Back in 2006, IT’S OUR FAULT supported Wellington to become a more resilient city through a comprehensive study of the likelihood of large Wellington earthquakes, their effects and impacts on humans and the built environment.
Today, the programme is supporting the region's growing resilience with targeted science and policy research projects in line with community and local government needs.
A core part of the Planning and Policy project, and its predecessors, are the Science to Practice Workshops.
A core part of the Planning and Policy project, and its predecessors, are the Science to Practice Workshops. For 2023–2024 the Planning and Policy workstream will focus on completing a multi-council Science to Practice Workshop. The team will work to establish a relationship and understanding of the natural hazard planning challenges the councils face and tailor a workshop to assist in addressing these challenges.
In the past few years, It’s Our Fault tsunami tasks have focused on tsunami hazard identification, tsunami arrival time estimates and evacuation modelling. In 2023-2024, It’s Our Fault Tsunami workstream team will work on two tsunami projects:
Recent international studies indicate that simultaneous occurrence of storm surge and tsunami could lead to increased wave amplitudes and current speeds in comparison to those estimated from separate events, especially also incoincidence with high tides. If tsunami and storm surges have been studied separately in the Wellington Harbour region over the past, this type of combined effects has not yet been investigated. This study aims to evaluate coastal impacts in the Wellington Harbour region under the co-occurrence of storm surge, tsunami, and high tides. We will use a hydrodynamic model (COMCOT)to simultaneously simulate storm surge and tsunami at various sea levels to understand the influence of such co-occurrence on current tsunami hazard assessments in the Wellington Harbour region. This study will provide insight to further improvements of current practice of tsunami hazard assessment and mitigation planning. It will also advance modelling methodologies in coastal hazard assessments as severe weather events become more frequent in the changing climate.
This work will focus on identifying and evaluating the challenges associated with tsunami evacuation for the coastal communities on the eastern side of Wellington Harbour, specifically those between Seaview and Eastbourne. The long, narrow coastal strip in front of mostly steep slopes leads to variations in tsunami arrival times and inundation patterns, and this, plus the risk that paths may be blocked by earthquake-triggered landslides, poses challenges to effective evacuation planning. In this study, we will use agent-based evacuation modelling together with tsunami inundation time estimates, and plausible landslide scenarios, to identify potential bottlenecks and optimise evacuation routes.
The southern Hikurangi Subduction Zone is one of the biggest sources of seismic and tsunami hazard for the Wellington Region. Recent It’s Our Fault research has identified four earthquakes during the past 2000 years. These earthquake ages represent a major constraint for hazard models, but overall the subduction zone is still poorly understood. The work this year focuses on extending the earthquake record back in time and modelling earthquake shaking on the subduction zone and faults in the overlying plate (upper-plate faults).
We will begin by focussing on the analysis of the cores collected in February 2023. We expect that through additional radiocarbon dating, it will be possible to improve age constraints on the previously inferred paleoearthquakes at ~500 and~800 years BP. There are also older layers in some cores, which may represent older paleoearthquakes. Work in the subduction task this year will aim to place constraints on the ages of these layers, to understand whether they represent deformation in past earthquakes and to estimate the magnitude of deformation in past earthquakes. Results from this work may: (1) help refine probabilistic estimates of a subduction earthquake affecting the Greater Wellington Region in the next 50 years; and (2) constrain the approximate magnitude and location of such an earthquake, with important follow-on effects for seismic hazard.
Subduction earthquakes not only represent a ground shaking and tsunami hazard for the Greater Wellington Region: future earthquakes will cause long-lasting, metre-scale uplift or subsidence of the coastline. For planning purposes —especially when considering critical infrastructure — it is important to understand the likelihood of a future earthquake impacting the coast during the next 50-100 years, and the likely magnitude of uplift or subsidence. Such coseismic deformation has the potential to exacerbate or ameliorate impacts of climate-driven sea-level rise. 8 We will make use of earthquake ruptures and probabilities from the state-of-the-art, recently released NZ National Seismic Hazard Model to create a probabilistic coseismic coastal deformation model for the Wellington Region. These ruptures and probabilities will be combined with modelling of earthquake surface displacements and a careful treatment of uncertainties to create a probabilistic coastal deformation model.
Past IOF tasks and other projects in the Wellington Region have been focused on natural hazard identification and have produced many hazard maps (incl. earthquake shaking, liquefication, landslide and tsunami).In this financial year, built on these available hazard layers, we will undertake a pilot study with a Māori community in the region to assess the impact to their key facility (e.g., Marae) and its community from these identified natural hazards.
Takapūwāhia Marae in Porirua is likely to be our pilot case study. The research will be mainly focused on following aspects: