UK gives new seismic data

By Eva McEnrue

A new range of seismic instruments operating in a deep hole in western Kentucky will provide valuable data on earthquake activity in the central United States.

The Kentucky Geological Survey, a UK research center, drilled nearly 2,000 feet to install and operate the New Central U.S. Seismic Observatory (CUSSO), the deepest seismic observatory in the eastern half of the U.S.

“The bedrock in the Mississippi Valley is overlain with thick deposits of sand, gravel and clay. The thickness is nearly 2,000 feet in western Kentucky and increases to over 3,000 feet by the time you reach Memphis, Tn.,” Earth and Environmental Sciences faculty member Ed Woolery said.

Woolery managed the development of CUSSO with KGS. The sediment can sometimes amplify or alter earthquake motions, but its extent has only been modeled. These geologic conditions are not found in other seismically active areas in the world. CUSSO will allow geologists for the first time to assess and calibrate those predictive ground motions, said Woolery.

“Date collected will help geologists and engineers better define the earthquake hazard in the region,” said KGS geologist Zhinming Wang. “Finding out more about the nature of the earthquake hazard will have an important effect on economic development in the region because data collected by the observatory will be used to insure that building codes and construction practices are appropriate for mitigating potential earthquake damages in the region.”

CUSSO includes an array of earthquake-sensing instruments and is able to record and transmit information to KGS scientists in Lexington. The observatory is located near the center of the New Madrid Seismic Zone, the source of several earthquakes in 1811 and 1812 which shook the eastern half of the U.S. and parts of Canada. CUSSO expects to acquire the most useful information in the shortest amount of time. The observatory recorded ground shaking at multiple depths from the small Dec. 30, 2010 Indiana earthquake, according to the KGS.

The KGS installed the instruments in a four-inch diameter, steel-cased borehole that was drilled 1,950 feet deep to bedrock at Sassafras Ridge in western Fulton County, Ky., according to the KGS. CUSSO joins 25 other seismic monitoring stations in the Kentucky Seismic and Strong-Motion Network operated by the KGS.

Drilling of the borehole was completed in late 2006. The KGS and its partners then applied for funding to build and install the instruments. Five partners involved in the project committed a total of $295,652, including the U.S. Department of Energy, the Kentucky Research Consortium for Energy and the Environment, the UK Department of Earth and Environmental Sciences, the KGS and the U.S. Geological Survey.

“It provides our students with a state-of-the-art field laboratory in which they can do hands-on data collection in order to answer fundamental scientific questions,” Woolery said.