Azores' Terceira Feels Fresh Tremors as Volcano Stirs; Stay Prepared

Minor Earthquakes Rattle Terceira, Tied to Ongoing Volcanic Unrest

Early Thursday morning, inhabitants of Terceira in the Azores felt a quick jolt when a shallow earthquake of magnitude 2.3 struck at 07:00 local time. According to the Centre for Information and Seismo-Volcanic Surveillance of the Azores (CIVISA) and the Portuguese Institute for Sea and Atmosphere (IPMA), the epicentre lay roughly six kilometres south-southeast of Altares, within the municipality of Angra do Heroísmo.

Where the shaking was felt

The event registered a maximum intensity of IV on the Modified Mercalli scale in several parishes of Angra do Heroísmo—São Bartolomeu dos Regatos, Terra Chã, São Bento, Nossa Senhora da Conceição and Ribeirinha—where residents reported swaying hanging objects and brief vibration similar to the passage of heavy vehicles. In Santa Bárbara the intensity reached III, noticeable mainly indoors but still considered weak.

A second tremor minutes later

Roughly an hour after the first quake, IPMA sensors detected a magnitude 2.6 shock about ten kilometres northwest of Angra do Heroísmo at a depth of just over five kilometres. That tremor was also felt, though lightly, by people near the epicentre.

Part of a broader seismic sequence

These incidents form part of a persistent seismo-volcanic crisis that started in June 2022 and centres on the Santa Bárbara volcano. Activity has remained above background levels since March 2024, prompting CIVISA to keep the volcanic alert for Santa Bárbara at V3 (reactivated system) and the fissural system of the island at V1. Scientists link the swarm of low-magnitude quakes to magma movement at depth rather than to tectonic faulting.

Recent days illustrate the pattern: on Tuesday a magnitude 3.0 shock east of Serreta reached intensity IV/V, and several smaller events—ranging from magnitude 1.4 to 2.7—were recorded on Wednesday near Raminho and Serreta. Earlier in the year, Terceira experienced quakes as strong as magnitude 4.5, the most energetic since the crisis began.

No damage, but vigilance urged

The Regional Civil Protection and Fire Service of the Azores (SRPCBA) reported no injuries or structural damage from Thursday’s tremors. Nevertheless, the agency is urging residents to keep emergency kits ready, secure heavy furniture, and familiarise themselves with safe zones inside their homes. Should stronger shocks occur, people are advised to drop, cover and hold on, or, if outdoors, move away from buildings and power lines.

What happens next?

CIVISA’s monitoring network continues to analyse seismicity, ground deformation and gas emissions on Terceira. Although the majority of events remain too weak to cause harm, the current alert level signals that more noticeable earthquakes are possible. Any significant change in the parameters being tracked will be communicated immediately to civil-protection authorities and the public.