Yellowstone National Park, Wyoming
1975 06 30 18:54 UTC
This widely felt earthquake downed one chimney in the park at Norris Junction and formed cracks 90 m long in a parking lot. Rock-falls and landslides closed or hindered traffic on many roads in the park. Two new gysers formed; the Gibbon River was muddied; and the earth settled and cracked in the backcountry. Several aftershocks occurred through early July. Also felt in Montana, Idaho, South Dakota, Nebraska, Nevada, Utah, and Washington.
Abridged from Seismicity of the United States, 1568-1989 (Revised), by Carl W. Stover and Jerry L. Coffman, U.S. Geological Survey Professional Paper 1527, United States Government Printing Office, Washington: 1993.