“7·22”岷县漳县地震地质灾害分布、特征及与影响因子间关系分析

DISTRIBUTION,CHARACTERISTICS,AND ASSOCIATED INFLUENCIAL FACTORS OF THE GEOHAZARDS INDUCED BY MINXIAN-ZHANGXIAN EARTHQUAKE ON 22 JULY,2013,GANSU,CHINA

2013年7月22日在甘肃省定西市岷县、漳县交界处发生了M S6.6级地震。此次地震造成了大量房屋、基础设施破坏以及人员伤亡,并诱发了一系列的滑坡、崩塌、不稳定斜坡等地质灾害隐患。通过现场调查和分析,对此次地震地质灾害隐患类型、分布与主要特点进行概括。利用边坡地质灾害数量和面积发育率两个统计指标,对受灾最为严重的岷县灾区的地震地质灾害分布与地形、地质、地震因子变量间关系进行分析,结果表明:(1)地震地质灾害隐患在高程为2200～2800m范围内集中分布,在0°～15°缓坡内分布最多,坡向为S、SW和W的斜坡在地震作用下易诱发地质灾害,坡位为中坡的边坡内分布地质灾害数量最多;(2)软弱岩层在地震作用下易发生地质灾害,区内泥盆系和二叠系板岩、灰岩岩组内分布近50%的地质灾害,面积发育率最大的则为新近系中厚层软弱泥岩、砂岩岩组。地质灾害主要沿发震断裂通过或距离较近的地方成片集中分布,地质灾害主要分布在距离发震断裂20km以内的范围内;(3)震中距和PGA与地质灾害数量对应关系不明显,但是面积发育率整体趋势是随着震中距增加而减小,随着PGA增大而增加;地质灾害易发程度随烈度增大而增强;(4)越靠近公路和河流,地质灾害越易发生,集中分布区间分别为距公路0～800m和距河流0～600m。

On July 22,2013a catastrophic earthquake with Ms 6.6 occurred at the conjunction of Min and Zhang Counties,Dingxi City,Gansu Province,China.The seismic activities have caused a wide spread of damages to houses and infrastructures,and induced a series of potential hazards such as landslides,collapses and unstable slopes.This paper summarizes the types,distribution and major characteristics of the potential geohazards induced by the earthquake.Two indices including number of the slope geohazards and area development rate are used to analyse the relationship between the potential geohazards initiated by the earthquake and other controlling factors such as topographical,geological and seismic conditions in the epicenter area of Min County.The results show that：（1）The potential geohazards initiated by the earthquake are distributed in the area where elevations are in the range of 2200m to 2800m,slope gradient in 0°～ 15°,slope aspects in S,SW and W,and topographically at the middle parts of slopes; （2）The soft rocks are prone to landslide under seismic vibrations.The Devonian and Permian slate and limestone group produces about 50％ of the geohazards in the whole earthquake affected area.The thick Neogene soft mudstone and sandstone group hosts the highest geohazards development rate.The main geohazards concentrate along or within 20km distance to the earthquake causative fault ; （3） The correlation between individual geohazard scales and their distances to the epicenter and PGA are not significant.However,the general trend is obvious,as the development rate decreases with the increasing distance to the epicenter and increases with the increasing PGA.The greater the seismic intensity,the higher the probability of geohazards occurrence ; （4） The closer to roads and river,the higher of the development rate of the geohazards,especially within the distance of 0～800m to the roads and 0 ～ 600m to the streams or rivers.