Apparently, there's a new United States Geological Survey (USGS) report published recently. The summary of the report and the full report (with comprehensive maps) listed the most likely affected area.
In a gist, the following is the excerpt from the summary report:
The probability of a magnitude 6.7 or larger earthquake over the next 30 years striking the greater Los Angeles area is 67%, and in the San Francisco Bay Area it is 63%, similar to previous Bay Area estimates. For the entire California region, the fault with the highest probability of generating at least one magnitude 6.7 quake or larger is the southern San Andreas (59% in the next 30 years).Am I worried? Yeah, sure. Even though my area isn't named as the epicenter, it's close enough. But am I going to move? Certainly not because of that! But I do hope the house for which I'm slaving to pay the mortgage will be left standing after the BIG one blows over... Heh.
For northern California, the most likely source of such earthquakes is the Hayward-Rodgers Creek Fault (31% in the next 30 years). Such quakes can be deadly, as shown by the 1989 magnitude 6.9 Loma Prieta and the 1994 magnitude 6.7 Northridge earthquakes.