Re: pinhole Large Magnitude Earthquakes

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From: Paul Doherty (pauld@exploratorium.edu)
Date: Thu Dec 09 2004 - 13:12:29 PST 

From: "Paul Doherty" <pauld@exploratorium.edu>
Subject: Re: pinhole Large Magnitude Earthquakes
Date: Thu, 09 Dec 2004 13:12:29 -0800
Message-ID: <web-7597340@exploratorium.edu>

Hi Rebecah

There are several different Magnitudes used to report
earthquakes.
http://www.msu.edu/~fujita/earthquake/bigquake.html#magnitudes

The one used in the last 30 years is Mw , the moment
magnitude
according to this scale the great Chilean earthquake of
1960 was magnitude 9.6

http://www.msu.edu/~fujita/earthquake/bigquake.html

however using the older scales
this same earthquake was magnitude 7.9 or 8.5

so using the older earthquake magnitude scales based on
ground motion there were no magnitude 9 earthquakes
however using the modern energy based scale there have
been magnitude 9's.

Paul D

On Thu, 9 Dec 2004 13:03:29 -0800
  Rebecah Davis <rdavis@ebfas.org> wrote:
>I have a question about earthquakes. My old textbook said
>that there has never been an earthquake recorded with a
>magnitude over 9.0. But my new textbook says that the
>1923 Tokyo earthquake was 9.2 and the 1960 Chile
>earthquake was 9.5. Is this true? I (going on the
>information in the old textbook) told my students that
>there has never been a magnitude 9.0, and then they
>(being the smart alecs they are) pointed out that the
>book said I was wrong.
>
>So which is it?
>
>A confused,
>Rebecah Davis
>
>
>"The tragedy of science - the slaying of a beautiful
>hypothesis by an ugly fact."
>
>--TH Huxley
>
>
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