Abstract:On December 18, 2023, a 6.2 magnitude earthquake in Jishishan County, Linxia Prefecture, Gansu Province triggered a special flowslide, which differed significantly from conventional landslides. Currently, the causes and mechanisms of such disasters are unclear, and their early identification remains challenging. This study conducted detailed field investigation and analysis of the Zhongchuan Township flowslide, which could provide important theoretical and practical implications for preventing such disasters. The geological disaster triggered by the Jishishan earthquake was a low-angle loess slope flowslide, with a long sliding distance and viscous mud outbursts in the accumulation area, submerging multiple houses and leaving 20 people missing. Through in-depth field investigation and analyses, the causes, movement patterns, and surge velocities of the flowslide were explored. The results showed that: (1) the flowslide occurred on the second and third terraces of the Yellow River,with an elevation difference of 79.2 m, a sliding distance of approximately 3.1 km, and an overall slope angle of merely 1.5°. This event was identified as a low-angle loess slope flowslide triggered by a strong earthquake. (2) The primary causes of the flowslide included high saturation of source loess induced by continuous irrigation, structural collapse of under-consolidated saturated loess triggered by a strong earthquake, flow failure of low-plasticity-index loess, and enhanced damage due to embankment failure and gully constriction.
