Here are some places that you can find ground motion records:

California Strong Motion Instrumentation Program (CSMIP)
US Geological Survey
Guerrero Strong Motion Network
Lamont-Doherty Earth Observatory
SAC (SEAOC-ATC-CUREe) Joint Venture
Pacific Earthquake Engineering Research Center (PEER)

Local networks:
Berkeley Digital Seismic Network
Northern California Earthquake Data Center (NCDEC)
Southern California Earthquake Center (SCEC)
CUBE