Why doesn’t this margin or error make me feel comfortable?

by David Safier

The east coast just had a 5.9 magnitude earthquake, with its epicenter in Mineral, Virginia.

Ten miles away are two nuclear power reactors at the North Anna site. They were shut down temporarily, but there was no damage. Good news.

The power plants "were designed to withstand a 5.9 to 6.1 quake." Not such good news.

What if the earthquake was a 6.2, or 6.5, or 7.0? That would be unusual for the area. Apparently, this was the biggest quake in the area since World War II. But shouldn't the safety margin be higher, so no one ends up saying, like in Fukujima, "We had no idea there could be a disaster of this intensity"?

The plants, by the way, are about 75 miles outside of Washington, D.C.

To me, being able to withstand a 6.1 magnitude earthquake is a ridiculously low bar, given the havoc a nuclear accident would cause.