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    Simulation of the 2012 Te Maari debris avalanche: Insight into the failure mechanics and the role of the hydrothermal system
    (Elsevier B V, 2025-09) Vicente J; Mead S; Kereszturi G; Miller C
    Composite volcanoes consist of alternating layers with varying mechanical properties, which contribute to the instability of the flanks. This instability can lead to the onset of mass flows down volcanic slopes, posing significant risks to nearby populations and infrastructures. Tongariro, an active andesite volcano, experienced one of New Zealand's most recent debris avalanches at the Upper Te Maari crater on August 6, 2012. This debris avalanche, initiated simultaneously with a small-magnitude earthquake, released a volume of 7 × 105 m3 of material from the source, which by unloading the pressurised vapour-dominated hydrothermal system, led to a phreatic eruption. This paper aims to better constrain the preparatory and triggering factors, along with the failure mechanics, that led to the 2012 debris avalanche. To achieve this, we applied slope stability finite-element modelling to assess the volcanic slope's sensitivity to varying groundwater, seismic and mechanical conditions. Model results closely match the observed failure when considering the strength of hydrothermally altered rocks subjected to an increased pore pressure at shallow depth. We found that even a relatively minor rise in pore pressure, ≈ 250 kPa in the upper layers, could replicate the observed failure at Te Maari. Our simulations also reveal that this debris avalanche might be a multiple-stage failure involving the progressive sliding of two distinct blocks. These findings enhance our understanding of Tongariro's structure and improve hazard assessments for future potential collapses at Tongariro and other New Zealand volcanoes.
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    The linear wave response of a single and a periodic line-array of floating elastic plates: a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Mathematics at Massey University, Albany, New Zealand
    (Massey University, 2004) Wang, Cynthia Dewi
    We propose an improved technique to calculate the linear response of a single and multiple plates models due to ocean waves. The single plate model is the basis for the multiple plates model which we take to be a periodic array of identical plates. For the single plate model we solve the plate displacement by the Finite Element Method (FEM) and the water potential by the Boundary Element Method (BEM). The displacement is expanded in terms of the basis functions of the FEM. The boundary integral equation representing the potential is approximated by these basis functions. The resulting integral operator involving the free-surface Green's function is solved using an elementary integration scheme. Results are presented for the single plate model. We then use the same technique to solve for the periodic array of plates problem because the single and the periodic array plates model differ only in the expression of the Green's function. For the periodic array plate model the boundary integral equation for the potential involves a periodic Green's function which can be obtained by taking an infinite sum of the free-surface Green's function for the single plate model. The solution for the periodic array plate is derived in the same way as the single plate model. From this solution we then calculate the waves scattered by this periodic array.