Posted on by Jón Frímann

Earthquakes in eastern part of Katla volcano (Mýrdalsjökull)

Last week something interesting started to happen in Katla volcano last week (Week 45). Earthquakes started to appear in the eastern part of the Katla volcano. This is higly unusual and is not the normal earthquake zone in Katla volcano. But normally the earthquakes take place in the western part of the Katla volcano (Goðabungu area) and few earthquakes take place in the caldera it self at regularly.

At 00:45 UTC there was a earthquake in eastern Katla volcano, the automatic SIL size of this earthquake was ML2,5 at the depth of 1,1Km (with a good quality of 90,05). Both figures are subject to a revision by a seismologist at later time, so both size and depth can change. I did manage to record this earthquake on my Hekla geophone, even if there currently is rather high wind noise at my geophone. What I did see on my geophone is interesting. But the earthquake appears to have low frequency component in it, even if it is mostly high-frequency type of earthquake. But those earthquakes are normally created by a fault in the crust, not by magma movement.

I need more data to confirm it. But there are clues that the earthquakes in eastern Katla volcano are due to magma movement, rather then tension changes in the crust not related to magma movement. What is happening there is unclear at the moment, as GPS stations around Katla volcano do not show anything interesting at the moment.

No eruption is imminent in Katla volcano at current time.

59 Replies to “Earthquakes in eastern part of Katla volcano (Mýrdalsjökull)”

  1. Well, I have been looking at this new post for a while now… and have responded twice to it already… but deleted them without posting. So that’s a “non responce” on my part. I figured that until I had my applocations in a condition that enabled me to plot again, I would remain quiet. Took the better part of a day to rebuild from the dead motherboard state.

    The quakes that you refer to seem to be shallow. Well, shallow as compared to most of the ones in the area. Is it possible that it’s a dike thing? The area from Mýrdalsjökull to Vatnajökull isn’t really known for it’s tectonic fury.

  3. I noticed that one, but didn’t think much about it since it didn’t show any tremors at Katla-vöktun.
    But I just noticed that the entire page have been stuch since mid september.

    Perhap’s you could get them to turn it on again Jón?

    2. Huh? AFAICS, the only things not up to date are the average Z-shake graphs from stations closest to Eyjafjallajökull.

      (BTW, that site has also a link to HI’s page of detrended GPS measurements, which I like to use: http://notendur.hi.is/runa/eyja_gps.html They have added stations to it lately)

      1. Seems like someone is reading this blog…
        All of the graphs where locked on 15th this month when I wrote the post above, now all of the tremorstations are up again. So I venture out and say that the rest will probably be running again soon.

      4. @Kultsi: Yes indeed I hope for your OTOH with regard to the safety of everyone in Iceland.

    1. All I have read is that the Katla volcanic system includes Láki and Eldgja. If I would hazard a guess judging by the volcanic zones in Iceland Westmannaeyjar is a volcanic system of its own.

      And to be honest..I think the Katla-Lakí-Eldgja combo is quite enough and should make it one of the most powerful volcanic systems in he world. 🙂 Excluding the yellowstone, toba and such of course. 🙂

      1. I just want to give my 2 cents to correct you point:

        As far as i know though reading papers with the topic of the volcanic systems in iceland:

        Laki belongs to the Grimsvötn Fissure Swarm, it has nothing to do with Katla or Eldgja, except the size of the Eruption which took place in the Eastern Volcanic Zone.

        Eldgja might have to to with Katla, or might belong to a Katla Fissure Swarm, but i’m not clear about that – perhaps Jon knows the answer to that.

        In Westmannaeyjar i think your right, It is the continuation of the Eastern Volcanic Zone towards the south, and is it’s own Volcanic System.

        Here you find a picture with the volcanic systems: http://www.geog.ucsb.edu/img/news/2010/1000px-Volcanic_system_of_Iceland-Map-en.png

        and another one:
        http://www3.hi.is/~arnie/pe_zone.gif

  6. I hope nothing happens next week, as I’ll be traveling… I was also traveling in April, when lady E forced me to take the train from Munich towards Scandinavia. I arrived in Finland 2,5 days later than planned. It was no more fun having the same socks and shoes on for 3 days in a row – without taking shoes off just because of the fellow travelers!!!

  7. Speaking of your last pargraph, Jón, with six months gone since Lady E started to peter out, can we now rule out the connection betwen E & K, i.e. “an eruption in E is followed by K”?

    1. I hope your ok if i answer your Question too : )

      I don’t think that this connection – if there is any – can be ruled out. Six months is a rather extremely short period of time when speaking of geological time-scales.

      But i also think that the assumption, that an eruption in Eyjafjöll is followed by an eruption in Katla is wrong. or as far as we know for now, it’s not proven by any means.

      1. Oh I agree Stefan, it cannot yet be ruled out with 100% certainty. However, the closest the two systems get is the Godabunga cryptodome, which is part of the E-system, just west of the Katla caldera. Judging by Norvol papers, the cryptodome would appear to contain at least one cu. km of magma, and in the latest report it approaches gigantic proportions. An eruption there would certainly affect Katla, in my opinion anyway!

      2. thanks for your reply:

        is there a way to find the Norvol papers? do you have a link to them or can you send me them? my adress would then bee: elessarelbenstein (at) hotmail dot com without the spaces

      6. I actualy don’t agree with you on the point, that the cryptodome belongs to the Eyjafjöll-Volcano. In my opinion it belongs to the Katla System or is even an individual – still developing – volcano.

        what i dont understand that good, is “what is a cryptodome really? Do i understand it correctly if i assume, that a cryptodome is something like a rhiolythic/obsidian intrusion which slowly rises and in some time, will make it to the surface? Or is it more like a small magma chamber, which will lead in the geological future to an eruption?

      7. As far as I understand it, its just a hidden dome which is below the iceshield of the glacier. Contrary to the ones which can be seen, like the one at Merapi for example.

    2. Actually the claimed connection would span 2 years after Eyja’s eruption. Lady E has erupted in 920, 1612, and 1821-1823. Katla has erupted 920 and 934 (the famous one), 1612 and 1625 (VEI5), and 1823. It also seems, Katla has a major one 10-15 years after Eyja? Just speculating, though!

      1. Or it just happened by chance. Katla had around 20 eruptions in the last thousand years, so there is the chance of an eruption every 50 years. Building up statistics on only three events is kind of shaky.

  8. I hope Katla keeps dormant until mid January. I will be travelling to Iceland. Then, it can blow, as I would like to see this life. And I have a feeling I will.

    But please no VEI6 eruption!

  9. “Be mindful when you beseech the Gods, that they may grant your prayers…” Let’s hope that you get no more than a VEI 2 or 3 at most.

    1. This would already cause quite some trouble in Iceland. The ice over Katla is much thicker than over Eyjafjallajökull.

  10. Call it a hunch or a gut feeling but to be totally honest I dont think we will see any eruption at Myrdalsjökull for a long time yet. I dont know why i get that feeling but looking at the GPS, tremors, EQ´s she just doesnt seem restless enough.

    If I were to look at a spot for the next eruption it would be beneath Vatnajökull. And which to go first is a good question as there has been some recent restless periods at several volcanoes.

    And even so nothing may happen beneath Vatnajökull either for many many months.

    But that may be for the best..At least the Myrdalsjökull “hunch”. An eruption there, big or small, will certainly disrupt every day life for the people living there and perhaps even a new airtraffic disruption.

    And as said before..The VEI scale is really outdated..Just look at Kilauea in Hawaii..It has erupted almost 3 km3 since it started in 1983 (based on an average 0.1Km3/annually) and that makes it a VEI-5 eruption. Same as the Mt St Helens eruption. The big difference between the two is the explosivity and the ejection rate which is not taken into consideration in the VEI scale..

    Rant over..:)

    1. According to Jon & co., Katla does not typically give any long-time warnings, but only last-minute signs before an eruption.

      1. Hmm maybe I need to revise my earlier statement regarding the lack of movement in the GPS. As homo sapiens we tend to look for patterns in all things and there is a clear pattern in the “up-trend” at GOLA station.

        http://i53.tinypic.com/qnww0y.jpg

      2. But yes Jon told that Katla is much like Hekla in that aspect..

        A few large quakes (mag4-5) hours before the eruption.
        Is that because the conduits are quite clear or that the icecover is heavy enough to nullify the tremors when the pressure is building up to the point of structural failure of the “roof”?

      3. Daniel:
        No, the ice-roof wont dampen out the tremors. Tremors are basically very low-frequent noise and noise travells well in non-dampening hard materials.
        Basalt is a really good sound carrier and can carry “noise” around the globe if needed. Water carries noise across the atlantic, and ice is an ever better sound-carrying version of water.

        Pretty much the only thing that might dampen noise would be the intersection between the ice and the rock. Especially if there is a lot of air in the intersection. Every time noise goes from one medium to another it looses energy, and with two intersections, rock to air and air to ice it would be harder to spot. But we are still talking about 1/4 of “noise-energy” surviving the transitions.
        Sorry for simplifying this, I guess that it is better to not go to technical on this subject.

      4. I agree with the “up” pattern in GOLA, but do note that the recent swing sort of correlated with the annual upswings earlier in the plot.

        It might not be anything.

  11. Speaking of Katla, tremors are on the rise around mama K, but winds are quite “slow”.

    1. Tremors rising can be due to bad weather further out to sea..And that the ocean is a bit restless creating bigger swells which affects the geophones.

      Need Jon to confirm that theory though..;)

      There should be a “wather/ocean” filter on those geophones. 🙂

      1. Waves are easy to filter out, I have such software. Problem is that it has to be applied to the pesky geophones raw data. To filter out wind you need to cross-filter with a wind-spedometer.

  13. Iceland looks calm.

    http://hraun.vedur.is/ja/oroi/allarsort.html

    In the name of Katla…My previous post said that my feeling was that there was nothing big happening at Myrdalsjökull. That feeling is still viable. Look at the above link and you will see that there is no significant increase in tremors.

    Now I know that Jón said that an eruption at Katla would be preceded by a short burst of large EQ´s (M4-5) or so…

    However I would be surprised if there were no “extra” inflation prior to these events. Tremors are normally generated by friction between rocks or magma bursting through rock right? And an inflating would mean more magma filling up and as such make more pressure up wards which would mean that the ground itself would shake. No this might happen fast so there will be no warning but still…I will keep a firm grip on my previous “Hunch” that there will be no eruption in Katla within the next year or so..

    1. Katla is allready inflated so no need for a large inflation episode.
      And Katla would have the same tremor-increase ratio as Hekla did on the stunning graph Jón gave just above.

      For Katla I would say that all it takes is a large enough quake to instigate a gas-release episode. Think of a beer bottle being hit… I wont go back into explaining again the function of gas release and complexity of magma reservoirs. But I will say this, probably both Katla and Hekla has very complicated magma reservoirs and that is why it just takes one large jolt on the magma beer-kegg!

    1. Thanks.

      What I found after doing a bit of digging is that there is probably a series (14 or so) of poorley located transform faults cutting across the Gulf of Mexico. These are all related to the break-up of the last supercontinent. The Port St Joe fault still sees a mag 1.0 to 2.0 every few years or so… but about it usually does is scare the wildlife.

    1. Katla don’t sleep, she has had her morning coffee, looked at her troublesome neighbour and is now contemplating taking a afternoon beer. When she will open her beer and drink it is the thing to guess about.
      But that is one volcano that never sleeps.

      What I mean is that it just takes a couple of larger quakes (4 and upwards) to shake loose some gas from the magma that is allready in the very complex magma reservoir and it will spew forth like a vomiting ulcerous alcoholic.

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