Tsunamis Were Killers after 1964 Earthquake
While visiting Kodiak recently, I scratched my Interior Alaska-biased head when I saw a street sign that also gave the elevation of that spot, 100 feet above sea level. I appreciated the information, but why did I need to know it?
One-hundred feet or higher above sea level is the best place to be on Alaska's coast following a large earthquake, said Paul Whitmore, a geophysicist with the West Coast and Alaska Tsunami Warning Center in Palmer. Tsunamis are the reason.
A tsunami is a massive wave that sometimes follows an earthquake or underwater landslide, volcanic eruption, nuclear explosion, or meteorite impact. Kodiak is one of the many Alaska communities that pay attention to this silent, terrifying threat, because a tsunami destroyed much of the town in March 1964.
On the afternoon of March 27, 1964, an earthquake with magnitude 9.2 ruptured Earth's crust about 14 miles beneath the seafloor of Prince William Sound. Near the boundary of the massive Pacific and North American plates, part of the seafloor rose, causing a bulge in sea level that gravity pushed back down, giving birth to a tsunami.
In the deep water of Prince William Sound, the tsunami began as a series of small wave fronts that extended for miles, so small that boat captains in deep water did not notice them. The tsunami grew stronger as the wave fronts moved like ripples in a pond into the Gulf of Alaska and the north Pacific Ocean. Moving at the speed of a jet aircraft, the tsunami slowed when reaching coastal areas, such as the shores of Kodiak Island. Even though the tsunami slowed, the total energy remained constant, and the wave height grew. The tsunami was not a great, towering wave reminiscent of The Perfect Storm; it was more like a rapidly rising tide, as described by a Kodiak resident in a letter saved by the Kodiak Historical Society:
"The water came up slowly the first time-the boat harbor dock covered, then about twenty cars were covered and the next time I looked, the small house by the pier was covered . . . It was about the third or fourth wave that really stirred things up. It hit the boat harbor and it was like a thousand guns going off as moorings and lines snapped like toothpicks. Everything moved toward town. The boats hit the stores and the stores hit each other and they all moved up the creek and away from the bay."
The tsunami killed eight people in Kodiak and destroyed 158 houses. The magnitude 9.2 earthquake was the second largest ever recorded, but tsunamis triggered by the earthquake and landslides that followed the earthquake killed 106 people out of 115 deaths in Alaska. When the tsunami reached Crescent City, California, it killed 11 people there, in addition to four people who were camping on the coast near Newport, Oregon when the ocean rose to engulf their campsite.
Valdez lost 32 people as a result of a local tsunami triggered when a chunk of waterfront land 4,000 feet by 600 feet slid into the sea. In Shoup Bay, 11 miles from Valdez, a researcher later measured the tsunami wave; it reached 67 meters above sea level, about 219 feet.
Following the earthquake in 1964, state and federal officials created the West Coast and Alaska Tsunami Warning Center in Palmer, which is by design far from the reach of the largest tsunami. Whitmore and other scientists who work at the center monitor Alaska's earthquakes around the clock, issuing warnings to the Alaska Department of Emergency Services, the Coast Guard, the National Weather Service, and others when a magnitude 7 earthquake occurs anywhere along the Pacific coast of the U.S. and Canada. If coastal Alaskans feel a strong earthquake, scientists at the center recommend they drop what they're doing and get to an elevation above the reach of most tsunamis-100 feet above sea level.
