Next, the Hayward fault will most probably present us with the biggest earthquake - and be the epicenter somewhere along the Berkeley and Oakland Hills. Closer to the epicenter the more important that your house is not in a landslide zone, not built on a downslope using 2x4's the only structural members supporting rooms, and seismically upgraded by an engineer.Both the house and the specific location are the indicators of how safe you and your family will be.
This is a pretty difficult one to predict, because none of us know when or exactly where the next big one will hit and honestly the location of the epicenter will affect the level of damage. You can check out the US Geological maps at http://ngmdb.usgs.gov/
In addition when you purchase a home there area a lot of things you can do for seismic safety. If you google seismic safety there is a ton of stuff that comes up that you can check out. When you purchase a home you may also want to discuss with the provider of your home owners insurance about earthquake insurance.
I am originally from NJ and now live in Oakland (near the Hayward Fault). I understand how you feel regarding earthquakes. We live in California, a seismically active area of the world, so there is a certain amount of calculated risk in that. That being said being prepared and informed goes a long way in dealing with the uncertainty.
Hope that helps!
This is actually a liability for anyone to really answer so please take any answers you receive in stride. In theory the closer you are to the epicenter on a fault line, the greater the chance for damage.
There are steps one can take to help reduce damage to your home, like seismic retrofitting. But even the retrofitters will tell you that even a structure that has been retrofitted may still be susceptible to damage, it just depends on the type and size of the earthquake. For example, I lived in Northridge when the Northridge quake happened in '04 and because it was a rolling earthquake, some houses were damaged and others on the same block weren't.
In addition, there are areas in the East Bay that aren't next to the fault line but are built on landfill- these areas may also be susceptible to natural hazard events.
Finally, you can obtain earthquake insurance, some people feel more comfortable having it, others don't.
Check out http://www.bayarearetrofit.com/ - these guys are pretty knowledgeable and their website has a lot of useful info.