A new study focused on New Zealand’s capital city considers why some homeowners do not take preventative measures to strengthen their property against earthquakes.
By Davitia James, Temblor Earthquake News Extern (@davitiaa)
Citation: James, D., 2021, Some New Zealanders are hesitant to retrofit homes. Researchers asked why, Temblor, http://doi.org/10.32858/temblor.217
New Zealanders are more likely to experience several small earthquakes during their lifetime than multiple large, catastrophic ones. Nevertheless, the last major earthquake that affected the capital city of Wellington took place in 2016, when the magnitude-7.8 Kaikōura earthquake leveled homes, collapsed cliff sides and destroyed roads across a 180-kilometer-long rupture.
In a new study, a team of researchers explored whether that event spurred the region’s residents to prepare for future earthquakes. They found that although earthquake retrofitting can reduce earthquake damage and save lives, many homeowners in New Zealand choose not to make such reinforcements to their properties.
Making a plan and sticking to it
Earthquake preparedness occurs in three stages, according to decades of work on the subject. In the first stage, a person becomes motivated to engage in damage-mitigation actions. They set the intention to do the work in the second stage. The final stage is carrying out the improvement plan.
Knowledge and feelings about past and potential future events and the behavior of peers play a role in each stage. Past studies have shown that the first two years after an earthquake are crucial to spread awareness and encourage residents to complete all three stages because the experience is still fresh. Unfortunately, though earthquake experiences can push a homeowner through the first two stages, many other influences prevent people from reaching the final stage.
To assess how people behaved after the Kaikōura earthquake and how past experiences affect preparation for future earthquakes, Catalina Miranda, a doctoral student at the University of Auckland, and colleagues distributed thousands of surveys to homeowners with wood-frame houses throughout Wellington. The questions inquired about individual experiences with earthquakes and resulting damage using New Zealand’s version of the Modified Mercalli Intensity scale. The standard Modified Mercalli Intensity (MMI) is a ten-step scale that describes the level of damage caused by an earthquake. Experts adapted this scale to suit New Zealand and produced twelve levels detailing the effects of shaking on the environment, structures, fittings and people.
The researchers asked residents whether they’ve done anything to protect themselves from future events, based on their likelihood and a seismic hazard assessment of their home. They also asked about the education residents have received on this topic and how much they believe what they were told about it.
Two thirds of survey respondents said they knew of improvements they could make to their homes to reduce future damage. Of this group, less than half had actually made the changes. Statistical tests support the idea that an individual’s earthquake experience influences preparedness, but experience alone does not drive all people to completion.
The researchers also considered whether the severity of someone’s experience may determine whether that person takes the next step towards preparedness. The Kaikōura earthquake is widely regarded as the most complex seismic event ever studied, and one of the largest to occur in New Zealand. Though shaking was felt in Wellington during the event, damage to homes in the city was minimal. The researchers suggest that because an event described using such strong language produced only limited damage, individuals likely thought that home improvements were unnecessary.
However, some people with more intense experiences still did not make changes to their homes, the researchers found. For those in harder hit areas, damage to new and reinforced buildings during the 2016 earthquake may have signaled that home strengthening measures don’t work. However, numerous retrofitting options exist, and the average homeowner likely knows neither which was applied, nor its efficacy. Because no set approach to earthquake damage mitigation for homes exists in New Zealand, the overwhelming options may also leave residents confused.
Earthquake mitigation measures like reinforcing walls and foundations can protect lives and property in the long run but they are not very popular, the study shows. Though they are ideal choices, they are expensive — not only in financial cost, but also in time for planning and implementation. “For a lot of people, it’s a very expensive step to take and we’re aware that a lot of people can’t afford it,” said Jo Horrocks, Chief Resilience and Research Officer at the New Zealand Earthquake Commission.
In New Zealand, policies are in place to strengthen high-rise buildings against earthquake damage, but owners are not required to reinforce one- and two-story residential homes
Horrocks says she considers this study critical to the commission’s work. “As an organization, we’re always trying to persuade people take actions to reduce their risks or build their resilience, such as strengthening their homes,” she says. “We do that through public education … [and] raising awareness about the hazards that we have around us and about preparedness steps we can all take.” The commission provides insurance for earthquakes and other geo-hazards that takes effect before private insurance coverage. It is invested in lowering vulnerability through safer construction for new buildings, and retrofitting or strengthening existing ones.
Discussing what happened during earthquakes and going over reinforcement options with the community is crucial to understanding what will drive them to undertake mitigation projects, Miranda says. Because researchers often assume what residents want, this study fills a key role of including the community in that conversation, she says.
“How do we persuade people to take actions, especially the ones that cost people a fair bit of money?” asks Horrocks. The next step for the researchers is to find ways to empower homeowners to build resilience, she says. “This is the real crux of it for us.”
Miranda, C., Becker, J. S., Toma, C. L., Vinnell, L. J., & Johnston, D. M. (2021). Seismic experience and structural preparedness of residential houses in Aotearoa New Zealand. International Journal of Disaster Risk Reduction, 66, 10259
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