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The Way We Measure Earthquakes is Stupid

posted by janrinok on Friday August 14 2015, @06:15PM   Printer-friendly
from the shake,-rattle-and-roll dept.

AnonTechie writes:

THIS WEEKEND, A 3.3-magnitude earthquake rattled San Francisco ever so slightly. The small quake, like so many before it, passed, and San Franciscans went back to conveniently ignoring their seismic reality. Magnitude 3.3 earthquakes are clearly no big deal, and the city survived a 6.9-magnitude earthquake in 1989 mostly fine—how how much bigger will the Big One, at 8.0, be than 1989?

Ten times! As smarty-pants among you who understand logarithms may be thinking. But...that's wrong. On the current logarithmic earthquake scale, a whole number increase, like from 7.0 to 8.0, actually means a 32-fold increase in earthquake energy. Even if you can mentally do that math—and feel smug doing it—the logarithmic scale for earthquakes is terrible for intuitively communicating risk. "It's arbitrary," says Lucy Jones, a seismologist with the US Geological Survey. "I've never particularly liked it."

[Suggested New Earthquake Scale]: Seismological Review Letters

Maybe SN could suggest a better way to measure earthquakes ...

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  • (Score: 2) by takyon on Saturday August 15 2015, @10:02PM

    by takyon (881) <takyonNO@SPAMsoylentnews.org> on Saturday August 15 2015, @10:02PM (#223368) Journal

    I would define the Aki to be equal to 1021 dynes-cm (or 1014 N-m for the SI police). The smallest earthquakes routinely recorded by most networks (M 2.0), would be about 0.01 Akis, a barely damaging earthquake (M 5) would be 400 Akis, Northridge would be 120,000 Akis, and the great Chilean earthquake would be two hundred billion Akis. Essentially every earthquake we would ever talk about would involve a range of numbers similar to our monetary system. From a penny for our thoughts to a 1980's United States federal deficit, these are numbers that may not fit on our hands but are ones we can live with.

    Lucy Jones seems to want to normalize the imperceptible tremors to a fraction of 1 unit, small earthquakes from 1 to low thousands of units, and then hundreds of thousands all the way to billions for the actual and biggest earthquakes. But it's all joules in the end.

    Jones wants this unit so that the public and journalists can understand earthquake strength more intuitively than "7.0 mag is 32 times stronger than 6.0 mag".

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  • (Score: 2) by maxwell demon on Sunday August 16 2015, @10:34AM

    by maxwell demon (1608) on Sunday August 16 2015, @10:34AM (#223489) Journal

    Let's rewrite his statement to Terajoule:

    The smallest earthquakes routinely recorded by most networks (M 2.0), would be about 1 Terajoule, a barely damaging earthquake (M 5) would be 40,000 Terajoule, Northridge would be 12 million Terajoule, and the great Chilean earthquake would be twenty trillion Exajoule.

    So how are his Akis better, again? Heck, even the "reporting threshold" is perfect with Terajoule

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    The Tao of math: The numbers you can count are not the real numbers.