On April 1, 1946, an undersea earthquake off the Alaskan coast triggers a massive tsunami that kills 159 people in Hawaii.
In the middle of the night, 13,000 feet beneath the ocean surface, a 7.4-magnitude tremor was recorded in the North Pacific. (The nearest land was Unimak Island, part of the Aleutian chain.) The quake triggered devastating tidal waves throughout the Pacific, particularly in Hawaii.
Unimak Island was hit by the tsunami shortly after the quake. An enormous wave estimated at nearly 100 feet high crashed onto the shore. A lighthouse located 30 feet above sea level, where five people lived, was smashed to pieces by the wave; all five were killed instantly. Meanwhile, the wave was heading toward the southern Pacific at 500 miles per hour.
In Hawaii, 2,400 miles south of the quake’s epicenter, Captain Wickland of the United States Navy was the first to spot the coming wave at about 7 a.m., four-and-a-half hours after the quake. His position on the bridge of a ship, 46 feet above sea level, put him at eye level with a “monster wave” that he described as two miles long.
As the first wave came in and receded, the water in Hawaii’s Hilo Bay seemed to disappear. Boats were left on the sea floor next to flopping fish. Then, the massive tsunami struck. In the city of Hilo, a 32-foot wave devastated the town, completely destroying almost a third of the city. The bridge crossing the Wailuku River was picked up by the wave and pushed 300 feet away. In Hilo, 96 people lost their lives.
On other parts of the island of Hawaii, waves reached as high as 60 feet. A schoolhouse in Laupahoehoe was crushed by the tsunami, killing the teacher and 25 students inside. The massive wave was seen as far away as Chile, where, 18 hours after the quake near Alaska, unusually large waves crashed ashore. There were no casualties.
This tsunami prompted the U.S. to establish the Seismic SeaWave Warning System two years later. The system, now known as the Pacific Tsunami Warning System, uses undersea buoys throughout the ocean, in combination with seismic-activity detectors, to find possible killer waves. The warning system was used for the first time on November 4, 1952. That day, an evacuation was successfully carried out, but the expected wave never materialized.