Retrieval of Reflections from Ambient Noise Using the Incident Fields (Point-spread Function) as a Diagnostic Tool

Seismic interferometry (SI) enables the retrieval of virtual-shot records at the location of receivers. SI with ambient noise allows the retrieval of the reflection response of the subsurface without the need of any active source. The quality of the retrieved response is dependent on the illumination characteristics of the ambient noise. For the exploration frequency band of interest, in low-seismicity regions most of the energy in the recorded noise comes from sources at or near the surface. Such sources would mainly contribute to retrieval of surface waves, which would show up as the most energetic arrivals in the retrieved results. Because of that, the generally weaker retrieved reflections would be buried by the retrieved surface waves. Aiming at improving SI retrieved reflections, we propose a diagnostic tool applied after cross-correlation that separates the correlated noise panels into surface-wave dominated and body-wave dominated. We show results of the application of the tool to modelled data for noise sources acting separately in time and for noise sources overlapping in time. Finally, we show results from the application of the diagnostic tool to ambient noise recorded in Northern Netherlands.