Abstract
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.
Highlights
Rayleigh wave exploration is a recently developed method of shallow seismic exploration
A Rayleigh wave is a type of surface wave that propagates along a free surface [Rayleigh, 1885]
To address the weaknesses of the existing multi-channel transient Rayleigh wave exploration, this paper presents a time difference method based on wavelet transform
Summary
Rayleigh wave exploration is a recently developed method of shallow seismic exploration. In 1996, Liu Yunzhen and others constructed their own multi-channel seismic data acquisition and processing system It can increase the effective depth of Rayleigh wave exploration to 30 m and even reach 50 m under good conditions, which basically met the requirements for geotechnical engineering investigation. Multi-channel transient Rayleigh wave exploration can only calculate the lateral average velocity of rocksoil body under the geophone arrays. Problems such as low efficiency and insufficient lateral resolution of the rock-soil body remain [Qi, 2001]. To address the weaknesses of the existing multi-channel transient Rayleigh wave exploration, this paper presents a time difference method based on wavelet transform. By combining several survey lines, 3-D wave velocity imaging can be completed
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