Iceland earthquake swarm: 484 earthquakes in less than 48 hours

Posted: April 3, 2013 by tallbloke in solar system dynamics, Uncertainty, volcanos

Many thanks to Alan Bond for sending in details of this seismic activity. Tectonic plates pulling apart off the north Icelandic coast have produced a swarm of earthquakes, including a 5.5 rattler, felt across the north of the country. Monitoring website earthquake report has this:

Update 10:49 UTC : The swarm continues and the most recently listed earthquakes had a Magnitude of M4.3 and M4.2. The number of earthquakes during the last 48 hours has risen to 484 ! The hypocenter depth is mainly varying in 3 layers, one at only a few hundred meter, another at 1.1 km and the last one at 20 km.
Most of the epicenters are located in an area of 15 to 30 km from Grimsey.
There have been earthquakes cycles of a similar nature in 1969, 1974, 1980, 1986, 1994 and 2002. The cycles were all from a few days up to several weeks.


This event follows a recent report that volcano Hekla in the south of Iceland is restless:

Associated Press
Published Tuesday, March 2, 2013 10:43AM EDT

LONDON — Icelandic police say seismic activity near the Hekla volcano has prompted them to declare an “uncertainty phase” — the lowest level of civil warning.

Monitoring of the area in southern Iceland has been increased. Police advise people not to hike in the area, though it is not forbidden.

Vidir Reynisson, the department manager for civil protection, said Tuesday that a swarm of earthquakes prompted the warning but are not necessarily a sign of pending eruption. Scientists worry that Hekla is overdue for an eruption; in recent decades it has erupted roughly every 10 years, most recently in 2000.

Concern about seismic activity in the north Atlantic nation has grown since April 2010, when ash from the Eyjafjallajokul volcano grounded flights across Europe for days, disrupting travel for 10 million people.

However the Icelandic MET office seems to e treating the Grimsey event as nothing unusual:

A M5.5 earthquake occurred at 00:59 on 2nd April 2013 about 15 km east of Grímsey island offshore North Iceland. The earthquake was felt at Grímsey, Húsavík, Raufarhöfn, Mývatnssveit, Akureyri and Sauðarkrókur. Several hundruds aftershocks have been detected following the mainshock. The source region is located on a fault system that reaching from Öxarfjörður to the north of Grímsey, the so called Grímsey lineament. Another M4.7 earthquake followed this morning at 08:56 and was located about 7.5km northwest of the night’s main event.

Both mainshocks are shown as black stars in the map, aftershocks that have been manually revised so far are shown as red dots. The M5.5 mainshock is located on a north-south striking left lateral strike-slip fault, see black lines in the map. The M4.7 event around 9 am was located on a normal fault to the north-west.

This cluster at about 7.5 km distance to the main cluster was most likely activated due to static stress changes induced by the M5.5 earthquake.

Earthquake sequences are common in this area. It is impossible to predict the further development of the seismic activity and how it might influence faults in its vicinity. Further large events can not be excluded.

  1. Gray says:

    May be the one we’ve been waiting for:

  2. tallbloke says:

    Thanks Gray, I’ve included some of that in the headline post.

  3. vukcevic says:

    With a strong tectonic action in the far N. Atlantic, UK (and N. W Europe) could expect warmer summers in a year or two, i.e.2014-15.
    NA SST (AMO) may respond a bit later, but that would require much stronger and longer activity in a wider area (North Atlantic Precursor – NAP)
    (Correlation may not be causation!)

  4. tallbloke says:

    Nice work Vuk. The bottom plot is new? What is the mechanism? Surely not something so simple as the seabed volcano vents turning up the heat to gas mark 6? 😉

  5. vukcevic says:

    Hi TB
    Yep, as a test I did the bottom graph from your post’s EQ numbers.
    I’ve been rattling on about this for couple of years now, I assume change of the currents balance through Denmark Straits affects circulation of the SPG – (subpolar gyre, the source of the AMO oscillations) .
    Arctic tectonic movements are regularly preceded or accompanied by changes in the area’s magnetic field, but that isn’t easy to pin down since there is a non-stationary correlation.

  6. vukcevic says:

    Congratulations Michele !

  7. Thanks vuk.

    I will pass (for mail) abstract (poster with graph and note ) to roger (at the end of the conference) for article on Tallbloke’s

  8. tallbloke says:

    Excellent, thanks Michele.

  9. Gray says:

    Local geology blog…

  10. Gray says:

    Interesting snippet:

    A submarine eruption was reported in 1372 near the Kolbeinsey Ridge NW of Grimsey Island. Kolbeinsey Island, the only subaerial expression of this portion of the Mid-Atlantic Ridge, is a small, rapidly eroding island that formed during the late-Pleistocene or Holocene. Dredged glass shards indicate submarine eruptive activity during the late-Pleistocene until at least 11,800 radiocarbon years ago.

    The island was 700 m long in 1616 AD, but had shrunk to 42 m long and 5 m high by 1985 and could be eroded below sea level in the early part of the 21st century. The Kolbeinsey Hydrothermal Field lies south of the island. Thorarinsson (1965) roughly plotted the location of the 1372 eruption at about 66 degrees 40 minutes North. Reidel et al. (2003) note that the location is uncertain, but could lie between the Kolbeinsey Ridge and Hóll Seamount. Other reports of submarine eruptions north of Iceland have an even more uncertain location (1755) or have been discredited (1783 and 1838).

  11. graphicconception says:

    Have they just started fracking?

  12. globalhotelblogger says:

    Congrats on the bloggers Award keep up the great work

  13. dp says:

    This is barely on topic, but Iceland has some of the most beautiful webcams to be found on the web. Here is Hekla: You may be lucky and witness a rattler in real time.

    Many are down (seasonal) but are worth the wait.

  14. Truthseeker says:

    How long before this is blamed on man-made CO2 and global warming?

  15. hunter says:

    Speaking off topic,
    Where is the CG3 data, Tallbloke?
    Come on. Stop hiding the decline of AGW hype and let the info go.

    [Reply] We’ve waited a year and a half. Another couple of weeks won’t hurt. Releasing info before it is properly filtered to comply with DPA could hurt a lot though. So unless you feel like putting up a couple of hundred thousand bond money, chill out and relax while the work gets done.

  16. hunter says:

    Thank you for the update.
    For me at least, an update is sufficient.
    It would be good to make this more widely known, imho.

  17. Roger, I am looking forward to a contribution from Michele Casati. I hope you can help or find someone to help with the English. I have noted Google translate does not fix the order of words. The translation of Dutch (eg blog makes difficult reading with the verb at the end of the sentence (German also has the verb at the end but I find it easier to understand even in the original German)

  18. steveta_uk says:

    The major Hekla eruption will occur between 5th and 18th of May, resulting in cancellation of transatlantic flights for the forseeable future.

    How do I know?

    I’m off to California on business, so it would be just my luck to be unable to get home ;(

  19. @ Cementafriend, be patient.
    Friday, April 12 in Vienna, I will publish (poster) my work.
    after….15-20 April, come back to Italy, I will contact TB for post on Tallbloke’s Talkshop.


  20. mkelly says:

    During one of my tours in Iceland in 1970, Helka erupted and on my birthday I was able to take a bus tour from Reykjavik to see Hekla. We were given helmets as we left the bus and could wander around near a lava flow. Some of the boulders were a big as houses and you could hear and feel the rumble of the volcano. I shall never forget that.

  21. Gray says:

    It’s at 561 Km depth.

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