【摘要】 四川省4·20芦山7.0级地震具有震级高、破坏性强等特点,地震次生地质灾害以崩塌落石为主,滑坡不发育.与汶川5.12特大地震诱发的次生地质灾害相比,无论规模还是数量均显示较轻,但是处于地震影响区的宝兴县城却是个例外,县城周边山体因地形陡峻,表现出崩、滑灾害发育的特点.通过地震前、后对宝兴县城周边地质灾害现场地质调查显示:崩塌、滑坡和泥石流数量分别由地震前的3、1、3个(条)变为地震后的21、1、3个(条);地质灾害发育密度和模数分别由地震前的0.38个/km、0.34万m3/km变为地震后的2.02个/km、5.59万m3/km;地震后发育密度及模数分别是地震前的5.3和16.4倍;地震产生的边坡破坏效应显著.在此基础上,通过分段剖析可知:地震地质灾害主要发生在单薄山脊以及地形坡度陡峭处,岩质边坡以崩塌落石为主,松散层边坡则以滑坡为特征,但大型滑坡少见;地震对处于斜坡地带(非单薄山脊部位)大型松散堆积体等整体复活很少,只是局部陡缓交界部位存在坍滑或震动裂缝,整体稳定性较好,说明强震并不一定会诱发古滑坡等大型松散堆积体的整体复活.更多还原

【Abstract】 Even though Lushan 4·20 strong earthquake has characteristics of high seismic magnitude and strong destructiveness,its secondary geological disasters are dominated by rockfalls rather than landslides.Compared with secondary geological disasters induced by 5·12 Wenchuan earthquake,their size and number are both mild.However,Baoxing County,which is in the earthquake-affected zone,is an exception.Rockfalls and landslides develop well around the county because of steep mountains.Geological field investigations of the geohazards around Baoxing County before and after the earthquake show that after earthquake the number of rockfall,landslide and debris flood changes into 21,1,and 3 from 3,1,and 3,respectively;geohazards development density and modulus change into 2.02 km-1 and 5.59×104 m3/km from 0.38 km-1 and 3.4×103 m3/km,respectively,which are 5.3 and 16.4 times that before the earthquake;and the effect of slope failure induced by the earthquake is significant.Based on the investigation,the following recognitions are obtained by segmental analysis: Seismic geological disasters occur mainly at thin ridges and steep slopes,rockfalls occur mostly at rock slopes,and landslides occur at loose deposited slopes,but large-scale landslides are rare.The overall revival of large-scale loose deposits is not caused by the earthquake,and only some collapse or vibration cracks take place in some parts of steep-gentle junctions.Thus,the loose deposited ancient landslides are stable.This suggests that strong earthquake may not induce overall revival of ancient landslides.更多还原