Operational Earthquake Forecasting and Risk Management

In daily life, the general public is commonly exposed to remote uncertain hazards, which would pose a threat to life and property if they were to materialize. Hazard warnings elicit a wide range of precautionary responses, many of which involve comparatively little cost. Air passengers buckle their safety belts during turbulence just in case they may be ejected from their seats. Homeowners in the Caribbean board up their windows with the approach of a tropical storm, just in case it intensifies into a damaging hurricane. U.S. citizens have bought duct tape to seal their homes, just in case of a terrorist attack involving toxic aerosols. Most major earthquakes occur without any observed precursory evidence on which to base a hazard warning decision. However, for some major earthquakes, a degree of precursory evidence may be available that identifies a time of increased probability (TIP). The task of quantifying the probability gain is being made easier by steady technological progress, such as in the higher resolution of fault monitoring. But the level of confidence in an earthquake forecast is extremely unlikely ever to justify the mandatory evacuation of a populous region: the toll of casualties anticipated from the mass evacuation process may be deterrent enough. Notwithstanding this ultimate limitation, a range of far less draconian, and more acceptable, risk mitigation measures may be warranted provided the expected benefits are commensurate with the costs. None of these measures need be mandatory or coercive. Indeed, they may be entirely voluntary. A lesson from the politically influential public policy discourse of Thaler and Sunstein (2008) is that citizens and organizations can be gently “nudged” into taking courses of safer action, without undue authoritarian pressure. Accordingly, the horizon of earthquake forecasting can be expanded far beyond the call for evacuation to justify and motivate practical voluntary …