| 利用远震研究四川盆地及其周缘瑞利面波相速度和方位各向异性 |
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| 引用本文： | 王小龙,雷兴林,马胜利,张烨,郭志,闻学泽.利用远震研究四川盆地及其周缘瑞利面波相速度和方位各向异性[J].地球物理学报,2020,63(2):445-459. |
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| 作者姓名： | 王小龙 雷兴林 马胜利 张烨 郭志 闻学泽 |
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| 作者单位： | 1. 中国地震局地质研究所, 地震动力学国家重点实验室, 北京 100029;2. 日本产业技术综合研究所, 筑波 305-8567;3. 重庆市地震局, 重庆 401137;4. 重庆地质矿产研究院, 页岩气勘探开发国家地方联合工程研究中心, 重庆 401120 |
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| 基金项目： | 页岩气勘探开发国家地方联合工程研究中心开放基金资助. |
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| 摘 要： | 基于四川盆地及周边的245个宽频带台站2010年9月—2014年9月期间的远震记录,提取双台路径瑞利面波相速度频散资料,反演得到四川盆地20～120s的高分辨率瑞利面波相速度及各向异性空间分布.在丰富区域地球物理基础数据的同时,结合已有研究成果对地壳上地幔变形耦合进行探讨,结果表明短周期(20～30s)的相速度分布与四川盆地的地质构造特征相吻合,作为川滇地块、松潘—甘孜地块和四川盆地之间的边界——龙门山断裂带和鲜水河断裂带对上述三个地块上地壳的速度结构具有明显的控制作用;松潘—甘孜地块,特别是川滇地块中下地壳普遍表现为明显的低速异常,表明中下地壳相对软弱;而四川盆地的中下地壳整体呈现相对高速,表明四川盆地具有相对坚硬的中下地壳.研究区域东南角接近北扬子地块与南扬子地块的缝合部位,呈现高速异常.四川盆地南部和东南邻区不同周期均具有较强的各向异性,且快波方向较为一致,反映这些地区不同深度变形耦合较好.四川盆地西部、北部及东北部邻区,不同周期的各向异性快波方向变化较大,不同深度变形耦合较差.这些特征与绕喜马拉雅东构造结的物质流动被扬子地块的高速地壳阻挡的宏观认识基本一致.
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| 关 键 词： | 瑞利面波 相速度 四川盆地 各向异性 壳幔耦合 |
| 收稿时间： | 2019-03-28 |
Phase velocity structure and azimuthal anisotropy beneath Sichuan Basin and surrounding areas from Rayleigh wave |
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| WANG XiaoLong,LEI XingLin,MA ShengLi,ZHANG Ye,GUO Zhi,WEN XueZe.Phase velocity structure and azimuthal anisotropy beneath Sichuan Basin and surrounding areas from Rayleigh wave[J].Chinese Journal of Geophysics,2020,63(2):445-459. |
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| Authors: | WANG XiaoLong LEI XingLin MA ShengLi ZHANG Ye GUO Zhi WEN XueZe |
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| Institution: | 1. State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China;2. Geological Survey of Japan, AIST, Tsukuba 305-8567, Japan;3. Chongqing Earthquake Administration, Chongqing 401137, China;4. National and Local Joint Engineering Research Center of Shale Gas Exploration and Development, Chongqing Institute of Geology and Mineral Resources, Chongqing 401120, China |
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| Abstract: | Based on fundamental mode Rayleigh waves from distant earthquakes recorded at 245 broadband seismic stations within Sichuan Basin and surrounding areas, we imaged phase velocity and azimuthal anisotropy of Rayleigh wave at periods from 20 to 120 s. Together with previous studies, we discussed the coupling between the crust and the upper mantle. Image of phase velocity at short periods (20~30 s) shows good coincidence with geological structures of the Sichuan Basin. Longmenshan Fault and Xianshuihe Fault, which are surficial tectonic boundaries between Chuan-Dian block, Songpan-Garzê block, and Sichuan Basin, have a role controlling the velocity structure of the crust. The Songpan-Garzê and the Chuan-Dian blocks show lower velocity in the middle and lower crust, which is a sign of relatively soft lithologies. Whereas, the middle and lower crust beneath the Sichuan Basin is relatively strong with higher velocity. In the southern Sichuan Basin, areas close to the boundary of north Yangzi block and south Yangzi block show higher velocity anomaly. The southern Sichuan Basin and its southeast surrounding areas demonstrated stronger anisotropy with an almost uniform fast wave direction for different periods, indicating strong coupling between different depths. In the western Sichuan Basin and its north and northeast surroundings, direction of the fast wave varies with period, indicating weak coupling. All these features agree with the understanding that the strong Yangzi block plays a role resisting the clockwise rotational flow around the east Himalaya syntaxis. |
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| Keywords: | Rayleigh wave Phase velocity Sichuan Basin Azimuthal anisotropy The coupling between the crust and the upper mantle |
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