It is not too clear what your major concerns are regarding the newer code requirements of 1997, so I would suggest that whatever you are concerned about you confirm with the City or County would be covered during this uniform change. As Kimberly has stated, code upgrades can be very expensive when dealing with structural issues and may not be cost effective.
A good home inspector will know the codes and be able to inspect the home that you are interested in purchasing in. You will also get a Natural Hazards Disclosure during your inspection period to note zones where the subject home is. Also you may want to consider purchasing earthquake insurance if that would bring some peace of mind.
Real Estate is all about location - so don't let an older house put you off if it offers the neighborhood and schools districts that you want. Most folks are concerned that the home has double pane windows, efficient heating and air conditioning systems, and double strapping of water heaters. While the floor plans may be dated in these older homes, usually they are on much larger lots in established neighborhoods. Another big plus is the area may be more stable when it comes to short sales and bank foreclosures, since the people have been in their homes for a while.
Jon, food for thought. Find a good REALTOR and home inspector. I frequently use an inspector that is a civil engineer for my Clients, which brings a great deal of expertise to his reports.
I have included a link to the California Building Standards Commission website for California.