Assessing Hazards

Assessing a natural hazard well is challenging. It involves five basic questions: how is the hazard defined? where will major hazardous events occur? when will they occur? how big will they be? what will happen when they occur? Because our estimates of all the quantities involved have large uncertainties, scientists' goal should be to do the best they can while recognizing the limitations involved. Sometimes this process works well. In other cases it doesn't, indicating the need for improvements. This chapter illustrates the current status of this process for earthquakes. Earthquake hazard maps often do not do well, largely because earthquakes turn out to be more variable in space, time, and magnitude than implied by the short record available. Although the specifics differ, similar issues arise for other hazards.