The world is filled with people believing that large earthquakes cause volcanoes to erupt far far away. Lately we have had quite a few very large earthquakes that all where above 8 in magnitudes and two that was on the mega-colossal scale (Tohoku and Boxing-day earthquakes).
Here is the list since 2000:
2001: June 23 Peru (8.4)
2003: September 25 Hokkaido Japan (8.3)
2004: December 23 Macquery Islands New Zealand (8.1), December 26 Sumatra Indonesia (9.1 Boxing day earthquake)
2005: March 28 Nias Indonesia (8.6)
2006: May 3 Tonga (8.0), November 15 Kuril Islands Russia (8.3)
2007: January 13 Kuril Islands Russia (8.1), April 1 Solomon Islands (8.1), August 15 Chincha Alta Peru (8.0), September 12 Sumatra Indonesia (8.5)
2009: September 29 Samoa Islands (8.1)
2010: February 27 Maule Chile (8.8)
2011: March 11 Japan (9.0 Tohoku)
2012: April 12 Sumatra Indonesia (8.5), April 12 Sumatra Indonesia (8.2)
Good, now we have raw data. Among these are 6 out of the 11 strongest earthquakes recorded by man. One of the earthquakes was the third largest earthquake ever recorded. If something could rock the boat it would be one of these ones. Oh, and before you go off on the “there are more earthquakes now than before train”, no it s not. It is just that we have far more seismometers available now.
What do we need now? Well, a couple of smoking close to eruption volcanoes would be good. Iceland is bound to have a couple. So let us check for the usual suspects. We had 3 eruptions happening (2 Grimsvötn and 1 Eyjafjallajökull). On top of that we have Hekla who is achingly close to erupting since 2007; Hekla is most likely the closest volcano on the planet to tipping over into an eruption. And for fun, let us throw in Etna; she is always up for a show.
Let us start with Grimsvötn, the penultimate bad-boy of Iceland. Grimsvötn has had more eruptions than any volcano during the last 300 years, and also the world’s largest fissure eruption during the same time period. We should find something there should we not?
2004 November 1? Nope, nothing happened then. 2011 May 21 (Grimsvötns largest eruption in a century). Nothing spectacular happening on that date.
Now you are going, Eyjafjallajökull, she disturbed airline traffic and was a messy bastard, surely that one was caused by an earthquake? 2010 March 17 (Fimmvörduhals-eruption) and April 14 (Eyjafjallajökull crater eruption). Well, I am sorry but nothing happened then.
Let us now go for Etna, she is having loads of small eruptions during this time-period, so statistically at least one should coincide with a large earthquake. Let us check. I am not going to write a long list of the eruptions, I will just write down those that occurred that coincides with an actual earthquake. And once again it shows that no major eruption coincides with an Earthquake. If we then go into the last eruption of Etna that started in August 2010 and is still ongoing we find that Etna had series of small eruptions called Paroxysms. These happen about monthly so one of them would surely be a jackpot.
Lo and behold! We have a match! After 10 days of being quiet Etna had a paroxysm in the morning of the 12th of April. Thank the Gods, we have proven that Earthquakes causes Eruptions!
Or did we really? No we did not. Etna is a very predictable volcano, and Dr. Boris Behncke had already warned about the eruption coming 36 hours before the earthquake. Hm, so the volcano was already going to erupt. In reality the eruption was actually not coupled that well with the earthquake, there was 4 hours in between them.
Well then Hekla, the most trigger happy volcano on the Planet. Locked and loaded to go off since at least 2007, one would think that nasty mess of a volcano would do something. Well she did, she shivered as jolly pudding. Here you can see both the 8.5 and the 8.2 earthquakes. It is a nice image, it shows that there is enough lava down there to actually shiver like a pudding, otherwise it proves nothing. The last eruption produced a motion 10 000 times larger. So, if the volcano closest to a large eruption on the planet did nothing more than behaves like Jell-O I would say that this matter is over with.
An Earthquake cannot cause an eruption in a far off volcano. Get over it.
Bonus volcano, Mount Merapi! We should not be euro-centric. Guess what, there were no earthquake then either.
It is actually quite simple, the waves generated are filtered by the vast mass of earth, when the waves from the earthquake finally arrives only the most low in frequency are left, and they span a lot of area, we are talking about waves that are 100s of meters wide up to kilometers wide. They do not cause a kick in the ass of the magma causing it to de-gas, instead it gently sloshes it a bit. Like the difference of dropping a beer-can on the floor and opening it, and gently pulling the tap and pouring it after having turned the can gently upside down a few times.
If you do not believe me about the filtering try this experiment. Put on your favorite recording on your loudspeakers. Tape a piece of cardboard over the tweeters, listen. You should now hear that the high frequencies are muted. Now repeat the same thing over the bas. Not much happening right? Now, let us have fun, put in some earplugs before doing this. Now go and crank up the volume and take a look at the cardboard. It should by now be pulsing with the base pretty visible. Gosh darn it; same does the earth do to the earthquake waves.
The gently rocking motion of a teleseism (distant earthquake) is quite reminding of the gentle slow-moving earth-tides. And they do not cause eruptions either (nor earthquakes), but that is another bedtime story for another evening.
Earthquake on Earthquake
The same principle also goes for Earthquakes. A distant Earthquake is not going to cause a distant fault-line to rupture. Why? Well again the waveforms are so large that they move all of the fault-line at the same time in a slow and equal movement. Think here about going for a massage and compare it to being hit a few times by a boxer. The massage does not really hurt you, but the boxer will.
In this case the boxer was the blow of 8.5 at Sumatra, it damaged a close by fault-line causing the following 8.2 Earthquake. So I am sad to say that physics do not allow teleseisms to set off series of large earthquakes all over the planet. Get over it 2012ers.