Publication Date:
2015-08-06
Description:
We analyzed the resonance characteristics of a prominent natural arch in Canyonlands National Park, Mesa Arch, as measured from ambient seismic data. Evaluating spectral and polarization attributes, we distinguished the first four resonant frequencies of the arch: 2.9, 6.0, 6.9, and 8.5 Hz, as well as basic properties of the associated mode shapes. We then affirmed experimental data using 3D numerical modal analysis, providing estimates of material properties and clarifying vibrational mode shapes. Monitoring resonant frequencies over time, we searched for shifts associated with changing environmental conditions and long-term progressive damage. We measured ~3% direct daily variation in resonant frequency associated with changing rock temperature, thermal stress and stiffening of the rock matrix. Independent tilt data showed similar diurnal cycles associated with thermo-elastic stresses and deformation of the arch. We observed no permanent resonant frequency shifts related to irreversible damage of Mesa arch during our study period.
Print ISSN:
0094-8276
Electronic ISSN:
1944-8007
Topics:
Geosciences
,
Physics
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