TFZ – Page 14 – Iceland geology

April 10, 2013

Less earthquake activity in Tjörnes Fracture Zone

Yesterday (09.April 2013) there has been less activity in Tjörnes Fracture Zone. The largest earthquakes yesterday did have the magnitude 4.0 and 3.3. A smaller earthquake with the magnitude 3.1 also took place. Many other smaller earthquakes also took place as is normal for this type of earthquake swarm. There are no signs of any volcano activity in the area during this earthquake activity.

Earthquake activity in Tjörnes Fracture Zone during the past 48 hours. Copyright of this image belongs to Icelandic Meteorological Office.

This earthquake swarm does not appear to be over. Even if it has slowed down from its peak one week ago following the magnitude 5.5 earthquake. This type of slowdown are common in this type of earthquake swarms. In many cases the activity stops altogether and starts again after some time. I now believe that current earthquake swarm is connected (not sure how yet) to the earthquake swarm that took place in TFZ in October 2012 and started view few smaller earthquakes and had one magnitude 5.6 earthquake. For now however the earthquake activity is dropping. But it is impossible to know for sure what happens next in TFZ area.

April 6, 2013

Update on the TFZ earthquake swarm at 01:01 UTC

This is a short update on the earthquake swarm in TFZ. This is going to be a long earthquake swarm from the looks of it (currently).

The earthquake swarm in TFZ continues as it has been doing for the past six days now. The strongest earthquakes for the past 24 hours have had the magnitude 3.5, 3.6 and now 3.3 (automatic magnitude). This is a extremely complex earthquake swarm. Over a period of 48 hours there have been around 368 earthquakes. That is a drop in activity, but in the first few hours after the magnitude 5.5 earthquake in TFZ there where recorded over 500 earthquakes.

Earthquake activity in TFZ for the past 48 hours. Copyright of this image belongs to Icelandic Meteorological Office.

The trace plot that shows the earthquake activity for the past 48 hours in TFZ. Copyright of this image belongs to Icelandic Meteorological Office.

This earthquake swarm is complex due to three factors. There is a both slip fault and normal fault taking place there. There also appears to be a volcano in the area. But it not properly understood and is extremely poorly studied. It is unclear at present time if this volcano is connected to this earthquakes swarms at present time. Since so little is known about it. It is also not known if the current earthquake swarm is going to start something in the volcano. The second volcano that is in this area last erupted in the year 1868 following an earthquake swarm in this area. Why that did happen is also not known. But it has a Global Volcanism profile here. The volcano that is closer to Grímsey Island is currently unnamed. There is also almost no studies or documentation on it. But from the little I did find

Please note that the earthquake swarm information is always changing so this information here do get outdated fast. This mostly applies the maps and number of earthquakes.

Scientific data on Tjörnes Fracture Zone

As I did say here above. The Tjörnes Fracture Zone is complex and that is making this earthquake swarm extremely complex as it is taking place.

The rift fault lines in TFZ. This is the simple version. It is from a science study that can be found here. Copyright of this image belongs to Icelandic Meteorological Office/Hjorleifur Sveinbjornsson.

More complex nature of the fault systems in TFZ. Copyright of this image belongs to Agust Gudmundsson. From study Infrastructure and evolution of ocean-ridge discontinuities in Iceland.

More complex image showing the fault lines in TFZ. Copyright Ragnar Stefansson, Gunnar B. Gudmundsson, Pall Halldorsson. From the study Tjörnes fracture zone. New and old seismic evidences for the link between the North Iceland rift zone and the Mid-Atlantic ridge.

The most detailed picture that I was able to find of Tjörnes Fracture Zone and the ocean floor. Copyright of this image belongs to many people. Please see the list of copyright holders in the following link. From the study First observations of high-temperature submarine hydrothermal vents and massive anhydrite deposits off the north coast of Iceland.

It is clearly worth watching this earthquake activity. Since it might have interesting effects on the volcano where this earthquake activity is taking place. Even on the second volcano just north of Þeystareykjabunga volcano.

April 3, 2013April 4, 2013

Update on the TFZ earthquake swarm at 18:31 UTC

This is a short update on the TFZ earthquake swarm. There is no point in making a long update about what is taking place in TFZ at the moment. Since information gets outdated quickly during this earthquake swarm.

About 775 earthquakes have been recorded by Icelandic Meteorological Office since this earthquake swarm started on 2. April 2013 (about 48 hour period). This number is going to be outdated soon or already is outdated by the time this blog post gets published. Since there are about 40 – 60 earthquakes every 1 hour currently. The earthquake swarm however drops regularly in terms of activity. Over 80 magnitude 3.0 earthquakes have been recorded so far. This number is going to increase if this earthquake swarm continues as it has been doing for the past 48 hour period.

The earthquake activity in TFZ. The green stars show the earthquakes with larger magnitudes then 3.0. There is a second fault that has gone active since the earthquake activity started yesterday (02.04.2013). Copyright of this image belongs to Icelandic Meteorological Office.

As can be seen here. The earthquake swarm has been really powerful at times. Copyright of this image belongs to Icelandic Meteorological Office.

This earthquake swarm is the largest one in the area for long time now. At the moment there are no sign about that this earthquake swarm is about to end any time soon.

Map showing the largest earthquakes in this swarm. Copyright of this image belongs to Icelandic Meteorological Office.

Earthquake activity as it appears on Grímsey SIL station. Copyright of this image belongs to Icelandic Meteorological Office.

Earthquake activity as it appears on Skrokkalda SIL station. Copyright of this image belongs to Icelandic Meteorological Office.

Reviewed area of earthquake activity on TFZ. This map does not show the current earthquakes. It is few hours old also. Copyright of this image belongs to Icelandic Meteorological Office.

This earthquake swarm is complex and might last for a long time. There is a continued risk of a large earthquake in this area. But there has not been a earthquake larger then magnitude in this part of TFZ since 1910 at least. So this area has a lot of build up stress. Since there has not been a strong earthquake there for a long time. But the magnitude 5.5 earthquake and the following aftershocks have just released tiny amount of the stress that has build up in this area.

Map showing historical earthquake activity in TFZ. The image is from here. Copyright of this image belongs to Gunnar B. Gudmundsson, Pall Halldorsson, Ragnar Stefansson and other connected people.

For the moment. It is just best to keep watching the activity that is taking place in TFZ. It is impossible to know for sure what happens in TFZ during the next few hours to days.

Other news about this in Icelandic.

Um jarðskjálftana austur af Grímsey (IMO, Icelandic)
Jarðskjálftahrinan við Grímsey heldur áfram (IMO, Icelandic)

Update 1: Here is a focal depth of the earthquakes for the past 15 days.

This is the focal depth and number of earthquakes for the past 15 days in north Iceland. This might not show all earthquakes that have happened in this area. Copyright of this image belongs to Icelandic Meteorological Office.

Blog post is updated at 21:17 UTC.

April 2, 2013April 2, 2013

Information on the magnitude 5.5 earthquake in TFZ

This is a short blog post about the earthquake swarm in Tjörnes Fraction Zone.

The largest earthquake so far is a magnitude 5.5. The largest aftershocks so far are magnitude 4.4 that took place at 01:14 UTC and 4.7 that took place at 08:55 UTC this morning. This earthquake swarm is taking place on a complex fault area that is highly active. There is also big question what effect this earthquake swarm is going to have on other faults in the area. There is a risk that this earthquake swarm is going to start other earthquake swarms in nearby faults. Uncertainty level has been declared for area from Sauðárkrókur to Raufarhöfn at least. This is the largest earthquake in this area since the year 2002 and 2005. But both this years there was a magnitude 5.0 earthquakes in this area.

The earthquake activity in TFZ. Green stars are earthquakes that are larger then magnitude 3.0. Copyright of this image belongs to Icelandic Meteorological Office.

This trace shows how dense this earthquake swarm has been. Copyright of this image belongs to Icelandic Meteorological Office.

The earthquake is appearing clearly on my geophone network. This is Böðvarshólar geophone station. This image is released under Creative Commons licence. Please see the CC Licence page for more details.

The largest earthquakes as they did appear on Heklubyggð geophone station. This image is released under Creative Commons licence. Please see the CC Licence page for more details.

There have been over 500 earthquake recorded since this earthquake swarm did start. It is impossible to know for sure when this earthquake swarm is going to stop, or if it is going to pick up again. But the earthquake swarm is already starting to shown signs of dropping activity. But that might change again if there is new larger earthquake in this area, or swarm of larger earthquake.

I am going to post update of anything major happens in this earthquake swarm. It is possible to monitor the current status of this earthquake swarm here on my geophone web page.

Blog post updated at 15:23 UTC on 02.04.2013.
Blog post updated at 16:14 UTC on 02.04.2013.
Blog post updated at 16:26 UTC on 02.04.2013.

April 2, 2013

Image of the TFZ earthquake

Here are the images of the earthquake that took place at 01:00 UTC in TFZ. I do not have correct magnitude for this earthquakes yet. So it is missing at the moment.

The earthquake at Böðvarshólar geophone station. This image is relased under Creative Common licence. Please see the CC Licence page for more details.

The earthquake at Heklubyggð geophone station. This image is relased under Creative Common licence. Please see the CC Licence page for more details.

April 2, 2013April 2, 2013

Large earthquake in TFZ

Few moments ago a large earthquake did hit TFZ. Details pending. Webicorders show this earthquake clearly here. Details are pending. I am going to post them soon as I can do so.

March 31, 2013

Earthquake swarm east of Grímsey island (TFZ)

Today at 05:25 UTC a earthquake swarm started east of Grímsey island. But this island is located in the Tjörnes Fracture Zone. The largest earthquake today is a magnitude 2.8. No larger earthquakes have taken place so far.

Earthquake swarm in TFZ today. Copyright of this image belongs to Icelandic Meteorological Office.

Earthquake activity is common in this area of Iceland so this is nothing unusual. This earthquake swarm is not connected to any volcano activity that I know of. If anything major happens. I am going to write a blog post about it soon as I can do so.

March 10, 2013

Earthquake swarm in TFZ

During the night an earthquake swarm started in TFZ. The first earthquake had the magnitude of Mw3.8 according Icelandic Meteorological Office. This earthquake was felt clearly in the area it has been reported. Above 20 aftershocks have been recorded in this area following this earthquake.

Location of the magnitude 3.8 earthquake in TFZ. Copyright of this image belongs to Icelandic Meteorological Office.

Trace of the earthquake activity. Copyright of this image belongs to Icelandic Meteorological Office.

This earthquake was well detected on my geophone in north Iceland. This image is released under CC Licence. Please see CC Licence page for more details.

It is possible to watch this earthquake activity on my geophone network page here. At the moment the earthquake activity has stopped. It is impossible to know if it is going to start again in this area or not. But this area is normally highly active in terms of earthquake activity during the year. So earthquakes swarms like this are not uncommon.

February 28, 2013February 28, 2013

Earthquake swarm east of Grímsey (TFZ) and in Grímsfjall volcano fissure swarm

Currently there is a minor earthquake swarm east of Grímsey Island in the Tjörnes Fracture Zone. So far the largest earthquake has had the magnitude of 2.9 according to Icelandic Meteorological Office reviewed earthquake overview. Earthquake swarms are common in this area of TFZ.

Earthquake activity in TFZ today. Copyright of this image belongs to Icelandic Meteorological Office.

Grímsfjall and Hamarinn volcanoes

Some internesting earthquake activity is now taking place in Grímsfjall volcano (outside the main volcano). This earthquake activity is in the fissure swarm that extents away from Grímsfjall volcano in the direction of Katla volcano fissure swarm. There has also been interesting earthquake activity taking place in Hamarinn volcano (no GVP page). But Hamarinn volcano last had a minor eruption in July of the year 2011. So far nothing suggests anything of volcanic nature is about to take place.

Earthquake activity in Grímsfjall volcano system today. Along with earthquake activity in Hamarinn volcano. Copyright of this image belongs to Icelandic Meteorological Office.

At the moment it appears that nothing besides earthquakes is going to take place in Grímsfjall volcano. But it hard to be sure given how often Grímsfjall volcano erupts. I do not yet have enough data on what is happening in Hamarinn volcano to say what is taking place there. So for now. It must just be observed.

January 30, 2013

Magnitude 3.2 earthquake in TFZ

At 04:03 UTC on 29.01.2013 an magnitude 3.2 earthquake did happen at TFZ. This earthquake was not felt according to news on this earthquake. Several aftershocks where detected following this magnitude 3.2 earthquake.

The magnitude 3.2 earthquake in TFZ. Along with aftershocks in the same area. Copyright of this image belongs to Icelandic Meteorological Office.

There is a lot of tension in TFZ. But this earthquake swarm does not mean it is ready to break yet. When that happens is impossible to know at this time. Earthquake detection is difficult in Iceland at the moment due to bad weather and strong winds.

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