Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
6439689 | Journal of Volcanology and Geothermal Research | 2014 | 17 Pages |
Abstract
Pre-eruption seismic activity includes numerous small unlocatable micro-earthquakes that began at 11:46:50. Two larger high frequency earthquakes were recorded at 11:49:06 and 11:49:21 followed directly by a third earthquake at 11:50:17. The first event was located within the scarp based on an arrival time location from good first P arrival times and probably represents the onset of the debris avalanche. The third event was a tornillo, characterised by a 0.8Â Hz single frequency resonance, and has a resonator attenuation factor of QÂ ~Â 40, consistent with a bubbly fluid filled resonator. This contrasts with a similar tornillo event occurring 2.5Â weeks earlier having QÂ ~Â 250-1000, consistent with a dusty gas charged resonator. We surmise from pre-eruption seismicity, and the observed attenuation change, that the debris avalanche resulted from the influx of fluids into the hydrothermal system, causing destabilisation and failure. The beheaded hydrothermal system may have then caused depressurisation frothing of the remaining gas charged system leading to the onset of explosive activity.
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Geochemistry and Petrology
Authors
A.D. Jolly, P. Jousset, J.J. Lyons, R. Carniel, N. Fournier, B. Fry, C. Miller,