Maryland EARTHQUAKE HAZARDS

The earliest recorded earthquake in Maryland occurred in Annapolis, on April 25, 1758. The shock lasted 30 seconds and was preceded by subterranean noises. Additional felt reports were received from a few points in Pennsylvania. The most recent significant event was on July 16, 2010 when a 3.6 magnitude earthquake occurred near Germantown. Ground shaking was felt as far away as Annapolis and Northern Virginia.

Between 1758 and 1987 Maryland experienced 22 minor earthquakes. However, from January 1990 through December 1996, Maryland experienced 35 small tremors—1 in Harford County, 2 in Cecil County, 3 in Baltimore County, and 29 in Howard County. In only seven years, the number of known earthquakes in Maryland more than doubled.

Harford County, Maryland, was shaken by earthquakes the night of March 11 and the morning of March 12, 1883. The intensity was in the IV - V range, (clocks stopped at Fallston) with felt points also noted in Baltimore County.

Another moderate shock occurred less than two years later, on January 2, 1885, in an area near the Frederick County, Maryland - Loudon County, Virginia, border (not believed to have originated in Maryland). Maximum intensity reached V, with the total felt area covering more than 3,500 square miles. Clarke, Fairfax, Fauquier, and Shenandoah Counties, Virginia, also reported this earthquake.

Since 1885, ground shaking felt in Maryland have been associated with sources for adjacent states and points as far away as the St. Lawrence Valley and Timiskaming, Canada. A single felt report was received from West Hyattsville, associated with a November 19, 1969, earthquake (magnitude 4.3) near Elgood, West Virginia. The February 10, 1972, tremor at Wilmington, Delaware, was felt at Elkton, Maryland. On February 28, 1973, residents throughout a broad area of the middle-Atlantic region of the United States were jolted out of their sleep by shock waves from a minor earthquake near the Delaware - New Jersey - Pennsylvania border. Numerous points in northeastern Maryland reported this earthquake.

The USGS National Earthquake Information Center maintains a national database of significant earthquake epicenters from 1568-2010. USGS defines significant earthquakes as those that caused deaths, property damage, or geological effects, or that were experienced by populations in the epicentral area.

Based on available data, the overall earthquake risk to all jurisdictions, with the exception of Cecil County, is low to medium-low, relative to Maryland. Cecil County is ranked as medium primarily driven by population vulnerability, density and geographic extent. Frederick, Montgomery, Prince George’s, Charles, Calvert, Anne Arundel, Baltimore and Wicomico counties and Baltimore City are ranked medium-low based primarily on population density and population vulnerability.

Please visit the following links for more information:

Maryland Department of Emergency Management
https://mdem.maryland.gov/Pages/default.aspx

USGS Maryland Earthquake Webpage
http://earthquake.usgs.gov/earthquakes/byregion/maryland.ph