Scientific Research_Institute of Geology,China Earthquake Administration

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Characteristics of landslides triggered by “7.22” Mixian – Zhangxian Ms6.6 earthquake

2014/5/27 9:38:57

The 2013 “7.22” Minxian-Zhangxian Ms6.6 earthquake has triggered a large number of landslides, which are diversified and mostly small loess cliff collapses and loess cliff landslides. There are also some rare earthquake-induced landslides, such as large or medium deep landslides and earth flows.

The landslides triggered by this earthquake have caused serious disasters, including human casualty and destruction of settlements (Fig. 1) and damage or destruction of cables, pipelines, highways, railways and other infrastructure facilities (Fig. 2). Yongguang Village which was hit hardest has two earthquake-induced landslides. One (#1 landslide at Yongguang Village) formed a long earthflow and claimed 12 lives (Fig. 3, 4, 5). Another adjacent landslide (#2 landslide at Yongguang Village) also caused a death toll of about four people (Fig. 6, 7). In the earthquake region, some ancient landslides are developed, too (Fig. 8, 9, 10). It is extremely likely that these ancient landslides have a link with historical earthquakes. Further research is worth doing.

According to our field study on landslides along a few routes cross earthquake regions and hundreds of positioned earthquake-induced landslides, we preliminarily analyzed and demarcated the area with dense distribution of earthquake-induced landslides (Fig. 11). Earthquake-induced landslides are mainly distributed in “Cagutan – Majiagou – Wendou – Chenlu – Yongguang – Yongxing – Lalu. The maximum width of this area is about 8 km and its length is about 30km. Features of landslides in this area: (1) The landslides are often developed densely and link each other. They often block highways by tens of meters, even more than 100m; (2) Large or medium landslides are often seen in this area. The two disastrous landslides at Yongguang Village are in this area; (3) The strike of the long axis of the area with dense distribution of landslides is consistent with the strike of the seismogenic structure. Further scientific research is needed to explain why it is several kilometers away from “Lintan – Dangchang” Fracture.科研动态/S20130725115945820104.jpg科研动态/S20130725115947370107.jpg

A house destroyed by earthquake-induced landslide

Joined earthquake-induced landslides on one side of a highway科研动态/S20130725115943280099.jpg科研动态/S20130725115947880108.jpg

Source area of #1 landslide at Yongguang Village (loess landslide), with almost vertical rear wall

#1 landslide at Yongguang Village flowed down along a ditch after becoming a debris flow科研动态/S20130725115944790102.jpg科研动态/S20130725115943760100.jpg

Front border of the accumulation body of #1 landslide at Yongguang Village, with substance stopped on a bridge

Source area of #2 landslide at Yongguang Village科研动态/S20130725115946850106.jpg科研动态/S20130725115946340105.jpg

#2 landslide at Yongguang Village shows obvious fluid characteristics

Ancient landslide 1 of the earthquake region科研动态/S20130725115944280101.jpg科研动态/S20130725115945310103.jpg

Ancient landslide 2 of the earthquake region

 Ancient landslide 3 of the earthquake region科研动态/S20130725125130160109.jpg

The red oval area is a preliminarily determined area with dense distribution of earthquake-induced landslides