USGS-developed earthquake scenarios describe the expected ground motions and effects of specific hypothetical large earthquakes. In planning and coordinating emergency response, utilities, emergency responders, and other agencies are best served by conducting training exercises based on realistic earthquake situations, ones that they are most likely to face. Earthquake scenarios can fill this role; they can be generated for any potential hypothetical future or past historic earthquake.
Once a model of expected ground motions has been developed for a given earthquake scenario, planners, engineers, emergency managers and others can pulse the built environment with the scenario earthquake ground motions. Software such as FEMA's HAZUS (Hazards US) and the USGS developed "ShakeCast", take these ground motion estimates and compare them to the fragility estimates for existing building stock to estimate damage and losses. More detailed building inventory information can further improve these estimates.
Earthquake scenarios can greatly improve the realism of emergency exercises and reveal cost effective targets for strengthening as part of a hazard mitigation plan.