Small earthquake swarm in Katla volcano caldera

At the moment there appears to be a small earthquake swarm in Katla volcano. Currently this is just a earthquake swarm. All the tremor plots are normal and show no signs of harmonic tremors and magma on the move. The largest earthquake in this earthquake swarm in inside Katla volcano caldera was a ML1.3 with the depth of 1.7 km according to reviewed data from Icelandic Met Office.

The earthquake swarm in Katla voclano. It is deep inside Katla volcano caldera as can clearly be seen. Copyright of this picture belongs in Icelandic Met Office.

The ML1.3 earthquake as I did record it on my Heklubyggð geophone. Given the shape and how low period this earthquake is. I would say that it was created by magma pushing upwards in the crust inside Katla volcano caldera. This picture is released under Creative Commons licence, see the licence web page for more details.

At the moment (when this is written) it seems that this earthquake swarm is over. For the moment anyway. But it hard to know for sure if it resumes or something else starts in Katla volcano.

Update 1: A earthquake with the magnitude ML3.8 did happen in Katla volcano caldera at 02:02 UTC. Following this earthquake there have been many aftershocks. It is not yet clear if this means that Katla volcano is starting a eruption or not. But that should be clear in few hours if that is the case or not.

The ML3.8 earthquake that happened at 02:02 UTC. This is by the automatic SIL system, so it’s size can change. This picture is released under Creative Commons licence, see the licence web page for more details.

The location of the ML3.8 earthquake in Katla volcano caldera and the following aftershocks. Copyright of this picture belongs to Icelandic Met Office.

Blog post updated at 02:26 UTC on 18. July 2011.
Blog post updated at 02:40 UTC on 18. July 2011.

393 Replies to “Small earthquake swarm in Katla volcano caldera”

  1. It would be fantastic if you could make a post explaining a little about how volcanoes work and the terminology you use.

    For example explain the what the caldera means and what harmonic tremors are?

    Do you know if the 1918 Katla had any ramifications beyond Iceland? Will we see fallout in Norway? Or will it just be invisible dust?

    Thanks for a great blog!

    1. I recommend that you check out this web page for full range of explanation of terms that I use.

      But in regards to your question. Here is your answer.

      Harmonic Tremor:

      * Continuous rhythmic earthquakes in the Earth’s upper lithosphere that can be detected by seismographs. Harmonic tremors often precede or accompany volcanic eruptions. (Teacher’s Packet)
      * A continuous release of seismic energy typically associated with the underground movement of magma. It contrasts distinctly with the sudden release and rapid decrease of seismic energy associated with the more common type of earthquake caused by slippage along a fault. (Foxworthy and Hill, 1982)


      * A caldera is a large, usually circular depression at the summit of a volcano formed when magma is withdrawn or erupted from a shallow underground magma reservoir. The removal of large volumes of magma may result in loss of structural support for the overlying rock, thereby leading to collapse of the ground and formation of a large depression. Calderas are different from craters, which are smaller, circular depressions created primarily by explosive excavation of rock during eruptions. (USGS/VHP)

      This is from the link that I gave here above.

  2. I just saw those..

    After a large period of no new earthquakes at atla, to two minor swarms(first of 3 then this one) in the last day..avtivity building once more…I think we might see the first proper 3.0 since a couple of days ago soon.

    1. Hard to know for sure, because of a lot background noise. If this was a harmonic tremor, it was just spike and is most likely over by now.

      1. After your blog post update IMO has a new 1.4 earthquake with 99 quality.

  3. Up to around 10 EQ on the myrdalsjokull page… not all in the caldera but it’s bubbling with activity, all be it small EQ’s.

    We just hit a 1.9 at 90% quality! There getting bigger….I can feel something brewing!

  4. No change in harmonic tremor yet. Just earthquakes. But while Katla volcano does have summer earthquakes this appears to be more then that. As this activity is concentrated at one point in the caldera, rather then being spread out.

    I have to sleep now. But I am going to check this at 07:00 UTC when I wake up.

    1. Are the quakes happening SW of Vík unusual? There has been another one now as this swarm continues.

  5. Why did you not just stay in Danmark Jón.
    (The main reasons is that I do not follow the living standards that society demands of me. That is to own a house, car and whatnot. I have no interest in following that path like the other people. I have no interest in owning a car and a house and whatnot. I also don’t drink alcohol or smoke, so that makes even more at odds in Iceland. )
    Hehe are you a sheep that follows the other sheep, living standards, bullshit. Just spend what you have for income…… works for me.

    If you are living on benefits we are in the same sone, use what you get in money and not more. No credid. You were working last mounth, did you tell TR about it?
    Why not shove some patient for 3 years and get an apartment from your local.
    3 years in not a long time in geo history 🙂

      1. Build a Wikiup, like in “Snowshoes and Solitude” and commute by canoe. Don’t they have a “Right to roam” law in the EU?

    1. Oddly it hasn’t appeared yet on the icelandic met office webside

      1. It also seems that two 1.8-2.0 magnitude earthquakes occurred after the larger earthquake, seeing Jon’s Hekla helicorder.

    1. Well, that’s nothing yet. In a high-stress volcanic area potentially hundreds of them might occur after such an earthquake (not necessarily ending up in an eruption).

    1. Thank you, Jón.
      Hope this gives us all some time to sleep.
      Dam camera is covered with fog.

    2. Jon, is this the type of activity you would expect to see before a full eruption or would you expect more +3 quakes before that would happen?

      1. Do we know that?
        If it will follow the path of Grimsfjal, we need some more. If we follow Eyjaf, we need many more. If it were Hekla we needed a 5.0.

      2. I think it mostly depends on how close to the surface is the magma source. As far as I can gather, on Katla it is has become recently already quite close.

      3. Definitely.
        We don’t even know for sure if an eruption has already occurred, four days ago.
        Lady K has plans for the future. Only hope she won’t spoil ours.

      4. Good point.

        Things are looking a little more calm on Jon’s geophone since the 2:20 mark.

      5. Someone posted a magnitude vs. time graph for a Hekla sequence not so long ago; Hekla went into full eruption with nothing larger than a 2.6 or so, IIRC

  6. Katla volcano sometimes has earthquake up to Mb4.5 and no eruption taking place following it. But I do think that current activity is different then that.

    But so far no harmonic tremor have been detected. But lets wait and see what happens in the next few hours.

    1. There’s a little more visibility at RUV’s Katla cam now.
      I only see the carpet of fog and a little “Plume” of steam at the tongue of the glacier, as seen on the other day, probably fog as well.

  7. Humm….maybe IMO system have frozen again. But I am not seeing any earthquakes on my geophone. But that might not mean that they are not happening.

  8. I think so too.
    Jón and everyone: have a sound sleep.
    We will still see see some thing happening at Katla, but I don’t think we need to spend our nights watching her.

    1. Yeah, looks like time for bed!

      Worried as soon as I turn on the computer a big EQ will strike!

      Goodnight all!

      1. The former M3.8 earthquake surely looked more than 10 times bigger in amplitude than M1.9-2.0 ones on Jon’s Helicorder. I can’t believe it was just a M2.9

        Could it be that the people in charge stopped the automatic location in order to not have a huge number of unchecked, low quality earthquake on the list and also temporarily lowered the M3.8 to 2.9 to avoid panic? That would be an excessively speculative hypothesis however…

      2. Thats quite interesting Mr. Moho…the quality of the 3.8 was 90% so its a big change when it went to 99%…ans as you said…it looked much bigger than 2.9 on the hellicorder…compared to the 1.9’s that barely disturbed it.

      3. A change of 1 in magnitude means a change of 10 times in wave amplitude (shaking). This is why I think that the M2.9 was bigger. The smaller M1.9-2.0 EQs happened in about the same place.

      4. Given it’s effect on my geophone with the distance about 61 km. I think that this earthquake has the size of ML3.5 or about that in my view.

  9. katla cam just clearing up is that snow or ash could someone have a look please

  10. It seems to me that lots of unusual things have been happening lately.
    like a small glacier flood from Tindafjallajökull

    And another one in the river Sveðja, from Hamarinn volcano, also late 2010

    Big lakes disapeared 2010.

    New cracks were found

    lots of activity in Vatnajökull, Mýrdalsjökull and under Hekla as we have noticed.

    I am not an expert, but it looks like our old volcano rock is coming to life, i wonder what kind of eruption we should expect.

  11. Cam is now free of fog. No ashes, no plumes.
    We might see some rise in harmonic tremors hereafter and maybe another jokühlaup, but that will be it for now.

  12. Down to 2.6….it is definately an error as the quality hasn’t changed since the last dowgrade.

      1. They were my exact thoughts…if it was 2.6, why was it completely dwarfing EQ’s of 1.9 on the hellicorder.

    1. And the quality is a little less than the original 3.8 listed.
      18.07.2011 02:02:27 63.660 -19.116 1.1 km 3.8 90.09 7.0 km ENE of Goðabunga

    2. Most certainly an error. A M2.6 earthquake causes less than twice the shaking of a M1.9 one.

      1. Sorry, I made an error in the calculation. A M2.6 earthquake causes almost exactly five times the shaking of a M1.9 one.

    1. Then, if it’s not an error, it’s possible that the M3.8 earthquake was actually an explosion (phreatic?) mixed with a M2.6 earthquake.

      1. I don’t think so…
        Even a freatic explosion would produce a plume of somekind.
        Camera is pointed right at the spot and weather has become clearer now.

  13. Another big burp and she’s feeling pretty sick latey, but will she throw up this time or try to push it back. I know one thing, medication won’t help at this point. She needs to get it out of her system….poor girl…poor us.

  14. Wow, that 2.6 cannot be right. I have seen other 2-3 mag quakes at Katla area on Jon’s geophone and they didn’t look anything like the quake that is on there now.

      1. Since in your charts depth is already self-represented with the position along the Y axis, wouldn’t it be better to color code magnitude or EQ date instead?

      2. Really depends on how much of a fight I feel like having with the data. That one came off of a 3D plot. I generally do those in order to be able to slew it to an interesting axis. By default the z coords get the color coding unless I force a 4D plot. 4D requires me to export everthing to a csv file first.

        In this case I wanted to highlight the most recent and also show the years activity.

        If you want a specific plot let me know and I can beat on it until something usable falls out.

    1. The swarm surely had some volcanic content, but it was not yet enough for anything else.

  15. RUV news says that if Katla was to erupt we should see harmonic tremors, since there are none, no cause for concern (Giggle):
    “Hjörleifur Sveinbjörnsson, a geologist at the Icelandic Meteorological Office, does not see the earthquake that prior to eruption. When Katla envision a change is always preceded jarðskjáftar Goss, and then increased steadily turmoil. It did not happen tonight, earthquakes that follow the big number was 15 to 25 minutes, but increasingly smaller and eventually were prices of marine turbulence. And nothing indicates that an eruption is about to begin, either gel or another.”

      1. But why does she not stop coughing. They do not have the history from 1918 or before.

  16. I told you all that stuff happens when I am in bed asleep!!
    Maybe that big quake was mixed with a glacial movement? Looking at Jon’s helicorder it looked more like a very sudden shift and it wasn’t deep enough to be tectonic I think. Maybe the smaller quakes have caused a collapse within the glacier. remember there are some huge cracks and presumably melt water tunnels under there. Just a suggestion. The depth of the quakes are mixed. Some larger and deep could cause movement under the ice that has become more unstable after the last “eruption” only a few days ago.
    Just throwing in a suggestion 🙂

    Oh My goodness the levels of Dopamine were certainly high whilst I was asleep!!
    @ RonF……. I loved your description of Katla’s gastric health! I wonder what would happen if we dosed her with a few tons of Sodium Bicarbonate? Rofl!!

      1. There is nothing wrong with poetic license.

        “Genius is the ability to reduce the complicated to the simple.”
        ( C. Ceram pen name of German Writer Kurt Marek )

  17. She is preparing. The old lady just prepares. Tomorrow or next year or more. Who knows but God. I still do not realy understand why the tremor graphs ade dividet into 3 frequency areas? (0.5 – 1, 1 – 2 and 2-4 Hz).

    1. I may be wrong here, I am not an expert but I use each band to roughly identify the depth of the tremor and also what may have caused it.
      Sotro me the blue band is deepest earthquakes, but also shows constant rhythmic tremors caused by wind, river, motor vehicles or waves pounding on the shore.
      The middle green band is less shallow earthquakes and tremors and the red are surface tremors. If the red band peaks obviously and at the same time as the other two bands ( A harmonic tremor ?) then I read this as something that is happening and pushing up from very deep and affecting the surface…like magma rising.

      If I am wrong about this simplistic explanation I hope the experts will please tell me. I know there is far more to it than this but it is hard to explain to us inexpert people 🙂

  18. Morning guys.

    Looks like all is quiet again in Katla after her late night rumbling!

  19. I’m watching the web cam like a hawk, I’ve got a bad feeling about tonight… 🙁

    1. I don’t think there is any need to watch the webcam at the moment. I think we would see more evidence of things happening below ground before anything happens that might be seen on a webcam, and right now everything is quiet. 🙂

  20. A lot of these recent swarms/burps seem to take place during the night. Is there some geological reason for this? I know from my trip to Iceland in 1997 that you get only a couple of hours of dark at Landmannalaugur (if even a couple of hours, I remember being in the hot springs as the sun went down and still being in as the sun came back up), so there’s a longer amount of time for the heat to build up from the sun and maybe there’s a lot of meltwater seeping through cracks all day and by midnight there’s enough dripping through to agitate magma?

    1. I’m not sure, I have seen talk that the moons gravitational force on water can occur with magma too. But I have no idea if that is true.

  21. Good morning, you night lurkers!
    Yes, Lady K is into something, but my guess is that it will take a long escalating time with more swarms, some harmonic spikes and glacier floods, and then, a really intense outburst of quakes in many different places around the glacier and some mag 3s and 4s within the caldera. Harmonic tremor will then skyrocket, and it will be time to pray for the people in the surrounding areas who will have been evacuated by then, and for the weather to be fair, because this camera will show it all, right from the spot and also for the jet stream to be heading towards elsewhere that not Europe. Another VEI 4. That’s the speculation of a RANK AMATEUR.

    1. Indeed RR … though suspect we are not going to be lucky – Lady K has decided that she is waiting until mid 2012 when many cameras will be focussed on the 2012 olympics in London…. and lots of people will be travelling to the UK by plane – and the ash cloud….?????

      1. Travel problems.?. Ever heard of Laki 1783 or climate changes etc. If it is a big one, you never know??.

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