FYI, (sorry if this was already
mentioned), the USGS Earthquake time travel calculator uses the IASP91
model, as per the note at the bottom of the page; see the following
link.

http://neic.usgs.gov/neis/travel_times/artim.html



The USGS "Theoretical P-Wave Travel Times" map with shadow zones, also
says it uses the IASP91 model.  Following is a link to an example for
the 6.0 Banda Sea quake on Dec 26...  see notes below map.

http://neic.usgs.gov/neis/bulletin/neic_qrat_t.html



  Stephen

  PSN Station #55



GPayton wrote:

  
  
  
  
Thanks to you, Larry and all that answered.  I've searched and
can only find that the IASP91 is the newer, but cannot discover that it
would matter that much in my limited sensor setup and environment. 
Looking at other posts, the JB seem to be the favorite, if not be
default.
  
 
  
Regards & Happy new Year to All
  
Jerry
  
 
  

    
-----
Original Message ----- 
    
From:
    Larry Cochrane 
    
To:
    psn-l@.............. 
    
Sent:
Thursday, December 31, 2009 2:46 PM
    
Subject:
Re: And Now A Simple Question
    


    
Hi Jerry,

    

The JB and IASP91 tables are different travel time models of the earth.
I think the 

IASP91 table is newer so it might be more accurate.

    

Regards,

Larry Cochrane

Redwood City, PSN

    

GPayton wrote:

> After the recent "high level" discussions, I would like to present
one at MY 

> intelligence level. (NO puns, please)

> 

> Please tell me the significant differences in using the JB vs. the
IASP91 

> tables?

> 

> Given a chosen event, switching between tables will result in
different 

> times, distances and etc.  How do I know WHICH to use in WinQuake.

> 

> Thanks,

> Jerry 

> 

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