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Research papers, University of Canterbury Library

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.

Images, UC QuakeStudies

Children at the River of Flowers memorial event. The photographer comments, "One year on, Riverside residents gather for a 2 minute silence and to cast flowers in the river. Riverside residents met at the Medway St bridge to commemorate the anniversary of the 22/2/11 quake".

Images, UC QuakeStudies

An aerial photograph of a residential area in Avonside. The photograph has been captioned by BeckerFraserPhotos, "The dominant road in this picture is Avondale Road which crosses the River Avon. To the left of this photograph is all zoned red apart from a small piece on the other side of the river. On the right-hand side of Avondale Road, some streets are zoned green although the streets closest to the river are red-zoned".

Images, Alexander Turnbull Library

The cartoon shows a platter of 'Brownbait patties $2 per kilo'. In the background is a 'contaminated' river. Refers to the contamination of Canterbury's waterways after the earthquake of 4th September which resulted in sewage pipes being damaged thus contaminating the rivers. This means that people should not be attempting to catch whitebait in these rivers during the annual whitebait season which is open between 15 August and 30 November. Quantity: 1 digital cartoon(s).