GIS Mapping of Earthquake-related Deaths and Hospital Admissions from the 1994 Northridge, California, Earthquake

Purpose: Earthquakes pose a persistent but unpredictable health threat. Although knowledge of geologic earthquake hazards for buildings has increased, spatial relations between injuries and seismic activity have not been explained.

Methods: Fatal and hospital-admitted earthquake injuries due to the 1994 Northridge Earthquake were identified. Geographical Information Systems software was used to map all injury locations. Injuries were analyzed with regard to distance from the earthquake epicenter, the Modified Mercalli Intensity Index, peak ground acceleration, and proportion of damaged residential buildings.

Results: Injury severity was inversely related to distance from the epicenter and increased with increasing ground motion and building damage. However, injury incidence and severity were not completely predicted by seismic hazard and building damage, and injuries of all severities occurred in a large geographic area. Average distance to the epicenter was smallest for injuries related to falling building parts and largest for cutting/piercing injuries and falls.

Conclusions: The injuries from the Northridge Earthquake extended beyond the areas of highest environmental activity. Factors such as age and activity during the earthquake may be equally important in predicting injury from earthquakes as seismic features.