Between 2010 and 2012, PG&E performed a series of three-dimensional and two-dimensional low-energy and high-energy seismic reflection surveys, along with other geologic and geophysical investigations, to image fault zones near the DCPP as recommended in the California Energy Commission’s 2008 document “An Assessment of California’s Nuclear Power Plants: AB1632 Report”. A three-component broadband ocean bottom seismometer/accelerometer array was also installed offshore of the DCPP in 2013 to increase earthquake detection capability and provide full waveform recording of events in the offshore area.
The studies conducted as part of the Central Coastal California Seismic Imaging Project (CCCSIP) provide new geologic and geophysical data to reduce uncertainty and improve seismic source characterization parameters for the Hosgri, Los Osos, San Luis Bay, Oceano and Shoreline fault zones. CCCSIP activities were prioritized with input from the CA Public Utilities Commission Independent Peer Review Panel. Prioritization was based on 1] identification of key seismic source parameters that had a significant impact on the probabilistic hazard at the DCPP site; and 2] the overall likelihood that information from the proposed surveys would reduce the uncertainty associated with each parameter. Key seismic source parameters considered for investigation included: Hosgri fault zone slip rate and dip; Shoreline fault zone extent, segmentation, and slip rate; Los Osos fault dip, sense of slip and slip rate; and joint ruptures of the Hosgri-Shoreline and/or the Hosgri-San Simeon fault zones.