The 1931 Fuyun earthquake (富蕴地震) occurred on August 10, 1931 at 21:18 UTC. The epicenter was near Fuyun County of northern Xinjiang, China. It was a M_w 8.0 earthquake and had a surface rupture of 171 km with a maximal horizontal displacement of 14 m along the Koktokay-Ertai fault zone (可可托海-二台断裂带). The Koktokay-Ertai fault has a slip rate of 4±2 mm per year. The rupture of this earthquake was caused by right-lateral strike-slip movement with normal component.