I found this brainstorm at CBC News. In a report on the Japanese earthquake, CBC meteorologist Johanna Wagstaffe opined:
" A magnitude 8.9 quake is actually 8,000 times more powerful than a 7.2 quake," said Wagstaffe. " Because the earthquake occurred under the ocean floor, massive amounts of water were displaced above the shaking ocean ground, generating a tsunami."
8,000 times? We know the Richter scale works on factors of ten. An 8.0 magnitude quake, for example, would be ten times greater than a 7.0 tremblor. Hence a 9.0 quake would be one hundred times more powerful than a 7.0. What beggars belief is how Wagstaffe comes up with the math than an 8.9 quake is eight thousand times more powerful than a 7.2.
If anything, meteorologists know far less about seismology than climatology. They're trained to guess whether it's going to rain tomorrow, not whether you've got a tsunami in your future. Yet when a story like the Japanese quake arrives, everybody and their cousins get to weigh in, even if they really know squat.
4 comments:
It's been reported in Australian papers that Japan's 8.9 is 8,000 times the 6.3 Christchurch quake. I've not read anything about 8.9 to 7.2 comparisons.
I wish somebody could explain that to me. This seems a bit ambiguous. When it comes to damage there are factors beyond force including distance from epicenter, the depth of the quake, its duration, the surface topography and man-made elements.
From what I understand of Richter scale measurements, a 7 would be 10X a six. An 8 would be 10X10 or 100X a 6. A 9 would be 10X10X10 or 1,000X a 6. Something around a 9.8 would approximate 8,000X a 6.
But we can't place too much emphasis on the number value. Remember Christchurch was hit by a relatively harmless low-7 quake a month before the deadly mid-6 tremblor.
I can help (after a trip to Wikipedia. The Richter scale measures the shaking amplitude/magnitude.
The energy release is actually a factor of 31.6 between each 1.0 magnitude difference. An 8.9 corresponds to ~7900 times the energy released by a 6.3 earthquake.
I have to assume that Wagstaffe mistakenly said 7.2 instead of probably 6.2...
Like you said, though, the energy released by a quake is as pointless as the category of a hurricane (such as Category 3 Katrina at landfall). There are plenty of other factors involved.
Johanna Wagstaffe is both a meteorologist and a seismologist! Bio: www.cbc.ca/vancouverweather/bio/
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