大規模土砂移動と地盤振動の生成および広域伝播の3次元数値解析

抄録

Deep-seated landslides generate seismic signals that can be used to determine their magnitude and location. Establishing a numerical approach for calculating the generation and propagation of ground vibrations would improve the estimation of landslide properties. In this study, a numerical model coupling 3D particle flow and the continuum model was developed to calculate the landslide movement and subsequent propagation of seismic signals over large areas. Two sediment transport scenarios were considered for the deep-seated landslide that occurred in 2011 in Akadani, Gojo City, Nara Prefecture. After the landslide in the model, a low-frequency (0.01-0.1 Hz) signal was received at a seismic station located 34.4 km apart. The simulation results adequately reproduced the signals observed when the landslide was assumed to be in two blocks rather than one. At the generation of ground vibrations caused by sediment transport, it was confirmed that the scenario of sediment transport affects the amplitude of ground vibration at low frequency in despite of the same sediment volume. Particle motion during sediment movement result of the simulation results around deep-seated landslide slope is bigger at upper points than lower ones. In particular, the direction of low-frequency horizontal displacement during sediment movement in the simulation coincided with the direction at the distant observation point, supporting that the direction of sediment movement can be estimated. On the other hand, a high-frequency (>about 1 Hz) signal was not represented on this study. More smaller mesh model or including the effect of water might be taken into account to simulate a high-frequency signal. It is an issue for the future.