| 川西地区瑞雷波方位各向异性 |
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| 引用本文： | 王怀富,吴建平,周仕勇,冯甜.川西地区瑞雷波方位各向异性[J].地震学报,2020,42(3):293-305. |
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| 作者姓名： | 王怀富 吴建平 周仕勇 冯甜 |
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| 作者单位： | 1.中国北京 100081 中国地震局地球物理研究所 |
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| 基金项目： | 国家自然科学基金（41774102）和国家重点研发计划（2018YFC1503400）联合资助 |
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| 摘 要： | 本文使用川西密集地震台阵记录的面波资料，利用程函方程面波成像方法获得了周期为14—60 s的瑞雷波相速度及方位各向异性分布。结果显示:川滇菱形地块的川西北地块内部的低速异常明显，其下地壳各向异性快波方向以NS向为主，松潘—甘孜地块内部的低速异常稍弱，下地壳各向异性快波方向以NW?SESE向为主，表明川西北地块可能存在下地壳通道流，松潘—甘孜地块内部存在的通道流相对较弱；龙门山断裂带和丽江—小金河断裂两侧的速度结构和方位各向异性均有明显差异，可推测青藏高原内部的地壳流在东部和南部分别受高速、高强度的四川盆地和滇中地块阻挡，沿高原边界带发生了侧向流动；周期大于25 s的面波方位各向异性方向为NW?SE；与SKS分裂优势方向相近，说明四川盆地的剪切波各向异性可能主要源于上地幔；而龙门山断裂带附近壳幔各向异性较为复杂，面波方位各向异性与SKS分裂的NW?SE向弱各向异性存在差异，表明该处的剪切波各向异性可能来自地幔更深处，有待进一步研究。
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| 关 键 词： | 程函方程 面波相速度 方位各向异性 剪切波分裂 |
| 收稿时间： | 2019-06-11 |
Rayleigh wave azimuthal anisotropy in western Sichuan region |
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| Institution: | 1.Institute of Geophysics，China Earthquake Administration，Beijing 100081，China2.Institute of Theoretical and Applied Geophysics，Peking University，Beijing 100871，China |
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| Abstract: | Based on the observation data of dense seismic array in western Sichuan, we obtain Rayleigh wave phase velocity and azimuthal anisotropy distribution images at 14?60 s period by eikonal surface wave tomography method. The results show that the low velocity of the northwestern block of the Sichuan-Yunnan diamond block is obvious and anisotropic fast wave direction of the lower crust is dominated by NS. The low velocity anomaly inside the Songpan-Garze block is slightly weaker and the anisotropic fast wave direction of the lower crust is dominated by NW-SE, indicating that there may be lower crust channel flow in the northwestern Sichuan-Yunnan diamond block and there is a relatively weak channel flow inside the Songpan-Garze block. The velocity structure and azimuthal anisotropy are significantly different on both sides of the Longmenshan fault zone and the Lijiang-Xiaojinhe fault zone. We speculate that the crustal flow inside the Tibetan Plateau is blocked by two high-velocity and high-intensity blocks in the Sichuan basin and the Central Yunnan block in the east and south, and lateral flows occur along the boundary zone. The azimuthal anisotropy of the surface wave over the period 25 s by NW-SE is similar to that of SKS splitting. It is concluded that the shear wave anisotropy in Sichuan basin may be mainly from the upper mantle. The anisotropy of the crust in the vicinity of the Longmenshan fault zone is complex and the azimuthal anisotropy of the surface wave is different from the weak anisotropy of SKS splitting by NW-SE, indicating that the shear wave anisotropy may be from the deeper mantle and needs further research. |
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