Tuesday's earthquake in Virginia, the largest to hit the East Coast in 67 years, made the United States question the safety of its nuclear power plants.

The earthquake, a 5.8 on the Richter scale, had an epicenter only a few miles from the North Anna nuclear power plant. The plant shut down automatically, as it was supposed to, averting a nuclear accident like the one that befell Japan's Fukushima plant March 11.

A spokesman for Noth Anna's operator. Dominion Resources, said there was no major damage to the power plant and that three diesel generators kept the reactor cool.  A fourth diesel unit failed to work.   

Nuclear power plants lose a significant margin of safety when they're forced to rely on these emergency backup systems, Paul Gunter, director of reactor oversight at the anti-nuclear group Beyond Nuclear, told Reuters. 

The U.S. Nuclear Regulatory Commission said North Anna's shutdown was a success and that the plant was no threat to the public. 

New York's emergency alert system told residents at 2:12 p.m. Eastern that This is an ACTUAL EARTHQUAKE ALERT.  Many buildings in Washington, D.C., were evacuated, and two corridors at the Pentagon were flooded when a pipe broke.