Vibration of natural rock arches and towers excited by helicopter-sourced infrasound

<p>Helicopters emit high-power infrasound in a frequency range that can coincide with the natural frequencies of rock landforms. While a single previous study demonstrated that close-proximity helicopter flight was able to excite potentially damaging vibration of rock pinnacles, the effects on...

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Autores principales:	R. Finnegan, J. R. Moore, P. R. Geimer
Formato:	article
Lenguaje:	EN
Publicado:	Copernicus Publications 2021
Materias:	Dynamic and structural geology QE500-639.5
Acceso en línea:	https://doaj.org/article/c22e1ac3a95a4d60b3666eb5bdb31344
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spelling	oai:doaj.org-article:c22e1ac3a95a4d60b3666eb5bdb313442021-11-19T11:16:15ZVibration of natural rock arches and towers excited by helicopter-sourced infrasound10.5194/esurf-9-1459-20212196-63112196-632Xhttps://doaj.org/article/c22e1ac3a95a4d60b3666eb5bdb313442021-11-01T00:00:00Zhttps://esurf.copernicus.org/articles/9/1459/2021/esurf-9-1459-2021.pdfhttps://doaj.org/toc/2196-6311https://doaj.org/toc/2196-632X<p>Helicopters emit high-power infrasound in a frequency range that can coincide with the natural frequencies of rock landforms. While a single previous study demonstrated that close-proximity helicopter flight was able to excite potentially damaging vibration of rock pinnacles, the effects on a broader range of landforms remain unknown. We performed a series of controlled flights at seven sandstone arches and towers in Utah, USA, recording their vibration response to helicopter-sourced infrasound. We found that landform vibration velocities increased by a factor of up to 1000 during close-proximity helicopter flight as compared to ambient conditions immediately prior and that precise spectral alignment between infrasound and landform natural frequencies is required to excite resonance. We define admittance as the ratio of vibration velocity to infrasound pressure and recorded values of up to 0.11 mm s<span class="inline-formula"><sup>−1</sup></span> Pa<span class="inline-formula"><sup>−1</sup></span>. While our results demonstrate a strong vibration response, the measured velocities are lower than likely instantaneously damaging values. Our results serve as a basis for predicting unfavorable degradation of culturally significant rock landforms due to regular helicopter overflights.</p>R. FinneganJ. R. MooreP. R. GeimerCopernicus PublicationsarticleDynamic and structural geologyQE500-639.5ENEarth Surface Dynamics, Vol 9, Pp 1459-1479 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Dynamic and structural geology QE500-639.5
spellingShingle	Dynamic and structural geology QE500-639.5 R. Finnegan J. R. Moore P. R. Geimer Vibration of natural rock arches and towers excited by helicopter-sourced infrasound
description	<p>Helicopters emit high-power infrasound in a frequency range that can coincide with the natural frequencies of rock landforms. While a single previous study demonstrated that close-proximity helicopter flight was able to excite potentially damaging vibration of rock pinnacles, the effects on a broader range of landforms remain unknown. We performed a series of controlled flights at seven sandstone arches and towers in Utah, USA, recording their vibration response to helicopter-sourced infrasound. We found that landform vibration velocities increased by a factor of up to 1000 during close-proximity helicopter flight as compared to ambient conditions immediately prior and that precise spectral alignment between infrasound and landform natural frequencies is required to excite resonance. We define admittance as the ratio of vibration velocity to infrasound pressure and recorded values of up to 0.11 mm s<span class="inline-formula"><sup>−1</sup></span> Pa<span class="inline-formula"><sup>−1</sup></span>. While our results demonstrate a strong vibration response, the measured velocities are lower than likely instantaneously damaging values. Our results serve as a basis for predicting unfavorable degradation of culturally significant rock landforms due to regular helicopter overflights.</p>
format	article
author	R. Finnegan J. R. Moore P. R. Geimer
author_facet	R. Finnegan J. R. Moore P. R. Geimer
author_sort	R. Finnegan
title	Vibration of natural rock arches and towers excited by helicopter-sourced infrasound
title_short	Vibration of natural rock arches and towers excited by helicopter-sourced infrasound
title_full	Vibration of natural rock arches and towers excited by helicopter-sourced infrasound
title_fullStr	Vibration of natural rock arches and towers excited by helicopter-sourced infrasound
title_full_unstemmed	Vibration of natural rock arches and towers excited by helicopter-sourced infrasound
title_sort	vibration of natural rock arches and towers excited by helicopter-sourced infrasound
publisher	Copernicus Publications
publishDate	2021
url	https://doaj.org/article/c22e1ac3a95a4d60b3666eb5bdb31344
work_keys_str_mv	AT rfinnegan vibrationofnaturalrockarchesandtowersexcitedbyhelicoptersourcedinfrasound AT jrmoore vibrationofnaturalrockarchesandtowersexcitedbyhelicoptersourcedinfrasound AT prgeimer vibrationofnaturalrockarchesandtowersexcitedbyhelicoptersourcedinfrasound
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Vibration of natural rock arches and towers excited by helicopter-sourced infrasound

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