Natural disasters exert a profound impact on the world population. In 2012, natural disasters affected 106 million people, forcing over 31.7 million people to leave their homes. Climate change has intensified natural disasters, resulting in more catastrophic events and making extreme weather more difficult to predict. Understanding and predicting human movements plays a critical role in disaster evacuation, response and relief. Researchers have developed different methodologies and applied several models to study human mobility patterns, including random walks, Lévy flight, and Brownian walks. However, the extent to which these models may apply to perturbed human mobility patterns during disasters and the associated implications for improving disaster evacuation, response and relief efforts is lacking. My PhD research aims to address the limitation in human mobility research and gain a ground truth understanding of human mobility patterns under the influence of natural disasters. The research contains three interdependent projects. In the first project, I developed a novel data collecting system. The system can be used to collect large scale data of human mobility from large online social networking platforms. By analyzing both the general characteristics of the collected data and conducting a case study in NYC, I confirmed that the data collecting system is a viable venue to collect empirical data for human mobility research. My second project examined human mobility patterns in NYC under the influence of Hurricane Sandy. Using the data collecting system developed in the first project, I collected 12 days of human mobility data from NYC. The data set contains movements during and several days after the strike of Hurricane Sandy. The results showed that human mobility was strongly perturbed by Hurricane Sandy, but meanwhile inherent resilience was observed in human movements. In the third project, I extended my research to fifteen additional natural disasters from five categories. Using over 3.5 million data entries of human movement, I found that while human mobility still followed the Lévy flight model during these disaster events, extremely powerful natural disasters could break the correlation between human mobility in steady states and perturbation states and thus destroy the inherent resilience in human mobility. The overall findings have significant implications in improving understanding and predicting human mobility under the influence of natural disasters and extreme events. / Ph. D.

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Submitted by Lucienne Costa (lucienneferreira@ufcg.edu.br) on 2018-05-03T17:57:55Z No. of bitstreams: 1 ALINE MARQUES DE MORAIS – TESE (PPGCC) 2018.pdf: 10249262 bytes, checksum: c0f35e5f7aa413cfd6fa1ee4abde4169 (MD5) / Made available in DSpace on 2018-05-03T17:57:55Z (GMT). No. of bitstreams: 1 ALINE MARQUES DE MORAIS – TESE (PPGCC) 2018.pdf: 10249262 bytes, checksum: c0f35e5f7aa413cfd6fa1ee4abde4169 (MD5) Previous issue date: 2018-01-29 / Redes Geossociais (RGs) representam um tipo de sistema colaborativo com informação geolocalizada encapsulada no conteúdo compartilhado. Essa formatação possibilita a interseção de informações presentes tanto no mundo real, quanto no virtual. Atualmente, a popularização das RGs já é algo concreto pelo mundo. Uma das razões para esse fenômeno é o suporte das RGs à tomada de decisão dos colaboradores sobre lugares. Além do mais, esses sistemas representam importantes ferramentas de monitoramento urbano, baseadas no fluxo de participação dos usuários. Entretanto, a presente tese detecta como problema de pesquisa o modo pelo qual as RGs tratam homogeneamente os seus participantes. Algumas consequências desse tratamento padronizado são um menor aproveitamento das potencialidades colaborativas dos usuários e uma menor eficiência na tomada de decisão dos participantes. Assim, este trabalho considera necessário a definição de parâmetros que caracterizem a diversidade de um tipo específico de participante: os criadores de conteúdo. Eles representam uma parcela dos usuários que efetivamente colaboram com as RGs. Trabalhos anteriores já investigaram aspectos da diversidade de criadores de conteúdo, em RGs usadas em diferentes regiões do mundo. Mas, nenhum deles analisou a diversidade dos criadores de conteúdo em RGs usadas em cidades brasileiras. Portanto, o presente trabalho realiza um mapeamento em larga escala da diversidade dos criadores de conteúdo geolocalizado em cidades brasileiras. Esse mapeamento é dividido em três abordagens. A primeira delas é a investigação da diversidade dos criadores, em relação à experiência dos contribuidores sobre os locais. A segunda abordagem é sobre a investigação da diversidade baseada nos padrões de comportamento ao contribuir. E, por fim, a última etapa do mapeamento se refere à diversidade dos participantes em relação ao comportamento espacial. Os resultados dos mapeamentos mostram que a diversidade dos criadores de conteúdo está presente em RGs usadas nas cidades brasileiras. Além do mais, a utilização dos resultados das abordagens é imprescindível para a concepção de RGs sensíveis aos tipos dos criadores e para mecanismos de recomendação de lugares. / Geo-Social Networks (GSNs) are a type of collaborative systems with geolocated information as their shared content. This specific content allows the linking between real and virtual worlds. Nowadays, the popularization of GSNs is something real in world. One reason of that phenomenon is because GSNs support their users during the making decision process about places. Moreover, GSNs are important tools for urban monitoring, based on flow of users’ participation. The present thesis detects as problem the way how GSNs treat their collaborators homogeneously. As consequence, GSNs do not use all collaboratives potentialities of their users and are not efficient during making decision process. We reinforce the necessity of definition of parameters about diversity of a specific user: the content creator. He presents a piece of users who shared geolocated information in GSNs. Previous studies did investigate aspects about creators’ diversity on GSNs over the world. But, none of them analyzed this diversity among content creators of GSNs in Brazilian cities. The present thesis does a large-scale mapping about geolocated content creators in cities of Brazil. This mapping is divided in three approaches. The former is the investigation of diversity, based on collaborators’ experiences about places. The next one is about diversity of content creators, according to their collaborative behaviors. The last approach is about diversity analysis, face to spatial patterns among GSNs participants. The results find out the diversity among geolocated content creators in Brazilian cities. Moreover, the results can be applied in GSNs designing and mechanism of places’ recommendation.

Increasingly, online social media networks allow users to use geotagging. This method of adding location data to various content shared in real time has introduced privacy related issues and threats to the users of such networks. Previous research present opposing findings on whether users actually care about their location privacy or not, and it has also been shown that users often display a behaviour inconsistent with their concerns. When asked, users tend to report high privacy concerns, but in contrast, they will then not let their privacy concerns affect or limit their behaviour online; the privacy paradox is a description of this dichotomy. The problem, however, is not only that location privacy seems to be a paradoxical issue; the sharing of location data provides users with new possibilities that can potentially have negative consequences for them, such as someone else being able to identify one’s identity, home location, habits or other sensitive information. Social media network users communicate that a part of this is due to the lack of control over which information they share, with whom and where.This study employs a qualitative method, using unstructured interviews in a pre-study and a self-completion questionnaire. The purpose of the study is to examine and gain a better understanding of how the privacy paradox can help to better explain users’ location data disclosure preferences in the context of social media networking, and to help social media network developers in order to reduce privacy-related issues in social media networking applications with geotagging capabilities. The findings indicate that the paradox indeed is evident in user’s stated geotagging behaviour, and that users are slightly more worried about their location privacy than their overall online privacy. The conclusions offer a couple of different explanations for the paradox, and we argue that the contradiction of the paradox can be seen as a constant trade-off between benefits and risks of geotagging. We also give some examples of such advantages and disadvantages.