Earthquake activity continued on Terceira Island as residents experienced the fourth tremor of the day, following three earlier quakes recorded between 10:13 a.m. and 12:26 p.m. local time.
The most recent seismic event, according to CIVISA, occurred at 6:45 p.m. local time, registering a magnitude of 2.3 on the Richter scale. The epicenter was located approximately 4 km northeast of the Santa Bárbara parish on Terceira Island.
Reports indicate the earthquake was felt with a maximum intensity of IV on the Modified Mercalli Intensity scale in the parishes of Santa Bárbara, Doze Ribeiras, Serreta, and São Bartolomeu de Regatos, within the municipality of Angra do Heroísmo.
The morning and early afternoon tremors, also centered northeast of Santa Bárbara, registered magnitudes of 1.9, 2.0, and 2.6 on the Richter scale, with perceived intensities of III and IV on the Modified Mercalli Intensity scale.
These seismic occurrences are part of an ongoing seismo-volcanic crisis affecting Terceira Island since June 2022.
On November 6, the CIVISA Crisis Office and the Azores University’s Volcano Institute (IVAR) upgraded the alert level for the Santa Bárbara volcano to V3, indicating “volcanic system in reactivation stage.”
The decision was based on an “increase in seismic activity,” with a “rising trend” compared to earlier in the year, alongside continued “crustal deformation” in the crisis area, albeit of low intensity.
The alert level for the Santa Bárbara volcano had previously been at V3 between June and December 2024, before being downgraded to V2, which signifies a “volcanic system in an unstable phase.”
Since June 2022, seismic activity at the Santa Bárbara volcano has remained “above normal reference values,” with the most significant event occurring on January 14, 2024, registering a magnitude of 4.5 on the Richter scale.
The IVAR volcanic alert scale comprises eight levels, with V0 indicating a volcanic system at rest and V7 denoting an ongoing magmatic or hydromagmatic eruption of colossal to mega-colossal explosivity.
According to the Portuguese Institute for Sea and Atmosphere (IPMA), a level IV intensity earthquake on the Modified Mercalli scale produces a sensation similar to the passage of heavy vehicles or the impact of a heavy ball against walls. Suspended objects swing, parked cars rock, windows, doors, and dishes rattle, and glassware clinks. At the upper range of this level, walls and wooden structures creak.
