【摘要】 2008年3月21日新疆于田7.1级地震发生在青藏高原北缘东昆仑山、西昆仑山和阿尔金山交汇的地区。文中介绍了此次地震的近断层破坏作用。此次地震在阿尔金断裂西端近南北向谷地海拔4 900~5 600m东坡形成了近31km长的地震地表破裂带。破裂带主要显示正断层滑动性质,其总体走向近南北,但局部追索北北西和北北东向共轭断裂发育,走向变化很大。受地形及滑塌作用影响,断裂陡坎高度最大可达20m,垂直位移为2m左右,最大水平拉张量也接近1.8m,此外局部还存在近1m的左旋位移。沿断裂发育一个近10hm2的滑坡体,以及大量中小规模的滑坡、崩塌,多为冰碛物、洪积物及残坡积物等松散堆积。虽位于陡峭的山坡上,也未见大规模基岩崩塌、滑坡。通过平地上巨石的翻滚推测,断层附近的最大加速度峰值可达1 g。同时根据不同坡度的边坡崩塌和滚石发育程度估算出距离断层不同距离地区的地震震动峰值加速度。地裂缝分布范围较宽,距断层1km的地区仍可见到长度超过100m的地裂缝。这些地裂缝可能是地震震动、谷地边坡变形及旁支断层地震触发滑动的综合产物。极震区最大烈度估计可达Ⅹ度,综合各方面资料文章提供了该次地震Ⅸ度、Ⅷ度、和Ⅶ度等震线;长轴方向呈NNE-SSW向,与余震方向大致一致。近断层破坏作用包括强地面运动、断层破裂带、地裂缝、滑坡、崩塌、滚石等。它们受到震级、断裂活动性质及场地条件等多因素控制。更多还原

【Abstract】 The near-fault damaging effects of 2008Yutian MS7.1earthquake in Xinjiang,China were investigated in May of 2011.This quake occurred at the junction of West Kunlun,East Kunlun and Altun Tag Mountains in the north margin of Tibetan Plateau.The characteristics of near fault damaging effects of this quake are introduced in this paper.After the earthquake,a 31km long surface rupture appeared along the eastern slope of a N-S trending valley with the elevation of 4900-5600m,developed in the western end of the Altun Tag fault.The general trending of the rupture is in N-S,but locally it extends following the conjugate breaks of NNE-NNW and varies greatly in trending.Due to the topography and slumping,the maximun height of the fault scarp on the steep slope is up to 20m.The largest vertical offset of the rupture is about 2m,and the maximum horizontal extension is about 1.8m.Besides,there are locally about 1msinistral displacements.A large landslide with area over 10hm2,as well as a large number of moderate and small landslides and collapses were developed during the quake in loose debris,including moraine,diluvial,and eluvial deposits,which can be seen along the surface ruptures on the mountainside.No large scale bedrock collapse or landslide was found,even on the steep slopes along the rupture.The peak acceleration of strong ground motion,inferred from the evidence of rolled or turned over of large boulders on the level ground,is up to 1 g.Based on the collapse of slopes and the development of large boulders,the peak acceleration values of the strong ground motion at various distance from the fault can be calculated.The distribution of the surface cracks is rather wide,and about 1km from the the fault,the surface cracks more than 100mlong still can be found.These cracks are probably the integrated results of earthquake tremor,valley slope deformation and quake-induced sliding of the branch faults.The maximum intensity of extreme seismic zone of this quake is estimated to beⅩdegree in Chinese Seismic Intensity Scale.The isoseismic lines of Ⅸ,Ⅷ,Ⅶ degrees were inferred from comprehensive observed data or phenomena.The long axis of the intensity district is trending to NNE-SSW,which is consistent with the distribution of aftershocks.The near-fault damage effects involved strong ground motion,fault ruptures,fissures,landslides,collapses,and rock falls.They were controlled by the magnitude and slip sense of the quake,and the site condition of the epicenter.更多还原