PSN-L Email List Message
Subject: Re: Mb problem
From: John or Jan Lahr JohnJan@........
Date: Thu, 31 Mar 2005 06:41:31 -0700
I've updated the page on mb: http://jclahr.com/science/software/mb/
It now includes the source and compiled code for computing magnitude via
the Q table
used by NEIC as well as by the formula given by Larry Braile.
There is a link to the graph by Gutenberg and Richter (1956) which is the
for the Q table.
At 01:57 PM 3/30/2005, you wrote:
>Well,, I just figured out my winquake Mb problem,,, a simple upgrade
>should take care of it,, HA!!!!
>It would still be fun to play with and compare if we had a table version
>that would run under dos or windows,,, hint hint,, ha!!!
> 38.828N 120.979W
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>Subject: Re: Mb question
>Thanks Larry,,, I did look at your help files on how winquake
>calculates Mb,, but it refers to a formula which requires the table,, so
>I assumed you had a file with the table, but couldn't find it,,, then I
>said, well I'll just let your program calculate Mb,, but for some reason
>it is not obvious to me how to do it???? That is when I went looking for
>a table to set up my own calculation!!
>Looking at Johns fortran info and table I realize it isn't as simple as I
>first thought it would be,,, a straight forward array, with depth on one
>side and distance on the other would be something on the order of 800 by
>108!! The fortran table is 17 by 108! And as near as I can tell from
>the formulas, it isn't just bands of depth,,, it appears that the full
>range of Q is wider than the limits in the table??? Per chance and just
>for fun, has anyone converted it to a PC or dos program????? Or perhaps
>a mathcad program???
>Thanks all,,, it is becoming a real education!!!
> 38.828N 120.979W
Larry Cochrane wrote:
>WinQuake uses the following formula to calculate mb magnitude
>mb = log10(A/T) + 0.01*D + 5.9
>A = Peak P wave displacement amplitude in micrometers, T = Period of the
>displacement amplitude and D = Distance in degrees
>See http://www.eas.purdue.edu/~braile/edumod/as1mag/as1mag3.pdf for more
>Redwood City, PSN
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