Benefits of scenario ground motion maps

Earthquake hazards can be communicated with both probabilistic seismic hazard maps and “deterministic” maps showing estimated ground motions expected from a subset of the possible earthquakes. This paper describes the latter class of maps as “scenario” ground motion maps. The principle behind the scenario maps is to portray a median estimate of ground motions from events that are reasonable, and regionally the most significant. The intent is that the scenario map answers the common question: “If the fault ruptures, what do you expect?” This paper proposes rules for construction of scenario maps, argues that a parallel map (a scenario probability map) should be constructed giving estimates of the annual recurrence rates of the scenario ground motions, and compares probabilistic and scenario ground motions for areas with high and moderate seismic hazards. Uses for scenario maps include educating the public about the earthquake hazards, some engineering applications and hazard response planning.