[3] Both earthquakes triggered tsunamis that were observed around the northern part of the Pacific Ocean.

The Kuril Islands form part of the island arc formed above the subduction zone, where the Pacific plate is being subducted beneath the North American plate.

The earthquake was made up of three sub events, each of which is interpreted to represent the rupture of an asperity roughly 50 km in length along the subduction interface.

The tsunami was also observed in Canada, Japan, Mexico, Hawaii, Alaska, California, and on many islands across the northern Pacific Ocean.

The tsunami associated with the October 20 event was larger in the nearby area, with a maximum recorded run-up of 15 m at Urup, but was only observed in the western part of the northern Pacific.