October 22, 2002
Earthquake strikes northern Lincoln County, Wyoming
Late Monday evening, October 21, a magnitude 4.4 earthquake occurred near Alpine. According to both the U.S. Bureau of Reclamation and the University of Utah, the epicenter was about 3 miles north of Alpine at a depth of about 7 kilometers. The U.S. Geological Survey located the epicenter approximately 20 miles south of Jackson and 8 miles east of Alpine in northern Lincoln County. The earthquake, which occurred at 10:11 pm, caused no damage, but was felt in the towns of Jackson, Alpine, and Thayne.
According to Jim Case at the Wyoming State Geological Survey (WSGS), this recent earthquake occurred on a buried active fault. There are exposed active faults in the region, such as the Teton fault and the Star Valley fault, that are capable of generating magnitude 7.2 to 7.5 earthquakes. A magnitude 7.5 earthquake would release approximately 30,000 times more energy than a magnitude 4.4 earthquake. As a result, a magnitude 4.4 earthquake is considered to be a light earthquake.
There have been many other earthquakes of similar magnitude in the same general area. On February 8, 1983, a magnitude 4.4, intensity V earthquake occurred in Idaho, approximately 12 miles northwest of Alpine. The earthquake, which was felt in Etna (Star Valley) and Teton Village, may have initiated snow avalanches. On August 21, 1985, a magnitude 4.8, intensity V earthquake occurred approximately 10 miles east of Alpine, and was felt in Lander, Alpine, Wilson, and Jackson. On September 6, 1985, a magnitude 4.6, intensity V earthquake occurred approximately 15 miles east-southeast of Alpine. An earthquake-induced landslide temporarily closed a part of U.S. Highway 89 in the Snake River Canyon.
The earthquake website of the WSGS, which is served by the Wyoming Water Resources Data System, shows that many more smaller magnitude earthquakes have occurred in the area over the last ten years. The web site can be accessed at http://www.wrds.uwyo.edu/wrds/wsgs/hazards/quakes/quake.html.
from the Office of the Wyoming State Geologist
Ron Surdam, State Geologist
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