SYNOPSIS
PERL PROGRAM NAME:
AUTHOR: Juan Lorenzo (Perl module only)
DATE:
DESCRIPTION:
Version:
USE
NOTES
Examples
SYNOPSIS
SEISMIC UNIX NOTES SUKDMIG2D - Kirchhoff Depth Migration of 2D poststack/prestack data
sukdmig2d infile= outfile= ttfile= [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
Optional Parameters:
dt= or from header (dt) time sampling interval of input data
ft= or from header (ft) first time sample of input data
dxm= or from header (d2) sampling interval of midpoints
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 ",
fxo=fxt x-coordinate of first output trace
dxo=0.5*dxt horizontal spacing of output trace
nxo=2*(nxt-1)+1 number of output traces ",
off0=0 first offest in output
doff=99999 offset increment in output
noff=1 number of offsets in output ",
absoff=0 flag for using absolute offsets of input traces
=0 means use offset=gx-sx
=1 means use abs(gx-sx)
limoff=0 flag for only using input traces that fall within the range
of defined output offset bins (off0,doff,noff)
=0 means use all input traces
=1 means limit traces used by offset
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
ls=1 flag for line source
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
npv=0 flag of computing quantities for velocity analysis
rscale=1000.0 scaling for roundoff error suppression
...if npv>0 specify the following three files:
tvfile=tvfile input file of traveltime variation tables
tv[ns][nxt][nzt]
csfile=csfile input file of cosine tables cs[ns][nxt][nzt]
outfile1=outfile1 file containning additional migration output
with extra amplitude
Notes:
1. Traveltime tables were generated by program rayt2d (or other ones)
on relatively coarse grids, with dimension ns*nxt*nzt. In the
migration process, traveltimes are interpolated into shot/gephone
positions and output grids.
2. Input seismic traces must be SU format and can be any type of
gathers (common shot, common offset, common CDP, and so on). ",
3. Migrated traces are output in CDP gathers if velocity analysis
is required, with dimension nxo*noff*nzo. ",
4. If the offset value of an input trace is not in the offset array
of output, the nearest one in the array is chosen.
5. Memory requirement for this program is about
[ns*nxt*nzt+noff*nxo*nzo+4*nr*nzt+5*nxt*nzt+npa*(2*ns*nxt*nzt
+noff*nxo*nzo+4*nxt*nzt)]*4 bytes
where nr = 1+min(nxt*dxt,0.5*offmax+aperx)/dxo.
6. Amplitudes are computed using the reference velocity profile, v(z),
specified by the parameters v0= and dvz=.
7. Input traces must specify source and receiver positions via the header
fields tr.sx and tr.gx. Offset is computed automatically.
8. if limoff=0, input traces from outside the range defined by off0, doff,
noff, will get migrated into the extremal offset bins/planes. E.g. if
absoff=0 and limoff=0, all traces with gx<sx will get migrated into the
off0 bin.
Author: Zhenyue Liu, 03/01/95, Colorado School of Mines
Modifcations:
Gary Billings, Talisman Energy, Sept 2005: added absoff, limoff.
Trace header fields accessed: ns, dt, delrt, d2
Trace header fields modified: sx, gx
User's notes (Juan Lorenzo) untested
CHANGES and their DATES
Import packages
instantiation of packages
Encapsulated hash of private variables
sub Step
collects switches and assembles bash instructions by adding the program name
sub note
collects switches and assembles bash instructions by adding the program name
sub clear
sub absoff
sub angmax
sub aperx
sub csfile
sub doff
sub ds
sub dt
sub dvz
sub dxm
sub dxo
sub dxt
sub dzo
sub dzt
sub fmax
sub fs
sub ft
sub fxo
sub fxt
sub fzo
sub fzt
sub infile
sub jpfile
sub limoff
sub ls
sub mtr
sub noff
sub npv
sub nr
sub ns
sub ntr
sub nxo
sub nxt
sub nzo
sub nzt
sub off0
sub offmax
sub offset
sub outfile
sub outfile1
sub rscale
sub ttfile
sub tvfile
sub v0
sub get_max_index
max index = number of input variables -1