Enhancing the Frequency–Bessel Spectrogram of Ambient Noise Cross-Correlation Functions


 The frequency–Bessel (F–J) spectrogram has been used for the extraction of multimodal dispersion curves to constrain the fine crustal shear-wave velocity structure. The original F–J spectrogram was contaminated with curved as well as straight crossed artifacts, which hindered obtaining the dispersion curves, while introducing a considerable error in the inversion result. Curved crossed artifacts in the multicomponent F–J spectrogram are typically removed using the modified F–J transform formulas; to remove straight crossed artifacts, we used the so-called k-filtering method. Based on a synthetic test and field data from the central Asian orogenic belt, we show that our proposed methods can enhance the multicomponent F–J spectrograms by efficiently removing the two types of crossed artifacts, while identifying more higher modes dispersion curves, and the accuracy of picking can also be improved.