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San Onofre Vigilant About Earthquakes, Even While Offline

Operators at the San Onofre nuclear power plant felt the earthquakes that shook Brawley over the weekend. Even though the reactors are currently shut down, earthquakes are still a threat at San Onofre.

The swarm of temblors that shook Brawley over the weekend did not trigger the earthquake sensors at San Onofre, but operators in the control room felt the quake. They sent out a “notification of an unusual event,” the lowest level of alert, to warn response personel to be prepared. It was cancelled a few hours later.

Earthquakes are a concern even though the reactors are all shut down, because of the nuclear fuel stored on site. The operator, Southern California Edison, is embarking on a $64 million study of quake faults off the coast.

The California Coastal Commission is working on a permit for this study, and a similar study for Diablo Canyon nuclear power plant near San Luis Obispo. Tom Luster of the Coastal Commission said the study will involve high energy sound pulses, powerful enough to penetrate the ocean floor.

"This is a very large survey vessel," he said, "that would be towing an array approximately four miles long, back and forth throughout the study area, for a period of up to two months."

Luster said this may involve closing nearby beaches and will risk damaging marine life. He says the timeline is short because Edison hopes to complete their study before the gray whale migration next January.

Scripps Institution of Oceanography, which will conduct the study for Edison, said the vessel will operate for less than a month off the coast of San Onofre and will be far enough off shore to make beach closures unnecessary.

The Coastal Commission will hold a public hearing in Oceanside on the permit for the Diablo Canyon quake study in October. The hearing on the study off San Onofre is expected to happen soon after.

The California State Lands Commission recently granted a permit for the study, on condition that it be completed by December. The research vessel is from the East Coast and San Onofre's operators hope to use it after the Diablo Canyon study is complete, before the boat returns to its home base.

Note : Scripps Institution of Oceanography commented on the original story, and their comments have been added.

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