NAME

     radgamma - radon transform and reverse radon transform using
     "gamma curve"

SYNOPSIS

     radgamma [ -Nfile_in ] [ -Ofile_out ] [ -Sfile_semb ] [ -R ]
     [  -semb ] [ -sigma1sigma1 ] [ -sigma2sigma2 ] [ -hminoffmin
     ] [ -hmaxoffmax ] [ -zminmindepth  ]  [  -zmaxmaxdepth  ]  [
     -gammaminmingamma  ]  [  -gammamaxmaxgamma  ]  [ -ncurvecur-
     venumber ] [ -dhdoffset ] [ -Mmaxmemory ]  [  -totalnodesto-
     talnodes ] [ -nodenumbernodenumber ] [ -V ] [ -? ]

DESCRIPTION

     radgamma Take a cube of common  reflection  point  as  input
     ranging  from  offset  hmin  to hmax and depth zmin to zmax,
     radgamma do the radon transform using  a  series  of  ncurve
     gamma  curves ranging from gammamin to gammamax. In order to
     apply the reverse radon transform, added to the  -R  option,
     you need to specify the offset sampling rate dh.

     Given an event in time associated with a flat and horizontal
     reflector  imbedded  in  a  homogeneous  velocity model, the
     gamma curve describe the moveout (with respect to offset) in
     a  common  reflection point of this time event migrated with
     an arbitrary homogeneous velocity model. The gamma parameter
     refer  to  the  ratio between the current velocity model and
     the exact velocity model.

     radgamma allows to do semblance weightning.  To  do  so  you
     have  to  first calculate this weightning file and output it
     using the semb option and then use this weightning  file  as
     input   (-S   option).   This   weighting   will  accentuate
     coherent/continuous events and  suppress  incoherent  events
     and can thus be very usefull for interpollation or extrapol-
     lation.

  Command line arguments
     -N file_in [default = stdin]
          Enter the usp input file name that contains the data to
          be  radon  transformed or reverse radon transformed (no
          default).

     -O file_out [default = stdout]
          This output file can be either the radon  transform  or
          the  semblance  weightning  file  (if  option  -semb is
          present). Enter the  stem  of  the  output  file  name.
          radgamma  will  automatically append a partial solution
          number to this stem to allow calculation across  multi-
          ple  computer  nodes,  by  multiple  passes through the
          data.  Thus,  if  file_out  =  /export/data2/crp_radon,
          radgamma    will    generate    files   of   the   form
          /export/data2/crp_radon__1__1,
          /export/data2/crp_radon__1__2,
          /export/data2/crp_radon__1__3, etc., where  the  second
          suffix corresponds to the computational node. If total-
          nodes is 1, there will be a single created output  file
          called  /export/data2/crp_radon.  If  there is a single
          created output file, it can be piped.  Otherwise,  rou-
          tine mrgrad will merge these files into a single file.

     -S file_semb
          Enter the usp input semblance weightning file name.

     -semb
          If this option is present, the output is the  semblance
          weightning file.

     -sigma1 sigma1
          Reject data whose depth average semblance  is  inferior
          to   this   value.   This   weighting  will  accentuate
          coherent/continuous  events  and  suppress   incoherent
          events.  This  parameter  is  only  active  if -semb is
          present. (Default=0.1)

     -sigma2 sigma2
          Pass data (with amplitude  100%)  whose  depth  average
          semblance  is  superior  to  this value. This weighting
          will accentuate coherent/continuous events and suppress
          incoherent  events.  This  parameter  is only active if
          -semb is present. (Default=0.2)

     -hmin offmin
          Enter the minimum offset value contained in  the  data.
          The default value is 0.

     -hmax offmax
          Enter the maximum offset value contained in  the  data.
          The default value is 0.

     -zmin mindepth
          Enter the minimum depth  contained  in  the  data.  The
          default value is 0.

     -zmax maxdepth
          Enter the maximum depth  contained  in  the  data.  The
          default value is 0.

     -gammamin mingamma
          Enter the minimum gamma value used, even if you perform
          a reverse radon transform. The default value is 0.7

     -gammamax maxgamma
          Enter the maximum gamma value to be  used,even  if  you
          perform a reverse radon transform. The default value is
          4.

     -ncurve curvenumber
          Enter the number of gamma curves  to  be  used  in  the
          radon  transform.  No  default  if  -R  option  is  not
          present.

     -dh doffset
          Enter the offset increment to be used  in  the  reverse
          radon transform. No default if -R option is present.

     -M maxmemory
          Enter the maximum memory allowed  for  the  program  in
          Megabytes. (Default=10).

     -totalnodes totalnodes
          Should be invoked by  a  careful  shellscript,  IKP  or
          spawn2    only.    Enter    the    total    number   of
          workstations/heads/nodes that the  multiprocessor  over
          which the job is being distributed. (Default=1).

     -nodenumber nodenumber
          Should be invoked by  a  careful  shellscript,  IKP  or
          spawn  only.  Enter  the  relative  node  number of the
          workstation/head/node  that  the  multiprocessor   over
          which the job is being distributed. (Default=1).

     -V   Enter the command line argument '-V' to obtain  verbose
          output.

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

BUGS

     No bugs known at present.

REFERENCES

     Al-Yahya, K. M., 1987, Velocity analysis by  iterative  pro-
     file migration: Ph.D. Thesis, Stanford University.

CONTRACT AGREEMENT

     This product is brought to you as a 4th quarter  deliverable
     (filtering  of  coherent  noise  in  the  depth  domain)  by
     Research Agreement D96-2518 (Seismic Signal Analysis). Thank
     you for your support.

AUTHORS

     Bertrand Duquet, Amoco EPTG, 1996.

COPYRIGHT

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