As the global population increases and is concentrated into megacities, there are widespread issues relating to pollution, overcrowding, poverty and health. But there’s another major threat to life and infrastructure that is often overlooked: earthquakes.
Many megacities in Asia have grown from smaller settlements that have been destroyed by earthquakes numerous times in the past. Take Tehran, current population around 10 million, which was badly damaged by earthquakes in 855, 958, 1177 and 1830. These events all happened when the city’s population was a small proportion of its present-day total. If an equivalent earthquake occurred today, the death-toll would probably be in the hundreds of thousands or millions. It’s a similar story in many major cities across the tectonically active parts of Asia, such as Delhi, Istanbul, Xi’an, Karachi, Almaty and Tbilisi.
This is not a coincidence. The original settlements from which these cities have grown were established on ancient trade routes running through Asia and the Middle East. These followed coastlines and the edges of the mountain ranges — which were formed by repeated earthquakes — because the interiors of the mountains and the intervening deserts were too hostile. This means that Asia’s megacities are concentrated in the areas of highest earthquake hazard, as the map opposite shows.