Seismic Surface Wave Dispersion Curve Inversion Research And Software Design Based On Artificial Fish Swarm Algorithm

The near-surface shear wave velocity structure is a very important parameter in engineering investigation,ultrasonic nondestructive testing and other engineering fields.The study of geophysical method to obtain the subsurface shear wave velocity structure is very important for engineering inspection and geological disaster prevention.The dispersion of Rayleigh surface wave is closely related to the velocity distribution of near-surface shear wave,so seismic surface wave can be used to survey the velocity structure of near-surface shear wave.The workflow of Rayleigh wave method for near-surface geophysical engineering can be described as follows: 1)Artificial source is used to excite Rayleigh wave,and multiple Rayleigh wave records are collected by seismograph;2)Using a wave field transformation method to generate the recorded dispersion spectrum;3)According to the principle of energy extremum,the phase velocity of Rayleigh wave varying with frequency is picked up from the dispersion spectrum,namely,the dispersion curve of Rayleigh wave;4)The1D S-wave velocity structure of the measured point is obtained by inversion of dispersion curve.It is a very important step to obtain the s-wave velocity structure of the measured point by inversion of dispersion curve,which directly affects the mechanical property analysis of the medium below the measured point.Therefore,it is necessary to study the inversion of Rayleigh wave dispersion curve.This paper introduces in detail the background of topic selection,the development status of relevant theories of seismic surface wave exploration at home and abroad,the principles and methods of seismic surface wave dispersion curve extraction and forward and inversion,and focuses on the application of artificial fish swarm algorithm in Rayleigh surface wave dispersion curve inversion.In view of the traditional artificial fish algorithm in dispersion curves inversion convergence speed is slow,late in the process of global optimization search results repeated shocks,easily trapped in local minima problem,this paper introduced the survival and competition mechanism to improve,reducing the artificial fish populations,needed for the algorithm running late to speed up the algorithm efficiency.Then,dynamic field of vision,step size and improved foraging behavior are used in the algorithm,which not only accelerates the convergence speed and strengthens the global optimization ability in the early stage,but also improves the oscillation phenomenon in the late stage of the algorithm and improves the accuracy of the inversion results.According to the characteristics of artificial fish swarm algorithm,a parallel algorithm is proposed to improve the running efficiency of the program.The theoretical model and measured seismic surface wave data are used to verify the application effect of the improved artificial fish swarm algorithm in Rayleigh surface wave dispersion curve inversion,and the experimental results show that the algorithm can quickly and accurately inverse the subsurface shear wave velocity structure.On the basis of the algorithm research,a visual seismic surface wave dispersion curve inversion software is developed by using the MATLAB App Designer platform.The software adopts the modular design,which can respectively achieve the seismic file reading,dispersion energy spectrum drawing and dispersion curve extraction,dispersion curve inversion,two-dimensional underground shear wave velocity profile drawing and other functions.The software interface design adopts visual interactive graphical user interface,which has the advantages of simple operation and low threshold.