More than 1,000 small to moderate earthquakes have been recorded in Yellowstone National Park since Sunday, according to the National Park Service.
That’s more than half the total annual average in the park — 1,600 a year. Last year, a swarm of more than 800 quakes near Yellowstone Lake was recorded in late December and early January. All told, more than 1,650 earthquakes were recorded in the park in 2009.
“A lot of these events are quite small,” said Peter Cervelli, acting scientist in charge of the Yellowstone Volcano Observatory. “The total energy released is less than a magnitude 4.”
The seismic activity is centered in the northwest corner of the Yellowstone Caldera, in the backcountry roughly halfway between Old Faithful and West Yellowstone. Ten of the earthquakes have been magnitude 3.0 or greater, with a 3.8 magnitude earthquake recorded late Wednesday evening. The larger quakes have been felt by people in Old Faithful, West Yellowstone, Canyon, Mammoth Hot Springs, Grant Village, Madison and Gardiner. No damage or injuries have been reported. More than 800 of the quakes have been less than magnitude 2.0.
Most earthquakes of magnitude 3.0 aren’t felt. It typically takes an earthquake of magnitude 4.0 or greater to cause structural damage, and a magnitude 6.5 earthquake to cause the surface of the ground to rupture.
The current earthquake activity is due to the shifting and changing pressures in the earth’s crust, and not to any change or increase in volcanic activity in Yellowstone, scientists agree.
Cervelli said scientists are detecting more of the smaller quakes because of better monitoring.
“Our ability to locate events keeps getting better,” he said.
Cervelli said there is no known reason why last year’s swarm and this year’s occurred in roughly the same season.
The National Park Service is using the occasion to reinforce earthquake preparedness and to remind employees and visitors how the unique and active geologic nature of the park has resulted in the creation of the world’s largest collection of geysers, hot springs and other hydrothermal features.
Earthquake activity is monitored around the clock by staff of the Yellowstone Volcano Observatory, a cooperative effort of the National Park Service, the U.S. Geological Survey and the University of Utah.
A continually updated map and list of earthquakes in Yellowstone is available online at http://www.seis.utah.edu/req2webdir/recenteqs/Maps/Yellowstone.html.
More information on the Yellowstone volcano and the park’s geothermal systems can be found on the Greater Yellowstone Science Learning Center Web site http://www.greateryellowstonescience.org.