Author: Jón Frímann

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Three strong earthquakes in Tjörnes Fracture Zone close to Gjögurtá

During the night (19-July-2020) three earthquakes took place in Tjörnes Fracture Zone on the Flatey – Húsvík fault. Around midnight earthquake activity started to increase on the Flatey – Húsavík fault. The first earthquake with magnitude Mw3,0 took place at 02:54 UTC and the largest earthquake with magnitude Mw4,4 took place at 03:07 UTC and the second largest earthquake with magnitude Mw3,3 took place at 07:05 UTC. More earthquakes with magnitude above Mw3,0 can’t be ruled out and there remains a risk of earthquake with magnitude of Mw7,0 is going to happen in this area.


The earthquake activity in Tjörnes Fracture Zone for the last 48 hours. Copyright of this image belongs to Icelandic Met Office.

This is the largest earthquake since 8th July 2020 when a magnitude Mw4,2 earthquake took place in this area in the rift valley that is also active during this earthquake swarm. Over 14.000 earthquakes have been recorded since start of this earthquake swarm on 19th June 2020. This earthquake swarm is ongoing at the writing of this article.

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Two strong earthquakes north of Grindavík town

This morning (18-July-2020) two strong earthquakes that were felt in Grindavík town and Reykjanes area took place this morning at 05:54 UTC and 05:56 UTC in the volcano Reykjanes. Earlier earthquake had a magnitude of Mw3,2 and the second earthquake had a magnitude of Mw4,1. There isn’t a lot to go on by the GPS data that is showing any inflation taking place following this earthquake swarm. The strongest earthquakes were also rather shallow being only at 2,5 km depth.


The earthquake activity north of Grindavík town. Copyright of this image belongs to Icelandic Met Office.

This magma intrusions are a repeated pattern and now strongly suggests that a eruption is going to happen in this volcano. When is impossible to know. What is most likely to happen is that more and stronger earthquake swarm might happen. Current depth of smaller earthquakes in this swarm is now from 8 km to 0,1 km. This appears just to be earthquakes in the rocks at the most shallow depths for now due to pressure changes at more depth from magma. There is a risk of stronger earthquakes in this area because of this dyke intrusions.

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Two strong earthquakes in Bárðarbunga volcano yesterday (14-July-2020)

This article is a bit late because I didn’t have the energy to write it yesterday (14-July-2020).

Two earthquakes with magnitude 3,0 (at 23:41 UTC on 13-Jyly-2020) and a magnitude Mw3,6 (at 00:56 UTC on 14-July-2020). This earthquakes are because Bárðarbunga volcano continue to inflate as it has been doing since the end of the eruption in Holuhraun in February 2015.


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

There were two aftershocks with magnitude of Mw2,5. Other earthquakes that happened were smaller in magnitude. This activity is normal now for Bárðarbunga volcano and no eruption is expected and would require a lot more earthquake activity as was seen during the 2014 August and September start of the eruption from Bárðarbunga volcano.

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Earthquake swarm in Herðurbreiðartögl

Yesterday (10-July-2020) an earthquake swarm took place in Herðurbreiðartögl mountains. There is no known volcano in this area and the source of this earthquake swarm is most likely an tectonic stresses in this area. The largest earthquake had a magnitude Mw3,2 (14:15 UTC) and Mw3,1 (17:47 UTC). This earthquake swarm is still ongoing but there aren’t many earthquakes happening at the writing of this article.


The earthquakes swarm in Herðubreiðartögl area. Copyright of this image belongs to Icelandic Met Office.

The mountains in this area where created in eruptions during last glacier period around 12.000 years ago or earlier.

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Earthquake swarm in Reykjanes volcano close to Grindavík town

Yesterday (9-July-2020) an earthquake swarm took place north-east of Grindavík town in the Reykjanes volcano. Largest earthquake in this swarm had a magnitude of Mw3,3 and the reason for this earthquake swarm was a magma injection at 4 to 6 km depth into a sill that is forming north-east of Grindavík town, close to what seems to be a old fissure in that area.


The earthquake swarm in the Reykjanes volcano yesterday. Copyright of this image belongs to Icelandic Met Office.

There is a chance that the magma that is pushing this activity might be as shallow as 3 km but currently it is difficult to know for sure but deformation that can be monitored by GPS data is going to give more clear picture in next few days. Currently there doesn’t seems to be enough magma in the higher level of the crust to start and eruption or the magma is blocked by some other unknown factors in the crust.

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Magnitude Mw4,2 earthquake in Tjörnes Fracture Zone yesterday (8-July-2020)

Yesterday (8-July-2020) at 17:41 UTC an magnitude Mw4,2 earthquake took place in the Tjörnes Fracture Zone. This earthquake was closer to land than other earthquakes and was felt over a wide area. The fault line that created this earthquake has almost north to south direction. The earthquake swarm that started on 19-June-2020 is ongoing but the amount of earthquakes that have been happening has dropped over the last few days to just around 300 earthquakes over 48 hour time period.


The current earthquake activity in Tjörnes Fracture Zone. Copyright of this image belongs to Icelandic Met Office.

The risk of a strong earthquake with magnitude Mw6,0 to Mw7,0 remains in the area and is going to do so for a while after this earthquake activity ends.

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Earthquake increase in Tjörnes Fracture Zone

Today (6-July-2020) was an earthquake with the magnitude of Mw3,5 at 18:35 UTC in Tjörnes Fracture Zone an earthquake with magnitude Mw3,2 took place at 15:40 UTC. It is possible that this earthquakes was felt. This earthquake swarm started on 19-June-2020 and has been going on for three weeks now.


Ongoing earthquake swarm in Tjörnes Fracture Zone. Copyright of this image belongs to Icelandic Met Office.

There continues to be a risk for a earthquake with magnitude Mw6,0 to Mw7,2. There are no sign that this earthquake swarm is about to stop. It drops every hours to days before increasing again.

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Minor earthquake swarm in Katla volcano

During the night there was a minor earthquake swarm in Katla volcano. Largest earthquake in this swarm had a magnitude of Mw2,9 but all other earthquakes where smaller in magnitude.


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

There is nothing suggesting that an eruption is about to happen. The earthquake activity is far too low to suggesting that an eruption is about to happen. It is a question if a cauldron is about to empty it self in the Mýrdalsjökull glacier as such events happen in the summer. It is often followed by small amount of earthquake activity before and after a glacier flood happen.

Data from 2010 to 2017 suggest that there is a steady increase in earthquake activity before an eruption happens. There was a small eruption in Katla volcano (based on harmonic tremors) in July 2011 and again in July 2017 (article can be found here). In July 2017 an magnitude Mw4,5 earthquake took place without an eruption happening. Article on that can be found here.

Katla volcano has been real quiet in 2020 and there are no signs of that is about to change at the writing of this article. Best that can be done now as before is just keep monitoring what is going on in Katla volcano.

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I am going to be adding Google adsense to this website by August or September depending on how quickly I can get this website to Google approved levels (this requires adding GDPR approve message). This should bring me more stable income from traffic to this website. There is however no guarantee that my website gest approved by Google Adsense after I apply and that is just because how this works.

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Update five on the earthquake swarm in Tjörnes Fracture Zone (TFZ)

This is the last update on the earthquake swarm activity until something more happens in Tjörnes Fracture Zone.

Current earthquake activity is getting smaller at the writing of this article and few earthquakes over magnitude Mw3,0 are happening now. Over the last 48 hours only 5 earthquakes have reached magnitude Mw3,0 and larger and only around 650 earthquakes have happened in the last 48 hours. Largest of this earthquakes had a magnitude of Mw4,1 today at 04:52 UTC.


The earthquake activity on the Tjörnes Fracture Zone. Copyright of this image belongs to Icelandic Met Office.

The risk of magnitude Mw7,0 to Mw7,4 earthquake remains in Tjörnes Fracture Zone after this activity and there is still a warning in place for it. The fault that moved on Sunday 21st June in the Mw6,0 (USGS/EMSC. IMO reports MW5,8) earthquake seems to have been 20km to 30km long based on the earthquake activity along the fault rupture in north-south direction about 33 km west-south-west of Grímsey island. At the writing of this article there have been over 7000 earthquakes been detected by Icelandic Met Office.

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Update four of the earthquake swarm in Tjörnes Fracture Zone (TFZ)

This is a short update on the earthquake swarm in Tjörnes Fracture Zone. The earthquake swarm continues but most earthquakes are smaller now and not many earthquakes with magnitude above Mw3,0 has happened. At the writing of this article around 1000 earthquakes have happened over the last 48 hours. Warning is still in place for the risk of Mw7,0 earthquake.


Current earthquake swarm in Tjörnes Fracture Zone (TFZ). Copyright of this image belongs to Icelandic Met Office.

Earthquake activity suggests that most north-western part of the Flatey – Húsavík fault line has now become active (small earthquakes along the fault). In the year 1755 it is estimated that fault had a magnitude Mw7,0 or stronger earthquake. Then a earthquake with a unknown magnitude happened in this area in the year 1260.

Other than this there has been little chance in activity in the western part of Tjörnes Fracture Zone since last article about this activity.

Science papers and information Tjörnes Fracture Zone

Earthquakes in North Iceland (Icelandic/English, pdf)
Jarðskjálftavirkni á Norðurlandi (Icelandic, summary in English, pdf)

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