Category: Swarm

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Earthquake swarm in Brennisteinsfjöll volcano

I am sorry that I am late on writing this article. I was moving from Denmark to Iceland and that was a lot of effort and I’ve been tired after this move.

On Sunday, 24 September 2023 an earthquake swarm took place in Brennisteinfjöll volcano, in a area called Geitarfell (Goat Mountain) in Brennisteinsfjöll volcano. Largest earthquakes had a magnitude of Mw3,0 to Mw3,2. A lot of smaller earthquakes took place at this same location.

Yellow dots at the location where the Sunday earthquake swarm took place. There's a lot of earthquake activity on the Reykjanes peninsula at the moment. Shown with two green stars, one at Svartsengi and the other in Kleifarvatn lake.
Yellow dots show the Sunday earthquake activity. Copyright of this image belongs to Icelandic Met Office.

This earthquake activity didn’t have any short term signs that an eruption is about to happen at this location. I don’t know when last eruption took in this location, but it was clearly more than 6000 years ago.

Earthquake webicoders

Since I have moved back to Iceland. I am now recording earthquakes again. The webicoders are going to go online tomorrow (if no delays). They can be found here once they are back online.

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Earthquake swarm north of Grindavík town

Today (18. September 2023) there was an earthquake swarm north of Grindavík town. Largest earthquake had a magnitude of Mw2,7 and was felt in Grindavík town according to Icelandic Met Office. This earthquake activity has the direction of SW to NE and is under the road to Grindavík town.

Earthquake activity north of Grindavík town. Shown with orange dots on this map from today.
Earthquake swarm activity north of Grindavík town. Copyright of this image belongs to Icelandic Met Office.

This is clearly a dyke intrusion taking place at this location. This location is bad, because this area has infrastructure that is important to Grindavík town. In this area both hot and cold water is transported along with electricity wires (I think, they might have a different path, but it is at most nearby). Eruption at this location would be a major hazard and a problem. Currently there are no signs that this magma is looking for a path to the surface.

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High earthquake activity in Fagradalsfjall volcano

Yesterday (15. September 2023) an earthquake swarm took place on Fagradalsfjall volcano. This earthquake swarm wasn’t in the news because it was only small earthquakes, that is earthquakes with magnitude less of Mw1,0. It was not even felt by the people standing on the volcano because of depth. If this earthquake swarm has stopped I don’t know. Since most of this earthquakes don’t show up in the automatic earthquake list at Icelandic Met Office website. They only appear after a manual review by Icelandic Met Office.

A lot of orange dots on Fargradalsfjall volcano showing high level of earthquake activity in the volcano.
High earthquake activity in Fagradalsfjall volcano. Copyright of this image belongs to Icelandic Met Office.

In my view, this means that next eruption might happen between November to February 2024 if this earthquake activity and dyke intrusion activity continues as it is currently doing. It has happened before earlier eruptions that a high period of activity is followed by a period of quiet until an eruption happens. Why that is I don’t know, that is a pattern I’ve observed. I don’t know if there has been change after last eruption in Fagradalsjall volcano. That is a possibility that should not be ruled out.

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Earthquake swarm close to Geirfugladrangur island

On Monday 11. September 2023 an earthquake swarm took place close to Geirfugladrangur island out on the Reykjanes ridge. Largest earthquake had a magnitude of Mw3,4. Other large earthquake had magnitude of Mw3,2 and Mw3,0. Other earthquakes where smaller in magnitude, according to Icelandic Met Office, but this earthquake swarm has not been reviewed yet so magnitudes might change when that happens.

Green stars and yellow dots on Reykjanes ridge far from the coastline that shows the location of this earthquake swarm. Its in the more deeper areas of the Reykjanes ridge.
Earthquake swarm on the Reykjanes ridge. Copyright of this image belongs to Icelandic Met Office.

Earthquakes in this earthquake swarm where not felt, because of distance from the coastline and populated areas.

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Earthquake swarm in Krýsuvík-Trölladyngja volcano

During the night of 9. September 2023 an earthquake swarm started at 03:24 UTC with a magnitude Mw3,8 earthquake. This earthquake was felt in Reykjavík area and other nearby areas.

Green star and red dots in Krýsuvík-Trölladyngja volcano on the Reykjanes peninsula. There are also many other dots over the Reykjanes peninsula showing earthquake activity in other volcanoes.
Green star in Krýsuvík-Trölladyngja volcano. Copyright of this image belongs to Icelandic Met office.

Its unclear if this earthquake swarm is ongoing. There is a lot of earthquake activity in this area because of inflation in Fagradalsfjall volcano.

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Dyke intrusion into Fagradalsfjall volcano

Today (7. September 2023) an tyke intrusion took place in Fagradalsfjall volcano. The main depth of the dyke intrusion is at around 7 km depth. All earthquakes following this dyke intrusion where small in magnitude, from Mw0,1 in magnitude and up to Mw1,0 in magnitude. This seems to be a rather large dyke intrusion, since part of it does not create any earthquake activity at all because of earlier dyke intrusions at this depth in this part of Fagradalsfjall mountain.

Earthquake activity in Fagradalsfjall volcano shown here with orange dots because all earthquakes are small. A area of dots just east of Keilir mountain, showing more earthquake activity.
Earthquake activity in Fagradalsfjall volcano. Copyright of this image belongs to Icelandic Met Office.

Morgunblaðið (link below) is reporting that inflation has now reached 15mm in this area. This is really soon after the end of the eruption, since in last three eruptions, dyke intrusions and other early signs of activity that an eruption is about to happen starts around three to six months earlier before an eruption happens at the ten month time, as has been the case in the last three eruptions. It is possible that next eruption is going to happen earlier than last three eruptions. It is possible to know when next eruption is going to happen.

Icelandic News about this

Skjálftavirkni og vísbending um kvikusöfnun (mbl.is, Icelandic)

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Earthquake in Reykjanes volcano

Today (1. September 2023) at 17:55 UTC an earthquake with the magnitude of Mw3,1 took place in Reykjanes volcano. This earthquake was located out in the ocean and some distance from the coastline. I don’t think it was felt. Few other smaller earthquakes took place at the same location following the largest earthquake.

Green star and red dots out in the ocean not far from Reykjanestá area in the volcano Reykjanes. Time on picture is 01. Sep. 2023 at 19:40.
Earthquake activity in Reykjanes volcano. Copyright of this image belongs to Icelandic Met Office.

There is a storm now in this area of Iceland. That makes detection of smaller earthquakes impossible, along with distance from the coastline. If this earthquake swarm is going to be ongoing when the storm ends is impossible to know.

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Dyke intrusion into Brennisteinsfjöll volcano

During the night of 26. August 2023 an dyke intrusion started in Brennisteinsfjöll volcano. This was in the form of many small earthquakes, most of them did not reach magnitude Mw1,0. What gives this away as an dyke intrusion is the fact the deepest earthquake in this swarm had a depth of 21,1 km. There was interestingly, a lot of surface earthquakes. I am not sure on why that is.

Yellow dots in Brennisteinsfjöll volcano the east of Fagradalsfjall volcano on Reykjanes peninsula. A lot of smaller earthquakes all over the Reykjanes peninsula on this map. Time on map is 26. August 2023 at 17:00 Icelandic time.
Earthquake activity in Brennisteinsfjöll volcano. Copyright of this image belongs to Icelandic Met Office.

There’s no risk of eruption at the moment from Brennisteinsfjöll volcano. Earthquake activity is too low and this process is clearly not far along now for an eruption too happen. That might change without much warning at some point.

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Strong earthquake swarm close to Geirfugladrangur on Reykjanes ridge

Yesterday (13. August 2023) an large earthquake swarm took place close to Geirfugladrangur (small rock island, population birds) on the Reykjanes ridge. The largest earthquake had a magnitude of Mw4,5 and was felt to Akranes town and possibly in other nearby towns on Reykjanes peninsula. There where not many reports about this earthquake being felt. Something above 400 earthquakes took place during the most active phase of this earthquake swarm.

A lot of green stars on Reykjanes ridge, a little off the coast of Iceland. Along with a lot of yellow dots showing the age of the earthquakes. A lot of dots showing earthquakes in other areas on the Reykjanes peninsula.
Earthquake activity on the Reykjanes ridge. Copyright of this image belongs to Icelandic Met Office.

This earthquake swarm seems to be ongoing. It is at the moment, at much slower rate than before. There are clues that suggest this might have been a earthquake activity connected to magma movements in this area. Its difficult to be sure, because this area is under the ocean and measuring what is going on gets more difficult as future away from land activity happens. Eruption at this distance is going to appear on the Icelandic Met Office SIL network.

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Earthquake swarm in Torfajökull volcano

Today (30. July 2023) an earthquake swarm took place in Torfajökull volcano. This volcano is located north of Katla volcano (Mýrdalsjökull glacier). This area has had regular earthquake swarms over the year. Why is not clear. There is no clear signal of magma movement in this area. Torfajökull erupts highly Felsic magma that’s mostly explosive and some type of magma that can flow as a lava flow (maybe in later stage of an eruption, I don’t know for sure).

Green star north of Katla volcano (Mýrdalsjökull glacier) and in Torfajökull volcano caldera rim to the north. Time on map is 30. July 2023 at 19:40 (Iceland time)
Earthquake activity in Torfajökull volcano. Copyright of this image belongs to Icelandic Met Office.

The largest earthquake in this swarm had a magnitude of Mw3,2. It was felt in nearby tourist areas and caused few rock slides. Icelandic Met Office is still warning against rock slides because of this earthquakes close to the earthquake swarm location. There is a ongoing risk of more stronger earthquakes in this area of the volcano at the writing of this article.