January 21, 2010
Jamie Farrell, Univ of Utah, 801-581-7856
University of Utah Seismograph Stations
Released: January 21, 2010 2PM MST
This release is a continuation of information updates building upon our two previous press releases on the ongoing earthquake swarm on the west side of Yellowstone National Park.
The University of Utah Seismograph Stations reports that a pair of earthquakes of magnitude 3.7 and 3.8 occurred in the evening of January 20, 2010 in Yellowstone National Park.
The first event of magnitude 3.7 occurred at 11:01 PM and was shortly followed by a magnitude 3.8 event at 11:16 PM. Both shocks were located around 9 miles to the southeast of West Yellowstone, MT and about 10 miles to the northwest of Old Faithful, WY. Both events were felt throughout the park and in surrounding communities in Wyoming, Montana, and Idaho.
These two earthquakes are part of an ongoing swarm in Yellowstone National Park that began January 17, 2010 (1:00 PM MST). The largest earthquake in the swarm as of 12 PM, January 21, 2010, was a magnitude 3.8.
There have been 901 located earthquakes in the swarm of magnitude 0.5 to 3.8. This includes 8 events of magnitude larger than 3, with 68 events of magnitude 2 to 3, and 825 events of magnitude less than 2.
There have been multiple personal reports of ground shaking from observations inside the Park and in surrounding areas for some of the larger events (for felt reports, please visit http://earthquake.usgs.gov/eqcenter/dyfi/). Earthquake swarms are relatively common in Yellowstone.
The swarm earthquakes are likely the result of slip on pre-existing faults rather than underground movement of magma. Currently there is no indication of premonitory volcanic or hydrothermal activity, but ongoing observations and analyses will continue to evaluate these different sources.
Seismic information on the earthquake can be viewed at the University of Utah Seismograph Stations: http://www.seis.utah.edu/.
Seismograph recordings from stations of the Yellowstone seismograph network can be viewed online at: http://quake.utah.edu/helicorder/yell_webi.htm.
Anyone who has felt earthquakes in the swarm are encouraged to fill out a form on the USGS Community Felt reports web site: http://earthquake.usgs.gov/eqcenter/dyfi/.
This press release was prepared by the Yellowstone Volcano Observatory partners of the U.S. Geol. Survey, the University of Utah, and the National Park Service: http://volcanoes.usgs.gov/yvo/