Posted on by Jón Frímann

Earthquake swarm in SISZ (South Icelandic Seismic Zone)

Today on 6-May-2017 a magnitude 4,4 – 4,5 earthquake hit South Icelandic Seismic Zone (SISZ) at 12:08:58 UTC. This earthquake was felt over a wide area, a magnitude 3,3 earthquake also took place around one minute after the main earthquake. The earthquake took place on a fault that might have last moved in the year 1623 or 1624, as is detailed here. Current earthquake activity does classify as a “Suðurlandsskjálfti”, only earthquakes with magnitude above 5,5 are classified as such. This is regardless a strong earthquake activity in SISZ for a long time now.


The earthquake activity on SISZ. The green stars mark the location of the magnitude 4,4 – 4,5 and the magnitude 3,3 earthquakes. Copyright of this image belongs to Icelandic Met Office.


The magnitude 4,4 – 4,5 earthquake as it appeared on my geophone in Böðvarshólar, north-west Iceland. This image is under Creative Commons Licence, please see CC licence page for more details.


The magnitude 4,4 – 4,5 earthquake as it appeared on my geophone in Heklubyggð, the earthquake happens just west of this geophone location. The geophone is saturated by incoming earthquake signal. This image is under Creative Commons Licence, please see CC licence page for more details.


The magnitude 3,3 earthquake as it appeared on my geophone in Heklubyggð, the earthquake happens just west of this geophone location. This earthquake also saturates the geophone (just a little). This image is under Creative Commons Licence, please see CC licence page for more details.

More aftershocks are expected in this are for the next few hours to days. It is difficult to know if this means there is going to be a larger earthquake activity at this location or nearby. It’s always a chance, but it is not possible to know that for sure.

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Article has been updated at 15:55 UTC. Minor text fixes.

13 Replies to “Earthquake swarm in SISZ (South Icelandic Seismic Zone)”

    1. This is the South Icelandic Seismic Zone, while this earthquake is not directly connected to the earthquake in 2008 that happened in the western part of the SISZ. The progress of the earthquake cycle is that it starts somewhere, normally moves west and once it has reached the end of the west SISZ it starts again on the east part of the SISZ. Earthquakes in the east part of SISZ can reach magnitude 7,0 due to thicker and more brittle crust.

      Activity in SISZ is not connected to Hekla volcano, but its not properly known if a large earthquake on SISZ can start an eruption in Hekla volcano. It might have happened in the 18th or 19th century, but its not properly document to fully confirm it (that might just have been coincidence).

      The earthquake cycle that started in 2000 is not yet over, due to lack of earthquake activity in the eastern part of SISZ.

  3. Real deep earthquake activity in Bárðarbunga volcano, deep going down to 29 km. This means something might happen soon when it comes to earthquake activity. Eruption is unlikely, but if this is high enough magma pressure, that might happen.

    1. Is it known what Katla’s plumbing system looks like at these depths? Or any theories?

  4. Remarkable!
    Also I want to add a deep one under Katla:
    12.05.2017 22:07 63,666 -19,131 25,0 km 1,0 99,0 6,6 km ANA af Goðabungu

      1. A couple of near-surface EQs in the same area of the caldera now. Nothing spectacular, but might be more to come.

  5. Due to the current low earthquake activity, I usually don’t check the conductivity around Myrdalsjökull. But now I did it anyway. And Mulakvisl station shows a huge increase in conductivity May 12, about 18:00. It starts very suddenly, with no apparent change in water level/temperature. The conductivity then evens out slowly, as one would expect, but still remains high to this moment.

    Also worth noting that Holmsa river shows a short spike in conductivity around the same time as Mulakvisl.

    What might this be causing this?

    Print screen image property of IMO:
    http://i.imgur.com/FLF9xbH.jpg

    1. The change in conductivity might be due to heavy rain in South Iceland in past few days. It moves old volcano ash around and gets it into the rivers.

  6. I’m sorry for lack of updates. There hasn’t been a lot going on in Iceland in last few days besides the bad weather. I plan on writing a new article tomorrow about TFZ and the earthquake activity there, even if its just a minor earthquake activity at the moment.

    I don’t know if I can write an article about the deep earthquake activity in Bárðarbunga volcano since what’s happening there is already established.

    Bárðarbunga volcano also had its normal magnitude 3,0 – 4,1 earthquake this weekend. This is a regular feature and I’ve given up on writing about them all. I already have written so many articles about Bárðarbunga volcano.

  7. Jon

    There is renewed interest in the press today with Campi Flegri near Naples (Italy). Hard to be sure where the idle chatter stops and the intelligent comment starts. Have you ever considered this volcano perhaps as one of your off-topic discussion threads?

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