Since Sunday, there have been 901 measured earthquakes underneath Yellowstone National Park. The largest has been of magnitude 3.8. The swarm is now comparable to an earthquake swarm located in the Yellowstone Lake area a year ago.
"The swarm earthquakes are likely the result of slip on pre-existing faults rather than underground movement of magma," reported the United States Geological Survey on Thursday. "Currently there is no indication of premonitory volcanic or hydrothermal activity."
Two of the strongest earthquakes were measured on Wednesday night. Eight of the earthquakes have measured a magnitude of 3.0 or more.
While the vast majority of the earthquakes have been too small to feel, people in and around the park have reported feeling a few of them. The earthquakes have centered near the northwest edge of the Yellowstone Caldera.
The USGS believes there is nothing to indicate any serious cause for concern. Earthquake swarms have been quite common in the area since the time of the last major eruption 640,000 years ago.
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