Month: January 2017

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Special article: Earthquake swarm in central Italy

Currently its quiet in Iceland, this is a fill up article while everything is quiet in Iceland.

Yesterday (18.01.2017) a earthquake swarm started in central Italy. First fore-shock had the magnitude of 5,3 (EMSC Information) and happened at 09:25 UTC (10:25 CET). The second earthquake had the magnitude of 5,7 (EMSC Information) and was clearly felt in central Italy. It was followed by aftershocks of the size 4,7 (EMSC information), 4,6 (EMSC Information), the largest aftershock during that hour had the magnitude of 5,3 (EMSC information). Since this earthquake activity more than 100 earthquakes have happened, many magnitude 4,0 earthquakes have taken place. At least one magnitude 5,2 earthquake (EMSC Information) took place at 13:33:37 UTC (14:33 CET).


The strongest earthquake so far, the magnitude Mw5,7 earthquake as it appeared on my geophone in Denmark. This image is under Creative Commons Licence, please see the CC Licence page for more details.

This earthquake swarm might mean that there are stronger earthquakes about to happen in central Italy, but there is no way to be sure about it due to complex nature of this area. I don’t fully understand the geology of this area at the moment or Italy geology in any details at the moment. I’m expecting more earthquake activity in this area for the next few days at least, based on current aftershock activity in the area. Current aftershock activity is heavy at the moment, with many earthquakes happening every hour.

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Minor earthquake activity on TFZ (Tjörnes Fracture Zone)

It is quiet in Iceland at the moment. Nothing much to report, so I’m reporting this minor earthquake activity in TFZ.

Few earthquakes have happened in TFZ for the last 48 hours, most earthquakes have been small and the largest ones have reached magnitude 2,5.


Minor earthquake activity in TFZ. Copyright of this image belongs to Icelandic Met Office.

This type of quiet period is common in Iceland. Since activity happens in bursts with long quiet spells between them. Since this website mostly reports current events, rather than anything historical I don’t have a lot to write about at the moment. I’m considering writing about other global activity while it’s quiet in Iceland.

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Magma inflow results in earthquake activity in Bárðarbunga volcano

On Friday 6th of January 2017 it was noted by one of my readers that a deep earthquake activity had happen in Bárðarbunga volcano, the earthquake in question was a magnitude 1,6 at depth of 25 km. At that depth the only earthquakes that happen are due to magma movement, at that depth the pressure is such tectonic (as explained by Icelandic geologists) earthquakes do not commonly happen at this depth. Today, 8th of January 2017 a magnitude 3,3 earthquake happened in Bárðarbunga volcano at the depth of 7,3 km and the earthquake had the magnitude of 3,5.


The earthquake activity in Bárðarbunga volcano. Copyright of this image belongs to Icelandic Met Office.

The inflation of Bárðarbunga volcano is now at considerable levels, it is not known if or when an next eruption happens. It appears, based on historical data that eruption cycles in Bárðarbunga volcano last for up to 20 years (depending), during such time there is an eruption every few years. At the moment there is also a rifting taking place in this area, making already a complex situation a lot more complex and harder to figure out. Since besides the main volcano, a volcano named Hamarinn can also erupt during this cycles. It has already erupted and did so in July-2011 when it had a 8 – 12 hour long eruption resulting a massive glacier flood, but it did not break the surface of the glacier (Vatnajökull).

Good example of this cycle and repeated eruption pattern can be found in historical data on Global Volcanism Program website (link above).

The last eruption cycle took place in the late 19th century and ended in early 20th century. The following eruptions happened (documented, there is a good chance that some eruption might have been missed due to how remote Bárðarbunga volcano is),

1862 June 30 – 1864 October 15 (error margin +- 45 days). Area of eruption was Tröllagígar.
1872 – Date not know nor eruption site, Dyngjuhals suspected.
1902 December – 1903 June. Eruption site not known, Dyngjuhals also suspected.
1910 June 18 – 1910 October, Loki-Fögrufjöll (East loki Cauldron). This is also known as Hamarinn volcano.

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Earthquakes in Bárðarbunga volcano

On the 4th and 6th of January 2017 earthquakes took place in Bárðarbunga volcano. The earthquake on 4th of January had the magnitude of 3,3 (I think) and the earthquake on the 6th of January had the magnitude of 3,5. Both earthquakes where inside the crater of Bárðarbunga volcano, along the fault rims. The reason for this earthquake activity is the inflation of Bárðarbunga volcano, that appears to be rather rapid and mostly steady process. Influx of magma happens in pulses and those pulses are in different size and how long they last.


The earthquake activity in Bárðarbunga volcano. Copyright of this image belongs to Icelandic Met Office.

This type of earthquake activity is a regular feature of Bárðarbunga volcano at the moment. I don’t expect that to change any time soon. What might change is the magnitude of the earthquakes happening, I suspect that with time they are going to get more rare but larger in magnitude instead.

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Earthquakes in Katla volcano

On the 5th of January 2017 a magnitude 3,5 earthquake took place in Katla volcano. This earthquake happening in January is extremely rare thing, since Katla volcano is normally quiet this time of the year. That seems to be over for now.


Earthquake activity in Katla volcano. Copyright of this image belongs to Icelandic Met Office.

This earthquake was the strong earthquake in a minor swarm that took place in Katla volcano during that day. Since then the activity has been mostly quiet. Bad weather is however interfering with detection of the earthquakes in most of Iceland, a storm is happening 1 to 2 days at the moment.

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The earthquake swarm in Hengill volcano

On the 4th of January 2017 a earthquake swarm took place in Hengill volcano. Largest earthquake had the magnitude of 3,7 and the second earthquake had the magnitude of 2,8. The largest earthquakes where felt in Reykjavík, Hveragerði and Selfoss towns (mostly). In total of 150 earthquakes took place in this earthquake swarm.


The earthquake swarm in Hengill volcano from 4th of January 2017. Copyright of this image belongs to Icelandic Met Office.

This earthquake swarm was due to a process called rifting, this means that where the earthquake swarm is happening the ground is dropping and cracking at the same time. This over time forms a rift valley (like Þingvellir). The area from Hveravellir and south into the ocean of the Reykjanes ridge is all just one big rift valley. Far as I know a period of high earthquake activity can happen in this area, last time this happened sometimes around the middle of 19th century with possible activity sometimes in the 20th (early) century. Since then it has been mostly quiet.

In the year 1789 (source in Icelandic, 1973) the area around Þingvallavatn lake dropped around 63 cm (that estimate is not accurate and it is estimated that it was far more) in a earthquake swarm. When this is going to happen next time is impossible to know.

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Earthquake activity in Bárðarbunga volcano

In 2016 Bárðarbunga volcano kept busy all year with inflating and preparing for the next eruption.

On 31-December-2016 a swarm of earthquake happened in Bárðarbunga volcano, largest earthquake in that swarm had the magnitude of 3,6 and the second largest earthquake had the magnitude of 3,3. On 02-January-2017 few earthquake happened, the largest one having the magnitude of 2,8.


The earthquake activity in Bárðarbunga volcano. Copyright of this image belongs to Icelandic Met Office.

At the moment, the Bárðarbunga volcano continues to inflate at what seems to be a rather fast rate. When that might lead to an eruption is difficult to know. Other more complex factors are also at work here that I don’t know to well and are impossible to figure out.

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