According to CIVISA, the earthquake was recorded at 11:31 AM local time (12:31 PM in Lisbon) and had its epicenter about four kilometers northeast of Santa Bárbara. “Based on the information available so far, the earthquake was felt with a maximum intensity of IV (Modified Mercalli Scale) in Santa Bárbara (municipality of Angra do Heroísmo),” CIVISA reported.
Another earthquake was felt on Terceira Island at 00:33 AM local time (01:33 AM in Lisbon) with its epicenter about five kilometers south of Altares, also in the municipality of Angra do Heroísmo. The quake, measuring 2.4 on the Richter scale, was felt with a maximum intensity of IV in São Bartolomeu, São Bento, Ribeirinha, and Raminho.
These earthquakes are part of the ongoing seismovolcanic crisis on Terceira Island since June 2022. On June 27, due to seismic activity on the island, CIVISA raised the alert level for the Santa Bárbara volcano to V3 and the island’s fissural volcanic system to V1.
According to the Richter scale, earthquakes are classified by their 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 greater than 10).
The Modified Mercalli Scale measures the “degrees of intensity and respective description.” With an intensity of IV, considered moderate, “suspended 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 sway, windows, doors, and dishes rattle, glasses and dishes clank or tinkle, and at the upper end of this degree, walls and wooden structures creak,” according to IPMA on their website.
