Swarm – Page 94 – Iceland geology

May 9, 2014May 9, 2014

Magnitude 3,9 earthquake in SISZ last night

Yesterday (8-May-2014) a magnitude 3,9 earthquake took place in SISZ (South Icelandic Seismic Zone). This earthquake was felt over all of south Iceland, no damage took place following this earthquake. This earthquake appears to have been on N-S fault in SISZ. Only few minor aftershocks took place following this earthquake. I don’t know why that is and this lack of aftershocks is interesting.

The star marks the magnitude 3,9 earthquake in SISZ. Copyright of this image belongs to Icelandic Meteorological Office.

The earthquake in SISZ as it appeared on my geophone station in Heklubyggð. This image is released under Creative Commons licence. Please see CC Licence page for more details.

It is possible to see any future earthquake activity here on my geophone station at Heklubyggð. The geophone station at Böðvarshólar is not updating due to failed 3G transmitter the area that I use to connect that geophone station to the internet. I hope it gets fixed soon. People can also used the website of Icelandic Meteorological Office to watch for any future earthquake activity in SISZ.

Update 1: According to Icelandic Meteorological Office this earthquake took place on a fault that had a magnitude 7,0 earthquake in the year 1784, on 14-August that year. More details can be found here, the text is in Icelandic.

Updated at 12:43 UTC on 9-May-2014.
Updated at 12:56 UTC on 9-May-2014.

May 9, 2014

Strong earthquake in South Iceland (SISZ)

Today (9-May-2014) at 23:15 UTC a strong earthquake took place in SISZ. Exact magnitude is not clear at this moment, but the magnitude of 4,0 is wrong in my view based on how this earthquake appeared on my geophone. This earthquake was felt in south Iceland and in the capital area. I am going to post updates on this earthquake once I have the details.

The earthquake can be seen here along with all the aftershocks that are going to take place.

May 6, 2014May 6, 2014

Herðubreiðartögl earthquake swarm update 6-May-2014

This is an update on the earthquake swarm in Herðubreiðartögl on 6-May-2014. This information might go outdated quickly if the activity in this earthquake swarm changes suddenly.

For the past 24 hours the earthquake activity in Herðubreiðartögl has been dropping. This means fewer earthquakes overall, the magnitude of earthquakes taking place has also been getting lower, with strongest earthquakes just in the magnitude 2,5 to 2,9 range. In the past 24 hours no magnitude 3,0 or larger earthquake has taken place.

The earthquake activity in Herðubreiðartögl on 6-May-2014. Copyright of this image belongs to Icelandic Meteorological Office.

The earthquake tracer at Icelandic Meteorological Office website clearly shows the drop in activity. Copyright of this image belongs to Icelandic Meteorological Office.

My earthquake counter clearly shows this drop in earthquake activity. It is for all of Iceland, but majority of earthquakes over the past days are from Herðubreiðartögl. This image is released under Creative Commons Licence. Please see CC Licence page for more details.

I did discover today that Icelandic Meteorological Office has updated its drumplot website. So its now possible to see the earthquakes directly. The drumplot here above is from Askja SIL station, it clearly shows the earthquake activity in Herðubreiðartögl. The website with the drumplots can be found here (I have just found this website in Icelandic, there does not appear to be English version available). Copyright of this image belongs to Icelandic Meteorological Office.

It remains difficult to know for sure what is the source of this earthquake swarm. There is a slight chance it might be due to magma injection at depth, but that remains unproven as is. My geophone stations (I only got two running now) are going to show the largest earthquakes and they are going appear clearly. It can be viewed here.

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Article updated at 21:22 UTC on 6-May-2014.
Article updated at 21:37 UTC on 6-May-2014.

May 4, 2014May 4, 2014

Update on ongoing earthquake swarm in Herðubreiðartögl

The earthquake swarm that started yesterday (03-May-2014) in Herðubreiðartöl continues. Information about this earthquake swarm changes quickly so this article about it is going to get obsoleted quickly. The largest earthquake in past 24 hours had the magnitude 3,9. Since around midnight over 370 earthquakes have been recorded. This means the earthquake swarm is more powerful in terms of earthquakes today than it was at the same time yesterday.

The earthquake swarm in Herðubreiðdartögl today. Copyright of this image belongs to Icelandic Meteorological Office.

The evolution of the earthquake swarm in Herðubreiðartögl today. As be seen here this earthquake swarm is heavy in number of earthquakes being detected. Copyright of this image belongs to Icelandic Meteorological Office.

The earthquake swarm in Herðubreiðartöl at Askja SIL station. As can be seen here this earthquake swarm is close to continuous. There is some minor drop in activity few hours ago before the earthquake activity picks up again. Copyright of this image belongs to Icelandic Meteorological Office.

The earthquake swarm seen on the SIL station at Mókollar. It is close to what is seen on Askja SIL stations and other SIL stations around this area. Copyright of this image belongs to Icelandic Meteorological Office.

My earthquake counter today showing all the activity. This gives me good comparison to how many earthquakes where recorded yesterday. This image is released under Creative Commons Licence. See CC Licence page for more details.

I am expecting more earthquake activity in Herðubreiðartögl next hours and even days. Since currently there are no signs of this earthquake swarm slowing down. The largest earthquakes (above magnitude 3,0) appear clearly on my geophone network website.

May 3, 2014May 3, 2014

Ongoing earthquake swarm north of Herðubreiðartögl

Today (03-May-2014) around midnight (00:02 UTC) a earthquake swarm started north of Herðubreiðartöglum (Global Volcanism Program link on Askja volcano can be found here), this area is an small mountain ridge that has built up with regular eruptions over some period of time. The largest earthquake in this swarm took place this morning at 05:49 UTC and had the magnitude of 3,5 with the depth of 7,6 km. After this earthquake took place the swarm increased with many minor earthquakes. So far over 265 earthquakes have been recorded today, this number gets obsoleted quickly since new earthquakes happens ever 1 to 3 minute when I am writing this text.

Tremor plot on nearby SIL stations show that a lot more earthquake activity is taking place than appears on IMO earthquake website. Reason for this is simple, the earthquakes cannot be located since they are only detected at one or two SIL stations, a minimal of three or four SIL station are required for location of each earthquake. The tremor plot in the area also show that no magma is erupting, but that does exclude the possibly that magma injection is responsible for this earthquake swarm. It has not reached the surface and currently there is no eruption taking place at this location. If an eruption takes place in this location, it is going to be Hawaiian eruption with large lava flows.

The earthquake swarm north of Herðubreiðartögl as they appear on Icelandic Meteorological Office maps. Copyright of this image belongs to Icelandic Meteorological Office.

The earthquake rate during this earthquake swarm. Copyright of this image belongs to Icelandic Meteorological Office.

The SIL station in Askja volcano. As can be seen the earthquake swarm is dense and highly active. Copyright of this image belongs to Icelandic Meteorological Office.

The SIL station south of Herðubreiðartögl, this SIL station is called Mókollar and the earthquake swarm appears clearly on it. Copyright of this image belongs to Icelandic Meteorological Office.

Earthquake swarms are common in this area and have been for a long time. Most of that earthquake activity has been contributed to normal tectonic activity in this region (plate tectonic movements). This area also has erupted in the past (last 12,000 years). I don’t think there have been any eruptions in this area in the past 1000 years, at least there are no such signs on the surface (crates, lavas). It is difficult to know what happens in this area for the next few hours to days, all that can be done is to continue monitor the activity that is now taking place. The largest earthquakes appears clearly on my Böðvarshólar geophone (link here), even if the distance is up to 200 km.

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April 27, 2014May 3, 2014

Minor earthquake swarm in Bárðarbunga volcano

Yesterday (26-April-2014) and today (27-April-2014) an minor earthquake swarm took place in Bárðarbunga volcano. I am not sure if this earthquake activity is due to dike intrusion or normal tectonic activity.

Minor earthquake swarm in Bárðarbunga volcano. Copyright of this belongs to Icelandic Meteorological Office.

This area of Bárðarbunga volcano is well known for high earthquake activity. If this is an dike intrusion as is an possibility, it does not increase the risk of an eruption, since dike intrusion without starting an eruptions are a common feature in Icelandic volcanoes.

April 27, 2014April 27, 2014

Minor earthquake swarm on Tjörnes Fracture Zone (TFZ)

Yesterday (26-April-2014) and today (27-April-2014) an minor earthquake swarm took place on TFZ not far from an island named Flatey. This was a small earthquake swarm and largest earthquakes had an magnitude around 2,0.

The minor earthquake swarm on TFZ. Copyright of this image belongs to Icelandic Meteorological Office.

It is difficult to know if this earthquake activity is going to continue. Earthquake activity at this location is only tectonic based, this area of Iceland is volcano free.

April 27, 2014

New earthquake swarm on the Reykjanes Ridge

Yesterday (26-April-2014) and today (27-April-2014) an earthquake swarm started on the Reykjanes Ridge (no GVP profile) in a submarine volcano south of Reykjanes volcano (I wrote about it few days ago here). This earthquake swarm was at the same location as an earthquake swarm that took place there on 13-April-2014 and I wrote about it here. There are clues pointing towards that magma might have been the reason for the earthquake swarm on the 13-April-2014. It has not been confirmed due to remote location of this volcano, observations are also limited due to depth of the ocean at this location (about 1 to 2 km depth is at this location).

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

Its difficult to know what is happening. Currently the earthquake swarm has continued, but with it stops for shorter or longer period of time at current time. I do not know why that is. So far everything has been quiet tremor wise on the closest SIL stations to this location. The closest SIL stations are some 35 to 45 km distance. I expect more earthquake activity to take place at this location in next few days to weeks. It is impossible to know if an eruption is going to take place out there in the ocean at current time.

April 24, 2014

Earthquake swarm on the Reykjanes ridge

Yesterday (23-April-2014) an earthquake swarm took place on the Reykjanes Ridge (GVP link here). The largest earthquake had the magnitude of 3,4 with the depth of 9,3 km. Earthquake swarm started following the magnitude 3,4 earthquake. It lasted for a two hour period and some 28 earthquakes took place during that time. The largest earthquake was felt in nearby towns and in Reykjavík (location dependent).

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

There is a possibility of more earthquake activity in this area during the next few days to weeks. Since activity in this place often starts slowly and builds up over an long period of time when it peaks and than drops off slowly, sometimes the drop off in earthquake activity is sharp. There are no signs that suggest this earthquake swarm was connected to magma movement in this volcano.

April 14, 2014

Renewed earthquake activity in Hekla volcano

Today (14-April-2014) an earthquake swarm took place in south part of Hekla volcano. The earthquake swarm took place close to Vatnafjöll mountains. This area is made up of crater rows from earlier eruptions. The largest earthquake in this swarm had the magnitude of 2,9 and the depth of 8,6 km. This earthquake did appear clearly on my geophone at Heklubyggð and it can be seen here.

The earthquake swarm in SW Hekla volcano system. The swarm is marked by orange dot (they change colour as they get older). Copyright of this image belongs to Icelandic Meteorological Office.

The largest earthquake did appear clearly on my geophone that is close to Hekla volcano. The magnitude 2,9 earthquake did appear like this on it.

The magnitude 2,9 earthquake in Hekla volcano system. Its the earthquake at the 04:00 UTC line and is clearly visible. This image is released under Creative Commons Licence. See CC Licence page for more details.

There are currently no signs of an eruption is about to start in Hekla volcano. After this earthquake swarm took place everything has remained quiet at present time. That might change, but there are currently no signs of such change. Even if there is earthquake activity taking place in Hekla volcano system.

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