Surface Wave Detection Research And Application Technology Of Complex Terrain Condition

MASW is a new type of near-surface seismic exploration method,which can be used in multi-target and multi-scale shallow surface engineering survey.The Rayleigh wave exploration theory is based on the ideal hypothesis of the horizontal interface semi?infinite space,but the actual survey area terrain is more complicated.Therefore,it is meaningful to study the influence of complex terrain conditions to MASW and the optimal arrangement under complex terrain conditions.Based on MASW as the technical means,several typical complex terrain geological model are constructed to carry out finite difference numerical simulation.The frequency-velocity domain frequency spectrums with the complex terrain conditions are compared.In this paper,we first introduce the basic theory of Rayleigh wave and the finite difference simulation theory of elastic wave and the finite difference simulation theory of elastic wave.We use the two types of complex terrain model to simulate semi-infinite space conditions.Using Ricker wavelet as the source and completely absorbing the boundary condition The forward modeling of Rayleigh wave field is carried out for the influence of topography,optimal permutation parameters and source excitation location.The frequency of the Rayleigh wave is used to disperse the data.The effects of complex terrain conditions on the dispersion characteristics and the selection of optimal permutation parameters under complex terrain conditions are summarized by comparing the results of single-gun recording,wave field snapshots and frequency velocity domain spectrum.The results show that the convex topography has little effect on the high-order dispersion,and the surface wave data and spectral energy are more convergent.The larger spacing is helpful to improve the resolving power of each wave in the frequency domain.Finally,according to the two groups of complex terrain field exploration test,and high density resistivity method for comprehensive comparison.The results show that the results are in good agreement with the results of high density resistivity method and are more sensitive to shallow voids.The paper also points out the shortcomings of the wave propagation technique with complex terrain conditions and the future research direction,especially,we should strengthen the correlation study of three-dimensional Rayleigh wave finite difference simulation and time domain full waveform inversion under complex terrain conditions.The results of this paper provide theoretical guidance for the problems that may be encountered in the application of multi-channel transient surface wave method under complex terrain conditions.