Infrasound Tornillos Produced by Volcán Cotopaxi's Deep Crater

J. B. Johnson; M. C. Ruiz; H. D. Ortiz; L. M. Watson; G. Viracucha; P. Ramon; M. Almeida

doi:10.1029/2018GL077766

Infrasound Tornillos Produced by Volcán Cotopaxi's Deep Crater

J. B. Johnson^*, M. C. Ruiz, H. D. Ortiz, L. M. Watson, G. Viracucha, P. Ramon, M. Almeida

^*Corresponding author for this work

Faculty of Exact and Natural Sciences

Research output: Contribution to journal › Article › peer-review

27 Scopus citations

Abstract

We characterize and interpret a new type of infrasound signal originating from the summit of Volcán Cotopaxi (Ecuador) that was primarily observed between September 2015 and March 2016, following the 2015 eruptive period. This infrasound waveform is a slowly decaying sinusoid with exceptional low-frequency (f_p = 0.2 Hz) and high quality factor (Q = ~10) and resembles the shape of tornillo seismic waveforms. The repeating events, occurring about once per day in early 2016, are stable in frequency content, and we attribute them to excitation of a vertical-walled crater, with radius of about 125 m and length of 300 m. Spectral properties of the tornillo permit constraints on crater sound speed (335 m/s ± 6%) and temperature (4–32°C). The initial polarity of the tornillos is predominantly a rarefaction and could reflect repeating crater bottom collapse events (implosions) or explosion sources whose infrasound is heavily modulated by the crater's pipe-like geometry.

Original language	English
Pages (from-to)	5436-5444
Number of pages	9
Journal	Geophysical Research Letters
Volume	45
Issue number	11
DOIs	https://doi.org/10.1029/2018GL077766
State	Published - 16 Jun 2018

Bibliographical note

Publisher Copyright:
©2018. American Geophysical Union. All Rights Reserved.

Funding

This work was funded in part by National Science Foundation grant EAR- 0838562 and by the Geological Sciences Martin Fund at the University of North Carolina, Chapel Hill. The Instituto Geográfico Militar (IGM) from Ecuador provided the orthophoto from 28 January 2016. Japan International Cooperation Agency (JICA) network infrasound data were used in part of this study. The infrasound signals from CIS analyzed in this study are available as a permanent DOI archive at https://scho-larworks.boisestate.edu/infrasound_ data/2/ and are openly shared via ScholarWorks, Boise State’s institutional research repository managed by Albertsons Library and released under a creative commons license. This work was funded in part by National Science Foundation grant EAR-0838562 and by the Geological Sciences Martin Fund at the University of North Carolina, Chapel Hill. The Instituto Geográfico Militar (IGM) from Ecuador provided the orthophoto from 28 January 2016. Japan International Cooperation Agency (JICA) network infrasound data were used in part of this study. The infrasound signals from CIS analyzed in this study are available as a permanent DOI archive at https://scholarworks.boisestate.edu/infrasound_data/2/ and are openly shared via ScholarWorks, Boise State's institutional research repository managed by Albertsons Library and released under a creative commons license.

Funders	Funder number
National Science Foundation	EAR- 0838562
University of North Carolina at Chapel Hill
University of North Carolina at Chapel Hill

Keywords

Cotopaxi Volcano
infrasound
tornillo
volcano monitoring

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title = "Infrasound Tornillos Produced by Volc{\'a}n Cotopaxi's Deep Crater",

abstract = "We characterize and interpret a new type of infrasound signal originating from the summit of Volc{\'a}n Cotopaxi (Ecuador) that was primarily observed between September 2015 and March 2016, following the 2015 eruptive period. This infrasound waveform is a slowly decaying sinusoid with exceptional low-frequency (fp = 0.2 Hz) and high quality factor (Q = ~10) and resembles the shape of tornillo seismic waveforms. The repeating events, occurring about once per day in early 2016, are stable in frequency content, and we attribute them to excitation of a vertical-walled crater, with radius of about 125 m and length of 300 m. Spectral properties of the tornillo permit constraints on crater sound speed (335 m/s ± 6%) and temperature (4–32°C). The initial polarity of the tornillos is predominantly a rarefaction and could reflect repeating crater bottom collapse events (implosions) or explosion sources whose infrasound is heavily modulated by the crater's pipe-like geometry.",

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AU - Ortiz, H. D.

AU - Watson, L. M.

AU - Viracucha, G.

AU - Ramon, P.

AU - Almeida, M.

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N2 - We characterize and interpret a new type of infrasound signal originating from the summit of Volcán Cotopaxi (Ecuador) that was primarily observed between September 2015 and March 2016, following the 2015 eruptive period. This infrasound waveform is a slowly decaying sinusoid with exceptional low-frequency (fp = 0.2 Hz) and high quality factor (Q = ~10) and resembles the shape of tornillo seismic waveforms. The repeating events, occurring about once per day in early 2016, are stable in frequency content, and we attribute them to excitation of a vertical-walled crater, with radius of about 125 m and length of 300 m. Spectral properties of the tornillo permit constraints on crater sound speed (335 m/s ± 6%) and temperature (4–32°C). The initial polarity of the tornillos is predominantly a rarefaction and could reflect repeating crater bottom collapse events (implosions) or explosion sources whose infrasound is heavily modulated by the crater's pipe-like geometry.

AB - We characterize and interpret a new type of infrasound signal originating from the summit of Volcán Cotopaxi (Ecuador) that was primarily observed between September 2015 and March 2016, following the 2015 eruptive period. This infrasound waveform is a slowly decaying sinusoid with exceptional low-frequency (fp = 0.2 Hz) and high quality factor (Q = ~10) and resembles the shape of tornillo seismic waveforms. The repeating events, occurring about once per day in early 2016, are stable in frequency content, and we attribute them to excitation of a vertical-walled crater, with radius of about 125 m and length of 300 m. Spectral properties of the tornillo permit constraints on crater sound speed (335 m/s ± 6%) and temperature (4–32°C). The initial polarity of the tornillos is predominantly a rarefaction and could reflect repeating crater bottom collapse events (implosions) or explosion sources whose infrasound is heavily modulated by the crater's pipe-like geometry.

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Infrasound Tornillos Produced by Volcán Cotopaxi's Deep Crater

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Keywords

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