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Fragility Functions: Key to Tsunami Risk Assessments

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Japan tsunami Stuart Fraser 400

Aftermath of Tohoku tsunami 2011. Photo: Stuart Fraser and IStructE Earthquake Engineering Field Investigation Team

Risk scientists examine the relationship between a natural hazard and an asset in many ways. To understand how tsunami may impact New Zealand’s buildings, we are developing fragility functions. These functions express the probability that a particular structural damage state − either low, moderate or high − will be reached or exceeded for a given measure of tsunami intensity, such as flow depth. This in turn enables hazard planners to develop impact and loss estimates. 

Fragility functions are developed using data obtained from previous events. In New Zealand, the lack of recent damaging tsunami means that we do not have impact data related to our own building stock.

To get around this, we are working alongside countries that have experienced tsunami and have similar building types to ours. Our long-standing collaboration with Japan is a good example.  A New Zealand research team participated in post-tsunami damage surveys following the 2011 Tohoku earthquake-tsunami sequence. The opportunity to participate in the data collection was valuable and allows us to apply the lessons in New Zealand.

Progress is being made by scientists from NIWA and GNS Science towards the application of these data in RiskScape to enhance New Zealand’s tsunami risk management. A technical report detailing this approach is due for release in mid-2016.

Contact: Shaun Williams, NIWA

Next: Observations from the Chile earthquake-tsunami (LINK)

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Last updated 13 Sep 2016