Chapter 3: Zero-Order Ray Theory
In this chapter, we briefly introduce high-frequency wave propagation in isotropic, inhomogeneous, layered 3D media as is described by zero-order ray theory. We will cover as much theory as is needed for the development and understanding of the imaging theory that is described in later chapters of this book. The main purpose of this chapter therefore is twofold. One aim is to formulate ray-theoretical expressions for the elementary seismic waves by which seismic reflections are described in seismic records (as, e.g., common-shot, common-receiver, common-midpoint, or common-offset gathers). It is these elementary waves from which the seismic images (e.g., depth-migrated images) are to be constructed by the imaging processes that are studied below. The other aim is to provide ray-theoretical expressions for all quantities that will appear in the imaging theory to be developed.
For a more detailed treatment of most of the topics discussed in this chapter, see Červený (1985, 1987, 1995, 2001). If your main interests involve true-amplitude imaging as presented in Chapter 2, without a need for the underlying details of forward wave propagation, we suggest that you continue your reading of this book with Chapter 7.