Large earthquakes are very likely to occur in California in the next 30 years. Most of the faults these earthquakes may rupture are locked during the times between large events, but some creep, slowly slipping much of the time. In the San Francisco Bay area, significant creeping faults include the Hayward fault and its connected companions to the north and the south, the Rodgers Creek and Calaveras faults, respectively, and these three faults also have the highest probabilities of producing a large earthquake in this region. Because these faults occur in a densely populated area, they also pose significant seismic risk. We used computer simulations and information about the San Francisco Bay area's rocks and stresses, along with simple ideas about how friction works, to simulate strong shaking from large (M7) scenario earthquakes on these faults.