玉树震区地质灾害分布规律与发育特征

DISTRIBUTION REGULARITY AND DEVELOPMENT CHARACTERISTICS OF GEOHAZARDS IN YUSHU EARTHQUAKE AREA

2010年4月14日7时49分,青海省玉树县发生MS7.1级地震。玉树地震不仅造成大量房屋破坏与人员伤亡,同时引发了大量的崩塌、滑坡和山体裂缝,并且形成了大量的诸如泥石流、碎屑流等链生灾害隐患,造成玉树震区地质灾害分布规律与发育特征发生显著改变。通过现场调查与数据统计,对地震前后地质灾害分布规律与发育特征进行分析、研究。结果表明:玉树震区震前地质灾害呈零星点状分布,以泥石流、不稳定斜坡为主要地质灾害类型,规模以小型为主,形成时间主要集中于每年的5～7月。震后,玉树震区地质灾害数量显著增加,在宏观震中结古镇主震断裂穿越的巴曲两岸与结古镇北部山区以及扎曲南部山区,沿主震断裂呈面状集中分布,距离主震断裂较远或远离宏观震中的区域呈零星点状分布。地质灾害受玉树主震断裂控制明显,并受坡型、坡高与坡度的控制;地质灾害主要分布于距主震断裂2km以内的北盘区域,在坡型上主要分布于凸型与直线型坡,高程为3800～4000m内,坡度在25°～40°范围内,且以30°～35°范围内地质灾害最为发育;地震造成山体地表裂缝所形成的地质灾害隐患比较突出,大中型规模的地质灾害数量明显增加,危害程度显著增高;汛期地质灾害发育更加集中,并加剧冻融期地质灾害的孕育。

At 7: 49a.m.April 14 th 2010,a Ms 7.1 earthquake occurred in Yushu county,Qinghai province,China.The Yushu earthquake not only resulted in destruction of lots of buildings and plenty of casualty,but also brought lots of geo-hazards such as debris flows,rock falls,landslides and ground cracks.So it evidently changed the distribution regularity and development characteristics of the geohazards at the region.Based on field investigations and statistics,the distribution regularity and development characteristics of the geohazards before and after the earthquake are analyzed.The results show that the geohazards scatter in the area and take place from May to July every year.The main types of the geohazards were debris flows and unstable slopes,as well as the main small scale of geohazards before the Yushu earthquake;After the earthquake,the numbers of geohazards increased obviously, and the distribution of geohazards concentrated in the areas where the main faults cross the Valley of Baqu river, the mountain areas of northern Jiegu town and southern of Zhaqu river,and the geohazards distribute sporadically in the areas where far away from the main faults or macroscopic epicenter.The geohazards are controlled evidently not only by the main faults,but also by the shape,altitude and gradient of slopes.The geohazards mainly distributed in the area of within 2km away from north of the main faults,and on the bulgy shape slopes,altitude of 3800 ～ 4000m,and the gradient of 25° ～ 40°,focused on the gradient of 30° ～ 35°.The geohazards induced by the ground cracks in the mountains develop distinctly,and the numbers of large and middle scales of geohazards increase clearly,so that the harm of geohazards increase greatly.Especially,the geohazards took place more frequently in rain season,which accelerates the development of geohazards in freezing and thawing periods.