Public health impact and medical consequences of earthquakes.

Worldwide, more than one million earthquakes occur each year, an average of about two every minute (1). Research indicates a 60% probability that an earthquake of Richter magnitude 7.5 or greater will occur on the San Andreas fault in southern Cal-ifornia within the next 30 years, and a 50% probability that an earthquake of 7.0 or greater magnitude will occur on the San Andreas or Hayward faults in the San Francisco Bay region within the same time period (2). As previewed by the significant damages resulting from the 1989 Loma Prieta earthquake in northern California (magnitude 7.1) and the 1994 Northridge earthquake in southern California (magnitude 6.8), the impact of the predicted higher magnitude earthquakes in California and the central United States could potentially kill and injure thousands of people, result in billions of dollars in property loss, and cause severe disruptions to the United States economy (3). Despite remarkable scientific progress in seismology and earthquake engineering during the past several years, achieving high standards of safety against earthquakes is a goal that has yet to be achieved in many parts of the world. During the past 20 years, earthquakes alone have caused more than a million deaths worldwide (4). for more than 80% of all fatalities in this century, and almost half of the total number of earthquake casualties in the world during this period have occurred in China alone (5). Recently, fast urbanization in other seismically active parts of the world whose population densities reach 20 000 to 60 000 inhabitants per square kilometer makes such areas vulnerable to similarly catastrophic numbers of earthquake-related deaths and injuries. In just the past 10 years, the world has witnessed four catastrophic earthquakes resulting in great loss of life: The United States has been somewhat fortunate; it has had relatively few earthquake-related casualties so far; only an estimated 1 600 deaths have been attributed to earthquakes since colonial times, with over 60% of these having been recorded in Califor-nia (6). The number of casualties caused by an earthquake will depend on its magnitude, its proximity to an urban center, and the degree of earthquake disaster preparedness and mitigation measures implemented in the urban center closest to where the earthquake takes place.