HR: 08:45h
AN: S31A-02    [Abstracts]
TI: A Physical Interpretation of "Passive Imaging" With Correlations of Scattered Wave Fields
AU: * Derode, A
EM: arnaud.derode@espci.fr
AF: LOA, Universite de Paris and CNRS, ESPCI, 10 rue Vauquelin, Paris, 75005 France
AU: Larose, E
EM: Eric.Larose@ujf-grenoble.fr
AF: LOA, Universite de Paris and CNRS, ESPCI, 10 rue Vauquelin, Paris, 75005 France
AU: Larose, E
EM: Eric.Larose@ujf-grenoble.fr
AF: LGIT, Universite Joseph Fourier and CNRS, BP 53, Grenoble, 38041 France
AU: Campillo, M
EM: Michel.Campillo@ujf-grenoble.fr
AF: LGIT, Universite Joseph Fourier and CNRS, BP 53, Grenoble, 38041 France
AB: Many recent works in seismology, underwater acoustics or ultrasound have shown that the correlation of a scattered wavefield recorded at two points A and B could be used to estimate the Green's function (or at least its first arrivals) between A and B, even though none of these points actually acts as a source. This led to the idea of "passive imaging" of a heterogeneous medium such as the earth's crust. Here we argue that the space- and time-correlation that is performed is more than a signal analysis trick: it has a deep physical interpretation. The correlation can be analysed in terms of time-reversed propagation of a scattered wave field inside the medium to be imaged. One advantage of this approach is that all the results that have been derived about time-reversed propagation in complex media can be fruitfully applied to passive imaging. The time-reversal approach can tell us in what circumstances the Greens function can or cannot be actually retrieved from correlations. We emphasize the role of several crucial points: the spatial distribution of the sources, the role of disorder and multiple scattering, the frequency bandwidth, and the advantage of performing one-bit correlations. The argument will be sustained by numerical simulations as well as experimental results, and its implication for imaging and detection purposes will be discussed.
DE: 7260 Theory and modeling
DE: 7294 Instruments and techniques
SC: Seismology [S]
MN: 2005 Joint Assembly