陈浩朋^1,,
李志伟^1,,,
储日升¹,
谢军¹,
崇加军¹,
叶庆东²
1. 中国科学院测量与地球物理研究所大地测量与地球动力学国家重点实验室, 武汉 430077
2. 中国地震局第一监测中心, 天津 300180

基金项目: 国家自然科学基金重大项目课题(41590854), 国家自然科学基金(41674065), 中国-东盟海洋地学研究与减灾计划(1062391)和中国博士后科学基金(2015M582311)联合资助


详细信息

作者简介: 陈浩朋, 男, 博士后, 主要从事面波层析成像和地壳上地幔结构反演研究.E-mail:hpchen@asch.whigg.ac.cn

通讯作者: 李志伟, 男, 研究员, 主要从事地壳浅层及深部结构地震成像方法和应用研究.E-mail:zwli@whigg.ac.cn

中图分类号: P315

收稿日期:2018-03-12
修回日期:2018-05-18
上线日期:2018-08-05

3D S-wave velocity and radial anisotropy structure of the crust and uppermost mantle in Yunnan, SE Tibet

CHEN HaoPeng^1,,
LI ZhiWei^1,,,
CHU RiSheng¹,
XIE Jun¹,
CHONG JiaJun¹,
YE QingDong²
1. State Key Laboratory of Geodesy and Earth's Dynamics, Institute of Geodesy and Geophysics, Chinese Academy of Sciences, Wuhan 430077, China
2. First Crust Monitoring and Application Center, China Earthquake Administration, Tianjin 300180, China


More Information

Corresponding author: LI ZhiWei,E-mail:zwli@whigg.ac.cn

MSC: P315

--> Received Date: 12 March 2018
Revised Date: 18 May 2018
Available Online: 05 August 2018


摘要
摘要:云南地区地处青藏高原东南缘, 一直是地球科学研究的热点地区.目前, 一些热点问题, 如云南地区是否存在中下地壳低速流及其空间分布, 仍有一定的争议.通过建立云南地区精细的地壳上地幔速度与各向异性结构, 可为深入认识上述问题提供重要信息.本文利用天然地震波形记录, 采用双台法提取了12~60 s周期的Rayleigh和Love波相速度频散, 并进一步反演获得了云南地区10~100 km的三维地壳上地幔SV和SH波速度及径向各向异性结构.结果表明:S波速度与径向各向异性结构在横向和垂向均存在显著变化.在20~30 km深度, 存在两个低速条带, 且条带内呈现出正径向各向异性(V_SH>V_SV)特征, 暗示了中下地壳低速物质的水平向运动.在80~100 km深度, 云南西南和东南部显示为低速异常和正径向各向异性特征, 暗示了软流圈物质的水平流动.在云南北部的丽江、攀枝花和昭通地区, 岩石圈地幔中则存在明显的负径向各向异性(V_SH<V_SV), 可能反映了地幔物质的上涌痕迹.历史强震多发生在地壳低速区域或高低速过渡带, 且地震附近的径向各向异性为负或者较弱.一些地震震源下方存在低速层, 地壳低速层可能会促进强震发生.
关键词: 面波层析成像/
S波速度/
径向各向异性/
强震

Abstract:Yunnan area is located to the southeast of Tibetan Plateau, which draws great attention of geo-scientists.Some hotspot problems, such as whether connected mid-lower crustal low-velocity (low-V) zones exist and what the spatial distributions are if they exist, are still not very clear.High resolution 3D velocity and anisotropy model of the crust and uppermost mantle can provide valuable information to address these problems.In this study, we measured the interstation phase velocities of Rayleigh and Love waves in the period range of 12~60 s using the seismic data recorded by permanent stations in Yunnan and adjacent areas, and then inverted for the SV, SH velocity and radial anisotropy model in the depth range of 10~100 km.The results show that the S-wave velocity and radial anisotropy have obvious variations both in lateral and vertical directions.There are two low-V belts in the depth range of 20~30 km, with positive radial anisotropy (V_SH>V_SV).These two low-V belts may hint horizontal flows in the mid-lower crust.In the depth range of 80~100 km, there are low-V anomalies in southwest and southeast Yunnan, where the radial anisotropy are positive, which may indicate the horizontal flow of the asthenosphere.In the area around Lijiang, Panzhihua and Zhaotong, negative radial anisotropy (V_SH<V_SV) exists in the lithospheric mantle, suggesting the upwelling of mantle material.Most strong earthquakes occurred in the low-V region or transition zone between high-velocity (high-V) and low-V, and the radial anisotropy around the hypocenters is negative or very weak.Low-V zones are shown beneath some strong earthquakes, which may suggest that crustal low-V zones may promote strong earthquakes.
Key words:Surface wave tomography/
S-wave velocity/
Radial anisotropy/
Strong earthquakes



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