An Approach To The Wave-Field Characteristic Analysis And Inversion Algorithm Of Rayleigh Surface Wavce For Layered Medium

Because of the dispersion characteristic and the similarity of velocity to shear wave, Rayleigh surface wave is widely used in various kinds of underground investigation areas, such as the natural earthquake research, oil seismic exploration, etc. In recent years, along with the rapidly development of computer technology and the need of engineering investigation, transient Rayleigh surface wave method with artificial excitation has been popularized in large civil engineering and environmental geology, such as medium stratification, karst cave distribution range investigation and antiseismic design for building engineering.Traditional research and application of Rayleigh surface wave method is based on its velocity dispersion characteristic (kinematic characteristic).The dispersion curve is usually extracted with the method of F-K domain filtering which needs to arrange many geophones and long array during observation, and the exploration depth is proportional to the length of the array. So, the traditional Rayleigh surface wave method is obviously limited to the space of the site, for example, it can not suitable for urban area with dense population and small spaces.To solve the application difficulties of the traditional Rayleigh surface wave method, we should exploration new theory with strengthening the research of dynamic characteristic of surface wave on the basic theory. In 1989, Nakamura proposed the H/V spectral ratio method (horizontal to vertical spectral ratio, HVSR) for micro-tremor information with passive source. In 2004, H.Arai and K.Tokimatsu successfully achieved the medium Vs structure by using the HVSR method of micro-tremor. The HVSR method is based on the dynamic characteristic of surface wave. Because of the essential component uncertainty and the randomicity and complexity of micro-tremor information with passive source, the forward numerical simulation of the micro-tremor wave-field is still incomplete till this day.In this dissertation, in order to solve the application difficulties in small site spaces limitation for the traditional surface wave method, it puts forward two approaches of inversion. The first is acquiring Rayleigh surface wave with fewer geophones and shorter array. To carry out this approach, the kinematic characteristic (verlocity dispersion characteristic) of Rayleigh surface wave field has been studied using numerical simulation, and the method of narrowband pass filtering and wavelet packet filtering have been discussed in this dissertation, which are used to extract the dispersion curve from time domain signial with shorter array. The second is using the HVSR characteristic (dynamic characteristic) of active source Rayleigh surface wave information acquired with single three-component geophone, combined with the advantages and disadvantages of micro-tremor HVSR method. Around this content, it studies not only dynamic characteristic of Rayleigh surface wave field with active source using numerical simulation method, but also the inversion method with the dynamic characteristic. About the two approaches, the second one dealt wth the dynamic characteristic of Rayleigh surface wave is mainly studied in the dissertation, and it is studied on two hands. On the one hand, the study is on the elliptic polarization characteristics of Rayleigh surface wave and the concept of elliptic polarization dispersion is put forword creatively, which is the physical mechanism for active source HVSR method, and the result of which shows that it has good corresponding relationship between the medium Vs structure and the elliptic polarization characteristics; on the other hand, the study is on the inversion method with using the HVSR characteristic, the dynamic characteristic of Rayleigh surface wave, the result of which shows that the medium Vs structure can be successfully achieved by inversion with the HVSR characteristic of Rayleigh surface wave with active source.Through the research of Rayleigh surface wave field characteristic (kinematic and dynamic characteristic) by numerical simulating for horizontal layered medium and the research of medium Vs structure inversion by using the field characteristic, the dissertation has realized not only the forward and inversion algorithms, but also the corresponding MATLAB language programs. Combined with the practical work, it is has been verified that the algorithms and programs is feasible and stable.The research results of this dissertation can successfully solve the application difficulties of the traditional Rayleigh surface wave method. It provides more perfect basic theory for expanding the applicable range in engineering. It not only has important research meanings for antiseismic design of building engineering, but also is very helpful for improving the scientific theory and promoting the development of the subject.