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Article

Characterizing Stalagmites’ Eigenfrequencies by Combining In Situ Vibration Measurements and Finite Element Modeling Based on 3D Scans

1
Seismology-Gravimetry, Royal Observatory of Belgium, 1180 Brussels, Belgium
2
AGEs, Department of Geology, University of Liège, 4000 Liège, Belgium
3
Institute of Geology and Mineralogy, University of Cologne, 50674 Köln, Germany
4
Geology and Applied Geology, Faculty of Engineering, University of Mons,7000 Mons, Belgium
*
Author to whom correspondence should be addressed.
Geosciences 2020, 10(10), 418; https://doi.org/10.3390/geosciences10100418
Received: 14 September 2020 / Revised: 13 October 2020 / Accepted: 17 October 2020 / Published: 20 October 2020
Broken or deformed speleothems have been used as indicators of paleo-earthquakes since the 1990s; however, a causal link is difficult to prove except for some thin speleothems. In contrast, the presence of intact speleothems permits estimating an upper limit of the level of horizontal ground motions of past seismicity in the area. The natural frequencies of speleothems are fundamental parameters for their response to earthquakes. This study proposes a new method of in situ characterization of these natural frequencies. Tested in the Han-sur-Lesse cave (Belgian Ardennes), the method is based on recording the ambient seismic noise using three-component sensors on a stalagmite and a 3D laser scan of its shape. The ambient seismic noise records allow a precise determination of the eigenfrequencies of the stalagmite. In addition, numerical models based on the 3D scan show good consistency between measured and modeled data. The joint analysis of these two techniques concludes that the shape of the stalagmite (elliptical cross-section and shape irregularities) influence the eigenfrequencies and polarization of the modes while also causing a near-orthogonal split of natural frequencies. The motions recorded on the stalagmite show significant amplification compared to those recorded at the free surface outside the cave, which has a strong impact on seismic hazard assessment based on speleothems. View Full-Text
Keywords: cave; stalagmite; natural frequency; 3D scan; numerical modeling; ambient seismic noise cave; stalagmite; natural frequency; 3D scan; numerical modeling; ambient seismic noise
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MDPI and ACS Style

Martin, A.; Lecocq, T.; Hinzen, K.-G.; Camelbeeck, T.; Quinif, Y.; Fagel, N. Characterizing Stalagmites’ Eigenfrequencies by Combining In Situ Vibration Measurements and Finite Element Modeling Based on 3D Scans. Geosciences 2020, 10, 418. https://doi.org/10.3390/geosciences10100418

AMA Style

Martin A, Lecocq T, Hinzen K-G, Camelbeeck T, Quinif Y, Fagel N. Characterizing Stalagmites’ Eigenfrequencies by Combining In Situ Vibration Measurements and Finite Element Modeling Based on 3D Scans. Geosciences. 2020; 10(10):418. https://doi.org/10.3390/geosciences10100418

Chicago/Turabian Style

Martin, Aurélie, Thomas Lecocq, Klaus-G. Hinzen, Thierry Camelbeeck, Yves Quinif, and Nathalie Fagel. 2020. "Characterizing Stalagmites’ Eigenfrequencies by Combining In Situ Vibration Measurements and Finite Element Modeling Based on 3D Scans" Geosciences 10, no. 10: 418. https://doi.org/10.3390/geosciences10100418

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