一般各向异性介质中qS1和qS2波波前分离  

Separation of wavefronts of qS1 and qS2 waves in general anisotropic medium

作　　者：李兴旺[1,2,3] 王迪[1] 白超英 LI XingWang;WANG Di;BAI ChaoYing(School of Geological Engineering and Geomatics,Chang'an University,Xi'an 710054,China;Institute of Computing Geophysics,Chang'an University,Xi'an 710054,China;National Engineering Research Center of Offshore Oil and Gas Exploration,Beijing 100028,China)

机构地区：[1]长安大学地质工程与测绘学院地球物理系,西安710054 [2]长安大学计算地球物理研究所,西安710054 [3]海洋油气勘探国家工程研究中心,北京100028

出　　处：《地球物理学报》2024年第7期2773-2784,共12页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(41830101,42304060);陕西省自然科学基金项目(2021JQ-245)联合资助。

摘　　要：地震波在各向异性介质中传播时存在横波分裂现象,可用于研究岩石中地震波传播特征和了解地下介质各向异性参数.一般各向异性介质中计算三种地震波(qP,qS1,qS2)相速度和群速度的研究日趋成熟,但分离qS1和qS2波的波前仍然是一项具有挑战性的工作.为此,本文基于新近给出的一般各向异性介质中三种波(qP,qS1,qS2)群速度的解析计算公式,依据相速度光滑连续的条件给出相邻方向上qS1和qS2波识别方法;为避免数值计算误差造成识别错误,构建了置信度函数,并借鉴快速行进法的思想逐点进行判别以分离qS1和qS2波的波前,最终得到三种波(qP,qS1,qS2)各自独立且完整的波前面.多个数值模拟试验结果表明,该算法适用于不同类型各向异性介质,且不受波前复杂程度的影响,具有较高的稳定性,可为一般各向异性介质中多次波射线追踪、多震相走时反演以及横波分裂研究等提供算法支持.Studying the shear wave splitting can provide another way to understand the characteristics of seismic wave propagation in anisotropic media and image the underground anisotropic parameters.Although there are various methods for calculating the group velocities of three seismic wave modes(qP,qS1,qS2)of general anisotropic media,it is still a challenge to separate the wavefronts of qS1 and qS2 waves.Based on the recently given analytical formula for calculating the group velocities of three seismic wave modes(qP,qS1,qS2),the qS1 and qS2 waves in adjacent directions can be identified under the assumptions as continuous phase velocities.To avoid being misled by the numerical calculation errors,a confidence function and the idea of fast marching method are introduced to identify the two qS waves point by point,and the independent wavefronts for the three waves(qP,qS1,qS2)are obtained.The numerical simulation results show that the algorithm is suitable for different types of anisotropic media and can stably obtain the separated wavefronts even for complex cases.This work can provide algorithmic support for multiple ray tracing,multi-phase traveltime tomography,and shear wave splitting in general anisotropic media.

关 键 词：一般各向异性介质 群速度 横波分裂 波前分离 

分 类 号：P631[天文地球—地质矿产勘探]