CATCHING SEISMIC WAVES

As we know from California's earthquake history, the North American tectonic plate is in a state of continual collision with the Pacific plate, creating faultlines throughout our state and offshore with earthquake zones reflecting this constant subductional grinding.  Last year's tragic earthquake and tsunami in Japan -- and the resuting damage to their nuclear power plant at Fukushima -- caused the Nuclear Regulatory Commission to require PG&E to install monitors along the coast near California's remaining nuclear power plant at Diablo Canyon.

As it happens, four new fault lines have been discovered off the Central Coast near Diablo Canyon and, while the plant was built to withstand up to a 7.8 temblor, no one knows what the new faultlines are capable of producing -- making the installation of seismic monitors even more critical. By way of background, Diablo Canyon is completely isolated on the coast, sitting on a promontory 100 feet above the Pacific. Its two reactors went online in 1985 and 1986.  Emergency power for the plant is located higher up on the cliff (300 feet), lowering any risk that a tsunami can destroy the facility as was the case at Fukushima.  However, seismic risk is high.

Under a $3 million dollar contract, Horst was instrumental (no pun intended!) in overseeing the installation of the seismic monitors, which are housed in titanium and incorporate sophisticated electronics to control gimbaling, monitor positioning, measure time and triaxial and vertical movement.  The monitors were loaded onto a ship out of Morro Bay and transported up the coast to the marine sanctuary adjacent to Diablo Canyon. Enroute they were encased in one ton concrete domes to prevent drag nets from displacing the monitors and to reduce any noise that might interfere with data collection.

One-by-one and over a 5 day period the montiors were lowered by cable to the sea floor in a daisy chain along 13 miles of coastline ranging in depth from 180 to 300 feet. The optic fiber data cable connecting the monitors was brought ashore at Diablo Canyon and pulled by hand up to the plant where data transmitted is uploaded into the computer for analysis.

Results are already coming in -- a recent 2.5 earthquake was registered, along with many micro quakes that are undetectable on land.  If and when the monitors encounter a substantial shake, an automated shut down of the plant will be triggered.

This effort will not only help ensure the safety of Diablo Canyon, it will provide new insight into the seismic forces at work along our Pacific coast.