Introduction and Overview

Least-squares migration (Nemeth et al., 1999) has been shown to have the following advantages: (1) it can reduce migration artifacts from limited recording aperture and/or coasre source and receiver sampling; (2) it can balance the amplitudes of the reflectors; and (3) it can improve the resolution of the migration images. However, least-squares migration is usually considered to be too expensive for practical use. In this dissertation, I propose a new algorithm to combine blended sources processing technique with least-squares migration to increase its computational efficiency. The proposed algorithm is first implemented with Kirchhoff migration method in Chapter 2, and then with reverse time migration method in Chapter 3. To adapt for marine-streamer geometry, plane-wave encoding can be used instead of random time-shift encoding. In the following chapters, the multisource least-squares migration algorithm is tested with synthetic and real data examples to illustrate its advantages.

when the horizontal reflectors are embedded in the migration velocity, reverse time migration can migrate prism waves correctly to illuminate the vertical reflectors such as salt flanks. In Chapter 4, I propose a new method to migrate prism waves separately and reduce the interference between primary reflections and prism waves. It also avoids the step of modifying migration velocity.