Last week, Yellowstone National Park experienced its largest earthquake in nearly five years, with a magnitude 4.2 earthquake happening about 23 miles northeast of the East Entrance to the park.
The earthquake happened in an area known for earthquakes, scientists said.
The University of Utah seismograph stations reported the earthquake at 7:32 a.m., on May 11.
The quake was felt as far away as Bozeman and is considered “light” or “weak,” according to the Yellowstone Volcano Observatory. More than 30 earthquakes with a magnitude of 4.0 or greater have been recorded since 1973 in Yellowstone National Park.
A total of five earthquakes with a 3.0 magnitude or greater have occurred within 16 miles of the epicenter of Wednesday’s quake since 1962, scientists at the Yellowstone Observatory said. The largest nearby was a M4.2 earthquake that happened 20 miles northeast of the fishing bridge on March 25, 2008.
Fifteen “felt” reports – those are tracking forms the observatory uses to track how widely felt the earthquake was – were submitted from last week’s quake.
The earthquake took place at a depth of 8.7 miles and is the largest event that has happened since June 15, 2017 when a M4.5 happened, according to the observatory.
Wednesday’s quake was also not unusual for the area. The area between Hebgen Lake and Norris Geyser Basin, northeast of West Yellowstone, Montana, has seen a swarm of small earthquakes during the course of years.
However, Michael Poland, the scientist-in-charge of the Yellowstone Volcano Observatory and a geophysicist, said even though earthquakes are common in the area, residents shouldn’t be alarmed.
Oftentimes, aftershocks, or smaller earthquakes happen after a larger event, something that scientists said is a normal process.
“The location of Wednesday’s M4.2 is a region of abundant seismicity – one of several such regions in Yellowstone – so it’s not surprising that an M4 earthquake would occur in this location,” Poland said.
And, as far as the timing, there’s little to suggest that earthquakes in Yellowstone happen at a certain time of year.
“There might be a slight tendency for more earthquakes to occur during summer months, sincere there is more subsurface water due to snowmelt recharging the groundwater,” Poland said. “Because pore pressure increases can help promote fault slip, it’s not surprising that we might see more small earthquakes when there is more water in the subsurface.”