Active Extension in a Foreland Trapped Between Two Contractional Chains: The South Apulia Fault System (SAFS)

The response of continental forelands to subduction and collision is a widely investigated topicin geodynamics. The deformation occurring within a foreland shared by two opposite‐verging chains,however, is uncommon and poorly understood. The Apulia Swell in the southern end of the Adriamicroplate (Africa‐Europe plate boundary, central Mediterranean Sea) represents one of these cases, as it isthe common foreland of the SW verging Albanides‐Hellenides and the NE verging Southern Apenninesmerging into the SSE verging Calabrian Arc. We investigated the internal deformation of the Apulia Swellusing multiscale geophysical data: multichannel seismic profiles recording up to 12‐s two‐way time (TWT)for a consistent image of the upper crust; high‐resolution multichannel seismic profiles, high‐resolutionmultibeam bathymetry, and CHIRP profiles acquired by R/V OGS Explora to constrain the Quaternarygeological record. The results of our analyses characterize the geometry of the South Apulia Fault System(SAFS), a 100‐km‐long and 12‐km‐wide structure attesting an extensional (and possibly transtensional)response of the foreland to the two contractional fronts. The SAFS consists of two NW‐SE right‐steppingmaster faults and several secondary structures. The SAFS activity spans from the Early Pleistocenethrough the Holocene, as testified by the bathymetric and high‐resolution seismic data, with long‐term sliprates in the range of 0.2–0.4 mm/yr. Considering the position within an area with few or none otheractive faults in the surroundings, the dimension, and the activity rates, the SAFS can be a candidatecausative fault of the 20 February 1743, M 6.7, earthquake.