Category: Swarm

Today (26.01.2017) at 15:14 UTC a magnitude 4,3 earthquake took place in Katla volcano. This earthquake was felt in Vík í Mýrdal (village) and nearby area. A second earthquake with the magnitude of 3,0 took place few moments after the largest earthquake, a magnitude 2,9 earthquake (3rd largest) took place soon after the magnitude 3,0 earthquake. Other earthquakes have been smaller in magnitude (at the moment).

The earthquake in Katla volcano, green star is the magnitude 4,3 earthquake. Copyright of this image belongs to Icelandic Met Office.

The magnitude 4,3 earthquake in Katla volcano as it appeared on my geophone in Heklubyggð (distance ~53 km). This image is under Creative Commons licence, please see CC Licence website for more details.

No major change has happened in tremor plots around Katla volcano following this earthquake. Unclear signals on one SIL stations suggest that hydrothermal areas might have gotten exited just before the main earthquake, but that is unconfirmed and unclear if it can be confirmed at all.

This article is going to be updated as new activity happens (if there is a reason to do so).

Update 27.01.2017

Science council of the Civil protection agency in Iceland (Almannavarnir) has issued the following statement. This is a rude translation of that statement since none has been issued in English yet.

Increased risk of eruption in Katla

Earthquake activity in Katla has been unusually high since August 2016, with three earthquakes larger than magnitude 4,0 and many more earthquakes with magnitude 3,0. Earthquake activity is shallow and spread around the caldera. No harmonic tremor has been detected following this earthquake activity. Following this increase in activity small increase in geothermal heat has been observed. GPS station show that small inflation has been taking place since 2010 in the top kilometres of the crust. When activity increases in Katla, as has been the case now, the risk of eruption grows and that has to be considered by the emergency response teams.

(The rest is about Bárðarbunga, just the basic translation of it.)

Since September 2015 Bárðarbunga has been inflating slowly under the caldera. It might be many years until the next eruption, until magma pressure is at the same levels before the eruption started in 2014. It is impossible to exclude new eruptions in next few years. Limited measurements are on geothermal activity in Bárðarbunga, to the best knowledge little has changed in last few months. It is important to monitor geothermal activity due to risk of water collection in the caldera.

My note: Water collection increases the risk of sudden glacier flood from Bárðarbunga.

The news announcement in Icelandic

Fundur í Vísindaráði almannavarna
Auknar líkur á eldgosi í Kötlu (Rúv News)

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Article updated on 27.01.2017 at 18:53 UTC.

In the last 24 hours there has been a sharp increase of earthquakes in Katla volcano. This started yesterday with few minor earthquakes swarms with long quiet period between activity happening. This is what happens when magma is trying to push it self out of a volcano, but doesn’t have the energy to do so just yet. It is not fully understood why most of the earthquakes happen at 0,1 km depth, but it has been theorised (not proven) that Katla volcano is already so hot in the magma tubes that no further earthquakes are possible (for now at least). Details can be found here and here (pdf).

The earthquake activity in Katla volcano during the last 24 hours. Copyright of this image belongs to Icelandic Met Office.

Largest earthquake so far had the magnitude of 3,3. Other earthquakes that have happened are smaller in magnitude at the moment. Current earthquake count is 74 earthquakes, I think that number is going to increase if this earthquake activity continues. I suspect that it is going to do so, there might however be a drop in activity for few hours, days and up to several weeks at the time. Why that happens is something I don’t know. It is also worth noticing that there has been a lot of negative value earthquakes taking place. Those don’t show up on the new Icelandic Met Office website, just the old one.

There is a good chance of conductivity changes in glacier rivers from Mýrdalsjökull glacier. That data can be viewed here, just click on station to view its data. Please note that linking to a station here (in the comment) doesn’t work, I don’t know why that is.

Update 25.01.2017

On 24.01.2017 at 11:13 UTC a magnitude 3,1 earthquake took place in Katla volcano caldera. This earthquake was close to the area where considerable earthquake swarm had taken place. Since then the earthquake activity has quieted down a bit.

The earthquake activity in Katla volcano during the last 24 hours. Copyright of this image belongs to Icelandic Met Office.

Currently there is a quiet in the earthquake activity, since it happens in pulses with drop or no activity between them. The earthquakes that have been happening and I have recorded are hybrid earthquakes (details here). I don’t know if there have been any low frequency earthquakes or very low frequency earthquakes. I expect this earthquake activity to continue.

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Article updated on 25.01.2017 at 04:38 UTC.

Since Saturday 21 of January 2017 there has been unusual earthquake activity taking place in Katla volcano (for this time of the year). Small earthquake swarms have been scattered all over the caldera, largest earthquakes so far have only reached magnitude of 2,4. Other earthquakes have been smaller in magnitude.

The earthquake activity in Katla volcano. Copyright of this image belongs to Icelandic Met Office.

This earthquake activity is unusual since normally Katla volcano is quiet in January and until June and often until mid-July when earthquake activity starts again. Current activity is unusual since snow has been adding on the glacier since it started snowing in Iceland this winter (November I think it was). Higher areas get snow sooner then lower areas, so it started earlier on Mýrdalsjökull glacier that is on top of Katla volcano. Currently the earthquake activity is ongoing, even if it has slowed down a little for the past few hours.

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