钮凤林1,2,,
1. 中国石油大学(北京)非常规天然气研究院和油气资源与探测国家重点实验室, 北京 102249
2. 莱斯大学地球科学学院, 美国休斯顿 77005
基金项目: 科技部重点研发项目（2017YFC1500300）资助
详细信息
作者简介: 左佳卉, 女, 1988年生, 博士研究生, 主要从事地震各向异性方面的研究工作.E-mail:zuojiahui_2007@126.com
通讯作者: 钮凤林, 男, 教授, 博士生导师, 主要从事地球深部构造和地球动力学等方面的研究工作.E-mail:niu@rice.edu/niu@cup.edu.cn
中图分类号: P315收稿日期:2019-01-26
修回日期:2019-04-25
上线日期:2019-08-05
Shear-wave splitting parameters of two-layer anisotropic media estimated from three different multilayer measurement methods
ZUO JiaHui1,,NIU FengLin1,2,,
1. State Key Laboratory of Petroleum Resource and Prospecting, and Unconventional Gas Institute, China University of Petroleum-Beijing, Beijing 102249, China
2. Department of Earth, Environmental and Planetary Sciences, Rice University, Houston, TX 77005, USA
More Information
Corresponding author: NIU FengLin,E-mail:niu@rice.edu; niu@cup.edu.cn
MSC: P315--> Received Date: 26 January 2019
Revised Date: 25 April 2019
Available Online: 05 August 2019
摘要
摘要:对实际两层各向异性介质，在一层假设条件下利用Silver和Chan（1991）的等效单层各向异性测量方法，以及在两层假设条件下利用剥去法和反演法，计算模型的分裂参数.首先利用理论雷克子波得到经过两层各向异性的观测数据，然后加入噪声之前和之后，分别计算不同反方位角覆盖条件下数据的各向异性，并与理论模型的分裂参数进行比较.结果发现在上层分裂特征已知的基础上，剥去法适用于任何模型，不管是否存在分裂，或者分裂特征在两层中如何分布；而反演法更适用于两层各向异性较强且不同的模型，其结果受噪声和方位角分布的影响.选取不同方位角分布的高信噪比数据，比较剥去法和反演法对下层分裂参数的计算结果，发现当入射方位角在两层快波方向之间时，反演结果比较可靠.最后利用这三种测量各向异性的方法，计算青藏高原东南缘CEArray台站观测到的SKS数据中记录的各向异性.除了云贵高原的台站YN.CUX表现出较明显的两层分裂特征，大部分台站下的岩石圈各向异性呈现一层或者较弱的各向异性.于是针对该台站，用反演法同时对这两层的分裂参数进行估计，上层的结果与接收函数计算的地壳分裂参数一致；下层的结果与剥去法计算的上地幔分裂参数一致，说明反演法同剥去法一样，都能有效的分析具有两层各向异性特征的介质.
关键词: 横波分裂/
两层各向异性介质/
青藏高原东南缘/
岩石圈
Abstract:For a two-layer anisotropic medium, we calculated the splitting parameters of the model, by using three different measurement methods:(1) the traditional one-layer estimating method of Silver and Chan (1991), (2) the top-layer stripping-off method, and (3) a simultaneous gridding search method. We generated a large waveform dataset for a total of 8 models using the Ricker wavelet as the source wavelet. We then investigated how well these three methods can recover the input models under different noise and limited backazimuthal coverage conditions. Our numerical tests indicate that the top-layer stripping-off method can recover the input models even when the data are from a narrow azimuthal range and have the level of noise in real data. In contrast, the grid-search based inversion method is more suitable for models with the fast directions of the two layers being a few tens of degrees away from each other. We also applied these three methods to the SKS waveform data recorded by 13 CEArray stations at the southeastern margin of Tibetan plateau. We found that the SKS data recorded by the YN.CUX station on the Yunnan-Guizhou plateau exhibit obvious two-layer splitting characteristics, while those from the other stations seem to be well explained by a one-layer anisotropic model.
Key words:Shear wave splitting/
Two-layer anisotropic media/
Southeastern margin of Tibetan Plateau/
Lithosphere
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