1946 Aleutian Tsunami

On April 1, 1946, at 12:29 GMT, an earthquake occurred in the Aleutian Islands of Alaska. A Pacific-wide tsunami was triggered by the earthquake, which had a surface-wave magnitude of 7.8, an epicenter of 52.8° N, 163.5° W, and a focal depth of 25 km. Before the tsunami dissipated it took the lives of more than 165 people and cause over $26 million (1946 dollars) in damage.

One of the structures affected by the tsunami was the newly built Scotch Cap Lighthouse on Unimak Island, Alaska. At the lighthouse 5 men lost their lives and the run-up reached 35.0 m. The Hawaiian Islands were one of the hardest hit locations by the tsunami. Pololu Valley recorded the highest run-up of 12.0 m on the Island of Hawaii. However, Hilo was the city that received the most damage on the Island of Hawaii. The tsunami arrived at Hilo 4.9 hours after it originated in the Aleutian Islands and the run-up was measured at 8.1 m. Hilo received $26 million in damage and 96 people died.

Scotch Cap Lighthouse on Unimak Island, Alaska as it looked before the earthquake and tsunami. The structure was built in 1940. It was 40 feet above the sea and was five stories high. Photograph Credit: U.S. Coast Guard. Source: National Geophysical Data Center.

All that remained of Scotch Cap Lighthouse on Unimak Island, Alaska after the tsunami. Photograph Credit: U.S. Coast Guard. Source: National Geophysical Data Center.

The large number of deaths from this event brought the realization that a warning system was necessary to ensure the safety of the populace. On August 12, 1948, a plan was approved and the Seismic Sea Wave Warning System was established. Later its name would be changed to the Pacific Tsunami Warning System.

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