PROCESS FKSHIFT

Document Date: 10 November 1992

Process FKSHIFT performs an extrapolation via a phase shift in the F-K
domain.  FKSHIFT is depth migration of a horizontally layered media 
whose velocity is always increasing.

The data must have been transformed into the F-K domain prior to process
FKSHIFT and it is left in the F-K domain.  Use process TX2FK prior to 
FKSHIFT and FK2TX after FKSHIFT.

FKSHIFT can be used to forward extrapolate shot gathers by specifying
the true velocity and extrapolation height (thickness).

FKSHIFT can be used to backwards extrapolate stacked data to the 
seafloor by halving the specified velocity and specifying the output
time delay.

Only one parameter list may be given.

PARAMETER DICTIONARY
--------- ----------

VEL     - The constant velocity.
          Preset = 0     e.g. 1500

DELTAX  - The distance between traces.
          Preset 1. e.g. deltax 100.

ZEXTRAP - The extrapolation height.
          Preset = 0.

ODELAY  - The time of the first output sample, in seconds.
          Preset = 0.    e.g.  odelay 1.

DELTAT  - The sample interval of the data in the time domain, in seconds.
          Preset = SEG-Y header.   e.g.  deltat .004

END     - Terminates each parameter list.

Copyright (C) by The Regents of The University of California, 1992
ALL RIGHTS RESERVED.