10:45 AM - 12:15 PM
[SSS07-P02] Heterogeneous seismic wave propagation inside a landslide estimated from dense seismic observation (Part 2)
Conventional methods for stability analysis and displacement estimation of a landslide such as Newmark method (Newmark, 1965) deals with a landslide as a rigid body. In order to sophisticate a stability analysis method considering internal deformation of a landslide, our previous study (Doi et al., 2022) performed a dense seismic observation and showed that internal deformation of the landslide was generated due to the complicated seismic wave propagation derive from heterogeneous structure inside the landslide. This study developed the observation system and the analysis to obtain further seismic wave propagation characteristics.
The target landslide was Semposhi landslide, located in Kushiro Town, Hokkaido, Japan. It had the size of 70 m length and 25 m width and was divided into several small parts according to the geomorphological characteristics. Its geology was mud-stone (Kawai, 1956). Totally 7 high-sensitivity velocimeters were placed in and around the landslide with the spacing of 10-20 m.
Phase differences among two stations were calculated for S-wave and S-coda parts. For relatively low frequencies, phase differences were near 0 and proportional to the frequency. Because phase difference should be proportional to the frequency when the travel time difference does not depend on the frequency, this suggests that no or small dispersion effect for this frequency bands. On the other hand, for higher frequencies, there are several cases: 1) the phase difference was proportional to the frequency but with a larger proportional constant, 2) the phase difference and frequency had non-linear relationship, and 3) the phase difference showed random trend. We discuss seismic wave propagation characteristics according to the frequency with the geomorphological characteristics of the landslide.
Acknowledgements: This research was supported by Japanese KAKENHI JP17H04734, JP20H01984, JP21K19854, and JP22H01309, and the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan, under its The Second Earthquake and Volcano Hazards Observation and Research Program (Earthquake and Volcano Hazard Reduction Research).
The target landslide was Semposhi landslide, located in Kushiro Town, Hokkaido, Japan. It had the size of 70 m length and 25 m width and was divided into several small parts according to the geomorphological characteristics. Its geology was mud-stone (Kawai, 1956). Totally 7 high-sensitivity velocimeters were placed in and around the landslide with the spacing of 10-20 m.
Phase differences among two stations were calculated for S-wave and S-coda parts. For relatively low frequencies, phase differences were near 0 and proportional to the frequency. Because phase difference should be proportional to the frequency when the travel time difference does not depend on the frequency, this suggests that no or small dispersion effect for this frequency bands. On the other hand, for higher frequencies, there are several cases: 1) the phase difference was proportional to the frequency but with a larger proportional constant, 2) the phase difference and frequency had non-linear relationship, and 3) the phase difference showed random trend. We discuss seismic wave propagation characteristics according to the frequency with the geomorphological characteristics of the landslide.
Acknowledgements: This research was supported by Japanese KAKENHI JP17H04734, JP20H01984, JP21K19854, and JP22H01309, and the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan, under its The Second Earthquake and Volcano Hazards Observation and Research Program (Earthquake and Volcano Hazard Reduction Research).