Abstract

Multifocusing imaging proposed by Gelchinsky (Gelchinsky et al., 1999a, b; Landa et al., 1999) belongs to a group of techniques that can be characterized as macro-model independent imaging methods. These methods, which also include the common-reflection surface method (Mann et al., 1999; Jäger et al., 2001), and optical stack (de Bazelaire, 1988), are described in a collection of papers published as a special issue of the Journal of Applied Geophysics (Hubral, 1999). Macro-model independent imaging methods represent a new alternative to the classical processing sequence of NMO, dip moveout (DMO), and stacking. They are based upon a new transformation of 2-D multicoverage prestack data into a simulated zero-offset stack section. This transformation involves stacking large supergathers of seismic traces, each of which can span many common-midpoint (CMP) gathers. Stacking of large supergathers is made possible by the use of a generalized moveout correction. For a given source-receiver pair, this correction depends on three parameters: the wavefront curvatures of the normal wave, the normal incidence point wave (Hubral, 1983), and the emergence angle of the central ray. For each supergather and each zero-offset time, T0, these parameters are obtained through a coherence analysis of the moveout corrected supergather.

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