Tephra fall impacts to buildings: The 2017-2018 Manaro Voui eruption, Ambae, Vanuatu

Building damage from tephra falls can significantly impact exposed communities around erupting volcanoes. There are limited empirical studies of tephra fall impacts on buildings, with none on tephra falls impacting traditional thatched timber buildings, despite their prevalence across South Pacific island nations and parts of Asia.

The 2017/2018 explosive eruption of Manaro Voui, Ambae Island, Vanuatu, resulted in damage to traditional (thatched timber), non-traditional (masonry), and hybrid buildings from tephra falls in March/April and July 2018. Field and photographic surveys were conducted across three separate field studies with building characteristics and damage recorded for a total of 589 buildings. Buildings were classified using a damage state framework customised for this study.

Overall, increasing tephra thickness correlated with increasing severity of building damage, corroborating previous damage surveys and vulnerability estimates. Traditional buildings were found to be less resistant to tephra loading than non-traditional buildings. We attribute variation in resistance within each building type to differences in the pre-eruption condition of the building and the implementation of mitigation strategies. Mitigation strategies included covering thatched roofs with tarpaulins, which helped shed tephra and consequently reduced loading, and providing an internal prop to the main roof beam, which aided structural resistance.

As is typical of post-event building damage surveys, we were limited in time and access, and we note the limitations this had for our findings. The presented results contribute to the limited empirical data available for tephra fall building damage, improving our evidence base for forecasting future impacts for similar construction types globally.