Earthquakes and their interpretation: The campaign for seismic safety in California, 1906-1933

In 1906, a severe earthquake devastated San Francisco and surrounding areas of central California. Yet the California public did not view this shock as an indication of a continuing seismic hazard. After a milder quake struck southern California in 1933, Californians reacted differently. By rapidly enacting local and state-wide building codes requiring earthquake-resistant construction, the public acknowledged that something had to be done about earthquake risks in the state. What happened between 1906 and 1933 to produce this profound shift in public attitudes toward seismic hazards in California?; I argue in this dissertation that after 1906 a small number of scientists and engineers developed a new interpretive framework for understanding earthquake risks in California, and that these scientists and engineers gradually acquired the means that allowed them to prevail with their interpretation after the 1933 earthquake. Underlying my argument is the contention that hazards and their implications for human action are never obvious, but rather are subject to interpretation and debate. At the same time, I maintain that the occurrence of natural disasters profoundly affects the persuasiveness of opposing interpretations of risks.; In 1906, even scientists and engineers did not perceive the need for greater earthquake preparedness in California. Not until 1909 did two geologists with roots in the Progressive conservation movement argue unequivocally that earthquakes would recur and that this hazard needed to be guarded against. Over the next two decades, California scientists, relying on patronage from local networks of supporters as well as a national foundation, developed a program of applied seismological research that amassed considerable evidence of continuing seismic activity in the state. These entrepreneurial scientists also honed a rhetoric of earthquake preparedness and engaged in extensive public relations efforts to urge Californians to protect themselves against future earthquakes. An attempt in the mid-1920s to scare Californians into earthquake preparedness by prophesying an imminent seismic catastrophe for southern California failed, however. The campaign for greater seismic safety did not succeed until an earthquake actually struck metropolitan Los Angeles in 1933. This event finally provided seismologists with the opportunity to convince Californians of the need for earthquake preparedness.