When a major tragedy occurs, how is the death toll calculated so quickly?

Question

Today we saw the devastating effects of the 7.8 earthquake in China.

The inital reports were the 900 students were trapped under rubble... but then it grew to 2,000... 4,000... 6,000... now I see over 8,500.

How is this number calculated? The earthquake happened less than 24 hours ago, so the number of bodies couldn't be counted that fast. Is it based on rough population? Do villages have a census, and if so, how accurate is it? Is it just a guess?

Please, serious responses only... and star the question if you find it interesting.

Answer 1

They probably do it based on loaction and census reports in the disaster area