Are U.S. Nuclear Plants Located Near Earthquake Faults?

*Updated March 16, 2 PM Pacific*

The vulnerability of a reactor to an earthquake depends on two factors:

1. Proximity to seismically active areas; and
2. The ability of the reactor and associated infrastructure to withstand an earthquake, which depends on its design and construction.

The World Nuclear Association estimates that 20 percent of nuclear reactors worldwide operate in areas vulnerable to earthquakes.

In the United States, several nuclear reactors in California and New York are located on or near known faults. Other parts of the country where nuclear plants now exist are seismically active, although not so much as the West Coast.

• Two reactors at Diablo Canyon, (near the town of San Luis Obispo, CA) are 3 miles from the Hosgri Fault line and about half a mile from an offshore fault line scientists discovered in 2008.
• Two reactors at San Onofre (next to Interstate 5 between Los Angeles and San Diego, CA) are 5 miles from the Newport-Inglewood-Rose Canyon fault.
• Two reactors at the Indian Point, NY nuclear power plant are one mile from a recently-discovered intersection of two active fault lines. Close to 10 million people live within 25 miles of the Indian Point facility.

The U.S. Nuclear Regulatory Commission notes that the Midwest and Eastern United States, while less seismically active than the West Coast, still face an appreciable risk of earthquakes. The commission notes that in the early 1800s, three large earthquakes – between 7 and 7.7 on the Richter scale – affected the Eastern United States, with an epicenter in Missouri. Another similar earthquake struck Charleston, South Carolina in 1886.

Western Ohio is the second-most seismically active area in the Eastern United States behind Missouri.  An earthquake there in 1986 affected the Perry nuclear power plant, for example, breaking pipes and equipment – but the plant had not yet begun operation.

Major earthquakes affected South Carolina, Missouri and Arkansas in the 1800s. One of them even made the Mississippi river run backwards for a time, according to a story by an investigative reporter at MSNBC.

The U.S. Geological Survey has learned a lot about earthquake hazards in the last 30 years, after most U.S. nuclear reactors were designed and built. In 2008, the U.S. Geological Survey updated their assessment of seismic hazard across the United States. The update generally resulted in increased estimates of the frequency and strength of possible earthquakes in many locations. (See the map and link below.)

Seismic Hazard Map for the U.S. as a whole from the U.S. Geological Survey

Strength of Infrastructure

Using data from the U.S. Nuclear Regulatory Commission about the construction strength of the infrastructure at each U.S. nuclear reactor, investigative reporters at MSNBC have ranked the reactors in terms of the likelihood that the reactor could be damaged by an earthquake.

We explore this new information in our following post: How large of an earthquake could U.S. nuclear power stations withstand?