Journal Articles
Permanent URI for this collectionhttps://mro.massey.ac.nz/handle/10179/7915
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Item Short-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.Item The 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%.