Hi eloraafrin5
If you have access to the original field files (SEG-D, SEG-Y, etc), that may shed some light about the units used, where in the header to search for reliable information, etc. SU may have captured the wrong original headers, or may have been used in a wrong way, etc. As others said, the trace header values look inconsistent with each other. Likewise, if there is any paper record or spreadsheet of the field work, that may help. In any case, we had sonobuoy records here with offsets of many km. Not to mention seismological records.
Otherwise, without other source of information, it becomes wild guesswork, as below.
You could try to rewrite the trace headers with these values (save the original file first), then try to plot the reduced velocity seismogram, to see if it makes sense.
1) Assuming the units are in feet, the old fashioned British/Imperial System, still the American way, doesn't help much. The conversion factor to meters is ~0.3048, and this would make the first offset 34279m, down from 112464m but still large.
2) Assuming the units are centimeters (yes, once upon a time, the CGS system was popular) is better, reducing the first offset to 1124.64m.
However, the units could be anything: mm, inches, yards, fathoms, furlongs, while the header values could just be dead wrong.
I hope this helps, Gus Correa
On Thu, Oct 27, 2022 at 1:54 PM Gary Billings obs681@gmail.com wrote:
I haven’t run su in a very long time… but it looks to me like your offset header values are wrong, so sureduce isn’t going to work right. Also, gx and gy which you might use to compute offset, appear to be constant (same value on all traces), so you won’t be able to calculate offset using them.
You might be able to make a “quick and dirty” offset value using tracl: subtract a constant (if a split spread, probably 318; if it is a 3D record from multiple receiver lines, etc., this won’t work) and multiply by the trace spacing in meters. This doesn’t fix your header values, but might get you the plot you need.
Gary Billings
On Oct 27, 2022, at 11:25 AM, 112464 wrote:
Hello greetings! I am a beginner. I have a big su file with huge shot
points, but I want to see a particular shot point in reduced velocity mode. I made a single file for those particular shot by using key=fldr. Now this file should have total 636 traces. I wrote a command suwind < indut su file key=tracl max=636 .......
However, in image I got values from2.84*10^5 to 2.85*10^5. Even when I
want to see the image in reduced velocity mode, I need to set rv= >1000 whereas it should be rv=1 to 2. It seems like there are something wrong with units in the headers. Would anyone please help me with how can I fix these??? I am a new user; I will appreciate your help and time. Here I attached the header info. Thanks
FYI 636 traces: tracl 1 636 (1-636) tracr 284929 285564 (284929-285564) fldr 2245 tracf 1 636 (1-636) cdp 2245 offset 112464 120401 (112464-120401) sx 376962 sy 5176643 gx 376962 gy 5176643 ns 2001 dt 4000 _______________________________________________ Seisunix mailing list -- seisunix@mailman.seismic-unix.org To unsubscribe send an email to seisunix-leave@mailman.seismic-unix.org
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