VELPERT - estimate velocity parameter perturbation from covariance of imaged depths in common image gathers (CIGs)

verpert <dfile dzfile=dzfile >outfile [parameters]

Required Parameters:
dfile input of imaged depths in CIGs
dzfile=dzfile input of dz/dv at the imaged depths in CIGs
outfile output of the estimated parameter
noff number of offsets
ncip number of common image gathers

Optional Parameters:
moff=noff number of first offsets used in velocity estimation

Notes:
1. This program is part of Zhenyue Liu's velocity analysis technique.
The input dzdv values are computed using the program dzdv.
2. For given depths, using moff smaller than noff may avoid poor
values of dz/dv at far offsets. However, a too small moff used
will the sensitivity of velocity error to the imaged depth.
3. Outfile contains three parts:
dlambda correction of the velocity paramter. dlambda plus
the initial parameter (used in migration) will be
the updated one.
deviation to measure how close imaged depths are to each other
in CIGs. Old deviation corresponds to the initial
parameter; new deviation corresponds to the updated one.
sensitivity to predict how sensitive the error in the estimated
parameter is to an error in the measurement of imaged
depths.

error of parameter <= sensitivity * error of depth.



Author: Zhenyue Liu, 12/29/93, Colorado School of Mines

Reference:
Liu, Z. 1995, "Migration Velocity Analysis", Ph.D. Thesis, Colorado
School of Mines, CWP report #168.