Crustal structure in the Southern Apennines from teleseismic receiver functions

While the upper crustal structure of the Southern Apennines is known, lack of control on the deep structure allows competing thin-skinned and thick-skinned models of the orogen. In thin-skinned models, the detachment decouples a stack of rootless nappes; from the basement. In thick-skinned models, basement is involved in the most recent phase of thrusting. To examine crustal structure, we use teleseismic data from the Calabria-Apennine-Tyrrhenian/Subduction-Accretion-Collision Network (CAT/SCAN) array in southern Italy. We use receiver functions (RF) processed into a common conversion point stack to generate images of the crust. Interpretation and correlation to geological structure are done using inversions of individual station RFs. We focus on a shallow discontinuity where P-to-S conversions occur. In the foreland, it corresponds to velocity jumps between carbonate and clastic strata with basement. A similar interpretation for the Apennines provides the most parsimonious explanation and supports a thick-skinned interpretation. In a thick-skinned reconstruction, the amount of shortening is much smaller than for a thin-skinned model. This implies considerably less Pliocene-Pleistocene shortening across the Apennines and suggests an east-southeast motion of the Calabrian arc subparallel to the southern Apennines rather than a radial expansion of the arc.