On the Dynamic Response of Unstable Rock Slopes: Characterization, monitoring, and modeling based on ambient vibration data
Reliable mapping, characterization and monitoring of unstable rock slopes is a prerequisite for mitigation of risks associated with landslides to protect lives, settlements, and infrastructure. Most state-of-the art surveying techniques rely on sensing the Earth’s surface only, as drillings are expe...
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Format: | Doctoral or Postdoctoral Thesis |
Language: | English |
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ETH Zurich
2021
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Online Access: | https://hdl.handle.net/20.500.11850/519400 https://doi.org/10.3929/ethz-b-000519400 |
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Open Polar |
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ETH Zürich Research Collection |
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ftethz |
language |
English |
topic |
Ambient vibration Landslide early warning Unstable rock slope Applied geophysics Landslide characterization Environmental seismology info:eu-repo/classification/ddc/550 info:eu-repo/classification/ddc/530 Earth sciences Physics |
spellingShingle |
Ambient vibration Landslide early warning Unstable rock slope Applied geophysics Landslide characterization Environmental seismology info:eu-repo/classification/ddc/550 info:eu-repo/classification/ddc/530 Earth sciences Physics Häusler, Mauro On the Dynamic Response of Unstable Rock Slopes: Characterization, monitoring, and modeling based on ambient vibration data |
topic_facet |
Ambient vibration Landslide early warning Unstable rock slope Applied geophysics Landslide characterization Environmental seismology info:eu-repo/classification/ddc/550 info:eu-repo/classification/ddc/530 Earth sciences Physics |
description |
Reliable mapping, characterization and monitoring of unstable rock slopes is a prerequisite for mitigation of risks associated with landslides to protect lives, settlements, and infrastructure. Most state-of-the art surveying techniques rely on sensing the Earth’s surface only, as drillings are expensive and spatially sparse measurements. Non-invasive geophysical techniques offer a wide range of possibilities to retrieve geological information at depth. In addition, they provide means to assess the hazard of coseismic slope failure, which is the most devastating secondary seismic hazard after tsunamis. In this thesis, I focus on recordings of ambient vibrations, which arise from distributed natural and artificial sources of vibration. The resulting continuous seismic signal can be measured at any time and location by seismometers. Measuring ambient vibration data allows for analyzing structural dynamic parameters of the unstable rock slope. These include the resonant frequency, polarization of vibration, energy dissipation (damping), seismic amplification, and seismic shear wave velocity. These parameters are proxies for properties of the slope instability and can be used to characterize and monitor a potential landslide. Rock stiffness and fracture properties govern the resonant frequency, while the orientation of fractures determines the polarization direction of the seismic wavefield. The amplification of seismic waves can reach factors exceeding ten within unstable slopes and strongly depends on the local fracture network. Therefore, amplification can be used to map the extent of the instability and simultaneously provide basic input parameters to model earthquake-induced slope failure. To confirm and analyze the normal mode behavior previously proposed for rock slope instabilities with deep compliant fractures, I apply different normal mode techniques to a set of unstable rock slopes by using field recordings and synthetic data. A key method is the Enhanced Frequency Domain Decomposition (EFDD) technique, which found broad application in civil engineering in the past decades. Besides the resonant frequencies and mode shapes, the technique also offers the possibility to retrieve the modal damping ratio, which is a measure for energy dissipation within and out of the system. In this work, I give first estimates of modal damping ratios in unstable rock slopes and provide potential explanations for the mechanisms driving this parameter. EFDD also enables the detection of close and higher order modes and can be applied as an efficient tool to map and structurally subdivide rock slopes instabilities. I implement the EFDD and other processing techniques for continuous real-time monitoring of unstable rock slopes to track the resonant properties and demonstrate how the seismic response of unstable slopes varies with changing environmental conditions and landslide kinematics. I monitor the dynamic response of three unstable rock slopes in Switzerland: the \textit{Frana del Valegion} instability near Preonzo, the Gemsstock northeast ridge in permafrost regime and the large and highly active Brienz/Brinzauls landslide. At the Brienz/Brinzauls landslide, the seismic amplification was observed to be elevated after periods of strong precipitation. This has direct implication for hazard assessment of coseismic slope failure, as the slope is more likely to be triggered by an earthquake during periods of increased amplification. The techniques and methodological approaches presented in this thesis have the potential for an efficient toolkit to characterize and monitor unstable slopes independent of surface displacement measurements. Therefore, they provide complementary techniques to conventional displacement measurements for landslide hazard assessment. The rapid and cost-effective mapping and subdivision of unstable rock masses could be especially beneficial in the early state of investigation to optimize subsequent monitoring systems and to plan more expensive in situ investigations. |
author2 |
Fäh, Donat Fichtner, Andreas Krautblatter, Michael Burjánek, Jan |
format |
Doctoral or Postdoctoral Thesis |
author |
Häusler, Mauro |
author_facet |
Häusler, Mauro |
author_sort |
Häusler, Mauro |
title |
On the Dynamic Response of Unstable Rock Slopes: Characterization, monitoring, and modeling based on ambient vibration data |
title_short |
On the Dynamic Response of Unstable Rock Slopes: Characterization, monitoring, and modeling based on ambient vibration data |
title_full |
On the Dynamic Response of Unstable Rock Slopes: Characterization, monitoring, and modeling based on ambient vibration data |
title_fullStr |
On the Dynamic Response of Unstable Rock Slopes: Characterization, monitoring, and modeling based on ambient vibration data |
title_full_unstemmed |
On the Dynamic Response of Unstable Rock Slopes: Characterization, monitoring, and modeling based on ambient vibration data |
title_sort |
on the dynamic response of unstable rock slopes: characterization, monitoring, and modeling based on ambient vibration data |
publisher |
ETH Zurich |
publishDate |
2021 |
url |
https://hdl.handle.net/20.500.11850/519400 https://doi.org/10.3929/ethz-b-000519400 |
genre |
permafrost |
genre_facet |
permafrost |
op_relation |
http://hdl.handle.net/20.500.11850/519400 doi:10.3929/ethz-b-000519400 |
op_rights |
info:eu-repo/semantics/openAccess http://rightsstatements.org/page/InC-NC/1.0/ In Copyright - Non-Commercial Use Permitted |
op_doi |
https://doi.org/20.500.11850/519400 https://doi.org/10.3929/ethz-b-000519400 |
_version_ |
1766167046292242432 |
spelling |
ftethz:oai:www.research-collection.ethz.ch:20.500.11850/519400 2023-05-15T17:58:26+02:00 On the Dynamic Response of Unstable Rock Slopes: Characterization, monitoring, and modeling based on ambient vibration data Häusler, Mauro Fäh, Donat Fichtner, Andreas Krautblatter, Michael Burjánek, Jan 2021 application/application/pdf https://hdl.handle.net/20.500.11850/519400 https://doi.org/10.3929/ethz-b-000519400 en eng ETH Zurich http://hdl.handle.net/20.500.11850/519400 doi:10.3929/ethz-b-000519400 info:eu-repo/semantics/openAccess http://rightsstatements.org/page/InC-NC/1.0/ In Copyright - Non-Commercial Use Permitted Ambient vibration Landslide early warning Unstable rock slope Applied geophysics Landslide characterization Environmental seismology info:eu-repo/classification/ddc/550 info:eu-repo/classification/ddc/530 Earth sciences Physics info:eu-repo/semantics/doctoralThesis 2021 ftethz https://doi.org/20.500.11850/519400 https://doi.org/10.3929/ethz-b-000519400 2022-04-25T14:37:53Z Reliable mapping, characterization and monitoring of unstable rock slopes is a prerequisite for mitigation of risks associated with landslides to protect lives, settlements, and infrastructure. Most state-of-the art surveying techniques rely on sensing the Earth’s surface only, as drillings are expensive and spatially sparse measurements. Non-invasive geophysical techniques offer a wide range of possibilities to retrieve geological information at depth. In addition, they provide means to assess the hazard of coseismic slope failure, which is the most devastating secondary seismic hazard after tsunamis. In this thesis, I focus on recordings of ambient vibrations, which arise from distributed natural and artificial sources of vibration. The resulting continuous seismic signal can be measured at any time and location by seismometers. Measuring ambient vibration data allows for analyzing structural dynamic parameters of the unstable rock slope. These include the resonant frequency, polarization of vibration, energy dissipation (damping), seismic amplification, and seismic shear wave velocity. These parameters are proxies for properties of the slope instability and can be used to characterize and monitor a potential landslide. Rock stiffness and fracture properties govern the resonant frequency, while the orientation of fractures determines the polarization direction of the seismic wavefield. The amplification of seismic waves can reach factors exceeding ten within unstable slopes and strongly depends on the local fracture network. Therefore, amplification can be used to map the extent of the instability and simultaneously provide basic input parameters to model earthquake-induced slope failure. To confirm and analyze the normal mode behavior previously proposed for rock slope instabilities with deep compliant fractures, I apply different normal mode techniques to a set of unstable rock slopes by using field recordings and synthetic data. A key method is the Enhanced Frequency Domain Decomposition (EFDD) technique, which found broad application in civil engineering in the past decades. Besides the resonant frequencies and mode shapes, the technique also offers the possibility to retrieve the modal damping ratio, which is a measure for energy dissipation within and out of the system. In this work, I give first estimates of modal damping ratios in unstable rock slopes and provide potential explanations for the mechanisms driving this parameter. EFDD also enables the detection of close and higher order modes and can be applied as an efficient tool to map and structurally subdivide rock slopes instabilities. I implement the EFDD and other processing techniques for continuous real-time monitoring of unstable rock slopes to track the resonant properties and demonstrate how the seismic response of unstable slopes varies with changing environmental conditions and landslide kinematics. I monitor the dynamic response of three unstable rock slopes in Switzerland: the \textit{Frana del Valegion} instability near Preonzo, the Gemsstock northeast ridge in permafrost regime and the large and highly active Brienz/Brinzauls landslide. At the Brienz/Brinzauls landslide, the seismic amplification was observed to be elevated after periods of strong precipitation. This has direct implication for hazard assessment of coseismic slope failure, as the slope is more likely to be triggered by an earthquake during periods of increased amplification. The techniques and methodological approaches presented in this thesis have the potential for an efficient toolkit to characterize and monitor unstable slopes independent of surface displacement measurements. Therefore, they provide complementary techniques to conventional displacement measurements for landslide hazard assessment. The rapid and cost-effective mapping and subdivision of unstable rock masses could be especially beneficial in the early state of investigation to optimize subsequent monitoring systems and to plan more expensive in situ investigations. Doctoral or Postdoctoral Thesis permafrost ETH Zürich Research Collection |