Posted on by Jón Frímann

Earthquake activity in Katla volcano increases again

I was going to write about something else (TFZ and other earthquakes around Iceland in the last few days). But that just has to wait for a little longer.

It seems that Katla volcano earthquakes are increasing again. This increase appears to be similar to the increase in earthquakes before the glacier flood from the 9th to 17th of June and onwards until the glacier flood on 8th and 9th of July. The only difference now is that I am seeing this pattern earlier since I now know what to look for this time around when this is in its early stages.

How this is going to develop now is a wait and see process. But this might take as long time to get interesting as it did in June to July, to the event that ended with the glacier flood from Mýrdalsjökull glacier.


Current earthquake activity in Katla volcano. Copyright of this picture belongs to Icelandic Met Office.

It is also worth noticing that the earthquake activity is not as focused as it was in early June and in July. But I am fully expecting that to happen soon. But it remains to be seen if that actually happens or not.

The earthquake activity SSE in the Katla volcano caldera rim is still interesting. I do not know why it is taking place there. But if a eruption would take place at this location. There would be a short glacier flood and some period with volcano ash explosions. But after that it should be lava eruption in that location if it where to last long enough to remove all that water from the crater. But this is all just a speculation and nothing more.

For now. It is just wait and see what happens next.

56 Replies to “Earthquake activity in Katla volcano increases again”

  1. Jon I have been following your posts in Eruptions for the past couple of years. I am a layman social worker, love the science of volcanos. anyway, I have been watching the Icelands volcano cams for 2-3 years now. Just noticed tonight a bright light growing on top of the glacier in the katla cam. Please take a look.

    1. The web-cam showing sheep. Momma and baby. I’ve been watching this as well.

  2. My take: activity has been occurring all along, but with the recent good weather allowed the icelandic met office to detect more earthquakes due to less noise.

  3. I am going to Iceland the 25th – 29th this month, if the weather is fair, we will fly around and film the area… any advice?

    Cheers and thank you for the good work on this blog 🙂
    Christian from Sweden

  4. Those clouds over the glacier are tricky I would swear a vent is smoking on the center of the Katla cam.

  7. Friday
    12.08.2011 04:08:14 63.942 -21.998 10.4 km 0.8 83.56 6.9 km NNE of Krýsuvík
    Friday
    12.08.2011 04:03:17 63.938 -21.990 8.3 km 2.9 90.05 6.7 km NNE of Krýsuvík

      1. Idd a nice swarm. Anyone also noticed that this swarm is taking place deeper than the previous swarms. The big one from (october last year?) had earthquakes around 5-7km. This one between 8-10km. though this might change as the quakes are reviewed. Could this mean that new magma is intruding or that “old” magma is retreating back into the earth>?

        Sander

      3. Also, it remains to be seen, if there are any changes (due to this swarm) observed in the lake nearby…

      4. It seems, this swarm has eased the strain between the continental plates. There is a clear step-like reduction in low-frequency (0,5-1,0 Hz) tremor at Hekla after the M2.9 quake that started the swarm at Krisuvik! See for yourself: http://hraun.vedur.is/ja/hekla/borholu_thensla.html

        I think this is the first time in Icelandic measurements when we can see far-ranging tremor effects due to continental drift.

      5. I see what you mean but I dont understand it. I understand the part that a quake can release tension between the plates. But how does that affect tremors? How can an earthquake lower tremors? It’s not that the plates are constantly moving at 0.5-1Hz or are they?

      6. A (continuous, solid) plate under tension vibrates quite easily, thus “amplifying” tremor and also conducting it farther.

      8. Also a hight tension material vibrates as a way to release energy.
        But, since there has been (I think) a lot of tectonic movement in Iceland across the bord alla the way from Reykjaness Ridge via Langjökull up to the TFZ, it might be ending up with the tremoring coming back with a vengeance. But, this is a hunch.

  10. In a way it’s funny that everytime someone mentions “Katla!”, something far more interesting happens elsewhere such as eruptions at Grímsvötn, deep earthquakes close to Hekla and now an atypically deep earthquake swarm at Krísuvik. 🙂

  11. New quakes in Krysuvik.. Wonder if it will be the same as the last swarm which had 600+ earthquakes if I am correct?

  13. I flew over Eyjafjallajökull on Tuesday. Landed by the new hills. Amazing experience.

    But the weather was perfect for it, so only fly if there are no clouds.

    I flew with Heli.is (Ask for Gudjon – outstanding pilot). Be warned though, it is not cheap – nearly €700 per person with a three person minimum.

  14. The ALF temmor graph looks interesting. The spike that has regulary been happening (has been refered to as the heartbeat of Katla) seems to have been replaced by a tremor of some sorts. Not sure what this means maybe some one else has a theory?

  15. So let me get this straight, on the tremor charts, blue and green are usually ocean and traffic noises, whereas the lower frequency bands (red) are usually seismic activity?

    Is that right?

      1. Thanks for that Tom, but as it turns out I am already following the earthquakes that happen in and around the Katla Caldera.

        But thanks again anyway! 🙂

      2. “Blue” spikes correspond suspisiusly to “normal road-construction working hours” – There was road construction in progress on the nearby-road, when I was there in late July. Possibly this has continued, only nearer to the tremor meter in last few days.

    2. Thank you for the article, unusually well written and non-alarmist.
      I already knew the points in it, but it is good to have it recapitulated. Few seems to remember that it always has been Hekla that is the most disruptive Volcano on average in Iceland. This since it is very explosive and pumps the ash high up.

  18. Good news for airline companies. Commercial-Jet aviation, in present form, is only marginal over 50-60 years old. However I do see lack of explanation. Why “only” 7,000 years. Ok. Ice-age only over by then in Iceland? (Causing eruptions not penetrating the Ice-shield or Volcanic activity in present form only starting 7,000 years ago.) I think last “Ice-Age” was over about 10-12,000 years ago, so why missing 3-5,000 years of records. No eruptions in that period?

    Ok. I will however continue my volcano watch.

    1. No, not entirelly.
      Problem is that the peat-bogs are only around 7000 years old. They where formed after the last iceage, and they took some time to form. The ash before that got deposited ontop of the ice and flushed wherever in one uggly concentrated slurry, or are not preserved due to lack of peatbogs…

  21. @Carl Le Strange re: BBC –
    Lurking’s responose on Erik’s blog – ( I vaguely remember the black swan reference form somewhere back in posts, but can’t come up with it now._)

    >Hopefully it’s not based on the UK-MET supercomputer output.
    Though it shows a 56 year return rate, always be wary of the Black Swan.<

    1. I remember my first black swan. I had a professor way back when teaching theory of science and scientific criticism, he always used black swans as an example of non-existing things. Lo and behold, swans started to mutate in France and now they have spread (still rare though).
      I saw one sailing in the Stockholm arhipelago.
      Black swans thought me that nothing is truly impossible or non-existant, they might just not exist yet, or no-one has come up with how to do it…
      So Lurking is around still?

      1. Carl – Just want to say welcome back. I tend to lurk, read and watch rather than comment and I have missed reading your colorful analogies. And Yes Lurking is still about and still as informative as ever.

  22. A lot of the earth quakes seem to be related to ice movement with a depth of < 0.5km (I believe the glacier is 750m thick in places).

    That said there has certainly been a pick up in earthquakes recently.

    I've mainly been using this tremor plot: http://hraun.vedur.is/ja/oroi/esk.gif

    There seems to be very little noise, and you can clearly see that movements in the 2Hz line are associated with earthquakes. On that note a question: Is the frequency of harmonic tremors associated with either the speed and/or the viscosity of magma, or do we just not know?

    It would be really useful to have a combined plot of earthquakes + harmonic tremors showing earthquake depth and size, this would give you a good idea as to the depth of the source of harmonic tremors, presumably as earthquakes associated with changes in the tremor graphs are a good indicator of the depth of the source?

    1. No.

      A proper earthquake has always both the P- and S-waves, as it involves solid rock cracking under tension. The birth mechanism of an ice quake is bit different, as they are typically due to collapse (and thus lacking with proper S-waves). For a seismometer it means that those with bad quality are usually ice quakes, and hence typically filtered out.

      The same applies to magmatic quakes, they lack proper S-waves (if I remember it correctly). The P-wave is still clear, and the quake can be recorded with decent quality. Additionally, magmatic quakes carry typically a distinct low-frequency component, which helps to differentiate it from ice quakes.

      The depth information is actually only a guess, if the quality is low. This is due to the automated process failing to recognize P- and S-waves properly. If quality is high, the location (incl. depth) can be modeled based on timing differences. However, if the quake was shallow (depth less than half of the distance to the seismometer), accuracy is lost quickly, and depth information is again merely a guess. Also, if the depth is approx. 1 km or less, topography does affect timing, and thus also depth (based on observations). If you want a proof, I’ll leave it to yourself. Trigonometry is all you need with some basics of calculating error propagation.

      I’m just trying to say that do not take the depth information as “word from God”, it is typically not like that accurate..

      On tremors: The blue line is mostly affected by weather, most notably wind. Earthquakes can be seen as spikes (on all color lines). Even strong quakes (M6+) at the opposite side of the Earth cause spikes on Icelandic tremor plots. Also ocean waves, car traffic, humans walking nearby, etc. can be seen on the tremor plots, so for the major part they contain only “noise” for a volcanophile.

      Magma causes tremor with the same physical phenomenon as flowing water in pipes creates sound: Friction of flow (due to viscosity of flowing fluid) causes vibration within the pipe (or conduit). However, this analogy fails for magma. While frequency of sound created by water flow is roughly dependent on speed of flow, for magma the frequency of highest interest seems always to be about 1 Hz or less. Don’t ask why, it just seems to be like that.

      Tremor plots can not be used for estimating the depth of the source. We’ve seen here that strong tremor sources can be listened to more than 100 km away. Also, the low frequencies are typically associated with more energy, and thus larger sources (and higher frequencies go with smaller energies and sources).

      I’m only a mad physicist…

      1. No we are not mad, we just see the reallity for what it is…
        Have you ever met Edward Fredkin? Either he is the craziest of us all, or the zanest. I am still debating with me, myself and I about him… 🙂

  23. I see many people referring to quakes below 1km deep to be ice related. It isnt always the case.

    First off there are alot of quakes registered at 0.1 km depth. Logically that would mean a tremor in the middle of the icecap. However a while back Jon explained that even if it in many cases actually are ice movement sometimes the depth is actually undetermined.

    0.1 usually means that the quakes is in the bedrock. Just that the exact depth is undetermined.

  24. Nice bottleneck of icebergs at Jökulsárlón as the tide goes out of the lagoon.

  26. Last night, 00.15, Jeff wrote: “Just noticed tonight a bright light growing on top of the glacier in the katla cam. Please take a look.”

    I would have liked to see this but was not awake at that time. Did anybody else see this light? Pictures?

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