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(a)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
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