Skip to main content

Fault system draws questions about Diablo Canyon nuclear plant’s safety

Submitted by Tjadendevries on Fri, 07/22/2011 - 4:32pm

Watch the full episode. See more Need To Know.


Fault system draws questions about Diablo Canyon nuclear plant’s safety

July 15, 2011 | Susanne Rust

    After the devastating tsunami damage to the Fukushima Daiichi nuclear plant in Japan, seismologists in the United States are focusing on a potentially dangerous fault system near the Diablo Canyon nuclear power plant in California.

    Perched over Point Buchon on the Central Coast, the PG&E plant was built four decades ago near two active faults: the Hosgri and the Shoreline. The electricity-generating facility on a barren stretch of coastline is about 12 miles from the college town of San Luis Obispo.

    While PG&E maintains the Hosgri and Shoreline are too small to threaten the aging plant, some government scientists suspect the faults – acting with others in the region – could produce an earthquake much more powerful than the plant was built to withstand.

    For now, the scientists are being cautious. Sam Johnson, a U.S. Geological Survey scientist, was reluctant to speculate about whether the area’s fault system is actually much longer, and therefore more powerful, than now predicted.

    “I don’t want to be the one who says there could be one long rupture,” he said in an interview, calling the subject a “hot-potato issue.”

    But during a presentation earlier this spring at the USGS headquarters in Menlo Park, Johnson laid out a scenario showing the Hosgri Fault stretching 250 miles from Point Conception all the way to Bolinas just north of San Francisco – far longer than its current official length of 105 miles.

    The longer the fault, the more powerful the rupture. Johnson’s scenario shows the Hosgri Fault connecting in a system with the San Simeon and San Gregorio faults to the north of the nuclear plant.

    “If the fault were to run from Point Conception to Bolinas, that would be close to an 8.0,” said Johnson. “That would be a big concern.”

    Johnson was quick to point out that the USGS has not said the fault runs that far. He and a team of researchers from the USGS, State Coastal Conservancy, National Oceanic and Atmospheric Administration and others, including PG&E, are collecting this information through the California Seafloor Mapping Program.

    Documents show that Diablo Canyon was constructed to withstand ground shaking from a magnitude 7.5 earthquake 3 miles offshore, on the Hosgri.

    In 1927, a magnitude 7.1 earthquake struck offshore near Lompoc, possibly on the Hosgri. Nobody was killed, but a concrete highway was cracked and a railroad bridge was thrown out of line, according to the Southern California Earthquake Data Center.

    [...]

Much more and links below

http://californiawatch.org/health-and-welfare/fault-system-draws-questions-about-diablo-canyon-nuclear-plant-s-safety-11460