"How Earthquakes Affect Buildings," by Ronald O. Hamburger, Buildings magazine
Throughout the 20th century, the intent of seismic design in building codes was to avoid earthquake-induced damage that would pose a significant risk to safety while still permitting economical designs. Thus, building code provisions were developed that would permit some damage to occur, but protect against damage likely to lead to either local or partial collapse, or the generation of dangerous falling debris. When these building codes were first developed, the technical community didn't have a good understanding of ground shaking, its magnitude, the dynamic response characteristics of structures, or nonlinear behavior. Today's codes still seek to protect life safety vs. minimize damage, but do so through a variety of prescriptive criteria based on observation, as well as laboratory and analytical research.