CRESCENT CITY, Calif. —
The town wasn't forewarned on Good Friday, 1964, when a huge earthquake in Alaska's Prince William Sound sent a bigger surges down the coast. They killed 11 people and wiped out 29 city blocks.
Lee Wilson recalls seeing his dad's fishing boat, the Gold Coast, tossed on the harbor breakwall like a toy to sit high and dry. There was no boat basin then, no docks. Wilson's dad repaired the boat, and Wilson still fishes it. But he had the engine out for an overhaul when this tsunami hit, and couldn't take it out to sea. Tucked in a sheltered corner of the boat basin, it rode out the surges, and just missed being slammed by the harbor dredge when it broke loose.
Tsunamis are different than storm seas, Dengler said. A storm wave is generated by the wind, and is only moving the top of the water column. A tsunami is generated by an upheaval on the ocean floor and the force extends from the surface to the ocean floor, even if the water is thousands of feet deep.
This tsunami was generated by one tectonic plate slipping violently underneath the other in a zone 350 miles long and 150 miles wide, Dengler said. The wave raced across the ocean at the speed of a jet airplane, 500 to 600 mph, crossing the Pacific.
To a ship at sea, it was not even noticeable. Three to four feet high. A bump in the ocean. As it moved east, the energy bounced off a huge underwater ridge extending out from Mendocino, deflecting part of it toward Crescent City. The deflection slowed the wave, making it a little higher.
Moving into shallower water, the energy built even more. It was focused again by the half-moon shape of the bay. The first surges to hit the shore were small. Bouncing back, they made the next surges bigger. When the biggest of the surges hit the tidal gauge, it measured 8.1 feet, Dengler said.