The optimisation processing of cross-correlation calculation and dispersion measurement

Ambient noise cross-correlation has been successfully carried out in many cases by utilising seismic data with vertical and transverse components from broadband seismographs, while both the processing of data or discussion about correlation of different components has been less demonstrated. This study concentrated on the juncture area of the Anhui, Jiangxi, and Zhejiang provinces of China, from where seismic data, between October 2014 and August 2015, were acquired through 10 domestic seismographs. Empirical Green’s functions were yielded from vertical correlations or the superposition of radial and vertical correlations for the Rayleigh waves and from transverse correlations the Love waves. Then, the group-velocity and phase-velocity dispersion curves for Rayleigh and Love waves were measured by applying a frequency-time analysis method. Finally, a one-dimensional S-wave velocity structure was obtained through the joint inversion of the above dispersion measurements. The conclusions out of data processing were drawn as follows. i) The superposition of vertical and radial correlations presented the interference phenomenon: when the differences between the ratio of vertical-correlation signal-to-noise ratios (SNRs) to radial-correlation SNRs and value 1 are less than, or equal to, 0.35, the SNRs of the stacked vertical and radial correlations are higher. ii) The effective length of some dispersion measurements from the stacked vertical and radial correlations is longer by 2-8 s than those from the vertical correlations.