Since there has not yet been an international standard definition for catastrophe,in this paper,a catastrophe is defined as any serious disaster which can hardly be coped with only by one nation or region and shall be handled by means of extemal forces and which is usually deemed as a one-hundred-year event.In China,Tangshan Earthquake and Wenchuan Earthquake are deemed as catastrophes; the flood in the mid and lower reaches of the Yangtze River in 1998 and the southern low-temperature freezing rain and snow-storm in the early 2008 are also deemed as catastrophes.