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Dynamic analysis of a large freestanding rock tower (Castleton Tower, Utah)

Jeffrey R. Moore, Paul R. Geimer, Riley Finnegan and Clotaire Michel
Dynamic analysis of a large freestanding rock tower (Castleton Tower, Utah)
Bulletin of the Seismological Society of America (August 2019) 109 (5): 2125-2131

Abstract

We acquired a unique ambient vibration dataset from Castleton Tower, a 120 m high bedrock monolith located near Moab, Utah, to resolve dynamic and material properties of the landform. We identified the first two resonant modes at 0.8 and 1.0 Hz, which consist of mutually perpendicular, linearly polarized horizontal ground motion at the top of the tower. Damping ratios for these modes were low at approximately 1%. We successfully reproduced field data in 3D numerical eigenfrequency simulation implementing a Young's modulus of 7 GPa, a value approximately 30% lower than measured on core samples. Our analysis confirms that modal deformation at the first resonant frequencies closely resembles that of a cantilever beam. The outcome is that with basic estimates of geometry and material properties, the resonant frequencies of other freestanding rock monoliths can be estimated a priori. Such estimates are crucial to evaluate the response of rock towers to external vibration inputs.


ISSN: 0037-1106
EISSN: 1943-3573
Coden: BSSAAP
Serial Title: Bulletin of the Seismological Society of America
Serial Volume: 109
Serial Issue: 5
Title: Dynamic analysis of a large freestanding rock tower (Castleton Tower, Utah)
Affiliation: University of Utah, Department of Geology and Geophysics, Salt Lake City, UT, United States
Pages: 2125-2131
Published: 20190827
Text Language: English
Publisher: Seismological Society of America, Berkeley, CA, United States
References: 30
Accession Number: 2019-081250
Categories: Seismology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sketch map
N38°30'00" - N39°31'00", W110°13'00" - W109°02'60"
Secondary Affiliation: Swiss Seismological Service, CHE, Switzerland
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Abstract, Copyright, Seismological Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201943
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