SUMMARY

The proof that NMO can be expressed as the superposition of N N^th 15-degree partial normal moveouts with arbitrary precision as $N \to \infty$, can be summarized in this way:

• The relation holds exactly for partial normal moveouts.
• The 15-degree partial normal moveout approximates a partial normal moveout with an error that tends to zero faster than 1/N with increasing N, so that the total error (=sum of N errors) tends to zero with increasing N.

In cascaded migrations, a small number of iterations is used; hence inequality (34) may be used for an estimation of the number of iterations required to achieve angle accuracy.