VELPERTAN - Velocity PERTerbation analysis in ANisotropic media to
determine the model update required to flatten image gathers",
velpertan boundary= par=cig.par refl1= refl2= npicks1=
npicks2= cdp1= cdp2= vfile= efile= dfile= nx= dx= fx=
ncdp= dcdp= fcdp= off0= noff= doff= >outfile [parameters]
Required Parameters:
refl1= file with picks on the 1st reflector
refl2= file with picks on the 2nd reflector
vfile= file defining VP0 at all grid points from prev. iter. ",
efile= file defining eps at all grid points from prev. iter. ",
dfile= file defining del at all grid points from prev. iter. ",
boundary= file defining the boundary above which
parameters are known; update is done below this ",
boundary ",
npicks1= number of picks on the 1st reflector
npicks2= number of picks on the 2nd reflector
ncdp= number of cdp's
dcdp= cdp spacing
fcdp= first cdp
off0= first offset in common image gathers
noff= number of offsets in common image gathers
doff= offset increment in common image gathers
cip1=x1,r1,r2,..., cip=xn,r1n,r2n description of input CIGS
cip2=x2,r1,r2,..., cip=xn,r1n,r2n description of input CIGS
x x-value of a common image point
r1 hyperbolic component of the residual moveout
r2 non-hyperbolic component of residual moveout
Optional Parameters:
method=akima for linear interpolation of the interface
=mono for monotonic cubic interpolation of interface
=akima for Akima's cubic interpolation of interface
=spline for cubic spline interpolation of interface
VP0=2000 Starting value for vertical velocity at a point in the
target layer
x00=0.0 x-coordinate at which VP0 is defined
z00=0.0 z-coordinate at which VP0 is defined
eps=0.0 Starting value for Thomsen's parameter epsilon
del=0.0 Starting value for Thomsen's parameter delta
kz =0.0 Starting value for the vertical gradient in VP0
kx =0.0 Starting value for the lateral gradient in VP0
nx =100 number of nodes in the horizontal direction for the
velocity grid
nz =100 number of nodes in the vertical direction for the
velocity grid
dx =10 horizontal grid increment
dz =10 vertical grid increment
fx =0 first horizontal grid point
fz =0 first vertical grid point
dt =0.008 traveltime increment
nt =500 no. of points on the ray
amax =360 max. angle of emergence
amin =0 min. angle of emergence
smoothing parameters
r1=0 smoothing parameter in the 1 direction
r2=0 smoothing parameter in the 2 direction
win=0,n1,0,n2 array for window range
rw=0 smoothing parameter for window function
nbound=2 number of points picked on the boundary
tol=0.1 tolerance in computing the offset (m)
Notes:
This program is used as part of the velocity analysis technique developed
by Debashish Sarkar, CWP:2003.
Notes:
The output par file contains the coefficients describing the residual
moveout. This program is used in conjunction with surelanan.
Author: CSM: Debashish Sarkar, December 2003