Question
How do I find the origin time in SAC header?
I downloaded a SAC file, and the KZTIME
header in the sac file is different from the origin time of the event that I requested. How do I get the origin time?
Answer
Here is an example SAC header:
SAC> read 1994.153.17.48.43.9891.II.WRAB.00.LHZ.D.SAC SAC> listhdr FILE: 1994.153.17.48.43.9891.II.WRAB.00.LHZ.D.SAC - 1 ------------------------------------------------- NPTS = 2944 B = 1.000000e-04 E = 2.942998e+03 IFTYPE = TIME SERIES FILE LEVEN = TRUE DELTA = 9.999994e-01 IDEP = UNKNOWN DEPMIN = -2.952368e+06 DEPMAX = 2.598185e+06 DEPMEN = 1.062373e+04 OMARKER = 1730 KZDATE = JUN 02 (153), 1994 KZTIME = 17:48:43.989 KSTNM = WRAB CMPAZ = 0.000000e+00 CMPINC = 0.000000e+00 STLA = -1.993360e+01 STLO = 1.343600e+02 STEL = 3.660000e+02 STDP = 1.000000e+02 EVLA = -1.047700e+01 EVLO = 1.128350e+02 EVDP = 1.840000e+04 KHOLE = 00 DIST = 2.534725e+03 AZ = 1.169120e+02 BAZ = 2.912198e+02 GCARC = 2.277521e+01 LOVROK = TRUE NVHDR = 6 SCALE = 1.243780e+10 NORID = 0 NEVID = 0 LPSPOL = FALSE LCALDA = TRUE KCMPNM = LHZ KNETWK = II MAG = 7.800000e+00
The origin offset is given by the OMARKER
field: 1730 seconds. This is the difference between the reference time (KZTIME
) and the origin time:
KZTIME
+ OMARKER
= 17:48:44 + 1720 seconds = 18:17:34 is the origin time.
Updated: 05/18/2017