介质各向异性和非均匀性对横波分裂参数测量的影响

发布时间：2018-02-25 07:30

本文关键词： 横波分裂各向异性非均匀性非正交矢量　出处：《科学通报》2017年23期 　论文类型：期刊论文

【摘要】：地震横波分裂参数是确定地球介质各向异性基本特征的重要依据.在过去几十年间,快横波偏振方向和快-慢横波到时差测量值的显著离散已经成为影响学界对地震各向异性和横波分裂进行深入研究的一个突出障碍.本文具体分析了实际地球介质的各向异性和非均匀性可能引起的地震记录上地震波震相观测走时和理论走时的偏离、观测偏振和理论偏振的偏离,以及震相观测序列和理论序列的偏离;指出了实际三分量地震记录上地震波震相矢量普遍存在的偏振非正交和路径非正交关系是传统正交分离和参数测量结果显著离散的根本原因;用仿真模拟实例分析了现有震相识别和波形分析方法可能带来的震相漏识别或误识别,介绍了利用矢量分析技术分离三分量观测记录上地震波震相完整波形的基本思路,推导了以地震波空间偏振矢量方向为参数的波形分离运算表达式,以及直接利用三分量地震记录的傅里叶频谱在不同坐标分量上的投影来测量地震记录上各个震相矢量空间方向的近似方法.
[Abstract]:Seismic shear wave splitting parameters are an important basis for determining the basic characteristics of anisotropy in the Earth's media. The polarization direction of fast shear wave and the apparent dispersion of measured values from fast to slow shear wave to moveout have become a prominent obstacle to the in-depth study of seismic anisotropy and shear wave splitting in academic circles. In this paper, the actual earth meshes are analyzed in detail. Anisotropy and inhomogeneity of mass may cause deviation between observed and theoretical travel times of seismic waves in seismic records. The deviation of observational polarization and theoretical polarization, as well as the departure of seismic observation sequence and theoretical sequence; It is pointed out that the polarization nonorthogonal and path nonorthogonal relations of seismic wave phase vectors on the actual three-component seismic records are the fundamental reasons for the traditional orthogonal separation and the remarkable discretization of parameter measurement results. In this paper, the leakage or false identification of seismic phase caused by the existing methods of phase identification and waveform analysis is analyzed with an example of simulation. The basic idea of separating the complete waveform of seismic wave phase from three-component observation record by using vector analysis technique is introduced. The formula of waveform separation based on the direction of spatial polarization vector of seismic wave is derived. And the approximate method of measuring the direction of each phase vector space of seismic records by directly using the Fourier spectrum of three component seismic records on different coordinate components is presented.
【作者单位】：北京大学地球与空间科学学院;
【基金】：国家自然科学基金(41674053)资助
【分类号】：P631.4

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