Self-organized criticality and its criterion in investigation of disaster

Selforganized criticality opens up a new way to the investigation of disasters. However, when selforganized criticality is used in the investigation of disasters, taking powerlaw distribution of the disaster′size only as the criterion of the selforganized criticality is not suitable and the attention should be paid to the three problems: the size of the system, the criterion of external perturbation, and the structure of the system. Based on the simulative experiment of sliding sand slope, it is suggested that the system can appear selforganized criticality, only when the size of the system, the structure of the system and the intensity of perturbation can keep whole system robust, which makes system maintain the critical state throughout. Five criteria of selforganized criticality are put forward.