South China Sea's tsunami history

It's been more than two centuries since a major tsunami resulted from an earthquake under the South China Sea, the worst the world was to see until recent events. An estimated 40,000 people died as a result of the tsunami in 1782, according to the US National Geophysical Data Centre, more than any tsunami in history until the events of December 26 last year.

Four tsunami have affected Hong Kong in the past half century but none have generated a tidal surge of more than half a metre, according to the Hong Kong Observatory, and none would be strong enough to trigger a tsunami warning.

In 1952, an earthquake in Kamchatka generated a 15cm tsunami in Hong Kong, while two earthquakes in Chile in 1960 and 1985, and a 1988 earthquake in Luzon measuring 5.4 on the Richter scale generated tsunami of up to 30cm high.

The biggest tidal surge in modern times in Hong Kong took place along the Tolo Harbour in the early 1900s, when a six-metre wall of water raced down the Tolo Harbour and swamped the northern New Territories, causing multiple deaths in the area's rural farming communities.

However, the University of Hong Kong's Dr Jason Ali said the huge wave was not a tsunami but a storm surge, a wall of water whipped up by a cyclone - a relatively common phenomenon in areas prone to typhoons, although one that usually occurs further out to sea.