Browsing by Author "Bebbington MS"
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- ItemA modular framework for the development of multi-hazard, multi-phase volcanic eruption scenario suites(Elsevier BV, 2022-07) Weir AM; Mead S; Bebbington MS; Wilson TM; Beaven S; Gordon T; Campbell-Smart CUnderstanding future volcanic eruptions and their potential impact is a critical component of disaster risk reduction, and necessitates the production of salient, robust hazard information for decision-makers and end-users. Volcanic eruptions are inherently multi-phase, multi-hazard events, and the uncertainty and complexity surrounding potential future hazard behaviour is exceedingly hard to communicate to decision-makers. Volcanic eruption scenarios are recognised to be an effective knowledge-sharing mechanism between scientists and practitioners, and recent hybrid scenario suites partially address the limitations surrounding the traditional deterministic scenario approach. Despite advances in scenario suite development, there is still a gap in the international knowledge base concerning the synthesis of multi-phase, multi-hazard volcano science and end-user needs. In this study we present a new modular framework for the development of complex, long-duration, multi-phase, multi-hazard volcanic eruption scenario suites. The framework was developed in collaboration with volcanic risk management agencies and researchers in Aotearoa-New Zealand, and is applied to Taranaki Mounga volcano, an area of high volcanic risk. This collaborative process aimed to meet end-user requirements, as well as the need for scientific rigour. This new scenario framework development process could be applied at other volcanic settings to produce robust, credible and relevant scenario suites that are demonstrative of the complex, varying-duration and multi-hazard nature of volcanic eruptions. In addressing this gap, the value of volcanic scenario development is enhanced by advancing multi-hazard assessment capabilities and cross-sector collaboration between scientists and practitioners for disaster risk reduction planning.
- ItemApproaching the challenge of multi-phase, multi-hazard volcanic impact assessment through the lens of systemic risk: application to Taranaki Mounga(Springer Nature, 2024-08-01) Weir AM; Wilson TM; Bebbington MS; Beaven S; Gordon T; Campbell-Smart C; Mead S; Williams JH; Fairclough REffective 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.
- ItemBrief communication: SWM - stochastic weather model for precipitation-related hazard assessments using ERA5-Land data(Copernicus Publications on behalf of the European Geosciences Union, 2024-06-11) Whitehead MG; Bebbington MS; Li DLong-term multi-hazard and risk assessments are produced by combining many hazard-model simulations, each using a slightly different set of inputs to cover the uncertainty space. While most input parameters for these models are relatively well constrained, atmospheric parameters remain problematic unless working on very short timescales (hours to days). Precipitation is a key trigger for many natural hazards including floods, landslides, and lahars. This work presents a stochastic weather model that takes openly available ERA5-Land data and produces long-term, spatially varying precipitation data that mimic the statistical dimensions of real data. This allows precipitation to be robustly included in hazard-model simulations. A working example is provided using 1981–2020 ERA5-Land data for the Rangitāiki–Tarawera catchment, Te Moana-a-Toi / Bay of Plenty, New Zealand.
- ItemIntra-Eruption Forecasting Using Analogue Volcano and Eruption Sets(John Wiley and Sons, Inc on behalf of the American Geophysical Union, 2022-06-23) Bebbington MS; Jenkins SFForecasting the likely style and chronology of activity within an eruption is a complex issue that has received far less attention than forecasting the onset and/or the magnitude. By developing a global data set of coded phases (discrete styles of activity within previous eruptions), we can model the resulting data using a semi-Markov chain. Given enough data, we were able to examine the question of whether analogue-based strategies for subsetting the data can improve forecasting performance of phase chronology and style within ongoing eruptions. This work required inclusion of a “null analogue” element to ensure no surprises, that is, phase transitions or durations that were not in the data set and hence cannot be predicted. We have significantly expanded, and made available, our curated data set on eruption phases, which now contains 2670 eruptions (6871 phases), of which 56% are multi-phase. This increases the data set by 283% and includes 95% of Holocene eruptions with text descriptions. We find that, with the notable exception of shields, limiting the analogue set on the basis of volcano morphology and/or composition is not significantly more informative than using the entire data set. Dynamically adjusting the data limits by eliminating eruptions without the observed phase as the eruption progresses provided little benefit, although subsetting on the basis of VEI may have some utility. At the individual volcano level, non-analogue models can outperform the entire data set, if the target volcano has relatively unique behavior and/or a large enough record of phased eruptions.
- ItemModelling spatial population exposure and evacuation clearance time for the Auckland Volcanic Field, New Zealand(Elsevier BV, 2021-08) Wild AJ; Bebbington MS; Lindsay JM; Charlton DHAuckland, New Zealand's largest city (population of ~1.6 million), is situated atop the monogenetic Auckland Volcanic Field (AVF). As in many places faced with volcanic activity, evacuation is seen as the best risk mitigation strategy for preserving lives in the event of volcanic unrest and/or an eruption. However, planning for an evacuation can be challenging. In particular, the uncertainty in vent location resulting from the monogenetic nature of the field makes identifying neighbourhoods to be evacuated impractical until well into the pre-eruption unrest period. This study uses spatial analysis methods to assess exposure for both population and private transport ownership as well as to identify those areas requiring public transport support for an evacuation. These data were overlaid on a range of possible vent locations across the AVF using a 500 × 500 m grid. At each possible vent location, a 5 km evacuation zone is modelled, following the official contingency plan for evacuation in a future AVF event. In order to simulate vent location uncertainty leading up to a future eruption, a range of buffer distances were applied around the modelled vent locations. The exposure data derived were then used to model evacuation clearance time, which considered four phases: 1) the time taken to decide to call an evacuation; 2) the public notification time; 3) the evacuee's time to prepare; and 4) evacuee's travel time to beyond the evacuation zone. The length of time involved in phases 1 to 3 are all independent of the vent location; our analysis found these phases could be completed within 36 h, with over 80% confidence. Travel times to beyond the evacuation zone were modelled using the exposure analysis for population and private transport ownership combined with road network data and vehicle carrying capacity. This revealed travel times for this phase ranging from less than 1 up to 11 h, depending on traffic congestion, when considering no vent uncertainty. By combining the times modelled for all four phases, we found that when there is high certainty in the vent location, the median total evacuation clearance time with no congestion is approximately 37 h. However, include a 10 km vent uncertainty buffer into the model, the evacuation clearance time can increase to between 38 and 55 h, dependent on traffic congestion. A vent in the densely populated inner Auckland and CBD area would result in the greatest population required to evacuate, and also the greatest need for public transport support given the low vehicle ownership in this area. Our results can be used to inform emergency management decision making, and the model can be adapted for other regions as well as for other hazards.
- ItemShort-Term Eruption Forecasting for Crisis Decision-Support in the Auckland Volcanic Field, New Zealand(Frontiers Media S.A., 2022-05-24) Wild AJ; Bebbington MS; Lindsay JM; Wright HMAuckland, a city of 1.6 million people, is situated atop the active monogenetic Auckland Volcanic Field (AVF). Thus, short-term eruption forecasting is critical to support crisis management in a future event, especially to inform decisions such as calling evacuations. Here we present an updated BET_EF for the AVF incorporating new data and the results of an expert-opinion workshop, and test the performance of the resulting BETEF_AVF on eight hypothetical eruption scenarios with pre-eruptive sequences. We carry out a sensitivity analysis into the selection of prior distributions for key model parameters to explore the utility of using BET_EF outputs as a potential input for evacuation decision making in areas of distributed volcanism such as the AVF. BETEF_AVF performed well based on the synthetic unrest dataset for assessing the probability of eruption, with the vent outbreaks eventuating within the zone of high spatial likelihood. Our analysis found that the selection of different spatial prior model inputs affects the estimated vent location due to the weighting between prior models and monitoring inputs within the BET_EF, which as unrest escalates may not be appropriate for distributed volcanic fields. This issue is compounded when the outputs are combined with cost-benefit analysis to inform evacuation decisions, leading to areas well beyond those with observed precursory activity being included in evacuation zones. We find that several default settings used in past work for the application of BET_EF and CBA to inform evacuation decision-support are not suitable for distributed volcanism; in particular, the default 50-50 weighting between priors and monitoring inputs for assessing spatial vent location does not produce useful results. We conclude by suggesting future cost-benefit analysis applications in volcanic fields appropriately consider the spatial and temporal variability and uncertainty characteristic of such systems.
- ItemThe geological history and hazards of a long-lived stratovolcano, Mt. Taranaki, New Zealand(Taylor and Francis Group on behalf of the Royal Society of New Zealand, 2021-03-17) Cronin SJ; Zernack AV; Ukstins IA; Turner MB; Torres-Orozco R; Stewart RB; Smith IEM; Procter JN; Price R; Platz T; Petterson M; Neall VE; McDonald GS; Lerner GA; Damaschcke M; Bebbington MSMt. Taranaki is an andesitic stratovolcano in the western North Island of New Zealand. Its magmas show slab-dehydration signatures and over the last 200 kyr they show gradually increasing incompatible element concentrations. Source basaltic melts from the upper mantle lithosphere pond at the base of the crust (∼25 km), interacting with other stalled melts rich in amphibole. Evolved hydrous magmas rise and pause in the mid crust (14–6 km), before taking separate pathways to eruption. Over 228 tephras erupted over the last 30 kyr display a 1000–1500 yr-periodic cycle with a five-fold variation in eruption frequency. Magmatic supply and/or tectonic regime could control this rate-variability. The volcano has collapsed and re-grown 16 times, producing large (2 to >7.5 km3) debris avalanches. Magma intrusion along N-S striking faults below the edifice are the most likely trigger for its failure. The largest Mt. Taranaki Plinian eruption columns reach ∼27 km high, dispersing 0.1 to 0.6 km3 falls throughout the North Island. Smaller explosive eruptions, or dome-growth and collapse episodes were more frequent. Block-and-ash flows reached up to 13 km from the vent, while the largest pumice pyroclastic density currents travelled >23 km. Mt. Taranaki last erupted in AD1790 and the present annual probability of eruption is 1–1.3%.
