Are California's Nuclear Power Plants Built to Withstand Earthquakes?

About 200 miles up the coast from Manhattan Beach Beach sits the El Diablo Canyon Power Plant, in close proximity to four earthquake faults.

Editor's Note: A version of this opinion piece originally published on Venice Patch. We decided to share the writer's sentiments with Manhattan Beach residents.

Looking at the failure of three cooling systems at nuclear power reactors in Japan, and a second containment building explosion, I can’t help but wonder about the shortsightedness of building nuclear plants near an earthquake fault. The question arises, are we at risk here in Southern California?

The San Onofre Nuclear Power Plant was built to withstand a 7-magnitude earthquake, whose epicenter would be within five miles of the plant, according to Southern California Edison officials.

More problematic is the aptly named El Diablo Canyon Power Plant, about 200 miles up the coast from Manhattana Beach in Avila Beach. It’s a good place to build a power plant, except for four earthquake faults in the vicinity.

The design was considered safe enough to resist shaking from the nearby San Andreas Fault when construction began in 1968. But then a new fault was discovered in 1973 three miles off shore, the Hosgri fault.

And a few miles farther out, it had produced a 7.1-magnitude quake in 1927. Yet construction at El Diablo continued.

Tens of thousands of protestors gathered to block the plant's construction in 1979, according to reports in The Journal of American History. The plant was ultimately finished with a design intended to withstand a 7.5-magnitude earthquake. It went online in the mid-1980s.

The nuclear power plant on the coast to the north of Manhattan Beach, and the one to the south, are designed to resist a 7.5 and 7.0 quake respectively—to put this in perspective, the plants would be safe in an earthquake the size of the one that hit Haiti last year.

They would not be safe in an earthquake as big as the one that leveled San Francisco in 1906, which was a 7.8-magnitude.

Because the Richter Scale is logarithmic, each whole number represents a change in earthquake amplitude by a factor of 10, but that only tells part of the story. As an estimate of energy expended by a quake, each whole number represents about 31 times more energy than the amount released by the previous number, according to the U.S. Geological Survey.

Experts are predicting that the next earthquake on the San Andreas Fault could reach 8.1-magnitude.

When? The San Andreas fault is "locked and loaded. It's been a long time since an earthquake has occurred on that fault—over 150 years," said Thomas Jordan, director of the Southern California Earthquake Center.

We are being reassured that quakes of around magnitude 8 are the most we could expect in California because the fault geology is different here than it is in Japan. The biggest quake recorded in California history was the 1857 Fort Tejon earthquake, on the San Andreas fault, which reached 7.9-magnitude, according to the USGS. 

But last week's 8.9-magnitude earthquake was the biggest in Japanese history, and now estimated to have killed more than 10,000 people.

President Barack Obama has mentioned that he supported new nuclear power plant construction to help wean us off fossil fuel dependency. Yet if we learn anything from the disaster in Japan, any additional nuclear plants should be in areas more seismically stable than El Diablo Canyon.

My heartfelt good wishes go out to the Japanese people. They have suffered a devastating blow and could use our help and prayers.

After earthquakes in close succession around the Pacific ring of fire, first in New Zealand and now Japan, I hope that California's faults remain quiescent.

Matt March 21, 2011 at 12:26 AM
The headline asks the wrong question and fans the already well-burning flames of misinformation regarding what happened and what continues to happen at the Fukushima plant in Japan. The earthquake did little or no damage to the power plant, it was the tsunami that took out the backup cooling systems which allegedly weren't very well protected. US plants have all been subjected to seismic reviews by the US NRC.
Catch A Wave March 21, 2011 at 02:02 AM
1. It's clear that earthquakes larger than El Diablo and San Onofre are rated to withstand are possible. 2. Both are on the ocean so Tsunami's are possible as well. 3. Most importantly, a five year old child with no scientific or engineering background whatsoever could tell you it is insane to build a nuclear power plant on or near an active earthquake zone.
Mitsuko March 21, 2011 at 08:34 AM
What happened at Fukushima is the result of playing with fire in a reckless way. Wrong location, wrong planning, wrong design, greed, lies and cover-up followed the silly thinking that no tsunamis will ever come to Japan. As scientist Michio Kaku said recently, the entire plant needs to be covered with a sarcophagus of thick concrete, in order to avoid the loss of the northern part of Japan.
Matt March 21, 2011 at 10:03 PM
This article conveniently ignores some important facts: (a) Japan's fault was a subduction fault; the ones in California, and off the coast of California, are not, and therefore, no sizeable tsunami will be created. Since the cooling problem the plants had were only after the tsunami hit, and not the earthquake, I don't understand how, "we learn anything from the disaster in Japan" that is relevant for Diablo Canyon or San Onofre. (b) Both San Onofre and Diablo Canyon have self-reliant cooling systems that are built into the containment building - Japan's relevant reactors do not. This means that after the plant falls off the electrical grid, cannot use its diesels, and has exhausted its batteries, the steam created by the increase in temperature when the fuel rods "heat up" are used to create electricity that circulate the coolant at both the reactor and spent fuel pools, keeping them at a constant and safe temperature. (c) The article's understanding of earthquakes is clearly limited to that which helps its argument. Its not the magnitude of the earthquake that the power plants are designed to sustain, it is the amount of ground motion. The 7.5 that was mentioned did not happen on any of the faults that would begin to propose any problem for the power plants, and because the magnitude of an earthquake is limited by the size of the fault that causes it, its comparing apples to oranges. An 8.1 from the San Andreas would not breach the threshold of acceptable movement
Catch A Wave March 22, 2011 at 05:32 AM
Matt, the Cascadia subduction fault stretches from mid-Vancouver Island to Northern California and is predicted to be able to generate earthquakes of over 9.0 which would certainly be able to cause catastrophic tsunamis.


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