On Aug. 17, 1959, back when Dwight D. Eisenhower was president, the U.S. had yet to send a human to space and the nation’s flag sported 49 stars, Yellowstone National Park shook violently for about 30 seconds. The shock was strong enough to drop the ground a full 20 feet in some places. It toppled the dining room fireplace in the Old Faithful Inn. Groundwater swelled up and down in wells as far away as Hawaii. Twenty-eight people died. It went down in Yellowstone history as the Hebgen Lake earthquake, with a magnitude of 7.2.
And in 2017, nearly 60 years and 11 presidents later, the Hebgen Lake quake shook Yellowstone again. A swarm of more than 3,000 small earthquakes in the Maple Creek area (in Yellowstone National Park but outside of the Yellowstone volcano caldera) between June 2017 and March 2018 are, at least in part, aftershocks of the 1959 quake. That’s according to a study published in Geophysical Research Letters by University of Utah geoscientists led by Guanning Pang and Keith Koper.
“These kinds of earthquakes in Yellowstone are very common,” says Koper, director of the University of Utah Seismograph Stations. “These swarms happen very frequently. This one was a little bit longer and had more events than normal.”
“We don’t think it will increase the risk of an eruption,” Pang adds.