Earthquakes and the Richter Scale

Why rounding some numbers is simply ludicrous

Earthquakes. The mere mention of one can send a person into shaking tremors. New York City and Washington DC experience a moderate earthquake and one would think Armageddon is upon us. Meanwhile, Sendei, Japan will require a decade or more to recover from their catastrophic 9.0Mg earthquake.

The Richter Scale is not a straight-line scale. The Richter Scale is logarithmic. In other words, a 4Mg earthquake is not twice as strong as a 2Mg earthquake. A 4Mg earthquake releases more than 60x’s as much energy as a 2Mg earthquake.

VA_DC_EQI was watching and reading about coverage of the East Coast earthquake. People ranting about “earthquake preparedness.” Newscasters mistakenly “rounding” the 5.9 earthquake to a 6.0. Preparing for an earthquake in DC makes about as much sense to me as having people in Montana prepare for a hurricane.

But, it did get me to wondering; “what is the difference in energy between a 5.9 and a 6.0 earthquake?”

Every 0.2 increase in earthquake magnitude corresponds to a doubling of energy released. Thus, a 5.9 earthquake releases TWICE the energy of a 5.7 earthquake.

Therefore, a magnitude cannot be “rounded up” or “rounded down.”

Check out this web site “WolframAlpha” for an earthquake energy calculator.

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