New York City alone could suffer damage as high as $20 billion if it suffered direct effects of an earthquake as large as the Aug. 23 earthquake that rattled the Middle Atlantic, catastrophe analysis firm Eqecat determined.

That would be greater than the damage Greater Los Angeles suffered from the 1994 Northridge earthquake.

The 5.8-magnitude earthquake, centered near Mineral, Va., shook up the Northeast, extending as far as Ohio and Canada, but caused damage only around $100 million, Eqecat reported.

Meanwhile, the Oakland, Calif.-based firm estimated the chances of New York experiencing such a large earthquake again should be once in 50 years. Calculated only over areas where damage occurred, chances are only once in 500 years.

Eqecat reported uncertainty in earthquake risk for the eastern U.S. is particularly high because of few historic events and the widespread shaking footprint they cause compared to the more localized impact of California quakes.

As a result, Eqecat's model considers the impact on an area 10 times as large for a given magnitude. That's how it came up with estimates in the range of $10 billion to $20 billion, which it acknowledges would be unprecedented for seismic activity in the eastern U.S.

Morever, Eqecat notes that a greater number of historic earthquakes have occurred in New York than Virginia, including a 5.0 magnitude quake centered in Ottawa in 2010, a 5.1 temblor in Upstate New York in 2002, a 5.9 quake centered near Montreal in 1988 and a 4.4 earthquake in eastern Pennsylvania in 1984.

While damage was low from the Virginia earthquake, largely confined to structures around Virginia as well as to parts of the Washington Monument and National Cathedral, a dozen nuclear plants shut down in the aftermath due to temporary power cuts.

Seismologist Lynn Sykes told IBTimes the 5.8-magnitude earthquake proved there is a great risk to New York from Entergy's two Indian Point nuclear plants in Buchanan, N.Y., only 30 miles north, as well as others.

Dominion Energy in Virginia still has not restarted its two North Anna plants near Mineral and is scheduled to report to the U.S. Nuclear Regulatory Commission Thursday about its findings. So far, the utility has said it believed the reactors experienced only cosmetic damage.

Sykes, of Lamont-Doherty Earth Observatory at Columbia University who has advised the NRC, said he was worried that plants like North Anna weren't designed to withstand large quakes and need to be carefully watched.