Characteristics and genetic mechanism of the Cuihua Rock Avalanche triggered by a paleo-earthquake in northwest China

The Cuihua Rock Avalanche, 30 km south of Xiʹan, China, is located within a marvelous geological landscape and was triggered by an ancient paleo-earthquake. The area is mainly characterized by cliffs, stone seas and a dammed lake (Shuiqiu Pool), with a total area of 5 × 105 m2 and a volume of 1.8 × 107 m3. Field investigations, historical records, dating methods and typical seismic profiles indicated that its occurrence could be correlated with an earthquake in 780 BC that most likely triggered the landslide. The results also showed that a) the formation of the rock avalanche was associated with high-steep slope created by lifting of Qinling Mountain and cutting of rock fractures, and b) the high-steep slope and several preferred structural planes play an important role in controlling the slope instability. Based on conjectures, the failure process of the rock avalanche can be divided into four stages: the preliminary stage, the starting-up stage, the accelerating stage, and the accumulating stage.