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Influência Da Orientação Do Eixo De Simetria Na Análise De Avo/Ava Em Meios Anisotrópicos
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 6th International Congress of the Brazilian Geophysical Society, Aug 1999, cp-215-00385
Abstract
Anisotropy is characterized by the angular dependence of the kinematical and dynamical quantities. In this way, any<br>rotation applied to an anisotropic medium can result in expressive changes in these quantities when observed from a<br>fixed reference system. This is the case for the so called true amplitude computations, as the AVO and AVA analysis in<br>anisotropic media. In particular, the amplitude in a general stratified anisotropic medium depends on directivity of the<br>source, geometrical spreading and reflection coeficients. Generally, all these three quantities have strong angular<br>dependence, such that the reflected amplitude in anisotropic media is highly sensitive to the angular orientation of the<br>symmetry axis. In this paper we investigate the effects of rotations in symmetry axis (planes) on each one of the named<br>quantities and their overall effects on the reflected amplitude for a plane interface model consisting of a TI or orthorombic<br>medium over an isotropic one. The results presented clearly show that suitable rotations in symmetry axis (e.g., dipping<br>rock fractures) can even reverse the amplitude response of the medium.