Wavefield extrapolation and prestack depth migration in anelastic inhomogeneous media

摘要

Wavefield depth extrapolation and prestack depth migration in complex anelastic media are studied. Kjartansson's frequency-independent Q law is used to describe the absorption of seismic energy. The macromodel used is analogous to the macromodel used for current migration schemes except that an additional frequency-independent Q macromodel needs to be provided. Absorption in the forward one-way propagator is introduced by assuming a complex phase velocity, and the inverse one-way propagator is obtained using the reciprocity theorem for one-way wavefields in dissipative media. The stability of the inverse propagator is achieved by limiting the angle of propagation of wavefields. A table-driven explicit operator scheme for imaging complex 2D anelastic media is presented. High-accuracy, short convolution operators are designed by the weighted least-squares method, and two kinds of imaging conditions are proposed. Numerical examples of depth extrapolation in laterally varying media, the migration of a spatial impulse with dispersion as well as shot record depth migration demonstrate the potential of the proposed explicit forward operator, the explicit inverse operator and the prestack depth migration scheme, respectively.