Thesis (Ph. D.)--University of Canterbury, 2008. / Typescript (photocopy). Includes bibliographical references. Also available via the World Wide Web.

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Thesis (M.Sc. Earth and Ocean Science)--University of Waikato, 2008. / Title from PDF cover (viewed August 26, 2008) Includes bibliographical references (p. 169-177)

Thesis (Ph. D.)--University of Oregon, 2004. / Vita. Includes bibliographical references (leaves 178-188). Also available for download via the World Wide Web; free to University of Oregon users.

Thesis (Ph. D.)--University of Oregon, 2004. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 178-188). Also available for download via the World Wide Web; free to University of Oregon users.

Explosive volcanic eruptions frequently expel ballistic projectiles, producing a significant proximal hazard to people, buildings, infrastructure and the environment from their high kinetic and thermal energies. Ballistic hazard assessments are undertaken as a risk mitigation measure, to determine probabilities of eruptions occurring that may produce ballistics, identify areas and elements likely to be impacted by ballistics, and the potential vulnerabilities of elements to ballistics. The 6 August, 2012 hydrothermal eruption of Upper Te Maari Crater, Tongariro, New Zealand ejected blocks over a 6 km2 area, impacting ~2.6 km of the Tongariro Alpine Crossing (TAC), a walking track hiked by ~80,000 people a year, and damaging an overnight hut along the track. In this thesis ballistic hazard and risk from Upper Te Maari Crater are assessed through a review of its eruptive history, field and orthophoto mapping of the 6 August ballistic impact distribution, forward modelling and analysis of possible future eruption scenarios using a calibrated 3D ballistic trajectory model, and analysis of the vulnerability of hikers along the impacted Tongariro Alpine Crossing. Orthophoto mapping of the 6 August ballistic impact crater distribution revealed 3,587 impact craters with a mean diameter of 2.4 m. However, field mapping of accessible regions indicated an average of at least four times more observable impact craters and a smaller mean crater diameter of 1.2 m. By combining the orthophoto and ground-truthed impact frequency and size distribution data, it is estimated that approximately 13,200 ballistic projectiles were generated during the eruption. Ballistic impact distribution was used to calibrate a 3D ballistic trajectory model for the 6 August eruption. The 3D ballistic trajectory model and a series of inverse models were used to constrain the eruption directions, angles and velocities. When combined with eruption observations and geophysical observations and compared to the mapped distribution, the model indicated that the blocks were ejected in five variously directed eruption pulses, in total lasting 19 seconds. The model successfully reproduced the mapped impact distribution using a mean initial particle velocity of 200 m/s with an accompanying average gas flow velocity over a 400 m radius of 150 m/s. Assessment of the vulnerability of hikers to ballistics from the August eruption along the TAC utilised the modelled spatial density of impacts and an assumption that an average ballistic impact will cause serious injury or death (casualty) over an 8 m2 area. It is estimated that the probability of casualty ranged from 1% to 16% along the affected track (assuming an eruption during the time of exposure). Future ballistic hazard and vulnerability along the TAC are also assessed through application of the calibrated model. A magnitude larger eruption (than the 6 August) in which 10x more particles were ejected, doubled the affected length of the TAC and illustrated that the probability of casualty could reach 100% in localised areas of the track. In contrast, ballistics ejected from a smaller eruption did not reach the track as was the case with the 21 November 2012 eruption. The calibrated ballistic model can therefore be used to improve management of ballistic hazards both at Tongariro and also, once recalibrated, to other volcanoes worldwide.

Thesis (Ph. D.)--University of Canterbury, 2009. / Typescript (photocopy). Includes bibliographical references (leaves 233-242). Also available via the World Wide Web.

Thesis (M.S.)--Oregon State University, 2006. / Printout. Includes bibliographical references (leaves 58-60). Also available online.

Volcanic eruptions and unrest have the potential to have large impacts on society causing social, economic and environmental losses. One of the primary goals of volcanological studies is to understand a volcano’s behaviour so that future instances of unrest or impending eruptions can be predicted. Despite this, our ability to predict the onset, location and size of future periods of unrest remains inadequate and one of the main problems in forecasting is associated with the inherent complexity of volcanoes. In practice, most reliable forecasts have employed a probabilistic approach where knowledge of volcanic activity triggers have been incorporated into scenarios to indicate the probability of unrest. The proposed relationship between large earthquakes and volcanic activity may, therefore, indicate an important precursory signal for volcanic activity forecasting. There have been numerous reports of a spatial and temporal link between volcanic activity and high magnitude seismic events and it has been suggested that significantly more periods of volcanic unrest occur in the months and years following an earthquake than expected by chance. Disparities between earthquake-volcano assessments and variability between responding volcanoes, however, has meant that the conditions that influence a volcano’s response to earthquakes have not been determined. Using data from the MODVOLC algorithm, a proxy for volcanic activity, this research examined a globally comparable database of satellite-derived volcanic radiant flux to identify significant changes in volcanic activity following an earthquake. Cases of potentially triggered volcanic activity were then analysed to identify the earthquake and volcano parameters that influence the relationship and evaluate the mechansisms proposed to trigger volcanic activity following an earthquake. At a global scale, this research identified that 57% [8 out of 14] of all large magnitude earthquakes were followed by increases in global volcanic activity. The most significant change in volcanic radiant flux, which demonstrates the potential of large earthquakes to influence volcanic activity at a global scale, occurred between December 2004 and April 2005. During this time, new thermal activity was detected at 10 volcanoes and the total daily volcanic radiant flux doubled within 52 days. Within a regional setting, this research also identified that instances of potentially triggered volcanic activity were statistically different to instances where no triggering was observed. In addition, assessments of earthquake and volcano parameters identified that earthquake fault characteristics increase the probability of triggered volcanic activity and variable response proportions at individual volcanoes and regionally demonstrated the critical role of the state of the volcanic system in determining if a volcano will respond. Despite the identification of these factors, this research was not able to define a model for the prediction of volcanic activity following earthquakes and, alternatively, proposed a process for response. In doing so, this thesis confirmed the potential use of earthquakes as a precursory indicator to volcanic activity and identified the most likely mechanisms that lead to seismically triggered volcanic unrest.

A multi-prong approach was taken in this dissertation to understand volcanic processes from both a long-term and more immediate hazard perspective. In the long-term, magma sources within the crust may produce measurable surficial response and long-wavelength gravity anomalies that provide information about the extent and depth of this magma. Long-term volcanic hazard forecasting is also improved by developing as complete a record as possible of past events. In the short-term, a long-standing question has been on the casting of precursory volcanic activity in terms of future volcanic hazards. Three studies are presented in this dissertation to address these issues. Inversion of high-resolution ground magnetic data in Amargosa Valley, NV indicates that anomaly B could be generated by a buried shield volcano. This new information changes the event count in this region which in turn affects the overall volcanic hazard estimation. Through the use of Finite Element Models (FEM) an in-depth characterization of the surficial response to magma underplating is provided for the Tohoku Volcanic Arc, Japan. These models indicate that surficial uplift was dominantly driven by mid-crustal intrusions and the magnitude and wavelength of this uplift was mainly controlled by the elastic layer thickness. In Dominica, seismic data were used as weights in spatial intensity maps to generate dynamic volcanic hazard maps influenced by changes in seismicity. These maps show an increasing trend in the north that may be indicative of an increase in earthquake and volcanic hazards.