Hi all:
While reading and writing sac files with obspy, I encountered a similar problem posted on the obspy forum in March 2014 (http://lists.swapbytes.de/archives/obspy-users/2014-March/001306.html).
In my case, the sac headers are not updated on obspy and I could not write to file the dist, az and baz computed in obspy. As a result, I manually input the stlo, stla, evlo and evla, into the obspy file. However, after writing the obspy mseed file in sac format, sac should automatically calculate the distance header, but this is not happening.
As suggested in the response (http://lists.swapbytes.de/archives/obspy-users/2014-March/001307.html), I tried the ‘wh’ option in SAC but the DIST, AZ and BAZ still were not computed, I am not sure if this is related to how obspy writes the output sac file.
I would appreciate anyone’s help.
Thank you,
Ayodeji
Seismology
University of Victoria