The good news is that there are seismic retrofits that can offset these potential hazards. Retrofitting projects can be tremendously expensive, but the price is not nearly as high as that of rebuilding your house. If you think that your older home is not seismically safe, you should hire a licensed inspector, contractor or engineer to assess the condition of the building and advise you on what work needs to be done. It's possible that you only might need to bolt the foundation to the walls of your house, a simple and not very costly process.

For further details on foundations, see The Homeowner's Guide to Earthquake Safety, produced by the Seismic Safety Commission of the State of California.

You should also review Is Your Home Protected From Earthquake Disaster? A Homeower's Guide to Earthquake Retrofit, prepared by the Institute for Business & Home Safety (IBHS), and the "Foundations" section of This Old House Online's "From the Ground Up" series.