On the retrieval of body waves from ambient noise based on regional seismic arrays

Abstract

SUMMARY Ambient noise technology can efficiently extract surface wave signals from seismic background noise and has been extensively utilized in imaging lithospheric structures. However, retrieving crustal body wave signals, such as PmP or SmS phases, still poses a challenge. Only a limited number of reports have successfully extracted these regional-scale body wave signals from ambient noise in only a few limited study areas. It remains unclear why these signals are difficult to retrieve from ambient noise data. To investigate the mechanism of recovering body wave signals in noise cross-correlations, we calculate cross-correlation functions at four regions and observe the similarity of the recovered body waves. Through a series of synthetic simulations, we demonstrate that the appearance of body wave signals in noise cross-correlations is closely related to the distribution of noise sources. Among these signals, the post-critical SmS wave proves to be the most readily recoverable from ambient noise data, primarily stemming from distant sources. In contrast, the recovery of P-wave requires the array to be in proximity to the sources. Our experiments also reveal that the main origin of PL waves is the multiple reflections of S-waves propagating in the crust.