Seismic Scale Effects: Dispersion, Attenuation, and Anisotropy by Multiple Scattering of Waves
Yinbin Liu1, Douglas R. Schmitt1
(1) University of Alberta, Edmonton, AB
The multiple scattering of seismic waves in heterogeneous media causes velocity dispersion and waveform distortion. A propagator matrix approach is used to model the scale-dependent velocity dispersion and waveform distortion caused by the interference of intrabed multiple reflections in strong 1D heterogeneous media. The results indicate that the velocity transition from ray to effective media domains mainly takes place at R=about 10 (R is the ratio of wavelength to layer spacing), and that velocities are equal to ray velocity for small R-values and effective media velocity for large R-values. The waveform distortion results in scale-dependent low frequency behavior and coda wave. The low frequency wave occurs as either coherent scattering attenuation for small R or coherent scattering enhancement for large R. Near the effective media region, the low-frequency energy transfers into an enhanced main wave-type and a high frequency coda wave. As R increases, the amplitude of coda wave decreases while the frequency increases. This work has implications for doing more accurate lithological and stratigraphic interpretations and subtle reservoir evaluation.