A large landslide triggered by the 2008 Wenchuan (M8.0) earthquake in Donghekou area: Phenomena and mechanisms

Abstract

During the 2008 Wenchuan earthquake, more than 60,000 landslides were triggered, resulting in about 20,000 casualties. Among these landslides, a catastrophic one occurred in Donghekou area of Qingchuan County. Donghekou landslide had a volume of about 1×10 7 m 3 , traveled fast for approximately 2 km, killing about 780 people. The source area consisted of unstable sedimentary strata and the runout path was made of colluvial deposits. During the earthquake, the colluvial deposits started to move first, before the arrival of the displaced landslide debris from the main source area. We performed undrained cyclic ring shear tests on samples taken from the runout path and concluded that liquefaction of the runout path material enhanced the mobility of the debris material. A fumarole was identified on the upper part of the runout path 6 months later. We analyzed the gas and water venting out, and concluded that the fumarole was not the result of fault movement; it resulted instead from the weathering of slate from the source area. The long-travel landslide materials blocked two rivers, forming two landslide dams that breached with the occurrence of overtopping. To better understand the internal structure of the landslide deposits and then provide evidence for a rational plan of countermeasures to stabilize the landslide dams, we measured the shear-wave-velocity of the landslide deposits by a surface-wave technique called multichannel analysis of surface waves (MASW). The results revealed that the landslide dams consisted

Two multi-temporal datasets that track the enhanced landsliding after the 2008 Wenchuan earthquake

“…Observations on the evolution of mass wasting after recent major earthquakes reveal a peak of landslide rates (remobilisations of coseismic landslide deposits and post-seismic landslides) soon after the earthquakes, followed by decay and normalisation within less than a decade (Fan et al, 2018a;Hovius et al, 2011;Zhang et al, 2016;Zhang and Zhang, 2017). The reasons for this normalisation, which seems quicker than that of the sediment export by nonlandslide processes (Ding et al, 2014;Wang et al, 2015, are still poorly understood. Various processes, such as the progressive depletion of the debris, grain coarsening and densification, restoration of the vegetation cover and bedrock healing have been shown to play a role (e.g.…”

Velocity‐dependent frictional weakening of large rock avalanche basal facies: Implications for rock avalanche hypermobility?

“…With ring shear apparatuses, Deganutti [] and Sadrekarimi and Olson [] studied the role of particle fragmentation on the friction of clasts and concluded that the decay of their friction induced by particle fragmentation is not sufficiently high to realize the hypermobility of rock avalanches. Using the ring shear apparatuses, many ring shear tests on clastic materials were carried out with soil liquefaction induced by the generation of excess pore pressure during undrained shearing, and this was proposed to explain the frictional weakening of some rock avalanches [ Lee and Sassa , ; Okada et al ., , ; Gratchev et al ., ; Li et al ., ; Wang et al ., , ; Hu et al ., ; Zhang et al ., ]. However, for some of the reported rock avalanches, there is very little proof of soil liquefaction occurring in their basal facies [ Cruden and Hungr , ; Pollet and Schneider , ; Boultbee et al ., ; McSaveney and Davies , ; Weidinger et al ., ; Wang et al ., , ].…”

“…The “hypermobility” of rock avalanche indicates much longer runout beyond the distance one expects from a frictional slide down an incline with a normal coefficient of friction of 0.62 [ Hsü , ]. Rock avalanches such as these have also been reported in other mountainous areas (Table shows some notable cases around the world), especially in recent decades, causing billions of dollars in damage and many casualties [ Boultbee et al ., ; Cox and Allen , ; Wang et al ., ; Deline et al ., ; Yin et al ., ; Zhang and Yin , ; Wang et al ., ], which highlights the importance of investigating the hypermobility mechanism of rock avalanches.…”

Dynamic Analysis of the High‐Speed and Long‐Runout Landslide Movement Process Based on the Discrete Element Method: A Case Study of the Shuicheng Landslide in Guizhou, China

“…High-speed and long-runout landslide is a landslide with great velocity and displacement, which has the characteristics of huge volume, strong destructiveness, and high fluidity [1][2][3]. China has a vast territory and complex geological structure, with a wide range of landslide hazards [4], especially in southwest mountainous areas [5], such as the Touzhai landslide [6], Yigong landslide [7], Donghekou landslide [8], Jiweishan landslide [9], Guanling landslide [10], and Xinmo landslide [11]. e high-speed and longrunout landslide often causes huge property losses and casualties due to the difficulty of early identification and spatial prediction.…”