Monitoring – Page 131 – Iceland geology

September 18, 2012

Earthquake swarm between in Denmark and Sweden

Today (18.09.2012) at small earthquake swarm started in northern Denanmark, with the fault line extending upwards Sweden. The reason for earthquakes in this area is old fault lines. Along with the fact the Alps pressure the crust in Denmark (from what I did read long time ago). There is also glacier rebound taking place in Denmark and Sweden, along with Norway and Finland. The largest earthquakes in this swarm have had magnitude of ML2.4 and ML2.3. Both with depth of 1 km. But that might also be subject to change.

The area of the earthquake swarm. Some earthquakes might not have correct location. Copyright of this image belongs to EMSC.

The ML2.4 earthquake that took place at 16:30 UTC. Copyright of this image belongs to EMSC.

The ML2.3 earthquake that took place at 17:04 UTC. Copyright of this image belongs to EMSC.

The last earthquake that took place in this area was at 17:04 UTC. Since then no new earthquake have taken place. There might be some earthquakes later. But I find it unlikely to happen. But it hard to know for sure. But this is continental crust. So it moves slowly, when it moves at all in when it comes to earthquakes or other such changes. More earthquakes from this earthquake swarm can be found on EMSC web site.

September 17, 2012

Earthquakes in Tindafjallajökull volcano

One of the most quiet volcanoes in Iceland had earthquake swarm today (17.09.2012). I am not aware of any major earthquake activity in Tindafjallajökull volcano during the past 20 years. I am not sure that if there has been any earthquake activity in Tindafjallajökull volcano during this time. One off-earthquake might have happened once in a while. As they do with every volcano in Iceland from time to time. It is unclear why this earthquake swarm took place. But this might be due to stress changes in the area. Rather then anything volcanic taking place in Tindafjallajökull volcano.

Activity in Tindafjallajökull volcano. Copyright of this image belongs to Icelandic Meteorological Office.

The largest earthquake in this swarm had the magnitude of 1.1. The depth of this earthquake swarm was from 10.7 km and up to 3.1 km. This earthquake swarm appears to be over by now.

Katla volcano

The image above also shows earthquake activity in Katla volcano. This earthquake activity is well below what did happen in May to end of July this summer (2012) in Katla volcano. Currently the activity in Katla volcano is low and has been so for many weeks now. I am not expecting that change without some increase in smaller earthquakes first. For the moment, everything is quiet in Katla volcano.

September 17, 2012September 17, 2012

Constant earthquake activity in El Hierro voclano

On the 14. September 2012 an earthquake swarm started in El Hierro volcano, Canary Islands, Spain. The earthquake swarm is currently ongoing and there have been more then 300 earthquakes already. The earthquake activity is more or less constant at the moment. Since yesterday (16.09.2012) had around 182 earthquakes have taken place during the past 24 hour period (when this is written). The depth of this earthquakes is around 18 to 28 km. But this suggests an new magma intrusion into El Hierro volcano, or at least that magma is on the move inside El Hierro volcano from older sill inside it.

Start of the earthquake activity in El Hierro volcano. Copyright of this image belongs to IGN.

The earthquake activity on 15.09.2012. There is also an harmonic tremor pulse in this image. The first harmonic tremor pulse starts at 09:00 and lasts until 09:25 UTC. The second harmonic tremor pulse starts at 18:50 and lasts until 19:25 UTC. Copyright of this image belongs to IGN.

The earthquake activity yesterday (16.09.2012) until 21:14 UTC when this image was saved. No harmonic tremor pulses can be seen on this image. But earthquakes appear clearly on this image. Copyright of this image belongs to IGN.

This magma that is being injected into El Hierro volcano now is unlikely to erupted. But there is an pocket of magma located North of the El Hierro Island that might erupt. That magma pocket is only located about 10 km from the top of crust. In the start of the current that area was making earthquakes. But it soon did go silent. Why that I do not know.

The current area of activity in El Hierro volcano. As can be seen it is mostly located at great depth. But the pocket of magma that is located at 10 km depth north in El Hierro volcano might be reason to worry about. This image shows the activity over the past 4 days. Copyright of this image belongs to IGN.

The area that I worry about is marked by blue dots in the image above.

The current activity over the past 36 hours in El Hierro volcano. This image clearly shows where most of the activity has been taking place during this time period. Copyright of this image belongs to IGN.

Earthquake data for the past 1 year in El Hierro volcano. Copyright of this image belongs to IGN.

It is only when we get the earthquake data for past 1 year when things get really interesting. Based on this data. Magma is now already at the depth of around 10 km in El Hierro volcano. Why it has not erupted is hard to answer (the answer might come after an eruption takes place. But no sooner). There are even clues in this image that some of the magma might be as shallow as 5 km. But it is hard to see it for sure. This image also suggest that amount of magma in El Hierro volcano, in the forms of magma sill is a lot more then what did erupt last year in El Hierro volcano. The tube that is feeding this magma into El Hierro volcano appears to be located at 18.05 longitude. That tube is marked by earthquakes going down well below 28 km depth.

The current earthquake activity in El Hierro volcano is creating new magma sill inside the volcano. That is just storing magma for possible future eruptions. The activity so far has been bit stronger in terms of amount of earthquakes since last earthquake swarm in June and July 2012. But that earthquake swarm did top at around 172 earthquakes during 24 hour period. So the current earthquake swarm is larger in that regard. But so far no earthquake has been larger then magnitude 3.2. But that might change if any larger earthquake happens. As often is the case.

It is hard to say what happens next in El Hierro volcano. But I would guess that once eruption starts in El Hierro volcano it might last for months. Based on the amount of magma that seems to have build up inside the volcano during the past few months. That build-up phase however does not seems to be completed at the moment. How long it is going to last is impossible to say at current time. But this is something that is worth keeping an watch for. El Hierro volcano is going to erupt basalt if the eruption is on land. Older volcano cones are not going erupt again. At least that is my assessment of what I have seen with satellite pictures.

September 17, 2012September 17, 2012

Earthquake swarm on Reykjanes Ridge last night (16.09.2012)

Last night there was an earthquake swarm on Reykjanes Ridge. Possibly on one of the volcanoes that are in this area of Iceland. The earthquake swarm lasted for several hours. Strongest earthquakes in this swarm had the magnitude of 3.5. With the depth from 23 km and up to 0.3 km. Strongest earthquakes in this swarm where visible on my geophone network.

The earthquake swarm on the Reykjanes Ridge. Copyright of this image belongs to Icelandic Meteorological Office.

Last earthquake swarm in this area was on 8. February 2012. There was also earthquake activity deep on the Reykjanes Ridge. With two earthquakes that did get the magnitude 4.4 (EMSC) at 12:51 UTC. The second earthquake took place at 14:30 UTC and had the magnitude of 4.4 (EMSC). This earthquake activity is far enough from land that only the largest earthquakes are detected.

But there seems to be a lot of earthquake activity both south and north of Iceland (Jan Mayen earthquake activity). But this not connected activity as such. But it is known that activity on Reykjanes Ridge happens in jumps. It is an question if such time has come that an new activity episode is about to start on the Reykjanes Ridge. But last major episode in activity on the Reykjanes Ridge ended about 671 years ago. But there is one eruption documented off the coast in the year 1926 according to Global Volcanism Program. That activity did last for 4 days or so.

I am not sure what is going to happen next on the Reykjanes Ridge. But I am going to report it best to my ability. With the best information that I can get when the time comes.

Icelandic news about this earthquake activity

34 skjálftar frá miðnætti (mbl.is, Icelandic)

Blog post updated at 02:47 UTC on 17.09.2012

September 14, 2012

Continued earthquake activity on Kolbeinsey Island ridge

In the past few days there has been considerable earthquake activity in Kolbeinsey Island ridge. Many of the earthquakes have been reaching the magnitude of at least 3.0. But some of it might be underestimation. As this earthquake activity is taking place far off Iceland coastline and far away from the SIL network. But that makes detection of earthquakes more difficult. Along with effects of weather and ocean waves that often prevent detection of smaller earthquakes in this area.

The location of the earthquake activity in Kolbeinsey Island ridge. Copyright of this image belongs to Icelandic Meteorological Office.

This is not the only activity in this area in the past few weeks. But the largest earthquake in this area was an magnitude 4.4 to 4.6 few weeks ago. So the activity in this area seems to be connected to something major. It is an question if this is due to volcano eruption currently taking place in this area now. But with depth of up to 4 km. It is impossible to know that for sure without actually going there on an ship. But given current weather. That is not going to happen any time soon. Maybe not for several years in fact.

September 12, 2012

Deep earthquake in Eyjafjallajökull volcano

On 11.09.2012 at 10:24 UTC there was an deep earthquake in Eyjafjallajökull volcano. The magnitude of this earthquake was 0.8. It had the depth of 14.9 km. But that is among the deepest that happens in Eyjafjallajökull volcano. But before and during the eruption of Eyjafjallajökull volcano in the year 2010 the most depth of earthquake detected at that time was around 30 km.

The earthquake in Eyjafjallajökull volcano. Copyright of this image belongs to Icelandic Meteorological Office.

I do not expect this earthquake to mean anything. This is just single earthquake that now happen from time to time in Eyjafjallajökull volcano. But after the eruption in the year 2010 there has almost been no earthquake activity in Eyjafjallajökull volcano.

Volcano ash from Eyjafjallajökull volcano

Even if there are now two years since the eruption in Eyjafjallajökull volcano the local area continues to have problems with volcano ash from it. In certain wind direction the volcano ash is blown up and carried out to the sea. This wind direction is mostly when wind is blowing from north and does not carry any snow or rain with it. So today and maybe in next few days. The local people that live in the area around Eyjafjallajökull volcano to live in ash cloud from the eruption two years ago.

I did try to find an MODIS picture of this volcano ash storm. But I did not have any luck doing so.

Icelandic news about this wind blown ash

„Stödd í öskubakkanum“ (DV.is)

September 7, 2012

Strong earthquake on Kolbeinsey Island ridge yesterday (06.09.2012)

Yesterday (06.09.2012) there was an earthquake about 200 km off Kolbeinsey Island. It was maybe on the Kolbeinsey Island or on SPAR fault zone in this area. I am not sure what is the actual case here. The earthquake had the magnitude of 4.4 and up to 4.7. Its magnitude has not yet been confirmed (EMSC web page can be found here). I do not know why that it. But this sometimes happen. This earthquake was not felt. But I did record it on my geophone network on two stations.

The location according to IMO. The second green star is an magnitude 3.6 earthquake in Jan Mayen. Copyright of this image belongs to Icelandic Meteorological Office.

The location according to EMSC. Copyright of this image belongs to EMSC.

This earthquake is one the strongest earthquakes that have been taking place in this area for the past few weeks. I do not know what is exactly happening in this area. This might be volcanic activity. But given depth of 2 km there. It is hard to know for sure. As any signs of eruption won’t appear on the surface of the ocean. Given that winter storm season has started in this area. Any sign of eruption are going to lost in the ocean waves. This area of the mid-Atlantic ridge might have more earthquakes in coming days to weeks.

September 2, 2012September 2, 2012

Harmonic tremor pulse activity maybe in Hamarinn volcano

Today (02.09.2012) a harmonic tremor pulse did start in Hamarinn volcano (best guess) (Bárðarbunga volcano). This harmonic tremor pulses are intermittent and normally last for up to 20 to 30 min., at the time. What is creating them is hard to say. But this might just be hydro-thermal activity taking place in Hamarinn volcano. This might also be magma on the move inside Hamarinn volcano. But nothing is confirmed so far. I do not expect anything to be confirmed any time soon.

The harmonic tremor pluses appear on the end of the traces on this image. They are bit hard to spot for the untrained eye. But they appear as higher then background noise change in the tremor plot image.

The harmonic tremor pulse as it appears on the SIL station at Grímsfjall volcano. This is high resolution image from this IMO web page. Copyright of image belongs to Icelandic Meteorological Office.

The harmonic tremor pulse at Skrokkalda SIL station. Copyright of image belongs to Icelandic Meteorological Office.

The harmonic tremor pulse at jok SIL station. Copyright of image belongs to Icelandic Meteorological Office.

Harmonic tremor pulse at dyn SIL station. Copyright of image belongs to Icelandic Meteorological Office.

It is impossible to know what this means exactly. But so far there are no signs of eruption in the area. This activity is less then activity in July 2011 that was created by an minor eruption in Hamarinn volcano. Stronger harmonic tremor pluses appear on SIL station at longer distance. But for now (when active) most of the activity only appears on SIL stations closest to the Vatnajökull glacier. I am going to continue to monitor the current situation. I will update or make a new blog post about what is going on if anything happens.

September 1, 2012

Magnitude 3.2 earthquake on the Reykjanes peninsula

Today (01.09.2012) at 16:33 UTC there was an earthquake with the magnitude of ML3.2. The depth was 7.6 km. Following this earthquake there was an swarm of smaller earthquakes following the first earthquake. None of those have been above magnitude 2.0. The earthquake took place in the Reykjanes volcano most likely. But it appears tectonic in nature. Rather then volcanic.

The magnitude ML3.2 earthquake on the Reykjanes peninsula. Copyright of this image belongs to Icelandic Meteorological Office.

It is hard to know for sure if this activity is going to continue. But since this earthquakes. Activity in this area has stopped. But it might resume at later time.

Icelandic news about this earthquake

Jarðskjálfti á Reykjanesskaga (Rúv.is)
3,2 stiga skjálfti við Grindavík (mbl.is)

August 31, 2012

Earthquake swarm on Kolbeinsey Ridge yesterday (30.08.2012)

Yesterday (30.08.2012) there was an earthquake swarm on Kolbeinsey Ridge. But earthquakes have been taking place there for several weeks already. This earthquake activity seems to be growing in number of earthquakes swarms taking place. In the year 1999 there might have been an dike intrusion or submarine eruption south of Spar Fracture Zone (more details here). Last earthquake swarm that was noticed by the SIL network was exacly two months ago (30.06.2012). My coverage of that can be found here. But it was not in the same place. But that earthquake swarm was south of Kolbeinsey Island, not north of it as was the case yesterday.

The earthquake area in question are the yellow dots north of Iceland on this map from IMO. Copyright of this image belongs to Icelandic Meteorological Office.

What happens next in this area in terms of earthquake activity, or possible volcano activity is hard to impossible to know. As it is really hard to monitor volcanoes and rift zones that are under 2 km deep ocean and good distance from the coast line. However if there is any major earthquake activity in this area. It is going to appear clearly on my geophone network and IMO SIL network in Iceland.

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