Posted on by Jón Frímann

Two earthquakes in Grímsfjall volcano

This two earthquakes did happen in Grímsfjall volcano today. There signature clearly shows that they are created by magma breaking the crust. The background noise (SIL tremor plot) in Grímsfjall volcano also appears to have changed following this two earthquakes. I am not sure why that it. But this two earthquakes might be a pre-sequence to a eruption in Grímsfjall volcano. But it is hard to be sure on that at this moment. But I am sure that it is getting shorter to a eruption in Grímsfjall volcano.


Unallocated earthquake, most likely from Grímsfjall volcano. This picture is released under Creative Commons Licence. See link at top for more information.


Unallocated earthquake. This earthquake is from Grímsfjall volcano. The automatic size is ML2.9. With the depth of 1.1 km. This picture is released under Creative Commons Licence. See link at top for more information.

If anything more interesting happens at Grímsfjall volcano. I am going to post more information about it soon after it happens.

55 Replies to “Two earthquakes in Grímsfjall volcano”

  1. How do you recognize these P and S waves? Or are they automatically recognized by some program?

    Very interesting development, thanks for sharing this.

    1. The S-wave starts in about where there is a drop in the wave form. That marks the start of the S-wave. The Icelandic Met Office has program that can detect the P and S wave automatically in most cases.

      I however have to do it manually with the software that I currently have.

      1. Thanks for your explanation, so the larger amplitudes should be the shear/surface waves arriving?

      2. The first wave is the normal P wave. But because this is a earthquake that appears to be created from magma the S wave is smaller and harder to locate then it would be in a tectonic earthquake.

  2. Jón,
    thanks for the update.
    We have been there before, but I think we might expect an eruption at the end of this sequence of scattered swarms.
    So I hope.

    1. If you look at the short history of volcanic eruptions in Iceland that I wrote earlier today (the reall long blog post). Then you see that Grímsfjall volcano is a busy volcano. So we can expect a volcanic eruption from it with a short notice and without much warning at all.

      1. Great post. Just left a comment over there.
        I will try to make a time table comparing the earthquakes and eruptions from these too last posts, when I have time.
        It could be interesting to compare both occurrences.
        Maybe Lurking has already made a plot about it.
        Thanks again.

      2. Not yet… been caught up with wedding junk. (daughter)

        I have also been fixated on apparent liquefaction features in satellite imagery south of Guy Arkansas. Based on what I have learned about that topology… they really shouldn’t be there. The nervous part is that they seem to be concentrated around the south end of where that pesky swarm is at.

        Either… the NMZ which is very far away, can generate much more energy than is supposed,

        Or there is a local fault that is capable of generating liquefaction… probably the very same one with the swarm.

        And yes, there is a third… one that most people leave out, but I won’t .

        >>-> I could be totally wrong.

      3. Hmm… synchronicity.

        I just read Jón Frímann 22:46

        “…So I am just guessing a location based on what I see and that might be totally wrong.”

        I KNEW there was a reason I liked this blog. Someone who has the fortitude to admit the potential for error on their part has my respect.

        BRAVO ZULU.

  4. Hi Jon (et all)

    I guess this has answered my question re the tremor chart readings from this afternoon.

    I think we have all been watching and waiting for this with fascination. One question, would this, if we do see an eruption, be a very small local event. This is my first experience watching a potential eruptive sequence in a caldera. Can eruptions in a caldera be localised to a small area?

  5. I think that there might be a small earthquake swarm in Grímsfjall volcano now. But it is so small that it doesn’t show up on the automatic SIL system.

      1. Because the tremor doesn’t look like a harmonic tremor, it looks more like a tremor from a dense earthquake swarm. There is a magma signal in the earthquake at 17:18 UTC. But that is it.

      2. How about the spike at 14:09 in your helicorder? It shows even stronger than the 17:18 one?

      3. That might be from Katla volcano (Austmannsbunga) and that might be tornillo event. But I am not sure on that. Because looking at the SIL stations it appears that signal is stronger around Vatnajökull glacier then it is around Katla volcano.

        So it might well be from Grímsfjall volcano also. But at the moment that is unconfirmed. So I am just guessing a location based on what I see and that might be totally wrong.

  6. Yes, it looked like one to my lay eyes.
    Something is up. A dike intrusion or a small eruption, I guess. Or just some hydrothermal event.
    We might expect a small jokullhlaup from this.

    1. I highly doubt that anything has started yet. There is no low-frequency harmonic tremor yet, which has to occur before anything sets of. I think this is just part of the run-up to an eruption, to which we seem to be very close in my eyes.

    2. Pieter has this correct. The eruption has not yet started. Normally there is a earthquake swarm in Grímsfjall volcano when a eruption is about to start.

      So far this is just the run up to the eruption. When it starts is a good question with no clear answer.

    1. Looks like Grímsfjal goes with little evidence to prove, sometimes.

    2. Haha…. pushing this with you !!!!

      Talk about willing this on !!!.. perhaps not the right thing considering the power of nature… 🙂

  8. The unconfirmed earthquake swarm in Grímsfjall volcano appears to be slowing down. But that might not mean a lot in the long run. As there is something going on at Grímsfjall volcano. Too bad I don’t have clear idea what that is yet.

  9. Does anyone have a link to the water monitoring (water level, temperature, conductivity) for the probable jökulhlaup paths? I have the links saved on my home PC, but just have my laptop while travelling and I’m having a difficult time finding the information again on IMO site.

    2. Speaking of water…. where is the Gígja?

      I seem to remember that gauge station Gígja; V159 was relatively important a while back.

      The reason I ask, is that it’s conductivity is up to 296.7 siemens per cm as of a couple of days ago.

      Increased conductivity means more concentrated dissolved salts or an increase in acidity…. I don’t know the river, or if it’s fed from Grímsvötn area of the icecap… but it might be telling.

      1. Bah.. never mind. It’s been higher in the last few months.

        It means jack.

  10. I can see it dropping.
    I think this is the first time I can understand a little bit form those graphs. 🙂

      1. Yes, I saw that too.
        Well, we ‘ll have to wait and see.
        Another sleepless night?

      2. I am wondering what is going on in Grímsfjall volcano. This is a odd behaviour. Maybe next eruption is going to be different then the eruptions of the years 1998 and 2004.

      3. Another quake under Vatnajökull:
        Monday
        04.04.2011 00:44:56 64.518 -17.690 2.6 km 1.6 90.02 6.7 km ENE of Hamarinn
        visible on your helicorder.

    1. I found it, thanks for notice this. I did think it was a noise. But it is a earthquake by the wave form data. But it was a weak wave form data.

      It looked more like a regular earthquake then a magma earthquake, from the poor recording that I got.

  12. I am the one who has to thank you for the encouragement.
    There is another wave of quakes happening in Iceland.
    Could the quakes on Grímsfjal be a part of it or the volcano is being triggered by it?
    We still have to see an isolated swarm to be sure it is the volcano and not the fault system that caused it, but this is just my speculation.

    1. It has been rather quiet in Iceland overt the past few weeks. Each week with between 100 to 300 earthquakes. That is quiet by icelandic earthquake standards.

      The answer to that question would be no. Based on the knowledge that I have on this subject.

      But before a eruption in Grímsfjall volcano there is going to be a earthquake swarm. When that happens, we know what is going on.

  13. I fear that the SIL station and other houses on Grímsfjall volcano might be in dangers if a fissure opens up as this earthquakes are suggesting it is going to.

    http://hraun.vedur.is/ja/viku/2011/vika_13/bab.gif

    Note the pattern on the week overview. It is NE-SW or about that. It crosses the SIL station and the only bed rock that is exposed in this area and used by scientists and tourist groups that travel Vatnajökull glacier.

    1. That’s the usual risk when you place equipment on an actice volcano. But the map is quite coarse, so I don’t expect the fissure to appear right on the ridge where the station is. I would expect it some hundred meters to the caldera side. Still ashfall and volcanic bombs could do damage but it will not be lost right with the start of an eruption.

    2. “houses on Grímsfjall volcano”, Jon? I’ll take one! But I would only rent, not buy… 😉

      Mike

  14. Hey,

    Any Official word from the people at the IMO or any other government group?

    I subscribed to your blog Jon, with my help that secret Helicopter that you have been planning for can happen now, i am in!! (:

    Learning allot from the site, might do a course in the future, Looking at the History of Iceland, A busy period might be on the way. I hope another LAKI type event does not happen. Any chance of this looking at the data so far?

    1. A Laki event can almost be ruled out for now, in Grimsvotn’s case. These events seems to occur about every 500-800 years. Laki was in 1783, so statistically we’re not up to one now. But luckily/sadly volcanoes aren’t statistics, so anything could happen anytime.

      In my opinion, the risk of a major fissure eruption Laki-style is the highest currently near Askja, which had such eruptions in the past, and the fissure-system has been rather active (earthquake-wise) the past few decades. According to some researches this is due to a dyke-forming process, which seems harmless. But as soon as these dykes reach the surface, it could get more serious. Please note that none of this is actually a prediction and just an interpretation of my own.

      1. I think that the Laki event was more like what did happen in Askja volcano in 19th century. It was a dike intrusion that did manage to go up the surface. In the case of Askja volcano, the fissure that was created was 25 km long.

        So the bottom line is this. This can happen at any time, without a warning. The time frame that you are guessing on does not work in this case.

      2. Well I highly doubt the fact that there will be no warning. In order for this huge mass to reach the surface through newly formed cracks (so no fresh conduits) I think there a huge amount of earthquake activity is needed.

  16. It is sure to go. The question is when? Perhaps not quite now, but just as likely it will rumble again within a month and again and again then suddenly, with little more warning, one will be an eruption.

  17. The size of the earthquakes where ML2.0 at 14:08 UTC, with the depth of 0.1 km (~100 meters). The second earthquake at 17:18 UTC had the size ML2.1 and had the depth 0.1 km (~100 meters). There where smaller earthquakes also recorded by the SIL network. But they where not recorded on my geophone.

    1. That would be in the bedrock. But that is not far from the ice or the water for that matter. Hydrothermal activity must be really high there now I would guess.

      1. I’ll be in Iceland in a week or two with luck. I’ll take a look up there and report; I know a guy with a super jeep, he thinks he can get up there…

        Mike

      2. have fun, Mike!! Wish I could be there too. Taker pictures, please.
        🙂

      4. Mike
        lots of fun and great weather and the right time in sight, but in safety
        Envy, Envy, Envy

  19. Thanks for the reply people, I was looking at the IMO site, looks like a mini active Night, BTW I am from Ireland, you can all live here if Iceland melts. (:

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