Iceland geology – Page 97 – Volcano and earthquake activity in Iceland

November 26, 2016

Increase in earthquakes in Katla volcano

During the past few days there has been a slight increase in earthquake activity in Katla volcano. Largest earthquakes in the past few days have reached magnitude 2,8. At the moment larger earthquakes have not happened in Katla volcano.

The earthquake activity in Katla volcano over the past few days. Copyright of this image belongs to Icelandic Met Office.

Interestingly there seems to be a concentration of earthquakes on the east side of the caldera, close to the area that erupted in the year 1918. This might be a clue to where in the caldera next eruption is going to happen, since magma seems to “bore” its way trough the crust and in many occasions that leads to a swarm of small earthquakes [note: This is not confirmed in any scientific way or by a study, this is just my observation of this phenomena]. Currently the earthquake activity in Katla volcano is small, compared to how much activity was taken place between end of August and mid-October. I suspect that current level of earthquake activity is going to continue until next spring.

Conductivity in few glacier rivers around Mýrdalsjökull glacier continue to be high, suggesting that new hydrothermal vents have opened up under the glacier inside the caldera. This type of warm-up in a volcano is not a good sign and is a clear sign that magma is now shallow in the caldera. For magma to warm ground water up to this levels, it needs to be less than 1 km up in the crust. This is a shallow depth for magma in a volcano.

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November 26, 2016

New swarm of earthquakes in Bárðarbunga volcano

During the night (26-November-2016) a swarm of earthquake took place in Bárðarbunga volcano. Largest earthquake had the magnitude of 3,8 other earthquakes where smaller in magnitude.

The magnitude 3,8 earthquake in Bárðarbunga volcano (green star). Copyright of this image belongs to Icelandic Met Office.

On 22-November-2016 a magnitude 3,6 earthquake took place in Bárðarbunga volcano. That earthquake took place in the south-west part of the caldera, close to the place where the dyke broke out in 2014.

The magnitude Mw3,6 earthquake in Bárðarbunga volcano on 22-November-2016. Copyright of this image belongs to Icelandic Met Office.

This type of earthquake activity is now so common in Bárðarbunga volcano that I can’t write about them all. If I did write about them all, there would be nothing but articles about Bárðarbunga volcano on this website.

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November 19, 2016November 19, 2016

Strong earthquake swarm in Bárðarbunga volcano

During the early hours of 19-November-2016 a strong earthquake swarm took place in Bárðarbunga volcano. This is the strongest earthquake swarm in Bárðarbunga volcano for a long time now. Strongest earthquake had the magnitude of 4,0, other magnitudes where 3,5 and 3,1. All other magnitudes where smaller.

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

This earthquake activity suggests that pressure is increasing fast inside the volcano. I don’t know how much Bárðarbunga volcano has inflated since September-2015 but that must be considerable amount since a earthquake of magnitude 4,0 means a slip of few millimetres (I don’t have the information of much movement happens when a earthquake happen. I didn’t find the data about it). Over the past one year there has been a lot of earthquakes taken place in the Bárðarbunga volcano caldera, suggesting a rapid inflation of the volcano. It is not known if this is going to result in a eruption soon or sometimes later, all that is known is that magma is flowing into shallow magma chamber from deep within the volcano.

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Article updated at 22:42 UTC. Added a missing part.

November 19, 2016

Earthquake activity in Bárðarbunga volcano

The regular earthquake activity in Bárðarbunga volcano continued on 18-November-2016. This activity has now been going on for 1 year plus few more weeks, at the moment it has slowed down a bit from when it was most active. I don’t know why that is, but the earthquakes are because magma is flowing into shallow magma chambers in Bárðarbunga volcano.

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

Largest earthquake in yesterdays (18-November-2016) earthquake swarm had the magnitude of 3,0. Other earthquakes so far have been smaller in magnitude. The activity appears to be mostly over by now, but it might resume at any moment since magma inflow and changes connected to it cannot be predicted.

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November 19, 2016

Earthquake swarm in Katla volcano

On 18-November-2016 a minor earthquake swarm took place in Katla volcano. This was a minor earthquake swarm with largest magnitude around 2,5. At the moment the earthquake activity appears to have ended, it might resume at later time.

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

The earthquake activity is in a area that had a minor eruption in the year 1999. There has not been a major eruption in this part of the caldera for a long time according to historical data. It is possible that last major eruption in this area took place in the year 1245, but that eruption is not properly documented due to old age of the historical documents.

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November 14, 2016November 14, 2016

Minor earthquake swarm on TFZ

Today (14-November-2016) a minor earthquake swarm started on TFZ (Tjörnes Fracture Zone). Largest earthquake so far has the magnitude of 3,2, other earthquakes have been smaller in magnitude.

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

So far this earthquake swarm has not been big and it doesn’t look like its going to develop into a big earthquake swarm at the moment. In other parts of Iceland everything is quiet, with just one off or few earthquakes happening in each location.

November 11, 2016

Magnitude 3,5 earthquake in Bárðarbunga volcano

Today (11-November-2016) a magnitude 3,5 earthquake took place in Bárðarbunga volcano. This earthquake, like so many before it, is due to inflation of the volcano that started in September-2015. This is going to be happening for a long time now, since last earthquake sequence that started this way started in 1973 and lasted until 1996 (science paper on it can be found here). After that it was quiet for few year until 2010-ish years before the eruption started in 2014.

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

This inflation and earthquake activity is going to lead to an eruption one day. When that is going to happen is impossible to know until it happens.

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November 5, 2016November 5, 2016

Minor earthquake activity in Esjufjöll volcano

For the few hours (on 05-November-2016) there has been a minor earthquake activity in Esjufjöll volcano [Wikipedia information]. Esjufjöll volcano is not a volcano that gets a lot of attention because most of the time its completely quiet, with last notable activity taking place in the year 2013. Earthquake activity started to appear in Esjufjöll volcano in the year 2002 (IMO map here and here).

Earthquake activity in Esjufjöll volcano (north east of Öræfajökull and south of Grímsvötn volcanoes). Copyright of this image belongs to Icelandic Met Office.

At the moment not many earthquakes have taken place in Esjufjöll volcano. That might maybe change, but I don’t expect it to. Maximum number of earthquakes recorded so far (in 2002 at least) is around 40 – 80 (I’m not sure to the exact number). The reason why Esjufjöll volcano is having earthquake activity is due to fresh magma pushing up the volcano from deep inside it. At the moment there isn’t anything suggesting that an eruption is about to happen and if an eruption does happen I would not expect it to be big. The chance of an eruption taking place in Eskjufjöll volcano is around ~2% at the moment in my view.

The only eruption that might have happened took place in the year 1927, at the moment it has not been confirmed. It may have only been active for around 4 days at maximum and took place on September 5. The information is not that good due to how remote this volcano is (map can be found here, Esjufjöll are located south of Grímsvötn, north-east of Öræfajökull volcano).

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November 4, 2016

All quiet in Iceland at the moment

Over the past three weeks things have been mostly quiet in Iceland. With no major activity taking place. There have been few magnitude 3,0 and above earthquakes. Over the past three weeks the average number of earthquakes over 24 hour period is just 10 earthquakes. This is based on my automatic counter and it has slightly lower number than manually checked earthquakes. Icelandic Met Office says there are around 300 – 400 earthquakes taking place in Iceland during the week (1200 earthquakes at month).

The earthquake activity in Iceland at the moment. All quiet at the moment. Copyright of this image belongs to Icelandic Met Office.

It is not possible to know for how long this quiet period is going to last. Its already been three and almost four weeks already into this quiet period. All that can be done now is to wait and relax a little.

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October 30, 2016November 1, 2016

Special report: The Italy major earthquake swarm

This is a special report on the earthquake swarm in Italy. Due this being a different country I only have limited information about what is going on in Italy and I don’t have complete knowledge of the area in question. News sources with detailed images of the affected earthquake area can be found here (English) and here (Italian). Those news articles also contains images of the affected areas and aftershock areas (I can only use the image from USGS on the English website).

The earthquake swarm in Central Italy

On 26-October-2016 an earthquake swarm started in Italy, it started with a magnitude 5,5 earthquake (EMSC Information). It was followed by a magnitude 6,1 earthquake (EMSC Information). The magnitude 5,5 earthquake is a foreshock (Wikipedia information) to the magnitude 6,1 earthquake and that is the main event in that earthquake swarm. The magnitude 6,5 earthquake (EMSC Information) today (30-October-2016) is a new earthquake swarm in the same area. It has been followed by a heavy aftershock activity, with more than 300 earthquakes/h taking place in the main earthquake area. It is my view, based on the aftershock pattern that one or more magnitude 6,0 or stronger earthquakes are going to happen in this area in the next few days to months (it’s impossible to know when they happen). It does not help that this area of Italy is crossed with fault lines and they are all active (in the sense they can and do make earthquakes every few decades to hundreds of years).

The magnitude 6,1 earthquake in Central Italy on 26-October-2016. This image is under Creative Commons Licence, please see CC Licence website for details.

The magnitude 6,5 earthquake in Italy on all axes (Z, N-S, E-W). According to the measurement that I saw on my geophone in Denmark, the movement was N-S rather than E-W. There appears to have been some vertical displacement in this earthquake. This image is under Creative Commons Licence, please see CC Licence website for details.

High resolution of the vertical component (Z) in my geophone. It clearly shows how the earthquake happened in central Italy. This image is under Creative Commons Licence, please see CC Licence website for details.

It is unclear how this is going to progress over the next few days, weeks and months. I don’t know enough about this area to make any type of guess. The area in question is a subduction zone (just not under a ocean) and that makes predicting this activity even more complicated and difficult.

Basic tectonic layout of Italy with earthquake activity on top. Image is from USGS.

There is also a factor that I don’t know about. How often does this happens over the century in Italy. There is only a small clue (and it’s not even clear) of the earthquake list for Italy on Wikipedia (best that I was able to find). In Iceland (for comparison), the SISZ has an earthquake swarm activity (major) every 13 – 90 years (I wrote a list about known earthquakes here). I don’t know how often this happens in Italy, but I suspect that it is at least every few hundred years. How often this happens is mostly controlled by how fast the faults move each year and I don’t have that information.

If anything more happens in Italy I’m going to update this article.

Update on 01-November-2016 at 23:50 UTC

This morning (1-November-2016) a magnitude 4,9 earthquake (EMSC Information) took place in Central Italy. Aftershock activity continues to be heavy in Central Italy. While this earthquake doesn’t look big, it is enough to create more damage into the effected areas. Aftershock activity continues to be heavy in Central Italy.

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Article updated at 23:19 UTC. Word fixes.
Article updated on 1-November-2016 at 23:52 UTC.

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