NAME

     avbf - computes the cumulative  amplitude  spectrum  from  a
     slab  of seismic data.  A least squares fit is computed from
     the spectrum and its coeficients are written into a  seismic
     data volume.

SYNOPSIS

     avbf [ -Nntap ] [ -Ootap ] [ -sist ] [ -eiend ] [ -f1frq1  ]
     [  -dfdfrq ] [ -nfnfrq ] [ -gscalgaus ] [ -rsnrst ] [ -Q ] [
     -ssam ] [ -V ] [ -? ]

DESCRIPTION

     avbf Amplitude variation with bandwidth  in  frequency  com-
     putes a cumulative amplitude spectrum over a specified range
     of frequencies.  This is specified as a start  frequency,  a
     frequency  interval, and number of frequencies.  A linear or
     quadratic least squares fit is applied to the  spectrum  and
     the  coefficients  and  a residual are output as samples for
     each trace location.


          Coeficients for linear fit:

              a0      intercept
              a1      slope
              res     residual

     a0, a1, res correspond with trace samples 1, 2, 3
     in the seismic data volume



          Coeficients for quadratic fit:

              a0     intercept
              a1     slope
              a2     curvature
              res    residual

     a0, a1, a2, res correspond with trace samples 1, 2, 3, 4
     in the seismic data volume



     The residual is intended to catch those features not  caught
     by the a0 and a1 coefficients.



     avbf was designed to run on a slab of  data  that  has  been
     flattened  to  a  horizon.    It  can also be applied to any
     seismic data set.  Experience  has  shown  that  the  linear
     least  squares  fit performs as well or better than the qua-
     dratic fit, which has the advantage of reducing  the  output
     by one slice in the data volume.


     avbf gets both its data and its parameters from command line
     arguments.   These  arguments specify the input, output, the
     start and end traces, the frequencies, and verbose printout,
     if desired.

  Command line arguments
     -N ntap
          Enter the input data set name or file immediately after
          typing -N unless the input is from a pipe in which case
          the -N entry must be omitted.  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 directory '/b/vsp'.

     -O otap
          Enter the output data  set  name  or  file  immediately
          after typing -O.  This output file is not required when
          piping the output to another process.  The output  data
          set also requires the full path name (see above).

     -s ist
          Enter the start time of the design window.  The default
          is  the  beginning  of  the  trace.  The filter will be
          applied to the whole trace, regardless of the -s and -e
          entries.

     -e iend
          Enter the end time of the design window.   The  default
          is the end of the trace.

     -f1 frq1
          Enter the start frequency (Hz)

     -df dfrq
          Enter the frequency interval (Hz)

     -nf nfrq
          Enter the number of frequencies

     -gscal gaus
          Enter the Gaussian scale parameter

     -Q   Use quadratic fit

     -rs nrst
          Enter start record number.  Default value is the  first
          record.

     -re nred
          Enter end record number.  Default value is last record.

     -ssam
          Enter the command line argument '-ssam' to get  a  real
          time status report as the job runs.

     -V   Enter the command line argument '-V' to get  additional
          printout.

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

BUGS

     None reported

AUTHOR

     Adam Gersztenkorn, Rob Piepul

COPYRIGHT

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