Category: Swarm

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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 “Suðurlandsskjálfti”, 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 Böðvarshólar, 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 Heklubyggð, 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 Heklubyggð, 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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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 Keflavík 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 Heklubyggð. 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 Heklubyggð 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 Heklubyggð. This image is under Creative Commons licence. Please see CC licence for more details.


The earthquake as it appeared on my geophone in Heklubyggð. 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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Strong earthquake swarm in Bárðarbunga volcano

Today (6-April-2017) a strong earthquake activity took place in Bárðarbunga volcano. This earthquake activity started this morning at 10:46 UTC and has continued during the day at slow phase. The largest earthquake so far took place at 15:08 UTC and had magnitude of 4,1 and second largest earthquake had a magnitude of 3,2. Other earthquakes are smaller and a around dozen or so have taken place today in Bárðarbunga volcano.


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

This earthquake activity is in line with earlier earthquake activity that has been going on in this area since September-2015. What is slightly different now is that I got two different seismic signals on my geophone stations in Böðvarshólar and the one in Heklubyggð on the North-South direction (Heklubyggð is west-south of Bárðarbunga, Böðvarshólar is west-north of Bárðarbunga). This difference seems to suggest that some type of slip movement took place during this earthquake. I don’t know for sure what this change in pattern means at the moment. The best I can do now is to monitor the earthquakes I detect in the future for more such earthquake signal changes like I did just see on my geophone. I’m not fully sure what is going on in Bárðarbunga volcano at the moment, what is known is that inflation is currently taking place in Bárðarbunga volcano and that process has been ongoing since September-2015.

Update 07.04.2017 – Anomaly detected on my Böðvarshólar geophone

This is the anomaly detected on my Böðvarshólar geophone. It can be seen on N-S direction. This is not the geophone, its working as expected and that got confirmed today when a minor (magnitude 2,1) earthquake took place not far from the Böðvarshólar geophone.


Böðvarshólar geophone.


Heklubyggð geophone.


Detailed image of the earthquake at Böðvarshólar geophone.


Detailed image of the earthquake in Heklubyggð geophone.

The difference is appearance of the P-wave and the S-wave. I don’t know why this is or why it happened. I’ve not seen this before.

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Article updated at 21:32 UTC on 07.04.2017.

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Minor earthquake activity in Hofsjökull volcano

On the 30th of March-2017 there was some minor earthquake activity in Hofsjökull volcano. This was a minor earthquake activity, with the largest earthquake having the magnitude of 1,3 at depth of 4,5 km. The deepest earthquake had magnitude of 1,0 and depth of 10,1 km.


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

I’m not expecting anything more to happen in Hofsjökull volcano. This volcano does not have any known eruption during the last 12.000 years that I know of. I don’t know what the latest research into activity in Hofsjökull volcano says, I was also unable to find any information about possible time frame when last eruption took place in Hofsjökull volcano. As it currently stands, I don’t expect anything more to happen besides maybe one or two extra earthquake appearing in Hofsjökull volcano.

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Strong earthquake swarm 80 km north of Kolbeinsey Island

During the night of 26-March-2017 there was an strong earthquake swarm about 80 km north of Kolbeinsey Island. This is around 250 km from the coast in north Iceland. It is not clear what is happening in this location, since this area has been seeing higher than usual earthquake activity in recent months. This is the largest earthquake swarm so far to take place.


The earthquake swarm as it appears on Icelandic Met Office maps. Green stars are earthquakes with magnitude above 3,0. Copyright of this image belongs to Icelandic Met Office.

Largest earthquakes in this swarm had the following magnitudes. Magnitude 4,6 (EMSC Information here), magnitude 5,0 (EMSC information here), magnitude 4,8 (EMSC information here). The largest earthquakes where not felt due to distance from the coast. It is not possible due to distance to see if there is an eruption taking place at this location. All harmonic tremor get lost due to distance from nearest SIL station. A really large eruption might slightly appear on tremor plot on Icelandic Met Office website, at the moment that has not happened.


The magnitude 5,0 earthquake as it appeared on my geophone in Böðvarshólar. This image is under Creative Commons Licence, please see CC licence for more details.


The magnitude 5,0 earthquake as it appeared on my geophone in Heklubyggð. This image is under Creative Commons Licence, please see CC licence for more details.

It is difficult to know if an earthquake activity is continuing in this area or not. Since the distance from nearest SIL stations does not allow for micro-earthquakes to be detected properly or at all.

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Earthquake swarm in Bárðarbunga volcano 21-March-2017

Yesterday (21-March-2017) there was an earthquake swarm in Bárðarbunga volcano. Largest earthquakes where magnitude 3,1 and 3,0. Other earthquakes that happened where smaller in magnitude.


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

There isn’t much to say about this earthquake activity (for those how do not know, please check older articles on Bárðarbunga volcano). This activity is happening due to continued inflation of Bárðarbunga volcano since the eruption ended in February-27 in 2015, inflation started in September that same year. Earthquake activity had started to drop in February, it now appears to be increasing again. When or if that results in a eruption soon is impossible to know.

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