SUDATUMK2DR - Kirchhoff datuming of receivers for 2D prestack data
(shot gathers are the input)
sudatumk2dr infile= outfile= [parameters]
Required parameters:
infile=stdin file for input seismic traces
outfile=stdout file for common offset migration output
ttfile= file for input traveltime tables
The following 9 parameters describe traveltime tables:
fzt= first depth sample in traveltime table
nzt= number of depth samples in traveltime table
dzt= depth interval in traveltime table
fxt= first lateral sample in traveltime table
nxt= number of lateral samples in traveltime table
dxt= lateral interval in traveltime table
fs= x-coordinate of first source
ns= number of sources
ds= x-coordinate increment of sources
fxi= x-coordinate of the first surface location
dxi= horizontal spacing on surface
nxi= number of input surface locations
sgn= Sign of the datuming process (up=-1 or down=1)
Optional Parameters:
dt= or from header (dt) time sampling interval of input data
ft= or from header (ft) first time sample of input data
surf="0,0;99999,0" The first surface defined the recording surface
surf="0,0;99999,0" and the second one, the new datum.
"x1,z1;x2,z2;x3,z3;...
fzo=fzt z-coordinate of first point in output trace
dzo=0.2*dzt vertical spacing of output trace
nzo=5*(nzt-1)+1 number of points in output trace ",
fxso=fxt x-coordinate of first shot
dxso=0.5*dxt shot horizontal spacing
nxso=2*(nxt-1)+1 number of shots
fxgo=fxt x-coordinate of first receiver
dxgo=0.5*dxt receiver horizontal spacing
nxgo=nxso number of receivers per shot
fmax=0.25/dt frequency-highcut for input traces
offmax=99999 maximum absolute offset allowed in migration
aperx=nxt*dxt/2 migration lateral aperature
angmax=60 migration angle aperature from vertical
v0=1500(m/s) reference velocity value at surface
dvz=0.0 reference velocity vertical gradient
antiali=1 Antialiase filter (no-filter = 0)
jpfile=stderr job print file name
mtr=100 print verbal information at every mtr traces
ntr=100000 maximum number of input traces to be migrated
verbose=0 silent, =1 chatty
Notes:
1. Traveltime tables were generated by program rayt2d (or other ones)
on relatively coarse grids, with dimension ns*nxt*nzt. In the
datuming process, traveltimes are interpolated into shot/gephone
positions and output grids.
2. Input traces must be SU format and organized in common rec. gathers
3. If the offset value of an input trace is not in the offset array
of output, the nearest one in the array is chosen.
4. Amplitudes are computed using the reference velocity profile, v(z),
specified by the parameters v0= and dvz=.
5. Input traces must specify source and receiver positions via the header
fields tr.sx and tr.gx. Offset is computed automatically.
Author: Trino Salinas, 05/01/96, Colorado School of Mines
This code is based on sukzmig2d.c written by Zhenyue Liu, 03/01/95.
Subroutines from Dave Hale's modeling library were adapted in
this code to define topography using cubic splines.
This code implements a Kirchhoff extraplolation operator that allows to
transfer data from one reference surface to another. The formula used in
this application is a far field approximation of the Berryhill's original
formula (Berryhill, 1979). This equation is the result of a stationary
phase analysis to get an analog asymptotic expansion for the two-and-one
half dimensional extrapolation formula (Bleistein, 1984).
The extrapolation formula permits the downward continuation of upgoing
waves and upward continuation of downgoing waves. For upward conti-
nuation of upgoing waves and downward continuation of downgoing waves,
the conjugate transpose of the equation is used (Bevc, 1993).
References :
Berryhill, J.R., 1979, Wave equation datuming: Geophysics,
44, 1329--1344.
_______________, 1984, Wave equation datuming before stack
(short note) : Geophysics, 49, 2064--2067.
Bevc, D., 1993, Data parallel wave equation datuming with
irregular acquisition topography : 63rd Ann. Internat.
Mtg., SEG, Expanded Abstracts, 197--200.
Bleistein, N., 1984, Mathematical methods for wave phenomena,
Academic Press Inc. (Harcourt Brace Jovanovich Publishers),
New York.