Ohio site added to study

Sunday, August 20, 2006 There have been 15 earthquakes registered in Ohio this year. DELAWARE, Ohio (AP) — A site in a central Ohio park has become the latest piece in a national earth-monitoring system that researchers hope will help them learn more about the forces that cause earthquakes. Workers this weekend were installing a global positioning device at Alum Creek State Park to chart movements made by the North American geological plate — a large slab of rock that lies beneath the continent. The plate is among several that make up the Earth's crust. They float on a layer of molten material and are constantly in slow motion. When they collide, they produce earthquakes. Technicians are anchoring a stainless steel pole, topped by an instrument dome, in a rock layer deep underground. They expect to see the equipment move — up, down or sideways — a few centimeters over a year. The sensor, which sends data to satellites, is the first in Ohio and one of 852 to be installed in North America by 2008. They will create the $219 million EarthScope network of ground and satellite monitors managed by the National Science Foundation. How fast are they? The underground plates being monitored move at about "the rate your fingernails grow," said Mike Hansen, coordinator of the Ohio Seismic Network. "There are a lot of internal forces," Hansen said. "Some parts are moving faster than others, some are moving up, some are moving down, some are stretching and some are compressing." Each sensor in the EarthScope project will collect data at the millimeter level every 15 seconds. Position reports will then be sent to a Boulder, Colo., station, where they will be compiled and analyzed. Ohio has registered 15 earthquakes so far this year, most in the northeastern part of the state, with the strongest registering a magnitude of 3.8 on June 20. "We really don't know what the seismic risk is in Ohio," Hansen said. "Can there be a magnitude 6 quake? I don't know." While scientists aren't able to predict earthquakes, they believe tracking the plates' movements and understanding stresses that accumulate within the slabs as they shift might help researchers better pin down areas at risk.