The southern Apennine chain (Italy) is one of the regions of Europe where historical seismicity is best known and studied.
Everyone remembers the devastating earthquakes of L’Aquila in 2009 and Amatrice in 2016 in this mountainous region that winds through the centre of the Italian peninsula. Despite these tragedies and decades of geological studies of the major fault zones causing these major earthquakes, they remain poorly identified or totally unknown. This is true not only of very old earthquakes, but also of recent ones, some of the most destructive to have hit Italy, such as those of magnitude > 7.0 that occurred on 5 December 1456 and 5 June 1688, which killed an estimated 70,000 and 10,000 people respectively in the kingdom of Naples and the province of Benevento. Italian scientific teams from various institutes and universities, as well as a French team from the LSCE (CEA DRF) and GEOPS (Université Paris-Saclay), have been working together for the past 2 years to determine the source(s) of these two seismic events. This group of researchers has carried out a highly innovative study using an interdisciplinary, multi-scale approach, combining detailed field investigations (stratigraphic, geomorphological, structural and palaeoseismological analyses), radioisotopic dating and a reassessment of the distribution of macro-seismic intensity based on historical archive sources.
The results of this study were published a few weeks ago and for the first time identify a probable source for these two earthquakes. It corresponds to a ~45 km normal fault system made up of two main branches (the eastern Calore fault and the western Calore fault) (figure attached). This study also provides the first evidence of the occurrence less than 14,000 years ago of a major palaeo-earthquake with a surface displacement ≳0.7 m, as well as a decametric offset affecting sediments younger than 9,000 years. These surface ruptures linked to large-magnitude earthquakes have a recurrence time estimated at around 1,400 years on this fault zone, according to the researchers. The two most recent events probably correspond to the Sannio earthquakes of Mw ~7.0, 1456 and 1688. Further, more detailed palaeoseismological studies are envisaged to discover direct evidence of coseismic displacements linked to the earthquakes of 1456, 1688 and other earlier earthquakes, in order to better anticipate the impact and recurrence of these major earthquakes and thus protect the populations of southern Italy.
* Amato et al., 2025, Quaternary Science Reviews. https://doi.org/10.1016/j.quascirev.2025.109282
CEA Contact: Sebastien Nomade