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Toward Seismic Microzonation—2-D Modeling and Ambient Seismic Noise Measurements: The Case of an Embanked, Deep Alpine Valley

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Published in Earthquake Spectra. 2005, vol. 21, no. 3, p. 635-651
Abstract In the Sion area of Switzerland, part of a deep, embanked sediment-filled valley, investigations on soil site effects have been conducted using two independent methods. Two-dimensional (2-D) modeling was performed with a program based on the Indirect Boundary Element Method (Pedersen et. al. 1994). Numerical simulations allow taking into account the subsurface geometry of the valley and its peculiar characteristics, such as a variable shape ratio and a high shear-wave velocity contrast. The H∕V method has been applied on ambient seismic noise measurements recorded on sites as close as possible to the 2-D modeling. This technique allows capturing the fundamental resonant frequency of the deepest sediments as well as identifying the existence of a surficial deposit. Both approaches agree on the fact that the fundamental resonant frequency of the valley is below 1 Hz. The amplification level of the predominant frequency obtained with numerical simulation is up to two times higher than the one given by the H∕V ratio. These results provide the basis for further investigations in order to resolve differences.
Keywords Site effectsSeismic noiseAlpine valley
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Article (Accepted version) (1.9 MB) - document accessible for UNIGE members only Limited access to UNIGE
Structures
Research group Physical Volcanology and Geological Risk
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FRISCHKNECHT, Corine, ROSSET, Philippe, WAGNER, Jean-Jacques. Toward Seismic Microzonation—2-D Modeling and Ambient Seismic Noise Measurements: The Case of an Embanked, Deep Alpine Valley. In: Earthquake Spectra, 2005, vol. 21, n° 3, p. 635-651. doi: 10.1193/1.1941252 https://archive-ouverte.unige.ch/unige:24363

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Deposited on : 2012-12-10

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