The seismic testing proposed by Pacific Gas & Electric is unnecessary. The Diablo Canyon Power Plant is located on the California Central Coast. The California Central Coast is laced with fault lines: We have earthquakes almost daily.
No test result, finding or protest is going to convince PG&E to disable and move the Diablo Canyon Power Plant. If there is any even remotely conceivable natural or manmade disaster for which PG&E does not have a plan (and a backup) to ensure the integrity and safety of the Diablo Canyon Power Plant, then such plans should be put in place immediately.
Both national and international incidents have demonstrated the terrible destructive power unleashed when nuclear power generation goes awry.
If there is any safeguard whatsoever that can be implemented to make Diablo Canyon safer, then such safeguards should be implemented.
This is common sense: The decision to increase the safety of Diablo Canyon to the maximum should require no testing of any sort.