The three events occurred within a period of about two hours.

The first was recorded at 10:13 am (11:13 am in Lisbon), with a magnitude of 1.9 on the Richter scale and an epicenter about 4 km northwest of the parish of Santa Bárbara, on Terceira Island.

According to CIVISA, it was felt with a maximum intensity of III, on the Modified Mercalli scale, in Santa Bárbara, in the municipality of Angra do Heroísmo.

At 10:35 (11:35 in Lisbon), a second earthquake was recorded, with a magnitude of 2.0 on the Richter scale and an epicenter approximately 5 km northeast of Santa Bárbara, felt with a maximum intensity of III/IV on the Modified Mercalli scale in the parish of Santa Bárbara.

The third event occurred at 12:26 (13:26 in Lisbon) and had a magnitude of 2.6 on the Richter scale, also with its epicenter approximately 5 km northwest of Santa Bárbara.

In this case, it was felt with a maximum intensity of IV on the Modified Mercalli scale in the parishes of Santa Bárbara, Cinco Ribeiras, Doze Ribeiras, Serreta, Raminho and Altares, in the municipality of Angra do Heroísmo, and in the parish of Biscoitos, in the municipality of Praia da Vitória.

These three earthquakes are part of the ongoing seismic-volcanic crisis on Terceira Island since June 2022.

Alert raised

On November 6th, the Crisis Office of CIVISA and the Institute of Volcanology of the University of the Azores (IVAR) raised the alert level for the Santa Bárbara volcano to V3, which means "volcanic system in a phase of reactivation".

The decision was based on "the increase in seismic activity", with a "growing trend" compared to the first months of the year and the fact that, "although not very intense", crustal deformation continues to be recorded in the area where the seismic-volcanic crisis is developing.

The alert level for the Santa Bárbara volcano had already been at V3 between June and December 2024, but since then it has remained at V2, which means "volcanic system in a phase of instability".

Since June 2022, seismic activity at the Santa Barbara volcano has been “above normal reference values,” with the most energetic event occurring on January 14, 2024, with a magnitude of 4.5 on the Richter scale.

The volcanic alert scale used by IVAR has eight levels, where V0 signifies a volcanic system in a resting phase and V7 an ongoing magmatic or hydromagmatic eruption, with colossal to mega-colossal explosiveness.

According to the Portuguese Institute of the Sea and the Atmosphere (IPMA), in an earthquake with an intensity of IV on the Modified Mercalli scale, the vibration is similar to that caused by the passage of heavy vehicles or the sensation of a heavy ball hitting the walls. Suspended objects sway, parked cars shake, windows, doors and dishes tremble, and glass and dishes clash or rattle. At the upper end of this degree, walls and wooden structures creak.