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March 11 quake freed hundreds of years of strain

36 Comments
By Brett Israel

The magnitude 9.0 earthquake that shook Japan on March 11 released hundreds of years of tectonic strain, and has provided researchers with clues about where such large quakes could strike in the future, according to a study published in the journal Nature that provides more information on how the epic quake occurred.

The March 11 earthquake is the fourth-largest ever recorded in the world. The quake struck off the coast of the Tohoku region of Japan, triggering a deadly tsunami that may have killed nearly 30,000 people.

The rumbling didn't end with this massive rupture, and it hasn't stopped today. Nearly 75 aftershocks of magnitude 6.0 or greater have struck the region. In the new study, scientists used Global Positioning System (GPS) stations from a network that has been in place for 15 years to document the shaking.

The quake deformed a stretch of ground 250 miles long and 124 miles wide, "a remarkably compact area," according to Jean-Philippe Avouac, a geophysicist at Caltech, who was not involved with the study.

The Japanese earthquake ruptured along the Japan Trench near the boundary between the Pacific and North American tectonic plates — huge, moving slabs of the Earth's crust. The quake was a megathrust earthquake, where the Pacific plate dove underneath Japan at the Japan Trench. The seafloor was pushed away from Japan sending waves roaring toward Hawaii and the U.S. West Coast.

The data suggest that the ground between the two tectonic plates slipped as much as 165 feet, twice the slip of other giant quakes such as the magnitude 9.4 off Sumatra in 2004 and the 9.0 in Chile in 2010. This massive movement is one reason why the Japan quake produced such a large tsunami. The slip was also shallower than might have been expected, and was in a notable location.

"A striking result is that the earthquake occurred at a place where these data were showing rapid strain buildup," Avouac told OurAmazingPlanet. "It says that places where strain is building up rapidly, more rapidly than it has been released by historical and recent earthquakes, are places of potential future earthquakes."

More analysis must be done to pinpoint specific places of rapid buildup, Avouac said. Yet despite worries that this year's quake could mean increased danger for a major quake near Tokyo, the data suggests that a plate interface south of the rupture zone shows "no indication of a major zone of strain buildup on that portion of the plate boundary that might threaten Tokyo," Avouac wrote in a commentary that accompanies the study.

The GPS data suggest that a significant amount of strain continues to leak via a process called afterslip, which is a nonviolent movement of the ground that follows an earthquake.

© Our Amazing Planet

©2021 GPlusMedia Inc.

36 Comments
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this was a really interesting article. Thanks for posting this JT.

2 ( +2 / -0 )

extremely interesting. thanks from me, too.

2 ( +2 / -0 )

So... is this article saying that we DON'T need to worry about another big quake destroying Tokyo or the Tokai area in the near future as everyone believes? That the pressure has been relieved and won't happen again for a long time?

1 ( +1 / -0 )

They say the next huge earthquake will be near the San Andreas faultline,

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Yet despite worries that this year’s quake could mean increased danger for a major quake near Tokyo, the data suggests that a plate interface south of the rupture zone shows “no indication of a major zone of strain buildup on that portion of the plate boundary that might threaten Tokyo

That's Good news.

1 ( +1 / -0 )

That is interesting. Good to know Kanto won't be torn in two in the near future. :) Earlier reports had it that the Tohoku quake loaded pressure onto a segment of the fault or adjacent fault much closer to Tokyo.

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Definitely a good read.

More analysis must be done to pinpoint specific places of rapid buildup, Avouac said. Yet despite worries that this year’s quake could mean increased danger for a major quake near Tokyo, the data suggests that a plate interface south of the rupture zone shows “no indication of a major zone of strain buildup on that portion of the plate boundary that might threaten Tokyo,” Avouac wrote in a commentary that accompanies the study.

Not so sure I agree with Tokyo being in the clear as far as earthquakes go.

-1 ( +1 / -2 )

really can`t rule out a big one ANYWHERE in the world - earthquakes being unpredictable and all that - but at least this article is informative.

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I drank some green tea while reading this. Good article. Amazed at how much the plates moved. I am going to print up a t-shirt that says " I survived the big one Japan 2011"

-3 ( +1 / -4 )

ihavegreatlegs - Not sure what your point is with the green tea other than you enjoy tempting fate, but I suggest not flaunting your tee shirt in Tohoku where many were not so lucky.

3 ( +6 / -3 )

dangerous times

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Good to see high-level journals like Nature being cited on JT! However, the quote from Avouac about not needing to worry in Tokyo is a bit misleading. In the very next sentence of the original Nature article, Avouac says "But it is clear that although geodetic networks are invaluable instruments for observing strain accumulation and seismic release at plate boundaries and major faults, we don’t yet have an adequate theory to use these data for earthquake and tsunami hazard assessment".

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Not so sure I agree with Tokyo being in the clear as far as earthquakes go.

What university are you a geophysicist at? ;)

-2 ( +0 / -2 )

@hoserfella;

I think the t-shirt idea would be great as long as all the money made from it in profits gets donated to the Northern hit areas. As far as green tea goes, I have continued to drink it on ice with my shouchu. Refreshing. You would have to drink hundreds of bottles a day for it to possibly hurt you. Plus, before the radiation got in the leaves, it went through the air that we are all breathing.

The amount of movement was significant here, but it still cannot be predicted. There was another 5.9 quaker yesterday.

1 ( +1 / -0 )

Interesting article. Just wondering why this site insists on citing secondary sources all the time. Kinda ruins reliability.

according to Jean-Philippe Avouac, a geophysicist at Caltech, ****who was not involved with the study.

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@MrDog I'm not a geophysicist. I'm freaked. Absolutely freaked...okay. I don't trust Big Government. I trust what the bloggers on this site have to say more than some guy who's getting paid to give us a report.

Earthquakes happen. They will happen again. Don't need to be a geophysicist. I can tell you this....I'm a Realist.

Anyway, if you agree with what this guy has to say then why don't you buy a house now? Buy a house in Tokyo or the Chiba peninsula. You have money in the bank, drop like it's hot on a new house south of Fukushima. Put your money where you mouth is.

-2 ( +3 / -5 )

ihavegreatlegs:

Nice thought, however.... I am not so sure the victims relatives would be too pleased seeing someone wearing a t-shirt which says 'I survived the big one Japan 2011'..

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the data suggests that a plate interface south of the rupture zone shows “no indication of a major zone of strain buildup on that portion of the plate boundary that might threaten Tokyo,”

This says nothing about there not being a risk for a Kanto quake, this says there's no indication of a risk along that particular plate boundary. Not to be a pessimist but a) no indication is fairly meaningless b) this says nothing about the Phillipine Sea plate boundaries. I wouldn't get too complacent about earthquake preparedness!

Nice to see a meaningful science article on JT. Can we get some more often?

0 ( +0 / -0 )

@MrDog I'm not a geophysicist. I'm freaked. Absolutely freaked...okay. I don't trust Big Government. I trust what the bloggers on this site have to say more than some guy who's getting paid to give us a report.

Okay. I think you should give me all your money and alcohol ;)

Anyway, if you agree with what this guy has to say then why don't you buy a house now? Buy a house in Tokyo or the Chiba peninsula.

I will buy a house. As soon as you give me all your money ;)

Earthquakes happen. They will happen again. Don't need to be a geophysicist.

Yeah, I know. But, it helps to listen to what expert say, rather then just getting "freaked".

I live in a pretty safe place. Absolutely no problems from the 3/11 quake, inland so no tsunami fears, no mountains nearby, close to a large U.S. military base (if the poo hits the senpuki, being close to a military base would be helpful).

I'm not "freaked", and I don't think you need to be. Just be prepared.

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Mankind has still a far way to go to combat the forces of nature. Meanwhile, let's all be nice to each other and live in harmony together.

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I also think this was an informative article, especially about relieving the hundreds of years of stress!

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If true, then this is a bit of good news in what has been a lot of bad (regarding the disasters). There's still pretty serious danger of big aftershocks, I would think, but if we can breathe a little easier knowing 'the (next) big one' isn't just around the corner then it's welcome news. I don't think people should be any less prepared, just in case, but still.

It would be interesting if they can expand on this kind of information and make a system that can give more specific info on one and roughly where the next big quake will occur. They already say, of course, that there will be one in this area within the next few decades or what have you, but that doesn't help much.

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I still am stunned by that 30000~ of deaths, so many lives gone...I realize it's not the focus of the article but to me it remains a very sad and humbling note. Certainly an interesting study, and we can only hope contingencies will be made and planned for any future catastrophies (not really holding my breath on that one though).

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Good articel but tetonics is still an inexact science. Other geologists are citing the "football" effect (not sure where the name came from). but in that theory massive shifts on one part of a fault line DO load up other parts. Anyway, no reason to not stay prepared.

0 ( +1 / -1 )

"poo hits the senpuki"... I like that.

0 ( +0 / -0 )

@hoserfella...there was a recent article of Strontium detected in Shizuoka green tea sent to France. The French said, "merci nai" and refused to admit it to the country. Not sure what happened to the tea next, but that is what @legs is referring to, I am pretty sure.

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Nobody predicted this one...they knew the stress was building, but not much more than that. They've been predicting the Tokai quake since the late 70s, all the earthquake prep funding has going to Tokyo and environs, and look what happened in Tohoku. The Hanshin quake was not predicted, either. The Hokudan fault that ruptured in the '95 quake was not on the top of the list for likely sites.

The Tokai and the Nankai are both overdue. They recur every 140 years or so, often come together or within a day of each other...they last occurred in 1703 and 1854. 157 years ago. There is also the matter of the big chunk of seismic plate jammed under Tokyo--

A massive slab of rock lurking beneath the Kanto Plain on the central Japanese island of Honshu is a major source of the earthquake threat that dogs Tokyo, scientists said on Sunday.

Around 100 kilometres (60 miles) wide and 25 kms (15 miles) thick, the chunk is jammed between tectonic plates that converge beneath the flat, densely-populated plain.

The giant fragment is a potent trigger for a hugely destructive kind of quake, for it wedges between two of the plates and prevents them from sliding smoothly over one other.

They point the finger at a large fragment broke away from the descending Pacific slab between two and three million years ago.

The main cause appears to have been a collision of two chains of seabed mountains into the Japan Trench on the ocean floor about 200 kms (120 miles) east of modern-day Tokyo.

"The fragment is now jammed between the Pacific and Philippine Sea slabs, like a pill that can't be fully swallowed," they said.

Who knows where is next? All you can do is be prepared, have supplies at hand, and an escape route and meeting place for family.

0 ( +0 / -0 )

I doubt that it will take hundreds of years for the next major earthquake.

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Tokyo is not 'clear' of earthquakes. Anyone with an ability to read, conduct analyses and conclude from historical recordings will easily see that. The cycle is approx every 70 years for the Kanto region, 1923 being the last Big One.

-1 ( +0 / -1 )

Ranger_Miffy - Thanks but I knew that. Hence the "tempting fate" bit..

-1 ( +0 / -1 )

I agree with YongYang. The big one may still strike Tokyo.

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"no indication of a major zone of strain buildup on that portion of the plate boundary that might threaten Tokyo"

Anyway, Tokyo has enough problems with Ishihara in charge for ANOTHER 4 years.

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It's not 'may' it is 'when'.

-1 ( +0 / -1 )

YongYang - according to your calculations, the Tokyo Big One is already 18 years overdue so you're way behind on your fear-mongering. Snap to it! (Shall we start burying and localizing Tokyo now?)

-1 ( +0 / -1 )

In the last ten years, about 20 what's called silent earthquakes ゆっくり地震 occurred along near the boundary between the Philippine Sea and North American plates, even in the Sagami Trough and off the Boso Peninsula where the Philippine Sea plate is wedged into two other plates. They release tectonic strain without earth tremors but the moment released by any one of those silent quakes to date comes short of M 7 the indicator of a great earthquake. However if the 3.11 quake of unprecedented magnitude with its unending aftershocks and afterslips should somehow or other help silent earthquakes occur more often in other areas and release strain in there more rapidly than it builds up, we may be spared major earthquakes for some time. What plate interface does the geophysicist of this news article mean by "a plate interface south of the rupture zone which shows no indication of a major zone of strain buildup on that portion of the plate boundary that might threaten Tokyo"? Beteween the Pacific and the Philippine Sea plates? Or does it include the area where those two plus the North American plates converge?

0 ( +0 / -0 )

Hoserfella, you seem to have missed the abbreviation "approx" which stands for approximately, there around.

-2 ( +0 / -2 )

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