Seismic Survey: How it works

Posted: Aug 28, 2012 9:13 AM by Cameron Polom, KSBY News
Updated: Sep 3, 2012 8:36 AM

There are multiple updates to this story. Please click here to get the latest information.

A plan to map seismic fault lines near Diablo Canyon Nuclear Power Plant received key approval this week from state officials.

However, there are big concerns about impact on marine life, local fisheries, and people using the waters.

The study had been planned since 2006 but gained a sense of urgency after an earthquake and tsunami off the coast of Japan in March 2011.

The study will be conducted by PG&E with a price tag of 64-million dollars.

PG&E began fast-tracking the seismic study and agreed to delay pursuing federal re-licensing of the 27-year-old power plant until the seismic study is complete.

Putting it simply, PG&E is spending a lot of money, to determine if an off shore earthquake occurred near diablo canyon, would it have the same disastrous meltdown we saw at the Fukishima plant during last years earthquake in Japan.

If all goes to plan, PG&E will begin seismic mapping off the central coast November first using advanced high frequency air cannons.

"Equipment will emit a sound," says Blair Jones, spokesperson for PG&E. "That sound will go down to the ocean bottom to the earths crust, it will then bounce back off, as sound does, the bottom of the ocean."

The sound is then received by four monitors being dragged behind the survey vessel.

"That equipment will help paint a 3d image of the seismic characteristics of the area," says Jones.

Scientist from PG&E say the survey will show the angle of the faults, how their shaped, and if they're interconnected, helping to determine how big of an earthquake can be generated by those faults.

This will help determine the safety of diablo canyon in the event of a large off shore quake.

The tests are being conducted in two phases.

"It will take thirty three days to preform the purposed work, the first window of opportunity to preform that is November through December of this year and the second opportunity will be the same time next year."

Two of the survey routes or race tracks will be completed this year and the final one during the same time next year.

As of now the studies are set to begin November 1st, however, PG&E still needs to secure approval of federal and other state agencies before it can proceed.