At 07.55.04 Hekla suffered an earthquake of M0.9 at 0.7km depth under the west slope of Hekla proper. After that followed two badly localized small tremors before a second earthquake with a temporary solution of M0.6 at the same place and depth. After that came a final (so far) small tremor.

This follows after ten days of GPS changes indicating relaxation of the Heklugjá fissure under Hekla. The earthquakes may therefore be due to resettling of the mountain after relieved pressure.

There is also the possibility that this is how a prelude to a Hekla eruption looks like when you have very good instrumentation to watch. Or in other words that Hekla erupts due to tectonic forces pulling the fissure apart that in turn lowers the pressure inside the magma reservoir rapidly releasing volatiles. That would neatly explain why onset of Hekla eruptions are so explosive.

Just prior to onset of Hekla eruptions (cirka 10 minutes) there will be very rapid changes registered on the strainmeters as the mountain pulls apart. So far nothing like that has occurred, but look at the image below and you will know roughly what to look for there.

If an eruption would start it would have a very violent beginning. It is though good to remember that Hekla had a larger earthquake swarm back in 2013 without any eruption occurring, that being said, if you see a M2+ earthquake and a brief smattering of smaller earthquakes COMBINED with a rapid strain drop at Burfell an eruption could perhaps be on the way. As I write this there are no such signals.

The post will be updated if anything interesting happens, if not another post will be published later in the day.

CARL REHNBERG