Local Earthquake Tomography in the Southern Tyrrhenian Region of Italy: Geophysical and Petrological Inferences on the Subducting Lithosphere

Abstract

We obtained a high-resolution seismic tomography of the Ionian litho- sphere subduction using a new approach based on: (a) the Double-Difference tech- nique for inversions and (b) the statistical post-processing of a great number of preliminary models (Weighted Average Model, WAM method); the latter was used to increase reliability and resolution. In the tomographic model, the high-velocity portion of the steeply dipping Ionian slab is well imaged, as is an underlying low-Vp (≈7.0 km/s) aseismic region. We propose that the low-velocity region can be assigned to a partially hydrated (serpentinized) mantle of the subducting Ionian slab, which progressively dehydrates with depth in dense high-pressure phases. In the mantle wedge overlying the slab, large areas, characterized by low-Vp (≤7.0 km/s) and high Vp/Vs (≥1.85), have been imaged beneath the Stromboli and Marsili volcanoes down to a maximum depth of 180 km. We have interpreted these areas as being regions where mantle partial melts form and accumulate and which then feed the present-day Aeolian Archipelago magmatism .