The ongoing seismic crisis on Terceira Island, in the Azores, is centered around the Santa Bárbara volcano, but has no abnormal values other than seismicity, the president of the Seismic Information and Surveillance Center said yesterday.
Gabriela Queiroz, from the Seismic Information and Surveillance Center of the Azores (CIVISA), explained that, on Terceira Island, there has been “seismic activity centered essentially in the area of the Santa Bárbara volcano”, which “has been felt more intensely since June 2022”.
“We’ve been raising our alert to V2 (possible reactivation of the system — signs of moderate activity) since then and what we’ve seen is that this seismic activity has manifested itself in more intense and less intense phases. We’re currently in a more intense phase,” says the head of CIVISA.
The Santa Bárbara volcano, on Terceira island, is considered an active volcano, having last erupted in 1761, with two calderas.
Since June 24, 2022, the seismic activity of the Santa Bárbara volcano has been “above normal reference values”, with a scientific alert level of V2.
Gabriela Queiroz does not dissociate [the crisis] at all from what has been happening in the archipelago for around two years, or from the seismic crisis in São Jorge, or even from the activity that has developed to the west of the island of Faial”.
The volcanologist points out that CIVISA’s monitoring systems “don’t indicate significant variations either in terms of coastal deformation or the release of volcanic gases”, and that the parameter that is “clearly above average is seismic activity”.
“We are always monitoring the evolution of the situation in order to eventually detect any signs or not,” says the volcanologist.
Asked if there are any reasons for concern, Gabriela Queiroz replies that we live in a region “with active volcanic systems”, and we have to “be aware of the situation”.
The last earthquake recorded on Terceira Island, measuring 3.7 on the Richter scale, was recorded on Sunday night with its epicenter southwest of Agualva, on Terceira Island, according to the Portuguese Institute for the Sea and Atmosphere (IPMA).
According to IPMA, the earthquake was recorded at the stations of the Seismic Network of the Azores Archipelago on Sunday at 23:56 local time (00:56 in Lisbon), with the epicenter located about six kilometers southwest of Agualva.
According to the Richter scale, earthquakes are classified according to their magnitude as micro (less than 2.0), very small (2.0-2.9), small (3.0-3.9), slight (4.0-4.9), moderate (5.0-5.9), strong (6.0-6.9), large (7.0-7.9), important (8.0-8.9), exceptional (9.0-9.9) and extreme (when greater than 10).
The Modified Mercalli scale measures “degrees of intensity and their description”.
When there is an intensity of IV, considered moderate, parked cars shake, windows, doors and crockery shake and “glass and crockery rattle or clink”, and walls or wooden structures may creak.
With intensity V, the shaking is felt outside the house and the direction of movement can be assessed, people are woken up; liquids sway and some leak, small objects in unstable balance move or are knocked over, doors swing, close or open and blinds and pictures move.
