The Pernicana Fault is a roughly 18-kilometre east-west fault on the northeastern flank of Mount Etna in eastern Sicily. It is the main structure accommodating the seaward sliding of Etna's unstable eastern flank as the volcano deforms under gravity and magma pressure.
It moves with left-lateral strike-slip and a normal component, and it is one of the fastest-slipping faults in the region, creeping and rupturing at rates far higher than typical tectonic faults because of the volcanic loading. Buildings, roads and walls straddling the fault are visibly offset and repeatedly cracked.
The Pernicana Fault generates frequent shallow earthquakes, usually small in magnitude but locally destructive because they occur just below densely built villages such as Piano Pernicana and Presa. Its activity is tightly linked to eruptive phases of Etna, making it a key monitoring target for flank instability.