Thanks Steve - those are generally the points I was trying to make. I would take issue with only your assertion that "most major code revisions go into effect after a significant seismic event . . ." That may be true or not. I don't know of any study to support it. It might just seem to be true, since there are notable examples of dramatic changes or additions to codes after dramatic events. Nobody notices the constant and continuing revisions and adaptations to engineering methods and codes that go on constantly in the background, but things such as the 1972 Alquist-Priolo Act, resulting from the 1971 Sylmar quake, are high-profile and well-known. Or the improvements in welding techniques on major structural members of high-rise buildings after Northridge. At any rate, it's working rather well. CalTrans, for instance, has either finished or nearly finished retro-fitting every single freeway overpass in the state to withstand predicted movement for its location. This was not due to any particular earthquake, but rather to a steadily improving understanding of earthquake dynamics and examination of cost/benefit ratios. When the REALLY big one occurs in a major metropolitan area, I am sure it will turn out that there were one or two miscalculations, but I think the overall performance of our infrastructe will turn out to have been quite impressive.

Michael Williams in Arroyo Grande, CA