Analyzing seismic signals to understand volcanic mass flow emplacement : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Earth Sciences at Massey University, Palmerston North, Manawatu, Aotearoa New Zealand
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Date
2017
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Massey University
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Abstract
Natural hazards are one of the greatest threats to life, industry, and infrastructure. It has been estimated that around a half billion people worldwide are in direct proximity to the danger of volcanic hazards. For volcanic mass flows, such as pyroclastic density currents and lahars, extreme runout distances are common. The close proximity of large population centers to volcanoes requires the implementation of early warning and realOtime monitoring systems. A large portion of the progress towards realOtime monitoring is through the use of geophysical instrumentation and techniques. This research looks into emerging geophysical methods and tries to better constrain and apply them for volcanic purposes. Specifically, multiple types of amplitude source location techniques are described and used for locating and estimating the dynamics of volcanic mass flows and eruptions. Other methods, such as semblance and back projection, are also employed. Applying the active seismic source method to a lahar that occurred on October 13th 2012 at Te Maari, New Zealand, locations and estimations of lahar energy were calculated in an increased noise environment. Additionally, the first ever calibration of the amplitude source location (ASL) method was conducted using active seismic sources. The calibration proved to decrease true error distances by over 50%. More calibration on the ASL method was accomplished by using all three components of the broadband seismometer. Initial results showed that using all three components reduced extreme errors and increase the overall precision of the locations. Finally, multiple geophysical methods (ASL, semblance, back projection, waveform migration, acoustic-seismic ratios) were used to show that a combination of instrumentation could produce more reliable results. This research has filled gaps in the preexisting knowledge for hazards. With these results, more effective hazard warnings can be produced, and systems for real time estimations of locations and dynamics of volcanic events could be developed.
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Figures 1.1 - 1.11 and Figures 1.14 - 1.16 have been removed for copyright reasons, but may be accessed through the sources listed in the Bibliography. Figures 1.12 & 1.13 remain, in the interests, respectively, of clarity and accessibility.
Keywords
Volcanic activity prediction, New Zealand, Volcanic eruptions, Tongariro National Park, Whakaari/White Island, Seismology, Methodology, Instruments, Tongariro, Mount (N.Z.), Eruption, 2012