Operational Earthquake Forecasting and Decision-Making

Abstract

Traditionally, seismic risk reduction is achieved only through a sound earth- quake building code. Nonetheless, some recent seismic disasters have highlighted the need for enlarging the range of risk mitigation actions beyond that. In particu- lar, the occurrence of a seismic sequence may increase the weekly probability of a large shock by orders of magnitude, although the absolute probability usually re- mains below 1/100. Here, we summarize the state of the art in short-term earth- quake forecasting and discuss how these forecasts may be used to mitigate seismic risk in this time horizon. Because of the low probabilities and high false alarm rates of possible advisories, mandatory mitigation actions would not be an effec- tive practical strategy to reduce risk. Alternatively, we propose some low cost strategies, such as increasing vigilance and preparedness, for using probabilistic forecasting to mitigate seismic risk. These are based on the ‘nudging’ principle of devolving decision-making down from civic authorities to the individual level.