The U-S Geological survey says aftershocks continue following a strong earthquake near Napa, California, northeast of San Francisco. The USGS reports on its website that the preliminary magnitude 6.0 quake hit around 3:20 this morning Pacific Daylight time at a depth of just under seven miles. It's the largest earthquake to shake the Bay Area since the 6.9 magnitude Loma Prieta quake in 1989.