[H-DS11] Human environment and disaster risk

[HDS11-05] Sediment disasters caused by the Noto Peninsula earthquake in January 2024 and subsequent rainstorm in September in Kawanishi, Machino Town, Wajima City, central Japan

★Invited Papers

*Hiromu Daimaru¹, Kota Miyamoto¹ (1.Faculty of Bioresources and Environment Ishikawa Prefectural University)

Keywords:The 2024 Noto Peninsula Earthquake, landslide, gravitational rock creep, The 2024 Noto Peninsula Heavy Rainfall

On the south slope of Mt. Tengai (234.9 m) in the western part of the Kawanishi area, two landslides of several hundred meters in scale occurred as a result of the January 2024 earthquake (Photo 1). Both landslides are considered to be reactions of the old landslide topography due to the presence of arc-shaped landslide scarps. A humic layer was found below the 2024 landslide deposit which is underlined by gravel layers that may have been formed by past landslide activity. The radiocarbon age for the bottom of the humic layer is ca. 6,000 years old, suggesting that landslide activity occurred prior to about 6,000 years ago. On the east-facing slope in the northern part of the Kawanishi area, significant gravity slope creep was occurred accompanied by numerous cracks and small landslides due to the January 2024 earthquake. Aerial photographs taken in March 2024 suggest that some expansions of the landslides occurred after the earthquake. On this slope, a large landslide has occurred due to heavy rainfall in September 2024. Groundwater gushing from the boundary between the saprolite and the underlying mudstone suggests that the landslide was caused by rapid rainfall infiltration into the slope, which was deformed by gravitational creep and had increased permeability.