Alaska Earthquake

November 12, 2002

Augustanack3 copy

Provided by: USGS
Summary authors & editors: USGS

The November 3 magnitude 7.9 earthquake in central Alaska created a scar across the landscape for more than 145 miles (233 km), according to surveys conducted by geologists from the U.S. Geological Survey and the Alaska Division of Geological and Geophysical Survey. The geologists, who followed the earthquake rupture by helicopter through valleys, across streams, and along glaciers, measured a maximum horizontal offset of 22 feet (6.6 m) across the Tok Highway Cutoff, a road that goes from Tok to Glenallen and intersects with the Alaska Highway. This earthquake, one of the largest ever recorded on U.S. soil, occurred on the Denali fault system, one of the longest strike-slip fault systems in the world, rivaling in size California's famed San Andreas strike-slip fault system.

The photo above is of the fault scarp near Augustana Creek, just west of Delta River. The offset was approximately 16 feet (4.8 m). Some cracks were up to 9 feet (2.7 m) deep. A pressure ridge is visible in the background.

Photo credit: Peter Haeussler, U.S. Geological Survey

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