Online map of the disaster index of China's natural disasters. Legend is coverage area index,in terms of severity,the ratio from strong to weak is 9.8-11.0;8.7-9.8;7.6-8.7;6.5-7.6;5.4-6.5;4.3-5.4; 3.2-4.3;2.1-3.2;1.0-2.1.