Strong earthquake swarm ongoing on Reykjanes ridge

At midnight on 1-August-2021 an earthquake swarm seems to have started deep on the Reykjanes ridge. The current distance seems to be around 220 km away from Reykjavík or 190 km from Grindavík town. At this distance the location from Icelandic Met Office are not accurate. At the writing of this article the earthquake swarm seems to be ongoing.

Earthquake activity deep on the Reykjanes ridge. Many green stars are on the map that goes south along the Reykjanes ridge
The earthquake activity as it is shown on Icelandic Met Office map. Copyright of this image belongs to Icelandic Met Office.

Largest earthquake recorded at the writing of this article had a magnitude of Mw5,2 and the rest of the earthquakes have magnitude between Mw4,0 and Mw4,8. Overview of this earthquake activity can be found here on EMSC website. This links works as I publish this article. How long it is going to work I don’t know.

The current distance makes it impossible to know for sure what is going on at this location. The pattern of this earthquake activity suggests that this might be earthquake activity because of magma movement in the crust, but there is not any way to confirm this because of the location. Even if there is an eruption at this location it won’t make any difference to the surface of the ocean, since depth of the ocean at this location is more than 1 km. I don’t know the exact depth.

More earthquake activity in Katla volcano

Today (31-July-2021) at 12:53 UTC an earthquake with magnitude of Mw3,3 took place in Katla volcano. A swarm of smaller earthquakes continued after the largest earthquake, this earthquake activity seems to be ongoing at the writing of this article.

Earthquake activity in Katla volcano at 18:50 UTC this image shows three green stars, two of the stars are earthquakes from 29-July activity. New green star is from the earthquake today (31-July)
Earthquake activity in Katla volcano. Copyright of this image belongs to Icelandic Met Office.

Summer earthquake activity in Katla volcano is common and that makes it less clear what is going on in Katla volcano at the writing of this article. There is now a chance of more earthquake activity in Katla volcano.

Earthquake activity in Katla volcano yesterday (29-July-2021)

Yesterday (29-July-2021) there was an earthquake activity in Katla volcano. Two strongest earthquakes had the magnitude of Mw3,2 at 19:20 and 19:22 UTC. Third largest earthquake at 19:28 UTC had a magnitude of Mw2,8.

Cluster of smaller earthquakes in blue and red colours inside Katla volcano caldera. Two green stars on the north-east side of the caldera show the largest earthquakes.
Earthquake activity in Katla volcano. Copyright of this image belongs to Icelandic Met Office.

It is unclear if this earthquake activity is just summer activity or part of a larger activity. At this time I am not expecting an eruption since the earthquake activity is currently too low for such event to about to take place. There are going to be thousands of earthquakes in Katla volcano before an large eruption. Until that happens. I do not worry about this activity.

Trace of the Mw8,2 earthquake in Alaska, United States

I don’t have anything to say about the earthquake that took place (on 29-July-2021 at 06:15 UTC) in Alaska, United States since I don’t know the area geology features. I am going to show the trace of this earthquake as it did appear on my geophone in Iceland.

The earthquake trace on north-south directed sensor that I have. It shows the P wave, the small S wave and the surface waves that I did record in Iceland.
The Mw8,2 earthquake as I did record it in Iceland.
Trace of the Mw8,2 earthquake in Alaska, shows the P wave that is strongest on the Z (vertical) line, along with the surface waves that I did record in a crude pattern
The Mw8,2 earthquake in Alaska, United States.
The Mw8,2 earthquake on a east-west direction. The P wave is the strongest followed by a small S wave and surface waves.
The Mw8,2 earthquake in Alaska, United States.

More earthquake activity in Katla volcano

Since yesterday (24-July-2021) and until today (25-July-2021) there has been rather strong earthquake activity in Katla volcano. The earthquakes are not strong with largest earthquakes having a magnitude of Mw2,6. It is unclear what is going on.

Earthquake activity in Katla volcano caldera. A lot of yellow dots showing the locations of the earthquakes from south to north and then turn to east direction.
Earthquake activity in Katla volcano. Copyright of this image belongs to Icelandic Met Office.

One of the reasons this earthquake activity is happening is that cauldron might be emptying in the Mýrdalsfjökull glacier. That creates a drop in pressure that can start earthquake activity. I don’t know if that is what happened now. If that is what is going on it is going to take the melt water few hours to reach the rivers in Mýrdalssandur sand area. There has not been any change in harmonic tremor activity following this earthquake activity.

Earthquake activity in Katla volcano

Since 22-July-2021 there has been an earthquake activity in Katla volcano. This earthquake activity has been mostly located to the east of the caldera and largest earthquake so far detected had a magnitude of Mw3,0.

Earthquake activity to the east of Katla volcano caldera shown on the image by ring line. A second smaller cluster of earthquakes is the west and little bit inside the caldera of Katla.
Earthquake activity in Katla volcano. Copyright of this image belongs to Icelandic Met Office.

There has not been any change in harmonic tremor activity following this earthquake activity. That strongly suggest that this is normal summer earthquake activity for Katla volcano. Earthquake activity is also far too low for it to signal any eruption risk. That might change if earthquake activity changes and grows in size.

Deep earthquakes in Fagradalsfjall mountain

Today (21-July-2021) few deep earthquakes took place in Fagradalsfjall mountain that is part of Krýsuvík-Trölladyngja volcano system.

This earthquake activity was not big and the largest magnitude recorded was a magnitude of Mw0,8. Most depth that appeared had a depth of 13,4km.

Earthquake activity in Fagradalsfjalli mountain shown by a red dot, orange dots and few blue dots on Reykjanes peninsula.
The earthquake activity in Fagradalsfjall mountain on Reykjanes peninsula. Copyright of this image belongs to Icelandic Met Office.

It is difficult to know what this means. What is possibly happening is that more magma is pushing up in the magma feeding that now exist where the eruption has been happening. If that is happening, it can result in new craters or fissure opening up and start erupting. At the writing of this article this earthquake activity seems to be ongoing, but at slow rate and small earthquakes only so far.

Fog continues to block view to the crater and Fagradalsfjall mountain. But harmonic tremor data shows that the Fagradalsfjall mountain eruption is currently not erupting.

Earthquake in Brennisteinsfjöll volcano

On 24-May-2021 at 21:36 UTC an earthquake took place in Brennisteinfjöll volcano. The magnitude of this earthquake was Mw3,6 and this earthquake was felt in Reykjavík area.

Green star in the middle of the image of Reykjanes peninsula showing the location of the earthquake that was felt in Reykjavík.
The location of the earthquake in Brennisteinfjöll volcano. Copyright of this image belongs to Icelandic Met Office.

There have been few smaller earthquakes in this area since the largest earthquake, but other than that it has been quiet. This earthquake is believed to have happened because of stress changes on the Reykjanes peninsula because of the eruption in Fagradalsfjall mountain.

Earthquake activity in Bárðarbunga volcano

Yesterday (12-May-2021) at 15:47 UTC an earthquake with magnitude of Mw3,5. This earthquake was in the normal area of Bárðarbunga volcano caldera. This earthquake activity is connected to inflation of Bárðarbunga volcano that started after the end of Holuhraun eruption in 2015.

Green star in Bárðarbunga volcano caldera and few red dots east of Bárðarbunga volcano showing new deep dyke activity taking place. Image is from 13:20 today (13-May-2021).
Earthquake activity in Bárðarbunga volcano. Copyright of this image belongs to Icelandic Met Office.

There has been a slow drop in earthquake activity during the last few months and it is unclear why that is. Eruptions in Bárðarbunga volcano can be as short apart in time as 18 years or less. The 1996 eruption in Gjálp fissure was from Bárðarbunga volcano, that places the time between eruptions 1996 and 2014 at 18 years.

Earthquake swarm in Krýsuvík volcano

Since last night (night of 3-May-2021) there has been earthquake swarm in Krýsuvík volcano close to Kleifarvatn lake. At the writing of this article this earthquake swarm is ongoing.

Earthquake swarm in Krýsuvík volcano shown by two green stars on top of each other
Earthquake swarm in Krýsuvík volcano. Copyright of this image belongs to Icelandic Met Office.

Largest earthquakes in this swarm had a magnitude of Mw3,2 and there where several other smaller earthquakes that also happened. The earthquake at 03:04 UTC was felt in Reykjavík but I don’t have any reports about the earthquake at 15:49 UTC with same magnitude being felt. It is difficult to know what this earthquake activity means but for now the idea is that this earthquake activity might be connected to stress changes because of the magma dyke connected to the eruption in Fagradalsfjall mountain that is happening within same volcano system.


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Vacation

I am taking a little vacation between 5 May and until 10 May. Unless something major happens next update won’t be until after 10 May 2021. I am hoping to see the eruption or the area if the eruption is not ongoing next weekend if weather allows for such a trip. I don’t know yet if I can see the eruption, but I hope that I am going to have a chance to see the eruption.