Historic Earthquakes and Future Insight
A new research project at the University of Tennessee, Knoxville will provide the first-ever record of seismic activity in the Tennessee Valley, providing new information not only on past quakes but insight into future activity, as well.
Led by Robert Hatcher, UT Knoxville distinguished scientist and professor of earth and planetary sciences, the research team will explore sites from just north of Knoxville, Tenn., through the Chattanooga area to just north of Rome, Ga.
The Second Most Active Area in the East
The area, known as the East Tennessee Seismic Zone (ETSZ), is the second most active area for earthquake activity in the eastern U.S. The Nuclear Regulatory Commission is funding the study.
There are currently more than 20 applications for new nuclear plants in the Southeast, and Hatcher says the need for new information in determining their feasibility is behind the study.
"We have been working to get this study funded for more than 20 years," said Hatcher. "An understanding of seismic history in the ETSZ will let us know what is possible here, and that's vital in planning new large engineered structures."
A lack of large historic earthquakes is the key factor in why the ETSZ receives less attention than an area such as the New Madrid seismic zone around Memphis. The team will scour the area, both on the ground and using satellite photos, for geologic features called "sandblows."
Hidden Faults That Do Not Cut The Surface
Major earthquakes in the eastern U.S. generally occur on faults below the earth's surface. Instead of leaving a gash in the earth, the activity can cause sand buried in stream deposits to liquefy and force its way to the surface forming sandblows. From the air, they look like mottled white spots on the ground.
Sandblows may act as a sign to pinpoint the sites of major earthquakes sometime in recent prehistory, said Hatcher. The government and private companies with plans to build major new facilities are most interested in quakes that have occurred in fairly recent times, at least in the geological scale, so team members are focusing on former streambeds that would show evidence of quakes that occurred in the past several thousand years.
"If we know that a major earthquake has occurred in an area," said Hatcher, "then it greatly increases the likelihood that one will occur again."
Information for Engineers and Architects
Knowing more about the possible strength and frequency of major earthquakes will allow engineers and architects to design new facilities, such as nuclear or conventional power plants, to stand up to the seismic rigors they may face over their lifetime.
For the research team, the information they'll discover will also help fill in the blanks of how and possibly why earthquakes occur in areas like the Tennessee Valley or the New Madrid seismic zone.
Located far from the edges of tectonic plates, where the mechanics of earthquakes are better understood, quakes in these "intraplate" areas have included some of the most devastating recent events, such as the one in Gujarat, India, that killed more than 20,000.
Members of the research team include Hatcher, Stephen Obermeier of the U.S. Geological Survey, an authority on seismic features in the New Madrid seismic zone in West Tennessee and adjacent states; James Vaughn of the Missouri Geological Survey, an authority on formation of the present landscape of the Appalachians; and Hugh Mills of Tennessee Technological University, an authority on Appalachian landscape evolution.
|Map of special seismic zones in the Central and
Eastern United States. Note the cluster of earthquakes that form the Eastern Tennessee Seismic Zone. USGS image.
|Earthquake hazard map for the 48 states showing the Eastern Tennessee Seismic Zone as an area of moderate earthquake hazard. USGS image.