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Snell’s   time  as   makes   originated   below,   discussions   out   source/re-   directly   below   appearing   a)  Assuming  constant   an   come  along  a  semicircle  drawn   Migration   swinging  circular  arcs
      141         for   of          the          two-dimensional   unmigrated   from   is   position  migrated  tangent   Migration  shallows,   unmigrated   updip

      Profiles   to  according   travel   and   “sideswipe”   if  they   the   and   in   common   been   point   event   on   trace  could  have   event.  b)   to  the  event. The  segment   line   the   arcs.  c)  shortens,  and  steepens  an  event,  moving  points  in  an

      Reflection   geometry   Such   appear   illustrated   3,   and   infinitely   the   have   not   any   been   the   6.5  FIGURE   velocity  material  and   structure,  an  event   seismic   anywhere   the   through   equivalent   through   of  theeventis   to  each  of  the   direction:



      on   interfaces,   in   section.   would   are  effects   2,   1,   extending   below   might   have   the  receiver. Thus,   of
      Structures   across   distortions   the   they   four   effects   and   directly   point   could   Potential   :   Pe  oint   OWI]  J@ACLL



      of   velocity   of  plane   than   The   For   striking   plotted   reflecting   point   from   ence   Sas  Positions
      Appearance   in  changes   effects  produce   the   of   sections   line.   survey   geometries.   structures,   events   actual   the   reflecting   away   time   ’   Inci   Raypat   7   i   a   i   .   /   ,   O.   co"





           by   out   from   seismic   on   the   complex   Effects   has   though   actual   travel   N On mal   ff   fe
           caused   Three-dimensional   deeper   beneath   two-dimensional   “Migration”   section   The   same       \,

           is   reflected   more   position,  even   6.1).   the   is   Seismic   Trace   8,  SM eRie
           bending   4.   are   appear   directly   then   page.   unmigrated   (Fig.   that   Event—         :


           The   Law.   events   events   from   simple   assume   the   Geometric   An   ceiver   below   surface   ’   4   \   Unmigrated   S

                             1.                                                                        7  \
                                                                               ,
                                                         W





          a        3   2
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          (Ss)  aul  janes,  Aef,-OM]        (Ss)  EWI  JeARLL  ABAA-OML              (un)  yideq             N.  Nasu   1982.   ©
       0.0                                                                 10.0   0.0    3             172.0   From   #4,
                                                                                         ©
                                                                                                               Data  Series

                                       oe                                                                  6.4   Fig   the  Nankai  Trough,  Japan.   Basic









       :                               RRR   SOI                      7   es                               Geophysics,   of a  seismic  profile from  Nanki  Trough,  /POD,  Japan
          Section                      SES                            ——S                                  Earth   University  of Tokyo,  Tokyo,  Japan.




          Time                         ems                              SS                                 Whole   Lillie,   and  depth  conversion  others,  Multi-channel  seismic  reflection  data  across

          Unmigrated                                                                                          Migration   Institute,  Research







         a)                            Aen                                                                    6.4  FIGURE   Ocean
                                                                                                               and
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