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Haiti aftershock: Why a 6.1 quake isn't that powerful
Christian Monitor ^

Posted on 01/20/2010 7:50:09 AM PST by marthemaria

A magnitude 6.1 aftershock struck near Port-au-Prince on Wednesday morning. With so many buildings damaged by the major Haiti earthquake last week, there are concerns about danger. But there's a world of difference between today's quake and the 7.0 earthquake that did so much damage last week. The aftershock that hit Haiti shortly after 6 a.m. on Wednesday frightened Haitians traumatized by last week's much stronger earthquake and raised concerns that it could bring down buildings weakened by the original earthquake and cause more loss of life. While a 6.1 magnitude earthquake sounds almost as strong as a 7.0 earthquake, the difference of the destructive power between the two is greater than an order of magnitude. Unlike temperature scales, in which units of increase are constant, the method used to measure earthquake magnitudes is logarithmic. What this generally means is that the amount of shaking at ground level caused by a 5.0 earthquake is 10 times less than that caused by a 6.0 earthquake and 100 times less of that caused by a 7.0 earthquake.

(Excerpt) Read more at csmonitor.com ...


TOPICS: News/Current Events
KEYWORDS: aftershock; haiti
I became very worried and scared when I read about the new quake. This helped a bit
1 posted on 01/20/2010 7:50:10 AM PST by marthemaria
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To: marthemaria
While a 6.1 magnitude earthquake sounds almost as strong as a 7.0 earthquake, the difference of the destructive power between the two is greater than an order of magnitude. Unlike temperature scales, in which units of increase are constant, the method used to measure earthquake magnitudes is logarithmic. What this generally means is that the amount of shaking at ground level caused by a 5.0 earthquake is 10 times less than that caused by a 6.0 earthquake and 100 times less of that caused by a 7.0 earthquake.

Huh? A ten times difference is an order of magnitude, thus the difference between 6.0 and 7.0 is exactly one order of magnitude. The difference between a 6.1 and 7.0 is less than one order of magnitude, being only a 7.94x difference.

2 posted on 01/20/2010 7:56:40 AM PST by KarlInOhio (Gore is the fifth horseman of the apocalypse. He rides an icy horse bringing cold wherever he goes.)
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To: KarlInOhio

No....take the number “50”....ten TIMES greater is 500. Ten “more” is 60.


3 posted on 01/20/2010 7:59:49 AM PST by KeepUSfree (WOSD = fascism pure and simple.)
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To: KeepUSfree

Reread your post....never mind....!!! ;-)


4 posted on 01/20/2010 8:00:53 AM PST by KeepUSfree (WOSD = fascism pure and simple.)
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To: KeepUSfree
No....take the number “50”....ten TIMES greater is 500. Ten “more” is 60. Huh?

Ten TIMES greater than 50 is 550.

5 posted on 01/20/2010 8:02:34 AM PST by Izzy Dunne (Hello, I'm a TAGLINE virus. Please help me spread by copying me into YOUR tag line.)
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To: KeepUSfree
But the Richter scale is logarithmic, similar to decibels in sound. Adding one on the Richter scale is the same as multiplying the "shaking" (I don't know if that is total power or amplitude of motion being measured) by ten.

If I create the Karl Scale for your number by using the logarithm, your 50 would be 1.7. One more than 1.7 is 2.7 on the Karl Scale, which is 500 (ten times) of your original measurement. Adding on a logarithmic scale is the same as multiplying on a linear scale.

6 posted on 01/20/2010 8:06:38 AM PST by KarlInOhio (Gore is the fifth horseman of the apocalypse. He rides an icy horse bringing cold wherever he goes.)
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To: marthemaria

The earthquake in Haiti plus Obama will wipe out one thing -Florida. Haitians and other illegals are turning it into a bankrupt third world state like Calif. Businesses are fleeing as the unemployment taxes have gone up 10 X in the past few months. Haitians are turning Florida into Haiti.


7 posted on 01/20/2010 8:08:02 AM PST by Frantzie (TV - sending Americans towards Islamic serfdom - Cancel TV service NOW)
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To: KarlInOhio

Generally when speaking in order of magnitudes you would round to the nearest power of 10; so that 7.94 = 10.

Try this one on for size: “President Obama has increased the yearly federal deficit by an order of magnitude over his predecessor.”


8 posted on 01/20/2010 8:08:48 AM PST by eclecticEel (The Most High rules in the kingdom of men ... and sets over it the basest of men.)
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To: marthemaria
Musically...."A Whole Lot of Shakin' Goin' on"
9 posted on 01/20/2010 8:11:40 AM PST by Don Corleone ("Oil the gun..eat the cannolis. Take it to the Mattress.")
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To: KarlInOhio
The article is exactly right, same as sound measurement on a log scale.
10 posted on 01/20/2010 8:12:03 AM PST by boomop1
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To: eclecticEel
If the author had said "almost an order of magnitude" he would have been right. If he had said "an order of magnitude" he would have been imprecise, but close enough for newspaper work with rounding. But saying "more than an order of magnitude" he showed that he really didn't know what an order of magnitude is.

Now don't get me started with misuse of the term "quantum leap".

11 posted on 01/20/2010 8:23:18 AM PST by KarlInOhio (Gore is the fifth horseman of the apocalypse. He rides an icy horse bringing cold wherever he goes.)
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To: marthemaria

This author is CRAZY. We in California can attest that a 6.1 is HUGE. Yes a 7 is much much worse but a 6.1 is massive. Trust me, I have been in two of them.


12 posted on 01/20/2010 8:23:28 AM PST by joinedafterattack
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To: Frantzie

Just read in the loathed and despised Dallas Morning News that Texas may get a new congressional seat as a result of the influx of New Orleans people after the hurricane.

If New Orleans is so great and magical, how come nobody wanted to go back?

Well, they didn’t. Increasing the population and crime rate of Houston, not to mention the poverty and welfare rate.

Looks like the same thing may happen to Florida.


13 posted on 01/20/2010 8:29:40 AM PST by altura
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To: marthemaria; All

This is yet another example of the basic scientific illiteracy of the press.

Why use the clumsy “10 times less” when “one tenth as strong” would be both accurate and more informative?

Also, I agree that this reporter does not really seem to understand that “by an order of magnitude” means “by a factor of 10”

I don’t know about you, but 1/10 the power of the quake that levelled Haiti still seems mighty powerful to me.


14 posted on 01/20/2010 8:33:34 AM PST by paterfamilias
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To: marthemaria

I heard a scientist on TV today say that after shocks are usually about 1 magnitude below the original


15 posted on 01/20/2010 8:37:50 AM PST by RnMomof7 (Here I stand. I can do no other. God help me. Amen.)
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To: marthemaria
OK. So a 6.1 is much less than a 7.0. But a 6.1 ain't small. I was driving my car in Pasadena, CA when a 5.1 hit (in the 1980’s). It felt like I just had a front-tire blowout, in fact, that is exactly what I thought happened. I pulled over and got out of the car when an aftershock hit with enough force that I held onto the car to steady myself. The aftershock was a 4.5. (overall there was pretty minor damage, mostly broken glass in Arcadia)
16 posted on 01/20/2010 8:41:12 AM PST by bobsatwork
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To: KarlInOhio

According to Wikipedia, the Richter is log base 10 of the magnitude of the (RMS?) displacement. They claim that the energy released is proportional to the 3/2 power of displacement, so a difference of one on the Richter Scale is a factor of 10 in displacement, but 31.6 in energy.

Too subtle for a general purpose news report, I suppose. I imagine that it’s not just the energy but the spectrum that contributes as well and local construction standards determine the actual damage.


17 posted on 01/20/2010 8:59:41 AM PST by Lonesome in Massachussets (Don't blame me, I'm from Massachusetts)
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