The ground shook twice on Thursday night in the Azores, with two small earthquakes rattling Terceira Island just hours after the volcanic alert for the nearby Santa Bárbara volcano was raised to level V3 – meaning the volcanic system is in a reactivation phase.
According to the Azores Seismic Information and Surveillance Centre (CIVISA), the tremors, measuring 3.6 and 3.5 on the Richter scale, struck at 9.54pm, with epicentres just a few kilometres from Santa Bárbara. The shocks were felt across Terceira and even on neighbouring São Jorge Island, reaching intensity V on the Modified Mercalli scale, considered strong enough to wake people, rattle doors and windows, and send small objects tumbling from shelves.
The Portuguese Institute for the Sea and Atmosphere (IPMA) registered just one, a 3.8 magnitude quake near Doze Ribeiras, confirming that the tremors were widely felt across the region.
These latest quakes form part of a seismovolcaniccrisis that has been ongoing on Terceira since June 2022, with activity at the Santa Bárbara volcano remaining above normal levels for more than three years.
João Luís Gaspar, coordinator of the Crisis Office at the University of the Azores’ Institute of Volcanology, said monitoring efforts have now been stepped up.
“We are currently doing some more field work and next week we will carry out some missions, which we are preparing, to collect gases and water on the perimeter of the Santa Bárbara volcano,” he told Lusa news agency.
The Santa Bárbara volcano’s alert level has fluctuated between V2 and V3 in recent years. The last major event, a 4.5-magnitude quake in January 2024, was the most energetic in the current cycle.
According to João Luís Gaspar, the alert level was raised due to an increase in seismic activity in September and October.
