Scientists monitor rash of Yellowstone quakes

CHEYENNE, Wyo. — Scientists were closely monitoring more than 250 small earthquakes that rattled Yellowstone National Park over the weekend and into Monday.

Swarms of small earthquakes happen frequently in Yellowstone. But Robert Smith, a professor of geophysics at the University of Utah, said it's very unusual for so many earthquakes to happen over several days.

"This is an active volcanic and tectonic area, and these are the kinds of things we have to pay attention to," Smith said. "We might be seeing something precursory.

"Could it develop into a bigger fault or something related to hydrothermal activity? We don't know. That's what we're there to do, to monitor it for public safety."

Smith directs the Yellowstone Seismic Network, which operates seismic stations around Yellowstone National Park. He said the quakes have ranged in strength from barely detectable to one of magnitude 3.8 that happened Saturday. A magnitude 4 quake is capable of producing moderate damage.

The strongest of dozens of tremors Monday was a magnitude 3.3 quake shortly after noon. All of the quakes were centered beneath the northwest end of Yellowstone Lake.

"They're certainly not normal," Smith said. "We haven't had earthquakes in this energy or extent in many years."