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Deriving Wavefield Characteristics and Shear-Velocity Profiles from Two- Dimensional Small-Aperture Arrays Analysis of Ambient Vibrations in a Small-Size Alluvial Basin, Colfiorito, Italy

Giuseppe Di Giulio 1 Cécile Cornou 2 Matthias Ohrnberger 3 Marc Wathelet 4 Antonio Rovelli 1
1 Istituto Nazionale di Geofisica e Vulcanologia
2 LGIT - Laboratoire de Géophysique Interne et Tectonophysique
3 Institute Geowissenschaften
4 GEOMAC
Abstract : We analyze the dispersion characteristics of ambient noise vibrations. For this purpose, two-dimensional (2D) seismic array data were acquired in four different sites in the Colfiorito plain, an alluvial intramountain basin that exhibits strong site effects. Assuming seismic noise being mainly composed of surface waves, we derive one-dimensional (1D) shallow shear-velocity profiles through the inversion of dispersion curves measured by frequency–wavenumber (f-k) methods. The inverted shear-wave velocity profiles are consistent with a priori information for those sites that can be approximated by 1D simple models. In these cases, the use of passive records of seismic vibrations can be a valuable tool for determining the shallow velocity profile if a detailed depiction of velocity structure is not required. The theoretical dispersion curves for Rayleigh and Love waves were compared with the measured dispersion curves for vertical and horizontal components, respectively. This allows us to discuss qualitatively the composition of ambient vibrations (outlining a large proportion of Love waves in the noise wave field) and the effects of higher modes. We also use the single-station method for investigating the origin of the horizontal-to-vertical (H/V) peak in the plain of Colfiorito in terms of ellipticity of the fundamental Rayleigh mode.
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Submitted on : Friday, March 21, 2008 - 11:47:32 AM
Last modification on : Tuesday, October 19, 2021 - 6:58:00 PM

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Giuseppe Di Giulio, Cécile Cornou, Matthias Ohrnberger, Marc Wathelet, Antonio Rovelli. Deriving Wavefield Characteristics and Shear-Velocity Profiles from Two- Dimensional Small-Aperture Arrays Analysis of Ambient Vibrations in a Small-Size Alluvial Basin, Colfiorito, Italy. Bulletin of the Seismological Society of America, Seismological Society of America, 2006, 96 (5), pp.1915-1933. ⟨10.1785/0120060119⟩. ⟨insu-00266188⟩

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