A magnitude 3.8, intensity IV earthquake occurred roughly 11 miles north-northwest of Douglas, Wyoming at 12:49 PM on Sunday, August 29, 2004. The event was reported to the Wyoming State Geological Survey (WSGS) by the U.S. Geological SurveyÕs National Earthquake Information Center in Golden, Colorado. The earthquake occurred approximately 3 miles below the surface. The quake was strong enough to be felt in Douglas, and there were reports of objects shifting and pictures falling from walls. No other damage was reported.

This is the second earthquake in the same general area during the last six months. On February 15, 2004, a non-damaging magnitude 3.5, intensity III event occurred. A magnitude 3.0 earthquake occurred in the general vicinity on June 30, 1993.

Earthquakes are not uncommon in eastern Wyoming. In fact, longer-term residents may remember a series of earthquakes in northern Albany County and southern Converse County in 1984. The largest earthquake, a magnitude 5.5, intensity VI event, occurred on October 18, 1984. That earthquake, with an epicenter located approximately 4 miles west-northwest of Toltec, was felt in Wyoming, South Dakota, Nebraska, Colorado, Utah, Montana, and Kansas. Cracks were found in the exterior brick walls of the Douglas City Hall and a public school in Medicine Bow. Chimneys were cracked at Casper, Douglas, Guernsey, Lusk, and Rock River.

Seismological characterizations of all Wyoming counties have been generated by the WSGS (see http://www.wrds.uwyo.edu/wrds/wsgs/hazards/quakes/seischar/seischar.html). The seismological characterizations include an analysis of historic seismicity as well as a projection of possible future earthquakes. The WSGS is currently completing a study of the potential for building damage from earthquakes in all Wyoming counties.

For more information on this topic please contact:
Jim Case, jcase@uwyo.edu
Phone: 307 766-2286 x225

Sales: (307)766-2286 x224
Fax: (307)766-2605
Email: sales-wsgs@uwyo.edu

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