Development and distribution characteristics of geohazards based on sedimentary-structural evolution in Xide County, southwest Sichuan

Xide County, located in Sichuan Province, lies at transitional zone between the western margin of the Yangtze Block and the eastern margin of the Qinghai-Xizang Plateau. The geological evolution in the area is complex and diverse, with a wide distribution and various types of geohazards. While previous research has extensively studied the mechanisms of endogenic disaster causation by predecessors, further investigation is needed into how key foundational geological factors contribute to disaster formation and their interrelationship at the county level. Based on field investigations, foundational geological data, and historical records of geohazards, this study conducted a comparative analysis of the geological conditions for disaster formation in different zones and the developmental trends of various types of geohazards, from the perspective of regional geological evolution. The deep coupling relationship between the two is deeply analyzed. The results show that distribution of regional stratigraphy, differences in structural transformation, and geological evolution history are key factors controlling the development of different types of geohazards in the study area. The main types of geohazards in the area are landslides (240 occurrences) and debris flows (81 occurrences), with less development of collapses (7 occurrences). The county can be divided into four disaster gestation model zones: the metamorphic basement area, the passive continental margin sedimentary area, the foreland basin sedimentary area, and the intracontinental depression basin area. The wide and gentle fold structures in red beds are the disaster-prone environment for landslide. Strong structural transformations are the primary factor driving the development of debris flows. Collapses occur primarily in areas where hard carbonate rocks and magmatic rocks overlay, combined with a long history of structural evolution. The distribution of the Baiguowan Formation carbonaceous mudstone and intense fault transformations are the key geological conditions that constrain the chain disasters of landslides and debris flows around Hongmo Town. This study provides further insight into the early identification of regional geohazards and offers important guidance for disaster prevention and reduction.