Exploring the evolutionary characteristics of social media data in metro emergencies: A case study of Zhengzhou metro flood

With the development of urban transportation, metros have become an important means of travel for residents. However, casualty and economic loss might occur in metro systems due to various emergencies. Social media has gradually become the main way to express people's needs, which provides a new analysis perspective for risk management in metros. This study takes the Zhengzhou metro flood as an example and collects relevant social media data. Then, the analysis method of social media data evolution characteristics in metro emergencies is proposed. Finally, the evolution characteristics of social media data are analyzed from three aspects: spatiotemporal distribution, emotional distribution, and hot topics classification. The results show that: the temporal distribution of social media data is affected by the emergency process and official media; the spatial distribution of social media data reflects the distribution of stations affected by emergency and temporary shelters; timely and appropriate official media reports are conducive to guiding public emotions toward positive; the key hot topics can be divided into disaster environment (DE), disaster impact (DI), disaster carriers (DC), emergency management (EM), positive comments (PC) and negative comments (NC). The proposed method can provide support for public opinion analysis and risk management in metro emergencies.