A seismic swarm started a few days ago on the island of São Jorge. Although this activity may be strictly of tectonic origin, vigilance is required as it could herald a future volcanic eruption. The authorities are on alert…
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The seismic activity began on Saturday March 19, with earthquakes relatively low magnitude, but in large numbers, localized and grouped in the central western part of the island. Monday, March 21, more than 1,800 earthquakes had already been recorded, including 94 felt by the inhabitants but without causing any damage. This seismicity is still ongoing today with still 20 events felt on the night of March 22 to 23!
Seismic activity continues at high levels on São Jorge Island (Azores). Since Saturday afternoon, +1800 earthquakes were recorded on the western half of São Jorge, at least 94 were felt by the population. For detailed information follow SRPCBA and CIVISA.https://t.co/M53oTyhxhbpic.twitter.com/UGV8hEZEQM
— Adriano Pimentel (@AdrianoAzoVolc) March 22, 2022
Map showing the current seismic swarm on the island of São Jorge, in the Azores.
The seismic activity in the Azores is not abnormal, because thearchipelago is original volcanic, but also because it is located in a place where tensions in the earth’s crust are particularly accumulating. Clearly, this activity can just as well betectonic or volcanic origin. In this second case, it would be generated by the rise of a magma towards the surface, which could be highlighted by a deformation of the ground which is not observed for the moment. However, a scientific team was dispatched to the site to try to find out more…
Here is a quick ASF interferogram with “wrapped” fringes (2.8 cm contours) from Sentinel-1 SAR acquired on 2022/03/09-03/21. There are some fringes on São Jorge, but there are also fringes on Ilhas Pico and Faial, so substantial atmospheric water vapor variations affect InSAR. pic.twitter.com/OBN0oOAX04
—Dr. Eric J Fielding, PhD (@EricFielding) March 22, 2022
The interferogram makes it possible to notice deformations of the ground between two passages of a satellite but, on this image, fringes are remarkable on the three islands and not only on São Jorge (the northernmost island), which makes rather think of atmospheric disturbances.
In this context, the authorities have asked the 10,000 inhabitants of the island to be vigilant, because a volcanic eruption is possible in the short or medium term. The last eruption in the Azores was that of Capelinhos, in 1958, on the island of Faial and if at least one underwater eruption took place off São Jorge for the last two centuries, the last on this island dates back to 1808! An eruption at this location would most certainly be fissural, much like in the Canary Islands lately, which also explains the very elongated shape of the island, 53 km long and 8 km wide.
The volcano on Sao Jorge Island in the Azores archipelago shows signs of activity: more than 1,800 in three days. © GeologyHub, YouTube
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