Volcanic eruptions can cause substantial damage and disruption to infrastructure and communities. Contemporary societies typically depend on petroleum infrastructure. Volcanic unrest and eruptions can cause considerable operational and structural challenges for the petroleum sector. The vulnerability of this sector to volcanic hazards is understudied when compared to other potentially dangerous phenomena (e.g. earthquakes). In this paper, we present new volcanic physical vulnerability models for the four key asset classes of the petroleum sector: wells, pipelines, production facilities and storage tanks. The vulnerability models are developed based on a literature review and facilitated expert judgement in the form of workshops with petroleum engineers and volcanic risk experts. These models consider four hazard intensity metrics (burial thickness, static load, dynamic pressure and airborne ash concentration) and are thus applicable to multiple volcanic hazards. We apply these models to pre-existing multi-hazard eruption scenarios for Taranaki Mounga volcano in Aotearoa New Zealand, using an available impact assessment framework to demonstrate their usability in impact and risk modelling. Our impact assessment indicates that a future eruption of Taranaki Mounga volcano could cause widespread impacts to the petroleum sector, which would in turn create a prolonged national emergency due to energy supply shortages for major industries and consumers. These vulnerability models may be applied in other volcanic regions worldwide to inform risk reduction and readiness actions.

Households are central to societal functionality and may be impacted directly or indirectly by natural hazard events, resulting in the displacement of residents. Emergency management practitioners and policy decision-makers require adaptable decision support tools capable of accounting for fine-scale variations in hazard exposure, vulnerability and demographics across the emergency response and recovery periods. Responding to this critical need, we present the newly developed agent-based Stay-or-Relocate Model (STORM) demonstrated through application to a multi-phase and multi-hazard volcanic eruption scenario affecting the Taranaki Region, Aotearoa-New Zealand. STORM evaluates resident decision-making whether to remain, relocate or return home given household characteristics and changing circumstances over time. Decision components include evacuations, building damage, electricity and water outages, loss of road access, school disruption and reduced community liveability. Incorporation of an empirical relocation module quantifies the displaced residents’ selection of accommodation type, area of relocation, duration at location before return or further relocation, and accommodation payment support requirements. Modelling results indicate a peak of 32,000 individuals displaced following the first phase of volcanic activity (24.9% of the population of Taranaki Region), reducing to 16,400 (12.8%) as some residents return during a period of volcanic quiescence, and rising to a second peak of 47,000 (36.5%) following a second phase of volcanic activity. STORM is hazard agnostic and can be readily adjusted to suit the local context of application.

The volcanic hazard and risk science for Taranaki Mounga (Taranaki volcano) in Aotearoa / New Zealand is in an advanced state, with robust probabilistic data and a series of direct impact scenarios modelled for the region. Here, we progress this work and demonstrate a method to provide risk information that is nuanced for factors such as location and economic sector and considers the dynamic nature of volcanism with hazards potentially repeated over time. Recognising the fundamental importance of the dairy sector to Taranaki region, this paper provides valuable insights into the potential impacts and risks to heterogeneous dairy cattle farms within the region from volcanic hazards. We provide volcanic impact and risk metrics in economic or monetary terms in order to improve its relevance to decision-makers while reducing the complexity of the impacts. To do this, we developed a dynamic, multi-event farm system model of response and recovery, which takes in hazard intensity metrics from a series of volcanic events and generates the resulting annualised revenues, expenditures, and recovery costs through time. The model is formulated in a generalised way such that it can be used for various other hazard types and agricultural land uses. In our application of the model, we create and apply a suite of 10 000 simulations that capture different iterations of possible future volcanic activity over a 50-year period. These include the generation of lahars following eruptions and associated failures for transport and water supply networks. Farms at five case study locations were modelled to capture the diversity in farm management and the spatial variation in hazard intensities and likelihoods across the region. We provide summaries of the distributions of economic impacts generated, both for individual events and for the 50-year volcanic future horizon. Drawing the information together, we also summarise the results for each case study farm in terms of the value at risk statistic. For the case study farms with negligible lahar risk, we find, with 90 % confidence, that volcanic losses over the next 50 years will not exceed around 10 % of property value. By comparison, for the farm with the most severe lahar and ashfall exposure, we find that, at the same level of confidence, losses extend to approximately half the property value. These results indicate that with access to sufficient risk information, we should anticipate volcanic risk as playing an important role in shaping the future dairy sector in Taranaki region. The modelling pipeline and assessment metrics demonstrated in this paper could be used to assess mitigation and adaptation strategies to reduce the risk from volcanic hazards and improve the resilience of farm businesses.

Human casualties related to rapid-onset natural hazards are usually proportional to the number of people directly exposed. Yet population mobility makes exposure difficult to assess due to temporal and spatial variability. Population exposure is a crucial dimension of risk, and often the dynamics of exposure are overlooked in disaster risk assessment and subsequent management. Here, we quantify how disaster risk in Aotearoa New Zealand changes across multiple temporal and a highly resolved spatial scales due to dynamic population mobility and observe the significant influence it has on resulting risk.We present a unique dataset from the highly touristic Piopiotahi Milford Sound in New Zealand using longitudinal data over a 790-day period, including throughout the COVID-19 pandemic. We demonstrate how minute-by-minute population changes of up to 1000-people within 5 minutes can dramatically affect the risk posed by a landslide-triggered tsunami in the fiord. During our study period, the societal risk fluctuated by two to three orders of magnitude, underscoring how dynamic population movement translates to the potential doubling of fatalities in a tsunami. Using an established threshold for acceptable risk, our dynamic approach reveals that the societal risk was only acceptable during the strictest COVID-19 lockdown measures, after which it became increasingly unacceptable as population mobility resumed.This New Zealand case study demonstrates that integrating high-resolution dynamic population data into disaster risk assessment can significantly improve assessments of risk, particularly in rapidly changing or high population mobility contexts. Understanding these dynamics is essential for developing effective risk reduction strategies and adaptation plans. Our findings show that incorporating longitudinal high-resolution data on dynamic exposure substantially improves assessment accuracy and reduces inherent uncertainty of dynamic disaster risk, especially in popular touristic areas and where population shifts are frequent and significant.

Water supply systems provide an essential service for society and are highly vulnerable to damage and disruption during volcanic eruptions. Impacts sustained by water supply systems during volcanic eruptions have resulted in prolonged and repeated supply outages. Previous approaches to assessing volcanic impacts to water supply systems have been relatively simplistic, based on hazard intensity thresholds, and only considering direct damage. There is a need for water supply risk assessment approaches informed by vulnerability models that consider the pivotal role of system design and indirect impacts; such as supply and demand fluctuations, personnel shortages, and disruptions to interdependent infrastructure networks. We present a whole-of-system volcanic vulnerability model and impact assessment framework for water supply systems that can be used to estimate system-wide impacts during future volcanic eruptions. This model is developed in collaboration with volcanic risk researchers and water supply engineers in Aotearoa New Zealand and applied to a case study in the Taranaki region for a long-duration and multi-hazard eruption scenario from the active stratovolcano Taranaki Mounga. The model provides an assessment of the functionality of water supply systems affected directly and indirectly by the scenario eruption, interdependent critical infrastructure services, and associated emergency management actions (e.g., evacuations). This scenario, and its modelled impacts, allows practitioners to explore potential mitigation and emergency response options. This framework can be applied in other volcanic contexts to assess impacts on water supplies from future eruptions, highlight key systemic vulnerabilities, and provide a basis for the prioritisation and implementation of risk management strategies.

This study presents a volcanic resilience assessment for the electricity network in Taranaki, New Zealand, modelling the distribution system as a standalone Critical Infrastructure (CI) and incorporating key interfaces such as transmission Grid Exit Points and generator nodes. Previous volcanic risk assessment studies have identified potentially severe impacts on the electricity infrastructure, but have not included power flow analysis. This research addresses this gap and applies natural hazard risk assessment approaches and power system resilience analysis to assess system level impacts for a complex multi-hazard volcanic hazard scenario. The impact is estimated through power flow calculations and Monte Carlo-based outage analysis.

Volcanic eruptions are complex and can generate multiple hazards, such as ashfall and lahar. Eruptions can significantly impact rural road transport network functionality, disrupting primary production, curtailing access to support services, and isolating communities. We propose a network modelling approach to assess multi-hazard volcanic impacts on rural transport systems. Rural communities in the Taranaki region are highly exposed to volcanic hazards. We apply our model to demonstrate how access between farms, marae (cultural gathering places for M & amacr;ori) and service towns (with healthcare, fuel, etc.) could be affected during a future eruption of Taranaki Mounga. Across the nine eruptive scenarios assessed, a maximum of 40% of roads (>1500 km) and 45% of bridges (>1500) in the region lost service, with half of these needing significant cleaning and repairs likely to take weeks, or months especially where bridges have been destroyed by lahars. At the conclusion of one large eruption scenario modelled (L1), 12 marae (>25%) and 5,000 farms become isolated, potentially for weeks to months. This highlights a significant issue in volcanic planning globally, where impacts to roading are likely to lead to populations becoming isolated, leaving people unable to evacuate, access essential services or resume social and economic activities.

Volcanic ash air-fall or tephra deposits comprise nearly 31% of the North Island of New Zealand. For those belonging to slightly weathered or negligible to little cohesionless nature (silty sands to sandy silts), the compressibility and collapsibility features of compacted tephras have not been largely investigated. Correspondingly, the compressibility and collapse potential (CP) of compacted airfall tephras (at 90% and 100% degrees of compaction) were evaluated. At vertical stresses up to 200 kPa, the consolidation coefficient cv and permeability coefficient k were in the range of 10-5-10-8 m2/s and 10-6-10-8 m/s. Interestingly, for feldspar-silica type cohesionless tephras, it was possible to correlate the weathering degree and mineralogy to the compressibility. The results of the CP tests showed that the CP increased with the decrease in degree of compaction and increase in vertical stress; with values ranging from 0% to 5% indicating low-to-moderate collapsibility of the tephras upon properly compacted placement condition. The compacted tephras, as such, could be considered suitable structural fills for typical geotechnical applications owing to features such as low compressibility, low permeability and low-to-moderate CP.

Infrastructure networks are vital for the communities and industries that rely on their continued operation. Disasters stress these complex networks and can provoke systemic disruptions that extend far beyond the spatial footprint of hazards. An enduring challenge for assessing infrastructure networks within disaster impact assessment frameworks has been to adequately quantify the high spatial interdependence of these networks, and to consider risk management interventions through time. This is of particular importance for volcanic eruptions, which can produce multiple hazards over highly variable spatiotemporal extents. In this study, we present a methodology for the quantification of systemic vulnerability of infrastructure networks, which can be coupled with physical vulnerability models for the purpose of impact assessment. The two-part methodology first quantifies the haard-agnostic criticality of infrastructural components, inclusive of interdependencies, and then incorporates representative hazard spatial footprints to derive the systemic vulnerability. We demonstrate this methodology using the case study of volcanic eruptions from Taranaki Mounga volcano, Aotearoa New Zealand, where there are many industrial sites of national importance, and a high likelihood of a complex multi-hazard volcanic eruption. We find a considerable increase in the systemic vulnerability of electricity and natural gas network components after incorporating infrastructure interdependencies, and a further increase in the systemic vulnerability of these critical components when cross-referenced with potential volcanic hazard spatial extent. The methodology of this study can be applied to other areas of interest in both its hazard-agnostic or hazard-dependent form, and the systemic vulnerability quantification should be incorporated into impact assessment frameworks.

The North Island of New Zealand is a region of high volcanic activity, with significant eruptions over the past. Analogous to past events, future volcanic eruptions would produce a considerable volume of ash and granular soils, covering widespread areas and raising concerns for their disposal and storage. Such deposits, primarily airfall tephra, could be potentially used in geotechnical engineering applications such as foundations, roadway embankments and land reclamations. However, before their use as structural fills can be recommended, detailed laboratory investigations of their physical, chemical, compaction, and geotechnical engineering properties (strength, compressibility, collapsibility, liquefaction potential, etc.) must be conducted. Different tephra deposits can be products of different eruptions, so chemical composition analyses can be combined with the physical, compaction, and engineering properties to characterize such deposits. Accordingly, this paper provides useful insights from physical (grain size, specific gravity, and morphology), chemical (elemental and mineralogy using X-ray fluorescence and X-ray diffraction), and compaction tests (maximum dry density, optimum water content, and particle breakage) for eleven selected volcanic tephra samples sourced from the North Island of New Zealand in the Rotorua, Taupo, and Auckland regions.

The use of weathered airfall tephra deposits for geotechnical applications such as backfilling in embankments or foundations requires investigation. As a part of an experimental laboratory investigation addressing this issue, this paper focuses on the monotonic shear strength evaluation under drained and undrained shearing conditions of three airfall tephra deposits—namely Kaharoa (white–grey and golden brown) and Maungataketake (black-grey) ashes belonging to New Zealand. The shear strength results include tephra samples compacted at 90

Volcanic eruptions can cause significant impacts on communities and infrastructure. There is an increasing need for effective risk assessments to inform decision-making and minimise the impact of volcanic hazards. Vulnerability models play a crucial role in these assessments, connecting the intensity of the hazard with the elements that are exposed to it, allowing for the calculation of potential impact or risk. There has been a large increase in the number of vulnerability models being developed for volcanic risk applications, and there is now a need to identify knowledge gaps for the field to take a strategic approach moving forward. This review aims to provide a high-level overview of the current state of volcanic vulnerability modelling and identify areas for future development. We evaluated 594 vulnerability models covering a range of elements and sectors, including buildings, critical infrastructure, transportation networks, agriculture, and human vulnerability. We reviewed the types of hazard intensity metrics and impact/risk metrics used in the models, modelling methodologies, underpinning data requirements, and uncertainty characterisation. A global clearinghouse for volcanic vulnerability models would be advantageous for the volcanic risk community to identify appropriate vulnerability models quickly and efficiently for their needs. As a first step towards such a clearinghouse, we have uploaded this volcano vulnerability model compilation to a repository and encourage additions/suggestions from the community on its future development. The results of this study will contribute to the advancement of the field and provide valuable insights for future research and development in volcanic risk assessment.

Auckland city (pop. 1.7 M) is Aotearoa New Zealand’s largest city and an important economic hub. The city is built upon the active intraplate basaltic Auckland Volcanic Field (AVF). An AVF eruption would cause considerable impacts. An important component of volcanic risk management is assessing the likely volcanic hazards to help inform emergency planning and other preparedness activities. Previous volcanic hazard assessments for the AVF, particularly those for emergency planning scenarios, have modeled multiple volcanic hazards including lava flows, pyroclastic density currents, ballistic projectiles and tephra fall. Despite volcanic gas being an important and impactful hazard from intraplate basaltic field eruptions, there has been limited consideration of volcanic gas in AVF hazard assessment to date. This project is one of the first to quantitatively assess potential volcanic gas hazards for an explosive eruption scenario. For basaltic volcanism, sulfur dioxide (SO 2 ) gas is typically the most consequential volcanic gas emitted. The aim of this exploratory study was to model SO 2 dispersion from a high impact eruption during weather conditions conducive to high ground level pollutant concentrations. Since ground level SO 2 concentrations are influenced by complex wind patterns resulting from interactions of locally driven flow circulations and topographically influenced weather, we modeled SO 2 dispersion using the HYSPLIT model, a state-of-the art hybrid Eulerian and Lagrangian dispersion model widely used for volcanic gases, using high-resolution meteorological forcing fields given by the Weather Research and Forecasting (WRF) model. Modeled air parcel trajectories and ground level SO 2 concentrations illustrate the effect of the converging sea breeze winds on SO 2 dispersion. Under worst-case dispersion conditions, extensive areas of up to hundreds of square kilometers to the north and northwest of the eruption location would exceed New Zealand short-term (24 h) air quality standards and guidelines for SO 2 , indicating heightened health risks to downwind communities. Using this numerical modeling approach, this work presents a methodology for future applications to other AVF eruption scenarios, with a wider range of meteorological conditions that can help in exploring consequences for health services such as anticipated emergency department respiratory admissions.

Effective volcanic impact and risk assessment underpins effective volcanic disaster risk management. Yet contemporary volcanic risk assessments face a number of challenges, including delineating hazard and impact sequences, and identifying and quantifying systemic risks. A more holistic approach to impact assessment is required, which incorporates the complex, multi-hazard nature of volcanic eruptions and the dynamic nature of vulnerability before, during and after a volcanic event. Addressing this need requires a multidisciplinary, integrated approach, involving scientists and stakeholders to co-develop decision-support tools that are scientifically credible and operationally relevant to provide a foundation for robust, evidence-based risk reduction decisions. This study presents a dynamic, longitudinal impact assessment framework for multi-phase, multi-hazard volcanic events, and applies the framework to interdependent critical infrastructure networks in the Taranaki region of Aotearoa New Zealand, where Taranaki Mounga volcano has a high likelihood of producing a multi-phase explosive eruption within the next 50 years. In the framework, multi-phase scenarios temporally alternate multi-hazard footprints with risk reduction opportunities. Thus direct and cascading impacts, and any risk management actions, carry through to the next phase of activity. The framework forms a testbed for more targeted mitigation and response planning, and allows the investigation of optimal intervention timing for mitigation strategies during an evolving eruption. Using ‘risk management’ scenarios, we find the timing of mitigation intervention to be crucial in reducing disaster losses associated with volcanic activity. This is particularly apparent in indirect, systemic losses that cascade from direct damage to infrastructure assets. This novel, dynamic impact assessment approach addresses the increasing end-user need for impact-based decision-support tools that inform robust response and resilience planning.

There is increasing evidence that access to social capital, and particularly linking capital can significantly enhance the resilience of minoritized and vulnerable communities impacted by disasters. Understanding levels and types of access to social capital within such communities before disasters occur is an important part of disaster risk management policy and planning. Migrant worker communities, however, remain an understudied group in general, and there are very few published findings concerned with the 3.5 million Filipino migrant workers who primarily live in high-income host countries. This article contributes to addressing this gap with an Aotearoa-New Zealand qualitative case study that aims to increase understanding of the social capital accessed pre-disaster by members of Filipino migrant worker organisations in the Canterbury region. Interview and focus group data indicated that worker organisations facilitated access to local Filipino migrant worker networks, contributing to consistently high reliance on bonding capital, but less access to bridging or linking capital. This trend is linked to the precarious immigration status afforded by temporary work visas, which increased the vulnerability of participants. Only one organisation provided access to the linking capital required to mitigate this vulnerability. Factors influencing the capacity of organisations to develop linking capital appeared to include establishment objectives, length of time since establishment and support from government and industry groups. These findings emphasize the valuable role that migrant worker organisations can play in mitigating disaster risks, through providing connections that facilitate support and resourcing from authorities and industry bodies.

When disasters occur, rapid impact assessments are required to prioritise response actions, support in-country efforts and inform the mobilisation of aid. The 15 January 2022 eruption of Hunga volcano, Tonga, and the resulting atmospheric shockwave, ashfall, underwater mass disturbance and tsunami, caused substantial impacts across the Kingdom of Tonga. Volcanic impacts on the scale observed after the eruption are rare, necessitating a reliance on international advice and assistance. The situation was complicated by the loss of Tonga’s international submarine fibreoptic cable (causing a complete loss of communications for approximately 20 days) along with border closures due to the COVID-19 pandemic. A need emerged for a rapid remote volcanic impact assessment and provision of specialist advice to help inform the response of international partners. Here we present a novel methodology for conducting rapid remote volcanic ashfall impact assessments, conducted over a 10-day period following the eruption. We used three different hazard models for ashfall thickness across the main island of Tongatapu and available asset information and vulnerability functions for buildings, agriculture, electricity networks, water supply and roads, to provide initial estimates of losses due to ashfall from the 15 January eruption. For buildings, we estimated losses both as total losses and as percentages of the total replacement cost of buildings on Tongatapu. For agriculture, we made probabilistic estimates of production losses for three different crop classes. For ashfall clean-up, we estimated ranges of ashfall volumes requiring clean-up from road surfaces and roofs. For water supply, electricity networks and roads, our analysis was limited to assessing the exposure of important assets to ashfall, as we had insufficient information on system configurations to take the analysis further. Key constraints on our analysis were the limited nature of critical infrastructure asset inventories and the lack of volcanic vulnerability models for tropical regions including Pacific Island nations. Key steps towards iteratively improving rapid remote impact assessments will include developing vulnerability functions for tropical environments as well as ground-truthing estimated losses from remote approaches against in-person impact assessment campaigns.

Building damage from tephra falls can have a substantial impact on exposed communities around erupting volcanoes. There are limited empirical studies of tephra fall impacts on buildings, with none on tephra falls impacting traditional thatched timber buildings, despite their prevalence across South Pacific island nations and parts of Asia. The 2017/2018 explosive eruption of Manaro Voui, Ambae Island, Vanuatu, resulted in damage to traditional (thatched timber), non-traditional (masonry), and hybrid buildings from tephra falls in March/April and July 2018. Field and photographic surveys were conducted across three separate field studies with building characteristics and damage recorded for a total of 589 buildings. Buildings were classified using a damage state framework customised for this study. Overall, increasing tephra thicknesses were related to increasing severity of building damage, corroborating previous damage surveys and vulnerability estimates. Traditional buildings were found to be less resistant to tephra loading than non-traditional buildings, although there was variation in resistance within each building type. For example, some traditional buildings collapsed under ∼40 mm thickness while others sustained no damage when exposed to >200 mm. We attribute this to differences in the pre-eruption condition of the building and the implementation of mitigation strategies. Mitigation strategies included covering thatched roofs with tarpaulins, which helped shed tephra and consequently reduced loading, and providing an internal prop to the main roof beam, which aided structural resistance. As is typical of post-event building damage surveys, we had limited time and access to the exposed communities, and we note the limitations this had for our findings. Our results contribute to the limited empirical data available for tephra fall building damage and can be used to calibrate existing fragility functions, improving our evidence base for forecasting future impacts for similar construction types globally.

Agent-based modelling is a useful tool for evacuation planning as it can increase understanding of the factors affecting potential evacuation outcomes. In New Zealand, Milford Sound has been shown to have a high risk from landslide-generated tsunami, with an estimated 1-in-1000-year wave runup of similar to 17 m arriving on shore within 2-7 min. With an annual average of >1500 people visiting a day, there is potential for widespread loss of life. However, the number of people present varies substantially with time of day and season, yet how this affects the ability to evacuate remains unknown. This research developed an agent-based model to understand how many people can be safely evacuated in Milford Sound and explored how the number of people initially exposed affected the evacuation outcome alongside the effect of potential changes to evacuation messaging. Assuming a 17 m wave, the results suggest that currently no one can safely evacuate before the shortest wave arrival time regardless of the number of people present. Altering evacuation messaging results in minimal gains, with only similar to 5 % of the exposed population reaching safety in time. This work demonstrates the importance of evacuation modelling for understanding risk in isolated tourism destinations where the population exposure can fluctuate dramatically across multiple timescales. Accounting for changing population exposure is essential to understand whether evacuation is a suitable risk treatment and can provide valuable information for determining safe levels of population exposure in locations with high hazard but limited evacuation options.

This paper reports and discusses the results of a series of monotonic compression drained and undrained triaxial tests performed on three compacted, slightly weathered silty sand tephras. In total, 18 drained and 18 undrained tests were performed on compacted specimens (at Dc ≈ 90 and 100%) isotropically consolidated at confining pressures of 50–200 kPa. It was observed that particle size distribution, weathering state, and mineralogy of the tephra deposits had significant effects on the stress–strain responses, friction angles, stress–dilatancy relations, and critical state characteristics. For instance, the coarser tephra (namely white–grey Kaharoa, that was less affected by weathering processes) showed a primarily dilative response. The effects of chemical composition, namely weathering degree and mineralogy, on geotechnical properties such as friction angle were investigated with an attempt to interlink the two characteristics for heterogeneous tephras. The measured friction angles (ϕ = 32.7°–42.8°), combined with the results of weathering degrees and mineralogical investigations, indicated that silty sand tephras, if properly compacted, are suitable fills for use in typical geotechnical applications.