Abhash Kumar
Hi,
I used SAC transfer function to remove the instrument response to get
the actual measure of ground velocity from raw voltage count as below:
SAC> r 2012.156.10.33.GREEN.EHE.SAC
SAC> ch LOVROK TRUE (raw sac file has false, so I first changed it to make
the file over-writable)
SAC> wh
SAC> rtr
SAC> taper
SAC> TRANS FROM EVALRESP FNAME RESP.GC.GREEN..EHE TO VEL FREQLIM 1 3 20 50
SAC> wh
SAC> exit
I checked the header of sac file after removing the response and now the
IDEP is velocity in NM/sec, which was in Displacement unit earlier. Also
the value of maximum amplitude (DEPMAX) and minimum amplitude (DEPMIN) of
the sac file is different than it was before for the raw sac file
(2012.156.10.33.GREEN.EHE.SAC).
/Users/abhashkumar> sac (relaunched SAC)
SAC> r 2012.156.10.33.GREEN.EHE.SAC (re-reading the file)
As soon as I quit SAC and re-read the response corrected file, the DEPMAX
and DEPMIN values goes back to the value of raw file, but the IDEP value is
in Velocity (NM/sec). I also checked data vector and it is exactly the
same for both raw and corrected sac file, which implies that "wh" command
does not help to store the instrument response corrected file with modified
data vector. Is it possible to save the file after removing instrument
response that will have the corrected sac header with modified data. I
would be extremely grateful for your help.
Thanks
Abhash Kumar
I used SAC transfer function to remove the instrument response to get
the actual measure of ground velocity from raw voltage count as below:
SAC> r 2012.156.10.33.GREEN.EHE.SAC
SAC> ch LOVROK TRUE (raw sac file has false, so I first changed it to make
the file over-writable)
SAC> wh
SAC> rtr
SAC> taper
SAC> TRANS FROM EVALRESP FNAME RESP.GC.GREEN..EHE TO VEL FREQLIM 1 3 20 50
SAC> wh
SAC> exit
I checked the header of sac file after removing the response and now the
IDEP is velocity in NM/sec, which was in Displacement unit earlier. Also
the value of maximum amplitude (DEPMAX) and minimum amplitude (DEPMIN) of
the sac file is different than it was before for the raw sac file
(2012.156.10.33.GREEN.EHE.SAC).
/Users/abhashkumar> sac (relaunched SAC)
SAC> r 2012.156.10.33.GREEN.EHE.SAC (re-reading the file)
As soon as I quit SAC and re-read the response corrected file, the DEPMAX
and DEPMIN values goes back to the value of raw file, but the IDEP value is
in Velocity (NM/sec). I also checked data vector and it is exactly the
same for both raw and corrected sac file, which implies that "wh" command
does not help to store the instrument response corrected file with modified
data vector. Is it possible to save the file after removing instrument
response that will have the corrected sac header with modified data. I
would be extremely grateful for your help.
Thanks
Abhash Kumar
Attachments
-
Hi Abhash,
Your seismograms will have to be in counts (IDEP is void) before you
perform the instrument response deconvolution (IRD). You have to make sure
that this is the case. If your seismograms are velocity traces, that would
imply that IRD has already been performed on your data.
Use W OVER or W my_filename.sac instead of WH if you want to save
deconvolved seismograms. Also, pay attention to your FREQLIMS. According to
your script, you are effectively filtering seismograms between 3 and 20 Hz
(or whatever your Nyquist frequency is = 1/[2*DELTA]).
Januka.
Januka Attanayake
Postdoctoral Research Associate
Institut für Geophysik
Westfälische Wilhelms - Universität Münster
CorrensstraBe 24
48149 Münster
Germany
University email: jattanayake<at>uni-muenster.de
Homepage: http://sites.google.com/site/janukaattanayake/
On 17 March 2016 at 21:03, Abhash Kumar <abhash.kumar84<at>gmail.com> wrote:
Hi,
I used SAC transfer function to remove the instrument response to get
the actual measure of ground velocity from raw voltage count as below:
SAC> r 2012.156.10.33.GREEN.EHE.SAC
SAC> ch LOVROK TRUE (raw sac file has false, so I first changed it to make
the file over-writable)
SAC> wh
SAC> rtr
SAC> taper
SAC> TRANS FROM EVALRESP FNAME RESP.GC.GREEN..EHE TO VEL FREQLIM 1 3 20 50
SAC> wh
SAC> exit
I checked the header of sac file after removing the response and now the
IDEP is velocity in NM/sec, which was in Displacement unit earlier. Also
the value of maximum amplitude (DEPMAX) and minimum amplitude (DEPMIN) of
the sac file is different than it was before for the raw sac file
(2012.156.10.33.GREEN.EHE.SAC).
/Users/abhashkumar> sac (relaunched SAC)
SAC> r 2012.156.10.33.GREEN.EHE.SAC (re-reading the file)
As soon as I quit SAC and re-read the response corrected file, the DEPMAX
and DEPMIN values goes back to the value of raw file, but the IDEP value is
in Velocity (NM/sec). I also checked data vector and it is exactly the
same for both raw and corrected sac file, which implies that "wh" command
does not help to store the instrument response corrected file with modified
data vector. Is it possible to save the file after removing instrument
response that will have the corrected sac header with modified data. I
would be extremely grateful for your help.
Thanks
Abhash Kumar
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