Research

How is the structural health of rock arches and towers affected by anthropogenic sources of energy?

Rock arches and towers are dynamic natural features that bend, sag, sway and shake in response to a variety of environmental forcings. My goal is to understand how arches respond to man-made energy sources, like helicopters, trains, highway noise, and even some earthquakes. We use seismometers to measure the resonant frequencies of rock arches and towers, and record their vibration response under exposure to controlled and uncontrolled anthropogenic energy sources. We compare the resulting vibrations to what the landform experiences naturally. The vibration velocity of the geologic landform can increase from 10–1000 times its normal level, so we are trying to learn what that means for the landform's health. If the arch or tower doesn't experience instantaneous damage, what is the result of the landform experiencing higher vibrations over time?

We combine numerical modeling methods with laboratory and field methods to approach these questions, which means we get to work in a number of beautiful places around Utah. We are funded by the National Science Foundation and by the University of Utah.

Helicopter Infrasound

Why do certain arches and towers shake faster than usual when they are exposed to this high-power, low-frequency sound energy? What does this mean for their long-term stability?

Field Methods

We use broadband seismometers and nodal geophones to measure the vibrations of arches and towers, and infrasound microphones to measure the incoming sound energy.

Modal Analysis

We use 3D models to perform modal analysis on and determine material properties of these landforms.

Other Energy Sources

How do ground vibrations from trains and highway noise affect natural arches and towers?

Conservation

Arches and towers have finite lifespans. How are humans changing that length of time?

Spectral Amplification

Can we use spectral amplification ratios created from ambient conditions to predict landform response during excitation from earthquakes?

Publications

Finnegan, R., J.R. Moore, P.R. Geimer, E.K. Bessette-Kirton, and A. Dzubay (2022). Ground Motion Amplification at Natural Rock Arches in the Colorado Plateau, The Seismic Record, 2(3), 156–166. doi.org/10.1785/0320220017

Finnegan, R., J.R. Moore, P.R. Geimer, A. Dzubay, E.K. Bessette-Kirton, J. Bodtker, and K. Vollinger (2022). Ambient vibration modal analysis of natural rock towers and fins, Seismological Research Letters, 93(3), 1777–1786. doi.org/10.1785/0220210325

Finnegan, R., J.R. Moore, and P.R. Geimer (2021). Vibration of Natural Rock Arches and Towers Excited by Helicopter-Sourced Infrasound, Earth Surface Dynamics, 9, 1459–1479. doi.org/10.5194/esurf-9-1459-2021

Häusler, M., P.R. Geimer, R. Finnegan, D. Fäh., and J.R. Moore (2021). An update on techniques to assess normal-mode behavior of rock arches by ambient vibrations, Earth Surface Dynamics, 9, 1441–1457. doi.org/10.5194/esurf-9-1441-2021

Moore, J.R., P.R. Geimer, R. Finnegan, and J. Bodtker (2020). Between a Beam and Catenary: Influence of Geometry on Gravitational Stresses and Stability of Natural Rock Arches, Geomorphology, 364. doi.org/10.1016/j.geomorph.2020.107244

Geimer, P.R., R. Finnegan, and J.R. Moore (2020). Sparse Ambient Resonance Measurements Reveal Dynamic Properties of Freestanding Rock Arches, Geophysical Research Letters, 47, e2020GL087239. doi.org/10.1029/2020GL087239

Moore, J.R., P.R. Geimer, R. Finnegan, and C. Michel (2019). Dynamic analysis of a large freestanding rock tower (Castleton Tower, Utah, USA), Bulletin of the Seismological Society of America, 109(5), 2125–2131. doi.org/10.1785/0120190118

Moore, J.R., P.R. Geimer, R. Finnegan, and M.S. Thorne (2018) Use of Seismic Resonance Measurements to Determine the Elastic Modulus of Freestanding Rock Masses, Rock Mechanics and Rock Engineering, 51(12), 3937–3944. doi.org/10.1007/s00603-018-1554-6

Presentations

Finnegan, R., J.R. Moore, P.R. Geimer, A. Dzubay, E.K. Bessette-Kirton, Häusler, M., and J. Bodtker (2021). Modal Analysis of Freestanding Rock Towers in Utah, USA. Abstract 819605, presented at American Geophysical Union Fall Meeting, Dec 13–17.

Bessette-Kirton, E.K., J.R. Moore, P.R. Geimer, and R. Finnegan (2021). Anomaly Detection in Ambient Vibration Monitoring Data from a Toppling Rock Slab Instability, Utah, USA. Abstract 823860, presented at American Geophysical Union Fall Meeting, Dec 13–17.

Finnegan, R., J.R. Moore, and P.R. Geimer (2020). Spectral Amplification and Seismic Response of Rock Arches. Abstract 684939, presented at: American Geophysical Union Fall Meeting, Dec 1–17.

Moore, J.R., R. Finnegan, and P.R. Geimer (2020). Gravitational Stresses in Natural Rock Arches: Implications for Subcritical Crack Growth. Presented at: American Geophysical Union Fall Meeting, Dec 1–17.

Geimer, P.R., J.R. Moore, and R. Finnegan (2020). Thermomechanical Response of Freestanding Geologic Structures to Environmental Stressors: Sensitivity Characterization Using Resonant Mode Monitoring. Presented at: American Geophysical Union Fall Meeting, Dec 1–17.

Bessette-Kirton, E., J.R. Moore, Geimer, P.R., and R. Finnegan (2020). Characterization of a Toppling Rock Slab Instability with Ambient Vibration Array Measurements. Presented at: American Geophysical Union Fall Meeting, Dec 1–17.

Finnegan, R., J.R. Moore, and P.R. Geimer (2019). Vibration response of rock arches and towers to helicopter-sourced infrasound. Abstract 506450, presented at: American Geophysical Union Fall Meeting, San Francisco, CA, Dec 9–13.

Moore, J.R., P.R. Geimer, R. Finnegan, and C. Michel (2019). Modal Analysis of a Freestanding Sandstone Monolith (Castleton Tower, Utah). Abstract 505782, presented at: American Geophysical Union Fall Meeting, San Francisco, CA, Dec 9–13.

Geimer, P.R., J.R. Moore, and R. Finnegan (2019). In-Situ Nonlinear Elastic Response of Sandstone Landforms Under Dynamic Loading. Abstract 507404, presented at: American Geophysical Union Fall Meeting, San Francisco, CA, Dec 9–13.

Finnegan, R. (2018). Helicopter-induced resonance of Two Bridges, Bryce Canyon National Park. Poster presented at: Global Change and Sustainability Center Symposium, Salt Lake City, UT, Feb 15.