DELAWARE, Ohio – Geologists registered a 4.2 magnitude earthquake at 10:03 p.m. Jan. 25 centered in Lake Erie 10 miles north of Ashtabula.
The quake was felt in Erie, Pa., and Toronto, and as far south as Canton, Ohio.
It is the largest earthquake to be registered in Ohio since 1986, according to Ohio Department of Natural Resources earthquake expert Mike Hansen. It follows a 2.6 magnitude earthquake registered Jan. 19 also in the Ashtabula area.
There were no immediate reports of injury, however minor structural damage has been noted in various Ashtabula County communities.
Seismic risk in Ohio is difficult to evaluate, Hansen said, because earthquakes are generally infrequent in comparison to plate-margin areas such as California.
Also, active faults do not reach the surface in Ohio and therefore cannot be mapped without the aid of expensive subsurface techniques.
And earthquakes don’t happen very often in eastern United States – the time between large earthquakes is commonly very long, on the order of hundreds or even thousands of years.
Hansen said earthquake risk in the eastern United States is further compounded by the fact that seismic waves tend to travel for long distances. The relatively brittle and flat-lying sedimentary rocks of this region tend to carry these waves throughout an area of thousands of square miles for even a moderate-size earthquake.
Damaging ground motion would occur in an area about 10 times larger than for a California earthquake of comparable intensity.
ODNR geologists recorded the recent earthquake on the OhioSeis system, a 20-station network of seismographs installed by the ODNR Division of Geological Survey in 1999.
The seismic network is the most comprehensive earthquake-monitoring system ever established in Ohio, and is considered by geologists to be among the best in the Midwest.
The exact epicenter, magnitude and timeframe of any seismic activity can now be determined in a matter of minutes by checking data from any three or more of the seismograph units.
The 20 monitoring units in the new network are located in the most seismically active areas of the state or near regions that provide ideal conditions for detecting and locating very small tremors – which are often undetected by humans.
The stations are located at universities and government facilities in or near Ashtabula, Athens, Bowling Green, Celina, Cincinnati, Cleveland, Columbus, Lancaster, Lima, Painesville, Portsmouth, Toledo and Wooster.