Seismic activity in Yellowstone National Park “has markedly decreased” in the past two days, possibly indicating that a swarm of quakes is ending, the Yellowstone Volcano Observatory said Tuesday.
However, observatory officials said, swarms of the size experienced beginning Dec. 26 “usually last for tens of days to many weeks.”
The swarm of tremors is the largest series of back-to-back quakes to hit the area in years, according to scientists.
The observatory said about 500 quakes occurred between Dec. 26 and Thursday.
Three hundred of the quakes have been reviewed by seismologists. Of the quakes, 86 had a magnitude of 2.0 or greater and 16 a magnitude of 3.0 or greater.
Most of the earthquakes have been from 1.8 to 6 miles underground. Scientists say that most of the quakes have been under Yellowstone Lake and have migrated northward.
“The recent swarm is well above typical at Yellowstone,” officials said. “Nevertheless, it is not unprecedented during the last 40 years of monitoring.”
Howard Pankratz: 303-954-1939 or hpankratz@denverpost.com
