At current time there are two main earthquake swarms taking place in Iceland. The first one is at Krísuvík volcano and has been going on since early this week. Currently there is nothing to suggest that it going to end any time soon. This earthquake swarm however sometimes stops for several hours and up to one to two days at the longest. Most of the earthquakes taking place are less then mag 2.5 in size. It is not clear why this earthquakes are taking place. This might be tectonic process or something to do with the magma intrusion that is taking place in Krísuvík volcano.
The second earthquake swarm is taking place at Herðubreiðartögl with earthquake taking place at Herðubreið at it’s north limits. Several mag 3.0+ earthquakes have taken place. This earthquakes appears to be due to tectonic process in the area. But I have heard theories that this process might have started due to influx of magma into the Askja volcano that is close to earthquake swarms in Herðubreiðartögl. At current time I cannot confirm that this ideas are correct or not. This earthquake swarm is ongoing and does not appear to be ending. But there are breaks in it that last from few hours and up to one day at the longest. Please note that Herðubreiðarfjöll is a central volcano that is active. It is not on the GVP volcano list for the area. This volcano is located inside Askja fissure swarm and has many active fault lines that cross it from north-south.
The newest earthquake swarm that appears to be at slow start is taking place in Esjufjöll volcano. But since activity started there in early October 2010 earthquakes appears to be on the rise in Esjufjöll volcano. It is worth noticing that earthquake swarms in Esjufjöll appear to start slowly but they due appear to peak after 20 to 180 hours after they starts. This earthquake activity is due to new flow of magma into Esjufjöll volcano.
A earthquake swarm that started out small earlier today has grown and is now a earthquake swarm with considerable size. According to automatic data from IMO and the SIL network the largest earthquakes have reached ML2.2 in size.
This area is known for a lot of earthquake activity. So this swarm is not a surprise. But this type of activity happens regularly in this area.
The earthquake that happened this morning at Hamarinn volcano appears to have magma signature in it based on what I see in my own wave data. The size of this earthquake was ML3.5 according to automatic SIL data. The automatic depth of this earthquake is 1.1 km. This data is a subject to a review by Icelandic Met Office.
So far this has been a single event and no aftershocks or other earthquakes have happened in Hamarinn volcano. That might however change. But sometimes large earthquake swarms take place in Hamarinn volcano. But this volcano is known for a lot of earthquake activity at times.
There are no indications of a eruption starting in Hamarinn volcano.
Other earthquake activity
The earthquake at Hamarinn volcano appears to have started a earthquake swarm in Herðurbreiðartögl. But the area must have been at breaking point anyway and the earthquake that happened in Hamarinn volcano might have just acted as a trigger.
There have been earthquake not far from Kolbeinsey island volcano. The strongest earthquake got ML3.3 by the automatic data by the SIL system. But due to the distance this is a underestimate in size of the earthquakes taken place at Kolbeinsey island volcano. I am not sure if the earthquake swarm that was taking place there has stopped or not, as small earthquakes are not detected by the IMO SIL Network.
Currently there is a quiet time taking place in Iceland. This sometimes happens. It does not mean that all activity has stopped. But it just means that the most of the earthquakes that are taking place are so called microearthquakes and that they are less then ML3.0 in size. But the thing about microearthquakes is that they are not useless, as this (pdf, English) report from Icelandic Met Office shows.
While it is quiet as it is I am going to relax a little. So that I can take on the busy times better.
It appears that the earthquake activity at Blöndulón and in Esjufjöll volcano has not stopped completely. The earthquake activity at Esjufjöll volcano started on the 20th of October 2010. The first week there where about 70 earthquakes recorded by Icelandic Met Office, the following week there was continued activity but there where fewer earthquakes taking place in Esjufjöll volcano at that time. But the activity had not stopped completely. When this is written there are clues that there is a new earthquake swarm about to start in Esjufjöll volcano. I must point out that so far the earthquake swarms in Esjufjöll volcano have started out slow before they pick up the in size and numbers of earthquakes.
The earthquake activity under Blöndulón lake (man made lake) continues. The earthquake activity is intermittent since it started. But the largest earthquakes that have happened under Blöndulóni lake have reached ML3.8 in size. But the largest earthquakes where felt in nearby farms (up to 80 km away far as I understand). It seems that the earthquake activity continues at this location. But with long stops in-between each earthquake swarm. I do expect the earthquake activity to continue there for coming months. But sometimes it happens that earthquake swarms in the areas outside the main faults take a long time to finish. The longest earthquake swarm that I know of lasted for almost two months. This earthquake swarm at Blöndulón lake might well do something like that. But only time is going to tell us what is going to happen in that area.
Last week something interesting started to happen in Katla volcano last week (Week 45). Earthquakes started to appear in the eastern part of the Katla volcano. This is higly unusual and is not the normal earthquake zone in Katla volcano. But normally the earthquakes take place in the western part of the Katla volcano (Goðabungu area) and few earthquakes take place in the caldera it self at regularly.
At 00:45 UTC there was a earthquake in eastern Katla volcano, the automatic SIL size of this earthquake was ML2,5 at the depth of 1,1Km (with a good quality of 90,05). Both figures are subject to a revision by a seismologist at later time, so both size and depth can change. I did manage to record this earthquake on my Hekla geophone, even if there currently is rather high wind noise at my geophone. What I did see on my geophone is interesting. But the earthquake appears to have low frequency component in it, even if it is mostly high-frequency type of earthquake. But those earthquakes are normally created by a fault in the crust, not by magma movement.
I need more data to confirm it. But there are clues that the earthquakes in eastern Katla volcano are due to magma movement, rather then tension changes in the crust not related to magma movement. What is happening there is unclear at the moment, as GPS stations around Katla volcano do not show anything interesting at the moment.
No eruption is imminent in Katla volcano at current time.
It seems that Esjufjöll volcano is not done with the earthquakes. But over the past few weeks since the original earthquakes swarm that started in early October in Esjufjöll volcano.
Like before it appears that the earthquakes have there origin, not tectonic as often is the case is in Iceland. But this means that each time a earthquake happens in Esjufjöll volcano a magma is on the move there. What is interesting about this is the fact the magma that is moving inside Esjufjöll volcano does appears to be moving at fast rate. For instance the earthquakes that are now taking place in Esjufjöll volcano indicate that the magma is moving faster then was the case with Eyjafjallajökull volcano before it erupted earlier this year. According to Week 42 data from Icelandic Met Office there where over 70 earthquake recorded. But in 2002 the earthquakes recorded then was over 90 earthquakes, with the biggest one ML3,5 in size.
The current earthquakes in Esjufjöll volcano are interesting and do signal a more active period ahead in that volcano. When that active period is going to peak with a eruption (?) is unknown at this time. But we at least might end up seeing (?) something like happened in the year 1927 when a small eruption did create a glacier flood from Esjufjöll volcano that did go down Breiðamerkujökull glacier.
I have seen a lot of people worrying about earthquakes and earthquake swarms that take place in Iceland on regular basic. Those worries are not needed as Iceland gets about one to two earthquake swarms on average over the course of one week. Most of the earthquakes that take place in Iceland are tectonic in nature. There are also volcano related earthquakes. But they can be spotted by there location in connection with the volcano in question (Katla, Grímsfjall, etc..).
The reasons for the earthquake swarms in Iceland is geological and is because Iceland sits on a rift zone. This can be shown clearly on this picture here.
Click on picture to get better resolution.
This map clearly shows all the zones in Iceland. In this areas most of Iceland earthquakes happens. But also a big part of Iceland earthquakes happen in areas like SISZ and TFZ.
On the normal week there are about 150 to 400 earthquakes in Iceland over the week. Most of them are in the size ML0.0 and up to ML2.8. Most week have one or two earthquakes that are ML3.0 to ML3.8 in size. On a quiet week there are about 50 to 100 earthquakes, most of them less then ML2.5 in size. When there is a busty week in Iceland the earthquakes numbers can easily go over 2000 and sometimes well over 5000 earthquakes. When that happens IMO doesn’t even bother in classifying and locating all the earthquakes that take place. But they are saved anyway in IMO database.
Picture taken from this blog: Earthquake in Iceland (2008); This blog has more images about the tectonic process in Iceland.
At 03:19 UTC there was a ML3.4 earthquake at 2,5km depth at Grímsfjall volcano according to the automatic SIL system that Icelandic Met Office has. This earthquake does not appear to be a after effect of the ML4.0 earthquake at Blöndulón few moments before that. Currently there have not been any other earthquake in Grímsfjall volcano. But that might change soon if this is a start of a eruption in Grímsfjall volcano. But it is going to take few moments to be clear on what is happening.
Currently there are no indicators that a eruption is starting in Grímsfjall volcano.
This earthquake was when reviewed size ML2.3 at the depth of 2.8 km.
Text updated at 14:40 UTC on the 31st of October 2010.
Over the past few days (since 26th of October 2010) there have been earthquakes happening at Blöndulón. This earthquakes are intraplate earthquakes and it unclear why these earthquakes are happening.
At 02:35 UTC a earthquake with the size of ML4.0 did hit Blöndulón according to automatic SIL system that Icelandic Met Office has. So far this is the strongest earthquake to hit this area since the earthquake swarm did start. This earthquake appears to be a start of new earthquake sequence in this area. But several smaller earthquakes have happened as a result of the ML4.0 earthquake. The depth of the main earthquake was 1km. I do expect that it was felt in nearby farms that are closest to Blöndulón.
I am expecting more earthquakes in this area over the next few days. It remains to be seen if they grow in size or not.
When reviewed the size of this earthquake was ML3.8 at the depth of 21.1 km.
Text updated at 14:41 on the 31st of October 2010.