When natural disasters strike, whether or not people in a community choose to evacuate may depend on the social ties present in that community, according to new research based on a 2018 earthquake in Japan.

The study, published May 17 in Climate Risk Management, found that towns that didn't face significant damage after a disaster saw much more evacuation if they had low trust in government and strong social ties among people who are different from one another in terms of race, religion, class, gender or age. These findings show that governments need to build and foster trust with their citizens, especially in the face of catastrophe.

However, in communities that did face significant damage, a strong trust in government and strong social ties among community members, both similar and dissimilar from one another, motivated greater evacuation to shelters compared to those that had lower social ties across all three dimensions. 

Timothy Fraser, Larissa Morikawa and Daniel Aldrich, in an interview with The Academic Times about their research, highlighted that proper evacuation can save lives, but evacuating when there is no real need costs time and money, potentially taking resources such as food, water and shelter from someone who might actually need them. All from Northeastern University, Aldrich is a professor, Fraser is a Ph.D. candidate and Morikawa is an alumna who just finished her master's degree.

"Different types of social ties have very different impact on behavior, especially during a shock," Aldrich said. "We have a lot of data on people not leaving before a disaster arrives. Even if it was predicted and forecast accurately, people don't necessarily leave."

Among the different types of social ties are bonding ties, which refer to social ties that include family, friends and kin; bridging ties, which are social ties to "people that are different than us," Aldrich said, who a person might meet through community activities like school, clubs or church; and linking ties, which refer to a person's trust in the government authorities and first responders, among other authorities.

Rather than using Facebook user data, post-hoc surveys or ad-hoc roadside interviews to measure evacuation rates as previous studies have done, the researchers used a mixed-methods approach to study the impact of social ties on evacuation behaviors following a disaster. They drew on a now publicly available dataset, meticulously gathered by Morikawa, of almost-daily tallies of evacuees at 660 local shelters following Japan's 2018 Eastern Iburi earthquake in Hokkaido, an island located in the north of Japan. 

The researchers paired this dataset with qualitative fieldwork, producing case studies from Japanese towns in Hokkaido, including Atsuma and Tomakomai. By speaking with the residents in these towns, the researchers were able to uncover what fueled the differences in evacuation responses, something that quantitative data alone is unable to provide.

In unaffected communities following a disaster, stronger bonding and bridging ties seemed to facilitate the spreading of rumors during blackouts — rumors that encouraged people to pack up and move to an evacuation shelter. 

Morikawa entered the fieldwork with the hypothesis that perhaps people who suffered the most damage or didn't have access to a necessity such as water would have evacuated the most. But when she spoke to people in Hokkaido, she discovered that talk on social media, such as Twitter and Facebook, spread rumors about water and electricity blackouts. 

"I went to talk to people in town hall [in Tomakomai]," Morikawa said, "and they showed me this graph of people in evacuation shelters during a period of time, maybe like a week or something … and then one time it would just like soar and [someone] had explained that, during that time, this rumor went around that water was going to shut out."

Morikawa recounted that people then took to social media and started calling their neighbors as this rumor spread. At that point, people started to move to evacuation shelters, even though they still had water at the time they evacuated and even though Tomakomai was experiencing little to no damage.

"We see a really interesting effect of bridging ties, which are usually good at spreading information," Fraser said. "But our qualitative insights from fieldwork suggests that, actually, maybe those key bridging networks were also sharing rumors that you really needed to evacuate in communities where it wasn't quite as necessary."

In contrast, Atsuma is a town that was greatly affected by the earthquake, with damage to 1,901 buildings, 36 deaths and 61 injured, all in a town of 4,838 people. Atsuma lined up perfectly with the researchers' models, which suggested that affected communities with stronger bridging ties, especially when aided by linking ties, motivate greater evacuation to shelters. 

Among these findings, a salient point emerges: In communities that didn't have extensive damage and had no issues with water or electricity supply, a low trust in government was associated with higher evacuation.

"What we're seeing is individuals who have low trust in the government … they get this information [rumors] and they're more likely to go out," Aldrich said. "Individuals who have high trust, the government tells them, 'You're fine, stay where you are,' they listen. So, what we're saying here is this combination of a lack of trust in government authorities plus false information makes you more likely to act."

The researchers emphasized that these findings highlight the need for government to be clear and transparent in its communications with the public and that governments need to foster trust during crises and disasters. 

The lack of trust among citizens vis-à-vis their governments indicates a social infrastructure problem, according to Aldrich, and just as the government can build infrastructure around roads and bridges, governments can also work on and invest in social infrastructure to produce better outcomes during a crisis. 

"If people don't trust their government, if they don't trust the first responders," Aldrich said, "then you're going to see behaviors that are detrimental to not only the individuals … you're going to see some outcomes no one really wants."

The study "Rumor has it: The role of social ties and misinformation in evacuation to nearby shelters after disaster," was co-authored by Timothy Fraser, Larissa Morikawa and Daniel P. Aldrich, Northeastern University.