Swarm Of Small Earthquakes Rattles Yellowstone National Park, U.S.

This energetic sequence of events was most intense on December 27, when the largest number of events of magnitude 3 and larger occurred.

The largest of the earthquakes was a magnitude 3.9 (revised from magnitude 3.8) at 10:15 pm MST on Dec. 27. The sequence has included nine events of magnitude 3 to 3.9 and approximately 24 of magnitude 2 to 3 at the time of this release. A total of more than 250 events large enough to be located have occurred in this swarm. Reliable depths of the larger events are up to a few miles. Visitors and National Park Service (NPS) employees in the Yellowstone Lake area reported feeling the largest of these earthquakes.

Earthquakes are a common occurrence in the Yellowstone National Park area, an active volcanic-tectonic area averaging 1,000 to 2,000 earthquakes a year. Yellowstone's 10,000 geysers and hot springs are the result of this geologic activity. A summary of the Yellowstone's volcanic history is available on the Yellowstone Volcano Observatory web site (listed below). This December 2008 earthquake sequence is the most intense in this area for some years and is centered on the east side of the Yellowstone caldera. Scientists cannot identify any causative fault or other feature without further analysis. Seismologists continue to monitor and analyze the data and will issue new information if the situation warrants it.

The University of Utah operates a seismic network in Yellowstone National Park in conjunction with the National Park Service and the U.S. Geological Survey (USGS). These three institutions are partners in the Yellowstone Volcano Observatory.

Data are transmitted to the University in real-time by radio and satellite links from a network of 28 seismographs in the Yellowstone area.