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.