Category: Earthquakes

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Earthquake swarm ~338 km east of Iceland (close to Faeroe Islands)

During the last 24 hours or so there has been some activity ~334 km east of Iceland. Largest earthquakes detected have had the magnitude of 3,1 and 3,1 and this are the only earthquakes that have been detected.


The earthquake activity way off the east coast of Iceland. This activity is closer to Faeroe Islands than Iceland. Copyright of this image belongs to Icelandic Met Office.

I have little knowledge about what is below the waves at this location. Depth at this area is around 2 – 3 km and no known volcano or fault area is at this exact location. Next ancient fault area is slight more to the north, that feature is called Aegir Ridge and is extinct. This earthquake activity is slight outside it but within its area it might effect. This might be a intra-plate earthquake activity, since this area is not active and has not been for millions of years according to studies.

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Earthquake swarm in Kolbeinsey island

Yesterday (24-May-2017) and today (during the night of 25-May-2017) there was an earthquake swarm in Kolbeinsey island. Largest earthquakes had the magnitude of 3,6 (x2) and one magnitude 3,5 earthquake took place. Other earthquakes where smaller in magnitude. No harmonic tremor where detected during this activity, that does not rule out that this activity is due to dyke intrusion taking place in Kolbeinsey island. It just didn’t reach the surface this time. Kolbeinsey island is far away from the SIL network, with the closest station being in GrĂ­msey island (~25 km) with other SIL station at ~60 km distance. If an eruption starts in Kolbeinsey Island, a harmonic tremor signal is going to appear in GrĂ­msey island SIL station.


Green star mark the area where the earthquake swarm took place in Kolbeinsey island. Copyright of this image belongs to Icelandic Met Office.

Last eruption in this area took place in the year 1755, but that eruption might not actually have been in Kolbeinsey Island, but in a other unnamed volcano north of it (where is not known). Last confirmed eruption in Kolbeinsey island took place in the year 1372, it was closer to land somewhere north-west of GrĂ­msey island (suggesting that fissure swarm of Kolbeinsey island comes close to GrĂ­msey island).

At the moment the activity has quieted down and no earthquakes are being detected by the SIL network.

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Strong earthquake activity in Bárðarbunga volcano yesterday (20-May-2017)

Yesterday there was a strong earthquake activity in BárĂ°arbunga volcano (GVP has new information about BárĂ°arbunga volcano). Two of the largest earthquakes had the magnitude of Mw3,9 and Mw3,8 other earthquakes where smaller in magnitude and around 10 earthquakes happened in BárĂ°arbunga volcano. This activity is also different from historical activity from 1970’s and towards 1994 (Gjálp eruption), when a magnitude 5 earthquake would happen in BárĂ°arbunga volcano once to twice a year. Current activity suggests that magma is inflating BárĂ°arbunga volcano faster than in the period between 1970’s and 1994. Why that is is not known to me.


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

Current change is that in recent weeks there are fewer earthquakes taking place in Bárðarbunga volcano, but when they happen they are often larger in magnitude and more than one large earthquake happens during the earthquake swarm.


The magnitude (Mw) 3,8 earthquake in Bárðarbunga volcano as it appeared on my geophone in Böðvarshólar. This image is under Creative Commons Licence, see CC licence for more details.


The magnitude (Mw) 3,8 earthquake in Bárðarbunga volcano as it appeared on my geophone in Heklubyggð. This image is under Creative Commons Licence, see CC licence for more details.


The magnitude (Mw) 3,9 earthquake in Bárðarbunga volcano as it appeared on my geophone in Böðvarshólar. This image is under Creative Commons Licence, see CC licence for more details.


The magnitude (Mw) 3,9 earthquake in Bárðarbunga volcano as it appeared on my geophone in Heklubyggð. This image is under Creative Commons Licence, see CC licence for more details.

According to reports on Global Volcanism Program the most magma collection is happening at the depth of 10 km (or around that depth), no clear or oblivious signs are that magma is collecting at shallower depth at the moment. If that is required for a eruption in BárĂ°arbunga volcano is not know at the moment, there is a possibility that magma might collect at 10 km depth and then pump out with a dike as was seen in the Holuhraun eruption (2014 – 2015). What has been confirmed is that magma is collecting under BárĂ°arbunga volcano and the volcano is inflating. This inflation is either going to stop or its going to continue until a new eruption happens.

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Earthquake activity in Tjörnes Fracture Zone (TFZ)

For the past month (or so) there has been a constant earthquake activity close to Flatey island on the Tjörnes Fracture Zone (TFZ). This earthquake swarm has not been strong, with majority of the earthquakes only having the magnitude of 0,0 – 2,5 and only one or two earthquakes with magnitude 2,8 – 3,0. While this earthquake swarm might not be a risk, it might suggest that something is about to give in this area.


The earthquake activity in TFZ as it is today. The activity close to Flatey island is clearly visible. Copyright of this image belongs to Icelandic Met Office.

Other areas of TFZ have also been having minor earthquake swarms. I don’t think they are connected to this activity near Flatey island. None of those earthquake swarm have been big in both number of earthquakes and magnitude. TFZ is Iceland most active earthquake area with hundreds of earthquakes taking place each year. What is unusual now is the earthquake activity close to Flatey island, but this is not the first time this type of earthquake swarm happens in TFZ. Normally this type of earthquake swarm slowly die out without anything major happening.

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Earthquake swarm in SISZ (South Icelandic Seismic Zone)

Today on 6-May-2017 a magnitude 4,4 – 4,5 earthquake hit South Icelandic Seismic Zone (SISZ) at 12:08:58 UTC. This earthquake was felt over a wide area, a magnitude 3,3 earthquake also took place around one minute after the main earthquake. The earthquake took place on a fault that might have last moved in the year 1623 or 1624, as is detailed here. Current earthquake activity does classify as a “SuĂ°urlandsskjálfti”, only earthquakes with magnitude above 5,5 are classified as such. This is regardless a strong earthquake activity in SISZ for a long time now.


The earthquake activity on SISZ. The green stars mark the location of the magnitude 4,4 – 4,5 and the magnitude 3,3 earthquakes. Copyright of this image belongs to Icelandic Met Office.


The magnitude 4,4 – 4,5 earthquake as it appeared on my geophone in BöðvarshĂłlar, north-west Iceland. This image is under Creative Commons Licence, please see CC licence page for more details.


The magnitude 4,4 – 4,5 earthquake as it appeared on my geophone in HeklubyggĂ°, the earthquake happens just west of this geophone location. The geophone is saturated by incoming earthquake signal. This image is under Creative Commons Licence, please see CC licence page for more details.


The magnitude 3,3 earthquake as it appeared on my geophone in HeklubyggĂ°, the earthquake happens just west of this geophone location. This earthquake also saturates the geophone (just a little). This image is under Creative Commons Licence, please see CC licence page for more details.

More aftershocks are expected in this are for the next few hours to days. It is difficult to know if this means there is going to be a larger earthquake activity at this location or nearby. It’s always a chance, but it is not possible to know that for sure.

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Article has been updated at 15:55 UTC. Minor text fixes.

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The April 17 earthquake sequence in Chile (ongoing) [test article]

During 14 to 18 day period in April a earthquake swarm took place in Chile. This earthquake swarm started with a minor earthquake swarm with around dozen or so earthquakes with magnitude above 3,0 (other magnitudes might not be registered with EMSC). This earthquake sequence appears to have started on 17th of April-2017 with just a few earthquakes. I don’t have the information on the exact time it started. The first earthquake swarm was located in a narrow area above the subduction zone (where compression takes place). Few days later after the earthquake activity started the first large earthquake hit and had a magnitude of Mw6,0 (EMSC Information). Largest earthquake in this activity so far had the magnitude of Mw6,9 (EMSC Information). I don’t have any information on total number of earthquakes, but just based on the amount of earthquake activity show on EMSC total number of earthquakes must run in the low thousands (up to 10.000 earthquakes).

I don’t have the number of total earthquakes with magnitude above 4,0, at least dozen or so earthquakes (or close it) must have happened in this earthquake swarm in Chile. This area where this swarm took place had a magnitude 8,3 earthquake in 2015 and a magnitude 8,8 earthquake in 2010. This means that this part of Chile has a well documented history with extremely large earthquakes happening. If that’s going to be the case now is difficult to know, it can’t be ruled out based on the area history.

Detailed reading material from people that know more

Earthquake sequence in Central Chile: what we know so far

Test article

This is a test article to see if there is any interest for articles like this on their own website. I would not update it in real-time like Iceland Geology, but few days after the main earthquake has happened. Major earthquakes might get a extra speedy article if required (not guaranteed). I might write one or two articles like this more to do more tests in next few weeks if there is any interest for this type of articles.

The new website would be on its own domain, not a sub-folder of the domain jonfr.com.

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Magnitude 4,3 earthquake on the Reykjanes ridge today (19.04.2017)

Today (19.04.2017) at 12:34 UTC an earthquake with the magnitude of 4,3 took place on the Reykjanes ridge. This earthquake was felt in KeflavĂ­k town and nearby areas. A swarm of aftershocks followed, none of them was above magnitude 3,0. Largest aftershock had the magnitude of 2,9.


The earthquake swarm on the Reykjanes Ridge. Green star is the location of the magnitude 4,3 earthquake. Copyright of this image belongs to Icelandic Met Office.

This earthquake activity appears to be normal rifting activity in line with earlier earthquakes like this that have been happening deeper on the Reykjanes ridge over the past few weeks. There is a good chance that new earthquake activity is going to happen in this same area or nearby area in next days to months.


The earthquake as it appeared on my geophone in HeklubyggĂ°. This image is released under Creative Commons Licence. Please see CC Licence website for more details.

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Strong earthquake swarm in Katla volcano today (19.04.2017)

Today (19.04.2017) a strong earthquake swarm started in Katla volcano. Largest earthquake in this swarm had magnitude of 3,0 and 3,1 other earthquakes that happened where smaller in magnitude. This is the strongest earthquake activity in Katla volcano since January 2017 when a magnitude 4,3 earthquake happened. No harmonic tremor was detected following this earthquake swarm.


The earthquake swarm in Katla volcano. Green stars show the magnitude 3,0 and 3,1 earthquakes. Copyright of this image belongs to Icelandic Met Office.

The earthquakes that I detected on my geophone in HeklubyggĂ° show that the largest earthquakes was a mixed type of volcano earthquakes. This means that magma was responsible for today’s earthquake swarm. It was reported today in the news that this earthquake swarm took place away from all major hydrothermal areas inside Katla volcano caldera. The area of activity is close to eruption area of 1755 and a minor eruption close to current earthquake area in 1955 (didn’t break the glacier).


The main earthquake with the magnitude of 3,1 in Katla volcano. The trace is filtered at 4Hz due to high wind in the area. This image is released under Creative Commons Licence. Please see CC licence for more details.

This earthquake activity might just be a early signs of more activity to come. Since current pattern of activity has been going on since August-2016, with minor drop in activity between January to April. How this evolves depends on many factors that cannot be predicted due to lack properly documented earthquake history. Scientists know some details of Katla volcano eruptions behaviour, but those accounts are not fully accurate due to lack of knowledge at the time, currently the best documented eruption in Katla volcano is from 1918.

Article updated at 20:41 UTC. Correction made to the information about strongest earthquake. I recalled that detail wrongly.

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Earthquake swarm in Bárðarbunga volcano

Today (17.04.2017) at 11:58 UTC a magnitude 4,2 earthquake took place in Bárðarbunga volcano. This is the strongest earthquake in Bárðarbunga volcano for several weeks now. Following this earthquake a earthquake swarm started and lasted for about one hour in Bárðarbunga volcano.


Green star shows the magnitude 4,2 earthquake in Bárðarbunga volcano. Copyright of this image belongs to Icelandic Met Office.

Largest aftershock activity had magnitude of 2,8 as the information is currently on Icelandic Met Office website. That might change tomorrow and it’s possible that I might update this article if any major change happens in earthquake magnitudes. No harmonic tremor was detected following this earthquake swarm. Weather is currently bad in Iceland and that’s going to last for few more hours.

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Magnitude 4,5 earthquake on Reykjanes ridge during the night

During the night of 10-April-2017 at around 03:39 a magnitude 4,5 earthquake happened and started a earthquake swarm at same location, total number of recorded earthquakes is around 71 but that number is not confirmed as of yet. There is also a good chance a few magnitude 3,0 earthquakes happened, but this earthquake swarm has not been reviewed by Icelandic Met Office as of yet (I don’t know why it’s slow today).


The earthquake swarm as it appears on Icelandic Met Office maps, green star is the location of the magnitude 4,5 earthquake. Copyright of this image belongs to Icelandic Met Office.


The earthquake as it appeared on my geophone in HeklubyggĂ°. This image is under Creative Commons licence. Please see CC licence for more details.


The earthquake as it appeared on my geophone in HeklubyggĂ°. This image is under Creative Commons licence. Please see CC licence for more details.

This appears to be a normal tectonic earthquake in the rift valley that is at this location. No change was observed in the harmonic tremor, that means there was no magma movement during this activity. Based on earlier earthquake behaviour in this area, there is a good chance that new earthquake swarm is going to happen in this area after few days or at most weeks before this area going quiet again.

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