Abstract .The role of subducting topography on the mode of fault slip—particularly whether it hinders or facilitates large megathrust earthquakes—remains a controversial topic in subduction dynamics1 , 2 , 3 , 4 , 5. Models have illustrated the potential for subducting topography to severely alter the structure, stress state and mechanics of subduction zones4 , 6; however, direct geophysical imaging of the complex fracture networks proposed and the hydrology of both ...