27 Oct
2022
27 Oct
'22
5:25 p.m.
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
27 Oct
27 Oct
5:49 p.m.
Hi,
1) sureduce assumes that the offset is in meters and the reduction
velocity in km/s. (or anything else with a ratio of 1000). Are the
offsets in meters ? The geometry of this collection looks very strange
(>100 km offset), with a recording of only 8s.
2) How can your data exhibit varying offsets with constant source and
receiver locations ?
Check the geometry of your traces and try again.
D.
Le 27/10/2022 à 19:25, eloraafrin5(a)gmail.com a écrit :
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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--
|Dominique Rousset LFCR UMR5150 / E2S UPPA / Dpt des géosciences|
|Univ. Pau et des Pays de l'Adour BP 1155 F-64013 Pau Cedex - France|
|mailto:dominique.rousset@univ-pau.fr http://lfc.univ-pau.fr|
| Off: +33 559 407 423 Cell: +33 660 861 391 |
5:54 p.m.
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, eloraafrin5(a)gmail.com
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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6:44 p.m.
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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To unsubscribe send an email to seisunix-leave(a)mailman.seismic-unix.org
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8 Dec
8 Dec
12:21 p.m.
New subject: segdread and 8015
I have been failing to get segdread to handle 8015 and 8036 SEGD files.
It handles 8058 without problem. I may end up seeing other formats, all
demultiplexed.
My example files can be viewed and headers examined in SegDSeeMp. The
header listings agree with what I can make out in a binary editor.
I've run segdread in a debugger to examine where things go wrong. It
looks as though it begins misinterpreting headers at some point. The
general header states there is one scan type, and 10 channel sets.
During the read it may encounter scan type 63 and channel set 46, which
are outside the bounds of an array. From there we segfault.
Before I go further, I thought I'd ask whether anyone else has had
similar issues.
regards
Graeme Murray
12:38 p.m.
New subject: segdread and 8015
Hi Graham,
Last time I had SEGDREAD problems , I managed to read the data straight off
using openseaseis so that might be the quickest route.
Prior to that I think I had to hack the code to bypass whatever issue it was
having. Pretty sure I have read 8015 format previously without issues
though.
Regards
Rob
-----Original Message-----
From: Graeme Murray <murray(a)geocom.com.au>
Sent: Thursday, 8 December, 2022 12:22 PM
To: seisunix(a)mailman.seismic-unix.org
Subject: [Seisunix] segdread and 8015
I have been failing to get segdread to handle 8015 and 8036 SEGD files.
It handles 8058 without problem. I may end up seeing other formats, all
demultiplexed.
My example files can be viewed and headers examined in SegDSeeMp. The header
listings agree with what I can make out in a binary editor.
I've run segdread in a debugger to examine where things go wrong. It looks
as though it begins misinterpreting headers at some point. The general
header states there is one scan type, and 10 channel sets.
During the read it may encounter scan type 63 and channel set 46, which are
outside the bounds of an array. From there we segfault.
Before I go further, I thought I'd ask whether anyone else has had similar
issues.
regards
Graeme Murray
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Seisunix mailing list -- seisunix(a)mailman.seismic-unix.org To unsubscribe
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1:49 p.m.
New subject: segdread and 8015
Rob,
Thanks for the reply.
I have been iterating through the debugger to try spot where goofy
numbers are being extracted. The dream is to identify a blindspot in the
code that I can fix and make it all work as expected :)
I am trying to design a workflow which uses dd to extract SEGD off tape,
tee the result to a disc file and feed stdout into segdread to
ultimately produce SEGY for production of near trace gathers for QC
image preparation. This is for the government of a developing nation and
there are over 15000 tapes.
Part of the job is to demonstrate the resulting SEGD disc files are
usable. SegDSeeMp can deal with these files fine. I have the source code
for SegDSeeMp, but its SEGD code is couched within their Qt framework.
Both SegDSeeMp and segdread are somewhat dense, which is to be expected
with a standard like SEGD.
regards
Graeme
On 8/12/22 20:38, rob(a)xsgeo.com wrote:
Hi Graham,
Last time I had SEGDREAD problems , I managed to read the data straight off
using openseaseis so that might be the quickest route.
Prior to that I think I had to hack the code to bypass whatever issue it was
having. Pretty sure I have read 8015 format previously without issues
though.
Regards
Rob
-----Original Message-----
From: Graeme Murray <murray(a)geocom.com.au>
Sent: Thursday, 8 December, 2022 12:22 PM
To: seisunix(a)mailman.seismic-unix.org
Subject: [Seisunix] segdread and 8015
I have been failing to get segdread to handle 8015 and 8036 SEGD files.
It handles 8058 without problem. I may end up seeing other formats, all
demultiplexed.
My example files can be viewed and headers examined in SegDSeeMp. The header
listings agree with what I can make out in a binary editor.
I've run segdread in a debugger to examine where things go wrong. It looks
as though it begins misinterpreting headers at some point. The general
header states there is one scan type, and 10 channel sets.
During the read it may encounter scan type 63 and channel set 46, which are
outside the bounds of an array. From there we segfault.
Before I go further, I thought I'd ask whether anyone else has had similar
issues.
regards
Graeme Murray
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days old
seisunix@mailman.seismic-unix.org
6 comments
6 participants
participants (6)
-
Dominique ROUSSET -
eloraafrin5＠gmail.com -
Gary Billings -
Graeme Murray -
Gus Correa -
rob＠xsgeo.com