Category: Earthquakes

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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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A ML3.7 (automatic size est.) earthquake happens on Reykjanes, close to town called Grindavík

A earthquake that had the automatic size of ML3.7 did happen at 22:14 UTC on the Reykjanes. This earthquake was only 2.6 km away from a town in called Grindavík. The earthquake was felt well in town according to reports that I got over Facebook.


The ML3.7 (automatic size) earthquake location. Copyright of this picture belongs to Icelandic Met Office.

So far no aftershocks have happened where the main earthquake took place. But that might change at any time.

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Earthquake swarms in Krýsuvík volcano, Tjörnes Fracture Zone and SPAR fracture zone (Kolbeinsey Ridge)

In the last few days there has been good earthquake activity in TFZ (Tjörnes Fracture Zone). The largest earthquakes have been up to ML3.0 in size. But this earthquakes swarm have mostly been small and lasted for a short time.

Last night a earthquake swarm started in Krýsuvík volcano. This was just a normal tectonic earthquake swarm that normally takes place in this area on regular basic. From what I can tell. But it is impossible to know if this earthquake swarm was created by magma movement or not.


The earthquake swarm as it did appear on my Heklubyggð geophone. This picture is released under Creative Common Licence, see the licence page for more details.


The location of the earthquake swarm. Copyright of this picture belongs to the Icelandic Met Office.

This earthquake swarm took place in and close to a lake called Kleifarvatn. The largest earthquake in this earthquake swarm was a ML2.9 (automatic size). Currently the earthquake swarm is ongoing. But it has slowed a lot down since it started last night. At the moment, it looks like this earthquake swarm in Krýsuvík volcano is over for now.

Some earthquake activity was also on the south part of the MAR SPAR fracture zone, south and north of Kolbeinsey Island. The largest earthquake there was a ML3.0 (automatic data). Earthquakes this area happen often also. Like on the Tjörnes Fracture Zone.

Blog post updated at 23:38 UTC.
Blog post updated at 22:06 UTC on 16. August 2011. Fixed a error in it.

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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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Earthquake swarm on the TFZ

There is currently a earthquake swarm taking place on the TFZ. This earthquake swarm appears to be rather small at the moment. The largest earthquake so far has been a ML3.2 according to the automatic earthquake list on Icelandic Met Office earthquake list.

There is no volcano activity connected to this earthquake swarm, as there are no volcanoes in this area off the coast of Iceland but there are volcanoes in part of what is considered part of TFZ. This area has its earthquakes from a slip faults. But they move in both north-east to north-west, but also in south-north direction in some cases.


The Tjörnes Fracture Zone. Copyright of this picture belongs to it’s owner. Picture found here.

Here is the latest earthquake image from Icelandic Met Office about this earthquake swarm.


Copyright of this picture belongs to Icelandic Met Office.

It is impossible to know how this earthquake swarm behaves. It is also known for the TFZ area that one earthquake swarm can start a new earthquake swarm nearby if a large enough earthquake happens. This happens sometimes, but not always. It is not a common thing to take place in the TFZ from what I remember about activity in TFZ.

I am going to update this blog post if this earthquake activity becomes something larger then it already is, or if a large earthquakes takes place in the TFZ.

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Earthquake swarm north of Langjökull glacier and volcano, new hole found in Selfoss town

This is a short update.

Langjökull glacier: Yesterday there was a minor earthquake swarm north of Langjökull glacier and volcano. This area did last time was last year when a good sized earthquake swarm did happen in this area, but last year it did start around this time of year and lasted until November. It remains to be seen if that happens now. So far all the data suggests that this earthquake swarm is just tectonic in nature. It also appears that earthquake swarms in this area start slowly with long breaks between them. So I am expecting more earthquakes there. Unless this has just been a single event with no repeats.

SISZ: On Selfoss town they have just found a new strange hole in the road. The opening of the hole is about 1.5 meter in size. But the depth is about 6 meters (guess?) and area that is hollow under the hole is few hundred meters (guess?) according to the news. It is believed that this did happen because of the SISZ Mb6.3 earthquake that did happen in this area in the year 2008.

Here are news about, with pictures of the hole.

Jarðskjálftahola á Selfossi (Rúv.is, Icelandic, Picture)
Hola myndaðist í jörðinni á Selfossi (Vísir.is, Icelandic, Pictures)

Katla volcano: I think that something might be about to start in Katla volcano. But that is just a speculation that I am doing now. I am far from sure about it. But it should be clear in few hours if something is happening in Katla volcano or not. I base my assessment on rather odd changes in the tremor plot. They are hard to spot, but still there and appears to be growing it seems. But I am going to check and see what happens in few hours time. This might be nothing. But only time is going to tell us that for sure.

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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.