NAME
fx3d - 3D Vxyz FX post-stack depth migration (DDS)
SYNOPSIS
fx3d [in=dict] [in_data=data] [in_format=fmt] [vel=dict]
[vel_data=data] [vel_format=fmt] [zmap=dict]
[zmap_data=data] [zmap_format=fmt] [out=dict]
[out_data=data] [out_format=fmt] [nwc=n] [nzc=n] [nz_mig=n]
[nx_ops=n] [coeffs=lsq|def] [li=yes|no] [nli_max=max]
[vtol=tol] [tiny_vtol=tol] [nkx_ops=n] [padx=n] [pady=n]
[sw=f] [na=n] [abs_base=f] [nabs=n] [mincode=n] [maxcode=n]
[restart=] [help=]
DESCRIPTION
fx3d is a 3-D program to do Vxyz FX poststack depth migra-
tion. It uses the Hale-McClellan algorithm. For now it only
works with square-gridded model (dx=dy). Data and model must
have same dx & dy. The input should be in "x y w" order and
the velocity should be in "x y z" order. The input and out-
put data cannot be piped because they are randomly read from
and written to.
The space domain convolution operators are allowed to vary
arbitrarily point by point to downward continue the surface
data. Since these operators must be truncated to some fin-
ite length, there is a loss of the steepest. Typical opera-
tors have a half-length of 20 points and can preserve dips
up to about 65 degrees. Going to 30 point half-length
operators might preserve up to 75 degree dips.
The data and model must be totally conformable. It uses f-x
extrapolation with 1-d convolutional operators and
Hale_McClellan transforms as proposed by Dave Hale (Hale,
D., 1991, 3-D Depth Migration via McClellan Transformations,
Geophysics, 56, 1778-1785). The latest version uses the
Biondi-McClellan transform. The input data files can be in
any DDS format. The input data must be complex samples as
produced by program "freq" and "transpose".
OPTIONS
in=dict
Specify the dds dictionary for the input "x y w" data.
in_data=data
Specify the binary file for the input data.
in_format=fmt
Specify the format for the input data.
vel=dict
Specify the dds dictionary for the velocity data.
vel_data=data
Specify the binary file for the velocity data.
vel_format=fmt
Specify the format for the velocity data.
zmap=dict
Optional input zmap dictionary filename. Specifying
this will cause the migration to use the zmap informa-
tion for irregular dz's. The zmap file is created by
"efficientz" with the correct nzc parameter specified.
zmap_data=data
Specify the binary file for the zmap data.
zmap_format=fmt
Specify the format for the zmap data.
out=dict
Specify the dds dictionary for the output data.
(default stdout:)
out_data=data
Specify the binary file for the output data. (default
'out' definition with DATA_PATH and DATA_SUFFIX).
out_format=fmt
Specify the format for the output data. (default
fcube)
nwc=n
Number of frequency slices to migrate each pass
(default all frequencies).
nzc=n
Number of depth slices to migrate at a time (default
16).
nz_mig=n
Number of depth steps to migrate (default nz from velo-
city model).
nx_ops=n
Operator length; must be 2+3n, typically between 20 &
32 (default 26).
coeffs=lsq|def
Specify the type of calculation for extrapolating coef-
ficients for downward continuation: "lsq" or "def".
The least squares operator is more expensive but pro-
duces better operators. (default "lsq").
li=yes|no
This is a switch to make "li" corrections to the
McClellan Transformation (Default yes).
nli_max=n
Override maximum number if "li" levels to use (Default
1).
vtol=f
Tolerance parameter used in determining the number of
"li" level to use (Default 0.1).
tiny_vtol=f
Tolerance parameter used in determining if more than 1
"li" level. (Default 0.02).
nkx_ops=n
Wavenumber-domain operator length (default 256).
padx=n
Specify any extra x-axis padding to be used with li
correction (default 0).
pady=n
Specify any extra y-axis padding to be used with li
correction (default 0).
sw=f Internal switch scale factor (default 0.95).
na=n Number of operators per table (default 512).
abs_base=f
Internal absorbtion factor (default 0.99).
nabs=n
Internal absorbtion length (default 10).
mincode=[1|2|3]
Specify the minimum accuracy level to use for the
McClellan Transformation. 1 is the fastest and least
accurate; 3 is the slowest and most accurate. The pro-
gram attempts to determine the code level to use, but
limited to the user specified minimum and maximum. For
fast crummy results (model building) use "mincode=1"
and "maxcode=1". For routine migrations up to 60
degrees dip use "mincode=2" and "maxcode=2". For steep
dip migrations up to 80 degrees dip use "mincode=1" and
"maxcode=3". (default 1 for CM5, 2 for SGI).
maxcode=[1|2|3]
Specify the maximum accuracy level to use for the
McClellan Transformation. See "mincode=" description.
(default 3 for CM5, 2 for SGI).
restart=n
Switch to restart migration. A "restart.state" file
must exist from a previous run which contains the fre-
quency and depth chunk last updated. This file is
created and maintained during processing and is deleted
upon successful completion.
help=
Switch to display this information.
SEE ALSO
dmo3d(1)
fkidmo(1)
AUTHOR
John Etgen, EPTG.
$Author: zjwe06 $
$Revision: 1.9 $
COPYRIGHT
copyright 2001, Amoco Production Company
All Rights Reserved
an affiliate of BP America Inc.
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