Social media has been established in many larger emergencies and crises. This process has not started just a few years ago, but already 15 years ago in 2001 after the terrorist attacks of 9/11. In the following years, especially in the last 10, sometimes summarized under the term crisis informatics, a variety of studies focusing on the use of ICT and social media before, during or after nearly every crisis and emergency has arisen. This article aimed to recapitulate 15 years of social media in emergencies and its research with a special emphasis on use patterns, role patterns and perception patterns that can be found across different cases to point out what has been achieved so far, and what future potentials exist.

Since the terrorist attacks of 9/11, the use of social media in emergency and crisis events has greatly increased and many studies have concentrated on the use of ICT and social media before, during, or after these events. The field of research that these studies fall under is called crisis informatics. In this article, we evaluate and analyze crisis informatics research by looking at case studies of social media use in emergencies, outlining the types of research found in crisis informatics, and expounding upon the forms of interaction that have been researched. Finally, we summarize the achievements from a humancomputer interaction perspective and outline trends and challenges for future research.

Various studies show that social media is used in emergenciesand that in spite of possible challenges for emergency services, beneficial use cases can be identified. However, relatively little empirical data is available regarding the attitudes of emergency services towards social media, and almost none of a comparative nature. This article summarizes the findings of a survey conducted of the EU project 'EmerGent' with 761 emergency service staff across 32 European countries from September to December 2014. The main aims of the survey were to explore the attitudes expressed by emergency service staff towards social media for private and organizational use as well as the levels and main factors influencing the current and likely future use of social media in their organizations. Based on our results, we discuss possible enhancements of the emergency management cycle using social media.

Social media is increasingly being used during emergencies. Most available studies are focused on how citizens and/or authorities use these technologies in concrete events. However, larger quantitative studies with significant results on attitudes, needs and future plans of citizens in such events are not available -especially such of a comparative nature related to emergency services. As part of the EU project 'EmerGent' this article presents the findings of a survey of 1034 citizens across 30 European countries conducted between February and June 2015 to explore citizens' attitudes towards the use of social media for private purposes and in emergency situations. The article briefly compares these findings with a second survey conducted with 761 emergency service staff across 32 European countries from September to December 2014. The aim of the overall study is to discuss citizens' attitudes towards social media in emergencies in order to derive challenges and opportunities for social resilience.

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