The Longmenshan Fault zone runs about 500 kilometres along the eastern margin of the Tibetan Plateau in Sichuan Province, China, where the high plateau abuts the lower Sichuan Basin. It absorbs the crustal shortening driven by the ongoing collision of the Indian and Eurasian plates.
It is primarily a thrust (reverse) fault system with a strike-slip component, pushing the Tibetan crust up and over the basin to build the steep Longmen Mountains. Despite its dramatic topography, the fault creeps slowly, and its long recurrence intervals had led some to underestimate its danger.
On 12 May 2008 the fault ruptured in the magnitude 7.9 Wenchuan earthquake, which killed roughly 70,000 to 90,000 people and left millions homeless. The 2013 Lushan earthquake struck a nearby segment, underscoring the continuing seismic hazard along the plateau's eastern edge.