Thread: SAC Command

Started: 2012-08-09 18:36:46
Last activity: 2012-08-11 00:27:36
Topics: SAC Help
Mohit Agrawal
2012-08-09 18:36:46
Hello Everyone,

Is there any command in SAC which can remove a particular header from a sac
file ?



*Mohit Agrawal
PhD Candidate | Research Assistant | Geophysics (Computational Seismology)
Dept. of Geology | Baylor University
Geophysics Lab, E453R | Baylor University Sciences Building (BSB) | Office:
Phone- 254-710-2172 ( lab), 254-710-2155(office), 281-460-8941(Personal)
Email : mohit_agrawal<at>, ism21.mohit<at>
Home Address : Apt # 207, 1500 s, 9th street, 76706, Waco, Texas, USA.*

  • Arthur Snoke
    2012-08-09 20:10:11
    I assume you mean that you want a header field to be "unset."

    Look at the change header help file:, you will see
    that subcommand UNDEF: Use this keyword instead of v to "undefine" a
    header field.

    Also, look at
    in the section that lists a "typical" header, you will see that the
    "unset" value for an integer field is -12345 and similar values for other
    variable types.

    On Thu, 9 Aug 2012, mohit agrawal wrote:

    Is there any command in SAC which can remove a particular header from a sac
    file ?

  • Juan Lorenzo
    2012-08-11 00:27:36
    Dear SAC users:

    Currently if when I try to convert a passcal segy file into a sac file,
    I get the following error:
    ERROR in scale factor w/ gain =1 & scale = 0.0000000 e00.

    I would like to change the scale_fac variable in the extended
    segy-header of a passcal-segy file so that scale_fac=1
    In the segymod.c file I read that all headers should be accessible.

    I use the following syntax: segymod -scale_fac 100.01 segyfile.1

    (I have been able to change some of the headers but not all. For
    example, I can not modify samp_rate)

    Ihave been able to read this passcal file in pql and also directly from
    SAC. Should I instead modify the scale factor and set
    the header values within SAC?

    What do you advise?

    Juan Lorenzo

18:21:10 v.22510d55