The Role of Risk Perception in Tradeoffs for Earthquakes and Other Hazards

It is the role of the professional risk engineer to help guide society in its investment to mitigate against the consequences of earthquakes and other hazards. Too often these trade-off decisions are made without a full quantification of the multiple sources of the risks involved. Risk assessment should take into account the manner in which the risk might be mitigated, and separately the frequency of occurrence and magnitude of consequence. This paper presents comparative results of many natural hazards in terms of their frequency of occurrence and economic cost, injury and loss of life. It then explores the subject of risk perception and the role it plays in investments against various hazards. Losses due to earthquakes are studied, using a recent 25-year period in the United States as an example. In addition, data are collected for a total of 18 different natural hazards. Then information from the social-psychology literature on perception of risk expands the concept of risk from the common engineering one of probability of occurrence multiplied by a quantitative measure of consequence, to a multi-attribute one. This expanded measure includes such items as dread, familiarity, degree of voluntariness and trust. Finally, graphical comparisons are made of the risk due to earthquakes and other natural hazards, and recommendations made regarding the perspectives of different players in deciding on mitigation investments. The interaction between engineering risk and societal risk are highlighted. The multi-attribute nature of societal risk factors advocates for multidisciplinary decision-making.