M3.6 earthquake and new seismic swarm recorded in Campi Flegrei supervolcano, Italy

An earthquake with a magnitude of 3.6 ± 0.3 was recorded in Campi Flegrei, Italy, at 12:36 UTC on October 16, 2023, coinciding with the start of a new earthquake swarm. The event comes amid rising concerns over the area’s seismic activity.

The quake hit at a depth of 1.9 km (1.2 miles) and coincided with the start of a new earthquake swarm, as reported by the Istituto Nazionale di Geofisica e Vulcanologia (INGV). It was preceded by M1.4 at 03:31 UTC on October 16, M1.9 at 17:59 UTC on October 15, and M1.4 at 14:18 UTC on October 15.

It was felt by the local population, with many reporting it on social media.

Today’s seismic activity adds to a trend of increasing disturbances in the region, punctuated by a series of new safety measures announced by the Italian cabinet on October 5, including the possible evacuation of tens of thousands of people.

These measures follow months of seismic activity that has featured more than 1 100 earthquakes, including one with a magnitude of 4.2, the strongest in the region in the last 40 years.

Geologists have linked the rising seismic events to a geological phenomenon known as bradyseism. Currently, the ground around Campi Flegrei is experiencing an uplift rate of 1.5 cm (0.6 inches) per month, bringing attention to the structural integrity of buildings in the surrounding area.

Nello Musumeci, the Civil Protection Minister, mentioned that evacuations would only occur in extreme cases. The government is also preparing to allocate additional resources to local civil protection agencies to enable prompt responses during emergencies. Moreover, there are plans to start a public awareness campaign to educate residents about the ongoing seismic issues.

Preemptive measures include evacuation tests to be conducted by local hospitals. Mauro Di Vito, Director of the INGV Vesuvian Observatory, stated that geophysical and geochemical indicators are under constant scrutiny. At this point, the data, including a soil uplift speed of 15 mm (0.6 inches) per month, suggests no significant changes in the system for the short term.

Campi Flegrei covers a 13 km (8 miles) wide caldera that encompasses part of Naples, with a population of 3 million, and extends south into the Gulf of Pozzuoli. The area is no stranger to seismic activity; episodes of bradyseism and seismic swarms have been observed particularly during 1969–72 and 1982–84. During these periods, nearly 40 000 people were temporarily evacuated from the nearby town of Pozzuoli.

In recent months, the ground uplift in the Rione Terra area reached approximately 113 cm (44 inches). The supervolcano’s last significant eruption was in 1538 (VEI 3), but its most devastating eruption occurred around 39 000 years ago. This cataclysmic event dispersed magma as far as 4 500 km (2,796 miles), reaching Greenland.

This adds to the ongoing concerns about the state of seismic activity in the Campi Flegrei region, as well as the preparedness level of nearby communities for future geological events.

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