Organizations and individuals in seismically vulnerable areas of the nation seek to reduce risks in diverse ways, including informed land-use planning, structural and nonstructural mitigation, the purchase of insurance, and planning for response and recovery. It is this last strategy for risk reduction that is the topic of this section. Response readiness—action associated with development of plans and conducting exercises—relies on seismic monitoring to describe long-, intermediate-, and short-term earthquake potential, to provide information on earthquake effects, and to estimate the impacts of earthquakes on the community.

For areas of high seismic risk, the U.S. Geological Survey (USGS), state-level geological agencies, and academic scientists have used monitored information to develop projections of long-term seismic potential based on fault characteristics, local geological conditions, recurrence intervals for large events, and other factors (WGCEP, 1988, 1995, 2003). These studies have provided state and local government agencies and private sector entities with essential information for earthquake hazard reduction actions that include focused planning and prioritized hazard mitigation for areas judged to have the highest probability of large damaging earthquakes. These studies have also provided the basic information needed for the development of exercise scenarios to improve response readiness.

Organizations that must respond rapidly to a significant earthquake or other disasters typically conduct drills and exercises to test their readiness and the quality of their planning. These exercises vary in extent of involvement and degree of detail, from limited “tabletop exercises” that include a few key decision-makers gathered around a conference table, to full-scale field exercises that include many departments and full activation of emergency operations centers. With the development of ShakeMap, emergency response exercise scenarios have reached degrees of sophistication that provide substantial benefits for response readiness.

When combined with loss estimates from HAZUS, ShakeMap earthquake scenarios provide important details of potential earthquake impacts on a city, county, or region. In the past, response organizations relied on vague projections that were largely the result of guesswork regarding earthquake size and effects. The currently available ShakeMap-HAZUS scenarios include empirically grounded estimates of shaking intensity and regional patterns of shaking, and as input data for HAZUS, ShakeMap contributes to plausible estimates of total dollar losses, utility damage, building damage, and population impacts including the number of deaths, various levels of injury, the number of people displaced from their homes, and the probable demand for shelter and mass care. When mapped, these

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