Imaging and Aliasing
The quality of 3D images is influenced strongly by the spatial sampling of the data and by whether the imaging operators properly take into account the data sampling. Strong aliasing artifacts degrade the images when the data are sampled poorly and the imaging operators are not implemented carefully. The sampling problem is more acute in 3D imaging than in 2D imaging, because the spatial axes of 3D data often are sampled sparsely and irregularly. In this chapter, I analyze the problems caused by regular data grids that are sampled too coarsely, although regularly. Chapter 9 discusses the issues related to irregularity of both data acquisition and reflector illumination.
Three types of aliasing are relevant to seismic imaging: data aliasing, image aliasing, and operator aliasing. Data aliasing and image aliasing are fairly straightforward to understand by using standard sampling theory, whereas operator aliasing is more specific to imaging operators and thus requires detailed analysis. From the earliest development of Kirchhoff migration methods (Schneider, 1978), it has been evident that aliasing artifacts appear in the image if one does not consider data and operator aliasing when one implements the summation operator (Gardner et al., 1974). Thus, methods for preventing operator aliasing during Kirchhoff migration are well established (Bevc and Claerbout, 1992; Gray, 1992; Lumley et al., 1994; Abma et al., 1998; Biondi, 2001). In the first part of this chapter, I discuss aliasing for Kirchhoff migration.
Figures & Tables
Concepts and Applications in 3D Seismic Imaging (SEG Distinguished Instructor Series No. 10) provides a broad and intuitive understanding of seismic-imaging concepts and methods that enables geoscientists to make appropriate decisions during acquisition, processing, imaging, and interpretation. This book, first published for use with the SEG/EAGE 2007 Distinguished Instructor Short Course, also exposes participants to current trends in imaging research and empowers them to adopt new technologies quickly. Seismic images are the basis of critical exploration, development, and production decisions. Optimal use of these images requires full understanding of the processes that create them, from data acquisition to final migration. (DISC on DVD, 756A, is also available.)