Multifocus moveout revisited: derivations and alternative expressions

The multifocus moveout of Gelchinsky et al. [Gelchinsky, B., Berkovitch, A. , Keydar, S., 1997. Multifocusing homeomorphic imaging: Parts I and II: Cou rse Notes, Special Course on Homeomorphic Imaging. Seeheim. Germany] is a p owerful tool for stacking multicoverage data in arbitrary configurations. B ased on general ray theoretical assumptions and on attractively simple geom etrical considerations, the multifocus moveout is designed to express the t raveltimes of neighbouring rays arbitrarily located around a fixed central, primary reflected or even diffracted, ray. In this work, the basic derivat ions and results concerning the multifocus approach are reviewed. A higher- order multifocus moveout expression that generalizes the corresponding one of Gelchinshy is obtained from slight modifications of the original derivat ion. An alternative form of the obtained multifocus expression that is best suited for numerical implementation is also provided. By means of a simple numerical experiment, we also comment on the accuracy of the multifocus tr aveltime approximations. (C) 1999 Elsevier Science B.V. All rights reserved .