PSN-L Email List Message

Subject: IASP91 table in Winquake
From: RLLaney@.......
Date: Sat, 6 May 2000 17:11:06 EDT

Hello all:

The recent quake on the Minahassa Peninsula, Sulawes reminded me of a 
question that I have had for some time about the use of the IASP91 table in 

The teleseismic table in Winquake cannot be used to calculate the P and S 
wave arrivals for distances beyond about 12,000 km because beyond this 
distance the arrival location is in the "shadow" of the earth's core and 
arrivals are modified by travel through or along the boundary of the core (my 
location is about 15,000 km from the Minahassa event location).  Thus, 
Winquake gives the error message "Can't place P and S markers" when one tries 
to calculate P and S wave arrivals beyond this distance using the teleseismic 
table.  Yet if one uses the IASP91 table beyond the critical distance, P and 
S markers can be calculated.  I guess I don't understand what the IASP91 
table does that the teleseismic table doesn't do.  Are the P and S wave 
arrivals that can be calculated using the IASP91 "real" beyond the critical 
distance?  I noticed that my event record using the IASP91 table to calculate 
P and S arrivals and some of the other event records posted for the Minahassa 
quake showed 3 to 4 minutes difference between the calculated P wave arrival 
and what looked like the first arrival on the record.

Can someone shed some light on this issue?


Bob Laney
Herndon, VA

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