The Role of Earthquake Hazard Maps in Loss Estimation: A Study of the Northridge Earthquake

Local-scale seismic hazard maps are an important component of loss estimation because they provide information on possible site effects. This paper evaluates how well seismic hazard maps predicted damage in the Northridge earthquake. Normalizing for residential density, the research found that structures built on several geologic map units shown on pre-1994 hazard maps had significantly more damage than the area-wide average. Specifically, buildings on fine-grained Holocene alluvium, hillside bedrock, and “moderate” and “very high” liquefaction susceptibility zones were 1.5 to 2.5 times more likely to be damaged than the area average. Pipes were four times more likely to break in “very high” liquefaction susceptibility zones than in the area as a whole. The use of hazard maps in loss estimation can help state and local governments to set priorities in managing land use, enforcing building codes, conducting seismic strengthening programs for existing structures, and planning for emergency response and longterm recovery.