【作者】 陈超群；

【导师】 刘永华；

【作者基本信息】 长安大学 ， 地球探测与信息技术， 2007， 硕士

【摘要】 地震波的射线追踪方法是地球物理学和地震勘探中的重要研究课题。射线追踪方法不但是研究介质任意速度分布情况下地震波传播问题的有效手段之一,而且在地震层析成像和叠前深度偏移等方而都起着重要的作用,射线追踪的计算精度和速度将直接影响着层析成像和叠前深度偏移的效果。射线追踪方法是建立在一定的地质模型上,对地质模型传统的描述,一般是采用网格划分或层状结构描述。对于简单地质模型,经典的层状结构描述具有其独特的优势。模型描述方便、射线追踪快速,但对复杂模型的描述会遇到困难,不过这些问题都可以找到相应的解决方法。本文基于Snell定律和Fermat原理对二维、三维任意界面情况下的两点间射线追踪问题进行了研究。文中采用一阶不完全Taylor展开方法,分别推导出适用于二维、三维介质分布情况下计算反(透)射点的公式;从任意给定的初始路径出发,对射线路径进行逐段迭代计算,当整条射线路径的校正量之和满足一定的精度要求时,迭代计算过程结束,以最后一次迭代计算所得的射线路径作为最终的二维、三维射线路径,进而实现二维、三维地层结构下射线追踪计算。通过对大量的二维、三维复杂模型测试表明,逐段迭代射线追踪算法速度快、精度高。当然,在追踪的过程中也遇到了一些问题,我们对其进行了讨论,并提出了具体的解决方案。算法的改进,使射线追踪效率大幅度提高,使逐段迭代射线追踪方法最大限度地发挥了其优势,更加具有实际应用价值。更多还原

【Abstract】 Seismic ray-tracing problem and inversion of wave equation is an important research topic in the geophysics and geophysical prospecting, The ray-tracing problem is not only an efficient method of studying seismic propagation in the random velocity distribution media, but also it plays an important role in the seismic tomography and pre-stack depth offset. The precision and speed of ray-tracing will influence of the results of tomography and pre-stack depth offset.The ray-tracing method is based on a geological model, to the geological model tradition description, generally used mesh or layered structure described. For the simple geological model, classic description of the layered structure has its unique advantages. Model Description convenient, ray-tracing is fast, when to complex model description can encounter the difficulty, but these questions all may find the corresponding solution.Based on Snell law and Fermat principle, the two-point ray-tracing method for two dimensional and three dimensional arbitrary interface is studied in this paper. First, by use of one order Taylor incomplete expansion, a positive definite formula, which is suitable to calculate reflection or refraction point in two-dimensional and three-dimensional constructs, is obtained. Then, starting from an arbitrary given initial ray path, ray-tracing is iteratively calculated segment by segment. The procedure is kept on until the sum of adjustment quantity in the whole path is in the range of precision and the last iterative result is regarded as final two dimensional or three dimensional ray path. Now, the iterative ray-tracing segment by segment in two dimensional or three dimensional construct is finished.Numerical tests show that this algorithm is fast and its calculating precision can reach any requirements needed. Iterative ray-tracing method segment by segment for 2-D and 3-D media and its application problems, and provided solving-method. The improvement of algorithm improve the efficiency of ray-tracing greatly, so make the iterative ray-tracing segment by segment do its best, and make the method improve its application value.更多还原