Transverse systems along the extensional Tyrrhenian margin of central Italy and their influence on volcanism

The Tyrrhenian margin of central Italy has undergone Plio‐Quaternary extension, developing NW‐SE normal faults and NE‐SW faults. The NE‐SW faults decrease in frequency toward NE with the stretching factor β, becoming negligible for β 0.21. These data suggest that the NE‐SW transtensive structures are transfer faults of the NW‐SE normal faults due to relevant differential extension (Δβ > 0.21) within a stretched crust (β > 1.3). The minor dip‐slip and strike‐slip components of the NE‐SW and NW‐SE faults, respectively, possibly result from the NW‐SE extension due to the southeastward slab retreat beneath the Calabrian arc. The NE‐SW and NW‐SE extensions in the central southern Tyrrhenian Sea account for the composite kinematics of the NE‐SW structures, which, in turn, exert a twofold role in controlling volcanism. Where their dip‐slip component forms basins, the associated decompression induces magma accumulation (developing central volcanoes) at the intersection among NW‐SE and NE‐SW systems. Where transfer faults are mainly strike slip, their inferred subvertical attitude enhances their permeability to magma, accounting for the observed NE‐SW fissure eruptions. Regional extension, forming NW‐SE faults, enhances the overall generation and rise of magma along the margin, but NE‐SW structures focus magma rise and emplacement at shallower levels.