Key to OhioSeis Catalog
Column Data

 
YEAR, MO (month), DA (day), HR (hour), MN (minute) SEC (second)

Time data, which may be very imprecise for noninstrumental historical events. Dates and times are given in Universal Coordinated Time (UTC), which is essentially equivalent to Greenwich Mean Time (GMT). UTC is five hours later than Eastern Standard Time (EST, local time in Ohio) and four hours later than Eastern Daylight Time (EDT). Owing to the difference between UTC and EST or EDT, some earthquakes on the lists are designated as occurring on the day after the actual date in local time.

LAT° N, LON° W

Latitude and longitude in decimal degrees. West longitude is a negative (-) number in many computer databases. The number of decimal places is indicative of the accuracy of the location; however, some historic events may be off by several tenths of a degree or more. One geocentric degree is equal to approximately 111 km (69 miles).

DP

Calculated depth of the earthquake in kilometers. All Ohio earthquakes are shallow, commonly between 5 and 10 km. It is standard practice among seismologists to constrain (fix) the depth of an instrumentally located event to 5 km in Ohio. Accurate hypocentral depth determinations for small, local earthquakes require seismometers to be very close to the event.

MAG

Magnitude of the earthquake. Recent, instrumentally located events in Ohio are mbLg magnitudes. Magnitudes for older, preinstrumental events were calculated by J. G. Armbruster using maximum Modified Mercalli intensity or felt area (see Seeber and Armbruster, 1991, for methodology). In general, earthquakes having magnitudes below 2.5 are not felt; however, events having instrumental magnitudes of 2.2 have been documented to have been felt in Ohio. An arbitrary cutoff of 2.0 magnitude was selected for this catalog in order to include all events that were, or may have been, felt by people. Not included in the catalog are aftershocks and other instrumental events below 2.0 magnitude.

MT

Magnitude type. Numerals indicate basis of magnitude determination.
1=instrumental magnitude, 2=felt area, 3=maximum Modified Mercalli intensity.

MMI

Modified Mercalli intensity. Modified Mercalli Intensity is a subjective, noninstrumental scale that uses Roman numerals (I-XII) and is based on observed effects and damage from an earthquake. For the table of earthquakes felt in Ohio but beyond the border region, epicentral intensity is followed by maximum intensity reported in Ohio.

FA

Felt area in 1,000 square kilometers.

COUNTY or ST (state)/PROV (province)

For Ohio events, the county in which the epicenter is located is noted by the first four letters of the county name. Locations of border-region and other felt events are defined by standard postal abbreviations for states and the Canadian provinces of Ontario ON) and Quebec (PQ).

SOURCE

Source of the data for a particular event. If two institutions are listed, it indicates that both institutions contributed to the solution or that the event has been relocated by the Ohio Seismic Network using the former institution's phase-arrival data.
 
ASN - Anna Seismic Network. Operated in western Ohio by the University of Michigan from 1977 to 1992.
 
CERI - Center for Earthquake Research and Information, University of Memphis (Tennessee).
 
GSC - Geological Survey of Canada.
 
JCU - John Carroll University Seismic Observatory. Operated between 1900 and 1992.
 
LDEO - Lamont-Doherty Earth Observatory
 
NCE - National Center for Earthquake Engineering Research (NCEER, now MCEER, Multidisciplinary Center for Earthquake Engineering Research). Catalog of Seeber and Armbruster (1991). Includes additional events provided to the Division of Geological Survey by J. G. Armbruster but not yet included in the formal NCEER catalog.
 
OSN - Ohio Seismic Network of the Ohio Geological Survey. Began operation in 1999.
 
SUSSN - Southeastern U. S. Seismic Network
 
UK - University of Kentucky Seismic Network.
 
USGS - U. S. Geological Survey.
 
UTLO - University of Toledo seismic station.