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

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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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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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