Today (07-March-2018) there has been deep earthquake activity in Bárðarbunga volcano. This earthquake activity was in two areas. In the main volcano and south-east of it.
The earthquake activity in Bárðarbunga volcano and south-east of Bárðarbunga volcano. Copyright of this image belongs to Icelandic Met Office.
The earthquake swarm in the main volcano is normal and is connected to current inflation activity of Bárðarbunga volcano. Earthquake activity happens mostly when magma is pushing the crust upwards when it flows into the volcano from depth. The earthquake swarm to the south-east of Bárðarbunga volcano is more interesting. That is a dyke and it has been in this area for numbers of years already. At the moment this dyke remains at depth of 15 – 23 km but this increase in activity might be increasing the risk of eruption if it does not quiet down. The increased magma activity in Bárðarbunga volcano has increased the earthquake activity in this dyke over the last few months.
There is a high risk of strong earthquakes in Bárðarbunga volcano in the next few days to weeks.
What also happened in this earthquake swarm was a high intensity tremor on the mid-band (1-2Hz) during the earthquake swarm. This is highly unusual. What it means is less clear.
The tremor activity (close to the end) on a SIL station close to Bárðarbunga volcano. Copyright of this image belongs to Icelandic Met Office.
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Is it the same dyke of the previous eruption?
No. This is a different dyke.
That dyke went in the direction of Askja; this dyke is on the southeast side of the mainvolcano.
https://blogs.egu.eu/geolog/2015/05/08/icelands-bardarbunga-holuhraun-a-remarkable-volcanic-eruption/
Yes it is the same Dyke, see map in link!
Hi Jon,
It seems that every time there is any activity in Bardarbunga there is a certain amount of activity around the same time in the dyke or fissure that fed Holuhraun. Is there a possibility that Holuhraun is still soft enough to reopen under the pressure building in Bardarbunga itself?
That might happen but I am not sure how that would work. I think the Holuhraun dyke has sealed up and is not going to erupt again unless something happens that changes that. Currently the dyke is cooling down but that is going to take 200+ years.
Is it my imagination, or has there been a slow increase in earthquakes in the western Vatnajökull – Laki area in the last couple of years or so?
You are correct. This increase is not much. It is only from 0 earthquakes and up to 2 – 7 earthquakes a month. Some months there are 0 earthquakes. This is inside the Laki fissure swarm and this increase in earthquake activity in this area started after the 2011 eruption in Grimsvötn-Þórðarhyrna volcano system where this fissure swarm belongs to.
Historically this area has fissure eruptions every few hundred years (VEI=2) and every few thousands years eruptions of the size of Laki (VEI=4).
The volcano Thordarhyrna (Þórðarhyrna) has not had an eruption since an eruption in the years 1902-December – 1904-January. How often Þórðarhyrna erupts is not well known but last activity was in the 19th century and it appears to have erupted every few years and often Grímsvötn and Þórðarhyrna erupted at the same time.
Historical overview of Grímsvötn-Þórðarhyrna volcano system (only named Grímsvötn in GVP database), https://volcano.si.edu/volcano.cfm?vn=373010
Wednesday
14.03.2018 21:10:34 65.024 -16.669 4.2 km 3.8 99.0 3.4 km WSW of Dreki
Good size bump near Dreki
Wednesday 14.03.2018 09:10:34 PM 65.024 -16.669 4.2 km 3.8 MAG 99%
3.4 km WSW of Dreki