OPTIMIZED OPERATORS FOR 3-D FOURIER FINITE-DIFFERENCE MIGRATION

In 3-D finite-difference migration we encounter at least three problem s: accurate imaging of steeply dipping reflectors, circular symmetry o f the operator response, frequency dispersion and other migration arti facts. 3-D FFD migration is a hybrid migration method containing a 3-D phase-shift operator in the frequency-wavenumber domain and an implic it 3-D finite-difference operator in the frequency-space domain. The 3 -D finite-difference component is approximated by the sequential appli cation of implicit 2-D finite-difference operators in two, four or eve n more directions. Because the 3-D phase-shift component does not cont ain the above-mentioned problems, its incorporation into the 3-D FFD s cheme will partially solve these problems. We discuss 3-D FFD (two-way splitting) and 3-D FFD (four-way splitting) and show that in both cas es the maximum migration angle and the circular symmetry are improved and the frequency dispersion is reduced.