PSN-L Email List Message

Subject: Re: mb - Ms disciminant
From: John Taber taber@.............
Date: Sat, 2 Dec 2000 04:46:07 +1300 (NZDT)


You can find a reasonable description of mb and Ms in the textbook 
"Modern Global Seismology" by Lay and Wallace, though they don't give 
an illustration of actually calculating the magnitudes.  They do
reference two papers which probably would give examples (I haven't
read the papers myself):

Veith and Clawson, 1972, Magnitude from short period P wave data,
Bull. Seismological Soc. Am., V. 62, 435-452.

Geller, 1976, Scaling relations for earthquake source parameters and
magnitudes, Bull. Seismological Soc. Am., V. 66, 1501-1523.


John Taber

From: "Richard J. Warburton" 
Sent: Friday, November 24, 2000 2:43 PM
Subject: mb - Ms disciminant

> Dear Larry,
> I manufacture a very stable gravity meter (the 'Superconducting
> Gravimeter'), which is very low noise up to about 1 mHz.  Until
> recently, I have not been much interested in higher frequencies, since
> the range of frequencies from 1 mHz to 10 Hz seemed well covered by
> other long period seismometers.  Now, I believe that I might be able to
> improve the 'SG' so that it could improve measurements in the 1 to 20
> mHz range.
> My knowledge of seismology is limited, but I know that the measurement
> of mb-Ms is an important discriminant for separating underground
> explosions from earthquakes.  However, I have not yet found a simple and
> clear explanation of how either mb or Ms is measured.  What would be
> most helpful would to find the exact definition of mb and Ms, and then
> as an example show the incoming seismic wave train, the spectrum of the
> wave train, and an illustration of the calculation of these two.
> Advanced mathematics is okay as long as the result is "clarified" with
> some examples.
> Is this available is any book or paper that you are aware of?
> Thanks much,
> Richard
> --
> Richard Warburton
> GWR Instruments, Inc.
> 6264 Ferris Square, Suite D
> San Diego, California 92121
> phone: (858) 452-7655
> fax: (858) 452-6965


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Larry Cochrane <cochrane@..............>