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Professor Ali Asgary: How the experts calculate the death toll in disasters

Professor Ali Asgary: How the experts calculate the death toll in disasters

The death toll in Japan has continued to climb since last Friday’s 9.0-magnitude earthquake and tsunami, wrote the National Post blog "Posted" March 16 in a Q&A article:

Official estimates suggest 10,000 people have died, although the police chief of the hard-hit Miyagi prefecture said this week he expects the toll to exceed that in his region alone. Official numbers released Wednesday confirm 4,314 deaths and 8,606 still missing. The National Post’s Aileen Donnelly asked Ali Asgary, professor in York University’s Disaster & Emergency Management Program, how death tolls are estimated and recorded after a catastrophe and why the figures vary.

Q: How are death toll estimates determined?

A: Estimates come through computer models, or through expert judgment. In Japan they have a system called the National Disaster Information System that has all the information about population and infrastructure in different parts of the country. As soon as something happens, they can run the model and figure out how much damage and how many potential losses they might have…. As time goes on, the model could become better by receiving actual or real information, for example, the exact magnitude of the earthquake. When [computer modelling] is not available, like in developing countries, what they do is they rely on expert judgment, [which] is not as accurate.

Q: How do experts estimate deaths without a computer model?

A: Rapid assessment is usually based on several factors: the population in the area that has been impacted and the damage or loss ratio for different earthquake magnitudes. This is a ratio they use for the number of casualties per different [earthquake] magnitudes in different physical environments. In Japan, another factor they often use is a ratio of number of fatalities to number of injured people. [The ratio there] is about 45, which means for every 45 injured people, you will have about one dead person…. These are the factors experts use. These are based on past experience, the existing population number and the building type and structure they have in the area. [Experts] might not need to go into the field to figure out how many people have been killed. They usually use the knowledge that they have about the area. But, by going there, it helps to make the estimate closer to the actual number.

Q: Why do you think the Japanese government has avoided releasing estimates?

A: Having an accurate estimation of dead people is not going to do a lot at this point. And that is probably why [the government is sticking] with the actual [count of] bodies. From an emergency management point of view, we look for the survivors and find out what their needs are and how we can help them…. I think people are cautious about providing numbers [now] because it’s not only an earthquake, it’s not only a tsunami, it’s a combination of different hazards hitting the country at the same time. Plus, we have the evacuation going on for the nuclear issues.

Posted by Elizabeth Monier-Williams, research communications officer, with files courtesy of YFile – York University’s daily e-bulletin.