Earthquake swarm started in Katla volcano at 13:33 UTC. This earthquake swarm lasted until 14:26 UTC (24 June, 2012). Most of the earthquakes in this swarm where small. Less them magnitude ML1.0 in size. The largest earthquakes did have magnitude of ML1.3 and ML2.0. No harmonic tremor did take place during this earthquake swarm. However, harmonic tremor data from IMO suggests a lot of hydro-thermal activity under Mýrdalsjökull glacier. This might result in small glacier floods coming from Mýrdalsjökull glacier in hours to days time. There is also a good chance that new earthquake swarm starts in Katla volcano at any time. Since there has been pattern of repeated earthquakes swarms in Katla volcano for several weeks now.
Earthquake activity in Katla volcano today. The newest earthquake also appears on this image. Copyright of this image belongs to Iceland Meteorological Office.
The harmonic tremor level at Álftagrof SIL station. This is normal background movement. There are however clues that hydro-thermal activity might have increased under Mýrdalsjökull glacier following this earthquake swarms. Copyright of this image belongs to Iceland Meteorological Office.
Harmonic tremor at Slysaalda SIL station. This is normal background noise. Spikes are earthquakes in Katla volcano. In this image there are also minor clues about increased hydro-thermal activity in Katla volcano. Copyright of this image belongs to Iceland Meteorological Office.
The earthquake at 13:45 UTC on Skeiðflöt geophone. This trace is filtered at 1Hz. This image is released under Creative Common Licence. See CC Licence page for more details.
The earthquake at 13:45 UTC on Heklubyggð geophone. This is filtered at 1Hz. This image is released under Creative Common Licence. See CC Licence page for more details.
It is hard to know for sure what happens next in Katla volcano. But I am sure this activity is currently taking place is going to continue. This does however not say anything about possibility of an eruption in Katla volcano. That possibility remains unclear, as earthquake activity does not mean that an eruption is imminent. For the moment, there are just earthquake swarms taking place in Katla volcano. But that can change without warning. Until then less speculation on what is taking place in Katla volcano is best (in the news media anyway).
Blog post updated at 08:34 UTC on 25.06.2012.
I am curious as to why the 2-4Hz line is remaining fairly flat at Snaebyli SIL station? It has done that for a couple of days now.
I am also making a suggestion to you Jon – why dont you do an article on identifying harmonic tremors from the graphs, a lot of people have difficulty knowing what is or is not harmonic. I am having to guess myself – for instance I believe that the datat from Grimsfjall is currently showing harmonic tremor ? http://hraun.vedur.is/ja/oroi/grf.gif
Am I right or wrong in believing that the merging of the three wavelengths and increased frequency is indicative of harmonic? Or is there something I am missing?
There are some members of your site who are in Iceland, and their local knowledge (like yours) is invaluable to people like myself, who cannot verify data. So maybe encourage them to respond to enquiries from new members who are probably seriously misguided by media articles, as I was when I first came to your site some time ago.
Cheers. SJ
I have already written a blog post about that. You can read it here.
http://icelandgeology.net/?p=1319
Also, Grímsfjall SIL station is not updating. This is data from few days ago. The SIL station is out of power or communications.
Jon is there any sign of ground change in the area
Not that I know of. But the area where this activity is taking place is under glacier. Only change that seems to be taking place is more hydro-thermal activity under Mýrdalsjökull glacier.
Thankyou Jon
Renewed activity with an earthquake swarm at El Hierro today. Largest quakes 3.3 and 3.8 .
This seems to be a new magma injection at 15 to 20 km depth. This might not result in an eruption. But it is worth keeping a eye on it.
How do u see that harmonic tremor is caused by hydrotermal activity?
Hydro-thermal activity tremor is weaker. As it is created by water boiling. Harmonic tremor created by magma is a lot stronger. Even if it is just flowing underground.