遥感技术在西藏当雄地区活动断裂调查中的应用

Application of Remote Sensing Data in Active Fault Surveying of Damxung Area

以遥感数据、地震资料以及震源机制解为基础,对西藏当雄地区亚东-谷露断裂以及嘉黎断裂进行遥感解译和对比分析。研究表明,亚东-谷露断裂北段地貌特征为正断拉张及右旋走滑综合作用的结果;中段存在拉张运动与左旋走滑运动,并发育地堑,冲沟位错显示该处具有6~66m的水平位移量,其中1411年当雄南8级地震在该处产生6~12m的水平位移;南段次级断层充分发育,北端表现为右旋运动,往南开始表现出左旋运动特征,同时地堑充分发育。结合震源机制解反演结果,推测走滑断层控制该区地壳浅部(8km以上)以走滑型为主的地震事件的发生,而该处的地堑形成于地壳深部(8km以下)的正断型应力机制,并控制地壳深部正断型地震事件的发生。嘉黎断裂整体断层隐伏,西段存在右旋运动,往东南则开始出现左旋运动,该处地震事件和应力机制均为走滑型。

In this paper, remote sensing interpretation and comparative analysis of active faults are made based on remote sensing data, earthquake data and focal mechanism solutions. Our research shows that the geomorphic features of the northern segment of the Yadong-Gulu fault are results of combined action of normal fault and dextral strike-slip fault. Extensional movement, sinistral strike slip movement and graben structures are found in the middle segment of the Yadong-Gulu fault, and gully dislocations show a horizontal displacement of 6 m to 66 m along this fault.The 1411 southern Damxung earthquake of M=8.0 caused a horizontal displacement of 6 m to 16 m along the fault. Secondary faults are fully developed in the southern segment of the Yadong-Gulu fault. The north end of the southern segment shows characteristics of dextral movement, while it turns to sinistral movement on the south side. Graben structures are also fully developed in this segment. The strike-slip faults control the occurrence of earthquakes in the shallow crust （above 8 km）, which are mainly strike-slip type. Graben structures are caused by normal fracture tress mechanism in the deep crust （below 8 km） and control the earthquakes in the deep crust. The Lhari fault is generally buried. The dextral motion is found in its west part, while the southeast part of the Lhari fault shows characteristics of sinistral movement. The stress mechanism and earthquake events in the Lhari fault area are strike-slip type.