Reflection energy from a linear reflector comes from the integrant over an aperture, often described by the Fresnel zone. Within the Fresnel zone, the diffraction energy constructively builds the reflection energy. To get true reflection amplitude, a migration aperture that is twice the Fresnel zone size must be considered. This paper derives the size of the prestack Fresnel zone as a function of half the source-receiver offset. It evaluates how the size of the migration aperture affects the migration result, then establishes an acceptable minimum migration aperture for horizontal reflectors. For both zero-offset and offset data, twice the Fresnel zone size is the minimum migration aperture to preserve true amplitude. A migration aperture that is larger does not improve the migration result.
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