To assess the volume of patients and the composition of their injuries and illnesses that presented to an emergency department (ED) close to the epicenter of an earthquake that occurred in a seismically prepared area.

A retrospective analysis of data abstracted from charts and ED logs for patient census and types of injuries and illnesses of the patients who presented in the ED of a community hospital before and after the earthquake (6.8 Richter scale) that occurred in 1994 in Los Angeles. Illnesses were classified as trauma- and non-trauma related. Data were compared with epidemiological profiles of earthquakes in seismically prepared and unprepared areas.

A statistically significant increase in ED patient census over baseline lasted 11 days. There was a large increase in the number of traumatic injuries such as lacerations and orthopedic injuries during the first 48 hours. Beginning on the third day after the event, primary care conditions predominated. When the effects of the LA quake were compared with those of similar Richter magnitude and disruptive capability, the ED epidemiology profile was similar to those in seismically unprepared areas, except for the total number of casualties.

The majority of patients with traumatic injuries presented within the first 48 hours. The increase relative to baseline lasted 11 days. Efforts to develop disaster response systems from resources outside the disaster-stricken area should focus on providing mostly primary care assistance. Communities in seismically prepared areas could require external medical assistance for their EDsfor up to two weeks following the event.