Detection of near-surface fissures by generalized S-transform of Rayleigh waves

Abstract

Because of the strong energy of Rayleigh wave, high signal to noise ratio and high efficiency, as a new type of engineering geophysical exploration methods, Rayleigh wave exploration get more and more attention in recent years.And because of the in-homogeneity of the earth's surface medium, the Rayleigh Wave velocity that spread in it changes with frequency. This kind of phenomenon is called the dispersion phenomenon of the Rayleigh Wave. So, making use of the dispersion characteristic of the Rayleigh Wave, the variety of the property and structure that underground medium could be opened out.A rotated the staggered-grid finite-difference method was adopted in wave field modeling to obtain the synthetic seismic record in this paper.Base on the study of Xia, we performed a little modification to the travel time equation for the Rayleigh-wave diffraction,and we use the generalized S-transform which is more suitable for non-stationary signal processing was adopted to extract the arrival times of the diffracted Rayleigh waves from the boundary of the fissure at a certain receiver.And then the arrival times were used to calculate the locations of the boundary of the fissure. Keywords—rayleigh wave; generalized s-transform; fissure