The earthquake occurred on the convergent boundary between the subducting Pacific and overriding North American crustal plates. This region, where the two plates are being forced directly into one another, is one of the world's most active seismic zones. Over one hundred earthquakes of magnitude seven or larger have occurred along this boundary in the past hundred years. The 1957 Mw 8.6 Andreanof Islands earthquake ruptured a ~600 km-long portion of the plate boundary in central Aleutian Islands. The current sequence of earthquakes is located within the eastern segment of the 1957 rupture zone.