The Xiaojiang Fault runs roughly north-south for about 400 kilometres through central Yunnan in southwest China, forming the eastern boundary of the Sichuan-Yunnan (Chuandian) block. It is a key structure accommodating the eastward and southward extrusion of crustal material squeezed out as the Indian Plate drives into Asia.
As a left-lateral strike-slip fault, the Xiaojiang system slips at several millimetres per year and links northward to the Xianshuihe and Anninghe faults, together forming a continuous boundary that channels the rotation of southeastern Tibet. Its steep, well-defined trace cuts across river valleys and highlands south of Kunming.
The fault has generated numerous strong historical earthquakes, including the devastating 1833 Songming event near magnitude 8, which caused widespread destruction and heavy loss of life. Its proximity to Kunming and other growing cities keeps the Xiaojiang Fault at the centre of seismic risk assessment for the region.