Posted on by Jón Frímann

The weekend earthquake swarm deep out on the Reykjanes Ridge

During the weekend there was as earthquake swarm deep outside on the Reykjanes Ridge. It was about 700 km south of Reykjavík city. It was not felt on land and was only noticed on instruments. The last earthquake to be recorded was at 22:04 UTC, on 20 November 2011. It’s size was Mb4.4 according to EMSC. The largest earthquakes in this earthquake swarm had the size of Mb4.8, but there where several earthquakes recorded with this size.

Due to the location it is impossible to know if there was a eruption in this area or not. The ocean depth there is greater then 1 km (if my memory is correct). This means that if a eruption is taking place in this location. Nothing is going to appear on the surface of the ocean. So why this earthquakes are taking place are only speculation everything besides normal tectonic activity in this area. But the Reykjanes Ridge is a rift zone that often has earthquakes without any eruption taking place. There have however been several earthquake swarm during the year in this location. But what the actual reason remains a mystery due the location.

Other then this it is now quiet time in Iceland. This is the type of quiet time that I always worry about. But lets wait and see what is up with this lack of activity in Iceland.

Note: Update on the eruption in El Hierro volcano eruption is due tomorrow. This is now a long term eruption as explained few blog posts ago. So there are only updates on what is going on once in a while.

24 Replies to “The weekend earthquake swarm deep out on the Reykjanes Ridge”

  1. Good evening, Jón.
    I’ve been in lurking mode lately, but still there. 🙂
    Concerning these deep submarine eruptions, could there be any kind of monitoring that would provide clues for an ongoing underwater eruption? I mean, visibly unnoticed degassing or something of the kind? Or it goes totally “silent”?

  2. There are interesting events taking place in Katla volcano at the moment. I am currently watching it in order to see what it means. But there seems to be a harmonic tremor spike following it. But so far it is not strong.

    1. Most of the eq activity at Katla seems to happen along the caldera rim. Do you expect to see multiple vents along the rim (when Katla finally erupts)?

  3. Magnitude ML 4.0
    Region AZORES ISLANDS REGION
    Date time 2011-11-22 08:44:57.0 UTC
    Localização 36.89 N. 22.51 w
    Profundidade 10 km
    Distâncias 1099 km NW San cristóbal de la laguna (139.928 pop; Hora local 08:44:57.3 2011-11-22)
    295 km E Ponta delgada (20.056 pop; Hora local 07:44:57.3 2011-11-22)
    km 273 E Vila franca do campo (5.035 pop; Hora local 07:44:57.3 2011-11-22)

    1. Not yet. But I am hoping that I can install it in December at the earliest. But I am going to install it no later then January 2012. I have not had time due to the school. But I finish school in December (and I am not returning to Icelandic school as I plan it).

      I might need to pay for new computer for the Katla volcano geophone. So I am trying to figure out how to pay for that. I am not choosing expensive hardware. It just cost money as always.

  7. Quiet times in Iceland do make you concerned that pressure might be building up somewhere. However, what is the normal level of activity for Iceland?

  8. Hi all, I’m new in earthquake and volcanology science and I wonder about Katla if one have already seen those patterns on the tremor graphs. It seems to have a lot of crisis at the Godabunga SIL network rather than all the other seismographs ; I found this seismograph very close of the volcano. Is this new for this volcano or is this a common thing for it , in other terms, if this is not usual, would’t it be the sign of a real magma eruption in the chamber, an this magma getting closer and closer from the surface, as the number of crisis seems to show.
    I understood that the weather, the cars, the ocean waves may have a real effect on the graph but since few days, the changes are really great !

    PS : I apologise for my rather bad english 🙂

    1. I think especially the GOD SIL is something not to takt THAT serious due to the elevated position, exposed to the heavy winds. Same with the Grimsfjall SIL station. Those ones are the first to indicate “something” when the wind is blowing.
      However, quite interesting to see that the higher frequencies tend to raise before the red line low frequency curve moves up. I could imagine that this comes from the waves, lagging in impact compared to pure winds pounding into the instruments.

    1. That looks like one GIANT jellyfish! I was going to ask if the white strands are bubbles or debris but looking at it again it appears to be a mixture of both. A fantastic picture, thanks for posting it humberto

  10. sorry, forget to say you must see the album there is some good photos of the new vent.

  13. There was a local earthquake on Hvammstangi geophone station. I did record it clear, even if there was some noise.

    Now I send a email to Iceland Met Office with the data that I have (gif images) in the hope that they can locate this earthquake for me.

    1. There where in fact two earthquakes around the same time. Both around ML1.0 in size. But the earlier one on Hvammstangi geophone did not appear on Hekla geophone due to how small they where.

      So this was one of the rare local events around Hvammstangi geophone. But I record about one to two of this earthquakes a year in this area. The distance now was about 25 km. But I have no idea where it was located, since I only have one geophone in Hvammstangi town. But I need three geophones to make a decent location.

      Now I am just hoping that Iceland Met Office did record this earthquake so I can get a location on it.

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