Two small earthquakes were felt on Terceira Island in the Azores in the early hours of this Thursday morning amid the archipelago’s ongoing seismo-volcanic crisis, the Azores Seismic and Volcanic Information Center (CIVISA) announced.
The first tremor, measuring 1.9 on the Richter scale, struck at 00.42am local time, with an epicentre about four kilometres southeast of Raminho, in the municipality of Angra do Heroísmo. Just one minute later, a second quake of magnitude 2.2 hit roughly five kilometres south-southwest of Altares.
Both quakes reached Intensity III on the Modified Mercalli scale – considered weak but noticeable indoors – and were felt in Serreta and Altares, according to CIVISA.
The events are part of the seismo-volcanic crisis that has been ongoing on Terceira since June 2022. This week, the University of the Azores’ Institute of Volcanology (IVAR) raised the alert level for the Terceira Western Fissural Volcanic System to V3 (reactivation phase), matching the alert already in place for the Santa Bárbara volcano.
IVAR says seismic activity has stayed well above normal throughout November, even if low in magnitude, and continues to rise around both Santa Bárbara and the Western Fissural System, particularly near the Mistérios Negros area, where the two volcanic systems intersect. This, the institute notes, explains the series of small tremors felt by residents.
Despite the uptick, IVAR’s Crisis Office has opted to maintain Santa Bárbara at alert level V3 while raising the neighbouring system to the same level due to their shared fracture zone.
For context, quakes below magnitude 3.0 are classed as very small, and Intensity III tremors are typically felt indoors, causing light vibration similar to the passing of heavy vehicles.
