General Outlines & Scientific Committee

Scientific Committee

  • Michel Campillo,
    Université de Grenoble, France.
  • Nicolas Shapiro,
    IPGP & CNRS, Paris, France.
  • Mathias Fink,
    Institut Langevin & ESPCI
  • W.A. Kuperman,
    Scripps, San Diego, USA.
  • R. L. Weaver,
    UIUC, USA.
  • Josselin Garnier,
    Paris, France.
  • Rob Van Der Hilst,
    Boston, USA.
  • Arie Verdel, Utrecht
    The Netherlands.
  • Haruo Sato
    Tohoku, Japan.

Scope of the workshop
The Green’s function (GF) of a medium between two points A and B represents the record we would get at A if an impulse source was applied at B. Passive imaging consists of the crosscorrelation of wavefields recorded at two points in order to converge to the GF of the medium, including all reflection, scattering and propagation modes. Various experimental, numerical and theoretical approaches have been developed to demonstrate passive imaging and to define more precisely under which assumption it is valid.

Historically speaking, Aki (1957) proposed a long time ago to use seismic noise in seismology to retrieve frequency by frequency the dispersion properties of surface waves in the subsoil. Later on, helioseismology was the first field where ambient noise crosscorrelation directly performed in the time-domain was used for imaging. The recordings of the Sun’s surface random motion were processed to retrieve time-distance information on the solar subsurface (Duvall et al., 1993, Gilles et al., 1997, Rickett and Claerbout, 1999). The same idea developed as day-light imaging was proposed by Claerbout (1968) in the context of geophysical prospecting. More recently, a seminal paper was published by Weaver and Lobkis (2001) that showed how diffuse thermal noise recorded and cross-correlated at two ultrasonic transducers (working at MHz frequencies) fastened to one face of a 10-cm side duralumin cube provided the complete time-domain GF between these two points. This spectacular result was the start of a complete revival of the subject since experimental evidence of ambient noise crosscorrelations were then demonstrated in :
– (1) acoustics and elastic plates (Lobkis and Weaver, 2001, Weaver and Lobkis, 2001, Larose et al., 2004, Larose et al., 2007, Sabra et al., 2008),
– (2) seismology (Paul and Campillo, 2001 ; Campillo and Paul, 2003, Schuster et al., 2004, Shapiro and Campillo, 2004), where passive seismic imaging (Shapiro et al., 2005, Sabra et al., 2005a) was performed in California from seismic noise at stations separated by distances of hundreds to thousands of kilometers,
– (3) seismic exploration (Draganov et al., 2007), where seismic body wave reflections were retrieved from noise measurements by an array of 3-component geophones laid out in a desert area,
– (4) oceanography where both direct and reflected wavefronts were retrieved from ambient noise crosscorrelation in shallow underwater acoustics (Roux and Kuperman, 2004, Sabra et al., 2005b).

The ambiant noise correlations are also now used to monitor active geophysical media like volcanoes (Brenguier et al, 2008) or active faults (Sens-Schonfelder & Wegler 2006, Brenguier et al 2008...)

The goal of the school is to gather young scientists (graduate students, post-docs) and senior scientists working in the field of ambient noise imaging through a multidisciplinary approach including geophysics, underwater acoustics, ultrasonics and wave physics in general.
Main topics

  1. Seismology
  2. Underwater Acoustics
  3. ultrasound Imaging
  4. Non Destructive Testing
  5. Wave Physics