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.
Yellowstone National Park has been hit by more than 2,500 since June, the second highest period of activity on record seismologists say. The Grand Prismatic hot spring is among the park’s many hydrothermal features created by a supervolcano beneath its surface
Earthquake swarms are common in Yellowstone and, on average, comprise about 50 per cent of the total activity in the Yellowstone region.
Swarms occur when many earthquakes take place over several weeks or months, with no clear sequence.
Traditional earthquakes feature a main event, followed by a series of aftershocks.
The University of Utah’s Seismograph Stations (UUSS) have been monitoring the activity since it began June 12.
Seismic activity could be a sign of an impending eruption of the supervolcano, although this is impossible to predict exactly.
Experts at the US Geological Survey (USGS) released the data as part of a monthly update.
Of the 115 quakes, 78 were part of an ongoing swarm six miles north of West Yellowstone.
The biggest event in the swarm last month was magnitude 2.3, which occurred at 6.59pm Mountain Time (8.59pm ET / 1.59am Sep 4 BST).
Speaking to Newsweek Mike Poland, the scientist in charge at the USGS’s Yellowstone Volcano Observatory, said it is a ‘bit too soon’ to say whether the swarm has ended.
He said: ‘The activity has certainly waned drastically since August, and the swarm appears to be winding down, if not completely over.
‘It will probably take a little while longer to declare it ‘over’.’
The ongoing swarm has included one earthquake of magnitude 4.4, 12 in the magnitude three range, and 185 earthquakes in the magnitude two range
Mr Poland says that the precise number of earthquakes that have taken place is difficult to work out, because they can overlap or are too small to be recorded.
There are methods available to work this out after the fact, however, so it may emerge that there have been many more earthquakes than initially reported.
‘This is the sort of work that will happen in the months to come, as we gather up all of the available data and start crunching numbers,’ he added.