Apparent AVA effects of fine layering

The line layering of the earth's subsurface causes apparent amplitude-varia tion-with-angle (AVA) effects in seismic reflection data. One can distingui sh between reflection- and propagation-related apparent AVA effects: the re flection of a package of thin layers is accompanied with angle-dependent wa velet interference, whereas propagation through finely layered media causes angle-dependent wavelet dispersion. Obviously, both types of apparent AVA effects hinder AVA inversion for the elastic parameters. Due to the band limitation of the seismic data, the reflection-related inte rference effects cannot be re moved. However, they can be equalized for all propagation angles by applying an angle-dependent filter in the imaging st ep in angle-dependent migration schemes. The underlying assumption is that the source function is known and that source directivity effects have been compensated prior to migration. The propagation-related dispersion effects can be compensated for in the downward extrapolation process by means of in verse generalized primary propagators. Angle-dependent migration, including the above mentioned modifications, yie lds an angle-dependent reflectivity section in which the apparent AVA effec ts of fine layering are suppressed.