Today (31-July-2014) a minor earthquake swarm took place in Torfajökull volcano. This was a minor earthquake swarm and no earthquake did go above magnitude 3,0. Strongest magnitude of this earthquake swarm had the magnitude of 2,3. Depth of this earthquake swarm was from 15,1 km to around 1,0 km.
The earthquake swarm in Torfajökull volcano. Copyright of this image belongs to Icelandic Meteorological Office.
This earthquake swarm appears to be over, at least at the moment. It might start again at later time. Earthquake activity is common in Torfajökull volcano and there are no signs of any other activity from Torfajökull volcano at the moment.
Am I the only one who is noticing the periods of EQ activity in the whole of Iceland are coming in waves and then dying down only to come again?
What is going on with the tremor graph for Grimsfjall? It looks harmonic to me.
Earthquake activity in Iceland sometimes appear to do this. I don’t think it is a real thing.
The tremor graph in Grímsfjall is normal. Harmonic tremor looks different than this.
I’ve studied several harmonic graphs and must be missing the point. Exactly what is different about harmonic tremor Jon? The graph looks very much like some of those posted elsewhere for harmonic tremor preceding eruptions.
I cant see what is different.
Harmonic tremor looks like this. It’s magnitude depends on the size of the eruption in question. Smaller eruptions create smaller harmonic tremor.
See here, the harmonic tremor of the Grímsfjall 2011 eruption.
http://icelandgeology.net/?p=960
http://icelandgeology.net/?p=994
Thanks Jon, I see the sudden jump into harmonic, but to better understand, is the harmonic because all three frequencies have jumped into this pattern at the same time?
Going back to the current Grimsfjall graph only the 2-4 Hz band is showing a pattern, if the other two bands showed the same pattern at the same time would this then be harmonic tremor?
I don’t know if I don’t ask. Thanks. SJ
The change you are seeing is just weather or some other noise source. Harmonic tremor change in relation to an eruption is clear and cannot be mistaken from things like weather.