What a Richter 8.8 earthquake means

I was just reading a comment on a blog from a Chilean citizen that says so far (as of 2 1/2 hours ago, anyway) there were 122 confirmed deaths from this morning’s earthquake in Chile, which rang up an 8.8 on the Richter scale.

Most folks immediately thought of Haiti when they got the news. The power of this quake compared to the one that wrecked Port-Au-Prince is enormous. The Richter scale is logarithmic, meaning that a quake of magnitude 7.5 is 10 times as powerful as a 6.5 and 100 times as powerful as a 5.5. The Haiti quake was a 7.0, so if I did my calculations right, the Chile quake was 63 times as powerful. The difference in surface energy release between quakes different by one unit of magnitude is event greater: 10^1.5 rather than 10^1. So today’s quake yielded some 500 times the amount of effective destructive potential as the Haiti quake, although the latter was far, far more catastrophic in terms of damage and loss of life.

Not to trivialize what’s happening right now, but I’m glad that Haiti didn’t have to suffer an 8.8 quake, hard though it is to imagine things being any worse than they already are.

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  1. #1 by pLow on February 27, 2010 - 7:25 pm

    Kev,

    The Richter scale was developed for quantifying medium sized, SoCal quakes. The moment magnitude scale is the more common method for quantifying the amount of energy released during a quake. A correct title would be “What a magnitude 8.8 earthquake means”

    …regardless, a massive quake.

  2. #2 by kemibe on February 27, 2010 - 7:31 pm

    Interesting. I didn’t know about that distinction. Neither do most news outlets, apparently.

    I guess the part I wanted to get right was the math–I don’t know that most people are aware that a lot of metrics (e.g., sonic pressure, stellar magnitude) involve log or semi-log scales. Then again maybe most don’t care. You must be some kind of geoscience nut, which means you like running up mountains and staircases.

  3. #3 by Jay on February 28, 2010 - 5:58 pm

    The Richter scale is logarithmic, meaning that a quake of magnitude 7.5 is 10 times as powerful as a 6.5 and 100 times as powerful as a 5.5. The Haiti quake was a 7.0, so if I did my calculations right, the Chile quake was 63 times as powerful.

    Just to be clear, “powerful” here refers to amplitude of ground motion, rather than energy release, which you correctly reference in the next sentence.

    The media has gotten better about referring to the magnitude scale, rather than the Richter scale, but it still crops up here and there. At least they now (mostly) say tsunami, rather than tidal wave.

  4. #4 by The Science Pundit on March 7, 2010 - 5:14 am

    Here’s a good summary of the equations for earthquake magnitude and intensity.

  5. #6 by kemibe on March 7, 2010 - 5:48 am

    That’s perfect. I guess I was kind of clueless when I posted this. I never knew there were multiple ways of calculating the power of earthquakes. I thought that the Richter scale was the be-all, end-all.

    One time when I was a teenager we had a quake in New Hampshire that was around a 4.5. It only lasted about 10 seconds–we’re not exactly on a fault line. I was more or less terrified when I was in Florida and Hurricane Wilma hit with 110-mile-an-hour gusts and fake terra cotta shit was blowing off the roof and smashing into cars in the parking lot. But at least you can plan for hurricanes, not that anyone in Florida bothers. At least it was cool that afternoon. I had a great run that day except for having to dodge live wires on the ground. I don’t miss that place. I just wonder what will happen first–a Cat 3/4/5 windstorm that wrecks Miami or a massive quake that destroys San Francisco/Oakland. If I had to pick I’d rather see the hurricane but my friend’s parents live in Fort Lauderdale and I know they wouldn’t leave and it would suck if her house got flattened.

  6. #7 by ignacio on April 1, 2010 - 2:48 pm

    Just to say I live in Chile and i was 400 hundred kilometers from the epicenter,and the destruction around me it is absoluty to 40% of the simple houses and 40% serious damage only 20% well,generally wood contruction. To me 8.8 is 700 kms around the epicenter with hard destruction.I dont remenber at least in Chile so extensive damage.

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