| 青藏高原东缘及东北缘S波速度结构和径向各向异性 |
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| 引用本文： | 杨志高,陈运泰,张雪梅,宋晓东.青藏高原东缘及东北缘S波速度结构和径向各向异性[J].地球物理学报,2019,62(12):4554-4570. |
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| 作者姓名： | 杨志高 陈运泰 张雪梅 宋晓东 |
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| 作者单位： | 1. 中国地震局地球物理研究所, 北京 100081;2. 中国地震台网中心地震台网部, 北京 100045;3. 中国科学院大学地球与行星科学学院, 北京 100049;4. 北京大学地球与空间科学学院, 北京 100871;5. Department of Geology, University of Illinois at Urbana-Champaign, IL 61801, USA |
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| 基金项目： | 科技部重大自然灾害监测预警与防范重点专项（2017YFC1500304）和国家自然基金项目（41774056和41774069）资助. |
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| 摘 要： | 青藏东缘和东北缘是高原生长和扩张的前缘,研究其地下物质及变形特征有助于理解青藏高原生长机制.本文收集187个固定地震台站记录的长达7年的三分量连续波形数据,辅以189个流动台站3年的数据,开展噪声瑞利波和勒夫波群速度层析成像工作.基于8～40 s周期瑞利波和勒夫波群速度,通过线性反演方法得到地下50 km深度范围的三维SH和SV速度结构.我们定义径向各向异性ψ=2(v_(SH)-v_(SV))/(v_(SH)+v_(SV)),以此来展示地下物质变形以水平方向(v_(SH)v_(SV))还是垂直方向(v_(SH)v_(SV))为主.径向各向异性显示青藏高原东缘和东北缘具有完全不同的变形机制.青藏东北缘以垂向变形为主,地壳流模型不太可能是该区域主要的变形机制.青藏东缘以水平变形为主,支持中下地壳流变模型.柴达木盆地和四川盆地下方径向各向异性差异显著,说明高原边缘稳定的地块在高原扩展中起到不同的作用.
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| 关 键 词： | 青藏高原 径向各向异性 噪声层析成像 高原生长机制 |
| 收稿时间： | 2019-04-12 |
S-wave velocity structure and radial anisotropy in eastern and north-eastern margins of Tibetan plateau |
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| YANG ZhiGao,CHEN YunTai,ZHANG XueMei,SONG XiaoDong.S-wave velocity structure and radial anisotropy in eastern and north-eastern margins of Tibetan plateau[J].Chinese Journal of Geophysics,2019,62(12):4554-4570. |
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| Authors: | YANG ZhiGao CHEN YunTai ZHANG XueMei SONG XiaoDong |
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| Institution: | 1. Institute of Geophysics, Chinese Earthquake Administration, Beijing 100081, China;2. Department of Seismic Networks, China Earthquake Networks Center, Beijing 100045, China;3. College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China;4. School of Earth and Space Sciences, Peking University, Beijing 100871, China;5. Department of Geology, University of Illinois at Urbana-Champaign, IL 61801, USA |
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| Abstract: | The northeastern and eastern margins of Tibetan Plateau (TP) are the frontiers of growth and expansion of the plateau. It is helpful to explore the growth mechanism of the plateau by studying the subsurface material and deformation characteristics. We collect 7 years of three-component continuous waveform data recorded by 187 seismic stations and 3 years of waveform data recorded by 189 transportable stations. The Rayleigh wave and Love wave dispersion at the periods of 8~40 s are carried out by ambient noise tomography. Based on the group velocities of Rayleigh wave and Love wave, the three-dimensional SH and SV velocity structures in the depth range of 0~50 km are inverted by linear inversion method. We define the radial anisotropy parameter as ψ=2(vSH-vSV)/(vSH+vSV) in the crust to show whether the subsurface deformation is dominated by horizontally extension (vSH>vSV) or vertically (vSH<vSV) thickening. The radial anisotropy shows distinct deformation mechanisms in the eastern and northeastern margins of the TP. The eastern margin is dominated by horizontal extension, which agrees with crustal flow model in this area. The northeastern margin shows prominent vertical thickening, which indicates that the crustal flow model is unlikely the main deformation mechanism in this region. Significant difference in radial anisotropy between Qaidam Basin and Sichuan Basin indicates that the stable blocks on the edge of the plateau play different roles in the plateau growth. |
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| Keywords: | Tibetan plateau Radial anisotropy Ambient noise tomography Plateau growth mechanism |
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