Evaluation and calibration of the array-layout effects in dispersion spectra obtained from the frequency-Bessel transform

Summary

Dispersion curves of surface waves are widely used for the inversion of subsurface structures. To extract dispersion curves, many methods have been developed. Among them, multichannel analysis of surface waves such as slant stack and frequency-Bessel transform can extract not only the fundamental mode but also overtones. Inversion with overtones is proven to be more stable and has better resolution at greater depths. However, with a limited number of array receivers, artifacts and misfits due to array-layout effects arise in the dispersion spectra and impede the identification of dispersion curves. We evaluate the array-layout effects in the frequency-Bessel transform and calculate the array response functions which can help to mitigate artifacts and calibrate dispersion curves. We apply this technique to synthetic simulated, active source and ambient noise data. The artifacts caused by array-layout effects can be mitigated, which helps the identification of dispersion curves. We further calculate the Pearson correlation coefficient between the array response function and the dispersion spectrum section. It is used to calibrate the biases produced by the array-layout effects if we select dispersion curves by maximum values. The confidence intervals of the dispersion curves are then determined based on the correlation coefficients. It is helpful for the design of array layouts according to the investigation depths of interest.