The University of Utah Seismograph Stations detected a magnitude 3.0 and 3.1 earthquake Sunday at 11:09 and 11:21 p.m., respectively, in Yellowstone National Park.
Both shocks were located around nine miles southeast of West Yellowstone and about 10 miles to the northwest of Old Faithful. There were no reports of the events being felt.
These two earthquakes are part of an ongoing swarm in Yellowstone National Park that began Jan. 17. The largest earthquake in the swarm was a magnitude 3.8.
There have been 1,271 located earthquakes in the swarm of magnitude 0.5 to 3.8. This includes 11 events of magnitude larger than 3, with 97 events of magnitude 2 to 3, and 1,163 events of magnitude less than 2. There have been several reports of the ground shaking from observers inside the park and in surrounding areas for some of the larger events.
Earthquake swarms are relatively common in Yellowstone.
The swarm is likely the result of slip on pre-existing faults. The quakes are not thought to be caused by underground movement of magma, according to the university. There is no indication of the swarm is leading up to a volcanic or hydrothermal event, but ongoing observations and analyses will continue.
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 is encouraged to fill out a form on the USGS Community Felt reports Web site: http://earthquake.usgs.gov/eqcenter/dyfi/.