| 多层垂直对称轴横向各向同性介质精确走时计算 |
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| 引用本文： | 唐巍,李磊.多层垂直对称轴横向各向同性介质精确走时计算[J].地震学报,2008,30(4):367-376. |
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| 作者姓名： | 唐巍 李磊 |
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| 作者单位： | 1) 中国北京100081中国地震局地球物理研究所2) 中国北京100029中国地震局地质研究所 |
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| 基金项目： | 国家自然科学基金，中国地震局地球物理研究所项目 |
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| 摘 要： | 给出了计算多层垂直对称轴横向各向同性（VTI）介质精确射线路径和走时的方法，所用的体波相速度公式、群速度公式和Snell定律都是严格的显式解析公式. 任意基本波的射线路径和走时计算问题都可以转化成一个等效的透射问题，再用文中的公式来计算，具体实现方法用一个多次波和一个首波的实例给出. 最后分别用精确公式和Thomsen近似公式计算了相同模型相同基本波的走时曲线. 比较两者计算结果可发现, 近似公式反复使用会使误差积累，同时揭示了近似公式适用范围的局限性，强调了使用近似公式需要注意其适用范围的重要性.
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| 关 键 词： | & Snell定律& VTI介质 & 各向异性 & 横向各向同性& 射线追踪& 走时 |
Exact traveltime computation in multi-layered transversely isotropic media with vertical symmetry axis |
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| Tang Wei,Li Lei.Exact traveltime computation in multi-layered transversely isotropic media with vertical symmetry axis[J].Acta Seismologica Sinica,2008,30(4):367-376. |
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| Authors: | Tang Wei Li Lei |
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| Abstract: | An approach to calculate accurate ray-paths and traveltimes in multi-layered VTI media (transversely isotropic media with a vertical symmetry axis) is proposed. The expressions of phase velocity, group velocity and Snell's law used for computation are all explicit and exact. For a given elementary wave, the calculation of ray-paths and traveltimes can be transformed into an equivalent refraction problem, which is easy to solve. The process of implementation is introduced by a multi-arrival example and a head-wave example. Finally, traveltime curves for the same models and same elementary waves are calculated by using the exact formulae and the Thomsen's approximations, respectively. A comparison between the two results shows the effect of increasing errors arising from the repeated use of approximations and reveals the limitation in applicable range of the approximation approach. It is stressed in this paper that researchers should pay much attention to the applicable range of an approximation approach. |
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| Keywords: | Snell's law VTI medium anisotropy transverse isotropy raytracing traveltime |
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