Posted on by Jón Frímann

New harmonic tremor detected. But it is not from Katla volcano

Some other and unknown volcano dedicated to join the spotlight in Iceland by starting making it’s own harmonic tremor. I do not yet know what volcano this is. But most likely it is the Hamarinn volcano. But that is part of Bárðarbunga volcano.


Skrokkalda SIL stations 07:49 UTC this morning. The first harmonic tremor spike seen on that SIL station. Copyright of this image belongs to Icelandic Met Office.


Skrokkalda SIL station 19:09 UTC. The third harmonic tremor spike in progress when this graph was saved. Copyright of this image belongs to Icelandic Met Office.

I do not know what volcano is making this noise since there are no earthquakes. But I now find this most likely to be an dike intrusion somewhere close to Skrokkalda SIL stations. Other volcanoes that might be creating this harmonic tremor is the volcano Tungnafellsjökull volcano or the volcano that Skrokkalda SIL station actually is on top of.

But both of those volcanoes have been dormant for an long time now. So I find that to be unlikely, but not impossible. Until a earthquakes happens or something else that actually shows the area of activity in question. This is all just a guess work out in the blue.

Update 1: There is more going on there now then when this first did start. I did record an earthquake from this harmonic tremor around 00:30 UTC. This earthquake was extremely low period as can be seen on this picture.


This earthquake took place around 00:30 UTC on 13. July 2011. It is filtered at 1Hz and is extremely long period earthquake. This suggests that magma did create this earthquake. This picture is released under Creative Commons Attribution-ShareAlike 3.0 Unported License. See the Creative Commons Licence web page for more information.

Blog post updated at 01:02 UTC on 13. July 2011.

86 Replies to “New harmonic tremor detected. But it is not from Katla volcano”

  1. That’s all we need for now: another volcano!
    As if Katla and Hekla were not enough for our speculating!
    I would say that Alftagrof saw a slight alteration too, but that’s not quite clear.
    Thanks, Jón

  2. Not sure I like the look of that station at the minute this latest tremor is on going.

  3. Tuesday
    12.07.2011 19:37:07 63.628 -19.114 1.1 km 2.2 77.89 5.4 km N of Hábunga

    Crap, I was getting ready to plan a walk across Katla this summer…now it looks like thats out

      1. Jon can look at the waveform to insure its indicative of magma or geothermal activity. IHO, a 2.2 is probably more rock fracturing from magma movement, which is indicative of continued weakness under consistent magmatic pressure from below and this along with some recent tremor spikes ‘probably’ indicate Katla continues to build towards an eruption.

        I just get a gut feeling of a large fizzure eruption coming soon ( days weeks months), but by end of summer.

        If you subscribe

    2. The area has been closed anyway because of the latest happenings. There are quite a number of really big and deep new cracks in the glacier now…

  4. For those like myself who are just learning more about Iceland I find this map very useful in locating volcanoes quickly.
    http://www.volcanodiscovery.com/iceland.html

    Jon this is most interesting. Thank you .
    @ Renato. Never mind our conservative and educated speculation….It’s all good practice! But what on earth would the newspapers make of it?

  5. For those like myself who are just learning more about Iceland I find this map very useful in locating volcanoes quickly.
    http://www.volcanodiscovery.com/iceland.html

    @ Jon this is most interesting. Thank you . I have sent you a private message on Facebook re a little support for you.
    @ Renato. Never mind our conservative and educated speculation….It’s all good practice! But what on earth would the newspapers make of it?

  6. How can draw the conclusion that katla is out on such little material. Does not these systems connect deep under the surface?.

    1. Well, yeah, down in the mantle.

      The crust under Vatnajökull is around 40 to 45 km thick. Much thicker than most volcanic islands. Over near Mýrdalsjökull it drops down to 15 to 18 km.

      In some papers I’ve read, one possible reason for the abnormally thick crust is that Iceland is a chunk of continental crust laying on top of a segment of oceanic crust… sort of like a pancake.

      Add to that that there is a mantle plume under the thickest part and you get this really odd dynamic of a mid-oceanic ridge (spreading center) making landfall and passing though Iceland, over the thick region (with it’s plume) and off to the north via the Tjörnes fracture zone.

      Now, before you get all weirded out about how that chuck of continental crust (typically lighter than oceanic crust) got to where it is, take note that the Jan Mayen microcontinent (off to the northeast of Iceland) is wholly underwater and welded to the Eurasian plate. The only part of that continental crust that is above water is tiny Jan Mayen island.

      In other words, a lot of things were going on to get Iceland where it is at… and a lot of those processes are still going.

      As for direct connections? No. Just sills, dikes, plutons, cryptodomes, fissures/fissure rows… and an occasional stratovolcano.

      1. This incredible context, with his complexity that for my part I “discovered” during my studies, made me fall in love with Iceland. Since then I knew that I wanted to see it, and as soon as I had money I made my first visit.
        Iceland is the spectacular proof that for nature, everything is possible, and it shows us how “small” we are. And I like what happens here in this blog – people knowing that there’s huge potential, trying to understand, but keeping their heads on their shoulders.
        I know I don’t add knowledge or valuable thinking by this post – just needed to let it out… 🙂

      1. That is because the source is between those stations. That is why I think it is Hamarinn volcano, rather then anything else.

        But with no earthquakes it hard to know for sure what this is. This might just be regular glacier flood from this area or something like that. A non-volcanic event.

  8. Now there is some EQ activity in what seems Askja for me? Is that the one causing the tremor

  9. Is it possible the tremor was from the main Bárðarbunga volcano and not Hamarinn?

  11. I’m off to bed, I hope the tremor settles down and nothing else happens over there. It’s very close to grims so has probably been badly effected already. For those who want an eruption think of Iceland and it’s people.

  12. Tremor is going wild, near Vatnajokull.

    I find this highly intriguing, that in the space of a week, we saw signs of activity in Hekla, then a possible mini-eruption in Katla, and now something under Vatnajokull.

    What if this is a flood about to happen from Vatnajokull, which resulted from last eruption of Grimsvotn in May? In 1996, the flood come 1.5 months after. If that is so, it would be the second large flood in space of a week, in two different glaciers!

    As a second theory (and a more wild one), this could be some deep unrest under Bardarbunga. It could be even a sign of a future large eruption between Myrdalsjokull and Vatnajokull, since both sides have been showing harmonic tremor. So far this is only my high dose of speculation.

    1. I’m not going there. Even with the temporary quake lineament pointing towards the south end of the Eldgjá region. Thankfully other quakes spoiled that thought.

  13. Irpsit, a group of people actually believe that your second theory is the one… and are actively waiting and watching for signs of -when- (not -if-) it will begin. Some even think that it will be this summer or fall.

  14. Irpsit:
    Grimsfjál is also showing rising harmonic tremors.
    I place my bet on your first hypothesis. The second is a too scary one.

    1. LOL RR, I agree.

      I pray Iceland will be spared a catastropic eruption and that all the ash concentrates over Russia and China and Iran and…well you get it

      1. I agree with the first part of your post but even if it was in jest the second part was distasteful.

  15. There appears to be some earthquake activity in this harmonic tremor rise around Skrokkalda and Grímsfjall volcano. But the earthquakes are so poor quality it seems that they are not registered on the automatic earthquake list at IMO web page.

    I did just record the earthquake from around 00:30 UTC. It was extremely low period earthquake. Update to the blog post is coming.

  16. Oh, dear. Here we go again.
    There’s some harmonic at your geophone and zero wind.

    1. If this is serious enough when I wake up. I am not going to work. Because this work is more important then a summer job that I have now.

      This earthquake is interesting in my opinion. What it means. I have no idea currently.

  17. What an interesting event. Tremor on Skrokkalda station has been steadily increasing since 18 hours ago and it’s starting to affect nearby (and not so nearby) SIL stations. I wonder what levels will it reach.

  18. This earthquake has the size ML2.0 and the depth of 0.1 km. The Icelandic Met Office team is up it seems. The location was in Hamarinn volcano.

    So this is something interesting for sure.

  19. Jón,
    how come I don’t see the harmonic tremors in your geophone any longer, and I can see the earthquakes you mentioned, instead? Looks like the fuzzy lines disappeared.

    1. It has to do with the filtering in the software that I use. It does not seem to handle the “live” time correctly. But it fixes it once it starts a new one. I do not know why that it.

      But there is little to no harmonic tremor being recorded on my geophone anyway. If it was above the noise floor on my geophone. It would appear on it. As it did when Eyjafjallajökull volcano was erupting last year.

  21. Could be this at the Loki-Fögrufjöll volcanic system, which produces possible eruptions /jökullhlaups every 3 years (last one in 2008)?
    Hammarín is the central volcano and they are all connected to Bardarbunga system, according to GVP.

  22. Lurking with interest from the west coast, so am able stay awake a little longer than usual. Normally all the interesting stuff happens on the night shift! Jón, you still need bread on the table, don’t give up the job too easily!

  23. Tremor at Skrokkalda seems to be subsiding.
    No need to quit your job. 🙂

  25. Things always seem to happen when I am asleep! Yes Renato. the tremors at Skrokkalda are certainly subsiding at present.@ Irpsit Your theories are most interesting and the second is scary! I certainly hope we are looking at glacial unrest.
    @ Helena, I speak for myself here. I watch here because I am interested in the prediction of Earthquakes and eruptions not as a voyeur. (I don’t think anyone would wish a huge eruption on the Icelandic people). All the eyes watching the recordings and the minds attempting to analyse the results is providing some safety for the Icelandic people. The geology of Iceland is unique and Oh! so Fascinating to me.

  26. Tremor is subsiding. It appear stronger near Haamarin and also in Grimsvotn. This appeared but very little around Katla. For this reason, I think, like Jon, that this is only activity under Vatnajokull and not connected to any fissure between both glaciers.

    This could be either: 1) a glacial flood preparing to happen from last eruption of Grimsvotn, 2) magma rising up inside the Bardarbunga fissure (Haamarin) which could indeed result in a small fissure event because that is along the Bardarbunga system. But apparently earthquakes only happened below Haamarin, so this would be a small event.

    So far, there is no indication of a glacial flood. Readings in Skafta river have not shown any changes. So I go for the small fissure event below Haamarin. Notes for the press: this is just my wild speculation, there are no further signs of an eruption or flood, and this is unrelated to Katla.

    1. There are also no GPS changes under Skrokkalda nor Grimnsfjall (nor even in Katla). This leads me to think that if this is magma movement it is a minor one, possibly a dike intrusion (that occurred with the 2.2 earthquakes yesterday at Haamarin), if this was enough to melt some ice, this could result in some minor flooding.

      What I find interesting is the number of dike intrusions we have already seen recently: in May Askja and Grimsvotn (actual eruption), in July, Hekla, Katla and Haamarin.

  27. Wednesday
    13.07.2011 07:40:48 63.627 -19.094 1.1 km 0.9 90.02 5.2 km N of Hábunga

  28. I stll think it is Katla. The old lady stats to move. She does not wake up in a hurry.

  31. Tremors are going down significantly at Skrokkalda, but remain at a higher level at Katla. What does this mean?

  32. The tremor does come from Haamarin. I am going to tell you why.

    The tremor is greatest in Skrokkalda, in NW edge of Vatnajokull, but also strong in Grimsfjall. Also to a less degree in Mokollar (mko) near S Askja, Vatnsfell (vat) near Veidivotn, and just a bit in Kalfafell (kal) near Laki, and Askja station.

    In Kalfafell the tremor was less clear than in Vatnfell. Near Skaftafell, the tremor was even smaller. This suggests that the tremor was up north, more in Bardarbunga system rather than Grimsvotn.

    The tremor was also quite detected in Mokollar and Askja, which are stations around Askja, but not stronger than the tremor detected in Vatnfell, suggesting the tremor is not in Askja, but to a volcano between both stations (which can only be Bardarbunga or Haamarin). The tremor is strongest in Skrokkalda followed by Grimsvotn, so this suggests that the tremor was indeed originated in Haamarin.

    If the tremor would be located in Bardarbunga central volcano, the tremor would be a bit stronger in stations around Askja than Vatnsfell and Grimsvotn rather than Skrokkalda, which is not the case.

    1. I find there is not much information available on Hamarinn compared to other Icelandic volcanoes.

      I see in an older post by Jon that it is also known as Loki-Fögrufjöll, and some seem to simply call it Loki.

      “Loki has erupted in 1910, 1938 and lastly in 1996 and has not been, in general, that severe. The 1910 eruption was evaluated at a Volcano Explosivity Index of 2. There was a smaller eruption (which only affected local air traffic) in 1996 to the East of the current activity. Loki lies under the Vatnajokull glacial cap, which is about half-a-mile thick. ”

      http://www.google.ie/url?sa=t&source=web&cd=1&ved=0CBgQFjAA&url=http%3A%2F%2Fbittooth.blogspot.com%2F2011%2F02%2Ficelandic-eruptions-no-need-to-panic.html&rct=j&q=loki%201910%20eruption&ei=unkdTsWxI4OChQeTzcjpBw&usg=AFQjCNGmpAccKWLQHbOON1q7X66MEnBvbw&cad=rja

      It seems that if Hamarinn/Loki does erupt it will probably not be anything to worrys about!

  33. Wednesday
    13.07.2011 10:51:19 63.322 -20.633 12.2 km 2.3 90.06 2.0 km WNW of Surtsey

      1. Am I looking at the wrong page? Cant see anything on Jons helicorder around this time. :S

  34. Was there earthquake just by Surtsey or am I getting my islands confused?? :S

  36. Yes, it was in Surtsey, and tremors seem to have had a slight increase in Vestmannaeyjar.
    Yesterday, there was a quake near Vík. Who said there seems to be a connection between Eyjaf and Vestmannaeyjar?

    1. I said that. But its not my theory. Its from a scientific paper I once read. The authors spoke there about a connection between Eyjafjallajokull, Katla and the volcanoes at the Westman Islands, as part of a connected system.

      I will remember that Bardarbunga fissure system is 250km, and when it erupted Torfajokull also erupted (north of Katla). Similarly, Edlgjá and Laki erupted at same time as Katla and Grimsvotn, and in fissures quite far from the central volcano.

      1. According to my map of Iceland fissure systems, Grimsvötn and Laki are the same fissure system.
        So is Katla and Edlgjá, a different one.
        As for Eyjaf and Katla, this is a very disputed argument.
        But who am I to know? 🙂

  37. neil, it´s a quake very near Surtsey, you have your geo-info correct 🙂

    it seems that a small event occurred under Lokahryggur (near Hamarinn) and a clacial flood came down under (or above) the Kölduhvísl glacier tounge and ended up in the Hágöngulón dam. it has risen more than 70 cm since midnight so this is -a lot- of water. the weather is bad there though, so there is no possibility to fly over and see what actually happened yet. It is remarkably like the event in Katla, but no earthquakes were measured according to the IMO. it will be interesting to see what they discover when scientist can fly over the area hopefully today.

      1. I don´t know, this was just in the news on MBL.is and they don´t say. I know staff at Landsvirkjun that handles the dam, but have not been able to contact them yet to ask 🙂

    1. Very similar pattern to what happened with Katla isnt it. Harmonic tremor, no big earthquakes, the tremor drops and then a glacial flood but no confirmed eruption.

      1. Irpsit:
        You got it right.
        Luckily it was not so hazardous.
        But indeed amazing to see those hlaups all in a row.
        Chris says that Myrdál is full of cracks. If these magmatic earthworms go on with their business, Iceland will be turned into a huge swamp!

  39. In RUV news:
    “Týndur ferðamaður á Fimmvörðuhálsi”
    Giggle translation:
    “Lost tourist on … Merapi !!!!”

      1. Daniel:
        People are allowed to make corrections in Google translator.
        Probably someone from EB did some confusion between the two volcanoes. Hahaha!
        Further in the article they talk about a “forest”. And the pictur shows a nearby glacier. 😀

  40. OK. There was a glacier flood:
    RUV news (Giggle again):
    “Floods from Vatnajökull
    Water level in Hágöngulóni has increased by seventy inches tonight and tomorrow.
    The reason is believed to be from Köldukvísl glacier glacier in the western part of Vatnajökull. Hjörleifur Sveinbjörnsson, a geologist at the Icelandic Meteorological Office said the unrest was seen in the seismic monitoring of seismic station and the body wave, but the turmoil is not a precursor to volcanic eruption, but rather by metabolism of the circuit. Hjörleifur says not clear which way the race has come: it could have come down channel Sveðju or Köldukvísl and down Hágöngulón. Meters Landsvirkjun reservoir have shown a significant increase in the water. Hjörleifur says no reason to expect a catastrophic flood.
    According to an announcement from the service came out in turbulence about 45 minutes early this morning, and another similar event was yesterday. Then at midnight has reduced this turmoil.”
    frettir@ruv.is

  41. it started with a big increase around 2 am and started to go down at 8 am this morning. its not over yet but Hagöngulón is now full of water again after more than 70 cm rise of water and estimated 26 giga-litres (how many cubic-meters is that?) of melt-water from the Kölduhvíslarjökull/Lokahryggir event.

    1. 26 giga-liters are 26.000.000 cubic meters of water… or 26 million cubic meters!

  42. Jón thinks it was caused by a small eruption.
    This morning’s quake in Hamarinn volcano seems to have been long period.

    1. Earlier RUV had said:
      Turmoil in Vatnajökull
      Turmoil was a seismometer in and around the Vatnajökull ice cap at night.
      Have not yet been established exactly where the turbulence is caused. Nothing indicates that the eruption is about to begin, say they authorized the ground shift IMO. The turmoil is only a vibration, no earthquakes have been recorded. Waiting for more data from the local Meteorological and scientists closely monitor developments

  43. I did cut my work day short because of this. But don’t worry about that. As this is just an summer job that I have and I quit next month anyway.

    I am going to write a blog post about this glacier flood in just a moment.

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