Earthquakes – Page 121 – Iceland geology

April 27, 2013June 17, 2013

Earthquake activity in Hekla, Katla, Krísuvík and Bárðarbunga volcanoes

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Hekla and Katla volcanoes

I am going to write about both this volcanoes here. Since I am going to be using the same image anyway for both volcanoes.

Yesterday (26.04.2013) there was a magnitude 1.1 earthquake in Hekla voclano. This earthquake was in the same area that triggered uncertainty level to be declared just before Easters in March. It was later cancelled when nothing more happened.

Earthquake in Hekla volcano. Also on this picture earthquake activity in Katla volcano (read more below). Copyright of this picture belongs to Icelandic Meteorological Office.

Katla volcano has been having some earthquake activity in past days. So far it has just been minor earthquakes and nothing more. But it has been taking place where a minor eruption took place in Katla volcano during the summer of 2011. That minor eruption created a minor glacier flood. But it did destroy a bridge and closed down the ring road (road 1) in this part of Iceland.

While this activity is currently nothing to worry about. It is worth keeping a eye on it. Just in case it increases, or if some other changes start to take place in Katla volcano.

Krísuvík volcano

A minor earthquake swarm took place in Krísuvík volcano today (27.04.2013). The largest earthquake had the magnitude of 1.9. The depth of this earthquakes was around 8.6 km. Activity in this area is normal and there does not seem anything strange about it. But Krísuvík volcano has been having periods of inflation and deflation for the past three years. Earthquake activity increases when Krísuvík volcano is in period of inflation. If that is the case now I do not know.

Earthquake activity in Krísuvík volcano. Copyright of this picture belongs to Icelandic Meteorological Office.

Bárðarbunga volcano

A minor earthquake swarm took place in Bárðarbunga volcano today. Largest earthquake in this swarm had the magnitude of 1.3. Depth range was from 18.8 km and up to 11.1 km. This earthquake swarm is important. Since it appears that this is a dike intrusion in Bárðarbunga volcano. But a minor dike intrusion also took place in this area few weeks ago. That also resulted in a minor earthquake swarm in this same area.

Earthquake activity in Bárðarbunga volcano. Most likely due to minor dike intrusion into the volcano. Copyright of this picture belongs to Icelandic Meteorological Office.

A minor dike intrusions into a volcano does not mean a eruption is going to take place. In many Icelandic volcanoes (and around the world also) dike intrusions into the volcanoes are common event and in most cases do not result in any eruptions. But it is worth keep a watch out for this type of eruptions. Since it might signal a more active period ahead in Bárðarbunga volcano. But it might also just equally don’t mean anything. There is no way to know for sure.

Other then this activity. It has been rather quiet in Iceland at the moment. No larger earthquakes have been taking place in the past two weeks since activity slowed down in Tjörnes Fracture Zone.

Blog post updated at 22:32 UTC on 27.04.2013.
Blog post updated at 22:53 UTC on 27.04.2013.

April 24, 2013April 24, 2013

Earthquake activity in Hekla, Askja volcanoes and TFZ

Before I start. I want to remind people that donations are import to me. Since they help me keeping this blog and my earthquake web page up and running.

Hekla volcano earthquake activity

A minor earthquake activity took place in Hekla volcano yesterday. None of the earthquake was larger then ML1.2. The depth of this earthquake activity was around 8.4 km. This earthquake activity took place outside the main volcano. But was in the connected fissure swarms that extends from Hekla volcano.

Earthquake activity in Hekla volcano system. The earthquakes are the orange dots just south-west of Hekla volcano. Copyright of this image belongs to Icelandic Meteorological Office.

Earthquakes have been taking place in this area for few years now. I do not know what they mean. This might just be a earthquake activity and nothing else. Uncertainty level has been canceled for few weeks now due to lack of any more activity in the main Hekla volcano.

Askja volcano

There has been minor earthquake activity in Askja volcano this past weeks. All of the earthquakes have been smaller then magnitude 1.5. Depth of this earthquakes is around 18 to 22 km. Suggesting that current earthquake activity has its source in magma movements rather then tectonic earthquakes.

Earthquakes in Askja volcano. Askja volcano is the volcano north-east of Vatnajökull glacier. Copyright of this image belongs to Icelandic Meteorological Office.

Tjörnes Fracture Zone

Activity in Tjörnes Fracture Zone has slowed down since 2. April when a large earthquake swarm started in it. But earthquake activity remains as is. Even if the earthquakes are smaller and fewer. This means the earthquake activity has been continuous for the past three weeks.

Earthquake activity in Tjörnes Fracture Zone. It remains in two areas as of now. New activity has also been taking place. Copyright of this image belongs to Icelandic Meteorological Office.

It is difficult to know for sure what happens next in TFZ. But tension in it remains as before and so does the risk for larger earthquake in this area. For the moment however, it remains rather quiet. When that might change is impossible to know for sure.

Blog post updated at 18:16 UTC on 24.04.2013.

April 13, 2013April 13, 2013

Earthquake swarm north of Kolbeinsey island

Around 11:00 UTC a earthquake swarm started just north of Kolbeinsey island. This earthquake swarm looks rather powerful. But due to distance from land only the largest earthquakes are appearing on the SIL network and on my geophone at Böðvarshólar. I am estimating the largest earthquakes having the magnitude of 4.0+. But that has not been confirmed yet. Last known eruption in Kolbeinsey island volcano took place in the year 1755. A dike intrusion or a volcano eruption took place north (100 km) of current location back in the year 1999. Last eruption before the eruption in the year 1755 took place around the year 1372.

The earthquake activity in Kolbeinsey island. It is marked by the green stars on this map. Copyright of this image belongs to Icelandic Meteorological Office.

The earthquake activity as it has been appearing on my geophone at Böðvarshólar. This image is under Creative Commons Licence. See CC licence page for more details.

No signs of eruption have appeared so far. If they do. They are going to appear on the SIL network. I am not sure if my geophone is going to pick them up due to the distance (around 300 km). There is a chance of more earthquake activity to take place in this area in the next few hours to days. I do not know if this activity is connected to what has been taking place in other parts of Tjörnes Fracture Zone. The smaller earthquakes that are taking place in Kolbeinsey island are not being detected by the SIL network or by my geophone.

It is possible to view the earthquake activity here, on my webicorder web page.

Blog post updated at 19:35 UTC on 13.04.2013.

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 6, 2013April 6, 2013

Minor dike intrusion in Bárðarbunga volcano

Today (05.04.2013) a minor earthquake swarm took place in Bárðarbunga volcano. The depth of this earthquakes was around 18 – 26 km. Meaning this is magma, rather then tectonic creating this earthquakes. None of this earthquakes had magnitude above 1.0.

Earthquakes in Bárðarbunga volcano. They are the orange dots. Copyright of this image belongs to Icelandic Meteorological Office.

Dike intrusions happens sometimes in Bárðarbunga volcano without it meaning there is a eruption going to take place soon it. This appears to be one of those cases.

April 6, 2013April 6, 2013

Magnitude 3.6 earthquake in Hamarinn volcano

Last night (05.04.2013) at 01:50 UTC a magnitude 3.6 earthquake took place in Hamarinn volcano (no GVP profile yet!). This earthquake had the depth of 2.1 km. This seems to be a dike intrusion taking place in Hamarinn volcano. No clear signs of harmonic tremor have been detected based on tremor data from Icelandic Meteorological Office.

The Hamarinn volcano is where the green star is. But that is the location of the magnitude 3.6 earthquake that took place last night. Copyright of this image belongs to Icelandic Meteorological Office.

Harmonic tremor plot do not show any harmonic tremor pulse. The signal on this harmonic tremor plot is the earthquake swarm in TFZ for most parts. Copyright of this image belongs to Icelandic Meteorological Office.

This earthquake activity is due to minor dike intrusion. Rather then something else. It is not clear if this activity is just normal activity for Hamarinn volcano or signal about something else is about take place. But as before. Hamarinn volcano remains mostly quiet for the moment.

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.

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