Structural heterogeneity in the megathrust zone and mechanism of the 2011 Tohoku-oki earthquake (Mw 9.0)

The great 2011 Tohoku‐oki earthquake (Mw 9.0) and its 339 foreshocks and 5,609 aftershocks (9–27 March 2011) were relocated using a three‐dimensional seismic velocity model and local P and S wave arrival times. The distribution of relocated hypocenters was compared with a tomographic image of the Northeast Japan forearc. The comparison indicates that the rupture nucleation of the largest events in the Tohoku‐oki sequence, including the mainshock, was controlled by structural heterogeneities in the megathrust zone. Key Points We relocated 5949 events of the 2011 Tohoku‐oki earthquake sequence The relocated hypocenters are compared with the tomography in the source zone Structural heterogeneities control the earthquake generation