Volcano Update from Archive

Monday, December 29, 2008 19:07 MST (Tuesday, December 30, 2008 02:07 UTC)

44.43°N 110.67°W, Summit Elevation 9203 ft (2805 m)
Volcano Alert Level: NORMAL
Aviation Color Code: GREEN

Earthquake swarm beneath Yellowstone Lake continues.


Released: December 29, 2008 05:00 PM MST

The University of Utah Seismograph Stations reports that a notable swarm of earthquakes has been underway since December 26 beneath Yellowstone Lake in Yellowstone National Park, three to six miles south-southeast of Fishing Bridge, Wyoming. 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 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 and are available on the web. Seismologists continue to analyze data from this swarm of earthquakes and provide updates to the NPS and USGS and to the public via the following web pages.

Information on U.S. earthquake activity including Yellowstone can be viewed at the U.S. Geological Survey web site: http://earthquake.usgs.gov/eqcenter/recenteqsus/

Information on earthquakes can also be viewed at the University of Utah Seismograph Stations web site:

Seismographic recordings from Yellowstone seismograph stations can be viewed online at:

Persons who felt any of the earthquakes are encouraged to fill out a survey form on the USGS 'Did You Feel It?' web site: http://earthquake.usgs.gov/eqcenter/dyfi/.

Geologic information, maps, and monitoring information for Yellowstone can be found on the Yellowstone Volcano Observatory web site at: http://volcanoes.usgs.gov/yvo/.

The Yellowstone Volcano Observatory (YVO) is a partnership of the U.S. Geological Survey (USGS), Yellowstone National Park, and University of Utah to strengthen the long-term monitoring of volcanic and earthquake unrest in the Yellowstone National Park region. Yellowstone is the site of the largest and most diverse collection of natural thermal features in the world and the first National Park. YVO is one of the five USGS Volcano Observatories that monitor volcanoes within the United States for science and public safety.