It's unclear how many residents of Washington, D.C. and New York City initially thought that Tuesday's earthquake on the eastern seaboard was instead a tremor caused by a terrorist attack.

To residents of both cities, the terrorist attacks of September 11, 2001 remain fresh in their minds as the 10th anniversary of the event is just weeks away. Plus, the recent death of Al Qaeda kingpin Osama bin Laden stoked fears that Muslim extremists were planning a reprisal on American soil.

The attorney general, Eric Holder, reportedly fled his Washington office shortly after the earthquake and was whisked away in a security-laden motorcade. In lower Manhattan, thousands of workers in the court district and the financial district - both downtown near the former site of the World Trade Center - ran out of their office buildings and onto the street in a panicked frenzy that recalled the chaos in New York City nearly ten years ago.

An earthquake registering 5.8 on the Richter Scale occurs once a year in California. On the east coast of the United States, however, it's a once-in-a-century event. That's why so many easterners who had never before experienced a large quake thought it could be the result of a manmade event.

In D.C., when you feel the building rumble, the first thing that goes through your head is you get worried that this could be an act of terrorism, a Congressional press aide, Zach Cikanek, told the Washington Post. Once people realized it was an earthquake, and more than likely over with, most people went through the evacuation procedure and went to their designated area.