A swarm of 91 earthquakes rattled the Yellowstone National Park region in just 24 hours on Thursday, according to the United States Geological Survey. The quakes trembled southwest of Yellowstone Lake between Heart Lake and West Thumb.
Although the area is one of the most seismically active regions in the U.S., the cluster of quakes “is on the large side in terms of number and magnitude, but nowhere near the largest,” Michael Poland, scientist-in-charge at the Yellowstone Volcano Observatory, told McClatchy News in an email.
“Yellowstone has had swarms that include many hundreds of earthquakes in a day,” Poland said. “For example, there was a 3-month-long swarm that occurred in June-September 2017 with 2,400 located earthquakes and maximum [magnitude] 4.4”.
The recent cluster of quakes didn’t pass 3.0 magnitude. The biggest temblor was recorded at 2.8 magnitude, while the weakest was measured at 0.1 magnitude. It’s when earthquakes reach magnitudes between 2.5 and 5.4 that activity is usually felt, with minor resulting damage.
What’s more, the 91 quakes rattled alongside “fake” tremors set off by a “vibroseis” truck driven through Old Faithful, West Thumb, Canyon Village and Lake Butte as part of an experiment conducted by the University of Utah and University of New Mexico, Poland added.
These trucks are giant vehicles that can weigh up to 70,000 pounds that vibrate steel plates on the ground, sending low frequency energy through it; they are helping to create images of the top of Yellowstone’s magma chamber — or that sleeping “supervolcano” people fear will explode unannounced — with the help of hundreds of temporary seismometers located across the park.
Read more: Miami Herald