西藏安多北断裂晚第四纪活动的基本特征

Basic Characters of the Late Quaternary Activities of the North-Andor Fault, Tibet

安多北断裂是青藏高原中部安多—错那盆地的北边界断裂(图1)。安多—错那盆地是青藏高原中部当雄—羊八井活动构造带北端的一个断陷盆地,盆地的北缘和南东缘分别为安多北断裂、安多南断裂和错那东断裂,这些断裂均为全新世活动断裂,安多北断裂和安多南断裂控制形成安多盆地,错那断裂控制形成错那盆地。安多盆地总体呈NNE走向,长约80km,南北宽约6~15km,盆地面的海拔高程为4580~4700m,呈东北部高、西南部低的趋势。以前的活动构造研究多集中在当雄—羊八井活动构造带的主体部分。

The North Andor fault is the northern boundary fault of the Andor-Cuona basin in central part of Qinghai-Tibet plateau.Tectonically,it is positioned at the northern end of the Danxiong-Yangbajing active tectonic belt in the middle Tibet.Previously,the active tectonics of the northern end has been less studied.In remote sensing image,the north Andor fault appears as a linear structure that dislocated Holocene layers and gullies,so that it is a Holocene highly active fault.Through quantitative studies of structural profiles and faulted landforms,we have determined that the fault possesses left-lateral strike-slip with normal component that is coincident with regional fault activities.The Holocene activities are mainly left lateral and the strike-slip rate is of 2.0~2.7mm/a.Faulted micro-landform reveal that it has characteristic seismic feature,and the maximum left lateral dislocation value reached 6~8m.