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February 4, 2010
By Jed Boal

SALT LAKE CITY -- Earthquakes are rumbling Yellowstone National Park with seismic activity not felt there in a quarter century. During the last two weeks, sensors recorded nearly 2,000 small earthquakes not far from Old Faithful geyser.

Map of Yellowstone National Park showing recent swarm earthquakes in red, previous swarms from 1995-2009 in green, and volcanic vents with yellow stars. The histogram at the top right shows the number of earthquakes per day from Jan. 15 to Feb. 3. Image by Jamie Farrell and Robert B. Smith (University of Utah), data from the University of Utah Seismograph Stations.

Experts say this swarm of temblers has nothing to do with the quake that rocked Haiti January 12. Also, the cluster of quakes does not mean a big one is ready to rock the region.

Still, scientists are fascinated and want to find out more. In fact, Yellowstone has been rumbling all day.

Ten miles northwest of Old Faithful and 10 miles southeast of West Yellowstone, a swarm of earthquakes has rumbled in the range of magnitude 2.5 to 3.9.

Robert Smith is a University of Utah geophysics professor and a science coordinator at the Yellowstone Volcano Observatory. Despite the remote area of the swarm, he says people are feeling the earth move and are reporting it.

"Things are rattling," says Smith. "Door jams are shaking. Chairs are shaking. I haven't heard of any damage."

The swarm started January 18 and peaked January 21. Activity declined for about 10 days, then picked up again Tuesday around 4:00 p.m. -- and it's still going on.

Earthquake Swarms

Earthquake swarms are common in Yellowstone, with magnitudes occasionally above 4.0.

• There were about 900 earthquakes during the December 2008-January 2009 Yellowstone Lake Swarm.

• Another large swarm occurred in July of 1995 west of the Norris Geyser Basin . There were approximately 480 events over a 7-day period ranging in magnitude from 0.2 to 3.1.

• The largest recorded swarm at Yellowstone remains the fall 1985 swarm, located in the NW corner of the Yellowstone Caldera. There were over 3,000 total events recorded, with magnitudes ranging up to 4.9.

Sensors at the University of Utah Seismograph Stations have picked up nearly 1,800 events in the swarm -- on average, more than 100 quakes a day.

Smith says Swarms are relatively common. Scientists have recorded about about 80 in the last 20 years.

"A swarm can last from a few minutes to days, to months," says Smith.

In 1985, a swarm of 3,000 quakes lasted three months. The geophysicist says this swarm of seismic activity is more cause for study than alarm.

"We see no evidence or change in safety," he said. "Yellowstone's still a great place to visit."

The Observatory has not recorded movement of magma deep below the earth's surface that would indicate a volcanic eruption.

"We can record very short period shakings versus very long period shakings, which might be indicative of fluid motion," Smith said.

Scientifically, Smith and his colleagues say this is very important, because their digital seismographs let them record the rumbling with great accuracy and view it in real time.

"The world's watching this on their computers, literally, from Europe, from Asia, from America, people are looking at it," says Smith. "Teachers are using it to teach with."

The earthquake in Haiti raised a lot of interest worldwide about earthquakes, and major national publications have talked to Smith about his work in recent days.