[H-DS07] Landslides and related phenomena

[HDS07-06] On the complex landsliding phenomena on Ichinose area triggered by the 2024 Noto Peninsula Earthquake

*Jiangkun He¹, Gonghui Wang², Gen Furuya³, Issei Doi², Koichi Hayashi², Yasuhiko OKADA⁴ (1.Graduate School of Science, Kyoto University, 2.Disaster Prevention Research Institute, Kyoto University, 3.Department of Environmental and Civil Engineering, Faculty of Engineering, Toyama Prefectural University, 4.Forestry and Forest Products Research Institute)

Keywords:earthquake, coseismic landslide, fluidization, retrogressive landsliding, complex landslide

During the 2024 Noto Peninsula Earthquake, thousands of landslides were triggered, including a large-scale landslide in the Ichinose area of Wajima City, Ishikawa Prefecture. This landslide exhibited complex movement patterns, originating from a gentle slope composed of tuffaceous silt, sandstone, and conglomerate. The displaced materials demonstrated high mobility, traveling over 1 km, destroying several houses and resulting in one casualty. To investigate the initiation and movement mechanisms of this landslide, we conducted field surveys, microtremor observations, seismic monitoring, and collected soil samples from various locations within the landslide area. Using the monitored data, we analyzed the slope's seismic response. A series of ring shear tests were performed on the samples under different conditions, including cyclic and seismic loadings inferred from nearby seismic recordings. Test results revealed that sandy layers could undergo liquefaction if fully saturated. In contrast, silty layers, sampled from the base of the displaced materials deposited on the exposed sliding surface in the upper source area, showed no significant reduction in shear strength under various loading conditions. These contrasting shear behaviors suggest that differences in soil properties contributed to the complex landsliding processes observed in this event.