Operator fold for finite-frequency migration operators

Calculating operator fold for finite-frequency migration operators is not as simple as modeling and migrating (or just migrating) a vector full of ones. A vector that is full of ones in the time domain has zero temporal frequency, and will not propagate in the same way as the frequencies of interest. Similarly, a vector that is full of ones in the frequency domain cause problems because it will be localized in time. Randomizing the phase may solve this particular problem, but it will cause others.

Duquet et al.'s approach 2000 is also not appropriate for normalizing wave-equation migrations because they are necessarily full-volume methods that cannot be implemented in a target-oriented manner. A naive implementation would require full modeling and migration for every point in model-space.

Fortunately the general formulation in Chapter  does not have these limitations, and is applicable to any linear operator provided an appropriate choice of reference model exists.