On October 13 at 05:17 UTC, the Kuril Islands earthquake of 1963 took place. An incident with a magnitude of Mw=7.8 occurred seven days after the 8.5-magnitude earthquake. Tsunamis were seen in the Pacific Ocean's northern region as a result of both earthquakes.

Tectonic context
The Pacific Plate is being subducted beneath the Eurasian Plate, and the Kuril Islands are a portion of the island arc that has developed above the subduction zone. Numerous significant megathrust earthquakes, including the second-largest earthquake ever recorded, have occurred along this convergent boundary.

Earthquake
The earthquake was divided into three smaller quakes, each of which is thought to have been caused by the rupture of an asperity along the subduction interface that was about 50 km long.

Tsunami
Locally, the October 13 earthquake's tsunami generated a 4.5 m wave. Additionally, the tsunami was seen in many islands in the northern Pacific Ocean, including those in Canada, Japan, Mexico, Hawaii, Alaska, and California. The October 20 tsunami was bigger in the immediate vicinity, with a maximum run-up of 15 meters at Urup, but it was only seen in the western part of the northern Pacific.