Abstract Just as synthetic seismic data can be created by expressing the wave field radiating from a seismic source as a set of Gaussian beams recorded data can be downward continued by expressing the recorded wave field as a set of Gaussian beams emerging at the earth’s surface In both cases the Gaussian beam description of the seismic-wave propagation can be advantageous when there are lateral variations in the seismic velocities. Gaussian-beam downward continuation enables wave-equation calculation of seismic propagation while it retains the interpretive raypath description of this propagation This paper describes a zero-offset depth migration method that employs Gaussian beam downward continuation of the recorded wave field. The Gaussian-beam migration method has advantages for imaging complex structures. Like finite-difference migration, it is especially compatible with lateral variations in velocity, but Gaussian beam migration can image steeply dipping reflectors and will not produce unwanted reflections from structure in the velocity model. Unlike other raypath methods, Gaussian beam migration has guaranteed regular behavior at caustics and shadows. In addition, the method determines the beam spacing that ensures efficient, accurate calculations The images produced by Gaussian beam migration are usually stable with respect to changes in beam parameters.

Abstract Kirchhoff million is the most popular method of three-dimensional prestack depth migration because of its flexibility and efficiency. Its effectiveness can become limited, however, when complex velocity structure causes multipathing of seismic energy. An alternative is Gaussian beam migration, which is an extension of Kirchhoff migration that overcomes many of the problems caused by multipathing. Unlike first-arrival and most-energetic-arrive methods, which retain only one traveltime, this alternative method retains most arrivals by the superposition of Gaussian beams. This paper presents a prestack Gaussian beam migration method that operates on common-offset gathers. The method is efficient because the computation of beam superposition isolates summations that do not depend on the seismic data and evaluates these integrals by considering their saddle points. Gaussian beam migration of the two-dimensional Marmousi test data set demonstrates the method’s effectiveness for structural imaging in a case where there is multipathing of seismic energy.