Geologists plan to install three portable devices known as seismometers or seismographs in the Challis area in central Idaho to help experts better understand a recent flurry of earthquakes.
The U.S. Geological Survey has recorded a sequence of quakes rumbling the area, the largest of which was a 4.9-magnitude quake on Saturday which shook pictures off walls. Challis residents also felt earthquakes above 4.0-magnitude on Monday and April 10.
Smaller quakes have also been recorded, including five on Monday ranging from 2.5 to 3.3 in magnitude. Three of the quakes took place within a 40-minute span starting about 9:12 p.m. Monday.
Virginia Gillerman with the Idaho Geological Survey told KBSX last week the lack of equipment made understanding what was going on in Challis difficult.
“We certainly could use a lot more seismometers that are installed within the state’s borders,” Gillerman says. “We rely heavily on distant seismometers; Salt Lake and some in Yellowstone and in other places. We don’t really have an Idaho seismic network like some states do.”
Gillerman explains the lack of seismic equipment in Idaho in one word: money.
The nearest seismograph to Challis is about 71 miles away in Montana, meaning earthquake locations in the Challis area could be off by 4 miles. Depths are also difficult to plot accurately. By putting three stations within 6 to 12 miles, the error could be reduced to about half a mile, according to Harley Benz, scientist in charge of the U.S. Geological Survey's National Earthquake Information Center. Benz said scientists decided Tuesday to put in the portable devices. One of them should be in place by Wednesday and two more within a week to record future earthquakes.
"It certainly has gotten the attention of the state and our regional partners," Benz said. "So what we're trying to do is put in an array to get a better feel for the location of the events and the depths and the rate of activity."
Benz said the three portable seismographs will provide real-time information and, using triangulation, allow scientists to pinpoint the locations of the earthquakes, including depth, should they continue. They'll also be able to record smaller quakes, down to about a 1.0 magnitude.
"We can find out where they are actually occurring and at what depth," Benz said. "One station will significantly help, and three will do better."
The plan is to put them in an L shape, he said.
"Ideally, you would like them to be in as quiet a spot as possible," Benz said. "The other problem with this part of the world is there is lots of snow. Finding sites is not going to be straightforward."
The seismographs will be installed by a field engineer from the University of Utah, he said. The engineer has two of the portable seismographs, and the U.S. Geological Survey is sending a third.
Idaho's quakes, Benz said, are caused by broad-scale deformation of the Western United States as a result of plate tectonics. The three portable seismographs could help scientists identify which fault is currently active, if the quakes continue.
The quakes have ranged from about 6 to 15 miles northwest of Challis in lightly populated Custer County.
"People are asking: 'Is this going to lead to a bigger earthquake?' "said Benz, based in Golden, Colo. "And the answer is we simply don't know."
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