Frictional properties of fault zone gouges from the J-FAST drilling project (Mw9.0 2011 Tohoku-Oki earthquake)

Smectite-rich fault gouges recovered during Integrated Ocean Drilling Program Expedition 343 (Japan Trench Fast Drilling Project (J-FAST)) from the plate boundary slip zone of the 2011 Mw 9.0 Tohoku-Oki earthquake were deformed at slip velocities of 10\u2009\ub5m\u2009s 121 to 3.5\u2009m\u2009s 121 and normal stresses up to 12\u2009MPa. Water-dampened gouges (1) are weaker (apparent friction coefficient, \u3bc* \u20090.1\u2009m\u2009s 121). A significant amount of amorphous material formed in room-humidity experiments at low- and high-slip velocities, likely by comminution and disordering of smectite. Our results indicate that the frictional properties of water-dampened gouges could have facilitated propagation of the Tohoku-oki rupture to the trench and large coseismic slip at shallow depths