The Search of Diffusive Properties in Ambient Seismic Noise
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Author/sPiña-Flores, José; Cárdenas-Soto, Martín; García-Jerez, Antonio; Campillo, Michel; Sánchez-Sesma, Francisco J.
Ambient seismic noise (ASN) is becoming of interest for geophysical exploration and engineering seismology as it is possible to exploit its potential for imaging. Theory asserts that the Green’s function can be retrieved from correlations within a diffuse field. Surface waves are the most conspicuous part of Green’s function in layered media. Thus, the velocities of surface waves can be obtained from ASN if the wavefield is diffuse. There is widespread interest in the conditions of emergence and properties of diffuse fields. In the applications, useful approximations of the Green’s function can be obtained from cross-correlations of recorded motions of ASN. An elastic field is diffuse if the illumination is azimuthally uniform and equipartitioned. It happens with the coda waves in earthquakes and has been verified in carefully planned experiments. For one of these data sets, the 1999 Chilpancingo (Mexico) experiment, there are some records of earthquake pre-events that undoubtedly are ...