According to CIVISA, the first tremor, with a magnitude of 3.0 on the Richter scale, occurred at 11:46 AM local time (12:46 PM in Lisbon), followed by a second tremor of 2.9 magnitude at 11:50 AM.
Both tremors were centered approximately four kilometers northeast of Doze Ribeiras, in the municipality of Angra do Heroísmo.
“Based on the available information so far, the earthquakes were felt with a maximum intensity of IV (Modified Mercalli Scale) in Doze Ribeiras, Santa Bárbara, Cinco Ribeiras, São Bartolomeu, Raminho, Altares (municipality of Angra do Heroísmo), and Biscoitos (municipality of Praia da Vitória),” stated CIVISA.
The tremors were also felt with an intensity of III in São Mateus da Calheta, São Pedro, Santa Luzia, Nossa Senhora da Conceição (Angra do Heroísmo), and in Agualva (municipality of Praia da Vitória).
These events are part of the “ongoing seismic-volcanic crisis on Terceira Island since June 2022.”
According to 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), exceptional (9.0-9.9), and extreme (over 10).
The Modified Mercalli Scale measures “degrees of intensity and corresponding descriptions.”
With an intensity of III, a tremor is considered weak and is felt indoors, with hanging objects swaying, producing a “vibration similar to the passage of heavy trucks,” according to the IPMA on its website.
At intensity IV, considered moderate, “hanging objects swing, the vibration is akin to the passage of heavy trucks or a heavy ball striking walls, parked cars rock, windows, doors, and dishes rattle, glasses and dishes collide or clink, and at the upper end of this intensity, walls and wooden structures creak.”
