Surface-wave dispersion measurements using Hilbert-Huang transform

An efficient procedure using the Hilbert-Huang transform (HHT) method for the determination of the dispersion curves of seismic surface waves is investigated in this study. The HHT method is compared with a Fourier-based time-frequency analysis in the extraction of dispersion data from a synthetic seismic waveform generated by a point source in a layered medium. The HHT method provides high-resolution measurement of the spectral content as a function of arrival time, and the dispersion curve of group velocity is determined more accurately than that derived using conventional Fourier-based frequency-time analysis. Using a simple polynomial fitting technique, the dispersion curve of the phase velocity can also be derived by integrating the dispersion curve of the group velocity. Numerical tests show that the HHT method is capable of mapping the energy distribution in the frequency-time domain accurately, and the procedure requires much less computer time than other methods for surface-wave dispersion analysis.