Earthquake fault near Diablo Canyon Power Plant links to second fault

By Amanda Starrantino:

Earthquake research shows there is potential for a bigger earthquake than once thought near Diablo Canyon Nuclear Power Plant.

The U.S. Geological Survey has found that an earthquake fault near the plant is linked to another seismic fault farther north.

The USGS says faults located within five kilometers of one another could potentially move together and produce stronger shaking. Diablo Canyon is situated near two major faults, the Hosgri Fault and San Gregorio Fault -- a 250-mile strand.

"If the Hosgri and the San Gregorio faults are truly linked in a straight line, then if you totally maxed out all parameters, worst case scenario, you would be something in the neighborhood of (magnitude) 7.7 size," says Cal Poly Associate Professor of Geology & Geophysics John Jasbinsek.

A PG&E report performed at the direction of the Nuclear Regulatory Commission shows that such an event has a one in two million chance of happening each year.

"Most earthquake faults don't take advantage of the total length. Most earthquakes are smaller than the theoretical maximum that it might support, and so even if the Hosgri and the San Gregorio faults are linked at 400 kilometers so simply, it would be very rare for the entire fault to rupture all at once," explains Jasbinsek.

PG&E officials say Diablo Canyon was built in the 1970s with the knowledge of a fault so close to the power plant.

PG&E also says it has studied for several years faults within five kilometers of one another and their potential to rupture together. The utility submitted a report on such earthquake hazards to the Nuclear Regulatory Commission in March.

The utility adds scientific experts have calculated potential earthquakes at the plant and found it can withstand all the way up to an 8.5 magnitude earthquake.

"Independent scientific experts have specifically looked at this and how the plant responds in such a rare event. And what they found is that the plant can withstand such a rare event," says PG&E spokesperson Blair Jones. "That is due to the design of the plant and the engineering that went into it."

The famous 1906 earthquake that destroyed most of San Francisco had a magnitude of 7.8, although seismic engineering has advanced significantly in the past 110 years.

PG&E officials say the plant is designed differently than regular structures, and if there was a significant earthquake, the plant would immediately shut down and be able to withstand the shaking.

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