Extracting body-wave signals from seismic ambient noise: Opportunities and challenges

Ambient noise tomography stands as one of the most significant seismological breakthroughs of the 21st century. By cross-correlating continuous time series data recorded at two seismic stations, empirical Green’s function between them can be retrieved. This approach mitigates the inherent limitations of traditional seismic imaging by reducing the dependence on precise earthquake source parameters, thereby proving advantageous for high-resolution imaging of the Earth’s crust and upper mantle. As surface waves dominate cross-correlation functions, most researchers have focused on surface wave tomography. In recent years, the widespread deployment of dense seismic arrays and advances in data processing techniques have made extracting body wave signals from ambient noise a growing research focus. Compared to surface waves, body waves penetrate more deeply, sampling deeper structures. Moreover, the distinct sensitivity patterns of body and surface waves provide constraints on both shallow and deep Earth structure. This paper reviews the major developments in body wave observations and methodologies using ambient seismic data over the past two decades. Taking regional-scale body wave phases as an example, we explore the influence of noise source distribution on the recovery of body wave signals. We also discuss the cross-term signals in noise cross-correlation functions that deviate from theoretical Green’s functions. Finally, we offer prospects for the future development of noise-based body wave techniques. We aim to further advance ambient noise technology and expand its potential applications in imaging Earth’s internal structure.