SUINVXZCO - Seismic INVersion of Common Offset data for a smooth
velocity function V(X,Z) plus a slowness perturbation vp(x,z)
suinvvxzco outfile [optional parameters]
Required Parameters:
vfile file containing velocity array v[nx][nz]
nx= number of x samples (2nd dimension) in velocity
nz= number of z samples (1st dimension) in velocity
nxm= number of midpoints of input traces
Optional Parameters:
dt= or from header (dt) time sampling interval of input data
offs= or from header (offset) source-receiver offset
dxm= or from header (d2) sampling interval of midpoints
fxm=0 first midpoint in input trace
nxd=5 skipped number of midpoints (see note)
dx=50.0 x sampling interval of velocity
fx=0.0 first x sample of velocity
dz=50.0 z sampling interval of velocity
nxb=nx/2 band centered at midpoints (see note)
nxc=0 hozizontal range in which velocity is changed
nzc=0 vertical range in which velocity is changed
fxo=0.0 x-coordinate of first output trace
dxo=15.0 horizontal spacing of output trace
nxo=101 number of output traces ",
fzo=0.0 z-coordinate of first point in output trace
dzo=15.0 vertical spacing of output trace
nzo=101 number of points in output trace ",
fmax=0.25/dt Maximum frequency set for operator antialiasing
ang=180 Maximum dip angle allowed in the image
ls=0 =1 for line source; =0 for point source
pert=0 =1 calculate time correction from v_p[nx][nz]
vpfile file containing slowness perturbation array v_p[nx][nz]
verbose=1 =1 to print some useful information
Notes:
Traveltime and amplitude are calculated by finite difference which
is done only in one of every NXD midpoints; in the skipped midpoint,
interpolation is used to calculate traveltime and amplitude. ",
For each midpoint, traveltime and amplitude are calculated in the
horizontal range of (xm-nxb*dx, xm+nxb*dx). Velocity is changed by
constant extropolation in two upper trianglar corners whose width is
nxc*dx and height is nzc*dz.
Eikonal equation will fail to solve if there is a polar turned ray.
In this case, the program shows the related geometric information.
There are three ways to remove the turned ray: smoothing velocity,
reducing nxb, and increaing nxc and nzc (if the turned ray occurs
in the shallow areas). To prevent traveltime distortion from a over
smoothed velocity, traveltime is corrected based on the slowness
perturbation.
Offsets are signed - may be positive or negative.
Author: Zhenyue Liu, 08/28/93, Colorado School of Mines
Reference:
Bleistein, N., Cohen, J. K., and Hagin, F., 1987,
Two-and-one-half dimensional Born inversion with an arbitrary reference
Geophysics Vol. 52, no.1, 26-36.