NAME

     taupmig  -  compute  interval  velocity-depth  spectra  from
     plane wave data using critically reflected/refracted energy

SYNOPSIS

     taupmig [ -Nntap ] [ -Ootap ] [ -reire ] [ -rsirs ] [  -nsns
     ]  [ -nene ] [ -nznz ] [ -dzdz ] [ -vminvmin ] [ -vmaxvmax ]
     [ -nvelnvel ] [ tmultmul ] [ dmuldmul ] [ -slnt ] [ -S  ]  [
     -log ] [ -V ] [ -? ]

DESCRIPTION

     A velocity vs depth spectrum 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 migra-
     tion 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.

     taupmig 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)

     -ns ns
          Define the starting trace for analysis (default = 1)

     -ne ne
          Define the last  trace  for  analysis  in  each  record
          (default = ns).  The use of the ns and ne pair are use-
          ful to be able to skip dead traces or to select just  a
          portion  of  the  data  set for analysis which is loga-
          rithmic scale of 2 cycle length.

     -S   If present, calculate the  velocity  spectra  in  equal
          increments      of      slowness     squared,     where
          v=sqrt(slowness**2).

     -log If present, the velocity (or slowness) scale  is  loga-
          rithmic.   This  can often resul t in superior sampling
          of the scans.

     -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).

     -nvel nvel
          Maximum number of velocities to use spaced between vmin
          and vmax (default =100) There is 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
          This flag tells the program that  the  input  data  has
          been written by program slnt.

     -?   Query mode.   With  this  flag,  taupmig  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.