Category: Monitoring

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Earthquake close to Hekla volcano. A earthquake swarm in Katla volcano

This has been a busy weekend in earthquakes, more then I was expecting. Here is a minor write up on the activity so far.

Hekla volcano:

A ML2.4 earthquake did happen close to Hekla volcano at 07:30 UTC. Depth of this earthquake was 3.7 km. The earthquake did happen on earthquake fault line that was created in a large earthquake in the year 1912. This fault line has been known since then and is well documented.


The SISZ earthquake this morning. This picture is released under Creative Common Licence. See Licence web page for more details.

Katla volcano:

Two new earthquake swarms took place in Katla volcano today. This earthquake started around 09:30 UTC this morning. Most of the earthquakes where smaller then ML1.0 in size. The depth was around 5.5 km on average. The largest earthquake was ML2.3 in size, with the depth of 5.5 km. That earthquake swarm was in Goðabunga area of Mýrdalsjökull glacier (Katla volcano). But here was also a minor earthquake swarm inside Katla volcano caldera. But in that earthquake swarm the earthquakes there where even smaller, most of those earthquake didn’t reach the size ML1.0. The earthquake swarm in Goðabunga area in Katla volcano might be due to dike intrusion in that area. I do not know if this might be something else. But given the data, this is the most likely the reason for this earthquake swarm in this area. The earthquake swarm did stop at 12:47 UTC. After that everything has been quiet so far.

Few earthquakes also did happen SE part of the Katla volcano caldera. But there have been earthquakes in this area since July. But this activity did start soon after the glacier flood from Mýrdalsjökull glacier.


Earthquake activity in Katla volcano. Copyright of this picture belongs to Icelandic Met Office.

All the earthquake swarms of today in Katla volcano, also the single earthquake close to Hekla volcano.

Icelandic news about this activity.

Mikið um smáskjálfta nærri Mýrdalsjökli (Vísir.is)
Jörð skelfur nálægt Hellu (Rúv.is)

Other: Short announcement. I have finally figured out how I am going to have my writing schedule. But my working period is going to be from 1. September to 1. June every year. This also means more activity on this blog and my other (Icelandic) blogs. During the summer time there is going to be reduced activity on all my blogs. But if something happens during the summer in earthquakes and volcanoes. I am going to write about it anyway or soon as I can do so.

Also note that I have started school to finish basic in electronic (house electronics and other basics in electronics). So I am busy during the day (most days). So my response might be slower then normal if anything happens in Iceland with earthquakes or volcano activity.

Other #2: I am having minor issues with uploading the gif images from my earthquake computer at the moment. So that is currently being done by the remote geophone computers at the moment. Because of this, there is no red colour if a large earthquakes happens in Iceland or close to a geophone station that I have up and running.

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Earthquakes in Öræfajökull volcano

I do not have a time for long blog post about this at the moment. But here is a short overview of earthquake activity in Öræfajökull volcano.

Since the year 1991 there have been total of three earthquake swarms (with the one in last week) in Öræfajökull volcano. The two earthquake swarms where in the year December 2005 and in September 2008. Total of 70 or so earthquakes have taken place in this earthquake swarms. But only 30 or so earthquakes in the main crater of Öræfajökull volcano.


Earthquake activity in Öræfajökull volcano between the year 1991 and to 2011. Copyright of this image belongs to Icelandic Met Office.


Earthquakes inside the main crater of Öræfajökull volcano from the year 1991 to 2011. Copyright of this image belongs to Icelandic Met Office.

All pictures are from here.

Currently the earthquake activity in Öræfajökull volcano is quite low. So I am not expecting anything for a long, long time now. The reason why earthquakes are taking place might be new magma. But this also might be due the glacier and pressure changes on the rock because of that. But I find the later idea less likely then the first one. But it hard to know for sure at the moment what actually is the real case now.

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Minor earthquake swarm in Öræfajökull volcano

Since early this morning there has been a minor earthquake swarm in Öræfajökull volcano. This earthquake swarm is so far just minor one, with the largest earthquake being ML2.0 at 4.3 km depth.

This earthquake swarm is most likely due to magma injection into Öræfajökull volcano. But this volcano is normally quiet and almost never has any earthquakes. But that has been changing during the past few years, but earthquake swarms have been getting more common in Öræfajökull volcano. Something that is in fact a big change from few years ago when no earthquakes where recorded from Öræfajökull volcano.

This increased activity in Öræfajökull volcano seems to be happening at the same time as there is increased activity in Esjufjöll volcano. The two volcanoes are not connected. But this might suggest a more inflow of magma under the general area. But that is just a speculation, based on rather limited amount of data.


Öræfajökull volcano is located to the south end of Vatnajökull glacier. Copyright of this image belongs to Icelandic Met Office.

The earthquakes in Öræfajökull volcano have been taking place in the main crater of the volcano. But it is important to know that currently there is nothing to suggest that a eruption is imminent in Öræfajökull volcano or in Esjufjöll volcano.

Interesting reading material on Öræfajökull volcano

The 1362 AD Öræfajökull eruption, Iceland: Petrology and geochemistry of large-volume homogeneous rhyolite (pdf)

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Katla volcano earthquake last night

Last night there was a earthquake with the size ML2.3 and with the depth of 1.3 km inside the caldera of Katla volcano. This earthquake might well be just part of the normal summer and autumn earthquake activity in Katla volcano. But at the moment it is hard to know for sure the difference at the moment.


Current area of activity in Katla volcano. It is mostly inside the caldera. Copyright of this picture belongs to Icelandic Met Office.


The ML2.3 earthquake in Katla volcano caldera last night. The P and S wave markers are unset. Picture Licence is Creative Commons.


The frequency spectrum of the Katla volcano caldera earthquake. As can be seen this earthquake has a lot of low frequency in it. Picture Licence is Creative Commons.


The Katla volcano caldera earthquake as it was recorded on my Hvammstangi geophone. It is quite unusual to record this small earthquake at this distance. This is filtered at 1Hz. Picture Licence is Creative Commons.


This earthquake here is from Goðabunga this morning. But Goðabunga is part of Katla volcano. But it is yet unknown if it is a volcano system on its own or not. The earthquakes from Goðabunga are different then the earthquakes from Katla volcano caldera, as can clearly been seen on this pictures. Picture Licence is Creative Commons.

Besides this minor earthquake activity. Everything remains quiet in Katla volcano at the moment. When that is going to change is impossible to know.

Blog post updated at 21:10 UTC.

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Background noise compared to a eruption and other events

Here are few examples of how the tremor plots looks like if anything important is going on in Iceland.


Normal quiet tremor plot. Few earthquakes create spikes on it. But besides that everything is quiet. Copyright of this pictures belongs to Icelandic Met Office.


This is from the Grímsfjall volcano eruption in May 2011. On this tremor plot it can be clearly seen how much noise a eruption actually makes. The background noise just goes away soon as there is something going on. Copyright of this pictures belongs to Icelandic Met Office.


This is Skrokkalda SIL stastion on 12 July 2011. It can clearly be seen where the harmonic tremor goes above the background noise. Copyright of this pictures belongs to Icelandic Met Office.

It is quite clear. Besides earthquakes and some harmonic tremors that are different then this signals that I have shown here. Unless you see this on Icelandic Met Office tremor plot you can be sure that it is quiet in Iceland. Volcano eruptions make a lot of noise when they are ongoing, even the small eruptions make some noise that can be detected by the SIL network in Iceland.

Note: I might update this blog post on later date and put in more examples about the difference between background noise and a eruption.

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Earthquake activity in Katla volcano increases again

I was going to write about something else (TFZ and other earthquakes around Iceland in the last few days). But that just has to wait for a little longer.

It seems that Katla volcano earthquakes are increasing again. This increase appears to be similar to the increase in earthquakes before the glacier flood from the 9th to 17th of June and onwards until the glacier flood on 8th and 9th of July. The only difference now is that I am seeing this pattern earlier since I now know what to look for this time around when this is in its early stages.

How this is going to develop now is a wait and see process. But this might take as long time to get interesting as it did in June to July, to the event that ended with the glacier flood from Mýrdalsjökull glacier.


Current earthquake activity in Katla volcano. Copyright of this picture belongs to Icelandic Met Office.

It is also worth noticing that the earthquake activity is not as focused as it was in early June and in July. But I am fully expecting that to happen soon. But it remains to be seen if that actually happens or not.

The earthquake activity SSE in the Katla volcano caldera rim is still interesting. I do not know why it is taking place there. But if a eruption would take place at this location. There would be a short glacier flood and some period with volcano ash explosions. But after that it should be lava eruption in that location if it where to last long enough to remove all that water from the crater. But this is all just a speculation and nothing more.

For now. It is just wait and see what happens next.

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Overview of Hamarinn volcano current activity

Here is a short overview of the Hamarinn volcano activity this summer. From what I can gather in the current data this is most likely not over. During the past few days there have been at least suspected two minor eruption in Hamarinn volcano. But it hard to confirm it due to glacier that is covering this area.

This all starts on 12. July 2011 at 07:30 UTC with this event here.


The tremor spike on 12. July 2011 at 07:49 UTC. Copyright of this picture belongs to Icelandic Met Office.

When the clock is around 19:10 UTC the same day the tremor chart looks like this.


The tremor spikes are now three on 12. July 2011 at 19:09 UTC. Copyright of this picture belongs to Icelandic Met Office.

On the 13. July 2011 the tremor plot looks like this. But at that time the glacier flood had started and broken from the Vatnajökull glacier.


The tremor chart at 13. July 2011 at 01:10 UTC. Copyright of this picture belongs to Icelandic Met Office.


The tremor chart at 13. July 2011 at 12:59 UTC. Copyright of this picture belongs to Icelandic Met Office.

Then there was a short period of break when nothing interesting happened in Hamarinn volcano. That break did last until 16. July 2011 when a new, but smaller spike did appear on Skrokkalda SIL station.


The tremor at 16. July 2011 at 15:22 UTC. It is not fully clear what did happen at this time. But this was most likely a earthquake in Hamarinn volcano. But that is yet unconfirmed at this time. Copyright of this picture belongs to Icelandic Met Office.

Then there is a new break that lasts until 1. August when a earthquakes happens deep under Bárðarbunga volcano. But the deepest earthquake had the depth of 25.2 km. But it is also important to notice this earthquake that took place on 13. July 2011 and it is from Hamarinn volcano.


The earthquake from Hamarinn volcano. This picture is released under Creative Commons licence. Please see licence web page for more details.

On the 3. August 2011 around 02:00 UTC a new harmonic tremor spike starts to be visible on Skrokkalda SIL station.


The tremor plot at 01:55 UTC on 3. August 2011. Copyright of this picture belongs to Icelandic Met Office.

This day two minor harmonic tremor happens. A change in Skaftá glacier river is noticed. That is higher conductivity and slightly more water. It was announced in the news that a Skaftá glacier river flood was about to start from the eastern glacier cauldron that is formed above the Hamarinn volcano. Today however that does not seem to be the case. As no glacier flood has taken place so far.

Today (5. August 2011) there was a new harmonic tremor spike on Skrokkalda SIL station. It did follow the same pattern as before. It started and lasted for about 20 to 60 minutes or about that long.


The tremor chart 5. August 2011 at 17:38 UTC. Copyright of this image belongs to Icelandic Met Office.

So far today only one harmonic tremor has been detected. But given the past experience that is unlikely to hold for a long time now. But it is impossible to know when a new event starts or how big it is going to be.

The original event on 12. July 2011 did create new cauldron in the glacier. This map from Icelandic Met Office shows the location of those new cauldrons. But it has been marked with a star on the map. The coloured dots are earthquakes in this area over the past few years.


Map of the area that is currently active in Hamarinn volcano. Copyright of this image belongs to Icelandic Met Office.

Given the current data I am expect a full scale eruption in this area soon. When is hard to know for sure. But until that happens there are going to be more smaller eruptions in this area. I do not know why there is a lack of earthquakes following this events. I cannot explain it. But because of that this can only be seen after it has started on the tremor charts.

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Sharp rise in harmonic tremor on Skrokkalda and Grímsfjall SIL station (among others)

There is a sharp rise in harmonic tremor on the Skrokkalda and Grímsfjall SIL station. I do not know yet what volcano is responsible for it. But the Hamarinn volcano is a suspect at the moment.

Current tremor plot.


The tremor spike is at the end of this tremor plot. Copyright of this picture belongs to Icelandic Met Office.


The tremor spike is at the end of this tremor plot. Copyright of this picture belongs to Icelandic Met Office.

I am going to post more information about what is going on when I know more. This blog post might get updated soon if needed.

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Glacier flood has started in Skaftá river

The latests news is that a glacier flood has started in Skaftá river. At the moment this glacier flood does not appear to be big, as there was also a glacier flood in this river last year. Because of this short time, there has not been a lot of water collected in the western cauldron that is emptying now. It was clear today that it was the western cauldron that had emptied when scientists did fly over the area earlier today.

This glacier flood is often early event and has been since the year 1955. Following this glacier flood there is often spike in harmonic tremor because magma goes on the move due to sudden pressure release in this area. So far it has not been able to trigger a eruption in Hamarinn volcano. It remains to be seen if that has changed or not.

Icelandic News about this

Hlaup hafið í Skaftá (Rúv.is, Pictures, Icelandic)
Rennsli eykst í Skaftá (Vísir.is)
Hlaupið komið í Skaftá (mbl.is)

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No glacier flood yet from Hamarinn volcano, but it is on it’s way

At current time (around 20:30 UTC) it has been observed that no glacier flood has started in Skaftá river. But the glacier flood is expected to start in the river around midnight, but the river might start to grow around 19:00 to 21:00 UTC. According to latest news the river has however started to get darker and conductivity in the water has started rise since this morning, but that was the signal that a glacier flood was about to start. Glacier flood tremor have also been dropping in the last few hours according to the latests news that I have seen (but I am hoping for a update on that detail).

The source of this glacier flood is a hydrothermal area in Hamarinn volcano (part of Bárðarbunga volcano). This area also did have a glacier flood last year. But last year there where two glacier floods in Skaftá river in June 2010, see reports here in Iceland at Icelandic Met Office web page.

This hydrothermal area in Hamarinn volcano is in two cauldrons in the Vatnajökull glacier. With time they fill with water that then breaks ice when the pressure is enough in the cauldrons due to water levels. It remains a question if the surprise glacier flood earlier this month from Hamarinn volcano has something to do with this. But at current time that is only speculation. But if the hydrothermal area is unusually highly active, or there has been some change it is hard to know for sure the size of this glacier flood.

Currently however the experts are expecting a small glacier flood due the fact there where two glacier floods from this area last year. But we however have to wait until midnight until we know what is the actual size of this glacier flood.

Icelandic News about this

Skaftárhlaup ekki enn hafið (Rúv.is)
Skaftárhlaupið komið í byggð eftir sólarhring (Vísir.is)
Engin merki um hlaup ennþá (mbl.is)