New methodological approach in the evaluation of fault interaction: insights from the central Apennines fault system

The central Apennines host several normal active faults, which are distributed along the Central Apennine Fault System (CAFS), known for generating dozens of earthquakes, of moderate to high magnitudes, in the last thousand years. The latest events caused by this system occurred in the epicentral area of Colfiorito in 1997 (M-W 6.0), L'Aquila in 2009 (M-W 6.2), and at the border between the Marche, Umbria, and Lazio regions in 2016 (M-W 6.6), this latter a catastrophic event with hundreds of victims and extensive damages. Thereafter, significant interest arose in the study of fault behaviour in the axial zone of the central Apennines. This work proposes a new methodological approach to studying fault interaction within the framework of the CAFS seismic cycle, modelling faults with a more complex geometry characterised by an elliptical outline, which better describes the actual shape of a fault at depth. All the destructive earthquakes (M-W > 6.0) that occurred in the last thousand years were taken into account, and the static stress between the causative fault and adjacent one was calculated. The results demonstrate how the newly modelled faults critically affect Coulomb stress transfer compared to planar and rectangular fault modelling usually adopted by previous authors.