Waite Gregory, University of Utah Department of Geology and Geophysics
This report describes the largest earthquake swarm in Yellowstone National Park's recorded history. For a little over 3 months beginning in October 1985, the swarm contained more than 3000 earthquakes with a magnitude greater than 5. The swarm had unusual characteristics that could be explained by the migration of hydrothermal fluids. Maps and numerous graphs support the text.