弱各向异性介质中qP波的一阶射线追踪  

First-order Ray-tracing for qP waves in weakly anisotropic media

作　　者：孙福利[1] 杨长春[1] 陈雨红[1,2] 李波涛[1] 吴萍[1] 

机构地区：[1]中国科学院地质与地球物理研究所,北京100029 [2]中国科学院兰州地质研究所,兰州730000

出　　处：《地球物理学进展》2009年第1期35-41,共7页Progress in Geophysics

基　　金：基金项目国家973计划项目(2005CB422104)资助

摘　　要：本文基于扰动理论来推导qP波一阶射线追踪方程,并使用此方程计算光滑弱各向异性介质中qP波传播的路径和走时.从方程中可以看到对于弱各向异性介质中传播的qP波,其一阶射线追踪方程只依赖于15个弱各向异性参数,方程的形式比准确的射线追踪方程简单得多.当各向异性强度为零时,此方程变为标准的各向同性射线追踪方程.并通过模型实算来测试本方法的精度,对于各向异性强度为10%的VTI均匀介质和各向异性为8%的VTI非均匀介质,射线的出射角在0~40°之间时,其相对误差不超过0.05%,而对于各向异性强度为20%的VTI均匀介质,当射线的出射角在0~50°之间时,其相对误差不超过0.46%,实算结果表明本方法具有很强的适应性,在出射角不太大的范围内具有很高的精度.该研究结果对海相油气勘探有重要意义.We use perturbation theory to derive the first-order ray-tracing equations for qP-waves and compute the raypaths and traveltimes of the qP-waves propagating in smooth,weakly anisotropic media.The first-order ray-tracing equations for qP-waves propagating in a weakly anisotropic medium depend on only 15 weak-anisotropy parameters.The equations are considerably simpler than the exact ray-tracing equations.For vanishing anisotropy,the first-order ray-tracing equations reduce to standard ray-tracing equations for isotropic media.We test the accuracy of the method in three examples.For the homogeneous VTI medium with anisotropy of 10% and the inhomogeneous VTI medium with anisotropy of 8%,when the take-off angle is between 0 degree and 40 degree,the relative errors are under 0.05%.For the homogeneous VTI medium with anisotropy of 20%,when the take-off angle is between 0 degree and 50 degree,the relative errors are under 0.46%.The results indicate that this method is suitable to various anisotropic media,and it＇s precision is high when the take-off angle is under some value.

关 键 词：弱各向异性 射线追踪 走时 非均匀 

分 类 号：P315[天文地球—地震学]