An earthquake swarm with the strongest quake registered as an M4.6 quake struck the Campi Flegrei area in southern Italy on June 30, 2025, prompting evacuations and train delays in the region. It was the strongest tremor to strike the region in 40 years, surpassing the M4.4 quakes of March and May.
A swarm of earthquakes struck Italy’s Campi Flegrei region early Thursday, June 5, 2025, starting at 04:39 UTC. At least nine tremors were recorded within hours, the strongest reaching magnitude 3.2. The activity adds to growing concerns in an area already showing long-term signs of volcanic unrest.
A study of Campi Flegrei’s crust has uncovered a damaged rock layer underground that may be driving the volcano’s long-running unrest. The zone, weakened by older magma intrusions, now appears to trap gas rising from deeper sources. This buildup of underground pressure could explain both the steady ground uplift and the swarms of small quakes recorded since 2005.
A new earthquake swarm began in the Campi Flegrei caldera at 14:23 local time on May 14, 2025, just five hours after Italy’s National Institute of Geophysics and Volcanology (INGV) reported the end of a previous swarm that led to a state of emergency declaration.
A state of emergency was declared for Italy’s Campi Flegrei area on May 13, 2025, following an M4.4 earthquake within a swarm of earthquakes that produced 49 registered events. The swarm began at 12:06 LT on May 13 and ended during the morning hours of May 14, according to the INGV Vesuvian Observatory. The Campi Flegrei caldera is one of Europe’s most closely monitored volcanic areas due to its dense population and history of significant unrest.
A shallow earthquake registered by the INGV as M4.4 hit the Campi Flegrei region of Italy at 00:25 UTC (01:25 LT) on March 13, 2025. The agency is reporting a depth of 2 km (1.2 miles). The earthquake matched the strongest event in 40 years but showed unprecedented ground accelerations, indicating greater intensity, according to the Vesuvius Observatory. The USGS and EMSC reported a magnitude of 4.2, with USGS reporting a depth of 10 km (6.2 miles) and EMSC 3 km (1.9 miles).
A new study published this month in Nature Communications reports that burst-like seismic swarms have been a defining feature of the volcanic unrest at Campi Flegrei since 2021.
Over 600 earthquakes were recorded at Campi Flegrei, Italy, between February 17 and 23, 2025, with the largest measuring M3.2. Around 1 cm (0.4 inches) of ground uplift was observed in the area of maximum deformation, coinciding with the onset of an earthquake swarm on February 15.
An intense earthquake swarm is in progress in the Campi Flegrei volcanic caldera, southern Italy, since 15:53 UTC on February 15, 2025. More than 556 earthquakes with magnitudes up to M3.9 were registered by 13:00 UTC on February 18. As a precautionary measure, schools in the town of Pozzuoli, which is close to the epicenter of the earthquakes, are closed today.
An earthquake swarm began in the Campi Flegrei area of southern Italy at 16:53 LT (15:53 UTC) on February 15, 2025. The strongest in the series thus far was M3.9 on February 16.
