An earthquake swarm at Yellowstone is now one of the biggest ever, with 2,475 tremors recorded since it began in in June.
Records show that 115 earthquakes were reported in the western part of the national park during September.
The largest swarm ever to occur at Yellowstone took place in 1985, with more than 3,000 events over a three month period.
Experts at the US Geological Survey (USGS) released the data as part of a monthly update.
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