Present-day seismicity of the Matese Massif (central-southern Apennines, Italy): new constraints on the seismotectonic setting of the central and southern sides

We investigated the 2009-2020 instrumental seismicity of the Matese Massif. With the exception of two relevant seismic sequences (2013-2014 and 2016-2017, MMAX = 4.9), the background seismicity consists of low magnitude seismic swarms (MMAX = 3.3) located at the borders of the massif, and sparse single events (MMAX = 3.5). The focal mechanisms of the single events located near the NW and west edges of the massif suggest that this seismicity occurs on SW dipping, ca. NW-SE striking normal fault segments, in accordance with the kinematics of the Aquae Iuliae Fault. The focal mechanisms of two low magnitude seismic swarms located in the morphological depression, separating the Matese Massif from the Sannio Mountains, provide seismological evidence, never previously observed in this area, of the existence of an active east-western fault segment with dextral strike-slip kinematics. To the west of this area, there is no seismological evidence of strike-slip kinematics, whereas such evidence is found to the east. This area could represent the westernmost expression of the active strike-slip regime that characterises the Apulian foreland. Along the faults situated on the southern side, the very rare detected seismicity could be related to the high emission of CO2-bearing gas vents located near these faults. Considering the time elapsed from the last destructive earthquake (1349), the possible sources of the poorly known 346 and 1293 earthquakes, and the rare seismicity detected in the last 25 years, we speculate that the south-western side of the Matese may be affected by large earthquakes in the future.