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De Angelis 2006
De Angelis, S. (2006). Analyses of unusual long-period earthquakes with extended coda recorded at Katmai National Park, Alaska, USA. Geophysical Research Letters 33: doi: 10.1029/2005GL025581. issn: 0094-8276.

A swarm of six long-period (LP) events with slowly decaying coda wave amplitudes and durations up to 120 s, was recorded by seismic stations located in the proximity of Mt. Griggs, a fumarolically active volcano in the Katmai National Park, Alaska, during December 8--21, 2004. Spectral analyses reveal the quasi-monochromatic character of the waveforms, dominated by a 2.5 Hz mode frequently accompanied by a weaker high-frequency onset (6.0--9.0 Hz). Particle motion azimuths and inclination angles show a dominant WNW-ESE direction of polarization for all the signals, and suggest that seismic energy is radiated by a stable source at shallow depth. Damping coefficients between 0.0014 and 0.0063 are estimated by fitting an exponential decay model to the signal's coda; corresponding quality factors range from 78 to 351. The source of the waveforms is modelled as a resonant cavity filled with a fluid/gas mixture.

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Abstract

Keywords
Seismology, Volcano seismology, Volcanology, Volcano monitoring, Volcanology, Hydrothermal systems (0450, 1034, 3017, 3616, 4832, 8135)
Journal
Geophysical Research Letters
http://www.agu.org/journals/gl/
Publisher
American Geophysical Union
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