New GPS System May Help Predict Ohio Earthquakes
A new, highly sophisticated global positioning "monument" was installed this month on the grounds of the Ohio Earthquake Information Center north of Columbus. The instrument - the only one of its kind in the state - will detect minute movement in subsurface rock, helping scientists better understand the shifting of the North American landmass. It may also help them predict earthquakes in Ohio.
A two-man crew from the U.S. Geological Survey drilled down through glacial debris earlier this month as they installed a tripod for the base of a new instrument. According to the Ohio Seismic Network's Michael Hansen the system will transmit data to satellites orbiting the earth.
"The monument is anchored into the bedrock," Hansen says. "So as the bedrock moves the elevation and horizontal position of the instrument is recorded very precisely by signals coming in from a satellite constellation of GPS satellites."
The instrument in Alum Creek State Park is one of 852 in North America. Scientists hope the new system, collectively known as the EarthScope Plate Boundary Observatory, will give them a better understanding of the consequences of the continent's movement. Ohio and the rest of North America are being pushed westward by crust that's forming in the middle of the Atlantic Ocean. Michael Hansen says the shift is only about a millimeter or two per year - about the speed that fingernails grow. It's only felt, he says, when the stress of colliding rock is released by an earthquake.
"We've had about 200 felt earthquakes in Ohio's history and we've had about 15 earthquakes this year in Ohio," Hansen says. "Those earthquakes are occurring along ancient fault zones because of the stress that is being put on the continent."
70 miles west of Columbus, the Shelby County Village of Anna is enjoying unprecedented prosperity. There's the constant rumble of 18-wheelers as they go to and from the Honda engine factory just south of town. But almost 70 years ago there was another kind of rumble that hit Anna.
"It's was a definite sound of its own, like I never heard before. It's like it was, I don't know, like it was coming from someway off or something."
Willis Boyer was at school the morning of March 2, 1937 when the first in a series of earthquakes occurred. Boyer says he and his third grade classmates were too young to know what was happening. But eigth grader Ed Fridley, who was in the school's gym, says he knew exactly what was it was.
"We'd had some tremors before that," Fridley says. "I remembered being out in the country with my mom and dad sitting along side this farmhouse and you could feel the ground shake a little bit and the car started to rock. That was the first time I ever knew what an earthquake was."
The March 2nd earthquake did so much damage to Anna's two-story brick school that it had to be torn down.
"You could stand in the basement and go against an outside wall and you could look out and see the sky where the floors had separated.
Then a few days later, a stronger quake, estimated at 5-point-4, shook residents out of their beds around midnight. No one was killed in the series of quakes, but most of the town's chimneys fell, along with the west wall of the Lutheran church. And in a local cemetery south of town, where several generations of Ed Fridley's family are buried, something more curious had occured.
"Some of these stones were turned clockwise," Fridley says. "And in the cemetery just north of town, some of the stones were turned counterclockwise and that proved that the fault line ran right through Anna."
No one was killed in the earthquakes in '37, but they earned Anna the nickname "Earthquake Capital of Ohio." That title may be claimed by the Cleveland area which has had more than a dozen small quakes - in the two to 3-point-8 magnitude this year alone. Scientists say they don't know if a catastrophic earthquake lies in Ohio's future. The Ohio Seismic Network's Michael Hansen says a repeat of 1811's New Madrid quake would take 10,000 to 20,000 lives in the region, rupture oil and gas pipelines and do hundreds of billions of dollars in damage.
"We've had, surprisingly, 15 damaging earthquakes in Ohio's history," Hansen says. "One of our great concerns is, in the Midwest, large earthquakes have very large recurrence intervals. They can be on the order of hundreds or perhaps thousands of years. And we've only been recording earthquakes for a relatively short period of time so we don't know if Ohio could generate a much larger earthquake causing significant damage. That's why we're so keen on studying these earthquakes and understanding them."