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.
Update!
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.
Bit of perspective, considering it’s so shallow and underneath a glacial ice sheet.
If a 811,691 tonne chunk of ice/rock suddenly drops one meter… it will release about the same amount of energy.
Ice is less dense the rock. So the effect would not be the same.
Density doesn’t matter when you are specifying a quantity of mass. It would just occupy a greater volume. The principle difference is how the mass of ice vs rock would respond to the drop. Likely ice would tend to shatter and generate a less pronounced spike. But considering the size of this “chunk” if that is what it is, the dynamics of how it would behave may be different that the cubes in a Vodka Martini.
An example. A one metric tonne cube of dense basalt is about 0.33 cubic meters. A one metric tonne cube of solid ice is about 1.09 cubic meters. Drop either one from a height of one meter, and the force of the impact is going to be pretty much the same.
I’m not saying that this is what the quake was, just that it’s shallow, and the size, though large by the standard run of the mill quakes here, is not something phenomenally odd in it’s size.
If I remember my school/college physics, both will have acquired the same amount of potential energy to be released when they hit the ground from the same height. The rock cube, however, will do so over a much smaller surface area which means that the force of its impact will be three times as high, even if the amount of energy released is the same. Now, let us assume that they strike much smaller object such as a football. In this case, the football will experience identical forces. Confused? No more than I then. 😉
The reviewed size from IMO says that this earthquake had the size of ML2.3 at the depth of 2.8 km.
“If a 811,691 tonne chunk of ice/rock suddenly drops one meter… it will release about the same amount of energy.” (ML 3.4)
This is not a particularly large chunk of ice for a glacier such as Vatnajökull. 811,691 tonnes is ~885,000 cubic metres. If the glacier is 1km thick and a slip occurs along an 885 meters long sector, it would only have to be 1 m wide/thick and, as Lurking says, drop 1 m to case an ML 3.4.
Is this correct? I know the numbers say so, but it’s hard to conceptualise.
Well that takes the fun out of it.
I’m still intrigued by the layout of those other quakes NE and SW of the Lake Swarm. They appear to be aligned along what used to be active rift area… but are so shallow that they really seem have no significant bearing. I would expect a few to be deep if they were related to the original formation of the region.
Ideas? Is there some sort of ice or surface related phenomena?
Additionally… I can’t mentally lump all of the Lake Swarm quakes into one box either. A few are waaaaaay too deep to be related to the mass of the water.
@Henrik
I get the difficult conceptualization thing too. This was all based on 7,943 MJoules for a Mag 3.4 quake… back when it was a 3.4.
The idea was to get a comparison of how much energy was in the event we were pondering.
Of course, I was also surprise a few months ago when someone pointed out that a Big Mac has about the same amount of energy as a Mag 1.0 or 1.1 quake… depending on sauce.
Jón: Is this the quake that is supposed to be a fake? It was measured at a great depth, didn’t it?
Sunday
31.10.2010 02:35:54 63.705 -19.176 19.8 km 3.1 30.69 8.1 km NNE of Goðabunga
This earthquake was not fake. But it’s size was over-estimated by the SIL system. That also happens from sometime.
Thanks, Jón.
I still see it on the site as Ml 3.1, but the quality is 30 or so. Sure they overestimated it?
I was using the interactive map that they have. The size was there. But the data has become a bit conflicting over the past few hours. I hope it clears up tomorrow on what the size of that earthquake really was.
@Lurking
Of course, I was also surprise a few months ago when someone pointed out that a Big Mac has about the same amount of energy as a Mag 1.0 or 1.1 quake… depending on sauce
So, a M 3.4 is about the same as dropping about 50,000 big Macs…
Just remember that the scale is logarithmic. You’ll have to augment that with an order of fries or a Happy Meal.
Hi Jon, Starwoman and Pieter
In response to the question about web-cams: I have no problem with getting images from this webcam. The link I have for Eyaf is: Míla í beinni – Eyjafjallajökull frá Þórólfsfelli.mht and for Katla, though I hope it won’t be needed – it’s a lovely sunny day today in Iceland – Katla Ríkisútvarpið vefur.mht
Best wishes
Good morning Alyson, something wrong with the address you gave for the camera, can you cut & paste exactly? Maybe it depends on where you are located whether or not you can receive? Thanks
Ok guys! How about putting the energy levels in terms of tons of TNT? LOL I did take physics, but it was a long time ago and part of it was a class called Electron Optics. In that class, I had to be able to describe what was going on with an electron from the time it left the electron gun in the scope to the time it hit the screen below. In addition to that, we had to measure the wave length of a red lazer beam. It wasn’t that difficult, but I don’t remember the formula now.
As for quakes, were did someone get the idea that a 1+ quake had the same energy as a Big Mac? Kilo-calaries? You guys are way beyond me when it comes to physics. :-}
@Diane N CA
Someone a few weeks ago, over in the Eruptions blog piped up about the food energy equivalent of small quakes. It was a humorous (as opposed to humerus) distraction while were rummaging around for Eyjafjallajökull data.
A 3.4 tallies up at about 7,943 MJ using the formula: log E = 1.5 M + 4.8
Or about 125.9 tons of TNT.
Sorry it isn’t coming up properly; you’re right, it doesn’t work, so something is missing. For me the website heading just gives its location on my computer…
Try to move to Firefox web browser, or Google Chrome or even Opera web browser. That might fix your issue.
Hi Jon – even curiouser is that if I try to open the tabs for the other cameras, and then the one I already have, I get the message that the cameras are down for maintenance… but if I open the one I have saved it is working! I have no explanation for this.