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São Jorge Island (Azores) volcano-seismic crisis 2022: latest updates

Обновленный: 26 июн 2022 13:47 GMT - Обновить
An earthquake swarm started under the NW part of the island on 19 March 2022. More than 2000 mostly small quakes of magnitudes from 1.6-3.5 have been registered within the first few days of the activity.
The swarm is likely caused by a magmatic intrusion at 10-15 km depth and could indicate renewed eruptive activity in the future. There is also a risk of larger quakes occurring as the processes continue.
On this page, we will collect information and updates on the events as they come in.

Seismic activity and inflation continue at lower levels

Update Fri 08 Apr 2022 06:56
Depth of quakes over time under Sao Jorge volcano
Depth of quakes over time under Sao Jorge volcano
The seismic swarm under the island's northwestern rift zone has decreased a lot during the past days, but it is still ongoing at lower levels.
Weak inflation also continued to be registered, which is why the official alert level remains at the second highest level of V4.

Earthquakes slow down

Update Fri 01 Apr 2022 18:38
Seismic trace of ROSA station on São Jorge island as of 1 April 2022 evening
Seismic trace of ROSA station on São Jorge island as of 1 April 2022 evening
Depth of quakes over time under Sao Jorge volcano
Depth of quakes over time under Sao Jorge volcano
The earthquake swarm continues but with reduced intensity. Only about 10 quakes above magnitude 2.0 occurred in the past 24 hours, although micro-seismic activity remains elevated, and seems to be increasing in the past hours.
Including quakes too small to be localized, official data speak of more than 25,000 tremors in total having occurred since the start of the seismic crisis.
In the absence of other published data, it is impossible to interpret the situation well or make well-founded predictions, but the scenario of a volcanic eruption in a near future seems to become less likely if seismic activity ceases. However, the official alert level remains at V4 (on a scale of 1-6).

Magnitude 4 quake rattles São Jorge island

Update Wed 30 Mar 2022 09:05
Seismic trace of ROSA station on São Jorge island, showing the magnitude 4 quake in the evening (image:
Seismic trace of ROSA station on São Jorge island, showing the magnitude 4 quake in the evening (image:
Accumulated seismic energy during the past 7 days
Accumulated seismic energy during the past 7 days
The seismic swarm continues with the first occurrence of a widely felt magnitude 4 quake last night at 9:56 pm local time, the strongest so-far in the current swarm. The quake was about 10 times larger than the previous largest-so-far quake, a magnitude 3.3 event at 6.41 pm on 19 March.
While the numbers of quakes has been lower in the past few days, it should be taken into account that last night's quake accounts for approximately the same seismic energy as all quakes during the past 7 days combined. This is because magnitude is a logarithmic scale: one magnitude 4 earthquake is approx. equivalent to 30 quakes of magnitude 3, or 1,000 magnitude 2 events.
Whether this marks a shift in the underlying processes, and whether it is tectonic in origin or caused by magmatic processes or a combination of both, remains unclear.
There were no damages reported by the magnitude 4 earthquake, but authorities and local population remain alarmed because the potential of stronger quakes and/or a volcanic eruption in the near future remains real.

São Jorge Island (Azores): likelihood of eruption increases as 20 million cubic meters of magma estimated intruded at depth

Tue, 29 Mar 2022, 07:08
Detected ground deformation at São Jorge island (image: CIVISA)
Detected ground deformation at São Jorge island (image: CIVISA)
Depth of quakes over time under São Jorge island
Depth of quakes over time under São Jorge island
According to latest calculations, the Volcanological Institute of the Canary Islands (INVOLCAN) estimated that as much as 20 million cubic meters of magma have intruded under the island of São Jorge since last March 19.
If the figures are correct, the likelihood of a volcanic eruption in the Azores is no longer a small one, and we therefore assign our color code "orange", as a warning of potential activity in the near future.
For comparison, the initial magma intrusion leading up to last year's eruption on La Palma Island in the Canary Islands was estimated to be only 11 million cubic meters only, while it erupted a total of approx. 300 cu m of magma in the course of the 3-month-long eruption from September-December 2021. The preceding seismic swarm lasted from 13-19 Sep 2021 and is in many ways quite similar to what is being observed now on São Jorge.

The estimates on magma intrusion volume are based on modeling the observed ground deformation, in particular its vertical inflation, from the analysis of synthetic aperture radar data acquired by the Sentinel-1 satellite of the European Space Agency. This method compares radar images of the same area but obtained on two different dates; small differences in phase variations of the reflected radio waves can be used to detect changes in the relief of the earth's surface on the scale of millimeters.
The areas with most uplift is near the northeastern coast approx. 10 km east of Velas, where ground uplift has amounted approx. 10 cm alone by now. It can be presumed that the center of the magma source is located under this area.
The seismic swarm under São Jorge itself so far contained more than 700 quakes of magnitudes above 2.0, with 26 quakes above magnitudes 3.0-3.6. In the past days, it has continued to decrease in intensity, although this does not necessarily mean that the danger is over. Earthquakes occur, when magma pressure opens new pathways, fracturing rock layers at depth. What if the rocks beneath the island are already fractured? This could be true as result of the quakes that already took place, the general setting of the island being in a tectonically active rift zone and the presence of older dikes from past eruptions. In that case, magma accumulation could take place without significant quake activity, and - as we had seen before and during La Cumbre Vieja's eruption on La Palma - an eruption could start any time with little immediate warning.

Possible scenarios for São Jorge volcano:
It is impossible to predict what will happen, whether an eruption will take place in the near future. All of the following scenarios are possible, but we do not know how likely each of them might be:
1) An eruption takes place within days or weeks from now, with little warning.
2) The seismic swarm and ground deformation end gradually or abruptly, only to be repeated in months or years from now. Eventually one of these will be leading up to an eruption then.
3) A stronger earthquake occurs and changes the configuration of the magma intrusion, either to stall or to break through to the surface in an eruption.
4) Activity dies down, and the magma intrusion at depth slowly cools over years and decades to come with no further activity directly related to it.

Authorities preparing for emergency

Update Mon 28 Mar 2022 15:29
While hundreds of people have already left the island, especially from Velas, authorities seem to take the situation very serious. Emergency plans are being activated and the army is setting up camps in case people need to evacuate their homes.

Uplift detected likely confirming magma intrusion at depth

Update Mon 28 Mar 2022 15:14
Seismic trace of ROSA station on São Jorge island, showing small quakes and what could be an episode of tremor (image:
Seismic trace of ROSA station on São Jorge island, showing small quakes and what could be an episode of tremor (image:
Depth of quakes over time under Sao Jorge volcano
Depth of quakes over time under Sao Jorge volcano
Preliminary satellite-based radar data confirm that a section of island's northern part, roughly corresponding to where the recent quakes have been occurring, has experienced uplift.
This almost certainly confirms that magma intrusion at depth is the cause of the seismic swarm.
The earthquake swarm itself continues, but has been decreasing in intensity. In the past 24 hours, São Jorge volcano had 1 quake of magnitude 3.0 and 25 quakes between 2.0 and 3.0. On the other hand, the seismic plot has been showing an episode of what could be volcanic tremor a short time ago this afternoon; it could also be a local disturbance (some machines running near the seismic station etc); we cannot judge this without other data available. However, it if IS volcanic origin, it could be sign that magma has been moving inside some of the newly created conduits.
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