Abstract：When the incident ray parameter is known, we can obtain the exact transmitted velocity and angle in HTI media. Then we deduce the exact AVO formula in azimuth based on this theory. We obtain the following observation with analysis of AVO scattering curves of two models: 1 the maximum reflectivity of compression wave occurs at the azimuth of 90°on Model 1 with isotropy homogeneous media over HTI media. The reflectivity changes little near 90°, but it changes a lot at 0°and 180°. At the same time the reflectivity of the fast shear wave has polarity reversal when it propagates across the symmetry axis plane and the fracture plane, but the reflectivity peak does not occur in these two planes. For the slow shear wave, it is opposite. 2 As for model 2 with HTI over HTI whose symmetry axis planes have an arbitrary angle, whatever the angle of both symmetry axis planes is, the reflectivity of compression wave is the same if its incident angle difference in azimuth is 180°. When the angle of both symmetry axis planes is 0°and 90°, the reflectivity of compression wave is the same about the symmetry axis plane and the fracture plane. The reflectivity of fast shear wave has continuous polarity reversal across the symmetry axis plane, but discontinuous polarity reversal across the fracture plane. For slow shear wave, it is opposite. 3 On the symmetry axis plane and the fracture plane, either fast shear or slow shear can occur. Based on the characteristics of fast and slow shear waves, we can precisely pinpoint the fracture strike.
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