Surface-rupturing earthquakes can trigger the sudden avulsion of river channels, causing rapid and persistent coseismic flooding of previously unaffected areas. This phenomenon, known as fault-rupture-induced river avulsion (FIRA), occurs when fault displacement significantly alters river channel topography. The importance of understanding FIRA as a secondary seismic hazard was highlighted by events during the 2010 Darfield and 2016 Kaikoura earthquakes in New Zealand. This thesis develops a national model to identify and quantify FIRA susceptibility across New Zealand by integrating hydrological datasets (NIWA RiverMaps and Flood Statistics) with active fault information (NZ Active Faults Database and RSQSim earthquake simulations). The methodology applies the F-index framework proposed by McEwan et al. (2023), which quantifies FIRA potential based on the ratio of fault throw plus discharge-dependent depth to bank full depth at each fault-river intersection. The model successfully identified 3,796 potential FIRA-susceptible fault-river intersections nationwide, with 451 involving waterways equal to or larger than the Hororata River. Regional analysis revealed higher concentrations of FIRA-susceptible sites in the Bay of Plenty, Canterbury, and Marlborough regions. Validation against historical events showed the model effectively located known FIRA occurrences from the Kaikoura and Darfield earthquakes, though with some limitations in accurately predicting F-index values due to complex fault displacement patterns and challenges in modelling bank full depths of large, braided rivers. This research establishes New Zealand's first nationwide assessment of fault-induced river avulsion susceptibility. The approach creates a structured methodology for identifying high-risk fault-river intersections and determining which sites require thorough localised examination. The methodology developed offers a template for similar assessments in other tectonically active regions and contributes to improving earthquake hazard assessment and disaster preparedness planning.
The foundation of this thesis rests upon previous research conducted as part of a QuakeCoRE summer scholarship project which investigated the health and safety regulations for utility workers within Aotearoa and in relation to the Canterbury Earthquake Sequence (CES). This project highlighted that the primary Health and Safety at Work Act 2015 was not directly applicable to these workers, given the unique set of risks and dangers. Additionally, the same research found that, in the absence of adequate intervention mechanisms, there is a reliance on internal health and safety procedures and standards, which may be compromised in an emergency scenario. A key element of Aotearoa’s disaster response framework regarding utility workers is the use of emergency powers, whereby the Director of Civil Defence Emergency Management may order utility workers, by proxy, to undertake any order during a state of national emergency or a national transition period.4 This power appears to be unrestrained and creates tension in relation to human rights and worker’s rights. The endangerment of utility workers in a disaster scenario is a global issue, with extensive research suggesting the involvement of utility workers within the immediate aftermath of disasters across many jurisdictions.5 This thesis investigates the involvement of utility workers in emergencies in two different jurisdictions, alongside the legal and non-legal protective measures taken within these jurisdictions to safeguard their mental and physical health.
The Canterbury Earthquake Sequence (CES) was a monumental natural disaster in Aotearoa New Zealand that permanently altered Ōtautahi Christchurch’s geography. Following the earthquake events, the central city was in need of recovery and regeneration to return to being an enhanced and thriving space. The Christchurch Central Recovery Plan (CCRP) was developed to outline the aspirations, visions and challenges associated with rebuilding the central city. The purpose of this research was to review the current status of the CCRP, with a particular focus on identifying the projects that have or have not progressed. This research sought to understand which aspects of a post-disaster recovery plan have contributed to successful post-disaster recovery in Ōtautahi Christchurch. Secondary data was used to identify successes and failures in this regard. The results highlighted the top-down approach taken by the central government in the recovery process and a notable lack of community engagement throughout the CCRP. However, there were some projects and aspirations that have enabled Ōtautahi Christchurch to become a thriving city and express its regenerated identity at a local, national, and international level.
The devastating consequences of past events, such as the 2004 Indian Ocean and 2011 Tōhoku tsunamis, emphasise the need for continued improvement in resilience measures. Given that 80% of magnitude 8+ earthquakes occur on the Pacific Rim, New Zealand's tsunami risk is significant. This research develops a novel tsunami inundation model. The proposed model applies equations based on hydraulic principles, including energy conservation (friction loss). While it does not fully replicate hydrodynamic models, it maintains a two-dimensional approach and offers significant improvements over currently implemented simplified methods. It retains excellent computational efficiency (seconds to minutes) while achieving a significant increase in accuracy that is comparable to traditional hydrodynamic models, which typically take hours to days. Calibration of the roughness input variables to hydrodynamic modelling at Gisborne and Christchurch, New Zealand, optimised the model to achieve similarity index values of above 84% for inundation extent, while 77% of inundation depths were within ±1 m and over 93% within ±2 m. This research then produces the first nationally consistent tsunami exposure assessment for New Zealand using a physics-based modelling method. Using probabilistic shoreline wave amplitude data, the study generates high-resolution (10 m) inundation maps for seven return periods (50th and 84th percentiles). These maps are integrated with land cover and infrastructure data to quantify exposure and identify the most vulnerable locations. The results highlight exposure not only to the commonly studied cities but also to several provincial areas. The identification of exposure is the foremost step towards practical resilience efforts; however, understanding specific infrastructure impacts ensures that countermeasures and risk reduction practices are implemented. Therefore, a detailed evaluation of the NZTA Bridge Manual is conducted. Comparisons are made between the NZTA methodology and the rapid model developed in this research. The results reveal a significant overestimation of bridge and culvert exposure by NZTA methods. The study further highlights critical exposure locations for bridge and culvert assets. Flow depths calculated at bridge locations are significantly overestimated using the NZTA method compared to results derived from hydrodynamic modelling and the rapid model. This research then conducts component-level modelling of culvert assets, due to their identified vulnerability in the transportation network. At a 1:15 geometrical scale, laboratory experiments evaluated the response of different culvert set-ups to tsunami bores. The findings provide a detailed description into overtopping, flow regimes and pressure distributions and give laboratory experiments as validation studies for future numerical modelling and design improvements. Overall, this research performs a multi-modal tsunami inundation assessment, uniting macro-level exposure modelling with micro-level component responses by integrating modelling, exposure analysis, and experimental validation. The findings support refining current tsunami guidelines, improving infrastructure planning, and enhancing community preparedness. Overall, the study’s multi-model approach strengthens many elements of New Zealand’s ability to mitigate and respond to future tsunami events
