August 21, 2003
Earthquake Shakes Northern Teton County
Dr. Robert Smith of the University of Utah reported to the Wyoming State Geological Survey (WSGS) that a Magnitude 4.4 earthquake occurred at 1:46 a.m., Thursday, August 21, 2003, approximately 7 miles east of Flagg Ranch. Flagg Ranch is about 2 miles south of the south entrance to Yellowstone National Park. The earthquake was felt at Flagg Ranch, Grant Village, and at the south entrance. There were reports of pictures moving and a few small items falling off shelves. The earthquake occurred in the Teton Wilderness within Teton National Forest. If such an earthquake occurred under a populated area, the damage would have been minor to moderate.
The earthquake was detected and located primarily from University of Utah seismometers sited in Yellowstone National Park. The location and depth of the earthquake is not precise because there is no longer a seismic network south of Yellowstone in the Jackson Hole area. The U.S. Bureau of Reclamation terminated their area network in late 2002.
This type of continuing event points out the need for a seismic network in such an active area. The Wyoming Congressional Delegation, Wyoming Governors Office, WSGS, U.S. Geological Survey, Teton County, the University of Utah, and the Geologists of Jackson Hole all are attempting to site and find funding for a new area seismic network.
This earthquake is not related to any of the Yellowstone Lake bulges or hydrothermal activity in Yellowstone National Park. In fact, some of the recent press on those features has been misleading to the public. There is no evidence that any of the bulges in Yellowstone Lake have been growing rapidly and there is no evidence yet that any of them are new. The most significant bulge in the Lake may have been there for decades, if not longer. The U.S. Geological Survey is currently studying the age of the bulges.
from the Office of the Wyoming State Geologist
Ron Surdam, State Geologist