Earthquake rupture stalled by a subducting fracture zone.

We showed that the rupture produced by the great Peru earthquake (moment magnitude 8.4) on 23 June 2001 propagated for approximately 70 kilometers before encountering a 6000-square-kilometer area of fault that acted as a barrier. The rupture continued around this barrier, which remained unbroken for approximately 30 seconds and then began to break when the main rupture front was approximately 200 kilometers from the epicenter. The barrier had relatively low rupture speed, slip, and aftershock density as compared to its surroundings, and the time of the main energy release in the earthquake coincided with the barrier's rupture. We associate this barrier with a fracture zone feature on the subducting oceanic plate.