January 7, 2004
Teton County Shaken by Largest Historic Earthquake

Four earthquakes, having magnitudes of 5.0, 3.7, 4.1, and 4.0, respectively, shook the Jackson Hole area this morning, January 7, 2004. The first earthquake, which occurred at 12:51 am, had a magnitude of 5.0, which is the largest historic earthquake recorded in Teton County. The University of Utah Seismograph Stations and the U.S. Geological SurveyÕs (USGSÕ) National Earthquake Information Center reported it was centered east of Kelly and about 3 miles southeast of Lower Slide Lake in the Gros Ventre River valley. The earthquake did not occur on the Teton fault, which is capable of generating a magnitude 7.5 earthquake. A local report indicated that the earthquake was felt for approximately six seconds.

The USGS also reported a number of aftershocks in the same general vicinity. A magnitude 3.7 earthquake occurred at 1:27 am, a magnitude 4.1 earthquake occurred at 1:44 am, and a magnitude 4.0 earthquake occurred at 2:23 am. There was a local report that the magnitude 3.7 earthquake was felt for 4.7 seconds. No significant damage was reported by any of todayÕs earthquakes, although they were felt throughout Jackson Hole.

There was a magnitude 3.5 earthquake in the same general area on Tuesday, December 30, 2003. That event, which occurred at 11:16 pm, caused no damage. In 1925, small earthquakes were reported to have occurred in the same general area as the above events. The 1925 earthquakes were thought to have played a role in destabilizing the Gros Ventre landslide, which dammed the Gros Ventre River. However, there is no indication that the recent events have caused any landslides. A complete earthquake history of Teton County and all other Wyoming counties can be found online at http://www.wrds.uwyo.edu/wrds/wsgs/hazards/quakes/seischar/seischar.html.

The State of Wyoming, Teton County, and the Geologists of Jackson Hole have successfully worked with WyomingÕs Congressional delegation and the USGS to acquire funding for a new seismic network in the Jackson Hole area. The U.S. Bureau of Reclamation removed their Jackson Lake Seismic Network last year and, as a result, locations of all earthquakes in the Jackson Hole area are approximate. Once the new stations are installed by the USGS, they will become part of the Advanced National Seismic System. Earthquakes can then be located much more precisely.

For more information about this topic contact Jim Case at (307) 766-2286, ext. 225.

Press Release
from the Office of the Wyoming State Geologist
Ron Surdam, State Geologist