[SAC-HELP] units of EVDP in SAC

Januka Attanayake jattanayake at yahoo.com
Tue Jul 19 18:47:27 PDT 2011


Hello Arthur, 
I use EVDP with taup_setsac to mark travel times in which case both units, meters and kilometers, are accommodated using different flags (evdp and evdpkm). If you are bringing in the same functionality with TRAVELTIME with km as the default unit, that would indeed be very helpful. However, I haven't come across a situation where I had to use meters instead of km. 

Januka.
 
_______________
Serenity isn't freedom from the storm, but peace within the storm

Januka Attanayake 
Earthquake Seismology & Economics
The University of Connecticut 
Beach Hall - U2045
354, Mansfield Rd; 
Storrs, CT 06269
Tel :  860 486 0475 (Office)
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Home page: http://sites.google.com/site/janukaattanayake/
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________________________________
From: Arthur Snoke <snoke at vt.edu>
To: SAC-help Listserv <sac-help at iris.washington.edu>
Sent: Tuesday, July 19, 2011 9:17 PM
Subject: [SAC-HELP] units of EVDP in SAC

To my knowledge, since IRIS/SAC v100, EVDP (focal depth in the SAC header) has not been used in any SAC command.  Please let me know if there are commands I have overlooked.

Because of historical reasons, EVDP (focal depth) in SAC has the units according to the SAC manual.  RDSEED converts EVDP from kilometers (which it is in blockette 71 in SEED) to meters when writing SAC waveforms.

For v101.5, the units of EVDP will be of interest because we will (re) introduce a version of the TRAVELTIME command, in which for waveforms with a defined location and origin time one can calculate arrival times for body-wave phases using the iaspei-tau tables for either ak135 or iasp91 velocity models.  For this command, the units of EVDP matter.

I personally would like to evolve towards having kilometers being the default unit for EVDP.  As a first step, kilometers would be the default choice for EVDP in TRAVELTIME.

The point of this note is a canvass of the community to find if there are any problems with using KM rather than M for EVDP.  Let me know if there are other programs that read SAC files and use EVDP assuming it is in meters.

Arthur
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