The great Mw8.7 Rat Islands underthrusting earthquake of February 4, 1965, ruptured a 600-km segment of the western end of the Aleutian megathrust.

The Rat Islands event was closely followed by a large tensional outer-rise event of March 30, 1965 (Ms 7.5), which was located oceanward of the largest moment release associated with the Rat Islands mainshock rupture.