OhioSeis, The Ohio Seismic Network

The Division of Geological Survey of the Ohio Department of Natural Resources coordinates a 29-station cooperative network of seismograph stations throughout the state in order to continuously record earthquake activity. The network, which went on line in January 1999, ended a five-year gap during which there was only one operating station in Ohio. The state was dependent on seismographs in Kentucky and Michigan to record Ohio earthquakes.

It is surprising to many Ohioans that the state has experienced more than 200 felt earthquakes since 1776, and that 15 of these events have caused minor to moderate damage. The largest historic earthquake centered in Ohio was in 1937 in Shelby County. This event, estimated to have had a magnitude of 5.4, caused considerable damage in Anna and several other western Ohio communities. At least 40 earthquakes have been felt in the Anna area since 1875. Northeastern Ohio, east of Cleveland, has experienced many small earthquakes, including a 5.0 magnitude event in 1986 that caused moderate damage and a damaging 4.5 magnitude earthquake at Ashtabula in 2001. A broad area of southern Ohio has experienced more than 30 felt earthquakes.

The 29 stations of the Ohio Seismic Network are distributed across the state, but are concentrated in the most seismically active areas or in areas that provide optimal conditions for detecting and locating small earthquakes. These small earthquakes are important because they occur more frequently and help to identify the location of faults that may periodically produce larger, potentially damaging earthquakes.

The Ohio Seismic Network stations are operated by volunteers and are hosted by colleges, universities, and other institutions. The seismographs employ modern technology that not only makes them very accurate but also relatively inexpensive and easy to operate and maintain. In contrast to the old technology, in which a pen made a squiggly line on a paper drum, the modern systems record digital data and use GPS (Global Positioning System) to keep very precise time on the continuously recorded seismogram. Each station's computer is connected to the Internet for rapid data transfer.

Each seismograph station is a cooperative effort. The seismometer, the instrument that detects Earth motions, and other seismic components were purchased by the Division of Geological Survey with funds provided by the Federal Emergency Management Agency (FEMA), through the Ohio Emergency Management Agency, as part of the National Earthquake Hazards Reduction Program. The computers and Internet connection were provided by the cooperating institution.

The Division of Geological Survey coordinates the seismic network and operates from the Ohio Earthquake Information Center at the Division's Laboratory at Alum Creek State Park, north of Columbus. This facility functions as a repository and laboratory for rock core and well cuttings but has a specially constructed room for earthquake recording. The seismograph system allows for rapid location of the epicenter and calculation of magnitude of any earthquake in the state. The earthquake records, or seismograms, from at least three seismograph stations are needed to determine earthquake locations (epicenters). These records can be downloaded from the Internet from any station on the network, and location and magnitude can be determined.

The Ohio Seismic Network provides a new dimension of understanding about the pulse of the Earth beneath Ohio. Although the seismic network cannot predict earthquakes or provide an alert prior to an event, it provides insight into earthquake risk in the state so that intelligent decisions about building and facility design and construction, insurance coverage, and other planning decisions can be made by individuals, business and industry, and governmental agencies.