Abstract
The Ms 6.2 Jishishan earthquake in Gansu on December 18, 2023, triggered a typical earthquake-induced liquefaction-type landslide-debris flow in Jintian Village and Caotan Village, Zhongchuan Township, Minhe County, Haidong City, Qinghai Province, resulting in numerous houses being surrounded and buried by mud several meters thick. Due to its remarkable suddenness and exceptional mobility, it was once misidentified as "sand boil." Through field investigation and remote sensing interpretation analysis, this geological hazard was confirmed to be an earthquake-triggered liquefaction-type landslide-debris flow, and its formation mechanism was explored. The results indicate that: (1) This geological disaster resulted from the vibration load during the earthquake causing liquefaction of the saturated silt layer (loessified) at the bottom of the plateau, forming a landslide that transformed into a debris flow; the debris flow traveled along the gully and, upon reaching the villages, spread out and caused disaster, rather than being a traditional in-situ "sand boil"; (2) The source sliding area exhibited two failure modes during the liquefaction process: dispersive failure and lateral spreading; (3) Earthquake-triggered soil liquefaction predominantly occurs in saturated granular materials (silty loess, fine sand, etc.) with pronounced strain-softening characteristics. Such geological hazards occur suddenly and often exhibit fluid-like long-distance movement after failure, easily causing catastrophic consequences and warranting heightened attention.
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Preamble
Preliminary Study on the Characteristics and Initiation Mechanism of Zhongchuan Flowslide Due to Liquefaction Triggered by the Ms 6.2 Jishishan Earthquake in Gansu Province
XU Qiang¹, PENG Dalei¹, FAN Xuanmei¹, DONG Xiujun¹, ZHANG Xiaochao¹, WANG Xin¹
¹State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, Chengdu University of Technology, Chengdu 610059
Abstract
On December 18, 2023, the Ms 6.2 Jishishan earthquake in Gansu triggered a characteristic liquefaction-induced landslide-mudflow in Zhongchuan Township, Minhe County, Haidong City, Qinghai Province. The disaster inundated and buried numerous houses in Jintian and Caotan villages under mud several meters thick. Due to its sudden onset and extraordinary mobility, it was initially misidentified as "sand boils." Through field investigation and remote sensing interpretation, this study confirms that the geohazard was a seismic liquefaction-induced landslide-mudflow and explores its initiation mechanism.
The results reveal three key findings. First, the disaster resulted from seismic vibration-induced liquefaction of a saturated silty sand layer (loessified) at the base of the plateau, which formed a landslide that transformed into a mudflow. The flow traveled along a gully before inundating the villages, rather than representing a traditional in-situ "sand boil" phenomenon. Second, the source area exhibited two distinct failure modes during liquefaction: disintegrative failure and lateral spreading. Third, seismically triggered soil liquefaction primarily occurs in saturated granular materials—such as loessial silt and fine sand—with pronounced strain-softening characteristics.
Such geological disasters are characterized by their sudden occurrence and typically exhibit fluid-like, long-runout behavior after failure, leading to catastrophic consequences that warrant significant attention.
Keywords: earthquake landslide-mudflow; disintegrative landslide; lateral spreading; seismic liquefaction; Jishishan earthquake