横向各向同性介质纵波非双曲线时差速度分析

在各向异性介质中，纵波反射旅行时具有非双曲线时差特性，随排列长度的增大非双曲线现象更加明显。显然，常规双曲线时距曲线方程已经不能满足描述地震勘探中日益复杂的地球介质模型的需求。为此，在时距关系中增加含炮检距的四次项，并采用分式展开法表示该四次项，同时引入远偏移距收敛因子。改进后的时距关系表达式在形式上接近于常规地震波双曲线型时距关系，清楚地描述了横向各向同性介质中速度随炮检距的变化。实例表明，该算法提高了各向异性介质速度分析精度，改善了剖面叠加效果。

P-wave nonhyperbolic moveout velocity analysis in transversely isotropic medium

P-wave reflections in horizontally layered anisotropic media display nonhyperbolic moveout. This phenomenon becomes more evident with increasing spread length. It is obvious that conventional traveltime equation that based on hyperbolic hypothesis is insufficient to describe the more and more complicated earth model. We propose adding a term that is related to the fourth power of offset into the traveltime equation, and expressed it by a fraction expansion. Meanwhile, a parameter is introduced to ensure the correct behavior of moveout at far offset. The form of improved equation is similar to that of the conventional one. The velocity versus offsets in transversely isotropic medium can be described clearly. It is shown from actual example that the accuracy of velocity analysis using this method is improved in anisotropic medium, and the stack effect is better.