A 3.5 earthquake hit Yellowstone National Park this afternoon as the swarm of earthquakes that started Sunday continues to intensify.

The earthquake occurred at 2:32 p.m., according to scientists monitoring the current swarm.

Originally, scientists had said two 3.6 earthquakes struck in less than a minute – a mile apart.

A woman at the West Yellowstone, Montana Chamber of Commerce said the earthquake created a “rumble like a truck driving down the road.”

She added that the earthquake caused the icicles on the Christmas tree at the Chamber, which has not been taken down, to shake.

The swarm of earthquakes that started Sunday have now entered their third day.

Earlier today, at 9:48 a.m. , a magnitude 3.3 tremor was recorded.

On Monday night, a magnitude 3.4 tremor was recorded at 8:39 p.m.

Al Nash, spokesman for Yellowstone National Park, said that 469 earthquakes had been recorded in the swarm as of 3 p.m. today.

Nash said the earthquakes have been reported by multiple people in the park itself, and in neighboring communities in Montana and Idaho.

Jamie Farrell, a doctoral student in geophysics at the University of Utah, said the quakes are occurring in an area about 5 miles from where the largest swarm of quakes was ever recorded in October 1985.

The area is six miles due west of Yellowstone National Park’s Lower Geyser Basin, which is several miles north of Old Faithful.

Farrell said that there have been no reports of the quakes affecting the geysers in the park, but added there is a probability they will affect some of those thermal features.

So far scientists monitoring the swarm say the tremors seem to be normal tectonic activity, and is “not an indication” that some sort of volcanic activity will occur. However, they continue to monitor the situation.

“At this time the Yellowstone Volcano Observatory does not consider the swarm to be unusual and the earthquakes are likely related to tectonic fault sources,” the University of Utah said in a press release.

The university has more than two dozen earthquake monitoring stations in the park.

Prof. Robert B. Smith, a geophysicist at the University of Utah and one of the leading experts on earthquake and volcanic activity at Yellowstone, said that the activity is a “notable swarm.”

Farrell said there is absolutely no connection between what is occurring in Yellowstone and the magnitude 7.0 earthquake in Haiti.

“They are completely different systems,” said Farrell. “They are not related.”

In late December 2008 and early January 2009, Yellowstone National Park experienced the second largest earthquake swarm in Yellowstone’s recorded seismic history. The swarm under the north end of Yellowstone Lake consisted of 813 earthquakes with magnitudes ranging up to 3.9.

The most devastating earthquake in recent history in the Yellowstone region occurred on Aug. 17, 1959, when a magnitude 7.3 earthquake hit. It was centered near Hebgen Lake, Mont., killed 28 people and caused more than $11 million in damage.

Mike Stickney, director of earthquake studies at the Montana Bureau of Mines and Geology, said there is no way to predict when the next big one will hit.

He said it will likely occur along one of the 45 faults that line two belts – one stretching from Yellowstone National Park up to Helena, Mont., and a second one along the Montana-Idaho border.

The Yellowstone Plateau is one of the largest super-volcanoes in the world and has gone through three volcanic cycles spanning two million years, which included some of the world’s largest known eruptions.

Howard Pankratz: 303-954-1939 or hpankratz@denverpost.com