On April 1st 1946, an undersea earthquake off the Alaskan coast triggered a massive tsunami that killed 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.

Here an abfab computer animation of the tidal wave:

As you can see from the animation Hawaii was slap dab in the middle of the path of the monster.

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.

Tsunami hitting Hawaii

The picture shows the tidal wave breaking over the Pier No. 1 in Hilo Harbor, Hawaii. The man in the foreground (lower left) became one of the 159 deaths on the islands.

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.

Going back to the animation you can see that the tsunami hit everywhere down the American Pacific Coast including Fort Bragg’s Noyo Harbour and the Navarro River. Remarkably there are photos of the event:

In 1946 the entrance to the River Noyo was vastly different from today

Effect of the Tsunami in Noyo Harbour

Noyo Harbour showing fishing fleet in a small area and esily affected by the Tsunami

Effects of the Tsunami in Navarro River

And it could happen again any time, any day.