The subducting plate

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Shape: the slab appears to be continuous from the northern Apennines to Sicily below 250 km depth, above this depth it is fragmented in two main arcs: Calabrian and Northern Apennines; paleomagnetic data suggest that this fragmentation is post-Messinian (6Ma). In Central-Southern Apennines no fast anomaly appears in the tomographic images.
Extent: the subducted plate in Northern Apennines reaches the 670-km mantle discontinuity, it is ~700 km long and ~100 km thick.

Structure: the absence of fast velocity anomaly in the central Apennines may be interpreted as a tear in the slab or as subducted continental lithosphere. Subcrustal seismicity is present in the Calabrian arc down to  600 km, but is confined to the upper 100 km in Northern Apennines, and is absent in Central Apennines. (Piromallo and Morelli, J. Geophys. Res., 108(B2), 2099, doi: 10.1029/2002JB001757, 2003; Lucente et al. J. Geophys.Res., 104, 20,307ñ 20,327, 1999).

The supraslab wedge

Location: tomography shows the asthenospheric wedge above the slab; in the uppermost mantle it seems to follow highest elevations of the Apennines.
Internal structure and strain field: the fast direction of shear wave propagation, as measured by SKS splitting, shows a clear rotation from E-W (trench perpendicular) in the "wedge" domain to NNW-SSE (trench parallel) in the "slab and forearc" domain. Pn anisotropy is trench parallel in the entire area occupied by a corresponding low in Pn velocity. (Margheriti et al.,  J. Geophys. Res., 108(B4), 2218, doi: 10.1029/2002JB001793, 2003; Mele et al. J. Geophys. Res., 103, 12,529ñ 12,543,1998.)

The Moho

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Structure and nature of the Moho:

the Adriatic Moho (about 35 km) is deeper than theTyrrhenian (about 25 km).
(Piana et al., Geophys. Res.Lett. 29(20), 1999, doi:10.1029/2002GL015109, 2002;
Levin et al.,Geophys.  Res. Lett.29, 258,doi: 10.1029/2001GL015438,2002;
Mele et al. E.P.S.L 211, 69-78, 2003)