Precursors to dyke-fed eruptions at basaltic volcanoes: insights from patterns of volcano-tectonic seismicity at Kilauea volcano,Hawaii |
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| Authors: | Andrew F Bell Christopher R J Kilburn |
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| Institution: | (1) School of GeoSciences, The University of Edinburgh, Grant Institute, The King’s Buildings, West Mains Road, Edinburgh, EH9 3JW, UK;(2) Aon Benfield UCL Hazard Centre, Department of Earth Sciences, University College London, Gower Street, London, WC1E 6BT, UK |
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| Abstract: | To investigate the physical controls on volcano-tectonic (VT) precursors to eruptions and intrusions at basaltic volcanoes,
we have analyzed the spatial and temporal patterns of VT earthquakes associated with 34 eruptions and 23 dyke intrusions that
occurred between 1960 and 1983 at Kilauea, in Hawaii. Eighteen of the 57 magmatic events were preceded by an acceleration
of the mean rate of VT earthquakes located close to the main shallow magma reservoir. Using a maximum-likelihood technique
and the Bayesian Information Criterion for model preference, we demonstrate that an exponential acceleration is preferred
over a power-law acceleration for all sequences. These sequences evolve over time-scales of weeks to months and are consistent
with theoretical models for the approach to volcanic eruptions based on the growth of a population of fractures in response
to an excess magma pressure. Among the remaining 40 magmatic events, we found a significant correlation between swarms of
VT earthquakes located in the mobile south-flank of Kilauea and eruptions and intrusions. The behaviour of these swarms suggests
that at least some of the magmatic events are triggered by transient episodes of elevated rates of aseismic flank movement,
which could explain why many eruptions and intrusions are not preceded by longer-term precursory signals. In none of the 57
cases could a precursory sequence be used to distinguish between the approach to an eruption or an intrusion, so that, even
when a precursory sequence is recognized, there remains an empirical chance of about 40% (24 intrusions from 57 magmatic events)
of issuing a false alarm for an imminent eruption. |
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