• asperity;
  • great earthquake;
  • numerical simulation;
  • slip deficit

[1] A numerical simulation is conducted for understanding the mechanics of the 2011 great Tohoku-oki earthquake (Mw = 9.0), which widely broke the plate interface at the Pacific plate subducting beneath northern Honshu (Tohoku), Japan. In the model, frictional stress on the plate interface is assumed to obey a rate- and state-dependent friction law. A strong patch (asperity) with higher effective normal stress and a large value of characteristic slip distance is assumed at a shallower part of the plate interface. This strong patch controls the occurrence of great earthquakes that broke the entire seismogenic plate interface with recurrence intervals of several hundred years. The present model explains large coseismic slip at a shallower part of the 2011 great earthquake and accumulation of slip deficit at deeper parts, where smaller M7 class earthquakes repeatedly occurred before the great earthquake.