Abstract: The evolvement of information towards emergencies (ITE) is usually triggered by emergences, and the negative public opinion crisis caused probably by the evolvement of ITE has a serious impact on the order in social life. Thus how to accurately grasp the evolving law of ITE is an important part of risk governance for public affairs under new situations of social development. However, few of the existing studies consider the problems of structured description and equilibrium changing law for the evolvement of ITE, and pay attention to modelling the evolvement process of ITE and its regulation mechanism from the perspective of system. Therefore, the internal and external attributes of the evolvement of ITE are first extracted by case analysis and structured description method. Then, an evolving system is designed according to the time sequence relationships of attributes. Further, a stochastic Petri net model of the system and its isomorphic Markov chain are constructed respectively. Finally, taking the evolvement of ITE in 2009 source blockage incident of Limin radiation factory in Qi county of Henan province as an example, some experiments of scenario simulation are carried out to study the system equilibrium changes and its regulation. The studies propose the structured description, evolving system and different evolving states of the evolvement of ITE, and obtain the changing law of system equilibrium and its regulation mechanism. The results not only can provide normative guidance for the equilibrium study of complex information evolving process, but also can help to identify the impact of regulation measures on the probability of information evolves to some negative states (negative public opinion, rumors and secondary events, etc.). On such basis, the problems of evolving law and its regulation for multiple ITE with collision and coupling mechanism are suggested to be taken into account in future studies.

Key words: emergencies, information evolvement, stochastic Petri net, Markov chain