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Lapo Boschi, Visiting Researcher at the Earth Sciences Institute of Paris, presents “Ambient-noise and coda interferometry in theory, in the laboratory and in the field.”
“Cross-correlating an approximately diffuse background signal recorded at a pair of receivers is an efficient and useful way of measuring the impulse response (Green function) of a medium. This technique has recently found applications in numerous different fields. I will briefly review its theoretical bases, illustrated by some laboratory experiments which served to validate it. These experiments explore, in particular, the role of reverberations within the medium of propagation, which contribute to the complexity of the Green function, but also to the “diffusivity” of the medium and thus to the potential accuracy of the method. I will then present an application to seismic ambient noise recorded in central Europe: estimates of Rayleigh and Love-wave dispersion obtained at each station pair from ambient noise are systematically compared to dispersion data based on the well established earthquake-station-station method. Finally, new tomography images of the Alpine crust are obtained from the combination of both data sets.”