Earthquake Damage Lessons from Big Bear Lake, California, 1992

Abstract

Apart from the anticipated damage to unreinforced stone and masonry chimneys, some disturbing results were observed in the June 28, 1992 earthquakes; namely, the unsatisfactory performance of recently built residential structures, some of which were clearly deficient, despite being subject to code‐enforcement procedures, and others that were in substantial compliance with the building codes. The fact that building standards, as reflected in the codes, have been subjected to stepwise developments over the last 60 years has produced a stock of buildings that possess a range of seismic resistance. However, it would be expected that, in general, the newer structures would perform better than the older ones. Experience in the Big Bear Lake area has shown departure from this pattern in several categories. One comprises buildings that failed prematurely, almost certainly as a result of negligent construction. A second includes buildings where failure appears to have been brought about by deficiencies that the codes do not address. Recent case studies are used to illustrate these disturbing facts.