Historic Earthquakes: Tectonic Summary

Magnitude 5.0 WYOMING
2004 January 07 07:51:37 UTC

This earthquake occurred within the Intermountain Seismic Belt, a zone of earthquake activity that extends from northern Montana to northern Arizona. The Intermountain Seismic Belt corresponds to a diffuse boundary between regions of high (to the west) and low(to the east) late-Cenozoic tectonic extension within the mountain states of the western U.S. The earthquake was in a section of the Intermountain seismic belt that has historically produced several earthquakes with magnitudes between 4.5 and 5. The Teton fault, a large normal fault that has the potential of producing earthquakes of magnitude 7 or larger, is situated several tens of kilometers west of the epicenter of the January 7 earthquake, along the east side of the Teton range. The January 7 earthquake, most of the analyzed historic earthquakes, and the Teton fault all reflect the response of the earth's crust to an east-west extensional stress. The January 7 earthquake and most of the analyzed historic earthquakes, however, occurred on faults that were distinct from the Teton fault.