Japan: Here we go again?

[Shooter]

TOKYO — Japan was rattled by a strong aftershock and tsunami warning Thursday night nearly a month after a devastating earthquake and tsunami flattened the northeastern coast.

Announcers on Japan's public broadcaster NHK told coastal residents to run to higher ground and away from the shore.

http://www.comcast.net/articles/news-general/20110405/AS.Japan.Earthquake/

 

[andalusian]

The Richter scale works in an exponential way sort-of - so this was a much smaller quake compared to the previous one (7.4 vs. 9).

To make it easy - every point on the scale is x31 in size. So a quake of 9.0 scale is 31 times more powerful than a quake of 8.0 scale.

This is not good - but this is a much much smaller risk than the previous one. The difference in size between a 9 and a 7.4 is around 80-83 times - so the last one was much, much bigger than this one.

 

[porkchopexpress]

The Richter scale works in an exponential way sort-of - so this was a much smaller quake compared to the previous one (7.4 vs. 9).

To make it easy - every point on the scale is x31 in size. So a quake of 9.0 scale is 31 times more powerful than a quake of 8.0 scale.

This is not good - but this is a much much smaller risk than the previous one. The difference in size between a 9 and a 7.4 is around 80-83 times - so the last one was much, much bigger than this one.

I think it's a lot bigger difference than that. A quick wiki check says the a 9.0 is about 1000X stronger than a 7.0.

 

[porkchopexpress]

Not saying it was a minor quake though. If this hit anywhere else, it'd be considered quite big. Just in comparison it's a lot weaker.

 

[barfo]

I think it's a lot bigger difference than that. A quick wiki check says the a 9.0 is about 1000X stronger than a 7.0.

Yes. 10**1.6**1.5 = 251

barfo

 

[andalusian]

I think it's a lot bigger difference than that. A quick wiki check says the a 9.0 is about 1000X stronger than a 7.0.

Look at the under "Examples"

http://en.wikipedia.org/wiki/Richter_magnitude_scale

A 7.5 quake had 6.6 megatons of energy, a 9.0 had 476, 476/6.6 = 87 - so I should have said somewhere around 90-100 - which is bigger than the 80-83 estimate I gave earlier (cut me some slack, it's early in the morning and I am multi-tasking). Bigger than my estimate, but not a tons bigger.

FWIW - The US measurements had it at 7.1 - which would make it much smaller. I went with 7.4 because that's what the Japanese are reporting.

 

[porkchopexpress]

Look at the under "Examples"

http://en.wikipedia.org/wiki/Richter_magnitude_scale

A 7.5 quake had 6.6 megatons of energy, a 9.0 had 476, 476/6.6 = 87 - so I should have said somewhere around 90-100 - which is bigger than the 80-83 estimate I gave earlier (cut me some slack, it's early in the morning and I am multi-tasking). Bigger than my estimate, but not a tons bigger.

FWIW - The US measurements had it at 7.1 - which would make it much smaller. I went with 7.4 because that's what the Japanese are reporting.

Yeah, in my head the difference was a lot bigger, but I guess not. Still a big quake, regardless if it's 7.4 or 7.1.

 

[Denny Crane]

I think every .1 is 10x...

 

[andalusian]

I think every .1 is 10x...

WiKi has the following numbers:

The energy release of an earthquake, which closely correlates to its destructive power, scales with the 3⁄2 power of the shaking amplitude. Thus, a difference in magnitude of 1.0 is equivalent to a factor of 31.6 ( = (101.0)(3 / 2)) in the energy released; a difference in magnitude of 2.0 is equivalent to a factor of 1000 ( = (102.0)(3 / 2) ) in the energy released

 

[THE HCP]

Denny the computer math nerds have taken over again! HELP!

 

[Denny Crane]

From the USGS WWW site:

http://pubs.usgs.gov/gip/earthq4/severitygip.html

Because of the logarithmic basis of the scale, each whole number increase in magnitude represents a tenfold increase in measured amplitude; as an estimate of energy, each whole number step in the magnitude scale corresponds to the release of about 31 times more energy than the amount associated with the preceding whole number value.