Posted on by Jón Frímann

Quiet days in Iceland geology

Over the past days there have been a quiet streak happening in Iceland geology. This regularly happens and doesn’t mean anything special. This quiet times can sometimes last for up to 10 to 20 days at the longest. The longest quiet time that I did see lasted something close to five weeks. But then activity started to pick up again slowly.

It also happens sometime that quiet period is end with a bang. Then with a ML/Mb 4.0 or 5.0 earthquake and following earthquake swarm. Even if quiet time happens in Iceland sometimes, it does not necessary mean that the year is going to be a quiet one. As we have already seen with Eyjafjallajökull eruption in 2010.

15 Replies to “Quiet days in Iceland geology”

  1. @Jón: not quite so quiet.
    Sunday /03.10.2010 / 18:48:54 / 63.814 /-18.577 / 6.6 km / 2.0 / 53.81 25.8 km W of Kirkjubæjarklaustur.
    Could this reflect the dimensions of a rising dike or a sill, or just tectonic?

    1. Forgot to mention this strong one in Vatnajökull:
      Sunday /03.10.2010 18:48:34 64.635 -16.695 3.5 km 2.8 90.06 3.6 km W of Kverkfjöll

  2. @Renato Rio, The event at Kirkjubæjarklaustur appears to be false. But that is a misplaced event by the SIL system that IMO runs. It appears to have happened due to the earthquake in Kverkfjöllum just second before that.

    At least we have to wait until this earthquake is confirmed to be sure.

  3. I’m perplexed.

    See, I have been sitting here beating my head against GPS data and have come to the conclusion that station GFUM has an average track of 57.4mm/yr at a bearing of 133°. So… why is it now tracking northward? (at a phenomenal 2000+ mm/yr rate over 5 days) Yeah, yeah, yeah, I know.. noise. But it works out to about 6 mm/day. All at the same time that it’s doing a lift. Sure, it does the lift every year, but to my untrained eye, it’s almost as if something to the south of it is inflating… and there have been virtually no quakes there. To the southwest, a few, and Bárðarbunga up to the north has been making noise.

    Any ideas?

  4. @Lurking, There was a dike intrusion in Bárðarbunga in March. That might explain the movement you are seeing in the GPS data. There also might have been a deep intrusion of magma in Bárðarbunga or other volcanoes nearby. Including Grímsfjall.

    Not all magma intrusions create earthquake. This happens if they are deep enough. But they usually create a harmonic spike while the intrusion takes place.

  5. @Lurking …. Re motion jumps & reverses at GFUM … Maybe from localized tilt of the long-legged GPS tripod (or whatever) caused by uneven freezing of the ground beneath it. A small anomalous tilt can cause many mm of apparent directional motion as seen on the GPS plot. … So, in that case, no real directional motion, just illusionary motion from a small the tilt of the station.

    1. Maybe so. Nevertheless, the following excerpt from a manuscript located by a general Google search makes me deeply suspicious that the science and processes which underlay it are reasonably well understood. Please excuse me. I need to go watch some 10:10 eco-attack-dog parodies to soothe my nerves …

      “… The overall retreat of Icelandic glaciers is causing uplift of over 2 cm/yr around Vatnajökull, the largest Icelandic ice cap. Recent modelling also suggests that the same phenomena is causing increased mantle melting and magma generation under Vatnajökull …”

      1. Dude… now that’s funny. I’d be laughing my arse off if it weren’t for the fact that those dolts actually believe that.

        BTW… still no registration E-mail….

      3. @Lurking: It seems plausible to me, and this is not the first time I heard about that. I would be curious to know what makes you find it so funny? Once again, I have no expertise and if I ask, it is just to exercise my critical view of things.

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