Wednesday, March 30, 2011

Re: [californiadisasters] San Onofre Nuke Plant Operators Propose New Seismic Study

Look at what I found...

Bulletin of the Seismological Society of America, Vol. 94, No. 2, pp. 747–752, April 2004
Activity of the Offshore Newport–Inglewood Rose Canyon Fault Zone,
Coastal Southern California, from Relocated Microseismicity
by Lisa B. Grant and Peter M. Shearer

"For hazard estimation of offshore faults, it is not as important to precisely locate active traces as it is for onshore faults in populated areas. A more important consideration is
the potential for a through-going rupture and an estimate of
the maximum magnitude earthquake. Our relocated microseismicity is too sparse to reveal whether or not there is a through-going strike-slip fault zone. The structure of the
ONI-RC fault zone may be similar to that of the onshore NIFZ, which contains multiple strike-slip traces. Others have mapped a fairly continuous structurally complex zone of
faulting 110 km long, subparallel to and within 10 km of
the coast (Fischer and Mills, 1991). The maximum magnitude of an ONI-RC fault rupture can be estimated from the length of the fault zone. Assuming a 110-km surface rupture
length of a strike-slip fault zone yields an estimated M 7.4 earthquake (Wells and Coppersmith, 1994).
If strike-slip faults do not terminate the Oceanside thrust, Rivero et al. (2000) estimate an Mw 7.5 maximum magnitude earthquake could result from rupture of the entire
thrust fault. The 6.5-km depth of the Newport Beach seismicity cluster does not provide information on the geometry or interaction between the strike-slip ONI-RC fault zone and
the Oceanside thrust. However, the location and 13 km
depth of the Oceanside cluster suggests that the Oceanside
thrust is terminated by active strike-slip faults. According to
Rivero et al. (2000), this geometry would lead to an Mw 7.3
maximum magnitude earthquake on the Oceanside thrust.
The maximum magnitude estimate is at the upper range of
magnitude estimated for an earthquake that uplifted the San
Joaquin Hills circa A.D. 1635–1769 (Grant et al., 2002)."

From: Kim Noyes <>
To: CaliforniaDisasters <>; California's Earthquake Forum <>
Sent: Wed, March 30, 2011 2:36:01 PM
Subject: [californiadisasters] San Onofre Nuke Plant Operators Propose New Seismic Study


San Onofre nuclear plant operators propose new seismic study

By Paloma Esquivel
Los Angeles Times
March 30, 2011 |  9:25 am

The operators of the San Onofre nuclear power plant are proposing a multimillion-dollar study that would use new technology to better assess seismic conditions near the complex.

The announcement by Southern California Edison follows calls by state and federal officials in the wake of Japan's nuclear crisis for comprehensive reviews of the state's two commercial nuclear power plants.

Edison officials said the study was planned long before the crisis, but officials were now reevaluating the scope of the project in light of recent events.

The study must first be approved by the California Public Utilities Commission, because its cost would be covered by higher rates, said spokesman Gil Alexander.

In recent weeks several elected officials have questioned whether operators of San Onofre, near San Clemente, and the Diablo Canyon nuclear plant, on the Central Coast, had underestimated the potential severity of earthquakes near the facilities.

Edison officials said the proposed study would tap into new technology that could lead to a more accurate threat assessment. San Onofre was made to withstand a magnitude 7 quake from a fault five miles away and is protected by a 30-foot seawall, Alexander said.

A study submitted by the utility to the utility commission in February reinforced those specifications, and officials said the plant could continue to operate reliably through its current license period, which expires in 2022.

"All of the best current available data still point in the direction of how the plant was designed," Alexander said. "San Onofre can protect the public. That's obviously the bottom line."


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