Improvement of Frequency–Bessel Phase-Velocity Spectra of Multicomponent Cross-Correlation Functions from Seismic Ambient Noise

Abstract

ABSTRACT The frequency–Bessel (F–J) transformation method is effective for the extraction of multimode surface wave dispersion data from ambient noise cross-correlation functions (CCFs). Recently, this method has been improved in terms of increasing resolution and reducing artifacts (or cycle skipping) in Rayleigh wave dispersion measurements. However, these advances are restricted to the ZZ-component F–J method, which is only applicable to Rayleigh waves. In contrast, they have not been extended to Love waves, which are fundamental for determining the horizontally polarized shear-wave velocity and the radial anisotropy associated with it. Furthermore, there is still a lack of a methodology for combining these advances. In this study, we propose a modified multicomponent F–J (MMFJ) method to extract high-quality dispersion data of both the Rayleigh and Love waves. To achieve high resolution, we derive formulas to optimize the MMFJ spectra. With synthetic ambient noise data and USArray data, we demonstrated the effectiveness of the MMFJ method in eliminating “crossed” artifacts and enhancing resolution. In particular, the “crossed” artifacts are greatly reduced using the MMFJ with small seismic arrays when the interstation distances in the seismic array are not dense enough. As such, the new MMFJ method has significant potential for handling seismic arrays with a limited number of receivers and the subsequent tomography of radial anisotropies at high precision.