R&D Center for Earthquake and Tsunami, Japan Agency for Marine-Earth Science and Technology, 3173-25, Showa-machi, Kanazawa-ku, Yokohama, Kanagawa, 2360001, Japan.
Department of Earth Sciences, University of Southern California, 3651 Trousdale Pkwy, Los Angeles, CA, 90089-0740, USA.
Nat Commun. 2019 Mar 26;10(1):1385. doi: 10.1038/s41467-019-08984-7.
The deformation transient following large subduction zone earthquakes is thought to originate from the interaction of viscoelastic flow in the asthenospheric mantle and slip on the megathrust that are both accelerated by the sudden coseismic stress change. Here, we show that combining insight from laboratory solid-state creep and friction experiments can successfully explain the spatial distribution of surface deformation in the first few years after the 2011 M 9.0 Tohoku-Oki earthquake. The transient reduction of effective viscosity resulting from dislocation creep in the asthenosphere explains the peculiar retrograde displacement revealed by seafloor geodesy, while the slip acceleration on the megathrust accounts for surface displacements on land and offshore outside the rupture area. Our results suggest that a rapid mantle flow takes place in the asthenosphere with temporarily decreased viscosity in response to large coseismic stress, presumably due to the activation of power-law creep during the post-earthquake period.
大俯冲带地震后的变形瞬变被认为源于软流圈中粘弹性流动与巨震上的滑动之间的相互作用，而这两者都被突然的同震应力变化加速。在这里，我们表明，结合实验室固态蠕变和摩擦实验的洞察力，可以成功解释 2011 年 M9.0 东日本大地震后最初几年的地表变形的空间分布。软流圈中位错蠕变导致的有效粘度的瞬时降低解释了海底大地测量揭示的特殊逆行位移，而巨震上的滑动加速则解释了破裂区以外陆地和近海的地表位移。我们的结果表明，在大地震后，由于幂律蠕变的激活，软流圈中会发生暂时粘度降低的快速地幔流。
