
The property at the basis of passive acoustic imaging is that, taken any two points, one of them can be seen as the source of the waves and the other as the recording station. This property, which was shown to hold also in nondiffuse fields, is here exploited: (1) to allow an undistorted passive imaging through the simple use of the statistical mode to estimate wave velocity, (2) to determine the azimuth of the instantaneous Huygens sources of the noise wavefield, and (3) to measure, provided that the noise bandwidth is wide with respect to that of the local system, the material dissipation constant as a function of frequency. The authors applied this theory to study the seismic noise field in the Ravenna, North-Central Italy, shore area and found it capable to provide velocity dispersion curves matching those of independent surveys, to track the sources of seismic noise to a few major firms in Ravenna port, with the prevailing source switching at the time scale of seconds, and to measure the dissipation quality factor Q at ∼20 independent of frequency in the range 1–30 Hz.
Italy, Earth Sciences, PASSIVE IMAGING; NONLINEAR ACOUSTICS; SELF FOCUSING; ARRAY SEISMOLOGY; DIFFUSE AND NON-DIFFUSE WAVE FIELDS, Acoustics, Models, Theoretical, Noise, Elasticity
Italy, Earth Sciences, PASSIVE IMAGING; NONLINEAR ACOUSTICS; SELF FOCUSING; ARRAY SEISMOLOGY; DIFFUSE AND NON-DIFFUSE WAVE FIELDS, Acoustics, Models, Theoretical, Noise, Elasticity
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