Preliminary study on the development characteristics and formation mechanism of the Zhongchuan Town liquefaction landslide-mudflow-blockage disaster chain induced by the 2023 Jishishan Earthquake in Gansu Province

On December 18, 2023, at 23:59, a magnitude M_S 6.2 earthquake struck Jishishan County, Gansu Province. The earthquake triggered a severe liquefaction landslide-mudflow-blockage disaster chain event near Zhongchuan Town in the neighboring Haidong City, Qinghai Province (referred to as the “disaster chain event”). This event caused extensive damage to infrastructure, including residential buildings, power transmission towers, and roads, leading to significant loss of life and property. Based on extensive geological surveys conducted at the disaster site, this study employs a combination of methods, including satellite remote sensing image interpretation and three-dimensional real-world models from unmanned aerial vehicles (UAVs). The primary objective is to elucidate the fundamental developmental characteristics and evolution process of the disaster chain event. Moreover, this study preliminarily explores the formation mechanism of this disaster by integrating the topography, lithology, hydrogeological conditions, and seismic triggering factors. The results suggest that the disaster chain event was controlled by unfavorable local hydrogeological conditions and was triggered by the intense shaking of the Jishishan earthquake, resulting in the occurrence of loess liquefaction landslides. The mobilized mudflow material flowed remotely along the low-friction frozen channel. During the movement stage along the channel, the landslide-mudflow chain transitioned into a blockage failure event due to the obstruction of the downstream earth dam, thereby exacerbating the destructive capability and disaster scope of this event. Further in-depth analysis of the formation conditions and mechanisms of the disaster chain event carries significant implications for guiding disaster reduction and prevention in potential hazard points with similar geological conditions in the northwest Loess Plateau region of China.