Killer earthquakes

There is a grisly debate about just which earthquake has killed the most people, but there is little doubt that they are the most deadly of natural hazards, ahead of severe weather.

There are thousands of small earthquakes every day, and on average one big one a year at or above 8 on the Richter scale.

According to Stephen Nelson ofTulane University in the US,'earthquakes don't kill people, buildings do”. He points to the biggest killer quake in recorded history, when some 830,000 people died in 1556 in Shanxi, China. They were living in caves cut into the soft blown soil called loess and were buried alive.

When Tokyo was devastated by an earthquake in 1923, much of the damage was done by fires which ran through wooden buildings. In the modern era, buildings in earthquake zones in the developed world are often very secure but the same cannot be said of the developing world.

However, the Boxing Day 2004 earthquake that affected Indonesia and other nations in south Asia and east Africa, with a death toll of almost 300,000, showed that it is harder to guard against the big waves (tsunamis) that a major subsea earthquake produces. A better early warning system that would allow enough time for evacuation is the preferred solution, but it will be hard to implement for the nearest communities because warnings would inevitably come only just before the tsunami itself. The near-total destruction of the city of Lisbon in 1755 was partly due to a tsunami which followed the initial quake, and Messina in Sicily suffered a similar fate in 1908.

Bill McGuire of University College London notes that the death tolls from natural hazards have been increasing, and attributes this to growing world poverty. The table opposite lists the most deadly earthquakes on record, as compiled by the US Geological Survey.