NAME

     taupvzs  - velocity-depth  image  profile  using  critically
     refracted plane wave data

SYNOPSIS

     taupvzs [ -Nntap ] [ -Ootap ] [ -reire ] [ -rsirs ] [  -nsns
     ]  [ -nene ] [ -nznz ] [ -dzdz ] [ -vminvmin ] [ -vmaxvmax ]
     [ -nvnvel ] [ tmultmul ] [ dmuldmul ] [ -slnt ] [ -V ] [  -?
     ]

DESCRIPTION

     A velocity vs depth profile (image) is obtained by  scanning
     forward  tau-p  transform (radonf) of a CMP gather of traces
     using a downward continuation  function  due  originally  to
     Clayton  &  McMechan  (Geoph. V.46, P.860-868).  A composite
     image of slowness or velocity is  built  up  by  essentially
     doing  a  number  of constant velocity plane wave migrations
     from some minimum velocity to some maximum  velocity.   Each
     such  migration  can  be done fairly efficiently in the time
     domain.

     The basic equation for the whole operation is

     tau(z) = 2*dz SUM { sqrt [ 1/v(z)**2 - p**2 ] }

     where the delay time at each depth is the sum of  all  delay
     times above (over the depth increment).  p is the ray param-
     eter which will be constant over time for each  input  plane
     wave  trace and v(z) is the velocity-depth function which is
     our case will be constant for each velocity scan.  Therefore
     at  each  output point of the image record we have a mapping
     back to the input plane wave record and  so  we  accumultate
     amplitudes  in the image by linearly interpolating the input
     amplitudes and summing them  onto  the  image  matrix.   The
     images  from successive scans are summed so that contructive
     interference will build up the true velocity  (or  slowness)
     vs depth function.

     The final output is a record of the same size as  the  input
     each  trace  corresponding  to the same ray parameter as the
     input (the record will be in reverse  trace  order  so  that
     velocity  increases left to right).  The vertical scale will
     be sampled in depth at the increment specified on  the  com-
     mand  line.   The  trace  velocity  will be written into the
     trace header mnemonic DstSgn.

     taupvzs gets processing controls from the command line. Rea-
     sonable defaults are set up.

  Command line arguments
     -N ntap
          Enter the full path of the  file  continuing  the  data
          set.  If  not specified, input is expected on the stan-
          dard input. If standard input  is  not  specified,  and
          there  is  no  input,  e.g., program run in background,
          expect a  very  ungracious  crash.   (default  standard
          input)

     -rs irs
          First record for processing (default = 1)

     -re ire
          Last record for processing (default = last)

     -V   Flag for verbose output on the  standard  output.  This
          lists  salient  trace header information as well as all
          command values used for processing,  the  default  ones
          given if not overridden.

     -nz nz
          Number of output  depths  samples.   Default  =  number
          input  time  samples.   This quantity combined with the
          depth  increment  (below)  defines  the  maximum  depth
          scanned.

     -dz dz
          Depth increment (ft,m).  Default = none

     -vmin vmin
          Minimum  interval  velocity  value  input   in   ft/sec
          (default = 1000.0).

     -vmax vmax
          Maximum  interval  velocity  value  input   in   ft/sec
          (default = 10,000.0).

     -nv nvel
          Maximum number of velocities to use spaced between vmin
          and  vmax (default =number of input traces) There is no
          maximum.

     -dmul dmul
          Multiply  each  distance,  DstSgn,   by   this   factor
          (default=1.0).  This is useful when the header has dif-
          ferent units than expected.

     -tmul tmul
          Multiply the sampling  interval,  dt,  by  this  factor
          (default  = 1.0). This is useful if the sampling inter-
          val is in different units than expected.

     -slnt
          If present, the data are from program slnt

     -?   Query mode.   With  this  flag,  taupvzs  will  give  a
          description  of the command line arguments and stop the
          program.

BUGS

     It is assumed that the record(s) to be analyzed should be in
     a CMP gather.

SEE ALSO

     radonf, taupspec, velspec, pomega, velin

AUTHOR

     Paul Gutowski, APR, zprg03@trc.amoco.com

COPYRIGHT

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