[H-DS11] Human environment and disaster risk

[HDS11-04] Investigation of Conditions Affecting Landfill Movement during Earthquakes

*Ryosei Oishi¹, Issei Doi² (1.Graduate School of Science, Kyoto University, 2.Disaster Prevention Research Institute, Kyoto University)

Residential landfills spread in urban areas have collapsed, accompanied by earthquakes and torrential rains. In the 1995 Hyogo-ken Nanbu Earthquake, the Nikawa landslide occurred in residential landfills and 34 people lost their lives. In the Hanshin area and Kobe region, it is estimated that 49% (in terms of area) of the residential landfills were damaged, including the landfills of the reservoirs (Kamai et al., 2000). The collapses of the houses and landfills have been reported with the following earthquakes such as the Mid Niigata Prefecture Earthquake in 2004 (Kamai et al., 2005), the Noto Hanto Earthquake in 2007(Tameshige et al., 2009), and the 2011 off the Pacific coast of Tohoku Earthquake (Miyajima et al., 2022).
Previous studies showed that not all the landfills, even the neighboring ones, show deformation during earthquakes, though all the landfills are considered to be dangerous in the current hazard maps and risk assessments. If we can identify the conditions that affected the landfill deformation and/or displacements, it will not only improve the accuracy of the hazard maps , but also lead to a better understanding of the mechanism of the landfill collapse.
In this study, we examined the factors that determine whether landslides took place in the residential landfills or not for the case of the 2024 Noto Peninsula Earthquake. Microtremor measurements were conducted in the landfill and on the nearby basement in order to grasp the seismic ground motion characteristics. As a result, a 4-8 Hz of H/V spectrum peak was observed in the landfill with ground surface deformation, suggesting that the amplification factors of the seismic waves in this frequency band were different between the landfill and the basement.