In the aftermath of Japan’s magnitude 9.0 quake, California lawmakers want a better grasp of the risks of a nuclear accident here. They’re pressuring the utilities that operate California’s nuclear power plants to complete new seismic studies.
Japan is more prepared than any county in the world to cope with massive earthquakes and tsunamis. Since seismologists began recording such events, a dozen massive earthquakes have rocked the island nation.
Geologists figured the fault line near Fukushima was capable of producing a 7.9-magnitude earthquake at most. But at a legislative hearing this week in Sacramento, Keith Knudsen with the US Geological Survey said the quake that hit this month blew a hole in those careful projections.
"The shaking that these people experienced - we’ve seen some of the videos online - the shaking went on for two to three minutes." Knudsen said.
The Japan quake was 900 times more powerful than Northern California’s 1989 Loma Prieta quake. Knudsen showed lawmakers a slide of what made the Japan quake so powerful: a massive rupture in the Earth’s crust under the water right off Fukushima’s eastern coast.
"This polygon here represents the area of the Earth that ruptured during this earthquake," Knudsen explained. "It wasn’t just ruptured at this epicenter but that entire area, roughly an area 300 by roughly 150 miles."
The Fukushima Dai-ichi nuclear power plant complex survived the giant quake. Its reactors shut down automatically and emergency generators powered up to run the cooling system.
But the tsunami flooded the emergency generators and they failed. The Fukushima plant was built to withstand a 22-foot wave but the giant wall of water that engulfed it was as much as 10 feet higher than that.
"What I hear you say is it’s not surprising that we underestimate the potentiality of a fault system like we did in Japan," Sen. Sam Blakeslee responded.
Blakeslee said California’s nuclear power plant operators need to do more to ensure the safety of facilities. The San Luis Obispo Republican has pushed Pacific Gas & Electric to conduct new seismic risk studies of its Diablo Canyon nuclear power plant. Diablo Canyon and Southern California Edison’s San Onofre nuclear plant lie near known fault lines. But three years ago, geologists discovered a new fault within a mile of Diablo Canyon.
"I’m a little concerned that PG&E, which had the primary responsibility for identifying the seismic safety of the facility and the seismic environment in which they were operating, failed to notice a fault of this size, given that earthquakes have been occurring throughout time virtually right under their nose," Blakeslee said.
PG&E insists there is “no uncertainty” about whether Diablo Canyon can withstand a seismic threat. At this week’s hearing, Blakeslee asked PG&E seismic expert Lloyd Cuff if the utility still thinks there’s “no uncertainty” about seismic risk at Diablo Canyon.
Cuff said there's always uncertainty in earthquakes, but "we don’t see a concern about the uncertainty because we’ve quantified where it is and what would happen if we changed the uncertainty."
"So PG&E still sees no concern about the uncertainty?" Blakeslee asked.
"No," Cuff insisted.
"You see uncertainty but you have no concern about it?" Blakeslee continued
"No, we do not," Cuff replied.
PG&E has applied to renew Diablo Canyon’s licenses despite the California Energy Commission’s request that the utility first conduct new studies on seismic risks.
PG&E’s Cuff said the company plans to apply in April for a permit to begin new seismic studies.
A spokeswoman for Southern Gas and Electric testified that San Onofre is invulnerable to massive quakes and can withstand a 30-foot tsunami.