![]() ![]() ![]() ![]() We review the following azimuthal techniques for quantifying seismic anisotropy: The discussion begins with a brief review of the nature and scale of real-world fractured rock systems, and then considers three simplified frameworks to represent this complicated reality mathematically. (The Azimuthal Fourier Coefficients approach resolves this: read on!)Īll techniques deliver estimates of anisotropy, but to understand these in terms of fracture properties you have to assume a physical model and the measurements mean something different in each model. The traditional near offset Rüger-style reflectivity AzAVO technique is limited by an inherent ambiguity in the fracture direction it estimates. S-wave Splitting and VVAz relate more to trends, while reflectivity AzAVO captures local deviations. The techniques ‘see’ different scales, or resolutions. Reflectivity Azimuthal AVO methods measure interface properties: they ‘see’ how the anisotropic layer contrasts to the overlying layer.Travel time methods – Shear-wave Splitting and Velocity Variation with Azimuth (VVAz) – measure layer properties: they see how the seismic wavefront is affected by traveling through the anisotropic zone.
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