A statement from the University of Utah, which monitors seismic activity in the Yellowstone region, said the earthquake hit on May 11 at 8:35 a.m. local time. The epicenter of the earthquake was 23 miles northeast of the eastern entrance to Yellowstone National Park.
“A total of five earthquakes of magnitude 3.0 or greater have occurred within 16 mi of the epicenter of this event since 1962,” the statement said. “The largest of these events was a magnitude 4.2 on March 25, 2008, 20 mi [northeast] of Fishing Bridge, [Wyoming].”
The Yellowstone region is one of the most seismically active areas in the U.S., with earthquakes recorded in the area all the time. In April, the region was hit by 141 earthquakes, the largest of which being a magnitude 2.5 event on April 30.
An annual report published by the U.S. Geological Survey (USGS) showed the total seismic activity at the park in 2021 included 2,773 earthquakes—1,000 more than how many hit the park in 2020.
At time of writing, 42 people had reported they felt the 4.2 magnitude earthquake. A statement from Yellowstone Volcano Observatory (YVO) said most reports described shaking as being “weak” or “light.” The YVO said over 30 earthquakes of magnitude 4.0 or above had hit Yellowstone since 1973.
“Today’s earthquake, which took place at a depth of 14 km (8.7 miles), is the largest to occur in Yellowstone National Park since a M4.5 event on June 15, 2017 (part of a long-lived swarm of small earthquakes in the area between Hebgen Lake and Norris Geyser Basin, northeast of West Yellowstone, [Montana],” the statement said.
Yellowstone 2017 Earthquake Swarm
The 2017 earthquake swarm at Yellowstone saw around 2,500 tremors recorded over a three-month period. It was one of the biggest earthquake swarms ever recorded at the park. The largest earthquake swarm on record took place in 1985, when over 3,000 earthquakes hit the area in three months.
In 2018, David Shelly, a seismologist with the USGS, examined the cause of the swarm, saying it appeared to have been driven by water moving through small cracks in the subsurface.
“Because this water is under great pressure in the deep crust where it is released, it tends to migrate upward and sometimes laterally,” he wrote in a blog post. “When it interacts with cooler, more brittle rocks stressed by tectonic and volcanic processes, this water may trigger earthquakes. In fact, earthquakes themselves may allow the fluid to migrate more efficiently, through faults in the rock.”