The Center for Information and Seismovolcanic Surveillance of the Azores (CIVISA) reported an earthquake recorded at 18:27 local time (19:27 in Lisbon) with its epicenter approximately four kilometers north-northeast of Santa Bárbara, in the municipality of Angra do Heroísmo.
“Based on the information available so far, the earthquake was felt with a maximum intensity of V (Modified Mercalli scale) in Santa Bárbara, Doze Ribeiras, Cinco Ribeiras, São Bartolomeu, Terra Chã, São Mateus, São Pedro, Posto Santo, Santa Luzia, and Nossa Senhora da Conceição (municipality of Angra do Heroísmo) and in Biscoitos (municipality of Praia da Vitória),” it was noted.
The tremor “was also felt with intensity IV in Serreta, São Bento, Ribeirinha, and Feteira (municipality of Angra do Heroísmo) and Quatro Ribeiras, Altares, and Agualva (municipality of Praia da Vitória).”
According to CIVISA, the event “is part of the ongoing seismovolcanic crisis on Terceira Island since June 2022.”
On the Richter scale, earthquakes are classified by magnitude as micro (less than 2.0), very minor (2.0-2.9), minor (3.0-3.9), light (4.0-4.9), moderate (5.0-5.9), strong (6.0-6.9), major (7.0-7.9), great (8.0-8.9), extraordinary (9.0-9.9), and extreme (above 10).
The Modified Mercalli scale measures “degrees of intensity and respective description”.
With an intensity V, considered strong, the tremor is “felt outside, the direction of the movement can be determined, people are awakened, liquids oscillate and some may spill, small objects in unstable equilibrium move or fall,” reveals the Portuguese Institute for Sea and Atmosphere (IPMA) on its website.
In this degree, “doors swing, close, or open, blinds and pictures move” and “clock pendulums may stop or start or change their oscillation state.”
With an intensity IV, considered moderate, “hanging objects swing, the vibration is similar to that caused by the passage of heavy vehicles or the sensation of a heavy ball hitting the walls, parked cars shake, windows, doors, and dishes vibrate, glass and dishes clash or tinkle and at the upper part of this degree, walls and wooden structures creak,” describes the IPMA.
