Human nature is no stranger to disaster, but when Wenchuan earthquake and the plain reality of the time, the natural power of human beings before the fragile, exposed completely.

The picture shows children of a primary school in Wenchuan earthquake-stricken area gathered in front of a tent donated by the United Nations Children's Fund.

With a recheck of the observing data of Wenchuan and some other earthquakes, also based on the concept of fracture mechanics, it is deemed that there exists a micro-fracture wave before earthquakes.