Seismic tremors on São Jorge

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From Saturday, March 19, 2022 at 4:05 pm, more than 1,300 tremors have already been recorded on the island of São Jorge in the Azores archipelago, of which more than 70 felt by the inhabitants.

(Data for March 21, 7 pm local time)

These are mainly weak tremors, max 3.3 on the Richter scale / 3-4 on the Mercalli scale. However, their frequency and location near the town of Velas are disturbing.

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Rui Marques, head of CIVISA (Centro de Informação e Vigilância Sismovulcânica dos Açores – Azores Seismic Information and Surveillance Center), said on the evening of March 21 that so far all the tremors had been of tectonic origin. However, due to their location in the area of ​​the rift zone, this seismic crisis should be considered tectonic-volcanic.

What actions are being taken?

The tremors, carbon dioxide levels and all other indicators are constantly monitored by the best volcanology specialists on the islands.

Residents prepare emergency backpacks with water, cookies, canned food, flashlights, batteries, thermal blankets, etc.

The authorities are prepared for the possible evacuation of the population – although we all hope that it won’t be necessary.

For clarification: The Azores are volcanic islands, situated at the interface between three tectonic plates. (I wrote about it in the article „Three active volcanoes in Terceira„). It’s perfectly normal to have tremors here. The earth in the Azores quakes daily, but the vast majority of these quakes are not felt.

In this case, what is disturbing is not the force but the frequency of the tremors on São Jorge.

Source: IVAR, March 22, 2022, 1:25 pm local time

What did it look like before?

Two historical land eruptions have been recorded on the western island of São Jorge: in 1580 and in 1808.

The 1580 eruption was the eruption of Queimada volcano. The eruption was preceded by several days of tremors and lasted about 4 months. At least 10 people and over 4,000 head of cattle were killed there. The gasses and volcanic ash also destroyed the crops.

In 1808, the Urzelina volcano erupted. It was preceded by weeks of tremors, intensified just before the eruption. Over 30 people lost their lives. Houses and farmlands were also destroyed.

The inhabitants of São Jorge remember one more eruption – in 1964, it was an eruption of an underwater volcano off the coast of Ponta dos Rosais. On the occasion of this eruption, a powerful seismic crisis also took place, which led to many devastations in Rosais and Velas.

In 1980, in turn, there was a powerful earthquake (7.2 on the Richter scale) with an epicenter about 34 km southwest of Angra, which destroyed much of Terceira and part of São Jorge, and affected Graciosa.

How will it be now?

No one knows this. It’s known that no one wants the worst to happen. That’s why everything is monitored on an ongoing basis and the population is secured.

Nothing unusual is happening on the other islands at the moment. We live and work, and only observe the development of events.

As they say here – um dia de cada vez. One day at a time.

Azory, São Jorge, Pico da Esperança
São Jorge, Pico da Esperança. Photo by Carla Silveira

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