Summary of Maryland Earthquakes, 1758-2005

NOTES:

1. Time (UTC): Coordinated Universal Time. For the Eastern time zone, subtract 5 hours from UTC time for Eastern Standard Time, 4 hours for Eastern Daylight Saving Time.  For example:  1200 UTC (noon) = 0800, or 8:00 am EDT = 0700, or 7 am EST.  Note that 00:00-04:59 UTC converts to 1800-23:59 of the previous day.
2. Epicenter, as calculated from seismograph stations =data and/or estimated by the Maryland Geological Survey on the basis of felt reports; 1962 marked the first instrumentally determined epicenter.
3. Except for event #6 in 1881 (see note 5 below), pre-instrumental (pre-1962) intensity estimates are earthquake catalogs published by various seismograph networks.
4. Except for event #6 in 1881 (see note 5 below) pre-instrumental magnitude estimates (shown in parentheses) by L. Seeber and J. Armbruster (Lamont Doherty Earth Observatory of Columbia University) and/or M. Chapman (Virginia Tech Seismological Observatory); magnitude estimates for a large number of pre‑instrumental earthquakes in the region were derived using the region-specific relationships between felt area, maximum intensity and mb(Lg) magnitude developed by Sibol et al. (1987).  Subsequent magnitudes are from instrumental measurements.
5. Event #6 has not been listed in any previously published earthquake list.  A rather detailed account of this event appeared in the January 8, 1881 edition of the American Sentinel newspaper.  Estimates of the epicenter and intensity have been made on the basis of the newspaper descriptions; magnitude estimates based on Sibol et al. (1987).
6. The Delaware Geological Survey states that this event may have been a sonic boom instead of an earthquake (S. Baxter, oral commun., Aug. 16, 2001).
7. Detected only by the Lamont Doherty Earth Observatory seismic network (http://www.ldeo.columbia.edu/cgi-bin/quake.cgi). There were no felt reports.