An earthquake was recorded at 9:00 PM local time (10:00 PM in Lisbon), with the epicenter approximately four kilometers south of Ribeirinha, in the municipality of Angra do Heroísmo, according to CIVISA.
“Based on the available information so far, the earthquake was felt with a maximum intensity of III/IV (Modified Mercalli scale) in Ribeirinha and Feteira (municipality of Angra do Heroísmo),” it stated.
The tremor was also felt with intensity III in Porto Judeu and Nossa Senhora da Conceição, also in the municipality of Angra do Heroísmo.
The event is part of the ongoing seismovolcanic crisis on Terceira Island since June 2022, according to CIVISA.
The Richter scale classifies earthquakes 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 over 10).
The Modified Mercalli scale measures “degrees of intensity and their respective description.”
With an intensity of IV, considered moderate, “hanging objects sway, the vibration is similar to that caused by the passage of heavy vehicles or the sensation of a heavy ball hitting walls, parked cars shake, windows, doors, and dishes rattle, glasses and dishes clink, and at the upper part of this degree, walls and wooden structures creak,” describes the Portuguese Institute for Sea and Atmosphere (IPMA) on its website.
At an intensity level of III, the quake is considered weak, felt indoors, with hanging objects swaying, and a “vibration similar to that caused by heavy vehicles passing,” according to IPMA.
