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Acoustic and microseismic characterization in steep bedrock permafrost on Matterhorn (CH)


Weber, Samuel; Faillettaz, Jérome; Meyer, Matthias; Beutel, Jan; Vieli, Andreas (2018). Acoustic and microseismic characterization in steep bedrock permafrost on Matterhorn (CH). Journal of Geophysical Research: Earth Surface, 123(6):1363-1385.

Abstract

Understanding of processes and factors influencing slope stability is essential for assessingthe stability of potentially hazardous slopes. Passive monitoring of acoustic emissions and microseismologyprovides subsurface information on fracturing (timing and identification of the mechanism) and thereforecomplement surface displacement data. This study investigates for the first time acoustic and microseismicsignals generated in steep, frac tured bedrock permafrost, covering the broad frequency range of 1 − 105Hz.The analysis of artificial forcing experiments using a rebound hammer in a controlled setting led to twomajor findings: First, statistically insignificant cross correlation between signals indicates that waveformschange strongly with propagation distance. Second, a signficant amplification is found in the frequencyband 33–67 Hz. This finding is strongly supported by evidence from artificial rockfall events and moreimportantly by naturally occurring fracture events identified in fracture displacement data. Thus, filteringthis frequency band enables enhanced detection of microseismic events relevant for slope stabilityassessment. The analysis of 2-year time series in this frequency band further suggests that the detectedenergy rate baseline of all automatically triggered events using the STA/LTA algorithm is not sensitive totemperature forcing, an observation of primary importance for long-term data collection, analysis, andinterpretation. The event detection in the established frequency band is not only improved but also notaffected by the short- and long-term temperature changes in such a rapidly changing environment.

Abstract

Understanding of processes and factors influencing slope stability is essential for assessingthe stability of potentially hazardous slopes. Passive monitoring of acoustic emissions and microseismologyprovides subsurface information on fracturing (timing and identification of the mechanism) and thereforecomplement surface displacement data. This study investigates for the first time acoustic and microseismicsignals generated in steep, frac tured bedrock permafrost, covering the broad frequency range of 1 − 105Hz.The analysis of artificial forcing experiments using a rebound hammer in a controlled setting led to twomajor findings: First, statistically insignificant cross correlation between signals indicates that waveformschange strongly with propagation distance. Second, a signficant amplification is found in the frequencyband 33–67 Hz. This finding is strongly supported by evidence from artificial rockfall events and moreimportantly by naturally occurring fracture events identified in fracture displacement data. Thus, filteringthis frequency band enables enhanced detection of microseismic events relevant for slope stabilityassessment. The analysis of 2-year time series in this frequency band further suggests that the detectedenergy rate baseline of all automatically triggered events using the STA/LTA algorithm is not sensitive totemperature forcing, an observation of primary importance for long-term data collection, analysis, andinterpretation. The event detection in the established frequency band is not only improved but also notaffected by the short- and long-term temperature changes in such a rapidly changing environment.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Geography
Dewey Decimal Classification:910 Geography & travel
Language:English
Date:24 May 2018
Deposited On:06 Aug 2018 14:11
Last Modified:24 Nov 2018 05:40
Publisher:Wiley-Blackwell Publishing, Inc.
ISSN:2169-9003
OA Status:Green
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1029/2018JF004615

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