I don’t have a lot to write about the earthquake swarm in Krísuvík volcano that took place there yesterday. But according to IMO the largest earthquake was felt in Hafnafjöður and in Reykjavík.
Here are the wave form data of the largest and the second largest earthquakes. There are no location data in this image. As I have not had time to put them into the wave form data.
From Hekubyggð. This is the ML2.8 earthquake.
From Hvammstangi. This is the ML2.8 earthquake. This one is low-pass filtered at 4Hz.
From Hekubyggð. This is the ML2.5 earthquake.
All pictures can be clicked to see the higher resolution of them.
Here are two earthquakes that I did record yesterday. The earthquakes took place at Arnarvatns highland and in Krísuvík yesterday. The difference between the earthquakes is that one of them took place where the crust is old and carries the earthquake wave well. The second earthquake(s) took place where the crust is young, fractured and does not carry the earthquake wave that well most of the time. If a fracture area is not in-between the epicentre and the sensor in question.
The earthquake at Arnarvatns highland. The earthquake wave clearly shows what type of crust it has been going trough. In this case a old crust that carries the wave well in my direction. I cannot tell what way the crust fractured in this case, as I need a minimal of three geophones to do so.
The Krísuvík earthquakes. This is actually a string of many earthquakes. When this happens the SIL system that IMO has major issues with locating the earthquakes. As the S wave often get absorbed by the next P wave that follows the next earthquakes. Sometimes however the waves get separated at some distance. That often helps to figure out how many earthquakes happened at the same minute. What is also interesting about this earthquake is the fact that it is “noisy”. But a normal earthquakes has a clear P wave and clear S wave. But on Reykjanes and Reykjanes Ridge there are often noisy earthquakes. I do not know why that happens and I don’t think the reasons for noisy earthquakes are not at all understood (far as I know anyway).
This map here shows how warm the hot water is in Iceland. Where I live the hot water is about 66C warm. It is a deep magma that warms the ground water up to this levels. There is a good article on this process at Wikipedia here.
Text updated at 17:15 UTC on the 11th of December 2010. Spelling error fixed and minor text changes.
Time has just put Eyjafjallajökull as the 4th biggest buzzword of the year 2010. The list can be seen on the web pages below.
Top 10 Buzzwords – 4. Eyjafjallajokull
The Top 10 Everything of 2010
Icelandic News about this. Use Google Translate to make sense of the Icelandic news.
Eyjafjallajökull á topp 10 lista (Rúv.is)
In a press release by Almannavarnir (Iceland Civil Protection) it is announced the lowering of the warning level around Eyjafjallajökull from danger area down to uncertainty level. There are also some travel restriction lifted that have been in place around Eyjafjallajökull volcano. The current warning level is the lowest warning level that Almannavarnir has.
The Press release by Almannavarnir in Icelandic. Use Google Translate at own risk.
Lækkun á almannavarnastigi frá neyðarstigi niður á óvissustig vegna eldgossins í Eyjafjallajökli (almannavarnir.is)
Icelandic News about this.
Almannavarnastig lækkað í óvissustig (mbl.is)
Almannavarnir lækka viðbúnaðarstig (Rúv.is)
Almannavarnastig vegna Eyjafjallajökuls lækkað (Vísir.is)
Over the past two weeks there have been signs appearing that a eruption might be close in Grímsfjall volcano. But a GPS station named Skrokkalda. This GPS station has started to move north, but this indicates that inflation has started in Grímsfjall volcano at full power. This did also happen at the same GPS station in 2004 before the eruption in Grímsfjall volcano that same year. But it is debated if this movement was created by ice or by a dike intrusion in Grímsfjall volcano. It is my just my personal opinion on this movement that takes place at the GPS station.
It currently remains to be seen if this northerly movement continues or if it starts to deflate again. So far this is the only indicator that Grímsfjall volcano is getting ready for a eruption. When this did happen in the year 2004 it was almost three weeks after this process started until a eruption took place. But then a glacier flood did trigger the start of the eruption in the year 2004.
For the moment the only thing to do is to wait and see what happens with Grímsfjall volcano. Nobody can tell how long the wait is going to be.
The earthquake swarm that started two days ago at Arnarvatns highlands continues in similar manner as was seen in the earthquake swarm that took place under Blöndulón lake few weeks ago.This earthquake swarm is taking place in a fracture zone known as West Iceland Fracture Zone (WIFZ). But that fracture zone sits between East Iceland Rift Zone and Snæfellsnes volcano zone. This area is known for strong earthquakes, but in the year 1974 there was a magnitude earthquake that had the size Mb5.5 to Mw6.1 (I am not sure on the exact size of this earthquake). According to news there is speculation that this earthquake swarm is somehow connected to the earthquake swarm that did happen under Blöndulón lake few weeks ago. This area is unpopulated and several tens of km to next farm in this area.
Click on the picture of better resolution. Picture is taken from here (Icelandic).
Explanation for the numbers in the picture. The number account for the fracture direction in the area. 1: Northwest-Southwest fracture. 2: West-East fracture. 3: North-South fracture. 4: Northeast-Southwest fracture.
Where the earthquakes are currently taking place are on the west-east fractures in the area. There are no active volcano where the earthquakes take place that I know of. The active volcanoes are south and west (Snæfellsnes volcanoes) of the current location of the earthquakes.
Currently is unclear if this activity did trigger earthquakes in the rift zone. That is Thingvellir and nearby areas that show earthquakes on IMO maps. This might just be poor locations from the SIL system. It is also a question if this earthquake activity is the reason for earthquakes close to Geysir (volcano) geothermal area.
Click on the picture for a full resolution. Picture is from Icelandic Met Office web site.
The earthquake swarm at 13:10 on the 6th of December 2010. Picture is from the IMO web site.
At current time is remains unclear if this earthquake activity is a pre-events before a bigger earthquake in this area. But about ten years ago there was a earthquake swarm south of this location with many earthquakes reaching ML4.0+ in size. But in any case it is worth keeping tab in this earthquake activity, as it might signal more interesting times ahead in this area. But that is just speculation on my part. Earthquake activity might fall down to nothing (normal for this area) in a short time span.
Due to how fractured this area appears to be. I am not recording the earthquakes in this area properly, as the energy of the earthquake wave appears to vanish rather quickly due to the fractures that are between me and the earthquakes that take place (the wave energy that goes north in this case). But this was not the case with earthquake swarm that took place in Blöndulón lake.
Icelandic News of this earthquake swarm. Use Google Translate at own risk.
Skjálftahrina stendur enn yfir (Rúv.is)
Skjálftavirkni á Arnarvatnsheiði (mbl.is)
Text updated at 13:57 UTC on 6th of December 2010. Minor error fixed.
Text updated at 08:33 UTC on 9th of December 2010. Error fixed.
According to Rúv it appears that British Geological Survey did pay for the set-up of six seismometers around Eyjafjallajökull and Katla volcanoes. This seismometers are able to detect lower frequencies better then current seismometers around Eyjafjallajökull and Katla. This type of sensors are normally called broadband seismometers and have frequency range down to 0.001Hz and up to 60Hz. I do not know how far the sensors that BSG did cost. But I am going to assume that they go down a bit farther then IMO sensors in the area. According to Rúv the sensors are already up and where on-line earlier this year.
They are located at following location.
Mælifellssandi not far from Slysaöldu, Rjúpnafell east of Mýrdalsjökul, two are located both sides of Eyjafjallajökull on Ásólfsskálaheiði at south and Smjörgili at north not far from Gígjökli glacier. Fifth sensor is going to be set-up in Pétursey in Mýrdal. The location of the six sensors has not been decided yet.
The cost of this project is about 100.000 pound according to Rúv.
The reason for this is that authorities in UK (and Europe) want to get more warning if there is a big eruption in Katla volcano. Mostly to prevent the air chaos that took place when Eyjafjallajökull erupted earlier this year.
Five sensors where in the area before. The sensor net is going to be really sensitive when the new sensors go on-line at IMO headquarters in Reykjavík. But more sensors give more accurate location of earthquakes, both in depth and location.
The news from Rúv in Icelandic. Use Google Translate at own risk.
Bretar setja upp jarðskjálftamæla (Rúv.is)
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.
Here are two maps of the geology in Iceland. The first map shows the fault zones with the active volcanoes in Iceland. Also in this map the age of the rock is shown. The second map shows the rock type, if it is acid, basic and so on.
A map of Iceland with fault zones and active volcanoes. This map is not up to date with newest research and stuff like that. Click on the picture to get a full size.
This map shows rock type in Iceland. Explanation is to the right. Click on the picture to get a full size.
Both pictures are from this web site here.
I am going to setup a new Geophone station in January 2011. The station is going to be located on the Vatnsnes peninsula where i currently live (Hvammstangi). But it is going to be located on a remote farm in that area.
I still need to by few things for this station. What I am currently missing is a GPS clock (going to buy that in two weeks time or so), WLAN hardware and antennas for getting a WLAN signal over 500 meters distance and a PC for the software that reads the data from the geophone. If everything works out I should be able have the station up and running before I move to Denmark. This station is going to take over the job of Hvammstangi geophone station that I currently have at my home.