In a constant-velocity isotropic medium, the reflection from a reflector dipping at the angle *α* has apparent dip *β* (Figure M-11a) given by the migration equation,

$\sin \alpha =\tan \beta \$

**Migration (a)** in two and (

**b**) three dimensions. (From Hagedoorn, 1954

^{[1]}.) A point in unmigrated space migrates to a wavefront surface and a point in migrated space specifies a diffraction surface. The shape of the wavefront and diffraction surfaces depends on the velocity distribution above the reflecting point. Lateral velocity variations distort the shape of these surfaces and shift the intersection of the surfaces away from the diffraction crest.

## References

- ↑ Hagedoorn, J. G., 1954, A process of seismic reflection interpretation: Geophys. Prosp., 2, 85–127.