NAME

     vtinmo  - forward or inverse vertically anisotropic,  nonhy-
     perbolic fourth order normal moveout correction

SYNOPSIS

     vtinmo [ -Nntap ] [ -Ootap ] [ -eetap ] [ -vvtap ] [  -uunit
     ] [ -R ] [ -nmo ] [ -? ] [ -h ]

DESCRIPTION

     vtinmo computes and applies either forward or inverse verti-
     cally anisotropic, nonhyperbolic fourth order normal moveout
     corretion  to seismic data from an eta field  (in  usp  for-
     mat).  See man page for vtispec.  The correction is given by
     the equation

     t(x) = sqrt{ t0**2 + (x/V)**2
           - 2eta*x**4 / [V**2(t0**2*V**2 + (1+2eta)x**2] }

     where the offset dependent time, t(x), is comprised  of  two
     terms: a sort offset  based standard moveout term and a long
     offset nonhyperbolic eta dependent moveout term. Here  x  is
     the  trace offset, t0 is the normal incidence time, V is the
     RMS stacking velocity determined before hand using  standard
     short  offset  velocity  analysis techniques, and eta is the
     nonhyperbolic fourth order parameter  related  to  the  true
     anisotropic parameters by

     eta = ( epsilon - delta ) / (1 + 2*delta)

     (see report by Tsvankin and Thomsen, 1995).

     vtinmo gets its global parameters from  command  line  argu-
     ments and its eta functions  and velocity functions from usp
     format files or secondary input data sets.

  Command line arguments
     -N ntap
          Enter the input data set name or file immediately after
          typing -N.  This input file should include the complete
          path name if the file resides in a different directory.
          Example  -N/b/vsp/dummy  tells  the program to look for
          file 'dummy' in sub-directory 'vsp' of directory 'b'.

     -O otap
          Enter the output data  set  name  or  file  immediately
          after typing -O.  The output data set also requires the
          full path name (see above).

     -e etap
          Enter the name of the file containing  the  eta  field.
          There  must  be  one eta trace (and one velocity trace)
          for each input gather. No default. In the  XIKP  vtinmo
          menu  panel the input socket 4 is for eta input; socket
          3 is for velocity input.

     -v vtap
          Enter the name of the file containing the corresponding
          velocity  field.  There must be one velocity trace (and
          one eta trace) for  each  input  gather.  In  the  XIKP
          vtinmo  menu  panel  the input socket 3 is for velocity
          input and socket 4 is for eta input.

     -nmo Enter the command line argument '-nmo' to  signal  that
          standard normal moveout (based on short offset velocity
          analysis) has already been applied and  that  only  the
          forth order term (eta field) need be applied.

     -R   Enter the command line argument '-R' to request inverse
          Normal  Moveout correction.  The default is for forward
          correction.

     -?   Enter the command line  argument  '-?'  to  get  online
          help.   The program terminates after the help screen is
          printed.

     -h, -?
          Enter the command line  argument  -H  or  '-?'  to  get
          online  help.   The  program  terminates after the help
          screen is printed.

AUTHOR

     Paul Gutowski, EPTG, pgutowski@amoco.com, 422-3146

COPYRIGHT

     copyright 2001, Amoco Production Company
               All Rights Reserved
          an affiliate of BP America Inc.