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Acoustic resonant oscillations between the atmosphere and the solid earth during the 1991 Mt. Pinatubo eruption

Watada, Shingo and Kanamori, Hiroo (2010) Acoustic resonant oscillations between the atmosphere and the solid earth during the 1991 Mt. Pinatubo eruption. Journal of Geophysical Research B, 115 . Art. No. B12319 . ISSN 0148-0227.

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Long-period harmonic Rayleigh waves were observed on seismometers during the 1991 Mt. Pinatubo eruption in the Philippines. The amplitude spectrum of the Rayleigh waves shows two distinct peaks at periods of about 230 and 270 s. In the Earth’s atmosphere, long-wavelength standing acoustic waves are bounded in a low-sound-velocity channel between the thermosphere and the ground. The Rayleigh waves and the fundamental and first overtone of atmospheric acoustic waves trapped in the low-sound-velocity channels have approximately the same horizontal wavelength and frequency at periods of 230 and 270 s, respectively, i.e., the atmosphere and the solid earth satisfy the condition for acoustic resonant oscillations. The standing atmospheric long-wavelength acoustic waves set off by the eruption selectively excited seismic spheroidal modes near the resonant period through acoustic resonant coupling and resulted in harmonic Rayleigh waves. In contrast, gravity waves and Lamb waves (atmospheric boundary waves) do not couple to the ground efficiently and are not easily observed as ground disturbance on seismograms during volcanic eruptions.

Item Type:Article
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Kanamori, Hiroo0000-0001-8219-9428
Additional Information:© 2010 American Geophysical Union. Received 1 June 2010; revised 23 September 2010; accepted 5 October 2010; published 21 December 2010. We would like to thank many people who helped us clarify the normal mode formulations from the basic physical first principles. D. Anderson, F. Gilbert, R. Hide, A. Ingersoll, G. Masters, J. Woodhouse, and all the participants of the seismolab coffee breaks convinced us that all the normal mode formalism for the Earth, the Sun, stars, tsunami, and the atmosphere can be derived indeed from a common set of first principles and are consistent with each other.
Subject Keywords:Rayleigh waves; Mt. Pinatubo eruption; resonance between the atmosphere and solid Earth; harmonic ground motion; air-ground coupling; anomalous excitation of spheroidal mode
Classification Code:7255 Seismology: Surface waves and free oscillations; 7280 Seismology: Volcano seismology (8419); 8409 Volcanology: Atmospheric effects (0370); 8428 Volcanology: Explosive volcanism; 3384 Atmospheric Processes: Acoustic-gravity waves.
Record Number:CaltechAUTHORS:20110201-152756860
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Official Citation:Watada, S., and H. Kanamori (2010), Acoustic resonant oscillations between the atmosphere and the solid earth during the 1991 Mt. Pinatubo eruption, J. Geophys. Res., 115, B12319, doi:10.1029/2010JB007747
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:21957
Deposited By: Tony Diaz
Deposited On:14 Feb 2011 18:34
Last Modified:09 Mar 2020 13:18

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