Caldera chronicle: 2,773 earthquakes in Yellowstone last year

Yellowstone Caldera Chronicles is a weekly column written by scientists and collaborators of the Yellowstone Volcano Observatory. This week’s contribution is from Dan Dzurisin, emeritus geologist with the U.S. Geological Survey.

How many earthquakes occurred in the Yellowstone region in 2021? How many times did Steamboat Geyser erupt? What geological mapping was completed during the year?

Good questions. And now, the answers to these questions, and more, are all compiled in one easy-to-navigate source—the Yellowstone Volcano Observatory 2021 Annual Report, which can be accessed at https://pubs.er.usgs.gov/publication/cir1494.

In the publication, you can find details about Yellowstone seismicity over the course of 2021. For example, there were 2,773 earthquakes located by the University of Utah Seismograph Stations, including 10 magnitude 3 earthquakes, 163 magnitude 2 earthquakes, and 2,600 earthquakes with magnitudes less than 2. Of the total number of earthquakes, 65% occurred as part of swarms (defined as the occurrence of many small earthquakes in the same small area over a relatively short period of time). The largest swarm of 2021 included 825 events beneath Yellowstone Lake during July 15–25.

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