Moth with silver marking on wings
Based on the overall apparence and the distinctive metallic patches on the wings it looks like a moth from the subfamily Plusiinae (Looper moths). I'm not familiar with North American moths, but after a quick check at species found there Megalographa biloba (Bilobed looper moth) seems likely, and this species is also found in California.


(picture from wikipedia)

Also see the pictures at Bugguide.net.