中文摘要：

非双曲（远偏移距）时差为各向异性介质中正、反演研究，特别是各向异性参数估计提供了重要信息.本文在任意空间取向TI（ATI）介质水平界面同类反射波四次时差系数（A4）精确解的基础上，进一步讨论我们推导得出的ATI介质中四次时差系数解析近似解，比较随CMP测线方位变化的近似解与精确解之间的差别，为利用近似解来解析研究ATI介质中非双曲时距以及参数反演提供有价值的信息．结合实际岩性资料的数值研究表明，ATI条件下四次时差系数近似解与精确解之间存在差别，不仅表现在A4数的大小及符号特征上，更突出地表现在A4系数随方位的变化特征上；在强各向异性条件下，近似解相比精确解存在较大误差．但在各向异性参数满足0〈ε-δ〈0.15、｜δ｜〈0.20的情况下，对于TI对称轴的特殊倾角范围（75°～80°），近似解与精确解的差别很小，可用近似解进行各向异性观测解释及参数反演．

英文摘要：

Nonhyperbolic （far-offset） moveout provides essential information for seismic modeling and inversion studies, particularly for parameter estimation in anisotropic media. Based on the exact analytic solution of the quartic moveout coefficient A4 for a horizontal interface in the TI media with an arbitrary spatial orientation of symmetry axis （ATI）, we discuss our derived approximate analytic expression of the A4 further, in order to study the difference between the approximate and exact solution of the A4 with the CMP survey line azimuth variation in the ATI media. This research may provide valuable information for the analysis of nonhyperbolic traveltime-offset and anisotropy parameter inversion by using approximation solution of the A4 in the ATI media. Combined with real rock data, the modeling results show that the distinction between the approximate and exact solution of the P-wave A4represents not only in the value and sign of the A44, but also prominently in the azimuthal signature of the A4. For the strongly anisotropic media, the approximate solution has notable errors comparing with the exact solution. At the same time, there is little difference between the approximate and exact solution of the A4 for the special dip angle of the symmetry axis in 0〈ε-δ〈0.15 and ｜δ｜〈0.20 of TI models, which is from 75° to 80°, and under this condition we can utilize the approximation solution of the A4 for making anisotropy observation, explanation and parameter inversion.