1964 Good Friday
Great Alaskan
EARTHQUAKE

What Happened?

The Aleutian Islands and Trench stretch across the northern Pacific Ocean between Kamchatka in Siberia and south central Alaska.

• In this area the Pacific Plate moves northwestward at a rate of approximately five to seven centimeters (2 to 2.75 inches) per year.(2)
• At the same time it is being subducted or pulled down and under the North American Plate.
• This causes some of the southern Alaskan crust to be compressed , folded, and warped.
• Some areas along the coast get depressed while others are uplifted .
• After tens to thousands of years the stress in the rocks becomes too much and they break, causing a sudden slipping of the earth’s crust.
• This breaking and slipping of the rocks is called an earthquake.
• The surface along which two blocks of rock slip is called a fault.
• Some faults are small and some are 1000's of kilometers long. The fault in Alaska is 1000's of kilometers long and divides two large plates of rock called the Pacific Plate and the North American Plate.
• In the case of the Alaskan earthquake, the focus , place under the surface of the Earth where the earthquake actually occurred, was thirty kilometers (18.6 miles) deep.
• This is a shallow earthquake. It means that a lot of the energy that the earthquake produced was felt at the Earth’s surface, over 1,300,000 square kilometers (over 500,000 square miles) throughout Alaska, parts of Canada, and the southern part of Washington State.(2)
• In addition, a magnitude of 8.6 means it had the same amount of energy as would be produced by detonating one billion tons of TNT.(3) It also had one hundred times more ground movement than the earthquake in Northridge, CA that took place on January 17, 1994.(4)

This earthquake caused the Earth to rupture , or break,eight hundred kilometers (497 miles)along a fault that runs parallel to the Aleutian Trench.(1) Rupture extended from Prince William Sound to the southwest end of Kodiak Island. This rupture caused the sea floor at Montague Island in Prince William’s Sound to uplift 4.8 meters (16ft)(4) and generated a powerful tsunami, which was responsible for 90% of the death and destruction caused by this earthquake. Within twenty-four hours of the quake, a zone two hundred fifty kilometers (155 mi) wide and eight hundred kilometers (497 miles) long had experienced twenty eight aftershocks, or smaller earthquakes after the main one, ten of which were over magnitude 6.0.(3)


Learn more the 1964 Good Friday Great Alaskan Earthquake

1964 Good Friday Great Alaskan Earthquake Overview	Great Chunks Of Earth Were Pushed Into The Sky
Giant Waves Caused Fifteen Deaths	A Huge Piece of Land Walked Into The Sea
It All Happened Here Before (And Probably Will Again)	What The Words All Mean (Vocabulary Definitions)




Other sites of interest:

Windows to Arizona Geology

United States Geological Survey Report on the Alaskan quake.



Credits

With many thanks to the following sources:

Macklin, T. for photos by his brother.

1) Bolt, B., 1993, Earthquakes. W.H.Freeman and Company.

2) Christensen, D. http://www.aeic.alaska.edu/Seis/64quake/quake_description.html
3) Lutgens, F. and Tarbeck, E., 1995, Essentials in Geology. Prentice Hall.

4) Pipkin, B. and Trent, D., 1997, Geology and the Environment. West/Wadsworth.

5) Sokolowski, T. http://wcatwc.gov/64quake.htm

6) United States Geological Survey. http://wwwneic.cr.usgs.gov/neis/eqlists/USA/1964_03_28.html


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Page by Nievita Bueno Hartness
Last Updated 12/06/2001


E-mail me at: nhartnes@geo.arizona.edu