Category: Swarm

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Harmonic tremor detected in Þórðarhyrna volcano

On the 21-November-2013 there was an earthquake swarm in Þórðarhyrna volcano (part of Grímsfjall volcano). This was not large earthquake swarm or a strong one. With the largest earthquake just having the magnitude of 1,9. While I did just suspect it I did not have it confirmed until today that following this earthquake swarm was an harmonic tremor pulse. This harmonic tremor lasted from 03:30 to 06:10 UTC. Based on nearby SIL station this was not a strong harmonic tremor, but this is important because it suggests that something is taking place in Þórðarhyrna volcano. If this is going to lead to an eruption is unknown at current time. This might be a dike intrusion into the volcano at depth, but that has not been confirmed.

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The harmonic tremor pulse can be seen at 21-November date on this tremor plot from Icelandic Meteorological Office. Copyright of this image belongs to Icelandic Meteorological Office.

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The harmonic tremor pulse as it did appear from Grímsfjall SIL station. Copyright of this image belongs to Icelandic Meteorological Office.

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Harmonic tremor pulse as it did appear on Jökulsel SIL station. Copyright of this image belongs to Icelandic Meteorological Office.

This activity might not lead to an eruption, but given the past history of this area and the eruption in Grímsfjall volcano in the spring of 2011 I find it to be highly likely outcome that eruption is going to take place in Þórðarhyrna volcano in near future, it is not possible to know when such eruption might take place. Last eruption took place in Þórðarhyrna volcano in the year 1902, it is not known if any later eruptions have taken place in Þórðarhyrna volcano.

Blog post updated at 14:47 UTC.

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Earthquake swarm in Tungnafellsjökull volcano

There is currently ongoing interesting earthquake swarm activity in Tungnafellsjökull volcano. This earthquake activity appears to be taking place due to magma injection at depth into the volcano. Currently the earthquake activity doesn’t appear so clearly on the Icelandic Meteorological Office earthquake maps. I am not sure why that is, the largest earthquake so far has had the magnitude of 2,3 at the depth of 0,5 km so activity is already rather shallow, deepest activity had the depth of 17,5 km. Earthquake activity started in Tungnafellsjökull volcano in the year 2012, before that earthquake activity had taken place in Tungnafellsjökull volcano following an eruption in Bárðarbunga / Grímsfjall volcano in the year 1996 [map here of Week 41 – 1996]. Current earthquake activity is not based on any such event.

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Earthquake activity in Tungnafellsjökull volcano. Copyright of this image belongs to Icelandic Meteorological Office.

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Tremor activity showing minor earthquakes taking place in Tungnafellsjökull volcano (most likely) over the past few hours. Copyright of this image belongs to Icelandic Meteorological Office.

I am not sure yet what is happening in Tungnafellsjökull volcano. But data in mounting and suggesting that magma is about to start flowing into the volcano at faster rates then before (via dike intrusions). Tungnafellsjökull volcano has not erupted in historical times (at least no eruption is documented) so it is impossible to know for sure what happens next in this volcano. If an eruption where to take place it would be mostly basalt based on post sub-glacier eruptions (when they erupted is not known). Current earthquake activity might die down as it did in the year 2012 when (and earlier this year [2013] also) this swarm like activity at depth (15+ km) started to happen.

Blog post updated at 04:36 UTC.
Blog post updated at 04:46 UTC.

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Minor earthquake swarm in Þórðarhyrna volcano

Today (21-November-2013) an minor earthquake swarm took place in Þórðarhyrna volcano. All of this earthquakes were small, with the largest having just the magnitude of 1,9. Depth of this earthquakes was from 6,0 to 0,1 km. This minor earthquake activity is now detected for the first time due to a new SIL stations in the area. How long this type of activity has been ongoing is impossible to know since in the past there have been fewer SIL stations in the area.

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Earthquake activity in Þórðarhyrna volcano. Copyright of this image belongs to Icelandic Meteorological Office.

This earthquake activity is not ice-quake activity, since the glacier is frozen now and with temperature down to -19C it is not going to move a lot. Last eruption in Þórðarhyrna volcano was in the year 1910 and it was connected to an eruption sequence that took place in Grímsfjall volcano at the same time (or that is at least the theory).

I am not yet sure what this means long term for activity in this volcano, since I know so little about how this volcano works due to lack of documented eruption history. If this earthquake activity intensifies from what is now taking place there is a small chance of something happening in Þórðarhyrna volcano. For the moment however, this is just a minor earthquake swarm and does not mean anything special. There have not been any changes in harmonic tremor on SIL stations close to Þórðarhyrna volcano.

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Minor earthquake swarm in Katla volcano

On the 20-November-2013 an minor earthquake swarm took place in Katla volcano, it started at 06:21 UTC and was over by 08:54 UTC. This earthquake swarm was minor one, with the largest earthquake having the magnitude of 1,2. The deepest earthquake had the depth of 26,1 km. That means this earthquake swarm was due to magma changes in Katla volcano at depth.

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Earthquake swarm in Katla volcano. This was a minor earthquake swarm. Copyright of this image belongs to Icelandic Meteorological Office.

No further activity has taken place in Katla volcano following this earthquake swarm since it took place. Future activity cannot be ruled out since Katla volcano is highly active when it comes to earthquake activity.

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Earthquake swarm on the Reykjanes

On Saturday (16-November-2013) an earthquake swarm started on the Reykjanes. This earthquake swarm started slowly with only few unnoticeable earthquakes for most of the time. There was also a second earthquake swarm taking place due to water being pumped back into the ground. That did hide the current earthquake swarm to start with. This earthquake swarm is taking place in Brennisteinsfjöll / Bláfjöll volcano area.

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The earthquake swarm on the Reykjanes. Copyright of this image belongs to Icelandic Meteorological Office.

Largest earthquakes in the current earthquake swarm have so far just had the magnitude of 2,9. Stronger earthquakes cannot be ruled out at current time. At the moment there is nothing to suggest this activity is related to any magma movement at present time. Currently the earthquake swarm is ongoing and it is impossible to know if it is going to continue or just die out slowly. The strongest earthquakes appear clearly on my geophone website here.

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Minor earthquake swarm in south-east of Katla volcano

Today (17-November-2013) a minor earthquake swarm took place in Katla volcano at 06:21 UTC and it lasted to 07:09 UTC. The largest earthquake has the automatic magnitude of 1,8 with the depth of 18 km. This earthquake swarm took place under an former island in the area called Hjörleifshöfði (in Deutsch, English is not available). It is possible that this former island has it’s origin is in an volcano activity in the area, while I do not have it confirmed it is at least an idea. The deepest earthquake in this area had the depth around 22 km according to automatic results from Icelandic Meteorological Office.

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The earthquake activity in the east part of Katla volcano system. Copyright of this image belongs to Icelandic Meteorological Office.

Based on the depth of this earthquake swarm, the origin of this earthquake swarm was in magma movement or dike intrusion. It is not a tectonic activity, since such earthquakes are not so common in this part of Iceland, but they do happen. I am not sure what this means for activity in Katla volcano since I have not seen this before as it appeared now. This area of Iceland can be viewed in Google Maps and with Street View here.

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Minor earthquake swarm on Reykjanes Ridge

Today (04-November-2013) at 04:03 UTC an minor earthquake swarm took place on the Reykjanes ridge. The largest earthquake in this swarm had the magnitude of 3,2 and the depth of 12,2 km.

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Earthquakes on the Reykjanes ridge. Copyright of this image belongs to Icelandic Meteorological Office.

Earthquakes are no uncommon in this area and there have been several earthquake swarm in past few weeks. Currently there are no signs of volcano activity taking place at this location and there are no clues or suggestions that such event is about to take place at present time. The largest earthquake did appear clearly on my geophone network and it can be viewed here on my geophone website.

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Earthquake swarm on Tjörnes Fracture Zone

Yesterday (18-October-2013) an earthquake swarm started on Tjörnes Fracture Zone. This earthquake swarm has not been big, with largest earthquake only having the magnitude 2,5. This earthquake swarm is taking place at the end of an unnamed volcano that is in this area. The earthquakes appear to be only tectonic at this moment.

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The earthquake swarm in Tjörnes Fracture Zone yesterday and today. Copyright of this image belongs to Icelandic Meteorological Office.

It is hard to know for sure if earthquake activity is going to continue in this area of Tjörnes Fractures Zone. Currently the activity remains low to moderate in this area, but no large earthquakes (over magnitude 4,0) have so far taken place in this area.

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New earthquake swarm on Reykjanes ridge

Today (19-October-2013) new earthquake swarm started on the Reykjanes ridge. So far this earthquake swarm has been small, with only 16 earthquakes recorded. Largest earthquake in this swarm had magnitude 3,3 at the depth of 6,1 km.

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The earthquake swarm on the Reykjanes ridge. The green star marks earthquakes with magnitude over 3,0. Copyright of this image belongs to Icelandic Meteorological Office.

I am expecting more earthquake activity in this area of the Reykjanes ridge over the next few days and weeks. It is impossible to know when an new earthquakes swarm starts. The best way is to monitor current activity at Icelandic Metorlogical Office website and on my webicorder website.

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Possible volcano eruption in the year 2002 off the coast of north Iceland

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Few years ago there was an strong earthquake swarm 45 km north of Grímsey island, the earthquake swarm location was between Grímsey island and Kolbeinsey island. The strongest earthquake in that swarm had the magnitude of 5,5. It’s now considered a possibility that an minor eruption took place at this location when this earthquake swarm took place in the year 2002. This is according to an recent study into the volcano activity in this area. Since this part of the rift zone where volcanic activity continues where the Tjörnes Fracture Zone ends.

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Storagrunn volcano. Image from Vísir.is news, copyright belongs to Bryndís Brandsdóttir and other people connected to this work.

This volcano is located at depth at this location so any minor eruption is not going to get noticed on the surface of the ocean.

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The earthquake swarm in this area in the year 2002 (vedur.is, Icelandic, images). Earthquakes larger than 3,0 are marked by green dots. Copyright on this image belongs to Icelandic Meteorological Office.

Icelandic News about this. Beware Google Translate.

Við misstum af síðasta eldgosi við Norðurland (Vísir.is, Icelandic)