[H-DS07] 地すべりおよび関連現象

[HDS07-18] On the initiation and movement mechanisms of Zhongchuan landslide triggered by the 2023 Jishishan M6.2 Earthquake, China

*王 高遠¹、範 宣梅¹、張 帆宇²、郝 瑞華²、王 功輝³ (1.成都理工大学　地質災害防治与地質環境保護国家重点実験室、2.蘭州大学　土木与力学学院、3.京都大学防災研究所)

キーワード：流動性地すべり、地震、液状化、灌漑、高速運動、長距離運動

At 23:59 on December 18, 2023, a destructive Ms 6.2 earthquake struck Jishishan County, Gansu Province, China. The earthquake triggered a large-scale loess landslide in Zhongchuan District, Qinghai Province, approximately 20 km from the epicenter. The landslide originated on a loess terrace used for farmland, where the displaced material fluidized and traveled down a narrow valley, devastating villages downslope before depositing in a residential area. With a travel distance of about 3 km and an elevation drop of approximately 80 m, the landslide exhibited an exceptionally low apparent friction coefficient (~0.0026). It destroyed over 50 houses and caused more than 20 fatalities. Notably, few landslides were triggered by this earthquake, yet this particular event displayed extreme mobility, underscoring the need to understand its initiation and movement mechanisms. To investigate this, we conducted geological and electrical resistivity tomography (ERT) surveys to assess the subsurface structure of the landslide area. Additionally, field double-ring infiltration tests and laboratory experiments (including direct shear, static triaxial, dynamic triaxial, and ring shear tests) were performed on soil samples taken from the landslide source area to evaluate their shear behavior under various conditions. Based on these results, we discussed the effect of earthquake and irrigation on the initiation and movement of this catastrophic landslide. The findings from both field and laboratory analyses provide critical insights into the triggering and movement processes of this highly mobile landslide.