The Institute of Volcanology of the University of the Azores (IVAR) increased the volcanic alert level of Santa Barbara volcano on Terceira Island to V3 on a scale ranging from V0 (green, normal) to V6 (red, erupting). The decision came after a new seismic crisis has been affecting the western part of the island since June 24, 2022, continues, with a current tendency of increasing.
The alert level 3 means that certain geophysical parameters (such as seismicity) are strongly elevated and while it is not thought likely that an eruption might occur in a near future, there is an increased risk of minor steam explosions caused by the shallow hydrothermal system, and of course, the situation can develop further and needs close monitoring.
The seismic activity has so far involved mostly micro-earthquakes (i.e. below magnitudes of 2) and been centered under the Santa Bárbara Volcano, the youngest volcano on the island, forming its western part. Overall, seismic activity of the central Azores has been elevated over the past few years, which is likely connected to the current crisis.
The volcano observatory reported that the most energetic quake occurred on January 14, 2024, at 7:19 am (local time), reached a magnitude of 4.5 on the Richter Scale and had an epicenter approximately 1 km E of Serreta, having been felt with a maximum intensity of VI on the Modified Mercalli Scale, in the western sector of the island.
This quake caused some cracks in houses with little resistance to seismic action; loose stone walls collapsed, and there was damage to some communication routes, as well as landslides in the interior of the island and on cliffs.
Terceira Fissure volcanic system raised to alert V1
Increased seismicity also involved, but less strongly, the Terceira Fissure Volcanic System, especially in a section that crosses the Serra de Santa Bárbara and extends to the vicinity of the Golf Club, to the east. The observatory raised the alert level for this part to V1 (meaning slightly elevated activity).
Seismic activity has also been detected further south, to the east of Santa Bárbara Volcano, between Cinco Ribeiras and Angra do Heroísmo, as well as in the sea, to the west and south of the island.
„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, facts that indicate the occurrence of a magmatic intrusion at depth, the Crisis Office has decided to raise the alert level of the Santa Bárbara Volcano to V3 and of the Terceira Fissural Volcanic System to V1.“
„The phenomenon that is affecting Terceira Island cannot be dissociated from the increase in seismic activity that has been occurring in the Azores region and, in particular, in the Central Group, since the beginning of 2022, and the pattern of activity observed indicates the possibility of continued occurrence of events felt by the population, which may eventually reach magnitudes and intensities greater than those recorded to date,“ the observatory wrote in its recent bulletin.