The "long" runout rock avalanche in Pusa, China, on August 28, 2017: a preliminary report

On August 28, 2017, a large rock avalanche occurred in Pusa, a village in the County of Nayong (Guizhou Province, China). About 500,000m(3) of rock detached from a mountain ridge, slid over debris from earlier landslides and buried several buildings. The rock mass, heavily fragmented, eventually formed a deposit of 800,000m(3), up to 4m thick. Twenty-six fatalities and 9 people missing were reported. Based on site investigation, live footage, UAV photography, GBSAR monitoring, historical records and remote sensing imagery, we describe characteristics of failure and runout of the avalanche. Extensive coal mining under the slope had probably weakened and fractured the rock mass, enhancing climate-induced weathering. Failure was anticipated by cracks opening and minor rockfalls in the past decade, which intensified in the last rainy season.