SUSYNVXZCS - SYNthetic seismograms of common shot in V(X,Z) media via Kirchhoff-style modeling

susynvxzcs<vfile >outfile nx= nz= [optional parameters]

Required Parameters:
<vfile file containing velocities v[nx][nz]
>outfile file containing seismograms of common ofset
nx= number of x samples (2nd dimension) in velocity
nz= number of z samples (1st dimension) in velocity

Optional Parameters:
nt=501 number of time samples
dt=0.004 time sampling interval (sec)
ft=0.0 first time (sec)
fpeak=0.2/dt peak frequency of symmetric Ricker wavelet (Hz)
nxg= number of receivers of input traces
dxg=15 receiver sampling interval (m)
fxg=0.0 first receiver (m)
nxd=5 skipped number of receivers
nxs=1 number of offsets
dxs=50 shot sampling interval (m)
fxs=0.0 first shot (m)
dx=50 x sampling interval (m)
fx=0. first x sample (m)
dz=50 z sampling interval (m)
nxb=nx/2 band width centered at midpoint (see note)
nxc=0 hozizontal range in which velocity is changed
nzc=0 vertical range in which velocity is changed
pert=0 =1 calculate time correction from v_p[nx][nz]
vpfile file containing slowness perturbation array v_p[nx][nz]
ref="1:1,2;4,2" reflector(s): "amplitude:x1,z1;x2,z2;x3,z3;...
smooth=0 =1 for smooth (piecewise cubic spline) reflectors
ls=0 =1 for line source; =0 for point source
tmin=10.0*dt minimum time of interest (sec)
ndpfz=5 number of diffractors per Fresnel zone
verbose=0 =1 to print some useful information

Notes:
This algorithm is based on formula (58) in Geo. Pros. 34, 686-703,
by N. Bleistein.

Traveltime and amplitude are calculated by finite difference which
is done only in one of every NXD receivers; in skipped receivers,
interpolation is used to calculate traveltime and amplitude. ",
For each receiver, traveltime and amplitude are calculated in the
horizontal range of (xg-nxb*dx, xg+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 rays: smoothing velocity,
reducing nxb, and increaing nxc and nzc (if the turned ray occurs
in shallow areas). To prevent traveltime distortion from an over-
smoothed velocity, traveltime is corrected based on the slowness
perturbation.

More than one ref (reflector) may be specified.
Note that reflectors are encoded as quoted strings, with an optional
reflector amplitude: preceding the x,z coordinates of each reflector.
Default amplitude is 1.0 if amplitude: part of the string is omitted.



Author: Zhenyue Liu, 07/20/92, Center for Wave Phenomena
Many subroutines borrowed from Dave Hale's program: SUSYNLV

Trino Salinas, 07/30/96, fixed a bug in the geometry
setting to allow the spread move with the shots.

Trace header fields set: trid, counit, ns, dt, delrt,
tracl. tracr, fldr, tracf,
sx, gx