Throughout this thesis, I assume that seismic wave fields recorded on the earth surface propagate through an isotropic, elastic medium. The wave fields in such a medium are vector fields consisting of the components of compressional waves (P-waves) and shear waves (S-waves). After P- and S-waves are decoupled from recorded seismic wave fields, each component honors a scalar wave equation. Therefore, I describe the imaging methods for a scalar wave field. The results can be applied to both P-waves and S-waves.

2/5/2001