Translations:Migration - book/8/en

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Digital implementation of migration involves massive data handling. All the traces must be amalgamated either by wave-equation methods (Claerbout, 1971[1]) or by the associated ray-theory methods (Hagedoorn, 1954[2]; Gray, 1986[3]). Such methods involve significant data manipulation, which in the last century generally overloaded the limited capacities of the available computers. To reduce the extent of computations, migration usually was limited to two dimensions (namely, a horizontal dimension and the depth dimension). In addition, it was expedient to break the migration problem down into smaller parts. Thus, migration was done by a sequence of partial operations, such as stacking, followed by normal move-out, followed by dip moveout, and then followed by migration after stack. The process of time migration often was used, which improved the records in time but stopped short of putting the events in their proper spatial positions. All sorts of modifications and adjustments were made to improve such piecemeal operations. This approach made seismic migration a complicated discipline and an art as much as a science. The use of this art required much insight. Seismic migration in three dimensions (namely, two horizontal dimensions and the depth dimension) rarely was used because of the prohibitive costs involved.

  1. Claerbout, J. F., 1971, Toward a unified theory of reflector mapping: Geophysics, 36, 467–481.
  2. Hagedoorn, B. B., 1954, A process of seismic reflection interpretation: Geophysical Prospecting, 2, 85–127.
  3. Gray, S. H., 1986, Efficient traveltime calculations for Kirchhoff migration: Geophysics, 51, 1685–1688.