Volcanic Iceland: Earthquake with magnitude M 5,2 in Þorbjörn mountain (Fagradalsfjall mountain)!!!p1492

then check out this one..

[link to hraun.vedur.is]

note that in summer 2011, the seismic moment was at around 1.5e+15, and on that first chart I showed you, the seismic moment since summer 2011 is now reaching up to 3.5e+15

so, in 12 years, from 1999 to 2011, it released 1.5e+15, and in the next 5 years, it released 3.5e+15, for a total so far of 5e+15, and about 2e+15 of that was TODAY

:Shocked-Kramer:

yep

all the katla doominess we've had on here over the years, and an event of this size happens, and everyone's ing

Quite a few shallow quakes

How thick is the glacier on top?
Lots of ice on Mýrdalsjökull.....

I think it's about 700 meters at it's thickest.

Yup..Katla measures 30 km in diameter, a total area of 100 square kilometers and depth about 400-700 meters.

I brought up iceland

Apparently..most recorded eruptions in Katla have occured during fall.

On the 24th i did

CNBC International ‏@CNBCi · 3m3 minutes ago

Icelandic volcano hit by earthquakes; could erupt

[link to www.cnbc.com]

Might have been mentioned, the Atlantic Ridge fault is one that pulls APART, separates at the ocean floor.

The inferred volume of magma accumulated in a
shallow magma chamber at Katla during the 1999–2004
inflation period is approximately 0.01 km


. This volume is miniscule compared to the erupted volume in 1918,
when about 1 km was erupted. The new magma was
emplaced at shallow levels within the plumbing system of
the Katla volcano. The high level of seismicity associated
with inflation of the volcano during this period suggests
that the volcano is close to failure and a new eruption or
intrusion event may be initiated if magma flow towards
shallow levels resumes. New material has been added to
the shallow magma chamber, rather small volumes in this
case, but this can thermally lubricate the pathways for deeper seated magma and give a fast track for the material
to reach the surface. With the volcano in an agitated state,
an eruption can take place without prolonged precursory
signals.

[link to earthice.hi.is]

On behalf of everyone on the thread I would like to offer our combined thanks for this.

You are herby awarded free tea and scones for the rest of 2016.

Luis, which is the eq magnitude in those posts? Tx

Interesting, that's also Aurora season up north. Lots of geomagnetic upticks in fall, especially around the solstice. (Sept, 21)

Answering for Luis, who is probably quite busy. Hope that's ok....

The eq magnitude is the number right after the 'km'.
The number right before the km is the depth (in kilometres).
In this case the quake is a magnitude 3.4 and was located at a depth of 4.2km.

If you go to the Icelandic meteorological website (where they post the eq's) and click on the 'table' tab, it's a bit easier to see what's what.
[link to en.vedur.is]

Thank's! Of course it's ok! By the way this is the third volcano with big quakes today!!!

Thanks much!!

Cbus05 29/08/2016 at 17:49
The thing that had started to pique my interest earlier in the year at Katla was the increase in deep earthquakes. I’ve noticed this year, that two volcanoes specifically have seen a notable uptick in deep quakes, with the first being Katla, and the second being the Askja system. Askja has gone quiet over the last 1-2 months, but Katla has kept chugging along.

Carl, do you have any thoughts on the alignment of the earthquakes? There are two pretty clear lines on the quake map, likely following faults or regions of a ring fracture. All of the green stars are on the north end, but I think the presence of the second line is really quite interesting.

I think this could maybe suggest an inflation point that is somewhat between the two regions, although more northerly focused judging by intensity.

As a final note for people, Katla HAS been inflating for years at a pretty constant rate. The problem here, is that there is not real historical data we can go off to compare the inflationary data to past eruptions.

Reply
Carl Carl 29/08/2016 at 17:55
I think that it could indeed be a representation of the outer edges of an inflating reservoir that is made manifest by two faultlines. But that is a guess on my part.

In regards of inflation, few Icelandic volcanoes suffer from a burst of inflation prior to eruption. Slow and steady is the pattern for most of them. I know that CBUS knows this, my comment is more for all new readers.
[link to www.volcanocafe.org]

Bjarki 29/08/2016 at 19:40
People are advised to keep a distance to Múlakvísl due to high gas levels.

“Glacial water is flowing into Múlakvísl river, south of Mýrdalsjökull. Increased conductivity has been measured in the river and gas measurements in the area show high concentrations of sulfur dioxide and hydrogen sulfide. People are advised not to travel near the river, due to gas pollution. It is not uncommon for glacial water to flow into Múlakvísl, causing increased conductivity and gas pollution.”

[link to www.volcanocafe.org]

Albert 29/08/2016 at 19:44
The IMO report also mentions the northern side:

“According to local reports, the level of the Bláfjallakvísl glacial river is unusually high. Bláfjallakvísl originates from the northern side of Mýrdalsjökull and people are advised to show caution when crossing the river.”

The earthquakes may have released melt water from underneath the glacier.

Things are not looking so good around the glacier at the moment.

Travelers are as of now being advised to stay away from Blàfjallakvísl that runs to the north of the glacier due to huge amounts of glacial water.
To add to this, geothermal water and sulfur gas is beung detected in Múkakvísl which runs to the south of the glacier.

I think we can be sure as hell that something cooking inside Katla.

Katla Reawakening?

Over the years I have written very little about Katla. The reason for this is that Katla has done very little to merit an article. Here at Volcanocafé we have written a few posts about Katla, but all have been attempts to put facts up against all the alarmist trash that has been written over the years.

This has though changed lately, but before we start talking about resent activity we need to look a bit at Katla to have our facts straight. In other words, we need a historic background to judge what is happening against previous eruptions. Below I will only write about eruptions that are known to really have happened and I am not included mini-eruptions or eruptions only to be found in the heads of people with feverish minds.

Background of Katla

Katla is the third largest volcano in Iceland with Bárdarbunga and Grímsvötn being slightly larger. All 3 of them come with slightly different “flavours”. Bárdarbunga is more into large effusive eruptions and small explosive eruptions. Grimsvötn is all over the map producing explosive eruptions ranging from VEI-2 to VEI-6 and has had 3 known large effusive rifting fissure eruptions.

And a plot showing todays hubbub. Notice that the twin M4.5 expended 1.5 times as much energy than all recorded Katla earthquakes in one go.

And a plot showing todays hubbub. Notice that the twin M4.5 expended 1.5 times as much energy than all recorded Katla earthquakes in one go.

Katla is more consistent with predominantly large explosive eruptions from the caldera and one prolonged large effusive eruption. Katla has had 30 eruptions since 820 giving an average of 40 years between eruptions. That average is though just a statistical number that obviously can differ a lot.

The longest repose time during that time was 100 years and the shortest well dated repose time is 12 years.

In regards of how explosive the eruptions has been we get a pretty good picture from the records. I am here only using those eruptions that has a classification in the Global Volcanism Program from 820 and onwards. 3 eruptions had a Volcanic Explosivity Index (VEI) of 3, 14 eruptions had a VEI of 4 and 4 eruptions had a VEI of 5.

The average size of the eruptions is why Katla has such a fearsome reputation, especially since it is located unusually close to settlements. After all, the volcano has an average size of eruptions that ranges somewhere between a medium sized VEI-4 to a borderline VEI-5.

During eruptions between 0.05 to 5 cubic kilometers of ash is released and here the bad news is that the ash is very fine grained and needle like, so the effects on air traffic during an eruption could be significant depending on the weather pattern during onset of eruption.

The greatest threat to the locals is the well known very large jökulhlaups that will come pouring out of the caldera during an eruption. These jökulhlaups are so large that they can remove entire farms, take out a long stretch of the national highway and usually changes the entire landscape. During the last eruption the jökulhlaup transformed the entire coastline below Myrdalsjökull and the ash, mud and stones deposited added several square kilometers to the surface of Iceland.

The extreme oddball of the eruptions is the Éldgja fissure eruption that started in 934 and lasted into 940 and deposited 18 cubic kilometers of fresh lava.

Current activity


In 2013 the earthquake pattern of Katla changed and recurrent brief episodes of small deep earthquakes started. Those earthquakes range between 20 and 30km+ depth and are a sign of magma moving upwards into the system of the volcano. During early 2016 the size and frequency of these earthquakes increased indicating an increased rate of magma influx from depth.

During all of the years that we have had instrumented recordings of earthquake sizes in Iceland Katla has suffered a few M3+ earthquakes with the record being at M3.4. So it was a bit of a surprise last week when Katla banged off an earthquake that was M3.5. It was shallow and the signature indicated that it was related to hydrothermal activity caused by fluid movement.

And here we come to today’s earthquakes. During the night leading to today there was a brief and intriguing earthquake swarm in the northern part of the caldera. A spot that Henrik Lovén already in 2011 pointed towards being both the most likely spot for an eruption, and as being the most likely for a slightly larger eruption in a series of articles he published here debunking that Katla would erupt soon (it was during the Katla scare following Eyjafjallajökull).

So, what makes this brief earthquake swarm so interesting? First of all we have to take into account the size. After all we had a new record earthquake size last week, and now we had 2 earthquakes within 20 seconds apart measuring M4.5. And as everyone knows the destructive force is 27 times larger in an M4.5 earthquake compared to an M3.5 earthquake. So, the record was not only broken, it was shattered completely.

Another way to look at it would be like this, within a minute Katla released more seismic energy than has been recorded by instrument for that volcano. Yes, those two earthquakes released more energy than all of the ten thousand plus recorded earthquakes at Katla, something to ponder indeed.

Another thing is that during the hour prior to the two large earthquakes we have several episodes that can be interpreted as fluid movement and one episode after. This would indicate that fluid started to move, putting pressure on the magma reservoir causing two large tectonic type earthquakes that in turn created a void that more fluid moved into.

The depth of the events makes it highly unclear if it was magma or hydrothermal fluid (super hot water) that was on the move. After the event the earthquake swarm has continued with smaller earthquakes with the largest as I write being M3.3.

Volcano forecast


Last week I wrote an article about Grimsvötn where I described my favorite method of modeling the likelihood of an upcoming eruption, the finite element threshold analysis modeling method. It basically is a way to try to calculate how much pressure increase a volcano can take before it ruptures like an old boiler tank.

And like an old boiler tank a volcano will creak and groan as it closes in on an explosion and that the amount of creaks and groans will increase exponentially as the volcano closes in on an eruption. For Katla we do not know how much of the creaks and groans there will be prior to an eruption being inevitable.

I will here return to the known increase of magma influx from depth and the very sudden increase in energy released as earthquakes at Katla. In my view a volcano that suddenly changes its pattern is about to do so in more ways than just as being more seismically active. In my way of modeling this is exactly the kind of sign a volcano would give as it comes close to the breaking point that the model predicts.

I am certain that the volcano has reached the tipping point of no return. If things calm down now it will still be closer to an eruption and if it continues or intensifies it is only a question of a relatively short time before we get the steady thrumming earthquake swarm that we know from other Icelandic eruption run ups. Right now I would say that we are days to years away from an eruption, but if the activity continues or intensifies I would say we are days to weeks away. The change in behavior is after all that significant.

In 2011 Henrik Lovén wrote this; “While a larger “proper” eruption of Katla in the VEI 3 – 5 range cannot be ruled out, I find one unlikely at present as the current activity mostly is in areas already depleted of evolved magmas by geologically speaking very recent major eruptions. Also there is little sign of the uplift required on GPS. If one were to occur, the odds for one towards the upper end of what Katla is able of ought to be better in the Eastern to Northern parts of the caldera.”

This also follows the modeling prediction that the greatest likelihood of an eruption occurring in a part that has not recently erupted since the pressure there should be larger, a pattern that is known for the Icelandic caldera volcanoes.

In short, if I use my own model of prediction (and I should) it seems to say that Katla is nearing an eruption. Due to lack of data prior to an eruption I can’t calculate when exactly it will occur, but if the current swarm continues over an extended period or suddenly intensifies and continues we should see an eruption in the not too distant future.

For those interested in a more in depth explanation of the finite element threshold method I recommend my previous article about Grimsvötn.

CARL REHNBERG
[link to www.volcanocafe.org]

Ouch!