("An earthquake-triggered tsunami sweeps along Iwanuma, northern Japan, March 11, 2011." Image source: Office of Disaster management, Dominica, 2024)
Since 1854, 21 tsunamis have impacted the Oregon Coast. The last two damaging tsunamis were in 1964 as a result of the Great Alaskan Earthquake, and in 2011 as a result of the Great Tohoku Japan Earthquake that caused severe damage and contributed to the deaths of four people on the Oregon Coast (OEM Hazards and Preparedness: Tsunami)
Significant tsunamis that have affected Oregon
1700 - Result of an North American Earthquake
1946 - Result of the Aleutian Island Earthquake
1964 - Result of the Great Alaskan Earthquake
2011 - Result of the Great Tohoku Japan Earthquake
Major tsunamis occur roughly every 300-600 years. A tsunami is a series of travelling ocean waves caused by a sudden disturbance of the ocean floor such as an underwater earthquake – when the sea floor quickly moves up or down – a rock slide, a volcanic eruption, or another high-energy event. It sets in motion a large mass of water that spreads outward in all directions.
Tsunamis have an extremely long wavelength. The distance between one wave crest (the top of one wave) to another crest can extend up to several hundred miles long and can travel across entire ocean basins away from the source area. The time between two successive waves can also be very long – about an hour in deep water. A tsunami can travel over 600 mph (970 km/h).
Tsunamis are sometimes incorrectly called "tidal waves" but tsunamis are not caused by the tides. Tides are caused by the gravitational interactions between the Sun, Moon and Earth.
Click on interactive maps of major Oregon coastal cities to view high water marks expected in a small and an extra large tsunami. The maps can move to view surrounding coastal areas.
The small tsunami ("SM") simulates an 8.7 magnitude quate that raises the ocean floor about 9 feet. The extra-extra large tsunami represents a 9.1 magnitude earthquake that raises the ocean floor 33 feet.
Schools, hospitals, fire stations, evacuation centers, and other critical resources are also included on these maps.
This is a video from 1964 replayed from the Portland television station, KGW News Channel 8.