Journal Article

Modal analysis of 2-D sedimentary basin from frequency domain decomposition of ambient vibration array recordings

Valerio Poggi, Laura Ermert, Jan Burjanek, Clotaire Michel and Donat Fäh

in Geophysical Journal International

Volume 200, issue 1, pages 615-626
ISSN: 0956-540X
Published online November 2014 | e-ISSN: 1365-246X | DOI: https://dx.doi.org/10.1093/gji/ggu420
Modal analysis of 2-D sedimentary basin from frequency domain decomposition of ambient vibration array recordings

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Frequency domain decomposition (FDD) is a well-established spectral technique used in civil engineering to analyse and monitor the modal response of buildings and structures. The method is based on singular value decomposition of the cross-power spectral density matrix from simultaneous array recordings of ambient vibrations. This method is advantageous to retrieve not only the resonance frequencies of the investigated structure, but also the corresponding modal shapes without the need for an absolute reference. This is an important piece of information, which can be used to validate the consistency of numerical models and analytical solutions. We apply this approach using advanced signal processing to evaluate the resonance characteristics of 2-D Alpine sedimentary valleys. In this study, we present the results obtained at Martigny, in the Rhône valley (Switzerland). For the analysis, we use 2 hr of ambient vibration recordings from a linear seismic array deployed perpendicularly to the valley axis. Only the horizontal-axial direction (SH) of the ground motion is considered. Using the FDD method, six separate resonant frequencies are retrieved together with their corresponding modal shapes. We compare the mode shapes with results from classical standard spectral ratios and numerical simulations of ambient vibration recordings.

Keywords: Site effects; Computational seismology; Wave propagation

Journal Article.  7515 words.  Illustrated.

Subjects: Volcanology and Seismology

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