Preprints
https://doi.org/10.5194/esurf-2021-43
https://doi.org/10.5194/esurf-2021-43

  26 May 2021

26 May 2021

Review status: this preprint is currently under review for the journal ESurf.

Vibration of Natural Rock Arches and Towers Excited by Helicopter-Sourced Infrasound

Riley Finnegan, Jeffrey R. Moore, and Paul R. Geimer Riley Finnegan et al.
  • Department of Geology and Geophysics, University of Utah, Salt Lake City, 84112, USA

Abstract. 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 up to 0.11 mm s−1 Pa−1. 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.

Riley Finnegan et al.

Status: open (until 07 Jul 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on esurf-2021-43', Michael Tsesarsky, 07 Jun 2021 reply

Riley Finnegan et al.

Data sets

Data for: Vibration of Natural Rock Arches and Towers Excited by Helicopter-Sourced Infrasound Riley Finnegan, Jeffrey R. Moore, and Paul R. Geimer https://doi.org/10.7278/S50D-41SW-THMA

Riley Finnegan et al.

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Short summary
We performed controlled helicopter flights near seven rock arches and towers in Utah, USA and recorded how their natural vibrations changed as the helicopter performed different maneuvers. We found arches and towers vibrate up to 1000 X stronger during these flights compared to time periods just before the helicopter’s approach. Our study provides data that can be used to predict long-term damage to culturally significant rock features from sustained helicopter flights over time.