The role of active faults and sliding mechanism analysis of the 2017 Maoxian postseismic landslide in Sichuan, China

A giant, high-position rockslide occurred in Xinmo village of Maoxian County, Sichuan, China, on June 24, 2017. It was the largest rockslide recorded since the 2008 Wenchuan earthquake, and caused great loss. We use field survey data and relevant information to describe the geometric and zoning of the Maoxian landslide, and we discuss its sliding mechanism and the role of active faults in its formation. The sliding mode of the Maoxian landslide involves a plane failure mechanism (sliding rupture), while the slipping process can be divided into two stages: a rock cracking and deterioration stage, and a high-speed sliding stage. The role of active faults (earthquake and fault movement) is probably the most important factor in the Maoxian landslide formation, while lithology played a catalytic role and rainfall acted as an inducing factor. The fault vertical combination model (“back thrust” dynamic model) proposed in this paper provides a reasonable explanation for the different distribution of the coseismic landslides caused by the 1933 M 7.5 Diexi earthquake. We consider that a steep slope near the active fault, especially where the active fault intersects, just like the “locked segment” of a fault, is the uppermost area to develop a large landslide.