Three North Carolina Central University students are participating this summer in the EarthScope project, a vast nationwide effort aimed at developing a broad understanding of the formation and structure of the North American continent.
The NCCU students — Philip Martin, James Howard and Thomas Horne — are seeking suitable locations in North Carolina and southern Virginia for 25 USArray seismic stations. The USArray component of EarthScope consists of 400 seismic stations that are deployed in a grid about 75 kilometers apart and transmit data for two years before moving to the next location.
The project began a decade ago in the West, and is now reaching the East Coast. Gordana Vlahovic, associate professor in the NCCU Department of Environmental, Earth and Geospatial Sciences, and post-doctoral associate Pierre Arroucau are overseeing the NCCU portion of the project, which is funded by the National Science Foundation. Last year, EarthScope was named “the most epic project in the universe” by Popular Science magazine’s website www.popsci.com
“We think of EarthScope as being like a telescope, only instead of looking up we’re looking down,” Vlahovic said. “We’re looking very deep into the earth to understand more about it.” Each USArray station includes instruments to continuously sense, record, and transmit ground motions from a wide range of seismic sources — local and distant earthquakes, artificial explosions, volcanic eruptions and other natural and human-induced activities.
“Distant earthquakes are like X-rays of the earth,” Vlahovic said. They transmit a wide frequency range of seismic waves through the Earth, and differences in arrival time tell us about the structure.”
The ideal sites for the stations are far from roads, railroads and other sources of noise that can interfere with seismic signals. They must have good cell phone reception so that data can be transmitted in real time, and the sites must belong to landowners willing to host the station for two years. Each station is about the size of a large refrigerator, containing instruments locked inside a vault and powered by solar panels.
“We look for sites in the middle of nowhere, but with good access,” said Vlahovic. Martin, one of the three students, said finding ideal sites has been a challenge. “There’s less middle-of-nowhere in North Carolina than you’d think,” he said. “We like to be at least 3 kilometers from a big highway and at least 1 kilometer from a local two-lane road. It’s hard to find a site without multiple crisscrossing highways.
“The golden ticket is a private landowner with enough land that you can get away from houses, trees and roads,” said Martin, a master’s student in earth science specializing in seismology. The general approach to finding a site said, was to first scan aerial and satellite photos of a given region to locate large roadless areas — usually on farms — and then use tax records to identify the owner.
More often than not, though, large tracts of farmland turned out to be owned by corporations, not local families. “There’s a lot of red tape involved in getting permission to use the site for two years or more,” Martin he said.
Martin, Howard and Horne prepared for the project by attending four days of training in May at the University of Pittsburgh, where they learned criteria for site selection, how to use GPS and GIS software and how to talk to landowners about hosting the stations. Since then, they have been driving 1,000 or more miles each week searching for the sites.
The information gathered from the seismic stations will have practical applications, Vlahovic said. “The geology of the Eastern and Central U.S. is very complicated,” she said, “and there is little understanding of big earthquakes in the region. They’re infrequent but they can be big.” An 1886 earthquake caused widespread damage and killed dozens of people in Charleston, S.C., and a series of earthquakes in southeastern Missouri in late 1811 and early 1812 were the strongest ever recorded anywhere in the East or Midwest.