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Title: Monitoring lava dome eruptions : a seismic, acoustic and experimental study
Author: Lamb, O. D.
ISNI:       0000 0004 6495 6394
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2017
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Lava dome eruptions are one of the most dangerous forms of volcanic activity. Geophysical, experimental, field or numerical investigations over the past few decades have improved our understanding of dynamic processes associated with these eruptions. In this thesis, I use multi-disciplinary approaches to analyse unrest at four different volcanoes: Volcán de Colima, Unzen, Santiaguito dome complex and Mt. Redoubt. At Volcán de Colima, waveform correlation and seismic interferometry techniques are used to analyse seismic data collected prior to the November 1998 eruption. A decrease in seismic velocity is observed during pre-eruptive activity, consistent with rock failure caused by increased stress associated with the migration of magma towards the surface. This mechanism is confirmed by measurements during experimental Brazil tests on lava samples from the volcano. Furthermore, repetitive micro-cracking during the experiments suggest some repeating earthquakes detected at Volcán de Colima were produced by repeated tensile failure. At Unzen, I analyse seismic data collected during the formation of a lava spine during the last phase of the 1991-95 eruption. Two large groups of repeating earthquakes are identified and further analysis demonstrates how their sources migrated during their period of activation. Citing experimental and field observations, repeated slip motion along the margins of the spine are inferred as the source mechanisms for these earthquakes. Santiaguito dome complex is one of the most active volcanoes in the world, and here I present the first long-term seismo-acoustic dataset to be recorded at the volcano. The dataset captures a major transition in explosive activity that took place in 2015. Variations in energies and waveform arrival times are used to gain insights into the explosion source dynamics. During its eruption in 2009, Mt. Redoubt volcano erupted 19 times, at least 16 of which produced ash plumes tall enough to disrupt air traffic in the region. Using infrasound data recorded during two of these explosions and a three-dimensional plume rise model, I demonstrate how it is possible to efficiently and accurately estimate the ash plume height soon after an eruption begins. These four case studies demonstrate how using a combination of geophysical, experimental, numerical, and field observations can provide more robust interpretations of dynamic processes prior to or during lava dome eruptions. Therefore, multi-disciplinary approaches to studying volcanic activity can have important implications for hazard assessments at active volcanoes worldwide.
Supervisor: Lavallee, Y. ; De Angelis, S. ; Kavanagh, J. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral