Two-dimensional Numerical Simulation Of The Wave Field Of Rayleigh Waves Over The Surface Of Layered Media

Rayleigh waves are widely used in various fields of underground investigation,such as natural earthquake research field and petroleum seismic exploration field.because the Rayleigh surface wave velocity is similar to the shear wave velocity and has the kinematic characteristics such as velocity dispersion.In the process of propagation of the medium,the elliptical polarization dispersion of the Rayleigh surface wave,like the velocity dispersion,also has a certain dispersion characteristic.The frequency dispersion of Rayleigh surface wave has long been widely used in engineering,while elliptical polarization dispersion has achieved some application effect in the field of excellent frequency test,but the application in the field of engineering exploration is still in the initial stage,the relevant forward modeling numerical simulation and theoretical research is still incomplete.In this paper,the numerical simulation method is used to study the horizontal dispersion medium and the dispersion of velocity and ellipsometry.The main contents are as follows:(1)Fundamental Theoretical Study on the Dispersion of Rayleigh Wave and the Dispersion of Elliptical Polarization.Firstly,the velocity dispersion of the Rayleigh surface wave and the calculation method of the dispersion of the elliptical polarization are discussed in detail.Then,the Fourier transform,F-K domain transform separation field,velocity dispersion curve extraction method and elliptical polarization dispersion method are discussed in Rayleigh wave dispersion analysis.(2)Numerical Simulation of Rayleigh Wave Velocity Dispersion and Elliptical Polarization Dispersion in Uniform Medium.For the uniform half-space,the full-wave field numerical simulation is carried out under the point source and plane wave source,respectively.Combined with the relevant theory,the wave field propagation characteristics were observed and analyzed to verify the correctness of the theoretical analysis results and numerical simulation method of accuracy.(3)Numerical Simulation of Rayleigh Surface Wave Velocity Dispersion and Elliptical Polarization Rate Dispersion in Horizontal Stratified Media.The two layer horizontal layered media with different low speed coverage and high speed coverage are selected,and the numerical model of the ratio of thickness to wavelength is obtained.The response characteristics of velocity dispersion and elliptical polarization dispersion to horizontal layered media are studied respectively.(4)Waveform Conversion and Energy Distribution Analysis at Layered Interface.Discuss the waveform conversion and energy distribution of surface wave at the layered interface.And analyzes the influence of the converted wave on the dispersion of the surface wave velocity and the dispersion of the elliptical polarization.Through the above research,the main results are as follows:(1)In the model of low velocity medium,the bulk wave propagates to the surface to regenerate the surface wave,which has a great influence on the propagation of the waves in the upper layer due to the conversion of the surface wave and the bulk wave.The results of the traditional single-sided wave mode propagation velocity dispersion and elliptical polarization dispersion analysis method are distorted.However,the effect of velocity dispersion is small,which has a great influence on the dispersion of elliptical polarization.(2)For the stratified layer of the two-layer medium and the cover is a low-speed medium model.Although there is still the transition of surface wave and bulk wave in the layered interface,most of the energy wave propagates in the low-speed medium,which has little effect on the elliptic polarization of the wave in the upper layer.The research content of this paper deepens the understanding of the mutual conversion between Rayleigh surface wave and the bulk wave at the stratified interface,and the understanding of Rayleigh surface wave velocity dispersion and elliptical polarization dispersion is strengthened,and the theoretical basis of Rayleigh surface wave detection in layered media is improved.It provides a more complete theoretical basis for the application of Rayleigh wave in engineering.It is helpful to improve the discipline theory,promote the development of disciplines and guide the application practice.