HR: 11:50h
AN: V32A-07    [Abstracts]
TI: Forecasting Lava Dome Eruptions from High Frequency Seismicity
AU: * Smith, R
EM: rosanna.smith@ucl.ac.uk
AF: Benfield Hazard Research Centre, Department of Earth Sciences, University College London, Gower Street, London, WC1E 6BT United Kingdom
AU: * Smith, R
EM: rosanna.smith@ucl.ac.uk
AF: Mineral, Ice, and Rock Physics Laboratory, Department of Earth Sciences, University College London, Gower Street, London, WC1E 6BT United Kingdom
AU: Kilburn, C R
EM: c.kilburn@ucl.ac.uk
AF: Benfield Hazard Research Centre, Department of Earth Sciences, University College London, Gower Street, London, WC1E 6BT United Kingdom
AU: Sammonds, P R
EM: p.sammonds@ucl.ac.uk
AF: Benfield Hazard Research Centre, Department of Earth Sciences, University College London, Gower Street, London, WC1E 6BT United Kingdom
AU: Sammonds, P R
EM: p.sammonds@ucl.ac.uk
AF: Mineral, Ice, and Rock Physics Laboratory, Department of Earth Sciences, University College London, Gower Street, London, WC1E 6BT United Kingdom
AB: Following its plinian eruption on 18 May 1980, Mount St Helens (Washington State, U.S.A.) entered a period of intermittent lava-dome extrusion until 1986. A re-analysis of the timing of volcano-tectonic (VT) earthquakes and eruptions indicates that: (1) all VT crises resulted in an eruption within 3 weeks (usually less than 10 days), (2) the majority of eruptions had VT precursors, and (3) patterns of precursory seismicity showed significant variations. Thus, although these seismic events could be used to warn of an impending eruption, specific forecasts were subject to significant uncertainty. It is proposed that: (1) Increased seismicity prior to later eruptions are a result of a larger more solidified dome acting as a greater impediment to magma ascent; (2) the consistency of seismic swarms resulting in an eruption indicate that stresses high enough to initiate fracturing in the country rock and lava dome carapace were only achieved once the approach to an eruption had already begun; and (3) discrepancies between models of accelerating rock fracture and the observed seismicity may arise due to a significant amount of the material failing and deforming through ductile mechanisms rather than seismogenic fracture.
DE: 5104 Fracture and flow
DE: 8419 Volcano monitoring (7280)
DE: 8429 Lava rheology and morphology
DE: 8488 Volcanic hazards and risks
DE: 8494 Instruments and techniques
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005