Sir

The recent earthquakes in Taiwan, Turkey and Greece are a reminder that the world's urban population is increasingly vulnerable to earthquakes. About one-third of the world's supercities — those with populations of more than two million — are located near tectonic plate boundaries, where damaging earthquakes have occurred and will recur.

Between 1950 and 2050 the world's population will have increased from 2.5 billion to 8.9 billion, most of whom will live in great cities. In 1950 there were two megacities with populations of more than eight million, whereas there are now 27. All cities close to plate boundaries, and many that are not, are vulnerable to earthquake damage some time during the next millennium. Although earthquakes with more than a million fatalities have not occurred in human history, the availability of many new urban targets with populations approaching tens of millions makes such an event possible during the next century.

Offsetting this bleak view of potential fatalities is the recognition that the additional three billion people anticipated in the next 50 years will require a 50 per cent increase in urban construction. Although half of this future growth is expected in parts of Africa where earthquakes are fortunately rare, much future growth is expected in Asia where rates of seismic activity are high. Loss of life from future earthquakes could be much reduced if new construction in known seismogenic zones was designed to withstand shaking.

The reconstruction costs following an urban earthquake have risen to levels that represent an economic burden not only on local economies, but also on the global economy, making the incorporation of earthquake resistance economically attractive.

The absence of earthquake resistant construction in future cities would be indefensible. But the issue may remain a low priority in many developing nations.