Earthquake swarm and minor harmonic tremor in Katla volcano

There has been a minor earthquake swarm in Katla volcano today. This earthquake swarm started around 09:00 UTC and lasted with breaks until 14:39 UTC. The largest earthquake in this swarm was ML1.7 with the depth of 3.5 km. Following this earthquake swarm there was a small harmonic tremor spike seen on few SIL stations around Katla volcano. It is unknown at this time if there has been a small glacier flood taking place. But if that is the case, it should be known in the next few hours if that is the case or not.


The earthquake swarm in Katla volcano caldera. Copyright of this picture belongs to Icelandic Met Office.


The harmonic tremor spike can be seen on this SIL station. It is located close to the end of tremor plot. Copyright of this picture belongs to Icelandic Met Office.


The harmonic tremor spike can be seen on this SIL station. It is located close to the end of tremor plot. Copyright of this picture belongs to Icelandic Met Office.

This harmonic tremor is small, but larger then last harmonic tremor that took place in this are about one week ago (far as I can remember). Currently there is nothing that suggests that eruption is imminent. This is just earthquake activity in the same place as it has been for the past five or so weeks.

Sorry for the short blog post. I have gone sick with some cold. No advice needed on how to get rid of it. That is going to take few days on it’s own.

Possible minor eruption in Hamarinn volcano yesterday. Update on Katla volcano

There appears to be more in this new hydrothermal activity in Hamarinn volcano then at first sight. It seems that this actually might have a eruption in Hamarinn volcano (Bárðarbunga volcano). If this event is confirmed, this is the first eruption in Hamarinn volcano since the year 1910.

This also mean that there is a chance of more activity in this area in coming weeks or months. But when it might happen is impossible to know.


The new cauldrons are marked with a “X” on this map. Copyright of this picture belongs to Icelandic Met Office.

This eruption was really small and did just last for few hours. But it was able to melt a lot of ice and create rather large glacier flood from Vatnajökull glacier. If the activity resumes in this area this is going to repeat it self in terms of glacier flood.

Icelandic News about this event.

Innskot af kviku (Rúv.is, Icelandic)
Eldgos gæti hafa brotist upp við Hamarinn (Vísir.is, Icelandic, Pictures)
Fundu nýjan sigketil (mbl.is, Icelandic, Pictures)

Sigketill við Lokahrygg (Icelandic Met Office, Icelandic, Pictures)

Update on Katla volcano

Here is a short update on Katla volcano. There have been repeated short burst of harmonic tremors taking place inside the Katla volcano caldera. This harmonic tremor spikes have been small and they are hard to see on the harmonic tremor graph that Icelandic Met Office has on-line. Other then this it has been quiet so far in Katla volcano.

Harmonic tremor drop down. New earthquake happen in Katla volcano caldera

It seems that on many SIL station around Katla volcano that the harmonic tremor has gone mostly down to background levels, on other stations it continues to drop. This are mostly SIL stations that are at the most distance to the source of the area that this minor eruption took place during the night. But at the moment this seems to be over. The main source of the activity appears to be where the eruption took place in the year 1918, or so scientists think at the moment.

According to the news there was an flood wave around 04:00 UTC during the night. When the water meters did show an rise of 5 meters suddenly. Soon after that the bridge over Múlakvísl river was lost in the glacier flood. This did close the main road 1 in this area, that area of the main road is going to remain closed for the next few weeks while they fix the damage done in the flood (build an new bridge).

Even if the harmonic tremor seems to be dropping. This does not seem to be over, as an earthquake activity did resume from around 13:00 UTC in the Katla. Since then the earthquake activity seems to have been building at slow rate.


Tremor plot at 18:23 UTC. The tremor is dropping. It also shows that earthquakes are taking place (spikes the tremor chart). Copyright of this picture belongs to the Icelandic Met Office.


Tremor chart from Goðabunga at 18:24 UTC. Copyright of this picture belongs to the Icelandic Met Office.


Dropping harmonic tremor on Lágu Hvolar. Earthquakes appear as spikes here. Copyright of this picture belongs to Icelandic Met Office.


Dropping tremor and earthquakes as before. Copyright of this picture belongs to Icelandic Met Office.


Earthquakes as they are tonight. The southern part of the caldera is having earthquake swarm, even if it is just an small one. Copyright of this picture belongs to Icelandic Met Office.

I am waiting too see how this develops. Something larger might happen. But nothing else might happen for an while in Katla volcano. The only thing that can be done is too wait and see what happens in Katla volcano.

Icelandic News about the road damage.

Meiri skemmdir en talið var (Rúv.is, Picture, Icelandic)

Harmonic tremor still high in Katla volcano

Currently harmonic tremor remains high in Katla volcano. But at the moment the harmonic tremor is dropping. Earthquakes have also stopped for the moment. But currently the harmonic tremor is well above the background level for this area. It is still not clear if this was an eruption or just hydrothermal areas clearing it self of extra water. But in the news at Rúv noon they did report that the ice cauldrons that are normally there had deepened over the past few weeks in Mýrdalsjökull glacier.

Update 1: Earthquake activity has stopped for the moment. But I am expecting it to resume soon. As I do not think that this event is over, even if it has just paused for the moment.

Three cauldron have formed in Mýrdalsjökull glacier and large cracks have formed around them. All traffic has been banned on Mýrdalsjökull glacier and the glacier that comes from it.

Here are the current tremor charts from Icelandic Met Office web page.


Harmonic tremor is dropping as can clearly be seen on this picture. Copyright of this picture belongs to Icelandic Met Office.


Harmonic tremor is dropping as can clearly be seen on this picture. Copyright of this picture belongs to Icelandic Met Office.


Harmonic tremor is dropping as can clearly be seen on this picture. Copyright of this picture belongs to Icelandic Met Office.

I am going to post update on Katla volcano later today and earlier if anything major happens.

News with picture of the Mýrdalsjökull glacier. It is covered with dark ash from Eyjafjallajökull volcano eruption last year and volcano ash from the eruption in Grímsfjall volcano 2011.

Miklar sprungur í sigkötlunum (mbl.is, Picture, Icelandic)
Svona lítur jökullinn út (Rúv.is, Icelandic, Picture)
Þrír greinilegir sigkatlar (Vísir.is, Icelandic, Picture)
Brúin rofnaði af í heilu lagi (Vísir.is, Icelandic, Picture)
Óvissa um hlaup eða lítið eldgos (Rúv.is, Icelandic, Pictures)

Blog post updated at 13:13 UTC 9. July 2011.

Harmonic tremor continue to increase in Katla volcano

When this is written around 00:36 UTC on 9. July 2011 the harmonic tremor levels on SIL stations around Katla volcano have continued to increase. The latest spike in harmonic tremor levels happened after an ML1.5 (automatic size) earthquake that took place at 22:13 UTC. There has been an small earthquake swarm in Katla volcano caldera yesterday. But the largest earthquake in that earthquake swarm had the size ML2.4.

The harmonic levels are getting so strong that they have started to appear on stations around Hekla and on my own geophone, even if it is located almost 60 km away from the source of the harmonic tremor. Currently there is little to suggests that this is slowing down at the moment. But that might yet happen. But it is impossible to know for sure at the moment.

The lack of earthquakes tells me that the magma has not yet reached the surface. When or if that might happen is an good question that I do not have the answer to. But this might take several more hours until something happens in terms of earthquakes or other activity in Katla volcano.


Harmonic tremor can clearly be seen on this SIL station at the end of the tremor chart. This is saved around 00:36 UTC 9. July 2011. Copyright of this picture belongs to Icelandic Met Office.


Harmonic tremor can clearly be seen on this SIL station at the end of the tremor chart. This is saved around 00:36 UTC 9. July 2011. Copyright of this picture belongs to Icelandic Met Office.

As sad before the harmonic tremor can now be seen on SIL stations far away from Katla volcano. But the maximum range so far is around 65 km or so at the moment.

This is the last update for tonight. I am going post an update tomorrow on what has happened during the night. Even just to say people that things have slowed down or gone back to normal. Whatever happens. I am going to post information about it tomorrow when I awake up.

Harmonic tremor in Katla volcano

At the moment there is an ongoing harmonic tremor going on in Katla volcano. It is just an small one, just above the background level noise floor. This is most likely an small dike intrusion. But nothing in the data from Icelandic Met Office suggests that an eruption has started in Katla volcano at this stage. But that might change without an warning, since this is an volcano after all. This change in harmonic tremor does not seems to be created by an glacier flood of some type. What is interesting is that this harmonic tremor pulse looks like an harmonic tremor pulse detected in the year 1999, just before an small eruption took place in Katla volcano southern caldera rim.

This harmonic tremor is in the high frequency range at the moment. But no change has been seen in the low frequency range at the moment. This is the same thing that did happen in the year 1999. At the moment however it is too early to know what is going to happen in Katla volcano for sure. All that can be done is to watch and wait. This might quiet down, or it might not. Only time is going to tell us what happens next. At the moment the harmonic is falling at fast rate, so this might be over.

Before the harmonic tremor pulse there was an earthquake swarm in Katla volcano caldera. The largest earthquake was ML2.1 and that was an long period event, but that tells me that magma was the source of this earthquakes in Katla volcano caldera. There where two earthquake swarms in the caldera today, but that makes total of three earthquake swarms in the Katla volcano caldera since the beginning of June.


The two earthquake swarms that took place in Katla volcano caldera today. Copyright of this picture belongs to Icelandic Met Office.


The only earthquake that I did record out of this earthquake swarm. This earthquake was ML2.40 with the depth of ~400 meters. This plot is filtered at 1Hz . This picture is released under Creative Common licence. See Licence web page for more detail.


Spectrogram of the ML2.4 earthquake in Katla volcano from this morning. This is filtered from 1Hz. This picture is released under Creative Common licence. See Licence web page for more detail.


Harmonic tremor can clearly be seen at the end of this tremor chart from the Icelandic Met Office. Copyright of this picture belongs to Icelandic Met Office.


Harmonic tremor can be seen at the end of this tremor chart from the Icelandic Met Office, but it is not clear at this SIL station. Copyright of this picture belongs to Icelandic Met Office.


Harmonic tremor can clearly be seen at the end of this tremor chart from the Icelandic Met Office. Copyright of this picture belongs to Icelandic Met Office.


Harmonic tremor can clearly be seen at the end of this tremor chart from the Icelandic Met Office. Copyright of this picture belongs to Icelandic Met Office.


Harmonic tremor can be seen (not clearly) at the end of this tremor chart from the Icelandic Met Office. Copyright of this picture belongs to Icelandic Met Office.


Harmonic tremor can clearly be seen at the end of this tremor chart from the Icelandic Met Office. Copyright of this picture belongs to Icelandic Met Office.

The harmonic tremor is strong enough on many SIL station to go above the background noise level on the SIL stations (wind, ocean waves etc..). But this is not an strong harmonic tremor. They can be stronger.

This does NOT mean an eruption is imminent in Katla volcano. What this does mean that is an magma is on the move inside the Katla volcano. What happens at later time is something that nobody can guess at current time. But it is now time to watch Katla volcano even closer.

It is also important to notice that nobody really knows how Katla volcano behaves before an eruption. We only get those answers after an eruption in Katla volcano. For the moment we can only wait and see what happens in Katla volcano.

I am going to post more updates if anything interesting happens. Also, there seems to have been an Long period earthquake at 22:14 UTC, most likely in Katla volcano. It appeared on my geophone close to Hekla volcano. I am guessing the size of this earthquake is ML2.0+.

Blog post updated at 22:39 UTC. Spectrogram picture added.

Earthquake swarm in Presthnjúkar volcano. Update on Katla volcano

Presthnjúkar volcano: Few days ago an earthquake swarm did start in Presthnjúkar volcano. This earthquake swarm is entirely tectonic in nature. There is nothing that suggests that this earthquake swarm is connected to magma movements inside Presthnjúkar volcano system. So far this earthquake swarm has been slow and small. But the largest earthquakes have gone up to ML3.3 in size according to Icelandic Met Office.


The location of current earthquake swarm in Presthnjúkar volcano. Copyright of this picture belongs to Icelandic Met Office.

Katla volcano: Over the last 18 hours it has been quiet in Katla volcano. As no more earthquakes have been detected from it. I would not be surprised if there are more earthquakes swarms in Katla volcano in the next few weeks and months. It is an well known fact that Katla volcano is heading to an eruption. But nobody knows when that is going to happen.


Location of the earthquakes in Katla volcano yesterday. Copyright of this picture belongs to Icelandic Met Office.

Besides this two highlights of earthquake activity in Iceland. It has been rather quiet in the past few weeks. With just from ~100 to ~300 earthquakes during the week.

Earthquake swarm in South Langjökull volcano and Krýsuvík volcano

Today has been spotted with earthquake swarms in Iceland. This earthquake swarms have not been big so far in both terms of earthquakes and size of the earthquakes. With the biggest earthquakes in South Langjökull volcano (Presthnjúkar). The biggest earthquakes in South Langjökull volcano have been around ML2.5 in size. With the average depth of 10 to 5 km. Total number of earthquakes is something around 39 and that is an small earthquake swarm.

The area in question is known for earthquake activity. Few years ago there was an earthquake swarm in this area with several ML4.0+ earthquakes. This area did also see earthquake swarm earlier this year. So far nothing suggests that an eruption is close in this area.


Map from Icelandic Met Office showing the area with the earthquake swarm. Click on the picture to get full size. Copyright of this picture belongs to Icelandic Met Office.

Krýsuvík volcano did also have an minor earthquake swarm today. The largest earthquake in Krýsuvík volcano was ML2.1 with the depth of 3.9 km. So far this earthquake swarm has been an minor one. With just over 32 earthquakes happening today.

Other earthquake activity in Iceland is currently not an lot. A ML3.1 earthquake took place few days ago in TFZ in an area that commonly has earthquake swarms. That area does not have any volcanoes, so earthquakes there are only connected to faults in the fault lines in that area.

Blog post updated at 23:29 UTC on 7. June 2011.
Blog post updated at 23:35 UTC on 7. June 2011.

Earthquake swarm close to Geirfuglasker on Reykjanes Ridge

Today at 15:08 UTC a earthquake swarm did start close to Geirfuglaskeri on Reykjanes Ridge. This earthquake swarm has so far been small, with the largest earthquake having the automatic size ML2.4 with the depth of 10 km.

So far this earthquake swarm has remained small. But it is unclear if this earthquake swarm is going to continue. But there was a break in this earthquake swarm from 16:12 UTC too 18:55 UTC. But I did think that this earthquake swarm was over, until it did start again.

It is impossible to know if this earthquake swarm is over or not.

Interesting earthquakes north of Askja volcano

There is a interesting cluster of earthquakes north of Askja volcano. What is most interesting is the fact that this earthquakes are shallow This cluster of earthquakes is most interesting for the fact that it is shallow. The depth of the earthquakes is from 8.4 km and up to 0.1 km (~100 meters). This suggests that this is a dike intrusion is making. But appears to be growing slowly (a bit unclear at the moment however). But at this time it is impossible to know if this possible dike intrusion makes it too the surface or not.

History tells that it is not unclear for Askja volcano to erupt in small fissures. But that last happened in the Askja eruption in the year 1961.

Currently it is unclear what is going on north of Askja volcano. But this is for sure evolving into something in my opinion. But the question remains how long this is going to take. But this process has already been ongoing now for about 14 months and counting.