In 2018, successive large-scale landslides occurred near the village of Baige in the Jinshajiang suture zone on the Qinghai–Tibet Plateau, posing substantial threat both to the lives and property of residents and to the engineering facilities along the upper and lower reaches of the Jinsha River. In this study, field investigation data, remote sensing images, aerial photography, microanalysis of rocks, and mechanical experiments were considered to ascertain the material and geomorphic conditions of the landslides and to explore the failure mechanism and process of evolution of the landslides under the coupled effect of exogenic and endogenic factors. Located in the Jinshajiang suture zone, the Baige landslides occurred close to the western boundary fault zone. The geological structure of the slope and the formation of landslides are controlled by the specific environmental tectonic dynamics of the suture zone. Tectonic damage has dramatically influenced the strength and hydraulic characteristics of the rock mass, and the rock’s uniaxial compressive strength and resistance to water disintegration have deteriorated markedly as a result. Strong weathering of the plateau and repeated groundwater infiltration have further reduced the mechanical properties of the unique rock and soil with inferior original strength characteristics. The intensive crustal uplift and the rapid river erosion have markedly altered the free face of the damaged rock mass, thereby increasing the gravitational potential energy of the rock mass. The long-term cumulative coupled effect of tectonic movement and surface denudation represents the fundamental mechanism of the Baige landslides. The Jinshajiang suture zone continues to face the risk of further massive landslides similar to those that occurred in Baige.

Primarily due to the scarce direct field evidence along a same fault, understanding the relationship between the pre‐existing off‐fault damage and coseismic slip distribution remains challenging. This study offers the first field‐based quantitative assessments of fault damage zones along the surface rupture generated by the 2008 M _w 7.9 Wenchuan earthquake in China over eight profiles with 254 outcrops. The width and mean tectonic fracture intensity of the damage zones exhibit pronounced variations along the fault strike. We introduce the damage index as a proxy to quantify the extent of pre‐existing damage. We find a statistically significant anti‐correlation between the damage index and coseismic on‐fault slip. We thus infer that pre‐existing off‐fault damage plays a significant role in dissipating rupture energy, thereby reducing coseismic on‐fault slip. This study provides a natural case for linking the long‐term fault zone evolution and the short‐term earthquake rupture dynamics.