Mapping the Tohoku forearc: Implications for the mechanism of the 2011 East Japan earthquake (Mw 9.0)

► A 3-D seismic model under the NE Japan forearc region was estimated. ► The velocity model implies strong interplate coupling in the main-shock area. ► The 2011 GEJ earthquake initiation by fluid extrusion into the rupture zone. ► The rupture could be influenced by the dehydration of the subducting Pacific slab. ► Fluids played a key role in earthquake generation and rupture process.