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

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: 4, Insightful) by Bot on Friday August 14 2015, @09:26PM

    by Bot (3902) on Friday August 14 2015, @09:26PM (#223014) Journal

    Alternative scales like the Mercalli scale are less relevant geologically, but quite useful, this one is interested in the surface damage at the epicenter.
    In fact Italian news outlet used to employ this one, then they resorted to Richter. Likely because of our tradition of obscuring information: when they talk about the stock exchange they tell you the variation in percentage without telling the absolute value of the index...

      TLDR, when a quake happen I first want to know if the house is still up.

    From wikipedia, the twelve degrees of the Mercalli scale.

    I. Not felt Not felt except by a very few under especially favorable conditions.
    II. Weak Felt only by a few persons at rest, especially on upper floors of buildings.
    III. Weak Felt quite noticeably by persons indoors, especially on upper floors of buildings. Many people do not recognize it as an earthquake. Standing motor cars may rock slightly. Vibrations similar to the passing of a truck. Duration estimated.
    IV. Light Felt indoors by many, outdoors by few during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing motor cars rocked noticeably.
    V. Moderate Felt by nearly everyone; many awakened. Some dishes, windows broken. Unstable objects overturned. Pendulum clocks may stop.
    VI. Strong Felt by all, many frightened. Some heavy furniture moved; a few instances of fallen plaster. Damage slight.
    VII. Very Strong Damage negligible in buildings of good design and construction; slight to moderate in well-built ordinary structures; considerable damage in poorly built or badly designed structures; some chimneys broken.
    VIII. Severe Damage slight in specially designed structures; considerable damage in ordinary substantial buildings with partial collapse. Damage great in poorly built structures. Fall of chimneys, factory stacks, columns, monuments, walls. Heavy furniture overturned.
    IX. Violent Damage considerable in specially designed structures; well-designed frame structures thrown out of plumb. Damage great in substantial buildings, with partial collapse. Buildings shifted off foundations.
    X. Extreme Some well-built wooden structures destroyed; most masonry and frame structures destroyed with foundations. Rails bent.
    XI. Extreme Few, if any (masonry), structures remain standing. Bridges destroyed. Broad fissures in ground. Underground pipe lines completely out of service. Earth slumps and land slips in soft ground. Rails bent greatly.
    XII. Extreme Damage total. Waves seen on ground surfaces. Lines of sight and level distorted. Objects thrown upward into the air.

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