Iceland geology

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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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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This is a short update about the Mw5,8 (USGS/EMSC have magnitude Mw6,0) earthquake in Tjörnes Fracture Zone (TFZ) that happened yesterday (21-June-2020) at 19:07 UTC. The Mw5,8 earthquake that happened yesterday was further out in the ocean and that resulted in the earthquake being less felt than if it would have been closer to populated areas. Currently there is a risk of Mw7,0 earthquake in this area according to Icelandic Met Office. It is not possible to know when such a earthquake might happen.

The activity is now along all of Eyjafjarðaráll rift valley. Copyright of this image belongs to Icelandic Met Office.

Earthquake activity remains dense. Copyright of this image belongs to Icelandic Met Office.

If a large earthquake happens I’ll try and publish update soon as possible.

Icelandic Met Office has put up an English article. It can be read below.

A strong earthquake swarm offshore North Iceland (vedur.is).

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I am waiting on the technical details of the earthquake that happened at 19:06 UTC on 21-June-2020. Those are going to be in a article tomorrow. This article is about pictures of the earthquake that I managed to get as it was happening. There is clearly something going because this trace was different from the Mw5,2 and Mw5,6 earthquake that happened earlier.

The earthquake as it happened.

The earthquake as it happened.

The earthquake as it happened.

The earthquake as it happened.

The earthquake on my Hvammstangi 1 station in greater details.

The earthquake on my Hvammstangi 2 station in greater details.

There is real high activity in TFZ currently and over 100 magnitude Mw3,0 earthquakes have happened. Copyright of this image belongs to Icelandic Met Office.

There is real high activity in TFZ currently and over 100 magnitude Mw3,0 earthquakes have happened. Copyright of this image belongs to Icelandic Met Office.

I have a working day tomorrow from 08:00 to 16:00 and that limits my ability to post updates on social media if anything major happens until after 16:00. This earthquake activity is far from over.

Yesterday (20-June-2020) at 19:26 UTC a magnitude Mw5,6 earthquake took place on the Tjörnes Fracture Zone. This earthquake was felt over a wide area and all the way to Kópavogur in south Iceland and all the way to Ísafjörður in west Iceland. Where I am located this earthquake was clearly felt but due to distance no damage happened. This earthquake created a lot of rock slides and possible landslides There is now a warning about being close and in mountains if a large earthquakes happens for this reason. In the Flatey fault there is now a risk of a large earthquake with magnitude up to Mw7,1 since there has not been a earthquake of that size since 1755 in that area. At the writing of this article there have been 72 earthquakes with magnitude larger than Mw3,0. Over 2000 earthquakes have been recorded since Friday 19-June-2020 when this earthquake swarm started. Activity happens in strong swarms with a drop in between. At the writing of this article there seems to be a low in the earthquake activity. Last large earthquake in Tjörnes Fracture Zone took place in eastern part of it in 1976 and last strong earthquake in the western part of Tjörnes Fracture Zone was in 1963.

Earthquake activity remains strong even if there is a minor drop in activity when this article is written. Copyright of this image belongs to Icelandic Met Office.

The earthquake activity remains dense as can be seen here. Copyright of this image belongs to Icelandic Met Office.

The magnitude Mw5,6 earthquake as it aooeared on my geophone (Hvammstangi 1).

The magnitude Mw5,6 earthquake as it appeared on my geophone (Hvammstangi 2).

The Mw5,6 earthquake as it appeared on my live computer that I use to monitor earthquakes.

It is impossible to know how this earthquake swarm is going to evolve and change over the next few hours but the risk of a larger earthquakes remains high for now and that won’t change until this earthquake swarm ends if a larger earthquake doesn’t happen in the earthquake swarm that is now ongoing.

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Today (20-June-2020) at 15:05 a magnitude Mw5,2 earthquake took place on Tjörnes Fracture Zone (TFZ). Information in this article is going to go outdated quickly.

Earthquake activity in the Tjörnes Fracture Zone. Copyright of this image belongs to Icelandic Met Office.

The earthquake activity is dense and there is a lot of earthquakes happening every minute. Copyright of this image belongs to Icelandic Met Office.

The earthquake as recorded by my geophone (Hvammstangi 2).

The earthquake as recorded by my geophone (Hvammstangi 1).

The earthquake as it appeared in the program I use to monitor earthquakes.

According to the news rock fall happened in mountains when the largest earthquake took place. There is also a risk of stronger earthquake due this earthquake swarm location according to Icelandic Met Office. If a stronger earthquake happens the risk of rock fall is high.

Yesterday (19-June-2020) a strong earthquake swarm started off Gjögurtá in the Tjörnes Fracture Zone. This are tectonic earthquakes and not connected to any known volcano. The area that is having this earthquakes might be a rift valley and that in it self is interesting. The rift valley seems to be connected to Kolbeinsey island and a volcano to the north. The rift valley is also connected to a slip-strike fault (Flatey fault) that is in this area and is connected to Flatey island to the east. That fault line is a transform fault according to Icelandic Met Office. This earthquake swarm is not over even if there is a bit of a quiet period in it now. Largest earthquake at the writing of this article had a magnitude of Mw3,8 at 03:47 UTC. More than 400 earthquakes have happened according to Icelandic Met Office.

The earthquake swarm as it was at 13:00 UTC. Copyright of this image belongs to Icelandic Met Office.

Reviewed earthquakes in this earthquake swarm. Larger circles means larger earthquake. Copyright of this image belongs to Icelandic Met Office.

Earthquake swarms in this area known to go on for several weeks. This earthquake swarm might go on for a while even if it drops down in activity every few hours.

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