Post-earthquake building functionality and habitability in New Zealand: Survey results

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Scheele FR, Uma, SR, Goded T, Coomer MA, Horspool NA, Moratalla J. 2019. Post-earthquake building functionality and habitability in New Zealand: Survey results. Lower Hutt (NZ): GNS Science. 21 p. (GNS Science report; 2019/23). doi:10.21420/TAT3-0313.

The habitability and functionality of buildings following earthquake events has a significant impact on the recovery process. Understanding the factors that influence levels of post-event habitability and functionality can assist in identifying areas for improvement in risk reduction and resilience and allows for improved modelling of social impacts. We developed an online survey to gather data from individuals that had experienced recent earthquake events in New Zealand. Broadly, questions were asked regarding the following categories: the earthquake event and personal experience, characteristics of the building that is being reported on, description of the building damage and utility outage, the relocation decisions made, and demographic information. We ran the survey from November 2018 to May 2019, and we received 147 completed responses. The majority of survey responses were regarding the impacts of the 2016 Kaikōura earthquake and the 2010–2011 Canterbury earthquake sequence, and most responses (over 80%) were regarding residential buildings. The frequency of responses was weighted towards lower levels of building damage. Relating building damage to utility outage time enabled the development of a cumulative density function for predicting electricity outage time, which can be used for impact modelling. The function is an example of what can be created using the type of data collected in the survey. The main reasons respondents moved out of buildings were building damage, disruption to utilities and fear of being in the building. This finding is in line with experiences from overseas events reported in the literature. Displaced residents tend to prefer to stay close to their original location and are out of their buildings for a wide variety of timeframes (close to a third do not return). The most common reasons respondents cited for returning to their building were restoring normal routine, restoration of utilities, being allowed to return, and feeling safe enough to return. The main limitations of the survey and results are due to the relatively small sample sizes for many questions, and the inability to account for all demographics, meaning the population may not be fully represented. The insights provided by the results of this survey are useful as a beginning step towards quantification of the social impacts of earthquakes in the built environment. Targeted data collection and efforts towards obtaining larger sample sizes have the potential to produce very useful datasets. Once developed into predictive functions, modelling of earthquake impacts could be significantly improved. (auth)