The CIVISA (Centre for Seismic Information and Surveillance of the Azores) reported that an earthquake struck at 5:58 PM local time (6:58 PM in Lisbon), with its epicenter located approximately five kilometers south-southeast of Raminho.
“According to the available information, the earthquake was felt with a maximum intensity of III (Modified Mercalli scale) in Raminho (municipality of Angra do Heroísmo),” stated the center.
The initial earthquake, registering a magnitude of 2.7 on the Richter scale, was detected south-southwest of Altares on Terceira Island, as confirmed by the Portuguese Institute for Sea and Atmosphere (IPMA).
This tremor was recorded at 3:33 AM local time (4:33 AM in Lisbon) by the Azores Seismic Network stations, with the epicenter roughly six kilometers south-southwest of Altares.
The IPMA noted that it was perceived with a maximum intensity of III/IV (Modified Mercalli scale) in the parish of São Bartolomeu de Regatos.
The event was also felt, albeit with lesser intensity, in the parish of Ribeirinha.
These earthquakes are part of the “ongoing seismic-volcanic crisis on Terceira Island since June 2022,” according to CIVISA.
On the Richter scale, earthquakes are categorized by magnitude as micro (less than 2.0), very small (2.0-2.9), small (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 (when exceeding 10).
The Modified Mercalli scale measures “degrees of intensity and their respective descriptions.”
At an intensity of IV, considered moderate, “hanging objects swing, the vibration feels similar to the passing of heavy vehicles or the impact of a heavy ball against walls, parked cars rock, windows, doors, and dishes shake, glasses and dishes rattle or clink, and at the upper end of this grade, walls and wooden structures creak,” describes the IPMA on its website.
At an intensity of III, the tremor is considered weak, felt inside the house, and hanging objects sway, with a “vibration similar to that caused by the passing of heavy vehicles.”
