Depth variations of 410km and 660km discontinuities in eastern North China Craton revealed by ambient noise interferometry

Recent studies have demonstrated that body waves between pairs of stations can be successfully retrieved from ambient noise cross correlation at both regional and global scales, although surface waves are the dominant signals. However, it is still difficult to use these retrieved body wave signals to map lateral depth variations of main structural discontinuities or velocity contrasts because of its low signal-to-noise ratio (SNR). In this research, based on a dense seismic array in eastern North China Craton, reflected P wave signals from 410km and 660km discontinuities can be successfully recovered from ambient noise cross correlation. To improve SNR, the cross correlations are stacked within each bin with the phase-weighted stack method. The retrieved P410P and P660P phases from stacked correlations reveal lateral variations of both depths and sharpness of the 410km and 660km discontinuities along two profiles, which may be related with hot material upwelling and the effect of stagnant Pacific Plate in the transition zone beneath North China Craton. The imaging results are generally consistent with the results from teleseismic receiver functions, which demonstrate the possibility of mapping high-resolution topography and sharpness of deep internal discontinuities without earthquake-station geometric limitations.