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Forty years since the big one, Alaska Science Forum

It's Alaska disaster anniversary week...

On that day 40 years ago, Alaska shook for about four minutes, about as long as it takes to listen to a song on the radio. During that time, the gargantuan Pacific plate slid under the North American plate an average of about 30 feet. The earthquake rupture began at the meeting place of the two plates about 15 miles deep under College Fiord.

The Alaska earthquake released 100 times as much energy as the 1906 San Francisco earthquake, and the only larger earthquake ever recorded was a 1960 magnitude 9.5 in Chile. Seismic waves traveled through the planet for weeks as Earth rang like a bell from the shock of the Alaska earthquake, wrote Doug Christensen, associate director of the University of Alaska’s Geophysical Institute. Water sloshed in lakes and harbors as far away as Louisiana, and water levels jumped in wells as far away as South Africa.

During the earthquake, more than 100,000 square miles of Alaska broke, twisted, tilted, dropped and rose. Seward moved about 47 feet south; Cordova migrated 46 feet southeast. Parts of Montague Island rose more than 30 feet; areas around Portage dropped nine feet. According to a National Academy of Sciences study commissioned by President Lyndon Johnson in 1964, the earthquake also killed 90 percent of the mussels in Prince William Sound, stopped the flow of Ship Creek in Anchorage for 18 hours, and shortened the intervals between eruptions of Old Faithful geyser in Yellowstone National Park.

Shake here.

March 28, 2004 in alaska | Permalink