Recently, the Jishishan Earthquake Geological Disaster Survey Team, established by the Institute for the Prevention and Treatment of Geological Disasters at the Gansu Academy of Sciences, conducted an in-depth study on the chain disasters of coseismic landslides and mudflows in Minhe. This investigation led to significant breakthroughs. After systematic analysis, the team proposed nine mechanisms of disaster formation driven by the coupled effects of chain disasters. Notably, the "vibratory liquefaction screening initiation effect" and the "funnel closure acceleration initiation effect" in the source area are scientific discoveries first proposed both domestically and internationally, receiving high acclaim from industry experts. The findings have been published in the journal "Journal of Glaciology and Geocryology."
At 23:59 on December 18, 2023, a magnitude 6.2 earthquake struck Jishishan County in Linxia Hui Autonomous Prefecture, Gansu Province, with a focal depth of 10km, resulting in 151 deaths. This powerful quake triggered a series of landslides and mudflows in Zhongchuan Township, Minhe County, Qinghai Province, causing 20 fatalities, which accounts for 13.5% of the total earthquake death toll. The complex mechanism behind these chain disasters has drawn widespread attention from both the public and academic communities due to its typicality and uniqueness on a global scale.
Nakagawa Landslide-Debris Flow Disaster Chain: Before and After Comparison. Image courtesy of Gansu Provincial Academy of Sciences.
Following the Jishi Mountain earthquake, the Gansu Provincial Academy of Sciences promptly organized disaster relief efforts and focused on addressing significant scientific challenges in disaster prevention and mitigation. The Institute for Geological Hazard Prevention established a research team for the Jishi Mountain earthquake geological disaster, led by researcher Su Xing and other technical professionals, who urgently headed to the affected area to conduct emergency investigations of geological hazards. Supported by the National Natural Science Foundation project and the second comprehensive scientific expedition to the Tibetan Plateau, the team systematically studied the Minhe co-seismic landslide-debris flow chain disaster. By delving into the characteristics and formation mechanisms of this cascading disaster, they achieved significant breakthroughs, providing crucial scientific evidence for post-disaster reconstruction and disaster prevention and mitigation efforts.
Damage in the Slit Source Area. Image provided by the Gansu Provincial Academy of Sciences.
Damage photos from the Huayuan area. Image provided by the Gansu Provincial Academy of Sciences.
According to reports, the "initiation effect of vibration liquefaction screening in the Huayuan area" is a significant feature of this chain disaster, which is markedly different from the typical characteristics of traditional landslides and debris flows. The majority of the materials involved in the evolution of the disaster are saturated loess in the lower layer, while the upper layer of unsaturated red soil mostly remains in the source area. Under the strong seismic action in Jiashi Mountain, the saturated loess in the lower layer rapidly vibrates and liquefies, causing high-speed flow and extrusion, while the initiation speed and movement distance of the upper unsaturated red soil are much smaller than those of the lower saturated loess, resulting in differential screening of vibration liquefaction.
The "acceleration initiation effect of funnel closure in the source area" is an important feature of this chain disaster. The source area of the Zhongchuan landslide-debris flow disaster chain has special morphological characteristics. The source area is approximately funnel-shaped, distinct from the morphological characteristics of traditional landslides such as circular or elongated shapes. This morphological feature causes the narrow outlet position of the landslide, resembling the mouth of a funnel. A small amount of unsaturated red soil is driven by the saturated loess in the lower layer to accumulate energy at the outlet during the closure. Under the action of strong seismic activity, the sliding body at the outlet instantly starts to slide in a flowing state, and lateral erosion and downcutting enlarge the outlet. A large amount of saturated loess continuously converges downward from the rear, pushing the front sliding body to move in a sliding motion. In the narrow and deep transition zone, under the effect of the closure, the sliding body continuously accelerates downward. This effect is similar to the "choked flow effect" or "gorge effect."
Related paper information: Link to the paper
