Public Response to Aftershock Warnings.

Abstract

This report is on public response to aftershock warnings after the Loma Prieta earthquake. The report reviews the short- and long-term aftershock warnings issued to the public after the earthquake. The results of past research are then synthesized into hypotheses tested in this research. Descriptive findings about public aftershock warning response in both San Francisco and Santa Cruz Counties are then reported. Finally, the causal theory of risk communication was tested on public perception of risk and response to aftershock warnings during the postimpact Loma Prieta earthquake emergency. Findings from samples of households in Santa Cruz and San Francisco Counties were consistent, confirm established propositions, and suggest theoretical refinement. It was concluded that the social psychological process which explains postimpact public warning response is not identical to the one which explains public response to pre-impact warnings. The lack of mainshock damage created a "normalization bias" for nonvictims. This bias limited their perception of risk to damaging aftershocks and protective response to warnings.