夏思茹^1,2,,
石磊^1,3,,,
李永华^1,3,
郭良辉²
1. 中国地震局地球物理研究所, 北京 100081
2. 中国地质大学(北京), 地球物理与信息技术学院, 北京 100083
3. 中国地震局震源物理重点实验室, 北京 100081

基金项目: 国家重点研发计划（2018YFC1503200），国家自然科学基金项目（U1839210，41974101，41774098，41874097），中央高校基本科研业务费专项资金和中国地震局地球物理研究所基本科研业务费专项（DQJB19B37）联合资助


详细信息

作者简介: 夏思茹, 女, 1996年生, 硕士在读研究生, 主要从事地震与重力联合反演成像研究.E-mail: xiasiru0401@163.com

通讯作者: 石磊, 女, 副研究员, 主要从事重力与天然地震联合方法研究及其在地壳深部结构中的应用.E-mail: shilei@cea-igp.ac.cn

中图分类号: P315

收稿日期:2021-01-04
修回日期:2021-04-30
上线日期:2021-09-10

Velocity structures of the crust and uppermost mantle beneath the northeastern margin of Tibetan plateau revealed by double-difference tomography

XIA SiRu^1,2,,
SHI Lei^1,3,,,
LI YongHua^1,3,
GUO LiangHui²
1. Institute of Geophysics, China Earthquake Adminstration, Beijing 100081, China
2. School of Geophysics and Information Technology, China University of Geosciences, Beijing 100083, China
3. Key Laboratory of Earthquake Source Physics, China EarthquakeAdministration, Beijing 100081, China


More Information

Corresponding author: SHI Lei,E-mail:shilei@cea-igp.ac.cn

MSC: P315

--> Received Date: 04 January 2021
Revised Date: 30 April 2021
Available Online: 10 September 2021


摘要
摘要:本文利用青藏高原东北缘71个固定台站与418个流动台站记录到的天然地震事件资料，采用双差层析成像方法对近震走时数据进行反演，获得了研究区高分辨率的三维P、S波速度结构和地震重定位结果.研究结果表明，本文给出的P、S波速度模型较已有的全球模型能更好的解释体波走时与面波相速度观测资料.松潘—甘孜和祁连构造带下方20~40 km深度范围表现为显著的P、S波低速异常，其中松潘—甘孜地块的壳内低速层可能与地壳部分熔融有关，而祁连构造带的壳内低速层则可能与地壳增厚有关.精定位后的岷漳6.7级地震和九寨沟7.0级地震震源深度都位于脆性的上地壳.两个地震的震源区地处不同块体的边界，均处在高、低速过渡带.震源区的壳内低速层可能处于部分熔融或易于蠕变的状态，脆性上地壳更容易积累应变能，从而导致地震的发生.
关键词: 青藏东北缘/
双差层析成像/
低速层分布/
岷漳和九寨沟地震

Abstract:We assemble the local earthquake data recorded by 71 permanent stations and 418 portable stations around the northeastern margin of the Tibetan plateau, and then utilize the double-difference tomography method to image high-resolution 3D P- and S-wave velocity structures of the crust and uppermost mantle in the study area along with hypocentral relocations. The resultant P- and S-wave velocity models fit both body-wave traveltime and Rayleigh-wave phase velocity dispersion data better than previous global models. Significant low-velocity anomalies of P- and S-waves appear in the depth interval of 20~40 km beneath the Songpan-Garzê block and Qilian orogenic belts. The low-velocity layer below the Songpan-Garzê block may be related to the crustal partial melting, while that of the Qilian orogenic belt possibly indicates the crustal thickening. The hypocenter depths of both the Minzhang M6.7 earthquake and Jiuzhaigou M7.0 earthquake after relocation lie around the high-and-low velocity transition zone within the brittle upper crust, showing both events occurred at the junction of distinct blocks. The low-velocity layer beneath these two earthquake areas may be partially melted or easier to creep, and the brittle upper crust is more likely to accumulate elastic strain, resulting in the occurrence of earthquakes.
Key words:Northeastern margin of Tibetan plateau/
Double-difference tomography/
Distribution of low-velocity layer/
Minzhang and Jiuzhaigou earthquakes



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