5:15 PM - 6:30 PM
[SSS11-P11] Estimation of Subsurface Structure and Ground Motion Characteristics in the Landslide Areas from Microtremor Observations – Case of Nawashiro and Amedaki, Kokufu-cho, Tottori City –
Keywords:Microtremor observation, H/V spectra, Landslide, Subsurface structure
In recent years, landslides caused by earthquakes have resulted in large-scale damage. It is important to understand the ground motion characteristics of landslide areas because landslides often occur repeatedly in the same area based on past activity history. Microtremor surveys have been used to evaluate the ground motions in landslide areas because the sediments above the slip surface are very soft and the velocity contrast is likely to be distinct (e.g., Shima, 1981). In this study, we conducted microtremor observations in Nawashiro and Amedaki, Kokufu-cho, Tottori City, that are classified as landslide areas in the landslide topography map published by the National Research Institute for Earth Science and Disaster Resilience (NIED), and examined the extent to which landslide deposits can be evaluated.
From the landslide topography distribution map, the Nawashiro landslide is classified into three blocks, and the Amedaki landslide is one large body. As a result of the analysis, the predominant periods of microtremor H/V were 0.06-0.35 seconds in both regions. At Nawashiro, each block has its own characteristics of predominant periods. In some blocks, predominant periods of 0.1 seconds or less were widely distributed, while in other blocks, periods of 0.3 seconds were concentrated. At Amedaki, the predominant period tended to be longer at the sites identified as landslide bodies. From the array observation, it was estimated that the layer of Vs = 200 m/s is 6m at Nawashiro and the layer of Vs = 130 m/s is 5m at Amedaki. The S-wave velocities and the predominant periods were used to estimate the layer thicknesses. The layer thicknesses tend to be thicker at the center of the landslide bodies, that may reflect the landslide deposits.
From the landslide topography distribution map, the Nawashiro landslide is classified into three blocks, and the Amedaki landslide is one large body. As a result of the analysis, the predominant periods of microtremor H/V were 0.06-0.35 seconds in both regions. At Nawashiro, each block has its own characteristics of predominant periods. In some blocks, predominant periods of 0.1 seconds or less were widely distributed, while in other blocks, periods of 0.3 seconds were concentrated. At Amedaki, the predominant period tended to be longer at the sites identified as landslide bodies. From the array observation, it was estimated that the layer of Vs = 200 m/s is 6m at Nawashiro and the layer of Vs = 130 m/s is 5m at Amedaki. The S-wave velocities and the predominant periods were used to estimate the layer thicknesses. The layer thicknesses tend to be thicker at the center of the landslide bodies, that may reflect the landslide deposits.