Kinematics in iterated correlations of a passive acoustic experiment

Abstract:

Correlating ambient seismic noise can yield the inter-station Green's function, but only if the energy that is excited by seismic background sources is sufficiently equipartitioned after averaging over all sources. If this requirement is not fulfilled, the reconstructed Green's function is imperfect. Secondary scattering can mitigate the directivity of the primary wave field emitted by the sources. To extract and utilize secondary scattering for Green's function reconstruction, we introduce a second correlation using an auxiliary station. We investigate the kinematics of the reconstructed Green's functions to understand the role of the positions of source, scatterer and auxiliary stations. Iterated correlations can use secondary scattering to mitigate the directivity in the background seismic wave field. In general, there will be additional spurious events in the retrieved Green's functions. Averaging the results of several sources and using a network of randomly distributed auxiliary stations can minimize these spurious events with respect to the correct events in the retrieved Green's functions.

Kinematics in iterated correlations of a passive acoustic experiment