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March 27, 1964: The Great Alaskan Earthquake


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One day earthquake and thunder decided to explore the world, but doing so they reached only a desolate and dry plateau. Earthquake noted that the land was located much too high in the sky for humans “They will have no food, if there is no place for the creatures of the sea to live in!” Earthquake begun to shake, stronger and stronger, until the earth finally collapsed and the sea inundated the land. Earthquake was satisfied “From here, they will obtain what they need to live, where prairie has become water…. This is what brings to the people life.” Thunder acknowledged what earthquake had done “It is true. So they will survive!” and so they went further north and together they lowered the land and created the western coast.
The creation of the world according to a legend of the Yurok people (Cascade Range)

In the late afternoon of March 27, 1964 Alaska was shaken for five minutes by one of the strongest earthquakes ever to be recorded in modern times, with a magnitude of 8.3 – 9.2 after Richter (the earthquake was so strong that no seismometer in the affected area recorded it correctly).
The earthquake displaced almost the entire southern coast of Alaska along the Prince William Sound, some areas were raised by 9 meters (30 feet) above the sea level, other level dropped below sea level and became inundated later by the sea (maybe the Yurok myth is based on the observation of such a similar environmental change after an earthquake in prehistoric times along the western coast of the U.S.).

Video 1. Showing the “Ghost Forest” of the 1964 ´quake. In the lowered regions the trees were killed by the salt water, later deposited marsh sediments again raised the surface and tundra vegetation recolonized the area.

The earthquake caused heavy damage on 75% of buildings and infrastructure in the affected area, most in the city of Anchorage, 131 people were killed.
Large fissures opened in the ground when the groundwater liquefied the soil and more than 2.000 landslides and avalanches occurred across south-central Alaska. Buildings in Seattle (Washington) begun to swing by the approaching seismic wave and the ground was measurable deformed even in Florida.

Fig.1. Rockslide – avalanche on Sherman Glacier. The source was from the area marked by the fresh scar on Shattered Peak (top center image). Photo by A. Post / image in public domain from the U.S.G.S. Photographic Library.

In some lakes in Alaska the movement of the water catapulted chunks of ice onto the land, causing damage on the surrounding trees up to 9 meters (30 feet) above ground. Unusual water movements, attributed cautiously to the earthquake, were observed in South Dakota and apparently even in Puerto Rico and Australia.
Most remarkable was the generated tsunami, waves higher than usual were observed even along the Japanese coast. The seaport of Valdez was destroyed by a 30 meter high tsunami, 32 people died there. For hours after the earthquake the sea was tumultuous and in the evening with the high tide the reflected waves of the first tsunami inundated the surviving area of the city of Valdez.
Six hours after the earthquake the tsunami reached the coasts of Vancouver Island, one hour later the coast of Oregon and the wave caused damage even in Crescent City and Los Angeles (California).


Fig.2. Aerial photographs of destructive landslides and damage in Anchorage, Photo by A. Grantz / image in public domain from the U.S.G.S. Photographic Library.

Many of these phenomena were studied for the very first time by scientists – only two hours after the earthquake the first geologists arrived to Anchorage.

Bibliography:

Committee on the Alaska Earthquake of the Division of Earth Sciences National Research Council (1968): The Great Alaska Earthquake of 1964. National Academy of Sciences, Washington: 473
GATES, A.E. & RITCHIE, D. (2007): Encyclopedia of earthquakes and Volcanoes. Facts on file science library. 3th ed. New York: 346
WALKER, B. (1982): Earthquake. Planet Earth. Time Life Books: 154

David Bressan About the Author: Freelance geologist dealing with quaternary outcrops interested in the history and the development of geological concepts through time. Follow on Twitter @David_Bressan.

The views expressed are those of the author and are not necessarily those of Scientific American.





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