Remobilization of Inverted Normal Faults Drives Active Extension in the
Axial Zone of the Southern Apennines Mountain Belt (Italy)
Abstract
The Irpinia region is one of the most seismically active areas of Italy
due to ongoing, late-orogenic extension in the axial zone of the
Apennines mountain belt. However, the 3D architecture and the nature of
the faults that drive this extension are still uncertain, posing
challenges to seismic hazard assessment. Here, we address these
uncertainties by integrating a new catalog of high-resolution
micro-seismicity (ML<3.5) complemented by earthquake focal
mechanisms, with existing 3D seismic velocity models and geological
data. We found that micro-seismicity is primarily taking place along a
segmented, approximately 60 km long, deep-seated, Mesozoic normal fault
that was inverted during the shortening stages of the Apennine orogeny
and then extensionally reactivated during the Quaternary. These findings
suggest that multiple events of reactivation of long-lived faults can
weaken their strength, making them prone to co-seismic remobilization
under newly-imposed strain fields in active mountain belts.