Buildings are complex. Foundation, walls, floors, roof, electrical, plumbing heating, cooling, insulation systems all come together through plans and labor to create a building. Understanding how such a system will perform under seismic stress (earthquake) is complex and hard to predict with precision. Good engineers and designers following standards can reduce loss when buildings shake, but not all earthquakes are the same and can vary in intensity, duration and the kind of shaking. Even the nature of the land underneath a building can make a major difference in impact. So when a major earthquake strikes, it is a living experiment, and there are always lessons to be learned. The 1971 San Fernando, 1989 Loma Prieta and 1994 Northridge earthquakes were costly in terms of lives and money, but we learned much about how to make things safer.
When freeways in California were built, engineers used the best practices of the day. But those three California quakes demonstrated that these were not adequate to withstand the impact of strong shaking. The vulnerabilities exposed by those quakes taught us valuable lessons, and since 1971 California has spent over $13 billion retrofitting thousands of freeway overpasses and bridges. In Los Angeles alone almost 850 were upgraded. This makes us safer on the road and reduces the costs of recovering from future seismic events.
Similar improvements have been made in building standards and codes, often driven by losses resulting from some natural or manmade disaster. Perhaps the first building code was the Code of Hammurabi (1800 B.C.), essentially a criminal statute that included capital punishment for shoddy workmanship. And major fires in history, including those in Rome, London, and Chicago have all led to the creation of new codes. Building codes have likewise been improved following storms and earthquakes. After hurricane Andrew in 1992, Florida instituted a statewide building code. And California has upgraded its code recommendations after major earthquakes.