【摘要】 提出一种对旅行时进行抛物线插值的地震射线追踪方法(简称PTI方法),它比基于旅行时线性插值方法(简称LTI方法)计算结果更准确.PTI和LTI方法都是基于2D网格单元模型,用于计算地震波的旅行时和射线路径.首先介绍了相关方法的一些基本概念.旅行时和射线路径都是在网格边界上进行计算的,因此,射线路径在同一恒速网格内是直线.其计算过程有两步.第一步,计算旅行时,第二步追踪射线路径.然后给出了LTI算法的基本公式.因为在炮点网格内可能存在折射波,文章也相应导出了其公式.最后详细推导了PTI方法的公式.通过模型试算对比说明,用PTI方法较LTI算法更精确、更有效,PTI方法是一种很有发展前途的地震射线追踪算法.更多还原

【Abstract】 A new seismic ray-tracing method was put forward based on parabolic travel-time interpolation(PTI) method,which is more accurate than the linear travel-time interpolation(LTI) method.Both PTI method and LTI method are used to compute seismic travel-times and ray-paths in a 2D gridded cell model.Firstly,some basic concepts related are introduced.The calculations of travel-times and ray-paths are carried out only on cell boundaries.So,the ray-path is always straight in the same cells with uniform velocity.Two steps are applied in the PTI and LTI method.Step 1 computes travel-times and step 2 traces ray-paths.then,the derivation of LTI’formulas process is described.Because of the presence of refraction wave in shot cell,the formula aiming at shot cell is also derivate.Finally,through the comprehension of above-mentioned works,the PTI method is presented.The calculations are more complex than that of LTI method,but the error is limited.Results of numerical model show that the PTI method can trace ray-paths more accurately and efficiently than LTI method does.更多还原