Conclusions

Reflection amplitude modeling analysis for anisotropic media is carried out in the $\tau-p$ domain. Working in the ``phase'' domain allows a robust estimate of reflection amplitudes. Interfering and triplicating events are handled accurately. The traveltime curve in the ``phase'' domain relates directly to the inverse of the phase slowness surface of the medium. Within the validity of crack models used, inline-crossline velocity anisotropy varies from 0-15 percent. However, the reflection amplitude exhibits a smaller degree of variation, typically less than 10 percent. The reflection response depends on the material filling the cracks, the crack shape, and the crack density. We used methane, water, and vacuum for filling materials. The PP reflection magnitude is affected greatest between P and S critical angles. The PS reflection coefficient seems to exhibit anisotropy over a larger angular range independent of the filling material. PS converted mode reflection seems more sensitive in attempting to distinguish gas- and fluid-filled fractures together with their orientations.