How big an earthquake will a retrofitted house go through without damage?
This question is asked frequently. Essentially, though, it is unanswerable. The movement during an earthquake is too complex, and there are too many unknowns to be able to answer this question directly. In past earthquake situations, two houses built at about the same time, right next to each other, and with many other similarities have performed very differently. Size and shape of the house, condition of the concrete foundation, how well it has been maintained, modifications and changes in the original construction which may have created structural weakness, and many other variable factors will affect earthquake damage. Given this, it is important to think of earthquake damage prevention as a risk reducing practice rather than have a more absolute expectation as to what may be accomplished. The comparison may be something like maintaining a good diet and exercising to reduce the risk of heart disease. Both are good health practices; they reduce the risk of a heart attack, but there is
