Campi Flegrei caldera hit by M4.0 quake in new seismic swarm, Italy
A new earthquake swarm began at 14:09 UTC on August 31, 2025, in the Campi Flegrei caldera, Italy. By 07:30 UTC on September 1, 94 earthquakes were recorded, including a shallow M4.0 event near Pozzuoli at 02:55 UTC.
Earthquake swarm in Campi Flegrei, Italy on August 31 and September 1, 2025. Credit: TW/SAM, ESRI
Italy’s National Institute of Geophysics and Volcanology (INGV) reports an ongoing earthquake swarm in the Campi Flegrei caldera that started at 14:09 UTC on August 31. At the time of its latest communiqué, INGV preliminarily counted 94 earthquakes with magnitudes up to 4.0±0.3.
The strongest event was an M4.0 earthquake at 02:55 UTC (04:55 LT local time) on September 1, at an estimated depth of 2 km (1.2 miles), with an epicenter near Pozzuoli. The sequence included two M3.3 earthquakes on August 31 at depths of 0.7 km (0.4 miles) and 1.8 km (1.1 miles), followed by several events of M2.0–M2.8 later that day. Among them were two M2.8 quakes at depths of 0.4 km (0.2 miles) and 0.8 km (0.5 miles) hours before the M4.0.
Residents in Pozzuoli and nearby districts reported strong shaking.
As a precaution, rail operator Ente Autonomo Volturno (EAV) suspended services on the Cumana and Circumflegrea lines to allow infrastructure checks. A replacement bus service operated by D’Agostino was activated on the Montesanto–Torregaveta and Montesanto–Licola routes.
Pozzuoli Mayor Gigi Manzoni said there were no reports of damage to people or property and noted the deployment of Municipal Police and Civil Protection teams to monitor the area.
“I have ordered the immediate deployment of Municipal Police patrols and Civil Protection teams to monitor the area and identify any critical issues. At present, there are no reports of injuries or structural damage,” said Manzoni.
Campi Flegrei is a large volcanic caldera affected by bradyseism driven by magmatic-hydrothermal processes. Since 2005, cumulative ground uplift has reached approximately 1.44 m (4.7 feet) by April 2025.
Significant recent events include M4.4 on March 13 and May 13, 2025, and M4.6 on June 30, 2025.
Teo Blašković founded The Watchers in 2011 and edited it until 2026, covering seismic and volcanic activity, extreme weather, space weather and near-Earth objects. Articles on this page are his archive.
Earlier reporting
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