2017年九寨沟地震地质灾害发育分布规律研究

Research on development and distribution rules of geohazards in Jiuzhaigou earthquake in 2017

2017年8月8日,四川阿坝州九寨沟县发生M s7.0地震。通过现场详查及无人机影像,共获得九寨沟景区内地质灾害点167处。在此基础上,分析地震地质灾害类型;并利用GIS技术在地形地貌、地质、地震构造等方面对地质灾害的分布进行统计分析。研究发现:(1)灾害类型以崩塌、浅表层滑坡为主,其中崩塌最为发育,具有沿沟谷和道路两侧呈线状分布的特点。(2)地震地质灾害多集中在坡度为30°~60°、坡向S、高程2400~2600 m及高差200~250 m范围内,具有较为显著“放大效应”和“背坡面效应”。(3)地层岩性、坡体结构与地质灾害的发育类型有关,其中崩塌灾害主要发育于灰岩等硬岩地层及顺向、斜向坡;在距离发震断裂0~6 km范围内灾害分布最多,随距离增加而减少,具有“距离效应”。(4)灾害点的发育分布与地震烈度等级呈正相关关系;且地震灾害的发育分布受人类工程活动影响较大,随着与公路距离的增加而减少,在公路0~500 m距离内占比最大。

In August 8,2017,M s7.0 earthquake occurred in Jiuzhaigou County,Aba Prefecture,Sichuan province.After a field investigation and uav images,167 geological hazards in Jiuzhaigou scenic spot have been obtained.Then,the distribution of these geohazards was investigated statistically using GIS techniques to determine how the occurrence of geohazards correlates with distance from topography,geology,seismology and human activities.The main results of this research can be summarized as follows:(1)The main types of geohazards are collapses and shallow topsoil landslides,and collapses are most likely to occur.The geohazards triggered by earthquake show the feature of linear distribution along the gullies and roads;(2)The distribution of earthquake-induced geological hazards mostly concentrate in the range of 30~60°,S of slope direction,2400~2600 m of elevation and 200~250 m of height difference.These geohazards have striking“amplification effect”and“back slope effect”;(3)Rock type and slope structure are related to the development types of geohazards.The collapse geohazard is mainly developed in hard rock stratum such as limestone,bedding and tangential slopes.The main geohazards concentrate along or within 6km distance to the earthquake causative fault,which decrease with distance and has“distance effect”;(4)There is a positive correlation between the density of geohazard spots and the magnitude of earthquake intensity.The distribution of geohazards triggered by earthquake is greatly influenced by human engineering activities and decrease with the increase of distance from highway,and in the area of 0~500 m distance,the ratio is the largest.