The USGS report of it I saw earlier said that it was a 6.0, located between Napa and Vallejo (in the NE SF Bay Area), and happened at ~03:21.
I live at the other end of the Bay in San Jose and did not feel it; OTOH, a lady I know who lives a very few miles from me posted on FB that she had felt it. Either those few miles made a difference (plausible, given CA's weird geology), or she sleeps much more lightly than I do. Several FB friends in Woodland (NE of Sacramento) posted that they had felt the quake quite strongly.
The Richter scale is logarithmic, so this 6.0 was about 1/10 the energy of the 1989 Loma Prieta (near Santa Cruz) Earthquake.