Yellowstone Volcano Earthquake Swarm Sees 100 Events Recorded in One Day

An earthquake swarm of almost 100 events in a single day has been recorded at Yellowstone volcano.

Scientists with the Yellowstone Volcano Observatory (YVO) said the event, which took place on September 10, was located between Heart Lake and West Thumb, to the southwest of Yellowstone Lake. "Seismologists will have their hands full analyzing all of these exciting data this fall and winter," the YVO said in a statement.

Earthquake swarms are a series of minor seismic events located in the same area at the same time. They may not be associated with a specific fault or initial, larger earthquake. They occur regularly in Yellowstone National Park, accounting for around half of all seismic activity in the region.

The September 10 event was a natural earthquake swarm recorded with some of the 600-plus seismic stations deployed across the park. According to the University of Utah, which tracks seismic activity in the park, the swarm included two earthquakes on September 9 and 95 earthquakes on September 10. Magnitudes ranged from -0.1 to 2.8.

This was the largest earthquake swarm recorded at the park for several months. Over August, a total of 82 earthquakes were recorded at the park, with a swarm of 12 earthquakes taking place around 12 miles from the Old Faithful geyser on August 18. In July, there were 135 earthquakes, including a swarm of 78 earthquakes with the largest event measuring magnitude 2.9. In June, there were 102 earthquakes in total.

Michael Poland, the scientist-in-charge at the YVO, told McClatchy News that although the swarm was on the "large side" it was nowhere near the biggest earthquake swarm to hit Yellowstone.

Poland told Newsweek the swarm appears to be associated with fault movement perhaps helped by hydrothermal fluids moving around the subsurface. "That is a common cause for many—perhaps most—Yellowstone earthquake swarms," he said in an email.

"The Yellowstone region is extensively faulted due to it's tectonic setting on the eastern boundary of the Basin and Range extensional province, so it's a very tectonically active area. All of that water in the subsurface, and overall weakening due to the heat supplied by the magmatic system, heightens that activity."

The September 10 recording happened during a major seismic experiment being conducted by researchers at the University of Utah and the University of New Mexico. At the end of August the team deployed hundreds of small seismometers around the park. They then generated synthetic earthquakes by shaking the ground with low-frequency waves using specialized trucks.

Because of these extra sensors deployed across the park, the latest earthquake swarm was recorded with an unparalleled level of accuracy.

"The purpose of this experiment is to use the seismic waves to image the shallow subsurface, including the top of Yellowstone's magma chamber," the YVO said. "It's a bit like taking an MRI of the Earth. Previous work has used naturally occurring earthquakes to do the imaging, which has resulted in a map of Yellowstone's magmatic system."

By generating synthetic earthquakes, the team will be able to see what lies beneath the surface of Yellowstone with a higher resolution than before. "The view of Yellowstone's upper magmatic system should get even better once scientists have a chance to examine these results," the statement said.

This article has been updated to include quotes from Michael Poland.