Category: Harmonic tremors

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Few harmonic tremor charts of Grímsvötn eruption

Here are few harmonic tremor charts from the Grímsfjall volcano / Grímsvatn eruption. It can clearly be seen where the eruption looses strength for an few hours. It is also clear when the eruption starts to regain it’s eruption strength again.

The volcanic tremor is best seen on 0.5 – 1Hz band, alongside 1 – 5Hz bands.


Grímsfjall volcano / Grímsvötn SIL station.


Skrokkalda SIL station.


Kalfafell SIL station.


Fagurhólsmýri SIL station.


Kreppurhaun SIL station.


Askja volcano SIL station.

All pictures are from Icelandic Met Office web page. Copyright of this pictures belongs to them.

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Sharp increase in harmonic tremors in Grímsfjall volcano

Something is happening at Grímsfjall volcano. The SIL seismomter on Grímsfjall volcano is shows a sharp increase in harmonic tremors in Grímsfjall volcano. It also appears that earthquake activity in increasing in Grímsfjall volcano.

I do believe (based on the data so far) that a eruption is about to start in Grímsfjall volcano. I am going to post more updates on this when I know more. But please note that I might be wrong. But this is what the data suggests so far.

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Possibility of dike intrusion in Hamarinn volcano

It appears that there is a chance of a dike intrusion in Hamarinn volcano (Loki-Fögrufjöll area). What suggest that there is a dike intrusion starting in Hamarinn volcano is a earthquake swarm that is unusually dense and has a really narrow area. But normal earthquake swarms usually spread over a small area in the align of the fault line.

How this is developing is a good question. But due to lack of earthquakes it is hard to know for sure at the moment. But at the moment it is worth to keep eye on Hamarinn volcano area.

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Changes in Grímsfjall volcano

Few days ago changes started to happen in Grímsfjall volcano. It is hard to describe this changes. But they appears to be changes in harmonic tremor levels in Grímsfjall volcano. But they appears to be above background levels and the reason why that is a bit unclear at the moment, but I do not think that this is ice movement as I did think it was first. As this has been lasting for too long. Following this has been a slow increase in earthquakes in and around Grímsfjall volcano. This earthquakes don’t appear on the automatic SIL system, even if they are up to ML2.0 in size. This suggest that there origin is from magma movements, not tectonics one (tectonics earthquakes also happen there).

So far nothing suggest that a eruption is immanent. But that can change without any warning. As Grímsfjall volcano is known to start a eruption with no warning at all.


Harmonic tremor levels in Grímsfjall volcano on 30th March 2011. Picture is from around 17:30 UTC. Copyright of this picture belongs to Icelandic Met Office. The picture is from there web site.


Earthquakes in Grímsfjall volcano on 30th March 2011. Picture is from 17:30 UTC. Copyright of this picture belongs to Icelandic Met Office. The picture is from there web site.

All that can be done for now is to wait and see what happens. But my opinion is that something is up in Grímsfjall volcano. But what that is remains unclear at the moment.

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Glacier flood subsides, harmonic tremors drops down

According to the news the glacier flood from Grímsvötn is subsiding and is expected to be over in the next two to three days. At the same time the harmonic tremor that started at 3rd of November 2010 is also subsiding. No clear reason is for the harmonic tremors.

Currently there is nothing that indicates that a eruption is about to start in Grímsfjalli. But that can change with a short notice, as Grímsfjall sometimes does not give a long warning before it starts erupting.

Icelandic News. Please use Google Translate.

Farginu létt af eldstöðinni (Vísir.is)
Hlaup í rénun (Rúv.is)

English news.

Flood waning, Iceland volcano eruption less likely (washingtonpost.com) – Thanks to Erik for this news.

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No signs of a eruption at Grímsfjall volcano, harmonic tremors continue

Since 02:30 UTC on the 3rd of November 2010 there has been constant harmonic tremor in Grímsfjall volcano. It is currently unclear why harmonic tremors are happening at Grímsfjall volcano. But there have been some ideas that this might be because a small eruption has started at Grímsfjall volcano.

According to news from few moments ago (around 14:00 UTC) there are no signs of a eruption at Grímsfjall volcano at present time. But harmonic tremors continue at this moment like they have been doing since 02:30 UTC last night.

The possible reason why the scientists don’t see any signs of a eruption is because none are visible on the glacier at the moment. But until something appears on surface what is going on in Grímsfjall it is going to remain unclear what is going on at the volcano.

Icelandic News. Please use Google Translate.

Hlaup og órói í Grímsfjalli (Rúv.is)
Engin merki um gos (Rúv.is)
Gos gæti verið hafið (Vísir.is)
Könnunarflug yfir Grímsvötn: Engin merki um gos (Vísir.is)
Vísindamenn fljúga yfir Grímsvötn (mbl.is)
Engin ummerki um eldsumbrot (mbl.is)

International news.

New eruption could be looming in Iceland, experts warn (AFP)

Updated at 14:59 UTC on the 3rd of November 2010. News link added.
Updated at 15:22 UTC on the 3rd of November 2010. News link added.

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Expecting a glacier flood and possibly of a eruption from Grímsfjall at any time

According to the Icelandic news today geological scientists in Iceland are expecting a eruption and a glacier flood from Grímsvötnum at any time and without a any warning. But last week they did detect harmonic tremors on the SIL station that is on Grímsfjall volcano. It is not known if the harmonic tremors where created by water or by magma.

Currently the Grímsvötn lake is full and is ready to burst at any time without warning. Because of that scientists and Iceland Met Office have increased the monitoring of Grímsvötn and Grímsfjall volcano. It has been six years since the last eruption at Grímsfjall (2004) and it only where six years before that eruption (1998).

Iceland News. Please use Google translate.

Enn skelfur jörðin undir Vatnajökli (Rúv.is)
Búast við hlaupi hvenær sem er (mbl.is)

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The harmonic tremors of a volcanic eruption

Many people want to know how to identify a volcanic tremor when they appear. Here are few examples of volcanic tremors that I have seen over the past few years.


The volcanic tremor following the eruption in Grímsfjall in 2004.


Harmonic tremor spike in 2005, following a glacier flood in Skaptárkötlum in Vatnajökull glacier (they are in Hamarinn volcano).

I hope that this two examples show people what to look for when something is going on in Icelandic volcanoes. All images are from Icelandic Met Office web page.

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Sudden rise in harmonic tremors around Katla and Eyjafjallajökull

There is a sudden and sharp rise in harmonic tremors around Katla and Eyjafjallajökull volcano. I currently do not know what volcano is responsible for the spike in harmonic tremor. But this does not look like is a noise from the weather. But that can happen often this time of the year, as the wind forecast is good for all of Iceland at current time.

I will post more information if and when I get them.

SIL stations where the harmonic tremor rise can be seen.

Mið-Mörk
Eystri-Skógar
Lágur Hvolar (Currently most rise here for some reason)
Snæbýli
Saurbær
Ásmúli

Icelandic Met Office tremor web page.

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Second harmonic pulse seen on Grímsvötn SIL station

Earlier tonight a second harmonic pulse was seen on Grímsvötn SIL station. This time the harmonic pulse has lasted longer and is still ongoing when this is written. What is creating this harmonic pulse is unclear at this moment. But at current time Grímsvötn lake is full of water. It might well be that the water is on the move and is leaving the Grímsvötn lake. However it is not going to be clear if that is the case or not in the next few hours. I would not be surprised if it goes both ways. That is the water is on the move and that it might not be on the move at all.


The second harmonic tremor seen on SIL station run by the IMO. Picture credit, Icelandic Met Office.

Grímsvötn SIL station. Click here for the full list of SIL station run by Icelandic Met Office.