The Analysis of Dynamics Characteristics of Large-Scale Wenjiagou Landslide-Sturzstrom Triggered by Wenchuan Earthquake

The M8.0 Wenchuan Earthquake induced a lot of huge landslide events in the Mt. Longmenshan area in 12th May, 2008. One event is the Wenjiagou Landslide-Sturzstrom Event in Qingping County, Mianzhu, China. It killed 48 people and induced a serious of geohazards. The distance between landslide and seismogenic fault (named Yingxiu-Beichuan Fault) is only 3.6 km. This event is a kind of landslide with high-locality, long run-off distance and very high-speed. The sliding mass transformed to sturzstrom by colliding with valley. Accompanied air cushion effect and front airblast effect, the sturzstrom-mass motion was a very complex process. The volume of sturzstrom deposit was more than 5 × 107 m3, it will make the debris flow occurring frequently in Qingping County area in future. For instance, the strong raining induced a great 6 × 106 m3 debris flow disaster in Wenjiagou Valley, 13th August, 2010. Authors preliminary studied on the kinematical characteristics of strong earthquake triggered massive rocky slope failure with methods of landslide dynamic. The final run-off distance is 4,170 m in horizontal direction, and 1,360 m in vertical direction, within about 1 min. The mass of landslide or sturzstrom is dry, and the sturzstrom was composed by air and solid deposit. The calculation shows that the sliding mass moved and accelerated to 74.6 m/s and then increased to 109.34 m/s when sliding mass started a short flight. The motion eigenvalue (μ) of this event is 0.36 which shows it is a strong sturzstrom process. However, its mobility is reduced by multiple impacts.