| 基于背景噪声的川滇地区勒夫波层析成像 |
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| 引用本文： | 郑定昌,王俊.基于背景噪声的川滇地区勒夫波层析成像[J].地震学报,2017,39(5):633-647. |
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| 作者姓名： | 郑定昌 王俊 |
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| 作者单位： | 1.中国昆明 650224 云南省地震局 |
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| 基金项目： | 人社部留学人员科技活动项目择优项目和云南省基金项目2010ZC143中国地震局行业专项201508020中国地震局行业专项(201508020)、人社部留学人员科技活动项目择优项目和云南省基金项目(2010ZC143)联合资助 |
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| 摘 要： | 本文选取了川滇地区98个固定台站记录到的三分量地震背景噪声数据，采用互相关方法提取了勒夫波互相关函数，并利用自适应时频分析方法获取了勒夫波群速度频散曲线，经反演得到周期为8—30 s的勒夫波群速度分布图像.层析成像结果显示:短周期的勒夫波群速度分布图像呈明显的横向不均匀性，且与地表地质和构造特征基本一致，其中四川盆地呈不均匀的低速异常，盆地内成都平原地区的群速度相对低于盆地中部的丘陵地区，速度分界线为遂宁与峨眉山之间的连线，四川盆地内的群速度变化反映出沉积层厚度的变化情况；攀枝花地区呈高速异常，可能与古地幔活动有关，幔源物质以侵入岩和底侵岩浆的形式停留在地壳的不同深度，从而形成高速异常的特征.本文结果为了解川滇地区的构造运动提供了地震学线索，并为下一步研究地壳径向各向异性奠定了基础.
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| 关 键 词： | 背景噪声 层析成像 勒夫波 地壳结构 川滇地区 |
| 收稿时间： | 2017-02-06 |
Love wave tomography in Sichuan-Yunnan area from ambient noise |
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| Affiliation: | 1.Earthquake Administration of Yunnan Province, Kunming 650224, China2.Earthquake Administration of Jiangsu Province, Nanjing 210014, China |
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| Abstract: | We collected seismic ambient noise data recorded at 98 permanent seismic stations in Sichuan-Yunnan area to image crustal structure. The Love wave cross-correlation functions are obtained by cross-correlation of ambient noise. The group velocity dispersion curves for Love wave are measured by automated time-frequency analysis. Love wave group velocity is mapped in the periods between 8 s and 30 s. The tomographies show seismic images at short periods exhibit apparent horizontal heterogeneities, which is largely consistent with geological features and geophysical studies. The Sichuan basin appears as low group velocity anomaly, and the Chengdu plain shows lower group velocity relative to the hilly area in Sichuan basin, with the line connecting Suining with Emeishan being the boundary between higher velocity and lower one. The variation of group velocity anomalies in Sichuan basin reflects variable sedimentary thicknesses. The Panzhihua area appears as high velocity anomaly, which is associated with an ancient mantle plume. The materials from mantle is remained at the different depth in crust in the form of intrusive rocks and magmatic underplating, resulting in the characteristics of high velocity anomaly. These seismic images provide necessary information for the research on crustal radial anisotropy and understanding of tectonic process. |
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