Bulletin of the Seismological Society of America; October 2006; v. 96; no. 5;
p. 1915-1933; DOI: 10.1785/0120060119
© 2006 Seismological Society of America
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 Giulio1,
Cecile Cornou2,
Matthias Ohrnberger3,
Marc Wathelet*,4 and
Antonio Rovelli5
1 Istituto Nazionale di Geofisica e
Vulcanologia,
Via Castello d'Aquino 13
Grotttaminarda, 83035,
Avellino, Italy
(G.D.G.)
2 Laboratoire de Géophysique
Interne et Tectonophysique (LGIT/IRD),
Maison des Geosciences
BP53, 38041
Grenoble Cédex 9
Grenoble, France
(C.C.)
3 Institut für Geowissenschaften,
Universität Potsdam (IGUP)
Karl-Liebknecht-Strasse 24
D-14476 Golm,
Potsdam, Germany
(M.O.)
4 GEOMAC, University of
Liège,
1 Chemin des Chevreuils, B52
4000 Liege,
Belgium
(M.W.)
5 Istituto Nazionale di Geofisica e
Vulcanologia,
Via di Vigna Murata 605
00143 Rome,
Italy
(A.R.)
Correspondence: * Present address: Laboratoire de Géophysique Interne et Tectonophysique (LGIT/IRD), Grenoble, France.
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
frequencywavenumber (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.
Copyright © 2009 by Seismological Society of America