo based non-linear inversion.The absolute S-wave velocity is resolved to a depth of approximately 200 km. A high-velocity anomaly of 3 per cent is observed in the southern Aegean attributed to the Hellenic subduction. In the northern part of the Aegean, in the prolongation of the North Anatolian Fault which is influenced by strong extensional movements, we found low absolute S-wave velocities at 50–100 km depth. This supports a model of a distributed deformation of the upper mantle in the area. Separate Rayleigh and Love wave phase velocity inversions along common profiles reveal a strong Love–Rayleigh discrepancy in the northern Aegean down to at least 150 km depth, i.e. most probably including the top of the asthenosphere.}

Fundamental mode Rayleigh waves generated by 380 teleseismic events were analyzed over the period range 10-100 s, in order to study the structure of the lithosphere and upper mantle of the Aegean region. Using the two-station method, 255 reliable phase velocity dispersion curves were calculated over 35 profiles and further inverted to obtain a new model of S-wave velocity with depth. S-wave velocities are resolved to a depth of 180 km. Important features are defined, such as a not completely amphitheatric geometry for the western (≈25° dipping angle) and eastern segments (≈35° dipping angle) of the subducted slab. In north Aegean, high velocities associate with the North Aegean Trough, which westernmost tip correlates with a high velocity anomaly in eastern continental Greece. This zone of high velocity contrast is extended in depth, dips southwards with an angle ≈350 and intersects with the subducted slab at an area where the direction of major tectonic axes changes from ENE-WSW to NNW-SSE towards the continental massif. In Central and North Aegean, where back arc extension and crustal thinning occur, the predominant low velocities observed could be interpreted by upper mantle high thermal flow and partial melting.