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| | Abstract | | Wave transmission test is an effective way to estimate the inner structure and characteristic of a rock sample. Since later phases of transmitted waves in a small finite sample were contaminated by reflected and converted waves, it was difficult to analyze entire waveform. For the purpose to clarify the propagation process of reflected and converted waveforms generated in a rock sample, we performed 3D finite difference method simulation. Using the snapshots of the wavefield and waveform obtained at laboratory, we tried to identify the generation process of each characteristic phase appeared on the waveforms. The result show the direct waves propagate through the sample with generating the reflected and converted waves at the curve boundary of the sample side surface, and a group of S wave which slowly propagate along the curved boundary. Then, these waves reflected at the opposite surface and propagate through the sample with generating reflected and converted wave again which form complex shape of seismic trace as we saw in the transmitted wave obtained by laboratory experiments. This propagation process was repeated many times, and when a time enough elapsed S wave component in the rock sample became much dominate than P wave. |
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