Urban Earthquake Fatalities: A Safer World, or Worse to Come?

The global fatality count from earthquakes continues to rise. This has occurred despite the adoption of earthquake resistant building codes in most countries where damaging earthquakes have historically caused loss of life. In the past five centuries the global deathtoll from earthquakes has averaged 100,000/year, a rate that is dominated by large infrequent disasters, mostly in the developing nations. Though an increased fatality rate might be expected from the steady increase in global population (Bilham, 1988), recent urban growth has been accompanied by a decline in the fatality rate as expressed as a percentage of instantaneous population. It is tempting to attribute this observation to the application of earthquake resistant construction code in new city construction. A more sinister interpretation, however, is that the apparent decline in risk is caused by the short exposure time (50 years) of the world's recently increased population to earthquakes with recurrence intervals of the order of centuries. Future extreme earthquake disasters in some of the world's megacities may arrest, or reverse, the current trend. Figure 1 (Left) City populations between 1960 and 2000 grew on average by a factor of 2.55. The mean urban growth rate in the developing nations (filled bars) is twice this, largely in cities with present populations of less than 1 million. (Right) Global urban population grows mostly in cities in the developing nations.