The strong ground motions, large crustal deformation, and tsunami generated by the 2011 Tohoku-oki earthquake (M_w 9.1) reveal that a large coseismic slip likely propagated to shallow depth in the Japan Trench. Although data acquired by onshore networks cannot resolve the slip behavior of the updip fault rupture, marine geophysical and geological studies provide direct evidence of coseismic slip to the trench. Differential bathymetry data show ∼50 m of coseismic seafloor displacement extending to the central Japan Trench (38–39.2°N). Seismic data show that coseismic slip ruptured the seafloor within the trench. Pelagic clays may have promoted slip propagation to shallow depths, whereas disturbed/metamorphosed clays may have restricted slip to the main rupture zone. Those observations imply that a smooth, broadly distributed, weak, clay-rich sediment in a shallow part of a subduction zone is a characteristic factor that can foster a large coseismic slip to the trench and, consequently, the generation of a large tsunami.

2011年东北OKI地震产生的强烈地震动，大地壳变形和海啸（M _w9.1）揭示了一个大的同震滑动可能在日本海沟中传播到了较浅的深度。尽管通过陆上网络获取的数据无法解决上倾断层破裂的滑移行为，但海洋地球物理和地质研究提供了同震滑移至海沟的直接证据。差分测深数据显示，同震海底位移约50 m延伸至日本海沟中部（38-39.2°N）。地震数据表明，同震滑动使海沟内的海底破裂。上层粘土可能促进了滑移传播至浅深度，而扰动/变质粘土可能限制了向主破裂带的滑动。这些观察结果表明，平滑，分布广泛，脆弱，