There seems to be more earthquakes in Ohio in recent years. What is causing this?
A glance at the Catalog of Ohio Earthquakes would suggest that earthquakes are much more frequent, beginning in the 1980's. This statistic is misleading, however. The comparatively small number of earthquakes in the 1800's can be attributed to a small population, lack of awareness of brief jolts or vibrations being earthquakes, and lack of rapid and widespread communications. Most earthquakes noted in the historic record prior to the late 1970's are greater than 3.0 magnitude, suggesting that many felt earthquakes in the 2.0 - 2.9 range were not reported by newspapers or not attributed to earthquakes. In addition to greater public awareness of earthquakes, the installation of numerous seismic stations in Ohio and a central reporting center (Ohio Earthquake Information Center) has resulted in the confirmation of many earthquakes that formerly may have escaped notice. The record of earthquakes in Ohio since the 1980's is skewed from the normal distribution because of the large number of felt earthquakes since 1987 at Ashtabula, Ohio. These earthquakes (at least 40) are thought to be associated with a now-abandoned deep injection well at Ashtabula. It is interesting to note that the second-most active decade of earthquakes was in the 1930's, when the Western Ohio Seismic Zone (Anna Zone) was very active.