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9.0 Earthquake strikes Japan


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Ok...back to reality. Did anyone notice how many "pre-shocks" there were to this quake on the 9th? 4 quakes of mag 6+, one of which was 7.2. In hindsight this was obviously predictive...did anyone say anything about this on the 9th or 10th?

http://earthquake.us.../quakes_all.php

I do recall the 7.2 being reported (as "breaking news") on NHK World when it occurred, as I was watching at the time, but didn't hear anything more about it. There was also one in China the following day which killed 22 people, which I think made the 7.2 a bit of an afterthought.

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Ok...back to reality. Did anyone notice how many "pre-shocks" there were to this quake on the 9th? 4 quakes of mag 6+, one of which was 7.2. In hindsight this was obviously predictive...did anyone say anything about this on the 9th or 10th?

http://earthquake.us.../quakes_all.php

The problem with foreshocks is that, of course, as you say, they are only obviously predictive in hindsight.

A lot of major quakes have foreshocks; a lot don't have foreshocks at all.

And there are a lot of 7.2 earthquakes on subduction zones that AREN'T followed by a larger quake.

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There was a strong foreshock before the big Chile quake also.

Apparently two before the Loma Prieta earthquake in 1989 and one before the 1906 shock (though that one was only a minute before the main shock). Problem with foreshocks is that it's usually hindsight that tells you it was one rather than foresight.

Steve

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Apparently two before the Loma Prieta earthquake in 1989 and one before the 1906 shock (though that one was only a minute before the main shock). Problem with foreshocks is that it's usually hindsight that tells you it was one rather than foresight.

Steve

Yes and so many quakes of that intensity are isolated incidents, that it's very hard to discern which might lead to something bigger.

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Apparently two before the Loma Prieta earthquake in 1989 and one before the 1906 shock (though that one was only a minute before the main shock). Problem with foreshocks is that it's usually hindsight that tells you it was one rather than foresight.

Steve

Does a bigger quake simply make the previous quake a foreshock? Or can there be 2 seperate big earthquakes that are not related?

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Does a bigger quake simply make the previous quake a foreshock? Or can there be 2 seperate big earthquakes that are not related?

Basically if there's a larger quake very near an earlier quake, the earlier quake is a foreshock.

If you have two big quakes near each other in a short time period, the odds are overwhelming they are related.

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IS IT possible that the 9.0 quake could be another foreshock of a greater earthquake later this week? Im curious and know its nearly impossible.

No.

It is possible that the stress released along the part of the subduction zone that ruptured could produce additional stress on parts that didn't, but in this case it seems like most of the subduction-zone in question ruptured.

We saw that kind of transfer of stress in Indonesia where there was another M8+ 'quake after the M9 quake due to shifting of stress to another (un-ruptured) part of the subduction zone.

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The problem with foreshocks is that, of course, as you say, they are only obviously predictive in hindsight.

A lot of major quakes have foreshocks; a lot don't have foreshocks at all.

And there are a lot of 7.2 earthquakes on subduction zones that AREN'T followed by a larger quake.

Jewish quakes have their foreshocks removed.

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No.

It is possible that the stress released along the part of the subduction zone that ruptured could produce additional stress on parts that didn't, but in this case it seems like most of the subduction-zone in question ruptured.

We saw that kind of transfer of stress in Indonesia where there was another M8+ 'quake after the M9 quake due to shifting of stress to another (un-ruptured) part of the subduction zone.

I had forgotten about that. How come a tsunami did not follow the M8 quake in Indonesia? it sure seems a quake that large would produce a pretty good water displacement.

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I had forgotten about that. How come a tsunami did not follow the M8 quake in Indonesia? it sure seems a quake that large would produce a pretty good water displacement.

I believe there was one, but it was minor, IIRC. It's all about the exact amount of displacement at the sea floor... so I guess there just wasn't enough in the second 'quake to cause a huge tsunami.

Also, of secondary (but non-trivial) importance is the shape of the coast near the earthquake.

EDIT: There was a tsunami of up to 3 meters with that 'quake:

http://en.wikipedia.org/wiki/2005_Sumatra_earthquake#Tsunami

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Sorry if this one has been posted...haven't been following the thread too closely...but this is one scary 1st person video of the Tsunami. Kind of seems like an ordinary flash flood...but after the 3:30 mark things really get insane.

http://gizmodo.com/#...pan-tsunami-yet

I always considered a major earthquake to be the natural disaster I feared most...after that video, Tsunami easily takes first place.

The person who filmed this had nerves of steel! Absolutely incredible power!

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True, but I don't know if you could say any more than "the risk of a large quake in this region is heightened"... like they do in Cali after a quake (as Josh likes to point out every time. :arrowhead: )

Don't let quake envy get the better of you. One day you'll experience a 4.7, and then you'll have some real experiences of your own to share. :hug:

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