Development of Softwares for Analysis of Elastic Waves

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1. Elastic Waves in horizontally layered structure are numerically simulated by a Days-2 code. As the result, the solution of numerical simulation is identical with the theoretical solution in terms of p waves, S waves, Rayleigh waves and reflected waves.2. After modifivation of a Days-2 code to use displacement as a initial input, elastic waves caused by several s wave sources are simulated, and thier characteristics are investigated.3. The possibility in resolution of thin layers by using amplitude of reflected waves is investigated. As the result, the horizontal changes of the thickness of thin layers are estimable by using amplitude of reflected wave.4. The effects of low velocity zone consisting of multiple thin layers on a P wave are investigated. As the results of experiments and numerical calculation, it is clarified that both reflected wave and transmitted wave are formed by the superposition of multiple reflected waves in thin layers.5. The effects of the cavity in rock mass on elastic waves are numerically simulated by a Days-2 code. As the result, due to the existence of the cavity, generation of s wave and the changes of maximum amplitude and period of transmitted P wave are confirmed.6. An effective ray tracing method based on the Huygens' principle is developed in order to use it in the seismic tomography. It is confirmed that thes ray tracing method is suitable for the seismic tomography because of its good accuracy and short calculation time.