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Instrumental records from coastal gauges, DART: Deep-ocean Assessment and Reporting of Tsunamis buoys, meteorological stations and post-event damage surveys are being used to shape our understanding of the physical processes associated with the eruption and associated tsunami, such as pressure changes, acoustic signals and tsunami wave arrival times. However, there is a need for more holistic understanding of how people in Aotearoa New Zealand understand, and experience tsunami hazard, in order to improve warnings and increase preparedness. On 15 January 2022, social media and news reports described booming and explosion noises throughout Aotearoa New Zealand and the Pacific, caused by atmospheric pressure waves from the eruption of Hunga-Tonga Hunga Ha’Apai volcano, Tonga. In response to this historic and complex event, a team of tsunami, volcano, and social scientists at GNS Science designed a survey to broaden our documentation of the event beyond the physical processes, and to promote public engagement with science. We sought to understand the spatial and temporal distribution of sound and tsunami observations using crowdsourced geospatial data, allowing the public to participate and report experiences. The survey was launched online from 21 January to 13 February 2022. Thirty-nine questions were posed to the public, asking about location, time, water colour, smells, damage to the built/natural environments and number of surges/booms observed. Respondents provided images and videos displaying impacted coastlines, flooded campgrounds, coastal erosion, unusual currents and audio of booms. This report summarises the results of this survey based on the anonymised responses from over 2,000 individuals. (The authors)

The Department of Conservation (DOC) has been undertaking a review of geological-based hazards and the management of those hazards on Public Conservation Lands and Waters. Deligne et al. (2020) reported on Part 6 of this work, which considered eruptive volcanic and geothermal hazards and defined two categories of volcanic or geothermal eruptions. However, the scope of this previous work did not allow the more commonly experienced hazards in geothermal areas to be addressed, and geothermal areas not associated with active cone volcanoes were not explicitly considered. This report, commissioned by DOC, fills these gaps by providing a comprehensive review of geothermal hazards and their potential impacts. Geothermal areas can be defined and mapped in multiple ways, including geophysical surveys to define heat source or heat flow at depth or by expressions at the surface. Here, we define geothermal systems by the expression of features at the surface from which hazards are produced. Geothermal surface features include primary and mixed flowing springs, non-flowing pools, mud pools, mud pots, geysers, heated or steaming ground and fumaroles. Multiple hazards can originate from geothermal surface features – both eruptive and non-eruptive. These include: geothermal gases; weak and unstable ground; heated ground; hot water, mud and steam within existing surface features; ground collapse; mild explosive activity such as jetting, splashing and bubbling; shallow earthquakes; infrastructure failures, including deterioration compromising boardwalks and viewing platforms and failures of bores, drill rigs and wells that cause artificial eruptions; hydrothermal eruptions, further divided into small, moderate and large eruptions; and phreatic eruptions. Hydrothermal and phreatic eruptions can produce multiple hazards including gas, slugs/geysers of water or mud, ballistic projectiles, pyroclastic density currents and wet ash (mud rain). Each hazard can impact different-sized areas, ranging from hot water, mud and steam being contained within surface features, and therefore dependent on the size of the feature, to large hydrothermal eruptions that eject material up to 4 km from the surface feature. Geothermal processes have various properties that make them hazardous, and these properties can vary in their ability to cause negative impacts. Temperature is an important hazard metric for heated or weak/unstable ground, ground collapse, hot water, mud and steam within features, mild explosive activity and pyroclastic density currents. Temperatures of surface features (and therefore any material ejected from them) can range between 20 and 100°C, while pyroclastic density currents can measure up to 250°C. These temperatures can cause burns and fatal injuries. Ballistic projectiles and pyroclastic density currents can travel with enough energy to injure or kill those exposed. Depending on the concentration of geothermal gases, particularly hydrogen sulphide and carbon dioxide, exposure can range from a nuisance to deadly. While many of the hazards produced in geothermal areas can cause casualties and fatalities, the frequency at which these are produced is important. Since 1800, around the time that records in New Zealand began, on average there has been one hydrothermal eruption every 1.1 years in New Zealand. In this same time period, there have been no recorded phreatic eruptions from geothermal areas in New Zealand, with the last documented occurrence around 700 years ago. A recorded ground collapse event has occurred on average every 3.8 years, while an artificial eruption or creation of a surface feature from infrastructure failure has occurred on average every 2.5 years. The risk from these hazards can be managed in multiple ways, including hazard and risk assessment, land-use planning, engineering solutions, communication and education products and processes, access restrictions and monitoring/surveillance. Monitoring is an important risk-mitigation strategy for eruptions from volcanoes and can provide some warning of impending volcanic eruptions. Monitoring of geothermal systems may include regular surveillance of surface features tracking any observed changes. This is usually based around staff walking all tracks on a regular basis to check for safety issues, including infrastructure health, ground collapse, landslides and enhanced feature activity. Deligne et al. (2020) included geothermal eruptions in Category A of their two-category classification (eruptions without useful precursory activity that occur due to shallow magma). However, this current review identified that the Category A definition does not adequately cover geothermal hazards. Geothermal eruptions can occur either with or without measurable precursory activity. In geothermal systems not associated with active cone volcanoes, eruptions are not driven by shallow magma but rather by deep magmatic sources, and non-eruptive hazards are also not included within the existing Category A. Additionally, although rare, magmatic eruptions can occur at geothermal systems associated with calderas. As such, we recommend that the Deligne et al. (2020) Category B (eruptions with precursory activity) be kept in relation to magmatic eruptions from geothermal areas not associated with active cone volcanoes, that Category A be used only for geothermal systems associated with active cone volcanoes and for those volcanoes themselves and that two new categories be created: Category C: Steam-driven eruptive hazards from geothermal systems not associated with active cone volcanoes – this includes all sizes of hydrothermal eruptions, phreatic eruptions and mild explosive activity from surface features; and Category D: Non-eruptive hazards from geothermal systems not associated with active cone volcanoes – this includes gas, ground collapse, heated or steaming ground, weak/unstable ground, failure of infrastructure associated with visitor access, and earthquakes. (The authors)

We present a revised version of the New Zealand Volcano Early Warning System (NZVEWS) volcano threat assessment, updating the 2012 assessment. The purpose of this assessment is to guide future investment in volcano monitoring instrumentation for New Zealand’s active volcanoes. This report ranks New Zealand’s volcanoes by an internationally recognised threat assessment method, which we modify for New Zealand conditions. The underlying assumption is that higher-threat volcanoes warrant higher levels of instrumentation. In this revised assessment, we include new exposure factors (gross domestic product [GDP] exposure and short-term visitors), as well as introduce a new vulnerability metric based on the 2018 New Zealand Deprivation Index. We group the threat ranking and vulnerability-modified threat rankings of volcanoes into ‘high’, ‘medium’ and ‘low’ groups based on 33% quantile distribution of threat scores. Where discrepancies between threat ranking and vulnerability-modified threat ranking exist, we take the higher value for final group assignment. Ōkataina Volcanic Centre, Auckland Volcanic Field, Taranaki, Ruapehu, Taupō and Tongariro/ Ngauruhoe are the highest-threat volcanoes in New Zealand and warrant prioritisation for future network upgrades pending the outcome of the second stage of this work, which investigates instrumentation requirements for each threat-level group. (The authors)

This report proposes an approach for assessing the impact (a return on investment) of resilience investments on wellbeing and a framework for assessing the impacts of the National Seismic Hazard Model (NSHM) research programme on wellbeing in New Zealand. The NSHM calculates the likelihood and strength of earthquake shaking across New Zealand to inform the design and standards for infrastructure, land-use planning and risk insurance, which affect wellbeing related to housing, safety and basic services, among others. A wellbeing impact assessment (WIA) approach is developed in this study to frame explanations of causalities, guide the selection of established indicators and inform the development of new ones. We propose several published indicators, primarily housing- and infrastructure-related, that could be used to measure the impact of the NSHM on New Zealand wellbeing. A step process comprising a Theory of Change, a results-chain framework and a monitoring and evaluation plan is then proposed to conduct and report on the WIA of the NSHM. This report did not go as far as assigning values to the NSHM-relevant (published) indicators, but it is our recommendation that the approach is sufficiently robust to warrant this next step, which may also include the development of new NSHM-specific indicators. We note that the data used to quantify indicators (both existing and new) may not be currently collected or may have sporadic coverage. The approach proposed here is transferable to assessing the impact of other resilience investments on New Zealand wellbeing. This work was funded by the GNS Science Capability Development Fund. Thank you to Joe Manning and Gary Wilson for their assistance on project proposal and stakeholder engagement ideas. (The authors)

On January 15th, 2022, social media and news reports emerged of booming and explosion noises throughout Aotearoa, caused by atmospheric pressure waves from the eruption of Hunga volcano, Tonga. Instrumental records from tidal gauges, DART buoys, meteorological stations and post-event damage surveys are being used to shape our understanding of the physical processes associated with the eruption and associated tsunami, such as pressure changes, acoustic signals and wave arrival times. To develop a more holistic understanding of this complex event and how it was experienced by or impacted communities, we designed a survey to capture insights and promote public engagement with science. We sought to understand the spatial and temporal distribution of sound and tsunami observations using crowdsourced geospatial data, allowing the public to participate and report experiences. An interdisciplinary team of social, volcano, and tsunami scientists from GNS Science deployed this survey online between January 21st and February 13th, 2022. Thirty-nine questions were posed to the public, asking about location, time, water colour, smells, damage to the built/natural environments and number of surges/booms observed. Respondents provided images and videos displaying impacted coastlines, flooded campgrounds, coastal erosion, unusual currents, and audio of booms. From this case study, we identify key lessons to improve crowdsourced data collection approaches for future hazardous events. These key lessons include using appropriate data collection methods to facilitate the intended use of the data, considering the ethical implications of collecting and sharing the data, and the technical requirements for sharing the data with various audiences.