NAME
kmcm [kmcmusp] - Kirchhoff Common Midpoint Poststack Depth
Migration
SYNOPSIS(1) - Using Embedded Menu Cards
kmcm -Nntap -Ootap -VELvtap -IOBLiobl -Sstretch -DXTdxgrid -DZTdzgrid \
-kmcm.crd"\
TIME ENDTIMEMS PADTIME BEGTIMEMS DTMS TMUTE
TIME tend padtime begtime dtms mute
FREQUENCY MINFREQHZ F2FREQHZ F3FREQHZ MAXFREQHZ
FREQUENCY f1 f2 f3 f4
DEPTH MAX DEPTH DELTA Z 1st DEPTH 2nd DEPTH
DEPTH zmax dztap zfrst z2nd
WIDTH DELTAX BEGTRACE NO TRACE
WIDTH dx itrbeg nx
MODE EMERG ANG DIPMAX
MODEL emerge dipmax
IMAGE MIG 1/2 AP DZMIG NRAYINC ISMOOTH ISTRIDE
IMAGE nap dzmig nrinc smooth stride
"
#...|....1....|....2....|....3....|....4....|....5....|....6....|....7
SYNOPSIS(2) - Using Command Line Arguments
kmcm [-Nntap] [-Ootap] [-VELvtap] [-IOBLiobl] [-Sstretch]
[-DXTdxgrid] [-DZTdzgrid] [-tetend] [-dtidtms] [-tmmute]
[-f1f1] [-f2f2] [-f3f3] [-f4f4] [-zxzmax] [-z1zfrst]
[-z2z2nd] [-dztdzmig] [-dzodztap] [-dxdx] [-nsitrbeg]
[-nxnx] [-ememerg] [-dmdipmax] [-apnap] [-ninrinc]
[-smsmooth] [-sdstride] [-h] [-?]
SYNOPSIS DESCRIPTIONS
kmcm and kmcmusp are combined into one program which can be
executed under the name of kmcm or kmcmusp. kmcm can be run
in two different modes. Mode 1 shown by Synopsis(1) above
accepts the input parameters from both command line argu-
ments and embedded menu cards. Mode 2 as shown by
Synopsis(2) below accepts all the input parameters as com-
mand line arguments. The command line argument keyword for
each parameter is shown inside square brackets with the
description of the parameter in the "Description of Parame-
ters" section below.
STARTJOB
Create a file that looks like synopsis(1) above with the
following command:
catpat kmcm > kmcm.job
This kmcm.job file will have some suggested parameter values
and the default values entered. Edit this job to suit your
needs and submit kmcm.job with the following command:
startjob kmcm.job
PROGRAM DESCRIPTION
kmcm images "normal incidence" time data into a depth sec-
tion with a poststack V(x,z) Kirchhoff depth migration algo-
rithm. The inputs are a "normal incidence" time section and
a V(x,z) velocity field, both of which are USP compatible
datasets. The "normal incidence" time section dataset is
typically a CMP stack, however it could be a single (nmo
corrected) offset section or a backscatter stack (see mbs
program bsstk). Other parameters are read from the embedded
menu cards as shown above and from the command line argu-
ments described below. Note: this program will migrate dips
that are greater than 90 degrees.
Command line arguments
-Nntap
Enter the name of the input "normal incidence" time
section after typing -N.
-Ootap
Enter the name of the output migrated depth section
after typing -O.
-VELvtap
Enter the name of the input velocity dataset after typ-
ing -VEL. This is a USP-formatted dataset where sample
values are interval velocities. The first trace of the
velocity field is assumed to be located at the same x-
location as the first trace to be used in the migration
(BEGTRACE itrbeg).
-IOBLiobl
Enter the obliquity flag after typing -IOBL.
0 = use cos weight
(theoretically correct and the default)
1 = use no weight
(enhances steeper dips and possibly noise)
-Sstretch
Enter the model velocity perturbation after typing -S.
The velocity, maxdepth and dztap parameters will be
multiplied by this number. This can be used to test a
constant multiplier of velocity without regenerating a
velocity field. Note that the depth spacing changes
with this parameter. Default is 1 (no stretch).
-DXTdxgrid
Enter the trace spacing (ft or meters) of the velocity
dataset after typing -DXT. Default is the velocity
dataset line header (Dx1000/1000).
-DZTdzgrid
Enter the depth sample spacing (ft or meters) of the
velocity dataset after typing -DZT. Default is to use
velocity dataset line header (Dz1000/1000).
-V Enter -V for a verbose printout.
-h -?
Enter -h or -? (or '-?' if running in a c-shell) for
online help. The program will terminate after printing
the information.
-kmcm.crd"\
When using the embedded menu card mode for this pro-
gram, this keyword, -kmcm.crd"\, must be entered
exactly as shown in Synopsis(1) above with no spaces
after the backslash. The embedded menu cards that fol-
low this keyword must be typed exactly as shown, with
the lower case parameter names being changed to the
actual values you want the program to use. All of the
parameter values must be entered in the correct
columns. The double quote following the embedded menu
cards must be present as shown.
When using the all command line arguments mode for this
program, use the keywords displayed inside the square
brackets below.
Description of Parameters
ENDTIMEMS[-te]tend
This value is in ms and should be less than or equal to
the maximum time on input. Default is the maximum time
on input.
PADTIMEpadtime
This value is the amount of time in ms needed to reduce
frequency wrap around. Because this migration is not
performed in the frequency domain, the pad is not
really necessary. Recommended value is 0. Default is
0.
BEGTIMEMSbegtime
Beginning time in ms to use from the input. This should
be a positive number. Used mainly for model data.
Default is zero.
This is the input sample spacing in ms. Default is the line
header value.
TMUTE[-tm] mute
This value is in ms. All data preceding this time is
muted. The default is 16 ms.
FREQUENCIES[-f1] [-f2] [-f3] [-f4] f1 f2 f3 f4
The points of a trapezoidal filter (in Hz). Default
for -f1 is 1.0. The other points have no defaults.
MAX DEPTH[-zx]zmax
The data will be migrated to this maximum depth (ft or
meters). No default.
Enter the depth sample spacing (ft or meters) for the output
migrated
depth section. The default is the dzmig parameter
described below.
1st DEPTH[-z1]zfrst
Enter the depth (ft or meters) to start the migration.
Depths above this value will have zero amplitudes on
the output dataset. Default is zero depth.
2nd DEPTH[-z2]z2nd
This value is the maximum depth (ft or meters) to
migrate. This must be greater than 1st DEPTH, but less
than or equal to the maximum depth. The default is the
maximum depth.
Enter the trace spacing (ft or meters) of the input seismic data.
No default.
BEGTRACE[-ns]itrbeg
This value is the first trace to use from input (as a
count from the beginning). Default is 1.
RACE[-nx]nx
The number of traces to migrate. Default is the number
of traces on the input dataset after and including
BEGTRACE.
EMERG ANG[-em]emerge
The traveltimes for the migration are generated from
ray tracing. The emergent angle (in degrees from the
vertical) determines the initial span of the rays at
the surface. The initial rays are between -emerge
angle to +emerge angle. Typical values are in the
range of 30 to 60 degrees. This parameter should be
chosen to be less than the dipmax parameter. The
default is 45 degrees.
The maximum angle (in degrees from the vertical) used in ray
tracing.
It can be larger than 90 degrees if the velocity gra-
dients are sufficient. The default is 90 degrees.
MIG 1/2 AP[-ap]nap
The number of traces to be included in the migration
half aperture. A suggested value is the maximum depth
divided by the trace spacing. The default is 100.
This is the depth spacing (ft or meters) used in migration. No
default.
This value may be different from the depth spacing for
the output dataset (dztap) described above. It should
be greater than or equal to dztap. If they are dif-
ferent, the output data will be resampled from dzmig to
dztap (watch Nyquist). The dzmig value should be less
than vmin/maxfreq*4 to prevent spatial aliasing. Run
time depends on dzmig, not dztap.
YINC[-ni]nrinc
The scattered rays are traced at each surface location
which is a multiple of NRAYINC. Travel times at a
specific trace are created by interpolation between the
two nearest computed travel times. For rapid lateral
velocity variations, this number should be small (3 to
9). For V(z) variations, choose this number to be
greater than the number of traces; this will SIGNIFI-
CANTLY decrease run time. The default is 10.
ISMOOTH[-sm]smooth
The is for velocity smoothing for the ray tracer. The
recommended value is 3. If the input velocity field
needs extra smoothing, this value can be increased. If
you have smoothed your velocity model externally, you
can set this value to 0. The default is 3.
ISTRIDE[-sd]stride
The input trace stride. Every ISTRIDE trace will be
used in the migration. Values of 2 to 4 can be used in
the iteration phase to help decrease cost - watch spa-
tial aliasing!!. The default is 1.
SEE ALSO
mbs, startjob, cmmvzn, fxcmmig, ellipmig
BUGS
None known.
AUTHOR
N. D. Whitmore, Jr., modified by Paul Gutowski
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