Harford county executive Craig issued a written statement shortly after 6 p.m. Tuesday, warning of the effects from possible aftershocks.

"There is a one in ten chance that an aftershock similar in strength could occur by 2 p.m. tomorrow [Wednesday]," the statement read. "Citizens are asked to report significant damage resulting from the earthquake to the 911 Center.

"Significant damage is defined as needing immediate attention to protect life and safety," the statement continued. "Individuals should look for anomalies such as cracked foundations or broken glass resulting from this event."

"Harford County is in the process of inspecting County owned facilities and bridges," the statement concluded. "Our Emergency Operations Center will continue to monitor the situation throughout the night and into tomorrow."

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Previous Harford shakes, quakes

Tuesday was not the first time the ground rumbled beneath the feet of Harford County residents because of seismic activity.

In September 2009, the Harford County Emergency Operations Center received several phone calls from Forest Hill, Hickory and northern Bel Air reporting a rumble or large bump.

While the sensation was not confirmed to be an earthquake, the Maryland Geological Survey website did show a spike in local activity on the seismography that morning.

In December 2008, an earthquake with a Richter magnitude of 3.4 occurred in southeastern Pennsylvania close enough for the quake to be felt in northern Harford County.

A U.S. Geological Survey spokesman said at the time the quake was minor and lasted only a few seconds. No damage was reported, but several people said their homes shook briefly.

Mild earth tremors were reported in Harford one early morning in 1973, according to Aegis archive records. Most people likely slept through the tremors, according to one article in the newspaper.