Ridge of Pennata islet collapses after the strongest earthquake in 40 years strikes Campi Flegrei, Italy

The epicenter of the M4.6 quake was located at a depth of 4 km (2.5 miles) near the Bacoli area and was associated with a swarm of 7 seismic events, according to the National Institute of Geophysics and Volcanology (INGV).

The 4.6-magnitude earthquake was the strongest in the region in 40 years, exceeding the M4.4 events recorded in March and May.

The ridge of Pennata islet collapsed during the earthquake, which struck at approximately 12:47 local time (10:47 UTC) on June 30. Tremors were felt across Naples, prompting residents in the affected areas to evacuate buildings and gather in the streets. The quake also caused widespread traffic disruptions throughout the region.

The Italian Civil Protection Agency said the quake prompted evacuations and disrupted train services.

The first checks following the quake didn’t reveal any damage to local infrastructure. Local media reported that multiple schools in Naples, including the Righi Institute in the Fuorigrotta district, were evacuated.

“We’re tracking the situation in real time after the 4.6 quake. The seismic swarm is still going on. At the moment there have been no reports or requests for assistance from the population. We have activated the swarm protocol for schools, we are proceeding with the checks for the municipal nursery, and we are preparing the ordinance to suspend teaching activities for private schools that are running summer camps until the RSPP issues the certification,” said the mayor of Pozzuoli, Luigi Manzon.

Italy’s state-owned railway operator Trenitalia warned of possible delays “of up to 120 minutes” or cancellations for high-speed, intercity, and regional services. 

The Campi Flegrei caldera is one of the most hazardous volcanic systems in Europe, located in a densely populated area that includes the city of Naples and the municipality of Pozzuoli.

The region has experienced increased seismic activity in recent months. It was rocked by a 4.4-magnitude quake on March 13, and by another tremor of the same magnitude on May 13.

The region is home to over 500 000 people living within the caldera’s immediate vicinity, making any volcanic or seismic unrest a major concern for civil protection authorities.

Seismic swarms in Campi Flegrei are linked to bradyseism, a phenomenon involving vertical ground displacement caused by underground magma or hydrothermal fluid movement. Recent scientific work suggests that managing groundwater extraction may reduce reservoir pressure and limit seismic activity.

Bradyseismic activity has been recurrent in this area for centuries, with notable episodes in the 1970s and 1980s resulting in significant ground uplift and the temporary evacuation of thousands.