Dissertation
Dissertation > Astronomy,Earth Sciences > Geology > Geology, mineral prospecting and exploration > Geophysical exploration > Seismic exploration

Theoretical, Numerical and Experimental Study of Love Wave in the Layered Madia

Author ZhangHongWu
Tutor ZhangTao
School Jilin University
Course Radio Physics
Keywords Transversely isotropic The music Love waves ( LOVE wave) Anisotropy parameters Axis of symmetry
CLC P631.4
Type Master's thesis
Year 2008
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Love waves are essentially horizontally polarized shear waves (SH waves) guided by an elastic layer, which is "welded" to an elastic half space on one side and borders vacuum on the other side. It is in the surface layer of the border after several reflect and collected in the surface layer. Love waves is to have actual being when earthquake occur, it is a kind of wave which diffuse along the border of two sorts of different medium. In fact, reveal and simulation in the coverage of the spread of the half-space laws of acoustics and geophysics is also an important research topic. The propagation of Love wave has important practical significance in the dissemination of earthquake engineering, geotechnical engineering and geophysics, and many other fields, and has an extensive attention. In recent years, the use of surface wave inversion for near-surface shear-wave velocity mapping has become common practice.This paper studies the Love wave’s propagation in the half-space coverage. The theoretical and numerical study for the Love wave propagation in the three-layer media is performed. Upper medium is transverse isotropic medium, the middle medium of is isotropic medium, and bottom medium is an isotropic elastic media. First is the theoretical basis of the formula. Based on theoretical formulas for acoustic waves in transversely isotropic medium, isotropic medium, and boundary conditions, the basic formula Love wave are presented. The dispersion equation for Love waves is obtained by using the boundary conditions. I used MATLAB software to make program codes for solving Love wave dispersion equation, and analyze the influence of both the parameters of transversely isotropic medium and the changes of symmetry axis for upper layer medium on phase velocity and cut-off frequency of Love waves.The numerical results show that the change of symmetric axis of transversely isotropic medium for upper layer medium has little effect on the cut off frequency of higher order modes. The numerical results for the case of upper layer is hard formation and soft formation show that the change of symmetric axis of transversely isotropic medium for upper layer medium has different influence on the phase velocity of each higher Love mode. The obvious changes of the cut-off frequency of higher order mode occurs when the parameters of upper layer medium changes.In addition to the theoretical and numerical study, the experiment survey to the Love wave in different layer medium is performed. The transducer for exiting SH wave is made a choice and analyzed firstly, and some sample materials are tested. The full waveforms of Love waves in two layered media are measured and analyzed preliminarily. The results of theoretical, numerical and experimental study of Love waves in layered media might be very significance in practical application.

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