NAME
vred - make reduced velocity traces (linear NMO)
SYNOPSIS
vred [ -Nntap ] [ -Ootap ] [ [ -vredvred ] [ -vvtap ] [
-threed ] ] [ -tit0 ] [ -Tnpadend ] [ -U ] [ -V ] [
-swstawrd ] [ -uunit ] [ -tmultmul ] [ -dmuldmul ] [ -nsns ]
[ -nene ] [ -rsrs ] [ -rere ] [ -? ]
DESCRIPTION
vred processes entire trace records at a time, performing a
time shift to yield a reduced travel time curve (linear
moveout). This is done either by entering a constant reduc-
tion velocity vred or by inputting a velocity tape (in the
case of the tape the first sample of each velocity trace is
used for the reduction velocity). The input traces are then
time shifted with the velocity and offset and the -t parame-
ter. The traces are of the same length as originally, but
the shifted traces have a zero fill at the start and/or the
end (if an end pad is requested). NOTE: this routine is
ideal for flattening a record based on a refraction velo-
city. By entering the -U flag with the otherwise same com-
mand line it can (in this case the zero pad is removed). If
the input data are 3D and the order is unsorted, e.g. shot
data, then as long as the input data have valid LI & DI
numbers in the trace headers appropriate for the CDP cells
then the flattening velocities can be applied in a surface
consistent manner (as long as the velocity volume is in the
proper LI/DI order).
One of the purposes of this module is to deal with linear
events either to flatten them for filtering (fkstrip) or
display or to move them into a dip quadrant different from
other events to be followed by dip quadrant filtering (e.g.
qdchop).
The shifts are basically offset dependent statics applied to
each trace independent of any other. The shifting process is
done in the frequency domain and so is exact. The process
results in no changes to the wavelets of the traces.
vred gets processing controls from the command line. Reason-
able defaults are set up. In addition, if no file name is
given, the binary trace data are expected to be on the stan-
dard input.
Command line arguments
-N ntap
Enter the full path of the file continuing the data
set. If not specified, input is expected on the stan-
dard input. If standard input is not specified, and
there is no input, e.g., program run in background,
expect a very ungracious crash. (default standard
input)
-O otap
Enter the full path of the file containing the output
file. If not specified, the output goes to the standard
output.
-vred vred
Constant reduction velocity in ft/s or m/s A nonzero
value must be entered although it may be positive or
negative. One can go full circle with vred by executing
first with a positive velocity followed at a later
stage in the processing by executing with a negative
velocity.
-v vtap
Enter optional velocity tape data set name. This option
will override the constant velocity command line argu-
ment. The input data gathers should be in the same
order as the velocity traces (even for 3D data). If the
program runs out of velocity traces before the end of
input data a warning is issued and the last velocity is
used. For unsorted 3D data with proper LI/DI numbers
(CDP cell numbers) red can still be used as long as the
CDP velocity volume has the correct number of LI & DI
dimensions. In the unsorted case if the program tries
to find a velocity outside the LI/DI dimensions it will
stop.
-threed
Include on command line if 3D data is unsorted, e.g.
shots. The data must have valid LI & DI numbers in the
trace headers (see program li_di). The
-t it0
Enter a distance constant time shift in ms. This will
zero pad the first it0 ms of each trace prior to apply-
ing the reduction velocity. This time shift is stored
in the line header such that a second initiat ion of
vred with the same command line as before will output
data whic h has this shift removed. You should use
this option if you intend to go full cir cle with vred
(i.e. first vred with a velocity followed some process-
ing step s later with vred with the same command line
entries plus -U) and the reduction velocity is low
enough to risk chopping off some of the higher velocity
events on the record. Default = none
-T npadend
Enter trailing trace pad in ms. Default = none
-U Include on command line to undo a prior vred run. To
undo properly use exactly th e same command line
entries as before but include the -U entry.
-sw stawrd
(Optional) Enter trace header word mnemonic to store
shifts for each trace. Defaul t is not to store shifts.
This is not necessary for the undo function which opera
tes on its own. After a forward and reverse vred the
resulting shift is computed by summing the shift from
the forward mode (negative) and the current reverse
shif t. The result is stored in the specified header
word.
-u unit
(Optional) Enter scale factor to apply to the shifts
before storing them as intege rs in the trace header
mnemonic above. Default = 1.0
-tmul tmul
Time multiplier. This can be used to fake out oddball
time units, e.g. ms -> micro secs. Default = 1.0
-dmul dmul
Distance multiplier. This can be used to fake out odd-
ball distance units, e.g. inc hes -> feet. Default =
1.0
-ns ns
Start trace (default = first trace).
-ne ne
End trace (default = last trace).
-rs rs
Start record (default = first record).
-re re
End record (default = last record).
-V Verbose mode with output on the standard error output.
-? Enter the command line argument '-?' to get online
help. The program terminates after the help screen is
printed.
BUGS
unknown
SEE ALSO
velspec, fkstrip, picker
AUTHOR
R. B. Herrmann, Saint Louis University, July 1985, P. R.
Gutowski, Amoco , extensively modified to include interpola-
tion by Kurt Marfurt & Paul Gutowski, EPTG, 1995
COPYRIGHT
copyright 2001, Amoco Production Company
All Rights Reserved
an affiliate of BP America Inc.
Man(1) output converted with
man2html