Abstract
On December 18, 2023, an Ms 6.2 earthquake struck Jishishan Bao'an, Dongxiang, and Salar Nationality Autonomous County, Linxia Hui Autonomous Prefecture, Gansu Province. The earthquake had an epicenter depth of 10 km and a maximum intensity of VIII. The study provides an intuitive and detailed co-seismic landsliding scene in the meizoseismal area based on our comprehensive field surveys immediately after the earthquake. This moderate-to-strong earthquake triggered more severe co-seismic landslides than expected, including the Zhongchuan Town mudflow, which resulted in the loss of > 20 lives. Most of the co-seismic landslides are small-to-middle scale shallow ones and concentrated in the loess area in Zhongchuan, Guanting towns of Qinghai Province and Dahejia, Shiyuan, Liugou towns in Gansu Province. Loess collapses are the most common co-seismic landslide type and are usually distributed on steep cut-slopes of roads and loess terraces where human activities are intense. The second-most common loess slides tend to occur on valley slopes covered by thick loose loess. Landslides in the bedrock area are less frequent and the majority are compound geo-disasters involving rockfalls and debris avalanches that originated in the upper part of the slopes and tend to cluster at the northern end of Jishishan Mountain. Generally, the distribution and occurrence mechanism of the co-seismic landslides are closely related to the lithology, terrain, hydrogeology, and seismic response of the areas where they originated. Lots of discontinuities (i.e., cracks or holes) and suspended loose debris on the slopes pose potential threats of re-sliding and should be given more attention.