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Ambient resonance of Mesa Arch, Canyonlands National Park, Utah
Author(s) -
Starr Alison M.,
Moore Jeffrey R.,
Thorne Michael S.
Publication year - 2015
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2015gl064917
Subject(s) - arch , national park , materials science , resonance (particle physics) , geology , atmospheric sciences , environmental science , physics , structural engineering , atomic physics , ecology , engineering , biology
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 3‐D 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 thermoelastic stresses and deformation of the arch. We observed no permanent resonant frequency shifts related to irreversible damage of Mesa Arch during our study period.