EarthScope: A Seismic Shift in Data Gathering - Miller-McCune
Two hundred years after the New Madrid quake rocked the U.S., Earthscope, a traveling scan of what lies underneath North America, reveals more about earthquakes and volcanoes.
On Feb. 7, 1812, a magnitude 7.7 earthquake pummeled the Mississippi River town of New Madrid. The quake, which was then the largest in U.S. history, was the fourth temblor to hit the region in a three-month span, and newspapers reported that people as far away as New York and Charleston, S.C. felt the vibrations. In one account, the shaking centered in the Louisiana Territory, about 150 miles south of St. Louis, caused bells to toll out of turn in Boston.
Even though hundreds of smaller quakes occur annually in the New Madrid Seismic Zone, scientists are at a loss to explain when and how the area’s faults become more active. Nothing as potent as the 1811-12 quakes has happened there since then. Plus, New Madrid is roughly at the center of the North American continent, thousands of miles away from the plate boundaries normally associated with seismic and volcanic activity.
“There’s geologic evidence that something about this area is different,” said Chuck Langston, director of the Center for Earthquake Research and Information (CERI) at the University of Memphis. “Gravitational pull is stronger there; it could be because of greater mass [below the surface].”
To gain a greater understanding of the subsurface geologic structure, researchers started a moving, continent-wide imaging effort called EarthScope. As it creeps across the continent, Earthscope measures subsurface conditions in multiple ways — one geologist compares it to giving North America a series of CT scans and MRIs — allowing scientists to compare different models and create a clearer, more complete picture of what it looks like down there.
“If you actually looked at the geologic features under the surface, it would be as striking as looking at the Himalayas,” Langston explained.