Two-dimensional Numerical Simulation To The Propagation Of Rayleigh Wave Under Varying Topography Condition

Rayleigh wave is widely used in engineering quality inspection and engineering survey.Because of its velocity is similar to the Shear wave and it possesses the kinematic characteristics of dispersion.In addition,it also has the dynamic characteristics of ellipticity dispersion,the ellipticity dispersion has some similarity with velocity dispersion.When media changes they will change too.Rayleigh wave had achieved the results that the velocity dispersion and ellipticity dispersion in the uniform half-space.However,the study of Rayleigh wave under varying topography condition is relatively less.This paper adopts the method of numerical simulation that simulates seismic wave.And then the velocity dispersion and ellipticity dispersion analysis.This article mainly from the following three aspects:The first,Discussion on velocity dispersion and ellipticity dispersion of Rayleigh wave on the base of seismic wave propagation.And then describes the extraction of Rayleigh wave that its velocity dispersion and ellipticity dispersion.Secondly,establish a uniform half-space model and then study on the propagation characteristics of Rayleigh wave.Verify the correctness of the theoretical analysis results and the rationality of the numerical simulation method.Then simulated seismic wave under varying topography condition.Study on the Rayleigh wave about the effects of gradient on the velocity dispersion and ellipticity dispersion.Thirdly,establish the model with a local anomalies body.Analysis of seismic wave propagation characteristics and compare with the simple one.Further study for the influence of a local anomalies body.According to the above study,the following results have been achieved:Compared with the uniform half-space model,the seismic wave under varying topography condition is more complicated than the unifonn half-space one.The terrain effect produces the converted wave.So it can cause the Rayleigh wave’s velocity to disperse.For the topographic uplift,the velocity of Rayleigh wave in the near-source zones will decreases,but the far-source zones increases.For the topographic depression the result is opposite.And this trend becomes more and more obvious as the gradient increases.Similarly,the terrain effect will also result in ellipticity dispersion.Performance is as follows:For the topographic uplift,the ellipticity value of Rayleigh wave in the near-source zones will become larger,but the far-source zones will become smaller.For the topographic depression,the result is opposite.And this trend becomes more and more obvious as the gradient increases.For the model with a local anomalies body,Compared with the simple terrain numerical model,the seismic wave becomes more complicated.The propagation of seismic wave is not only affected by the terrain effect but also by the local anomalies body.When the seismic wave passes through the local anomalies body.The anomalies body is equivalent to a source.The study found that the terrain effect on Rayleigh wave’s velocity dispersion and ellipticity dispersion is more profound.The local anomalies body only deepens this effect in local area.Through the study of this paper,we deepen the understanding of Rayleigh wave’s propagation under varying topography condition.The recognition of Rayleigh wave’s velocity dispersion and ellipticity dispersion is strengthened.At the same time perfect the theoretical basis of Rayleigh wave.There will be greater benefits to promote discipline development.