Earthquakes – Page 86 – Iceland geology

September 29, 2016September 29, 2016

Overview of micro-earthquake activity in Iceland 28-September-2016

This is a short overview of the micro-earthquake activity in Iceland on 28-September-2016. Please note that some of this earthquake activity may have started some days ago and only got really busy on 28th September 2016.

Kolbeinsey Island / Ridge

Late on the 28-September-2016 an earthquake swarm took place in Kolbeinsey Island / Ridge. This is the largest earthquake swarm in this article. With the largest earthquakes having the magnitude above 3,0. Due to distance from the SIL network exact calculation of the magnitude and depth doesn’t appear to be possible. Last eruption taking place in Kolbeinsey Island / Ridge took place in the year 1755. No other eruptions have been documented since, but they might regardless have happened. The area is far from land and difficult to observe.

East of Grímsey Island (Tjörnes Fracture Zone)

Minor earthquake swarm has been taking place earth of Grímsey Island in a area that many suspect is a volcano (it is marked as such in the GVP database). The earthquake swarm in question does not appear to be a volcanic in origin. This appear to be a tectonic activity taking place, as the movement of TFZ is 20mm lateral movement/year (they fault slide each other 20mm/year) the rift movement is only 5mm/year (eastern part only). Image showing the movements can be found here (vedur.is).

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

South Seismic Zone (SISZ)

A small swarm of earthquakes has been taking place in SISZ this week. The largest earthquake in this swarm has only had the magnitude of 2,1. The activity is only minor and does not suggest a large earthquake is about to happen. This might be aftershocks of the earthquakes in 2000 or 2008.

The earthquake activity in SISZ. It’s only minor and west of Selfoss (red dot). Copyright of this image belongs to Icelandic Met Office.

Reykjanes peninsula

Earthquake swarm started on 28-September-2016 on the Reykjanes peninsula. This earthquake swarm was not strong and the largest earthquake in this swarm only had the magnitude of 2,1 and all other earthquakes where smaller in magnitude. Total of 60 earthquake happened when the swarm was active.

The earthquake swarm on the Reykjanes peninsula. It was not big in magnitude, but had a total of 60 earthquakes. Copyright of this image belongs to Icelandic Met Office.

Few earthquake have also been taking place around Iceland without any other activity. This type of one-off earthquake activity is common in Iceland. Why it happens is unclear.

Article updated at 02:03 UTC on 29-September-2016. Word corrections.

September 26, 2016September 27, 2016

Magnitude 3,9 earthquake in Katla volcano

Today (26-September-2016) an magnitude 3,9 earthquake took place in Katla volcano caldera. This earthquake had the unusual depth of 0,0 km (error margin is around +-200 meters or more). This was the largest earthquake in a earthquake swarm that started yesterday (25-September-2016). It has for the past 48 hours been slowly increasing in magnitude and size. Most of the earthquakes where smaller than 1,0 in magnitude. Few magnitude 2,0 (and larger) earthquakes took place today in Katla volcano. In total 30 earthquakes have so far taken place in Katla volcano during the past 48 hours.

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

This earthquake swarm and the largest earthquake happen slightly south of the area that had the magnitude 4,5 and 4,6 earthquake swarm almost a month ago (article can be found here). This same area was also active month ago, but only with minor earthquakes. What this pattern suggests is that possible two or more fissures might open up inside the caldera once it erupts. The east-west fissure might be up to 10 km long and south of it a fissure that is up to 5 km long might open up. This is only my view and only speculation, but I cannot ignore the fact that this earthquake swarm activity is lining up in interesting way and that highly suggests that a fissure or a rift process has started in Katla volcano. If it continues or stop is impossible to know.

During documented history (~1000 years) Katla volcano has had most eruption during the period of July until end of November. With few eruptions taking place in January and February. There are huge gaps in this information due to historical inaccuracy, lost information and so on. As before, there are no clear signs of eruption being imminent, but I got the feeling that its not long now, at least less than 10 years until an eruption in Katla volcano.

Article update at 22:11 UTC on 27-September-2016. Minor spelling fixes.

September 19, 2016

The earthquake swarm in Hengill volcano

For the past two days swarm of earthquakes have been taking place in Hengill volcano. Looking at the earthquake swarm it might look like something was about to happen in this volcano. The fact is however that nothing is happening in the volcano, this earthquake swarm is entirely human made. Largest earthquakes so far have had the magnitude of 3,0 (x2), 3,2 (x1), 3,6 (x1). Over 300 earthquakes in total have happened so far, most less than magnitude 1,0 few dozen above magnitude 2,0.

The earthquake swarm as it was at 19:20 UTC. Copyright of this image belongs to Iceland Met Office.

Source of this activity is water pumping into the ground. The hydro-thermal electric plant (it also serves hot water to Reykjavík area and other towns nearby) does that with unwanted waste water, since that water is full of toxic chemicals. The hot water used in hot taps and showers in Reykjavík now is warmed up cold water (they use thermal exchangers to do this, some houses have this unit installed inside the house).

This earthquake swarm is currently on-going and if anything major happens I will update this article.

Weather warning for Thursday 22-September-2016

It appears that a strong low pressure system is on its way to Iceland and is going to at the south coast on 22-September-2016. I don’t have a exact time at the moment. This might the first real storm in Iceland this fall. More weather details are going to appear tomorrow as the forecast gets better.

September 18, 2016

Earthquake activity in Bárðarbunga volcano

Two earthquakes with magnitude above 3,0 have taken place in Bárðarbunga volcano. The earlier earthquake had the magnitude of 3,8 and the second earthquake had the magnitude of 3,8. Other minor earthquakes also happened.

Earthquake activity in Bárðarbunga volcano. Copyright of this image belongs to Iceland Met Office.

This type of earthquake activity in Bárðarbunga volcano has been going on for months already. What has mostly changed over the last four months is the magnitude of the earthquakes. The rate they are happening is about the same at the moment, once to twice a week currently. I don’t expect this to change until it does.

September 11, 2016

Fresh earthquake activity in Katla volcano

Today at 12:19 UTC an earthquake swarm started in Katla volcano. This has been mostly normal earthquake activity for Katla volcano, with earthquakes that are small in magnitude and most not reaching magnitude 2,0. Largest earthquake took place at 15:57 UTC and was a magnitude 3,0 and at magnitude 16:12 UTC and had the magnitude of 3,3.

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

It is difficult to know if this earthquake activity was due to change in hydrothermal systems that exist in this area or due to magma or gas pressure changes. No harmonic tremor changes have taken place following this earthquake activity. Since the largest earthquakes happened the activity has quieted down considerably. This earthquake activity or a new one might start without warning in Katla volcano.

September 8, 2016

Earthquake swarm in Tungnafellsjökull volcano

For the past 48 hours (7th and 8th September-2016) an earthquake swarm took place in Tungnafellsjökull volcano. As earlier earthquake swarms this swarm has a small one, with only few dozen of earthquakes and the largest one only having the magnitude of 2,9. Most depth in this earthquake swarm was around 12 km.

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

For the moment nothing suggests that an eruption is about to start in Tungnafellsjökull volcano. This volcano doesn’t have any recorded history of eruptions and that makes it impossible to know when next eruption cycle starts in it. Current earthquake activity started in the year 2012 and has continued since then, with long period of quiet between times of activity.

September 7, 2016

Deep earthquake activity in Bárðarbunga volcano

Yesterday (06-September-2016) and today (07-September-2016) deep earthquake activity happened in Bárðarbunga volcano system. Most depth was at 25,9km in Trölladyngja, it is one of several deep earthquakes that have happened in that area. Few earthquakes at depth of 20,8 km took place in Bárðarbunga volcano (outside of the caldera).

The deep earthquakes on this image are at south-east to Bárðarbunga (in the direction of Grímsvötn, north-east of Grímsvötn) and in Trölladyngja (one blue dot). Copyright of this image belongs to Icelandic Met Office.

In Iceland earthquakes at this depth only happens due to movement of magma. Crust stresses do have effects at this depth far as I know. At the moment no magnitude 3,0 earthquakes have happened in Bárðarbunga, that might be unusual since normally after a swarm of deep earthquake few strong earthquakes happens in Bárðarbunga. That has at time of writing of this article not happened. If that happens remains to be seen. I got the feeling there might be something more in the works, but I’m going to wait and see what is going on now. At least wait for a word from Iceland Met Office about what is going on, if anything is going on at all.

All that can be done now is to wait for what happens next. (This is what geology is mostly about, endless waiting for something to happen.)

September 7, 2016

New earthquake activity in Katla volcano

Early this morning (7-September-2016) an earthquake with the magnitude of 3,5 took place in Katla volcano. There was little earthquake activity before the main earthquake and after it, since this morning activity has remained low.

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

This earthquake activity is in the same area of the magnitude 4,9 earthquake two weeks ago. No harmonic tremor has been detected following this earthquake. I don’t know if anything more is going to happen. All that can be done is to wait and see what happens next.

September 3, 2016

Earthquake activity in Bárðarbunga volcano 2-September-2016

On 02-September-2016 two earthquakes with the magnitude 3,3 and 3,5 took place in Bárðarbunga volcano. The magnitude was 3,3 for the earlier earthquake and 3,5 for the second earthquake.

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

This type of earthquake activity is so common now in Bárðarbunga volcano that I rarely bother now to write about it. This type of earthquakes now happen once to twice in Bárðarbunga volcano each week. The reason for this earthquake activity are stress changes in the caldera. This is I suspect going to take a long time, I’m looking at years of this type of earthquake activity in Bárðarbunga. What also makes this more complicated is the rifting currently taking place inside the volcano and on nearby fissures. The results of this mixture might get interesting in the future.

August 30, 2016

Earthquake swarm in Bárðarbunga volcano

Today (30-August-2016) an earthquake swarm started in Bárðarbunga volcano. The earthquake swarm took place in the caldera of Bárðarbunga volcano, as has been the case for the past few months. Nothing suggests that magma is on the move or that eruption is imminent, this seems to be tectonic or tectonic related activity in Bárðarbunga volcano after the eruption in 2014, that ended in February 2015.

The earthquakes in Bárðarbunga volcano. Green stars are earthquakes larger then magnitude 3,0. Copyright of this image belongs to Iceland Met Office.

Largest earthquakes so far have the magnitude of 3,8 (at 13:33 UTC) and 3,4 (at 16:58 UTC), other earthquakes have been smaller in magnitude. The reason for this earthquakes is inflow of magma at depth (more than 10 km) into Bárðarbunga volcano. This is creating stress changes higher up in the crust, resulting in earthquake swarms. More earthquakes can be expected from Bárðarbunga volcano in next few hours to days. This type of earthquake activity almost happens weekly at the moment and that has been the activity pattern since September-2015. I’m not expecting any change in this activity pattern for next few months.

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