Umansky Casapa, NataliaNataliaUmansky Casapa2022-12-072022-12-072022 the A2022http://hdl.handle.net/10197/13289Famously coined by the Copenhagen School of Barry Buzan, Ole Wæver, and Jaap de Wilde (1998), the concept of securitization focuses on political communication to explain how security threats come into existence. Rather than treating security as a given object, securitization understands security as a linguistic practice (Aradau et al., 2014) and builds on the constructivist idea that by 'speaking security' a given issue becomes a security problem (Austin, 1975; Stritzel, 2014; Wæver, 1995). As with other forms of political communication, the advent of social media has brought about important implications for securitization, accommodating a wider range of actors and providing more accessible means to make effective claims about threats. Yet on the basis that 'security is only articulated in an institutional voice by the elites' (Wæver, 1995: 57), the securitization scholarship has been slow to adapt to the new context of online political communication, leaving many open questions about the ways in which online networks contribute to the emergence of security problems. This dissertation explores this puzzle by integrating tools from the field of Computational Social Science to study the working mechanisms that bolster securitization on online networks. The three studies that are part of this analysis seek to address the gap between the important theoretical advancements that have been developed in previous work and their limited empirical applications by adopting diverse methodological approaches to re-examine theoretical questions in the field of security studies. In particular, this work contributes to our understating of securitization by three means: 1) it offers a systematic empirical framework to study securitization as discourse networks; 2) it delves into the question of who are the actors that define security problems online; and 3) it analyses the ways in which securitization spreads on online networks. This project, therefore, contributes to the literature both theoretically and methodologically. Most importantly, it challenges the top-down approach that has been widely adopted by the securitization scholarship and shows that the online behaviour of elite and non-elite actors has significant implications for international security.enSecurity studiesPolitical communicationComputational social scienceSocial mediaDoctoral Thesis2022-11-30https://creativecommons.org/licenses/by-nc-nd/3.0/ie/