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Denali Fault

On a Sunday afternoon in November of 2002, an earthquake of magnitude 7.9 occurred in south-central Alaska. It was one of the largest recorded earthquakes in the United States, and rocked boats as far away as Louisiana. The quake originated on the Denali-Totschunda fault system, a strike-slip fault zone that curves for over 700km (434 miles) through Alaska into Canada, and, like the San Andreas fault system, results from the interaction between the Pacific plate and the North American plate. Part of the fault system is shown here, with the Denali fault outlined in red and the Totschunda fault outlined in orange. In general, the earth to the north of the fault system is moving east relative to the ground south of the fault. This was the case during the November 2002 earthquake, where the eastward horizontal shift of the ground measured up to 6.6 meters (22 feet). The earthquake triggered rock and snow slides, and formed a rupture about 323 km (200 miles) in length that passed beneath the Trans-Alaska Oil Pipeline.

This photograph shows a highway near Tok, Alaska, that has been affected by the fault. Researchers estimated the horizontal offset of the road to be about 6.6 m (22 ft). This picture was taken by Peter Haeussler of the USGS. More information can be found on a USGS Earthquake Hazards Program news page as well as in the Denali Fault Earthquake Fact Sheet. This and other photographs can be found here.