Jan. 21, 2010

The number of earthquakes experienced since Sunday at Yellowstone National Park has now risen to 901 with two of the strongest quakes occurring late Wednesday, according to scientists monitoring the situation.

The swarm of earthquakes is one of the largest ever recorded at the park.

According to the University of Utah, which has more than two dozen monitoring stations in the park, a magnitude 3.7 quake occurred at 11:01 p.m. Wednesday followed by a 3.8 quake at 11:16 p.m.

Both shocks were nine miles southeast of West Yellowstone, Mont., according to the university.

Both quakes were felt throughout Yellowstone National Park and surrounding communities.

University scientists said that the two earthquakes are part of an ongoing swarm.

They said there have been 901 quakes in the swarm ranging from 0.5 to 3.8.

This includes eight events of magnitudes larger than 3, with 68 events of magnitude 2-to-3, and 825 events of a magnitude less than 2.

They say the swarm is likely the result of a slip in pre-existing faults and not a sign of a potential volcanic eruption.

However, they say they continue to monitor the situation.

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."

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

The largest swarm was 3,156 earthquakes during a three month period starting on Oct. 4, 1985, according to the university. The strongest earthquake in the swarm registered a magnitude of 4.9.

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.

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