Research And Application Of Multi-component Surface Wave Imaging Based On Traffic-induced Seismic Ambient Noise

As one of the most used noise sources in passive source surface wave exploration,traffic-induced seismic ambient noise is widely used in urban underground shear-wave velocity structure imaging.In this paper,the two-dimensional staggered-grid finitedifference method is used to simulate the multi-component traffic-induced seismic ambient noise.By the numerical simulation results,the characteristics of the original traffic-induced ambient noise were analyzed,and the influence of the observation system on the extraction of effective surface wave information in traffic-induced noise was studied.Firstly,in the process of data processing,the Rayleigh-wave dispersion energy images were generated from the simulated seismic-ambient noise by the passive-source frequency wavenumber transform method and the Frequency-Bessel transform method respectively.Then,the difference in Rayleigh wave imaging in different components is compared,and the difference in surface wave dispersion energy imaging effect between the two methods is analyzed.The acquisition scheme for obtaining more effective surface-wave information from traffic seismic noise is summarized.Secondly,the Levenberg-Marquardt method is used to invert the surface wave dispersion curve,and the advantages of the joint inversion of the multi-component surface-wave dispersion curve are analyzed.Finally,a real-world data set is processed and analyzed.The data was acquired by a receiver spread with three-component geophones,which were configured along an urban road in Hangzhou city.The Rayleigh wave dispersion curves extracted from the vertical component and the radial component were used to invert the shear wave velocity structure corresponding to the survey area,and the applicability and effectiveness of multi-component traffic-induced seismic noise in practical application are verified.The results show that the variation of the parameters of the observation system has a great influence on the surface wave dispersion energy imaging of different types of traffic ambient noise.For the seismic ambient noise generated by vehicle motion,the seismic noise collected by large trace intervals contains more high-frequency information,but it needs a long acquisition time to extract an effective surface-wave dispersion curve.For the seismic noise generated by pedestrian movement,the variations of trace intervals will change the effective frequency range of surface-wave dispersion energy images.Rayleigh wave dispersion energy imaging shows different characteristics in different components,and different types of traffic seismic noise also show different surface wave dispersion characteristics in the same frequency band of the same component.The inversion of shear-wave velocity by combining multi-component dispersion curves can greatly supplement the deficiency of surface-wave dispersion information in each frequency band,which not only improves the stability of the inversion process but also improves the accuracy of the inversion results.The real-world example further indicated the difference in surface wave dispersion characteristics between the vertical component and the radial component and proved the feasibility and necessity of multi-component and multi-mode surface wave dispersion curve inversion.