| In order to deal with large computer storage and long time of calculation in the finite element modeling of elastic wave, we used finite domains to substitute for infinite domains. There are great difference in physics quality between the inner and the outer of boundary and the local of grid in boundary, so the boundary and artificial boundary became a very strong interface to reflection wave. Because reflection wave from artificial boundary has strongly wreck to elastic wave field, the way of effectively absorbing reflection wave from artificial boundary is a very important research subject in elastic wave numerical simulation. Among of many artificial boundary conditions, the transmitting boundary conditions are the best because they can absorb more reflection wave.After demonstrating the finite element equation of elastic wave in detail, this paper discusses the transmitting boundary condition by the numbers, and integrates the transmitting boundary condition with artificial one to get good absorption effect on artificial boundary condition reflection, and it makes the seismogram clearer. The author compares the effects of Dirichlet boundary condition and attenuation one on artificial boundary with that on transmitting boundary, so does the absorption effects, the author also demonstrates the advantage of transmitting boundary. In order to get better absorption effect on boundary, the author applies the attenuation boundary condition and transmitting one on artificial boundary to the mixed boundary condition cone true, and this makes the absorption effects very ideal. At the same time, the error from boundary reflection is controlled at the level of calculation error. The dispersion caused by the division of grid and the computational error becomes weak after using micro-damp in computation.Which all of achievements are applied in the simulation of seismic wave of Researches on Exploration of Hidden Caves in Loss District, get expectant effects. |
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