Earthquake Monitors Placed in North Dakota

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North Dakota, known for blizzards and floods, is getting sensors to check for earthquakes as part of a national project listening to what happens underground.

The possibility of a big quake damaging the state is remote: Only a handful of quakes have been recorded in North Dakota, and the biggest one 40 years ago shook barely enough to rattle dishes. Still, scientists say they are finding low-level tremors.

Seismometers were installed last fall in Westby in northwest North Dakota and near Maddock in the north central part of the state, said Fred Anderson, a geologist with the state Geological Survey in Bismarck. The sites have recorded one small earthquake each, he said.

Another 28 seismometers are being installed around the state this summer, and seven more will be buried next year, Anderson said. The equipment will remain in place for two years and then be moved as the project “leapfrogs” eastward, he said.

“We’re hoping to learn everything from fundamental science of the earth to refining our understanding of when and where earthquakes are occurring,” Anderson said.

The National Science Foundation’s EarthScope project will cover the entire U.S. with sensors, said Bob Woodward, a project director in Washington, D.C. Started in 2003, it will wrap up in 2013.

“It’s sort of like doing an ultrasound across the belly of Mother Earth,” Woodward said.”‘We’re hoping to learn a lot about structure inside the earth.”

Four hundred monitors are in place at one time, and data is transmitted to centers in Seattle and San Diego for use by researchers, Woodward said. About 1,600 sites across the country have been chosen for the project, and instruments have been placed at 800 locations so far, he said.

The 28 monitors being placed in North Dakota over the next few weeks will be mainly on private land, Anderson said. The seismographs usually are in a grid, some 43 square miles apart, he said.

The instruments are buried a few feet underground, and typically have “a solar panel, a couple of antennas, and maybe some fence around them to keep the cows out,” Anderson said.

Data is transmitted from the locations using mostly cell phone technology, Woodward said.

While most of the seismometers will be dug up and moved after two years, the site at Maddock has been proposed as permanent seismic monitoring station. North Dakota is one of the last states without a permanent facility, Woodward said.

North Dakota’s only earthquake to be felt by people struck the state on July 8, 1968. Its epicenter was reported southwest of Huff, near Bismarck, and the quake was felt over a 3,000-square-mile area, Anderson said.

Only four other quakes, including the two in the past year, have been “instrumentally verified” in North Dakota, Anderson said. But more low-magnitude quakes likely will be recorded now that seismographs are in place.

“The likelihood of what we’re going to see is going to increase,” Anderson said, “just because we’re listening.”