2012 earthquake showing rare surface break in Italy. Trench excavation revealed previous ruptures every 1,000-2,000 years, establishing recurrence for a fault previously thought inactive.
A seismic surprise
On October 25, 2012, a moderate earthquake, with a moment magnitude of 5.2, struck the Pollino massif on the border between Calabria and Basilicata. While moderate earthquakes are common along the Apennine mountain range, this event was different. Field geologists from Italy's National Institute of Geophysics and Volcanology (INGV) discovered a subtle but distinct crack in the earth's surface near the epicenter. This surface rupture, a feature typically associated with much stronger earthquakes, extended for approximately 5 kilometers.
The faulting occurred on a previously unmapped segment of a normal fault system, where the earth's crust is being stretched apart. The displacement was small, only a few centimeters, but its existence was a scientific puzzle. The Pollino region was long considered a "seismic gap," an area with active faults but a surprising lack of large historical earthquakes. The 2012 event and its unusual surface break prompted a deeper investigation into the ground itself to study the region's seismic past.
Reading the layers of time
To understand the history of this newly revealed fault, scientists conducted a paleoseismological study. This involved digging a trench several meters deep directly across the 2012 surface rupture in an area known as Piano di Novacco. The walls of this trench exposed the layers of soil and sediment that had accumulated over thousands of years. Within these layers, geologists found clear evidence of past seismic events. Disrupted and offset soil horizons showed where the ground had broken during ancient earthquakes.
Using radiocarbon dating on organic material found within the disturbed layers, the researchers could establish a timeline of past ruptures. The evidence showed that the fault had produced similar, and likely larger, earthquakes before. At least four major surface-faulting events have been identified on related faults in the region over the last 10,000 years. Paleoseismological studies on the nearby Castrovillari fault, part of the same system, suggest major earthquakes with magnitudes between 6.5 and 7.0 occur with a recurrence interval between roughly 940 and 3,000 years. The 2012 earthquake was not an isolated incident and part of a long-term pattern of seismic activity on a fault system that was far more active than previously understood. This discovery fundamentally changed the seismic hazard assessment for this part of southern Italy.
💡Fun Facts
The Pollino region was historically considered a "seismic gap," a 100 km-long section of the Apennines that lacked records of major earthquakes.
The 2012 earthquake was part of a long seismic swarm that began in 2010 and included over 6,000 recorded earthquakes.
Normal faulting, the type that caused this rupture, is common in the Apennines and is responsible for the gradual stretching of the Italian peninsula at a rate of about 2.5 millimeters per year in this region.
Pollino National Park, where the rupture occurred, is Italy's largest protected area, covering nearly 2,000 square kilometers.
The site is in an open, public national park and is accessible 24/7.
Admission
Free.
Accessibility
The rupture site is in a mountainous, undeveloped area within Pollino National Park. Access requires hiking over uneven terrain. It is not accessible by wheelchair.