Figure 3 shows the effects of the different boundary conditions on the two spatial axes. The fast spatial axis (top and bottom of Figure) have helical boundary conditions, and show wrap-around. The slow spatial axis (left and right of Figure) has a zero-value boundary condition, and hence is reflective.

For the examples in this paper, we set the `one-sixth' parameter Claerbout (1985), , and used the isotropic nine-point Laplacian from equation (8).

3Dtimeslice
Depth-slice of centered impulse response corresponding to a dip of
45. Note the azimuthally isotropic nature of the
full implicit migration. Evanescent energy has been removed by
dip-filtering prior to migration.
Figure 2 |

3Dboundary
Depth-slice of offset impulse response corresponding to a dip of
45. Note the helical boundary conditions on the fast spatial axis.
Figure 3 |

7/5/1998