Seismic Tomography of the Southern Tyrrhenian by Means of Teleseismic Data

Seismic tomography is a very relevant method designed to investigate subduction zones. This is the case of the Southern Tyrrhenian oceanic back-arc basin. The subducting lithosphere has been mostly consumed along the Tyrrhenian-Apennine system, with the exception of the Calabrian arc sector. The Ionian subduction is documented by several previous works, including local seismic tomographies that have discovered the presence of a high seismic velocity body beneath the Calabrian zone. In this work, tomography was obtained by means of inversion of teleseismic data and an iterative computation of them to obtain the so-called residual, which is the difference between the observed traveltimes and the theoretical traveltimes. The final tridimensional velocity model corresponds to the one having the minimum residual. The new seismic tomography, derived from the inversion of traveltimes of teleseismic ray paths, traveling in the upper mantle at high depths. Summarizing the results, the horizontal sections show an evolution of the high-velocity body that represents the Ionian slab. It is visible both at a depth of 50 km and at a depth of 100 km beneath the Calabrian arc and extends to northern Sicily beneath the Eolian arc, with a maximum of 0.6–0.8 km/s. At a depth of 250 km, the tomography evidences a sort of “transition” due to the absence of the Southern Tyrrhenian HVA. The presence of this “window slab” could be interpreted as a tear in which unperturbed mantle inserts itself.