Abstract:Transverse isotropy with a horizontal axis of symmetry(HTI)is the simplest azimuthally anisotropic model used to describe fractured reservoirs that contain parallel vertical cracks.Aimed at horizontal reflection plane in HTI medium with arbitrary anisotropic degree and according to converted wave NMO velocity formula at discretional azimuth angle(the angle between line orientation and direction of main axis),in this paper we inverse anisotropic parameters using genetic algorithm.In 3-D exploration by multiple component,the vertical velocity of P wave,Thomsen parameter δand azimuth angle of the cracks is inversed through P-P wave NMO velocity that varies with azimuth.S1-S1 NMO velocity in different azimuth angle can be obtained by using P-P and PS1 NMO velocity and the vertical velocity of S1 wave and the Thomsen parameter γis inversed.To effectively limit nonlinear problem and problem of multiple peak values in optimazation,genetic algorithm is used to get global extreme in this paper.During optimization,we use pseudo-parallel genetic algorithm to avoid the occurrence of premature convergence in searching procedure.