“Considering that since March 2024, seismic activity in the western sector of Terceira island has been clearly above normal levels and has been accompanied by some signs of crustal deformation [in rocky bodies], facts that indicate the occurrence of a magmatic intrusion at depth, the crisis office decided to raise the alert level of the Santa Bárbara volcano to V3 and the Fissural Volcanic System of Terceira to V1”, reads the website of the Azores Seismovolcanic Information and Surveillance Center (CIVISA).
At volcanic alert levels, V0 means “resting state” and V6 “ongoing eruption”, according to the information available on the CIVISA website.
The Santa Bárbara volcano was at level V2, which means a possible reactivation of the system, now moving to the next level (confirmation of system reactivation).
According to the Institute of Volcanology of the University of the Azores (IVAR), the information obtained through the monitoring network managed by CIVISA allows us to verify that the seismovolcanic crisis that has been registered on the island of Terceira since 24 June 2022 “continues, showing clear increment.”
Within the scope of this crisis, seismic activity has been centered “with greater incidence within the perimeter of the Santa Bárbara volcano and has been essentially characterised by the occurrence of microseisms”.
The most energetic earthquake occurred on 14 January, 2024, at 07:19 am local time, with a magnitude of 4.5 on the Richter scale and an epicenter approximately one kilometer east of Serreta, and was felt with a maximum intensity of VI on the Modified Mercalli scale, in the western sector of the island.
At the time, and according to CIVISA, “some cracks were recorded in houses with little resistance to seismic action, the fall of loose stone walls, damage to some communication routes and landslides in the interior of the island and on cliffs”.
On the other hand, CIVISA explains that the recorded seismicity has also covered, although less frequently, the Fissural Volcanic System of Terceira, especially in a section that crosses the Santa Bárbara mountain range and extends to the vicinity of the Golf Club, the east.
The organization also states that activity has been generated further south, to the east of the area of influence of the Santa Bárbara volcano, in an area between Cinco Ribeiras and Angra do Heroísmo, “and in the sea, to the west and south of the island”.
“The phenomenon that is affecting the island of Terceira cannot be dissociated from the increase in seismovolcanic activity that has occurred in the Azores region and, in particular, in the Central group, since the beginning of 2022”, he explains.
CIVISA admits the possibility that events experienced by the population will continue to occur, which could reach magnitudes and intensities greater than those recorded to date, taking into account “the pattern of activity observed”.