NAME
stack - stack selected traces in selected records
SYNOPSIS
stack [ -Nntap ] [ -Ootap ] [ -d2negd2neg ] [ -d1negd1neg ]
[ -d2posd2pos ] [ -d1posd1pos ] [ -nsns ] [ -nene ] [ -rsirs
] [ -reire ] [ -trntpr ] [ -gathigath ] [ -pwpower ] [ -H ]
[ -B ] [ -D ] [ -sem ] [ -swt ] [ -S ] [ -L ] [ -R ] [
-threed ] [ -BC ] [ -V ] [ -? ]
DESCRIPTION
stack will sum all selected traces within a selected record
to make a single summed trace for that record.
stack will continue through all selected records and will
produce an output file containing the composited gathers.
Options are available to output the stacked data in user
specified traces per record groups and to normalize the data
according to the number of live traces. In addition one can
override the input number of traces/gather.
Command line arguments
-N ntap
Enter the full path name of the file containing the
data set. If not specified, input is expected to be on
standard input. The program will give an error message
if the input file is read protected. If no input file
is given, and there is no standard input, the program
will hang. (default is standard input )
-O otap
Enter the full path name for the output file. If not
specified, standered output is expected to be on stan-
dard output. The program will give an error message if
the output file is being written to a write protect
directory. (default is standard output )
-d2neg d2neg
Far trace distance to use: negative side of spread.
(default = largest negative distance ). Note: must be
a negative number.
-d1neg d1neg
Near trace distance to use: negative side of spread.
(default = smallest negative distance ). Note: must be
a negative number.
-d1pos d1pos
Near trace distance to use: positive side of spread.
(default = smallest positive distance )
-d2pos d2pos
Far trace distance to use: positive side of spread.
(default = largest positive distance )
-rs irs
First record to process. (default = 1 )
-re ire
Last record to process. (default = all )
-ns ns
First trace in each record to process. (default = 1 )
-ne ne
Last trace in each record to process. (default = all )
-tr ntpr
Enter output number of traces per record. If necessary
last record will be padded with dead traces. (default
= 1 )
-gath igath
Enter number of traces/gather to be summed (the default
is the input number traces/gather). This may be any
number from 1 to the total number of traces in the
input data set. Note: if this number is not defaulted
or not equal to the input traces/gather you cannot use
the rs, re and ns, ne options 1 )
-pw power
Enter nth root stacking power. The samples of each
trace in the gather are first raised to the 1/power
power before summing. After all the traces in the
gather have been summed the result is the raised to the
power power. (default = 1)
-H If present, calculate stack using Hamming weights,
w(x)=0.54+0.46*cos(y), where where y=2*pi*(x-
xcenter)/(xspread).
-B If present, calculate stack using Blackman weights,
w(x)=0.42+0.5*cos(y)+0.08*cos(2y), where y=2*pi*(x-
xcenter)/(xspread).
-D If present, calculate stack using distances as weights.
-swt If present, output semblance weighted stack
-sem If present output semblance values across gathers (sem-
blance stack?)
-R If present put out a single record, with multiple
traces (for MBS velocity building). (Not designed to
work with -ntpr option).
-S If present generate weights to reflect the number of
live traces in the gather (constant for all times).
-L If present generate weights to reflect the number of
live samples at each time.
-threed
If present data are assumed to be 3D from sr3d2. This
will set the number of traces per record to be the
number of LIs and the number of records will be the
number if DI's. Only the line header is affected.
-BC If present data are assumed to be 3D CDP gathers
without proper CDPBCX & CDPBCY header values but with
the source & receiver XYs all filled in. The program
then computes an average CDP XY from these values.
-V Verbose mode. All parameters from the command line and
lineheader will be sent to standard error output.
-? -h or -help
With this flag, stack will send a description of the
command line arguments to stderr and stop.
BUGS
No trap for running program without an input file and noth-
ing in stdin.
When using trace distance limitation options [-dpos1 -dpos2
-dneg1 -dneg2 above] it is necessary to specify both the
positive and negative distances wanted if you have a zero
offset in your data regardless of whether you have a split
spread or not. Zero is a member of both sets and since the
code does a simultaneous positive/negative check for range
you will always have the zero offset included in the stacked
output if you use the defaults for either set. If you do
not want the zero offset in the stacked output enter values
for both positive and negative entries so a to explicitly
exclude zero.
DISCUSSION
The power of the stack array can be significantly enhanced
for coherent noise rejection by using various weights and
tapers on the gathers. An excellent summary of the technique
can be found in the book by Gijs Vermeer, Seismic Wavefield
Sampling , SEG press, 1990. Specifically, long period multi-
ple rejection can be improved by tapering (using the -H, -B
options) and by weighting the data by the source receiver
distance (the -D option). At present, application of these
weights may cause some attenuation of the total power in the
mute zone.
AUTHORS
Original version by K. B. Taylor and R. B. Herrmann, Saint
Louis University. (1986), P. R. Gutowski, Amoco Research.
Major rewrite and weighting options by K. J. Marfurt, APR
(1992).
COPYRIGHT
copyright 2001, Amoco Production Company
All Rights Reserved
an affiliate of BP America Inc.
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