Research and Application of Rayleigh Wave 3-D Phase Velocity Imaging Based on Wavelet Transform

Rayleigh wave detection is a recently developed method for shallow seismic exploration. Current Rayleigh wave data processing and interpretation methods can only provide the transverse average wave velocity of rock-soil bodies under the geophone array range, resulting in a low lateral resolution of wave velocity. To solve this problem, this paper presents a Rayleigh wave data processing method based on wavelet transform. First, the Hankel matrix is constructed from the intercepted Rayleigh wave, and the effective singular value is preserved by singular value decomposition to filter the Rayleigh wave. Then, the appropriate center frequency is selected and the corresponding relationship between the time and frequency of the Rayleigh wave is obtained via wavelet transform. The waveform of each frequency component can be extracted and the complete time difference of each frequency component between two geophones will be obtained and used to calculate the phase velocity-depth profile of the Rayleigh wave in a rock-soil body. This method is applied to examine unfavorable geological bodies that are underground in a yard. By combining the phase velocity-depth profiles of several survey lines, the 3-D image of phase velocity of Rayleigh wave underground can be obtained. This method can provide the phase velocity distribution of the formation below the survey line by only one measurement, which greatly improves upon the work efficiency and lateral resolution of the traditional Rayleigh wave data processing method.