https://repo.nzsee.org.nz/xmlui/handle/nzsee/1 2026-07-22T03:32:58Z 2026-07-22T03:32:58Z https://repo.nzsee.org.nz/xmlui/handle/nzsee/2898 2026-07-14T20:44:53Z

Performance evaluation and cost assessment of weak-story retrofits in RC buildings surveyed after the 2024 Hualien Earthquake To provide evidence on the performance of retrofitting systems for informing retrofit practice in New Zealand, 18 buildings with retrofits including reinforced concrete (RC) column jacketing, RC wing walls, RC shear walls, and steel frames with braces were surveyed after the 2024 Hualien Earthquake in Taiwan. The primary goal of this study was to quantity amounts of retrofitting installed in vulnerable existing buildings prior to the earthquake observed to be sufficient to prevent severe structural damage and disruption to building functionality. The idea would be to use these quantified amounts as a rough threshold for comparing between competing retrofitting systems in preliminary design. In general, the retrofits observed in Taiwan were low-cost and designed to target mitigation of soft and weak first stories, a well-known structural vulnerability within the Taiwanese building stock. Nevertheless, the scope of retrofits ranged from being installed in first story only to along the full height of the building. Simple indices estimated as ratios of cross-sectional areas of columns and walls to total floor area used as a proxy for base shear strength showed that on average, retrofitting nearly doubled the base shear capacity compared with the original state. To observe the effect of retrofitting on observed earthquake damage, case studies consisting of sets of building pairs, one building without retrofitting that experienced severe or moderate damage and one building with low-cost retrofitting that had minor or no damage, were investigated. Building pairs were selected to have similar size, structural layout, and seismic demand. Based on three case studies, if the amount of retrofitting increased column and wall indices to a certain threshold, no severe damage was observed. A cost assessment of typical retrofitting systems was performed based on estimated cost schedules provided by Taiwanese structural consulting firms. For a 5-story mixed-use building consisting of both commercial and residential units, and assuming the cost to build a new structure is approximately USD $1000 per square meter, the cost of installing a retrofitting system comprising RC column jacketing and additional shear walls to double base shear strength was estimated to be between 15-20% of the rebuilding cost of the original building (USD $165/m2) based on current construction practice in Taiwan. The average cost of retrofitting installed in 23 private residential buildings was less expensive at approximately USD $130/m2 indicating that increasing seismic capacity of vulnerable buildings can be achieved at a reasonable cost.

https://repo.nzsee.org.nz/xmlui/handle/nzsee/2899 2026-07-14T20:44:53Z

Comparison between the emergency responses to the 2010-11 Canterbury earthquakes and the 2024 Noto Peninsula earthquake This technical note presents comparisons between the emergency response and recovery efforts following two significant seismic events: the 2010–11 Canterbury Earthquake Sequence in New Zealand and the 2024 Noto Peninsula Earthquake in Japan. Drawing on the author’s firsthand observations from both events, the paper highlights key differences in infrastructure resilience, emergency coordination, and community recovery. The aim is to inform future disaster response strategies in New Zealand by learning from Japan’s approach, particularly in terms of speed, adaptability, and community integration.

https://repo.nzsee.org.nz/xmlui/handle/nzsee/2887 2026-07-14T20:44:52Z

Ground motion simulations for Dunedin and Mosgiel, Otago, New Zealand We develop large scenario earthquakes on active faults in the vicinity of Dunedin and use them to develop ground motion simulations for a site in Dunedin (St Kilda – St Clair area, referred to as “St Beach”) and Mosgiel (centre of Mosgiel, referred to as “Taieri Basin”). The scenarios are developed to represent large Akatore Fault (within 15 km of Dunedin and Mosgiel) and Hyde Fault (within 40-50 km) earthquakes. The simulations utilise the Southern California Earthquake Centre Broadband Simulation Platform and the Graves–Pitarka simulation method. Site response analysis is conducted with two-dimensional basin models, and the nonlinear finite element software OpenSees. The dynamic response characteristics of the soft sedimentary layers are modelled with a pressure-independent multi-yield plasticity model.  Some confidence in the simulation method is gained by undertaking historical validations, using the only instrumentally recorded earthquake of significance in the region (the Mw 4.7 2015 Lees Valley earthquake). The simulations provide close matches to the amplitudes and durations of the recorded time histories. The Akatore and Hyde fault earthquake simulations show peak ground accelerations of up to 0.8 g and 0.3g respectively, with durations of strong shaking of around 10 to 20 seconds. Uncertainty in the simulated ground motions due to source is quantified by comparing the spectra for repeated simulations, in which the range of source parameters are sampled. The resulting range of simulations shows a spread of as much as 0.5g. The Akatore – St Beach spectra are also compared to NZS1170.5 and New Zealand national seismic hazard model 2022 (NZ NSHM 2022) spectra, for site classes relevant to those of the St Beach site. In general, the simulated spectra exceed the NZS1170.5 spectra at the 0.1-0.3 second periods, but are similar to the mean NZ NSHM 2022 spectra at these periods. Future updates to NZS1170.5 based on NZ NSHM 2022 will therefore be expected to produce design spectra that are more consistent with the results of our study. The study represents the first ground motion simulations developed for southern New Zealand, and the simulation methods could be used to further advance understanding of seismic hazard in the region.

https://repo.nzsee.org.nz/xmlui/handle/nzsee/2895 2026-07-14T20:44:52Z

Functional recovery of buildings for seismic resilience of communities: Lessons from the 2024 Hualien, Taiwan earthquake Functional recovery is a new design strategy in earthquake engineering that prioritises rapid recovery and building re-use after severe natural disasters. It suggests holistic building performance goals focused on structural robustness, enhanced safety, and a rapid return to operations post-event. To paint a realistic picture of post-earthquake building recovery trajectories, there remains a significant gap in knowledge for calibrating existing building seismic performance assessment frameworks using empirical data from earthquakes. The 2024 Hualien Earthquake in Taiwan provides a unique opportunity to calibrate this approach and improve our understanding of building seismic performance and how the functional recovery of buildings affects community resilience. A reconnaissance trip was undertaken in Hualien, and damage data from 16 buildings were collected to generate functional recovery lessons and benchmark the FEMA-P58 framework using SP3 software. The research suggests that the closure or limited use of some residential buildings was largely due to extensive damage to non-structural elements, including egress and elevators, ceilings, partitions, facades, and glazing. Business disruptions were mainly caused by restricted access or cordons put in place for the safe demolition of adjacent buildings. The adaptive resilience and preparedness of building owners, residents, and businesses appeared to play a significant role in the re-use of buildings. The functional recovery data and lessons learned from Hualien, particularly the positive outcomes of its building retrofit programmes, would support the ongoing development of low-damage design guidelines and seismic design practice in New Zealand that can enhance the seismic performance and recovery of buildings.