Earthquake swarm on the Reykjanes ridge

Today (21-September-2015) a minor (so far) earthquake swarm has been taking place on the Reykjanes ridge. Largest earthquake so far had the magnitude of 3,5 so far other earthquakes have been smaller in magnitude.

150921_2325
The earthquake swarm on the Reykjanes ridge. Copyright of this image belongs to Icelandic Met Office.

It is difficult to know for sure what happens. Earthquake swarms in this part of the Reykjanes ridge often end quietly, but they can also just pick up as easily, it is impossible to know for sure.

16 Replies to “Earthquake swarm on the Reykjanes ridge”

      1. I don’t really know how to read the tremor plots, but there’s a spike yesterday evening and again early this morning. Is this harmonic tremor – and therefore magma on the move? (I think I understand what HT is, but I’m not at all sure I can spot it on the plots.)

      2. Ah, great – thanks Down Under. I’ve searched off and on for a picture that shows what HT looks like on the Icelandic plots but haven’t been able to find one. Do you happen to know of one and if so, could you provide a link, please?

        Cheers.

      3. If one thinks about it, the term ‘harmonic tremor’ is kind of self-explanatory and is ever present, everywhere, all the time. I guess you can think of it as a very deep continuous hum (far too low and faint for the human ear, of course). It’s when the harmonic tremor picks up (at the different measured frequencies) that one can suspect something is going on in the crust.

        Earthquakes show as distinct spikes in the tremor plots, while HT shows in the ‘fatness’ and rise of the graphs over a longer duration.

        I often go to this site and scroll through all (well, not everyone is presented) the stations, looking for something out of the ordinary.
        http://hraun.vedur.is/ja/oroi/allarsort.html

      4. Thanks very much, Z. As I said, I think I understand what harmonic tremor is – and you have confirmed that I do – Result! 🙂

        I’ve been watching the plots and lurking around here and VC for several years but I’ve never been confident that I have grasped the elements of differential diagnosis that would enable me to say that I have actually *seen* the HT that others refer to. But I’ll keep lurking and, hopefully, learning.

Comments are closed.