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地震 ›› 2021, Vol. 41 ›› Issue (4): 121-135.doi: 10.12196/j.issn.1000-3274.2021.04.009

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利用同震和震后位移数据联合反演2011年日本MW9.0地震同震断层滑动

陈伟1, 刘泰1,2, 佘雅文1, 付广裕3   

  1. 1.中国地震局地震预测重点实验室(地震预测研究所), 北京 100036;
    2.中国科学院精密测量科学与技术创新研究院大地测量与地球动力学国家重点实验室, 湖北 武汉 430077;
    3.中国地质大学(北京)地球物理与信息技术学院, 北京 100083
  • 收稿日期:2021-07-09 修回日期:2021-08-18 出版日期:2021-10-31 发布日期:2022-03-25
  • 通讯作者: 付广裕,教授。E-mail:fugy@cugb.edu.cn
  • 作者简介:陈伟(1998-),男,安徽六安人,在读硕士研究生,主要从事地震位错形变研究。
  • 基金资助:
    国家重点研发计划项目(2018YFC1503704), 中国地震局地震预测研究所基本科研业务费专项(2021IEF0504), 中国科学院精密测量科学与技术创新研究院大地测量与地球动力学国家重点实验室开放基金资助项目(SKLGED2021-2-1)联合资助

Co-Seismic Fault Slip Distribution of the 2011 Tohoku-Oki MW9.0 Earthquake Retrieved from Co- and Post-seismic Displacements

CHEN Wei1, LIU Tai1,2, SHE Ya-wen1, FU Guang-yu3   

  1. 1. Key Laboratory of Earthquake Forecast, Institute of Earthquake Forecasting, CEA, Beijing 100036, China;
    2. State Key Laboratory of Geodesy and Earth’s Dynamics, Innovation Academy for Precision Measurement Science and Technology, CAS, Wuhan 430077, China;
    3. School of Geophysics and information Technology, China University of Geosciences, Beijing 100083, China
  • Received:2021-07-09 Revised:2021-08-18 Online:2021-10-31 Published:2022-03-25

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摘要： 基于黏弹性球体位错理论, 联合陆地和海底同震GPS数据以及日本本岛330个陆地GPS站点5~10年的震后数据, 反演了日本MW9.0地震的断层滑动模型, 提升了断层滑动分布在细节上的合理性。 首先, 基于日本本岛330个陆地GPS站点震前2年和震后10年的连续观测数据, 获取了日本MW9.0地震震后5~10年的年平均位移, 该时段的位移几乎完全由地幔黏弹性松弛效应引起; 接着, 利用黏弹性球体位错理论对震后5~10年的位移进行反复拟合, 确定了日本MW9.0地震震源及周边地区的地幔黏滞性系数最优解(9.0×1018 Pa·s)。 然后, 联合同震和震后位移数据, 引入黏弹性位错格林函数, 反演了2011年日本MW9.0地震的断层滑动分布。 结果表明, 该地震同震破裂的最大值达到了62.72 m, 同震滑动的总地震矩为4.48×1022 Nm, 相应的矩震级为MW9.03。 由于黏弹性松弛效应引起的震后位移中包含了同震破裂的信息, 基于黏弹性球体地震位错理论, 联合同震和震后位移数据反演断层同震破裂, 有效提高了日本MW9.0地震断层滑动分布的可靠性。 最后, 本文提出的反演方法为同震观测结果缺乏的大地震震后科考提供了理论支撑: 在大地震发生之后, 即使在同震期间没有足够的观测数据, 也可以在震后通过对震源区的加密观测积累的震后数据, 使用本文提出的反演方法优化同震断层滑动模型。

关键词: 2011年日本MW9.0地震, 球体位错理论, 地幔黏弹性松弛, 震后位移, 滑动分布反演

Abstract: Based on the viscoelastic sphere dislocation theory, combined with co-seismic data on land and seafloor and 5-10 years post-seismic data from 330 land GPS stations on the main island of Japan, we inverted the fault slip distribution of the 2011 Tohoku-Oki MW9.0 earthquake and improved its rationality in details. Firstly, based on the continuous observation data of 330 land GPS stations on the main island of Japan 2 years before and 10 years after the earthquake, we obtained the annual average displacement of 5~10 years after the 2011 Tohoku-Oki MW9.0 earthquake. The displacement generated during this period can be almost completely regarded as the viscoelastic relaxation of the mantle. Secondly, we used the viscoelastic sphere dislocation theory to simulate the displacements of 5~10 years after the earthquake. Comparing the observed displacement with the simulated ones, we found the optimal viscosity of the mantle is 9.0×1018 Pa·s. Then, we used the viscoelastic Green function and combined co-seismic and post-seismic data to continuously invert the fault slip distribution of the 2011 Tohoku-Oki MW9.0 earthquake. The results showed that the maximum co-seismic dislocation of the 2011 Tohoku-Oki MW9.0 earthquake reached 62.72 meters, and the seismic moment of co-seismic slip was 4.48×1022 Nm, and the corresponding moment magnitude was MW9.03. Since post-seismic displacement caused by the viscoelastic relaxation includes information of the co-seismic slip, the inversion based on the co-seismic and post-seismic data based on the viscoelastic sphere dislocation theory can effectively improve the reliability of the fault slip distribution of the 2011 Tohoku-Oki MW9.0 earthquake. Finally, the inversion method proposed in this paper provides theoretical support for the post-seismic scientific investigation of major earthquakes where the co-seismic data is not enough: the fault slip distribution can be optimized by densifying the observational network and collecting post-seismic data, even if the co-seismic data is not sufficient.

Key words: The 2011 Tohoku-Oki MW9.0 earthquake, Spherical dislocation theory, Viscoelastic relaxation of the mantle, Post-seismic deformation, Fault slip distribution inversion

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