Posted on by Jón Frímann

A magnitude ML3.5 and ML4.2 (IMO) and ML4.0 (EMSC) earthquake hits Grímsfjall volcano

A magnitude ML3.8 earthquake has hit Kverkfjöll volcano. This earthquake had the depth of 14,4 km according to the automatic SIL system.

This earthquake appears to have triggered earthquakes in Grímsfjall volcano. But two earthquakes appeared imminently after the ML3.8 earthquake in Kverkfjöll volcano. – This is not the case, the earthquakes happened before (09:06 UTC) the ML3.8 earthquake in Kverkfjöll volcano.

I have been going over the reviewed data on this earthquake. The web site EMSC is reporting this to be a ML4.0 earthquake that took place at 09:22 UTC, with the depth of 10 km. While IMO is reporting this earthquake to have the size ML4.2 (depth unkown). There was a earlier earthquake that took place at 09:06 UTC, it has has the size of ML3.5 (depth unkown). Both of this earthquakes took place in Grímsfjall volcano. There is a good chance that Icelandic Met Office is underestimating the size of this earthquake, given the data from EMSC and the fact that this earthquake was recorded on remote seismometer networks in Europe.

I am going to post updates on this if anything more happens.

Text updated at 09:49 UTC on 13th January 2011.
Text updated at 10:21 UTC on 13th of January 2011.
Text updated at 12:55 UTC on 13th of January 2011.

38 Replies to “A magnitude ML3.5 and ML4.2 (IMO) and ML4.0 (EMSC) earthquake hits Grímsfjall volcano”

  1. IS

    Thursday
    13.01.2011 09:22:27 64.084 -17.261 1.1 km 3.9 54.47 15.4 km WNW of Skaftafell

    really just a reflection from

    Thursday
    13.01.2011 09:22:27 64.666 -16.860 14.4 km 3.8 90.01 11.9 km WNW of Kverkfjöll

    ?

  2. Harmonic tremor across all frequencies has been rising steadily across all stations around Myrdalsjokull; could this be weather related?

  3. The position the earthquake has been review already, now it was in the middle of grimsfjall. and at a very low depth

    Sander

  4. Is

    Thursday
    13.01.2011 09:22:22 64.415 -17.269 0.1 km 2.7 99.0 1.2 km N of Grímsfjall

    a large ice split? Undermined glacier collapse?

  6. GFZ Potsdam – Earthquake Bulletin
    2011-01-13 09:22:27 4.5 Mag 64.27 N 17.81 W 10 (Depth km) A Iceland

  7. I would say that it was 2 earthquakes taking place.
    Both under Grimsfjöll for obvious reasons. The first smaller one would then be between 2,7 and 3,0 and the second one between 3,9 and 4,3.
    I would say that the amount of gosting we are getting comes from the quakes being pretty much directly underneath the GFUM station (makes automated directioning harder).
    Just my five cents.

  8. IMO have just re-calculated it all again. They are clearly having resolution problems – prob due to more that 1 earthquake at once, but that is just a guess.

  9. Also note that all the depths have changed in their latest evaluation. If Carl thinks their resolution difficulties are due to it being too close to the GFUM station, his guess is more likely to be right than mine.

    1. But, and this is a largish but, they have other stations that help with the positioning when doing it manually. But for an automated system it can be a nuisance if a large enough quake happens to close.
      Think here about a care with external rearview mirrors only. If something happens exactly behind the car you will have a problem seeing exactly what it was.

  10. You had better change your thread title again Jon! They have revised the magnitude yet again.

  11. Aaagh! they have just altered it yet again! I guess we have to wait to see what they finally decide!

    1. I would say that we would have to wait and see what they do with the big one.

      EMSC still had it as a sollid 4,0 at 10 kilometres (dummy depth) and at Kverkfjöll.

      I would go with how far out the quake overloaded the SIL-stations. It gives a good pictures of how powerfull it was. The only SIL that is overloaded in all frequencies is GRF itself. The otherones might overload, but not in all frequencies, and the more fare out ones are not even overloading. SO a safe bet is that it was not Kverkfjöll since then the BRU would also be as overloaded as GRF, and it is only partially overloaded. Deductioning is a powerfull tool.

  12. I am going out, but I am going to update the title when I get back. But IMO has put this up on there web site in Icelandic.

    Icelandic Met Office notice.

    At 09:22 there was a magnitude 4,2 earthquake nearby Grímsfjall. Few moments earlier there at 09:06 was a magnitude 3,5 earthquake around the same area.

    1. How much earthquaking does Grimsvotn usually give as warning of eruption? Does it always trigger a jokulhlaup soon before, or can it quake a few times and erupt through the ice with little warning?

      1. If I remember correctly the Gjalp-eruption was triggered by a 5,4 at Bardarbunga that started a swarm that wandered away to Grimsvötn and ended with a 4,2 in Grimsvötn and right after that the eruption started. After the eruption the Jökulhlaup happened then.
        So, basically yes.

  14. Considering that there were a few EQ´s in the grimsvötn vicinity could this be the one to get things started?

    After all Grimsvötn did show some signs of unrest with the jökulhlaup earlier and the inflation that has been going on.

    1. I would say it is fifty fifty that it is enough, at Gjalp the quake that triggered it was a 4,2, but on the other hand it was after a strong swarm that started with a 5,4 at Bardarbunga.
      We will know in just a few hours, keap a close eye on the tremoring.

    1. The one we are seeing so far up untill the quake overload spike yes.

      Take a look at this link. The huge tremoring around 1 of november is the Jökulhlaup. And that is rather weekish for it to have been an eruption. The Gjalp went through the roof. A bit like the second link that is from Eyja-eruption.

      http://hraun.vedur.is/ja/vatnajokulsvoktun/grf_trem.html

      http://hraun.vedur.is/ja/Katla2009/god_trem.gif

      So if we see a brutal and sharp uplift of tremoring somewhere above the Jökulhlaup of November, then we know. Before that it is probably nothing.

  16. @all:
    Nota bene, if it goes blank, then it might be a good sign that something have happened to. Ie, that it has been broken or gone out of existence. Due to the placement it would be rather likely that it goes dead.

  18. The quakes are in the news now. According this them IMO is observing the situation very close (no surprise) and doesn’t know, if anything else will happen.
    Unfortunately we have a storm over southern Iceland, so small quakes are most likely lost in the background noise. So we don’t have small quake swarms as a warning.

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