Degassing and Hydrothermal Activity at Mt. Spurr, Alaska During the Summer of 2004 Inferred from the Complex Frequencies of Long-Period Events
Digital Object Identifier (DOI)
Results of analyses of unusual long-period earthquakes, recorded between July and September 2004 at Mt. Spurr, Alaska, are presented. The waveforms of these events are characterized by quasi-sinusoidal signatures of long duration (up to 40 sec) with slowly decaying amplitudes; bandwidths of 0.5–4.0 Hz are typical; amplitude spectra are marked by strong and sharp peaks, reflecting the quasi-monochromatic nature of the signal. The temporal variations of the complex frequencies are investigated by use of the Sompi method; the dominant mode is resolved and its Q factor estimated for each available event. Dominant frequencies are found in the band 0.8–2.2 Hz with Q varying between 25 and 100. The variations of the complex frequencies show an overall decline with time. The dynamic response of a shallow fracture filled with bubbly water to the flux of hot gases from depth, is proposed as a possible mechanism for the generation of the observed waveforms.
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Citation / Publisher Attribution
Geophysical Research Letters, v. 32, issue 12, art. L12312
Scholar Commons Citation
De Angelis, S. and McNutt, Stephen R., "Degassing and Hydrothermal Activity at Mt. Spurr, Alaska During the Summer of 2004 Inferred from the Complex Frequencies of Long-Period Events" (2005). School of Geosciences Faculty and Staff Publications. 308.