Three Million Exposed to Quake's Severe Rumbling

(Jan. 14) -- Despite Haiti's relatively small size, the close proximity of Tuesday's 7.0-magnitude earthquake to the capital city of Port-au-Prince meant that an estimated 2.9 million people were exposed to the severe ground shaking that's the chief cause of building collapses and fatalities.

Only four other earthquakes since 1970 have put as many people at risk, according to data from the U.S. Geological Survey. The 2008 quake in Sichuan, China, which killed 69,000, was the most powerful of these, registering 7.9 on the Richter scale and putting 5.6 million people in harm's way. But high exposure doesn't necessarily lead to widespread casualties. The 6.7-magnitude quake in Northridge, Calif., in 1994 killed 33, while 1.5 million residents lived through the most dangerous moments.

The number of casualties caused by earthquakes is largely dictated by the disaster's raw force, the population density in the most severely hit areas, and the ability of the infrastructure in those areas to withstand powerful shocks -- meaning Tuesday's quake is likely to be the most devastating catastrophe in Haiti's history. The latest estimate from the Red Cross puts the death toll at 45,000 to 50,000, or about 10 times worse than the 5,000 fatalities caused by Hurricane Flora in 1963.

If there is anything to be thankful for, it's that, at this time, the percentage of those expected to have died is small compared to the total number of people at the greatest levels of risk. If the Red Cross' estimate is reasonably accurate, then about 1 percent of the exposed Haitian population perished. The following chart shows how this compares with other quakes since 1970 that killed at least 10,000 people (green bars represent quakes where the number of people at risk was less than 1 million):

*Figures on Haiti are based on early estimates.

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