The March 11, 2011 Tohoku-Oki earthquake produced the largest slip ever recorded in an earthquake, over 50 meters. Such huge fault movement on the shallow portion of the megathrust boundary came as a surprise to seismologists because this portion of the subduction zone was not thought to be accumulating stress prior to the earthquake. In a recently published study, scientists shed light on the stress state on the fault that controls the very large slip....