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:

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!!!
>   Stephen
>   38.828N  120.979W
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>Date: Tue, 29 Mar 2005 21:12:37 -0800
>From: Stephen & Kathy 
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>Subject: Re: Mb question
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>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!!!
>   Stephen
>   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 for more 
>Larry Cochrane
>Redwood City, PSN


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