THREE EARTHQUAKES RECORDED IN OHIO DURING 1995
(from Spring 1996 Ohio Geology)
Three small earthquakes were recorded in Ohio during 1995. The first one struck at 7:57 a.m. local time on Sunday, February 19, in southeastern Highland County. Ronald Street, seismologist at the University of Kentucky, recorded this event on two of his seismograph stations in northern Kentucky and was able to provide the epicentral location and a magnitude of 3.6. The earthquake also was recorded on the MOMA seismic array.
The U.S. Geological Survey reported Modified Mercalli intensities of V at Cynthiana in western Pike County, IV at Seaman and III at Winchester in northern Adams County, and III at Mowrystown in southwestern Highland County.
Locations of 1995 earthquakes.
Robert G. Van Horn, Deputy Chief of the Ohio Geological Survey, felt the earthquake at his weekend farm in southwestern Ross County, near Bainbridge. Fred N. Bowman, of the same area, also felt the earthquake.
Historically, Highland County and adjacent Pike and Ross Counties have had very low seismic activity--each county had recorded only one event, all of them in the last century. However, in 1994, a 2.5-magnitude event was recorded in western Pike County.
Another earthquake occurred at about 4:32 a.m. local time on Thursday, February 23, in Ashtabula, in northeastern Ohio. According to Ed Somppie, Ashtabula County Emergency Management director, this 2.9-magnitude event woke many residents, as numerous felt reports were received at his office. Many people thought that it was a sonic boom. The lack of seismographs in the area made it difficult for the Division of Geological Survey to confirm that the event was an earthquake and to obtain a magnitude. Seismologists at Lamont-Doherty Earth Observatory of Columbia University in Palisades, New York, analyzed data from seismic stations near Buffalo, New York, and from Ottawa, Canada, and provided a magnitude and general location. Felt reports were confined to the City of Ashtabula, suggesting that this event occurred beneath this community. The seismic stations at Ottawa and Buffalo are at sufficient distance that a precise epicentral location was difficult to determine.
There was some concern that the earthquake may have been related to a Class I injection well in Ashtabula, although the well was shut down in December 1994. Lamont-Doherty seismologists have suggested that series of small earthquakes--one in 1987, two in 1989, and three in 1992--were triggered by this injection well. The cause of the 1995 earthquake is unknown.
On Sunday, May 14, at 4:21 p.m. local time, Dr. Street recorded a 2.5-magnitude earthquake on his Kentucky network. The epicenter was in northern Lawrence County, in southern Ohio. Although this earthquake was large enough to have been felt in the epicentral area, no felt reports were received from this sparsely populated county. No earthquakes have previously been documented from this area.
The second half of 1995 yielded no documented earthquakes in Ohio, although periodic calls were received by the Survey from citizens indicating that they felt vibrations that they suspected to be earthquakes. None of these events could be confirmed as small earthquakes because, in part, operating seismographs are located at considerable distance from the areas of reports.
---Michael C. Hansen
Last update March 03, 2003