Advanced Methods for Prestack Depth Migration
The choice of an appropriate migration method is crucial to the success of any imaging project. In Chapters 2 and 3 I introduced the basic concepts underlying the two main types of migration methods; Kirchhoff migration and wavefield-continuation migration. In this chapter I discuss the actual algorithms that are implemented in several advanced depth-migration programs and discuss their respective strength and weaknesses. Because migration technology is evolving rapidly, the specific details of migration algorithms quickly become obsolete. However, the intrinsic properties and characteristics of the different migration methods do not change as quickly as their implementations do. Therefore, in my discussion I often overlook the algorithmic details in favor of a conceptual view of the methods.
The first section of this chapter is dedicated to Kirchhoff depth-migration methods. These methods are still the workhorse of the industry, although they are being slowly supplanted by the more accurate and robust wavefield-continuation methods.
In the second section, I briefly introduce Gaussian-beam migration methods. In many ways, Gaussian-beam methods are in between Kirchhoff methods and wavefield-continuation methods. Gaussian-beam migration provides an often-attractive compromise between the accuracy of wavefield methods and the computational efficiency of Kirchhoff migration. As is the case with Kirchhoff migration, Gaussian-beam migration relies on ray tracing to propagate wavefields. However, it is more accurate in handling multipathing wavefields than Kirchhoff migration is.
The last and most extensive section of this chapter is dedicated to wavefield-continuation migration methods because that is the area of migration technology that