LARAMIE, Wyo. -- On Aug. 17, 1959, a magnitude 7.5 earthquake shook Yellowstone National Park and most of northern and western Wyoming.
Roads collapsed. Streams jumped their banks. An avalanche roared down one side of the Madison River Canyon, blocking the river and creating a new lake. The avalanche buried a campground under 225 feet of rock, killing 28 campers.The event affected an area encompassing 600,000 square miles surrounding the epicenter, which was a few miles west of Yellowstone near Hebgen Lake, Mont.
A total of 156 aftershocks were recorded within the first 21 hours after the main shock, including several magnitude 6.0 to 6.5 events.
Geologists say the Hebgen Lake quake is a model for what can occur in the western quarter of Wyoming. The Teton Fault near Jackson, Star Valley fault near Afton, Rock Creek fault near Fossil Butte National Monument and Bear River fault system near Evanston are all capable of generating magnitude 7.5 quakes, they say.
"It is not known, however, when a magnitude 7.5 earthquake might occur in the area," a Wyoming State Geological Survey release states. "It could happen next week, or it may not occur for hundreds of years or even longer."
Three weeks ago, a magnitude 3.7 earthquake centered in eastern Idaho rattled dishes but caused no significant damage.
In 1994, a magnitude 5.9 earthquake damaged the Auburn Fish Hatchery and a home near Auburn, while aftershocks caused minor damage in Grover and Fairview.
To mark the 40-year anniversary of the Hebgen quake, the Geological Survey aims to increase awareness of the possibility of a major earthquake in the state.
The survey's Geologic Hazards Section recently obtained funding from the Federal Emergency Management Agency to find ways to alert residents of the danger. The funds will also be used to reduce the possible effects of earthquakes and associated hazards such as landslides.
The Geological Survey is asking anyone who felt the Hebgen Lake quake or any other in Wyoming to contact the survey.