This study formulates a model where (i) players are characterized by a knowledge set that changes endogenously by communication and (ii) some players have homophily preferences, while others have heterophily preferences. The study thus demonstrates that heterophilous players bridge different components and extend networks in an early stage and, subsequently, homophilous players take the role of a network hub that maintains network ties. It also illustrates the long-run knowledge distribution. Further, the model is embedded with new structural components that illustrate the strength of weak ties and the small-world phenomenon.

Foreigners tend to be vulnerable to disasters due to religious and cultural differences. In Japan, Muslim foreign residents, who are minorities, likely face difficulties in terms of food and religious practices in evacuation shelters. In this study, we propose the use of mosques as voluntary shelters for Muslim foreigners in Japan and evaluate their potential to function as shelters. Mosques are expected to have a large space, including a prayer space, and to store food familiar to daily users. We conducted field surveys targeting two mosques in Isesaki, Gunma, Japan, to investigate their equipment and building environment in relation to how they could function as shelters; the number of evacuees they could accommodate; the amount of food they could supply to evacuees; and the willingness of the administrators to use the mosques as shelters. Both mosques were found to be equipped with toilets and shower rooms and had enough space for approximately 60–80 evacuees. They also had sufficient kitchen space and tableware to prepare meals for about 100 people. Although they did not always stock a large amount of food, they could quickly receive food from nearby stores. Moreover, the administrators were willing to use the mosques as shelters. Therefore, it was suggested that the mosques could serve as shelters accommodating and feeding many evacuees. Finally, measures to improve the function of mosques as shelters are discussed. This study lays the groundwork for the future use of mosques as shelters.

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Abstract. To improve the efficiency of flood early warning systems (FEWS), it is important to understand the interactions between natural and social systems. The high level of trust in authorities and experts is necessary to improve the likeliness of individuals to take preparedness actions responding to warnings. Despite many efforts to develop the dynamic model of human and water in socio-hydrology, no socio-hydrological models explicitly simulate social collective trust in FEWS. Here, we develop the stylized model to simulate the interactions of flood, social collective memory, social collective trust in FEWS, and preparedness actions responding to warnings by extending the existing socio-hydrological model. We realistically simulate the cry wolf effect in which many false alarms undermine the credibility of the early warning systems and make it difficult to induce preparedness actions. We found that (1) considering the dynamics of social collective trust in FEWS is more important in the technological society with infrequent flood events than in the green society with frequent flood events; and (2) as the natural scientific skill to predict flood events is improved, the efficiency of FEWS gets more sensitive to the behavior of social collective trust, so that forecasters need to determine their warning threshold by considering the social aspects.

Participation in community events such as local festivals can provide people with opportunities to collaborate with community members whom they would have never met otherwise. Furthermore, such collaboration through community events is likely to expand interaction even in daily life. In addition, if the physical properties of a public space in which community events are held change, the number and variety of the participants may also change, which could result in additional collaborations in the events. Therefore, the expansion of interaction in daily life is likely to be greater. Through the application of a social network model based on game theory, this study formulates a multilayer network model that expresses interaction in community events and in daily life by using different network layers. The study analyzes the extent to which new interactions in a layer of daily life are expanded through interactions in a layer of community events that are created through participation in the event. In terms of the expansion of networks in daily life, this study quantitatively evaluates the roles of community events and the physical properties of public spaces in which events are held.

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Ethnic minorities with different languages and religions are potentially vulnerable not only during natural hazard-related disasters, but also during the coronavirus disease 2019 (COVID-19) pandemic. Their vaccination coverage may be lower, and vaccination strategies should prevent them from being left behind. This report presents the first case in Japan where a mosque, being the hub of foreign Muslims, was used as a vaccination site from the end of July 2021. The targeted mosque was Ebina Mosque in Kanagawa Prefecture, and most of the vaccine recipients were foreign Muslims. The mosque differed from other vaccination sites in that reservations could be made easily through the managers, and linguistic diversity (i.e., the mosque managers and mosque-related volunteers served as interpreters) and gender were considered. These efforts are likely to have removed some barriers to vaccination for ethnic minorities and contributed to “no one will be left behind.”