Azimuthal AVO of P-wave at the Boundary between Two TTI Media

3-D P-wave reflection coefficient between two weakly anisotropic TTI media is derived. The approximation is a function of azimuth, incidence, dip angles and anisotropic parameters. Expression is group into intercept, gradient and curvature just like Shuey-three terms, but there is a fourth item called disturbance, which is the function of the gamma, one of Thomsen parameters. The derived formula is not only consistent with the formula of VTI/HTI by Ruger, also demonstrates good accuracy.